Imported Upstream version 2.0.3

138 files changed, 149685 insertions, 0 deletions

diff --git a/src/alter.c b/src/alter.c
new file mode 100644
index 0000000..fb6d89d
--- /dev/null
+++ b/src/alter.c
@@ -0,0 +1,826 @@
+/*
+** 2005 February 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains C code routines that used to generate VDBE code
+** that implements the ALTER TABLE command.
+*/
+#include "sqliteInt.h"
+
+/*
+** The code in this file only exists if we are not omitting the
+** ALTER TABLE logic from the build.
+*/
+#ifndef SQLITE_OMIT_ALTERTABLE
+
+
+/*
+** This function is used by SQL generated to implement the 
+** ALTER TABLE command. The first argument is the text of a CREATE TABLE or
+** CREATE INDEX command. The second is a table name. The table name in 
+** the CREATE TABLE or CREATE INDEX statement is replaced with the third
+** argument and the result returned. Examples:
+**
+** sqlite_rename_table('CREATE TABLE abc(a, b, c)', 'def')
+**     -> 'CREATE TABLE def(a, b, c)'
+**
+** sqlite_rename_table('CREATE INDEX i ON abc(a)', 'def')
+**     -> 'CREATE INDEX i ON def(a, b, c)'
+*/
+static void renameTableFunc(
+  sqlite3_context *context,
+  int NotUsed,
+  sqlite3_value **argv
+){
+  unsigned char const *zSql = sqlite3_value_text(argv[0]);
+  unsigned char const *zTableName = sqlite3_value_text(argv[1]);
+
+  int token;
+  Token tname;
+  unsigned char const *zCsr = zSql;
+  int len = 0;
+  char *zRet;
+
+  sqlite3 *db = sqlite3_context_db_handle(context);
+
+  UNUSED_PARAMETER(NotUsed);
+
+  /* The principle used to locate the table name in the CREATE TABLE 
+  ** statement is that the table name is the first non-space token that
+  ** is immediately followed by a TK_LP or TK_USING token.
+  */
+  if( zSql ){
+    do {
+      if( !*zCsr ){
+        /* Ran out of input before finding an opening bracket. Return NULL. */
+        return;
+      }
+
+      /* Store the token that zCsr points to in tname. */
+      tname.z = (char*)zCsr;
+      tname.n = len;
+
+      /* Advance zCsr to the next token. Store that token type in 'token',
+      ** and its length in 'len' (to be used next iteration of this loop).
+      */
+      do {
+        zCsr += len;
+        len = sqlite3GetToken(zCsr, &token);
+      } while( token==TK_SPACE );
+      assert( len>0 );
+    } while( token!=TK_LP && token!=TK_USING );
+
+    zRet = sqlite3MPrintf(db, "%.*s\"%w\"%s", ((u8*)tname.z) - zSql, zSql, 
+       zTableName, tname.z+tname.n);
+    sqlite3_result_text(context, zRet, -1, SQLITE_DYNAMIC);
+  }
+}
+
+/*
+** This C function implements an SQL user function that is used by SQL code
+** generated by the ALTER TABLE ... RENAME command to modify the definition
+** of any foreign key constraints that use the table being renamed as the 
+** parent table. It is passed three arguments:
+**
+**   1) The complete text of the CREATE TABLE statement being modified,
+**   2) The old name of the table being renamed, and
+**   3) The new name of the table being renamed.
+**
+** It returns the new CREATE TABLE statement. For example:
+**
+**   sqlite_rename_parent('CREATE TABLE t1(a REFERENCES t2)', 't2', 't3')
+**       -> 'CREATE TABLE t1(a REFERENCES t3)'
+*/
+#ifndef SQLITE_OMIT_FOREIGN_KEY
+static void renameParentFunc(
+  sqlite3_context *context,
+  int NotUsed,
+  sqlite3_value **argv
+){
+  sqlite3 *db = sqlite3_context_db_handle(context);
+  char *zOutput = 0;
+  char *zResult;
+  unsigned char const *zInput = sqlite3_value_text(argv[0]);
+  unsigned char const *zOld = sqlite3_value_text(argv[1]);
+  unsigned char const *zNew = sqlite3_value_text(argv[2]);
+
+  unsigned const char *z;         /* Pointer to token */
+  int n;                          /* Length of token z */
+  int token;                      /* Type of token */
+
+  UNUSED_PARAMETER(NotUsed);
+  for(z=zInput; *z; z=z+n){
+    n = sqlite3GetToken(z, &token);
+    if( token==TK_REFERENCES ){
+      char *zParent;
+      do {
+        z += n;
+        n = sqlite3GetToken(z, &token);
+      }while( token==TK_SPACE );
+
+      zParent = sqlite3DbStrNDup(db, (const char *)z, n);
+      if( zParent==0 ) break;
+      sqlite3Dequote(zParent);
+      if( 0==sqlite3StrICmp((const char *)zOld, zParent) ){
+        char *zOut = sqlite3MPrintf(db, "%s%.*s\"%w\"", 
+            (zOutput?zOutput:""), z-zInput, zInput, (const char *)zNew
+        );
+        sqlite3DbFree(db, zOutput);
+        zOutput = zOut;
+        zInput = &z[n];
+      }
+      sqlite3DbFree(db, zParent);
+    }
+  }
+
+  zResult = sqlite3MPrintf(db, "%s%s", (zOutput?zOutput:""), zInput), 
+  sqlite3_result_text(context, zResult, -1, SQLITE_DYNAMIC);
+  sqlite3DbFree(db, zOutput);
+}
+#endif
+
+#ifndef SQLITE_OMIT_TRIGGER
+/* This function is used by SQL generated to implement the
+** ALTER TABLE command. The first argument is the text of a CREATE TRIGGER 
+** statement. The second is a table name. The table name in the CREATE 
+** TRIGGER statement is replaced with the third argument and the result 
+** returned. This is analagous to renameTableFunc() above, except for CREATE
+** TRIGGER, not CREATE INDEX and CREATE TABLE.
+*/
+static void renameTriggerFunc(
+  sqlite3_context *context,
+  int NotUsed,
+  sqlite3_value **argv
+){
+  unsigned char const *zSql = sqlite3_value_text(argv[0]);
+  unsigned char const *zTableName = sqlite3_value_text(argv[1]);
+
+  int token;
+  Token tname;
+  int dist = 3;
+  unsigned char const *zCsr = zSql;
+  int len = 0;
+  char *zRet;
+  sqlite3 *db = sqlite3_context_db_handle(context);
+
+  UNUSED_PARAMETER(NotUsed);
+
+  /* The principle used to locate the table name in the CREATE TRIGGER 
+  ** statement is that the table name is the first token that is immediatedly
+  ** preceded by either TK_ON or TK_DOT and immediatedly followed by one
+  ** of TK_WHEN, TK_BEGIN or TK_FOR.
+  */
+  if( zSql ){
+    do {
+
+      if( !*zCsr ){
+        /* Ran out of input before finding the table name. Return NULL. */
+        return;
+      }
+
+      /* Store the token that zCsr points to in tname. */
+      tname.z = (char*)zCsr;
+      tname.n = len;
+
+      /* Advance zCsr to the next token. Store that token type in 'token',
+      ** and its length in 'len' (to be used next iteration of this loop).
+      */
+      do {
+        zCsr += len;
+        len = sqlite3GetToken(zCsr, &token);
+      }while( token==TK_SPACE );
+      assert( len>0 );
+
+      /* Variable 'dist' stores the number of tokens read since the most
+      ** recent TK_DOT or TK_ON. This means that when a WHEN, FOR or BEGIN 
+      ** token is read and 'dist' equals 2, the condition stated above
+      ** to be met.
+      **
+      ** Note that ON cannot be a database, table or column name, so
+      ** there is no need to worry about syntax like 
+      ** "CREATE TRIGGER ... ON ON.ON BEGIN ..." etc.
+      */
+      dist++;
+      if( token==TK_DOT || token==TK_ON ){
+        dist = 0;
+      }
+    } while( dist!=2 || (token!=TK_WHEN && token!=TK_FOR && token!=TK_BEGIN) );
+
+    /* Variable tname now contains the token that is the old table-name
+    ** in the CREATE TRIGGER statement.
+    */
+    zRet = sqlite3MPrintf(db, "%.*s\"%w\"%s", ((u8*)tname.z) - zSql, zSql, 
+       zTableName, tname.z+tname.n);
+    sqlite3_result_text(context, zRet, -1, SQLITE_DYNAMIC);
+  }
+}
+#endif   /* !SQLITE_OMIT_TRIGGER */
+
+/*
+** Register built-in functions used to help implement ALTER TABLE
+*/
+void sqlite3AlterFunctions(void){
+  static SQLITE_WSD FuncDef aAlterTableFuncs[] = {
+    FUNCTION(sqlite_rename_table,   2, 0, 0, renameTableFunc),
+#ifndef SQLITE_OMIT_TRIGGER
+    FUNCTION(sqlite_rename_trigger, 2, 0, 0, renameTriggerFunc),
+#endif
+#ifndef SQLITE_OMIT_FOREIGN_KEY
+    FUNCTION(sqlite_rename_parent,  3, 0, 0, renameParentFunc),
+#endif
+  };
+  int i;
+  FuncDefHash *pHash = &GLOBAL(FuncDefHash, sqlite3GlobalFunctions);
+  FuncDef *aFunc = (FuncDef*)&GLOBAL(FuncDef, aAlterTableFuncs);
+
+  for(i=0; i<ArraySize(aAlterTableFuncs); i++){
+    sqlite3FuncDefInsert(pHash, &aFunc[i]);
+  }
+}
+
+/*
+** This function is used to create the text of expressions of the form:
+**
+**   name=<constant1> OR name=<constant2> OR ...
+**
+** If argument zWhere is NULL, then a pointer string containing the text 
+** "name=<constant>" is returned, where <constant> is the quoted version
+** of the string passed as argument zConstant. The returned buffer is
+** allocated using sqlite3DbMalloc(). It is the responsibility of the
+** caller to ensure that it is eventually freed.
+**
+** If argument zWhere is not NULL, then the string returned is 
+** "<where> OR name=<constant>", where <where> is the contents of zWhere.
+** In this case zWhere is passed to sqlite3DbFree() before returning.
+** 
+*/
+static char *whereOrName(sqlite3 *db, char *zWhere, char *zConstant){
+  char *zNew;
+  if( !zWhere ){
+    zNew = sqlite3MPrintf(db, "name=%Q", zConstant);
+  }else{
+    zNew = sqlite3MPrintf(db, "%s OR name=%Q", zWhere, zConstant);
+    sqlite3DbFree(db, zWhere);
+  }
+  return zNew;
+}
+
+#if !defined(SQLITE_OMIT_FOREIGN_KEY) && !defined(SQLITE_OMIT_TRIGGER)
+/*
+** Generate the text of a WHERE expression which can be used to select all
+** tables that have foreign key constraints that refer to table pTab (i.e.
+** constraints for which pTab is the parent table) from the sqlite_master
+** table.
+*/
+static char *whereForeignKeys(Parse *pParse, Table *pTab){
+  FKey *p;
+  char *zWhere = 0;
+  for(p=sqlite3FkReferences(pTab); p; p=p->pNextTo){
+    zWhere = whereOrName(pParse->db, zWhere, p->pFrom->zName);
+  }
+  return zWhere;
+}
+#endif
+
+/*
+** Generate the text of a WHERE expression which can be used to select all
+** temporary triggers on table pTab from the sqlite_temp_master table. If
+** table pTab has no temporary triggers, or is itself stored in the 
+** temporary database, NULL is returned.
+*/
+static char *whereTempTriggers(Parse *pParse, Table *pTab){
+  Trigger *pTrig;
+  char *zWhere = 0;
+  const Schema *pTempSchema = pParse->db->aDb[1].pSchema; /* Temp db schema */
+
+  /* If the table is not located in the temp-db (in which case NULL is 
+  ** returned, loop through the tables list of triggers. For each trigger
+  ** that is not part of the temp-db schema, add a clause to the WHERE 
+  ** expression being built up in zWhere.
+  */
+  if( pTab->pSchema!=pTempSchema ){
+    sqlite3 *db = pParse->db;
+    for(pTrig=sqlite3TriggerList(pParse, pTab); pTrig; pTrig=pTrig->pNext){
+      if( pTrig->pSchema==pTempSchema ){
+        zWhere = whereOrName(db, zWhere, pTrig->zName);
+      }
+    }
+  }
+  if( zWhere ){
+    char *zNew = sqlite3MPrintf(pParse->db, "type='trigger' AND (%s)", zWhere);
+    sqlite3DbFree(pParse->db, zWhere);
+    zWhere = zNew;
+  }
+  return zWhere;
+}
+
+/*
+** Generate code to drop and reload the internal representation of table
+** pTab from the database, including triggers and temporary triggers.
+** Argument zName is the name of the table in the database schema at
+** the time the generated code is executed. This can be different from
+** pTab->zName if this function is being called to code part of an 
+** "ALTER TABLE RENAME TO" statement.
+*/
+static void reloadTableSchema(Parse *pParse, Table *pTab, const char *zName){
+  Vdbe *v;
+  char *zWhere;
+  int iDb;                   /* Index of database containing pTab */
+#ifndef SQLITE_OMIT_TRIGGER
+  Trigger *pTrig;
+#endif
+
+  v = sqlite3GetVdbe(pParse);
+  if( NEVER(v==0) ) return;
+  assert( sqlite3BtreeHoldsAllMutexes(pParse->db) );
+  iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
+  assert( iDb>=0 );
+
+#ifndef SQLITE_OMIT_TRIGGER
+  /* Drop any table triggers from the internal schema. */
+  for(pTrig=sqlite3TriggerList(pParse, pTab); pTrig; pTrig=pTrig->pNext){
+    int iTrigDb = sqlite3SchemaToIndex(pParse->db, pTrig->pSchema);
+    assert( iTrigDb==iDb || iTrigDb==1 );
+    sqlite3VdbeAddOp4(v, OP_DropTrigger, iTrigDb, 0, 0, pTrig->zName, 0);
+  }
+#endif
+
+  /* Drop the table and index from the internal schema.  */
+  sqlite3VdbeAddOp4(v, OP_DropTable, iDb, 0, 0, pTab->zName, 0);
+
+  /* Reload the table, index and permanent trigger schemas. */
+  zWhere = sqlite3MPrintf(pParse->db, "tbl_name=%Q", zName);
+  if( !zWhere ) return;
+  sqlite3VdbeAddParseSchemaOp(v, iDb, zWhere);
+
+#ifndef SQLITE_OMIT_TRIGGER
+  /* Now, if the table is not stored in the temp database, reload any temp 
+  ** triggers. Don't use IN(...) in case SQLITE_OMIT_SUBQUERY is defined. 
+  */
+  if( (zWhere=whereTempTriggers(pParse, pTab))!=0 ){
+    sqlite3VdbeAddParseSchemaOp(v, 1, zWhere);
+  }
+#endif
+}
+
+/*
+** Parameter zName is the name of a table that is about to be altered
+** (either with ALTER TABLE ... RENAME TO or ALTER TABLE ... ADD COLUMN).
+** If the table is a system table, this function leaves an error message
+** in pParse->zErr (system tables may not be altered) and returns non-zero.
+**
+** Or, if zName is not a system table, zero is returned.
+*/
+static int isSystemTable(Parse *pParse, const char *zName){
+  if( sqlite3Strlen30(zName)>6 && 0==sqlite3StrNICmp(zName, "sqlite_", 7) ){
+    sqlite3ErrorMsg(pParse, "table %s may not be altered", zName);
+    return 1;
+  }
+  return 0;
+}
+
+/*
+** Generate code to implement the "ALTER TABLE xxx RENAME TO yyy" 
+** command. 
+*/
+void sqlite3AlterRenameTable(
+  Parse *pParse,            /* Parser context. */
+  SrcList *pSrc,            /* The table to rename. */
+  Token *pName              /* The new table name. */
+){
+  int iDb;                  /* Database that contains the table */
+  char *zDb;                /* Name of database iDb */
+  Table *pTab;              /* Table being renamed */
+  char *zName = 0;          /* NULL-terminated version of pName */ 
+  sqlite3 *db = pParse->db; /* Database connection */
+  int nTabName;             /* Number of UTF-8 characters in zTabName */
+  const char *zTabName;     /* Original name of the table */
+  Vdbe *v;
+#ifndef SQLITE_OMIT_TRIGGER
+  char *zWhere = 0;         /* Where clause to locate temp triggers */
+#endif
+  VTable *pVTab = 0;        /* Non-zero if this is a v-tab with an xRename() */
+  int savedDbFlags;         /* Saved value of db->flags */
+
+  savedDbFlags = db->flags;  
+  if( NEVER(db->mallocFailed) ) goto exit_rename_table;
+  assert( pSrc->nSrc==1 );
+  assert( sqlite3BtreeHoldsAllMutexes(pParse->db) );
+
+  pTab = sqlite3LocateTable(pParse, 0, pSrc->a[0].zName, pSrc->a[0].zDatabase);
+  if( !pTab ) goto exit_rename_table;
+  iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
+  zDb = db->aDb[iDb].zName;
+  db->flags |= SQLITE_PreferBuiltin;
+
+  /* Get a NULL terminated version of the new table name. */
+  zName = sqlite3NameFromToken(db, pName);
+  if( !zName ) goto exit_rename_table;
+
+  /* Check that a table or index named 'zName' does not already exist
+  ** in database iDb. If so, this is an error.
+  */
+  if( sqlite3FindTable(db, zName, zDb) || sqlite3FindIndex(db, zName, zDb) ){
+    sqlite3ErrorMsg(pParse, 
+        "there is already another table or index with this name: %s", zName);
+    goto exit_rename_table;
+  }
+
+  /* Make sure it is not a system table being altered, or a reserved name
+  ** that the table is being renamed to.
+  */
+  if( SQLITE_OK!=isSystemTable(pParse, pTab->zName) ){
+    goto exit_rename_table;
+  }
+  if( SQLITE_OK!=sqlite3CheckObjectName(pParse, zName) ){ goto
+    exit_rename_table;
+  }
+
+#ifndef SQLITE_OMIT_VIEW
+  if( pTab->pSelect ){
+    sqlite3ErrorMsg(pParse, "view %s may not be altered", pTab->zName);
+    goto exit_rename_table;
+  }
+#endif
+
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  /* Invoke the authorization callback. */
+  if( sqlite3AuthCheck(pParse, SQLITE_ALTER_TABLE, zDb, pTab->zName, 0) ){
+    goto exit_rename_table;
+  }
+#endif
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  if( sqlite3ViewGetColumnNames(pParse, pTab) ){
+    goto exit_rename_table;
+  }
+  if( IsVirtual(pTab) ){
+    pVTab = sqlite3GetVTable(db, pTab);
+    if( pVTab->pVtab->pModule->xRename==0 ){
+      pVTab = 0;
+    }
+  }
+#endif
+
+  /* Begin a transaction and code the VerifyCookie for database iDb. 
+  ** Then modify the schema cookie (since the ALTER TABLE modifies the
+  ** schema). Open a statement transaction if the table is a virtual
+  ** table.
+  */
+  v = sqlite3GetVdbe(pParse);
+  if( v==0 ){
+    goto exit_rename_table;
+  }
+  sqlite3BeginWriteOperation(pParse, pVTab!=0, iDb);
+  sqlite3ChangeCookie(pParse, iDb);
+
+  /* If this is a virtual table, invoke the xRename() function if
+  ** one is defined. The xRename() callback will modify the names
+  ** of any resources used by the v-table implementation (including other
+  ** SQLite tables) that are identified by the name of the virtual table.
+  */
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  if( pVTab ){
+    int i = ++pParse->nMem;
+    sqlite3VdbeAddOp4(v, OP_String8, 0, i, 0, zName, 0);
+    sqlite3VdbeAddOp4(v, OP_VRename, i, 0, 0,(const char*)pVTab, P4_VTAB);
+    sqlite3MayAbort(pParse);
+  }
+#endif
+
+  /* figure out how many UTF-8 characters are in zName */
+  zTabName = pTab->zName;
+  nTabName = sqlite3Utf8CharLen(zTabName, -1);
+
+#if !defined(SQLITE_OMIT_FOREIGN_KEY) && !defined(SQLITE_OMIT_TRIGGER)
+  if( db->flags&SQLITE_ForeignKeys ){
+    /* If foreign-key support is enabled, rewrite the CREATE TABLE 
+    ** statements corresponding to all child tables of foreign key constraints
+    ** for which the renamed table is the parent table.  */
+    if( (zWhere=whereForeignKeys(pParse, pTab))!=0 ){
+      sqlite3NestedParse(pParse, 
+          "UPDATE \"%w\".%s SET "
+              "sql = sqlite_rename_parent(sql, %Q, %Q) "
+              "WHERE %s;", zDb, SCHEMA_TABLE(iDb), zTabName, zName, zWhere);
+      sqlite3DbFree(db, zWhere);
+    }
+  }
+#endif
+
+  /* Modify the sqlite_master table to use the new table name. */
+  sqlite3NestedParse(pParse,
+      "UPDATE %Q.%s SET "
+#ifdef SQLITE_OMIT_TRIGGER
+          "sql = sqlite_rename_table(sql, %Q), "
+#else
+          "sql = CASE "
+            "WHEN type = 'trigger' THEN sqlite_rename_trigger(sql, %Q)"
+            "ELSE sqlite_rename_table(sql, %Q) END, "
+#endif
+          "tbl_name = %Q, "
+          "name = CASE "
+            "WHEN type='table' THEN %Q "
+            "WHEN name LIKE 'sqlite_autoindex%%' AND type='index' THEN "
+             "'sqlite_autoindex_' || %Q || substr(name,%d+18) "
+            "ELSE name END "
+      "WHERE tbl_name=%Q AND "
+          "(type='table' OR type='index' OR type='trigger');", 
+      zDb, SCHEMA_TABLE(iDb), zName, zName, zName, 
+#ifndef SQLITE_OMIT_TRIGGER
+      zName,
+#endif
+      zName, nTabName, zTabName
+  );
+
+#ifndef SQLITE_OMIT_AUTOINCREMENT
+  /* If the sqlite_sequence table exists in this database, then update 
+  ** it with the new table name.
+  */
+  if( sqlite3FindTable(db, "sqlite_sequence", zDb) ){
+    sqlite3NestedParse(pParse,
+        "UPDATE \"%w\".sqlite_sequence set name = %Q WHERE name = %Q",
+        zDb, zName, pTab->zName);
+  }
+#endif
+
+#ifndef SQLITE_OMIT_TRIGGER
+  /* If there are TEMP triggers on this table, modify the sqlite_temp_master
+  ** table. Don't do this if the table being ALTERed is itself located in
+  ** the temp database.
+  */
+  if( (zWhere=whereTempTriggers(pParse, pTab))!=0 ){
+    sqlite3NestedParse(pParse, 
+        "UPDATE sqlite_temp_master SET "
+            "sql = sqlite_rename_trigger(sql, %Q), "
+            "tbl_name = %Q "
+            "WHERE %s;", zName, zName, zWhere);
+    sqlite3DbFree(db, zWhere);
+  }
+#endif
+
+#if !defined(SQLITE_OMIT_FOREIGN_KEY) && !defined(SQLITE_OMIT_TRIGGER)
+  if( db->flags&SQLITE_ForeignKeys ){
+    FKey *p;
+    for(p=sqlite3FkReferences(pTab); p; p=p->pNextTo){
+      Table *pFrom = p->pFrom;
+      if( pFrom!=pTab ){
+        reloadTableSchema(pParse, p->pFrom, pFrom->zName);
+      }
+    }
+  }
+#endif
+
+  /* Drop and reload the internal table schema. */
+  reloadTableSchema(pParse, pTab, zName);
+
+exit_rename_table:
+  sqlite3SrcListDelete(db, pSrc);
+  sqlite3DbFree(db, zName);
+  db->flags = savedDbFlags;
+}
+
+
+/*
+** Generate code to make sure the file format number is at least minFormat.
+** The generated code will increase the file format number if necessary.
+*/
+void sqlite3MinimumFileFormat(Parse *pParse, int iDb, int minFormat){
+  Vdbe *v;
+  v = sqlite3GetVdbe(pParse);
+  /* The VDBE should have been allocated before this routine is called.
+  ** If that allocation failed, we would have quit before reaching this
+  ** point */
+  if( ALWAYS(v) ){
+    int r1 = sqlite3GetTempReg(pParse);
+    int r2 = sqlite3GetTempReg(pParse);
+    int j1;
+    sqlite3VdbeAddOp3(v, OP_ReadCookie, iDb, r1, BTREE_FILE_FORMAT);
+    sqlite3VdbeUsesBtree(v, iDb);
+    sqlite3VdbeAddOp2(v, OP_Integer, minFormat, r2);
+    j1 = sqlite3VdbeAddOp3(v, OP_Ge, r2, 0, r1);
+    sqlite3VdbeAddOp3(v, OP_SetCookie, iDb, BTREE_FILE_FORMAT, r2);
+    sqlite3VdbeJumpHere(v, j1);
+    sqlite3ReleaseTempReg(pParse, r1);
+    sqlite3ReleaseTempReg(pParse, r2);
+  }
+}
+
+/*
+** This function is called after an "ALTER TABLE ... ADD" statement
+** has been parsed. Argument pColDef contains the text of the new
+** column definition.
+**
+** The Table structure pParse->pNewTable was extended to include
+** the new column during parsing.
+*/
+void sqlite3AlterFinishAddColumn(Parse *pParse, Token *pColDef){
+  Table *pNew;              /* Copy of pParse->pNewTable */
+  Table *pTab;              /* Table being altered */
+  int iDb;                  /* Database number */
+  const char *zDb;          /* Database name */
+  const char *zTab;         /* Table name */
+  char *zCol;               /* Null-terminated column definition */
+  Column *pCol;             /* The new column */
+  Expr *pDflt;              /* Default value for the new column */
+  sqlite3 *db;              /* The database connection; */
+
+  db = pParse->db;
+  if( pParse->nErr || db->mallocFailed ) return;
+  pNew = pParse->pNewTable;
+  assert( pNew );
+
+  assert( sqlite3BtreeHoldsAllMutexes(db) );
+  iDb = sqlite3SchemaToIndex(db, pNew->pSchema);
+  zDb = db->aDb[iDb].zName;
+  zTab = &pNew->zName[16];  /* Skip the "sqlite_altertab_" prefix on the name */
+  pCol = &pNew->aCol[pNew->nCol-1];
+  pDflt = pCol->pDflt;
+  pTab = sqlite3FindTable(db, zTab, zDb);
+  assert( pTab );
+
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  /* Invoke the authorization callback. */
+  if( sqlite3AuthCheck(pParse, SQLITE_ALTER_TABLE, zDb, pTab->zName, 0) ){
+    return;
+  }
+#endif
+
+  /* If the default value for the new column was specified with a 
+  ** literal NULL, then set pDflt to 0. This simplifies checking
+  ** for an SQL NULL default below.
+  */
+  if( pDflt && pDflt->op==TK_NULL ){
+    pDflt = 0;
+  }
+
+  /* Check that the new column is not specified as PRIMARY KEY or UNIQUE.
+  ** If there is a NOT NULL constraint, then the default value for the
+  ** column must not be NULL.
+  */
+  if( pCol->isPrimKey ){
+    sqlite3ErrorMsg(pParse, "Cannot add a PRIMARY KEY column");
+    return;
+  }
+  if( pNew->pIndex ){
+    sqlite3ErrorMsg(pParse, "Cannot add a UNIQUE column");
+    return;
+  }
+  if( (db->flags&SQLITE_ForeignKeys) && pNew->pFKey && pDflt ){
+    sqlite3ErrorMsg(pParse, 
+        "Cannot add a REFERENCES column with non-NULL default value");
+    return;
+  }
+  if( pCol->notNull && !pDflt ){
+    sqlite3ErrorMsg(pParse, 
+        "Cannot add a NOT NULL column with default value NULL");
+    return;
+  }
+
+  /* Ensure the default expression is something that sqlite3ValueFromExpr()
+  ** can handle (i.e. not CURRENT_TIME etc.)
+  */
+  if( pDflt ){
+    sqlite3_value *pVal;
+    if( sqlite3ValueFromExpr(db, pDflt, SQLITE_UTF8, SQLITE_AFF_NONE, &pVal) ){
+      db->mallocFailed = 1;
+      return;
+    }
+    if( !pVal ){
+      sqlite3ErrorMsg(pParse, "Cannot add a column with non-constant default");
+      return;
+    }
+    sqlite3ValueFree(pVal);
+  }
+
+  /* Modify the CREATE TABLE statement. */
+  zCol = sqlite3DbStrNDup(db, (char*)pColDef->z, pColDef->n);
+  if( zCol ){
+    char *zEnd = &zCol[pColDef->n-1];
+    int savedDbFlags = db->flags;
+    while( zEnd>zCol && (*zEnd==';' || sqlite3Isspace(*zEnd)) ){
+      *zEnd-- = '\0';
+    }
+    db->flags |= SQLITE_PreferBuiltin;
+    sqlite3NestedParse(pParse, 
+        "UPDATE \"%w\".%s SET "
+          "sql = substr(sql,1,%d) || ', ' || %Q || substr(sql,%d) "
+        "WHERE type = 'table' AND name = %Q", 
+      zDb, SCHEMA_TABLE(iDb), pNew->addColOffset, zCol, pNew->addColOffset+1,
+      zTab
+    );
+    sqlite3DbFree(db, zCol);
+    db->flags = savedDbFlags;
+  }
+
+  /* If the default value of the new column is NULL, then set the file
+  ** format to 2. If the default value of the new column is not NULL,
+  ** the file format becomes 3.
+  */
+  sqlite3MinimumFileFormat(pParse, iDb, pDflt ? 3 : 2);
+
+  /* Reload the schema of the modified table. */
+  reloadTableSchema(pParse, pTab, pTab->zName);
+}
+
+/*
+** This function is called by the parser after the table-name in
+** an "ALTER TABLE <table-name> ADD" statement is parsed. Argument 
+** pSrc is the full-name of the table being altered.
+**
+** This routine makes a (partial) copy of the Table structure
+** for the table being altered and sets Parse.pNewTable to point
+** to it. Routines called by the parser as the column definition
+** is parsed (i.e. sqlite3AddColumn()) add the new Column data to 
+** the copy. The copy of the Table structure is deleted by tokenize.c 
+** after parsing is finished.
+**
+** Routine sqlite3AlterFinishAddColumn() will be called to complete
+** coding the "ALTER TABLE ... ADD" statement.
+*/
+void sqlite3AlterBeginAddColumn(Parse *pParse, SrcList *pSrc){
+  Table *pNew;
+  Table *pTab;
+  Vdbe *v;
+  int iDb;
+  int i;
+  int nAlloc;
+  sqlite3 *db = pParse->db;
+
+  /* Look up the table being altered. */
+  assert( pParse->pNewTable==0 );
+  assert( sqlite3BtreeHoldsAllMutexes(db) );
+  if( db->mallocFailed ) goto exit_begin_add_column;
+  pTab = sqlite3LocateTable(pParse, 0, pSrc->a[0].zName, pSrc->a[0].zDatabase);
+  if( !pTab ) goto exit_begin_add_column;
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  if( IsVirtual(pTab) ){
+    sqlite3ErrorMsg(pParse, "virtual tables may not be altered");
+    goto exit_begin_add_column;
+  }
+#endif
+
+  /* Make sure this is not an attempt to ALTER a view. */
+  if( pTab->pSelect ){
+    sqlite3ErrorMsg(pParse, "Cannot add a column to a view");
+    goto exit_begin_add_column;
+  }
+  if( SQLITE_OK!=isSystemTable(pParse, pTab->zName) ){
+    goto exit_begin_add_column;
+  }
+
+  assert( pTab->addColOffset>0 );
+  iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+
+  /* Put a copy of the Table struct in Parse.pNewTable for the
+  ** sqlite3AddColumn() function and friends to modify.  But modify
+  ** the name by adding an "sqlite_altertab_" prefix.  By adding this
+  ** prefix, we insure that the name will not collide with an existing
+  ** table because user table are not allowed to have the "sqlite_"
+  ** prefix on their name.
+  */
+  pNew = (Table*)sqlite3DbMallocZero(db, sizeof(Table));
+  if( !pNew ) goto exit_begin_add_column;
+  pParse->pNewTable = pNew;
+  pNew->nRef = 1;
+  pNew->nCol = pTab->nCol;
+  assert( pNew->nCol>0 );
+  nAlloc = (((pNew->nCol-1)/8)*8)+8;
+  assert( nAlloc>=pNew->nCol && nAlloc%8==0 && nAlloc-pNew->nCol<8 );
+  pNew->aCol = (Column*)sqlite3DbMallocZero(db, sizeof(Column)*nAlloc);
+  pNew->zName = sqlite3MPrintf(db, "sqlite_altertab_%s", pTab->zName);
+  if( !pNew->aCol || !pNew->zName ){
+    db->mallocFailed = 1;
+    goto exit_begin_add_column;
+  }
+  memcpy(pNew->aCol, pTab->aCol, sizeof(Column)*pNew->nCol);
+  for(i=0; i<pNew->nCol; i++){
+    Column *pCol = &pNew->aCol[i];
+    pCol->zName = sqlite3DbStrDup(db, pCol->zName);
+    pCol->zColl = 0;
+    pCol->zType = 0;
+    pCol->pDflt = 0;
+    pCol->zDflt = 0;
+  }
+  pNew->pSchema = db->aDb[iDb].pSchema;
+  pNew->addColOffset = pTab->addColOffset;
+  pNew->nRef = 1;
+
+  /* Begin a transaction and increment the schema cookie.  */
+  sqlite3BeginWriteOperation(pParse, 0, iDb);
+  v = sqlite3GetVdbe(pParse);
+  if( !v ) goto exit_begin_add_column;
+  sqlite3ChangeCookie(pParse, iDb);
+
+exit_begin_add_column:
+  sqlite3SrcListDelete(db, pSrc);
+  return;
+}
+#endif  /* SQLITE_ALTER_TABLE */
diff --git a/src/analyze.c b/src/analyze.c
new file mode 100644
index 0000000..b6a987a
--- /dev/null
+++ b/src/analyze.c
@@ -0,0 +1,1120 @@
+/*
+** 2005 July 8
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains code associated with the ANALYZE command.
+**
+** The ANALYZE command gather statistics about the content of tables
+** and indices.  These statistics are made available to the query planner
+** to help it make better decisions about how to perform queries.
+**
+** The following system tables are or have been supported:
+**
+**    CREATE TABLE sqlite_stat1(tbl, idx, stat);
+**    CREATE TABLE sqlite_stat2(tbl, idx, sampleno, sample);
+**    CREATE TABLE sqlite_stat3(tbl, idx, nEq, nLt, nDLt, sample);
+**
+** Additional tables might be added in future releases of SQLite.
+** The sqlite_stat2 table is not created or used unless the SQLite version
+** is between 3.6.18 and 3.7.8, inclusive, and unless SQLite is compiled
+** with SQLITE_ENABLE_STAT2.  The sqlite_stat2 table is deprecated.
+** The sqlite_stat2 table is superceded by sqlite_stat3, which is only
+** created and used by SQLite versions 3.7.9 and later and with
+** SQLITE_ENABLE_STAT3 defined.  The fucntionality of sqlite_stat3
+** is a superset of sqlite_stat2.  
+**
+** Format of sqlite_stat1:
+**
+** There is normally one row per index, with the index identified by the
+** name in the idx column.  The tbl column is the name of the table to
+** which the index belongs.  In each such row, the stat column will be
+** a string consisting of a list of integers.  The first integer in this
+** list is the number of rows in the index and in the table.  The second
+** integer is the average number of rows in the index that have the same
+** value in the first column of the index.  The third integer is the average
+** number of rows in the index that have the same value for the first two
+** columns.  The N-th integer (for N>1) is the average number of rows in 
+** the index which have the same value for the first N-1 columns.  For
+** a K-column index, there will be K+1 integers in the stat column.  If
+** the index is unique, then the last integer will be 1.
+**
+** The list of integers in the stat column can optionally be followed
+** by the keyword "unordered".  The "unordered" keyword, if it is present,
+** must be separated from the last integer by a single space.  If the
+** "unordered" keyword is present, then the query planner assumes that
+** the index is unordered and will not use the index for a range query.
+** 
+** If the sqlite_stat1.idx column is NULL, then the sqlite_stat1.stat
+** column contains a single integer which is the (estimated) number of
+** rows in the table identified by sqlite_stat1.tbl.
+**
+** Format of sqlite_stat2:
+**
+** The sqlite_stat2 is only created and is only used if SQLite is compiled
+** with SQLITE_ENABLE_STAT2 and if the SQLite version number is between
+** 3.6.18 and 3.7.8.  The "stat2" table contains additional information
+** about the distribution of keys within an index.  The index is identified by
+** the "idx" column and the "tbl" column is the name of the table to which
+** the index belongs.  There are usually 10 rows in the sqlite_stat2
+** table for each index.
+**
+** The sqlite_stat2 entries for an index that have sampleno between 0 and 9
+** inclusive are samples of the left-most key value in the index taken at
+** evenly spaced points along the index.  Let the number of samples be S
+** (10 in the standard build) and let C be the number of rows in the index.
+** Then the sampled rows are given by:
+**
+**     rownumber = (i*C*2 + C)/(S*2)
+**
+** For i between 0 and S-1.  Conceptually, the index space is divided into
+** S uniform buckets and the samples are the middle row from each bucket.
+**
+** The format for sqlite_stat2 is recorded here for legacy reference.  This
+** version of SQLite does not support sqlite_stat2.  It neither reads nor
+** writes the sqlite_stat2 table.  This version of SQLite only supports
+** sqlite_stat3.
+**
+** Format for sqlite_stat3:
+**
+** The sqlite_stat3 is an enhancement to sqlite_stat2.  A new name is
+** used to avoid compatibility problems.  
+**
+** The format of the sqlite_stat3 table is similar to the format of
+** the sqlite_stat2 table.  There are multiple entries for each index.
+** The idx column names the index and the tbl column is the table of the
+** index.  If the idx and tbl columns are the same, then the sample is
+** of the INTEGER PRIMARY KEY.  The sample column is a value taken from
+** the left-most column of the index.  The nEq column is the approximate
+** number of entires in the index whose left-most column exactly matches
+** the sample.  nLt is the approximate number of entires whose left-most
+** column is less than the sample.  The nDLt column is the approximate
+** number of distinct left-most entries in the index that are less than
+** the sample.
+**
+** Future versions of SQLite might change to store a string containing
+** multiple integers values in the nDLt column of sqlite_stat3.  The first
+** integer will be the number of prior index entires that are distinct in
+** the left-most column.  The second integer will be the number of prior index
+** entries that are distinct in the first two columns.  The third integer
+** will be the number of prior index entries that are distinct in the first
+** three columns.  And so forth.  With that extension, the nDLt field is
+** similar in function to the sqlite_stat1.stat field.
+**
+** There can be an arbitrary number of sqlite_stat3 entries per index.
+** The ANALYZE command will typically generate sqlite_stat3 tables
+** that contain between 10 and 40 samples which are distributed across
+** the key space, though not uniformly, and which include samples with
+** largest possible nEq values.
+*/
+#ifndef SQLITE_OMIT_ANALYZE
+#include "sqliteInt.h"
+
+/*
+** This routine generates code that opens the sqlite_stat1 table for
+** writing with cursor iStatCur. If the library was built with the
+** SQLITE_ENABLE_STAT3 macro defined, then the sqlite_stat3 table is
+** opened for writing using cursor (iStatCur+1)
+**
+** If the sqlite_stat1 tables does not previously exist, it is created.
+** Similarly, if the sqlite_stat3 table does not exist and the library
+** is compiled with SQLITE_ENABLE_STAT3 defined, it is created. 
+**
+** Argument zWhere may be a pointer to a buffer containing a table name,
+** or it may be a NULL pointer. If it is not NULL, then all entries in
+** the sqlite_stat1 and (if applicable) sqlite_stat3 tables associated
+** with the named table are deleted. If zWhere==0, then code is generated
+** to delete all stat table entries.
+*/
+static void openStatTable(
+  Parse *pParse,          /* Parsing context */
+  int iDb,                /* The database we are looking in */
+  int iStatCur,           /* Open the sqlite_stat1 table on this cursor */
+  const char *zWhere,     /* Delete entries for this table or index */
+  const char *zWhereType  /* Either "tbl" or "idx" */
+){
+  static const struct {
+    const char *zName;
+    const char *zCols;
+  } aTable[] = {
+    { "sqlite_stat1", "tbl,idx,stat" },
+#ifdef SQLITE_ENABLE_STAT3
+    { "sqlite_stat3", "tbl,idx,neq,nlt,ndlt,sample" },
+#endif
+  };
+
+  int aRoot[] = {0, 0};
+  u8 aCreateTbl[] = {0, 0};
+
+  int i;
+  sqlite3 *db = pParse->db;
+  Db *pDb;
+  Vdbe *v = sqlite3GetVdbe(pParse);
+  if( v==0 ) return;
+  assert( sqlite3BtreeHoldsAllMutexes(db) );
+  assert( sqlite3VdbeDb(v)==db );
+  pDb = &db->aDb[iDb];
+
+  /* Create new statistic tables if they do not exist, or clear them
+  ** if they do already exist.
+  */
+  for(i=0; i<ArraySize(aTable); i++){
+    const char *zTab = aTable[i].zName;
+    Table *pStat;
+    if( (pStat = sqlite3FindTable(db, zTab, pDb->zName))==0 ){
+      /* The sqlite_stat[12] table does not exist. Create it. Note that a 
+      ** side-effect of the CREATE TABLE statement is to leave the rootpage 
+      ** of the new table in register pParse->regRoot. This is important 
+      ** because the OpenWrite opcode below will be needing it. */
+      sqlite3NestedParse(pParse,
+          "CREATE TABLE %Q.%s(%s)", pDb->zName, zTab, aTable[i].zCols
+      );
+      aRoot[i] = pParse->regRoot;
+      aCreateTbl[i] = 1;
+    }else{
+      /* The table already exists. If zWhere is not NULL, delete all entries 
+      ** associated with the table zWhere. If zWhere is NULL, delete the
+      ** entire contents of the table. */
+      aRoot[i] = pStat->tnum;
+      sqlite3TableLock(pParse, iDb, aRoot[i], 1, zTab);
+      if( zWhere ){
+        sqlite3NestedParse(pParse,
+           "DELETE FROM %Q.%s WHERE %s=%Q", pDb->zName, zTab, zWhereType, zWhere
+        );
+      }else{
+        /* The sqlite_stat[12] table already exists.  Delete all rows. */
+        sqlite3VdbeAddOp2(v, OP_Clear, aRoot[i], iDb);
+      }
+    }
+  }
+
+  /* Open the sqlite_stat[13] tables for writing. */
+  for(i=0; i<ArraySize(aTable); i++){
+    sqlite3VdbeAddOp3(v, OP_OpenWrite, iStatCur+i, aRoot[i], iDb);
+    sqlite3VdbeChangeP4(v, -1, (char *)3, P4_INT32);
+    sqlite3VdbeChangeP5(v, aCreateTbl[i]);
+  }
+}
+
+/*
+** Recommended number of samples for sqlite_stat3
+*/
+#ifndef SQLITE_STAT3_SAMPLES
+# define SQLITE_STAT3_SAMPLES 24
+#endif
+
+/*
+** Three SQL functions - stat3_init(), stat3_push(), and stat3_pop() -
+** share an instance of the following structure to hold their state
+** information.
+*/
+typedef struct Stat3Accum Stat3Accum;
+struct Stat3Accum {
+  tRowcnt nRow;             /* Number of rows in the entire table */
+  tRowcnt nPSample;         /* How often to do a periodic sample */
+  int iMin;                 /* Index of entry with minimum nEq and hash */
+  int mxSample;             /* Maximum number of samples to accumulate */
+  int nSample;              /* Current number of samples */
+  u32 iPrn;                 /* Pseudo-random number used for sampling */
+  struct Stat3Sample {
+    i64 iRowid;                /* Rowid in main table of the key */
+    tRowcnt nEq;               /* sqlite_stat3.nEq */
+    tRowcnt nLt;               /* sqlite_stat3.nLt */
+    tRowcnt nDLt;              /* sqlite_stat3.nDLt */
+    u8 isPSample;              /* True if a periodic sample */
+    u32 iHash;                 /* Tiebreaker hash */
+  } *a;                     /* An array of samples */
+};
+
+#ifdef SQLITE_ENABLE_STAT3
+/*
+** Implementation of the stat3_init(C,S) SQL function.  The two parameters
+** are the number of rows in the table or index (C) and the number of samples
+** to accumulate (S).
+**
+** This routine allocates the Stat3Accum object.
+**
+** The return value is the Stat3Accum object (P).
+*/
+static void stat3Init(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  Stat3Accum *p;
+  tRowcnt nRow;
+  int mxSample;
+  int n;
+
+  UNUSED_PARAMETER(argc);
+  nRow = (tRowcnt)sqlite3_value_int64(argv[0]);
+  mxSample = sqlite3_value_int(argv[1]);
+  n = sizeof(*p) + sizeof(p->a[0])*mxSample;
+  p = sqlite3_malloc( n );
+  if( p==0 ){
+    sqlite3_result_error_nomem(context);
+    return;
+  }
+  memset(p, 0, n);
+  p->a = (struct Stat3Sample*)&p[1];
+  p->nRow = nRow;
+  p->mxSample = mxSample;
+  p->nPSample = p->nRow/(mxSample/3+1) + 1;
+  sqlite3_randomness(sizeof(p->iPrn), &p->iPrn);
+  sqlite3_result_blob(context, p, sizeof(p), sqlite3_free);
+}
+static const FuncDef stat3InitFuncdef = {
+  2,                /* nArg */
+  SQLITE_UTF8,      /* iPrefEnc */
+  0,                /* flags */
+  0,                /* pUserData */
+  0,                /* pNext */
+  stat3Init,        /* xFunc */
+  0,                /* xStep */
+  0,                /* xFinalize */
+  "stat3_init",     /* zName */
+  0,                /* pHash */
+  0                 /* pDestructor */
+};
+
+
+/*
+** Implementation of the stat3_push(nEq,nLt,nDLt,rowid,P) SQL function.  The
+** arguments describe a single key instance.  This routine makes the 
+** decision about whether or not to retain this key for the sqlite_stat3
+** table.
+**
+** The return value is NULL.
+*/
+static void stat3Push(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  Stat3Accum *p = (Stat3Accum*)sqlite3_value_blob(argv[4]);
+  tRowcnt nEq = sqlite3_value_int64(argv[0]);
+  tRowcnt nLt = sqlite3_value_int64(argv[1]);
+  tRowcnt nDLt = sqlite3_value_int64(argv[2]);
+  i64 rowid = sqlite3_value_int64(argv[3]);
+  u8 isPSample = 0;
+  u8 doInsert = 0;
+  int iMin = p->iMin;
+  struct Stat3Sample *pSample;
+  int i;
+  u32 h;
+
+  UNUSED_PARAMETER(context);
+  UNUSED_PARAMETER(argc);
+  if( nEq==0 ) return;
+  h = p->iPrn = p->iPrn*1103515245 + 12345;
+  if( (nLt/p->nPSample)!=((nEq+nLt)/p->nPSample) ){
+    doInsert = isPSample = 1;
+  }else if( p->nSample<p->mxSample ){
+    doInsert = 1;
+  }else{
+    if( nEq>p->a[iMin].nEq || (nEq==p->a[iMin].nEq && h>p->a[iMin].iHash) ){
+      doInsert = 1;
+    }
+  }
+  if( !doInsert ) return;
+  if( p->nSample==p->mxSample ){
+    assert( p->nSample - iMin - 1 >= 0 );
+    memmove(&p->a[iMin], &p->a[iMin+1], sizeof(p->a[0])*(p->nSample-iMin-1));
+    pSample = &p->a[p->nSample-1];
+  }else{
+    pSample = &p->a[p->nSample++];
+  }
+  pSample->iRowid = rowid;
+  pSample->nEq = nEq;
+  pSample->nLt = nLt;
+  pSample->nDLt = nDLt;
+  pSample->iHash = h;
+  pSample->isPSample = isPSample;
+
+  /* Find the new minimum */
+  if( p->nSample==p->mxSample ){
+    pSample = p->a;
+    i = 0;
+    while( pSample->isPSample ){
+      i++;
+      pSample++;
+      assert( i<p->nSample );
+    }
+    nEq = pSample->nEq;
+    h = pSample->iHash;
+    iMin = i;
+    for(i++, pSample++; i<p->nSample; i++, pSample++){
+      if( pSample->isPSample ) continue;
+      if( pSample->nEq<nEq
+       || (pSample->nEq==nEq && pSample->iHash<h)
+      ){
+        iMin = i;
+        nEq = pSample->nEq;
+        h = pSample->iHash;
+      }
+    }
+    p->iMin = iMin;
+  }
+}
+static const FuncDef stat3PushFuncdef = {
+  5,                /* nArg */
+  SQLITE_UTF8,      /* iPrefEnc */
+  0,                /* flags */
+  0,                /* pUserData */
+  0,                /* pNext */
+  stat3Push,        /* xFunc */
+  0,                /* xStep */
+  0,                /* xFinalize */
+  "stat3_push",     /* zName */
+  0,                /* pHash */
+  0                 /* pDestructor */
+};
+
+/*
+** Implementation of the stat3_get(P,N,...) SQL function.  This routine is
+** used to query the results.  Content is returned for the Nth sqlite_stat3
+** row where N is between 0 and S-1 and S is the number of samples.  The
+** value returned depends on the number of arguments.
+**
+**   argc==2    result:  rowid
+**   argc==3    result:  nEq
+**   argc==4    result:  nLt
+**   argc==5    result:  nDLt
+*/
+static void stat3Get(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  int n = sqlite3_value_int(argv[1]);
+  Stat3Accum *p = (Stat3Accum*)sqlite3_value_blob(argv[0]);
+
+  assert( p!=0 );
+  if( p->nSample<=n ) return;
+  switch( argc ){
+    case 2:  sqlite3_result_int64(context, p->a[n].iRowid); break;
+    case 3:  sqlite3_result_int64(context, p->a[n].nEq);    break;
+    case 4:  sqlite3_result_int64(context, p->a[n].nLt);    break;
+    default: sqlite3_result_int64(context, p->a[n].nDLt);   break;
+  }
+}
+static const FuncDef stat3GetFuncdef = {
+  -1,               /* nArg */
+  SQLITE_UTF8,      /* iPrefEnc */
+  0,                /* flags */
+  0,                /* pUserData */
+  0,                /* pNext */
+  stat3Get,         /* xFunc */
+  0,                /* xStep */
+  0,                /* xFinalize */
+  "stat3_get",     /* zName */
+  0,                /* pHash */
+  0                 /* pDestructor */
+};
+#endif /* SQLITE_ENABLE_STAT3 */
+
+
+
+
+/*
+** Generate code to do an analysis of all indices associated with
+** a single table.
+*/
+static void analyzeOneTable(
+  Parse *pParse,   /* Parser context */
+  Table *pTab,     /* Table whose indices are to be analyzed */
+  Index *pOnlyIdx, /* If not NULL, only analyze this one index */
+  int iStatCur,    /* Index of VdbeCursor that writes the sqlite_stat1 table */
+  int iMem         /* Available memory locations begin here */
+){
+  sqlite3 *db = pParse->db;    /* Database handle */
+  Index *pIdx;                 /* An index to being analyzed */
+  int iIdxCur;                 /* Cursor open on index being analyzed */
+  Vdbe *v;                     /* The virtual machine being built up */
+  int i;                       /* Loop counter */
+  int topOfLoop;               /* The top of the loop */
+  int endOfLoop;               /* The end of the loop */
+  int jZeroRows = -1;          /* Jump from here if number of rows is zero */
+  int iDb;                     /* Index of database containing pTab */
+  int regTabname = iMem++;     /* Register containing table name */
+  int regIdxname = iMem++;     /* Register containing index name */
+  int regStat1 = iMem++;       /* The stat column of sqlite_stat1 */
+#ifdef SQLITE_ENABLE_STAT3
+  int regNumEq = regStat1;     /* Number of instances.  Same as regStat1 */
+  int regNumLt = iMem++;       /* Number of keys less than regSample */
+  int regNumDLt = iMem++;      /* Number of distinct keys less than regSample */
+  int regSample = iMem++;      /* The next sample value */
+  int regRowid = regSample;    /* Rowid of a sample */
+  int regAccum = iMem++;       /* Register to hold Stat3Accum object */
+  int regLoop = iMem++;        /* Loop counter */
+  int regCount = iMem++;       /* Number of rows in the table or index */
+  int regTemp1 = iMem++;       /* Intermediate register */
+  int regTemp2 = iMem++;       /* Intermediate register */
+  int once = 1;                /* One-time initialization */
+  int shortJump = 0;           /* Instruction address */
+  int iTabCur = pParse->nTab++; /* Table cursor */
+#endif
+  int regCol = iMem++;         /* Content of a column in analyzed table */
+  int regRec = iMem++;         /* Register holding completed record */
+  int regTemp = iMem++;        /* Temporary use register */
+  int regNewRowid = iMem++;    /* Rowid for the inserted record */
+
+
+  v = sqlite3GetVdbe(pParse);
+  if( v==0 || NEVER(pTab==0) ){
+    return;
+  }
+  if( pTab->tnum==0 ){
+    /* Do not gather statistics on views or virtual tables */
+    return;
+  }
+  if( memcmp(pTab->zName, "sqlite_", 7)==0 ){
+    /* Do not gather statistics on system tables */
+    return;
+  }
+  assert( sqlite3BtreeHoldsAllMutexes(db) );
+  iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+  assert( iDb>=0 );
+  assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  if( sqlite3AuthCheck(pParse, SQLITE_ANALYZE, pTab->zName, 0,
+      db->aDb[iDb].zName ) ){
+    return;
+  }
+#endif
+
+  /* Establish a read-lock on the table at the shared-cache level. */
+  sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);
+
+  iIdxCur = pParse->nTab++;
+  sqlite3VdbeAddOp4(v, OP_String8, 0, regTabname, 0, pTab->zName, 0);
+  for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+    int nCol;
+    KeyInfo *pKey;
+    int addrIfNot = 0;           /* address of OP_IfNot */
+    int *aChngAddr;              /* Array of jump instruction addresses */
+
+    if( pOnlyIdx && pOnlyIdx!=pIdx ) continue;
+    VdbeNoopComment((v, "Begin analysis of %s", pIdx->zName));
+    nCol = pIdx->nColumn;
+    aChngAddr = sqlite3DbMallocRaw(db, sizeof(int)*nCol);
+    if( aChngAddr==0 ) continue;
+    pKey = sqlite3IndexKeyinfo(pParse, pIdx);
+    if( iMem+1+(nCol*2)>pParse->nMem ){
+      pParse->nMem = iMem+1+(nCol*2);
+    }
+
+    /* Open a cursor to the index to be analyzed. */
+    assert( iDb==sqlite3SchemaToIndex(db, pIdx->pSchema) );
+    sqlite3VdbeAddOp4(v, OP_OpenRead, iIdxCur, pIdx->tnum, iDb,
+        (char *)pKey, P4_KEYINFO_HANDOFF);
+    VdbeComment((v, "%s", pIdx->zName));
+
+    /* Populate the register containing the index name. */
+    sqlite3VdbeAddOp4(v, OP_String8, 0, regIdxname, 0, pIdx->zName, 0);
+
+#ifdef SQLITE_ENABLE_STAT3
+    if( once ){
+      once = 0;
+      sqlite3OpenTable(pParse, iTabCur, iDb, pTab, OP_OpenRead);
+    }
+    sqlite3VdbeAddOp2(v, OP_Count, iIdxCur, regCount);
+    sqlite3VdbeAddOp2(v, OP_Integer, SQLITE_STAT3_SAMPLES, regTemp1);
+    sqlite3VdbeAddOp2(v, OP_Integer, 0, regNumEq);
+    sqlite3VdbeAddOp2(v, OP_Integer, 0, regNumLt);
+    sqlite3VdbeAddOp2(v, OP_Integer, -1, regNumDLt);
+    sqlite3VdbeAddOp4(v, OP_Function, 1, regCount, regAccum,
+                      (char*)&stat3InitFuncdef, P4_FUNCDEF);
+    sqlite3VdbeChangeP5(v, 2);
+#endif /* SQLITE_ENABLE_STAT3 */
+
+    /* The block of memory cells initialized here is used as follows.
+    **
+    **    iMem:                
+    **        The total number of rows in the table.
+    **
+    **    iMem+1 .. iMem+nCol: 
+    **        Number of distinct entries in index considering the 
+    **        left-most N columns only, where N is between 1 and nCol, 
+    **        inclusive.
+    **
+    **    iMem+nCol+1 .. Mem+2*nCol:  
+    **        Previous value of indexed columns, from left to right.
+    **
+    ** Cells iMem through iMem+nCol are initialized to 0. The others are 
+    ** initialized to contain an SQL NULL.
+    */
+    for(i=0; i<=nCol; i++){
+      sqlite3VdbeAddOp2(v, OP_Integer, 0, iMem+i);
+    }
+    for(i=0; i<nCol; i++){
+      sqlite3VdbeAddOp2(v, OP_Null, 0, iMem+nCol+i+1);
+    }
+
+    /* Start the analysis loop. This loop runs through all the entries in
+    ** the index b-tree.  */
+    endOfLoop = sqlite3VdbeMakeLabel(v);
+    sqlite3VdbeAddOp2(v, OP_Rewind, iIdxCur, endOfLoop);
+    topOfLoop = sqlite3VdbeCurrentAddr(v);
+    sqlite3VdbeAddOp2(v, OP_AddImm, iMem, 1);  /* Increment row counter */
+
+    for(i=0; i<nCol; i++){
+      CollSeq *pColl;
+      sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, i, regCol);
+      if( i==0 ){
+        /* Always record the very first row */
+        addrIfNot = sqlite3VdbeAddOp1(v, OP_IfNot, iMem+1);
+      }
+      assert( pIdx->azColl!=0 );
+      assert( pIdx->azColl[i]!=0 );
+      pColl = sqlite3LocateCollSeq(pParse, pIdx->azColl[i]);
+      aChngAddr[i] = sqlite3VdbeAddOp4(v, OP_Ne, regCol, 0, iMem+nCol+i+1,
+                                      (char*)pColl, P4_COLLSEQ);
+      sqlite3VdbeChangeP5(v, SQLITE_NULLEQ);
+      VdbeComment((v, "jump if column %d changed", i));
+#ifdef SQLITE_ENABLE_STAT3
+      if( i==0 ){
+        sqlite3VdbeAddOp2(v, OP_AddImm, regNumEq, 1);
+        VdbeComment((v, "incr repeat count"));
+      }
+#endif
+    }
+    sqlite3VdbeAddOp2(v, OP_Goto, 0, endOfLoop);
+    for(i=0; i<nCol; i++){
+      sqlite3VdbeJumpHere(v, aChngAddr[i]);  /* Set jump dest for the OP_Ne */
+      if( i==0 ){
+        sqlite3VdbeJumpHere(v, addrIfNot);   /* Jump dest for OP_IfNot */
+#ifdef SQLITE_ENABLE_STAT3
+        sqlite3VdbeAddOp4(v, OP_Function, 1, regNumEq, regTemp2,
+                          (char*)&stat3PushFuncdef, P4_FUNCDEF);
+        sqlite3VdbeChangeP5(v, 5);
+        sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, pIdx->nColumn, regRowid);
+        sqlite3VdbeAddOp3(v, OP_Add, regNumEq, regNumLt, regNumLt);
+        sqlite3VdbeAddOp2(v, OP_AddImm, regNumDLt, 1);
+        sqlite3VdbeAddOp2(v, OP_Integer, 1, regNumEq);
+#endif        
+      }
+      sqlite3VdbeAddOp2(v, OP_AddImm, iMem+i+1, 1);
+      sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, i, iMem+nCol+i+1);
+    }
+    sqlite3DbFree(db, aChngAddr);
+
+    /* Always jump here after updating the iMem+1...iMem+1+nCol counters */
+    sqlite3VdbeResolveLabel(v, endOfLoop);
+
+    sqlite3VdbeAddOp2(v, OP_Next, iIdxCur, topOfLoop);
+    sqlite3VdbeAddOp1(v, OP_Close, iIdxCur);
+#ifdef SQLITE_ENABLE_STAT3
+    sqlite3VdbeAddOp4(v, OP_Function, 1, regNumEq, regTemp2,
+                      (char*)&stat3PushFuncdef, P4_FUNCDEF);
+    sqlite3VdbeChangeP5(v, 5);
+    sqlite3VdbeAddOp2(v, OP_Integer, -1, regLoop);
+    shortJump = 
+    sqlite3VdbeAddOp2(v, OP_AddImm, regLoop, 1);
+    sqlite3VdbeAddOp4(v, OP_Function, 1, regAccum, regTemp1,
+                      (char*)&stat3GetFuncdef, P4_FUNCDEF);
+    sqlite3VdbeChangeP5(v, 2);
+    sqlite3VdbeAddOp1(v, OP_IsNull, regTemp1);
+    sqlite3VdbeAddOp3(v, OP_NotExists, iTabCur, shortJump, regTemp1);
+    sqlite3VdbeAddOp3(v, OP_Column, iTabCur, pIdx->aiColumn[0], regSample);
+    sqlite3ColumnDefault(v, pTab, pIdx->aiColumn[0], regSample);
+    sqlite3VdbeAddOp4(v, OP_Function, 1, regAccum, regNumEq,
+                      (char*)&stat3GetFuncdef, P4_FUNCDEF);
+    sqlite3VdbeChangeP5(v, 3);
+    sqlite3VdbeAddOp4(v, OP_Function, 1, regAccum, regNumLt,
+                      (char*)&stat3GetFuncdef, P4_FUNCDEF);
+    sqlite3VdbeChangeP5(v, 4);
+    sqlite3VdbeAddOp4(v, OP_Function, 1, regAccum, regNumDLt,
+                      (char*)&stat3GetFuncdef, P4_FUNCDEF);
+    sqlite3VdbeChangeP5(v, 5);
+    sqlite3VdbeAddOp4(v, OP_MakeRecord, regTabname, 6, regRec, "bbbbbb", 0);
+    sqlite3VdbeAddOp2(v, OP_NewRowid, iStatCur+1, regNewRowid);
+    sqlite3VdbeAddOp3(v, OP_Insert, iStatCur+1, regRec, regNewRowid);
+    sqlite3VdbeAddOp2(v, OP_Goto, 0, shortJump);
+    sqlite3VdbeJumpHere(v, shortJump+2);
+#endif        
+
+    /* Store the results in sqlite_stat1.
+    **
+    ** The result is a single row of the sqlite_stat1 table.  The first
+    ** two columns are the names of the table and index.  The third column
+    ** is a string composed of a list of integer statistics about the
+    ** index.  The first integer in the list is the total number of entries
+    ** in the index.  There is one additional integer in the list for each
+    ** column of the table.  This additional integer is a guess of how many
+    ** rows of the table the index will select.  If D is the count of distinct
+    ** values and K is the total number of rows, then the integer is computed
+    ** as:
+    **
+    **        I = (K+D-1)/D
+    **
+    ** If K==0 then no entry is made into the sqlite_stat1 table.  
+    ** If K>0 then it is always the case the D>0 so division by zero
+    ** is never possible.
+    */
+    sqlite3VdbeAddOp2(v, OP_SCopy, iMem, regStat1);
+    if( jZeroRows<0 ){
+      jZeroRows = sqlite3VdbeAddOp1(v, OP_IfNot, iMem);
+    }
+    for(i=0; i<nCol; i++){
+      sqlite3VdbeAddOp4(v, OP_String8, 0, regTemp, 0, " ", 0);
+      sqlite3VdbeAddOp3(v, OP_Concat, regTemp, regStat1, regStat1);
+      sqlite3VdbeAddOp3(v, OP_Add, iMem, iMem+i+1, regTemp);
+      sqlite3VdbeAddOp2(v, OP_AddImm, regTemp, -1);
+      sqlite3VdbeAddOp3(v, OP_Divide, iMem+i+1, regTemp, regTemp);
+      sqlite3VdbeAddOp1(v, OP_ToInt, regTemp);
+      sqlite3VdbeAddOp3(v, OP_Concat, regTemp, regStat1, regStat1);
+    }
+    sqlite3VdbeAddOp4(v, OP_MakeRecord, regTabname, 3, regRec, "aaa", 0);
+    sqlite3VdbeAddOp2(v, OP_NewRowid, iStatCur, regNewRowid);
+    sqlite3VdbeAddOp3(v, OP_Insert, iStatCur, regRec, regNewRowid);
+    sqlite3VdbeChangeP5(v, OPFLAG_APPEND);
+  }
+
+  /* If the table has no indices, create a single sqlite_stat1 entry
+  ** containing NULL as the index name and the row count as the content.
+  */
+  if( pTab->pIndex==0 ){
+    sqlite3VdbeAddOp3(v, OP_OpenRead, iIdxCur, pTab->tnum, iDb);
+    VdbeComment((v, "%s", pTab->zName));
+    sqlite3VdbeAddOp2(v, OP_Count, iIdxCur, regStat1);
+    sqlite3VdbeAddOp1(v, OP_Close, iIdxCur);
+    jZeroRows = sqlite3VdbeAddOp1(v, OP_IfNot, regStat1);
+  }else{
+    sqlite3VdbeJumpHere(v, jZeroRows);
+    jZeroRows = sqlite3VdbeAddOp0(v, OP_Goto);
+  }
+  sqlite3VdbeAddOp2(v, OP_Null, 0, regIdxname);
+  sqlite3VdbeAddOp4(v, OP_MakeRecord, regTabname, 3, regRec, "aaa", 0);
+  sqlite3VdbeAddOp2(v, OP_NewRowid, iStatCur, regNewRowid);
+  sqlite3VdbeAddOp3(v, OP_Insert, iStatCur, regRec, regNewRowid);
+  sqlite3VdbeChangeP5(v, OPFLAG_APPEND);
+  if( pParse->nMem<regRec ) pParse->nMem = regRec;
+  sqlite3VdbeJumpHere(v, jZeroRows);
+}
+
+
+/*
+** Generate code that will cause the most recent index analysis to
+** be loaded into internal hash tables where is can be used.
+*/
+static void loadAnalysis(Parse *pParse, int iDb){
+  Vdbe *v = sqlite3GetVdbe(pParse);
+  if( v ){
+    sqlite3VdbeAddOp1(v, OP_LoadAnalysis, iDb);
+  }
+}
+
+/*
+** Generate code that will do an analysis of an entire database
+*/
+static void analyzeDatabase(Parse *pParse, int iDb){
+  sqlite3 *db = pParse->db;
+  Schema *pSchema = db->aDb[iDb].pSchema;    /* Schema of database iDb */
+  HashElem *k;
+  int iStatCur;
+  int iMem;
+
+  sqlite3BeginWriteOperation(pParse, 0, iDb);
+  iStatCur = pParse->nTab;
+  pParse->nTab += 3;
+  openStatTable(pParse, iDb, iStatCur, 0, 0);
+  iMem = pParse->nMem+1;
+  assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+  for(k=sqliteHashFirst(&pSchema->tblHash); k; k=sqliteHashNext(k)){
+    Table *pTab = (Table*)sqliteHashData(k);
+    analyzeOneTable(pParse, pTab, 0, iStatCur, iMem);
+  }
+  loadAnalysis(pParse, iDb);
+}
+
+/*
+** Generate code that will do an analysis of a single table in
+** a database.  If pOnlyIdx is not NULL then it is a single index
+** in pTab that should be analyzed.
+*/
+static void analyzeTable(Parse *pParse, Table *pTab, Index *pOnlyIdx){
+  int iDb;
+  int iStatCur;
+
+  assert( pTab!=0 );
+  assert( sqlite3BtreeHoldsAllMutexes(pParse->db) );
+  iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
+  sqlite3BeginWriteOperation(pParse, 0, iDb);
+  iStatCur = pParse->nTab;
+  pParse->nTab += 3;
+  if( pOnlyIdx ){
+    openStatTable(pParse, iDb, iStatCur, pOnlyIdx->zName, "idx");
+  }else{
+    openStatTable(pParse, iDb, iStatCur, pTab->zName, "tbl");
+  }
+  analyzeOneTable(pParse, pTab, pOnlyIdx, iStatCur, pParse->nMem+1);
+  loadAnalysis(pParse, iDb);
+}
+
+/*
+** Generate code for the ANALYZE command.  The parser calls this routine
+** when it recognizes an ANALYZE command.
+**
+**        ANALYZE                            -- 1
+**        ANALYZE  <database>                -- 2
+**        ANALYZE  ?<database>.?<tablename>  -- 3
+**
+** Form 1 causes all indices in all attached databases to be analyzed.
+** Form 2 analyzes all indices the single database named.
+** Form 3 analyzes all indices associated with the named table.
+*/
+void sqlite3Analyze(Parse *pParse, Token *pName1, Token *pName2){
+  sqlite3 *db = pParse->db;
+  int iDb;
+  int i;
+  char *z, *zDb;
+  Table *pTab;
+  Index *pIdx;
+  Token *pTableName;
+
+  /* Read the database schema. If an error occurs, leave an error message
+  ** and code in pParse and return NULL. */
+  assert( sqlite3BtreeHoldsAllMutexes(pParse->db) );
+  if( SQLITE_OK!=sqlite3ReadSchema(pParse) ){
+    return;
+  }
+
+  assert( pName2!=0 || pName1==0 );
+  if( pName1==0 ){
+    /* Form 1:  Analyze everything */
+    for(i=0; i<db->nDb; i++){
+      if( i==1 ) continue;  /* Do not analyze the TEMP database */
+      analyzeDatabase(pParse, i);
+    }
+  }else if( pName2->n==0 ){
+    /* Form 2:  Analyze the database or table named */
+    iDb = sqlite3FindDb(db, pName1);
+    if( iDb>=0 ){
+      analyzeDatabase(pParse, iDb);
+    }else{
+      z = sqlite3NameFromToken(db, pName1);
+      if( z ){
+        if( (pIdx = sqlite3FindIndex(db, z, 0))!=0 ){
+          analyzeTable(pParse, pIdx->pTable, pIdx);
+        }else if( (pTab = sqlite3LocateTable(pParse, 0, z, 0))!=0 ){
+          analyzeTable(pParse, pTab, 0);
+        }
+        sqlite3DbFree(db, z);
+      }
+    }
+  }else{
+    /* Form 3: Analyze the fully qualified table name */
+    iDb = sqlite3TwoPartName(pParse, pName1, pName2, &pTableName);
+    if( iDb>=0 ){
+      zDb = db->aDb[iDb].zName;
+      z = sqlite3NameFromToken(db, pTableName);
+      if( z ){
+        if( (pIdx = sqlite3FindIndex(db, z, zDb))!=0 ){
+          analyzeTable(pParse, pIdx->pTable, pIdx);
+        }else if( (pTab = sqlite3LocateTable(pParse, 0, z, zDb))!=0 ){
+          analyzeTable(pParse, pTab, 0);
+        }
+        sqlite3DbFree(db, z);
+      }
+    }   
+  }
+}
+
+/*
+** Used to pass information from the analyzer reader through to the
+** callback routine.
+*/
+typedef struct analysisInfo analysisInfo;
+struct analysisInfo {
+  sqlite3 *db;
+  const char *zDatabase;
+};
+
+/*
+** This callback is invoked once for each index when reading the
+** sqlite_stat1 table.  
+**
+**     argv[0] = name of the table
+**     argv[1] = name of the index (might be NULL)
+**     argv[2] = results of analysis - on integer for each column
+**
+** Entries for which argv[1]==NULL simply record the number of rows in
+** the table.
+*/
+static int analysisLoader(void *pData, int argc, char **argv, char **NotUsed){
+  analysisInfo *pInfo = (analysisInfo*)pData;
+  Index *pIndex;
+  Table *pTable;
+  int i, c, n;
+  tRowcnt v;
+  const char *z;
+
+  assert( argc==3 );
+  UNUSED_PARAMETER2(NotUsed, argc);
+
+  if( argv==0 || argv[0]==0 || argv[2]==0 ){
+    return 0;
+  }
+  pTable = sqlite3FindTable(pInfo->db, argv[0], pInfo->zDatabase);
+  if( pTable==0 ){
+    return 0;
+  }
+  if( argv[1] ){
+    pIndex = sqlite3FindIndex(pInfo->db, argv[1], pInfo->zDatabase);
+  }else{
+    pIndex = 0;
+  }
+  n = pIndex ? pIndex->nColumn : 0;
+  z = argv[2];
+  for(i=0; *z && i<=n; i++){
+    v = 0;
+    while( (c=z[0])>='0' && c<='9' ){
+      v = v*10 + c - '0';
+      z++;
+    }
+    if( i==0 ) pTable->nRowEst = v;
+    if( pIndex==0 ) break;
+    pIndex->aiRowEst[i] = v;
+    if( *z==' ' ) z++;
+    if( memcmp(z, "unordered", 10)==0 ){
+      pIndex->bUnordered = 1;
+      break;
+    }
+  }
+  return 0;
+}
+
+/*
+** If the Index.aSample variable is not NULL, delete the aSample[] array
+** and its contents.
+*/
+void sqlite3DeleteIndexSamples(sqlite3 *db, Index *pIdx){
+#ifdef SQLITE_ENABLE_STAT3
+  if( pIdx->aSample ){
+    int j;
+    for(j=0; j<pIdx->nSample; j++){
+      IndexSample *p = &pIdx->aSample[j];
+      if( p->eType==SQLITE_TEXT || p->eType==SQLITE_BLOB ){
+        sqlite3DbFree(db, p->u.z);
+      }
+    }
+    sqlite3DbFree(db, pIdx->aSample);
+  }
+  if( db && db->pnBytesFreed==0 ){
+    pIdx->nSample = 0;
+    pIdx->aSample = 0;
+  }
+#else
+  UNUSED_PARAMETER(db);
+  UNUSED_PARAMETER(pIdx);
+#endif
+}
+
+#ifdef SQLITE_ENABLE_STAT3
+/*
+** Load content from the sqlite_stat3 table into the Index.aSample[]
+** arrays of all indices.
+*/
+static int loadStat3(sqlite3 *db, const char *zDb){
+  int rc;                       /* Result codes from subroutines */
+  sqlite3_stmt *pStmt = 0;      /* An SQL statement being run */
+  char *zSql;                   /* Text of the SQL statement */
+  Index *pPrevIdx = 0;          /* Previous index in the loop */
+  int idx = 0;                  /* slot in pIdx->aSample[] for next sample */
+  int eType;                    /* Datatype of a sample */
+  IndexSample *pSample;         /* A slot in pIdx->aSample[] */
+
+  if( !sqlite3FindTable(db, "sqlite_stat3", zDb) ){
+    return SQLITE_OK;
+  }
+
+  zSql = sqlite3MPrintf(db, 
+      "SELECT idx,count(*) FROM %Q.sqlite_stat3"
+      " GROUP BY idx", zDb);
+  if( !zSql ){
+    return SQLITE_NOMEM;
+  }
+  rc = sqlite3_prepare(db, zSql, -1, &pStmt, 0);
+  sqlite3DbFree(db, zSql);
+  if( rc ) return rc;
+
+  while( sqlite3_step(pStmt)==SQLITE_ROW ){
+    char *zIndex;   /* Index name */
+    Index *pIdx;    /* Pointer to the index object */
+    int nSample;    /* Number of samples */
+
+    zIndex = (char *)sqlite3_column_text(pStmt, 0);
+    if( zIndex==0 ) continue;
+    nSample = sqlite3_column_int(pStmt, 1);
+    pIdx = sqlite3FindIndex(db, zIndex, zDb);
+    if( pIdx==0 ) continue;
+    assert( pIdx->nSample==0 );
+    pIdx->nSample = nSample;
+    pIdx->aSample = sqlite3MallocZero( nSample*sizeof(IndexSample) );
+    pIdx->avgEq = pIdx->aiRowEst[1];
+    if( pIdx->aSample==0 ){
+      db->mallocFailed = 1;
+      sqlite3_finalize(pStmt);
+      return SQLITE_NOMEM;
+    }
+  }
+  rc = sqlite3_finalize(pStmt);
+  if( rc ) return rc;
+
+  zSql = sqlite3MPrintf(db, 
+      "SELECT idx,neq,nlt,ndlt,sample FROM %Q.sqlite_stat3", zDb);
+  if( !zSql ){
+    return SQLITE_NOMEM;
+  }
+  rc = sqlite3_prepare(db, zSql, -1, &pStmt, 0);
+  sqlite3DbFree(db, zSql);
+  if( rc ) return rc;
+
+  while( sqlite3_step(pStmt)==SQLITE_ROW ){
+    char *zIndex;   /* Index name */
+    Index *pIdx;    /* Pointer to the index object */
+    int i;          /* Loop counter */
+    tRowcnt sumEq;  /* Sum of the nEq values */
+
+    zIndex = (char *)sqlite3_column_text(pStmt, 0);
+    if( zIndex==0 ) continue;
+    pIdx = sqlite3FindIndex(db, zIndex, zDb);
+    if( pIdx==0 ) continue;
+    if( pIdx==pPrevIdx ){
+      idx++;
+    }else{
+      pPrevIdx = pIdx;
+      idx = 0;
+    }
+    assert( idx<pIdx->nSample );
+    pSample = &pIdx->aSample[idx];
+    pSample->nEq = (tRowcnt)sqlite3_column_int64(pStmt, 1);
+    pSample->nLt = (tRowcnt)sqlite3_column_int64(pStmt, 2);
+    pSample->nDLt = (tRowcnt)sqlite3_column_int64(pStmt, 3);
+    if( idx==pIdx->nSample-1 ){
+      if( pSample->nDLt>0 ){
+        for(i=0, sumEq=0; i<=idx-1; i++) sumEq += pIdx->aSample[i].nEq;
+        pIdx->avgEq = (pSample->nLt - sumEq)/pSample->nDLt;
+      }
+      if( pIdx->avgEq<=0 ) pIdx->avgEq = 1;
+    }
+    eType = sqlite3_column_type(pStmt, 4);
+    pSample->eType = (u8)eType;
+    switch( eType ){
+      case SQLITE_INTEGER: {
+        pSample->u.i = sqlite3_column_int64(pStmt, 4);
+        break;
+      }
+      case SQLITE_FLOAT: {
+        pSample->u.r = sqlite3_column_double(pStmt, 4);
+        break;
+      }
+      case SQLITE_NULL: {
+        break;
+      }
+      default: assert( eType==SQLITE_TEXT || eType==SQLITE_BLOB ); {
+        const char *z = (const char *)(
+              (eType==SQLITE_BLOB) ?
+              sqlite3_column_blob(pStmt, 4):
+              sqlite3_column_text(pStmt, 4)
+           );
+        int n = z ? sqlite3_column_bytes(pStmt, 4) : 0;
+        pSample->nByte = n;
+        if( n < 1){
+          pSample->u.z = 0;
+        }else{
+          pSample->u.z = sqlite3Malloc(n);
+          if( pSample->u.z==0 ){
+            db->mallocFailed = 1;
+            sqlite3_finalize(pStmt);
+            return SQLITE_NOMEM;
+          }
+          memcpy(pSample->u.z, z, n);
+        }
+      }
+    }
+  }
+  return sqlite3_finalize(pStmt);
+}
+#endif /* SQLITE_ENABLE_STAT3 */
+
+/*
+** Load the content of the sqlite_stat1 and sqlite_stat3 tables. The
+** contents of sqlite_stat1 are used to populate the Index.aiRowEst[]
+** arrays. The contents of sqlite_stat3 are used to populate the
+** Index.aSample[] arrays.
+**
+** If the sqlite_stat1 table is not present in the database, SQLITE_ERROR
+** is returned. In this case, even if SQLITE_ENABLE_STAT3 was defined 
+** during compilation and the sqlite_stat3 table is present, no data is 
+** read from it.
+**
+** If SQLITE_ENABLE_STAT3 was defined during compilation and the 
+** sqlite_stat3 table is not present in the database, SQLITE_ERROR is
+** returned. However, in this case, data is read from the sqlite_stat1
+** table (if it is present) before returning.
+**
+** If an OOM error occurs, this function always sets db->mallocFailed.
+** This means if the caller does not care about other errors, the return
+** code may be ignored.
+*/
+int sqlite3AnalysisLoad(sqlite3 *db, int iDb){
+  analysisInfo sInfo;
+  HashElem *i;
+  char *zSql;
+  int rc;
+
+  assert( iDb>=0 && iDb<db->nDb );
+  assert( db->aDb[iDb].pBt!=0 );
+
+  /* Clear any prior statistics */
+  assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+  for(i=sqliteHashFirst(&db->aDb[iDb].pSchema->idxHash);i;i=sqliteHashNext(i)){
+    Index *pIdx = sqliteHashData(i);
+    sqlite3DefaultRowEst(pIdx);
+#ifdef SQLITE_ENABLE_STAT3
+    sqlite3DeleteIndexSamples(db, pIdx);
+    pIdx->aSample = 0;
+#endif
+  }
+
+  /* Check to make sure the sqlite_stat1 table exists */
+  sInfo.db = db;
+  sInfo.zDatabase = db->aDb[iDb].zName;
+  if( sqlite3FindTable(db, "sqlite_stat1", sInfo.zDatabase)==0 ){
+    return SQLITE_ERROR;
+  }
+
+  /* Load new statistics out of the sqlite_stat1 table */
+  zSql = sqlite3MPrintf(db, 
+      "SELECT tbl,idx,stat FROM %Q.sqlite_stat1", sInfo.zDatabase);
+  if( zSql==0 ){
+    rc = SQLITE_NOMEM;
+  }else{
+    rc = sqlite3_exec(db, zSql, analysisLoader, &sInfo, 0);
+    sqlite3DbFree(db, zSql);
+  }
+
+
+  /* Load the statistics from the sqlite_stat3 table. */
+#ifdef SQLITE_ENABLE_STAT3
+  if( rc==SQLITE_OK ){
+    rc = loadStat3(db, sInfo.zDatabase);
+  }
+#endif
+
+  if( rc==SQLITE_NOMEM ){
+    db->mallocFailed = 1;
+  }
+  return rc;
+}
+
+
+#endif /* SQLITE_OMIT_ANALYZE */
diff --git a/src/attach.c b/src/attach.c
new file mode 100644
index 0000000..18f8823
--- /dev/null
+++ b/src/attach.c
@@ -0,0 +1,557 @@
+/*
+** 2003 April 6
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains code used to implement the ATTACH and DETACH commands.
+*/
+#include "sqliteInt.h"
+
+#ifndef SQLITE_OMIT_ATTACH
+/*
+** Resolve an expression that was part of an ATTACH or DETACH statement. This
+** is slightly different from resolving a normal SQL expression, because simple
+** identifiers are treated as strings, not possible column names or aliases.
+**
+** i.e. if the parser sees:
+**
+**     ATTACH DATABASE abc AS def
+**
+** it treats the two expressions as literal strings 'abc' and 'def' instead of
+** looking for columns of the same name.
+**
+** This only applies to the root node of pExpr, so the statement:
+**
+**     ATTACH DATABASE abc||def AS 'db2'
+**
+** will fail because neither abc or def can be resolved.
+*/
+static int resolveAttachExpr(NameContext *pName, Expr *pExpr)
+{
+  int rc = SQLITE_OK;
+  if( pExpr ){
+    if( pExpr->op!=TK_ID ){
+      rc = sqlite3ResolveExprNames(pName, pExpr);
+      if( rc==SQLITE_OK && !sqlite3ExprIsConstant(pExpr) ){
+        sqlite3ErrorMsg(pName->pParse, "invalid name: \"%s\"", pExpr->u.zToken);
+        return SQLITE_ERROR;
+      }
+    }else{
+      pExpr->op = TK_STRING;
+    }
+  }
+  return rc;
+}
+
+/*
+** An SQL user-function registered to do the work of an ATTACH statement. The
+** three arguments to the function come directly from an attach statement:
+**
+**     ATTACH DATABASE x AS y KEY z
+**
+**     SELECT sqlite_attach(x, y, z)
+**
+** If the optional "KEY z" syntax is omitted, an SQL NULL is passed as the
+** third argument.
+*/
+static void attachFunc(
+  sqlite3_context *context,
+  int NotUsed,
+  sqlite3_value **argv
+){
+  int i;
+  int rc = 0;
+  sqlite3 *db = sqlite3_context_db_handle(context);
+  const char *zName;
+  const char *zFile;
+  char *zPath = 0;
+  char *zErr = 0;
+  unsigned int flags;
+  Db *aNew;
+  char *zErrDyn = 0;
+  sqlite3_vfs *pVfs;
+
+  UNUSED_PARAMETER(NotUsed);
+
+  zFile = (const char *)sqlite3_value_text(argv[0]);
+  zName = (const char *)sqlite3_value_text(argv[1]);
+  if( zFile==0 ) zFile = "";
+  if( zName==0 ) zName = "";
+
+  /* Check for the following errors:
+  **
+  **     * Too many attached databases,
+  **     * Transaction currently open
+  **     * Specified database name already being used.
+  */
+  if( db->nDb>=db->aLimit[SQLITE_LIMIT_ATTACHED]+2 ){
+    zErrDyn = sqlite3MPrintf(db, "too many attached databases - max %d", 
+      db->aLimit[SQLITE_LIMIT_ATTACHED]
+    );
+    goto attach_error;
+  }
+  if( !db->autoCommit ){
+    zErrDyn = sqlite3MPrintf(db, "cannot ATTACH database within transaction");
+    goto attach_error;
+  }
+  for(i=0; i<db->nDb; i++){
+    char *z = db->aDb[i].zName;
+    assert( z && zName );
+    if( sqlite3StrICmp(z, zName)==0 ){
+      zErrDyn = sqlite3MPrintf(db, "database %s is already in use", zName);
+      goto attach_error;
+    }
+  }
+
+  /* Allocate the new entry in the db->aDb[] array and initialise the schema
+  ** hash tables.
+  */
+  if( db->aDb==db->aDbStatic ){
+    aNew = sqlite3DbMallocRaw(db, sizeof(db->aDb[0])*3 );
+    if( aNew==0 ) return;
+    memcpy(aNew, db->aDb, sizeof(db->aDb[0])*2);
+  }else{
+    aNew = sqlite3DbRealloc(db, db->aDb, sizeof(db->aDb[0])*(db->nDb+1) );
+    if( aNew==0 ) return;
+  }
+  db->aDb = aNew;
+  aNew = &db->aDb[db->nDb];
+  memset(aNew, 0, sizeof(*aNew));
+
+  /* Open the database file. If the btree is successfully opened, use
+  ** it to obtain the database schema. At this point the schema may
+  ** or may not be initialised.
+  */
+  flags = db->openFlags;
+  rc = sqlite3ParseUri(db->pVfs->zName, zFile, &flags, &pVfs, &zPath, &zErr);
+  if( rc!=SQLITE_OK ){
+    if( rc==SQLITE_NOMEM ) db->mallocFailed = 1;
+    sqlite3_result_error(context, zErr, -1);
+    sqlite3_free(zErr);
+    return;
+  }
+  assert( pVfs );
+  flags |= SQLITE_OPEN_MAIN_DB;
+  rc = sqlite3BtreeOpen(pVfs, zPath, db, &aNew->pBt, 0, flags);
+  sqlite3_free( zPath );
+  db->nDb++;
+  if( rc==SQLITE_CONSTRAINT ){
+    rc = SQLITE_ERROR;
+    zErrDyn = sqlite3MPrintf(db, "database is already attached");
+  }else if( rc==SQLITE_OK ){
+    Pager *pPager;
+    aNew->pSchema = sqlite3SchemaGet(db, aNew->pBt);
+    if( !aNew->pSchema ){
+      rc = SQLITE_NOMEM;
+    }else if( aNew->pSchema->file_format && aNew->pSchema->enc!=ENC(db) ){
+      zErrDyn = sqlite3MPrintf(db, 
+        "attached databases must use the same text encoding as main database");
+      rc = SQLITE_ERROR;
+    }
+    pPager = sqlite3BtreePager(aNew->pBt);
+    sqlite3PagerLockingMode(pPager, db->dfltLockMode);
+    sqlite3BtreeSecureDelete(aNew->pBt,
+                             sqlite3BtreeSecureDelete(db->aDb[0].pBt,-1) );
+  }
+  aNew->safety_level = 3;
+  aNew->zName = sqlite3DbStrDup(db, zName);
+  if( rc==SQLITE_OK && aNew->zName==0 ){
+    rc = SQLITE_NOMEM;
+  }
+
+
+#ifdef SQLITE_HAS_CODEC
+  if( rc==SQLITE_OK ){
+    extern int sqlite3CodecAttach(sqlite3*, int, const void*, int);
+    extern void sqlite3CodecGetKey(sqlite3*, int, void**, int*);
+    int nKey;
+    char *zKey;
+    int t = sqlite3_value_type(argv[2]);
+    switch( t ){
+      case SQLITE_INTEGER:
+      case SQLITE_FLOAT:
+        zErrDyn = sqlite3DbStrDup(db, "Invalid key value");
+        rc = SQLITE_ERROR;
+        break;
+        
+      case SQLITE_TEXT:
+      case SQLITE_BLOB:
+        nKey = sqlite3_value_bytes(argv[2]);
+        zKey = (char *)sqlite3_value_blob(argv[2]);
+        rc = sqlite3CodecAttach(db, db->nDb-1, zKey, nKey);
+        break;
+
+      case SQLITE_NULL:
+        /* No key specified.  Use the key from the main database */
+        sqlite3CodecGetKey(db, 0, (void**)&zKey, &nKey);
+        if( nKey>0 || sqlite3BtreeGetReserve(db->aDb[0].pBt)>0 ){
+          rc = sqlite3CodecAttach(db, db->nDb-1, zKey, nKey);
+        }
+        break;
+    }
+  }
+#endif
+
+  /* If the file was opened successfully, read the schema for the new database.
+  ** If this fails, or if opening the file failed, then close the file and 
+  ** remove the entry from the db->aDb[] array. i.e. put everything back the way
+  ** we found it.
+  */
+  if( rc==SQLITE_OK ){
+    sqlite3BtreeEnterAll(db);
+    rc = sqlite3Init(db, &zErrDyn);
+    sqlite3BtreeLeaveAll(db);
+  }
+  if( rc ){
+    int iDb = db->nDb - 1;
+    assert( iDb>=2 );
+    if( db->aDb[iDb].pBt ){
+      sqlite3BtreeClose(db->aDb[iDb].pBt);
+      db->aDb[iDb].pBt = 0;
+      db->aDb[iDb].pSchema = 0;
+    }
+    sqlite3ResetInternalSchema(db, -1);
+    db->nDb = iDb;
+    if( rc==SQLITE_NOMEM || rc==SQLITE_IOERR_NOMEM ){
+      db->mallocFailed = 1;
+      sqlite3DbFree(db, zErrDyn);
+      zErrDyn = sqlite3MPrintf(db, "out of memory");
+    }else if( zErrDyn==0 ){
+      zErrDyn = sqlite3MPrintf(db, "unable to open database: %s", zFile);
+    }
+    goto attach_error;
+  }
+  
+  return;
+
+attach_error:
+  /* Return an error if we get here */
+  if( zErrDyn ){
+    sqlite3_result_error(context, zErrDyn, -1);
+    sqlite3DbFree(db, zErrDyn);
+  }
+  if( rc ) sqlite3_result_error_code(context, rc);
+}
+
+/*
+** An SQL user-function registered to do the work of an DETACH statement. The
+** three arguments to the function come directly from a detach statement:
+**
+**     DETACH DATABASE x
+**
+**     SELECT sqlite_detach(x)
+*/
+static void detachFunc(
+  sqlite3_context *context,
+  int NotUsed,
+  sqlite3_value **argv
+){
+  const char *zName = (const char *)sqlite3_value_text(argv[0]);
+  sqlite3 *db = sqlite3_context_db_handle(context);
+  int i;
+  Db *pDb = 0;
+  char zErr[128];
+
+  UNUSED_PARAMETER(NotUsed);
+
+  if( zName==0 ) zName = "";
+  for(i=0; i<db->nDb; i++){
+    pDb = &db->aDb[i];
+    if( pDb->pBt==0 ) continue;
+    if( sqlite3StrICmp(pDb->zName, zName)==0 ) break;
+  }
+
+  if( i>=db->nDb ){
+    sqlite3_snprintf(sizeof(zErr),zErr, "no such database: %s", zName);
+    goto detach_error;
+  }
+  if( i<2 ){
+    sqlite3_snprintf(sizeof(zErr),zErr, "cannot detach database %s", zName);
+    goto detach_error;
+  }
+  if( !db->autoCommit ){
+    sqlite3_snprintf(sizeof(zErr), zErr,
+                     "cannot DETACH database within transaction");
+    goto detach_error;
+  }
+  if( sqlite3BtreeIsInReadTrans(pDb->pBt) || sqlite3BtreeIsInBackup(pDb->pBt) ){
+    sqlite3_snprintf(sizeof(zErr),zErr, "database %s is locked", zName);
+    goto detach_error;
+  }
+
+  sqlite3BtreeClose(pDb->pBt);
+  pDb->pBt = 0;
+  pDb->pSchema = 0;
+  sqlite3ResetInternalSchema(db, -1);
+  return;
+
+detach_error:
+  sqlite3_result_error(context, zErr, -1);
+}
+
+/*
+** This procedure generates VDBE code for a single invocation of either the
+** sqlite_detach() or sqlite_attach() SQL user functions.
+*/
+static void codeAttach(
+  Parse *pParse,       /* The parser context */
+  int type,            /* Either SQLITE_ATTACH or SQLITE_DETACH */
+  FuncDef const *pFunc,/* FuncDef wrapper for detachFunc() or attachFunc() */
+  Expr *pAuthArg,      /* Expression to pass to authorization callback */
+  Expr *pFilename,     /* Name of database file */
+  Expr *pDbname,       /* Name of the database to use internally */
+  Expr *pKey           /* Database key for encryption extension */
+){
+  int rc;
+  NameContext sName;
+  Vdbe *v;
+  sqlite3* db = pParse->db;
+  int regArgs;
+
+  memset(&sName, 0, sizeof(NameContext));
+  sName.pParse = pParse;
+
+  if( 
+      SQLITE_OK!=(rc = resolveAttachExpr(&sName, pFilename)) ||
+      SQLITE_OK!=(rc = resolveAttachExpr(&sName, pDbname)) ||
+      SQLITE_OK!=(rc = resolveAttachExpr(&sName, pKey))
+  ){
+    pParse->nErr++;
+    goto attach_end;
+  }
+
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  if( pAuthArg ){
+    char *zAuthArg;
+    if( pAuthArg->op==TK_STRING ){
+      zAuthArg = pAuthArg->u.zToken;
+    }else{
+      zAuthArg = 0;
+    }
+    rc = sqlite3AuthCheck(pParse, type, zAuthArg, 0, 0);
+    if(rc!=SQLITE_OK ){
+      goto attach_end;
+    }
+  }
+#endif /* SQLITE_OMIT_AUTHORIZATION */
+
+
+  v = sqlite3GetVdbe(pParse);
+  regArgs = sqlite3GetTempRange(pParse, 4);
+  sqlite3ExprCode(pParse, pFilename, regArgs);
+  sqlite3ExprCode(pParse, pDbname, regArgs+1);
+  sqlite3ExprCode(pParse, pKey, regArgs+2);
+
+  assert( v || db->mallocFailed );
+  if( v ){
+    sqlite3VdbeAddOp3(v, OP_Function, 0, regArgs+3-pFunc->nArg, regArgs+3);
+    assert( pFunc->nArg==-1 || (pFunc->nArg&0xff)==pFunc->nArg );
+    sqlite3VdbeChangeP5(v, (u8)(pFunc->nArg));
+    sqlite3VdbeChangeP4(v, -1, (char *)pFunc, P4_FUNCDEF);
+
+    /* Code an OP_Expire. For an ATTACH statement, set P1 to true (expire this
+    ** statement only). For DETACH, set it to false (expire all existing
+    ** statements).
+    */
+    sqlite3VdbeAddOp1(v, OP_Expire, (type==SQLITE_ATTACH));
+  }
+  
+attach_end:
+  sqlite3ExprDelete(db, pFilename);
+  sqlite3ExprDelete(db, pDbname);
+  sqlite3ExprDelete(db, pKey);
+}
+
+/*
+** Called by the parser to compile a DETACH statement.
+**
+**     DETACH pDbname
+*/
+void sqlite3Detach(Parse *pParse, Expr *pDbname){
+  static const FuncDef detach_func = {
+    1,                /* nArg */
+    SQLITE_UTF8,      /* iPrefEnc */
+    0,                /* flags */
+    0,                /* pUserData */
+    0,                /* pNext */
+    detachFunc,       /* xFunc */
+    0,                /* xStep */
+    0,                /* xFinalize */
+    "sqlite_detach",  /* zName */
+    0,                /* pHash */
+    0                 /* pDestructor */
+  };
+  codeAttach(pParse, SQLITE_DETACH, &detach_func, pDbname, 0, 0, pDbname);
+}
+
+/*
+** Called by the parser to compile an ATTACH statement.
+**
+**     ATTACH p AS pDbname KEY pKey
+*/
+void sqlite3Attach(Parse *pParse, Expr *p, Expr *pDbname, Expr *pKey){
+  static const FuncDef attach_func = {
+    3,                /* nArg */
+    SQLITE_UTF8,      /* iPrefEnc */
+    0,                /* flags */
+    0,                /* pUserData */
+    0,                /* pNext */
+    attachFunc,       /* xFunc */
+    0,                /* xStep */
+    0,                /* xFinalize */
+    "sqlite_attach",  /* zName */
+    0,                /* pHash */
+    0                 /* pDestructor */
+  };
+  codeAttach(pParse, SQLITE_ATTACH, &attach_func, p, p, pDbname, pKey);
+}
+#endif /* SQLITE_OMIT_ATTACH */
+
+/*
+** Initialize a DbFixer structure.  This routine must be called prior
+** to passing the structure to one of the sqliteFixAAAA() routines below.
+**
+** The return value indicates whether or not fixation is required.  TRUE
+** means we do need to fix the database references, FALSE means we do not.
+*/
+int sqlite3FixInit(
+  DbFixer *pFix,      /* The fixer to be initialized */
+  Parse *pParse,      /* Error messages will be written here */
+  int iDb,            /* This is the database that must be used */
+  const char *zType,  /* "view", "trigger", or "index" */
+  const Token *pName  /* Name of the view, trigger, or index */
+){
+  sqlite3 *db;
+
+  if( NEVER(iDb<0) || iDb==1 ) return 0;
+  db = pParse->db;
+  assert( db->nDb>iDb );
+  pFix->pParse = pParse;
+  pFix->zDb = db->aDb[iDb].zName;
+  pFix->zType = zType;
+  pFix->pName = pName;
+  return 1;
+}
+
+/*
+** The following set of routines walk through the parse tree and assign
+** a specific database to all table references where the database name
+** was left unspecified in the original SQL statement.  The pFix structure
+** must have been initialized by a prior call to sqlite3FixInit().
+**
+** These routines are used to make sure that an index, trigger, or
+** view in one database does not refer to objects in a different database.
+** (Exception: indices, triggers, and views in the TEMP database are
+** allowed to refer to anything.)  If a reference is explicitly made
+** to an object in a different database, an error message is added to
+** pParse->zErrMsg and these routines return non-zero.  If everything
+** checks out, these routines return 0.
+*/
+int sqlite3FixSrcList(
+  DbFixer *pFix,       /* Context of the fixation */
+  SrcList *pList       /* The Source list to check and modify */
+){
+  int i;
+  const char *zDb;
+  struct SrcList_item *pItem;
+
+  if( NEVER(pList==0) ) return 0;
+  zDb = pFix->zDb;
+  for(i=0, pItem=pList->a; i<pList->nSrc; i++, pItem++){
+    if( pItem->zDatabase==0 ){
+      pItem->zDatabase = sqlite3DbStrDup(pFix->pParse->db, zDb);
+    }else if( sqlite3StrICmp(pItem->zDatabase,zDb)!=0 ){
+      sqlite3ErrorMsg(pFix->pParse,
+         "%s %T cannot reference objects in database %s",
+         pFix->zType, pFix->pName, pItem->zDatabase);
+      return 1;
+    }
+#if !defined(SQLITE_OMIT_VIEW) || !defined(SQLITE_OMIT_TRIGGER)
+    if( sqlite3FixSelect(pFix, pItem->pSelect) ) return 1;
+    if( sqlite3FixExpr(pFix, pItem->pOn) ) return 1;
+#endif
+  }
+  return 0;
+}
+#if !defined(SQLITE_OMIT_VIEW) || !defined(SQLITE_OMIT_TRIGGER)
+int sqlite3FixSelect(
+  DbFixer *pFix,       /* Context of the fixation */
+  Select *pSelect      /* The SELECT statement to be fixed to one database */
+){
+  while( pSelect ){
+    if( sqlite3FixExprList(pFix, pSelect->pEList) ){
+      return 1;
+    }
+    if( sqlite3FixSrcList(pFix, pSelect->pSrc) ){
+      return 1;
+    }
+    if( sqlite3FixExpr(pFix, pSelect->pWhere) ){
+      return 1;
+    }
+    if( sqlite3FixExpr(pFix, pSelect->pHaving) ){
+      return 1;
+    }
+    pSelect = pSelect->pPrior;
+  }
+  return 0;
+}
+int sqlite3FixExpr(
+  DbFixer *pFix,     /* Context of the fixation */
+  Expr *pExpr        /* The expression to be fixed to one database */
+){
+  while( pExpr ){
+    if( ExprHasAnyProperty(pExpr, EP_TokenOnly) ) break;
+    if( ExprHasProperty(pExpr, EP_xIsSelect) ){
+      if( sqlite3FixSelect(pFix, pExpr->x.pSelect) ) return 1;
+    }else{
+      if( sqlite3FixExprList(pFix, pExpr->x.pList) ) return 1;
+    }
+    if( sqlite3FixExpr(pFix, pExpr->pRight) ){
+      return 1;
+    }
+    pExpr = pExpr->pLeft;
+  }
+  return 0;
+}
+int sqlite3FixExprList(
+  DbFixer *pFix,     /* Context of the fixation */
+  ExprList *pList    /* The expression to be fixed to one database */
+){
+  int i;
+  struct ExprList_item *pItem;
+  if( pList==0 ) return 0;
+  for(i=0, pItem=pList->a; i<pList->nExpr; i++, pItem++){
+    if( sqlite3FixExpr(pFix, pItem->pExpr) ){
+      return 1;
+    }
+  }
+  return 0;
+}
+#endif
+
+#ifndef SQLITE_OMIT_TRIGGER
+int sqlite3FixTriggerStep(
+  DbFixer *pFix,     /* Context of the fixation */
+  TriggerStep *pStep /* The trigger step be fixed to one database */
+){
+  while( pStep ){
+    if( sqlite3FixSelect(pFix, pStep->pSelect) ){
+      return 1;
+    }
+    if( sqlite3FixExpr(pFix, pStep->pWhere) ){
+      return 1;
+    }
+    if( sqlite3FixExprList(pFix, pStep->pExprList) ){
+      return 1;
+    }
+    pStep = pStep->pNext;
+  }
+  return 0;
+}
+#endif
diff --git a/src/auth.c b/src/auth.c
new file mode 100644
index 0000000..d38bb83
--- /dev/null
+++ b/src/auth.c
@@ -0,0 +1,249 @@
+/*
+** 2003 January 11
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains code used to implement the sqlite3_set_authorizer()
+** API.  This facility is an optional feature of the library.  Embedded
+** systems that do not need this facility may omit it by recompiling
+** the library with -DSQLITE_OMIT_AUTHORIZATION=1
+*/
+#include "sqliteInt.h"
+
+/*
+** All of the code in this file may be omitted by defining a single
+** macro.
+*/
+#ifndef SQLITE_OMIT_AUTHORIZATION
+
+/*
+** Set or clear the access authorization function.
+**
+** The access authorization function is be called during the compilation
+** phase to verify that the user has read and/or write access permission on
+** various fields of the database.  The first argument to the auth function
+** is a copy of the 3rd argument to this routine.  The second argument
+** to the auth function is one of these constants:
+**
+**       SQLITE_CREATE_INDEX
+**       SQLITE_CREATE_TABLE
+**       SQLITE_CREATE_TEMP_INDEX
+**       SQLITE_CREATE_TEMP_TABLE
+**       SQLITE_CREATE_TEMP_TRIGGER
+**       SQLITE_CREATE_TEMP_VIEW
+**       SQLITE_CREATE_TRIGGER
+**       SQLITE_CREATE_VIEW
+**       SQLITE_DELETE
+**       SQLITE_DROP_INDEX
+**       SQLITE_DROP_TABLE
+**       SQLITE_DROP_TEMP_INDEX
+**       SQLITE_DROP_TEMP_TABLE
+**       SQLITE_DROP_TEMP_TRIGGER
+**       SQLITE_DROP_TEMP_VIEW
+**       SQLITE_DROP_TRIGGER
+**       SQLITE_DROP_VIEW
+**       SQLITE_INSERT
+**       SQLITE_PRAGMA
+**       SQLITE_READ
+**       SQLITE_SELECT
+**       SQLITE_TRANSACTION
+**       SQLITE_UPDATE
+**
+** The third and fourth arguments to the auth function are the name of
+** the table and the column that are being accessed.  The auth function
+** should return either SQLITE_OK, SQLITE_DENY, or SQLITE_IGNORE.  If
+** SQLITE_OK is returned, it means that access is allowed.  SQLITE_DENY
+** means that the SQL statement will never-run - the sqlite3_exec() call
+** will return with an error.  SQLITE_IGNORE means that the SQL statement
+** should run but attempts to read the specified column will return NULL
+** and attempts to write the column will be ignored.
+**
+** Setting the auth function to NULL disables this hook.  The default
+** setting of the auth function is NULL.
+*/
+int sqlite3_set_authorizer(
+  sqlite3 *db,
+  int (*xAuth)(void*,int,const char*,const char*,const char*,const char*),
+  void *pArg
+){
+  sqlite3_mutex_enter(db->mutex);
+  db->xAuth = xAuth;
+  db->pAuthArg = pArg;
+  sqlite3ExpirePreparedStatements(db);
+  sqlite3_mutex_leave(db->mutex);
+  return SQLITE_OK;
+}
+
+/*
+** Write an error message into pParse->zErrMsg that explains that the
+** user-supplied authorization function returned an illegal value.
+*/
+static void sqliteAuthBadReturnCode(Parse *pParse){
+  sqlite3ErrorMsg(pParse, "authorizer malfunction");
+  pParse->rc = SQLITE_ERROR;
+}
+
+/*
+** Invoke the authorization callback for permission to read column zCol from
+** table zTab in database zDb. This function assumes that an authorization
+** callback has been registered (i.e. that sqlite3.xAuth is not NULL).
+**
+** If SQLITE_IGNORE is returned and pExpr is not NULL, then pExpr is changed
+** to an SQL NULL expression. Otherwise, if pExpr is NULL, then SQLITE_IGNORE
+** is treated as SQLITE_DENY. In this case an error is left in pParse.
+*/
+int sqlite3AuthReadCol(
+  Parse *pParse,                  /* The parser context */
+  const char *zTab,               /* Table name */
+  const char *zCol,               /* Column name */
+  int iDb                         /* Index of containing database. */
+){
+  sqlite3 *db = pParse->db;       /* Database handle */
+  char *zDb = db->aDb[iDb].zName; /* Name of attached database */
+  int rc;                         /* Auth callback return code */
+
+  rc = db->xAuth(db->pAuthArg, SQLITE_READ, zTab,zCol,zDb,pParse->zAuthContext);
+  if( rc==SQLITE_DENY ){
+    if( db->nDb>2 || iDb!=0 ){
+      sqlite3ErrorMsg(pParse, "access to %s.%s.%s is prohibited",zDb,zTab,zCol);
+    }else{
+      sqlite3ErrorMsg(pParse, "access to %s.%s is prohibited", zTab, zCol);
+    }
+    pParse->rc = SQLITE_AUTH;
+  }else if( rc!=SQLITE_IGNORE && rc!=SQLITE_OK ){
+    sqliteAuthBadReturnCode(pParse);
+  }
+  return rc;
+}
+
+/*
+** The pExpr should be a TK_COLUMN expression.  The table referred to
+** is in pTabList or else it is the NEW or OLD table of a trigger.  
+** Check to see if it is OK to read this particular column.
+**
+** If the auth function returns SQLITE_IGNORE, change the TK_COLUMN 
+** instruction into a TK_NULL.  If the auth function returns SQLITE_DENY,
+** then generate an error.
+*/
+void sqlite3AuthRead(
+  Parse *pParse,        /* The parser context */
+  Expr *pExpr,          /* The expression to check authorization on */
+  Schema *pSchema,      /* The schema of the expression */
+  SrcList *pTabList     /* All table that pExpr might refer to */
+){
+  sqlite3 *db = pParse->db;
+  Table *pTab = 0;      /* The table being read */
+  const char *zCol;     /* Name of the column of the table */
+  int iSrc;             /* Index in pTabList->a[] of table being read */
+  int iDb;              /* The index of the database the expression refers to */
+  int iCol;             /* Index of column in table */
+
+  if( db->xAuth==0 ) return;
+  iDb = sqlite3SchemaToIndex(pParse->db, pSchema);
+  if( iDb<0 ){
+    /* An attempt to read a column out of a subquery or other
+    ** temporary table. */
+    return;
+  }
+
+  assert( pExpr->op==TK_COLUMN || pExpr->op==TK_TRIGGER );
+  if( pExpr->op==TK_TRIGGER ){
+    pTab = pParse->pTriggerTab;
+  }else{
+    assert( pTabList );
+    for(iSrc=0; ALWAYS(iSrc<pTabList->nSrc); iSrc++){
+      if( pExpr->iTable==pTabList->a[iSrc].iCursor ){
+        pTab = pTabList->a[iSrc].pTab;
+        break;
+      }
+    }
+  }
+  iCol = pExpr->iColumn;
+  if( NEVER(pTab==0) ) return;
+
+  if( iCol>=0 ){
+    assert( iCol<pTab->nCol );
+    zCol = pTab->aCol[iCol].zName;
+  }else if( pTab->iPKey>=0 ){
+    assert( pTab->iPKey<pTab->nCol );
+    zCol = pTab->aCol[pTab->iPKey].zName;
+  }else{
+    zCol = "ROWID";
+  }
+  assert( iDb>=0 && iDb<db->nDb );
+  if( SQLITE_IGNORE==sqlite3AuthReadCol(pParse, pTab->zName, zCol, iDb) ){
+    pExpr->op = TK_NULL;
+  }
+}
+
+/*
+** Do an authorization check using the code and arguments given.  Return
+** either SQLITE_OK (zero) or SQLITE_IGNORE or SQLITE_DENY.  If SQLITE_DENY
+** is returned, then the error count and error message in pParse are
+** modified appropriately.
+*/
+int sqlite3AuthCheck(
+  Parse *pParse,
+  int code,
+  const char *zArg1,
+  const char *zArg2,
+  const char *zArg3
+){
+  sqlite3 *db = pParse->db;
+  int rc;
+
+  /* Don't do any authorization checks if the database is initialising
+  ** or if the parser is being invoked from within sqlite3_declare_vtab.
+  */
+  if( db->init.busy || IN_DECLARE_VTAB ){
+    return SQLITE_OK;
+  }
+
+  if( db->xAuth==0 ){
+    return SQLITE_OK;
+  }
+  rc = db->xAuth(db->pAuthArg, code, zArg1, zArg2, zArg3, pParse->zAuthContext);
+  if( rc==SQLITE_DENY ){
+    sqlite3ErrorMsg(pParse, "not authorized");
+    pParse->rc = SQLITE_AUTH;
+  }else if( rc!=SQLITE_OK && rc!=SQLITE_IGNORE ){
+    rc = SQLITE_DENY;
+    sqliteAuthBadReturnCode(pParse);
+  }
+  return rc;
+}
+
+/*
+** Push an authorization context.  After this routine is called, the
+** zArg3 argument to authorization callbacks will be zContext until
+** popped.  Or if pParse==0, this routine is a no-op.
+*/
+void sqlite3AuthContextPush(
+  Parse *pParse,
+  AuthContext *pContext, 
+  const char *zContext
+){
+  assert( pParse );
+  pContext->pParse = pParse;
+  pContext->zAuthContext = pParse->zAuthContext;
+  pParse->zAuthContext = zContext;
+}
+
+/*
+** Pop an authorization context that was previously pushed
+** by sqlite3AuthContextPush
+*/
+void sqlite3AuthContextPop(AuthContext *pContext){
+  if( pContext->pParse ){
+    pContext->pParse->zAuthContext = pContext->zAuthContext;
+    pContext->pParse = 0;
+  }
+}
+
+#endif /* SQLITE_OMIT_AUTHORIZATION */
diff --git a/src/backup.c b/src/backup.c
new file mode 100644
index 0000000..bdf96bd
--- /dev/null
+++ b/src/backup.c
@@ -0,0 +1,716 @@
+/*
+** 2009 January 28
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains the implementation of the sqlite3_backup_XXX() 
+** API functions and the related features.
+*/
+#include "sqliteInt.h"
+#include "btreeInt.h"
+
+/* Macro to find the minimum of two numeric values.
+*/
+#ifndef MIN
+# define MIN(x,y) ((x)<(y)?(x):(y))
+#endif
+
+/*
+** Structure allocated for each backup operation.
+*/
+struct sqlite3_backup {
+  sqlite3* pDestDb;        /* Destination database handle */
+  Btree *pDest;            /* Destination b-tree file */
+  u32 iDestSchema;         /* Original schema cookie in destination */
+  int bDestLocked;         /* True once a write-transaction is open on pDest */
+
+  Pgno iNext;              /* Page number of the next source page to copy */
+  sqlite3* pSrcDb;         /* Source database handle */
+  Btree *pSrc;             /* Source b-tree file */
+
+  int rc;                  /* Backup process error code */
+
+  /* These two variables are set by every call to backup_step(). They are
+  ** read by calls to backup_remaining() and backup_pagecount().
+  */
+  Pgno nRemaining;         /* Number of pages left to copy */
+  Pgno nPagecount;         /* Total number of pages to copy */
+
+  int isAttached;          /* True once backup has been registered with pager */
+  sqlite3_backup *pNext;   /* Next backup associated with source pager */
+};
+
+/*
+** THREAD SAFETY NOTES:
+**
+**   Once it has been created using backup_init(), a single sqlite3_backup
+**   structure may be accessed via two groups of thread-safe entry points:
+**
+**     * Via the sqlite3_backup_XXX() API function backup_step() and 
+**       backup_finish(). Both these functions obtain the source database
+**       handle mutex and the mutex associated with the source BtShared 
+**       structure, in that order.
+**
+**     * Via the BackupUpdate() and BackupRestart() functions, which are
+**       invoked by the pager layer to report various state changes in
+**       the page cache associated with the source database. The mutex
+**       associated with the source database BtShared structure will always 
+**       be held when either of these functions are invoked.
+**
+**   The other sqlite3_backup_XXX() API functions, backup_remaining() and
+**   backup_pagecount() are not thread-safe functions. If they are called
+**   while some other thread is calling backup_step() or backup_finish(),
+**   the values returned may be invalid. There is no way for a call to
+**   BackupUpdate() or BackupRestart() to interfere with backup_remaining()
+**   or backup_pagecount().
+**
+**   Depending on the SQLite configuration, the database handles and/or
+**   the Btree objects may have their own mutexes that require locking.
+**   Non-sharable Btrees (in-memory databases for example), do not have
+**   associated mutexes.
+*/
+
+/*
+** Return a pointer corresponding to database zDb (i.e. "main", "temp")
+** in connection handle pDb. If such a database cannot be found, return
+** a NULL pointer and write an error message to pErrorDb.
+**
+** If the "temp" database is requested, it may need to be opened by this 
+** function. If an error occurs while doing so, return 0 and write an 
+** error message to pErrorDb.
+*/
+static Btree *findBtree(sqlite3 *pErrorDb, sqlite3 *pDb, const char *zDb){
+  int i = sqlite3FindDbName(pDb, zDb);
+
+  if( i==1 ){
+    Parse *pParse;
+    int rc = 0;
+    pParse = sqlite3StackAllocZero(pErrorDb, sizeof(*pParse));
+    if( pParse==0 ){
+      sqlite3Error(pErrorDb, SQLITE_NOMEM, "out of memory");
+      rc = SQLITE_NOMEM;
+    }else{
+      pParse->db = pDb;
+      if( sqlite3OpenTempDatabase(pParse) ){
+        sqlite3Error(pErrorDb, pParse->rc, "%s", pParse->zErrMsg);
+        rc = SQLITE_ERROR;
+      }
+      sqlite3DbFree(pErrorDb, pParse->zErrMsg);
+      sqlite3StackFree(pErrorDb, pParse);
+    }
+    if( rc ){
+      return 0;
+    }
+  }
+
+  if( i<0 ){
+    sqlite3Error(pErrorDb, SQLITE_ERROR, "unknown database %s", zDb);
+    return 0;
+  }
+
+  return pDb->aDb[i].pBt;
+}
+
+/*
+** Attempt to set the page size of the destination to match the page size
+** of the source.
+*/
+static int setDestPgsz(sqlite3_backup *p){
+  int rc;
+  rc = sqlite3BtreeSetPageSize(p->pDest,sqlite3BtreeGetPageSize(p->pSrc),-1,0);
+  return rc;
+}
+
+/*
+** Create an sqlite3_backup process to copy the contents of zSrcDb from
+** connection handle pSrcDb to zDestDb in pDestDb. If successful, return
+** a pointer to the new sqlite3_backup object.
+**
+** If an error occurs, NULL is returned and an error code and error message
+** stored in database handle pDestDb.
+*/
+sqlite3_backup *sqlite3_backup_init(
+  sqlite3* pDestDb,                     /* Database to write to */
+  const char *zDestDb,                  /* Name of database within pDestDb */
+  sqlite3* pSrcDb,                      /* Database connection to read from */
+  const char *zSrcDb                    /* Name of database within pSrcDb */
+){
+  sqlite3_backup *p;                    /* Value to return */
+
+  /* Lock the source database handle. The destination database
+  ** handle is not locked in this routine, but it is locked in
+  ** sqlite3_backup_step(). The user is required to ensure that no
+  ** other thread accesses the destination handle for the duration
+  ** of the backup operation.  Any attempt to use the destination
+  ** database connection while a backup is in progress may cause
+  ** a malfunction or a deadlock.
+  */
+  sqlite3_mutex_enter(pSrcDb->mutex);
+  sqlite3_mutex_enter(pDestDb->mutex);
+
+  if( pSrcDb==pDestDb ){
+    sqlite3Error(
+        pDestDb, SQLITE_ERROR, "source and destination must be distinct"
+    );
+    p = 0;
+  }else {
+    /* Allocate space for a new sqlite3_backup object...
+    ** EVIDENCE-OF: R-64852-21591 The sqlite3_backup object is created by a
+    ** call to sqlite3_backup_init() and is destroyed by a call to
+    ** sqlite3_backup_finish(). */
+    p = (sqlite3_backup *)sqlite3_malloc(sizeof(sqlite3_backup));
+    if( !p ){
+      sqlite3Error(pDestDb, SQLITE_NOMEM, 0);
+    }
+  }
+
+  /* If the allocation succeeded, populate the new object. */
+  if( p ){
+    memset(p, 0, sizeof(sqlite3_backup));
+    p->pSrc = findBtree(pDestDb, pSrcDb, zSrcDb);
+    p->pDest = findBtree(pDestDb, pDestDb, zDestDb);
+    p->pDestDb = pDestDb;
+    p->pSrcDb = pSrcDb;
+    p->iNext = 1;
+    p->isAttached = 0;
+
+    if( 0==p->pSrc || 0==p->pDest || setDestPgsz(p)==SQLITE_NOMEM ){
+      /* One (or both) of the named databases did not exist or an OOM
+      ** error was hit.  The error has already been written into the
+      ** pDestDb handle.  All that is left to do here is free the
+      ** sqlite3_backup structure.
+      */
+      sqlite3_free(p);
+      p = 0;
+    }
+  }
+  if( p ){
+    p->pSrc->nBackup++;
+  }
+
+  sqlite3_mutex_leave(pDestDb->mutex);
+  sqlite3_mutex_leave(pSrcDb->mutex);
+  return p;
+}
+
+/*
+** Argument rc is an SQLite error code. Return true if this error is 
+** considered fatal if encountered during a backup operation. All errors
+** are considered fatal except for SQLITE_BUSY and SQLITE_LOCKED.
+*/
+static int isFatalError(int rc){
+  return (rc!=SQLITE_OK && rc!=SQLITE_BUSY && ALWAYS(rc!=SQLITE_LOCKED));
+}
+
+/*
+** Parameter zSrcData points to a buffer containing the data for 
+** page iSrcPg from the source database. Copy this data into the 
+** destination database.
+*/
+static int backupOnePage(sqlite3_backup *p, Pgno iSrcPg, const u8 *zSrcData){
+  Pager * const pDestPager = sqlite3BtreePager(p->pDest);
+  const int nSrcPgsz = sqlite3BtreeGetPageSize(p->pSrc);
+  int nDestPgsz = sqlite3BtreeGetPageSize(p->pDest);
+  const int nCopy = MIN(nSrcPgsz, nDestPgsz);
+  const i64 iEnd = (i64)iSrcPg*(i64)nSrcPgsz;
+#ifdef SQLITE_HAS_CODEC
+  int nSrcReserve = sqlite3BtreeGetReserve(p->pSrc);
+  int nDestReserve = sqlite3BtreeGetReserve(p->pDest);
+#endif
+
+  int rc = SQLITE_OK;
+  i64 iOff;
+
+  assert( p->bDestLocked );
+  assert( !isFatalError(p->rc) );
+  assert( iSrcPg!=PENDING_BYTE_PAGE(p->pSrc->pBt) );
+  assert( zSrcData );
+
+  /* Catch the case where the destination is an in-memory database and the
+  ** page sizes of the source and destination differ. 
+  */
+  if( nSrcPgsz!=nDestPgsz && sqlite3PagerIsMemdb(pDestPager) ){
+    rc = SQLITE_READONLY;
+  }
+
+#ifdef SQLITE_HAS_CODEC
+  /* Backup is not possible if the page size of the destination is changing
+  ** and a codec is in use.
+  */
+  if( nSrcPgsz!=nDestPgsz && sqlite3PagerGetCodec(pDestPager)!=0 ){
+    rc = SQLITE_READONLY;
+  }
+
+  /* Backup is not possible if the number of bytes of reserve space differ
+  ** between source and destination.  If there is a difference, try to
+  ** fix the destination to agree with the source.  If that is not possible,
+  ** then the backup cannot proceed.
+  */
+  if( nSrcReserve!=nDestReserve ){
+    u32 newPgsz = nSrcPgsz;
+    rc = sqlite3PagerSetPagesize(pDestPager, &newPgsz, nSrcReserve);
+    if( rc==SQLITE_OK && newPgsz!=nSrcPgsz ) rc = SQLITE_READONLY;
+  }
+#endif
+
+  /* This loop runs once for each destination page spanned by the source 
+  ** page. For each iteration, variable iOff is set to the byte offset
+  ** of the destination page.
+  */
+  for(iOff=iEnd-(i64)nSrcPgsz; rc==SQLITE_OK && iOff<iEnd; iOff+=nDestPgsz){
+    DbPage *pDestPg = 0;
+    Pgno iDest = (Pgno)(iOff/nDestPgsz)+1;
+    if( iDest==PENDING_BYTE_PAGE(p->pDest->pBt) ) continue;
+    if( SQLITE_OK==(rc = sqlite3PagerGet(pDestPager, iDest, &pDestPg))
+     && SQLITE_OK==(rc = sqlite3PagerWrite(pDestPg))
+    ){
+      const u8 *zIn = &zSrcData[iOff%nSrcPgsz];
+      u8 *zDestData = sqlite3PagerGetData(pDestPg);
+      u8 *zOut = &zDestData[iOff%nDestPgsz];
+
+      /* Copy the data from the source page into the destination page.
+      ** Then clear the Btree layer MemPage.isInit flag. Both this module
+      ** and the pager code use this trick (clearing the first byte
+      ** of the page 'extra' space to invalidate the Btree layers
+      ** cached parse of the page). MemPage.isInit is marked 
+      ** "MUST BE FIRST" for this purpose.
+      */
+      memcpy(zOut, zIn, nCopy);
+      ((u8 *)sqlite3PagerGetExtra(pDestPg))[0] = 0;
+    }
+    sqlite3PagerUnref(pDestPg);
+  }
+
+  return rc;
+}
+
+/*
+** If pFile is currently larger than iSize bytes, then truncate it to
+** exactly iSize bytes. If pFile is not larger than iSize bytes, then
+** this function is a no-op.
+**
+** Return SQLITE_OK if everything is successful, or an SQLite error 
+** code if an error occurs.
+*/
+static int backupTruncateFile(sqlite3_file *pFile, i64 iSize){
+  i64 iCurrent;
+  int rc = sqlite3OsFileSize(pFile, &iCurrent);
+  if( rc==SQLITE_OK && iCurrent>iSize ){
+    rc = sqlite3OsTruncate(pFile, iSize);
+  }
+  return rc;
+}
+
+/*
+** Register this backup object with the associated source pager for
+** callbacks when pages are changed or the cache invalidated.
+*/
+static void attachBackupObject(sqlite3_backup *p){
+  sqlite3_backup **pp;
+  assert( sqlite3BtreeHoldsMutex(p->pSrc) );
+  pp = sqlite3PagerBackupPtr(sqlite3BtreePager(p->pSrc));
+  p->pNext = *pp;
+  *pp = p;
+  p->isAttached = 1;
+}
+
+/*
+** Copy nPage pages from the source b-tree to the destination.
+*/
+int sqlite3_backup_step(sqlite3_backup *p, int nPage){
+  int rc;
+  int destMode;       /* Destination journal mode */
+  int pgszSrc = 0;    /* Source page size */
+  int pgszDest = 0;   /* Destination page size */
+
+  sqlite3_mutex_enter(p->pSrcDb->mutex);
+  sqlite3BtreeEnter(p->pSrc);
+  if( p->pDestDb ){
+    sqlite3_mutex_enter(p->pDestDb->mutex);
+  }
+
+  rc = p->rc;
+  if( !isFatalError(rc) ){
+    Pager * const pSrcPager = sqlite3BtreePager(p->pSrc);     /* Source pager */
+    Pager * const pDestPager = sqlite3BtreePager(p->pDest);   /* Dest pager */
+    int ii;                            /* Iterator variable */
+    int nSrcPage = -1;                 /* Size of source db in pages */
+    int bCloseTrans = 0;               /* True if src db requires unlocking */
+
+    /* If the source pager is currently in a write-transaction, return
+    ** SQLITE_BUSY immediately.
+    */
+    if( p->pDestDb && p->pSrc->pBt->inTransaction==TRANS_WRITE ){
+      rc = SQLITE_BUSY;
+    }else{
+      rc = SQLITE_OK;
+    }
+
+    /* Lock the destination database, if it is not locked already. */
+    if( SQLITE_OK==rc && p->bDestLocked==0
+     && SQLITE_OK==(rc = sqlite3BtreeBeginTrans(p->pDest, 2)) 
+    ){
+      p->bDestLocked = 1;
+      sqlite3BtreeGetMeta(p->pDest, BTREE_SCHEMA_VERSION, &p->iDestSchema);
+    }
+
+    /* If there is no open read-transaction on the source database, open
+    ** one now. If a transaction is opened here, then it will be closed
+    ** before this function exits.
+    */
+    if( rc==SQLITE_OK && 0==sqlite3BtreeIsInReadTrans(p->pSrc) ){
+      rc = sqlite3BtreeBeginTrans(p->pSrc, 0);
+      bCloseTrans = 1;
+    }
+
+    /* Do not allow backup if the destination database is in WAL mode
+    ** and the page sizes are different between source and destination */
+    pgszSrc = sqlite3BtreeGetPageSize(p->pSrc);
+    pgszDest = sqlite3BtreeGetPageSize(p->pDest);
+    destMode = sqlite3PagerGetJournalMode(sqlite3BtreePager(p->pDest));
+    if( SQLITE_OK==rc && destMode==PAGER_JOURNALMODE_WAL && pgszSrc!=pgszDest ){
+      rc = SQLITE_READONLY;
+    }
+  
+    /* Now that there is a read-lock on the source database, query the
+    ** source pager for the number of pages in the database.
+    */
+    nSrcPage = (int)sqlite3BtreeLastPage(p->pSrc);
+    assert( nSrcPage>=0 );
+    for(ii=0; (nPage<0 || ii<nPage) && p->iNext<=(Pgno)nSrcPage && !rc; ii++){
+      const Pgno iSrcPg = p->iNext;                 /* Source page number */
+      if( iSrcPg!=PENDING_BYTE_PAGE(p->pSrc->pBt) ){
+        DbPage *pSrcPg;                             /* Source page object */
+        rc = sqlite3PagerGet(pSrcPager, iSrcPg, &pSrcPg);
+        if( rc==SQLITE_OK ){
+          rc = backupOnePage(p, iSrcPg, sqlite3PagerGetData(pSrcPg));
+          sqlite3PagerUnref(pSrcPg);
+        }
+      }
+      p->iNext++;
+    }
+    if( rc==SQLITE_OK ){
+      p->nPagecount = nSrcPage;
+      p->nRemaining = nSrcPage+1-p->iNext;
+      if( p->iNext>(Pgno)nSrcPage ){
+        rc = SQLITE_DONE;
+      }else if( !p->isAttached ){
+        attachBackupObject(p);
+      }
+    }
+  
+    /* Update the schema version field in the destination database. This
+    ** is to make sure that the schema-version really does change in
+    ** the case where the source and destination databases have the
+    ** same schema version.
+    */
+    if( rc==SQLITE_DONE ){
+      rc = sqlite3BtreeUpdateMeta(p->pDest,1,p->iDestSchema+1);
+      if( rc==SQLITE_OK ){
+        if( p->pDestDb ){
+          sqlite3ResetInternalSchema(p->pDestDb, -1);
+        }
+        if( destMode==PAGER_JOURNALMODE_WAL ){
+          rc = sqlite3BtreeSetVersion(p->pDest, 2);
+        }
+      }
+      if( rc==SQLITE_OK ){
+        int nDestTruncate;
+        /* Set nDestTruncate to the final number of pages in the destination
+        ** database. The complication here is that the destination page
+        ** size may be different to the source page size. 
+        **
+        ** If the source page size is smaller than the destination page size, 
+        ** round up. In this case the call to sqlite3OsTruncate() below will
+        ** fix the size of the file. However it is important to call
+        ** sqlite3PagerTruncateImage() here so that any pages in the 
+        ** destination file that lie beyond the nDestTruncate page mark are
+        ** journalled by PagerCommitPhaseOne() before they are destroyed
+        ** by the file truncation.
+        */
+        assert( pgszSrc==sqlite3BtreeGetPageSize(p->pSrc) );
+        assert( pgszDest==sqlite3BtreeGetPageSize(p->pDest) );
+        if( pgszSrc<pgszDest ){
+          int ratio = pgszDest/pgszSrc;
+          nDestTruncate = (nSrcPage+ratio-1)/ratio;
+          if( nDestTruncate==(int)PENDING_BYTE_PAGE(p->pDest->pBt) ){
+            nDestTruncate--;
+          }
+        }else{
+          nDestTruncate = nSrcPage * (pgszSrc/pgszDest);
+        }
+        sqlite3PagerTruncateImage(pDestPager, nDestTruncate);
+
+        if( pgszSrc<pgszDest ){
+          /* If the source page-size is smaller than the destination page-size,
+          ** two extra things may need to happen:
+          **
+          **   * The destination may need to be truncated, and
+          **
+          **   * Data stored on the pages immediately following the 
+          **     pending-byte page in the source database may need to be
+          **     copied into the destination database.
+          */
+          const i64 iSize = (i64)pgszSrc * (i64)nSrcPage;
+          sqlite3_file * const pFile = sqlite3PagerFile(pDestPager);
+          i64 iOff;
+          i64 iEnd;
+
+          assert( pFile );
+          assert( (i64)nDestTruncate*(i64)pgszDest >= iSize || (
+                nDestTruncate==(int)(PENDING_BYTE_PAGE(p->pDest->pBt)-1)
+             && iSize>=PENDING_BYTE && iSize<=PENDING_BYTE+pgszDest
+          ));
+
+          /* This call ensures that all data required to recreate the original
+          ** database has been stored in the journal for pDestPager and the
+          ** journal synced to disk. So at this point we may safely modify
+          ** the database file in any way, knowing that if a power failure
+          ** occurs, the original database will be reconstructed from the 
+          ** journal file.  */
+          rc = sqlite3PagerCommitPhaseOne(pDestPager, 0, 1);
+
+          /* Write the extra pages and truncate the database file as required */
+          iEnd = MIN(PENDING_BYTE + pgszDest, iSize);
+          for(
+            iOff=PENDING_BYTE+pgszSrc; 
+            rc==SQLITE_OK && iOff<iEnd; 
+            iOff+=pgszSrc
+          ){
+            PgHdr *pSrcPg = 0;
+            const Pgno iSrcPg = (Pgno)((iOff/pgszSrc)+1);
+            rc = sqlite3PagerGet(pSrcPager, iSrcPg, &pSrcPg);
+            if( rc==SQLITE_OK ){
+              u8 *zData = sqlite3PagerGetData(pSrcPg);
+              rc = sqlite3OsWrite(pFile, zData, pgszSrc, iOff);
+            }
+            sqlite3PagerUnref(pSrcPg);
+          }
+          if( rc==SQLITE_OK ){
+            rc = backupTruncateFile(pFile, iSize);
+          }
+
+          /* Sync the database file to disk. */
+          if( rc==SQLITE_OK ){
+            rc = sqlite3PagerSync(pDestPager);
+          }
+        }else{
+          rc = sqlite3PagerCommitPhaseOne(pDestPager, 0, 0);
+        }
+    
+        /* Finish committing the transaction to the destination database. */
+        if( SQLITE_OK==rc
+         && SQLITE_OK==(rc = sqlite3BtreeCommitPhaseTwo(p->pDest, 0))
+        ){
+          rc = SQLITE_DONE;
+        }
+      }
+    }
+  
+    /* If bCloseTrans is true, then this function opened a read transaction
+    ** on the source database. Close the read transaction here. There is
+    ** no need to check the return values of the btree methods here, as
+    ** "committing" a read-only transaction cannot fail.
+    */
+    if( bCloseTrans ){
+      TESTONLY( int rc2 );
+      TESTONLY( rc2  = ) sqlite3BtreeCommitPhaseOne(p->pSrc, 0);
+      TESTONLY( rc2 |= ) sqlite3BtreeCommitPhaseTwo(p->pSrc, 0);
+      assert( rc2==SQLITE_OK );
+    }
+  
+    if( rc==SQLITE_IOERR_NOMEM ){
+      rc = SQLITE_NOMEM;
+    }
+    p->rc = rc;
+  }
+  if( p->pDestDb ){
+    sqlite3_mutex_leave(p->pDestDb->mutex);
+  }
+  sqlite3BtreeLeave(p->pSrc);
+  sqlite3_mutex_leave(p->pSrcDb->mutex);
+  return rc;
+}
+
+/*
+** Release all resources associated with an sqlite3_backup* handle.
+*/
+int sqlite3_backup_finish(sqlite3_backup *p){
+  sqlite3_backup **pp;                 /* Ptr to head of pagers backup list */
+  MUTEX_LOGIC( sqlite3_mutex *mutex; ) /* Mutex to protect source database */
+  int rc;                              /* Value to return */
+
+  /* Enter the mutexes */
+  if( p==0 ) return SQLITE_OK;
+  sqlite3_mutex_enter(p->pSrcDb->mutex);
+  sqlite3BtreeEnter(p->pSrc);
+  MUTEX_LOGIC( mutex = p->pSrcDb->mutex; )
+  if( p->pDestDb ){
+    sqlite3_mutex_enter(p->pDestDb->mutex);
+  }
+
+  /* Detach this backup from the source pager. */
+  if( p->pDestDb ){
+    p->pSrc->nBackup--;
+  }
+  if( p->isAttached ){
+    pp = sqlite3PagerBackupPtr(sqlite3BtreePager(p->pSrc));
+    while( *pp!=p ){
+      pp = &(*pp)->pNext;
+    }
+    *pp = p->pNext;
+  }
+
+  /* If a transaction is still open on the Btree, roll it back. */
+  sqlite3BtreeRollback(p->pDest);
+
+  /* Set the error code of the destination database handle. */
+  rc = (p->rc==SQLITE_DONE) ? SQLITE_OK : p->rc;
+  sqlite3Error(p->pDestDb, rc, 0);
+
+  /* Exit the mutexes and free the backup context structure. */
+  if( p->pDestDb ){
+    sqlite3_mutex_leave(p->pDestDb->mutex);
+  }
+  sqlite3BtreeLeave(p->pSrc);
+  if( p->pDestDb ){
+    /* EVIDENCE-OF: R-64852-21591 The sqlite3_backup object is created by a
+    ** call to sqlite3_backup_init() and is destroyed by a call to
+    ** sqlite3_backup_finish(). */
+    sqlite3_free(p);
+  }
+  sqlite3_mutex_leave(mutex);
+  return rc;
+}
+
+/*
+** Return the number of pages still to be backed up as of the most recent
+** call to sqlite3_backup_step().
+*/
+int sqlite3_backup_remaining(sqlite3_backup *p){
+  return p->nRemaining;
+}
+
+/*
+** Return the total number of pages in the source database as of the most 
+** recent call to sqlite3_backup_step().
+*/
+int sqlite3_backup_pagecount(sqlite3_backup *p){
+  return p->nPagecount;
+}
+
+/*
+** This function is called after the contents of page iPage of the
+** source database have been modified. If page iPage has already been 
+** copied into the destination database, then the data written to the
+** destination is now invalidated. The destination copy of iPage needs
+** to be updated with the new data before the backup operation is
+** complete.
+**
+** It is assumed that the mutex associated with the BtShared object
+** corresponding to the source database is held when this function is
+** called.
+*/
+void sqlite3BackupUpdate(sqlite3_backup *pBackup, Pgno iPage, const u8 *aData){
+  sqlite3_backup *p;                   /* Iterator variable */
+  for(p=pBackup; p; p=p->pNext){
+    assert( sqlite3_mutex_held(p->pSrc->pBt->mutex) );
+    if( !isFatalError(p->rc) && iPage<p->iNext ){
+      /* The backup process p has already copied page iPage. But now it
+      ** has been modified by a transaction on the source pager. Copy
+      ** the new data into the backup.
+      */
+      int rc;
+      assert( p->pDestDb );
+      sqlite3_mutex_enter(p->pDestDb->mutex);
+      rc = backupOnePage(p, iPage, aData);
+      sqlite3_mutex_leave(p->pDestDb->mutex);
+      assert( rc!=SQLITE_BUSY && rc!=SQLITE_LOCKED );
+      if( rc!=SQLITE_OK ){
+        p->rc = rc;
+      }
+    }
+  }
+}
+
+/*
+** Restart the backup process. This is called when the pager layer
+** detects that the database has been modified by an external database
+** connection. In this case there is no way of knowing which of the
+** pages that have been copied into the destination database are still 
+** valid and which are not, so the entire process needs to be restarted.
+**
+** It is assumed that the mutex associated with the BtShared object
+** corresponding to the source database is held when this function is
+** called.
+*/
+void sqlite3BackupRestart(sqlite3_backup *pBackup){
+  sqlite3_backup *p;                   /* Iterator variable */
+  for(p=pBackup; p; p=p->pNext){
+    assert( sqlite3_mutex_held(p->pSrc->pBt->mutex) );
+    p->iNext = 1;
+  }
+}
+
+#ifndef SQLITE_OMIT_VACUUM
+/*
+** Copy the complete content of pBtFrom into pBtTo.  A transaction
+** must be active for both files.
+**
+** The size of file pTo may be reduced by this operation. If anything 
+** goes wrong, the transaction on pTo is rolled back. If successful, the 
+** transaction is committed before returning.
+*/
+int sqlite3BtreeCopyFile(Btree *pTo, Btree *pFrom){
+  int rc;
+  sqlite3_file *pFd;              /* File descriptor for database pTo */
+  sqlite3_backup b;
+  sqlite3BtreeEnter(pTo);
+  sqlite3BtreeEnter(pFrom);
+
+  assert( sqlite3BtreeIsInTrans(pTo) );
+  pFd = sqlite3PagerFile(sqlite3BtreePager(pTo));
+  if( pFd->pMethods ){
+    i64 nByte = sqlite3BtreeGetPageSize(pFrom)*(i64)sqlite3BtreeLastPage(pFrom);
+    sqlite3OsFileControl(pFd, SQLITE_FCNTL_OVERWRITE, &nByte);
+  }
+
+  /* Set up an sqlite3_backup object. sqlite3_backup.pDestDb must be set
+  ** to 0. This is used by the implementations of sqlite3_backup_step()
+  ** and sqlite3_backup_finish() to detect that they are being called
+  ** from this function, not directly by the user.
+  */
+  memset(&b, 0, sizeof(b));
+  b.pSrcDb = pFrom->db;
+  b.pSrc = pFrom;
+  b.pDest = pTo;
+  b.iNext = 1;
+
+  /* 0x7FFFFFFF is the hard limit for the number of pages in a database
+  ** file. By passing this as the number of pages to copy to
+  ** sqlite3_backup_step(), we can guarantee that the copy finishes 
+  ** within a single call (unless an error occurs). The assert() statement
+  ** checks this assumption - (p->rc) should be set to either SQLITE_DONE 
+  ** or an error code.
+  */
+  sqlite3_backup_step(&b, 0x7FFFFFFF);
+  assert( b.rc!=SQLITE_OK );
+  rc = sqlite3_backup_finish(&b);
+  if( rc==SQLITE_OK ){
+    pTo->pBt->pageSizeFixed = 0;
+  }else{
+    sqlite3PagerClearCache(sqlite3BtreePager(b.pDest));
+  }
+
+  assert( sqlite3BtreeIsInTrans(pTo)==0 );
+  sqlite3BtreeLeave(pFrom);
+  sqlite3BtreeLeave(pTo);
+  return rc;
+}
+#endif /* SQLITE_OMIT_VACUUM */
diff --git a/src/bitvec.c b/src/bitvec.c
new file mode 100644
index 0000000..47d33ea
--- /dev/null
+++ b/src/bitvec.c
@@ -0,0 +1,408 @@
+/*
+** 2008 February 16
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file implements an object that represents a fixed-length
+** bitmap.  Bits are numbered starting with 1.
+**
+** A bitmap is used to record which pages of a database file have been
+** journalled during a transaction, or which pages have the "dont-write"
+** property.  Usually only a few pages are meet either condition.
+** So the bitmap is usually sparse and has low cardinality.
+** But sometimes (for example when during a DROP of a large table) most
+** or all of the pages in a database can get journalled.  In those cases, 
+** the bitmap becomes dense with high cardinality.  The algorithm needs 
+** to handle both cases well.
+**
+** The size of the bitmap is fixed when the object is created.
+**
+** All bits are clear when the bitmap is created.  Individual bits
+** may be set or cleared one at a time.
+**
+** Test operations are about 100 times more common that set operations.
+** Clear operations are exceedingly rare.  There are usually between
+** 5 and 500 set operations per Bitvec object, though the number of sets can
+** sometimes grow into tens of thousands or larger.  The size of the
+** Bitvec object is the number of pages in the database file at the
+** start of a transaction, and is thus usually less than a few thousand,
+** but can be as large as 2 billion for a really big database.
+*/
+#include "sqliteInt.h"
+
+/* Size of the Bitvec structure in bytes. */
+#define BITVEC_SZ        512
+
+/* Round the union size down to the nearest pointer boundary, since that's how 
+** it will be aligned within the Bitvec struct. */
+#define BITVEC_USIZE     (((BITVEC_SZ-(3*sizeof(u32)))/sizeof(Bitvec*))*sizeof(Bitvec*))
+
+/* Type of the array "element" for the bitmap representation. 
+** Should be a power of 2, and ideally, evenly divide into BITVEC_USIZE. 
+** Setting this to the "natural word" size of your CPU may improve
+** performance. */
+#define BITVEC_TELEM     u8
+/* Size, in bits, of the bitmap element. */
+#define BITVEC_SZELEM    8
+/* Number of elements in a bitmap array. */
+#define BITVEC_NELEM     (BITVEC_USIZE/sizeof(BITVEC_TELEM))
+/* Number of bits in the bitmap array. */
+#define BITVEC_NBIT      (BITVEC_NELEM*BITVEC_SZELEM)
+
+/* Number of u32 values in hash table. */
+#define BITVEC_NINT      (BITVEC_USIZE/sizeof(u32))
+/* Maximum number of entries in hash table before 
+** sub-dividing and re-hashing. */
+#define BITVEC_MXHASH    (BITVEC_NINT/2)
+/* Hashing function for the aHash representation.
+** Empirical testing showed that the *37 multiplier 
+** (an arbitrary prime)in the hash function provided 
+** no fewer collisions than the no-op *1. */
+#define BITVEC_HASH(X)   (((X)*1)%BITVEC_NINT)
+
+#define BITVEC_NPTR      (BITVEC_USIZE/sizeof(Bitvec *))
+
+
+/*
+** A bitmap is an instance of the following structure.
+**
+** This bitmap records the existance of zero or more bits
+** with values between 1 and iSize, inclusive.
+**
+** There are three possible representations of the bitmap.
+** If iSize<=BITVEC_NBIT, then Bitvec.u.aBitmap[] is a straight
+** bitmap.  The least significant bit is bit 1.
+**
+** If iSize>BITVEC_NBIT and iDivisor==0 then Bitvec.u.aHash[] is
+** a hash table that will hold up to BITVEC_MXHASH distinct values.
+**
+** Otherwise, the value i is redirected into one of BITVEC_NPTR
+** sub-bitmaps pointed to by Bitvec.u.apSub[].  Each subbitmap
+** handles up to iDivisor separate values of i.  apSub[0] holds
+** values between 1 and iDivisor.  apSub[1] holds values between
+** iDivisor+1 and 2*iDivisor.  apSub[N] holds values between
+** N*iDivisor+1 and (N+1)*iDivisor.  Each subbitmap is normalized
+** to hold deal with values between 1 and iDivisor.
+*/
+struct Bitvec {
+  u32 iSize;      /* Maximum bit index.  Max iSize is 4,294,967,296. */
+  u32 nSet;       /* Number of bits that are set - only valid for aHash
+                  ** element.  Max is BITVEC_NINT.  For BITVEC_SZ of 512,
+                  ** this would be 125. */
+  u32 iDivisor;   /* Number of bits handled by each apSub[] entry. */
+                  /* Should >=0 for apSub element. */
+                  /* Max iDivisor is max(u32) / BITVEC_NPTR + 1.  */
+                  /* For a BITVEC_SZ of 512, this would be 34,359,739. */
+  union {
+    BITVEC_TELEM aBitmap[BITVEC_NELEM];    /* Bitmap representation */
+    u32 aHash[BITVEC_NINT];      /* Hash table representation */
+    Bitvec *apSub[BITVEC_NPTR];  /* Recursive representation */
+  } u;
+};
+
+/*
+** Create a new bitmap object able to handle bits between 0 and iSize,
+** inclusive.  Return a pointer to the new object.  Return NULL if 
+** malloc fails.
+*/
+Bitvec *sqlite3BitvecCreate(u32 iSize){
+  Bitvec *p;
+  assert( sizeof(*p)==BITVEC_SZ );
+  p = sqlite3MallocZero( sizeof(*p) );
+  if( p ){
+    p->iSize = iSize;
+  }
+  return p;
+}
+
+/*
+** Check to see if the i-th bit is set.  Return true or false.
+** If p is NULL (if the bitmap has not been created) or if
+** i is out of range, then return false.
+*/
+int sqlite3BitvecTest(Bitvec *p, u32 i){
+  if( p==0 ) return 0;
+  if( i>p->iSize || i==0 ) return 0;
+  i--;
+  while( p->iDivisor ){
+    u32 bin = i/p->iDivisor;
+    i = i%p->iDivisor;
+    p = p->u.apSub[bin];
+    if (!p) {
+      return 0;
+    }
+  }
+  if( p->iSize<=BITVEC_NBIT ){
+    return (p->u.aBitmap[i/BITVEC_SZELEM] & (1<<(i&(BITVEC_SZELEM-1))))!=0;
+  } else{
+    u32 h = BITVEC_HASH(i++);
+    while( p->u.aHash[h] ){
+      if( p->u.aHash[h]==i ) return 1;
+      h = (h+1) % BITVEC_NINT;
+    }
+    return 0;
+  }
+}
+
+/*
+** Set the i-th bit.  Return 0 on success and an error code if
+** anything goes wrong.
+**
+** This routine might cause sub-bitmaps to be allocated.  Failing
+** to get the memory needed to hold the sub-bitmap is the only
+** that can go wrong with an insert, assuming p and i are valid.
+**
+** The calling function must ensure that p is a valid Bitvec object
+** and that the value for "i" is within range of the Bitvec object.
+** Otherwise the behavior is undefined.
+*/
+int sqlite3BitvecSet(Bitvec *p, u32 i){
+  u32 h;
+  if( p==0 ) return SQLITE_OK;
+  assert( i>0 );
+  assert( i<=p->iSize );
+  i--;
+  while((p->iSize > BITVEC_NBIT) && p->iDivisor) {
+    u32 bin = i/p->iDivisor;
+    i = i%p->iDivisor;
+    if( p->u.apSub[bin]==0 ){
+      p->u.apSub[bin] = sqlite3BitvecCreate( p->iDivisor );
+      if( p->u.apSub[bin]==0 ) return SQLITE_NOMEM;
+    }
+    p = p->u.apSub[bin];
+  }
+  if( p->iSize<=BITVEC_NBIT ){
+    p->u.aBitmap[i/BITVEC_SZELEM] |= 1 << (i&(BITVEC_SZELEM-1));
+    return SQLITE_OK;
+  }
+  h = BITVEC_HASH(i++);
+  /* if there wasn't a hash collision, and this doesn't */
+  /* completely fill the hash, then just add it without */
+  /* worring about sub-dividing and re-hashing. */
+  if( !p->u.aHash[h] ){
+    if (p->nSet<(BITVEC_NINT-1)) {
+      goto bitvec_set_end;
+    } else {
+      goto bitvec_set_rehash;
+    }
+  }
+  /* there was a collision, check to see if it's already */
+  /* in hash, if not, try to find a spot for it */
+  do {
+    if( p->u.aHash[h]==i ) return SQLITE_OK;
+    h++;
+    if( h>=BITVEC_NINT ) h = 0;
+  } while( p->u.aHash[h] );
+  /* we didn't find it in the hash.  h points to the first */
+  /* available free spot. check to see if this is going to */
+  /* make our hash too "full".  */
+bitvec_set_rehash:
+  if( p->nSet>=BITVEC_MXHASH ){
+    unsigned int j;
+    int rc;
+    u32 *aiValues = sqlite3StackAllocRaw(0, sizeof(p->u.aHash));
+    if( aiValues==0 ){
+      return SQLITE_NOMEM;
+    }else{
+      memcpy(aiValues, p->u.aHash, sizeof(p->u.aHash));
+      memset(p->u.apSub, 0, sizeof(p->u.apSub));
+      p->iDivisor = (p->iSize + BITVEC_NPTR - 1)/BITVEC_NPTR;
+      rc = sqlite3BitvecSet(p, i);
+      for(j=0; j<BITVEC_NINT; j++){
+        if( aiValues[j] ) rc |= sqlite3BitvecSet(p, aiValues[j]);
+      }
+      sqlite3StackFree(0, aiValues);
+      return rc;
+    }
+  }
+bitvec_set_end:
+  p->nSet++;
+  p->u.aHash[h] = i;
+  return SQLITE_OK;
+}
+
+/*
+** Clear the i-th bit.
+**
+** pBuf must be a pointer to at least BITVEC_SZ bytes of temporary storage
+** that BitvecClear can use to rebuilt its hash table.
+*/
+void sqlite3BitvecClear(Bitvec *p, u32 i, void *pBuf){
+  if( p==0 ) return;
+  assert( i>0 );
+  i--;
+  while( p->iDivisor ){
+    u32 bin = i/p->iDivisor;
+    i = i%p->iDivisor;
+    p = p->u.apSub[bin];
+    if (!p) {
+      return;
+    }
+  }
+  if( p->iSize<=BITVEC_NBIT ){
+    p->u.aBitmap[i/BITVEC_SZELEM] &= ~(1 << (i&(BITVEC_SZELEM-1)));
+  }else{
+    unsigned int j;
+    u32 *aiValues = pBuf;
+    memcpy(aiValues, p->u.aHash, sizeof(p->u.aHash));
+    memset(p->u.aHash, 0, sizeof(p->u.aHash));
+    p->nSet = 0;
+    for(j=0; j<BITVEC_NINT; j++){
+      if( aiValues[j] && aiValues[j]!=(i+1) ){
+        u32 h = BITVEC_HASH(aiValues[j]-1);
+        p->nSet++;
+        while( p->u.aHash[h] ){
+          h++;
+          if( h>=BITVEC_NINT ) h = 0;
+        }
+        p->u.aHash[h] = aiValues[j];
+      }
+    }
+  }
+}
+
+/*
+** Destroy a bitmap object.  Reclaim all memory used.
+*/
+void sqlite3BitvecDestroy(Bitvec *p){
+  if( p==0 ) return;
+  if( p->iDivisor ){
+    unsigned int i;
+    for(i=0; i<BITVEC_NPTR; i++){
+      sqlite3BitvecDestroy(p->u.apSub[i]);
+    }
+  }
+  sqlite3_free(p);
+}
+
+/*
+** Return the value of the iSize parameter specified when Bitvec *p
+** was created.
+*/
+u32 sqlite3BitvecSize(Bitvec *p){
+  return p->iSize;
+}
+
+#ifndef SQLITE_OMIT_BUILTIN_TEST
+/*
+** Let V[] be an array of unsigned characters sufficient to hold
+** up to N bits.  Let I be an integer between 0 and N.  0<=I<N.
+** Then the following macros can be used to set, clear, or test
+** individual bits within V.
+*/
+#define SETBIT(V,I)      V[I>>3] |= (1<<(I&7))
+#define CLEARBIT(V,I)    V[I>>3] &= ~(1<<(I&7))
+#define TESTBIT(V,I)     (V[I>>3]&(1<<(I&7)))!=0
+
+/*
+** This routine runs an extensive test of the Bitvec code.
+**
+** The input is an array of integers that acts as a program
+** to test the Bitvec.  The integers are opcodes followed
+** by 0, 1, or 3 operands, depending on the opcode.  Another
+** opcode follows immediately after the last operand.
+**
+** There are 6 opcodes numbered from 0 through 5.  0 is the
+** "halt" opcode and causes the test to end.
+**
+**    0          Halt and return the number of errors
+**    1 N S X    Set N bits beginning with S and incrementing by X
+**    2 N S X    Clear N bits beginning with S and incrementing by X
+**    3 N        Set N randomly chosen bits
+**    4 N        Clear N randomly chosen bits
+**    5 N S X    Set N bits from S increment X in array only, not in bitvec
+**
+** The opcodes 1 through 4 perform set and clear operations are performed
+** on both a Bitvec object and on a linear array of bits obtained from malloc.
+** Opcode 5 works on the linear array only, not on the Bitvec.
+** Opcode 5 is used to deliberately induce a fault in order to
+** confirm that error detection works.
+**
+** At the conclusion of the test the linear array is compared
+** against the Bitvec object.  If there are any differences,
+** an error is returned.  If they are the same, zero is returned.
+**
+** If a memory allocation error occurs, return -1.
+*/
+int sqlite3BitvecBuiltinTest(int sz, int *aOp){
+  Bitvec *pBitvec = 0;
+  unsigned char *pV = 0;
+  int rc = -1;
+  int i, nx, pc, op;
+  void *pTmpSpace;
+
+  /* Allocate the Bitvec to be tested and a linear array of
+  ** bits to act as the reference */
+  pBitvec = sqlite3BitvecCreate( sz );
+  pV = sqlite3_malloc( (sz+7)/8 + 1 );
+  pTmpSpace = sqlite3_malloc(BITVEC_SZ);
+  if( pBitvec==0 || pV==0 || pTmpSpace==0  ) goto bitvec_end;
+  memset(pV, 0, (sz+7)/8 + 1);
+
+  /* NULL pBitvec tests */
+  sqlite3BitvecSet(0, 1);
+  sqlite3BitvecClear(0, 1, pTmpSpace);
+
+  /* Run the program */
+  pc = 0;
+  while( (op = aOp[pc])!=0 ){
+    switch( op ){
+      case 1:
+      case 2:
+      case 5: {
+        nx = 4;
+        i = aOp[pc+2] - 1;
+        aOp[pc+2] += aOp[pc+3];
+        break;
+      }
+      case 3:
+      case 4: 
+      default: {
+        nx = 2;
+        sqlite3_randomness(sizeof(i), &i);
+        break;
+      }
+    }
+    if( (--aOp[pc+1]) > 0 ) nx = 0;
+    pc += nx;
+    i = (i & 0x7fffffff)%sz;
+    if( (op & 1)!=0 ){
+      SETBIT(pV, (i+1));
+      if( op!=5 ){
+        if( sqlite3BitvecSet(pBitvec, i+1) ) goto bitvec_end;
+      }
+    }else{
+      CLEARBIT(pV, (i+1));
+      sqlite3BitvecClear(pBitvec, i+1, pTmpSpace);
+    }
+  }
+
+  /* Test to make sure the linear array exactly matches the
+  ** Bitvec object.  Start with the assumption that they do
+  ** match (rc==0).  Change rc to non-zero if a discrepancy
+  ** is found.
+  */
+  rc = sqlite3BitvecTest(0,0) + sqlite3BitvecTest(pBitvec, sz+1)
+          + sqlite3BitvecTest(pBitvec, 0)
+          + (sqlite3BitvecSize(pBitvec) - sz);
+  for(i=1; i<=sz; i++){
+    if(  (TESTBIT(pV,i))!=sqlite3BitvecTest(pBitvec,i) ){
+      rc = i;
+      break;
+    }
+  }
+
+  /* Free allocated structure */
+bitvec_end:
+  sqlite3_free(pTmpSpace);
+  sqlite3_free(pV);
+  sqlite3BitvecDestroy(pBitvec);
+  return rc;
+}
+#endif /* SQLITE_OMIT_BUILTIN_TEST */
diff --git a/src/btmutex.c b/src/btmutex.c
new file mode 100644
index 0000000..d87d4d5
--- /dev/null
+++ b/src/btmutex.c
@@ -0,0 +1,287 @@
+/*
+** 2007 August 27
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains code used to implement mutexes on Btree objects.
+** This code really belongs in btree.c.  But btree.c is getting too
+** big and we want to break it down some.  This packaged seemed like
+** a good breakout.
+*/
+#include "btreeInt.h"
+#ifndef SQLITE_OMIT_SHARED_CACHE
+#if SQLITE_THREADSAFE
+
+/*
+** Obtain the BtShared mutex associated with B-Tree handle p. Also,
+** set BtShared.db to the database handle associated with p and the
+** p->locked boolean to true.
+*/
+static void lockBtreeMutex(Btree *p){
+  assert( p->locked==0 );
+  assert( sqlite3_mutex_notheld(p->pBt->mutex) );
+  assert( sqlite3_mutex_held(p->db->mutex) );
+
+  sqlite3_mutex_enter(p->pBt->mutex);
+  p->pBt->db = p->db;
+  p->locked = 1;
+}
+
+/*
+** Release the BtShared mutex associated with B-Tree handle p and
+** clear the p->locked boolean.
+*/
+static void unlockBtreeMutex(Btree *p){
+  BtShared *pBt = p->pBt;
+  assert( p->locked==1 );
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  assert( sqlite3_mutex_held(p->db->mutex) );
+  assert( p->db==pBt->db );
+
+  sqlite3_mutex_leave(pBt->mutex);
+  p->locked = 0;
+}
+
+/*
+** Enter a mutex on the given BTree object.
+**
+** If the object is not sharable, then no mutex is ever required
+** and this routine is a no-op.  The underlying mutex is non-recursive.
+** But we keep a reference count in Btree.wantToLock so the behavior
+** of this interface is recursive.
+**
+** To avoid deadlocks, multiple Btrees are locked in the same order
+** by all database connections.  The p->pNext is a list of other
+** Btrees belonging to the same database connection as the p Btree
+** which need to be locked after p.  If we cannot get a lock on
+** p, then first unlock all of the others on p->pNext, then wait
+** for the lock to become available on p, then relock all of the
+** subsequent Btrees that desire a lock.
+*/
+void sqlite3BtreeEnter(Btree *p){
+  Btree *pLater;
+
+  /* Some basic sanity checking on the Btree.  The list of Btrees
+  ** connected by pNext and pPrev should be in sorted order by
+  ** Btree.pBt value. All elements of the list should belong to
+  ** the same connection. Only shared Btrees are on the list. */
+  assert( p->pNext==0 || p->pNext->pBt>p->pBt );
+  assert( p->pPrev==0 || p->pPrev->pBt<p->pBt );
+  assert( p->pNext==0 || p->pNext->db==p->db );
+  assert( p->pPrev==0 || p->pPrev->db==p->db );
+  assert( p->sharable || (p->pNext==0 && p->pPrev==0) );
+
+  /* Check for locking consistency */
+  assert( !p->locked || p->wantToLock>0 );
+  assert( p->sharable || p->wantToLock==0 );
+
+  /* We should already hold a lock on the database connection */
+  assert( sqlite3_mutex_held(p->db->mutex) );
+
+  /* Unless the database is sharable and unlocked, then BtShared.db
+  ** should already be set correctly. */
+  assert( (p->locked==0 && p->sharable) || p->pBt->db==p->db );
+
+  if( !p->sharable ) return;
+  p->wantToLock++;
+  if( p->locked ) return;
+
+  /* In most cases, we should be able to acquire the lock we
+  ** want without having to go throught the ascending lock
+  ** procedure that follows.  Just be sure not to block.
+  */
+  if( sqlite3_mutex_try(p->pBt->mutex)==SQLITE_OK ){
+    p->pBt->db = p->db;
+    p->locked = 1;
+    return;
+  }
+
+  /* To avoid deadlock, first release all locks with a larger
+  ** BtShared address.  Then acquire our lock.  Then reacquire
+  ** the other BtShared locks that we used to hold in ascending
+  ** order.
+  */
+  for(pLater=p->pNext; pLater; pLater=pLater->pNext){
+    assert( pLater->sharable );
+    assert( pLater->pNext==0 || pLater->pNext->pBt>pLater->pBt );
+    assert( !pLater->locked || pLater->wantToLock>0 );
+    if( pLater->locked ){
+      unlockBtreeMutex(pLater);
+    }
+  }
+  lockBtreeMutex(p);
+  for(pLater=p->pNext; pLater; pLater=pLater->pNext){
+    if( pLater->wantToLock ){
+      lockBtreeMutex(pLater);
+    }
+  }
+}
+
+/*
+** Exit the recursive mutex on a Btree.
+*/
+void sqlite3BtreeLeave(Btree *p){
+  if( p->sharable ){
+    assert( p->wantToLock>0 );
+    p->wantToLock--;
+    if( p->wantToLock==0 ){
+      unlockBtreeMutex(p);
+    }
+  }
+}
+
+#ifndef NDEBUG
+/*
+** Return true if the BtShared mutex is held on the btree, or if the
+** B-Tree is not marked as sharable.
+**
+** This routine is used only from within assert() statements.
+*/
+int sqlite3BtreeHoldsMutex(Btree *p){
+  assert( p->sharable==0 || p->locked==0 || p->wantToLock>0 );
+  assert( p->sharable==0 || p->locked==0 || p->db==p->pBt->db );
+  assert( p->sharable==0 || p->locked==0 || sqlite3_mutex_held(p->pBt->mutex) );
+  assert( p->sharable==0 || p->locked==0 || sqlite3_mutex_held(p->db->mutex) );
+
+  return (p->sharable==0 || p->locked);
+}
+#endif
+
+
+#ifndef SQLITE_OMIT_INCRBLOB
+/*
+** Enter and leave a mutex on a Btree given a cursor owned by that
+** Btree.  These entry points are used by incremental I/O and can be
+** omitted if that module is not used.
+*/
+void sqlite3BtreeEnterCursor(BtCursor *pCur){
+  sqlite3BtreeEnter(pCur->pBtree);
+}
+void sqlite3BtreeLeaveCursor(BtCursor *pCur){
+  sqlite3BtreeLeave(pCur->pBtree);
+}
+#endif /* SQLITE_OMIT_INCRBLOB */
+
+
+/*
+** Enter the mutex on every Btree associated with a database
+** connection.  This is needed (for example) prior to parsing
+** a statement since we will be comparing table and column names
+** against all schemas and we do not want those schemas being
+** reset out from under us.
+**
+** There is a corresponding leave-all procedures.
+**
+** Enter the mutexes in accending order by BtShared pointer address
+** to avoid the possibility of deadlock when two threads with
+** two or more btrees in common both try to lock all their btrees
+** at the same instant.
+*/
+void sqlite3BtreeEnterAll(sqlite3 *db){
+  int i;
+  Btree *p;
+  assert( sqlite3_mutex_held(db->mutex) );
+  for(i=0; i<db->nDb; i++){
+    p = db->aDb[i].pBt;
+    if( p ) sqlite3BtreeEnter(p);
+  }
+}
+void sqlite3BtreeLeaveAll(sqlite3 *db){
+  int i;
+  Btree *p;
+  assert( sqlite3_mutex_held(db->mutex) );
+  for(i=0; i<db->nDb; i++){
+    p = db->aDb[i].pBt;
+    if( p ) sqlite3BtreeLeave(p);
+  }
+}
+
+/*
+** Return true if a particular Btree requires a lock.  Return FALSE if
+** no lock is ever required since it is not sharable.
+*/
+int sqlite3BtreeSharable(Btree *p){
+  return p->sharable;
+}
+
+#ifndef NDEBUG
+/*
+** Return true if the current thread holds the database connection
+** mutex and all required BtShared mutexes.
+**
+** This routine is used inside assert() statements only.
+*/
+int sqlite3BtreeHoldsAllMutexes(sqlite3 *db){
+  int i;
+  if( !sqlite3_mutex_held(db->mutex) ){
+    return 0;
+  }
+  for(i=0; i<db->nDb; i++){
+    Btree *p;
+    p = db->aDb[i].pBt;
+    if( p && p->sharable &&
+         (p->wantToLock==0 || !sqlite3_mutex_held(p->pBt->mutex)) ){
+      return 0;
+    }
+  }
+  return 1;
+}
+#endif /* NDEBUG */
+
+#ifndef NDEBUG
+/*
+** Return true if the correct mutexes are held for accessing the
+** db->aDb[iDb].pSchema structure.  The mutexes required for schema
+** access are:
+**
+**   (1) The mutex on db
+**   (2) if iDb!=1, then the mutex on db->aDb[iDb].pBt.
+**
+** If pSchema is not NULL, then iDb is computed from pSchema and
+** db using sqlite3SchemaToIndex().
+*/
+int sqlite3SchemaMutexHeld(sqlite3 *db, int iDb, Schema *pSchema){
+  Btree *p;
+  assert( db!=0 );
+  if( pSchema ) iDb = sqlite3SchemaToIndex(db, pSchema);
+  assert( iDb>=0 && iDb<db->nDb );
+  if( !sqlite3_mutex_held(db->mutex) ) return 0;
+  if( iDb==1 ) return 1;
+  p = db->aDb[iDb].pBt;
+  assert( p!=0 );
+  return p->sharable==0 || p->locked==1;
+}
+#endif /* NDEBUG */
+
+#else /* SQLITE_THREADSAFE>0 above.  SQLITE_THREADSAFE==0 below */
+/*
+** The following are special cases for mutex enter routines for use
+** in single threaded applications that use shared cache.  Except for
+** these two routines, all mutex operations are no-ops in that case and
+** are null #defines in btree.h.
+**
+** If shared cache is disabled, then all btree mutex routines, including
+** the ones below, are no-ops and are null #defines in btree.h.
+*/
+
+void sqlite3BtreeEnter(Btree *p){
+  p->pBt->db = p->db;
+}
+void sqlite3BtreeEnterAll(sqlite3 *db){
+  int i;
+  for(i=0; i<db->nDb; i++){
+    Btree *p = db->aDb[i].pBt;
+    if( p ){
+      p->pBt->db = p->db;
+    }
+  }
+}
+#endif /* if SQLITE_THREADSAFE */
+#endif /* ifndef SQLITE_OMIT_SHARED_CACHE */
diff --git a/src/btree.c b/src/btree.c
new file mode 100644
index 0000000..d64e172
--- /dev/null
+++ b/src/btree.c
@@ -0,0 +1,8225 @@
+/*
+** 2004 April 6
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file implements a external (disk-based) database using BTrees.
+** See the header comment on "btreeInt.h" for additional information.
+** Including a description of file format and an overview of operation.
+*/
+#include "btreeInt.h"
+
+/*
+** The header string that appears at the beginning of every
+** SQLite database.
+*/
+static const char zMagicHeader[] = SQLITE_FILE_HEADER;
+
+/*
+** Set this global variable to 1 to enable tracing using the TRACE
+** macro.
+*/
+#if 0
+int sqlite3BtreeTrace=1;  /* True to enable tracing */
+# define TRACE(X)  if(sqlite3BtreeTrace){printf X;fflush(stdout);}
+#else
+# define TRACE(X)
+#endif
+
+/*
+** Extract a 2-byte big-endian integer from an array of unsigned bytes.
+** But if the value is zero, make it 65536.
+**
+** This routine is used to extract the "offset to cell content area" value
+** from the header of a btree page.  If the page size is 65536 and the page
+** is empty, the offset should be 65536, but the 2-byte value stores zero.
+** This routine makes the necessary adjustment to 65536.
+*/
+#define get2byteNotZero(X)  (((((int)get2byte(X))-1)&0xffff)+1)
+
+#ifndef SQLITE_OMIT_SHARED_CACHE
+/*
+** A list of BtShared objects that are eligible for participation
+** in shared cache.  This variable has file scope during normal builds,
+** but the test harness needs to access it so we make it global for 
+** test builds.
+**
+** Access to this variable is protected by SQLITE_MUTEX_STATIC_MASTER.
+*/
+#ifdef SQLITE_TEST
+BtShared *SQLITE_WSD sqlite3SharedCacheList = 0;
+#else
+static BtShared *SQLITE_WSD sqlite3SharedCacheList = 0;
+#endif
+#endif /* SQLITE_OMIT_SHARED_CACHE */
+
+#ifndef SQLITE_OMIT_SHARED_CACHE
+/*
+** Enable or disable the shared pager and schema features.
+**
+** This routine has no effect on existing database connections.
+** The shared cache setting effects only future calls to
+** sqlite3_open(), sqlite3_open16(), or sqlite3_open_v2().
+*/
+int sqlite3_enable_shared_cache(int enable){
+  sqlite3GlobalConfig.sharedCacheEnabled = enable;
+  return SQLITE_OK;
+}
+#endif
+
+
+
+#ifdef SQLITE_OMIT_SHARED_CACHE
+  /*
+  ** The functions querySharedCacheTableLock(), setSharedCacheTableLock(),
+  ** and clearAllSharedCacheTableLocks()
+  ** manipulate entries in the BtShared.pLock linked list used to store
+  ** shared-cache table level locks. If the library is compiled with the
+  ** shared-cache feature disabled, then there is only ever one user
+  ** of each BtShared structure and so this locking is not necessary. 
+  ** So define the lock related functions as no-ops.
+  */
+  #define querySharedCacheTableLock(a,b,c) SQLITE_OK
+  #define setSharedCacheTableLock(a,b,c) SQLITE_OK
+  #define clearAllSharedCacheTableLocks(a)
+  #define downgradeAllSharedCacheTableLocks(a)
+  #define hasSharedCacheTableLock(a,b,c,d) 1
+  #define hasReadConflicts(a, b) 0
+#endif
+
+#ifndef SQLITE_OMIT_SHARED_CACHE
+
+#ifdef SQLITE_DEBUG
+/*
+**** This function is only used as part of an assert() statement. ***
+**
+** Check to see if pBtree holds the required locks to read or write to the 
+** table with root page iRoot.   Return 1 if it does and 0 if not.
+**
+** For example, when writing to a table with root-page iRoot via 
+** Btree connection pBtree:
+**
+**    assert( hasSharedCacheTableLock(pBtree, iRoot, 0, WRITE_LOCK) );
+**
+** When writing to an index that resides in a sharable database, the 
+** caller should have first obtained a lock specifying the root page of
+** the corresponding table. This makes things a bit more complicated,
+** as this module treats each table as a separate structure. To determine
+** the table corresponding to the index being written, this
+** function has to search through the database schema.
+**
+** Instead of a lock on the table/index rooted at page iRoot, the caller may
+** hold a write-lock on the schema table (root page 1). This is also
+** acceptable.
+*/
+static int hasSharedCacheTableLock(
+  Btree *pBtree,         /* Handle that must hold lock */
+  Pgno iRoot,            /* Root page of b-tree */
+  int isIndex,           /* True if iRoot is the root of an index b-tree */
+  int eLockType          /* Required lock type (READ_LOCK or WRITE_LOCK) */
+){
+  Schema *pSchema = (Schema *)pBtree->pBt->pSchema;
+  Pgno iTab = 0;
+  BtLock *pLock;
+
+  /* If this database is not shareable, or if the client is reading
+  ** and has the read-uncommitted flag set, then no lock is required. 
+  ** Return true immediately.
+  */
+  if( (pBtree->sharable==0)
+   || (eLockType==READ_LOCK && (pBtree->db->flags & SQLITE_ReadUncommitted))
+  ){
+    return 1;
+  }
+
+  /* If the client is reading  or writing an index and the schema is
+  ** not loaded, then it is too difficult to actually check to see if
+  ** the correct locks are held.  So do not bother - just return true.
+  ** This case does not come up very often anyhow.
+  */
+  if( isIndex && (!pSchema || (pSchema->flags&DB_SchemaLoaded)==0) ){
+    return 1;
+  }
+
+  /* Figure out the root-page that the lock should be held on. For table
+  ** b-trees, this is just the root page of the b-tree being read or
+  ** written. For index b-trees, it is the root page of the associated
+  ** table.  */
+  if( isIndex ){
+    HashElem *p;
+    for(p=sqliteHashFirst(&pSchema->idxHash); p; p=sqliteHashNext(p)){
+      Index *pIdx = (Index *)sqliteHashData(p);
+      if( pIdx->tnum==(int)iRoot ){
+        iTab = pIdx->pTable->tnum;
+      }
+    }
+  }else{
+    iTab = iRoot;
+  }
+
+  /* Search for the required lock. Either a write-lock on root-page iTab, a 
+  ** write-lock on the schema table, or (if the client is reading) a
+  ** read-lock on iTab will suffice. Return 1 if any of these are found.  */
+  for(pLock=pBtree->pBt->pLock; pLock; pLock=pLock->pNext){
+    if( pLock->pBtree==pBtree 
+     && (pLock->iTable==iTab || (pLock->eLock==WRITE_LOCK && pLock->iTable==1))
+     && pLock->eLock>=eLockType 
+    ){
+      return 1;
+    }
+  }
+
+  /* Failed to find the required lock. */
+  return 0;
+}
+#endif /* SQLITE_DEBUG */
+
+#ifdef SQLITE_DEBUG
+/*
+**** This function may be used as part of assert() statements only. ****
+**
+** Return true if it would be illegal for pBtree to write into the
+** table or index rooted at iRoot because other shared connections are
+** simultaneously reading that same table or index.
+**
+** It is illegal for pBtree to write if some other Btree object that
+** shares the same BtShared object is currently reading or writing
+** the iRoot table.  Except, if the other Btree object has the
+** read-uncommitted flag set, then it is OK for the other object to
+** have a read cursor.
+**
+** For example, before writing to any part of the table or index
+** rooted at page iRoot, one should call:
+**
+**    assert( !hasReadConflicts(pBtree, iRoot) );
+*/
+static int hasReadConflicts(Btree *pBtree, Pgno iRoot){
+  BtCursor *p;
+  for(p=pBtree->pBt->pCursor; p; p=p->pNext){
+    if( p->pgnoRoot==iRoot 
+     && p->pBtree!=pBtree
+     && 0==(p->pBtree->db->flags & SQLITE_ReadUncommitted)
+    ){
+      return 1;
+    }
+  }
+  return 0;
+}
+#endif    /* #ifdef SQLITE_DEBUG */
+
+/*
+** Query to see if Btree handle p may obtain a lock of type eLock 
+** (READ_LOCK or WRITE_LOCK) on the table with root-page iTab. Return
+** SQLITE_OK if the lock may be obtained (by calling
+** setSharedCacheTableLock()), or SQLITE_LOCKED if not.
+*/
+static int querySharedCacheTableLock(Btree *p, Pgno iTab, u8 eLock){
+  BtShared *pBt = p->pBt;
+  BtLock *pIter;
+
+  assert( sqlite3BtreeHoldsMutex(p) );
+  assert( eLock==READ_LOCK || eLock==WRITE_LOCK );
+  assert( p->db!=0 );
+  assert( !(p->db->flags&SQLITE_ReadUncommitted)||eLock==WRITE_LOCK||iTab==1 );
+  
+  /* If requesting a write-lock, then the Btree must have an open write
+  ** transaction on this file. And, obviously, for this to be so there 
+  ** must be an open write transaction on the file itself.
+  */
+  assert( eLock==READ_LOCK || (p==pBt->pWriter && p->inTrans==TRANS_WRITE) );
+  assert( eLock==READ_LOCK || pBt->inTransaction==TRANS_WRITE );
+  
+  /* This routine is a no-op if the shared-cache is not enabled */
+  if( !p->sharable ){
+    return SQLITE_OK;
+  }
+
+  /* If some other connection is holding an exclusive lock, the
+  ** requested lock may not be obtained.
+  */
+  if( pBt->pWriter!=p && pBt->isExclusive ){
+    sqlite3ConnectionBlocked(p->db, pBt->pWriter->db);
+    return SQLITE_LOCKED_SHAREDCACHE;
+  }
+
+  for(pIter=pBt->pLock; pIter; pIter=pIter->pNext){
+    /* The condition (pIter->eLock!=eLock) in the following if(...) 
+    ** statement is a simplification of:
+    **
+    **   (eLock==WRITE_LOCK || pIter->eLock==WRITE_LOCK)
+    **
+    ** since we know that if eLock==WRITE_LOCK, then no other connection
+    ** may hold a WRITE_LOCK on any table in this file (since there can
+    ** only be a single writer).
+    */
+    assert( pIter->eLock==READ_LOCK || pIter->eLock==WRITE_LOCK );
+    assert( eLock==READ_LOCK || pIter->pBtree==p || pIter->eLock==READ_LOCK);
+    if( pIter->pBtree!=p && pIter->iTable==iTab && pIter->eLock!=eLock ){
+      sqlite3ConnectionBlocked(p->db, pIter->pBtree->db);
+      if( eLock==WRITE_LOCK ){
+        assert( p==pBt->pWriter );
+        pBt->isPending = 1;
+      }
+      return SQLITE_LOCKED_SHAREDCACHE;
+    }
+  }
+  return SQLITE_OK;
+}
+#endif /* !SQLITE_OMIT_SHARED_CACHE */
+
+#ifndef SQLITE_OMIT_SHARED_CACHE
+/*
+** Add a lock on the table with root-page iTable to the shared-btree used
+** by Btree handle p. Parameter eLock must be either READ_LOCK or 
+** WRITE_LOCK.
+**
+** This function assumes the following:
+**
+**   (a) The specified Btree object p is connected to a sharable
+**       database (one with the BtShared.sharable flag set), and
+**
+**   (b) No other Btree objects hold a lock that conflicts
+**       with the requested lock (i.e. querySharedCacheTableLock() has
+**       already been called and returned SQLITE_OK).
+**
+** SQLITE_OK is returned if the lock is added successfully. SQLITE_NOMEM 
+** is returned if a malloc attempt fails.
+*/
+static int setSharedCacheTableLock(Btree *p, Pgno iTable, u8 eLock){
+  BtShared *pBt = p->pBt;
+  BtLock *pLock = 0;
+  BtLock *pIter;
+
+  assert( sqlite3BtreeHoldsMutex(p) );
+  assert( eLock==READ_LOCK || eLock==WRITE_LOCK );
+  assert( p->db!=0 );
+
+  /* A connection with the read-uncommitted flag set will never try to
+  ** obtain a read-lock using this function. The only read-lock obtained
+  ** by a connection in read-uncommitted mode is on the sqlite_master 
+  ** table, and that lock is obtained in BtreeBeginTrans().  */
+  assert( 0==(p->db->flags&SQLITE_ReadUncommitted) || eLock==WRITE_LOCK );
+
+  /* This function should only be called on a sharable b-tree after it 
+  ** has been determined that no other b-tree holds a conflicting lock.  */
+  assert( p->sharable );
+  assert( SQLITE_OK==querySharedCacheTableLock(p, iTable, eLock) );
+
+  /* First search the list for an existing lock on this table. */
+  for(pIter=pBt->pLock; pIter; pIter=pIter->pNext){
+    if( pIter->iTable==iTable && pIter->pBtree==p ){
+      pLock = pIter;
+      break;
+    }
+  }
+
+  /* If the above search did not find a BtLock struct associating Btree p
+  ** with table iTable, allocate one and link it into the list.
+  */
+  if( !pLock ){
+    pLock = (BtLock *)sqlite3MallocZero(sizeof(BtLock));
+    if( !pLock ){
+      return SQLITE_NOMEM;
+    }
+    pLock->iTable = iTable;
+    pLock->pBtree = p;
+    pLock->pNext = pBt->pLock;
+    pBt->pLock = pLock;
+  }
+
+  /* Set the BtLock.eLock variable to the maximum of the current lock
+  ** and the requested lock. This means if a write-lock was already held
+  ** and a read-lock requested, we don't incorrectly downgrade the lock.
+  */
+  assert( WRITE_LOCK>READ_LOCK );
+  if( eLock>pLock->eLock ){
+    pLock->eLock = eLock;
+  }
+
+  return SQLITE_OK;
+}
+#endif /* !SQLITE_OMIT_SHARED_CACHE */
+
+#ifndef SQLITE_OMIT_SHARED_CACHE
+/*
+** Release all the table locks (locks obtained via calls to
+** the setSharedCacheTableLock() procedure) held by Btree object p.
+**
+** This function assumes that Btree p has an open read or write 
+** transaction. If it does not, then the BtShared.isPending variable
+** may be incorrectly cleared.
+*/
+static void clearAllSharedCacheTableLocks(Btree *p){
+  BtShared *pBt = p->pBt;
+  BtLock **ppIter = &pBt->pLock;
+
+  assert( sqlite3BtreeHoldsMutex(p) );
+  assert( p->sharable || 0==*ppIter );
+  assert( p->inTrans>0 );
+
+  while( *ppIter ){
+    BtLock *pLock = *ppIter;
+    assert( pBt->isExclusive==0 || pBt->pWriter==pLock->pBtree );
+    assert( pLock->pBtree->inTrans>=pLock->eLock );
+    if( pLock->pBtree==p ){
+      *ppIter = pLock->pNext;
+      assert( pLock->iTable!=1 || pLock==&p->lock );
+      if( pLock->iTable!=1 ){
+        sqlite3_free(pLock);
+      }
+    }else{
+      ppIter = &pLock->pNext;
+    }
+  }
+
+  assert( pBt->isPending==0 || pBt->pWriter );
+  if( pBt->pWriter==p ){
+    pBt->pWriter = 0;
+    pBt->isExclusive = 0;
+    pBt->isPending = 0;
+  }else if( pBt->nTransaction==2 ){
+    /* This function is called when Btree p is concluding its 
+    ** transaction. If there currently exists a writer, and p is not
+    ** that writer, then the number of locks held by connections other
+    ** than the writer must be about to drop to zero. In this case
+    ** set the isPending flag to 0.
+    **
+    ** If there is not currently a writer, then BtShared.isPending must
+    ** be zero already. So this next line is harmless in that case.
+    */
+    pBt->isPending = 0;
+  }
+}
+
+/*
+** This function changes all write-locks held by Btree p into read-locks.
+*/
+static void downgradeAllSharedCacheTableLocks(Btree *p){
+  BtShared *pBt = p->pBt;
+  if( pBt->pWriter==p ){
+    BtLock *pLock;
+    pBt->pWriter = 0;
+    pBt->isExclusive = 0;
+    pBt->isPending = 0;
+    for(pLock=pBt->pLock; pLock; pLock=pLock->pNext){
+      assert( pLock->eLock==READ_LOCK || pLock->pBtree==p );
+      pLock->eLock = READ_LOCK;
+    }
+  }
+}
+
+#endif /* SQLITE_OMIT_SHARED_CACHE */
+
+static void releasePage(MemPage *pPage);  /* Forward reference */
+
+/*
+***** This routine is used inside of assert() only ****
+**
+** Verify that the cursor holds the mutex on its BtShared
+*/
+#ifdef SQLITE_DEBUG
+static int cursorHoldsMutex(BtCursor *p){
+  return sqlite3_mutex_held(p->pBt->mutex);
+}
+#endif
+
+
+#ifndef SQLITE_OMIT_INCRBLOB
+/*
+** Invalidate the overflow page-list cache for cursor pCur, if any.
+*/
+static void invalidateOverflowCache(BtCursor *pCur){
+  assert( cursorHoldsMutex(pCur) );
+  sqlite3_free(pCur->aOverflow);
+  pCur->aOverflow = 0;
+}
+
+/*
+** Invalidate the overflow page-list cache for all cursors opened
+** on the shared btree structure pBt.
+*/
+static void invalidateAllOverflowCache(BtShared *pBt){
+  BtCursor *p;
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  for(p=pBt->pCursor; p; p=p->pNext){
+    invalidateOverflowCache(p);
+  }
+}
+
+/*
+** This function is called before modifying the contents of a table
+** to invalidate any incrblob cursors that are open on the
+** row or one of the rows being modified.
+**
+** If argument isClearTable is true, then the entire contents of the
+** table is about to be deleted. In this case invalidate all incrblob
+** cursors open on any row within the table with root-page pgnoRoot.
+**
+** Otherwise, if argument isClearTable is false, then the row with
+** rowid iRow is being replaced or deleted. In this case invalidate
+** only those incrblob cursors open on that specific row.
+*/
+static void invalidateIncrblobCursors(
+  Btree *pBtree,          /* The database file to check */
+  i64 iRow,               /* The rowid that might be changing */
+  int isClearTable        /* True if all rows are being deleted */
+){
+  BtCursor *p;
+  BtShared *pBt = pBtree->pBt;
+  assert( sqlite3BtreeHoldsMutex(pBtree) );
+  for(p=pBt->pCursor; p; p=p->pNext){
+    if( p->isIncrblobHandle && (isClearTable || p->info.nKey==iRow) ){
+      p->eState = CURSOR_INVALID;
+    }
+  }
+}
+
+#else
+  /* Stub functions when INCRBLOB is omitted */
+  #define invalidateOverflowCache(x)
+  #define invalidateAllOverflowCache(x)
+  #define invalidateIncrblobCursors(x,y,z)
+#endif /* SQLITE_OMIT_INCRBLOB */
+
+/*
+** Set bit pgno of the BtShared.pHasContent bitvec. This is called 
+** when a page that previously contained data becomes a free-list leaf 
+** page.
+**
+** The BtShared.pHasContent bitvec exists to work around an obscure
+** bug caused by the interaction of two useful IO optimizations surrounding
+** free-list leaf pages:
+**
+**   1) When all data is deleted from a page and the page becomes
+**      a free-list leaf page, the page is not written to the database
+**      (as free-list leaf pages contain no meaningful data). Sometimes
+**      such a page is not even journalled (as it will not be modified,
+**      why bother journalling it?).
+**
+**   2) When a free-list leaf page is reused, its content is not read
+**      from the database or written to the journal file (why should it
+**      be, if it is not at all meaningful?).
+**
+** By themselves, these optimizations work fine and provide a handy
+** performance boost to bulk delete or insert operations. However, if
+** a page is moved to the free-list and then reused within the same
+** transaction, a problem comes up. If the page is not journalled when
+** it is moved to the free-list and it is also not journalled when it
+** is extracted from the free-list and reused, then the original data
+** may be lost. In the event of a rollback, it may not be possible
+** to restore the database to its original configuration.
+**
+** The solution is the BtShared.pHasContent bitvec. Whenever a page is 
+** moved to become a free-list leaf page, the corresponding bit is
+** set in the bitvec. Whenever a leaf page is extracted from the free-list,
+** optimization 2 above is omitted if the corresponding bit is already
+** set in BtShared.pHasContent. The contents of the bitvec are cleared
+** at the end of every transaction.
+*/
+static int btreeSetHasContent(BtShared *pBt, Pgno pgno){
+  int rc = SQLITE_OK;
+  if( !pBt->pHasContent ){
+    assert( pgno<=pBt->nPage );
+    pBt->pHasContent = sqlite3BitvecCreate(pBt->nPage);
+    if( !pBt->pHasContent ){
+      rc = SQLITE_NOMEM;
+    }
+  }
+  if( rc==SQLITE_OK && pgno<=sqlite3BitvecSize(pBt->pHasContent) ){
+    rc = sqlite3BitvecSet(pBt->pHasContent, pgno);
+  }
+  return rc;
+}
+
+/*
+** Query the BtShared.pHasContent vector.
+**
+** This function is called when a free-list leaf page is removed from the
+** free-list for reuse. It returns false if it is safe to retrieve the
+** page from the pager layer with the 'no-content' flag set. True otherwise.
+*/
+static int btreeGetHasContent(BtShared *pBt, Pgno pgno){
+  Bitvec *p = pBt->pHasContent;
+  return (p && (pgno>sqlite3BitvecSize(p) || sqlite3BitvecTest(p, pgno)));
+}
+
+/*
+** Clear (destroy) the BtShared.pHasContent bitvec. This should be
+** invoked at the conclusion of each write-transaction.
+*/
+static void btreeClearHasContent(BtShared *pBt){
+  sqlite3BitvecDestroy(pBt->pHasContent);
+  pBt->pHasContent = 0;
+}
+
+/*
+** Save the current cursor position in the variables BtCursor.nKey 
+** and BtCursor.pKey. The cursor's state is set to CURSOR_REQUIRESEEK.
+**
+** The caller must ensure that the cursor is valid (has eState==CURSOR_VALID)
+** prior to calling this routine.  
+*/
+static int saveCursorPosition(BtCursor *pCur){
+  int rc;
+
+  assert( CURSOR_VALID==pCur->eState );
+  assert( 0==pCur->pKey );
+  assert( cursorHoldsMutex(pCur) );
+
+  rc = sqlite3BtreeKeySize(pCur, &pCur->nKey);
+  assert( rc==SQLITE_OK );  /* KeySize() cannot fail */
+
+  /* If this is an intKey table, then the above call to BtreeKeySize()
+  ** stores the integer key in pCur->nKey. In this case this value is
+  ** all that is required. Otherwise, if pCur is not open on an intKey
+  ** table, then malloc space for and store the pCur->nKey bytes of key 
+  ** data.
+  */
+  if( 0==pCur->apPage[0]->intKey ){
+    void *pKey = sqlite3Malloc( (int)pCur->nKey );
+    if( pKey ){
+      rc = sqlite3BtreeKey(pCur, 0, (int)pCur->nKey, pKey);
+      if( rc==SQLITE_OK ){
+        pCur->pKey = pKey;
+      }else{
+        sqlite3_free(pKey);
+      }
+    }else{
+      rc = SQLITE_NOMEM;
+    }
+  }
+  assert( !pCur->apPage[0]->intKey || !pCur->pKey );
+
+  if( rc==SQLITE_OK ){
+    int i;
+    for(i=0; i<=pCur->iPage; i++){
+      releasePage(pCur->apPage[i]);
+      pCur->apPage[i] = 0;
+    }
+    pCur->iPage = -1;
+    pCur->eState = CURSOR_REQUIRESEEK;
+  }
+
+  invalidateOverflowCache(pCur);
+  return rc;
+}
+
+/*
+** Save the positions of all cursors (except pExcept) that are open on
+** the table  with root-page iRoot. Usually, this is called just before cursor
+** pExcept is used to modify the table (BtreeDelete() or BtreeInsert()).
+*/
+static int saveAllCursors(BtShared *pBt, Pgno iRoot, BtCursor *pExcept){
+  BtCursor *p;
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  assert( pExcept==0 || pExcept->pBt==pBt );
+  for(p=pBt->pCursor; p; p=p->pNext){
+    if( p!=pExcept && (0==iRoot || p->pgnoRoot==iRoot) && 
+        p->eState==CURSOR_VALID ){
+      int rc = saveCursorPosition(p);
+      if( SQLITE_OK!=rc ){
+        return rc;
+      }
+    }
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Clear the current cursor position.
+*/
+void sqlite3BtreeClearCursor(BtCursor *pCur){
+  assert( cursorHoldsMutex(pCur) );
+  sqlite3_free(pCur->pKey);
+  pCur->pKey = 0;
+  pCur->eState = CURSOR_INVALID;
+}
+
+/*
+** In this version of BtreeMoveto, pKey is a packed index record
+** such as is generated by the OP_MakeRecord opcode.  Unpack the
+** record and then call BtreeMovetoUnpacked() to do the work.
+*/
+static int btreeMoveto(
+  BtCursor *pCur,     /* Cursor open on the btree to be searched */
+  const void *pKey,   /* Packed key if the btree is an index */
+  i64 nKey,           /* Integer key for tables.  Size of pKey for indices */
+  int bias,           /* Bias search to the high end */
+  int *pRes           /* Write search results here */
+){
+  int rc;                    /* Status code */
+  UnpackedRecord *pIdxKey;   /* Unpacked index key */
+  char aSpace[150];          /* Temp space for pIdxKey - to avoid a malloc */
+  char *pFree = 0;
+
+  if( pKey ){
+    assert( nKey==(i64)(int)nKey );
+    pIdxKey = sqlite3VdbeAllocUnpackedRecord(
+        pCur->pKeyInfo, aSpace, sizeof(aSpace), &pFree
+    );
+    if( pIdxKey==0 ) return SQLITE_NOMEM;
+    sqlite3VdbeRecordUnpack(pCur->pKeyInfo, (int)nKey, pKey, pIdxKey);
+  }else{
+    pIdxKey = 0;
+  }
+  rc = sqlite3BtreeMovetoUnpacked(pCur, pIdxKey, nKey, bias, pRes);
+  if( pFree ){
+    sqlite3DbFree(pCur->pKeyInfo->db, pFree);
+  }
+  return rc;
+}
+
+/*
+** Restore the cursor to the position it was in (or as close to as possible)
+** when saveCursorPosition() was called. Note that this call deletes the 
+** saved position info stored by saveCursorPosition(), so there can be
+** at most one effective restoreCursorPosition() call after each 
+** saveCursorPosition().
+*/
+static int btreeRestoreCursorPosition(BtCursor *pCur){
+  int rc;
+  assert( cursorHoldsMutex(pCur) );
+  assert( pCur->eState>=CURSOR_REQUIRESEEK );
+  if( pCur->eState==CURSOR_FAULT ){
+    return pCur->skipNext;
+  }
+  pCur->eState = CURSOR_INVALID;
+  rc = btreeMoveto(pCur, pCur->pKey, pCur->nKey, 0, &pCur->skipNext);
+  if( rc==SQLITE_OK ){
+    sqlite3_free(pCur->pKey);
+    pCur->pKey = 0;
+    assert( pCur->eState==CURSOR_VALID || pCur->eState==CURSOR_INVALID );
+  }
+  return rc;
+}
+
+#define restoreCursorPosition(p) \
+  (p->eState>=CURSOR_REQUIRESEEK ? \
+         btreeRestoreCursorPosition(p) : \
+         SQLITE_OK)
+
+/*
+** Determine whether or not a cursor has moved from the position it
+** was last placed at.  Cursors can move when the row they are pointing
+** at is deleted out from under them.
+**
+** This routine returns an error code if something goes wrong.  The
+** integer *pHasMoved is set to one if the cursor has moved and 0 if not.
+*/
+int sqlite3BtreeCursorHasMoved(BtCursor *pCur, int *pHasMoved){
+  int rc;
+
+  rc = restoreCursorPosition(pCur);
+  if( rc ){
+    *pHasMoved = 1;
+    return rc;
+  }
+  if( pCur->eState!=CURSOR_VALID || pCur->skipNext!=0 ){
+    *pHasMoved = 1;
+  }else{
+    *pHasMoved = 0;
+  }
+  return SQLITE_OK;
+}
+
+#ifndef SQLITE_OMIT_AUTOVACUUM
+/*
+** Given a page number of a regular database page, return the page
+** number for the pointer-map page that contains the entry for the
+** input page number.
+**
+** Return 0 (not a valid page) for pgno==1 since there is
+** no pointer map associated with page 1.  The integrity_check logic
+** requires that ptrmapPageno(*,1)!=1.
+*/
+static Pgno ptrmapPageno(BtShared *pBt, Pgno pgno){
+  int nPagesPerMapPage;
+  Pgno iPtrMap, ret;
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  if( pgno<2 ) return 0;
+  nPagesPerMapPage = (pBt->usableSize/5)+1;
+  iPtrMap = (pgno-2)/nPagesPerMapPage;
+  ret = (iPtrMap*nPagesPerMapPage) + 2; 
+  if( ret==PENDING_BYTE_PAGE(pBt) ){
+    ret++;
+  }
+  return ret;
+}
+
+/*
+** Write an entry into the pointer map.
+**
+** This routine updates the pointer map entry for page number 'key'
+** so that it maps to type 'eType' and parent page number 'pgno'.
+**
+** If *pRC is initially non-zero (non-SQLITE_OK) then this routine is
+** a no-op.  If an error occurs, the appropriate error code is written
+** into *pRC.
+*/
+static void ptrmapPut(BtShared *pBt, Pgno key, u8 eType, Pgno parent, int *pRC){
+  DbPage *pDbPage;  /* The pointer map page */
+  u8 *pPtrmap;      /* The pointer map data */
+  Pgno iPtrmap;     /* The pointer map page number */
+  int offset;       /* Offset in pointer map page */
+  int rc;           /* Return code from subfunctions */
+
+  if( *pRC ) return;
+
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  /* The master-journal page number must never be used as a pointer map page */
+  assert( 0==PTRMAP_ISPAGE(pBt, PENDING_BYTE_PAGE(pBt)) );
+
+  assert( pBt->autoVacuum );
+  if( key==0 ){
+    *pRC = SQLITE_CORRUPT_BKPT;
+    return;
+  }
+  iPtrmap = PTRMAP_PAGENO(pBt, key);
+  rc = sqlite3PagerGet(pBt->pPager, iPtrmap, &pDbPage);
+  if( rc!=SQLITE_OK ){
+    *pRC = rc;
+    return;
+  }
+  offset = PTRMAP_PTROFFSET(iPtrmap, key);
+  if( offset<0 ){
+    *pRC = SQLITE_CORRUPT_BKPT;
+    goto ptrmap_exit;
+  }
+  assert( offset <= (int)pBt->usableSize-5 );
+  pPtrmap = (u8 *)sqlite3PagerGetData(pDbPage);
+
+  if( eType!=pPtrmap[offset] || get4byte(&pPtrmap[offset+1])!=parent ){
+    TRACE(("PTRMAP_UPDATE: %d->(%d,%d)\n", key, eType, parent));
+    *pRC= rc = sqlite3PagerWrite(pDbPage);
+    if( rc==SQLITE_OK ){
+      pPtrmap[offset] = eType;
+      put4byte(&pPtrmap[offset+1], parent);
+    }
+  }
+
+ptrmap_exit:
+  sqlite3PagerUnref(pDbPage);
+}
+
+/*
+** Read an entry from the pointer map.
+**
+** This routine retrieves the pointer map entry for page 'key', writing
+** the type and parent page number to *pEType and *pPgno respectively.
+** An error code is returned if something goes wrong, otherwise SQLITE_OK.
+*/
+static int ptrmapGet(BtShared *pBt, Pgno key, u8 *pEType, Pgno *pPgno){
+  DbPage *pDbPage;   /* The pointer map page */
+  int iPtrmap;       /* Pointer map page index */
+  u8 *pPtrmap;       /* Pointer map page data */
+  int offset;        /* Offset of entry in pointer map */
+  int rc;
+
+  assert( sqlite3_mutex_held(pBt->mutex) );
+
+  iPtrmap = PTRMAP_PAGENO(pBt, key);
+  rc = sqlite3PagerGet(pBt->pPager, iPtrmap, &pDbPage);
+  if( rc!=0 ){
+    return rc;
+  }
+  pPtrmap = (u8 *)sqlite3PagerGetData(pDbPage);
+
+  offset = PTRMAP_PTROFFSET(iPtrmap, key);
+  if( offset<0 ){
+    sqlite3PagerUnref(pDbPage);
+    return SQLITE_CORRUPT_BKPT;
+  }
+  assert( offset <= (int)pBt->usableSize-5 );
+  assert( pEType!=0 );
+  *pEType = pPtrmap[offset];
+  if( pPgno ) *pPgno = get4byte(&pPtrmap[offset+1]);
+
+  sqlite3PagerUnref(pDbPage);
+  if( *pEType<1 || *pEType>5 ) return SQLITE_CORRUPT_BKPT;
+  return SQLITE_OK;
+}
+
+#else /* if defined SQLITE_OMIT_AUTOVACUUM */
+  #define ptrmapPut(w,x,y,z,rc)
+  #define ptrmapGet(w,x,y,z) SQLITE_OK
+  #define ptrmapPutOvflPtr(x, y, rc)
+#endif
+
+/*
+** Given a btree page and a cell index (0 means the first cell on
+** the page, 1 means the second cell, and so forth) return a pointer
+** to the cell content.
+**
+** This routine works only for pages that do not contain overflow cells.
+*/
+#define findCell(P,I) \
+  ((P)->aData + ((P)->maskPage & get2byte(&(P)->aData[(P)->cellOffset+2*(I)])))
+#define findCellv2(D,M,O,I) (D+(M&get2byte(D+(O+2*(I)))))
+
+
+/*
+** This a more complex version of findCell() that works for
+** pages that do contain overflow cells.
+*/
+static u8 *findOverflowCell(MemPage *pPage, int iCell){
+  int i;
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  for(i=pPage->nOverflow-1; i>=0; i--){
+    int k;
+    struct _OvflCell *pOvfl;
+    pOvfl = &pPage->aOvfl[i];
+    k = pOvfl->idx;
+    if( k<=iCell ){
+      if( k==iCell ){
+        return pOvfl->pCell;
+      }
+      iCell--;
+    }
+  }
+  return findCell(pPage, iCell);
+}
+
+/*
+** Parse a cell content block and fill in the CellInfo structure.  There
+** are two versions of this function.  btreeParseCell() takes a 
+** cell index as the second argument and btreeParseCellPtr() 
+** takes a pointer to the body of the cell as its second argument.
+**
+** Within this file, the parseCell() macro can be called instead of
+** btreeParseCellPtr(). Using some compilers, this will be faster.
+*/
+static void btreeParseCellPtr(
+  MemPage *pPage,         /* Page containing the cell */
+  u8 *pCell,              /* Pointer to the cell text. */
+  CellInfo *pInfo         /* Fill in this structure */
+){
+  u16 n;                  /* Number bytes in cell content header */
+  u32 nPayload;           /* Number of bytes of cell payload */
+
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+
+  pInfo->pCell = pCell;
+  assert( pPage->leaf==0 || pPage->leaf==1 );
+  n = pPage->childPtrSize;
+  assert( n==4-4*pPage->leaf );
+  if( pPage->intKey ){
+    if( pPage->hasData ){
+      n += getVarint32(&pCell[n], nPayload);
+    }else{
+      nPayload = 0;
+    }
+    n += getVarint(&pCell[n], (u64*)&pInfo->nKey);
+    pInfo->nData = nPayload;
+  }else{
+    pInfo->nData = 0;
+    n += getVarint32(&pCell[n], nPayload);
+    pInfo->nKey = nPayload;
+  }
+  pInfo->nPayload = nPayload;
+  pInfo->nHeader = n;
+  testcase( nPayload==pPage->maxLocal );
+  testcase( nPayload==pPage->maxLocal+1 );
+  if( likely(nPayload<=pPage->maxLocal) ){
+    /* This is the (easy) common case where the entire payload fits
+    ** on the local page.  No overflow is required.
+    */
+    if( (pInfo->nSize = (u16)(n+nPayload))<4 ) pInfo->nSize = 4;
+    pInfo->nLocal = (u16)nPayload;
+    pInfo->iOverflow = 0;
+  }else{
+    /* If the payload will not fit completely on the local page, we have
+    ** to decide how much to store locally and how much to spill onto
+    ** overflow pages.  The strategy is to minimize the amount of unused
+    ** space on overflow pages while keeping the amount of local storage
+    ** in between minLocal and maxLocal.
+    **
+    ** Warning:  changing the way overflow payload is distributed in any
+    ** way will result in an incompatible file format.
+    */
+    int minLocal;  /* Minimum amount of payload held locally */
+    int maxLocal;  /* Maximum amount of payload held locally */
+    int surplus;   /* Overflow payload available for local storage */
+
+    minLocal = pPage->minLocal;
+    maxLocal = pPage->maxLocal;
+    surplus = minLocal + (nPayload - minLocal)%(pPage->pBt->usableSize - 4);
+    testcase( surplus==maxLocal );
+    testcase( surplus==maxLocal+1 );
+    if( surplus <= maxLocal ){
+      pInfo->nLocal = (u16)surplus;
+    }else{
+      pInfo->nLocal = (u16)minLocal;
+    }
+    pInfo->iOverflow = (u16)(pInfo->nLocal + n);
+    pInfo->nSize = pInfo->iOverflow + 4;
+  }
+}
+#define parseCell(pPage, iCell, pInfo) \
+  btreeParseCellPtr((pPage), findCell((pPage), (iCell)), (pInfo))
+static void btreeParseCell(
+  MemPage *pPage,         /* Page containing the cell */
+  int iCell,              /* The cell index.  First cell is 0 */
+  CellInfo *pInfo         /* Fill in this structure */
+){
+  parseCell(pPage, iCell, pInfo);
+}
+
+/*
+** Compute the total number of bytes that a Cell needs in the cell
+** data area of the btree-page.  The return number includes the cell
+** data header and the local payload, but not any overflow page or
+** the space used by the cell pointer.
+*/
+static u16 cellSizePtr(MemPage *pPage, u8 *pCell){
+  u8 *pIter = &pCell[pPage->childPtrSize];
+  u32 nSize;
+
+#ifdef SQLITE_DEBUG
+  /* The value returned by this function should always be the same as
+  ** the (CellInfo.nSize) value found by doing a full parse of the
+  ** cell. If SQLITE_DEBUG is defined, an assert() at the bottom of
+  ** this function verifies that this invariant is not violated. */
+  CellInfo debuginfo;
+  btreeParseCellPtr(pPage, pCell, &debuginfo);
+#endif
+
+  if( pPage->intKey ){
+    u8 *pEnd;
+    if( pPage->hasData ){
+      pIter += getVarint32(pIter, nSize);
+    }else{
+      nSize = 0;
+    }
+
+    /* pIter now points at the 64-bit integer key value, a variable length 
+    ** integer. The following block moves pIter to point at the first byte
+    ** past the end of the key value. */
+    pEnd = &pIter[9];
+    while( (*pIter++)&0x80 && pIter<pEnd );
+  }else{
+    pIter += getVarint32(pIter, nSize);
+  }
+
+  testcase( nSize==pPage->maxLocal );
+  testcase( nSize==pPage->maxLocal+1 );
+  if( nSize>pPage->maxLocal ){
+    int minLocal = pPage->minLocal;
+    nSize = minLocal + (nSize - minLocal) % (pPage->pBt->usableSize - 4);
+    testcase( nSize==pPage->maxLocal );
+    testcase( nSize==pPage->maxLocal+1 );
+    if( nSize>pPage->maxLocal ){
+      nSize = minLocal;
+    }
+    nSize += 4;
+  }
+  nSize += (u32)(pIter - pCell);
+
+  /* The minimum size of any cell is 4 bytes. */
+  if( nSize<4 ){
+    nSize = 4;
+  }
+
+  assert( nSize==debuginfo.nSize );
+  return (u16)nSize;
+}
+
+#ifdef SQLITE_DEBUG
+/* This variation on cellSizePtr() is used inside of assert() statements
+** only. */
+static u16 cellSize(MemPage *pPage, int iCell){
+  return cellSizePtr(pPage, findCell(pPage, iCell));
+}
+#endif
+
+#ifndef SQLITE_OMIT_AUTOVACUUM
+/*
+** If the cell pCell, part of page pPage contains a pointer
+** to an overflow page, insert an entry into the pointer-map
+** for the overflow page.
+*/
+static void ptrmapPutOvflPtr(MemPage *pPage, u8 *pCell, int *pRC){
+  CellInfo info;
+  if( *pRC ) return;
+  assert( pCell!=0 );
+  btreeParseCellPtr(pPage, pCell, &info);
+  assert( (info.nData+(pPage->intKey?0:info.nKey))==info.nPayload );
+  if( info.iOverflow ){
+    Pgno ovfl = get4byte(&pCell[info.iOverflow]);
+    ptrmapPut(pPage->pBt, ovfl, PTRMAP_OVERFLOW1, pPage->pgno, pRC);
+  }
+}
+#endif
+
+
+/*
+** Defragment the page given.  All Cells are moved to the
+** end of the page and all free space is collected into one
+** big FreeBlk that occurs in between the header and cell
+** pointer array and the cell content area.
+*/
+static int defragmentPage(MemPage *pPage){
+  int i;                     /* Loop counter */
+  int pc;                    /* Address of a i-th cell */
+  int hdr;                   /* Offset to the page header */
+  int size;                  /* Size of a cell */
+  int usableSize;            /* Number of usable bytes on a page */
+  int cellOffset;            /* Offset to the cell pointer array */
+  int cbrk;                  /* Offset to the cell content area */
+  int nCell;                 /* Number of cells on the page */
+  unsigned char *data;       /* The page data */
+  unsigned char *temp;       /* Temp area for cell content */
+  int iCellFirst;            /* First allowable cell index */
+  int iCellLast;             /* Last possible cell index */
+
+
+  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
+  assert( pPage->pBt!=0 );
+  assert( pPage->pBt->usableSize <= SQLITE_MAX_PAGE_SIZE );
+  assert( pPage->nOverflow==0 );
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  temp = sqlite3PagerTempSpace(pPage->pBt->pPager);
+  data = pPage->aData;
+  hdr = pPage->hdrOffset;
+  cellOffset = pPage->cellOffset;
+  nCell = pPage->nCell;
+  assert( nCell==get2byte(&data[hdr+3]) );
+  usableSize = pPage->pBt->usableSize;
+  cbrk = get2byte(&data[hdr+5]);
+  memcpy(&temp[cbrk], &data[cbrk], usableSize - cbrk);
+  cbrk = usableSize;
+  iCellFirst = cellOffset + 2*nCell;
+  iCellLast = usableSize - 4;
+  for(i=0; i<nCell; i++){
+    u8 *pAddr;     /* The i-th cell pointer */
+    pAddr = &data[cellOffset + i*2];
+    pc = get2byte(pAddr);
+    testcase( pc==iCellFirst );
+    testcase( pc==iCellLast );
+#if !defined(SQLITE_ENABLE_OVERSIZE_CELL_CHECK)
+    /* These conditions have already been verified in btreeInitPage()
+    ** if SQLITE_ENABLE_OVERSIZE_CELL_CHECK is defined 
+    */
+    if( pc<iCellFirst || pc>iCellLast ){
+      return SQLITE_CORRUPT_BKPT;
+    }
+#endif
+    assert( pc>=iCellFirst && pc<=iCellLast );
+    size = cellSizePtr(pPage, &temp[pc]);
+    cbrk -= size;
+#if defined(SQLITE_ENABLE_OVERSIZE_CELL_CHECK)
+    if( cbrk<iCellFirst ){
+      return SQLITE_CORRUPT_BKPT;
+    }
+#else
+    if( cbrk<iCellFirst || pc+size>usableSize ){
+      return SQLITE_CORRUPT_BKPT;
+    }
+#endif
+    assert( cbrk+size<=usableSize && cbrk>=iCellFirst );
+    testcase( cbrk+size==usableSize );
+    testcase( pc+size==usableSize );
+    memcpy(&data[cbrk], &temp[pc], size);
+    put2byte(pAddr, cbrk);
+  }
+  assert( cbrk>=iCellFirst );
+  put2byte(&data[hdr+5], cbrk);
+  data[hdr+1] = 0;
+  data[hdr+2] = 0;
+  data[hdr+7] = 0;
+  memset(&data[iCellFirst], 0, cbrk-iCellFirst);
+  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
+  if( cbrk-iCellFirst!=pPage->nFree ){
+    return SQLITE_CORRUPT_BKPT;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Allocate nByte bytes of space from within the B-Tree page passed
+** as the first argument. Write into *pIdx the index into pPage->aData[]
+** of the first byte of allocated space. Return either SQLITE_OK or
+** an error code (usually SQLITE_CORRUPT).
+**
+** The caller guarantees that there is sufficient space to make the
+** allocation.  This routine might need to defragment in order to bring
+** all the space together, however.  This routine will avoid using
+** the first two bytes past the cell pointer area since presumably this
+** allocation is being made in order to insert a new cell, so we will
+** also end up needing a new cell pointer.
+*/
+static int allocateSpace(MemPage *pPage, int nByte, int *pIdx){
+  const int hdr = pPage->hdrOffset;    /* Local cache of pPage->hdrOffset */
+  u8 * const data = pPage->aData;      /* Local cache of pPage->aData */
+  int nFrag;                           /* Number of fragmented bytes on pPage */
+  int top;                             /* First byte of cell content area */
+  int gap;        /* First byte of gap between cell pointers and cell content */
+  int rc;         /* Integer return code */
+  int usableSize; /* Usable size of the page */
+  
+  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
+  assert( pPage->pBt );
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  assert( nByte>=0 );  /* Minimum cell size is 4 */
+  assert( pPage->nFree>=nByte );
+  assert( pPage->nOverflow==0 );
+  usableSize = pPage->pBt->usableSize;
+  assert( nByte < usableSize-8 );
+
+  nFrag = data[hdr+7];
+  assert( pPage->cellOffset == hdr + 12 - 4*pPage->leaf );
+  gap = pPage->cellOffset + 2*pPage->nCell;
+  top = get2byteNotZero(&data[hdr+5]);
+  if( gap>top ) return SQLITE_CORRUPT_BKPT;
+  testcase( gap+2==top );
+  testcase( gap+1==top );
+  testcase( gap==top );
+
+  if( nFrag>=60 ){
+    /* Always defragment highly fragmented pages */
+    rc = defragmentPage(pPage);
+    if( rc ) return rc;
+    top = get2byteNotZero(&data[hdr+5]);
+  }else if( gap+2<=top ){
+    /* Search the freelist looking for a free slot big enough to satisfy 
+    ** the request. The allocation is made from the first free slot in 
+    ** the list that is large enough to accomadate it.
+    */
+    int pc, addr;
+    for(addr=hdr+1; (pc = get2byte(&data[addr]))>0; addr=pc){
+      int size;            /* Size of the free slot */
+      if( pc>usableSize-4 || pc<addr+4 ){
+        return SQLITE_CORRUPT_BKPT;
+      }
+      size = get2byte(&data[pc+2]);
+      if( size>=nByte ){
+        int x = size - nByte;
+        testcase( x==4 );
+        testcase( x==3 );
+        if( x<4 ){
+          /* Remove the slot from the free-list. Update the number of
+          ** fragmented bytes within the page. */
+          memcpy(&data[addr], &data[pc], 2);
+          data[hdr+7] = (u8)(nFrag + x);
+        }else if( size+pc > usableSize ){
+          return SQLITE_CORRUPT_BKPT;
+        }else{
+          /* The slot remains on the free-list. Reduce its size to account
+          ** for the portion used by the new allocation. */
+          put2byte(&data[pc+2], x);
+        }
+        *pIdx = pc + x;
+        return SQLITE_OK;
+      }
+    }
+  }
+
+  /* Check to make sure there is enough space in the gap to satisfy
+  ** the allocation.  If not, defragment.
+  */
+  testcase( gap+2+nByte==top );
+  if( gap+2+nByte>top ){
+    rc = defragmentPage(pPage);
+    if( rc ) return rc;
+    top = get2byteNotZero(&data[hdr+5]);
+    assert( gap+nByte<=top );
+  }
+
+
+  /* Allocate memory from the gap in between the cell pointer array
+  ** and the cell content area.  The btreeInitPage() call has already
+  ** validated the freelist.  Given that the freelist is valid, there
+  ** is no way that the allocation can extend off the end of the page.
+  ** The assert() below verifies the previous sentence.
+  */
+  top -= nByte;
+  put2byte(&data[hdr+5], top);
+  assert( top+nByte <= (int)pPage->pBt->usableSize );
+  *pIdx = top;
+  return SQLITE_OK;
+}
+
+/*
+** Return a section of the pPage->aData to the freelist.
+** The first byte of the new free block is pPage->aDisk[start]
+** and the size of the block is "size" bytes.
+**
+** Most of the effort here is involved in coalesing adjacent
+** free blocks into a single big free block.
+*/
+static int freeSpace(MemPage *pPage, int start, int size){
+  int addr, pbegin, hdr;
+  int iLast;                        /* Largest possible freeblock offset */
+  unsigned char *data = pPage->aData;
+
+  assert( pPage->pBt!=0 );
+  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
+  assert( start>=pPage->hdrOffset+6+pPage->childPtrSize );
+  assert( (start + size) <= (int)pPage->pBt->usableSize );
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  assert( size>=0 );   /* Minimum cell size is 4 */
+
+  if( pPage->pBt->secureDelete ){
+    /* Overwrite deleted information with zeros when the secure_delete
+    ** option is enabled */
+    memset(&data[start], 0, size);
+  }
+
+  /* Add the space back into the linked list of freeblocks.  Note that
+  ** even though the freeblock list was checked by btreeInitPage(),
+  ** btreeInitPage() did not detect overlapping cells or
+  ** freeblocks that overlapped cells.   Nor does it detect when the
+  ** cell content area exceeds the value in the page header.  If these
+  ** situations arise, then subsequent insert operations might corrupt
+  ** the freelist.  So we do need to check for corruption while scanning
+  ** the freelist.
+  */
+  hdr = pPage->hdrOffset;
+  addr = hdr + 1;
+  iLast = pPage->pBt->usableSize - 4;
+  assert( start<=iLast );
+  while( (pbegin = get2byte(&data[addr]))<start && pbegin>0 ){
+    if( pbegin<addr+4 ){
+      return SQLITE_CORRUPT_BKPT;
+    }
+    addr = pbegin;
+  }
+  if( pbegin>iLast ){
+    return SQLITE_CORRUPT_BKPT;
+  }
+  assert( pbegin>addr || pbegin==0 );
+  put2byte(&data[addr], start);
+  put2byte(&data[start], pbegin);
+  put2byte(&data[start+2], size);
+  pPage->nFree = pPage->nFree + (u16)size;
+
+  /* Coalesce adjacent free blocks */
+  addr = hdr + 1;
+  while( (pbegin = get2byte(&data[addr]))>0 ){
+    int pnext, psize, x;
+    assert( pbegin>addr );
+    assert( pbegin <= (int)pPage->pBt->usableSize-4 );
+    pnext = get2byte(&data[pbegin]);
+    psize = get2byte(&data[pbegin+2]);
+    if( pbegin + psize + 3 >= pnext && pnext>0 ){
+      int frag = pnext - (pbegin+psize);
+      if( (frag<0) || (frag>(int)data[hdr+7]) ){
+        return SQLITE_CORRUPT_BKPT;
+      }
+      data[hdr+7] -= (u8)frag;
+      x = get2byte(&data[pnext]);
+      put2byte(&data[pbegin], x);
+      x = pnext + get2byte(&data[pnext+2]) - pbegin;
+      put2byte(&data[pbegin+2], x);
+    }else{
+      addr = pbegin;
+    }
+  }
+
+  /* If the cell content area begins with a freeblock, remove it. */
+  if( data[hdr+1]==data[hdr+5] && data[hdr+2]==data[hdr+6] ){
+    int top;
+    pbegin = get2byte(&data[hdr+1]);
+    memcpy(&data[hdr+1], &data[pbegin], 2);
+    top = get2byte(&data[hdr+5]) + get2byte(&data[pbegin+2]);
+    put2byte(&data[hdr+5], top);
+  }
+  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
+  return SQLITE_OK;
+}
+
+/*
+** Decode the flags byte (the first byte of the header) for a page
+** and initialize fields of the MemPage structure accordingly.
+**
+** Only the following combinations are supported.  Anything different
+** indicates a corrupt database files:
+**
+**         PTF_ZERODATA
+**         PTF_ZERODATA | PTF_LEAF
+**         PTF_LEAFDATA | PTF_INTKEY
+**         PTF_LEAFDATA | PTF_INTKEY | PTF_LEAF
+*/
+static int decodeFlags(MemPage *pPage, int flagByte){
+  BtShared *pBt;     /* A copy of pPage->pBt */
+
+  assert( pPage->hdrOffset==(pPage->pgno==1 ? 100 : 0) );
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  pPage->leaf = (u8)(flagByte>>3);  assert( PTF_LEAF == 1<<3 );
+  flagByte &= ~PTF_LEAF;
+  pPage->childPtrSize = 4-4*pPage->leaf;
+  pBt = pPage->pBt;
+  if( flagByte==(PTF_LEAFDATA | PTF_INTKEY) ){
+    pPage->intKey = 1;
+    pPage->hasData = pPage->leaf;
+    pPage->maxLocal = pBt->maxLeaf;
+    pPage->minLocal = pBt->minLeaf;
+  }else if( flagByte==PTF_ZERODATA ){
+    pPage->intKey = 0;
+    pPage->hasData = 0;
+    pPage->maxLocal = pBt->maxLocal;
+    pPage->minLocal = pBt->minLocal;
+  }else{
+    return SQLITE_CORRUPT_BKPT;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Initialize the auxiliary information for a disk block.
+**
+** Return SQLITE_OK on success.  If we see that the page does
+** not contain a well-formed database page, then return 
+** SQLITE_CORRUPT.  Note that a return of SQLITE_OK does not
+** guarantee that the page is well-formed.  It only shows that
+** we failed to detect any corruption.
+*/
+static int btreeInitPage(MemPage *pPage){
+
+  assert( pPage->pBt!=0 );
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  assert( pPage->pgno==sqlite3PagerPagenumber(pPage->pDbPage) );
+  assert( pPage == sqlite3PagerGetExtra(pPage->pDbPage) );
+  assert( pPage->aData == sqlite3PagerGetData(pPage->pDbPage) );
+
+  if( !pPage->isInit ){
+    u16 pc;            /* Address of a freeblock within pPage->aData[] */
+    u8 hdr;            /* Offset to beginning of page header */
+    u8 *data;          /* Equal to pPage->aData */
+    BtShared *pBt;        /* The main btree structure */
+    int usableSize;    /* Amount of usable space on each page */
+    u16 cellOffset;    /* Offset from start of page to first cell pointer */
+    int nFree;         /* Number of unused bytes on the page */
+    int top;           /* First byte of the cell content area */
+    int iCellFirst;    /* First allowable cell or freeblock offset */
+    int iCellLast;     /* Last possible cell or freeblock offset */
+
+    pBt = pPage->pBt;
+
+    hdr = pPage->hdrOffset;
+    data = pPage->aData;
+    if( decodeFlags(pPage, data[hdr]) ) return SQLITE_CORRUPT_BKPT;
+    assert( pBt->pageSize>=512 && pBt->pageSize<=65536 );
+    pPage->maskPage = (u16)(pBt->pageSize - 1);
+    pPage->nOverflow = 0;
+    usableSize = pBt->usableSize;
+    pPage->cellOffset = cellOffset = hdr + 12 - 4*pPage->leaf;
+    top = get2byteNotZero(&data[hdr+5]);
+    pPage->nCell = get2byte(&data[hdr+3]);
+    if( pPage->nCell>MX_CELL(pBt) ){
+      /* To many cells for a single page.  The page must be corrupt */
+      return SQLITE_CORRUPT_BKPT;
+    }
+    testcase( pPage->nCell==MX_CELL(pBt) );
+
+    /* A malformed database page might cause us to read past the end
+    ** of page when parsing a cell.  
+    **
+    ** The following block of code checks early to see if a cell extends
+    ** past the end of a page boundary and causes SQLITE_CORRUPT to be 
+    ** returned if it does.
+    */
+    iCellFirst = cellOffset + 2*pPage->nCell;
+    iCellLast = usableSize - 4;
+#if defined(SQLITE_ENABLE_OVERSIZE_CELL_CHECK)
+    {
+      int i;            /* Index into the cell pointer array */
+      int sz;           /* Size of a cell */
+
+      if( !pPage->leaf ) iCellLast--;
+      for(i=0; i<pPage->nCell; i++){
+        pc = get2byte(&data[cellOffset+i*2]);
+        testcase( pc==iCellFirst );
+        testcase( pc==iCellLast );
+        if( pc<iCellFirst || pc>iCellLast ){
+          return SQLITE_CORRUPT_BKPT;
+        }
+        sz = cellSizePtr(pPage, &data[pc]);
+        testcase( pc+sz==usableSize );
+        if( pc+sz>usableSize ){
+          return SQLITE_CORRUPT_BKPT;
+        }
+      }
+      if( !pPage->leaf ) iCellLast++;
+    }  
+#endif
+
+    /* Compute the total free space on the page */
+    pc = get2byte(&data[hdr+1]);
+    nFree = data[hdr+7] + top;
+    while( pc>0 ){
+      u16 next, size;
+      if( pc<iCellFirst || pc>iCellLast ){
+        /* Start of free block is off the page */
+        return SQLITE_CORRUPT_BKPT; 
+      }
+      next = get2byte(&data[pc]);
+      size = get2byte(&data[pc+2]);
+      if( (next>0 && next<=pc+size+3) || pc+size>usableSize ){
+        /* Free blocks must be in ascending order. And the last byte of
+	** the free-block must lie on the database page.  */
+        return SQLITE_CORRUPT_BKPT; 
+      }
+      nFree = nFree + size;
+      pc = next;
+    }
+
+    /* At this point, nFree contains the sum of the offset to the start
+    ** of the cell-content area plus the number of free bytes within
+    ** the cell-content area. If this is greater than the usable-size
+    ** of the page, then the page must be corrupted. This check also
+    ** serves to verify that the offset to the start of the cell-content
+    ** area, according to the page header, lies within the page.
+    */
+    if( nFree>usableSize ){
+      return SQLITE_CORRUPT_BKPT; 
+    }
+    pPage->nFree = (u16)(nFree - iCellFirst);
+    pPage->isInit = 1;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Set up a raw page so that it looks like a database page holding
+** no entries.
+*/
+static void zeroPage(MemPage *pPage, int flags){
+  unsigned char *data = pPage->aData;
+  BtShared *pBt = pPage->pBt;
+  u8 hdr = pPage->hdrOffset;
+  u16 first;
+
+  assert( sqlite3PagerPagenumber(pPage->pDbPage)==pPage->pgno );
+  assert( sqlite3PagerGetExtra(pPage->pDbPage) == (void*)pPage );
+  assert( sqlite3PagerGetData(pPage->pDbPage) == data );
+  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  if( pBt->secureDelete ){
+    memset(&data[hdr], 0, pBt->usableSize - hdr);
+  }
+  data[hdr] = (char)flags;
+  first = hdr + 8 + 4*((flags&PTF_LEAF)==0 ?1:0);
+  memset(&data[hdr+1], 0, 4);
+  data[hdr+7] = 0;
+  put2byte(&data[hdr+5], pBt->usableSize);
+  pPage->nFree = (u16)(pBt->usableSize - first);
+  decodeFlags(pPage, flags);
+  pPage->hdrOffset = hdr;
+  pPage->cellOffset = first;
+  pPage->nOverflow = 0;
+  assert( pBt->pageSize>=512 && pBt->pageSize<=65536 );
+  pPage->maskPage = (u16)(pBt->pageSize - 1);
+  pPage->nCell = 0;
+  pPage->isInit = 1;
+}
+
+
+/*
+** Convert a DbPage obtained from the pager into a MemPage used by
+** the btree layer.
+*/
+static MemPage *btreePageFromDbPage(DbPage *pDbPage, Pgno pgno, BtShared *pBt){
+  MemPage *pPage = (MemPage*)sqlite3PagerGetExtra(pDbPage);
+  pPage->aData = sqlite3PagerGetData(pDbPage);
+  pPage->pDbPage = pDbPage;
+  pPage->pBt = pBt;
+  pPage->pgno = pgno;
+  pPage->hdrOffset = pPage->pgno==1 ? 100 : 0;
+  return pPage; 
+}
+
+/*
+** Get a page from the pager.  Initialize the MemPage.pBt and
+** MemPage.aData elements if needed.
+**
+** If the noContent flag is set, it means that we do not care about
+** the content of the page at this time.  So do not go to the disk
+** to fetch the content.  Just fill in the content with zeros for now.
+** If in the future we call sqlite3PagerWrite() on this page, that
+** means we have started to be concerned about content and the disk
+** read should occur at that point.
+*/
+static int btreeGetPage(
+  BtShared *pBt,       /* The btree */
+  Pgno pgno,           /* Number of the page to fetch */
+  MemPage **ppPage,    /* Return the page in this parameter */
+  int noContent        /* Do not load page content if true */
+){
+  int rc;
+  DbPage *pDbPage;
+
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  rc = sqlite3PagerAcquire(pBt->pPager, pgno, (DbPage**)&pDbPage, noContent);
+  if( rc ) return rc;
+  *ppPage = btreePageFromDbPage(pDbPage, pgno, pBt);
+  return SQLITE_OK;
+}
+
+/*
+** Retrieve a page from the pager cache. If the requested page is not
+** already in the pager cache return NULL. Initialize the MemPage.pBt and
+** MemPage.aData elements if needed.
+*/
+static MemPage *btreePageLookup(BtShared *pBt, Pgno pgno){
+  DbPage *pDbPage;
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  pDbPage = sqlite3PagerLookup(pBt->pPager, pgno);
+  if( pDbPage ){
+    return btreePageFromDbPage(pDbPage, pgno, pBt);
+  }
+  return 0;
+}
+
+/*
+** Return the size of the database file in pages. If there is any kind of
+** error, return ((unsigned int)-1).
+*/
+static Pgno btreePagecount(BtShared *pBt){
+  return pBt->nPage;
+}
+u32 sqlite3BtreeLastPage(Btree *p){
+  assert( sqlite3BtreeHoldsMutex(p) );
+  assert( ((p->pBt->nPage)&0x8000000)==0 );
+  return (int)btreePagecount(p->pBt);
+}
+
+/*
+** Get a page from the pager and initialize it.  This routine is just a
+** convenience wrapper around separate calls to btreeGetPage() and 
+** btreeInitPage().
+**
+** If an error occurs, then the value *ppPage is set to is undefined. It
+** may remain unchanged, or it may be set to an invalid value.
+*/
+static int getAndInitPage(
+  BtShared *pBt,          /* The database file */
+  Pgno pgno,           /* Number of the page to get */
+  MemPage **ppPage     /* Write the page pointer here */
+){
+  int rc;
+  assert( sqlite3_mutex_held(pBt->mutex) );
+
+  if( pgno>btreePagecount(pBt) ){
+    rc = SQLITE_CORRUPT_BKPT;
+  }else{
+    rc = btreeGetPage(pBt, pgno, ppPage, 0);
+    if( rc==SQLITE_OK ){
+      rc = btreeInitPage(*ppPage);
+      if( rc!=SQLITE_OK ){
+        releasePage(*ppPage);
+      }
+    }
+  }
+
+  testcase( pgno==0 );
+  assert( pgno!=0 || rc==SQLITE_CORRUPT );
+  return rc;
+}
+
+/*
+** Release a MemPage.  This should be called once for each prior
+** call to btreeGetPage.
+*/
+static void releasePage(MemPage *pPage){
+  if( pPage ){
+    assert( pPage->aData );
+    assert( pPage->pBt );
+    assert( sqlite3PagerGetExtra(pPage->pDbPage) == (void*)pPage );
+    assert( sqlite3PagerGetData(pPage->pDbPage)==pPage->aData );
+    assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+    sqlite3PagerUnref(pPage->pDbPage);
+  }
+}
+
+/*
+** During a rollback, when the pager reloads information into the cache
+** so that the cache is restored to its original state at the start of
+** the transaction, for each page restored this routine is called.
+**
+** This routine needs to reset the extra data section at the end of the
+** page to agree with the restored data.
+*/
+static void pageReinit(DbPage *pData){
+  MemPage *pPage;
+  pPage = (MemPage *)sqlite3PagerGetExtra(pData);
+  assert( sqlite3PagerPageRefcount(pData)>0 );
+  if( pPage->isInit ){
+    assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+    pPage->isInit = 0;
+    if( sqlite3PagerPageRefcount(pData)>1 ){
+      /* pPage might not be a btree page;  it might be an overflow page
+      ** or ptrmap page or a free page.  In those cases, the following
+      ** call to btreeInitPage() will likely return SQLITE_CORRUPT.
+      ** But no harm is done by this.  And it is very important that
+      ** btreeInitPage() be called on every btree page so we make
+      ** the call for every page that comes in for re-initing. */
+      btreeInitPage(pPage);
+    }
+  }
+}
+
+/*
+** Invoke the busy handler for a btree.
+*/
+static int btreeInvokeBusyHandler(void *pArg){
+  BtShared *pBt = (BtShared*)pArg;
+  assert( pBt->db );
+  assert( sqlite3_mutex_held(pBt->db->mutex) );
+  return sqlite3InvokeBusyHandler(&pBt->db->busyHandler);
+}
+
+/*
+** Open a database file.
+** 
+** zFilename is the name of the database file.  If zFilename is NULL
+** then an ephemeral database is created.  The ephemeral database might
+** be exclusively in memory, or it might use a disk-based memory cache.
+** Either way, the ephemeral database will be automatically deleted 
+** when sqlite3BtreeClose() is called.
+**
+** If zFilename is ":memory:" then an in-memory database is created
+** that is automatically destroyed when it is closed.
+**
+** The "flags" parameter is a bitmask that might contain bits
+** BTREE_OMIT_JOURNAL and/or BTREE_NO_READLOCK.  The BTREE_NO_READLOCK
+** bit is also set if the SQLITE_NoReadlock flags is set in db->flags.
+** These flags are passed through into sqlite3PagerOpen() and must
+** be the same values as PAGER_OMIT_JOURNAL and PAGER_NO_READLOCK.
+**
+** If the database is already opened in the same database connection
+** and we are in shared cache mode, then the open will fail with an
+** SQLITE_CONSTRAINT error.  We cannot allow two or more BtShared
+** objects in the same database connection since doing so will lead
+** to problems with locking.
+*/
+int sqlite3BtreeOpen(
+  sqlite3_vfs *pVfs,      /* VFS to use for this b-tree */
+  const char *zFilename,  /* Name of the file containing the BTree database */
+  sqlite3 *db,            /* Associated database handle */
+  Btree **ppBtree,        /* Pointer to new Btree object written here */
+  int flags,              /* Options */
+  int vfsFlags            /* Flags passed through to sqlite3_vfs.xOpen() */
+){
+  BtShared *pBt = 0;             /* Shared part of btree structure */
+  Btree *p;                      /* Handle to return */
+  sqlite3_mutex *mutexOpen = 0;  /* Prevents a race condition. Ticket #3537 */
+  int rc = SQLITE_OK;            /* Result code from this function */
+  u8 nReserve;                   /* Byte of unused space on each page */
+  unsigned char zDbHeader[100];  /* Database header content */
+
+  /* True if opening an ephemeral, temporary database */
+  const int isTempDb = zFilename==0 || zFilename[0]==0;
+
+  /* Set the variable isMemdb to true for an in-memory database, or 
+  ** false for a file-based database.
+  */
+#ifdef SQLITE_OMIT_MEMORYDB
+  const int isMemdb = 0;
+#else
+  const int isMemdb = (zFilename && strcmp(zFilename, ":memory:")==0)
+                       || (isTempDb && sqlite3TempInMemory(db));
+#endif
+
+  assert( db!=0 );
+  assert( pVfs!=0 );
+  assert( sqlite3_mutex_held(db->mutex) );
+  assert( (flags&0xff)==flags );   /* flags fit in 8 bits */
+
+  /* Only a BTREE_SINGLE database can be BTREE_UNORDERED */
+  assert( (flags & BTREE_UNORDERED)==0 || (flags & BTREE_SINGLE)!=0 );
+
+  /* A BTREE_SINGLE database is always a temporary and/or ephemeral */
+  assert( (flags & BTREE_SINGLE)==0 || isTempDb );
+
+  if( db->flags & SQLITE_NoReadlock ){
+    flags |= BTREE_NO_READLOCK;
+  }
+  if( isMemdb ){
+    flags |= BTREE_MEMORY;
+  }
+  if( (vfsFlags & SQLITE_OPEN_MAIN_DB)!=0 && (isMemdb || isTempDb) ){
+    vfsFlags = (vfsFlags & ~SQLITE_OPEN_MAIN_DB) | SQLITE_OPEN_TEMP_DB;
+  }
+  p = sqlite3MallocZero(sizeof(Btree));
+  if( !p ){
+    return SQLITE_NOMEM;
+  }
+  p->inTrans = TRANS_NONE;
+  p->db = db;
+#ifndef SQLITE_OMIT_SHARED_CACHE
+  p->lock.pBtree = p;
+  p->lock.iTable = 1;
+#endif
+
+#if !defined(SQLITE_OMIT_SHARED_CACHE) && !defined(SQLITE_OMIT_DISKIO)
+  /*
+  ** If this Btree is a candidate for shared cache, try to find an
+  ** existing BtShared object that we can share with
+  */
+  if( isMemdb==0 && isTempDb==0 ){
+    if( vfsFlags & SQLITE_OPEN_SHAREDCACHE ){
+      int nFullPathname = pVfs->mxPathname+1;
+      char *zFullPathname = sqlite3Malloc(nFullPathname);
+      MUTEX_LOGIC( sqlite3_mutex *mutexShared; )
+      p->sharable = 1;
+      if( !zFullPathname ){
+        sqlite3_free(p);
+        return SQLITE_NOMEM;
+      }
+      sqlite3OsFullPathname(pVfs, zFilename, nFullPathname, zFullPathname);
+#if SQLITE_THREADSAFE
+      mutexOpen = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_OPEN);
+      sqlite3_mutex_enter(mutexOpen);
+      mutexShared = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER);
+      sqlite3_mutex_enter(mutexShared);
+#endif
+      for(pBt=GLOBAL(BtShared*,sqlite3SharedCacheList); pBt; pBt=pBt->pNext){
+        assert( pBt->nRef>0 );
+        if( 0==strcmp(zFullPathname, sqlite3PagerFilename(pBt->pPager))
+                 && sqlite3PagerVfs(pBt->pPager)==pVfs ){
+          int iDb;
+          for(iDb=db->nDb-1; iDb>=0; iDb--){
+            Btree *pExisting = db->aDb[iDb].pBt;
+            if( pExisting && pExisting->pBt==pBt ){
+              sqlite3_mutex_leave(mutexShared);
+              sqlite3_mutex_leave(mutexOpen);
+              sqlite3_free(zFullPathname);
+              sqlite3_free(p);
+              return SQLITE_CONSTRAINT;
+            }
+          }
+          p->pBt = pBt;
+          pBt->nRef++;
+          break;
+        }
+      }
+      sqlite3_mutex_leave(mutexShared);
+      sqlite3_free(zFullPathname);
+    }
+#ifdef SQLITE_DEBUG
+    else{
+      /* In debug mode, we mark all persistent databases as sharable
+      ** even when they are not.  This exercises the locking code and
+      ** gives more opportunity for asserts(sqlite3_mutex_held())
+      ** statements to find locking problems.
+      */
+      p->sharable = 1;
+    }
+#endif
+  }
+#endif
+  if( pBt==0 ){
+    /*
+    ** The following asserts make sure that structures used by the btree are
+    ** the right size.  This is to guard against size changes that result
+    ** when compiling on a different architecture.
+    */
+    assert( sizeof(i64)==8 || sizeof(i64)==4 );
+    assert( sizeof(u64)==8 || sizeof(u64)==4 );
+    assert( sizeof(u32)==4 );
+    assert( sizeof(u16)==2 );
+    assert( sizeof(Pgno)==4 );
+  
+    pBt = sqlite3MallocZero( sizeof(*pBt) );
+    if( pBt==0 ){
+      rc = SQLITE_NOMEM;
+      goto btree_open_out;
+    }
+    rc = sqlite3PagerOpen(pVfs, &pBt->pPager, zFilename,
+                          EXTRA_SIZE, flags, vfsFlags, pageReinit);
+    if( rc==SQLITE_OK ){
+      rc = sqlite3PagerReadFileheader(pBt->pPager,sizeof(zDbHeader),zDbHeader);
+    }
+    if( rc!=SQLITE_OK ){
+      goto btree_open_out;
+    }
+    pBt->openFlags = (u8)flags;
+    pBt->db = db;
+    sqlite3PagerSetBusyhandler(pBt->pPager, btreeInvokeBusyHandler, pBt);
+    p->pBt = pBt;
+  
+    pBt->pCursor = 0;
+    pBt->pPage1 = 0;
+    pBt->readOnly = sqlite3PagerIsreadonly(pBt->pPager);
+#ifdef SQLITE_SECURE_DELETE
+    pBt->secureDelete = 1;
+#endif
+    pBt->pageSize = (zDbHeader[16]<<8) | (zDbHeader[17]<<16);
+    if( pBt->pageSize<512 || pBt->pageSize>SQLITE_MAX_PAGE_SIZE
+         || ((pBt->pageSize-1)&pBt->pageSize)!=0 ){
+      pBt->pageSize = 0;
+#ifndef SQLITE_OMIT_AUTOVACUUM
+      /* If the magic name ":memory:" will create an in-memory database, then
+      ** leave the autoVacuum mode at 0 (do not auto-vacuum), even if
+      ** SQLITE_DEFAULT_AUTOVACUUM is true. On the other hand, if
+      ** SQLITE_OMIT_MEMORYDB has been defined, then ":memory:" is just a
+      ** regular file-name. In this case the auto-vacuum applies as per normal.
+      */
+      if( zFilename && !isMemdb ){
+        pBt->autoVacuum = (SQLITE_DEFAULT_AUTOVACUUM ? 1 : 0);
+        pBt->incrVacuum = (SQLITE_DEFAULT_AUTOVACUUM==2 ? 1 : 0);
+      }
+#endif
+      nReserve = 0;
+    }else{
+      nReserve = zDbHeader[20];
+      pBt->pageSizeFixed = 1;
+#ifndef SQLITE_OMIT_AUTOVACUUM
+      pBt->autoVacuum = (get4byte(&zDbHeader[36 + 4*4])?1:0);
+      pBt->incrVacuum = (get4byte(&zDbHeader[36 + 7*4])?1:0);
+#endif
+    }
+    rc = sqlite3PagerSetPagesize(pBt->pPager, &pBt->pageSize, nReserve);
+    if( rc ) goto btree_open_out;
+    pBt->usableSize = pBt->pageSize - nReserve;
+    assert( (pBt->pageSize & 7)==0 );  /* 8-byte alignment of pageSize */
+   
+#if !defined(SQLITE_OMIT_SHARED_CACHE) && !defined(SQLITE_OMIT_DISKIO)
+    /* Add the new BtShared object to the linked list sharable BtShareds.
+    */
+    if( p->sharable ){
+      MUTEX_LOGIC( sqlite3_mutex *mutexShared; )
+      pBt->nRef = 1;
+      MUTEX_LOGIC( mutexShared = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER);)
+      if( SQLITE_THREADSAFE && sqlite3GlobalConfig.bCoreMutex ){
+        pBt->mutex = sqlite3MutexAlloc(SQLITE_MUTEX_FAST);
+        if( pBt->mutex==0 ){
+          rc = SQLITE_NOMEM;
+          db->mallocFailed = 0;
+          goto btree_open_out;
+        }
+      }
+      sqlite3_mutex_enter(mutexShared);
+      pBt->pNext = GLOBAL(BtShared*,sqlite3SharedCacheList);
+      GLOBAL(BtShared*,sqlite3SharedCacheList) = pBt;
+      sqlite3_mutex_leave(mutexShared);
+    }
+#endif
+  }
+
+#if !defined(SQLITE_OMIT_SHARED_CACHE) && !defined(SQLITE_OMIT_DISKIO)
+  /* If the new Btree uses a sharable pBtShared, then link the new
+  ** Btree into the list of all sharable Btrees for the same connection.
+  ** The list is kept in ascending order by pBt address.
+  */
+  if( p->sharable ){
+    int i;
+    Btree *pSib;
+    for(i=0; i<db->nDb; i++){
+      if( (pSib = db->aDb[i].pBt)!=0 && pSib->sharable ){
+        while( pSib->pPrev ){ pSib = pSib->pPrev; }
+        if( p->pBt<pSib->pBt ){
+          p->pNext = pSib;
+          p->pPrev = 0;
+          pSib->pPrev = p;
+        }else{
+          while( pSib->pNext && pSib->pNext->pBt<p->pBt ){
+            pSib = pSib->pNext;
+          }
+          p->pNext = pSib->pNext;
+          p->pPrev = pSib;
+          if( p->pNext ){
+            p->pNext->pPrev = p;
+          }
+          pSib->pNext = p;
+        }
+        break;
+      }
+    }
+  }
+#endif
+  *ppBtree = p;
+
+btree_open_out:
+  if( rc!=SQLITE_OK ){
+    if( pBt && pBt->pPager ){
+      sqlite3PagerClose(pBt->pPager);
+    }
+    sqlite3_free(pBt);
+    sqlite3_free(p);
+    *ppBtree = 0;
+  }else{
+    /* If the B-Tree was successfully opened, set the pager-cache size to the
+    ** default value. Except, when opening on an existing shared pager-cache,
+    ** do not change the pager-cache size.
+    */
+    if( sqlite3BtreeSchema(p, 0, 0)==0 ){
+      sqlite3PagerSetCachesize(p->pBt->pPager, SQLITE_DEFAULT_CACHE_SIZE);
+    }
+  }
+  if( mutexOpen ){
+    assert( sqlite3_mutex_held(mutexOpen) );
+    sqlite3_mutex_leave(mutexOpen);
+  }
+  return rc;
+}
+
+/*
+** Decrement the BtShared.nRef counter.  When it reaches zero,
+** remove the BtShared structure from the sharing list.  Return
+** true if the BtShared.nRef counter reaches zero and return
+** false if it is still positive.
+*/
+static int removeFromSharingList(BtShared *pBt){
+#ifndef SQLITE_OMIT_SHARED_CACHE
+  MUTEX_LOGIC( sqlite3_mutex *pMaster; )
+  BtShared *pList;
+  int removed = 0;
+
+  assert( sqlite3_mutex_notheld(pBt->mutex) );
+  MUTEX_LOGIC( pMaster = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER); )
+  sqlite3_mutex_enter(pMaster);
+  pBt->nRef--;
+  if( pBt->nRef<=0 ){
+    if( GLOBAL(BtShared*,sqlite3SharedCacheList)==pBt ){
+      GLOBAL(BtShared*,sqlite3SharedCacheList) = pBt->pNext;
+    }else{
+      pList = GLOBAL(BtShared*,sqlite3SharedCacheList);
+      while( ALWAYS(pList) && pList->pNext!=pBt ){
+        pList=pList->pNext;
+      }
+      if( ALWAYS(pList) ){
+        pList->pNext = pBt->pNext;
+      }
+    }
+    if( SQLITE_THREADSAFE ){
+      sqlite3_mutex_free(pBt->mutex);
+    }
+    removed = 1;
+  }
+  sqlite3_mutex_leave(pMaster);
+  return removed;
+#else
+  return 1;
+#endif
+}
+
+/*
+** Make sure pBt->pTmpSpace points to an allocation of 
+** MX_CELL_SIZE(pBt) bytes.
+*/
+static void allocateTempSpace(BtShared *pBt){
+  if( !pBt->pTmpSpace ){
+    pBt->pTmpSpace = sqlite3PageMalloc( pBt->pageSize );
+  }
+}
+
+/*
+** Free the pBt->pTmpSpace allocation
+*/
+static void freeTempSpace(BtShared *pBt){
+  sqlite3PageFree( pBt->pTmpSpace);
+  pBt->pTmpSpace = 0;
+}
+
+/*
+** Close an open database and invalidate all cursors.
+*/
+int sqlite3BtreeClose(Btree *p){
+  BtShared *pBt = p->pBt;
+  BtCursor *pCur;
+
+  /* Close all cursors opened via this handle.  */
+  assert( sqlite3_mutex_held(p->db->mutex) );
+  sqlite3BtreeEnter(p);
+  pCur = pBt->pCursor;
+  while( pCur ){
+    BtCursor *pTmp = pCur;
+    pCur = pCur->pNext;
+    if( pTmp->pBtree==p ){
+      sqlite3BtreeCloseCursor(pTmp);
+    }
+  }
+
+  /* Rollback any active transaction and free the handle structure.
+  ** The call to sqlite3BtreeRollback() drops any table-locks held by
+  ** this handle.
+  */
+  sqlite3BtreeRollback(p);
+  sqlite3BtreeLeave(p);
+
+  /* If there are still other outstanding references to the shared-btree
+  ** structure, return now. The remainder of this procedure cleans 
+  ** up the shared-btree.
+  */
+  assert( p->wantToLock==0 && p->locked==0 );
+  if( !p->sharable || removeFromSharingList(pBt) ){
+    /* The pBt is no longer on the sharing list, so we can access
+    ** it without having to hold the mutex.
+    **
+    ** Clean out and delete the BtShared object.
+    */
+    assert( !pBt->pCursor );
+    sqlite3PagerClose(pBt->pPager);
+    if( pBt->xFreeSchema && pBt->pSchema ){
+      pBt->xFreeSchema(pBt->pSchema);
+    }
+    sqlite3DbFree(0, pBt->pSchema);
+    freeTempSpace(pBt);
+    sqlite3_free(pBt);
+  }
+
+#ifndef SQLITE_OMIT_SHARED_CACHE
+  assert( p->wantToLock==0 );
+  assert( p->locked==0 );
+  if( p->pPrev ) p->pPrev->pNext = p->pNext;
+  if( p->pNext ) p->pNext->pPrev = p->pPrev;
+#endif
+
+  sqlite3_free(p);
+  return SQLITE_OK;
+}
+
+/*
+** Change the limit on the number of pages allowed in the cache.
+**
+** The maximum number of cache pages is set to the absolute
+** value of mxPage.  If mxPage is negative, the pager will
+** operate asynchronously - it will not stop to do fsync()s
+** to insure data is written to the disk surface before
+** continuing.  Transactions still work if synchronous is off,
+** and the database cannot be corrupted if this program
+** crashes.  But if the operating system crashes or there is
+** an abrupt power failure when synchronous is off, the database
+** could be left in an inconsistent and unrecoverable state.
+** Synchronous is on by default so database corruption is not
+** normally a worry.
+*/
+int sqlite3BtreeSetCacheSize(Btree *p, int mxPage){
+  BtShared *pBt = p->pBt;
+  assert( sqlite3_mutex_held(p->db->mutex) );
+  sqlite3BtreeEnter(p);
+  sqlite3PagerSetCachesize(pBt->pPager, mxPage);
+  sqlite3BtreeLeave(p);
+  return SQLITE_OK;
+}
+
+/*
+** Change the way data is synced to disk in order to increase or decrease
+** how well the database resists damage due to OS crashes and power
+** failures.  Level 1 is the same as asynchronous (no syncs() occur and
+** there is a high probability of damage)  Level 2 is the default.  There
+** is a very low but non-zero probability of damage.  Level 3 reduces the
+** probability of damage to near zero but with a write performance reduction.
+*/
+#ifndef SQLITE_OMIT_PAGER_PRAGMAS
+int sqlite3BtreeSetSafetyLevel(
+  Btree *p,              /* The btree to set the safety level on */
+  int level,             /* PRAGMA synchronous.  1=OFF, 2=NORMAL, 3=FULL */
+  int fullSync,          /* PRAGMA fullfsync. */
+  int ckptFullSync       /* PRAGMA checkpoint_fullfync */
+){
+  BtShared *pBt = p->pBt;
+  assert( sqlite3_mutex_held(p->db->mutex) );
+  assert( level>=1 && level<=3 );
+  sqlite3BtreeEnter(p);
+  sqlite3PagerSetSafetyLevel(pBt->pPager, level, fullSync, ckptFullSync);
+  sqlite3BtreeLeave(p);
+  return SQLITE_OK;
+}
+#endif
+
+/*
+** Return TRUE if the given btree is set to safety level 1.  In other
+** words, return TRUE if no sync() occurs on the disk files.
+*/
+int sqlite3BtreeSyncDisabled(Btree *p){
+  BtShared *pBt = p->pBt;
+  int rc;
+  assert( sqlite3_mutex_held(p->db->mutex) );  
+  sqlite3BtreeEnter(p);
+  assert( pBt && pBt->pPager );
+  rc = sqlite3PagerNosync(pBt->pPager);
+  sqlite3BtreeLeave(p);
+  return rc;
+}
+
+/*
+** Change the default pages size and the number of reserved bytes per page.
+** Or, if the page size has already been fixed, return SQLITE_READONLY 
+** without changing anything.
+**
+** The page size must be a power of 2 between 512 and 65536.  If the page
+** size supplied does not meet this constraint then the page size is not
+** changed.
+**
+** Page sizes are constrained to be a power of two so that the region
+** of the database file used for locking (beginning at PENDING_BYTE,
+** the first byte past the 1GB boundary, 0x40000000) needs to occur
+** at the beginning of a page.
+**
+** If parameter nReserve is less than zero, then the number of reserved
+** bytes per page is left unchanged.
+**
+** If the iFix!=0 then the pageSizeFixed flag is set so that the page size
+** and autovacuum mode can no longer be changed.
+*/
+int sqlite3BtreeSetPageSize(Btree *p, int pageSize, int nReserve, int iFix){
+  int rc = SQLITE_OK;
+  BtShared *pBt = p->pBt;
+  assert( nReserve>=-1 && nReserve<=255 );
+  sqlite3BtreeEnter(p);
+  if( pBt->pageSizeFixed ){
+    sqlite3BtreeLeave(p);
+    return SQLITE_READONLY;
+  }
+  if( nReserve<0 ){
+    nReserve = pBt->pageSize - pBt->usableSize;
+  }
+  assert( nReserve>=0 && nReserve<=255 );
+  if( pageSize>=512 && pageSize<=SQLITE_MAX_PAGE_SIZE &&
+        ((pageSize-1)&pageSize)==0 ){
+    assert( (pageSize & 7)==0 );
+    assert( !pBt->pPage1 && !pBt->pCursor );
+    pBt->pageSize = (u32)pageSize;
+    freeTempSpace(pBt);
+  }
+  rc = sqlite3PagerSetPagesize(pBt->pPager, &pBt->pageSize, nReserve);
+  pBt->usableSize = pBt->pageSize - (u16)nReserve;
+  if( iFix ) pBt->pageSizeFixed = 1;
+  sqlite3BtreeLeave(p);
+  return rc;
+}
+
+/*
+** Return the currently defined page size
+*/
+int sqlite3BtreeGetPageSize(Btree *p){
+  return p->pBt->pageSize;
+}
+
+#if !defined(SQLITE_OMIT_PAGER_PRAGMAS) || !defined(SQLITE_OMIT_VACUUM)
+/*
+** Return the number of bytes of space at the end of every page that
+** are intentually left unused.  This is the "reserved" space that is
+** sometimes used by extensions.
+*/
+int sqlite3BtreeGetReserve(Btree *p){
+  int n;
+  sqlite3BtreeEnter(p);
+  n = p->pBt->pageSize - p->pBt->usableSize;
+  sqlite3BtreeLeave(p);
+  return n;
+}
+
+/*
+** Set the maximum page count for a database if mxPage is positive.
+** No changes are made if mxPage is 0 or negative.
+** Regardless of the value of mxPage, return the maximum page count.
+*/
+int sqlite3BtreeMaxPageCount(Btree *p, int mxPage){
+  int n;
+  sqlite3BtreeEnter(p);
+  n = sqlite3PagerMaxPageCount(p->pBt->pPager, mxPage);
+  sqlite3BtreeLeave(p);
+  return n;
+}
+
+/*
+** Set the secureDelete flag if newFlag is 0 or 1.  If newFlag is -1,
+** then make no changes.  Always return the value of the secureDelete
+** setting after the change.
+*/
+int sqlite3BtreeSecureDelete(Btree *p, int newFlag){
+  int b;
+  if( p==0 ) return 0;
+  sqlite3BtreeEnter(p);
+  if( newFlag>=0 ){
+    p->pBt->secureDelete = (newFlag!=0) ? 1 : 0;
+  } 
+  b = p->pBt->secureDelete;
+  sqlite3BtreeLeave(p);
+  return b;
+}
+#endif /* !defined(SQLITE_OMIT_PAGER_PRAGMAS) || !defined(SQLITE_OMIT_VACUUM) */
+
+/*
+** Change the 'auto-vacuum' property of the database. If the 'autoVacuum'
+** parameter is non-zero, then auto-vacuum mode is enabled. If zero, it
+** is disabled. The default value for the auto-vacuum property is 
+** determined by the SQLITE_DEFAULT_AUTOVACUUM macro.
+*/
+int sqlite3BtreeSetAutoVacuum(Btree *p, int autoVacuum){
+#ifdef SQLITE_OMIT_AUTOVACUUM
+  return SQLITE_READONLY;
+#else
+  BtShared *pBt = p->pBt;
+  int rc = SQLITE_OK;
+  u8 av = (u8)autoVacuum;
+
+  sqlite3BtreeEnter(p);
+  if( pBt->pageSizeFixed && (av ?1:0)!=pBt->autoVacuum ){
+    rc = SQLITE_READONLY;
+  }else{
+    pBt->autoVacuum = av ?1:0;
+    pBt->incrVacuum = av==2 ?1:0;
+  }
+  sqlite3BtreeLeave(p);
+  return rc;
+#endif
+}
+
+/*
+** Return the value of the 'auto-vacuum' property. If auto-vacuum is 
+** enabled 1 is returned. Otherwise 0.
+*/
+int sqlite3BtreeGetAutoVacuum(Btree *p){
+#ifdef SQLITE_OMIT_AUTOVACUUM
+  return BTREE_AUTOVACUUM_NONE;
+#else
+  int rc;
+  sqlite3BtreeEnter(p);
+  rc = (
+    (!p->pBt->autoVacuum)?BTREE_AUTOVACUUM_NONE:
+    (!p->pBt->incrVacuum)?BTREE_AUTOVACUUM_FULL:
+    BTREE_AUTOVACUUM_INCR
+  );
+  sqlite3BtreeLeave(p);
+  return rc;
+#endif
+}
+
+
+/*
+** Get a reference to pPage1 of the database file.  This will
+** also acquire a readlock on that file.
+**
+** SQLITE_OK is returned on success.  If the file is not a
+** well-formed database file, then SQLITE_CORRUPT is returned.
+** SQLITE_BUSY is returned if the database is locked.  SQLITE_NOMEM
+** is returned if we run out of memory. 
+*/
+static int lockBtree(BtShared *pBt){
+  int rc;              /* Result code from subfunctions */
+  MemPage *pPage1;     /* Page 1 of the database file */
+  int nPage;           /* Number of pages in the database */
+  int nPageFile = 0;   /* Number of pages in the database file */
+  int nPageHeader;     /* Number of pages in the database according to hdr */
+
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  assert( pBt->pPage1==0 );
+  rc = sqlite3PagerSharedLock(pBt->pPager);
+  if( rc!=SQLITE_OK ) return rc;
+  rc = btreeGetPage(pBt, 1, &pPage1, 0);
+  if( rc!=SQLITE_OK ) return rc;
+
+  /* Do some checking to help insure the file we opened really is
+  ** a valid database file. 
+  */
+  nPage = nPageHeader = get4byte(28+(u8*)pPage1->aData);
+  sqlite3PagerPagecount(pBt->pPager, &nPageFile);
+  if( nPage==0 || memcmp(24+(u8*)pPage1->aData, 92+(u8*)pPage1->aData,4)!=0 ){
+    nPage = nPageFile;
+  }
+  if( nPage>0 ){
+    u32 pageSize;
+    u32 usableSize;
+    u8 *page1 = pPage1->aData;
+    rc = SQLITE_NOTADB;
+    if( memcmp(page1, zMagicHeader, 16)!=0 ){
+      goto page1_init_failed;
+    }
+
+#ifdef SQLITE_OMIT_WAL
+    if( page1[18]>1 ){
+      pBt->readOnly = 1;
+    }
+    if( page1[19]>1 ){
+      goto page1_init_failed;
+    }
+#else
+    if( page1[18]>2 ){
+      pBt->readOnly = 1;
+    }
+    if( page1[19]>2 ){
+      goto page1_init_failed;
+    }
+
+    /* If the write version is set to 2, this database should be accessed
+    ** in WAL mode. If the log is not already open, open it now. Then 
+    ** return SQLITE_OK and return without populating BtShared.pPage1.
+    ** The caller detects this and calls this function again. This is
+    ** required as the version of page 1 currently in the page1 buffer
+    ** may not be the latest version - there may be a newer one in the log
+    ** file.
+    */
+    if( page1[19]==2 && pBt->doNotUseWAL==0 ){
+      int isOpen = 0;
+      rc = sqlite3PagerOpenWal(pBt->pPager, &isOpen);
+      if( rc!=SQLITE_OK ){
+        goto page1_init_failed;
+      }else if( isOpen==0 ){
+        releasePage(pPage1);
+        return SQLITE_OK;
+      }
+      rc = SQLITE_NOTADB;
+    }
+#endif
+
+    /* The maximum embedded fraction must be exactly 25%.  And the minimum
+    ** embedded fraction must be 12.5% for both leaf-data and non-leaf-data.
+    ** The original design allowed these amounts to vary, but as of
+    ** version 3.6.0, we require them to be fixed.
+    */
+    if( memcmp(&page1[21], "\100\040\040",3)!=0 ){
+      goto page1_init_failed;
+    }
+    pageSize = (page1[16]<<8) | (page1[17]<<16);
+    if( ((pageSize-1)&pageSize)!=0
+     || pageSize>SQLITE_MAX_PAGE_SIZE 
+     || pageSize<=256 
+    ){
+      goto page1_init_failed;
+    }
+    assert( (pageSize & 7)==0 );
+    usableSize = pageSize - page1[20];
+    if( (u32)pageSize!=pBt->pageSize ){
+      /* After reading the first page of the database assuming a page size
+      ** of BtShared.pageSize, we have discovered that the page-size is
+      ** actually pageSize. Unlock the database, leave pBt->pPage1 at
+      ** zero and return SQLITE_OK. The caller will call this function
+      ** again with the correct page-size.
+      */
+      releasePage(pPage1);
+      pBt->usableSize = usableSize;
+      pBt->pageSize = pageSize;
+      freeTempSpace(pBt);
+      rc = sqlite3PagerSetPagesize(pBt->pPager, &pBt->pageSize,
+                                   pageSize-usableSize);
+      return rc;
+    }
+    if( (pBt->db->flags & SQLITE_RecoveryMode)==0 && nPage>nPageFile ){
+      rc = SQLITE_CORRUPT_BKPT;
+      goto page1_init_failed;
+    }
+    if( usableSize<480 ){
+      goto page1_init_failed;
+    }
+    pBt->pageSize = pageSize;
+    pBt->usableSize = usableSize;
+#ifndef SQLITE_OMIT_AUTOVACUUM
+    pBt->autoVacuum = (get4byte(&page1[36 + 4*4])?1:0);
+    pBt->incrVacuum = (get4byte(&page1[36 + 7*4])?1:0);
+#endif
+  }
+
+  /* maxLocal is the maximum amount of payload to store locally for
+  ** a cell.  Make sure it is small enough so that at least minFanout
+  ** cells can will fit on one page.  We assume a 10-byte page header.
+  ** Besides the payload, the cell must store:
+  **     2-byte pointer to the cell
+  **     4-byte child pointer
+  **     9-byte nKey value
+  **     4-byte nData value
+  **     4-byte overflow page pointer
+  ** So a cell consists of a 2-byte pointer, a header which is as much as
+  ** 17 bytes long, 0 to N bytes of payload, and an optional 4 byte overflow
+  ** page pointer.
+  */
+  pBt->maxLocal = (u16)((pBt->usableSize-12)*64/255 - 23);
+  pBt->minLocal = (u16)((pBt->usableSize-12)*32/255 - 23);
+  pBt->maxLeaf = (u16)(pBt->usableSize - 35);
+  pBt->minLeaf = (u16)((pBt->usableSize-12)*32/255 - 23);
+  assert( pBt->maxLeaf + 23 <= MX_CELL_SIZE(pBt) );
+  pBt->pPage1 = pPage1;
+  pBt->nPage = nPage;
+  return SQLITE_OK;
+
+page1_init_failed:
+  releasePage(pPage1);
+  pBt->pPage1 = 0;
+  return rc;
+}
+
+/*
+** If there are no outstanding cursors and we are not in the middle
+** of a transaction but there is a read lock on the database, then
+** this routine unrefs the first page of the database file which 
+** has the effect of releasing the read lock.
+**
+** If there is a transaction in progress, this routine is a no-op.
+*/
+static void unlockBtreeIfUnused(BtShared *pBt){
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  assert( pBt->pCursor==0 || pBt->inTransaction>TRANS_NONE );
+  if( pBt->inTransaction==TRANS_NONE && pBt->pPage1!=0 ){
+    assert( pBt->pPage1->aData );
+    assert( sqlite3PagerRefcount(pBt->pPager)==1 );
+    assert( pBt->pPage1->aData );
+    releasePage(pBt->pPage1);
+    pBt->pPage1 = 0;
+  }
+}
+
+/*
+** If pBt points to an empty file then convert that empty file
+** into a new empty database by initializing the first page of
+** the database.
+*/
+static int newDatabase(BtShared *pBt){
+  MemPage *pP1;
+  unsigned char *data;
+  int rc;
+
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  if( pBt->nPage>0 ){
+    return SQLITE_OK;
+  }
+  pP1 = pBt->pPage1;
+  assert( pP1!=0 );
+  data = pP1->aData;
+  rc = sqlite3PagerWrite(pP1->pDbPage);
+  if( rc ) return rc;
+  memcpy(data, zMagicHeader, sizeof(zMagicHeader));
+  assert( sizeof(zMagicHeader)==16 );
+  data[16] = (u8)((pBt->pageSize>>8)&0xff);
+  data[17] = (u8)((pBt->pageSize>>16)&0xff);
+  data[18] = 1;
+  data[19] = 1;
+  assert( pBt->usableSize<=pBt->pageSize && pBt->usableSize+255>=pBt->pageSize);
+  data[20] = (u8)(pBt->pageSize - pBt->usableSize);
+  data[21] = 64;
+  data[22] = 32;
+  data[23] = 32;
+  memset(&data[24], 0, 100-24);
+  zeroPage(pP1, PTF_INTKEY|PTF_LEAF|PTF_LEAFDATA );
+  pBt->pageSizeFixed = 1;
+#ifndef SQLITE_OMIT_AUTOVACUUM
+  assert( pBt->autoVacuum==1 || pBt->autoVacuum==0 );
+  assert( pBt->incrVacuum==1 || pBt->incrVacuum==0 );
+  put4byte(&data[36 + 4*4], pBt->autoVacuum);
+  put4byte(&data[36 + 7*4], pBt->incrVacuum);
+#endif
+  pBt->nPage = 1;
+  data[31] = 1;
+  return SQLITE_OK;
+}
+
+/*
+** Attempt to start a new transaction. A write-transaction
+** is started if the second argument is nonzero, otherwise a read-
+** transaction.  If the second argument is 2 or more and exclusive
+** transaction is started, meaning that no other process is allowed
+** to access the database.  A preexisting transaction may not be
+** upgraded to exclusive by calling this routine a second time - the
+** exclusivity flag only works for a new transaction.
+**
+** A write-transaction must be started before attempting any 
+** changes to the database.  None of the following routines 
+** will work unless a transaction is started first:
+**
+**      sqlite3BtreeCreateTable()
+**      sqlite3BtreeCreateIndex()
+**      sqlite3BtreeClearTable()
+**      sqlite3BtreeDropTable()
+**      sqlite3BtreeInsert()
+**      sqlite3BtreeDelete()
+**      sqlite3BtreeUpdateMeta()
+**
+** If an initial attempt to acquire the lock fails because of lock contention
+** and the database was previously unlocked, then invoke the busy handler
+** if there is one.  But if there was previously a read-lock, do not
+** invoke the busy handler - just return SQLITE_BUSY.  SQLITE_BUSY is 
+** returned when there is already a read-lock in order to avoid a deadlock.
+**
+** Suppose there are two processes A and B.  A has a read lock and B has
+** a reserved lock.  B tries to promote to exclusive but is blocked because
+** of A's read lock.  A tries to promote to reserved but is blocked by B.
+** One or the other of the two processes must give way or there can be
+** no progress.  By returning SQLITE_BUSY and not invoking the busy callback
+** when A already has a read lock, we encourage A to give up and let B
+** proceed.
+*/
+int sqlite3BtreeBeginTrans(Btree *p, int wrflag){
+  sqlite3 *pBlock = 0;
+  BtShared *pBt = p->pBt;
+  int rc = SQLITE_OK;
+
+  sqlite3BtreeEnter(p);
+  btreeIntegrity(p);
+
+  /* If the btree is already in a write-transaction, or it
+  ** is already in a read-transaction and a read-transaction
+  ** is requested, this is a no-op.
+  */
+  if( p->inTrans==TRANS_WRITE || (p->inTrans==TRANS_READ && !wrflag) ){
+    goto trans_begun;
+  }
+
+  /* Write transactions are not possible on a read-only database */
+  if( pBt->readOnly && wrflag ){
+    rc = SQLITE_READONLY;
+    goto trans_begun;
+  }
+
+#ifndef SQLITE_OMIT_SHARED_CACHE
+  /* If another database handle has already opened a write transaction 
+  ** on this shared-btree structure and a second write transaction is
+  ** requested, return SQLITE_LOCKED.
+  */
+  if( (wrflag && pBt->inTransaction==TRANS_WRITE) || pBt->isPending ){
+    pBlock = pBt->pWriter->db;
+  }else if( wrflag>1 ){
+    BtLock *pIter;
+    for(pIter=pBt->pLock; pIter; pIter=pIter->pNext){
+      if( pIter->pBtree!=p ){
+        pBlock = pIter->pBtree->db;
+        break;
+      }
+    }
+  }
+  if( pBlock ){
+    sqlite3ConnectionBlocked(p->db, pBlock);
+    rc = SQLITE_LOCKED_SHAREDCACHE;
+    goto trans_begun;
+  }
+#endif
+
+  /* Any read-only or read-write transaction implies a read-lock on 
+  ** page 1. So if some other shared-cache client already has a write-lock 
+  ** on page 1, the transaction cannot be opened. */
+  rc = querySharedCacheTableLock(p, MASTER_ROOT, READ_LOCK);
+  if( SQLITE_OK!=rc ) goto trans_begun;
+
+  pBt->initiallyEmpty = (u8)(pBt->nPage==0);
+  do {
+    /* Call lockBtree() until either pBt->pPage1 is populated or
+    ** lockBtree() returns something other than SQLITE_OK. lockBtree()
+    ** may return SQLITE_OK but leave pBt->pPage1 set to 0 if after
+    ** reading page 1 it discovers that the page-size of the database 
+    ** file is not pBt->pageSize. In this case lockBtree() will update
+    ** pBt->pageSize to the page-size of the file on disk.
+    */
+    while( pBt->pPage1==0 && SQLITE_OK==(rc = lockBtree(pBt)) );
+
+    if( rc==SQLITE_OK && wrflag ){
+      if( pBt->readOnly ){
+        rc = SQLITE_READONLY;
+      }else{
+        rc = sqlite3PagerBegin(pBt->pPager,wrflag>1,sqlite3TempInMemory(p->db));
+        if( rc==SQLITE_OK ){
+          rc = newDatabase(pBt);
+        }
+      }
+    }
+  
+    if( rc!=SQLITE_OK ){
+      unlockBtreeIfUnused(pBt);
+    }
+  }while( (rc&0xFF)==SQLITE_BUSY && pBt->inTransaction==TRANS_NONE &&
+          btreeInvokeBusyHandler(pBt) );
+
+  if( rc==SQLITE_OK ){
+    if( p->inTrans==TRANS_NONE ){
+      pBt->nTransaction++;
+#ifndef SQLITE_OMIT_SHARED_CACHE
+      if( p->sharable ){
+	assert( p->lock.pBtree==p && p->lock.iTable==1 );
+        p->lock.eLock = READ_LOCK;
+        p->lock.pNext = pBt->pLock;
+        pBt->pLock = &p->lock;
+      }
+#endif
+    }
+    p->inTrans = (wrflag?TRANS_WRITE:TRANS_READ);
+    if( p->inTrans>pBt->inTransaction ){
+      pBt->inTransaction = p->inTrans;
+    }
+    if( wrflag ){
+      MemPage *pPage1 = pBt->pPage1;
+#ifndef SQLITE_OMIT_SHARED_CACHE
+      assert( !pBt->pWriter );
+      pBt->pWriter = p;
+      pBt->isExclusive = (u8)(wrflag>1);
+#endif
+
+      /* If the db-size header field is incorrect (as it may be if an old
+      ** client has been writing the database file), update it now. Doing
+      ** this sooner rather than later means the database size can safely 
+      ** re-read the database size from page 1 if a savepoint or transaction
+      ** rollback occurs within the transaction.
+      */
+      if( pBt->nPage!=get4byte(&pPage1->aData[28]) ){
+        rc = sqlite3PagerWrite(pPage1->pDbPage);
+        if( rc==SQLITE_OK ){
+          put4byte(&pPage1->aData[28], pBt->nPage);
+        }
+      }
+    }
+  }
+
+
+trans_begun:
+  if( rc==SQLITE_OK && wrflag ){
+    /* This call makes sure that the pager has the correct number of
+    ** open savepoints. If the second parameter is greater than 0 and
+    ** the sub-journal is not already open, then it will be opened here.
+    */
+    rc = sqlite3PagerOpenSavepoint(pBt->pPager, p->db->nSavepoint);
+  }
+
+  btreeIntegrity(p);
+  sqlite3BtreeLeave(p);
+  return rc;
+}
+
+#ifndef SQLITE_OMIT_AUTOVACUUM
+
+/*
+** Set the pointer-map entries for all children of page pPage. Also, if
+** pPage contains cells that point to overflow pages, set the pointer
+** map entries for the overflow pages as well.
+*/
+static int setChildPtrmaps(MemPage *pPage){
+  int i;                             /* Counter variable */
+  int nCell;                         /* Number of cells in page pPage */
+  int rc;                            /* Return code */
+  BtShared *pBt = pPage->pBt;
+  u8 isInitOrig = pPage->isInit;
+  Pgno pgno = pPage->pgno;
+
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  rc = btreeInitPage(pPage);
+  if( rc!=SQLITE_OK ){
+    goto set_child_ptrmaps_out;
+  }
+  nCell = pPage->nCell;
+
+  for(i=0; i<nCell; i++){
+    u8 *pCell = findCell(pPage, i);
+
+    ptrmapPutOvflPtr(pPage, pCell, &rc);
+
+    if( !pPage->leaf ){
+      Pgno childPgno = get4byte(pCell);
+      ptrmapPut(pBt, childPgno, PTRMAP_BTREE, pgno, &rc);
+    }
+  }
+
+  if( !pPage->leaf ){
+    Pgno childPgno = get4byte(&pPage->aData[pPage->hdrOffset+8]);
+    ptrmapPut(pBt, childPgno, PTRMAP_BTREE, pgno, &rc);
+  }
+
+set_child_ptrmaps_out:
+  pPage->isInit = isInitOrig;
+  return rc;
+}
+
+/*
+** Somewhere on pPage is a pointer to page iFrom.  Modify this pointer so
+** that it points to iTo. Parameter eType describes the type of pointer to
+** be modified, as  follows:
+**
+** PTRMAP_BTREE:     pPage is a btree-page. The pointer points at a child 
+**                   page of pPage.
+**
+** PTRMAP_OVERFLOW1: pPage is a btree-page. The pointer points at an overflow
+**                   page pointed to by one of the cells on pPage.
+**
+** PTRMAP_OVERFLOW2: pPage is an overflow-page. The pointer points at the next
+**                   overflow page in the list.
+*/
+static int modifyPagePointer(MemPage *pPage, Pgno iFrom, Pgno iTo, u8 eType){
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
+  if( eType==PTRMAP_OVERFLOW2 ){
+    /* The pointer is always the first 4 bytes of the page in this case.  */
+    if( get4byte(pPage->aData)!=iFrom ){
+      return SQLITE_CORRUPT_BKPT;
+    }
+    put4byte(pPage->aData, iTo);
+  }else{
+    u8 isInitOrig = pPage->isInit;
+    int i;
+    int nCell;
+
+    btreeInitPage(pPage);
+    nCell = pPage->nCell;
+
+    for(i=0; i<nCell; i++){
+      u8 *pCell = findCell(pPage, i);
+      if( eType==PTRMAP_OVERFLOW1 ){
+        CellInfo info;
+        btreeParseCellPtr(pPage, pCell, &info);
+        if( info.iOverflow
+         && pCell+info.iOverflow+3<=pPage->aData+pPage->maskPage
+         && iFrom==get4byte(&pCell[info.iOverflow])
+        ){
+          put4byte(&pCell[info.iOverflow], iTo);
+          break;
+        }
+      }else{
+        if( get4byte(pCell)==iFrom ){
+          put4byte(pCell, iTo);
+          break;
+        }
+      }
+    }
+  
+    if( i==nCell ){
+      if( eType!=PTRMAP_BTREE || 
+          get4byte(&pPage->aData[pPage->hdrOffset+8])!=iFrom ){
+        return SQLITE_CORRUPT_BKPT;
+      }
+      put4byte(&pPage->aData[pPage->hdrOffset+8], iTo);
+    }
+
+    pPage->isInit = isInitOrig;
+  }
+  return SQLITE_OK;
+}
+
+
+/*
+** Move the open database page pDbPage to location iFreePage in the 
+** database. The pDbPage reference remains valid.
+**
+** The isCommit flag indicates that there is no need to remember that
+** the journal needs to be sync()ed before database page pDbPage->pgno 
+** can be written to. The caller has already promised not to write to that
+** page.
+*/
+static int relocatePage(
+  BtShared *pBt,           /* Btree */
+  MemPage *pDbPage,        /* Open page to move */
+  u8 eType,                /* Pointer map 'type' entry for pDbPage */
+  Pgno iPtrPage,           /* Pointer map 'page-no' entry for pDbPage */
+  Pgno iFreePage,          /* The location to move pDbPage to */
+  int isCommit             /* isCommit flag passed to sqlite3PagerMovepage */
+){
+  MemPage *pPtrPage;   /* The page that contains a pointer to pDbPage */
+  Pgno iDbPage = pDbPage->pgno;
+  Pager *pPager = pBt->pPager;
+  int rc;
+
+  assert( eType==PTRMAP_OVERFLOW2 || eType==PTRMAP_OVERFLOW1 || 
+      eType==PTRMAP_BTREE || eType==PTRMAP_ROOTPAGE );
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  assert( pDbPage->pBt==pBt );
+
+  /* Move page iDbPage from its current location to page number iFreePage */
+  TRACE(("AUTOVACUUM: Moving %d to free page %d (ptr page %d type %d)\n", 
+      iDbPage, iFreePage, iPtrPage, eType));
+  rc = sqlite3PagerMovepage(pPager, pDbPage->pDbPage, iFreePage, isCommit);
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+  pDbPage->pgno = iFreePage;
+
+  /* If pDbPage was a btree-page, then it may have child pages and/or cells
+  ** that point to overflow pages. The pointer map entries for all these
+  ** pages need to be changed.
+  **
+  ** If pDbPage is an overflow page, then the first 4 bytes may store a
+  ** pointer to a subsequent overflow page. If this is the case, then
+  ** the pointer map needs to be updated for the subsequent overflow page.
+  */
+  if( eType==PTRMAP_BTREE || eType==PTRMAP_ROOTPAGE ){
+    rc = setChildPtrmaps(pDbPage);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+  }else{
+    Pgno nextOvfl = get4byte(pDbPage->aData);
+    if( nextOvfl!=0 ){
+      ptrmapPut(pBt, nextOvfl, PTRMAP_OVERFLOW2, iFreePage, &rc);
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+    }
+  }
+
+  /* Fix the database pointer on page iPtrPage that pointed at iDbPage so
+  ** that it points at iFreePage. Also fix the pointer map entry for
+  ** iPtrPage.
+  */
+  if( eType!=PTRMAP_ROOTPAGE ){
+    rc = btreeGetPage(pBt, iPtrPage, &pPtrPage, 0);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+    rc = sqlite3PagerWrite(pPtrPage->pDbPage);
+    if( rc!=SQLITE_OK ){
+      releasePage(pPtrPage);
+      return rc;
+    }
+    rc = modifyPagePointer(pPtrPage, iDbPage, iFreePage, eType);
+    releasePage(pPtrPage);
+    if( rc==SQLITE_OK ){
+      ptrmapPut(pBt, iFreePage, eType, iPtrPage, &rc);
+    }
+  }
+  return rc;
+}
+
+/* Forward declaration required by incrVacuumStep(). */
+static int allocateBtreePage(BtShared *, MemPage **, Pgno *, Pgno, u8);
+
+/*
+** Perform a single step of an incremental-vacuum. If successful,
+** return SQLITE_OK. If there is no work to do (and therefore no
+** point in calling this function again), return SQLITE_DONE.
+**
+** More specificly, this function attempts to re-organize the 
+** database so that the last page of the file currently in use
+** is no longer in use.
+**
+** If the nFin parameter is non-zero, this function assumes
+** that the caller will keep calling incrVacuumStep() until
+** it returns SQLITE_DONE or an error, and that nFin is the
+** number of pages the database file will contain after this 
+** process is complete.  If nFin is zero, it is assumed that
+** incrVacuumStep() will be called a finite amount of times
+** which may or may not empty the freelist.  A full autovacuum
+** has nFin>0.  A "PRAGMA incremental_vacuum" has nFin==0.
+*/
+static int incrVacuumStep(BtShared *pBt, Pgno nFin, Pgno iLastPg){
+  Pgno nFreeList;           /* Number of pages still on the free-list */
+  int rc;
+
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  assert( iLastPg>nFin );
+
+  if( !PTRMAP_ISPAGE(pBt, iLastPg) && iLastPg!=PENDING_BYTE_PAGE(pBt) ){
+    u8 eType;
+    Pgno iPtrPage;
+
+    nFreeList = get4byte(&pBt->pPage1->aData[36]);
+    if( nFreeList==0 ){
+      return SQLITE_DONE;
+    }
+
+    rc = ptrmapGet(pBt, iLastPg, &eType, &iPtrPage);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+    if( eType==PTRMAP_ROOTPAGE ){
+      return SQLITE_CORRUPT_BKPT;
+    }
+
+    if( eType==PTRMAP_FREEPAGE ){
+      if( nFin==0 ){
+        /* Remove the page from the files free-list. This is not required
+        ** if nFin is non-zero. In that case, the free-list will be
+        ** truncated to zero after this function returns, so it doesn't 
+        ** matter if it still contains some garbage entries.
+        */
+        Pgno iFreePg;
+        MemPage *pFreePg;
+        rc = allocateBtreePage(pBt, &pFreePg, &iFreePg, iLastPg, 1);
+        if( rc!=SQLITE_OK ){
+          return rc;
+        }
+        assert( iFreePg==iLastPg );
+        releasePage(pFreePg);
+      }
+    } else {
+      Pgno iFreePg;             /* Index of free page to move pLastPg to */
+      MemPage *pLastPg;
+
+      rc = btreeGetPage(pBt, iLastPg, &pLastPg, 0);
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+
+      /* If nFin is zero, this loop runs exactly once and page pLastPg
+      ** is swapped with the first free page pulled off the free list.
+      **
+      ** On the other hand, if nFin is greater than zero, then keep
+      ** looping until a free-page located within the first nFin pages
+      ** of the file is found.
+      */
+      do {
+        MemPage *pFreePg;
+        rc = allocateBtreePage(pBt, &pFreePg, &iFreePg, 0, 0);
+        if( rc!=SQLITE_OK ){
+          releasePage(pLastPg);
+          return rc;
+        }
+        releasePage(pFreePg);
+      }while( nFin!=0 && iFreePg>nFin );
+      assert( iFreePg<iLastPg );
+      
+      rc = sqlite3PagerWrite(pLastPg->pDbPage);
+      if( rc==SQLITE_OK ){
+        rc = relocatePage(pBt, pLastPg, eType, iPtrPage, iFreePg, nFin!=0);
+      }
+      releasePage(pLastPg);
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+    }
+  }
+
+  if( nFin==0 ){
+    iLastPg--;
+    while( iLastPg==PENDING_BYTE_PAGE(pBt)||PTRMAP_ISPAGE(pBt, iLastPg) ){
+      if( PTRMAP_ISPAGE(pBt, iLastPg) ){
+        MemPage *pPg;
+        rc = btreeGetPage(pBt, iLastPg, &pPg, 0);
+        if( rc!=SQLITE_OK ){
+          return rc;
+        }
+        rc = sqlite3PagerWrite(pPg->pDbPage);
+        releasePage(pPg);
+        if( rc!=SQLITE_OK ){
+          return rc;
+        }
+      }
+      iLastPg--;
+    }
+    sqlite3PagerTruncateImage(pBt->pPager, iLastPg);
+    pBt->nPage = iLastPg;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** A write-transaction must be opened before calling this function.
+** It performs a single unit of work towards an incremental vacuum.
+**
+** If the incremental vacuum is finished after this function has run,
+** SQLITE_DONE is returned. If it is not finished, but no error occurred,
+** SQLITE_OK is returned. Otherwise an SQLite error code. 
+*/
+int sqlite3BtreeIncrVacuum(Btree *p){
+  int rc;
+  BtShared *pBt = p->pBt;
+
+  sqlite3BtreeEnter(p);
+  assert( pBt->inTransaction==TRANS_WRITE && p->inTrans==TRANS_WRITE );
+  if( !pBt->autoVacuum ){
+    rc = SQLITE_DONE;
+  }else{
+    invalidateAllOverflowCache(pBt);
+    rc = incrVacuumStep(pBt, 0, btreePagecount(pBt));
+    if( rc==SQLITE_OK ){
+      rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
+      put4byte(&pBt->pPage1->aData[28], pBt->nPage);
+    }
+  }
+  sqlite3BtreeLeave(p);
+  return rc;
+}
+
+/*
+** This routine is called prior to sqlite3PagerCommit when a transaction
+** is commited for an auto-vacuum database.
+**
+** If SQLITE_OK is returned, then *pnTrunc is set to the number of pages
+** the database file should be truncated to during the commit process. 
+** i.e. the database has been reorganized so that only the first *pnTrunc
+** pages are in use.
+*/
+static int autoVacuumCommit(BtShared *pBt){
+  int rc = SQLITE_OK;
+  Pager *pPager = pBt->pPager;
+  VVA_ONLY( int nRef = sqlite3PagerRefcount(pPager) );
+
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  invalidateAllOverflowCache(pBt);
+  assert(pBt->autoVacuum);
+  if( !pBt->incrVacuum ){
+    Pgno nFin;         /* Number of pages in database after autovacuuming */
+    Pgno nFree;        /* Number of pages on the freelist initially */
+    Pgno nPtrmap;      /* Number of PtrMap pages to be freed */
+    Pgno iFree;        /* The next page to be freed */
+    int nEntry;        /* Number of entries on one ptrmap page */
+    Pgno nOrig;        /* Database size before freeing */
+
+    nOrig = btreePagecount(pBt);
+    if( PTRMAP_ISPAGE(pBt, nOrig) || nOrig==PENDING_BYTE_PAGE(pBt) ){
+      /* It is not possible to create a database for which the final page
+      ** is either a pointer-map page or the pending-byte page. If one
+      ** is encountered, this indicates corruption.
+      */
+      return SQLITE_CORRUPT_BKPT;
+    }
+
+    nFree = get4byte(&pBt->pPage1->aData[36]);
+    nEntry = pBt->usableSize/5;
+    nPtrmap = (nFree-nOrig+PTRMAP_PAGENO(pBt, nOrig)+nEntry)/nEntry;
+    nFin = nOrig - nFree - nPtrmap;
+    if( nOrig>PENDING_BYTE_PAGE(pBt) && nFin<PENDING_BYTE_PAGE(pBt) ){
+      nFin--;
+    }
+    while( PTRMAP_ISPAGE(pBt, nFin) || nFin==PENDING_BYTE_PAGE(pBt) ){
+      nFin--;
+    }
+    if( nFin>nOrig ) return SQLITE_CORRUPT_BKPT;
+
+    for(iFree=nOrig; iFree>nFin && rc==SQLITE_OK; iFree--){
+      rc = incrVacuumStep(pBt, nFin, iFree);
+    }
+    if( (rc==SQLITE_DONE || rc==SQLITE_OK) && nFree>0 ){
+      rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
+      put4byte(&pBt->pPage1->aData[32], 0);
+      put4byte(&pBt->pPage1->aData[36], 0);
+      put4byte(&pBt->pPage1->aData[28], nFin);
+      sqlite3PagerTruncateImage(pBt->pPager, nFin);
+      pBt->nPage = nFin;
+    }
+    if( rc!=SQLITE_OK ){
+      sqlite3PagerRollback(pPager);
+    }
+  }
+
+  assert( nRef==sqlite3PagerRefcount(pPager) );
+  return rc;
+}
+
+#else /* ifndef SQLITE_OMIT_AUTOVACUUM */
+# define setChildPtrmaps(x) SQLITE_OK
+#endif
+
+/*
+** This routine does the first phase of a two-phase commit.  This routine
+** causes a rollback journal to be created (if it does not already exist)
+** and populated with enough information so that if a power loss occurs
+** the database can be restored to its original state by playing back
+** the journal.  Then the contents of the journal are flushed out to
+** the disk.  After the journal is safely on oxide, the changes to the
+** database are written into the database file and flushed to oxide.
+** At the end of this call, the rollback journal still exists on the
+** disk and we are still holding all locks, so the transaction has not
+** committed.  See sqlite3BtreeCommitPhaseTwo() for the second phase of the
+** commit process.
+**
+** This call is a no-op if no write-transaction is currently active on pBt.
+**
+** Otherwise, sync the database file for the btree pBt. zMaster points to
+** the name of a master journal file that should be written into the
+** individual journal file, or is NULL, indicating no master journal file 
+** (single database transaction).
+**
+** When this is called, the master journal should already have been
+** created, populated with this journal pointer and synced to disk.
+**
+** Once this is routine has returned, the only thing required to commit
+** the write-transaction for this database file is to delete the journal.
+*/
+int sqlite3BtreeCommitPhaseOne(Btree *p, const char *zMaster){
+  int rc = SQLITE_OK;
+  if( p->inTrans==TRANS_WRITE ){
+    BtShared *pBt = p->pBt;
+    sqlite3BtreeEnter(p);
+#ifndef SQLITE_OMIT_AUTOVACUUM
+    if( pBt->autoVacuum ){
+      rc = autoVacuumCommit(pBt);
+      if( rc!=SQLITE_OK ){
+        sqlite3BtreeLeave(p);
+        return rc;
+      }
+    }
+#endif
+    rc = sqlite3PagerCommitPhaseOne(pBt->pPager, zMaster, 0);
+    sqlite3BtreeLeave(p);
+  }
+  return rc;
+}
+
+/*
+** This function is called from both BtreeCommitPhaseTwo() and BtreeRollback()
+** at the conclusion of a transaction.
+*/
+static void btreeEndTransaction(Btree *p){
+  BtShared *pBt = p->pBt;
+  assert( sqlite3BtreeHoldsMutex(p) );
+
+  btreeClearHasContent(pBt);
+  if( p->inTrans>TRANS_NONE && p->db->activeVdbeCnt>1 ){
+    /* If there are other active statements that belong to this database
+    ** handle, downgrade to a read-only transaction. The other statements
+    ** may still be reading from the database.  */
+    downgradeAllSharedCacheTableLocks(p);
+    p->inTrans = TRANS_READ;
+  }else{
+    /* If the handle had any kind of transaction open, decrement the 
+    ** transaction count of the shared btree. If the transaction count 
+    ** reaches 0, set the shared state to TRANS_NONE. The unlockBtreeIfUnused()
+    ** call below will unlock the pager.  */
+    if( p->inTrans!=TRANS_NONE ){
+      clearAllSharedCacheTableLocks(p);
+      pBt->nTransaction--;
+      if( 0==pBt->nTransaction ){
+        pBt->inTransaction = TRANS_NONE;
+      }
+    }
+
+    /* Set the current transaction state to TRANS_NONE and unlock the 
+    ** pager if this call closed the only read or write transaction.  */
+    p->inTrans = TRANS_NONE;
+    unlockBtreeIfUnused(pBt);
+  }
+
+  btreeIntegrity(p);
+}
+
+/*
+** Commit the transaction currently in progress.
+**
+** This routine implements the second phase of a 2-phase commit.  The
+** sqlite3BtreeCommitPhaseOne() routine does the first phase and should
+** be invoked prior to calling this routine.  The sqlite3BtreeCommitPhaseOne()
+** routine did all the work of writing information out to disk and flushing the
+** contents so that they are written onto the disk platter.  All this
+** routine has to do is delete or truncate or zero the header in the
+** the rollback journal (which causes the transaction to commit) and
+** drop locks.
+**
+** Normally, if an error occurs while the pager layer is attempting to 
+** finalize the underlying journal file, this function returns an error and
+** the upper layer will attempt a rollback. However, if the second argument
+** is non-zero then this b-tree transaction is part of a multi-file 
+** transaction. In this case, the transaction has already been committed 
+** (by deleting a master journal file) and the caller will ignore this 
+** functions return code. So, even if an error occurs in the pager layer,
+** reset the b-tree objects internal state to indicate that the write
+** transaction has been closed. This is quite safe, as the pager will have
+** transitioned to the error state.
+**
+** This will release the write lock on the database file.  If there
+** are no active cursors, it also releases the read lock.
+*/
+int sqlite3BtreeCommitPhaseTwo(Btree *p, int bCleanup){
+
+  if( p->inTrans==TRANS_NONE ) return SQLITE_OK;
+  sqlite3BtreeEnter(p);
+  btreeIntegrity(p);
+
+  /* If the handle has a write-transaction open, commit the shared-btrees 
+  ** transaction and set the shared state to TRANS_READ.
+  */
+  if( p->inTrans==TRANS_WRITE ){
+    int rc;
+    BtShared *pBt = p->pBt;
+    assert( pBt->inTransaction==TRANS_WRITE );
+    assert( pBt->nTransaction>0 );
+    rc = sqlite3PagerCommitPhaseTwo(pBt->pPager);
+    if( rc!=SQLITE_OK && bCleanup==0 ){
+      sqlite3BtreeLeave(p);
+      return rc;
+    }
+    pBt->inTransaction = TRANS_READ;
+  }
+
+  btreeEndTransaction(p);
+  sqlite3BtreeLeave(p);
+  return SQLITE_OK;
+}
+
+/*
+** Do both phases of a commit.
+*/
+int sqlite3BtreeCommit(Btree *p){
+  int rc;
+  sqlite3BtreeEnter(p);
+  rc = sqlite3BtreeCommitPhaseOne(p, 0);
+  if( rc==SQLITE_OK ){
+    rc = sqlite3BtreeCommitPhaseTwo(p, 0);
+  }
+  sqlite3BtreeLeave(p);
+  return rc;
+}
+
+#ifndef NDEBUG
+/*
+** Return the number of write-cursors open on this handle. This is for use
+** in assert() expressions, so it is only compiled if NDEBUG is not
+** defined.
+**
+** For the purposes of this routine, a write-cursor is any cursor that
+** is capable of writing to the databse.  That means the cursor was
+** originally opened for writing and the cursor has not be disabled
+** by having its state changed to CURSOR_FAULT.
+*/
+static int countWriteCursors(BtShared *pBt){
+  BtCursor *pCur;
+  int r = 0;
+  for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
+    if( pCur->wrFlag && pCur->eState!=CURSOR_FAULT ) r++; 
+  }
+  return r;
+}
+#endif
+
+/*
+** This routine sets the state to CURSOR_FAULT and the error
+** code to errCode for every cursor on BtShared that pBtree
+** references.
+**
+** Every cursor is tripped, including cursors that belong
+** to other database connections that happen to be sharing
+** the cache with pBtree.
+**
+** This routine gets called when a rollback occurs.
+** All cursors using the same cache must be tripped
+** to prevent them from trying to use the btree after
+** the rollback.  The rollback may have deleted tables
+** or moved root pages, so it is not sufficient to
+** save the state of the cursor.  The cursor must be
+** invalidated.
+*/
+void sqlite3BtreeTripAllCursors(Btree *pBtree, int errCode){
+  BtCursor *p;
+  sqlite3BtreeEnter(pBtree);
+  for(p=pBtree->pBt->pCursor; p; p=p->pNext){
+    int i;
+    sqlite3BtreeClearCursor(p);
+    p->eState = CURSOR_FAULT;
+    p->skipNext = errCode;
+    for(i=0; i<=p->iPage; i++){
+      releasePage(p->apPage[i]);
+      p->apPage[i] = 0;
+    }
+  }
+  sqlite3BtreeLeave(pBtree);
+}
+
+/*
+** Rollback the transaction in progress.  All cursors will be
+** invalided by this operation.  Any attempt to use a cursor
+** that was open at the beginning of this operation will result
+** in an error.
+**
+** This will release the write lock on the database file.  If there
+** are no active cursors, it also releases the read lock.
+*/
+int sqlite3BtreeRollback(Btree *p){
+  int rc;
+  BtShared *pBt = p->pBt;
+  MemPage *pPage1;
+
+  sqlite3BtreeEnter(p);
+  rc = saveAllCursors(pBt, 0, 0);
+#ifndef SQLITE_OMIT_SHARED_CACHE
+  if( rc!=SQLITE_OK ){
+    /* This is a horrible situation. An IO or malloc() error occurred whilst
+    ** trying to save cursor positions. If this is an automatic rollback (as
+    ** the result of a constraint, malloc() failure or IO error) then 
+    ** the cache may be internally inconsistent (not contain valid trees) so
+    ** we cannot simply return the error to the caller. Instead, abort 
+    ** all queries that may be using any of the cursors that failed to save.
+    */
+    sqlite3BtreeTripAllCursors(p, rc);
+  }
+#endif
+  btreeIntegrity(p);
+
+  if( p->inTrans==TRANS_WRITE ){
+    int rc2;
+
+    assert( TRANS_WRITE==pBt->inTransaction );
+    rc2 = sqlite3PagerRollback(pBt->pPager);
+    if( rc2!=SQLITE_OK ){
+      rc = rc2;
+    }
+
+    /* The rollback may have destroyed the pPage1->aData value.  So
+    ** call btreeGetPage() on page 1 again to make
+    ** sure pPage1->aData is set correctly. */
+    if( btreeGetPage(pBt, 1, &pPage1, 0)==SQLITE_OK ){
+      int nPage = get4byte(28+(u8*)pPage1->aData);
+      testcase( nPage==0 );
+      if( nPage==0 ) sqlite3PagerPagecount(pBt->pPager, &nPage);
+      testcase( pBt->nPage!=nPage );
+      pBt->nPage = nPage;
+      releasePage(pPage1);
+    }
+    assert( countWriteCursors(pBt)==0 );
+    pBt->inTransaction = TRANS_READ;
+  }
+
+  btreeEndTransaction(p);
+  sqlite3BtreeLeave(p);
+  return rc;
+}
+
+/*
+** Start a statement subtransaction. The subtransaction can can be rolled
+** back independently of the main transaction. You must start a transaction 
+** before starting a subtransaction. The subtransaction is ended automatically 
+** if the main transaction commits or rolls back.
+**
+** Statement subtransactions are used around individual SQL statements
+** that are contained within a BEGIN...COMMIT block.  If a constraint
+** error occurs within the statement, the effect of that one statement
+** can be rolled back without having to rollback the entire transaction.
+**
+** A statement sub-transaction is implemented as an anonymous savepoint. The
+** value passed as the second parameter is the total number of savepoints,
+** including the new anonymous savepoint, open on the B-Tree. i.e. if there
+** are no active savepoints and no other statement-transactions open,
+** iStatement is 1. This anonymous savepoint can be released or rolled back
+** using the sqlite3BtreeSavepoint() function.
+*/
+int sqlite3BtreeBeginStmt(Btree *p, int iStatement){
+  int rc;
+  BtShared *pBt = p->pBt;
+  sqlite3BtreeEnter(p);
+  assert( p->inTrans==TRANS_WRITE );
+  assert( pBt->readOnly==0 );
+  assert( iStatement>0 );
+  assert( iStatement>p->db->nSavepoint );
+  assert( pBt->inTransaction==TRANS_WRITE );
+  /* At the pager level, a statement transaction is a savepoint with
+  ** an index greater than all savepoints created explicitly using
+  ** SQL statements. It is illegal to open, release or rollback any
+  ** such savepoints while the statement transaction savepoint is active.
+  */
+  rc = sqlite3PagerOpenSavepoint(pBt->pPager, iStatement);
+  sqlite3BtreeLeave(p);
+  return rc;
+}
+
+/*
+** The second argument to this function, op, is always SAVEPOINT_ROLLBACK
+** or SAVEPOINT_RELEASE. This function either releases or rolls back the
+** savepoint identified by parameter iSavepoint, depending on the value 
+** of op.
+**
+** Normally, iSavepoint is greater than or equal to zero. However, if op is
+** SAVEPOINT_ROLLBACK, then iSavepoint may also be -1. In this case the 
+** contents of the entire transaction are rolled back. This is different
+** from a normal transaction rollback, as no locks are released and the
+** transaction remains open.
+*/
+int sqlite3BtreeSavepoint(Btree *p, int op, int iSavepoint){
+  int rc = SQLITE_OK;
+  if( p && p->inTrans==TRANS_WRITE ){
+    BtShared *pBt = p->pBt;
+    assert( op==SAVEPOINT_RELEASE || op==SAVEPOINT_ROLLBACK );
+    assert( iSavepoint>=0 || (iSavepoint==-1 && op==SAVEPOINT_ROLLBACK) );
+    sqlite3BtreeEnter(p);
+    rc = sqlite3PagerSavepoint(pBt->pPager, op, iSavepoint);
+    if( rc==SQLITE_OK ){
+      if( iSavepoint<0 && pBt->initiallyEmpty ) pBt->nPage = 0;
+      rc = newDatabase(pBt);
+      pBt->nPage = get4byte(28 + pBt->pPage1->aData);
+
+      /* The database size was written into the offset 28 of the header
+      ** when the transaction started, so we know that the value at offset
+      ** 28 is nonzero. */
+      assert( pBt->nPage>0 );
+    }
+    sqlite3BtreeLeave(p);
+  }
+  return rc;
+}
+
+/*
+** Create a new cursor for the BTree whose root is on the page
+** iTable. If a read-only cursor is requested, it is assumed that
+** the caller already has at least a read-only transaction open
+** on the database already. If a write-cursor is requested, then
+** the caller is assumed to have an open write transaction.
+**
+** If wrFlag==0, then the cursor can only be used for reading.
+** If wrFlag==1, then the cursor can be used for reading or for
+** writing if other conditions for writing are also met.  These
+** are the conditions that must be met in order for writing to
+** be allowed:
+**
+** 1:  The cursor must have been opened with wrFlag==1
+**
+** 2:  Other database connections that share the same pager cache
+**     but which are not in the READ_UNCOMMITTED state may not have
+**     cursors open with wrFlag==0 on the same table.  Otherwise
+**     the changes made by this write cursor would be visible to
+**     the read cursors in the other database connection.
+**
+** 3:  The database must be writable (not on read-only media)
+**
+** 4:  There must be an active transaction.
+**
+** No checking is done to make sure that page iTable really is the
+** root page of a b-tree.  If it is not, then the cursor acquired
+** will not work correctly.
+**
+** It is assumed that the sqlite3BtreeCursorZero() has been called
+** on pCur to initialize the memory space prior to invoking this routine.
+*/
+static int btreeCursor(
+  Btree *p,                              /* The btree */
+  int iTable,                            /* Root page of table to open */
+  int wrFlag,                            /* 1 to write. 0 read-only */
+  struct KeyInfo *pKeyInfo,              /* First arg to comparison function */
+  BtCursor *pCur                         /* Space for new cursor */
+){
+  BtShared *pBt = p->pBt;                /* Shared b-tree handle */
+
+  assert( sqlite3BtreeHoldsMutex(p) );
+  assert( wrFlag==0 || wrFlag==1 );
+
+  /* The following assert statements verify that if this is a sharable 
+  ** b-tree database, the connection is holding the required table locks, 
+  ** and that no other connection has any open cursor that conflicts with 
+  ** this lock.  */
+  assert( hasSharedCacheTableLock(p, iTable, pKeyInfo!=0, wrFlag+1) );
+  assert( wrFlag==0 || !hasReadConflicts(p, iTable) );
+
+  /* Assert that the caller has opened the required transaction. */
+  assert( p->inTrans>TRANS_NONE );
+  assert( wrFlag==0 || p->inTrans==TRANS_WRITE );
+  assert( pBt->pPage1 && pBt->pPage1->aData );
+
+  if( NEVER(wrFlag && pBt->readOnly) ){
+    return SQLITE_READONLY;
+  }
+  if( iTable==1 && btreePagecount(pBt)==0 ){
+    assert( wrFlag==0 );
+    iTable = 0;
+  }
+
+  /* Now that no other errors can occur, finish filling in the BtCursor
+  ** variables and link the cursor into the BtShared list.  */
+  pCur->pgnoRoot = (Pgno)iTable;
+  pCur->iPage = -1;
+  pCur->pKeyInfo = pKeyInfo;
+  pCur->pBtree = p;
+  pCur->pBt = pBt;
+  pCur->wrFlag = (u8)wrFlag;
+  pCur->pNext = pBt->pCursor;
+  if( pCur->pNext ){
+    pCur->pNext->pPrev = pCur;
+  }
+  pBt->pCursor = pCur;
+  pCur->eState = CURSOR_INVALID;
+  pCur->cachedRowid = 0;
+  return SQLITE_OK;
+}
+int sqlite3BtreeCursor(
+  Btree *p,                                   /* The btree */
+  int iTable,                                 /* Root page of table to open */
+  int wrFlag,                                 /* 1 to write. 0 read-only */
+  struct KeyInfo *pKeyInfo,                   /* First arg to xCompare() */
+  BtCursor *pCur                              /* Write new cursor here */
+){
+  int rc;
+  sqlite3BtreeEnter(p);
+  rc = btreeCursor(p, iTable, wrFlag, pKeyInfo, pCur);
+  sqlite3BtreeLeave(p);
+  return rc;
+}
+
+/*
+** Return the size of a BtCursor object in bytes.
+**
+** This interfaces is needed so that users of cursors can preallocate
+** sufficient storage to hold a cursor.  The BtCursor object is opaque
+** to users so they cannot do the sizeof() themselves - they must call
+** this routine.
+*/
+int sqlite3BtreeCursorSize(void){
+  return ROUND8(sizeof(BtCursor));
+}
+
+/*
+** Initialize memory that will be converted into a BtCursor object.
+**
+** The simple approach here would be to memset() the entire object
+** to zero.  But it turns out that the apPage[] and aiIdx[] arrays
+** do not need to be zeroed and they are large, so we can save a lot
+** of run-time by skipping the initialization of those elements.
+*/
+void sqlite3BtreeCursorZero(BtCursor *p){
+  memset(p, 0, offsetof(BtCursor, iPage));
+}
+
+/*
+** Set the cached rowid value of every cursor in the same database file
+** as pCur and having the same root page number as pCur.  The value is
+** set to iRowid.
+**
+** Only positive rowid values are considered valid for this cache.
+** The cache is initialized to zero, indicating an invalid cache.
+** A btree will work fine with zero or negative rowids.  We just cannot
+** cache zero or negative rowids, which means tables that use zero or
+** negative rowids might run a little slower.  But in practice, zero
+** or negative rowids are very uncommon so this should not be a problem.
+*/
+void sqlite3BtreeSetCachedRowid(BtCursor *pCur, sqlite3_int64 iRowid){
+  BtCursor *p;
+  for(p=pCur->pBt->pCursor; p; p=p->pNext){
+    if( p->pgnoRoot==pCur->pgnoRoot ) p->cachedRowid = iRowid;
+  }
+  assert( pCur->cachedRowid==iRowid );
+}
+
+/*
+** Return the cached rowid for the given cursor.  A negative or zero
+** return value indicates that the rowid cache is invalid and should be
+** ignored.  If the rowid cache has never before been set, then a
+** zero is returned.
+*/
+sqlite3_int64 sqlite3BtreeGetCachedRowid(BtCursor *pCur){
+  return pCur->cachedRowid;
+}
+
+/*
+** Close a cursor.  The read lock on the database file is released
+** when the last cursor is closed.
+*/
+int sqlite3BtreeCloseCursor(BtCursor *pCur){
+  Btree *pBtree = pCur->pBtree;
+  if( pBtree ){
+    int i;
+    BtShared *pBt = pCur->pBt;
+    sqlite3BtreeEnter(pBtree);
+    sqlite3BtreeClearCursor(pCur);
+    if( pCur->pPrev ){
+      pCur->pPrev->pNext = pCur->pNext;
+    }else{
+      pBt->pCursor = pCur->pNext;
+    }
+    if( pCur->pNext ){
+      pCur->pNext->pPrev = pCur->pPrev;
+    }
+    for(i=0; i<=pCur->iPage; i++){
+      releasePage(pCur->apPage[i]);
+    }
+    unlockBtreeIfUnused(pBt);
+    invalidateOverflowCache(pCur);
+    /* sqlite3_free(pCur); */
+    sqlite3BtreeLeave(pBtree);
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Make sure the BtCursor* given in the argument has a valid
+** BtCursor.info structure.  If it is not already valid, call
+** btreeParseCell() to fill it in.
+**
+** BtCursor.info is a cache of the information in the current cell.
+** Using this cache reduces the number of calls to btreeParseCell().
+**
+** 2007-06-25:  There is a bug in some versions of MSVC that cause the
+** compiler to crash when getCellInfo() is implemented as a macro.
+** But there is a measureable speed advantage to using the macro on gcc
+** (when less compiler optimizations like -Os or -O0 are used and the
+** compiler is not doing agressive inlining.)  So we use a real function
+** for MSVC and a macro for everything else.  Ticket #2457.
+*/
+#ifndef NDEBUG
+  static void assertCellInfo(BtCursor *pCur){
+    CellInfo info;
+    int iPage = pCur->iPage;
+    memset(&info, 0, sizeof(info));
+    btreeParseCell(pCur->apPage[iPage], pCur->aiIdx[iPage], &info);
+    assert( memcmp(&info, &pCur->info, sizeof(info))==0 );
+  }
+#else
+  #define assertCellInfo(x)
+#endif
+#ifdef _MSC_VER
+  /* Use a real function in MSVC to work around bugs in that compiler. */
+  static void getCellInfo(BtCursor *pCur){
+    if( pCur->info.nSize==0 ){
+      int iPage = pCur->iPage;
+      btreeParseCell(pCur->apPage[iPage],pCur->aiIdx[iPage],&pCur->info);
+      pCur->validNKey = 1;
+    }else{
+      assertCellInfo(pCur);
+    }
+  }
+#else /* if not _MSC_VER */
+  /* Use a macro in all other compilers so that the function is inlined */
+#define getCellInfo(pCur)                                                      \
+  if( pCur->info.nSize==0 ){                                                   \
+    int iPage = pCur->iPage;                                                   \
+    btreeParseCell(pCur->apPage[iPage],pCur->aiIdx[iPage],&pCur->info); \
+    pCur->validNKey = 1;                                                       \
+  }else{                                                                       \
+    assertCellInfo(pCur);                                                      \
+  }
+#endif /* _MSC_VER */
+
+#ifndef NDEBUG  /* The next routine used only within assert() statements */
+/*
+** Return true if the given BtCursor is valid.  A valid cursor is one
+** that is currently pointing to a row in a (non-empty) table.
+** This is a verification routine is used only within assert() statements.
+*/
+int sqlite3BtreeCursorIsValid(BtCursor *pCur){
+  return pCur && pCur->eState==CURSOR_VALID;
+}
+#endif /* NDEBUG */
+
+/*
+** Set *pSize to the size of the buffer needed to hold the value of
+** the key for the current entry.  If the cursor is not pointing
+** to a valid entry, *pSize is set to 0. 
+**
+** For a table with the INTKEY flag set, this routine returns the key
+** itself, not the number of bytes in the key.
+**
+** The caller must position the cursor prior to invoking this routine.
+** 
+** This routine cannot fail.  It always returns SQLITE_OK.  
+*/
+int sqlite3BtreeKeySize(BtCursor *pCur, i64 *pSize){
+  assert( cursorHoldsMutex(pCur) );
+  assert( pCur->eState==CURSOR_INVALID || pCur->eState==CURSOR_VALID );
+  if( pCur->eState!=CURSOR_VALID ){
+    *pSize = 0;
+  }else{
+    getCellInfo(pCur);
+    *pSize = pCur->info.nKey;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Set *pSize to the number of bytes of data in the entry the
+** cursor currently points to.
+**
+** The caller must guarantee that the cursor is pointing to a non-NULL
+** valid entry.  In other words, the calling procedure must guarantee
+** that the cursor has Cursor.eState==CURSOR_VALID.
+**
+** Failure is not possible.  This function always returns SQLITE_OK.
+** It might just as well be a procedure (returning void) but we continue
+** to return an integer result code for historical reasons.
+*/
+int sqlite3BtreeDataSize(BtCursor *pCur, u32 *pSize){
+  assert( cursorHoldsMutex(pCur) );
+  assert( pCur->eState==CURSOR_VALID );
+  getCellInfo(pCur);
+  *pSize = pCur->info.nData;
+  return SQLITE_OK;
+}
+
+/*
+** Given the page number of an overflow page in the database (parameter
+** ovfl), this function finds the page number of the next page in the 
+** linked list of overflow pages. If possible, it uses the auto-vacuum
+** pointer-map data instead of reading the content of page ovfl to do so. 
+**
+** If an error occurs an SQLite error code is returned. Otherwise:
+**
+** The page number of the next overflow page in the linked list is 
+** written to *pPgnoNext. If page ovfl is the last page in its linked 
+** list, *pPgnoNext is set to zero. 
+**
+** If ppPage is not NULL, and a reference to the MemPage object corresponding
+** to page number pOvfl was obtained, then *ppPage is set to point to that
+** reference. It is the responsibility of the caller to call releasePage()
+** on *ppPage to free the reference. In no reference was obtained (because
+** the pointer-map was used to obtain the value for *pPgnoNext), then
+** *ppPage is set to zero.
+*/
+static int getOverflowPage(
+  BtShared *pBt,               /* The database file */
+  Pgno ovfl,                   /* Current overflow page number */
+  MemPage **ppPage,            /* OUT: MemPage handle (may be NULL) */
+  Pgno *pPgnoNext              /* OUT: Next overflow page number */
+){
+  Pgno next = 0;
+  MemPage *pPage = 0;
+  int rc = SQLITE_OK;
+
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  assert(pPgnoNext);
+
+#ifndef SQLITE_OMIT_AUTOVACUUM
+  /* Try to find the next page in the overflow list using the
+  ** autovacuum pointer-map pages. Guess that the next page in 
+  ** the overflow list is page number (ovfl+1). If that guess turns 
+  ** out to be wrong, fall back to loading the data of page 
+  ** number ovfl to determine the next page number.
+  */
+  if( pBt->autoVacuum ){
+    Pgno pgno;
+    Pgno iGuess = ovfl+1;
+    u8 eType;
+
+    while( PTRMAP_ISPAGE(pBt, iGuess) || iGuess==PENDING_BYTE_PAGE(pBt) ){
+      iGuess++;
+    }
+
+    if( iGuess<=btreePagecount(pBt) ){
+      rc = ptrmapGet(pBt, iGuess, &eType, &pgno);
+      if( rc==SQLITE_OK && eType==PTRMAP_OVERFLOW2 && pgno==ovfl ){
+        next = iGuess;
+        rc = SQLITE_DONE;
+      }
+    }
+  }
+#endif
+
+  assert( next==0 || rc==SQLITE_DONE );
+  if( rc==SQLITE_OK ){
+    rc = btreeGetPage(pBt, ovfl, &pPage, 0);
+    assert( rc==SQLITE_OK || pPage==0 );
+    if( rc==SQLITE_OK ){
+      next = get4byte(pPage->aData);
+    }
+  }
+
+  *pPgnoNext = next;
+  if( ppPage ){
+    *ppPage = pPage;
+  }else{
+    releasePage(pPage);
+  }
+  return (rc==SQLITE_DONE ? SQLITE_OK : rc);
+}
+
+/*
+** Copy data from a buffer to a page, or from a page to a buffer.
+**
+** pPayload is a pointer to data stored on database page pDbPage.
+** If argument eOp is false, then nByte bytes of data are copied
+** from pPayload to the buffer pointed at by pBuf. If eOp is true,
+** then sqlite3PagerWrite() is called on pDbPage and nByte bytes
+** of data are copied from the buffer pBuf to pPayload.
+**
+** SQLITE_OK is returned on success, otherwise an error code.
+*/
+static int copyPayload(
+  void *pPayload,           /* Pointer to page data */
+  void *pBuf,               /* Pointer to buffer */
+  int nByte,                /* Number of bytes to copy */
+  int eOp,                  /* 0 -> copy from page, 1 -> copy to page */
+  DbPage *pDbPage           /* Page containing pPayload */
+){
+  if( eOp ){
+    /* Copy data from buffer to page (a write operation) */
+    int rc = sqlite3PagerWrite(pDbPage);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+    memcpy(pPayload, pBuf, nByte);
+  }else{
+    /* Copy data from page to buffer (a read operation) */
+    memcpy(pBuf, pPayload, nByte);
+  }
+  return SQLITE_OK;
+}
+
+/*
+** This function is used to read or overwrite payload information
+** for the entry that the pCur cursor is pointing to. If the eOp
+** parameter is 0, this is a read operation (data copied into
+** buffer pBuf). If it is non-zero, a write (data copied from
+** buffer pBuf).
+**
+** A total of "amt" bytes are read or written beginning at "offset".
+** Data is read to or from the buffer pBuf.
+**
+** The content being read or written might appear on the main page
+** or be scattered out on multiple overflow pages.
+**
+** If the BtCursor.isIncrblobHandle flag is set, and the current
+** cursor entry uses one or more overflow pages, this function
+** allocates space for and lazily popluates the overflow page-list 
+** cache array (BtCursor.aOverflow). Subsequent calls use this
+** cache to make seeking to the supplied offset more efficient.
+**
+** Once an overflow page-list cache has been allocated, it may be
+** invalidated if some other cursor writes to the same table, or if
+** the cursor is moved to a different row. Additionally, in auto-vacuum
+** mode, the following events may invalidate an overflow page-list cache.
+**
+**   * An incremental vacuum,
+**   * A commit in auto_vacuum="full" mode,
+**   * Creating a table (may require moving an overflow page).
+*/
+static int accessPayload(
+  BtCursor *pCur,      /* Cursor pointing to entry to read from */
+  u32 offset,          /* Begin reading this far into payload */
+  u32 amt,             /* Read this many bytes */
+  unsigned char *pBuf, /* Write the bytes into this buffer */ 
+  int eOp              /* zero to read. non-zero to write. */
+){
+  unsigned char *aPayload;
+  int rc = SQLITE_OK;
+  u32 nKey;
+  int iIdx = 0;
+  MemPage *pPage = pCur->apPage[pCur->iPage]; /* Btree page of current entry */
+  BtShared *pBt = pCur->pBt;                  /* Btree this cursor belongs to */
+
+  assert( pPage );
+  assert( pCur->eState==CURSOR_VALID );
+  assert( pCur->aiIdx[pCur->iPage]<pPage->nCell );
+  assert( cursorHoldsMutex(pCur) );
+
+  getCellInfo(pCur);
+  aPayload = pCur->info.pCell + pCur->info.nHeader;
+  nKey = (pPage->intKey ? 0 : (int)pCur->info.nKey);
+
+  if( NEVER(offset+amt > nKey+pCur->info.nData) 
+   || &aPayload[pCur->info.nLocal] > &pPage->aData[pBt->usableSize]
+  ){
+    /* Trying to read or write past the end of the data is an error */
+    return SQLITE_CORRUPT_BKPT;
+  }
+
+  /* Check if data must be read/written to/from the btree page itself. */
+  if( offset<pCur->info.nLocal ){
+    int a = amt;
+    if( a+offset>pCur->info.nLocal ){
+      a = pCur->info.nLocal - offset;
+    }
+    rc = copyPayload(&aPayload[offset], pBuf, a, eOp, pPage->pDbPage);
+    offset = 0;
+    pBuf += a;
+    amt -= a;
+  }else{
+    offset -= pCur->info.nLocal;
+  }
+
+  if( rc==SQLITE_OK && amt>0 ){
+    const u32 ovflSize = pBt->usableSize - 4;  /* Bytes content per ovfl page */
+    Pgno nextPage;
+
+    nextPage = get4byte(&aPayload[pCur->info.nLocal]);
+
+#ifndef SQLITE_OMIT_INCRBLOB
+    /* If the isIncrblobHandle flag is set and the BtCursor.aOverflow[]
+    ** has not been allocated, allocate it now. The array is sized at
+    ** one entry for each overflow page in the overflow chain. The
+    ** page number of the first overflow page is stored in aOverflow[0],
+    ** etc. A value of 0 in the aOverflow[] array means "not yet known"
+    ** (the cache is lazily populated).
+    */
+    if( pCur->isIncrblobHandle && !pCur->aOverflow ){
+      int nOvfl = (pCur->info.nPayload-pCur->info.nLocal+ovflSize-1)/ovflSize;
+      pCur->aOverflow = (Pgno *)sqlite3MallocZero(sizeof(Pgno)*nOvfl);
+      /* nOvfl is always positive.  If it were zero, fetchPayload would have
+      ** been used instead of this routine. */
+      if( ALWAYS(nOvfl) && !pCur->aOverflow ){
+        rc = SQLITE_NOMEM;
+      }
+    }
+
+    /* If the overflow page-list cache has been allocated and the
+    ** entry for the first required overflow page is valid, skip
+    ** directly to it.
+    */
+    if( pCur->aOverflow && pCur->aOverflow[offset/ovflSize] ){
+      iIdx = (offset/ovflSize);
+      nextPage = pCur->aOverflow[iIdx];
+      offset = (offset%ovflSize);
+    }
+#endif
+
+    for( ; rc==SQLITE_OK && amt>0 && nextPage; iIdx++){
+
+#ifndef SQLITE_OMIT_INCRBLOB
+      /* If required, populate the overflow page-list cache. */
+      if( pCur->aOverflow ){
+        assert(!pCur->aOverflow[iIdx] || pCur->aOverflow[iIdx]==nextPage);
+        pCur->aOverflow[iIdx] = nextPage;
+      }
+#endif
+
+      if( offset>=ovflSize ){
+        /* The only reason to read this page is to obtain the page
+        ** number for the next page in the overflow chain. The page
+        ** data is not required. So first try to lookup the overflow
+        ** page-list cache, if any, then fall back to the getOverflowPage()
+        ** function.
+        */
+#ifndef SQLITE_OMIT_INCRBLOB
+        if( pCur->aOverflow && pCur->aOverflow[iIdx+1] ){
+          nextPage = pCur->aOverflow[iIdx+1];
+        } else 
+#endif
+          rc = getOverflowPage(pBt, nextPage, 0, &nextPage);
+        offset -= ovflSize;
+      }else{
+        /* Need to read this page properly. It contains some of the
+        ** range of data that is being read (eOp==0) or written (eOp!=0).
+        */
+#ifdef SQLITE_DIRECT_OVERFLOW_READ
+        sqlite3_file *fd;
+#endif
+        int a = amt;
+        if( a + offset > ovflSize ){
+          a = ovflSize - offset;
+        }
+
+#ifdef SQLITE_DIRECT_OVERFLOW_READ
+        /* If all the following are true:
+        **
+        **   1) this is a read operation, and 
+        **   2) data is required from the start of this overflow page, and
+        **   3) the database is file-backed, and
+        **   4) there is no open write-transaction, and
+        **   5) the database is not a WAL database,
+        **
+        ** then data can be read directly from the database file into the
+        ** output buffer, bypassing the page-cache altogether. This speeds
+        ** up loading large records that span many overflow pages.
+        */
+        if( eOp==0                                             /* (1) */
+         && offset==0                                          /* (2) */
+         && pBt->inTransaction==TRANS_READ                     /* (4) */
+         && (fd = sqlite3PagerFile(pBt->pPager))->pMethods     /* (3) */
+         && pBt->pPage1->aData[19]==0x01                       /* (5) */
+        ){
+          u8 aSave[4];
+          u8 *aWrite = &pBuf[-4];
+          memcpy(aSave, aWrite, 4);
+          rc = sqlite3OsRead(fd, aWrite, a+4, pBt->pageSize * (nextPage-1));
+          nextPage = get4byte(aWrite);
+          memcpy(aWrite, aSave, 4);
+        }else
+#endif
+
+        {
+          DbPage *pDbPage;
+          rc = sqlite3PagerGet(pBt->pPager, nextPage, &pDbPage);
+          if( rc==SQLITE_OK ){
+            aPayload = sqlite3PagerGetData(pDbPage);
+            nextPage = get4byte(aPayload);
+            rc = copyPayload(&aPayload[offset+4], pBuf, a, eOp, pDbPage);
+            sqlite3PagerUnref(pDbPage);
+            offset = 0;
+          }
+        }
+        amt -= a;
+        pBuf += a;
+      }
+    }
+  }
+
+  if( rc==SQLITE_OK && amt>0 ){
+    return SQLITE_CORRUPT_BKPT;
+  }
+  return rc;
+}
+
+/*
+** Read part of the key associated with cursor pCur.  Exactly
+** "amt" bytes will be transfered into pBuf[].  The transfer
+** begins at "offset".
+**
+** The caller must ensure that pCur is pointing to a valid row
+** in the table.
+**
+** Return SQLITE_OK on success or an error code if anything goes
+** wrong.  An error is returned if "offset+amt" is larger than
+** the available payload.
+*/
+int sqlite3BtreeKey(BtCursor *pCur, u32 offset, u32 amt, void *pBuf){
+  assert( cursorHoldsMutex(pCur) );
+  assert( pCur->eState==CURSOR_VALID );
+  assert( pCur->iPage>=0 && pCur->apPage[pCur->iPage] );
+  assert( pCur->aiIdx[pCur->iPage]<pCur->apPage[pCur->iPage]->nCell );
+  return accessPayload(pCur, offset, amt, (unsigned char*)pBuf, 0);
+}
+
+/*
+** Read part of the data associated with cursor pCur.  Exactly
+** "amt" bytes will be transfered into pBuf[].  The transfer
+** begins at "offset".
+**
+** Return SQLITE_OK on success or an error code if anything goes
+** wrong.  An error is returned if "offset+amt" is larger than
+** the available payload.
+*/
+int sqlite3BtreeData(BtCursor *pCur, u32 offset, u32 amt, void *pBuf){
+  int rc;
+
+#ifndef SQLITE_OMIT_INCRBLOB
+  if ( pCur->eState==CURSOR_INVALID ){
+    return SQLITE_ABORT;
+  }
+#endif
+
+  assert( cursorHoldsMutex(pCur) );
+  rc = restoreCursorPosition(pCur);
+  if( rc==SQLITE_OK ){
+    assert( pCur->eState==CURSOR_VALID );
+    assert( pCur->iPage>=0 && pCur->apPage[pCur->iPage] );
+    assert( pCur->aiIdx[pCur->iPage]<pCur->apPage[pCur->iPage]->nCell );
+    rc = accessPayload(pCur, offset, amt, pBuf, 0);
+  }
+  return rc;
+}
+
+/*
+** Return a pointer to payload information from the entry that the 
+** pCur cursor is pointing to.  The pointer is to the beginning of
+** the key if skipKey==0 and it points to the beginning of data if
+** skipKey==1.  The number of bytes of available key/data is written
+** into *pAmt.  If *pAmt==0, then the value returned will not be
+** a valid pointer.
+**
+** This routine is an optimization.  It is common for the entire key
+** and data to fit on the local page and for there to be no overflow
+** pages.  When that is so, this routine can be used to access the
+** key and data without making a copy.  If the key and/or data spills
+** onto overflow pages, then accessPayload() must be used to reassemble
+** the key/data and copy it into a preallocated buffer.
+**
+** The pointer returned by this routine looks directly into the cached
+** page of the database.  The data might change or move the next time
+** any btree routine is called.
+*/
+static const unsigned char *fetchPayload(
+  BtCursor *pCur,      /* Cursor pointing to entry to read from */
+  int *pAmt,           /* Write the number of available bytes here */
+  int skipKey          /* read beginning at data if this is true */
+){
+  unsigned char *aPayload;
+  MemPage *pPage;
+  u32 nKey;
+  u32 nLocal;
+
+  assert( pCur!=0 && pCur->iPage>=0 && pCur->apPage[pCur->iPage]);
+  assert( pCur->eState==CURSOR_VALID );
+  assert( cursorHoldsMutex(pCur) );
+  pPage = pCur->apPage[pCur->iPage];
+  assert( pCur->aiIdx[pCur->iPage]<pPage->nCell );
+  if( NEVER(pCur->info.nSize==0) ){
+    btreeParseCell(pCur->apPage[pCur->iPage], pCur->aiIdx[pCur->iPage],
+                   &pCur->info);
+  }
+  aPayload = pCur->info.pCell;
+  aPayload += pCur->info.nHeader;
+  if( pPage->intKey ){
+    nKey = 0;
+  }else{
+    nKey = (int)pCur->info.nKey;
+  }
+  if( skipKey ){
+    aPayload += nKey;
+    nLocal = pCur->info.nLocal - nKey;
+  }else{
+    nLocal = pCur->info.nLocal;
+    assert( nLocal<=nKey );
+  }
+  *pAmt = nLocal;
+  return aPayload;
+}
+
+
+/*
+** For the entry that cursor pCur is point to, return as
+** many bytes of the key or data as are available on the local
+** b-tree page.  Write the number of available bytes into *pAmt.
+**
+** The pointer returned is ephemeral.  The key/data may move
+** or be destroyed on the next call to any Btree routine,
+** including calls from other threads against the same cache.
+** Hence, a mutex on the BtShared should be held prior to calling
+** this routine.
+**
+** These routines is used to get quick access to key and data
+** in the common case where no overflow pages are used.
+*/
+const void *sqlite3BtreeKeyFetch(BtCursor *pCur, int *pAmt){
+  const void *p = 0;
+  assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
+  assert( cursorHoldsMutex(pCur) );
+  if( ALWAYS(pCur->eState==CURSOR_VALID) ){
+    p = (const void*)fetchPayload(pCur, pAmt, 0);
+  }
+  return p;
+}
+const void *sqlite3BtreeDataFetch(BtCursor *pCur, int *pAmt){
+  const void *p = 0;
+  assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
+  assert( cursorHoldsMutex(pCur) );
+  if( ALWAYS(pCur->eState==CURSOR_VALID) ){
+    p = (const void*)fetchPayload(pCur, pAmt, 1);
+  }
+  return p;
+}
+
+
+/*
+** Move the cursor down to a new child page.  The newPgno argument is the
+** page number of the child page to move to.
+**
+** This function returns SQLITE_CORRUPT if the page-header flags field of
+** the new child page does not match the flags field of the parent (i.e.
+** if an intkey page appears to be the parent of a non-intkey page, or
+** vice-versa).
+*/
+static int moveToChild(BtCursor *pCur, u32 newPgno){
+  int rc;
+  int i = pCur->iPage;
+  MemPage *pNewPage;
+  BtShared *pBt = pCur->pBt;
+
+  assert( cursorHoldsMutex(pCur) );
+  assert( pCur->eState==CURSOR_VALID );
+  assert( pCur->iPage<BTCURSOR_MAX_DEPTH );
+  if( pCur->iPage>=(BTCURSOR_MAX_DEPTH-1) ){
+    return SQLITE_CORRUPT_BKPT;
+  }
+  rc = getAndInitPage(pBt, newPgno, &pNewPage);
+  if( rc ) return rc;
+  pCur->apPage[i+1] = pNewPage;
+  pCur->aiIdx[i+1] = 0;
+  pCur->iPage++;
+
+  pCur->info.nSize = 0;
+  pCur->validNKey = 0;
+  if( pNewPage->nCell<1 || pNewPage->intKey!=pCur->apPage[i]->intKey ){
+    return SQLITE_CORRUPT_BKPT;
+  }
+  return SQLITE_OK;
+}
+
+#ifndef NDEBUG
+/*
+** Page pParent is an internal (non-leaf) tree page. This function 
+** asserts that page number iChild is the left-child if the iIdx'th
+** cell in page pParent. Or, if iIdx is equal to the total number of
+** cells in pParent, that page number iChild is the right-child of
+** the page.
+*/
+static void assertParentIndex(MemPage *pParent, int iIdx, Pgno iChild){
+  assert( iIdx<=pParent->nCell );
+  if( iIdx==pParent->nCell ){
+    assert( get4byte(&pParent->aData[pParent->hdrOffset+8])==iChild );
+  }else{
+    assert( get4byte(findCell(pParent, iIdx))==iChild );
+  }
+}
+#else
+#  define assertParentIndex(x,y,z) 
+#endif
+
+/*
+** Move the cursor up to the parent page.
+**
+** pCur->idx is set to the cell index that contains the pointer
+** to the page we are coming from.  If we are coming from the
+** right-most child page then pCur->idx is set to one more than
+** the largest cell index.
+*/
+static void moveToParent(BtCursor *pCur){
+  assert( cursorHoldsMutex(pCur) );
+  assert( pCur->eState==CURSOR_VALID );
+  assert( pCur->iPage>0 );
+  assert( pCur->apPage[pCur->iPage] );
+  assertParentIndex(
+    pCur->apPage[pCur->iPage-1], 
+    pCur->aiIdx[pCur->iPage-1], 
+    pCur->apPage[pCur->iPage]->pgno
+  );
+  releasePage(pCur->apPage[pCur->iPage]);
+  pCur->iPage--;
+  pCur->info.nSize = 0;
+  pCur->validNKey = 0;
+}
+
+/*
+** Move the cursor to point to the root page of its b-tree structure.
+**
+** If the table has a virtual root page, then the cursor is moved to point
+** to the virtual root page instead of the actual root page. A table has a
+** virtual root page when the actual root page contains no cells and a 
+** single child page. This can only happen with the table rooted at page 1.
+**
+** If the b-tree structure is empty, the cursor state is set to 
+** CURSOR_INVALID. Otherwise, the cursor is set to point to the first
+** cell located on the root (or virtual root) page and the cursor state
+** is set to CURSOR_VALID.
+**
+** If this function returns successfully, it may be assumed that the
+** page-header flags indicate that the [virtual] root-page is the expected 
+** kind of b-tree page (i.e. if when opening the cursor the caller did not
+** specify a KeyInfo structure the flags byte is set to 0x05 or 0x0D,
+** indicating a table b-tree, or if the caller did specify a KeyInfo 
+** structure the flags byte is set to 0x02 or 0x0A, indicating an index
+** b-tree).
+*/
+static int moveToRoot(BtCursor *pCur){
+  MemPage *pRoot;
+  int rc = SQLITE_OK;
+  Btree *p = pCur->pBtree;
+  BtShared *pBt = p->pBt;
+
+  assert( cursorHoldsMutex(pCur) );
+  assert( CURSOR_INVALID < CURSOR_REQUIRESEEK );
+  assert( CURSOR_VALID   < CURSOR_REQUIRESEEK );
+  assert( CURSOR_FAULT   > CURSOR_REQUIRESEEK );
+  if( pCur->eState>=CURSOR_REQUIRESEEK ){
+    if( pCur->eState==CURSOR_FAULT ){
+      assert( pCur->skipNext!=SQLITE_OK );
+      return pCur->skipNext;
+    }
+    sqlite3BtreeClearCursor(pCur);
+  }
+
+  if( pCur->iPage>=0 ){
+    int i;
+    for(i=1; i<=pCur->iPage; i++){
+      releasePage(pCur->apPage[i]);
+    }
+    pCur->iPage = 0;
+  }else if( pCur->pgnoRoot==0 ){
+    pCur->eState = CURSOR_INVALID;
+    return SQLITE_OK;
+  }else{
+    rc = getAndInitPage(pBt, pCur->pgnoRoot, &pCur->apPage[0]);
+    if( rc!=SQLITE_OK ){
+      pCur->eState = CURSOR_INVALID;
+      return rc;
+    }
+    pCur->iPage = 0;
+
+    /* If pCur->pKeyInfo is not NULL, then the caller that opened this cursor
+    ** expected to open it on an index b-tree. Otherwise, if pKeyInfo is
+    ** NULL, the caller expects a table b-tree. If this is not the case,
+    ** return an SQLITE_CORRUPT error.  */
+    assert( pCur->apPage[0]->intKey==1 || pCur->apPage[0]->intKey==0 );
+    if( (pCur->pKeyInfo==0)!=pCur->apPage[0]->intKey ){
+      return SQLITE_CORRUPT_BKPT;
+    }
+  }
+
+  /* Assert that the root page is of the correct type. This must be the
+  ** case as the call to this function that loaded the root-page (either
+  ** this call or a previous invocation) would have detected corruption 
+  ** if the assumption were not true, and it is not possible for the flags 
+  ** byte to have been modified while this cursor is holding a reference
+  ** to the page.  */
+  pRoot = pCur->apPage[0];
+  assert( pRoot->pgno==pCur->pgnoRoot );
+  assert( pRoot->isInit && (pCur->pKeyInfo==0)==pRoot->intKey );
+
+  pCur->aiIdx[0] = 0;
+  pCur->info.nSize = 0;
+  pCur->atLast = 0;
+  pCur->validNKey = 0;
+
+  if( pRoot->nCell==0 && !pRoot->leaf ){
+    Pgno subpage;
+    if( pRoot->pgno!=1 ) return SQLITE_CORRUPT_BKPT;
+    subpage = get4byte(&pRoot->aData[pRoot->hdrOffset+8]);
+    pCur->eState = CURSOR_VALID;
+    rc = moveToChild(pCur, subpage);
+  }else{
+    pCur->eState = ((pRoot->nCell>0)?CURSOR_VALID:CURSOR_INVALID);
+  }
+  return rc;
+}
+
+/*
+** Move the cursor down to the left-most leaf entry beneath the
+** entry to which it is currently pointing.
+**
+** The left-most leaf is the one with the smallest key - the first
+** in ascending order.
+*/
+static int moveToLeftmost(BtCursor *pCur){
+  Pgno pgno;
+  int rc = SQLITE_OK;
+  MemPage *pPage;
+
+  assert( cursorHoldsMutex(pCur) );
+  assert( pCur->eState==CURSOR_VALID );
+  while( rc==SQLITE_OK && !(pPage = pCur->apPage[pCur->iPage])->leaf ){
+    assert( pCur->aiIdx[pCur->iPage]<pPage->nCell );
+    pgno = get4byte(findCell(pPage, pCur->aiIdx[pCur->iPage]));
+    rc = moveToChild(pCur, pgno);
+  }
+  return rc;
+}
+
+/*
+** Move the cursor down to the right-most leaf entry beneath the
+** page to which it is currently pointing.  Notice the difference
+** between moveToLeftmost() and moveToRightmost().  moveToLeftmost()
+** finds the left-most entry beneath the *entry* whereas moveToRightmost()
+** finds the right-most entry beneath the *page*.
+**
+** The right-most entry is the one with the largest key - the last
+** key in ascending order.
+*/
+static int moveToRightmost(BtCursor *pCur){
+  Pgno pgno;
+  int rc = SQLITE_OK;
+  MemPage *pPage = 0;
+
+  assert( cursorHoldsMutex(pCur) );
+  assert( pCur->eState==CURSOR_VALID );
+  while( rc==SQLITE_OK && !(pPage = pCur->apPage[pCur->iPage])->leaf ){
+    pgno = get4byte(&pPage->aData[pPage->hdrOffset+8]);
+    pCur->aiIdx[pCur->iPage] = pPage->nCell;
+    rc = moveToChild(pCur, pgno);
+  }
+  if( rc==SQLITE_OK ){
+    pCur->aiIdx[pCur->iPage] = pPage->nCell-1;
+    pCur->info.nSize = 0;
+    pCur->validNKey = 0;
+  }
+  return rc;
+}
+
+/* Move the cursor to the first entry in the table.  Return SQLITE_OK
+** on success.  Set *pRes to 0 if the cursor actually points to something
+** or set *pRes to 1 if the table is empty.
+*/
+int sqlite3BtreeFirst(BtCursor *pCur, int *pRes){
+  int rc;
+
+  assert( cursorHoldsMutex(pCur) );
+  assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
+  rc = moveToRoot(pCur);
+  if( rc==SQLITE_OK ){
+    if( pCur->eState==CURSOR_INVALID ){
+      assert( pCur->pgnoRoot==0 || pCur->apPage[pCur->iPage]->nCell==0 );
+      *pRes = 1;
+    }else{
+      assert( pCur->apPage[pCur->iPage]->nCell>0 );
+      *pRes = 0;
+      rc = moveToLeftmost(pCur);
+    }
+  }
+  return rc;
+}
+
+/* Move the cursor to the last entry in the table.  Return SQLITE_OK
+** on success.  Set *pRes to 0 if the cursor actually points to something
+** or set *pRes to 1 if the table is empty.
+*/
+int sqlite3BtreeLast(BtCursor *pCur, int *pRes){
+  int rc;
+ 
+  assert( cursorHoldsMutex(pCur) );
+  assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
+
+  /* If the cursor already points to the last entry, this is a no-op. */
+  if( CURSOR_VALID==pCur->eState && pCur->atLast ){
+#ifdef SQLITE_DEBUG
+    /* This block serves to assert() that the cursor really does point 
+    ** to the last entry in the b-tree. */
+    int ii;
+    for(ii=0; ii<pCur->iPage; ii++){
+      assert( pCur->aiIdx[ii]==pCur->apPage[ii]->nCell );
+    }
+    assert( pCur->aiIdx[pCur->iPage]==pCur->apPage[pCur->iPage]->nCell-1 );
+    assert( pCur->apPage[pCur->iPage]->leaf );
+#endif
+    return SQLITE_OK;
+  }
+
+  rc = moveToRoot(pCur);
+  if( rc==SQLITE_OK ){
+    if( CURSOR_INVALID==pCur->eState ){
+      assert( pCur->pgnoRoot==0 || pCur->apPage[pCur->iPage]->nCell==0 );
+      *pRes = 1;
+    }else{
+      assert( pCur->eState==CURSOR_VALID );
+      *pRes = 0;
+      rc = moveToRightmost(pCur);
+      pCur->atLast = rc==SQLITE_OK ?1:0;
+    }
+  }
+  return rc;
+}
+
+/* Move the cursor so that it points to an entry near the key 
+** specified by pIdxKey or intKey.   Return a success code.
+**
+** For INTKEY tables, the intKey parameter is used.  pIdxKey 
+** must be NULL.  For index tables, pIdxKey is used and intKey
+** is ignored.
+**
+** If an exact match is not found, then the cursor is always
+** left pointing at a leaf page which would hold the entry if it
+** were present.  The cursor might point to an entry that comes
+** before or after the key.
+**
+** An integer is written into *pRes which is the result of
+** comparing the key with the entry to which the cursor is 
+** pointing.  The meaning of the integer written into
+** *pRes is as follows:
+**
+**     *pRes<0      The cursor is left pointing at an entry that
+**                  is smaller than intKey/pIdxKey or if the table is empty
+**                  and the cursor is therefore left point to nothing.
+**
+**     *pRes==0     The cursor is left pointing at an entry that
+**                  exactly matches intKey/pIdxKey.
+**
+**     *pRes>0      The cursor is left pointing at an entry that
+**                  is larger than intKey/pIdxKey.
+**
+*/
+int sqlite3BtreeMovetoUnpacked(
+  BtCursor *pCur,          /* The cursor to be moved */
+  UnpackedRecord *pIdxKey, /* Unpacked index key */
+  i64 intKey,              /* The table key */
+  int biasRight,           /* If true, bias the search to the high end */
+  int *pRes                /* Write search results here */
+){
+  int rc;
+
+  assert( cursorHoldsMutex(pCur) );
+  assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
+  assert( pRes );
+  assert( (pIdxKey==0)==(pCur->pKeyInfo==0) );
+
+  /* If the cursor is already positioned at the point we are trying
+  ** to move to, then just return without doing any work */
+  if( pCur->eState==CURSOR_VALID && pCur->validNKey 
+   && pCur->apPage[0]->intKey 
+  ){
+    if( pCur->info.nKey==intKey ){
+      *pRes = 0;
+      return SQLITE_OK;
+    }
+    if( pCur->atLast && pCur->info.nKey<intKey ){
+      *pRes = -1;
+      return SQLITE_OK;
+    }
+  }
+
+  rc = moveToRoot(pCur);
+  if( rc ){
+    return rc;
+  }
+  assert( pCur->pgnoRoot==0 || pCur->apPage[pCur->iPage] );
+  assert( pCur->pgnoRoot==0 || pCur->apPage[pCur->iPage]->isInit );
+  assert( pCur->eState==CURSOR_INVALID || pCur->apPage[pCur->iPage]->nCell>0 );
+  if( pCur->eState==CURSOR_INVALID ){
+    *pRes = -1;
+    assert( pCur->pgnoRoot==0 || pCur->apPage[pCur->iPage]->nCell==0 );
+    return SQLITE_OK;
+  }
+  assert( pCur->apPage[0]->intKey || pIdxKey );
+  for(;;){
+    int lwr, upr, idx;
+    Pgno chldPg;
+    MemPage *pPage = pCur->apPage[pCur->iPage];
+    int c;
+
+    /* pPage->nCell must be greater than zero. If this is the root-page
+    ** the cursor would have been INVALID above and this for(;;) loop
+    ** not run. If this is not the root-page, then the moveToChild() routine
+    ** would have already detected db corruption. Similarly, pPage must
+    ** be the right kind (index or table) of b-tree page. Otherwise
+    ** a moveToChild() or moveToRoot() call would have detected corruption.  */
+    assert( pPage->nCell>0 );
+    assert( pPage->intKey==(pIdxKey==0) );
+    lwr = 0;
+    upr = pPage->nCell-1;
+    if( biasRight ){
+      pCur->aiIdx[pCur->iPage] = (u16)(idx = upr);
+    }else{
+      pCur->aiIdx[pCur->iPage] = (u16)(idx = (upr+lwr)/2);
+    }
+    for(;;){
+      u8 *pCell;                          /* Pointer to current cell in pPage */
+
+      assert( idx==pCur->aiIdx[pCur->iPage] );
+      pCur->info.nSize = 0;
+      pCell = findCell(pPage, idx) + pPage->childPtrSize;
+      if( pPage->intKey ){
+        i64 nCellKey;
+        if( pPage->hasData ){
+          u32 dummy;
+          pCell += getVarint32(pCell, dummy);
+        }
+        getVarint(pCell, (u64*)&nCellKey);
+        if( nCellKey==intKey ){
+          c = 0;
+        }else if( nCellKey<intKey ){
+          c = -1;
+        }else{
+          assert( nCellKey>intKey );
+          c = +1;
+        }
+        pCur->validNKey = 1;
+        pCur->info.nKey = nCellKey;
+      }else{
+        /* The maximum supported page-size is 65536 bytes. This means that
+        ** the maximum number of record bytes stored on an index B-Tree
+        ** page is less than 16384 bytes and may be stored as a 2-byte
+        ** varint. This information is used to attempt to avoid parsing 
+        ** the entire cell by checking for the cases where the record is 
+        ** stored entirely within the b-tree page by inspecting the first 
+        ** 2 bytes of the cell.
+        */
+        int nCell = pCell[0];
+        if( !(nCell & 0x80) && nCell<=pPage->maxLocal ){
+          /* This branch runs if the record-size field of the cell is a
+          ** single byte varint and the record fits entirely on the main
+          ** b-tree page.  */
+          c = sqlite3VdbeRecordCompare(nCell, (void*)&pCell[1], pIdxKey);
+        }else if( !(pCell[1] & 0x80) 
+          && (nCell = ((nCell&0x7f)<<7) + pCell[1])<=pPage->maxLocal
+        ){
+          /* The record-size field is a 2 byte varint and the record 
+          ** fits entirely on the main b-tree page.  */
+          c = sqlite3VdbeRecordCompare(nCell, (void*)&pCell[2], pIdxKey);
+        }else{
+          /* The record flows over onto one or more overflow pages. In
+          ** this case the whole cell needs to be parsed, a buffer allocated
+          ** and accessPayload() used to retrieve the record into the
+          ** buffer before VdbeRecordCompare() can be called. */
+          void *pCellKey;
+          u8 * const pCellBody = pCell - pPage->childPtrSize;
+          btreeParseCellPtr(pPage, pCellBody, &pCur->info);
+          nCell = (int)pCur->info.nKey;
+          pCellKey = sqlite3Malloc( nCell );
+          if( pCellKey==0 ){
+            rc = SQLITE_NOMEM;
+            goto moveto_finish;
+          }
+          rc = accessPayload(pCur, 0, nCell, (unsigned char*)pCellKey, 0);
+          if( rc ){
+            sqlite3_free(pCellKey);
+            goto moveto_finish;
+          }
+          c = sqlite3VdbeRecordCompare(nCell, pCellKey, pIdxKey);
+          sqlite3_free(pCellKey);
+        }
+      }
+      if( c==0 ){
+        if( pPage->intKey && !pPage->leaf ){
+          lwr = idx;
+          break;
+        }else{
+          *pRes = 0;
+          rc = SQLITE_OK;
+          goto moveto_finish;
+        }
+      }
+      if( c<0 ){
+        lwr = idx+1;
+      }else{
+        upr = idx-1;
+      }
+      if( lwr>upr ){
+        break;
+      }
+      pCur->aiIdx[pCur->iPage] = (u16)(idx = (lwr+upr)/2);
+    }
+    assert( lwr==upr+1 || (pPage->intKey && !pPage->leaf) );
+    assert( pPage->isInit );
+    if( pPage->leaf ){
+      chldPg = 0;
+    }else if( lwr>=pPage->nCell ){
+      chldPg = get4byte(&pPage->aData[pPage->hdrOffset+8]);
+    }else{
+      chldPg = get4byte(findCell(pPage, lwr));
+    }
+    if( chldPg==0 ){
+      assert( pCur->aiIdx[pCur->iPage]<pCur->apPage[pCur->iPage]->nCell );
+      *pRes = c;
+      rc = SQLITE_OK;
+      goto moveto_finish;
+    }
+    pCur->aiIdx[pCur->iPage] = (u16)lwr;
+    pCur->info.nSize = 0;
+    pCur->validNKey = 0;
+    rc = moveToChild(pCur, chldPg);
+    if( rc ) goto moveto_finish;
+  }
+moveto_finish:
+  return rc;
+}
+
+
+/*
+** Return TRUE if the cursor is not pointing at an entry of the table.
+**
+** TRUE will be returned after a call to sqlite3BtreeNext() moves
+** past the last entry in the table or sqlite3BtreePrev() moves past
+** the first entry.  TRUE is also returned if the table is empty.
+*/
+int sqlite3BtreeEof(BtCursor *pCur){
+  /* TODO: What if the cursor is in CURSOR_REQUIRESEEK but all table entries
+  ** have been deleted? This API will need to change to return an error code
+  ** as well as the boolean result value.
+  */
+  return (CURSOR_VALID!=pCur->eState);
+}
+
+/*
+** Advance the cursor to the next entry in the database.  If
+** successful then set *pRes=0.  If the cursor
+** was already pointing to the last entry in the database before
+** this routine was called, then set *pRes=1.
+*/
+int sqlite3BtreeNext(BtCursor *pCur, int *pRes){
+  int rc;
+  int idx;
+  MemPage *pPage;
+
+  assert( cursorHoldsMutex(pCur) );
+  rc = restoreCursorPosition(pCur);
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+  assert( pRes!=0 );
+  if( CURSOR_INVALID==pCur->eState ){
+    *pRes = 1;
+    return SQLITE_OK;
+  }
+  if( pCur->skipNext>0 ){
+    pCur->skipNext = 0;
+    *pRes = 0;
+    return SQLITE_OK;
+  }
+  pCur->skipNext = 0;
+
+  pPage = pCur->apPage[pCur->iPage];
+  idx = ++pCur->aiIdx[pCur->iPage];
+  assert( pPage->isInit );
+  assert( idx<=pPage->nCell );
+
+  pCur->info.nSize = 0;
+  pCur->validNKey = 0;
+  if( idx>=pPage->nCell ){
+    if( !pPage->leaf ){
+      rc = moveToChild(pCur, get4byte(&pPage->aData[pPage->hdrOffset+8]));
+      if( rc ) return rc;
+      rc = moveToLeftmost(pCur);
+      *pRes = 0;
+      return rc;
+    }
+    do{
+      if( pCur->iPage==0 ){
+        *pRes = 1;
+        pCur->eState = CURSOR_INVALID;
+        return SQLITE_OK;
+      }
+      moveToParent(pCur);
+      pPage = pCur->apPage[pCur->iPage];
+    }while( pCur->aiIdx[pCur->iPage]>=pPage->nCell );
+    *pRes = 0;
+    if( pPage->intKey ){
+      rc = sqlite3BtreeNext(pCur, pRes);
+    }else{
+      rc = SQLITE_OK;
+    }
+    return rc;
+  }
+  *pRes = 0;
+  if( pPage->leaf ){
+    return SQLITE_OK;
+  }
+  rc = moveToLeftmost(pCur);
+  return rc;
+}
+
+
+/*
+** Step the cursor to the back to the previous entry in the database.  If
+** successful then set *pRes=0.  If the cursor
+** was already pointing to the first entry in the database before
+** this routine was called, then set *pRes=1.
+*/
+int sqlite3BtreePrevious(BtCursor *pCur, int *pRes){
+  int rc;
+  MemPage *pPage;
+
+  assert( cursorHoldsMutex(pCur) );
+  rc = restoreCursorPosition(pCur);
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+  pCur->atLast = 0;
+  if( CURSOR_INVALID==pCur->eState ){
+    *pRes = 1;
+    return SQLITE_OK;
+  }
+  if( pCur->skipNext<0 ){
+    pCur->skipNext = 0;
+    *pRes = 0;
+    return SQLITE_OK;
+  }
+  pCur->skipNext = 0;
+
+  pPage = pCur->apPage[pCur->iPage];
+  assert( pPage->isInit );
+  if( !pPage->leaf ){
+    int idx = pCur->aiIdx[pCur->iPage];
+    rc = moveToChild(pCur, get4byte(findCell(pPage, idx)));
+    if( rc ){
+      return rc;
+    }
+    rc = moveToRightmost(pCur);
+  }else{
+    while( pCur->aiIdx[pCur->iPage]==0 ){
+      if( pCur->iPage==0 ){
+        pCur->eState = CURSOR_INVALID;
+        *pRes = 1;
+        return SQLITE_OK;
+      }
+      moveToParent(pCur);
+    }
+    pCur->info.nSize = 0;
+    pCur->validNKey = 0;
+
+    pCur->aiIdx[pCur->iPage]--;
+    pPage = pCur->apPage[pCur->iPage];
+    if( pPage->intKey && !pPage->leaf ){
+      rc = sqlite3BtreePrevious(pCur, pRes);
+    }else{
+      rc = SQLITE_OK;
+    }
+  }
+  *pRes = 0;
+  return rc;
+}
+
+/*
+** Allocate a new page from the database file.
+**
+** The new page is marked as dirty.  (In other words, sqlite3PagerWrite()
+** has already been called on the new page.)  The new page has also
+** been referenced and the calling routine is responsible for calling
+** sqlite3PagerUnref() on the new page when it is done.
+**
+** SQLITE_OK is returned on success.  Any other return value indicates
+** an error.  *ppPage and *pPgno are undefined in the event of an error.
+** Do not invoke sqlite3PagerUnref() on *ppPage if an error is returned.
+**
+** If the "nearby" parameter is not 0, then a (feeble) effort is made to 
+** locate a page close to the page number "nearby".  This can be used in an
+** attempt to keep related pages close to each other in the database file,
+** which in turn can make database access faster.
+**
+** If the "exact" parameter is not 0, and the page-number nearby exists 
+** anywhere on the free-list, then it is guarenteed to be returned. This
+** is only used by auto-vacuum databases when allocating a new table.
+*/
+static int allocateBtreePage(
+  BtShared *pBt, 
+  MemPage **ppPage, 
+  Pgno *pPgno, 
+  Pgno nearby,
+  u8 exact
+){
+  MemPage *pPage1;
+  int rc;
+  u32 n;     /* Number of pages on the freelist */
+  u32 k;     /* Number of leaves on the trunk of the freelist */
+  MemPage *pTrunk = 0;
+  MemPage *pPrevTrunk = 0;
+  Pgno mxPage;     /* Total size of the database file */
+
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  pPage1 = pBt->pPage1;
+  mxPage = btreePagecount(pBt);
+  n = get4byte(&pPage1->aData[36]);
+  testcase( n==mxPage-1 );
+  if( n>=mxPage ){
+    return SQLITE_CORRUPT_BKPT;
+  }
+  if( n>0 ){
+    /* There are pages on the freelist.  Reuse one of those pages. */
+    Pgno iTrunk;
+    u8 searchList = 0; /* If the free-list must be searched for 'nearby' */
+    
+    /* If the 'exact' parameter was true and a query of the pointer-map
+    ** shows that the page 'nearby' is somewhere on the free-list, then
+    ** the entire-list will be searched for that page.
+    */
+#ifndef SQLITE_OMIT_AUTOVACUUM
+    if( exact && nearby<=mxPage ){
+      u8 eType;
+      assert( nearby>0 );
+      assert( pBt->autoVacuum );
+      rc = ptrmapGet(pBt, nearby, &eType, 0);
+      if( rc ) return rc;
+      if( eType==PTRMAP_FREEPAGE ){
+        searchList = 1;
+      }
+      *pPgno = nearby;
+    }
+#endif
+
+    /* Decrement the free-list count by 1. Set iTrunk to the index of the
+    ** first free-list trunk page. iPrevTrunk is initially 1.
+    */
+    rc = sqlite3PagerWrite(pPage1->pDbPage);
+    if( rc ) return rc;
+    put4byte(&pPage1->aData[36], n-1);
+
+    /* The code within this loop is run only once if the 'searchList' variable
+    ** is not true. Otherwise, it runs once for each trunk-page on the
+    ** free-list until the page 'nearby' is located.
+    */
+    do {
+      pPrevTrunk = pTrunk;
+      if( pPrevTrunk ){
+        iTrunk = get4byte(&pPrevTrunk->aData[0]);
+      }else{
+        iTrunk = get4byte(&pPage1->aData[32]);
+      }
+      testcase( iTrunk==mxPage );
+      if( iTrunk>mxPage ){
+        rc = SQLITE_CORRUPT_BKPT;
+      }else{
+        rc = btreeGetPage(pBt, iTrunk, &pTrunk, 0);
+      }
+      if( rc ){
+        pTrunk = 0;
+        goto end_allocate_page;
+      }
+      assert( pTrunk!=0 );
+      assert( pTrunk->aData!=0 );
+
+      k = get4byte(&pTrunk->aData[4]); /* # of leaves on this trunk page */
+      if( k==0 && !searchList ){
+        /* The trunk has no leaves and the list is not being searched. 
+        ** So extract the trunk page itself and use it as the newly 
+        ** allocated page */
+        assert( pPrevTrunk==0 );
+        rc = sqlite3PagerWrite(pTrunk->pDbPage);
+        if( rc ){
+          goto end_allocate_page;
+        }
+        *pPgno = iTrunk;
+        memcpy(&pPage1->aData[32], &pTrunk->aData[0], 4);
+        *ppPage = pTrunk;
+        pTrunk = 0;
+        TRACE(("ALLOCATE: %d trunk - %d free pages left\n", *pPgno, n-1));
+      }else if( k>(u32)(pBt->usableSize/4 - 2) ){
+        /* Value of k is out of range.  Database corruption */
+        rc = SQLITE_CORRUPT_BKPT;
+        goto end_allocate_page;
+#ifndef SQLITE_OMIT_AUTOVACUUM
+      }else if( searchList && nearby==iTrunk ){
+        /* The list is being searched and this trunk page is the page
+        ** to allocate, regardless of whether it has leaves.
+        */
+        assert( *pPgno==iTrunk );
+        *ppPage = pTrunk;
+        searchList = 0;
+        rc = sqlite3PagerWrite(pTrunk->pDbPage);
+        if( rc ){
+          goto end_allocate_page;
+        }
+        if( k==0 ){
+          if( !pPrevTrunk ){
+            memcpy(&pPage1->aData[32], &pTrunk->aData[0], 4);
+          }else{
+            rc = sqlite3PagerWrite(pPrevTrunk->pDbPage);
+            if( rc!=SQLITE_OK ){
+              goto end_allocate_page;
+            }
+            memcpy(&pPrevTrunk->aData[0], &pTrunk->aData[0], 4);
+          }
+        }else{
+          /* The trunk page is required by the caller but it contains 
+          ** pointers to free-list leaves. The first leaf becomes a trunk
+          ** page in this case.
+          */
+          MemPage *pNewTrunk;
+          Pgno iNewTrunk = get4byte(&pTrunk->aData[8]);
+          if( iNewTrunk>mxPage ){ 
+            rc = SQLITE_CORRUPT_BKPT;
+            goto end_allocate_page;
+          }
+          testcase( iNewTrunk==mxPage );
+          rc = btreeGetPage(pBt, iNewTrunk, &pNewTrunk, 0);
+          if( rc!=SQLITE_OK ){
+            goto end_allocate_page;
+          }
+          rc = sqlite3PagerWrite(pNewTrunk->pDbPage);
+          if( rc!=SQLITE_OK ){
+            releasePage(pNewTrunk);
+            goto end_allocate_page;
+          }
+          memcpy(&pNewTrunk->aData[0], &pTrunk->aData[0], 4);
+          put4byte(&pNewTrunk->aData[4], k-1);
+          memcpy(&pNewTrunk->aData[8], &pTrunk->aData[12], (k-1)*4);
+          releasePage(pNewTrunk);
+          if( !pPrevTrunk ){
+            assert( sqlite3PagerIswriteable(pPage1->pDbPage) );
+            put4byte(&pPage1->aData[32], iNewTrunk);
+          }else{
+            rc = sqlite3PagerWrite(pPrevTrunk->pDbPage);
+            if( rc ){
+              goto end_allocate_page;
+            }
+            put4byte(&pPrevTrunk->aData[0], iNewTrunk);
+          }
+        }
+        pTrunk = 0;
+        TRACE(("ALLOCATE: %d trunk - %d free pages left\n", *pPgno, n-1));
+#endif
+      }else if( k>0 ){
+        /* Extract a leaf from the trunk */
+        u32 closest;
+        Pgno iPage;
+        unsigned char *aData = pTrunk->aData;
+        if( nearby>0 ){
+          u32 i;
+          int dist;
+          closest = 0;
+          dist = sqlite3AbsInt32(get4byte(&aData[8]) - nearby);
+          for(i=1; i<k; i++){
+            int d2 = sqlite3AbsInt32(get4byte(&aData[8+i*4]) - nearby);
+            if( d2<dist ){
+              closest = i;
+              dist = d2;
+            }
+          }
+        }else{
+          closest = 0;
+        }
+
+        iPage = get4byte(&aData[8+closest*4]);
+        testcase( iPage==mxPage );
+        if( iPage>mxPage ){
+          rc = SQLITE_CORRUPT_BKPT;
+          goto end_allocate_page;
+        }
+        testcase( iPage==mxPage );
+        if( !searchList || iPage==nearby ){
+          int noContent;
+          *pPgno = iPage;
+          TRACE(("ALLOCATE: %d was leaf %d of %d on trunk %d"
+                 ": %d more free pages\n",
+                 *pPgno, closest+1, k, pTrunk->pgno, n-1));
+          rc = sqlite3PagerWrite(pTrunk->pDbPage);
+          if( rc ) goto end_allocate_page;
+          if( closest<k-1 ){
+            memcpy(&aData[8+closest*4], &aData[4+k*4], 4);
+          }
+          put4byte(&aData[4], k-1);
+          noContent = !btreeGetHasContent(pBt, *pPgno);
+          rc = btreeGetPage(pBt, *pPgno, ppPage, noContent);
+          if( rc==SQLITE_OK ){
+            rc = sqlite3PagerWrite((*ppPage)->pDbPage);
+            if( rc!=SQLITE_OK ){
+              releasePage(*ppPage);
+            }
+          }
+          searchList = 0;
+        }
+      }
+      releasePage(pPrevTrunk);
+      pPrevTrunk = 0;
+    }while( searchList );
+  }else{
+    /* There are no pages on the freelist, so create a new page at the
+    ** end of the file */
+    rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
+    if( rc ) return rc;
+    pBt->nPage++;
+    if( pBt->nPage==PENDING_BYTE_PAGE(pBt) ) pBt->nPage++;
+
+#ifndef SQLITE_OMIT_AUTOVACUUM
+    if( pBt->autoVacuum && PTRMAP_ISPAGE(pBt, pBt->nPage) ){
+      /* If *pPgno refers to a pointer-map page, allocate two new pages
+      ** at the end of the file instead of one. The first allocated page
+      ** becomes a new pointer-map page, the second is used by the caller.
+      */
+      MemPage *pPg = 0;
+      TRACE(("ALLOCATE: %d from end of file (pointer-map page)\n", pBt->nPage));
+      assert( pBt->nPage!=PENDING_BYTE_PAGE(pBt) );
+      rc = btreeGetPage(pBt, pBt->nPage, &pPg, 1);
+      if( rc==SQLITE_OK ){
+        rc = sqlite3PagerWrite(pPg->pDbPage);
+        releasePage(pPg);
+      }
+      if( rc ) return rc;
+      pBt->nPage++;
+      if( pBt->nPage==PENDING_BYTE_PAGE(pBt) ){ pBt->nPage++; }
+    }
+#endif
+    put4byte(28 + (u8*)pBt->pPage1->aData, pBt->nPage);
+    *pPgno = pBt->nPage;
+
+    assert( *pPgno!=PENDING_BYTE_PAGE(pBt) );
+    rc = btreeGetPage(pBt, *pPgno, ppPage, 1);
+    if( rc ) return rc;
+    rc = sqlite3PagerWrite((*ppPage)->pDbPage);
+    if( rc!=SQLITE_OK ){
+      releasePage(*ppPage);
+    }
+    TRACE(("ALLOCATE: %d from end of file\n", *pPgno));
+  }
+
+  assert( *pPgno!=PENDING_BYTE_PAGE(pBt) );
+
+end_allocate_page:
+  releasePage(pTrunk);
+  releasePage(pPrevTrunk);
+  if( rc==SQLITE_OK ){
+    if( sqlite3PagerPageRefcount((*ppPage)->pDbPage)>1 ){
+      releasePage(*ppPage);
+      return SQLITE_CORRUPT_BKPT;
+    }
+    (*ppPage)->isInit = 0;
+  }else{
+    *ppPage = 0;
+  }
+  assert( rc!=SQLITE_OK || sqlite3PagerIswriteable((*ppPage)->pDbPage) );
+  return rc;
+}
+
+/*
+** This function is used to add page iPage to the database file free-list. 
+** It is assumed that the page is not already a part of the free-list.
+**
+** The value passed as the second argument to this function is optional.
+** If the caller happens to have a pointer to the MemPage object 
+** corresponding to page iPage handy, it may pass it as the second value. 
+** Otherwise, it may pass NULL.
+**
+** If a pointer to a MemPage object is passed as the second argument,
+** its reference count is not altered by this function.
+*/
+static int freePage2(BtShared *pBt, MemPage *pMemPage, Pgno iPage){
+  MemPage *pTrunk = 0;                /* Free-list trunk page */
+  Pgno iTrunk = 0;                    /* Page number of free-list trunk page */ 
+  MemPage *pPage1 = pBt->pPage1;      /* Local reference to page 1 */
+  MemPage *pPage;                     /* Page being freed. May be NULL. */
+  int rc;                             /* Return Code */
+  int nFree;                          /* Initial number of pages on free-list */
+
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  assert( iPage>1 );
+  assert( !pMemPage || pMemPage->pgno==iPage );
+
+  if( pMemPage ){
+    pPage = pMemPage;
+    sqlite3PagerRef(pPage->pDbPage);
+  }else{
+    pPage = btreePageLookup(pBt, iPage);
+  }
+
+  /* Increment the free page count on pPage1 */
+  rc = sqlite3PagerWrite(pPage1->pDbPage);
+  if( rc ) goto freepage_out;
+  nFree = get4byte(&pPage1->aData[36]);
+  put4byte(&pPage1->aData[36], nFree+1);
+
+  if( pBt->secureDelete ){
+    /* If the secure_delete option is enabled, then
+    ** always fully overwrite deleted information with zeros.
+    */
+    if( (!pPage && ((rc = btreeGetPage(pBt, iPage, &pPage, 0))!=0) )
+     ||            ((rc = sqlite3PagerWrite(pPage->pDbPage))!=0)
+    ){
+      goto freepage_out;
+    }
+    memset(pPage->aData, 0, pPage->pBt->pageSize);
+  }
+
+  /* If the database supports auto-vacuum, write an entry in the pointer-map
+  ** to indicate that the page is free.
+  */
+  if( ISAUTOVACUUM ){
+    ptrmapPut(pBt, iPage, PTRMAP_FREEPAGE, 0, &rc);
+    if( rc ) goto freepage_out;
+  }
+
+  /* Now manipulate the actual database free-list structure. There are two
+  ** possibilities. If the free-list is currently empty, or if the first
+  ** trunk page in the free-list is full, then this page will become a
+  ** new free-list trunk page. Otherwise, it will become a leaf of the
+  ** first trunk page in the current free-list. This block tests if it
+  ** is possible to add the page as a new free-list leaf.
+  */
+  if( nFree!=0 ){
+    u32 nLeaf;                /* Initial number of leaf cells on trunk page */
+
+    iTrunk = get4byte(&pPage1->aData[32]);
+    rc = btreeGetPage(pBt, iTrunk, &pTrunk, 0);
+    if( rc!=SQLITE_OK ){
+      goto freepage_out;
+    }
+
+    nLeaf = get4byte(&pTrunk->aData[4]);
+    assert( pBt->usableSize>32 );
+    if( nLeaf > (u32)pBt->usableSize/4 - 2 ){
+      rc = SQLITE_CORRUPT_BKPT;
+      goto freepage_out;
+    }
+    if( nLeaf < (u32)pBt->usableSize/4 - 8 ){
+      /* In this case there is room on the trunk page to insert the page
+      ** being freed as a new leaf.
+      **
+      ** Note that the trunk page is not really full until it contains
+      ** usableSize/4 - 2 entries, not usableSize/4 - 8 entries as we have
+      ** coded.  But due to a coding error in versions of SQLite prior to
+      ** 3.6.0, databases with freelist trunk pages holding more than
+      ** usableSize/4 - 8 entries will be reported as corrupt.  In order
+      ** to maintain backwards compatibility with older versions of SQLite,
+      ** we will continue to restrict the number of entries to usableSize/4 - 8
+      ** for now.  At some point in the future (once everyone has upgraded
+      ** to 3.6.0 or later) we should consider fixing the conditional above
+      ** to read "usableSize/4-2" instead of "usableSize/4-8".
+      */
+      rc = sqlite3PagerWrite(pTrunk->pDbPage);
+      if( rc==SQLITE_OK ){
+        put4byte(&pTrunk->aData[4], nLeaf+1);
+        put4byte(&pTrunk->aData[8+nLeaf*4], iPage);
+        if( pPage && !pBt->secureDelete ){
+          sqlite3PagerDontWrite(pPage->pDbPage);
+        }
+        rc = btreeSetHasContent(pBt, iPage);
+      }
+      TRACE(("FREE-PAGE: %d leaf on trunk page %d\n",pPage->pgno,pTrunk->pgno));
+      goto freepage_out;
+    }
+  }
+
+  /* If control flows to this point, then it was not possible to add the
+  ** the page being freed as a leaf page of the first trunk in the free-list.
+  ** Possibly because the free-list is empty, or possibly because the 
+  ** first trunk in the free-list is full. Either way, the page being freed
+  ** will become the new first trunk page in the free-list.
+  */
+  if( pPage==0 && SQLITE_OK!=(rc = btreeGetPage(pBt, iPage, &pPage, 0)) ){
+    goto freepage_out;
+  }
+  rc = sqlite3PagerWrite(pPage->pDbPage);
+  if( rc!=SQLITE_OK ){
+    goto freepage_out;
+  }
+  put4byte(pPage->aData, iTrunk);
+  put4byte(&pPage->aData[4], 0);
+  put4byte(&pPage1->aData[32], iPage);
+  TRACE(("FREE-PAGE: %d new trunk page replacing %d\n", pPage->pgno, iTrunk));
+
+freepage_out:
+  if( pPage ){
+    pPage->isInit = 0;
+  }
+  releasePage(pPage);
+  releasePage(pTrunk);
+  return rc;
+}
+static void freePage(MemPage *pPage, int *pRC){
+  if( (*pRC)==SQLITE_OK ){
+    *pRC = freePage2(pPage->pBt, pPage, pPage->pgno);
+  }
+}
+
+/*
+** Free any overflow pages associated with the given Cell.
+*/
+static int clearCell(MemPage *pPage, unsigned char *pCell){
+  BtShared *pBt = pPage->pBt;
+  CellInfo info;
+  Pgno ovflPgno;
+  int rc;
+  int nOvfl;
+  u32 ovflPageSize;
+
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  btreeParseCellPtr(pPage, pCell, &info);
+  if( info.iOverflow==0 ){
+    return SQLITE_OK;  /* No overflow pages. Return without doing anything */
+  }
+  if( pCell+info.iOverflow+3 > pPage->aData+pPage->maskPage ){
+    return SQLITE_CORRUPT;  /* Cell extends past end of page */
+  }
+  ovflPgno = get4byte(&pCell[info.iOverflow]);
+  assert( pBt->usableSize > 4 );
+  ovflPageSize = pBt->usableSize - 4;
+  nOvfl = (info.nPayload - info.nLocal + ovflPageSize - 1)/ovflPageSize;
+  assert( ovflPgno==0 || nOvfl>0 );
+  while( nOvfl-- ){
+    Pgno iNext = 0;
+    MemPage *pOvfl = 0;
+    if( ovflPgno<2 || ovflPgno>btreePagecount(pBt) ){
+      /* 0 is not a legal page number and page 1 cannot be an 
+      ** overflow page. Therefore if ovflPgno<2 or past the end of the 
+      ** file the database must be corrupt. */
+      return SQLITE_CORRUPT_BKPT;
+    }
+    if( nOvfl ){
+      rc = getOverflowPage(pBt, ovflPgno, &pOvfl, &iNext);
+      if( rc ) return rc;
+    }
+
+    if( ( pOvfl || ((pOvfl = btreePageLookup(pBt, ovflPgno))!=0) )
+     && sqlite3PagerPageRefcount(pOvfl->pDbPage)!=1
+    ){
+      /* There is no reason any cursor should have an outstanding reference 
+      ** to an overflow page belonging to a cell that is being deleted/updated.
+      ** So if there exists more than one reference to this page, then it 
+      ** must not really be an overflow page and the database must be corrupt. 
+      ** It is helpful to detect this before calling freePage2(), as 
+      ** freePage2() may zero the page contents if secure-delete mode is
+      ** enabled. If this 'overflow' page happens to be a page that the
+      ** caller is iterating through or using in some other way, this
+      ** can be problematic.
+      */
+      rc = SQLITE_CORRUPT_BKPT;
+    }else{
+      rc = freePage2(pBt, pOvfl, ovflPgno);
+    }
+
+    if( pOvfl ){
+      sqlite3PagerUnref(pOvfl->pDbPage);
+    }
+    if( rc ) return rc;
+    ovflPgno = iNext;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Create the byte sequence used to represent a cell on page pPage
+** and write that byte sequence into pCell[].  Overflow pages are
+** allocated and filled in as necessary.  The calling procedure
+** is responsible for making sure sufficient space has been allocated
+** for pCell[].
+**
+** Note that pCell does not necessary need to point to the pPage->aData
+** area.  pCell might point to some temporary storage.  The cell will
+** be constructed in this temporary area then copied into pPage->aData
+** later.
+*/
+static int fillInCell(
+  MemPage *pPage,                /* The page that contains the cell */
+  unsigned char *pCell,          /* Complete text of the cell */
+  const void *pKey, i64 nKey,    /* The key */
+  const void *pData,int nData,   /* The data */
+  int nZero,                     /* Extra zero bytes to append to pData */
+  int *pnSize                    /* Write cell size here */
+){
+  int nPayload;
+  const u8 *pSrc;
+  int nSrc, n, rc;
+  int spaceLeft;
+  MemPage *pOvfl = 0;
+  MemPage *pToRelease = 0;
+  unsigned char *pPrior;
+  unsigned char *pPayload;
+  BtShared *pBt = pPage->pBt;
+  Pgno pgnoOvfl = 0;
+  int nHeader;
+  CellInfo info;
+
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+
+  /* pPage is not necessarily writeable since pCell might be auxiliary
+  ** buffer space that is separate from the pPage buffer area */
+  assert( pCell<pPage->aData || pCell>=&pPage->aData[pBt->pageSize]
+            || sqlite3PagerIswriteable(pPage->pDbPage) );
+
+  /* Fill in the header. */
+  nHeader = 0;
+  if( !pPage->leaf ){
+    nHeader += 4;
+  }
+  if( pPage->hasData ){
+    nHeader += putVarint(&pCell[nHeader], nData+nZero);
+  }else{
+    nData = nZero = 0;
+  }
+  nHeader += putVarint(&pCell[nHeader], *(u64*)&nKey);
+  btreeParseCellPtr(pPage, pCell, &info);
+  assert( info.nHeader==nHeader );
+  assert( info.nKey==nKey );
+  assert( info.nData==(u32)(nData+nZero) );
+  
+  /* Fill in the payload */
+  nPayload = nData + nZero;
+  if( pPage->intKey ){
+    pSrc = pData;
+    nSrc = nData;
+    nData = 0;
+  }else{ 
+    if( NEVER(nKey>0x7fffffff || pKey==0) ){
+      return SQLITE_CORRUPT_BKPT;
+    }
+    nPayload += (int)nKey;
+    pSrc = pKey;
+    nSrc = (int)nKey;
+  }
+  *pnSize = info.nSize;
+  spaceLeft = info.nLocal;
+  pPayload = &pCell[nHeader];
+  pPrior = &pCell[info.iOverflow];
+
+  while( nPayload>0 ){
+    if( spaceLeft==0 ){
+#ifndef SQLITE_OMIT_AUTOVACUUM
+      Pgno pgnoPtrmap = pgnoOvfl; /* Overflow page pointer-map entry page */
+      if( pBt->autoVacuum ){
+        do{
+          pgnoOvfl++;
+        } while( 
+          PTRMAP_ISPAGE(pBt, pgnoOvfl) || pgnoOvfl==PENDING_BYTE_PAGE(pBt) 
+        );
+      }
+#endif
+      rc = allocateBtreePage(pBt, &pOvfl, &pgnoOvfl, pgnoOvfl, 0);
+#ifndef SQLITE_OMIT_AUTOVACUUM
+      /* If the database supports auto-vacuum, and the second or subsequent
+      ** overflow page is being allocated, add an entry to the pointer-map
+      ** for that page now. 
+      **
+      ** If this is the first overflow page, then write a partial entry 
+      ** to the pointer-map. If we write nothing to this pointer-map slot,
+      ** then the optimistic overflow chain processing in clearCell()
+      ** may misinterpret the uninitialised values and delete the
+      ** wrong pages from the database.
+      */
+      if( pBt->autoVacuum && rc==SQLITE_OK ){
+        u8 eType = (pgnoPtrmap?PTRMAP_OVERFLOW2:PTRMAP_OVERFLOW1);
+        ptrmapPut(pBt, pgnoOvfl, eType, pgnoPtrmap, &rc);
+        if( rc ){
+          releasePage(pOvfl);
+        }
+      }
+#endif
+      if( rc ){
+        releasePage(pToRelease);
+        return rc;
+      }
+
+      /* If pToRelease is not zero than pPrior points into the data area
+      ** of pToRelease.  Make sure pToRelease is still writeable. */
+      assert( pToRelease==0 || sqlite3PagerIswriteable(pToRelease->pDbPage) );
+
+      /* If pPrior is part of the data area of pPage, then make sure pPage
+      ** is still writeable */
+      assert( pPrior<pPage->aData || pPrior>=&pPage->aData[pBt->pageSize]
+            || sqlite3PagerIswriteable(pPage->pDbPage) );
+
+      put4byte(pPrior, pgnoOvfl);
+      releasePage(pToRelease);
+      pToRelease = pOvfl;
+      pPrior = pOvfl->aData;
+      put4byte(pPrior, 0);
+      pPayload = &pOvfl->aData[4];
+      spaceLeft = pBt->usableSize - 4;
+    }
+    n = nPayload;
+    if( n>spaceLeft ) n = spaceLeft;
+
+    /* If pToRelease is not zero than pPayload points into the data area
+    ** of pToRelease.  Make sure pToRelease is still writeable. */
+    assert( pToRelease==0 || sqlite3PagerIswriteable(pToRelease->pDbPage) );
+
+    /* If pPayload is part of the data area of pPage, then make sure pPage
+    ** is still writeable */
+    assert( pPayload<pPage->aData || pPayload>=&pPage->aData[pBt->pageSize]
+            || sqlite3PagerIswriteable(pPage->pDbPage) );
+
+    if( nSrc>0 ){
+      if( n>nSrc ) n = nSrc;
+      assert( pSrc );
+      memcpy(pPayload, pSrc, n);
+    }else{
+      memset(pPayload, 0, n);
+    }
+    nPayload -= n;
+    pPayload += n;
+    pSrc += n;
+    nSrc -= n;
+    spaceLeft -= n;
+    if( nSrc==0 ){
+      nSrc = nData;
+      pSrc = pData;
+    }
+  }
+  releasePage(pToRelease);
+  return SQLITE_OK;
+}
+
+/*
+** Remove the i-th cell from pPage.  This routine effects pPage only.
+** The cell content is not freed or deallocated.  It is assumed that
+** the cell content has been copied someplace else.  This routine just
+** removes the reference to the cell from pPage.
+**
+** "sz" must be the number of bytes in the cell.
+*/
+static void dropCell(MemPage *pPage, int idx, int sz, int *pRC){
+  u32 pc;         /* Offset to cell content of cell being deleted */
+  u8 *data;       /* pPage->aData */
+  u8 *ptr;        /* Used to move bytes around within data[] */
+  u8 *endPtr;     /* End of loop */
+  int rc;         /* The return code */
+  int hdr;        /* Beginning of the header.  0 most pages.  100 page 1 */
+
+  if( *pRC ) return;
+
+  assert( idx>=0 && idx<pPage->nCell );
+  assert( sz==cellSize(pPage, idx) );
+  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  data = pPage->aData;
+  ptr = &data[pPage->cellOffset + 2*idx];
+  pc = get2byte(ptr);
+  hdr = pPage->hdrOffset;
+  testcase( pc==get2byte(&data[hdr+5]) );
+  testcase( pc+sz==pPage->pBt->usableSize );
+  if( pc < (u32)get2byte(&data[hdr+5]) || pc+sz > pPage->pBt->usableSize ){
+    *pRC = SQLITE_CORRUPT_BKPT;
+    return;
+  }
+  rc = freeSpace(pPage, pc, sz);
+  if( rc ){
+    *pRC = rc;
+    return;
+  }
+  endPtr = &data[pPage->cellOffset + 2*pPage->nCell - 2];
+  assert( (SQLITE_PTR_TO_INT(ptr)&1)==0 );  /* ptr is always 2-byte aligned */
+  while( ptr<endPtr ){
+    *(u16*)ptr = *(u16*)&ptr[2];
+    ptr += 2;
+  }
+  pPage->nCell--;
+  put2byte(&data[hdr+3], pPage->nCell);
+  pPage->nFree += 2;
+}
+
+/*
+** Insert a new cell on pPage at cell index "i".  pCell points to the
+** content of the cell.
+**
+** If the cell content will fit on the page, then put it there.  If it
+** will not fit, then make a copy of the cell content into pTemp if
+** pTemp is not null.  Regardless of pTemp, allocate a new entry
+** in pPage->aOvfl[] and make it point to the cell content (either
+** in pTemp or the original pCell) and also record its index. 
+** Allocating a new entry in pPage->aCell[] implies that 
+** pPage->nOverflow is incremented.
+**
+** If nSkip is non-zero, then do not copy the first nSkip bytes of the
+** cell. The caller will overwrite them after this function returns. If
+** nSkip is non-zero, then pCell may not point to an invalid memory location 
+** (but pCell+nSkip is always valid).
+*/
+static void insertCell(
+  MemPage *pPage,   /* Page into which we are copying */
+  int i,            /* New cell becomes the i-th cell of the page */
+  u8 *pCell,        /* Content of the new cell */
+  int sz,           /* Bytes of content in pCell */
+  u8 *pTemp,        /* Temp storage space for pCell, if needed */
+  Pgno iChild,      /* If non-zero, replace first 4 bytes with this value */
+  int *pRC          /* Read and write return code from here */
+){
+  int idx = 0;      /* Where to write new cell content in data[] */
+  int j;            /* Loop counter */
+  int end;          /* First byte past the last cell pointer in data[] */
+  int ins;          /* Index in data[] where new cell pointer is inserted */
+  int cellOffset;   /* Address of first cell pointer in data[] */
+  u8 *data;         /* The content of the whole page */
+  u8 *ptr;          /* Used for moving information around in data[] */
+  u8 *endPtr;       /* End of the loop */
+
+  int nSkip = (iChild ? 4 : 0);
+
+  if( *pRC ) return;
+
+  assert( i>=0 && i<=pPage->nCell+pPage->nOverflow );
+  assert( pPage->nCell<=MX_CELL(pPage->pBt) && MX_CELL(pPage->pBt)<=10921 );
+  assert( pPage->nOverflow<=ArraySize(pPage->aOvfl) );
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  /* The cell should normally be sized correctly.  However, when moving a
+  ** malformed cell from a leaf page to an interior page, if the cell size
+  ** wanted to be less than 4 but got rounded up to 4 on the leaf, then size
+  ** might be less than 8 (leaf-size + pointer) on the interior node.  Hence
+  ** the term after the || in the following assert(). */
+  assert( sz==cellSizePtr(pPage, pCell) || (sz==8 && iChild>0) );
+  if( pPage->nOverflow || sz+2>pPage->nFree ){
+    if( pTemp ){
+      memcpy(pTemp+nSkip, pCell+nSkip, sz-nSkip);
+      pCell = pTemp;
+    }
+    if( iChild ){
+      put4byte(pCell, iChild);
+    }
+    j = pPage->nOverflow++;
+    assert( j<(int)(sizeof(pPage->aOvfl)/sizeof(pPage->aOvfl[0])) );
+    pPage->aOvfl[j].pCell = pCell;
+    pPage->aOvfl[j].idx = (u16)i;
+  }else{
+    int rc = sqlite3PagerWrite(pPage->pDbPage);
+    if( rc!=SQLITE_OK ){
+      *pRC = rc;
+      return;
+    }
+    assert( sqlite3PagerIswriteable(pPage->pDbPage) );
+    data = pPage->aData;
+    cellOffset = pPage->cellOffset;
+    end = cellOffset + 2*pPage->nCell;
+    ins = cellOffset + 2*i;
+    rc = allocateSpace(pPage, sz, &idx);
+    if( rc ){ *pRC = rc; return; }
+    /* The allocateSpace() routine guarantees the following two properties
+    ** if it returns success */
+    assert( idx >= end+2 );
+    assert( idx+sz <= (int)pPage->pBt->usableSize );
+    pPage->nCell++;
+    pPage->nFree -= (u16)(2 + sz);
+    memcpy(&data[idx+nSkip], pCell+nSkip, sz-nSkip);
+    if( iChild ){
+      put4byte(&data[idx], iChild);
+    }
+    ptr = &data[end];
+    endPtr = &data[ins];
+    assert( (SQLITE_PTR_TO_INT(ptr)&1)==0 );  /* ptr is always 2-byte aligned */
+    while( ptr>endPtr ){
+      *(u16*)ptr = *(u16*)&ptr[-2];
+      ptr -= 2;
+    }
+    put2byte(&data[ins], idx);
+    put2byte(&data[pPage->hdrOffset+3], pPage->nCell);
+#ifndef SQLITE_OMIT_AUTOVACUUM
+    if( pPage->pBt->autoVacuum ){
+      /* The cell may contain a pointer to an overflow page. If so, write
+      ** the entry for the overflow page into the pointer map.
+      */
+      ptrmapPutOvflPtr(pPage, pCell, pRC);
+    }
+#endif
+  }
+}
+
+/*
+** Add a list of cells to a page.  The page should be initially empty.
+** The cells are guaranteed to fit on the page.
+*/
+static void assemblePage(
+  MemPage *pPage,   /* The page to be assemblied */
+  int nCell,        /* The number of cells to add to this page */
+  u8 **apCell,      /* Pointers to cell bodies */
+  u16 *aSize        /* Sizes of the cells */
+){
+  int i;            /* Loop counter */
+  u8 *pCellptr;     /* Address of next cell pointer */
+  int cellbody;     /* Address of next cell body */
+  u8 * const data = pPage->aData;             /* Pointer to data for pPage */
+  const int hdr = pPage->hdrOffset;           /* Offset of header on pPage */
+  const int nUsable = pPage->pBt->usableSize; /* Usable size of page */
+
+  assert( pPage->nOverflow==0 );
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  assert( nCell>=0 && nCell<=(int)MX_CELL(pPage->pBt)
+            && (int)MX_CELL(pPage->pBt)<=10921);
+  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
+
+  /* Check that the page has just been zeroed by zeroPage() */
+  assert( pPage->nCell==0 );
+  assert( get2byteNotZero(&data[hdr+5])==nUsable );
+
+  pCellptr = &data[pPage->cellOffset + nCell*2];
+  cellbody = nUsable;
+  for(i=nCell-1; i>=0; i--){
+    u16 sz = aSize[i];
+    pCellptr -= 2;
+    cellbody -= sz;
+    put2byte(pCellptr, cellbody);
+    memcpy(&data[cellbody], apCell[i], sz);
+  }
+  put2byte(&data[hdr+3], nCell);
+  put2byte(&data[hdr+5], cellbody);
+  pPage->nFree -= (nCell*2 + nUsable - cellbody);
+  pPage->nCell = (u16)nCell;
+}
+
+/*
+** The following parameters determine how many adjacent pages get involved
+** in a balancing operation.  NN is the number of neighbors on either side
+** of the page that participate in the balancing operation.  NB is the
+** total number of pages that participate, including the target page and
+** NN neighbors on either side.
+**
+** The minimum value of NN is 1 (of course).  Increasing NN above 1
+** (to 2 or 3) gives a modest improvement in SELECT and DELETE performance
+** in exchange for a larger degradation in INSERT and UPDATE performance.
+** The value of NN appears to give the best results overall.
+*/
+#define NN 1             /* Number of neighbors on either side of pPage */
+#define NB (NN*2+1)      /* Total pages involved in the balance */
+
+
+#ifndef SQLITE_OMIT_QUICKBALANCE
+/*
+** This version of balance() handles the common special case where
+** a new entry is being inserted on the extreme right-end of the
+** tree, in other words, when the new entry will become the largest
+** entry in the tree.
+**
+** Instead of trying to balance the 3 right-most leaf pages, just add
+** a new page to the right-hand side and put the one new entry in
+** that page.  This leaves the right side of the tree somewhat
+** unbalanced.  But odds are that we will be inserting new entries
+** at the end soon afterwards so the nearly empty page will quickly
+** fill up.  On average.
+**
+** pPage is the leaf page which is the right-most page in the tree.
+** pParent is its parent.  pPage must have a single overflow entry
+** which is also the right-most entry on the page.
+**
+** The pSpace buffer is used to store a temporary copy of the divider
+** cell that will be inserted into pParent. Such a cell consists of a 4
+** byte page number followed by a variable length integer. In other
+** words, at most 13 bytes. Hence the pSpace buffer must be at
+** least 13 bytes in size.
+*/
+static int balance_quick(MemPage *pParent, MemPage *pPage, u8 *pSpace){
+  BtShared *const pBt = pPage->pBt;    /* B-Tree Database */
+  MemPage *pNew;                       /* Newly allocated page */
+  int rc;                              /* Return Code */
+  Pgno pgnoNew;                        /* Page number of pNew */
+
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  assert( sqlite3PagerIswriteable(pParent->pDbPage) );
+  assert( pPage->nOverflow==1 );
+
+  /* This error condition is now caught prior to reaching this function */
+  if( pPage->nCell<=0 ) return SQLITE_CORRUPT_BKPT;
+
+  /* Allocate a new page. This page will become the right-sibling of 
+  ** pPage. Make the parent page writable, so that the new divider cell
+  ** may be inserted. If both these operations are successful, proceed.
+  */
+  rc = allocateBtreePage(pBt, &pNew, &pgnoNew, 0, 0);
+
+  if( rc==SQLITE_OK ){
+
+    u8 *pOut = &pSpace[4];
+    u8 *pCell = pPage->aOvfl[0].pCell;
+    u16 szCell = cellSizePtr(pPage, pCell);
+    u8 *pStop;
+
+    assert( sqlite3PagerIswriteable(pNew->pDbPage) );
+    assert( pPage->aData[0]==(PTF_INTKEY|PTF_LEAFDATA|PTF_LEAF) );
+    zeroPage(pNew, PTF_INTKEY|PTF_LEAFDATA|PTF_LEAF);
+    assemblePage(pNew, 1, &pCell, &szCell);
+
+    /* If this is an auto-vacuum database, update the pointer map
+    ** with entries for the new page, and any pointer from the 
+    ** cell on the page to an overflow page. If either of these
+    ** operations fails, the return code is set, but the contents
+    ** of the parent page are still manipulated by thh code below.
+    ** That is Ok, at this point the parent page is guaranteed to
+    ** be marked as dirty. Returning an error code will cause a
+    ** rollback, undoing any changes made to the parent page.
+    */
+    if( ISAUTOVACUUM ){
+      ptrmapPut(pBt, pgnoNew, PTRMAP_BTREE, pParent->pgno, &rc);
+      if( szCell>pNew->minLocal ){
+        ptrmapPutOvflPtr(pNew, pCell, &rc);
+      }
+    }
+  
+    /* Create a divider cell to insert into pParent. The divider cell
+    ** consists of a 4-byte page number (the page number of pPage) and
+    ** a variable length key value (which must be the same value as the
+    ** largest key on pPage).
+    **
+    ** To find the largest key value on pPage, first find the right-most 
+    ** cell on pPage. The first two fields of this cell are the 
+    ** record-length (a variable length integer at most 32-bits in size)
+    ** and the key value (a variable length integer, may have any value).
+    ** The first of the while(...) loops below skips over the record-length
+    ** field. The second while(...) loop copies the key value from the
+    ** cell on pPage into the pSpace buffer.
+    */
+    pCell = findCell(pPage, pPage->nCell-1);
+    pStop = &pCell[9];
+    while( (*(pCell++)&0x80) && pCell<pStop );
+    pStop = &pCell[9];
+    while( ((*(pOut++) = *(pCell++))&0x80) && pCell<pStop );
+
+    /* Insert the new divider cell into pParent. */
+    insertCell(pParent, pParent->nCell, pSpace, (int)(pOut-pSpace),
+               0, pPage->pgno, &rc);
+
+    /* Set the right-child pointer of pParent to point to the new page. */
+    put4byte(&pParent->aData[pParent->hdrOffset+8], pgnoNew);
+  
+    /* Release the reference to the new page. */
+    releasePage(pNew);
+  }
+
+  return rc;
+}
+#endif /* SQLITE_OMIT_QUICKBALANCE */
+
+#if 0
+/*
+** This function does not contribute anything to the operation of SQLite.
+** it is sometimes activated temporarily while debugging code responsible 
+** for setting pointer-map entries.
+*/
+static int ptrmapCheckPages(MemPage **apPage, int nPage){
+  int i, j;
+  for(i=0; i<nPage; i++){
+    Pgno n;
+    u8 e;
+    MemPage *pPage = apPage[i];
+    BtShared *pBt = pPage->pBt;
+    assert( pPage->isInit );
+
+    for(j=0; j<pPage->nCell; j++){
+      CellInfo info;
+      u8 *z;
+     
+      z = findCell(pPage, j);
+      btreeParseCellPtr(pPage, z, &info);
+      if( info.iOverflow ){
+        Pgno ovfl = get4byte(&z[info.iOverflow]);
+        ptrmapGet(pBt, ovfl, &e, &n);
+        assert( n==pPage->pgno && e==PTRMAP_OVERFLOW1 );
+      }
+      if( !pPage->leaf ){
+        Pgno child = get4byte(z);
+        ptrmapGet(pBt, child, &e, &n);
+        assert( n==pPage->pgno && e==PTRMAP_BTREE );
+      }
+    }
+    if( !pPage->leaf ){
+      Pgno child = get4byte(&pPage->aData[pPage->hdrOffset+8]);
+      ptrmapGet(pBt, child, &e, &n);
+      assert( n==pPage->pgno && e==PTRMAP_BTREE );
+    }
+  }
+  return 1;
+}
+#endif
+
+/*
+** This function is used to copy the contents of the b-tree node stored 
+** on page pFrom to page pTo. If page pFrom was not a leaf page, then
+** the pointer-map entries for each child page are updated so that the
+** parent page stored in the pointer map is page pTo. If pFrom contained
+** any cells with overflow page pointers, then the corresponding pointer
+** map entries are also updated so that the parent page is page pTo.
+**
+** If pFrom is currently carrying any overflow cells (entries in the
+** MemPage.aOvfl[] array), they are not copied to pTo. 
+**
+** Before returning, page pTo is reinitialized using btreeInitPage().
+**
+** The performance of this function is not critical. It is only used by 
+** the balance_shallower() and balance_deeper() procedures, neither of
+** which are called often under normal circumstances.
+*/
+static void copyNodeContent(MemPage *pFrom, MemPage *pTo, int *pRC){
+  if( (*pRC)==SQLITE_OK ){
+    BtShared * const pBt = pFrom->pBt;
+    u8 * const aFrom = pFrom->aData;
+    u8 * const aTo = pTo->aData;
+    int const iFromHdr = pFrom->hdrOffset;
+    int const iToHdr = ((pTo->pgno==1) ? 100 : 0);
+    int rc;
+    int iData;
+  
+  
+    assert( pFrom->isInit );
+    assert( pFrom->nFree>=iToHdr );
+    assert( get2byte(&aFrom[iFromHdr+5]) <= (int)pBt->usableSize );
+  
+    /* Copy the b-tree node content from page pFrom to page pTo. */
+    iData = get2byte(&aFrom[iFromHdr+5]);
+    memcpy(&aTo[iData], &aFrom[iData], pBt->usableSize-iData);
+    memcpy(&aTo[iToHdr], &aFrom[iFromHdr], pFrom->cellOffset + 2*pFrom->nCell);
+  
+    /* Reinitialize page pTo so that the contents of the MemPage structure
+    ** match the new data. The initialization of pTo can actually fail under
+    ** fairly obscure circumstances, even though it is a copy of initialized 
+    ** page pFrom.
+    */
+    pTo->isInit = 0;
+    rc = btreeInitPage(pTo);
+    if( rc!=SQLITE_OK ){
+      *pRC = rc;
+      return;
+    }
+  
+    /* If this is an auto-vacuum database, update the pointer-map entries
+    ** for any b-tree or overflow pages that pTo now contains the pointers to.
+    */
+    if( ISAUTOVACUUM ){
+      *pRC = setChildPtrmaps(pTo);
+    }
+  }
+}
+
+/*
+** This routine redistributes cells on the iParentIdx'th child of pParent
+** (hereafter "the page") and up to 2 siblings so that all pages have about the
+** same amount of free space. Usually a single sibling on either side of the
+** page are used in the balancing, though both siblings might come from one
+** side if the page is the first or last child of its parent. If the page 
+** has fewer than 2 siblings (something which can only happen if the page
+** is a root page or a child of a root page) then all available siblings
+** participate in the balancing.
+**
+** The number of siblings of the page might be increased or decreased by 
+** one or two in an effort to keep pages nearly full but not over full. 
+**
+** Note that when this routine is called, some of the cells on the page
+** might not actually be stored in MemPage.aData[]. This can happen
+** if the page is overfull. This routine ensures that all cells allocated
+** to the page and its siblings fit into MemPage.aData[] before returning.
+**
+** In the course of balancing the page and its siblings, cells may be
+** inserted into or removed from the parent page (pParent). Doing so
+** may cause the parent page to become overfull or underfull. If this
+** happens, it is the responsibility of the caller to invoke the correct
+** balancing routine to fix this problem (see the balance() routine). 
+**
+** If this routine fails for any reason, it might leave the database
+** in a corrupted state. So if this routine fails, the database should
+** be rolled back.
+**
+** The third argument to this function, aOvflSpace, is a pointer to a
+** buffer big enough to hold one page. If while inserting cells into the parent
+** page (pParent) the parent page becomes overfull, this buffer is
+** used to store the parent's overflow cells. Because this function inserts
+** a maximum of four divider cells into the parent page, and the maximum
+** size of a cell stored within an internal node is always less than 1/4
+** of the page-size, the aOvflSpace[] buffer is guaranteed to be large
+** enough for all overflow cells.
+**
+** If aOvflSpace is set to a null pointer, this function returns 
+** SQLITE_NOMEM.
+*/
+static int balance_nonroot(
+  MemPage *pParent,               /* Parent page of siblings being balanced */
+  int iParentIdx,                 /* Index of "the page" in pParent */
+  u8 *aOvflSpace,                 /* page-size bytes of space for parent ovfl */
+  int isRoot                      /* True if pParent is a root-page */
+){
+  BtShared *pBt;               /* The whole database */
+  int nCell = 0;               /* Number of cells in apCell[] */
+  int nMaxCells = 0;           /* Allocated size of apCell, szCell, aFrom. */
+  int nNew = 0;                /* Number of pages in apNew[] */
+  int nOld;                    /* Number of pages in apOld[] */
+  int i, j, k;                 /* Loop counters */
+  int nxDiv;                   /* Next divider slot in pParent->aCell[] */
+  int rc = SQLITE_OK;          /* The return code */
+  u16 leafCorrection;          /* 4 if pPage is a leaf.  0 if not */
+  int leafData;                /* True if pPage is a leaf of a LEAFDATA tree */
+  int usableSpace;             /* Bytes in pPage beyond the header */
+  int pageFlags;               /* Value of pPage->aData[0] */
+  int subtotal;                /* Subtotal of bytes in cells on one page */
+  int iSpace1 = 0;             /* First unused byte of aSpace1[] */
+  int iOvflSpace = 0;          /* First unused byte of aOvflSpace[] */
+  int szScratch;               /* Size of scratch memory requested */
+  MemPage *apOld[NB];          /* pPage and up to two siblings */
+  MemPage *apCopy[NB];         /* Private copies of apOld[] pages */
+  MemPage *apNew[NB+2];        /* pPage and up to NB siblings after balancing */
+  u8 *pRight;                  /* Location in parent of right-sibling pointer */
+  u8 *apDiv[NB-1];             /* Divider cells in pParent */
+  int cntNew[NB+2];            /* Index in aCell[] of cell after i-th page */
+  int szNew[NB+2];             /* Combined size of cells place on i-th page */
+  u8 **apCell = 0;             /* All cells begin balanced */
+  u16 *szCell;                 /* Local size of all cells in apCell[] */
+  u8 *aSpace1;                 /* Space for copies of dividers cells */
+  Pgno pgno;                   /* Temp var to store a page number in */
+
+  pBt = pParent->pBt;
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  assert( sqlite3PagerIswriteable(pParent->pDbPage) );
+
+#if 0
+  TRACE(("BALANCE: begin page %d child of %d\n", pPage->pgno, pParent->pgno));
+#endif
+
+  /* At this point pParent may have at most one overflow cell. And if
+  ** this overflow cell is present, it must be the cell with 
+  ** index iParentIdx. This scenario comes about when this function
+  ** is called (indirectly) from sqlite3BtreeDelete().
+  */
+  assert( pParent->nOverflow==0 || pParent->nOverflow==1 );
+  assert( pParent->nOverflow==0 || pParent->aOvfl[0].idx==iParentIdx );
+
+  if( !aOvflSpace ){
+    return SQLITE_NOMEM;
+  }
+
+  /* Find the sibling pages to balance. Also locate the cells in pParent 
+  ** that divide the siblings. An attempt is made to find NN siblings on 
+  ** either side of pPage. More siblings are taken from one side, however, 
+  ** if there are fewer than NN siblings on the other side. If pParent
+  ** has NB or fewer children then all children of pParent are taken.  
+  **
+  ** This loop also drops the divider cells from the parent page. This
+  ** way, the remainder of the function does not have to deal with any
+  ** overflow cells in the parent page, since if any existed they will
+  ** have already been removed.
+  */
+  i = pParent->nOverflow + pParent->nCell;
+  if( i<2 ){
+    nxDiv = 0;
+    nOld = i+1;
+  }else{
+    nOld = 3;
+    if( iParentIdx==0 ){                 
+      nxDiv = 0;
+    }else if( iParentIdx==i ){
+      nxDiv = i-2;
+    }else{
+      nxDiv = iParentIdx-1;
+    }
+    i = 2;
+  }
+  if( (i+nxDiv-pParent->nOverflow)==pParent->nCell ){
+    pRight = &pParent->aData[pParent->hdrOffset+8];
+  }else{
+    pRight = findCell(pParent, i+nxDiv-pParent->nOverflow);
+  }
+  pgno = get4byte(pRight);
+  while( 1 ){
+    rc = getAndInitPage(pBt, pgno, &apOld[i]);
+    if( rc ){
+      memset(apOld, 0, (i+1)*sizeof(MemPage*));
+      goto balance_cleanup;
+    }
+    nMaxCells += 1+apOld[i]->nCell+apOld[i]->nOverflow;
+    if( (i--)==0 ) break;
+
+    if( i+nxDiv==pParent->aOvfl[0].idx && pParent->nOverflow ){
+      apDiv[i] = pParent->aOvfl[0].pCell;
+      pgno = get4byte(apDiv[i]);
+      szNew[i] = cellSizePtr(pParent, apDiv[i]);
+      pParent->nOverflow = 0;
+    }else{
+      apDiv[i] = findCell(pParent, i+nxDiv-pParent->nOverflow);
+      pgno = get4byte(apDiv[i]);
+      szNew[i] = cellSizePtr(pParent, apDiv[i]);
+
+      /* Drop the cell from the parent page. apDiv[i] still points to
+      ** the cell within the parent, even though it has been dropped.
+      ** This is safe because dropping a cell only overwrites the first
+      ** four bytes of it, and this function does not need the first
+      ** four bytes of the divider cell. So the pointer is safe to use
+      ** later on.  
+      **
+      ** But not if we are in secure-delete mode. In secure-delete mode,
+      ** the dropCell() routine will overwrite the entire cell with zeroes.
+      ** In this case, temporarily copy the cell into the aOvflSpace[]
+      ** buffer. It will be copied out again as soon as the aSpace[] buffer
+      ** is allocated.  */
+      if( pBt->secureDelete ){
+        int iOff;
+
+        iOff = SQLITE_PTR_TO_INT(apDiv[i]) - SQLITE_PTR_TO_INT(pParent->aData);
+        if( (iOff+szNew[i])>(int)pBt->usableSize ){
+          rc = SQLITE_CORRUPT_BKPT;
+          memset(apOld, 0, (i+1)*sizeof(MemPage*));
+          goto balance_cleanup;
+        }else{
+          memcpy(&aOvflSpace[iOff], apDiv[i], szNew[i]);
+          apDiv[i] = &aOvflSpace[apDiv[i]-pParent->aData];
+        }
+      }
+      dropCell(pParent, i+nxDiv-pParent->nOverflow, szNew[i], &rc);
+    }
+  }
+
+  /* Make nMaxCells a multiple of 4 in order to preserve 8-byte
+  ** alignment */
+  nMaxCells = (nMaxCells + 3)&~3;
+
+  /*
+  ** Allocate space for memory structures
+  */
+  k = pBt->pageSize + ROUND8(sizeof(MemPage));
+  szScratch =
+       nMaxCells*sizeof(u8*)                       /* apCell */
+     + nMaxCells*sizeof(u16)                       /* szCell */
+     + pBt->pageSize                               /* aSpace1 */
+     + k*nOld;                                     /* Page copies (apCopy) */
+  apCell = sqlite3ScratchMalloc( szScratch ); 
+  if( apCell==0 ){
+    rc = SQLITE_NOMEM;
+    goto balance_cleanup;
+  }
+  szCell = (u16*)&apCell[nMaxCells];
+  aSpace1 = (u8*)&szCell[nMaxCells];
+  assert( EIGHT_BYTE_ALIGNMENT(aSpace1) );
+
+  /*
+  ** Load pointers to all cells on sibling pages and the divider cells
+  ** into the local apCell[] array.  Make copies of the divider cells
+  ** into space obtained from aSpace1[] and remove the the divider Cells
+  ** from pParent.
+  **
+  ** If the siblings are on leaf pages, then the child pointers of the
+  ** divider cells are stripped from the cells before they are copied
+  ** into aSpace1[].  In this way, all cells in apCell[] are without
+  ** child pointers.  If siblings are not leaves, then all cell in
+  ** apCell[] include child pointers.  Either way, all cells in apCell[]
+  ** are alike.
+  **
+  ** leafCorrection:  4 if pPage is a leaf.  0 if pPage is not a leaf.
+  **       leafData:  1 if pPage holds key+data and pParent holds only keys.
+  */
+  leafCorrection = apOld[0]->leaf*4;
+  leafData = apOld[0]->hasData;
+  for(i=0; i<nOld; i++){
+    int limit;
+    
+    /* Before doing anything else, take a copy of the i'th original sibling
+    ** The rest of this function will use data from the copies rather
+    ** that the original pages since the original pages will be in the
+    ** process of being overwritten.  */
+    MemPage *pOld = apCopy[i] = (MemPage*)&aSpace1[pBt->pageSize + k*i];
+    memcpy(pOld, apOld[i], sizeof(MemPage));
+    pOld->aData = (void*)&pOld[1];
+    memcpy(pOld->aData, apOld[i]->aData, pBt->pageSize);
+
+    limit = pOld->nCell+pOld->nOverflow;
+    if( pOld->nOverflow>0 ){
+      for(j=0; j<limit; j++){
+        assert( nCell<nMaxCells );
+        apCell[nCell] = findOverflowCell(pOld, j);
+        szCell[nCell] = cellSizePtr(pOld, apCell[nCell]);
+        nCell++;
+      }
+    }else{
+      u8 *aData = pOld->aData;
+      u16 maskPage = pOld->maskPage;
+      u16 cellOffset = pOld->cellOffset;
+      for(j=0; j<limit; j++){
+        assert( nCell<nMaxCells );
+        apCell[nCell] = findCellv2(aData, maskPage, cellOffset, j);
+        szCell[nCell] = cellSizePtr(pOld, apCell[nCell]);
+        nCell++;
+      }
+    }       
+    if( i<nOld-1 && !leafData){
+      u16 sz = (u16)szNew[i];
+      u8 *pTemp;
+      assert( nCell<nMaxCells );
+      szCell[nCell] = sz;
+      pTemp = &aSpace1[iSpace1];
+      iSpace1 += sz;
+      assert( sz<=pBt->maxLocal+23 );
+      assert( iSpace1 <= (int)pBt->pageSize );
+      memcpy(pTemp, apDiv[i], sz);
+      apCell[nCell] = pTemp+leafCorrection;
+      assert( leafCorrection==0 || leafCorrection==4 );
+      szCell[nCell] = szCell[nCell] - leafCorrection;
+      if( !pOld->leaf ){
+        assert( leafCorrection==0 );
+        assert( pOld->hdrOffset==0 );
+        /* The right pointer of the child page pOld becomes the left
+        ** pointer of the divider cell */
+        memcpy(apCell[nCell], &pOld->aData[8], 4);
+      }else{
+        assert( leafCorrection==4 );
+        if( szCell[nCell]<4 ){
+          /* Do not allow any cells smaller than 4 bytes. */
+          szCell[nCell] = 4;
+        }
+      }
+      nCell++;
+    }
+  }
+
+  /*
+  ** Figure out the number of pages needed to hold all nCell cells.
+  ** Store this number in "k".  Also compute szNew[] which is the total
+  ** size of all cells on the i-th page and cntNew[] which is the index
+  ** in apCell[] of the cell that divides page i from page i+1.  
+  ** cntNew[k] should equal nCell.
+  **
+  ** Values computed by this block:
+  **
+  **           k: The total number of sibling pages
+  **    szNew[i]: Spaced used on the i-th sibling page.
+  **   cntNew[i]: Index in apCell[] and szCell[] for the first cell to
+  **              the right of the i-th sibling page.
+  ** usableSpace: Number of bytes of space available on each sibling.
+  ** 
+  */
+  usableSpace = pBt->usableSize - 12 + leafCorrection;
+  for(subtotal=k=i=0; i<nCell; i++){
+    assert( i<nMaxCells );
+    subtotal += szCell[i] + 2;
+    if( subtotal > usableSpace ){
+      szNew[k] = subtotal - szCell[i];
+      cntNew[k] = i;
+      if( leafData ){ i--; }
+      subtotal = 0;
+      k++;
+      if( k>NB+1 ){ rc = SQLITE_CORRUPT_BKPT; goto balance_cleanup; }
+    }
+  }
+  szNew[k] = subtotal;
+  cntNew[k] = nCell;
+  k++;
+
+  /*
+  ** The packing computed by the previous block is biased toward the siblings
+  ** on the left side.  The left siblings are always nearly full, while the
+  ** right-most sibling might be nearly empty.  This block of code attempts
+  ** to adjust the packing of siblings to get a better balance.
+  **
+  ** This adjustment is more than an optimization.  The packing above might
+  ** be so out of balance as to be illegal.  For example, the right-most
+  ** sibling might be completely empty.  This adjustment is not optional.
+  */
+  for(i=k-1; i>0; i--){
+    int szRight = szNew[i];  /* Size of sibling on the right */
+    int szLeft = szNew[i-1]; /* Size of sibling on the left */
+    int r;              /* Index of right-most cell in left sibling */
+    int d;              /* Index of first cell to the left of right sibling */
+
+    r = cntNew[i-1] - 1;
+    d = r + 1 - leafData;
+    assert( d<nMaxCells );
+    assert( r<nMaxCells );
+    while( szRight==0 || szRight+szCell[d]+2<=szLeft-(szCell[r]+2) ){
+      szRight += szCell[d] + 2;
+      szLeft -= szCell[r] + 2;
+      cntNew[i-1]--;
+      r = cntNew[i-1] - 1;
+      d = r + 1 - leafData;
+    }
+    szNew[i] = szRight;
+    szNew[i-1] = szLeft;
+  }
+
+  /* Either we found one or more cells (cntnew[0])>0) or pPage is
+  ** a virtual root page.  A virtual root page is when the real root
+  ** page is page 1 and we are the only child of that page.
+  */
+  assert( cntNew[0]>0 || (pParent->pgno==1 && pParent->nCell==0) );
+
+  TRACE(("BALANCE: old: %d %d %d  ",
+    apOld[0]->pgno, 
+    nOld>=2 ? apOld[1]->pgno : 0,
+    nOld>=3 ? apOld[2]->pgno : 0
+  ));
+
+  /*
+  ** Allocate k new pages.  Reuse old pages where possible.
+  */
+  if( apOld[0]->pgno<=1 ){
+    rc = SQLITE_CORRUPT_BKPT;
+    goto balance_cleanup;
+  }
+  pageFlags = apOld[0]->aData[0];
+  for(i=0; i<k; i++){
+    MemPage *pNew;
+    if( i<nOld ){
+      pNew = apNew[i] = apOld[i];
+      apOld[i] = 0;
+      rc = sqlite3PagerWrite(pNew->pDbPage);
+      nNew++;
+      if( rc ) goto balance_cleanup;
+    }else{
+      assert( i>0 );
+      rc = allocateBtreePage(pBt, &pNew, &pgno, pgno, 0);
+      if( rc ) goto balance_cleanup;
+      apNew[i] = pNew;
+      nNew++;
+
+      /* Set the pointer-map entry for the new sibling page. */
+      if( ISAUTOVACUUM ){
+        ptrmapPut(pBt, pNew->pgno, PTRMAP_BTREE, pParent->pgno, &rc);
+        if( rc!=SQLITE_OK ){
+          goto balance_cleanup;
+        }
+      }
+    }
+  }
+
+  /* Free any old pages that were not reused as new pages.
+  */
+  while( i<nOld ){
+    freePage(apOld[i], &rc);
+    if( rc ) goto balance_cleanup;
+    releasePage(apOld[i]);
+    apOld[i] = 0;
+    i++;
+  }
+
+  /*
+  ** Put the new pages in accending order.  This helps to
+  ** keep entries in the disk file in order so that a scan
+  ** of the table is a linear scan through the file.  That
+  ** in turn helps the operating system to deliver pages
+  ** from the disk more rapidly.
+  **
+  ** An O(n^2) insertion sort algorithm is used, but since
+  ** n is never more than NB (a small constant), that should
+  ** not be a problem.
+  **
+  ** When NB==3, this one optimization makes the database
+  ** about 25% faster for large insertions and deletions.
+  */
+  for(i=0; i<k-1; i++){
+    int minV = apNew[i]->pgno;
+    int minI = i;
+    for(j=i+1; j<k; j++){
+      if( apNew[j]->pgno<(unsigned)minV ){
+        minI = j;
+        minV = apNew[j]->pgno;
+      }
+    }
+    if( minI>i ){
+      MemPage *pT;
+      pT = apNew[i];
+      apNew[i] = apNew[minI];
+      apNew[minI] = pT;
+    }
+  }
+  TRACE(("new: %d(%d) %d(%d) %d(%d) %d(%d) %d(%d)\n",
+    apNew[0]->pgno, szNew[0],
+    nNew>=2 ? apNew[1]->pgno : 0, nNew>=2 ? szNew[1] : 0,
+    nNew>=3 ? apNew[2]->pgno : 0, nNew>=3 ? szNew[2] : 0,
+    nNew>=4 ? apNew[3]->pgno : 0, nNew>=4 ? szNew[3] : 0,
+    nNew>=5 ? apNew[4]->pgno : 0, nNew>=5 ? szNew[4] : 0));
+
+  assert( sqlite3PagerIswriteable(pParent->pDbPage) );
+  put4byte(pRight, apNew[nNew-1]->pgno);
+
+  /*
+  ** Evenly distribute the data in apCell[] across the new pages.
+  ** Insert divider cells into pParent as necessary.
+  */
+  j = 0;
+  for(i=0; i<nNew; i++){
+    /* Assemble the new sibling page. */
+    MemPage *pNew = apNew[i];
+    assert( j<nMaxCells );
+    zeroPage(pNew, pageFlags);
+    assemblePage(pNew, cntNew[i]-j, &apCell[j], &szCell[j]);
+    assert( pNew->nCell>0 || (nNew==1 && cntNew[0]==0) );
+    assert( pNew->nOverflow==0 );
+
+    j = cntNew[i];
+
+    /* If the sibling page assembled above was not the right-most sibling,
+    ** insert a divider cell into the parent page.
+    */
+    assert( i<nNew-1 || j==nCell );
+    if( j<nCell ){
+      u8 *pCell;
+      u8 *pTemp;
+      int sz;
+
+      assert( j<nMaxCells );
+      pCell = apCell[j];
+      sz = szCell[j] + leafCorrection;
+      pTemp = &aOvflSpace[iOvflSpace];
+      if( !pNew->leaf ){
+        memcpy(&pNew->aData[8], pCell, 4);
+      }else if( leafData ){
+        /* If the tree is a leaf-data tree, and the siblings are leaves, 
+        ** then there is no divider cell in apCell[]. Instead, the divider 
+        ** cell consists of the integer key for the right-most cell of 
+        ** the sibling-page assembled above only.
+        */
+        CellInfo info;
+        j--;
+        btreeParseCellPtr(pNew, apCell[j], &info);
+        pCell = pTemp;
+        sz = 4 + putVarint(&pCell[4], info.nKey);
+        pTemp = 0;
+      }else{
+        pCell -= 4;
+        /* Obscure case for non-leaf-data trees: If the cell at pCell was
+        ** previously stored on a leaf node, and its reported size was 4
+        ** bytes, then it may actually be smaller than this 
+        ** (see btreeParseCellPtr(), 4 bytes is the minimum size of
+        ** any cell). But it is important to pass the correct size to 
+        ** insertCell(), so reparse the cell now.
+        **
+        ** Note that this can never happen in an SQLite data file, as all
+        ** cells are at least 4 bytes. It only happens in b-trees used
+        ** to evaluate "IN (SELECT ...)" and similar clauses.
+        */
+        if( szCell[j]==4 ){
+          assert(leafCorrection==4);
+          sz = cellSizePtr(pParent, pCell);
+        }
+      }
+      iOvflSpace += sz;
+      assert( sz<=pBt->maxLocal+23 );
+      assert( iOvflSpace <= (int)pBt->pageSize );
+      insertCell(pParent, nxDiv, pCell, sz, pTemp, pNew->pgno, &rc);
+      if( rc!=SQLITE_OK ) goto balance_cleanup;
+      assert( sqlite3PagerIswriteable(pParent->pDbPage) );
+
+      j++;
+      nxDiv++;
+    }
+  }
+  assert( j==nCell );
+  assert( nOld>0 );
+  assert( nNew>0 );
+  if( (pageFlags & PTF_LEAF)==0 ){
+    u8 *zChild = &apCopy[nOld-1]->aData[8];
+    memcpy(&apNew[nNew-1]->aData[8], zChild, 4);
+  }
+
+  if( isRoot && pParent->nCell==0 && pParent->hdrOffset<=apNew[0]->nFree ){
+    /* The root page of the b-tree now contains no cells. The only sibling
+    ** page is the right-child of the parent. Copy the contents of the
+    ** child page into the parent, decreasing the overall height of the
+    ** b-tree structure by one. This is described as the "balance-shallower"
+    ** sub-algorithm in some documentation.
+    **
+    ** If this is an auto-vacuum database, the call to copyNodeContent() 
+    ** sets all pointer-map entries corresponding to database image pages 
+    ** for which the pointer is stored within the content being copied.
+    **
+    ** The second assert below verifies that the child page is defragmented
+    ** (it must be, as it was just reconstructed using assemblePage()). This
+    ** is important if the parent page happens to be page 1 of the database
+    ** image.  */
+    assert( nNew==1 );
+    assert( apNew[0]->nFree == 
+        (get2byte(&apNew[0]->aData[5])-apNew[0]->cellOffset-apNew[0]->nCell*2) 
+    );
+    copyNodeContent(apNew[0], pParent, &rc);
+    freePage(apNew[0], &rc);
+  }else if( ISAUTOVACUUM ){
+    /* Fix the pointer-map entries for all the cells that were shifted around. 
+    ** There are several different types of pointer-map entries that need to
+    ** be dealt with by this routine. Some of these have been set already, but
+    ** many have not. The following is a summary:
+    **
+    **   1) The entries associated with new sibling pages that were not
+    **      siblings when this function was called. These have already
+    **      been set. We don't need to worry about old siblings that were
+    **      moved to the free-list - the freePage() code has taken care
+    **      of those.
+    **
+    **   2) The pointer-map entries associated with the first overflow
+    **      page in any overflow chains used by new divider cells. These 
+    **      have also already been taken care of by the insertCell() code.
+    **
+    **   3) If the sibling pages are not leaves, then the child pages of
+    **      cells stored on the sibling pages may need to be updated.
+    **
+    **   4) If the sibling pages are not internal intkey nodes, then any
+    **      overflow pages used by these cells may need to be updated
+    **      (internal intkey nodes never contain pointers to overflow pages).
+    **
+    **   5) If the sibling pages are not leaves, then the pointer-map
+    **      entries for the right-child pages of each sibling may need
+    **      to be updated.
+    **
+    ** Cases 1 and 2 are dealt with above by other code. The next
+    ** block deals with cases 3 and 4 and the one after that, case 5. Since
+    ** setting a pointer map entry is a relatively expensive operation, this
+    ** code only sets pointer map entries for child or overflow pages that have
+    ** actually moved between pages.  */
+    MemPage *pNew = apNew[0];
+    MemPage *pOld = apCopy[0];
+    int nOverflow = pOld->nOverflow;
+    int iNextOld = pOld->nCell + nOverflow;
+    int iOverflow = (nOverflow ? pOld->aOvfl[0].idx : -1);
+    j = 0;                             /* Current 'old' sibling page */
+    k = 0;                             /* Current 'new' sibling page */
+    for(i=0; i<nCell; i++){
+      int isDivider = 0;
+      while( i==iNextOld ){
+        /* Cell i is the cell immediately following the last cell on old
+        ** sibling page j. If the siblings are not leaf pages of an
+        ** intkey b-tree, then cell i was a divider cell. */
+        assert( j+1 < ArraySize(apCopy) );
+        pOld = apCopy[++j];
+        iNextOld = i + !leafData + pOld->nCell + pOld->nOverflow;
+        if( pOld->nOverflow ){
+          nOverflow = pOld->nOverflow;
+          iOverflow = i + !leafData + pOld->aOvfl[0].idx;
+        }
+        isDivider = !leafData;  
+      }
+
+      assert(nOverflow>0 || iOverflow<i );
+      assert(nOverflow<2 || pOld->aOvfl[0].idx==pOld->aOvfl[1].idx-1);
+      assert(nOverflow<3 || pOld->aOvfl[1].idx==pOld->aOvfl[2].idx-1);
+      if( i==iOverflow ){
+        isDivider = 1;
+        if( (--nOverflow)>0 ){
+          iOverflow++;
+        }
+      }
+
+      if( i==cntNew[k] ){
+        /* Cell i is the cell immediately following the last cell on new
+        ** sibling page k. If the siblings are not leaf pages of an
+        ** intkey b-tree, then cell i is a divider cell.  */
+        pNew = apNew[++k];
+        if( !leafData ) continue;
+      }
+      assert( j<nOld );
+      assert( k<nNew );
+
+      /* If the cell was originally divider cell (and is not now) or
+      ** an overflow cell, or if the cell was located on a different sibling
+      ** page before the balancing, then the pointer map entries associated
+      ** with any child or overflow pages need to be updated.  */
+      if( isDivider || pOld->pgno!=pNew->pgno ){
+        if( !leafCorrection ){
+          ptrmapPut(pBt, get4byte(apCell[i]), PTRMAP_BTREE, pNew->pgno, &rc);
+        }
+        if( szCell[i]>pNew->minLocal ){
+          ptrmapPutOvflPtr(pNew, apCell[i], &rc);
+        }
+      }
+    }
+
+    if( !leafCorrection ){
+      for(i=0; i<nNew; i++){
+        u32 key = get4byte(&apNew[i]->aData[8]);
+        ptrmapPut(pBt, key, PTRMAP_BTREE, apNew[i]->pgno, &rc);
+      }
+    }
+
+#if 0
+    /* The ptrmapCheckPages() contains assert() statements that verify that
+    ** all pointer map pages are set correctly. This is helpful while 
+    ** debugging. This is usually disabled because a corrupt database may
+    ** cause an assert() statement to fail.  */
+    ptrmapCheckPages(apNew, nNew);
+    ptrmapCheckPages(&pParent, 1);
+#endif
+  }
+
+  assert( pParent->isInit );
+  TRACE(("BALANCE: finished: old=%d new=%d cells=%d\n",
+          nOld, nNew, nCell));
+
+  /*
+  ** Cleanup before returning.
+  */
+balance_cleanup:
+  sqlite3ScratchFree(apCell);
+  for(i=0; i<nOld; i++){
+    releasePage(apOld[i]);
+  }
+  for(i=0; i<nNew; i++){
+    releasePage(apNew[i]);
+  }
+
+  return rc;
+}
+
+
+/*
+** This function is called when the root page of a b-tree structure is
+** overfull (has one or more overflow pages).
+**
+** A new child page is allocated and the contents of the current root
+** page, including overflow cells, are copied into the child. The root
+** page is then overwritten to make it an empty page with the right-child 
+** pointer pointing to the new page.
+**
+** Before returning, all pointer-map entries corresponding to pages 
+** that the new child-page now contains pointers to are updated. The
+** entry corresponding to the new right-child pointer of the root
+** page is also updated.
+**
+** If successful, *ppChild is set to contain a reference to the child 
+** page and SQLITE_OK is returned. In this case the caller is required
+** to call releasePage() on *ppChild exactly once. If an error occurs,
+** an error code is returned and *ppChild is set to 0.
+*/
+static int balance_deeper(MemPage *pRoot, MemPage **ppChild){
+  int rc;                        /* Return value from subprocedures */
+  MemPage *pChild = 0;           /* Pointer to a new child page */
+  Pgno pgnoChild = 0;            /* Page number of the new child page */
+  BtShared *pBt = pRoot->pBt;    /* The BTree */
+
+  assert( pRoot->nOverflow>0 );
+  assert( sqlite3_mutex_held(pBt->mutex) );
+
+  /* Make pRoot, the root page of the b-tree, writable. Allocate a new 
+  ** page that will become the new right-child of pPage. Copy the contents
+  ** of the node stored on pRoot into the new child page.
+  */
+  rc = sqlite3PagerWrite(pRoot->pDbPage);
+  if( rc==SQLITE_OK ){
+    rc = allocateBtreePage(pBt,&pChild,&pgnoChild,pRoot->pgno,0);
+    copyNodeContent(pRoot, pChild, &rc);
+    if( ISAUTOVACUUM ){
+      ptrmapPut(pBt, pgnoChild, PTRMAP_BTREE, pRoot->pgno, &rc);
+    }
+  }
+  if( rc ){
+    *ppChild = 0;
+    releasePage(pChild);
+    return rc;
+  }
+  assert( sqlite3PagerIswriteable(pChild->pDbPage) );
+  assert( sqlite3PagerIswriteable(pRoot->pDbPage) );
+  assert( pChild->nCell==pRoot->nCell );
+
+  TRACE(("BALANCE: copy root %d into %d\n", pRoot->pgno, pChild->pgno));
+
+  /* Copy the overflow cells from pRoot to pChild */
+  memcpy(pChild->aOvfl, pRoot->aOvfl, pRoot->nOverflow*sizeof(pRoot->aOvfl[0]));
+  pChild->nOverflow = pRoot->nOverflow;
+
+  /* Zero the contents of pRoot. Then install pChild as the right-child. */
+  zeroPage(pRoot, pChild->aData[0] & ~PTF_LEAF);
+  put4byte(&pRoot->aData[pRoot->hdrOffset+8], pgnoChild);
+
+  *ppChild = pChild;
+  return SQLITE_OK;
+}
+
+/*
+** The page that pCur currently points to has just been modified in
+** some way. This function figures out if this modification means the
+** tree needs to be balanced, and if so calls the appropriate balancing 
+** routine. Balancing routines are:
+**
+**   balance_quick()
+**   balance_deeper()
+**   balance_nonroot()
+*/
+static int balance(BtCursor *pCur){
+  int rc = SQLITE_OK;
+  const int nMin = pCur->pBt->usableSize * 2 / 3;
+  u8 aBalanceQuickSpace[13];
+  u8 *pFree = 0;
+
+  TESTONLY( int balance_quick_called = 0 );
+  TESTONLY( int balance_deeper_called = 0 );
+
+  do {
+    int iPage = pCur->iPage;
+    MemPage *pPage = pCur->apPage[iPage];
+
+    if( iPage==0 ){
+      if( pPage->nOverflow ){
+        /* The root page of the b-tree is overfull. In this case call the
+        ** balance_deeper() function to create a new child for the root-page
+        ** and copy the current contents of the root-page to it. The
+        ** next iteration of the do-loop will balance the child page.
+        */ 
+        assert( (balance_deeper_called++)==0 );
+        rc = balance_deeper(pPage, &pCur->apPage[1]);
+        if( rc==SQLITE_OK ){
+          pCur->iPage = 1;
+          pCur->aiIdx[0] = 0;
+          pCur->aiIdx[1] = 0;
+          assert( pCur->apPage[1]->nOverflow );
+        }
+      }else{
+        break;
+      }
+    }else if( pPage->nOverflow==0 && pPage->nFree<=nMin ){
+      break;
+    }else{
+      MemPage * const pParent = pCur->apPage[iPage-1];
+      int const iIdx = pCur->aiIdx[iPage-1];
+
+      rc = sqlite3PagerWrite(pParent->pDbPage);
+      if( rc==SQLITE_OK ){
+#ifndef SQLITE_OMIT_QUICKBALANCE
+        if( pPage->hasData
+         && pPage->nOverflow==1
+         && pPage->aOvfl[0].idx==pPage->nCell
+         && pParent->pgno!=1
+         && pParent->nCell==iIdx
+        ){
+          /* Call balance_quick() to create a new sibling of pPage on which
+          ** to store the overflow cell. balance_quick() inserts a new cell
+          ** into pParent, which may cause pParent overflow. If this
+          ** happens, the next interation of the do-loop will balance pParent 
+          ** use either balance_nonroot() or balance_deeper(). Until this
+          ** happens, the overflow cell is stored in the aBalanceQuickSpace[]
+          ** buffer. 
+          **
+          ** The purpose of the following assert() is to check that only a
+          ** single call to balance_quick() is made for each call to this
+          ** function. If this were not verified, a subtle bug involving reuse
+          ** of the aBalanceQuickSpace[] might sneak in.
+          */
+          assert( (balance_quick_called++)==0 );
+          rc = balance_quick(pParent, pPage, aBalanceQuickSpace);
+        }else
+#endif
+        {
+          /* In this case, call balance_nonroot() to redistribute cells
+          ** between pPage and up to 2 of its sibling pages. This involves
+          ** modifying the contents of pParent, which may cause pParent to
+          ** become overfull or underfull. The next iteration of the do-loop
+          ** will balance the parent page to correct this.
+          ** 
+          ** If the parent page becomes overfull, the overflow cell or cells
+          ** are stored in the pSpace buffer allocated immediately below. 
+          ** A subsequent iteration of the do-loop will deal with this by
+          ** calling balance_nonroot() (balance_deeper() may be called first,
+          ** but it doesn't deal with overflow cells - just moves them to a
+          ** different page). Once this subsequent call to balance_nonroot() 
+          ** has completed, it is safe to release the pSpace buffer used by
+          ** the previous call, as the overflow cell data will have been 
+          ** copied either into the body of a database page or into the new
+          ** pSpace buffer passed to the latter call to balance_nonroot().
+          */
+          u8 *pSpace = sqlite3PageMalloc(pCur->pBt->pageSize);
+          rc = balance_nonroot(pParent, iIdx, pSpace, iPage==1);
+          if( pFree ){
+            /* If pFree is not NULL, it points to the pSpace buffer used 
+            ** by a previous call to balance_nonroot(). Its contents are
+            ** now stored either on real database pages or within the 
+            ** new pSpace buffer, so it may be safely freed here. */
+            sqlite3PageFree(pFree);
+          }
+
+          /* The pSpace buffer will be freed after the next call to
+          ** balance_nonroot(), or just before this function returns, whichever
+          ** comes first. */
+          pFree = pSpace;
+        }
+      }
+
+      pPage->nOverflow = 0;
+
+      /* The next iteration of the do-loop balances the parent page. */
+      releasePage(pPage);
+      pCur->iPage--;
+    }
+  }while( rc==SQLITE_OK );
+
+  if( pFree ){
+    sqlite3PageFree(pFree);
+  }
+  return rc;
+}
+
+
+/*
+** Insert a new record into the BTree.  The key is given by (pKey,nKey)
+** and the data is given by (pData,nData).  The cursor is used only to
+** define what table the record should be inserted into.  The cursor
+** is left pointing at a random location.
+**
+** For an INTKEY table, only the nKey value of the key is used.  pKey is
+** ignored.  For a ZERODATA table, the pData and nData are both ignored.
+**
+** If the seekResult parameter is non-zero, then a successful call to
+** MovetoUnpacked() to seek cursor pCur to (pKey, nKey) has already
+** been performed. seekResult is the search result returned (a negative
+** number if pCur points at an entry that is smaller than (pKey, nKey), or
+** a positive value if pCur points at an etry that is larger than 
+** (pKey, nKey)). 
+**
+** If the seekResult parameter is non-zero, then the caller guarantees that
+** cursor pCur is pointing at the existing copy of a row that is to be
+** overwritten.  If the seekResult parameter is 0, then cursor pCur may
+** point to any entry or to no entry at all and so this function has to seek
+** the cursor before the new key can be inserted.
+*/
+int sqlite3BtreeInsert(
+  BtCursor *pCur,                /* Insert data into the table of this cursor */
+  const void *pKey, i64 nKey,    /* The key of the new record */
+  const void *pData, int nData,  /* The data of the new record */
+  int nZero,                     /* Number of extra 0 bytes to append to data */
+  int appendBias,                /* True if this is likely an append */
+  int seekResult                 /* Result of prior MovetoUnpacked() call */
+){
+  int rc;
+  int loc = seekResult;          /* -1: before desired location  +1: after */
+  int szNew = 0;
+  int idx;
+  MemPage *pPage;
+  Btree *p = pCur->pBtree;
+  BtShared *pBt = p->pBt;
+  unsigned char *oldCell;
+  unsigned char *newCell = 0;
+
+  if( pCur->eState==CURSOR_FAULT ){
+    assert( pCur->skipNext!=SQLITE_OK );
+    return pCur->skipNext;
+  }
+
+  assert( cursorHoldsMutex(pCur) );
+  assert( pCur->wrFlag && pBt->inTransaction==TRANS_WRITE && !pBt->readOnly );
+  assert( hasSharedCacheTableLock(p, pCur->pgnoRoot, pCur->pKeyInfo!=0, 2) );
+
+  /* Assert that the caller has been consistent. If this cursor was opened
+  ** expecting an index b-tree, then the caller should be inserting blob
+  ** keys with no associated data. If the cursor was opened expecting an
+  ** intkey table, the caller should be inserting integer keys with a
+  ** blob of associated data.  */
+  assert( (pKey==0)==(pCur->pKeyInfo==0) );
+
+  /* If this is an insert into a table b-tree, invalidate any incrblob 
+  ** cursors open on the row being replaced (assuming this is a replace
+  ** operation - if it is not, the following is a no-op).  */
+  if( pCur->pKeyInfo==0 ){
+    invalidateIncrblobCursors(p, nKey, 0);
+  }
+
+  /* Save the positions of any other cursors open on this table.
+  **
+  ** In some cases, the call to btreeMoveto() below is a no-op. For
+  ** example, when inserting data into a table with auto-generated integer
+  ** keys, the VDBE layer invokes sqlite3BtreeLast() to figure out the 
+  ** integer key to use. It then calls this function to actually insert the 
+  ** data into the intkey B-Tree. In this case btreeMoveto() recognizes
+  ** that the cursor is already where it needs to be and returns without
+  ** doing any work. To avoid thwarting these optimizations, it is important
+  ** not to clear the cursor here.
+  */
+  rc = saveAllCursors(pBt, pCur->pgnoRoot, pCur);
+  if( rc ) return rc;
+  if( !loc ){
+    rc = btreeMoveto(pCur, pKey, nKey, appendBias, &loc);
+    if( rc ) return rc;
+  }
+  assert( pCur->eState==CURSOR_VALID || (pCur->eState==CURSOR_INVALID && loc) );
+
+  pPage = pCur->apPage[pCur->iPage];
+  assert( pPage->intKey || nKey>=0 );
+  assert( pPage->leaf || !pPage->intKey );
+
+  TRACE(("INSERT: table=%d nkey=%lld ndata=%d page=%d %s\n",
+          pCur->pgnoRoot, nKey, nData, pPage->pgno,
+          loc==0 ? "overwrite" : "new entry"));
+  assert( pPage->isInit );
+  allocateTempSpace(pBt);
+  newCell = pBt->pTmpSpace;
+  if( newCell==0 ) return SQLITE_NOMEM;
+  rc = fillInCell(pPage, newCell, pKey, nKey, pData, nData, nZero, &szNew);
+  if( rc ) goto end_insert;
+  assert( szNew==cellSizePtr(pPage, newCell) );
+  assert( szNew <= MX_CELL_SIZE(pBt) );
+  idx = pCur->aiIdx[pCur->iPage];
+  if( loc==0 ){
+    u16 szOld;
+    assert( idx<pPage->nCell );
+    rc = sqlite3PagerWrite(pPage->pDbPage);
+    if( rc ){
+      goto end_insert;
+    }
+    oldCell = findCell(pPage, idx);
+    if( !pPage->leaf ){
+      memcpy(newCell, oldCell, 4);
+    }
+    szOld = cellSizePtr(pPage, oldCell);
+    rc = clearCell(pPage, oldCell);
+    dropCell(pPage, idx, szOld, &rc);
+    if( rc ) goto end_insert;
+  }else if( loc<0 && pPage->nCell>0 ){
+    assert( pPage->leaf );
+    idx = ++pCur->aiIdx[pCur->iPage];
+  }else{
+    assert( pPage->leaf );
+  }
+  insertCell(pPage, idx, newCell, szNew, 0, 0, &rc);
+  assert( rc!=SQLITE_OK || pPage->nCell>0 || pPage->nOverflow>0 );
+
+  /* If no error has occured and pPage has an overflow cell, call balance() 
+  ** to redistribute the cells within the tree. Since balance() may move
+  ** the cursor, zero the BtCursor.info.nSize and BtCursor.validNKey
+  ** variables.
+  **
+  ** Previous versions of SQLite called moveToRoot() to move the cursor
+  ** back to the root page as balance() used to invalidate the contents
+  ** of BtCursor.apPage[] and BtCursor.aiIdx[]. Instead of doing that,
+  ** set the cursor state to "invalid". This makes common insert operations
+  ** slightly faster.
+  **
+  ** There is a subtle but important optimization here too. When inserting
+  ** multiple records into an intkey b-tree using a single cursor (as can
+  ** happen while processing an "INSERT INTO ... SELECT" statement), it
+  ** is advantageous to leave the cursor pointing to the last entry in
+  ** the b-tree if possible. If the cursor is left pointing to the last
+  ** entry in the table, and the next row inserted has an integer key
+  ** larger than the largest existing key, it is possible to insert the
+  ** row without seeking the cursor. This can be a big performance boost.
+  */
+  pCur->info.nSize = 0;
+  pCur->validNKey = 0;
+  if( rc==SQLITE_OK && pPage->nOverflow ){
+    rc = balance(pCur);
+
+    /* Must make sure nOverflow is reset to zero even if the balance()
+    ** fails. Internal data structure corruption will result otherwise. 
+    ** Also, set the cursor state to invalid. This stops saveCursorPosition()
+    ** from trying to save the current position of the cursor.  */
+    pCur->apPage[pCur->iPage]->nOverflow = 0;
+    pCur->eState = CURSOR_INVALID;
+  }
+  assert( pCur->apPage[pCur->iPage]->nOverflow==0 );
+
+end_insert:
+  return rc;
+}
+
+/*
+** Delete the entry that the cursor is pointing to.  The cursor
+** is left pointing at a arbitrary location.
+*/
+int sqlite3BtreeDelete(BtCursor *pCur){
+  Btree *p = pCur->pBtree;
+  BtShared *pBt = p->pBt;              
+  int rc;                              /* Return code */
+  MemPage *pPage;                      /* Page to delete cell from */
+  unsigned char *pCell;                /* Pointer to cell to delete */
+  int iCellIdx;                        /* Index of cell to delete */
+  int iCellDepth;                      /* Depth of node containing pCell */ 
+
+  assert( cursorHoldsMutex(pCur) );
+  assert( pBt->inTransaction==TRANS_WRITE );
+  assert( !pBt->readOnly );
+  assert( pCur->wrFlag );
+  assert( hasSharedCacheTableLock(p, pCur->pgnoRoot, pCur->pKeyInfo!=0, 2) );
+  assert( !hasReadConflicts(p, pCur->pgnoRoot) );
+
+  if( NEVER(pCur->aiIdx[pCur->iPage]>=pCur->apPage[pCur->iPage]->nCell) 
+   || NEVER(pCur->eState!=CURSOR_VALID)
+  ){
+    return SQLITE_ERROR;  /* Something has gone awry. */
+  }
+
+  /* If this is a delete operation to remove a row from a table b-tree,
+  ** invalidate any incrblob cursors open on the row being deleted.  */
+  if( pCur->pKeyInfo==0 ){
+    invalidateIncrblobCursors(p, pCur->info.nKey, 0);
+  }
+
+  iCellDepth = pCur->iPage;
+  iCellIdx = pCur->aiIdx[iCellDepth];
+  pPage = pCur->apPage[iCellDepth];
+  pCell = findCell(pPage, iCellIdx);
+
+  /* If the page containing the entry to delete is not a leaf page, move
+  ** the cursor to the largest entry in the tree that is smaller than
+  ** the entry being deleted. This cell will replace the cell being deleted
+  ** from the internal node. The 'previous' entry is used for this instead
+  ** of the 'next' entry, as the previous entry is always a part of the
+  ** sub-tree headed by the child page of the cell being deleted. This makes
+  ** balancing the tree following the delete operation easier.  */
+  if( !pPage->leaf ){
+    int notUsed;
+    rc = sqlite3BtreePrevious(pCur, &notUsed);
+    if( rc ) return rc;
+  }
+
+  /* Save the positions of any other cursors open on this table before
+  ** making any modifications. Make the page containing the entry to be 
+  ** deleted writable. Then free any overflow pages associated with the 
+  ** entry and finally remove the cell itself from within the page.  
+  */
+  rc = saveAllCursors(pBt, pCur->pgnoRoot, pCur);
+  if( rc ) return rc;
+  rc = sqlite3PagerWrite(pPage->pDbPage);
+  if( rc ) return rc;
+  rc = clearCell(pPage, pCell);
+  dropCell(pPage, iCellIdx, cellSizePtr(pPage, pCell), &rc);
+  if( rc ) return rc;
+
+  /* If the cell deleted was not located on a leaf page, then the cursor
+  ** is currently pointing to the largest entry in the sub-tree headed
+  ** by the child-page of the cell that was just deleted from an internal
+  ** node. The cell from the leaf node needs to be moved to the internal
+  ** node to replace the deleted cell.  */
+  if( !pPage->leaf ){
+    MemPage *pLeaf = pCur->apPage[pCur->iPage];
+    int nCell;
+    Pgno n = pCur->apPage[iCellDepth+1]->pgno;
+    unsigned char *pTmp;
+
+    pCell = findCell(pLeaf, pLeaf->nCell-1);
+    nCell = cellSizePtr(pLeaf, pCell);
+    assert( MX_CELL_SIZE(pBt) >= nCell );
+
+    allocateTempSpace(pBt);
+    pTmp = pBt->pTmpSpace;
+
+    rc = sqlite3PagerWrite(pLeaf->pDbPage);
+    insertCell(pPage, iCellIdx, pCell-4, nCell+4, pTmp, n, &rc);
+    dropCell(pLeaf, pLeaf->nCell-1, nCell, &rc);
+    if( rc ) return rc;
+  }
+
+  /* Balance the tree. If the entry deleted was located on a leaf page,
+  ** then the cursor still points to that page. In this case the first
+  ** call to balance() repairs the tree, and the if(...) condition is
+  ** never true.
+  **
+  ** Otherwise, if the entry deleted was on an internal node page, then
+  ** pCur is pointing to the leaf page from which a cell was removed to
+  ** replace the cell deleted from the internal node. This is slightly
+  ** tricky as the leaf node may be underfull, and the internal node may
+  ** be either under or overfull. In this case run the balancing algorithm
+  ** on the leaf node first. If the balance proceeds far enough up the
+  ** tree that we can be sure that any problem in the internal node has
+  ** been corrected, so be it. Otherwise, after balancing the leaf node,
+  ** walk the cursor up the tree to the internal node and balance it as 
+  ** well.  */
+  rc = balance(pCur);
+  if( rc==SQLITE_OK && pCur->iPage>iCellDepth ){
+    while( pCur->iPage>iCellDepth ){
+      releasePage(pCur->apPage[pCur->iPage--]);
+    }
+    rc = balance(pCur);
+  }
+
+  if( rc==SQLITE_OK ){
+    moveToRoot(pCur);
+  }
+  return rc;
+}
+
+/*
+** Create a new BTree table.  Write into *piTable the page
+** number for the root page of the new table.
+**
+** The type of type is determined by the flags parameter.  Only the
+** following values of flags are currently in use.  Other values for
+** flags might not work:
+**
+**     BTREE_INTKEY|BTREE_LEAFDATA     Used for SQL tables with rowid keys
+**     BTREE_ZERODATA                  Used for SQL indices
+*/
+static int btreeCreateTable(Btree *p, int *piTable, int createTabFlags){
+  BtShared *pBt = p->pBt;
+  MemPage *pRoot;
+  Pgno pgnoRoot;
+  int rc;
+  int ptfFlags;          /* Page-type flage for the root page of new table */
+
+  assert( sqlite3BtreeHoldsMutex(p) );
+  assert( pBt->inTransaction==TRANS_WRITE );
+  assert( !pBt->readOnly );
+
+#ifdef SQLITE_OMIT_AUTOVACUUM
+  rc = allocateBtreePage(pBt, &pRoot, &pgnoRoot, 1, 0);
+  if( rc ){
+    return rc;
+  }
+#else
+  if( pBt->autoVacuum ){
+    Pgno pgnoMove;      /* Move a page here to make room for the root-page */
+    MemPage *pPageMove; /* The page to move to. */
+
+    /* Creating a new table may probably require moving an existing database
+    ** to make room for the new tables root page. In case this page turns
+    ** out to be an overflow page, delete all overflow page-map caches
+    ** held by open cursors.
+    */
+    invalidateAllOverflowCache(pBt);
+
+    /* Read the value of meta[3] from the database to determine where the
+    ** root page of the new table should go. meta[3] is the largest root-page
+    ** created so far, so the new root-page is (meta[3]+1).
+    */
+    sqlite3BtreeGetMeta(p, BTREE_LARGEST_ROOT_PAGE, &pgnoRoot);
+    pgnoRoot++;
+
+    /* The new root-page may not be allocated on a pointer-map page, or the
+    ** PENDING_BYTE page.
+    */
+    while( pgnoRoot==PTRMAP_PAGENO(pBt, pgnoRoot) ||
+        pgnoRoot==PENDING_BYTE_PAGE(pBt) ){
+      pgnoRoot++;
+    }
+    assert( pgnoRoot>=3 );
+
+    /* Allocate a page. The page that currently resides at pgnoRoot will
+    ** be moved to the allocated page (unless the allocated page happens
+    ** to reside at pgnoRoot).
+    */
+    rc = allocateBtreePage(pBt, &pPageMove, &pgnoMove, pgnoRoot, 1);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+
+    if( pgnoMove!=pgnoRoot ){
+      /* pgnoRoot is the page that will be used for the root-page of
+      ** the new table (assuming an error did not occur). But we were
+      ** allocated pgnoMove. If required (i.e. if it was not allocated
+      ** by extending the file), the current page at position pgnoMove
+      ** is already journaled.
+      */
+      u8 eType = 0;
+      Pgno iPtrPage = 0;
+
+      releasePage(pPageMove);
+
+      /* Move the page currently at pgnoRoot to pgnoMove. */
+      rc = btreeGetPage(pBt, pgnoRoot, &pRoot, 0);
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+      rc = ptrmapGet(pBt, pgnoRoot, &eType, &iPtrPage);
+      if( eType==PTRMAP_ROOTPAGE || eType==PTRMAP_FREEPAGE ){
+        rc = SQLITE_CORRUPT_BKPT;
+      }
+      if( rc!=SQLITE_OK ){
+        releasePage(pRoot);
+        return rc;
+      }
+      assert( eType!=PTRMAP_ROOTPAGE );
+      assert( eType!=PTRMAP_FREEPAGE );
+      rc = relocatePage(pBt, pRoot, eType, iPtrPage, pgnoMove, 0);
+      releasePage(pRoot);
+
+      /* Obtain the page at pgnoRoot */
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+      rc = btreeGetPage(pBt, pgnoRoot, &pRoot, 0);
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+      rc = sqlite3PagerWrite(pRoot->pDbPage);
+      if( rc!=SQLITE_OK ){
+        releasePage(pRoot);
+        return rc;
+      }
+    }else{
+      pRoot = pPageMove;
+    } 
+
+    /* Update the pointer-map and meta-data with the new root-page number. */
+    ptrmapPut(pBt, pgnoRoot, PTRMAP_ROOTPAGE, 0, &rc);
+    if( rc ){
+      releasePage(pRoot);
+      return rc;
+    }
+
+    /* When the new root page was allocated, page 1 was made writable in
+    ** order either to increase the database filesize, or to decrement the
+    ** freelist count.  Hence, the sqlite3BtreeUpdateMeta() call cannot fail.
+    */
+    assert( sqlite3PagerIswriteable(pBt->pPage1->pDbPage) );
+    rc = sqlite3BtreeUpdateMeta(p, 4, pgnoRoot);
+    if( NEVER(rc) ){
+      releasePage(pRoot);
+      return rc;
+    }
+
+  }else{
+    rc = allocateBtreePage(pBt, &pRoot, &pgnoRoot, 1, 0);
+    if( rc ) return rc;
+  }
+#endif
+  assert( sqlite3PagerIswriteable(pRoot->pDbPage) );
+  if( createTabFlags & BTREE_INTKEY ){
+    ptfFlags = PTF_INTKEY | PTF_LEAFDATA | PTF_LEAF;
+  }else{
+    ptfFlags = PTF_ZERODATA | PTF_LEAF;
+  }
+  zeroPage(pRoot, ptfFlags);
+  sqlite3PagerUnref(pRoot->pDbPage);
+  assert( (pBt->openFlags & BTREE_SINGLE)==0 || pgnoRoot==2 );
+  *piTable = (int)pgnoRoot;
+  return SQLITE_OK;
+}
+int sqlite3BtreeCreateTable(Btree *p, int *piTable, int flags){
+  int rc;
+  sqlite3BtreeEnter(p);
+  rc = btreeCreateTable(p, piTable, flags);
+  sqlite3BtreeLeave(p);
+  return rc;
+}
+
+/*
+** Erase the given database page and all its children.  Return
+** the page to the freelist.
+*/
+static int clearDatabasePage(
+  BtShared *pBt,           /* The BTree that contains the table */
+  Pgno pgno,               /* Page number to clear */
+  int freePageFlag,        /* Deallocate page if true */
+  int *pnChange            /* Add number of Cells freed to this counter */
+){
+  MemPage *pPage;
+  int rc;
+  unsigned char *pCell;
+  int i;
+
+  assert( sqlite3_mutex_held(pBt->mutex) );
+  if( pgno>btreePagecount(pBt) ){
+    return SQLITE_CORRUPT_BKPT;
+  }
+
+  rc = getAndInitPage(pBt, pgno, &pPage);
+  if( rc ) return rc;
+  for(i=0; i<pPage->nCell; i++){
+    pCell = findCell(pPage, i);
+    if( !pPage->leaf ){
+      rc = clearDatabasePage(pBt, get4byte(pCell), 1, pnChange);
+      if( rc ) goto cleardatabasepage_out;
+    }
+    rc = clearCell(pPage, pCell);
+    if( rc ) goto cleardatabasepage_out;
+  }
+  if( !pPage->leaf ){
+    rc = clearDatabasePage(pBt, get4byte(&pPage->aData[8]), 1, pnChange);
+    if( rc ) goto cleardatabasepage_out;
+  }else if( pnChange ){
+    assert( pPage->intKey );
+    *pnChange += pPage->nCell;
+  }
+  if( freePageFlag ){
+    freePage(pPage, &rc);
+  }else if( (rc = sqlite3PagerWrite(pPage->pDbPage))==0 ){
+    zeroPage(pPage, pPage->aData[0] | PTF_LEAF);
+  }
+
+cleardatabasepage_out:
+  releasePage(pPage);
+  return rc;
+}
+
+/*
+** Delete all information from a single table in the database.  iTable is
+** the page number of the root of the table.  After this routine returns,
+** the root page is empty, but still exists.
+**
+** This routine will fail with SQLITE_LOCKED if there are any open
+** read cursors on the table.  Open write cursors are moved to the
+** root of the table.
+**
+** If pnChange is not NULL, then table iTable must be an intkey table. The
+** integer value pointed to by pnChange is incremented by the number of
+** entries in the table.
+*/
+int sqlite3BtreeClearTable(Btree *p, int iTable, int *pnChange){
+  int rc;
+  BtShared *pBt = p->pBt;
+  sqlite3BtreeEnter(p);
+  assert( p->inTrans==TRANS_WRITE );
+
+  /* Invalidate all incrblob cursors open on table iTable (assuming iTable
+  ** is the root of a table b-tree - if it is not, the following call is
+  ** a no-op).  */
+  invalidateIncrblobCursors(p, 0, 1);
+
+  rc = saveAllCursors(pBt, (Pgno)iTable, 0);
+  if( SQLITE_OK==rc ){
+    rc = clearDatabasePage(pBt, (Pgno)iTable, 0, pnChange);
+  }
+  sqlite3BtreeLeave(p);
+  return rc;
+}
+
+/*
+** Erase all information in a table and add the root of the table to
+** the freelist.  Except, the root of the principle table (the one on
+** page 1) is never added to the freelist.
+**
+** This routine will fail with SQLITE_LOCKED if there are any open
+** cursors on the table.
+**
+** If AUTOVACUUM is enabled and the page at iTable is not the last
+** root page in the database file, then the last root page 
+** in the database file is moved into the slot formerly occupied by
+** iTable and that last slot formerly occupied by the last root page
+** is added to the freelist instead of iTable.  In this say, all
+** root pages are kept at the beginning of the database file, which
+** is necessary for AUTOVACUUM to work right.  *piMoved is set to the 
+** page number that used to be the last root page in the file before
+** the move.  If no page gets moved, *piMoved is set to 0.
+** The last root page is recorded in meta[3] and the value of
+** meta[3] is updated by this procedure.
+*/
+static int btreeDropTable(Btree *p, Pgno iTable, int *piMoved){
+  int rc;
+  MemPage *pPage = 0;
+  BtShared *pBt = p->pBt;
+
+  assert( sqlite3BtreeHoldsMutex(p) );
+  assert( p->inTrans==TRANS_WRITE );
+
+  /* It is illegal to drop a table if any cursors are open on the
+  ** database. This is because in auto-vacuum mode the backend may
+  ** need to move another root-page to fill a gap left by the deleted
+  ** root page. If an open cursor was using this page a problem would 
+  ** occur.
+  **
+  ** This error is caught long before control reaches this point.
+  */
+  if( NEVER(pBt->pCursor) ){
+    sqlite3ConnectionBlocked(p->db, pBt->pCursor->pBtree->db);
+    return SQLITE_LOCKED_SHAREDCACHE;
+  }
+
+  rc = btreeGetPage(pBt, (Pgno)iTable, &pPage, 0);
+  if( rc ) return rc;
+  rc = sqlite3BtreeClearTable(p, iTable, 0);
+  if( rc ){
+    releasePage(pPage);
+    return rc;
+  }
+
+  *piMoved = 0;
+
+  if( iTable>1 ){
+#ifdef SQLITE_OMIT_AUTOVACUUM
+    freePage(pPage, &rc);
+    releasePage(pPage);
+#else
+    if( pBt->autoVacuum ){
+      Pgno maxRootPgno;
+      sqlite3BtreeGetMeta(p, BTREE_LARGEST_ROOT_PAGE, &maxRootPgno);
+
+      if( iTable==maxRootPgno ){
+        /* If the table being dropped is the table with the largest root-page
+        ** number in the database, put the root page on the free list. 
+        */
+        freePage(pPage, &rc);
+        releasePage(pPage);
+        if( rc!=SQLITE_OK ){
+          return rc;
+        }
+      }else{
+        /* The table being dropped does not have the largest root-page
+        ** number in the database. So move the page that does into the 
+        ** gap left by the deleted root-page.
+        */
+        MemPage *pMove;
+        releasePage(pPage);
+        rc = btreeGetPage(pBt, maxRootPgno, &pMove, 0);
+        if( rc!=SQLITE_OK ){
+          return rc;
+        }
+        rc = relocatePage(pBt, pMove, PTRMAP_ROOTPAGE, 0, iTable, 0);
+        releasePage(pMove);
+        if( rc!=SQLITE_OK ){
+          return rc;
+        }
+        pMove = 0;
+        rc = btreeGetPage(pBt, maxRootPgno, &pMove, 0);
+        freePage(pMove, &rc);
+        releasePage(pMove);
+        if( rc!=SQLITE_OK ){
+          return rc;
+        }
+        *piMoved = maxRootPgno;
+      }
+
+      /* Set the new 'max-root-page' value in the database header. This
+      ** is the old value less one, less one more if that happens to
+      ** be a root-page number, less one again if that is the
+      ** PENDING_BYTE_PAGE.
+      */
+      maxRootPgno--;
+      while( maxRootPgno==PENDING_BYTE_PAGE(pBt)
+             || PTRMAP_ISPAGE(pBt, maxRootPgno) ){
+        maxRootPgno--;
+      }
+      assert( maxRootPgno!=PENDING_BYTE_PAGE(pBt) );
+
+      rc = sqlite3BtreeUpdateMeta(p, 4, maxRootPgno);
+    }else{
+      freePage(pPage, &rc);
+      releasePage(pPage);
+    }
+#endif
+  }else{
+    /* If sqlite3BtreeDropTable was called on page 1.
+    ** This really never should happen except in a corrupt
+    ** database. 
+    */
+    zeroPage(pPage, PTF_INTKEY|PTF_LEAF );
+    releasePage(pPage);
+  }
+  return rc;  
+}
+int sqlite3BtreeDropTable(Btree *p, int iTable, int *piMoved){
+  int rc;
+  sqlite3BtreeEnter(p);
+  rc = btreeDropTable(p, iTable, piMoved);
+  sqlite3BtreeLeave(p);
+  return rc;
+}
+
+
+/*
+** This function may only be called if the b-tree connection already
+** has a read or write transaction open on the database.
+**
+** Read the meta-information out of a database file.  Meta[0]
+** is the number of free pages currently in the database.  Meta[1]
+** through meta[15] are available for use by higher layers.  Meta[0]
+** is read-only, the others are read/write.
+** 
+** The schema layer numbers meta values differently.  At the schema
+** layer (and the SetCookie and ReadCookie opcodes) the number of
+** free pages is not visible.  So Cookie[0] is the same as Meta[1].
+*/
+void sqlite3BtreeGetMeta(Btree *p, int idx, u32 *pMeta){
+  BtShared *pBt = p->pBt;
+
+  sqlite3BtreeEnter(p);
+  assert( p->inTrans>TRANS_NONE );
+  assert( SQLITE_OK==querySharedCacheTableLock(p, MASTER_ROOT, READ_LOCK) );
+  assert( pBt->pPage1 );
+  assert( idx>=0 && idx<=15 );
+
+  *pMeta = get4byte(&pBt->pPage1->aData[36 + idx*4]);
+
+  /* If auto-vacuum is disabled in this build and this is an auto-vacuum
+  ** database, mark the database as read-only.  */
+#ifdef SQLITE_OMIT_AUTOVACUUM
+  if( idx==BTREE_LARGEST_ROOT_PAGE && *pMeta>0 ) pBt->readOnly = 1;
+#endif
+
+  sqlite3BtreeLeave(p);
+}
+
+/*
+** Write meta-information back into the database.  Meta[0] is
+** read-only and may not be written.
+*/
+int sqlite3BtreeUpdateMeta(Btree *p, int idx, u32 iMeta){
+  BtShared *pBt = p->pBt;
+  unsigned char *pP1;
+  int rc;
+  assert( idx>=1 && idx<=15 );
+  sqlite3BtreeEnter(p);
+  assert( p->inTrans==TRANS_WRITE );
+  assert( pBt->pPage1!=0 );
+  pP1 = pBt->pPage1->aData;
+  rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
+  if( rc==SQLITE_OK ){
+    put4byte(&pP1[36 + idx*4], iMeta);
+#ifndef SQLITE_OMIT_AUTOVACUUM
+    if( idx==BTREE_INCR_VACUUM ){
+      assert( pBt->autoVacuum || iMeta==0 );
+      assert( iMeta==0 || iMeta==1 );
+      pBt->incrVacuum = (u8)iMeta;
+    }
+#endif
+  }
+  sqlite3BtreeLeave(p);
+  return rc;
+}
+
+#ifndef SQLITE_OMIT_BTREECOUNT
+/*
+** The first argument, pCur, is a cursor opened on some b-tree. Count the
+** number of entries in the b-tree and write the result to *pnEntry.
+**
+** SQLITE_OK is returned if the operation is successfully executed. 
+** Otherwise, if an error is encountered (i.e. an IO error or database
+** corruption) an SQLite error code is returned.
+*/
+int sqlite3BtreeCount(BtCursor *pCur, i64 *pnEntry){
+  i64 nEntry = 0;                      /* Value to return in *pnEntry */
+  int rc;                              /* Return code */
+
+  if( pCur->pgnoRoot==0 ){
+    *pnEntry = 0;
+    return SQLITE_OK;
+  }
+  rc = moveToRoot(pCur);
+
+  /* Unless an error occurs, the following loop runs one iteration for each
+  ** page in the B-Tree structure (not including overflow pages). 
+  */
+  while( rc==SQLITE_OK ){
+    int iIdx;                          /* Index of child node in parent */
+    MemPage *pPage;                    /* Current page of the b-tree */
+
+    /* If this is a leaf page or the tree is not an int-key tree, then 
+    ** this page contains countable entries. Increment the entry counter
+    ** accordingly.
+    */
+    pPage = pCur->apPage[pCur->iPage];
+    if( pPage->leaf || !pPage->intKey ){
+      nEntry += pPage->nCell;
+    }
+
+    /* pPage is a leaf node. This loop navigates the cursor so that it 
+    ** points to the first interior cell that it points to the parent of
+    ** the next page in the tree that has not yet been visited. The
+    ** pCur->aiIdx[pCur->iPage] value is set to the index of the parent cell
+    ** of the page, or to the number of cells in the page if the next page
+    ** to visit is the right-child of its parent.
+    **
+    ** If all pages in the tree have been visited, return SQLITE_OK to the
+    ** caller.
+    */
+    if( pPage->leaf ){
+      do {
+        if( pCur->iPage==0 ){
+          /* All pages of the b-tree have been visited. Return successfully. */
+          *pnEntry = nEntry;
+          return SQLITE_OK;
+        }
+        moveToParent(pCur);
+      }while ( pCur->aiIdx[pCur->iPage]>=pCur->apPage[pCur->iPage]->nCell );
+
+      pCur->aiIdx[pCur->iPage]++;
+      pPage = pCur->apPage[pCur->iPage];
+    }
+
+    /* Descend to the child node of the cell that the cursor currently 
+    ** points at. This is the right-child if (iIdx==pPage->nCell).
+    */
+    iIdx = pCur->aiIdx[pCur->iPage];
+    if( iIdx==pPage->nCell ){
+      rc = moveToChild(pCur, get4byte(&pPage->aData[pPage->hdrOffset+8]));
+    }else{
+      rc = moveToChild(pCur, get4byte(findCell(pPage, iIdx)));
+    }
+  }
+
+  /* An error has occurred. Return an error code. */
+  return rc;
+}
+#endif
+
+/*
+** Return the pager associated with a BTree.  This routine is used for
+** testing and debugging only.
+*/
+Pager *sqlite3BtreePager(Btree *p){
+  return p->pBt->pPager;
+}
+
+#ifndef SQLITE_OMIT_INTEGRITY_CHECK
+/*
+** Append a message to the error message string.
+*/
+static void checkAppendMsg(
+  IntegrityCk *pCheck,
+  char *zMsg1,
+  const char *zFormat,
+  ...
+){
+  va_list ap;
+  if( !pCheck->mxErr ) return;
+  pCheck->mxErr--;
+  pCheck->nErr++;
+  va_start(ap, zFormat);
+  if( pCheck->errMsg.nChar ){
+    sqlite3StrAccumAppend(&pCheck->errMsg, "\n", 1);
+  }
+  if( zMsg1 ){
+    sqlite3StrAccumAppend(&pCheck->errMsg, zMsg1, -1);
+  }
+  sqlite3VXPrintf(&pCheck->errMsg, 1, zFormat, ap);
+  va_end(ap);
+  if( pCheck->errMsg.mallocFailed ){
+    pCheck->mallocFailed = 1;
+  }
+}
+#endif /* SQLITE_OMIT_INTEGRITY_CHECK */
+
+#ifndef SQLITE_OMIT_INTEGRITY_CHECK
+/*
+** Add 1 to the reference count for page iPage.  If this is the second
+** reference to the page, add an error message to pCheck->zErrMsg.
+** Return 1 if there are 2 ore more references to the page and 0 if
+** if this is the first reference to the page.
+**
+** Also check that the page number is in bounds.
+*/
+static int checkRef(IntegrityCk *pCheck, Pgno iPage, char *zContext){
+  if( iPage==0 ) return 1;
+  if( iPage>pCheck->nPage ){
+    checkAppendMsg(pCheck, zContext, "invalid page number %d", iPage);
+    return 1;
+  }
+  if( pCheck->anRef[iPage]==1 ){
+    checkAppendMsg(pCheck, zContext, "2nd reference to page %d", iPage);
+    return 1;
+  }
+  return  (pCheck->anRef[iPage]++)>1;
+}
+
+#ifndef SQLITE_OMIT_AUTOVACUUM
+/*
+** Check that the entry in the pointer-map for page iChild maps to 
+** page iParent, pointer type ptrType. If not, append an error message
+** to pCheck.
+*/
+static void checkPtrmap(
+  IntegrityCk *pCheck,   /* Integrity check context */
+  Pgno iChild,           /* Child page number */
+  u8 eType,              /* Expected pointer map type */
+  Pgno iParent,          /* Expected pointer map parent page number */
+  char *zContext         /* Context description (used for error msg) */
+){
+  int rc;
+  u8 ePtrmapType;
+  Pgno iPtrmapParent;
+
+  rc = ptrmapGet(pCheck->pBt, iChild, &ePtrmapType, &iPtrmapParent);
+  if( rc!=SQLITE_OK ){
+    if( rc==SQLITE_NOMEM || rc==SQLITE_IOERR_NOMEM ) pCheck->mallocFailed = 1;
+    checkAppendMsg(pCheck, zContext, "Failed to read ptrmap key=%d", iChild);
+    return;
+  }
+
+  if( ePtrmapType!=eType || iPtrmapParent!=iParent ){
+    checkAppendMsg(pCheck, zContext, 
+      "Bad ptr map entry key=%d expected=(%d,%d) got=(%d,%d)", 
+      iChild, eType, iParent, ePtrmapType, iPtrmapParent);
+  }
+}
+#endif
+
+/*
+** Check the integrity of the freelist or of an overflow page list.
+** Verify that the number of pages on the list is N.
+*/
+static void checkList(
+  IntegrityCk *pCheck,  /* Integrity checking context */
+  int isFreeList,       /* True for a freelist.  False for overflow page list */
+  int iPage,            /* Page number for first page in the list */
+  int N,                /* Expected number of pages in the list */
+  char *zContext        /* Context for error messages */
+){
+  int i;
+  int expected = N;
+  int iFirst = iPage;
+  while( N-- > 0 && pCheck->mxErr ){
+    DbPage *pOvflPage;
+    unsigned char *pOvflData;
+    if( iPage<1 ){
+      checkAppendMsg(pCheck, zContext,
+         "%d of %d pages missing from overflow list starting at %d",
+          N+1, expected, iFirst);
+      break;
+    }
+    if( checkRef(pCheck, iPage, zContext) ) break;
+    if( sqlite3PagerGet(pCheck->pPager, (Pgno)iPage, &pOvflPage) ){
+      checkAppendMsg(pCheck, zContext, "failed to get page %d", iPage);
+      break;
+    }
+    pOvflData = (unsigned char *)sqlite3PagerGetData(pOvflPage);
+    if( isFreeList ){
+      int n = get4byte(&pOvflData[4]);
+#ifndef SQLITE_OMIT_AUTOVACUUM
+      if( pCheck->pBt->autoVacuum ){
+        checkPtrmap(pCheck, iPage, PTRMAP_FREEPAGE, 0, zContext);
+      }
+#endif
+      if( n>(int)pCheck->pBt->usableSize/4-2 ){
+        checkAppendMsg(pCheck, zContext,
+           "freelist leaf count too big on page %d", iPage);
+        N--;
+      }else{
+        for(i=0; i<n; i++){
+          Pgno iFreePage = get4byte(&pOvflData[8+i*4]);
+#ifndef SQLITE_OMIT_AUTOVACUUM
+          if( pCheck->pBt->autoVacuum ){
+            checkPtrmap(pCheck, iFreePage, PTRMAP_FREEPAGE, 0, zContext);
+          }
+#endif
+          checkRef(pCheck, iFreePage, zContext);
+        }
+        N -= n;
+      }
+    }
+#ifndef SQLITE_OMIT_AUTOVACUUM
+    else{
+      /* If this database supports auto-vacuum and iPage is not the last
+      ** page in this overflow list, check that the pointer-map entry for
+      ** the following page matches iPage.
+      */
+      if( pCheck->pBt->autoVacuum && N>0 ){
+        i = get4byte(pOvflData);
+        checkPtrmap(pCheck, i, PTRMAP_OVERFLOW2, iPage, zContext);
+      }
+    }
+#endif
+    iPage = get4byte(pOvflData);
+    sqlite3PagerUnref(pOvflPage);
+  }
+}
+#endif /* SQLITE_OMIT_INTEGRITY_CHECK */
+
+#ifndef SQLITE_OMIT_INTEGRITY_CHECK
+/*
+** Do various sanity checks on a single page of a tree.  Return
+** the tree depth.  Root pages return 0.  Parents of root pages
+** return 1, and so forth.
+** 
+** These checks are done:
+**
+**      1.  Make sure that cells and freeblocks do not overlap
+**          but combine to completely cover the page.
+**  NO  2.  Make sure cell keys are in order.
+**  NO  3.  Make sure no key is less than or equal to zLowerBound.
+**  NO  4.  Make sure no key is greater than or equal to zUpperBound.
+**      5.  Check the integrity of overflow pages.
+**      6.  Recursively call checkTreePage on all children.
+**      7.  Verify that the depth of all children is the same.
+**      8.  Make sure this page is at least 33% full or else it is
+**          the root of the tree.
+*/
+static int checkTreePage(
+  IntegrityCk *pCheck,  /* Context for the sanity check */
+  int iPage,            /* Page number of the page to check */
+  char *zParentContext, /* Parent context */
+  i64 *pnParentMinKey, 
+  i64 *pnParentMaxKey
+){
+  MemPage *pPage;
+  int i, rc, depth, d2, pgno, cnt;
+  int hdr, cellStart;
+  int nCell;
+  u8 *data;
+  BtShared *pBt;
+  int usableSize;
+  char zContext[100];
+  char *hit = 0;
+  i64 nMinKey = 0;
+  i64 nMaxKey = 0;
+
+  sqlite3_snprintf(sizeof(zContext), zContext, "Page %d: ", iPage);
+
+  /* Check that the page exists
+  */
+  pBt = pCheck->pBt;
+  usableSize = pBt->usableSize;
+  if( iPage==0 ) return 0;
+  if( checkRef(pCheck, iPage, zParentContext) ) return 0;
+  if( (rc = btreeGetPage(pBt, (Pgno)iPage, &pPage, 0))!=0 ){
+    checkAppendMsg(pCheck, zContext,
+       "unable to get the page. error code=%d", rc);
+    return 0;
+  }
+
+  /* Clear MemPage.isInit to make sure the corruption detection code in
+  ** btreeInitPage() is executed.  */
+  pPage->isInit = 0;
+  if( (rc = btreeInitPage(pPage))!=0 ){
+    assert( rc==SQLITE_CORRUPT );  /* The only possible error from InitPage */
+    checkAppendMsg(pCheck, zContext, 
+                   "btreeInitPage() returns error code %d", rc);
+    releasePage(pPage);
+    return 0;
+  }
+
+  /* Check out all the cells.
+  */
+  depth = 0;
+  for(i=0; i<pPage->nCell && pCheck->mxErr; i++){
+    u8 *pCell;
+    u32 sz;
+    CellInfo info;
+
+    /* Check payload overflow pages
+    */
+    sqlite3_snprintf(sizeof(zContext), zContext,
+             "On tree page %d cell %d: ", iPage, i);
+    pCell = findCell(pPage,i);
+    btreeParseCellPtr(pPage, pCell, &info);
+    sz = info.nData;
+    if( !pPage->intKey ) sz += (int)info.nKey;
+    /* For intKey pages, check that the keys are in order.
+    */
+    else if( i==0 ) nMinKey = nMaxKey = info.nKey;
+    else{
+      if( info.nKey <= nMaxKey ){
+        checkAppendMsg(pCheck, zContext, 
+            "Rowid %lld out of order (previous was %lld)", info.nKey, nMaxKey);
+      }
+      nMaxKey = info.nKey;
+    }
+    assert( sz==info.nPayload );
+    if( (sz>info.nLocal) 
+     && (&pCell[info.iOverflow]<=&pPage->aData[pBt->usableSize])
+    ){
+      int nPage = (sz - info.nLocal + usableSize - 5)/(usableSize - 4);
+      Pgno pgnoOvfl = get4byte(&pCell[info.iOverflow]);
+#ifndef SQLITE_OMIT_AUTOVACUUM
+      if( pBt->autoVacuum ){
+        checkPtrmap(pCheck, pgnoOvfl, PTRMAP_OVERFLOW1, iPage, zContext);
+      }
+#endif
+      checkList(pCheck, 0, pgnoOvfl, nPage, zContext);
+    }
+
+    /* Check sanity of left child page.
+    */
+    if( !pPage->leaf ){
+      pgno = get4byte(pCell);
+#ifndef SQLITE_OMIT_AUTOVACUUM
+      if( pBt->autoVacuum ){
+        checkPtrmap(pCheck, pgno, PTRMAP_BTREE, iPage, zContext);
+      }
+#endif
+      d2 = checkTreePage(pCheck, pgno, zContext, &nMinKey, i==0 ? NULL : &nMaxKey);
+      if( i>0 && d2!=depth ){
+        checkAppendMsg(pCheck, zContext, "Child page depth differs");
+      }
+      depth = d2;
+    }
+  }
+
+  if( !pPage->leaf ){
+    pgno = get4byte(&pPage->aData[pPage->hdrOffset+8]);
+    sqlite3_snprintf(sizeof(zContext), zContext, 
+                     "On page %d at right child: ", iPage);
+#ifndef SQLITE_OMIT_AUTOVACUUM
+    if( pBt->autoVacuum ){
+      checkPtrmap(pCheck, pgno, PTRMAP_BTREE, iPage, zContext);
+    }
+#endif
+    checkTreePage(pCheck, pgno, zContext, NULL, !pPage->nCell ? NULL : &nMaxKey);
+  }
+ 
+  /* For intKey leaf pages, check that the min/max keys are in order
+  ** with any left/parent/right pages.
+  */
+  if( pPage->leaf && pPage->intKey ){
+    /* if we are a left child page */
+    if( pnParentMinKey ){
+      /* if we are the left most child page */
+      if( !pnParentMaxKey ){
+        if( nMaxKey > *pnParentMinKey ){
+          checkAppendMsg(pCheck, zContext, 
+              "Rowid %lld out of order (max larger than parent min of %lld)",
+              nMaxKey, *pnParentMinKey);
+        }
+      }else{
+        if( nMinKey <= *pnParentMinKey ){
+          checkAppendMsg(pCheck, zContext, 
+              "Rowid %lld out of order (min less than parent min of %lld)",
+              nMinKey, *pnParentMinKey);
+        }
+        if( nMaxKey > *pnParentMaxKey ){
+          checkAppendMsg(pCheck, zContext, 
+              "Rowid %lld out of order (max larger than parent max of %lld)",
+              nMaxKey, *pnParentMaxKey);
+        }
+        *pnParentMinKey = nMaxKey;
+      }
+    /* else if we're a right child page */
+    } else if( pnParentMaxKey ){
+      if( nMinKey <= *pnParentMaxKey ){
+        checkAppendMsg(pCheck, zContext, 
+            "Rowid %lld out of order (min less than parent max of %lld)",
+            nMinKey, *pnParentMaxKey);
+      }
+    }
+  }
+
+  /* Check for complete coverage of the page
+  */
+  data = pPage->aData;
+  hdr = pPage->hdrOffset;
+  hit = sqlite3PageMalloc( pBt->pageSize );
+  if( hit==0 ){
+    pCheck->mallocFailed = 1;
+  }else{
+    int contentOffset = get2byteNotZero(&data[hdr+5]);
+    assert( contentOffset<=usableSize );  /* Enforced by btreeInitPage() */
+    memset(hit+contentOffset, 0, usableSize-contentOffset);
+    memset(hit, 1, contentOffset);
+    nCell = get2byte(&data[hdr+3]);
+    cellStart = hdr + 12 - 4*pPage->leaf;
+    for(i=0; i<nCell; i++){
+      int pc = get2byte(&data[cellStart+i*2]);
+      u32 size = 65536;
+      int j;
+      if( pc<=usableSize-4 ){
+        size = cellSizePtr(pPage, &data[pc]);
+      }
+      if( (int)(pc+size-1)>=usableSize ){
+        checkAppendMsg(pCheck, 0, 
+            "Corruption detected in cell %d on page %d",i,iPage);
+      }else{
+        for(j=pc+size-1; j>=pc; j--) hit[j]++;
+      }
+    }
+    i = get2byte(&data[hdr+1]);
+    while( i>0 ){
+      int size, j;
+      assert( i<=usableSize-4 );     /* Enforced by btreeInitPage() */
+      size = get2byte(&data[i+2]);
+      assert( i+size<=usableSize );  /* Enforced by btreeInitPage() */
+      for(j=i+size-1; j>=i; j--) hit[j]++;
+      j = get2byte(&data[i]);
+      assert( j==0 || j>i+size );  /* Enforced by btreeInitPage() */
+      assert( j<=usableSize-4 );   /* Enforced by btreeInitPage() */
+      i = j;
+    }
+    for(i=cnt=0; i<usableSize; i++){
+      if( hit[i]==0 ){
+        cnt++;
+      }else if( hit[i]>1 ){
+        checkAppendMsg(pCheck, 0,
+          "Multiple uses for byte %d of page %d", i, iPage);
+        break;
+      }
+    }
+    if( cnt!=data[hdr+7] ){
+      checkAppendMsg(pCheck, 0, 
+          "Fragmentation of %d bytes reported as %d on page %d",
+          cnt, data[hdr+7], iPage);
+    }
+  }
+  sqlite3PageFree(hit);
+  releasePage(pPage);
+  return depth+1;
+}
+#endif /* SQLITE_OMIT_INTEGRITY_CHECK */
+
+#ifndef SQLITE_OMIT_INTEGRITY_CHECK
+/*
+** This routine does a complete check of the given BTree file.  aRoot[] is
+** an array of pages numbers were each page number is the root page of
+** a table.  nRoot is the number of entries in aRoot.
+**
+** A read-only or read-write transaction must be opened before calling
+** this function.
+**
+** Write the number of error seen in *pnErr.  Except for some memory
+** allocation errors,  an error message held in memory obtained from
+** malloc is returned if *pnErr is non-zero.  If *pnErr==0 then NULL is
+** returned.  If a memory allocation error occurs, NULL is returned.
+*/
+char *sqlite3BtreeIntegrityCheck(
+  Btree *p,     /* The btree to be checked */
+  int *aRoot,   /* An array of root pages numbers for individual trees */
+  int nRoot,    /* Number of entries in aRoot[] */
+  int mxErr,    /* Stop reporting errors after this many */
+  int *pnErr    /* Write number of errors seen to this variable */
+){
+  Pgno i;
+  int nRef;
+  IntegrityCk sCheck;
+  BtShared *pBt = p->pBt;
+  char zErr[100];
+
+  sqlite3BtreeEnter(p);
+  assert( p->inTrans>TRANS_NONE && pBt->inTransaction>TRANS_NONE );
+  nRef = sqlite3PagerRefcount(pBt->pPager);
+  sCheck.pBt = pBt;
+  sCheck.pPager = pBt->pPager;
+  sCheck.nPage = btreePagecount(sCheck.pBt);
+  sCheck.mxErr = mxErr;
+  sCheck.nErr = 0;
+  sCheck.mallocFailed = 0;
+  *pnErr = 0;
+  if( sCheck.nPage==0 ){
+    sqlite3BtreeLeave(p);
+    return 0;
+  }
+  sCheck.anRef = sqlite3Malloc( (sCheck.nPage+1)*sizeof(sCheck.anRef[0]) );
+  if( !sCheck.anRef ){
+    *pnErr = 1;
+    sqlite3BtreeLeave(p);
+    return 0;
+  }
+  for(i=0; i<=sCheck.nPage; i++){ sCheck.anRef[i] = 0; }
+  i = PENDING_BYTE_PAGE(pBt);
+  if( i<=sCheck.nPage ){
+    sCheck.anRef[i] = 1;
+  }
+  sqlite3StrAccumInit(&sCheck.errMsg, zErr, sizeof(zErr), 20000);
+  sCheck.errMsg.useMalloc = 2;
+
+  /* Check the integrity of the freelist
+  */
+  checkList(&sCheck, 1, get4byte(&pBt->pPage1->aData[32]),
+            get4byte(&pBt->pPage1->aData[36]), "Main freelist: ");
+
+  /* Check all the tables.
+  */
+  for(i=0; (int)i<nRoot && sCheck.mxErr; i++){
+    if( aRoot[i]==0 ) continue;
+#ifndef SQLITE_OMIT_AUTOVACUUM
+    if( pBt->autoVacuum && aRoot[i]>1 ){
+      checkPtrmap(&sCheck, aRoot[i], PTRMAP_ROOTPAGE, 0, 0);
+    }
+#endif
+    checkTreePage(&sCheck, aRoot[i], "List of tree roots: ", NULL, NULL);
+  }
+
+  /* Make sure every page in the file is referenced
+  */
+  for(i=1; i<=sCheck.nPage && sCheck.mxErr; i++){
+#ifdef SQLITE_OMIT_AUTOVACUUM
+    if( sCheck.anRef[i]==0 ){
+      checkAppendMsg(&sCheck, 0, "Page %d is never used", i);
+    }
+#else
+    /* If the database supports auto-vacuum, make sure no tables contain
+    ** references to pointer-map pages.
+    */
+    if( sCheck.anRef[i]==0 && 
+       (PTRMAP_PAGENO(pBt, i)!=i || !pBt->autoVacuum) ){
+      checkAppendMsg(&sCheck, 0, "Page %d is never used", i);
+    }
+    if( sCheck.anRef[i]!=0 && 
+       (PTRMAP_PAGENO(pBt, i)==i && pBt->autoVacuum) ){
+      checkAppendMsg(&sCheck, 0, "Pointer map page %d is referenced", i);
+    }
+#endif
+  }
+
+  /* Make sure this analysis did not leave any unref() pages.
+  ** This is an internal consistency check; an integrity check
+  ** of the integrity check.
+  */
+  if( NEVER(nRef != sqlite3PagerRefcount(pBt->pPager)) ){
+    checkAppendMsg(&sCheck, 0, 
+      "Outstanding page count goes from %d to %d during this analysis",
+      nRef, sqlite3PagerRefcount(pBt->pPager)
+    );
+  }
+
+  /* Clean  up and report errors.
+  */
+  sqlite3BtreeLeave(p);
+  sqlite3_free(sCheck.anRef);
+  if( sCheck.mallocFailed ){
+    sqlite3StrAccumReset(&sCheck.errMsg);
+    *pnErr = sCheck.nErr+1;
+    return 0;
+  }
+  *pnErr = sCheck.nErr;
+  if( sCheck.nErr==0 ) sqlite3StrAccumReset(&sCheck.errMsg);
+  return sqlite3StrAccumFinish(&sCheck.errMsg);
+}
+#endif /* SQLITE_OMIT_INTEGRITY_CHECK */
+
+/*
+** Return the full pathname of the underlying database file.
+**
+** The pager filename is invariant as long as the pager is
+** open so it is safe to access without the BtShared mutex.
+*/
+const char *sqlite3BtreeGetFilename(Btree *p){
+  assert( p->pBt->pPager!=0 );
+  return sqlite3PagerFilename(p->pBt->pPager);
+}
+
+/*
+** Return the pathname of the journal file for this database. The return
+** value of this routine is the same regardless of whether the journal file
+** has been created or not.
+**
+** The pager journal filename is invariant as long as the pager is
+** open so it is safe to access without the BtShared mutex.
+*/
+const char *sqlite3BtreeGetJournalname(Btree *p){
+  assert( p->pBt->pPager!=0 );
+  return sqlite3PagerJournalname(p->pBt->pPager);
+}
+
+/*
+** Return non-zero if a transaction is active.
+*/
+int sqlite3BtreeIsInTrans(Btree *p){
+  assert( p==0 || sqlite3_mutex_held(p->db->mutex) );
+  return (p && (p->inTrans==TRANS_WRITE));
+}
+
+#ifndef SQLITE_OMIT_WAL
+/*
+** Run a checkpoint on the Btree passed as the first argument.
+**
+** Return SQLITE_LOCKED if this or any other connection has an open 
+** transaction on the shared-cache the argument Btree is connected to.
+**
+** Parameter eMode is one of SQLITE_CHECKPOINT_PASSIVE, FULL or RESTART.
+*/
+int sqlite3BtreeCheckpoint(Btree *p, int eMode, int *pnLog, int *pnCkpt){
+  int rc = SQLITE_OK;
+  if( p ){
+    BtShared *pBt = p->pBt;
+    sqlite3BtreeEnter(p);
+    if( pBt->inTransaction!=TRANS_NONE ){
+      rc = SQLITE_LOCKED;
+    }else{
+      rc = sqlite3PagerCheckpoint(pBt->pPager, eMode, pnLog, pnCkpt);
+    }
+    sqlite3BtreeLeave(p);
+  }
+  return rc;
+}
+#endif
+
+/*
+** Return non-zero if a read (or write) transaction is active.
+*/
+int sqlite3BtreeIsInReadTrans(Btree *p){
+  assert( p );
+  assert( sqlite3_mutex_held(p->db->mutex) );
+  return p->inTrans!=TRANS_NONE;
+}
+
+int sqlite3BtreeIsInBackup(Btree *p){
+  assert( p );
+  assert( sqlite3_mutex_held(p->db->mutex) );
+  return p->nBackup!=0;
+}
+
+/*
+** This function returns a pointer to a blob of memory associated with
+** a single shared-btree. The memory is used by client code for its own
+** purposes (for example, to store a high-level schema associated with 
+** the shared-btree). The btree layer manages reference counting issues.
+**
+** The first time this is called on a shared-btree, nBytes bytes of memory
+** are allocated, zeroed, and returned to the caller. For each subsequent 
+** call the nBytes parameter is ignored and a pointer to the same blob
+** of memory returned. 
+**
+** If the nBytes parameter is 0 and the blob of memory has not yet been
+** allocated, a null pointer is returned. If the blob has already been
+** allocated, it is returned as normal.
+**
+** Just before the shared-btree is closed, the function passed as the 
+** xFree argument when the memory allocation was made is invoked on the 
+** blob of allocated memory. The xFree function should not call sqlite3_free()
+** on the memory, the btree layer does that.
+*/
+void *sqlite3BtreeSchema(Btree *p, int nBytes, void(*xFree)(void *)){
+  BtShared *pBt = p->pBt;
+  sqlite3BtreeEnter(p);
+  if( !pBt->pSchema && nBytes ){
+    pBt->pSchema = sqlite3DbMallocZero(0, nBytes);
+    pBt->xFreeSchema = xFree;
+  }
+  sqlite3BtreeLeave(p);
+  return pBt->pSchema;
+}
+
+/*
+** Return SQLITE_LOCKED_SHAREDCACHE if another user of the same shared 
+** btree as the argument handle holds an exclusive lock on the 
+** sqlite_master table. Otherwise SQLITE_OK.
+*/
+int sqlite3BtreeSchemaLocked(Btree *p){
+  int rc;
+  assert( sqlite3_mutex_held(p->db->mutex) );
+  sqlite3BtreeEnter(p);
+  rc = querySharedCacheTableLock(p, MASTER_ROOT, READ_LOCK);
+  assert( rc==SQLITE_OK || rc==SQLITE_LOCKED_SHAREDCACHE );
+  sqlite3BtreeLeave(p);
+  return rc;
+}
+
+
+#ifndef SQLITE_OMIT_SHARED_CACHE
+/*
+** Obtain a lock on the table whose root page is iTab.  The
+** lock is a write lock if isWritelock is true or a read lock
+** if it is false.
+*/
+int sqlite3BtreeLockTable(Btree *p, int iTab, u8 isWriteLock){
+  int rc = SQLITE_OK;
+  assert( p->inTrans!=TRANS_NONE );
+  if( p->sharable ){
+    u8 lockType = READ_LOCK + isWriteLock;
+    assert( READ_LOCK+1==WRITE_LOCK );
+    assert( isWriteLock==0 || isWriteLock==1 );
+
+    sqlite3BtreeEnter(p);
+    rc = querySharedCacheTableLock(p, iTab, lockType);
+    if( rc==SQLITE_OK ){
+      rc = setSharedCacheTableLock(p, iTab, lockType);
+    }
+    sqlite3BtreeLeave(p);
+  }
+  return rc;
+}
+#endif
+
+#ifndef SQLITE_OMIT_INCRBLOB
+/*
+** Argument pCsr must be a cursor opened for writing on an 
+** INTKEY table currently pointing at a valid table entry. 
+** This function modifies the data stored as part of that entry.
+**
+** Only the data content may only be modified, it is not possible to 
+** change the length of the data stored. If this function is called with
+** parameters that attempt to write past the end of the existing data,
+** no modifications are made and SQLITE_CORRUPT is returned.
+*/
+int sqlite3BtreePutData(BtCursor *pCsr, u32 offset, u32 amt, void *z){
+  int rc;
+  assert( cursorHoldsMutex(pCsr) );
+  assert( sqlite3_mutex_held(pCsr->pBtree->db->mutex) );
+  assert( pCsr->isIncrblobHandle );
+
+  rc = restoreCursorPosition(pCsr);
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+  assert( pCsr->eState!=CURSOR_REQUIRESEEK );
+  if( pCsr->eState!=CURSOR_VALID ){
+    return SQLITE_ABORT;
+  }
+
+  /* Check some assumptions: 
+  **   (a) the cursor is open for writing,
+  **   (b) there is a read/write transaction open,
+  **   (c) the connection holds a write-lock on the table (if required),
+  **   (d) there are no conflicting read-locks, and
+  **   (e) the cursor points at a valid row of an intKey table.
+  */
+  if( !pCsr->wrFlag ){
+    return SQLITE_READONLY;
+  }
+  assert( !pCsr->pBt->readOnly && pCsr->pBt->inTransaction==TRANS_WRITE );
+  assert( hasSharedCacheTableLock(pCsr->pBtree, pCsr->pgnoRoot, 0, 2) );
+  assert( !hasReadConflicts(pCsr->pBtree, pCsr->pgnoRoot) );
+  assert( pCsr->apPage[pCsr->iPage]->intKey );
+
+  return accessPayload(pCsr, offset, amt, (unsigned char *)z, 1);
+}
+
+/* 
+** Set a flag on this cursor to cache the locations of pages from the 
+** overflow list for the current row. This is used by cursors opened
+** for incremental blob IO only.
+**
+** This function sets a flag only. The actual page location cache
+** (stored in BtCursor.aOverflow[]) is allocated and used by function
+** accessPayload() (the worker function for sqlite3BtreeData() and
+** sqlite3BtreePutData()).
+*/
+void sqlite3BtreeCacheOverflow(BtCursor *pCur){
+  assert( cursorHoldsMutex(pCur) );
+  assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
+  invalidateOverflowCache(pCur);
+  pCur->isIncrblobHandle = 1;
+}
+#endif
+
+/*
+** Set both the "read version" (single byte at byte offset 18) and 
+** "write version" (single byte at byte offset 19) fields in the database
+** header to iVersion.
+*/
+int sqlite3BtreeSetVersion(Btree *pBtree, int iVersion){
+  BtShared *pBt = pBtree->pBt;
+  int rc;                         /* Return code */
+ 
+  assert( iVersion==1 || iVersion==2 );
+
+  /* If setting the version fields to 1, do not automatically open the
+  ** WAL connection, even if the version fields are currently set to 2.
+  */
+  pBt->doNotUseWAL = (u8)(iVersion==1);
+
+  rc = sqlite3BtreeBeginTrans(pBtree, 0);
+  if( rc==SQLITE_OK ){
+    u8 *aData = pBt->pPage1->aData;
+    if( aData[18]!=(u8)iVersion || aData[19]!=(u8)iVersion ){
+      rc = sqlite3BtreeBeginTrans(pBtree, 2);
+      if( rc==SQLITE_OK ){
+        rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
+        if( rc==SQLITE_OK ){
+          aData[18] = (u8)iVersion;
+          aData[19] = (u8)iVersion;
+        }
+      }
+    }
+  }
+
+  pBt->doNotUseWAL = 0;
+  return rc;
+}
diff --git a/src/btree.h b/src/btree.h
new file mode 100644
index 0000000..9e3a73b
--- /dev/null
+++ b/src/btree.h
@@ -0,0 +1,241 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This header file defines the interface that the sqlite B-Tree file
+** subsystem.  See comments in the source code for a detailed description
+** of what each interface routine does.
+*/
+#ifndef _BTREE_H_
+#define _BTREE_H_
+
+/* TODO: This definition is just included so other modules compile. It
+** needs to be revisited.
+*/
+#define SQLITE_N_BTREE_META 10
+
+/*
+** If defined as non-zero, auto-vacuum is enabled by default. Otherwise
+** it must be turned on for each database using "PRAGMA auto_vacuum = 1".
+*/
+#ifndef SQLITE_DEFAULT_AUTOVACUUM
+  #define SQLITE_DEFAULT_AUTOVACUUM 0
+#endif
+
+#define BTREE_AUTOVACUUM_NONE 0        /* Do not do auto-vacuum */
+#define BTREE_AUTOVACUUM_FULL 1        /* Do full auto-vacuum */
+#define BTREE_AUTOVACUUM_INCR 2        /* Incremental vacuum */
+
+/*
+** Forward declarations of structure
+*/
+typedef struct Btree Btree;
+typedef struct BtCursor BtCursor;
+typedef struct BtShared BtShared;
+
+
+int sqlite3BtreeOpen(
+  sqlite3_vfs *pVfs,       /* VFS to use with this b-tree */
+  const char *zFilename,   /* Name of database file to open */
+  sqlite3 *db,             /* Associated database connection */
+  Btree **ppBtree,         /* Return open Btree* here */
+  int flags,               /* Flags */
+  int vfsFlags             /* Flags passed through to VFS open */
+);
+
+/* The flags parameter to sqlite3BtreeOpen can be the bitwise or of the
+** following values.
+**
+** NOTE:  These values must match the corresponding PAGER_ values in
+** pager.h.
+*/
+#define BTREE_OMIT_JOURNAL  1  /* Do not create or use a rollback journal */
+#define BTREE_NO_READLOCK   2  /* Omit readlocks on readonly files */
+#define BTREE_MEMORY        4  /* This is an in-memory DB */
+#define BTREE_SINGLE        8  /* The file contains at most 1 b-tree */
+#define BTREE_UNORDERED    16  /* Use of a hash implementation is OK */
+
+int sqlite3BtreeClose(Btree*);
+int sqlite3BtreeSetCacheSize(Btree*,int);
+int sqlite3BtreeSetSafetyLevel(Btree*,int,int,int);
+int sqlite3BtreeSyncDisabled(Btree*);
+int sqlite3BtreeSetPageSize(Btree *p, int nPagesize, int nReserve, int eFix);
+int sqlite3BtreeGetPageSize(Btree*);
+int sqlite3BtreeMaxPageCount(Btree*,int);
+u32 sqlite3BtreeLastPage(Btree*);
+int sqlite3BtreeSecureDelete(Btree*,int);
+int sqlite3BtreeGetReserve(Btree*);
+int sqlite3BtreeSetAutoVacuum(Btree *, int);
+int sqlite3BtreeGetAutoVacuum(Btree *);
+int sqlite3BtreeBeginTrans(Btree*,int);
+int sqlite3BtreeCommitPhaseOne(Btree*, const char *zMaster);
+int sqlite3BtreeCommitPhaseTwo(Btree*, int);
+int sqlite3BtreeCommit(Btree*);
+int sqlite3BtreeRollback(Btree*);
+int sqlite3BtreeBeginStmt(Btree*,int);
+int sqlite3BtreeCreateTable(Btree*, int*, int flags);
+int sqlite3BtreeIsInTrans(Btree*);
+int sqlite3BtreeIsInReadTrans(Btree*);
+int sqlite3BtreeIsInBackup(Btree*);
+void *sqlite3BtreeSchema(Btree *, int, void(*)(void *));
+int sqlite3BtreeSchemaLocked(Btree *pBtree);
+int sqlite3BtreeLockTable(Btree *pBtree, int iTab, u8 isWriteLock);
+int sqlite3BtreeSavepoint(Btree *, int, int);
+
+const char *sqlite3BtreeGetFilename(Btree *);
+const char *sqlite3BtreeGetJournalname(Btree *);
+int sqlite3BtreeCopyFile(Btree *, Btree *);
+
+int sqlite3BtreeIncrVacuum(Btree *);
+
+/* The flags parameter to sqlite3BtreeCreateTable can be the bitwise OR
+** of the flags shown below.
+**
+** Every SQLite table must have either BTREE_INTKEY or BTREE_BLOBKEY set.
+** With BTREE_INTKEY, the table key is a 64-bit integer and arbitrary data
+** is stored in the leaves.  (BTREE_INTKEY is used for SQL tables.)  With
+** BTREE_BLOBKEY, the key is an arbitrary BLOB and no content is stored
+** anywhere - the key is the content.  (BTREE_BLOBKEY is used for SQL
+** indices.)
+*/
+#define BTREE_INTKEY     1    /* Table has only 64-bit signed integer keys */
+#define BTREE_BLOBKEY    2    /* Table has keys only - no data */
+
+int sqlite3BtreeDropTable(Btree*, int, int*);
+int sqlite3BtreeClearTable(Btree*, int, int*);
+void sqlite3BtreeTripAllCursors(Btree*, int);
+
+void sqlite3BtreeGetMeta(Btree *pBtree, int idx, u32 *pValue);
+int sqlite3BtreeUpdateMeta(Btree*, int idx, u32 value);
+
+/*
+** The second parameter to sqlite3BtreeGetMeta or sqlite3BtreeUpdateMeta
+** should be one of the following values. The integer values are assigned 
+** to constants so that the offset of the corresponding field in an
+** SQLite database header may be found using the following formula:
+**
+**   offset = 36 + (idx * 4)
+**
+** For example, the free-page-count field is located at byte offset 36 of
+** the database file header. The incr-vacuum-flag field is located at
+** byte offset 64 (== 36+4*7).
+*/
+#define BTREE_FREE_PAGE_COUNT     0
+#define BTREE_SCHEMA_VERSION      1
+#define BTREE_FILE_FORMAT         2
+#define BTREE_DEFAULT_CACHE_SIZE  3
+#define BTREE_LARGEST_ROOT_PAGE   4
+#define BTREE_TEXT_ENCODING       5
+#define BTREE_USER_VERSION        6
+#define BTREE_INCR_VACUUM         7
+
+int sqlite3BtreeCursor(
+  Btree*,                              /* BTree containing table to open */
+  int iTable,                          /* Index of root page */
+  int wrFlag,                          /* 1 for writing.  0 for read-only */
+  struct KeyInfo*,                     /* First argument to compare function */
+  BtCursor *pCursor                    /* Space to write cursor structure */
+);
+int sqlite3BtreeCursorSize(void);
+void sqlite3BtreeCursorZero(BtCursor*);
+
+int sqlite3BtreeCloseCursor(BtCursor*);
+int sqlite3BtreeMovetoUnpacked(
+  BtCursor*,
+  UnpackedRecord *pUnKey,
+  i64 intKey,
+  int bias,
+  int *pRes
+);
+int sqlite3BtreeCursorHasMoved(BtCursor*, int*);
+int sqlite3BtreeDelete(BtCursor*);
+int sqlite3BtreeInsert(BtCursor*, const void *pKey, i64 nKey,
+                                  const void *pData, int nData,
+                                  int nZero, int bias, int seekResult);
+int sqlite3BtreeFirst(BtCursor*, int *pRes);
+int sqlite3BtreeLast(BtCursor*, int *pRes);
+int sqlite3BtreeNext(BtCursor*, int *pRes);
+int sqlite3BtreeEof(BtCursor*);
+int sqlite3BtreePrevious(BtCursor*, int *pRes);
+int sqlite3BtreeKeySize(BtCursor*, i64 *pSize);
+int sqlite3BtreeKey(BtCursor*, u32 offset, u32 amt, void*);
+const void *sqlite3BtreeKeyFetch(BtCursor*, int *pAmt);
+const void *sqlite3BtreeDataFetch(BtCursor*, int *pAmt);
+int sqlite3BtreeDataSize(BtCursor*, u32 *pSize);
+int sqlite3BtreeData(BtCursor*, u32 offset, u32 amt, void*);
+void sqlite3BtreeSetCachedRowid(BtCursor*, sqlite3_int64);
+sqlite3_int64 sqlite3BtreeGetCachedRowid(BtCursor*);
+
+char *sqlite3BtreeIntegrityCheck(Btree*, int *aRoot, int nRoot, int, int*);
+struct Pager *sqlite3BtreePager(Btree*);
+
+int sqlite3BtreePutData(BtCursor*, u32 offset, u32 amt, void*);
+void sqlite3BtreeCacheOverflow(BtCursor *);
+void sqlite3BtreeClearCursor(BtCursor *);
+
+int sqlite3BtreeSetVersion(Btree *pBt, int iVersion);
+
+#ifndef NDEBUG
+int sqlite3BtreeCursorIsValid(BtCursor*);
+#endif
+
+#ifndef SQLITE_OMIT_BTREECOUNT
+int sqlite3BtreeCount(BtCursor *, i64 *);
+#endif
+
+#ifdef SQLITE_TEST
+int sqlite3BtreeCursorInfo(BtCursor*, int*, int);
+void sqlite3BtreeCursorList(Btree*);
+#endif
+
+#ifndef SQLITE_OMIT_WAL
+  int sqlite3BtreeCheckpoint(Btree*, int, int *, int *);
+#endif
+
+/*
+** If we are not using shared cache, then there is no need to
+** use mutexes to access the BtShared structures.  So make the
+** Enter and Leave procedures no-ops.
+*/
+#ifndef SQLITE_OMIT_SHARED_CACHE
+  void sqlite3BtreeEnter(Btree*);
+  void sqlite3BtreeEnterAll(sqlite3*);
+#else
+# define sqlite3BtreeEnter(X) 
+# define sqlite3BtreeEnterAll(X)
+#endif
+
+#if !defined(SQLITE_OMIT_SHARED_CACHE) && SQLITE_THREADSAFE
+  int sqlite3BtreeSharable(Btree*);
+  void sqlite3BtreeLeave(Btree*);
+  void sqlite3BtreeEnterCursor(BtCursor*);
+  void sqlite3BtreeLeaveCursor(BtCursor*);
+  void sqlite3BtreeLeaveAll(sqlite3*);
+#ifndef NDEBUG
+  /* These routines are used inside assert() statements only. */
+  int sqlite3BtreeHoldsMutex(Btree*);
+  int sqlite3BtreeHoldsAllMutexes(sqlite3*);
+  int sqlite3SchemaMutexHeld(sqlite3*,int,Schema*);
+#endif
+#else
+
+# define sqlite3BtreeSharable(X) 0
+# define sqlite3BtreeLeave(X)
+# define sqlite3BtreeEnterCursor(X)
+# define sqlite3BtreeLeaveCursor(X)
+# define sqlite3BtreeLeaveAll(X)
+
+# define sqlite3BtreeHoldsMutex(X) 1
+# define sqlite3BtreeHoldsAllMutexes(X) 1
+# define sqlite3SchemaMutexHeld(X,Y,Z) 1
+#endif
+
+
+#endif /* _BTREE_H_ */
diff --git a/src/btreeInt.h b/src/btreeInt.h
new file mode 100644
index 0000000..55469cf
--- /dev/null
+++ b/src/btreeInt.h
@@ -0,0 +1,643 @@
+/*
+** 2004 April 6
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file implements a external (disk-based) database using BTrees.
+** For a detailed discussion of BTrees, refer to
+**
+**     Donald E. Knuth, THE ART OF COMPUTER PROGRAMMING, Volume 3:
+**     "Sorting And Searching", pages 473-480. Addison-Wesley
+**     Publishing Company, Reading, Massachusetts.
+**
+** The basic idea is that each page of the file contains N database
+** entries and N+1 pointers to subpages.
+**
+**   ----------------------------------------------------------------
+**   |  Ptr(0) | Key(0) | Ptr(1) | Key(1) | ... | Key(N-1) | Ptr(N) |
+**   ----------------------------------------------------------------
+**
+** All of the keys on the page that Ptr(0) points to have values less
+** than Key(0).  All of the keys on page Ptr(1) and its subpages have
+** values greater than Key(0) and less than Key(1).  All of the keys
+** on Ptr(N) and its subpages have values greater than Key(N-1).  And
+** so forth.
+**
+** Finding a particular key requires reading O(log(M)) pages from the 
+** disk where M is the number of entries in the tree.
+**
+** In this implementation, a single file can hold one or more separate 
+** BTrees.  Each BTree is identified by the index of its root page.  The
+** key and data for any entry are combined to form the "payload".  A
+** fixed amount of payload can be carried directly on the database
+** page.  If the payload is larger than the preset amount then surplus
+** bytes are stored on overflow pages.  The payload for an entry
+** and the preceding pointer are combined to form a "Cell".  Each 
+** page has a small header which contains the Ptr(N) pointer and other
+** information such as the size of key and data.
+**
+** FORMAT DETAILS
+**
+** The file is divided into pages.  The first page is called page 1,
+** the second is page 2, and so forth.  A page number of zero indicates
+** "no such page".  The page size can be any power of 2 between 512 and 65536.
+** Each page can be either a btree page, a freelist page, an overflow
+** page, or a pointer-map page.
+**
+** The first page is always a btree page.  The first 100 bytes of the first
+** page contain a special header (the "file header") that describes the file.
+** The format of the file header is as follows:
+**
+**   OFFSET   SIZE    DESCRIPTION
+**      0      16     Header string: "SQLite format 3\000"
+**     16       2     Page size in bytes.  
+**     18       1     File format write version
+**     19       1     File format read version
+**     20       1     Bytes of unused space at the end of each page
+**     21       1     Max embedded payload fraction
+**     22       1     Min embedded payload fraction
+**     23       1     Min leaf payload fraction
+**     24       4     File change counter
+**     28       4     Reserved for future use
+**     32       4     First freelist page
+**     36       4     Number of freelist pages in the file
+**     40      60     15 4-byte meta values passed to higher layers
+**
+**     40       4     Schema cookie
+**     44       4     File format of schema layer
+**     48       4     Size of page cache
+**     52       4     Largest root-page (auto/incr_vacuum)
+**     56       4     1=UTF-8 2=UTF16le 3=UTF16be
+**     60       4     User version
+**     64       4     Incremental vacuum mode
+**     68       4     unused
+**     72       4     unused
+**     76       4     unused
+**
+** All of the integer values are big-endian (most significant byte first).
+**
+** The file change counter is incremented when the database is changed
+** This counter allows other processes to know when the file has changed
+** and thus when they need to flush their cache.
+**
+** The max embedded payload fraction is the amount of the total usable
+** space in a page that can be consumed by a single cell for standard
+** B-tree (non-LEAFDATA) tables.  A value of 255 means 100%.  The default
+** is to limit the maximum cell size so that at least 4 cells will fit
+** on one page.  Thus the default max embedded payload fraction is 64.
+**
+** If the payload for a cell is larger than the max payload, then extra
+** payload is spilled to overflow pages.  Once an overflow page is allocated,
+** as many bytes as possible are moved into the overflow pages without letting
+** the cell size drop below the min embedded payload fraction.
+**
+** The min leaf payload fraction is like the min embedded payload fraction
+** except that it applies to leaf nodes in a LEAFDATA tree.  The maximum
+** payload fraction for a LEAFDATA tree is always 100% (or 255) and it
+** not specified in the header.
+**
+** Each btree pages is divided into three sections:  The header, the
+** cell pointer array, and the cell content area.  Page 1 also has a 100-byte
+** file header that occurs before the page header.
+**
+**      |----------------|
+**      | file header    |   100 bytes.  Page 1 only.
+**      |----------------|
+**      | page header    |   8 bytes for leaves.  12 bytes for interior nodes
+**      |----------------|
+**      | cell pointer   |   |  2 bytes per cell.  Sorted order.
+**      | array          |   |  Grows downward
+**      |                |   v
+**      |----------------|
+**      | unallocated    |
+**      | space          |
+**      |----------------|   ^  Grows upwards
+**      | cell content   |   |  Arbitrary order interspersed with freeblocks.
+**      | area           |   |  and free space fragments.
+**      |----------------|
+**
+** The page headers looks like this:
+**
+**   OFFSET   SIZE     DESCRIPTION
+**      0       1      Flags. 1: intkey, 2: zerodata, 4: leafdata, 8: leaf
+**      1       2      byte offset to the first freeblock
+**      3       2      number of cells on this page
+**      5       2      first byte of the cell content area
+**      7       1      number of fragmented free bytes
+**      8       4      Right child (the Ptr(N) value).  Omitted on leaves.
+**
+** The flags define the format of this btree page.  The leaf flag means that
+** this page has no children.  The zerodata flag means that this page carries
+** only keys and no data.  The intkey flag means that the key is a integer
+** which is stored in the key size entry of the cell header rather than in
+** the payload area.
+**
+** The cell pointer array begins on the first byte after the page header.
+** The cell pointer array contains zero or more 2-byte numbers which are
+** offsets from the beginning of the page to the cell content in the cell
+** content area.  The cell pointers occur in sorted order.  The system strives
+** to keep free space after the last cell pointer so that new cells can
+** be easily added without having to defragment the page.
+**
+** Cell content is stored at the very end of the page and grows toward the
+** beginning of the page.
+**
+** Unused space within the cell content area is collected into a linked list of
+** freeblocks.  Each freeblock is at least 4 bytes in size.  The byte offset
+** to the first freeblock is given in the header.  Freeblocks occur in
+** increasing order.  Because a freeblock must be at least 4 bytes in size,
+** any group of 3 or fewer unused bytes in the cell content area cannot
+** exist on the freeblock chain.  A group of 3 or fewer free bytes is called
+** a fragment.  The total number of bytes in all fragments is recorded.
+** in the page header at offset 7.
+**
+**    SIZE    DESCRIPTION
+**      2     Byte offset of the next freeblock
+**      2     Bytes in this freeblock
+**
+** Cells are of variable length.  Cells are stored in the cell content area at
+** the end of the page.  Pointers to the cells are in the cell pointer array
+** that immediately follows the page header.  Cells is not necessarily
+** contiguous or in order, but cell pointers are contiguous and in order.
+**
+** Cell content makes use of variable length integers.  A variable
+** length integer is 1 to 9 bytes where the lower 7 bits of each 
+** byte are used.  The integer consists of all bytes that have bit 8 set and
+** the first byte with bit 8 clear.  The most significant byte of the integer
+** appears first.  A variable-length integer may not be more than 9 bytes long.
+** As a special case, all 8 bytes of the 9th byte are used as data.  This
+** allows a 64-bit integer to be encoded in 9 bytes.
+**
+**    0x00                      becomes  0x00000000
+**    0x7f                      becomes  0x0000007f
+**    0x81 0x00                 becomes  0x00000080
+**    0x82 0x00                 becomes  0x00000100
+**    0x80 0x7f                 becomes  0x0000007f
+**    0x8a 0x91 0xd1 0xac 0x78  becomes  0x12345678
+**    0x81 0x81 0x81 0x81 0x01  becomes  0x10204081
+**
+** Variable length integers are used for rowids and to hold the number of
+** bytes of key and data in a btree cell.
+**
+** The content of a cell looks like this:
+**
+**    SIZE    DESCRIPTION
+**      4     Page number of the left child. Omitted if leaf flag is set.
+**     var    Number of bytes of data. Omitted if the zerodata flag is set.
+**     var    Number of bytes of key. Or the key itself if intkey flag is set.
+**      *     Payload
+**      4     First page of the overflow chain.  Omitted if no overflow
+**
+** Overflow pages form a linked list.  Each page except the last is completely
+** filled with data (pagesize - 4 bytes).  The last page can have as little
+** as 1 byte of data.
+**
+**    SIZE    DESCRIPTION
+**      4     Page number of next overflow page
+**      *     Data
+**
+** Freelist pages come in two subtypes: trunk pages and leaf pages.  The
+** file header points to the first in a linked list of trunk page.  Each trunk
+** page points to multiple leaf pages.  The content of a leaf page is
+** unspecified.  A trunk page looks like this:
+**
+**    SIZE    DESCRIPTION
+**      4     Page number of next trunk page
+**      4     Number of leaf pointers on this page
+**      *     zero or more pages numbers of leaves
+*/
+#include "sqliteInt.h"
+
+
+/* The following value is the maximum cell size assuming a maximum page
+** size give above.
+*/
+#define MX_CELL_SIZE(pBt)  ((int)(pBt->pageSize-8))
+
+/* The maximum number of cells on a single page of the database.  This
+** assumes a minimum cell size of 6 bytes  (4 bytes for the cell itself
+** plus 2 bytes for the index to the cell in the page header).  Such
+** small cells will be rare, but they are possible.
+*/
+#define MX_CELL(pBt) ((pBt->pageSize-8)/6)
+
+/* Forward declarations */
+typedef struct MemPage MemPage;
+typedef struct BtLock BtLock;
+
+/*
+** This is a magic string that appears at the beginning of every
+** SQLite database in order to identify the file as a real database.
+**
+** You can change this value at compile-time by specifying a
+** -DSQLITE_FILE_HEADER="..." on the compiler command-line.  The
+** header must be exactly 16 bytes including the zero-terminator so
+** the string itself should be 15 characters long.  If you change
+** the header, then your custom library will not be able to read 
+** databases generated by the standard tools and the standard tools
+** will not be able to read databases created by your custom library.
+*/
+#ifndef SQLITE_FILE_HEADER /* 123456789 123456 */
+#  define SQLITE_FILE_HEADER "SQLite format 3"
+#endif
+
+/*
+** Page type flags.  An ORed combination of these flags appear as the
+** first byte of on-disk image of every BTree page.
+*/
+#define PTF_INTKEY    0x01
+#define PTF_ZERODATA  0x02
+#define PTF_LEAFDATA  0x04
+#define PTF_LEAF      0x08
+
+/*
+** As each page of the file is loaded into memory, an instance of the following
+** structure is appended and initialized to zero.  This structure stores
+** information about the page that is decoded from the raw file page.
+**
+** The pParent field points back to the parent page.  This allows us to
+** walk up the BTree from any leaf to the root.  Care must be taken to
+** unref() the parent page pointer when this page is no longer referenced.
+** The pageDestructor() routine handles that chore.
+**
+** Access to all fields of this structure is controlled by the mutex
+** stored in MemPage.pBt->mutex.
+*/
+struct MemPage {
+  u8 isInit;           /* True if previously initialized. MUST BE FIRST! */
+  u8 nOverflow;        /* Number of overflow cell bodies in aCell[] */
+  u8 intKey;           /* True if intkey flag is set */
+  u8 leaf;             /* True if leaf flag is set */
+  u8 hasData;          /* True if this page stores data */
+  u8 hdrOffset;        /* 100 for page 1.  0 otherwise */
+  u8 childPtrSize;     /* 0 if leaf==1.  4 if leaf==0 */
+  u16 maxLocal;        /* Copy of BtShared.maxLocal or BtShared.maxLeaf */
+  u16 minLocal;        /* Copy of BtShared.minLocal or BtShared.minLeaf */
+  u16 cellOffset;      /* Index in aData of first cell pointer */
+  u16 nFree;           /* Number of free bytes on the page */
+  u16 nCell;           /* Number of cells on this page, local and ovfl */
+  u16 maskPage;        /* Mask for page offset */
+  struct _OvflCell {   /* Cells that will not fit on aData[] */
+    u8 *pCell;          /* Pointers to the body of the overflow cell */
+    u16 idx;            /* Insert this cell before idx-th non-overflow cell */
+  } aOvfl[5];
+  BtShared *pBt;       /* Pointer to BtShared that this page is part of */
+  u8 *aData;           /* Pointer to disk image of the page data */
+  DbPage *pDbPage;     /* Pager page handle */
+  Pgno pgno;           /* Page number for this page */
+};
+
+/*
+** The in-memory image of a disk page has the auxiliary information appended
+** to the end.  EXTRA_SIZE is the number of bytes of space needed to hold
+** that extra information.
+*/
+#define EXTRA_SIZE sizeof(MemPage)
+
+/*
+** A linked list of the following structures is stored at BtShared.pLock.
+** Locks are added (or upgraded from READ_LOCK to WRITE_LOCK) when a cursor 
+** is opened on the table with root page BtShared.iTable. Locks are removed
+** from this list when a transaction is committed or rolled back, or when
+** a btree handle is closed.
+*/
+struct BtLock {
+  Btree *pBtree;        /* Btree handle holding this lock */
+  Pgno iTable;          /* Root page of table */
+  u8 eLock;             /* READ_LOCK or WRITE_LOCK */
+  BtLock *pNext;        /* Next in BtShared.pLock list */
+};
+
+/* Candidate values for BtLock.eLock */
+#define READ_LOCK     1
+#define WRITE_LOCK    2
+
+/* A Btree handle
+**
+** A database connection contains a pointer to an instance of
+** this object for every database file that it has open.  This structure
+** is opaque to the database connection.  The database connection cannot
+** see the internals of this structure and only deals with pointers to
+** this structure.
+**
+** For some database files, the same underlying database cache might be 
+** shared between multiple connections.  In that case, each connection
+** has it own instance of this object.  But each instance of this object
+** points to the same BtShared object.  The database cache and the
+** schema associated with the database file are all contained within
+** the BtShared object.
+**
+** All fields in this structure are accessed under sqlite3.mutex.
+** The pBt pointer itself may not be changed while there exists cursors 
+** in the referenced BtShared that point back to this Btree since those
+** cursors have to go through this Btree to find their BtShared and
+** they often do so without holding sqlite3.mutex.
+*/
+struct Btree {
+  sqlite3 *db;       /* The database connection holding this btree */
+  BtShared *pBt;     /* Sharable content of this btree */
+  u8 inTrans;        /* TRANS_NONE, TRANS_READ or TRANS_WRITE */
+  u8 sharable;       /* True if we can share pBt with another db */
+  u8 locked;         /* True if db currently has pBt locked */
+  int wantToLock;    /* Number of nested calls to sqlite3BtreeEnter() */
+  int nBackup;       /* Number of backup operations reading this btree */
+  Btree *pNext;      /* List of other sharable Btrees from the same db */
+  Btree *pPrev;      /* Back pointer of the same list */
+#ifndef SQLITE_OMIT_SHARED_CACHE
+  BtLock lock;       /* Object used to lock page 1 */
+#endif
+};
+
+/*
+** Btree.inTrans may take one of the following values.
+**
+** If the shared-data extension is enabled, there may be multiple users
+** of the Btree structure. At most one of these may open a write transaction,
+** but any number may have active read transactions.
+*/
+#define TRANS_NONE  0
+#define TRANS_READ  1
+#define TRANS_WRITE 2
+
+/*
+** An instance of this object represents a single database file.
+** 
+** A single database file can be in use as the same time by two
+** or more database connections.  When two or more connections are
+** sharing the same database file, each connection has it own
+** private Btree object for the file and each of those Btrees points
+** to this one BtShared object.  BtShared.nRef is the number of
+** connections currently sharing this database file.
+**
+** Fields in this structure are accessed under the BtShared.mutex
+** mutex, except for nRef and pNext which are accessed under the
+** global SQLITE_MUTEX_STATIC_MASTER mutex.  The pPager field
+** may not be modified once it is initially set as long as nRef>0.
+** The pSchema field may be set once under BtShared.mutex and
+** thereafter is unchanged as long as nRef>0.
+**
+** isPending:
+**
+**   If a BtShared client fails to obtain a write-lock on a database
+**   table (because there exists one or more read-locks on the table),
+**   the shared-cache enters 'pending-lock' state and isPending is
+**   set to true.
+**
+**   The shared-cache leaves the 'pending lock' state when either of
+**   the following occur:
+**
+**     1) The current writer (BtShared.pWriter) concludes its transaction, OR
+**     2) The number of locks held by other connections drops to zero.
+**
+**   while in the 'pending-lock' state, no connection may start a new
+**   transaction.
+**
+**   This feature is included to help prevent writer-starvation.
+*/
+struct BtShared {
+  Pager *pPager;        /* The page cache */
+  sqlite3 *db;          /* Database connection currently using this Btree */
+  BtCursor *pCursor;    /* A list of all open cursors */
+  MemPage *pPage1;      /* First page of the database */
+  u8 readOnly;          /* True if the underlying file is readonly */
+  u8 pageSizeFixed;     /* True if the page size can no longer be changed */
+  u8 secureDelete;      /* True if secure_delete is enabled */
+  u8 initiallyEmpty;    /* Database is empty at start of transaction */
+  u8 openFlags;         /* Flags to sqlite3BtreeOpen() */
+#ifndef SQLITE_OMIT_AUTOVACUUM
+  u8 autoVacuum;        /* True if auto-vacuum is enabled */
+  u8 incrVacuum;        /* True if incr-vacuum is enabled */
+#endif
+  u8 inTransaction;     /* Transaction state */
+  u8 doNotUseWAL;       /* If true, do not open write-ahead-log file */
+  u16 maxLocal;         /* Maximum local payload in non-LEAFDATA tables */
+  u16 minLocal;         /* Minimum local payload in non-LEAFDATA tables */
+  u16 maxLeaf;          /* Maximum local payload in a LEAFDATA table */
+  u16 minLeaf;          /* Minimum local payload in a LEAFDATA table */
+  u32 pageSize;         /* Total number of bytes on a page */
+  u32 usableSize;       /* Number of usable bytes on each page */
+  int nTransaction;     /* Number of open transactions (read + write) */
+  u32 nPage;            /* Number of pages in the database */
+  void *pSchema;        /* Pointer to space allocated by sqlite3BtreeSchema() */
+  void (*xFreeSchema)(void*);  /* Destructor for BtShared.pSchema */
+  sqlite3_mutex *mutex; /* Non-recursive mutex required to access this object */
+  Bitvec *pHasContent;  /* Set of pages moved to free-list this transaction */
+#ifndef SQLITE_OMIT_SHARED_CACHE
+  int nRef;             /* Number of references to this structure */
+  BtShared *pNext;      /* Next on a list of sharable BtShared structs */
+  BtLock *pLock;        /* List of locks held on this shared-btree struct */
+  Btree *pWriter;       /* Btree with currently open write transaction */
+  u8 isExclusive;       /* True if pWriter has an EXCLUSIVE lock on the db */
+  u8 isPending;         /* If waiting for read-locks to clear */
+#endif
+  u8 *pTmpSpace;        /* BtShared.pageSize bytes of space for tmp use */
+};
+
+/*
+** An instance of the following structure is used to hold information
+** about a cell.  The parseCellPtr() function fills in this structure
+** based on information extract from the raw disk page.
+*/
+typedef struct CellInfo CellInfo;
+struct CellInfo {
+  i64 nKey;      /* The key for INTKEY tables, or number of bytes in key */
+  u8 *pCell;     /* Pointer to the start of cell content */
+  u32 nData;     /* Number of bytes of data */
+  u32 nPayload;  /* Total amount of payload */
+  u16 nHeader;   /* Size of the cell content header in bytes */
+  u16 nLocal;    /* Amount of payload held locally */
+  u16 iOverflow; /* Offset to overflow page number.  Zero if no overflow */
+  u16 nSize;     /* Size of the cell content on the main b-tree page */
+};
+
+/*
+** Maximum depth of an SQLite B-Tree structure. Any B-Tree deeper than
+** this will be declared corrupt. This value is calculated based on a
+** maximum database size of 2^31 pages a minimum fanout of 2 for a
+** root-node and 3 for all other internal nodes.
+**
+** If a tree that appears to be taller than this is encountered, it is
+** assumed that the database is corrupt.
+*/
+#define BTCURSOR_MAX_DEPTH 20
+
+/*
+** A cursor is a pointer to a particular entry within a particular
+** b-tree within a database file.
+**
+** The entry is identified by its MemPage and the index in
+** MemPage.aCell[] of the entry.
+**
+** A single database file can shared by two more database connections,
+** but cursors cannot be shared.  Each cursor is associated with a
+** particular database connection identified BtCursor.pBtree.db.
+**
+** Fields in this structure are accessed under the BtShared.mutex
+** found at self->pBt->mutex. 
+*/
+struct BtCursor {
+  Btree *pBtree;            /* The Btree to which this cursor belongs */
+  BtShared *pBt;            /* The BtShared this cursor points to */
+  BtCursor *pNext, *pPrev;  /* Forms a linked list of all cursors */
+  struct KeyInfo *pKeyInfo; /* Argument passed to comparison function */
+  Pgno pgnoRoot;            /* The root page of this tree */
+  sqlite3_int64 cachedRowid; /* Next rowid cache.  0 means not valid */
+  CellInfo info;            /* A parse of the cell we are pointing at */
+  i64 nKey;        /* Size of pKey, or last integer key */
+  void *pKey;      /* Saved key that was cursor's last known position */
+  int skipNext;    /* Prev() is noop if negative. Next() is noop if positive */
+  u8 wrFlag;                /* True if writable */
+  u8 atLast;                /* Cursor pointing to the last entry */
+  u8 validNKey;             /* True if info.nKey is valid */
+  u8 eState;                /* One of the CURSOR_XXX constants (see below) */
+#ifndef SQLITE_OMIT_INCRBLOB
+  Pgno *aOverflow;          /* Cache of overflow page locations */
+  u8 isIncrblobHandle;      /* True if this cursor is an incr. io handle */
+#endif
+  i16 iPage;                            /* Index of current page in apPage */
+  u16 aiIdx[BTCURSOR_MAX_DEPTH];        /* Current index in apPage[i] */
+  MemPage *apPage[BTCURSOR_MAX_DEPTH];  /* Pages from root to current page */
+};
+
+/*
+** Potential values for BtCursor.eState.
+**
+** CURSOR_VALID:
+**   Cursor points to a valid entry. getPayload() etc. may be called.
+**
+** CURSOR_INVALID:
+**   Cursor does not point to a valid entry. This can happen (for example) 
+**   because the table is empty or because BtreeCursorFirst() has not been
+**   called.
+**
+** CURSOR_REQUIRESEEK:
+**   The table that this cursor was opened on still exists, but has been 
+**   modified since the cursor was last used. The cursor position is saved
+**   in variables BtCursor.pKey and BtCursor.nKey. When a cursor is in 
+**   this state, restoreCursorPosition() can be called to attempt to
+**   seek the cursor to the saved position.
+**
+** CURSOR_FAULT:
+**   A unrecoverable error (an I/O error or a malloc failure) has occurred
+**   on a different connection that shares the BtShared cache with this
+**   cursor.  The error has left the cache in an inconsistent state.
+**   Do nothing else with this cursor.  Any attempt to use the cursor
+**   should return the error code stored in BtCursor.skip
+*/
+#define CURSOR_INVALID           0
+#define CURSOR_VALID             1
+#define CURSOR_REQUIRESEEK       2
+#define CURSOR_FAULT             3
+
+/* 
+** The database page the PENDING_BYTE occupies. This page is never used.
+*/
+# define PENDING_BYTE_PAGE(pBt) PAGER_MJ_PGNO(pBt)
+
+/*
+** These macros define the location of the pointer-map entry for a 
+** database page. The first argument to each is the number of usable
+** bytes on each page of the database (often 1024). The second is the
+** page number to look up in the pointer map.
+**
+** PTRMAP_PAGENO returns the database page number of the pointer-map
+** page that stores the required pointer. PTRMAP_PTROFFSET returns
+** the offset of the requested map entry.
+**
+** If the pgno argument passed to PTRMAP_PAGENO is a pointer-map page,
+** then pgno is returned. So (pgno==PTRMAP_PAGENO(pgsz, pgno)) can be
+** used to test if pgno is a pointer-map page. PTRMAP_ISPAGE implements
+** this test.
+*/
+#define PTRMAP_PAGENO(pBt, pgno) ptrmapPageno(pBt, pgno)
+#define PTRMAP_PTROFFSET(pgptrmap, pgno) (5*(pgno-pgptrmap-1))
+#define PTRMAP_ISPAGE(pBt, pgno) (PTRMAP_PAGENO((pBt),(pgno))==(pgno))
+
+/*
+** The pointer map is a lookup table that identifies the parent page for
+** each child page in the database file.  The parent page is the page that
+** contains a pointer to the child.  Every page in the database contains
+** 0 or 1 parent pages.  (In this context 'database page' refers
+** to any page that is not part of the pointer map itself.)  Each pointer map
+** entry consists of a single byte 'type' and a 4 byte parent page number.
+** The PTRMAP_XXX identifiers below are the valid types.
+**
+** The purpose of the pointer map is to facility moving pages from one
+** position in the file to another as part of autovacuum.  When a page
+** is moved, the pointer in its parent must be updated to point to the
+** new location.  The pointer map is used to locate the parent page quickly.
+**
+** PTRMAP_ROOTPAGE: The database page is a root-page. The page-number is not
+**                  used in this case.
+**
+** PTRMAP_FREEPAGE: The database page is an unused (free) page. The page-number 
+**                  is not used in this case.
+**
+** PTRMAP_OVERFLOW1: The database page is the first page in a list of 
+**                   overflow pages. The page number identifies the page that
+**                   contains the cell with a pointer to this overflow page.
+**
+** PTRMAP_OVERFLOW2: The database page is the second or later page in a list of
+**                   overflow pages. The page-number identifies the previous
+**                   page in the overflow page list.
+**
+** PTRMAP_BTREE: The database page is a non-root btree page. The page number
+**               identifies the parent page in the btree.
+*/
+#define PTRMAP_ROOTPAGE 1
+#define PTRMAP_FREEPAGE 2
+#define PTRMAP_OVERFLOW1 3
+#define PTRMAP_OVERFLOW2 4
+#define PTRMAP_BTREE 5
+
+/* A bunch of assert() statements to check the transaction state variables
+** of handle p (type Btree*) are internally consistent.
+*/
+#define btreeIntegrity(p) \
+  assert( p->pBt->inTransaction!=TRANS_NONE || p->pBt->nTransaction==0 ); \
+  assert( p->pBt->inTransaction>=p->inTrans ); 
+
+
+/*
+** The ISAUTOVACUUM macro is used within balance_nonroot() to determine
+** if the database supports auto-vacuum or not. Because it is used
+** within an expression that is an argument to another macro 
+** (sqliteMallocRaw), it is not possible to use conditional compilation.
+** So, this macro is defined instead.
+*/
+#ifndef SQLITE_OMIT_AUTOVACUUM
+#define ISAUTOVACUUM (pBt->autoVacuum)
+#else
+#define ISAUTOVACUUM 0
+#endif
+
+
+/*
+** This structure is passed around through all the sanity checking routines
+** in order to keep track of some global state information.
+*/
+typedef struct IntegrityCk IntegrityCk;
+struct IntegrityCk {
+  BtShared *pBt;    /* The tree being checked out */
+  Pager *pPager;    /* The associated pager.  Also accessible by pBt->pPager */
+  Pgno nPage;       /* Number of pages in the database */
+  int *anRef;       /* Number of times each page is referenced */
+  int mxErr;        /* Stop accumulating errors when this reaches zero */
+  int nErr;         /* Number of messages written to zErrMsg so far */
+  int mallocFailed; /* A memory allocation error has occurred */
+  StrAccum errMsg;  /* Accumulate the error message text here */
+};
+
+/*
+** Read or write a two- and four-byte big-endian integer values.
+*/
+#define get2byte(x)   ((x)[0]<<8 | (x)[1])
+#define put2byte(p,v) ((p)[0] = (u8)((v)>>8), (p)[1] = (u8)(v))
+#define get4byte sqlite3Get4byte
+#define put4byte sqlite3Put4byte
diff --git a/src/build.c b/src/build.c
new file mode 100644
index 0000000..e23aab6
--- /dev/null
+++ b/src/build.c
@@ -0,0 +1,3818 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains C code routines that are called by the SQLite parser
+** when syntax rules are reduced.  The routines in this file handle the
+** following kinds of SQL syntax:
+**
+**     CREATE TABLE
+**     DROP TABLE
+**     CREATE INDEX
+**     DROP INDEX
+**     creating ID lists
+**     BEGIN TRANSACTION
+**     COMMIT
+**     ROLLBACK
+*/
+#include "sqliteInt.h"
+
+/*
+** This routine is called when a new SQL statement is beginning to
+** be parsed.  Initialize the pParse structure as needed.
+*/
+void sqlite3BeginParse(Parse *pParse, int explainFlag){
+  pParse->explain = (u8)explainFlag;
+  pParse->nVar = 0;
+}
+
+#ifndef SQLITE_OMIT_SHARED_CACHE
+/*
+** The TableLock structure is only used by the sqlite3TableLock() and
+** codeTableLocks() functions.
+*/
+struct TableLock {
+  int iDb;             /* The database containing the table to be locked */
+  int iTab;            /* The root page of the table to be locked */
+  u8 isWriteLock;      /* True for write lock.  False for a read lock */
+  const char *zName;   /* Name of the table */
+};
+
+/*
+** Record the fact that we want to lock a table at run-time.  
+**
+** The table to be locked has root page iTab and is found in database iDb.
+** A read or a write lock can be taken depending on isWritelock.
+**
+** This routine just records the fact that the lock is desired.  The
+** code to make the lock occur is generated by a later call to
+** codeTableLocks() which occurs during sqlite3FinishCoding().
+*/
+void sqlite3TableLock(
+  Parse *pParse,     /* Parsing context */
+  int iDb,           /* Index of the database containing the table to lock */
+  int iTab,          /* Root page number of the table to be locked */
+  u8 isWriteLock,    /* True for a write lock */
+  const char *zName  /* Name of the table to be locked */
+){
+  Parse *pToplevel = sqlite3ParseToplevel(pParse);
+  int i;
+  int nBytes;
+  TableLock *p;
+  assert( iDb>=0 );
+
+  for(i=0; i<pToplevel->nTableLock; i++){
+    p = &pToplevel->aTableLock[i];
+    if( p->iDb==iDb && p->iTab==iTab ){
+      p->isWriteLock = (p->isWriteLock || isWriteLock);
+      return;
+    }
+  }
+
+  nBytes = sizeof(TableLock) * (pToplevel->nTableLock+1);
+  pToplevel->aTableLock =
+      sqlite3DbReallocOrFree(pToplevel->db, pToplevel->aTableLock, nBytes);
+  if( pToplevel->aTableLock ){
+    p = &pToplevel->aTableLock[pToplevel->nTableLock++];
+    p->iDb = iDb;
+    p->iTab = iTab;
+    p->isWriteLock = isWriteLock;
+    p->zName = zName;
+  }else{
+    pToplevel->nTableLock = 0;
+    pToplevel->db->mallocFailed = 1;
+  }
+}
+
+/*
+** Code an OP_TableLock instruction for each table locked by the
+** statement (configured by calls to sqlite3TableLock()).
+*/
+static void codeTableLocks(Parse *pParse){
+  int i;
+  Vdbe *pVdbe; 
+
+  pVdbe = sqlite3GetVdbe(pParse);
+  assert( pVdbe!=0 ); /* sqlite3GetVdbe cannot fail: VDBE already allocated */
+
+  for(i=0; i<pParse->nTableLock; i++){
+    TableLock *p = &pParse->aTableLock[i];
+    int p1 = p->iDb;
+    sqlite3VdbeAddOp4(pVdbe, OP_TableLock, p1, p->iTab, p->isWriteLock,
+                      p->zName, P4_STATIC);
+  }
+}
+#else
+  #define codeTableLocks(x)
+#endif
+
+/*
+** This routine is called after a single SQL statement has been
+** parsed and a VDBE program to execute that statement has been
+** prepared.  This routine puts the finishing touches on the
+** VDBE program and resets the pParse structure for the next
+** parse.
+**
+** Note that if an error occurred, it might be the case that
+** no VDBE code was generated.
+*/
+void sqlite3FinishCoding(Parse *pParse){
+  sqlite3 *db;
+  Vdbe *v;
+
+  db = pParse->db;
+  if( db->mallocFailed ) return;
+  if( pParse->nested ) return;
+  if( pParse->nErr ) return;
+
+  /* Begin by generating some termination code at the end of the
+  ** vdbe program
+  */
+  v = sqlite3GetVdbe(pParse);
+  assert( !pParse->isMultiWrite 
+       || sqlite3VdbeAssertMayAbort(v, pParse->mayAbort));
+  if( v ){
+    sqlite3VdbeAddOp0(v, OP_Halt);
+
+    /* The cookie mask contains one bit for each database file open.
+    ** (Bit 0 is for main, bit 1 is for temp, and so forth.)  Bits are
+    ** set for each database that is used.  Generate code to start a
+    ** transaction on each used database and to verify the schema cookie
+    ** on each used database.
+    */
+    if( pParse->cookieGoto>0 ){
+      yDbMask mask;
+      int iDb;
+      sqlite3VdbeJumpHere(v, pParse->cookieGoto-1);
+      for(iDb=0, mask=1; iDb<db->nDb; mask<<=1, iDb++){
+        if( (mask & pParse->cookieMask)==0 ) continue;
+        sqlite3VdbeUsesBtree(v, iDb);
+        sqlite3VdbeAddOp2(v,OP_Transaction, iDb, (mask & pParse->writeMask)!=0);
+        if( db->init.busy==0 ){
+          assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+          sqlite3VdbeAddOp3(v, OP_VerifyCookie,
+                            iDb, pParse->cookieValue[iDb],
+                            db->aDb[iDb].pSchema->iGeneration);
+        }
+      }
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+      {
+        int i;
+        for(i=0; i<pParse->nVtabLock; i++){
+          char *vtab = (char *)sqlite3GetVTable(db, pParse->apVtabLock[i]);
+          sqlite3VdbeAddOp4(v, OP_VBegin, 0, 0, 0, vtab, P4_VTAB);
+        }
+        pParse->nVtabLock = 0;
+      }
+#endif
+
+      /* Once all the cookies have been verified and transactions opened, 
+      ** obtain the required table-locks. This is a no-op unless the 
+      ** shared-cache feature is enabled.
+      */
+      codeTableLocks(pParse);
+
+      /* Initialize any AUTOINCREMENT data structures required.
+      */
+      sqlite3AutoincrementBegin(pParse);
+
+      /* Finally, jump back to the beginning of the executable code. */
+      sqlite3VdbeAddOp2(v, OP_Goto, 0, pParse->cookieGoto);
+    }
+  }
+
+
+  /* Get the VDBE program ready for execution
+  */
+  if( v && ALWAYS(pParse->nErr==0) && !db->mallocFailed ){
+#ifdef SQLITE_DEBUG
+    FILE *trace = (db->flags & SQLITE_VdbeTrace)!=0 ? stdout : 0;
+    sqlite3VdbeTrace(v, trace);
+#endif
+    assert( pParse->iCacheLevel==0 );  /* Disables and re-enables match */
+    /* A minimum of one cursor is required if autoincrement is used
+    *  See ticket [a696379c1f08866] */
+    if( pParse->pAinc!=0 && pParse->nTab==0 ) pParse->nTab = 1;
+    sqlite3VdbeMakeReady(v, pParse);
+    pParse->rc = SQLITE_DONE;
+    pParse->colNamesSet = 0;
+  }else{
+    pParse->rc = SQLITE_ERROR;
+  }
+  pParse->nTab = 0;
+  pParse->nMem = 0;
+  pParse->nSet = 0;
+  pParse->nVar = 0;
+  pParse->cookieMask = 0;
+  pParse->cookieGoto = 0;
+}
+
+/*
+** Run the parser and code generator recursively in order to generate
+** code for the SQL statement given onto the end of the pParse context
+** currently under construction.  When the parser is run recursively
+** this way, the final OP_Halt is not appended and other initialization
+** and finalization steps are omitted because those are handling by the
+** outermost parser.
+**
+** Not everything is nestable.  This facility is designed to permit
+** INSERT, UPDATE, and DELETE operations against SQLITE_MASTER.  Use
+** care if you decide to try to use this routine for some other purposes.
+*/
+void sqlite3NestedParse(Parse *pParse, const char *zFormat, ...){
+  va_list ap;
+  char *zSql;
+  char *zErrMsg = 0;
+  sqlite3 *db = pParse->db;
+# define SAVE_SZ  (sizeof(Parse) - offsetof(Parse,nVar))
+  char saveBuf[SAVE_SZ];
+
+  if( pParse->nErr ) return;
+  assert( pParse->nested<10 );  /* Nesting should only be of limited depth */
+  va_start(ap, zFormat);
+  zSql = sqlite3VMPrintf(db, zFormat, ap);
+  va_end(ap);
+  if( zSql==0 ){
+    return;   /* A malloc must have failed */
+  }
+  pParse->nested++;
+  memcpy(saveBuf, &pParse->nVar, SAVE_SZ);
+  memset(&pParse->nVar, 0, SAVE_SZ);
+  sqlite3RunParser(pParse, zSql, &zErrMsg);
+  sqlite3DbFree(db, zErrMsg);
+  sqlite3DbFree(db, zSql);
+  memcpy(&pParse->nVar, saveBuf, SAVE_SZ);
+  pParse->nested--;
+}
+
+/*
+** Locate the in-memory structure that describes a particular database
+** table given the name of that table and (optionally) the name of the
+** database containing the table.  Return NULL if not found.
+**
+** If zDatabase is 0, all databases are searched for the table and the
+** first matching table is returned.  (No checking for duplicate table
+** names is done.)  The search order is TEMP first, then MAIN, then any
+** auxiliary databases added using the ATTACH command.
+**
+** See also sqlite3LocateTable().
+*/
+Table *sqlite3FindTable(sqlite3 *db, const char *zName, const char *zDatabase){
+  Table *p = 0;
+  int i;
+  int nName;
+  assert( zName!=0 );
+  nName = sqlite3Strlen30(zName);
+  /* All mutexes are required for schema access.  Make sure we hold them. */
+  assert( zDatabase!=0 || sqlite3BtreeHoldsAllMutexes(db) );
+  for(i=OMIT_TEMPDB; i<db->nDb; i++){
+    int j = (i<2) ? i^1 : i;   /* Search TEMP before MAIN */
+    if( zDatabase!=0 && sqlite3StrICmp(zDatabase, db->aDb[j].zName) ) continue;
+    assert( sqlite3SchemaMutexHeld(db, j, 0) );
+    p = sqlite3HashFind(&db->aDb[j].pSchema->tblHash, zName, nName);
+    if( p ) break;
+  }
+  return p;
+}
+
+/*
+** Locate the in-memory structure that describes a particular database
+** table given the name of that table and (optionally) the name of the
+** database containing the table.  Return NULL if not found.  Also leave an
+** error message in pParse->zErrMsg.
+**
+** The difference between this routine and sqlite3FindTable() is that this
+** routine leaves an error message in pParse->zErrMsg where
+** sqlite3FindTable() does not.
+*/
+Table *sqlite3LocateTable(
+  Parse *pParse,         /* context in which to report errors */
+  int isView,            /* True if looking for a VIEW rather than a TABLE */
+  const char *zName,     /* Name of the table we are looking for */
+  const char *zDbase     /* Name of the database.  Might be NULL */
+){
+  Table *p;
+
+  /* Read the database schema. If an error occurs, leave an error message
+  ** and code in pParse and return NULL. */
+  if( SQLITE_OK!=sqlite3ReadSchema(pParse) ){
+    return 0;
+  }
+
+  p = sqlite3FindTable(pParse->db, zName, zDbase);
+  if( p==0 ){
+    const char *zMsg = isView ? "no such view" : "no such table";
+    if( zDbase ){
+      sqlite3ErrorMsg(pParse, "%s: %s.%s", zMsg, zDbase, zName);
+    }else{
+      sqlite3ErrorMsg(pParse, "%s: %s", zMsg, zName);
+    }
+    pParse->checkSchema = 1;
+  }
+  return p;
+}
+
+/*
+** Locate the in-memory structure that describes 
+** a particular index given the name of that index
+** and the name of the database that contains the index.
+** Return NULL if not found.
+**
+** If zDatabase is 0, all databases are searched for the
+** table and the first matching index is returned.  (No checking
+** for duplicate index names is done.)  The search order is
+** TEMP first, then MAIN, then any auxiliary databases added
+** using the ATTACH command.
+*/
+Index *sqlite3FindIndex(sqlite3 *db, const char *zName, const char *zDb){
+  Index *p = 0;
+  int i;
+  int nName = sqlite3Strlen30(zName);
+  /* All mutexes are required for schema access.  Make sure we hold them. */
+  assert( zDb!=0 || sqlite3BtreeHoldsAllMutexes(db) );
+  for(i=OMIT_TEMPDB; i<db->nDb; i++){
+    int j = (i<2) ? i^1 : i;  /* Search TEMP before MAIN */
+    Schema *pSchema = db->aDb[j].pSchema;
+    assert( pSchema );
+    if( zDb && sqlite3StrICmp(zDb, db->aDb[j].zName) ) continue;
+    assert( sqlite3SchemaMutexHeld(db, j, 0) );
+    p = sqlite3HashFind(&pSchema->idxHash, zName, nName);
+    if( p ) break;
+  }
+  return p;
+}
+
+/*
+** Reclaim the memory used by an index
+*/
+static void freeIndex(sqlite3 *db, Index *p){
+#ifndef SQLITE_OMIT_ANALYZE
+  sqlite3DeleteIndexSamples(db, p);
+#endif
+  sqlite3DbFree(db, p->zColAff);
+  sqlite3DbFree(db, p);
+}
+
+/*
+** For the index called zIdxName which is found in the database iDb,
+** unlike that index from its Table then remove the index from
+** the index hash table and free all memory structures associated
+** with the index.
+*/
+void sqlite3UnlinkAndDeleteIndex(sqlite3 *db, int iDb, const char *zIdxName){
+  Index *pIndex;
+  int len;
+  Hash *pHash;
+
+  assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+  pHash = &db->aDb[iDb].pSchema->idxHash;
+  len = sqlite3Strlen30(zIdxName);
+  pIndex = sqlite3HashInsert(pHash, zIdxName, len, 0);
+  if( ALWAYS(pIndex) ){
+    if( pIndex->pTable->pIndex==pIndex ){
+      pIndex->pTable->pIndex = pIndex->pNext;
+    }else{
+      Index *p;
+      /* Justification of ALWAYS();  The index must be on the list of
+      ** indices. */
+      p = pIndex->pTable->pIndex;
+      while( ALWAYS(p) && p->pNext!=pIndex ){ p = p->pNext; }
+      if( ALWAYS(p && p->pNext==pIndex) ){
+        p->pNext = pIndex->pNext;
+      }
+    }
+    freeIndex(db, pIndex);
+  }
+  db->flags |= SQLITE_InternChanges;
+}
+
+/*
+** Erase all schema information from the in-memory hash tables of
+** a single database.  This routine is called to reclaim memory
+** before the database closes.  It is also called during a rollback
+** if there were schema changes during the transaction or if a
+** schema-cookie mismatch occurs.
+**
+** If iDb<0 then reset the internal schema tables for all database
+** files.  If iDb>=0 then reset the internal schema for only the
+** single file indicated.
+*/
+void sqlite3ResetInternalSchema(sqlite3 *db, int iDb){
+  int i, j;
+  assert( iDb<db->nDb );
+
+  if( iDb>=0 ){
+    /* Case 1:  Reset the single schema identified by iDb */
+    Db *pDb = &db->aDb[iDb];
+    assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+    assert( pDb->pSchema!=0 );
+    sqlite3SchemaClear(pDb->pSchema);
+
+    /* If any database other than TEMP is reset, then also reset TEMP
+    ** since TEMP might be holding triggers that reference tables in the
+    ** other database.
+    */
+    if( iDb!=1 ){
+      pDb = &db->aDb[1];
+      assert( pDb->pSchema!=0 );
+      sqlite3SchemaClear(pDb->pSchema);
+    }
+    return;
+  }
+  /* Case 2 (from here to the end): Reset all schemas for all attached
+  ** databases. */
+  assert( iDb<0 );
+  sqlite3BtreeEnterAll(db);
+  for(i=0; i<db->nDb; i++){
+    Db *pDb = &db->aDb[i];
+    if( pDb->pSchema ){
+      sqlite3SchemaClear(pDb->pSchema);
+    }
+  }
+  db->flags &= ~SQLITE_InternChanges;
+  sqlite3VtabUnlockList(db);
+  sqlite3BtreeLeaveAll(db);
+
+  /* If one or more of the auxiliary database files has been closed,
+  ** then remove them from the auxiliary database list.  We take the
+  ** opportunity to do this here since we have just deleted all of the
+  ** schema hash tables and therefore do not have to make any changes
+  ** to any of those tables.
+  */
+  for(i=j=2; i<db->nDb; i++){
+    struct Db *pDb = &db->aDb[i];
+    if( pDb->pBt==0 ){
+      sqlite3DbFree(db, pDb->zName);
+      pDb->zName = 0;
+      continue;
+    }
+    if( j<i ){
+      db->aDb[j] = db->aDb[i];
+    }
+    j++;
+  }
+  memset(&db->aDb[j], 0, (db->nDb-j)*sizeof(db->aDb[j]));
+  db->nDb = j;
+  if( db->nDb<=2 && db->aDb!=db->aDbStatic ){
+    memcpy(db->aDbStatic, db->aDb, 2*sizeof(db->aDb[0]));
+    sqlite3DbFree(db, db->aDb);
+    db->aDb = db->aDbStatic;
+  }
+}
+
+/*
+** This routine is called when a commit occurs.
+*/
+void sqlite3CommitInternalChanges(sqlite3 *db){
+  db->flags &= ~SQLITE_InternChanges;
+}
+
+/*
+** Delete memory allocated for the column names of a table or view (the
+** Table.aCol[] array).
+*/
+static void sqliteDeleteColumnNames(sqlite3 *db, Table *pTable){
+  int i;
+  Column *pCol;
+  assert( pTable!=0 );
+  if( (pCol = pTable->aCol)!=0 ){
+    for(i=0; i<pTable->nCol; i++, pCol++){
+      sqlite3DbFree(db, pCol->zName);
+      sqlite3ExprDelete(db, pCol->pDflt);
+      sqlite3DbFree(db, pCol->zDflt);
+      sqlite3DbFree(db, pCol->zType);
+      sqlite3DbFree(db, pCol->zColl);
+    }
+    sqlite3DbFree(db, pTable->aCol);
+  }
+}
+
+/*
+** Remove the memory data structures associated with the given
+** Table.  No changes are made to disk by this routine.
+**
+** This routine just deletes the data structure.  It does not unlink
+** the table data structure from the hash table.  But it does destroy
+** memory structures of the indices and foreign keys associated with 
+** the table.
+*/
+void sqlite3DeleteTable(sqlite3 *db, Table *pTable){
+  Index *pIndex, *pNext;
+
+  assert( !pTable || pTable->nRef>0 );
+
+  /* Do not delete the table until the reference count reaches zero. */
+  if( !pTable ) return;
+  if( ((!db || db->pnBytesFreed==0) && (--pTable->nRef)>0) ) return;
+
+  /* Delete all indices associated with this table. */
+  for(pIndex = pTable->pIndex; pIndex; pIndex=pNext){
+    pNext = pIndex->pNext;
+    assert( pIndex->pSchema==pTable->pSchema );
+    if( !db || db->pnBytesFreed==0 ){
+      char *zName = pIndex->zName; 
+      TESTONLY ( Index *pOld = ) sqlite3HashInsert(
+	  &pIndex->pSchema->idxHash, zName, sqlite3Strlen30(zName), 0
+      );
+      assert( db==0 || sqlite3SchemaMutexHeld(db, 0, pIndex->pSchema) );
+      assert( pOld==pIndex || pOld==0 );
+    }
+    freeIndex(db, pIndex);
+  }
+
+  /* Delete any foreign keys attached to this table. */
+  sqlite3FkDelete(db, pTable);
+
+  /* Delete the Table structure itself.
+  */
+  sqliteDeleteColumnNames(db, pTable);
+  sqlite3DbFree(db, pTable->zName);
+  sqlite3DbFree(db, pTable->zColAff);
+  sqlite3SelectDelete(db, pTable->pSelect);
+#ifndef SQLITE_OMIT_CHECK
+  sqlite3ExprDelete(db, pTable->pCheck);
+#endif
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  sqlite3VtabClear(db, pTable);
+#endif
+  sqlite3DbFree(db, pTable);
+}
+
+/*
+** Unlink the given table from the hash tables and the delete the
+** table structure with all its indices and foreign keys.
+*/
+void sqlite3UnlinkAndDeleteTable(sqlite3 *db, int iDb, const char *zTabName){
+  Table *p;
+  Db *pDb;
+
+  assert( db!=0 );
+  assert( iDb>=0 && iDb<db->nDb );
+  assert( zTabName );
+  assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+  testcase( zTabName[0]==0 );  /* Zero-length table names are allowed */
+  pDb = &db->aDb[iDb];
+  p = sqlite3HashInsert(&pDb->pSchema->tblHash, zTabName,
+                        sqlite3Strlen30(zTabName),0);
+  sqlite3DeleteTable(db, p);
+  db->flags |= SQLITE_InternChanges;
+}
+
+/*
+** Given a token, return a string that consists of the text of that
+** token.  Space to hold the returned string
+** is obtained from sqliteMalloc() and must be freed by the calling
+** function.
+**
+** Any quotation marks (ex:  "name", 'name', [name], or `name`) that
+** surround the body of the token are removed.
+**
+** Tokens are often just pointers into the original SQL text and so
+** are not \000 terminated and are not persistent.  The returned string
+** is \000 terminated and is persistent.
+*/
+char *sqlite3NameFromToken(sqlite3 *db, Token *pName){
+  char *zName;
+  if( pName ){
+    zName = sqlite3DbStrNDup(db, (char*)pName->z, pName->n);
+    sqlite3Dequote(zName);
+  }else{
+    zName = 0;
+  }
+  return zName;
+}
+
+/*
+** Open the sqlite_master table stored in database number iDb for
+** writing. The table is opened using cursor 0.
+*/
+void sqlite3OpenMasterTable(Parse *p, int iDb){
+  Vdbe *v = sqlite3GetVdbe(p);
+  sqlite3TableLock(p, iDb, MASTER_ROOT, 1, SCHEMA_TABLE(iDb));
+  sqlite3VdbeAddOp3(v, OP_OpenWrite, 0, MASTER_ROOT, iDb);
+  sqlite3VdbeChangeP4(v, -1, (char *)5, P4_INT32);  /* 5 column table */
+  if( p->nTab==0 ){
+    p->nTab = 1;
+  }
+}
+
+/*
+** Parameter zName points to a nul-terminated buffer containing the name
+** of a database ("main", "temp" or the name of an attached db). This
+** function returns the index of the named database in db->aDb[], or
+** -1 if the named db cannot be found.
+*/
+int sqlite3FindDbName(sqlite3 *db, const char *zName){
+  int i = -1;         /* Database number */
+  if( zName ){
+    Db *pDb;
+    int n = sqlite3Strlen30(zName);
+    for(i=(db->nDb-1), pDb=&db->aDb[i]; i>=0; i--, pDb--){
+      if( (!OMIT_TEMPDB || i!=1 ) && n==sqlite3Strlen30(pDb->zName) && 
+          0==sqlite3StrICmp(pDb->zName, zName) ){
+        break;
+      }
+    }
+  }
+  return i;
+}
+
+/*
+** The token *pName contains the name of a database (either "main" or
+** "temp" or the name of an attached db). This routine returns the
+** index of the named database in db->aDb[], or -1 if the named db 
+** does not exist.
+*/
+int sqlite3FindDb(sqlite3 *db, Token *pName){
+  int i;                               /* Database number */
+  char *zName;                         /* Name we are searching for */
+  zName = sqlite3NameFromToken(db, pName);
+  i = sqlite3FindDbName(db, zName);
+  sqlite3DbFree(db, zName);
+  return i;
+}
+
+/* The table or view or trigger name is passed to this routine via tokens
+** pName1 and pName2. If the table name was fully qualified, for example:
+**
+** CREATE TABLE xxx.yyy (...);
+** 
+** Then pName1 is set to "xxx" and pName2 "yyy". On the other hand if
+** the table name is not fully qualified, i.e.:
+**
+** CREATE TABLE yyy(...);
+**
+** Then pName1 is set to "yyy" and pName2 is "".
+**
+** This routine sets the *ppUnqual pointer to point at the token (pName1 or
+** pName2) that stores the unqualified table name.  The index of the
+** database "xxx" is returned.
+*/
+int sqlite3TwoPartName(
+  Parse *pParse,      /* Parsing and code generating context */
+  Token *pName1,      /* The "xxx" in the name "xxx.yyy" or "xxx" */
+  Token *pName2,      /* The "yyy" in the name "xxx.yyy" */
+  Token **pUnqual     /* Write the unqualified object name here */
+){
+  int iDb;                    /* Database holding the object */
+  sqlite3 *db = pParse->db;
+
+  if( ALWAYS(pName2!=0) && pName2->n>0 ){
+    if( db->init.busy ) {
+      sqlite3ErrorMsg(pParse, "corrupt database");
+      pParse->nErr++;
+      return -1;
+    }
+    *pUnqual = pName2;
+    iDb = sqlite3FindDb(db, pName1);
+    if( iDb<0 ){
+      sqlite3ErrorMsg(pParse, "unknown database %T", pName1);
+      pParse->nErr++;
+      return -1;
+    }
+  }else{
+    assert( db->init.iDb==0 || db->init.busy );
+    iDb = db->init.iDb;
+    *pUnqual = pName1;
+  }
+  return iDb;
+}
+
+/*
+** This routine is used to check if the UTF-8 string zName is a legal
+** unqualified name for a new schema object (table, index, view or
+** trigger). All names are legal except those that begin with the string
+** "sqlite_" (in upper, lower or mixed case). This portion of the namespace
+** is reserved for internal use.
+*/
+int sqlite3CheckObjectName(Parse *pParse, const char *zName){
+  if( !pParse->db->init.busy && pParse->nested==0 
+          && (pParse->db->flags & SQLITE_WriteSchema)==0
+          && 0==sqlite3StrNICmp(zName, "sqlite_", 7) ){
+    sqlite3ErrorMsg(pParse, "object name reserved for internal use: %s", zName);
+    return SQLITE_ERROR;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Begin constructing a new table representation in memory.  This is
+** the first of several action routines that get called in response
+** to a CREATE TABLE statement.  In particular, this routine is called
+** after seeing tokens "CREATE" and "TABLE" and the table name. The isTemp
+** flag is true if the table should be stored in the auxiliary database
+** file instead of in the main database file.  This is normally the case
+** when the "TEMP" or "TEMPORARY" keyword occurs in between
+** CREATE and TABLE.
+**
+** The new table record is initialized and put in pParse->pNewTable.
+** As more of the CREATE TABLE statement is parsed, additional action
+** routines will be called to add more information to this record.
+** At the end of the CREATE TABLE statement, the sqlite3EndTable() routine
+** is called to complete the construction of the new table record.
+*/
+void sqlite3StartTable(
+  Parse *pParse,   /* Parser context */
+  Token *pName1,   /* First part of the name of the table or view */
+  Token *pName2,   /* Second part of the name of the table or view */
+  int isTemp,      /* True if this is a TEMP table */
+  int isView,      /* True if this is a VIEW */
+  int isVirtual,   /* True if this is a VIRTUAL table */
+  int noErr        /* Do nothing if table already exists */
+){
+  Table *pTable;
+  char *zName = 0; /* The name of the new table */
+  sqlite3 *db = pParse->db;
+  Vdbe *v;
+  int iDb;         /* Database number to create the table in */
+  Token *pName;    /* Unqualified name of the table to create */
+
+  /* The table or view name to create is passed to this routine via tokens
+  ** pName1 and pName2. If the table name was fully qualified, for example:
+  **
+  ** CREATE TABLE xxx.yyy (...);
+  ** 
+  ** Then pName1 is set to "xxx" and pName2 "yyy". On the other hand if
+  ** the table name is not fully qualified, i.e.:
+  **
+  ** CREATE TABLE yyy(...);
+  **
+  ** Then pName1 is set to "yyy" and pName2 is "".
+  **
+  ** The call below sets the pName pointer to point at the token (pName1 or
+  ** pName2) that stores the unqualified table name. The variable iDb is
+  ** set to the index of the database that the table or view is to be
+  ** created in.
+  */
+  iDb = sqlite3TwoPartName(pParse, pName1, pName2, &pName);
+  if( iDb<0 ) return;
+  if( !OMIT_TEMPDB && isTemp && pName2->n>0 && iDb!=1 ){
+    /* If creating a temp table, the name may not be qualified. Unless 
+    ** the database name is "temp" anyway.  */
+    sqlite3ErrorMsg(pParse, "temporary table name must be unqualified");
+    return;
+  }
+  if( !OMIT_TEMPDB && isTemp ) iDb = 1;
+
+  pParse->sNameToken = *pName;
+  zName = sqlite3NameFromToken(db, pName);
+  if( zName==0 ) return;
+  if( SQLITE_OK!=sqlite3CheckObjectName(pParse, zName) ){
+    goto begin_table_error;
+  }
+  if( db->init.iDb==1 ) isTemp = 1;
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  assert( (isTemp & 1)==isTemp );
+  {
+    int code;
+    char *zDb = db->aDb[iDb].zName;
+    if( sqlite3AuthCheck(pParse, SQLITE_INSERT, SCHEMA_TABLE(isTemp), 0, zDb) ){
+      goto begin_table_error;
+    }
+    if( isView ){
+      if( !OMIT_TEMPDB && isTemp ){
+        code = SQLITE_CREATE_TEMP_VIEW;
+      }else{
+        code = SQLITE_CREATE_VIEW;
+      }
+    }else{
+      if( !OMIT_TEMPDB && isTemp ){
+        code = SQLITE_CREATE_TEMP_TABLE;
+      }else{
+        code = SQLITE_CREATE_TABLE;
+      }
+    }
+    if( !isVirtual && sqlite3AuthCheck(pParse, code, zName, 0, zDb) ){
+      goto begin_table_error;
+    }
+  }
+#endif
+
+  /* Make sure the new table name does not collide with an existing
+  ** index or table name in the same database.  Issue an error message if
+  ** it does. The exception is if the statement being parsed was passed
+  ** to an sqlite3_declare_vtab() call. In that case only the column names
+  ** and types will be used, so there is no need to test for namespace
+  ** collisions.
+  */
+  if( !IN_DECLARE_VTAB ){
+    char *zDb = db->aDb[iDb].zName;
+    if( SQLITE_OK!=sqlite3ReadSchema(pParse) ){
+      goto begin_table_error;
+    }
+    pTable = sqlite3FindTable(db, zName, zDb);
+    if( pTable ){
+      if( !noErr ){
+        sqlite3ErrorMsg(pParse, "table %T already exists", pName);
+      }else{
+        assert( !db->init.busy );
+        sqlite3CodeVerifySchema(pParse, iDb);
+      }
+      goto begin_table_error;
+    }
+    if( sqlite3FindIndex(db, zName, zDb)!=0 ){
+      sqlite3ErrorMsg(pParse, "there is already an index named %s", zName);
+      goto begin_table_error;
+    }
+  }
+
+  pTable = sqlite3DbMallocZero(db, sizeof(Table));
+  if( pTable==0 ){
+    db->mallocFailed = 1;
+    pParse->rc = SQLITE_NOMEM;
+    pParse->nErr++;
+    goto begin_table_error;
+  }
+  pTable->zName = zName;
+  pTable->iPKey = -1;
+  pTable->pSchema = db->aDb[iDb].pSchema;
+  pTable->nRef = 1;
+  pTable->nRowEst = 1000000;
+  assert( pParse->pNewTable==0 );
+  pParse->pNewTable = pTable;
+
+  /* If this is the magic sqlite_sequence table used by autoincrement,
+  ** then record a pointer to this table in the main database structure
+  ** so that INSERT can find the table easily.
+  */
+#ifndef SQLITE_OMIT_AUTOINCREMENT
+  if( !pParse->nested && strcmp(zName, "sqlite_sequence")==0 ){
+    assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+    pTable->pSchema->pSeqTab = pTable;
+  }
+#endif
+
+  /* Begin generating the code that will insert the table record into
+  ** the SQLITE_MASTER table.  Note in particular that we must go ahead
+  ** and allocate the record number for the table entry now.  Before any
+  ** PRIMARY KEY or UNIQUE keywords are parsed.  Those keywords will cause
+  ** indices to be created and the table record must come before the 
+  ** indices.  Hence, the record number for the table must be allocated
+  ** now.
+  */
+  if( !db->init.busy && (v = sqlite3GetVdbe(pParse))!=0 ){
+    int j1;
+    int fileFormat;
+    int reg1, reg2, reg3;
+    sqlite3BeginWriteOperation(pParse, 0, iDb);
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+    if( isVirtual ){
+      sqlite3VdbeAddOp0(v, OP_VBegin);
+    }
+#endif
+
+    /* If the file format and encoding in the database have not been set, 
+    ** set them now.
+    */
+    reg1 = pParse->regRowid = ++pParse->nMem;
+    reg2 = pParse->regRoot = ++pParse->nMem;
+    reg3 = ++pParse->nMem;
+    sqlite3VdbeAddOp3(v, OP_ReadCookie, iDb, reg3, BTREE_FILE_FORMAT);
+    sqlite3VdbeUsesBtree(v, iDb);
+    j1 = sqlite3VdbeAddOp1(v, OP_If, reg3);
+    fileFormat = (db->flags & SQLITE_LegacyFileFmt)!=0 ?
+                  1 : SQLITE_MAX_FILE_FORMAT;
+    sqlite3VdbeAddOp2(v, OP_Integer, fileFormat, reg3);
+    sqlite3VdbeAddOp3(v, OP_SetCookie, iDb, BTREE_FILE_FORMAT, reg3);
+    sqlite3VdbeAddOp2(v, OP_Integer, ENC(db), reg3);
+    sqlite3VdbeAddOp3(v, OP_SetCookie, iDb, BTREE_TEXT_ENCODING, reg3);
+    sqlite3VdbeJumpHere(v, j1);
+
+    /* This just creates a place-holder record in the sqlite_master table.
+    ** The record created does not contain anything yet.  It will be replaced
+    ** by the real entry in code generated at sqlite3EndTable().
+    **
+    ** The rowid for the new entry is left in register pParse->regRowid.
+    ** The root page number of the new table is left in reg pParse->regRoot.
+    ** The rowid and root page number values are needed by the code that
+    ** sqlite3EndTable will generate.
+    */
+#if !defined(SQLITE_OMIT_VIEW) || !defined(SQLITE_OMIT_VIRTUALTABLE)
+    if( isView || isVirtual ){
+      sqlite3VdbeAddOp2(v, OP_Integer, 0, reg2);
+    }else
+#endif
+    {
+      sqlite3VdbeAddOp2(v, OP_CreateTable, iDb, reg2);
+    }
+    sqlite3OpenMasterTable(pParse, iDb);
+    sqlite3VdbeAddOp2(v, OP_NewRowid, 0, reg1);
+    sqlite3VdbeAddOp2(v, OP_Null, 0, reg3);
+    sqlite3VdbeAddOp3(v, OP_Insert, 0, reg3, reg1);
+    sqlite3VdbeChangeP5(v, OPFLAG_APPEND);
+    sqlite3VdbeAddOp0(v, OP_Close);
+  }
+
+  /* Normal (non-error) return. */
+  return;
+
+  /* If an error occurs, we jump here */
+begin_table_error:
+  sqlite3DbFree(db, zName);
+  return;
+}
+
+/*
+** This macro is used to compare two strings in a case-insensitive manner.
+** It is slightly faster than calling sqlite3StrICmp() directly, but
+** produces larger code.
+**
+** WARNING: This macro is not compatible with the strcmp() family. It
+** returns true if the two strings are equal, otherwise false.
+*/
+#define STRICMP(x, y) (\
+sqlite3UpperToLower[*(unsigned char *)(x)]==   \
+sqlite3UpperToLower[*(unsigned char *)(y)]     \
+&& sqlite3StrICmp((x)+1,(y)+1)==0 )
+
+/*
+** Add a new column to the table currently being constructed.
+**
+** The parser calls this routine once for each column declaration
+** in a CREATE TABLE statement.  sqlite3StartTable() gets called
+** first to get things going.  Then this routine is called for each
+** column.
+*/
+void sqlite3AddColumn(Parse *pParse, Token *pName){
+  Table *p;
+  int i;
+  char *z;
+  Column *pCol;
+  sqlite3 *db = pParse->db;
+  if( (p = pParse->pNewTable)==0 ) return;
+#if SQLITE_MAX_COLUMN
+  if( p->nCol+1>db->aLimit[SQLITE_LIMIT_COLUMN] ){
+    sqlite3ErrorMsg(pParse, "too many columns on %s", p->zName);
+    return;
+  }
+#endif
+  z = sqlite3NameFromToken(db, pName);
+  if( z==0 ) return;
+  for(i=0; i<p->nCol; i++){
+    if( STRICMP(z, p->aCol[i].zName) ){
+      sqlite3ErrorMsg(pParse, "duplicate column name: %s", z);
+      sqlite3DbFree(db, z);
+      return;
+    }
+  }
+  if( (p->nCol & 0x7)==0 ){
+    Column *aNew;
+    aNew = sqlite3DbRealloc(db,p->aCol,(p->nCol+8)*sizeof(p->aCol[0]));
+    if( aNew==0 ){
+      sqlite3DbFree(db, z);
+      return;
+    }
+    p->aCol = aNew;
+  }
+  pCol = &p->aCol[p->nCol];
+  memset(pCol, 0, sizeof(p->aCol[0]));
+  pCol->zName = z;
+ 
+  /* If there is no type specified, columns have the default affinity
+  ** 'NONE'. If there is a type specified, then sqlite3AddColumnType() will
+  ** be called next to set pCol->affinity correctly.
+  */
+  pCol->affinity = SQLITE_AFF_NONE;
+  p->nCol++;
+}
+
+/*
+** This routine is called by the parser while in the middle of
+** parsing a CREATE TABLE statement.  A "NOT NULL" constraint has
+** been seen on a column.  This routine sets the notNull flag on
+** the column currently under construction.
+*/
+void sqlite3AddNotNull(Parse *pParse, int onError){
+  Table *p;
+  p = pParse->pNewTable;
+  if( p==0 || NEVER(p->nCol<1) ) return;
+  p->aCol[p->nCol-1].notNull = (u8)onError;
+}
+
+/*
+** Scan the column type name zType (length nType) and return the
+** associated affinity type.
+**
+** This routine does a case-independent search of zType for the 
+** substrings in the following table. If one of the substrings is
+** found, the corresponding affinity is returned. If zType contains
+** more than one of the substrings, entries toward the top of 
+** the table take priority. For example, if zType is 'BLOBINT', 
+** SQLITE_AFF_INTEGER is returned.
+**
+** Substring     | Affinity
+** --------------------------------
+** 'INT'         | SQLITE_AFF_INTEGER
+** 'CHAR'        | SQLITE_AFF_TEXT
+** 'CLOB'        | SQLITE_AFF_TEXT
+** 'TEXT'        | SQLITE_AFF_TEXT
+** 'BLOB'        | SQLITE_AFF_NONE
+** 'REAL'        | SQLITE_AFF_REAL
+** 'FLOA'        | SQLITE_AFF_REAL
+** 'DOUB'        | SQLITE_AFF_REAL
+**
+** If none of the substrings in the above table are found,
+** SQLITE_AFF_NUMERIC is returned.
+*/
+char sqlite3AffinityType(const char *zIn){
+  u32 h = 0;
+  char aff = SQLITE_AFF_NUMERIC;
+
+  if( zIn ) while( zIn[0] ){
+    h = (h<<8) + sqlite3UpperToLower[(*zIn)&0xff];
+    zIn++;
+    if( h==(('c'<<24)+('h'<<16)+('a'<<8)+'r') ){             /* CHAR */
+      aff = SQLITE_AFF_TEXT; 
+    }else if( h==(('c'<<24)+('l'<<16)+('o'<<8)+'b') ){       /* CLOB */
+      aff = SQLITE_AFF_TEXT;
+    }else if( h==(('t'<<24)+('e'<<16)+('x'<<8)+'t') ){       /* TEXT */
+      aff = SQLITE_AFF_TEXT;
+    }else if( h==(('b'<<24)+('l'<<16)+('o'<<8)+'b')          /* BLOB */
+        && (aff==SQLITE_AFF_NUMERIC || aff==SQLITE_AFF_REAL) ){
+      aff = SQLITE_AFF_NONE;
+#ifndef SQLITE_OMIT_FLOATING_POINT
+    }else if( h==(('r'<<24)+('e'<<16)+('a'<<8)+'l')          /* REAL */
+        && aff==SQLITE_AFF_NUMERIC ){
+      aff = SQLITE_AFF_REAL;
+    }else if( h==(('f'<<24)+('l'<<16)+('o'<<8)+'a')          /* FLOA */
+        && aff==SQLITE_AFF_NUMERIC ){
+      aff = SQLITE_AFF_REAL;
+    }else if( h==(('d'<<24)+('o'<<16)+('u'<<8)+'b')          /* DOUB */
+        && aff==SQLITE_AFF_NUMERIC ){
+      aff = SQLITE_AFF_REAL;
+#endif
+    }else if( (h&0x00FFFFFF)==(('i'<<16)+('n'<<8)+'t') ){    /* INT */
+      aff = SQLITE_AFF_INTEGER;
+      break;
+    }
+  }
+
+  return aff;
+}
+
+/*
+** This routine is called by the parser while in the middle of
+** parsing a CREATE TABLE statement.  The pFirst token is the first
+** token in the sequence of tokens that describe the type of the
+** column currently under construction.   pLast is the last token
+** in the sequence.  Use this information to construct a string
+** that contains the typename of the column and store that string
+** in zType.
+*/ 
+void sqlite3AddColumnType(Parse *pParse, Token *pType){
+  Table *p;
+  Column *pCol;
+
+  p = pParse->pNewTable;
+  if( p==0 || NEVER(p->nCol<1) ) return;
+  pCol = &p->aCol[p->nCol-1];
+  assert( pCol->zType==0 );
+  pCol->zType = sqlite3NameFromToken(pParse->db, pType);
+  pCol->affinity = sqlite3AffinityType(pCol->zType);
+}
+
+/*
+** The expression is the default value for the most recently added column
+** of the table currently under construction.
+**
+** Default value expressions must be constant.  Raise an exception if this
+** is not the case.
+**
+** This routine is called by the parser while in the middle of
+** parsing a CREATE TABLE statement.
+*/
+void sqlite3AddDefaultValue(Parse *pParse, ExprSpan *pSpan){
+  Table *p;
+  Column *pCol;
+  sqlite3 *db = pParse->db;
+  p = pParse->pNewTable;
+  if( p!=0 ){
+    pCol = &(p->aCol[p->nCol-1]);
+    if( !sqlite3ExprIsConstantOrFunction(pSpan->pExpr) ){
+      sqlite3ErrorMsg(pParse, "default value of column [%s] is not constant",
+          pCol->zName);
+    }else{
+      /* A copy of pExpr is used instead of the original, as pExpr contains
+      ** tokens that point to volatile memory. The 'span' of the expression
+      ** is required by pragma table_info.
+      */
+      sqlite3ExprDelete(db, pCol->pDflt);
+      pCol->pDflt = sqlite3ExprDup(db, pSpan->pExpr, EXPRDUP_REDUCE);
+      sqlite3DbFree(db, pCol->zDflt);
+      pCol->zDflt = sqlite3DbStrNDup(db, (char*)pSpan->zStart,
+                                     (int)(pSpan->zEnd - pSpan->zStart));
+    }
+  }
+  sqlite3ExprDelete(db, pSpan->pExpr);
+}
+
+/*
+** Designate the PRIMARY KEY for the table.  pList is a list of names 
+** of columns that form the primary key.  If pList is NULL, then the
+** most recently added column of the table is the primary key.
+**
+** A table can have at most one primary key.  If the table already has
+** a primary key (and this is the second primary key) then create an
+** error.
+**
+** If the PRIMARY KEY is on a single column whose datatype is INTEGER,
+** then we will try to use that column as the rowid.  Set the Table.iPKey
+** field of the table under construction to be the index of the
+** INTEGER PRIMARY KEY column.  Table.iPKey is set to -1 if there is
+** no INTEGER PRIMARY KEY.
+**
+** If the key is not an INTEGER PRIMARY KEY, then create a unique
+** index for the key.  No index is created for INTEGER PRIMARY KEYs.
+*/
+void sqlite3AddPrimaryKey(
+  Parse *pParse,    /* Parsing context */
+  ExprList *pList,  /* List of field names to be indexed */
+  int onError,      /* What to do with a uniqueness conflict */
+  int autoInc,      /* True if the AUTOINCREMENT keyword is present */
+  int sortOrder     /* SQLITE_SO_ASC or SQLITE_SO_DESC */
+){
+  Table *pTab = pParse->pNewTable;
+  char *zType = 0;
+  int iCol = -1, i;
+  if( pTab==0 || IN_DECLARE_VTAB ) goto primary_key_exit;
+  if( pTab->tabFlags & TF_HasPrimaryKey ){
+    sqlite3ErrorMsg(pParse, 
+      "table \"%s\" has more than one primary key", pTab->zName);
+    goto primary_key_exit;
+  }
+  pTab->tabFlags |= TF_HasPrimaryKey;
+  if( pList==0 ){
+    iCol = pTab->nCol - 1;
+    pTab->aCol[iCol].isPrimKey = 1;
+  }else{
+    for(i=0; i<pList->nExpr; i++){
+      for(iCol=0; iCol<pTab->nCol; iCol++){
+        if( sqlite3StrICmp(pList->a[i].zName, pTab->aCol[iCol].zName)==0 ){
+          break;
+        }
+      }
+      if( iCol<pTab->nCol ){
+        pTab->aCol[iCol].isPrimKey = 1;
+      }
+    }
+    if( pList->nExpr>1 ) iCol = -1;
+  }
+  if( iCol>=0 && iCol<pTab->nCol ){
+    zType = pTab->aCol[iCol].zType;
+  }
+  if( zType && sqlite3StrICmp(zType, "INTEGER")==0
+        && sortOrder==SQLITE_SO_ASC ){
+    pTab->iPKey = iCol;
+    pTab->keyConf = (u8)onError;
+    assert( autoInc==0 || autoInc==1 );
+    pTab->tabFlags |= autoInc*TF_Autoincrement;
+  }else if( autoInc ){
+#ifndef SQLITE_OMIT_AUTOINCREMENT
+    sqlite3ErrorMsg(pParse, "AUTOINCREMENT is only allowed on an "
+       "INTEGER PRIMARY KEY");
+#endif
+  }else{
+    Index *p;
+    p = sqlite3CreateIndex(pParse, 0, 0, 0, pList, onError, 0, 0, sortOrder, 0);
+    if( p ){
+      p->autoIndex = 2;
+    }
+    pList = 0;
+  }
+
+primary_key_exit:
+  sqlite3ExprListDelete(pParse->db, pList);
+  return;
+}
+
+/*
+** Add a new CHECK constraint to the table currently under construction.
+*/
+void sqlite3AddCheckConstraint(
+  Parse *pParse,    /* Parsing context */
+  Expr *pCheckExpr  /* The check expression */
+){
+  sqlite3 *db = pParse->db;
+#ifndef SQLITE_OMIT_CHECK
+  Table *pTab = pParse->pNewTable;
+  if( pTab && !IN_DECLARE_VTAB ){
+    pTab->pCheck = sqlite3ExprAnd(db, pTab->pCheck, pCheckExpr);
+  }else
+#endif
+  {
+    sqlite3ExprDelete(db, pCheckExpr);
+  }
+}
+
+/*
+** Set the collation function of the most recently parsed table column
+** to the CollSeq given.
+*/
+void sqlite3AddCollateType(Parse *pParse, Token *pToken){
+  Table *p;
+  int i;
+  char *zColl;              /* Dequoted name of collation sequence */
+  sqlite3 *db;
+
+  if( (p = pParse->pNewTable)==0 ) return;
+  i = p->nCol-1;
+  db = pParse->db;
+  zColl = sqlite3NameFromToken(db, pToken);
+  if( !zColl ) return;
+
+  if( sqlite3LocateCollSeq(pParse, zColl) ){
+    Index *pIdx;
+    p->aCol[i].zColl = zColl;
+  
+    /* If the column is declared as "<name> PRIMARY KEY COLLATE <type>",
+    ** then an index may have been created on this column before the
+    ** collation type was added. Correct this if it is the case.
+    */
+    for(pIdx=p->pIndex; pIdx; pIdx=pIdx->pNext){
+      assert( pIdx->nColumn==1 );
+      if( pIdx->aiColumn[0]==i ){
+        pIdx->azColl[0] = p->aCol[i].zColl;
+      }
+    }
+  }else{
+    sqlite3DbFree(db, zColl);
+  }
+}
+
+/*
+** This function returns the collation sequence for database native text
+** encoding identified by the string zName, length nName.
+**
+** If the requested collation sequence is not available, or not available
+** in the database native encoding, the collation factory is invoked to
+** request it. If the collation factory does not supply such a sequence,
+** and the sequence is available in another text encoding, then that is
+** returned instead.
+**
+** If no versions of the requested collations sequence are available, or
+** another error occurs, NULL is returned and an error message written into
+** pParse.
+**
+** This routine is a wrapper around sqlite3FindCollSeq().  This routine
+** invokes the collation factory if the named collation cannot be found
+** and generates an error message.
+**
+** See also: sqlite3FindCollSeq(), sqlite3GetCollSeq()
+*/
+CollSeq *sqlite3LocateCollSeq(Parse *pParse, const char *zName){
+  sqlite3 *db = pParse->db;
+  u8 enc = ENC(db);
+  u8 initbusy = db->init.busy;
+  CollSeq *pColl;
+
+  pColl = sqlite3FindCollSeq(db, enc, zName, initbusy);
+  if( !initbusy && (!pColl || !pColl->xCmp) ){
+    pColl = sqlite3GetCollSeq(db, enc, pColl, zName);
+    if( !pColl ){
+      sqlite3ErrorMsg(pParse, "no such collation sequence: %s", zName);
+    }
+  }
+
+  return pColl;
+}
+
+
+/*
+** Generate code that will increment the schema cookie.
+**
+** The schema cookie is used to determine when the schema for the
+** database changes.  After each schema change, the cookie value
+** changes.  When a process first reads the schema it records the
+** cookie.  Thereafter, whenever it goes to access the database,
+** it checks the cookie to make sure the schema has not changed
+** since it was last read.
+**
+** This plan is not completely bullet-proof.  It is possible for
+** the schema to change multiple times and for the cookie to be
+** set back to prior value.  But schema changes are infrequent
+** and the probability of hitting the same cookie value is only
+** 1 chance in 2^32.  So we're safe enough.
+*/
+void sqlite3ChangeCookie(Parse *pParse, int iDb){
+  int r1 = sqlite3GetTempReg(pParse);
+  sqlite3 *db = pParse->db;
+  Vdbe *v = pParse->pVdbe;
+  assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+  sqlite3VdbeAddOp2(v, OP_Integer, db->aDb[iDb].pSchema->schema_cookie+1, r1);
+  sqlite3VdbeAddOp3(v, OP_SetCookie, iDb, BTREE_SCHEMA_VERSION, r1);
+  sqlite3ReleaseTempReg(pParse, r1);
+}
+
+/*
+** Measure the number of characters needed to output the given
+** identifier.  The number returned includes any quotes used
+** but does not include the null terminator.
+**
+** The estimate is conservative.  It might be larger that what is
+** really needed.
+*/
+static int identLength(const char *z){
+  int n;
+  for(n=0; *z; n++, z++){
+    if( *z=='"' ){ n++; }
+  }
+  return n + 2;
+}
+
+/*
+** The first parameter is a pointer to an output buffer. The second 
+** parameter is a pointer to an integer that contains the offset at
+** which to write into the output buffer. This function copies the
+** nul-terminated string pointed to by the third parameter, zSignedIdent,
+** to the specified offset in the buffer and updates *pIdx to refer
+** to the first byte after the last byte written before returning.
+** 
+** If the string zSignedIdent consists entirely of alpha-numeric
+** characters, does not begin with a digit and is not an SQL keyword,
+** then it is copied to the output buffer exactly as it is. Otherwise,
+** it is quoted using double-quotes.
+*/
+static void identPut(char *z, int *pIdx, char *zSignedIdent){
+  unsigned char *zIdent = (unsigned char*)zSignedIdent;
+  int i, j, needQuote;
+  i = *pIdx;
+
+  for(j=0; zIdent[j]; j++){
+    if( !sqlite3Isalnum(zIdent[j]) && zIdent[j]!='_' ) break;
+  }
+  needQuote = sqlite3Isdigit(zIdent[0]) || sqlite3KeywordCode(zIdent, j)!=TK_ID;
+  if( !needQuote ){
+    needQuote = zIdent[j];
+  }
+
+  if( needQuote ) z[i++] = '"';
+  for(j=0; zIdent[j]; j++){
+    z[i++] = zIdent[j];
+    if( zIdent[j]=='"' ) z[i++] = '"';
+  }
+  if( needQuote ) z[i++] = '"';
+  z[i] = 0;
+  *pIdx = i;
+}
+
+/*
+** Generate a CREATE TABLE statement appropriate for the given
+** table.  Memory to hold the text of the statement is obtained
+** from sqliteMalloc() and must be freed by the calling function.
+*/
+static char *createTableStmt(sqlite3 *db, Table *p){
+  int i, k, n;
+  char *zStmt;
+  char *zSep, *zSep2, *zEnd;
+  Column *pCol;
+  n = 0;
+  for(pCol = p->aCol, i=0; i<p->nCol; i++, pCol++){
+    n += identLength(pCol->zName) + 5;
+  }
+  n += identLength(p->zName);
+  if( n<50 ){ 
+    zSep = "";
+    zSep2 = ",";
+    zEnd = ")";
+  }else{
+    zSep = "\n  ";
+    zSep2 = ",\n  ";
+    zEnd = "\n)";
+  }
+  n += 35 + 6*p->nCol;
+  zStmt = sqlite3DbMallocRaw(0, n);
+  if( zStmt==0 ){
+    db->mallocFailed = 1;
+    return 0;
+  }
+  sqlite3_snprintf(n, zStmt, "CREATE TABLE ");
+  k = sqlite3Strlen30(zStmt);
+  identPut(zStmt, &k, p->zName);
+  zStmt[k++] = '(';
+  for(pCol=p->aCol, i=0; i<p->nCol; i++, pCol++){
+    static const char * const azType[] = {
+        /* SQLITE_AFF_TEXT    */ " TEXT",
+        /* SQLITE_AFF_NONE    */ "",
+        /* SQLITE_AFF_NUMERIC */ " NUM",
+        /* SQLITE_AFF_INTEGER */ " INT",
+        /* SQLITE_AFF_REAL    */ " REAL"
+    };
+    int len;
+    const char *zType;
+
+    sqlite3_snprintf(n-k, &zStmt[k], zSep);
+    k += sqlite3Strlen30(&zStmt[k]);
+    zSep = zSep2;
+    identPut(zStmt, &k, pCol->zName);
+    assert( pCol->affinity-SQLITE_AFF_TEXT >= 0 );
+    assert( pCol->affinity-SQLITE_AFF_TEXT < ArraySize(azType) );
+    testcase( pCol->affinity==SQLITE_AFF_TEXT );
+    testcase( pCol->affinity==SQLITE_AFF_NONE );
+    testcase( pCol->affinity==SQLITE_AFF_NUMERIC );
+    testcase( pCol->affinity==SQLITE_AFF_INTEGER );
+    testcase( pCol->affinity==SQLITE_AFF_REAL );
+    
+    zType = azType[pCol->affinity - SQLITE_AFF_TEXT];
+    len = sqlite3Strlen30(zType);
+    assert( pCol->affinity==SQLITE_AFF_NONE 
+            || pCol->affinity==sqlite3AffinityType(zType) );
+    memcpy(&zStmt[k], zType, len);
+    k += len;
+    assert( k<=n );
+  }
+  sqlite3_snprintf(n-k, &zStmt[k], "%s", zEnd);
+  return zStmt;
+}
+
+/*
+** This routine is called to report the final ")" that terminates
+** a CREATE TABLE statement.
+**
+** The table structure that other action routines have been building
+** is added to the internal hash tables, assuming no errors have
+** occurred.
+**
+** An entry for the table is made in the master table on disk, unless
+** this is a temporary table or db->init.busy==1.  When db->init.busy==1
+** it means we are reading the sqlite_master table because we just
+** connected to the database or because the sqlite_master table has
+** recently changed, so the entry for this table already exists in
+** the sqlite_master table.  We do not want to create it again.
+**
+** If the pSelect argument is not NULL, it means that this routine
+** was called to create a table generated from a 
+** "CREATE TABLE ... AS SELECT ..." statement.  The column names of
+** the new table will match the result set of the SELECT.
+*/
+void sqlite3EndTable(
+  Parse *pParse,          /* Parse context */
+  Token *pCons,           /* The ',' token after the last column defn. */
+  Token *pEnd,            /* The final ')' token in the CREATE TABLE */
+  Select *pSelect         /* Select from a "CREATE ... AS SELECT" */
+){
+  Table *p;
+  sqlite3 *db = pParse->db;
+  int iDb;
+
+  if( (pEnd==0 && pSelect==0) || db->mallocFailed ){
+    return;
+  }
+  p = pParse->pNewTable;
+  if( p==0 ) return;
+
+  assert( !db->init.busy || !pSelect );
+
+  iDb = sqlite3SchemaToIndex(db, p->pSchema);
+
+#ifndef SQLITE_OMIT_CHECK
+  /* Resolve names in all CHECK constraint expressions.
+  */
+  if( p->pCheck ){
+    SrcList sSrc;                   /* Fake SrcList for pParse->pNewTable */
+    NameContext sNC;                /* Name context for pParse->pNewTable */
+
+    memset(&sNC, 0, sizeof(sNC));
+    memset(&sSrc, 0, sizeof(sSrc));
+    sSrc.nSrc = 1;
+    sSrc.a[0].zName = p->zName;
+    sSrc.a[0].pTab = p;
+    sSrc.a[0].iCursor = -1;
+    sNC.pParse = pParse;
+    sNC.pSrcList = &sSrc;
+    sNC.isCheck = 1;
+    if( sqlite3ResolveExprNames(&sNC, p->pCheck) ){
+      return;
+    }
+  }
+#endif /* !defined(SQLITE_OMIT_CHECK) */
+
+  /* If the db->init.busy is 1 it means we are reading the SQL off the
+  ** "sqlite_master" or "sqlite_temp_master" table on the disk.
+  ** So do not write to the disk again.  Extract the root page number
+  ** for the table from the db->init.newTnum field.  (The page number
+  ** should have been put there by the sqliteOpenCb routine.)
+  */
+  if( db->init.busy ){
+    p->tnum = db->init.newTnum;
+  }
+
+  /* If not initializing, then create a record for the new table
+  ** in the SQLITE_MASTER table of the database.
+  **
+  ** If this is a TEMPORARY table, write the entry into the auxiliary
+  ** file instead of into the main database file.
+  */
+  if( !db->init.busy ){
+    int n;
+    Vdbe *v;
+    char *zType;    /* "view" or "table" */
+    char *zType2;   /* "VIEW" or "TABLE" */
+    char *zStmt;    /* Text of the CREATE TABLE or CREATE VIEW statement */
+
+    v = sqlite3GetVdbe(pParse);
+    if( NEVER(v==0) ) return;
+
+    sqlite3VdbeAddOp1(v, OP_Close, 0);
+
+    /* 
+    ** Initialize zType for the new view or table.
+    */
+    if( p->pSelect==0 ){
+      /* A regular table */
+      zType = "table";
+      zType2 = "TABLE";
+#ifndef SQLITE_OMIT_VIEW
+    }else{
+      /* A view */
+      zType = "view";
+      zType2 = "VIEW";
+#endif
+    }
+
+    /* If this is a CREATE TABLE xx AS SELECT ..., execute the SELECT
+    ** statement to populate the new table. The root-page number for the
+    ** new table is in register pParse->regRoot.
+    **
+    ** Once the SELECT has been coded by sqlite3Select(), it is in a
+    ** suitable state to query for the column names and types to be used
+    ** by the new table.
+    **
+    ** A shared-cache write-lock is not required to write to the new table,
+    ** as a schema-lock must have already been obtained to create it. Since
+    ** a schema-lock excludes all other database users, the write-lock would
+    ** be redundant.
+    */
+    if( pSelect ){
+      SelectDest dest;
+      Table *pSelTab;
+
+      assert(pParse->nTab==1);
+      sqlite3VdbeAddOp3(v, OP_OpenWrite, 1, pParse->regRoot, iDb);
+      sqlite3VdbeChangeP5(v, 1);
+      pParse->nTab = 2;
+      sqlite3SelectDestInit(&dest, SRT_Table, 1);
+      sqlite3Select(pParse, pSelect, &dest);
+      sqlite3VdbeAddOp1(v, OP_Close, 1);
+      if( pParse->nErr==0 ){
+        pSelTab = sqlite3ResultSetOfSelect(pParse, pSelect);
+        if( pSelTab==0 ) return;
+        assert( p->aCol==0 );
+        p->nCol = pSelTab->nCol;
+        p->aCol = pSelTab->aCol;
+        pSelTab->nCol = 0;
+        pSelTab->aCol = 0;
+        sqlite3DeleteTable(db, pSelTab);
+      }
+    }
+
+    /* Compute the complete text of the CREATE statement */
+    if( pSelect ){
+      zStmt = createTableStmt(db, p);
+    }else{
+      n = (int)(pEnd->z - pParse->sNameToken.z) + 1;
+      zStmt = sqlite3MPrintf(db, 
+          "CREATE %s %.*s", zType2, n, pParse->sNameToken.z
+      );
+    }
+
+    /* A slot for the record has already been allocated in the 
+    ** SQLITE_MASTER table.  We just need to update that slot with all
+    ** the information we've collected.
+    */
+    sqlite3NestedParse(pParse,
+      "UPDATE %Q.%s "
+         "SET type='%s', name=%Q, tbl_name=%Q, rootpage=#%d, sql=%Q "
+       "WHERE rowid=#%d",
+      db->aDb[iDb].zName, SCHEMA_TABLE(iDb),
+      zType,
+      p->zName,
+      p->zName,
+      pParse->regRoot,
+      zStmt,
+      pParse->regRowid
+    );
+    sqlite3DbFree(db, zStmt);
+    sqlite3ChangeCookie(pParse, iDb);
+
+#ifndef SQLITE_OMIT_AUTOINCREMENT
+    /* Check to see if we need to create an sqlite_sequence table for
+    ** keeping track of autoincrement keys.
+    */
+    if( p->tabFlags & TF_Autoincrement ){
+      Db *pDb = &db->aDb[iDb];
+      assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+      if( pDb->pSchema->pSeqTab==0 ){
+        sqlite3NestedParse(pParse,
+          "CREATE TABLE %Q.sqlite_sequence(name,seq)",
+          pDb->zName
+        );
+      }
+    }
+#endif
+
+    /* Reparse everything to update our internal data structures */
+    sqlite3VdbeAddParseSchemaOp(v, iDb,
+               sqlite3MPrintf(db, "tbl_name='%q'", p->zName));
+  }
+
+
+  /* Add the table to the in-memory representation of the database.
+  */
+  if( db->init.busy ){
+    Table *pOld;
+    Schema *pSchema = p->pSchema;
+    assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+    pOld = sqlite3HashInsert(&pSchema->tblHash, p->zName,
+                             sqlite3Strlen30(p->zName),p);
+    if( pOld ){
+      assert( p==pOld );  /* Malloc must have failed inside HashInsert() */
+      db->mallocFailed = 1;
+      return;
+    }
+    pParse->pNewTable = 0;
+    db->nTable++;
+    db->flags |= SQLITE_InternChanges;
+
+#ifndef SQLITE_OMIT_ALTERTABLE
+    if( !p->pSelect ){
+      const char *zName = (const char *)pParse->sNameToken.z;
+      int nName;
+      assert( !pSelect && pCons && pEnd );
+      if( pCons->z==0 ){
+        pCons = pEnd;
+      }
+      nName = (int)((const char *)pCons->z - zName);
+      p->addColOffset = 13 + sqlite3Utf8CharLen(zName, nName);
+    }
+#endif
+  }
+}
+
+#ifndef SQLITE_OMIT_VIEW
+/*
+** The parser calls this routine in order to create a new VIEW
+*/
+void sqlite3CreateView(
+  Parse *pParse,     /* The parsing context */
+  Token *pBegin,     /* The CREATE token that begins the statement */
+  Token *pName1,     /* The token that holds the name of the view */
+  Token *pName2,     /* The token that holds the name of the view */
+  Select *pSelect,   /* A SELECT statement that will become the new view */
+  int isTemp,        /* TRUE for a TEMPORARY view */
+  int noErr          /* Suppress error messages if VIEW already exists */
+){
+  Table *p;
+  int n;
+  const char *z;
+  Token sEnd;
+  DbFixer sFix;
+  Token *pName = 0;
+  int iDb;
+  sqlite3 *db = pParse->db;
+
+  if( pParse->nVar>0 ){
+    sqlite3ErrorMsg(pParse, "parameters are not allowed in views");
+    sqlite3SelectDelete(db, pSelect);
+    return;
+  }
+  sqlite3StartTable(pParse, pName1, pName2, isTemp, 1, 0, noErr);
+  p = pParse->pNewTable;
+  if( p==0 || pParse->nErr ){
+    sqlite3SelectDelete(db, pSelect);
+    return;
+  }
+  sqlite3TwoPartName(pParse, pName1, pName2, &pName);
+  iDb = sqlite3SchemaToIndex(db, p->pSchema);
+  if( sqlite3FixInit(&sFix, pParse, iDb, "view", pName)
+    && sqlite3FixSelect(&sFix, pSelect)
+  ){
+    sqlite3SelectDelete(db, pSelect);
+    return;
+  }
+
+  /* Make a copy of the entire SELECT statement that defines the view.
+  ** This will force all the Expr.token.z values to be dynamically
+  ** allocated rather than point to the input string - which means that
+  ** they will persist after the current sqlite3_exec() call returns.
+  */
+  p->pSelect = sqlite3SelectDup(db, pSelect, EXPRDUP_REDUCE);
+  sqlite3SelectDelete(db, pSelect);
+  if( db->mallocFailed ){
+    return;
+  }
+  if( !db->init.busy ){
+    sqlite3ViewGetColumnNames(pParse, p);
+  }
+
+  /* Locate the end of the CREATE VIEW statement.  Make sEnd point to
+  ** the end.
+  */
+  sEnd = pParse->sLastToken;
+  if( ALWAYS(sEnd.z[0]!=0) && sEnd.z[0]!=';' ){
+    sEnd.z += sEnd.n;
+  }
+  sEnd.n = 0;
+  n = (int)(sEnd.z - pBegin->z);
+  z = pBegin->z;
+  while( ALWAYS(n>0) && sqlite3Isspace(z[n-1]) ){ n--; }
+  sEnd.z = &z[n-1];
+  sEnd.n = 1;
+
+  /* Use sqlite3EndTable() to add the view to the SQLITE_MASTER table */
+  sqlite3EndTable(pParse, 0, &sEnd, 0);
+  return;
+}
+#endif /* SQLITE_OMIT_VIEW */
+
+#if !defined(SQLITE_OMIT_VIEW) || !defined(SQLITE_OMIT_VIRTUALTABLE)
+/*
+** The Table structure pTable is really a VIEW.  Fill in the names of
+** the columns of the view in the pTable structure.  Return the number
+** of errors.  If an error is seen leave an error message in pParse->zErrMsg.
+*/
+int sqlite3ViewGetColumnNames(Parse *pParse, Table *pTable){
+  Table *pSelTab;   /* A fake table from which we get the result set */
+  Select *pSel;     /* Copy of the SELECT that implements the view */
+  int nErr = 0;     /* Number of errors encountered */
+  int n;            /* Temporarily holds the number of cursors assigned */
+  sqlite3 *db = pParse->db;  /* Database connection for malloc errors */
+  int (*xAuth)(void*,int,const char*,const char*,const char*,const char*);
+
+  assert( pTable );
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  if( sqlite3VtabCallConnect(pParse, pTable) ){
+    return SQLITE_ERROR;
+  }
+  if( IsVirtual(pTable) ) return 0;
+#endif
+
+#ifndef SQLITE_OMIT_VIEW
+  /* A positive nCol means the columns names for this view are
+  ** already known.
+  */
+  if( pTable->nCol>0 ) return 0;
+
+  /* A negative nCol is a special marker meaning that we are currently
+  ** trying to compute the column names.  If we enter this routine with
+  ** a negative nCol, it means two or more views form a loop, like this:
+  **
+  **     CREATE VIEW one AS SELECT * FROM two;
+  **     CREATE VIEW two AS SELECT * FROM one;
+  **
+  ** Actually, the error above is now caught prior to reaching this point.
+  ** But the following test is still important as it does come up
+  ** in the following:
+  ** 
+  **     CREATE TABLE main.ex1(a);
+  **     CREATE TEMP VIEW ex1 AS SELECT a FROM ex1;
+  **     SELECT * FROM temp.ex1;
+  */
+  if( pTable->nCol<0 ){
+    sqlite3ErrorMsg(pParse, "view %s is circularly defined", pTable->zName);
+    return 1;
+  }
+  assert( pTable->nCol>=0 );
+
+  /* If we get this far, it means we need to compute the table names.
+  ** Note that the call to sqlite3ResultSetOfSelect() will expand any
+  ** "*" elements in the results set of the view and will assign cursors
+  ** to the elements of the FROM clause.  But we do not want these changes
+  ** to be permanent.  So the computation is done on a copy of the SELECT
+  ** statement that defines the view.
+  */
+  assert( pTable->pSelect );
+  pSel = sqlite3SelectDup(db, pTable->pSelect, 0);
+  if( pSel ){
+    u8 enableLookaside = db->lookaside.bEnabled;
+    n = pParse->nTab;
+    sqlite3SrcListAssignCursors(pParse, pSel->pSrc);
+    pTable->nCol = -1;
+    db->lookaside.bEnabled = 0;
+#ifndef SQLITE_OMIT_AUTHORIZATION
+    xAuth = db->xAuth;
+    db->xAuth = 0;
+    pSelTab = sqlite3ResultSetOfSelect(pParse, pSel);
+    db->xAuth = xAuth;
+#else
+    pSelTab = sqlite3ResultSetOfSelect(pParse, pSel);
+#endif
+    db->lookaside.bEnabled = enableLookaside;
+    pParse->nTab = n;
+    if( pSelTab ){
+      assert( pTable->aCol==0 );
+      pTable->nCol = pSelTab->nCol;
+      pTable->aCol = pSelTab->aCol;
+      pSelTab->nCol = 0;
+      pSelTab->aCol = 0;
+      sqlite3DeleteTable(db, pSelTab);
+      assert( sqlite3SchemaMutexHeld(db, 0, pTable->pSchema) );
+      pTable->pSchema->flags |= DB_UnresetViews;
+    }else{
+      pTable->nCol = 0;
+      nErr++;
+    }
+    sqlite3SelectDelete(db, pSel);
+  } else {
+    nErr++;
+  }
+#endif /* SQLITE_OMIT_VIEW */
+  return nErr;  
+}
+#endif /* !defined(SQLITE_OMIT_VIEW) || !defined(SQLITE_OMIT_VIRTUALTABLE) */
+
+#ifndef SQLITE_OMIT_VIEW
+/*
+** Clear the column names from every VIEW in database idx.
+*/
+static void sqliteViewResetAll(sqlite3 *db, int idx){
+  HashElem *i;
+  assert( sqlite3SchemaMutexHeld(db, idx, 0) );
+  if( !DbHasProperty(db, idx, DB_UnresetViews) ) return;
+  for(i=sqliteHashFirst(&db->aDb[idx].pSchema->tblHash); i;i=sqliteHashNext(i)){
+    Table *pTab = sqliteHashData(i);
+    if( pTab->pSelect ){
+      sqliteDeleteColumnNames(db, pTab);
+      pTab->aCol = 0;
+      pTab->nCol = 0;
+    }
+  }
+  DbClearProperty(db, idx, DB_UnresetViews);
+}
+#else
+# define sqliteViewResetAll(A,B)
+#endif /* SQLITE_OMIT_VIEW */
+
+/*
+** This function is called by the VDBE to adjust the internal schema
+** used by SQLite when the btree layer moves a table root page. The
+** root-page of a table or index in database iDb has changed from iFrom
+** to iTo.
+**
+** Ticket #1728:  The symbol table might still contain information
+** on tables and/or indices that are the process of being deleted.
+** If you are unlucky, one of those deleted indices or tables might
+** have the same rootpage number as the real table or index that is
+** being moved.  So we cannot stop searching after the first match 
+** because the first match might be for one of the deleted indices
+** or tables and not the table/index that is actually being moved.
+** We must continue looping until all tables and indices with
+** rootpage==iFrom have been converted to have a rootpage of iTo
+** in order to be certain that we got the right one.
+*/
+#ifndef SQLITE_OMIT_AUTOVACUUM
+void sqlite3RootPageMoved(sqlite3 *db, int iDb, int iFrom, int iTo){
+  HashElem *pElem;
+  Hash *pHash;
+  Db *pDb;
+
+  assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+  pDb = &db->aDb[iDb];
+  pHash = &pDb->pSchema->tblHash;
+  for(pElem=sqliteHashFirst(pHash); pElem; pElem=sqliteHashNext(pElem)){
+    Table *pTab = sqliteHashData(pElem);
+    if( pTab->tnum==iFrom ){
+      pTab->tnum = iTo;
+    }
+  }
+  pHash = &pDb->pSchema->idxHash;
+  for(pElem=sqliteHashFirst(pHash); pElem; pElem=sqliteHashNext(pElem)){
+    Index *pIdx = sqliteHashData(pElem);
+    if( pIdx->tnum==iFrom ){
+      pIdx->tnum = iTo;
+    }
+  }
+}
+#endif
+
+/*
+** Write code to erase the table with root-page iTable from database iDb.
+** Also write code to modify the sqlite_master table and internal schema
+** if a root-page of another table is moved by the btree-layer whilst
+** erasing iTable (this can happen with an auto-vacuum database).
+*/ 
+static void destroyRootPage(Parse *pParse, int iTable, int iDb){
+  Vdbe *v = sqlite3GetVdbe(pParse);
+  int r1 = sqlite3GetTempReg(pParse);
+  sqlite3VdbeAddOp3(v, OP_Destroy, iTable, r1, iDb);
+  sqlite3MayAbort(pParse);
+#ifndef SQLITE_OMIT_AUTOVACUUM
+  /* OP_Destroy stores an in integer r1. If this integer
+  ** is non-zero, then it is the root page number of a table moved to
+  ** location iTable. The following code modifies the sqlite_master table to
+  ** reflect this.
+  **
+  ** The "#NNN" in the SQL is a special constant that means whatever value
+  ** is in register NNN.  See grammar rules associated with the TK_REGISTER
+  ** token for additional information.
+  */
+  sqlite3NestedParse(pParse, 
+     "UPDATE %Q.%s SET rootpage=%d WHERE #%d AND rootpage=#%d",
+     pParse->db->aDb[iDb].zName, SCHEMA_TABLE(iDb), iTable, r1, r1);
+#endif
+  sqlite3ReleaseTempReg(pParse, r1);
+}
+
+/*
+** Write VDBE code to erase table pTab and all associated indices on disk.
+** Code to update the sqlite_master tables and internal schema definitions
+** in case a root-page belonging to another table is moved by the btree layer
+** is also added (this can happen with an auto-vacuum database).
+*/
+static void destroyTable(Parse *pParse, Table *pTab){
+#ifdef SQLITE_OMIT_AUTOVACUUM
+  Index *pIdx;
+  int iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
+  destroyRootPage(pParse, pTab->tnum, iDb);
+  for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+    destroyRootPage(pParse, pIdx->tnum, iDb);
+  }
+#else
+  /* If the database may be auto-vacuum capable (if SQLITE_OMIT_AUTOVACUUM
+  ** is not defined), then it is important to call OP_Destroy on the
+  ** table and index root-pages in order, starting with the numerically 
+  ** largest root-page number. This guarantees that none of the root-pages
+  ** to be destroyed is relocated by an earlier OP_Destroy. i.e. if the
+  ** following were coded:
+  **
+  ** OP_Destroy 4 0
+  ** ...
+  ** OP_Destroy 5 0
+  **
+  ** and root page 5 happened to be the largest root-page number in the
+  ** database, then root page 5 would be moved to page 4 by the 
+  ** "OP_Destroy 4 0" opcode. The subsequent "OP_Destroy 5 0" would hit
+  ** a free-list page.
+  */
+  int iTab = pTab->tnum;
+  int iDestroyed = 0;
+
+  while( 1 ){
+    Index *pIdx;
+    int iLargest = 0;
+
+    if( iDestroyed==0 || iTab<iDestroyed ){
+      iLargest = iTab;
+    }
+    for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+      int iIdx = pIdx->tnum;
+      assert( pIdx->pSchema==pTab->pSchema );
+      if( (iDestroyed==0 || (iIdx<iDestroyed)) && iIdx>iLargest ){
+        iLargest = iIdx;
+      }
+    }
+    if( iLargest==0 ){
+      return;
+    }else{
+      int iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
+      destroyRootPage(pParse, iLargest, iDb);
+      iDestroyed = iLargest;
+    }
+  }
+#endif
+}
+
+/*
+** Remove entries from the sqlite_statN tables (for N in (1,2,3))
+** after a DROP INDEX or DROP TABLE command.
+*/
+static void sqlite3ClearStatTables(
+  Parse *pParse,         /* The parsing context */
+  int iDb,               /* The database number */
+  const char *zType,     /* "idx" or "tbl" */
+  const char *zName      /* Name of index or table */
+){
+  int i;
+  const char *zDbName = pParse->db->aDb[iDb].zName;
+  for(i=1; i<=3; i++){
+    char zTab[24];
+    sqlite3_snprintf(sizeof(zTab),zTab,"sqlite_stat%d",i);
+    if( sqlite3FindTable(pParse->db, zTab, zDbName) ){
+      sqlite3NestedParse(pParse,
+        "DELETE FROM %Q.%s WHERE %s=%Q",
+        zDbName, zTab, zType, zName
+      );
+    }
+  }
+}
+
+/*
+** Generate code to drop a table.
+*/
+void sqlite3CodeDropTable(Parse *pParse, Table *pTab, int iDb, int isView){
+  Vdbe *v;
+  sqlite3 *db = pParse->db;
+  Trigger *pTrigger;
+  Db *pDb = &db->aDb[iDb];
+
+  v = sqlite3GetVdbe(pParse);
+  assert( v!=0 );
+  sqlite3BeginWriteOperation(pParse, 1, iDb);
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  if( IsVirtual(pTab) ){
+    sqlite3VdbeAddOp0(v, OP_VBegin);
+  }
+#endif
+
+  /* Drop all triggers associated with the table being dropped. Code
+  ** is generated to remove entries from sqlite_master and/or
+  ** sqlite_temp_master if required.
+  */
+  pTrigger = sqlite3TriggerList(pParse, pTab);
+  while( pTrigger ){
+    assert( pTrigger->pSchema==pTab->pSchema || 
+        pTrigger->pSchema==db->aDb[1].pSchema );
+    sqlite3DropTriggerPtr(pParse, pTrigger);
+    pTrigger = pTrigger->pNext;
+  }
+
+#ifndef SQLITE_OMIT_AUTOINCREMENT
+  /* Remove any entries of the sqlite_sequence table associated with
+  ** the table being dropped. This is done before the table is dropped
+  ** at the btree level, in case the sqlite_sequence table needs to
+  ** move as a result of the drop (can happen in auto-vacuum mode).
+  */
+  if( pTab->tabFlags & TF_Autoincrement ){
+    sqlite3NestedParse(pParse,
+      "DELETE FROM %Q.sqlite_sequence WHERE name=%Q",
+      pDb->zName, pTab->zName
+    );
+  }
+#endif
+
+  /* Drop all SQLITE_MASTER table and index entries that refer to the
+  ** table. The program name loops through the master table and deletes
+  ** every row that refers to a table of the same name as the one being
+  ** dropped. Triggers are handled seperately because a trigger can be
+  ** created in the temp database that refers to a table in another
+  ** database.
+  */
+  sqlite3NestedParse(pParse, 
+      "DELETE FROM %Q.%s WHERE tbl_name=%Q and type!='trigger'",
+      pDb->zName, SCHEMA_TABLE(iDb), pTab->zName);
+  if( !isView && !IsVirtual(pTab) ){
+    destroyTable(pParse, pTab);
+  }
+
+  /* Remove the table entry from SQLite's internal schema and modify
+  ** the schema cookie.
+  */
+  if( IsVirtual(pTab) ){
+    sqlite3VdbeAddOp4(v, OP_VDestroy, iDb, 0, 0, pTab->zName, 0);
+  }
+  sqlite3VdbeAddOp4(v, OP_DropTable, iDb, 0, 0, pTab->zName, 0);
+  sqlite3ChangeCookie(pParse, iDb);
+  sqliteViewResetAll(db, iDb);
+}
+
+/*
+** This routine is called to do the work of a DROP TABLE statement.
+** pName is the name of the table to be dropped.
+*/
+void sqlite3DropTable(Parse *pParse, SrcList *pName, int isView, int noErr){
+  Table *pTab;
+  Vdbe *v;
+  sqlite3 *db = pParse->db;
+  int iDb;
+
+  if( db->mallocFailed ){
+    goto exit_drop_table;
+  }
+  assert( pParse->nErr==0 );
+  assert( pName->nSrc==1 );
+  if( noErr ) db->suppressErr++;
+  pTab = sqlite3LocateTable(pParse, isView, 
+                            pName->a[0].zName, pName->a[0].zDatabase);
+  if( noErr ) db->suppressErr--;
+
+  if( pTab==0 ){
+    if( noErr ) sqlite3CodeVerifyNamedSchema(pParse, pName->a[0].zDatabase);
+    goto exit_drop_table;
+  }
+  iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+  assert( iDb>=0 && iDb<db->nDb );
+
+  /* If pTab is a virtual table, call ViewGetColumnNames() to ensure
+  ** it is initialized.
+  */
+  if( IsVirtual(pTab) && sqlite3ViewGetColumnNames(pParse, pTab) ){
+    goto exit_drop_table;
+  }
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  {
+    int code;
+    const char *zTab = SCHEMA_TABLE(iDb);
+    const char *zDb = db->aDb[iDb].zName;
+    const char *zArg2 = 0;
+    if( sqlite3AuthCheck(pParse, SQLITE_DELETE, zTab, 0, zDb)){
+      goto exit_drop_table;
+    }
+    if( isView ){
+      if( !OMIT_TEMPDB && iDb==1 ){
+        code = SQLITE_DROP_TEMP_VIEW;
+      }else{
+        code = SQLITE_DROP_VIEW;
+      }
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+    }else if( IsVirtual(pTab) ){
+      code = SQLITE_DROP_VTABLE;
+      zArg2 = sqlite3GetVTable(db, pTab)->pMod->zName;
+#endif
+    }else{
+      if( !OMIT_TEMPDB && iDb==1 ){
+        code = SQLITE_DROP_TEMP_TABLE;
+      }else{
+        code = SQLITE_DROP_TABLE;
+      }
+    }
+    if( sqlite3AuthCheck(pParse, code, pTab->zName, zArg2, zDb) ){
+      goto exit_drop_table;
+    }
+    if( sqlite3AuthCheck(pParse, SQLITE_DELETE, pTab->zName, 0, zDb) ){
+      goto exit_drop_table;
+    }
+  }
+#endif
+  if( sqlite3StrNICmp(pTab->zName, "sqlite_", 7)==0 
+    && sqlite3StrNICmp(pTab->zName, "sqlite_stat", 11)!=0 ){
+    sqlite3ErrorMsg(pParse, "table %s may not be dropped", pTab->zName);
+    goto exit_drop_table;
+  }
+
+#ifndef SQLITE_OMIT_VIEW
+  /* Ensure DROP TABLE is not used on a view, and DROP VIEW is not used
+  ** on a table.
+  */
+  if( isView && pTab->pSelect==0 ){
+    sqlite3ErrorMsg(pParse, "use DROP TABLE to delete table %s", pTab->zName);
+    goto exit_drop_table;
+  }
+  if( !isView && pTab->pSelect ){
+    sqlite3ErrorMsg(pParse, "use DROP VIEW to delete view %s", pTab->zName);
+    goto exit_drop_table;
+  }
+#endif
+
+  /* Generate code to remove the table from the master table
+  ** on disk.
+  */
+  v = sqlite3GetVdbe(pParse);
+  if( v ){
+    sqlite3BeginWriteOperation(pParse, 1, iDb);
+    sqlite3ClearStatTables(pParse, iDb, "tbl", pTab->zName);
+    sqlite3FkDropTable(pParse, pName, pTab);
+    sqlite3CodeDropTable(pParse, pTab, iDb, isView);
+  }
+
+exit_drop_table:
+  sqlite3SrcListDelete(db, pName);
+}
+
+/*
+** This routine is called to create a new foreign key on the table
+** currently under construction.  pFromCol determines which columns
+** in the current table point to the foreign key.  If pFromCol==0 then
+** connect the key to the last column inserted.  pTo is the name of
+** the table referred to.  pToCol is a list of tables in the other
+** pTo table that the foreign key points to.  flags contains all
+** information about the conflict resolution algorithms specified
+** in the ON DELETE, ON UPDATE and ON INSERT clauses.
+**
+** An FKey structure is created and added to the table currently
+** under construction in the pParse->pNewTable field.
+**
+** The foreign key is set for IMMEDIATE processing.  A subsequent call
+** to sqlite3DeferForeignKey() might change this to DEFERRED.
+*/
+void sqlite3CreateForeignKey(
+  Parse *pParse,       /* Parsing context */
+  ExprList *pFromCol,  /* Columns in this table that point to other table */
+  Token *pTo,          /* Name of the other table */
+  ExprList *pToCol,    /* Columns in the other table */
+  int flags            /* Conflict resolution algorithms. */
+){
+  sqlite3 *db = pParse->db;
+#ifndef SQLITE_OMIT_FOREIGN_KEY
+  FKey *pFKey = 0;
+  FKey *pNextTo;
+  Table *p = pParse->pNewTable;
+  int nByte;
+  int i;
+  int nCol;
+  char *z;
+
+  assert( pTo!=0 );
+  if( p==0 || IN_DECLARE_VTAB ) goto fk_end;
+  if( pFromCol==0 ){
+    int iCol = p->nCol-1;
+    if( NEVER(iCol<0) ) goto fk_end;
+    if( pToCol && pToCol->nExpr!=1 ){
+      sqlite3ErrorMsg(pParse, "foreign key on %s"
+         " should reference only one column of table %T",
+         p->aCol[iCol].zName, pTo);
+      goto fk_end;
+    }
+    nCol = 1;
+  }else if( pToCol && pToCol->nExpr!=pFromCol->nExpr ){
+    sqlite3ErrorMsg(pParse,
+        "number of columns in foreign key does not match the number of "
+        "columns in the referenced table");
+    goto fk_end;
+  }else{
+    nCol = pFromCol->nExpr;
+  }
+  nByte = sizeof(*pFKey) + (nCol-1)*sizeof(pFKey->aCol[0]) + pTo->n + 1;
+  if( pToCol ){
+    for(i=0; i<pToCol->nExpr; i++){
+      nByte += sqlite3Strlen30(pToCol->a[i].zName) + 1;
+    }
+  }
+  pFKey = sqlite3DbMallocZero(db, nByte );
+  if( pFKey==0 ){
+    goto fk_end;
+  }
+  pFKey->pFrom = p;
+  pFKey->pNextFrom = p->pFKey;
+  z = (char*)&pFKey->aCol[nCol];
+  pFKey->zTo = z;
+  memcpy(z, pTo->z, pTo->n);
+  z[pTo->n] = 0;
+  sqlite3Dequote(z);
+  z += pTo->n+1;
+  pFKey->nCol = nCol;
+  if( pFromCol==0 ){
+    pFKey->aCol[0].iFrom = p->nCol-1;
+  }else{
+    for(i=0; i<nCol; i++){
+      int j;
+      for(j=0; j<p->nCol; j++){
+        if( sqlite3StrICmp(p->aCol[j].zName, pFromCol->a[i].zName)==0 ){
+          pFKey->aCol[i].iFrom = j;
+          break;
+        }
+      }
+      if( j>=p->nCol ){
+        sqlite3ErrorMsg(pParse, 
+          "unknown column \"%s\" in foreign key definition", 
+          pFromCol->a[i].zName);
+        goto fk_end;
+      }
+    }
+  }
+  if( pToCol ){
+    for(i=0; i<nCol; i++){
+      int n = sqlite3Strlen30(pToCol->a[i].zName);
+      pFKey->aCol[i].zCol = z;
+      memcpy(z, pToCol->a[i].zName, n);
+      z[n] = 0;
+      z += n+1;
+    }
+  }
+  pFKey->isDeferred = 0;
+  pFKey->aAction[0] = (u8)(flags & 0xff);            /* ON DELETE action */
+  pFKey->aAction[1] = (u8)((flags >> 8 ) & 0xff);    /* ON UPDATE action */
+
+  assert( sqlite3SchemaMutexHeld(db, 0, p->pSchema) );
+  pNextTo = (FKey *)sqlite3HashInsert(&p->pSchema->fkeyHash, 
+      pFKey->zTo, sqlite3Strlen30(pFKey->zTo), (void *)pFKey
+  );
+  if( pNextTo==pFKey ){
+    db->mallocFailed = 1;
+    goto fk_end;
+  }
+  if( pNextTo ){
+    assert( pNextTo->pPrevTo==0 );
+    pFKey->pNextTo = pNextTo;
+    pNextTo->pPrevTo = pFKey;
+  }
+
+  /* Link the foreign key to the table as the last step.
+  */
+  p->pFKey = pFKey;
+  pFKey = 0;
+
+fk_end:
+  sqlite3DbFree(db, pFKey);
+#endif /* !defined(SQLITE_OMIT_FOREIGN_KEY) */
+  sqlite3ExprListDelete(db, pFromCol);
+  sqlite3ExprListDelete(db, pToCol);
+}
+
+/*
+** This routine is called when an INITIALLY IMMEDIATE or INITIALLY DEFERRED
+** clause is seen as part of a foreign key definition.  The isDeferred
+** parameter is 1 for INITIALLY DEFERRED and 0 for INITIALLY IMMEDIATE.
+** The behavior of the most recently created foreign key is adjusted
+** accordingly.
+*/
+void sqlite3DeferForeignKey(Parse *pParse, int isDeferred){
+#ifndef SQLITE_OMIT_FOREIGN_KEY
+  Table *pTab;
+  FKey *pFKey;
+  if( (pTab = pParse->pNewTable)==0 || (pFKey = pTab->pFKey)==0 ) return;
+  assert( isDeferred==0 || isDeferred==1 ); /* EV: R-30323-21917 */
+  pFKey->isDeferred = (u8)isDeferred;
+#endif
+}
+
+/*
+** Generate code that will erase and refill index *pIdx.  This is
+** used to initialize a newly created index or to recompute the
+** content of an index in response to a REINDEX command.
+**
+** if memRootPage is not negative, it means that the index is newly
+** created.  The register specified by memRootPage contains the
+** root page number of the index.  If memRootPage is negative, then
+** the index already exists and must be cleared before being refilled and
+** the root page number of the index is taken from pIndex->tnum.
+*/
+static void sqlite3RefillIndex(Parse *pParse, Index *pIndex, int memRootPage){
+  Table *pTab = pIndex->pTable;  /* The table that is indexed */
+  int iTab = pParse->nTab++;     /* Btree cursor used for pTab */
+  int iIdx = pParse->nTab++;     /* Btree cursor used for pIndex */
+  int iSorter;                   /* Cursor opened by OpenSorter (if in use) */
+  int addr1;                     /* Address of top of loop */
+  int addr2;                     /* Address to jump to for next iteration */
+  int tnum;                      /* Root page of index */
+  Vdbe *v;                       /* Generate code into this virtual machine */
+  KeyInfo *pKey;                 /* KeyInfo for index */
+#ifdef SQLITE_OMIT_MERGE_SORT
+  int regIdxKey;                 /* Registers containing the index key */
+#endif
+  int regRecord;                 /* Register holding assemblied index record */
+  sqlite3 *db = pParse->db;      /* The database connection */
+  int iDb = sqlite3SchemaToIndex(db, pIndex->pSchema);
+
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  if( sqlite3AuthCheck(pParse, SQLITE_REINDEX, pIndex->zName, 0,
+      db->aDb[iDb].zName ) ){
+    return;
+  }
+#endif
+
+  /* Require a write-lock on the table to perform this operation */
+  sqlite3TableLock(pParse, iDb, pTab->tnum, 1, pTab->zName);
+
+  v = sqlite3GetVdbe(pParse);
+  if( v==0 ) return;
+  if( memRootPage>=0 ){
+    tnum = memRootPage;
+  }else{
+    tnum = pIndex->tnum;
+    sqlite3VdbeAddOp2(v, OP_Clear, tnum, iDb);
+  }
+  pKey = sqlite3IndexKeyinfo(pParse, pIndex);
+  sqlite3VdbeAddOp4(v, OP_OpenWrite, iIdx, tnum, iDb, 
+                    (char *)pKey, P4_KEYINFO_HANDOFF);
+  if( memRootPage>=0 ){
+    sqlite3VdbeChangeP5(v, 1);
+  }
+
+#ifndef SQLITE_OMIT_MERGE_SORT
+  /* Open the sorter cursor if we are to use one. */
+  iSorter = pParse->nTab++;
+  sqlite3VdbeAddOp4(v, OP_SorterOpen, iSorter, 0, 0, (char*)pKey, P4_KEYINFO);
+#else
+  iSorter = iTab;
+#endif
+
+  /* Open the table. Loop through all rows of the table, inserting index
+  ** records into the sorter. */
+  sqlite3OpenTable(pParse, iTab, iDb, pTab, OP_OpenRead);
+  addr1 = sqlite3VdbeAddOp2(v, OP_Rewind, iTab, 0);
+  regRecord = sqlite3GetTempReg(pParse);
+
+#ifndef SQLITE_OMIT_MERGE_SORT
+  sqlite3GenerateIndexKey(pParse, pIndex, iTab, regRecord, 1);
+  sqlite3VdbeAddOp2(v, OP_SorterInsert, iSorter, regRecord);
+  sqlite3VdbeAddOp2(v, OP_Next, iTab, addr1+1);
+  sqlite3VdbeJumpHere(v, addr1);
+  addr1 = sqlite3VdbeAddOp2(v, OP_SorterSort, iSorter, 0);
+  if( pIndex->onError!=OE_None ){
+    int j2 = sqlite3VdbeCurrentAddr(v) + 3;
+    sqlite3VdbeAddOp2(v, OP_Goto, 0, j2);
+    addr2 = sqlite3VdbeCurrentAddr(v);
+    sqlite3VdbeAddOp3(v, OP_SorterCompare, iSorter, j2, regRecord);
+    sqlite3HaltConstraint(
+        pParse, OE_Abort, "indexed columns are not unique", P4_STATIC
+    );
+  }else{
+    addr2 = sqlite3VdbeCurrentAddr(v);
+  }
+  sqlite3VdbeAddOp2(v, OP_SorterData, iSorter, regRecord);
+  sqlite3VdbeAddOp3(v, OP_IdxInsert, iIdx, regRecord, 1);
+  sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);
+#else
+  regIdxKey = sqlite3GenerateIndexKey(pParse, pIndex, iTab, regRecord, 1);
+  addr2 = addr1 + 1;
+  if( pIndex->onError!=OE_None ){
+    const int regRowid = regIdxKey + pIndex->nColumn;
+    const int j2 = sqlite3VdbeCurrentAddr(v) + 2;
+    void * const pRegKey = SQLITE_INT_TO_PTR(regIdxKey);
+
+    /* The registers accessed by the OP_IsUnique opcode were allocated
+    ** using sqlite3GetTempRange() inside of the sqlite3GenerateIndexKey()
+    ** call above. Just before that function was freed they were released
+    ** (made available to the compiler for reuse) using 
+    ** sqlite3ReleaseTempRange(). So in some ways having the OP_IsUnique
+    ** opcode use the values stored within seems dangerous. However, since
+    ** we can be sure that no other temp registers have been allocated
+    ** since sqlite3ReleaseTempRange() was called, it is safe to do so.
+    */
+    sqlite3VdbeAddOp4(v, OP_IsUnique, iIdx, j2, regRowid, pRegKey, P4_INT32);
+    sqlite3HaltConstraint(
+        pParse, OE_Abort, "indexed columns are not unique", P4_STATIC);
+  }
+  sqlite3VdbeAddOp3(v, OP_IdxInsert, iIdx, regRecord, 0);
+  sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);
+#endif
+  sqlite3ReleaseTempReg(pParse, regRecord);
+  sqlite3VdbeAddOp2(v, OP_SorterNext, iSorter, addr2);
+  sqlite3VdbeJumpHere(v, addr1);
+
+  sqlite3VdbeAddOp1(v, OP_Close, iTab);
+  sqlite3VdbeAddOp1(v, OP_Close, iIdx);
+  sqlite3VdbeAddOp1(v, OP_Close, iSorter);
+}
+
+/*
+** Create a new index for an SQL table.  pName1.pName2 is the name of the index 
+** and pTblList is the name of the table that is to be indexed.  Both will 
+** be NULL for a primary key or an index that is created to satisfy a
+** UNIQUE constraint.  If pTable and pIndex are NULL, use pParse->pNewTable
+** as the table to be indexed.  pParse->pNewTable is a table that is
+** currently being constructed by a CREATE TABLE statement.
+**
+** pList is a list of columns to be indexed.  pList will be NULL if this
+** is a primary key or unique-constraint on the most recent column added
+** to the table currently under construction.  
+**
+** If the index is created successfully, return a pointer to the new Index
+** structure. This is used by sqlite3AddPrimaryKey() to mark the index
+** as the tables primary key (Index.autoIndex==2).
+*/
+Index *sqlite3CreateIndex(
+  Parse *pParse,     /* All information about this parse */
+  Token *pName1,     /* First part of index name. May be NULL */
+  Token *pName2,     /* Second part of index name. May be NULL */
+  SrcList *pTblName, /* Table to index. Use pParse->pNewTable if 0 */
+  ExprList *pList,   /* A list of columns to be indexed */
+  int onError,       /* OE_Abort, OE_Ignore, OE_Replace, or OE_None */
+  Token *pStart,     /* The CREATE token that begins this statement */
+  Token *pEnd,       /* The ")" that closes the CREATE INDEX statement */
+  int sortOrder,     /* Sort order of primary key when pList==NULL */
+  int ifNotExist     /* Omit error if index already exists */
+){
+  Index *pRet = 0;     /* Pointer to return */
+  Table *pTab = 0;     /* Table to be indexed */
+  Index *pIndex = 0;   /* The index to be created */
+  char *zName = 0;     /* Name of the index */
+  int nName;           /* Number of characters in zName */
+  int i, j;
+  Token nullId;        /* Fake token for an empty ID list */
+  DbFixer sFix;        /* For assigning database names to pTable */
+  int sortOrderMask;   /* 1 to honor DESC in index.  0 to ignore. */
+  sqlite3 *db = pParse->db;
+  Db *pDb;             /* The specific table containing the indexed database */
+  int iDb;             /* Index of the database that is being written */
+  Token *pName = 0;    /* Unqualified name of the index to create */
+  struct ExprList_item *pListItem; /* For looping over pList */
+  int nCol;
+  int nExtra = 0;
+  char *zExtra;
+
+  assert( pStart==0 || pEnd!=0 ); /* pEnd must be non-NULL if pStart is */
+  assert( pParse->nErr==0 );      /* Never called with prior errors */
+  if( db->mallocFailed || IN_DECLARE_VTAB ){
+    goto exit_create_index;
+  }
+  if( SQLITE_OK!=sqlite3ReadSchema(pParse) ){
+    goto exit_create_index;
+  }
+
+  /*
+  ** Find the table that is to be indexed.  Return early if not found.
+  */
+  if( pTblName!=0 ){
+
+    /* Use the two-part index name to determine the database 
+    ** to search for the table. 'Fix' the table name to this db
+    ** before looking up the table.
+    */
+    assert( pName1 && pName2 );
+    iDb = sqlite3TwoPartName(pParse, pName1, pName2, &pName);
+    if( iDb<0 ) goto exit_create_index;
+    assert( pName && pName->z );
+
+#ifndef SQLITE_OMIT_TEMPDB
+    /* If the index name was unqualified, check if the the table
+    ** is a temp table. If so, set the database to 1. Do not do this
+    ** if initialising a database schema.
+    */
+    if( !db->init.busy ){
+      pTab = sqlite3SrcListLookup(pParse, pTblName);
+      if( pName2->n==0 && pTab && pTab->pSchema==db->aDb[1].pSchema ){
+        iDb = 1;
+      }
+    }
+#endif
+
+    if( sqlite3FixInit(&sFix, pParse, iDb, "index", pName) &&
+        sqlite3FixSrcList(&sFix, pTblName)
+    ){
+      /* Because the parser constructs pTblName from a single identifier,
+      ** sqlite3FixSrcList can never fail. */
+      assert(0);
+    }
+    pTab = sqlite3LocateTable(pParse, 0, pTblName->a[0].zName, 
+        pTblName->a[0].zDatabase);
+    if( !pTab || db->mallocFailed ) goto exit_create_index;
+    assert( db->aDb[iDb].pSchema==pTab->pSchema );
+  }else{
+    assert( pName==0 );
+    assert( pStart==0 );
+    pTab = pParse->pNewTable;
+    if( !pTab ) goto exit_create_index;
+    iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+  }
+  pDb = &db->aDb[iDb];
+
+  assert( pTab!=0 );
+  assert( pParse->nErr==0 );
+  if( sqlite3StrNICmp(pTab->zName, "sqlite_", 7)==0 
+       && memcmp(&pTab->zName[7],"altertab_",9)!=0 ){
+    sqlite3ErrorMsg(pParse, "table %s may not be indexed", pTab->zName);
+    goto exit_create_index;
+  }
+#ifndef SQLITE_OMIT_VIEW
+  if( pTab->pSelect ){
+    sqlite3ErrorMsg(pParse, "views may not be indexed");
+    goto exit_create_index;
+  }
+#endif
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  if( IsVirtual(pTab) ){
+    sqlite3ErrorMsg(pParse, "virtual tables may not be indexed");
+    goto exit_create_index;
+  }
+#endif
+
+  /*
+  ** Find the name of the index.  Make sure there is not already another
+  ** index or table with the same name.  
+  **
+  ** Exception:  If we are reading the names of permanent indices from the
+  ** sqlite_master table (because some other process changed the schema) and
+  ** one of the index names collides with the name of a temporary table or
+  ** index, then we will continue to process this index.
+  **
+  ** If pName==0 it means that we are
+  ** dealing with a primary key or UNIQUE constraint.  We have to invent our
+  ** own name.
+  */
+  if( pName ){
+    zName = sqlite3NameFromToken(db, pName);
+    if( zName==0 ) goto exit_create_index;
+    assert( pName->z!=0 );
+    if( SQLITE_OK!=sqlite3CheckObjectName(pParse, zName) ){
+      goto exit_create_index;
+    }
+    if( !db->init.busy ){
+      if( sqlite3FindTable(db, zName, 0)!=0 ){
+        sqlite3ErrorMsg(pParse, "there is already a table named %s", zName);
+        goto exit_create_index;
+      }
+    }
+    if( sqlite3FindIndex(db, zName, pDb->zName)!=0 ){
+      if( !ifNotExist ){
+        sqlite3ErrorMsg(pParse, "index %s already exists", zName);
+      }else{
+        assert( !db->init.busy );
+        sqlite3CodeVerifySchema(pParse, iDb);
+      }
+      goto exit_create_index;
+    }
+  }else{
+    int n;
+    Index *pLoop;
+    for(pLoop=pTab->pIndex, n=1; pLoop; pLoop=pLoop->pNext, n++){}
+    zName = sqlite3MPrintf(db, "sqlite_autoindex_%s_%d", pTab->zName, n);
+    if( zName==0 ){
+      goto exit_create_index;
+    }
+  }
+
+  /* Check for authorization to create an index.
+  */
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  {
+    const char *zDb = pDb->zName;
+    if( sqlite3AuthCheck(pParse, SQLITE_INSERT, SCHEMA_TABLE(iDb), 0, zDb) ){
+      goto exit_create_index;
+    }
+    i = SQLITE_CREATE_INDEX;
+    if( !OMIT_TEMPDB && iDb==1 ) i = SQLITE_CREATE_TEMP_INDEX;
+    if( sqlite3AuthCheck(pParse, i, zName, pTab->zName, zDb) ){
+      goto exit_create_index;
+    }
+  }
+#endif
+
+  /* If pList==0, it means this routine was called to make a primary
+  ** key out of the last column added to the table under construction.
+  ** So create a fake list to simulate this.
+  */
+  if( pList==0 ){
+    nullId.z = pTab->aCol[pTab->nCol-1].zName;
+    nullId.n = sqlite3Strlen30((char*)nullId.z);
+    pList = sqlite3ExprListAppend(pParse, 0, 0);
+    if( pList==0 ) goto exit_create_index;
+    sqlite3ExprListSetName(pParse, pList, &nullId, 0);
+    pList->a[0].sortOrder = (u8)sortOrder;
+  }
+
+  /* Figure out how many bytes of space are required to store explicitly
+  ** specified collation sequence names.
+  */
+  for(i=0; i<pList->nExpr; i++){
+    Expr *pExpr = pList->a[i].pExpr;
+    if( pExpr ){
+      CollSeq *pColl = pExpr->pColl;
+      /* Either pColl!=0 or there was an OOM failure.  But if an OOM
+      ** failure we have quit before reaching this point. */
+      if( ALWAYS(pColl) ){
+        nExtra += (1 + sqlite3Strlen30(pColl->zName));
+      }
+    }
+  }
+
+  /* 
+  ** Allocate the index structure. 
+  */
+  nName = sqlite3Strlen30(zName);
+  nCol = pList->nExpr;
+  pIndex = sqlite3DbMallocZero(db, 
+      sizeof(Index) +              /* Index structure  */
+      sizeof(tRowcnt)*(nCol+1) +   /* Index.aiRowEst   */
+      sizeof(int)*nCol +           /* Index.aiColumn   */
+      sizeof(char *)*nCol +        /* Index.azColl     */
+      sizeof(u8)*nCol +            /* Index.aSortOrder */
+      nName + 1 +                  /* Index.zName      */
+      nExtra                       /* Collation sequence names */
+  );
+  if( db->mallocFailed ){
+    goto exit_create_index;
+  }
+  pIndex->aiRowEst = (tRowcnt*)(&pIndex[1]);
+  pIndex->azColl = (char**)(&pIndex->aiRowEst[nCol+1]);
+  pIndex->aiColumn = (int *)(&pIndex->azColl[nCol]);
+  pIndex->aSortOrder = (u8 *)(&pIndex->aiColumn[nCol]);
+  pIndex->zName = (char *)(&pIndex->aSortOrder[nCol]);
+  zExtra = (char *)(&pIndex->zName[nName+1]);
+  memcpy(pIndex->zName, zName, nName+1);
+  pIndex->pTable = pTab;
+  pIndex->nColumn = pList->nExpr;
+  pIndex->onError = (u8)onError;
+  pIndex->autoIndex = (u8)(pName==0);
+  pIndex->pSchema = db->aDb[iDb].pSchema;
+  assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+
+  /* Check to see if we should honor DESC requests on index columns
+  */
+  if( pDb->pSchema->file_format>=4 ){
+    sortOrderMask = -1;   /* Honor DESC */
+  }else{
+    sortOrderMask = 0;    /* Ignore DESC */
+  }
+
+  /* Scan the names of the columns of the table to be indexed and
+  ** load the column indices into the Index structure.  Report an error
+  ** if any column is not found.
+  **
+  ** TODO:  Add a test to make sure that the same column is not named
+  ** more than once within the same index.  Only the first instance of
+  ** the column will ever be used by the optimizer.  Note that using the
+  ** same column more than once cannot be an error because that would 
+  ** break backwards compatibility - it needs to be a warning.
+  */
+  for(i=0, pListItem=pList->a; i<pList->nExpr; i++, pListItem++){
+    const char *zColName = pListItem->zName;
+    Column *pTabCol;
+    int requestedSortOrder;
+    char *zColl;                   /* Collation sequence name */
+
+    for(j=0, pTabCol=pTab->aCol; j<pTab->nCol; j++, pTabCol++){
+      if( sqlite3StrICmp(zColName, pTabCol->zName)==0 ) break;
+    }
+    if( j>=pTab->nCol ){
+      sqlite3ErrorMsg(pParse, "table %s has no column named %s",
+        pTab->zName, zColName);
+      pParse->checkSchema = 1;
+      goto exit_create_index;
+    }
+    pIndex->aiColumn[i] = j;
+    /* Justification of the ALWAYS(pListItem->pExpr->pColl):  Because of
+    ** the way the "idxlist" non-terminal is constructed by the parser,
+    ** if pListItem->pExpr is not null then either pListItem->pExpr->pColl
+    ** must exist or else there must have been an OOM error.  But if there
+    ** was an OOM error, we would never reach this point. */
+    if( pListItem->pExpr && ALWAYS(pListItem->pExpr->pColl) ){
+      int nColl;
+      zColl = pListItem->pExpr->pColl->zName;
+      nColl = sqlite3Strlen30(zColl) + 1;
+      assert( nExtra>=nColl );
+      memcpy(zExtra, zColl, nColl);
+      zColl = zExtra;
+      zExtra += nColl;
+      nExtra -= nColl;
+    }else{
+      zColl = pTab->aCol[j].zColl;
+      if( !zColl ){
+        zColl = db->pDfltColl->zName;
+      }
+    }
+    if( !db->init.busy && !sqlite3LocateCollSeq(pParse, zColl) ){
+      goto exit_create_index;
+    }
+    pIndex->azColl[i] = zColl;
+    requestedSortOrder = pListItem->sortOrder & sortOrderMask;
+    pIndex->aSortOrder[i] = (u8)requestedSortOrder;
+  }
+  sqlite3DefaultRowEst(pIndex);
+
+  if( pTab==pParse->pNewTable ){
+    /* This routine has been called to create an automatic index as a
+    ** result of a PRIMARY KEY or UNIQUE clause on a column definition, or
+    ** a PRIMARY KEY or UNIQUE clause following the column definitions.
+    ** i.e. one of:
+    **
+    ** CREATE TABLE t(x PRIMARY KEY, y);
+    ** CREATE TABLE t(x, y, UNIQUE(x, y));
+    **
+    ** Either way, check to see if the table already has such an index. If
+    ** so, don't bother creating this one. This only applies to
+    ** automatically created indices. Users can do as they wish with
+    ** explicit indices.
+    **
+    ** Two UNIQUE or PRIMARY KEY constraints are considered equivalent
+    ** (and thus suppressing the second one) even if they have different
+    ** sort orders.
+    **
+    ** If there are different collating sequences or if the columns of
+    ** the constraint occur in different orders, then the constraints are
+    ** considered distinct and both result in separate indices.
+    */
+    Index *pIdx;
+    for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+      int k;
+      assert( pIdx->onError!=OE_None );
+      assert( pIdx->autoIndex );
+      assert( pIndex->onError!=OE_None );
+
+      if( pIdx->nColumn!=pIndex->nColumn ) continue;
+      for(k=0; k<pIdx->nColumn; k++){
+        const char *z1;
+        const char *z2;
+        if( pIdx->aiColumn[k]!=pIndex->aiColumn[k] ) break;
+        z1 = pIdx->azColl[k];
+        z2 = pIndex->azColl[k];
+        if( z1!=z2 && sqlite3StrICmp(z1, z2) ) break;
+      }
+      if( k==pIdx->nColumn ){
+        if( pIdx->onError!=pIndex->onError ){
+          /* This constraint creates the same index as a previous
+          ** constraint specified somewhere in the CREATE TABLE statement.
+          ** However the ON CONFLICT clauses are different. If both this 
+          ** constraint and the previous equivalent constraint have explicit
+          ** ON CONFLICT clauses this is an error. Otherwise, use the
+          ** explicitly specified behaviour for the index.
+          */
+          if( !(pIdx->onError==OE_Default || pIndex->onError==OE_Default) ){
+            sqlite3ErrorMsg(pParse, 
+                "conflicting ON CONFLICT clauses specified", 0);
+          }
+          if( pIdx->onError==OE_Default ){
+            pIdx->onError = pIndex->onError;
+          }
+        }
+        goto exit_create_index;
+      }
+    }
+  }
+
+  /* Link the new Index structure to its table and to the other
+  ** in-memory database structures. 
+  */
+  if( db->init.busy ){
+    Index *p;
+    assert( sqlite3SchemaMutexHeld(db, 0, pIndex->pSchema) );
+    p = sqlite3HashInsert(&pIndex->pSchema->idxHash, 
+                          pIndex->zName, sqlite3Strlen30(pIndex->zName),
+                          pIndex);
+    if( p ){
+      assert( p==pIndex );  /* Malloc must have failed */
+      db->mallocFailed = 1;
+      goto exit_create_index;
+    }
+    db->flags |= SQLITE_InternChanges;
+    if( pTblName!=0 ){
+      pIndex->tnum = db->init.newTnum;
+    }
+  }
+
+  /* If the db->init.busy is 0 then create the index on disk.  This
+  ** involves writing the index into the master table and filling in the
+  ** index with the current table contents.
+  **
+  ** The db->init.busy is 0 when the user first enters a CREATE INDEX 
+  ** command.  db->init.busy is 1 when a database is opened and 
+  ** CREATE INDEX statements are read out of the master table.  In
+  ** the latter case the index already exists on disk, which is why
+  ** we don't want to recreate it.
+  **
+  ** If pTblName==0 it means this index is generated as a primary key
+  ** or UNIQUE constraint of a CREATE TABLE statement.  Since the table
+  ** has just been created, it contains no data and the index initialization
+  ** step can be skipped.
+  */
+  else{ /* if( db->init.busy==0 ) */
+    Vdbe *v;
+    char *zStmt;
+    int iMem = ++pParse->nMem;
+
+    v = sqlite3GetVdbe(pParse);
+    if( v==0 ) goto exit_create_index;
+
+
+    /* Create the rootpage for the index
+    */
+    sqlite3BeginWriteOperation(pParse, 1, iDb);
+    sqlite3VdbeAddOp2(v, OP_CreateIndex, iDb, iMem);
+
+    /* Gather the complete text of the CREATE INDEX statement into
+    ** the zStmt variable
+    */
+    if( pStart ){
+      assert( pEnd!=0 );
+      /* A named index with an explicit CREATE INDEX statement */
+      zStmt = sqlite3MPrintf(db, "CREATE%s INDEX %.*s",
+        onError==OE_None ? "" : " UNIQUE",
+        (int)(pEnd->z - pName->z) + 1,
+        pName->z);
+    }else{
+      /* An automatic index created by a PRIMARY KEY or UNIQUE constraint */
+      /* zStmt = sqlite3MPrintf(""); */
+      zStmt = 0;
+    }
+
+    /* Add an entry in sqlite_master for this index
+    */
+    sqlite3NestedParse(pParse, 
+        "INSERT INTO %Q.%s VALUES('index',%Q,%Q,#%d,%Q);",
+        db->aDb[iDb].zName, SCHEMA_TABLE(iDb),
+        pIndex->zName,
+        pTab->zName,
+        iMem,
+        zStmt
+    );
+    sqlite3DbFree(db, zStmt);
+
+    /* Fill the index with data and reparse the schema. Code an OP_Expire
+    ** to invalidate all pre-compiled statements.
+    */
+    if( pTblName ){
+      sqlite3RefillIndex(pParse, pIndex, iMem);
+      sqlite3ChangeCookie(pParse, iDb);
+      sqlite3VdbeAddParseSchemaOp(v, iDb,
+         sqlite3MPrintf(db, "name='%q' AND type='index'", pIndex->zName));
+      sqlite3VdbeAddOp1(v, OP_Expire, 0);
+    }
+  }
+
+  /* When adding an index to the list of indices for a table, make
+  ** sure all indices labeled OE_Replace come after all those labeled
+  ** OE_Ignore.  This is necessary for the correct constraint check
+  ** processing (in sqlite3GenerateConstraintChecks()) as part of
+  ** UPDATE and INSERT statements.  
+  */
+  if( db->init.busy || pTblName==0 ){
+    if( onError!=OE_Replace || pTab->pIndex==0
+         || pTab->pIndex->onError==OE_Replace){
+      pIndex->pNext = pTab->pIndex;
+      pTab->pIndex = pIndex;
+    }else{
+      Index *pOther = pTab->pIndex;
+      while( pOther->pNext && pOther->pNext->onError!=OE_Replace ){
+        pOther = pOther->pNext;
+      }
+      pIndex->pNext = pOther->pNext;
+      pOther->pNext = pIndex;
+    }
+    pRet = pIndex;
+    pIndex = 0;
+  }
+
+  /* Clean up before exiting */
+exit_create_index:
+  if( pIndex ){
+    sqlite3DbFree(db, pIndex->zColAff);
+    sqlite3DbFree(db, pIndex);
+  }
+  sqlite3ExprListDelete(db, pList);
+  sqlite3SrcListDelete(db, pTblName);
+  sqlite3DbFree(db, zName);
+  return pRet;
+}
+
+/*
+** Fill the Index.aiRowEst[] array with default information - information
+** to be used when we have not run the ANALYZE command.
+**
+** aiRowEst[0] is suppose to contain the number of elements in the index.
+** Since we do not know, guess 1 million.  aiRowEst[1] is an estimate of the
+** number of rows in the table that match any particular value of the
+** first column of the index.  aiRowEst[2] is an estimate of the number
+** of rows that match any particular combiniation of the first 2 columns
+** of the index.  And so forth.  It must always be the case that
+*
+**           aiRowEst[N]<=aiRowEst[N-1]
+**           aiRowEst[N]>=1
+**
+** Apart from that, we have little to go on besides intuition as to
+** how aiRowEst[] should be initialized.  The numbers generated here
+** are based on typical values found in actual indices.
+*/
+void sqlite3DefaultRowEst(Index *pIdx){
+  tRowcnt *a = pIdx->aiRowEst;
+  int i;
+  tRowcnt n;
+  assert( a!=0 );
+  a[0] = pIdx->pTable->nRowEst;
+  if( a[0]<10 ) a[0] = 10;
+  n = 10;
+  for(i=1; i<=pIdx->nColumn; i++){
+    a[i] = n;
+    if( n>5 ) n--;
+  }
+  if( pIdx->onError!=OE_None ){
+    a[pIdx->nColumn] = 1;
+  }
+}
+
+/*
+** This routine will drop an existing named index.  This routine
+** implements the DROP INDEX statement.
+*/
+void sqlite3DropIndex(Parse *pParse, SrcList *pName, int ifExists){
+  Index *pIndex;
+  Vdbe *v;
+  sqlite3 *db = pParse->db;
+  int iDb;
+
+  assert( pParse->nErr==0 );   /* Never called with prior errors */
+  if( db->mallocFailed ){
+    goto exit_drop_index;
+  }
+  assert( pName->nSrc==1 );
+  if( SQLITE_OK!=sqlite3ReadSchema(pParse) ){
+    goto exit_drop_index;
+  }
+  pIndex = sqlite3FindIndex(db, pName->a[0].zName, pName->a[0].zDatabase);
+  if( pIndex==0 ){
+    if( !ifExists ){
+      sqlite3ErrorMsg(pParse, "no such index: %S", pName, 0);
+    }else{
+      sqlite3CodeVerifyNamedSchema(pParse, pName->a[0].zDatabase);
+    }
+    pParse->checkSchema = 1;
+    goto exit_drop_index;
+  }
+  if( pIndex->autoIndex ){
+    sqlite3ErrorMsg(pParse, "index associated with UNIQUE "
+      "or PRIMARY KEY constraint cannot be dropped", 0);
+    goto exit_drop_index;
+  }
+  iDb = sqlite3SchemaToIndex(db, pIndex->pSchema);
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  {
+    int code = SQLITE_DROP_INDEX;
+    Table *pTab = pIndex->pTable;
+    const char *zDb = db->aDb[iDb].zName;
+    const char *zTab = SCHEMA_TABLE(iDb);
+    if( sqlite3AuthCheck(pParse, SQLITE_DELETE, zTab, 0, zDb) ){
+      goto exit_drop_index;
+    }
+    if( !OMIT_TEMPDB && iDb ) code = SQLITE_DROP_TEMP_INDEX;
+    if( sqlite3AuthCheck(pParse, code, pIndex->zName, pTab->zName, zDb) ){
+      goto exit_drop_index;
+    }
+  }
+#endif
+
+  /* Generate code to remove the index and from the master table */
+  v = sqlite3GetVdbe(pParse);
+  if( v ){
+    sqlite3BeginWriteOperation(pParse, 1, iDb);
+    sqlite3NestedParse(pParse,
+       "DELETE FROM %Q.%s WHERE name=%Q AND type='index'",
+       db->aDb[iDb].zName, SCHEMA_TABLE(iDb), pIndex->zName
+    );
+    sqlite3ClearStatTables(pParse, iDb, "idx", pIndex->zName);
+    sqlite3ChangeCookie(pParse, iDb);
+    destroyRootPage(pParse, pIndex->tnum, iDb);
+    sqlite3VdbeAddOp4(v, OP_DropIndex, iDb, 0, 0, pIndex->zName, 0);
+  }
+
+exit_drop_index:
+  sqlite3SrcListDelete(db, pName);
+}
+
+/*
+** pArray is a pointer to an array of objects.  Each object in the
+** array is szEntry bytes in size.  This routine allocates a new
+** object on the end of the array.
+**
+** *pnEntry is the number of entries already in use.  *pnAlloc is
+** the previously allocated size of the array.  initSize is the
+** suggested initial array size allocation.
+**
+** The index of the new entry is returned in *pIdx.
+**
+** This routine returns a pointer to the array of objects.  This
+** might be the same as the pArray parameter or it might be a different
+** pointer if the array was resized.
+*/
+void *sqlite3ArrayAllocate(
+  sqlite3 *db,      /* Connection to notify of malloc failures */
+  void *pArray,     /* Array of objects.  Might be reallocated */
+  int szEntry,      /* Size of each object in the array */
+  int initSize,     /* Suggested initial allocation, in elements */
+  int *pnEntry,     /* Number of objects currently in use */
+  int *pnAlloc,     /* Current size of the allocation, in elements */
+  int *pIdx         /* Write the index of a new slot here */
+){
+  char *z;
+  if( *pnEntry >= *pnAlloc ){
+    void *pNew;
+    int newSize;
+    newSize = (*pnAlloc)*2 + initSize;
+    pNew = sqlite3DbRealloc(db, pArray, newSize*szEntry);
+    if( pNew==0 ){
+      *pIdx = -1;
+      return pArray;
+    }
+    *pnAlloc = sqlite3DbMallocSize(db, pNew)/szEntry;
+    pArray = pNew;
+  }
+  z = (char*)pArray;
+  memset(&z[*pnEntry * szEntry], 0, szEntry);
+  *pIdx = *pnEntry;
+  ++*pnEntry;
+  return pArray;
+}
+
+/*
+** Append a new element to the given IdList.  Create a new IdList if
+** need be.
+**
+** A new IdList is returned, or NULL if malloc() fails.
+*/
+IdList *sqlite3IdListAppend(sqlite3 *db, IdList *pList, Token *pToken){
+  int i;
+  if( pList==0 ){
+    pList = sqlite3DbMallocZero(db, sizeof(IdList) );
+    if( pList==0 ) return 0;
+    pList->nAlloc = 0;
+  }
+  pList->a = sqlite3ArrayAllocate(
+      db,
+      pList->a,
+      sizeof(pList->a[0]),
+      5,
+      &pList->nId,
+      &pList->nAlloc,
+      &i
+  );
+  if( i<0 ){
+    sqlite3IdListDelete(db, pList);
+    return 0;
+  }
+  pList->a[i].zName = sqlite3NameFromToken(db, pToken);
+  return pList;
+}
+
+/*
+** Delete an IdList.
+*/
+void sqlite3IdListDelete(sqlite3 *db, IdList *pList){
+  int i;
+  if( pList==0 ) return;
+  for(i=0; i<pList->nId; i++){
+    sqlite3DbFree(db, pList->a[i].zName);
+  }
+  sqlite3DbFree(db, pList->a);
+  sqlite3DbFree(db, pList);
+}
+
+/*
+** Return the index in pList of the identifier named zId.  Return -1
+** if not found.
+*/
+int sqlite3IdListIndex(IdList *pList, const char *zName){
+  int i;
+  if( pList==0 ) return -1;
+  for(i=0; i<pList->nId; i++){
+    if( sqlite3StrICmp(pList->a[i].zName, zName)==0 ) return i;
+  }
+  return -1;
+}
+
+/*
+** Expand the space allocated for the given SrcList object by
+** creating nExtra new slots beginning at iStart.  iStart is zero based.
+** New slots are zeroed.
+**
+** For example, suppose a SrcList initially contains two entries: A,B.
+** To append 3 new entries onto the end, do this:
+**
+**    sqlite3SrcListEnlarge(db, pSrclist, 3, 2);
+**
+** After the call above it would contain:  A, B, nil, nil, nil.
+** If the iStart argument had been 1 instead of 2, then the result
+** would have been:  A, nil, nil, nil, B.  To prepend the new slots,
+** the iStart value would be 0.  The result then would
+** be: nil, nil, nil, A, B.
+**
+** If a memory allocation fails the SrcList is unchanged.  The
+** db->mallocFailed flag will be set to true.
+*/
+SrcList *sqlite3SrcListEnlarge(
+  sqlite3 *db,       /* Database connection to notify of OOM errors */
+  SrcList *pSrc,     /* The SrcList to be enlarged */
+  int nExtra,        /* Number of new slots to add to pSrc->a[] */
+  int iStart         /* Index in pSrc->a[] of first new slot */
+){
+  int i;
+
+  /* Sanity checking on calling parameters */
+  assert( iStart>=0 );
+  assert( nExtra>=1 );
+  assert( pSrc!=0 );
+  assert( iStart<=pSrc->nSrc );
+
+  /* Allocate additional space if needed */
+  if( pSrc->nSrc+nExtra>pSrc->nAlloc ){
+    SrcList *pNew;
+    int nAlloc = pSrc->nSrc+nExtra;
+    int nGot;
+    pNew = sqlite3DbRealloc(db, pSrc,
+               sizeof(*pSrc) + (nAlloc-1)*sizeof(pSrc->a[0]) );
+    if( pNew==0 ){
+      assert( db->mallocFailed );
+      return pSrc;
+    }
+    pSrc = pNew;
+    nGot = (sqlite3DbMallocSize(db, pNew) - sizeof(*pSrc))/sizeof(pSrc->a[0])+1;
+    pSrc->nAlloc = (u16)nGot;
+  }
+
+  /* Move existing slots that come after the newly inserted slots
+  ** out of the way */
+  for(i=pSrc->nSrc-1; i>=iStart; i--){
+    pSrc->a[i+nExtra] = pSrc->a[i];
+  }
+  pSrc->nSrc += (i16)nExtra;
+
+  /* Zero the newly allocated slots */
+  memset(&pSrc->a[iStart], 0, sizeof(pSrc->a[0])*nExtra);
+  for(i=iStart; i<iStart+nExtra; i++){
+    pSrc->a[i].iCursor = -1;
+  }
+
+  /* Return a pointer to the enlarged SrcList */
+  return pSrc;
+}
+
+
+/*
+** Append a new table name to the given SrcList.  Create a new SrcList if
+** need be.  A new entry is created in the SrcList even if pTable is NULL.
+**
+** A SrcList is returned, or NULL if there is an OOM error.  The returned
+** SrcList might be the same as the SrcList that was input or it might be
+** a new one.  If an OOM error does occurs, then the prior value of pList
+** that is input to this routine is automatically freed.
+**
+** If pDatabase is not null, it means that the table has an optional
+** database name prefix.  Like this:  "database.table".  The pDatabase
+** points to the table name and the pTable points to the database name.
+** The SrcList.a[].zName field is filled with the table name which might
+** come from pTable (if pDatabase is NULL) or from pDatabase.  
+** SrcList.a[].zDatabase is filled with the database name from pTable,
+** or with NULL if no database is specified.
+**
+** In other words, if call like this:
+**
+**         sqlite3SrcListAppend(D,A,B,0);
+**
+** Then B is a table name and the database name is unspecified.  If called
+** like this:
+**
+**         sqlite3SrcListAppend(D,A,B,C);
+**
+** Then C is the table name and B is the database name.  If C is defined
+** then so is B.  In other words, we never have a case where:
+**
+**         sqlite3SrcListAppend(D,A,0,C);
+**
+** Both pTable and pDatabase are assumed to be quoted.  They are dequoted
+** before being added to the SrcList.
+*/
+SrcList *sqlite3SrcListAppend(
+  sqlite3 *db,        /* Connection to notify of malloc failures */
+  SrcList *pList,     /* Append to this SrcList. NULL creates a new SrcList */
+  Token *pTable,      /* Table to append */
+  Token *pDatabase    /* Database of the table */
+){
+  struct SrcList_item *pItem;
+  assert( pDatabase==0 || pTable!=0 );  /* Cannot have C without B */
+  if( pList==0 ){
+    pList = sqlite3DbMallocZero(db, sizeof(SrcList) );
+    if( pList==0 ) return 0;
+    pList->nAlloc = 1;
+  }
+  pList = sqlite3SrcListEnlarge(db, pList, 1, pList->nSrc);
+  if( db->mallocFailed ){
+    sqlite3SrcListDelete(db, pList);
+    return 0;
+  }
+  pItem = &pList->a[pList->nSrc-1];
+  if( pDatabase && pDatabase->z==0 ){
+    pDatabase = 0;
+  }
+  if( pDatabase ){
+    Token *pTemp = pDatabase;
+    pDatabase = pTable;
+    pTable = pTemp;
+  }
+  pItem->zName = sqlite3NameFromToken(db, pTable);
+  pItem->zDatabase = sqlite3NameFromToken(db, pDatabase);
+  return pList;
+}
+
+/*
+** Assign VdbeCursor index numbers to all tables in a SrcList
+*/
+void sqlite3SrcListAssignCursors(Parse *pParse, SrcList *pList){
+  int i;
+  struct SrcList_item *pItem;
+  assert(pList || pParse->db->mallocFailed );
+  if( pList ){
+    for(i=0, pItem=pList->a; i<pList->nSrc; i++, pItem++){
+      if( pItem->iCursor>=0 ) break;
+      pItem->iCursor = pParse->nTab++;
+      if( pItem->pSelect ){
+        sqlite3SrcListAssignCursors(pParse, pItem->pSelect->pSrc);
+      }
+    }
+  }
+}
+
+/*
+** Delete an entire SrcList including all its substructure.
+*/
+void sqlite3SrcListDelete(sqlite3 *db, SrcList *pList){
+  int i;
+  struct SrcList_item *pItem;
+  if( pList==0 ) return;
+  for(pItem=pList->a, i=0; i<pList->nSrc; i++, pItem++){
+    sqlite3DbFree(db, pItem->zDatabase);
+    sqlite3DbFree(db, pItem->zName);
+    sqlite3DbFree(db, pItem->zAlias);
+    sqlite3DbFree(db, pItem->zIndex);
+    sqlite3DeleteTable(db, pItem->pTab);
+    sqlite3SelectDelete(db, pItem->pSelect);
+    sqlite3ExprDelete(db, pItem->pOn);
+    sqlite3IdListDelete(db, pItem->pUsing);
+  }
+  sqlite3DbFree(db, pList);
+}
+
+/*
+** This routine is called by the parser to add a new term to the
+** end of a growing FROM clause.  The "p" parameter is the part of
+** the FROM clause that has already been constructed.  "p" is NULL
+** if this is the first term of the FROM clause.  pTable and pDatabase
+** are the name of the table and database named in the FROM clause term.
+** pDatabase is NULL if the database name qualifier is missing - the
+** usual case.  If the term has a alias, then pAlias points to the
+** alias token.  If the term is a subquery, then pSubquery is the
+** SELECT statement that the subquery encodes.  The pTable and
+** pDatabase parameters are NULL for subqueries.  The pOn and pUsing
+** parameters are the content of the ON and USING clauses.
+**
+** Return a new SrcList which encodes is the FROM with the new
+** term added.
+*/
+SrcList *sqlite3SrcListAppendFromTerm(
+  Parse *pParse,          /* Parsing context */
+  SrcList *p,             /* The left part of the FROM clause already seen */
+  Token *pTable,          /* Name of the table to add to the FROM clause */
+  Token *pDatabase,       /* Name of the database containing pTable */
+  Token *pAlias,          /* The right-hand side of the AS subexpression */
+  Select *pSubquery,      /* A subquery used in place of a table name */
+  Expr *pOn,              /* The ON clause of a join */
+  IdList *pUsing          /* The USING clause of a join */
+){
+  struct SrcList_item *pItem;
+  sqlite3 *db = pParse->db;
+  if( !p && (pOn || pUsing) ){
+    sqlite3ErrorMsg(pParse, "a JOIN clause is required before %s", 
+      (pOn ? "ON" : "USING")
+    );
+    goto append_from_error;
+  }
+  p = sqlite3SrcListAppend(db, p, pTable, pDatabase);
+  if( p==0 || NEVER(p->nSrc==0) ){
+    goto append_from_error;
+  }
+  pItem = &p->a[p->nSrc-1];
+  assert( pAlias!=0 );
+  if( pAlias->n ){
+    pItem->zAlias = sqlite3NameFromToken(db, pAlias);
+  }
+  pItem->pSelect = pSubquery;
+  pItem->pOn = pOn;
+  pItem->pUsing = pUsing;
+  return p;
+
+ append_from_error:
+  assert( p==0 );
+  sqlite3ExprDelete(db, pOn);
+  sqlite3IdListDelete(db, pUsing);
+  sqlite3SelectDelete(db, pSubquery);
+  return 0;
+}
+
+/*
+** Add an INDEXED BY or NOT INDEXED clause to the most recently added 
+** element of the source-list passed as the second argument.
+*/
+void sqlite3SrcListIndexedBy(Parse *pParse, SrcList *p, Token *pIndexedBy){
+  assert( pIndexedBy!=0 );
+  if( p && ALWAYS(p->nSrc>0) ){
+    struct SrcList_item *pItem = &p->a[p->nSrc-1];
+    assert( pItem->notIndexed==0 && pItem->zIndex==0 );
+    if( pIndexedBy->n==1 && !pIndexedBy->z ){
+      /* A "NOT INDEXED" clause was supplied. See parse.y 
+      ** construct "indexed_opt" for details. */
+      pItem->notIndexed = 1;
+    }else{
+      pItem->zIndex = sqlite3NameFromToken(pParse->db, pIndexedBy);
+    }
+  }
+}
+
+/*
+** When building up a FROM clause in the parser, the join operator
+** is initially attached to the left operand.  But the code generator
+** expects the join operator to be on the right operand.  This routine
+** Shifts all join operators from left to right for an entire FROM
+** clause.
+**
+** Example: Suppose the join is like this:
+**
+**           A natural cross join B
+**
+** The operator is "natural cross join".  The A and B operands are stored
+** in p->a[0] and p->a[1], respectively.  The parser initially stores the
+** operator with A.  This routine shifts that operator over to B.
+*/
+void sqlite3SrcListShiftJoinType(SrcList *p){
+  if( p ){
+    int i;
+    assert( p->a || p->nSrc==0 );
+    for(i=p->nSrc-1; i>0; i--){
+      p->a[i].jointype = p->a[i-1].jointype;
+    }
+    p->a[0].jointype = 0;
+  }
+}
+
+/*
+** Begin a transaction
+*/
+void sqlite3BeginTransaction(Parse *pParse, int type){
+  sqlite3 *db;
+  Vdbe *v;
+  int i;
+
+  assert( pParse!=0 );
+  db = pParse->db;
+  assert( db!=0 );
+/*  if( db->aDb[0].pBt==0 ) return; */
+  if( sqlite3AuthCheck(pParse, SQLITE_TRANSACTION, "BEGIN", 0, 0) ){
+    return;
+  }
+  v = sqlite3GetVdbe(pParse);
+  if( !v ) return;
+  if( type!=TK_DEFERRED ){
+    for(i=0; i<db->nDb; i++){
+      sqlite3VdbeAddOp2(v, OP_Transaction, i, (type==TK_EXCLUSIVE)+1);
+      sqlite3VdbeUsesBtree(v, i);
+    }
+  }
+  sqlite3VdbeAddOp2(v, OP_AutoCommit, 0, 0);
+}
+
+/*
+** Commit a transaction
+*/
+void sqlite3CommitTransaction(Parse *pParse){
+  Vdbe *v;
+
+  assert( pParse!=0 );
+  assert( pParse->db!=0 );
+  if( sqlite3AuthCheck(pParse, SQLITE_TRANSACTION, "COMMIT", 0, 0) ){
+    return;
+  }
+  v = sqlite3GetVdbe(pParse);
+  if( v ){
+    sqlite3VdbeAddOp2(v, OP_AutoCommit, 1, 0);
+  }
+}
+
+/*
+** Rollback a transaction
+*/
+void sqlite3RollbackTransaction(Parse *pParse){
+  Vdbe *v;
+
+  assert( pParse!=0 );
+  assert( pParse->db!=0 );
+  if( sqlite3AuthCheck(pParse, SQLITE_TRANSACTION, "ROLLBACK", 0, 0) ){
+    return;
+  }
+  v = sqlite3GetVdbe(pParse);
+  if( v ){
+    sqlite3VdbeAddOp2(v, OP_AutoCommit, 1, 1);
+  }
+}
+
+/*
+** This function is called by the parser when it parses a command to create,
+** release or rollback an SQL savepoint. 
+*/
+void sqlite3Savepoint(Parse *pParse, int op, Token *pName){
+  char *zName = sqlite3NameFromToken(pParse->db, pName);
+  if( zName ){
+    Vdbe *v = sqlite3GetVdbe(pParse);
+#ifndef SQLITE_OMIT_AUTHORIZATION
+    static const char * const az[] = { "BEGIN", "RELEASE", "ROLLBACK" };
+    assert( !SAVEPOINT_BEGIN && SAVEPOINT_RELEASE==1 && SAVEPOINT_ROLLBACK==2 );
+#endif
+    if( !v || sqlite3AuthCheck(pParse, SQLITE_SAVEPOINT, az[op], zName, 0) ){
+      sqlite3DbFree(pParse->db, zName);
+      return;
+    }
+    sqlite3VdbeAddOp4(v, OP_Savepoint, op, 0, 0, zName, P4_DYNAMIC);
+  }
+}
+
+/*
+** Make sure the TEMP database is open and available for use.  Return
+** the number of errors.  Leave any error messages in the pParse structure.
+*/
+int sqlite3OpenTempDatabase(Parse *pParse){
+  sqlite3 *db = pParse->db;
+  if( db->aDb[1].pBt==0 && !pParse->explain ){
+    int rc;
+    Btree *pBt;
+    static const int flags = 
+          SQLITE_OPEN_READWRITE |
+          SQLITE_OPEN_CREATE |
+          SQLITE_OPEN_EXCLUSIVE |
+          SQLITE_OPEN_DELETEONCLOSE |
+          SQLITE_OPEN_TEMP_DB;
+
+    rc = sqlite3BtreeOpen(db->pVfs, 0, db, &pBt, 0, flags);
+    if( rc!=SQLITE_OK ){
+      sqlite3ErrorMsg(pParse, "unable to open a temporary database "
+        "file for storing temporary tables");
+      pParse->rc = rc;
+      return 1;
+    }
+    db->aDb[1].pBt = pBt;
+    assert( db->aDb[1].pSchema );
+    if( SQLITE_NOMEM==sqlite3BtreeSetPageSize(pBt, db->nextPagesize, -1, 0) ){
+      db->mallocFailed = 1;
+      return 1;
+    }
+  }
+  return 0;
+}
+
+/*
+** Generate VDBE code that will verify the schema cookie and start
+** a read-transaction for all named database files.
+**
+** It is important that all schema cookies be verified and all
+** read transactions be started before anything else happens in
+** the VDBE program.  But this routine can be called after much other
+** code has been generated.  So here is what we do:
+**
+** The first time this routine is called, we code an OP_Goto that
+** will jump to a subroutine at the end of the program.  Then we
+** record every database that needs its schema verified in the
+** pParse->cookieMask field.  Later, after all other code has been
+** generated, the subroutine that does the cookie verifications and
+** starts the transactions will be coded and the OP_Goto P2 value
+** will be made to point to that subroutine.  The generation of the
+** cookie verification subroutine code happens in sqlite3FinishCoding().
+**
+** If iDb<0 then code the OP_Goto only - don't set flag to verify the
+** schema on any databases.  This can be used to position the OP_Goto
+** early in the code, before we know if any database tables will be used.
+*/
+void sqlite3CodeVerifySchema(Parse *pParse, int iDb){
+  Parse *pToplevel = sqlite3ParseToplevel(pParse);
+
+  if( pToplevel->cookieGoto==0 ){
+    Vdbe *v = sqlite3GetVdbe(pToplevel);
+    if( v==0 ) return;  /* This only happens if there was a prior error */
+    pToplevel->cookieGoto = sqlite3VdbeAddOp2(v, OP_Goto, 0, 0)+1;
+  }
+  if( iDb>=0 ){
+    sqlite3 *db = pToplevel->db;
+    yDbMask mask;
+
+    assert( iDb<db->nDb );
+    assert( db->aDb[iDb].pBt!=0 || iDb==1 );
+    assert( iDb<SQLITE_MAX_ATTACHED+2 );
+    assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+    mask = ((yDbMask)1)<<iDb;
+    if( (pToplevel->cookieMask & mask)==0 ){
+      pToplevel->cookieMask |= mask;
+      pToplevel->cookieValue[iDb] = db->aDb[iDb].pSchema->schema_cookie;
+      if( !OMIT_TEMPDB && iDb==1 ){
+        sqlite3OpenTempDatabase(pToplevel);
+      }
+    }
+  }
+}
+
+/*
+** If argument zDb is NULL, then call sqlite3CodeVerifySchema() for each 
+** attached database. Otherwise, invoke it for the database named zDb only.
+*/
+void sqlite3CodeVerifyNamedSchema(Parse *pParse, const char *zDb){
+  sqlite3 *db = pParse->db;
+  int i;
+  for(i=0; i<db->nDb; i++){
+    Db *pDb = &db->aDb[i];
+    if( pDb->pBt && (!zDb || 0==sqlite3StrICmp(zDb, pDb->zName)) ){
+      sqlite3CodeVerifySchema(pParse, i);
+    }
+  }
+}
+
+/*
+** Generate VDBE code that prepares for doing an operation that
+** might change the database.
+**
+** This routine starts a new transaction if we are not already within
+** a transaction.  If we are already within a transaction, then a checkpoint
+** is set if the setStatement parameter is true.  A checkpoint should
+** be set for operations that might fail (due to a constraint) part of
+** the way through and which will need to undo some writes without having to
+** rollback the whole transaction.  For operations where all constraints
+** can be checked before any changes are made to the database, it is never
+** necessary to undo a write and the checkpoint should not be set.
+*/
+void sqlite3BeginWriteOperation(Parse *pParse, int setStatement, int iDb){
+  Parse *pToplevel = sqlite3ParseToplevel(pParse);
+  sqlite3CodeVerifySchema(pParse, iDb);
+  pToplevel->writeMask |= ((yDbMask)1)<<iDb;
+  pToplevel->isMultiWrite |= setStatement;
+}
+
+/*
+** Indicate that the statement currently under construction might write
+** more than one entry (example: deleting one row then inserting another,
+** inserting multiple rows in a table, or inserting a row and index entries.)
+** If an abort occurs after some of these writes have completed, then it will
+** be necessary to undo the completed writes.
+*/
+void sqlite3MultiWrite(Parse *pParse){
+  Parse *pToplevel = sqlite3ParseToplevel(pParse);
+  pToplevel->isMultiWrite = 1;
+}
+
+/* 
+** The code generator calls this routine if is discovers that it is
+** possible to abort a statement prior to completion.  In order to 
+** perform this abort without corrupting the database, we need to make
+** sure that the statement is protected by a statement transaction.
+**
+** Technically, we only need to set the mayAbort flag if the
+** isMultiWrite flag was previously set.  There is a time dependency
+** such that the abort must occur after the multiwrite.  This makes
+** some statements involving the REPLACE conflict resolution algorithm
+** go a little faster.  But taking advantage of this time dependency
+** makes it more difficult to prove that the code is correct (in 
+** particular, it prevents us from writing an effective
+** implementation of sqlite3AssertMayAbort()) and so we have chosen
+** to take the safe route and skip the optimization.
+*/
+void sqlite3MayAbort(Parse *pParse){
+  Parse *pToplevel = sqlite3ParseToplevel(pParse);
+  pToplevel->mayAbort = 1;
+}
+
+/*
+** Code an OP_Halt that causes the vdbe to return an SQLITE_CONSTRAINT
+** error. The onError parameter determines which (if any) of the statement
+** and/or current transaction is rolled back.
+*/
+void sqlite3HaltConstraint(Parse *pParse, int onError, char *p4, int p4type){
+  Vdbe *v = sqlite3GetVdbe(pParse);
+  if( onError==OE_Abort ){
+    sqlite3MayAbort(pParse);
+  }
+  sqlite3VdbeAddOp4(v, OP_Halt, SQLITE_CONSTRAINT, onError, 0, p4, p4type);
+}
+
+/*
+** Check to see if pIndex uses the collating sequence pColl.  Return
+** true if it does and false if it does not.
+*/
+#ifndef SQLITE_OMIT_REINDEX
+static int collationMatch(const char *zColl, Index *pIndex){
+  int i;
+  assert( zColl!=0 );
+  for(i=0; i<pIndex->nColumn; i++){
+    const char *z = pIndex->azColl[i];
+    assert( z!=0 );
+    if( 0==sqlite3StrICmp(z, zColl) ){
+      return 1;
+    }
+  }
+  return 0;
+}
+#endif
+
+/*
+** Recompute all indices of pTab that use the collating sequence pColl.
+** If pColl==0 then recompute all indices of pTab.
+*/
+#ifndef SQLITE_OMIT_REINDEX
+static void reindexTable(Parse *pParse, Table *pTab, char const *zColl){
+  Index *pIndex;              /* An index associated with pTab */
+
+  for(pIndex=pTab->pIndex; pIndex; pIndex=pIndex->pNext){
+    if( zColl==0 || collationMatch(zColl, pIndex) ){
+      int iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
+      sqlite3BeginWriteOperation(pParse, 0, iDb);
+      sqlite3RefillIndex(pParse, pIndex, -1);
+    }
+  }
+}
+#endif
+
+/*
+** Recompute all indices of all tables in all databases where the
+** indices use the collating sequence pColl.  If pColl==0 then recompute
+** all indices everywhere.
+*/
+#ifndef SQLITE_OMIT_REINDEX
+static void reindexDatabases(Parse *pParse, char const *zColl){
+  Db *pDb;                    /* A single database */
+  int iDb;                    /* The database index number */
+  sqlite3 *db = pParse->db;   /* The database connection */
+  HashElem *k;                /* For looping over tables in pDb */
+  Table *pTab;                /* A table in the database */
+
+  assert( sqlite3BtreeHoldsAllMutexes(db) );  /* Needed for schema access */
+  for(iDb=0, pDb=db->aDb; iDb<db->nDb; iDb++, pDb++){
+    assert( pDb!=0 );
+    for(k=sqliteHashFirst(&pDb->pSchema->tblHash);  k; k=sqliteHashNext(k)){
+      pTab = (Table*)sqliteHashData(k);
+      reindexTable(pParse, pTab, zColl);
+    }
+  }
+}
+#endif
+
+/*
+** Generate code for the REINDEX command.
+**
+**        REINDEX                            -- 1
+**        REINDEX  <collation>               -- 2
+**        REINDEX  ?<database>.?<tablename>  -- 3
+**        REINDEX  ?<database>.?<indexname>  -- 4
+**
+** Form 1 causes all indices in all attached databases to be rebuilt.
+** Form 2 rebuilds all indices in all databases that use the named
+** collating function.  Forms 3 and 4 rebuild the named index or all
+** indices associated with the named table.
+*/
+#ifndef SQLITE_OMIT_REINDEX
+void sqlite3Reindex(Parse *pParse, Token *pName1, Token *pName2){
+  CollSeq *pColl;             /* Collating sequence to be reindexed, or NULL */
+  char *z;                    /* Name of a table or index */
+  const char *zDb;            /* Name of the database */
+  Table *pTab;                /* A table in the database */
+  Index *pIndex;              /* An index associated with pTab */
+  int iDb;                    /* The database index number */
+  sqlite3 *db = pParse->db;   /* The database connection */
+  Token *pObjName;            /* Name of the table or index to be reindexed */
+
+  /* Read the database schema. If an error occurs, leave an error message
+  ** and code in pParse and return NULL. */
+  if( SQLITE_OK!=sqlite3ReadSchema(pParse) ){
+    return;
+  }
+
+  if( pName1==0 ){
+    reindexDatabases(pParse, 0);
+    return;
+  }else if( NEVER(pName2==0) || pName2->z==0 ){
+    char *zColl;
+    assert( pName1->z );
+    zColl = sqlite3NameFromToken(pParse->db, pName1);
+    if( !zColl ) return;
+    pColl = sqlite3FindCollSeq(db, ENC(db), zColl, 0);
+    if( pColl ){
+      reindexDatabases(pParse, zColl);
+      sqlite3DbFree(db, zColl);
+      return;
+    }
+    sqlite3DbFree(db, zColl);
+  }
+  iDb = sqlite3TwoPartName(pParse, pName1, pName2, &pObjName);
+  if( iDb<0 ) return;
+  z = sqlite3NameFromToken(db, pObjName);
+  if( z==0 ) return;
+  zDb = db->aDb[iDb].zName;
+  pTab = sqlite3FindTable(db, z, zDb);
+  if( pTab ){
+    reindexTable(pParse, pTab, 0);
+    sqlite3DbFree(db, z);
+    return;
+  }
+  pIndex = sqlite3FindIndex(db, z, zDb);
+  sqlite3DbFree(db, z);
+  if( pIndex ){
+    sqlite3BeginWriteOperation(pParse, 0, iDb);
+    sqlite3RefillIndex(pParse, pIndex, -1);
+    return;
+  }
+  sqlite3ErrorMsg(pParse, "unable to identify the object to be reindexed");
+}
+#endif
+
+/*
+** Return a dynamicly allocated KeyInfo structure that can be used
+** with OP_OpenRead or OP_OpenWrite to access database index pIdx.
+**
+** If successful, a pointer to the new structure is returned. In this case
+** the caller is responsible for calling sqlite3DbFree(db, ) on the returned 
+** pointer. If an error occurs (out of memory or missing collation 
+** sequence), NULL is returned and the state of pParse updated to reflect
+** the error.
+*/
+KeyInfo *sqlite3IndexKeyinfo(Parse *pParse, Index *pIdx){
+  int i;
+  int nCol = pIdx->nColumn;
+  int nBytes = sizeof(KeyInfo) + (nCol-1)*sizeof(CollSeq*) + nCol;
+  sqlite3 *db = pParse->db;
+  KeyInfo *pKey = (KeyInfo *)sqlite3DbMallocZero(db, nBytes);
+
+  if( pKey ){
+    pKey->db = pParse->db;
+    pKey->aSortOrder = (u8 *)&(pKey->aColl[nCol]);
+    assert( &pKey->aSortOrder[nCol]==&(((u8 *)pKey)[nBytes]) );
+    for(i=0; i<nCol; i++){
+      char *zColl = pIdx->azColl[i];
+      assert( zColl );
+      pKey->aColl[i] = sqlite3LocateCollSeq(pParse, zColl);
+      pKey->aSortOrder[i] = pIdx->aSortOrder[i];
+    }
+    pKey->nField = (u16)nCol;
+  }
+
+  if( pParse->nErr ){
+    sqlite3DbFree(db, pKey);
+    pKey = 0;
+  }
+  return pKey;
+}
diff --git a/src/callback.c b/src/callback.c
new file mode 100644
index 0000000..ce84908
--- /dev/null
+++ b/src/callback.c
@@ -0,0 +1,457 @@
+/*
+** 2005 May 23 
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains functions used to access the internal hash tables
+** of user defined functions and collation sequences.
+*/
+
+#include "sqliteInt.h"
+
+/*
+** Invoke the 'collation needed' callback to request a collation sequence
+** in the encoding enc of name zName, length nName.
+*/
+static void callCollNeeded(sqlite3 *db, int enc, const char *zName){
+  assert( !db->xCollNeeded || !db->xCollNeeded16 );
+  if( db->xCollNeeded ){
+    char *zExternal = sqlite3DbStrDup(db, zName);
+    if( !zExternal ) return;
+    db->xCollNeeded(db->pCollNeededArg, db, enc, zExternal);
+    sqlite3DbFree(db, zExternal);
+  }
+#ifndef SQLITE_OMIT_UTF16
+  if( db->xCollNeeded16 ){
+    char const *zExternal;
+    sqlite3_value *pTmp = sqlite3ValueNew(db);
+    sqlite3ValueSetStr(pTmp, -1, zName, SQLITE_UTF8, SQLITE_STATIC);
+    zExternal = sqlite3ValueText(pTmp, SQLITE_UTF16NATIVE);
+    if( zExternal ){
+      db->xCollNeeded16(db->pCollNeededArg, db, (int)ENC(db), zExternal);
+    }
+    sqlite3ValueFree(pTmp);
+  }
+#endif
+}
+
+/*
+** This routine is called if the collation factory fails to deliver a
+** collation function in the best encoding but there may be other versions
+** of this collation function (for other text encodings) available. Use one
+** of these instead if they exist. Avoid a UTF-8 <-> UTF-16 conversion if
+** possible.
+*/
+static int synthCollSeq(sqlite3 *db, CollSeq *pColl){
+  CollSeq *pColl2;
+  char *z = pColl->zName;
+  int i;
+  static const u8 aEnc[] = { SQLITE_UTF16BE, SQLITE_UTF16LE, SQLITE_UTF8 };
+  for(i=0; i<3; i++){
+    pColl2 = sqlite3FindCollSeq(db, aEnc[i], z, 0);
+    if( pColl2->xCmp!=0 ){
+      memcpy(pColl, pColl2, sizeof(CollSeq));
+      pColl->xDel = 0;         /* Do not copy the destructor */
+      return SQLITE_OK;
+    }
+  }
+  return SQLITE_ERROR;
+}
+
+/*
+** This function is responsible for invoking the collation factory callback
+** or substituting a collation sequence of a different encoding when the
+** requested collation sequence is not available in the desired encoding.
+** 
+** If it is not NULL, then pColl must point to the database native encoding 
+** collation sequence with name zName, length nName.
+**
+** The return value is either the collation sequence to be used in database
+** db for collation type name zName, length nName, or NULL, if no collation
+** sequence can be found.
+**
+** See also: sqlite3LocateCollSeq(), sqlite3FindCollSeq()
+*/
+CollSeq *sqlite3GetCollSeq(
+  sqlite3* db,          /* The database connection */
+  u8 enc,               /* The desired encoding for the collating sequence */
+  CollSeq *pColl,       /* Collating sequence with native encoding, or NULL */
+  const char *zName     /* Collating sequence name */
+){
+  CollSeq *p;
+
+  p = pColl;
+  if( !p ){
+    p = sqlite3FindCollSeq(db, enc, zName, 0);
+  }
+  if( !p || !p->xCmp ){
+    /* No collation sequence of this type for this encoding is registered.
+    ** Call the collation factory to see if it can supply us with one.
+    */
+    callCollNeeded(db, enc, zName);
+    p = sqlite3FindCollSeq(db, enc, zName, 0);
+  }
+  if( p && !p->xCmp && synthCollSeq(db, p) ){
+    p = 0;
+  }
+  assert( !p || p->xCmp );
+  return p;
+}
+
+/*
+** This routine is called on a collation sequence before it is used to
+** check that it is defined. An undefined collation sequence exists when
+** a database is loaded that contains references to collation sequences
+** that have not been defined by sqlite3_create_collation() etc.
+**
+** If required, this routine calls the 'collation needed' callback to
+** request a definition of the collating sequence. If this doesn't work, 
+** an equivalent collating sequence that uses a text encoding different
+** from the main database is substituted, if one is available.
+*/
+int sqlite3CheckCollSeq(Parse *pParse, CollSeq *pColl){
+  if( pColl ){
+    const char *zName = pColl->zName;
+    sqlite3 *db = pParse->db;
+    CollSeq *p = sqlite3GetCollSeq(db, ENC(db), pColl, zName);
+    if( !p ){
+      sqlite3ErrorMsg(pParse, "no such collation sequence: %s", zName);
+      pParse->nErr++;
+      return SQLITE_ERROR;
+    }
+    assert( p==pColl );
+  }
+  return SQLITE_OK;
+}
+
+
+
+/*
+** Locate and return an entry from the db.aCollSeq hash table. If the entry
+** specified by zName and nName is not found and parameter 'create' is
+** true, then create a new entry. Otherwise return NULL.
+**
+** Each pointer stored in the sqlite3.aCollSeq hash table contains an
+** array of three CollSeq structures. The first is the collation sequence
+** prefferred for UTF-8, the second UTF-16le, and the third UTF-16be.
+**
+** Stored immediately after the three collation sequences is a copy of
+** the collation sequence name. A pointer to this string is stored in
+** each collation sequence structure.
+*/
+static CollSeq *findCollSeqEntry(
+  sqlite3 *db,          /* Database connection */
+  const char *zName,    /* Name of the collating sequence */
+  int create            /* Create a new entry if true */
+){
+  CollSeq *pColl;
+  int nName = sqlite3Strlen30(zName);
+  pColl = sqlite3HashFind(&db->aCollSeq, zName, nName);
+
+  if( 0==pColl && create ){
+    pColl = sqlite3DbMallocZero(db, 3*sizeof(*pColl) + nName + 1 );
+    if( pColl ){
+      CollSeq *pDel = 0;
+      pColl[0].zName = (char*)&pColl[3];
+      pColl[0].enc = SQLITE_UTF8;
+      pColl[1].zName = (char*)&pColl[3];
+      pColl[1].enc = SQLITE_UTF16LE;
+      pColl[2].zName = (char*)&pColl[3];
+      pColl[2].enc = SQLITE_UTF16BE;
+      memcpy(pColl[0].zName, zName, nName);
+      pColl[0].zName[nName] = 0;
+      pDel = sqlite3HashInsert(&db->aCollSeq, pColl[0].zName, nName, pColl);
+
+      /* If a malloc() failure occurred in sqlite3HashInsert(), it will 
+      ** return the pColl pointer to be deleted (because it wasn't added
+      ** to the hash table).
+      */
+      assert( pDel==0 || pDel==pColl );
+      if( pDel!=0 ){
+        db->mallocFailed = 1;
+        sqlite3DbFree(db, pDel);
+        pColl = 0;
+      }
+    }
+  }
+  return pColl;
+}
+
+/*
+** Parameter zName points to a UTF-8 encoded string nName bytes long.
+** Return the CollSeq* pointer for the collation sequence named zName
+** for the encoding 'enc' from the database 'db'.
+**
+** If the entry specified is not found and 'create' is true, then create a
+** new entry.  Otherwise return NULL.
+**
+** A separate function sqlite3LocateCollSeq() is a wrapper around
+** this routine.  sqlite3LocateCollSeq() invokes the collation factory
+** if necessary and generates an error message if the collating sequence
+** cannot be found.
+**
+** See also: sqlite3LocateCollSeq(), sqlite3GetCollSeq()
+*/
+CollSeq *sqlite3FindCollSeq(
+  sqlite3 *db,
+  u8 enc,
+  const char *zName,
+  int create
+){
+  CollSeq *pColl;
+  if( zName ){
+    pColl = findCollSeqEntry(db, zName, create);
+  }else{
+    pColl = db->pDfltColl;
+  }
+  assert( SQLITE_UTF8==1 && SQLITE_UTF16LE==2 && SQLITE_UTF16BE==3 );
+  assert( enc>=SQLITE_UTF8 && enc<=SQLITE_UTF16BE );
+  if( pColl ) pColl += enc-1;
+  return pColl;
+}
+
+/* During the search for the best function definition, this procedure
+** is called to test how well the function passed as the first argument
+** matches the request for a function with nArg arguments in a system
+** that uses encoding enc. The value returned indicates how well the
+** request is matched. A higher value indicates a better match.
+**
+** The returned value is always between 0 and 6, as follows:
+**
+** 0: Not a match, or if nArg<0 and the function is has no implementation.
+** 1: A variable arguments function that prefers UTF-8 when a UTF-16
+**    encoding is requested, or vice versa.
+** 2: A variable arguments function that uses UTF-16BE when UTF-16LE is
+**    requested, or vice versa.
+** 3: A variable arguments function using the same text encoding.
+** 4: A function with the exact number of arguments requested that
+**    prefers UTF-8 when a UTF-16 encoding is requested, or vice versa.
+** 5: A function with the exact number of arguments requested that
+**    prefers UTF-16LE when UTF-16BE is requested, or vice versa.
+** 6: An exact match.
+**
+*/
+static int matchQuality(FuncDef *p, int nArg, u8 enc){
+  int match = 0;
+  if( p->nArg==-1 || p->nArg==nArg 
+   || (nArg==-1 && (p->xFunc!=0 || p->xStep!=0))
+  ){
+    match = 1;
+    if( p->nArg==nArg || nArg==-1 ){
+      match = 4;
+    }
+    if( enc==p->iPrefEnc ){
+      match += 2;
+    }
+    else if( (enc==SQLITE_UTF16LE && p->iPrefEnc==SQLITE_UTF16BE) ||
+             (enc==SQLITE_UTF16BE && p->iPrefEnc==SQLITE_UTF16LE) ){
+      match += 1;
+    }
+  }
+  return match;
+}
+
+/*
+** Search a FuncDefHash for a function with the given name.  Return
+** a pointer to the matching FuncDef if found, or 0 if there is no match.
+*/
+static FuncDef *functionSearch(
+  FuncDefHash *pHash,  /* Hash table to search */
+  int h,               /* Hash of the name */
+  const char *zFunc,   /* Name of function */
+  int nFunc            /* Number of bytes in zFunc */
+){
+  FuncDef *p;
+  for(p=pHash->a[h]; p; p=p->pHash){
+    if( sqlite3StrNICmp(p->zName, zFunc, nFunc)==0 && p->zName[nFunc]==0 ){
+      return p;
+    }
+  }
+  return 0;
+}
+
+/*
+** Insert a new FuncDef into a FuncDefHash hash table.
+*/
+void sqlite3FuncDefInsert(
+  FuncDefHash *pHash,  /* The hash table into which to insert */
+  FuncDef *pDef        /* The function definition to insert */
+){
+  FuncDef *pOther;
+  int nName = sqlite3Strlen30(pDef->zName);
+  u8 c1 = (u8)pDef->zName[0];
+  int h = (sqlite3UpperToLower[c1] + nName) % ArraySize(pHash->a);
+  pOther = functionSearch(pHash, h, pDef->zName, nName);
+  if( pOther ){
+    assert( pOther!=pDef && pOther->pNext!=pDef );
+    pDef->pNext = pOther->pNext;
+    pOther->pNext = pDef;
+  }else{
+    pDef->pNext = 0;
+    pDef->pHash = pHash->a[h];
+    pHash->a[h] = pDef;
+  }
+}
+  
+  
+
+/*
+** Locate a user function given a name, a number of arguments and a flag
+** indicating whether the function prefers UTF-16 over UTF-8.  Return a
+** pointer to the FuncDef structure that defines that function, or return
+** NULL if the function does not exist.
+**
+** If the createFlag argument is true, then a new (blank) FuncDef
+** structure is created and liked into the "db" structure if a
+** no matching function previously existed.  When createFlag is true
+** and the nArg parameter is -1, then only a function that accepts
+** any number of arguments will be returned.
+**
+** If createFlag is false and nArg is -1, then the first valid
+** function found is returned.  A function is valid if either xFunc
+** or xStep is non-zero.
+**
+** If createFlag is false, then a function with the required name and
+** number of arguments may be returned even if the eTextRep flag does not
+** match that requested.
+*/
+FuncDef *sqlite3FindFunction(
+  sqlite3 *db,       /* An open database */
+  const char *zName, /* Name of the function.  Not null-terminated */
+  int nName,         /* Number of characters in the name */
+  int nArg,          /* Number of arguments.  -1 means any number */
+  u8 enc,            /* Preferred text encoding */
+  int createFlag     /* Create new entry if true and does not otherwise exist */
+){
+  FuncDef *p;         /* Iterator variable */
+  FuncDef *pBest = 0; /* Best match found so far */
+  int bestScore = 0;  /* Score of best match */
+  int h;              /* Hash value */
+
+
+  assert( enc==SQLITE_UTF8 || enc==SQLITE_UTF16LE || enc==SQLITE_UTF16BE );
+  h = (sqlite3UpperToLower[(u8)zName[0]] + nName) % ArraySize(db->aFunc.a);
+
+  /* First search for a match amongst the application-defined functions.
+  */
+  p = functionSearch(&db->aFunc, h, zName, nName);
+  while( p ){
+    int score = matchQuality(p, nArg, enc);
+    if( score>bestScore ){
+      pBest = p;
+      bestScore = score;
+    }
+    p = p->pNext;
+  }
+
+  /* If no match is found, search the built-in functions.
+  **
+  ** If the SQLITE_PreferBuiltin flag is set, then search the built-in
+  ** functions even if a prior app-defined function was found.  And give
+  ** priority to built-in functions.
+  **
+  ** Except, if createFlag is true, that means that we are trying to
+  ** install a new function.  Whatever FuncDef structure is returned it will
+  ** have fields overwritten with new information appropriate for the
+  ** new function.  But the FuncDefs for built-in functions are read-only.
+  ** So we must not search for built-ins when creating a new function.
+  */ 
+  if( !createFlag && (pBest==0 || (db->flags & SQLITE_PreferBuiltin)!=0) ){
+    FuncDefHash *pHash = &GLOBAL(FuncDefHash, sqlite3GlobalFunctions);
+    bestScore = 0;
+    p = functionSearch(pHash, h, zName, nName);
+    while( p ){
+      int score = matchQuality(p, nArg, enc);
+      if( score>bestScore ){
+        pBest = p;
+        bestScore = score;
+      }
+      p = p->pNext;
+    }
+  }
+
+  /* If the createFlag parameter is true and the search did not reveal an
+  ** exact match for the name, number of arguments and encoding, then add a
+  ** new entry to the hash table and return it.
+  */
+  if( createFlag && (bestScore<6 || pBest->nArg!=nArg) && 
+      (pBest = sqlite3DbMallocZero(db, sizeof(*pBest)+nName+1))!=0 ){
+    pBest->zName = (char *)&pBest[1];
+    pBest->nArg = (u16)nArg;
+    pBest->iPrefEnc = enc;
+    memcpy(pBest->zName, zName, nName);
+    pBest->zName[nName] = 0;
+    sqlite3FuncDefInsert(&db->aFunc, pBest);
+  }
+
+  if( pBest && (pBest->xStep || pBest->xFunc || createFlag) ){
+    return pBest;
+  }
+  return 0;
+}
+
+/*
+** Free all resources held by the schema structure. The void* argument points
+** at a Schema struct. This function does not call sqlite3DbFree(db, ) on the 
+** pointer itself, it just cleans up subsidiary resources (i.e. the contents
+** of the schema hash tables).
+**
+** The Schema.cache_size variable is not cleared.
+*/
+void sqlite3SchemaClear(void *p){
+  Hash temp1;
+  Hash temp2;
+  HashElem *pElem;
+  Schema *pSchema = (Schema *)p;
+
+  temp1 = pSchema->tblHash;
+  temp2 = pSchema->trigHash;
+  sqlite3HashInit(&pSchema->trigHash);
+  sqlite3HashClear(&pSchema->idxHash);
+  for(pElem=sqliteHashFirst(&temp2); pElem; pElem=sqliteHashNext(pElem)){
+    sqlite3DeleteTrigger(0, (Trigger*)sqliteHashData(pElem));
+  }
+  sqlite3HashClear(&temp2);
+  sqlite3HashInit(&pSchema->tblHash);
+  for(pElem=sqliteHashFirst(&temp1); pElem; pElem=sqliteHashNext(pElem)){
+    Table *pTab = sqliteHashData(pElem);
+    sqlite3DeleteTable(0, pTab);
+  }
+  sqlite3HashClear(&temp1);
+  sqlite3HashClear(&pSchema->fkeyHash);
+  pSchema->pSeqTab = 0;
+  if( pSchema->flags & DB_SchemaLoaded ){
+    pSchema->iGeneration++;
+    pSchema->flags &= ~DB_SchemaLoaded;
+  }
+}
+
+/*
+** Find and return the schema associated with a BTree.  Create
+** a new one if necessary.
+*/
+Schema *sqlite3SchemaGet(sqlite3 *db, Btree *pBt){
+  Schema * p;
+  if( pBt ){
+    p = (Schema *)sqlite3BtreeSchema(pBt, sizeof(Schema), sqlite3SchemaClear);
+  }else{
+    p = (Schema *)sqlite3DbMallocZero(0, sizeof(Schema));
+  }
+  if( !p ){
+    db->mallocFailed = 1;
+  }else if ( 0==p->file_format ){
+    sqlite3HashInit(&p->tblHash);
+    sqlite3HashInit(&p->idxHash);
+    sqlite3HashInit(&p->trigHash);
+    sqlite3HashInit(&p->fkeyHash);
+    p->enc = SQLITE_UTF8;
+  }
+  return p;
+}
diff --git a/src/complete.c b/src/complete.c
new file mode 100644
index 0000000..9e91400
--- /dev/null
+++ b/src/complete.c
@@ -0,0 +1,283 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** An tokenizer for SQL
+**
+** This file contains C code that implements the sqlite3_complete() API.
+** This code used to be part of the tokenizer.c source file.  But by
+** separating it out, the code will be automatically omitted from
+** static links that do not use it.
+*/
+#include "sqliteInt.h"
+#ifndef SQLITE_OMIT_COMPLETE
+
+/*
+** This is defined in tokenize.c.  We just have to import the definition.
+*/
+#ifndef SQLITE_AMALGAMATION
+#ifdef SQLITE_ASCII
+#define IdChar(C)  ((sqlite3CtypeMap[(unsigned char)C]&0x46)!=0)
+#endif
+#ifdef SQLITE_EBCDIC
+extern const char sqlite3IsEbcdicIdChar[];
+#define IdChar(C)  (((c=C)>=0x42 && sqlite3IsEbcdicIdChar[c-0x40]))
+#endif
+#endif /* SQLITE_AMALGAMATION */
+
+
+/*
+** Token types used by the sqlite3_complete() routine.  See the header
+** comments on that procedure for additional information.
+*/
+#define tkSEMI    0
+#define tkWS      1
+#define tkOTHER   2
+#ifndef SQLITE_OMIT_TRIGGER
+#define tkEXPLAIN 3
+#define tkCREATE  4
+#define tkTEMP    5
+#define tkTRIGGER 6
+#define tkEND     7
+#endif
+
+/*
+** Return TRUE if the given SQL string ends in a semicolon.
+**
+** Special handling is require for CREATE TRIGGER statements.
+** Whenever the CREATE TRIGGER keywords are seen, the statement
+** must end with ";END;".
+**
+** This implementation uses a state machine with 8 states:
+**
+**   (0) INVALID   We have not yet seen a non-whitespace character.
+**
+**   (1) START     At the beginning or end of an SQL statement.  This routine
+**                 returns 1 if it ends in the START state and 0 if it ends
+**                 in any other state.
+**
+**   (2) NORMAL    We are in the middle of statement which ends with a single
+**                 semicolon.
+**
+**   (3) EXPLAIN   The keyword EXPLAIN has been seen at the beginning of 
+**                 a statement.
+**
+**   (4) CREATE    The keyword CREATE has been seen at the beginning of a
+**                 statement, possibly preceeded by EXPLAIN and/or followed by
+**                 TEMP or TEMPORARY
+**
+**   (5) TRIGGER   We are in the middle of a trigger definition that must be
+**                 ended by a semicolon, the keyword END, and another semicolon.
+**
+**   (6) SEMI      We've seen the first semicolon in the ";END;" that occurs at
+**                 the end of a trigger definition.
+**
+**   (7) END       We've seen the ";END" of the ";END;" that occurs at the end
+**                 of a trigger difinition.
+**
+** Transitions between states above are determined by tokens extracted
+** from the input.  The following tokens are significant:
+**
+**   (0) tkSEMI      A semicolon.
+**   (1) tkWS        Whitespace.
+**   (2) tkOTHER     Any other SQL token.
+**   (3) tkEXPLAIN   The "explain" keyword.
+**   (4) tkCREATE    The "create" keyword.
+**   (5) tkTEMP      The "temp" or "temporary" keyword.
+**   (6) tkTRIGGER   The "trigger" keyword.
+**   (7) tkEND       The "end" keyword.
+**
+** Whitespace never causes a state transition and is always ignored.
+** This means that a SQL string of all whitespace is invalid.
+**
+** If we compile with SQLITE_OMIT_TRIGGER, all of the computation needed
+** to recognize the end of a trigger can be omitted.  All we have to do
+** is look for a semicolon that is not part of an string or comment.
+*/
+int sqlite3_complete(const char *zSql){
+  u8 state = 0;   /* Current state, using numbers defined in header comment */
+  u8 token;       /* Value of the next token */
+
+#ifndef SQLITE_OMIT_TRIGGER
+  /* A complex statement machine used to detect the end of a CREATE TRIGGER
+  ** statement.  This is the normal case.
+  */
+  static const u8 trans[8][8] = {
+                     /* Token:                                                */
+     /* State:       **  SEMI  WS  OTHER  EXPLAIN  CREATE  TEMP  TRIGGER  END */
+     /* 0 INVALID: */ {    1,  0,     2,       3,      4,    2,       2,   2, },
+     /* 1   START: */ {    1,  1,     2,       3,      4,    2,       2,   2, },
+     /* 2  NORMAL: */ {    1,  2,     2,       2,      2,    2,       2,   2, },
+     /* 3 EXPLAIN: */ {    1,  3,     3,       2,      4,    2,       2,   2, },
+     /* 4  CREATE: */ {    1,  4,     2,       2,      2,    4,       5,   2, },
+     /* 5 TRIGGER: */ {    6,  5,     5,       5,      5,    5,       5,   5, },
+     /* 6    SEMI: */ {    6,  6,     5,       5,      5,    5,       5,   7, },
+     /* 7     END: */ {    1,  7,     5,       5,      5,    5,       5,   5, },
+  };
+#else
+  /* If triggers are not supported by this compile then the statement machine
+  ** used to detect the end of a statement is much simplier
+  */
+  static const u8 trans[3][3] = {
+                     /* Token:           */
+     /* State:       **  SEMI  WS  OTHER */
+     /* 0 INVALID: */ {    1,  0,     2, },
+     /* 1   START: */ {    1,  1,     2, },
+     /* 2  NORMAL: */ {    1,  2,     2, },
+  };
+#endif /* SQLITE_OMIT_TRIGGER */
+
+  while( *zSql ){
+    switch( *zSql ){
+      case ';': {  /* A semicolon */
+        token = tkSEMI;
+        break;
+      }
+      case ' ':
+      case '\r':
+      case '\t':
+      case '\n':
+      case '\f': {  /* White space is ignored */
+        token = tkWS;
+        break;
+      }
+      case '/': {   /* C-style comments */
+        if( zSql[1]!='*' ){
+          token = tkOTHER;
+          break;
+        }
+        zSql += 2;
+        while( zSql[0] && (zSql[0]!='*' || zSql[1]!='/') ){ zSql++; }
+        if( zSql[0]==0 ) return 0;
+        zSql++;
+        token = tkWS;
+        break;
+      }
+      case '-': {   /* SQL-style comments from "--" to end of line */
+        if( zSql[1]!='-' ){
+          token = tkOTHER;
+          break;
+        }
+        while( *zSql && *zSql!='\n' ){ zSql++; }
+        if( *zSql==0 ) return state==1;
+        token = tkWS;
+        break;
+      }
+      case '[': {   /* Microsoft-style identifiers in [...] */
+        zSql++;
+        while( *zSql && *zSql!=']' ){ zSql++; }
+        if( *zSql==0 ) return 0;
+        token = tkOTHER;
+        break;
+      }
+      case '`':     /* Grave-accent quoted symbols used by MySQL */
+      case '"':     /* single- and double-quoted strings */
+      case '\'': {
+        int c = *zSql;
+        zSql++;
+        while( *zSql && *zSql!=c ){ zSql++; }
+        if( *zSql==0 ) return 0;
+        token = tkOTHER;
+        break;
+      }
+      default: {
+#ifdef SQLITE_EBCDIC
+        unsigned char c;
+#endif
+        if( IdChar((u8)*zSql) ){
+          /* Keywords and unquoted identifiers */
+          int nId;
+          for(nId=1; IdChar(zSql[nId]); nId++){}
+#ifdef SQLITE_OMIT_TRIGGER
+          token = tkOTHER;
+#else
+          switch( *zSql ){
+            case 'c': case 'C': {
+              if( nId==6 && sqlite3StrNICmp(zSql, "create", 6)==0 ){
+                token = tkCREATE;
+              }else{
+                token = tkOTHER;
+              }
+              break;
+            }
+            case 't': case 'T': {
+              if( nId==7 && sqlite3StrNICmp(zSql, "trigger", 7)==0 ){
+                token = tkTRIGGER;
+              }else if( nId==4 && sqlite3StrNICmp(zSql, "temp", 4)==0 ){
+                token = tkTEMP;
+              }else if( nId==9 && sqlite3StrNICmp(zSql, "temporary", 9)==0 ){
+                token = tkTEMP;
+              }else{
+                token = tkOTHER;
+              }
+              break;
+            }
+            case 'e':  case 'E': {
+              if( nId==3 && sqlite3StrNICmp(zSql, "end", 3)==0 ){
+                token = tkEND;
+              }else
+#ifndef SQLITE_OMIT_EXPLAIN
+              if( nId==7 && sqlite3StrNICmp(zSql, "explain", 7)==0 ){
+                token = tkEXPLAIN;
+              }else
+#endif
+              {
+                token = tkOTHER;
+              }
+              break;
+            }
+            default: {
+              token = tkOTHER;
+              break;
+            }
+          }
+#endif /* SQLITE_OMIT_TRIGGER */
+          zSql += nId-1;
+        }else{
+          /* Operators and special symbols */
+          token = tkOTHER;
+        }
+        break;
+      }
+    }
+    state = trans[state][token];
+    zSql++;
+  }
+  return state==1;
+}
+
+#ifndef SQLITE_OMIT_UTF16
+/*
+** This routine is the same as the sqlite3_complete() routine described
+** above, except that the parameter is required to be UTF-16 encoded, not
+** UTF-8.
+*/
+int sqlite3_complete16(const void *zSql){
+  sqlite3_value *pVal;
+  char const *zSql8;
+  int rc = SQLITE_NOMEM;
+
+#ifndef SQLITE_OMIT_AUTOINIT
+  rc = sqlite3_initialize();
+  if( rc ) return rc;
+#endif
+  pVal = sqlite3ValueNew(0);
+  sqlite3ValueSetStr(pVal, -1, zSql, SQLITE_UTF16NATIVE, SQLITE_STATIC);
+  zSql8 = sqlite3ValueText(pVal, SQLITE_UTF8);
+  if( zSql8 ){
+    rc = sqlite3_complete(zSql8);
+  }else{
+    rc = SQLITE_NOMEM;
+  }
+  sqlite3ValueFree(pVal);
+  return sqlite3ApiExit(0, rc);
+}
+#endif /* SQLITE_OMIT_UTF16 */
+#endif /* SQLITE_OMIT_COMPLETE */
diff --git a/src/crypto.c b/src/crypto.c
new file mode 100644
index 0000000..5c8b2d6
--- /dev/null
+++ b/src/crypto.c
@@ -0,0 +1,345 @@
+/* 
+** SQLCipher
+** crypto.c developed by Stephen Lombardo (Zetetic LLC) 
+** sjlombardo at zetetic dot net
+** http://zetetic.net
+** 
+** Copyright (c) 2009, ZETETIC LLC
+** All rights reserved.
+** 
+** Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are met:
+**     * Redistributions of source code must retain the above copyright
+**       notice, this list of conditions and the following disclaimer.
+**     * Redistributions in binary form must reproduce the above copyright
+**       notice, this list of conditions and the following disclaimer in the
+**       documentation and/or other materials provided with the distribution.
+**     * Neither the name of the ZETETIC LLC nor the
+**       names of its contributors may be used to endorse or promote products
+**       derived from this software without specific prior written permission.
+** 
+** THIS SOFTWARE IS PROVIDED BY ZETETIC LLC ''AS IS'' AND ANY
+** EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+** WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+** DISCLAIMED. IN NO EVENT SHALL ZETETIC LLC BE LIABLE FOR ANY
+** DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+** (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+** ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+** SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+**  
+*/
+/* BEGIN CRYPTO */
+#ifdef SQLITE_HAS_CODEC
+
+#include <assert.h>
+#include "sqliteInt.h"
+#include "btreeInt.h"
+#include "crypto.h"
+
+int codec_set_kdf_iter(sqlite3* db, int nDb, int kdf_iter, int for_ctx) {
+  struct Db *pDb = &db->aDb[nDb];
+  CODEC_TRACE(("codec_set_kdf_iter: entered db=%d nDb=%d kdf_iter=%d for_ctx=%d\n", db, nDb, kdf_iter, for_ctx));
+
+  if(pDb->pBt) {
+    codec_ctx *ctx;
+    sqlite3pager_get_codec(pDb->pBt->pBt->pPager, (void **) &ctx);
+    if(ctx) return sqlcipher_codec_ctx_set_kdf_iter(ctx, kdf_iter, for_ctx);
+  }
+  return SQLITE_ERROR;
+}
+
+int codec_set_fast_kdf_iter(sqlite3* db, int nDb, int kdf_iter, int for_ctx) {
+  struct Db *pDb = &db->aDb[nDb];
+  CODEC_TRACE(("codec_set_kdf_iter: entered db=%d nDb=%d kdf_iter=%d for_ctx=%d\n", db, nDb, kdf_iter, for_ctx));
+
+  if(pDb->pBt) {
+    codec_ctx *ctx;
+    sqlite3pager_get_codec(pDb->pBt->pBt->pPager, (void **) &ctx);
+    if(ctx) return sqlcipher_codec_ctx_set_fast_kdf_iter(ctx, kdf_iter, for_ctx);
+  }
+  return SQLITE_ERROR;
+}
+
+static int codec_set_btree_to_codec_pagesize(sqlite3 *db, Db *pDb, codec_ctx *ctx) {
+  int rc, page_sz, reserve_sz; 
+
+  page_sz = sqlcipher_codec_ctx_get_pagesize(ctx);
+  reserve_sz = sqlcipher_codec_ctx_get_reservesize(ctx);
+
+  sqlite3_mutex_enter(db->mutex);
+  db->nextPagesize = page_sz; 
+  pDb->pBt->pBt->pageSizeFixed = 0; 
+  CODEC_TRACE(("codec_set_btree_to_codec_pagesize: sqlite3BtreeSetPageSize() size=%d reserve=%d\n", page_sz, reserve_sz));
+  rc = sqlite3BtreeSetPageSize(pDb->pBt, page_sz, reserve_sz, 0);
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+
+int codec_set_use_hmac(sqlite3* db, int nDb, int use) {
+  struct Db *pDb = &db->aDb[nDb];
+
+  CODEC_TRACE(("codec_set_use_hmac: entered db=%d nDb=%d use=%d\n", db, nDb, use));
+
+  if(pDb->pBt) {
+    int rc;
+    codec_ctx *ctx;
+    sqlite3pager_get_codec(pDb->pBt->pBt->pPager, (void **) &ctx);
+    if(ctx) {
+      rc = sqlcipher_codec_ctx_set_use_hmac(ctx, use);
+      if(rc != SQLITE_OK) return rc;
+      /* since the use of hmac has changed, the page size may also change */
+      /* Note: before forcing the page size we need to force pageSizeFixed to 0, else  
+             sqliteBtreeSetPageSize will block the change  */
+      return codec_set_btree_to_codec_pagesize(db, pDb, ctx);
+    }
+  }
+  return SQLITE_ERROR;
+}
+
+int codec_set_page_size(sqlite3* db, int nDb, int size) {
+  struct Db *pDb = &db->aDb[nDb];
+  CODEC_TRACE(("codec_set_page_size: entered db=%d nDb=%d size=%d\n", db, nDb, size));
+
+  if(pDb->pBt) {
+    int rc;
+    codec_ctx *ctx;
+    sqlite3pager_get_codec(pDb->pBt->pBt->pPager, (void **) &ctx);
+
+    if(ctx) {
+      rc = sqlcipher_codec_ctx_set_pagesize(ctx, size);
+      if(rc != SQLITE_OK) return rc;
+      return codec_set_btree_to_codec_pagesize(db, pDb, ctx);
+    }
+  }
+  return SQLITE_ERROR;
+}
+
+/**
+  * 
+  * when for_ctx == 0 then it will change for read
+  * when for_ctx == 1 then it will change for write
+  * when for_ctx == 2 then it will change for both
+  */
+int codec_set_cipher_name(sqlite3* db, int nDb, const char *cipher_name, int for_ctx) {
+  struct Db *pDb = &db->aDb[nDb];
+  CODEC_TRACE(("codec_set_cipher_name: entered db=%d nDb=%d cipher_name=%s for_ctx=%d\n", db, nDb, cipher_name, for_ctx));
+
+  if(pDb->pBt) {
+    codec_ctx *ctx;
+    sqlite3pager_get_codec(pDb->pBt->pBt->pPager, (void **) &ctx);
+    if(ctx) return sqlcipher_codec_ctx_set_cipher(ctx, cipher_name, for_ctx);
+  }
+  return SQLITE_ERROR;
+}
+
+int codec_set_pass_key(sqlite3* db, int nDb, const void *zKey, int nKey, int for_ctx) {
+  struct Db *pDb = &db->aDb[nDb];
+  CODEC_TRACE(("codec_set_pass_key: entered db=%d nDb=%d cipher_name=%s nKey=%d for_ctx=%d\n", db, nDb, zKey, nKey, for_ctx));
+  if(pDb->pBt) {
+    codec_ctx *ctx;
+    sqlite3pager_get_codec(pDb->pBt->pBt->pPager, (void **) &ctx);
+    if(ctx) return sqlcipher_codec_ctx_set_pass(ctx, zKey, nKey, for_ctx);
+  }
+  return SQLITE_ERROR;
+} 
+
+/*
+ * sqlite3Codec can be called in multiple modes.
+ * encrypt mode - expected to return a pointer to the 
+ *   encrypted data without altering pData.
+ * decrypt mode - expected to return a pointer to pData, with
+ *   the data decrypted in the input buffer
+ */
+void* sqlite3Codec(void *iCtx, void *data, Pgno pgno, int mode) {
+  codec_ctx *ctx = (codec_ctx *) iCtx;
+  int offset = 0, rc = 0;
+  int page_sz = sqlcipher_codec_ctx_get_pagesize(ctx); 
+  unsigned char *pData = (unsigned char *) data;
+  void *buffer = sqlcipher_codec_ctx_get_data(ctx);
+  void *kdf_salt = sqlcipher_codec_ctx_get_kdf_salt(ctx);
+  CODEC_TRACE(("sqlite3Codec: entered pgno=%d, mode=%d, page_sz=%d\n", pgno, mode, page_sz));
+
+  /* call to derive keys if not present yet */
+  if((rc = sqlcipher_codec_key_derive(ctx)) != SQLITE_OK) {
+   sqlcipher_codec_ctx_set_error(ctx, rc); 
+   return NULL;
+  }
+
+  if(pgno == 1) offset = FILE_HEADER_SZ; /* adjust starting pointers in data page for header offset on first page*/
+
+  CODEC_TRACE(("sqlite3Codec: switch mode=%d offset=%d\n",  mode, offset));
+  switch(mode) {
+    case 0: /* decrypt */
+    case 2:
+    case 3:
+      if(pgno == 1) memcpy(buffer, SQLITE_FILE_HEADER, FILE_HEADER_SZ); /* copy file header to the first 16 bytes of the page */ 
+      rc = sqlcipher_page_cipher(ctx, CIPHER_READ_CTX, pgno, CIPHER_DECRYPT, page_sz - offset, pData + offset, (unsigned char*)buffer + offset);
+      if(rc != SQLITE_OK) sqlcipher_codec_ctx_set_error(ctx, rc);
+      memcpy(pData, buffer, page_sz); /* copy buffer data back to pData and return */
+      return pData;
+      break;
+    case 6: /* encrypt */
+      if(pgno == 1) memcpy(buffer, kdf_salt, FILE_HEADER_SZ); /* copy salt to output buffer */ 
+      rc = sqlcipher_page_cipher(ctx, CIPHER_WRITE_CTX, pgno, CIPHER_ENCRYPT, page_sz - offset, pData + offset, (unsigned char*)buffer + offset);
+      if(rc != SQLITE_OK) sqlcipher_codec_ctx_set_error(ctx, rc);
+      return buffer; /* return persistent buffer data, pData remains intact */
+      break;
+    case 7:
+      if(pgno == 1) memcpy(buffer, kdf_salt, FILE_HEADER_SZ); /* copy salt to output buffer */ 
+      rc = sqlcipher_page_cipher(ctx, CIPHER_READ_CTX, pgno, CIPHER_ENCRYPT, page_sz - offset, pData + offset, (unsigned char*)buffer + offset);
+      if(rc != SQLITE_OK) sqlcipher_codec_ctx_set_error(ctx, rc);
+      return buffer; /* return persistent buffer data, pData remains intact */
+      break;
+    default:
+      return pData;
+      break;
+  }
+}
+
+void sqlite3FreeCodecArg(void *pCodecArg) {
+  codec_ctx *ctx = (codec_ctx *) pCodecArg;
+  if(pCodecArg == NULL) return;
+  sqlcipher_codec_ctx_free(&ctx); // wipe and free allocated memory for the context 
+}
+
+int sqlite3CodecAttach(sqlite3* db, int nDb, const void *zKey, int nKey) {
+  struct Db *pDb = &db->aDb[nDb];
+
+  CODEC_TRACE(("sqlite3CodecAttach: entered nDb=%d zKey=%s, nKey=%d\n", nDb, zKey, nKey));
+
+  sqlcipher_activate();
+
+  if(nKey && zKey && pDb->pBt) {
+    int rc;
+    Pager *pPager = pDb->pBt->pBt->pPager;
+    sqlite3_file *fd = sqlite3Pager_get_fd(pPager);
+    codec_ctx *ctx;
+
+    /* point the internal codec argument against the contet to be prepared */
+    rc = sqlcipher_codec_ctx_init(&ctx, pDb, pDb->pBt->pBt->pPager, fd, zKey, nKey); 
+
+    sqlite3pager_sqlite3PagerSetCodec(sqlite3BtreePager(pDb->pBt), sqlite3Codec, NULL, sqlite3FreeCodecArg, (void *) ctx);
+
+    codec_set_btree_to_codec_pagesize(db, pDb, ctx);
+
+    /* if fd is null, then this is an in-memory database and
+       we dont' want to overwrite the AutoVacuum settings
+       if not null, then set to the default */
+    sqlite3_mutex_enter(db->mutex);
+    if(fd != NULL) { 
+      sqlite3BtreeSetAutoVacuum(pDb->pBt, SQLITE_DEFAULT_AUTOVACUUM);
+    }
+    sqlite3_mutex_leave(db->mutex);
+  }
+  return SQLITE_OK;
+}
+
+void sqlite3_activate_see(const char* in) {
+  /* do nothing, security enhancements are always active */
+}
+
+int sqlite3_key(sqlite3 *db, const void *pKey, int nKey) {
+  CODEC_TRACE(("sqlite3_key: entered db=%d pKey=%s nKey=%d\n", db, pKey, nKey));
+  /* attach key if db and pKey are not null and nKey is > 0 */
+  if(db && pKey && nKey) {
+    sqlite3CodecAttach(db, 0, pKey, nKey); // operate only on the main db 
+    return SQLITE_OK;
+  }
+  return SQLITE_ERROR;
+}
+
+/* sqlite3_rekey 
+** Given a database, this will reencrypt the database using a new key.
+** There is only one possible modes of operation - to encrypt a database
+** that is already encrpyted. If the database is not already encrypted
+** this should do nothing
+** The proposed logic for this function follows:
+** 1. Determine if the database is already encryptped
+** 2. If there is NOT already a key present do nothing
+** 3. If there is a key present, re-encrypt the database with the new key
+*/
+int sqlite3_rekey(sqlite3 *db, const void *pKey, int nKey) {
+  CODEC_TRACE(("sqlite3_rekey: entered db=%d pKey=%s, nKey=%d\n", db, pKey, nKey));
+  sqlcipher_activate();
+  if(db && pKey && nKey) {
+    struct Db *pDb = &db->aDb[0];
+    CODEC_TRACE(("sqlite3_rekey: database pDb=%d\n", pDb));
+    if(pDb->pBt) {
+      codec_ctx *ctx;
+      int rc, page_count;
+      Pgno pgno;
+      PgHdr *page;
+      Pager *pPager = pDb->pBt->pBt->pPager;
+
+      sqlite3pager_get_codec(pDb->pBt->pBt->pPager, (void **) &ctx);
+     
+      if(ctx == NULL) { 
+        /* there was no codec attached to this database, so this should do nothing! */ 
+        CODEC_TRACE(("sqlite3_rekey: no codec attached to db, exiting\n"));
+        return SQLITE_OK;
+      }
+
+      sqlite3_mutex_enter(db->mutex);
+
+      codec_set_pass_key(db, 0, pKey, nKey, CIPHER_WRITE_CTX);
+    
+      /* do stuff here to rewrite the database 
+      ** 1. Create a transaction on the database
+      ** 2. Iterate through each page, reading it and then writing it.
+      ** 3. If that goes ok then commit and put ctx->rekey into ctx->key
+      **    note: don't deallocate rekey since it may be used in a subsequent iteration 
+      */
+      rc = sqlite3BtreeBeginTrans(pDb->pBt, 1); /* begin write transaction */
+      sqlite3PagerPagecount(pPager, &page_count);
+      for(pgno = 1; rc == SQLITE_OK && pgno <= page_count; pgno++) { /* pgno's start at 1 see pager.c:pagerAcquire */
+        if(!sqlite3pager_is_mj_pgno(pPager, pgno)) { /* skip this page (see pager.c:pagerAcquire for reasoning) */
+          rc = sqlite3PagerGet(pPager, pgno, &page);
+          if(rc == SQLITE_OK) { /* write page see pager_incr_changecounter for example */
+            rc = sqlite3PagerWrite(page);
+            //printf("sqlite3PagerWrite(%d)\n", pgno);
+            if(rc == SQLITE_OK) {
+              sqlite3PagerUnref(page);
+            } 
+          } 
+        } 
+      }
+
+      /* if commit was successful commit and copy the rekey data to current key, else rollback to release locks */
+      if(rc == SQLITE_OK) { 
+        CODEC_TRACE(("sqlite3_rekey: committing\n"));
+        rc = sqlite3BtreeCommit(pDb->pBt); 
+        sqlcipher_codec_key_copy(ctx, CIPHER_WRITE_CTX);
+      } else {
+        CODEC_TRACE(("sqlite3_rekey: rollback\n"));
+        sqlite3BtreeRollback(pDb->pBt);
+      }
+
+      sqlite3_mutex_leave(db->mutex);
+    }
+    return SQLITE_OK;
+  }
+  return SQLITE_ERROR;
+}
+
+void sqlite3CodecGetKey(sqlite3* db, int nDb, void **zKey, int *nKey) {
+  struct Db *pDb = &db->aDb[nDb];
+  CODEC_TRACE(("sqlite3CodecGetKey: entered db=%d, nDb=%d\n", db, nDb));
+  
+  if( pDb->pBt ) {
+    codec_ctx *ctx;
+    sqlite3pager_get_codec(pDb->pBt->pBt->pPager, (void **) &ctx);
+
+    if(ctx) { /* if the codec has an attached codec_context user the raw key data */
+      sqlcipher_codec_get_pass(ctx, zKey, nKey);
+    } else {
+      *zKey = NULL;
+      *nKey = 0;
+    }
+  }
+}
+
+
+/* END CRYPTO */
+#endif
diff --git a/src/crypto.h b/src/crypto.h
new file mode 100644
index 0000000..a5a62ec
--- /dev/null
+++ b/src/crypto.h
@@ -0,0 +1,157 @@
+/* 
+** SQLCipher
+** crypto.h developed by Stephen Lombardo (Zetetic LLC) 
+** sjlombardo at zetetic dot net
+** http://zetetic.net
+** 
+** Copyright (c) 2008, ZETETIC LLC
+** All rights reserved.
+** 
+** Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are met:
+**     * Redistributions of source code must retain the above copyright
+**       notice, this list of conditions and the following disclaimer.
+**     * Redistributions in binary form must reproduce the above copyright
+**       notice, this list of conditions and the following disclaimer in the
+**       documentation and/or other materials provided with the distribution.
+**     * Neither the name of the ZETETIC LLC nor the
+**       names of its contributors may be used to endorse or promote products
+**       derived from this software without specific prior written permission.
+** 
+** THIS SOFTWARE IS PROVIDED BY ZETETIC LLC ''AS IS'' AND ANY
+** EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+** WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+** DISCLAIMED. IN NO EVENT SHALL ZETETIC LLC BE LIABLE FOR ANY
+** DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+** (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+** ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+** SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+**  
+*/
+/* BEGIN CRYPTO */
+#ifdef SQLITE_HAS_CODEC
+#ifndef CRYPTO_H
+#define CRYPTO_H
+
+#define FILE_HEADER_SZ 16
+
+#ifndef CIPHER
+#define CIPHER "aes-256-cbc"
+#endif
+
+#define CIPHER_DECRYPT 0
+#define CIPHER_ENCRYPT 1
+
+#define CIPHER_READ_CTX 0
+#define CIPHER_WRITE_CTX 1
+#define CIPHER_READWRITE_CTX 2
+
+#ifndef PBKDF2_ITER
+#define PBKDF2_ITER 4000
+#endif
+
+#ifndef DEFAULT_USE_HMAC
+#define DEFAULT_USE_HMAC 1
+#endif
+
+/* by default, sqlcipher will use a reduced number of iterations to generate
+   the HMAC key / or transform a raw cipher key 
+   */
+#ifndef FAST_PBKDF2_ITER
+#define FAST_PBKDF2_ITER 2
+#endif
+
+/* this if a fixed random array that will be xor'd with the database salt to ensure that the
+   salt passed to the HMAC key derivation function is not the same as that used to derive
+   the encryption key. This can be overridden at compile time but it will make the resulting
+   binary incompatible with the default builds when using HMAC. A future version of SQLcipher
+   will likely allow this to be defined at runtime via pragma */ 
+#ifndef HMAC_SALT_MASK
+#define HMAC_SALT_MASK 0x3a
+#endif
+
+#ifdef CODEC_DEBUG
+#define CODEC_TRACE(X)  {printf X;fflush(stdout);}
+#else
+#define CODEC_TRACE(X)
+#endif
+
+
+/* extensions defined in pragma.c */ 
+   
+void sqlite3pager_get_codec(Pager *pPager, void **ctx);
+int sqlite3pager_is_mj_pgno(Pager *pPager, Pgno pgno);
+sqlite3_file *sqlite3Pager_get_fd(Pager *pPager);
+void sqlite3pager_sqlite3PagerSetCodec(
+  Pager *pPager,
+  void *(*xCodec)(void*,void*,Pgno,int),
+  void (*xCodecSizeChng)(void*,int,int),
+  void (*xCodecFree)(void*),
+  void *pCodec
+);
+/* end extensions defined in pragma.c */
+ 
+/*
+**  Simple shared routines for converting hex char strings to binary data
+ */
+static int cipher_hex2int(char c) {
+  return (c>='0' && c<='9') ? (c)-'0' :
+         (c>='A' && c<='F') ? (c)-'A'+10 :
+         (c>='a' && c<='f') ? (c)-'a'+10 : 0;
+}
+
+static void cipher_hex2bin(const char *hex, int sz, unsigned char *out){
+  int i;
+  for(i = 0; i < sz; i += 2){
+    out[i/2] = (cipher_hex2int(hex[i])<<4) | cipher_hex2int(hex[i+1]);
+  }
+}
+
+/* extensions defined in crypto_impl.c */
+
+typedef struct codec_ctx codec_ctx;
+
+/* utility functions */
+int sqlcipher_memcmp(const unsigned char *a0, const unsigned char *a1, int len);
+int sqlcipher_pseudorandom(void *, int);
+void sqlcipher_free(void *, int);
+
+/* activation and initialization */
+void sqlcipher_activate();
+int sqlcipher_codec_ctx_init(codec_ctx **, Db *, Pager *, sqlite3_file *, const void *, int);
+void sqlcipher_codec_ctx_free(codec_ctx **);
+int sqlcipher_codec_key_derive(codec_ctx *);
+int sqlcipher_codec_key_copy(codec_ctx *, int);
+
+/* page cipher implementation */
+int sqlcipher_page_cipher(codec_ctx *, int, Pgno, int, int, unsigned char *, unsigned char *);
+
+/* context setters & getters */
+void sqlcipher_codec_ctx_set_error(codec_ctx *, int);
+
+int sqlcipher_codec_ctx_set_pass(codec_ctx *, const void *, int, int);
+void sqlcipher_codec_get_pass(codec_ctx *, void **zKey, int *nKey);
+
+int sqlcipher_codec_ctx_set_pagesize(codec_ctx *, int);
+int sqlcipher_codec_ctx_get_pagesize(codec_ctx *);
+int sqlcipher_codec_ctx_get_reservesize(codec_ctx *);
+
+int sqlcipher_codec_ctx_set_kdf_iter(codec_ctx *, int, int);
+void* sqlcipher_codec_ctx_get_kdf_salt(codec_ctx *ctx);
+
+int sqlcipher_codec_ctx_set_fast_kdf_iter(codec_ctx *, int, int);
+
+int sqlcipher_codec_ctx_set_cipher(codec_ctx *, const char *, int);
+
+void* sqlcipher_codec_ctx_get_data(codec_ctx *);
+
+void sqlcipher_exportFunc(sqlite3_context *, int, sqlite3_value **);
+
+int sqlcipher_codec_ctx_set_use_hmac(codec_ctx *ctx, int use);
+/* end extensions defined in crypto_impl.c */
+
+#endif
+#endif
+/* END CRYPTO */
diff --git a/src/crypto_impl.c b/src/crypto_impl.c
new file mode 100644
index 0000000..336afbd
--- /dev/null
+++ b/src/crypto_impl.c
@@ -0,0 +1,833 @@
+/* 
+** SQLCipher
+** crypto_impl.c developed by Stephen Lombardo (Zetetic LLC) 
+** sjlombardo at zetetic dot net
+** http://zetetic.net
+** 
+** Copyright (c) 2011, ZETETIC LLC
+** All rights reserved.
+** 
+** Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are met:
+**     * Redistributions of source code must retain the above copyright
+**       notice, this list of conditions and the following disclaimer.
+**     * Redistributions in binary form must reproduce the above copyright
+**       notice, this list of conditions and the following disclaimer in the
+**       documentation and/or other materials provided with the distribution.
+**     * Neither the name of the ZETETIC LLC nor the
+**       names of its contributors may be used to endorse or promote products
+**       derived from this software without specific prior written permission.
+** 
+** THIS SOFTWARE IS PROVIDED BY ZETETIC LLC ''AS IS'' AND ANY
+** EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+** WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+** DISCLAIMED. IN NO EVENT SHALL ZETETIC LLC BE LIABLE FOR ANY
+** DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+** (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+** ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+** SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+**  
+*/
+/* BEGIN CRYPTO */
+#ifdef SQLITE_HAS_CODEC
+
+#include <openssl/rand.h>
+#include <openssl/evp.h>
+#include <openssl/hmac.h>
+#include "sqliteInt.h"
+#include "btreeInt.h"
+#include "crypto.h"
+#ifndef OMIT_MEMLOCK
+#if defined(__unix__) || defined(__APPLE__) 
+#include <sys/mman.h>
+#elif defined(_WIN32)
+# include <windows.h>
+#endif
+#endif
+
+/* the default implementation of SQLCipher uses a cipher_ctx
+   to keep track of read / write state separately. The following
+   struct and associated functions are defined here */
+typedef struct {
+  int derive_key;
+  EVP_CIPHER *evp_cipher;
+  EVP_CIPHER_CTX ectx;
+  HMAC_CTX hctx;
+  int kdf_iter;
+  int fast_kdf_iter;
+  int key_sz;
+  int iv_sz;
+  int block_sz;
+  int pass_sz;
+  int reserve_sz;
+  int hmac_sz;
+  int use_hmac;
+  unsigned char *key;
+  unsigned char *hmac_key;
+  char *pass;
+} cipher_ctx;
+
+void sqlcipher_cipher_ctx_free(cipher_ctx **);
+int sqlcipher_cipher_ctx_cmp(cipher_ctx *, cipher_ctx *);
+int sqlcipher_cipher_ctx_copy(cipher_ctx *, cipher_ctx *);
+int sqlcipher_cipher_ctx_init(cipher_ctx **);
+int sqlcipher_cipher_ctx_set_pass(cipher_ctx *, const void *, int);
+int sqlcipher_cipher_ctx_key_derive(codec_ctx *, cipher_ctx *);
+
+/* prototype for pager HMAC function */
+int sqlcipher_page_hmac(cipher_ctx *, Pgno, unsigned char *, int, unsigned char *);
+
+struct codec_ctx {
+  int kdf_salt_sz;
+  int page_sz;
+  unsigned char *kdf_salt;
+  unsigned char *hmac_kdf_salt;
+  unsigned char *buffer;
+  Btree *pBt;
+  cipher_ctx *read_ctx;
+  cipher_ctx *write_ctx;
+};
+
+void sqlcipher_activate() {
+  sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
+  if(EVP_get_cipherbyname(CIPHER) == NULL) {
+    OpenSSL_add_all_algorithms();
+  } 
+  sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
+}
+
+/* fixed time memory comparison routine */
+int sqlcipher_memcmp(const unsigned char *a0, const unsigned char *a1, int len) {
+  int i = 0, noMatch = 0;
+
+  for(i = 0; i < len; i++) {
+    noMatch = (noMatch || (a0[i] != a1[i]));
+  }
+  
+  return noMatch;
+}
+
+/* generate a defined number of pseudorandom bytes */
+int sqlcipher_random (void *buffer, int length) {
+  return RAND_bytes((unsigned char *)buffer, length);
+}
+
+/**
+  * Free and wipe memory. Uses SQLites internal sqlite3_free so that memory
+  * can be countend and memory leak detection works in the tet suite. 
+  * If ptr is not null memory will be freed. 
+  * If sz is greater than zero, the memory will be overwritten with zero before it is freed
+  * If sz is > 0, and not compiled with OMIT_MEMLOCK, system will attempt to unlock the
+  * memory segment so it can be paged
+  */
+void sqlcipher_free(void *ptr, int sz) {
+  if(ptr) {
+    if(sz > 0) {
+      memset(ptr, 0, sz);
+#ifndef OMIT_MEMLOCK
+#if defined(__unix__) || defined(__APPLE__) 
+      munlock(ptr, sz);
+#elif defined(_WIN32)
+      VirtualUnlock(ptr, sz);
+#endif
+#endif
+    }
+    sqlite3_free(ptr);
+  }
+}
+
+/**
+  * allocate memory. Uses sqlite's internall malloc wrapper so memory can be 
+  * reference counted and leak detection works. Unless compiled with OMIT_MEMLOCK
+  * attempts to lock the memory pages so sensitive information won't be swapped
+  */
+void* sqlcipher_malloc(int sz) {
+  void *ptr = sqlite3Malloc(sz);
+#ifndef OMIT_MEMLOCK
+  if(ptr) {
+#if defined(__unix__) || defined(__APPLE__) 
+    mlock(ptr, sz);
+#elif defined(_WIN32)
+    VirtualLock(ptr, sz);
+#endif
+  }
+#endif
+  return ptr;
+}
+
+
+/**
+  * Initialize a a new cipher_ctx struct. This function will allocate memory
+  * for the cipher context and for the key
+  * 
+  * returns SQLITE_OK if initialization was successful
+  * returns SQLITE_NOMEM if an error occured allocating memory
+  */
+int sqlcipher_cipher_ctx_init(cipher_ctx **iCtx) {
+  cipher_ctx *ctx;
+  *iCtx = (cipher_ctx *) sqlcipher_malloc(sizeof(cipher_ctx));
+  ctx = *iCtx;
+  if(ctx == NULL) return SQLITE_NOMEM;
+  memset(ctx, 0, sizeof(cipher_ctx)); 
+  ctx->key = (unsigned char *) sqlcipher_malloc(EVP_MAX_KEY_LENGTH);
+  ctx->hmac_key = (unsigned char *) sqlcipher_malloc(EVP_MAX_KEY_LENGTH);
+  if(ctx->key == NULL) return SQLITE_NOMEM;
+  if(ctx->hmac_key == NULL) return SQLITE_NOMEM;
+  return SQLITE_OK;
+}
+
+/**
+  * Free and wipe memory associated with a cipher_ctx
+  */
+void sqlcipher_cipher_ctx_free(cipher_ctx **iCtx) {
+  cipher_ctx *ctx = *iCtx;
+  CODEC_TRACE(("cipher_ctx_free: entered iCtx=%d\n", iCtx));
+  sqlcipher_free(ctx->key, ctx->key_sz);
+  sqlcipher_free(ctx->hmac_key, ctx->key_sz);
+  sqlcipher_free(ctx->pass, ctx->pass_sz);
+  sqlcipher_free(ctx, sizeof(cipher_ctx)); 
+}
+
+/**
+  * Compare one cipher_ctx to another.
+  *
+  * returns 0 if all the parameters (except the derived key data) are the same
+  * returns 1 otherwise
+  */
+int sqlcipher_cipher_ctx_cmp(cipher_ctx *c1, cipher_ctx *c2) {
+  CODEC_TRACE(("sqlcipher_cipher_ctx_cmp: entered c1=%d c2=%d\n", c1, c2));
+
+  if(
+    c1->evp_cipher == c2->evp_cipher
+    && c1->iv_sz == c2->iv_sz
+    && c1->kdf_iter == c2->kdf_iter
+    && c1->fast_kdf_iter == c2->fast_kdf_iter
+    && c1->key_sz == c2->key_sz
+    && c1->pass_sz == c2->pass_sz
+    && (
+      c1->pass == c2->pass
+      || !sqlcipher_memcmp((const unsigned char*)c1->pass,
+                           (const unsigned char*)c2->pass,
+                           c1->pass_sz)
+    ) 
+  ) return 0;
+  return 1;
+}
+
+/**
+  * Copy one cipher_ctx to another. For instance, assuming that read_ctx is a 
+  * fully initialized context, you could copy it to write_ctx and all yet data
+  * and pass information across
+  *
+  * returns SQLITE_OK if initialization was successful
+  * returns SQLITE_NOMEM if an error occured allocating memory
+  */
+int sqlcipher_cipher_ctx_copy(cipher_ctx *target, cipher_ctx *source) {
+  void *key = target->key; 
+  void *hmac_key = target->hmac_key; 
+
+  CODEC_TRACE(("sqlcipher_cipher_ctx_copy: entered target=%d, source=%d\n", target, source));
+  sqlcipher_free(target->pass, target->pass_sz); 
+  memcpy(target, source, sizeof(cipher_ctx));
+  
+  target->key = key; //restore pointer to previously allocated key data
+  memcpy(target->key, source->key, EVP_MAX_KEY_LENGTH);
+
+  target->hmac_key = hmac_key; //restore pointer to previously allocated hmac key data
+  memcpy(target->hmac_key, source->hmac_key, EVP_MAX_KEY_LENGTH);
+
+  target->pass = sqlcipher_malloc(source->pass_sz);
+  if(target->pass == NULL) return SQLITE_NOMEM;
+  memcpy(target->pass, source->pass, source->pass_sz);
+
+  return SQLITE_OK;
+}
+
+
+/**
+  * Set the raw password / key data for a cipher context
+  * 
+  * returns SQLITE_OK if assignment was successfull
+  * returns SQLITE_NOMEM if an error occured allocating memory
+  * returns SQLITE_ERROR if the key couldn't be set because the pass was null or size was zero
+  */
+int sqlcipher_cipher_ctx_set_pass(cipher_ctx *ctx, const void *zKey, int nKey) {
+  sqlcipher_free(ctx->pass, ctx->pass_sz);
+  ctx->pass_sz = nKey;
+  if(zKey && nKey) {
+    ctx->pass = sqlcipher_malloc(nKey);
+    if(ctx->pass == NULL) return SQLITE_NOMEM;
+    memcpy(ctx->pass, zKey, nKey);
+    return SQLITE_OK;
+  }
+  return SQLITE_ERROR;
+}
+
+int sqlcipher_codec_ctx_set_pass(codec_ctx *ctx, const void *zKey, int nKey, int for_ctx) {
+  cipher_ctx *c_ctx = for_ctx ? ctx->write_ctx : ctx->read_ctx;
+  int rc;
+
+  if((rc = sqlcipher_cipher_ctx_set_pass(c_ctx, zKey, nKey)) != SQLITE_OK) return rc; 
+  c_ctx->derive_key = 1;
+
+  if(for_ctx == 2)
+    if((rc = sqlcipher_cipher_ctx_copy( for_ctx ? ctx->read_ctx : ctx->write_ctx, c_ctx)) != SQLITE_OK) 
+      return rc; 
+
+  return SQLITE_OK;
+} 
+
+int sqlcipher_codec_ctx_set_cipher(codec_ctx *ctx, const char *cipher_name, int for_ctx) {
+  cipher_ctx *c_ctx = for_ctx ? ctx->write_ctx : ctx->read_ctx;
+  int rc;
+
+  c_ctx->evp_cipher = (EVP_CIPHER *) EVP_get_cipherbyname(cipher_name);
+  c_ctx->key_sz = EVP_CIPHER_key_length(c_ctx->evp_cipher);
+  c_ctx->iv_sz = EVP_CIPHER_iv_length(c_ctx->evp_cipher);
+  c_ctx->block_sz = EVP_CIPHER_block_size(c_ctx->evp_cipher);
+  c_ctx->hmac_sz = EVP_MD_size(EVP_sha1());
+  c_ctx->derive_key = 1;
+
+  if(for_ctx == 2)
+    if((rc = sqlcipher_cipher_ctx_copy( for_ctx ? ctx->read_ctx : ctx->write_ctx, c_ctx)) != SQLITE_OK)
+      return rc; 
+
+  return SQLITE_OK;
+}
+
+int sqlcipher_codec_ctx_set_kdf_iter(codec_ctx *ctx, int kdf_iter, int for_ctx) {
+  cipher_ctx *c_ctx = for_ctx ? ctx->write_ctx : ctx->read_ctx;
+  int rc;
+
+  c_ctx->kdf_iter = kdf_iter;
+  c_ctx->derive_key = 1;
+
+  if(for_ctx == 2)
+    if((rc = sqlcipher_cipher_ctx_copy( for_ctx ? ctx->read_ctx : ctx->write_ctx, c_ctx)) != SQLITE_OK)
+      return rc; 
+
+  return SQLITE_OK;
+}
+
+int sqlcipher_codec_ctx_set_fast_kdf_iter(codec_ctx *ctx, int fast_kdf_iter, int for_ctx) {
+  cipher_ctx *c_ctx = for_ctx ? ctx->write_ctx : ctx->read_ctx;
+  int rc;
+
+  c_ctx->fast_kdf_iter = fast_kdf_iter;
+  c_ctx->derive_key = 1;
+
+  if(for_ctx == 2)
+    if((rc = sqlcipher_cipher_ctx_copy( for_ctx ? ctx->read_ctx : ctx->write_ctx, c_ctx)) != SQLITE_OK)
+      return rc; 
+
+  return SQLITE_OK;
+}
+
+
+int sqlcipher_codec_ctx_set_use_hmac(codec_ctx *ctx, int use) {
+  int reserve = EVP_MAX_IV_LENGTH; /* base reserve size will be IV only */ 
+
+  if(use) reserve += ctx->read_ctx->hmac_sz; /* if reserve will include hmac, update that size */
+
+  /* calculate the amount of reserve needed in even increments of the cipher block size */
+
+  reserve = ((reserve % ctx->read_ctx->block_sz) == 0) ? reserve :
+               ((reserve / ctx->read_ctx->block_sz) + 1) * ctx->read_ctx->block_sz;  
+
+  CODEC_TRACE(("sqlcipher_codec_ctx_set_use_hmac: use=%d block_sz=%d md_size=%d reserve=%d\n", 
+                use, ctx->read_ctx->block_sz, ctx->read_ctx->hmac_sz, reserve)); 
+
+  ctx->write_ctx->use_hmac = ctx->read_ctx->use_hmac = use;
+  ctx->write_ctx->reserve_sz = ctx->read_ctx->reserve_sz = reserve;
+
+  return SQLITE_OK;
+}
+
+void sqlcipher_codec_ctx_set_error(codec_ctx *ctx, int error) {
+  ctx->pBt->db->errCode = error;
+}
+
+int sqlcipher_codec_ctx_get_pagesize(codec_ctx *ctx) {
+  return ctx->page_sz;
+}
+
+int sqlcipher_codec_ctx_get_reservesize(codec_ctx *ctx) {
+  return ctx->read_ctx->reserve_sz;
+}
+
+void* sqlcipher_codec_ctx_get_data(codec_ctx *ctx) {
+  return ctx->buffer;
+}
+
+void* sqlcipher_codec_ctx_get_kdf_salt(codec_ctx *ctx) {
+  return ctx->kdf_salt;
+}
+
+void sqlcipher_codec_get_pass(codec_ctx *ctx, void **zKey, int *nKey) {
+  *zKey = ctx->read_ctx->pass;
+  *nKey = ctx->read_ctx->pass_sz;
+}
+
+int sqlcipher_codec_ctx_set_pagesize(codec_ctx *ctx, int size) {
+  /* attempt to free the existing page buffer */
+  sqlcipher_free(ctx->buffer,ctx->page_sz);
+  ctx->page_sz = size;
+
+  /* pre-allocate a page buffer of PageSize bytes. This will
+     be used as a persistent buffer for encryption and decryption 
+     operations to avoid overhead of multiple memory allocations*/
+  ctx->buffer = sqlcipher_malloc(size);
+  if(ctx->buffer == NULL) return SQLITE_NOMEM;
+
+  return SQLITE_OK;
+}
+
+int sqlcipher_codec_ctx_init(codec_ctx **iCtx, Db *pDb, Pager *pPager, sqlite3_file *fd, const void *zKey, int nKey) {
+  int rc;
+  codec_ctx *ctx;
+  *iCtx = sqlcipher_malloc(sizeof(codec_ctx));
+  ctx = *iCtx;
+
+  if(ctx == NULL) return SQLITE_NOMEM;
+
+  memset(ctx, 0, sizeof(codec_ctx)); /* initialize all pointers and values to 0 */
+  ctx->pBt = pDb->pBt; /* assign pointer to database btree structure */
+
+  /* allocate space for salt data. Then read the first 16 bytes 
+       directly off the database file. This is the salt for the
+       key derivation function. If we get a short read allocate
+       a new random salt value */
+  ctx->kdf_salt_sz = FILE_HEADER_SZ;
+  ctx->kdf_salt = sqlcipher_malloc(ctx->kdf_salt_sz);
+  if(ctx->kdf_salt == NULL) return SQLITE_NOMEM;
+
+  /* allocate space for separate hmac salt data. We want the
+     HMAC derivation salt to be different than the encryption
+     key derivation salt */
+  ctx->hmac_kdf_salt = sqlcipher_malloc(ctx->kdf_salt_sz);
+  if(ctx->hmac_kdf_salt == NULL) return SQLITE_NOMEM;
+
+
+  /*
+     Always overwrite page size and set to the default because the first page of the database
+     in encrypted and thus sqlite can't effectively determine the pagesize. this causes an issue in 
+     cases where bytes 16 & 17 of the page header are a power of 2 as reported by John Lehman
+  */
+  if((rc = sqlcipher_codec_ctx_set_pagesize(ctx, SQLITE_DEFAULT_PAGE_SIZE)) != SQLITE_OK) return rc;
+
+  if((rc = sqlcipher_cipher_ctx_init(&ctx->read_ctx)) != SQLITE_OK) return rc; 
+  if((rc = sqlcipher_cipher_ctx_init(&ctx->write_ctx)) != SQLITE_OK) return rc; 
+
+  if(fd == NULL || sqlite3OsRead(fd, ctx->kdf_salt, FILE_HEADER_SZ, 0) != SQLITE_OK) {
+    /* if unable to read the bytes, generate random salt */
+    if(sqlcipher_random(ctx->kdf_salt, FILE_HEADER_SZ) != 1) return SQLITE_ERROR;
+  }
+
+  if((rc = sqlcipher_codec_ctx_set_cipher(ctx, CIPHER, 0)) != SQLITE_OK) return rc;
+  if((rc = sqlcipher_codec_ctx_set_kdf_iter(ctx, PBKDF2_ITER, 0)) != SQLITE_OK) return rc;
+  if((rc = sqlcipher_codec_ctx_set_fast_kdf_iter(ctx, FAST_PBKDF2_ITER, 0)) != SQLITE_OK) return rc;
+  if((rc = sqlcipher_codec_ctx_set_pass(ctx, zKey, nKey, 0)) != SQLITE_OK) return rc;
+
+  /* Use HMAC signatures by default. Note that codec_set_use_hmac will implicity call
+     codec_set_page_size to set the default */
+  if((rc = sqlcipher_codec_ctx_set_use_hmac(ctx, DEFAULT_USE_HMAC)) != SQLITE_OK) return rc;
+
+  if((rc = sqlcipher_cipher_ctx_copy(ctx->write_ctx, ctx->read_ctx)) != SQLITE_OK) return rc;
+
+  return SQLITE_OK;
+}
+
+/**
+  * Free and wipe memory associated with a cipher_ctx, including the allocated
+  * read_ctx and write_ctx.
+  */
+void sqlcipher_codec_ctx_free(codec_ctx **iCtx) {
+  codec_ctx *ctx = *iCtx;
+  CODEC_TRACE(("codec_ctx_free: entered iCtx=%d\n", iCtx));
+  sqlcipher_free(ctx->kdf_salt, ctx->kdf_salt_sz);
+  sqlcipher_free(ctx->hmac_kdf_salt, ctx->kdf_salt_sz);
+  sqlcipher_free(ctx->buffer, 0);
+  sqlcipher_cipher_ctx_free(&ctx->read_ctx);
+  sqlcipher_cipher_ctx_free(&ctx->write_ctx);
+  sqlcipher_free(ctx, sizeof(codec_ctx)); 
+}
+
+int sqlcipher_page_hmac(cipher_ctx *ctx, Pgno pgno, unsigned char *in, int in_sz, unsigned char *out) {
+  HMAC_CTX_init(&ctx->hctx);
+  
+  HMAC_Init_ex(&ctx->hctx, ctx->hmac_key, ctx->key_sz, EVP_sha1(), NULL);
+
+  /* include the encrypted page data,  initialization vector, and page number in HMAC. This will 
+     prevent both tampering with the ciphertext, manipulation of the IV, or resequencing otherwise
+     valid pages out of order in a database */ 
+  HMAC_Update(&ctx->hctx, in, in_sz);
+  HMAC_Update(&ctx->hctx, (const unsigned char*) &pgno, sizeof(Pgno));
+  HMAC_Final(&ctx->hctx, out, NULL);
+  HMAC_CTX_cleanup(&ctx->hctx);
+  return SQLITE_OK; 
+}
+
+/*
+ * ctx - codec context
+ * pgno - page number in database
+ * size - size in bytes of input and output buffers
+ * mode - 1 to encrypt, 0 to decrypt
+ * in - pointer to input bytes
+ * out - pouter to output bytes
+ */
+int sqlcipher_page_cipher(codec_ctx *ctx, int for_ctx, Pgno pgno, int mode, int page_sz, unsigned char *in, unsigned char *out) {
+  cipher_ctx *c_ctx = for_ctx ? ctx->write_ctx : ctx->read_ctx;
+  unsigned char *iv_in, *iv_out, *hmac_in, *hmac_out, *out_start;
+  int tmp_csz, csz, size;
+
+  /* calculate some required positions into various buffers */
+  size = page_sz - c_ctx->reserve_sz; /* adjust size to useable size and memset reserve at end of page */
+  iv_out = out + size;
+  iv_in = in + size;
+
+  /* hmac will be written immediately after the initialization vector. the remainder of the page reserve will contain
+     random bytes. note, these pointers are only valid when use_hmac is true */
+  hmac_in = in + size + c_ctx->iv_sz; 
+  hmac_out = out + size + c_ctx->iv_sz;
+  out_start = out; /* note the original position of the output buffer pointer, as out will be rewritten during encryption */
+
+  CODEC_TRACE(("codec_cipher:entered pgno=%d, mode=%d, size=%d\n", pgno, mode, size));
+
+  /* just copy raw data from in to out when key size is 0
+   * i.e. during a rekey of a plaintext database */ 
+  if(c_ctx->key_sz == 0) {
+    memcpy(out, in, size);
+    return SQLITE_OK;
+  } 
+
+  if(mode == CIPHER_ENCRYPT) {
+    /* start at front of the reserve block, write random data to the end */
+    if(sqlcipher_random(iv_out, c_ctx->reserve_sz) != 1) return SQLITE_ERROR; 
+  } else { /* CIPHER_DECRYPT */
+    memcpy(iv_out, iv_in, c_ctx->iv_sz); /* copy the iv from the input to output buffer */
+  } 
+
+  if(c_ctx->use_hmac && (mode == CIPHER_DECRYPT)) {
+    if(sqlcipher_page_hmac(c_ctx, pgno, in, size + c_ctx->iv_sz, hmac_out) != SQLITE_OK) {
+      memset(out, 0, page_sz); 
+      CODEC_TRACE(("codec_cipher: hmac operations failed for pgno=%d\n", pgno));
+      return SQLITE_ERROR;
+    }
+
+    CODEC_TRACE(("codec_cipher: comparing hmac on in=%d out=%d hmac_sz=%d\n", hmac_in, hmac_out, c_ctx->hmac_sz));
+    if(sqlcipher_memcmp(hmac_in, hmac_out, c_ctx->hmac_sz) != 0) {
+      /* the hmac check failed, which means the data was tampered with or
+         corrupted in some way. we will return an error, and zero out the page data
+         to force an error */
+      memset(out, 0, page_sz); 
+      CODEC_TRACE(("codec_cipher: hmac check failed for pgno=%d\n", pgno));
+      return SQLITE_ERROR;
+    }
+  } 
+
+  EVP_CipherInit(&c_ctx->ectx, c_ctx->evp_cipher, NULL, NULL, mode);
+  EVP_CIPHER_CTX_set_padding(&c_ctx->ectx, 0);
+  EVP_CipherInit(&c_ctx->ectx, NULL, c_ctx->key, iv_out, mode);
+  EVP_CipherUpdate(&c_ctx->ectx, out, &tmp_csz, in, size);
+  csz = tmp_csz;  
+  out += tmp_csz;
+  EVP_CipherFinal(&c_ctx->ectx, out, &tmp_csz);
+  csz += tmp_csz;
+  EVP_CIPHER_CTX_cleanup(&c_ctx->ectx);
+  assert(size == csz);
+
+  if(c_ctx->use_hmac && (mode == CIPHER_ENCRYPT)) {
+    sqlcipher_page_hmac(c_ctx, pgno, out_start, size + c_ctx->iv_sz, hmac_out); 
+  }
+
+  return SQLITE_OK;
+}
+
+/**
+  * Derive an encryption key for a cipher contex key based on the raw password.
+  *
+  * If the raw key data is formated as x'hex' and there are exactly enough hex chars to fill
+  * the key space (i.e 64 hex chars for a 256 bit key) then the key data will be used directly. 
+  * 
+  * Otherwise, a key data will be derived using PBKDF2
+  * 
+  * returns SQLITE_OK if initialization was successful
+  * returns SQLITE_ERROR if the key could't be derived (for instance if pass is NULL or pass_sz is 0)
+  */
+int sqlcipher_cipher_ctx_key_derive(codec_ctx *ctx, cipher_ctx *c_ctx) {
+  CODEC_TRACE(("codec_key_derive: entered c_ctx->pass=%s, c_ctx->pass_sz=%d \
+                ctx->kdf_salt=%d ctx->kdf_salt_sz=%d c_ctx->kdf_iter=%d \
+                ctx->hmac_kdf_salt=%d, c_ctx->fast_kdf_iter=%d c_ctx->key_sz=%d\n", 
+                c_ctx->pass, c_ctx->pass_sz, ctx->kdf_salt, ctx->kdf_salt_sz, c_ctx->kdf_iter, 
+                ctx->hmac_kdf_salt, c_ctx->fast_kdf_iter, c_ctx->key_sz)); 
+                
+
+  if(c_ctx->pass && c_ctx->pass_sz) { // if pass is not null
+    if (c_ctx->pass_sz == ((c_ctx->key_sz*2)+3) && sqlite3StrNICmp(c_ctx->pass ,"x'", 2) == 0) { 
+      int n = c_ctx->pass_sz - 3; /* adjust for leading x' and tailing ' */
+      const char *z = c_ctx->pass + 2; /* adjust lead offset of x' */
+      CODEC_TRACE(("codec_key_derive: using raw key from hex\n")); 
+      cipher_hex2bin(z, n, c_ctx->key);
+    } else { 
+      CODEC_TRACE(("codec_key_derive: deriving key using full PBKDF2 with %d iterations\n", c_ctx->kdf_iter)); 
+      PKCS5_PBKDF2_HMAC_SHA1( c_ctx->pass, c_ctx->pass_sz, 
+                              ctx->kdf_salt, ctx->kdf_salt_sz, 
+                              c_ctx->kdf_iter, c_ctx->key_sz, c_ctx->key);
+                              
+    }
+
+    /* if this context is setup to use hmac checks, generate a seperate and different 
+       key for HMAC. In this case, we use the output of the previous KDF as the input to 
+       this KDF run. This ensures a distinct but predictable HMAC key. */
+    if(c_ctx->use_hmac) {
+      int i;
+
+      /* start by copying the kdf key into the hmac salt slot
+         then XOR it with the fixed hmac salt defined at compile time
+         this ensures that the salt passed in to derive the hmac key, while 
+         easy to derive and publically known, is not the same as the salt used 
+         to generate the encryption key */ 
+      memcpy(ctx->hmac_kdf_salt, ctx->kdf_salt, ctx->kdf_salt_sz);
+      for(i = 0; i < ctx->kdf_salt_sz; i++) {
+        ctx->hmac_kdf_salt[i] ^= HMAC_SALT_MASK;
+      } 
+
+      CODEC_TRACE(("codec_key_derive: deriving hmac key from encryption key using PBKDF2 with %d iterations\n", 
+        c_ctx->fast_kdf_iter)); 
+      PKCS5_PBKDF2_HMAC_SHA1( (const char*)c_ctx->key, c_ctx->key_sz, 
+                              ctx->hmac_kdf_salt, ctx->kdf_salt_sz, 
+                              c_ctx->fast_kdf_iter, c_ctx->key_sz, c_ctx->hmac_key); 
+    }
+
+    c_ctx->derive_key = 0;
+    return SQLITE_OK;
+  };
+  return SQLITE_ERROR;
+}
+
+int sqlcipher_codec_key_derive(codec_ctx *ctx) {
+  /* derive key on first use if necessary */
+  if(ctx->read_ctx->derive_key) {
+    if(sqlcipher_cipher_ctx_key_derive(ctx, ctx->read_ctx) != SQLITE_OK) return SQLITE_ERROR;
+  }
+
+  if(ctx->write_ctx->derive_key) {
+    if(sqlcipher_cipher_ctx_cmp(ctx->write_ctx, ctx->read_ctx) == 0) {
+      // the relevant parameters are the same, just copy read key
+      if(sqlcipher_cipher_ctx_copy(ctx->write_ctx, ctx->read_ctx) != SQLITE_OK) return SQLITE_ERROR;
+    } else {
+      if(sqlcipher_cipher_ctx_key_derive(ctx, ctx->write_ctx) != SQLITE_OK) return SQLITE_ERROR;
+    }
+  }
+  return SQLITE_OK; 
+}
+
+int sqlcipher_codec_key_copy(codec_ctx *ctx, int source) {
+  if(source == CIPHER_READ_CTX) { 
+      return sqlcipher_cipher_ctx_copy(ctx->write_ctx, ctx->read_ctx); 
+  } else {
+      return sqlcipher_cipher_ctx_copy(ctx->read_ctx, ctx->write_ctx); 
+  }
+}
+
+
+#ifndef OMIT_EXPORT
+
+/*
+ * Implementation of an "export" function that allows a caller
+ * to duplicate the main database to an attached database. This is intended
+ * as a conveneince for users who need to:
+ * 
+ *   1. migrate from an non-encrypted database to an encrypted database
+ *   2. move from an encrypted database to a non-encrypted database
+ *   3. convert beween the various flavors of encrypted databases.  
+ *
+ * This implementation is based heavily on the procedure and code used
+ * in vacuum.c, but is exposed as a function that allows export to any
+ * named attached database.
+ */
+
+/*
+** Finalize a prepared statement.  If there was an error, store the
+** text of the error message in *pzErrMsg.  Return the result code.
+** 
+** Based on vacuumFinalize from vacuum.c
+*/
+static int sqlcipher_finalize(sqlite3 *db, sqlite3_stmt *pStmt, char **pzErrMsg){
+  int rc;
+  rc = sqlite3VdbeFinalize((Vdbe*)pStmt);
+  if( rc ){
+    sqlite3SetString(pzErrMsg, db, sqlite3_errmsg(db));
+  }
+  return rc;
+}
+
+/*
+** Execute zSql on database db. Return an error code.
+** 
+** Based on execSql from vacuum.c
+*/
+static int sqlcipher_execSql(sqlite3 *db, char **pzErrMsg, const char *zSql){
+  sqlite3_stmt *pStmt;
+  VVA_ONLY( int rc; )
+  if( !zSql ){
+    return SQLITE_NOMEM;
+  }
+  if( SQLITE_OK!=sqlite3_prepare(db, zSql, -1, &pStmt, 0) ){
+    sqlite3SetString(pzErrMsg, db, sqlite3_errmsg(db));
+    return sqlite3_errcode(db);
+  }
+  VVA_ONLY( rc = ) sqlite3_step(pStmt);
+  assert( rc!=SQLITE_ROW );
+  return sqlcipher_finalize(db, pStmt, pzErrMsg);
+}
+
+/*
+** Execute zSql on database db. The statement returns exactly
+** one column. Execute this as SQL on the same database.
+** 
+** Based on execExecSql from vacuum.c
+*/
+static int sqlcipher_execExecSql(sqlite3 *db, char **pzErrMsg, const char *zSql){
+  sqlite3_stmt *pStmt;
+  int rc;
+
+  rc = sqlite3_prepare(db, zSql, -1, &pStmt, 0);
+  if( rc!=SQLITE_OK ) return rc;
+
+  while( SQLITE_ROW==sqlite3_step(pStmt) ){
+    rc = sqlcipher_execSql(db, pzErrMsg, (char*)sqlite3_column_text(pStmt, 0));
+    if( rc!=SQLITE_OK ){
+      sqlcipher_finalize(db, pStmt, pzErrMsg);
+      return rc;
+    }
+  }
+
+  return sqlcipher_finalize(db, pStmt, pzErrMsg);
+}
+
+/*
+ * copy database and schema from the main database to an attached database
+ * 
+ * Based on sqlite3RunVacuum from vacuum.c
+*/
+void sqlcipher_exportFunc(sqlite3_context *context, int argc, sqlite3_value **argv) {
+  sqlite3 *db = sqlite3_context_db_handle(context);
+  const char* attachedDb = (const char*) sqlite3_value_text(argv[0]);
+  int saved_flags;        /* Saved value of the db->flags */
+  int saved_nChange;      /* Saved value of db->nChange */
+  int saved_nTotalChange; /* Saved value of db->nTotalChange */
+  void (*saved_xTrace)(void*,const char*);  /* Saved db->xTrace */
+  int rc = SQLITE_OK;     /* Return code from service routines */
+  char *zSql = NULL;         /* SQL statements */
+  char *pzErrMsg = NULL;
+  
+  saved_flags = db->flags;
+  saved_nChange = db->nChange;
+  saved_nTotalChange = db->nTotalChange;
+  saved_xTrace = db->xTrace;
+  db->flags |= SQLITE_WriteSchema | SQLITE_IgnoreChecks | SQLITE_PreferBuiltin;
+  db->flags &= ~(SQLITE_ForeignKeys | SQLITE_ReverseOrder);
+  db->xTrace = 0;
+
+  /* Query the schema of the main database. Create a mirror schema
+  ** in the temporary database.
+  */
+  zSql = sqlite3_mprintf(
+    "SELECT 'CREATE TABLE %s.' || substr(sql,14) "
+    "  FROM sqlite_master WHERE type='table' AND name!='sqlite_sequence'"
+    "   AND rootpage>0"
+  , attachedDb);
+  rc = (zSql == NULL) ? SQLITE_NOMEM : sqlcipher_execExecSql(db, &pzErrMsg, zSql); 
+  if( rc!=SQLITE_OK ) goto end_of_export;
+  sqlite3_free(zSql);
+
+  zSql = sqlite3_mprintf(
+    "SELECT 'CREATE INDEX %s.' || substr(sql,14)"
+    "  FROM sqlite_master WHERE sql LIKE 'CREATE INDEX %%' "
+  , attachedDb);
+  rc = (zSql == NULL) ? SQLITE_NOMEM : sqlcipher_execExecSql(db, &pzErrMsg, zSql); 
+  if( rc!=SQLITE_OK ) goto end_of_export;
+  sqlite3_free(zSql);
+
+  zSql = sqlite3_mprintf(
+    "SELECT 'CREATE UNIQUE INDEX %s.' || substr(sql,21) "
+    "  FROM sqlite_master WHERE sql LIKE 'CREATE UNIQUE INDEX %%'"
+  , attachedDb);
+  rc = (zSql == NULL) ? SQLITE_NOMEM : sqlcipher_execExecSql(db, &pzErrMsg, zSql); 
+  if( rc!=SQLITE_OK ) goto end_of_export;
+  sqlite3_free(zSql);
+
+  /* Loop through the tables in the main database. For each, do
+  ** an "INSERT INTO rekey_db.xxx SELECT * FROM main.xxx;" to copy
+  ** the contents to the temporary database.
+  */
+  zSql = sqlite3_mprintf(
+    "SELECT 'INSERT INTO %s.' || quote(name) "
+    "|| ' SELECT * FROM main.' || quote(name) || ';'"
+    "FROM main.sqlite_master "
+    "WHERE type = 'table' AND name!='sqlite_sequence' "
+    "  AND rootpage>0"
+  , attachedDb);
+  rc = (zSql == NULL) ? SQLITE_NOMEM : sqlcipher_execExecSql(db, &pzErrMsg, zSql); 
+  if( rc!=SQLITE_OK ) goto end_of_export;
+  sqlite3_free(zSql);
+
+  /* Copy over the sequence table
+  */
+  zSql = sqlite3_mprintf(
+    "SELECT 'DELETE FROM %s.' || quote(name) || ';' "
+    "FROM %s.sqlite_master WHERE name='sqlite_sequence' "
+  , attachedDb, attachedDb);
+  rc = (zSql == NULL) ? SQLITE_NOMEM : sqlcipher_execExecSql(db, &pzErrMsg, zSql); 
+  if( rc!=SQLITE_OK ) goto end_of_export;
+  sqlite3_free(zSql);
+
+  zSql = sqlite3_mprintf(
+    "SELECT 'INSERT INTO %s.' || quote(name) "
+    "|| ' SELECT * FROM main.' || quote(name) || ';' "
+    "FROM %s.sqlite_master WHERE name=='sqlite_sequence';"
+  , attachedDb, attachedDb);
+  rc = (zSql == NULL) ? SQLITE_NOMEM : sqlcipher_execExecSql(db, &pzErrMsg, zSql); 
+  if( rc!=SQLITE_OK ) goto end_of_export;
+  sqlite3_free(zSql);
+
+  /* Copy the triggers, views, and virtual tables from the main database
+  ** over to the temporary database.  None of these objects has any
+  ** associated storage, so all we have to do is copy their entries
+  ** from the SQLITE_MASTER table.
+  */
+  zSql = sqlite3_mprintf(
+    "INSERT INTO %s.sqlite_master "
+    "  SELECT type, name, tbl_name, rootpage, sql"
+    "    FROM main.sqlite_master"
+    "   WHERE type='view' OR type='trigger'"
+    "      OR (type='table' AND rootpage=0)"
+  , attachedDb);
+  rc = (zSql == NULL) ? SQLITE_NOMEM : sqlcipher_execSql(db, &pzErrMsg, zSql); 
+  if( rc!=SQLITE_OK ) goto end_of_export;
+  sqlite3_free(zSql);
+
+  zSql = NULL;
+end_of_export:
+  db->flags = saved_flags;
+  db->nChange = saved_nChange;
+  db->nTotalChange = saved_nTotalChange;
+  db->xTrace = saved_xTrace;
+
+  sqlite3_free(zSql);
+
+  if(rc) {
+    if(pzErrMsg != NULL) {
+      sqlite3_result_error(context, pzErrMsg, -1);
+      sqlite3DbFree(db, pzErrMsg);
+    } else {
+      sqlite3_result_error(context, sqlite3ErrStr(rc), -1);
+    }
+  }
+}
+
+#endif
+#endif
diff --git a/src/ctime.c b/src/ctime.c
new file mode 100644
index 0000000..1688069
--- /dev/null
+++ b/src/ctime.c
@@ -0,0 +1,399 @@
+/*
+** 2010 February 23
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file implements routines used to report what compile-time options
+** SQLite was built with.
+*/
+
+#ifndef SQLITE_OMIT_COMPILEOPTION_DIAGS
+
+#include "sqliteInt.h"
+
+/*
+** An array of names of all compile-time options.  This array should 
+** be sorted A-Z.
+**
+** This array looks large, but in a typical installation actually uses
+** only a handful of compile-time options, so most times this array is usually
+** rather short and uses little memory space.
+*/
+static const char * const azCompileOpt[] = {
+
+/* These macros are provided to "stringify" the value of the define
+** for those options in which the value is meaningful. */
+#define CTIMEOPT_VAL_(opt) #opt
+#define CTIMEOPT_VAL(opt) CTIMEOPT_VAL_(opt)
+
+#ifdef SQLITE_32BIT_ROWID
+  "32BIT_ROWID",
+#endif
+#ifdef SQLITE_4_BYTE_ALIGNED_MALLOC
+  "4_BYTE_ALIGNED_MALLOC",
+#endif
+#ifdef SQLITE_CASE_SENSITIVE_LIKE
+  "CASE_SENSITIVE_LIKE",
+#endif
+#ifdef SQLITE_CHECK_PAGES
+  "CHECK_PAGES",
+#endif
+#ifdef SQLITE_COVERAGE_TEST
+  "COVERAGE_TEST",
+#endif
+#ifdef SQLITE_DEBUG
+  "DEBUG",
+#endif
+#ifdef SQLITE_DEFAULT_LOCKING_MODE
+  "DEFAULT_LOCKING_MODE=" CTIMEOPT_VAL(SQLITE_DEFAULT_LOCKING_MODE),
+#endif
+#ifdef SQLITE_DISABLE_DIRSYNC
+  "DISABLE_DIRSYNC",
+#endif
+#ifdef SQLITE_DISABLE_LFS
+  "DISABLE_LFS",
+#endif
+#ifdef SQLITE_ENABLE_ATOMIC_WRITE
+  "ENABLE_ATOMIC_WRITE",
+#endif
+#ifdef SQLITE_ENABLE_CEROD
+  "ENABLE_CEROD",
+#endif
+#ifdef SQLITE_ENABLE_COLUMN_METADATA
+  "ENABLE_COLUMN_METADATA",
+#endif
+#ifdef SQLITE_ENABLE_EXPENSIVE_ASSERT
+  "ENABLE_EXPENSIVE_ASSERT",
+#endif
+#ifdef SQLITE_ENABLE_FTS1
+  "ENABLE_FTS1",
+#endif
+#ifdef SQLITE_ENABLE_FTS2
+  "ENABLE_FTS2",
+#endif
+#ifdef SQLITE_ENABLE_FTS3
+  "ENABLE_FTS3",
+#endif
+#ifdef SQLITE_ENABLE_FTS3_PARENTHESIS
+  "ENABLE_FTS3_PARENTHESIS",
+#endif
+#ifdef SQLITE_ENABLE_FTS4
+  "ENABLE_FTS4",
+#endif
+#ifdef SQLITE_ENABLE_ICU
+  "ENABLE_ICU",
+#endif
+#ifdef SQLITE_ENABLE_IOTRACE
+  "ENABLE_IOTRACE",
+#endif
+#ifdef SQLITE_ENABLE_LOAD_EXTENSION
+  "ENABLE_LOAD_EXTENSION",
+#endif
+#ifdef SQLITE_ENABLE_LOCKING_STYLE
+  "ENABLE_LOCKING_STYLE=" CTIMEOPT_VAL(SQLITE_ENABLE_LOCKING_STYLE),
+#endif
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
+  "ENABLE_MEMORY_MANAGEMENT",
+#endif
+#ifdef SQLITE_ENABLE_MEMSYS3
+  "ENABLE_MEMSYS3",
+#endif
+#ifdef SQLITE_ENABLE_MEMSYS5
+  "ENABLE_MEMSYS5",
+#endif
+#ifdef SQLITE_ENABLE_OVERSIZE_CELL_CHECK
+  "ENABLE_OVERSIZE_CELL_CHECK",
+#endif
+#ifdef SQLITE_ENABLE_RTREE
+  "ENABLE_RTREE",
+#endif
+#ifdef SQLITE_ENABLE_STAT3
+  "ENABLE_STAT3",
+#endif
+#ifdef SQLITE_ENABLE_UNLOCK_NOTIFY
+  "ENABLE_UNLOCK_NOTIFY",
+#endif
+#ifdef SQLITE_ENABLE_UPDATE_DELETE_LIMIT
+  "ENABLE_UPDATE_DELETE_LIMIT",
+#endif
+#ifdef SQLITE_HAS_CODEC
+  "HAS_CODEC",
+#endif
+#ifdef SQLITE_HAVE_ISNAN
+  "HAVE_ISNAN",
+#endif
+#ifdef SQLITE_HOMEGROWN_RECURSIVE_MUTEX
+  "HOMEGROWN_RECURSIVE_MUTEX",
+#endif
+#ifdef SQLITE_IGNORE_AFP_LOCK_ERRORS
+  "IGNORE_AFP_LOCK_ERRORS",
+#endif
+#ifdef SQLITE_IGNORE_FLOCK_LOCK_ERRORS
+  "IGNORE_FLOCK_LOCK_ERRORS",
+#endif
+#ifdef SQLITE_INT64_TYPE
+  "INT64_TYPE",
+#endif
+#ifdef SQLITE_LOCK_TRACE
+  "LOCK_TRACE",
+#endif
+#ifdef SQLITE_MAX_SCHEMA_RETRY
+  "MAX_SCHEMA_RETRY=" CTIMEOPT_VAL(SQLITE_MAX_SCHEMA_RETRY),
+#endif
+#ifdef SQLITE_MEMDEBUG
+  "MEMDEBUG",
+#endif
+#ifdef SQLITE_MIXED_ENDIAN_64BIT_FLOAT
+  "MIXED_ENDIAN_64BIT_FLOAT",
+#endif
+#ifdef SQLITE_NO_SYNC
+  "NO_SYNC",
+#endif
+#ifdef SQLITE_OMIT_ALTERTABLE
+  "OMIT_ALTERTABLE",
+#endif
+#ifdef SQLITE_OMIT_ANALYZE
+  "OMIT_ANALYZE",
+#endif
+#ifdef SQLITE_OMIT_ATTACH
+  "OMIT_ATTACH",
+#endif
+#ifdef SQLITE_OMIT_AUTHORIZATION
+  "OMIT_AUTHORIZATION",
+#endif
+#ifdef SQLITE_OMIT_AUTOINCREMENT
+  "OMIT_AUTOINCREMENT",
+#endif
+#ifdef SQLITE_OMIT_AUTOINIT
+  "OMIT_AUTOINIT",
+#endif
+#ifdef SQLITE_OMIT_AUTOMATIC_INDEX
+  "OMIT_AUTOMATIC_INDEX",
+#endif
+#ifdef SQLITE_OMIT_AUTORESET
+  "OMIT_AUTORESET",
+#endif
+#ifdef SQLITE_OMIT_AUTOVACUUM
+  "OMIT_AUTOVACUUM",
+#endif
+#ifdef SQLITE_OMIT_BETWEEN_OPTIMIZATION
+  "OMIT_BETWEEN_OPTIMIZATION",
+#endif
+#ifdef SQLITE_OMIT_BLOB_LITERAL
+  "OMIT_BLOB_LITERAL",
+#endif
+#ifdef SQLITE_OMIT_BTREECOUNT
+  "OMIT_BTREECOUNT",
+#endif
+#ifdef SQLITE_OMIT_BUILTIN_TEST
+  "OMIT_BUILTIN_TEST",
+#endif
+#ifdef SQLITE_OMIT_CAST
+  "OMIT_CAST",
+#endif
+#ifdef SQLITE_OMIT_CHECK
+  "OMIT_CHECK",
+#endif
+/* // redundant
+** #ifdef SQLITE_OMIT_COMPILEOPTION_DIAGS
+**   "OMIT_COMPILEOPTION_DIAGS",
+** #endif
+*/
+#ifdef SQLITE_OMIT_COMPLETE
+  "OMIT_COMPLETE",
+#endif
+#ifdef SQLITE_OMIT_COMPOUND_SELECT
+  "OMIT_COMPOUND_SELECT",
+#endif
+#ifdef SQLITE_OMIT_DATETIME_FUNCS
+  "OMIT_DATETIME_FUNCS",
+#endif
+#ifdef SQLITE_OMIT_DECLTYPE
+  "OMIT_DECLTYPE",
+#endif
+#ifdef SQLITE_OMIT_DEPRECATED
+  "OMIT_DEPRECATED",
+#endif
+#ifdef SQLITE_OMIT_DISKIO
+  "OMIT_DISKIO",
+#endif
+#ifdef SQLITE_OMIT_EXPLAIN
+  "OMIT_EXPLAIN",
+#endif
+#ifdef SQLITE_OMIT_FLAG_PRAGMAS
+  "OMIT_FLAG_PRAGMAS",
+#endif
+#ifdef SQLITE_OMIT_FLOATING_POINT
+  "OMIT_FLOATING_POINT",
+#endif
+#ifdef SQLITE_OMIT_FOREIGN_KEY
+  "OMIT_FOREIGN_KEY",
+#endif
+#ifdef SQLITE_OMIT_GET_TABLE
+  "OMIT_GET_TABLE",
+#endif
+#ifdef SQLITE_OMIT_INCRBLOB
+  "OMIT_INCRBLOB",
+#endif
+#ifdef SQLITE_OMIT_INTEGRITY_CHECK
+  "OMIT_INTEGRITY_CHECK",
+#endif
+#ifdef SQLITE_OMIT_LIKE_OPTIMIZATION
+  "OMIT_LIKE_OPTIMIZATION",
+#endif
+#ifdef SQLITE_OMIT_LOAD_EXTENSION
+  "OMIT_LOAD_EXTENSION",
+#endif
+#ifdef SQLITE_OMIT_LOCALTIME
+  "OMIT_LOCALTIME",
+#endif
+#ifdef SQLITE_OMIT_LOOKASIDE
+  "OMIT_LOOKASIDE",
+#endif
+#ifdef SQLITE_OMIT_MEMORYDB
+  "OMIT_MEMORYDB",
+#endif
+#ifdef SQLITE_OMIT_MERGE_SORT
+  "OMIT_MERGE_SORT",
+#endif
+#ifdef SQLITE_OMIT_OR_OPTIMIZATION
+  "OMIT_OR_OPTIMIZATION",
+#endif
+#ifdef SQLITE_OMIT_PAGER_PRAGMAS
+  "OMIT_PAGER_PRAGMAS",
+#endif
+#ifdef SQLITE_OMIT_PRAGMA
+  "OMIT_PRAGMA",
+#endif
+#ifdef SQLITE_OMIT_PROGRESS_CALLBACK
+  "OMIT_PROGRESS_CALLBACK",
+#endif
+#ifdef SQLITE_OMIT_QUICKBALANCE
+  "OMIT_QUICKBALANCE",
+#endif
+#ifdef SQLITE_OMIT_REINDEX
+  "OMIT_REINDEX",
+#endif
+#ifdef SQLITE_OMIT_SCHEMA_PRAGMAS
+  "OMIT_SCHEMA_PRAGMAS",
+#endif
+#ifdef SQLITE_OMIT_SCHEMA_VERSION_PRAGMAS
+  "OMIT_SCHEMA_VERSION_PRAGMAS",
+#endif
+#ifdef SQLITE_OMIT_SHARED_CACHE
+  "OMIT_SHARED_CACHE",
+#endif
+#ifdef SQLITE_OMIT_SUBQUERY
+  "OMIT_SUBQUERY",
+#endif
+#ifdef SQLITE_OMIT_TCL_VARIABLE
+  "OMIT_TCL_VARIABLE",
+#endif
+#ifdef SQLITE_OMIT_TEMPDB
+  "OMIT_TEMPDB",
+#endif
+#ifdef SQLITE_OMIT_TRACE
+  "OMIT_TRACE",
+#endif
+#ifdef SQLITE_OMIT_TRIGGER
+  "OMIT_TRIGGER",
+#endif
+#ifdef SQLITE_OMIT_TRUNCATE_OPTIMIZATION
+  "OMIT_TRUNCATE_OPTIMIZATION",
+#endif
+#ifdef SQLITE_OMIT_UTF16
+  "OMIT_UTF16",
+#endif
+#ifdef SQLITE_OMIT_VACUUM
+  "OMIT_VACUUM",
+#endif
+#ifdef SQLITE_OMIT_VIEW
+  "OMIT_VIEW",
+#endif
+#ifdef SQLITE_OMIT_VIRTUALTABLE
+  "OMIT_VIRTUALTABLE",
+#endif
+#ifdef SQLITE_OMIT_WAL
+  "OMIT_WAL",
+#endif
+#ifdef SQLITE_OMIT_WSD
+  "OMIT_WSD",
+#endif
+#ifdef SQLITE_OMIT_XFER_OPT
+  "OMIT_XFER_OPT",
+#endif
+#ifdef SQLITE_PERFORMANCE_TRACE
+  "PERFORMANCE_TRACE",
+#endif
+#ifdef SQLITE_PROXY_DEBUG
+  "PROXY_DEBUG",
+#endif
+#ifdef SQLITE_SECURE_DELETE
+  "SECURE_DELETE",
+#endif
+#ifdef SQLITE_SMALL_STACK
+  "SMALL_STACK",
+#endif
+#ifdef SQLITE_SOUNDEX
+  "SOUNDEX",
+#endif
+#ifdef SQLITE_TCL
+  "TCL",
+#endif
+#ifdef SQLITE_TEMP_STORE
+  "TEMP_STORE=" CTIMEOPT_VAL(SQLITE_TEMP_STORE),
+#endif
+#ifdef SQLITE_TEST
+  "TEST",
+#endif
+#ifdef SQLITE_THREADSAFE
+  "THREADSAFE=" CTIMEOPT_VAL(SQLITE_THREADSAFE),
+#endif
+#ifdef SQLITE_USE_ALLOCA
+  "USE_ALLOCA",
+#endif
+#ifdef SQLITE_ZERO_MALLOC
+  "ZERO_MALLOC"
+#endif
+};
+
+/*
+** Given the name of a compile-time option, return true if that option
+** was used and false if not.
+**
+** The name can optionally begin with "SQLITE_" but the "SQLITE_" prefix
+** is not required for a match.
+*/
+int sqlite3_compileoption_used(const char *zOptName){
+  int i, n;
+  if( sqlite3StrNICmp(zOptName, "SQLITE_", 7)==0 ) zOptName += 7;
+  n = sqlite3Strlen30(zOptName);
+
+  /* Since ArraySize(azCompileOpt) is normally in single digits, a
+  ** linear search is adequate.  No need for a binary search. */
+  for(i=0; i<ArraySize(azCompileOpt); i++){
+    if(   (sqlite3StrNICmp(zOptName, azCompileOpt[i], n)==0)
+       && ( (azCompileOpt[i][n]==0) || (azCompileOpt[i][n]=='=') ) ) return 1;
+  }
+  return 0;
+}
+
+/*
+** Return the N-th compile-time option string.  If N is out of range,
+** return a NULL pointer.
+*/
+const char *sqlite3_compileoption_get(int N){
+  if( N>=0 && N<ArraySize(azCompileOpt) ){
+    return azCompileOpt[N];
+  }
+  return 0;
+}
+
+#endif /* SQLITE_OMIT_COMPILEOPTION_DIAGS */
diff --git a/src/date.c b/src/date.c
new file mode 100644
index 0000000..758dd7c
--- /dev/null
+++ b/src/date.c
@@ -0,0 +1,1128 @@
+/*
+** 2003 October 31
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains the C functions that implement date and time
+** functions for SQLite.  
+**
+** There is only one exported symbol in this file - the function
+** sqlite3RegisterDateTimeFunctions() found at the bottom of the file.
+** All other code has file scope.
+**
+** SQLite processes all times and dates as Julian Day numbers.  The
+** dates and times are stored as the number of days since noon
+** in Greenwich on November 24, 4714 B.C. according to the Gregorian
+** calendar system. 
+**
+** 1970-01-01 00:00:00 is JD 2440587.5
+** 2000-01-01 00:00:00 is JD 2451544.5
+**
+** This implemention requires years to be expressed as a 4-digit number
+** which means that only dates between 0000-01-01 and 9999-12-31 can
+** be represented, even though julian day numbers allow a much wider
+** range of dates.
+**
+** The Gregorian calendar system is used for all dates and times,
+** even those that predate the Gregorian calendar.  Historians usually
+** use the Julian calendar for dates prior to 1582-10-15 and for some
+** dates afterwards, depending on locale.  Beware of this difference.
+**
+** The conversion algorithms are implemented based on descriptions
+** in the following text:
+**
+**      Jean Meeus
+**      Astronomical Algorithms, 2nd Edition, 1998
+**      ISBM 0-943396-61-1
+**      Willmann-Bell, Inc
+**      Richmond, Virginia (USA)
+*/
+#include "sqliteInt.h"
+#include <stdlib.h>
+#include <assert.h>
+#include <time.h>
+
+#ifndef SQLITE_OMIT_DATETIME_FUNCS
+
+
+/*
+** A structure for holding a single date and time.
+*/
+typedef struct DateTime DateTime;
+struct DateTime {
+  sqlite3_int64 iJD; /* The julian day number times 86400000 */
+  int Y, M, D;       /* Year, month, and day */
+  int h, m;          /* Hour and minutes */
+  int tz;            /* Timezone offset in minutes */
+  double s;          /* Seconds */
+  char validYMD;     /* True (1) if Y,M,D are valid */
+  char validHMS;     /* True (1) if h,m,s are valid */
+  char validJD;      /* True (1) if iJD is valid */
+  char validTZ;      /* True (1) if tz is valid */
+};
+
+
+/*
+** Convert zDate into one or more integers.  Additional arguments
+** come in groups of 5 as follows:
+**
+**       N       number of digits in the integer
+**       min     minimum allowed value of the integer
+**       max     maximum allowed value of the integer
+**       nextC   first character after the integer
+**       pVal    where to write the integers value.
+**
+** Conversions continue until one with nextC==0 is encountered.
+** The function returns the number of successful conversions.
+*/
+static int getDigits(const char *zDate, ...){
+  va_list ap;
+  int val;
+  int N;
+  int min;
+  int max;
+  int nextC;
+  int *pVal;
+  int cnt = 0;
+  va_start(ap, zDate);
+  do{
+    N = va_arg(ap, int);
+    min = va_arg(ap, int);
+    max = va_arg(ap, int);
+    nextC = va_arg(ap, int);
+    pVal = va_arg(ap, int*);
+    val = 0;
+    while( N-- ){
+      if( !sqlite3Isdigit(*zDate) ){
+        goto end_getDigits;
+      }
+      val = val*10 + *zDate - '0';
+      zDate++;
+    }
+    if( val<min || val>max || (nextC!=0 && nextC!=*zDate) ){
+      goto end_getDigits;
+    }
+    *pVal = val;
+    zDate++;
+    cnt++;
+  }while( nextC );
+end_getDigits:
+  va_end(ap);
+  return cnt;
+}
+
+/*
+** Parse a timezone extension on the end of a date-time.
+** The extension is of the form:
+**
+**        (+/-)HH:MM
+**
+** Or the "zulu" notation:
+**
+**        Z
+**
+** If the parse is successful, write the number of minutes
+** of change in p->tz and return 0.  If a parser error occurs,
+** return non-zero.
+**
+** A missing specifier is not considered an error.
+*/
+static int parseTimezone(const char *zDate, DateTime *p){
+  int sgn = 0;
+  int nHr, nMn;
+  int c;
+  while( sqlite3Isspace(*zDate) ){ zDate++; }
+  p->tz = 0;
+  c = *zDate;
+  if( c=='-' ){
+    sgn = -1;
+  }else if( c=='+' ){
+    sgn = +1;
+  }else if( c=='Z' || c=='z' ){
+    zDate++;
+    goto zulu_time;
+  }else{
+    return c!=0;
+  }
+  zDate++;
+  if( getDigits(zDate, 2, 0, 14, ':', &nHr, 2, 0, 59, 0, &nMn)!=2 ){
+    return 1;
+  }
+  zDate += 5;
+  p->tz = sgn*(nMn + nHr*60);
+zulu_time:
+  while( sqlite3Isspace(*zDate) ){ zDate++; }
+  return *zDate!=0;
+}
+
+/*
+** Parse times of the form HH:MM or HH:MM:SS or HH:MM:SS.FFFF.
+** The HH, MM, and SS must each be exactly 2 digits.  The
+** fractional seconds FFFF can be one or more digits.
+**
+** Return 1 if there is a parsing error and 0 on success.
+*/
+static int parseHhMmSs(const char *zDate, DateTime *p){
+  int h, m, s;
+  double ms = 0.0;
+  if( getDigits(zDate, 2, 0, 24, ':', &h, 2, 0, 59, 0, &m)!=2 ){
+    return 1;
+  }
+  zDate += 5;
+  if( *zDate==':' ){
+    zDate++;
+    if( getDigits(zDate, 2, 0, 59, 0, &s)!=1 ){
+      return 1;
+    }
+    zDate += 2;
+    if( *zDate=='.' && sqlite3Isdigit(zDate[1]) ){
+      double rScale = 1.0;
+      zDate++;
+      while( sqlite3Isdigit(*zDate) ){
+        ms = ms*10.0 + *zDate - '0';
+        rScale *= 10.0;
+        zDate++;
+      }
+      ms /= rScale;
+    }
+  }else{
+    s = 0;
+  }
+  p->validJD = 0;
+  p->validHMS = 1;
+  p->h = h;
+  p->m = m;
+  p->s = s + ms;
+  if( parseTimezone(zDate, p) ) return 1;
+  p->validTZ = (p->tz!=0)?1:0;
+  return 0;
+}
+
+/*
+** Convert from YYYY-MM-DD HH:MM:SS to julian day.  We always assume
+** that the YYYY-MM-DD is according to the Gregorian calendar.
+**
+** Reference:  Meeus page 61
+*/
+static void computeJD(DateTime *p){
+  int Y, M, D, A, B, X1, X2;
+
+  if( p->validJD ) return;
+  if( p->validYMD ){
+    Y = p->Y;
+    M = p->M;
+    D = p->D;
+  }else{
+    Y = 2000;  /* If no YMD specified, assume 2000-Jan-01 */
+    M = 1;
+    D = 1;
+  }
+  if( M<=2 ){
+    Y--;
+    M += 12;
+  }
+  A = Y/100;
+  B = 2 - A + (A/4);
+  X1 = 36525*(Y+4716)/100;
+  X2 = 306001*(M+1)/10000;
+  p->iJD = (sqlite3_int64)((X1 + X2 + D + B - 1524.5 ) * 86400000);
+  p->validJD = 1;
+  if( p->validHMS ){
+    p->iJD += p->h*3600000 + p->m*60000 + (sqlite3_int64)(p->s*1000);
+    if( p->validTZ ){
+      p->iJD -= p->tz*60000;
+      p->validYMD = 0;
+      p->validHMS = 0;
+      p->validTZ = 0;
+    }
+  }
+}
+
+/*
+** Parse dates of the form
+**
+**     YYYY-MM-DD HH:MM:SS.FFF
+**     YYYY-MM-DD HH:MM:SS
+**     YYYY-MM-DD HH:MM
+**     YYYY-MM-DD
+**
+** Write the result into the DateTime structure and return 0
+** on success and 1 if the input string is not a well-formed
+** date.
+*/
+static int parseYyyyMmDd(const char *zDate, DateTime *p){
+  int Y, M, D, neg;
+
+  if( zDate[0]=='-' ){
+    zDate++;
+    neg = 1;
+  }else{
+    neg = 0;
+  }
+  if( getDigits(zDate,4,0,9999,'-',&Y,2,1,12,'-',&M,2,1,31,0,&D)!=3 ){
+    return 1;
+  }
+  zDate += 10;
+  while( sqlite3Isspace(*zDate) || 'T'==*(u8*)zDate ){ zDate++; }
+  if( parseHhMmSs(zDate, p)==0 ){
+    /* We got the time */
+  }else if( *zDate==0 ){
+    p->validHMS = 0;
+  }else{
+    return 1;
+  }
+  p->validJD = 0;
+  p->validYMD = 1;
+  p->Y = neg ? -Y : Y;
+  p->M = M;
+  p->D = D;
+  if( p->validTZ ){
+    computeJD(p);
+  }
+  return 0;
+}
+
+/*
+** Set the time to the current time reported by the VFS.
+**
+** Return the number of errors.
+*/
+static int setDateTimeToCurrent(sqlite3_context *context, DateTime *p){
+  sqlite3 *db = sqlite3_context_db_handle(context);
+  if( sqlite3OsCurrentTimeInt64(db->pVfs, &p->iJD)==SQLITE_OK ){
+    p->validJD = 1;
+    return 0;
+  }else{
+    return 1;
+  }
+}
+
+/*
+** Attempt to parse the given string into a Julian Day Number.  Return
+** the number of errors.
+**
+** The following are acceptable forms for the input string:
+**
+**      YYYY-MM-DD HH:MM:SS.FFF  +/-HH:MM
+**      DDDD.DD 
+**      now
+**
+** In the first form, the +/-HH:MM is always optional.  The fractional
+** seconds extension (the ".FFF") is optional.  The seconds portion
+** (":SS.FFF") is option.  The year and date can be omitted as long
+** as there is a time string.  The time string can be omitted as long
+** as there is a year and date.
+*/
+static int parseDateOrTime(
+  sqlite3_context *context, 
+  const char *zDate, 
+  DateTime *p
+){
+  double r;
+  if( parseYyyyMmDd(zDate,p)==0 ){
+    return 0;
+  }else if( parseHhMmSs(zDate, p)==0 ){
+    return 0;
+  }else if( sqlite3StrICmp(zDate,"now")==0){
+    return setDateTimeToCurrent(context, p);
+  }else if( sqlite3AtoF(zDate, &r, sqlite3Strlen30(zDate), SQLITE_UTF8) ){
+    p->iJD = (sqlite3_int64)(r*86400000.0 + 0.5);
+    p->validJD = 1;
+    return 0;
+  }
+  return 1;
+}
+
+/*
+** Compute the Year, Month, and Day from the julian day number.
+*/
+static void computeYMD(DateTime *p){
+  int Z, A, B, C, D, E, X1;
+  if( p->validYMD ) return;
+  if( !p->validJD ){
+    p->Y = 2000;
+    p->M = 1;
+    p->D = 1;
+  }else{
+    Z = (int)((p->iJD + 43200000)/86400000);
+    A = (int)((Z - 1867216.25)/36524.25);
+    A = Z + 1 + A - (A/4);
+    B = A + 1524;
+    C = (int)((B - 122.1)/365.25);
+    D = (36525*C)/100;
+    E = (int)((B-D)/30.6001);
+    X1 = (int)(30.6001*E);
+    p->D = B - D - X1;
+    p->M = E<14 ? E-1 : E-13;
+    p->Y = p->M>2 ? C - 4716 : C - 4715;
+  }
+  p->validYMD = 1;
+}
+
+/*
+** Compute the Hour, Minute, and Seconds from the julian day number.
+*/
+static void computeHMS(DateTime *p){
+  int s;
+  if( p->validHMS ) return;
+  computeJD(p);
+  s = (int)((p->iJD + 43200000) % 86400000);
+  p->s = s/1000.0;
+  s = (int)p->s;
+  p->s -= s;
+  p->h = s/3600;
+  s -= p->h*3600;
+  p->m = s/60;
+  p->s += s - p->m*60;
+  p->validHMS = 1;
+}
+
+/*
+** Compute both YMD and HMS
+*/
+static void computeYMD_HMS(DateTime *p){
+  computeYMD(p);
+  computeHMS(p);
+}
+
+/*
+** Clear the YMD and HMS and the TZ
+*/
+static void clearYMD_HMS_TZ(DateTime *p){
+  p->validYMD = 0;
+  p->validHMS = 0;
+  p->validTZ = 0;
+}
+
+/*
+** On recent Windows platforms, the localtime_s() function is available
+** as part of the "Secure CRT". It is essentially equivalent to 
+** localtime_r() available under most POSIX platforms, except that the 
+** order of the parameters is reversed.
+**
+** See http://msdn.microsoft.com/en-us/library/a442x3ye(VS.80).aspx.
+**
+** If the user has not indicated to use localtime_r() or localtime_s()
+** already, check for an MSVC build environment that provides 
+** localtime_s().
+*/
+#if !defined(HAVE_LOCALTIME_R) && !defined(HAVE_LOCALTIME_S) && \
+     defined(_MSC_VER) && defined(_CRT_INSECURE_DEPRECATE)
+#define HAVE_LOCALTIME_S 1
+#endif
+
+#ifndef SQLITE_OMIT_LOCALTIME
+/*
+** The following routine implements the rough equivalent of localtime_r()
+** using whatever operating-system specific localtime facility that
+** is available.  This routine returns 0 on success and
+** non-zero on any kind of error.
+**
+** If the sqlite3GlobalConfig.bLocaltimeFault variable is true then this
+** routine will always fail.
+*/
+static int osLocaltime(time_t *t, struct tm *pTm){
+  int rc;
+#if (!defined(HAVE_LOCALTIME_R) || !HAVE_LOCALTIME_R) \
+      && (!defined(HAVE_LOCALTIME_S) || !HAVE_LOCALTIME_S)
+  struct tm *pX;
+#if SQLITE_THREADSAFE>0
+  sqlite3_mutex *mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER);
+#endif
+  sqlite3_mutex_enter(mutex);
+  pX = localtime(t);
+#ifndef SQLITE_OMIT_BUILTIN_TEST
+  if( sqlite3GlobalConfig.bLocaltimeFault ) pX = 0;
+#endif
+  if( pX ) *pTm = *pX;
+  sqlite3_mutex_leave(mutex);
+  rc = pX==0;
+#else
+#ifndef SQLITE_OMIT_BUILTIN_TEST
+  if( sqlite3GlobalConfig.bLocaltimeFault ) return 1;
+#endif
+#if defined(HAVE_LOCALTIME_R) && HAVE_LOCALTIME_R
+  rc = localtime_r(t, pTm)==0;
+#else
+  rc = localtime_s(pTm, t);
+#endif /* HAVE_LOCALTIME_R */
+#endif /* HAVE_LOCALTIME_R || HAVE_LOCALTIME_S */
+  return rc;
+}
+#endif /* SQLITE_OMIT_LOCALTIME */
+
+
+#ifndef SQLITE_OMIT_LOCALTIME
+/*
+** Compute the difference (in milliseconds) between localtime and UTC
+** (a.k.a. GMT) for the time value p where p is in UTC. If no error occurs,
+** return this value and set *pRc to SQLITE_OK. 
+**
+** Or, if an error does occur, set *pRc to SQLITE_ERROR. The returned value
+** is undefined in this case.
+*/
+static sqlite3_int64 localtimeOffset(
+  DateTime *p,                    /* Date at which to calculate offset */
+  sqlite3_context *pCtx,          /* Write error here if one occurs */
+  int *pRc                        /* OUT: Error code. SQLITE_OK or ERROR */
+){
+  DateTime x, y;
+  time_t t;
+  struct tm sLocal;
+
+  /* Initialize the contents of sLocal to avoid a compiler warning. */
+  memset(&sLocal, 0, sizeof(sLocal));
+
+  x = *p;
+  computeYMD_HMS(&x);
+  if( x.Y<1971 || x.Y>=2038 ){
+    x.Y = 2000;
+    x.M = 1;
+    x.D = 1;
+    x.h = 0;
+    x.m = 0;
+    x.s = 0.0;
+  } else {
+    int s = (int)(x.s + 0.5);
+    x.s = s;
+  }
+  x.tz = 0;
+  x.validJD = 0;
+  computeJD(&x);
+  t = (time_t)(x.iJD/1000 - 21086676*(i64)10000);
+  if( osLocaltime(&t, &sLocal) ){
+    sqlite3_result_error(pCtx, "local time unavailable", -1);
+    *pRc = SQLITE_ERROR;
+    return 0;
+  }
+  y.Y = sLocal.tm_year + 1900;
+  y.M = sLocal.tm_mon + 1;
+  y.D = sLocal.tm_mday;
+  y.h = sLocal.tm_hour;
+  y.m = sLocal.tm_min;
+  y.s = sLocal.tm_sec;
+  y.validYMD = 1;
+  y.validHMS = 1;
+  y.validJD = 0;
+  y.validTZ = 0;
+  computeJD(&y);
+  *pRc = SQLITE_OK;
+  return y.iJD - x.iJD;
+}
+#endif /* SQLITE_OMIT_LOCALTIME */
+
+/*
+** Process a modifier to a date-time stamp.  The modifiers are
+** as follows:
+**
+**     NNN days
+**     NNN hours
+**     NNN minutes
+**     NNN.NNNN seconds
+**     NNN months
+**     NNN years
+**     start of month
+**     start of year
+**     start of week
+**     start of day
+**     weekday N
+**     unixepoch
+**     localtime
+**     utc
+**
+** Return 0 on success and 1 if there is any kind of error. If the error
+** is in a system call (i.e. localtime()), then an error message is written
+** to context pCtx. If the error is an unrecognized modifier, no error is
+** written to pCtx.
+*/
+static int parseModifier(sqlite3_context *pCtx, const char *zMod, DateTime *p){
+  int rc = 1;
+  int n;
+  double r;
+  char *z, zBuf[30];
+  z = zBuf;
+  for(n=0; n<ArraySize(zBuf)-1 && zMod[n]; n++){
+    z[n] = (char)sqlite3UpperToLower[(u8)zMod[n]];
+  }
+  z[n] = 0;
+  switch( z[0] ){
+#ifndef SQLITE_OMIT_LOCALTIME
+    case 'l': {
+      /*    localtime
+      **
+      ** Assuming the current time value is UTC (a.k.a. GMT), shift it to
+      ** show local time.
+      */
+      if( strcmp(z, "localtime")==0 ){
+        computeJD(p);
+        p->iJD += localtimeOffset(p, pCtx, &rc);
+        clearYMD_HMS_TZ(p);
+      }
+      break;
+    }
+#endif
+    case 'u': {
+      /*
+      **    unixepoch
+      **
+      ** Treat the current value of p->iJD as the number of
+      ** seconds since 1970.  Convert to a real julian day number.
+      */
+      if( strcmp(z, "unixepoch")==0 && p->validJD ){
+        p->iJD = (p->iJD + 43200)/86400 + 21086676*(i64)10000000;
+        clearYMD_HMS_TZ(p);
+        rc = 0;
+      }
+#ifndef SQLITE_OMIT_LOCALTIME
+      else if( strcmp(z, "utc")==0 ){
+        sqlite3_int64 c1;
+        computeJD(p);
+        c1 = localtimeOffset(p, pCtx, &rc);
+        if( rc==SQLITE_OK ){
+          p->iJD -= c1;
+          clearYMD_HMS_TZ(p);
+          p->iJD += c1 - localtimeOffset(p, pCtx, &rc);
+        }
+      }
+#endif
+      break;
+    }
+    case 'w': {
+      /*
+      **    weekday N
+      **
+      ** Move the date to the same time on the next occurrence of
+      ** weekday N where 0==Sunday, 1==Monday, and so forth.  If the
+      ** date is already on the appropriate weekday, this is a no-op.
+      */
+      if( strncmp(z, "weekday ", 8)==0
+               && sqlite3AtoF(&z[8], &r, sqlite3Strlen30(&z[8]), SQLITE_UTF8)
+               && (n=(int)r)==r && n>=0 && r<7 ){
+        sqlite3_int64 Z;
+        computeYMD_HMS(p);
+        p->validTZ = 0;
+        p->validJD = 0;
+        computeJD(p);
+        Z = ((p->iJD + 129600000)/86400000) % 7;
+        if( Z>n ) Z -= 7;
+        p->iJD += (n - Z)*86400000;
+        clearYMD_HMS_TZ(p);
+        rc = 0;
+      }
+      break;
+    }
+    case 's': {
+      /*
+      **    start of TTTTT
+      **
+      ** Move the date backwards to the beginning of the current day,
+      ** or month or year.
+      */
+      if( strncmp(z, "start of ", 9)!=0 ) break;
+      z += 9;
+      computeYMD(p);
+      p->validHMS = 1;
+      p->h = p->m = 0;
+      p->s = 0.0;
+      p->validTZ = 0;
+      p->validJD = 0;
+      if( strcmp(z,"month")==0 ){
+        p->D = 1;
+        rc = 0;
+      }else if( strcmp(z,"year")==0 ){
+        computeYMD(p);
+        p->M = 1;
+        p->D = 1;
+        rc = 0;
+      }else if( strcmp(z,"day")==0 ){
+        rc = 0;
+      }
+      break;
+    }
+    case '+':
+    case '-':
+    case '0':
+    case '1':
+    case '2':
+    case '3':
+    case '4':
+    case '5':
+    case '6':
+    case '7':
+    case '8':
+    case '9': {
+      double rRounder;
+      for(n=1; z[n] && z[n]!=':' && !sqlite3Isspace(z[n]); n++){}
+      if( !sqlite3AtoF(z, &r, n, SQLITE_UTF8) ){
+        rc = 1;
+        break;
+      }
+      if( z[n]==':' ){
+        /* A modifier of the form (+|-)HH:MM:SS.FFF adds (or subtracts) the
+        ** specified number of hours, minutes, seconds, and fractional seconds
+        ** to the time.  The ".FFF" may be omitted.  The ":SS.FFF" may be
+        ** omitted.
+        */
+        const char *z2 = z;
+        DateTime tx;
+        sqlite3_int64 day;
+        if( !sqlite3Isdigit(*z2) ) z2++;
+        memset(&tx, 0, sizeof(tx));
+        if( parseHhMmSs(z2, &tx) ) break;
+        computeJD(&tx);
+        tx.iJD -= 43200000;
+        day = tx.iJD/86400000;
+        tx.iJD -= day*86400000;
+        if( z[0]=='-' ) tx.iJD = -tx.iJD;
+        computeJD(p);
+        clearYMD_HMS_TZ(p);
+        p->iJD += tx.iJD;
+        rc = 0;
+        break;
+      }
+      z += n;
+      while( sqlite3Isspace(*z) ) z++;
+      n = sqlite3Strlen30(z);
+      if( n>10 || n<3 ) break;
+      if( z[n-1]=='s' ){ z[n-1] = 0; n--; }
+      computeJD(p);
+      rc = 0;
+      rRounder = r<0 ? -0.5 : +0.5;
+      if( n==3 && strcmp(z,"day")==0 ){
+        p->iJD += (sqlite3_int64)(r*86400000.0 + rRounder);
+      }else if( n==4 && strcmp(z,"hour")==0 ){
+        p->iJD += (sqlite3_int64)(r*(86400000.0/24.0) + rRounder);
+      }else if( n==6 && strcmp(z,"minute")==0 ){
+        p->iJD += (sqlite3_int64)(r*(86400000.0/(24.0*60.0)) + rRounder);
+      }else if( n==6 && strcmp(z,"second")==0 ){
+        p->iJD += (sqlite3_int64)(r*(86400000.0/(24.0*60.0*60.0)) + rRounder);
+      }else if( n==5 && strcmp(z,"month")==0 ){
+        int x, y;
+        computeYMD_HMS(p);
+        p->M += (int)r;
+        x = p->M>0 ? (p->M-1)/12 : (p->M-12)/12;
+        p->Y += x;
+        p->M -= x*12;
+        p->validJD = 0;
+        computeJD(p);
+        y = (int)r;
+        if( y!=r ){
+          p->iJD += (sqlite3_int64)((r - y)*30.0*86400000.0 + rRounder);
+        }
+      }else if( n==4 && strcmp(z,"year")==0 ){
+        int y = (int)r;
+        computeYMD_HMS(p);
+        p->Y += y;
+        p->validJD = 0;
+        computeJD(p);
+        if( y!=r ){
+          p->iJD += (sqlite3_int64)((r - y)*365.0*86400000.0 + rRounder);
+        }
+      }else{
+        rc = 1;
+      }
+      clearYMD_HMS_TZ(p);
+      break;
+    }
+    default: {
+      break;
+    }
+  }
+  return rc;
+}
+
+/*
+** Process time function arguments.  argv[0] is a date-time stamp.
+** argv[1] and following are modifiers.  Parse them all and write
+** the resulting time into the DateTime structure p.  Return 0
+** on success and 1 if there are any errors.
+**
+** If there are zero parameters (if even argv[0] is undefined)
+** then assume a default value of "now" for argv[0].
+*/
+static int isDate(
+  sqlite3_context *context, 
+  int argc, 
+  sqlite3_value **argv, 
+  DateTime *p
+){
+  int i;
+  const unsigned char *z;
+  int eType;
+  memset(p, 0, sizeof(*p));
+  if( argc==0 ){
+    return setDateTimeToCurrent(context, p);
+  }
+  if( (eType = sqlite3_value_type(argv[0]))==SQLITE_FLOAT
+                   || eType==SQLITE_INTEGER ){
+    p->iJD = (sqlite3_int64)(sqlite3_value_double(argv[0])*86400000.0 + 0.5);
+    p->validJD = 1;
+  }else{
+    z = sqlite3_value_text(argv[0]);
+    if( !z || parseDateOrTime(context, (char*)z, p) ){
+      return 1;
+    }
+  }
+  for(i=1; i<argc; i++){
+    z = sqlite3_value_text(argv[i]);
+    if( z==0 || parseModifier(context, (char*)z, p) ) return 1;
+  }
+  return 0;
+}
+
+
+/*
+** The following routines implement the various date and time functions
+** of SQLite.
+*/
+
+/*
+**    julianday( TIMESTRING, MOD, MOD, ...)
+**
+** Return the julian day number of the date specified in the arguments
+*/
+static void juliandayFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  DateTime x;
+  if( isDate(context, argc, argv, &x)==0 ){
+    computeJD(&x);
+    sqlite3_result_double(context, x.iJD/86400000.0);
+  }
+}
+
+/*
+**    datetime( TIMESTRING, MOD, MOD, ...)
+**
+** Return YYYY-MM-DD HH:MM:SS
+*/
+static void datetimeFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  DateTime x;
+  if( isDate(context, argc, argv, &x)==0 ){
+    char zBuf[100];
+    computeYMD_HMS(&x);
+    sqlite3_snprintf(sizeof(zBuf), zBuf, "%04d-%02d-%02d %02d:%02d:%02d",
+                     x.Y, x.M, x.D, x.h, x.m, (int)(x.s));
+    sqlite3_result_text(context, zBuf, -1, SQLITE_TRANSIENT);
+  }
+}
+
+/*
+**    time( TIMESTRING, MOD, MOD, ...)
+**
+** Return HH:MM:SS
+*/
+static void timeFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  DateTime x;
+  if( isDate(context, argc, argv, &x)==0 ){
+    char zBuf[100];
+    computeHMS(&x);
+    sqlite3_snprintf(sizeof(zBuf), zBuf, "%02d:%02d:%02d", x.h, x.m, (int)x.s);
+    sqlite3_result_text(context, zBuf, -1, SQLITE_TRANSIENT);
+  }
+}
+
+/*
+**    date( TIMESTRING, MOD, MOD, ...)
+**
+** Return YYYY-MM-DD
+*/
+static void dateFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  DateTime x;
+  if( isDate(context, argc, argv, &x)==0 ){
+    char zBuf[100];
+    computeYMD(&x);
+    sqlite3_snprintf(sizeof(zBuf), zBuf, "%04d-%02d-%02d", x.Y, x.M, x.D);
+    sqlite3_result_text(context, zBuf, -1, SQLITE_TRANSIENT);
+  }
+}
+
+/*
+**    strftime( FORMAT, TIMESTRING, MOD, MOD, ...)
+**
+** Return a string described by FORMAT.  Conversions as follows:
+**
+**   %d  day of month
+**   %f  ** fractional seconds  SS.SSS
+**   %H  hour 00-24
+**   %j  day of year 000-366
+**   %J  ** Julian day number
+**   %m  month 01-12
+**   %M  minute 00-59
+**   %s  seconds since 1970-01-01
+**   %S  seconds 00-59
+**   %w  day of week 0-6  sunday==0
+**   %W  week of year 00-53
+**   %Y  year 0000-9999
+**   %%  %
+*/
+static void strftimeFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  DateTime x;
+  u64 n;
+  size_t i,j;
+  char *z;
+  sqlite3 *db;
+  const char *zFmt = (const char*)sqlite3_value_text(argv[0]);
+  char zBuf[100];
+  if( zFmt==0 || isDate(context, argc-1, argv+1, &x) ) return;
+  db = sqlite3_context_db_handle(context);
+  for(i=0, n=1; zFmt[i]; i++, n++){
+    if( zFmt[i]=='%' ){
+      switch( zFmt[i+1] ){
+        case 'd':
+        case 'H':
+        case 'm':
+        case 'M':
+        case 'S':
+        case 'W':
+          n++;
+          /* fall thru */
+        case 'w':
+        case '%':
+          break;
+        case 'f':
+          n += 8;
+          break;
+        case 'j':
+          n += 3;
+          break;
+        case 'Y':
+          n += 8;
+          break;
+        case 's':
+        case 'J':
+          n += 50;
+          break;
+        default:
+          return;  /* ERROR.  return a NULL */
+      }
+      i++;
+    }
+  }
+  testcase( n==sizeof(zBuf)-1 );
+  testcase( n==sizeof(zBuf) );
+  testcase( n==(u64)db->aLimit[SQLITE_LIMIT_LENGTH]+1 );
+  testcase( n==(u64)db->aLimit[SQLITE_LIMIT_LENGTH] );
+  if( n<sizeof(zBuf) ){
+    z = zBuf;
+  }else if( n>(u64)db->aLimit[SQLITE_LIMIT_LENGTH] ){
+    sqlite3_result_error_toobig(context);
+    return;
+  }else{
+    z = sqlite3DbMallocRaw(db, (int)n);
+    if( z==0 ){
+      sqlite3_result_error_nomem(context);
+      return;
+    }
+  }
+  computeJD(&x);
+  computeYMD_HMS(&x);
+  for(i=j=0; zFmt[i]; i++){
+    if( zFmt[i]!='%' ){
+      z[j++] = zFmt[i];
+    }else{
+      i++;
+      switch( zFmt[i] ){
+        case 'd':  sqlite3_snprintf(3, &z[j],"%02d",x.D); j+=2; break;
+        case 'f': {
+          double s = x.s;
+          if( s>59.999 ) s = 59.999;
+          sqlite3_snprintf(7, &z[j],"%06.3f", s);
+          j += sqlite3Strlen30(&z[j]);
+          break;
+        }
+        case 'H':  sqlite3_snprintf(3, &z[j],"%02d",x.h); j+=2; break;
+        case 'W': /* Fall thru */
+        case 'j': {
+          int nDay;             /* Number of days since 1st day of year */
+          DateTime y = x;
+          y.validJD = 0;
+          y.M = 1;
+          y.D = 1;
+          computeJD(&y);
+          nDay = (int)((x.iJD-y.iJD+43200000)/86400000);
+          if( zFmt[i]=='W' ){
+            int wd;   /* 0=Monday, 1=Tuesday, ... 6=Sunday */
+            wd = (int)(((x.iJD+43200000)/86400000)%7);
+            sqlite3_snprintf(3, &z[j],"%02d",(nDay+7-wd)/7);
+            j += 2;
+          }else{
+            sqlite3_snprintf(4, &z[j],"%03d",nDay+1);
+            j += 3;
+          }
+          break;
+        }
+        case 'J': {
+          sqlite3_snprintf(20, &z[j],"%.16g",x.iJD/86400000.0);
+          j+=sqlite3Strlen30(&z[j]);
+          break;
+        }
+        case 'm':  sqlite3_snprintf(3, &z[j],"%02d",x.M); j+=2; break;
+        case 'M':  sqlite3_snprintf(3, &z[j],"%02d",x.m); j+=2; break;
+        case 's': {
+          sqlite3_snprintf(30,&z[j],"%lld",
+                           (i64)(x.iJD/1000 - 21086676*(i64)10000));
+          j += sqlite3Strlen30(&z[j]);
+          break;
+        }
+        case 'S':  sqlite3_snprintf(3,&z[j],"%02d",(int)x.s); j+=2; break;
+        case 'w': {
+          z[j++] = (char)(((x.iJD+129600000)/86400000) % 7) + '0';
+          break;
+        }
+        case 'Y': {
+          sqlite3_snprintf(5,&z[j],"%04d",x.Y); j+=sqlite3Strlen30(&z[j]);
+          break;
+        }
+        default:   z[j++] = '%'; break;
+      }
+    }
+  }
+  z[j] = 0;
+  sqlite3_result_text(context, z, -1,
+                      z==zBuf ? SQLITE_TRANSIENT : SQLITE_DYNAMIC);
+}
+
+/*
+** current_time()
+**
+** This function returns the same value as time('now').
+*/
+static void ctimeFunc(
+  sqlite3_context *context,
+  int NotUsed,
+  sqlite3_value **NotUsed2
+){
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  timeFunc(context, 0, 0);
+}
+
+/*
+** current_date()
+**
+** This function returns the same value as date('now').
+*/
+static void cdateFunc(
+  sqlite3_context *context,
+  int NotUsed,
+  sqlite3_value **NotUsed2
+){
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  dateFunc(context, 0, 0);
+}
+
+/*
+** current_timestamp()
+**
+** This function returns the same value as datetime('now').
+*/
+static void ctimestampFunc(
+  sqlite3_context *context,
+  int NotUsed,
+  sqlite3_value **NotUsed2
+){
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  datetimeFunc(context, 0, 0);
+}
+#endif /* !defined(SQLITE_OMIT_DATETIME_FUNCS) */
+
+#ifdef SQLITE_OMIT_DATETIME_FUNCS
+/*
+** If the library is compiled to omit the full-scale date and time
+** handling (to get a smaller binary), the following minimal version
+** of the functions current_time(), current_date() and current_timestamp()
+** are included instead. This is to support column declarations that
+** include "DEFAULT CURRENT_TIME" etc.
+**
+** This function uses the C-library functions time(), gmtime()
+** and strftime(). The format string to pass to strftime() is supplied
+** as the user-data for the function.
+*/
+static void currentTimeFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  time_t t;
+  char *zFormat = (char *)sqlite3_user_data(context);
+  sqlite3 *db;
+  sqlite3_int64 iT;
+  struct tm *pTm;
+  struct tm sNow;
+  char zBuf[20];
+
+  UNUSED_PARAMETER(argc);
+  UNUSED_PARAMETER(argv);
+
+  db = sqlite3_context_db_handle(context);
+  if( sqlite3OsCurrentTimeInt64(db->pVfs, &iT) ) return;
+  t = iT/1000 - 10000*(sqlite3_int64)21086676;
+#ifdef HAVE_GMTIME_R
+  pTm = gmtime_r(&t, &sNow);
+#else
+  sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
+  pTm = gmtime(&t);
+  if( pTm ) memcpy(&sNow, pTm, sizeof(sNow));
+  sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
+#endif
+  if( pTm ){
+    strftime(zBuf, 20, zFormat, &sNow);
+    sqlite3_result_text(context, zBuf, -1, SQLITE_TRANSIENT);
+  }
+}
+#endif
+
+/*
+** This function registered all of the above C functions as SQL
+** functions.  This should be the only routine in this file with
+** external linkage.
+*/
+void sqlite3RegisterDateTimeFunctions(void){
+  static SQLITE_WSD FuncDef aDateTimeFuncs[] = {
+#ifndef SQLITE_OMIT_DATETIME_FUNCS
+    FUNCTION(julianday,        -1, 0, 0, juliandayFunc ),
+    FUNCTION(date,             -1, 0, 0, dateFunc      ),
+    FUNCTION(time,             -1, 0, 0, timeFunc      ),
+    FUNCTION(datetime,         -1, 0, 0, datetimeFunc  ),
+    FUNCTION(strftime,         -1, 0, 0, strftimeFunc  ),
+    FUNCTION(current_time,      0, 0, 0, ctimeFunc     ),
+    FUNCTION(current_timestamp, 0, 0, 0, ctimestampFunc),
+    FUNCTION(current_date,      0, 0, 0, cdateFunc     ),
+#else
+    STR_FUNCTION(current_time,      0, "%H:%M:%S",          0, currentTimeFunc),
+    STR_FUNCTION(current_date,      0, "%Y-%m-%d",          0, currentTimeFunc),
+    STR_FUNCTION(current_timestamp, 0, "%Y-%m-%d %H:%M:%S", 0, currentTimeFunc),
+#endif
+  };
+  int i;
+  FuncDefHash *pHash = &GLOBAL(FuncDefHash, sqlite3GlobalFunctions);
+  FuncDef *aFunc = (FuncDef*)&GLOBAL(FuncDef, aDateTimeFuncs);
+
+  for(i=0; i<ArraySize(aDateTimeFuncs); i++){
+    sqlite3FuncDefInsert(pHash, &aFunc[i]);
+  }
+}
diff --git a/src/delete.c b/src/delete.c
new file mode 100644
index 0000000..147a5ca
--- /dev/null
+++ b/src/delete.c
@@ -0,0 +1,652 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains C code routines that are called by the parser
+** in order to generate code for DELETE FROM statements.
+*/
+#include "sqliteInt.h"
+
+/*
+** While a SrcList can in general represent multiple tables and subqueries
+** (as in the FROM clause of a SELECT statement) in this case it contains
+** the name of a single table, as one might find in an INSERT, DELETE,
+** or UPDATE statement.  Look up that table in the symbol table and
+** return a pointer.  Set an error message and return NULL if the table 
+** name is not found or if any other error occurs.
+**
+** The following fields are initialized appropriate in pSrc:
+**
+**    pSrc->a[0].pTab       Pointer to the Table object
+**    pSrc->a[0].pIndex     Pointer to the INDEXED BY index, if there is one
+**
+*/
+Table *sqlite3SrcListLookup(Parse *pParse, SrcList *pSrc){
+  struct SrcList_item *pItem = pSrc->a;
+  Table *pTab;
+  assert( pItem && pSrc->nSrc==1 );
+  pTab = sqlite3LocateTable(pParse, 0, pItem->zName, pItem->zDatabase);
+  sqlite3DeleteTable(pParse->db, pItem->pTab);
+  pItem->pTab = pTab;
+  if( pTab ){
+    pTab->nRef++;
+  }
+  if( sqlite3IndexedByLookup(pParse, pItem) ){
+    pTab = 0;
+  }
+  return pTab;
+}
+
+/*
+** Check to make sure the given table is writable.  If it is not
+** writable, generate an error message and return 1.  If it is
+** writable return 0;
+*/
+int sqlite3IsReadOnly(Parse *pParse, Table *pTab, int viewOk){
+  /* A table is not writable under the following circumstances:
+  **
+  **   1) It is a virtual table and no implementation of the xUpdate method
+  **      has been provided, or
+  **   2) It is a system table (i.e. sqlite_master), this call is not
+  **      part of a nested parse and writable_schema pragma has not 
+  **      been specified.
+  **
+  ** In either case leave an error message in pParse and return non-zero.
+  */
+  if( ( IsVirtual(pTab) 
+     && sqlite3GetVTable(pParse->db, pTab)->pMod->pModule->xUpdate==0 )
+   || ( (pTab->tabFlags & TF_Readonly)!=0
+     && (pParse->db->flags & SQLITE_WriteSchema)==0
+     && pParse->nested==0 )
+  ){
+    sqlite3ErrorMsg(pParse, "table %s may not be modified", pTab->zName);
+    return 1;
+  }
+
+#ifndef SQLITE_OMIT_VIEW
+  if( !viewOk && pTab->pSelect ){
+    sqlite3ErrorMsg(pParse,"cannot modify %s because it is a view",pTab->zName);
+    return 1;
+  }
+#endif
+  return 0;
+}
+
+
+#if !defined(SQLITE_OMIT_VIEW) && !defined(SQLITE_OMIT_TRIGGER)
+/*
+** Evaluate a view and store its result in an ephemeral table.  The
+** pWhere argument is an optional WHERE clause that restricts the
+** set of rows in the view that are to be added to the ephemeral table.
+*/
+void sqlite3MaterializeView(
+  Parse *pParse,       /* Parsing context */
+  Table *pView,        /* View definition */
+  Expr *pWhere,        /* Optional WHERE clause to be added */
+  int iCur             /* Cursor number for ephemerial table */
+){
+  SelectDest dest;
+  Select *pDup;
+  sqlite3 *db = pParse->db;
+
+  pDup = sqlite3SelectDup(db, pView->pSelect, 0);
+  if( pWhere ){
+    SrcList *pFrom;
+    
+    pWhere = sqlite3ExprDup(db, pWhere, 0);
+    pFrom = sqlite3SrcListAppend(db, 0, 0, 0);
+    if( pFrom ){
+      assert( pFrom->nSrc==1 );
+      pFrom->a[0].zAlias = sqlite3DbStrDup(db, pView->zName);
+      pFrom->a[0].pSelect = pDup;
+      assert( pFrom->a[0].pOn==0 );
+      assert( pFrom->a[0].pUsing==0 );
+    }else{
+      sqlite3SelectDelete(db, pDup);
+    }
+    pDup = sqlite3SelectNew(pParse, 0, pFrom, pWhere, 0, 0, 0, 0, 0, 0);
+  }
+  sqlite3SelectDestInit(&dest, SRT_EphemTab, iCur);
+  sqlite3Select(pParse, pDup, &dest);
+  sqlite3SelectDelete(db, pDup);
+}
+#endif /* !defined(SQLITE_OMIT_VIEW) && !defined(SQLITE_OMIT_TRIGGER) */
+
+#if defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT) && !defined(SQLITE_OMIT_SUBQUERY)
+/*
+** Generate an expression tree to implement the WHERE, ORDER BY,
+** and LIMIT/OFFSET portion of DELETE and UPDATE statements.
+**
+**     DELETE FROM table_wxyz WHERE a<5 ORDER BY a LIMIT 1;
+**                            \__________________________/
+**                               pLimitWhere (pInClause)
+*/
+Expr *sqlite3LimitWhere(
+  Parse *pParse,               /* The parser context */
+  SrcList *pSrc,               /* the FROM clause -- which tables to scan */
+  Expr *pWhere,                /* The WHERE clause.  May be null */
+  ExprList *pOrderBy,          /* The ORDER BY clause.  May be null */
+  Expr *pLimit,                /* The LIMIT clause.  May be null */
+  Expr *pOffset,               /* The OFFSET clause.  May be null */
+  char *zStmtType              /* Either DELETE or UPDATE.  For error messages. */
+){
+  Expr *pWhereRowid = NULL;    /* WHERE rowid .. */
+  Expr *pInClause = NULL;      /* WHERE rowid IN ( select ) */
+  Expr *pSelectRowid = NULL;   /* SELECT rowid ... */
+  ExprList *pEList = NULL;     /* Expression list contaning only pSelectRowid */
+  SrcList *pSelectSrc = NULL;  /* SELECT rowid FROM x ... (dup of pSrc) */
+  Select *pSelect = NULL;      /* Complete SELECT tree */
+
+  /* Check that there isn't an ORDER BY without a LIMIT clause.
+  */
+  if( pOrderBy && (pLimit == 0) ) {
+    sqlite3ErrorMsg(pParse, "ORDER BY without LIMIT on %s", zStmtType);
+    pParse->parseError = 1;
+    goto limit_where_cleanup_2;
+  }
+
+  /* We only need to generate a select expression if there
+  ** is a limit/offset term to enforce.
+  */
+  if( pLimit == 0 ) {
+    /* if pLimit is null, pOffset will always be null as well. */
+    assert( pOffset == 0 );
+    return pWhere;
+  }
+
+  /* Generate a select expression tree to enforce the limit/offset 
+  ** term for the DELETE or UPDATE statement.  For example:
+  **   DELETE FROM table_a WHERE col1=1 ORDER BY col2 LIMIT 1 OFFSET 1
+  ** becomes:
+  **   DELETE FROM table_a WHERE rowid IN ( 
+  **     SELECT rowid FROM table_a WHERE col1=1 ORDER BY col2 LIMIT 1 OFFSET 1
+  **   );
+  */
+
+  pSelectRowid = sqlite3PExpr(pParse, TK_ROW, 0, 0, 0);
+  if( pSelectRowid == 0 ) goto limit_where_cleanup_2;
+  pEList = sqlite3ExprListAppend(pParse, 0, pSelectRowid);
+  if( pEList == 0 ) goto limit_where_cleanup_2;
+
+  /* duplicate the FROM clause as it is needed by both the DELETE/UPDATE tree
+  ** and the SELECT subtree. */
+  pSelectSrc = sqlite3SrcListDup(pParse->db, pSrc, 0);
+  if( pSelectSrc == 0 ) {
+    sqlite3ExprListDelete(pParse->db, pEList);
+    goto limit_where_cleanup_2;
+  }
+
+  /* generate the SELECT expression tree. */
+  pSelect = sqlite3SelectNew(pParse,pEList,pSelectSrc,pWhere,0,0,
+                             pOrderBy,0,pLimit,pOffset);
+  if( pSelect == 0 ) return 0;
+
+  /* now generate the new WHERE rowid IN clause for the DELETE/UDPATE */
+  pWhereRowid = sqlite3PExpr(pParse, TK_ROW, 0, 0, 0);
+  if( pWhereRowid == 0 ) goto limit_where_cleanup_1;
+  pInClause = sqlite3PExpr(pParse, TK_IN, pWhereRowid, 0, 0);
+  if( pInClause == 0 ) goto limit_where_cleanup_1;
+
+  pInClause->x.pSelect = pSelect;
+  pInClause->flags |= EP_xIsSelect;
+  sqlite3ExprSetHeight(pParse, pInClause);
+  return pInClause;
+
+  /* something went wrong. clean up anything allocated. */
+limit_where_cleanup_1:
+  sqlite3SelectDelete(pParse->db, pSelect);
+  return 0;
+
+limit_where_cleanup_2:
+  sqlite3ExprDelete(pParse->db, pWhere);
+  sqlite3ExprListDelete(pParse->db, pOrderBy);
+  sqlite3ExprDelete(pParse->db, pLimit);
+  sqlite3ExprDelete(pParse->db, pOffset);
+  return 0;
+}
+#endif /* defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT) && !defined(SQLITE_OMIT_SUBQUERY) */
+
+/*
+** Generate code for a DELETE FROM statement.
+**
+**     DELETE FROM table_wxyz WHERE a<5 AND b NOT NULL;
+**                 \________/       \________________/
+**                  pTabList              pWhere
+*/
+void sqlite3DeleteFrom(
+  Parse *pParse,         /* The parser context */
+  SrcList *pTabList,     /* The table from which we should delete things */
+  Expr *pWhere           /* The WHERE clause.  May be null */
+){
+  Vdbe *v;               /* The virtual database engine */
+  Table *pTab;           /* The table from which records will be deleted */
+  const char *zDb;       /* Name of database holding pTab */
+  int end, addr = 0;     /* A couple addresses of generated code */
+  int i;                 /* Loop counter */
+  WhereInfo *pWInfo;     /* Information about the WHERE clause */
+  Index *pIdx;           /* For looping over indices of the table */
+  int iCur;              /* VDBE Cursor number for pTab */
+  sqlite3 *db;           /* Main database structure */
+  AuthContext sContext;  /* Authorization context */
+  NameContext sNC;       /* Name context to resolve expressions in */
+  int iDb;               /* Database number */
+  int memCnt = -1;       /* Memory cell used for change counting */
+  int rcauth;            /* Value returned by authorization callback */
+
+#ifndef SQLITE_OMIT_TRIGGER
+  int isView;                  /* True if attempting to delete from a view */
+  Trigger *pTrigger;           /* List of table triggers, if required */
+#endif
+
+  memset(&sContext, 0, sizeof(sContext));
+  db = pParse->db;
+  if( pParse->nErr || db->mallocFailed ){
+    goto delete_from_cleanup;
+  }
+  assert( pTabList->nSrc==1 );
+
+  /* Locate the table which we want to delete.  This table has to be
+  ** put in an SrcList structure because some of the subroutines we
+  ** will be calling are designed to work with multiple tables and expect
+  ** an SrcList* parameter instead of just a Table* parameter.
+  */
+  pTab = sqlite3SrcListLookup(pParse, pTabList);
+  if( pTab==0 )  goto delete_from_cleanup;
+
+  /* Figure out if we have any triggers and if the table being
+  ** deleted from is a view
+  */
+#ifndef SQLITE_OMIT_TRIGGER
+  pTrigger = sqlite3TriggersExist(pParse, pTab, TK_DELETE, 0, 0);
+  isView = pTab->pSelect!=0;
+#else
+# define pTrigger 0
+# define isView 0
+#endif
+#ifdef SQLITE_OMIT_VIEW
+# undef isView
+# define isView 0
+#endif
+
+  /* If pTab is really a view, make sure it has been initialized.
+  */
+  if( sqlite3ViewGetColumnNames(pParse, pTab) ){
+    goto delete_from_cleanup;
+  }
+
+  if( sqlite3IsReadOnly(pParse, pTab, (pTrigger?1:0)) ){
+    goto delete_from_cleanup;
+  }
+  iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+  assert( iDb<db->nDb );
+  zDb = db->aDb[iDb].zName;
+  rcauth = sqlite3AuthCheck(pParse, SQLITE_DELETE, pTab->zName, 0, zDb);
+  assert( rcauth==SQLITE_OK || rcauth==SQLITE_DENY || rcauth==SQLITE_IGNORE );
+  if( rcauth==SQLITE_DENY ){
+    goto delete_from_cleanup;
+  }
+  assert(!isView || pTrigger);
+
+  /* Assign  cursor number to the table and all its indices.
+  */
+  assert( pTabList->nSrc==1 );
+  iCur = pTabList->a[0].iCursor = pParse->nTab++;
+  for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+    pParse->nTab++;
+  }
+
+  /* Start the view context
+  */
+  if( isView ){
+    sqlite3AuthContextPush(pParse, &sContext, pTab->zName);
+  }
+
+  /* Begin generating code.
+  */
+  v = sqlite3GetVdbe(pParse);
+  if( v==0 ){
+    goto delete_from_cleanup;
+  }
+  if( pParse->nested==0 ) sqlite3VdbeCountChanges(v);
+  sqlite3BeginWriteOperation(pParse, 1, iDb);
+
+  /* If we are trying to delete from a view, realize that view into
+  ** a ephemeral table.
+  */
+#if !defined(SQLITE_OMIT_VIEW) && !defined(SQLITE_OMIT_TRIGGER)
+  if( isView ){
+    sqlite3MaterializeView(pParse, pTab, pWhere, iCur);
+  }
+#endif
+
+  /* Resolve the column names in the WHERE clause.
+  */
+  memset(&sNC, 0, sizeof(sNC));
+  sNC.pParse = pParse;
+  sNC.pSrcList = pTabList;
+  if( sqlite3ResolveExprNames(&sNC, pWhere) ){
+    goto delete_from_cleanup;
+  }
+
+  /* Initialize the counter of the number of rows deleted, if
+  ** we are counting rows.
+  */
+  if( db->flags & SQLITE_CountRows ){
+    memCnt = ++pParse->nMem;
+    sqlite3VdbeAddOp2(v, OP_Integer, 0, memCnt);
+  }
+
+#ifndef SQLITE_OMIT_TRUNCATE_OPTIMIZATION
+  /* Special case: A DELETE without a WHERE clause deletes everything.
+  ** It is easier just to erase the whole table. Prior to version 3.6.5,
+  ** this optimization caused the row change count (the value returned by 
+  ** API function sqlite3_count_changes) to be set incorrectly.  */
+  if( rcauth==SQLITE_OK && pWhere==0 && !pTrigger && !IsVirtual(pTab) 
+   && 0==sqlite3FkRequired(pParse, pTab, 0, 0)
+  ){
+    assert( !isView );
+    sqlite3VdbeAddOp4(v, OP_Clear, pTab->tnum, iDb, memCnt,
+                      pTab->zName, P4_STATIC);
+    for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+      assert( pIdx->pSchema==pTab->pSchema );
+      sqlite3VdbeAddOp2(v, OP_Clear, pIdx->tnum, iDb);
+    }
+  }else
+#endif /* SQLITE_OMIT_TRUNCATE_OPTIMIZATION */
+  /* The usual case: There is a WHERE clause so we have to scan through
+  ** the table and pick which records to delete.
+  */
+  {
+    int iRowSet = ++pParse->nMem;   /* Register for rowset of rows to delete */
+    int iRowid = ++pParse->nMem;    /* Used for storing rowid values. */
+    int regRowid;                   /* Actual register containing rowids */
+
+    /* Collect rowids of every row to be deleted.
+    */
+    sqlite3VdbeAddOp2(v, OP_Null, 0, iRowSet);
+    pWInfo = sqlite3WhereBegin(
+        pParse, pTabList, pWhere, 0, 0, WHERE_DUPLICATES_OK
+    );
+    if( pWInfo==0 ) goto delete_from_cleanup;
+    regRowid = sqlite3ExprCodeGetColumn(pParse, pTab, -1, iCur, iRowid);
+    sqlite3VdbeAddOp2(v, OP_RowSetAdd, iRowSet, regRowid);
+    if( db->flags & SQLITE_CountRows ){
+      sqlite3VdbeAddOp2(v, OP_AddImm, memCnt, 1);
+    }
+    sqlite3WhereEnd(pWInfo);
+
+    /* Delete every item whose key was written to the list during the
+    ** database scan.  We have to delete items after the scan is complete
+    ** because deleting an item can change the scan order.  */
+    end = sqlite3VdbeMakeLabel(v);
+
+    /* Unless this is a view, open cursors for the table we are 
+    ** deleting from and all its indices. If this is a view, then the
+    ** only effect this statement has is to fire the INSTEAD OF 
+    ** triggers.  */
+    if( !isView ){
+      sqlite3OpenTableAndIndices(pParse, pTab, iCur, OP_OpenWrite);
+    }
+
+    addr = sqlite3VdbeAddOp3(v, OP_RowSetRead, iRowSet, end, iRowid);
+
+    /* Delete the row */
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+    if( IsVirtual(pTab) ){
+      const char *pVTab = (const char *)sqlite3GetVTable(db, pTab);
+      sqlite3VtabMakeWritable(pParse, pTab);
+      sqlite3VdbeAddOp4(v, OP_VUpdate, 0, 1, iRowid, pVTab, P4_VTAB);
+      sqlite3VdbeChangeP5(v, OE_Abort);
+      sqlite3MayAbort(pParse);
+    }else
+#endif
+    {
+      int count = (pParse->nested==0);    /* True to count changes */
+      sqlite3GenerateRowDelete(pParse, pTab, iCur, iRowid, count, pTrigger, OE_Default);
+    }
+
+    /* End of the delete loop */
+    sqlite3VdbeAddOp2(v, OP_Goto, 0, addr);
+    sqlite3VdbeResolveLabel(v, end);
+
+    /* Close the cursors open on the table and its indexes. */
+    if( !isView && !IsVirtual(pTab) ){
+      for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){
+        sqlite3VdbeAddOp2(v, OP_Close, iCur + i, pIdx->tnum);
+      }
+      sqlite3VdbeAddOp1(v, OP_Close, iCur);
+    }
+  }
+
+  /* Update the sqlite_sequence table by storing the content of the
+  ** maximum rowid counter values recorded while inserting into
+  ** autoincrement tables.
+  */
+  if( pParse->nested==0 && pParse->pTriggerTab==0 ){
+    sqlite3AutoincrementEnd(pParse);
+  }
+
+  /* Return the number of rows that were deleted. If this routine is 
+  ** generating code because of a call to sqlite3NestedParse(), do not
+  ** invoke the callback function.
+  */
+  if( (db->flags&SQLITE_CountRows) && !pParse->nested && !pParse->pTriggerTab ){
+    sqlite3VdbeAddOp2(v, OP_ResultRow, memCnt, 1);
+    sqlite3VdbeSetNumCols(v, 1);
+    sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "rows deleted", SQLITE_STATIC);
+  }
+
+delete_from_cleanup:
+  sqlite3AuthContextPop(&sContext);
+  sqlite3SrcListDelete(db, pTabList);
+  sqlite3ExprDelete(db, pWhere);
+  return;
+}
+/* Make sure "isView" and other macros defined above are undefined. Otherwise
+** thely may interfere with compilation of other functions in this file
+** (or in another file, if this file becomes part of the amalgamation).  */
+#ifdef isView
+ #undef isView
+#endif
+#ifdef pTrigger
+ #undef pTrigger
+#endif
+
+/*
+** This routine generates VDBE code that causes a single row of a
+** single table to be deleted.
+**
+** The VDBE must be in a particular state when this routine is called.
+** These are the requirements:
+**
+**   1.  A read/write cursor pointing to pTab, the table containing the row
+**       to be deleted, must be opened as cursor number $iCur.
+**
+**   2.  Read/write cursors for all indices of pTab must be open as
+**       cursor number base+i for the i-th index.
+**
+**   3.  The record number of the row to be deleted must be stored in
+**       memory cell iRowid.
+**
+** This routine generates code to remove both the table record and all 
+** index entries that point to that record.
+*/
+void sqlite3GenerateRowDelete(
+  Parse *pParse,     /* Parsing context */
+  Table *pTab,       /* Table containing the row to be deleted */
+  int iCur,          /* Cursor number for the table */
+  int iRowid,        /* Memory cell that contains the rowid to delete */
+  int count,         /* If non-zero, increment the row change counter */
+  Trigger *pTrigger, /* List of triggers to (potentially) fire */
+  int onconf         /* Default ON CONFLICT policy for triggers */
+){
+  Vdbe *v = pParse->pVdbe;        /* Vdbe */
+  int iOld = 0;                   /* First register in OLD.* array */
+  int iLabel;                     /* Label resolved to end of generated code */
+
+  /* Vdbe is guaranteed to have been allocated by this stage. */
+  assert( v );
+
+  /* Seek cursor iCur to the row to delete. If this row no longer exists 
+  ** (this can happen if a trigger program has already deleted it), do
+  ** not attempt to delete it or fire any DELETE triggers.  */
+  iLabel = sqlite3VdbeMakeLabel(v);
+  sqlite3VdbeAddOp3(v, OP_NotExists, iCur, iLabel, iRowid);
+ 
+  /* If there are any triggers to fire, allocate a range of registers to
+  ** use for the old.* references in the triggers.  */
+  if( sqlite3FkRequired(pParse, pTab, 0, 0) || pTrigger ){
+    u32 mask;                     /* Mask of OLD.* columns in use */
+    int iCol;                     /* Iterator used while populating OLD.* */
+
+    /* TODO: Could use temporary registers here. Also could attempt to
+    ** avoid copying the contents of the rowid register.  */
+    mask = sqlite3TriggerColmask(
+        pParse, pTrigger, 0, 0, TRIGGER_BEFORE|TRIGGER_AFTER, pTab, onconf
+    );
+    mask |= sqlite3FkOldmask(pParse, pTab);
+    iOld = pParse->nMem+1;
+    pParse->nMem += (1 + pTab->nCol);
+
+    /* Populate the OLD.* pseudo-table register array. These values will be 
+    ** used by any BEFORE and AFTER triggers that exist.  */
+    sqlite3VdbeAddOp2(v, OP_Copy, iRowid, iOld);
+    for(iCol=0; iCol<pTab->nCol; iCol++){
+      if( mask==0xffffffff || mask&(1<<iCol) ){
+        sqlite3ExprCodeGetColumnOfTable(v, pTab, iCur, iCol, iOld+iCol+1);
+      }
+    }
+
+    /* Invoke BEFORE DELETE trigger programs. */
+    sqlite3CodeRowTrigger(pParse, pTrigger, 
+        TK_DELETE, 0, TRIGGER_BEFORE, pTab, iOld, onconf, iLabel
+    );
+
+    /* Seek the cursor to the row to be deleted again. It may be that
+    ** the BEFORE triggers coded above have already removed the row
+    ** being deleted. Do not attempt to delete the row a second time, and 
+    ** do not fire AFTER triggers.  */
+    sqlite3VdbeAddOp3(v, OP_NotExists, iCur, iLabel, iRowid);
+
+    /* Do FK processing. This call checks that any FK constraints that
+    ** refer to this table (i.e. constraints attached to other tables) 
+    ** are not violated by deleting this row.  */
+    sqlite3FkCheck(pParse, pTab, iOld, 0);
+  }
+
+  /* Delete the index and table entries. Skip this step if pTab is really
+  ** a view (in which case the only effect of the DELETE statement is to
+  ** fire the INSTEAD OF triggers).  */ 
+  if( pTab->pSelect==0 ){
+    sqlite3GenerateRowIndexDelete(pParse, pTab, iCur, 0);
+    sqlite3VdbeAddOp2(v, OP_Delete, iCur, (count?OPFLAG_NCHANGE:0));
+    if( count ){
+      sqlite3VdbeChangeP4(v, -1, pTab->zName, P4_TRANSIENT);
+    }
+  }
+
+  /* Do any ON CASCADE, SET NULL or SET DEFAULT operations required to
+  ** handle rows (possibly in other tables) that refer via a foreign key
+  ** to the row just deleted. */ 
+  sqlite3FkActions(pParse, pTab, 0, iOld);
+
+  /* Invoke AFTER DELETE trigger programs. */
+  sqlite3CodeRowTrigger(pParse, pTrigger, 
+      TK_DELETE, 0, TRIGGER_AFTER, pTab, iOld, onconf, iLabel
+  );
+
+  /* Jump here if the row had already been deleted before any BEFORE
+  ** trigger programs were invoked. Or if a trigger program throws a 
+  ** RAISE(IGNORE) exception.  */
+  sqlite3VdbeResolveLabel(v, iLabel);
+}
+
+/*
+** This routine generates VDBE code that causes the deletion of all
+** index entries associated with a single row of a single table.
+**
+** The VDBE must be in a particular state when this routine is called.
+** These are the requirements:
+**
+**   1.  A read/write cursor pointing to pTab, the table containing the row
+**       to be deleted, must be opened as cursor number "iCur".
+**
+**   2.  Read/write cursors for all indices of pTab must be open as
+**       cursor number iCur+i for the i-th index.
+**
+**   3.  The "iCur" cursor must be pointing to the row that is to be
+**       deleted.
+*/
+void sqlite3GenerateRowIndexDelete(
+  Parse *pParse,     /* Parsing and code generating context */
+  Table *pTab,       /* Table containing the row to be deleted */
+  int iCur,          /* Cursor number for the table */
+  int *aRegIdx       /* Only delete if aRegIdx!=0 && aRegIdx[i]>0 */
+){
+  int i;
+  Index *pIdx;
+  int r1;
+
+  for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){
+    if( aRegIdx!=0 && aRegIdx[i-1]==0 ) continue;
+    r1 = sqlite3GenerateIndexKey(pParse, pIdx, iCur, 0, 0);
+    sqlite3VdbeAddOp3(pParse->pVdbe, OP_IdxDelete, iCur+i, r1,pIdx->nColumn+1);
+  }
+}
+
+/*
+** Generate code that will assemble an index key and put it in register
+** regOut.  The key with be for index pIdx which is an index on pTab.
+** iCur is the index of a cursor open on the pTab table and pointing to
+** the entry that needs indexing.
+**
+** Return a register number which is the first in a block of
+** registers that holds the elements of the index key.  The
+** block of registers has already been deallocated by the time
+** this routine returns.
+*/
+int sqlite3GenerateIndexKey(
+  Parse *pParse,     /* Parsing context */
+  Index *pIdx,       /* The index for which to generate a key */
+  int iCur,          /* Cursor number for the pIdx->pTable table */
+  int regOut,        /* Write the new index key to this register */
+  int doMakeRec      /* Run the OP_MakeRecord instruction if true */
+){
+  Vdbe *v = pParse->pVdbe;
+  int j;
+  Table *pTab = pIdx->pTable;
+  int regBase;
+  int nCol;
+
+  nCol = pIdx->nColumn;
+  regBase = sqlite3GetTempRange(pParse, nCol+1);
+  sqlite3VdbeAddOp2(v, OP_Rowid, iCur, regBase+nCol);
+  for(j=0; j<nCol; j++){
+    int idx = pIdx->aiColumn[j];
+    if( idx==pTab->iPKey ){
+      sqlite3VdbeAddOp2(v, OP_SCopy, regBase+nCol, regBase+j);
+    }else{
+      sqlite3VdbeAddOp3(v, OP_Column, iCur, idx, regBase+j);
+      sqlite3ColumnDefault(v, pTab, idx, -1);
+    }
+  }
+  if( doMakeRec ){
+    const char *zAff;
+    if( pTab->pSelect || (pParse->db->flags & SQLITE_IdxRealAsInt)!=0 ){
+      zAff = 0;
+    }else{
+      zAff = sqlite3IndexAffinityStr(v, pIdx);
+    }
+    sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase, nCol+1, regOut);
+    sqlite3VdbeChangeP4(v, -1, zAff, P4_TRANSIENT);
+  }
+  sqlite3ReleaseTempRange(pParse, regBase, nCol+1);
+  return regBase;
+}
diff --git a/src/expr.c b/src/expr.c
new file mode 100644
index 0000000..d506173
--- /dev/null
+++ b/src/expr.c
@@ -0,0 +1,3764 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains routines used for analyzing expressions and
+** for generating VDBE code that evaluates expressions in SQLite.
+*/
+#include "sqliteInt.h"
+
+/*
+** Return the 'affinity' of the expression pExpr if any.
+**
+** If pExpr is a column, a reference to a column via an 'AS' alias,
+** or a sub-select with a column as the return value, then the 
+** affinity of that column is returned. Otherwise, 0x00 is returned,
+** indicating no affinity for the expression.
+**
+** i.e. the WHERE clause expresssions in the following statements all
+** have an affinity:
+**
+** CREATE TABLE t1(a);
+** SELECT * FROM t1 WHERE a;
+** SELECT a AS b FROM t1 WHERE b;
+** SELECT * FROM t1 WHERE (select a from t1);
+*/
+char sqlite3ExprAffinity(Expr *pExpr){
+  int op = pExpr->op;
+  if( op==TK_SELECT ){
+    assert( pExpr->flags&EP_xIsSelect );
+    return sqlite3ExprAffinity(pExpr->x.pSelect->pEList->a[0].pExpr);
+  }
+#ifndef SQLITE_OMIT_CAST
+  if( op==TK_CAST ){
+    assert( !ExprHasProperty(pExpr, EP_IntValue) );
+    return sqlite3AffinityType(pExpr->u.zToken);
+  }
+#endif
+  if( (op==TK_AGG_COLUMN || op==TK_COLUMN || op==TK_REGISTER) 
+   && pExpr->pTab!=0
+  ){
+    /* op==TK_REGISTER && pExpr->pTab!=0 happens when pExpr was originally
+    ** a TK_COLUMN but was previously evaluated and cached in a register */
+    int j = pExpr->iColumn;
+    if( j<0 ) return SQLITE_AFF_INTEGER;
+    assert( pExpr->pTab && j<pExpr->pTab->nCol );
+    return pExpr->pTab->aCol[j].affinity;
+  }
+  return pExpr->affinity;
+}
+
+/*
+** Set the explicit collating sequence for an expression to the
+** collating sequence supplied in the second argument.
+*/
+Expr *sqlite3ExprSetColl(Expr *pExpr, CollSeq *pColl){
+  if( pExpr && pColl ){
+    pExpr->pColl = pColl;
+    pExpr->flags |= EP_ExpCollate;
+  }
+  return pExpr;
+}
+
+/*
+** Set the collating sequence for expression pExpr to be the collating
+** sequence named by pToken.   Return a pointer to the revised expression.
+** The collating sequence is marked as "explicit" using the EP_ExpCollate
+** flag.  An explicit collating sequence will override implicit
+** collating sequences.
+*/
+Expr *sqlite3ExprSetCollByToken(Parse *pParse, Expr *pExpr, Token *pCollName){
+  char *zColl = 0;            /* Dequoted name of collation sequence */
+  CollSeq *pColl;
+  sqlite3 *db = pParse->db;
+  zColl = sqlite3NameFromToken(db, pCollName);
+  pColl = sqlite3LocateCollSeq(pParse, zColl);
+  sqlite3ExprSetColl(pExpr, pColl);
+  sqlite3DbFree(db, zColl);
+  return pExpr;
+}
+
+/*
+** Return the default collation sequence for the expression pExpr. If
+** there is no default collation type, return 0.
+*/
+CollSeq *sqlite3ExprCollSeq(Parse *pParse, Expr *pExpr){
+  CollSeq *pColl = 0;
+  Expr *p = pExpr;
+  while( p ){
+    int op;
+    pColl = p->pColl;
+    if( pColl ) break;
+    op = p->op;
+    if( p->pTab!=0 && (
+        op==TK_AGG_COLUMN || op==TK_COLUMN || op==TK_REGISTER || op==TK_TRIGGER
+    )){
+      /* op==TK_REGISTER && p->pTab!=0 happens when pExpr was originally
+      ** a TK_COLUMN but was previously evaluated and cached in a register */
+      const char *zColl;
+      int j = p->iColumn;
+      if( j>=0 ){
+        sqlite3 *db = pParse->db;
+        zColl = p->pTab->aCol[j].zColl;
+        pColl = sqlite3FindCollSeq(db, ENC(db), zColl, 0);
+        pExpr->pColl = pColl;
+      }
+      break;
+    }
+    if( op!=TK_CAST && op!=TK_UPLUS ){
+      break;
+    }
+    p = p->pLeft;
+  }
+  if( sqlite3CheckCollSeq(pParse, pColl) ){ 
+    pColl = 0;
+  }
+  return pColl;
+}
+
+/*
+** pExpr is an operand of a comparison operator.  aff2 is the
+** type affinity of the other operand.  This routine returns the
+** type affinity that should be used for the comparison operator.
+*/
+char sqlite3CompareAffinity(Expr *pExpr, char aff2){
+  char aff1 = sqlite3ExprAffinity(pExpr);
+  if( aff1 && aff2 ){
+    /* Both sides of the comparison are columns. If one has numeric
+    ** affinity, use that. Otherwise use no affinity.
+    */
+    if( sqlite3IsNumericAffinity(aff1) || sqlite3IsNumericAffinity(aff2) ){
+      return SQLITE_AFF_NUMERIC;
+    }else{
+      return SQLITE_AFF_NONE;
+    }
+  }else if( !aff1 && !aff2 ){
+    /* Neither side of the comparison is a column.  Compare the
+    ** results directly.
+    */
+    return SQLITE_AFF_NONE;
+  }else{
+    /* One side is a column, the other is not. Use the columns affinity. */
+    assert( aff1==0 || aff2==0 );
+    return (aff1 + aff2);
+  }
+}
+
+/*
+** pExpr is a comparison operator.  Return the type affinity that should
+** be applied to both operands prior to doing the comparison.
+*/
+static char comparisonAffinity(Expr *pExpr){
+  char aff;
+  assert( pExpr->op==TK_EQ || pExpr->op==TK_IN || pExpr->op==TK_LT ||
+          pExpr->op==TK_GT || pExpr->op==TK_GE || pExpr->op==TK_LE ||
+          pExpr->op==TK_NE || pExpr->op==TK_IS || pExpr->op==TK_ISNOT );
+  assert( pExpr->pLeft );
+  aff = sqlite3ExprAffinity(pExpr->pLeft);
+  if( pExpr->pRight ){
+    aff = sqlite3CompareAffinity(pExpr->pRight, aff);
+  }else if( ExprHasProperty(pExpr, EP_xIsSelect) ){
+    aff = sqlite3CompareAffinity(pExpr->x.pSelect->pEList->a[0].pExpr, aff);
+  }else if( !aff ){
+    aff = SQLITE_AFF_NONE;
+  }
+  return aff;
+}
+
+/*
+** pExpr is a comparison expression, eg. '=', '<', IN(...) etc.
+** idx_affinity is the affinity of an indexed column. Return true
+** if the index with affinity idx_affinity may be used to implement
+** the comparison in pExpr.
+*/
+int sqlite3IndexAffinityOk(Expr *pExpr, char idx_affinity){
+  char aff = comparisonAffinity(pExpr);
+  switch( aff ){
+    case SQLITE_AFF_NONE:
+      return 1;
+    case SQLITE_AFF_TEXT:
+      return idx_affinity==SQLITE_AFF_TEXT;
+    default:
+      return sqlite3IsNumericAffinity(idx_affinity);
+  }
+}
+
+/*
+** Return the P5 value that should be used for a binary comparison
+** opcode (OP_Eq, OP_Ge etc.) used to compare pExpr1 and pExpr2.
+*/
+static u8 binaryCompareP5(Expr *pExpr1, Expr *pExpr2, int jumpIfNull){
+  u8 aff = (char)sqlite3ExprAffinity(pExpr2);
+  aff = (u8)sqlite3CompareAffinity(pExpr1, aff) | (u8)jumpIfNull;
+  return aff;
+}
+
+/*
+** Return a pointer to the collation sequence that should be used by
+** a binary comparison operator comparing pLeft and pRight.
+**
+** If the left hand expression has a collating sequence type, then it is
+** used. Otherwise the collation sequence for the right hand expression
+** is used, or the default (BINARY) if neither expression has a collating
+** type.
+**
+** Argument pRight (but not pLeft) may be a null pointer. In this case,
+** it is not considered.
+*/
+CollSeq *sqlite3BinaryCompareCollSeq(
+  Parse *pParse, 
+  Expr *pLeft, 
+  Expr *pRight
+){
+  CollSeq *pColl;
+  assert( pLeft );
+  if( pLeft->flags & EP_ExpCollate ){
+    assert( pLeft->pColl );
+    pColl = pLeft->pColl;
+  }else if( pRight && pRight->flags & EP_ExpCollate ){
+    assert( pRight->pColl );
+    pColl = pRight->pColl;
+  }else{
+    pColl = sqlite3ExprCollSeq(pParse, pLeft);
+    if( !pColl ){
+      pColl = sqlite3ExprCollSeq(pParse, pRight);
+    }
+  }
+  return pColl;
+}
+
+/*
+** Generate code for a comparison operator.
+*/
+static int codeCompare(
+  Parse *pParse,    /* The parsing (and code generating) context */
+  Expr *pLeft,      /* The left operand */
+  Expr *pRight,     /* The right operand */
+  int opcode,       /* The comparison opcode */
+  int in1, int in2, /* Register holding operands */
+  int dest,         /* Jump here if true.  */
+  int jumpIfNull    /* If true, jump if either operand is NULL */
+){
+  int p5;
+  int addr;
+  CollSeq *p4;
+
+  p4 = sqlite3BinaryCompareCollSeq(pParse, pLeft, pRight);
+  p5 = binaryCompareP5(pLeft, pRight, jumpIfNull);
+  addr = sqlite3VdbeAddOp4(pParse->pVdbe, opcode, in2, dest, in1,
+                           (void*)p4, P4_COLLSEQ);
+  sqlite3VdbeChangeP5(pParse->pVdbe, (u8)p5);
+  return addr;
+}
+
+#if SQLITE_MAX_EXPR_DEPTH>0
+/*
+** Check that argument nHeight is less than or equal to the maximum
+** expression depth allowed. If it is not, leave an error message in
+** pParse.
+*/
+int sqlite3ExprCheckHeight(Parse *pParse, int nHeight){
+  int rc = SQLITE_OK;
+  int mxHeight = pParse->db->aLimit[SQLITE_LIMIT_EXPR_DEPTH];
+  if( nHeight>mxHeight ){
+    sqlite3ErrorMsg(pParse, 
+       "Expression tree is too large (maximum depth %d)", mxHeight
+    );
+    rc = SQLITE_ERROR;
+  }
+  return rc;
+}
+
+/* The following three functions, heightOfExpr(), heightOfExprList()
+** and heightOfSelect(), are used to determine the maximum height
+** of any expression tree referenced by the structure passed as the
+** first argument.
+**
+** If this maximum height is greater than the current value pointed
+** to by pnHeight, the second parameter, then set *pnHeight to that
+** value.
+*/
+static void heightOfExpr(Expr *p, int *pnHeight){
+  if( p ){
+    if( p->nHeight>*pnHeight ){
+      *pnHeight = p->nHeight;
+    }
+  }
+}
+static void heightOfExprList(ExprList *p, int *pnHeight){
+  if( p ){
+    int i;
+    for(i=0; i<p->nExpr; i++){
+      heightOfExpr(p->a[i].pExpr, pnHeight);
+    }
+  }
+}
+static void heightOfSelect(Select *p, int *pnHeight){
+  if( p ){
+    heightOfExpr(p->pWhere, pnHeight);
+    heightOfExpr(p->pHaving, pnHeight);
+    heightOfExpr(p->pLimit, pnHeight);
+    heightOfExpr(p->pOffset, pnHeight);
+    heightOfExprList(p->pEList, pnHeight);
+    heightOfExprList(p->pGroupBy, pnHeight);
+    heightOfExprList(p->pOrderBy, pnHeight);
+    heightOfSelect(p->pPrior, pnHeight);
+  }
+}
+
+/*
+** Set the Expr.nHeight variable in the structure passed as an 
+** argument. An expression with no children, Expr.pList or 
+** Expr.pSelect member has a height of 1. Any other expression
+** has a height equal to the maximum height of any other 
+** referenced Expr plus one.
+*/
+static void exprSetHeight(Expr *p){
+  int nHeight = 0;
+  heightOfExpr(p->pLeft, &nHeight);
+  heightOfExpr(p->pRight, &nHeight);
+  if( ExprHasProperty(p, EP_xIsSelect) ){
+    heightOfSelect(p->x.pSelect, &nHeight);
+  }else{
+    heightOfExprList(p->x.pList, &nHeight);
+  }
+  p->nHeight = nHeight + 1;
+}
+
+/*
+** Set the Expr.nHeight variable using the exprSetHeight() function. If
+** the height is greater than the maximum allowed expression depth,
+** leave an error in pParse.
+*/
+void sqlite3ExprSetHeight(Parse *pParse, Expr *p){
+  exprSetHeight(p);
+  sqlite3ExprCheckHeight(pParse, p->nHeight);
+}
+
+/*
+** Return the maximum height of any expression tree referenced
+** by the select statement passed as an argument.
+*/
+int sqlite3SelectExprHeight(Select *p){
+  int nHeight = 0;
+  heightOfSelect(p, &nHeight);
+  return nHeight;
+}
+#else
+  #define exprSetHeight(y)
+#endif /* SQLITE_MAX_EXPR_DEPTH>0 */
+
+/*
+** This routine is the core allocator for Expr nodes.
+**
+** Construct a new expression node and return a pointer to it.  Memory
+** for this node and for the pToken argument is a single allocation
+** obtained from sqlite3DbMalloc().  The calling function
+** is responsible for making sure the node eventually gets freed.
+**
+** If dequote is true, then the token (if it exists) is dequoted.
+** If dequote is false, no dequoting is performance.  The deQuote
+** parameter is ignored if pToken is NULL or if the token does not
+** appear to be quoted.  If the quotes were of the form "..." (double-quotes)
+** then the EP_DblQuoted flag is set on the expression node.
+**
+** Special case:  If op==TK_INTEGER and pToken points to a string that
+** can be translated into a 32-bit integer, then the token is not
+** stored in u.zToken.  Instead, the integer values is written
+** into u.iValue and the EP_IntValue flag is set.  No extra storage
+** is allocated to hold the integer text and the dequote flag is ignored.
+*/
+Expr *sqlite3ExprAlloc(
+  sqlite3 *db,            /* Handle for sqlite3DbMallocZero() (may be null) */
+  int op,                 /* Expression opcode */
+  const Token *pToken,    /* Token argument.  Might be NULL */
+  int dequote             /* True to dequote */
+){
+  Expr *pNew;
+  int nExtra = 0;
+  int iValue = 0;
+
+  if( pToken ){
+    if( op!=TK_INTEGER || pToken->z==0
+          || sqlite3GetInt32(pToken->z, &iValue)==0 ){
+      nExtra = pToken->n+1;
+      assert( iValue>=0 );
+    }
+  }
+  pNew = sqlite3DbMallocZero(db, sizeof(Expr)+nExtra);
+  if( pNew ){
+    pNew->op = (u8)op;
+    pNew->iAgg = -1;
+    if( pToken ){
+      if( nExtra==0 ){
+        pNew->flags |= EP_IntValue;
+        pNew->u.iValue = iValue;
+      }else{
+        int c;
+        pNew->u.zToken = (char*)&pNew[1];
+        assert( pToken->z!=0 || pToken->n==0 );
+        if( pToken->n ) memcpy(pNew->u.zToken, pToken->z, pToken->n);
+        pNew->u.zToken[pToken->n] = 0;
+        if( dequote && nExtra>=3 
+             && ((c = pToken->z[0])=='\'' || c=='"' || c=='[' || c=='`') ){
+          sqlite3Dequote(pNew->u.zToken);
+          if( c=='"' ) pNew->flags |= EP_DblQuoted;
+        }
+      }
+    }
+#if SQLITE_MAX_EXPR_DEPTH>0
+    pNew->nHeight = 1;
+#endif  
+  }
+  return pNew;
+}
+
+/*
+** Allocate a new expression node from a zero-terminated token that has
+** already been dequoted.
+*/
+Expr *sqlite3Expr(
+  sqlite3 *db,            /* Handle for sqlite3DbMallocZero() (may be null) */
+  int op,                 /* Expression opcode */
+  const char *zToken      /* Token argument.  Might be NULL */
+){
+  Token x;
+  x.z = zToken;
+  x.n = zToken ? sqlite3Strlen30(zToken) : 0;
+  return sqlite3ExprAlloc(db, op, &x, 0);
+}
+
+/*
+** Attach subtrees pLeft and pRight to the Expr node pRoot.
+**
+** If pRoot==NULL that means that a memory allocation error has occurred.
+** In that case, delete the subtrees pLeft and pRight.
+*/
+void sqlite3ExprAttachSubtrees(
+  sqlite3 *db,
+  Expr *pRoot,
+  Expr *pLeft,
+  Expr *pRight
+){
+  if( pRoot==0 ){
+    assert( db->mallocFailed );
+    sqlite3ExprDelete(db, pLeft);
+    sqlite3ExprDelete(db, pRight);
+  }else{
+    if( pRight ){
+      pRoot->pRight = pRight;
+      if( pRight->flags & EP_ExpCollate ){
+        pRoot->flags |= EP_ExpCollate;
+        pRoot->pColl = pRight->pColl;
+      }
+    }
+    if( pLeft ){
+      pRoot->pLeft = pLeft;
+      if( pLeft->flags & EP_ExpCollate ){
+        pRoot->flags |= EP_ExpCollate;
+        pRoot->pColl = pLeft->pColl;
+      }
+    }
+    exprSetHeight(pRoot);
+  }
+}
+
+/*
+** Allocate a Expr node which joins as many as two subtrees.
+**
+** One or both of the subtrees can be NULL.  Return a pointer to the new
+** Expr node.  Or, if an OOM error occurs, set pParse->db->mallocFailed,
+** free the subtrees and return NULL.
+*/
+Expr *sqlite3PExpr(
+  Parse *pParse,          /* Parsing context */
+  int op,                 /* Expression opcode */
+  Expr *pLeft,            /* Left operand */
+  Expr *pRight,           /* Right operand */
+  const Token *pToken     /* Argument token */
+){
+  Expr *p = sqlite3ExprAlloc(pParse->db, op, pToken, 1);
+  sqlite3ExprAttachSubtrees(pParse->db, p, pLeft, pRight);
+  if( p ) {
+    sqlite3ExprCheckHeight(pParse, p->nHeight);
+  }
+  return p;
+}
+
+/*
+** Join two expressions using an AND operator.  If either expression is
+** NULL, then just return the other expression.
+*/
+Expr *sqlite3ExprAnd(sqlite3 *db, Expr *pLeft, Expr *pRight){
+  if( pLeft==0 ){
+    return pRight;
+  }else if( pRight==0 ){
+    return pLeft;
+  }else{
+    Expr *pNew = sqlite3ExprAlloc(db, TK_AND, 0, 0);
+    sqlite3ExprAttachSubtrees(db, pNew, pLeft, pRight);
+    return pNew;
+  }
+}
+
+/*
+** Construct a new expression node for a function with multiple
+** arguments.
+*/
+Expr *sqlite3ExprFunction(Parse *pParse, ExprList *pList, Token *pToken){
+  Expr *pNew;
+  sqlite3 *db = pParse->db;
+  assert( pToken );
+  pNew = sqlite3ExprAlloc(db, TK_FUNCTION, pToken, 1);
+  if( pNew==0 ){
+    sqlite3ExprListDelete(db, pList); /* Avoid memory leak when malloc fails */
+    return 0;
+  }
+  pNew->x.pList = pList;
+  assert( !ExprHasProperty(pNew, EP_xIsSelect) );
+  sqlite3ExprSetHeight(pParse, pNew);
+  return pNew;
+}
+
+/*
+** Assign a variable number to an expression that encodes a wildcard
+** in the original SQL statement.  
+**
+** Wildcards consisting of a single "?" are assigned the next sequential
+** variable number.
+**
+** Wildcards of the form "?nnn" are assigned the number "nnn".  We make
+** sure "nnn" is not too be to avoid a denial of service attack when
+** the SQL statement comes from an external source.
+**
+** Wildcards of the form ":aaa", "@aaa", or "$aaa" are assigned the same number
+** as the previous instance of the same wildcard.  Or if this is the first
+** instance of the wildcard, the next sequenial variable number is
+** assigned.
+*/
+void sqlite3ExprAssignVarNumber(Parse *pParse, Expr *pExpr){
+  sqlite3 *db = pParse->db;
+  const char *z;
+
+  if( pExpr==0 ) return;
+  assert( !ExprHasAnyProperty(pExpr, EP_IntValue|EP_Reduced|EP_TokenOnly) );
+  z = pExpr->u.zToken;
+  assert( z!=0 );
+  assert( z[0]!=0 );
+  if( z[1]==0 ){
+    /* Wildcard of the form "?".  Assign the next variable number */
+    assert( z[0]=='?' );
+    pExpr->iColumn = (ynVar)(++pParse->nVar);
+  }else{
+    ynVar x = 0;
+    u32 n = sqlite3Strlen30(z);
+    if( z[0]=='?' ){
+      /* Wildcard of the form "?nnn".  Convert "nnn" to an integer and
+      ** use it as the variable number */
+      i64 i;
+      int bOk = 0==sqlite3Atoi64(&z[1], &i, n-1, SQLITE_UTF8);
+      pExpr->iColumn = x = (ynVar)i;
+      testcase( i==0 );
+      testcase( i==1 );
+      testcase( i==db->aLimit[SQLITE_LIMIT_VARIABLE_NUMBER]-1 );
+      testcase( i==db->aLimit[SQLITE_LIMIT_VARIABLE_NUMBER] );
+      if( bOk==0 || i<1 || i>db->aLimit[SQLITE_LIMIT_VARIABLE_NUMBER] ){
+        sqlite3ErrorMsg(pParse, "variable number must be between ?1 and ?%d",
+            db->aLimit[SQLITE_LIMIT_VARIABLE_NUMBER]);
+        x = 0;
+      }
+      if( i>pParse->nVar ){
+        pParse->nVar = (int)i;
+      }
+    }else{
+      /* Wildcards like ":aaa", "$aaa" or "@aaa".  Reuse the same variable
+      ** number as the prior appearance of the same name, or if the name
+      ** has never appeared before, reuse the same variable number
+      */
+      ynVar i;
+      for(i=0; i<pParse->nzVar; i++){
+        if( pParse->azVar[i] && memcmp(pParse->azVar[i],z,n+1)==0 ){
+          pExpr->iColumn = x = (ynVar)i+1;
+          break;
+        }
+      }
+      if( x==0 ) x = pExpr->iColumn = (ynVar)(++pParse->nVar);
+    }
+    if( x>0 ){
+      if( x>pParse->nzVar ){
+        char **a;
+        a = sqlite3DbRealloc(db, pParse->azVar, x*sizeof(a[0]));
+        if( a==0 ) return;  /* Error reported through db->mallocFailed */
+        pParse->azVar = a;
+        memset(&a[pParse->nzVar], 0, (x-pParse->nzVar)*sizeof(a[0]));
+        pParse->nzVar = x;
+      }
+      if( z[0]!='?' || pParse->azVar[x-1]==0 ){
+        sqlite3DbFree(db, pParse->azVar[x-1]);
+        pParse->azVar[x-1] = sqlite3DbStrNDup(db, z, n);
+      }
+    }
+  } 
+  if( !pParse->nErr && pParse->nVar>db->aLimit[SQLITE_LIMIT_VARIABLE_NUMBER] ){
+    sqlite3ErrorMsg(pParse, "too many SQL variables");
+  }
+}
+
+/*
+** Recursively delete an expression tree.
+*/
+void sqlite3ExprDelete(sqlite3 *db, Expr *p){
+  if( p==0 ) return;
+  /* Sanity check: Assert that the IntValue is non-negative if it exists */
+  assert( !ExprHasProperty(p, EP_IntValue) || p->u.iValue>=0 );
+  if( !ExprHasAnyProperty(p, EP_TokenOnly) ){
+    sqlite3ExprDelete(db, p->pLeft);
+    sqlite3ExprDelete(db, p->pRight);
+    if( !ExprHasProperty(p, EP_Reduced) && (p->flags2 & EP2_MallocedToken)!=0 ){
+      sqlite3DbFree(db, p->u.zToken);
+    }
+    if( ExprHasProperty(p, EP_xIsSelect) ){
+      sqlite3SelectDelete(db, p->x.pSelect);
+    }else{
+      sqlite3ExprListDelete(db, p->x.pList);
+    }
+  }
+  if( !ExprHasProperty(p, EP_Static) ){
+    sqlite3DbFree(db, p);
+  }
+}
+
+/*
+** Return the number of bytes allocated for the expression structure 
+** passed as the first argument. This is always one of EXPR_FULLSIZE,
+** EXPR_REDUCEDSIZE or EXPR_TOKENONLYSIZE.
+*/
+static int exprStructSize(Expr *p){
+  if( ExprHasProperty(p, EP_TokenOnly) ) return EXPR_TOKENONLYSIZE;
+  if( ExprHasProperty(p, EP_Reduced) ) return EXPR_REDUCEDSIZE;
+  return EXPR_FULLSIZE;
+}
+
+/*
+** The dupedExpr*Size() routines each return the number of bytes required
+** to store a copy of an expression or expression tree.  They differ in
+** how much of the tree is measured.
+**
+**     dupedExprStructSize()     Size of only the Expr structure 
+**     dupedExprNodeSize()       Size of Expr + space for token
+**     dupedExprSize()           Expr + token + subtree components
+**
+***************************************************************************
+**
+** The dupedExprStructSize() function returns two values OR-ed together:  
+** (1) the space required for a copy of the Expr structure only and 
+** (2) the EP_xxx flags that indicate what the structure size should be.
+** The return values is always one of:
+**
+**      EXPR_FULLSIZE
+**      EXPR_REDUCEDSIZE   | EP_Reduced
+**      EXPR_TOKENONLYSIZE | EP_TokenOnly
+**
+** The size of the structure can be found by masking the return value
+** of this routine with 0xfff.  The flags can be found by masking the
+** return value with EP_Reduced|EP_TokenOnly.
+**
+** Note that with flags==EXPRDUP_REDUCE, this routines works on full-size
+** (unreduced) Expr objects as they or originally constructed by the parser.
+** During expression analysis, extra information is computed and moved into
+** later parts of teh Expr object and that extra information might get chopped
+** off if the expression is reduced.  Note also that it does not work to
+** make a EXPRDUP_REDUCE copy of a reduced expression.  It is only legal
+** to reduce a pristine expression tree from the parser.  The implementation
+** of dupedExprStructSize() contain multiple assert() statements that attempt
+** to enforce this constraint.
+*/
+static int dupedExprStructSize(Expr *p, int flags){
+  int nSize;
+  assert( flags==EXPRDUP_REDUCE || flags==0 ); /* Only one flag value allowed */
+  if( 0==(flags&EXPRDUP_REDUCE) ){
+    nSize = EXPR_FULLSIZE;
+  }else{
+    assert( !ExprHasAnyProperty(p, EP_TokenOnly|EP_Reduced) );
+    assert( !ExprHasProperty(p, EP_FromJoin) ); 
+    assert( (p->flags2 & EP2_MallocedToken)==0 );
+    assert( (p->flags2 & EP2_Irreducible)==0 );
+    if( p->pLeft || p->pRight || p->pColl || p->x.pList ){
+      nSize = EXPR_REDUCEDSIZE | EP_Reduced;
+    }else{
+      nSize = EXPR_TOKENONLYSIZE | EP_TokenOnly;
+    }
+  }
+  return nSize;
+}
+
+/*
+** This function returns the space in bytes required to store the copy 
+** of the Expr structure and a copy of the Expr.u.zToken string (if that
+** string is defined.)
+*/
+static int dupedExprNodeSize(Expr *p, int flags){
+  int nByte = dupedExprStructSize(p, flags) & 0xfff;
+  if( !ExprHasProperty(p, EP_IntValue) && p->u.zToken ){
+    nByte += sqlite3Strlen30(p->u.zToken)+1;
+  }
+  return ROUND8(nByte);
+}
+
+/*
+** Return the number of bytes required to create a duplicate of the 
+** expression passed as the first argument. The second argument is a
+** mask containing EXPRDUP_XXX flags.
+**
+** The value returned includes space to create a copy of the Expr struct
+** itself and the buffer referred to by Expr.u.zToken, if any.
+**
+** If the EXPRDUP_REDUCE flag is set, then the return value includes 
+** space to duplicate all Expr nodes in the tree formed by Expr.pLeft 
+** and Expr.pRight variables (but not for any structures pointed to or 
+** descended from the Expr.x.pList or Expr.x.pSelect variables).
+*/
+static int dupedExprSize(Expr *p, int flags){
+  int nByte = 0;
+  if( p ){
+    nByte = dupedExprNodeSize(p, flags);
+    if( flags&EXPRDUP_REDUCE ){
+      nByte += dupedExprSize(p->pLeft, flags) + dupedExprSize(p->pRight, flags);
+    }
+  }
+  return nByte;
+}
+
+/*
+** This function is similar to sqlite3ExprDup(), except that if pzBuffer 
+** is not NULL then *pzBuffer is assumed to point to a buffer large enough 
+** to store the copy of expression p, the copies of p->u.zToken
+** (if applicable), and the copies of the p->pLeft and p->pRight expressions,
+** if any. Before returning, *pzBuffer is set to the first byte passed the
+** portion of the buffer copied into by this function.
+*/
+static Expr *exprDup(sqlite3 *db, Expr *p, int flags, u8 **pzBuffer){
+  Expr *pNew = 0;                      /* Value to return */
+  if( p ){
+    const int isReduced = (flags&EXPRDUP_REDUCE);
+    u8 *zAlloc;
+    u32 staticFlag = 0;
+
+    assert( pzBuffer==0 || isReduced );
+
+    /* Figure out where to write the new Expr structure. */
+    if( pzBuffer ){
+      zAlloc = *pzBuffer;
+      staticFlag = EP_Static;
+    }else{
+      zAlloc = sqlite3DbMallocRaw(db, dupedExprSize(p, flags));
+    }
+    pNew = (Expr *)zAlloc;
+
+    if( pNew ){
+      /* Set nNewSize to the size allocated for the structure pointed to
+      ** by pNew. This is either EXPR_FULLSIZE, EXPR_REDUCEDSIZE or
+      ** EXPR_TOKENONLYSIZE. nToken is set to the number of bytes consumed
+      ** by the copy of the p->u.zToken string (if any).
+      */
+      const unsigned nStructSize = dupedExprStructSize(p, flags);
+      const int nNewSize = nStructSize & 0xfff;
+      int nToken;
+      if( !ExprHasProperty(p, EP_IntValue) && p->u.zToken ){
+        nToken = sqlite3Strlen30(p->u.zToken) + 1;
+      }else{
+        nToken = 0;
+      }
+      if( isReduced ){
+        assert( ExprHasProperty(p, EP_Reduced)==0 );
+        memcpy(zAlloc, p, nNewSize);
+      }else{
+        int nSize = exprStructSize(p);
+        memcpy(zAlloc, p, nSize);
+        memset(&zAlloc[nSize], 0, EXPR_FULLSIZE-nSize);
+      }
+
+      /* Set the EP_Reduced, EP_TokenOnly, and EP_Static flags appropriately. */
+      pNew->flags &= ~(EP_Reduced|EP_TokenOnly|EP_Static);
+      pNew->flags |= nStructSize & (EP_Reduced|EP_TokenOnly);
+      pNew->flags |= staticFlag;
+
+      /* Copy the p->u.zToken string, if any. */
+      if( nToken ){
+        char *zToken = pNew->u.zToken = (char*)&zAlloc[nNewSize];
+        memcpy(zToken, p->u.zToken, nToken);
+      }
+
+      if( 0==((p->flags|pNew->flags) & EP_TokenOnly) ){
+        /* Fill in the pNew->x.pSelect or pNew->x.pList member. */
+        if( ExprHasProperty(p, EP_xIsSelect) ){
+          pNew->x.pSelect = sqlite3SelectDup(db, p->x.pSelect, isReduced);
+        }else{
+          pNew->x.pList = sqlite3ExprListDup(db, p->x.pList, isReduced);
+        }
+      }
+
+      /* Fill in pNew->pLeft and pNew->pRight. */
+      if( ExprHasAnyProperty(pNew, EP_Reduced|EP_TokenOnly) ){
+        zAlloc += dupedExprNodeSize(p, flags);
+        if( ExprHasProperty(pNew, EP_Reduced) ){
+          pNew->pLeft = exprDup(db, p->pLeft, EXPRDUP_REDUCE, &zAlloc);
+          pNew->pRight = exprDup(db, p->pRight, EXPRDUP_REDUCE, &zAlloc);
+        }
+        if( pzBuffer ){
+          *pzBuffer = zAlloc;
+        }
+      }else{
+        pNew->flags2 = 0;
+        if( !ExprHasAnyProperty(p, EP_TokenOnly) ){
+          pNew->pLeft = sqlite3ExprDup(db, p->pLeft, 0);
+          pNew->pRight = sqlite3ExprDup(db, p->pRight, 0);
+        }
+      }
+
+    }
+  }
+  return pNew;
+}
+
+/*
+** The following group of routines make deep copies of expressions,
+** expression lists, ID lists, and select statements.  The copies can
+** be deleted (by being passed to their respective ...Delete() routines)
+** without effecting the originals.
+**
+** The expression list, ID, and source lists return by sqlite3ExprListDup(),
+** sqlite3IdListDup(), and sqlite3SrcListDup() can not be further expanded 
+** by subsequent calls to sqlite*ListAppend() routines.
+**
+** Any tables that the SrcList might point to are not duplicated.
+**
+** The flags parameter contains a combination of the EXPRDUP_XXX flags.
+** If the EXPRDUP_REDUCE flag is set, then the structure returned is a
+** truncated version of the usual Expr structure that will be stored as
+** part of the in-memory representation of the database schema.
+*/
+Expr *sqlite3ExprDup(sqlite3 *db, Expr *p, int flags){
+  return exprDup(db, p, flags, 0);
+}
+ExprList *sqlite3ExprListDup(sqlite3 *db, ExprList *p, int flags){
+  ExprList *pNew;
+  struct ExprList_item *pItem, *pOldItem;
+  int i;
+  if( p==0 ) return 0;
+  pNew = sqlite3DbMallocRaw(db, sizeof(*pNew) );
+  if( pNew==0 ) return 0;
+  pNew->iECursor = 0;
+  pNew->nExpr = pNew->nAlloc = p->nExpr;
+  pNew->a = pItem = sqlite3DbMallocRaw(db,  p->nExpr*sizeof(p->a[0]) );
+  if( pItem==0 ){
+    sqlite3DbFree(db, pNew);
+    return 0;
+  } 
+  pOldItem = p->a;
+  for(i=0; i<p->nExpr; i++, pItem++, pOldItem++){
+    Expr *pOldExpr = pOldItem->pExpr;
+    pItem->pExpr = sqlite3ExprDup(db, pOldExpr, flags);
+    pItem->zName = sqlite3DbStrDup(db, pOldItem->zName);
+    pItem->zSpan = sqlite3DbStrDup(db, pOldItem->zSpan);
+    pItem->sortOrder = pOldItem->sortOrder;
+    pItem->done = 0;
+    pItem->iCol = pOldItem->iCol;
+    pItem->iAlias = pOldItem->iAlias;
+  }
+  return pNew;
+}
+
+/*
+** If cursors, triggers, views and subqueries are all omitted from
+** the build, then none of the following routines, except for 
+** sqlite3SelectDup(), can be called. sqlite3SelectDup() is sometimes
+** called with a NULL argument.
+*/
+#if !defined(SQLITE_OMIT_VIEW) || !defined(SQLITE_OMIT_TRIGGER) \
+ || !defined(SQLITE_OMIT_SUBQUERY)
+SrcList *sqlite3SrcListDup(sqlite3 *db, SrcList *p, int flags){
+  SrcList *pNew;
+  int i;
+  int nByte;
+  if( p==0 ) return 0;
+  nByte = sizeof(*p) + (p->nSrc>0 ? sizeof(p->a[0]) * (p->nSrc-1) : 0);
+  pNew = sqlite3DbMallocRaw(db, nByte );
+  if( pNew==0 ) return 0;
+  pNew->nSrc = pNew->nAlloc = p->nSrc;
+  for(i=0; i<p->nSrc; i++){
+    struct SrcList_item *pNewItem = &pNew->a[i];
+    struct SrcList_item *pOldItem = &p->a[i];
+    Table *pTab;
+    pNewItem->zDatabase = sqlite3DbStrDup(db, pOldItem->zDatabase);
+    pNewItem->zName = sqlite3DbStrDup(db, pOldItem->zName);
+    pNewItem->zAlias = sqlite3DbStrDup(db, pOldItem->zAlias);
+    pNewItem->jointype = pOldItem->jointype;
+    pNewItem->iCursor = pOldItem->iCursor;
+    pNewItem->addrFillSub = pOldItem->addrFillSub;
+    pNewItem->regReturn = pOldItem->regReturn;
+    pNewItem->isCorrelated = pOldItem->isCorrelated;
+    pNewItem->zIndex = sqlite3DbStrDup(db, pOldItem->zIndex);
+    pNewItem->notIndexed = pOldItem->notIndexed;
+    pNewItem->pIndex = pOldItem->pIndex;
+    pTab = pNewItem->pTab = pOldItem->pTab;
+    if( pTab ){
+      pTab->nRef++;
+    }
+    pNewItem->pSelect = sqlite3SelectDup(db, pOldItem->pSelect, flags);
+    pNewItem->pOn = sqlite3ExprDup(db, pOldItem->pOn, flags);
+    pNewItem->pUsing = sqlite3IdListDup(db, pOldItem->pUsing);
+    pNewItem->colUsed = pOldItem->colUsed;
+  }
+  return pNew;
+}
+IdList *sqlite3IdListDup(sqlite3 *db, IdList *p){
+  IdList *pNew;
+  int i;
+  if( p==0 ) return 0;
+  pNew = sqlite3DbMallocRaw(db, sizeof(*pNew) );
+  if( pNew==0 ) return 0;
+  pNew->nId = pNew->nAlloc = p->nId;
+  pNew->a = sqlite3DbMallocRaw(db, p->nId*sizeof(p->a[0]) );
+  if( pNew->a==0 ){
+    sqlite3DbFree(db, pNew);
+    return 0;
+  }
+  for(i=0; i<p->nId; i++){
+    struct IdList_item *pNewItem = &pNew->a[i];
+    struct IdList_item *pOldItem = &p->a[i];
+    pNewItem->zName = sqlite3DbStrDup(db, pOldItem->zName);
+    pNewItem->idx = pOldItem->idx;
+  }
+  return pNew;
+}
+Select *sqlite3SelectDup(sqlite3 *db, Select *p, int flags){
+  Select *pNew;
+  if( p==0 ) return 0;
+  pNew = sqlite3DbMallocRaw(db, sizeof(*p) );
+  if( pNew==0 ) return 0;
+  pNew->pEList = sqlite3ExprListDup(db, p->pEList, flags);
+  pNew->pSrc = sqlite3SrcListDup(db, p->pSrc, flags);
+  pNew->pWhere = sqlite3ExprDup(db, p->pWhere, flags);
+  pNew->pGroupBy = sqlite3ExprListDup(db, p->pGroupBy, flags);
+  pNew->pHaving = sqlite3ExprDup(db, p->pHaving, flags);
+  pNew->pOrderBy = sqlite3ExprListDup(db, p->pOrderBy, flags);
+  pNew->op = p->op;
+  pNew->pPrior = sqlite3SelectDup(db, p->pPrior, flags);
+  pNew->pLimit = sqlite3ExprDup(db, p->pLimit, flags);
+  pNew->pOffset = sqlite3ExprDup(db, p->pOffset, flags);
+  pNew->iLimit = 0;
+  pNew->iOffset = 0;
+  pNew->selFlags = p->selFlags & ~SF_UsesEphemeral;
+  pNew->pRightmost = 0;
+  pNew->addrOpenEphm[0] = -1;
+  pNew->addrOpenEphm[1] = -1;
+  pNew->addrOpenEphm[2] = -1;
+  return pNew;
+}
+#else
+Select *sqlite3SelectDup(sqlite3 *db, Select *p, int flags){
+  assert( p==0 );
+  return 0;
+}
+#endif
+
+
+/*
+** Add a new element to the end of an expression list.  If pList is
+** initially NULL, then create a new expression list.
+**
+** If a memory allocation error occurs, the entire list is freed and
+** NULL is returned.  If non-NULL is returned, then it is guaranteed
+** that the new entry was successfully appended.
+*/
+ExprList *sqlite3ExprListAppend(
+  Parse *pParse,          /* Parsing context */
+  ExprList *pList,        /* List to which to append. Might be NULL */
+  Expr *pExpr             /* Expression to be appended. Might be NULL */
+){
+  sqlite3 *db = pParse->db;
+  if( pList==0 ){
+    pList = sqlite3DbMallocZero(db, sizeof(ExprList) );
+    if( pList==0 ){
+      goto no_mem;
+    }
+    assert( pList->nAlloc==0 );
+  }
+  if( pList->nAlloc<=pList->nExpr ){
+    struct ExprList_item *a;
+    int n = pList->nAlloc*2 + 4;
+    a = sqlite3DbRealloc(db, pList->a, n*sizeof(pList->a[0]));
+    if( a==0 ){
+      goto no_mem;
+    }
+    pList->a = a;
+    pList->nAlloc = sqlite3DbMallocSize(db, a)/sizeof(a[0]);
+  }
+  assert( pList->a!=0 );
+  if( 1 ){
+    struct ExprList_item *pItem = &pList->a[pList->nExpr++];
+    memset(pItem, 0, sizeof(*pItem));
+    pItem->pExpr = pExpr;
+  }
+  return pList;
+
+no_mem:     
+  /* Avoid leaking memory if malloc has failed. */
+  sqlite3ExprDelete(db, pExpr);
+  sqlite3ExprListDelete(db, pList);
+  return 0;
+}
+
+/*
+** Set the ExprList.a[].zName element of the most recently added item
+** on the expression list.
+**
+** pList might be NULL following an OOM error.  But pName should never be
+** NULL.  If a memory allocation fails, the pParse->db->mallocFailed flag
+** is set.
+*/
+void sqlite3ExprListSetName(
+  Parse *pParse,          /* Parsing context */
+  ExprList *pList,        /* List to which to add the span. */
+  Token *pName,           /* Name to be added */
+  int dequote             /* True to cause the name to be dequoted */
+){
+  assert( pList!=0 || pParse->db->mallocFailed!=0 );
+  if( pList ){
+    struct ExprList_item *pItem;
+    assert( pList->nExpr>0 );
+    pItem = &pList->a[pList->nExpr-1];
+    assert( pItem->zName==0 );
+    pItem->zName = sqlite3DbStrNDup(pParse->db, pName->z, pName->n);
+    if( dequote && pItem->zName ) sqlite3Dequote(pItem->zName);
+  }
+}
+
+/*
+** Set the ExprList.a[].zSpan element of the most recently added item
+** on the expression list.
+**
+** pList might be NULL following an OOM error.  But pSpan should never be
+** NULL.  If a memory allocation fails, the pParse->db->mallocFailed flag
+** is set.
+*/
+void sqlite3ExprListSetSpan(
+  Parse *pParse,          /* Parsing context */
+  ExprList *pList,        /* List to which to add the span. */
+  ExprSpan *pSpan         /* The span to be added */
+){
+  sqlite3 *db = pParse->db;
+  assert( pList!=0 || db->mallocFailed!=0 );
+  if( pList ){
+    struct ExprList_item *pItem = &pList->a[pList->nExpr-1];
+    assert( pList->nExpr>0 );
+    assert( db->mallocFailed || pItem->pExpr==pSpan->pExpr );
+    sqlite3DbFree(db, pItem->zSpan);
+    pItem->zSpan = sqlite3DbStrNDup(db, (char*)pSpan->zStart,
+                                    (int)(pSpan->zEnd - pSpan->zStart));
+  }
+}
+
+/*
+** If the expression list pEList contains more than iLimit elements,
+** leave an error message in pParse.
+*/
+void sqlite3ExprListCheckLength(
+  Parse *pParse,
+  ExprList *pEList,
+  const char *zObject
+){
+  int mx = pParse->db->aLimit[SQLITE_LIMIT_COLUMN];
+  testcase( pEList && pEList->nExpr==mx );
+  testcase( pEList && pEList->nExpr==mx+1 );
+  if( pEList && pEList->nExpr>mx ){
+    sqlite3ErrorMsg(pParse, "too many columns in %s", zObject);
+  }
+}
+
+/*
+** Delete an entire expression list.
+*/
+void sqlite3ExprListDelete(sqlite3 *db, ExprList *pList){
+  int i;
+  struct ExprList_item *pItem;
+  if( pList==0 ) return;
+  assert( pList->a!=0 || (pList->nExpr==0 && pList->nAlloc==0) );
+  assert( pList->nExpr<=pList->nAlloc );
+  for(pItem=pList->a, i=0; i<pList->nExpr; i++, pItem++){
+    sqlite3ExprDelete(db, pItem->pExpr);
+    sqlite3DbFree(db, pItem->zName);
+    sqlite3DbFree(db, pItem->zSpan);
+  }
+  sqlite3DbFree(db, pList->a);
+  sqlite3DbFree(db, pList);
+}
+
+/*
+** These routines are Walker callbacks.  Walker.u.pi is a pointer
+** to an integer.  These routines are checking an expression to see
+** if it is a constant.  Set *Walker.u.pi to 0 if the expression is
+** not constant.
+**
+** These callback routines are used to implement the following:
+**
+**     sqlite3ExprIsConstant()
+**     sqlite3ExprIsConstantNotJoin()
+**     sqlite3ExprIsConstantOrFunction()
+**
+*/
+static int exprNodeIsConstant(Walker *pWalker, Expr *pExpr){
+
+  /* If pWalker->u.i is 3 then any term of the expression that comes from
+  ** the ON or USING clauses of a join disqualifies the expression
+  ** from being considered constant. */
+  if( pWalker->u.i==3 && ExprHasAnyProperty(pExpr, EP_FromJoin) ){
+    pWalker->u.i = 0;
+    return WRC_Abort;
+  }
+
+  switch( pExpr->op ){
+    /* Consider functions to be constant if all their arguments are constant
+    ** and pWalker->u.i==2 */
+    case TK_FUNCTION:
+      if( pWalker->u.i==2 ) return 0;
+      /* Fall through */
+    case TK_ID:
+    case TK_COLUMN:
+    case TK_AGG_FUNCTION:
+    case TK_AGG_COLUMN:
+      testcase( pExpr->op==TK_ID );
+      testcase( pExpr->op==TK_COLUMN );
+      testcase( pExpr->op==TK_AGG_FUNCTION );
+      testcase( pExpr->op==TK_AGG_COLUMN );
+      pWalker->u.i = 0;
+      return WRC_Abort;
+    default:
+      testcase( pExpr->op==TK_SELECT ); /* selectNodeIsConstant will disallow */
+      testcase( pExpr->op==TK_EXISTS ); /* selectNodeIsConstant will disallow */
+      return WRC_Continue;
+  }
+}
+static int selectNodeIsConstant(Walker *pWalker, Select *NotUsed){
+  UNUSED_PARAMETER(NotUsed);
+  pWalker->u.i = 0;
+  return WRC_Abort;
+}
+static int exprIsConst(Expr *p, int initFlag){
+  Walker w;
+  w.u.i = initFlag;
+  w.xExprCallback = exprNodeIsConstant;
+  w.xSelectCallback = selectNodeIsConstant;
+  sqlite3WalkExpr(&w, p);
+  return w.u.i;
+}
+
+/*
+** Walk an expression tree.  Return 1 if the expression is constant
+** and 0 if it involves variables or function calls.
+**
+** For the purposes of this function, a double-quoted string (ex: "abc")
+** is considered a variable but a single-quoted string (ex: 'abc') is
+** a constant.
+*/
+int sqlite3ExprIsConstant(Expr *p){
+  return exprIsConst(p, 1);
+}
+
+/*
+** Walk an expression tree.  Return 1 if the expression is constant
+** that does no originate from the ON or USING clauses of a join.
+** Return 0 if it involves variables or function calls or terms from
+** an ON or USING clause.
+*/
+int sqlite3ExprIsConstantNotJoin(Expr *p){
+  return exprIsConst(p, 3);
+}
+
+/*
+** Walk an expression tree.  Return 1 if the expression is constant
+** or a function call with constant arguments.  Return and 0 if there
+** are any variables.
+**
+** For the purposes of this function, a double-quoted string (ex: "abc")
+** is considered a variable but a single-quoted string (ex: 'abc') is
+** a constant.
+*/
+int sqlite3ExprIsConstantOrFunction(Expr *p){
+  return exprIsConst(p, 2);
+}
+
+/*
+** If the expression p codes a constant integer that is small enough
+** to fit in a 32-bit integer, return 1 and put the value of the integer
+** in *pValue.  If the expression is not an integer or if it is too big
+** to fit in a signed 32-bit integer, return 0 and leave *pValue unchanged.
+*/
+int sqlite3ExprIsInteger(Expr *p, int *pValue){
+  int rc = 0;
+
+  /* If an expression is an integer literal that fits in a signed 32-bit
+  ** integer, then the EP_IntValue flag will have already been set */
+  assert( p->op!=TK_INTEGER || (p->flags & EP_IntValue)!=0
+           || sqlite3GetInt32(p->u.zToken, &rc)==0 );
+
+  if( p->flags & EP_IntValue ){
+    *pValue = p->u.iValue;
+    return 1;
+  }
+  switch( p->op ){
+    case TK_UPLUS: {
+      rc = sqlite3ExprIsInteger(p->pLeft, pValue);
+      break;
+    }
+    case TK_UMINUS: {
+      int v;
+      if( sqlite3ExprIsInteger(p->pLeft, &v) ){
+        *pValue = -v;
+        rc = 1;
+      }
+      break;
+    }
+    default: break;
+  }
+  return rc;
+}
+
+/*
+** Return FALSE if there is no chance that the expression can be NULL.
+**
+** If the expression might be NULL or if the expression is too complex
+** to tell return TRUE.  
+**
+** This routine is used as an optimization, to skip OP_IsNull opcodes
+** when we know that a value cannot be NULL.  Hence, a false positive
+** (returning TRUE when in fact the expression can never be NULL) might
+** be a small performance hit but is otherwise harmless.  On the other
+** hand, a false negative (returning FALSE when the result could be NULL)
+** will likely result in an incorrect answer.  So when in doubt, return
+** TRUE.
+*/
+int sqlite3ExprCanBeNull(const Expr *p){
+  u8 op;
+  while( p->op==TK_UPLUS || p->op==TK_UMINUS ){ p = p->pLeft; }
+  op = p->op;
+  if( op==TK_REGISTER ) op = p->op2;
+  switch( op ){
+    case TK_INTEGER:
+    case TK_STRING:
+    case TK_FLOAT:
+    case TK_BLOB:
+      return 0;
+    default:
+      return 1;
+  }
+}
+
+/*
+** Generate an OP_IsNull instruction that tests register iReg and jumps
+** to location iDest if the value in iReg is NULL.  The value in iReg 
+** was computed by pExpr.  If we can look at pExpr at compile-time and
+** determine that it can never generate a NULL, then the OP_IsNull operation
+** can be omitted.
+*/
+void sqlite3ExprCodeIsNullJump(
+  Vdbe *v,            /* The VDBE under construction */
+  const Expr *pExpr,  /* Only generate OP_IsNull if this expr can be NULL */
+  int iReg,           /* Test the value in this register for NULL */
+  int iDest           /* Jump here if the value is null */
+){
+  if( sqlite3ExprCanBeNull(pExpr) ){
+    sqlite3VdbeAddOp2(v, OP_IsNull, iReg, iDest);
+  }
+}
+
+/*
+** Return TRUE if the given expression is a constant which would be
+** unchanged by OP_Affinity with the affinity given in the second
+** argument.
+**
+** This routine is used to determine if the OP_Affinity operation
+** can be omitted.  When in doubt return FALSE.  A false negative
+** is harmless.  A false positive, however, can result in the wrong
+** answer.
+*/
+int sqlite3ExprNeedsNoAffinityChange(const Expr *p, char aff){
+  u8 op;
+  if( aff==SQLITE_AFF_NONE ) return 1;
+  while( p->op==TK_UPLUS || p->op==TK_UMINUS ){ p = p->pLeft; }
+  op = p->op;
+  if( op==TK_REGISTER ) op = p->op2;
+  switch( op ){
+    case TK_INTEGER: {
+      return aff==SQLITE_AFF_INTEGER || aff==SQLITE_AFF_NUMERIC;
+    }
+    case TK_FLOAT: {
+      return aff==SQLITE_AFF_REAL || aff==SQLITE_AFF_NUMERIC;
+    }
+    case TK_STRING: {
+      return aff==SQLITE_AFF_TEXT;
+    }
+    case TK_BLOB: {
+      return 1;
+    }
+    case TK_COLUMN: {
+      assert( p->iTable>=0 );  /* p cannot be part of a CHECK constraint */
+      return p->iColumn<0
+          && (aff==SQLITE_AFF_INTEGER || aff==SQLITE_AFF_NUMERIC);
+    }
+    default: {
+      return 0;
+    }
+  }
+}
+
+/*
+** Return TRUE if the given string is a row-id column name.
+*/
+int sqlite3IsRowid(const char *z){
+  if( sqlite3StrICmp(z, "_ROWID_")==0 ) return 1;
+  if( sqlite3StrICmp(z, "ROWID")==0 ) return 1;
+  if( sqlite3StrICmp(z, "OID")==0 ) return 1;
+  return 0;
+}
+
+/*
+** Return true if we are able to the IN operator optimization on a
+** query of the form
+**
+**       x IN (SELECT ...)
+**
+** Where the SELECT... clause is as specified by the parameter to this
+** routine.
+**
+** The Select object passed in has already been preprocessed and no
+** errors have been found.
+*/
+#ifndef SQLITE_OMIT_SUBQUERY
+static int isCandidateForInOpt(Select *p){
+  SrcList *pSrc;
+  ExprList *pEList;
+  Table *pTab;
+  if( p==0 ) return 0;                   /* right-hand side of IN is SELECT */
+  if( p->pPrior ) return 0;              /* Not a compound SELECT */
+  if( p->selFlags & (SF_Distinct|SF_Aggregate) ){
+    testcase( (p->selFlags & (SF_Distinct|SF_Aggregate))==SF_Distinct );
+    testcase( (p->selFlags & (SF_Distinct|SF_Aggregate))==SF_Aggregate );
+    return 0; /* No DISTINCT keyword and no aggregate functions */
+  }
+  assert( p->pGroupBy==0 );              /* Has no GROUP BY clause */
+  if( p->pLimit ) return 0;              /* Has no LIMIT clause */
+  assert( p->pOffset==0 );               /* No LIMIT means no OFFSET */
+  if( p->pWhere ) return 0;              /* Has no WHERE clause */
+  pSrc = p->pSrc;
+  assert( pSrc!=0 );
+  if( pSrc->nSrc!=1 ) return 0;          /* Single term in FROM clause */
+  if( pSrc->a[0].pSelect ) return 0;     /* FROM is not a subquery or view */
+  pTab = pSrc->a[0].pTab;
+  if( NEVER(pTab==0) ) return 0;
+  assert( pTab->pSelect==0 );            /* FROM clause is not a view */
+  if( IsVirtual(pTab) ) return 0;        /* FROM clause not a virtual table */
+  pEList = p->pEList;
+  if( pEList->nExpr!=1 ) return 0;       /* One column in the result set */
+  if( pEList->a[0].pExpr->op!=TK_COLUMN ) return 0; /* Result is a column */
+  return 1;
+}
+#endif /* SQLITE_OMIT_SUBQUERY */
+
+/*
+** This function is used by the implementation of the IN (...) operator.
+** It's job is to find or create a b-tree structure that may be used
+** either to test for membership of the (...) set or to iterate through
+** its members, skipping duplicates.
+**
+** The index of the cursor opened on the b-tree (database table, database index 
+** or ephermal table) is stored in pX->iTable before this function returns.
+** The returned value of this function indicates the b-tree type, as follows:
+**
+**   IN_INDEX_ROWID - The cursor was opened on a database table.
+**   IN_INDEX_INDEX - The cursor was opened on a database index.
+**   IN_INDEX_EPH -   The cursor was opened on a specially created and
+**                    populated epheremal table.
+**
+** An existing b-tree may only be used if the SELECT is of the simple
+** form:
+**
+**     SELECT <column> FROM <table>
+**
+** If the prNotFound parameter is 0, then the b-tree will be used to iterate
+** through the set members, skipping any duplicates. In this case an
+** epheremal table must be used unless the selected <column> is guaranteed
+** to be unique - either because it is an INTEGER PRIMARY KEY or it
+** has a UNIQUE constraint or UNIQUE index.
+**
+** If the prNotFound parameter is not 0, then the b-tree will be used 
+** for fast set membership tests. In this case an epheremal table must 
+** be used unless <column> is an INTEGER PRIMARY KEY or an index can 
+** be found with <column> as its left-most column.
+**
+** When the b-tree is being used for membership tests, the calling function
+** needs to know whether or not the structure contains an SQL NULL 
+** value in order to correctly evaluate expressions like "X IN (Y, Z)".
+** If there is any chance that the (...) might contain a NULL value at
+** runtime, then a register is allocated and the register number written
+** to *prNotFound. If there is no chance that the (...) contains a
+** NULL value, then *prNotFound is left unchanged.
+**
+** If a register is allocated and its location stored in *prNotFound, then
+** its initial value is NULL.  If the (...) does not remain constant
+** for the duration of the query (i.e. the SELECT within the (...)
+** is a correlated subquery) then the value of the allocated register is
+** reset to NULL each time the subquery is rerun. This allows the
+** caller to use vdbe code equivalent to the following:
+**
+**   if( register==NULL ){
+**     has_null = <test if data structure contains null>
+**     register = 1
+**   }
+**
+** in order to avoid running the <test if data structure contains null>
+** test more often than is necessary.
+*/
+#ifndef SQLITE_OMIT_SUBQUERY
+int sqlite3FindInIndex(Parse *pParse, Expr *pX, int *prNotFound){
+  Select *p;                            /* SELECT to the right of IN operator */
+  int eType = 0;                        /* Type of RHS table. IN_INDEX_* */
+  int iTab = pParse->nTab++;            /* Cursor of the RHS table */
+  int mustBeUnique = (prNotFound==0);   /* True if RHS must be unique */
+
+  assert( pX->op==TK_IN );
+
+  /* Check to see if an existing table or index can be used to
+  ** satisfy the query.  This is preferable to generating a new 
+  ** ephemeral table.
+  */
+  p = (ExprHasProperty(pX, EP_xIsSelect) ? pX->x.pSelect : 0);
+  if( ALWAYS(pParse->nErr==0) && isCandidateForInOpt(p) ){
+    sqlite3 *db = pParse->db;              /* Database connection */
+    Vdbe *v = sqlite3GetVdbe(pParse);      /* Virtual machine being coded */
+    Table *pTab;                           /* Table <table>. */
+    Expr *pExpr;                           /* Expression <column> */
+    int iCol;                              /* Index of column <column> */
+    int iDb;                               /* Database idx for pTab */
+
+    assert( p );                        /* Because of isCandidateForInOpt(p) */
+    assert( p->pEList!=0 );             /* Because of isCandidateForInOpt(p) */
+    assert( p->pEList->a[0].pExpr!=0 ); /* Because of isCandidateForInOpt(p) */
+    assert( p->pSrc!=0 );               /* Because of isCandidateForInOpt(p) */
+    pTab = p->pSrc->a[0].pTab;
+    pExpr = p->pEList->a[0].pExpr;
+    iCol = pExpr->iColumn;
+   
+    /* Code an OP_VerifyCookie and OP_TableLock for <table>. */
+    iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+    sqlite3CodeVerifySchema(pParse, iDb);
+    sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);
+
+    /* This function is only called from two places. In both cases the vdbe
+    ** has already been allocated. So assume sqlite3GetVdbe() is always
+    ** successful here.
+    */
+    assert(v);
+    if( iCol<0 ){
+      int iMem = ++pParse->nMem;
+      int iAddr;
+
+      iAddr = sqlite3VdbeAddOp1(v, OP_Once, iMem);
+
+      sqlite3OpenTable(pParse, iTab, iDb, pTab, OP_OpenRead);
+      eType = IN_INDEX_ROWID;
+
+      sqlite3VdbeJumpHere(v, iAddr);
+    }else{
+      Index *pIdx;                         /* Iterator variable */
+
+      /* The collation sequence used by the comparison. If an index is to
+      ** be used in place of a temp-table, it must be ordered according
+      ** to this collation sequence.  */
+      CollSeq *pReq = sqlite3BinaryCompareCollSeq(pParse, pX->pLeft, pExpr);
+
+      /* Check that the affinity that will be used to perform the 
+      ** comparison is the same as the affinity of the column. If
+      ** it is not, it is not possible to use any index.
+      */
+      char aff = comparisonAffinity(pX);
+      int affinity_ok = (pTab->aCol[iCol].affinity==aff||aff==SQLITE_AFF_NONE);
+
+      for(pIdx=pTab->pIndex; pIdx && eType==0 && affinity_ok; pIdx=pIdx->pNext){
+        if( (pIdx->aiColumn[0]==iCol)
+         && sqlite3FindCollSeq(db, ENC(db), pIdx->azColl[0], 0)==pReq
+         && (!mustBeUnique || (pIdx->nColumn==1 && pIdx->onError!=OE_None))
+        ){
+          int iMem = ++pParse->nMem;
+          int iAddr;
+          char *pKey;
+  
+          pKey = (char *)sqlite3IndexKeyinfo(pParse, pIdx);
+          iAddr = sqlite3VdbeAddOp1(v, OP_Once, iMem);
+  
+          sqlite3VdbeAddOp4(v, OP_OpenRead, iTab, pIdx->tnum, iDb,
+                               pKey,P4_KEYINFO_HANDOFF);
+          VdbeComment((v, "%s", pIdx->zName));
+          eType = IN_INDEX_INDEX;
+
+          sqlite3VdbeJumpHere(v, iAddr);
+          if( prNotFound && !pTab->aCol[iCol].notNull ){
+            *prNotFound = ++pParse->nMem;
+          }
+        }
+      }
+    }
+  }
+
+  if( eType==0 ){
+    /* Could not found an existing table or index to use as the RHS b-tree.
+    ** We will have to generate an ephemeral table to do the job.
+    */
+    double savedNQueryLoop = pParse->nQueryLoop;
+    int rMayHaveNull = 0;
+    eType = IN_INDEX_EPH;
+    if( prNotFound ){
+      *prNotFound = rMayHaveNull = ++pParse->nMem;
+    }else{
+      testcase( pParse->nQueryLoop>(double)1 );
+      pParse->nQueryLoop = (double)1;
+      if( pX->pLeft->iColumn<0 && !ExprHasAnyProperty(pX, EP_xIsSelect) ){
+        eType = IN_INDEX_ROWID;
+      }
+    }
+    sqlite3CodeSubselect(pParse, pX, rMayHaveNull, eType==IN_INDEX_ROWID);
+    pParse->nQueryLoop = savedNQueryLoop;
+  }else{
+    pX->iTable = iTab;
+  }
+  return eType;
+}
+#endif
+
+/*
+** Generate code for scalar subqueries used as a subquery expression, EXISTS,
+** or IN operators.  Examples:
+**
+**     (SELECT a FROM b)          -- subquery
+**     EXISTS (SELECT a FROM b)   -- EXISTS subquery
+**     x IN (4,5,11)              -- IN operator with list on right-hand side
+**     x IN (SELECT a FROM b)     -- IN operator with subquery on the right
+**
+** The pExpr parameter describes the expression that contains the IN
+** operator or subquery.
+**
+** If parameter isRowid is non-zero, then expression pExpr is guaranteed
+** to be of the form "<rowid> IN (?, ?, ?)", where <rowid> is a reference
+** to some integer key column of a table B-Tree. In this case, use an
+** intkey B-Tree to store the set of IN(...) values instead of the usual
+** (slower) variable length keys B-Tree.
+**
+** If rMayHaveNull is non-zero, that means that the operation is an IN
+** (not a SELECT or EXISTS) and that the RHS might contains NULLs.
+** Furthermore, the IN is in a WHERE clause and that we really want
+** to iterate over the RHS of the IN operator in order to quickly locate
+** all corresponding LHS elements.  All this routine does is initialize
+** the register given by rMayHaveNull to NULL.  Calling routines will take
+** care of changing this register value to non-NULL if the RHS is NULL-free.
+**
+** If rMayHaveNull is zero, that means that the subquery is being used
+** for membership testing only.  There is no need to initialize any
+** registers to indicate the presense or absence of NULLs on the RHS.
+**
+** For a SELECT or EXISTS operator, return the register that holds the
+** result.  For IN operators or if an error occurs, the return value is 0.
+*/
+#ifndef SQLITE_OMIT_SUBQUERY
+int sqlite3CodeSubselect(
+  Parse *pParse,          /* Parsing context */
+  Expr *pExpr,            /* The IN, SELECT, or EXISTS operator */
+  int rMayHaveNull,       /* Register that records whether NULLs exist in RHS */
+  int isRowid             /* If true, LHS of IN operator is a rowid */
+){
+  int testAddr = -1;                      /* One-time test address */
+  int rReg = 0;                           /* Register storing resulting */
+  Vdbe *v = sqlite3GetVdbe(pParse);
+  if( NEVER(v==0) ) return 0;
+  sqlite3ExprCachePush(pParse);
+
+  /* This code must be run in its entirety every time it is encountered
+  ** if any of the following is true:
+  **
+  **    *  The right-hand side is a correlated subquery
+  **    *  The right-hand side is an expression list containing variables
+  **    *  We are inside a trigger
+  **
+  ** If all of the above are false, then we can run this code just once
+  ** save the results, and reuse the same result on subsequent invocations.
+  */
+  if( !ExprHasAnyProperty(pExpr, EP_VarSelect) && !pParse->pTriggerTab ){
+    int mem = ++pParse->nMem;
+    testAddr = sqlite3VdbeAddOp1(v, OP_Once, mem);
+  }
+
+#ifndef SQLITE_OMIT_EXPLAIN
+  if( pParse->explain==2 ){
+    char *zMsg = sqlite3MPrintf(
+        pParse->db, "EXECUTE %s%s SUBQUERY %d", testAddr>=0?"":"CORRELATED ",
+        pExpr->op==TK_IN?"LIST":"SCALAR", pParse->iNextSelectId
+    );
+    sqlite3VdbeAddOp4(v, OP_Explain, pParse->iSelectId, 0, 0, zMsg, P4_DYNAMIC);
+  }
+#endif
+
+  switch( pExpr->op ){
+    case TK_IN: {
+      char affinity;              /* Affinity of the LHS of the IN */
+      KeyInfo keyInfo;            /* Keyinfo for the generated table */
+      int addr;                   /* Address of OP_OpenEphemeral instruction */
+      Expr *pLeft = pExpr->pLeft; /* the LHS of the IN operator */
+
+      if( rMayHaveNull ){
+        sqlite3VdbeAddOp2(v, OP_Null, 0, rMayHaveNull);
+      }
+
+      affinity = sqlite3ExprAffinity(pLeft);
+
+      /* Whether this is an 'x IN(SELECT...)' or an 'x IN(<exprlist>)'
+      ** expression it is handled the same way.  An ephemeral table is 
+      ** filled with single-field index keys representing the results
+      ** from the SELECT or the <exprlist>.
+      **
+      ** If the 'x' expression is a column value, or the SELECT...
+      ** statement returns a column value, then the affinity of that
+      ** column is used to build the index keys. If both 'x' and the
+      ** SELECT... statement are columns, then numeric affinity is used
+      ** if either column has NUMERIC or INTEGER affinity. If neither
+      ** 'x' nor the SELECT... statement are columns, then numeric affinity
+      ** is used.
+      */
+      pExpr->iTable = pParse->nTab++;
+      addr = sqlite3VdbeAddOp2(v, OP_OpenEphemeral, pExpr->iTable, !isRowid);
+      if( rMayHaveNull==0 ) sqlite3VdbeChangeP5(v, BTREE_UNORDERED);
+      memset(&keyInfo, 0, sizeof(keyInfo));
+      keyInfo.nField = 1;
+
+      if( ExprHasProperty(pExpr, EP_xIsSelect) ){
+        /* Case 1:     expr IN (SELECT ...)
+        **
+        ** Generate code to write the results of the select into the temporary
+        ** table allocated and opened above.
+        */
+        SelectDest dest;
+        ExprList *pEList;
+
+        assert( !isRowid );
+        sqlite3SelectDestInit(&dest, SRT_Set, pExpr->iTable);
+        dest.affinity = (u8)affinity;
+        assert( (pExpr->iTable&0x0000FFFF)==pExpr->iTable );
+        pExpr->x.pSelect->iLimit = 0;
+        if( sqlite3Select(pParse, pExpr->x.pSelect, &dest) ){
+          return 0;
+        }
+        pEList = pExpr->x.pSelect->pEList;
+        if( ALWAYS(pEList!=0 && pEList->nExpr>0) ){ 
+          keyInfo.aColl[0] = sqlite3BinaryCompareCollSeq(pParse, pExpr->pLeft,
+              pEList->a[0].pExpr);
+        }
+      }else if( ALWAYS(pExpr->x.pList!=0) ){
+        /* Case 2:     expr IN (exprlist)
+        **
+        ** For each expression, build an index key from the evaluation and
+        ** store it in the temporary table. If <expr> is a column, then use
+        ** that columns affinity when building index keys. If <expr> is not
+        ** a column, use numeric affinity.
+        */
+        int i;
+        ExprList *pList = pExpr->x.pList;
+        struct ExprList_item *pItem;
+        int r1, r2, r3;
+
+        if( !affinity ){
+          affinity = SQLITE_AFF_NONE;
+        }
+        keyInfo.aColl[0] = sqlite3ExprCollSeq(pParse, pExpr->pLeft);
+
+        /* Loop through each expression in <exprlist>. */
+        r1 = sqlite3GetTempReg(pParse);
+        r2 = sqlite3GetTempReg(pParse);
+        sqlite3VdbeAddOp2(v, OP_Null, 0, r2);
+        for(i=pList->nExpr, pItem=pList->a; i>0; i--, pItem++){
+          Expr *pE2 = pItem->pExpr;
+          int iValToIns;
+
+          /* If the expression is not constant then we will need to
+          ** disable the test that was generated above that makes sure
+          ** this code only executes once.  Because for a non-constant
+          ** expression we need to rerun this code each time.
+          */
+          if( testAddr>=0 && !sqlite3ExprIsConstant(pE2) ){
+            sqlite3VdbeChangeToNoop(v, testAddr);
+            testAddr = -1;
+          }
+
+          /* Evaluate the expression and insert it into the temp table */
+          if( isRowid && sqlite3ExprIsInteger(pE2, &iValToIns) ){
+            sqlite3VdbeAddOp3(v, OP_InsertInt, pExpr->iTable, r2, iValToIns);
+          }else{
+            r3 = sqlite3ExprCodeTarget(pParse, pE2, r1);
+            if( isRowid ){
+              sqlite3VdbeAddOp2(v, OP_MustBeInt, r3,
+                                sqlite3VdbeCurrentAddr(v)+2);
+              sqlite3VdbeAddOp3(v, OP_Insert, pExpr->iTable, r2, r3);
+            }else{
+              sqlite3VdbeAddOp4(v, OP_MakeRecord, r3, 1, r2, &affinity, 1);
+              sqlite3ExprCacheAffinityChange(pParse, r3, 1);
+              sqlite3VdbeAddOp2(v, OP_IdxInsert, pExpr->iTable, r2);
+            }
+          }
+        }
+        sqlite3ReleaseTempReg(pParse, r1);
+        sqlite3ReleaseTempReg(pParse, r2);
+      }
+      if( !isRowid ){
+        sqlite3VdbeChangeP4(v, addr, (void *)&keyInfo, P4_KEYINFO);
+      }
+      break;
+    }
+
+    case TK_EXISTS:
+    case TK_SELECT:
+    default: {
+      /* If this has to be a scalar SELECT.  Generate code to put the
+      ** value of this select in a memory cell and record the number
+      ** of the memory cell in iColumn.  If this is an EXISTS, write
+      ** an integer 0 (not exists) or 1 (exists) into a memory cell
+      ** and record that memory cell in iColumn.
+      */
+      Select *pSel;                         /* SELECT statement to encode */
+      SelectDest dest;                      /* How to deal with SELECt result */
+
+      testcase( pExpr->op==TK_EXISTS );
+      testcase( pExpr->op==TK_SELECT );
+      assert( pExpr->op==TK_EXISTS || pExpr->op==TK_SELECT );
+
+      assert( ExprHasProperty(pExpr, EP_xIsSelect) );
+      pSel = pExpr->x.pSelect;
+      sqlite3SelectDestInit(&dest, 0, ++pParse->nMem);
+      if( pExpr->op==TK_SELECT ){
+        dest.eDest = SRT_Mem;
+        sqlite3VdbeAddOp2(v, OP_Null, 0, dest.iParm);
+        VdbeComment((v, "Init subquery result"));
+      }else{
+        dest.eDest = SRT_Exists;
+        sqlite3VdbeAddOp2(v, OP_Integer, 0, dest.iParm);
+        VdbeComment((v, "Init EXISTS result"));
+      }
+      sqlite3ExprDelete(pParse->db, pSel->pLimit);
+      pSel->pLimit = sqlite3PExpr(pParse, TK_INTEGER, 0, 0,
+                                  &sqlite3IntTokens[1]);
+      pSel->iLimit = 0;
+      if( sqlite3Select(pParse, pSel, &dest) ){
+        return 0;
+      }
+      rReg = dest.iParm;
+      ExprSetIrreducible(pExpr);
+      break;
+    }
+  }
+
+  if( testAddr>=0 ){
+    sqlite3VdbeJumpHere(v, testAddr);
+  }
+  sqlite3ExprCachePop(pParse, 1);
+
+  return rReg;
+}
+#endif /* SQLITE_OMIT_SUBQUERY */
+
+#ifndef SQLITE_OMIT_SUBQUERY
+/*
+** Generate code for an IN expression.
+**
+**      x IN (SELECT ...)
+**      x IN (value, value, ...)
+**
+** The left-hand side (LHS) is a scalar expression.  The right-hand side (RHS)
+** is an array of zero or more values.  The expression is true if the LHS is
+** contained within the RHS.  The value of the expression is unknown (NULL)
+** if the LHS is NULL or if the LHS is not contained within the RHS and the
+** RHS contains one or more NULL values.
+**
+** This routine generates code will jump to destIfFalse if the LHS is not 
+** contained within the RHS.  If due to NULLs we cannot determine if the LHS
+** is contained in the RHS then jump to destIfNull.  If the LHS is contained
+** within the RHS then fall through.
+*/
+static void sqlite3ExprCodeIN(
+  Parse *pParse,        /* Parsing and code generating context */
+  Expr *pExpr,          /* The IN expression */
+  int destIfFalse,      /* Jump here if LHS is not contained in the RHS */
+  int destIfNull        /* Jump here if the results are unknown due to NULLs */
+){
+  int rRhsHasNull = 0;  /* Register that is true if RHS contains NULL values */
+  char affinity;        /* Comparison affinity to use */
+  int eType;            /* Type of the RHS */
+  int r1;               /* Temporary use register */
+  Vdbe *v;              /* Statement under construction */
+
+  /* Compute the RHS.   After this step, the table with cursor
+  ** pExpr->iTable will contains the values that make up the RHS.
+  */
+  v = pParse->pVdbe;
+  assert( v!=0 );       /* OOM detected prior to this routine */
+  VdbeNoopComment((v, "begin IN expr"));
+  eType = sqlite3FindInIndex(pParse, pExpr, &rRhsHasNull);
+
+  /* Figure out the affinity to use to create a key from the results
+  ** of the expression. affinityStr stores a static string suitable for
+  ** P4 of OP_MakeRecord.
+  */
+  affinity = comparisonAffinity(pExpr);
+
+  /* Code the LHS, the <expr> from "<expr> IN (...)".
+  */
+  sqlite3ExprCachePush(pParse);
+  r1 = sqlite3GetTempReg(pParse);
+  sqlite3ExprCode(pParse, pExpr->pLeft, r1);
+
+  /* If the LHS is NULL, then the result is either false or NULL depending
+  ** on whether the RHS is empty or not, respectively.
+  */
+  if( destIfNull==destIfFalse ){
+    /* Shortcut for the common case where the false and NULL outcomes are
+    ** the same. */
+    sqlite3VdbeAddOp2(v, OP_IsNull, r1, destIfNull);
+  }else{
+    int addr1 = sqlite3VdbeAddOp1(v, OP_NotNull, r1);
+    sqlite3VdbeAddOp2(v, OP_Rewind, pExpr->iTable, destIfFalse);
+    sqlite3VdbeAddOp2(v, OP_Goto, 0, destIfNull);
+    sqlite3VdbeJumpHere(v, addr1);
+  }
+
+  if( eType==IN_INDEX_ROWID ){
+    /* In this case, the RHS is the ROWID of table b-tree
+    */
+    sqlite3VdbeAddOp2(v, OP_MustBeInt, r1, destIfFalse);
+    sqlite3VdbeAddOp3(v, OP_NotExists, pExpr->iTable, destIfFalse, r1);
+  }else{
+    /* In this case, the RHS is an index b-tree.
+    */
+    sqlite3VdbeAddOp4(v, OP_Affinity, r1, 1, 0, &affinity, 1);
+
+    /* If the set membership test fails, then the result of the 
+    ** "x IN (...)" expression must be either 0 or NULL. If the set
+    ** contains no NULL values, then the result is 0. If the set 
+    ** contains one or more NULL values, then the result of the
+    ** expression is also NULL.
+    */
+    if( rRhsHasNull==0 || destIfFalse==destIfNull ){
+      /* This branch runs if it is known at compile time that the RHS
+      ** cannot contain NULL values. This happens as the result
+      ** of a "NOT NULL" constraint in the database schema.
+      **
+      ** Also run this branch if NULL is equivalent to FALSE
+      ** for this particular IN operator.
+      */
+      sqlite3VdbeAddOp4Int(v, OP_NotFound, pExpr->iTable, destIfFalse, r1, 1);
+
+    }else{
+      /* In this branch, the RHS of the IN might contain a NULL and
+      ** the presence of a NULL on the RHS makes a difference in the
+      ** outcome.
+      */
+      int j1, j2, j3;
+
+      /* First check to see if the LHS is contained in the RHS.  If so,
+      ** then the presence of NULLs in the RHS does not matter, so jump
+      ** over all of the code that follows.
+      */
+      j1 = sqlite3VdbeAddOp4Int(v, OP_Found, pExpr->iTable, 0, r1, 1);
+
+      /* Here we begin generating code that runs if the LHS is not
+      ** contained within the RHS.  Generate additional code that
+      ** tests the RHS for NULLs.  If the RHS contains a NULL then
+      ** jump to destIfNull.  If there are no NULLs in the RHS then
+      ** jump to destIfFalse.
+      */
+      j2 = sqlite3VdbeAddOp1(v, OP_NotNull, rRhsHasNull);
+      j3 = sqlite3VdbeAddOp4Int(v, OP_Found, pExpr->iTable, 0, rRhsHasNull, 1);
+      sqlite3VdbeAddOp2(v, OP_Integer, -1, rRhsHasNull);
+      sqlite3VdbeJumpHere(v, j3);
+      sqlite3VdbeAddOp2(v, OP_AddImm, rRhsHasNull, 1);
+      sqlite3VdbeJumpHere(v, j2);
+
+      /* Jump to the appropriate target depending on whether or not
+      ** the RHS contains a NULL
+      */
+      sqlite3VdbeAddOp2(v, OP_If, rRhsHasNull, destIfNull);
+      sqlite3VdbeAddOp2(v, OP_Goto, 0, destIfFalse);
+
+      /* The OP_Found at the top of this branch jumps here when true, 
+      ** causing the overall IN expression evaluation to fall through.
+      */
+      sqlite3VdbeJumpHere(v, j1);
+    }
+  }
+  sqlite3ReleaseTempReg(pParse, r1);
+  sqlite3ExprCachePop(pParse, 1);
+  VdbeComment((v, "end IN expr"));
+}
+#endif /* SQLITE_OMIT_SUBQUERY */
+
+/*
+** Duplicate an 8-byte value
+*/
+static char *dup8bytes(Vdbe *v, const char *in){
+  char *out = sqlite3DbMallocRaw(sqlite3VdbeDb(v), 8);
+  if( out ){
+    memcpy(out, in, 8);
+  }
+  return out;
+}
+
+#ifndef SQLITE_OMIT_FLOATING_POINT
+/*
+** Generate an instruction that will put the floating point
+** value described by z[0..n-1] into register iMem.
+**
+** The z[] string will probably not be zero-terminated.  But the 
+** z[n] character is guaranteed to be something that does not look
+** like the continuation of the number.
+*/
+static void codeReal(Vdbe *v, const char *z, int negateFlag, int iMem){
+  if( ALWAYS(z!=0) ){
+    double value;
+    char *zV;
+    sqlite3AtoF(z, &value, sqlite3Strlen30(z), SQLITE_UTF8);
+    assert( !sqlite3IsNaN(value) ); /* The new AtoF never returns NaN */
+    if( negateFlag ) value = -value;
+    zV = dup8bytes(v, (char*)&value);
+    sqlite3VdbeAddOp4(v, OP_Real, 0, iMem, 0, zV, P4_REAL);
+  }
+}
+#endif
+
+
+/*
+** Generate an instruction that will put the integer describe by
+** text z[0..n-1] into register iMem.
+**
+** Expr.u.zToken is always UTF8 and zero-terminated.
+*/
+static void codeInteger(Parse *pParse, Expr *pExpr, int negFlag, int iMem){
+  Vdbe *v = pParse->pVdbe;
+  if( pExpr->flags & EP_IntValue ){
+    int i = pExpr->u.iValue;
+    assert( i>=0 );
+    if( negFlag ) i = -i;
+    sqlite3VdbeAddOp2(v, OP_Integer, i, iMem);
+  }else{
+    int c;
+    i64 value;
+    const char *z = pExpr->u.zToken;
+    assert( z!=0 );
+    c = sqlite3Atoi64(z, &value, sqlite3Strlen30(z), SQLITE_UTF8);
+    if( c==0 || (c==2 && negFlag) ){
+      char *zV;
+      if( negFlag ){ value = c==2 ? SMALLEST_INT64 : -value; }
+      zV = dup8bytes(v, (char*)&value);
+      sqlite3VdbeAddOp4(v, OP_Int64, 0, iMem, 0, zV, P4_INT64);
+    }else{
+#ifdef SQLITE_OMIT_FLOATING_POINT
+      sqlite3ErrorMsg(pParse, "oversized integer: %s%s", negFlag ? "-" : "", z);
+#else
+      codeReal(v, z, negFlag, iMem);
+#endif
+    }
+  }
+}
+
+/*
+** Clear a cache entry.
+*/
+static void cacheEntryClear(Parse *pParse, struct yColCache *p){
+  if( p->tempReg ){
+    if( pParse->nTempReg<ArraySize(pParse->aTempReg) ){
+      pParse->aTempReg[pParse->nTempReg++] = p->iReg;
+    }
+    p->tempReg = 0;
+  }
+}
+
+
+/*
+** Record in the column cache that a particular column from a
+** particular table is stored in a particular register.
+*/
+void sqlite3ExprCacheStore(Parse *pParse, int iTab, int iCol, int iReg){
+  int i;
+  int minLru;
+  int idxLru;
+  struct yColCache *p;
+
+  assert( iReg>0 );  /* Register numbers are always positive */
+  assert( iCol>=-1 && iCol<32768 );  /* Finite column numbers */
+
+  /* The SQLITE_ColumnCache flag disables the column cache.  This is used
+  ** for testing only - to verify that SQLite always gets the same answer
+  ** with and without the column cache.
+  */
+  if( pParse->db->flags & SQLITE_ColumnCache ) return;
+
+  /* First replace any existing entry.
+  **
+  ** Actually, the way the column cache is currently used, we are guaranteed
+  ** that the object will never already be in cache.  Verify this guarantee.
+  */
+#ifndef NDEBUG
+  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
+#if 0 /* This code wold remove the entry from the cache if it existed */
+    if( p->iReg && p->iTable==iTab && p->iColumn==iCol ){
+      cacheEntryClear(pParse, p);
+      p->iLevel = pParse->iCacheLevel;
+      p->iReg = iReg;
+      p->lru = pParse->iCacheCnt++;
+      return;
+    }
+#endif
+    assert( p->iReg==0 || p->iTable!=iTab || p->iColumn!=iCol );
+  }
+#endif
+
+  /* Find an empty slot and replace it */
+  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
+    if( p->iReg==0 ){
+      p->iLevel = pParse->iCacheLevel;
+      p->iTable = iTab;
+      p->iColumn = iCol;
+      p->iReg = iReg;
+      p->tempReg = 0;
+      p->lru = pParse->iCacheCnt++;
+      return;
+    }
+  }
+
+  /* Replace the last recently used */
+  minLru = 0x7fffffff;
+  idxLru = -1;
+  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
+    if( p->lru<minLru ){
+      idxLru = i;
+      minLru = p->lru;
+    }
+  }
+  if( ALWAYS(idxLru>=0) ){
+    p = &pParse->aColCache[idxLru];
+    p->iLevel = pParse->iCacheLevel;
+    p->iTable = iTab;
+    p->iColumn = iCol;
+    p->iReg = iReg;
+    p->tempReg = 0;
+    p->lru = pParse->iCacheCnt++;
+    return;
+  }
+}
+
+/*
+** Indicate that registers between iReg..iReg+nReg-1 are being overwritten.
+** Purge the range of registers from the column cache.
+*/
+void sqlite3ExprCacheRemove(Parse *pParse, int iReg, int nReg){
+  int i;
+  int iLast = iReg + nReg - 1;
+  struct yColCache *p;
+  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
+    int r = p->iReg;
+    if( r>=iReg && r<=iLast ){
+      cacheEntryClear(pParse, p);
+      p->iReg = 0;
+    }
+  }
+}
+
+/*
+** Remember the current column cache context.  Any new entries added
+** added to the column cache after this call are removed when the
+** corresponding pop occurs.
+*/
+void sqlite3ExprCachePush(Parse *pParse){
+  pParse->iCacheLevel++;
+}
+
+/*
+** Remove from the column cache any entries that were added since the
+** the previous N Push operations.  In other words, restore the cache
+** to the state it was in N Pushes ago.
+*/
+void sqlite3ExprCachePop(Parse *pParse, int N){
+  int i;
+  struct yColCache *p;
+  assert( N>0 );
+  assert( pParse->iCacheLevel>=N );
+  pParse->iCacheLevel -= N;
+  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
+    if( p->iReg && p->iLevel>pParse->iCacheLevel ){
+      cacheEntryClear(pParse, p);
+      p->iReg = 0;
+    }
+  }
+}
+
+/*
+** When a cached column is reused, make sure that its register is
+** no longer available as a temp register.  ticket #3879:  that same
+** register might be in the cache in multiple places, so be sure to
+** get them all.
+*/
+static void sqlite3ExprCachePinRegister(Parse *pParse, int iReg){
+  int i;
+  struct yColCache *p;
+  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
+    if( p->iReg==iReg ){
+      p->tempReg = 0;
+    }
+  }
+}
+
+/*
+** Generate code to extract the value of the iCol-th column of a table.
+*/
+void sqlite3ExprCodeGetColumnOfTable(
+  Vdbe *v,        /* The VDBE under construction */
+  Table *pTab,    /* The table containing the value */
+  int iTabCur,    /* The cursor for this table */
+  int iCol,       /* Index of the column to extract */
+  int regOut      /* Extract the valud into this register */
+){
+  if( iCol<0 || iCol==pTab->iPKey ){
+    sqlite3VdbeAddOp2(v, OP_Rowid, iTabCur, regOut);
+  }else{
+    int op = IsVirtual(pTab) ? OP_VColumn : OP_Column;
+    sqlite3VdbeAddOp3(v, op, iTabCur, iCol, regOut);
+  }
+  if( iCol>=0 ){
+    sqlite3ColumnDefault(v, pTab, iCol, regOut);
+  }
+}
+
+/*
+** Generate code that will extract the iColumn-th column from
+** table pTab and store the column value in a register.  An effort
+** is made to store the column value in register iReg, but this is
+** not guaranteed.  The location of the column value is returned.
+**
+** There must be an open cursor to pTab in iTable when this routine
+** is called.  If iColumn<0 then code is generated that extracts the rowid.
+*/
+int sqlite3ExprCodeGetColumn(
+  Parse *pParse,   /* Parsing and code generating context */
+  Table *pTab,     /* Description of the table we are reading from */
+  int iColumn,     /* Index of the table column */
+  int iTable,      /* The cursor pointing to the table */
+  int iReg         /* Store results here */
+){
+  Vdbe *v = pParse->pVdbe;
+  int i;
+  struct yColCache *p;
+
+  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
+    if( p->iReg>0 && p->iTable==iTable && p->iColumn==iColumn ){
+      p->lru = pParse->iCacheCnt++;
+      sqlite3ExprCachePinRegister(pParse, p->iReg);
+      return p->iReg;
+    }
+  }  
+  assert( v!=0 );
+  sqlite3ExprCodeGetColumnOfTable(v, pTab, iTable, iColumn, iReg);
+  sqlite3ExprCacheStore(pParse, iTable, iColumn, iReg);
+  return iReg;
+}
+
+/*
+** Clear all column cache entries.
+*/
+void sqlite3ExprCacheClear(Parse *pParse){
+  int i;
+  struct yColCache *p;
+
+  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
+    if( p->iReg ){
+      cacheEntryClear(pParse, p);
+      p->iReg = 0;
+    }
+  }
+}
+
+/*
+** Record the fact that an affinity change has occurred on iCount
+** registers starting with iStart.
+*/
+void sqlite3ExprCacheAffinityChange(Parse *pParse, int iStart, int iCount){
+  sqlite3ExprCacheRemove(pParse, iStart, iCount);
+}
+
+/*
+** Generate code to move content from registers iFrom...iFrom+nReg-1
+** over to iTo..iTo+nReg-1. Keep the column cache up-to-date.
+*/
+void sqlite3ExprCodeMove(Parse *pParse, int iFrom, int iTo, int nReg){
+  int i;
+  struct yColCache *p;
+  if( NEVER(iFrom==iTo) ) return;
+  sqlite3VdbeAddOp3(pParse->pVdbe, OP_Move, iFrom, iTo, nReg);
+  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
+    int x = p->iReg;
+    if( x>=iFrom && x<iFrom+nReg ){
+      p->iReg += iTo-iFrom;
+    }
+  }
+}
+
+/*
+** Generate code to copy content from registers iFrom...iFrom+nReg-1
+** over to iTo..iTo+nReg-1.
+*/
+void sqlite3ExprCodeCopy(Parse *pParse, int iFrom, int iTo, int nReg){
+  int i;
+  if( NEVER(iFrom==iTo) ) return;
+  for(i=0; i<nReg; i++){
+    sqlite3VdbeAddOp2(pParse->pVdbe, OP_Copy, iFrom+i, iTo+i);
+  }
+}
+
+#if defined(SQLITE_DEBUG) || defined(SQLITE_COVERAGE_TEST)
+/*
+** Return true if any register in the range iFrom..iTo (inclusive)
+** is used as part of the column cache.
+**
+** This routine is used within assert() and testcase() macros only
+** and does not appear in a normal build.
+*/
+static int usedAsColumnCache(Parse *pParse, int iFrom, int iTo){
+  int i;
+  struct yColCache *p;
+  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
+    int r = p->iReg;
+    if( r>=iFrom && r<=iTo ) return 1;    /*NO_TEST*/
+  }
+  return 0;
+}
+#endif /* SQLITE_DEBUG || SQLITE_COVERAGE_TEST */
+
+/*
+** Generate code into the current Vdbe to evaluate the given
+** expression.  Attempt to store the results in register "target".
+** Return the register where results are stored.
+**
+** With this routine, there is no guarantee that results will
+** be stored in target.  The result might be stored in some other
+** register if it is convenient to do so.  The calling function
+** must check the return code and move the results to the desired
+** register.
+*/
+int sqlite3ExprCodeTarget(Parse *pParse, Expr *pExpr, int target){
+  Vdbe *v = pParse->pVdbe;  /* The VM under construction */
+  int op;                   /* The opcode being coded */
+  int inReg = target;       /* Results stored in register inReg */
+  int regFree1 = 0;         /* If non-zero free this temporary register */
+  int regFree2 = 0;         /* If non-zero free this temporary register */
+  int r1, r2, r3, r4;       /* Various register numbers */
+  sqlite3 *db = pParse->db; /* The database connection */
+
+  assert( target>0 && target<=pParse->nMem );
+  if( v==0 ){
+    assert( pParse->db->mallocFailed );
+    return 0;
+  }
+
+  if( pExpr==0 ){
+    op = TK_NULL;
+  }else{
+    op = pExpr->op;
+  }
+  switch( op ){
+    case TK_AGG_COLUMN: {
+      AggInfo *pAggInfo = pExpr->pAggInfo;
+      struct AggInfo_col *pCol = &pAggInfo->aCol[pExpr->iAgg];
+      if( !pAggInfo->directMode ){
+        assert( pCol->iMem>0 );
+        inReg = pCol->iMem;
+        break;
+      }else if( pAggInfo->useSortingIdx ){
+        sqlite3VdbeAddOp3(v, OP_Column, pAggInfo->sortingIdxPTab,
+                              pCol->iSorterColumn, target);
+        break;
+      }
+      /* Otherwise, fall thru into the TK_COLUMN case */
+    }
+    case TK_COLUMN: {
+      if( pExpr->iTable<0 ){
+        /* This only happens when coding check constraints */
+        assert( pParse->ckBase>0 );
+        inReg = pExpr->iColumn + pParse->ckBase;
+      }else{
+        inReg = sqlite3ExprCodeGetColumn(pParse, pExpr->pTab,
+                                 pExpr->iColumn, pExpr->iTable, target);
+      }
+      break;
+    }
+    case TK_INTEGER: {
+      codeInteger(pParse, pExpr, 0, target);
+      break;
+    }
+#ifndef SQLITE_OMIT_FLOATING_POINT
+    case TK_FLOAT: {
+      assert( !ExprHasProperty(pExpr, EP_IntValue) );
+      codeReal(v, pExpr->u.zToken, 0, target);
+      break;
+    }
+#endif
+    case TK_STRING: {
+      assert( !ExprHasProperty(pExpr, EP_IntValue) );
+      sqlite3VdbeAddOp4(v, OP_String8, 0, target, 0, pExpr->u.zToken, 0);
+      break;
+    }
+    case TK_NULL: {
+      sqlite3VdbeAddOp2(v, OP_Null, 0, target);
+      break;
+    }
+#ifndef SQLITE_OMIT_BLOB_LITERAL
+    case TK_BLOB: {
+      int n;
+      const char *z;
+      char *zBlob;
+      assert( !ExprHasProperty(pExpr, EP_IntValue) );
+      assert( pExpr->u.zToken[0]=='x' || pExpr->u.zToken[0]=='X' );
+      assert( pExpr->u.zToken[1]=='\'' );
+      z = &pExpr->u.zToken[2];
+      n = sqlite3Strlen30(z) - 1;
+      assert( z[n]=='\'' );
+      zBlob = sqlite3HexToBlob(sqlite3VdbeDb(v), z, n);
+      sqlite3VdbeAddOp4(v, OP_Blob, n/2, target, 0, zBlob, P4_DYNAMIC);
+      break;
+    }
+#endif
+    case TK_VARIABLE: {
+      assert( !ExprHasProperty(pExpr, EP_IntValue) );
+      assert( pExpr->u.zToken!=0 );
+      assert( pExpr->u.zToken[0]!=0 );
+      sqlite3VdbeAddOp2(v, OP_Variable, pExpr->iColumn, target);
+      if( pExpr->u.zToken[1]!=0 ){
+        assert( pExpr->u.zToken[0]=='?' 
+             || strcmp(pExpr->u.zToken, pParse->azVar[pExpr->iColumn-1])==0 );
+        sqlite3VdbeChangeP4(v, -1, pParse->azVar[pExpr->iColumn-1], P4_STATIC);
+      }
+      break;
+    }
+    case TK_REGISTER: {
+      inReg = pExpr->iTable;
+      break;
+    }
+    case TK_AS: {
+      inReg = sqlite3ExprCodeTarget(pParse, pExpr->pLeft, target);
+      break;
+    }
+#ifndef SQLITE_OMIT_CAST
+    case TK_CAST: {
+      /* Expressions of the form:   CAST(pLeft AS token) */
+      int aff, to_op;
+      inReg = sqlite3ExprCodeTarget(pParse, pExpr->pLeft, target);
+      assert( !ExprHasProperty(pExpr, EP_IntValue) );
+      aff = sqlite3AffinityType(pExpr->u.zToken);
+      to_op = aff - SQLITE_AFF_TEXT + OP_ToText;
+      assert( to_op==OP_ToText    || aff!=SQLITE_AFF_TEXT    );
+      assert( to_op==OP_ToBlob    || aff!=SQLITE_AFF_NONE    );
+      assert( to_op==OP_ToNumeric || aff!=SQLITE_AFF_NUMERIC );
+      assert( to_op==OP_ToInt     || aff!=SQLITE_AFF_INTEGER );
+      assert( to_op==OP_ToReal    || aff!=SQLITE_AFF_REAL    );
+      testcase( to_op==OP_ToText );
+      testcase( to_op==OP_ToBlob );
+      testcase( to_op==OP_ToNumeric );
+      testcase( to_op==OP_ToInt );
+      testcase( to_op==OP_ToReal );
+      if( inReg!=target ){
+        sqlite3VdbeAddOp2(v, OP_SCopy, inReg, target);
+        inReg = target;
+      }
+      sqlite3VdbeAddOp1(v, to_op, inReg);
+      testcase( usedAsColumnCache(pParse, inReg, inReg) );
+      sqlite3ExprCacheAffinityChange(pParse, inReg, 1);
+      break;
+    }
+#endif /* SQLITE_OMIT_CAST */
+    case TK_LT:
+    case TK_LE:
+    case TK_GT:
+    case TK_GE:
+    case TK_NE:
+    case TK_EQ: {
+      assert( TK_LT==OP_Lt );
+      assert( TK_LE==OP_Le );
+      assert( TK_GT==OP_Gt );
+      assert( TK_GE==OP_Ge );
+      assert( TK_EQ==OP_Eq );
+      assert( TK_NE==OP_Ne );
+      testcase( op==TK_LT );
+      testcase( op==TK_LE );
+      testcase( op==TK_GT );
+      testcase( op==TK_GE );
+      testcase( op==TK_EQ );
+      testcase( op==TK_NE );
+      r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
+      r2 = sqlite3ExprCodeTemp(pParse, pExpr->pRight, &regFree2);
+      codeCompare(pParse, pExpr->pLeft, pExpr->pRight, op,
+                  r1, r2, inReg, SQLITE_STOREP2);
+      testcase( regFree1==0 );
+      testcase( regFree2==0 );
+      break;
+    }
+    case TK_IS:
+    case TK_ISNOT: {
+      testcase( op==TK_IS );
+      testcase( op==TK_ISNOT );
+      r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
+      r2 = sqlite3ExprCodeTemp(pParse, pExpr->pRight, &regFree2);
+      op = (op==TK_IS) ? TK_EQ : TK_NE;
+      codeCompare(pParse, pExpr->pLeft, pExpr->pRight, op,
+                  r1, r2, inReg, SQLITE_STOREP2 | SQLITE_NULLEQ);
+      testcase( regFree1==0 );
+      testcase( regFree2==0 );
+      break;
+    }
+    case TK_AND:
+    case TK_OR:
+    case TK_PLUS:
+    case TK_STAR:
+    case TK_MINUS:
+    case TK_REM:
+    case TK_BITAND:
+    case TK_BITOR:
+    case TK_SLASH:
+    case TK_LSHIFT:
+    case TK_RSHIFT: 
+    case TK_CONCAT: {
+      assert( TK_AND==OP_And );
+      assert( TK_OR==OP_Or );
+      assert( TK_PLUS==OP_Add );
+      assert( TK_MINUS==OP_Subtract );
+      assert( TK_REM==OP_Remainder );
+      assert( TK_BITAND==OP_BitAnd );
+      assert( TK_BITOR==OP_BitOr );
+      assert( TK_SLASH==OP_Divide );
+      assert( TK_LSHIFT==OP_ShiftLeft );
+      assert( TK_RSHIFT==OP_ShiftRight );
+      assert( TK_CONCAT==OP_Concat );
+      testcase( op==TK_AND );
+      testcase( op==TK_OR );
+      testcase( op==TK_PLUS );
+      testcase( op==TK_MINUS );
+      testcase( op==TK_REM );
+      testcase( op==TK_BITAND );
+      testcase( op==TK_BITOR );
+      testcase( op==TK_SLASH );
+      testcase( op==TK_LSHIFT );
+      testcase( op==TK_RSHIFT );
+      testcase( op==TK_CONCAT );
+      r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
+      r2 = sqlite3ExprCodeTemp(pParse, pExpr->pRight, &regFree2);
+      sqlite3VdbeAddOp3(v, op, r2, r1, target);
+      testcase( regFree1==0 );
+      testcase( regFree2==0 );
+      break;
+    }
+    case TK_UMINUS: {
+      Expr *pLeft = pExpr->pLeft;
+      assert( pLeft );
+      if( pLeft->op==TK_INTEGER ){
+        codeInteger(pParse, pLeft, 1, target);
+#ifndef SQLITE_OMIT_FLOATING_POINT
+      }else if( pLeft->op==TK_FLOAT ){
+        assert( !ExprHasProperty(pExpr, EP_IntValue) );
+        codeReal(v, pLeft->u.zToken, 1, target);
+#endif
+      }else{
+        regFree1 = r1 = sqlite3GetTempReg(pParse);
+        sqlite3VdbeAddOp2(v, OP_Integer, 0, r1);
+        r2 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree2);
+        sqlite3VdbeAddOp3(v, OP_Subtract, r2, r1, target);
+        testcase( regFree2==0 );
+      }
+      inReg = target;
+      break;
+    }
+    case TK_BITNOT:
+    case TK_NOT: {
+      assert( TK_BITNOT==OP_BitNot );
+      assert( TK_NOT==OP_Not );
+      testcase( op==TK_BITNOT );
+      testcase( op==TK_NOT );
+      r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
+      testcase( regFree1==0 );
+      inReg = target;
+      sqlite3VdbeAddOp2(v, op, r1, inReg);
+      break;
+    }
+    case TK_ISNULL:
+    case TK_NOTNULL: {
+      int addr;
+      assert( TK_ISNULL==OP_IsNull );
+      assert( TK_NOTNULL==OP_NotNull );
+      testcase( op==TK_ISNULL );
+      testcase( op==TK_NOTNULL );
+      sqlite3VdbeAddOp2(v, OP_Integer, 1, target);
+      r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
+      testcase( regFree1==0 );
+      addr = sqlite3VdbeAddOp1(v, op, r1);
+      sqlite3VdbeAddOp2(v, OP_AddImm, target, -1);
+      sqlite3VdbeJumpHere(v, addr);
+      break;
+    }
+    case TK_AGG_FUNCTION: {
+      AggInfo *pInfo = pExpr->pAggInfo;
+      if( pInfo==0 ){
+        assert( !ExprHasProperty(pExpr, EP_IntValue) );
+        sqlite3ErrorMsg(pParse, "misuse of aggregate: %s()", pExpr->u.zToken);
+      }else{
+        inReg = pInfo->aFunc[pExpr->iAgg].iMem;
+      }
+      break;
+    }
+    case TK_CONST_FUNC:
+    case TK_FUNCTION: {
+      ExprList *pFarg;       /* List of function arguments */
+      int nFarg;             /* Number of function arguments */
+      FuncDef *pDef;         /* The function definition object */
+      int nId;               /* Length of the function name in bytes */
+      const char *zId;       /* The function name */
+      int constMask = 0;     /* Mask of function arguments that are constant */
+      int i;                 /* Loop counter */
+      u8 enc = ENC(db);      /* The text encoding used by this database */
+      CollSeq *pColl = 0;    /* A collating sequence */
+
+      assert( !ExprHasProperty(pExpr, EP_xIsSelect) );
+      testcase( op==TK_CONST_FUNC );
+      testcase( op==TK_FUNCTION );
+      if( ExprHasAnyProperty(pExpr, EP_TokenOnly) ){
+        pFarg = 0;
+      }else{
+        pFarg = pExpr->x.pList;
+      }
+      nFarg = pFarg ? pFarg->nExpr : 0;
+      assert( !ExprHasProperty(pExpr, EP_IntValue) );
+      zId = pExpr->u.zToken;
+      nId = sqlite3Strlen30(zId);
+      pDef = sqlite3FindFunction(db, zId, nId, nFarg, enc, 0);
+      if( pDef==0 ){
+        sqlite3ErrorMsg(pParse, "unknown function: %.*s()", nId, zId);
+        break;
+      }
+
+      /* Attempt a direct implementation of the built-in COALESCE() and
+      ** IFNULL() functions.  This avoids unnecessary evalation of
+      ** arguments past the first non-NULL argument.
+      */
+      if( pDef->flags & SQLITE_FUNC_COALESCE ){
+        int endCoalesce = sqlite3VdbeMakeLabel(v);
+        assert( nFarg>=2 );
+        sqlite3ExprCode(pParse, pFarg->a[0].pExpr, target);
+        for(i=1; i<nFarg; i++){
+          sqlite3VdbeAddOp2(v, OP_NotNull, target, endCoalesce);
+          sqlite3ExprCacheRemove(pParse, target, 1);
+          sqlite3ExprCachePush(pParse);
+          sqlite3ExprCode(pParse, pFarg->a[i].pExpr, target);
+          sqlite3ExprCachePop(pParse, 1);
+        }
+        sqlite3VdbeResolveLabel(v, endCoalesce);
+        break;
+      }
+
+
+      if( pFarg ){
+        r1 = sqlite3GetTempRange(pParse, nFarg);
+        sqlite3ExprCachePush(pParse);     /* Ticket 2ea2425d34be */
+        sqlite3ExprCodeExprList(pParse, pFarg, r1, 1);
+        sqlite3ExprCachePop(pParse, 1);   /* Ticket 2ea2425d34be */
+      }else{
+        r1 = 0;
+      }
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+      /* Possibly overload the function if the first argument is
+      ** a virtual table column.
+      **
+      ** For infix functions (LIKE, GLOB, REGEXP, and MATCH) use the
+      ** second argument, not the first, as the argument to test to
+      ** see if it is a column in a virtual table.  This is done because
+      ** the left operand of infix functions (the operand we want to
+      ** control overloading) ends up as the second argument to the
+      ** function.  The expression "A glob B" is equivalent to 
+      ** "glob(B,A).  We want to use the A in "A glob B" to test
+      ** for function overloading.  But we use the B term in "glob(B,A)".
+      */
+      if( nFarg>=2 && (pExpr->flags & EP_InfixFunc) ){
+        pDef = sqlite3VtabOverloadFunction(db, pDef, nFarg, pFarg->a[1].pExpr);
+      }else if( nFarg>0 ){
+        pDef = sqlite3VtabOverloadFunction(db, pDef, nFarg, pFarg->a[0].pExpr);
+      }
+#endif
+      for(i=0; i<nFarg; i++){
+        if( i<32 && sqlite3ExprIsConstant(pFarg->a[i].pExpr) ){
+          constMask |= (1<<i);
+        }
+        if( (pDef->flags & SQLITE_FUNC_NEEDCOLL)!=0 && !pColl ){
+          pColl = sqlite3ExprCollSeq(pParse, pFarg->a[i].pExpr);
+        }
+      }
+      if( pDef->flags & SQLITE_FUNC_NEEDCOLL ){
+        if( !pColl ) pColl = db->pDfltColl; 
+        sqlite3VdbeAddOp4(v, OP_CollSeq, 0, 0, 0, (char *)pColl, P4_COLLSEQ);
+      }
+      sqlite3VdbeAddOp4(v, OP_Function, constMask, r1, target,
+                        (char*)pDef, P4_FUNCDEF);
+      sqlite3VdbeChangeP5(v, (u8)nFarg);
+      if( nFarg ){
+        sqlite3ReleaseTempRange(pParse, r1, nFarg);
+      }
+      break;
+    }
+#ifndef SQLITE_OMIT_SUBQUERY
+    case TK_EXISTS:
+    case TK_SELECT: {
+      testcase( op==TK_EXISTS );
+      testcase( op==TK_SELECT );
+      inReg = sqlite3CodeSubselect(pParse, pExpr, 0, 0);
+      break;
+    }
+    case TK_IN: {
+      int destIfFalse = sqlite3VdbeMakeLabel(v);
+      int destIfNull = sqlite3VdbeMakeLabel(v);
+      sqlite3VdbeAddOp2(v, OP_Null, 0, target);
+      sqlite3ExprCodeIN(pParse, pExpr, destIfFalse, destIfNull);
+      sqlite3VdbeAddOp2(v, OP_Integer, 1, target);
+      sqlite3VdbeResolveLabel(v, destIfFalse);
+      sqlite3VdbeAddOp2(v, OP_AddImm, target, 0);
+      sqlite3VdbeResolveLabel(v, destIfNull);
+      break;
+    }
+#endif /* SQLITE_OMIT_SUBQUERY */
+
+
+    /*
+    **    x BETWEEN y AND z
+    **
+    ** This is equivalent to
+    **
+    **    x>=y AND x<=z
+    **
+    ** X is stored in pExpr->pLeft.
+    ** Y is stored in pExpr->pList->a[0].pExpr.
+    ** Z is stored in pExpr->pList->a[1].pExpr.
+    */
+    case TK_BETWEEN: {
+      Expr *pLeft = pExpr->pLeft;
+      struct ExprList_item *pLItem = pExpr->x.pList->a;
+      Expr *pRight = pLItem->pExpr;
+
+      r1 = sqlite3ExprCodeTemp(pParse, pLeft, &regFree1);
+      r2 = sqlite3ExprCodeTemp(pParse, pRight, &regFree2);
+      testcase( regFree1==0 );
+      testcase( regFree2==0 );
+      r3 = sqlite3GetTempReg(pParse);
+      r4 = sqlite3GetTempReg(pParse);
+      codeCompare(pParse, pLeft, pRight, OP_Ge,
+                  r1, r2, r3, SQLITE_STOREP2);
+      pLItem++;
+      pRight = pLItem->pExpr;
+      sqlite3ReleaseTempReg(pParse, regFree2);
+      r2 = sqlite3ExprCodeTemp(pParse, pRight, &regFree2);
+      testcase( regFree2==0 );
+      codeCompare(pParse, pLeft, pRight, OP_Le, r1, r2, r4, SQLITE_STOREP2);
+      sqlite3VdbeAddOp3(v, OP_And, r3, r4, target);
+      sqlite3ReleaseTempReg(pParse, r3);
+      sqlite3ReleaseTempReg(pParse, r4);
+      break;
+    }
+    case TK_UPLUS: {
+      inReg = sqlite3ExprCodeTarget(pParse, pExpr->pLeft, target);
+      break;
+    }
+
+    case TK_TRIGGER: {
+      /* If the opcode is TK_TRIGGER, then the expression is a reference
+      ** to a column in the new.* or old.* pseudo-tables available to
+      ** trigger programs. In this case Expr.iTable is set to 1 for the
+      ** new.* pseudo-table, or 0 for the old.* pseudo-table. Expr.iColumn
+      ** is set to the column of the pseudo-table to read, or to -1 to
+      ** read the rowid field.
+      **
+      ** The expression is implemented using an OP_Param opcode. The p1
+      ** parameter is set to 0 for an old.rowid reference, or to (i+1)
+      ** to reference another column of the old.* pseudo-table, where 
+      ** i is the index of the column. For a new.rowid reference, p1 is
+      ** set to (n+1), where n is the number of columns in each pseudo-table.
+      ** For a reference to any other column in the new.* pseudo-table, p1
+      ** is set to (n+2+i), where n and i are as defined previously. For
+      ** example, if the table on which triggers are being fired is
+      ** declared as:
+      **
+      **   CREATE TABLE t1(a, b);
+      **
+      ** Then p1 is interpreted as follows:
+      **
+      **   p1==0   ->    old.rowid     p1==3   ->    new.rowid
+      **   p1==1   ->    old.a         p1==4   ->    new.a
+      **   p1==2   ->    old.b         p1==5   ->    new.b       
+      */
+      Table *pTab = pExpr->pTab;
+      int p1 = pExpr->iTable * (pTab->nCol+1) + 1 + pExpr->iColumn;
+
+      assert( pExpr->iTable==0 || pExpr->iTable==1 );
+      assert( pExpr->iColumn>=-1 && pExpr->iColumn<pTab->nCol );
+      assert( pTab->iPKey<0 || pExpr->iColumn!=pTab->iPKey );
+      assert( p1>=0 && p1<(pTab->nCol*2+2) );
+
+      sqlite3VdbeAddOp2(v, OP_Param, p1, target);
+      VdbeComment((v, "%s.%s -> $%d",
+        (pExpr->iTable ? "new" : "old"),
+        (pExpr->iColumn<0 ? "rowid" : pExpr->pTab->aCol[pExpr->iColumn].zName),
+        target
+      ));
+
+#ifndef SQLITE_OMIT_FLOATING_POINT
+      /* If the column has REAL affinity, it may currently be stored as an
+      ** integer. Use OP_RealAffinity to make sure it is really real.  */
+      if( pExpr->iColumn>=0 
+       && pTab->aCol[pExpr->iColumn].affinity==SQLITE_AFF_REAL
+      ){
+        sqlite3VdbeAddOp1(v, OP_RealAffinity, target);
+      }
+#endif
+      break;
+    }
+
+
+    /*
+    ** Form A:
+    **   CASE x WHEN e1 THEN r1 WHEN e2 THEN r2 ... WHEN eN THEN rN ELSE y END
+    **
+    ** Form B:
+    **   CASE WHEN e1 THEN r1 WHEN e2 THEN r2 ... WHEN eN THEN rN ELSE y END
+    **
+    ** Form A is can be transformed into the equivalent form B as follows:
+    **   CASE WHEN x=e1 THEN r1 WHEN x=e2 THEN r2 ...
+    **        WHEN x=eN THEN rN ELSE y END
+    **
+    ** X (if it exists) is in pExpr->pLeft.
+    ** Y is in pExpr->pRight.  The Y is also optional.  If there is no
+    ** ELSE clause and no other term matches, then the result of the
+    ** exprssion is NULL.
+    ** Ei is in pExpr->pList->a[i*2] and Ri is pExpr->pList->a[i*2+1].
+    **
+    ** The result of the expression is the Ri for the first matching Ei,
+    ** or if there is no matching Ei, the ELSE term Y, or if there is
+    ** no ELSE term, NULL.
+    */
+    default: assert( op==TK_CASE ); {
+      int endLabel;                     /* GOTO label for end of CASE stmt */
+      int nextCase;                     /* GOTO label for next WHEN clause */
+      int nExpr;                        /* 2x number of WHEN terms */
+      int i;                            /* Loop counter */
+      ExprList *pEList;                 /* List of WHEN terms */
+      struct ExprList_item *aListelem;  /* Array of WHEN terms */
+      Expr opCompare;                   /* The X==Ei expression */
+      Expr cacheX;                      /* Cached expression X */
+      Expr *pX;                         /* The X expression */
+      Expr *pTest = 0;                  /* X==Ei (form A) or just Ei (form B) */
+      VVA_ONLY( int iCacheLevel = pParse->iCacheLevel; )
+
+      assert( !ExprHasProperty(pExpr, EP_xIsSelect) && pExpr->x.pList );
+      assert((pExpr->x.pList->nExpr % 2) == 0);
+      assert(pExpr->x.pList->nExpr > 0);
+      pEList = pExpr->x.pList;
+      aListelem = pEList->a;
+      nExpr = pEList->nExpr;
+      endLabel = sqlite3VdbeMakeLabel(v);
+      if( (pX = pExpr->pLeft)!=0 ){
+        cacheX = *pX;
+        testcase( pX->op==TK_COLUMN );
+        testcase( pX->op==TK_REGISTER );
+        cacheX.iTable = sqlite3ExprCodeTemp(pParse, pX, &regFree1);
+        testcase( regFree1==0 );
+        cacheX.op = TK_REGISTER;
+        opCompare.op = TK_EQ;
+        opCompare.pLeft = &cacheX;
+        pTest = &opCompare;
+        /* Ticket b351d95f9cd5ef17e9d9dbae18f5ca8611190001:
+        ** The value in regFree1 might get SCopy-ed into the file result.
+        ** So make sure that the regFree1 register is not reused for other
+        ** purposes and possibly overwritten.  */
+        regFree1 = 0;
+      }
+      for(i=0; i<nExpr; i=i+2){
+        sqlite3ExprCachePush(pParse);
+        if( pX ){
+          assert( pTest!=0 );
+          opCompare.pRight = aListelem[i].pExpr;
+        }else{
+          pTest = aListelem[i].pExpr;
+        }
+        nextCase = sqlite3VdbeMakeLabel(v);
+        testcase( pTest->op==TK_COLUMN );
+        sqlite3ExprIfFalse(pParse, pTest, nextCase, SQLITE_JUMPIFNULL);
+        testcase( aListelem[i+1].pExpr->op==TK_COLUMN );
+        testcase( aListelem[i+1].pExpr->op==TK_REGISTER );
+        sqlite3ExprCode(pParse, aListelem[i+1].pExpr, target);
+        sqlite3VdbeAddOp2(v, OP_Goto, 0, endLabel);
+        sqlite3ExprCachePop(pParse, 1);
+        sqlite3VdbeResolveLabel(v, nextCase);
+      }
+      if( pExpr->pRight ){
+        sqlite3ExprCachePush(pParse);
+        sqlite3ExprCode(pParse, pExpr->pRight, target);
+        sqlite3ExprCachePop(pParse, 1);
+      }else{
+        sqlite3VdbeAddOp2(v, OP_Null, 0, target);
+      }
+      assert( db->mallocFailed || pParse->nErr>0 
+           || pParse->iCacheLevel==iCacheLevel );
+      sqlite3VdbeResolveLabel(v, endLabel);
+      break;
+    }
+#ifndef SQLITE_OMIT_TRIGGER
+    case TK_RAISE: {
+      assert( pExpr->affinity==OE_Rollback 
+           || pExpr->affinity==OE_Abort
+           || pExpr->affinity==OE_Fail
+           || pExpr->affinity==OE_Ignore
+      );
+      if( !pParse->pTriggerTab ){
+        sqlite3ErrorMsg(pParse,
+                       "RAISE() may only be used within a trigger-program");
+        return 0;
+      }
+      if( pExpr->affinity==OE_Abort ){
+        sqlite3MayAbort(pParse);
+      }
+      assert( !ExprHasProperty(pExpr, EP_IntValue) );
+      if( pExpr->affinity==OE_Ignore ){
+        sqlite3VdbeAddOp4(
+            v, OP_Halt, SQLITE_OK, OE_Ignore, 0, pExpr->u.zToken,0);
+      }else{
+        sqlite3HaltConstraint(pParse, pExpr->affinity, pExpr->u.zToken, 0);
+      }
+
+      break;
+    }
+#endif
+  }
+  sqlite3ReleaseTempReg(pParse, regFree1);
+  sqlite3ReleaseTempReg(pParse, regFree2);
+  return inReg;
+}
+
+/*
+** Generate code to evaluate an expression and store the results
+** into a register.  Return the register number where the results
+** are stored.
+**
+** If the register is a temporary register that can be deallocated,
+** then write its number into *pReg.  If the result register is not
+** a temporary, then set *pReg to zero.
+*/
+int sqlite3ExprCodeTemp(Parse *pParse, Expr *pExpr, int *pReg){
+  int r1 = sqlite3GetTempReg(pParse);
+  int r2 = sqlite3ExprCodeTarget(pParse, pExpr, r1);
+  if( r2==r1 ){
+    *pReg = r1;
+  }else{
+    sqlite3ReleaseTempReg(pParse, r1);
+    *pReg = 0;
+  }
+  return r2;
+}
+
+/*
+** Generate code that will evaluate expression pExpr and store the
+** results in register target.  The results are guaranteed to appear
+** in register target.
+*/
+int sqlite3ExprCode(Parse *pParse, Expr *pExpr, int target){
+  int inReg;
+
+  assert( target>0 && target<=pParse->nMem );
+  if( pExpr && pExpr->op==TK_REGISTER ){
+    sqlite3VdbeAddOp2(pParse->pVdbe, OP_Copy, pExpr->iTable, target);
+  }else{
+    inReg = sqlite3ExprCodeTarget(pParse, pExpr, target);
+    assert( pParse->pVdbe || pParse->db->mallocFailed );
+    if( inReg!=target && pParse->pVdbe ){
+      sqlite3VdbeAddOp2(pParse->pVdbe, OP_SCopy, inReg, target);
+    }
+  }
+  return target;
+}
+
+/*
+** Generate code that evalutes the given expression and puts the result
+** in register target.
+**
+** Also make a copy of the expression results into another "cache" register
+** and modify the expression so that the next time it is evaluated,
+** the result is a copy of the cache register.
+**
+** This routine is used for expressions that are used multiple 
+** times.  They are evaluated once and the results of the expression
+** are reused.
+*/
+int sqlite3ExprCodeAndCache(Parse *pParse, Expr *pExpr, int target){
+  Vdbe *v = pParse->pVdbe;
+  int inReg;
+  inReg = sqlite3ExprCode(pParse, pExpr, target);
+  assert( target>0 );
+  /* This routine is called for terms to INSERT or UPDATE.  And the only
+  ** other place where expressions can be converted into TK_REGISTER is
+  ** in WHERE clause processing.  So as currently implemented, there is
+  ** no way for a TK_REGISTER to exist here.  But it seems prudent to
+  ** keep the ALWAYS() in case the conditions above change with future
+  ** modifications or enhancements. */
+  if( ALWAYS(pExpr->op!=TK_REGISTER) ){  
+    int iMem;
+    iMem = ++pParse->nMem;
+    sqlite3VdbeAddOp2(v, OP_Copy, inReg, iMem);
+    pExpr->iTable = iMem;
+    pExpr->op2 = pExpr->op;
+    pExpr->op = TK_REGISTER;
+  }
+  return inReg;
+}
+
+/*
+** Return TRUE if pExpr is an constant expression that is appropriate
+** for factoring out of a loop.  Appropriate expressions are:
+**
+**    *  Any expression that evaluates to two or more opcodes.
+**
+**    *  Any OP_Integer, OP_Real, OP_String, OP_Blob, OP_Null, 
+**       or OP_Variable that does not need to be placed in a 
+**       specific register.
+**
+** There is no point in factoring out single-instruction constant
+** expressions that need to be placed in a particular register.  
+** We could factor them out, but then we would end up adding an
+** OP_SCopy instruction to move the value into the correct register
+** later.  We might as well just use the original instruction and
+** avoid the OP_SCopy.
+*/
+static int isAppropriateForFactoring(Expr *p){
+  if( !sqlite3ExprIsConstantNotJoin(p) ){
+    return 0;  /* Only constant expressions are appropriate for factoring */
+  }
+  if( (p->flags & EP_FixedDest)==0 ){
+    return 1;  /* Any constant without a fixed destination is appropriate */
+  }
+  while( p->op==TK_UPLUS ) p = p->pLeft;
+  switch( p->op ){
+#ifndef SQLITE_OMIT_BLOB_LITERAL
+    case TK_BLOB:
+#endif
+    case TK_VARIABLE:
+    case TK_INTEGER:
+    case TK_FLOAT:
+    case TK_NULL:
+    case TK_STRING: {
+      testcase( p->op==TK_BLOB );
+      testcase( p->op==TK_VARIABLE );
+      testcase( p->op==TK_INTEGER );
+      testcase( p->op==TK_FLOAT );
+      testcase( p->op==TK_NULL );
+      testcase( p->op==TK_STRING );
+      /* Single-instruction constants with a fixed destination are
+      ** better done in-line.  If we factor them, they will just end
+      ** up generating an OP_SCopy to move the value to the destination
+      ** register. */
+      return 0;
+    }
+    case TK_UMINUS: {
+      if( p->pLeft->op==TK_FLOAT || p->pLeft->op==TK_INTEGER ){
+        return 0;
+      }
+      break;
+    }
+    default: {
+      break;
+    }
+  }
+  return 1;
+}
+
+/*
+** If pExpr is a constant expression that is appropriate for
+** factoring out of a loop, then evaluate the expression
+** into a register and convert the expression into a TK_REGISTER
+** expression.
+*/
+static int evalConstExpr(Walker *pWalker, Expr *pExpr){
+  Parse *pParse = pWalker->pParse;
+  switch( pExpr->op ){
+    case TK_IN:
+    case TK_REGISTER: {
+      return WRC_Prune;
+    }
+    case TK_FUNCTION:
+    case TK_AGG_FUNCTION:
+    case TK_CONST_FUNC: {
+      /* The arguments to a function have a fixed destination.
+      ** Mark them this way to avoid generated unneeded OP_SCopy
+      ** instructions. 
+      */
+      ExprList *pList = pExpr->x.pList;
+      assert( !ExprHasProperty(pExpr, EP_xIsSelect) );
+      if( pList ){
+        int i = pList->nExpr;
+        struct ExprList_item *pItem = pList->a;
+        for(; i>0; i--, pItem++){
+          if( ALWAYS(pItem->pExpr) ) pItem->pExpr->flags |= EP_FixedDest;
+        }
+      }
+      break;
+    }
+  }
+  if( isAppropriateForFactoring(pExpr) ){
+    int r1 = ++pParse->nMem;
+    int r2;
+    r2 = sqlite3ExprCodeTarget(pParse, pExpr, r1);
+    if( NEVER(r1!=r2) ) sqlite3ReleaseTempReg(pParse, r1);
+    pExpr->op2 = pExpr->op;
+    pExpr->op = TK_REGISTER;
+    pExpr->iTable = r2;
+    return WRC_Prune;
+  }
+  return WRC_Continue;
+}
+
+/*
+** Preevaluate constant subexpressions within pExpr and store the
+** results in registers.  Modify pExpr so that the constant subexpresions
+** are TK_REGISTER opcodes that refer to the precomputed values.
+**
+** This routine is a no-op if the jump to the cookie-check code has
+** already occur.  Since the cookie-check jump is generated prior to
+** any other serious processing, this check ensures that there is no
+** way to accidently bypass the constant initializations.
+**
+** This routine is also a no-op if the SQLITE_FactorOutConst optimization
+** is disabled via the sqlite3_test_control(SQLITE_TESTCTRL_OPTIMIZATIONS)
+** interface.  This allows test logic to verify that the same answer is
+** obtained for queries regardless of whether or not constants are
+** precomputed into registers or if they are inserted in-line.
+*/
+void sqlite3ExprCodeConstants(Parse *pParse, Expr *pExpr){
+  Walker w;
+  if( pParse->cookieGoto ) return;
+  if( (pParse->db->flags & SQLITE_FactorOutConst)!=0 ) return;
+  w.xExprCallback = evalConstExpr;
+  w.xSelectCallback = 0;
+  w.pParse = pParse;
+  sqlite3WalkExpr(&w, pExpr);
+}
+
+
+/*
+** Generate code that pushes the value of every element of the given
+** expression list into a sequence of registers beginning at target.
+**
+** Return the number of elements evaluated.
+*/
+int sqlite3ExprCodeExprList(
+  Parse *pParse,     /* Parsing context */
+  ExprList *pList,   /* The expression list to be coded */
+  int target,        /* Where to write results */
+  int doHardCopy     /* Make a hard copy of every element */
+){
+  struct ExprList_item *pItem;
+  int i, n;
+  assert( pList!=0 );
+  assert( target>0 );
+  assert( pParse->pVdbe!=0 );  /* Never gets this far otherwise */
+  n = pList->nExpr;
+  for(pItem=pList->a, i=0; i<n; i++, pItem++){
+    Expr *pExpr = pItem->pExpr;
+    int inReg = sqlite3ExprCodeTarget(pParse, pExpr, target+i);
+    if( inReg!=target+i ){
+      sqlite3VdbeAddOp2(pParse->pVdbe, doHardCopy ? OP_Copy : OP_SCopy,
+                        inReg, target+i);
+    }
+  }
+  return n;
+}
+
+/*
+** Generate code for a BETWEEN operator.
+**
+**    x BETWEEN y AND z
+**
+** The above is equivalent to 
+**
+**    x>=y AND x<=z
+**
+** Code it as such, taking care to do the common subexpression
+** elementation of x.
+*/
+static void exprCodeBetween(
+  Parse *pParse,    /* Parsing and code generating context */
+  Expr *pExpr,      /* The BETWEEN expression */
+  int dest,         /* Jump here if the jump is taken */
+  int jumpIfTrue,   /* Take the jump if the BETWEEN is true */
+  int jumpIfNull    /* Take the jump if the BETWEEN is NULL */
+){
+  Expr exprAnd;     /* The AND operator in  x>=y AND x<=z  */
+  Expr compLeft;    /* The  x>=y  term */
+  Expr compRight;   /* The  x<=z  term */
+  Expr exprX;       /* The  x  subexpression */
+  int regFree1 = 0; /* Temporary use register */
+
+  assert( !ExprHasProperty(pExpr, EP_xIsSelect) );
+  exprX = *pExpr->pLeft;
+  exprAnd.op = TK_AND;
+  exprAnd.pLeft = &compLeft;
+  exprAnd.pRight = &compRight;
+  compLeft.op = TK_GE;
+  compLeft.pLeft = &exprX;
+  compLeft.pRight = pExpr->x.pList->a[0].pExpr;
+  compRight.op = TK_LE;
+  compRight.pLeft = &exprX;
+  compRight.pRight = pExpr->x.pList->a[1].pExpr;
+  exprX.iTable = sqlite3ExprCodeTemp(pParse, &exprX, &regFree1);
+  exprX.op = TK_REGISTER;
+  if( jumpIfTrue ){
+    sqlite3ExprIfTrue(pParse, &exprAnd, dest, jumpIfNull);
+  }else{
+    sqlite3ExprIfFalse(pParse, &exprAnd, dest, jumpIfNull);
+  }
+  sqlite3ReleaseTempReg(pParse, regFree1);
+
+  /* Ensure adequate test coverage */
+  testcase( jumpIfTrue==0 && jumpIfNull==0 && regFree1==0 );
+  testcase( jumpIfTrue==0 && jumpIfNull==0 && regFree1!=0 );
+  testcase( jumpIfTrue==0 && jumpIfNull!=0 && regFree1==0 );
+  testcase( jumpIfTrue==0 && jumpIfNull!=0 && regFree1!=0 );
+  testcase( jumpIfTrue!=0 && jumpIfNull==0 && regFree1==0 );
+  testcase( jumpIfTrue!=0 && jumpIfNull==0 && regFree1!=0 );
+  testcase( jumpIfTrue!=0 && jumpIfNull!=0 && regFree1==0 );
+  testcase( jumpIfTrue!=0 && jumpIfNull!=0 && regFree1!=0 );
+}
+
+/*
+** Generate code for a boolean expression such that a jump is made
+** to the label "dest" if the expression is true but execution
+** continues straight thru if the expression is false.
+**
+** If the expression evaluates to NULL (neither true nor false), then
+** take the jump if the jumpIfNull flag is SQLITE_JUMPIFNULL.
+**
+** This code depends on the fact that certain token values (ex: TK_EQ)
+** are the same as opcode values (ex: OP_Eq) that implement the corresponding
+** operation.  Special comments in vdbe.c and the mkopcodeh.awk script in
+** the make process cause these values to align.  Assert()s in the code
+** below verify that the numbers are aligned correctly.
+*/
+void sqlite3ExprIfTrue(Parse *pParse, Expr *pExpr, int dest, int jumpIfNull){
+  Vdbe *v = pParse->pVdbe;
+  int op = 0;
+  int regFree1 = 0;
+  int regFree2 = 0;
+  int r1, r2;
+
+  assert( jumpIfNull==SQLITE_JUMPIFNULL || jumpIfNull==0 );
+  if( NEVER(v==0) )     return;  /* Existance of VDBE checked by caller */
+  if( NEVER(pExpr==0) ) return;  /* No way this can happen */
+  op = pExpr->op;
+  switch( op ){
+    case TK_AND: {
+      int d2 = sqlite3VdbeMakeLabel(v);
+      testcase( jumpIfNull==0 );
+      sqlite3ExprCachePush(pParse);
+      sqlite3ExprIfFalse(pParse, pExpr->pLeft, d2,jumpIfNull^SQLITE_JUMPIFNULL);
+      sqlite3ExprIfTrue(pParse, pExpr->pRight, dest, jumpIfNull);
+      sqlite3VdbeResolveLabel(v, d2);
+      sqlite3ExprCachePop(pParse, 1);
+      break;
+    }
+    case TK_OR: {
+      testcase( jumpIfNull==0 );
+      sqlite3ExprIfTrue(pParse, pExpr->pLeft, dest, jumpIfNull);
+      sqlite3ExprIfTrue(pParse, pExpr->pRight, dest, jumpIfNull);
+      break;
+    }
+    case TK_NOT: {
+      testcase( jumpIfNull==0 );
+      sqlite3ExprIfFalse(pParse, pExpr->pLeft, dest, jumpIfNull);
+      break;
+    }
+    case TK_LT:
+    case TK_LE:
+    case TK_GT:
+    case TK_GE:
+    case TK_NE:
+    case TK_EQ: {
+      assert( TK_LT==OP_Lt );
+      assert( TK_LE==OP_Le );
+      assert( TK_GT==OP_Gt );
+      assert( TK_GE==OP_Ge );
+      assert( TK_EQ==OP_Eq );
+      assert( TK_NE==OP_Ne );
+      testcase( op==TK_LT );
+      testcase( op==TK_LE );
+      testcase( op==TK_GT );
+      testcase( op==TK_GE );
+      testcase( op==TK_EQ );
+      testcase( op==TK_NE );
+      testcase( jumpIfNull==0 );
+      r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
+      r2 = sqlite3ExprCodeTemp(pParse, pExpr->pRight, &regFree2);
+      codeCompare(pParse, pExpr->pLeft, pExpr->pRight, op,
+                  r1, r2, dest, jumpIfNull);
+      testcase( regFree1==0 );
+      testcase( regFree2==0 );
+      break;
+    }
+    case TK_IS:
+    case TK_ISNOT: {
+      testcase( op==TK_IS );
+      testcase( op==TK_ISNOT );
+      r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
+      r2 = sqlite3ExprCodeTemp(pParse, pExpr->pRight, &regFree2);
+      op = (op==TK_IS) ? TK_EQ : TK_NE;
+      codeCompare(pParse, pExpr->pLeft, pExpr->pRight, op,
+                  r1, r2, dest, SQLITE_NULLEQ);
+      testcase( regFree1==0 );
+      testcase( regFree2==0 );
+      break;
+    }
+    case TK_ISNULL:
+    case TK_NOTNULL: {
+      assert( TK_ISNULL==OP_IsNull );
+      assert( TK_NOTNULL==OP_NotNull );
+      testcase( op==TK_ISNULL );
+      testcase( op==TK_NOTNULL );
+      r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
+      sqlite3VdbeAddOp2(v, op, r1, dest);
+      testcase( regFree1==0 );
+      break;
+    }
+    case TK_BETWEEN: {
+      testcase( jumpIfNull==0 );
+      exprCodeBetween(pParse, pExpr, dest, 1, jumpIfNull);
+      break;
+    }
+#ifndef SQLITE_OMIT_SUBQUERY
+    case TK_IN: {
+      int destIfFalse = sqlite3VdbeMakeLabel(v);
+      int destIfNull = jumpIfNull ? dest : destIfFalse;
+      sqlite3ExprCodeIN(pParse, pExpr, destIfFalse, destIfNull);
+      sqlite3VdbeAddOp2(v, OP_Goto, 0, dest);
+      sqlite3VdbeResolveLabel(v, destIfFalse);
+      break;
+    }
+#endif
+    default: {
+      r1 = sqlite3ExprCodeTemp(pParse, pExpr, &regFree1);
+      sqlite3VdbeAddOp3(v, OP_If, r1, dest, jumpIfNull!=0);
+      testcase( regFree1==0 );
+      testcase( jumpIfNull==0 );
+      break;
+    }
+  }
+  sqlite3ReleaseTempReg(pParse, regFree1);
+  sqlite3ReleaseTempReg(pParse, regFree2);  
+}
+
+/*
+** Generate code for a boolean expression such that a jump is made
+** to the label "dest" if the expression is false but execution
+** continues straight thru if the expression is true.
+**
+** If the expression evaluates to NULL (neither true nor false) then
+** jump if jumpIfNull is SQLITE_JUMPIFNULL or fall through if jumpIfNull
+** is 0.
+*/
+void sqlite3ExprIfFalse(Parse *pParse, Expr *pExpr, int dest, int jumpIfNull){
+  Vdbe *v = pParse->pVdbe;
+  int op = 0;
+  int regFree1 = 0;
+  int regFree2 = 0;
+  int r1, r2;
+
+  assert( jumpIfNull==SQLITE_JUMPIFNULL || jumpIfNull==0 );
+  if( NEVER(v==0) ) return; /* Existance of VDBE checked by caller */
+  if( pExpr==0 )    return;
+
+  /* The value of pExpr->op and op are related as follows:
+  **
+  **       pExpr->op            op
+  **       ---------          ----------
+  **       TK_ISNULL          OP_NotNull
+  **       TK_NOTNULL         OP_IsNull
+  **       TK_NE              OP_Eq
+  **       TK_EQ              OP_Ne
+  **       TK_GT              OP_Le
+  **       TK_LE              OP_Gt
+  **       TK_GE              OP_Lt
+  **       TK_LT              OP_Ge
+  **
+  ** For other values of pExpr->op, op is undefined and unused.
+  ** The value of TK_ and OP_ constants are arranged such that we
+  ** can compute the mapping above using the following expression.
+  ** Assert()s verify that the computation is correct.
+  */
+  op = ((pExpr->op+(TK_ISNULL&1))^1)-(TK_ISNULL&1);
+
+  /* Verify correct alignment of TK_ and OP_ constants
+  */
+  assert( pExpr->op!=TK_ISNULL || op==OP_NotNull );
+  assert( pExpr->op!=TK_NOTNULL || op==OP_IsNull );
+  assert( pExpr->op!=TK_NE || op==OP_Eq );
+  assert( pExpr->op!=TK_EQ || op==OP_Ne );
+  assert( pExpr->op!=TK_LT || op==OP_Ge );
+  assert( pExpr->op!=TK_LE || op==OP_Gt );
+  assert( pExpr->op!=TK_GT || op==OP_Le );
+  assert( pExpr->op!=TK_GE || op==OP_Lt );
+
+  switch( pExpr->op ){
+    case TK_AND: {
+      testcase( jumpIfNull==0 );
+      sqlite3ExprIfFalse(pParse, pExpr->pLeft, dest, jumpIfNull);
+      sqlite3ExprIfFalse(pParse, pExpr->pRight, dest, jumpIfNull);
+      break;
+    }
+    case TK_OR: {
+      int d2 = sqlite3VdbeMakeLabel(v);
+      testcase( jumpIfNull==0 );
+      sqlite3ExprCachePush(pParse);
+      sqlite3ExprIfTrue(pParse, pExpr->pLeft, d2, jumpIfNull^SQLITE_JUMPIFNULL);
+      sqlite3ExprIfFalse(pParse, pExpr->pRight, dest, jumpIfNull);
+      sqlite3VdbeResolveLabel(v, d2);
+      sqlite3ExprCachePop(pParse, 1);
+      break;
+    }
+    case TK_NOT: {
+      testcase( jumpIfNull==0 );
+      sqlite3ExprIfTrue(pParse, pExpr->pLeft, dest, jumpIfNull);
+      break;
+    }
+    case TK_LT:
+    case TK_LE:
+    case TK_GT:
+    case TK_GE:
+    case TK_NE:
+    case TK_EQ: {
+      testcase( op==TK_LT );
+      testcase( op==TK_LE );
+      testcase( op==TK_GT );
+      testcase( op==TK_GE );
+      testcase( op==TK_EQ );
+      testcase( op==TK_NE );
+      testcase( jumpIfNull==0 );
+      r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
+      r2 = sqlite3ExprCodeTemp(pParse, pExpr->pRight, &regFree2);
+      codeCompare(pParse, pExpr->pLeft, pExpr->pRight, op,
+                  r1, r2, dest, jumpIfNull);
+      testcase( regFree1==0 );
+      testcase( regFree2==0 );
+      break;
+    }
+    case TK_IS:
+    case TK_ISNOT: {
+      testcase( pExpr->op==TK_IS );
+      testcase( pExpr->op==TK_ISNOT );
+      r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
+      r2 = sqlite3ExprCodeTemp(pParse, pExpr->pRight, &regFree2);
+      op = (pExpr->op==TK_IS) ? TK_NE : TK_EQ;
+      codeCompare(pParse, pExpr->pLeft, pExpr->pRight, op,
+                  r1, r2, dest, SQLITE_NULLEQ);
+      testcase( regFree1==0 );
+      testcase( regFree2==0 );
+      break;
+    }
+    case TK_ISNULL:
+    case TK_NOTNULL: {
+      testcase( op==TK_ISNULL );
+      testcase( op==TK_NOTNULL );
+      r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
+      sqlite3VdbeAddOp2(v, op, r1, dest);
+      testcase( regFree1==0 );
+      break;
+    }
+    case TK_BETWEEN: {
+      testcase( jumpIfNull==0 );
+      exprCodeBetween(pParse, pExpr, dest, 0, jumpIfNull);
+      break;
+    }
+#ifndef SQLITE_OMIT_SUBQUERY
+    case TK_IN: {
+      if( jumpIfNull ){
+        sqlite3ExprCodeIN(pParse, pExpr, dest, dest);
+      }else{
+        int destIfNull = sqlite3VdbeMakeLabel(v);
+        sqlite3ExprCodeIN(pParse, pExpr, dest, destIfNull);
+        sqlite3VdbeResolveLabel(v, destIfNull);
+      }
+      break;
+    }
+#endif
+    default: {
+      r1 = sqlite3ExprCodeTemp(pParse, pExpr, &regFree1);
+      sqlite3VdbeAddOp3(v, OP_IfNot, r1, dest, jumpIfNull!=0);
+      testcase( regFree1==0 );
+      testcase( jumpIfNull==0 );
+      break;
+    }
+  }
+  sqlite3ReleaseTempReg(pParse, regFree1);
+  sqlite3ReleaseTempReg(pParse, regFree2);
+}
+
+/*
+** Do a deep comparison of two expression trees.  Return 0 if the two
+** expressions are completely identical.  Return 1 if they differ only
+** by a COLLATE operator at the top level.  Return 2 if there are differences
+** other than the top-level COLLATE operator.
+**
+** Sometimes this routine will return 2 even if the two expressions
+** really are equivalent.  If we cannot prove that the expressions are
+** identical, we return 2 just to be safe.  So if this routine
+** returns 2, then you do not really know for certain if the two
+** expressions are the same.  But if you get a 0 or 1 return, then you
+** can be sure the expressions are the same.  In the places where
+** this routine is used, it does not hurt to get an extra 2 - that
+** just might result in some slightly slower code.  But returning
+** an incorrect 0 or 1 could lead to a malfunction.
+*/
+int sqlite3ExprCompare(Expr *pA, Expr *pB){
+  if( pA==0||pB==0 ){
+    return pB==pA ? 0 : 2;
+  }
+  assert( !ExprHasAnyProperty(pA, EP_TokenOnly|EP_Reduced) );
+  assert( !ExprHasAnyProperty(pB, EP_TokenOnly|EP_Reduced) );
+  if( ExprHasProperty(pA, EP_xIsSelect) || ExprHasProperty(pB, EP_xIsSelect) ){
+    return 2;
+  }
+  if( (pA->flags & EP_Distinct)!=(pB->flags & EP_Distinct) ) return 2;
+  if( pA->op!=pB->op ) return 2;
+  if( sqlite3ExprCompare(pA->pLeft, pB->pLeft) ) return 2;
+  if( sqlite3ExprCompare(pA->pRight, pB->pRight) ) return 2;
+  if( sqlite3ExprListCompare(pA->x.pList, pB->x.pList) ) return 2;
+  if( pA->iTable!=pB->iTable || pA->iColumn!=pB->iColumn ) return 2;
+  if( ExprHasProperty(pA, EP_IntValue) ){
+    if( !ExprHasProperty(pB, EP_IntValue) || pA->u.iValue!=pB->u.iValue ){
+      return 2;
+    }
+  }else if( pA->op!=TK_COLUMN && pA->u.zToken ){
+    if( ExprHasProperty(pB, EP_IntValue) || NEVER(pB->u.zToken==0) ) return 2;
+    if( strcmp(pA->u.zToken,pB->u.zToken)!=0 ){
+      return 2;
+    }
+  }
+  if( (pA->flags & EP_ExpCollate)!=(pB->flags & EP_ExpCollate) ) return 1;
+  if( (pA->flags & EP_ExpCollate)!=0 && pA->pColl!=pB->pColl ) return 2;
+  return 0;
+}
+
+/*
+** Compare two ExprList objects.  Return 0 if they are identical and 
+** non-zero if they differ in any way.
+**
+** This routine might return non-zero for equivalent ExprLists.  The
+** only consequence will be disabled optimizations.  But this routine
+** must never return 0 if the two ExprList objects are different, or
+** a malfunction will result.
+**
+** Two NULL pointers are considered to be the same.  But a NULL pointer
+** always differs from a non-NULL pointer.
+*/
+int sqlite3ExprListCompare(ExprList *pA, ExprList *pB){
+  int i;
+  if( pA==0 && pB==0 ) return 0;
+  if( pA==0 || pB==0 ) return 1;
+  if( pA->nExpr!=pB->nExpr ) return 1;
+  for(i=0; i<pA->nExpr; i++){
+    Expr *pExprA = pA->a[i].pExpr;
+    Expr *pExprB = pB->a[i].pExpr;
+    if( pA->a[i].sortOrder!=pB->a[i].sortOrder ) return 1;
+    if( sqlite3ExprCompare(pExprA, pExprB) ) return 1;
+  }
+  return 0;
+}
+
+/*
+** Add a new element to the pAggInfo->aCol[] array.  Return the index of
+** the new element.  Return a negative number if malloc fails.
+*/
+static int addAggInfoColumn(sqlite3 *db, AggInfo *pInfo){
+  int i;
+  pInfo->aCol = sqlite3ArrayAllocate(
+       db,
+       pInfo->aCol,
+       sizeof(pInfo->aCol[0]),
+       3,
+       &pInfo->nColumn,
+       &pInfo->nColumnAlloc,
+       &i
+  );
+  return i;
+}    
+
+/*
+** Add a new element to the pAggInfo->aFunc[] array.  Return the index of
+** the new element.  Return a negative number if malloc fails.
+*/
+static int addAggInfoFunc(sqlite3 *db, AggInfo *pInfo){
+  int i;
+  pInfo->aFunc = sqlite3ArrayAllocate(
+       db, 
+       pInfo->aFunc,
+       sizeof(pInfo->aFunc[0]),
+       3,
+       &pInfo->nFunc,
+       &pInfo->nFuncAlloc,
+       &i
+  );
+  return i;
+}    
+
+/*
+** This is the xExprCallback for a tree walker.  It is used to
+** implement sqlite3ExprAnalyzeAggregates().  See sqlite3ExprAnalyzeAggregates
+** for additional information.
+*/
+static int analyzeAggregate(Walker *pWalker, Expr *pExpr){
+  int i;
+  NameContext *pNC = pWalker->u.pNC;
+  Parse *pParse = pNC->pParse;
+  SrcList *pSrcList = pNC->pSrcList;
+  AggInfo *pAggInfo = pNC->pAggInfo;
+
+  switch( pExpr->op ){
+    case TK_AGG_COLUMN:
+    case TK_COLUMN: {
+      testcase( pExpr->op==TK_AGG_COLUMN );
+      testcase( pExpr->op==TK_COLUMN );
+      /* Check to see if the column is in one of the tables in the FROM
+      ** clause of the aggregate query */
+      if( ALWAYS(pSrcList!=0) ){
+        struct SrcList_item *pItem = pSrcList->a;
+        for(i=0; i<pSrcList->nSrc; i++, pItem++){
+          struct AggInfo_col *pCol;
+          assert( !ExprHasAnyProperty(pExpr, EP_TokenOnly|EP_Reduced) );
+          if( pExpr->iTable==pItem->iCursor ){
+            /* If we reach this point, it means that pExpr refers to a table
+            ** that is in the FROM clause of the aggregate query.  
+            **
+            ** Make an entry for the column in pAggInfo->aCol[] if there
+            ** is not an entry there already.
+            */
+            int k;
+            pCol = pAggInfo->aCol;
+            for(k=0; k<pAggInfo->nColumn; k++, pCol++){
+              if( pCol->iTable==pExpr->iTable &&
+                  pCol->iColumn==pExpr->iColumn ){
+                break;
+              }
+            }
+            if( (k>=pAggInfo->nColumn)
+             && (k = addAggInfoColumn(pParse->db, pAggInfo))>=0 
+            ){
+              pCol = &pAggInfo->aCol[k];
+              pCol->pTab = pExpr->pTab;
+              pCol->iTable = pExpr->iTable;
+              pCol->iColumn = pExpr->iColumn;
+              pCol->iMem = ++pParse->nMem;
+              pCol->iSorterColumn = -1;
+              pCol->pExpr = pExpr;
+              if( pAggInfo->pGroupBy ){
+                int j, n;
+                ExprList *pGB = pAggInfo->pGroupBy;
+                struct ExprList_item *pTerm = pGB->a;
+                n = pGB->nExpr;
+                for(j=0; j<n; j++, pTerm++){
+                  Expr *pE = pTerm->pExpr;
+                  if( pE->op==TK_COLUMN && pE->iTable==pExpr->iTable &&
+                      pE->iColumn==pExpr->iColumn ){
+                    pCol->iSorterColumn = j;
+                    break;
+                  }
+                }
+              }
+              if( pCol->iSorterColumn<0 ){
+                pCol->iSorterColumn = pAggInfo->nSortingColumn++;
+              }
+            }
+            /* There is now an entry for pExpr in pAggInfo->aCol[] (either
+            ** because it was there before or because we just created it).
+            ** Convert the pExpr to be a TK_AGG_COLUMN referring to that
+            ** pAggInfo->aCol[] entry.
+            */
+            ExprSetIrreducible(pExpr);
+            pExpr->pAggInfo = pAggInfo;
+            pExpr->op = TK_AGG_COLUMN;
+            pExpr->iAgg = (i16)k;
+            break;
+          } /* endif pExpr->iTable==pItem->iCursor */
+        } /* end loop over pSrcList */
+      }
+      return WRC_Prune;
+    }
+    case TK_AGG_FUNCTION: {
+      /* The pNC->nDepth==0 test causes aggregate functions in subqueries
+      ** to be ignored */
+      if( pNC->nDepth==0 ){
+        /* Check to see if pExpr is a duplicate of another aggregate 
+        ** function that is already in the pAggInfo structure
+        */
+        struct AggInfo_func *pItem = pAggInfo->aFunc;
+        for(i=0; i<pAggInfo->nFunc; i++, pItem++){
+          if( sqlite3ExprCompare(pItem->pExpr, pExpr)==0 ){
+            break;
+          }
+        }
+        if( i>=pAggInfo->nFunc ){
+          /* pExpr is original.  Make a new entry in pAggInfo->aFunc[]
+          */
+          u8 enc = ENC(pParse->db);
+          i = addAggInfoFunc(pParse->db, pAggInfo);
+          if( i>=0 ){
+            assert( !ExprHasProperty(pExpr, EP_xIsSelect) );
+            pItem = &pAggInfo->aFunc[i];
+            pItem->pExpr = pExpr;
+            pItem->iMem = ++pParse->nMem;
+            assert( !ExprHasProperty(pExpr, EP_IntValue) );
+            pItem->pFunc = sqlite3FindFunction(pParse->db,
+                   pExpr->u.zToken, sqlite3Strlen30(pExpr->u.zToken),
+                   pExpr->x.pList ? pExpr->x.pList->nExpr : 0, enc, 0);
+            if( pExpr->flags & EP_Distinct ){
+              pItem->iDistinct = pParse->nTab++;
+            }else{
+              pItem->iDistinct = -1;
+            }
+          }
+        }
+        /* Make pExpr point to the appropriate pAggInfo->aFunc[] entry
+        */
+        assert( !ExprHasAnyProperty(pExpr, EP_TokenOnly|EP_Reduced) );
+        ExprSetIrreducible(pExpr);
+        pExpr->iAgg = (i16)i;
+        pExpr->pAggInfo = pAggInfo;
+        return WRC_Prune;
+      }
+    }
+  }
+  return WRC_Continue;
+}
+static int analyzeAggregatesInSelect(Walker *pWalker, Select *pSelect){
+  NameContext *pNC = pWalker->u.pNC;
+  if( pNC->nDepth==0 ){
+    pNC->nDepth++;
+    sqlite3WalkSelect(pWalker, pSelect);
+    pNC->nDepth--;
+    return WRC_Prune;
+  }else{
+    return WRC_Continue;
+  }
+}
+
+/*
+** Analyze the given expression looking for aggregate functions and
+** for variables that need to be added to the pParse->aAgg[] array.
+** Make additional entries to the pParse->aAgg[] array as necessary.
+**
+** This routine should only be called after the expression has been
+** analyzed by sqlite3ResolveExprNames().
+*/
+void sqlite3ExprAnalyzeAggregates(NameContext *pNC, Expr *pExpr){
+  Walker w;
+  w.xExprCallback = analyzeAggregate;
+  w.xSelectCallback = analyzeAggregatesInSelect;
+  w.u.pNC = pNC;
+  assert( pNC->pSrcList!=0 );
+  sqlite3WalkExpr(&w, pExpr);
+}
+
+/*
+** Call sqlite3ExprAnalyzeAggregates() for every expression in an
+** expression list.  Return the number of errors.
+**
+** If an error is found, the analysis is cut short.
+*/
+void sqlite3ExprAnalyzeAggList(NameContext *pNC, ExprList *pList){
+  struct ExprList_item *pItem;
+  int i;
+  if( pList ){
+    for(pItem=pList->a, i=0; i<pList->nExpr; i++, pItem++){
+      sqlite3ExprAnalyzeAggregates(pNC, pItem->pExpr);
+    }
+  }
+}
+
+/*
+** Allocate a single new register for use to hold some intermediate result.
+*/
+int sqlite3GetTempReg(Parse *pParse){
+  if( pParse->nTempReg==0 ){
+    return ++pParse->nMem;
+  }
+  return pParse->aTempReg[--pParse->nTempReg];
+}
+
+/*
+** Deallocate a register, making available for reuse for some other
+** purpose.
+**
+** If a register is currently being used by the column cache, then
+** the dallocation is deferred until the column cache line that uses
+** the register becomes stale.
+*/
+void sqlite3ReleaseTempReg(Parse *pParse, int iReg){
+  if( iReg && pParse->nTempReg<ArraySize(pParse->aTempReg) ){
+    int i;
+    struct yColCache *p;
+    for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
+      if( p->iReg==iReg ){
+        p->tempReg = 1;
+        return;
+      }
+    }
+    pParse->aTempReg[pParse->nTempReg++] = iReg;
+  }
+}
+
+/*
+** Allocate or deallocate a block of nReg consecutive registers
+*/
+int sqlite3GetTempRange(Parse *pParse, int nReg){
+  int i, n;
+  i = pParse->iRangeReg;
+  n = pParse->nRangeReg;
+  if( nReg<=n ){
+    assert( !usedAsColumnCache(pParse, i, i+n-1) );
+    pParse->iRangeReg += nReg;
+    pParse->nRangeReg -= nReg;
+  }else{
+    i = pParse->nMem+1;
+    pParse->nMem += nReg;
+  }
+  return i;
+}
+void sqlite3ReleaseTempRange(Parse *pParse, int iReg, int nReg){
+  sqlite3ExprCacheRemove(pParse, iReg, nReg);
+  if( nReg>pParse->nRangeReg ){
+    pParse->nRangeReg = nReg;
+    pParse->iRangeReg = iReg;
+  }
+}
diff --git a/src/fault.c b/src/fault.c
new file mode 100644
index 0000000..c3028c4
--- /dev/null
+++ b/src/fault.c
@@ -0,0 +1,87 @@
+/*
+** 2008 Jan 22
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains code to support the concept of "benign" 
+** malloc failures (when the xMalloc() or xRealloc() method of the
+** sqlite3_mem_methods structure fails to allocate a block of memory
+** and returns 0). 
+**
+** Most malloc failures are non-benign. After they occur, SQLite
+** abandons the current operation and returns an error code (usually
+** SQLITE_NOMEM) to the user. However, sometimes a fault is not necessarily
+** fatal. For example, if a malloc fails while resizing a hash table, this 
+** is completely recoverable simply by not carrying out the resize. The 
+** hash table will continue to function normally.  So a malloc failure 
+** during a hash table resize is a benign fault.
+*/
+
+#include "sqliteInt.h"
+
+#ifndef SQLITE_OMIT_BUILTIN_TEST
+
+/*
+** Global variables.
+*/
+typedef struct BenignMallocHooks BenignMallocHooks;
+static SQLITE_WSD struct BenignMallocHooks {
+  void (*xBenignBegin)(void);
+  void (*xBenignEnd)(void);
+} sqlite3Hooks = { 0, 0 };
+
+/* The "wsdHooks" macro will resolve to the appropriate BenignMallocHooks
+** structure.  If writable static data is unsupported on the target,
+** we have to locate the state vector at run-time.  In the more common
+** case where writable static data is supported, wsdHooks can refer directly
+** to the "sqlite3Hooks" state vector declared above.
+*/
+#ifdef SQLITE_OMIT_WSD
+# define wsdHooksInit \
+  BenignMallocHooks *x = &GLOBAL(BenignMallocHooks,sqlite3Hooks)
+# define wsdHooks x[0]
+#else
+# define wsdHooksInit
+# define wsdHooks sqlite3Hooks
+#endif
+
+
+/*
+** Register hooks to call when sqlite3BeginBenignMalloc() and
+** sqlite3EndBenignMalloc() are called, respectively.
+*/
+void sqlite3BenignMallocHooks(
+  void (*xBenignBegin)(void),
+  void (*xBenignEnd)(void)
+){
+  wsdHooksInit;
+  wsdHooks.xBenignBegin = xBenignBegin;
+  wsdHooks.xBenignEnd = xBenignEnd;
+}
+
+/*
+** This (sqlite3EndBenignMalloc()) is called by SQLite code to indicate that
+** subsequent malloc failures are benign. A call to sqlite3EndBenignMalloc()
+** indicates that subsequent malloc failures are non-benign.
+*/
+void sqlite3BeginBenignMalloc(void){
+  wsdHooksInit;
+  if( wsdHooks.xBenignBegin ){
+    wsdHooks.xBenignBegin();
+  }
+}
+void sqlite3EndBenignMalloc(void){
+  wsdHooksInit;
+  if( wsdHooks.xBenignEnd ){
+    wsdHooks.xBenignEnd();
+  }
+}
+
+#endif   /* #ifndef SQLITE_OMIT_BUILTIN_TEST */
diff --git a/src/fkey.c b/src/fkey.c
new file mode 100644
index 0000000..82e4cdc
--- /dev/null
+++ b/src/fkey.c
@@ -0,0 +1,1219 @@
+/*
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains code used by the compiler to add foreign key
+** support to compiled SQL statements.
+*/
+#include "sqliteInt.h"
+
+#ifndef SQLITE_OMIT_FOREIGN_KEY
+#ifndef SQLITE_OMIT_TRIGGER
+
+/*
+** Deferred and Immediate FKs
+** --------------------------
+**
+** Foreign keys in SQLite come in two flavours: deferred and immediate.
+** If an immediate foreign key constraint is violated, SQLITE_CONSTRAINT
+** is returned and the current statement transaction rolled back. If a 
+** deferred foreign key constraint is violated, no action is taken 
+** immediately. However if the application attempts to commit the 
+** transaction before fixing the constraint violation, the attempt fails.
+**
+** Deferred constraints are implemented using a simple counter associated
+** with the database handle. The counter is set to zero each time a 
+** database transaction is opened. Each time a statement is executed 
+** that causes a foreign key violation, the counter is incremented. Each
+** time a statement is executed that removes an existing violation from
+** the database, the counter is decremented. When the transaction is
+** committed, the commit fails if the current value of the counter is
+** greater than zero. This scheme has two big drawbacks:
+**
+**   * When a commit fails due to a deferred foreign key constraint, 
+**     there is no way to tell which foreign constraint is not satisfied,
+**     or which row it is not satisfied for.
+**
+**   * If the database contains foreign key violations when the 
+**     transaction is opened, this may cause the mechanism to malfunction.
+**
+** Despite these problems, this approach is adopted as it seems simpler
+** than the alternatives.
+**
+** INSERT operations:
+**
+**   I.1) For each FK for which the table is the child table, search
+**        the parent table for a match. If none is found increment the
+**        constraint counter.
+**
+**   I.2) For each FK for which the table is the parent table, 
+**        search the child table for rows that correspond to the new
+**        row in the parent table. Decrement the counter for each row
+**        found (as the constraint is now satisfied).
+**
+** DELETE operations:
+**
+**   D.1) For each FK for which the table is the child table, 
+**        search the parent table for a row that corresponds to the 
+**        deleted row in the child table. If such a row is not found, 
+**        decrement the counter.
+**
+**   D.2) For each FK for which the table is the parent table, search 
+**        the child table for rows that correspond to the deleted row 
+**        in the parent table. For each found increment the counter.
+**
+** UPDATE operations:
+**
+**   An UPDATE command requires that all 4 steps above are taken, but only
+**   for FK constraints for which the affected columns are actually 
+**   modified (values must be compared at runtime).
+**
+** Note that I.1 and D.1 are very similar operations, as are I.2 and D.2.
+** This simplifies the implementation a bit.
+**
+** For the purposes of immediate FK constraints, the OR REPLACE conflict
+** resolution is considered to delete rows before the new row is inserted.
+** If a delete caused by OR REPLACE violates an FK constraint, an exception
+** is thrown, even if the FK constraint would be satisfied after the new 
+** row is inserted.
+**
+** Immediate constraints are usually handled similarly. The only difference 
+** is that the counter used is stored as part of each individual statement
+** object (struct Vdbe). If, after the statement has run, its immediate
+** constraint counter is greater than zero, it returns SQLITE_CONSTRAINT
+** and the statement transaction is rolled back. An exception is an INSERT
+** statement that inserts a single row only (no triggers). In this case,
+** instead of using a counter, an exception is thrown immediately if the
+** INSERT violates a foreign key constraint. This is necessary as such
+** an INSERT does not open a statement transaction.
+**
+** TODO: How should dropping a table be handled? How should renaming a 
+** table be handled?
+**
+**
+** Query API Notes
+** ---------------
+**
+** Before coding an UPDATE or DELETE row operation, the code-generator
+** for those two operations needs to know whether or not the operation
+** requires any FK processing and, if so, which columns of the original
+** row are required by the FK processing VDBE code (i.e. if FKs were
+** implemented using triggers, which of the old.* columns would be 
+** accessed). No information is required by the code-generator before
+** coding an INSERT operation. The functions used by the UPDATE/DELETE
+** generation code to query for this information are:
+**
+**   sqlite3FkRequired() - Test to see if FK processing is required.
+**   sqlite3FkOldmask()  - Query for the set of required old.* columns.
+**
+**
+** Externally accessible module functions
+** --------------------------------------
+**
+**   sqlite3FkCheck()    - Check for foreign key violations.
+**   sqlite3FkActions()  - Code triggers for ON UPDATE/ON DELETE actions.
+**   sqlite3FkDelete()   - Delete an FKey structure.
+*/
+
+/*
+** VDBE Calling Convention
+** -----------------------
+**
+** Example:
+**
+**   For the following INSERT statement:
+**
+**     CREATE TABLE t1(a, b INTEGER PRIMARY KEY, c);
+**     INSERT INTO t1 VALUES(1, 2, 3.1);
+**
+**   Register (x):        2    (type integer)
+**   Register (x+1):      1    (type integer)
+**   Register (x+2):      NULL (type NULL)
+**   Register (x+3):      3.1  (type real)
+*/
+
+/*
+** A foreign key constraint requires that the key columns in the parent
+** table are collectively subject to a UNIQUE or PRIMARY KEY constraint.
+** Given that pParent is the parent table for foreign key constraint pFKey, 
+** search the schema a unique index on the parent key columns. 
+**
+** If successful, zero is returned. If the parent key is an INTEGER PRIMARY 
+** KEY column, then output variable *ppIdx is set to NULL. Otherwise, *ppIdx 
+** is set to point to the unique index. 
+** 
+** If the parent key consists of a single column (the foreign key constraint
+** is not a composite foreign key), output variable *paiCol is set to NULL.
+** Otherwise, it is set to point to an allocated array of size N, where
+** N is the number of columns in the parent key. The first element of the
+** array is the index of the child table column that is mapped by the FK
+** constraint to the parent table column stored in the left-most column
+** of index *ppIdx. The second element of the array is the index of the
+** child table column that corresponds to the second left-most column of
+** *ppIdx, and so on.
+**
+** If the required index cannot be found, either because:
+**
+**   1) The named parent key columns do not exist, or
+**
+**   2) The named parent key columns do exist, but are not subject to a
+**      UNIQUE or PRIMARY KEY constraint, or
+**
+**   3) No parent key columns were provided explicitly as part of the
+**      foreign key definition, and the parent table does not have a
+**      PRIMARY KEY, or
+**
+**   4) No parent key columns were provided explicitly as part of the
+**      foreign key definition, and the PRIMARY KEY of the parent table 
+**      consists of a a different number of columns to the child key in 
+**      the child table.
+**
+** then non-zero is returned, and a "foreign key mismatch" error loaded
+** into pParse. If an OOM error occurs, non-zero is returned and the
+** pParse->db->mallocFailed flag is set.
+*/
+static int locateFkeyIndex(
+  Parse *pParse,                  /* Parse context to store any error in */
+  Table *pParent,                 /* Parent table of FK constraint pFKey */
+  FKey *pFKey,                    /* Foreign key to find index for */
+  Index **ppIdx,                  /* OUT: Unique index on parent table */
+  int **paiCol                    /* OUT: Map of index columns in pFKey */
+){
+  Index *pIdx = 0;                    /* Value to return via *ppIdx */
+  int *aiCol = 0;                     /* Value to return via *paiCol */
+  int nCol = pFKey->nCol;             /* Number of columns in parent key */
+  char *zKey = pFKey->aCol[0].zCol;   /* Name of left-most parent key column */
+
+  /* The caller is responsible for zeroing output parameters. */
+  assert( ppIdx && *ppIdx==0 );
+  assert( !paiCol || *paiCol==0 );
+  assert( pParse );
+
+  /* If this is a non-composite (single column) foreign key, check if it 
+  ** maps to the INTEGER PRIMARY KEY of table pParent. If so, leave *ppIdx 
+  ** and *paiCol set to zero and return early. 
+  **
+  ** Otherwise, for a composite foreign key (more than one column), allocate
+  ** space for the aiCol array (returned via output parameter *paiCol).
+  ** Non-composite foreign keys do not require the aiCol array.
+  */
+  if( nCol==1 ){
+    /* The FK maps to the IPK if any of the following are true:
+    **
+    **   1) There is an INTEGER PRIMARY KEY column and the FK is implicitly 
+    **      mapped to the primary key of table pParent, or
+    **   2) The FK is explicitly mapped to a column declared as INTEGER
+    **      PRIMARY KEY.
+    */
+    if( pParent->iPKey>=0 ){
+      if( !zKey ) return 0;
+      if( !sqlite3StrICmp(pParent->aCol[pParent->iPKey].zName, zKey) ) return 0;
+    }
+  }else if( paiCol ){
+    assert( nCol>1 );
+    aiCol = (int *)sqlite3DbMallocRaw(pParse->db, nCol*sizeof(int));
+    if( !aiCol ) return 1;
+    *paiCol = aiCol;
+  }
+
+  for(pIdx=pParent->pIndex; pIdx; pIdx=pIdx->pNext){
+    if( pIdx->nColumn==nCol && pIdx->onError!=OE_None ){ 
+      /* pIdx is a UNIQUE index (or a PRIMARY KEY) and has the right number
+      ** of columns. If each indexed column corresponds to a foreign key
+      ** column of pFKey, then this index is a winner.  */
+
+      if( zKey==0 ){
+        /* If zKey is NULL, then this foreign key is implicitly mapped to 
+        ** the PRIMARY KEY of table pParent. The PRIMARY KEY index may be 
+        ** identified by the test (Index.autoIndex==2).  */
+        if( pIdx->autoIndex==2 ){
+          if( aiCol ){
+            int i;
+            for(i=0; i<nCol; i++) aiCol[i] = pFKey->aCol[i].iFrom;
+          }
+          break;
+        }
+      }else{
+        /* If zKey is non-NULL, then this foreign key was declared to
+        ** map to an explicit list of columns in table pParent. Check if this
+        ** index matches those columns. Also, check that the index uses
+        ** the default collation sequences for each column. */
+        int i, j;
+        for(i=0; i<nCol; i++){
+          int iCol = pIdx->aiColumn[i];     /* Index of column in parent tbl */
+          char *zDfltColl;                  /* Def. collation for column */
+          char *zIdxCol;                    /* Name of indexed column */
+
+          /* If the index uses a collation sequence that is different from
+          ** the default collation sequence for the column, this index is
+          ** unusable. Bail out early in this case.  */
+          zDfltColl = pParent->aCol[iCol].zColl;
+          if( !zDfltColl ){
+            zDfltColl = "BINARY";
+          }
+          if( sqlite3StrICmp(pIdx->azColl[i], zDfltColl) ) break;
+
+          zIdxCol = pParent->aCol[iCol].zName;
+          for(j=0; j<nCol; j++){
+            if( sqlite3StrICmp(pFKey->aCol[j].zCol, zIdxCol)==0 ){
+              if( aiCol ) aiCol[i] = pFKey->aCol[j].iFrom;
+              break;
+            }
+          }
+          if( j==nCol ) break;
+        }
+        if( i==nCol ) break;      /* pIdx is usable */
+      }
+    }
+  }
+
+  if( !pIdx ){
+    if( !pParse->disableTriggers ){
+      sqlite3ErrorMsg(pParse, "foreign key mismatch");
+    }
+    sqlite3DbFree(pParse->db, aiCol);
+    return 1;
+  }
+
+  *ppIdx = pIdx;
+  return 0;
+}
+
+/*
+** This function is called when a row is inserted into or deleted from the 
+** child table of foreign key constraint pFKey. If an SQL UPDATE is executed 
+** on the child table of pFKey, this function is invoked twice for each row
+** affected - once to "delete" the old row, and then again to "insert" the
+** new row.
+**
+** Each time it is called, this function generates VDBE code to locate the
+** row in the parent table that corresponds to the row being inserted into 
+** or deleted from the child table. If the parent row can be found, no 
+** special action is taken. Otherwise, if the parent row can *not* be
+** found in the parent table:
+**
+**   Operation | FK type   | Action taken
+**   --------------------------------------------------------------------------
+**   INSERT      immediate   Increment the "immediate constraint counter".
+**
+**   DELETE      immediate   Decrement the "immediate constraint counter".
+**
+**   INSERT      deferred    Increment the "deferred constraint counter".
+**
+**   DELETE      deferred    Decrement the "deferred constraint counter".
+**
+** These operations are identified in the comment at the top of this file 
+** (fkey.c) as "I.1" and "D.1".
+*/
+static void fkLookupParent(
+  Parse *pParse,        /* Parse context */
+  int iDb,              /* Index of database housing pTab */
+  Table *pTab,          /* Parent table of FK pFKey */
+  Index *pIdx,          /* Unique index on parent key columns in pTab */
+  FKey *pFKey,          /* Foreign key constraint */
+  int *aiCol,           /* Map from parent key columns to child table columns */
+  int regData,          /* Address of array containing child table row */
+  int nIncr,            /* Increment constraint counter by this */
+  int isIgnore          /* If true, pretend pTab contains all NULL values */
+){
+  int i;                                    /* Iterator variable */
+  Vdbe *v = sqlite3GetVdbe(pParse);         /* Vdbe to add code to */
+  int iCur = pParse->nTab - 1;              /* Cursor number to use */
+  int iOk = sqlite3VdbeMakeLabel(v);        /* jump here if parent key found */
+
+  /* If nIncr is less than zero, then check at runtime if there are any
+  ** outstanding constraints to resolve. If there are not, there is no need
+  ** to check if deleting this row resolves any outstanding violations.
+  **
+  ** Check if any of the key columns in the child table row are NULL. If 
+  ** any are, then the constraint is considered satisfied. No need to 
+  ** search for a matching row in the parent table.  */
+  if( nIncr<0 ){
+    sqlite3VdbeAddOp2(v, OP_FkIfZero, pFKey->isDeferred, iOk);
+  }
+  for(i=0; i<pFKey->nCol; i++){
+    int iReg = aiCol[i] + regData + 1;
+    sqlite3VdbeAddOp2(v, OP_IsNull, iReg, iOk);
+  }
+
+  if( isIgnore==0 ){
+    if( pIdx==0 ){
+      /* If pIdx is NULL, then the parent key is the INTEGER PRIMARY KEY
+      ** column of the parent table (table pTab).  */
+      int iMustBeInt;               /* Address of MustBeInt instruction */
+      int regTemp = sqlite3GetTempReg(pParse);
+  
+      /* Invoke MustBeInt to coerce the child key value to an integer (i.e. 
+      ** apply the affinity of the parent key). If this fails, then there
+      ** is no matching parent key. Before using MustBeInt, make a copy of
+      ** the value. Otherwise, the value inserted into the child key column
+      ** will have INTEGER affinity applied to it, which may not be correct.  */
+      sqlite3VdbeAddOp2(v, OP_SCopy, aiCol[0]+1+regData, regTemp);
+      iMustBeInt = sqlite3VdbeAddOp2(v, OP_MustBeInt, regTemp, 0);
+  
+      /* If the parent table is the same as the child table, and we are about
+      ** to increment the constraint-counter (i.e. this is an INSERT operation),
+      ** then check if the row being inserted matches itself. If so, do not
+      ** increment the constraint-counter.  */
+      if( pTab==pFKey->pFrom && nIncr==1 ){
+        sqlite3VdbeAddOp3(v, OP_Eq, regData, iOk, regTemp);
+      }
+  
+      sqlite3OpenTable(pParse, iCur, iDb, pTab, OP_OpenRead);
+      sqlite3VdbeAddOp3(v, OP_NotExists, iCur, 0, regTemp);
+      sqlite3VdbeAddOp2(v, OP_Goto, 0, iOk);
+      sqlite3VdbeJumpHere(v, sqlite3VdbeCurrentAddr(v)-2);
+      sqlite3VdbeJumpHere(v, iMustBeInt);
+      sqlite3ReleaseTempReg(pParse, regTemp);
+    }else{
+      int nCol = pFKey->nCol;
+      int regTemp = sqlite3GetTempRange(pParse, nCol);
+      int regRec = sqlite3GetTempReg(pParse);
+      KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIdx);
+  
+      sqlite3VdbeAddOp3(v, OP_OpenRead, iCur, pIdx->tnum, iDb);
+      sqlite3VdbeChangeP4(v, -1, (char*)pKey, P4_KEYINFO_HANDOFF);
+      for(i=0; i<nCol; i++){
+        sqlite3VdbeAddOp2(v, OP_Copy, aiCol[i]+1+regData, regTemp+i);
+      }
+  
+      /* If the parent table is the same as the child table, and we are about
+      ** to increment the constraint-counter (i.e. this is an INSERT operation),
+      ** then check if the row being inserted matches itself. If so, do not
+      ** increment the constraint-counter. 
+      **
+      ** If any of the parent-key values are NULL, then the row cannot match 
+      ** itself. So set JUMPIFNULL to make sure we do the OP_Found if any
+      ** of the parent-key values are NULL (at this point it is known that
+      ** none of the child key values are).
+      */
+      if( pTab==pFKey->pFrom && nIncr==1 ){
+        int iJump = sqlite3VdbeCurrentAddr(v) + nCol + 1;
+        for(i=0; i<nCol; i++){
+          int iChild = aiCol[i]+1+regData;
+          int iParent = pIdx->aiColumn[i]+1+regData;
+          assert( aiCol[i]!=pTab->iPKey );
+          if( pIdx->aiColumn[i]==pTab->iPKey ){
+            /* The parent key is a composite key that includes the IPK column */
+            iParent = regData;
+          }
+          sqlite3VdbeAddOp3(v, OP_Ne, iChild, iJump, iParent);
+          sqlite3VdbeChangeP5(v, SQLITE_JUMPIFNULL);
+        }
+        sqlite3VdbeAddOp2(v, OP_Goto, 0, iOk);
+      }
+  
+      sqlite3VdbeAddOp3(v, OP_MakeRecord, regTemp, nCol, regRec);
+      sqlite3VdbeChangeP4(v, -1, sqlite3IndexAffinityStr(v,pIdx), P4_TRANSIENT);
+      sqlite3VdbeAddOp4Int(v, OP_Found, iCur, iOk, regRec, 0);
+  
+      sqlite3ReleaseTempReg(pParse, regRec);
+      sqlite3ReleaseTempRange(pParse, regTemp, nCol);
+    }
+  }
+
+  if( !pFKey->isDeferred && !pParse->pToplevel && !pParse->isMultiWrite ){
+    /* Special case: If this is an INSERT statement that will insert exactly
+    ** one row into the table, raise a constraint immediately instead of
+    ** incrementing a counter. This is necessary as the VM code is being
+    ** generated for will not open a statement transaction.  */
+    assert( nIncr==1 );
+    sqlite3HaltConstraint(
+        pParse, OE_Abort, "foreign key constraint failed", P4_STATIC
+    );
+  }else{
+    if( nIncr>0 && pFKey->isDeferred==0 ){
+      sqlite3ParseToplevel(pParse)->mayAbort = 1;
+    }
+    sqlite3VdbeAddOp2(v, OP_FkCounter, pFKey->isDeferred, nIncr);
+  }
+
+  sqlite3VdbeResolveLabel(v, iOk);
+  sqlite3VdbeAddOp1(v, OP_Close, iCur);
+}
+
+/*
+** This function is called to generate code executed when a row is deleted
+** from the parent table of foreign key constraint pFKey and, if pFKey is 
+** deferred, when a row is inserted into the same table. When generating
+** code for an SQL UPDATE operation, this function may be called twice -
+** once to "delete" the old row and once to "insert" the new row.
+**
+** The code generated by this function scans through the rows in the child
+** table that correspond to the parent table row being deleted or inserted.
+** For each child row found, one of the following actions is taken:
+**
+**   Operation | FK type   | Action taken
+**   --------------------------------------------------------------------------
+**   DELETE      immediate   Increment the "immediate constraint counter".
+**                           Or, if the ON (UPDATE|DELETE) action is RESTRICT,
+**                           throw a "foreign key constraint failed" exception.
+**
+**   INSERT      immediate   Decrement the "immediate constraint counter".
+**
+**   DELETE      deferred    Increment the "deferred constraint counter".
+**                           Or, if the ON (UPDATE|DELETE) action is RESTRICT,
+**                           throw a "foreign key constraint failed" exception.
+**
+**   INSERT      deferred    Decrement the "deferred constraint counter".
+**
+** These operations are identified in the comment at the top of this file 
+** (fkey.c) as "I.2" and "D.2".
+*/
+static void fkScanChildren(
+  Parse *pParse,                  /* Parse context */
+  SrcList *pSrc,                  /* SrcList containing the table to scan */
+  Table *pTab,
+  Index *pIdx,                    /* Foreign key index */
+  FKey *pFKey,                    /* Foreign key relationship */
+  int *aiCol,                     /* Map from pIdx cols to child table cols */
+  int regData,                    /* Referenced table data starts here */
+  int nIncr                       /* Amount to increment deferred counter by */
+){
+  sqlite3 *db = pParse->db;       /* Database handle */
+  int i;                          /* Iterator variable */
+  Expr *pWhere = 0;               /* WHERE clause to scan with */
+  NameContext sNameContext;       /* Context used to resolve WHERE clause */
+  WhereInfo *pWInfo;              /* Context used by sqlite3WhereXXX() */
+  int iFkIfZero = 0;              /* Address of OP_FkIfZero */
+  Vdbe *v = sqlite3GetVdbe(pParse);
+
+  assert( !pIdx || pIdx->pTable==pTab );
+
+  if( nIncr<0 ){
+    iFkIfZero = sqlite3VdbeAddOp2(v, OP_FkIfZero, pFKey->isDeferred, 0);
+  }
+
+  /* Create an Expr object representing an SQL expression like:
+  **
+  **   <parent-key1> = <child-key1> AND <parent-key2> = <child-key2> ...
+  **
+  ** The collation sequence used for the comparison should be that of
+  ** the parent key columns. The affinity of the parent key column should
+  ** be applied to each child key value before the comparison takes place.
+  */
+  for(i=0; i<pFKey->nCol; i++){
+    Expr *pLeft;                  /* Value from parent table row */
+    Expr *pRight;                 /* Column ref to child table */
+    Expr *pEq;                    /* Expression (pLeft = pRight) */
+    int iCol;                     /* Index of column in child table */ 
+    const char *zCol;             /* Name of column in child table */
+
+    pLeft = sqlite3Expr(db, TK_REGISTER, 0);
+    if( pLeft ){
+      /* Set the collation sequence and affinity of the LHS of each TK_EQ
+      ** expression to the parent key column defaults.  */
+      if( pIdx ){
+        Column *pCol;
+        iCol = pIdx->aiColumn[i];
+        pCol = &pTab->aCol[iCol];
+        if( pTab->iPKey==iCol ) iCol = -1;
+        pLeft->iTable = regData+iCol+1;
+        pLeft->affinity = pCol->affinity;
+        pLeft->pColl = sqlite3LocateCollSeq(pParse, pCol->zColl);
+      }else{
+        pLeft->iTable = regData;
+        pLeft->affinity = SQLITE_AFF_INTEGER;
+      }
+    }
+    iCol = aiCol ? aiCol[i] : pFKey->aCol[0].iFrom;
+    assert( iCol>=0 );
+    zCol = pFKey->pFrom->aCol[iCol].zName;
+    pRight = sqlite3Expr(db, TK_ID, zCol);
+    pEq = sqlite3PExpr(pParse, TK_EQ, pLeft, pRight, 0);
+    pWhere = sqlite3ExprAnd(db, pWhere, pEq);
+  }
+
+  /* If the child table is the same as the parent table, and this scan
+  ** is taking place as part of a DELETE operation (operation D.2), omit the
+  ** row being deleted from the scan by adding ($rowid != rowid) to the WHERE 
+  ** clause, where $rowid is the rowid of the row being deleted.  */
+  if( pTab==pFKey->pFrom && nIncr>0 ){
+    Expr *pEq;                    /* Expression (pLeft = pRight) */
+    Expr *pLeft;                  /* Value from parent table row */
+    Expr *pRight;                 /* Column ref to child table */
+    pLeft = sqlite3Expr(db, TK_REGISTER, 0);
+    pRight = sqlite3Expr(db, TK_COLUMN, 0);
+    if( pLeft && pRight ){
+      pLeft->iTable = regData;
+      pLeft->affinity = SQLITE_AFF_INTEGER;
+      pRight->iTable = pSrc->a[0].iCursor;
+      pRight->iColumn = -1;
+    }
+    pEq = sqlite3PExpr(pParse, TK_NE, pLeft, pRight, 0);
+    pWhere = sqlite3ExprAnd(db, pWhere, pEq);
+  }
+
+  /* Resolve the references in the WHERE clause. */
+  memset(&sNameContext, 0, sizeof(NameContext));
+  sNameContext.pSrcList = pSrc;
+  sNameContext.pParse = pParse;
+  sqlite3ResolveExprNames(&sNameContext, pWhere);
+
+  /* Create VDBE to loop through the entries in pSrc that match the WHERE
+  ** clause. If the constraint is not deferred, throw an exception for
+  ** each row found. Otherwise, for deferred constraints, increment the
+  ** deferred constraint counter by nIncr for each row selected.  */
+  pWInfo = sqlite3WhereBegin(pParse, pSrc, pWhere, 0, 0, 0);
+  if( nIncr>0 && pFKey->isDeferred==0 ){
+    sqlite3ParseToplevel(pParse)->mayAbort = 1;
+  }
+  sqlite3VdbeAddOp2(v, OP_FkCounter, pFKey->isDeferred, nIncr);
+  if( pWInfo ){
+    sqlite3WhereEnd(pWInfo);
+  }
+
+  /* Clean up the WHERE clause constructed above. */
+  sqlite3ExprDelete(db, pWhere);
+  if( iFkIfZero ){
+    sqlite3VdbeJumpHere(v, iFkIfZero);
+  }
+}
+
+/*
+** This function returns a pointer to the head of a linked list of FK
+** constraints for which table pTab is the parent table. For example,
+** given the following schema:
+**
+**   CREATE TABLE t1(a PRIMARY KEY);
+**   CREATE TABLE t2(b REFERENCES t1(a);
+**
+** Calling this function with table "t1" as an argument returns a pointer
+** to the FKey structure representing the foreign key constraint on table
+** "t2". Calling this function with "t2" as the argument would return a
+** NULL pointer (as there are no FK constraints for which t2 is the parent
+** table).
+*/
+FKey *sqlite3FkReferences(Table *pTab){
+  int nName = sqlite3Strlen30(pTab->zName);
+  return (FKey *)sqlite3HashFind(&pTab->pSchema->fkeyHash, pTab->zName, nName);
+}
+
+/*
+** The second argument is a Trigger structure allocated by the 
+** fkActionTrigger() routine. This function deletes the Trigger structure
+** and all of its sub-components.
+**
+** The Trigger structure or any of its sub-components may be allocated from
+** the lookaside buffer belonging to database handle dbMem.
+*/
+static void fkTriggerDelete(sqlite3 *dbMem, Trigger *p){
+  if( p ){
+    TriggerStep *pStep = p->step_list;
+    sqlite3ExprDelete(dbMem, pStep->pWhere);
+    sqlite3ExprListDelete(dbMem, pStep->pExprList);
+    sqlite3SelectDelete(dbMem, pStep->pSelect);
+    sqlite3ExprDelete(dbMem, p->pWhen);
+    sqlite3DbFree(dbMem, p);
+  }
+}
+
+/*
+** This function is called to generate code that runs when table pTab is
+** being dropped from the database. The SrcList passed as the second argument
+** to this function contains a single entry guaranteed to resolve to
+** table pTab.
+**
+** Normally, no code is required. However, if either
+**
+**   (a) The table is the parent table of a FK constraint, or
+**   (b) The table is the child table of a deferred FK constraint and it is
+**       determined at runtime that there are outstanding deferred FK 
+**       constraint violations in the database,
+**
+** then the equivalent of "DELETE FROM <tbl>" is executed before dropping
+** the table from the database. Triggers are disabled while running this
+** DELETE, but foreign key actions are not.
+*/
+void sqlite3FkDropTable(Parse *pParse, SrcList *pName, Table *pTab){
+  sqlite3 *db = pParse->db;
+  if( (db->flags&SQLITE_ForeignKeys) && !IsVirtual(pTab) && !pTab->pSelect ){
+    int iSkip = 0;
+    Vdbe *v = sqlite3GetVdbe(pParse);
+
+    assert( v );                  /* VDBE has already been allocated */
+    if( sqlite3FkReferences(pTab)==0 ){
+      /* Search for a deferred foreign key constraint for which this table
+      ** is the child table. If one cannot be found, return without 
+      ** generating any VDBE code. If one can be found, then jump over
+      ** the entire DELETE if there are no outstanding deferred constraints
+      ** when this statement is run.  */
+      FKey *p;
+      for(p=pTab->pFKey; p; p=p->pNextFrom){
+        if( p->isDeferred ) break;
+      }
+      if( !p ) return;
+      iSkip = sqlite3VdbeMakeLabel(v);
+      sqlite3VdbeAddOp2(v, OP_FkIfZero, 1, iSkip);
+    }
+
+    pParse->disableTriggers = 1;
+    sqlite3DeleteFrom(pParse, sqlite3SrcListDup(db, pName, 0), 0);
+    pParse->disableTriggers = 0;
+
+    /* If the DELETE has generated immediate foreign key constraint 
+    ** violations, halt the VDBE and return an error at this point, before
+    ** any modifications to the schema are made. This is because statement
+    ** transactions are not able to rollback schema changes.  */
+    sqlite3VdbeAddOp2(v, OP_FkIfZero, 0, sqlite3VdbeCurrentAddr(v)+2);
+    sqlite3HaltConstraint(
+        pParse, OE_Abort, "foreign key constraint failed", P4_STATIC
+    );
+
+    if( iSkip ){
+      sqlite3VdbeResolveLabel(v, iSkip);
+    }
+  }
+}
+
+/*
+** This function is called when inserting, deleting or updating a row of
+** table pTab to generate VDBE code to perform foreign key constraint 
+** processing for the operation.
+**
+** For a DELETE operation, parameter regOld is passed the index of the
+** first register in an array of (pTab->nCol+1) registers containing the
+** rowid of the row being deleted, followed by each of the column values
+** of the row being deleted, from left to right. Parameter regNew is passed
+** zero in this case.
+**
+** For an INSERT operation, regOld is passed zero and regNew is passed the
+** first register of an array of (pTab->nCol+1) registers containing the new
+** row data.
+**
+** For an UPDATE operation, this function is called twice. Once before
+** the original record is deleted from the table using the calling convention
+** described for DELETE. Then again after the original record is deleted
+** but before the new record is inserted using the INSERT convention. 
+*/
+void sqlite3FkCheck(
+  Parse *pParse,                  /* Parse context */
+  Table *pTab,                    /* Row is being deleted from this table */ 
+  int regOld,                     /* Previous row data is stored here */
+  int regNew                      /* New row data is stored here */
+){
+  sqlite3 *db = pParse->db;       /* Database handle */
+  FKey *pFKey;                    /* Used to iterate through FKs */
+  int iDb;                        /* Index of database containing pTab */
+  const char *zDb;                /* Name of database containing pTab */
+  int isIgnoreErrors = pParse->disableTriggers;
+
+  /* Exactly one of regOld and regNew should be non-zero. */
+  assert( (regOld==0)!=(regNew==0) );
+
+  /* If foreign-keys are disabled, this function is a no-op. */
+  if( (db->flags&SQLITE_ForeignKeys)==0 ) return;
+
+  iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+  zDb = db->aDb[iDb].zName;
+
+  /* Loop through all the foreign key constraints for which pTab is the
+  ** child table (the table that the foreign key definition is part of).  */
+  for(pFKey=pTab->pFKey; pFKey; pFKey=pFKey->pNextFrom){
+    Table *pTo;                   /* Parent table of foreign key pFKey */
+    Index *pIdx = 0;              /* Index on key columns in pTo */
+    int *aiFree = 0;
+    int *aiCol;
+    int iCol;
+    int i;
+    int isIgnore = 0;
+
+    /* Find the parent table of this foreign key. Also find a unique index 
+    ** on the parent key columns in the parent table. If either of these 
+    ** schema items cannot be located, set an error in pParse and return 
+    ** early.  */
+    if( pParse->disableTriggers ){
+      pTo = sqlite3FindTable(db, pFKey->zTo, zDb);
+    }else{
+      pTo = sqlite3LocateTable(pParse, 0, pFKey->zTo, zDb);
+    }
+    if( !pTo || locateFkeyIndex(pParse, pTo, pFKey, &pIdx, &aiFree) ){
+      assert( isIgnoreErrors==0 || (regOld!=0 && regNew==0) );
+      if( !isIgnoreErrors || db->mallocFailed ) return;
+      if( pTo==0 ){
+        /* If isIgnoreErrors is true, then a table is being dropped. In this
+        ** case SQLite runs a "DELETE FROM xxx" on the table being dropped
+        ** before actually dropping it in order to check FK constraints.
+        ** If the parent table of an FK constraint on the current table is
+        ** missing, behave as if it is empty. i.e. decrement the relevant
+        ** FK counter for each row of the current table with non-NULL keys.
+        */
+        Vdbe *v = sqlite3GetVdbe(pParse);
+        int iJump = sqlite3VdbeCurrentAddr(v) + pFKey->nCol + 1;
+        for(i=0; i<pFKey->nCol; i++){
+          int iReg = pFKey->aCol[i].iFrom + regOld + 1;
+          sqlite3VdbeAddOp2(v, OP_IsNull, iReg, iJump);
+        }
+        sqlite3VdbeAddOp2(v, OP_FkCounter, pFKey->isDeferred, -1);
+      }
+      continue;
+    }
+    assert( pFKey->nCol==1 || (aiFree && pIdx) );
+
+    if( aiFree ){
+      aiCol = aiFree;
+    }else{
+      iCol = pFKey->aCol[0].iFrom;
+      aiCol = &iCol;
+    }
+    for(i=0; i<pFKey->nCol; i++){
+      if( aiCol[i]==pTab->iPKey ){
+        aiCol[i] = -1;
+      }
+#ifndef SQLITE_OMIT_AUTHORIZATION
+      /* Request permission to read the parent key columns. If the 
+      ** authorization callback returns SQLITE_IGNORE, behave as if any
+      ** values read from the parent table are NULL. */
+      if( db->xAuth ){
+        int rcauth;
+        char *zCol = pTo->aCol[pIdx ? pIdx->aiColumn[i] : pTo->iPKey].zName;
+        rcauth = sqlite3AuthReadCol(pParse, pTo->zName, zCol, iDb);
+        isIgnore = (rcauth==SQLITE_IGNORE);
+      }
+#endif
+    }
+
+    /* Take a shared-cache advisory read-lock on the parent table. Allocate 
+    ** a cursor to use to search the unique index on the parent key columns 
+    ** in the parent table.  */
+    sqlite3TableLock(pParse, iDb, pTo->tnum, 0, pTo->zName);
+    pParse->nTab++;
+
+    if( regOld!=0 ){
+      /* A row is being removed from the child table. Search for the parent.
+      ** If the parent does not exist, removing the child row resolves an 
+      ** outstanding foreign key constraint violation. */
+      fkLookupParent(pParse, iDb, pTo, pIdx, pFKey, aiCol, regOld, -1,isIgnore);
+    }
+    if( regNew!=0 ){
+      /* A row is being added to the child table. If a parent row cannot
+      ** be found, adding the child row has violated the FK constraint. */ 
+      fkLookupParent(pParse, iDb, pTo, pIdx, pFKey, aiCol, regNew, +1,isIgnore);
+    }
+
+    sqlite3DbFree(db, aiFree);
+  }
+
+  /* Loop through all the foreign key constraints that refer to this table */
+  for(pFKey = sqlite3FkReferences(pTab); pFKey; pFKey=pFKey->pNextTo){
+    Index *pIdx = 0;              /* Foreign key index for pFKey */
+    SrcList *pSrc;
+    int *aiCol = 0;
+
+    if( !pFKey->isDeferred && !pParse->pToplevel && !pParse->isMultiWrite ){
+      assert( regOld==0 && regNew!=0 );
+      /* Inserting a single row into a parent table cannot cause an immediate
+      ** foreign key violation. So do nothing in this case.  */
+      continue;
+    }
+
+    if( locateFkeyIndex(pParse, pTab, pFKey, &pIdx, &aiCol) ){
+      if( !isIgnoreErrors || db->mallocFailed ) return;
+      continue;
+    }
+    assert( aiCol || pFKey->nCol==1 );
+
+    /* Create a SrcList structure containing a single table (the table 
+    ** the foreign key that refers to this table is attached to). This
+    ** is required for the sqlite3WhereXXX() interface.  */
+    pSrc = sqlite3SrcListAppend(db, 0, 0, 0);
+    if( pSrc ){
+      struct SrcList_item *pItem = pSrc->a;
+      pItem->pTab = pFKey->pFrom;
+      pItem->zName = pFKey->pFrom->zName;
+      pItem->pTab->nRef++;
+      pItem->iCursor = pParse->nTab++;
+  
+      if( regNew!=0 ){
+        fkScanChildren(pParse, pSrc, pTab, pIdx, pFKey, aiCol, regNew, -1);
+      }
+      if( regOld!=0 ){
+        /* If there is a RESTRICT action configured for the current operation
+        ** on the parent table of this FK, then throw an exception 
+        ** immediately if the FK constraint is violated, even if this is a
+        ** deferred trigger. That's what RESTRICT means. To defer checking
+        ** the constraint, the FK should specify NO ACTION (represented
+        ** using OE_None). NO ACTION is the default.  */
+        fkScanChildren(pParse, pSrc, pTab, pIdx, pFKey, aiCol, regOld, 1);
+      }
+      pItem->zName = 0;
+      sqlite3SrcListDelete(db, pSrc);
+    }
+    sqlite3DbFree(db, aiCol);
+  }
+}
+
+#define COLUMN_MASK(x) (((x)>31) ? 0xffffffff : ((u32)1<<(x)))
+
+/*
+** This function is called before generating code to update or delete a 
+** row contained in table pTab.
+*/
+u32 sqlite3FkOldmask(
+  Parse *pParse,                  /* Parse context */
+  Table *pTab                     /* Table being modified */
+){
+  u32 mask = 0;
+  if( pParse->db->flags&SQLITE_ForeignKeys ){
+    FKey *p;
+    int i;
+    for(p=pTab->pFKey; p; p=p->pNextFrom){
+      for(i=0; i<p->nCol; i++) mask |= COLUMN_MASK(p->aCol[i].iFrom);
+    }
+    for(p=sqlite3FkReferences(pTab); p; p=p->pNextTo){
+      Index *pIdx = 0;
+      locateFkeyIndex(pParse, pTab, p, &pIdx, 0);
+      if( pIdx ){
+        for(i=0; i<pIdx->nColumn; i++) mask |= COLUMN_MASK(pIdx->aiColumn[i]);
+      }
+    }
+  }
+  return mask;
+}
+
+/*
+** This function is called before generating code to update or delete a 
+** row contained in table pTab. If the operation is a DELETE, then
+** parameter aChange is passed a NULL value. For an UPDATE, aChange points
+** to an array of size N, where N is the number of columns in table pTab.
+** If the i'th column is not modified by the UPDATE, then the corresponding 
+** entry in the aChange[] array is set to -1. If the column is modified,
+** the value is 0 or greater. Parameter chngRowid is set to true if the
+** UPDATE statement modifies the rowid fields of the table.
+**
+** If any foreign key processing will be required, this function returns
+** true. If there is no foreign key related processing, this function 
+** returns false.
+*/
+int sqlite3FkRequired(
+  Parse *pParse,                  /* Parse context */
+  Table *pTab,                    /* Table being modified */
+  int *aChange,                   /* Non-NULL for UPDATE operations */
+  int chngRowid                   /* True for UPDATE that affects rowid */
+){
+  if( pParse->db->flags&SQLITE_ForeignKeys ){
+    if( !aChange ){
+      /* A DELETE operation. Foreign key processing is required if the 
+      ** table in question is either the child or parent table for any 
+      ** foreign key constraint.  */
+      return (sqlite3FkReferences(pTab) || pTab->pFKey);
+    }else{
+      /* This is an UPDATE. Foreign key processing is only required if the
+      ** operation modifies one or more child or parent key columns. */
+      int i;
+      FKey *p;
+
+      /* Check if any child key columns are being modified. */
+      for(p=pTab->pFKey; p; p=p->pNextFrom){
+        for(i=0; i<p->nCol; i++){
+          int iChildKey = p->aCol[i].iFrom;
+          if( aChange[iChildKey]>=0 ) return 1;
+          if( iChildKey==pTab->iPKey && chngRowid ) return 1;
+        }
+      }
+
+      /* Check if any parent key columns are being modified. */
+      for(p=sqlite3FkReferences(pTab); p; p=p->pNextTo){
+        for(i=0; i<p->nCol; i++){
+          char *zKey = p->aCol[i].zCol;
+          int iKey;
+          for(iKey=0; iKey<pTab->nCol; iKey++){
+            Column *pCol = &pTab->aCol[iKey];
+            if( (zKey ? !sqlite3StrICmp(pCol->zName, zKey) : pCol->isPrimKey) ){
+              if( aChange[iKey]>=0 ) return 1;
+              if( iKey==pTab->iPKey && chngRowid ) return 1;
+            }
+          }
+        }
+      }
+    }
+  }
+  return 0;
+}
+
+/*
+** This function is called when an UPDATE or DELETE operation is being 
+** compiled on table pTab, which is the parent table of foreign-key pFKey.
+** If the current operation is an UPDATE, then the pChanges parameter is
+** passed a pointer to the list of columns being modified. If it is a
+** DELETE, pChanges is passed a NULL pointer.
+**
+** It returns a pointer to a Trigger structure containing a trigger
+** equivalent to the ON UPDATE or ON DELETE action specified by pFKey.
+** If the action is "NO ACTION" or "RESTRICT", then a NULL pointer is
+** returned (these actions require no special handling by the triggers
+** sub-system, code for them is created by fkScanChildren()).
+**
+** For example, if pFKey is the foreign key and pTab is table "p" in 
+** the following schema:
+**
+**   CREATE TABLE p(pk PRIMARY KEY);
+**   CREATE TABLE c(ck REFERENCES p ON DELETE CASCADE);
+**
+** then the returned trigger structure is equivalent to:
+**
+**   CREATE TRIGGER ... DELETE ON p BEGIN
+**     DELETE FROM c WHERE ck = old.pk;
+**   END;
+**
+** The returned pointer is cached as part of the foreign key object. It
+** is eventually freed along with the rest of the foreign key object by 
+** sqlite3FkDelete().
+*/
+static Trigger *fkActionTrigger(
+  Parse *pParse,                  /* Parse context */
+  Table *pTab,                    /* Table being updated or deleted from */
+  FKey *pFKey,                    /* Foreign key to get action for */
+  ExprList *pChanges              /* Change-list for UPDATE, NULL for DELETE */
+){
+  sqlite3 *db = pParse->db;       /* Database handle */
+  int action;                     /* One of OE_None, OE_Cascade etc. */
+  Trigger *pTrigger;              /* Trigger definition to return */
+  int iAction = (pChanges!=0);    /* 1 for UPDATE, 0 for DELETE */
+
+  action = pFKey->aAction[iAction];
+  pTrigger = pFKey->apTrigger[iAction];
+
+  if( action!=OE_None && !pTrigger ){
+    u8 enableLookaside;           /* Copy of db->lookaside.bEnabled */
+    char const *zFrom;            /* Name of child table */
+    int nFrom;                    /* Length in bytes of zFrom */
+    Index *pIdx = 0;              /* Parent key index for this FK */
+    int *aiCol = 0;               /* child table cols -> parent key cols */
+    TriggerStep *pStep = 0;        /* First (only) step of trigger program */
+    Expr *pWhere = 0;             /* WHERE clause of trigger step */
+    ExprList *pList = 0;          /* Changes list if ON UPDATE CASCADE */
+    Select *pSelect = 0;          /* If RESTRICT, "SELECT RAISE(...)" */
+    int i;                        /* Iterator variable */
+    Expr *pWhen = 0;              /* WHEN clause for the trigger */
+
+    if( locateFkeyIndex(pParse, pTab, pFKey, &pIdx, &aiCol) ) return 0;
+    assert( aiCol || pFKey->nCol==1 );
+
+    for(i=0; i<pFKey->nCol; i++){
+      Token tOld = { "old", 3 };  /* Literal "old" token */
+      Token tNew = { "new", 3 };  /* Literal "new" token */
+      Token tFromCol;             /* Name of column in child table */
+      Token tToCol;               /* Name of column in parent table */
+      int iFromCol;               /* Idx of column in child table */
+      Expr *pEq;                  /* tFromCol = OLD.tToCol */
+
+      iFromCol = aiCol ? aiCol[i] : pFKey->aCol[0].iFrom;
+      assert( iFromCol>=0 );
+      tToCol.z = pIdx ? pTab->aCol[pIdx->aiColumn[i]].zName : "oid";
+      tFromCol.z = pFKey->pFrom->aCol[iFromCol].zName;
+
+      tToCol.n = sqlite3Strlen30(tToCol.z);
+      tFromCol.n = sqlite3Strlen30(tFromCol.z);
+
+      /* Create the expression "OLD.zToCol = zFromCol". It is important
+      ** that the "OLD.zToCol" term is on the LHS of the = operator, so
+      ** that the affinity and collation sequence associated with the
+      ** parent table are used for the comparison. */
+      pEq = sqlite3PExpr(pParse, TK_EQ,
+          sqlite3PExpr(pParse, TK_DOT, 
+            sqlite3PExpr(pParse, TK_ID, 0, 0, &tOld),
+            sqlite3PExpr(pParse, TK_ID, 0, 0, &tToCol)
+          , 0),
+          sqlite3PExpr(pParse, TK_ID, 0, 0, &tFromCol)
+      , 0);
+      pWhere = sqlite3ExprAnd(db, pWhere, pEq);
+
+      /* For ON UPDATE, construct the next term of the WHEN clause.
+      ** The final WHEN clause will be like this:
+      **
+      **    WHEN NOT(old.col1 IS new.col1 AND ... AND old.colN IS new.colN)
+      */
+      if( pChanges ){
+        pEq = sqlite3PExpr(pParse, TK_IS,
+            sqlite3PExpr(pParse, TK_DOT, 
+              sqlite3PExpr(pParse, TK_ID, 0, 0, &tOld),
+              sqlite3PExpr(pParse, TK_ID, 0, 0, &tToCol),
+              0),
+            sqlite3PExpr(pParse, TK_DOT, 
+              sqlite3PExpr(pParse, TK_ID, 0, 0, &tNew),
+              sqlite3PExpr(pParse, TK_ID, 0, 0, &tToCol),
+              0),
+            0);
+        pWhen = sqlite3ExprAnd(db, pWhen, pEq);
+      }
+  
+      if( action!=OE_Restrict && (action!=OE_Cascade || pChanges) ){
+        Expr *pNew;
+        if( action==OE_Cascade ){
+          pNew = sqlite3PExpr(pParse, TK_DOT, 
+            sqlite3PExpr(pParse, TK_ID, 0, 0, &tNew),
+            sqlite3PExpr(pParse, TK_ID, 0, 0, &tToCol)
+          , 0);
+        }else if( action==OE_SetDflt ){
+          Expr *pDflt = pFKey->pFrom->aCol[iFromCol].pDflt;
+          if( pDflt ){
+            pNew = sqlite3ExprDup(db, pDflt, 0);
+          }else{
+            pNew = sqlite3PExpr(pParse, TK_NULL, 0, 0, 0);
+          }
+        }else{
+          pNew = sqlite3PExpr(pParse, TK_NULL, 0, 0, 0);
+        }
+        pList = sqlite3ExprListAppend(pParse, pList, pNew);
+        sqlite3ExprListSetName(pParse, pList, &tFromCol, 0);
+      }
+    }
+    sqlite3DbFree(db, aiCol);
+
+    zFrom = pFKey->pFrom->zName;
+    nFrom = sqlite3Strlen30(zFrom);
+
+    if( action==OE_Restrict ){
+      Token tFrom;
+      Expr *pRaise; 
+
+      tFrom.z = zFrom;
+      tFrom.n = nFrom;
+      pRaise = sqlite3Expr(db, TK_RAISE, "foreign key constraint failed");
+      if( pRaise ){
+        pRaise->affinity = OE_Abort;
+      }
+      pSelect = sqlite3SelectNew(pParse, 
+          sqlite3ExprListAppend(pParse, 0, pRaise),
+          sqlite3SrcListAppend(db, 0, &tFrom, 0),
+          pWhere,
+          0, 0, 0, 0, 0, 0
+      );
+      pWhere = 0;
+    }
+
+    /* Disable lookaside memory allocation */
+    enableLookaside = db->lookaside.bEnabled;
+    db->lookaside.bEnabled = 0;
+
+    pTrigger = (Trigger *)sqlite3DbMallocZero(db, 
+        sizeof(Trigger) +         /* struct Trigger */
+        sizeof(TriggerStep) +     /* Single step in trigger program */
+        nFrom + 1                 /* Space for pStep->target.z */
+    );
+    if( pTrigger ){
+      pStep = pTrigger->step_list = (TriggerStep *)&pTrigger[1];
+      pStep->target.z = (char *)&pStep[1];
+      pStep->target.n = nFrom;
+      memcpy((char *)pStep->target.z, zFrom, nFrom);
+  
+      pStep->pWhere = sqlite3ExprDup(db, pWhere, EXPRDUP_REDUCE);
+      pStep->pExprList = sqlite3ExprListDup(db, pList, EXPRDUP_REDUCE);
+      pStep->pSelect = sqlite3SelectDup(db, pSelect, EXPRDUP_REDUCE);
+      if( pWhen ){
+        pWhen = sqlite3PExpr(pParse, TK_NOT, pWhen, 0, 0);
+        pTrigger->pWhen = sqlite3ExprDup(db, pWhen, EXPRDUP_REDUCE);
+      }
+    }
+
+    /* Re-enable the lookaside buffer, if it was disabled earlier. */
+    db->lookaside.bEnabled = enableLookaside;
+
+    sqlite3ExprDelete(db, pWhere);
+    sqlite3ExprDelete(db, pWhen);
+    sqlite3ExprListDelete(db, pList);
+    sqlite3SelectDelete(db, pSelect);
+    if( db->mallocFailed==1 ){
+      fkTriggerDelete(db, pTrigger);
+      return 0;
+    }
+    assert( pStep!=0 );
+
+    switch( action ){
+      case OE_Restrict:
+        pStep->op = TK_SELECT; 
+        break;
+      case OE_Cascade: 
+        if( !pChanges ){ 
+          pStep->op = TK_DELETE; 
+          break; 
+        }
+      default:
+        pStep->op = TK_UPDATE;
+    }
+    pStep->pTrig = pTrigger;
+    pTrigger->pSchema = pTab->pSchema;
+    pTrigger->pTabSchema = pTab->pSchema;
+    pFKey->apTrigger[iAction] = pTrigger;
+    pTrigger->op = (pChanges ? TK_UPDATE : TK_DELETE);
+  }
+
+  return pTrigger;
+}
+
+/*
+** This function is called when deleting or updating a row to implement
+** any required CASCADE, SET NULL or SET DEFAULT actions.
+*/
+void sqlite3FkActions(
+  Parse *pParse,                  /* Parse context */
+  Table *pTab,                    /* Table being updated or deleted from */
+  ExprList *pChanges,             /* Change-list for UPDATE, NULL for DELETE */
+  int regOld                      /* Address of array containing old row */
+){
+  /* If foreign-key support is enabled, iterate through all FKs that 
+  ** refer to table pTab. If there is an action associated with the FK 
+  ** for this operation (either update or delete), invoke the associated 
+  ** trigger sub-program.  */
+  if( pParse->db->flags&SQLITE_ForeignKeys ){
+    FKey *pFKey;                  /* Iterator variable */
+    for(pFKey = sqlite3FkReferences(pTab); pFKey; pFKey=pFKey->pNextTo){
+      Trigger *pAction = fkActionTrigger(pParse, pTab, pFKey, pChanges);
+      if( pAction ){
+        sqlite3CodeRowTriggerDirect(pParse, pAction, pTab, regOld, OE_Abort, 0);
+      }
+    }
+  }
+}
+
+#endif /* ifndef SQLITE_OMIT_TRIGGER */
+
+/*
+** Free all memory associated with foreign key definitions attached to
+** table pTab. Remove the deleted foreign keys from the Schema.fkeyHash
+** hash table.
+*/
+void sqlite3FkDelete(sqlite3 *db, Table *pTab){
+  FKey *pFKey;                    /* Iterator variable */
+  FKey *pNext;                    /* Copy of pFKey->pNextFrom */
+
+  assert( db==0 || sqlite3SchemaMutexHeld(db, 0, pTab->pSchema) );
+  for(pFKey=pTab->pFKey; pFKey; pFKey=pNext){
+
+    /* Remove the FK from the fkeyHash hash table. */
+    if( !db || db->pnBytesFreed==0 ){
+      if( pFKey->pPrevTo ){
+        pFKey->pPrevTo->pNextTo = pFKey->pNextTo;
+      }else{
+        void *p = (void *)pFKey->pNextTo;
+        const char *z = (p ? pFKey->pNextTo->zTo : pFKey->zTo);
+        sqlite3HashInsert(&pTab->pSchema->fkeyHash, z, sqlite3Strlen30(z), p);
+      }
+      if( pFKey->pNextTo ){
+        pFKey->pNextTo->pPrevTo = pFKey->pPrevTo;
+      }
+    }
+
+    /* EV: R-30323-21917 Each foreign key constraint in SQLite is
+    ** classified as either immediate or deferred.
+    */
+    assert( pFKey->isDeferred==0 || pFKey->isDeferred==1 );
+
+    /* Delete any triggers created to implement actions for this FK. */
+#ifndef SQLITE_OMIT_TRIGGER
+    fkTriggerDelete(db, pFKey->apTrigger[0]);
+    fkTriggerDelete(db, pFKey->apTrigger[1]);
+#endif
+
+    pNext = pFKey->pNextFrom;
+    sqlite3DbFree(db, pFKey);
+  }
+}
+#endif /* ifndef SQLITE_OMIT_FOREIGN_KEY */
diff --git a/src/func.c b/src/func.c
new file mode 100644
index 0000000..10b61df
--- /dev/null
+++ b/src/func.c
@@ -0,0 +1,1611 @@
+/*
+** 2002 February 23
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains the C functions that implement various SQL
+** functions of SQLite.  
+**
+** There is only one exported symbol in this file - the function
+** sqliteRegisterBuildinFunctions() found at the bottom of the file.
+** All other code has file scope.
+*/
+#include "sqliteInt.h"
+#include <stdlib.h>
+#include <assert.h>
+#include "vdbeInt.h"
+
+/*
+** Return the collating function associated with a function.
+*/
+static CollSeq *sqlite3GetFuncCollSeq(sqlite3_context *context){
+  return context->pColl;
+}
+
+/*
+** Implementation of the non-aggregate min() and max() functions
+*/
+static void minmaxFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  int i;
+  int mask;    /* 0 for min() or 0xffffffff for max() */
+  int iBest;
+  CollSeq *pColl;
+
+  assert( argc>1 );
+  mask = sqlite3_user_data(context)==0 ? 0 : -1;
+  pColl = sqlite3GetFuncCollSeq(context);
+  assert( pColl );
+  assert( mask==-1 || mask==0 );
+  iBest = 0;
+  if( sqlite3_value_type(argv[0])==SQLITE_NULL ) return;
+  for(i=1; i<argc; i++){
+    if( sqlite3_value_type(argv[i])==SQLITE_NULL ) return;
+    if( (sqlite3MemCompare(argv[iBest], argv[i], pColl)^mask)>=0 ){
+      testcase( mask==0 );
+      iBest = i;
+    }
+  }
+  sqlite3_result_value(context, argv[iBest]);
+}
+
+/*
+** Return the type of the argument.
+*/
+static void typeofFunc(
+  sqlite3_context *context,
+  int NotUsed,
+  sqlite3_value **argv
+){
+  const char *z = 0;
+  UNUSED_PARAMETER(NotUsed);
+  switch( sqlite3_value_type(argv[0]) ){
+    case SQLITE_INTEGER: z = "integer"; break;
+    case SQLITE_TEXT:    z = "text";    break;
+    case SQLITE_FLOAT:   z = "real";    break;
+    case SQLITE_BLOB:    z = "blob";    break;
+    default:             z = "null";    break;
+  }
+  sqlite3_result_text(context, z, -1, SQLITE_STATIC);
+}
+
+
+/*
+** Implementation of the length() function
+*/
+static void lengthFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  int len;
+
+  assert( argc==1 );
+  UNUSED_PARAMETER(argc);
+  switch( sqlite3_value_type(argv[0]) ){
+    case SQLITE_BLOB:
+    case SQLITE_INTEGER:
+    case SQLITE_FLOAT: {
+      sqlite3_result_int(context, sqlite3_value_bytes(argv[0]));
+      break;
+    }
+    case SQLITE_TEXT: {
+      const unsigned char *z = sqlite3_value_text(argv[0]);
+      if( z==0 ) return;
+      len = 0;
+      while( *z ){
+        len++;
+        SQLITE_SKIP_UTF8(z);
+      }
+      sqlite3_result_int(context, len);
+      break;
+    }
+    default: {
+      sqlite3_result_null(context);
+      break;
+    }
+  }
+}
+
+/*
+** Implementation of the abs() function.
+**
+** IMP: R-23979-26855 The abs(X) function returns the absolute value of
+** the numeric argument X. 
+*/
+static void absFunc(sqlite3_context *context, int argc, sqlite3_value **argv){
+  assert( argc==1 );
+  UNUSED_PARAMETER(argc);
+  switch( sqlite3_value_type(argv[0]) ){
+    case SQLITE_INTEGER: {
+      i64 iVal = sqlite3_value_int64(argv[0]);
+      if( iVal<0 ){
+        if( (iVal<<1)==0 ){
+          /* IMP: R-35460-15084 If X is the integer -9223372036854775807 then
+          ** abs(X) throws an integer overflow error since there is no
+          ** equivalent positive 64-bit two complement value. */
+          sqlite3_result_error(context, "integer overflow", -1);
+          return;
+        }
+        iVal = -iVal;
+      } 
+      sqlite3_result_int64(context, iVal);
+      break;
+    }
+    case SQLITE_NULL: {
+      /* IMP: R-37434-19929 Abs(X) returns NULL if X is NULL. */
+      sqlite3_result_null(context);
+      break;
+    }
+    default: {
+      /* Because sqlite3_value_double() returns 0.0 if the argument is not
+      ** something that can be converted into a number, we have:
+      ** IMP: R-57326-31541 Abs(X) return 0.0 if X is a string or blob that
+      ** cannot be converted to a numeric value. 
+      */
+      double rVal = sqlite3_value_double(argv[0]);
+      if( rVal<0 ) rVal = -rVal;
+      sqlite3_result_double(context, rVal);
+      break;
+    }
+  }
+}
+
+/*
+** Implementation of the substr() function.
+**
+** substr(x,p1,p2)  returns p2 characters of x[] beginning with p1.
+** p1 is 1-indexed.  So substr(x,1,1) returns the first character
+** of x.  If x is text, then we actually count UTF-8 characters.
+** If x is a blob, then we count bytes.
+**
+** If p1 is negative, then we begin abs(p1) from the end of x[].
+**
+** If p2 is negative, return the p2 characters preceeding p1.
+*/
+static void substrFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  const unsigned char *z;
+  const unsigned char *z2;
+  int len;
+  int p0type;
+  i64 p1, p2;
+  int negP2 = 0;
+
+  assert( argc==3 || argc==2 );
+  if( sqlite3_value_type(argv[1])==SQLITE_NULL
+   || (argc==3 && sqlite3_value_type(argv[2])==SQLITE_NULL)
+  ){
+    return;
+  }
+  p0type = sqlite3_value_type(argv[0]);
+  p1 = sqlite3_value_int(argv[1]);
+  if( p0type==SQLITE_BLOB ){
+    len = sqlite3_value_bytes(argv[0]);
+    z = sqlite3_value_blob(argv[0]);
+    if( z==0 ) return;
+    assert( len==sqlite3_value_bytes(argv[0]) );
+  }else{
+    z = sqlite3_value_text(argv[0]);
+    if( z==0 ) return;
+    len = 0;
+    if( p1<0 ){
+      for(z2=z; *z2; len++){
+        SQLITE_SKIP_UTF8(z2);
+      }
+    }
+  }
+  if( argc==3 ){
+    p2 = sqlite3_value_int(argv[2]);
+    if( p2<0 ){
+      p2 = -p2;
+      negP2 = 1;
+    }
+  }else{
+    p2 = sqlite3_context_db_handle(context)->aLimit[SQLITE_LIMIT_LENGTH];
+  }
+  if( p1<0 ){
+    p1 += len;
+    if( p1<0 ){
+      p2 += p1;
+      if( p2<0 ) p2 = 0;
+      p1 = 0;
+    }
+  }else if( p1>0 ){
+    p1--;
+  }else if( p2>0 ){
+    p2--;
+  }
+  if( negP2 ){
+    p1 -= p2;
+    if( p1<0 ){
+      p2 += p1;
+      p1 = 0;
+    }
+  }
+  assert( p1>=0 && p2>=0 );
+  if( p0type!=SQLITE_BLOB ){
+    while( *z && p1 ){
+      SQLITE_SKIP_UTF8(z);
+      p1--;
+    }
+    for(z2=z; *z2 && p2; p2--){
+      SQLITE_SKIP_UTF8(z2);
+    }
+    sqlite3_result_text(context, (char*)z, (int)(z2-z), SQLITE_TRANSIENT);
+  }else{
+    if( p1+p2>len ){
+      p2 = len-p1;
+      if( p2<0 ) p2 = 0;
+    }
+    sqlite3_result_blob(context, (char*)&z[p1], (int)p2, SQLITE_TRANSIENT);
+  }
+}
+
+/*
+** Implementation of the round() function
+*/
+#ifndef SQLITE_OMIT_FLOATING_POINT
+static void roundFunc(sqlite3_context *context, int argc, sqlite3_value **argv){
+  int n = 0;
+  double r;
+  char *zBuf;
+  assert( argc==1 || argc==2 );
+  if( argc==2 ){
+    if( SQLITE_NULL==sqlite3_value_type(argv[1]) ) return;
+    n = sqlite3_value_int(argv[1]);
+    if( n>30 ) n = 30;
+    if( n<0 ) n = 0;
+  }
+  if( sqlite3_value_type(argv[0])==SQLITE_NULL ) return;
+  r = sqlite3_value_double(argv[0]);
+  /* If Y==0 and X will fit in a 64-bit int,
+  ** handle the rounding directly,
+  ** otherwise use printf.
+  */
+  if( n==0 && r>=0 && r<LARGEST_INT64-1 ){
+    r = (double)((sqlite_int64)(r+0.5));
+  }else if( n==0 && r<0 && (-r)<LARGEST_INT64-1 ){
+    r = -(double)((sqlite_int64)((-r)+0.5));
+  }else{
+    zBuf = sqlite3_mprintf("%.*f",n,r);
+    if( zBuf==0 ){
+      sqlite3_result_error_nomem(context);
+      return;
+    }
+    sqlite3AtoF(zBuf, &r, sqlite3Strlen30(zBuf), SQLITE_UTF8);
+    sqlite3_free(zBuf);
+  }
+  sqlite3_result_double(context, r);
+}
+#endif
+
+/*
+** Allocate nByte bytes of space using sqlite3_malloc(). If the
+** allocation fails, call sqlite3_result_error_nomem() to notify
+** the database handle that malloc() has failed and return NULL.
+** If nByte is larger than the maximum string or blob length, then
+** raise an SQLITE_TOOBIG exception and return NULL.
+*/
+static void *contextMalloc(sqlite3_context *context, i64 nByte){
+  char *z;
+  sqlite3 *db = sqlite3_context_db_handle(context);
+  assert( nByte>0 );
+  testcase( nByte==db->aLimit[SQLITE_LIMIT_LENGTH] );
+  testcase( nByte==db->aLimit[SQLITE_LIMIT_LENGTH]+1 );
+  if( nByte>db->aLimit[SQLITE_LIMIT_LENGTH] ){
+    sqlite3_result_error_toobig(context);
+    z = 0;
+  }else{
+    z = sqlite3Malloc((int)nByte);
+    if( !z ){
+      sqlite3_result_error_nomem(context);
+    }
+  }
+  return z;
+}
+
+/*
+** Implementation of the upper() and lower() SQL functions.
+*/
+static void upperFunc(sqlite3_context *context, int argc, sqlite3_value **argv){
+  char *z1;
+  const char *z2;
+  int i, n;
+  UNUSED_PARAMETER(argc);
+  z2 = (char*)sqlite3_value_text(argv[0]);
+  n = sqlite3_value_bytes(argv[0]);
+  /* Verify that the call to _bytes() does not invalidate the _text() pointer */
+  assert( z2==(char*)sqlite3_value_text(argv[0]) );
+  if( z2 ){
+    z1 = contextMalloc(context, ((i64)n)+1);
+    if( z1 ){
+      for(i=0; i<n; i++){
+        z1[i] = (char)sqlite3Toupper(z2[i]);
+      }
+      sqlite3_result_text(context, z1, n, sqlite3_free);
+    }
+  }
+}
+static void lowerFunc(sqlite3_context *context, int argc, sqlite3_value **argv){
+  char *z1;
+  const char *z2;
+  int i, n;
+  UNUSED_PARAMETER(argc);
+  z2 = (char*)sqlite3_value_text(argv[0]);
+  n = sqlite3_value_bytes(argv[0]);
+  /* Verify that the call to _bytes() does not invalidate the _text() pointer */
+  assert( z2==(char*)sqlite3_value_text(argv[0]) );
+  if( z2 ){
+    z1 = contextMalloc(context, ((i64)n)+1);
+    if( z1 ){
+      for(i=0; i<n; i++){
+        z1[i] = sqlite3Tolower(z2[i]);
+      }
+      sqlite3_result_text(context, z1, n, sqlite3_free);
+    }
+  }
+}
+
+
+#if 0  /* This function is never used. */
+/*
+** The COALESCE() and IFNULL() functions used to be implemented as shown
+** here.  But now they are implemented as VDBE code so that unused arguments
+** do not have to be computed.  This legacy implementation is retained as
+** comment.
+*/
+/*
+** Implementation of the IFNULL(), NVL(), and COALESCE() functions.  
+** All three do the same thing.  They return the first non-NULL
+** argument.
+*/
+static void ifnullFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  int i;
+  for(i=0; i<argc; i++){
+    if( SQLITE_NULL!=sqlite3_value_type(argv[i]) ){
+      sqlite3_result_value(context, argv[i]);
+      break;
+    }
+  }
+}
+#endif /* NOT USED */
+#define ifnullFunc versionFunc   /* Substitute function - never called */
+
+/*
+** Implementation of random().  Return a random integer.  
+*/
+static void randomFunc(
+  sqlite3_context *context,
+  int NotUsed,
+  sqlite3_value **NotUsed2
+){
+  sqlite_int64 r;
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  sqlite3_randomness(sizeof(r), &r);
+  if( r<0 ){
+    /* We need to prevent a random number of 0x8000000000000000 
+    ** (or -9223372036854775808) since when you do abs() of that
+    ** number of you get the same value back again.  To do this
+    ** in a way that is testable, mask the sign bit off of negative
+    ** values, resulting in a positive value.  Then take the 
+    ** 2s complement of that positive value.  The end result can
+    ** therefore be no less than -9223372036854775807.
+    */
+    r = -(r ^ (((sqlite3_int64)1)<<63));
+  }
+  sqlite3_result_int64(context, r);
+}
+
+/*
+** Implementation of randomblob(N).  Return a random blob
+** that is N bytes long.
+*/
+static void randomBlob(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  int n;
+  unsigned char *p;
+  assert( argc==1 );
+  UNUSED_PARAMETER(argc);
+  n = sqlite3_value_int(argv[0]);
+  if( n<1 ){
+    n = 1;
+  }
+  p = contextMalloc(context, n);
+  if( p ){
+    sqlite3_randomness(n, p);
+    sqlite3_result_blob(context, (char*)p, n, sqlite3_free);
+  }
+}
+
+/*
+** Implementation of the last_insert_rowid() SQL function.  The return
+** value is the same as the sqlite3_last_insert_rowid() API function.
+*/
+static void last_insert_rowid(
+  sqlite3_context *context, 
+  int NotUsed, 
+  sqlite3_value **NotUsed2
+){
+  sqlite3 *db = sqlite3_context_db_handle(context);
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  /* IMP: R-51513-12026 The last_insert_rowid() SQL function is a
+  ** wrapper around the sqlite3_last_insert_rowid() C/C++ interface
+  ** function. */
+  sqlite3_result_int64(context, sqlite3_last_insert_rowid(db));
+}
+
+/*
+** Implementation of the changes() SQL function.
+**
+** IMP: R-62073-11209 The changes() SQL function is a wrapper
+** around the sqlite3_changes() C/C++ function and hence follows the same
+** rules for counting changes.
+*/
+static void changes(
+  sqlite3_context *context,
+  int NotUsed,
+  sqlite3_value **NotUsed2
+){
+  sqlite3 *db = sqlite3_context_db_handle(context);
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  sqlite3_result_int(context, sqlite3_changes(db));
+}
+
+/*
+** Implementation of the total_changes() SQL function.  The return value is
+** the same as the sqlite3_total_changes() API function.
+*/
+static void total_changes(
+  sqlite3_context *context,
+  int NotUsed,
+  sqlite3_value **NotUsed2
+){
+  sqlite3 *db = sqlite3_context_db_handle(context);
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  /* IMP: R-52756-41993 This function is a wrapper around the
+  ** sqlite3_total_changes() C/C++ interface. */
+  sqlite3_result_int(context, sqlite3_total_changes(db));
+}
+
+/*
+** A structure defining how to do GLOB-style comparisons.
+*/
+struct compareInfo {
+  u8 matchAll;
+  u8 matchOne;
+  u8 matchSet;
+  u8 noCase;
+};
+
+/*
+** For LIKE and GLOB matching on EBCDIC machines, assume that every
+** character is exactly one byte in size.  Also, all characters are
+** able to participate in upper-case-to-lower-case mappings in EBCDIC
+** whereas only characters less than 0x80 do in ASCII.
+*/
+#if defined(SQLITE_EBCDIC)
+# define sqlite3Utf8Read(A,C)  (*(A++))
+# define GlogUpperToLower(A)   A = sqlite3UpperToLower[A]
+#else
+# define GlogUpperToLower(A)   if( !((A)&~0x7f) ){ A = sqlite3UpperToLower[A]; }
+#endif
+
+static const struct compareInfo globInfo = { '*', '?', '[', 0 };
+/* The correct SQL-92 behavior is for the LIKE operator to ignore
+** case.  Thus  'a' LIKE 'A' would be true. */
+static const struct compareInfo likeInfoNorm = { '%', '_',   0, 1 };
+/* If SQLITE_CASE_SENSITIVE_LIKE is defined, then the LIKE operator
+** is case sensitive causing 'a' LIKE 'A' to be false */
+static const struct compareInfo likeInfoAlt = { '%', '_',   0, 0 };
+
+/*
+** Compare two UTF-8 strings for equality where the first string can
+** potentially be a "glob" expression.  Return true (1) if they
+** are the same and false (0) if they are different.
+**
+** Globbing rules:
+**
+**      '*'       Matches any sequence of zero or more characters.
+**
+**      '?'       Matches exactly one character.
+**
+**     [...]      Matches one character from the enclosed list of
+**                characters.
+**
+**     [^...]     Matches one character not in the enclosed list.
+**
+** With the [...] and [^...] matching, a ']' character can be included
+** in the list by making it the first character after '[' or '^'.  A
+** range of characters can be specified using '-'.  Example:
+** "[a-z]" matches any single lower-case letter.  To match a '-', make
+** it the last character in the list.
+**
+** This routine is usually quick, but can be N**2 in the worst case.
+**
+** Hints: to match '*' or '?', put them in "[]".  Like this:
+**
+**         abc[*]xyz        Matches "abc*xyz" only
+*/
+static int patternCompare(
+  const u8 *zPattern,              /* The glob pattern */
+  const u8 *zString,               /* The string to compare against the glob */
+  const struct compareInfo *pInfo, /* Information about how to do the compare */
+  u32 esc                          /* The escape character */
+){
+  u32 c, c2;
+  int invert;
+  int seen;
+  u8 matchOne = pInfo->matchOne;
+  u8 matchAll = pInfo->matchAll;
+  u8 matchSet = pInfo->matchSet;
+  u8 noCase = pInfo->noCase; 
+  int prevEscape = 0;     /* True if the previous character was 'escape' */
+
+  while( (c = sqlite3Utf8Read(zPattern,&zPattern))!=0 ){
+    if( !prevEscape && c==matchAll ){
+      while( (c=sqlite3Utf8Read(zPattern,&zPattern)) == matchAll
+               || c == matchOne ){
+        if( c==matchOne && sqlite3Utf8Read(zString, &zString)==0 ){
+          return 0;
+        }
+      }
+      if( c==0 ){
+        return 1;
+      }else if( c==esc ){
+        c = sqlite3Utf8Read(zPattern, &zPattern);
+        if( c==0 ){
+          return 0;
+        }
+      }else if( c==matchSet ){
+        assert( esc==0 );         /* This is GLOB, not LIKE */
+        assert( matchSet<0x80 );  /* '[' is a single-byte character */
+        while( *zString && patternCompare(&zPattern[-1],zString,pInfo,esc)==0 ){
+          SQLITE_SKIP_UTF8(zString);
+        }
+        return *zString!=0;
+      }
+      while( (c2 = sqlite3Utf8Read(zString,&zString))!=0 ){
+        if( noCase ){
+          GlogUpperToLower(c2);
+          GlogUpperToLower(c);
+          while( c2 != 0 && c2 != c ){
+            c2 = sqlite3Utf8Read(zString, &zString);
+            GlogUpperToLower(c2);
+          }
+        }else{
+          while( c2 != 0 && c2 != c ){
+            c2 = sqlite3Utf8Read(zString, &zString);
+          }
+        }
+        if( c2==0 ) return 0;
+        if( patternCompare(zPattern,zString,pInfo,esc) ) return 1;
+      }
+      return 0;
+    }else if( !prevEscape && c==matchOne ){
+      if( sqlite3Utf8Read(zString, &zString)==0 ){
+        return 0;
+      }
+    }else if( c==matchSet ){
+      u32 prior_c = 0;
+      assert( esc==0 );    /* This only occurs for GLOB, not LIKE */
+      seen = 0;
+      invert = 0;
+      c = sqlite3Utf8Read(zString, &zString);
+      if( c==0 ) return 0;
+      c2 = sqlite3Utf8Read(zPattern, &zPattern);
+      if( c2=='^' ){
+        invert = 1;
+        c2 = sqlite3Utf8Read(zPattern, &zPattern);
+      }
+      if( c2==']' ){
+        if( c==']' ) seen = 1;
+        c2 = sqlite3Utf8Read(zPattern, &zPattern);
+      }
+      while( c2 && c2!=']' ){
+        if( c2=='-' && zPattern[0]!=']' && zPattern[0]!=0 && prior_c>0 ){
+          c2 = sqlite3Utf8Read(zPattern, &zPattern);
+          if( c>=prior_c && c<=c2 ) seen = 1;
+          prior_c = 0;
+        }else{
+          if( c==c2 ){
+            seen = 1;
+          }
+          prior_c = c2;
+        }
+        c2 = sqlite3Utf8Read(zPattern, &zPattern);
+      }
+      if( c2==0 || (seen ^ invert)==0 ){
+        return 0;
+      }
+    }else if( esc==c && !prevEscape ){
+      prevEscape = 1;
+    }else{
+      c2 = sqlite3Utf8Read(zString, &zString);
+      if( noCase ){
+        GlogUpperToLower(c);
+        GlogUpperToLower(c2);
+      }
+      if( c!=c2 ){
+        return 0;
+      }
+      prevEscape = 0;
+    }
+  }
+  return *zString==0;
+}
+
+/*
+** Count the number of times that the LIKE operator (or GLOB which is
+** just a variation of LIKE) gets called.  This is used for testing
+** only.
+*/
+#ifdef SQLITE_TEST
+int sqlite3_like_count = 0;
+#endif
+
+
+/*
+** Implementation of the like() SQL function.  This function implements
+** the build-in LIKE operator.  The first argument to the function is the
+** pattern and the second argument is the string.  So, the SQL statements:
+**
+**       A LIKE B
+**
+** is implemented as like(B,A).
+**
+** This same function (with a different compareInfo structure) computes
+** the GLOB operator.
+*/
+static void likeFunc(
+  sqlite3_context *context, 
+  int argc, 
+  sqlite3_value **argv
+){
+  const unsigned char *zA, *zB;
+  u32 escape = 0;
+  int nPat;
+  sqlite3 *db = sqlite3_context_db_handle(context);
+
+  zB = sqlite3_value_text(argv[0]);
+  zA = sqlite3_value_text(argv[1]);
+
+  /* Limit the length of the LIKE or GLOB pattern to avoid problems
+  ** of deep recursion and N*N behavior in patternCompare().
+  */
+  nPat = sqlite3_value_bytes(argv[0]);
+  testcase( nPat==db->aLimit[SQLITE_LIMIT_LIKE_PATTERN_LENGTH] );
+  testcase( nPat==db->aLimit[SQLITE_LIMIT_LIKE_PATTERN_LENGTH]+1 );
+  if( nPat > db->aLimit[SQLITE_LIMIT_LIKE_PATTERN_LENGTH] ){
+    sqlite3_result_error(context, "LIKE or GLOB pattern too complex", -1);
+    return;
+  }
+  assert( zB==sqlite3_value_text(argv[0]) );  /* Encoding did not change */
+
+  if( argc==3 ){
+    /* The escape character string must consist of a single UTF-8 character.
+    ** Otherwise, return an error.
+    */
+    const unsigned char *zEsc = sqlite3_value_text(argv[2]);
+    if( zEsc==0 ) return;
+    if( sqlite3Utf8CharLen((char*)zEsc, -1)!=1 ){
+      sqlite3_result_error(context, 
+          "ESCAPE expression must be a single character", -1);
+      return;
+    }
+    escape = sqlite3Utf8Read(zEsc, &zEsc);
+  }
+  if( zA && zB ){
+    struct compareInfo *pInfo = sqlite3_user_data(context);
+#ifdef SQLITE_TEST
+    sqlite3_like_count++;
+#endif
+    
+    sqlite3_result_int(context, patternCompare(zB, zA, pInfo, escape));
+  }
+}
+
+/*
+** Implementation of the NULLIF(x,y) function.  The result is the first
+** argument if the arguments are different.  The result is NULL if the
+** arguments are equal to each other.
+*/
+static void nullifFunc(
+  sqlite3_context *context,
+  int NotUsed,
+  sqlite3_value **argv
+){
+  CollSeq *pColl = sqlite3GetFuncCollSeq(context);
+  UNUSED_PARAMETER(NotUsed);
+  if( sqlite3MemCompare(argv[0], argv[1], pColl)!=0 ){
+    sqlite3_result_value(context, argv[0]);
+  }
+}
+
+/*
+** Implementation of the sqlite_version() function.  The result is the version
+** of the SQLite library that is running.
+*/
+static void versionFunc(
+  sqlite3_context *context,
+  int NotUsed,
+  sqlite3_value **NotUsed2
+){
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  /* IMP: R-48699-48617 This function is an SQL wrapper around the
+  ** sqlite3_libversion() C-interface. */
+  sqlite3_result_text(context, sqlite3_libversion(), -1, SQLITE_STATIC);
+}
+
+/*
+** Implementation of the sqlite_source_id() function. The result is a string
+** that identifies the particular version of the source code used to build
+** SQLite.
+*/
+static void sourceidFunc(
+  sqlite3_context *context,
+  int NotUsed,
+  sqlite3_value **NotUsed2
+){
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  /* IMP: R-24470-31136 This function is an SQL wrapper around the
+  ** sqlite3_sourceid() C interface. */
+  sqlite3_result_text(context, sqlite3_sourceid(), -1, SQLITE_STATIC);
+}
+
+/*
+** Implementation of the sqlite_log() function.  This is a wrapper around
+** sqlite3_log().  The return value is NULL.  The function exists purely for
+** its side-effects.
+*/
+static void errlogFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  UNUSED_PARAMETER(argc);
+  UNUSED_PARAMETER(context);
+  sqlite3_log(sqlite3_value_int(argv[0]), "%s", sqlite3_value_text(argv[1]));
+}
+
+/*
+** Implementation of the sqlite_compileoption_used() function.
+** The result is an integer that identifies if the compiler option
+** was used to build SQLite.
+*/
+#ifndef SQLITE_OMIT_COMPILEOPTION_DIAGS
+static void compileoptionusedFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  const char *zOptName;
+  assert( argc==1 );
+  UNUSED_PARAMETER(argc);
+  /* IMP: R-39564-36305 The sqlite_compileoption_used() SQL
+  ** function is a wrapper around the sqlite3_compileoption_used() C/C++
+  ** function.
+  */
+  if( (zOptName = (const char*)sqlite3_value_text(argv[0]))!=0 ){
+    sqlite3_result_int(context, sqlite3_compileoption_used(zOptName));
+  }
+}
+#endif /* SQLITE_OMIT_COMPILEOPTION_DIAGS */
+
+/*
+** Implementation of the sqlite_compileoption_get() function. 
+** The result is a string that identifies the compiler options 
+** used to build SQLite.
+*/
+#ifndef SQLITE_OMIT_COMPILEOPTION_DIAGS
+static void compileoptiongetFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  int n;
+  assert( argc==1 );
+  UNUSED_PARAMETER(argc);
+  /* IMP: R-04922-24076 The sqlite_compileoption_get() SQL function
+  ** is a wrapper around the sqlite3_compileoption_get() C/C++ function.
+  */
+  n = sqlite3_value_int(argv[0]);
+  sqlite3_result_text(context, sqlite3_compileoption_get(n), -1, SQLITE_STATIC);
+}
+#endif /* SQLITE_OMIT_COMPILEOPTION_DIAGS */
+
+/* Array for converting from half-bytes (nybbles) into ASCII hex
+** digits. */
+static const char hexdigits[] = {
+  '0', '1', '2', '3', '4', '5', '6', '7',
+  '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' 
+};
+
+/*
+** EXPERIMENTAL - This is not an official function.  The interface may
+** change.  This function may disappear.  Do not write code that depends
+** on this function.
+**
+** Implementation of the QUOTE() function.  This function takes a single
+** argument.  If the argument is numeric, the return value is the same as
+** the argument.  If the argument is NULL, the return value is the string
+** "NULL".  Otherwise, the argument is enclosed in single quotes with
+** single-quote escapes.
+*/
+static void quoteFunc(sqlite3_context *context, int argc, sqlite3_value **argv){
+  assert( argc==1 );
+  UNUSED_PARAMETER(argc);
+  switch( sqlite3_value_type(argv[0]) ){
+    case SQLITE_INTEGER:
+    case SQLITE_FLOAT: {
+      sqlite3_result_value(context, argv[0]);
+      break;
+    }
+    case SQLITE_BLOB: {
+      char *zText = 0;
+      char const *zBlob = sqlite3_value_blob(argv[0]);
+      int nBlob = sqlite3_value_bytes(argv[0]);
+      assert( zBlob==sqlite3_value_blob(argv[0]) ); /* No encoding change */
+      zText = (char *)contextMalloc(context, (2*(i64)nBlob)+4); 
+      if( zText ){
+        int i;
+        for(i=0; i<nBlob; i++){
+          zText[(i*2)+2] = hexdigits[(zBlob[i]>>4)&0x0F];
+          zText[(i*2)+3] = hexdigits[(zBlob[i])&0x0F];
+        }
+        zText[(nBlob*2)+2] = '\'';
+        zText[(nBlob*2)+3] = '\0';
+        zText[0] = 'X';
+        zText[1] = '\'';
+        sqlite3_result_text(context, zText, -1, SQLITE_TRANSIENT);
+        sqlite3_free(zText);
+      }
+      break;
+    }
+    case SQLITE_TEXT: {
+      int i,j;
+      u64 n;
+      const unsigned char *zArg = sqlite3_value_text(argv[0]);
+      char *z;
+
+      if( zArg==0 ) return;
+      for(i=0, n=0; zArg[i]; i++){ if( zArg[i]=='\'' ) n++; }
+      z = contextMalloc(context, ((i64)i)+((i64)n)+3);
+      if( z ){
+        z[0] = '\'';
+        for(i=0, j=1; zArg[i]; i++){
+          z[j++] = zArg[i];
+          if( zArg[i]=='\'' ){
+            z[j++] = '\'';
+          }
+        }
+        z[j++] = '\'';
+        z[j] = 0;
+        sqlite3_result_text(context, z, j, sqlite3_free);
+      }
+      break;
+    }
+    default: {
+      assert( sqlite3_value_type(argv[0])==SQLITE_NULL );
+      sqlite3_result_text(context, "NULL", 4, SQLITE_STATIC);
+      break;
+    }
+  }
+}
+
+/*
+** The hex() function.  Interpret the argument as a blob.  Return
+** a hexadecimal rendering as text.
+*/
+static void hexFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  int i, n;
+  const unsigned char *pBlob;
+  char *zHex, *z;
+  assert( argc==1 );
+  UNUSED_PARAMETER(argc);
+  pBlob = sqlite3_value_blob(argv[0]);
+  n = sqlite3_value_bytes(argv[0]);
+  assert( pBlob==sqlite3_value_blob(argv[0]) );  /* No encoding change */
+  z = zHex = contextMalloc(context, ((i64)n)*2 + 1);
+  if( zHex ){
+    for(i=0; i<n; i++, pBlob++){
+      unsigned char c = *pBlob;
+      *(z++) = hexdigits[(c>>4)&0xf];
+      *(z++) = hexdigits[c&0xf];
+    }
+    *z = 0;
+    sqlite3_result_text(context, zHex, n*2, sqlite3_free);
+  }
+}
+
+/*
+** The zeroblob(N) function returns a zero-filled blob of size N bytes.
+*/
+static void zeroblobFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  i64 n;
+  sqlite3 *db = sqlite3_context_db_handle(context);
+  assert( argc==1 );
+  UNUSED_PARAMETER(argc);
+  n = sqlite3_value_int64(argv[0]);
+  testcase( n==db->aLimit[SQLITE_LIMIT_LENGTH] );
+  testcase( n==db->aLimit[SQLITE_LIMIT_LENGTH]+1 );
+  if( n>db->aLimit[SQLITE_LIMIT_LENGTH] ){
+    sqlite3_result_error_toobig(context);
+  }else{
+    sqlite3_result_zeroblob(context, (int)n); /* IMP: R-00293-64994 */
+  }
+}
+
+/*
+** The replace() function.  Three arguments are all strings: call
+** them A, B, and C. The result is also a string which is derived
+** from A by replacing every occurance of B with C.  The match
+** must be exact.  Collating sequences are not used.
+*/
+static void replaceFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  const unsigned char *zStr;        /* The input string A */
+  const unsigned char *zPattern;    /* The pattern string B */
+  const unsigned char *zRep;        /* The replacement string C */
+  unsigned char *zOut;              /* The output */
+  int nStr;                /* Size of zStr */
+  int nPattern;            /* Size of zPattern */
+  int nRep;                /* Size of zRep */
+  i64 nOut;                /* Maximum size of zOut */
+  int loopLimit;           /* Last zStr[] that might match zPattern[] */
+  int i, j;                /* Loop counters */
+
+  assert( argc==3 );
+  UNUSED_PARAMETER(argc);
+  zStr = sqlite3_value_text(argv[0]);
+  if( zStr==0 ) return;
+  nStr = sqlite3_value_bytes(argv[0]);
+  assert( zStr==sqlite3_value_text(argv[0]) );  /* No encoding change */
+  zPattern = sqlite3_value_text(argv[1]);
+  if( zPattern==0 ){
+    assert( sqlite3_value_type(argv[1])==SQLITE_NULL
+            || sqlite3_context_db_handle(context)->mallocFailed );
+    return;
+  }
+  if( zPattern[0]==0 ){
+    assert( sqlite3_value_type(argv[1])!=SQLITE_NULL );
+    sqlite3_result_value(context, argv[0]);
+    return;
+  }
+  nPattern = sqlite3_value_bytes(argv[1]);
+  assert( zPattern==sqlite3_value_text(argv[1]) );  /* No encoding change */
+  zRep = sqlite3_value_text(argv[2]);
+  if( zRep==0 ) return;
+  nRep = sqlite3_value_bytes(argv[2]);
+  assert( zRep==sqlite3_value_text(argv[2]) );
+  nOut = nStr + 1;
+  assert( nOut<SQLITE_MAX_LENGTH );
+  zOut = contextMalloc(context, (i64)nOut);
+  if( zOut==0 ){
+    return;
+  }
+  loopLimit = nStr - nPattern;  
+  for(i=j=0; i<=loopLimit; i++){
+    if( zStr[i]!=zPattern[0] || memcmp(&zStr[i], zPattern, nPattern) ){
+      zOut[j++] = zStr[i];
+    }else{
+      u8 *zOld;
+      sqlite3 *db = sqlite3_context_db_handle(context);
+      nOut += nRep - nPattern;
+      testcase( nOut-1==db->aLimit[SQLITE_LIMIT_LENGTH] );
+      testcase( nOut-2==db->aLimit[SQLITE_LIMIT_LENGTH] );
+      if( nOut-1>db->aLimit[SQLITE_LIMIT_LENGTH] ){
+        sqlite3_result_error_toobig(context);
+        sqlite3_free(zOut);
+        return;
+      }
+      zOld = zOut;
+      zOut = sqlite3_realloc(zOut, (int)nOut);
+      if( zOut==0 ){
+        sqlite3_result_error_nomem(context);
+        sqlite3_free(zOld);
+        return;
+      }
+      memcpy(&zOut[j], zRep, nRep);
+      j += nRep;
+      i += nPattern-1;
+    }
+  }
+  assert( j+nStr-i+1==nOut );
+  memcpy(&zOut[j], &zStr[i], nStr-i);
+  j += nStr - i;
+  assert( j<=nOut );
+  zOut[j] = 0;
+  sqlite3_result_text(context, (char*)zOut, j, sqlite3_free);
+}
+
+/*
+** Implementation of the TRIM(), LTRIM(), and RTRIM() functions.
+** The userdata is 0x1 for left trim, 0x2 for right trim, 0x3 for both.
+*/
+static void trimFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  const unsigned char *zIn;         /* Input string */
+  const unsigned char *zCharSet;    /* Set of characters to trim */
+  int nIn;                          /* Number of bytes in input */
+  int flags;                        /* 1: trimleft  2: trimright  3: trim */
+  int i;                            /* Loop counter */
+  unsigned char *aLen = 0;          /* Length of each character in zCharSet */
+  unsigned char **azChar = 0;       /* Individual characters in zCharSet */
+  int nChar;                        /* Number of characters in zCharSet */
+
+  if( sqlite3_value_type(argv[0])==SQLITE_NULL ){
+    return;
+  }
+  zIn = sqlite3_value_text(argv[0]);
+  if( zIn==0 ) return;
+  nIn = sqlite3_value_bytes(argv[0]);
+  assert( zIn==sqlite3_value_text(argv[0]) );
+  if( argc==1 ){
+    static const unsigned char lenOne[] = { 1 };
+    static unsigned char * const azOne[] = { (u8*)" " };
+    nChar = 1;
+    aLen = (u8*)lenOne;
+    azChar = (unsigned char **)azOne;
+    zCharSet = 0;
+  }else if( (zCharSet = sqlite3_value_text(argv[1]))==0 ){
+    return;
+  }else{
+    const unsigned char *z;
+    for(z=zCharSet, nChar=0; *z; nChar++){
+      SQLITE_SKIP_UTF8(z);
+    }
+    if( nChar>0 ){
+      azChar = contextMalloc(context, ((i64)nChar)*(sizeof(char*)+1));
+      if( azChar==0 ){
+        return;
+      }
+      aLen = (unsigned char*)&azChar[nChar];
+      for(z=zCharSet, nChar=0; *z; nChar++){
+        azChar[nChar] = (unsigned char *)z;
+        SQLITE_SKIP_UTF8(z);
+        aLen[nChar] = (u8)(z - azChar[nChar]);
+      }
+    }
+  }
+  if( nChar>0 ){
+    flags = SQLITE_PTR_TO_INT(sqlite3_user_data(context));
+    if( flags & 1 ){
+      while( nIn>0 ){
+        int len = 0;
+        for(i=0; i<nChar; i++){
+          len = aLen[i];
+          if( len<=nIn && memcmp(zIn, azChar[i], len)==0 ) break;
+        }
+        if( i>=nChar ) break;
+        zIn += len;
+        nIn -= len;
+      }
+    }
+    if( flags & 2 ){
+      while( nIn>0 ){
+        int len = 0;
+        for(i=0; i<nChar; i++){
+          len = aLen[i];
+          if( len<=nIn && memcmp(&zIn[nIn-len],azChar[i],len)==0 ) break;
+        }
+        if( i>=nChar ) break;
+        nIn -= len;
+      }
+    }
+    if( zCharSet ){
+      sqlite3_free(azChar);
+    }
+  }
+  sqlite3_result_text(context, (char*)zIn, nIn, SQLITE_TRANSIENT);
+}
+
+
+/* IMP: R-25361-16150 This function is omitted from SQLite by default. It
+** is only available if the SQLITE_SOUNDEX compile-time option is used
+** when SQLite is built.
+*/
+#ifdef SQLITE_SOUNDEX
+/*
+** Compute the soundex encoding of a word.
+**
+** IMP: R-59782-00072 The soundex(X) function returns a string that is the
+** soundex encoding of the string X. 
+*/
+static void soundexFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  char zResult[8];
+  const u8 *zIn;
+  int i, j;
+  static const unsigned char iCode[] = {
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 1, 2, 3, 0, 1, 2, 0, 0, 2, 2, 4, 5, 5, 0,
+    1, 2, 6, 2, 3, 0, 1, 0, 2, 0, 2, 0, 0, 0, 0, 0,
+    0, 0, 1, 2, 3, 0, 1, 2, 0, 0, 2, 2, 4, 5, 5, 0,
+    1, 2, 6, 2, 3, 0, 1, 0, 2, 0, 2, 0, 0, 0, 0, 0,
+  };
+  assert( argc==1 );
+  zIn = (u8*)sqlite3_value_text(argv[0]);
+  if( zIn==0 ) zIn = (u8*)"";
+  for(i=0; zIn[i] && !sqlite3Isalpha(zIn[i]); i++){}
+  if( zIn[i] ){
+    u8 prevcode = iCode[zIn[i]&0x7f];
+    zResult[0] = sqlite3Toupper(zIn[i]);
+    for(j=1; j<4 && zIn[i]; i++){
+      int code = iCode[zIn[i]&0x7f];
+      if( code>0 ){
+        if( code!=prevcode ){
+          prevcode = code;
+          zResult[j++] = code + '0';
+        }
+      }else{
+        prevcode = 0;
+      }
+    }
+    while( j<4 ){
+      zResult[j++] = '0';
+    }
+    zResult[j] = 0;
+    sqlite3_result_text(context, zResult, 4, SQLITE_TRANSIENT);
+  }else{
+    /* IMP: R-64894-50321 The string "?000" is returned if the argument
+    ** is NULL or contains no ASCII alphabetic characters. */
+    sqlite3_result_text(context, "?000", 4, SQLITE_STATIC);
+  }
+}
+#endif /* SQLITE_SOUNDEX */
+
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+/*
+** A function that loads a shared-library extension then returns NULL.
+*/
+static void loadExt(sqlite3_context *context, int argc, sqlite3_value **argv){
+  const char *zFile = (const char *)sqlite3_value_text(argv[0]);
+  const char *zProc;
+  sqlite3 *db = sqlite3_context_db_handle(context);
+  char *zErrMsg = 0;
+
+  if( argc==2 ){
+    zProc = (const char *)sqlite3_value_text(argv[1]);
+  }else{
+    zProc = 0;
+  }
+  if( zFile && sqlite3_load_extension(db, zFile, zProc, &zErrMsg) ){
+    sqlite3_result_error(context, zErrMsg, -1);
+    sqlite3_free(zErrMsg);
+  }
+}
+#endif
+
+
+/*
+** An instance of the following structure holds the context of a
+** sum() or avg() aggregate computation.
+*/
+typedef struct SumCtx SumCtx;
+struct SumCtx {
+  double rSum;      /* Floating point sum */
+  i64 iSum;         /* Integer sum */   
+  i64 cnt;          /* Number of elements summed */
+  u8 overflow;      /* True if integer overflow seen */
+  u8 approx;        /* True if non-integer value was input to the sum */
+};
+
+/*
+** Routines used to compute the sum, average, and total.
+**
+** The SUM() function follows the (broken) SQL standard which means
+** that it returns NULL if it sums over no inputs.  TOTAL returns
+** 0.0 in that case.  In addition, TOTAL always returns a float where
+** SUM might return an integer if it never encounters a floating point
+** value.  TOTAL never fails, but SUM might through an exception if
+** it overflows an integer.
+*/
+static void sumStep(sqlite3_context *context, int argc, sqlite3_value **argv){
+  SumCtx *p;
+  int type;
+  assert( argc==1 );
+  UNUSED_PARAMETER(argc);
+  p = sqlite3_aggregate_context(context, sizeof(*p));
+  type = sqlite3_value_numeric_type(argv[0]);
+  if( p && type!=SQLITE_NULL ){
+    p->cnt++;
+    if( type==SQLITE_INTEGER ){
+      i64 v = sqlite3_value_int64(argv[0]);
+      p->rSum += v;
+      if( (p->approx|p->overflow)==0 && sqlite3AddInt64(&p->iSum, v) ){
+        p->overflow = 1;
+      }
+    }else{
+      p->rSum += sqlite3_value_double(argv[0]);
+      p->approx = 1;
+    }
+  }
+}
+static void sumFinalize(sqlite3_context *context){
+  SumCtx *p;
+  p = sqlite3_aggregate_context(context, 0);
+  if( p && p->cnt>0 ){
+    if( p->overflow ){
+      sqlite3_result_error(context,"integer overflow",-1);
+    }else if( p->approx ){
+      sqlite3_result_double(context, p->rSum);
+    }else{
+      sqlite3_result_int64(context, p->iSum);
+    }
+  }
+}
+static void avgFinalize(sqlite3_context *context){
+  SumCtx *p;
+  p = sqlite3_aggregate_context(context, 0);
+  if( p && p->cnt>0 ){
+    sqlite3_result_double(context, p->rSum/(double)p->cnt);
+  }
+}
+static void totalFinalize(sqlite3_context *context){
+  SumCtx *p;
+  p = sqlite3_aggregate_context(context, 0);
+  /* (double)0 In case of SQLITE_OMIT_FLOATING_POINT... */
+  sqlite3_result_double(context, p ? p->rSum : (double)0);
+}
+
+/*
+** The following structure keeps track of state information for the
+** count() aggregate function.
+*/
+typedef struct CountCtx CountCtx;
+struct CountCtx {
+  i64 n;
+};
+
+/*
+** Routines to implement the count() aggregate function.
+*/
+static void countStep(sqlite3_context *context, int argc, sqlite3_value **argv){
+  CountCtx *p;
+  p = sqlite3_aggregate_context(context, sizeof(*p));
+  if( (argc==0 || SQLITE_NULL!=sqlite3_value_type(argv[0])) && p ){
+    p->n++;
+  }
+
+#ifndef SQLITE_OMIT_DEPRECATED
+  /* The sqlite3_aggregate_count() function is deprecated.  But just to make
+  ** sure it still operates correctly, verify that its count agrees with our 
+  ** internal count when using count(*) and when the total count can be
+  ** expressed as a 32-bit integer. */
+  assert( argc==1 || p==0 || p->n>0x7fffffff
+          || p->n==sqlite3_aggregate_count(context) );
+#endif
+}   
+static void countFinalize(sqlite3_context *context){
+  CountCtx *p;
+  p = sqlite3_aggregate_context(context, 0);
+  sqlite3_result_int64(context, p ? p->n : 0);
+}
+
+/*
+** Routines to implement min() and max() aggregate functions.
+*/
+static void minmaxStep(
+  sqlite3_context *context, 
+  int NotUsed, 
+  sqlite3_value **argv
+){
+  Mem *pArg  = (Mem *)argv[0];
+  Mem *pBest;
+  UNUSED_PARAMETER(NotUsed);
+
+  if( sqlite3_value_type(argv[0])==SQLITE_NULL ) return;
+  pBest = (Mem *)sqlite3_aggregate_context(context, sizeof(*pBest));
+  if( !pBest ) return;
+
+  if( pBest->flags ){
+    int max;
+    int cmp;
+    CollSeq *pColl = sqlite3GetFuncCollSeq(context);
+    /* This step function is used for both the min() and max() aggregates,
+    ** the only difference between the two being that the sense of the
+    ** comparison is inverted. For the max() aggregate, the
+    ** sqlite3_user_data() function returns (void *)-1. For min() it
+    ** returns (void *)db, where db is the sqlite3* database pointer.
+    ** Therefore the next statement sets variable 'max' to 1 for the max()
+    ** aggregate, or 0 for min().
+    */
+    max = sqlite3_user_data(context)!=0;
+    cmp = sqlite3MemCompare(pBest, pArg, pColl);
+    if( (max && cmp<0) || (!max && cmp>0) ){
+      sqlite3VdbeMemCopy(pBest, pArg);
+    }
+  }else{
+    sqlite3VdbeMemCopy(pBest, pArg);
+  }
+}
+static void minMaxFinalize(sqlite3_context *context){
+  sqlite3_value *pRes;
+  pRes = (sqlite3_value *)sqlite3_aggregate_context(context, 0);
+  if( pRes ){
+    if( ALWAYS(pRes->flags) ){
+      sqlite3_result_value(context, pRes);
+    }
+    sqlite3VdbeMemRelease(pRes);
+  }
+}
+
+/*
+** group_concat(EXPR, ?SEPARATOR?)
+*/
+static void groupConcatStep(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  const char *zVal;
+  StrAccum *pAccum;
+  const char *zSep;
+  int nVal, nSep;
+  assert( argc==1 || argc==2 );
+  if( sqlite3_value_type(argv[0])==SQLITE_NULL ) return;
+  pAccum = (StrAccum*)sqlite3_aggregate_context(context, sizeof(*pAccum));
+
+  if( pAccum ){
+    sqlite3 *db = sqlite3_context_db_handle(context);
+    int firstTerm = pAccum->useMalloc==0;
+    pAccum->useMalloc = 2;
+    pAccum->mxAlloc = db->aLimit[SQLITE_LIMIT_LENGTH];
+    if( !firstTerm ){
+      if( argc==2 ){
+        zSep = (char*)sqlite3_value_text(argv[1]);
+        nSep = sqlite3_value_bytes(argv[1]);
+      }else{
+        zSep = ",";
+        nSep = 1;
+      }
+      sqlite3StrAccumAppend(pAccum, zSep, nSep);
+    }
+    zVal = (char*)sqlite3_value_text(argv[0]);
+    nVal = sqlite3_value_bytes(argv[0]);
+    sqlite3StrAccumAppend(pAccum, zVal, nVal);
+  }
+}
+static void groupConcatFinalize(sqlite3_context *context){
+  StrAccum *pAccum;
+  pAccum = sqlite3_aggregate_context(context, 0);
+  if( pAccum ){
+    if( pAccum->tooBig ){
+      sqlite3_result_error_toobig(context);
+    }else if( pAccum->mallocFailed ){
+      sqlite3_result_error_nomem(context);
+    }else{    
+      sqlite3_result_text(context, sqlite3StrAccumFinish(pAccum), -1, 
+                          sqlite3_free);
+    }
+  }
+}
+
+/*
+** This routine does per-connection function registration.  Most
+** of the built-in functions above are part of the global function set.
+** This routine only deals with those that are not global.
+*/
+void sqlite3RegisterBuiltinFunctions(sqlite3 *db){
+  int rc = sqlite3_overload_function(db, "MATCH", 2);
+#ifndef OMIT_EXPORT
+  extern void sqlcipher_exportFunc(sqlite3_context *, int, sqlite3_value **);
+#endif
+  assert( rc==SQLITE_NOMEM || rc==SQLITE_OK );
+  if( rc==SQLITE_NOMEM ){
+    db->mallocFailed = 1;
+  }
+#ifndef OMIT_EXPORT
+  sqlite3CreateFunc(db, "sqlcipher_export", 1, SQLITE_TEXT, 0, sqlcipher_exportFunc, 0, 0, 0);
+#endif
+}
+
+/*
+** Set the LIKEOPT flag on the 2-argument function with the given name.
+*/
+static void setLikeOptFlag(sqlite3 *db, const char *zName, u8 flagVal){
+  FuncDef *pDef;
+  pDef = sqlite3FindFunction(db, zName, sqlite3Strlen30(zName),
+                             2, SQLITE_UTF8, 0);
+  if( ALWAYS(pDef) ){
+    pDef->flags = flagVal;
+  }
+}
+
+/*
+** Register the built-in LIKE and GLOB functions.  The caseSensitive
+** parameter determines whether or not the LIKE operator is case
+** sensitive.  GLOB is always case sensitive.
+*/
+void sqlite3RegisterLikeFunctions(sqlite3 *db, int caseSensitive){
+  struct compareInfo *pInfo;
+  if( caseSensitive ){
+    pInfo = (struct compareInfo*)&likeInfoAlt;
+  }else{
+    pInfo = (struct compareInfo*)&likeInfoNorm;
+  }
+  sqlite3CreateFunc(db, "like", 2, SQLITE_UTF8, pInfo, likeFunc, 0, 0, 0);
+  sqlite3CreateFunc(db, "like", 3, SQLITE_UTF8, pInfo, likeFunc, 0, 0, 0);
+  sqlite3CreateFunc(db, "glob", 2, SQLITE_UTF8, 
+      (struct compareInfo*)&globInfo, likeFunc, 0, 0, 0);
+  setLikeOptFlag(db, "glob", SQLITE_FUNC_LIKE | SQLITE_FUNC_CASE);
+  setLikeOptFlag(db, "like", 
+      caseSensitive ? (SQLITE_FUNC_LIKE | SQLITE_FUNC_CASE) : SQLITE_FUNC_LIKE);
+}
+
+/*
+** pExpr points to an expression which implements a function.  If
+** it is appropriate to apply the LIKE optimization to that function
+** then set aWc[0] through aWc[2] to the wildcard characters and
+** return TRUE.  If the function is not a LIKE-style function then
+** return FALSE.
+*/
+int sqlite3IsLikeFunction(sqlite3 *db, Expr *pExpr, int *pIsNocase, char *aWc){
+  FuncDef *pDef;
+  if( pExpr->op!=TK_FUNCTION 
+   || !pExpr->x.pList 
+   || pExpr->x.pList->nExpr!=2
+  ){
+    return 0;
+  }
+  assert( !ExprHasProperty(pExpr, EP_xIsSelect) );
+  pDef = sqlite3FindFunction(db, pExpr->u.zToken, 
+                             sqlite3Strlen30(pExpr->u.zToken),
+                             2, SQLITE_UTF8, 0);
+  if( NEVER(pDef==0) || (pDef->flags & SQLITE_FUNC_LIKE)==0 ){
+    return 0;
+  }
+
+  /* The memcpy() statement assumes that the wildcard characters are
+  ** the first three statements in the compareInfo structure.  The
+  ** asserts() that follow verify that assumption
+  */
+  memcpy(aWc, pDef->pUserData, 3);
+  assert( (char*)&likeInfoAlt == (char*)&likeInfoAlt.matchAll );
+  assert( &((char*)&likeInfoAlt)[1] == (char*)&likeInfoAlt.matchOne );
+  assert( &((char*)&likeInfoAlt)[2] == (char*)&likeInfoAlt.matchSet );
+  *pIsNocase = (pDef->flags & SQLITE_FUNC_CASE)==0;
+  return 1;
+}
+
+/*
+** All all of the FuncDef structures in the aBuiltinFunc[] array above
+** to the global function hash table.  This occurs at start-time (as
+** a consequence of calling sqlite3_initialize()).
+**
+** After this routine runs
+*/
+void sqlite3RegisterGlobalFunctions(void){
+  /*
+  ** The following array holds FuncDef structures for all of the functions
+  ** defined in this file.
+  **
+  ** The array cannot be constant since changes are made to the
+  ** FuncDef.pHash elements at start-time.  The elements of this array
+  ** are read-only after initialization is complete.
+  */
+  static SQLITE_WSD FuncDef aBuiltinFunc[] = {
+    FUNCTION(ltrim,              1, 1, 0, trimFunc         ),
+    FUNCTION(ltrim,              2, 1, 0, trimFunc         ),
+    FUNCTION(rtrim,              1, 2, 0, trimFunc         ),
+    FUNCTION(rtrim,              2, 2, 0, trimFunc         ),
+    FUNCTION(trim,               1, 3, 0, trimFunc         ),
+    FUNCTION(trim,               2, 3, 0, trimFunc         ),
+    FUNCTION(min,               -1, 0, 1, minmaxFunc       ),
+    FUNCTION(min,                0, 0, 1, 0                ),
+    AGGREGATE(min,               1, 0, 1, minmaxStep,      minMaxFinalize ),
+    FUNCTION(max,               -1, 1, 1, minmaxFunc       ),
+    FUNCTION(max,                0, 1, 1, 0                ),
+    AGGREGATE(max,               1, 1, 1, minmaxStep,      minMaxFinalize ),
+    FUNCTION(typeof,             1, 0, 0, typeofFunc       ),
+    FUNCTION(length,             1, 0, 0, lengthFunc       ),
+    FUNCTION(substr,             2, 0, 0, substrFunc       ),
+    FUNCTION(substr,             3, 0, 0, substrFunc       ),
+    FUNCTION(abs,                1, 0, 0, absFunc          ),
+#ifndef SQLITE_OMIT_FLOATING_POINT
+    FUNCTION(round,              1, 0, 0, roundFunc        ),
+    FUNCTION(round,              2, 0, 0, roundFunc        ),
+#endif
+    FUNCTION(upper,              1, 0, 0, upperFunc        ),
+    FUNCTION(lower,              1, 0, 0, lowerFunc        ),
+    FUNCTION(coalesce,           1, 0, 0, 0                ),
+    FUNCTION(coalesce,           0, 0, 0, 0                ),
+/*  FUNCTION(coalesce,          -1, 0, 0, ifnullFunc       ), */
+    {-1,SQLITE_UTF8,SQLITE_FUNC_COALESCE,0,0,ifnullFunc,0,0,"coalesce",0,0},
+    FUNCTION(hex,                1, 0, 0, hexFunc          ),
+/*  FUNCTION(ifnull,             2, 0, 0, ifnullFunc       ), */
+    {2,SQLITE_UTF8,SQLITE_FUNC_COALESCE,0,0,ifnullFunc,0,0,"ifnull",0,0},
+    FUNCTION(random,             0, 0, 0, randomFunc       ),
+    FUNCTION(randomblob,         1, 0, 0, randomBlob       ),
+    FUNCTION(nullif,             2, 0, 1, nullifFunc       ),
+    FUNCTION(sqlite_version,     0, 0, 0, versionFunc      ),
+    FUNCTION(sqlite_source_id,   0, 0, 0, sourceidFunc     ),
+    FUNCTION(sqlite_log,         2, 0, 0, errlogFunc       ),
+#ifndef SQLITE_OMIT_COMPILEOPTION_DIAGS
+    FUNCTION(sqlite_compileoption_used,1, 0, 0, compileoptionusedFunc  ),
+    FUNCTION(sqlite_compileoption_get, 1, 0, 0, compileoptiongetFunc  ),
+#endif /* SQLITE_OMIT_COMPILEOPTION_DIAGS */
+    FUNCTION(quote,              1, 0, 0, quoteFunc        ),
+    FUNCTION(last_insert_rowid,  0, 0, 0, last_insert_rowid),
+    FUNCTION(changes,            0, 0, 0, changes          ),
+    FUNCTION(total_changes,      0, 0, 0, total_changes    ),
+    FUNCTION(replace,            3, 0, 0, replaceFunc      ),
+    FUNCTION(zeroblob,           1, 0, 0, zeroblobFunc     ),
+  #ifdef SQLITE_SOUNDEX
+    FUNCTION(soundex,            1, 0, 0, soundexFunc      ),
+  #endif
+  #ifndef SQLITE_OMIT_LOAD_EXTENSION
+    FUNCTION(load_extension,     1, 0, 0, loadExt          ),
+    FUNCTION(load_extension,     2, 0, 0, loadExt          ),
+  #endif
+    AGGREGATE(sum,               1, 0, 0, sumStep,         sumFinalize    ),
+    AGGREGATE(total,             1, 0, 0, sumStep,         totalFinalize    ),
+    AGGREGATE(avg,               1, 0, 0, sumStep,         avgFinalize    ),
+ /* AGGREGATE(count,             0, 0, 0, countStep,       countFinalize  ), */
+    {0,SQLITE_UTF8,SQLITE_FUNC_COUNT,0,0,0,countStep,countFinalize,"count",0,0},
+    AGGREGATE(count,             1, 0, 0, countStep,       countFinalize  ),
+    AGGREGATE(group_concat,      1, 0, 0, groupConcatStep, groupConcatFinalize),
+    AGGREGATE(group_concat,      2, 0, 0, groupConcatStep, groupConcatFinalize),
+  
+    LIKEFUNC(glob, 2, &globInfo, SQLITE_FUNC_LIKE|SQLITE_FUNC_CASE),
+  #ifdef SQLITE_CASE_SENSITIVE_LIKE
+    LIKEFUNC(like, 2, &likeInfoAlt, SQLITE_FUNC_LIKE|SQLITE_FUNC_CASE),
+    LIKEFUNC(like, 3, &likeInfoAlt, SQLITE_FUNC_LIKE|SQLITE_FUNC_CASE),
+  #else
+    LIKEFUNC(like, 2, &likeInfoNorm, SQLITE_FUNC_LIKE),
+    LIKEFUNC(like, 3, &likeInfoNorm, SQLITE_FUNC_LIKE),
+  #endif
+  };
+
+  int i;
+  FuncDefHash *pHash = &GLOBAL(FuncDefHash, sqlite3GlobalFunctions);
+  FuncDef *aFunc = (FuncDef*)&GLOBAL(FuncDef, aBuiltinFunc);
+
+  for(i=0; i<ArraySize(aBuiltinFunc); i++){
+    sqlite3FuncDefInsert(pHash, &aFunc[i]);
+  }
+  sqlite3RegisterDateTimeFunctions();
+#ifndef SQLITE_OMIT_ALTERTABLE
+  sqlite3AlterFunctions();
+#endif
+}
diff --git a/src/global.c b/src/global.c
new file mode 100644
index 0000000..1e691c4
--- /dev/null
+++ b/src/global.c
@@ -0,0 +1,221 @@
+/*
+** 2008 June 13
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains definitions of global variables and contants.
+*/
+#include "sqliteInt.h"
+
+/* An array to map all upper-case characters into their corresponding
+** lower-case character. 
+**
+** SQLite only considers US-ASCII (or EBCDIC) characters.  We do not
+** handle case conversions for the UTF character set since the tables
+** involved are nearly as big or bigger than SQLite itself.
+*/
+const unsigned char sqlite3UpperToLower[] = {
+#ifdef SQLITE_ASCII
+      0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15, 16, 17,
+     18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35,
+     36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53,
+     54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 97, 98, 99,100,101,102,103,
+    104,105,106,107,108,109,110,111,112,113,114,115,116,117,118,119,120,121,
+    122, 91, 92, 93, 94, 95, 96, 97, 98, 99,100,101,102,103,104,105,106,107,
+    108,109,110,111,112,113,114,115,116,117,118,119,120,121,122,123,124,125,
+    126,127,128,129,130,131,132,133,134,135,136,137,138,139,140,141,142,143,
+    144,145,146,147,148,149,150,151,152,153,154,155,156,157,158,159,160,161,
+    162,163,164,165,166,167,168,169,170,171,172,173,174,175,176,177,178,179,
+    180,181,182,183,184,185,186,187,188,189,190,191,192,193,194,195,196,197,
+    198,199,200,201,202,203,204,205,206,207,208,209,210,211,212,213,214,215,
+    216,217,218,219,220,221,222,223,224,225,226,227,228,229,230,231,232,233,
+    234,235,236,237,238,239,240,241,242,243,244,245,246,247,248,249,250,251,
+    252,253,254,255
+#endif
+#ifdef SQLITE_EBCDIC
+      0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15, /* 0x */
+     16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, /* 1x */
+     32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, /* 2x */
+     48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, /* 3x */
+     64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, /* 4x */
+     80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, /* 5x */
+     96, 97, 66, 67, 68, 69, 70, 71, 72, 73,106,107,108,109,110,111, /* 6x */
+    112, 81, 82, 83, 84, 85, 86, 87, 88, 89,122,123,124,125,126,127, /* 7x */
+    128,129,130,131,132,133,134,135,136,137,138,139,140,141,142,143, /* 8x */
+    144,145,146,147,148,149,150,151,152,153,154,155,156,157,156,159, /* 9x */
+    160,161,162,163,164,165,166,167,168,169,170,171,140,141,142,175, /* Ax */
+    176,177,178,179,180,181,182,183,184,185,186,187,188,189,190,191, /* Bx */
+    192,129,130,131,132,133,134,135,136,137,202,203,204,205,206,207, /* Cx */
+    208,145,146,147,148,149,150,151,152,153,218,219,220,221,222,223, /* Dx */
+    224,225,162,163,164,165,166,167,168,169,232,203,204,205,206,207, /* Ex */
+    239,240,241,242,243,244,245,246,247,248,249,219,220,221,222,255, /* Fx */
+#endif
+};
+
+/*
+** The following 256 byte lookup table is used to support SQLites built-in
+** equivalents to the following standard library functions:
+**
+**   isspace()                        0x01
+**   isalpha()                        0x02
+**   isdigit()                        0x04
+**   isalnum()                        0x06
+**   isxdigit()                       0x08
+**   toupper()                        0x20
+**   SQLite identifier character      0x40
+**
+** Bit 0x20 is set if the mapped character requires translation to upper
+** case. i.e. if the character is a lower-case ASCII character.
+** If x is a lower-case ASCII character, then its upper-case equivalent
+** is (x - 0x20). Therefore toupper() can be implemented as:
+**
+**   (x & ~(map[x]&0x20))
+**
+** Standard function tolower() is implemented using the sqlite3UpperToLower[]
+** array. tolower() is used more often than toupper() by SQLite.
+**
+** Bit 0x40 is set if the character non-alphanumeric and can be used in an 
+** SQLite identifier.  Identifiers are alphanumerics, "_", "$", and any
+** non-ASCII UTF character. Hence the test for whether or not a character is
+** part of an identifier is 0x46.
+**
+** SQLite's versions are identical to the standard versions assuming a
+** locale of "C". They are implemented as macros in sqliteInt.h.
+*/
+#ifdef SQLITE_ASCII
+const unsigned char sqlite3CtypeMap[256] = {
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,  /* 00..07    ........ */
+  0x00, 0x01, 0x01, 0x01, 0x01, 0x01, 0x00, 0x00,  /* 08..0f    ........ */
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,  /* 10..17    ........ */
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,  /* 18..1f    ........ */
+  0x01, 0x00, 0x00, 0x00, 0x40, 0x00, 0x00, 0x00,  /* 20..27     !"#$%&' */
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,  /* 28..2f    ()*+,-./ */
+  0x0c, 0x0c, 0x0c, 0x0c, 0x0c, 0x0c, 0x0c, 0x0c,  /* 30..37    01234567 */
+  0x0c, 0x0c, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,  /* 38..3f    89:;<=>? */
+
+  0x00, 0x0a, 0x0a, 0x0a, 0x0a, 0x0a, 0x0a, 0x02,  /* 40..47    @ABCDEFG */
+  0x02, 0x02, 0x02, 0x02, 0x02, 0x02, 0x02, 0x02,  /* 48..4f    HIJKLMNO */
+  0x02, 0x02, 0x02, 0x02, 0x02, 0x02, 0x02, 0x02,  /* 50..57    PQRSTUVW */
+  0x02, 0x02, 0x02, 0x00, 0x00, 0x00, 0x00, 0x40,  /* 58..5f    XYZ[\]^_ */
+  0x00, 0x2a, 0x2a, 0x2a, 0x2a, 0x2a, 0x2a, 0x22,  /* 60..67    `abcdefg */
+  0x22, 0x22, 0x22, 0x22, 0x22, 0x22, 0x22, 0x22,  /* 68..6f    hijklmno */
+  0x22, 0x22, 0x22, 0x22, 0x22, 0x22, 0x22, 0x22,  /* 70..77    pqrstuvw */
+  0x22, 0x22, 0x22, 0x00, 0x00, 0x00, 0x00, 0x00,  /* 78..7f    xyz{|}~. */
+
+  0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40,  /* 80..87    ........ */
+  0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40,  /* 88..8f    ........ */
+  0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40,  /* 90..97    ........ */
+  0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40,  /* 98..9f    ........ */
+  0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40,  /* a0..a7    ........ */
+  0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40,  /* a8..af    ........ */
+  0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40,  /* b0..b7    ........ */
+  0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40,  /* b8..bf    ........ */
+
+  0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40,  /* c0..c7    ........ */
+  0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40,  /* c8..cf    ........ */
+  0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40,  /* d0..d7    ........ */
+  0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40,  /* d8..df    ........ */
+  0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40,  /* e0..e7    ........ */
+  0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40,  /* e8..ef    ........ */
+  0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40,  /* f0..f7    ........ */
+  0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40   /* f8..ff    ........ */
+};
+#endif
+
+#ifndef SQLITE_USE_URI
+# define  SQLITE_USE_URI 0
+#endif
+
+/*
+** The following singleton contains the global configuration for
+** the SQLite library.
+*/
+SQLITE_WSD struct Sqlite3Config sqlite3Config = {
+   SQLITE_DEFAULT_MEMSTATUS,  /* bMemstat */
+   1,                         /* bCoreMutex */
+   SQLITE_THREADSAFE==1,      /* bFullMutex */
+   SQLITE_USE_URI,            /* bOpenUri */
+   0x7ffffffe,                /* mxStrlen */
+   128,                       /* szLookaside */
+   500,                       /* nLookaside */
+   {0,0,0,0,0,0,0,0},         /* m */
+   {0,0,0,0,0,0,0,0,0},       /* mutex */
+   {0,0,0,0,0,0,0,0,0,0,0},   /* pcache */
+   (void*)0,                  /* pHeap */
+   0,                         /* nHeap */
+   0, 0,                      /* mnHeap, mxHeap */
+   (void*)0,                  /* pScratch */
+   0,                         /* szScratch */
+   0,                         /* nScratch */
+   (void*)0,                  /* pPage */
+   0,                         /* szPage */
+   0,                         /* nPage */
+   0,                         /* mxParserStack */
+   0,                         /* sharedCacheEnabled */
+   /* All the rest should always be initialized to zero */
+   0,                         /* isInit */
+   0,                         /* inProgress */
+   0,                         /* isMutexInit */
+   0,                         /* isMallocInit */
+   0,                         /* isPCacheInit */
+   0,                         /* pInitMutex */
+   0,                         /* nRefInitMutex */
+   0,                         /* xLog */
+   0,                         /* pLogArg */
+   0,                         /* bLocaltimeFault */
+};
+
+
+/*
+** Hash table for global functions - functions common to all
+** database connections.  After initialization, this table is
+** read-only.
+*/
+SQLITE_WSD FuncDefHash sqlite3GlobalFunctions;
+
+/*
+** Constant tokens for values 0 and 1.
+*/
+const Token sqlite3IntTokens[] = {
+   { "0", 1 },
+   { "1", 1 }
+};
+
+
+/*
+** The value of the "pending" byte must be 0x40000000 (1 byte past the
+** 1-gibabyte boundary) in a compatible database.  SQLite never uses
+** the database page that contains the pending byte.  It never attempts
+** to read or write that page.  The pending byte page is set assign
+** for use by the VFS layers as space for managing file locks.
+**
+** During testing, it is often desirable to move the pending byte to
+** a different position in the file.  This allows code that has to
+** deal with the pending byte to run on files that are much smaller
+** than 1 GiB.  The sqlite3_test_control() interface can be used to
+** move the pending byte.
+**
+** IMPORTANT:  Changing the pending byte to any value other than
+** 0x40000000 results in an incompatible database file format!
+** Changing the pending byte during operating results in undefined
+** and dileterious behavior.
+*/
+#ifndef SQLITE_OMIT_WSD
+int sqlite3PendingByte = 0x40000000;
+#endif
+
+#include "opcodes.h"
+/*
+** Properties of opcodes.  The OPFLG_INITIALIZER macro is
+** created by mkopcodeh.awk during compilation.  Data is obtained
+** from the comments following the "case OP_xxxx:" statements in
+** the vdbe.c file.  
+*/
+const unsigned char sqlite3OpcodeProperty[] = OPFLG_INITIALIZER;
diff --git a/src/hash.c b/src/hash.c
new file mode 100644
index 0000000..d4daf92
--- /dev/null
+++ b/src/hash.c
@@ -0,0 +1,277 @@
+/*
+** 2001 September 22
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This is the implementation of generic hash-tables
+** used in SQLite.
+*/
+#include "sqliteInt.h"
+#include <assert.h>
+
+/* Turn bulk memory into a hash table object by initializing the
+** fields of the Hash structure.
+**
+** "pNew" is a pointer to the hash table that is to be initialized.
+*/
+void sqlite3HashInit(Hash *pNew){
+  assert( pNew!=0 );
+  pNew->first = 0;
+  pNew->count = 0;
+  pNew->htsize = 0;
+  pNew->ht = 0;
+}
+
+/* Remove all entries from a hash table.  Reclaim all memory.
+** Call this routine to delete a hash table or to reset a hash table
+** to the empty state.
+*/
+void sqlite3HashClear(Hash *pH){
+  HashElem *elem;         /* For looping over all elements of the table */
+
+  assert( pH!=0 );
+  elem = pH->first;
+  pH->first = 0;
+  sqlite3_free(pH->ht);
+  pH->ht = 0;
+  pH->htsize = 0;
+  while( elem ){
+    HashElem *next_elem = elem->next;
+    sqlite3_free(elem);
+    elem = next_elem;
+  }
+  pH->count = 0;
+}
+
+/*
+** The hashing function.
+*/
+static unsigned int strHash(const char *z, int nKey){
+  int h = 0;
+  assert( nKey>=0 );
+  while( nKey > 0  ){
+    h = (h<<3) ^ h ^ sqlite3UpperToLower[(unsigned char)*z++];
+    nKey--;
+  }
+  return h;
+}
+
+
+/* Link pNew element into the hash table pH.  If pEntry!=0 then also
+** insert pNew into the pEntry hash bucket.
+*/
+static void insertElement(
+  Hash *pH,              /* The complete hash table */
+  struct _ht *pEntry,    /* The entry into which pNew is inserted */
+  HashElem *pNew         /* The element to be inserted */
+){
+  HashElem *pHead;       /* First element already in pEntry */
+  if( pEntry ){
+    pHead = pEntry->count ? pEntry->chain : 0;
+    pEntry->count++;
+    pEntry->chain = pNew;
+  }else{
+    pHead = 0;
+  }
+  if( pHead ){
+    pNew->next = pHead;
+    pNew->prev = pHead->prev;
+    if( pHead->prev ){ pHead->prev->next = pNew; }
+    else             { pH->first = pNew; }
+    pHead->prev = pNew;
+  }else{
+    pNew->next = pH->first;
+    if( pH->first ){ pH->first->prev = pNew; }
+    pNew->prev = 0;
+    pH->first = pNew;
+  }
+}
+
+
+/* Resize the hash table so that it cantains "new_size" buckets.
+**
+** The hash table might fail to resize if sqlite3_malloc() fails or
+** if the new size is the same as the prior size.
+** Return TRUE if the resize occurs and false if not.
+*/
+static int rehash(Hash *pH, unsigned int new_size){
+  struct _ht *new_ht;            /* The new hash table */
+  HashElem *elem, *next_elem;    /* For looping over existing elements */
+
+#if SQLITE_MALLOC_SOFT_LIMIT>0
+  if( new_size*sizeof(struct _ht)>SQLITE_MALLOC_SOFT_LIMIT ){
+    new_size = SQLITE_MALLOC_SOFT_LIMIT/sizeof(struct _ht);
+  }
+  if( new_size==pH->htsize ) return 0;
+#endif
+
+  /* The inability to allocates space for a larger hash table is
+  ** a performance hit but it is not a fatal error.  So mark the
+  ** allocation as a benign.
+  */
+  sqlite3BeginBenignMalloc();
+  new_ht = (struct _ht *)sqlite3Malloc( new_size*sizeof(struct _ht) );
+  sqlite3EndBenignMalloc();
+
+  if( new_ht==0 ) return 0;
+  sqlite3_free(pH->ht);
+  pH->ht = new_ht;
+  pH->htsize = new_size = sqlite3MallocSize(new_ht)/sizeof(struct _ht);
+  memset(new_ht, 0, new_size*sizeof(struct _ht));
+  for(elem=pH->first, pH->first=0; elem; elem = next_elem){
+    unsigned int h = strHash(elem->pKey, elem->nKey) % new_size;
+    next_elem = elem->next;
+    insertElement(pH, &new_ht[h], elem);
+  }
+  return 1;
+}
+
+/* This function (for internal use only) locates an element in an
+** hash table that matches the given key.  The hash for this key has
+** already been computed and is passed as the 4th parameter.
+*/
+static HashElem *findElementGivenHash(
+  const Hash *pH,     /* The pH to be searched */
+  const char *pKey,   /* The key we are searching for */
+  int nKey,           /* Bytes in key (not counting zero terminator) */
+  unsigned int h      /* The hash for this key. */
+){
+  HashElem *elem;                /* Used to loop thru the element list */
+  int count;                     /* Number of elements left to test */
+
+  if( pH->ht ){
+    struct _ht *pEntry = &pH->ht[h];
+    elem = pEntry->chain;
+    count = pEntry->count;
+  }else{
+    elem = pH->first;
+    count = pH->count;
+  }
+  while( count-- && ALWAYS(elem) ){
+    if( elem->nKey==nKey && sqlite3StrNICmp(elem->pKey,pKey,nKey)==0 ){ 
+      return elem;
+    }
+    elem = elem->next;
+  }
+  return 0;
+}
+
+/* Remove a single entry from the hash table given a pointer to that
+** element and a hash on the element's key.
+*/
+static void removeElementGivenHash(
+  Hash *pH,         /* The pH containing "elem" */
+  HashElem* elem,   /* The element to be removed from the pH */
+  unsigned int h    /* Hash value for the element */
+){
+  struct _ht *pEntry;
+  if( elem->prev ){
+    elem->prev->next = elem->next; 
+  }else{
+    pH->first = elem->next;
+  }
+  if( elem->next ){
+    elem->next->prev = elem->prev;
+  }
+  if( pH->ht ){
+    pEntry = &pH->ht[h];
+    if( pEntry->chain==elem ){
+      pEntry->chain = elem->next;
+    }
+    pEntry->count--;
+    assert( pEntry->count>=0 );
+  }
+  sqlite3_free( elem );
+  pH->count--;
+  if( pH->count<=0 ){
+    assert( pH->first==0 );
+    assert( pH->count==0 );
+    sqlite3HashClear(pH);
+  }
+}
+
+/* Attempt to locate an element of the hash table pH with a key
+** that matches pKey,nKey.  Return the data for this element if it is
+** found, or NULL if there is no match.
+*/
+void *sqlite3HashFind(const Hash *pH, const char *pKey, int nKey){
+  HashElem *elem;    /* The element that matches key */
+  unsigned int h;    /* A hash on key */
+
+  assert( pH!=0 );
+  assert( pKey!=0 );
+  assert( nKey>=0 );
+  if( pH->ht ){
+    h = strHash(pKey, nKey) % pH->htsize;
+  }else{
+    h = 0;
+  }
+  elem = findElementGivenHash(pH, pKey, nKey, h);
+  return elem ? elem->data : 0;
+}
+
+/* Insert an element into the hash table pH.  The key is pKey,nKey
+** and the data is "data".
+**
+** If no element exists with a matching key, then a new
+** element is created and NULL is returned.
+**
+** If another element already exists with the same key, then the
+** new data replaces the old data and the old data is returned.
+** The key is not copied in this instance.  If a malloc fails, then
+** the new data is returned and the hash table is unchanged.
+**
+** If the "data" parameter to this function is NULL, then the
+** element corresponding to "key" is removed from the hash table.
+*/
+void *sqlite3HashInsert(Hash *pH, const char *pKey, int nKey, void *data){
+  unsigned int h;       /* the hash of the key modulo hash table size */
+  HashElem *elem;       /* Used to loop thru the element list */
+  HashElem *new_elem;   /* New element added to the pH */
+
+  assert( pH!=0 );
+  assert( pKey!=0 );
+  assert( nKey>=0 );
+  if( pH->htsize ){
+    h = strHash(pKey, nKey) % pH->htsize;
+  }else{
+    h = 0;
+  }
+  elem = findElementGivenHash(pH,pKey,nKey,h);
+  if( elem ){
+    void *old_data = elem->data;
+    if( data==0 ){
+      removeElementGivenHash(pH,elem,h);
+    }else{
+      elem->data = data;
+      elem->pKey = pKey;
+      assert(nKey==elem->nKey);
+    }
+    return old_data;
+  }
+  if( data==0 ) return 0;
+  new_elem = (HashElem*)sqlite3Malloc( sizeof(HashElem) );
+  if( new_elem==0 ) return data;
+  new_elem->pKey = pKey;
+  new_elem->nKey = nKey;
+  new_elem->data = data;
+  pH->count++;
+  if( pH->count>=10 && pH->count > 2*pH->htsize ){
+    if( rehash(pH, pH->count*2) ){
+      assert( pH->htsize>0 );
+      h = strHash(pKey, nKey) % pH->htsize;
+    }
+  }
+  if( pH->ht ){
+    insertElement(pH, &pH->ht[h], new_elem);
+  }else{
+    insertElement(pH, 0, new_elem);
+  }
+  return 0;
+}
diff --git a/src/hash.h b/src/hash.h
new file mode 100644
index 0000000..990a2d6
--- /dev/null
+++ b/src/hash.h
@@ -0,0 +1,96 @@
+/*
+** 2001 September 22
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This is the header file for the generic hash-table implemenation
+** used in SQLite.
+*/
+#ifndef _SQLITE_HASH_H_
+#define _SQLITE_HASH_H_
+
+/* Forward declarations of structures. */
+typedef struct Hash Hash;
+typedef struct HashElem HashElem;
+
+/* A complete hash table is an instance of the following structure.
+** The internals of this structure are intended to be opaque -- client
+** code should not attempt to access or modify the fields of this structure
+** directly.  Change this structure only by using the routines below.
+** However, some of the "procedures" and "functions" for modifying and
+** accessing this structure are really macros, so we can't really make
+** this structure opaque.
+**
+** All elements of the hash table are on a single doubly-linked list.
+** Hash.first points to the head of this list.
+**
+** There are Hash.htsize buckets.  Each bucket points to a spot in
+** the global doubly-linked list.  The contents of the bucket are the
+** element pointed to plus the next _ht.count-1 elements in the list.
+**
+** Hash.htsize and Hash.ht may be zero.  In that case lookup is done
+** by a linear search of the global list.  For small tables, the 
+** Hash.ht table is never allocated because if there are few elements
+** in the table, it is faster to do a linear search than to manage
+** the hash table.
+*/
+struct Hash {
+  unsigned int htsize;      /* Number of buckets in the hash table */
+  unsigned int count;       /* Number of entries in this table */
+  HashElem *first;          /* The first element of the array */
+  struct _ht {              /* the hash table */
+    int count;                 /* Number of entries with this hash */
+    HashElem *chain;           /* Pointer to first entry with this hash */
+  } *ht;
+};
+
+/* Each element in the hash table is an instance of the following 
+** structure.  All elements are stored on a single doubly-linked list.
+**
+** Again, this structure is intended to be opaque, but it can't really
+** be opaque because it is used by macros.
+*/
+struct HashElem {
+  HashElem *next, *prev;       /* Next and previous elements in the table */
+  void *data;                  /* Data associated with this element */
+  const char *pKey; int nKey;  /* Key associated with this element */
+};
+
+/*
+** Access routines.  To delete, insert a NULL pointer.
+*/
+void sqlite3HashInit(Hash*);
+void *sqlite3HashInsert(Hash*, const char *pKey, int nKey, void *pData);
+void *sqlite3HashFind(const Hash*, const char *pKey, int nKey);
+void sqlite3HashClear(Hash*);
+
+/*
+** Macros for looping over all elements of a hash table.  The idiom is
+** like this:
+**
+**   Hash h;
+**   HashElem *p;
+**   ...
+**   for(p=sqliteHashFirst(&h); p; p=sqliteHashNext(p)){
+**     SomeStructure *pData = sqliteHashData(p);
+**     // do something with pData
+**   }
+*/
+#define sqliteHashFirst(H)  ((H)->first)
+#define sqliteHashNext(E)   ((E)->next)
+#define sqliteHashData(E)   ((E)->data)
+/* #define sqliteHashKey(E)    ((E)->pKey) // NOT USED */
+/* #define sqliteHashKeysize(E) ((E)->nKey)  // NOT USED */
+
+/*
+** Number of entries in a hash table
+*/
+/* #define sqliteHashCount(H)  ((H)->count) // NOT USED */
+
+#endif /* _SQLITE_HASH_H_ */
diff --git a/src/hwtime.h b/src/hwtime.h
new file mode 100644
index 0000000..b8bc5a2
--- /dev/null
+++ b/src/hwtime.h
@@ -0,0 +1,85 @@
+/*
+** 2008 May 27
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains inline asm code for retrieving "high-performance"
+** counters for x86 class CPUs.
+*/
+#ifndef _HWTIME_H_
+#define _HWTIME_H_
+
+/*
+** The following routine only works on pentium-class (or newer) processors.
+** It uses the RDTSC opcode to read the cycle count value out of the
+** processor and returns that value.  This can be used for high-res
+** profiling.
+*/
+#if (defined(__GNUC__) || defined(_MSC_VER)) && \
+      (defined(i386) || defined(__i386__) || defined(_M_IX86))
+
+  #if defined(__GNUC__)
+
+  __inline__ sqlite_uint64 sqlite3Hwtime(void){
+     unsigned int lo, hi;
+     __asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi));
+     return (sqlite_uint64)hi << 32 | lo;
+  }
+
+  #elif defined(_MSC_VER)
+
+  __declspec(naked) __inline sqlite_uint64 __cdecl sqlite3Hwtime(void){
+     __asm {
+        rdtsc
+        ret       ; return value at EDX:EAX
+     }
+  }
+
+  #endif
+
+#elif (defined(__GNUC__) && defined(__x86_64__))
+
+  __inline__ sqlite_uint64 sqlite3Hwtime(void){
+      unsigned long val;
+      __asm__ __volatile__ ("rdtsc" : "=A" (val));
+      return val;
+  }
+ 
+#elif (defined(__GNUC__) && defined(__ppc__))
+
+  __inline__ sqlite_uint64 sqlite3Hwtime(void){
+      unsigned long long retval;
+      unsigned long junk;
+      __asm__ __volatile__ ("\n\
+          1:      mftbu   %1\n\
+                  mftb    %L0\n\
+                  mftbu   %0\n\
+                  cmpw    %0,%1\n\
+                  bne     1b"
+                  : "=r" (retval), "=r" (junk));
+      return retval;
+  }
+
+#else
+
+  #error Need implementation of sqlite3Hwtime() for your platform.
+
+  /*
+  ** To compile without implementing sqlite3Hwtime() for your platform,
+  ** you can remove the above #error and use the following
+  ** stub function.  You will lose timing support for many
+  ** of the debugging and testing utilities, but it should at
+  ** least compile and run.
+  */
+  sqlite_uint64 sqlite3Hwtime(void){ return ((sqlite_uint64)0); }
+
+#endif
+
+#endif /* !defined(_HWTIME_H_) */
diff --git a/src/insert.c b/src/insert.c
new file mode 100644
index 0000000..277a852
--- /dev/null
+++ b/src/insert.c
@@ -0,0 +1,1846 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains C code routines that are called by the parser
+** to handle INSERT statements in SQLite.
+*/
+#include "sqliteInt.h"
+
+/*
+** Generate code that will open a table for reading.
+*/
+void sqlite3OpenTable(
+  Parse *p,       /* Generate code into this VDBE */
+  int iCur,       /* The cursor number of the table */
+  int iDb,        /* The database index in sqlite3.aDb[] */
+  Table *pTab,    /* The table to be opened */
+  int opcode      /* OP_OpenRead or OP_OpenWrite */
+){
+  Vdbe *v;
+  if( IsVirtual(pTab) ) return;
+  v = sqlite3GetVdbe(p);
+  assert( opcode==OP_OpenWrite || opcode==OP_OpenRead );
+  sqlite3TableLock(p, iDb, pTab->tnum, (opcode==OP_OpenWrite)?1:0, pTab->zName);
+  sqlite3VdbeAddOp3(v, opcode, iCur, pTab->tnum, iDb);
+  sqlite3VdbeChangeP4(v, -1, SQLITE_INT_TO_PTR(pTab->nCol), P4_INT32);
+  VdbeComment((v, "%s", pTab->zName));
+}
+
+/*
+** Return a pointer to the column affinity string associated with index
+** pIdx. A column affinity string has one character for each column in 
+** the table, according to the affinity of the column:
+**
+**  Character      Column affinity
+**  ------------------------------
+**  'a'            TEXT
+**  'b'            NONE
+**  'c'            NUMERIC
+**  'd'            INTEGER
+**  'e'            REAL
+**
+** An extra 'b' is appended to the end of the string to cover the
+** rowid that appears as the last column in every index.
+**
+** Memory for the buffer containing the column index affinity string
+** is managed along with the rest of the Index structure. It will be
+** released when sqlite3DeleteIndex() is called.
+*/
+const char *sqlite3IndexAffinityStr(Vdbe *v, Index *pIdx){
+  if( !pIdx->zColAff ){
+    /* The first time a column affinity string for a particular index is
+    ** required, it is allocated and populated here. It is then stored as
+    ** a member of the Index structure for subsequent use.
+    **
+    ** The column affinity string will eventually be deleted by
+    ** sqliteDeleteIndex() when the Index structure itself is cleaned
+    ** up.
+    */
+    int n;
+    Table *pTab = pIdx->pTable;
+    sqlite3 *db = sqlite3VdbeDb(v);
+    pIdx->zColAff = (char *)sqlite3DbMallocRaw(0, pIdx->nColumn+2);
+    if( !pIdx->zColAff ){
+      db->mallocFailed = 1;
+      return 0;
+    }
+    for(n=0; n<pIdx->nColumn; n++){
+      pIdx->zColAff[n] = pTab->aCol[pIdx->aiColumn[n]].affinity;
+    }
+    pIdx->zColAff[n++] = SQLITE_AFF_NONE;
+    pIdx->zColAff[n] = 0;
+  }
+ 
+  return pIdx->zColAff;
+}
+
+/*
+** Set P4 of the most recently inserted opcode to a column affinity
+** string for table pTab. A column affinity string has one character
+** for each column indexed by the index, according to the affinity of the
+** column:
+**
+**  Character      Column affinity
+**  ------------------------------
+**  'a'            TEXT
+**  'b'            NONE
+**  'c'            NUMERIC
+**  'd'            INTEGER
+**  'e'            REAL
+*/
+void sqlite3TableAffinityStr(Vdbe *v, Table *pTab){
+  /* The first time a column affinity string for a particular table
+  ** is required, it is allocated and populated here. It is then 
+  ** stored as a member of the Table structure for subsequent use.
+  **
+  ** The column affinity string will eventually be deleted by
+  ** sqlite3DeleteTable() when the Table structure itself is cleaned up.
+  */
+  if( !pTab->zColAff ){
+    char *zColAff;
+    int i;
+    sqlite3 *db = sqlite3VdbeDb(v);
+
+    zColAff = (char *)sqlite3DbMallocRaw(0, pTab->nCol+1);
+    if( !zColAff ){
+      db->mallocFailed = 1;
+      return;
+    }
+
+    for(i=0; i<pTab->nCol; i++){
+      zColAff[i] = pTab->aCol[i].affinity;
+    }
+    zColAff[pTab->nCol] = '\0';
+
+    pTab->zColAff = zColAff;
+  }
+
+  sqlite3VdbeChangeP4(v, -1, pTab->zColAff, P4_TRANSIENT);
+}
+
+/*
+** Return non-zero if the table pTab in database iDb or any of its indices
+** have been opened at any point in the VDBE program beginning at location
+** iStartAddr throught the end of the program.  This is used to see if 
+** a statement of the form  "INSERT INTO <iDb, pTab> SELECT ..." can 
+** run without using temporary table for the results of the SELECT. 
+*/
+static int readsTable(Parse *p, int iStartAddr, int iDb, Table *pTab){
+  Vdbe *v = sqlite3GetVdbe(p);
+  int i;
+  int iEnd = sqlite3VdbeCurrentAddr(v);
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  VTable *pVTab = IsVirtual(pTab) ? sqlite3GetVTable(p->db, pTab) : 0;
+#endif
+
+  for(i=iStartAddr; i<iEnd; i++){
+    VdbeOp *pOp = sqlite3VdbeGetOp(v, i);
+    assert( pOp!=0 );
+    if( pOp->opcode==OP_OpenRead && pOp->p3==iDb ){
+      Index *pIndex;
+      int tnum = pOp->p2;
+      if( tnum==pTab->tnum ){
+        return 1;
+      }
+      for(pIndex=pTab->pIndex; pIndex; pIndex=pIndex->pNext){
+        if( tnum==pIndex->tnum ){
+          return 1;
+        }
+      }
+    }
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+    if( pOp->opcode==OP_VOpen && pOp->p4.pVtab==pVTab ){
+      assert( pOp->p4.pVtab!=0 );
+      assert( pOp->p4type==P4_VTAB );
+      return 1;
+    }
+#endif
+  }
+  return 0;
+}
+
+#ifndef SQLITE_OMIT_AUTOINCREMENT
+/*
+** Locate or create an AutoincInfo structure associated with table pTab
+** which is in database iDb.  Return the register number for the register
+** that holds the maximum rowid.
+**
+** There is at most one AutoincInfo structure per table even if the
+** same table is autoincremented multiple times due to inserts within
+** triggers.  A new AutoincInfo structure is created if this is the
+** first use of table pTab.  On 2nd and subsequent uses, the original
+** AutoincInfo structure is used.
+**
+** Three memory locations are allocated:
+**
+**   (1)  Register to hold the name of the pTab table.
+**   (2)  Register to hold the maximum ROWID of pTab.
+**   (3)  Register to hold the rowid in sqlite_sequence of pTab
+**
+** The 2nd register is the one that is returned.  That is all the
+** insert routine needs to know about.
+*/
+static int autoIncBegin(
+  Parse *pParse,      /* Parsing context */
+  int iDb,            /* Index of the database holding pTab */
+  Table *pTab         /* The table we are writing to */
+){
+  int memId = 0;      /* Register holding maximum rowid */
+  if( pTab->tabFlags & TF_Autoincrement ){
+    Parse *pToplevel = sqlite3ParseToplevel(pParse);
+    AutoincInfo *pInfo;
+
+    pInfo = pToplevel->pAinc;
+    while( pInfo && pInfo->pTab!=pTab ){ pInfo = pInfo->pNext; }
+    if( pInfo==0 ){
+      pInfo = sqlite3DbMallocRaw(pParse->db, sizeof(*pInfo));
+      if( pInfo==0 ) return 0;
+      pInfo->pNext = pToplevel->pAinc;
+      pToplevel->pAinc = pInfo;
+      pInfo->pTab = pTab;
+      pInfo->iDb = iDb;
+      pToplevel->nMem++;                  /* Register to hold name of table */
+      pInfo->regCtr = ++pToplevel->nMem;  /* Max rowid register */
+      pToplevel->nMem++;                  /* Rowid in sqlite_sequence */
+    }
+    memId = pInfo->regCtr;
+  }
+  return memId;
+}
+
+/*
+** This routine generates code that will initialize all of the
+** register used by the autoincrement tracker.  
+*/
+void sqlite3AutoincrementBegin(Parse *pParse){
+  AutoincInfo *p;            /* Information about an AUTOINCREMENT */
+  sqlite3 *db = pParse->db;  /* The database connection */
+  Db *pDb;                   /* Database only autoinc table */
+  int memId;                 /* Register holding max rowid */
+  int addr;                  /* A VDBE address */
+  Vdbe *v = pParse->pVdbe;   /* VDBE under construction */
+
+  /* This routine is never called during trigger-generation.  It is
+  ** only called from the top-level */
+  assert( pParse->pTriggerTab==0 );
+  assert( pParse==sqlite3ParseToplevel(pParse) );
+
+  assert( v );   /* We failed long ago if this is not so */
+  for(p = pParse->pAinc; p; p = p->pNext){
+    pDb = &db->aDb[p->iDb];
+    memId = p->regCtr;
+    assert( sqlite3SchemaMutexHeld(db, 0, pDb->pSchema) );
+    sqlite3OpenTable(pParse, 0, p->iDb, pDb->pSchema->pSeqTab, OP_OpenRead);
+    addr = sqlite3VdbeCurrentAddr(v);
+    sqlite3VdbeAddOp4(v, OP_String8, 0, memId-1, 0, p->pTab->zName, 0);
+    sqlite3VdbeAddOp2(v, OP_Rewind, 0, addr+9);
+    sqlite3VdbeAddOp3(v, OP_Column, 0, 0, memId);
+    sqlite3VdbeAddOp3(v, OP_Ne, memId-1, addr+7, memId);
+    sqlite3VdbeChangeP5(v, SQLITE_JUMPIFNULL);
+    sqlite3VdbeAddOp2(v, OP_Rowid, 0, memId+1);
+    sqlite3VdbeAddOp3(v, OP_Column, 0, 1, memId);
+    sqlite3VdbeAddOp2(v, OP_Goto, 0, addr+9);
+    sqlite3VdbeAddOp2(v, OP_Next, 0, addr+2);
+    sqlite3VdbeAddOp2(v, OP_Integer, 0, memId);
+    sqlite3VdbeAddOp0(v, OP_Close);
+  }
+}
+
+/*
+** Update the maximum rowid for an autoincrement calculation.
+**
+** This routine should be called when the top of the stack holds a
+** new rowid that is about to be inserted.  If that new rowid is
+** larger than the maximum rowid in the memId memory cell, then the
+** memory cell is updated.  The stack is unchanged.
+*/
+static void autoIncStep(Parse *pParse, int memId, int regRowid){
+  if( memId>0 ){
+    sqlite3VdbeAddOp2(pParse->pVdbe, OP_MemMax, memId, regRowid);
+  }
+}
+
+/*
+** This routine generates the code needed to write autoincrement
+** maximum rowid values back into the sqlite_sequence register.
+** Every statement that might do an INSERT into an autoincrement
+** table (either directly or through triggers) needs to call this
+** routine just before the "exit" code.
+*/
+void sqlite3AutoincrementEnd(Parse *pParse){
+  AutoincInfo *p;
+  Vdbe *v = pParse->pVdbe;
+  sqlite3 *db = pParse->db;
+
+  assert( v );
+  for(p = pParse->pAinc; p; p = p->pNext){
+    Db *pDb = &db->aDb[p->iDb];
+    int j1, j2, j3, j4, j5;
+    int iRec;
+    int memId = p->regCtr;
+
+    iRec = sqlite3GetTempReg(pParse);
+    assert( sqlite3SchemaMutexHeld(db, 0, pDb->pSchema) );
+    sqlite3OpenTable(pParse, 0, p->iDb, pDb->pSchema->pSeqTab, OP_OpenWrite);
+    j1 = sqlite3VdbeAddOp1(v, OP_NotNull, memId+1);
+    j2 = sqlite3VdbeAddOp0(v, OP_Rewind);
+    j3 = sqlite3VdbeAddOp3(v, OP_Column, 0, 0, iRec);
+    j4 = sqlite3VdbeAddOp3(v, OP_Eq, memId-1, 0, iRec);
+    sqlite3VdbeAddOp2(v, OP_Next, 0, j3);
+    sqlite3VdbeJumpHere(v, j2);
+    sqlite3VdbeAddOp2(v, OP_NewRowid, 0, memId+1);
+    j5 = sqlite3VdbeAddOp0(v, OP_Goto);
+    sqlite3VdbeJumpHere(v, j4);
+    sqlite3VdbeAddOp2(v, OP_Rowid, 0, memId+1);
+    sqlite3VdbeJumpHere(v, j1);
+    sqlite3VdbeJumpHere(v, j5);
+    sqlite3VdbeAddOp3(v, OP_MakeRecord, memId-1, 2, iRec);
+    sqlite3VdbeAddOp3(v, OP_Insert, 0, iRec, memId+1);
+    sqlite3VdbeChangeP5(v, OPFLAG_APPEND);
+    sqlite3VdbeAddOp0(v, OP_Close);
+    sqlite3ReleaseTempReg(pParse, iRec);
+  }
+}
+#else
+/*
+** If SQLITE_OMIT_AUTOINCREMENT is defined, then the three routines
+** above are all no-ops
+*/
+# define autoIncBegin(A,B,C) (0)
+# define autoIncStep(A,B,C)
+#endif /* SQLITE_OMIT_AUTOINCREMENT */
+
+
+/* Forward declaration */
+static int xferOptimization(
+  Parse *pParse,        /* Parser context */
+  Table *pDest,         /* The table we are inserting into */
+  Select *pSelect,      /* A SELECT statement to use as the data source */
+  int onError,          /* How to handle constraint errors */
+  int iDbDest           /* The database of pDest */
+);
+
+/*
+** This routine is call to handle SQL of the following forms:
+**
+**    insert into TABLE (IDLIST) values(EXPRLIST)
+**    insert into TABLE (IDLIST) select
+**
+** The IDLIST following the table name is always optional.  If omitted,
+** then a list of all columns for the table is substituted.  The IDLIST
+** appears in the pColumn parameter.  pColumn is NULL if IDLIST is omitted.
+**
+** The pList parameter holds EXPRLIST in the first form of the INSERT
+** statement above, and pSelect is NULL.  For the second form, pList is
+** NULL and pSelect is a pointer to the select statement used to generate
+** data for the insert.
+**
+** The code generated follows one of four templates.  For a simple
+** select with data coming from a VALUES clause, the code executes
+** once straight down through.  Pseudo-code follows (we call this
+** the "1st template"):
+**
+**         open write cursor to <table> and its indices
+**         puts VALUES clause expressions onto the stack
+**         write the resulting record into <table>
+**         cleanup
+**
+** The three remaining templates assume the statement is of the form
+**
+**   INSERT INTO <table> SELECT ...
+**
+** If the SELECT clause is of the restricted form "SELECT * FROM <table2>" -
+** in other words if the SELECT pulls all columns from a single table
+** and there is no WHERE or LIMIT or GROUP BY or ORDER BY clauses, and
+** if <table2> and <table1> are distinct tables but have identical
+** schemas, including all the same indices, then a special optimization
+** is invoked that copies raw records from <table2> over to <table1>.
+** See the xferOptimization() function for the implementation of this
+** template.  This is the 2nd template.
+**
+**         open a write cursor to <table>
+**         open read cursor on <table2>
+**         transfer all records in <table2> over to <table>
+**         close cursors
+**         foreach index on <table>
+**           open a write cursor on the <table> index
+**           open a read cursor on the corresponding <table2> index
+**           transfer all records from the read to the write cursors
+**           close cursors
+**         end foreach
+**
+** The 3rd template is for when the second template does not apply
+** and the SELECT clause does not read from <table> at any time.
+** The generated code follows this template:
+**
+**         EOF <- 0
+**         X <- A
+**         goto B
+**      A: setup for the SELECT
+**         loop over the rows in the SELECT
+**           load values into registers R..R+n
+**           yield X
+**         end loop
+**         cleanup after the SELECT
+**         EOF <- 1
+**         yield X
+**         goto A
+**      B: open write cursor to <table> and its indices
+**      C: yield X
+**         if EOF goto D
+**         insert the select result into <table> from R..R+n
+**         goto C
+**      D: cleanup
+**
+** The 4th template is used if the insert statement takes its
+** values from a SELECT but the data is being inserted into a table
+** that is also read as part of the SELECT.  In the third form,
+** we have to use a intermediate table to store the results of
+** the select.  The template is like this:
+**
+**         EOF <- 0
+**         X <- A
+**         goto B
+**      A: setup for the SELECT
+**         loop over the tables in the SELECT
+**           load value into register R..R+n
+**           yield X
+**         end loop
+**         cleanup after the SELECT
+**         EOF <- 1
+**         yield X
+**         halt-error
+**      B: open temp table
+**      L: yield X
+**         if EOF goto M
+**         insert row from R..R+n into temp table
+**         goto L
+**      M: open write cursor to <table> and its indices
+**         rewind temp table
+**      C: loop over rows of intermediate table
+**           transfer values form intermediate table into <table>
+**         end loop
+**      D: cleanup
+*/
+void sqlite3Insert(
+  Parse *pParse,        /* Parser context */
+  SrcList *pTabList,    /* Name of table into which we are inserting */
+  ExprList *pList,      /* List of values to be inserted */
+  Select *pSelect,      /* A SELECT statement to use as the data source */
+  IdList *pColumn,      /* Column names corresponding to IDLIST. */
+  int onError           /* How to handle constraint errors */
+){
+  sqlite3 *db;          /* The main database structure */
+  Table *pTab;          /* The table to insert into.  aka TABLE */
+  char *zTab;           /* Name of the table into which we are inserting */
+  const char *zDb;      /* Name of the database holding this table */
+  int i, j, idx;        /* Loop counters */
+  Vdbe *v;              /* Generate code into this virtual machine */
+  Index *pIdx;          /* For looping over indices of the table */
+  int nColumn;          /* Number of columns in the data */
+  int nHidden = 0;      /* Number of hidden columns if TABLE is virtual */
+  int baseCur = 0;      /* VDBE Cursor number for pTab */
+  int keyColumn = -1;   /* Column that is the INTEGER PRIMARY KEY */
+  int endOfLoop;        /* Label for the end of the insertion loop */
+  int useTempTable = 0; /* Store SELECT results in intermediate table */
+  int srcTab = 0;       /* Data comes from this temporary cursor if >=0 */
+  int addrInsTop = 0;   /* Jump to label "D" */
+  int addrCont = 0;     /* Top of insert loop. Label "C" in templates 3 and 4 */
+  int addrSelect = 0;   /* Address of coroutine that implements the SELECT */
+  SelectDest dest;      /* Destination for SELECT on rhs of INSERT */
+  int iDb;              /* Index of database holding TABLE */
+  Db *pDb;              /* The database containing table being inserted into */
+  int appendFlag = 0;   /* True if the insert is likely to be an append */
+
+  /* Register allocations */
+  int regFromSelect = 0;/* Base register for data coming from SELECT */
+  int regAutoinc = 0;   /* Register holding the AUTOINCREMENT counter */
+  int regRowCount = 0;  /* Memory cell used for the row counter */
+  int regIns;           /* Block of regs holding rowid+data being inserted */
+  int regRowid;         /* registers holding insert rowid */
+  int regData;          /* register holding first column to insert */
+  int regEof = 0;       /* Register recording end of SELECT data */
+  int *aRegIdx = 0;     /* One register allocated to each index */
+
+#ifndef SQLITE_OMIT_TRIGGER
+  int isView;                 /* True if attempting to insert into a view */
+  Trigger *pTrigger;          /* List of triggers on pTab, if required */
+  int tmask;                  /* Mask of trigger times */
+#endif
+
+  db = pParse->db;
+  memset(&dest, 0, sizeof(dest));
+  if( pParse->nErr || db->mallocFailed ){
+    goto insert_cleanup;
+  }
+
+  /* Locate the table into which we will be inserting new information.
+  */
+  assert( pTabList->nSrc==1 );
+  zTab = pTabList->a[0].zName;
+  if( NEVER(zTab==0) ) goto insert_cleanup;
+  pTab = sqlite3SrcListLookup(pParse, pTabList);
+  if( pTab==0 ){
+    goto insert_cleanup;
+  }
+  iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+  assert( iDb<db->nDb );
+  pDb = &db->aDb[iDb];
+  zDb = pDb->zName;
+  if( sqlite3AuthCheck(pParse, SQLITE_INSERT, pTab->zName, 0, zDb) ){
+    goto insert_cleanup;
+  }
+
+  /* Figure out if we have any triggers and if the table being
+  ** inserted into is a view
+  */
+#ifndef SQLITE_OMIT_TRIGGER
+  pTrigger = sqlite3TriggersExist(pParse, pTab, TK_INSERT, 0, &tmask);
+  isView = pTab->pSelect!=0;
+#else
+# define pTrigger 0
+# define tmask 0
+# define isView 0
+#endif
+#ifdef SQLITE_OMIT_VIEW
+# undef isView
+# define isView 0
+#endif
+  assert( (pTrigger && tmask) || (pTrigger==0 && tmask==0) );
+
+  /* If pTab is really a view, make sure it has been initialized.
+  ** ViewGetColumnNames() is a no-op if pTab is not a view (or virtual 
+  ** module table).
+  */
+  if( sqlite3ViewGetColumnNames(pParse, pTab) ){
+    goto insert_cleanup;
+  }
+
+  /* Ensure that:
+  *  (a) the table is not read-only, 
+  *  (b) that if it is a view then ON INSERT triggers exist
+  */
+  if( sqlite3IsReadOnly(pParse, pTab, tmask) ){
+    goto insert_cleanup;
+  }
+
+  /* Allocate a VDBE
+  */
+  v = sqlite3GetVdbe(pParse);
+  if( v==0 ) goto insert_cleanup;
+  if( pParse->nested==0 ) sqlite3VdbeCountChanges(v);
+  sqlite3BeginWriteOperation(pParse, pSelect || pTrigger, iDb);
+
+#ifndef SQLITE_OMIT_XFER_OPT
+  /* If the statement is of the form
+  **
+  **       INSERT INTO <table1> SELECT * FROM <table2>;
+  **
+  ** Then special optimizations can be applied that make the transfer
+  ** very fast and which reduce fragmentation of indices.
+  **
+  ** This is the 2nd template.
+  */
+  if( pColumn==0 && xferOptimization(pParse, pTab, pSelect, onError, iDb) ){
+    assert( !pTrigger );
+    assert( pList==0 );
+    goto insert_end;
+  }
+#endif /* SQLITE_OMIT_XFER_OPT */
+
+  /* If this is an AUTOINCREMENT table, look up the sequence number in the
+  ** sqlite_sequence table and store it in memory cell regAutoinc.
+  */
+  regAutoinc = autoIncBegin(pParse, iDb, pTab);
+
+  /* Figure out how many columns of data are supplied.  If the data
+  ** is coming from a SELECT statement, then generate a co-routine that
+  ** produces a single row of the SELECT on each invocation.  The
+  ** co-routine is the common header to the 3rd and 4th templates.
+  */
+  if( pSelect ){
+    /* Data is coming from a SELECT.  Generate code to implement that SELECT
+    ** as a co-routine.  The code is common to both the 3rd and 4th
+    ** templates:
+    **
+    **         EOF <- 0
+    **         X <- A
+    **         goto B
+    **      A: setup for the SELECT
+    **         loop over the tables in the SELECT
+    **           load value into register R..R+n
+    **           yield X
+    **         end loop
+    **         cleanup after the SELECT
+    **         EOF <- 1
+    **         yield X
+    **         halt-error
+    **
+    ** On each invocation of the co-routine, it puts a single row of the
+    ** SELECT result into registers dest.iMem...dest.iMem+dest.nMem-1.
+    ** (These output registers are allocated by sqlite3Select().)  When
+    ** the SELECT completes, it sets the EOF flag stored in regEof.
+    */
+    int rc, j1;
+
+    regEof = ++pParse->nMem;
+    sqlite3VdbeAddOp2(v, OP_Integer, 0, regEof);      /* EOF <- 0 */
+    VdbeComment((v, "SELECT eof flag"));
+    sqlite3SelectDestInit(&dest, SRT_Coroutine, ++pParse->nMem);
+    addrSelect = sqlite3VdbeCurrentAddr(v)+2;
+    sqlite3VdbeAddOp2(v, OP_Integer, addrSelect-1, dest.iParm);
+    j1 = sqlite3VdbeAddOp2(v, OP_Goto, 0, 0);
+    VdbeComment((v, "Jump over SELECT coroutine"));
+
+    /* Resolve the expressions in the SELECT statement and execute it. */
+    rc = sqlite3Select(pParse, pSelect, &dest);
+    assert( pParse->nErr==0 || rc );
+    if( rc || NEVER(pParse->nErr) || db->mallocFailed ){
+      goto insert_cleanup;
+    }
+    sqlite3VdbeAddOp2(v, OP_Integer, 1, regEof);         /* EOF <- 1 */
+    sqlite3VdbeAddOp1(v, OP_Yield, dest.iParm);   /* yield X */
+    sqlite3VdbeAddOp2(v, OP_Halt, SQLITE_INTERNAL, OE_Abort);
+    VdbeComment((v, "End of SELECT coroutine"));
+    sqlite3VdbeJumpHere(v, j1);                          /* label B: */
+
+    regFromSelect = dest.iMem;
+    assert( pSelect->pEList );
+    nColumn = pSelect->pEList->nExpr;
+    assert( dest.nMem==nColumn );
+
+    /* Set useTempTable to TRUE if the result of the SELECT statement
+    ** should be written into a temporary table (template 4).  Set to
+    ** FALSE if each* row of the SELECT can be written directly into
+    ** the destination table (template 3).
+    **
+    ** A temp table must be used if the table being updated is also one
+    ** of the tables being read by the SELECT statement.  Also use a 
+    ** temp table in the case of row triggers.
+    */
+    if( pTrigger || readsTable(pParse, addrSelect, iDb, pTab) ){
+      useTempTable = 1;
+    }
+
+    if( useTempTable ){
+      /* Invoke the coroutine to extract information from the SELECT
+      ** and add it to a transient table srcTab.  The code generated
+      ** here is from the 4th template:
+      **
+      **      B: open temp table
+      **      L: yield X
+      **         if EOF goto M
+      **         insert row from R..R+n into temp table
+      **         goto L
+      **      M: ...
+      */
+      int regRec;          /* Register to hold packed record */
+      int regTempRowid;    /* Register to hold temp table ROWID */
+      int addrTop;         /* Label "L" */
+      int addrIf;          /* Address of jump to M */
+
+      srcTab = pParse->nTab++;
+      regRec = sqlite3GetTempReg(pParse);
+      regTempRowid = sqlite3GetTempReg(pParse);
+      sqlite3VdbeAddOp2(v, OP_OpenEphemeral, srcTab, nColumn);
+      addrTop = sqlite3VdbeAddOp1(v, OP_Yield, dest.iParm);
+      addrIf = sqlite3VdbeAddOp1(v, OP_If, regEof);
+      sqlite3VdbeAddOp3(v, OP_MakeRecord, regFromSelect, nColumn, regRec);
+      sqlite3VdbeAddOp2(v, OP_NewRowid, srcTab, regTempRowid);
+      sqlite3VdbeAddOp3(v, OP_Insert, srcTab, regRec, regTempRowid);
+      sqlite3VdbeAddOp2(v, OP_Goto, 0, addrTop);
+      sqlite3VdbeJumpHere(v, addrIf);
+      sqlite3ReleaseTempReg(pParse, regRec);
+      sqlite3ReleaseTempReg(pParse, regTempRowid);
+    }
+  }else{
+    /* This is the case if the data for the INSERT is coming from a VALUES
+    ** clause
+    */
+    NameContext sNC;
+    memset(&sNC, 0, sizeof(sNC));
+    sNC.pParse = pParse;
+    srcTab = -1;
+    assert( useTempTable==0 );
+    nColumn = pList ? pList->nExpr : 0;
+    for(i=0; i<nColumn; i++){
+      if( sqlite3ResolveExprNames(&sNC, pList->a[i].pExpr) ){
+        goto insert_cleanup;
+      }
+    }
+  }
+
+  /* Make sure the number of columns in the source data matches the number
+  ** of columns to be inserted into the table.
+  */
+  if( IsVirtual(pTab) ){
+    for(i=0; i<pTab->nCol; i++){
+      nHidden += (IsHiddenColumn(&pTab->aCol[i]) ? 1 : 0);
+    }
+  }
+  if( pColumn==0 && nColumn && nColumn!=(pTab->nCol-nHidden) ){
+    sqlite3ErrorMsg(pParse, 
+       "table %S has %d columns but %d values were supplied",
+       pTabList, 0, pTab->nCol-nHidden, nColumn);
+    goto insert_cleanup;
+  }
+  if( pColumn!=0 && nColumn!=pColumn->nId ){
+    sqlite3ErrorMsg(pParse, "%d values for %d columns", nColumn, pColumn->nId);
+    goto insert_cleanup;
+  }
+
+  /* If the INSERT statement included an IDLIST term, then make sure
+  ** all elements of the IDLIST really are columns of the table and 
+  ** remember the column indices.
+  **
+  ** If the table has an INTEGER PRIMARY KEY column and that column
+  ** is named in the IDLIST, then record in the keyColumn variable
+  ** the index into IDLIST of the primary key column.  keyColumn is
+  ** the index of the primary key as it appears in IDLIST, not as
+  ** is appears in the original table.  (The index of the primary
+  ** key in the original table is pTab->iPKey.)
+  */
+  if( pColumn ){
+    for(i=0; i<pColumn->nId; i++){
+      pColumn->a[i].idx = -1;
+    }
+    for(i=0; i<pColumn->nId; i++){
+      for(j=0; j<pTab->nCol; j++){
+        if( sqlite3StrICmp(pColumn->a[i].zName, pTab->aCol[j].zName)==0 ){
+          pColumn->a[i].idx = j;
+          if( j==pTab->iPKey ){
+            keyColumn = i;
+          }
+          break;
+        }
+      }
+      if( j>=pTab->nCol ){
+        if( sqlite3IsRowid(pColumn->a[i].zName) ){
+          keyColumn = i;
+        }else{
+          sqlite3ErrorMsg(pParse, "table %S has no column named %s",
+              pTabList, 0, pColumn->a[i].zName);
+          pParse->checkSchema = 1;
+          goto insert_cleanup;
+        }
+      }
+    }
+  }
+
+  /* If there is no IDLIST term but the table has an integer primary
+  ** key, the set the keyColumn variable to the primary key column index
+  ** in the original table definition.
+  */
+  if( pColumn==0 && nColumn>0 ){
+    keyColumn = pTab->iPKey;
+  }
+    
+  /* Initialize the count of rows to be inserted
+  */
+  if( db->flags & SQLITE_CountRows ){
+    regRowCount = ++pParse->nMem;
+    sqlite3VdbeAddOp2(v, OP_Integer, 0, regRowCount);
+  }
+
+  /* If this is not a view, open the table and and all indices */
+  if( !isView ){
+    int nIdx;
+
+    baseCur = pParse->nTab;
+    nIdx = sqlite3OpenTableAndIndices(pParse, pTab, baseCur, OP_OpenWrite);
+    aRegIdx = sqlite3DbMallocRaw(db, sizeof(int)*(nIdx+1));
+    if( aRegIdx==0 ){
+      goto insert_cleanup;
+    }
+    for(i=0; i<nIdx; i++){
+      aRegIdx[i] = ++pParse->nMem;
+    }
+  }
+
+  /* This is the top of the main insertion loop */
+  if( useTempTable ){
+    /* This block codes the top of loop only.  The complete loop is the
+    ** following pseudocode (template 4):
+    **
+    **         rewind temp table
+    **      C: loop over rows of intermediate table
+    **           transfer values form intermediate table into <table>
+    **         end loop
+    **      D: ...
+    */
+    addrInsTop = sqlite3VdbeAddOp1(v, OP_Rewind, srcTab);
+    addrCont = sqlite3VdbeCurrentAddr(v);
+  }else if( pSelect ){
+    /* This block codes the top of loop only.  The complete loop is the
+    ** following pseudocode (template 3):
+    **
+    **      C: yield X
+    **         if EOF goto D
+    **         insert the select result into <table> from R..R+n
+    **         goto C
+    **      D: ...
+    */
+    addrCont = sqlite3VdbeAddOp1(v, OP_Yield, dest.iParm);
+    addrInsTop = sqlite3VdbeAddOp1(v, OP_If, regEof);
+  }
+
+  /* Allocate registers for holding the rowid of the new row,
+  ** the content of the new row, and the assemblied row record.
+  */
+  regRowid = regIns = pParse->nMem+1;
+  pParse->nMem += pTab->nCol + 1;
+  if( IsVirtual(pTab) ){
+    regRowid++;
+    pParse->nMem++;
+  }
+  regData = regRowid+1;
+
+  /* Run the BEFORE and INSTEAD OF triggers, if there are any
+  */
+  endOfLoop = sqlite3VdbeMakeLabel(v);
+  if( tmask & TRIGGER_BEFORE ){
+    int regCols = sqlite3GetTempRange(pParse, pTab->nCol+1);
+
+    /* build the NEW.* reference row.  Note that if there is an INTEGER
+    ** PRIMARY KEY into which a NULL is being inserted, that NULL will be
+    ** translated into a unique ID for the row.  But on a BEFORE trigger,
+    ** we do not know what the unique ID will be (because the insert has
+    ** not happened yet) so we substitute a rowid of -1
+    */
+    if( keyColumn<0 ){
+      sqlite3VdbeAddOp2(v, OP_Integer, -1, regCols);
+    }else{
+      int j1;
+      if( useTempTable ){
+        sqlite3VdbeAddOp3(v, OP_Column, srcTab, keyColumn, regCols);
+      }else{
+        assert( pSelect==0 );  /* Otherwise useTempTable is true */
+        sqlite3ExprCode(pParse, pList->a[keyColumn].pExpr, regCols);
+      }
+      j1 = sqlite3VdbeAddOp1(v, OP_NotNull, regCols);
+      sqlite3VdbeAddOp2(v, OP_Integer, -1, regCols);
+      sqlite3VdbeJumpHere(v, j1);
+      sqlite3VdbeAddOp1(v, OP_MustBeInt, regCols);
+    }
+
+    /* Cannot have triggers on a virtual table. If it were possible,
+    ** this block would have to account for hidden column.
+    */
+    assert( !IsVirtual(pTab) );
+
+    /* Create the new column data
+    */
+    for(i=0; i<pTab->nCol; i++){
+      if( pColumn==0 ){
+        j = i;
+      }else{
+        for(j=0; j<pColumn->nId; j++){
+          if( pColumn->a[j].idx==i ) break;
+        }
+      }
+      if( (!useTempTable && !pList) || (pColumn && j>=pColumn->nId) ){
+        sqlite3ExprCode(pParse, pTab->aCol[i].pDflt, regCols+i+1);
+      }else if( useTempTable ){
+        sqlite3VdbeAddOp3(v, OP_Column, srcTab, j, regCols+i+1); 
+      }else{
+        assert( pSelect==0 ); /* Otherwise useTempTable is true */
+        sqlite3ExprCodeAndCache(pParse, pList->a[j].pExpr, regCols+i+1);
+      }
+    }
+
+    /* If this is an INSERT on a view with an INSTEAD OF INSERT trigger,
+    ** do not attempt any conversions before assembling the record.
+    ** If this is a real table, attempt conversions as required by the
+    ** table column affinities.
+    */
+    if( !isView ){
+      sqlite3VdbeAddOp2(v, OP_Affinity, regCols+1, pTab->nCol);
+      sqlite3TableAffinityStr(v, pTab);
+    }
+
+    /* Fire BEFORE or INSTEAD OF triggers */
+    sqlite3CodeRowTrigger(pParse, pTrigger, TK_INSERT, 0, TRIGGER_BEFORE, 
+        pTab, regCols-pTab->nCol-1, onError, endOfLoop);
+
+    sqlite3ReleaseTempRange(pParse, regCols, pTab->nCol+1);
+  }
+
+  /* Push the record number for the new entry onto the stack.  The
+  ** record number is a randomly generate integer created by NewRowid
+  ** except when the table has an INTEGER PRIMARY KEY column, in which
+  ** case the record number is the same as that column. 
+  */
+  if( !isView ){
+    if( IsVirtual(pTab) ){
+      /* The row that the VUpdate opcode will delete: none */
+      sqlite3VdbeAddOp2(v, OP_Null, 0, regIns);
+    }
+    if( keyColumn>=0 ){
+      if( useTempTable ){
+        sqlite3VdbeAddOp3(v, OP_Column, srcTab, keyColumn, regRowid);
+      }else if( pSelect ){
+        sqlite3VdbeAddOp2(v, OP_SCopy, regFromSelect+keyColumn, regRowid);
+      }else{
+        VdbeOp *pOp;
+        sqlite3ExprCode(pParse, pList->a[keyColumn].pExpr, regRowid);
+        pOp = sqlite3VdbeGetOp(v, -1);
+        if( ALWAYS(pOp) && pOp->opcode==OP_Null && !IsVirtual(pTab) ){
+          appendFlag = 1;
+          pOp->opcode = OP_NewRowid;
+          pOp->p1 = baseCur;
+          pOp->p2 = regRowid;
+          pOp->p3 = regAutoinc;
+        }
+      }
+      /* If the PRIMARY KEY expression is NULL, then use OP_NewRowid
+      ** to generate a unique primary key value.
+      */
+      if( !appendFlag ){
+        int j1;
+        if( !IsVirtual(pTab) ){
+          j1 = sqlite3VdbeAddOp1(v, OP_NotNull, regRowid);
+          sqlite3VdbeAddOp3(v, OP_NewRowid, baseCur, regRowid, regAutoinc);
+          sqlite3VdbeJumpHere(v, j1);
+        }else{
+          j1 = sqlite3VdbeCurrentAddr(v);
+          sqlite3VdbeAddOp2(v, OP_IsNull, regRowid, j1+2);
+        }
+        sqlite3VdbeAddOp1(v, OP_MustBeInt, regRowid);
+      }
+    }else if( IsVirtual(pTab) ){
+      sqlite3VdbeAddOp2(v, OP_Null, 0, regRowid);
+    }else{
+      sqlite3VdbeAddOp3(v, OP_NewRowid, baseCur, regRowid, regAutoinc);
+      appendFlag = 1;
+    }
+    autoIncStep(pParse, regAutoinc, regRowid);
+
+    /* Push onto the stack, data for all columns of the new entry, beginning
+    ** with the first column.
+    */
+    nHidden = 0;
+    for(i=0; i<pTab->nCol; i++){
+      int iRegStore = regRowid+1+i;
+      if( i==pTab->iPKey ){
+        /* The value of the INTEGER PRIMARY KEY column is always a NULL.
+        ** Whenever this column is read, the record number will be substituted
+        ** in its place.  So will fill this column with a NULL to avoid
+        ** taking up data space with information that will never be used. */
+        sqlite3VdbeAddOp2(v, OP_Null, 0, iRegStore);
+        continue;
+      }
+      if( pColumn==0 ){
+        if( IsHiddenColumn(&pTab->aCol[i]) ){
+          assert( IsVirtual(pTab) );
+          j = -1;
+          nHidden++;
+        }else{
+          j = i - nHidden;
+        }
+      }else{
+        for(j=0; j<pColumn->nId; j++){
+          if( pColumn->a[j].idx==i ) break;
+        }
+      }
+      if( j<0 || nColumn==0 || (pColumn && j>=pColumn->nId) ){
+        sqlite3ExprCode(pParse, pTab->aCol[i].pDflt, iRegStore);
+      }else if( useTempTable ){
+        sqlite3VdbeAddOp3(v, OP_Column, srcTab, j, iRegStore); 
+      }else if( pSelect ){
+        sqlite3VdbeAddOp2(v, OP_SCopy, regFromSelect+j, iRegStore);
+      }else{
+        sqlite3ExprCode(pParse, pList->a[j].pExpr, iRegStore);
+      }
+    }
+
+    /* Generate code to check constraints and generate index keys and
+    ** do the insertion.
+    */
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+    if( IsVirtual(pTab) ){
+      const char *pVTab = (const char *)sqlite3GetVTable(db, pTab);
+      sqlite3VtabMakeWritable(pParse, pTab);
+      sqlite3VdbeAddOp4(v, OP_VUpdate, 1, pTab->nCol+2, regIns, pVTab, P4_VTAB);
+      sqlite3VdbeChangeP5(v, onError==OE_Default ? OE_Abort : onError);
+      sqlite3MayAbort(pParse);
+    }else
+#endif
+    {
+      int isReplace;    /* Set to true if constraints may cause a replace */
+      sqlite3GenerateConstraintChecks(pParse, pTab, baseCur, regIns, aRegIdx,
+          keyColumn>=0, 0, onError, endOfLoop, &isReplace
+      );
+      sqlite3FkCheck(pParse, pTab, 0, regIns);
+      sqlite3CompleteInsertion(
+          pParse, pTab, baseCur, regIns, aRegIdx, 0, appendFlag, isReplace==0
+      );
+    }
+  }
+
+  /* Update the count of rows that are inserted
+  */
+  if( (db->flags & SQLITE_CountRows)!=0 ){
+    sqlite3VdbeAddOp2(v, OP_AddImm, regRowCount, 1);
+  }
+
+  if( pTrigger ){
+    /* Code AFTER triggers */
+    sqlite3CodeRowTrigger(pParse, pTrigger, TK_INSERT, 0, TRIGGER_AFTER, 
+        pTab, regData-2-pTab->nCol, onError, endOfLoop);
+  }
+
+  /* The bottom of the main insertion loop, if the data source
+  ** is a SELECT statement.
+  */
+  sqlite3VdbeResolveLabel(v, endOfLoop);
+  if( useTempTable ){
+    sqlite3VdbeAddOp2(v, OP_Next, srcTab, addrCont);
+    sqlite3VdbeJumpHere(v, addrInsTop);
+    sqlite3VdbeAddOp1(v, OP_Close, srcTab);
+  }else if( pSelect ){
+    sqlite3VdbeAddOp2(v, OP_Goto, 0, addrCont);
+    sqlite3VdbeJumpHere(v, addrInsTop);
+  }
+
+  if( !IsVirtual(pTab) && !isView ){
+    /* Close all tables opened */
+    sqlite3VdbeAddOp1(v, OP_Close, baseCur);
+    for(idx=1, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, idx++){
+      sqlite3VdbeAddOp1(v, OP_Close, idx+baseCur);
+    }
+  }
+
+insert_end:
+  /* Update the sqlite_sequence table by storing the content of the
+  ** maximum rowid counter values recorded while inserting into
+  ** autoincrement tables.
+  */
+  if( pParse->nested==0 && pParse->pTriggerTab==0 ){
+    sqlite3AutoincrementEnd(pParse);
+  }
+
+  /*
+  ** Return the number of rows inserted. If this routine is 
+  ** generating code because of a call to sqlite3NestedParse(), do not
+  ** invoke the callback function.
+  */
+  if( (db->flags&SQLITE_CountRows) && !pParse->nested && !pParse->pTriggerTab ){
+    sqlite3VdbeAddOp2(v, OP_ResultRow, regRowCount, 1);
+    sqlite3VdbeSetNumCols(v, 1);
+    sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "rows inserted", SQLITE_STATIC);
+  }
+
+insert_cleanup:
+  sqlite3SrcListDelete(db, pTabList);
+  sqlite3ExprListDelete(db, pList);
+  sqlite3SelectDelete(db, pSelect);
+  sqlite3IdListDelete(db, pColumn);
+  sqlite3DbFree(db, aRegIdx);
+}
+
+/* Make sure "isView" and other macros defined above are undefined. Otherwise
+** thely may interfere with compilation of other functions in this file
+** (or in another file, if this file becomes part of the amalgamation).  */
+#ifdef isView
+ #undef isView
+#endif
+#ifdef pTrigger
+ #undef pTrigger
+#endif
+#ifdef tmask
+ #undef tmask
+#endif
+
+
+/*
+** Generate code to do constraint checks prior to an INSERT or an UPDATE.
+**
+** The input is a range of consecutive registers as follows:
+**
+**    1.  The rowid of the row after the update.
+**
+**    2.  The data in the first column of the entry after the update.
+**
+**    i.  Data from middle columns...
+**
+**    N.  The data in the last column of the entry after the update.
+**
+** The regRowid parameter is the index of the register containing (1).
+**
+** If isUpdate is true and rowidChng is non-zero, then rowidChng contains
+** the address of a register containing the rowid before the update takes
+** place. isUpdate is true for UPDATEs and false for INSERTs. If isUpdate
+** is false, indicating an INSERT statement, then a non-zero rowidChng 
+** indicates that the rowid was explicitly specified as part of the
+** INSERT statement. If rowidChng is false, it means that  the rowid is
+** computed automatically in an insert or that the rowid value is not 
+** modified by an update.
+**
+** The code generated by this routine store new index entries into
+** registers identified by aRegIdx[].  No index entry is created for
+** indices where aRegIdx[i]==0.  The order of indices in aRegIdx[] is
+** the same as the order of indices on the linked list of indices
+** attached to the table.
+**
+** This routine also generates code to check constraints.  NOT NULL,
+** CHECK, and UNIQUE constraints are all checked.  If a constraint fails,
+** then the appropriate action is performed.  There are five possible
+** actions: ROLLBACK, ABORT, FAIL, REPLACE, and IGNORE.
+**
+**  Constraint type  Action       What Happens
+**  ---------------  ----------   ----------------------------------------
+**  any              ROLLBACK     The current transaction is rolled back and
+**                                sqlite3_exec() returns immediately with a
+**                                return code of SQLITE_CONSTRAINT.
+**
+**  any              ABORT        Back out changes from the current command
+**                                only (do not do a complete rollback) then
+**                                cause sqlite3_exec() to return immediately
+**                                with SQLITE_CONSTRAINT.
+**
+**  any              FAIL         Sqlite_exec() returns immediately with a
+**                                return code of SQLITE_CONSTRAINT.  The
+**                                transaction is not rolled back and any
+**                                prior changes are retained.
+**
+**  any              IGNORE       The record number and data is popped from
+**                                the stack and there is an immediate jump
+**                                to label ignoreDest.
+**
+**  NOT NULL         REPLACE      The NULL value is replace by the default
+**                                value for that column.  If the default value
+**                                is NULL, the action is the same as ABORT.
+**
+**  UNIQUE           REPLACE      The other row that conflicts with the row
+**                                being inserted is removed.
+**
+**  CHECK            REPLACE      Illegal.  The results in an exception.
+**
+** Which action to take is determined by the overrideError parameter.
+** Or if overrideError==OE_Default, then the pParse->onError parameter
+** is used.  Or if pParse->onError==OE_Default then the onError value
+** for the constraint is used.
+**
+** The calling routine must open a read/write cursor for pTab with
+** cursor number "baseCur".  All indices of pTab must also have open
+** read/write cursors with cursor number baseCur+i for the i-th cursor.
+** Except, if there is no possibility of a REPLACE action then
+** cursors do not need to be open for indices where aRegIdx[i]==0.
+*/
+void sqlite3GenerateConstraintChecks(
+  Parse *pParse,      /* The parser context */
+  Table *pTab,        /* the table into which we are inserting */
+  int baseCur,        /* Index of a read/write cursor pointing at pTab */
+  int regRowid,       /* Index of the range of input registers */
+  int *aRegIdx,       /* Register used by each index.  0 for unused indices */
+  int rowidChng,      /* True if the rowid might collide with existing entry */
+  int isUpdate,       /* True for UPDATE, False for INSERT */
+  int overrideError,  /* Override onError to this if not OE_Default */
+  int ignoreDest,     /* Jump to this label on an OE_Ignore resolution */
+  int *pbMayReplace   /* OUT: Set to true if constraint may cause a replace */
+){
+  int i;              /* loop counter */
+  Vdbe *v;            /* VDBE under constrution */
+  int nCol;           /* Number of columns */
+  int onError;        /* Conflict resolution strategy */
+  int j1;             /* Addresss of jump instruction */
+  int j2 = 0, j3;     /* Addresses of jump instructions */
+  int regData;        /* Register containing first data column */
+  int iCur;           /* Table cursor number */
+  Index *pIdx;         /* Pointer to one of the indices */
+  int seenReplace = 0; /* True if REPLACE is used to resolve INT PK conflict */
+  int regOldRowid = (rowidChng && isUpdate) ? rowidChng : regRowid;
+
+  v = sqlite3GetVdbe(pParse);
+  assert( v!=0 );
+  assert( pTab->pSelect==0 );  /* This table is not a VIEW */
+  nCol = pTab->nCol;
+  regData = regRowid + 1;
+
+  /* Test all NOT NULL constraints.
+  */
+  for(i=0; i<nCol; i++){
+    if( i==pTab->iPKey ){
+      continue;
+    }
+    onError = pTab->aCol[i].notNull;
+    if( onError==OE_None ) continue;
+    if( overrideError!=OE_Default ){
+      onError = overrideError;
+    }else if( onError==OE_Default ){
+      onError = OE_Abort;
+    }
+    if( onError==OE_Replace && pTab->aCol[i].pDflt==0 ){
+      onError = OE_Abort;
+    }
+    assert( onError==OE_Rollback || onError==OE_Abort || onError==OE_Fail
+        || onError==OE_Ignore || onError==OE_Replace );
+    switch( onError ){
+      case OE_Abort:
+        sqlite3MayAbort(pParse);
+      case OE_Rollback:
+      case OE_Fail: {
+        char *zMsg;
+        sqlite3VdbeAddOp3(v, OP_HaltIfNull,
+                                  SQLITE_CONSTRAINT, onError, regData+i);
+        zMsg = sqlite3MPrintf(pParse->db, "%s.%s may not be NULL",
+                              pTab->zName, pTab->aCol[i].zName);
+        sqlite3VdbeChangeP4(v, -1, zMsg, P4_DYNAMIC);
+        break;
+      }
+      case OE_Ignore: {
+        sqlite3VdbeAddOp2(v, OP_IsNull, regData+i, ignoreDest);
+        break;
+      }
+      default: {
+        assert( onError==OE_Replace );
+        j1 = sqlite3VdbeAddOp1(v, OP_NotNull, regData+i);
+        sqlite3ExprCode(pParse, pTab->aCol[i].pDflt, regData+i);
+        sqlite3VdbeJumpHere(v, j1);
+        break;
+      }
+    }
+  }
+
+  /* Test all CHECK constraints
+  */
+#ifndef SQLITE_OMIT_CHECK
+  if( pTab->pCheck && (pParse->db->flags & SQLITE_IgnoreChecks)==0 ){
+    int allOk = sqlite3VdbeMakeLabel(v);
+    pParse->ckBase = regData;
+    sqlite3ExprIfTrue(pParse, pTab->pCheck, allOk, SQLITE_JUMPIFNULL);
+    onError = overrideError!=OE_Default ? overrideError : OE_Abort;
+    if( onError==OE_Ignore ){
+      sqlite3VdbeAddOp2(v, OP_Goto, 0, ignoreDest);
+    }else{
+      if( onError==OE_Replace ) onError = OE_Abort; /* IMP: R-15569-63625 */
+      sqlite3HaltConstraint(pParse, onError, 0, 0);
+    }
+    sqlite3VdbeResolveLabel(v, allOk);
+  }
+#endif /* !defined(SQLITE_OMIT_CHECK) */
+
+  /* If we have an INTEGER PRIMARY KEY, make sure the primary key
+  ** of the new record does not previously exist.  Except, if this
+  ** is an UPDATE and the primary key is not changing, that is OK.
+  */
+  if( rowidChng ){
+    onError = pTab->keyConf;
+    if( overrideError!=OE_Default ){
+      onError = overrideError;
+    }else if( onError==OE_Default ){
+      onError = OE_Abort;
+    }
+    
+    if( isUpdate ){
+      j2 = sqlite3VdbeAddOp3(v, OP_Eq, regRowid, 0, rowidChng);
+    }
+    j3 = sqlite3VdbeAddOp3(v, OP_NotExists, baseCur, 0, regRowid);
+    switch( onError ){
+      default: {
+        onError = OE_Abort;
+        /* Fall thru into the next case */
+      }
+      case OE_Rollback:
+      case OE_Abort:
+      case OE_Fail: {
+        sqlite3HaltConstraint(
+          pParse, onError, "PRIMARY KEY must be unique", P4_STATIC);
+        break;
+      }
+      case OE_Replace: {
+        /* If there are DELETE triggers on this table and the
+        ** recursive-triggers flag is set, call GenerateRowDelete() to
+        ** remove the conflicting row from the the table. This will fire
+        ** the triggers and remove both the table and index b-tree entries.
+        **
+        ** Otherwise, if there are no triggers or the recursive-triggers
+        ** flag is not set, but the table has one or more indexes, call 
+        ** GenerateRowIndexDelete(). This removes the index b-tree entries 
+        ** only. The table b-tree entry will be replaced by the new entry 
+        ** when it is inserted.  
+        **
+        ** If either GenerateRowDelete() or GenerateRowIndexDelete() is called,
+        ** also invoke MultiWrite() to indicate that this VDBE may require
+        ** statement rollback (if the statement is aborted after the delete
+        ** takes place). Earlier versions called sqlite3MultiWrite() regardless,
+        ** but being more selective here allows statements like:
+        **
+        **   REPLACE INTO t(rowid) VALUES($newrowid)
+        **
+        ** to run without a statement journal if there are no indexes on the
+        ** table.
+        */
+        Trigger *pTrigger = 0;
+        if( pParse->db->flags&SQLITE_RecTriggers ){
+          pTrigger = sqlite3TriggersExist(pParse, pTab, TK_DELETE, 0, 0);
+        }
+        if( pTrigger || sqlite3FkRequired(pParse, pTab, 0, 0) ){
+          sqlite3MultiWrite(pParse);
+          sqlite3GenerateRowDelete(
+              pParse, pTab, baseCur, regRowid, 0, pTrigger, OE_Replace
+          );
+        }else if( pTab->pIndex ){
+          sqlite3MultiWrite(pParse);
+          sqlite3GenerateRowIndexDelete(pParse, pTab, baseCur, 0);
+        }
+        seenReplace = 1;
+        break;
+      }
+      case OE_Ignore: {
+        assert( seenReplace==0 );
+        sqlite3VdbeAddOp2(v, OP_Goto, 0, ignoreDest);
+        break;
+      }
+    }
+    sqlite3VdbeJumpHere(v, j3);
+    if( isUpdate ){
+      sqlite3VdbeJumpHere(v, j2);
+    }
+  }
+
+  /* Test all UNIQUE constraints by creating entries for each UNIQUE
+  ** index and making sure that duplicate entries do not already exist.
+  ** Add the new records to the indices as we go.
+  */
+  for(iCur=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, iCur++){
+    int regIdx;
+    int regR;
+
+    if( aRegIdx[iCur]==0 ) continue;  /* Skip unused indices */
+
+    /* Create a key for accessing the index entry */
+    regIdx = sqlite3GetTempRange(pParse, pIdx->nColumn+1);
+    for(i=0; i<pIdx->nColumn; i++){
+      int idx = pIdx->aiColumn[i];
+      if( idx==pTab->iPKey ){
+        sqlite3VdbeAddOp2(v, OP_SCopy, regRowid, regIdx+i);
+      }else{
+        sqlite3VdbeAddOp2(v, OP_SCopy, regData+idx, regIdx+i);
+      }
+    }
+    sqlite3VdbeAddOp2(v, OP_SCopy, regRowid, regIdx+i);
+    sqlite3VdbeAddOp3(v, OP_MakeRecord, regIdx, pIdx->nColumn+1, aRegIdx[iCur]);
+    sqlite3VdbeChangeP4(v, -1, sqlite3IndexAffinityStr(v, pIdx), P4_TRANSIENT);
+    sqlite3ExprCacheAffinityChange(pParse, regIdx, pIdx->nColumn+1);
+
+    /* Find out what action to take in case there is an indexing conflict */
+    onError = pIdx->onError;
+    if( onError==OE_None ){ 
+      sqlite3ReleaseTempRange(pParse, regIdx, pIdx->nColumn+1);
+      continue;  /* pIdx is not a UNIQUE index */
+    }
+    if( overrideError!=OE_Default ){
+      onError = overrideError;
+    }else if( onError==OE_Default ){
+      onError = OE_Abort;
+    }
+    if( seenReplace ){
+      if( onError==OE_Ignore ) onError = OE_Replace;
+      else if( onError==OE_Fail ) onError = OE_Abort;
+    }
+    
+    /* Check to see if the new index entry will be unique */
+    regR = sqlite3GetTempReg(pParse);
+    sqlite3VdbeAddOp2(v, OP_SCopy, regOldRowid, regR);
+    j3 = sqlite3VdbeAddOp4(v, OP_IsUnique, baseCur+iCur+1, 0,
+                           regR, SQLITE_INT_TO_PTR(regIdx),
+                           P4_INT32);
+    sqlite3ReleaseTempRange(pParse, regIdx, pIdx->nColumn+1);
+
+    /* Generate code that executes if the new index entry is not unique */
+    assert( onError==OE_Rollback || onError==OE_Abort || onError==OE_Fail
+        || onError==OE_Ignore || onError==OE_Replace );
+    switch( onError ){
+      case OE_Rollback:
+      case OE_Abort:
+      case OE_Fail: {
+        int j;
+        StrAccum errMsg;
+        const char *zSep;
+        char *zErr;
+
+        sqlite3StrAccumInit(&errMsg, 0, 0, 200);
+        errMsg.db = pParse->db;
+        zSep = pIdx->nColumn>1 ? "columns " : "column ";
+        for(j=0; j<pIdx->nColumn; j++){
+          char *zCol = pTab->aCol[pIdx->aiColumn[j]].zName;
+          sqlite3StrAccumAppend(&errMsg, zSep, -1);
+          zSep = ", ";
+          sqlite3StrAccumAppend(&errMsg, zCol, -1);
+        }
+        sqlite3StrAccumAppend(&errMsg,
+            pIdx->nColumn>1 ? " are not unique" : " is not unique", -1);
+        zErr = sqlite3StrAccumFinish(&errMsg);
+        sqlite3HaltConstraint(pParse, onError, zErr, 0);
+        sqlite3DbFree(errMsg.db, zErr);
+        break;
+      }
+      case OE_Ignore: {
+        assert( seenReplace==0 );
+        sqlite3VdbeAddOp2(v, OP_Goto, 0, ignoreDest);
+        break;
+      }
+      default: {
+        Trigger *pTrigger = 0;
+        assert( onError==OE_Replace );
+        sqlite3MultiWrite(pParse);
+        if( pParse->db->flags&SQLITE_RecTriggers ){
+          pTrigger = sqlite3TriggersExist(pParse, pTab, TK_DELETE, 0, 0);
+        }
+        sqlite3GenerateRowDelete(
+            pParse, pTab, baseCur, regR, 0, pTrigger, OE_Replace
+        );
+        seenReplace = 1;
+        break;
+      }
+    }
+    sqlite3VdbeJumpHere(v, j3);
+    sqlite3ReleaseTempReg(pParse, regR);
+  }
+  
+  if( pbMayReplace ){
+    *pbMayReplace = seenReplace;
+  }
+}
+
+/*
+** This routine generates code to finish the INSERT or UPDATE operation
+** that was started by a prior call to sqlite3GenerateConstraintChecks.
+** A consecutive range of registers starting at regRowid contains the
+** rowid and the content to be inserted.
+**
+** The arguments to this routine should be the same as the first six
+** arguments to sqlite3GenerateConstraintChecks.
+*/
+void sqlite3CompleteInsertion(
+  Parse *pParse,      /* The parser context */
+  Table *pTab,        /* the table into which we are inserting */
+  int baseCur,        /* Index of a read/write cursor pointing at pTab */
+  int regRowid,       /* Range of content */
+  int *aRegIdx,       /* Register used by each index.  0 for unused indices */
+  int isUpdate,       /* True for UPDATE, False for INSERT */
+  int appendBias,     /* True if this is likely to be an append */
+  int useSeekResult   /* True to set the USESEEKRESULT flag on OP_[Idx]Insert */
+){
+  int i;
+  Vdbe *v;
+  int nIdx;
+  Index *pIdx;
+  u8 pik_flags;
+  int regData;
+  int regRec;
+
+  v = sqlite3GetVdbe(pParse);
+  assert( v!=0 );
+  assert( pTab->pSelect==0 );  /* This table is not a VIEW */
+  for(nIdx=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, nIdx++){}
+  for(i=nIdx-1; i>=0; i--){
+    if( aRegIdx[i]==0 ) continue;
+    sqlite3VdbeAddOp2(v, OP_IdxInsert, baseCur+i+1, aRegIdx[i]);
+    if( useSeekResult ){
+      sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);
+    }
+  }
+  regData = regRowid + 1;
+  regRec = sqlite3GetTempReg(pParse);
+  sqlite3VdbeAddOp3(v, OP_MakeRecord, regData, pTab->nCol, regRec);
+  sqlite3TableAffinityStr(v, pTab);
+  sqlite3ExprCacheAffinityChange(pParse, regData, pTab->nCol);
+  if( pParse->nested ){
+    pik_flags = 0;
+  }else{
+    pik_flags = OPFLAG_NCHANGE;
+    pik_flags |= (isUpdate?OPFLAG_ISUPDATE:OPFLAG_LASTROWID);
+  }
+  if( appendBias ){
+    pik_flags |= OPFLAG_APPEND;
+  }
+  if( useSeekResult ){
+    pik_flags |= OPFLAG_USESEEKRESULT;
+  }
+  sqlite3VdbeAddOp3(v, OP_Insert, baseCur, regRec, regRowid);
+  if( !pParse->nested ){
+    sqlite3VdbeChangeP4(v, -1, pTab->zName, P4_TRANSIENT);
+  }
+  sqlite3VdbeChangeP5(v, pik_flags);
+}
+
+/*
+** Generate code that will open cursors for a table and for all
+** indices of that table.  The "baseCur" parameter is the cursor number used
+** for the table.  Indices are opened on subsequent cursors.
+**
+** Return the number of indices on the table.
+*/
+int sqlite3OpenTableAndIndices(
+  Parse *pParse,   /* Parsing context */
+  Table *pTab,     /* Table to be opened */
+  int baseCur,     /* Cursor number assigned to the table */
+  int op           /* OP_OpenRead or OP_OpenWrite */
+){
+  int i;
+  int iDb;
+  Index *pIdx;
+  Vdbe *v;
+
+  if( IsVirtual(pTab) ) return 0;
+  iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
+  v = sqlite3GetVdbe(pParse);
+  assert( v!=0 );
+  sqlite3OpenTable(pParse, baseCur, iDb, pTab, op);
+  for(i=1, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, i++){
+    KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIdx);
+    assert( pIdx->pSchema==pTab->pSchema );
+    sqlite3VdbeAddOp4(v, op, i+baseCur, pIdx->tnum, iDb,
+                      (char*)pKey, P4_KEYINFO_HANDOFF);
+    VdbeComment((v, "%s", pIdx->zName));
+  }
+  if( pParse->nTab<baseCur+i ){
+    pParse->nTab = baseCur+i;
+  }
+  return i-1;
+}
+
+
+#ifdef SQLITE_TEST
+/*
+** The following global variable is incremented whenever the
+** transfer optimization is used.  This is used for testing
+** purposes only - to make sure the transfer optimization really
+** is happening when it is suppose to.
+*/
+int sqlite3_xferopt_count;
+#endif /* SQLITE_TEST */
+
+
+#ifndef SQLITE_OMIT_XFER_OPT
+/*
+** Check to collation names to see if they are compatible.
+*/
+static int xferCompatibleCollation(const char *z1, const char *z2){
+  if( z1==0 ){
+    return z2==0;
+  }
+  if( z2==0 ){
+    return 0;
+  }
+  return sqlite3StrICmp(z1, z2)==0;
+}
+
+
+/*
+** Check to see if index pSrc is compatible as a source of data
+** for index pDest in an insert transfer optimization.  The rules
+** for a compatible index:
+**
+**    *   The index is over the same set of columns
+**    *   The same DESC and ASC markings occurs on all columns
+**    *   The same onError processing (OE_Abort, OE_Ignore, etc)
+**    *   The same collating sequence on each column
+*/
+static int xferCompatibleIndex(Index *pDest, Index *pSrc){
+  int i;
+  assert( pDest && pSrc );
+  assert( pDest->pTable!=pSrc->pTable );
+  if( pDest->nColumn!=pSrc->nColumn ){
+    return 0;   /* Different number of columns */
+  }
+  if( pDest->onError!=pSrc->onError ){
+    return 0;   /* Different conflict resolution strategies */
+  }
+  for(i=0; i<pSrc->nColumn; i++){
+    if( pSrc->aiColumn[i]!=pDest->aiColumn[i] ){
+      return 0;   /* Different columns indexed */
+    }
+    if( pSrc->aSortOrder[i]!=pDest->aSortOrder[i] ){
+      return 0;   /* Different sort orders */
+    }
+    if( !xferCompatibleCollation(pSrc->azColl[i],pDest->azColl[i]) ){
+      return 0;   /* Different collating sequences */
+    }
+  }
+
+  /* If no test above fails then the indices must be compatible */
+  return 1;
+}
+
+/*
+** Attempt the transfer optimization on INSERTs of the form
+**
+**     INSERT INTO tab1 SELECT * FROM tab2;
+**
+** This optimization is only attempted if
+**
+**    (1)  tab1 and tab2 have identical schemas including all the
+**         same indices and constraints
+**
+**    (2)  tab1 and tab2 are different tables
+**
+**    (3)  There must be no triggers on tab1
+**
+**    (4)  The result set of the SELECT statement is "*"
+**
+**    (5)  The SELECT statement has no WHERE, HAVING, ORDER BY, GROUP BY,
+**         or LIMIT clause.
+**
+**    (6)  The SELECT statement is a simple (not a compound) select that
+**         contains only tab2 in its FROM clause
+**
+** This method for implementing the INSERT transfers raw records from
+** tab2 over to tab1.  The columns are not decoded.  Raw records from
+** the indices of tab2 are transfered to tab1 as well.  In so doing,
+** the resulting tab1 has much less fragmentation.
+**
+** This routine returns TRUE if the optimization is attempted.  If any
+** of the conditions above fail so that the optimization should not
+** be attempted, then this routine returns FALSE.
+*/
+static int xferOptimization(
+  Parse *pParse,        /* Parser context */
+  Table *pDest,         /* The table we are inserting into */
+  Select *pSelect,      /* A SELECT statement to use as the data source */
+  int onError,          /* How to handle constraint errors */
+  int iDbDest           /* The database of pDest */
+){
+  ExprList *pEList;                /* The result set of the SELECT */
+  Table *pSrc;                     /* The table in the FROM clause of SELECT */
+  Index *pSrcIdx, *pDestIdx;       /* Source and destination indices */
+  struct SrcList_item *pItem;      /* An element of pSelect->pSrc */
+  int i;                           /* Loop counter */
+  int iDbSrc;                      /* The database of pSrc */
+  int iSrc, iDest;                 /* Cursors from source and destination */
+  int addr1, addr2;                /* Loop addresses */
+  int emptyDestTest;               /* Address of test for empty pDest */
+  int emptySrcTest;                /* Address of test for empty pSrc */
+  Vdbe *v;                         /* The VDBE we are building */
+  KeyInfo *pKey;                   /* Key information for an index */
+  int regAutoinc;                  /* Memory register used by AUTOINC */
+  int destHasUniqueIdx = 0;        /* True if pDest has a UNIQUE index */
+  int regData, regRowid;           /* Registers holding data and rowid */
+
+  if( pSelect==0 ){
+    return 0;   /* Must be of the form  INSERT INTO ... SELECT ... */
+  }
+  if( sqlite3TriggerList(pParse, pDest) ){
+    return 0;   /* tab1 must not have triggers */
+  }
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  if( pDest->tabFlags & TF_Virtual ){
+    return 0;   /* tab1 must not be a virtual table */
+  }
+#endif
+  if( onError==OE_Default ){
+    onError = OE_Abort;
+  }
+  if( onError!=OE_Abort && onError!=OE_Rollback ){
+    return 0;   /* Cannot do OR REPLACE or OR IGNORE or OR FAIL */
+  }
+  assert(pSelect->pSrc);   /* allocated even if there is no FROM clause */
+  if( pSelect->pSrc->nSrc!=1 ){
+    return 0;   /* FROM clause must have exactly one term */
+  }
+  if( pSelect->pSrc->a[0].pSelect ){
+    return 0;   /* FROM clause cannot contain a subquery */
+  }
+  if( pSelect->pWhere ){
+    return 0;   /* SELECT may not have a WHERE clause */
+  }
+  if( pSelect->pOrderBy ){
+    return 0;   /* SELECT may not have an ORDER BY clause */
+  }
+  /* Do not need to test for a HAVING clause.  If HAVING is present but
+  ** there is no ORDER BY, we will get an error. */
+  if( pSelect->pGroupBy ){
+    return 0;   /* SELECT may not have a GROUP BY clause */
+  }
+  if( pSelect->pLimit ){
+    return 0;   /* SELECT may not have a LIMIT clause */
+  }
+  assert( pSelect->pOffset==0 );  /* Must be so if pLimit==0 */
+  if( pSelect->pPrior ){
+    return 0;   /* SELECT may not be a compound query */
+  }
+  if( pSelect->selFlags & SF_Distinct ){
+    return 0;   /* SELECT may not be DISTINCT */
+  }
+  pEList = pSelect->pEList;
+  assert( pEList!=0 );
+  if( pEList->nExpr!=1 ){
+    return 0;   /* The result set must have exactly one column */
+  }
+  assert( pEList->a[0].pExpr );
+  if( pEList->a[0].pExpr->op!=TK_ALL ){
+    return 0;   /* The result set must be the special operator "*" */
+  }
+
+  /* At this point we have established that the statement is of the
+  ** correct syntactic form to participate in this optimization.  Now
+  ** we have to check the semantics.
+  */
+  pItem = pSelect->pSrc->a;
+  pSrc = sqlite3LocateTable(pParse, 0, pItem->zName, pItem->zDatabase);
+  if( pSrc==0 ){
+    return 0;   /* FROM clause does not contain a real table */
+  }
+  if( pSrc==pDest ){
+    return 0;   /* tab1 and tab2 may not be the same table */
+  }
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  if( pSrc->tabFlags & TF_Virtual ){
+    return 0;   /* tab2 must not be a virtual table */
+  }
+#endif
+  if( pSrc->pSelect ){
+    return 0;   /* tab2 may not be a view */
+  }
+  if( pDest->nCol!=pSrc->nCol ){
+    return 0;   /* Number of columns must be the same in tab1 and tab2 */
+  }
+  if( pDest->iPKey!=pSrc->iPKey ){
+    return 0;   /* Both tables must have the same INTEGER PRIMARY KEY */
+  }
+  for(i=0; i<pDest->nCol; i++){
+    if( pDest->aCol[i].affinity!=pSrc->aCol[i].affinity ){
+      return 0;    /* Affinity must be the same on all columns */
+    }
+    if( !xferCompatibleCollation(pDest->aCol[i].zColl, pSrc->aCol[i].zColl) ){
+      return 0;    /* Collating sequence must be the same on all columns */
+    }
+    if( pDest->aCol[i].notNull && !pSrc->aCol[i].notNull ){
+      return 0;    /* tab2 must be NOT NULL if tab1 is */
+    }
+  }
+  for(pDestIdx=pDest->pIndex; pDestIdx; pDestIdx=pDestIdx->pNext){
+    if( pDestIdx->onError!=OE_None ){
+      destHasUniqueIdx = 1;
+    }
+    for(pSrcIdx=pSrc->pIndex; pSrcIdx; pSrcIdx=pSrcIdx->pNext){
+      if( xferCompatibleIndex(pDestIdx, pSrcIdx) ) break;
+    }
+    if( pSrcIdx==0 ){
+      return 0;    /* pDestIdx has no corresponding index in pSrc */
+    }
+  }
+#ifndef SQLITE_OMIT_CHECK
+  if( pDest->pCheck && sqlite3ExprCompare(pSrc->pCheck, pDest->pCheck) ){
+    return 0;   /* Tables have different CHECK constraints.  Ticket #2252 */
+  }
+#endif
+#ifndef SQLITE_OMIT_FOREIGN_KEY
+  /* Disallow the transfer optimization if the destination table constains
+  ** any foreign key constraints.  This is more restrictive than necessary.
+  ** But the main beneficiary of the transfer optimization is the VACUUM 
+  ** command, and the VACUUM command disables foreign key constraints.  So
+  ** the extra complication to make this rule less restrictive is probably
+  ** not worth the effort.  Ticket [6284df89debdfa61db8073e062908af0c9b6118e]
+  */
+  if( (pParse->db->flags & SQLITE_ForeignKeys)!=0 && pDest->pFKey!=0 ){
+    return 0;
+  }
+#endif
+  if( (pParse->db->flags & SQLITE_CountRows)!=0 ){
+    return 0;
+  }
+
+  /* If we get this far, it means either:
+  **
+  **    *   We can always do the transfer if the table contains an
+  **        an integer primary key
+  **
+  **    *   We can conditionally do the transfer if the destination
+  **        table is empty.
+  */
+#ifdef SQLITE_TEST
+  sqlite3_xferopt_count++;
+#endif
+  iDbSrc = sqlite3SchemaToIndex(pParse->db, pSrc->pSchema);
+  v = sqlite3GetVdbe(pParse);
+  sqlite3CodeVerifySchema(pParse, iDbSrc);
+  iSrc = pParse->nTab++;
+  iDest = pParse->nTab++;
+  regAutoinc = autoIncBegin(pParse, iDbDest, pDest);
+  sqlite3OpenTable(pParse, iDest, iDbDest, pDest, OP_OpenWrite);
+  if( (pDest->iPKey<0 && pDest->pIndex!=0) || destHasUniqueIdx ){
+    /* If tables do not have an INTEGER PRIMARY KEY and there
+    ** are indices to be copied and the destination is not empty,
+    ** we have to disallow the transfer optimization because the
+    ** the rowids might change which will mess up indexing.
+    **
+    ** Or if the destination has a UNIQUE index and is not empty,
+    ** we also disallow the transfer optimization because we cannot
+    ** insure that all entries in the union of DEST and SRC will be
+    ** unique.
+    */
+    addr1 = sqlite3VdbeAddOp2(v, OP_Rewind, iDest, 0);
+    emptyDestTest = sqlite3VdbeAddOp2(v, OP_Goto, 0, 0);
+    sqlite3VdbeJumpHere(v, addr1);
+  }else{
+    emptyDestTest = 0;
+  }
+  sqlite3OpenTable(pParse, iSrc, iDbSrc, pSrc, OP_OpenRead);
+  emptySrcTest = sqlite3VdbeAddOp2(v, OP_Rewind, iSrc, 0);
+  regData = sqlite3GetTempReg(pParse);
+  regRowid = sqlite3GetTempReg(pParse);
+  if( pDest->iPKey>=0 ){
+    addr1 = sqlite3VdbeAddOp2(v, OP_Rowid, iSrc, regRowid);
+    addr2 = sqlite3VdbeAddOp3(v, OP_NotExists, iDest, 0, regRowid);
+    sqlite3HaltConstraint(
+        pParse, onError, "PRIMARY KEY must be unique", P4_STATIC);
+    sqlite3VdbeJumpHere(v, addr2);
+    autoIncStep(pParse, regAutoinc, regRowid);
+  }else if( pDest->pIndex==0 ){
+    addr1 = sqlite3VdbeAddOp2(v, OP_NewRowid, iDest, regRowid);
+  }else{
+    addr1 = sqlite3VdbeAddOp2(v, OP_Rowid, iSrc, regRowid);
+    assert( (pDest->tabFlags & TF_Autoincrement)==0 );
+  }
+  sqlite3VdbeAddOp2(v, OP_RowData, iSrc, regData);
+  sqlite3VdbeAddOp3(v, OP_Insert, iDest, regData, regRowid);
+  sqlite3VdbeChangeP5(v, OPFLAG_NCHANGE|OPFLAG_LASTROWID|OPFLAG_APPEND);
+  sqlite3VdbeChangeP4(v, -1, pDest->zName, 0);
+  sqlite3VdbeAddOp2(v, OP_Next, iSrc, addr1);
+  for(pDestIdx=pDest->pIndex; pDestIdx; pDestIdx=pDestIdx->pNext){
+    for(pSrcIdx=pSrc->pIndex; ALWAYS(pSrcIdx); pSrcIdx=pSrcIdx->pNext){
+      if( xferCompatibleIndex(pDestIdx, pSrcIdx) ) break;
+    }
+    assert( pSrcIdx );
+    sqlite3VdbeAddOp2(v, OP_Close, iSrc, 0);
+    sqlite3VdbeAddOp2(v, OP_Close, iDest, 0);
+    pKey = sqlite3IndexKeyinfo(pParse, pSrcIdx);
+    sqlite3VdbeAddOp4(v, OP_OpenRead, iSrc, pSrcIdx->tnum, iDbSrc,
+                      (char*)pKey, P4_KEYINFO_HANDOFF);
+    VdbeComment((v, "%s", pSrcIdx->zName));
+    pKey = sqlite3IndexKeyinfo(pParse, pDestIdx);
+    sqlite3VdbeAddOp4(v, OP_OpenWrite, iDest, pDestIdx->tnum, iDbDest,
+                      (char*)pKey, P4_KEYINFO_HANDOFF);
+    VdbeComment((v, "%s", pDestIdx->zName));
+    addr1 = sqlite3VdbeAddOp2(v, OP_Rewind, iSrc, 0);
+    sqlite3VdbeAddOp2(v, OP_RowKey, iSrc, regData);
+    sqlite3VdbeAddOp3(v, OP_IdxInsert, iDest, regData, 1);
+    sqlite3VdbeAddOp2(v, OP_Next, iSrc, addr1+1);
+    sqlite3VdbeJumpHere(v, addr1);
+  }
+  sqlite3VdbeJumpHere(v, emptySrcTest);
+  sqlite3ReleaseTempReg(pParse, regRowid);
+  sqlite3ReleaseTempReg(pParse, regData);
+  sqlite3VdbeAddOp2(v, OP_Close, iSrc, 0);
+  sqlite3VdbeAddOp2(v, OP_Close, iDest, 0);
+  if( emptyDestTest ){
+    sqlite3VdbeAddOp2(v, OP_Halt, SQLITE_OK, 0);
+    sqlite3VdbeJumpHere(v, emptyDestTest);
+    sqlite3VdbeAddOp2(v, OP_Close, iDest, 0);
+    return 0;
+  }else{
+    return 1;
+  }
+}
+#endif /* SQLITE_OMIT_XFER_OPT */
diff --git a/src/journal.c b/src/journal.c
new file mode 100644
index 0000000..2f9e222
--- /dev/null
+++ b/src/journal.c
@@ -0,0 +1,238 @@
+/*
+** 2007 August 22
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file implements a special kind of sqlite3_file object used
+** by SQLite to create journal files if the atomic-write optimization
+** is enabled.
+**
+** The distinctive characteristic of this sqlite3_file is that the
+** actual on disk file is created lazily. When the file is created,
+** the caller specifies a buffer size for an in-memory buffer to
+** be used to service read() and write() requests. The actual file
+** on disk is not created or populated until either:
+**
+**   1) The in-memory representation grows too large for the allocated 
+**      buffer, or
+**   2) The sqlite3JournalCreate() function is called.
+*/
+#ifdef SQLITE_ENABLE_ATOMIC_WRITE
+#include "sqliteInt.h"
+
+
+/*
+** A JournalFile object is a subclass of sqlite3_file used by
+** as an open file handle for journal files.
+*/
+struct JournalFile {
+  sqlite3_io_methods *pMethod;    /* I/O methods on journal files */
+  int nBuf;                       /* Size of zBuf[] in bytes */
+  char *zBuf;                     /* Space to buffer journal writes */
+  int iSize;                      /* Amount of zBuf[] currently used */
+  int flags;                      /* xOpen flags */
+  sqlite3_vfs *pVfs;              /* The "real" underlying VFS */
+  sqlite3_file *pReal;            /* The "real" underlying file descriptor */
+  const char *zJournal;           /* Name of the journal file */
+};
+typedef struct JournalFile JournalFile;
+
+/*
+** If it does not already exists, create and populate the on-disk file 
+** for JournalFile p.
+*/
+static int createFile(JournalFile *p){
+  int rc = SQLITE_OK;
+  if( !p->pReal ){
+    sqlite3_file *pReal = (sqlite3_file *)&p[1];
+    rc = sqlite3OsOpen(p->pVfs, p->zJournal, pReal, p->flags, 0);
+    if( rc==SQLITE_OK ){
+      p->pReal = pReal;
+      if( p->iSize>0 ){
+        assert(p->iSize<=p->nBuf);
+        rc = sqlite3OsWrite(p->pReal, p->zBuf, p->iSize, 0);
+      }
+    }
+  }
+  return rc;
+}
+
+/*
+** Close the file.
+*/
+static int jrnlClose(sqlite3_file *pJfd){
+  JournalFile *p = (JournalFile *)pJfd;
+  if( p->pReal ){
+    sqlite3OsClose(p->pReal);
+  }
+  sqlite3_free(p->zBuf);
+  return SQLITE_OK;
+}
+
+/*
+** Read data from the file.
+*/
+static int jrnlRead(
+  sqlite3_file *pJfd,    /* The journal file from which to read */
+  void *zBuf,            /* Put the results here */
+  int iAmt,              /* Number of bytes to read */
+  sqlite_int64 iOfst     /* Begin reading at this offset */
+){
+  int rc = SQLITE_OK;
+  JournalFile *p = (JournalFile *)pJfd;
+  if( p->pReal ){
+    rc = sqlite3OsRead(p->pReal, zBuf, iAmt, iOfst);
+  }else if( (iAmt+iOfst)>p->iSize ){
+    rc = SQLITE_IOERR_SHORT_READ;
+  }else{
+    memcpy(zBuf, &p->zBuf[iOfst], iAmt);
+  }
+  return rc;
+}
+
+/*
+** Write data to the file.
+*/
+static int jrnlWrite(
+  sqlite3_file *pJfd,    /* The journal file into which to write */
+  const void *zBuf,      /* Take data to be written from here */
+  int iAmt,              /* Number of bytes to write */
+  sqlite_int64 iOfst     /* Begin writing at this offset into the file */
+){
+  int rc = SQLITE_OK;
+  JournalFile *p = (JournalFile *)pJfd;
+  if( !p->pReal && (iOfst+iAmt)>p->nBuf ){
+    rc = createFile(p);
+  }
+  if( rc==SQLITE_OK ){
+    if( p->pReal ){
+      rc = sqlite3OsWrite(p->pReal, zBuf, iAmt, iOfst);
+    }else{
+      memcpy(&p->zBuf[iOfst], zBuf, iAmt);
+      if( p->iSize<(iOfst+iAmt) ){
+        p->iSize = (iOfst+iAmt);
+      }
+    }
+  }
+  return rc;
+}
+
+/*
+** Truncate the file.
+*/
+static int jrnlTruncate(sqlite3_file *pJfd, sqlite_int64 size){
+  int rc = SQLITE_OK;
+  JournalFile *p = (JournalFile *)pJfd;
+  if( p->pReal ){
+    rc = sqlite3OsTruncate(p->pReal, size);
+  }else if( size<p->iSize ){
+    p->iSize = size;
+  }
+  return rc;
+}
+
+/*
+** Sync the file.
+*/
+static int jrnlSync(sqlite3_file *pJfd, int flags){
+  int rc;
+  JournalFile *p = (JournalFile *)pJfd;
+  if( p->pReal ){
+    rc = sqlite3OsSync(p->pReal, flags);
+  }else{
+    rc = SQLITE_OK;
+  }
+  return rc;
+}
+
+/*
+** Query the size of the file in bytes.
+*/
+static int jrnlFileSize(sqlite3_file *pJfd, sqlite_int64 *pSize){
+  int rc = SQLITE_OK;
+  JournalFile *p = (JournalFile *)pJfd;
+  if( p->pReal ){
+    rc = sqlite3OsFileSize(p->pReal, pSize);
+  }else{
+    *pSize = (sqlite_int64) p->iSize;
+  }
+  return rc;
+}
+
+/*
+** Table of methods for JournalFile sqlite3_file object.
+*/
+static struct sqlite3_io_methods JournalFileMethods = {
+  1,             /* iVersion */
+  jrnlClose,     /* xClose */
+  jrnlRead,      /* xRead */
+  jrnlWrite,     /* xWrite */
+  jrnlTruncate,  /* xTruncate */
+  jrnlSync,      /* xSync */
+  jrnlFileSize,  /* xFileSize */
+  0,             /* xLock */
+  0,             /* xUnlock */
+  0,             /* xCheckReservedLock */
+  0,             /* xFileControl */
+  0,             /* xSectorSize */
+  0,             /* xDeviceCharacteristics */
+  0,             /* xShmMap */
+  0,             /* xShmLock */
+  0,             /* xShmBarrier */
+  0              /* xShmUnmap */
+};
+
+/* 
+** Open a journal file.
+*/
+int sqlite3JournalOpen(
+  sqlite3_vfs *pVfs,         /* The VFS to use for actual file I/O */
+  const char *zName,         /* Name of the journal file */
+  sqlite3_file *pJfd,        /* Preallocated, blank file handle */
+  int flags,                 /* Opening flags */
+  int nBuf                   /* Bytes buffered before opening the file */
+){
+  JournalFile *p = (JournalFile *)pJfd;
+  memset(p, 0, sqlite3JournalSize(pVfs));
+  if( nBuf>0 ){
+    p->zBuf = sqlite3MallocZero(nBuf);
+    if( !p->zBuf ){
+      return SQLITE_NOMEM;
+    }
+  }else{
+    return sqlite3OsOpen(pVfs, zName, pJfd, flags, 0);
+  }
+  p->pMethod = &JournalFileMethods;
+  p->nBuf = nBuf;
+  p->flags = flags;
+  p->zJournal = zName;
+  p->pVfs = pVfs;
+  return SQLITE_OK;
+}
+
+/*
+** If the argument p points to a JournalFile structure, and the underlying
+** file has not yet been created, create it now.
+*/
+int sqlite3JournalCreate(sqlite3_file *p){
+  if( p->pMethods!=&JournalFileMethods ){
+    return SQLITE_OK;
+  }
+  return createFile((JournalFile *)p);
+}
+
+/* 
+** Return the number of bytes required to store a JournalFile that uses vfs
+** pVfs to create the underlying on-disk files.
+*/
+int sqlite3JournalSize(sqlite3_vfs *pVfs){
+  return (pVfs->szOsFile+sizeof(JournalFile));
+}
+#endif
diff --git a/src/legacy.c b/src/legacy.c
new file mode 100644
index 0000000..ebab2de
--- /dev/null
+++ b/src/legacy.c
@@ -0,0 +1,145 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Main file for the SQLite library.  The routines in this file
+** implement the programmer interface to the library.  Routines in
+** other files are for internal use by SQLite and should not be
+** accessed by users of the library.
+*/
+
+#include "sqliteInt.h"
+
+/*
+** Execute SQL code.  Return one of the SQLITE_ success/failure
+** codes.  Also write an error message into memory obtained from
+** malloc() and make *pzErrMsg point to that message.
+**
+** If the SQL is a query, then for each row in the query result
+** the xCallback() function is called.  pArg becomes the first
+** argument to xCallback().  If xCallback=NULL then no callback
+** is invoked, even for queries.
+*/
+int sqlite3_exec(
+  sqlite3 *db,                /* The database on which the SQL executes */
+  const char *zSql,           /* The SQL to be executed */
+  sqlite3_callback xCallback, /* Invoke this callback routine */
+  void *pArg,                 /* First argument to xCallback() */
+  char **pzErrMsg             /* Write error messages here */
+){
+  int rc = SQLITE_OK;         /* Return code */
+  const char *zLeftover;      /* Tail of unprocessed SQL */
+  sqlite3_stmt *pStmt = 0;    /* The current SQL statement */
+  char **azCols = 0;          /* Names of result columns */
+  int nRetry = 0;             /* Number of retry attempts */
+  int callbackIsInit;         /* True if callback data is initialized */
+
+  if( !sqlite3SafetyCheckOk(db) ) return SQLITE_MISUSE_BKPT;
+  if( zSql==0 ) zSql = "";
+
+  sqlite3_mutex_enter(db->mutex);
+  sqlite3Error(db, SQLITE_OK, 0);
+  while( (rc==SQLITE_OK || (rc==SQLITE_SCHEMA && (++nRetry)<2)) && zSql[0] ){
+    int nCol;
+    char **azVals = 0;
+
+    pStmt = 0;
+    rc = sqlite3_prepare(db, zSql, -1, &pStmt, &zLeftover);
+    assert( rc==SQLITE_OK || pStmt==0 );
+    if( rc!=SQLITE_OK ){
+      continue;
+    }
+    if( !pStmt ){
+      /* this happens for a comment or white-space */
+      zSql = zLeftover;
+      continue;
+    }
+
+    callbackIsInit = 0;
+    nCol = sqlite3_column_count(pStmt);
+
+    while( 1 ){
+      int i;
+      rc = sqlite3_step(pStmt);
+
+      /* Invoke the callback function if required */
+      if( xCallback && (SQLITE_ROW==rc || 
+          (SQLITE_DONE==rc && !callbackIsInit
+                           && db->flags&SQLITE_NullCallback)) ){
+        if( !callbackIsInit ){
+          azCols = sqlite3DbMallocZero(db, 2*nCol*sizeof(const char*) + 1);
+          if( azCols==0 ){
+            goto exec_out;
+          }
+          for(i=0; i<nCol; i++){
+            azCols[i] = (char *)sqlite3_column_name(pStmt, i);
+            /* sqlite3VdbeSetColName() installs column names as UTF8
+            ** strings so there is no way for sqlite3_column_name() to fail. */
+            assert( azCols[i]!=0 );
+          }
+          callbackIsInit = 1;
+        }
+        if( rc==SQLITE_ROW ){
+          azVals = &azCols[nCol];
+          for(i=0; i<nCol; i++){
+            azVals[i] = (char *)sqlite3_column_text(pStmt, i);
+            if( !azVals[i] && sqlite3_column_type(pStmt, i)!=SQLITE_NULL ){
+              db->mallocFailed = 1;
+              goto exec_out;
+            }
+          }
+        }
+        if( xCallback(pArg, nCol, azVals, azCols) ){
+          rc = SQLITE_ABORT;
+          sqlite3VdbeFinalize((Vdbe *)pStmt);
+          pStmt = 0;
+          sqlite3Error(db, SQLITE_ABORT, 0);
+          goto exec_out;
+        }
+      }
+
+      if( rc!=SQLITE_ROW ){
+        rc = sqlite3VdbeFinalize((Vdbe *)pStmt);
+        pStmt = 0;
+        if( rc!=SQLITE_SCHEMA ){
+          nRetry = 0;
+          zSql = zLeftover;
+          while( sqlite3Isspace(zSql[0]) ) zSql++;
+        }
+        break;
+      }
+    }
+
+    sqlite3DbFree(db, azCols);
+    azCols = 0;
+  }
+
+exec_out:
+  if( pStmt ) sqlite3VdbeFinalize((Vdbe *)pStmt);
+  sqlite3DbFree(db, azCols);
+
+  rc = sqlite3ApiExit(db, rc);
+  if( rc!=SQLITE_OK && ALWAYS(rc==sqlite3_errcode(db)) && pzErrMsg ){
+    int nErrMsg = 1 + sqlite3Strlen30(sqlite3_errmsg(db));
+    *pzErrMsg = sqlite3Malloc(nErrMsg);
+    if( *pzErrMsg ){
+      memcpy(*pzErrMsg, sqlite3_errmsg(db), nErrMsg);
+    }else{
+      rc = SQLITE_NOMEM;
+      sqlite3Error(db, SQLITE_NOMEM, 0);
+    }
+  }else if( pzErrMsg ){
+    *pzErrMsg = 0;
+  }
+
+  assert( (rc&db->errMask)==rc );
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
diff --git a/src/lempar.c b/src/lempar.c
new file mode 100644
index 0000000..cb6025e
--- /dev/null
+++ b/src/lempar.c
@@ -0,0 +1,863 @@
+/* Driver template for the LEMON parser generator.
+** The author disclaims copyright to this source code.
+**
+** This version of "lempar.c" is modified, slightly, for use by SQLite.
+** The only modifications are the addition of a couple of NEVER()
+** macros to disable tests that are needed in the case of a general
+** LALR(1) grammar but which are always false in the
+** specific grammar used by SQLite.
+*/
+/* First off, code is included that follows the "include" declaration
+** in the input grammar file. */
+#include <stdio.h>
+%%
+/* Next is all token values, in a form suitable for use by makeheaders.
+** This section will be null unless lemon is run with the -m switch.
+*/
+/* 
+** These constants (all generated automatically by the parser generator)
+** specify the various kinds of tokens (terminals) that the parser
+** understands. 
+**
+** Each symbol here is a terminal symbol in the grammar.
+*/
+%%
+/* Make sure the INTERFACE macro is defined.
+*/
+#ifndef INTERFACE
+# define INTERFACE 1
+#endif
+/* The next thing included is series of defines which control
+** various aspects of the generated parser.
+**    YYCODETYPE         is the data type used for storing terminal
+**                       and nonterminal numbers.  "unsigned char" is
+**                       used if there are fewer than 250 terminals
+**                       and nonterminals.  "int" is used otherwise.
+**    YYNOCODE           is a number of type YYCODETYPE which corresponds
+**                       to no legal terminal or nonterminal number.  This
+**                       number is used to fill in empty slots of the hash 
+**                       table.
+**    YYFALLBACK         If defined, this indicates that one or more tokens
+**                       have fall-back values which should be used if the
+**                       original value of the token will not parse.
+**    YYACTIONTYPE       is the data type used for storing terminal
+**                       and nonterminal numbers.  "unsigned char" is
+**                       used if there are fewer than 250 rules and
+**                       states combined.  "int" is used otherwise.
+**    ParseTOKENTYPE     is the data type used for minor tokens given 
+**                       directly to the parser from the tokenizer.
+**    YYMINORTYPE        is the data type used for all minor tokens.
+**                       This is typically a union of many types, one of
+**                       which is ParseTOKENTYPE.  The entry in the union
+**                       for base tokens is called "yy0".
+**    YYSTACKDEPTH       is the maximum depth of the parser's stack.  If
+**                       zero the stack is dynamically sized using realloc()
+**    ParseARG_SDECL     A static variable declaration for the %extra_argument
+**    ParseARG_PDECL     A parameter declaration for the %extra_argument
+**    ParseARG_STORE     Code to store %extra_argument into yypParser
+**    ParseARG_FETCH     Code to extract %extra_argument from yypParser
+**    YYNSTATE           the combined number of states.
+**    YYNRULE            the number of rules in the grammar
+**    YYERRORSYMBOL      is the code number of the error symbol.  If not
+**                       defined, then do no error processing.
+*/
+%%
+#define YY_NO_ACTION      (YYNSTATE+YYNRULE+2)
+#define YY_ACCEPT_ACTION  (YYNSTATE+YYNRULE+1)
+#define YY_ERROR_ACTION   (YYNSTATE+YYNRULE)
+
+/* The yyzerominor constant is used to initialize instances of
+** YYMINORTYPE objects to zero. */
+static const YYMINORTYPE yyzerominor = { 0 };
+
+/* Define the yytestcase() macro to be a no-op if is not already defined
+** otherwise.
+**
+** Applications can choose to define yytestcase() in the %include section
+** to a macro that can assist in verifying code coverage.  For production
+** code the yytestcase() macro should be turned off.  But it is useful
+** for testing.
+*/
+#ifndef yytestcase
+# define yytestcase(X)
+#endif
+
+
+/* Next are the tables used to determine what action to take based on the
+** current state and lookahead token.  These tables are used to implement
+** functions that take a state number and lookahead value and return an
+** action integer.  
+**
+** Suppose the action integer is N.  Then the action is determined as
+** follows
+**
+**   0 <= N < YYNSTATE                  Shift N.  That is, push the lookahead
+**                                      token onto the stack and goto state N.
+**
+**   YYNSTATE <= N < YYNSTATE+YYNRULE   Reduce by rule N-YYNSTATE.
+**
+**   N == YYNSTATE+YYNRULE              A syntax error has occurred.
+**
+**   N == YYNSTATE+YYNRULE+1            The parser accepts its input.
+**
+**   N == YYNSTATE+YYNRULE+2            No such action.  Denotes unused
+**                                      slots in the yy_action[] table.
+**
+** The action table is constructed as a single large table named yy_action[].
+** Given state S and lookahead X, the action is computed as
+**
+**      yy_action[ yy_shift_ofst[S] + X ]
+**
+** If the index value yy_shift_ofst[S]+X is out of range or if the value
+** yy_lookahead[yy_shift_ofst[S]+X] is not equal to X or if yy_shift_ofst[S]
+** is equal to YY_SHIFT_USE_DFLT, it means that the action is not in the table
+** and that yy_default[S] should be used instead.  
+**
+** The formula above is for computing the action when the lookahead is
+** a terminal symbol.  If the lookahead is a non-terminal (as occurs after
+** a reduce action) then the yy_reduce_ofst[] array is used in place of
+** the yy_shift_ofst[] array and YY_REDUCE_USE_DFLT is used in place of
+** YY_SHIFT_USE_DFLT.
+**
+** The following are the tables generated in this section:
+**
+**  yy_action[]        A single table containing all actions.
+**  yy_lookahead[]     A table containing the lookahead for each entry in
+**                     yy_action.  Used to detect hash collisions.
+**  yy_shift_ofst[]    For each state, the offset into yy_action for
+**                     shifting terminals.
+**  yy_reduce_ofst[]   For each state, the offset into yy_action for
+**                     shifting non-terminals after a reduce.
+**  yy_default[]       Default action for each state.
+*/
+%%
+
+/* The next table maps tokens into fallback tokens.  If a construct
+** like the following:
+** 
+**      %fallback ID X Y Z.
+**
+** appears in the grammar, then ID becomes a fallback token for X, Y,
+** and Z.  Whenever one of the tokens X, Y, or Z is input to the parser
+** but it does not parse, the type of the token is changed to ID and
+** the parse is retried before an error is thrown.
+*/
+#ifdef YYFALLBACK
+static const YYCODETYPE yyFallback[] = {
+%%
+};
+#endif /* YYFALLBACK */
+
+/* The following structure represents a single element of the
+** parser's stack.  Information stored includes:
+**
+**   +  The state number for the parser at this level of the stack.
+**
+**   +  The value of the token stored at this level of the stack.
+**      (In other words, the "major" token.)
+**
+**   +  The semantic value stored at this level of the stack.  This is
+**      the information used by the action routines in the grammar.
+**      It is sometimes called the "minor" token.
+*/
+struct yyStackEntry {
+  YYACTIONTYPE stateno;  /* The state-number */
+  YYCODETYPE major;      /* The major token value.  This is the code
+                         ** number for the token at this stack level */
+  YYMINORTYPE minor;     /* The user-supplied minor token value.  This
+                         ** is the value of the token  */
+};
+typedef struct yyStackEntry yyStackEntry;
+
+/* The state of the parser is completely contained in an instance of
+** the following structure */
+struct yyParser {
+  int yyidx;                    /* Index of top element in stack */
+#ifdef YYTRACKMAXSTACKDEPTH
+  int yyidxMax;                 /* Maximum value of yyidx */
+#endif
+  int yyerrcnt;                 /* Shifts left before out of the error */
+  ParseARG_SDECL                /* A place to hold %extra_argument */
+#if YYSTACKDEPTH<=0
+  int yystksz;                  /* Current side of the stack */
+  yyStackEntry *yystack;        /* The parser's stack */
+#else
+  yyStackEntry yystack[YYSTACKDEPTH];  /* The parser's stack */
+#endif
+};
+typedef struct yyParser yyParser;
+
+#ifndef NDEBUG
+#include <stdio.h>
+static FILE *yyTraceFILE = 0;
+static char *yyTracePrompt = 0;
+#endif /* NDEBUG */
+
+#ifndef NDEBUG
+/* 
+** Turn parser tracing on by giving a stream to which to write the trace
+** and a prompt to preface each trace message.  Tracing is turned off
+** by making either argument NULL 
+**
+** Inputs:
+** <ul>
+** <li> A FILE* to which trace output should be written.
+**      If NULL, then tracing is turned off.
+** <li> A prefix string written at the beginning of every
+**      line of trace output.  If NULL, then tracing is
+**      turned off.
+** </ul>
+**
+** Outputs:
+** None.
+*/
+void ParseTrace(FILE *TraceFILE, char *zTracePrompt){
+  yyTraceFILE = TraceFILE;
+  yyTracePrompt = zTracePrompt;
+  if( yyTraceFILE==0 ) yyTracePrompt = 0;
+  else if( yyTracePrompt==0 ) yyTraceFILE = 0;
+}
+#endif /* NDEBUG */
+
+#ifndef NDEBUG
+/* For tracing shifts, the names of all terminals and nonterminals
+** are required.  The following table supplies these names */
+static const char *const yyTokenName[] = { 
+%%
+};
+#endif /* NDEBUG */
+
+#ifndef NDEBUG
+/* For tracing reduce actions, the names of all rules are required.
+*/
+static const char *const yyRuleName[] = {
+%%
+};
+#endif /* NDEBUG */
+
+
+#if YYSTACKDEPTH<=0
+/*
+** Try to increase the size of the parser stack.
+*/
+static void yyGrowStack(yyParser *p){
+  int newSize;
+  yyStackEntry *pNew;
+
+  newSize = p->yystksz*2 + 100;
+  pNew = realloc(p->yystack, newSize*sizeof(pNew[0]));
+  if( pNew ){
+    p->yystack = pNew;
+    p->yystksz = newSize;
+#ifndef NDEBUG
+    if( yyTraceFILE ){
+      fprintf(yyTraceFILE,"%sStack grows to %d entries!\n",
+              yyTracePrompt, p->yystksz);
+    }
+#endif
+  }
+}
+#endif
+
+/* 
+** This function allocates a new parser.
+** The only argument is a pointer to a function which works like
+** malloc.
+**
+** Inputs:
+** A pointer to the function used to allocate memory.
+**
+** Outputs:
+** A pointer to a parser.  This pointer is used in subsequent calls
+** to Parse and ParseFree.
+*/
+void *ParseAlloc(void *(*mallocProc)(size_t)){
+  yyParser *pParser;
+  pParser = (yyParser*)(*mallocProc)( (size_t)sizeof(yyParser) );
+  if( pParser ){
+    pParser->yyidx = -1;
+#ifdef YYTRACKMAXSTACKDEPTH
+    pParser->yyidxMax = 0;
+#endif
+#if YYSTACKDEPTH<=0
+    pParser->yystack = NULL;
+    pParser->yystksz = 0;
+    yyGrowStack(pParser);
+#endif
+  }
+  return pParser;
+}
+
+/* The following function deletes the value associated with a
+** symbol.  The symbol can be either a terminal or nonterminal.
+** "yymajor" is the symbol code, and "yypminor" is a pointer to
+** the value.
+*/
+static void yy_destructor(
+  yyParser *yypParser,    /* The parser */
+  YYCODETYPE yymajor,     /* Type code for object to destroy */
+  YYMINORTYPE *yypminor   /* The object to be destroyed */
+){
+  ParseARG_FETCH;
+  switch( yymajor ){
+    /* Here is inserted the actions which take place when a
+    ** terminal or non-terminal is destroyed.  This can happen
+    ** when the symbol is popped from the stack during a
+    ** reduce or during error processing or when a parser is 
+    ** being destroyed before it is finished parsing.
+    **
+    ** Note: during a reduce, the only symbols destroyed are those
+    ** which appear on the RHS of the rule, but which are not used
+    ** inside the C code.
+    */
+%%
+    default:  break;   /* If no destructor action specified: do nothing */
+  }
+}
+
+/*
+** Pop the parser's stack once.
+**
+** If there is a destructor routine associated with the token which
+** is popped from the stack, then call it.
+**
+** Return the major token number for the symbol popped.
+*/
+static int yy_pop_parser_stack(yyParser *pParser){
+  YYCODETYPE yymajor;
+  yyStackEntry *yytos = &pParser->yystack[pParser->yyidx];
+
+  /* There is no mechanism by which the parser stack can be popped below
+  ** empty in SQLite.  */
+  if( NEVER(pParser->yyidx<0) ) return 0;
+#ifndef NDEBUG
+  if( yyTraceFILE && pParser->yyidx>=0 ){
+    fprintf(yyTraceFILE,"%sPopping %s\n",
+      yyTracePrompt,
+      yyTokenName[yytos->major]);
+  }
+#endif
+  yymajor = yytos->major;
+  yy_destructor(pParser, yymajor, &yytos->minor);
+  pParser->yyidx--;
+  return yymajor;
+}
+
+/* 
+** Deallocate and destroy a parser.  Destructors are all called for
+** all stack elements before shutting the parser down.
+**
+** Inputs:
+** <ul>
+** <li>  A pointer to the parser.  This should be a pointer
+**       obtained from ParseAlloc.
+** <li>  A pointer to a function used to reclaim memory obtained
+**       from malloc.
+** </ul>
+*/
+void ParseFree(
+  void *p,                    /* The parser to be deleted */
+  void (*freeProc)(void*)     /* Function used to reclaim memory */
+){
+  yyParser *pParser = (yyParser*)p;
+  /* In SQLite, we never try to destroy a parser that was not successfully
+  ** created in the first place. */
+  if( NEVER(pParser==0) ) return;
+  while( pParser->yyidx>=0 ) yy_pop_parser_stack(pParser);
+#if YYSTACKDEPTH<=0
+  free(pParser->yystack);
+#endif
+  (*freeProc)((void*)pParser);
+}
+
+/*
+** Return the peak depth of the stack for a parser.
+*/
+#ifdef YYTRACKMAXSTACKDEPTH
+int ParseStackPeak(void *p){
+  yyParser *pParser = (yyParser*)p;
+  return pParser->yyidxMax;
+}
+#endif
+
+/*
+** Find the appropriate action for a parser given the terminal
+** look-ahead token iLookAhead.
+**
+** If the look-ahead token is YYNOCODE, then check to see if the action is
+** independent of the look-ahead.  If it is, return the action, otherwise
+** return YY_NO_ACTION.
+*/
+static int yy_find_shift_action(
+  yyParser *pParser,        /* The parser */
+  YYCODETYPE iLookAhead     /* The look-ahead token */
+){
+  int i;
+  int stateno = pParser->yystack[pParser->yyidx].stateno;
+ 
+  if( stateno>YY_SHIFT_COUNT
+   || (i = yy_shift_ofst[stateno])==YY_SHIFT_USE_DFLT ){
+    return yy_default[stateno];
+  }
+  assert( iLookAhead!=YYNOCODE );
+  i += iLookAhead;
+  if( i<0 || i>=YY_ACTTAB_COUNT || yy_lookahead[i]!=iLookAhead ){
+    if( iLookAhead>0 ){
+#ifdef YYFALLBACK
+      YYCODETYPE iFallback;            /* Fallback token */
+      if( iLookAhead<sizeof(yyFallback)/sizeof(yyFallback[0])
+             && (iFallback = yyFallback[iLookAhead])!=0 ){
+#ifndef NDEBUG
+        if( yyTraceFILE ){
+          fprintf(yyTraceFILE, "%sFALLBACK %s => %s\n",
+             yyTracePrompt, yyTokenName[iLookAhead], yyTokenName[iFallback]);
+        }
+#endif
+        return yy_find_shift_action(pParser, iFallback);
+      }
+#endif
+#ifdef YYWILDCARD
+      {
+        int j = i - iLookAhead + YYWILDCARD;
+        if( 
+#if YY_SHIFT_MIN+YYWILDCARD<0
+          j>=0 &&
+#endif
+#if YY_SHIFT_MAX+YYWILDCARD>=YY_ACTTAB_COUNT
+          j<YY_ACTTAB_COUNT &&
+#endif
+          yy_lookahead[j]==YYWILDCARD
+        ){
+#ifndef NDEBUG
+          if( yyTraceFILE ){
+            fprintf(yyTraceFILE, "%sWILDCARD %s => %s\n",
+               yyTracePrompt, yyTokenName[iLookAhead], yyTokenName[YYWILDCARD]);
+          }
+#endif /* NDEBUG */
+          return yy_action[j];
+        }
+      }
+#endif /* YYWILDCARD */
+    }
+    return yy_default[stateno];
+  }else{
+    return yy_action[i];
+  }
+}
+
+/*
+** Find the appropriate action for a parser given the non-terminal
+** look-ahead token iLookAhead.
+**
+** If the look-ahead token is YYNOCODE, then check to see if the action is
+** independent of the look-ahead.  If it is, return the action, otherwise
+** return YY_NO_ACTION.
+*/
+static int yy_find_reduce_action(
+  int stateno,              /* Current state number */
+  YYCODETYPE iLookAhead     /* The look-ahead token */
+){
+  int i;
+#ifdef YYERRORSYMBOL
+  if( stateno>YY_REDUCE_COUNT ){
+    return yy_default[stateno];
+  }
+#else
+  assert( stateno<=YY_REDUCE_COUNT );
+#endif
+  i = yy_reduce_ofst[stateno];
+  assert( i!=YY_REDUCE_USE_DFLT );
+  assert( iLookAhead!=YYNOCODE );
+  i += iLookAhead;
+#ifdef YYERRORSYMBOL
+  if( i<0 || i>=YY_ACTTAB_COUNT || yy_lookahead[i]!=iLookAhead ){
+    return yy_default[stateno];
+  }
+#else
+  assert( i>=0 && i<YY_ACTTAB_COUNT );
+  assert( yy_lookahead[i]==iLookAhead );
+#endif
+  return yy_action[i];
+}
+
+/*
+** The following routine is called if the stack overflows.
+*/
+static void yyStackOverflow(yyParser *yypParser, YYMINORTYPE *yypMinor){
+   ParseARG_FETCH;
+   yypParser->yyidx--;
+#ifndef NDEBUG
+   if( yyTraceFILE ){
+     fprintf(yyTraceFILE,"%sStack Overflow!\n",yyTracePrompt);
+   }
+#endif
+   while( yypParser->yyidx>=0 ) yy_pop_parser_stack(yypParser);
+   /* Here code is inserted which will execute if the parser
+   ** stack every overflows */
+%%
+   ParseARG_STORE; /* Suppress warning about unused %extra_argument var */
+}
+
+/*
+** Perform a shift action.
+*/
+static void yy_shift(
+  yyParser *yypParser,          /* The parser to be shifted */
+  int yyNewState,               /* The new state to shift in */
+  int yyMajor,                  /* The major token to shift in */
+  YYMINORTYPE *yypMinor         /* Pointer to the minor token to shift in */
+){
+  yyStackEntry *yytos;
+  yypParser->yyidx++;
+#ifdef YYTRACKMAXSTACKDEPTH
+  if( yypParser->yyidx>yypParser->yyidxMax ){
+    yypParser->yyidxMax = yypParser->yyidx;
+  }
+#endif
+#if YYSTACKDEPTH>0 
+  if( yypParser->yyidx>=YYSTACKDEPTH ){
+    yyStackOverflow(yypParser, yypMinor);
+    return;
+  }
+#else
+  if( yypParser->yyidx>=yypParser->yystksz ){
+    yyGrowStack(yypParser);
+    if( yypParser->yyidx>=yypParser->yystksz ){
+      yyStackOverflow(yypParser, yypMinor);
+      return;
+    }
+  }
+#endif
+  yytos = &yypParser->yystack[yypParser->yyidx];
+  yytos->stateno = (YYACTIONTYPE)yyNewState;
+  yytos->major = (YYCODETYPE)yyMajor;
+  yytos->minor = *yypMinor;
+#ifndef NDEBUG
+  if( yyTraceFILE && yypParser->yyidx>0 ){
+    int i;
+    fprintf(yyTraceFILE,"%sShift %d\n",yyTracePrompt,yyNewState);
+    fprintf(yyTraceFILE,"%sStack:",yyTracePrompt);
+    for(i=1; i<=yypParser->yyidx; i++)
+      fprintf(yyTraceFILE," %s",yyTokenName[yypParser->yystack[i].major]);
+    fprintf(yyTraceFILE,"\n");
+  }
+#endif
+}
+
+/* The following table contains information about every rule that
+** is used during the reduce.
+*/
+static const struct {
+  YYCODETYPE lhs;         /* Symbol on the left-hand side of the rule */
+  unsigned char nrhs;     /* Number of right-hand side symbols in the rule */
+} yyRuleInfo[] = {
+%%
+};
+
+static void yy_accept(yyParser*);  /* Forward Declaration */
+
+/*
+** Perform a reduce action and the shift that must immediately
+** follow the reduce.
+*/
+static void yy_reduce(
+  yyParser *yypParser,         /* The parser */
+  int yyruleno                 /* Number of the rule by which to reduce */
+){
+  int yygoto;                     /* The next state */
+  int yyact;                      /* The next action */
+  YYMINORTYPE yygotominor;        /* The LHS of the rule reduced */
+  yyStackEntry *yymsp;            /* The top of the parser's stack */
+  int yysize;                     /* Amount to pop the stack */
+  ParseARG_FETCH;
+  yymsp = &yypParser->yystack[yypParser->yyidx];
+#ifndef NDEBUG
+  if( yyTraceFILE && yyruleno>=0 
+        && yyruleno<(int)(sizeof(yyRuleName)/sizeof(yyRuleName[0])) ){
+    fprintf(yyTraceFILE, "%sReduce [%s].\n", yyTracePrompt,
+      yyRuleName[yyruleno]);
+  }
+#endif /* NDEBUG */
+
+  /* Silence complaints from purify about yygotominor being uninitialized
+  ** in some cases when it is copied into the stack after the following
+  ** switch.  yygotominor is uninitialized when a rule reduces that does
+  ** not set the value of its left-hand side nonterminal.  Leaving the
+  ** value of the nonterminal uninitialized is utterly harmless as long
+  ** as the value is never used.  So really the only thing this code
+  ** accomplishes is to quieten purify.  
+  **
+  ** 2007-01-16:  The wireshark project (www.wireshark.org) reports that
+  ** without this code, their parser segfaults.  I'm not sure what there
+  ** parser is doing to make this happen.  This is the second bug report
+  ** from wireshark this week.  Clearly they are stressing Lemon in ways
+  ** that it has not been previously stressed...  (SQLite ticket #2172)
+  */
+  /*memset(&yygotominor, 0, sizeof(yygotominor));*/
+  yygotominor = yyzerominor;
+
+
+  switch( yyruleno ){
+  /* Beginning here are the reduction cases.  A typical example
+  ** follows:
+  **   case 0:
+  **  #line <lineno> <grammarfile>
+  **     { ... }           // User supplied code
+  **  #line <lineno> <thisfile>
+  **     break;
+  */
+%%
+  };
+  yygoto = yyRuleInfo[yyruleno].lhs;
+  yysize = yyRuleInfo[yyruleno].nrhs;
+  yypParser->yyidx -= yysize;
+  yyact = yy_find_reduce_action(yymsp[-yysize].stateno,(YYCODETYPE)yygoto);
+  if( yyact < YYNSTATE ){
+#ifdef NDEBUG
+    /* If we are not debugging and the reduce action popped at least
+    ** one element off the stack, then we can push the new element back
+    ** onto the stack here, and skip the stack overflow test in yy_shift().
+    ** That gives a significant speed improvement. */
+    if( yysize ){
+      yypParser->yyidx++;
+      yymsp -= yysize-1;
+      yymsp->stateno = (YYACTIONTYPE)yyact;
+      yymsp->major = (YYCODETYPE)yygoto;
+      yymsp->minor = yygotominor;
+    }else
+#endif
+    {
+      yy_shift(yypParser,yyact,yygoto,&yygotominor);
+    }
+  }else{
+    assert( yyact == YYNSTATE + YYNRULE + 1 );
+    yy_accept(yypParser);
+  }
+}
+
+/*
+** The following code executes when the parse fails
+*/
+#ifndef YYNOERRORRECOVERY
+static void yy_parse_failed(
+  yyParser *yypParser           /* The parser */
+){
+  ParseARG_FETCH;
+#ifndef NDEBUG
+  if( yyTraceFILE ){
+    fprintf(yyTraceFILE,"%sFail!\n",yyTracePrompt);
+  }
+#endif
+  while( yypParser->yyidx>=0 ) yy_pop_parser_stack(yypParser);
+  /* Here code is inserted which will be executed whenever the
+  ** parser fails */
+%%
+  ParseARG_STORE; /* Suppress warning about unused %extra_argument variable */
+}
+#endif /* YYNOERRORRECOVERY */
+
+/*
+** The following code executes when a syntax error first occurs.
+*/
+static void yy_syntax_error(
+  yyParser *yypParser,           /* The parser */
+  int yymajor,                   /* The major type of the error token */
+  YYMINORTYPE yyminor            /* The minor type of the error token */
+){
+  ParseARG_FETCH;
+#define TOKEN (yyminor.yy0)
+%%
+  ParseARG_STORE; /* Suppress warning about unused %extra_argument variable */
+}
+
+/*
+** The following is executed when the parser accepts
+*/
+static void yy_accept(
+  yyParser *yypParser           /* The parser */
+){
+  ParseARG_FETCH;
+#ifndef NDEBUG
+  if( yyTraceFILE ){
+    fprintf(yyTraceFILE,"%sAccept!\n",yyTracePrompt);
+  }
+#endif
+  while( yypParser->yyidx>=0 ) yy_pop_parser_stack(yypParser);
+  /* Here code is inserted which will be executed whenever the
+  ** parser accepts */
+%%
+  ParseARG_STORE; /* Suppress warning about unused %extra_argument variable */
+}
+
+/* The main parser program.
+** The first argument is a pointer to a structure obtained from
+** "ParseAlloc" which describes the current state of the parser.
+** The second argument is the major token number.  The third is
+** the minor token.  The fourth optional argument is whatever the
+** user wants (and specified in the grammar) and is available for
+** use by the action routines.
+**
+** Inputs:
+** <ul>
+** <li> A pointer to the parser (an opaque structure.)
+** <li> The major token number.
+** <li> The minor token number.
+** <li> An option argument of a grammar-specified type.
+** </ul>
+**
+** Outputs:
+** None.
+*/
+void Parse(
+  void *yyp,                   /* The parser */
+  int yymajor,                 /* The major token code number */
+  ParseTOKENTYPE yyminor       /* The value for the token */
+  ParseARG_PDECL               /* Optional %extra_argument parameter */
+){
+  YYMINORTYPE yyminorunion;
+  int yyact;            /* The parser action. */
+#if !defined(YYERRORSYMBOL) && !defined(YYNOERRORRECOVERY)
+  int yyendofinput;     /* True if we are at the end of input */
+#endif
+#ifdef YYERRORSYMBOL
+  int yyerrorhit = 0;   /* True if yymajor has invoked an error */
+#endif
+  yyParser *yypParser;  /* The parser */
+
+  /* (re)initialize the parser, if necessary */
+  yypParser = (yyParser*)yyp;
+  if( yypParser->yyidx<0 ){
+#if YYSTACKDEPTH<=0
+    if( yypParser->yystksz <=0 ){
+      /*memset(&yyminorunion, 0, sizeof(yyminorunion));*/
+      yyminorunion = yyzerominor;
+      yyStackOverflow(yypParser, &yyminorunion);
+      return;
+    }
+#endif
+    yypParser->yyidx = 0;
+    yypParser->yyerrcnt = -1;
+    yypParser->yystack[0].stateno = 0;
+    yypParser->yystack[0].major = 0;
+  }
+  yyminorunion.yy0 = yyminor;
+#if !defined(YYERRORSYMBOL) && !defined(YYNOERRORRECOVERY)
+  yyendofinput = (yymajor==0);
+#endif
+  ParseARG_STORE;
+
+#ifndef NDEBUG
+  if( yyTraceFILE ){
+    fprintf(yyTraceFILE,"%sInput %s\n",yyTracePrompt,yyTokenName[yymajor]);
+  }
+#endif
+
+  do{
+    yyact = yy_find_shift_action(yypParser,(YYCODETYPE)yymajor);
+    if( yyact<YYNSTATE ){
+      yy_shift(yypParser,yyact,yymajor,&yyminorunion);
+      yypParser->yyerrcnt--;
+      yymajor = YYNOCODE;
+    }else if( yyact < YYNSTATE + YYNRULE ){
+      yy_reduce(yypParser,yyact-YYNSTATE);
+    }else{
+      assert( yyact == YY_ERROR_ACTION );
+#ifdef YYERRORSYMBOL
+      int yymx;
+#endif
+#ifndef NDEBUG
+      if( yyTraceFILE ){
+        fprintf(yyTraceFILE,"%sSyntax Error!\n",yyTracePrompt);
+      }
+#endif
+#ifdef YYERRORSYMBOL
+      /* A syntax error has occurred.
+      ** The response to an error depends upon whether or not the
+      ** grammar defines an error token "ERROR".  
+      **
+      ** This is what we do if the grammar does define ERROR:
+      **
+      **  * Call the %syntax_error function.
+      **
+      **  * Begin popping the stack until we enter a state where
+      **    it is legal to shift the error symbol, then shift
+      **    the error symbol.
+      **
+      **  * Set the error count to three.
+      **
+      **  * Begin accepting and shifting new tokens.  No new error
+      **    processing will occur until three tokens have been
+      **    shifted successfully.
+      **
+      */
+      if( yypParser->yyerrcnt<0 ){
+        yy_syntax_error(yypParser,yymajor,yyminorunion);
+      }
+      yymx = yypParser->yystack[yypParser->yyidx].major;
+      if( yymx==YYERRORSYMBOL || yyerrorhit ){
+#ifndef NDEBUG
+        if( yyTraceFILE ){
+          fprintf(yyTraceFILE,"%sDiscard input token %s\n",
+             yyTracePrompt,yyTokenName[yymajor]);
+        }
+#endif
+        yy_destructor(yypParser, (YYCODETYPE)yymajor,&yyminorunion);
+        yymajor = YYNOCODE;
+      }else{
+         while(
+          yypParser->yyidx >= 0 &&
+          yymx != YYERRORSYMBOL &&
+          (yyact = yy_find_reduce_action(
+                        yypParser->yystack[yypParser->yyidx].stateno,
+                        YYERRORSYMBOL)) >= YYNSTATE
+        ){
+          yy_pop_parser_stack(yypParser);
+        }
+        if( yypParser->yyidx < 0 || yymajor==0 ){
+          yy_destructor(yypParser,(YYCODETYPE)yymajor,&yyminorunion);
+          yy_parse_failed(yypParser);
+          yymajor = YYNOCODE;
+        }else if( yymx!=YYERRORSYMBOL ){
+          YYMINORTYPE u2;
+          u2.YYERRSYMDT = 0;
+          yy_shift(yypParser,yyact,YYERRORSYMBOL,&u2);
+        }
+      }
+      yypParser->yyerrcnt = 3;
+      yyerrorhit = 1;
+#elif defined(YYNOERRORRECOVERY)
+      /* If the YYNOERRORRECOVERY macro is defined, then do not attempt to
+      ** do any kind of error recovery.  Instead, simply invoke the syntax
+      ** error routine and continue going as if nothing had happened.
+      **
+      ** Applications can set this macro (for example inside %include) if
+      ** they intend to abandon the parse upon the first syntax error seen.
+      */
+      yy_syntax_error(yypParser,yymajor,yyminorunion);
+      yy_destructor(yypParser,(YYCODETYPE)yymajor,&yyminorunion);
+      yymajor = YYNOCODE;
+      
+#else  /* YYERRORSYMBOL is not defined */
+      /* This is what we do if the grammar does not define ERROR:
+      **
+      **  * Report an error message, and throw away the input token.
+      **
+      **  * If the input token is $, then fail the parse.
+      **
+      ** As before, subsequent error messages are suppressed until
+      ** three input tokens have been successfully shifted.
+      */
+      if( yypParser->yyerrcnt<=0 ){
+        yy_syntax_error(yypParser,yymajor,yyminorunion);
+      }
+      yypParser->yyerrcnt = 3;
+      yy_destructor(yypParser,(YYCODETYPE)yymajor,&yyminorunion);
+      if( yyendofinput ){
+        yy_parse_failed(yypParser);
+      }
+      yymajor = YYNOCODE;
+#endif
+    }
+  }while( yymajor!=YYNOCODE && yypParser->yyidx>=0 );
+  return;
+}
diff --git a/src/loadext.c b/src/loadext.c
new file mode 100644
index 0000000..e9c97ad
--- /dev/null
+++ b/src/loadext.c
@@ -0,0 +1,657 @@
+/*
+** 2006 June 7
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains code used to dynamically load extensions into
+** the SQLite library.
+*/
+
+#ifndef SQLITE_CORE
+  #define SQLITE_CORE 1  /* Disable the API redefinition in sqlite3ext.h */
+#endif
+#include "sqlite3ext.h"
+#include "sqliteInt.h"
+#include <string.h>
+
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+
+/*
+** Some API routines are omitted when various features are
+** excluded from a build of SQLite.  Substitute a NULL pointer
+** for any missing APIs.
+*/
+#ifndef SQLITE_ENABLE_COLUMN_METADATA
+# define sqlite3_column_database_name   0
+# define sqlite3_column_database_name16 0
+# define sqlite3_column_table_name      0
+# define sqlite3_column_table_name16    0
+# define sqlite3_column_origin_name     0
+# define sqlite3_column_origin_name16   0
+# define sqlite3_table_column_metadata  0
+#endif
+
+#ifdef SQLITE_OMIT_AUTHORIZATION
+# define sqlite3_set_authorizer         0
+#endif
+
+#ifdef SQLITE_OMIT_UTF16
+# define sqlite3_bind_text16            0
+# define sqlite3_collation_needed16     0
+# define sqlite3_column_decltype16      0
+# define sqlite3_column_name16          0
+# define sqlite3_column_text16          0
+# define sqlite3_complete16             0
+# define sqlite3_create_collation16     0
+# define sqlite3_create_function16      0
+# define sqlite3_errmsg16               0
+# define sqlite3_open16                 0
+# define sqlite3_prepare16              0
+# define sqlite3_prepare16_v2           0
+# define sqlite3_result_error16         0
+# define sqlite3_result_text16          0
+# define sqlite3_result_text16be        0
+# define sqlite3_result_text16le        0
+# define sqlite3_value_text16           0
+# define sqlite3_value_text16be         0
+# define sqlite3_value_text16le         0
+# define sqlite3_column_database_name16 0
+# define sqlite3_column_table_name16    0
+# define sqlite3_column_origin_name16   0
+#endif
+
+#ifdef SQLITE_OMIT_COMPLETE
+# define sqlite3_complete 0
+# define sqlite3_complete16 0
+#endif
+
+#ifdef SQLITE_OMIT_DECLTYPE
+# define sqlite3_column_decltype16      0
+# define sqlite3_column_decltype        0
+#endif
+
+#ifdef SQLITE_OMIT_PROGRESS_CALLBACK
+# define sqlite3_progress_handler 0
+#endif
+
+#ifdef SQLITE_OMIT_VIRTUALTABLE
+# define sqlite3_create_module 0
+# define sqlite3_create_module_v2 0
+# define sqlite3_declare_vtab 0
+# define sqlite3_vtab_config 0
+# define sqlite3_vtab_on_conflict 0
+#endif
+
+#ifdef SQLITE_OMIT_SHARED_CACHE
+# define sqlite3_enable_shared_cache 0
+#endif
+
+#ifdef SQLITE_OMIT_TRACE
+# define sqlite3_profile       0
+# define sqlite3_trace         0
+#endif
+
+#ifdef SQLITE_OMIT_GET_TABLE
+# define sqlite3_free_table    0
+# define sqlite3_get_table     0
+#endif
+
+#ifdef SQLITE_OMIT_INCRBLOB
+#define sqlite3_bind_zeroblob  0
+#define sqlite3_blob_bytes     0
+#define sqlite3_blob_close     0
+#define sqlite3_blob_open      0
+#define sqlite3_blob_read      0
+#define sqlite3_blob_write     0
+#define sqlite3_blob_reopen    0
+#endif
+
+/*
+** The following structure contains pointers to all SQLite API routines.
+** A pointer to this structure is passed into extensions when they are
+** loaded so that the extension can make calls back into the SQLite
+** library.
+**
+** When adding new APIs, add them to the bottom of this structure
+** in order to preserve backwards compatibility.
+**
+** Extensions that use newer APIs should first call the
+** sqlite3_libversion_number() to make sure that the API they
+** intend to use is supported by the library.  Extensions should
+** also check to make sure that the pointer to the function is
+** not NULL before calling it.
+*/
+static const sqlite3_api_routines sqlite3Apis = {
+  sqlite3_aggregate_context,
+#ifndef SQLITE_OMIT_DEPRECATED
+  sqlite3_aggregate_count,
+#else
+  0,
+#endif
+  sqlite3_bind_blob,
+  sqlite3_bind_double,
+  sqlite3_bind_int,
+  sqlite3_bind_int64,
+  sqlite3_bind_null,
+  sqlite3_bind_parameter_count,
+  sqlite3_bind_parameter_index,
+  sqlite3_bind_parameter_name,
+  sqlite3_bind_text,
+  sqlite3_bind_text16,
+  sqlite3_bind_value,
+  sqlite3_busy_handler,
+  sqlite3_busy_timeout,
+  sqlite3_changes,
+  sqlite3_close,
+  sqlite3_collation_needed,
+  sqlite3_collation_needed16,
+  sqlite3_column_blob,
+  sqlite3_column_bytes,
+  sqlite3_column_bytes16,
+  sqlite3_column_count,
+  sqlite3_column_database_name,
+  sqlite3_column_database_name16,
+  sqlite3_column_decltype,
+  sqlite3_column_decltype16,
+  sqlite3_column_double,
+  sqlite3_column_int,
+  sqlite3_column_int64,
+  sqlite3_column_name,
+  sqlite3_column_name16,
+  sqlite3_column_origin_name,
+  sqlite3_column_origin_name16,
+  sqlite3_column_table_name,
+  sqlite3_column_table_name16,
+  sqlite3_column_text,
+  sqlite3_column_text16,
+  sqlite3_column_type,
+  sqlite3_column_value,
+  sqlite3_commit_hook,
+  sqlite3_complete,
+  sqlite3_complete16,
+  sqlite3_create_collation,
+  sqlite3_create_collation16,
+  sqlite3_create_function,
+  sqlite3_create_function16,
+  sqlite3_create_module,
+  sqlite3_data_count,
+  sqlite3_db_handle,
+  sqlite3_declare_vtab,
+  sqlite3_enable_shared_cache,
+  sqlite3_errcode,
+  sqlite3_errmsg,
+  sqlite3_errmsg16,
+  sqlite3_exec,
+#ifndef SQLITE_OMIT_DEPRECATED
+  sqlite3_expired,
+#else
+  0,
+#endif
+  sqlite3_finalize,
+  sqlite3_free,
+  sqlite3_free_table,
+  sqlite3_get_autocommit,
+  sqlite3_get_auxdata,
+  sqlite3_get_table,
+  0,     /* Was sqlite3_global_recover(), but that function is deprecated */
+  sqlite3_interrupt,
+  sqlite3_last_insert_rowid,
+  sqlite3_libversion,
+  sqlite3_libversion_number,
+  sqlite3_malloc,
+  sqlite3_mprintf,
+  sqlite3_open,
+  sqlite3_open16,
+  sqlite3_prepare,
+  sqlite3_prepare16,
+  sqlite3_profile,
+  sqlite3_progress_handler,
+  sqlite3_realloc,
+  sqlite3_reset,
+  sqlite3_result_blob,
+  sqlite3_result_double,
+  sqlite3_result_error,
+  sqlite3_result_error16,
+  sqlite3_result_int,
+  sqlite3_result_int64,
+  sqlite3_result_null,
+  sqlite3_result_text,
+  sqlite3_result_text16,
+  sqlite3_result_text16be,
+  sqlite3_result_text16le,
+  sqlite3_result_value,
+  sqlite3_rollback_hook,
+  sqlite3_set_authorizer,
+  sqlite3_set_auxdata,
+  sqlite3_snprintf,
+  sqlite3_step,
+  sqlite3_table_column_metadata,
+#ifndef SQLITE_OMIT_DEPRECATED
+  sqlite3_thread_cleanup,
+#else
+  0,
+#endif
+  sqlite3_total_changes,
+  sqlite3_trace,
+#ifndef SQLITE_OMIT_DEPRECATED
+  sqlite3_transfer_bindings,
+#else
+  0,
+#endif
+  sqlite3_update_hook,
+  sqlite3_user_data,
+  sqlite3_value_blob,
+  sqlite3_value_bytes,
+  sqlite3_value_bytes16,
+  sqlite3_value_double,
+  sqlite3_value_int,
+  sqlite3_value_int64,
+  sqlite3_value_numeric_type,
+  sqlite3_value_text,
+  sqlite3_value_text16,
+  sqlite3_value_text16be,
+  sqlite3_value_text16le,
+  sqlite3_value_type,
+  sqlite3_vmprintf,
+  /*
+  ** The original API set ends here.  All extensions can call any
+  ** of the APIs above provided that the pointer is not NULL.  But
+  ** before calling APIs that follow, extension should check the
+  ** sqlite3_libversion_number() to make sure they are dealing with
+  ** a library that is new enough to support that API.
+  *************************************************************************
+  */
+  sqlite3_overload_function,
+
+  /*
+  ** Added after 3.3.13
+  */
+  sqlite3_prepare_v2,
+  sqlite3_prepare16_v2,
+  sqlite3_clear_bindings,
+
+  /*
+  ** Added for 3.4.1
+  */
+  sqlite3_create_module_v2,
+
+  /*
+  ** Added for 3.5.0
+  */
+  sqlite3_bind_zeroblob,
+  sqlite3_blob_bytes,
+  sqlite3_blob_close,
+  sqlite3_blob_open,
+  sqlite3_blob_read,
+  sqlite3_blob_write,
+  sqlite3_create_collation_v2,
+  sqlite3_file_control,
+  sqlite3_memory_highwater,
+  sqlite3_memory_used,
+#ifdef SQLITE_MUTEX_OMIT
+  0, 
+  0, 
+  0,
+  0,
+  0,
+#else
+  sqlite3_mutex_alloc,
+  sqlite3_mutex_enter,
+  sqlite3_mutex_free,
+  sqlite3_mutex_leave,
+  sqlite3_mutex_try,
+#endif
+  sqlite3_open_v2,
+  sqlite3_release_memory,
+  sqlite3_result_error_nomem,
+  sqlite3_result_error_toobig,
+  sqlite3_sleep,
+  sqlite3_soft_heap_limit,
+  sqlite3_vfs_find,
+  sqlite3_vfs_register,
+  sqlite3_vfs_unregister,
+
+  /*
+  ** Added for 3.5.8
+  */
+  sqlite3_threadsafe,
+  sqlite3_result_zeroblob,
+  sqlite3_result_error_code,
+  sqlite3_test_control,
+  sqlite3_randomness,
+  sqlite3_context_db_handle,
+
+  /*
+  ** Added for 3.6.0
+  */
+  sqlite3_extended_result_codes,
+  sqlite3_limit,
+  sqlite3_next_stmt,
+  sqlite3_sql,
+  sqlite3_status,
+
+  /*
+  ** Added for 3.7.4
+  */
+  sqlite3_backup_finish,
+  sqlite3_backup_init,
+  sqlite3_backup_pagecount,
+  sqlite3_backup_remaining,
+  sqlite3_backup_step,
+#ifndef SQLITE_OMIT_COMPILEOPTION_DIAGS
+  sqlite3_compileoption_get,
+  sqlite3_compileoption_used,
+#else
+  0,
+  0,
+#endif
+  sqlite3_create_function_v2,
+  sqlite3_db_config,
+  sqlite3_db_mutex,
+  sqlite3_db_status,
+  sqlite3_extended_errcode,
+  sqlite3_log,
+  sqlite3_soft_heap_limit64,
+  sqlite3_sourceid,
+  sqlite3_stmt_status,
+  sqlite3_strnicmp,
+#ifdef SQLITE_ENABLE_UNLOCK_NOTIFY
+  sqlite3_unlock_notify,
+#else
+  0,
+#endif
+#ifndef SQLITE_OMIT_WAL
+  sqlite3_wal_autocheckpoint,
+  sqlite3_wal_checkpoint,
+  sqlite3_wal_hook,
+#else
+  0,
+  0,
+  0,
+#endif
+  sqlite3_blob_reopen,
+  sqlite3_vtab_config,
+  sqlite3_vtab_on_conflict,
+};
+
+/*
+** Attempt to load an SQLite extension library contained in the file
+** zFile.  The entry point is zProc.  zProc may be 0 in which case a
+** default entry point name (sqlite3_extension_init) is used.  Use
+** of the default name is recommended.
+**
+** Return SQLITE_OK on success and SQLITE_ERROR if something goes wrong.
+**
+** If an error occurs and pzErrMsg is not 0, then fill *pzErrMsg with 
+** error message text.  The calling function should free this memory
+** by calling sqlite3DbFree(db, ).
+*/
+static int sqlite3LoadExtension(
+  sqlite3 *db,          /* Load the extension into this database connection */
+  const char *zFile,    /* Name of the shared library containing extension */
+  const char *zProc,    /* Entry point.  Use "sqlite3_extension_init" if 0 */
+  char **pzErrMsg       /* Put error message here if not 0 */
+){
+  sqlite3_vfs *pVfs = db->pVfs;
+  void *handle;
+  int (*xInit)(sqlite3*,char**,const sqlite3_api_routines*);
+  char *zErrmsg = 0;
+  void **aHandle;
+  int nMsg = 300 + sqlite3Strlen30(zFile);
+
+  if( pzErrMsg ) *pzErrMsg = 0;
+
+  /* Ticket #1863.  To avoid a creating security problems for older
+  ** applications that relink against newer versions of SQLite, the
+  ** ability to run load_extension is turned off by default.  One
+  ** must call sqlite3_enable_load_extension() to turn on extension
+  ** loading.  Otherwise you get the following error.
+  */
+  if( (db->flags & SQLITE_LoadExtension)==0 ){
+    if( pzErrMsg ){
+      *pzErrMsg = sqlite3_mprintf("not authorized");
+    }
+    return SQLITE_ERROR;
+  }
+
+  if( zProc==0 ){
+    zProc = "sqlite3_extension_init";
+  }
+
+  handle = sqlite3OsDlOpen(pVfs, zFile);
+  if( handle==0 ){
+    if( pzErrMsg ){
+      *pzErrMsg = zErrmsg = sqlite3_malloc(nMsg);
+      if( zErrmsg ){
+        sqlite3_snprintf(nMsg, zErrmsg, 
+            "unable to open shared library [%s]", zFile);
+        sqlite3OsDlError(pVfs, nMsg-1, zErrmsg);
+      }
+    }
+    return SQLITE_ERROR;
+  }
+  xInit = (int(*)(sqlite3*,char**,const sqlite3_api_routines*))
+                   sqlite3OsDlSym(pVfs, handle, zProc);
+  if( xInit==0 ){
+    if( pzErrMsg ){
+      nMsg += sqlite3Strlen30(zProc);
+      *pzErrMsg = zErrmsg = sqlite3_malloc(nMsg);
+      if( zErrmsg ){
+        sqlite3_snprintf(nMsg, zErrmsg,
+            "no entry point [%s] in shared library [%s]", zProc,zFile);
+        sqlite3OsDlError(pVfs, nMsg-1, zErrmsg);
+      }
+      sqlite3OsDlClose(pVfs, handle);
+    }
+    return SQLITE_ERROR;
+  }else if( xInit(db, &zErrmsg, &sqlite3Apis) ){
+    if( pzErrMsg ){
+      *pzErrMsg = sqlite3_mprintf("error during initialization: %s", zErrmsg);
+    }
+    sqlite3_free(zErrmsg);
+    sqlite3OsDlClose(pVfs, handle);
+    return SQLITE_ERROR;
+  }
+
+  /* Append the new shared library handle to the db->aExtension array. */
+  aHandle = sqlite3DbMallocZero(db, sizeof(handle)*(db->nExtension+1));
+  if( aHandle==0 ){
+    return SQLITE_NOMEM;
+  }
+  if( db->nExtension>0 ){
+    memcpy(aHandle, db->aExtension, sizeof(handle)*db->nExtension);
+  }
+  sqlite3DbFree(db, db->aExtension);
+  db->aExtension = aHandle;
+
+  db->aExtension[db->nExtension++] = handle;
+  return SQLITE_OK;
+}
+int sqlite3_load_extension(
+  sqlite3 *db,          /* Load the extension into this database connection */
+  const char *zFile,    /* Name of the shared library containing extension */
+  const char *zProc,    /* Entry point.  Use "sqlite3_extension_init" if 0 */
+  char **pzErrMsg       /* Put error message here if not 0 */
+){
+  int rc;
+  sqlite3_mutex_enter(db->mutex);
+  rc = sqlite3LoadExtension(db, zFile, zProc, pzErrMsg);
+  rc = sqlite3ApiExit(db, rc);
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+
+/*
+** Call this routine when the database connection is closing in order
+** to clean up loaded extensions
+*/
+void sqlite3CloseExtensions(sqlite3 *db){
+  int i;
+  assert( sqlite3_mutex_held(db->mutex) );
+  for(i=0; i<db->nExtension; i++){
+    sqlite3OsDlClose(db->pVfs, db->aExtension[i]);
+  }
+  sqlite3DbFree(db, db->aExtension);
+}
+
+/*
+** Enable or disable extension loading.  Extension loading is disabled by
+** default so as not to open security holes in older applications.
+*/
+int sqlite3_enable_load_extension(sqlite3 *db, int onoff){
+  sqlite3_mutex_enter(db->mutex);
+  if( onoff ){
+    db->flags |= SQLITE_LoadExtension;
+  }else{
+    db->flags &= ~SQLITE_LoadExtension;
+  }
+  sqlite3_mutex_leave(db->mutex);
+  return SQLITE_OK;
+}
+
+#endif /* SQLITE_OMIT_LOAD_EXTENSION */
+
+/*
+** The auto-extension code added regardless of whether or not extension
+** loading is supported.  We need a dummy sqlite3Apis pointer for that
+** code if regular extension loading is not available.  This is that
+** dummy pointer.
+*/
+#ifdef SQLITE_OMIT_LOAD_EXTENSION
+static const sqlite3_api_routines sqlite3Apis = { 0 };
+#endif
+
+
+/*
+** The following object holds the list of automatically loaded
+** extensions.
+**
+** This list is shared across threads.  The SQLITE_MUTEX_STATIC_MASTER
+** mutex must be held while accessing this list.
+*/
+typedef struct sqlite3AutoExtList sqlite3AutoExtList;
+static SQLITE_WSD struct sqlite3AutoExtList {
+  int nExt;              /* Number of entries in aExt[] */          
+  void (**aExt)(void);   /* Pointers to the extension init functions */
+} sqlite3Autoext = { 0, 0 };
+
+/* The "wsdAutoext" macro will resolve to the autoextension
+** state vector.  If writable static data is unsupported on the target,
+** we have to locate the state vector at run-time.  In the more common
+** case where writable static data is supported, wsdStat can refer directly
+** to the "sqlite3Autoext" state vector declared above.
+*/
+#ifdef SQLITE_OMIT_WSD
+# define wsdAutoextInit \
+  sqlite3AutoExtList *x = &GLOBAL(sqlite3AutoExtList,sqlite3Autoext)
+# define wsdAutoext x[0]
+#else
+# define wsdAutoextInit
+# define wsdAutoext sqlite3Autoext
+#endif
+
+
+/*
+** Register a statically linked extension that is automatically
+** loaded by every new database connection.
+*/
+int sqlite3_auto_extension(void (*xInit)(void)){
+  int rc = SQLITE_OK;
+#ifndef SQLITE_OMIT_AUTOINIT
+  rc = sqlite3_initialize();
+  if( rc ){
+    return rc;
+  }else
+#endif
+  {
+    int i;
+#if SQLITE_THREADSAFE
+    sqlite3_mutex *mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER);
+#endif
+    wsdAutoextInit;
+    sqlite3_mutex_enter(mutex);
+    for(i=0; i<wsdAutoext.nExt; i++){
+      if( wsdAutoext.aExt[i]==xInit ) break;
+    }
+    if( i==wsdAutoext.nExt ){
+      int nByte = (wsdAutoext.nExt+1)*sizeof(wsdAutoext.aExt[0]);
+      void (**aNew)(void);
+      aNew = sqlite3_realloc(wsdAutoext.aExt, nByte);
+      if( aNew==0 ){
+        rc = SQLITE_NOMEM;
+      }else{
+        wsdAutoext.aExt = aNew;
+        wsdAutoext.aExt[wsdAutoext.nExt] = xInit;
+        wsdAutoext.nExt++;
+      }
+    }
+    sqlite3_mutex_leave(mutex);
+    assert( (rc&0xff)==rc );
+    return rc;
+  }
+}
+
+/*
+** Reset the automatic extension loading mechanism.
+*/
+void sqlite3_reset_auto_extension(void){
+#ifndef SQLITE_OMIT_AUTOINIT
+  if( sqlite3_initialize()==SQLITE_OK )
+#endif
+  {
+#if SQLITE_THREADSAFE
+    sqlite3_mutex *mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER);
+#endif
+    wsdAutoextInit;
+    sqlite3_mutex_enter(mutex);
+    sqlite3_free(wsdAutoext.aExt);
+    wsdAutoext.aExt = 0;
+    wsdAutoext.nExt = 0;
+    sqlite3_mutex_leave(mutex);
+  }
+}
+
+/*
+** Load all automatic extensions.
+**
+** If anything goes wrong, set an error in the database connection.
+*/
+void sqlite3AutoLoadExtensions(sqlite3 *db){
+  int i;
+  int go = 1;
+  int (*xInit)(sqlite3*,char**,const sqlite3_api_routines*);
+
+  wsdAutoextInit;
+  if( wsdAutoext.nExt==0 ){
+    /* Common case: early out without every having to acquire a mutex */
+    return;
+  }
+  for(i=0; go; i++){
+    char *zErrmsg;
+#if SQLITE_THREADSAFE
+    sqlite3_mutex *mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER);
+#endif
+    sqlite3_mutex_enter(mutex);
+    if( i>=wsdAutoext.nExt ){
+      xInit = 0;
+      go = 0;
+    }else{
+      xInit = (int(*)(sqlite3*,char**,const sqlite3_api_routines*))
+              wsdAutoext.aExt[i];
+    }
+    sqlite3_mutex_leave(mutex);
+    zErrmsg = 0;
+    if( xInit && xInit(db, &zErrmsg, &sqlite3Apis) ){
+      sqlite3Error(db, SQLITE_ERROR,
+            "automatic extension loading failed: %s", zErrmsg);
+      go = 0;
+    }
+    sqlite3_free(zErrmsg);
+  }
+}
diff --git a/src/main.c b/src/main.c
new file mode 100644
index 0000000..42bbba5
--- /dev/null
+++ b/src/main.c
@@ -0,0 +1,2954 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Main file for the SQLite library.  The routines in this file
+** implement the programmer interface to the library.  Routines in
+** other files are for internal use by SQLite and should not be
+** accessed by users of the library.
+*/
+#include "sqliteInt.h"
+
+#ifdef SQLITE_ENABLE_FTS3
+# include "fts3.h"
+#endif
+#ifdef SQLITE_ENABLE_RTREE
+# include "rtree.h"
+#endif
+#ifdef SQLITE_ENABLE_ICU
+# include "sqliteicu.h"
+#endif
+
+#ifndef SQLITE_AMALGAMATION
+/* IMPLEMENTATION-OF: R-46656-45156 The sqlite3_version[] string constant
+** contains the text of SQLITE_VERSION macro. 
+*/
+const char sqlite3_version[] = SQLITE_VERSION;
+#endif
+
+/* IMPLEMENTATION-OF: R-53536-42575 The sqlite3_libversion() function returns
+** a pointer to the to the sqlite3_version[] string constant. 
+*/
+const char *sqlite3_libversion(void){ return sqlite3_version; }
+
+/* IMPLEMENTATION-OF: R-63124-39300 The sqlite3_sourceid() function returns a
+** pointer to a string constant whose value is the same as the
+** SQLITE_SOURCE_ID C preprocessor macro. 
+*/
+const char *sqlite3_sourceid(void){ return SQLITE_SOURCE_ID; }
+
+/* IMPLEMENTATION-OF: R-35210-63508 The sqlite3_libversion_number() function
+** returns an integer equal to SQLITE_VERSION_NUMBER.
+*/
+int sqlite3_libversion_number(void){ return SQLITE_VERSION_NUMBER; }
+
+/* IMPLEMENTATION-OF: R-54823-41343 The sqlite3_threadsafe() function returns
+** zero if and only if SQLite was compiled mutexing code omitted due to
+** the SQLITE_THREADSAFE compile-time option being set to 0.
+*/
+int sqlite3_threadsafe(void){ return SQLITE_THREADSAFE; }
+
+#if !defined(SQLITE_OMIT_TRACE) && defined(SQLITE_ENABLE_IOTRACE)
+/*
+** If the following function pointer is not NULL and if
+** SQLITE_ENABLE_IOTRACE is enabled, then messages describing
+** I/O active are written using this function.  These messages
+** are intended for debugging activity only.
+*/
+void (*sqlite3IoTrace)(const char*, ...) = 0;
+#endif
+
+/*
+** If the following global variable points to a string which is the
+** name of a directory, then that directory will be used to store
+** temporary files.
+**
+** See also the "PRAGMA temp_store_directory" SQL command.
+*/
+char *sqlite3_temp_directory = 0;
+
+/*
+** Initialize SQLite.  
+**
+** This routine must be called to initialize the memory allocation,
+** VFS, and mutex subsystems prior to doing any serious work with
+** SQLite.  But as long as you do not compile with SQLITE_OMIT_AUTOINIT
+** this routine will be called automatically by key routines such as
+** sqlite3_open().  
+**
+** This routine is a no-op except on its very first call for the process,
+** or for the first call after a call to sqlite3_shutdown.
+**
+** The first thread to call this routine runs the initialization to
+** completion.  If subsequent threads call this routine before the first
+** thread has finished the initialization process, then the subsequent
+** threads must block until the first thread finishes with the initialization.
+**
+** The first thread might call this routine recursively.  Recursive
+** calls to this routine should not block, of course.  Otherwise the
+** initialization process would never complete.
+**
+** Let X be the first thread to enter this routine.  Let Y be some other
+** thread.  Then while the initial invocation of this routine by X is
+** incomplete, it is required that:
+**
+**    *  Calls to this routine from Y must block until the outer-most
+**       call by X completes.
+**
+**    *  Recursive calls to this routine from thread X return immediately
+**       without blocking.
+*/
+int sqlite3_initialize(void){
+  MUTEX_LOGIC( sqlite3_mutex *pMaster; )       /* The main static mutex */
+  int rc;                                      /* Result code */
+
+#ifdef SQLITE_OMIT_WSD
+  rc = sqlite3_wsd_init(4096, 24);
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+#endif
+
+  /* If SQLite is already completely initialized, then this call
+  ** to sqlite3_initialize() should be a no-op.  But the initialization
+  ** must be complete.  So isInit must not be set until the very end
+  ** of this routine.
+  */
+  if( sqlite3GlobalConfig.isInit ) return SQLITE_OK;
+
+  /* Make sure the mutex subsystem is initialized.  If unable to 
+  ** initialize the mutex subsystem, return early with the error.
+  ** If the system is so sick that we are unable to allocate a mutex,
+  ** there is not much SQLite is going to be able to do.
+  **
+  ** The mutex subsystem must take care of serializing its own
+  ** initialization.
+  */
+  rc = sqlite3MutexInit();
+  if( rc ) return rc;
+
+  /* Initialize the malloc() system and the recursive pInitMutex mutex.
+  ** This operation is protected by the STATIC_MASTER mutex.  Note that
+  ** MutexAlloc() is called for a static mutex prior to initializing the
+  ** malloc subsystem - this implies that the allocation of a static
+  ** mutex must not require support from the malloc subsystem.
+  */
+  MUTEX_LOGIC( pMaster = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER); )
+  sqlite3_mutex_enter(pMaster);
+  sqlite3GlobalConfig.isMutexInit = 1;
+  if( !sqlite3GlobalConfig.isMallocInit ){
+    rc = sqlite3MallocInit();
+  }
+  if( rc==SQLITE_OK ){
+    sqlite3GlobalConfig.isMallocInit = 1;
+    if( !sqlite3GlobalConfig.pInitMutex ){
+      sqlite3GlobalConfig.pInitMutex =
+           sqlite3MutexAlloc(SQLITE_MUTEX_RECURSIVE);
+      if( sqlite3GlobalConfig.bCoreMutex && !sqlite3GlobalConfig.pInitMutex ){
+        rc = SQLITE_NOMEM;
+      }
+    }
+  }
+  if( rc==SQLITE_OK ){
+    sqlite3GlobalConfig.nRefInitMutex++;
+  }
+  sqlite3_mutex_leave(pMaster);
+
+  /* If rc is not SQLITE_OK at this point, then either the malloc
+  ** subsystem could not be initialized or the system failed to allocate
+  ** the pInitMutex mutex. Return an error in either case.  */
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+
+  /* Do the rest of the initialization under the recursive mutex so
+  ** that we will be able to handle recursive calls into
+  ** sqlite3_initialize().  The recursive calls normally come through
+  ** sqlite3_os_init() when it invokes sqlite3_vfs_register(), but other
+  ** recursive calls might also be possible.
+  **
+  ** IMPLEMENTATION-OF: R-00140-37445 SQLite automatically serializes calls
+  ** to the xInit method, so the xInit method need not be threadsafe.
+  **
+  ** The following mutex is what serializes access to the appdef pcache xInit
+  ** methods.  The sqlite3_pcache_methods.xInit() all is embedded in the
+  ** call to sqlite3PcacheInitialize().
+  */
+  sqlite3_mutex_enter(sqlite3GlobalConfig.pInitMutex);
+  if( sqlite3GlobalConfig.isInit==0 && sqlite3GlobalConfig.inProgress==0 ){
+    FuncDefHash *pHash = &GLOBAL(FuncDefHash, sqlite3GlobalFunctions);
+    sqlite3GlobalConfig.inProgress = 1;
+    memset(pHash, 0, sizeof(sqlite3GlobalFunctions));
+    sqlite3RegisterGlobalFunctions();
+    if( sqlite3GlobalConfig.isPCacheInit==0 ){
+      rc = sqlite3PcacheInitialize();
+    }
+    if( rc==SQLITE_OK ){
+      sqlite3GlobalConfig.isPCacheInit = 1;
+      rc = sqlite3OsInit();
+    }
+    if( rc==SQLITE_OK ){
+      sqlite3PCacheBufferSetup( sqlite3GlobalConfig.pPage, 
+          sqlite3GlobalConfig.szPage, sqlite3GlobalConfig.nPage);
+      sqlite3GlobalConfig.isInit = 1;
+    }
+    sqlite3GlobalConfig.inProgress = 0;
+  }
+  sqlite3_mutex_leave(sqlite3GlobalConfig.pInitMutex);
+
+  /* Go back under the static mutex and clean up the recursive
+  ** mutex to prevent a resource leak.
+  */
+  sqlite3_mutex_enter(pMaster);
+  sqlite3GlobalConfig.nRefInitMutex--;
+  if( sqlite3GlobalConfig.nRefInitMutex<=0 ){
+    assert( sqlite3GlobalConfig.nRefInitMutex==0 );
+    sqlite3_mutex_free(sqlite3GlobalConfig.pInitMutex);
+    sqlite3GlobalConfig.pInitMutex = 0;
+  }
+  sqlite3_mutex_leave(pMaster);
+
+  /* The following is just a sanity check to make sure SQLite has
+  ** been compiled correctly.  It is important to run this code, but
+  ** we don't want to run it too often and soak up CPU cycles for no
+  ** reason.  So we run it once during initialization.
+  */
+#ifndef NDEBUG
+#ifndef SQLITE_OMIT_FLOATING_POINT
+  /* This section of code's only "output" is via assert() statements. */
+  if ( rc==SQLITE_OK ){
+    u64 x = (((u64)1)<<63)-1;
+    double y;
+    assert(sizeof(x)==8);
+    assert(sizeof(x)==sizeof(y));
+    memcpy(&y, &x, 8);
+    assert( sqlite3IsNaN(y) );
+  }
+#endif
+#endif
+
+  /* Do extra initialization steps requested by the SQLITE_EXTRA_INIT
+  ** compile-time option.
+  */
+#ifdef SQLITE_EXTRA_INIT
+  if( rc==SQLITE_OK && sqlite3GlobalConfig.isInit ){
+    int SQLITE_EXTRA_INIT(void);
+    rc = SQLITE_EXTRA_INIT();
+  }
+#endif
+
+  return rc;
+}
+
+/*
+** Undo the effects of sqlite3_initialize().  Must not be called while
+** there are outstanding database connections or memory allocations or
+** while any part of SQLite is otherwise in use in any thread.  This
+** routine is not threadsafe.  But it is safe to invoke this routine
+** on when SQLite is already shut down.  If SQLite is already shut down
+** when this routine is invoked, then this routine is a harmless no-op.
+*/
+int sqlite3_shutdown(void){
+  if( sqlite3GlobalConfig.isInit ){
+    sqlite3_os_end();
+    sqlite3_reset_auto_extension();
+    sqlite3GlobalConfig.isInit = 0;
+  }
+  if( sqlite3GlobalConfig.isPCacheInit ){
+    sqlite3PcacheShutdown();
+    sqlite3GlobalConfig.isPCacheInit = 0;
+  }
+  if( sqlite3GlobalConfig.isMallocInit ){
+    sqlite3MallocEnd();
+    sqlite3GlobalConfig.isMallocInit = 0;
+  }
+  if( sqlite3GlobalConfig.isMutexInit ){
+    sqlite3MutexEnd();
+    sqlite3GlobalConfig.isMutexInit = 0;
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** This API allows applications to modify the global configuration of
+** the SQLite library at run-time.
+**
+** This routine should only be called when there are no outstanding
+** database connections or memory allocations.  This routine is not
+** threadsafe.  Failure to heed these warnings can lead to unpredictable
+** behavior.
+*/
+int sqlite3_config(int op, ...){
+  va_list ap;
+  int rc = SQLITE_OK;
+
+  /* sqlite3_config() shall return SQLITE_MISUSE if it is invoked while
+  ** the SQLite library is in use. */
+  if( sqlite3GlobalConfig.isInit ) return SQLITE_MISUSE_BKPT;
+
+  va_start(ap, op);
+  switch( op ){
+
+    /* Mutex configuration options are only available in a threadsafe
+    ** compile. 
+    */
+#if defined(SQLITE_THREADSAFE) && SQLITE_THREADSAFE>0
+    case SQLITE_CONFIG_SINGLETHREAD: {
+      /* Disable all mutexing */
+      sqlite3GlobalConfig.bCoreMutex = 0;
+      sqlite3GlobalConfig.bFullMutex = 0;
+      break;
+    }
+    case SQLITE_CONFIG_MULTITHREAD: {
+      /* Disable mutexing of database connections */
+      /* Enable mutexing of core data structures */
+      sqlite3GlobalConfig.bCoreMutex = 1;
+      sqlite3GlobalConfig.bFullMutex = 0;
+      break;
+    }
+    case SQLITE_CONFIG_SERIALIZED: {
+      /* Enable all mutexing */
+      sqlite3GlobalConfig.bCoreMutex = 1;
+      sqlite3GlobalConfig.bFullMutex = 1;
+      break;
+    }
+    case SQLITE_CONFIG_MUTEX: {
+      /* Specify an alternative mutex implementation */
+      sqlite3GlobalConfig.mutex = *va_arg(ap, sqlite3_mutex_methods*);
+      break;
+    }
+    case SQLITE_CONFIG_GETMUTEX: {
+      /* Retrieve the current mutex implementation */
+      *va_arg(ap, sqlite3_mutex_methods*) = sqlite3GlobalConfig.mutex;
+      break;
+    }
+#endif
+
+
+    case SQLITE_CONFIG_MALLOC: {
+      /* Specify an alternative malloc implementation */
+      sqlite3GlobalConfig.m = *va_arg(ap, sqlite3_mem_methods*);
+      break;
+    }
+    case SQLITE_CONFIG_GETMALLOC: {
+      /* Retrieve the current malloc() implementation */
+      if( sqlite3GlobalConfig.m.xMalloc==0 ) sqlite3MemSetDefault();
+      *va_arg(ap, sqlite3_mem_methods*) = sqlite3GlobalConfig.m;
+      break;
+    }
+    case SQLITE_CONFIG_MEMSTATUS: {
+      /* Enable or disable the malloc status collection */
+      sqlite3GlobalConfig.bMemstat = va_arg(ap, int);
+      break;
+    }
+    case SQLITE_CONFIG_SCRATCH: {
+      /* Designate a buffer for scratch memory space */
+      sqlite3GlobalConfig.pScratch = va_arg(ap, void*);
+      sqlite3GlobalConfig.szScratch = va_arg(ap, int);
+      sqlite3GlobalConfig.nScratch = va_arg(ap, int);
+      break;
+    }
+    case SQLITE_CONFIG_PAGECACHE: {
+      /* Designate a buffer for page cache memory space */
+      sqlite3GlobalConfig.pPage = va_arg(ap, void*);
+      sqlite3GlobalConfig.szPage = va_arg(ap, int);
+      sqlite3GlobalConfig.nPage = va_arg(ap, int);
+      break;
+    }
+
+    case SQLITE_CONFIG_PCACHE: {
+      /* Specify an alternative page cache implementation */
+      sqlite3GlobalConfig.pcache = *va_arg(ap, sqlite3_pcache_methods*);
+      break;
+    }
+
+    case SQLITE_CONFIG_GETPCACHE: {
+      if( sqlite3GlobalConfig.pcache.xInit==0 ){
+        sqlite3PCacheSetDefault();
+      }
+      *va_arg(ap, sqlite3_pcache_methods*) = sqlite3GlobalConfig.pcache;
+      break;
+    }
+
+#if defined(SQLITE_ENABLE_MEMSYS3) || defined(SQLITE_ENABLE_MEMSYS5)
+    case SQLITE_CONFIG_HEAP: {
+      /* Designate a buffer for heap memory space */
+      sqlite3GlobalConfig.pHeap = va_arg(ap, void*);
+      sqlite3GlobalConfig.nHeap = va_arg(ap, int);
+      sqlite3GlobalConfig.mnReq = va_arg(ap, int);
+
+      if( sqlite3GlobalConfig.mnReq<1 ){
+        sqlite3GlobalConfig.mnReq = 1;
+      }else if( sqlite3GlobalConfig.mnReq>(1<<12) ){
+        /* cap min request size at 2^12 */
+        sqlite3GlobalConfig.mnReq = (1<<12);
+      }
+
+      if( sqlite3GlobalConfig.pHeap==0 ){
+        /* If the heap pointer is NULL, then restore the malloc implementation
+        ** back to NULL pointers too.  This will cause the malloc to go
+        ** back to its default implementation when sqlite3_initialize() is
+        ** run.
+        */
+        memset(&sqlite3GlobalConfig.m, 0, sizeof(sqlite3GlobalConfig.m));
+      }else{
+        /* The heap pointer is not NULL, then install one of the
+        ** mem5.c/mem3.c methods. If neither ENABLE_MEMSYS3 nor
+        ** ENABLE_MEMSYS5 is defined, return an error.
+        */
+#ifdef SQLITE_ENABLE_MEMSYS3
+        sqlite3GlobalConfig.m = *sqlite3MemGetMemsys3();
+#endif
+#ifdef SQLITE_ENABLE_MEMSYS5
+        sqlite3GlobalConfig.m = *sqlite3MemGetMemsys5();
+#endif
+      }
+      break;
+    }
+#endif
+
+    case SQLITE_CONFIG_LOOKASIDE: {
+      sqlite3GlobalConfig.szLookaside = va_arg(ap, int);
+      sqlite3GlobalConfig.nLookaside = va_arg(ap, int);
+      break;
+    }
+    
+    /* Record a pointer to the logger funcction and its first argument.
+    ** The default is NULL.  Logging is disabled if the function pointer is
+    ** NULL.
+    */
+    case SQLITE_CONFIG_LOG: {
+      /* MSVC is picky about pulling func ptrs from va lists.
+      ** http://support.microsoft.com/kb/47961
+      ** sqlite3GlobalConfig.xLog = va_arg(ap, void(*)(void*,int,const char*));
+      */
+      typedef void(*LOGFUNC_t)(void*,int,const char*);
+      sqlite3GlobalConfig.xLog = va_arg(ap, LOGFUNC_t);
+      sqlite3GlobalConfig.pLogArg = va_arg(ap, void*);
+      break;
+    }
+
+    case SQLITE_CONFIG_URI: {
+      sqlite3GlobalConfig.bOpenUri = va_arg(ap, int);
+      break;
+    }
+
+    default: {
+      rc = SQLITE_ERROR;
+      break;
+    }
+  }
+  va_end(ap);
+  return rc;
+}
+
+/*
+** Set up the lookaside buffers for a database connection.
+** Return SQLITE_OK on success.  
+** If lookaside is already active, return SQLITE_BUSY.
+**
+** The sz parameter is the number of bytes in each lookaside slot.
+** The cnt parameter is the number of slots.  If pStart is NULL the
+** space for the lookaside memory is obtained from sqlite3_malloc().
+** If pStart is not NULL then it is sz*cnt bytes of memory to use for
+** the lookaside memory.
+*/
+static int setupLookaside(sqlite3 *db, void *pBuf, int sz, int cnt){
+  void *pStart;
+  if( db->lookaside.nOut ){
+    return SQLITE_BUSY;
+  }
+  /* Free any existing lookaside buffer for this handle before
+  ** allocating a new one so we don't have to have space for 
+  ** both at the same time.
+  */
+  if( db->lookaside.bMalloced ){
+    sqlite3_free(db->lookaside.pStart);
+  }
+  /* The size of a lookaside slot needs to be larger than a pointer
+  ** to be useful.
+  */
+  if( sz<=(int)sizeof(LookasideSlot*) ) sz = 0;
+  if( cnt<0 ) cnt = 0;
+  if( sz==0 || cnt==0 ){
+    sz = 0;
+    pStart = 0;
+  }else if( pBuf==0 ){
+    sz = ROUNDDOWN8(sz); /* IMP: R-33038-09382 */
+    sqlite3BeginBenignMalloc();
+    pStart = sqlite3Malloc( sz*cnt );  /* IMP: R-61949-35727 */
+    sqlite3EndBenignMalloc();
+  }else{
+    sz = ROUNDDOWN8(sz); /* IMP: R-33038-09382 */
+    pStart = pBuf;
+  }
+  db->lookaside.pStart = pStart;
+  db->lookaside.pFree = 0;
+  db->lookaside.sz = (u16)sz;
+  if( pStart ){
+    int i;
+    LookasideSlot *p;
+    assert( sz > (int)sizeof(LookasideSlot*) );
+    p = (LookasideSlot*)pStart;
+    for(i=cnt-1; i>=0; i--){
+      p->pNext = db->lookaside.pFree;
+      db->lookaside.pFree = p;
+      p = (LookasideSlot*)&((u8*)p)[sz];
+    }
+    db->lookaside.pEnd = p;
+    db->lookaside.bEnabled = 1;
+    db->lookaside.bMalloced = pBuf==0 ?1:0;
+  }else{
+    db->lookaside.pEnd = 0;
+    db->lookaside.bEnabled = 0;
+    db->lookaside.bMalloced = 0;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Return the mutex associated with a database connection.
+*/
+sqlite3_mutex *sqlite3_db_mutex(sqlite3 *db){
+  return db->mutex;
+}
+
+/*
+** Configuration settings for an individual database connection
+*/
+int sqlite3_db_config(sqlite3 *db, int op, ...){
+  va_list ap;
+  int rc;
+  va_start(ap, op);
+  switch( op ){
+    case SQLITE_DBCONFIG_LOOKASIDE: {
+      void *pBuf = va_arg(ap, void*); /* IMP: R-26835-10964 */
+      int sz = va_arg(ap, int);       /* IMP: R-47871-25994 */
+      int cnt = va_arg(ap, int);      /* IMP: R-04460-53386 */
+      rc = setupLookaside(db, pBuf, sz, cnt);
+      break;
+    }
+    default: {
+      static const struct {
+        int op;      /* The opcode */
+        u32 mask;    /* Mask of the bit in sqlite3.flags to set/clear */
+      } aFlagOp[] = {
+        { SQLITE_DBCONFIG_ENABLE_FKEY,    SQLITE_ForeignKeys    },
+        { SQLITE_DBCONFIG_ENABLE_TRIGGER, SQLITE_EnableTrigger  },
+      };
+      unsigned int i;
+      rc = SQLITE_ERROR; /* IMP: R-42790-23372 */
+      for(i=0; i<ArraySize(aFlagOp); i++){
+        if( aFlagOp[i].op==op ){
+          int onoff = va_arg(ap, int);
+          int *pRes = va_arg(ap, int*);
+          int oldFlags = db->flags;
+          if( onoff>0 ){
+            db->flags |= aFlagOp[i].mask;
+          }else if( onoff==0 ){
+            db->flags &= ~aFlagOp[i].mask;
+          }
+          if( oldFlags!=db->flags ){
+            sqlite3ExpirePreparedStatements(db);
+          }
+          if( pRes ){
+            *pRes = (db->flags & aFlagOp[i].mask)!=0;
+          }
+          rc = SQLITE_OK;
+          break;
+        }
+      }
+      break;
+    }
+  }
+  va_end(ap);
+  return rc;
+}
+
+
+/*
+** Return true if the buffer z[0..n-1] contains all spaces.
+*/
+static int allSpaces(const char *z, int n){
+  while( n>0 && z[n-1]==' ' ){ n--; }
+  return n==0;
+}
+
+/*
+** This is the default collating function named "BINARY" which is always
+** available.
+**
+** If the padFlag argument is not NULL then space padding at the end
+** of strings is ignored.  This implements the RTRIM collation.
+*/
+static int binCollFunc(
+  void *padFlag,
+  int nKey1, const void *pKey1,
+  int nKey2, const void *pKey2
+){
+  int rc, n;
+  n = nKey1<nKey2 ? nKey1 : nKey2;
+  rc = memcmp(pKey1, pKey2, n);
+  if( rc==0 ){
+    if( padFlag
+     && allSpaces(((char*)pKey1)+n, nKey1-n)
+     && allSpaces(((char*)pKey2)+n, nKey2-n)
+    ){
+      /* Leave rc unchanged at 0 */
+    }else{
+      rc = nKey1 - nKey2;
+    }
+  }
+  return rc;
+}
+
+/*
+** Another built-in collating sequence: NOCASE. 
+**
+** This collating sequence is intended to be used for "case independant
+** comparison". SQLite's knowledge of upper and lower case equivalents
+** extends only to the 26 characters used in the English language.
+**
+** At the moment there is only a UTF-8 implementation.
+*/
+static int nocaseCollatingFunc(
+  void *NotUsed,
+  int nKey1, const void *pKey1,
+  int nKey2, const void *pKey2
+){
+  int r = sqlite3StrNICmp(
+      (const char *)pKey1, (const char *)pKey2, (nKey1<nKey2)?nKey1:nKey2);
+  UNUSED_PARAMETER(NotUsed);
+  if( 0==r ){
+    r = nKey1-nKey2;
+  }
+  return r;
+}
+
+/*
+** Return the ROWID of the most recent insert
+*/
+sqlite_int64 sqlite3_last_insert_rowid(sqlite3 *db){
+  return db->lastRowid;
+}
+
+/*
+** Return the number of changes in the most recent call to sqlite3_exec().
+*/
+int sqlite3_changes(sqlite3 *db){
+  return db->nChange;
+}
+
+/*
+** Return the number of changes since the database handle was opened.
+*/
+int sqlite3_total_changes(sqlite3 *db){
+  return db->nTotalChange;
+}
+
+/*
+** Close all open savepoints. This function only manipulates fields of the
+** database handle object, it does not close any savepoints that may be open
+** at the b-tree/pager level.
+*/
+void sqlite3CloseSavepoints(sqlite3 *db){
+  while( db->pSavepoint ){
+    Savepoint *pTmp = db->pSavepoint;
+    db->pSavepoint = pTmp->pNext;
+    sqlite3DbFree(db, pTmp);
+  }
+  db->nSavepoint = 0;
+  db->nStatement = 0;
+  db->isTransactionSavepoint = 0;
+}
+
+/*
+** Invoke the destructor function associated with FuncDef p, if any. Except,
+** if this is not the last copy of the function, do not invoke it. Multiple
+** copies of a single function are created when create_function() is called
+** with SQLITE_ANY as the encoding.
+*/
+static void functionDestroy(sqlite3 *db, FuncDef *p){
+  FuncDestructor *pDestructor = p->pDestructor;
+  if( pDestructor ){
+    pDestructor->nRef--;
+    if( pDestructor->nRef==0 ){
+      pDestructor->xDestroy(pDestructor->pUserData);
+      sqlite3DbFree(db, pDestructor);
+    }
+  }
+}
+
+/*
+** Close an existing SQLite database
+*/
+int sqlite3_close(sqlite3 *db){
+  HashElem *i;                    /* Hash table iterator */
+  int j;
+
+  if( !db ){
+    return SQLITE_OK;
+  }
+  if( !sqlite3SafetyCheckSickOrOk(db) ){
+    return SQLITE_MISUSE_BKPT;
+  }
+  sqlite3_mutex_enter(db->mutex);
+
+  /* Force xDestroy calls on all virtual tables */
+  sqlite3ResetInternalSchema(db, -1);
+
+  /* If a transaction is open, the ResetInternalSchema() call above
+  ** will not have called the xDisconnect() method on any virtual
+  ** tables in the db->aVTrans[] array. The following sqlite3VtabRollback()
+  ** call will do so. We need to do this before the check for active
+  ** SQL statements below, as the v-table implementation may be storing
+  ** some prepared statements internally.
+  */
+  sqlite3VtabRollback(db);
+
+  /* If there are any outstanding VMs, return SQLITE_BUSY. */
+  if( db->pVdbe ){
+    sqlite3Error(db, SQLITE_BUSY, 
+        "unable to close due to unfinalised statements");
+    sqlite3_mutex_leave(db->mutex);
+    return SQLITE_BUSY;
+  }
+  assert( sqlite3SafetyCheckSickOrOk(db) );
+
+  for(j=0; j<db->nDb; j++){
+    Btree *pBt = db->aDb[j].pBt;
+    if( pBt && sqlite3BtreeIsInBackup(pBt) ){
+      sqlite3Error(db, SQLITE_BUSY, 
+          "unable to close due to unfinished backup operation");
+      sqlite3_mutex_leave(db->mutex);
+      return SQLITE_BUSY;
+    }
+  }
+
+  /* Free any outstanding Savepoint structures. */
+  sqlite3CloseSavepoints(db);
+
+  for(j=0; j<db->nDb; j++){
+    struct Db *pDb = &db->aDb[j];
+    if( pDb->pBt ){
+      sqlite3BtreeClose(pDb->pBt);
+      pDb->pBt = 0;
+      if( j!=1 ){
+        pDb->pSchema = 0;
+      }
+    }
+  }
+  sqlite3ResetInternalSchema(db, -1);
+
+  /* Tell the code in notify.c that the connection no longer holds any
+  ** locks and does not require any further unlock-notify callbacks.
+  */
+  sqlite3ConnectionClosed(db);
+
+  assert( db->nDb<=2 );
+  assert( db->aDb==db->aDbStatic );
+  for(j=0; j<ArraySize(db->aFunc.a); j++){
+    FuncDef *pNext, *pHash, *p;
+    for(p=db->aFunc.a[j]; p; p=pHash){
+      pHash = p->pHash;
+      while( p ){
+        functionDestroy(db, p);
+        pNext = p->pNext;
+        sqlite3DbFree(db, p);
+        p = pNext;
+      }
+    }
+  }
+  for(i=sqliteHashFirst(&db->aCollSeq); i; i=sqliteHashNext(i)){
+    CollSeq *pColl = (CollSeq *)sqliteHashData(i);
+    /* Invoke any destructors registered for collation sequence user data. */
+    for(j=0; j<3; j++){
+      if( pColl[j].xDel ){
+        pColl[j].xDel(pColl[j].pUser);
+      }
+    }
+    sqlite3DbFree(db, pColl);
+  }
+  sqlite3HashClear(&db->aCollSeq);
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  for(i=sqliteHashFirst(&db->aModule); i; i=sqliteHashNext(i)){
+    Module *pMod = (Module *)sqliteHashData(i);
+    if( pMod->xDestroy ){
+      pMod->xDestroy(pMod->pAux);
+    }
+    sqlite3DbFree(db, pMod);
+  }
+  sqlite3HashClear(&db->aModule);
+#endif
+
+  sqlite3Error(db, SQLITE_OK, 0); /* Deallocates any cached error strings. */
+  if( db->pErr ){
+    sqlite3ValueFree(db->pErr);
+  }
+  sqlite3CloseExtensions(db);
+
+  db->magic = SQLITE_MAGIC_ERROR;
+
+  /* The temp-database schema is allocated differently from the other schema
+  ** objects (using sqliteMalloc() directly, instead of sqlite3BtreeSchema()).
+  ** So it needs to be freed here. Todo: Why not roll the temp schema into
+  ** the same sqliteMalloc() as the one that allocates the database 
+  ** structure?
+  */
+  sqlite3DbFree(db, db->aDb[1].pSchema);
+  sqlite3_mutex_leave(db->mutex);
+  db->magic = SQLITE_MAGIC_CLOSED;
+  sqlite3_mutex_free(db->mutex);
+  assert( db->lookaside.nOut==0 );  /* Fails on a lookaside memory leak */
+  if( db->lookaside.bMalloced ){
+    sqlite3_free(db->lookaside.pStart);
+  }
+  sqlite3_free(db);
+  return SQLITE_OK;
+}
+
+/*
+** Rollback all database files.
+*/
+void sqlite3RollbackAll(sqlite3 *db){
+  int i;
+  int inTrans = 0;
+  assert( sqlite3_mutex_held(db->mutex) );
+  sqlite3BeginBenignMalloc();
+  for(i=0; i<db->nDb; i++){
+    if( db->aDb[i].pBt ){
+      if( sqlite3BtreeIsInTrans(db->aDb[i].pBt) ){
+        inTrans = 1;
+      }
+      sqlite3BtreeRollback(db->aDb[i].pBt);
+      db->aDb[i].inTrans = 0;
+    }
+  }
+  sqlite3VtabRollback(db);
+  sqlite3EndBenignMalloc();
+
+  if( db->flags&SQLITE_InternChanges ){
+    sqlite3ExpirePreparedStatements(db);
+    sqlite3ResetInternalSchema(db, -1);
+  }
+
+  /* Any deferred constraint violations have now been resolved. */
+  db->nDeferredCons = 0;
+
+  /* If one has been configured, invoke the rollback-hook callback */
+  if( db->xRollbackCallback && (inTrans || !db->autoCommit) ){
+    db->xRollbackCallback(db->pRollbackArg);
+  }
+}
+
+/*
+** Return a static string that describes the kind of error specified in the
+** argument.
+*/
+const char *sqlite3ErrStr(int rc){
+  static const char* const aMsg[] = {
+    /* SQLITE_OK          */ "not an error",
+    /* SQLITE_ERROR       */ "SQL logic error or missing database",
+    /* SQLITE_INTERNAL    */ 0,
+    /* SQLITE_PERM        */ "access permission denied",
+    /* SQLITE_ABORT       */ "callback requested query abort",
+    /* SQLITE_BUSY        */ "database is locked",
+    /* SQLITE_LOCKED      */ "database table is locked",
+    /* SQLITE_NOMEM       */ "out of memory",
+    /* SQLITE_READONLY    */ "attempt to write a readonly database",
+    /* SQLITE_INTERRUPT   */ "interrupted",
+    /* SQLITE_IOERR       */ "disk I/O error",
+    /* SQLITE_CORRUPT     */ "database disk image is malformed",
+    /* SQLITE_NOTFOUND    */ "unknown operation",
+    /* SQLITE_FULL        */ "database or disk is full",
+    /* SQLITE_CANTOPEN    */ "unable to open database file",
+    /* SQLITE_PROTOCOL    */ "locking protocol",
+    /* SQLITE_EMPTY       */ "table contains no data",
+    /* SQLITE_SCHEMA      */ "database schema has changed",
+    /* SQLITE_TOOBIG      */ "string or blob too big",
+    /* SQLITE_CONSTRAINT  */ "constraint failed",
+    /* SQLITE_MISMATCH    */ "datatype mismatch",
+    /* SQLITE_MISUSE      */ "library routine called out of sequence",
+    /* SQLITE_NOLFS       */ "large file support is disabled",
+    /* SQLITE_AUTH        */ "authorization denied",
+    /* SQLITE_FORMAT      */ "auxiliary database format error",
+    /* SQLITE_RANGE       */ "bind or column index out of range",
+    /* SQLITE_NOTADB      */ "file is encrypted or is not a database",
+  };
+  rc &= 0xff;
+  if( ALWAYS(rc>=0) && rc<(int)(sizeof(aMsg)/sizeof(aMsg[0])) && aMsg[rc]!=0 ){
+    return aMsg[rc];
+  }else{
+    return "unknown error";
+  }
+}
+
+/*
+** This routine implements a busy callback that sleeps and tries
+** again until a timeout value is reached.  The timeout value is
+** an integer number of milliseconds passed in as the first
+** argument.
+*/
+static int sqliteDefaultBusyCallback(
+ void *ptr,               /* Database connection */
+ int count                /* Number of times table has been busy */
+){
+#if SQLITE_OS_WIN || (defined(HAVE_USLEEP) && HAVE_USLEEP)
+  static const u8 delays[] =
+     { 1, 2, 5, 10, 15, 20, 25, 25,  25,  50,  50, 100 };
+  static const u8 totals[] =
+     { 0, 1, 3,  8, 18, 33, 53, 78, 103, 128, 178, 228 };
+# define NDELAY ArraySize(delays)
+  sqlite3 *db = (sqlite3 *)ptr;
+  int timeout = db->busyTimeout;
+  int delay, prior;
+
+  assert( count>=0 );
+  if( count < NDELAY ){
+    delay = delays[count];
+    prior = totals[count];
+  }else{
+    delay = delays[NDELAY-1];
+    prior = totals[NDELAY-1] + delay*(count-(NDELAY-1));
+  }
+  if( prior + delay > timeout ){
+    delay = timeout - prior;
+    if( delay<=0 ) return 0;
+  }
+  sqlite3OsSleep(db->pVfs, delay*1000);
+  return 1;
+#else
+  sqlite3 *db = (sqlite3 *)ptr;
+  int timeout = ((sqlite3 *)ptr)->busyTimeout;
+  if( (count+1)*1000 > timeout ){
+    return 0;
+  }
+  sqlite3OsSleep(db->pVfs, 1000000);
+  return 1;
+#endif
+}
+
+/*
+** Invoke the given busy handler.
+**
+** This routine is called when an operation failed with a lock.
+** If this routine returns non-zero, the lock is retried.  If it
+** returns 0, the operation aborts with an SQLITE_BUSY error.
+*/
+int sqlite3InvokeBusyHandler(BusyHandler *p){
+  int rc;
+  if( NEVER(p==0) || p->xFunc==0 || p->nBusy<0 ) return 0;
+  rc = p->xFunc(p->pArg, p->nBusy);
+  if( rc==0 ){
+    p->nBusy = -1;
+  }else{
+    p->nBusy++;
+  }
+  return rc; 
+}
+
+/*
+** This routine sets the busy callback for an Sqlite database to the
+** given callback function with the given argument.
+*/
+int sqlite3_busy_handler(
+  sqlite3 *db,
+  int (*xBusy)(void*,int),
+  void *pArg
+){
+  sqlite3_mutex_enter(db->mutex);
+  db->busyHandler.xFunc = xBusy;
+  db->busyHandler.pArg = pArg;
+  db->busyHandler.nBusy = 0;
+  sqlite3_mutex_leave(db->mutex);
+  return SQLITE_OK;
+}
+
+#ifndef SQLITE_OMIT_PROGRESS_CALLBACK
+/*
+** This routine sets the progress callback for an Sqlite database to the
+** given callback function with the given argument. The progress callback will
+** be invoked every nOps opcodes.
+*/
+void sqlite3_progress_handler(
+  sqlite3 *db, 
+  int nOps,
+  int (*xProgress)(void*), 
+  void *pArg
+){
+  sqlite3_mutex_enter(db->mutex);
+  if( nOps>0 ){
+    db->xProgress = xProgress;
+    db->nProgressOps = nOps;
+    db->pProgressArg = pArg;
+  }else{
+    db->xProgress = 0;
+    db->nProgressOps = 0;
+    db->pProgressArg = 0;
+  }
+  sqlite3_mutex_leave(db->mutex);
+}
+#endif
+
+
+/*
+** This routine installs a default busy handler that waits for the
+** specified number of milliseconds before returning 0.
+*/
+int sqlite3_busy_timeout(sqlite3 *db, int ms){
+  if( ms>0 ){
+    db->busyTimeout = ms;
+    sqlite3_busy_handler(db, sqliteDefaultBusyCallback, (void*)db);
+  }else{
+    sqlite3_busy_handler(db, 0, 0);
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Cause any pending operation to stop at its earliest opportunity.
+*/
+void sqlite3_interrupt(sqlite3 *db){
+  db->u1.isInterrupted = 1;
+}
+
+
+/*
+** This function is exactly the same as sqlite3_create_function(), except
+** that it is designed to be called by internal code. The difference is
+** that if a malloc() fails in sqlite3_create_function(), an error code
+** is returned and the mallocFailed flag cleared. 
+*/
+int sqlite3CreateFunc(
+  sqlite3 *db,
+  const char *zFunctionName,
+  int nArg,
+  int enc,
+  void *pUserData,
+  void (*xFunc)(sqlite3_context*,int,sqlite3_value **),
+  void (*xStep)(sqlite3_context*,int,sqlite3_value **),
+  void (*xFinal)(sqlite3_context*),
+  FuncDestructor *pDestructor
+){
+  FuncDef *p;
+  int nName;
+
+  assert( sqlite3_mutex_held(db->mutex) );
+  if( zFunctionName==0 ||
+      (xFunc && (xFinal || xStep)) || 
+      (!xFunc && (xFinal && !xStep)) ||
+      (!xFunc && (!xFinal && xStep)) ||
+      (nArg<-1 || nArg>SQLITE_MAX_FUNCTION_ARG) ||
+      (255<(nName = sqlite3Strlen30( zFunctionName))) ){
+    return SQLITE_MISUSE_BKPT;
+  }
+  
+#ifndef SQLITE_OMIT_UTF16
+  /* If SQLITE_UTF16 is specified as the encoding type, transform this
+  ** to one of SQLITE_UTF16LE or SQLITE_UTF16BE using the
+  ** SQLITE_UTF16NATIVE macro. SQLITE_UTF16 is not used internally.
+  **
+  ** If SQLITE_ANY is specified, add three versions of the function
+  ** to the hash table.
+  */
+  if( enc==SQLITE_UTF16 ){
+    enc = SQLITE_UTF16NATIVE;
+  }else if( enc==SQLITE_ANY ){
+    int rc;
+    rc = sqlite3CreateFunc(db, zFunctionName, nArg, SQLITE_UTF8,
+         pUserData, xFunc, xStep, xFinal, pDestructor);
+    if( rc==SQLITE_OK ){
+      rc = sqlite3CreateFunc(db, zFunctionName, nArg, SQLITE_UTF16LE,
+          pUserData, xFunc, xStep, xFinal, pDestructor);
+    }
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+    enc = SQLITE_UTF16BE;
+  }
+#else
+  enc = SQLITE_UTF8;
+#endif
+  
+  /* Check if an existing function is being overridden or deleted. If so,
+  ** and there are active VMs, then return SQLITE_BUSY. If a function
+  ** is being overridden/deleted but there are no active VMs, allow the
+  ** operation to continue but invalidate all precompiled statements.
+  */
+  p = sqlite3FindFunction(db, zFunctionName, nName, nArg, (u8)enc, 0);
+  if( p && p->iPrefEnc==enc && p->nArg==nArg ){
+    if( db->activeVdbeCnt ){
+      sqlite3Error(db, SQLITE_BUSY, 
+        "unable to delete/modify user-function due to active statements");
+      assert( !db->mallocFailed );
+      return SQLITE_BUSY;
+    }else{
+      sqlite3ExpirePreparedStatements(db);
+    }
+  }
+
+  p = sqlite3FindFunction(db, zFunctionName, nName, nArg, (u8)enc, 1);
+  assert(p || db->mallocFailed);
+  if( !p ){
+    return SQLITE_NOMEM;
+  }
+
+  /* If an older version of the function with a configured destructor is
+  ** being replaced invoke the destructor function here. */
+  functionDestroy(db, p);
+
+  if( pDestructor ){
+    pDestructor->nRef++;
+  }
+  p->pDestructor = pDestructor;
+  p->flags = 0;
+  p->xFunc = xFunc;
+  p->xStep = xStep;
+  p->xFinalize = xFinal;
+  p->pUserData = pUserData;
+  p->nArg = (u16)nArg;
+  return SQLITE_OK;
+}
+
+/*
+** Create new user functions.
+*/
+int sqlite3_create_function(
+  sqlite3 *db,
+  const char *zFunc,
+  int nArg,
+  int enc,
+  void *p,
+  void (*xFunc)(sqlite3_context*,int,sqlite3_value **),
+  void (*xStep)(sqlite3_context*,int,sqlite3_value **),
+  void (*xFinal)(sqlite3_context*)
+){
+  return sqlite3_create_function_v2(db, zFunc, nArg, enc, p, xFunc, xStep,
+                                    xFinal, 0);
+}
+
+int sqlite3_create_function_v2(
+  sqlite3 *db,
+  const char *zFunc,
+  int nArg,
+  int enc,
+  void *p,
+  void (*xFunc)(sqlite3_context*,int,sqlite3_value **),
+  void (*xStep)(sqlite3_context*,int,sqlite3_value **),
+  void (*xFinal)(sqlite3_context*),
+  void (*xDestroy)(void *)
+){
+  int rc = SQLITE_ERROR;
+  FuncDestructor *pArg = 0;
+  sqlite3_mutex_enter(db->mutex);
+  if( xDestroy ){
+    pArg = (FuncDestructor *)sqlite3DbMallocZero(db, sizeof(FuncDestructor));
+    if( !pArg ){
+      xDestroy(p);
+      goto out;
+    }
+    pArg->xDestroy = xDestroy;
+    pArg->pUserData = p;
+  }
+  rc = sqlite3CreateFunc(db, zFunc, nArg, enc, p, xFunc, xStep, xFinal, pArg);
+  if( pArg && pArg->nRef==0 ){
+    assert( rc!=SQLITE_OK );
+    xDestroy(p);
+    sqlite3DbFree(db, pArg);
+  }
+
+ out:
+  rc = sqlite3ApiExit(db, rc);
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+
+#ifndef SQLITE_OMIT_UTF16
+int sqlite3_create_function16(
+  sqlite3 *db,
+  const void *zFunctionName,
+  int nArg,
+  int eTextRep,
+  void *p,
+  void (*xFunc)(sqlite3_context*,int,sqlite3_value**),
+  void (*xStep)(sqlite3_context*,int,sqlite3_value**),
+  void (*xFinal)(sqlite3_context*)
+){
+  int rc;
+  char *zFunc8;
+  sqlite3_mutex_enter(db->mutex);
+  assert( !db->mallocFailed );
+  zFunc8 = sqlite3Utf16to8(db, zFunctionName, -1, SQLITE_UTF16NATIVE);
+  rc = sqlite3CreateFunc(db, zFunc8, nArg, eTextRep, p, xFunc, xStep, xFinal,0);
+  sqlite3DbFree(db, zFunc8);
+  rc = sqlite3ApiExit(db, rc);
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+#endif
+
+
+/*
+** Declare that a function has been overloaded by a virtual table.
+**
+** If the function already exists as a regular global function, then
+** this routine is a no-op.  If the function does not exist, then create
+** a new one that always throws a run-time error.  
+**
+** When virtual tables intend to provide an overloaded function, they
+** should call this routine to make sure the global function exists.
+** A global function must exist in order for name resolution to work
+** properly.
+*/
+int sqlite3_overload_function(
+  sqlite3 *db,
+  const char *zName,
+  int nArg
+){
+  int nName = sqlite3Strlen30(zName);
+  int rc = SQLITE_OK;
+  sqlite3_mutex_enter(db->mutex);
+  if( sqlite3FindFunction(db, zName, nName, nArg, SQLITE_UTF8, 0)==0 ){
+    rc = sqlite3CreateFunc(db, zName, nArg, SQLITE_UTF8,
+                           0, sqlite3InvalidFunction, 0, 0, 0);
+  }
+  rc = sqlite3ApiExit(db, rc);
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+
+#ifndef SQLITE_OMIT_TRACE
+/*
+** Register a trace function.  The pArg from the previously registered trace
+** is returned.  
+**
+** A NULL trace function means that no tracing is executes.  A non-NULL
+** trace is a pointer to a function that is invoked at the start of each
+** SQL statement.
+*/
+void *sqlite3_trace(sqlite3 *db, void (*xTrace)(void*,const char*), void *pArg){
+  void *pOld;
+  sqlite3_mutex_enter(db->mutex);
+  pOld = db->pTraceArg;
+  db->xTrace = xTrace;
+  db->pTraceArg = pArg;
+  sqlite3_mutex_leave(db->mutex);
+  return pOld;
+}
+/*
+** Register a profile function.  The pArg from the previously registered 
+** profile function is returned.  
+**
+** A NULL profile function means that no profiling is executes.  A non-NULL
+** profile is a pointer to a function that is invoked at the conclusion of
+** each SQL statement that is run.
+*/
+void *sqlite3_profile(
+  sqlite3 *db,
+  void (*xProfile)(void*,const char*,sqlite_uint64),
+  void *pArg
+){
+  void *pOld;
+  sqlite3_mutex_enter(db->mutex);
+  pOld = db->pProfileArg;
+  db->xProfile = xProfile;
+  db->pProfileArg = pArg;
+  sqlite3_mutex_leave(db->mutex);
+  return pOld;
+}
+#endif /* SQLITE_OMIT_TRACE */
+
+/*** EXPERIMENTAL ***
+**
+** Register a function to be invoked when a transaction comments.
+** If the invoked function returns non-zero, then the commit becomes a
+** rollback.
+*/
+void *sqlite3_commit_hook(
+  sqlite3 *db,              /* Attach the hook to this database */
+  int (*xCallback)(void*),  /* Function to invoke on each commit */
+  void *pArg                /* Argument to the function */
+){
+  void *pOld;
+  sqlite3_mutex_enter(db->mutex);
+  pOld = db->pCommitArg;
+  db->xCommitCallback = xCallback;
+  db->pCommitArg = pArg;
+  sqlite3_mutex_leave(db->mutex);
+  return pOld;
+}
+
+/*
+** Register a callback to be invoked each time a row is updated,
+** inserted or deleted using this database connection.
+*/
+void *sqlite3_update_hook(
+  sqlite3 *db,              /* Attach the hook to this database */
+  void (*xCallback)(void*,int,char const *,char const *,sqlite_int64),
+  void *pArg                /* Argument to the function */
+){
+  void *pRet;
+  sqlite3_mutex_enter(db->mutex);
+  pRet = db->pUpdateArg;
+  db->xUpdateCallback = xCallback;
+  db->pUpdateArg = pArg;
+  sqlite3_mutex_leave(db->mutex);
+  return pRet;
+}
+
+/*
+** Register a callback to be invoked each time a transaction is rolled
+** back by this database connection.
+*/
+void *sqlite3_rollback_hook(
+  sqlite3 *db,              /* Attach the hook to this database */
+  void (*xCallback)(void*), /* Callback function */
+  void *pArg                /* Argument to the function */
+){
+  void *pRet;
+  sqlite3_mutex_enter(db->mutex);
+  pRet = db->pRollbackArg;
+  db->xRollbackCallback = xCallback;
+  db->pRollbackArg = pArg;
+  sqlite3_mutex_leave(db->mutex);
+  return pRet;
+}
+
+#ifndef SQLITE_OMIT_WAL
+/*
+** The sqlite3_wal_hook() callback registered by sqlite3_wal_autocheckpoint().
+** Invoke sqlite3_wal_checkpoint if the number of frames in the log file
+** is greater than sqlite3.pWalArg cast to an integer (the value configured by
+** wal_autocheckpoint()).
+*/ 
+int sqlite3WalDefaultHook(
+  void *pClientData,     /* Argument */
+  sqlite3 *db,           /* Connection */
+  const char *zDb,       /* Database */
+  int nFrame             /* Size of WAL */
+){
+  if( nFrame>=SQLITE_PTR_TO_INT(pClientData) ){
+    sqlite3BeginBenignMalloc();
+    sqlite3_wal_checkpoint(db, zDb);
+    sqlite3EndBenignMalloc();
+  }
+  return SQLITE_OK;
+}
+#endif /* SQLITE_OMIT_WAL */
+
+/*
+** Configure an sqlite3_wal_hook() callback to automatically checkpoint
+** a database after committing a transaction if there are nFrame or
+** more frames in the log file. Passing zero or a negative value as the
+** nFrame parameter disables automatic checkpoints entirely.
+**
+** The callback registered by this function replaces any existing callback
+** registered using sqlite3_wal_hook(). Likewise, registering a callback
+** using sqlite3_wal_hook() disables the automatic checkpoint mechanism
+** configured by this function.
+*/
+int sqlite3_wal_autocheckpoint(sqlite3 *db, int nFrame){
+#ifdef SQLITE_OMIT_WAL
+  UNUSED_PARAMETER(db);
+  UNUSED_PARAMETER(nFrame);
+#else
+  if( nFrame>0 ){
+    sqlite3_wal_hook(db, sqlite3WalDefaultHook, SQLITE_INT_TO_PTR(nFrame));
+  }else{
+    sqlite3_wal_hook(db, 0, 0);
+  }
+#endif
+  return SQLITE_OK;
+}
+
+/*
+** Register a callback to be invoked each time a transaction is written
+** into the write-ahead-log by this database connection.
+*/
+void *sqlite3_wal_hook(
+  sqlite3 *db,                    /* Attach the hook to this db handle */
+  int(*xCallback)(void *, sqlite3*, const char*, int),
+  void *pArg                      /* First argument passed to xCallback() */
+){
+#ifndef SQLITE_OMIT_WAL
+  void *pRet;
+  sqlite3_mutex_enter(db->mutex);
+  pRet = db->pWalArg;
+  db->xWalCallback = xCallback;
+  db->pWalArg = pArg;
+  sqlite3_mutex_leave(db->mutex);
+  return pRet;
+#else
+  return 0;
+#endif
+}
+
+/*
+** Checkpoint database zDb.
+*/
+int sqlite3_wal_checkpoint_v2(
+  sqlite3 *db,                    /* Database handle */
+  const char *zDb,                /* Name of attached database (or NULL) */
+  int eMode,                      /* SQLITE_CHECKPOINT_* value */
+  int *pnLog,                     /* OUT: Size of WAL log in frames */
+  int *pnCkpt                     /* OUT: Total number of frames checkpointed */
+){
+#ifdef SQLITE_OMIT_WAL
+  return SQLITE_OK;
+#else
+  int rc;                         /* Return code */
+  int iDb = SQLITE_MAX_ATTACHED;  /* sqlite3.aDb[] index of db to checkpoint */
+
+  /* Initialize the output variables to -1 in case an error occurs. */
+  if( pnLog ) *pnLog = -1;
+  if( pnCkpt ) *pnCkpt = -1;
+
+  assert( SQLITE_CHECKPOINT_FULL>SQLITE_CHECKPOINT_PASSIVE );
+  assert( SQLITE_CHECKPOINT_FULL<SQLITE_CHECKPOINT_RESTART );
+  assert( SQLITE_CHECKPOINT_PASSIVE+2==SQLITE_CHECKPOINT_RESTART );
+  if( eMode<SQLITE_CHECKPOINT_PASSIVE || eMode>SQLITE_CHECKPOINT_RESTART ){
+    return SQLITE_MISUSE;
+  }
+
+  sqlite3_mutex_enter(db->mutex);
+  if( zDb && zDb[0] ){
+    iDb = sqlite3FindDbName(db, zDb);
+  }
+  if( iDb<0 ){
+    rc = SQLITE_ERROR;
+    sqlite3Error(db, SQLITE_ERROR, "unknown database: %s", zDb);
+  }else{
+    rc = sqlite3Checkpoint(db, iDb, eMode, pnLog, pnCkpt);
+    sqlite3Error(db, rc, 0);
+  }
+  rc = sqlite3ApiExit(db, rc);
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+#endif
+}
+
+
+/*
+** Checkpoint database zDb. If zDb is NULL, or if the buffer zDb points
+** to contains a zero-length string, all attached databases are 
+** checkpointed.
+*/
+int sqlite3_wal_checkpoint(sqlite3 *db, const char *zDb){
+  return sqlite3_wal_checkpoint_v2(db, zDb, SQLITE_CHECKPOINT_PASSIVE, 0, 0);
+}
+
+#ifndef SQLITE_OMIT_WAL
+/*
+** Run a checkpoint on database iDb. This is a no-op if database iDb is
+** not currently open in WAL mode.
+**
+** If a transaction is open on the database being checkpointed, this 
+** function returns SQLITE_LOCKED and a checkpoint is not attempted. If 
+** an error occurs while running the checkpoint, an SQLite error code is 
+** returned (i.e. SQLITE_IOERR). Otherwise, SQLITE_OK.
+**
+** The mutex on database handle db should be held by the caller. The mutex
+** associated with the specific b-tree being checkpointed is taken by
+** this function while the checkpoint is running.
+**
+** If iDb is passed SQLITE_MAX_ATTACHED, then all attached databases are
+** checkpointed. If an error is encountered it is returned immediately -
+** no attempt is made to checkpoint any remaining databases.
+**
+** Parameter eMode is one of SQLITE_CHECKPOINT_PASSIVE, FULL or RESTART.
+*/
+int sqlite3Checkpoint(sqlite3 *db, int iDb, int eMode, int *pnLog, int *pnCkpt){
+  int rc = SQLITE_OK;             /* Return code */
+  int i;                          /* Used to iterate through attached dbs */
+  int bBusy = 0;                  /* True if SQLITE_BUSY has been encountered */
+
+  assert( sqlite3_mutex_held(db->mutex) );
+  assert( !pnLog || *pnLog==-1 );
+  assert( !pnCkpt || *pnCkpt==-1 );
+
+  for(i=0; i<db->nDb && rc==SQLITE_OK; i++){
+    if( i==iDb || iDb==SQLITE_MAX_ATTACHED ){
+      rc = sqlite3BtreeCheckpoint(db->aDb[i].pBt, eMode, pnLog, pnCkpt);
+      pnLog = 0;
+      pnCkpt = 0;
+      if( rc==SQLITE_BUSY ){
+        bBusy = 1;
+        rc = SQLITE_OK;
+      }
+    }
+  }
+
+  return (rc==SQLITE_OK && bBusy) ? SQLITE_BUSY : rc;
+}
+#endif /* SQLITE_OMIT_WAL */
+
+/*
+** This function returns true if main-memory should be used instead of
+** a temporary file for transient pager files and statement journals.
+** The value returned depends on the value of db->temp_store (runtime
+** parameter) and the compile time value of SQLITE_TEMP_STORE. The
+** following table describes the relationship between these two values
+** and this functions return value.
+**
+**   SQLITE_TEMP_STORE     db->temp_store     Location of temporary database
+**   -----------------     --------------     ------------------------------
+**   0                     any                file      (return 0)
+**   1                     1                  file      (return 0)
+**   1                     2                  memory    (return 1)
+**   1                     0                  file      (return 0)
+**   2                     1                  file      (return 0)
+**   2                     2                  memory    (return 1)
+**   2                     0                  memory    (return 1)
+**   3                     any                memory    (return 1)
+*/
+int sqlite3TempInMemory(const sqlite3 *db){
+#if SQLITE_TEMP_STORE==1
+  return ( db->temp_store==2 );
+#endif
+#if SQLITE_TEMP_STORE==2
+  return ( db->temp_store!=1 );
+#endif
+#if SQLITE_TEMP_STORE==3
+  return 1;
+#endif
+#if SQLITE_TEMP_STORE<1 || SQLITE_TEMP_STORE>3
+  return 0;
+#endif
+}
+
+/*
+** Return UTF-8 encoded English language explanation of the most recent
+** error.
+*/
+const char *sqlite3_errmsg(sqlite3 *db){
+  const char *z;
+  if( !db ){
+    return sqlite3ErrStr(SQLITE_NOMEM);
+  }
+  if( !sqlite3SafetyCheckSickOrOk(db) ){
+    return sqlite3ErrStr(SQLITE_MISUSE_BKPT);
+  }
+  sqlite3_mutex_enter(db->mutex);
+  if( db->mallocFailed ){
+    z = sqlite3ErrStr(SQLITE_NOMEM);
+  }else{
+    z = (char*)sqlite3_value_text(db->pErr);
+    assert( !db->mallocFailed );
+    if( z==0 ){
+      z = sqlite3ErrStr(db->errCode);
+    }
+  }
+  sqlite3_mutex_leave(db->mutex);
+  return z;
+}
+
+#ifndef SQLITE_OMIT_UTF16
+/*
+** Return UTF-16 encoded English language explanation of the most recent
+** error.
+*/
+const void *sqlite3_errmsg16(sqlite3 *db){
+  static const u16 outOfMem[] = {
+    'o', 'u', 't', ' ', 'o', 'f', ' ', 'm', 'e', 'm', 'o', 'r', 'y', 0
+  };
+  static const u16 misuse[] = {
+    'l', 'i', 'b', 'r', 'a', 'r', 'y', ' ', 
+    'r', 'o', 'u', 't', 'i', 'n', 'e', ' ', 
+    'c', 'a', 'l', 'l', 'e', 'd', ' ', 
+    'o', 'u', 't', ' ', 
+    'o', 'f', ' ', 
+    's', 'e', 'q', 'u', 'e', 'n', 'c', 'e', 0
+  };
+
+  const void *z;
+  if( !db ){
+    return (void *)outOfMem;
+  }
+  if( !sqlite3SafetyCheckSickOrOk(db) ){
+    return (void *)misuse;
+  }
+  sqlite3_mutex_enter(db->mutex);
+  if( db->mallocFailed ){
+    z = (void *)outOfMem;
+  }else{
+    z = sqlite3_value_text16(db->pErr);
+    if( z==0 ){
+      sqlite3ValueSetStr(db->pErr, -1, sqlite3ErrStr(db->errCode),
+           SQLITE_UTF8, SQLITE_STATIC);
+      z = sqlite3_value_text16(db->pErr);
+    }
+    /* A malloc() may have failed within the call to sqlite3_value_text16()
+    ** above. If this is the case, then the db->mallocFailed flag needs to
+    ** be cleared before returning. Do this directly, instead of via
+    ** sqlite3ApiExit(), to avoid setting the database handle error message.
+    */
+    db->mallocFailed = 0;
+  }
+  sqlite3_mutex_leave(db->mutex);
+  return z;
+}
+#endif /* SQLITE_OMIT_UTF16 */
+
+/*
+** Return the most recent error code generated by an SQLite routine. If NULL is
+** passed to this function, we assume a malloc() failed during sqlite3_open().
+*/
+int sqlite3_errcode(sqlite3 *db){
+  if( db && !sqlite3SafetyCheckSickOrOk(db) ){
+    return SQLITE_MISUSE_BKPT;
+  }
+  if( !db || db->mallocFailed ){
+    return SQLITE_NOMEM;
+  }
+  return db->errCode & db->errMask;
+}
+int sqlite3_extended_errcode(sqlite3 *db){
+  if( db && !sqlite3SafetyCheckSickOrOk(db) ){
+    return SQLITE_MISUSE_BKPT;
+  }
+  if( !db || db->mallocFailed ){
+    return SQLITE_NOMEM;
+  }
+  return db->errCode;
+}
+
+/*
+** Create a new collating function for database "db".  The name is zName
+** and the encoding is enc.
+*/
+static int createCollation(
+  sqlite3* db,
+  const char *zName, 
+  u8 enc,
+  u8 collType,
+  void* pCtx,
+  int(*xCompare)(void*,int,const void*,int,const void*),
+  void(*xDel)(void*)
+){
+  CollSeq *pColl;
+  int enc2;
+  int nName = sqlite3Strlen30(zName);
+  
+  assert( sqlite3_mutex_held(db->mutex) );
+
+  /* If SQLITE_UTF16 is specified as the encoding type, transform this
+  ** to one of SQLITE_UTF16LE or SQLITE_UTF16BE using the
+  ** SQLITE_UTF16NATIVE macro. SQLITE_UTF16 is not used internally.
+  */
+  enc2 = enc;
+  testcase( enc2==SQLITE_UTF16 );
+  testcase( enc2==SQLITE_UTF16_ALIGNED );
+  if( enc2==SQLITE_UTF16 || enc2==SQLITE_UTF16_ALIGNED ){
+    enc2 = SQLITE_UTF16NATIVE;
+  }
+  if( enc2<SQLITE_UTF8 || enc2>SQLITE_UTF16BE ){
+    return SQLITE_MISUSE_BKPT;
+  }
+
+  /* Check if this call is removing or replacing an existing collation 
+  ** sequence. If so, and there are active VMs, return busy. If there
+  ** are no active VMs, invalidate any pre-compiled statements.
+  */
+  pColl = sqlite3FindCollSeq(db, (u8)enc2, zName, 0);
+  if( pColl && pColl->xCmp ){
+    if( db->activeVdbeCnt ){
+      sqlite3Error(db, SQLITE_BUSY, 
+        "unable to delete/modify collation sequence due to active statements");
+      return SQLITE_BUSY;
+    }
+    sqlite3ExpirePreparedStatements(db);
+
+    /* If collation sequence pColl was created directly by a call to
+    ** sqlite3_create_collation, and not generated by synthCollSeq(),
+    ** then any copies made by synthCollSeq() need to be invalidated.
+    ** Also, collation destructor - CollSeq.xDel() - function may need
+    ** to be called.
+    */ 
+    if( (pColl->enc & ~SQLITE_UTF16_ALIGNED)==enc2 ){
+      CollSeq *aColl = sqlite3HashFind(&db->aCollSeq, zName, nName);
+      int j;
+      for(j=0; j<3; j++){
+        CollSeq *p = &aColl[j];
+        if( p->enc==pColl->enc ){
+          if( p->xDel ){
+            p->xDel(p->pUser);
+          }
+          p->xCmp = 0;
+        }
+      }
+    }
+  }
+
+  pColl = sqlite3FindCollSeq(db, (u8)enc2, zName, 1);
+  if( pColl==0 ) return SQLITE_NOMEM;
+  pColl->xCmp = xCompare;
+  pColl->pUser = pCtx;
+  pColl->xDel = xDel;
+  pColl->enc = (u8)(enc2 | (enc & SQLITE_UTF16_ALIGNED));
+  pColl->type = collType;
+  sqlite3Error(db, SQLITE_OK, 0);
+  return SQLITE_OK;
+}
+
+
+/*
+** This array defines hard upper bounds on limit values.  The
+** initializer must be kept in sync with the SQLITE_LIMIT_*
+** #defines in sqlite3.h.
+*/
+static const int aHardLimit[] = {
+  SQLITE_MAX_LENGTH,
+  SQLITE_MAX_SQL_LENGTH,
+  SQLITE_MAX_COLUMN,
+  SQLITE_MAX_EXPR_DEPTH,
+  SQLITE_MAX_COMPOUND_SELECT,
+  SQLITE_MAX_VDBE_OP,
+  SQLITE_MAX_FUNCTION_ARG,
+  SQLITE_MAX_ATTACHED,
+  SQLITE_MAX_LIKE_PATTERN_LENGTH,
+  SQLITE_MAX_VARIABLE_NUMBER,
+  SQLITE_MAX_TRIGGER_DEPTH,
+};
+
+/*
+** Make sure the hard limits are set to reasonable values
+*/
+#if SQLITE_MAX_LENGTH<100
+# error SQLITE_MAX_LENGTH must be at least 100
+#endif
+#if SQLITE_MAX_SQL_LENGTH<100
+# error SQLITE_MAX_SQL_LENGTH must be at least 100
+#endif
+#if SQLITE_MAX_SQL_LENGTH>SQLITE_MAX_LENGTH
+# error SQLITE_MAX_SQL_LENGTH must not be greater than SQLITE_MAX_LENGTH
+#endif
+#if SQLITE_MAX_COMPOUND_SELECT<2
+# error SQLITE_MAX_COMPOUND_SELECT must be at least 2
+#endif
+#if SQLITE_MAX_VDBE_OP<40
+# error SQLITE_MAX_VDBE_OP must be at least 40
+#endif
+#if SQLITE_MAX_FUNCTION_ARG<0 || SQLITE_MAX_FUNCTION_ARG>1000
+# error SQLITE_MAX_FUNCTION_ARG must be between 0 and 1000
+#endif
+#if SQLITE_MAX_ATTACHED<0 || SQLITE_MAX_ATTACHED>62
+# error SQLITE_MAX_ATTACHED must be between 0 and 62
+#endif
+#if SQLITE_MAX_LIKE_PATTERN_LENGTH<1
+# error SQLITE_MAX_LIKE_PATTERN_LENGTH must be at least 1
+#endif
+#if SQLITE_MAX_COLUMN>32767
+# error SQLITE_MAX_COLUMN must not exceed 32767
+#endif
+#if SQLITE_MAX_TRIGGER_DEPTH<1
+# error SQLITE_MAX_TRIGGER_DEPTH must be at least 1
+#endif
+
+
+/*
+** Change the value of a limit.  Report the old value.
+** If an invalid limit index is supplied, report -1.
+** Make no changes but still report the old value if the
+** new limit is negative.
+**
+** A new lower limit does not shrink existing constructs.
+** It merely prevents new constructs that exceed the limit
+** from forming.
+*/
+int sqlite3_limit(sqlite3 *db, int limitId, int newLimit){
+  int oldLimit;
+
+
+  /* EVIDENCE-OF: R-30189-54097 For each limit category SQLITE_LIMIT_NAME
+  ** there is a hard upper bound set at compile-time by a C preprocessor
+  ** macro called SQLITE_MAX_NAME. (The "_LIMIT_" in the name is changed to
+  ** "_MAX_".)
+  */
+  assert( aHardLimit[SQLITE_LIMIT_LENGTH]==SQLITE_MAX_LENGTH );
+  assert( aHardLimit[SQLITE_LIMIT_SQL_LENGTH]==SQLITE_MAX_SQL_LENGTH );
+  assert( aHardLimit[SQLITE_LIMIT_COLUMN]==SQLITE_MAX_COLUMN );
+  assert( aHardLimit[SQLITE_LIMIT_EXPR_DEPTH]==SQLITE_MAX_EXPR_DEPTH );
+  assert( aHardLimit[SQLITE_LIMIT_COMPOUND_SELECT]==SQLITE_MAX_COMPOUND_SELECT);
+  assert( aHardLimit[SQLITE_LIMIT_VDBE_OP]==SQLITE_MAX_VDBE_OP );
+  assert( aHardLimit[SQLITE_LIMIT_FUNCTION_ARG]==SQLITE_MAX_FUNCTION_ARG );
+  assert( aHardLimit[SQLITE_LIMIT_ATTACHED]==SQLITE_MAX_ATTACHED );
+  assert( aHardLimit[SQLITE_LIMIT_LIKE_PATTERN_LENGTH]==
+                                               SQLITE_MAX_LIKE_PATTERN_LENGTH );
+  assert( aHardLimit[SQLITE_LIMIT_VARIABLE_NUMBER]==SQLITE_MAX_VARIABLE_NUMBER);
+  assert( aHardLimit[SQLITE_LIMIT_TRIGGER_DEPTH]==SQLITE_MAX_TRIGGER_DEPTH );
+  assert( SQLITE_LIMIT_TRIGGER_DEPTH==(SQLITE_N_LIMIT-1) );
+
+
+  if( limitId<0 || limitId>=SQLITE_N_LIMIT ){
+    return -1;
+  }
+  oldLimit = db->aLimit[limitId];
+  if( newLimit>=0 ){                   /* IMP: R-52476-28732 */
+    if( newLimit>aHardLimit[limitId] ){
+      newLimit = aHardLimit[limitId];  /* IMP: R-51463-25634 */
+    }
+    db->aLimit[limitId] = newLimit;
+  }
+  return oldLimit;                     /* IMP: R-53341-35419 */
+}
+
+/*
+** This function is used to parse both URIs and non-URI filenames passed by the
+** user to API functions sqlite3_open() or sqlite3_open_v2(), and for database
+** URIs specified as part of ATTACH statements.
+**
+** The first argument to this function is the name of the VFS to use (or
+** a NULL to signify the default VFS) if the URI does not contain a "vfs=xxx"
+** query parameter. The second argument contains the URI (or non-URI filename)
+** itself. When this function is called the *pFlags variable should contain
+** the default flags to open the database handle with. The value stored in
+** *pFlags may be updated before returning if the URI filename contains 
+** "cache=xxx" or "mode=xxx" query parameters.
+**
+** If successful, SQLITE_OK is returned. In this case *ppVfs is set to point to
+** the VFS that should be used to open the database file. *pzFile is set to
+** point to a buffer containing the name of the file to open. It is the 
+** responsibility of the caller to eventually call sqlite3_free() to release
+** this buffer.
+**
+** If an error occurs, then an SQLite error code is returned and *pzErrMsg
+** may be set to point to a buffer containing an English language error 
+** message. It is the responsibility of the caller to eventually release
+** this buffer by calling sqlite3_free().
+*/
+int sqlite3ParseUri(
+  const char *zDefaultVfs,        /* VFS to use if no "vfs=xxx" query option */
+  const char *zUri,               /* Nul-terminated URI to parse */
+  unsigned int *pFlags,           /* IN/OUT: SQLITE_OPEN_XXX flags */
+  sqlite3_vfs **ppVfs,            /* OUT: VFS to use */ 
+  char **pzFile,                  /* OUT: Filename component of URI */
+  char **pzErrMsg                 /* OUT: Error message (if rc!=SQLITE_OK) */
+){
+  int rc = SQLITE_OK;
+  unsigned int flags = *pFlags;
+  const char *zVfs = zDefaultVfs;
+  char *zFile;
+  char c;
+  int nUri = sqlite3Strlen30(zUri);
+
+  assert( *pzErrMsg==0 );
+
+  if( ((flags & SQLITE_OPEN_URI) || sqlite3GlobalConfig.bOpenUri) 
+   && nUri>=5 && memcmp(zUri, "file:", 5)==0 
+  ){
+    char *zOpt;
+    int eState;                   /* Parser state when parsing URI */
+    int iIn;                      /* Input character index */
+    int iOut = 0;                 /* Output character index */
+    int nByte = nUri+2;           /* Bytes of space to allocate */
+
+    /* Make sure the SQLITE_OPEN_URI flag is set to indicate to the VFS xOpen 
+    ** method that there may be extra parameters following the file-name.  */
+    flags |= SQLITE_OPEN_URI;
+
+    for(iIn=0; iIn<nUri; iIn++) nByte += (zUri[iIn]=='&');
+    zFile = sqlite3_malloc(nByte);
+    if( !zFile ) return SQLITE_NOMEM;
+
+    /* Discard the scheme and authority segments of the URI. */
+    if( zUri[5]=='/' && zUri[6]=='/' ){
+      iIn = 7;
+      while( zUri[iIn] && zUri[iIn]!='/' ) iIn++;
+
+      if( iIn!=7 && (iIn!=16 || memcmp("localhost", &zUri[7], 9)) ){
+        *pzErrMsg = sqlite3_mprintf("invalid uri authority: %.*s", 
+            iIn-7, &zUri[7]);
+        rc = SQLITE_ERROR;
+        goto parse_uri_out;
+      }
+    }else{
+      iIn = 5;
+    }
+
+    /* Copy the filename and any query parameters into the zFile buffer. 
+    ** Decode %HH escape codes along the way. 
+    **
+    ** Within this loop, variable eState may be set to 0, 1 or 2, depending
+    ** on the parsing context. As follows:
+    **
+    **   0: Parsing file-name.
+    **   1: Parsing name section of a name=value query parameter.
+    **   2: Parsing value section of a name=value query parameter.
+    */
+    eState = 0;
+    while( (c = zUri[iIn])!=0 && c!='#' ){
+      iIn++;
+      if( c=='%' 
+       && sqlite3Isxdigit(zUri[iIn]) 
+       && sqlite3Isxdigit(zUri[iIn+1]) 
+      ){
+        int octet = (sqlite3HexToInt(zUri[iIn++]) << 4);
+        octet += sqlite3HexToInt(zUri[iIn++]);
+
+        assert( octet>=0 && octet<256 );
+        if( octet==0 ){
+          /* This branch is taken when "%00" appears within the URI. In this
+          ** case we ignore all text in the remainder of the path, name or
+          ** value currently being parsed. So ignore the current character
+          ** and skip to the next "?", "=" or "&", as appropriate. */
+          while( (c = zUri[iIn])!=0 && c!='#' 
+              && (eState!=0 || c!='?')
+              && (eState!=1 || (c!='=' && c!='&'))
+              && (eState!=2 || c!='&')
+          ){
+            iIn++;
+          }
+          continue;
+        }
+        c = octet;
+      }else if( eState==1 && (c=='&' || c=='=') ){
+        if( zFile[iOut-1]==0 ){
+          /* An empty option name. Ignore this option altogether. */
+          while( zUri[iIn] && zUri[iIn]!='#' && zUri[iIn-1]!='&' ) iIn++;
+          continue;
+        }
+        if( c=='&' ){
+          zFile[iOut++] = '\0';
+        }else{
+          eState = 2;
+        }
+        c = 0;
+      }else if( (eState==0 && c=='?') || (eState==2 && c=='&') ){
+        c = 0;
+        eState = 1;
+      }
+      zFile[iOut++] = c;
+    }
+    if( eState==1 ) zFile[iOut++] = '\0';
+    zFile[iOut++] = '\0';
+    zFile[iOut++] = '\0';
+
+    /* Check if there were any options specified that should be interpreted 
+    ** here. Options that are interpreted here include "vfs" and those that
+    ** correspond to flags that may be passed to the sqlite3_open_v2()
+    ** method. */
+    zOpt = &zFile[sqlite3Strlen30(zFile)+1];
+    while( zOpt[0] ){
+      int nOpt = sqlite3Strlen30(zOpt);
+      char *zVal = &zOpt[nOpt+1];
+      int nVal = sqlite3Strlen30(zVal);
+
+      if( nOpt==3 && memcmp("vfs", zOpt, 3)==0 ){
+        zVfs = zVal;
+      }else{
+        struct OpenMode {
+          const char *z;
+          int mode;
+        } *aMode = 0;
+        char *zModeType = 0;
+        int mask = 0;
+        int limit = 0;
+
+        if( nOpt==5 && memcmp("cache", zOpt, 5)==0 ){
+          static struct OpenMode aCacheMode[] = {
+            { "shared",  SQLITE_OPEN_SHAREDCACHE },
+            { "private", SQLITE_OPEN_PRIVATECACHE },
+            { 0, 0 }
+          };
+
+          mask = SQLITE_OPEN_SHAREDCACHE|SQLITE_OPEN_PRIVATECACHE;
+          aMode = aCacheMode;
+          limit = mask;
+          zModeType = "cache";
+        }
+        if( nOpt==4 && memcmp("mode", zOpt, 4)==0 ){
+          static struct OpenMode aOpenMode[] = {
+            { "ro",  SQLITE_OPEN_READONLY },
+            { "rw",  SQLITE_OPEN_READWRITE }, 
+            { "rwc", SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE },
+            { 0, 0 }
+          };
+
+          mask = SQLITE_OPEN_READONLY|SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE;
+          aMode = aOpenMode;
+          limit = mask & flags;
+          zModeType = "access";
+        }
+
+        if( aMode ){
+          int i;
+          int mode = 0;
+          for(i=0; aMode[i].z; i++){
+            const char *z = aMode[i].z;
+            if( nVal==sqlite3Strlen30(z) && 0==memcmp(zVal, z, nVal) ){
+              mode = aMode[i].mode;
+              break;
+            }
+          }
+          if( mode==0 ){
+            *pzErrMsg = sqlite3_mprintf("no such %s mode: %s", zModeType, zVal);
+            rc = SQLITE_ERROR;
+            goto parse_uri_out;
+          }
+          if( mode>limit ){
+            *pzErrMsg = sqlite3_mprintf("%s mode not allowed: %s",
+                                        zModeType, zVal);
+            rc = SQLITE_PERM;
+            goto parse_uri_out;
+          }
+          flags = (flags & ~mask) | mode;
+        }
+      }
+
+      zOpt = &zVal[nVal+1];
+    }
+
+  }else{
+    zFile = sqlite3_malloc(nUri+2);
+    if( !zFile ) return SQLITE_NOMEM;
+    memcpy(zFile, zUri, nUri);
+    zFile[nUri] = '\0';
+    zFile[nUri+1] = '\0';
+  }
+
+  *ppVfs = sqlite3_vfs_find(zVfs);
+  if( *ppVfs==0 ){
+    *pzErrMsg = sqlite3_mprintf("no such vfs: %s", zVfs);
+    rc = SQLITE_ERROR;
+  }
+ parse_uri_out:
+  if( rc!=SQLITE_OK ){
+    sqlite3_free(zFile);
+    zFile = 0;
+  }
+  *pFlags = flags;
+  *pzFile = zFile;
+  return rc;
+}
+
+
+/*
+** This routine does the work of opening a database on behalf of
+** sqlite3_open() and sqlite3_open16(). The database filename "zFilename"  
+** is UTF-8 encoded.
+*/
+static int openDatabase(
+  const char *zFilename, /* Database filename UTF-8 encoded */
+  sqlite3 **ppDb,        /* OUT: Returned database handle */
+  unsigned int flags,    /* Operational flags */
+  const char *zVfs       /* Name of the VFS to use */
+){
+  sqlite3 *db;                    /* Store allocated handle here */
+  int rc;                         /* Return code */
+  int isThreadsafe;               /* True for threadsafe connections */
+  char *zOpen = 0;                /* Filename argument to pass to BtreeOpen() */
+  char *zErrMsg = 0;              /* Error message from sqlite3ParseUri() */
+
+  *ppDb = 0;
+#ifndef SQLITE_OMIT_AUTOINIT
+  rc = sqlite3_initialize();
+  if( rc ) return rc;
+#endif
+
+  /* Only allow sensible combinations of bits in the flags argument.  
+  ** Throw an error if any non-sense combination is used.  If we
+  ** do not block illegal combinations here, it could trigger
+  ** assert() statements in deeper layers.  Sensible combinations
+  ** are:
+  **
+  **  1:  SQLITE_OPEN_READONLY
+  **  2:  SQLITE_OPEN_READWRITE
+  **  6:  SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE
+  */
+  assert( SQLITE_OPEN_READONLY  == 0x01 );
+  assert( SQLITE_OPEN_READWRITE == 0x02 );
+  assert( SQLITE_OPEN_CREATE    == 0x04 );
+  testcase( (1<<(flags&7))==0x02 ); /* READONLY */
+  testcase( (1<<(flags&7))==0x04 ); /* READWRITE */
+  testcase( (1<<(flags&7))==0x40 ); /* READWRITE | CREATE */
+  if( ((1<<(flags&7)) & 0x46)==0 ) return SQLITE_MISUSE_BKPT;
+
+  if( sqlite3GlobalConfig.bCoreMutex==0 ){
+    isThreadsafe = 0;
+  }else if( flags & SQLITE_OPEN_NOMUTEX ){
+    isThreadsafe = 0;
+  }else if( flags & SQLITE_OPEN_FULLMUTEX ){
+    isThreadsafe = 1;
+  }else{
+    isThreadsafe = sqlite3GlobalConfig.bFullMutex;
+  }
+  if( flags & SQLITE_OPEN_PRIVATECACHE ){
+    flags &= ~SQLITE_OPEN_SHAREDCACHE;
+  }else if( sqlite3GlobalConfig.sharedCacheEnabled ){
+    flags |= SQLITE_OPEN_SHAREDCACHE;
+  }
+
+  /* Remove harmful bits from the flags parameter
+  **
+  ** The SQLITE_OPEN_NOMUTEX and SQLITE_OPEN_FULLMUTEX flags were
+  ** dealt with in the previous code block.  Besides these, the only
+  ** valid input flags for sqlite3_open_v2() are SQLITE_OPEN_READONLY,
+  ** SQLITE_OPEN_READWRITE, SQLITE_OPEN_CREATE, SQLITE_OPEN_SHAREDCACHE,
+  ** SQLITE_OPEN_PRIVATECACHE, and some reserved bits.  Silently mask
+  ** off all other flags.
+  */
+  flags &=  ~( SQLITE_OPEN_DELETEONCLOSE |
+               SQLITE_OPEN_EXCLUSIVE |
+               SQLITE_OPEN_MAIN_DB |
+               SQLITE_OPEN_TEMP_DB | 
+               SQLITE_OPEN_TRANSIENT_DB | 
+               SQLITE_OPEN_MAIN_JOURNAL | 
+               SQLITE_OPEN_TEMP_JOURNAL | 
+               SQLITE_OPEN_SUBJOURNAL | 
+               SQLITE_OPEN_MASTER_JOURNAL |
+               SQLITE_OPEN_NOMUTEX |
+               SQLITE_OPEN_FULLMUTEX |
+               SQLITE_OPEN_WAL
+             );
+
+  /* Allocate the sqlite data structure */
+  db = sqlite3MallocZero( sizeof(sqlite3) );
+  if( db==0 ) goto opendb_out;
+  if( isThreadsafe ){
+    db->mutex = sqlite3MutexAlloc(SQLITE_MUTEX_RECURSIVE);
+    if( db->mutex==0 ){
+      sqlite3_free(db);
+      db = 0;
+      goto opendb_out;
+    }
+  }
+  sqlite3_mutex_enter(db->mutex);
+  db->errMask = 0xff;
+  db->nDb = 2;
+  db->magic = SQLITE_MAGIC_BUSY;
+  db->aDb = db->aDbStatic;
+
+  assert( sizeof(db->aLimit)==sizeof(aHardLimit) );
+  memcpy(db->aLimit, aHardLimit, sizeof(db->aLimit));
+  db->autoCommit = 1;
+  db->nextAutovac = -1;
+  db->nextPagesize = 0;
+  db->flags |= SQLITE_ShortColNames | SQLITE_AutoIndex | SQLITE_EnableTrigger
+#if SQLITE_DEFAULT_FILE_FORMAT<4
+                 | SQLITE_LegacyFileFmt
+#endif
+#ifdef SQLITE_ENABLE_LOAD_EXTENSION
+                 | SQLITE_LoadExtension
+#endif
+#if SQLITE_DEFAULT_RECURSIVE_TRIGGERS
+                 | SQLITE_RecTriggers
+#endif
+#if defined(SQLITE_DEFAULT_FOREIGN_KEYS) && SQLITE_DEFAULT_FOREIGN_KEYS
+                 | SQLITE_ForeignKeys
+#endif
+      ;
+  sqlite3HashInit(&db->aCollSeq);
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  sqlite3HashInit(&db->aModule);
+#endif
+
+  /* Add the default collation sequence BINARY. BINARY works for both UTF-8
+  ** and UTF-16, so add a version for each to avoid any unnecessary
+  ** conversions. The only error that can occur here is a malloc() failure.
+  */
+  createCollation(db, "BINARY", SQLITE_UTF8, SQLITE_COLL_BINARY, 0,
+                  binCollFunc, 0);
+  createCollation(db, "BINARY", SQLITE_UTF16BE, SQLITE_COLL_BINARY, 0,
+                  binCollFunc, 0);
+  createCollation(db, "BINARY", SQLITE_UTF16LE, SQLITE_COLL_BINARY, 0,
+                  binCollFunc, 0);
+  createCollation(db, "RTRIM", SQLITE_UTF8, SQLITE_COLL_USER, (void*)1,
+                  binCollFunc, 0);
+  if( db->mallocFailed ){
+    goto opendb_out;
+  }
+  db->pDfltColl = sqlite3FindCollSeq(db, SQLITE_UTF8, "BINARY", 0);
+  assert( db->pDfltColl!=0 );
+
+  /* Also add a UTF-8 case-insensitive collation sequence. */
+  createCollation(db, "NOCASE", SQLITE_UTF8, SQLITE_COLL_NOCASE, 0,
+                  nocaseCollatingFunc, 0);
+
+  /* Parse the filename/URI argument. */
+  db->openFlags = flags;
+  rc = sqlite3ParseUri(zVfs, zFilename, &flags, &db->pVfs, &zOpen, &zErrMsg);
+  if( rc!=SQLITE_OK ){
+    if( rc==SQLITE_NOMEM ) db->mallocFailed = 1;
+    sqlite3Error(db, rc, zErrMsg ? "%s" : 0, zErrMsg);
+    sqlite3_free(zErrMsg);
+    goto opendb_out;
+  }
+
+  /* Open the backend database driver */
+  rc = sqlite3BtreeOpen(db->pVfs, zOpen, db, &db->aDb[0].pBt, 0,
+                        flags | SQLITE_OPEN_MAIN_DB);
+  if( rc!=SQLITE_OK ){
+    if( rc==SQLITE_IOERR_NOMEM ){
+      rc = SQLITE_NOMEM;
+    }
+    sqlite3Error(db, rc, 0);
+    goto opendb_out;
+  }
+  db->aDb[0].pSchema = sqlite3SchemaGet(db, db->aDb[0].pBt);
+  db->aDb[1].pSchema = sqlite3SchemaGet(db, 0);
+
+
+  /* The default safety_level for the main database is 'full'; for the temp
+  ** database it is 'NONE'. This matches the pager layer defaults.  
+  */
+  db->aDb[0].zName = "main";
+  db->aDb[0].safety_level = 3;
+  db->aDb[1].zName = "temp";
+  db->aDb[1].safety_level = 1;
+
+  db->magic = SQLITE_MAGIC_OPEN;
+  if( db->mallocFailed ){
+    goto opendb_out;
+  }
+
+  /* Register all built-in functions, but do not attempt to read the
+  ** database schema yet. This is delayed until the first time the database
+  ** is accessed.
+  */
+  sqlite3Error(db, SQLITE_OK, 0);
+  sqlite3RegisterBuiltinFunctions(db);
+
+  /* Load automatic extensions - extensions that have been registered
+  ** using the sqlite3_automatic_extension() API.
+  */
+  sqlite3AutoLoadExtensions(db);
+  rc = sqlite3_errcode(db);
+  if( rc!=SQLITE_OK ){
+    goto opendb_out;
+  }
+
+#ifdef SQLITE_ENABLE_FTS1
+  if( !db->mallocFailed ){
+    extern int sqlite3Fts1Init(sqlite3*);
+    rc = sqlite3Fts1Init(db);
+  }
+#endif
+
+#ifdef SQLITE_ENABLE_FTS2
+  if( !db->mallocFailed && rc==SQLITE_OK ){
+    extern int sqlite3Fts2Init(sqlite3*);
+    rc = sqlite3Fts2Init(db);
+  }
+#endif
+
+#ifdef SQLITE_ENABLE_FTS3
+  if( !db->mallocFailed && rc==SQLITE_OK ){
+    rc = sqlite3Fts3Init(db);
+  }
+#endif
+
+#ifdef SQLITE_ENABLE_ICU
+  if( !db->mallocFailed && rc==SQLITE_OK ){
+    rc = sqlite3IcuInit(db);
+  }
+#endif
+
+#ifdef SQLITE_ENABLE_RTREE
+  if( !db->mallocFailed && rc==SQLITE_OK){
+    rc = sqlite3RtreeInit(db);
+  }
+#endif
+
+  sqlite3Error(db, rc, 0);
+
+  /* -DSQLITE_DEFAULT_LOCKING_MODE=1 makes EXCLUSIVE the default locking
+  ** mode.  -DSQLITE_DEFAULT_LOCKING_MODE=0 make NORMAL the default locking
+  ** mode.  Doing nothing at all also makes NORMAL the default.
+  */
+#ifdef SQLITE_DEFAULT_LOCKING_MODE
+  db->dfltLockMode = SQLITE_DEFAULT_LOCKING_MODE;
+  sqlite3PagerLockingMode(sqlite3BtreePager(db->aDb[0].pBt),
+                          SQLITE_DEFAULT_LOCKING_MODE);
+#endif
+
+  /* Enable the lookaside-malloc subsystem */
+  setupLookaside(db, 0, sqlite3GlobalConfig.szLookaside,
+                        sqlite3GlobalConfig.nLookaside);
+
+  sqlite3_wal_autocheckpoint(db, SQLITE_DEFAULT_WAL_AUTOCHECKPOINT);
+
+opendb_out:
+  sqlite3_free(zOpen);
+  if( db ){
+    assert( db->mutex!=0 || isThreadsafe==0 || sqlite3GlobalConfig.bFullMutex==0 );
+    sqlite3_mutex_leave(db->mutex);
+  }
+  rc = sqlite3_errcode(db);
+  assert( db!=0 || rc==SQLITE_NOMEM );
+  if( rc==SQLITE_NOMEM ){
+    sqlite3_close(db);
+    db = 0;
+  }else if( rc!=SQLITE_OK ){
+    db->magic = SQLITE_MAGIC_SICK;
+  }
+  *ppDb = db;
+  return sqlite3ApiExit(0, rc);
+}
+
+/*
+** Open a new database handle.
+*/
+int sqlite3_open(
+  const char *zFilename, 
+  sqlite3 **ppDb 
+){
+  return openDatabase(zFilename, ppDb,
+                      SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE, 0);
+}
+int sqlite3_open_v2(
+  const char *filename,   /* Database filename (UTF-8) */
+  sqlite3 **ppDb,         /* OUT: SQLite db handle */
+  int flags,              /* Flags */
+  const char *zVfs        /* Name of VFS module to use */
+){
+  return openDatabase(filename, ppDb, (unsigned int)flags, zVfs);
+}
+
+#ifndef SQLITE_OMIT_UTF16
+/*
+** Open a new database handle.
+*/
+int sqlite3_open16(
+  const void *zFilename, 
+  sqlite3 **ppDb
+){
+  char const *zFilename8;   /* zFilename encoded in UTF-8 instead of UTF-16 */
+  sqlite3_value *pVal;
+  int rc;
+
+  assert( zFilename );
+  assert( ppDb );
+  *ppDb = 0;
+#ifndef SQLITE_OMIT_AUTOINIT
+  rc = sqlite3_initialize();
+  if( rc ) return rc;
+#endif
+  pVal = sqlite3ValueNew(0);
+  sqlite3ValueSetStr(pVal, -1, zFilename, SQLITE_UTF16NATIVE, SQLITE_STATIC);
+  zFilename8 = sqlite3ValueText(pVal, SQLITE_UTF8);
+  if( zFilename8 ){
+    rc = openDatabase(zFilename8, ppDb,
+                      SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE, 0);
+    assert( *ppDb || rc==SQLITE_NOMEM );
+    if( rc==SQLITE_OK && !DbHasProperty(*ppDb, 0, DB_SchemaLoaded) ){
+      ENC(*ppDb) = SQLITE_UTF16NATIVE;
+    }
+  }else{
+    rc = SQLITE_NOMEM;
+  }
+  sqlite3ValueFree(pVal);
+
+  return sqlite3ApiExit(0, rc);
+}
+#endif /* SQLITE_OMIT_UTF16 */
+
+/*
+** Register a new collation sequence with the database handle db.
+*/
+int sqlite3_create_collation(
+  sqlite3* db, 
+  const char *zName, 
+  int enc, 
+  void* pCtx,
+  int(*xCompare)(void*,int,const void*,int,const void*)
+){
+  int rc;
+  sqlite3_mutex_enter(db->mutex);
+  assert( !db->mallocFailed );
+  rc = createCollation(db, zName, (u8)enc, SQLITE_COLL_USER, pCtx, xCompare, 0);
+  rc = sqlite3ApiExit(db, rc);
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+
+/*
+** Register a new collation sequence with the database handle db.
+*/
+int sqlite3_create_collation_v2(
+  sqlite3* db, 
+  const char *zName, 
+  int enc, 
+  void* pCtx,
+  int(*xCompare)(void*,int,const void*,int,const void*),
+  void(*xDel)(void*)
+){
+  int rc;
+  sqlite3_mutex_enter(db->mutex);
+  assert( !db->mallocFailed );
+  rc = createCollation(db, zName, (u8)enc, SQLITE_COLL_USER, pCtx, xCompare, xDel);
+  rc = sqlite3ApiExit(db, rc);
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+
+#ifndef SQLITE_OMIT_UTF16
+/*
+** Register a new collation sequence with the database handle db.
+*/
+int sqlite3_create_collation16(
+  sqlite3* db, 
+  const void *zName,
+  int enc, 
+  void* pCtx,
+  int(*xCompare)(void*,int,const void*,int,const void*)
+){
+  int rc = SQLITE_OK;
+  char *zName8;
+  sqlite3_mutex_enter(db->mutex);
+  assert( !db->mallocFailed );
+  zName8 = sqlite3Utf16to8(db, zName, -1, SQLITE_UTF16NATIVE);
+  if( zName8 ){
+    rc = createCollation(db, zName8, (u8)enc, SQLITE_COLL_USER, pCtx, xCompare, 0);
+    sqlite3DbFree(db, zName8);
+  }
+  rc = sqlite3ApiExit(db, rc);
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+#endif /* SQLITE_OMIT_UTF16 */
+
+/*
+** Register a collation sequence factory callback with the database handle
+** db. Replace any previously installed collation sequence factory.
+*/
+int sqlite3_collation_needed(
+  sqlite3 *db, 
+  void *pCollNeededArg, 
+  void(*xCollNeeded)(void*,sqlite3*,int eTextRep,const char*)
+){
+  sqlite3_mutex_enter(db->mutex);
+  db->xCollNeeded = xCollNeeded;
+  db->xCollNeeded16 = 0;
+  db->pCollNeededArg = pCollNeededArg;
+  sqlite3_mutex_leave(db->mutex);
+  return SQLITE_OK;
+}
+
+#ifndef SQLITE_OMIT_UTF16
+/*
+** Register a collation sequence factory callback with the database handle
+** db. Replace any previously installed collation sequence factory.
+*/
+int sqlite3_collation_needed16(
+  sqlite3 *db, 
+  void *pCollNeededArg, 
+  void(*xCollNeeded16)(void*,sqlite3*,int eTextRep,const void*)
+){
+  sqlite3_mutex_enter(db->mutex);
+  db->xCollNeeded = 0;
+  db->xCollNeeded16 = xCollNeeded16;
+  db->pCollNeededArg = pCollNeededArg;
+  sqlite3_mutex_leave(db->mutex);
+  return SQLITE_OK;
+}
+#endif /* SQLITE_OMIT_UTF16 */
+
+#ifndef SQLITE_OMIT_DEPRECATED
+/*
+** This function is now an anachronism. It used to be used to recover from a
+** malloc() failure, but SQLite now does this automatically.
+*/
+int sqlite3_global_recover(void){
+  return SQLITE_OK;
+}
+#endif
+
+/*
+** Test to see whether or not the database connection is in autocommit
+** mode.  Return TRUE if it is and FALSE if not.  Autocommit mode is on
+** by default.  Autocommit is disabled by a BEGIN statement and reenabled
+** by the next COMMIT or ROLLBACK.
+**
+******* THIS IS AN EXPERIMENTAL API AND IS SUBJECT TO CHANGE ******
+*/
+int sqlite3_get_autocommit(sqlite3 *db){
+  return db->autoCommit;
+}
+
+/*
+** The following routines are subtitutes for constants SQLITE_CORRUPT,
+** SQLITE_MISUSE, SQLITE_CANTOPEN, SQLITE_IOERR and possibly other error
+** constants.  They server two purposes:
+**
+**   1.  Serve as a convenient place to set a breakpoint in a debugger
+**       to detect when version error conditions occurs.
+**
+**   2.  Invoke sqlite3_log() to provide the source code location where
+**       a low-level error is first detected.
+*/
+int sqlite3CorruptError(int lineno){
+  testcase( sqlite3GlobalConfig.xLog!=0 );
+  sqlite3_log(SQLITE_CORRUPT,
+              "database corruption at line %d of [%.10s]",
+              lineno, 20+sqlite3_sourceid());
+  return SQLITE_CORRUPT;
+}
+int sqlite3MisuseError(int lineno){
+  testcase( sqlite3GlobalConfig.xLog!=0 );
+  sqlite3_log(SQLITE_MISUSE, 
+              "misuse at line %d of [%.10s]",
+              lineno, 20+sqlite3_sourceid());
+  return SQLITE_MISUSE;
+}
+int sqlite3CantopenError(int lineno){
+  testcase( sqlite3GlobalConfig.xLog!=0 );
+  sqlite3_log(SQLITE_CANTOPEN, 
+              "cannot open file at line %d of [%.10s]",
+              lineno, 20+sqlite3_sourceid());
+  return SQLITE_CANTOPEN;
+}
+
+
+#ifndef SQLITE_OMIT_DEPRECATED
+/*
+** This is a convenience routine that makes sure that all thread-specific
+** data for this thread has been deallocated.
+**
+** SQLite no longer uses thread-specific data so this routine is now a
+** no-op.  It is retained for historical compatibility.
+*/
+void sqlite3_thread_cleanup(void){
+}
+#endif
+
+/*
+** Return meta information about a specific column of a database table.
+** See comment in sqlite3.h (sqlite.h.in) for details.
+*/
+#ifdef SQLITE_ENABLE_COLUMN_METADATA
+int sqlite3_table_column_metadata(
+  sqlite3 *db,                /* Connection handle */
+  const char *zDbName,        /* Database name or NULL */
+  const char *zTableName,     /* Table name */
+  const char *zColumnName,    /* Column name */
+  char const **pzDataType,    /* OUTPUT: Declared data type */
+  char const **pzCollSeq,     /* OUTPUT: Collation sequence name */
+  int *pNotNull,              /* OUTPUT: True if NOT NULL constraint exists */
+  int *pPrimaryKey,           /* OUTPUT: True if column part of PK */
+  int *pAutoinc               /* OUTPUT: True if column is auto-increment */
+){
+  int rc;
+  char *zErrMsg = 0;
+  Table *pTab = 0;
+  Column *pCol = 0;
+  int iCol;
+
+  char const *zDataType = 0;
+  char const *zCollSeq = 0;
+  int notnull = 0;
+  int primarykey = 0;
+  int autoinc = 0;
+
+  /* Ensure the database schema has been loaded */
+  sqlite3_mutex_enter(db->mutex);
+  sqlite3BtreeEnterAll(db);
+  rc = sqlite3Init(db, &zErrMsg);
+  if( SQLITE_OK!=rc ){
+    goto error_out;
+  }
+
+  /* Locate the table in question */
+  pTab = sqlite3FindTable(db, zTableName, zDbName);
+  if( !pTab || pTab->pSelect ){
+    pTab = 0;
+    goto error_out;
+  }
+
+  /* Find the column for which info is requested */
+  if( sqlite3IsRowid(zColumnName) ){
+    iCol = pTab->iPKey;
+    if( iCol>=0 ){
+      pCol = &pTab->aCol[iCol];
+    }
+  }else{
+    for(iCol=0; iCol<pTab->nCol; iCol++){
+      pCol = &pTab->aCol[iCol];
+      if( 0==sqlite3StrICmp(pCol->zName, zColumnName) ){
+        break;
+      }
+    }
+    if( iCol==pTab->nCol ){
+      pTab = 0;
+      goto error_out;
+    }
+  }
+
+  /* The following block stores the meta information that will be returned
+  ** to the caller in local variables zDataType, zCollSeq, notnull, primarykey
+  ** and autoinc. At this point there are two possibilities:
+  ** 
+  **     1. The specified column name was rowid", "oid" or "_rowid_" 
+  **        and there is no explicitly declared IPK column. 
+  **
+  **     2. The table is not a view and the column name identified an 
+  **        explicitly declared column. Copy meta information from *pCol.
+  */ 
+  if( pCol ){
+    zDataType = pCol->zType;
+    zCollSeq = pCol->zColl;
+    notnull = pCol->notNull!=0;
+    primarykey  = pCol->isPrimKey!=0;
+    autoinc = pTab->iPKey==iCol && (pTab->tabFlags & TF_Autoincrement)!=0;
+  }else{
+    zDataType = "INTEGER";
+    primarykey = 1;
+  }
+  if( !zCollSeq ){
+    zCollSeq = "BINARY";
+  }
+
+error_out:
+  sqlite3BtreeLeaveAll(db);
+
+  /* Whether the function call succeeded or failed, set the output parameters
+  ** to whatever their local counterparts contain. If an error did occur,
+  ** this has the effect of zeroing all output parameters.
+  */
+  if( pzDataType ) *pzDataType = zDataType;
+  if( pzCollSeq ) *pzCollSeq = zCollSeq;
+  if( pNotNull ) *pNotNull = notnull;
+  if( pPrimaryKey ) *pPrimaryKey = primarykey;
+  if( pAutoinc ) *pAutoinc = autoinc;
+
+  if( SQLITE_OK==rc && !pTab ){
+    sqlite3DbFree(db, zErrMsg);
+    zErrMsg = sqlite3MPrintf(db, "no such table column: %s.%s", zTableName,
+        zColumnName);
+    rc = SQLITE_ERROR;
+  }
+  sqlite3Error(db, rc, (zErrMsg?"%s":0), zErrMsg);
+  sqlite3DbFree(db, zErrMsg);
+  rc = sqlite3ApiExit(db, rc);
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+#endif
+
+/*
+** Sleep for a little while.  Return the amount of time slept.
+*/
+int sqlite3_sleep(int ms){
+  sqlite3_vfs *pVfs;
+  int rc;
+  pVfs = sqlite3_vfs_find(0);
+  if( pVfs==0 ) return 0;
+
+  /* This function works in milliseconds, but the underlying OsSleep() 
+  ** API uses microseconds. Hence the 1000's.
+  */
+  rc = (sqlite3OsSleep(pVfs, 1000*ms)/1000);
+  return rc;
+}
+
+/*
+** Enable or disable the extended result codes.
+*/
+int sqlite3_extended_result_codes(sqlite3 *db, int onoff){
+  sqlite3_mutex_enter(db->mutex);
+  db->errMask = onoff ? 0xffffffff : 0xff;
+  sqlite3_mutex_leave(db->mutex);
+  return SQLITE_OK;
+}
+
+/*
+** Invoke the xFileControl method on a particular database.
+*/
+int sqlite3_file_control(sqlite3 *db, const char *zDbName, int op, void *pArg){
+  int rc = SQLITE_ERROR;
+  int iDb;
+  sqlite3_mutex_enter(db->mutex);
+  if( zDbName==0 ){
+    iDb = 0;
+  }else{
+    for(iDb=0; iDb<db->nDb; iDb++){
+      if( strcmp(db->aDb[iDb].zName, zDbName)==0 ) break;
+    }
+  }
+  if( iDb<db->nDb ){
+    Btree *pBtree = db->aDb[iDb].pBt;
+    if( pBtree ){
+      Pager *pPager;
+      sqlite3_file *fd;
+      sqlite3BtreeEnter(pBtree);
+      pPager = sqlite3BtreePager(pBtree);
+      assert( pPager!=0 );
+      fd = sqlite3PagerFile(pPager);
+      assert( fd!=0 );
+      if( op==SQLITE_FCNTL_FILE_POINTER ){
+        *(sqlite3_file**)pArg = fd;
+        rc = SQLITE_OK;
+      }else if( fd->pMethods ){
+        rc = sqlite3OsFileControl(fd, op, pArg);
+      }else{
+        rc = SQLITE_NOTFOUND;
+      }
+      sqlite3BtreeLeave(pBtree);
+    }
+  }
+  sqlite3_mutex_leave(db->mutex);
+  return rc;   
+}
+
+/*
+** Interface to the testing logic.
+*/
+int sqlite3_test_control(int op, ...){
+  int rc = 0;
+#ifndef SQLITE_OMIT_BUILTIN_TEST
+  va_list ap;
+  va_start(ap, op);
+  switch( op ){
+
+    /*
+    ** Save the current state of the PRNG.
+    */
+    case SQLITE_TESTCTRL_PRNG_SAVE: {
+      sqlite3PrngSaveState();
+      break;
+    }
+
+    /*
+    ** Restore the state of the PRNG to the last state saved using
+    ** PRNG_SAVE.  If PRNG_SAVE has never before been called, then
+    ** this verb acts like PRNG_RESET.
+    */
+    case SQLITE_TESTCTRL_PRNG_RESTORE: {
+      sqlite3PrngRestoreState();
+      break;
+    }
+
+    /*
+    ** Reset the PRNG back to its uninitialized state.  The next call
+    ** to sqlite3_randomness() will reseed the PRNG using a single call
+    ** to the xRandomness method of the default VFS.
+    */
+    case SQLITE_TESTCTRL_PRNG_RESET: {
+      sqlite3PrngResetState();
+      break;
+    }
+
+    /*
+    **  sqlite3_test_control(BITVEC_TEST, size, program)
+    **
+    ** Run a test against a Bitvec object of size.  The program argument
+    ** is an array of integers that defines the test.  Return -1 on a
+    ** memory allocation error, 0 on success, or non-zero for an error.
+    ** See the sqlite3BitvecBuiltinTest() for additional information.
+    */
+    case SQLITE_TESTCTRL_BITVEC_TEST: {
+      int sz = va_arg(ap, int);
+      int *aProg = va_arg(ap, int*);
+      rc = sqlite3BitvecBuiltinTest(sz, aProg);
+      break;
+    }
+
+    /*
+    **  sqlite3_test_control(BENIGN_MALLOC_HOOKS, xBegin, xEnd)
+    **
+    ** Register hooks to call to indicate which malloc() failures 
+    ** are benign.
+    */
+    case SQLITE_TESTCTRL_BENIGN_MALLOC_HOOKS: {
+      typedef void (*void_function)(void);
+      void_function xBenignBegin;
+      void_function xBenignEnd;
+      xBenignBegin = va_arg(ap, void_function);
+      xBenignEnd = va_arg(ap, void_function);
+      sqlite3BenignMallocHooks(xBenignBegin, xBenignEnd);
+      break;
+    }
+
+    /*
+    **  sqlite3_test_control(SQLITE_TESTCTRL_PENDING_BYTE, unsigned int X)
+    **
+    ** Set the PENDING byte to the value in the argument, if X>0.
+    ** Make no changes if X==0.  Return the value of the pending byte
+    ** as it existing before this routine was called.
+    **
+    ** IMPORTANT:  Changing the PENDING byte from 0x40000000 results in
+    ** an incompatible database file format.  Changing the PENDING byte
+    ** while any database connection is open results in undefined and
+    ** dileterious behavior.
+    */
+    case SQLITE_TESTCTRL_PENDING_BYTE: {
+      rc = PENDING_BYTE;
+#ifndef SQLITE_OMIT_WSD
+      {
+        unsigned int newVal = va_arg(ap, unsigned int);
+        if( newVal ) sqlite3PendingByte = newVal;
+      }
+#endif
+      break;
+    }
+
+    /*
+    **  sqlite3_test_control(SQLITE_TESTCTRL_ASSERT, int X)
+    **
+    ** This action provides a run-time test to see whether or not
+    ** assert() was enabled at compile-time.  If X is true and assert()
+    ** is enabled, then the return value is true.  If X is true and
+    ** assert() is disabled, then the return value is zero.  If X is
+    ** false and assert() is enabled, then the assertion fires and the
+    ** process aborts.  If X is false and assert() is disabled, then the
+    ** return value is zero.
+    */
+    case SQLITE_TESTCTRL_ASSERT: {
+      volatile int x = 0;
+      assert( (x = va_arg(ap,int))!=0 );
+      rc = x;
+      break;
+    }
+
+
+    /*
+    **  sqlite3_test_control(SQLITE_TESTCTRL_ALWAYS, int X)
+    **
+    ** This action provides a run-time test to see how the ALWAYS and
+    ** NEVER macros were defined at compile-time.
+    **
+    ** The return value is ALWAYS(X).  
+    **
+    ** The recommended test is X==2.  If the return value is 2, that means
+    ** ALWAYS() and NEVER() are both no-op pass-through macros, which is the
+    ** default setting.  If the return value is 1, then ALWAYS() is either
+    ** hard-coded to true or else it asserts if its argument is false.
+    ** The first behavior (hard-coded to true) is the case if
+    ** SQLITE_TESTCTRL_ASSERT shows that assert() is disabled and the second
+    ** behavior (assert if the argument to ALWAYS() is false) is the case if
+    ** SQLITE_TESTCTRL_ASSERT shows that assert() is enabled.
+    **
+    ** The run-time test procedure might look something like this:
+    **
+    **    if( sqlite3_test_control(SQLITE_TESTCTRL_ALWAYS, 2)==2 ){
+    **      // ALWAYS() and NEVER() are no-op pass-through macros
+    **    }else if( sqlite3_test_control(SQLITE_TESTCTRL_ASSERT, 1) ){
+    **      // ALWAYS(x) asserts that x is true. NEVER(x) asserts x is false.
+    **    }else{
+    **      // ALWAYS(x) is a constant 1.  NEVER(x) is a constant 0.
+    **    }
+    */
+    case SQLITE_TESTCTRL_ALWAYS: {
+      int x = va_arg(ap,int);
+      rc = ALWAYS(x);
+      break;
+    }
+
+    /*   sqlite3_test_control(SQLITE_TESTCTRL_RESERVE, sqlite3 *db, int N)
+    **
+    ** Set the nReserve size to N for the main database on the database
+    ** connection db.
+    */
+    case SQLITE_TESTCTRL_RESERVE: {
+      sqlite3 *db = va_arg(ap, sqlite3*);
+      int x = va_arg(ap,int);
+      sqlite3_mutex_enter(db->mutex);
+      sqlite3BtreeSetPageSize(db->aDb[0].pBt, 0, x, 0);
+      sqlite3_mutex_leave(db->mutex);
+      break;
+    }
+
+    /*  sqlite3_test_control(SQLITE_TESTCTRL_OPTIMIZATIONS, sqlite3 *db, int N)
+    **
+    ** Enable or disable various optimizations for testing purposes.  The 
+    ** argument N is a bitmask of optimizations to be disabled.  For normal
+    ** operation N should be 0.  The idea is that a test program (like the
+    ** SQL Logic Test or SLT test module) can run the same SQL multiple times
+    ** with various optimizations disabled to verify that the same answer
+    ** is obtained in every case.
+    */
+    case SQLITE_TESTCTRL_OPTIMIZATIONS: {
+      sqlite3 *db = va_arg(ap, sqlite3*);
+      int x = va_arg(ap,int);
+      db->flags = (x & SQLITE_OptMask) | (db->flags & ~SQLITE_OptMask);
+      break;
+    }
+
+#ifdef SQLITE_N_KEYWORD
+    /* sqlite3_test_control(SQLITE_TESTCTRL_ISKEYWORD, const char *zWord)
+    **
+    ** If zWord is a keyword recognized by the parser, then return the
+    ** number of keywords.  Or if zWord is not a keyword, return 0.
+    ** 
+    ** This test feature is only available in the amalgamation since
+    ** the SQLITE_N_KEYWORD macro is not defined in this file if SQLite
+    ** is built using separate source files.
+    */
+    case SQLITE_TESTCTRL_ISKEYWORD: {
+      const char *zWord = va_arg(ap, const char*);
+      int n = sqlite3Strlen30(zWord);
+      rc = (sqlite3KeywordCode((u8*)zWord, n)!=TK_ID) ? SQLITE_N_KEYWORD : 0;
+      break;
+    }
+#endif 
+
+    /* sqlite3_test_control(SQLITE_TESTCTRL_PGHDRSZ)
+    **
+    ** Return the size of a pcache header in bytes.
+    */
+    case SQLITE_TESTCTRL_PGHDRSZ: {
+      rc = sizeof(PgHdr);
+      break;
+    }
+
+    /* sqlite3_test_control(SQLITE_TESTCTRL_SCRATCHMALLOC, sz, &pNew, pFree);
+    **
+    ** Pass pFree into sqlite3ScratchFree(). 
+    ** If sz>0 then allocate a scratch buffer into pNew.  
+    */
+    case SQLITE_TESTCTRL_SCRATCHMALLOC: {
+      void *pFree, **ppNew;
+      int sz;
+      sz = va_arg(ap, int);
+      ppNew = va_arg(ap, void**);
+      pFree = va_arg(ap, void*);
+      if( sz ) *ppNew = sqlite3ScratchMalloc(sz);
+      sqlite3ScratchFree(pFree);
+      break;
+    }
+
+    /*   sqlite3_test_control(SQLITE_TESTCTRL_LOCALTIME_FAULT, int onoff);
+    **
+    ** If parameter onoff is non-zero, configure the wrappers so that all
+    ** subsequent calls to localtime() and variants fail. If onoff is zero,
+    ** undo this setting.
+    */
+    case SQLITE_TESTCTRL_LOCALTIME_FAULT: {
+      sqlite3GlobalConfig.bLocaltimeFault = va_arg(ap, int);
+      break;
+    }
+
+  }
+  va_end(ap);
+#endif /* SQLITE_OMIT_BUILTIN_TEST */
+  return rc;
+}
+
+/*
+** This is a utility routine, useful to VFS implementations, that checks
+** to see if a database file was a URI that contained a specific query 
+** parameter, and if so obtains the value of the query parameter.
+**
+** The zFilename argument is the filename pointer passed into the xOpen()
+** method of a VFS implementation.  The zParam argument is the name of the
+** query parameter we seek.  This routine returns the value of the zParam
+** parameter if it exists.  If the parameter does not exist, this routine
+** returns a NULL pointer.
+*/
+const char *sqlite3_uri_parameter(const char *zFilename, const char *zParam){
+  zFilename += sqlite3Strlen30(zFilename) + 1;
+  while( zFilename[0] ){
+    int x = strcmp(zFilename, zParam);
+    zFilename += sqlite3Strlen30(zFilename) + 1;
+    if( x==0 ) return zFilename;
+    zFilename += sqlite3Strlen30(zFilename) + 1;
+  }
+  return 0;
+}
diff --git a/src/malloc.c b/src/malloc.c
new file mode 100644
index 0000000..3e38d1d
--- /dev/null
+++ b/src/malloc.c
@@ -0,0 +1,777 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** Memory allocation functions used throughout sqlite.
+*/
+#include "sqliteInt.h"
+#include <stdarg.h>
+
+/*
+** Attempt to release up to n bytes of non-essential memory currently
+** held by SQLite. An example of non-essential memory is memory used to
+** cache database pages that are not currently in use.
+*/
+int sqlite3_release_memory(int n){
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
+  return sqlite3PcacheReleaseMemory(n);
+#else
+  /* IMPLEMENTATION-OF: R-34391-24921 The sqlite3_release_memory() routine
+  ** is a no-op returning zero if SQLite is not compiled with
+  ** SQLITE_ENABLE_MEMORY_MANAGEMENT. */
+  UNUSED_PARAMETER(n);
+  return 0;
+#endif
+}
+
+/*
+** An instance of the following object records the location of
+** each unused scratch buffer.
+*/
+typedef struct ScratchFreeslot {
+  struct ScratchFreeslot *pNext;   /* Next unused scratch buffer */
+} ScratchFreeslot;
+
+/*
+** State information local to the memory allocation subsystem.
+*/
+static SQLITE_WSD struct Mem0Global {
+  sqlite3_mutex *mutex;         /* Mutex to serialize access */
+
+  /*
+  ** The alarm callback and its arguments.  The mem0.mutex lock will
+  ** be held while the callback is running.  Recursive calls into
+  ** the memory subsystem are allowed, but no new callbacks will be
+  ** issued.
+  */
+  sqlite3_int64 alarmThreshold;
+  void (*alarmCallback)(void*, sqlite3_int64,int);
+  void *alarmArg;
+
+  /*
+  ** Pointers to the end of sqlite3GlobalConfig.pScratch memory
+  ** (so that a range test can be used to determine if an allocation
+  ** being freed came from pScratch) and a pointer to the list of
+  ** unused scratch allocations.
+  */
+  void *pScratchEnd;
+  ScratchFreeslot *pScratchFree;
+  u32 nScratchFree;
+
+  /*
+  ** True if heap is nearly "full" where "full" is defined by the
+  ** sqlite3_soft_heap_limit() setting.
+  */
+  int nearlyFull;
+} mem0 = { 0, 0, 0, 0, 0, 0, 0, 0 };
+
+#define mem0 GLOBAL(struct Mem0Global, mem0)
+
+/*
+** This routine runs when the memory allocator sees that the
+** total memory allocation is about to exceed the soft heap
+** limit.
+*/
+static void softHeapLimitEnforcer(
+  void *NotUsed, 
+  sqlite3_int64 NotUsed2,
+  int allocSize
+){
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  sqlite3_release_memory(allocSize);
+}
+
+/*
+** Change the alarm callback
+*/
+static int sqlite3MemoryAlarm(
+  void(*xCallback)(void *pArg, sqlite3_int64 used,int N),
+  void *pArg,
+  sqlite3_int64 iThreshold
+){
+  int nUsed;
+  sqlite3_mutex_enter(mem0.mutex);
+  mem0.alarmCallback = xCallback;
+  mem0.alarmArg = pArg;
+  mem0.alarmThreshold = iThreshold;
+  nUsed = sqlite3StatusValue(SQLITE_STATUS_MEMORY_USED);
+  mem0.nearlyFull = (iThreshold>0 && iThreshold<=nUsed);
+  sqlite3_mutex_leave(mem0.mutex);
+  return SQLITE_OK;
+}
+
+#ifndef SQLITE_OMIT_DEPRECATED
+/*
+** Deprecated external interface.  Internal/core SQLite code
+** should call sqlite3MemoryAlarm.
+*/
+int sqlite3_memory_alarm(
+  void(*xCallback)(void *pArg, sqlite3_int64 used,int N),
+  void *pArg,
+  sqlite3_int64 iThreshold
+){
+  return sqlite3MemoryAlarm(xCallback, pArg, iThreshold);
+}
+#endif
+
+/*
+** Set the soft heap-size limit for the library. Passing a zero or 
+** negative value indicates no limit.
+*/
+sqlite3_int64 sqlite3_soft_heap_limit64(sqlite3_int64 n){
+  sqlite3_int64 priorLimit;
+  sqlite3_int64 excess;
+#ifndef SQLITE_OMIT_AUTOINIT
+  sqlite3_initialize();
+#endif
+  sqlite3_mutex_enter(mem0.mutex);
+  priorLimit = mem0.alarmThreshold;
+  sqlite3_mutex_leave(mem0.mutex);
+  if( n<0 ) return priorLimit;
+  if( n>0 ){
+    sqlite3MemoryAlarm(softHeapLimitEnforcer, 0, n);
+  }else{
+    sqlite3MemoryAlarm(0, 0, 0);
+  }
+  excess = sqlite3_memory_used() - n;
+  if( excess>0 ) sqlite3_release_memory((int)(excess & 0x7fffffff));
+  return priorLimit;
+}
+void sqlite3_soft_heap_limit(int n){
+  if( n<0 ) n = 0;
+  sqlite3_soft_heap_limit64(n);
+}
+
+/*
+** Initialize the memory allocation subsystem.
+*/
+int sqlite3MallocInit(void){
+  if( sqlite3GlobalConfig.m.xMalloc==0 ){
+    sqlite3MemSetDefault();
+  }
+  memset(&mem0, 0, sizeof(mem0));
+  if( sqlite3GlobalConfig.bCoreMutex ){
+    mem0.mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MEM);
+  }
+  if( sqlite3GlobalConfig.pScratch && sqlite3GlobalConfig.szScratch>=100
+      && sqlite3GlobalConfig.nScratch>0 ){
+    int i, n, sz;
+    ScratchFreeslot *pSlot;
+    sz = ROUNDDOWN8(sqlite3GlobalConfig.szScratch);
+    sqlite3GlobalConfig.szScratch = sz;
+    pSlot = (ScratchFreeslot*)sqlite3GlobalConfig.pScratch;
+    n = sqlite3GlobalConfig.nScratch;
+    mem0.pScratchFree = pSlot;
+    mem0.nScratchFree = n;
+    for(i=0; i<n-1; i++){
+      pSlot->pNext = (ScratchFreeslot*)(sz+(char*)pSlot);
+      pSlot = pSlot->pNext;
+    }
+    pSlot->pNext = 0;
+    mem0.pScratchEnd = (void*)&pSlot[1];
+  }else{
+    mem0.pScratchEnd = 0;
+    sqlite3GlobalConfig.pScratch = 0;
+    sqlite3GlobalConfig.szScratch = 0;
+    sqlite3GlobalConfig.nScratch = 0;
+  }
+  if( sqlite3GlobalConfig.pPage==0 || sqlite3GlobalConfig.szPage<512
+      || sqlite3GlobalConfig.nPage<1 ){
+    sqlite3GlobalConfig.pPage = 0;
+    sqlite3GlobalConfig.szPage = 0;
+    sqlite3GlobalConfig.nPage = 0;
+  }
+  return sqlite3GlobalConfig.m.xInit(sqlite3GlobalConfig.m.pAppData);
+}
+
+/*
+** Return true if the heap is currently under memory pressure - in other
+** words if the amount of heap used is close to the limit set by
+** sqlite3_soft_heap_limit().
+*/
+int sqlite3HeapNearlyFull(void){
+  return mem0.nearlyFull;
+}
+
+/*
+** Deinitialize the memory allocation subsystem.
+*/
+void sqlite3MallocEnd(void){
+  if( sqlite3GlobalConfig.m.xShutdown ){
+    sqlite3GlobalConfig.m.xShutdown(sqlite3GlobalConfig.m.pAppData);
+  }
+  memset(&mem0, 0, sizeof(mem0));
+}
+
+/*
+** Return the amount of memory currently checked out.
+*/
+sqlite3_int64 sqlite3_memory_used(void){
+  int n, mx;
+  sqlite3_int64 res;
+  sqlite3_status(SQLITE_STATUS_MEMORY_USED, &n, &mx, 0);
+  res = (sqlite3_int64)n;  /* Work around bug in Borland C. Ticket #3216 */
+  return res;
+}
+
+/*
+** Return the maximum amount of memory that has ever been
+** checked out since either the beginning of this process
+** or since the most recent reset.
+*/
+sqlite3_int64 sqlite3_memory_highwater(int resetFlag){
+  int n, mx;
+  sqlite3_int64 res;
+  sqlite3_status(SQLITE_STATUS_MEMORY_USED, &n, &mx, resetFlag);
+  res = (sqlite3_int64)mx;  /* Work around bug in Borland C. Ticket #3216 */
+  return res;
+}
+
+/*
+** Trigger the alarm 
+*/
+static void sqlite3MallocAlarm(int nByte){
+  void (*xCallback)(void*,sqlite3_int64,int);
+  sqlite3_int64 nowUsed;
+  void *pArg;
+  if( mem0.alarmCallback==0 ) return;
+  xCallback = mem0.alarmCallback;
+  nowUsed = sqlite3StatusValue(SQLITE_STATUS_MEMORY_USED);
+  pArg = mem0.alarmArg;
+  mem0.alarmCallback = 0;
+  sqlite3_mutex_leave(mem0.mutex);
+  xCallback(pArg, nowUsed, nByte);
+  sqlite3_mutex_enter(mem0.mutex);
+  mem0.alarmCallback = xCallback;
+  mem0.alarmArg = pArg;
+}
+
+/*
+** Do a memory allocation with statistics and alarms.  Assume the
+** lock is already held.
+*/
+static int mallocWithAlarm(int n, void **pp){
+  int nFull;
+  void *p;
+  assert( sqlite3_mutex_held(mem0.mutex) );
+  nFull = sqlite3GlobalConfig.m.xRoundup(n);
+  sqlite3StatusSet(SQLITE_STATUS_MALLOC_SIZE, n);
+  if( mem0.alarmCallback!=0 ){
+    int nUsed = sqlite3StatusValue(SQLITE_STATUS_MEMORY_USED);
+    if( nUsed >= mem0.alarmThreshold - nFull ){
+      mem0.nearlyFull = 1;
+      sqlite3MallocAlarm(nFull);
+    }else{
+      mem0.nearlyFull = 0;
+    }
+  }
+  p = sqlite3GlobalConfig.m.xMalloc(nFull);
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
+  if( p==0 && mem0.alarmCallback ){
+    sqlite3MallocAlarm(nFull);
+    p = sqlite3GlobalConfig.m.xMalloc(nFull);
+  }
+#endif
+  if( p ){
+    nFull = sqlite3MallocSize(p);
+    sqlite3StatusAdd(SQLITE_STATUS_MEMORY_USED, nFull);
+    sqlite3StatusAdd(SQLITE_STATUS_MALLOC_COUNT, 1);
+  }
+  *pp = p;
+  return nFull;
+}
+
+/*
+** Allocate memory.  This routine is like sqlite3_malloc() except that it
+** assumes the memory subsystem has already been initialized.
+*/
+void *sqlite3Malloc(int n){
+  void *p;
+  if( n<=0               /* IMP: R-65312-04917 */ 
+   || n>=0x7fffff00
+  ){
+    /* A memory allocation of a number of bytes which is near the maximum
+    ** signed integer value might cause an integer overflow inside of the
+    ** xMalloc().  Hence we limit the maximum size to 0x7fffff00, giving
+    ** 255 bytes of overhead.  SQLite itself will never use anything near
+    ** this amount.  The only way to reach the limit is with sqlite3_malloc() */
+    p = 0;
+  }else if( sqlite3GlobalConfig.bMemstat ){
+    sqlite3_mutex_enter(mem0.mutex);
+    mallocWithAlarm(n, &p);
+    sqlite3_mutex_leave(mem0.mutex);
+  }else{
+    p = sqlite3GlobalConfig.m.xMalloc(n);
+  }
+  assert( EIGHT_BYTE_ALIGNMENT(p) );  /* IMP: R-04675-44850 */
+  return p;
+}
+
+/*
+** This version of the memory allocation is for use by the application.
+** First make sure the memory subsystem is initialized, then do the
+** allocation.
+*/
+void *sqlite3_malloc(int n){
+#ifndef SQLITE_OMIT_AUTOINIT
+  if( sqlite3_initialize() ) return 0;
+#endif
+  return sqlite3Malloc(n);
+}
+
+/*
+** Each thread may only have a single outstanding allocation from
+** xScratchMalloc().  We verify this constraint in the single-threaded
+** case by setting scratchAllocOut to 1 when an allocation
+** is outstanding clearing it when the allocation is freed.
+*/
+#if SQLITE_THREADSAFE==0 && !defined(NDEBUG)
+static int scratchAllocOut = 0;
+#endif
+
+
+/*
+** Allocate memory that is to be used and released right away.
+** This routine is similar to alloca() in that it is not intended
+** for situations where the memory might be held long-term.  This
+** routine is intended to get memory to old large transient data
+** structures that would not normally fit on the stack of an
+** embedded processor.
+*/
+void *sqlite3ScratchMalloc(int n){
+  void *p;
+  assert( n>0 );
+
+  sqlite3_mutex_enter(mem0.mutex);
+  if( mem0.nScratchFree && sqlite3GlobalConfig.szScratch>=n ){
+    p = mem0.pScratchFree;
+    mem0.pScratchFree = mem0.pScratchFree->pNext;
+    mem0.nScratchFree--;
+    sqlite3StatusAdd(SQLITE_STATUS_SCRATCH_USED, 1);
+    sqlite3StatusSet(SQLITE_STATUS_SCRATCH_SIZE, n);
+    sqlite3_mutex_leave(mem0.mutex);
+  }else{
+    if( sqlite3GlobalConfig.bMemstat ){
+      sqlite3StatusSet(SQLITE_STATUS_SCRATCH_SIZE, n);
+      n = mallocWithAlarm(n, &p);
+      if( p ) sqlite3StatusAdd(SQLITE_STATUS_SCRATCH_OVERFLOW, n);
+      sqlite3_mutex_leave(mem0.mutex);
+    }else{
+      sqlite3_mutex_leave(mem0.mutex);
+      p = sqlite3GlobalConfig.m.xMalloc(n);
+    }
+    sqlite3MemdebugSetType(p, MEMTYPE_SCRATCH);
+  }
+  assert( sqlite3_mutex_notheld(mem0.mutex) );
+
+
+#if SQLITE_THREADSAFE==0 && !defined(NDEBUG)
+  /* Verify that no more than two scratch allocations per thread
+  ** are outstanding at one time.  (This is only checked in the
+  ** single-threaded case since checking in the multi-threaded case
+  ** would be much more complicated.) */
+  assert( scratchAllocOut<=1 );
+  if( p ) scratchAllocOut++;
+#endif
+
+  return p;
+}
+void sqlite3ScratchFree(void *p){
+  if( p ){
+
+#if SQLITE_THREADSAFE==0 && !defined(NDEBUG)
+    /* Verify that no more than two scratch allocation per thread
+    ** is outstanding at one time.  (This is only checked in the
+    ** single-threaded case since checking in the multi-threaded case
+    ** would be much more complicated.) */
+    assert( scratchAllocOut>=1 && scratchAllocOut<=2 );
+    scratchAllocOut--;
+#endif
+
+    if( p>=sqlite3GlobalConfig.pScratch && p<mem0.pScratchEnd ){
+      /* Release memory from the SQLITE_CONFIG_SCRATCH allocation */
+      ScratchFreeslot *pSlot;
+      pSlot = (ScratchFreeslot*)p;
+      sqlite3_mutex_enter(mem0.mutex);
+      pSlot->pNext = mem0.pScratchFree;
+      mem0.pScratchFree = pSlot;
+      mem0.nScratchFree++;
+      assert( mem0.nScratchFree <= (u32)sqlite3GlobalConfig.nScratch );
+      sqlite3StatusAdd(SQLITE_STATUS_SCRATCH_USED, -1);
+      sqlite3_mutex_leave(mem0.mutex);
+    }else{
+      /* Release memory back to the heap */
+      assert( sqlite3MemdebugHasType(p, MEMTYPE_SCRATCH) );
+      assert( sqlite3MemdebugNoType(p, ~MEMTYPE_SCRATCH) );
+      sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
+      if( sqlite3GlobalConfig.bMemstat ){
+        int iSize = sqlite3MallocSize(p);
+        sqlite3_mutex_enter(mem0.mutex);
+        sqlite3StatusAdd(SQLITE_STATUS_SCRATCH_OVERFLOW, -iSize);
+        sqlite3StatusAdd(SQLITE_STATUS_MEMORY_USED, -iSize);
+        sqlite3StatusAdd(SQLITE_STATUS_MALLOC_COUNT, -1);
+        sqlite3GlobalConfig.m.xFree(p);
+        sqlite3_mutex_leave(mem0.mutex);
+      }else{
+        sqlite3GlobalConfig.m.xFree(p);
+      }
+    }
+  }
+}
+
+/*
+** TRUE if p is a lookaside memory allocation from db
+*/
+#ifndef SQLITE_OMIT_LOOKASIDE
+static int isLookaside(sqlite3 *db, void *p){
+  return p && p>=db->lookaside.pStart && p<db->lookaside.pEnd;
+}
+#else
+#define isLookaside(A,B) 0
+#endif
+
+/*
+** Return the size of a memory allocation previously obtained from
+** sqlite3Malloc() or sqlite3_malloc().
+*/
+int sqlite3MallocSize(void *p){
+  assert( sqlite3MemdebugHasType(p, MEMTYPE_HEAP) );
+  assert( sqlite3MemdebugNoType(p, MEMTYPE_DB) );
+  return sqlite3GlobalConfig.m.xSize(p);
+}
+int sqlite3DbMallocSize(sqlite3 *db, void *p){
+  assert( db==0 || sqlite3_mutex_held(db->mutex) );
+  if( db && isLookaside(db, p) ){
+    return db->lookaside.sz;
+  }else{
+    assert( sqlite3MemdebugHasType(p, MEMTYPE_DB) );
+    assert( sqlite3MemdebugHasType(p, MEMTYPE_LOOKASIDE|MEMTYPE_HEAP) );
+    assert( db!=0 || sqlite3MemdebugNoType(p, MEMTYPE_LOOKASIDE) );
+    return sqlite3GlobalConfig.m.xSize(p);
+  }
+}
+
+/*
+** Free memory previously obtained from sqlite3Malloc().
+*/
+void sqlite3_free(void *p){
+  if( p==0 ) return;  /* IMP: R-49053-54554 */
+  assert( sqlite3MemdebugNoType(p, MEMTYPE_DB) );
+  assert( sqlite3MemdebugHasType(p, MEMTYPE_HEAP) );
+  if( sqlite3GlobalConfig.bMemstat ){
+    sqlite3_mutex_enter(mem0.mutex);
+    sqlite3StatusAdd(SQLITE_STATUS_MEMORY_USED, -sqlite3MallocSize(p));
+    sqlite3StatusAdd(SQLITE_STATUS_MALLOC_COUNT, -1);
+    sqlite3GlobalConfig.m.xFree(p);
+    sqlite3_mutex_leave(mem0.mutex);
+  }else{
+    sqlite3GlobalConfig.m.xFree(p);
+  }
+}
+
+/*
+** Free memory that might be associated with a particular database
+** connection.
+*/
+void sqlite3DbFree(sqlite3 *db, void *p){
+  assert( db==0 || sqlite3_mutex_held(db->mutex) );
+  if( db ){
+    if( db->pnBytesFreed ){
+      *db->pnBytesFreed += sqlite3DbMallocSize(db, p);
+      return;
+    }
+    if( isLookaside(db, p) ){
+      LookasideSlot *pBuf = (LookasideSlot*)p;
+      pBuf->pNext = db->lookaside.pFree;
+      db->lookaside.pFree = pBuf;
+      db->lookaside.nOut--;
+      return;
+    }
+  }
+  assert( sqlite3MemdebugHasType(p, MEMTYPE_DB) );
+  assert( sqlite3MemdebugHasType(p, MEMTYPE_LOOKASIDE|MEMTYPE_HEAP) );
+  assert( db!=0 || sqlite3MemdebugNoType(p, MEMTYPE_LOOKASIDE) );
+  sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
+  sqlite3_free(p);
+}
+
+/*
+** Change the size of an existing memory allocation
+*/
+void *sqlite3Realloc(void *pOld, int nBytes){
+  int nOld, nNew, nDiff;
+  void *pNew;
+  if( pOld==0 ){
+    return sqlite3Malloc(nBytes); /* IMP: R-28354-25769 */
+  }
+  if( nBytes<=0 ){
+    sqlite3_free(pOld); /* IMP: R-31593-10574 */
+    return 0;
+  }
+  if( nBytes>=0x7fffff00 ){
+    /* The 0x7ffff00 limit term is explained in comments on sqlite3Malloc() */
+    return 0;
+  }
+  nOld = sqlite3MallocSize(pOld);
+  /* IMPLEMENTATION-OF: R-46199-30249 SQLite guarantees that the second
+  ** argument to xRealloc is always a value returned by a prior call to
+  ** xRoundup. */
+  nNew = sqlite3GlobalConfig.m.xRoundup(nBytes);
+  if( nOld==nNew ){
+    pNew = pOld;
+  }else if( sqlite3GlobalConfig.bMemstat ){
+    sqlite3_mutex_enter(mem0.mutex);
+    sqlite3StatusSet(SQLITE_STATUS_MALLOC_SIZE, nBytes);
+    nDiff = nNew - nOld;
+    if( sqlite3StatusValue(SQLITE_STATUS_MEMORY_USED) >= 
+          mem0.alarmThreshold-nDiff ){
+      sqlite3MallocAlarm(nDiff);
+    }
+    assert( sqlite3MemdebugHasType(pOld, MEMTYPE_HEAP) );
+    assert( sqlite3MemdebugNoType(pOld, ~MEMTYPE_HEAP) );
+    pNew = sqlite3GlobalConfig.m.xRealloc(pOld, nNew);
+    if( pNew==0 && mem0.alarmCallback ){
+      sqlite3MallocAlarm(nBytes);
+      pNew = sqlite3GlobalConfig.m.xRealloc(pOld, nNew);
+    }
+    if( pNew ){
+      nNew = sqlite3MallocSize(pNew);
+      sqlite3StatusAdd(SQLITE_STATUS_MEMORY_USED, nNew-nOld);
+    }
+    sqlite3_mutex_leave(mem0.mutex);
+  }else{
+    pNew = sqlite3GlobalConfig.m.xRealloc(pOld, nNew);
+  }
+  assert( EIGHT_BYTE_ALIGNMENT(pNew) ); /* IMP: R-04675-44850 */
+  return pNew;
+}
+
+/*
+** The public interface to sqlite3Realloc.  Make sure that the memory
+** subsystem is initialized prior to invoking sqliteRealloc.
+*/
+void *sqlite3_realloc(void *pOld, int n){
+#ifndef SQLITE_OMIT_AUTOINIT
+  if( sqlite3_initialize() ) return 0;
+#endif
+  return sqlite3Realloc(pOld, n);
+}
+
+
+/*
+** Allocate and zero memory.
+*/ 
+void *sqlite3MallocZero(int n){
+  void *p = sqlite3Malloc(n);
+  if( p ){
+    memset(p, 0, n);
+  }
+  return p;
+}
+
+/*
+** Allocate and zero memory.  If the allocation fails, make
+** the mallocFailed flag in the connection pointer.
+*/
+void *sqlite3DbMallocZero(sqlite3 *db, int n){
+  void *p = sqlite3DbMallocRaw(db, n);
+  if( p ){
+    memset(p, 0, n);
+  }
+  return p;
+}
+
+/*
+** Allocate and zero memory.  If the allocation fails, make
+** the mallocFailed flag in the connection pointer.
+**
+** If db!=0 and db->mallocFailed is true (indicating a prior malloc
+** failure on the same database connection) then always return 0.
+** Hence for a particular database connection, once malloc starts
+** failing, it fails consistently until mallocFailed is reset.
+** This is an important assumption.  There are many places in the
+** code that do things like this:
+**
+**         int *a = (int*)sqlite3DbMallocRaw(db, 100);
+**         int *b = (int*)sqlite3DbMallocRaw(db, 200);
+**         if( b ) a[10] = 9;
+**
+** In other words, if a subsequent malloc (ex: "b") worked, it is assumed
+** that all prior mallocs (ex: "a") worked too.
+*/
+void *sqlite3DbMallocRaw(sqlite3 *db, int n){
+  void *p;
+  assert( db==0 || sqlite3_mutex_held(db->mutex) );
+  assert( db==0 || db->pnBytesFreed==0 );
+#ifndef SQLITE_OMIT_LOOKASIDE
+  if( db ){
+    LookasideSlot *pBuf;
+    if( db->mallocFailed ){
+      return 0;
+    }
+    if( db->lookaside.bEnabled ){
+      if( n>db->lookaside.sz ){
+        db->lookaside.anStat[1]++;
+      }else if( (pBuf = db->lookaside.pFree)==0 ){
+        db->lookaside.anStat[2]++;
+      }else{
+        db->lookaside.pFree = pBuf->pNext;
+        db->lookaside.nOut++;
+        db->lookaside.anStat[0]++;
+        if( db->lookaside.nOut>db->lookaside.mxOut ){
+          db->lookaside.mxOut = db->lookaside.nOut;
+        }
+        return (void*)pBuf;
+      }
+    }
+  }
+#else
+  if( db && db->mallocFailed ){
+    return 0;
+  }
+#endif
+  p = sqlite3Malloc(n);
+  if( !p && db ){
+    db->mallocFailed = 1;
+  }
+  sqlite3MemdebugSetType(p, MEMTYPE_DB |
+         ((db && db->lookaside.bEnabled) ? MEMTYPE_LOOKASIDE : MEMTYPE_HEAP));
+  return p;
+}
+
+/*
+** Resize the block of memory pointed to by p to n bytes. If the
+** resize fails, set the mallocFailed flag in the connection object.
+*/
+void *sqlite3DbRealloc(sqlite3 *db, void *p, int n){
+  void *pNew = 0;
+  assert( db!=0 );
+  assert( sqlite3_mutex_held(db->mutex) );
+  if( db->mallocFailed==0 ){
+    if( p==0 ){
+      return sqlite3DbMallocRaw(db, n);
+    }
+    if( isLookaside(db, p) ){
+      if( n<=db->lookaside.sz ){
+        return p;
+      }
+      pNew = sqlite3DbMallocRaw(db, n);
+      if( pNew ){
+        memcpy(pNew, p, db->lookaside.sz);
+        sqlite3DbFree(db, p);
+      }
+    }else{
+      assert( sqlite3MemdebugHasType(p, MEMTYPE_DB) );
+      assert( sqlite3MemdebugHasType(p, MEMTYPE_LOOKASIDE|MEMTYPE_HEAP) );
+      sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
+      pNew = sqlite3_realloc(p, n);
+      if( !pNew ){
+        sqlite3MemdebugSetType(p, MEMTYPE_DB|MEMTYPE_HEAP);
+        db->mallocFailed = 1;
+      }
+      sqlite3MemdebugSetType(pNew, MEMTYPE_DB | 
+            (db->lookaside.bEnabled ? MEMTYPE_LOOKASIDE : MEMTYPE_HEAP));
+    }
+  }
+  return pNew;
+}
+
+/*
+** Attempt to reallocate p.  If the reallocation fails, then free p
+** and set the mallocFailed flag in the database connection.
+*/
+void *sqlite3DbReallocOrFree(sqlite3 *db, void *p, int n){
+  void *pNew;
+  pNew = sqlite3DbRealloc(db, p, n);
+  if( !pNew ){
+    sqlite3DbFree(db, p);
+  }
+  return pNew;
+}
+
+/*
+** Make a copy of a string in memory obtained from sqliteMalloc(). These 
+** functions call sqlite3MallocRaw() directly instead of sqliteMalloc(). This
+** is because when memory debugging is turned on, these two functions are 
+** called via macros that record the current file and line number in the
+** ThreadData structure.
+*/
+char *sqlite3DbStrDup(sqlite3 *db, const char *z){
+  char *zNew;
+  size_t n;
+  if( z==0 ){
+    return 0;
+  }
+  n = sqlite3Strlen30(z) + 1;
+  assert( (n&0x7fffffff)==n );
+  zNew = sqlite3DbMallocRaw(db, (int)n);
+  if( zNew ){
+    memcpy(zNew, z, n);
+  }
+  return zNew;
+}
+char *sqlite3DbStrNDup(sqlite3 *db, const char *z, int n){
+  char *zNew;
+  if( z==0 ){
+    return 0;
+  }
+  assert( (n&0x7fffffff)==n );
+  zNew = sqlite3DbMallocRaw(db, n+1);
+  if( zNew ){
+    memcpy(zNew, z, n);
+    zNew[n] = 0;
+  }
+  return zNew;
+}
+
+/*
+** Create a string from the zFromat argument and the va_list that follows.
+** Store the string in memory obtained from sqliteMalloc() and make *pz
+** point to that string.
+*/
+void sqlite3SetString(char **pz, sqlite3 *db, const char *zFormat, ...){
+  va_list ap;
+  char *z;
+
+  va_start(ap, zFormat);
+  z = sqlite3VMPrintf(db, zFormat, ap);
+  va_end(ap);
+  sqlite3DbFree(db, *pz);
+  *pz = z;
+}
+
+
+/*
+** This function must be called before exiting any API function (i.e. 
+** returning control to the user) that has called sqlite3_malloc or
+** sqlite3_realloc.
+**
+** The returned value is normally a copy of the second argument to this
+** function. However, if a malloc() failure has occurred since the previous
+** invocation SQLITE_NOMEM is returned instead. 
+**
+** If the first argument, db, is not NULL and a malloc() error has occurred,
+** then the connection error-code (the value returned by sqlite3_errcode())
+** is set to SQLITE_NOMEM.
+*/
+int sqlite3ApiExit(sqlite3* db, int rc){
+  /* If the db handle is not NULL, then we must hold the connection handle
+  ** mutex here. Otherwise the read (and possible write) of db->mallocFailed 
+  ** is unsafe, as is the call to sqlite3Error().
+  */
+  assert( !db || sqlite3_mutex_held(db->mutex) );
+  if( db && (db->mallocFailed || rc==SQLITE_IOERR_NOMEM) ){
+    sqlite3Error(db, SQLITE_NOMEM, 0);
+    db->mallocFailed = 0;
+    rc = SQLITE_NOMEM;
+  }
+  return rc & (db ? db->errMask : 0xff);
+}
diff --git a/src/mem0.c b/src/mem0.c
new file mode 100644
index 0000000..0d0b666
--- /dev/null
+++ b/src/mem0.c
@@ -0,0 +1,59 @@
+/*
+** 2008 October 28
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains a no-op memory allocation drivers for use when
+** SQLITE_ZERO_MALLOC is defined.  The allocation drivers implemented
+** here always fail.  SQLite will not operate with these drivers.  These
+** are merely placeholders.  Real drivers must be substituted using
+** sqlite3_config() before SQLite will operate.
+*/
+#include "sqliteInt.h"
+
+/*
+** This version of the memory allocator is the default.  It is
+** used when no other memory allocator is specified using compile-time
+** macros.
+*/
+#ifdef SQLITE_ZERO_MALLOC
+
+/*
+** No-op versions of all memory allocation routines
+*/
+static void *sqlite3MemMalloc(int nByte){ return 0; }
+static void sqlite3MemFree(void *pPrior){ return; }
+static void *sqlite3MemRealloc(void *pPrior, int nByte){ return 0; }
+static int sqlite3MemSize(void *pPrior){ return 0; }
+static int sqlite3MemRoundup(int n){ return n; }
+static int sqlite3MemInit(void *NotUsed){ return SQLITE_OK; }
+static void sqlite3MemShutdown(void *NotUsed){ return; }
+
+/*
+** This routine is the only routine in this file with external linkage.
+**
+** Populate the low-level memory allocation function pointers in
+** sqlite3GlobalConfig.m with pointers to the routines in this file.
+*/
+void sqlite3MemSetDefault(void){
+  static const sqlite3_mem_methods defaultMethods = {
+     sqlite3MemMalloc,
+     sqlite3MemFree,
+     sqlite3MemRealloc,
+     sqlite3MemSize,
+     sqlite3MemRoundup,
+     sqlite3MemInit,
+     sqlite3MemShutdown,
+     0
+  };
+  sqlite3_config(SQLITE_CONFIG_MALLOC, &defaultMethods);
+}
+
+#endif /* SQLITE_ZERO_MALLOC */
diff --git a/src/mem1.c b/src/mem1.c
new file mode 100644
index 0000000..61fbf4b
--- /dev/null
+++ b/src/mem1.c
@@ -0,0 +1,150 @@
+/*
+** 2007 August 14
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains low-level memory allocation drivers for when
+** SQLite will use the standard C-library malloc/realloc/free interface
+** to obtain the memory it needs.
+**
+** This file contains implementations of the low-level memory allocation
+** routines specified in the sqlite3_mem_methods object.
+*/
+#include "sqliteInt.h"
+
+/*
+** This version of the memory allocator is the default.  It is
+** used when no other memory allocator is specified using compile-time
+** macros.
+*/
+#ifdef SQLITE_SYSTEM_MALLOC
+
+/*
+** Like malloc(), but remember the size of the allocation
+** so that we can find it later using sqlite3MemSize().
+**
+** For this low-level routine, we are guaranteed that nByte>0 because
+** cases of nByte<=0 will be intercepted and dealt with by higher level
+** routines.
+*/
+static void *sqlite3MemMalloc(int nByte){
+  sqlite3_int64 *p;
+  assert( nByte>0 );
+  nByte = ROUND8(nByte);
+  p = malloc( nByte+8 );
+  if( p ){
+    p[0] = nByte;
+    p++;
+  }else{
+    testcase( sqlite3GlobalConfig.xLog!=0 );
+    sqlite3_log(SQLITE_NOMEM, "failed to allocate %u bytes of memory", nByte);
+  }
+  return (void *)p;
+}
+
+/*
+** Like free() but works for allocations obtained from sqlite3MemMalloc()
+** or sqlite3MemRealloc().
+**
+** For this low-level routine, we already know that pPrior!=0 since
+** cases where pPrior==0 will have been intecepted and dealt with
+** by higher-level routines.
+*/
+static void sqlite3MemFree(void *pPrior){
+  sqlite3_int64 *p = (sqlite3_int64*)pPrior;
+  assert( pPrior!=0 );
+  p--;
+  free(p);
+}
+
+/*
+** Report the allocated size of a prior return from xMalloc()
+** or xRealloc().
+*/
+static int sqlite3MemSize(void *pPrior){
+  sqlite3_int64 *p;
+  if( pPrior==0 ) return 0;
+  p = (sqlite3_int64*)pPrior;
+  p--;
+  return (int)p[0];
+}
+
+/*
+** Like realloc().  Resize an allocation previously obtained from
+** sqlite3MemMalloc().
+**
+** For this low-level interface, we know that pPrior!=0.  Cases where
+** pPrior==0 while have been intercepted by higher-level routine and
+** redirected to xMalloc.  Similarly, we know that nByte>0 becauses
+** cases where nByte<=0 will have been intercepted by higher-level
+** routines and redirected to xFree.
+*/
+static void *sqlite3MemRealloc(void *pPrior, int nByte){
+  sqlite3_int64 *p = (sqlite3_int64*)pPrior;
+  assert( pPrior!=0 && nByte>0 );
+  assert( nByte==ROUND8(nByte) ); /* EV: R-46199-30249 */
+  p--;
+  p = realloc(p, nByte+8 );
+  if( p ){
+    p[0] = nByte;
+    p++;
+  }else{
+    testcase( sqlite3GlobalConfig.xLog!=0 );
+    sqlite3_log(SQLITE_NOMEM,
+      "failed memory resize %u to %u bytes",
+      sqlite3MemSize(pPrior), nByte);
+  }
+  return (void*)p;
+}
+
+/*
+** Round up a request size to the next valid allocation size.
+*/
+static int sqlite3MemRoundup(int n){
+  return ROUND8(n);
+}
+
+/*
+** Initialize this module.
+*/
+static int sqlite3MemInit(void *NotUsed){
+  UNUSED_PARAMETER(NotUsed);
+  return SQLITE_OK;
+}
+
+/*
+** Deinitialize this module.
+*/
+static void sqlite3MemShutdown(void *NotUsed){
+  UNUSED_PARAMETER(NotUsed);
+  return;
+}
+
+/*
+** This routine is the only routine in this file with external linkage.
+**
+** Populate the low-level memory allocation function pointers in
+** sqlite3GlobalConfig.m with pointers to the routines in this file.
+*/
+void sqlite3MemSetDefault(void){
+  static const sqlite3_mem_methods defaultMethods = {
+     sqlite3MemMalloc,
+     sqlite3MemFree,
+     sqlite3MemRealloc,
+     sqlite3MemSize,
+     sqlite3MemRoundup,
+     sqlite3MemInit,
+     sqlite3MemShutdown,
+     0
+  };
+  sqlite3_config(SQLITE_CONFIG_MALLOC, &defaultMethods);
+}
+
+#endif /* SQLITE_SYSTEM_MALLOC */
diff --git a/src/mem2.c b/src/mem2.c
new file mode 100644
index 0000000..26448ea
--- /dev/null
+++ b/src/mem2.c
@@ -0,0 +1,528 @@
+/*
+** 2007 August 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains low-level memory allocation drivers for when
+** SQLite will use the standard C-library malloc/realloc/free interface
+** to obtain the memory it needs while adding lots of additional debugging
+** information to each allocation in order to help detect and fix memory
+** leaks and memory usage errors.
+**
+** This file contains implementations of the low-level memory allocation
+** routines specified in the sqlite3_mem_methods object.
+*/
+#include "sqliteInt.h"
+
+/*
+** This version of the memory allocator is used only if the
+** SQLITE_MEMDEBUG macro is defined
+*/
+#ifdef SQLITE_MEMDEBUG
+
+/*
+** The backtrace functionality is only available with GLIBC
+*/
+#ifdef __GLIBC__
+  extern int backtrace(void**,int);
+  extern void backtrace_symbols_fd(void*const*,int,int);
+#else
+# define backtrace(A,B) 1
+# define backtrace_symbols_fd(A,B,C)
+#endif
+#include <stdio.h>
+
+/*
+** Each memory allocation looks like this:
+**
+**  ------------------------------------------------------------------------
+**  | Title |  backtrace pointers |  MemBlockHdr |  allocation |  EndGuard |
+**  ------------------------------------------------------------------------
+**
+** The application code sees only a pointer to the allocation.  We have
+** to back up from the allocation pointer to find the MemBlockHdr.  The
+** MemBlockHdr tells us the size of the allocation and the number of
+** backtrace pointers.  There is also a guard word at the end of the
+** MemBlockHdr.
+*/
+struct MemBlockHdr {
+  i64 iSize;                          /* Size of this allocation */
+  struct MemBlockHdr *pNext, *pPrev;  /* Linked list of all unfreed memory */
+  char nBacktrace;                    /* Number of backtraces on this alloc */
+  char nBacktraceSlots;               /* Available backtrace slots */
+  u8 nTitle;                          /* Bytes of title; includes '\0' */
+  u8 eType;                           /* Allocation type code */
+  int iForeGuard;                     /* Guard word for sanity */
+};
+
+/*
+** Guard words
+*/
+#define FOREGUARD 0x80F5E153
+#define REARGUARD 0xE4676B53
+
+/*
+** Number of malloc size increments to track.
+*/
+#define NCSIZE  1000
+
+/*
+** All of the static variables used by this module are collected
+** into a single structure named "mem".  This is to keep the
+** static variables organized and to reduce namespace pollution
+** when this module is combined with other in the amalgamation.
+*/
+static struct {
+  
+  /*
+  ** Mutex to control access to the memory allocation subsystem.
+  */
+  sqlite3_mutex *mutex;
+
+  /*
+  ** Head and tail of a linked list of all outstanding allocations
+  */
+  struct MemBlockHdr *pFirst;
+  struct MemBlockHdr *pLast;
+  
+  /*
+  ** The number of levels of backtrace to save in new allocations.
+  */
+  int nBacktrace;
+  void (*xBacktrace)(int, int, void **);
+
+  /*
+  ** Title text to insert in front of each block
+  */
+  int nTitle;        /* Bytes of zTitle to save.  Includes '\0' and padding */
+  char zTitle[100];  /* The title text */
+
+  /* 
+  ** sqlite3MallocDisallow() increments the following counter.
+  ** sqlite3MallocAllow() decrements it.
+  */
+  int disallow; /* Do not allow memory allocation */
+
+  /*
+  ** Gather statistics on the sizes of memory allocations.
+  ** nAlloc[i] is the number of allocation attempts of i*8
+  ** bytes.  i==NCSIZE is the number of allocation attempts for
+  ** sizes more than NCSIZE*8 bytes.
+  */
+  int nAlloc[NCSIZE];      /* Total number of allocations */
+  int nCurrent[NCSIZE];    /* Current number of allocations */
+  int mxCurrent[NCSIZE];   /* Highwater mark for nCurrent */
+
+} mem;
+
+
+/*
+** Adjust memory usage statistics
+*/
+static void adjustStats(int iSize, int increment){
+  int i = ROUND8(iSize)/8;
+  if( i>NCSIZE-1 ){
+    i = NCSIZE - 1;
+  }
+  if( increment>0 ){
+    mem.nAlloc[i]++;
+    mem.nCurrent[i]++;
+    if( mem.nCurrent[i]>mem.mxCurrent[i] ){
+      mem.mxCurrent[i] = mem.nCurrent[i];
+    }
+  }else{
+    mem.nCurrent[i]--;
+    assert( mem.nCurrent[i]>=0 );
+  }
+}
+
+/*
+** Given an allocation, find the MemBlockHdr for that allocation.
+**
+** This routine checks the guards at either end of the allocation and
+** if they are incorrect it asserts.
+*/
+static struct MemBlockHdr *sqlite3MemsysGetHeader(void *pAllocation){
+  struct MemBlockHdr *p;
+  int *pInt;
+  u8 *pU8;
+  int nReserve;
+
+  p = (struct MemBlockHdr*)pAllocation;
+  p--;
+  assert( p->iForeGuard==(int)FOREGUARD );
+  nReserve = ROUND8(p->iSize);
+  pInt = (int*)pAllocation;
+  pU8 = (u8*)pAllocation;
+  assert( pInt[nReserve/sizeof(int)]==(int)REARGUARD );
+  /* This checks any of the "extra" bytes allocated due
+  ** to rounding up to an 8 byte boundary to ensure 
+  ** they haven't been overwritten.
+  */
+  while( nReserve-- > p->iSize ) assert( pU8[nReserve]==0x65 );
+  return p;
+}
+
+/*
+** Return the number of bytes currently allocated at address p.
+*/
+static int sqlite3MemSize(void *p){
+  struct MemBlockHdr *pHdr;
+  if( !p ){
+    return 0;
+  }
+  pHdr = sqlite3MemsysGetHeader(p);
+  return pHdr->iSize;
+}
+
+/*
+** Initialize the memory allocation subsystem.
+*/
+static int sqlite3MemInit(void *NotUsed){
+  UNUSED_PARAMETER(NotUsed);
+  assert( (sizeof(struct MemBlockHdr)&7) == 0 );
+  if( !sqlite3GlobalConfig.bMemstat ){
+    /* If memory status is enabled, then the malloc.c wrapper will already
+    ** hold the STATIC_MEM mutex when the routines here are invoked. */
+    mem.mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MEM);
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Deinitialize the memory allocation subsystem.
+*/
+static void sqlite3MemShutdown(void *NotUsed){
+  UNUSED_PARAMETER(NotUsed);
+  mem.mutex = 0;
+}
+
+/*
+** Round up a request size to the next valid allocation size.
+*/
+static int sqlite3MemRoundup(int n){
+  return ROUND8(n);
+}
+
+/*
+** Fill a buffer with pseudo-random bytes.  This is used to preset
+** the content of a new memory allocation to unpredictable values and
+** to clear the content of a freed allocation to unpredictable values.
+*/
+static void randomFill(char *pBuf, int nByte){
+  unsigned int x, y, r;
+  x = SQLITE_PTR_TO_INT(pBuf);
+  y = nByte | 1;
+  while( nByte >= 4 ){
+    x = (x>>1) ^ (-(x&1) & 0xd0000001);
+    y = y*1103515245 + 12345;
+    r = x ^ y;
+    *(int*)pBuf = r;
+    pBuf += 4;
+    nByte -= 4;
+  }
+  while( nByte-- > 0 ){
+    x = (x>>1) ^ (-(x&1) & 0xd0000001);
+    y = y*1103515245 + 12345;
+    r = x ^ y;
+    *(pBuf++) = r & 0xff;
+  }
+}
+
+/*
+** Allocate nByte bytes of memory.
+*/
+static void *sqlite3MemMalloc(int nByte){
+  struct MemBlockHdr *pHdr;
+  void **pBt;
+  char *z;
+  int *pInt;
+  void *p = 0;
+  int totalSize;
+  int nReserve;
+  sqlite3_mutex_enter(mem.mutex);
+  assert( mem.disallow==0 );
+  nReserve = ROUND8(nByte);
+  totalSize = nReserve + sizeof(*pHdr) + sizeof(int) +
+               mem.nBacktrace*sizeof(void*) + mem.nTitle;
+  p = malloc(totalSize);
+  if( p ){
+    z = p;
+    pBt = (void**)&z[mem.nTitle];
+    pHdr = (struct MemBlockHdr*)&pBt[mem.nBacktrace];
+    pHdr->pNext = 0;
+    pHdr->pPrev = mem.pLast;
+    if( mem.pLast ){
+      mem.pLast->pNext = pHdr;
+    }else{
+      mem.pFirst = pHdr;
+    }
+    mem.pLast = pHdr;
+    pHdr->iForeGuard = FOREGUARD;
+    pHdr->eType = MEMTYPE_HEAP;
+    pHdr->nBacktraceSlots = mem.nBacktrace;
+    pHdr->nTitle = mem.nTitle;
+    if( mem.nBacktrace ){
+      void *aAddr[40];
+      pHdr->nBacktrace = backtrace(aAddr, mem.nBacktrace+1)-1;
+      memcpy(pBt, &aAddr[1], pHdr->nBacktrace*sizeof(void*));
+      assert(pBt[0]);
+      if( mem.xBacktrace ){
+        mem.xBacktrace(nByte, pHdr->nBacktrace-1, &aAddr[1]);
+      }
+    }else{
+      pHdr->nBacktrace = 0;
+    }
+    if( mem.nTitle ){
+      memcpy(z, mem.zTitle, mem.nTitle);
+    }
+    pHdr->iSize = nByte;
+    adjustStats(nByte, +1);
+    pInt = (int*)&pHdr[1];
+    pInt[nReserve/sizeof(int)] = REARGUARD;
+    randomFill((char*)pInt, nByte);
+    memset(((char*)pInt)+nByte, 0x65, nReserve-nByte);
+    p = (void*)pInt;
+  }
+  sqlite3_mutex_leave(mem.mutex);
+  return p; 
+}
+
+/*
+** Free memory.
+*/
+static void sqlite3MemFree(void *pPrior){
+  struct MemBlockHdr *pHdr;
+  void **pBt;
+  char *z;
+  assert( sqlite3GlobalConfig.bMemstat || sqlite3GlobalConfig.bCoreMutex==0 
+       || mem.mutex!=0 );
+  pHdr = sqlite3MemsysGetHeader(pPrior);
+  pBt = (void**)pHdr;
+  pBt -= pHdr->nBacktraceSlots;
+  sqlite3_mutex_enter(mem.mutex);
+  if( pHdr->pPrev ){
+    assert( pHdr->pPrev->pNext==pHdr );
+    pHdr->pPrev->pNext = pHdr->pNext;
+  }else{
+    assert( mem.pFirst==pHdr );
+    mem.pFirst = pHdr->pNext;
+  }
+  if( pHdr->pNext ){
+    assert( pHdr->pNext->pPrev==pHdr );
+    pHdr->pNext->pPrev = pHdr->pPrev;
+  }else{
+    assert( mem.pLast==pHdr );
+    mem.pLast = pHdr->pPrev;
+  }
+  z = (char*)pBt;
+  z -= pHdr->nTitle;
+  adjustStats(pHdr->iSize, -1);
+  randomFill(z, sizeof(void*)*pHdr->nBacktraceSlots + sizeof(*pHdr) +
+                pHdr->iSize + sizeof(int) + pHdr->nTitle);
+  free(z);
+  sqlite3_mutex_leave(mem.mutex);  
+}
+
+/*
+** Change the size of an existing memory allocation.
+**
+** For this debugging implementation, we *always* make a copy of the
+** allocation into a new place in memory.  In this way, if the 
+** higher level code is using pointer to the old allocation, it is 
+** much more likely to break and we are much more liking to find
+** the error.
+*/
+static void *sqlite3MemRealloc(void *pPrior, int nByte){
+  struct MemBlockHdr *pOldHdr;
+  void *pNew;
+  assert( mem.disallow==0 );
+  assert( (nByte & 7)==0 );     /* EV: R-46199-30249 */
+  pOldHdr = sqlite3MemsysGetHeader(pPrior);
+  pNew = sqlite3MemMalloc(nByte);
+  if( pNew ){
+    memcpy(pNew, pPrior, nByte<pOldHdr->iSize ? nByte : pOldHdr->iSize);
+    if( nByte>pOldHdr->iSize ){
+      randomFill(&((char*)pNew)[pOldHdr->iSize], nByte - pOldHdr->iSize);
+    }
+    sqlite3MemFree(pPrior);
+  }
+  return pNew;
+}
+
+/*
+** Populate the low-level memory allocation function pointers in
+** sqlite3GlobalConfig.m with pointers to the routines in this file.
+*/
+void sqlite3MemSetDefault(void){
+  static const sqlite3_mem_methods defaultMethods = {
+     sqlite3MemMalloc,
+     sqlite3MemFree,
+     sqlite3MemRealloc,
+     sqlite3MemSize,
+     sqlite3MemRoundup,
+     sqlite3MemInit,
+     sqlite3MemShutdown,
+     0
+  };
+  sqlite3_config(SQLITE_CONFIG_MALLOC, &defaultMethods);
+}
+
+/*
+** Set the "type" of an allocation.
+*/
+void sqlite3MemdebugSetType(void *p, u8 eType){
+  if( p && sqlite3GlobalConfig.m.xMalloc==sqlite3MemMalloc ){
+    struct MemBlockHdr *pHdr;
+    pHdr = sqlite3MemsysGetHeader(p);
+    assert( pHdr->iForeGuard==FOREGUARD );
+    pHdr->eType = eType;
+  }
+}
+
+/*
+** Return TRUE if the mask of type in eType matches the type of the
+** allocation p.  Also return true if p==NULL.
+**
+** This routine is designed for use within an assert() statement, to
+** verify the type of an allocation.  For example:
+**
+**     assert( sqlite3MemdebugHasType(p, MEMTYPE_DB) );
+*/
+int sqlite3MemdebugHasType(void *p, u8 eType){
+  int rc = 1;
+  if( p && sqlite3GlobalConfig.m.xMalloc==sqlite3MemMalloc ){
+    struct MemBlockHdr *pHdr;
+    pHdr = sqlite3MemsysGetHeader(p);
+    assert( pHdr->iForeGuard==FOREGUARD );         /* Allocation is valid */
+    if( (pHdr->eType&eType)==0 ){
+      rc = 0;
+    }
+  }
+  return rc;
+}
+
+/*
+** Return TRUE if the mask of type in eType matches no bits of the type of the
+** allocation p.  Also return true if p==NULL.
+**
+** This routine is designed for use within an assert() statement, to
+** verify the type of an allocation.  For example:
+**
+**     assert( sqlite3MemdebugNoType(p, MEMTYPE_DB) );
+*/
+int sqlite3MemdebugNoType(void *p, u8 eType){
+  int rc = 1;
+  if( p && sqlite3GlobalConfig.m.xMalloc==sqlite3MemMalloc ){
+    struct MemBlockHdr *pHdr;
+    pHdr = sqlite3MemsysGetHeader(p);
+    assert( pHdr->iForeGuard==FOREGUARD );         /* Allocation is valid */
+    if( (pHdr->eType&eType)!=0 ){
+      rc = 0;
+    }
+  }
+  return rc;
+}
+
+/*
+** Set the number of backtrace levels kept for each allocation.
+** A value of zero turns off backtracing.  The number is always rounded
+** up to a multiple of 2.
+*/
+void sqlite3MemdebugBacktrace(int depth){
+  if( depth<0 ){ depth = 0; }
+  if( depth>20 ){ depth = 20; }
+  depth = (depth+1)&0xfe;
+  mem.nBacktrace = depth;
+}
+
+void sqlite3MemdebugBacktraceCallback(void (*xBacktrace)(int, int, void **)){
+  mem.xBacktrace = xBacktrace;
+}
+
+/*
+** Set the title string for subsequent allocations.
+*/
+void sqlite3MemdebugSettitle(const char *zTitle){
+  unsigned int n = sqlite3Strlen30(zTitle) + 1;
+  sqlite3_mutex_enter(mem.mutex);
+  if( n>=sizeof(mem.zTitle) ) n = sizeof(mem.zTitle)-1;
+  memcpy(mem.zTitle, zTitle, n);
+  mem.zTitle[n] = 0;
+  mem.nTitle = ROUND8(n);
+  sqlite3_mutex_leave(mem.mutex);
+}
+
+void sqlite3MemdebugSync(){
+  struct MemBlockHdr *pHdr;
+  for(pHdr=mem.pFirst; pHdr; pHdr=pHdr->pNext){
+    void **pBt = (void**)pHdr;
+    pBt -= pHdr->nBacktraceSlots;
+    mem.xBacktrace(pHdr->iSize, pHdr->nBacktrace-1, &pBt[1]);
+  }
+}
+
+/*
+** Open the file indicated and write a log of all unfreed memory 
+** allocations into that log.
+*/
+void sqlite3MemdebugDump(const char *zFilename){
+  FILE *out;
+  struct MemBlockHdr *pHdr;
+  void **pBt;
+  int i;
+  out = fopen(zFilename, "w");
+  if( out==0 ){
+    fprintf(stderr, "** Unable to output memory debug output log: %s **\n",
+                    zFilename);
+    return;
+  }
+  for(pHdr=mem.pFirst; pHdr; pHdr=pHdr->pNext){
+    char *z = (char*)pHdr;
+    z -= pHdr->nBacktraceSlots*sizeof(void*) + pHdr->nTitle;
+    fprintf(out, "**** %lld bytes at %p from %s ****\n", 
+            pHdr->iSize, &pHdr[1], pHdr->nTitle ? z : "???");
+    if( pHdr->nBacktrace ){
+      fflush(out);
+      pBt = (void**)pHdr;
+      pBt -= pHdr->nBacktraceSlots;
+      backtrace_symbols_fd(pBt, pHdr->nBacktrace, fileno(out));
+      fprintf(out, "\n");
+    }
+  }
+  fprintf(out, "COUNTS:\n");
+  for(i=0; i<NCSIZE-1; i++){
+    if( mem.nAlloc[i] ){
+      fprintf(out, "   %5d: %10d %10d %10d\n", 
+            i*8, mem.nAlloc[i], mem.nCurrent[i], mem.mxCurrent[i]);
+    }
+  }
+  if( mem.nAlloc[NCSIZE-1] ){
+    fprintf(out, "   %5d: %10d %10d %10d\n",
+             NCSIZE*8-8, mem.nAlloc[NCSIZE-1],
+             mem.nCurrent[NCSIZE-1], mem.mxCurrent[NCSIZE-1]);
+  }
+  fclose(out);
+}
+
+/*
+** Return the number of times sqlite3MemMalloc() has been called.
+*/
+int sqlite3MemdebugMallocCount(){
+  int i;
+  int nTotal = 0;
+  for(i=0; i<NCSIZE; i++){
+    nTotal += mem.nAlloc[i];
+  }
+  return nTotal;
+}
+
+
+#endif /* SQLITE_MEMDEBUG */
diff --git a/src/mem3.c b/src/mem3.c
new file mode 100644
index 0000000..1a1b791
--- /dev/null
+++ b/src/mem3.c
@@ -0,0 +1,687 @@
+/*
+** 2007 October 14
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains the C functions that implement a memory
+** allocation subsystem for use by SQLite. 
+**
+** This version of the memory allocation subsystem omits all
+** use of malloc(). The SQLite user supplies a block of memory
+** before calling sqlite3_initialize() from which allocations
+** are made and returned by the xMalloc() and xRealloc() 
+** implementations. Once sqlite3_initialize() has been called,
+** the amount of memory available to SQLite is fixed and cannot
+** be changed.
+**
+** This version of the memory allocation subsystem is included
+** in the build only if SQLITE_ENABLE_MEMSYS3 is defined.
+*/
+#include "sqliteInt.h"
+
+/*
+** This version of the memory allocator is only built into the library
+** SQLITE_ENABLE_MEMSYS3 is defined. Defining this symbol does not
+** mean that the library will use a memory-pool by default, just that
+** it is available. The mempool allocator is activated by calling
+** sqlite3_config().
+*/
+#ifdef SQLITE_ENABLE_MEMSYS3
+
+/*
+** Maximum size (in Mem3Blocks) of a "small" chunk.
+*/
+#define MX_SMALL 10
+
+
+/*
+** Number of freelist hash slots
+*/
+#define N_HASH  61
+
+/*
+** A memory allocation (also called a "chunk") consists of two or 
+** more blocks where each block is 8 bytes.  The first 8 bytes are 
+** a header that is not returned to the user.
+**
+** A chunk is two or more blocks that is either checked out or
+** free.  The first block has format u.hdr.  u.hdr.size4x is 4 times the
+** size of the allocation in blocks if the allocation is free.
+** The u.hdr.size4x&1 bit is true if the chunk is checked out and
+** false if the chunk is on the freelist.  The u.hdr.size4x&2 bit
+** is true if the previous chunk is checked out and false if the
+** previous chunk is free.  The u.hdr.prevSize field is the size of
+** the previous chunk in blocks if the previous chunk is on the
+** freelist. If the previous chunk is checked out, then
+** u.hdr.prevSize can be part of the data for that chunk and should
+** not be read or written.
+**
+** We often identify a chunk by its index in mem3.aPool[].  When
+** this is done, the chunk index refers to the second block of
+** the chunk.  In this way, the first chunk has an index of 1.
+** A chunk index of 0 means "no such chunk" and is the equivalent
+** of a NULL pointer.
+**
+** The second block of free chunks is of the form u.list.  The
+** two fields form a double-linked list of chunks of related sizes.
+** Pointers to the head of the list are stored in mem3.aiSmall[] 
+** for smaller chunks and mem3.aiHash[] for larger chunks.
+**
+** The second block of a chunk is user data if the chunk is checked 
+** out.  If a chunk is checked out, the user data may extend into
+** the u.hdr.prevSize value of the following chunk.
+*/
+typedef struct Mem3Block Mem3Block;
+struct Mem3Block {
+  union {
+    struct {
+      u32 prevSize;   /* Size of previous chunk in Mem3Block elements */
+      u32 size4x;     /* 4x the size of current chunk in Mem3Block elements */
+    } hdr;
+    struct {
+      u32 next;       /* Index in mem3.aPool[] of next free chunk */
+      u32 prev;       /* Index in mem3.aPool[] of previous free chunk */
+    } list;
+  } u;
+};
+
+/*
+** All of the static variables used by this module are collected
+** into a single structure named "mem3".  This is to keep the
+** static variables organized and to reduce namespace pollution
+** when this module is combined with other in the amalgamation.
+*/
+static SQLITE_WSD struct Mem3Global {
+  /*
+  ** Memory available for allocation. nPool is the size of the array
+  ** (in Mem3Blocks) pointed to by aPool less 2.
+  */
+  u32 nPool;
+  Mem3Block *aPool;
+
+  /*
+  ** True if we are evaluating an out-of-memory callback.
+  */
+  int alarmBusy;
+  
+  /*
+  ** Mutex to control access to the memory allocation subsystem.
+  */
+  sqlite3_mutex *mutex;
+  
+  /*
+  ** The minimum amount of free space that we have seen.
+  */
+  u32 mnMaster;
+
+  /*
+  ** iMaster is the index of the master chunk.  Most new allocations
+  ** occur off of this chunk.  szMaster is the size (in Mem3Blocks)
+  ** of the current master.  iMaster is 0 if there is not master chunk.
+  ** The master chunk is not in either the aiHash[] or aiSmall[].
+  */
+  u32 iMaster;
+  u32 szMaster;
+
+  /*
+  ** Array of lists of free blocks according to the block size 
+  ** for smaller chunks, or a hash on the block size for larger
+  ** chunks.
+  */
+  u32 aiSmall[MX_SMALL-1];   /* For sizes 2 through MX_SMALL, inclusive */
+  u32 aiHash[N_HASH];        /* For sizes MX_SMALL+1 and larger */
+} mem3 = { 97535575 };
+
+#define mem3 GLOBAL(struct Mem3Global, mem3)
+
+/*
+** Unlink the chunk at mem3.aPool[i] from list it is currently
+** on.  *pRoot is the list that i is a member of.
+*/
+static void memsys3UnlinkFromList(u32 i, u32 *pRoot){
+  u32 next = mem3.aPool[i].u.list.next;
+  u32 prev = mem3.aPool[i].u.list.prev;
+  assert( sqlite3_mutex_held(mem3.mutex) );
+  if( prev==0 ){
+    *pRoot = next;
+  }else{
+    mem3.aPool[prev].u.list.next = next;
+  }
+  if( next ){
+    mem3.aPool[next].u.list.prev = prev;
+  }
+  mem3.aPool[i].u.list.next = 0;
+  mem3.aPool[i].u.list.prev = 0;
+}
+
+/*
+** Unlink the chunk at index i from 
+** whatever list is currently a member of.
+*/
+static void memsys3Unlink(u32 i){
+  u32 size, hash;
+  assert( sqlite3_mutex_held(mem3.mutex) );
+  assert( (mem3.aPool[i-1].u.hdr.size4x & 1)==0 );
+  assert( i>=1 );
+  size = mem3.aPool[i-1].u.hdr.size4x/4;
+  assert( size==mem3.aPool[i+size-1].u.hdr.prevSize );
+  assert( size>=2 );
+  if( size <= MX_SMALL ){
+    memsys3UnlinkFromList(i, &mem3.aiSmall[size-2]);
+  }else{
+    hash = size % N_HASH;
+    memsys3UnlinkFromList(i, &mem3.aiHash[hash]);
+  }
+}
+
+/*
+** Link the chunk at mem3.aPool[i] so that is on the list rooted
+** at *pRoot.
+*/
+static void memsys3LinkIntoList(u32 i, u32 *pRoot){
+  assert( sqlite3_mutex_held(mem3.mutex) );
+  mem3.aPool[i].u.list.next = *pRoot;
+  mem3.aPool[i].u.list.prev = 0;
+  if( *pRoot ){
+    mem3.aPool[*pRoot].u.list.prev = i;
+  }
+  *pRoot = i;
+}
+
+/*
+** Link the chunk at index i into either the appropriate
+** small chunk list, or into the large chunk hash table.
+*/
+static void memsys3Link(u32 i){
+  u32 size, hash;
+  assert( sqlite3_mutex_held(mem3.mutex) );
+  assert( i>=1 );
+  assert( (mem3.aPool[i-1].u.hdr.size4x & 1)==0 );
+  size = mem3.aPool[i-1].u.hdr.size4x/4;
+  assert( size==mem3.aPool[i+size-1].u.hdr.prevSize );
+  assert( size>=2 );
+  if( size <= MX_SMALL ){
+    memsys3LinkIntoList(i, &mem3.aiSmall[size-2]);
+  }else{
+    hash = size % N_HASH;
+    memsys3LinkIntoList(i, &mem3.aiHash[hash]);
+  }
+}
+
+/*
+** If the STATIC_MEM mutex is not already held, obtain it now. The mutex
+** will already be held (obtained by code in malloc.c) if
+** sqlite3GlobalConfig.bMemStat is true.
+*/
+static void memsys3Enter(void){
+  if( sqlite3GlobalConfig.bMemstat==0 && mem3.mutex==0 ){
+    mem3.mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MEM);
+  }
+  sqlite3_mutex_enter(mem3.mutex);
+}
+static void memsys3Leave(void){
+  sqlite3_mutex_leave(mem3.mutex);
+}
+
+/*
+** Called when we are unable to satisfy an allocation of nBytes.
+*/
+static void memsys3OutOfMemory(int nByte){
+  if( !mem3.alarmBusy ){
+    mem3.alarmBusy = 1;
+    assert( sqlite3_mutex_held(mem3.mutex) );
+    sqlite3_mutex_leave(mem3.mutex);
+    sqlite3_release_memory(nByte);
+    sqlite3_mutex_enter(mem3.mutex);
+    mem3.alarmBusy = 0;
+  }
+}
+
+
+/*
+** Chunk i is a free chunk that has been unlinked.  Adjust its 
+** size parameters for check-out and return a pointer to the 
+** user portion of the chunk.
+*/
+static void *memsys3Checkout(u32 i, u32 nBlock){
+  u32 x;
+  assert( sqlite3_mutex_held(mem3.mutex) );
+  assert( i>=1 );
+  assert( mem3.aPool[i-1].u.hdr.size4x/4==nBlock );
+  assert( mem3.aPool[i+nBlock-1].u.hdr.prevSize==nBlock );
+  x = mem3.aPool[i-1].u.hdr.size4x;
+  mem3.aPool[i-1].u.hdr.size4x = nBlock*4 | 1 | (x&2);
+  mem3.aPool[i+nBlock-1].u.hdr.prevSize = nBlock;
+  mem3.aPool[i+nBlock-1].u.hdr.size4x |= 2;
+  return &mem3.aPool[i];
+}
+
+/*
+** Carve a piece off of the end of the mem3.iMaster free chunk.
+** Return a pointer to the new allocation.  Or, if the master chunk
+** is not large enough, return 0.
+*/
+static void *memsys3FromMaster(u32 nBlock){
+  assert( sqlite3_mutex_held(mem3.mutex) );
+  assert( mem3.szMaster>=nBlock );
+  if( nBlock>=mem3.szMaster-1 ){
+    /* Use the entire master */
+    void *p = memsys3Checkout(mem3.iMaster, mem3.szMaster);
+    mem3.iMaster = 0;
+    mem3.szMaster = 0;
+    mem3.mnMaster = 0;
+    return p;
+  }else{
+    /* Split the master block.  Return the tail. */
+    u32 newi, x;
+    newi = mem3.iMaster + mem3.szMaster - nBlock;
+    assert( newi > mem3.iMaster+1 );
+    mem3.aPool[mem3.iMaster+mem3.szMaster-1].u.hdr.prevSize = nBlock;
+    mem3.aPool[mem3.iMaster+mem3.szMaster-1].u.hdr.size4x |= 2;
+    mem3.aPool[newi-1].u.hdr.size4x = nBlock*4 + 1;
+    mem3.szMaster -= nBlock;
+    mem3.aPool[newi-1].u.hdr.prevSize = mem3.szMaster;
+    x = mem3.aPool[mem3.iMaster-1].u.hdr.size4x & 2;
+    mem3.aPool[mem3.iMaster-1].u.hdr.size4x = mem3.szMaster*4 | x;
+    if( mem3.szMaster < mem3.mnMaster ){
+      mem3.mnMaster = mem3.szMaster;
+    }
+    return (void*)&mem3.aPool[newi];
+  }
+}
+
+/*
+** *pRoot is the head of a list of free chunks of the same size
+** or same size hash.  In other words, *pRoot is an entry in either
+** mem3.aiSmall[] or mem3.aiHash[].  
+**
+** This routine examines all entries on the given list and tries
+** to coalesce each entries with adjacent free chunks.  
+**
+** If it sees a chunk that is larger than mem3.iMaster, it replaces 
+** the current mem3.iMaster with the new larger chunk.  In order for
+** this mem3.iMaster replacement to work, the master chunk must be
+** linked into the hash tables.  That is not the normal state of
+** affairs, of course.  The calling routine must link the master
+** chunk before invoking this routine, then must unlink the (possibly
+** changed) master chunk once this routine has finished.
+*/
+static void memsys3Merge(u32 *pRoot){
+  u32 iNext, prev, size, i, x;
+
+  assert( sqlite3_mutex_held(mem3.mutex) );
+  for(i=*pRoot; i>0; i=iNext){
+    iNext = mem3.aPool[i].u.list.next;
+    size = mem3.aPool[i-1].u.hdr.size4x;
+    assert( (size&1)==0 );
+    if( (size&2)==0 ){
+      memsys3UnlinkFromList(i, pRoot);
+      assert( i > mem3.aPool[i-1].u.hdr.prevSize );
+      prev = i - mem3.aPool[i-1].u.hdr.prevSize;
+      if( prev==iNext ){
+        iNext = mem3.aPool[prev].u.list.next;
+      }
+      memsys3Unlink(prev);
+      size = i + size/4 - prev;
+      x = mem3.aPool[prev-1].u.hdr.size4x & 2;
+      mem3.aPool[prev-1].u.hdr.size4x = size*4 | x;
+      mem3.aPool[prev+size-1].u.hdr.prevSize = size;
+      memsys3Link(prev);
+      i = prev;
+    }else{
+      size /= 4;
+    }
+    if( size>mem3.szMaster ){
+      mem3.iMaster = i;
+      mem3.szMaster = size;
+    }
+  }
+}
+
+/*
+** Return a block of memory of at least nBytes in size.
+** Return NULL if unable.
+**
+** This function assumes that the necessary mutexes, if any, are
+** already held by the caller. Hence "Unsafe".
+*/
+static void *memsys3MallocUnsafe(int nByte){
+  u32 i;
+  u32 nBlock;
+  u32 toFree;
+
+  assert( sqlite3_mutex_held(mem3.mutex) );
+  assert( sizeof(Mem3Block)==8 );
+  if( nByte<=12 ){
+    nBlock = 2;
+  }else{
+    nBlock = (nByte + 11)/8;
+  }
+  assert( nBlock>=2 );
+
+  /* STEP 1:
+  ** Look for an entry of the correct size in either the small
+  ** chunk table or in the large chunk hash table.  This is
+  ** successful most of the time (about 9 times out of 10).
+  */
+  if( nBlock <= MX_SMALL ){
+    i = mem3.aiSmall[nBlock-2];
+    if( i>0 ){
+      memsys3UnlinkFromList(i, &mem3.aiSmall[nBlock-2]);
+      return memsys3Checkout(i, nBlock);
+    }
+  }else{
+    int hash = nBlock % N_HASH;
+    for(i=mem3.aiHash[hash]; i>0; i=mem3.aPool[i].u.list.next){
+      if( mem3.aPool[i-1].u.hdr.size4x/4==nBlock ){
+        memsys3UnlinkFromList(i, &mem3.aiHash[hash]);
+        return memsys3Checkout(i, nBlock);
+      }
+    }
+  }
+
+  /* STEP 2:
+  ** Try to satisfy the allocation by carving a piece off of the end
+  ** of the master chunk.  This step usually works if step 1 fails.
+  */
+  if( mem3.szMaster>=nBlock ){
+    return memsys3FromMaster(nBlock);
+  }
+
+
+  /* STEP 3:  
+  ** Loop through the entire memory pool.  Coalesce adjacent free
+  ** chunks.  Recompute the master chunk as the largest free chunk.
+  ** Then try again to satisfy the allocation by carving a piece off
+  ** of the end of the master chunk.  This step happens very
+  ** rarely (we hope!)
+  */
+  for(toFree=nBlock*16; toFree<(mem3.nPool*16); toFree *= 2){
+    memsys3OutOfMemory(toFree);
+    if( mem3.iMaster ){
+      memsys3Link(mem3.iMaster);
+      mem3.iMaster = 0;
+      mem3.szMaster = 0;
+    }
+    for(i=0; i<N_HASH; i++){
+      memsys3Merge(&mem3.aiHash[i]);
+    }
+    for(i=0; i<MX_SMALL-1; i++){
+      memsys3Merge(&mem3.aiSmall[i]);
+    }
+    if( mem3.szMaster ){
+      memsys3Unlink(mem3.iMaster);
+      if( mem3.szMaster>=nBlock ){
+        return memsys3FromMaster(nBlock);
+      }
+    }
+  }
+
+  /* If none of the above worked, then we fail. */
+  return 0;
+}
+
+/*
+** Free an outstanding memory allocation.
+**
+** This function assumes that the necessary mutexes, if any, are
+** already held by the caller. Hence "Unsafe".
+*/
+static void memsys3FreeUnsafe(void *pOld){
+  Mem3Block *p = (Mem3Block*)pOld;
+  int i;
+  u32 size, x;
+  assert( sqlite3_mutex_held(mem3.mutex) );
+  assert( p>mem3.aPool && p<&mem3.aPool[mem3.nPool] );
+  i = p - mem3.aPool;
+  assert( (mem3.aPool[i-1].u.hdr.size4x&1)==1 );
+  size = mem3.aPool[i-1].u.hdr.size4x/4;
+  assert( i+size<=mem3.nPool+1 );
+  mem3.aPool[i-1].u.hdr.size4x &= ~1;
+  mem3.aPool[i+size-1].u.hdr.prevSize = size;
+  mem3.aPool[i+size-1].u.hdr.size4x &= ~2;
+  memsys3Link(i);
+
+  /* Try to expand the master using the newly freed chunk */
+  if( mem3.iMaster ){
+    while( (mem3.aPool[mem3.iMaster-1].u.hdr.size4x&2)==0 ){
+      size = mem3.aPool[mem3.iMaster-1].u.hdr.prevSize;
+      mem3.iMaster -= size;
+      mem3.szMaster += size;
+      memsys3Unlink(mem3.iMaster);
+      x = mem3.aPool[mem3.iMaster-1].u.hdr.size4x & 2;
+      mem3.aPool[mem3.iMaster-1].u.hdr.size4x = mem3.szMaster*4 | x;
+      mem3.aPool[mem3.iMaster+mem3.szMaster-1].u.hdr.prevSize = mem3.szMaster;
+    }
+    x = mem3.aPool[mem3.iMaster-1].u.hdr.size4x & 2;
+    while( (mem3.aPool[mem3.iMaster+mem3.szMaster-1].u.hdr.size4x&1)==0 ){
+      memsys3Unlink(mem3.iMaster+mem3.szMaster);
+      mem3.szMaster += mem3.aPool[mem3.iMaster+mem3.szMaster-1].u.hdr.size4x/4;
+      mem3.aPool[mem3.iMaster-1].u.hdr.size4x = mem3.szMaster*4 | x;
+      mem3.aPool[mem3.iMaster+mem3.szMaster-1].u.hdr.prevSize = mem3.szMaster;
+    }
+  }
+}
+
+/*
+** Return the size of an outstanding allocation, in bytes.  The
+** size returned omits the 8-byte header overhead.  This only
+** works for chunks that are currently checked out.
+*/
+static int memsys3Size(void *p){
+  Mem3Block *pBlock;
+  if( p==0 ) return 0;
+  pBlock = (Mem3Block*)p;
+  assert( (pBlock[-1].u.hdr.size4x&1)!=0 );
+  return (pBlock[-1].u.hdr.size4x&~3)*2 - 4;
+}
+
+/*
+** Round up a request size to the next valid allocation size.
+*/
+static int memsys3Roundup(int n){
+  if( n<=12 ){
+    return 12;
+  }else{
+    return ((n+11)&~7) - 4;
+  }
+}
+
+/*
+** Allocate nBytes of memory.
+*/
+static void *memsys3Malloc(int nBytes){
+  sqlite3_int64 *p;
+  assert( nBytes>0 );          /* malloc.c filters out 0 byte requests */
+  memsys3Enter();
+  p = memsys3MallocUnsafe(nBytes);
+  memsys3Leave();
+  return (void*)p; 
+}
+
+/*
+** Free memory.
+*/
+static void memsys3Free(void *pPrior){
+  assert( pPrior );
+  memsys3Enter();
+  memsys3FreeUnsafe(pPrior);
+  memsys3Leave();
+}
+
+/*
+** Change the size of an existing memory allocation
+*/
+static void *memsys3Realloc(void *pPrior, int nBytes){
+  int nOld;
+  void *p;
+  if( pPrior==0 ){
+    return sqlite3_malloc(nBytes);
+  }
+  if( nBytes<=0 ){
+    sqlite3_free(pPrior);
+    return 0;
+  }
+  nOld = memsys3Size(pPrior);
+  if( nBytes<=nOld && nBytes>=nOld-128 ){
+    return pPrior;
+  }
+  memsys3Enter();
+  p = memsys3MallocUnsafe(nBytes);
+  if( p ){
+    if( nOld<nBytes ){
+      memcpy(p, pPrior, nOld);
+    }else{
+      memcpy(p, pPrior, nBytes);
+    }
+    memsys3FreeUnsafe(pPrior);
+  }
+  memsys3Leave();
+  return p;
+}
+
+/*
+** Initialize this module.
+*/
+static int memsys3Init(void *NotUsed){
+  UNUSED_PARAMETER(NotUsed);
+  if( !sqlite3GlobalConfig.pHeap ){
+    return SQLITE_ERROR;
+  }
+
+  /* Store a pointer to the memory block in global structure mem3. */
+  assert( sizeof(Mem3Block)==8 );
+  mem3.aPool = (Mem3Block *)sqlite3GlobalConfig.pHeap;
+  mem3.nPool = (sqlite3GlobalConfig.nHeap / sizeof(Mem3Block)) - 2;
+
+  /* Initialize the master block. */
+  mem3.szMaster = mem3.nPool;
+  mem3.mnMaster = mem3.szMaster;
+  mem3.iMaster = 1;
+  mem3.aPool[0].u.hdr.size4x = (mem3.szMaster<<2) + 2;
+  mem3.aPool[mem3.nPool].u.hdr.prevSize = mem3.nPool;
+  mem3.aPool[mem3.nPool].u.hdr.size4x = 1;
+
+  return SQLITE_OK;
+}
+
+/*
+** Deinitialize this module.
+*/
+static void memsys3Shutdown(void *NotUsed){
+  UNUSED_PARAMETER(NotUsed);
+  mem3.mutex = 0;
+  return;
+}
+
+
+
+/*
+** Open the file indicated and write a log of all unfreed memory 
+** allocations into that log.
+*/
+void sqlite3Memsys3Dump(const char *zFilename){
+#ifdef SQLITE_DEBUG
+  FILE *out;
+  u32 i, j;
+  u32 size;
+  if( zFilename==0 || zFilename[0]==0 ){
+    out = stdout;
+  }else{
+    out = fopen(zFilename, "w");
+    if( out==0 ){
+      fprintf(stderr, "** Unable to output memory debug output log: %s **\n",
+                      zFilename);
+      return;
+    }
+  }
+  memsys3Enter();
+  fprintf(out, "CHUNKS:\n");
+  for(i=1; i<=mem3.nPool; i+=size/4){
+    size = mem3.aPool[i-1].u.hdr.size4x;
+    if( size/4<=1 ){
+      fprintf(out, "%p size error\n", &mem3.aPool[i]);
+      assert( 0 );
+      break;
+    }
+    if( (size&1)==0 && mem3.aPool[i+size/4-1].u.hdr.prevSize!=size/4 ){
+      fprintf(out, "%p tail size does not match\n", &mem3.aPool[i]);
+      assert( 0 );
+      break;
+    }
+    if( ((mem3.aPool[i+size/4-1].u.hdr.size4x&2)>>1)!=(size&1) ){
+      fprintf(out, "%p tail checkout bit is incorrect\n", &mem3.aPool[i]);
+      assert( 0 );
+      break;
+    }
+    if( size&1 ){
+      fprintf(out, "%p %6d bytes checked out\n", &mem3.aPool[i], (size/4)*8-8);
+    }else{
+      fprintf(out, "%p %6d bytes free%s\n", &mem3.aPool[i], (size/4)*8-8,
+                  i==mem3.iMaster ? " **master**" : "");
+    }
+  }
+  for(i=0; i<MX_SMALL-1; i++){
+    if( mem3.aiSmall[i]==0 ) continue;
+    fprintf(out, "small(%2d):", i);
+    for(j = mem3.aiSmall[i]; j>0; j=mem3.aPool[j].u.list.next){
+      fprintf(out, " %p(%d)", &mem3.aPool[j],
+              (mem3.aPool[j-1].u.hdr.size4x/4)*8-8);
+    }
+    fprintf(out, "\n"); 
+  }
+  for(i=0; i<N_HASH; i++){
+    if( mem3.aiHash[i]==0 ) continue;
+    fprintf(out, "hash(%2d):", i);
+    for(j = mem3.aiHash[i]; j>0; j=mem3.aPool[j].u.list.next){
+      fprintf(out, " %p(%d)", &mem3.aPool[j],
+              (mem3.aPool[j-1].u.hdr.size4x/4)*8-8);
+    }
+    fprintf(out, "\n"); 
+  }
+  fprintf(out, "master=%d\n", mem3.iMaster);
+  fprintf(out, "nowUsed=%d\n", mem3.nPool*8 - mem3.szMaster*8);
+  fprintf(out, "mxUsed=%d\n", mem3.nPool*8 - mem3.mnMaster*8);
+  sqlite3_mutex_leave(mem3.mutex);
+  if( out==stdout ){
+    fflush(stdout);
+  }else{
+    fclose(out);
+  }
+#else
+  UNUSED_PARAMETER(zFilename);
+#endif
+}
+
+/*
+** This routine is the only routine in this file with external 
+** linkage.
+**
+** Populate the low-level memory allocation function pointers in
+** sqlite3GlobalConfig.m with pointers to the routines in this file. The
+** arguments specify the block of memory to manage.
+**
+** This routine is only called by sqlite3_config(), and therefore
+** is not required to be threadsafe (it is not).
+*/
+const sqlite3_mem_methods *sqlite3MemGetMemsys3(void){
+  static const sqlite3_mem_methods mempoolMethods = {
+     memsys3Malloc,
+     memsys3Free,
+     memsys3Realloc,
+     memsys3Size,
+     memsys3Roundup,
+     memsys3Init,
+     memsys3Shutdown,
+     0
+  };
+  return &mempoolMethods;
+}
+
+#endif /* SQLITE_ENABLE_MEMSYS3 */
diff --git a/src/mem5.c b/src/mem5.c
new file mode 100644
index 0000000..783cef6
--- /dev/null
+++ b/src/mem5.c
@@ -0,0 +1,581 @@
+/*
+** 2007 October 14
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains the C functions that implement a memory
+** allocation subsystem for use by SQLite. 
+**
+** This version of the memory allocation subsystem omits all
+** use of malloc(). The application gives SQLite a block of memory
+** before calling sqlite3_initialize() from which allocations
+** are made and returned by the xMalloc() and xRealloc() 
+** implementations. Once sqlite3_initialize() has been called,
+** the amount of memory available to SQLite is fixed and cannot
+** be changed.
+**
+** This version of the memory allocation subsystem is included
+** in the build only if SQLITE_ENABLE_MEMSYS5 is defined.
+**
+** This memory allocator uses the following algorithm:
+**
+**   1.  All memory allocations sizes are rounded up to a power of 2.
+**
+**   2.  If two adjacent free blocks are the halves of a larger block,
+**       then the two blocks are coalesed into the single larger block.
+**
+**   3.  New memory is allocated from the first available free block.
+**
+** This algorithm is described in: J. M. Robson. "Bounds for Some Functions
+** Concerning Dynamic Storage Allocation". Journal of the Association for
+** Computing Machinery, Volume 21, Number 8, July 1974, pages 491-499.
+** 
+** Let n be the size of the largest allocation divided by the minimum
+** allocation size (after rounding all sizes up to a power of 2.)  Let M
+** be the maximum amount of memory ever outstanding at one time.  Let
+** N be the total amount of memory available for allocation.  Robson
+** proved that this memory allocator will never breakdown due to 
+** fragmentation as long as the following constraint holds:
+**
+**      N >=  M*(1 + log2(n)/2) - n + 1
+**
+** The sqlite3_status() logic tracks the maximum values of n and M so
+** that an application can, at any time, verify this constraint.
+*/
+#include "sqliteInt.h"
+
+/*
+** This version of the memory allocator is used only when 
+** SQLITE_ENABLE_MEMSYS5 is defined.
+*/
+#ifdef SQLITE_ENABLE_MEMSYS5
+
+/*
+** A minimum allocation is an instance of the following structure.
+** Larger allocations are an array of these structures where the
+** size of the array is a power of 2.
+**
+** The size of this object must be a power of two.  That fact is
+** verified in memsys5Init().
+*/
+typedef struct Mem5Link Mem5Link;
+struct Mem5Link {
+  int next;       /* Index of next free chunk */
+  int prev;       /* Index of previous free chunk */
+};
+
+/*
+** Maximum size of any allocation is ((1<<LOGMAX)*mem5.szAtom). Since
+** mem5.szAtom is always at least 8 and 32-bit integers are used,
+** it is not actually possible to reach this limit.
+*/
+#define LOGMAX 30
+
+/*
+** Masks used for mem5.aCtrl[] elements.
+*/
+#define CTRL_LOGSIZE  0x1f    /* Log2 Size of this block */
+#define CTRL_FREE     0x20    /* True if not checked out */
+
+/*
+** All of the static variables used by this module are collected
+** into a single structure named "mem5".  This is to keep the
+** static variables organized and to reduce namespace pollution
+** when this module is combined with other in the amalgamation.
+*/
+static SQLITE_WSD struct Mem5Global {
+  /*
+  ** Memory available for allocation
+  */
+  int szAtom;      /* Smallest possible allocation in bytes */
+  int nBlock;      /* Number of szAtom sized blocks in zPool */
+  u8 *zPool;       /* Memory available to be allocated */
+  
+  /*
+  ** Mutex to control access to the memory allocation subsystem.
+  */
+  sqlite3_mutex *mutex;
+
+  /*
+  ** Performance statistics
+  */
+  u64 nAlloc;         /* Total number of calls to malloc */
+  u64 totalAlloc;     /* Total of all malloc calls - includes internal frag */
+  u64 totalExcess;    /* Total internal fragmentation */
+  u32 currentOut;     /* Current checkout, including internal fragmentation */
+  u32 currentCount;   /* Current number of distinct checkouts */
+  u32 maxOut;         /* Maximum instantaneous currentOut */
+  u32 maxCount;       /* Maximum instantaneous currentCount */
+  u32 maxRequest;     /* Largest allocation (exclusive of internal frag) */
+  
+  /*
+  ** Lists of free blocks.  aiFreelist[0] is a list of free blocks of
+  ** size mem5.szAtom.  aiFreelist[1] holds blocks of size szAtom*2.
+  ** and so forth.
+  */
+  int aiFreelist[LOGMAX+1];
+
+  /*
+  ** Space for tracking which blocks are checked out and the size
+  ** of each block.  One byte per block.
+  */
+  u8 *aCtrl;
+
+} mem5;
+
+/*
+** Access the static variable through a macro for SQLITE_OMIT_WSD
+*/
+#define mem5 GLOBAL(struct Mem5Global, mem5)
+
+/*
+** Assuming mem5.zPool is divided up into an array of Mem5Link
+** structures, return a pointer to the idx-th such lik.
+*/
+#define MEM5LINK(idx) ((Mem5Link *)(&mem5.zPool[(idx)*mem5.szAtom]))
+
+/*
+** Unlink the chunk at mem5.aPool[i] from list it is currently
+** on.  It should be found on mem5.aiFreelist[iLogsize].
+*/
+static void memsys5Unlink(int i, int iLogsize){
+  int next, prev;
+  assert( i>=0 && i<mem5.nBlock );
+  assert( iLogsize>=0 && iLogsize<=LOGMAX );
+  assert( (mem5.aCtrl[i] & CTRL_LOGSIZE)==iLogsize );
+
+  next = MEM5LINK(i)->next;
+  prev = MEM5LINK(i)->prev;
+  if( prev<0 ){
+    mem5.aiFreelist[iLogsize] = next;
+  }else{
+    MEM5LINK(prev)->next = next;
+  }
+  if( next>=0 ){
+    MEM5LINK(next)->prev = prev;
+  }
+}
+
+/*
+** Link the chunk at mem5.aPool[i] so that is on the iLogsize
+** free list.
+*/
+static void memsys5Link(int i, int iLogsize){
+  int x;
+  assert( sqlite3_mutex_held(mem5.mutex) );
+  assert( i>=0 && i<mem5.nBlock );
+  assert( iLogsize>=0 && iLogsize<=LOGMAX );
+  assert( (mem5.aCtrl[i] & CTRL_LOGSIZE)==iLogsize );
+
+  x = MEM5LINK(i)->next = mem5.aiFreelist[iLogsize];
+  MEM5LINK(i)->prev = -1;
+  if( x>=0 ){
+    assert( x<mem5.nBlock );
+    MEM5LINK(x)->prev = i;
+  }
+  mem5.aiFreelist[iLogsize] = i;
+}
+
+/*
+** If the STATIC_MEM mutex is not already held, obtain it now. The mutex
+** will already be held (obtained by code in malloc.c) if
+** sqlite3GlobalConfig.bMemStat is true.
+*/
+static void memsys5Enter(void){
+  sqlite3_mutex_enter(mem5.mutex);
+}
+static void memsys5Leave(void){
+  sqlite3_mutex_leave(mem5.mutex);
+}
+
+/*
+** Return the size of an outstanding allocation, in bytes.  The
+** size returned omits the 8-byte header overhead.  This only
+** works for chunks that are currently checked out.
+*/
+static int memsys5Size(void *p){
+  int iSize = 0;
+  if( p ){
+    int i = ((u8 *)p-mem5.zPool)/mem5.szAtom;
+    assert( i>=0 && i<mem5.nBlock );
+    iSize = mem5.szAtom * (1 << (mem5.aCtrl[i]&CTRL_LOGSIZE));
+  }
+  return iSize;
+}
+
+/*
+** Find the first entry on the freelist iLogsize.  Unlink that
+** entry and return its index. 
+*/
+static int memsys5UnlinkFirst(int iLogsize){
+  int i;
+  int iFirst;
+
+  assert( iLogsize>=0 && iLogsize<=LOGMAX );
+  i = iFirst = mem5.aiFreelist[iLogsize];
+  assert( iFirst>=0 );
+  while( i>0 ){
+    if( i<iFirst ) iFirst = i;
+    i = MEM5LINK(i)->next;
+  }
+  memsys5Unlink(iFirst, iLogsize);
+  return iFirst;
+}
+
+/*
+** Return a block of memory of at least nBytes in size.
+** Return NULL if unable.  Return NULL if nBytes==0.
+**
+** The caller guarantees that nByte positive.
+**
+** The caller has obtained a mutex prior to invoking this
+** routine so there is never any chance that two or more
+** threads can be in this routine at the same time.
+*/
+static void *memsys5MallocUnsafe(int nByte){
+  int i;           /* Index of a mem5.aPool[] slot */
+  int iBin;        /* Index into mem5.aiFreelist[] */
+  int iFullSz;     /* Size of allocation rounded up to power of 2 */
+  int iLogsize;    /* Log2 of iFullSz/POW2_MIN */
+
+  /* nByte must be a positive */
+  assert( nByte>0 );
+
+  /* Keep track of the maximum allocation request.  Even unfulfilled
+  ** requests are counted */
+  if( (u32)nByte>mem5.maxRequest ){
+    mem5.maxRequest = nByte;
+  }
+
+  /* Abort if the requested allocation size is larger than the largest
+  ** power of two that we can represent using 32-bit signed integers.
+  */
+  if( nByte > 0x40000000 ){
+    return 0;
+  }
+
+  /* Round nByte up to the next valid power of two */
+  for(iFullSz=mem5.szAtom, iLogsize=0; iFullSz<nByte; iFullSz *= 2, iLogsize++){}
+
+  /* Make sure mem5.aiFreelist[iLogsize] contains at least one free
+  ** block.  If not, then split a block of the next larger power of
+  ** two in order to create a new free block of size iLogsize.
+  */
+  for(iBin=iLogsize; mem5.aiFreelist[iBin]<0 && iBin<=LOGMAX; iBin++){}
+  if( iBin>LOGMAX ){
+    testcase( sqlite3GlobalConfig.xLog!=0 );
+    sqlite3_log(SQLITE_NOMEM, "failed to allocate %u bytes", nByte);
+    return 0;
+  }
+  i = memsys5UnlinkFirst(iBin);
+  while( iBin>iLogsize ){
+    int newSize;
+
+    iBin--;
+    newSize = 1 << iBin;
+    mem5.aCtrl[i+newSize] = CTRL_FREE | iBin;
+    memsys5Link(i+newSize, iBin);
+  }
+  mem5.aCtrl[i] = iLogsize;
+
+  /* Update allocator performance statistics. */
+  mem5.nAlloc++;
+  mem5.totalAlloc += iFullSz;
+  mem5.totalExcess += iFullSz - nByte;
+  mem5.currentCount++;
+  mem5.currentOut += iFullSz;
+  if( mem5.maxCount<mem5.currentCount ) mem5.maxCount = mem5.currentCount;
+  if( mem5.maxOut<mem5.currentOut ) mem5.maxOut = mem5.currentOut;
+
+  /* Return a pointer to the allocated memory. */
+  return (void*)&mem5.zPool[i*mem5.szAtom];
+}
+
+/*
+** Free an outstanding memory allocation.
+*/
+static void memsys5FreeUnsafe(void *pOld){
+  u32 size, iLogsize;
+  int iBlock;
+
+  /* Set iBlock to the index of the block pointed to by pOld in 
+  ** the array of mem5.szAtom byte blocks pointed to by mem5.zPool.
+  */
+  iBlock = ((u8 *)pOld-mem5.zPool)/mem5.szAtom;
+
+  /* Check that the pointer pOld points to a valid, non-free block. */
+  assert( iBlock>=0 && iBlock<mem5.nBlock );
+  assert( ((u8 *)pOld-mem5.zPool)%mem5.szAtom==0 );
+  assert( (mem5.aCtrl[iBlock] & CTRL_FREE)==0 );
+
+  iLogsize = mem5.aCtrl[iBlock] & CTRL_LOGSIZE;
+  size = 1<<iLogsize;
+  assert( iBlock+size-1<(u32)mem5.nBlock );
+
+  mem5.aCtrl[iBlock] |= CTRL_FREE;
+  mem5.aCtrl[iBlock+size-1] |= CTRL_FREE;
+  assert( mem5.currentCount>0 );
+  assert( mem5.currentOut>=(size*mem5.szAtom) );
+  mem5.currentCount--;
+  mem5.currentOut -= size*mem5.szAtom;
+  assert( mem5.currentOut>0 || mem5.currentCount==0 );
+  assert( mem5.currentCount>0 || mem5.currentOut==0 );
+
+  mem5.aCtrl[iBlock] = CTRL_FREE | iLogsize;
+  while( ALWAYS(iLogsize<LOGMAX) ){
+    int iBuddy;
+    if( (iBlock>>iLogsize) & 1 ){
+      iBuddy = iBlock - size;
+    }else{
+      iBuddy = iBlock + size;
+    }
+    assert( iBuddy>=0 );
+    if( (iBuddy+(1<<iLogsize))>mem5.nBlock ) break;
+    if( mem5.aCtrl[iBuddy]!=(CTRL_FREE | iLogsize) ) break;
+    memsys5Unlink(iBuddy, iLogsize);
+    iLogsize++;
+    if( iBuddy<iBlock ){
+      mem5.aCtrl[iBuddy] = CTRL_FREE | iLogsize;
+      mem5.aCtrl[iBlock] = 0;
+      iBlock = iBuddy;
+    }else{
+      mem5.aCtrl[iBlock] = CTRL_FREE | iLogsize;
+      mem5.aCtrl[iBuddy] = 0;
+    }
+    size *= 2;
+  }
+  memsys5Link(iBlock, iLogsize);
+}
+
+/*
+** Allocate nBytes of memory
+*/
+static void *memsys5Malloc(int nBytes){
+  sqlite3_int64 *p = 0;
+  if( nBytes>0 ){
+    memsys5Enter();
+    p = memsys5MallocUnsafe(nBytes);
+    memsys5Leave();
+  }
+  return (void*)p; 
+}
+
+/*
+** Free memory.
+**
+** The outer layer memory allocator prevents this routine from
+** being called with pPrior==0.
+*/
+static void memsys5Free(void *pPrior){
+  assert( pPrior!=0 );
+  memsys5Enter();
+  memsys5FreeUnsafe(pPrior);
+  memsys5Leave();  
+}
+
+/*
+** Change the size of an existing memory allocation.
+**
+** The outer layer memory allocator prevents this routine from
+** being called with pPrior==0.  
+**
+** nBytes is always a value obtained from a prior call to
+** memsys5Round().  Hence nBytes is always a non-negative power
+** of two.  If nBytes==0 that means that an oversize allocation
+** (an allocation larger than 0x40000000) was requested and this
+** routine should return 0 without freeing pPrior.
+*/
+static void *memsys5Realloc(void *pPrior, int nBytes){
+  int nOld;
+  void *p;
+  assert( pPrior!=0 );
+  assert( (nBytes&(nBytes-1))==0 );  /* EV: R-46199-30249 */
+  assert( nBytes>=0 );
+  if( nBytes==0 ){
+    return 0;
+  }
+  nOld = memsys5Size(pPrior);
+  if( nBytes<=nOld ){
+    return pPrior;
+  }
+  memsys5Enter();
+  p = memsys5MallocUnsafe(nBytes);
+  if( p ){
+    memcpy(p, pPrior, nOld);
+    memsys5FreeUnsafe(pPrior);
+  }
+  memsys5Leave();
+  return p;
+}
+
+/*
+** Round up a request size to the next valid allocation size.  If
+** the allocation is too large to be handled by this allocation system,
+** return 0.
+**
+** All allocations must be a power of two and must be expressed by a
+** 32-bit signed integer.  Hence the largest allocation is 0x40000000
+** or 1073741824 bytes.
+*/
+static int memsys5Roundup(int n){
+  int iFullSz;
+  if( n > 0x40000000 ) return 0;
+  for(iFullSz=mem5.szAtom; iFullSz<n; iFullSz *= 2);
+  return iFullSz;
+}
+
+/*
+** Return the ceiling of the logarithm base 2 of iValue.
+**
+** Examples:   memsys5Log(1) -> 0
+**             memsys5Log(2) -> 1
+**             memsys5Log(4) -> 2
+**             memsys5Log(5) -> 3
+**             memsys5Log(8) -> 3
+**             memsys5Log(9) -> 4
+*/
+static int memsys5Log(int iValue){
+  int iLog;
+  for(iLog=0; (iLog<(int)((sizeof(int)*8)-1)) && (1<<iLog)<iValue; iLog++);
+  return iLog;
+}
+
+/*
+** Initialize the memory allocator.
+**
+** This routine is not threadsafe.  The caller must be holding a mutex
+** to prevent multiple threads from entering at the same time.
+*/
+static int memsys5Init(void *NotUsed){
+  int ii;            /* Loop counter */
+  int nByte;         /* Number of bytes of memory available to this allocator */
+  u8 *zByte;         /* Memory usable by this allocator */
+  int nMinLog;       /* Log base 2 of minimum allocation size in bytes */
+  int iOffset;       /* An offset into mem5.aCtrl[] */
+
+  UNUSED_PARAMETER(NotUsed);
+
+  /* For the purposes of this routine, disable the mutex */
+  mem5.mutex = 0;
+
+  /* The size of a Mem5Link object must be a power of two.  Verify that
+  ** this is case.
+  */
+  assert( (sizeof(Mem5Link)&(sizeof(Mem5Link)-1))==0 );
+
+  nByte = sqlite3GlobalConfig.nHeap;
+  zByte = (u8*)sqlite3GlobalConfig.pHeap;
+  assert( zByte!=0 );  /* sqlite3_config() does not allow otherwise */
+
+  /* boundaries on sqlite3GlobalConfig.mnReq are enforced in sqlite3_config() */
+  nMinLog = memsys5Log(sqlite3GlobalConfig.mnReq);
+  mem5.szAtom = (1<<nMinLog);
+  while( (int)sizeof(Mem5Link)>mem5.szAtom ){
+    mem5.szAtom = mem5.szAtom << 1;
+  }
+
+  mem5.nBlock = (nByte / (mem5.szAtom+sizeof(u8)));
+  mem5.zPool = zByte;
+  mem5.aCtrl = (u8 *)&mem5.zPool[mem5.nBlock*mem5.szAtom];
+
+  for(ii=0; ii<=LOGMAX; ii++){
+    mem5.aiFreelist[ii] = -1;
+  }
+
+  iOffset = 0;
+  for(ii=LOGMAX; ii>=0; ii--){
+    int nAlloc = (1<<ii);
+    if( (iOffset+nAlloc)<=mem5.nBlock ){
+      mem5.aCtrl[iOffset] = ii | CTRL_FREE;
+      memsys5Link(iOffset, ii);
+      iOffset += nAlloc;
+    }
+    assert((iOffset+nAlloc)>mem5.nBlock);
+  }
+
+  /* If a mutex is required for normal operation, allocate one */
+  if( sqlite3GlobalConfig.bMemstat==0 ){
+    mem5.mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MEM);
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** Deinitialize this module.
+*/
+static void memsys5Shutdown(void *NotUsed){
+  UNUSED_PARAMETER(NotUsed);
+  mem5.mutex = 0;
+  return;
+}
+
+#ifdef SQLITE_TEST
+/*
+** Open the file indicated and write a log of all unfreed memory 
+** allocations into that log.
+*/
+void sqlite3Memsys5Dump(const char *zFilename){
+  FILE *out;
+  int i, j, n;
+  int nMinLog;
+
+  if( zFilename==0 || zFilename[0]==0 ){
+    out = stdout;
+  }else{
+    out = fopen(zFilename, "w");
+    if( out==0 ){
+      fprintf(stderr, "** Unable to output memory debug output log: %s **\n",
+                      zFilename);
+      return;
+    }
+  }
+  memsys5Enter();
+  nMinLog = memsys5Log(mem5.szAtom);
+  for(i=0; i<=LOGMAX && i+nMinLog<32; i++){
+    for(n=0, j=mem5.aiFreelist[i]; j>=0; j = MEM5LINK(j)->next, n++){}
+    fprintf(out, "freelist items of size %d: %d\n", mem5.szAtom << i, n);
+  }
+  fprintf(out, "mem5.nAlloc       = %llu\n", mem5.nAlloc);
+  fprintf(out, "mem5.totalAlloc   = %llu\n", mem5.totalAlloc);
+  fprintf(out, "mem5.totalExcess  = %llu\n", mem5.totalExcess);
+  fprintf(out, "mem5.currentOut   = %u\n", mem5.currentOut);
+  fprintf(out, "mem5.currentCount = %u\n", mem5.currentCount);
+  fprintf(out, "mem5.maxOut       = %u\n", mem5.maxOut);
+  fprintf(out, "mem5.maxCount     = %u\n", mem5.maxCount);
+  fprintf(out, "mem5.maxRequest   = %u\n", mem5.maxRequest);
+  memsys5Leave();
+  if( out==stdout ){
+    fflush(stdout);
+  }else{
+    fclose(out);
+  }
+}
+#endif
+
+/*
+** This routine is the only routine in this file with external 
+** linkage. It returns a pointer to a static sqlite3_mem_methods
+** struct populated with the memsys5 methods.
+*/
+const sqlite3_mem_methods *sqlite3MemGetMemsys5(void){
+  static const sqlite3_mem_methods memsys5Methods = {
+     memsys5Malloc,
+     memsys5Free,
+     memsys5Realloc,
+     memsys5Size,
+     memsys5Roundup,
+     memsys5Init,
+     memsys5Shutdown,
+     0
+  };
+  return &memsys5Methods;
+}
+
+#endif /* SQLITE_ENABLE_MEMSYS5 */
diff --git a/src/memjournal.c b/src/memjournal.c
new file mode 100644
index 0000000..3e66e21
--- /dev/null
+++ b/src/memjournal.c
@@ -0,0 +1,259 @@
+/*
+** 2008 October 7
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains code use to implement an in-memory rollback journal.
+** The in-memory rollback journal is used to journal transactions for
+** ":memory:" databases and when the journal_mode=MEMORY pragma is used.
+*/
+#include "sqliteInt.h"
+
+/* Forward references to internal structures */
+typedef struct MemJournal MemJournal;
+typedef struct FilePoint FilePoint;
+typedef struct FileChunk FileChunk;
+
+/* Space to hold the rollback journal is allocated in increments of
+** this many bytes.
+**
+** The size chosen is a little less than a power of two.  That way,
+** the FileChunk object will have a size that almost exactly fills
+** a power-of-two allocation.  This mimimizes wasted space in power-of-two
+** memory allocators.
+*/
+#define JOURNAL_CHUNKSIZE ((int)(1024-sizeof(FileChunk*)))
+
+/* Macro to find the minimum of two numeric values.
+*/
+#ifndef MIN
+# define MIN(x,y) ((x)<(y)?(x):(y))
+#endif
+
+/*
+** The rollback journal is composed of a linked list of these structures.
+*/
+struct FileChunk {
+  FileChunk *pNext;               /* Next chunk in the journal */
+  u8 zChunk[JOURNAL_CHUNKSIZE];   /* Content of this chunk */
+};
+
+/*
+** An instance of this object serves as a cursor into the rollback journal.
+** The cursor can be either for reading or writing.
+*/
+struct FilePoint {
+  sqlite3_int64 iOffset;          /* Offset from the beginning of the file */
+  FileChunk *pChunk;              /* Specific chunk into which cursor points */
+};
+
+/*
+** This subclass is a subclass of sqlite3_file.  Each open memory-journal
+** is an instance of this class.
+*/
+struct MemJournal {
+  sqlite3_io_methods *pMethod;    /* Parent class. MUST BE FIRST */
+  FileChunk *pFirst;              /* Head of in-memory chunk-list */
+  FilePoint endpoint;             /* Pointer to the end of the file */
+  FilePoint readpoint;            /* Pointer to the end of the last xRead() */
+};
+
+/*
+** Read data from the in-memory journal file.  This is the implementation
+** of the sqlite3_vfs.xRead method.
+*/
+static int memjrnlRead(
+  sqlite3_file *pJfd,    /* The journal file from which to read */
+  void *zBuf,            /* Put the results here */
+  int iAmt,              /* Number of bytes to read */
+  sqlite_int64 iOfst     /* Begin reading at this offset */
+){
+  MemJournal *p = (MemJournal *)pJfd;
+  u8 *zOut = zBuf;
+  int nRead = iAmt;
+  int iChunkOffset;
+  FileChunk *pChunk;
+
+  /* SQLite never tries to read past the end of a rollback journal file */
+  assert( iOfst+iAmt<=p->endpoint.iOffset );
+
+  if( p->readpoint.iOffset!=iOfst || iOfst==0 ){
+    sqlite3_int64 iOff = 0;
+    for(pChunk=p->pFirst; 
+        ALWAYS(pChunk) && (iOff+JOURNAL_CHUNKSIZE)<=iOfst;
+        pChunk=pChunk->pNext
+    ){
+      iOff += JOURNAL_CHUNKSIZE;
+    }
+  }else{
+    pChunk = p->readpoint.pChunk;
+  }
+
+  iChunkOffset = (int)(iOfst%JOURNAL_CHUNKSIZE);
+  do {
+    int iSpace = JOURNAL_CHUNKSIZE - iChunkOffset;
+    int nCopy = MIN(nRead, (JOURNAL_CHUNKSIZE - iChunkOffset));
+    memcpy(zOut, &pChunk->zChunk[iChunkOffset], nCopy);
+    zOut += nCopy;
+    nRead -= iSpace;
+    iChunkOffset = 0;
+  } while( nRead>=0 && (pChunk=pChunk->pNext)!=0 && nRead>0 );
+  p->readpoint.iOffset = iOfst+iAmt;
+  p->readpoint.pChunk = pChunk;
+
+  return SQLITE_OK;
+}
+
+/*
+** Write data to the file.
+*/
+static int memjrnlWrite(
+  sqlite3_file *pJfd,    /* The journal file into which to write */
+  const void *zBuf,      /* Take data to be written from here */
+  int iAmt,              /* Number of bytes to write */
+  sqlite_int64 iOfst     /* Begin writing at this offset into the file */
+){
+  MemJournal *p = (MemJournal *)pJfd;
+  int nWrite = iAmt;
+  u8 *zWrite = (u8 *)zBuf;
+
+  /* An in-memory journal file should only ever be appended to. Random
+  ** access writes are not required by sqlite.
+  */
+  assert( iOfst==p->endpoint.iOffset );
+  UNUSED_PARAMETER(iOfst);
+
+  while( nWrite>0 ){
+    FileChunk *pChunk = p->endpoint.pChunk;
+    int iChunkOffset = (int)(p->endpoint.iOffset%JOURNAL_CHUNKSIZE);
+    int iSpace = MIN(nWrite, JOURNAL_CHUNKSIZE - iChunkOffset);
+
+    if( iChunkOffset==0 ){
+      /* New chunk is required to extend the file. */
+      FileChunk *pNew = sqlite3_malloc(sizeof(FileChunk));
+      if( !pNew ){
+        return SQLITE_IOERR_NOMEM;
+      }
+      pNew->pNext = 0;
+      if( pChunk ){
+        assert( p->pFirst );
+        pChunk->pNext = pNew;
+      }else{
+        assert( !p->pFirst );
+        p->pFirst = pNew;
+      }
+      p->endpoint.pChunk = pNew;
+    }
+
+    memcpy(&p->endpoint.pChunk->zChunk[iChunkOffset], zWrite, iSpace);
+    zWrite += iSpace;
+    nWrite -= iSpace;
+    p->endpoint.iOffset += iSpace;
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** Truncate the file.
+*/
+static int memjrnlTruncate(sqlite3_file *pJfd, sqlite_int64 size){
+  MemJournal *p = (MemJournal *)pJfd;
+  FileChunk *pChunk;
+  assert(size==0);
+  UNUSED_PARAMETER(size);
+  pChunk = p->pFirst;
+  while( pChunk ){
+    FileChunk *pTmp = pChunk;
+    pChunk = pChunk->pNext;
+    sqlite3_free(pTmp);
+  }
+  sqlite3MemJournalOpen(pJfd);
+  return SQLITE_OK;
+}
+
+/*
+** Close the file.
+*/
+static int memjrnlClose(sqlite3_file *pJfd){
+  memjrnlTruncate(pJfd, 0);
+  return SQLITE_OK;
+}
+
+
+/*
+** Sync the file.
+**
+** Syncing an in-memory journal is a no-op.  And, in fact, this routine
+** is never called in a working implementation.  This implementation
+** exists purely as a contingency, in case some malfunction in some other
+** part of SQLite causes Sync to be called by mistake.
+*/
+static int memjrnlSync(sqlite3_file *NotUsed, int NotUsed2){
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  return SQLITE_OK;
+}
+
+/*
+** Query the size of the file in bytes.
+*/
+static int memjrnlFileSize(sqlite3_file *pJfd, sqlite_int64 *pSize){
+  MemJournal *p = (MemJournal *)pJfd;
+  *pSize = (sqlite_int64) p->endpoint.iOffset;
+  return SQLITE_OK;
+}
+
+/*
+** Table of methods for MemJournal sqlite3_file object.
+*/
+static const struct sqlite3_io_methods MemJournalMethods = {
+  1,                /* iVersion */
+  memjrnlClose,     /* xClose */
+  memjrnlRead,      /* xRead */
+  memjrnlWrite,     /* xWrite */
+  memjrnlTruncate,  /* xTruncate */
+  memjrnlSync,      /* xSync */
+  memjrnlFileSize,  /* xFileSize */
+  0,                /* xLock */
+  0,                /* xUnlock */
+  0,                /* xCheckReservedLock */
+  0,                /* xFileControl */
+  0,                /* xSectorSize */
+  0,                /* xDeviceCharacteristics */
+  0,                /* xShmMap */
+  0,                /* xShmLock */
+  0,                /* xShmBarrier */
+  0                 /* xShmUnlock */
+};
+
+/* 
+** Open a journal file.
+*/
+void sqlite3MemJournalOpen(sqlite3_file *pJfd){
+  MemJournal *p = (MemJournal *)pJfd;
+  assert( EIGHT_BYTE_ALIGNMENT(p) );
+  memset(p, 0, sqlite3MemJournalSize());
+  p->pMethod = (sqlite3_io_methods*)&MemJournalMethods;
+}
+
+/*
+** Return true if the file-handle passed as an argument is 
+** an in-memory journal 
+*/
+int sqlite3IsMemJournal(sqlite3_file *pJfd){
+  return pJfd->pMethods==&MemJournalMethods;
+}
+
+/* 
+** Return the number of bytes required to store a MemJournal file descriptor.
+*/
+int sqlite3MemJournalSize(void){
+  return sizeof(MemJournal);
+}
diff --git a/src/mutex.c b/src/mutex.c
new file mode 100644
index 0000000..869a4ae
--- /dev/null
+++ b/src/mutex.c
@@ -0,0 +1,153 @@
+/*
+** 2007 August 14
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains the C functions that implement mutexes.
+**
+** This file contains code that is common across all mutex implementations.
+*/
+#include "sqliteInt.h"
+
+#if defined(SQLITE_DEBUG) && !defined(SQLITE_MUTEX_OMIT)
+/*
+** For debugging purposes, record when the mutex subsystem is initialized
+** and uninitialized so that we can assert() if there is an attempt to
+** allocate a mutex while the system is uninitialized.
+*/
+static SQLITE_WSD int mutexIsInit = 0;
+#endif /* SQLITE_DEBUG */
+
+
+#ifndef SQLITE_MUTEX_OMIT
+/*
+** Initialize the mutex system.
+*/
+int sqlite3MutexInit(void){ 
+  int rc = SQLITE_OK;
+  if( !sqlite3GlobalConfig.mutex.xMutexAlloc ){
+    /* If the xMutexAlloc method has not been set, then the user did not
+    ** install a mutex implementation via sqlite3_config() prior to 
+    ** sqlite3_initialize() being called. This block copies pointers to
+    ** the default implementation into the sqlite3GlobalConfig structure.
+    */
+    sqlite3_mutex_methods const *pFrom;
+    sqlite3_mutex_methods *pTo = &sqlite3GlobalConfig.mutex;
+
+    if( sqlite3GlobalConfig.bCoreMutex ){
+      pFrom = sqlite3DefaultMutex();
+    }else{
+      pFrom = sqlite3NoopMutex();
+    }
+    memcpy(pTo, pFrom, offsetof(sqlite3_mutex_methods, xMutexAlloc));
+    memcpy(&pTo->xMutexFree, &pFrom->xMutexFree,
+           sizeof(*pTo) - offsetof(sqlite3_mutex_methods, xMutexFree));
+    pTo->xMutexAlloc = pFrom->xMutexAlloc;
+  }
+  rc = sqlite3GlobalConfig.mutex.xMutexInit();
+
+#ifdef SQLITE_DEBUG
+  GLOBAL(int, mutexIsInit) = 1;
+#endif
+
+  return rc;
+}
+
+/*
+** Shutdown the mutex system. This call frees resources allocated by
+** sqlite3MutexInit().
+*/
+int sqlite3MutexEnd(void){
+  int rc = SQLITE_OK;
+  if( sqlite3GlobalConfig.mutex.xMutexEnd ){
+    rc = sqlite3GlobalConfig.mutex.xMutexEnd();
+  }
+
+#ifdef SQLITE_DEBUG
+  GLOBAL(int, mutexIsInit) = 0;
+#endif
+
+  return rc;
+}
+
+/*
+** Retrieve a pointer to a static mutex or allocate a new dynamic one.
+*/
+sqlite3_mutex *sqlite3_mutex_alloc(int id){
+#ifndef SQLITE_OMIT_AUTOINIT
+  if( sqlite3_initialize() ) return 0;
+#endif
+  return sqlite3GlobalConfig.mutex.xMutexAlloc(id);
+}
+
+sqlite3_mutex *sqlite3MutexAlloc(int id){
+  if( !sqlite3GlobalConfig.bCoreMutex ){
+    return 0;
+  }
+  assert( GLOBAL(int, mutexIsInit) );
+  return sqlite3GlobalConfig.mutex.xMutexAlloc(id);
+}
+
+/*
+** Free a dynamic mutex.
+*/
+void sqlite3_mutex_free(sqlite3_mutex *p){
+  if( p ){
+    sqlite3GlobalConfig.mutex.xMutexFree(p);
+  }
+}
+
+/*
+** Obtain the mutex p. If some other thread already has the mutex, block
+** until it can be obtained.
+*/
+void sqlite3_mutex_enter(sqlite3_mutex *p){
+  if( p ){
+    sqlite3GlobalConfig.mutex.xMutexEnter(p);
+  }
+}
+
+/*
+** Obtain the mutex p. If successful, return SQLITE_OK. Otherwise, if another
+** thread holds the mutex and it cannot be obtained, return SQLITE_BUSY.
+*/
+int sqlite3_mutex_try(sqlite3_mutex *p){
+  int rc = SQLITE_OK;
+  if( p ){
+    return sqlite3GlobalConfig.mutex.xMutexTry(p);
+  }
+  return rc;
+}
+
+/*
+** The sqlite3_mutex_leave() routine exits a mutex that was previously
+** entered by the same thread.  The behavior is undefined if the mutex 
+** is not currently entered. If a NULL pointer is passed as an argument
+** this function is a no-op.
+*/
+void sqlite3_mutex_leave(sqlite3_mutex *p){
+  if( p ){
+    sqlite3GlobalConfig.mutex.xMutexLeave(p);
+  }
+}
+
+#ifndef NDEBUG
+/*
+** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routine are
+** intended for use inside assert() statements.
+*/
+int sqlite3_mutex_held(sqlite3_mutex *p){
+  return p==0 || sqlite3GlobalConfig.mutex.xMutexHeld(p);
+}
+int sqlite3_mutex_notheld(sqlite3_mutex *p){
+  return p==0 || sqlite3GlobalConfig.mutex.xMutexNotheld(p);
+}
+#endif
+
+#endif /* SQLITE_MUTEX_OMIT */
diff --git a/src/mutex.h b/src/mutex.h
new file mode 100644
index 0000000..b0e552c
--- /dev/null
+++ b/src/mutex.h
@@ -0,0 +1,74 @@
+/*
+** 2007 August 28
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains the common header for all mutex implementations.
+** The sqliteInt.h header #includes this file so that it is available
+** to all source files.  We break it out in an effort to keep the code
+** better organized.
+**
+** NOTE:  source files should *not* #include this header file directly.
+** Source files should #include the sqliteInt.h file and let that file
+** include this one indirectly.
+*/
+
+
+/*
+** Figure out what version of the code to use.  The choices are
+**
+**   SQLITE_MUTEX_OMIT         No mutex logic.  Not even stubs.  The
+**                             mutexes implemention cannot be overridden
+**                             at start-time.
+**
+**   SQLITE_MUTEX_NOOP         For single-threaded applications.  No
+**                             mutual exclusion is provided.  But this
+**                             implementation can be overridden at
+**                             start-time.
+**
+**   SQLITE_MUTEX_PTHREADS     For multi-threaded applications on Unix.
+**
+**   SQLITE_MUTEX_W32          For multi-threaded applications on Win32.
+**
+**   SQLITE_MUTEX_OS2          For multi-threaded applications on OS/2.
+*/
+#if !SQLITE_THREADSAFE
+# define SQLITE_MUTEX_OMIT
+#endif
+#if SQLITE_THREADSAFE && !defined(SQLITE_MUTEX_NOOP)
+#  if SQLITE_OS_UNIX
+#    define SQLITE_MUTEX_PTHREADS
+#  elif SQLITE_OS_WIN
+#    define SQLITE_MUTEX_W32
+#  elif SQLITE_OS_OS2
+#    define SQLITE_MUTEX_OS2
+#  else
+#    define SQLITE_MUTEX_NOOP
+#  endif
+#endif
+
+#ifdef SQLITE_MUTEX_OMIT
+/*
+** If this is a no-op implementation, implement everything as macros.
+*/
+#define sqlite3_mutex_alloc(X)    ((sqlite3_mutex*)8)
+#define sqlite3_mutex_free(X)
+#define sqlite3_mutex_enter(X)    
+#define sqlite3_mutex_try(X)      SQLITE_OK
+#define sqlite3_mutex_leave(X)    
+#define sqlite3_mutex_held(X)     ((void)(X),1)
+#define sqlite3_mutex_notheld(X)  ((void)(X),1)
+#define sqlite3MutexAlloc(X)      ((sqlite3_mutex*)8)
+#define sqlite3MutexInit()        SQLITE_OK
+#define sqlite3MutexEnd()
+#define MUTEX_LOGIC(X)
+#else
+#define MUTEX_LOGIC(X)            X
+#endif /* defined(SQLITE_MUTEX_OMIT) */
diff --git a/src/mutex_noop.c b/src/mutex_noop.c
new file mode 100644
index 0000000..c5fd520
--- /dev/null
+++ b/src/mutex_noop.c
@@ -0,0 +1,206 @@
+/*
+** 2008 October 07
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains the C functions that implement mutexes.
+**
+** This implementation in this file does not provide any mutual
+** exclusion and is thus suitable for use only in applications
+** that use SQLite in a single thread.  The routines defined
+** here are place-holders.  Applications can substitute working
+** mutex routines at start-time using the
+**
+**     sqlite3_config(SQLITE_CONFIG_MUTEX,...)
+**
+** interface.
+**
+** If compiled with SQLITE_DEBUG, then additional logic is inserted
+** that does error checking on mutexes to make sure they are being
+** called correctly.
+*/
+#include "sqliteInt.h"
+
+#ifndef SQLITE_MUTEX_OMIT
+
+#ifndef SQLITE_DEBUG
+/*
+** Stub routines for all mutex methods.
+**
+** This routines provide no mutual exclusion or error checking.
+*/
+static int noopMutexInit(void){ return SQLITE_OK; }
+static int noopMutexEnd(void){ return SQLITE_OK; }
+static sqlite3_mutex *noopMutexAlloc(int id){ 
+  UNUSED_PARAMETER(id);
+  return (sqlite3_mutex*)8; 
+}
+static void noopMutexFree(sqlite3_mutex *p){ UNUSED_PARAMETER(p); return; }
+static void noopMutexEnter(sqlite3_mutex *p){ UNUSED_PARAMETER(p); return; }
+static int noopMutexTry(sqlite3_mutex *p){
+  UNUSED_PARAMETER(p);
+  return SQLITE_OK;
+}
+static void noopMutexLeave(sqlite3_mutex *p){ UNUSED_PARAMETER(p); return; }
+
+sqlite3_mutex_methods const *sqlite3NoopMutex(void){
+  static const sqlite3_mutex_methods sMutex = {
+    noopMutexInit,
+    noopMutexEnd,
+    noopMutexAlloc,
+    noopMutexFree,
+    noopMutexEnter,
+    noopMutexTry,
+    noopMutexLeave,
+
+    0,
+    0,
+  };
+
+  return &sMutex;
+}
+#endif /* !SQLITE_DEBUG */
+
+#ifdef SQLITE_DEBUG
+/*
+** In this implementation, error checking is provided for testing
+** and debugging purposes.  The mutexes still do not provide any
+** mutual exclusion.
+*/
+
+/*
+** The mutex object
+*/
+typedef struct sqlite3_debug_mutex {
+  int id;     /* The mutex type */
+  int cnt;    /* Number of entries without a matching leave */
+} sqlite3_debug_mutex;
+
+/*
+** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routine are
+** intended for use inside assert() statements.
+*/
+static int debugMutexHeld(sqlite3_mutex *pX){
+  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
+  return p==0 || p->cnt>0;
+}
+static int debugMutexNotheld(sqlite3_mutex *pX){
+  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
+  return p==0 || p->cnt==0;
+}
+
+/*
+** Initialize and deinitialize the mutex subsystem.
+*/
+static int debugMutexInit(void){ return SQLITE_OK; }
+static int debugMutexEnd(void){ return SQLITE_OK; }
+
+/*
+** The sqlite3_mutex_alloc() routine allocates a new
+** mutex and returns a pointer to it.  If it returns NULL
+** that means that a mutex could not be allocated. 
+*/
+static sqlite3_mutex *debugMutexAlloc(int id){
+  static sqlite3_debug_mutex aStatic[6];
+  sqlite3_debug_mutex *pNew = 0;
+  switch( id ){
+    case SQLITE_MUTEX_FAST:
+    case SQLITE_MUTEX_RECURSIVE: {
+      pNew = sqlite3Malloc(sizeof(*pNew));
+      if( pNew ){
+        pNew->id = id;
+        pNew->cnt = 0;
+      }
+      break;
+    }
+    default: {
+      assert( id-2 >= 0 );
+      assert( id-2 < (int)(sizeof(aStatic)/sizeof(aStatic[0])) );
+      pNew = &aStatic[id-2];
+      pNew->id = id;
+      break;
+    }
+  }
+  return (sqlite3_mutex*)pNew;
+}
+
+/*
+** This routine deallocates a previously allocated mutex.
+*/
+static void debugMutexFree(sqlite3_mutex *pX){
+  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
+  assert( p->cnt==0 );
+  assert( p->id==SQLITE_MUTEX_FAST || p->id==SQLITE_MUTEX_RECURSIVE );
+  sqlite3_free(p);
+}
+
+/*
+** The sqlite3_mutex_enter() and sqlite3_mutex_try() routines attempt
+** to enter a mutex.  If another thread is already within the mutex,
+** sqlite3_mutex_enter() will block and sqlite3_mutex_try() will return
+** SQLITE_BUSY.  The sqlite3_mutex_try() interface returns SQLITE_OK
+** upon successful entry.  Mutexes created using SQLITE_MUTEX_RECURSIVE can
+** be entered multiple times by the same thread.  In such cases the,
+** mutex must be exited an equal number of times before another thread
+** can enter.  If the same thread tries to enter any other kind of mutex
+** more than once, the behavior is undefined.
+*/
+static void debugMutexEnter(sqlite3_mutex *pX){
+  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || debugMutexNotheld(pX) );
+  p->cnt++;
+}
+static int debugMutexTry(sqlite3_mutex *pX){
+  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || debugMutexNotheld(pX) );
+  p->cnt++;
+  return SQLITE_OK;
+}
+
+/*
+** The sqlite3_mutex_leave() routine exits a mutex that was
+** previously entered by the same thread.  The behavior
+** is undefined if the mutex is not currently entered or
+** is not currently allocated.  SQLite will never do either.
+*/
+static void debugMutexLeave(sqlite3_mutex *pX){
+  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
+  assert( debugMutexHeld(pX) );
+  p->cnt--;
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || debugMutexNotheld(pX) );
+}
+
+sqlite3_mutex_methods const *sqlite3NoopMutex(void){
+  static const sqlite3_mutex_methods sMutex = {
+    debugMutexInit,
+    debugMutexEnd,
+    debugMutexAlloc,
+    debugMutexFree,
+    debugMutexEnter,
+    debugMutexTry,
+    debugMutexLeave,
+
+    debugMutexHeld,
+    debugMutexNotheld
+  };
+
+  return &sMutex;
+}
+#endif /* SQLITE_DEBUG */
+
+/*
+** If compiled with SQLITE_MUTEX_NOOP, then the no-op mutex implementation
+** is used regardless of the run-time threadsafety setting.
+*/
+#ifdef SQLITE_MUTEX_NOOP
+sqlite3_mutex_methods const *sqlite3DefaultMutex(void){
+  return sqlite3NoopMutex();
+}
+#endif /* SQLITE_MUTEX_NOOP */
+#endif /* SQLITE_MUTEX_OMIT */
diff --git a/src/mutex_os2.c b/src/mutex_os2.c
new file mode 100644
index 0000000..ce650d9
--- /dev/null
+++ b/src/mutex_os2.c
@@ -0,0 +1,274 @@
+/*
+** 2007 August 28
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains the C functions that implement mutexes for OS/2
+*/
+#include "sqliteInt.h"
+
+/*
+** The code in this file is only used if SQLITE_MUTEX_OS2 is defined.
+** See the mutex.h file for details.
+*/
+#ifdef SQLITE_MUTEX_OS2
+
+/********************** OS/2 Mutex Implementation **********************
+**
+** This implementation of mutexes is built using the OS/2 API.
+*/
+
+/*
+** The mutex object
+** Each recursive mutex is an instance of the following structure.
+*/
+struct sqlite3_mutex {
+  HMTX mutex;       /* Mutex controlling the lock */
+  int  id;          /* Mutex type */
+#ifdef SQLITE_DEBUG
+ int   trace;       /* True to trace changes */
+#endif
+};
+
+#ifdef SQLITE_DEBUG
+#define SQLITE3_MUTEX_INITIALIZER { 0, 0, 0 }
+#else
+#define SQLITE3_MUTEX_INITIALIZER { 0, 0 }
+#endif
+
+/*
+** Initialize and deinitialize the mutex subsystem.
+*/
+static int os2MutexInit(void){ return SQLITE_OK; }
+static int os2MutexEnd(void){ return SQLITE_OK; }
+
+/*
+** The sqlite3_mutex_alloc() routine allocates a new
+** mutex and returns a pointer to it.  If it returns NULL
+** that means that a mutex could not be allocated. 
+** SQLite will unwind its stack and return an error.  The argument
+** to sqlite3_mutex_alloc() is one of these integer constants:
+**
+** <ul>
+** <li>  SQLITE_MUTEX_FAST
+** <li>  SQLITE_MUTEX_RECURSIVE
+** <li>  SQLITE_MUTEX_STATIC_MASTER
+** <li>  SQLITE_MUTEX_STATIC_MEM
+** <li>  SQLITE_MUTEX_STATIC_MEM2
+** <li>  SQLITE_MUTEX_STATIC_PRNG
+** <li>  SQLITE_MUTEX_STATIC_LRU
+** <li>  SQLITE_MUTEX_STATIC_LRU2
+** </ul>
+**
+** The first two constants cause sqlite3_mutex_alloc() to create
+** a new mutex.  The new mutex is recursive when SQLITE_MUTEX_RECURSIVE
+** is used but not necessarily so when SQLITE_MUTEX_FAST is used.
+** The mutex implementation does not need to make a distinction
+** between SQLITE_MUTEX_RECURSIVE and SQLITE_MUTEX_FAST if it does
+** not want to.  But SQLite will only request a recursive mutex in
+** cases where it really needs one.  If a faster non-recursive mutex
+** implementation is available on the host platform, the mutex subsystem
+** might return such a mutex in response to SQLITE_MUTEX_FAST.
+**
+** The other allowed parameters to sqlite3_mutex_alloc() each return
+** a pointer to a static preexisting mutex.  Six static mutexes are
+** used by the current version of SQLite.  Future versions of SQLite
+** may add additional static mutexes.  Static mutexes are for internal
+** use by SQLite only.  Applications that use SQLite mutexes should
+** use only the dynamic mutexes returned by SQLITE_MUTEX_FAST or
+** SQLITE_MUTEX_RECURSIVE.
+**
+** Note that if one of the dynamic mutex parameters (SQLITE_MUTEX_FAST
+** or SQLITE_MUTEX_RECURSIVE) is used then sqlite3_mutex_alloc()
+** returns a different mutex on every call.  But for the static
+** mutex types, the same mutex is returned on every call that has
+** the same type number.
+*/
+static sqlite3_mutex *os2MutexAlloc(int iType){
+  sqlite3_mutex *p = NULL;
+  switch( iType ){
+    case SQLITE_MUTEX_FAST:
+    case SQLITE_MUTEX_RECURSIVE: {
+      p = sqlite3MallocZero( sizeof(*p) );
+      if( p ){
+        p->id = iType;
+        if( DosCreateMutexSem( 0, &p->mutex, 0, FALSE ) != NO_ERROR ){
+          sqlite3_free( p );
+          p = NULL;
+        }
+      }
+      break;
+    }
+    default: {
+      static volatile int isInit = 0;
+      static sqlite3_mutex staticMutexes[6] = {
+        SQLITE3_MUTEX_INITIALIZER,
+        SQLITE3_MUTEX_INITIALIZER,
+        SQLITE3_MUTEX_INITIALIZER,
+        SQLITE3_MUTEX_INITIALIZER,
+        SQLITE3_MUTEX_INITIALIZER,
+        SQLITE3_MUTEX_INITIALIZER,
+      };
+      if ( !isInit ){
+        APIRET rc;
+        PTIB ptib;
+        PPIB ppib;
+        HMTX mutex;
+        char name[32];
+        DosGetInfoBlocks( &ptib, &ppib );
+        sqlite3_snprintf( sizeof(name), name, "\\SEM32\\SQLITE%04x",
+                          ppib->pib_ulpid );
+        while( !isInit ){
+          mutex = 0;
+          rc = DosCreateMutexSem( name, &mutex, 0, FALSE);
+          if( rc == NO_ERROR ){
+            unsigned int i;
+            if( !isInit ){
+              for( i = 0; i < sizeof(staticMutexes)/sizeof(staticMutexes[0]); i++ ){
+                DosCreateMutexSem( 0, &staticMutexes[i].mutex, 0, FALSE );
+              }
+              isInit = 1;
+            }
+            DosCloseMutexSem( mutex );
+          }else if( rc == ERROR_DUPLICATE_NAME ){
+            DosSleep( 1 );
+          }else{
+            return p;
+          }
+        }
+      }
+      assert( iType-2 >= 0 );
+      assert( iType-2 < sizeof(staticMutexes)/sizeof(staticMutexes[0]) );
+      p = &staticMutexes[iType-2];
+      p->id = iType;
+      break;
+    }
+  }
+  return p;
+}
+
+
+/*
+** This routine deallocates a previously allocated mutex.
+** SQLite is careful to deallocate every mutex that it allocates.
+*/
+static void os2MutexFree(sqlite3_mutex *p){
+#ifdef SQLITE_DEBUG
+  TID tid;
+  PID pid;
+  ULONG ulCount;
+  DosQueryMutexSem(p->mutex, &pid, &tid, &ulCount);
+  assert( ulCount==0 );
+  assert( p->id==SQLITE_MUTEX_FAST || p->id==SQLITE_MUTEX_RECURSIVE );
+#endif
+  DosCloseMutexSem( p->mutex );
+  sqlite3_free( p );
+}
+
+#ifdef SQLITE_DEBUG
+/*
+** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routine are
+** intended for use inside assert() statements.
+*/
+static int os2MutexHeld(sqlite3_mutex *p){
+  TID tid;
+  PID pid;
+  ULONG ulCount;
+  PTIB ptib;
+  DosQueryMutexSem(p->mutex, &pid, &tid, &ulCount);
+  if( ulCount==0 || ( ulCount>1 && p->id!=SQLITE_MUTEX_RECURSIVE ) )
+    return 0;
+  DosGetInfoBlocks(&ptib, NULL);
+  return tid==ptib->tib_ptib2->tib2_ultid;
+}
+static int os2MutexNotheld(sqlite3_mutex *p){
+  TID tid;
+  PID pid;
+  ULONG ulCount;
+  PTIB ptib;
+  DosQueryMutexSem(p->mutex, &pid, &tid, &ulCount);
+  if( ulCount==0 )
+    return 1;
+  DosGetInfoBlocks(&ptib, NULL);
+  return tid!=ptib->tib_ptib2->tib2_ultid;
+}
+static void os2MutexTrace(sqlite3_mutex *p, char *pAction){
+  TID   tid;
+  PID   pid;
+  ULONG ulCount;
+  DosQueryMutexSem(p->mutex, &pid, &tid, &ulCount);
+  printf("%s mutex %p (%d) with nRef=%ld\n", pAction, (void*)p, p->trace, ulCount);
+}
+#endif
+
+/*
+** The sqlite3_mutex_enter() and sqlite3_mutex_try() routines attempt
+** to enter a mutex.  If another thread is already within the mutex,
+** sqlite3_mutex_enter() will block and sqlite3_mutex_try() will return
+** SQLITE_BUSY.  The sqlite3_mutex_try() interface returns SQLITE_OK
+** upon successful entry.  Mutexes created using SQLITE_MUTEX_RECURSIVE can
+** be entered multiple times by the same thread.  In such cases the,
+** mutex must be exited an equal number of times before another thread
+** can enter.  If the same thread tries to enter any other kind of mutex
+** more than once, the behavior is undefined.
+*/
+static void os2MutexEnter(sqlite3_mutex *p){
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || os2MutexNotheld(p) );
+  DosRequestMutexSem(p->mutex, SEM_INDEFINITE_WAIT);
+#ifdef SQLITE_DEBUG
+  if( p->trace ) os2MutexTrace(p, "enter");
+#endif
+}
+static int os2MutexTry(sqlite3_mutex *p){
+  int rc = SQLITE_BUSY;
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || os2MutexNotheld(p) );
+  if( DosRequestMutexSem(p->mutex, SEM_IMMEDIATE_RETURN) == NO_ERROR ) {
+    rc = SQLITE_OK;
+#ifdef SQLITE_DEBUG
+    if( p->trace ) os2MutexTrace(p, "try");
+#endif
+  }
+  return rc;
+}
+
+/*
+** The sqlite3_mutex_leave() routine exits a mutex that was
+** previously entered by the same thread.  The behavior
+** is undefined if the mutex is not currently entered or
+** is not currently allocated.  SQLite will never do either.
+*/
+static void os2MutexLeave(sqlite3_mutex *p){
+  assert( os2MutexHeld(p) );
+  DosReleaseMutexSem(p->mutex);
+#ifdef SQLITE_DEBUG
+  if( p->trace ) os2MutexTrace(p, "leave");
+#endif
+}
+
+sqlite3_mutex_methods const *sqlite3DefaultMutex(void){
+  static const sqlite3_mutex_methods sMutex = {
+    os2MutexInit,
+    os2MutexEnd,
+    os2MutexAlloc,
+    os2MutexFree,
+    os2MutexEnter,
+    os2MutexTry,
+    os2MutexLeave,
+#ifdef SQLITE_DEBUG
+    os2MutexHeld,
+    os2MutexNotheld
+#else
+    0,
+    0
+#endif
+  };
+
+  return &sMutex;
+}
+#endif /* SQLITE_MUTEX_OS2 */
diff --git a/src/mutex_unix.c b/src/mutex_unix.c
new file mode 100644
index 0000000..aa9a8cf
--- /dev/null
+++ b/src/mutex_unix.c
@@ -0,0 +1,351 @@
+/*
+** 2007 August 28
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains the C functions that implement mutexes for pthreads
+*/
+#include "sqliteInt.h"
+
+/*
+** The code in this file is only used if we are compiling threadsafe
+** under unix with pthreads.
+**
+** Note that this implementation requires a version of pthreads that
+** supports recursive mutexes.
+*/
+#ifdef SQLITE_MUTEX_PTHREADS
+
+#include <pthread.h>
+
+/*
+** The sqlite3_mutex.id, sqlite3_mutex.nRef, and sqlite3_mutex.owner fields
+** are necessary under two condidtions:  (1) Debug builds and (2) using
+** home-grown mutexes.  Encapsulate these conditions into a single #define.
+*/
+#if defined(SQLITE_DEBUG) || defined(SQLITE_HOMEGROWN_RECURSIVE_MUTEX)
+# define SQLITE_MUTEX_NREF 1
+#else
+# define SQLITE_MUTEX_NREF 0
+#endif
+
+/*
+** Each recursive mutex is an instance of the following structure.
+*/
+struct sqlite3_mutex {
+  pthread_mutex_t mutex;     /* Mutex controlling the lock */
+#if SQLITE_MUTEX_NREF
+  int id;                    /* Mutex type */
+  volatile int nRef;         /* Number of entrances */
+  volatile pthread_t owner;  /* Thread that is within this mutex */
+  int trace;                 /* True to trace changes */
+#endif
+};
+#if SQLITE_MUTEX_NREF
+#define SQLITE3_MUTEX_INITIALIZER { PTHREAD_MUTEX_INITIALIZER, 0, 0, (pthread_t)0, 0 }
+#else
+#define SQLITE3_MUTEX_INITIALIZER { PTHREAD_MUTEX_INITIALIZER }
+#endif
+
+/*
+** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routine are
+** intended for use only inside assert() statements.  On some platforms,
+** there might be race conditions that can cause these routines to
+** deliver incorrect results.  In particular, if pthread_equal() is
+** not an atomic operation, then these routines might delivery
+** incorrect results.  On most platforms, pthread_equal() is a 
+** comparison of two integers and is therefore atomic.  But we are
+** told that HPUX is not such a platform.  If so, then these routines
+** will not always work correctly on HPUX.
+**
+** On those platforms where pthread_equal() is not atomic, SQLite
+** should be compiled without -DSQLITE_DEBUG and with -DNDEBUG to
+** make sure no assert() statements are evaluated and hence these
+** routines are never called.
+*/
+#if !defined(NDEBUG) || defined(SQLITE_DEBUG)
+static int pthreadMutexHeld(sqlite3_mutex *p){
+  return (p->nRef!=0 && pthread_equal(p->owner, pthread_self()));
+}
+static int pthreadMutexNotheld(sqlite3_mutex *p){
+  return p->nRef==0 || pthread_equal(p->owner, pthread_self())==0;
+}
+#endif
+
+/*
+** Initialize and deinitialize the mutex subsystem.
+*/
+static int pthreadMutexInit(void){ return SQLITE_OK; }
+static int pthreadMutexEnd(void){ return SQLITE_OK; }
+
+/*
+** The sqlite3_mutex_alloc() routine allocates a new
+** mutex and returns a pointer to it.  If it returns NULL
+** that means that a mutex could not be allocated.  SQLite
+** will unwind its stack and return an error.  The argument
+** to sqlite3_mutex_alloc() is one of these integer constants:
+**
+** <ul>
+** <li>  SQLITE_MUTEX_FAST
+** <li>  SQLITE_MUTEX_RECURSIVE
+** <li>  SQLITE_MUTEX_STATIC_MASTER
+** <li>  SQLITE_MUTEX_STATIC_MEM
+** <li>  SQLITE_MUTEX_STATIC_MEM2
+** <li>  SQLITE_MUTEX_STATIC_PRNG
+** <li>  SQLITE_MUTEX_STATIC_LRU
+** <li>  SQLITE_MUTEX_STATIC_PMEM
+** </ul>
+**
+** The first two constants cause sqlite3_mutex_alloc() to create
+** a new mutex.  The new mutex is recursive when SQLITE_MUTEX_RECURSIVE
+** is used but not necessarily so when SQLITE_MUTEX_FAST is used.
+** The mutex implementation does not need to make a distinction
+** between SQLITE_MUTEX_RECURSIVE and SQLITE_MUTEX_FAST if it does
+** not want to.  But SQLite will only request a recursive mutex in
+** cases where it really needs one.  If a faster non-recursive mutex
+** implementation is available on the host platform, the mutex subsystem
+** might return such a mutex in response to SQLITE_MUTEX_FAST.
+**
+** The other allowed parameters to sqlite3_mutex_alloc() each return
+** a pointer to a static preexisting mutex.  Six static mutexes are
+** used by the current version of SQLite.  Future versions of SQLite
+** may add additional static mutexes.  Static mutexes are for internal
+** use by SQLite only.  Applications that use SQLite mutexes should
+** use only the dynamic mutexes returned by SQLITE_MUTEX_FAST or
+** SQLITE_MUTEX_RECURSIVE.
+**
+** Note that if one of the dynamic mutex parameters (SQLITE_MUTEX_FAST
+** or SQLITE_MUTEX_RECURSIVE) is used then sqlite3_mutex_alloc()
+** returns a different mutex on every call.  But for the static 
+** mutex types, the same mutex is returned on every call that has
+** the same type number.
+*/
+static sqlite3_mutex *pthreadMutexAlloc(int iType){
+  static sqlite3_mutex staticMutexes[] = {
+    SQLITE3_MUTEX_INITIALIZER,
+    SQLITE3_MUTEX_INITIALIZER,
+    SQLITE3_MUTEX_INITIALIZER,
+    SQLITE3_MUTEX_INITIALIZER,
+    SQLITE3_MUTEX_INITIALIZER,
+    SQLITE3_MUTEX_INITIALIZER
+  };
+  sqlite3_mutex *p;
+  switch( iType ){
+    case SQLITE_MUTEX_RECURSIVE: {
+      p = sqlite3MallocZero( sizeof(*p) );
+      if( p ){
+#ifdef SQLITE_HOMEGROWN_RECURSIVE_MUTEX
+        /* If recursive mutexes are not available, we will have to
+        ** build our own.  See below. */
+        pthread_mutex_init(&p->mutex, 0);
+#else
+        /* Use a recursive mutex if it is available */
+        pthread_mutexattr_t recursiveAttr;
+        pthread_mutexattr_init(&recursiveAttr);
+        pthread_mutexattr_settype(&recursiveAttr, PTHREAD_MUTEX_RECURSIVE);
+        pthread_mutex_init(&p->mutex, &recursiveAttr);
+        pthread_mutexattr_destroy(&recursiveAttr);
+#endif
+#if SQLITE_MUTEX_NREF
+        p->id = iType;
+#endif
+      }
+      break;
+    }
+    case SQLITE_MUTEX_FAST: {
+      p = sqlite3MallocZero( sizeof(*p) );
+      if( p ){
+#if SQLITE_MUTEX_NREF
+        p->id = iType;
+#endif
+        pthread_mutex_init(&p->mutex, 0);
+      }
+      break;
+    }
+    default: {
+      assert( iType-2 >= 0 );
+      assert( iType-2 < ArraySize(staticMutexes) );
+      p = &staticMutexes[iType-2];
+#if SQLITE_MUTEX_NREF
+      p->id = iType;
+#endif
+      break;
+    }
+  }
+  return p;
+}
+
+
+/*
+** This routine deallocates a previously
+** allocated mutex.  SQLite is careful to deallocate every
+** mutex that it allocates.
+*/
+static void pthreadMutexFree(sqlite3_mutex *p){
+  assert( p->nRef==0 );
+  assert( p->id==SQLITE_MUTEX_FAST || p->id==SQLITE_MUTEX_RECURSIVE );
+  pthread_mutex_destroy(&p->mutex);
+  sqlite3_free(p);
+}
+
+/*
+** The sqlite3_mutex_enter() and sqlite3_mutex_try() routines attempt
+** to enter a mutex.  If another thread is already within the mutex,
+** sqlite3_mutex_enter() will block and sqlite3_mutex_try() will return
+** SQLITE_BUSY.  The sqlite3_mutex_try() interface returns SQLITE_OK
+** upon successful entry.  Mutexes created using SQLITE_MUTEX_RECURSIVE can
+** be entered multiple times by the same thread.  In such cases the,
+** mutex must be exited an equal number of times before another thread
+** can enter.  If the same thread tries to enter any other kind of mutex
+** more than once, the behavior is undefined.
+*/
+static void pthreadMutexEnter(sqlite3_mutex *p){
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || pthreadMutexNotheld(p) );
+
+#ifdef SQLITE_HOMEGROWN_RECURSIVE_MUTEX
+  /* If recursive mutexes are not available, then we have to grow
+  ** our own.  This implementation assumes that pthread_equal()
+  ** is atomic - that it cannot be deceived into thinking self
+  ** and p->owner are equal if p->owner changes between two values
+  ** that are not equal to self while the comparison is taking place.
+  ** This implementation also assumes a coherent cache - that 
+  ** separate processes cannot read different values from the same
+  ** address at the same time.  If either of these two conditions
+  ** are not met, then the mutexes will fail and problems will result.
+  */
+  {
+    pthread_t self = pthread_self();
+    if( p->nRef>0 && pthread_equal(p->owner, self) ){
+      p->nRef++;
+    }else{
+      pthread_mutex_lock(&p->mutex);
+      assert( p->nRef==0 );
+      p->owner = self;
+      p->nRef = 1;
+    }
+  }
+#else
+  /* Use the built-in recursive mutexes if they are available.
+  */
+  pthread_mutex_lock(&p->mutex);
+#if SQLITE_MUTEX_NREF
+  assert( p->nRef>0 || p->owner==0 );
+  p->owner = pthread_self();
+  p->nRef++;
+#endif
+#endif
+
+#ifdef SQLITE_DEBUG
+  if( p->trace ){
+    printf("enter mutex %p (%d) with nRef=%d\n", p, p->trace, p->nRef);
+  }
+#endif
+}
+static int pthreadMutexTry(sqlite3_mutex *p){
+  int rc;
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || pthreadMutexNotheld(p) );
+
+#ifdef SQLITE_HOMEGROWN_RECURSIVE_MUTEX
+  /* If recursive mutexes are not available, then we have to grow
+  ** our own.  This implementation assumes that pthread_equal()
+  ** is atomic - that it cannot be deceived into thinking self
+  ** and p->owner are equal if p->owner changes between two values
+  ** that are not equal to self while the comparison is taking place.
+  ** This implementation also assumes a coherent cache - that 
+  ** separate processes cannot read different values from the same
+  ** address at the same time.  If either of these two conditions
+  ** are not met, then the mutexes will fail and problems will result.
+  */
+  {
+    pthread_t self = pthread_self();
+    if( p->nRef>0 && pthread_equal(p->owner, self) ){
+      p->nRef++;
+      rc = SQLITE_OK;
+    }else if( pthread_mutex_trylock(&p->mutex)==0 ){
+      assert( p->nRef==0 );
+      p->owner = self;
+      p->nRef = 1;
+      rc = SQLITE_OK;
+    }else{
+      rc = SQLITE_BUSY;
+    }
+  }
+#else
+  /* Use the built-in recursive mutexes if they are available.
+  */
+  if( pthread_mutex_trylock(&p->mutex)==0 ){
+#if SQLITE_MUTEX_NREF
+    p->owner = pthread_self();
+    p->nRef++;
+#endif
+    rc = SQLITE_OK;
+  }else{
+    rc = SQLITE_BUSY;
+  }
+#endif
+
+#ifdef SQLITE_DEBUG
+  if( rc==SQLITE_OK && p->trace ){
+    printf("enter mutex %p (%d) with nRef=%d\n", p, p->trace, p->nRef);
+  }
+#endif
+  return rc;
+}
+
+/*
+** The sqlite3_mutex_leave() routine exits a mutex that was
+** previously entered by the same thread.  The behavior
+** is undefined if the mutex is not currently entered or
+** is not currently allocated.  SQLite will never do either.
+*/
+static void pthreadMutexLeave(sqlite3_mutex *p){
+  assert( pthreadMutexHeld(p) );
+#if SQLITE_MUTEX_NREF
+  p->nRef--;
+  if( p->nRef==0 ) p->owner = 0;
+#endif
+  assert( p->nRef==0 || p->id==SQLITE_MUTEX_RECURSIVE );
+
+#ifdef SQLITE_HOMEGROWN_RECURSIVE_MUTEX
+  if( p->nRef==0 ){
+    pthread_mutex_unlock(&p->mutex);
+  }
+#else
+  pthread_mutex_unlock(&p->mutex);
+#endif
+
+#ifdef SQLITE_DEBUG
+  if( p->trace ){
+    printf("leave mutex %p (%d) with nRef=%d\n", p, p->trace, p->nRef);
+  }
+#endif
+}
+
+sqlite3_mutex_methods const *sqlite3DefaultMutex(void){
+  static const sqlite3_mutex_methods sMutex = {
+    pthreadMutexInit,
+    pthreadMutexEnd,
+    pthreadMutexAlloc,
+    pthreadMutexFree,
+    pthreadMutexEnter,
+    pthreadMutexTry,
+    pthreadMutexLeave,
+#ifdef SQLITE_DEBUG
+    pthreadMutexHeld,
+    pthreadMutexNotheld
+#else
+    0,
+    0
+#endif
+  };
+
+  return &sMutex;
+}
+
+#endif /* SQLITE_MUTEX_PTHREAD */
diff --git a/src/mutex_w32.c b/src/mutex_w32.c
new file mode 100644
index 0000000..bfd9dac
--- /dev/null
+++ b/src/mutex_w32.c
@@ -0,0 +1,332 @@
+/*
+** 2007 August 14
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains the C functions that implement mutexes for win32
+*/
+#include "sqliteInt.h"
+
+/*
+** The code in this file is only used if we are compiling multithreaded
+** on a win32 system.
+*/
+#ifdef SQLITE_MUTEX_W32
+
+/*
+** Each recursive mutex is an instance of the following structure.
+*/
+struct sqlite3_mutex {
+  CRITICAL_SECTION mutex;    /* Mutex controlling the lock */
+  int id;                    /* Mutex type */
+#ifdef SQLITE_DEBUG
+  volatile int nRef;         /* Number of enterances */
+  volatile DWORD owner;      /* Thread holding this mutex */
+  int trace;                 /* True to trace changes */
+#endif
+};
+#define SQLITE_W32_MUTEX_INITIALIZER { 0 }
+#ifdef SQLITE_DEBUG
+#define SQLITE3_MUTEX_INITIALIZER { SQLITE_W32_MUTEX_INITIALIZER, 0, 0L, (DWORD)0, 0 }
+#else
+#define SQLITE3_MUTEX_INITIALIZER { SQLITE_W32_MUTEX_INITIALIZER, 0 }
+#endif
+
+/*
+** Return true (non-zero) if we are running under WinNT, Win2K, WinXP,
+** or WinCE.  Return false (zero) for Win95, Win98, or WinME.
+**
+** Here is an interesting observation:  Win95, Win98, and WinME lack
+** the LockFileEx() API.  But we can still statically link against that
+** API as long as we don't call it win running Win95/98/ME.  A call to
+** this routine is used to determine if the host is Win95/98/ME or
+** WinNT/2K/XP so that we will know whether or not we can safely call
+** the LockFileEx() API.
+**
+** mutexIsNT() is only used for the TryEnterCriticalSection() API call,
+** which is only available if your application was compiled with 
+** _WIN32_WINNT defined to a value >= 0x0400.  Currently, the only
+** call to TryEnterCriticalSection() is #ifdef'ed out, so #ifdef 
+** this out as well.
+*/
+#if 0
+#if SQLITE_OS_WINCE
+# define mutexIsNT()  (1)
+#else
+  static int mutexIsNT(void){
+    static int osType = 0;
+    if( osType==0 ){
+      OSVERSIONINFO sInfo;
+      sInfo.dwOSVersionInfoSize = sizeof(sInfo);
+      GetVersionEx(&sInfo);
+      osType = sInfo.dwPlatformId==VER_PLATFORM_WIN32_NT ? 2 : 1;
+    }
+    return osType==2;
+  }
+#endif /* SQLITE_OS_WINCE */
+#endif
+
+#ifdef SQLITE_DEBUG
+/*
+** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routine are
+** intended for use only inside assert() statements.
+*/
+static int winMutexHeld(sqlite3_mutex *p){
+  return p->nRef!=0 && p->owner==GetCurrentThreadId();
+}
+static int winMutexNotheld2(sqlite3_mutex *p, DWORD tid){
+  return p->nRef==0 || p->owner!=tid;
+}
+static int winMutexNotheld(sqlite3_mutex *p){
+  DWORD tid = GetCurrentThreadId(); 
+  return winMutexNotheld2(p, tid);
+}
+#endif
+
+
+/*
+** Initialize and deinitialize the mutex subsystem.
+*/
+static sqlite3_mutex winMutex_staticMutexes[6] = {
+  SQLITE3_MUTEX_INITIALIZER,
+  SQLITE3_MUTEX_INITIALIZER,
+  SQLITE3_MUTEX_INITIALIZER,
+  SQLITE3_MUTEX_INITIALIZER,
+  SQLITE3_MUTEX_INITIALIZER,
+  SQLITE3_MUTEX_INITIALIZER
+};
+static int winMutex_isInit = 0;
+/* As winMutexInit() and winMutexEnd() are called as part
+** of the sqlite3_initialize and sqlite3_shutdown()
+** processing, the "interlocked" magic is probably not
+** strictly necessary.
+*/
+static long winMutex_lock = 0;
+
+static int winMutexInit(void){ 
+  /* The first to increment to 1 does actual initialization */
+  if( InterlockedCompareExchange(&winMutex_lock, 1, 0)==0 ){
+    int i;
+    for(i=0; i<ArraySize(winMutex_staticMutexes); i++){
+      InitializeCriticalSection(&winMutex_staticMutexes[i].mutex);
+    }
+    winMutex_isInit = 1;
+  }else{
+    /* Someone else is in the process of initing the static mutexes */
+    while( !winMutex_isInit ){
+      Sleep(1);
+    }
+  }
+  return SQLITE_OK; 
+}
+
+static int winMutexEnd(void){ 
+  /* The first to decrement to 0 does actual shutdown 
+  ** (which should be the last to shutdown.) */
+  if( InterlockedCompareExchange(&winMutex_lock, 0, 1)==1 ){
+    if( winMutex_isInit==1 ){
+      int i;
+      for(i=0; i<ArraySize(winMutex_staticMutexes); i++){
+        DeleteCriticalSection(&winMutex_staticMutexes[i].mutex);
+      }
+      winMutex_isInit = 0;
+    }
+  }
+  return SQLITE_OK; 
+}
+
+/*
+** The sqlite3_mutex_alloc() routine allocates a new
+** mutex and returns a pointer to it.  If it returns NULL
+** that means that a mutex could not be allocated.  SQLite
+** will unwind its stack and return an error.  The argument
+** to sqlite3_mutex_alloc() is one of these integer constants:
+**
+** <ul>
+** <li>  SQLITE_MUTEX_FAST
+** <li>  SQLITE_MUTEX_RECURSIVE
+** <li>  SQLITE_MUTEX_STATIC_MASTER
+** <li>  SQLITE_MUTEX_STATIC_MEM
+** <li>  SQLITE_MUTEX_STATIC_MEM2
+** <li>  SQLITE_MUTEX_STATIC_PRNG
+** <li>  SQLITE_MUTEX_STATIC_LRU
+** <li>  SQLITE_MUTEX_STATIC_PMEM
+** </ul>
+**
+** The first two constants cause sqlite3_mutex_alloc() to create
+** a new mutex.  The new mutex is recursive when SQLITE_MUTEX_RECURSIVE
+** is used but not necessarily so when SQLITE_MUTEX_FAST is used.
+** The mutex implementation does not need to make a distinction
+** between SQLITE_MUTEX_RECURSIVE and SQLITE_MUTEX_FAST if it does
+** not want to.  But SQLite will only request a recursive mutex in
+** cases where it really needs one.  If a faster non-recursive mutex
+** implementation is available on the host platform, the mutex subsystem
+** might return such a mutex in response to SQLITE_MUTEX_FAST.
+**
+** The other allowed parameters to sqlite3_mutex_alloc() each return
+** a pointer to a static preexisting mutex.  Six static mutexes are
+** used by the current version of SQLite.  Future versions of SQLite
+** may add additional static mutexes.  Static mutexes are for internal
+** use by SQLite only.  Applications that use SQLite mutexes should
+** use only the dynamic mutexes returned by SQLITE_MUTEX_FAST or
+** SQLITE_MUTEX_RECURSIVE.
+**
+** Note that if one of the dynamic mutex parameters (SQLITE_MUTEX_FAST
+** or SQLITE_MUTEX_RECURSIVE) is used then sqlite3_mutex_alloc()
+** returns a different mutex on every call.  But for the static 
+** mutex types, the same mutex is returned on every call that has
+** the same type number.
+*/
+static sqlite3_mutex *winMutexAlloc(int iType){
+  sqlite3_mutex *p;
+
+  switch( iType ){
+    case SQLITE_MUTEX_FAST:
+    case SQLITE_MUTEX_RECURSIVE: {
+      p = sqlite3MallocZero( sizeof(*p) );
+      if( p ){  
+#ifdef SQLITE_DEBUG
+        p->id = iType;
+#endif
+        InitializeCriticalSection(&p->mutex);
+      }
+      break;
+    }
+    default: {
+      assert( winMutex_isInit==1 );
+      assert( iType-2 >= 0 );
+      assert( iType-2 < ArraySize(winMutex_staticMutexes) );
+      p = &winMutex_staticMutexes[iType-2];
+#ifdef SQLITE_DEBUG
+      p->id = iType;
+#endif
+      break;
+    }
+  }
+  return p;
+}
+
+
+/*
+** This routine deallocates a previously
+** allocated mutex.  SQLite is careful to deallocate every
+** mutex that it allocates.
+*/
+static void winMutexFree(sqlite3_mutex *p){
+  assert( p );
+  assert( p->nRef==0 && p->owner==0 );
+  assert( p->id==SQLITE_MUTEX_FAST || p->id==SQLITE_MUTEX_RECURSIVE );
+  DeleteCriticalSection(&p->mutex);
+  sqlite3_free(p);
+}
+
+/*
+** The sqlite3_mutex_enter() and sqlite3_mutex_try() routines attempt
+** to enter a mutex.  If another thread is already within the mutex,
+** sqlite3_mutex_enter() will block and sqlite3_mutex_try() will return
+** SQLITE_BUSY.  The sqlite3_mutex_try() interface returns SQLITE_OK
+** upon successful entry.  Mutexes created using SQLITE_MUTEX_RECURSIVE can
+** be entered multiple times by the same thread.  In such cases the,
+** mutex must be exited an equal number of times before another thread
+** can enter.  If the same thread tries to enter any other kind of mutex
+** more than once, the behavior is undefined.
+*/
+static void winMutexEnter(sqlite3_mutex *p){
+#ifdef SQLITE_DEBUG
+  DWORD tid = GetCurrentThreadId(); 
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || winMutexNotheld2(p, tid) );
+#endif
+  EnterCriticalSection(&p->mutex);
+#ifdef SQLITE_DEBUG
+  assert( p->nRef>0 || p->owner==0 );
+  p->owner = tid; 
+  p->nRef++;
+  if( p->trace ){
+    printf("enter mutex %p (%d) with nRef=%d\n", p, p->trace, p->nRef);
+  }
+#endif
+}
+static int winMutexTry(sqlite3_mutex *p){
+#ifndef NDEBUG
+  DWORD tid = GetCurrentThreadId(); 
+#endif
+  int rc = SQLITE_BUSY;
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || winMutexNotheld2(p, tid) );
+  /*
+  ** The sqlite3_mutex_try() routine is very rarely used, and when it
+  ** is used it is merely an optimization.  So it is OK for it to always
+  ** fail.  
+  **
+  ** The TryEnterCriticalSection() interface is only available on WinNT.
+  ** And some windows compilers complain if you try to use it without
+  ** first doing some #defines that prevent SQLite from building on Win98.
+  ** For that reason, we will omit this optimization for now.  See
+  ** ticket #2685.
+  */
+#if 0
+  if( mutexIsNT() && TryEnterCriticalSection(&p->mutex) ){
+    p->owner = tid;
+    p->nRef++;
+    rc = SQLITE_OK;
+  }
+#else
+  UNUSED_PARAMETER(p);
+#endif
+#ifdef SQLITE_DEBUG
+  if( rc==SQLITE_OK && p->trace ){
+    printf("try mutex %p (%d) with nRef=%d\n", p, p->trace, p->nRef);
+  }
+#endif
+  return rc;
+}
+
+/*
+** The sqlite3_mutex_leave() routine exits a mutex that was
+** previously entered by the same thread.  The behavior
+** is undefined if the mutex is not currently entered or
+** is not currently allocated.  SQLite will never do either.
+*/
+static void winMutexLeave(sqlite3_mutex *p){
+#ifndef NDEBUG
+  DWORD tid = GetCurrentThreadId();
+  assert( p->nRef>0 );
+  assert( p->owner==tid );
+  p->nRef--;
+  if( p->nRef==0 ) p->owner = 0;
+  assert( p->nRef==0 || p->id==SQLITE_MUTEX_RECURSIVE );
+#endif
+  LeaveCriticalSection(&p->mutex);
+#ifdef SQLITE_DEBUG
+  if( p->trace ){
+    printf("leave mutex %p (%d) with nRef=%d\n", p, p->trace, p->nRef);
+  }
+#endif
+}
+
+sqlite3_mutex_methods const *sqlite3DefaultMutex(void){
+  static const sqlite3_mutex_methods sMutex = {
+    winMutexInit,
+    winMutexEnd,
+    winMutexAlloc,
+    winMutexFree,
+    winMutexEnter,
+    winMutexTry,
+    winMutexLeave,
+#ifdef SQLITE_DEBUG
+    winMutexHeld,
+    winMutexNotheld
+#else
+    0,
+    0
+#endif
+  };
+
+  return &sMutex;
+}
+#endif /* SQLITE_MUTEX_W32 */
diff --git a/src/notify.c b/src/notify.c
new file mode 100644
index 0000000..fcab5bf
--- /dev/null
+++ b/src/notify.c
@@ -0,0 +1,332 @@
+/*
+** 2009 March 3
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains the implementation of the sqlite3_unlock_notify()
+** API method and its associated functionality.
+*/
+#include "sqliteInt.h"
+#include "btreeInt.h"
+
+/* Omit this entire file if SQLITE_ENABLE_UNLOCK_NOTIFY is not defined. */
+#ifdef SQLITE_ENABLE_UNLOCK_NOTIFY
+
+/*
+** Public interfaces:
+**
+**   sqlite3ConnectionBlocked()
+**   sqlite3ConnectionUnlocked()
+**   sqlite3ConnectionClosed()
+**   sqlite3_unlock_notify()
+*/
+
+#define assertMutexHeld() \
+  assert( sqlite3_mutex_held(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER)) )
+
+/*
+** Head of a linked list of all sqlite3 objects created by this process
+** for which either sqlite3.pBlockingConnection or sqlite3.pUnlockConnection
+** is not NULL. This variable may only accessed while the STATIC_MASTER
+** mutex is held.
+*/
+static sqlite3 *SQLITE_WSD sqlite3BlockedList = 0;
+
+#ifndef NDEBUG
+/*
+** This function is a complex assert() that verifies the following 
+** properties of the blocked connections list:
+**
+**   1) Each entry in the list has a non-NULL value for either 
+**      pUnlockConnection or pBlockingConnection, or both.
+**
+**   2) All entries in the list that share a common value for 
+**      xUnlockNotify are grouped together.
+**
+**   3) If the argument db is not NULL, then none of the entries in the
+**      blocked connections list have pUnlockConnection or pBlockingConnection
+**      set to db. This is used when closing connection db.
+*/
+static void checkListProperties(sqlite3 *db){
+  sqlite3 *p;
+  for(p=sqlite3BlockedList; p; p=p->pNextBlocked){
+    int seen = 0;
+    sqlite3 *p2;
+
+    /* Verify property (1) */
+    assert( p->pUnlockConnection || p->pBlockingConnection );
+
+    /* Verify property (2) */
+    for(p2=sqlite3BlockedList; p2!=p; p2=p2->pNextBlocked){
+      if( p2->xUnlockNotify==p->xUnlockNotify ) seen = 1;
+      assert( p2->xUnlockNotify==p->xUnlockNotify || !seen );
+      assert( db==0 || p->pUnlockConnection!=db );
+      assert( db==0 || p->pBlockingConnection!=db );
+    }
+  }
+}
+#else
+# define checkListProperties(x)
+#endif
+
+/*
+** Remove connection db from the blocked connections list. If connection
+** db is not currently a part of the list, this function is a no-op.
+*/
+static void removeFromBlockedList(sqlite3 *db){
+  sqlite3 **pp;
+  assertMutexHeld();
+  for(pp=&sqlite3BlockedList; *pp; pp = &(*pp)->pNextBlocked){
+    if( *pp==db ){
+      *pp = (*pp)->pNextBlocked;
+      break;
+    }
+  }
+}
+
+/*
+** Add connection db to the blocked connections list. It is assumed
+** that it is not already a part of the list.
+*/
+static void addToBlockedList(sqlite3 *db){
+  sqlite3 **pp;
+  assertMutexHeld();
+  for(
+    pp=&sqlite3BlockedList; 
+    *pp && (*pp)->xUnlockNotify!=db->xUnlockNotify; 
+    pp=&(*pp)->pNextBlocked
+  );
+  db->pNextBlocked = *pp;
+  *pp = db;
+}
+
+/*
+** Obtain the STATIC_MASTER mutex.
+*/
+static void enterMutex(void){
+  sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
+  checkListProperties(0);
+}
+
+/*
+** Release the STATIC_MASTER mutex.
+*/
+static void leaveMutex(void){
+  assertMutexHeld();
+  checkListProperties(0);
+  sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
+}
+
+/*
+** Register an unlock-notify callback.
+**
+** This is called after connection "db" has attempted some operation
+** but has received an SQLITE_LOCKED error because another connection
+** (call it pOther) in the same process was busy using the same shared
+** cache.  pOther is found by looking at db->pBlockingConnection.
+**
+** If there is no blocking connection, the callback is invoked immediately,
+** before this routine returns.
+**
+** If pOther is already blocked on db, then report SQLITE_LOCKED, to indicate
+** a deadlock.
+**
+** Otherwise, make arrangements to invoke xNotify when pOther drops
+** its locks.
+**
+** Each call to this routine overrides any prior callbacks registered
+** on the same "db".  If xNotify==0 then any prior callbacks are immediately
+** cancelled.
+*/
+int sqlite3_unlock_notify(
+  sqlite3 *db,
+  void (*xNotify)(void **, int),
+  void *pArg
+){
+  int rc = SQLITE_OK;
+
+  sqlite3_mutex_enter(db->mutex);
+  enterMutex();
+
+  if( xNotify==0 ){
+    removeFromBlockedList(db);
+    db->pBlockingConnection = 0;
+    db->pUnlockConnection = 0;
+    db->xUnlockNotify = 0;
+    db->pUnlockArg = 0;
+  }else if( 0==db->pBlockingConnection ){
+    /* The blocking transaction has been concluded. Or there never was a 
+    ** blocking transaction. In either case, invoke the notify callback
+    ** immediately. 
+    */
+    xNotify(&pArg, 1);
+  }else{
+    sqlite3 *p;
+
+    for(p=db->pBlockingConnection; p && p!=db; p=p->pUnlockConnection){}
+    if( p ){
+      rc = SQLITE_LOCKED;              /* Deadlock detected. */
+    }else{
+      db->pUnlockConnection = db->pBlockingConnection;
+      db->xUnlockNotify = xNotify;
+      db->pUnlockArg = pArg;
+      removeFromBlockedList(db);
+      addToBlockedList(db);
+    }
+  }
+
+  leaveMutex();
+  assert( !db->mallocFailed );
+  sqlite3Error(db, rc, (rc?"database is deadlocked":0));
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+
+/*
+** This function is called while stepping or preparing a statement 
+** associated with connection db. The operation will return SQLITE_LOCKED
+** to the user because it requires a lock that will not be available
+** until connection pBlocker concludes its current transaction.
+*/
+void sqlite3ConnectionBlocked(sqlite3 *db, sqlite3 *pBlocker){
+  enterMutex();
+  if( db->pBlockingConnection==0 && db->pUnlockConnection==0 ){
+    addToBlockedList(db);
+  }
+  db->pBlockingConnection = pBlocker;
+  leaveMutex();
+}
+
+/*
+** This function is called when
+** the transaction opened by database db has just finished. Locks held 
+** by database connection db have been released.
+**
+** This function loops through each entry in the blocked connections
+** list and does the following:
+**
+**   1) If the sqlite3.pBlockingConnection member of a list entry is
+**      set to db, then set pBlockingConnection=0.
+**
+**   2) If the sqlite3.pUnlockConnection member of a list entry is
+**      set to db, then invoke the configured unlock-notify callback and
+**      set pUnlockConnection=0.
+**
+**   3) If the two steps above mean that pBlockingConnection==0 and
+**      pUnlockConnection==0, remove the entry from the blocked connections
+**      list.
+*/
+void sqlite3ConnectionUnlocked(sqlite3 *db){
+  void (*xUnlockNotify)(void **, int) = 0; /* Unlock-notify cb to invoke */
+  int nArg = 0;                            /* Number of entries in aArg[] */
+  sqlite3 **pp;                            /* Iterator variable */
+  void **aArg;               /* Arguments to the unlock callback */
+  void **aDyn = 0;           /* Dynamically allocated space for aArg[] */
+  void *aStatic[16];         /* Starter space for aArg[].  No malloc required */
+
+  aArg = aStatic;
+  enterMutex();         /* Enter STATIC_MASTER mutex */
+
+  /* This loop runs once for each entry in the blocked-connections list. */
+  for(pp=&sqlite3BlockedList; *pp; /* no-op */ ){
+    sqlite3 *p = *pp;
+
+    /* Step 1. */
+    if( p->pBlockingConnection==db ){
+      p->pBlockingConnection = 0;
+    }
+
+    /* Step 2. */
+    if( p->pUnlockConnection==db ){
+      assert( p->xUnlockNotify );
+      if( p->xUnlockNotify!=xUnlockNotify && nArg!=0 ){
+        xUnlockNotify(aArg, nArg);
+        nArg = 0;
+      }
+
+      sqlite3BeginBenignMalloc();
+      assert( aArg==aDyn || (aDyn==0 && aArg==aStatic) );
+      assert( nArg<=(int)ArraySize(aStatic) || aArg==aDyn );
+      if( (!aDyn && nArg==(int)ArraySize(aStatic))
+       || (aDyn && nArg==(int)(sqlite3MallocSize(aDyn)/sizeof(void*)))
+      ){
+        /* The aArg[] array needs to grow. */
+        void **pNew = (void **)sqlite3Malloc(nArg*sizeof(void *)*2);
+        if( pNew ){
+          memcpy(pNew, aArg, nArg*sizeof(void *));
+          sqlite3_free(aDyn);
+          aDyn = aArg = pNew;
+        }else{
+          /* This occurs when the array of context pointers that need to
+          ** be passed to the unlock-notify callback is larger than the
+          ** aStatic[] array allocated on the stack and the attempt to 
+          ** allocate a larger array from the heap has failed.
+          **
+          ** This is a difficult situation to handle. Returning an error
+          ** code to the caller is insufficient, as even if an error code
+          ** is returned the transaction on connection db will still be
+          ** closed and the unlock-notify callbacks on blocked connections
+          ** will go unissued. This might cause the application to wait
+          ** indefinitely for an unlock-notify callback that will never 
+          ** arrive.
+          **
+          ** Instead, invoke the unlock-notify callback with the context
+          ** array already accumulated. We can then clear the array and
+          ** begin accumulating any further context pointers without 
+          ** requiring any dynamic allocation. This is sub-optimal because
+          ** it means that instead of one callback with a large array of
+          ** context pointers the application will receive two or more
+          ** callbacks with smaller arrays of context pointers, which will
+          ** reduce the applications ability to prioritize multiple 
+          ** connections. But it is the best that can be done under the
+          ** circumstances.
+          */
+          xUnlockNotify(aArg, nArg);
+          nArg = 0;
+        }
+      }
+      sqlite3EndBenignMalloc();
+
+      aArg[nArg++] = p->pUnlockArg;
+      xUnlockNotify = p->xUnlockNotify;
+      p->pUnlockConnection = 0;
+      p->xUnlockNotify = 0;
+      p->pUnlockArg = 0;
+    }
+
+    /* Step 3. */
+    if( p->pBlockingConnection==0 && p->pUnlockConnection==0 ){
+      /* Remove connection p from the blocked connections list. */
+      *pp = p->pNextBlocked;
+      p->pNextBlocked = 0;
+    }else{
+      pp = &p->pNextBlocked;
+    }
+  }
+
+  if( nArg!=0 ){
+    xUnlockNotify(aArg, nArg);
+  }
+  sqlite3_free(aDyn);
+  leaveMutex();         /* Leave STATIC_MASTER mutex */
+}
+
+/*
+** This is called when the database connection passed as an argument is 
+** being closed. The connection is removed from the blocked list.
+*/
+void sqlite3ConnectionClosed(sqlite3 *db){
+  sqlite3ConnectionUnlocked(db);
+  enterMutex();
+  removeFromBlockedList(db);
+  checkListProperties(db);
+  leaveMutex();
+}
+#endif
diff --git a/src/os.c b/src/os.c
new file mode 100644
index 0000000..0b13c86
--- /dev/null
+++ b/src/os.c
@@ -0,0 +1,331 @@
+/*
+** 2005 November 29
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains OS interface code that is common to all
+** architectures.
+*/
+#define _SQLITE_OS_C_ 1
+#include "sqliteInt.h"
+#undef _SQLITE_OS_C_
+
+/*
+** The default SQLite sqlite3_vfs implementations do not allocate
+** memory (actually, os_unix.c allocates a small amount of memory
+** from within OsOpen()), but some third-party implementations may.
+** So we test the effects of a malloc() failing and the sqlite3OsXXX()
+** function returning SQLITE_IOERR_NOMEM using the DO_OS_MALLOC_TEST macro.
+**
+** The following functions are instrumented for malloc() failure 
+** testing:
+**
+**     sqlite3OsOpen()
+**     sqlite3OsRead()
+**     sqlite3OsWrite()
+**     sqlite3OsSync()
+**     sqlite3OsLock()
+**
+*/
+#if defined(SQLITE_TEST)
+int sqlite3_memdebug_vfs_oom_test = 1;
+  #define DO_OS_MALLOC_TEST(x)                                       \
+  if (sqlite3_memdebug_vfs_oom_test && (!x || !sqlite3IsMemJournal(x))) {  \
+    void *pTstAlloc = sqlite3Malloc(10);                             \
+    if (!pTstAlloc) return SQLITE_IOERR_NOMEM;                       \
+    sqlite3_free(pTstAlloc);                                         \
+  }
+#else
+  #define DO_OS_MALLOC_TEST(x)
+#endif
+
+/*
+** The following routines are convenience wrappers around methods
+** of the sqlite3_file object.  This is mostly just syntactic sugar. All
+** of this would be completely automatic if SQLite were coded using
+** C++ instead of plain old C.
+*/
+int sqlite3OsClose(sqlite3_file *pId){
+  int rc = SQLITE_OK;
+  if( pId->pMethods ){
+    rc = pId->pMethods->xClose(pId);
+    pId->pMethods = 0;
+  }
+  return rc;
+}
+int sqlite3OsRead(sqlite3_file *id, void *pBuf, int amt, i64 offset){
+  DO_OS_MALLOC_TEST(id);
+  return id->pMethods->xRead(id, pBuf, amt, offset);
+}
+int sqlite3OsWrite(sqlite3_file *id, const void *pBuf, int amt, i64 offset){
+  DO_OS_MALLOC_TEST(id);
+  return id->pMethods->xWrite(id, pBuf, amt, offset);
+}
+int sqlite3OsTruncate(sqlite3_file *id, i64 size){
+  return id->pMethods->xTruncate(id, size);
+}
+int sqlite3OsSync(sqlite3_file *id, int flags){
+  DO_OS_MALLOC_TEST(id);
+  return id->pMethods->xSync(id, flags);
+}
+int sqlite3OsFileSize(sqlite3_file *id, i64 *pSize){
+  DO_OS_MALLOC_TEST(id);
+  return id->pMethods->xFileSize(id, pSize);
+}
+int sqlite3OsLock(sqlite3_file *id, int lockType){
+  DO_OS_MALLOC_TEST(id);
+  return id->pMethods->xLock(id, lockType);
+}
+int sqlite3OsUnlock(sqlite3_file *id, int lockType){
+  return id->pMethods->xUnlock(id, lockType);
+}
+int sqlite3OsCheckReservedLock(sqlite3_file *id, int *pResOut){
+  DO_OS_MALLOC_TEST(id);
+  return id->pMethods->xCheckReservedLock(id, pResOut);
+}
+int sqlite3OsFileControl(sqlite3_file *id, int op, void *pArg){
+  return id->pMethods->xFileControl(id, op, pArg);
+}
+int sqlite3OsSectorSize(sqlite3_file *id){
+  int (*xSectorSize)(sqlite3_file*) = id->pMethods->xSectorSize;
+  return (xSectorSize ? xSectorSize(id) : SQLITE_DEFAULT_SECTOR_SIZE);
+}
+int sqlite3OsDeviceCharacteristics(sqlite3_file *id){
+  return id->pMethods->xDeviceCharacteristics(id);
+}
+int sqlite3OsShmLock(sqlite3_file *id, int offset, int n, int flags){
+  return id->pMethods->xShmLock(id, offset, n, flags);
+}
+void sqlite3OsShmBarrier(sqlite3_file *id){
+  id->pMethods->xShmBarrier(id);
+}
+int sqlite3OsShmUnmap(sqlite3_file *id, int deleteFlag){
+  return id->pMethods->xShmUnmap(id, deleteFlag);
+}
+int sqlite3OsShmMap(
+  sqlite3_file *id,               /* Database file handle */
+  int iPage,
+  int pgsz,
+  int bExtend,                    /* True to extend file if necessary */
+  void volatile **pp              /* OUT: Pointer to mapping */
+){
+  return id->pMethods->xShmMap(id, iPage, pgsz, bExtend, pp);
+}
+
+/*
+** The next group of routines are convenience wrappers around the
+** VFS methods.
+*/
+int sqlite3OsOpen(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  sqlite3_file *pFile, 
+  int flags, 
+  int *pFlagsOut
+){
+  int rc;
+  DO_OS_MALLOC_TEST(0);
+  /* 0x87f3f is a mask of SQLITE_OPEN_ flags that are valid to be passed
+  ** down into the VFS layer.  Some SQLITE_OPEN_ flags (for example,
+  ** SQLITE_OPEN_FULLMUTEX or SQLITE_OPEN_SHAREDCACHE) are blocked before
+  ** reaching the VFS. */
+  rc = pVfs->xOpen(pVfs, zPath, pFile, flags & 0x87f7f, pFlagsOut);
+  assert( rc==SQLITE_OK || pFile->pMethods==0 );
+  return rc;
+}
+int sqlite3OsDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
+  return pVfs->xDelete(pVfs, zPath, dirSync);
+}
+int sqlite3OsAccess(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  int flags, 
+  int *pResOut
+){
+  DO_OS_MALLOC_TEST(0);
+  return pVfs->xAccess(pVfs, zPath, flags, pResOut);
+}
+int sqlite3OsFullPathname(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  int nPathOut, 
+  char *zPathOut
+){
+  zPathOut[0] = 0;
+  return pVfs->xFullPathname(pVfs, zPath, nPathOut, zPathOut);
+}
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+void *sqlite3OsDlOpen(sqlite3_vfs *pVfs, const char *zPath){
+  return pVfs->xDlOpen(pVfs, zPath);
+}
+void sqlite3OsDlError(sqlite3_vfs *pVfs, int nByte, char *zBufOut){
+  pVfs->xDlError(pVfs, nByte, zBufOut);
+}
+void (*sqlite3OsDlSym(sqlite3_vfs *pVfs, void *pHdle, const char *zSym))(void){
+  return pVfs->xDlSym(pVfs, pHdle, zSym);
+}
+void sqlite3OsDlClose(sqlite3_vfs *pVfs, void *pHandle){
+  pVfs->xDlClose(pVfs, pHandle);
+}
+#endif /* SQLITE_OMIT_LOAD_EXTENSION */
+int sqlite3OsRandomness(sqlite3_vfs *pVfs, int nByte, char *zBufOut){
+  return pVfs->xRandomness(pVfs, nByte, zBufOut);
+}
+int sqlite3OsSleep(sqlite3_vfs *pVfs, int nMicro){
+  return pVfs->xSleep(pVfs, nMicro);
+}
+int sqlite3OsCurrentTimeInt64(sqlite3_vfs *pVfs, sqlite3_int64 *pTimeOut){
+  int rc;
+  /* IMPLEMENTATION-OF: R-49045-42493 SQLite will use the xCurrentTimeInt64()
+  ** method to get the current date and time if that method is available
+  ** (if iVersion is 2 or greater and the function pointer is not NULL) and
+  ** will fall back to xCurrentTime() if xCurrentTimeInt64() is
+  ** unavailable.
+  */
+  if( pVfs->iVersion>=2 && pVfs->xCurrentTimeInt64 ){
+    rc = pVfs->xCurrentTimeInt64(pVfs, pTimeOut);
+  }else{
+    double r;
+    rc = pVfs->xCurrentTime(pVfs, &r);
+    *pTimeOut = (sqlite3_int64)(r*86400000.0);
+  }
+  return rc;
+}
+
+int sqlite3OsOpenMalloc(
+  sqlite3_vfs *pVfs, 
+  const char *zFile, 
+  sqlite3_file **ppFile, 
+  int flags,
+  int *pOutFlags
+){
+  int rc = SQLITE_NOMEM;
+  sqlite3_file *pFile;
+  pFile = (sqlite3_file *)sqlite3MallocZero(pVfs->szOsFile);
+  if( pFile ){
+    rc = sqlite3OsOpen(pVfs, zFile, pFile, flags, pOutFlags);
+    if( rc!=SQLITE_OK ){
+      sqlite3_free(pFile);
+    }else{
+      *ppFile = pFile;
+    }
+  }
+  return rc;
+}
+int sqlite3OsCloseFree(sqlite3_file *pFile){
+  int rc = SQLITE_OK;
+  assert( pFile );
+  rc = sqlite3OsClose(pFile);
+  sqlite3_free(pFile);
+  return rc;
+}
+
+/*
+** This function is a wrapper around the OS specific implementation of
+** sqlite3_os_init(). The purpose of the wrapper is to provide the
+** ability to simulate a malloc failure, so that the handling of an
+** error in sqlite3_os_init() by the upper layers can be tested.
+*/
+int sqlite3OsInit(void){
+  void *p = sqlite3_malloc(10);
+  if( p==0 ) return SQLITE_NOMEM;
+  sqlite3_free(p);
+  return sqlite3_os_init();
+}
+
+/*
+** The list of all registered VFS implementations.
+*/
+static sqlite3_vfs * SQLITE_WSD vfsList = 0;
+#define vfsList GLOBAL(sqlite3_vfs *, vfsList)
+
+/*
+** Locate a VFS by name.  If no name is given, simply return the
+** first VFS on the list.
+*/
+sqlite3_vfs *sqlite3_vfs_find(const char *zVfs){
+  sqlite3_vfs *pVfs = 0;
+#if SQLITE_THREADSAFE
+  sqlite3_mutex *mutex;
+#endif
+#ifndef SQLITE_OMIT_AUTOINIT
+  int rc = sqlite3_initialize();
+  if( rc ) return 0;
+#endif
+#if SQLITE_THREADSAFE
+  mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER);
+#endif
+  sqlite3_mutex_enter(mutex);
+  for(pVfs = vfsList; pVfs; pVfs=pVfs->pNext){
+    if( zVfs==0 ) break;
+    if( strcmp(zVfs, pVfs->zName)==0 ) break;
+  }
+  sqlite3_mutex_leave(mutex);
+  return pVfs;
+}
+
+/*
+** Unlink a VFS from the linked list
+*/
+static void vfsUnlink(sqlite3_vfs *pVfs){
+  assert( sqlite3_mutex_held(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER)) );
+  if( pVfs==0 ){
+    /* No-op */
+  }else if( vfsList==pVfs ){
+    vfsList = pVfs->pNext;
+  }else if( vfsList ){
+    sqlite3_vfs *p = vfsList;
+    while( p->pNext && p->pNext!=pVfs ){
+      p = p->pNext;
+    }
+    if( p->pNext==pVfs ){
+      p->pNext = pVfs->pNext;
+    }
+  }
+}
+
+/*
+** Register a VFS with the system.  It is harmless to register the same
+** VFS multiple times.  The new VFS becomes the default if makeDflt is
+** true.
+*/
+int sqlite3_vfs_register(sqlite3_vfs *pVfs, int makeDflt){
+  MUTEX_LOGIC(sqlite3_mutex *mutex;)
+#ifndef SQLITE_OMIT_AUTOINIT
+  int rc = sqlite3_initialize();
+  if( rc ) return rc;
+#endif
+  MUTEX_LOGIC( mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER); )
+  sqlite3_mutex_enter(mutex);
+  vfsUnlink(pVfs);
+  if( makeDflt || vfsList==0 ){
+    pVfs->pNext = vfsList;
+    vfsList = pVfs;
+  }else{
+    pVfs->pNext = vfsList->pNext;
+    vfsList->pNext = pVfs;
+  }
+  assert(vfsList);
+  sqlite3_mutex_leave(mutex);
+  return SQLITE_OK;
+}
+
+/*
+** Unregister a VFS so that it is no longer accessible.
+*/
+int sqlite3_vfs_unregister(sqlite3_vfs *pVfs){
+#if SQLITE_THREADSAFE
+  sqlite3_mutex *mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER);
+#endif
+  sqlite3_mutex_enter(mutex);
+  vfsUnlink(pVfs);
+  sqlite3_mutex_leave(mutex);
+  return SQLITE_OK;
+}
diff --git a/src/os.h b/src/os.h
new file mode 100644
index 0000000..7f17c20
--- /dev/null
+++ b/src/os.h
@@ -0,0 +1,279 @@
+/*
+** 2001 September 16
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This header file (together with is companion C source-code file
+** "os.c") attempt to abstract the underlying operating system so that
+** the SQLite library will work on both POSIX and windows systems.
+**
+** This header file is #include-ed by sqliteInt.h and thus ends up
+** being included by every source file.
+*/
+#ifndef _SQLITE_OS_H_
+#define _SQLITE_OS_H_
+
+/*
+** Figure out if we are dealing with Unix, Windows, or some other
+** operating system.  After the following block of preprocess macros,
+** all of SQLITE_OS_UNIX, SQLITE_OS_WIN, SQLITE_OS_OS2, and SQLITE_OS_OTHER 
+** will defined to either 1 or 0.  One of the four will be 1.  The other 
+** three will be 0.
+*/
+#if defined(SQLITE_OS_OTHER)
+# if SQLITE_OS_OTHER==1
+#   undef SQLITE_OS_UNIX
+#   define SQLITE_OS_UNIX 0
+#   undef SQLITE_OS_WIN
+#   define SQLITE_OS_WIN 0
+#   undef SQLITE_OS_OS2
+#   define SQLITE_OS_OS2 0
+# else
+#   undef SQLITE_OS_OTHER
+# endif
+#endif
+#if !defined(SQLITE_OS_UNIX) && !defined(SQLITE_OS_OTHER)
+# define SQLITE_OS_OTHER 0
+# ifndef SQLITE_OS_WIN
+#   if defined(_WIN32) || defined(WIN32) || defined(__CYGWIN__) || defined(__MINGW32__) || defined(__BORLANDC__)
+#     define SQLITE_OS_WIN 1
+#     define SQLITE_OS_UNIX 0
+#     define SQLITE_OS_OS2 0
+#   elif defined(__EMX__) || defined(_OS2) || defined(OS2) || defined(_OS2_) || defined(__OS2__)
+#     define SQLITE_OS_WIN 0
+#     define SQLITE_OS_UNIX 0
+#     define SQLITE_OS_OS2 1
+#   else
+#     define SQLITE_OS_WIN 0
+#     define SQLITE_OS_UNIX 1
+#     define SQLITE_OS_OS2 0
+#  endif
+# else
+#  define SQLITE_OS_UNIX 0
+#  define SQLITE_OS_OS2 0
+# endif
+#else
+# ifndef SQLITE_OS_WIN
+#  define SQLITE_OS_WIN 0
+# endif
+#endif
+
+/*
+** Determine if we are dealing with WindowsCE - which has a much
+** reduced API.
+*/
+#if defined(_WIN32_WCE)
+# define SQLITE_OS_WINCE 1
+#else
+# define SQLITE_OS_WINCE 0
+#endif
+
+
+/*
+** Define the maximum size of a temporary filename
+*/
+#if SQLITE_OS_WIN
+# include <windows.h>
+# define SQLITE_TEMPNAME_SIZE (MAX_PATH+50)
+#elif SQLITE_OS_OS2
+# if (__GNUC__ > 3 || __GNUC__ == 3 && __GNUC_MINOR__ >= 3) && defined(OS2_HIGH_MEMORY)
+#  include <os2safe.h> /* has to be included before os2.h for linking to work */
+# endif
+# define INCL_DOSDATETIME
+# define INCL_DOSFILEMGR
+# define INCL_DOSERRORS
+# define INCL_DOSMISC
+# define INCL_DOSPROCESS
+# define INCL_DOSMODULEMGR
+# define INCL_DOSSEMAPHORES
+# include <os2.h>
+# include <uconv.h>
+# define SQLITE_TEMPNAME_SIZE (CCHMAXPATHCOMP)
+#else
+# define SQLITE_TEMPNAME_SIZE 200
+#endif
+
+/* If the SET_FULLSYNC macro is not defined above, then make it
+** a no-op
+*/
+#ifndef SET_FULLSYNC
+# define SET_FULLSYNC(x,y)
+#endif
+
+/*
+** The default size of a disk sector
+*/
+#ifndef SQLITE_DEFAULT_SECTOR_SIZE
+# define SQLITE_DEFAULT_SECTOR_SIZE 512
+#endif
+
+/*
+** Temporary files are named starting with this prefix followed by 16 random
+** alphanumeric characters, and no file extension. They are stored in the
+** OS's standard temporary file directory, and are deleted prior to exit.
+** If sqlite is being embedded in another program, you may wish to change the
+** prefix to reflect your program's name, so that if your program exits
+** prematurely, old temporary files can be easily identified. This can be done
+** using -DSQLITE_TEMP_FILE_PREFIX=myprefix_ on the compiler command line.
+**
+** 2006-10-31:  The default prefix used to be "sqlite_".  But then
+** Mcafee started using SQLite in their anti-virus product and it
+** started putting files with the "sqlite" name in the c:/temp folder.
+** This annoyed many windows users.  Those users would then do a 
+** Google search for "sqlite", find the telephone numbers of the
+** developers and call to wake them up at night and complain.
+** For this reason, the default name prefix is changed to be "sqlite" 
+** spelled backwards.  So the temp files are still identified, but
+** anybody smart enough to figure out the code is also likely smart
+** enough to know that calling the developer will not help get rid
+** of the file.
+*/
+#ifndef SQLITE_TEMP_FILE_PREFIX
+# define SQLITE_TEMP_FILE_PREFIX "etilqs_"
+#endif
+
+/*
+** The following values may be passed as the second argument to
+** sqlite3OsLock(). The various locks exhibit the following semantics:
+**
+** SHARED:    Any number of processes may hold a SHARED lock simultaneously.
+** RESERVED:  A single process may hold a RESERVED lock on a file at
+**            any time. Other processes may hold and obtain new SHARED locks.
+** PENDING:   A single process may hold a PENDING lock on a file at
+**            any one time. Existing SHARED locks may persist, but no new
+**            SHARED locks may be obtained by other processes.
+** EXCLUSIVE: An EXCLUSIVE lock precludes all other locks.
+**
+** PENDING_LOCK may not be passed directly to sqlite3OsLock(). Instead, a
+** process that requests an EXCLUSIVE lock may actually obtain a PENDING
+** lock. This can be upgraded to an EXCLUSIVE lock by a subsequent call to
+** sqlite3OsLock().
+*/
+#define NO_LOCK         0
+#define SHARED_LOCK     1
+#define RESERVED_LOCK   2
+#define PENDING_LOCK    3
+#define EXCLUSIVE_LOCK  4
+
+/*
+** File Locking Notes:  (Mostly about windows but also some info for Unix)
+**
+** We cannot use LockFileEx() or UnlockFileEx() on Win95/98/ME because
+** those functions are not available.  So we use only LockFile() and
+** UnlockFile().
+**
+** LockFile() prevents not just writing but also reading by other processes.
+** A SHARED_LOCK is obtained by locking a single randomly-chosen 
+** byte out of a specific range of bytes. The lock byte is obtained at 
+** random so two separate readers can probably access the file at the 
+** same time, unless they are unlucky and choose the same lock byte.
+** An EXCLUSIVE_LOCK is obtained by locking all bytes in the range.
+** There can only be one writer.  A RESERVED_LOCK is obtained by locking
+** a single byte of the file that is designated as the reserved lock byte.
+** A PENDING_LOCK is obtained by locking a designated byte different from
+** the RESERVED_LOCK byte.
+**
+** On WinNT/2K/XP systems, LockFileEx() and UnlockFileEx() are available,
+** which means we can use reader/writer locks.  When reader/writer locks
+** are used, the lock is placed on the same range of bytes that is used
+** for probabilistic locking in Win95/98/ME.  Hence, the locking scheme
+** will support two or more Win95 readers or two or more WinNT readers.
+** But a single Win95 reader will lock out all WinNT readers and a single
+** WinNT reader will lock out all other Win95 readers.
+**
+** The following #defines specify the range of bytes used for locking.
+** SHARED_SIZE is the number of bytes available in the pool from which
+** a random byte is selected for a shared lock.  The pool of bytes for
+** shared locks begins at SHARED_FIRST. 
+**
+** The same locking strategy and
+** byte ranges are used for Unix.  This leaves open the possiblity of having
+** clients on win95, winNT, and unix all talking to the same shared file
+** and all locking correctly.  To do so would require that samba (or whatever
+** tool is being used for file sharing) implements locks correctly between
+** windows and unix.  I'm guessing that isn't likely to happen, but by
+** using the same locking range we are at least open to the possibility.
+**
+** Locking in windows is manditory.  For this reason, we cannot store
+** actual data in the bytes used for locking.  The pager never allocates
+** the pages involved in locking therefore.  SHARED_SIZE is selected so
+** that all locks will fit on a single page even at the minimum page size.
+** PENDING_BYTE defines the beginning of the locks.  By default PENDING_BYTE
+** is set high so that we don't have to allocate an unused page except
+** for very large databases.  But one should test the page skipping logic 
+** by setting PENDING_BYTE low and running the entire regression suite.
+**
+** Changing the value of PENDING_BYTE results in a subtly incompatible
+** file format.  Depending on how it is changed, you might not notice
+** the incompatibility right away, even running a full regression test.
+** The default location of PENDING_BYTE is the first byte past the
+** 1GB boundary.
+**
+*/
+#ifdef SQLITE_OMIT_WSD
+# define PENDING_BYTE     (0x40000000)
+#else
+# define PENDING_BYTE      sqlite3PendingByte
+#endif
+#define RESERVED_BYTE     (PENDING_BYTE+1)
+#define SHARED_FIRST      (PENDING_BYTE+2)
+#define SHARED_SIZE       510
+
+/*
+** Wrapper around OS specific sqlite3_os_init() function.
+*/
+int sqlite3OsInit(void);
+
+/* 
+** Functions for accessing sqlite3_file methods 
+*/
+int sqlite3OsClose(sqlite3_file*);
+int sqlite3OsRead(sqlite3_file*, void*, int amt, i64 offset);
+int sqlite3OsWrite(sqlite3_file*, const void*, int amt, i64 offset);
+int sqlite3OsTruncate(sqlite3_file*, i64 size);
+int sqlite3OsSync(sqlite3_file*, int);
+int sqlite3OsFileSize(sqlite3_file*, i64 *pSize);
+int sqlite3OsLock(sqlite3_file*, int);
+int sqlite3OsUnlock(sqlite3_file*, int);
+int sqlite3OsCheckReservedLock(sqlite3_file *id, int *pResOut);
+int sqlite3OsFileControl(sqlite3_file*,int,void*);
+#define SQLITE_FCNTL_DB_UNCHANGED 0xca093fa0
+int sqlite3OsSectorSize(sqlite3_file *id);
+int sqlite3OsDeviceCharacteristics(sqlite3_file *id);
+int sqlite3OsShmMap(sqlite3_file *,int,int,int,void volatile **);
+int sqlite3OsShmLock(sqlite3_file *id, int, int, int);
+void sqlite3OsShmBarrier(sqlite3_file *id);
+int sqlite3OsShmUnmap(sqlite3_file *id, int);
+
+/* 
+** Functions for accessing sqlite3_vfs methods 
+*/
+int sqlite3OsOpen(sqlite3_vfs *, const char *, sqlite3_file*, int, int *);
+int sqlite3OsDelete(sqlite3_vfs *, const char *, int);
+int sqlite3OsAccess(sqlite3_vfs *, const char *, int, int *pResOut);
+int sqlite3OsFullPathname(sqlite3_vfs *, const char *, int, char *);
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+void *sqlite3OsDlOpen(sqlite3_vfs *, const char *);
+void sqlite3OsDlError(sqlite3_vfs *, int, char *);
+void (*sqlite3OsDlSym(sqlite3_vfs *, void *, const char *))(void);
+void sqlite3OsDlClose(sqlite3_vfs *, void *);
+#endif /* SQLITE_OMIT_LOAD_EXTENSION */
+int sqlite3OsRandomness(sqlite3_vfs *, int, char *);
+int sqlite3OsSleep(sqlite3_vfs *, int);
+int sqlite3OsCurrentTimeInt64(sqlite3_vfs *, sqlite3_int64*);
+
+/*
+** Convenience functions for opening and closing files using 
+** sqlite3_malloc() to obtain space for the file-handle structure.
+*/
+int sqlite3OsOpenMalloc(sqlite3_vfs *, const char *, sqlite3_file **, int,int*);
+int sqlite3OsCloseFree(sqlite3_file *);
+
+#endif /* _SQLITE_OS_H_ */
diff --git a/src/os_common.h b/src/os_common.h
new file mode 100644
index 0000000..f6c3e7f
--- /dev/null
+++ b/src/os_common.h
@@ -0,0 +1,115 @@
+/*
+** 2004 May 22
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains macros and a little bit of code that is common to
+** all of the platform-specific files (os_*.c) and is #included into those
+** files.
+**
+** This file should be #included by the os_*.c files only.  It is not a
+** general purpose header file.
+*/
+#ifndef _OS_COMMON_H_
+#define _OS_COMMON_H_
+
+/*
+** At least two bugs have slipped in because we changed the MEMORY_DEBUG
+** macro to SQLITE_DEBUG and some older makefiles have not yet made the
+** switch.  The following code should catch this problem at compile-time.
+*/
+#ifdef MEMORY_DEBUG
+# error "The MEMORY_DEBUG macro is obsolete.  Use SQLITE_DEBUG instead."
+#endif
+
+#if defined(SQLITE_TEST) && defined(SQLITE_DEBUG)
+# ifndef SQLITE_DEBUG_OS_TRACE
+#   define SQLITE_DEBUG_OS_TRACE 0
+# endif
+  int sqlite3OSTrace = SQLITE_DEBUG_OS_TRACE;
+# define OSTRACE(X)          if( sqlite3OSTrace ) sqlite3DebugPrintf X
+#else
+# define OSTRACE(X)
+#endif
+
+/*
+** Macros for performance tracing.  Normally turned off.  Only works
+** on i486 hardware.
+*/
+#ifdef SQLITE_PERFORMANCE_TRACE
+
+/* 
+** hwtime.h contains inline assembler code for implementing 
+** high-performance timing routines.
+*/
+#include "hwtime.h"
+
+static sqlite_uint64 g_start;
+static sqlite_uint64 g_elapsed;
+#define TIMER_START       g_start=sqlite3Hwtime()
+#define TIMER_END         g_elapsed=sqlite3Hwtime()-g_start
+#define TIMER_ELAPSED     g_elapsed
+#else
+#define TIMER_START
+#define TIMER_END
+#define TIMER_ELAPSED     ((sqlite_uint64)0)
+#endif
+
+/*
+** If we compile with the SQLITE_TEST macro set, then the following block
+** of code will give us the ability to simulate a disk I/O error.  This
+** is used for testing the I/O recovery logic.
+*/
+#ifdef SQLITE_TEST
+int sqlite3_io_error_hit = 0;            /* Total number of I/O Errors */
+int sqlite3_io_error_hardhit = 0;        /* Number of non-benign errors */
+int sqlite3_io_error_pending = 0;        /* Count down to first I/O error */
+int sqlite3_io_error_persist = 0;        /* True if I/O errors persist */
+int sqlite3_io_error_benign = 0;         /* True if errors are benign */
+int sqlite3_diskfull_pending = 0;
+int sqlite3_diskfull = 0;
+#define SimulateIOErrorBenign(X) sqlite3_io_error_benign=(X)
+#define SimulateIOError(CODE)  \
+  if( (sqlite3_io_error_persist && sqlite3_io_error_hit) \
+       || sqlite3_io_error_pending-- == 1 )  \
+              { local_ioerr(); CODE; }
+static void local_ioerr(){
+  IOTRACE(("IOERR\n"));
+  sqlite3_io_error_hit++;
+  if( !sqlite3_io_error_benign ) sqlite3_io_error_hardhit++;
+}
+#define SimulateDiskfullError(CODE) \
+   if( sqlite3_diskfull_pending ){ \
+     if( sqlite3_diskfull_pending == 1 ){ \
+       local_ioerr(); \
+       sqlite3_diskfull = 1; \
+       sqlite3_io_error_hit = 1; \
+       CODE; \
+     }else{ \
+       sqlite3_diskfull_pending--; \
+     } \
+   }
+#else
+#define SimulateIOErrorBenign(X)
+#define SimulateIOError(A)
+#define SimulateDiskfullError(A)
+#endif
+
+/*
+** When testing, keep a count of the number of open files.
+*/
+#ifdef SQLITE_TEST
+int sqlite3_open_file_count = 0;
+#define OpenCounter(X)  sqlite3_open_file_count+=(X)
+#else
+#define OpenCounter(X)
+#endif
+
+#endif /* !defined(_OS_COMMON_H_) */
diff --git a/src/os_os2.c b/src/os_os2.c
new file mode 100644
index 0000000..487ac3c
--- /dev/null
+++ b/src/os_os2.c
@@ -0,0 +1,1924 @@
+/*
+** 2006 Feb 14
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains code that is specific to OS/2.
+*/
+
+#include "sqliteInt.h"
+
+#if SQLITE_OS_OS2
+
+/*
+** A Note About Memory Allocation:
+**
+** This driver uses malloc()/free() directly rather than going through
+** the SQLite-wrappers sqlite3_malloc()/sqlite3_free().  Those wrappers
+** are designed for use on embedded systems where memory is scarce and
+** malloc failures happen frequently.  OS/2 does not typically run on
+** embedded systems, and when it does the developers normally have bigger
+** problems to worry about than running out of memory.  So there is not
+** a compelling need to use the wrappers.
+**
+** But there is a good reason to not use the wrappers.  If we use the
+** wrappers then we will get simulated malloc() failures within this
+** driver.  And that causes all kinds of problems for our tests.  We
+** could enhance SQLite to deal with simulated malloc failures within
+** the OS driver, but the code to deal with those failure would not
+** be exercised on Linux (which does not need to malloc() in the driver)
+** and so we would have difficulty writing coverage tests for that
+** code.  Better to leave the code out, we think.
+**
+** The point of this discussion is as follows:  When creating a new
+** OS layer for an embedded system, if you use this file as an example,
+** avoid the use of malloc()/free().  Those routines work ok on OS/2
+** desktops but not so well in embedded systems.
+*/
+
+/*
+** Macros used to determine whether or not to use threads.
+*/
+#if defined(SQLITE_THREADSAFE) && SQLITE_THREADSAFE
+# define SQLITE_OS2_THREADS 1
+#endif
+
+/*
+** Include code that is common to all os_*.c files
+*/
+#include "os_common.h"
+
+/* Forward references */
+typedef struct os2File os2File;         /* The file structure */
+typedef struct os2ShmNode os2ShmNode;   /* A shared descritive memory node */
+typedef struct os2ShmLink os2ShmLink;   /* A connection to shared-memory */
+
+/*
+** The os2File structure is subclass of sqlite3_file specific for the OS/2
+** protability layer.
+*/
+struct os2File {
+  const sqlite3_io_methods *pMethod;  /* Always the first entry */
+  HFILE h;                  /* Handle for accessing the file */
+  int flags;                /* Flags provided to os2Open() */
+  int locktype;             /* Type of lock currently held on this file */
+  int szChunk;              /* Chunk size configured by FCNTL_CHUNK_SIZE */
+  char *zFullPathCp;        /* Full path name of this file */
+  os2ShmLink *pShmLink;     /* Instance of shared memory on this file */
+};
+
+#define LOCK_TIMEOUT 10L /* the default locking timeout */
+
+/*
+** Missing from some versions of the OS/2 toolkit -
+** used to allocate from high memory if possible
+*/
+#ifndef OBJ_ANY
+# define OBJ_ANY 0x00000400
+#endif
+
+/*****************************************************************************
+** The next group of routines implement the I/O methods specified
+** by the sqlite3_io_methods object.
+******************************************************************************/
+
+/*
+** Close a file.
+*/
+static int os2Close( sqlite3_file *id ){
+  APIRET rc;
+  os2File *pFile = (os2File*)id;
+
+  assert( id!=0 );
+  OSTRACE(( "CLOSE %d (%s)\n", pFile->h, pFile->zFullPathCp ));
+
+  rc = DosClose( pFile->h );
+
+  if( pFile->flags & SQLITE_OPEN_DELETEONCLOSE )
+    DosForceDelete( (PSZ)pFile->zFullPathCp );
+
+  free( pFile->zFullPathCp );
+  pFile->zFullPathCp = NULL;
+  pFile->locktype = NO_LOCK;
+  pFile->h = (HFILE)-1;
+  pFile->flags = 0;
+
+  OpenCounter( -1 );
+  return rc == NO_ERROR ? SQLITE_OK : SQLITE_IOERR;
+}
+
+/*
+** Read data from a file into a buffer.  Return SQLITE_OK if all
+** bytes were read successfully and SQLITE_IOERR if anything goes
+** wrong.
+*/
+static int os2Read(
+  sqlite3_file *id,               /* File to read from */
+  void *pBuf,                     /* Write content into this buffer */
+  int amt,                        /* Number of bytes to read */
+  sqlite3_int64 offset            /* Begin reading at this offset */
+){
+  ULONG fileLocation = 0L;
+  ULONG got;
+  os2File *pFile = (os2File*)id;
+  assert( id!=0 );
+  SimulateIOError( return SQLITE_IOERR_READ );
+  OSTRACE(( "READ %d lock=%d\n", pFile->h, pFile->locktype ));
+  if( DosSetFilePtr(pFile->h, offset, FILE_BEGIN, &fileLocation) != NO_ERROR ){
+    return SQLITE_IOERR;
+  }
+  if( DosRead( pFile->h, pBuf, amt, &got ) != NO_ERROR ){
+    return SQLITE_IOERR_READ;
+  }
+  if( got == (ULONG)amt )
+    return SQLITE_OK;
+  else {
+    /* Unread portions of the input buffer must be zero-filled */
+    memset(&((char*)pBuf)[got], 0, amt-got);
+    return SQLITE_IOERR_SHORT_READ;
+  }
+}
+
+/*
+** Write data from a buffer into a file.  Return SQLITE_OK on success
+** or some other error code on failure.
+*/
+static int os2Write(
+  sqlite3_file *id,               /* File to write into */
+  const void *pBuf,               /* The bytes to be written */
+  int amt,                        /* Number of bytes to write */
+  sqlite3_int64 offset            /* Offset into the file to begin writing at */
+){
+  ULONG fileLocation = 0L;
+  APIRET rc = NO_ERROR;
+  ULONG wrote;
+  os2File *pFile = (os2File*)id;
+  assert( id!=0 );
+  SimulateIOError( return SQLITE_IOERR_WRITE );
+  SimulateDiskfullError( return SQLITE_FULL );
+  OSTRACE(( "WRITE %d lock=%d\n", pFile->h, pFile->locktype ));
+  if( DosSetFilePtr(pFile->h, offset, FILE_BEGIN, &fileLocation) != NO_ERROR ){
+    return SQLITE_IOERR;
+  }
+  assert( amt>0 );
+  while( amt > 0 &&
+         ( rc = DosWrite( pFile->h, (PVOID)pBuf, amt, &wrote ) ) == NO_ERROR &&
+         wrote > 0
+  ){
+    amt -= wrote;
+    pBuf = &((char*)pBuf)[wrote];
+  }
+
+  return ( rc != NO_ERROR || amt > (int)wrote ) ? SQLITE_FULL : SQLITE_OK;
+}
+
+/*
+** Truncate an open file to a specified size
+*/
+static int os2Truncate( sqlite3_file *id, i64 nByte ){
+  APIRET rc;
+  os2File *pFile = (os2File*)id;
+  assert( id!=0 );
+  OSTRACE(( "TRUNCATE %d %lld\n", pFile->h, nByte ));
+  SimulateIOError( return SQLITE_IOERR_TRUNCATE );
+
+  /* If the user has configured a chunk-size for this file, truncate the
+  ** file so that it consists of an integer number of chunks (i.e. the
+  ** actual file size after the operation may be larger than the requested
+  ** size).
+  */
+  if( pFile->szChunk ){
+    nByte = ((nByte + pFile->szChunk - 1)/pFile->szChunk) * pFile->szChunk;
+  }
+  
+  rc = DosSetFileSize( pFile->h, nByte );
+  return rc == NO_ERROR ? SQLITE_OK : SQLITE_IOERR_TRUNCATE;
+}
+
+#ifdef SQLITE_TEST
+/*
+** Count the number of fullsyncs and normal syncs.  This is used to test
+** that syncs and fullsyncs are occuring at the right times.
+*/
+int sqlite3_sync_count = 0;
+int sqlite3_fullsync_count = 0;
+#endif
+
+/*
+** Make sure all writes to a particular file are committed to disk.
+*/
+static int os2Sync( sqlite3_file *id, int flags ){
+  os2File *pFile = (os2File*)id;
+  OSTRACE(( "SYNC %d lock=%d\n", pFile->h, pFile->locktype ));
+#ifdef SQLITE_TEST
+  if( flags & SQLITE_SYNC_FULL){
+    sqlite3_fullsync_count++;
+  }
+  sqlite3_sync_count++;
+#endif
+  /* If we compiled with the SQLITE_NO_SYNC flag, then syncing is a
+  ** no-op
+  */
+#ifdef SQLITE_NO_SYNC
+  UNUSED_PARAMETER(pFile);
+  return SQLITE_OK;
+#else
+  return DosResetBuffer( pFile->h ) == NO_ERROR ? SQLITE_OK : SQLITE_IOERR;
+#endif
+}
+
+/*
+** Determine the current size of a file in bytes
+*/
+static int os2FileSize( sqlite3_file *id, sqlite3_int64 *pSize ){
+  APIRET rc = NO_ERROR;
+  FILESTATUS3 fsts3FileInfo;
+  memset(&fsts3FileInfo, 0, sizeof(fsts3FileInfo));
+  assert( id!=0 );
+  SimulateIOError( return SQLITE_IOERR_FSTAT );
+  rc = DosQueryFileInfo( ((os2File*)id)->h, FIL_STANDARD, &fsts3FileInfo, sizeof(FILESTATUS3) );
+  if( rc == NO_ERROR ){
+    *pSize = fsts3FileInfo.cbFile;
+    return SQLITE_OK;
+  }else{
+    return SQLITE_IOERR_FSTAT;
+  }
+}
+
+/*
+** Acquire a reader lock.
+*/
+static int getReadLock( os2File *pFile ){
+  FILELOCK  LockArea,
+            UnlockArea;
+  APIRET res;
+  memset(&LockArea, 0, sizeof(LockArea));
+  memset(&UnlockArea, 0, sizeof(UnlockArea));
+  LockArea.lOffset = SHARED_FIRST;
+  LockArea.lRange = SHARED_SIZE;
+  UnlockArea.lOffset = 0L;
+  UnlockArea.lRange = 0L;
+  res = DosSetFileLocks( pFile->h, &UnlockArea, &LockArea, LOCK_TIMEOUT, 1L );
+  OSTRACE(( "GETREADLOCK %d res=%d\n", pFile->h, res ));
+  return res;
+}
+
+/*
+** Undo a readlock
+*/
+static int unlockReadLock( os2File *id ){
+  FILELOCK  LockArea,
+            UnlockArea;
+  APIRET res;
+  memset(&LockArea, 0, sizeof(LockArea));
+  memset(&UnlockArea, 0, sizeof(UnlockArea));
+  LockArea.lOffset = 0L;
+  LockArea.lRange = 0L;
+  UnlockArea.lOffset = SHARED_FIRST;
+  UnlockArea.lRange = SHARED_SIZE;
+  res = DosSetFileLocks( id->h, &UnlockArea, &LockArea, LOCK_TIMEOUT, 1L );
+  OSTRACE(( "UNLOCK-READLOCK file handle=%d res=%d?\n", id->h, res ));
+  return res;
+}
+
+/*
+** Lock the file with the lock specified by parameter locktype - one
+** of the following:
+**
+**     (1) SHARED_LOCK
+**     (2) RESERVED_LOCK
+**     (3) PENDING_LOCK
+**     (4) EXCLUSIVE_LOCK
+**
+** Sometimes when requesting one lock state, additional lock states
+** are inserted in between.  The locking might fail on one of the later
+** transitions leaving the lock state different from what it started but
+** still short of its goal.  The following chart shows the allowed
+** transitions and the inserted intermediate states:
+**
+**    UNLOCKED -> SHARED
+**    SHARED -> RESERVED
+**    SHARED -> (PENDING) -> EXCLUSIVE
+**    RESERVED -> (PENDING) -> EXCLUSIVE
+**    PENDING -> EXCLUSIVE
+**
+** This routine will only increase a lock.  The os2Unlock() routine
+** erases all locks at once and returns us immediately to locking level 0.
+** It is not possible to lower the locking level one step at a time.  You
+** must go straight to locking level 0.
+*/
+static int os2Lock( sqlite3_file *id, int locktype ){
+  int rc = SQLITE_OK;       /* Return code from subroutines */
+  APIRET res = NO_ERROR;    /* Result of an OS/2 lock call */
+  int newLocktype;       /* Set pFile->locktype to this value before exiting */
+  int gotPendingLock = 0;/* True if we acquired a PENDING lock this time */
+  FILELOCK  LockArea,
+            UnlockArea;
+  os2File *pFile = (os2File*)id;
+  memset(&LockArea, 0, sizeof(LockArea));
+  memset(&UnlockArea, 0, sizeof(UnlockArea));
+  assert( pFile!=0 );
+  OSTRACE(( "LOCK %d %d was %d\n", pFile->h, locktype, pFile->locktype ));
+
+  /* If there is already a lock of this type or more restrictive on the
+  ** os2File, do nothing. Don't use the end_lock: exit path, as
+  ** sqlite3_mutex_enter() hasn't been called yet.
+  */
+  if( pFile->locktype>=locktype ){
+    OSTRACE(( "LOCK %d %d ok (already held)\n", pFile->h, locktype ));
+    return SQLITE_OK;
+  }
+
+  /* Make sure the locking sequence is correct
+  */
+  assert( pFile->locktype!=NO_LOCK || locktype==SHARED_LOCK );
+  assert( locktype!=PENDING_LOCK );
+  assert( locktype!=RESERVED_LOCK || pFile->locktype==SHARED_LOCK );
+
+  /* Lock the PENDING_LOCK byte if we need to acquire a PENDING lock or
+  ** a SHARED lock.  If we are acquiring a SHARED lock, the acquisition of
+  ** the PENDING_LOCK byte is temporary.
+  */
+  newLocktype = pFile->locktype;
+  if( pFile->locktype==NO_LOCK
+      || (locktype==EXCLUSIVE_LOCK && pFile->locktype==RESERVED_LOCK)
+  ){
+    LockArea.lOffset = PENDING_BYTE;
+    LockArea.lRange = 1L;
+    UnlockArea.lOffset = 0L;
+    UnlockArea.lRange = 0L;
+
+    /* wait longer than LOCK_TIMEOUT here not to have to try multiple times */
+    res = DosSetFileLocks( pFile->h, &UnlockArea, &LockArea, 100L, 0L );
+    if( res == NO_ERROR ){
+      gotPendingLock = 1;
+      OSTRACE(( "LOCK %d pending lock boolean set.  res=%d\n", pFile->h, res ));
+    }
+  }
+
+  /* Acquire a shared lock
+  */
+  if( locktype==SHARED_LOCK && res == NO_ERROR ){
+    assert( pFile->locktype==NO_LOCK );
+    res = getReadLock(pFile);
+    if( res == NO_ERROR ){
+      newLocktype = SHARED_LOCK;
+    }
+    OSTRACE(( "LOCK %d acquire shared lock. res=%d\n", pFile->h, res ));
+  }
+
+  /* Acquire a RESERVED lock
+  */
+  if( locktype==RESERVED_LOCK && res == NO_ERROR ){
+    assert( pFile->locktype==SHARED_LOCK );
+    LockArea.lOffset = RESERVED_BYTE;
+    LockArea.lRange = 1L;
+    UnlockArea.lOffset = 0L;
+    UnlockArea.lRange = 0L;
+    res = DosSetFileLocks( pFile->h, &UnlockArea, &LockArea, LOCK_TIMEOUT, 0L );
+    if( res == NO_ERROR ){
+      newLocktype = RESERVED_LOCK;
+    }
+    OSTRACE(( "LOCK %d acquire reserved lock. res=%d\n", pFile->h, res ));
+  }
+
+  /* Acquire a PENDING lock
+  */
+  if( locktype==EXCLUSIVE_LOCK && res == NO_ERROR ){
+    newLocktype = PENDING_LOCK;
+    gotPendingLock = 0;
+    OSTRACE(( "LOCK %d acquire pending lock. pending lock boolean unset.\n",
+               pFile->h ));
+  }
+
+  /* Acquire an EXCLUSIVE lock
+  */
+  if( locktype==EXCLUSIVE_LOCK && res == NO_ERROR ){
+    assert( pFile->locktype>=SHARED_LOCK );
+    res = unlockReadLock(pFile);
+    OSTRACE(( "unreadlock = %d\n", res ));
+    LockArea.lOffset = SHARED_FIRST;
+    LockArea.lRange = SHARED_SIZE;
+    UnlockArea.lOffset = 0L;
+    UnlockArea.lRange = 0L;
+    res = DosSetFileLocks( pFile->h, &UnlockArea, &LockArea, LOCK_TIMEOUT, 0L );
+    if( res == NO_ERROR ){
+      newLocktype = EXCLUSIVE_LOCK;
+    }else{
+      OSTRACE(( "OS/2 error-code = %d\n", res ));
+      getReadLock(pFile);
+    }
+    OSTRACE(( "LOCK %d acquire exclusive lock.  res=%d\n", pFile->h, res ));
+  }
+
+  /* If we are holding a PENDING lock that ought to be released, then
+  ** release it now.
+  */
+  if( gotPendingLock && locktype==SHARED_LOCK ){
+    int r;
+    LockArea.lOffset = 0L;
+    LockArea.lRange = 0L;
+    UnlockArea.lOffset = PENDING_BYTE;
+    UnlockArea.lRange = 1L;
+    r = DosSetFileLocks( pFile->h, &UnlockArea, &LockArea, LOCK_TIMEOUT, 0L );
+    OSTRACE(( "LOCK %d unlocking pending/is shared. r=%d\n", pFile->h, r ));
+  }
+
+  /* Update the state of the lock has held in the file descriptor then
+  ** return the appropriate result code.
+  */
+  if( res == NO_ERROR ){
+    rc = SQLITE_OK;
+  }else{
+    OSTRACE(( "LOCK FAILED %d trying for %d but got %d\n", pFile->h,
+              locktype, newLocktype ));
+    rc = SQLITE_BUSY;
+  }
+  pFile->locktype = newLocktype;
+  OSTRACE(( "LOCK %d now %d\n", pFile->h, pFile->locktype ));
+  return rc;
+}
+
+/*
+** This routine checks if there is a RESERVED lock held on the specified
+** file by this or any other process. If such a lock is held, return
+** non-zero, otherwise zero.
+*/
+static int os2CheckReservedLock( sqlite3_file *id, int *pOut ){
+  int r = 0;
+  os2File *pFile = (os2File*)id;
+  assert( pFile!=0 );
+  if( pFile->locktype>=RESERVED_LOCK ){
+    r = 1;
+    OSTRACE(( "TEST WR-LOCK %d %d (local)\n", pFile->h, r ));
+  }else{
+    FILELOCK  LockArea,
+              UnlockArea;
+    APIRET rc = NO_ERROR;
+    memset(&LockArea, 0, sizeof(LockArea));
+    memset(&UnlockArea, 0, sizeof(UnlockArea));
+    LockArea.lOffset = RESERVED_BYTE;
+    LockArea.lRange = 1L;
+    UnlockArea.lOffset = 0L;
+    UnlockArea.lRange = 0L;
+    rc = DosSetFileLocks( pFile->h, &UnlockArea, &LockArea, LOCK_TIMEOUT, 0L );
+    OSTRACE(( "TEST WR-LOCK %d lock reserved byte rc=%d\n", pFile->h, rc ));
+    if( rc == NO_ERROR ){
+      APIRET rcu = NO_ERROR; /* return code for unlocking */
+      LockArea.lOffset = 0L;
+      LockArea.lRange = 0L;
+      UnlockArea.lOffset = RESERVED_BYTE;
+      UnlockArea.lRange = 1L;
+      rcu = DosSetFileLocks( pFile->h, &UnlockArea, &LockArea, LOCK_TIMEOUT, 0L );
+      OSTRACE(( "TEST WR-LOCK %d unlock reserved byte r=%d\n", pFile->h, rcu ));
+    }
+    r = !(rc == NO_ERROR);
+    OSTRACE(( "TEST WR-LOCK %d %d (remote)\n", pFile->h, r ));
+  }
+  *pOut = r;
+  return SQLITE_OK;
+}
+
+/*
+** Lower the locking level on file descriptor id to locktype.  locktype
+** must be either NO_LOCK or SHARED_LOCK.
+**
+** If the locking level of the file descriptor is already at or below
+** the requested locking level, this routine is a no-op.
+**
+** It is not possible for this routine to fail if the second argument
+** is NO_LOCK.  If the second argument is SHARED_LOCK then this routine
+** might return SQLITE_IOERR;
+*/
+static int os2Unlock( sqlite3_file *id, int locktype ){
+  int type;
+  os2File *pFile = (os2File*)id;
+  APIRET rc = SQLITE_OK;
+  APIRET res = NO_ERROR;
+  FILELOCK  LockArea,
+            UnlockArea;
+  memset(&LockArea, 0, sizeof(LockArea));
+  memset(&UnlockArea, 0, sizeof(UnlockArea));
+  assert( pFile!=0 );
+  assert( locktype<=SHARED_LOCK );
+  OSTRACE(( "UNLOCK %d to %d was %d\n", pFile->h, locktype, pFile->locktype ));
+  type = pFile->locktype;
+  if( type>=EXCLUSIVE_LOCK ){
+    LockArea.lOffset = 0L;
+    LockArea.lRange = 0L;
+    UnlockArea.lOffset = SHARED_FIRST;
+    UnlockArea.lRange = SHARED_SIZE;
+    res = DosSetFileLocks( pFile->h, &UnlockArea, &LockArea, LOCK_TIMEOUT, 0L );
+    OSTRACE(( "UNLOCK %d exclusive lock res=%d\n", pFile->h, res ));
+    if( locktype==SHARED_LOCK && getReadLock(pFile) != NO_ERROR ){
+      /* This should never happen.  We should always be able to
+      ** reacquire the read lock */
+      OSTRACE(( "UNLOCK %d to %d getReadLock() failed\n", pFile->h, locktype ));
+      rc = SQLITE_IOERR_UNLOCK;
+    }
+  }
+  if( type>=RESERVED_LOCK ){
+    LockArea.lOffset = 0L;
+    LockArea.lRange = 0L;
+    UnlockArea.lOffset = RESERVED_BYTE;
+    UnlockArea.lRange = 1L;
+    res = DosSetFileLocks( pFile->h, &UnlockArea, &LockArea, LOCK_TIMEOUT, 0L );
+    OSTRACE(( "UNLOCK %d reserved res=%d\n", pFile->h, res ));
+  }
+  if( locktype==NO_LOCK && type>=SHARED_LOCK ){
+    res = unlockReadLock(pFile);
+    OSTRACE(( "UNLOCK %d is %d want %d res=%d\n",
+              pFile->h, type, locktype, res ));
+  }
+  if( type>=PENDING_LOCK ){
+    LockArea.lOffset = 0L;
+    LockArea.lRange = 0L;
+    UnlockArea.lOffset = PENDING_BYTE;
+    UnlockArea.lRange = 1L;
+    res = DosSetFileLocks( pFile->h, &UnlockArea, &LockArea, LOCK_TIMEOUT, 0L );
+    OSTRACE(( "UNLOCK %d pending res=%d\n", pFile->h, res ));
+  }
+  pFile->locktype = locktype;
+  OSTRACE(( "UNLOCK %d now %d\n", pFile->h, pFile->locktype ));
+  return rc;
+}
+
+/*
+** Control and query of the open file handle.
+*/
+static int os2FileControl(sqlite3_file *id, int op, void *pArg){
+  switch( op ){
+    case SQLITE_FCNTL_LOCKSTATE: {
+      *(int*)pArg = ((os2File*)id)->locktype;
+      OSTRACE(( "FCNTL_LOCKSTATE %d lock=%d\n",
+                ((os2File*)id)->h, ((os2File*)id)->locktype ));
+      return SQLITE_OK;
+    }
+    case SQLITE_FCNTL_CHUNK_SIZE: {
+      ((os2File*)id)->szChunk = *(int*)pArg;
+      return SQLITE_OK;
+    }
+    case SQLITE_FCNTL_SIZE_HINT: {
+      sqlite3_int64 sz = *(sqlite3_int64*)pArg;
+      SimulateIOErrorBenign(1);
+      os2Truncate(id, sz);
+      SimulateIOErrorBenign(0);
+      return SQLITE_OK;
+    }
+    case SQLITE_FCNTL_SYNC_OMITTED: {
+      return SQLITE_OK;
+    }
+  }
+  return SQLITE_NOTFOUND;
+}
+
+/*
+** Return the sector size in bytes of the underlying block device for
+** the specified file. This is almost always 512 bytes, but may be
+** larger for some devices.
+**
+** SQLite code assumes this function cannot fail. It also assumes that
+** if two files are created in the same file-system directory (i.e.
+** a database and its journal file) that the sector size will be the
+** same for both.
+*/
+static int os2SectorSize(sqlite3_file *id){
+  UNUSED_PARAMETER(id);
+  return SQLITE_DEFAULT_SECTOR_SIZE;
+}
+
+/*
+** Return a vector of device characteristics.
+*/
+static int os2DeviceCharacteristics(sqlite3_file *id){
+  UNUSED_PARAMETER(id);
+  return SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN;
+}
+
+
+/*
+** Character set conversion objects used by conversion routines.
+*/
+static UconvObject ucUtf8 = NULL; /* convert between UTF-8 and UCS-2 */
+static UconvObject uclCp = NULL;  /* convert between local codepage and UCS-2 */
+
+/*
+** Helper function to initialize the conversion objects from and to UTF-8.
+*/
+static void initUconvObjects( void ){
+  if( UniCreateUconvObject( UTF_8, &ucUtf8 ) != ULS_SUCCESS )
+    ucUtf8 = NULL;
+  if ( UniCreateUconvObject( (UniChar *)L"@path=yes", &uclCp ) != ULS_SUCCESS )
+    uclCp = NULL;
+}
+
+/*
+** Helper function to free the conversion objects from and to UTF-8.
+*/
+static void freeUconvObjects( void ){
+  if ( ucUtf8 )
+    UniFreeUconvObject( ucUtf8 );
+  if ( uclCp )
+    UniFreeUconvObject( uclCp );
+  ucUtf8 = NULL;
+  uclCp = NULL;
+}
+
+/*
+** Helper function to convert UTF-8 filenames to local OS/2 codepage.
+** The two-step process: first convert the incoming UTF-8 string
+** into UCS-2 and then from UCS-2 to the current codepage.
+** The returned char pointer has to be freed.
+*/
+static char *convertUtf8PathToCp( const char *in ){
+  UniChar tempPath[CCHMAXPATH];
+  char *out = (char *)calloc( CCHMAXPATH, 1 );
+
+  if( !out )
+    return NULL;
+
+  if( !ucUtf8 || !uclCp )
+    initUconvObjects();
+
+  /* determine string for the conversion of UTF-8 which is CP1208 */
+  if( UniStrToUcs( ucUtf8, tempPath, (char *)in, CCHMAXPATH ) != ULS_SUCCESS )
+    return out; /* if conversion fails, return the empty string */
+
+  /* conversion for current codepage which can be used for paths */
+  UniStrFromUcs( uclCp, out, tempPath, CCHMAXPATH );
+
+  return out;
+}
+
+/*
+** Helper function to convert filenames from local codepage to UTF-8.
+** The two-step process: first convert the incoming codepage-specific
+** string into UCS-2 and then from UCS-2 to the codepage of UTF-8.
+** The returned char pointer has to be freed.
+**
+** This function is non-static to be able to use this in shell.c and
+** similar applications that take command line arguments.
+*/
+char *convertCpPathToUtf8( const char *in ){
+  UniChar tempPath[CCHMAXPATH];
+  char *out = (char *)calloc( CCHMAXPATH, 1 );
+
+  if( !out )
+    return NULL;
+
+  if( !ucUtf8 || !uclCp )
+    initUconvObjects();
+
+  /* conversion for current codepage which can be used for paths */
+  if( UniStrToUcs( uclCp, tempPath, (char *)in, CCHMAXPATH ) != ULS_SUCCESS )
+    return out; /* if conversion fails, return the empty string */
+
+  /* determine string for the conversion of UTF-8 which is CP1208 */
+  UniStrFromUcs( ucUtf8, out, tempPath, CCHMAXPATH );
+
+  return out;
+}
+
+
+#ifndef SQLITE_OMIT_WAL
+
+/*
+** Use main database file for interprocess locking. If un-defined
+** a separate file is created for this purpose. The file will be
+** used only to set file locks. There will be no data written to it.
+*/
+#define SQLITE_OS2_NO_WAL_LOCK_FILE     
+
+#if 0
+static void _ERR_TRACE( const char *fmt, ... ) {
+  va_list  ap;
+  va_start(ap, fmt);
+  vfprintf(stderr, fmt, ap);
+  fflush(stderr);
+}
+#define ERR_TRACE(rc, msg)        \
+        if( (rc) != SQLITE_OK ) _ERR_TRACE msg;
+#else
+#define ERR_TRACE(rc, msg)
+#endif
+
+/*
+** Helper functions to obtain and relinquish the global mutex. The
+** global mutex is used to protect os2ShmNodeList.
+**
+** Function os2ShmMutexHeld() is used to assert() that the global mutex 
+** is held when required. This function is only used as part of assert() 
+** statements. e.g.
+**
+**   os2ShmEnterMutex()
+**     assert( os2ShmMutexHeld() );
+**   os2ShmLeaveMutex()
+*/
+static void os2ShmEnterMutex(void){
+  sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
+}
+static void os2ShmLeaveMutex(void){
+  sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
+}
+#ifdef SQLITE_DEBUG
+static int os2ShmMutexHeld(void) {
+  return sqlite3_mutex_held(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
+}
+int GetCurrentProcessId(void) {
+  PPIB pib;
+  DosGetInfoBlocks(NULL, &pib);
+  return (int)pib->pib_ulpid;
+}
+#endif
+
+/*
+** Object used to represent a the shared memory area for a single log file.
+** When multiple threads all reference the same log-summary, each thread has
+** its own os2File object, but they all point to a single instance of this 
+** object.  In other words, each log-summary is opened only once per process.
+**
+** os2ShmMutexHeld() must be true when creating or destroying
+** this object or while reading or writing the following fields:
+**
+**      nRef
+**      pNext 
+**
+** The following fields are read-only after the object is created:
+** 
+**      szRegion
+**      hLockFile
+**      shmBaseName
+**
+** Either os2ShmNode.mutex must be held or os2ShmNode.nRef==0 and
+** os2ShmMutexHeld() is true when reading or writing any other field
+** in this structure.
+**
+*/
+struct os2ShmNode {
+  sqlite3_mutex *mutex;      /* Mutex to access this object */
+  os2ShmNode *pNext;         /* Next in list of all os2ShmNode objects */
+
+  int szRegion;              /* Size of shared-memory regions */
+
+  int nRegion;               /* Size of array apRegion */
+  void **apRegion;           /* Array of pointers to shared-memory regions */
+
+  int nRef;                  /* Number of os2ShmLink objects pointing to this */
+  os2ShmLink *pFirst;        /* First os2ShmLink object pointing to this */
+
+  HFILE hLockFile;           /* File used for inter-process memory locking */
+  char shmBaseName[1];       /* Name of the memory object !!! must last !!! */
+};
+
+
+/*
+** Structure used internally by this VFS to record the state of an
+** open shared memory connection.
+**
+** The following fields are initialized when this object is created and
+** are read-only thereafter:
+**
+**    os2Shm.pShmNode
+**    os2Shm.id
+**
+** All other fields are read/write.  The os2Shm.pShmNode->mutex must be held
+** while accessing any read/write fields.
+*/
+struct os2ShmLink {
+  os2ShmNode *pShmNode;      /* The underlying os2ShmNode object */
+  os2ShmLink *pNext;         /* Next os2Shm with the same os2ShmNode */
+  u32 sharedMask;            /* Mask of shared locks held */
+  u32 exclMask;              /* Mask of exclusive locks held */
+#ifdef SQLITE_DEBUG
+  u8 id;                     /* Id of this connection with its os2ShmNode */
+#endif
+};
+
+
+/*
+** A global list of all os2ShmNode objects.
+**
+** The os2ShmMutexHeld() must be true while reading or writing this list.
+*/
+static os2ShmNode *os2ShmNodeList = NULL;
+
+/*
+** Constants used for locking
+*/
+#ifdef  SQLITE_OS2_NO_WAL_LOCK_FILE
+#define OS2_SHM_BASE   (PENDING_BYTE + 0x10000)         /* first lock byte */
+#else
+#define OS2_SHM_BASE   ((22+SQLITE_SHM_NLOCK)*4)        /* first lock byte */
+#endif
+
+#define OS2_SHM_DMS    (OS2_SHM_BASE+SQLITE_SHM_NLOCK)  /* deadman switch */
+
+/*
+** Apply advisory locks for all n bytes beginning at ofst.
+*/
+#define _SHM_UNLCK  1   /* no lock */
+#define _SHM_RDLCK  2   /* shared lock, no wait */
+#define _SHM_WRLCK  3   /* exlusive lock, no wait */
+#define _SHM_WRLCK_WAIT 4 /* exclusive lock, wait */
+static int os2ShmSystemLock(
+  os2ShmNode *pNode,    /* Apply locks to this open shared-memory segment */
+  int lockType,         /* _SHM_UNLCK, _SHM_RDLCK, _SHM_WRLCK or _SHM_WRLCK_WAIT */
+  int ofst,             /* Offset to first byte to be locked/unlocked */
+  int nByte             /* Number of bytes to lock or unlock */
+){
+  APIRET rc;
+  FILELOCK area;
+  ULONG mode, timeout;
+
+  /* Access to the os2ShmNode object is serialized by the caller */
+  assert( sqlite3_mutex_held(pNode->mutex) || pNode->nRef==0 );
+
+  mode = 1;     /* shared lock */
+  timeout = 0;  /* no wait */
+  area.lOffset = ofst;
+  area.lRange = nByte;
+
+  switch( lockType ) {
+    case _SHM_WRLCK_WAIT:
+      timeout = (ULONG)-1;      /* wait forever */
+    case _SHM_WRLCK:
+      mode = 0;                 /* exclusive lock */
+    case _SHM_RDLCK:
+      rc = DosSetFileLocks(pNode->hLockFile, 
+                           NULL, &area, timeout, mode);
+      break;
+    /* case _SHM_UNLCK: */
+    default:
+      rc = DosSetFileLocks(pNode->hLockFile, 
+                           &area, NULL, 0, 0);
+      break;
+  }
+                          
+  OSTRACE(("SHM-LOCK %d %s %s 0x%08lx\n", 
+           pNode->hLockFile,
+           rc==SQLITE_OK ? "ok" : "failed",
+           lockType==_SHM_UNLCK ? "Unlock" : "Lock",
+           rc));
+
+  ERR_TRACE(rc, ("os2ShmSystemLock: %d %s\n", rc, pNode->shmBaseName))
+
+  return ( rc == 0 ) ?  SQLITE_OK : SQLITE_BUSY;
+}
+
+/*
+** Find an os2ShmNode in global list or allocate a new one, if not found.
+**
+** This is not a VFS shared-memory method; it is a utility function called
+** by VFS shared-memory methods.
+*/
+static int os2OpenSharedMemory( os2File *fd, int szRegion ) {
+  os2ShmLink *pLink;
+  os2ShmNode *pNode;
+  int cbShmName, rc = SQLITE_OK;
+  char shmName[CCHMAXPATH + 30];
+#ifndef SQLITE_OS2_NO_WAL_LOCK_FILE
+  ULONG action;
+#endif
+  
+  /* We need some additional space at the end to append the region number */
+  cbShmName = sprintf(shmName, "\\SHAREMEM\\%s", fd->zFullPathCp );
+  if( cbShmName >= CCHMAXPATH-8 )
+    return SQLITE_IOERR_SHMOPEN; 
+
+  /* Replace colon in file name to form a valid shared memory name */
+  shmName[10+1] = '!';
+
+  /* Allocate link object (we free it later in case of failure) */
+  pLink = sqlite3_malloc( sizeof(*pLink) );
+  if( !pLink )
+    return SQLITE_NOMEM;
+
+  /* Access node list */
+  os2ShmEnterMutex();
+
+  /* Find node by it's shared memory base name */
+  for( pNode = os2ShmNodeList; 
+       pNode && stricmp(shmName, pNode->shmBaseName) != 0; 
+       pNode = pNode->pNext )   ;
+
+  /* Not found: allocate a new node */
+  if( !pNode ) {
+    pNode = sqlite3_malloc( sizeof(*pNode) + cbShmName );
+    if( pNode ) {
+      memset(pNode, 0, sizeof(*pNode) );
+      pNode->szRegion = szRegion;
+      pNode->hLockFile = (HFILE)-1;      
+      strcpy(pNode->shmBaseName, shmName);
+
+#ifdef SQLITE_OS2_NO_WAL_LOCK_FILE
+      if( DosDupHandle(fd->h, &pNode->hLockFile) != 0 ) {
+#else
+      sprintf(shmName, "%s-lck", fd->zFullPathCp);
+      if( DosOpen((PSZ)shmName, &pNode->hLockFile, &action, 0, FILE_NORMAL, 
+                  OPEN_ACTION_OPEN_IF_EXISTS | OPEN_ACTION_CREATE_IF_NEW,
+                  OPEN_ACCESS_READWRITE | OPEN_SHARE_DENYNONE | 
+                  OPEN_FLAGS_NOINHERIT | OPEN_FLAGS_FAIL_ON_ERROR,
+                  NULL) != 0 ) {
+#endif
+        sqlite3_free(pNode);  
+        rc = SQLITE_IOERR;
+      } else {
+        pNode->mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_FAST);
+        if( !pNode->mutex ) {
+          sqlite3_free(pNode);  
+          rc = SQLITE_NOMEM;
+        }
+      }   
+    } else {
+      rc = SQLITE_NOMEM;
+    }
+    
+    if( rc == SQLITE_OK ) {
+      pNode->pNext = os2ShmNodeList;
+      os2ShmNodeList = pNode;
+    } else {
+      pNode = NULL;
+    }
+  } else if( pNode->szRegion != szRegion ) {
+    rc = SQLITE_IOERR_SHMSIZE;
+    pNode = NULL;
+  }
+
+  if( pNode ) {
+    sqlite3_mutex_enter(pNode->mutex);
+
+    memset(pLink, 0, sizeof(*pLink));
+
+    pLink->pShmNode = pNode;
+    pLink->pNext = pNode->pFirst;
+    pNode->pFirst = pLink;
+    pNode->nRef++;
+
+    fd->pShmLink = pLink;
+
+    sqlite3_mutex_leave(pNode->mutex);
+    
+  } else {
+    /* Error occured. Free our link object. */
+    sqlite3_free(pLink);  
+  }
+
+  os2ShmLeaveMutex();
+
+  ERR_TRACE(rc, ("os2OpenSharedMemory: %d  %s\n", rc, fd->zFullPathCp))  
+  
+  return rc;
+}
+
+/*
+** Purge the os2ShmNodeList list of all entries with nRef==0.
+**
+** This is not a VFS shared-memory method; it is a utility function called
+** by VFS shared-memory methods.
+*/
+static void os2PurgeShmNodes( int deleteFlag ) {
+  os2ShmNode *pNode;
+  os2ShmNode **ppNode;
+
+  os2ShmEnterMutex();
+  
+  ppNode = &os2ShmNodeList;
+
+  while( *ppNode ) {
+    pNode = *ppNode;
+
+    if( pNode->nRef == 0 ) {
+      *ppNode = pNode->pNext;   
+     
+      if( pNode->apRegion ) {
+        /* Prevent other processes from resizing the shared memory */
+        os2ShmSystemLock(pNode, _SHM_WRLCK_WAIT, OS2_SHM_DMS, 1);
+
+        while( pNode->nRegion-- ) {
+#ifdef SQLITE_DEBUG
+          int rc = 
+#endif          
+          DosFreeMem(pNode->apRegion[pNode->nRegion]);
+
+          OSTRACE(("SHM-PURGE pid-%d unmap region=%d %s\n",
+                  (int)GetCurrentProcessId(), pNode->nRegion,
+                  rc == 0 ? "ok" : "failed"));
+        }
+
+        /* Allow other processes to resize the shared memory */
+        os2ShmSystemLock(pNode, _SHM_UNLCK, OS2_SHM_DMS, 1);
+
+        sqlite3_free(pNode->apRegion);
+      }  
+
+      DosClose(pNode->hLockFile);
+      
+#ifndef SQLITE_OS2_NO_WAL_LOCK_FILE
+      if( deleteFlag ) {
+         char fileName[CCHMAXPATH];
+         /* Skip "\\SHAREMEM\\" */
+         sprintf(fileName, "%s-lck", pNode->shmBaseName + 10);
+         /* restore colon */
+         fileName[1] = ':';
+         
+         DosForceDelete(fileName); 
+      }
+#endif
+
+      sqlite3_mutex_free(pNode->mutex);
+
+      sqlite3_free(pNode);
+      
+    } else {
+      ppNode = &pNode->pNext;
+    }
+  } 
+
+  os2ShmLeaveMutex();
+}
+
+/*
+** This function is called to obtain a pointer to region iRegion of the
+** shared-memory associated with the database file id. Shared-memory regions
+** are numbered starting from zero. Each shared-memory region is szRegion
+** bytes in size.
+**
+** If an error occurs, an error code is returned and *pp is set to NULL.
+**
+** Otherwise, if the bExtend parameter is 0 and the requested shared-memory
+** region has not been allocated (by any client, including one running in a
+** separate process), then *pp is set to NULL and SQLITE_OK returned. If
+** bExtend is non-zero and the requested shared-memory region has not yet
+** been allocated, it is allocated by this function.
+**
+** If the shared-memory region has already been allocated or is allocated by
+** this call as described above, then it is mapped into this processes
+** address space (if it is not already), *pp is set to point to the mapped
+** memory and SQLITE_OK returned.
+*/
+static int os2ShmMap(
+  sqlite3_file *id,               /* Handle open on database file */
+  int iRegion,                    /* Region to retrieve */
+  int szRegion,                   /* Size of regions */
+  int bExtend,                    /* True to extend block if necessary */
+  void volatile **pp              /* OUT: Mapped memory */
+){
+  PVOID pvTemp;
+  void **apRegion;
+  os2ShmNode *pNode;
+  int n, rc = SQLITE_OK;
+  char shmName[CCHMAXPATH];
+  os2File *pFile = (os2File*)id;
+  
+  *pp = NULL;
+
+  if( !pFile->pShmLink )
+    rc = os2OpenSharedMemory( pFile, szRegion );
+  
+  if( rc == SQLITE_OK ) {
+    pNode = pFile->pShmLink->pShmNode ;
+    
+    sqlite3_mutex_enter(pNode->mutex);
+    
+    assert( szRegion==pNode->szRegion );
+
+    /* Unmapped region ? */
+    if( iRegion >= pNode->nRegion ) {
+      /* Prevent other processes from resizing the shared memory */
+      os2ShmSystemLock(pNode, _SHM_WRLCK_WAIT, OS2_SHM_DMS, 1);
+
+      apRegion = sqlite3_realloc(
+        pNode->apRegion, (iRegion + 1) * sizeof(apRegion[0]));
+
+      if( apRegion ) {
+        pNode->apRegion = apRegion;
+
+        while( pNode->nRegion <= iRegion ) {
+          sprintf(shmName, "%s-%u", 
+                  pNode->shmBaseName, pNode->nRegion);
+
+          if( DosGetNamedSharedMem(&pvTemp, (PSZ)shmName, 
+                PAG_READ | PAG_WRITE) != NO_ERROR ) {
+            if( !bExtend )
+              break;
+
+            if( DosAllocSharedMem(&pvTemp, (PSZ)shmName, szRegion,
+                  PAG_READ | PAG_WRITE | PAG_COMMIT | OBJ_ANY) != NO_ERROR && 
+                DosAllocSharedMem(&pvTemp, (PSZ)shmName, szRegion,
+                  PAG_READ | PAG_WRITE | PAG_COMMIT) != NO_ERROR ) { 
+              rc = SQLITE_NOMEM;
+              break;
+            }
+          }
+
+          apRegion[pNode->nRegion++] = pvTemp;
+        }
+
+        /* zero out remaining entries */ 
+        for( n = pNode->nRegion; n <= iRegion; n++ )
+          pNode->apRegion[n] = NULL;
+
+        /* Return this region (maybe zero) */
+        *pp = pNode->apRegion[iRegion];
+      } else {
+        rc = SQLITE_NOMEM;
+      }
+
+      /* Allow other processes to resize the shared memory */
+      os2ShmSystemLock(pNode, _SHM_UNLCK, OS2_SHM_DMS, 1);
+      
+    } else {
+      /* Region has been mapped previously */
+      *pp = pNode->apRegion[iRegion];
+    }
+
+    sqlite3_mutex_leave(pNode->mutex);
+  } 
+
+  ERR_TRACE(rc, ("os2ShmMap: %s iRgn = %d, szRgn = %d, bExt = %d : %d\n", 
+                 pFile->zFullPathCp, iRegion, szRegion, bExtend, rc))
+          
+  return rc;
+}
+
+/*
+** Close a connection to shared-memory.  Delete the underlying
+** storage if deleteFlag is true.
+**
+** If there is no shared memory associated with the connection then this
+** routine is a harmless no-op.
+*/
+static int os2ShmUnmap(
+  sqlite3_file *id,               /* The underlying database file */
+  int deleteFlag                  /* Delete shared-memory if true */
+){
+  os2File *pFile = (os2File*)id;
+  os2ShmLink *pLink = pFile->pShmLink;
+  
+  if( pLink ) {
+    int nRef = -1;
+    os2ShmLink **ppLink;
+    os2ShmNode *pNode = pLink->pShmNode;
+
+    sqlite3_mutex_enter(pNode->mutex);
+    
+    for( ppLink = &pNode->pFirst;
+         *ppLink && *ppLink != pLink;
+         ppLink = &(*ppLink)->pNext )   ;
+         
+    assert(*ppLink);
+
+    if( *ppLink ) {
+      *ppLink = pLink->pNext;
+      nRef = --pNode->nRef;
+    } else {
+      ERR_TRACE(1, ("os2ShmUnmap: link not found ! %s\n", 
+                    pNode->shmBaseName))
+    }
+    
+    pFile->pShmLink = NULL;
+    sqlite3_free(pLink);
+
+    sqlite3_mutex_leave(pNode->mutex);
+    
+    if( nRef == 0 )
+      os2PurgeShmNodes( deleteFlag );
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** Change the lock state for a shared-memory segment.
+**
+** Note that the relationship between SHAREd and EXCLUSIVE locks is a little
+** different here than in posix.  In xShmLock(), one can go from unlocked
+** to shared and back or from unlocked to exclusive and back.  But one may
+** not go from shared to exclusive or from exclusive to shared.
+*/
+static int os2ShmLock(
+  sqlite3_file *id,          /* Database file holding the shared memory */
+  int ofst,                  /* First lock to acquire or release */
+  int n,                     /* Number of locks to acquire or release */
+  int flags                  /* What to do with the lock */
+){
+  u32 mask;                             /* Mask of locks to take or release */
+  int rc = SQLITE_OK;                   /* Result code */
+  os2File *pFile = (os2File*)id;
+  os2ShmLink *p = pFile->pShmLink;      /* The shared memory being locked */
+  os2ShmLink *pX;                       /* For looping over all siblings */
+  os2ShmNode *pShmNode = p->pShmNode;   /* Our node */
+  
+  assert( ofst>=0 && ofst+n<=SQLITE_SHM_NLOCK );
+  assert( n>=1 );
+  assert( flags==(SQLITE_SHM_LOCK | SQLITE_SHM_SHARED)
+       || flags==(SQLITE_SHM_LOCK | SQLITE_SHM_EXCLUSIVE)
+       || flags==(SQLITE_SHM_UNLOCK | SQLITE_SHM_SHARED)
+       || flags==(SQLITE_SHM_UNLOCK | SQLITE_SHM_EXCLUSIVE) );
+  assert( n==1 || (flags & SQLITE_SHM_EXCLUSIVE)!=0 );
+
+  mask = (u32)((1U<<(ofst+n)) - (1U<<ofst));
+  assert( n>1 || mask==(1<<ofst) );
+
+
+  sqlite3_mutex_enter(pShmNode->mutex);
+
+  if( flags & SQLITE_SHM_UNLOCK ){
+    u32 allMask = 0; /* Mask of locks held by siblings */
+
+    /* See if any siblings hold this same lock */
+    for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
+      if( pX==p ) continue;
+      assert( (pX->exclMask & (p->exclMask|p->sharedMask))==0 );
+      allMask |= pX->sharedMask;
+    }
+
+    /* Unlock the system-level locks */
+    if( (mask & allMask)==0 ){
+      rc = os2ShmSystemLock(pShmNode, _SHM_UNLCK, ofst+OS2_SHM_BASE, n);
+    }else{
+      rc = SQLITE_OK;
+    }
+
+    /* Undo the local locks */
+    if( rc==SQLITE_OK ){
+      p->exclMask &= ~mask;
+      p->sharedMask &= ~mask;
+    } 
+  }else if( flags & SQLITE_SHM_SHARED ){
+    u32 allShared = 0;  /* Union of locks held by connections other than "p" */
+
+    /* Find out which shared locks are already held by sibling connections.
+    ** If any sibling already holds an exclusive lock, go ahead and return
+    ** SQLITE_BUSY.
+    */
+    for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
+      if( (pX->exclMask & mask)!=0 ){
+        rc = SQLITE_BUSY;
+        break;
+      }
+      allShared |= pX->sharedMask;
+    }
+
+    /* Get shared locks at the system level, if necessary */
+    if( rc==SQLITE_OK ){
+      if( (allShared & mask)==0 ){
+        rc = os2ShmSystemLock(pShmNode, _SHM_RDLCK, ofst+OS2_SHM_BASE, n);
+      }else{
+        rc = SQLITE_OK;
+      }
+    }
+
+    /* Get the local shared locks */
+    if( rc==SQLITE_OK ){
+      p->sharedMask |= mask;
+    }
+  }else{
+    /* Make sure no sibling connections hold locks that will block this
+    ** lock.  If any do, return SQLITE_BUSY right away.
+    */
+    for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
+      if( (pX->exclMask & mask)!=0 || (pX->sharedMask & mask)!=0 ){
+        rc = SQLITE_BUSY;
+        break;
+      }
+    }
+  
+    /* Get the exclusive locks at the system level.  Then if successful
+    ** also mark the local connection as being locked.
+    */
+    if( rc==SQLITE_OK ){
+      rc = os2ShmSystemLock(pShmNode, _SHM_WRLCK, ofst+OS2_SHM_BASE, n);
+      if( rc==SQLITE_OK ){
+        assert( (p->sharedMask & mask)==0 );
+        p->exclMask |= mask;
+      }
+    }
+  }
+
+  sqlite3_mutex_leave(pShmNode->mutex);
+  
+  OSTRACE(("SHM-LOCK shmid-%d, pid-%d got %03x,%03x %s\n",
+           p->id, (int)GetCurrentProcessId(), p->sharedMask, p->exclMask,
+           rc ? "failed" : "ok"));
+
+  ERR_TRACE(rc, ("os2ShmLock: ofst = %d, n = %d, flags = 0x%x -> %d \n", 
+                 ofst, n, flags, rc))
+                  
+  return rc; 
+}
+
+/*
+** Implement a memory barrier or memory fence on shared memory.
+**
+** All loads and stores begun before the barrier must complete before
+** any load or store begun after the barrier.
+*/
+static void os2ShmBarrier(
+  sqlite3_file *id                /* Database file holding the shared memory */
+){
+  UNUSED_PARAMETER(id);
+  os2ShmEnterMutex();
+  os2ShmLeaveMutex();
+}
+
+#else
+# define os2ShmMap     0
+# define os2ShmLock    0
+# define os2ShmBarrier 0
+# define os2ShmUnmap   0
+#endif /* #ifndef SQLITE_OMIT_WAL */
+
+
+/*
+** This vector defines all the methods that can operate on an
+** sqlite3_file for os2.
+*/
+static const sqlite3_io_methods os2IoMethod = {
+  2,                              /* iVersion */
+  os2Close,                       /* xClose */
+  os2Read,                        /* xRead */
+  os2Write,                       /* xWrite */
+  os2Truncate,                    /* xTruncate */
+  os2Sync,                        /* xSync */
+  os2FileSize,                    /* xFileSize */
+  os2Lock,                        /* xLock */
+  os2Unlock,                      /* xUnlock */
+  os2CheckReservedLock,           /* xCheckReservedLock */
+  os2FileControl,                 /* xFileControl */
+  os2SectorSize,                  /* xSectorSize */
+  os2DeviceCharacteristics,       /* xDeviceCharacteristics */
+  os2ShmMap,                      /* xShmMap */
+  os2ShmLock,                     /* xShmLock */
+  os2ShmBarrier,                  /* xShmBarrier */
+  os2ShmUnmap                     /* xShmUnmap */
+};
+
+
+/***************************************************************************
+** Here ends the I/O methods that form the sqlite3_io_methods object.
+**
+** The next block of code implements the VFS methods.
+****************************************************************************/
+
+/*
+** Create a temporary file name in zBuf.  zBuf must be big enough to
+** hold at pVfs->mxPathname characters.
+*/
+static int getTempname(int nBuf, char *zBuf ){
+  static const char zChars[] =
+    "abcdefghijklmnopqrstuvwxyz"
+    "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+    "0123456789";
+  int i, j;
+  PSZ zTempPathCp;      
+  char zTempPath[CCHMAXPATH];
+  ULONG ulDriveNum, ulDriveMap;
+  
+  /* It's odd to simulate an io-error here, but really this is just
+  ** using the io-error infrastructure to test that SQLite handles this
+  ** function failing. 
+  */
+  SimulateIOError( return SQLITE_IOERR );
+
+  if( sqlite3_temp_directory ) {
+    sqlite3_snprintf(CCHMAXPATH-30, zTempPath, "%s", sqlite3_temp_directory);
+  } else if( DosScanEnv( (PSZ)"TEMP",   &zTempPathCp ) == NO_ERROR ||
+             DosScanEnv( (PSZ)"TMP",    &zTempPathCp ) == NO_ERROR ||
+             DosScanEnv( (PSZ)"TMPDIR", &zTempPathCp ) == NO_ERROR ) {
+    char *zTempPathUTF = convertCpPathToUtf8( (char *)zTempPathCp );
+    sqlite3_snprintf(CCHMAXPATH-30, zTempPath, "%s", zTempPathUTF);
+    free( zTempPathUTF );
+  } else if( DosQueryCurrentDisk( &ulDriveNum, &ulDriveMap ) == NO_ERROR ) {
+    zTempPath[0] = (char)('A' + ulDriveNum - 1);
+    zTempPath[1] = ':'; 
+    zTempPath[2] = '\0'; 
+  } else {
+    zTempPath[0] = '\0'; 
+  }
+  
+  /* Strip off a trailing slashes or backslashes, otherwise we would get *
+   * multiple (back)slashes which causes DosOpen() to fail.              *
+   * Trailing spaces are not allowed, either.                            */
+  j = sqlite3Strlen30(zTempPath);
+  while( j > 0 && ( zTempPath[j-1] == '\\' || zTempPath[j-1] == '/' || 
+                    zTempPath[j-1] == ' ' ) ){
+    j--;
+  }
+  zTempPath[j] = '\0';
+  
+  /* We use 20 bytes to randomize the name */
+  sqlite3_snprintf(nBuf-22, zBuf,
+                   "%s\\"SQLITE_TEMP_FILE_PREFIX, zTempPath);
+  j = sqlite3Strlen30(zBuf);
+  sqlite3_randomness( 20, &zBuf[j] );
+  for( i = 0; i < 20; i++, j++ ){
+    zBuf[j] = zChars[ ((unsigned char)zBuf[j])%(sizeof(zChars)-1) ];
+  }
+  zBuf[j] = 0;
+
+  OSTRACE(( "TEMP FILENAME: %s\n", zBuf ));
+  return SQLITE_OK;
+}
+
+
+/*
+** Turn a relative pathname into a full pathname.  Write the full
+** pathname into zFull[].  zFull[] will be at least pVfs->mxPathname
+** bytes in size.
+*/
+static int os2FullPathname(
+  sqlite3_vfs *pVfs,          /* Pointer to vfs object */
+  const char *zRelative,      /* Possibly relative input path */
+  int nFull,                  /* Size of output buffer in bytes */
+  char *zFull                 /* Output buffer */
+){
+  char *zRelativeCp = convertUtf8PathToCp( zRelative );
+  char zFullCp[CCHMAXPATH] = "\0";
+  char *zFullUTF;
+  APIRET rc = DosQueryPathInfo( (PSZ)zRelativeCp, FIL_QUERYFULLNAME, 
+                                zFullCp, CCHMAXPATH );
+  free( zRelativeCp );
+  zFullUTF = convertCpPathToUtf8( zFullCp );
+  sqlite3_snprintf( nFull, zFull, zFullUTF );
+  free( zFullUTF );
+  return rc == NO_ERROR ? SQLITE_OK : SQLITE_IOERR;
+}
+
+
+/*
+** Open a file.
+*/
+static int os2Open(
+  sqlite3_vfs *pVfs,            /* Not used */
+  const char *zName,            /* Name of the file (UTF-8) */
+  sqlite3_file *id,             /* Write the SQLite file handle here */
+  int flags,                    /* Open mode flags */
+  int *pOutFlags                /* Status return flags */
+){
+  HFILE h;
+  ULONG ulOpenFlags = 0;
+  ULONG ulOpenMode = 0;
+  ULONG ulAction = 0;
+  ULONG rc;
+  os2File *pFile = (os2File*)id;
+  const char *zUtf8Name = zName;
+  char *zNameCp;
+  char  zTmpname[CCHMAXPATH];
+
+  int isExclusive  = (flags & SQLITE_OPEN_EXCLUSIVE);
+  int isCreate     = (flags & SQLITE_OPEN_CREATE);
+  int isReadWrite  = (flags & SQLITE_OPEN_READWRITE);
+#ifndef NDEBUG
+  int isDelete     = (flags & SQLITE_OPEN_DELETEONCLOSE);
+  int isReadonly   = (flags & SQLITE_OPEN_READONLY);
+  int eType        = (flags & 0xFFFFFF00);
+  int isOpenJournal = (isCreate && (
+        eType==SQLITE_OPEN_MASTER_JOURNAL 
+     || eType==SQLITE_OPEN_MAIN_JOURNAL 
+     || eType==SQLITE_OPEN_WAL
+  ));
+#endif
+
+  UNUSED_PARAMETER(pVfs);
+  assert( id!=0 );
+
+  /* Check the following statements are true: 
+  **
+  **   (a) Exactly one of the READWRITE and READONLY flags must be set, and 
+  **   (b) if CREATE is set, then READWRITE must also be set, and
+  **   (c) if EXCLUSIVE is set, then CREATE must also be set.
+  **   (d) if DELETEONCLOSE is set, then CREATE must also be set.
+  */
+  assert((isReadonly==0 || isReadWrite==0) && (isReadWrite || isReadonly));
+  assert(isCreate==0 || isReadWrite);
+  assert(isExclusive==0 || isCreate);
+  assert(isDelete==0 || isCreate);
+
+  /* The main DB, main journal, WAL file and master journal are never 
+  ** automatically deleted. Nor are they ever temporary files.  */
+  assert( (!isDelete && zName) || eType!=SQLITE_OPEN_MAIN_DB );
+  assert( (!isDelete && zName) || eType!=SQLITE_OPEN_MAIN_JOURNAL );
+  assert( (!isDelete && zName) || eType!=SQLITE_OPEN_MASTER_JOURNAL );
+  assert( (!isDelete && zName) || eType!=SQLITE_OPEN_WAL );
+
+  /* Assert that the upper layer has set one of the "file-type" flags. */
+  assert( eType==SQLITE_OPEN_MAIN_DB      || eType==SQLITE_OPEN_TEMP_DB 
+       || eType==SQLITE_OPEN_MAIN_JOURNAL || eType==SQLITE_OPEN_TEMP_JOURNAL 
+       || eType==SQLITE_OPEN_SUBJOURNAL   || eType==SQLITE_OPEN_MASTER_JOURNAL 
+       || eType==SQLITE_OPEN_TRANSIENT_DB || eType==SQLITE_OPEN_WAL
+  );
+
+  memset( pFile, 0, sizeof(*pFile) );
+  pFile->h = (HFILE)-1;
+
+  /* If the second argument to this function is NULL, generate a 
+  ** temporary file name to use 
+  */
+  if( !zUtf8Name ){
+    assert(isDelete && !isOpenJournal);
+    rc = getTempname(CCHMAXPATH, zTmpname);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+    zUtf8Name = zTmpname;
+  }
+
+  if( isReadWrite ){
+    ulOpenMode |= OPEN_ACCESS_READWRITE;
+  }else{
+    ulOpenMode |= OPEN_ACCESS_READONLY;
+  }
+
+  /* Open in random access mode for possibly better speed.  Allow full
+  ** sharing because file locks will provide exclusive access when needed.
+  ** The handle should not be inherited by child processes and we don't 
+  ** want popups from the critical error handler.
+  */
+  ulOpenMode |= OPEN_FLAGS_RANDOM | OPEN_SHARE_DENYNONE | 
+                OPEN_FLAGS_NOINHERIT | OPEN_FLAGS_FAIL_ON_ERROR;
+
+  /* SQLITE_OPEN_EXCLUSIVE is used to make sure that a new file is 
+  ** created. SQLite doesn't use it to indicate "exclusive access" 
+  ** as it is usually understood.
+  */
+  if( isExclusive ){
+    /* Creates a new file, only if it does not already exist. */
+    /* If the file exists, it fails. */
+    ulOpenFlags |= OPEN_ACTION_CREATE_IF_NEW | OPEN_ACTION_FAIL_IF_EXISTS;
+  }else if( isCreate ){
+    /* Open existing file, or create if it doesn't exist */
+    ulOpenFlags |= OPEN_ACTION_CREATE_IF_NEW | OPEN_ACTION_OPEN_IF_EXISTS;
+  }else{
+    /* Opens a file, only if it exists. */
+    ulOpenFlags |= OPEN_ACTION_FAIL_IF_NEW | OPEN_ACTION_OPEN_IF_EXISTS;
+  }
+
+  zNameCp = convertUtf8PathToCp( zUtf8Name );
+  rc = DosOpen( (PSZ)zNameCp,
+                &h,
+                &ulAction,
+                0L,
+                FILE_NORMAL,
+                ulOpenFlags,
+                ulOpenMode,
+                (PEAOP2)NULL );
+  free( zNameCp );
+
+  if( rc != NO_ERROR ){
+    OSTRACE(( "OPEN Invalid handle rc=%d: zName=%s, ulAction=%#lx, ulFlags=%#lx, ulMode=%#lx\n",
+              rc, zUtf8Name, ulAction, ulOpenFlags, ulOpenMode ));
+
+    if( isReadWrite ){
+      return os2Open( pVfs, zName, id,
+                      ((flags|SQLITE_OPEN_READONLY)&~(SQLITE_OPEN_CREATE|SQLITE_OPEN_READWRITE)),
+                      pOutFlags );
+    }else{
+      return SQLITE_CANTOPEN;
+    }
+  }
+
+  if( pOutFlags ){
+    *pOutFlags = isReadWrite ? SQLITE_OPEN_READWRITE : SQLITE_OPEN_READONLY;
+  }
+
+  os2FullPathname( pVfs, zUtf8Name, sizeof( zTmpname ), zTmpname );
+  pFile->zFullPathCp = convertUtf8PathToCp( zTmpname );
+  pFile->pMethod = &os2IoMethod;
+  pFile->flags = flags;
+  pFile->h = h;
+
+  OpenCounter(+1);
+  OSTRACE(( "OPEN %d pOutFlags=%d\n", pFile->h, pOutFlags ));
+  return SQLITE_OK;
+}
+
+/*
+** Delete the named file.
+*/
+static int os2Delete(
+  sqlite3_vfs *pVfs,                     /* Not used on os2 */
+  const char *zFilename,                 /* Name of file to delete */
+  int syncDir                            /* Not used on os2 */
+){
+  APIRET rc;
+  char *zFilenameCp;
+  SimulateIOError( return SQLITE_IOERR_DELETE );
+  zFilenameCp = convertUtf8PathToCp( zFilename );
+  rc = DosDelete( (PSZ)zFilenameCp );
+  free( zFilenameCp );
+  OSTRACE(( "DELETE \"%s\"\n", zFilename ));
+  return (rc == NO_ERROR ||
+          rc == ERROR_FILE_NOT_FOUND ||
+          rc == ERROR_PATH_NOT_FOUND ) ? SQLITE_OK : SQLITE_IOERR_DELETE;
+}
+
+/*
+** Check the existance and status of a file.
+*/
+static int os2Access(
+  sqlite3_vfs *pVfs,        /* Not used on os2 */
+  const char *zFilename,    /* Name of file to check */
+  int flags,                /* Type of test to make on this file */
+  int *pOut                 /* Write results here */
+){
+  APIRET rc;
+  FILESTATUS3 fsts3ConfigInfo;
+  char *zFilenameCp;
+
+  UNUSED_PARAMETER(pVfs);
+  SimulateIOError( return SQLITE_IOERR_ACCESS; );
+  
+  zFilenameCp = convertUtf8PathToCp( zFilename );
+  rc = DosQueryPathInfo( (PSZ)zFilenameCp, FIL_STANDARD,
+                         &fsts3ConfigInfo, sizeof(FILESTATUS3) );
+  free( zFilenameCp );
+  OSTRACE(( "ACCESS fsts3ConfigInfo.attrFile=%d flags=%d rc=%d\n",
+            fsts3ConfigInfo.attrFile, flags, rc ));
+
+  switch( flags ){
+    case SQLITE_ACCESS_EXISTS:
+      /* For an SQLITE_ACCESS_EXISTS query, treat a zero-length file
+      ** as if it does not exist.
+      */
+      if( fsts3ConfigInfo.cbFile == 0 ) 
+        rc = ERROR_FILE_NOT_FOUND;
+      break;
+    case SQLITE_ACCESS_READ:
+      break;
+    case SQLITE_ACCESS_READWRITE:
+      if( fsts3ConfigInfo.attrFile & FILE_READONLY )
+        rc = ERROR_ACCESS_DENIED;
+      break;
+    default:
+      rc = ERROR_FILE_NOT_FOUND;
+      assert( !"Invalid flags argument" );
+  }
+
+  *pOut = (rc == NO_ERROR);
+  OSTRACE(( "ACCESS %s flags %d: rc=%d\n", zFilename, flags, *pOut ));
+
+  return SQLITE_OK;
+}
+
+
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+/*
+** Interfaces for opening a shared library, finding entry points
+** within the shared library, and closing the shared library.
+*/
+/*
+** Interfaces for opening a shared library, finding entry points
+** within the shared library, and closing the shared library.
+*/
+static void *os2DlOpen(sqlite3_vfs *pVfs, const char *zFilename){
+  HMODULE hmod;
+  APIRET rc;
+  char *zFilenameCp = convertUtf8PathToCp(zFilename);
+  rc = DosLoadModule(NULL, 0, (PSZ)zFilenameCp, &hmod);
+  free(zFilenameCp);
+  return rc != NO_ERROR ? 0 : (void*)hmod;
+}
+/*
+** A no-op since the error code is returned on the DosLoadModule call.
+** os2Dlopen returns zero if DosLoadModule is not successful.
+*/
+static void os2DlError(sqlite3_vfs *pVfs, int nBuf, char *zBufOut){
+/* no-op */
+}
+static void (*os2DlSym(sqlite3_vfs *pVfs, void *pHandle, const char *zSymbol))(void){
+  PFN pfn;
+  APIRET rc;
+  rc = DosQueryProcAddr((HMODULE)pHandle, 0L, (PSZ)zSymbol, &pfn);
+  if( rc != NO_ERROR ){
+    /* if the symbol itself was not found, search again for the same
+     * symbol with an extra underscore, that might be needed depending
+     * on the calling convention */
+    char _zSymbol[256] = "_";
+    strncat(_zSymbol, zSymbol, 254);
+    rc = DosQueryProcAddr((HMODULE)pHandle, 0L, (PSZ)_zSymbol, &pfn);
+  }
+  return rc != NO_ERROR ? 0 : (void(*)(void))pfn;
+}
+static void os2DlClose(sqlite3_vfs *pVfs, void *pHandle){
+  DosFreeModule((HMODULE)pHandle);
+}
+#else /* if SQLITE_OMIT_LOAD_EXTENSION is defined: */
+  #define os2DlOpen 0
+  #define os2DlError 0
+  #define os2DlSym 0
+  #define os2DlClose 0
+#endif
+
+
+/*
+** Write up to nBuf bytes of randomness into zBuf.
+*/
+static int os2Randomness(sqlite3_vfs *pVfs, int nBuf, char *zBuf ){
+  int n = 0;
+#if defined(SQLITE_TEST)
+  n = nBuf;
+  memset(zBuf, 0, nBuf);
+#else
+  int i;                           
+  PPIB ppib;
+  PTIB ptib;
+  DATETIME dt; 
+  static unsigned c = 0;
+  /* Ordered by variation probability */
+  static ULONG svIdx[6] = { QSV_MS_COUNT, QSV_TIME_LOW,
+                            QSV_MAXPRMEM, QSV_MAXSHMEM,
+                            QSV_TOTAVAILMEM, QSV_TOTRESMEM };
+
+  /* 8 bytes; timezone and weekday don't increase the randomness much */
+  if( (int)sizeof(dt)-3 <= nBuf - n ){
+    c += 0x0100;
+    DosGetDateTime(&dt);
+    dt.year = (USHORT)((dt.year - 1900) | c);
+    memcpy(&zBuf[n], &dt, sizeof(dt)-3);
+    n += sizeof(dt)-3;
+  }
+
+  /* 4 bytes; PIDs and TIDs are 16 bit internally, so combine them */
+  if( (int)sizeof(ULONG) <= nBuf - n ){
+    DosGetInfoBlocks(&ptib, &ppib);
+    *(PULONG)&zBuf[n] = MAKELONG(ppib->pib_ulpid,
+                                 ptib->tib_ptib2->tib2_ultid);
+    n += sizeof(ULONG);
+  }
+
+  /* Up to 6 * 4 bytes; variables depend on the system state */
+  for( i = 0; i < 6 && (int)sizeof(ULONG) <= nBuf - n; i++ ){
+    DosQuerySysInfo(svIdx[i], svIdx[i], 
+                    (PULONG)&zBuf[n], sizeof(ULONG));
+    n += sizeof(ULONG);
+  } 
+#endif
+
+  return n;
+}
+
+/*
+** Sleep for a little while.  Return the amount of time slept.
+** The argument is the number of microseconds we want to sleep.
+** The return value is the number of microseconds of sleep actually
+** requested from the underlying operating system, a number which
+** might be greater than or equal to the argument, but not less
+** than the argument.
+*/
+static int os2Sleep( sqlite3_vfs *pVfs, int microsec ){
+  DosSleep( (microsec/1000) );
+  return microsec;
+}
+
+/*
+** The following variable, if set to a non-zero value, becomes the result
+** returned from sqlite3OsCurrentTime().  This is used for testing.
+*/
+#ifdef SQLITE_TEST
+int sqlite3_current_time = 0;
+#endif
+
+/*
+** Find the current time (in Universal Coordinated Time).  Write into *piNow
+** the current time and date as a Julian Day number times 86_400_000.  In
+** other words, write into *piNow the number of milliseconds since the Julian
+** epoch of noon in Greenwich on November 24, 4714 B.C according to the
+** proleptic Gregorian calendar.
+**
+** On success, return 0.  Return 1 if the time and date cannot be found.
+*/
+static int os2CurrentTimeInt64(sqlite3_vfs *pVfs, sqlite3_int64 *piNow){
+#ifdef SQLITE_TEST
+  static const sqlite3_int64 unixEpoch = 24405875*(sqlite3_int64)8640000;
+#endif
+  int year, month, datepart, timepart;
+ 
+  DATETIME dt;
+  DosGetDateTime( &dt );
+
+  year = dt.year;
+  month = dt.month;
+
+  /* Calculations from http://www.astro.keele.ac.uk/~rno/Astronomy/hjd.html
+  ** http://www.astro.keele.ac.uk/~rno/Astronomy/hjd-0.1.c
+  ** Calculate the Julian days
+  */
+  datepart = (int)dt.day - 32076 +
+    1461*(year + 4800 + (month - 14)/12)/4 +
+    367*(month - 2 - (month - 14)/12*12)/12 -
+    3*((year + 4900 + (month - 14)/12)/100)/4;
+
+  /* Time in milliseconds, hours to noon added */
+  timepart = 12*3600*1000 + dt.hundredths*10 + dt.seconds*1000 +
+    ((int)dt.minutes + dt.timezone)*60*1000 + dt.hours*3600*1000;
+
+  *piNow = (sqlite3_int64)datepart*86400*1000 + timepart;
+   
+#ifdef SQLITE_TEST
+  if( sqlite3_current_time ){
+    *piNow = 1000*(sqlite3_int64)sqlite3_current_time + unixEpoch;
+  }
+#endif
+
+  UNUSED_PARAMETER(pVfs);
+  return 0;
+}
+
+/*
+** Find the current time (in Universal Coordinated Time).  Write the
+** current time and date as a Julian Day number into *prNow and
+** return 0.  Return 1 if the time and date cannot be found.
+*/
+static int os2CurrentTime( sqlite3_vfs *pVfs, double *prNow ){
+  int rc;
+  sqlite3_int64 i;
+  rc = os2CurrentTimeInt64(pVfs, &i);
+  if( !rc ){
+    *prNow = i/86400000.0;
+  }
+  return rc;
+}
+
+/*
+** The idea is that this function works like a combination of
+** GetLastError() and FormatMessage() on windows (or errno and
+** strerror_r() on unix). After an error is returned by an OS
+** function, SQLite calls this function with zBuf pointing to
+** a buffer of nBuf bytes. The OS layer should populate the
+** buffer with a nul-terminated UTF-8 encoded error message
+** describing the last IO error to have occurred within the calling
+** thread.
+**
+** If the error message is too large for the supplied buffer,
+** it should be truncated. The return value of xGetLastError
+** is zero if the error message fits in the buffer, or non-zero
+** otherwise (if the message was truncated). If non-zero is returned,
+** then it is not necessary to include the nul-terminator character
+** in the output buffer.
+**
+** Not supplying an error message will have no adverse effect
+** on SQLite. It is fine to have an implementation that never
+** returns an error message:
+**
+**   int xGetLastError(sqlite3_vfs *pVfs, int nBuf, char *zBuf){
+**     assert(zBuf[0]=='\0');
+**     return 0;
+**   }
+**
+** However if an error message is supplied, it will be incorporated
+** by sqlite into the error message available to the user using
+** sqlite3_errmsg(), possibly making IO errors easier to debug.
+*/
+static int os2GetLastError(sqlite3_vfs *pVfs, int nBuf, char *zBuf){
+  assert(zBuf[0]=='\0');
+  return 0;
+}
+
+/*
+** Initialize and deinitialize the operating system interface.
+*/
+int sqlite3_os_init(void){
+  static sqlite3_vfs os2Vfs = {
+    3,                 /* iVersion */
+    sizeof(os2File),   /* szOsFile */
+    CCHMAXPATH,        /* mxPathname */
+    0,                 /* pNext */
+    "os2",             /* zName */
+    0,                 /* pAppData */
+
+    os2Open,           /* xOpen */
+    os2Delete,         /* xDelete */
+    os2Access,         /* xAccess */
+    os2FullPathname,   /* xFullPathname */
+    os2DlOpen,         /* xDlOpen */
+    os2DlError,        /* xDlError */
+    os2DlSym,          /* xDlSym */
+    os2DlClose,        /* xDlClose */
+    os2Randomness,     /* xRandomness */
+    os2Sleep,          /* xSleep */
+    os2CurrentTime,    /* xCurrentTime */
+    os2GetLastError,   /* xGetLastError */
+    os2CurrentTimeInt64, /* xCurrentTimeInt64 */
+    0,                 /* xSetSystemCall */
+    0,                 /* xGetSystemCall */
+    0                  /* xNextSystemCall */
+  };
+  sqlite3_vfs_register(&os2Vfs, 1);
+  initUconvObjects();
+/*  sqlite3OSTrace = 1; */
+  return SQLITE_OK;
+}
+int sqlite3_os_end(void){
+  freeUconvObjects();
+  return SQLITE_OK;
+}
+
+#endif /* SQLITE_OS_OS2 */
diff --git a/src/os_unix.c b/src/os_unix.c
new file mode 100644
index 0000000..0ea6daf
--- /dev/null
+++ b/src/os_unix.c
@@ -0,0 +1,6774 @@
+/*
+** 2004 May 22
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains the VFS implementation for unix-like operating systems
+** include Linux, MacOSX, *BSD, QNX, VxWorks, AIX, HPUX, and others.
+**
+** There are actually several different VFS implementations in this file.
+** The differences are in the way that file locking is done.  The default
+** implementation uses Posix Advisory Locks.  Alternative implementations
+** use flock(), dot-files, various proprietary locking schemas, or simply
+** skip locking all together.
+**
+** This source file is organized into divisions where the logic for various
+** subfunctions is contained within the appropriate division.  PLEASE
+** KEEP THE STRUCTURE OF THIS FILE INTACT.  New code should be placed
+** in the correct division and should be clearly labeled.
+**
+** The layout of divisions is as follows:
+**
+**   *  General-purpose declarations and utility functions.
+**   *  Unique file ID logic used by VxWorks.
+**   *  Various locking primitive implementations (all except proxy locking):
+**      + for Posix Advisory Locks
+**      + for no-op locks
+**      + for dot-file locks
+**      + for flock() locking
+**      + for named semaphore locks (VxWorks only)
+**      + for AFP filesystem locks (MacOSX only)
+**   *  sqlite3_file methods not associated with locking.
+**   *  Definitions of sqlite3_io_methods objects for all locking
+**      methods plus "finder" functions for each locking method.
+**   *  sqlite3_vfs method implementations.
+**   *  Locking primitives for the proxy uber-locking-method. (MacOSX only)
+**   *  Definitions of sqlite3_vfs objects for all locking methods
+**      plus implementations of sqlite3_os_init() and sqlite3_os_end().
+*/
+#include "sqliteInt.h"
+#if SQLITE_OS_UNIX              /* This file is used on unix only */
+
+/*
+** There are various methods for file locking used for concurrency
+** control:
+**
+**   1. POSIX locking (the default),
+**   2. No locking,
+**   3. Dot-file locking,
+**   4. flock() locking,
+**   5. AFP locking (OSX only),
+**   6. Named POSIX semaphores (VXWorks only),
+**   7. proxy locking. (OSX only)
+**
+** Styles 4, 5, and 7 are only available of SQLITE_ENABLE_LOCKING_STYLE
+** is defined to 1.  The SQLITE_ENABLE_LOCKING_STYLE also enables automatic
+** selection of the appropriate locking style based on the filesystem
+** where the database is located.  
+*/
+#if !defined(SQLITE_ENABLE_LOCKING_STYLE)
+#  if defined(__APPLE__)
+#    define SQLITE_ENABLE_LOCKING_STYLE 1
+#  else
+#    define SQLITE_ENABLE_LOCKING_STYLE 0
+#  endif
+#endif
+
+/*
+** Define the OS_VXWORKS pre-processor macro to 1 if building on 
+** vxworks, or 0 otherwise.
+*/
+#ifndef OS_VXWORKS
+#  if defined(__RTP__) || defined(_WRS_KERNEL)
+#    define OS_VXWORKS 1
+#  else
+#    define OS_VXWORKS 0
+#  endif
+#endif
+
+/*
+** These #defines should enable >2GB file support on Posix if the
+** underlying operating system supports it.  If the OS lacks
+** large file support, these should be no-ops.
+**
+** Large file support can be disabled using the -DSQLITE_DISABLE_LFS switch
+** on the compiler command line.  This is necessary if you are compiling
+** on a recent machine (ex: RedHat 7.2) but you want your code to work
+** on an older machine (ex: RedHat 6.0).  If you compile on RedHat 7.2
+** without this option, LFS is enable.  But LFS does not exist in the kernel
+** in RedHat 6.0, so the code won't work.  Hence, for maximum binary
+** portability you should omit LFS.
+**
+** The previous paragraph was written in 2005.  (This paragraph is written
+** on 2008-11-28.) These days, all Linux kernels support large files, so
+** you should probably leave LFS enabled.  But some embedded platforms might
+** lack LFS in which case the SQLITE_DISABLE_LFS macro might still be useful.
+*/
+#ifndef SQLITE_DISABLE_LFS
+# define _LARGE_FILE       1
+# ifndef _FILE_OFFSET_BITS
+#   define _FILE_OFFSET_BITS 64
+# endif
+# define _LARGEFILE_SOURCE 1
+#endif
+
+/*
+** standard include files.
+*/
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <time.h>
+#include <sys/time.h>
+#include <errno.h>
+#ifndef SQLITE_OMIT_WAL
+#include <sys/mman.h>
+#endif
+
+#if SQLITE_ENABLE_LOCKING_STYLE
+# include <sys/ioctl.h>
+# if OS_VXWORKS
+#  include <semaphore.h>
+#  include <limits.h>
+# else
+#  include <sys/file.h>
+#  include <sys/param.h>
+# endif
+#endif /* SQLITE_ENABLE_LOCKING_STYLE */
+
+#if defined(__APPLE__) || (SQLITE_ENABLE_LOCKING_STYLE && !OS_VXWORKS)
+# include <sys/mount.h>
+#endif
+
+#ifdef HAVE_UTIME
+# include <utime.h>
+#endif
+
+/*
+** Allowed values of unixFile.fsFlags
+*/
+#define SQLITE_FSFLAGS_IS_MSDOS     0x1
+
+/*
+** If we are to be thread-safe, include the pthreads header and define
+** the SQLITE_UNIX_THREADS macro.
+*/
+#if SQLITE_THREADSAFE
+# include <pthread.h>
+# define SQLITE_UNIX_THREADS 1
+#endif
+
+/*
+** Default permissions when creating a new file
+*/
+#ifndef SQLITE_DEFAULT_FILE_PERMISSIONS
+# define SQLITE_DEFAULT_FILE_PERMISSIONS 0644
+#endif
+
+/*
+ ** Default permissions when creating auto proxy dir
+ */
+#ifndef SQLITE_DEFAULT_PROXYDIR_PERMISSIONS
+# define SQLITE_DEFAULT_PROXYDIR_PERMISSIONS 0755
+#endif
+
+/*
+** Maximum supported path-length.
+*/
+#define MAX_PATHNAME 512
+
+/*
+** Only set the lastErrno if the error code is a real error and not 
+** a normal expected return code of SQLITE_BUSY or SQLITE_OK
+*/
+#define IS_LOCK_ERROR(x)  ((x != SQLITE_OK) && (x != SQLITE_BUSY))
+
+/* Forward references */
+typedef struct unixShm unixShm;               /* Connection shared memory */
+typedef struct unixShmNode unixShmNode;       /* Shared memory instance */
+typedef struct unixInodeInfo unixInodeInfo;   /* An i-node */
+typedef struct UnixUnusedFd UnixUnusedFd;     /* An unused file descriptor */
+
+/*
+** Sometimes, after a file handle is closed by SQLite, the file descriptor
+** cannot be closed immediately. In these cases, instances of the following
+** structure are used to store the file descriptor while waiting for an
+** opportunity to either close or reuse it.
+*/
+struct UnixUnusedFd {
+  int fd;                   /* File descriptor to close */
+  int flags;                /* Flags this file descriptor was opened with */
+  UnixUnusedFd *pNext;      /* Next unused file descriptor on same file */
+};
+
+/*
+** The unixFile structure is subclass of sqlite3_file specific to the unix
+** VFS implementations.
+*/
+typedef struct unixFile unixFile;
+struct unixFile {
+  sqlite3_io_methods const *pMethod;  /* Always the first entry */
+  unixInodeInfo *pInode;              /* Info about locks on this inode */
+  int h;                              /* The file descriptor */
+  unsigned char eFileLock;            /* The type of lock held on this fd */
+  unsigned char ctrlFlags;            /* Behavioral bits.  UNIXFILE_* flags */
+  int lastErrno;                      /* The unix errno from last I/O error */
+  void *lockingContext;               /* Locking style specific state */
+  UnixUnusedFd *pUnused;              /* Pre-allocated UnixUnusedFd */
+  const char *zPath;                  /* Name of the file */
+  unixShm *pShm;                      /* Shared memory segment information */
+  int szChunk;                        /* Configured by FCNTL_CHUNK_SIZE */
+#if SQLITE_ENABLE_LOCKING_STYLE
+  int openFlags;                      /* The flags specified at open() */
+#endif
+#if SQLITE_ENABLE_LOCKING_STYLE || defined(__APPLE__)
+  unsigned fsFlags;                   /* cached details from statfs() */
+#endif
+#if OS_VXWORKS
+  int isDelete;                       /* Delete on close if true */
+  struct vxworksFileId *pId;          /* Unique file ID */
+#endif
+#ifndef NDEBUG
+  /* The next group of variables are used to track whether or not the
+  ** transaction counter in bytes 24-27 of database files are updated
+  ** whenever any part of the database changes.  An assertion fault will
+  ** occur if a file is updated without also updating the transaction
+  ** counter.  This test is made to avoid new problems similar to the
+  ** one described by ticket #3584. 
+  */
+  unsigned char transCntrChng;   /* True if the transaction counter changed */
+  unsigned char dbUpdate;        /* True if any part of database file changed */
+  unsigned char inNormalWrite;   /* True if in a normal write operation */
+#endif
+#ifdef SQLITE_TEST
+  /* In test mode, increase the size of this structure a bit so that 
+  ** it is larger than the struct CrashFile defined in test6.c.
+  */
+  char aPadding[32];
+#endif
+};
+
+/*
+** Allowed values for the unixFile.ctrlFlags bitmask:
+*/
+#define UNIXFILE_EXCL        0x01     /* Connections from one process only */
+#define UNIXFILE_RDONLY      0x02     /* Connection is read only */
+#define UNIXFILE_PERSIST_WAL 0x04     /* Persistent WAL mode */
+#ifndef SQLITE_DISABLE_DIRSYNC
+# define UNIXFILE_DIRSYNC    0x08     /* Directory sync needed */
+#else
+# define UNIXFILE_DIRSYNC    0x00
+#endif
+
+/*
+** Include code that is common to all os_*.c files
+*/
+#include "os_common.h"
+
+/*
+** Define various macros that are missing from some systems.
+*/
+#ifndef O_LARGEFILE
+# define O_LARGEFILE 0
+#endif
+#ifdef SQLITE_DISABLE_LFS
+# undef O_LARGEFILE
+# define O_LARGEFILE 0
+#endif
+#ifndef O_NOFOLLOW
+# define O_NOFOLLOW 0
+#endif
+#ifndef O_BINARY
+# define O_BINARY 0
+#endif
+
+/*
+** The threadid macro resolves to the thread-id or to 0.  Used for
+** testing and debugging only.
+*/
+#if SQLITE_THREADSAFE
+#define threadid pthread_self()
+#else
+#define threadid 0
+#endif
+
+/*
+** Different Unix systems declare open() in different ways.  Same use
+** open(const char*,int,mode_t).  Others use open(const char*,int,...).
+** The difference is important when using a pointer to the function.
+**
+** The safest way to deal with the problem is to always use this wrapper
+** which always has the same well-defined interface.
+*/
+static int posixOpen(const char *zFile, int flags, int mode){
+  return open(zFile, flags, mode);
+}
+
+/* Forward reference */
+static int openDirectory(const char*, int*);
+
+/*
+** Many system calls are accessed through pointer-to-functions so that
+** they may be overridden at runtime to facilitate fault injection during
+** testing and sandboxing.  The following array holds the names and pointers
+** to all overrideable system calls.
+*/
+static struct unix_syscall {
+  const char *zName;            /* Name of the sytem call */
+  sqlite3_syscall_ptr pCurrent; /* Current value of the system call */
+  sqlite3_syscall_ptr pDefault; /* Default value */
+} aSyscall[] = {
+  { "open",         (sqlite3_syscall_ptr)posixOpen,  0  },
+#define osOpen      ((int(*)(const char*,int,int))aSyscall[0].pCurrent)
+
+  { "close",        (sqlite3_syscall_ptr)close,      0  },
+#define osClose     ((int(*)(int))aSyscall[1].pCurrent)
+
+  { "access",       (sqlite3_syscall_ptr)access,     0  },
+#define osAccess    ((int(*)(const char*,int))aSyscall[2].pCurrent)
+
+  { "getcwd",       (sqlite3_syscall_ptr)getcwd,     0  },
+#define osGetcwd    ((char*(*)(char*,size_t))aSyscall[3].pCurrent)
+
+  { "stat",         (sqlite3_syscall_ptr)stat,       0  },
+#define osStat      ((int(*)(const char*,struct stat*))aSyscall[4].pCurrent)
+
+/*
+** The DJGPP compiler environment looks mostly like Unix, but it
+** lacks the fcntl() system call.  So redefine fcntl() to be something
+** that always succeeds.  This means that locking does not occur under
+** DJGPP.  But it is DOS - what did you expect?
+*/
+#ifdef __DJGPP__
+  { "fstat",        0,                 0  },
+#define osFstat(a,b,c)    0
+#else     
+  { "fstat",        (sqlite3_syscall_ptr)fstat,      0  },
+#define osFstat     ((int(*)(int,struct stat*))aSyscall[5].pCurrent)
+#endif
+
+  { "ftruncate",    (sqlite3_syscall_ptr)ftruncate,  0  },
+#define osFtruncate ((int(*)(int,off_t))aSyscall[6].pCurrent)
+
+  { "fcntl",        (sqlite3_syscall_ptr)fcntl,      0  },
+#define osFcntl     ((int(*)(int,int,...))aSyscall[7].pCurrent)
+
+  { "read",         (sqlite3_syscall_ptr)read,       0  },
+#define osRead      ((ssize_t(*)(int,void*,size_t))aSyscall[8].pCurrent)
+
+#if defined(USE_PREAD) || SQLITE_ENABLE_LOCKING_STYLE
+  { "pread",        (sqlite3_syscall_ptr)pread,      0  },
+#else
+  { "pread",        (sqlite3_syscall_ptr)0,          0  },
+#endif
+#define osPread     ((ssize_t(*)(int,void*,size_t,off_t))aSyscall[9].pCurrent)
+
+#if defined(USE_PREAD64)
+  { "pread64",      (sqlite3_syscall_ptr)pread64,    0  },
+#else
+  { "pread64",      (sqlite3_syscall_ptr)0,          0  },
+#endif
+#define osPread64   ((ssize_t(*)(int,void*,size_t,off_t))aSyscall[10].pCurrent)
+
+  { "write",        (sqlite3_syscall_ptr)write,      0  },
+#define osWrite     ((ssize_t(*)(int,const void*,size_t))aSyscall[11].pCurrent)
+
+#if defined(USE_PREAD) || SQLITE_ENABLE_LOCKING_STYLE
+  { "pwrite",       (sqlite3_syscall_ptr)pwrite,     0  },
+#else
+  { "pwrite",       (sqlite3_syscall_ptr)0,          0  },
+#endif
+#define osPwrite    ((ssize_t(*)(int,const void*,size_t,off_t))\
+                    aSyscall[12].pCurrent)
+
+#if defined(USE_PREAD64)
+  { "pwrite64",     (sqlite3_syscall_ptr)pwrite64,   0  },
+#else
+  { "pwrite64",     (sqlite3_syscall_ptr)0,          0  },
+#endif
+#define osPwrite64  ((ssize_t(*)(int,const void*,size_t,off_t))\
+                    aSyscall[13].pCurrent)
+
+#if SQLITE_ENABLE_LOCKING_STYLE
+  { "fchmod",       (sqlite3_syscall_ptr)fchmod,     0  },
+#else
+  { "fchmod",       (sqlite3_syscall_ptr)0,          0  },
+#endif
+#define osFchmod    ((int(*)(int,mode_t))aSyscall[14].pCurrent)
+
+#if defined(HAVE_POSIX_FALLOCATE) && HAVE_POSIX_FALLOCATE
+  { "fallocate",    (sqlite3_syscall_ptr)posix_fallocate,  0 },
+#else
+  { "fallocate",    (sqlite3_syscall_ptr)0,                0 },
+#endif
+#define osFallocate ((int(*)(int,off_t,off_t))aSyscall[15].pCurrent)
+
+  { "unlink",       (sqlite3_syscall_ptr)unlink,           0 },
+#define osUnlink    ((int(*)(const char*))aSyscall[16].pCurrent)
+
+  { "openDirectory",    (sqlite3_syscall_ptr)openDirectory,      0 },
+#define osOpenDirectory ((int(*)(const char*,int*))aSyscall[17].pCurrent)
+
+}; /* End of the overrideable system calls */
+
+/*
+** This is the xSetSystemCall() method of sqlite3_vfs for all of the
+** "unix" VFSes.  Return SQLITE_OK opon successfully updating the
+** system call pointer, or SQLITE_NOTFOUND if there is no configurable
+** system call named zName.
+*/
+static int unixSetSystemCall(
+  sqlite3_vfs *pNotUsed,        /* The VFS pointer.  Not used */
+  const char *zName,            /* Name of system call to override */
+  sqlite3_syscall_ptr pNewFunc  /* Pointer to new system call value */
+){
+  unsigned int i;
+  int rc = SQLITE_NOTFOUND;
+
+  UNUSED_PARAMETER(pNotUsed);
+  if( zName==0 ){
+    /* If no zName is given, restore all system calls to their default
+    ** settings and return NULL
+    */
+    rc = SQLITE_OK;
+    for(i=0; i<sizeof(aSyscall)/sizeof(aSyscall[0]); i++){
+      if( aSyscall[i].pDefault ){
+        aSyscall[i].pCurrent = aSyscall[i].pDefault;
+      }
+    }
+  }else{
+    /* If zName is specified, operate on only the one system call
+    ** specified.
+    */
+    for(i=0; i<sizeof(aSyscall)/sizeof(aSyscall[0]); i++){
+      if( strcmp(zName, aSyscall[i].zName)==0 ){
+        if( aSyscall[i].pDefault==0 ){
+          aSyscall[i].pDefault = aSyscall[i].pCurrent;
+        }
+        rc = SQLITE_OK;
+        if( pNewFunc==0 ) pNewFunc = aSyscall[i].pDefault;
+        aSyscall[i].pCurrent = pNewFunc;
+        break;
+      }
+    }
+  }
+  return rc;
+}
+
+/*
+** Return the value of a system call.  Return NULL if zName is not a
+** recognized system call name.  NULL is also returned if the system call
+** is currently undefined.
+*/
+static sqlite3_syscall_ptr unixGetSystemCall(
+  sqlite3_vfs *pNotUsed,
+  const char *zName
+){
+  unsigned int i;
+
+  UNUSED_PARAMETER(pNotUsed);
+  for(i=0; i<sizeof(aSyscall)/sizeof(aSyscall[0]); i++){
+    if( strcmp(zName, aSyscall[i].zName)==0 ) return aSyscall[i].pCurrent;
+  }
+  return 0;
+}
+
+/*
+** Return the name of the first system call after zName.  If zName==NULL
+** then return the name of the first system call.  Return NULL if zName
+** is the last system call or if zName is not the name of a valid
+** system call.
+*/
+static const char *unixNextSystemCall(sqlite3_vfs *p, const char *zName){
+  int i = -1;
+
+  UNUSED_PARAMETER(p);
+  if( zName ){
+    for(i=0; i<ArraySize(aSyscall)-1; i++){
+      if( strcmp(zName, aSyscall[i].zName)==0 ) break;
+    }
+  }
+  for(i++; i<ArraySize(aSyscall); i++){
+    if( aSyscall[i].pCurrent!=0 ) return aSyscall[i].zName;
+  }
+  return 0;
+}
+
+/*
+** Retry open() calls that fail due to EINTR
+*/
+static int robust_open(const char *z, int f, int m){
+  int rc;
+  do{ rc = osOpen(z,f,m); }while( rc<0 && errno==EINTR );
+  return rc;
+}
+
+/*
+** Helper functions to obtain and relinquish the global mutex. The
+** global mutex is used to protect the unixInodeInfo and
+** vxworksFileId objects used by this file, all of which may be 
+** shared by multiple threads.
+**
+** Function unixMutexHeld() is used to assert() that the global mutex 
+** is held when required. This function is only used as part of assert() 
+** statements. e.g.
+**
+**   unixEnterMutex()
+**     assert( unixMutexHeld() );
+**   unixEnterLeave()
+*/
+static void unixEnterMutex(void){
+  sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
+}
+static void unixLeaveMutex(void){
+  sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
+}
+#ifdef SQLITE_DEBUG
+static int unixMutexHeld(void) {
+  return sqlite3_mutex_held(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
+}
+#endif
+
+
+#if defined(SQLITE_TEST) && defined(SQLITE_DEBUG)
+/*
+** Helper function for printing out trace information from debugging
+** binaries. This returns the string represetation of the supplied
+** integer lock-type.
+*/
+static const char *azFileLock(int eFileLock){
+  switch( eFileLock ){
+    case NO_LOCK: return "NONE";
+    case SHARED_LOCK: return "SHARED";
+    case RESERVED_LOCK: return "RESERVED";
+    case PENDING_LOCK: return "PENDING";
+    case EXCLUSIVE_LOCK: return "EXCLUSIVE";
+  }
+  return "ERROR";
+}
+#endif
+
+#ifdef SQLITE_LOCK_TRACE
+/*
+** Print out information about all locking operations.
+**
+** This routine is used for troubleshooting locks on multithreaded
+** platforms.  Enable by compiling with the -DSQLITE_LOCK_TRACE
+** command-line option on the compiler.  This code is normally
+** turned off.
+*/
+static int lockTrace(int fd, int op, struct flock *p){
+  char *zOpName, *zType;
+  int s;
+  int savedErrno;
+  if( op==F_GETLK ){
+    zOpName = "GETLK";
+  }else if( op==F_SETLK ){
+    zOpName = "SETLK";
+  }else{
+    s = osFcntl(fd, op, p);
+    sqlite3DebugPrintf("fcntl unknown %d %d %d\n", fd, op, s);
+    return s;
+  }
+  if( p->l_type==F_RDLCK ){
+    zType = "RDLCK";
+  }else if( p->l_type==F_WRLCK ){
+    zType = "WRLCK";
+  }else if( p->l_type==F_UNLCK ){
+    zType = "UNLCK";
+  }else{
+    assert( 0 );
+  }
+  assert( p->l_whence==SEEK_SET );
+  s = osFcntl(fd, op, p);
+  savedErrno = errno;
+  sqlite3DebugPrintf("fcntl %d %d %s %s %d %d %d %d\n",
+     threadid, fd, zOpName, zType, (int)p->l_start, (int)p->l_len,
+     (int)p->l_pid, s);
+  if( s==(-1) && op==F_SETLK && (p->l_type==F_RDLCK || p->l_type==F_WRLCK) ){
+    struct flock l2;
+    l2 = *p;
+    osFcntl(fd, F_GETLK, &l2);
+    if( l2.l_type==F_RDLCK ){
+      zType = "RDLCK";
+    }else if( l2.l_type==F_WRLCK ){
+      zType = "WRLCK";
+    }else if( l2.l_type==F_UNLCK ){
+      zType = "UNLCK";
+    }else{
+      assert( 0 );
+    }
+    sqlite3DebugPrintf("fcntl-failure-reason: %s %d %d %d\n",
+       zType, (int)l2.l_start, (int)l2.l_len, (int)l2.l_pid);
+  }
+  errno = savedErrno;
+  return s;
+}
+#undef osFcntl
+#define osFcntl lockTrace
+#endif /* SQLITE_LOCK_TRACE */
+
+/*
+** Retry ftruncate() calls that fail due to EINTR
+*/
+static int robust_ftruncate(int h, sqlite3_int64 sz){
+  int rc;
+  do{ rc = osFtruncate(h,sz); }while( rc<0 && errno==EINTR );
+  return rc;
+}
+
+/*
+** This routine translates a standard POSIX errno code into something
+** useful to the clients of the sqlite3 functions.  Specifically, it is
+** intended to translate a variety of "try again" errors into SQLITE_BUSY
+** and a variety of "please close the file descriptor NOW" errors into 
+** SQLITE_IOERR
+** 
+** Errors during initialization of locks, or file system support for locks,
+** should handle ENOLCK, ENOTSUP, EOPNOTSUPP separately.
+*/
+static int sqliteErrorFromPosixError(int posixError, int sqliteIOErr) {
+  switch (posixError) {
+#if 0
+  /* At one point this code was not commented out. In theory, this branch
+  ** should never be hit, as this function should only be called after
+  ** a locking-related function (i.e. fcntl()) has returned non-zero with
+  ** the value of errno as the first argument. Since a system call has failed,
+  ** errno should be non-zero.
+  **
+  ** Despite this, if errno really is zero, we still don't want to return
+  ** SQLITE_OK. The system call failed, and *some* SQLite error should be
+  ** propagated back to the caller. Commenting this branch out means errno==0
+  ** will be handled by the "default:" case below.
+  */
+  case 0: 
+    return SQLITE_OK;
+#endif
+
+  case EAGAIN:
+  case ETIMEDOUT:
+  case EBUSY:
+  case EINTR:
+  case ENOLCK:  
+    /* random NFS retry error, unless during file system support 
+     * introspection, in which it actually means what it says */
+    return SQLITE_BUSY;
+    
+  case EACCES: 
+    /* EACCES is like EAGAIN during locking operations, but not any other time*/
+    if( (sqliteIOErr == SQLITE_IOERR_LOCK) || 
+	(sqliteIOErr == SQLITE_IOERR_UNLOCK) || 
+	(sqliteIOErr == SQLITE_IOERR_RDLOCK) ||
+	(sqliteIOErr == SQLITE_IOERR_CHECKRESERVEDLOCK) ){
+      return SQLITE_BUSY;
+    }
+    /* else fall through */
+  case EPERM: 
+    return SQLITE_PERM;
+    
+  /* EDEADLK is only possible if a call to fcntl(F_SETLKW) is made. And
+  ** this module never makes such a call. And the code in SQLite itself 
+  ** asserts that SQLITE_IOERR_BLOCKED is never returned. For these reasons
+  ** this case is also commented out. If the system does set errno to EDEADLK,
+  ** the default SQLITE_IOERR_XXX code will be returned. */
+#if 0
+  case EDEADLK:
+    return SQLITE_IOERR_BLOCKED;
+#endif
+    
+#if EOPNOTSUPP!=ENOTSUP
+  case EOPNOTSUPP: 
+    /* something went terribly awry, unless during file system support 
+     * introspection, in which it actually means what it says */
+#endif
+#ifdef ENOTSUP
+  case ENOTSUP: 
+    /* invalid fd, unless during file system support introspection, in which 
+     * it actually means what it says */
+#endif
+  case EIO:
+  case EBADF:
+  case EINVAL:
+  case ENOTCONN:
+  case ENODEV:
+  case ENXIO:
+  case ENOENT:
+#ifdef ESTALE                     /* ESTALE is not defined on Interix systems */
+  case ESTALE:
+#endif
+  case ENOSYS:
+    /* these should force the client to close the file and reconnect */
+    
+  default: 
+    return sqliteIOErr;
+  }
+}
+
+
+
+/******************************************************************************
+****************** Begin Unique File ID Utility Used By VxWorks ***************
+**
+** On most versions of unix, we can get a unique ID for a file by concatenating
+** the device number and the inode number.  But this does not work on VxWorks.
+** On VxWorks, a unique file id must be based on the canonical filename.
+**
+** A pointer to an instance of the following structure can be used as a
+** unique file ID in VxWorks.  Each instance of this structure contains
+** a copy of the canonical filename.  There is also a reference count.  
+** The structure is reclaimed when the number of pointers to it drops to
+** zero.
+**
+** There are never very many files open at one time and lookups are not
+** a performance-critical path, so it is sufficient to put these
+** structures on a linked list.
+*/
+struct vxworksFileId {
+  struct vxworksFileId *pNext;  /* Next in a list of them all */
+  int nRef;                     /* Number of references to this one */
+  int nName;                    /* Length of the zCanonicalName[] string */
+  char *zCanonicalName;         /* Canonical filename */
+};
+
+#if OS_VXWORKS
+/* 
+** All unique filenames are held on a linked list headed by this
+** variable:
+*/
+static struct vxworksFileId *vxworksFileList = 0;
+
+/*
+** Simplify a filename into its canonical form
+** by making the following changes:
+**
+**  * removing any trailing and duplicate /
+**  * convert /./ into just /
+**  * convert /A/../ where A is any simple name into just /
+**
+** Changes are made in-place.  Return the new name length.
+**
+** The original filename is in z[0..n-1].  Return the number of
+** characters in the simplified name.
+*/
+static int vxworksSimplifyName(char *z, int n){
+  int i, j;
+  while( n>1 && z[n-1]=='/' ){ n--; }
+  for(i=j=0; i<n; i++){
+    if( z[i]=='/' ){
+      if( z[i+1]=='/' ) continue;
+      if( z[i+1]=='.' && i+2<n && z[i+2]=='/' ){
+        i += 1;
+        continue;
+      }
+      if( z[i+1]=='.' && i+3<n && z[i+2]=='.' && z[i+3]=='/' ){
+        while( j>0 && z[j-1]!='/' ){ j--; }
+        if( j>0 ){ j--; }
+        i += 2;
+        continue;
+      }
+    }
+    z[j++] = z[i];
+  }
+  z[j] = 0;
+  return j;
+}
+
+/*
+** Find a unique file ID for the given absolute pathname.  Return
+** a pointer to the vxworksFileId object.  This pointer is the unique
+** file ID.
+**
+** The nRef field of the vxworksFileId object is incremented before
+** the object is returned.  A new vxworksFileId object is created
+** and added to the global list if necessary.
+**
+** If a memory allocation error occurs, return NULL.
+*/
+static struct vxworksFileId *vxworksFindFileId(const char *zAbsoluteName){
+  struct vxworksFileId *pNew;         /* search key and new file ID */
+  struct vxworksFileId *pCandidate;   /* For looping over existing file IDs */
+  int n;                              /* Length of zAbsoluteName string */
+
+  assert( zAbsoluteName[0]=='/' );
+  n = (int)strlen(zAbsoluteName);
+  pNew = sqlite3_malloc( sizeof(*pNew) + (n+1) );
+  if( pNew==0 ) return 0;
+  pNew->zCanonicalName = (char*)&pNew[1];
+  memcpy(pNew->zCanonicalName, zAbsoluteName, n+1);
+  n = vxworksSimplifyName(pNew->zCanonicalName, n);
+
+  /* Search for an existing entry that matching the canonical name.
+  ** If found, increment the reference count and return a pointer to
+  ** the existing file ID.
+  */
+  unixEnterMutex();
+  for(pCandidate=vxworksFileList; pCandidate; pCandidate=pCandidate->pNext){
+    if( pCandidate->nName==n 
+     && memcmp(pCandidate->zCanonicalName, pNew->zCanonicalName, n)==0
+    ){
+       sqlite3_free(pNew);
+       pCandidate->nRef++;
+       unixLeaveMutex();
+       return pCandidate;
+    }
+  }
+
+  /* No match was found.  We will make a new file ID */
+  pNew->nRef = 1;
+  pNew->nName = n;
+  pNew->pNext = vxworksFileList;
+  vxworksFileList = pNew;
+  unixLeaveMutex();
+  return pNew;
+}
+
+/*
+** Decrement the reference count on a vxworksFileId object.  Free
+** the object when the reference count reaches zero.
+*/
+static void vxworksReleaseFileId(struct vxworksFileId *pId){
+  unixEnterMutex();
+  assert( pId->nRef>0 );
+  pId->nRef--;
+  if( pId->nRef==0 ){
+    struct vxworksFileId **pp;
+    for(pp=&vxworksFileList; *pp && *pp!=pId; pp = &((*pp)->pNext)){}
+    assert( *pp==pId );
+    *pp = pId->pNext;
+    sqlite3_free(pId);
+  }
+  unixLeaveMutex();
+}
+#endif /* OS_VXWORKS */
+/*************** End of Unique File ID Utility Used By VxWorks ****************
+******************************************************************************/
+
+
+/******************************************************************************
+*************************** Posix Advisory Locking ****************************
+**
+** POSIX advisory locks are broken by design.  ANSI STD 1003.1 (1996)
+** section 6.5.2.2 lines 483 through 490 specify that when a process
+** sets or clears a lock, that operation overrides any prior locks set
+** by the same process.  It does not explicitly say so, but this implies
+** that it overrides locks set by the same process using a different
+** file descriptor.  Consider this test case:
+**
+**       int fd1 = open("./file1", O_RDWR|O_CREAT, 0644);
+**       int fd2 = open("./file2", O_RDWR|O_CREAT, 0644);
+**
+** Suppose ./file1 and ./file2 are really the same file (because
+** one is a hard or symbolic link to the other) then if you set
+** an exclusive lock on fd1, then try to get an exclusive lock
+** on fd2, it works.  I would have expected the second lock to
+** fail since there was already a lock on the file due to fd1.
+** But not so.  Since both locks came from the same process, the
+** second overrides the first, even though they were on different
+** file descriptors opened on different file names.
+**
+** This means that we cannot use POSIX locks to synchronize file access
+** among competing threads of the same process.  POSIX locks will work fine
+** to synchronize access for threads in separate processes, but not
+** threads within the same process.
+**
+** To work around the problem, SQLite has to manage file locks internally
+** on its own.  Whenever a new database is opened, we have to find the
+** specific inode of the database file (the inode is determined by the
+** st_dev and st_ino fields of the stat structure that fstat() fills in)
+** and check for locks already existing on that inode.  When locks are
+** created or removed, we have to look at our own internal record of the
+** locks to see if another thread has previously set a lock on that same
+** inode.
+**
+** (Aside: The use of inode numbers as unique IDs does not work on VxWorks.
+** For VxWorks, we have to use the alternative unique ID system based on
+** canonical filename and implemented in the previous division.)
+**
+** The sqlite3_file structure for POSIX is no longer just an integer file
+** descriptor.  It is now a structure that holds the integer file
+** descriptor and a pointer to a structure that describes the internal
+** locks on the corresponding inode.  There is one locking structure
+** per inode, so if the same inode is opened twice, both unixFile structures
+** point to the same locking structure.  The locking structure keeps
+** a reference count (so we will know when to delete it) and a "cnt"
+** field that tells us its internal lock status.  cnt==0 means the
+** file is unlocked.  cnt==-1 means the file has an exclusive lock.
+** cnt>0 means there are cnt shared locks on the file.
+**
+** Any attempt to lock or unlock a file first checks the locking
+** structure.  The fcntl() system call is only invoked to set a 
+** POSIX lock if the internal lock structure transitions between
+** a locked and an unlocked state.
+**
+** But wait:  there are yet more problems with POSIX advisory locks.
+**
+** If you close a file descriptor that points to a file that has locks,
+** all locks on that file that are owned by the current process are
+** released.  To work around this problem, each unixInodeInfo object
+** maintains a count of the number of pending locks on tha inode.
+** When an attempt is made to close an unixFile, if there are
+** other unixFile open on the same inode that are holding locks, the call
+** to close() the file descriptor is deferred until all of the locks clear.
+** The unixInodeInfo structure keeps a list of file descriptors that need to
+** be closed and that list is walked (and cleared) when the last lock
+** clears.
+**
+** Yet another problem:  LinuxThreads do not play well with posix locks.
+**
+** Many older versions of linux use the LinuxThreads library which is
+** not posix compliant.  Under LinuxThreads, a lock created by thread
+** A cannot be modified or overridden by a different thread B.
+** Only thread A can modify the lock.  Locking behavior is correct
+** if the appliation uses the newer Native Posix Thread Library (NPTL)
+** on linux - with NPTL a lock created by thread A can override locks
+** in thread B.  But there is no way to know at compile-time which
+** threading library is being used.  So there is no way to know at
+** compile-time whether or not thread A can override locks on thread B.
+** One has to do a run-time check to discover the behavior of the
+** current process.
+**
+** SQLite used to support LinuxThreads.  But support for LinuxThreads
+** was dropped beginning with version 3.7.0.  SQLite will still work with
+** LinuxThreads provided that (1) there is no more than one connection 
+** per database file in the same process and (2) database connections
+** do not move across threads.
+*/
+
+/*
+** An instance of the following structure serves as the key used
+** to locate a particular unixInodeInfo object.
+*/
+struct unixFileId {
+  dev_t dev;                  /* Device number */
+#if OS_VXWORKS
+  struct vxworksFileId *pId;  /* Unique file ID for vxworks. */
+#else
+  ino_t ino;                  /* Inode number */
+#endif
+};
+
+/*
+** An instance of the following structure is allocated for each open
+** inode.  Or, on LinuxThreads, there is one of these structures for
+** each inode opened by each thread.
+**
+** A single inode can have multiple file descriptors, so each unixFile
+** structure contains a pointer to an instance of this object and this
+** object keeps a count of the number of unixFile pointing to it.
+*/
+struct unixInodeInfo {
+  struct unixFileId fileId;       /* The lookup key */
+  int nShared;                    /* Number of SHARED locks held */
+  unsigned char eFileLock;        /* One of SHARED_LOCK, RESERVED_LOCK etc. */
+  unsigned char bProcessLock;     /* An exclusive process lock is held */
+  int nRef;                       /* Number of pointers to this structure */
+  unixShmNode *pShmNode;          /* Shared memory associated with this inode */
+  int nLock;                      /* Number of outstanding file locks */
+  UnixUnusedFd *pUnused;          /* Unused file descriptors to close */
+  unixInodeInfo *pNext;           /* List of all unixInodeInfo objects */
+  unixInodeInfo *pPrev;           /*    .... doubly linked */
+#if SQLITE_ENABLE_LOCKING_STYLE
+  unsigned long long sharedByte;  /* for AFP simulated shared lock */
+#endif
+#if OS_VXWORKS
+  sem_t *pSem;                    /* Named POSIX semaphore */
+  char aSemName[MAX_PATHNAME+2];  /* Name of that semaphore */
+#endif
+};
+
+/*
+** A lists of all unixInodeInfo objects.
+*/
+static unixInodeInfo *inodeList = 0;
+
+/*
+**
+** This function - unixLogError_x(), is only ever called via the macro
+** unixLogError().
+**
+** It is invoked after an error occurs in an OS function and errno has been
+** set. It logs a message using sqlite3_log() containing the current value of
+** errno and, if possible, the human-readable equivalent from strerror() or
+** strerror_r().
+**
+** The first argument passed to the macro should be the error code that
+** will be returned to SQLite (e.g. SQLITE_IOERR_DELETE, SQLITE_CANTOPEN). 
+** The two subsequent arguments should be the name of the OS function that
+** failed (e.g. "unlink", "open") and the the associated file-system path,
+** if any.
+*/
+#define unixLogError(a,b,c)     unixLogErrorAtLine(a,b,c,__LINE__)
+static int unixLogErrorAtLine(
+  int errcode,                    /* SQLite error code */
+  const char *zFunc,              /* Name of OS function that failed */
+  const char *zPath,              /* File path associated with error */
+  int iLine                       /* Source line number where error occurred */
+){
+  char *zErr;                     /* Message from strerror() or equivalent */
+  int iErrno = errno;             /* Saved syscall error number */
+
+  /* If this is not a threadsafe build (SQLITE_THREADSAFE==0), then use
+  ** the strerror() function to obtain the human-readable error message
+  ** equivalent to errno. Otherwise, use strerror_r().
+  */ 
+#if SQLITE_THREADSAFE && defined(HAVE_STRERROR_R)
+  char aErr[80];
+  memset(aErr, 0, sizeof(aErr));
+  zErr = aErr;
+
+  /* If STRERROR_R_CHAR_P (set by autoconf scripts) or __USE_GNU is defined,
+  ** assume that the system provides the the GNU version of strerror_r() that 
+  ** returns a pointer to a buffer containing the error message. That pointer 
+  ** may point to aErr[], or it may point to some static storage somewhere. 
+  ** Otherwise, assume that the system provides the POSIX version of 
+  ** strerror_r(), which always writes an error message into aErr[].
+  **
+  ** If the code incorrectly assumes that it is the POSIX version that is
+  ** available, the error message will often be an empty string. Not a
+  ** huge problem. Incorrectly concluding that the GNU version is available 
+  ** could lead to a segfault though.
+  */
+#if defined(STRERROR_R_CHAR_P) || defined(__USE_GNU)
+  zErr = 
+# endif
+  strerror_r(iErrno, aErr, sizeof(aErr)-1);
+
+#elif SQLITE_THREADSAFE
+  /* This is a threadsafe build, but strerror_r() is not available. */
+  zErr = "";
+#else
+  /* Non-threadsafe build, use strerror(). */
+  zErr = strerror(iErrno);
+#endif
+
+  assert( errcode!=SQLITE_OK );
+  if( zPath==0 ) zPath = "";
+  sqlite3_log(errcode,
+      "os_unix.c:%d: (%d) %s(%s) - %s",
+      iLine, iErrno, zFunc, zPath, zErr
+  );
+
+  return errcode;
+}
+
+/*
+** Close a file descriptor.
+**
+** We assume that close() almost always works, since it is only in a
+** very sick application or on a very sick platform that it might fail.
+** If it does fail, simply leak the file descriptor, but do log the
+** error.
+**
+** Note that it is not safe to retry close() after EINTR since the
+** file descriptor might have already been reused by another thread.
+** So we don't even try to recover from an EINTR.  Just log the error
+** and move on.
+*/
+static void robust_close(unixFile *pFile, int h, int lineno){
+  if( osClose(h) ){
+    unixLogErrorAtLine(SQLITE_IOERR_CLOSE, "close",
+                       pFile ? pFile->zPath : 0, lineno);
+  }
+}
+
+/*
+** Close all file descriptors accumuated in the unixInodeInfo->pUnused list.
+*/ 
+static void closePendingFds(unixFile *pFile){
+  unixInodeInfo *pInode = pFile->pInode;
+  UnixUnusedFd *p;
+  UnixUnusedFd *pNext;
+  for(p=pInode->pUnused; p; p=pNext){
+    pNext = p->pNext;
+    robust_close(pFile, p->fd, __LINE__);
+    sqlite3_free(p);
+  }
+  pInode->pUnused = 0;
+}
+
+/*
+** Release a unixInodeInfo structure previously allocated by findInodeInfo().
+**
+** The mutex entered using the unixEnterMutex() function must be held
+** when this function is called.
+*/
+static void releaseInodeInfo(unixFile *pFile){
+  unixInodeInfo *pInode = pFile->pInode;
+  assert( unixMutexHeld() );
+  if( ALWAYS(pInode) ){
+    pInode->nRef--;
+    if( pInode->nRef==0 ){
+      assert( pInode->pShmNode==0 );
+      closePendingFds(pFile);
+      if( pInode->pPrev ){
+        assert( pInode->pPrev->pNext==pInode );
+        pInode->pPrev->pNext = pInode->pNext;
+      }else{
+        assert( inodeList==pInode );
+        inodeList = pInode->pNext;
+      }
+      if( pInode->pNext ){
+        assert( pInode->pNext->pPrev==pInode );
+        pInode->pNext->pPrev = pInode->pPrev;
+      }
+      sqlite3_free(pInode);
+    }
+  }
+}
+
+/*
+** Given a file descriptor, locate the unixInodeInfo object that
+** describes that file descriptor.  Create a new one if necessary.  The
+** return value might be uninitialized if an error occurs.
+**
+** The mutex entered using the unixEnterMutex() function must be held
+** when this function is called.
+**
+** Return an appropriate error code.
+*/
+static int findInodeInfo(
+  unixFile *pFile,               /* Unix file with file desc used in the key */
+  unixInodeInfo **ppInode        /* Return the unixInodeInfo object here */
+){
+  int rc;                        /* System call return code */
+  int fd;                        /* The file descriptor for pFile */
+  struct unixFileId fileId;      /* Lookup key for the unixInodeInfo */
+  struct stat statbuf;           /* Low-level file information */
+  unixInodeInfo *pInode = 0;     /* Candidate unixInodeInfo object */
+
+  assert( unixMutexHeld() );
+
+  /* Get low-level information about the file that we can used to
+  ** create a unique name for the file.
+  */
+  fd = pFile->h;
+  rc = osFstat(fd, &statbuf);
+  if( rc!=0 ){
+    pFile->lastErrno = errno;
+#ifdef EOVERFLOW
+    if( pFile->lastErrno==EOVERFLOW ) return SQLITE_NOLFS;
+#endif
+    return SQLITE_IOERR;
+  }
+
+#ifdef __APPLE__
+  /* On OS X on an msdos filesystem, the inode number is reported
+  ** incorrectly for zero-size files.  See ticket #3260.  To work
+  ** around this problem (we consider it a bug in OS X, not SQLite)
+  ** we always increase the file size to 1 by writing a single byte
+  ** prior to accessing the inode number.  The one byte written is
+  ** an ASCII 'S' character which also happens to be the first byte
+  ** in the header of every SQLite database.  In this way, if there
+  ** is a race condition such that another thread has already populated
+  ** the first page of the database, no damage is done.
+  */
+  if( statbuf.st_size==0 && (pFile->fsFlags & SQLITE_FSFLAGS_IS_MSDOS)!=0 ){
+    do{ rc = osWrite(fd, "S", 1); }while( rc<0 && errno==EINTR );
+    if( rc!=1 ){
+      pFile->lastErrno = errno;
+      return SQLITE_IOERR;
+    }
+    rc = osFstat(fd, &statbuf);
+    if( rc!=0 ){
+      pFile->lastErrno = errno;
+      return SQLITE_IOERR;
+    }
+  }
+#endif
+
+  memset(&fileId, 0, sizeof(fileId));
+  fileId.dev = statbuf.st_dev;
+#if OS_VXWORKS
+  fileId.pId = pFile->pId;
+#else
+  fileId.ino = statbuf.st_ino;
+#endif
+  pInode = inodeList;
+  while( pInode && memcmp(&fileId, &pInode->fileId, sizeof(fileId)) ){
+    pInode = pInode->pNext;
+  }
+  if( pInode==0 ){
+    pInode = sqlite3_malloc( sizeof(*pInode) );
+    if( pInode==0 ){
+      return SQLITE_NOMEM;
+    }
+    memset(pInode, 0, sizeof(*pInode));
+    memcpy(&pInode->fileId, &fileId, sizeof(fileId));
+    pInode->nRef = 1;
+    pInode->pNext = inodeList;
+    pInode->pPrev = 0;
+    if( inodeList ) inodeList->pPrev = pInode;
+    inodeList = pInode;
+  }else{
+    pInode->nRef++;
+  }
+  *ppInode = pInode;
+  return SQLITE_OK;
+}
+
+
+/*
+** This routine checks if there is a RESERVED lock held on the specified
+** file by this or any other process. If such a lock is held, set *pResOut
+** to a non-zero value otherwise *pResOut is set to zero.  The return value
+** is set to SQLITE_OK unless an I/O error occurs during lock checking.
+*/
+static int unixCheckReservedLock(sqlite3_file *id, int *pResOut){
+  int rc = SQLITE_OK;
+  int reserved = 0;
+  unixFile *pFile = (unixFile*)id;
+
+  SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
+
+  assert( pFile );
+  unixEnterMutex(); /* Because pFile->pInode is shared across threads */
+
+  /* Check if a thread in this process holds such a lock */
+  if( pFile->pInode->eFileLock>SHARED_LOCK ){
+    reserved = 1;
+  }
+
+  /* Otherwise see if some other process holds it.
+  */
+#ifndef __DJGPP__
+  if( !reserved && !pFile->pInode->bProcessLock ){
+    struct flock lock;
+    lock.l_whence = SEEK_SET;
+    lock.l_start = RESERVED_BYTE;
+    lock.l_len = 1;
+    lock.l_type = F_WRLCK;
+    if( osFcntl(pFile->h, F_GETLK, &lock) ){
+      rc = SQLITE_IOERR_CHECKRESERVEDLOCK;
+      pFile->lastErrno = errno;
+    } else if( lock.l_type!=F_UNLCK ){
+      reserved = 1;
+    }
+  }
+#endif
+  
+  unixLeaveMutex();
+  OSTRACE(("TEST WR-LOCK %d %d %d (unix)\n", pFile->h, rc, reserved));
+
+  *pResOut = reserved;
+  return rc;
+}
+
+/*
+** Attempt to set a system-lock on the file pFile.  The lock is 
+** described by pLock.
+**
+** If the pFile was opened read/write from unix-excl, then the only lock
+** ever obtained is an exclusive lock, and it is obtained exactly once
+** the first time any lock is attempted.  All subsequent system locking
+** operations become no-ops.  Locking operations still happen internally,
+** in order to coordinate access between separate database connections
+** within this process, but all of that is handled in memory and the
+** operating system does not participate.
+**
+** This function is a pass-through to fcntl(F_SETLK) if pFile is using
+** any VFS other than "unix-excl" or if pFile is opened on "unix-excl"
+** and is read-only.
+**
+** Zero is returned if the call completes successfully, or -1 if a call
+** to fcntl() fails. In this case, errno is set appropriately (by fcntl()).
+*/
+static int unixFileLock(unixFile *pFile, struct flock *pLock){
+  int rc;
+  unixInodeInfo *pInode = pFile->pInode;
+  assert( unixMutexHeld() );
+  assert( pInode!=0 );
+  if( ((pFile->ctrlFlags & UNIXFILE_EXCL)!=0 || pInode->bProcessLock)
+   && ((pFile->ctrlFlags & UNIXFILE_RDONLY)==0)
+  ){
+    if( pInode->bProcessLock==0 ){
+      struct flock lock;
+      assert( pInode->nLock==0 );
+      lock.l_whence = SEEK_SET;
+      lock.l_start = SHARED_FIRST;
+      lock.l_len = SHARED_SIZE;
+      lock.l_type = F_WRLCK;
+      rc = osFcntl(pFile->h, F_SETLK, &lock);
+      if( rc<0 ) return rc;
+      pInode->bProcessLock = 1;
+      pInode->nLock++;
+    }else{
+      rc = 0;
+    }
+  }else{
+    rc = osFcntl(pFile->h, F_SETLK, pLock);
+  }
+  return rc;
+}
+
+/*
+** Lock the file with the lock specified by parameter eFileLock - one
+** of the following:
+**
+**     (1) SHARED_LOCK
+**     (2) RESERVED_LOCK
+**     (3) PENDING_LOCK
+**     (4) EXCLUSIVE_LOCK
+**
+** Sometimes when requesting one lock state, additional lock states
+** are inserted in between.  The locking might fail on one of the later
+** transitions leaving the lock state different from what it started but
+** still short of its goal.  The following chart shows the allowed
+** transitions and the inserted intermediate states:
+**
+**    UNLOCKED -> SHARED
+**    SHARED -> RESERVED
+**    SHARED -> (PENDING) -> EXCLUSIVE
+**    RESERVED -> (PENDING) -> EXCLUSIVE
+**    PENDING -> EXCLUSIVE
+**
+** This routine will only increase a lock.  Use the sqlite3OsUnlock()
+** routine to lower a locking level.
+*/
+static int unixLock(sqlite3_file *id, int eFileLock){
+  /* The following describes the implementation of the various locks and
+  ** lock transitions in terms of the POSIX advisory shared and exclusive
+  ** lock primitives (called read-locks and write-locks below, to avoid
+  ** confusion with SQLite lock names). The algorithms are complicated
+  ** slightly in order to be compatible with windows systems simultaneously
+  ** accessing the same database file, in case that is ever required.
+  **
+  ** Symbols defined in os.h indentify the 'pending byte' and the 'reserved
+  ** byte', each single bytes at well known offsets, and the 'shared byte
+  ** range', a range of 510 bytes at a well known offset.
+  **
+  ** To obtain a SHARED lock, a read-lock is obtained on the 'pending
+  ** byte'.  If this is successful, a random byte from the 'shared byte
+  ** range' is read-locked and the lock on the 'pending byte' released.
+  **
+  ** A process may only obtain a RESERVED lock after it has a SHARED lock.
+  ** A RESERVED lock is implemented by grabbing a write-lock on the
+  ** 'reserved byte'. 
+  **
+  ** A process may only obtain a PENDING lock after it has obtained a
+  ** SHARED lock. A PENDING lock is implemented by obtaining a write-lock
+  ** on the 'pending byte'. This ensures that no new SHARED locks can be
+  ** obtained, but existing SHARED locks are allowed to persist. A process
+  ** does not have to obtain a RESERVED lock on the way to a PENDING lock.
+  ** This property is used by the algorithm for rolling back a journal file
+  ** after a crash.
+  **
+  ** An EXCLUSIVE lock, obtained after a PENDING lock is held, is
+  ** implemented by obtaining a write-lock on the entire 'shared byte
+  ** range'. Since all other locks require a read-lock on one of the bytes
+  ** within this range, this ensures that no other locks are held on the
+  ** database. 
+  **
+  ** The reason a single byte cannot be used instead of the 'shared byte
+  ** range' is that some versions of windows do not support read-locks. By
+  ** locking a random byte from a range, concurrent SHARED locks may exist
+  ** even if the locking primitive used is always a write-lock.
+  */
+  int rc = SQLITE_OK;
+  unixFile *pFile = (unixFile*)id;
+  unixInodeInfo *pInode;
+  struct flock lock;
+  int tErrno = 0;
+
+  assert( pFile );
+  OSTRACE(("LOCK    %d %s was %s(%s,%d) pid=%d (unix)\n", pFile->h,
+      azFileLock(eFileLock), azFileLock(pFile->eFileLock),
+      azFileLock(pFile->pInode->eFileLock), pFile->pInode->nShared , getpid()));
+
+  /* If there is already a lock of this type or more restrictive on the
+  ** unixFile, do nothing. Don't use the end_lock: exit path, as
+  ** unixEnterMutex() hasn't been called yet.
+  */
+  if( pFile->eFileLock>=eFileLock ){
+    OSTRACE(("LOCK    %d %s ok (already held) (unix)\n", pFile->h,
+            azFileLock(eFileLock)));
+    return SQLITE_OK;
+  }
+
+  /* Make sure the locking sequence is correct.
+  **  (1) We never move from unlocked to anything higher than shared lock.
+  **  (2) SQLite never explicitly requests a pendig lock.
+  **  (3) A shared lock is always held when a reserve lock is requested.
+  */
+  assert( pFile->eFileLock!=NO_LOCK || eFileLock==SHARED_LOCK );
+  assert( eFileLock!=PENDING_LOCK );
+  assert( eFileLock!=RESERVED_LOCK || pFile->eFileLock==SHARED_LOCK );
+
+  /* This mutex is needed because pFile->pInode is shared across threads
+  */
+  unixEnterMutex();
+  pInode = pFile->pInode;
+
+  /* If some thread using this PID has a lock via a different unixFile*
+  ** handle that precludes the requested lock, return BUSY.
+  */
+  if( (pFile->eFileLock!=pInode->eFileLock && 
+          (pInode->eFileLock>=PENDING_LOCK || eFileLock>SHARED_LOCK))
+  ){
+    rc = SQLITE_BUSY;
+    goto end_lock;
+  }
+
+  /* If a SHARED lock is requested, and some thread using this PID already
+  ** has a SHARED or RESERVED lock, then increment reference counts and
+  ** return SQLITE_OK.
+  */
+  if( eFileLock==SHARED_LOCK && 
+      (pInode->eFileLock==SHARED_LOCK || pInode->eFileLock==RESERVED_LOCK) ){
+    assert( eFileLock==SHARED_LOCK );
+    assert( pFile->eFileLock==0 );
+    assert( pInode->nShared>0 );
+    pFile->eFileLock = SHARED_LOCK;
+    pInode->nShared++;
+    pInode->nLock++;
+    goto end_lock;
+  }
+
+
+  /* A PENDING lock is needed before acquiring a SHARED lock and before
+  ** acquiring an EXCLUSIVE lock.  For the SHARED lock, the PENDING will
+  ** be released.
+  */
+  lock.l_len = 1L;
+  lock.l_whence = SEEK_SET;
+  if( eFileLock==SHARED_LOCK 
+      || (eFileLock==EXCLUSIVE_LOCK && pFile->eFileLock<PENDING_LOCK)
+  ){
+    lock.l_type = (eFileLock==SHARED_LOCK?F_RDLCK:F_WRLCK);
+    lock.l_start = PENDING_BYTE;
+    if( unixFileLock(pFile, &lock) ){
+      tErrno = errno;
+      rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK);
+      if( rc!=SQLITE_BUSY ){
+        pFile->lastErrno = tErrno;
+      }
+      goto end_lock;
+    }
+  }
+
+
+  /* If control gets to this point, then actually go ahead and make
+  ** operating system calls for the specified lock.
+  */
+  if( eFileLock==SHARED_LOCK ){
+    assert( pInode->nShared==0 );
+    assert( pInode->eFileLock==0 );
+    assert( rc==SQLITE_OK );
+
+    /* Now get the read-lock */
+    lock.l_start = SHARED_FIRST;
+    lock.l_len = SHARED_SIZE;
+    if( unixFileLock(pFile, &lock) ){
+      tErrno = errno;
+      rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK);
+    }
+
+    /* Drop the temporary PENDING lock */
+    lock.l_start = PENDING_BYTE;
+    lock.l_len = 1L;
+    lock.l_type = F_UNLCK;
+    if( unixFileLock(pFile, &lock) && rc==SQLITE_OK ){
+      /* This could happen with a network mount */
+      tErrno = errno;
+      rc = SQLITE_IOERR_UNLOCK; 
+    }
+
+    if( rc ){
+      if( rc!=SQLITE_BUSY ){
+        pFile->lastErrno = tErrno;
+      }
+      goto end_lock;
+    }else{
+      pFile->eFileLock = SHARED_LOCK;
+      pInode->nLock++;
+      pInode->nShared = 1;
+    }
+  }else if( eFileLock==EXCLUSIVE_LOCK && pInode->nShared>1 ){
+    /* We are trying for an exclusive lock but another thread in this
+    ** same process is still holding a shared lock. */
+    rc = SQLITE_BUSY;
+  }else{
+    /* The request was for a RESERVED or EXCLUSIVE lock.  It is
+    ** assumed that there is a SHARED or greater lock on the file
+    ** already.
+    */
+    assert( 0!=pFile->eFileLock );
+    lock.l_type = F_WRLCK;
+
+    assert( eFileLock==RESERVED_LOCK || eFileLock==EXCLUSIVE_LOCK );
+    if( eFileLock==RESERVED_LOCK ){
+      lock.l_start = RESERVED_BYTE;
+      lock.l_len = 1L;
+    }else{
+      lock.l_start = SHARED_FIRST;
+      lock.l_len = SHARED_SIZE;
+    }
+
+    if( unixFileLock(pFile, &lock) ){
+      tErrno = errno;
+      rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK);
+      if( rc!=SQLITE_BUSY ){
+        pFile->lastErrno = tErrno;
+      }
+    }
+  }
+  
+
+#ifndef NDEBUG
+  /* Set up the transaction-counter change checking flags when
+  ** transitioning from a SHARED to a RESERVED lock.  The change
+  ** from SHARED to RESERVED marks the beginning of a normal
+  ** write operation (not a hot journal rollback).
+  */
+  if( rc==SQLITE_OK
+   && pFile->eFileLock<=SHARED_LOCK
+   && eFileLock==RESERVED_LOCK
+  ){
+    pFile->transCntrChng = 0;
+    pFile->dbUpdate = 0;
+    pFile->inNormalWrite = 1;
+  }
+#endif
+
+
+  if( rc==SQLITE_OK ){
+    pFile->eFileLock = eFileLock;
+    pInode->eFileLock = eFileLock;
+  }else if( eFileLock==EXCLUSIVE_LOCK ){
+    pFile->eFileLock = PENDING_LOCK;
+    pInode->eFileLock = PENDING_LOCK;
+  }
+
+end_lock:
+  unixLeaveMutex();
+  OSTRACE(("LOCK    %d %s %s (unix)\n", pFile->h, azFileLock(eFileLock), 
+      rc==SQLITE_OK ? "ok" : "failed"));
+  return rc;
+}
+
+/*
+** Add the file descriptor used by file handle pFile to the corresponding
+** pUnused list.
+*/
+static void setPendingFd(unixFile *pFile){
+  unixInodeInfo *pInode = pFile->pInode;
+  UnixUnusedFd *p = pFile->pUnused;
+  p->pNext = pInode->pUnused;
+  pInode->pUnused = p;
+  pFile->h = -1;
+  pFile->pUnused = 0;
+}
+
+/*
+** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
+** must be either NO_LOCK or SHARED_LOCK.
+**
+** If the locking level of the file descriptor is already at or below
+** the requested locking level, this routine is a no-op.
+** 
+** If handleNFSUnlock is true, then on downgrading an EXCLUSIVE_LOCK to SHARED
+** the byte range is divided into 2 parts and the first part is unlocked then
+** set to a read lock, then the other part is simply unlocked.  This works 
+** around a bug in BSD NFS lockd (also seen on MacOSX 10.3+) that fails to 
+** remove the write lock on a region when a read lock is set.
+*/
+static int posixUnlock(sqlite3_file *id, int eFileLock, int handleNFSUnlock){
+  unixFile *pFile = (unixFile*)id;
+  unixInodeInfo *pInode;
+  struct flock lock;
+  int rc = SQLITE_OK;
+
+  assert( pFile );
+  OSTRACE(("UNLOCK  %d %d was %d(%d,%d) pid=%d (unix)\n", pFile->h, eFileLock,
+      pFile->eFileLock, pFile->pInode->eFileLock, pFile->pInode->nShared,
+      getpid()));
+
+  assert( eFileLock<=SHARED_LOCK );
+  if( pFile->eFileLock<=eFileLock ){
+    return SQLITE_OK;
+  }
+  unixEnterMutex();
+  pInode = pFile->pInode;
+  assert( pInode->nShared!=0 );
+  if( pFile->eFileLock>SHARED_LOCK ){
+    assert( pInode->eFileLock==pFile->eFileLock );
+
+#ifndef NDEBUG
+    /* When reducing a lock such that other processes can start
+    ** reading the database file again, make sure that the
+    ** transaction counter was updated if any part of the database
+    ** file changed.  If the transaction counter is not updated,
+    ** other connections to the same file might not realize that
+    ** the file has changed and hence might not know to flush their
+    ** cache.  The use of a stale cache can lead to database corruption.
+    */
+    pFile->inNormalWrite = 0;
+#endif
+
+    /* downgrading to a shared lock on NFS involves clearing the write lock
+    ** before establishing the readlock - to avoid a race condition we downgrade
+    ** the lock in 2 blocks, so that part of the range will be covered by a 
+    ** write lock until the rest is covered by a read lock:
+    **  1:   [WWWWW]
+    **  2:   [....W]
+    **  3:   [RRRRW]
+    **  4:   [RRRR.]
+    */
+    if( eFileLock==SHARED_LOCK ){
+
+#if !defined(__APPLE__) || !SQLITE_ENABLE_LOCKING_STYLE
+      (void)handleNFSUnlock;
+      assert( handleNFSUnlock==0 );
+#endif
+#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
+      if( handleNFSUnlock ){
+        int tErrno;               /* Error code from system call errors */
+        off_t divSize = SHARED_SIZE - 1;
+        
+        lock.l_type = F_UNLCK;
+        lock.l_whence = SEEK_SET;
+        lock.l_start = SHARED_FIRST;
+        lock.l_len = divSize;
+        if( unixFileLock(pFile, &lock)==(-1) ){
+          tErrno = errno;
+          rc = SQLITE_IOERR_UNLOCK;
+          if( IS_LOCK_ERROR(rc) ){
+            pFile->lastErrno = tErrno;
+          }
+          goto end_unlock;
+        }
+        lock.l_type = F_RDLCK;
+        lock.l_whence = SEEK_SET;
+        lock.l_start = SHARED_FIRST;
+        lock.l_len = divSize;
+        if( unixFileLock(pFile, &lock)==(-1) ){
+          tErrno = errno;
+          rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_RDLOCK);
+          if( IS_LOCK_ERROR(rc) ){
+            pFile->lastErrno = tErrno;
+          }
+          goto end_unlock;
+        }
+        lock.l_type = F_UNLCK;
+        lock.l_whence = SEEK_SET;
+        lock.l_start = SHARED_FIRST+divSize;
+        lock.l_len = SHARED_SIZE-divSize;
+        if( unixFileLock(pFile, &lock)==(-1) ){
+          tErrno = errno;
+          rc = SQLITE_IOERR_UNLOCK;
+          if( IS_LOCK_ERROR(rc) ){
+            pFile->lastErrno = tErrno;
+          }
+          goto end_unlock;
+        }
+      }else
+#endif /* defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE */
+      {
+        lock.l_type = F_RDLCK;
+        lock.l_whence = SEEK_SET;
+        lock.l_start = SHARED_FIRST;
+        lock.l_len = SHARED_SIZE;
+        if( unixFileLock(pFile, &lock) ){
+          /* In theory, the call to unixFileLock() cannot fail because another
+          ** process is holding an incompatible lock. If it does, this 
+          ** indicates that the other process is not following the locking
+          ** protocol. If this happens, return SQLITE_IOERR_RDLOCK. Returning
+          ** SQLITE_BUSY would confuse the upper layer (in practice it causes 
+          ** an assert to fail). */ 
+          rc = SQLITE_IOERR_RDLOCK;
+          pFile->lastErrno = errno;
+          goto end_unlock;
+        }
+      }
+    }
+    lock.l_type = F_UNLCK;
+    lock.l_whence = SEEK_SET;
+    lock.l_start = PENDING_BYTE;
+    lock.l_len = 2L;  assert( PENDING_BYTE+1==RESERVED_BYTE );
+    if( unixFileLock(pFile, &lock)==0 ){
+      pInode->eFileLock = SHARED_LOCK;
+    }else{
+      rc = SQLITE_IOERR_UNLOCK;
+      pFile->lastErrno = errno;
+      goto end_unlock;
+    }
+  }
+  if( eFileLock==NO_LOCK ){
+    /* Decrement the shared lock counter.  Release the lock using an
+    ** OS call only when all threads in this same process have released
+    ** the lock.
+    */
+    pInode->nShared--;
+    if( pInode->nShared==0 ){
+      lock.l_type = F_UNLCK;
+      lock.l_whence = SEEK_SET;
+      lock.l_start = lock.l_len = 0L;
+      if( unixFileLock(pFile, &lock)==0 ){
+        pInode->eFileLock = NO_LOCK;
+      }else{
+        rc = SQLITE_IOERR_UNLOCK;
+	pFile->lastErrno = errno;
+        pInode->eFileLock = NO_LOCK;
+        pFile->eFileLock = NO_LOCK;
+      }
+    }
+
+    /* Decrement the count of locks against this same file.  When the
+    ** count reaches zero, close any other file descriptors whose close
+    ** was deferred because of outstanding locks.
+    */
+    pInode->nLock--;
+    assert( pInode->nLock>=0 );
+    if( pInode->nLock==0 ){
+      closePendingFds(pFile);
+    }
+  }
+	
+end_unlock:
+  unixLeaveMutex();
+  if( rc==SQLITE_OK ) pFile->eFileLock = eFileLock;
+  return rc;
+}
+
+/*
+** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
+** must be either NO_LOCK or SHARED_LOCK.
+**
+** If the locking level of the file descriptor is already at or below
+** the requested locking level, this routine is a no-op.
+*/
+static int unixUnlock(sqlite3_file *id, int eFileLock){
+  return posixUnlock(id, eFileLock, 0);
+}
+
+/*
+** This function performs the parts of the "close file" operation 
+** common to all locking schemes. It closes the directory and file
+** handles, if they are valid, and sets all fields of the unixFile
+** structure to 0.
+**
+** It is *not* necessary to hold the mutex when this routine is called,
+** even on VxWorks.  A mutex will be acquired on VxWorks by the
+** vxworksReleaseFileId() routine.
+*/
+static int closeUnixFile(sqlite3_file *id){
+  unixFile *pFile = (unixFile*)id;
+  if( pFile->h>=0 ){
+    robust_close(pFile, pFile->h, __LINE__);
+    pFile->h = -1;
+  }
+#if OS_VXWORKS
+  if( pFile->pId ){
+    if( pFile->isDelete ){
+      osUnlink(pFile->pId->zCanonicalName);
+    }
+    vxworksReleaseFileId(pFile->pId);
+    pFile->pId = 0;
+  }
+#endif
+  OSTRACE(("CLOSE   %-3d\n", pFile->h));
+  OpenCounter(-1);
+  sqlite3_free(pFile->pUnused);
+  memset(pFile, 0, sizeof(unixFile));
+  return SQLITE_OK;
+}
+
+/*
+** Close a file.
+*/
+static int unixClose(sqlite3_file *id){
+  int rc = SQLITE_OK;
+  unixFile *pFile = (unixFile *)id;
+  unixUnlock(id, NO_LOCK);
+  unixEnterMutex();
+
+  /* unixFile.pInode is always valid here. Otherwise, a different close
+  ** routine (e.g. nolockClose()) would be called instead.
+  */
+  assert( pFile->pInode->nLock>0 || pFile->pInode->bProcessLock==0 );
+  if( ALWAYS(pFile->pInode) && pFile->pInode->nLock ){
+    /* If there are outstanding locks, do not actually close the file just
+    ** yet because that would clear those locks.  Instead, add the file
+    ** descriptor to pInode->pUnused list.  It will be automatically closed 
+    ** when the last lock is cleared.
+    */
+    setPendingFd(pFile);
+  }
+  releaseInodeInfo(pFile);
+  rc = closeUnixFile(id);
+  unixLeaveMutex();
+  return rc;
+}
+
+/************** End of the posix advisory lock implementation *****************
+******************************************************************************/
+
+/******************************************************************************
+****************************** No-op Locking **********************************
+**
+** Of the various locking implementations available, this is by far the
+** simplest:  locking is ignored.  No attempt is made to lock the database
+** file for reading or writing.
+**
+** This locking mode is appropriate for use on read-only databases
+** (ex: databases that are burned into CD-ROM, for example.)  It can
+** also be used if the application employs some external mechanism to
+** prevent simultaneous access of the same database by two or more
+** database connections.  But there is a serious risk of database
+** corruption if this locking mode is used in situations where multiple
+** database connections are accessing the same database file at the same
+** time and one or more of those connections are writing.
+*/
+
+static int nolockCheckReservedLock(sqlite3_file *NotUsed, int *pResOut){
+  UNUSED_PARAMETER(NotUsed);
+  *pResOut = 0;
+  return SQLITE_OK;
+}
+static int nolockLock(sqlite3_file *NotUsed, int NotUsed2){
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  return SQLITE_OK;
+}
+static int nolockUnlock(sqlite3_file *NotUsed, int NotUsed2){
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  return SQLITE_OK;
+}
+
+/*
+** Close the file.
+*/
+static int nolockClose(sqlite3_file *id) {
+  return closeUnixFile(id);
+}
+
+/******************* End of the no-op lock implementation *********************
+******************************************************************************/
+
+/******************************************************************************
+************************* Begin dot-file Locking ******************************
+**
+** The dotfile locking implementation uses the existance of separate lock
+** files in order to control access to the database.  This works on just
+** about every filesystem imaginable.  But there are serious downsides:
+**
+**    (1)  There is zero concurrency.  A single reader blocks all other
+**         connections from reading or writing the database.
+**
+**    (2)  An application crash or power loss can leave stale lock files
+**         sitting around that need to be cleared manually.
+**
+** Nevertheless, a dotlock is an appropriate locking mode for use if no
+** other locking strategy is available.
+**
+** Dotfile locking works by creating a file in the same directory as the
+** database and with the same name but with a ".lock" extension added.
+** The existance of a lock file implies an EXCLUSIVE lock.  All other lock
+** types (SHARED, RESERVED, PENDING) are mapped into EXCLUSIVE.
+*/
+
+/*
+** The file suffix added to the data base filename in order to create the
+** lock file.
+*/
+#define DOTLOCK_SUFFIX ".lock"
+
+/*
+** This routine checks if there is a RESERVED lock held on the specified
+** file by this or any other process. If such a lock is held, set *pResOut
+** to a non-zero value otherwise *pResOut is set to zero.  The return value
+** is set to SQLITE_OK unless an I/O error occurs during lock checking.
+**
+** In dotfile locking, either a lock exists or it does not.  So in this
+** variation of CheckReservedLock(), *pResOut is set to true if any lock
+** is held on the file and false if the file is unlocked.
+*/
+static int dotlockCheckReservedLock(sqlite3_file *id, int *pResOut) {
+  int rc = SQLITE_OK;
+  int reserved = 0;
+  unixFile *pFile = (unixFile*)id;
+
+  SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
+  
+  assert( pFile );
+
+  /* Check if a thread in this process holds such a lock */
+  if( pFile->eFileLock>SHARED_LOCK ){
+    /* Either this connection or some other connection in the same process
+    ** holds a lock on the file.  No need to check further. */
+    reserved = 1;
+  }else{
+    /* The lock is held if and only if the lockfile exists */
+    const char *zLockFile = (const char*)pFile->lockingContext;
+    reserved = osAccess(zLockFile, 0)==0;
+  }
+  OSTRACE(("TEST WR-LOCK %d %d %d (dotlock)\n", pFile->h, rc, reserved));
+  *pResOut = reserved;
+  return rc;
+}
+
+/*
+** Lock the file with the lock specified by parameter eFileLock - one
+** of the following:
+**
+**     (1) SHARED_LOCK
+**     (2) RESERVED_LOCK
+**     (3) PENDING_LOCK
+**     (4) EXCLUSIVE_LOCK
+**
+** Sometimes when requesting one lock state, additional lock states
+** are inserted in between.  The locking might fail on one of the later
+** transitions leaving the lock state different from what it started but
+** still short of its goal.  The following chart shows the allowed
+** transitions and the inserted intermediate states:
+**
+**    UNLOCKED -> SHARED
+**    SHARED -> RESERVED
+**    SHARED -> (PENDING) -> EXCLUSIVE
+**    RESERVED -> (PENDING) -> EXCLUSIVE
+**    PENDING -> EXCLUSIVE
+**
+** This routine will only increase a lock.  Use the sqlite3OsUnlock()
+** routine to lower a locking level.
+**
+** With dotfile locking, we really only support state (4): EXCLUSIVE.
+** But we track the other locking levels internally.
+*/
+static int dotlockLock(sqlite3_file *id, int eFileLock) {
+  unixFile *pFile = (unixFile*)id;
+  int fd;
+  char *zLockFile = (char *)pFile->lockingContext;
+  int rc = SQLITE_OK;
+
+
+  /* If we have any lock, then the lock file already exists.  All we have
+  ** to do is adjust our internal record of the lock level.
+  */
+  if( pFile->eFileLock > NO_LOCK ){
+    pFile->eFileLock = eFileLock;
+    /* Always update the timestamp on the old file */
+#ifdef HAVE_UTIME
+    utime(zLockFile, NULL);
+#else
+    utimes(zLockFile, NULL);
+#endif
+    return SQLITE_OK;
+  }
+  
+  /* grab an exclusive lock */
+  fd = robust_open(zLockFile,O_RDONLY|O_CREAT|O_EXCL,0600);
+  if( fd<0 ){
+    /* failed to open/create the file, someone else may have stolen the lock */
+    int tErrno = errno;
+    if( EEXIST == tErrno ){
+      rc = SQLITE_BUSY;
+    } else {
+      rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK);
+      if( IS_LOCK_ERROR(rc) ){
+        pFile->lastErrno = tErrno;
+      }
+    }
+    return rc;
+  } 
+  robust_close(pFile, fd, __LINE__);
+  
+  /* got it, set the type and return ok */
+  pFile->eFileLock = eFileLock;
+  return rc;
+}
+
+/*
+** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
+** must be either NO_LOCK or SHARED_LOCK.
+**
+** If the locking level of the file descriptor is already at or below
+** the requested locking level, this routine is a no-op.
+**
+** When the locking level reaches NO_LOCK, delete the lock file.
+*/
+static int dotlockUnlock(sqlite3_file *id, int eFileLock) {
+  unixFile *pFile = (unixFile*)id;
+  char *zLockFile = (char *)pFile->lockingContext;
+
+  assert( pFile );
+  OSTRACE(("UNLOCK  %d %d was %d pid=%d (dotlock)\n", pFile->h, eFileLock,
+	   pFile->eFileLock, getpid()));
+  assert( eFileLock<=SHARED_LOCK );
+  
+  /* no-op if possible */
+  if( pFile->eFileLock==eFileLock ){
+    return SQLITE_OK;
+  }
+
+  /* To downgrade to shared, simply update our internal notion of the
+  ** lock state.  No need to mess with the file on disk.
+  */
+  if( eFileLock==SHARED_LOCK ){
+    pFile->eFileLock = SHARED_LOCK;
+    return SQLITE_OK;
+  }
+  
+  /* To fully unlock the database, delete the lock file */
+  assert( eFileLock==NO_LOCK );
+  if( osUnlink(zLockFile) ){
+    int rc = 0;
+    int tErrno = errno;
+    if( ENOENT != tErrno ){
+      rc = SQLITE_IOERR_UNLOCK;
+    }
+    if( IS_LOCK_ERROR(rc) ){
+      pFile->lastErrno = tErrno;
+    }
+    return rc; 
+  }
+  pFile->eFileLock = NO_LOCK;
+  return SQLITE_OK;
+}
+
+/*
+** Close a file.  Make sure the lock has been released before closing.
+*/
+static int dotlockClose(sqlite3_file *id) {
+  int rc;
+  if( id ){
+    unixFile *pFile = (unixFile*)id;
+    dotlockUnlock(id, NO_LOCK);
+    sqlite3_free(pFile->lockingContext);
+  }
+  rc = closeUnixFile(id);
+  return rc;
+}
+/****************** End of the dot-file lock implementation *******************
+******************************************************************************/
+
+/******************************************************************************
+************************** Begin flock Locking ********************************
+**
+** Use the flock() system call to do file locking.
+**
+** flock() locking is like dot-file locking in that the various
+** fine-grain locking levels supported by SQLite are collapsed into
+** a single exclusive lock.  In other words, SHARED, RESERVED, and
+** PENDING locks are the same thing as an EXCLUSIVE lock.  SQLite
+** still works when you do this, but concurrency is reduced since
+** only a single process can be reading the database at a time.
+**
+** Omit this section if SQLITE_ENABLE_LOCKING_STYLE is turned off or if
+** compiling for VXWORKS.
+*/
+#if SQLITE_ENABLE_LOCKING_STYLE && !OS_VXWORKS
+
+/*
+** Retry flock() calls that fail with EINTR
+*/
+#ifdef EINTR
+static int robust_flock(int fd, int op){
+  int rc;
+  do{ rc = flock(fd,op); }while( rc<0 && errno==EINTR );
+  return rc;
+}
+#else
+# define robust_flock(a,b) flock(a,b)
+#endif
+     
+
+/*
+** This routine checks if there is a RESERVED lock held on the specified
+** file by this or any other process. If such a lock is held, set *pResOut
+** to a non-zero value otherwise *pResOut is set to zero.  The return value
+** is set to SQLITE_OK unless an I/O error occurs during lock checking.
+*/
+static int flockCheckReservedLock(sqlite3_file *id, int *pResOut){
+  int rc = SQLITE_OK;
+  int reserved = 0;
+  unixFile *pFile = (unixFile*)id;
+  
+  SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
+  
+  assert( pFile );
+  
+  /* Check if a thread in this process holds such a lock */
+  if( pFile->eFileLock>SHARED_LOCK ){
+    reserved = 1;
+  }
+  
+  /* Otherwise see if some other process holds it. */
+  if( !reserved ){
+    /* attempt to get the lock */
+    int lrc = robust_flock(pFile->h, LOCK_EX | LOCK_NB);
+    if( !lrc ){
+      /* got the lock, unlock it */
+      lrc = robust_flock(pFile->h, LOCK_UN);
+      if ( lrc ) {
+        int tErrno = errno;
+        /* unlock failed with an error */
+        lrc = SQLITE_IOERR_UNLOCK; 
+        if( IS_LOCK_ERROR(lrc) ){
+          pFile->lastErrno = tErrno;
+          rc = lrc;
+        }
+      }
+    } else {
+      int tErrno = errno;
+      reserved = 1;
+      /* someone else might have it reserved */
+      lrc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK); 
+      if( IS_LOCK_ERROR(lrc) ){
+        pFile->lastErrno = tErrno;
+        rc = lrc;
+      }
+    }
+  }
+  OSTRACE(("TEST WR-LOCK %d %d %d (flock)\n", pFile->h, rc, reserved));
+
+#ifdef SQLITE_IGNORE_FLOCK_LOCK_ERRORS
+  if( (rc & SQLITE_IOERR) == SQLITE_IOERR ){
+    rc = SQLITE_OK;
+    reserved=1;
+  }
+#endif /* SQLITE_IGNORE_FLOCK_LOCK_ERRORS */
+  *pResOut = reserved;
+  return rc;
+}
+
+/*
+** Lock the file with the lock specified by parameter eFileLock - one
+** of the following:
+**
+**     (1) SHARED_LOCK
+**     (2) RESERVED_LOCK
+**     (3) PENDING_LOCK
+**     (4) EXCLUSIVE_LOCK
+**
+** Sometimes when requesting one lock state, additional lock states
+** are inserted in between.  The locking might fail on one of the later
+** transitions leaving the lock state different from what it started but
+** still short of its goal.  The following chart shows the allowed
+** transitions and the inserted intermediate states:
+**
+**    UNLOCKED -> SHARED
+**    SHARED -> RESERVED
+**    SHARED -> (PENDING) -> EXCLUSIVE
+**    RESERVED -> (PENDING) -> EXCLUSIVE
+**    PENDING -> EXCLUSIVE
+**
+** flock() only really support EXCLUSIVE locks.  We track intermediate
+** lock states in the sqlite3_file structure, but all locks SHARED or
+** above are really EXCLUSIVE locks and exclude all other processes from
+** access the file.
+**
+** This routine will only increase a lock.  Use the sqlite3OsUnlock()
+** routine to lower a locking level.
+*/
+static int flockLock(sqlite3_file *id, int eFileLock) {
+  int rc = SQLITE_OK;
+  unixFile *pFile = (unixFile*)id;
+
+  assert( pFile );
+
+  /* if we already have a lock, it is exclusive.  
+  ** Just adjust level and punt on outta here. */
+  if (pFile->eFileLock > NO_LOCK) {
+    pFile->eFileLock = eFileLock;
+    return SQLITE_OK;
+  }
+  
+  /* grab an exclusive lock */
+  
+  if (robust_flock(pFile->h, LOCK_EX | LOCK_NB)) {
+    int tErrno = errno;
+    /* didn't get, must be busy */
+    rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK);
+    if( IS_LOCK_ERROR(rc) ){
+      pFile->lastErrno = tErrno;
+    }
+  } else {
+    /* got it, set the type and return ok */
+    pFile->eFileLock = eFileLock;
+  }
+  OSTRACE(("LOCK    %d %s %s (flock)\n", pFile->h, azFileLock(eFileLock), 
+           rc==SQLITE_OK ? "ok" : "failed"));
+#ifdef SQLITE_IGNORE_FLOCK_LOCK_ERRORS
+  if( (rc & SQLITE_IOERR) == SQLITE_IOERR ){
+    rc = SQLITE_BUSY;
+  }
+#endif /* SQLITE_IGNORE_FLOCK_LOCK_ERRORS */
+  return rc;
+}
+
+
+/*
+** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
+** must be either NO_LOCK or SHARED_LOCK.
+**
+** If the locking level of the file descriptor is already at or below
+** the requested locking level, this routine is a no-op.
+*/
+static int flockUnlock(sqlite3_file *id, int eFileLock) {
+  unixFile *pFile = (unixFile*)id;
+  
+  assert( pFile );
+  OSTRACE(("UNLOCK  %d %d was %d pid=%d (flock)\n", pFile->h, eFileLock,
+           pFile->eFileLock, getpid()));
+  assert( eFileLock<=SHARED_LOCK );
+  
+  /* no-op if possible */
+  if( pFile->eFileLock==eFileLock ){
+    return SQLITE_OK;
+  }
+  
+  /* shared can just be set because we always have an exclusive */
+  if (eFileLock==SHARED_LOCK) {
+    pFile->eFileLock = eFileLock;
+    return SQLITE_OK;
+  }
+  
+  /* no, really, unlock. */
+  if( robust_flock(pFile->h, LOCK_UN) ){
+#ifdef SQLITE_IGNORE_FLOCK_LOCK_ERRORS
+    return SQLITE_OK;
+#endif /* SQLITE_IGNORE_FLOCK_LOCK_ERRORS */
+    return SQLITE_IOERR_UNLOCK;
+  }else{
+    pFile->eFileLock = NO_LOCK;
+    return SQLITE_OK;
+  }
+}
+
+/*
+** Close a file.
+*/
+static int flockClose(sqlite3_file *id) {
+  if( id ){
+    flockUnlock(id, NO_LOCK);
+  }
+  return closeUnixFile(id);
+}
+
+#endif /* SQLITE_ENABLE_LOCKING_STYLE && !OS_VXWORK */
+
+/******************* End of the flock lock implementation *********************
+******************************************************************************/
+
+/******************************************************************************
+************************ Begin Named Semaphore Locking ************************
+**
+** Named semaphore locking is only supported on VxWorks.
+**
+** Semaphore locking is like dot-lock and flock in that it really only
+** supports EXCLUSIVE locking.  Only a single process can read or write
+** the database file at a time.  This reduces potential concurrency, but
+** makes the lock implementation much easier.
+*/
+#if OS_VXWORKS
+
+/*
+** This routine checks if there is a RESERVED lock held on the specified
+** file by this or any other process. If such a lock is held, set *pResOut
+** to a non-zero value otherwise *pResOut is set to zero.  The return value
+** is set to SQLITE_OK unless an I/O error occurs during lock checking.
+*/
+static int semCheckReservedLock(sqlite3_file *id, int *pResOut) {
+  int rc = SQLITE_OK;
+  int reserved = 0;
+  unixFile *pFile = (unixFile*)id;
+
+  SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
+  
+  assert( pFile );
+
+  /* Check if a thread in this process holds such a lock */
+  if( pFile->eFileLock>SHARED_LOCK ){
+    reserved = 1;
+  }
+  
+  /* Otherwise see if some other process holds it. */
+  if( !reserved ){
+    sem_t *pSem = pFile->pInode->pSem;
+    struct stat statBuf;
+
+    if( sem_trywait(pSem)==-1 ){
+      int tErrno = errno;
+      if( EAGAIN != tErrno ){
+        rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_CHECKRESERVEDLOCK);
+        pFile->lastErrno = tErrno;
+      } else {
+        /* someone else has the lock when we are in NO_LOCK */
+        reserved = (pFile->eFileLock < SHARED_LOCK);
+      }
+    }else{
+      /* we could have it if we want it */
+      sem_post(pSem);
+    }
+  }
+  OSTRACE(("TEST WR-LOCK %d %d %d (sem)\n", pFile->h, rc, reserved));
+
+  *pResOut = reserved;
+  return rc;
+}
+
+/*
+** Lock the file with the lock specified by parameter eFileLock - one
+** of the following:
+**
+**     (1) SHARED_LOCK
+**     (2) RESERVED_LOCK
+**     (3) PENDING_LOCK
+**     (4) EXCLUSIVE_LOCK
+**
+** Sometimes when requesting one lock state, additional lock states
+** are inserted in between.  The locking might fail on one of the later
+** transitions leaving the lock state different from what it started but
+** still short of its goal.  The following chart shows the allowed
+** transitions and the inserted intermediate states:
+**
+**    UNLOCKED -> SHARED
+**    SHARED -> RESERVED
+**    SHARED -> (PENDING) -> EXCLUSIVE
+**    RESERVED -> (PENDING) -> EXCLUSIVE
+**    PENDING -> EXCLUSIVE
+**
+** Semaphore locks only really support EXCLUSIVE locks.  We track intermediate
+** lock states in the sqlite3_file structure, but all locks SHARED or
+** above are really EXCLUSIVE locks and exclude all other processes from
+** access the file.
+**
+** This routine will only increase a lock.  Use the sqlite3OsUnlock()
+** routine to lower a locking level.
+*/
+static int semLock(sqlite3_file *id, int eFileLock) {
+  unixFile *pFile = (unixFile*)id;
+  int fd;
+  sem_t *pSem = pFile->pInode->pSem;
+  int rc = SQLITE_OK;
+
+  /* if we already have a lock, it is exclusive.  
+  ** Just adjust level and punt on outta here. */
+  if (pFile->eFileLock > NO_LOCK) {
+    pFile->eFileLock = eFileLock;
+    rc = SQLITE_OK;
+    goto sem_end_lock;
+  }
+  
+  /* lock semaphore now but bail out when already locked. */
+  if( sem_trywait(pSem)==-1 ){
+    rc = SQLITE_BUSY;
+    goto sem_end_lock;
+  }
+
+  /* got it, set the type and return ok */
+  pFile->eFileLock = eFileLock;
+
+ sem_end_lock:
+  return rc;
+}
+
+/*
+** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
+** must be either NO_LOCK or SHARED_LOCK.
+**
+** If the locking level of the file descriptor is already at or below
+** the requested locking level, this routine is a no-op.
+*/
+static int semUnlock(sqlite3_file *id, int eFileLock) {
+  unixFile *pFile = (unixFile*)id;
+  sem_t *pSem = pFile->pInode->pSem;
+
+  assert( pFile );
+  assert( pSem );
+  OSTRACE(("UNLOCK  %d %d was %d pid=%d (sem)\n", pFile->h, eFileLock,
+	   pFile->eFileLock, getpid()));
+  assert( eFileLock<=SHARED_LOCK );
+  
+  /* no-op if possible */
+  if( pFile->eFileLock==eFileLock ){
+    return SQLITE_OK;
+  }
+  
+  /* shared can just be set because we always have an exclusive */
+  if (eFileLock==SHARED_LOCK) {
+    pFile->eFileLock = eFileLock;
+    return SQLITE_OK;
+  }
+  
+  /* no, really unlock. */
+  if ( sem_post(pSem)==-1 ) {
+    int rc, tErrno = errno;
+    rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_UNLOCK);
+    if( IS_LOCK_ERROR(rc) ){
+      pFile->lastErrno = tErrno;
+    }
+    return rc; 
+  }
+  pFile->eFileLock = NO_LOCK;
+  return SQLITE_OK;
+}
+
+/*
+ ** Close a file.
+ */
+static int semClose(sqlite3_file *id) {
+  if( id ){
+    unixFile *pFile = (unixFile*)id;
+    semUnlock(id, NO_LOCK);
+    assert( pFile );
+    unixEnterMutex();
+    releaseInodeInfo(pFile);
+    unixLeaveMutex();
+    closeUnixFile(id);
+  }
+  return SQLITE_OK;
+}
+
+#endif /* OS_VXWORKS */
+/*
+** Named semaphore locking is only available on VxWorks.
+**
+*************** End of the named semaphore lock implementation ****************
+******************************************************************************/
+
+
+/******************************************************************************
+*************************** Begin AFP Locking *********************************
+**
+** AFP is the Apple Filing Protocol.  AFP is a network filesystem found
+** on Apple Macintosh computers - both OS9 and OSX.
+**
+** Third-party implementations of AFP are available.  But this code here
+** only works on OSX.
+*/
+
+#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
+/*
+** The afpLockingContext structure contains all afp lock specific state
+*/
+typedef struct afpLockingContext afpLockingContext;
+struct afpLockingContext {
+  int reserved;
+  const char *dbPath;             /* Name of the open file */
+};
+
+struct ByteRangeLockPB2
+{
+  unsigned long long offset;        /* offset to first byte to lock */
+  unsigned long long length;        /* nbr of bytes to lock */
+  unsigned long long retRangeStart; /* nbr of 1st byte locked if successful */
+  unsigned char unLockFlag;         /* 1 = unlock, 0 = lock */
+  unsigned char startEndFlag;       /* 1=rel to end of fork, 0=rel to start */
+  int fd;                           /* file desc to assoc this lock with */
+};
+
+#define afpfsByteRangeLock2FSCTL        _IOWR('z', 23, struct ByteRangeLockPB2)
+
+/*
+** This is a utility for setting or clearing a bit-range lock on an
+** AFP filesystem.
+** 
+** Return SQLITE_OK on success, SQLITE_BUSY on failure.
+*/
+static int afpSetLock(
+  const char *path,              /* Name of the file to be locked or unlocked */
+  unixFile *pFile,               /* Open file descriptor on path */
+  unsigned long long offset,     /* First byte to be locked */
+  unsigned long long length,     /* Number of bytes to lock */
+  int setLockFlag                /* True to set lock.  False to clear lock */
+){
+  struct ByteRangeLockPB2 pb;
+  int err;
+  
+  pb.unLockFlag = setLockFlag ? 0 : 1;
+  pb.startEndFlag = 0;
+  pb.offset = offset;
+  pb.length = length; 
+  pb.fd = pFile->h;
+  
+  OSTRACE(("AFPSETLOCK [%s] for %d%s in range %llx:%llx\n", 
+    (setLockFlag?"ON":"OFF"), pFile->h, (pb.fd==-1?"[testval-1]":""),
+    offset, length));
+  err = fsctl(path, afpfsByteRangeLock2FSCTL, &pb, 0);
+  if ( err==-1 ) {
+    int rc;
+    int tErrno = errno;
+    OSTRACE(("AFPSETLOCK failed to fsctl() '%s' %d %s\n",
+             path, tErrno, strerror(tErrno)));
+#ifdef SQLITE_IGNORE_AFP_LOCK_ERRORS
+    rc = SQLITE_BUSY;
+#else
+    rc = sqliteErrorFromPosixError(tErrno,
+                    setLockFlag ? SQLITE_IOERR_LOCK : SQLITE_IOERR_UNLOCK);
+#endif /* SQLITE_IGNORE_AFP_LOCK_ERRORS */
+    if( IS_LOCK_ERROR(rc) ){
+      pFile->lastErrno = tErrno;
+    }
+    return rc;
+  } else {
+    return SQLITE_OK;
+  }
+}
+
+/*
+** This routine checks if there is a RESERVED lock held on the specified
+** file by this or any other process. If such a lock is held, set *pResOut
+** to a non-zero value otherwise *pResOut is set to zero.  The return value
+** is set to SQLITE_OK unless an I/O error occurs during lock checking.
+*/
+static int afpCheckReservedLock(sqlite3_file *id, int *pResOut){
+  int rc = SQLITE_OK;
+  int reserved = 0;
+  unixFile *pFile = (unixFile*)id;
+  afpLockingContext *context;
+  
+  SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
+  
+  assert( pFile );
+  context = (afpLockingContext *) pFile->lockingContext;
+  if( context->reserved ){
+    *pResOut = 1;
+    return SQLITE_OK;
+  }
+  unixEnterMutex(); /* Because pFile->pInode is shared across threads */
+  
+  /* Check if a thread in this process holds such a lock */
+  if( pFile->pInode->eFileLock>SHARED_LOCK ){
+    reserved = 1;
+  }
+  
+  /* Otherwise see if some other process holds it.
+   */
+  if( !reserved ){
+    /* lock the RESERVED byte */
+    int lrc = afpSetLock(context->dbPath, pFile, RESERVED_BYTE, 1,1);  
+    if( SQLITE_OK==lrc ){
+      /* if we succeeded in taking the reserved lock, unlock it to restore
+      ** the original state */
+      lrc = afpSetLock(context->dbPath, pFile, RESERVED_BYTE, 1, 0);
+    } else {
+      /* if we failed to get the lock then someone else must have it */
+      reserved = 1;
+    }
+    if( IS_LOCK_ERROR(lrc) ){
+      rc=lrc;
+    }
+  }
+  
+  unixLeaveMutex();
+  OSTRACE(("TEST WR-LOCK %d %d %d (afp)\n", pFile->h, rc, reserved));
+  
+  *pResOut = reserved;
+  return rc;
+}
+
+/*
+** Lock the file with the lock specified by parameter eFileLock - one
+** of the following:
+**
+**     (1) SHARED_LOCK
+**     (2) RESERVED_LOCK
+**     (3) PENDING_LOCK
+**     (4) EXCLUSIVE_LOCK
+**
+** Sometimes when requesting one lock state, additional lock states
+** are inserted in between.  The locking might fail on one of the later
+** transitions leaving the lock state different from what it started but
+** still short of its goal.  The following chart shows the allowed
+** transitions and the inserted intermediate states:
+**
+**    UNLOCKED -> SHARED
+**    SHARED -> RESERVED
+**    SHARED -> (PENDING) -> EXCLUSIVE
+**    RESERVED -> (PENDING) -> EXCLUSIVE
+**    PENDING -> EXCLUSIVE
+**
+** This routine will only increase a lock.  Use the sqlite3OsUnlock()
+** routine to lower a locking level.
+*/
+static int afpLock(sqlite3_file *id, int eFileLock){
+  int rc = SQLITE_OK;
+  unixFile *pFile = (unixFile*)id;
+  unixInodeInfo *pInode = pFile->pInode;
+  afpLockingContext *context = (afpLockingContext *) pFile->lockingContext;
+  
+  assert( pFile );
+  OSTRACE(("LOCK    %d %s was %s(%s,%d) pid=%d (afp)\n", pFile->h,
+           azFileLock(eFileLock), azFileLock(pFile->eFileLock),
+           azFileLock(pInode->eFileLock), pInode->nShared , getpid()));
+
+  /* If there is already a lock of this type or more restrictive on the
+  ** unixFile, do nothing. Don't use the afp_end_lock: exit path, as
+  ** unixEnterMutex() hasn't been called yet.
+  */
+  if( pFile->eFileLock>=eFileLock ){
+    OSTRACE(("LOCK    %d %s ok (already held) (afp)\n", pFile->h,
+           azFileLock(eFileLock)));
+    return SQLITE_OK;
+  }
+
+  /* Make sure the locking sequence is correct
+  **  (1) We never move from unlocked to anything higher than shared lock.
+  **  (2) SQLite never explicitly requests a pendig lock.
+  **  (3) A shared lock is always held when a reserve lock is requested.
+  */
+  assert( pFile->eFileLock!=NO_LOCK || eFileLock==SHARED_LOCK );
+  assert( eFileLock!=PENDING_LOCK );
+  assert( eFileLock!=RESERVED_LOCK || pFile->eFileLock==SHARED_LOCK );
+  
+  /* This mutex is needed because pFile->pInode is shared across threads
+  */
+  unixEnterMutex();
+  pInode = pFile->pInode;
+
+  /* If some thread using this PID has a lock via a different unixFile*
+  ** handle that precludes the requested lock, return BUSY.
+  */
+  if( (pFile->eFileLock!=pInode->eFileLock && 
+       (pInode->eFileLock>=PENDING_LOCK || eFileLock>SHARED_LOCK))
+     ){
+    rc = SQLITE_BUSY;
+    goto afp_end_lock;
+  }
+  
+  /* If a SHARED lock is requested, and some thread using this PID already
+  ** has a SHARED or RESERVED lock, then increment reference counts and
+  ** return SQLITE_OK.
+  */
+  if( eFileLock==SHARED_LOCK && 
+     (pInode->eFileLock==SHARED_LOCK || pInode->eFileLock==RESERVED_LOCK) ){
+    assert( eFileLock==SHARED_LOCK );
+    assert( pFile->eFileLock==0 );
+    assert( pInode->nShared>0 );
+    pFile->eFileLock = SHARED_LOCK;
+    pInode->nShared++;
+    pInode->nLock++;
+    goto afp_end_lock;
+  }
+    
+  /* A PENDING lock is needed before acquiring a SHARED lock and before
+  ** acquiring an EXCLUSIVE lock.  For the SHARED lock, the PENDING will
+  ** be released.
+  */
+  if( eFileLock==SHARED_LOCK 
+      || (eFileLock==EXCLUSIVE_LOCK && pFile->eFileLock<PENDING_LOCK)
+  ){
+    int failed;
+    failed = afpSetLock(context->dbPath, pFile, PENDING_BYTE, 1, 1);
+    if (failed) {
+      rc = failed;
+      goto afp_end_lock;
+    }
+  }
+  
+  /* If control gets to this point, then actually go ahead and make
+  ** operating system calls for the specified lock.
+  */
+  if( eFileLock==SHARED_LOCK ){
+    int lrc1, lrc2, lrc1Errno = 0;
+    long lk, mask;
+    
+    assert( pInode->nShared==0 );
+    assert( pInode->eFileLock==0 );
+        
+    mask = (sizeof(long)==8) ? LARGEST_INT64 : 0x7fffffff;
+    /* Now get the read-lock SHARED_LOCK */
+    /* note that the quality of the randomness doesn't matter that much */
+    lk = random(); 
+    pInode->sharedByte = (lk & mask)%(SHARED_SIZE - 1);
+    lrc1 = afpSetLock(context->dbPath, pFile, 
+          SHARED_FIRST+pInode->sharedByte, 1, 1);
+    if( IS_LOCK_ERROR(lrc1) ){
+      lrc1Errno = pFile->lastErrno;
+    }
+    /* Drop the temporary PENDING lock */
+    lrc2 = afpSetLock(context->dbPath, pFile, PENDING_BYTE, 1, 0);
+    
+    if( IS_LOCK_ERROR(lrc1) ) {
+      pFile->lastErrno = lrc1Errno;
+      rc = lrc1;
+      goto afp_end_lock;
+    } else if( IS_LOCK_ERROR(lrc2) ){
+      rc = lrc2;
+      goto afp_end_lock;
+    } else if( lrc1 != SQLITE_OK ) {
+      rc = lrc1;
+    } else {
+      pFile->eFileLock = SHARED_LOCK;
+      pInode->nLock++;
+      pInode->nShared = 1;
+    }
+  }else if( eFileLock==EXCLUSIVE_LOCK && pInode->nShared>1 ){
+    /* We are trying for an exclusive lock but another thread in this
+     ** same process is still holding a shared lock. */
+    rc = SQLITE_BUSY;
+  }else{
+    /* The request was for a RESERVED or EXCLUSIVE lock.  It is
+    ** assumed that there is a SHARED or greater lock on the file
+    ** already.
+    */
+    int failed = 0;
+    assert( 0!=pFile->eFileLock );
+    if (eFileLock >= RESERVED_LOCK && pFile->eFileLock < RESERVED_LOCK) {
+        /* Acquire a RESERVED lock */
+        failed = afpSetLock(context->dbPath, pFile, RESERVED_BYTE, 1,1);
+      if( !failed ){
+        context->reserved = 1;
+      }
+    }
+    if (!failed && eFileLock == EXCLUSIVE_LOCK) {
+      /* Acquire an EXCLUSIVE lock */
+        
+      /* Remove the shared lock before trying the range.  we'll need to 
+      ** reestablish the shared lock if we can't get the  afpUnlock
+      */
+      if( !(failed = afpSetLock(context->dbPath, pFile, SHARED_FIRST +
+                         pInode->sharedByte, 1, 0)) ){
+        int failed2 = SQLITE_OK;
+        /* now attemmpt to get the exclusive lock range */
+        failed = afpSetLock(context->dbPath, pFile, SHARED_FIRST, 
+                               SHARED_SIZE, 1);
+        if( failed && (failed2 = afpSetLock(context->dbPath, pFile, 
+                       SHARED_FIRST + pInode->sharedByte, 1, 1)) ){
+          /* Can't reestablish the shared lock.  Sqlite can't deal, this is
+          ** a critical I/O error
+          */
+          rc = ((failed & SQLITE_IOERR) == SQLITE_IOERR) ? failed2 : 
+               SQLITE_IOERR_LOCK;
+          goto afp_end_lock;
+        } 
+      }else{
+        rc = failed; 
+      }
+    }
+    if( failed ){
+      rc = failed;
+    }
+  }
+  
+  if( rc==SQLITE_OK ){
+    pFile->eFileLock = eFileLock;
+    pInode->eFileLock = eFileLock;
+  }else if( eFileLock==EXCLUSIVE_LOCK ){
+    pFile->eFileLock = PENDING_LOCK;
+    pInode->eFileLock = PENDING_LOCK;
+  }
+  
+afp_end_lock:
+  unixLeaveMutex();
+  OSTRACE(("LOCK    %d %s %s (afp)\n", pFile->h, azFileLock(eFileLock), 
+         rc==SQLITE_OK ? "ok" : "failed"));
+  return rc;
+}
+
+/*
+** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
+** must be either NO_LOCK or SHARED_LOCK.
+**
+** If the locking level of the file descriptor is already at or below
+** the requested locking level, this routine is a no-op.
+*/
+static int afpUnlock(sqlite3_file *id, int eFileLock) {
+  int rc = SQLITE_OK;
+  unixFile *pFile = (unixFile*)id;
+  unixInodeInfo *pInode;
+  afpLockingContext *context = (afpLockingContext *) pFile->lockingContext;
+  int skipShared = 0;
+#ifdef SQLITE_TEST
+  int h = pFile->h;
+#endif
+
+  assert( pFile );
+  OSTRACE(("UNLOCK  %d %d was %d(%d,%d) pid=%d (afp)\n", pFile->h, eFileLock,
+           pFile->eFileLock, pFile->pInode->eFileLock, pFile->pInode->nShared,
+           getpid()));
+
+  assert( eFileLock<=SHARED_LOCK );
+  if( pFile->eFileLock<=eFileLock ){
+    return SQLITE_OK;
+  }
+  unixEnterMutex();
+  pInode = pFile->pInode;
+  assert( pInode->nShared!=0 );
+  if( pFile->eFileLock>SHARED_LOCK ){
+    assert( pInode->eFileLock==pFile->eFileLock );
+    SimulateIOErrorBenign(1);
+    SimulateIOError( h=(-1) )
+    SimulateIOErrorBenign(0);
+    
+#ifndef NDEBUG
+    /* When reducing a lock such that other processes can start
+    ** reading the database file again, make sure that the
+    ** transaction counter was updated if any part of the database
+    ** file changed.  If the transaction counter is not updated,
+    ** other connections to the same file might not realize that
+    ** the file has changed and hence might not know to flush their
+    ** cache.  The use of a stale cache can lead to database corruption.
+    */
+    assert( pFile->inNormalWrite==0
+           || pFile->dbUpdate==0
+           || pFile->transCntrChng==1 );
+    pFile->inNormalWrite = 0;
+#endif
+    
+    if( pFile->eFileLock==EXCLUSIVE_LOCK ){
+      rc = afpSetLock(context->dbPath, pFile, SHARED_FIRST, SHARED_SIZE, 0);
+      if( rc==SQLITE_OK && (eFileLock==SHARED_LOCK || pInode->nShared>1) ){
+        /* only re-establish the shared lock if necessary */
+        int sharedLockByte = SHARED_FIRST+pInode->sharedByte;
+        rc = afpSetLock(context->dbPath, pFile, sharedLockByte, 1, 1);
+      } else {
+        skipShared = 1;
+      }
+    }
+    if( rc==SQLITE_OK && pFile->eFileLock>=PENDING_LOCK ){
+      rc = afpSetLock(context->dbPath, pFile, PENDING_BYTE, 1, 0);
+    } 
+    if( rc==SQLITE_OK && pFile->eFileLock>=RESERVED_LOCK && context->reserved ){
+      rc = afpSetLock(context->dbPath, pFile, RESERVED_BYTE, 1, 0);
+      if( !rc ){ 
+        context->reserved = 0; 
+      }
+    }
+    if( rc==SQLITE_OK && (eFileLock==SHARED_LOCK || pInode->nShared>1)){
+      pInode->eFileLock = SHARED_LOCK;
+    }
+  }
+  if( rc==SQLITE_OK && eFileLock==NO_LOCK ){
+
+    /* Decrement the shared lock counter.  Release the lock using an
+    ** OS call only when all threads in this same process have released
+    ** the lock.
+    */
+    unsigned long long sharedLockByte = SHARED_FIRST+pInode->sharedByte;
+    pInode->nShared--;
+    if( pInode->nShared==0 ){
+      SimulateIOErrorBenign(1);
+      SimulateIOError( h=(-1) )
+      SimulateIOErrorBenign(0);
+      if( !skipShared ){
+        rc = afpSetLock(context->dbPath, pFile, sharedLockByte, 1, 0);
+      }
+      if( !rc ){
+        pInode->eFileLock = NO_LOCK;
+        pFile->eFileLock = NO_LOCK;
+      }
+    }
+    if( rc==SQLITE_OK ){
+      pInode->nLock--;
+      assert( pInode->nLock>=0 );
+      if( pInode->nLock==0 ){
+        closePendingFds(pFile);
+      }
+    }
+  }
+  
+  unixLeaveMutex();
+  if( rc==SQLITE_OK ) pFile->eFileLock = eFileLock;
+  return rc;
+}
+
+/*
+** Close a file & cleanup AFP specific locking context 
+*/
+static int afpClose(sqlite3_file *id) {
+  int rc = SQLITE_OK;
+  if( id ){
+    unixFile *pFile = (unixFile*)id;
+    afpUnlock(id, NO_LOCK);
+    unixEnterMutex();
+    if( pFile->pInode && pFile->pInode->nLock ){
+      /* If there are outstanding locks, do not actually close the file just
+      ** yet because that would clear those locks.  Instead, add the file
+      ** descriptor to pInode->aPending.  It will be automatically closed when
+      ** the last lock is cleared.
+      */
+      setPendingFd(pFile);
+    }
+    releaseInodeInfo(pFile);
+    sqlite3_free(pFile->lockingContext);
+    rc = closeUnixFile(id);
+    unixLeaveMutex();
+  }
+  return rc;
+}
+
+#endif /* defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE */
+/*
+** The code above is the AFP lock implementation.  The code is specific
+** to MacOSX and does not work on other unix platforms.  No alternative
+** is available.  If you don't compile for a mac, then the "unix-afp"
+** VFS is not available.
+**
+********************* End of the AFP lock implementation **********************
+******************************************************************************/
+
+/******************************************************************************
+*************************** Begin NFS Locking ********************************/
+
+#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
+/*
+ ** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
+ ** must be either NO_LOCK or SHARED_LOCK.
+ **
+ ** If the locking level of the file descriptor is already at or below
+ ** the requested locking level, this routine is a no-op.
+ */
+static int nfsUnlock(sqlite3_file *id, int eFileLock){
+  return posixUnlock(id, eFileLock, 1);
+}
+
+#endif /* defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE */
+/*
+** The code above is the NFS lock implementation.  The code is specific
+** to MacOSX and does not work on other unix platforms.  No alternative
+** is available.  
+**
+********************* End of the NFS lock implementation **********************
+******************************************************************************/
+
+/******************************************************************************
+**************** Non-locking sqlite3_file methods *****************************
+**
+** The next division contains implementations for all methods of the 
+** sqlite3_file object other than the locking methods.  The locking
+** methods were defined in divisions above (one locking method per
+** division).  Those methods that are common to all locking modes
+** are gather together into this division.
+*/
+
+/*
+** Seek to the offset passed as the second argument, then read cnt 
+** bytes into pBuf. Return the number of bytes actually read.
+**
+** NB:  If you define USE_PREAD or USE_PREAD64, then it might also
+** be necessary to define _XOPEN_SOURCE to be 500.  This varies from
+** one system to another.  Since SQLite does not define USE_PREAD
+** any any form by default, we will not attempt to define _XOPEN_SOURCE.
+** See tickets #2741 and #2681.
+**
+** To avoid stomping the errno value on a failed read the lastErrno value
+** is set before returning.
+*/
+static int seekAndRead(unixFile *id, sqlite3_int64 offset, void *pBuf, int cnt){
+  int got;
+#if (!defined(USE_PREAD) && !defined(USE_PREAD64))
+  i64 newOffset;
+#endif
+  TIMER_START;
+#if defined(USE_PREAD)
+  do{ got = osPread(id->h, pBuf, cnt, offset); }while( got<0 && errno==EINTR );
+  SimulateIOError( got = -1 );
+#elif defined(USE_PREAD64)
+  do{ got = osPread64(id->h, pBuf, cnt, offset); }while( got<0 && errno==EINTR);
+  SimulateIOError( got = -1 );
+#else
+  newOffset = lseek(id->h, offset, SEEK_SET);
+  SimulateIOError( newOffset-- );
+  if( newOffset!=offset ){
+    if( newOffset == -1 ){
+      ((unixFile*)id)->lastErrno = errno;
+    }else{
+      ((unixFile*)id)->lastErrno = 0;			
+    }
+    return -1;
+  }
+  do{ got = osRead(id->h, pBuf, cnt); }while( got<0 && errno==EINTR );
+#endif
+  TIMER_END;
+  if( got<0 ){
+    ((unixFile*)id)->lastErrno = errno;
+  }
+  OSTRACE(("READ    %-3d %5d %7lld %llu\n", id->h, got, offset, TIMER_ELAPSED));
+  return got;
+}
+
+/*
+** Read data from a file into a buffer.  Return SQLITE_OK if all
+** bytes were read successfully and SQLITE_IOERR if anything goes
+** wrong.
+*/
+static int unixRead(
+  sqlite3_file *id, 
+  void *pBuf, 
+  int amt,
+  sqlite3_int64 offset
+){
+  unixFile *pFile = (unixFile *)id;
+  int got;
+  assert( id );
+
+  /* If this is a database file (not a journal, master-journal or temp
+  ** file), the bytes in the locking range should never be read or written. */
+#if 0
+  assert( pFile->pUnused==0
+       || offset>=PENDING_BYTE+512
+       || offset+amt<=PENDING_BYTE 
+  );
+#endif
+
+  got = seekAndRead(pFile, offset, pBuf, amt);
+  if( got==amt ){
+    return SQLITE_OK;
+  }else if( got<0 ){
+    /* lastErrno set by seekAndRead */
+    return SQLITE_IOERR_READ;
+  }else{
+    pFile->lastErrno = 0; /* not a system error */
+    /* Unread parts of the buffer must be zero-filled */
+    memset(&((char*)pBuf)[got], 0, amt-got);
+    return SQLITE_IOERR_SHORT_READ;
+  }
+}
+
+/*
+** Seek to the offset in id->offset then read cnt bytes into pBuf.
+** Return the number of bytes actually read.  Update the offset.
+**
+** To avoid stomping the errno value on a failed write the lastErrno value
+** is set before returning.
+*/
+static int seekAndWrite(unixFile *id, i64 offset, const void *pBuf, int cnt){
+  int got;
+#if (!defined(USE_PREAD) && !defined(USE_PREAD64))
+  i64 newOffset;
+#endif
+  TIMER_START;
+#if defined(USE_PREAD)
+  do{ got = osPwrite(id->h, pBuf, cnt, offset); }while( got<0 && errno==EINTR );
+#elif defined(USE_PREAD64)
+  do{ got = osPwrite64(id->h, pBuf, cnt, offset);}while( got<0 && errno==EINTR);
+#else
+  do{
+    newOffset = lseek(id->h, offset, SEEK_SET);
+    SimulateIOError( newOffset-- );
+    if( newOffset!=offset ){
+      if( newOffset == -1 ){
+        ((unixFile*)id)->lastErrno = errno;
+      }else{
+        ((unixFile*)id)->lastErrno = 0;			
+      }
+      return -1;
+    }
+    got = osWrite(id->h, pBuf, cnt);
+  }while( got<0 && errno==EINTR );
+#endif
+  TIMER_END;
+  if( got<0 ){
+    ((unixFile*)id)->lastErrno = errno;
+  }
+
+  OSTRACE(("WRITE   %-3d %5d %7lld %llu\n", id->h, got, offset, TIMER_ELAPSED));
+  return got;
+}
+
+
+/*
+** Write data from a buffer into a file.  Return SQLITE_OK on success
+** or some other error code on failure.
+*/
+static int unixWrite(
+  sqlite3_file *id, 
+  const void *pBuf, 
+  int amt,
+  sqlite3_int64 offset 
+){
+  unixFile *pFile = (unixFile*)id;
+  int wrote = 0;
+  assert( id );
+  assert( amt>0 );
+
+  /* If this is a database file (not a journal, master-journal or temp
+  ** file), the bytes in the locking range should never be read or written. */
+#if 0
+  assert( pFile->pUnused==0
+       || offset>=PENDING_BYTE+512
+       || offset+amt<=PENDING_BYTE 
+  );
+#endif
+
+#ifndef NDEBUG
+  /* If we are doing a normal write to a database file (as opposed to
+  ** doing a hot-journal rollback or a write to some file other than a
+  ** normal database file) then record the fact that the database
+  ** has changed.  If the transaction counter is modified, record that
+  ** fact too.
+  */
+  if( pFile->inNormalWrite ){
+    pFile->dbUpdate = 1;  /* The database has been modified */
+    if( offset<=24 && offset+amt>=27 ){
+      int rc;
+      char oldCntr[4];
+      SimulateIOErrorBenign(1);
+      rc = seekAndRead(pFile, 24, oldCntr, 4);
+      SimulateIOErrorBenign(0);
+      if( rc!=4 || memcmp(oldCntr, &((char*)pBuf)[24-offset], 4)!=0 ){
+        pFile->transCntrChng = 1;  /* The transaction counter has changed */
+      }
+    }
+  }
+#endif
+
+  while( amt>0 && (wrote = seekAndWrite(pFile, offset, pBuf, amt))>0 ){
+    amt -= wrote;
+    offset += wrote;
+    pBuf = &((char*)pBuf)[wrote];
+  }
+  SimulateIOError(( wrote=(-1), amt=1 ));
+  SimulateDiskfullError(( wrote=0, amt=1 ));
+
+  if( amt>0 ){
+    if( wrote<0 && pFile->lastErrno!=ENOSPC ){
+      /* lastErrno set by seekAndWrite */
+      return SQLITE_IOERR_WRITE;
+    }else{
+      pFile->lastErrno = 0; /* not a system error */
+      return SQLITE_FULL;
+    }
+  }
+
+  return SQLITE_OK;
+}
+
+#ifdef SQLITE_TEST
+/*
+** Count the number of fullsyncs and normal syncs.  This is used to test
+** that syncs and fullsyncs are occurring at the right times.
+*/
+int sqlite3_sync_count = 0;
+int sqlite3_fullsync_count = 0;
+#endif
+
+/*
+** We do not trust systems to provide a working fdatasync().  Some do.
+** Others do no.  To be safe, we will stick with the (slightly slower)
+** fsync(). If you know that your system does support fdatasync() correctly,
+** then simply compile with -Dfdatasync=fdatasync
+*/
+#if !defined(fdatasync)
+# define fdatasync fsync
+#endif
+
+/*
+** Define HAVE_FULLFSYNC to 0 or 1 depending on whether or not
+** the F_FULLFSYNC macro is defined.  F_FULLFSYNC is currently
+** only available on Mac OS X.  But that could change.
+*/
+#ifdef F_FULLFSYNC
+# define HAVE_FULLFSYNC 1
+#else
+# define HAVE_FULLFSYNC 0
+#endif
+
+
+/*
+** The fsync() system call does not work as advertised on many
+** unix systems.  The following procedure is an attempt to make
+** it work better.
+**
+** The SQLITE_NO_SYNC macro disables all fsync()s.  This is useful
+** for testing when we want to run through the test suite quickly.
+** You are strongly advised *not* to deploy with SQLITE_NO_SYNC
+** enabled, however, since with SQLITE_NO_SYNC enabled, an OS crash
+** or power failure will likely corrupt the database file.
+**
+** SQLite sets the dataOnly flag if the size of the file is unchanged.
+** The idea behind dataOnly is that it should only write the file content
+** to disk, not the inode.  We only set dataOnly if the file size is 
+** unchanged since the file size is part of the inode.  However, 
+** Ted Ts'o tells us that fdatasync() will also write the inode if the
+** file size has changed.  The only real difference between fdatasync()
+** and fsync(), Ted tells us, is that fdatasync() will not flush the
+** inode if the mtime or owner or other inode attributes have changed.
+** We only care about the file size, not the other file attributes, so
+** as far as SQLite is concerned, an fdatasync() is always adequate.
+** So, we always use fdatasync() if it is available, regardless of
+** the value of the dataOnly flag.
+*/
+static int full_fsync(int fd, int fullSync, int dataOnly){
+  int rc;
+
+  /* The following "ifdef/elif/else/" block has the same structure as
+  ** the one below. It is replicated here solely to avoid cluttering 
+  ** up the real code with the UNUSED_PARAMETER() macros.
+  */
+#ifdef SQLITE_NO_SYNC
+  UNUSED_PARAMETER(fd);
+  UNUSED_PARAMETER(fullSync);
+  UNUSED_PARAMETER(dataOnly);
+#elif HAVE_FULLFSYNC
+  UNUSED_PARAMETER(dataOnly);
+#else
+  UNUSED_PARAMETER(fullSync);
+  UNUSED_PARAMETER(dataOnly);
+#endif
+
+  /* Record the number of times that we do a normal fsync() and 
+  ** FULLSYNC.  This is used during testing to verify that this procedure
+  ** gets called with the correct arguments.
+  */
+#ifdef SQLITE_TEST
+  if( fullSync ) sqlite3_fullsync_count++;
+  sqlite3_sync_count++;
+#endif
+
+  /* If we compiled with the SQLITE_NO_SYNC flag, then syncing is a
+  ** no-op
+  */
+#ifdef SQLITE_NO_SYNC
+  rc = SQLITE_OK;
+#elif HAVE_FULLFSYNC
+  if( fullSync ){
+    rc = osFcntl(fd, F_FULLFSYNC, 0);
+  }else{
+    rc = 1;
+  }
+  /* If the FULLFSYNC failed, fall back to attempting an fsync().
+  ** It shouldn't be possible for fullfsync to fail on the local 
+  ** file system (on OSX), so failure indicates that FULLFSYNC
+  ** isn't supported for this file system. So, attempt an fsync 
+  ** and (for now) ignore the overhead of a superfluous fcntl call.  
+  ** It'd be better to detect fullfsync support once and avoid 
+  ** the fcntl call every time sync is called.
+  */
+  if( rc ) rc = fsync(fd);
+
+#elif defined(__APPLE__)
+  /* fdatasync() on HFS+ doesn't yet flush the file size if it changed correctly
+  ** so currently we default to the macro that redefines fdatasync to fsync
+  */
+  rc = fsync(fd);
+#else 
+  rc = fdatasync(fd);
+#if OS_VXWORKS
+  if( rc==-1 && errno==ENOTSUP ){
+    rc = fsync(fd);
+  }
+#endif /* OS_VXWORKS */
+#endif /* ifdef SQLITE_NO_SYNC elif HAVE_FULLFSYNC */
+
+  if( OS_VXWORKS && rc!= -1 ){
+    rc = 0;
+  }
+  return rc;
+}
+
+/*
+** Open a file descriptor to the directory containing file zFilename.
+** If successful, *pFd is set to the opened file descriptor and
+** SQLITE_OK is returned. If an error occurs, either SQLITE_NOMEM
+** or SQLITE_CANTOPEN is returned and *pFd is set to an undefined
+** value.
+**
+** The directory file descriptor is used for only one thing - to
+** fsync() a directory to make sure file creation and deletion events
+** are flushed to disk.  Such fsyncs are not needed on newer
+** journaling filesystems, but are required on older filesystems.
+**
+** This routine can be overridden using the xSetSysCall interface.
+** The ability to override this routine was added in support of the
+** chromium sandbox.  Opening a directory is a security risk (we are
+** told) so making it overrideable allows the chromium sandbox to
+** replace this routine with a harmless no-op.  To make this routine
+** a no-op, replace it with a stub that returns SQLITE_OK but leaves
+** *pFd set to a negative number.
+**
+** If SQLITE_OK is returned, the caller is responsible for closing
+** the file descriptor *pFd using close().
+*/
+static int openDirectory(const char *zFilename, int *pFd){
+  int ii;
+  int fd = -1;
+  char zDirname[MAX_PATHNAME+1];
+
+  sqlite3_snprintf(MAX_PATHNAME, zDirname, "%s", zFilename);
+  for(ii=(int)strlen(zDirname); ii>1 && zDirname[ii]!='/'; ii--);
+  if( ii>0 ){
+    zDirname[ii] = '\0';
+    fd = robust_open(zDirname, O_RDONLY|O_BINARY, 0);
+    if( fd>=0 ){
+#ifdef FD_CLOEXEC
+      osFcntl(fd, F_SETFD, osFcntl(fd, F_GETFD, 0) | FD_CLOEXEC);
+#endif
+      OSTRACE(("OPENDIR %-3d %s\n", fd, zDirname));
+    }
+  }
+  *pFd = fd;
+  return (fd>=0?SQLITE_OK:unixLogError(SQLITE_CANTOPEN_BKPT, "open", zDirname));
+}
+
+/*
+** Make sure all writes to a particular file are committed to disk.
+**
+** If dataOnly==0 then both the file itself and its metadata (file
+** size, access time, etc) are synced.  If dataOnly!=0 then only the
+** file data is synced.
+**
+** Under Unix, also make sure that the directory entry for the file
+** has been created by fsync-ing the directory that contains the file.
+** If we do not do this and we encounter a power failure, the directory
+** entry for the journal might not exist after we reboot.  The next
+** SQLite to access the file will not know that the journal exists (because
+** the directory entry for the journal was never created) and the transaction
+** will not roll back - possibly leading to database corruption.
+*/
+static int unixSync(sqlite3_file *id, int flags){
+  int rc;
+  unixFile *pFile = (unixFile*)id;
+
+  int isDataOnly = (flags&SQLITE_SYNC_DATAONLY);
+  int isFullsync = (flags&0x0F)==SQLITE_SYNC_FULL;
+
+  /* Check that one of SQLITE_SYNC_NORMAL or FULL was passed */
+  assert((flags&0x0F)==SQLITE_SYNC_NORMAL
+      || (flags&0x0F)==SQLITE_SYNC_FULL
+  );
+
+  /* Unix cannot, but some systems may return SQLITE_FULL from here. This
+  ** line is to test that doing so does not cause any problems.
+  */
+  SimulateDiskfullError( return SQLITE_FULL );
+
+  assert( pFile );
+  OSTRACE(("SYNC    %-3d\n", pFile->h));
+  rc = full_fsync(pFile->h, isFullsync, isDataOnly);
+  SimulateIOError( rc=1 );
+  if( rc ){
+    pFile->lastErrno = errno;
+    return unixLogError(SQLITE_IOERR_FSYNC, "full_fsync", pFile->zPath);
+  }
+
+  /* Also fsync the directory containing the file if the DIRSYNC flag
+  ** is set.  This is a one-time occurrance.  Many systems (examples: AIX)
+  ** are unable to fsync a directory, so ignore errors on the fsync.
+  */
+  if( pFile->ctrlFlags & UNIXFILE_DIRSYNC ){
+    int dirfd;
+    OSTRACE(("DIRSYNC %s (have_fullfsync=%d fullsync=%d)\n", pFile->zPath,
+            HAVE_FULLFSYNC, isFullsync));
+    rc = osOpenDirectory(pFile->zPath, &dirfd);
+    if( rc==SQLITE_OK && dirfd>=0 ){
+      full_fsync(dirfd, 0, 0);
+      robust_close(pFile, dirfd, __LINE__);
+    }else if( rc==SQLITE_CANTOPEN ){
+      rc = SQLITE_OK;
+    }
+    pFile->ctrlFlags &= ~UNIXFILE_DIRSYNC;
+  }
+  return rc;
+}
+
+/*
+** Truncate an open file to a specified size
+*/
+static int unixTruncate(sqlite3_file *id, i64 nByte){
+  unixFile *pFile = (unixFile *)id;
+  int rc;
+  assert( pFile );
+  SimulateIOError( return SQLITE_IOERR_TRUNCATE );
+
+  /* If the user has configured a chunk-size for this file, truncate the
+  ** file so that it consists of an integer number of chunks (i.e. the
+  ** actual file size after the operation may be larger than the requested
+  ** size).
+  */
+  if( pFile->szChunk ){
+    nByte = ((nByte + pFile->szChunk - 1)/pFile->szChunk) * pFile->szChunk;
+  }
+
+  rc = robust_ftruncate(pFile->h, (off_t)nByte);
+  if( rc ){
+    pFile->lastErrno = errno;
+    return unixLogError(SQLITE_IOERR_TRUNCATE, "ftruncate", pFile->zPath);
+  }else{
+#ifndef NDEBUG
+    /* If we are doing a normal write to a database file (as opposed to
+    ** doing a hot-journal rollback or a write to some file other than a
+    ** normal database file) and we truncate the file to zero length,
+    ** that effectively updates the change counter.  This might happen
+    ** when restoring a database using the backup API from a zero-length
+    ** source.
+    */
+    if( pFile->inNormalWrite && nByte==0 ){
+      pFile->transCntrChng = 1;
+    }
+#endif
+
+    return SQLITE_OK;
+  }
+}
+
+/*
+** Determine the current size of a file in bytes
+*/
+static int unixFileSize(sqlite3_file *id, i64 *pSize){
+  int rc;
+  struct stat buf;
+  assert( id );
+  rc = osFstat(((unixFile*)id)->h, &buf);
+  SimulateIOError( rc=1 );
+  if( rc!=0 ){
+    ((unixFile*)id)->lastErrno = errno;
+    return SQLITE_IOERR_FSTAT;
+  }
+  *pSize = buf.st_size;
+
+  /* When opening a zero-size database, the findInodeInfo() procedure
+  ** writes a single byte into that file in order to work around a bug
+  ** in the OS-X msdos filesystem.  In order to avoid problems with upper
+  ** layers, we need to report this file size as zero even though it is
+  ** really 1.   Ticket #3260.
+  */
+  if( *pSize==1 ) *pSize = 0;
+
+
+  return SQLITE_OK;
+}
+
+#if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__)
+/*
+** Handler for proxy-locking file-control verbs.  Defined below in the
+** proxying locking division.
+*/
+static int proxyFileControl(sqlite3_file*,int,void*);
+#endif
+
+/* 
+** This function is called to handle the SQLITE_FCNTL_SIZE_HINT 
+** file-control operation.  Enlarge the database to nBytes in size
+** (rounded up to the next chunk-size).  If the database is already
+** nBytes or larger, this routine is a no-op.
+*/
+static int fcntlSizeHint(unixFile *pFile, i64 nByte){
+  if( pFile->szChunk>0 ){
+    i64 nSize;                    /* Required file size */
+    struct stat buf;              /* Used to hold return values of fstat() */
+   
+    if( osFstat(pFile->h, &buf) ) return SQLITE_IOERR_FSTAT;
+
+    nSize = ((nByte+pFile->szChunk-1) / pFile->szChunk) * pFile->szChunk;
+    if( nSize>(i64)buf.st_size ){
+
+#if defined(HAVE_POSIX_FALLOCATE) && HAVE_POSIX_FALLOCATE
+      /* The code below is handling the return value of osFallocate() 
+      ** correctly. posix_fallocate() is defined to "returns zero on success, 
+      ** or an error number on  failure". See the manpage for details. */
+      int err;
+      do{
+        err = osFallocate(pFile->h, buf.st_size, nSize-buf.st_size);
+      }while( err==EINTR );
+      if( err ) return SQLITE_IOERR_WRITE;
+#else
+      /* If the OS does not have posix_fallocate(), fake it. First use
+      ** ftruncate() to set the file size, then write a single byte to
+      ** the last byte in each block within the extended region. This
+      ** is the same technique used by glibc to implement posix_fallocate()
+      ** on systems that do not have a real fallocate() system call.
+      */
+      int nBlk = buf.st_blksize;  /* File-system block size */
+      i64 iWrite;                 /* Next offset to write to */
+
+      if( robust_ftruncate(pFile->h, nSize) ){
+        pFile->lastErrno = errno;
+        return unixLogError(SQLITE_IOERR_TRUNCATE, "ftruncate", pFile->zPath);
+      }
+      iWrite = ((buf.st_size + 2*nBlk - 1)/nBlk)*nBlk-1;
+      while( iWrite<nSize ){
+        int nWrite = seekAndWrite(pFile, iWrite, "", 1);
+        if( nWrite!=1 ) return SQLITE_IOERR_WRITE;
+        iWrite += nBlk;
+      }
+#endif
+    }
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** Information and control of an open file handle.
+*/
+static int unixFileControl(sqlite3_file *id, int op, void *pArg){
+  unixFile *pFile = (unixFile*)id;
+  switch( op ){
+    case SQLITE_FCNTL_LOCKSTATE: {
+      *(int*)pArg = pFile->eFileLock;
+      return SQLITE_OK;
+    }
+    case SQLITE_LAST_ERRNO: {
+      *(int*)pArg = pFile->lastErrno;
+      return SQLITE_OK;
+    }
+    case SQLITE_FCNTL_CHUNK_SIZE: {
+      pFile->szChunk = *(int *)pArg;
+      return SQLITE_OK;
+    }
+    case SQLITE_FCNTL_SIZE_HINT: {
+      int rc;
+      SimulateIOErrorBenign(1);
+      rc = fcntlSizeHint(pFile, *(i64 *)pArg);
+      SimulateIOErrorBenign(0);
+      return rc;
+    }
+    case SQLITE_FCNTL_PERSIST_WAL: {
+      int bPersist = *(int*)pArg;
+      if( bPersist<0 ){
+        *(int*)pArg = (pFile->ctrlFlags & UNIXFILE_PERSIST_WAL)!=0;
+      }else if( bPersist==0 ){
+        pFile->ctrlFlags &= ~UNIXFILE_PERSIST_WAL;
+      }else{
+        pFile->ctrlFlags |= UNIXFILE_PERSIST_WAL;
+      }
+      return SQLITE_OK;
+    }
+#ifndef NDEBUG
+    /* The pager calls this method to signal that it has done
+    ** a rollback and that the database is therefore unchanged and
+    ** it hence it is OK for the transaction change counter to be
+    ** unchanged.
+    */
+    case SQLITE_FCNTL_DB_UNCHANGED: {
+      ((unixFile*)id)->dbUpdate = 0;
+      return SQLITE_OK;
+    }
+#endif
+#if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__)
+    case SQLITE_SET_LOCKPROXYFILE:
+    case SQLITE_GET_LOCKPROXYFILE: {
+      return proxyFileControl(id,op,pArg);
+    }
+#endif /* SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__) */
+    case SQLITE_FCNTL_SYNC_OMITTED: {
+      return SQLITE_OK;  /* A no-op */
+    }
+  }
+  return SQLITE_NOTFOUND;
+}
+
+/*
+** Return the sector size in bytes of the underlying block device for
+** the specified file. This is almost always 512 bytes, but may be
+** larger for some devices.
+**
+** SQLite code assumes this function cannot fail. It also assumes that
+** if two files are created in the same file-system directory (i.e.
+** a database and its journal file) that the sector size will be the
+** same for both.
+*/
+static int unixSectorSize(sqlite3_file *NotUsed){
+  UNUSED_PARAMETER(NotUsed);
+  return SQLITE_DEFAULT_SECTOR_SIZE;
+}
+
+/*
+** Return the device characteristics for the file. This is always 0 for unix.
+*/
+static int unixDeviceCharacteristics(sqlite3_file *NotUsed){
+  UNUSED_PARAMETER(NotUsed);
+  return 0;
+}
+
+#ifndef SQLITE_OMIT_WAL
+
+
+/*
+** Object used to represent an shared memory buffer.  
+**
+** When multiple threads all reference the same wal-index, each thread
+** has its own unixShm object, but they all point to a single instance
+** of this unixShmNode object.  In other words, each wal-index is opened
+** only once per process.
+**
+** Each unixShmNode object is connected to a single unixInodeInfo object.
+** We could coalesce this object into unixInodeInfo, but that would mean
+** every open file that does not use shared memory (in other words, most
+** open files) would have to carry around this extra information.  So
+** the unixInodeInfo object contains a pointer to this unixShmNode object
+** and the unixShmNode object is created only when needed.
+**
+** unixMutexHeld() must be true when creating or destroying
+** this object or while reading or writing the following fields:
+**
+**      nRef
+**
+** The following fields are read-only after the object is created:
+** 
+**      fid
+**      zFilename
+**
+** Either unixShmNode.mutex must be held or unixShmNode.nRef==0 and
+** unixMutexHeld() is true when reading or writing any other field
+** in this structure.
+*/
+struct unixShmNode {
+  unixInodeInfo *pInode;     /* unixInodeInfo that owns this SHM node */
+  sqlite3_mutex *mutex;      /* Mutex to access this object */
+  char *zFilename;           /* Name of the mmapped file */
+  int h;                     /* Open file descriptor */
+  int szRegion;              /* Size of shared-memory regions */
+  u16 nRegion;               /* Size of array apRegion */
+  u8 isReadonly;             /* True if read-only */
+  char **apRegion;           /* Array of mapped shared-memory regions */
+  int nRef;                  /* Number of unixShm objects pointing to this */
+  unixShm *pFirst;           /* All unixShm objects pointing to this */
+#ifdef SQLITE_DEBUG
+  u8 exclMask;               /* Mask of exclusive locks held */
+  u8 sharedMask;             /* Mask of shared locks held */
+  u8 nextShmId;              /* Next available unixShm.id value */
+#endif
+};
+
+/*
+** Structure used internally by this VFS to record the state of an
+** open shared memory connection.
+**
+** The following fields are initialized when this object is created and
+** are read-only thereafter:
+**
+**    unixShm.pFile
+**    unixShm.id
+**
+** All other fields are read/write.  The unixShm.pFile->mutex must be held
+** while accessing any read/write fields.
+*/
+struct unixShm {
+  unixShmNode *pShmNode;     /* The underlying unixShmNode object */
+  unixShm *pNext;            /* Next unixShm with the same unixShmNode */
+  u8 hasMutex;               /* True if holding the unixShmNode mutex */
+  u8 id;                     /* Id of this connection within its unixShmNode */
+  u16 sharedMask;            /* Mask of shared locks held */
+  u16 exclMask;              /* Mask of exclusive locks held */
+};
+
+/*
+** Constants used for locking
+*/
+#define UNIX_SHM_BASE   ((22+SQLITE_SHM_NLOCK)*4)         /* first lock byte */
+#define UNIX_SHM_DMS    (UNIX_SHM_BASE+SQLITE_SHM_NLOCK)  /* deadman switch */
+
+/*
+** Apply posix advisory locks for all bytes from ofst through ofst+n-1.
+**
+** Locks block if the mask is exactly UNIX_SHM_C and are non-blocking
+** otherwise.
+*/
+static int unixShmSystemLock(
+  unixShmNode *pShmNode, /* Apply locks to this open shared-memory segment */
+  int lockType,          /* F_UNLCK, F_RDLCK, or F_WRLCK */
+  int ofst,              /* First byte of the locking range */
+  int n                  /* Number of bytes to lock */
+){
+  struct flock f;       /* The posix advisory locking structure */
+  int rc = SQLITE_OK;   /* Result code form fcntl() */
+
+  /* Access to the unixShmNode object is serialized by the caller */
+  assert( sqlite3_mutex_held(pShmNode->mutex) || pShmNode->nRef==0 );
+
+  /* Shared locks never span more than one byte */
+  assert( n==1 || lockType!=F_RDLCK );
+
+  /* Locks are within range */
+  assert( n>=1 && n<SQLITE_SHM_NLOCK );
+
+  if( pShmNode->h>=0 ){
+    /* Initialize the locking parameters */
+    memset(&f, 0, sizeof(f));
+    f.l_type = lockType;
+    f.l_whence = SEEK_SET;
+    f.l_start = ofst;
+    f.l_len = n;
+
+    rc = osFcntl(pShmNode->h, F_SETLK, &f);
+    rc = (rc!=(-1)) ? SQLITE_OK : SQLITE_BUSY;
+  }
+
+  /* Update the global lock state and do debug tracing */
+#ifdef SQLITE_DEBUG
+  { u16 mask;
+  OSTRACE(("SHM-LOCK "));
+  mask = (1<<(ofst+n)) - (1<<ofst);
+  if( rc==SQLITE_OK ){
+    if( lockType==F_UNLCK ){
+      OSTRACE(("unlock %d ok", ofst));
+      pShmNode->exclMask &= ~mask;
+      pShmNode->sharedMask &= ~mask;
+    }else if( lockType==F_RDLCK ){
+      OSTRACE(("read-lock %d ok", ofst));
+      pShmNode->exclMask &= ~mask;
+      pShmNode->sharedMask |= mask;
+    }else{
+      assert( lockType==F_WRLCK );
+      OSTRACE(("write-lock %d ok", ofst));
+      pShmNode->exclMask |= mask;
+      pShmNode->sharedMask &= ~mask;
+    }
+  }else{
+    if( lockType==F_UNLCK ){
+      OSTRACE(("unlock %d failed", ofst));
+    }else if( lockType==F_RDLCK ){
+      OSTRACE(("read-lock failed"));
+    }else{
+      assert( lockType==F_WRLCK );
+      OSTRACE(("write-lock %d failed", ofst));
+    }
+  }
+  OSTRACE((" - afterwards %03x,%03x\n",
+           pShmNode->sharedMask, pShmNode->exclMask));
+  }
+#endif
+
+  return rc;        
+}
+
+
+/*
+** Purge the unixShmNodeList list of all entries with unixShmNode.nRef==0.
+**
+** This is not a VFS shared-memory method; it is a utility function called
+** by VFS shared-memory methods.
+*/
+static void unixShmPurge(unixFile *pFd){
+  unixShmNode *p = pFd->pInode->pShmNode;
+  assert( unixMutexHeld() );
+  if( p && p->nRef==0 ){
+    int i;
+    assert( p->pInode==pFd->pInode );
+    sqlite3_mutex_free(p->mutex);
+    for(i=0; i<p->nRegion; i++){
+      if( p->h>=0 ){
+        munmap(p->apRegion[i], p->szRegion);
+      }else{
+        sqlite3_free(p->apRegion[i]);
+      }
+    }
+    sqlite3_free(p->apRegion);
+    if( p->h>=0 ){
+      robust_close(pFd, p->h, __LINE__);
+      p->h = -1;
+    }
+    p->pInode->pShmNode = 0;
+    sqlite3_free(p);
+  }
+}
+
+/*
+** Open a shared-memory area associated with open database file pDbFd.  
+** This particular implementation uses mmapped files.
+**
+** The file used to implement shared-memory is in the same directory
+** as the open database file and has the same name as the open database
+** file with the "-shm" suffix added.  For example, if the database file
+** is "/home/user1/config.db" then the file that is created and mmapped
+** for shared memory will be called "/home/user1/config.db-shm".  
+**
+** Another approach to is to use files in /dev/shm or /dev/tmp or an
+** some other tmpfs mount. But if a file in a different directory
+** from the database file is used, then differing access permissions
+** or a chroot() might cause two different processes on the same
+** database to end up using different files for shared memory - 
+** meaning that their memory would not really be shared - resulting
+** in database corruption.  Nevertheless, this tmpfs file usage
+** can be enabled at compile-time using -DSQLITE_SHM_DIRECTORY="/dev/shm"
+** or the equivalent.  The use of the SQLITE_SHM_DIRECTORY compile-time
+** option results in an incompatible build of SQLite;  builds of SQLite
+** that with differing SQLITE_SHM_DIRECTORY settings attempt to use the
+** same database file at the same time, database corruption will likely
+** result. The SQLITE_SHM_DIRECTORY compile-time option is considered
+** "unsupported" and may go away in a future SQLite release.
+**
+** When opening a new shared-memory file, if no other instances of that
+** file are currently open, in this process or in other processes, then
+** the file must be truncated to zero length or have its header cleared.
+**
+** If the original database file (pDbFd) is using the "unix-excl" VFS
+** that means that an exclusive lock is held on the database file and
+** that no other processes are able to read or write the database.  In
+** that case, we do not really need shared memory.  No shared memory
+** file is created.  The shared memory will be simulated with heap memory.
+*/
+static int unixOpenSharedMemory(unixFile *pDbFd){
+  struct unixShm *p = 0;          /* The connection to be opened */
+  struct unixShmNode *pShmNode;   /* The underlying mmapped file */
+  int rc;                         /* Result code */
+  unixInodeInfo *pInode;          /* The inode of fd */
+  char *zShmFilename;             /* Name of the file used for SHM */
+  int nShmFilename;               /* Size of the SHM filename in bytes */
+
+  /* Allocate space for the new unixShm object. */
+  p = sqlite3_malloc( sizeof(*p) );
+  if( p==0 ) return SQLITE_NOMEM;
+  memset(p, 0, sizeof(*p));
+  assert( pDbFd->pShm==0 );
+
+  /* Check to see if a unixShmNode object already exists. Reuse an existing
+  ** one if present. Create a new one if necessary.
+  */
+  unixEnterMutex();
+  pInode = pDbFd->pInode;
+  pShmNode = pInode->pShmNode;
+  if( pShmNode==0 ){
+    struct stat sStat;                 /* fstat() info for database file */
+
+    /* Call fstat() to figure out the permissions on the database file. If
+    ** a new *-shm file is created, an attempt will be made to create it
+    ** with the same permissions. The actual permissions the file is created
+    ** with are subject to the current umask setting.
+    */
+    if( osFstat(pDbFd->h, &sStat) && pInode->bProcessLock==0 ){
+      rc = SQLITE_IOERR_FSTAT;
+      goto shm_open_err;
+    }
+
+#ifdef SQLITE_SHM_DIRECTORY
+    nShmFilename = sizeof(SQLITE_SHM_DIRECTORY) + 30;
+#else
+    nShmFilename = 5 + (int)strlen(pDbFd->zPath);
+#endif
+    pShmNode = sqlite3_malloc( sizeof(*pShmNode) + nShmFilename );
+    if( pShmNode==0 ){
+      rc = SQLITE_NOMEM;
+      goto shm_open_err;
+    }
+    memset(pShmNode, 0, sizeof(*pShmNode));
+    zShmFilename = pShmNode->zFilename = (char*)&pShmNode[1];
+#ifdef SQLITE_SHM_DIRECTORY
+    sqlite3_snprintf(nShmFilename, zShmFilename, 
+                     SQLITE_SHM_DIRECTORY "/sqlite-shm-%x-%x",
+                     (u32)sStat.st_ino, (u32)sStat.st_dev);
+#else
+    sqlite3_snprintf(nShmFilename, zShmFilename, "%s-shm", pDbFd->zPath);
+    sqlite3FileSuffix3(pDbFd->zPath, zShmFilename);
+#endif
+    pShmNode->h = -1;
+    pDbFd->pInode->pShmNode = pShmNode;
+    pShmNode->pInode = pDbFd->pInode;
+    pShmNode->mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_FAST);
+    if( pShmNode->mutex==0 ){
+      rc = SQLITE_NOMEM;
+      goto shm_open_err;
+    }
+
+    if( pInode->bProcessLock==0 ){
+      const char *zRO;
+      int openFlags = O_RDWR | O_CREAT;
+      zRO = sqlite3_uri_parameter(pDbFd->zPath, "readonly_shm");
+      if( zRO && sqlite3GetBoolean(zRO) ){
+        openFlags = O_RDONLY;
+        pShmNode->isReadonly = 1;
+      }
+      pShmNode->h = robust_open(zShmFilename, openFlags, (sStat.st_mode&0777));
+      if( pShmNode->h<0 ){
+        if( pShmNode->h<0 ){
+          rc = unixLogError(SQLITE_CANTOPEN_BKPT, "open", zShmFilename);
+          goto shm_open_err;
+        }
+      }
+  
+      /* Check to see if another process is holding the dead-man switch.
+      ** If not, truncate the file to zero length. 
+      */
+      rc = SQLITE_OK;
+      if( unixShmSystemLock(pShmNode, F_WRLCK, UNIX_SHM_DMS, 1)==SQLITE_OK ){
+        if( robust_ftruncate(pShmNode->h, 0) ){
+          rc = unixLogError(SQLITE_IOERR_SHMOPEN, "ftruncate", zShmFilename);
+        }
+      }
+      if( rc==SQLITE_OK ){
+        rc = unixShmSystemLock(pShmNode, F_RDLCK, UNIX_SHM_DMS, 1);
+      }
+      if( rc ) goto shm_open_err;
+    }
+  }
+
+  /* Make the new connection a child of the unixShmNode */
+  p->pShmNode = pShmNode;
+#ifdef SQLITE_DEBUG
+  p->id = pShmNode->nextShmId++;
+#endif
+  pShmNode->nRef++;
+  pDbFd->pShm = p;
+  unixLeaveMutex();
+
+  /* The reference count on pShmNode has already been incremented under
+  ** the cover of the unixEnterMutex() mutex and the pointer from the
+  ** new (struct unixShm) object to the pShmNode has been set. All that is
+  ** left to do is to link the new object into the linked list starting
+  ** at pShmNode->pFirst. This must be done while holding the pShmNode->mutex 
+  ** mutex.
+  */
+  sqlite3_mutex_enter(pShmNode->mutex);
+  p->pNext = pShmNode->pFirst;
+  pShmNode->pFirst = p;
+  sqlite3_mutex_leave(pShmNode->mutex);
+  return SQLITE_OK;
+
+  /* Jump here on any error */
+shm_open_err:
+  unixShmPurge(pDbFd);       /* This call frees pShmNode if required */
+  sqlite3_free(p);
+  unixLeaveMutex();
+  return rc;
+}
+
+/*
+** This function is called to obtain a pointer to region iRegion of the 
+** shared-memory associated with the database file fd. Shared-memory regions 
+** are numbered starting from zero. Each shared-memory region is szRegion 
+** bytes in size.
+**
+** If an error occurs, an error code is returned and *pp is set to NULL.
+**
+** Otherwise, if the bExtend parameter is 0 and the requested shared-memory
+** region has not been allocated (by any client, including one running in a
+** separate process), then *pp is set to NULL and SQLITE_OK returned. If 
+** bExtend is non-zero and the requested shared-memory region has not yet 
+** been allocated, it is allocated by this function.
+**
+** If the shared-memory region has already been allocated or is allocated by
+** this call as described above, then it is mapped into this processes 
+** address space (if it is not already), *pp is set to point to the mapped 
+** memory and SQLITE_OK returned.
+*/
+static int unixShmMap(
+  sqlite3_file *fd,               /* Handle open on database file */
+  int iRegion,                    /* Region to retrieve */
+  int szRegion,                   /* Size of regions */
+  int bExtend,                    /* True to extend file if necessary */
+  void volatile **pp              /* OUT: Mapped memory */
+){
+  unixFile *pDbFd = (unixFile*)fd;
+  unixShm *p;
+  unixShmNode *pShmNode;
+  int rc = SQLITE_OK;
+
+  /* If the shared-memory file has not yet been opened, open it now. */
+  if( pDbFd->pShm==0 ){
+    rc = unixOpenSharedMemory(pDbFd);
+    if( rc!=SQLITE_OK ) return rc;
+  }
+
+  p = pDbFd->pShm;
+  pShmNode = p->pShmNode;
+  sqlite3_mutex_enter(pShmNode->mutex);
+  assert( szRegion==pShmNode->szRegion || pShmNode->nRegion==0 );
+  assert( pShmNode->pInode==pDbFd->pInode );
+  assert( pShmNode->h>=0 || pDbFd->pInode->bProcessLock==1 );
+  assert( pShmNode->h<0 || pDbFd->pInode->bProcessLock==0 );
+
+  if( pShmNode->nRegion<=iRegion ){
+    char **apNew;                      /* New apRegion[] array */
+    int nByte = (iRegion+1)*szRegion;  /* Minimum required file size */
+    struct stat sStat;                 /* Used by fstat() */
+
+    pShmNode->szRegion = szRegion;
+
+    if( pShmNode->h>=0 ){
+      /* The requested region is not mapped into this processes address space.
+      ** Check to see if it has been allocated (i.e. if the wal-index file is
+      ** large enough to contain the requested region).
+      */
+      if( osFstat(pShmNode->h, &sStat) ){
+        rc = SQLITE_IOERR_SHMSIZE;
+        goto shmpage_out;
+      }
+  
+      if( sStat.st_size<nByte ){
+        /* The requested memory region does not exist. If bExtend is set to
+        ** false, exit early. *pp will be set to NULL and SQLITE_OK returned.
+        **
+        ** Alternatively, if bExtend is true, use ftruncate() to allocate
+        ** the requested memory region.
+        */
+        if( !bExtend ) goto shmpage_out;
+        if( robust_ftruncate(pShmNode->h, nByte) ){
+          rc = unixLogError(SQLITE_IOERR_SHMSIZE, "ftruncate",
+                            pShmNode->zFilename);
+          goto shmpage_out;
+        }
+      }
+    }
+
+    /* Map the requested memory region into this processes address space. */
+    apNew = (char **)sqlite3_realloc(
+        pShmNode->apRegion, (iRegion+1)*sizeof(char *)
+    );
+    if( !apNew ){
+      rc = SQLITE_IOERR_NOMEM;
+      goto shmpage_out;
+    }
+    pShmNode->apRegion = apNew;
+    while(pShmNode->nRegion<=iRegion){
+      void *pMem;
+      if( pShmNode->h>=0 ){
+        pMem = mmap(0, szRegion,
+            pShmNode->isReadonly ? PROT_READ : PROT_READ|PROT_WRITE, 
+            MAP_SHARED, pShmNode->h, pShmNode->nRegion*szRegion
+        );
+        if( pMem==MAP_FAILED ){
+          rc = unixLogError(SQLITE_IOERR_SHMMAP, "mmap", pShmNode->zFilename);
+          goto shmpage_out;
+        }
+      }else{
+        pMem = sqlite3_malloc(szRegion);
+        if( pMem==0 ){
+          rc = SQLITE_NOMEM;
+          goto shmpage_out;
+        }
+        memset(pMem, 0, szRegion);
+      }
+      pShmNode->apRegion[pShmNode->nRegion] = pMem;
+      pShmNode->nRegion++;
+    }
+  }
+
+shmpage_out:
+  if( pShmNode->nRegion>iRegion ){
+    *pp = pShmNode->apRegion[iRegion];
+  }else{
+    *pp = 0;
+  }
+  if( pShmNode->isReadonly && rc==SQLITE_OK ) rc = SQLITE_READONLY;
+  sqlite3_mutex_leave(pShmNode->mutex);
+  return rc;
+}
+
+/*
+** Change the lock state for a shared-memory segment.
+**
+** Note that the relationship between SHAREd and EXCLUSIVE locks is a little
+** different here than in posix.  In xShmLock(), one can go from unlocked
+** to shared and back or from unlocked to exclusive and back.  But one may
+** not go from shared to exclusive or from exclusive to shared.
+*/
+static int unixShmLock(
+  sqlite3_file *fd,          /* Database file holding the shared memory */
+  int ofst,                  /* First lock to acquire or release */
+  int n,                     /* Number of locks to acquire or release */
+  int flags                  /* What to do with the lock */
+){
+  unixFile *pDbFd = (unixFile*)fd;      /* Connection holding shared memory */
+  unixShm *p = pDbFd->pShm;             /* The shared memory being locked */
+  unixShm *pX;                          /* For looping over all siblings */
+  unixShmNode *pShmNode = p->pShmNode;  /* The underlying file iNode */
+  int rc = SQLITE_OK;                   /* Result code */
+  u16 mask;                             /* Mask of locks to take or release */
+
+  assert( pShmNode==pDbFd->pInode->pShmNode );
+  assert( pShmNode->pInode==pDbFd->pInode );
+  assert( ofst>=0 && ofst+n<=SQLITE_SHM_NLOCK );
+  assert( n>=1 );
+  assert( flags==(SQLITE_SHM_LOCK | SQLITE_SHM_SHARED)
+       || flags==(SQLITE_SHM_LOCK | SQLITE_SHM_EXCLUSIVE)
+       || flags==(SQLITE_SHM_UNLOCK | SQLITE_SHM_SHARED)
+       || flags==(SQLITE_SHM_UNLOCK | SQLITE_SHM_EXCLUSIVE) );
+  assert( n==1 || (flags & SQLITE_SHM_EXCLUSIVE)!=0 );
+  assert( pShmNode->h>=0 || pDbFd->pInode->bProcessLock==1 );
+  assert( pShmNode->h<0 || pDbFd->pInode->bProcessLock==0 );
+
+  mask = (1<<(ofst+n)) - (1<<ofst);
+  assert( n>1 || mask==(1<<ofst) );
+  sqlite3_mutex_enter(pShmNode->mutex);
+  if( flags & SQLITE_SHM_UNLOCK ){
+    u16 allMask = 0; /* Mask of locks held by siblings */
+
+    /* See if any siblings hold this same lock */
+    for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
+      if( pX==p ) continue;
+      assert( (pX->exclMask & (p->exclMask|p->sharedMask))==0 );
+      allMask |= pX->sharedMask;
+    }
+
+    /* Unlock the system-level locks */
+    if( (mask & allMask)==0 ){
+      rc = unixShmSystemLock(pShmNode, F_UNLCK, ofst+UNIX_SHM_BASE, n);
+    }else{
+      rc = SQLITE_OK;
+    }
+
+    /* Undo the local locks */
+    if( rc==SQLITE_OK ){
+      p->exclMask &= ~mask;
+      p->sharedMask &= ~mask;
+    } 
+  }else if( flags & SQLITE_SHM_SHARED ){
+    u16 allShared = 0;  /* Union of locks held by connections other than "p" */
+
+    /* Find out which shared locks are already held by sibling connections.
+    ** If any sibling already holds an exclusive lock, go ahead and return
+    ** SQLITE_BUSY.
+    */
+    for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
+      if( (pX->exclMask & mask)!=0 ){
+        rc = SQLITE_BUSY;
+        break;
+      }
+      allShared |= pX->sharedMask;
+    }
+
+    /* Get shared locks at the system level, if necessary */
+    if( rc==SQLITE_OK ){
+      if( (allShared & mask)==0 ){
+        rc = unixShmSystemLock(pShmNode, F_RDLCK, ofst+UNIX_SHM_BASE, n);
+      }else{
+        rc = SQLITE_OK;
+      }
+    }
+
+    /* Get the local shared locks */
+    if( rc==SQLITE_OK ){
+      p->sharedMask |= mask;
+    }
+  }else{
+    /* Make sure no sibling connections hold locks that will block this
+    ** lock.  If any do, return SQLITE_BUSY right away.
+    */
+    for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
+      if( (pX->exclMask & mask)!=0 || (pX->sharedMask & mask)!=0 ){
+        rc = SQLITE_BUSY;
+        break;
+      }
+    }
+  
+    /* Get the exclusive locks at the system level.  Then if successful
+    ** also mark the local connection as being locked.
+    */
+    if( rc==SQLITE_OK ){
+      rc = unixShmSystemLock(pShmNode, F_WRLCK, ofst+UNIX_SHM_BASE, n);
+      if( rc==SQLITE_OK ){
+        assert( (p->sharedMask & mask)==0 );
+        p->exclMask |= mask;
+      }
+    }
+  }
+  sqlite3_mutex_leave(pShmNode->mutex);
+  OSTRACE(("SHM-LOCK shmid-%d, pid-%d got %03x,%03x\n",
+           p->id, getpid(), p->sharedMask, p->exclMask));
+  return rc;
+}
+
+/*
+** Implement a memory barrier or memory fence on shared memory.  
+**
+** All loads and stores begun before the barrier must complete before
+** any load or store begun after the barrier.
+*/
+static void unixShmBarrier(
+  sqlite3_file *fd                /* Database file holding the shared memory */
+){
+  UNUSED_PARAMETER(fd);
+  unixEnterMutex();
+  unixLeaveMutex();
+}
+
+/*
+** Close a connection to shared-memory.  Delete the underlying 
+** storage if deleteFlag is true.
+**
+** If there is no shared memory associated with the connection then this
+** routine is a harmless no-op.
+*/
+static int unixShmUnmap(
+  sqlite3_file *fd,               /* The underlying database file */
+  int deleteFlag                  /* Delete shared-memory if true */
+){
+  unixShm *p;                     /* The connection to be closed */
+  unixShmNode *pShmNode;          /* The underlying shared-memory file */
+  unixShm **pp;                   /* For looping over sibling connections */
+  unixFile *pDbFd;                /* The underlying database file */
+
+  pDbFd = (unixFile*)fd;
+  p = pDbFd->pShm;
+  if( p==0 ) return SQLITE_OK;
+  pShmNode = p->pShmNode;
+
+  assert( pShmNode==pDbFd->pInode->pShmNode );
+  assert( pShmNode->pInode==pDbFd->pInode );
+
+  /* Remove connection p from the set of connections associated
+  ** with pShmNode */
+  sqlite3_mutex_enter(pShmNode->mutex);
+  for(pp=&pShmNode->pFirst; (*pp)!=p; pp = &(*pp)->pNext){}
+  *pp = p->pNext;
+
+  /* Free the connection p */
+  sqlite3_free(p);
+  pDbFd->pShm = 0;
+  sqlite3_mutex_leave(pShmNode->mutex);
+
+  /* If pShmNode->nRef has reached 0, then close the underlying
+  ** shared-memory file, too */
+  unixEnterMutex();
+  assert( pShmNode->nRef>0 );
+  pShmNode->nRef--;
+  if( pShmNode->nRef==0 ){
+    if( deleteFlag && pShmNode->h>=0 ) osUnlink(pShmNode->zFilename);
+    unixShmPurge(pDbFd);
+  }
+  unixLeaveMutex();
+
+  return SQLITE_OK;
+}
+
+
+#else
+# define unixShmMap     0
+# define unixShmLock    0
+# define unixShmBarrier 0
+# define unixShmUnmap   0
+#endif /* #ifndef SQLITE_OMIT_WAL */
+
+/*
+** Here ends the implementation of all sqlite3_file methods.
+**
+********************** End sqlite3_file Methods *******************************
+******************************************************************************/
+
+/*
+** This division contains definitions of sqlite3_io_methods objects that
+** implement various file locking strategies.  It also contains definitions
+** of "finder" functions.  A finder-function is used to locate the appropriate
+** sqlite3_io_methods object for a particular database file.  The pAppData
+** field of the sqlite3_vfs VFS objects are initialized to be pointers to
+** the correct finder-function for that VFS.
+**
+** Most finder functions return a pointer to a fixed sqlite3_io_methods
+** object.  The only interesting finder-function is autolockIoFinder, which
+** looks at the filesystem type and tries to guess the best locking
+** strategy from that.
+**
+** For finder-funtion F, two objects are created:
+**
+**    (1) The real finder-function named "FImpt()".
+**
+**    (2) A constant pointer to this function named just "F".
+**
+**
+** A pointer to the F pointer is used as the pAppData value for VFS
+** objects.  We have to do this instead of letting pAppData point
+** directly at the finder-function since C90 rules prevent a void*
+** from be cast into a function pointer.
+**
+**
+** Each instance of this macro generates two objects:
+**
+**   *  A constant sqlite3_io_methods object call METHOD that has locking
+**      methods CLOSE, LOCK, UNLOCK, CKRESLOCK.
+**
+**   *  An I/O method finder function called FINDER that returns a pointer
+**      to the METHOD object in the previous bullet.
+*/
+#define IOMETHODS(FINDER, METHOD, VERSION, CLOSE, LOCK, UNLOCK, CKLOCK)      \
+static const sqlite3_io_methods METHOD = {                                   \
+   VERSION,                    /* iVersion */                                \
+   CLOSE,                      /* xClose */                                  \
+   unixRead,                   /* xRead */                                   \
+   unixWrite,                  /* xWrite */                                  \
+   unixTruncate,               /* xTruncate */                               \
+   unixSync,                   /* xSync */                                   \
+   unixFileSize,               /* xFileSize */                               \
+   LOCK,                       /* xLock */                                   \
+   UNLOCK,                     /* xUnlock */                                 \
+   CKLOCK,                     /* xCheckReservedLock */                      \
+   unixFileControl,            /* xFileControl */                            \
+   unixSectorSize,             /* xSectorSize */                             \
+   unixDeviceCharacteristics,  /* xDeviceCapabilities */                     \
+   unixShmMap,                 /* xShmMap */                                 \
+   unixShmLock,                /* xShmLock */                                \
+   unixShmBarrier,             /* xShmBarrier */                             \
+   unixShmUnmap                /* xShmUnmap */                               \
+};                                                                           \
+static const sqlite3_io_methods *FINDER##Impl(const char *z, unixFile *p){   \
+  UNUSED_PARAMETER(z); UNUSED_PARAMETER(p);                                  \
+  return &METHOD;                                                            \
+}                                                                            \
+static const sqlite3_io_methods *(*const FINDER)(const char*,unixFile *p)    \
+    = FINDER##Impl;
+
+/*
+** Here are all of the sqlite3_io_methods objects for each of the
+** locking strategies.  Functions that return pointers to these methods
+** are also created.
+*/
+IOMETHODS(
+  posixIoFinder,            /* Finder function name */
+  posixIoMethods,           /* sqlite3_io_methods object name */
+  2,                        /* shared memory is enabled */
+  unixClose,                /* xClose method */
+  unixLock,                 /* xLock method */
+  unixUnlock,               /* xUnlock method */
+  unixCheckReservedLock     /* xCheckReservedLock method */
+)
+IOMETHODS(
+  nolockIoFinder,           /* Finder function name */
+  nolockIoMethods,          /* sqlite3_io_methods object name */
+  1,                        /* shared memory is disabled */
+  nolockClose,              /* xClose method */
+  nolockLock,               /* xLock method */
+  nolockUnlock,             /* xUnlock method */
+  nolockCheckReservedLock   /* xCheckReservedLock method */
+)
+IOMETHODS(
+  dotlockIoFinder,          /* Finder function name */
+  dotlockIoMethods,         /* sqlite3_io_methods object name */
+  1,                        /* shared memory is disabled */
+  dotlockClose,             /* xClose method */
+  dotlockLock,              /* xLock method */
+  dotlockUnlock,            /* xUnlock method */
+  dotlockCheckReservedLock  /* xCheckReservedLock method */
+)
+
+#if SQLITE_ENABLE_LOCKING_STYLE && !OS_VXWORKS
+IOMETHODS(
+  flockIoFinder,            /* Finder function name */
+  flockIoMethods,           /* sqlite3_io_methods object name */
+  1,                        /* shared memory is disabled */
+  flockClose,               /* xClose method */
+  flockLock,                /* xLock method */
+  flockUnlock,              /* xUnlock method */
+  flockCheckReservedLock    /* xCheckReservedLock method */
+)
+#endif
+
+#if OS_VXWORKS
+IOMETHODS(
+  semIoFinder,              /* Finder function name */
+  semIoMethods,             /* sqlite3_io_methods object name */
+  1,                        /* shared memory is disabled */
+  semClose,                 /* xClose method */
+  semLock,                  /* xLock method */
+  semUnlock,                /* xUnlock method */
+  semCheckReservedLock      /* xCheckReservedLock method */
+)
+#endif
+
+#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
+IOMETHODS(
+  afpIoFinder,              /* Finder function name */
+  afpIoMethods,             /* sqlite3_io_methods object name */
+  1,                        /* shared memory is disabled */
+  afpClose,                 /* xClose method */
+  afpLock,                  /* xLock method */
+  afpUnlock,                /* xUnlock method */
+  afpCheckReservedLock      /* xCheckReservedLock method */
+)
+#endif
+
+/*
+** The proxy locking method is a "super-method" in the sense that it
+** opens secondary file descriptors for the conch and lock files and
+** it uses proxy, dot-file, AFP, and flock() locking methods on those
+** secondary files.  For this reason, the division that implements
+** proxy locking is located much further down in the file.  But we need
+** to go ahead and define the sqlite3_io_methods and finder function
+** for proxy locking here.  So we forward declare the I/O methods.
+*/
+#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
+static int proxyClose(sqlite3_file*);
+static int proxyLock(sqlite3_file*, int);
+static int proxyUnlock(sqlite3_file*, int);
+static int proxyCheckReservedLock(sqlite3_file*, int*);
+IOMETHODS(
+  proxyIoFinder,            /* Finder function name */
+  proxyIoMethods,           /* sqlite3_io_methods object name */
+  1,                        /* shared memory is disabled */
+  proxyClose,               /* xClose method */
+  proxyLock,                /* xLock method */
+  proxyUnlock,              /* xUnlock method */
+  proxyCheckReservedLock    /* xCheckReservedLock method */
+)
+#endif
+
+/* nfs lockd on OSX 10.3+ doesn't clear write locks when a read lock is set */
+#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
+IOMETHODS(
+  nfsIoFinder,               /* Finder function name */
+  nfsIoMethods,              /* sqlite3_io_methods object name */
+  1,                         /* shared memory is disabled */
+  unixClose,                 /* xClose method */
+  unixLock,                  /* xLock method */
+  nfsUnlock,                 /* xUnlock method */
+  unixCheckReservedLock      /* xCheckReservedLock method */
+)
+#endif
+
+#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
+/* 
+** This "finder" function attempts to determine the best locking strategy 
+** for the database file "filePath".  It then returns the sqlite3_io_methods
+** object that implements that strategy.
+**
+** This is for MacOSX only.
+*/
+static const sqlite3_io_methods *autolockIoFinderImpl(
+  const char *filePath,    /* name of the database file */
+  unixFile *pNew           /* open file object for the database file */
+){
+  static const struct Mapping {
+    const char *zFilesystem;              /* Filesystem type name */
+    const sqlite3_io_methods *pMethods;   /* Appropriate locking method */
+  } aMap[] = {
+    { "hfs",    &posixIoMethods },
+    { "ufs",    &posixIoMethods },
+    { "afpfs",  &afpIoMethods },
+    { "smbfs",  &afpIoMethods },
+    { "webdav", &nolockIoMethods },
+    { 0, 0 }
+  };
+  int i;
+  struct statfs fsInfo;
+  struct flock lockInfo;
+
+  if( !filePath ){
+    /* If filePath==NULL that means we are dealing with a transient file
+    ** that does not need to be locked. */
+    return &nolockIoMethods;
+  }
+  if( statfs(filePath, &fsInfo) != -1 ){
+    if( fsInfo.f_flags & MNT_RDONLY ){
+      return &nolockIoMethods;
+    }
+    for(i=0; aMap[i].zFilesystem; i++){
+      if( strcmp(fsInfo.f_fstypename, aMap[i].zFilesystem)==0 ){
+        return aMap[i].pMethods;
+      }
+    }
+  }
+
+  /* Default case. Handles, amongst others, "nfs".
+  ** Test byte-range lock using fcntl(). If the call succeeds, 
+  ** assume that the file-system supports POSIX style locks. 
+  */
+  lockInfo.l_len = 1;
+  lockInfo.l_start = 0;
+  lockInfo.l_whence = SEEK_SET;
+  lockInfo.l_type = F_RDLCK;
+  if( osFcntl(pNew->h, F_GETLK, &lockInfo)!=-1 ) {
+    if( strcmp(fsInfo.f_fstypename, "nfs")==0 ){
+      return &nfsIoMethods;
+    } else {
+      return &posixIoMethods;
+    }
+  }else{
+    return &dotlockIoMethods;
+  }
+}
+static const sqlite3_io_methods 
+  *(*const autolockIoFinder)(const char*,unixFile*) = autolockIoFinderImpl;
+
+#endif /* defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE */
+
+#if OS_VXWORKS && SQLITE_ENABLE_LOCKING_STYLE
+/* 
+** This "finder" function attempts to determine the best locking strategy 
+** for the database file "filePath".  It then returns the sqlite3_io_methods
+** object that implements that strategy.
+**
+** This is for VXWorks only.
+*/
+static const sqlite3_io_methods *autolockIoFinderImpl(
+  const char *filePath,    /* name of the database file */
+  unixFile *pNew           /* the open file object */
+){
+  struct flock lockInfo;
+
+  if( !filePath ){
+    /* If filePath==NULL that means we are dealing with a transient file
+    ** that does not need to be locked. */
+    return &nolockIoMethods;
+  }
+
+  /* Test if fcntl() is supported and use POSIX style locks.
+  ** Otherwise fall back to the named semaphore method.
+  */
+  lockInfo.l_len = 1;
+  lockInfo.l_start = 0;
+  lockInfo.l_whence = SEEK_SET;
+  lockInfo.l_type = F_RDLCK;
+  if( osFcntl(pNew->h, F_GETLK, &lockInfo)!=-1 ) {
+    return &posixIoMethods;
+  }else{
+    return &semIoMethods;
+  }
+}
+static const sqlite3_io_methods 
+  *(*const autolockIoFinder)(const char*,unixFile*) = autolockIoFinderImpl;
+
+#endif /* OS_VXWORKS && SQLITE_ENABLE_LOCKING_STYLE */
+
+/*
+** An abstract type for a pointer to a IO method finder function:
+*/
+typedef const sqlite3_io_methods *(*finder_type)(const char*,unixFile*);
+
+
+/****************************************************************************
+**************************** sqlite3_vfs methods ****************************
+**
+** This division contains the implementation of methods on the
+** sqlite3_vfs object.
+*/
+
+/*
+** Initialize the contents of the unixFile structure pointed to by pId.
+*/
+static int fillInUnixFile(
+  sqlite3_vfs *pVfs,      /* Pointer to vfs object */
+  int h,                  /* Open file descriptor of file being opened */
+  int syncDir,            /* True to sync directory on first sync */
+  sqlite3_file *pId,      /* Write to the unixFile structure here */
+  const char *zFilename,  /* Name of the file being opened */
+  int noLock,             /* Omit locking if true */
+  int isDelete,           /* Delete on close if true */
+  int isReadOnly          /* True if the file is opened read-only */
+){
+  const sqlite3_io_methods *pLockingStyle;
+  unixFile *pNew = (unixFile *)pId;
+  int rc = SQLITE_OK;
+
+  assert( pNew->pInode==NULL );
+
+  /* Parameter isDelete is only used on vxworks. Express this explicitly 
+  ** here to prevent compiler warnings about unused parameters.
+  */
+  UNUSED_PARAMETER(isDelete);
+
+  /* Usually the path zFilename should not be a relative pathname. The
+  ** exception is when opening the proxy "conch" file in builds that
+  ** include the special Apple locking styles.
+  */
+#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
+  assert( zFilename==0 || zFilename[0]=='/' 
+    || pVfs->pAppData==(void*)&autolockIoFinder );
+#else
+  assert( zFilename==0 || zFilename[0]=='/' );
+#endif
+
+  /* No locking occurs in temporary files */
+  assert( zFilename!=0 || noLock );
+
+  OSTRACE(("OPEN    %-3d %s\n", h, zFilename));
+  pNew->h = h;
+  pNew->zPath = zFilename;
+  if( memcmp(pVfs->zName,"unix-excl",10)==0 ){
+    pNew->ctrlFlags = UNIXFILE_EXCL;
+  }else{
+    pNew->ctrlFlags = 0;
+  }
+  if( isReadOnly ){
+    pNew->ctrlFlags |= UNIXFILE_RDONLY;
+  }
+  if( syncDir ){
+    pNew->ctrlFlags |= UNIXFILE_DIRSYNC;
+  }
+
+#if OS_VXWORKS
+  pNew->pId = vxworksFindFileId(zFilename);
+  if( pNew->pId==0 ){
+    noLock = 1;
+    rc = SQLITE_NOMEM;
+  }
+#endif
+
+  if( noLock ){
+    pLockingStyle = &nolockIoMethods;
+  }else{
+    pLockingStyle = (**(finder_type*)pVfs->pAppData)(zFilename, pNew);
+#if SQLITE_ENABLE_LOCKING_STYLE
+    /* Cache zFilename in the locking context (AFP and dotlock override) for
+    ** proxyLock activation is possible (remote proxy is based on db name)
+    ** zFilename remains valid until file is closed, to support */
+    pNew->lockingContext = (void*)zFilename;
+#endif
+  }
+
+  if( pLockingStyle == &posixIoMethods
+#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
+    || pLockingStyle == &nfsIoMethods
+#endif
+  ){
+    unixEnterMutex();
+    rc = findInodeInfo(pNew, &pNew->pInode);
+    if( rc!=SQLITE_OK ){
+      /* If an error occured in findInodeInfo(), close the file descriptor
+      ** immediately, before releasing the mutex. findInodeInfo() may fail
+      ** in two scenarios:
+      **
+      **   (a) A call to fstat() failed.
+      **   (b) A malloc failed.
+      **
+      ** Scenario (b) may only occur if the process is holding no other
+      ** file descriptors open on the same file. If there were other file
+      ** descriptors on this file, then no malloc would be required by
+      ** findInodeInfo(). If this is the case, it is quite safe to close
+      ** handle h - as it is guaranteed that no posix locks will be released
+      ** by doing so.
+      **
+      ** If scenario (a) caused the error then things are not so safe. The
+      ** implicit assumption here is that if fstat() fails, things are in
+      ** such bad shape that dropping a lock or two doesn't matter much.
+      */
+      robust_close(pNew, h, __LINE__);
+      h = -1;
+    }
+    unixLeaveMutex();
+  }
+
+#if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__)
+  else if( pLockingStyle == &afpIoMethods ){
+    /* AFP locking uses the file path so it needs to be included in
+    ** the afpLockingContext.
+    */
+    afpLockingContext *pCtx;
+    pNew->lockingContext = pCtx = sqlite3_malloc( sizeof(*pCtx) );
+    if( pCtx==0 ){
+      rc = SQLITE_NOMEM;
+    }else{
+      /* NB: zFilename exists and remains valid until the file is closed
+      ** according to requirement F11141.  So we do not need to make a
+      ** copy of the filename. */
+      pCtx->dbPath = zFilename;
+      pCtx->reserved = 0;
+      srandomdev();
+      unixEnterMutex();
+      rc = findInodeInfo(pNew, &pNew->pInode);
+      if( rc!=SQLITE_OK ){
+        sqlite3_free(pNew->lockingContext);
+        robust_close(pNew, h, __LINE__);
+        h = -1;
+      }
+      unixLeaveMutex();        
+    }
+  }
+#endif
+
+  else if( pLockingStyle == &dotlockIoMethods ){
+    /* Dotfile locking uses the file path so it needs to be included in
+    ** the dotlockLockingContext 
+    */
+    char *zLockFile;
+    int nFilename;
+    assert( zFilename!=0 );
+    nFilename = (int)strlen(zFilename) + 6;
+    zLockFile = (char *)sqlite3_malloc(nFilename);
+    if( zLockFile==0 ){
+      rc = SQLITE_NOMEM;
+    }else{
+      sqlite3_snprintf(nFilename, zLockFile, "%s" DOTLOCK_SUFFIX, zFilename);
+    }
+    pNew->lockingContext = zLockFile;
+  }
+
+#if OS_VXWORKS
+  else if( pLockingStyle == &semIoMethods ){
+    /* Named semaphore locking uses the file path so it needs to be
+    ** included in the semLockingContext
+    */
+    unixEnterMutex();
+    rc = findInodeInfo(pNew, &pNew->pInode);
+    if( (rc==SQLITE_OK) && (pNew->pInode->pSem==NULL) ){
+      char *zSemName = pNew->pInode->aSemName;
+      int n;
+      sqlite3_snprintf(MAX_PATHNAME, zSemName, "/%s.sem",
+                       pNew->pId->zCanonicalName);
+      for( n=1; zSemName[n]; n++ )
+        if( zSemName[n]=='/' ) zSemName[n] = '_';
+      pNew->pInode->pSem = sem_open(zSemName, O_CREAT, 0666, 1);
+      if( pNew->pInode->pSem == SEM_FAILED ){
+        rc = SQLITE_NOMEM;
+        pNew->pInode->aSemName[0] = '\0';
+      }
+    }
+    unixLeaveMutex();
+  }
+#endif
+  
+  pNew->lastErrno = 0;
+#if OS_VXWORKS
+  if( rc!=SQLITE_OK ){
+    if( h>=0 ) robust_close(pNew, h, __LINE__);
+    h = -1;
+    osUnlink(zFilename);
+    isDelete = 0;
+  }
+  pNew->isDelete = isDelete;
+#endif
+  if( rc!=SQLITE_OK ){
+    if( h>=0 ) robust_close(pNew, h, __LINE__);
+  }else{
+    pNew->pMethod = pLockingStyle;
+    OpenCounter(+1);
+  }
+  return rc;
+}
+
+/*
+** Return the name of a directory in which to put temporary files.
+** If no suitable temporary file directory can be found, return NULL.
+*/
+static const char *unixTempFileDir(void){
+  static const char *azDirs[] = {
+     0,
+     0,
+     "/var/tmp",
+     "/usr/tmp",
+     "/tmp",
+     0        /* List terminator */
+  };
+  unsigned int i;
+  struct stat buf;
+  const char *zDir = 0;
+
+  azDirs[0] = sqlite3_temp_directory;
+  if( !azDirs[1] ) azDirs[1] = getenv("TMPDIR");
+  for(i=0; i<sizeof(azDirs)/sizeof(azDirs[0]); zDir=azDirs[i++]){
+    if( zDir==0 ) continue;
+    if( osStat(zDir, &buf) ) continue;
+    if( !S_ISDIR(buf.st_mode) ) continue;
+    if( osAccess(zDir, 07) ) continue;
+    break;
+  }
+  return zDir;
+}
+
+/*
+** Create a temporary file name in zBuf.  zBuf must be allocated
+** by the calling process and must be big enough to hold at least
+** pVfs->mxPathname bytes.
+*/
+static int unixGetTempname(int nBuf, char *zBuf){
+  static const unsigned char zChars[] =
+    "abcdefghijklmnopqrstuvwxyz"
+    "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+    "0123456789";
+  unsigned int i, j;
+  const char *zDir;
+
+  /* It's odd to simulate an io-error here, but really this is just
+  ** using the io-error infrastructure to test that SQLite handles this
+  ** function failing. 
+  */
+  SimulateIOError( return SQLITE_IOERR );
+
+  zDir = unixTempFileDir();
+  if( zDir==0 ) zDir = ".";
+
+  /* Check that the output buffer is large enough for the temporary file 
+  ** name. If it is not, return SQLITE_ERROR.
+  */
+  if( (strlen(zDir) + strlen(SQLITE_TEMP_FILE_PREFIX) + 17) >= (size_t)nBuf ){
+    return SQLITE_ERROR;
+  }
+
+  do{
+    sqlite3_snprintf(nBuf-17, zBuf, "%s/"SQLITE_TEMP_FILE_PREFIX, zDir);
+    j = (int)strlen(zBuf);
+    sqlite3_randomness(15, &zBuf[j]);
+    for(i=0; i<15; i++, j++){
+      zBuf[j] = (char)zChars[ ((unsigned char)zBuf[j])%(sizeof(zChars)-1) ];
+    }
+    zBuf[j] = 0;
+  }while( osAccess(zBuf,0)==0 );
+  return SQLITE_OK;
+}
+
+#if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__)
+/*
+** Routine to transform a unixFile into a proxy-locking unixFile.
+** Implementation in the proxy-lock division, but used by unixOpen()
+** if SQLITE_PREFER_PROXY_LOCKING is defined.
+*/
+static int proxyTransformUnixFile(unixFile*, const char*);
+#endif
+
+/*
+** Search for an unused file descriptor that was opened on the database 
+** file (not a journal or master-journal file) identified by pathname
+** zPath with SQLITE_OPEN_XXX flags matching those passed as the second
+** argument to this function.
+**
+** Such a file descriptor may exist if a database connection was closed
+** but the associated file descriptor could not be closed because some
+** other file descriptor open on the same file is holding a file-lock.
+** Refer to comments in the unixClose() function and the lengthy comment
+** describing "Posix Advisory Locking" at the start of this file for 
+** further details. Also, ticket #4018.
+**
+** If a suitable file descriptor is found, then it is returned. If no
+** such file descriptor is located, -1 is returned.
+*/
+static UnixUnusedFd *findReusableFd(const char *zPath, int flags){
+  UnixUnusedFd *pUnused = 0;
+
+  /* Do not search for an unused file descriptor on vxworks. Not because
+  ** vxworks would not benefit from the change (it might, we're not sure),
+  ** but because no way to test it is currently available. It is better 
+  ** not to risk breaking vxworks support for the sake of such an obscure 
+  ** feature.  */
+#if !OS_VXWORKS
+  struct stat sStat;                   /* Results of stat() call */
+
+  /* A stat() call may fail for various reasons. If this happens, it is
+  ** almost certain that an open() call on the same path will also fail.
+  ** For this reason, if an error occurs in the stat() call here, it is
+  ** ignored and -1 is returned. The caller will try to open a new file
+  ** descriptor on the same path, fail, and return an error to SQLite.
+  **
+  ** Even if a subsequent open() call does succeed, the consequences of
+  ** not searching for a resusable file descriptor are not dire.  */
+  if( 0==osStat(zPath, &sStat) ){
+    unixInodeInfo *pInode;
+
+    unixEnterMutex();
+    pInode = inodeList;
+    while( pInode && (pInode->fileId.dev!=sStat.st_dev
+                     || pInode->fileId.ino!=sStat.st_ino) ){
+       pInode = pInode->pNext;
+    }
+    if( pInode ){
+      UnixUnusedFd **pp;
+      for(pp=&pInode->pUnused; *pp && (*pp)->flags!=flags; pp=&((*pp)->pNext));
+      pUnused = *pp;
+      if( pUnused ){
+        *pp = pUnused->pNext;
+      }
+    }
+    unixLeaveMutex();
+  }
+#endif    /* if !OS_VXWORKS */
+  return pUnused;
+}
+
+/*
+** This function is called by unixOpen() to determine the unix permissions
+** to create new files with. If no error occurs, then SQLITE_OK is returned
+** and a value suitable for passing as the third argument to open(2) is
+** written to *pMode. If an IO error occurs, an SQLite error code is 
+** returned and the value of *pMode is not modified.
+**
+** If the file being opened is a temporary file, it is always created with
+** the octal permissions 0600 (read/writable by owner only). If the file
+** is a database or master journal file, it is created with the permissions 
+** mask SQLITE_DEFAULT_FILE_PERMISSIONS.
+**
+** Finally, if the file being opened is a WAL or regular journal file, then 
+** this function queries the file-system for the permissions on the 
+** corresponding database file and sets *pMode to this value. Whenever 
+** possible, WAL and journal files are created using the same permissions 
+** as the associated database file.
+**
+** If the SQLITE_ENABLE_8_3_NAMES option is enabled, then the
+** original filename is unavailable.  But 8_3_NAMES is only used for
+** FAT filesystems and permissions do not matter there, so just use
+** the default permissions.
+*/
+static int findCreateFileMode(
+  const char *zPath,              /* Path of file (possibly) being created */
+  int flags,                      /* Flags passed as 4th argument to xOpen() */
+  mode_t *pMode                   /* OUT: Permissions to open file with */
+){
+  int rc = SQLITE_OK;             /* Return Code */
+  *pMode = SQLITE_DEFAULT_FILE_PERMISSIONS;
+  if( flags & (SQLITE_OPEN_WAL|SQLITE_OPEN_MAIN_JOURNAL) ){
+    char zDb[MAX_PATHNAME+1];     /* Database file path */
+    int nDb;                      /* Number of valid bytes in zDb */
+    struct stat sStat;            /* Output of stat() on database file */
+
+    /* zPath is a path to a WAL or journal file. The following block derives
+    ** the path to the associated database file from zPath. This block handles
+    ** the following naming conventions:
+    **
+    **   "<path to db>-journal"
+    **   "<path to db>-wal"
+    **   "<path to db>-journalNN"
+    **   "<path to db>-walNN"
+    **
+    ** where NN is a decimal number. The NN naming schemes are 
+    ** used by the test_multiplex.c module.
+    */
+    nDb = sqlite3Strlen30(zPath) - 1; 
+#ifdef SQLITE_ENABLE_8_3_NAMES
+    while( nDb>0 && !sqlite3Isalnum(zPath[nDb]) ) nDb--;
+    if( nDb==0 || zPath[nDb]!='-' ) return SQLITE_OK;
+#else
+    while( zPath[nDb]!='-' ){
+      assert( nDb>0 );
+      assert( zPath[nDb]!='\n' );
+      nDb--;
+    }
+#endif
+    memcpy(zDb, zPath, nDb);
+    zDb[nDb] = '\0';
+
+    if( 0==osStat(zDb, &sStat) ){
+      *pMode = sStat.st_mode & 0777;
+    }else{
+      rc = SQLITE_IOERR_FSTAT;
+    }
+  }else if( flags & SQLITE_OPEN_DELETEONCLOSE ){
+    *pMode = 0600;
+  }
+  return rc;
+}
+
+/*
+** Open the file zPath.
+** 
+** Previously, the SQLite OS layer used three functions in place of this
+** one:
+**
+**     sqlite3OsOpenReadWrite();
+**     sqlite3OsOpenReadOnly();
+**     sqlite3OsOpenExclusive();
+**
+** These calls correspond to the following combinations of flags:
+**
+**     ReadWrite() ->     (READWRITE | CREATE)
+**     ReadOnly()  ->     (READONLY) 
+**     OpenExclusive() -> (READWRITE | CREATE | EXCLUSIVE)
+**
+** The old OpenExclusive() accepted a boolean argument - "delFlag". If
+** true, the file was configured to be automatically deleted when the
+** file handle closed. To achieve the same effect using this new 
+** interface, add the DELETEONCLOSE flag to those specified above for 
+** OpenExclusive().
+*/
+static int unixOpen(
+  sqlite3_vfs *pVfs,           /* The VFS for which this is the xOpen method */
+  const char *zPath,           /* Pathname of file to be opened */
+  sqlite3_file *pFile,         /* The file descriptor to be filled in */
+  int flags,                   /* Input flags to control the opening */
+  int *pOutFlags               /* Output flags returned to SQLite core */
+){
+  unixFile *p = (unixFile *)pFile;
+  int fd = -1;                   /* File descriptor returned by open() */
+  int openFlags = 0;             /* Flags to pass to open() */
+  int eType = flags&0xFFFFFF00;  /* Type of file to open */
+  int noLock;                    /* True to omit locking primitives */
+  int rc = SQLITE_OK;            /* Function Return Code */
+
+  int isExclusive  = (flags & SQLITE_OPEN_EXCLUSIVE);
+  int isDelete     = (flags & SQLITE_OPEN_DELETEONCLOSE);
+  int isCreate     = (flags & SQLITE_OPEN_CREATE);
+  int isReadonly   = (flags & SQLITE_OPEN_READONLY);
+  int isReadWrite  = (flags & SQLITE_OPEN_READWRITE);
+#if SQLITE_ENABLE_LOCKING_STYLE
+  int isAutoProxy  = (flags & SQLITE_OPEN_AUTOPROXY);
+#endif
+#if defined(__APPLE__) || SQLITE_ENABLE_LOCKING_STYLE
+  struct statfs fsInfo;
+#endif
+
+  /* If creating a master or main-file journal, this function will open
+  ** a file-descriptor on the directory too. The first time unixSync()
+  ** is called the directory file descriptor will be fsync()ed and close()d.
+  */
+  int syncDir = (isCreate && (
+        eType==SQLITE_OPEN_MASTER_JOURNAL 
+     || eType==SQLITE_OPEN_MAIN_JOURNAL 
+     || eType==SQLITE_OPEN_WAL
+  ));
+
+  /* If argument zPath is a NULL pointer, this function is required to open
+  ** a temporary file. Use this buffer to store the file name in.
+  */
+  char zTmpname[MAX_PATHNAME+1];
+  const char *zName = zPath;
+
+  /* Check the following statements are true: 
+  **
+  **   (a) Exactly one of the READWRITE and READONLY flags must be set, and 
+  **   (b) if CREATE is set, then READWRITE must also be set, and
+  **   (c) if EXCLUSIVE is set, then CREATE must also be set.
+  **   (d) if DELETEONCLOSE is set, then CREATE must also be set.
+  */
+  assert((isReadonly==0 || isReadWrite==0) && (isReadWrite || isReadonly));
+  assert(isCreate==0 || isReadWrite);
+  assert(isExclusive==0 || isCreate);
+  assert(isDelete==0 || isCreate);
+
+  /* The main DB, main journal, WAL file and master journal are never 
+  ** automatically deleted. Nor are they ever temporary files.  */
+  assert( (!isDelete && zName) || eType!=SQLITE_OPEN_MAIN_DB );
+  assert( (!isDelete && zName) || eType!=SQLITE_OPEN_MAIN_JOURNAL );
+  assert( (!isDelete && zName) || eType!=SQLITE_OPEN_MASTER_JOURNAL );
+  assert( (!isDelete && zName) || eType!=SQLITE_OPEN_WAL );
+
+  /* Assert that the upper layer has set one of the "file-type" flags. */
+  assert( eType==SQLITE_OPEN_MAIN_DB      || eType==SQLITE_OPEN_TEMP_DB 
+       || eType==SQLITE_OPEN_MAIN_JOURNAL || eType==SQLITE_OPEN_TEMP_JOURNAL 
+       || eType==SQLITE_OPEN_SUBJOURNAL   || eType==SQLITE_OPEN_MASTER_JOURNAL 
+       || eType==SQLITE_OPEN_TRANSIENT_DB || eType==SQLITE_OPEN_WAL
+  );
+
+  memset(p, 0, sizeof(unixFile));
+
+  if( eType==SQLITE_OPEN_MAIN_DB ){
+    UnixUnusedFd *pUnused;
+    pUnused = findReusableFd(zName, flags);
+    if( pUnused ){
+      fd = pUnused->fd;
+    }else{
+      pUnused = sqlite3_malloc(sizeof(*pUnused));
+      if( !pUnused ){
+        return SQLITE_NOMEM;
+      }
+    }
+    p->pUnused = pUnused;
+  }else if( !zName ){
+    /* If zName is NULL, the upper layer is requesting a temp file. */
+    assert(isDelete && !syncDir);
+    rc = unixGetTempname(MAX_PATHNAME+1, zTmpname);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+    zName = zTmpname;
+  }
+
+  /* Determine the value of the flags parameter passed to POSIX function
+  ** open(). These must be calculated even if open() is not called, as
+  ** they may be stored as part of the file handle and used by the 
+  ** 'conch file' locking functions later on.  */
+  if( isReadonly )  openFlags |= O_RDONLY;
+  if( isReadWrite ) openFlags |= O_RDWR;
+  if( isCreate )    openFlags |= O_CREAT;
+  if( isExclusive ) openFlags |= (O_EXCL|O_NOFOLLOW);
+  openFlags |= (O_LARGEFILE|O_BINARY);
+
+  if( fd<0 ){
+    mode_t openMode;              /* Permissions to create file with */
+    rc = findCreateFileMode(zName, flags, &openMode);
+    if( rc!=SQLITE_OK ){
+      assert( !p->pUnused );
+      assert( eType==SQLITE_OPEN_WAL || eType==SQLITE_OPEN_MAIN_JOURNAL );
+      return rc;
+    }
+    fd = robust_open(zName, openFlags, openMode);
+    OSTRACE(("OPENX   %-3d %s 0%o\n", fd, zName, openFlags));
+    if( fd<0 && errno!=EISDIR && isReadWrite && !isExclusive ){
+      /* Failed to open the file for read/write access. Try read-only. */
+      flags &= ~(SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE);
+      openFlags &= ~(O_RDWR|O_CREAT);
+      flags |= SQLITE_OPEN_READONLY;
+      openFlags |= O_RDONLY;
+      isReadonly = 1;
+      fd = robust_open(zName, openFlags, openMode);
+    }
+    if( fd<0 ){
+      rc = unixLogError(SQLITE_CANTOPEN_BKPT, "open", zName);
+      goto open_finished;
+    }
+  }
+  assert( fd>=0 );
+  if( pOutFlags ){
+    *pOutFlags = flags;
+  }
+
+  if( p->pUnused ){
+    p->pUnused->fd = fd;
+    p->pUnused->flags = flags;
+  }
+
+  if( isDelete ){
+#if OS_VXWORKS
+    zPath = zName;
+#else
+    osUnlink(zName);
+#endif
+  }
+#if SQLITE_ENABLE_LOCKING_STYLE
+  else{
+    p->openFlags = openFlags;
+  }
+#endif
+
+#ifdef FD_CLOEXEC
+  osFcntl(fd, F_SETFD, osFcntl(fd, F_GETFD, 0) | FD_CLOEXEC);
+#endif
+
+  noLock = eType!=SQLITE_OPEN_MAIN_DB;
+
+  
+#if defined(__APPLE__) || SQLITE_ENABLE_LOCKING_STYLE
+  if( fstatfs(fd, &fsInfo) == -1 ){
+    ((unixFile*)pFile)->lastErrno = errno;
+    robust_close(p, fd, __LINE__);
+    return SQLITE_IOERR_ACCESS;
+  }
+  if (0 == strncmp("msdos", fsInfo.f_fstypename, 5)) {
+    ((unixFile*)pFile)->fsFlags |= SQLITE_FSFLAGS_IS_MSDOS;
+  }
+#endif
+  
+#if SQLITE_ENABLE_LOCKING_STYLE
+#if SQLITE_PREFER_PROXY_LOCKING
+  isAutoProxy = 1;
+#endif
+  if( isAutoProxy && (zPath!=NULL) && (!noLock) && pVfs->xOpen ){
+    char *envforce = getenv("SQLITE_FORCE_PROXY_LOCKING");
+    int useProxy = 0;
+
+    /* SQLITE_FORCE_PROXY_LOCKING==1 means force always use proxy, 0 means 
+    ** never use proxy, NULL means use proxy for non-local files only.  */
+    if( envforce!=NULL ){
+      useProxy = atoi(envforce)>0;
+    }else{
+      if( statfs(zPath, &fsInfo) == -1 ){
+        /* In theory, the close(fd) call is sub-optimal. If the file opened
+        ** with fd is a database file, and there are other connections open
+        ** on that file that are currently holding advisory locks on it,
+        ** then the call to close() will cancel those locks. In practice,
+        ** we're assuming that statfs() doesn't fail very often. At least
+        ** not while other file descriptors opened by the same process on
+        ** the same file are working.  */
+        p->lastErrno = errno;
+        robust_close(p, fd, __LINE__);
+        rc = SQLITE_IOERR_ACCESS;
+        goto open_finished;
+      }
+      useProxy = !(fsInfo.f_flags&MNT_LOCAL);
+    }
+    if( useProxy ){
+      rc = fillInUnixFile(pVfs, fd, syncDir, pFile, zPath, noLock,
+                          isDelete, isReadonly);
+      if( rc==SQLITE_OK ){
+        rc = proxyTransformUnixFile((unixFile*)pFile, ":auto:");
+        if( rc!=SQLITE_OK ){
+          /* Use unixClose to clean up the resources added in fillInUnixFile 
+          ** and clear all the structure's references.  Specifically, 
+          ** pFile->pMethods will be NULL so sqlite3OsClose will be a no-op 
+          */
+          unixClose(pFile);
+          return rc;
+        }
+      }
+      goto open_finished;
+    }
+  }
+#endif
+  
+  rc = fillInUnixFile(pVfs, fd, syncDir, pFile, zPath, noLock,
+                      isDelete, isReadonly);
+open_finished:
+  if( rc!=SQLITE_OK ){
+    sqlite3_free(p->pUnused);
+  }
+  return rc;
+}
+
+
+/*
+** Delete the file at zPath. If the dirSync argument is true, fsync()
+** the directory after deleting the file.
+*/
+static int unixDelete(
+  sqlite3_vfs *NotUsed,     /* VFS containing this as the xDelete method */
+  const char *zPath,        /* Name of file to be deleted */
+  int dirSync               /* If true, fsync() directory after deleting file */
+){
+  int rc = SQLITE_OK;
+  UNUSED_PARAMETER(NotUsed);
+  SimulateIOError(return SQLITE_IOERR_DELETE);
+  if( osUnlink(zPath)==(-1) && errno!=ENOENT ){
+    return unixLogError(SQLITE_IOERR_DELETE, "unlink", zPath);
+  }
+#ifndef SQLITE_DISABLE_DIRSYNC
+  if( dirSync ){
+    int fd;
+    rc = osOpenDirectory(zPath, &fd);
+    if( rc==SQLITE_OK ){
+#if OS_VXWORKS
+      if( fsync(fd)==-1 )
+#else
+      if( fsync(fd) )
+#endif
+      {
+        rc = unixLogError(SQLITE_IOERR_DIR_FSYNC, "fsync", zPath);
+      }
+      robust_close(0, fd, __LINE__);
+    }else if( rc==SQLITE_CANTOPEN ){
+      rc = SQLITE_OK;
+    }
+  }
+#endif
+  return rc;
+}
+
+/*
+** Test the existance of or access permissions of file zPath. The
+** test performed depends on the value of flags:
+**
+**     SQLITE_ACCESS_EXISTS: Return 1 if the file exists
+**     SQLITE_ACCESS_READWRITE: Return 1 if the file is read and writable.
+**     SQLITE_ACCESS_READONLY: Return 1 if the file is readable.
+**
+** Otherwise return 0.
+*/
+static int unixAccess(
+  sqlite3_vfs *NotUsed,   /* The VFS containing this xAccess method */
+  const char *zPath,      /* Path of the file to examine */
+  int flags,              /* What do we want to learn about the zPath file? */
+  int *pResOut            /* Write result boolean here */
+){
+  int amode = 0;
+  UNUSED_PARAMETER(NotUsed);
+  SimulateIOError( return SQLITE_IOERR_ACCESS; );
+  switch( flags ){
+    case SQLITE_ACCESS_EXISTS:
+      amode = F_OK;
+      break;
+    case SQLITE_ACCESS_READWRITE:
+      amode = W_OK|R_OK;
+      break;
+    case SQLITE_ACCESS_READ:
+      amode = R_OK;
+      break;
+
+    default:
+      assert(!"Invalid flags argument");
+  }
+  *pResOut = (osAccess(zPath, amode)==0);
+  if( flags==SQLITE_ACCESS_EXISTS && *pResOut ){
+    struct stat buf;
+    if( 0==osStat(zPath, &buf) && buf.st_size==0 ){
+      *pResOut = 0;
+    }
+  }
+  return SQLITE_OK;
+}
+
+
+/*
+** Turn a relative pathname into a full pathname. The relative path
+** is stored as a nul-terminated string in the buffer pointed to by
+** zPath. 
+**
+** zOut points to a buffer of at least sqlite3_vfs.mxPathname bytes 
+** (in this case, MAX_PATHNAME bytes). The full-path is written to
+** this buffer before returning.
+*/
+static int unixFullPathname(
+  sqlite3_vfs *pVfs,            /* Pointer to vfs object */
+  const char *zPath,            /* Possibly relative input path */
+  int nOut,                     /* Size of output buffer in bytes */
+  char *zOut                    /* Output buffer */
+){
+
+  /* It's odd to simulate an io-error here, but really this is just
+  ** using the io-error infrastructure to test that SQLite handles this
+  ** function failing. This function could fail if, for example, the
+  ** current working directory has been unlinked.
+  */
+  SimulateIOError( return SQLITE_ERROR );
+
+  assert( pVfs->mxPathname==MAX_PATHNAME );
+  UNUSED_PARAMETER(pVfs);
+
+  zOut[nOut-1] = '\0';
+  if( zPath[0]=='/' ){
+    sqlite3_snprintf(nOut, zOut, "%s", zPath);
+  }else{
+    int nCwd;
+    if( osGetcwd(zOut, nOut-1)==0 ){
+      return unixLogError(SQLITE_CANTOPEN_BKPT, "getcwd", zPath);
+    }
+    nCwd = (int)strlen(zOut);
+    sqlite3_snprintf(nOut-nCwd, &zOut[nCwd], "/%s", zPath);
+  }
+  return SQLITE_OK;
+}
+
+
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+/*
+** Interfaces for opening a shared library, finding entry points
+** within the shared library, and closing the shared library.
+*/
+#include <dlfcn.h>
+static void *unixDlOpen(sqlite3_vfs *NotUsed, const char *zFilename){
+  UNUSED_PARAMETER(NotUsed);
+  return dlopen(zFilename, RTLD_NOW | RTLD_GLOBAL);
+}
+
+/*
+** SQLite calls this function immediately after a call to unixDlSym() or
+** unixDlOpen() fails (returns a null pointer). If a more detailed error
+** message is available, it is written to zBufOut. If no error message
+** is available, zBufOut is left unmodified and SQLite uses a default
+** error message.
+*/
+static void unixDlError(sqlite3_vfs *NotUsed, int nBuf, char *zBufOut){
+  const char *zErr;
+  UNUSED_PARAMETER(NotUsed);
+  unixEnterMutex();
+  zErr = dlerror();
+  if( zErr ){
+    sqlite3_snprintf(nBuf, zBufOut, "%s", zErr);
+  }
+  unixLeaveMutex();
+}
+static void (*unixDlSym(sqlite3_vfs *NotUsed, void *p, const char*zSym))(void){
+  /* 
+  ** GCC with -pedantic-errors says that C90 does not allow a void* to be
+  ** cast into a pointer to a function.  And yet the library dlsym() routine
+  ** returns a void* which is really a pointer to a function.  So how do we
+  ** use dlsym() with -pedantic-errors?
+  **
+  ** Variable x below is defined to be a pointer to a function taking
+  ** parameters void* and const char* and returning a pointer to a function.
+  ** We initialize x by assigning it a pointer to the dlsym() function.
+  ** (That assignment requires a cast.)  Then we call the function that
+  ** x points to.  
+  **
+  ** This work-around is unlikely to work correctly on any system where
+  ** you really cannot cast a function pointer into void*.  But then, on the
+  ** other hand, dlsym() will not work on such a system either, so we have
+  ** not really lost anything.
+  */
+  void (*(*x)(void*,const char*))(void);
+  UNUSED_PARAMETER(NotUsed);
+  x = (void(*(*)(void*,const char*))(void))dlsym;
+  return (*x)(p, zSym);
+}
+static void unixDlClose(sqlite3_vfs *NotUsed, void *pHandle){
+  UNUSED_PARAMETER(NotUsed);
+  dlclose(pHandle);
+}
+#else /* if SQLITE_OMIT_LOAD_EXTENSION is defined: */
+  #define unixDlOpen  0
+  #define unixDlError 0
+  #define unixDlSym   0
+  #define unixDlClose 0
+#endif
+
+/*
+** Write nBuf bytes of random data to the supplied buffer zBuf.
+*/
+static int unixRandomness(sqlite3_vfs *NotUsed, int nBuf, char *zBuf){
+  UNUSED_PARAMETER(NotUsed);
+  assert((size_t)nBuf>=(sizeof(time_t)+sizeof(int)));
+
+  /* We have to initialize zBuf to prevent valgrind from reporting
+  ** errors.  The reports issued by valgrind are incorrect - we would
+  ** prefer that the randomness be increased by making use of the
+  ** uninitialized space in zBuf - but valgrind errors tend to worry
+  ** some users.  Rather than argue, it seems easier just to initialize
+  ** the whole array and silence valgrind, even if that means less randomness
+  ** in the random seed.
+  **
+  ** When testing, initializing zBuf[] to zero is all we do.  That means
+  ** that we always use the same random number sequence.  This makes the
+  ** tests repeatable.
+  */
+  memset(zBuf, 0, nBuf);
+#if !defined(SQLITE_TEST)
+  {
+    int pid, fd;
+    fd = robust_open("/dev/urandom", O_RDONLY, 0);
+    if( fd<0 ){
+      time_t t;
+      time(&t);
+      memcpy(zBuf, &t, sizeof(t));
+      pid = getpid();
+      memcpy(&zBuf[sizeof(t)], &pid, sizeof(pid));
+      assert( sizeof(t)+sizeof(pid)<=(size_t)nBuf );
+      nBuf = sizeof(t) + sizeof(pid);
+    }else{
+      do{ nBuf = osRead(fd, zBuf, nBuf); }while( nBuf<0 && errno==EINTR );
+      robust_close(0, fd, __LINE__);
+    }
+  }
+#endif
+  return nBuf;
+}
+
+
+/*
+** Sleep for a little while.  Return the amount of time slept.
+** The argument is the number of microseconds we want to sleep.
+** The return value is the number of microseconds of sleep actually
+** requested from the underlying operating system, a number which
+** might be greater than or equal to the argument, but not less
+** than the argument.
+*/
+static int unixSleep(sqlite3_vfs *NotUsed, int microseconds){
+#if OS_VXWORKS
+  struct timespec sp;
+
+  sp.tv_sec = microseconds / 1000000;
+  sp.tv_nsec = (microseconds % 1000000) * 1000;
+  nanosleep(&sp, NULL);
+  UNUSED_PARAMETER(NotUsed);
+  return microseconds;
+#elif defined(HAVE_USLEEP) && HAVE_USLEEP
+  usleep(microseconds);
+  UNUSED_PARAMETER(NotUsed);
+  return microseconds;
+#else
+  int seconds = (microseconds+999999)/1000000;
+  sleep(seconds);
+  UNUSED_PARAMETER(NotUsed);
+  return seconds*1000000;
+#endif
+}
+
+/*
+** The following variable, if set to a non-zero value, is interpreted as
+** the number of seconds since 1970 and is used to set the result of
+** sqlite3OsCurrentTime() during testing.
+*/
+#ifdef SQLITE_TEST
+int sqlite3_current_time = 0;  /* Fake system time in seconds since 1970. */
+#endif
+
+/*
+** Find the current time (in Universal Coordinated Time).  Write into *piNow
+** the current time and date as a Julian Day number times 86_400_000.  In
+** other words, write into *piNow the number of milliseconds since the Julian
+** epoch of noon in Greenwich on November 24, 4714 B.C according to the
+** proleptic Gregorian calendar.
+**
+** On success, return SQLITE_OK.  Return SQLITE_ERROR if the time and date 
+** cannot be found.
+*/
+static int unixCurrentTimeInt64(sqlite3_vfs *NotUsed, sqlite3_int64 *piNow){
+  static const sqlite3_int64 unixEpoch = 24405875*(sqlite3_int64)8640000;
+  int rc = SQLITE_OK;
+#if defined(NO_GETTOD)
+  time_t t;
+  time(&t);
+  *piNow = ((sqlite3_int64)t)*1000 + unixEpoch;
+#elif OS_VXWORKS
+  struct timespec sNow;
+  clock_gettime(CLOCK_REALTIME, &sNow);
+  *piNow = unixEpoch + 1000*(sqlite3_int64)sNow.tv_sec + sNow.tv_nsec/1000000;
+#else
+  struct timeval sNow;
+  if( gettimeofday(&sNow, 0)==0 ){
+    *piNow = unixEpoch + 1000*(sqlite3_int64)sNow.tv_sec + sNow.tv_usec/1000;
+  }else{
+    rc = SQLITE_ERROR;
+  }
+#endif
+
+#ifdef SQLITE_TEST
+  if( sqlite3_current_time ){
+    *piNow = 1000*(sqlite3_int64)sqlite3_current_time + unixEpoch;
+  }
+#endif
+  UNUSED_PARAMETER(NotUsed);
+  return rc;
+}
+
+/*
+** Find the current time (in Universal Coordinated Time).  Write the
+** current time and date as a Julian Day number into *prNow and
+** return 0.  Return 1 if the time and date cannot be found.
+*/
+static int unixCurrentTime(sqlite3_vfs *NotUsed, double *prNow){
+  sqlite3_int64 i = 0;
+  int rc;
+  UNUSED_PARAMETER(NotUsed);
+  rc = unixCurrentTimeInt64(0, &i);
+  *prNow = i/86400000.0;
+  return rc;
+}
+
+/*
+** We added the xGetLastError() method with the intention of providing
+** better low-level error messages when operating-system problems come up
+** during SQLite operation.  But so far, none of that has been implemented
+** in the core.  So this routine is never called.  For now, it is merely
+** a place-holder.
+*/
+static int unixGetLastError(sqlite3_vfs *NotUsed, int NotUsed2, char *NotUsed3){
+  UNUSED_PARAMETER(NotUsed);
+  UNUSED_PARAMETER(NotUsed2);
+  UNUSED_PARAMETER(NotUsed3);
+  return 0;
+}
+
+
+/*
+************************ End of sqlite3_vfs methods ***************************
+******************************************************************************/
+
+/******************************************************************************
+************************** Begin Proxy Locking ********************************
+**
+** Proxy locking is a "uber-locking-method" in this sense:  It uses the
+** other locking methods on secondary lock files.  Proxy locking is a
+** meta-layer over top of the primitive locking implemented above.  For
+** this reason, the division that implements of proxy locking is deferred
+** until late in the file (here) after all of the other I/O methods have
+** been defined - so that the primitive locking methods are available
+** as services to help with the implementation of proxy locking.
+**
+****
+**
+** The default locking schemes in SQLite use byte-range locks on the
+** database file to coordinate safe, concurrent access by multiple readers
+** and writers [http://sqlite.org/lockingv3.html].  The five file locking
+** states (UNLOCKED, PENDING, SHARED, RESERVED, EXCLUSIVE) are implemented
+** as POSIX read & write locks over fixed set of locations (via fsctl),
+** on AFP and SMB only exclusive byte-range locks are available via fsctl
+** with _IOWR('z', 23, struct ByteRangeLockPB2) to track the same 5 states.
+** To simulate a F_RDLCK on the shared range, on AFP a randomly selected
+** address in the shared range is taken for a SHARED lock, the entire
+** shared range is taken for an EXCLUSIVE lock):
+**
+**      PENDING_BYTE        0x40000000		   	
+**      RESERVED_BYTE       0x40000001
+**      SHARED_RANGE        0x40000002 -> 0x40000200
+**
+** This works well on the local file system, but shows a nearly 100x
+** slowdown in read performance on AFP because the AFP client disables
+** the read cache when byte-range locks are present.  Enabling the read
+** cache exposes a cache coherency problem that is present on all OS X
+** supported network file systems.  NFS and AFP both observe the
+** close-to-open semantics for ensuring cache coherency
+** [http://nfs.sourceforge.net/#faq_a8], which does not effectively
+** address the requirements for concurrent database access by multiple
+** readers and writers
+** [http://www.nabble.com/SQLite-on-NFS-cache-coherency-td15655701.html].
+**
+** To address the performance and cache coherency issues, proxy file locking
+** changes the way database access is controlled by limiting access to a
+** single host at a time and moving file locks off of the database file
+** and onto a proxy file on the local file system.  
+**
+**
+** Using proxy locks
+** -----------------
+**
+** C APIs
+**
+**  sqlite3_file_control(db, dbname, SQLITE_SET_LOCKPROXYFILE,
+**                       <proxy_path> | ":auto:");
+**  sqlite3_file_control(db, dbname, SQLITE_GET_LOCKPROXYFILE, &<proxy_path>);
+**
+**
+** SQL pragmas
+**
+**  PRAGMA [database.]lock_proxy_file=<proxy_path> | :auto:
+**  PRAGMA [database.]lock_proxy_file
+**
+** Specifying ":auto:" means that if there is a conch file with a matching
+** host ID in it, the proxy path in the conch file will be used, otherwise
+** a proxy path based on the user's temp dir
+** (via confstr(_CS_DARWIN_USER_TEMP_DIR,...)) will be used and the
+** actual proxy file name is generated from the name and path of the
+** database file.  For example:
+**
+**       For database path "/Users/me/foo.db" 
+**       The lock path will be "<tmpdir>/sqliteplocks/_Users_me_foo.db:auto:")
+**
+** Once a lock proxy is configured for a database connection, it can not
+** be removed, however it may be switched to a different proxy path via
+** the above APIs (assuming the conch file is not being held by another
+** connection or process). 
+**
+**
+** How proxy locking works
+** -----------------------
+**
+** Proxy file locking relies primarily on two new supporting files: 
+**
+**   *  conch file to limit access to the database file to a single host
+**      at a time
+**
+**   *  proxy file to act as a proxy for the advisory locks normally
+**      taken on the database
+**
+** The conch file - to use a proxy file, sqlite must first "hold the conch"
+** by taking an sqlite-style shared lock on the conch file, reading the
+** contents and comparing the host's unique host ID (see below) and lock
+** proxy path against the values stored in the conch.  The conch file is
+** stored in the same directory as the database file and the file name
+** is patterned after the database file name as ".<databasename>-conch".
+** If the conch file does not exist, or it's contents do not match the
+** host ID and/or proxy path, then the lock is escalated to an exclusive
+** lock and the conch file contents is updated with the host ID and proxy
+** path and the lock is downgraded to a shared lock again.  If the conch
+** is held by another process (with a shared lock), the exclusive lock
+** will fail and SQLITE_BUSY is returned.
+**
+** The proxy file - a single-byte file used for all advisory file locks
+** normally taken on the database file.   This allows for safe sharing
+** of the database file for multiple readers and writers on the same
+** host (the conch ensures that they all use the same local lock file).
+**
+** Requesting the lock proxy does not immediately take the conch, it is
+** only taken when the first request to lock database file is made.  
+** This matches the semantics of the traditional locking behavior, where
+** opening a connection to a database file does not take a lock on it.
+** The shared lock and an open file descriptor are maintained until 
+** the connection to the database is closed. 
+**
+** The proxy file and the lock file are never deleted so they only need
+** to be created the first time they are used.
+**
+** Configuration options
+** ---------------------
+**
+**  SQLITE_PREFER_PROXY_LOCKING
+**
+**       Database files accessed on non-local file systems are
+**       automatically configured for proxy locking, lock files are
+**       named automatically using the same logic as
+**       PRAGMA lock_proxy_file=":auto:"
+**    
+**  SQLITE_PROXY_DEBUG
+**
+**       Enables the logging of error messages during host id file
+**       retrieval and creation
+**
+**  LOCKPROXYDIR
+**
+**       Overrides the default directory used for lock proxy files that
+**       are named automatically via the ":auto:" setting
+**
+**  SQLITE_DEFAULT_PROXYDIR_PERMISSIONS
+**
+**       Permissions to use when creating a directory for storing the
+**       lock proxy files, only used when LOCKPROXYDIR is not set.
+**    
+**    
+** As mentioned above, when compiled with SQLITE_PREFER_PROXY_LOCKING,
+** setting the environment variable SQLITE_FORCE_PROXY_LOCKING to 1 will
+** force proxy locking to be used for every database file opened, and 0
+** will force automatic proxy locking to be disabled for all database
+** files (explicity calling the SQLITE_SET_LOCKPROXYFILE pragma or
+** sqlite_file_control API is not affected by SQLITE_FORCE_PROXY_LOCKING).
+*/
+
+/*
+** Proxy locking is only available on MacOSX 
+*/
+#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
+
+/*
+** The proxyLockingContext has the path and file structures for the remote 
+** and local proxy files in it
+*/
+typedef struct proxyLockingContext proxyLockingContext;
+struct proxyLockingContext {
+  unixFile *conchFile;         /* Open conch file */
+  char *conchFilePath;         /* Name of the conch file */
+  unixFile *lockProxy;         /* Open proxy lock file */
+  char *lockProxyPath;         /* Name of the proxy lock file */
+  char *dbPath;                /* Name of the open file */
+  int conchHeld;               /* 1 if the conch is held, -1 if lockless */
+  void *oldLockingContext;     /* Original lockingcontext to restore on close */
+  sqlite3_io_methods const *pOldMethod;     /* Original I/O methods for close */
+};
+
+/* 
+** The proxy lock file path for the database at dbPath is written into lPath, 
+** which must point to valid, writable memory large enough for a maxLen length
+** file path. 
+*/
+static int proxyGetLockPath(const char *dbPath, char *lPath, size_t maxLen){
+  int len;
+  int dbLen;
+  int i;
+
+#ifdef LOCKPROXYDIR
+  len = strlcpy(lPath, LOCKPROXYDIR, maxLen);
+#else
+# ifdef _CS_DARWIN_USER_TEMP_DIR
+  {
+    if( !confstr(_CS_DARWIN_USER_TEMP_DIR, lPath, maxLen) ){
+      OSTRACE(("GETLOCKPATH  failed %s errno=%d pid=%d\n",
+               lPath, errno, getpid()));
+      return SQLITE_IOERR_LOCK;
+    }
+    len = strlcat(lPath, "sqliteplocks", maxLen);    
+  }
+# else
+  len = strlcpy(lPath, "/tmp/", maxLen);
+# endif
+#endif
+
+  if( lPath[len-1]!='/' ){
+    len = strlcat(lPath, "/", maxLen);
+  }
+  
+  /* transform the db path to a unique cache name */
+  dbLen = (int)strlen(dbPath);
+  for( i=0; i<dbLen && (i+len+7)<(int)maxLen; i++){
+    char c = dbPath[i];
+    lPath[i+len] = (c=='/')?'_':c;
+  }
+  lPath[i+len]='\0';
+  strlcat(lPath, ":auto:", maxLen);
+  OSTRACE(("GETLOCKPATH  proxy lock path=%s pid=%d\n", lPath, getpid()));
+  return SQLITE_OK;
+}
+
+/* 
+ ** Creates the lock file and any missing directories in lockPath
+ */
+static int proxyCreateLockPath(const char *lockPath){
+  int i, len;
+  char buf[MAXPATHLEN];
+  int start = 0;
+  
+  assert(lockPath!=NULL);
+  /* try to create all the intermediate directories */
+  len = (int)strlen(lockPath);
+  buf[0] = lockPath[0];
+  for( i=1; i<len; i++ ){
+    if( lockPath[i] == '/' && (i - start > 0) ){
+      /* only mkdir if leaf dir != "." or "/" or ".." */
+      if( i-start>2 || (i-start==1 && buf[start] != '.' && buf[start] != '/') 
+         || (i-start==2 && buf[start] != '.' && buf[start+1] != '.') ){
+        buf[i]='\0';
+        if( mkdir(buf, SQLITE_DEFAULT_PROXYDIR_PERMISSIONS) ){
+          int err=errno;
+          if( err!=EEXIST ) {
+            OSTRACE(("CREATELOCKPATH  FAILED creating %s, "
+                     "'%s' proxy lock path=%s pid=%d\n",
+                     buf, strerror(err), lockPath, getpid()));
+            return err;
+          }
+        }
+      }
+      start=i+1;
+    }
+    buf[i] = lockPath[i];
+  }
+  OSTRACE(("CREATELOCKPATH  proxy lock path=%s pid=%d\n", lockPath, getpid()));
+  return 0;
+}
+
+/*
+** Create a new VFS file descriptor (stored in memory obtained from
+** sqlite3_malloc) and open the file named "path" in the file descriptor.
+**
+** The caller is responsible not only for closing the file descriptor
+** but also for freeing the memory associated with the file descriptor.
+*/
+static int proxyCreateUnixFile(
+    const char *path,        /* path for the new unixFile */
+    unixFile **ppFile,       /* unixFile created and returned by ref */
+    int islockfile           /* if non zero missing dirs will be created */
+) {
+  int fd = -1;
+  unixFile *pNew;
+  int rc = SQLITE_OK;
+  int openFlags = O_RDWR | O_CREAT;
+  sqlite3_vfs dummyVfs;
+  int terrno = 0;
+  UnixUnusedFd *pUnused = NULL;
+
+  /* 1. first try to open/create the file
+  ** 2. if that fails, and this is a lock file (not-conch), try creating
+  ** the parent directories and then try again.
+  ** 3. if that fails, try to open the file read-only
+  ** otherwise return BUSY (if lock file) or CANTOPEN for the conch file
+  */
+  pUnused = findReusableFd(path, openFlags);
+  if( pUnused ){
+    fd = pUnused->fd;
+  }else{
+    pUnused = sqlite3_malloc(sizeof(*pUnused));
+    if( !pUnused ){
+      return SQLITE_NOMEM;
+    }
+  }
+  if( fd<0 ){
+    fd = robust_open(path, openFlags, SQLITE_DEFAULT_FILE_PERMISSIONS);
+    terrno = errno;
+    if( fd<0 && errno==ENOENT && islockfile ){
+      if( proxyCreateLockPath(path) == SQLITE_OK ){
+        fd = robust_open(path, openFlags, SQLITE_DEFAULT_FILE_PERMISSIONS);
+      }
+    }
+  }
+  if( fd<0 ){
+    openFlags = O_RDONLY;
+    fd = robust_open(path, openFlags, SQLITE_DEFAULT_FILE_PERMISSIONS);
+    terrno = errno;
+  }
+  if( fd<0 ){
+    if( islockfile ){
+      return SQLITE_BUSY;
+    }
+    switch (terrno) {
+      case EACCES:
+        return SQLITE_PERM;
+      case EIO: 
+        return SQLITE_IOERR_LOCK; /* even though it is the conch */
+      default:
+        return SQLITE_CANTOPEN_BKPT;
+    }
+  }
+  
+  pNew = (unixFile *)sqlite3_malloc(sizeof(*pNew));
+  if( pNew==NULL ){
+    rc = SQLITE_NOMEM;
+    goto end_create_proxy;
+  }
+  memset(pNew, 0, sizeof(unixFile));
+  pNew->openFlags = openFlags;
+  memset(&dummyVfs, 0, sizeof(dummyVfs));
+  dummyVfs.pAppData = (void*)&autolockIoFinder;
+  dummyVfs.zName = "dummy";
+  pUnused->fd = fd;
+  pUnused->flags = openFlags;
+  pNew->pUnused = pUnused;
+  
+  rc = fillInUnixFile(&dummyVfs, fd, 0, (sqlite3_file*)pNew, path, 0, 0, 0);
+  if( rc==SQLITE_OK ){
+    *ppFile = pNew;
+    return SQLITE_OK;
+  }
+end_create_proxy:    
+  robust_close(pNew, fd, __LINE__);
+  sqlite3_free(pNew);
+  sqlite3_free(pUnused);
+  return rc;
+}
+
+#ifdef SQLITE_TEST
+/* simulate multiple hosts by creating unique hostid file paths */
+int sqlite3_hostid_num = 0;
+#endif
+
+#define PROXY_HOSTIDLEN    16  /* conch file host id length */
+
+/* Not always defined in the headers as it ought to be */
+extern int gethostuuid(uuid_t id, const struct timespec *wait);
+
+/* get the host ID via gethostuuid(), pHostID must point to PROXY_HOSTIDLEN 
+** bytes of writable memory.
+*/
+static int proxyGetHostID(unsigned char *pHostID, int *pError){
+  assert(PROXY_HOSTIDLEN == sizeof(uuid_t));
+  memset(pHostID, 0, PROXY_HOSTIDLEN);
+#if defined(__MAX_OS_X_VERSION_MIN_REQUIRED)\
+               && __MAC_OS_X_VERSION_MIN_REQUIRED<1050
+  {
+    static const struct timespec timeout = {1, 0}; /* 1 sec timeout */
+    if( gethostuuid(pHostID, &timeout) ){
+      int err = errno;
+      if( pError ){
+        *pError = err;
+      }
+      return SQLITE_IOERR;
+    }
+  }
+#else
+  UNUSED_PARAMETER(pError);
+#endif
+#ifdef SQLITE_TEST
+  /* simulate multiple hosts by creating unique hostid file paths */
+  if( sqlite3_hostid_num != 0){
+    pHostID[0] = (char)(pHostID[0] + (char)(sqlite3_hostid_num & 0xFF));
+  }
+#endif
+  
+  return SQLITE_OK;
+}
+
+/* The conch file contains the header, host id and lock file path
+ */
+#define PROXY_CONCHVERSION 2   /* 1-byte header, 16-byte host id, path */
+#define PROXY_HEADERLEN    1   /* conch file header length */
+#define PROXY_PATHINDEX    (PROXY_HEADERLEN+PROXY_HOSTIDLEN)
+#define PROXY_MAXCONCHLEN  (PROXY_HEADERLEN+PROXY_HOSTIDLEN+MAXPATHLEN)
+
+/* 
+** Takes an open conch file, copies the contents to a new path and then moves 
+** it back.  The newly created file's file descriptor is assigned to the
+** conch file structure and finally the original conch file descriptor is 
+** closed.  Returns zero if successful.
+*/
+static int proxyBreakConchLock(unixFile *pFile, uuid_t myHostID){
+  proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext; 
+  unixFile *conchFile = pCtx->conchFile;
+  char tPath[MAXPATHLEN];
+  char buf[PROXY_MAXCONCHLEN];
+  char *cPath = pCtx->conchFilePath;
+  size_t readLen = 0;
+  size_t pathLen = 0;
+  char errmsg[64] = "";
+  int fd = -1;
+  int rc = -1;
+  UNUSED_PARAMETER(myHostID);
+
+  /* create a new path by replace the trailing '-conch' with '-break' */
+  pathLen = strlcpy(tPath, cPath, MAXPATHLEN);
+  if( pathLen>MAXPATHLEN || pathLen<6 || 
+     (strlcpy(&tPath[pathLen-5], "break", 6) != 5) ){
+    sqlite3_snprintf(sizeof(errmsg),errmsg,"path error (len %d)",(int)pathLen);
+    goto end_breaklock;
+  }
+  /* read the conch content */
+  readLen = osPread(conchFile->h, buf, PROXY_MAXCONCHLEN, 0);
+  if( readLen<PROXY_PATHINDEX ){
+    sqlite3_snprintf(sizeof(errmsg),errmsg,"read error (len %d)",(int)readLen);
+    goto end_breaklock;
+  }
+  /* write it out to the temporary break file */
+  fd = robust_open(tPath, (O_RDWR|O_CREAT|O_EXCL),
+                   SQLITE_DEFAULT_FILE_PERMISSIONS);
+  if( fd<0 ){
+    sqlite3_snprintf(sizeof(errmsg), errmsg, "create failed (%d)", errno);
+    goto end_breaklock;
+  }
+  if( osPwrite(fd, buf, readLen, 0) != (ssize_t)readLen ){
+    sqlite3_snprintf(sizeof(errmsg), errmsg, "write failed (%d)", errno);
+    goto end_breaklock;
+  }
+  if( rename(tPath, cPath) ){
+    sqlite3_snprintf(sizeof(errmsg), errmsg, "rename failed (%d)", errno);
+    goto end_breaklock;
+  }
+  rc = 0;
+  fprintf(stderr, "broke stale lock on %s\n", cPath);
+  robust_close(pFile, conchFile->h, __LINE__);
+  conchFile->h = fd;
+  conchFile->openFlags = O_RDWR | O_CREAT;
+
+end_breaklock:
+  if( rc ){
+    if( fd>=0 ){
+      osUnlink(tPath);
+      robust_close(pFile, fd, __LINE__);
+    }
+    fprintf(stderr, "failed to break stale lock on %s, %s\n", cPath, errmsg);
+  }
+  return rc;
+}
+
+/* Take the requested lock on the conch file and break a stale lock if the 
+** host id matches.
+*/
+static int proxyConchLock(unixFile *pFile, uuid_t myHostID, int lockType){
+  proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext; 
+  unixFile *conchFile = pCtx->conchFile;
+  int rc = SQLITE_OK;
+  int nTries = 0;
+  struct timespec conchModTime;
+  
+  memset(&conchModTime, 0, sizeof(conchModTime));
+  do {
+    rc = conchFile->pMethod->xLock((sqlite3_file*)conchFile, lockType);
+    nTries ++;
+    if( rc==SQLITE_BUSY ){
+      /* If the lock failed (busy):
+       * 1st try: get the mod time of the conch, wait 0.5s and try again. 
+       * 2nd try: fail if the mod time changed or host id is different, wait 
+       *           10 sec and try again
+       * 3rd try: break the lock unless the mod time has changed.
+       */
+      struct stat buf;
+      if( osFstat(conchFile->h, &buf) ){
+        pFile->lastErrno = errno;
+        return SQLITE_IOERR_LOCK;
+      }
+      
+      if( nTries==1 ){
+        conchModTime = buf.st_mtimespec;
+        usleep(500000); /* wait 0.5 sec and try the lock again*/
+        continue;  
+      }
+
+      assert( nTries>1 );
+      if( conchModTime.tv_sec != buf.st_mtimespec.tv_sec || 
+         conchModTime.tv_nsec != buf.st_mtimespec.tv_nsec ){
+        return SQLITE_BUSY;
+      }
+      
+      if( nTries==2 ){  
+        char tBuf[PROXY_MAXCONCHLEN];
+        int len = osPread(conchFile->h, tBuf, PROXY_MAXCONCHLEN, 0);
+        if( len<0 ){
+          pFile->lastErrno = errno;
+          return SQLITE_IOERR_LOCK;
+        }
+        if( len>PROXY_PATHINDEX && tBuf[0]==(char)PROXY_CONCHVERSION){
+          /* don't break the lock if the host id doesn't match */
+          if( 0!=memcmp(&tBuf[PROXY_HEADERLEN], myHostID, PROXY_HOSTIDLEN) ){
+            return SQLITE_BUSY;
+          }
+        }else{
+          /* don't break the lock on short read or a version mismatch */
+          return SQLITE_BUSY;
+        }
+        usleep(10000000); /* wait 10 sec and try the lock again */
+        continue; 
+      }
+      
+      assert( nTries==3 );
+      if( 0==proxyBreakConchLock(pFile, myHostID) ){
+        rc = SQLITE_OK;
+        if( lockType==EXCLUSIVE_LOCK ){
+          rc = conchFile->pMethod->xLock((sqlite3_file*)conchFile, SHARED_LOCK);          
+        }
+        if( !rc ){
+          rc = conchFile->pMethod->xLock((sqlite3_file*)conchFile, lockType);
+        }
+      }
+    }
+  } while( rc==SQLITE_BUSY && nTries<3 );
+  
+  return rc;
+}
+
+/* Takes the conch by taking a shared lock and read the contents conch, if 
+** lockPath is non-NULL, the host ID and lock file path must match.  A NULL 
+** lockPath means that the lockPath in the conch file will be used if the 
+** host IDs match, or a new lock path will be generated automatically 
+** and written to the conch file.
+*/
+static int proxyTakeConch(unixFile *pFile){
+  proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext; 
+  
+  if( pCtx->conchHeld!=0 ){
+    return SQLITE_OK;
+  }else{
+    unixFile *conchFile = pCtx->conchFile;
+    uuid_t myHostID;
+    int pError = 0;
+    char readBuf[PROXY_MAXCONCHLEN];
+    char lockPath[MAXPATHLEN];
+    char *tempLockPath = NULL;
+    int rc = SQLITE_OK;
+    int createConch = 0;
+    int hostIdMatch = 0;
+    int readLen = 0;
+    int tryOldLockPath = 0;
+    int forceNewLockPath = 0;
+    
+    OSTRACE(("TAKECONCH  %d for %s pid=%d\n", conchFile->h,
+             (pCtx->lockProxyPath ? pCtx->lockProxyPath : ":auto:"), getpid()));
+
+    rc = proxyGetHostID(myHostID, &pError);
+    if( (rc&0xff)==SQLITE_IOERR ){
+      pFile->lastErrno = pError;
+      goto end_takeconch;
+    }
+    rc = proxyConchLock(pFile, myHostID, SHARED_LOCK);
+    if( rc!=SQLITE_OK ){
+      goto end_takeconch;
+    }
+    /* read the existing conch file */
+    readLen = seekAndRead((unixFile*)conchFile, 0, readBuf, PROXY_MAXCONCHLEN);
+    if( readLen<0 ){
+      /* I/O error: lastErrno set by seekAndRead */
+      pFile->lastErrno = conchFile->lastErrno;
+      rc = SQLITE_IOERR_READ;
+      goto end_takeconch;
+    }else if( readLen<=(PROXY_HEADERLEN+PROXY_HOSTIDLEN) || 
+             readBuf[0]!=(char)PROXY_CONCHVERSION ){
+      /* a short read or version format mismatch means we need to create a new 
+      ** conch file. 
+      */
+      createConch = 1;
+    }
+    /* if the host id matches and the lock path already exists in the conch
+    ** we'll try to use the path there, if we can't open that path, we'll 
+    ** retry with a new auto-generated path 
+    */
+    do { /* in case we need to try again for an :auto: named lock file */
+
+      if( !createConch && !forceNewLockPath ){
+        hostIdMatch = !memcmp(&readBuf[PROXY_HEADERLEN], myHostID, 
+                                  PROXY_HOSTIDLEN);
+        /* if the conch has data compare the contents */
+        if( !pCtx->lockProxyPath ){
+          /* for auto-named local lock file, just check the host ID and we'll
+           ** use the local lock file path that's already in there
+           */
+          if( hostIdMatch ){
+            size_t pathLen = (readLen - PROXY_PATHINDEX);
+            
+            if( pathLen>=MAXPATHLEN ){
+              pathLen=MAXPATHLEN-1;
+            }
+            memcpy(lockPath, &readBuf[PROXY_PATHINDEX], pathLen);
+            lockPath[pathLen] = 0;
+            tempLockPath = lockPath;
+            tryOldLockPath = 1;
+            /* create a copy of the lock path if the conch is taken */
+            goto end_takeconch;
+          }
+        }else if( hostIdMatch
+               && !strncmp(pCtx->lockProxyPath, &readBuf[PROXY_PATHINDEX],
+                           readLen-PROXY_PATHINDEX)
+        ){
+          /* conch host and lock path match */
+          goto end_takeconch; 
+        }
+      }
+      
+      /* if the conch isn't writable and doesn't match, we can't take it */
+      if( (conchFile->openFlags&O_RDWR) == 0 ){
+        rc = SQLITE_BUSY;
+        goto end_takeconch;
+      }
+      
+      /* either the conch didn't match or we need to create a new one */
+      if( !pCtx->lockProxyPath ){
+        proxyGetLockPath(pCtx->dbPath, lockPath, MAXPATHLEN);
+        tempLockPath = lockPath;
+        /* create a copy of the lock path _only_ if the conch is taken */
+      }
+      
+      /* update conch with host and path (this will fail if other process
+      ** has a shared lock already), if the host id matches, use the big
+      ** stick.
+      */
+      futimes(conchFile->h, NULL);
+      if( hostIdMatch && !createConch ){
+        if( conchFile->pInode && conchFile->pInode->nShared>1 ){
+          /* We are trying for an exclusive lock but another thread in this
+           ** same process is still holding a shared lock. */
+          rc = SQLITE_BUSY;
+        } else {          
+          rc = proxyConchLock(pFile, myHostID, EXCLUSIVE_LOCK);
+        }
+      }else{
+        rc = conchFile->pMethod->xLock((sqlite3_file*)conchFile, EXCLUSIVE_LOCK);
+      }
+      if( rc==SQLITE_OK ){
+        char writeBuffer[PROXY_MAXCONCHLEN];
+        int writeSize = 0;
+        
+        writeBuffer[0] = (char)PROXY_CONCHVERSION;
+        memcpy(&writeBuffer[PROXY_HEADERLEN], myHostID, PROXY_HOSTIDLEN);
+        if( pCtx->lockProxyPath!=NULL ){
+          strlcpy(&writeBuffer[PROXY_PATHINDEX], pCtx->lockProxyPath, MAXPATHLEN);
+        }else{
+          strlcpy(&writeBuffer[PROXY_PATHINDEX], tempLockPath, MAXPATHLEN);
+        }
+        writeSize = PROXY_PATHINDEX + strlen(&writeBuffer[PROXY_PATHINDEX]);
+        robust_ftruncate(conchFile->h, writeSize);
+        rc = unixWrite((sqlite3_file *)conchFile, writeBuffer, writeSize, 0);
+        fsync(conchFile->h);
+        /* If we created a new conch file (not just updated the contents of a 
+         ** valid conch file), try to match the permissions of the database 
+         */
+        if( rc==SQLITE_OK && createConch ){
+          struct stat buf;
+          int err = osFstat(pFile->h, &buf);
+          if( err==0 ){
+            mode_t cmode = buf.st_mode&(S_IRUSR|S_IWUSR | S_IRGRP|S_IWGRP |
+                                        S_IROTH|S_IWOTH);
+            /* try to match the database file R/W permissions, ignore failure */
+#ifndef SQLITE_PROXY_DEBUG
+            osFchmod(conchFile->h, cmode);
+#else
+            do{
+              rc = osFchmod(conchFile->h, cmode);
+            }while( rc==(-1) && errno==EINTR );
+            if( rc!=0 ){
+              int code = errno;
+              fprintf(stderr, "fchmod %o FAILED with %d %s\n",
+                      cmode, code, strerror(code));
+            } else {
+              fprintf(stderr, "fchmod %o SUCCEDED\n",cmode);
+            }
+          }else{
+            int code = errno;
+            fprintf(stderr, "STAT FAILED[%d] with %d %s\n", 
+                    err, code, strerror(code));
+#endif
+          }
+        }
+      }
+      conchFile->pMethod->xUnlock((sqlite3_file*)conchFile, SHARED_LOCK);
+      
+    end_takeconch:
+      OSTRACE(("TRANSPROXY: CLOSE  %d\n", pFile->h));
+      if( rc==SQLITE_OK && pFile->openFlags ){
+        int fd;
+        if( pFile->h>=0 ){
+          robust_close(pFile, pFile->h, __LINE__);
+        }
+        pFile->h = -1;
+        fd = robust_open(pCtx->dbPath, pFile->openFlags,
+                      SQLITE_DEFAULT_FILE_PERMISSIONS);
+        OSTRACE(("TRANSPROXY: OPEN  %d\n", fd));
+        if( fd>=0 ){
+          pFile->h = fd;
+        }else{
+          rc=SQLITE_CANTOPEN_BKPT; /* SQLITE_BUSY? proxyTakeConch called
+           during locking */
+        }
+      }
+      if( rc==SQLITE_OK && !pCtx->lockProxy ){
+        char *path = tempLockPath ? tempLockPath : pCtx->lockProxyPath;
+        rc = proxyCreateUnixFile(path, &pCtx->lockProxy, 1);
+        if( rc!=SQLITE_OK && rc!=SQLITE_NOMEM && tryOldLockPath ){
+          /* we couldn't create the proxy lock file with the old lock file path
+           ** so try again via auto-naming 
+           */
+          forceNewLockPath = 1;
+          tryOldLockPath = 0;
+          continue; /* go back to the do {} while start point, try again */
+        }
+      }
+      if( rc==SQLITE_OK ){
+        /* Need to make a copy of path if we extracted the value
+         ** from the conch file or the path was allocated on the stack
+         */
+        if( tempLockPath ){
+          pCtx->lockProxyPath = sqlite3DbStrDup(0, tempLockPath);
+          if( !pCtx->lockProxyPath ){
+            rc = SQLITE_NOMEM;
+          }
+        }
+      }
+      if( rc==SQLITE_OK ){
+        pCtx->conchHeld = 1;
+        
+        if( pCtx->lockProxy->pMethod == &afpIoMethods ){
+          afpLockingContext *afpCtx;
+          afpCtx = (afpLockingContext *)pCtx->lockProxy->lockingContext;
+          afpCtx->dbPath = pCtx->lockProxyPath;
+        }
+      } else {
+        conchFile->pMethod->xUnlock((sqlite3_file*)conchFile, NO_LOCK);
+      }
+      OSTRACE(("TAKECONCH  %d %s\n", conchFile->h,
+               rc==SQLITE_OK?"ok":"failed"));
+      return rc;
+    } while (1); /* in case we need to retry the :auto: lock file - 
+                 ** we should never get here except via the 'continue' call. */
+  }
+}
+
+/*
+** If pFile holds a lock on a conch file, then release that lock.
+*/
+static int proxyReleaseConch(unixFile *pFile){
+  int rc = SQLITE_OK;         /* Subroutine return code */
+  proxyLockingContext *pCtx;  /* The locking context for the proxy lock */
+  unixFile *conchFile;        /* Name of the conch file */
+
+  pCtx = (proxyLockingContext *)pFile->lockingContext;
+  conchFile = pCtx->conchFile;
+  OSTRACE(("RELEASECONCH  %d for %s pid=%d\n", conchFile->h,
+           (pCtx->lockProxyPath ? pCtx->lockProxyPath : ":auto:"), 
+           getpid()));
+  if( pCtx->conchHeld>0 ){
+    rc = conchFile->pMethod->xUnlock((sqlite3_file*)conchFile, NO_LOCK);
+  }
+  pCtx->conchHeld = 0;
+  OSTRACE(("RELEASECONCH  %d %s\n", conchFile->h,
+           (rc==SQLITE_OK ? "ok" : "failed")));
+  return rc;
+}
+
+/*
+** Given the name of a database file, compute the name of its conch file.
+** Store the conch filename in memory obtained from sqlite3_malloc().
+** Make *pConchPath point to the new name.  Return SQLITE_OK on success
+** or SQLITE_NOMEM if unable to obtain memory.
+**
+** The caller is responsible for ensuring that the allocated memory
+** space is eventually freed.
+**
+** *pConchPath is set to NULL if a memory allocation error occurs.
+*/
+static int proxyCreateConchPathname(char *dbPath, char **pConchPath){
+  int i;                        /* Loop counter */
+  int len = (int)strlen(dbPath); /* Length of database filename - dbPath */
+  char *conchPath;              /* buffer in which to construct conch name */
+
+  /* Allocate space for the conch filename and initialize the name to
+  ** the name of the original database file. */  
+  *pConchPath = conchPath = (char *)sqlite3_malloc(len + 8);
+  if( conchPath==0 ){
+    return SQLITE_NOMEM;
+  }
+  memcpy(conchPath, dbPath, len+1);
+  
+  /* now insert a "." before the last / character */
+  for( i=(len-1); i>=0; i-- ){
+    if( conchPath[i]=='/' ){
+      i++;
+      break;
+    }
+  }
+  conchPath[i]='.';
+  while ( i<len ){
+    conchPath[i+1]=dbPath[i];
+    i++;
+  }
+
+  /* append the "-conch" suffix to the file */
+  memcpy(&conchPath[i+1], "-conch", 7);
+  assert( (int)strlen(conchPath) == len+7 );
+
+  return SQLITE_OK;
+}
+
+
+/* Takes a fully configured proxy locking-style unix file and switches
+** the local lock file path 
+*/
+static int switchLockProxyPath(unixFile *pFile, const char *path) {
+  proxyLockingContext *pCtx = (proxyLockingContext*)pFile->lockingContext;
+  char *oldPath = pCtx->lockProxyPath;
+  int rc = SQLITE_OK;
+
+  if( pFile->eFileLock!=NO_LOCK ){
+    return SQLITE_BUSY;
+  }  
+
+  /* nothing to do if the path is NULL, :auto: or matches the existing path */
+  if( !path || path[0]=='\0' || !strcmp(path, ":auto:") ||
+    (oldPath && !strncmp(oldPath, path, MAXPATHLEN)) ){
+    return SQLITE_OK;
+  }else{
+    unixFile *lockProxy = pCtx->lockProxy;
+    pCtx->lockProxy=NULL;
+    pCtx->conchHeld = 0;
+    if( lockProxy!=NULL ){
+      rc=lockProxy->pMethod->xClose((sqlite3_file *)lockProxy);
+      if( rc ) return rc;
+      sqlite3_free(lockProxy);
+    }
+    sqlite3_free(oldPath);
+    pCtx->lockProxyPath = sqlite3DbStrDup(0, path);
+  }
+  
+  return rc;
+}
+
+/*
+** pFile is a file that has been opened by a prior xOpen call.  dbPath
+** is a string buffer at least MAXPATHLEN+1 characters in size.
+**
+** This routine find the filename associated with pFile and writes it
+** int dbPath.
+*/
+static int proxyGetDbPathForUnixFile(unixFile *pFile, char *dbPath){
+#if defined(__APPLE__)
+  if( pFile->pMethod == &afpIoMethods ){
+    /* afp style keeps a reference to the db path in the filePath field 
+    ** of the struct */
+    assert( (int)strlen((char*)pFile->lockingContext)<=MAXPATHLEN );
+    strlcpy(dbPath, ((afpLockingContext *)pFile->lockingContext)->dbPath, MAXPATHLEN);
+  } else
+#endif
+  if( pFile->pMethod == &dotlockIoMethods ){
+    /* dot lock style uses the locking context to store the dot lock
+    ** file path */
+    int len = strlen((char *)pFile->lockingContext) - strlen(DOTLOCK_SUFFIX);
+    memcpy(dbPath, (char *)pFile->lockingContext, len + 1);
+  }else{
+    /* all other styles use the locking context to store the db file path */
+    assert( strlen((char*)pFile->lockingContext)<=MAXPATHLEN );
+    strlcpy(dbPath, (char *)pFile->lockingContext, MAXPATHLEN);
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Takes an already filled in unix file and alters it so all file locking 
+** will be performed on the local proxy lock file.  The following fields
+** are preserved in the locking context so that they can be restored and 
+** the unix structure properly cleaned up at close time:
+**  ->lockingContext
+**  ->pMethod
+*/
+static int proxyTransformUnixFile(unixFile *pFile, const char *path) {
+  proxyLockingContext *pCtx;
+  char dbPath[MAXPATHLEN+1];       /* Name of the database file */
+  char *lockPath=NULL;
+  int rc = SQLITE_OK;
+  
+  if( pFile->eFileLock!=NO_LOCK ){
+    return SQLITE_BUSY;
+  }
+  proxyGetDbPathForUnixFile(pFile, dbPath);
+  if( !path || path[0]=='\0' || !strcmp(path, ":auto:") ){
+    lockPath=NULL;
+  }else{
+    lockPath=(char *)path;
+  }
+  
+  OSTRACE(("TRANSPROXY  %d for %s pid=%d\n", pFile->h,
+           (lockPath ? lockPath : ":auto:"), getpid()));
+
+  pCtx = sqlite3_malloc( sizeof(*pCtx) );
+  if( pCtx==0 ){
+    return SQLITE_NOMEM;
+  }
+  memset(pCtx, 0, sizeof(*pCtx));
+
+  rc = proxyCreateConchPathname(dbPath, &pCtx->conchFilePath);
+  if( rc==SQLITE_OK ){
+    rc = proxyCreateUnixFile(pCtx->conchFilePath, &pCtx->conchFile, 0);
+    if( rc==SQLITE_CANTOPEN && ((pFile->openFlags&O_RDWR) == 0) ){
+      /* if (a) the open flags are not O_RDWR, (b) the conch isn't there, and
+      ** (c) the file system is read-only, then enable no-locking access.
+      ** Ugh, since O_RDONLY==0x0000 we test for !O_RDWR since unixOpen asserts
+      ** that openFlags will have only one of O_RDONLY or O_RDWR.
+      */
+      struct statfs fsInfo;
+      struct stat conchInfo;
+      int goLockless = 0;
+
+      if( osStat(pCtx->conchFilePath, &conchInfo) == -1 ) {
+        int err = errno;
+        if( (err==ENOENT) && (statfs(dbPath, &fsInfo) != -1) ){
+          goLockless = (fsInfo.f_flags&MNT_RDONLY) == MNT_RDONLY;
+        }
+      }
+      if( goLockless ){
+        pCtx->conchHeld = -1; /* read only FS/ lockless */
+        rc = SQLITE_OK;
+      }
+    }
+  }  
+  if( rc==SQLITE_OK && lockPath ){
+    pCtx->lockProxyPath = sqlite3DbStrDup(0, lockPath);
+  }
+
+  if( rc==SQLITE_OK ){
+    pCtx->dbPath = sqlite3DbStrDup(0, dbPath);
+    if( pCtx->dbPath==NULL ){
+      rc = SQLITE_NOMEM;
+    }
+  }
+  if( rc==SQLITE_OK ){
+    /* all memory is allocated, proxys are created and assigned, 
+    ** switch the locking context and pMethod then return.
+    */
+    pCtx->oldLockingContext = pFile->lockingContext;
+    pFile->lockingContext = pCtx;
+    pCtx->pOldMethod = pFile->pMethod;
+    pFile->pMethod = &proxyIoMethods;
+  }else{
+    if( pCtx->conchFile ){ 
+      pCtx->conchFile->pMethod->xClose((sqlite3_file *)pCtx->conchFile);
+      sqlite3_free(pCtx->conchFile);
+    }
+    sqlite3DbFree(0, pCtx->lockProxyPath);
+    sqlite3_free(pCtx->conchFilePath); 
+    sqlite3_free(pCtx);
+  }
+  OSTRACE(("TRANSPROXY  %d %s\n", pFile->h,
+           (rc==SQLITE_OK ? "ok" : "failed")));
+  return rc;
+}
+
+
+/*
+** This routine handles sqlite3_file_control() calls that are specific
+** to proxy locking.
+*/
+static int proxyFileControl(sqlite3_file *id, int op, void *pArg){
+  switch( op ){
+    case SQLITE_GET_LOCKPROXYFILE: {
+      unixFile *pFile = (unixFile*)id;
+      if( pFile->pMethod == &proxyIoMethods ){
+        proxyLockingContext *pCtx = (proxyLockingContext*)pFile->lockingContext;
+        proxyTakeConch(pFile);
+        if( pCtx->lockProxyPath ){
+          *(const char **)pArg = pCtx->lockProxyPath;
+        }else{
+          *(const char **)pArg = ":auto: (not held)";
+        }
+      } else {
+        *(const char **)pArg = NULL;
+      }
+      return SQLITE_OK;
+    }
+    case SQLITE_SET_LOCKPROXYFILE: {
+      unixFile *pFile = (unixFile*)id;
+      int rc = SQLITE_OK;
+      int isProxyStyle = (pFile->pMethod == &proxyIoMethods);
+      if( pArg==NULL || (const char *)pArg==0 ){
+        if( isProxyStyle ){
+          /* turn off proxy locking - not supported */
+          rc = SQLITE_ERROR /*SQLITE_PROTOCOL? SQLITE_MISUSE?*/;
+        }else{
+          /* turn off proxy locking - already off - NOOP */
+          rc = SQLITE_OK;
+        }
+      }else{
+        const char *proxyPath = (const char *)pArg;
+        if( isProxyStyle ){
+          proxyLockingContext *pCtx = 
+            (proxyLockingContext*)pFile->lockingContext;
+          if( !strcmp(pArg, ":auto:") 
+           || (pCtx->lockProxyPath &&
+               !strncmp(pCtx->lockProxyPath, proxyPath, MAXPATHLEN))
+          ){
+            rc = SQLITE_OK;
+          }else{
+            rc = switchLockProxyPath(pFile, proxyPath);
+          }
+        }else{
+          /* turn on proxy file locking */
+          rc = proxyTransformUnixFile(pFile, proxyPath);
+        }
+      }
+      return rc;
+    }
+    default: {
+      assert( 0 );  /* The call assures that only valid opcodes are sent */
+    }
+  }
+  /*NOTREACHED*/
+  return SQLITE_ERROR;
+}
+
+/*
+** Within this division (the proxying locking implementation) the procedures
+** above this point are all utilities.  The lock-related methods of the
+** proxy-locking sqlite3_io_method object follow.
+*/
+
+
+/*
+** This routine checks if there is a RESERVED lock held on the specified
+** file by this or any other process. If such a lock is held, set *pResOut
+** to a non-zero value otherwise *pResOut is set to zero.  The return value
+** is set to SQLITE_OK unless an I/O error occurs during lock checking.
+*/
+static int proxyCheckReservedLock(sqlite3_file *id, int *pResOut) {
+  unixFile *pFile = (unixFile*)id;
+  int rc = proxyTakeConch(pFile);
+  if( rc==SQLITE_OK ){
+    proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext;
+    if( pCtx->conchHeld>0 ){
+      unixFile *proxy = pCtx->lockProxy;
+      return proxy->pMethod->xCheckReservedLock((sqlite3_file*)proxy, pResOut);
+    }else{ /* conchHeld < 0 is lockless */
+      pResOut=0;
+    }
+  }
+  return rc;
+}
+
+/*
+** Lock the file with the lock specified by parameter eFileLock - one
+** of the following:
+**
+**     (1) SHARED_LOCK
+**     (2) RESERVED_LOCK
+**     (3) PENDING_LOCK
+**     (4) EXCLUSIVE_LOCK
+**
+** Sometimes when requesting one lock state, additional lock states
+** are inserted in between.  The locking might fail on one of the later
+** transitions leaving the lock state different from what it started but
+** still short of its goal.  The following chart shows the allowed
+** transitions and the inserted intermediate states:
+**
+**    UNLOCKED -> SHARED
+**    SHARED -> RESERVED
+**    SHARED -> (PENDING) -> EXCLUSIVE
+**    RESERVED -> (PENDING) -> EXCLUSIVE
+**    PENDING -> EXCLUSIVE
+**
+** This routine will only increase a lock.  Use the sqlite3OsUnlock()
+** routine to lower a locking level.
+*/
+static int proxyLock(sqlite3_file *id, int eFileLock) {
+  unixFile *pFile = (unixFile*)id;
+  int rc = proxyTakeConch(pFile);
+  if( rc==SQLITE_OK ){
+    proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext;
+    if( pCtx->conchHeld>0 ){
+      unixFile *proxy = pCtx->lockProxy;
+      rc = proxy->pMethod->xLock((sqlite3_file*)proxy, eFileLock);
+      pFile->eFileLock = proxy->eFileLock;
+    }else{
+      /* conchHeld < 0 is lockless */
+    }
+  }
+  return rc;
+}
+
+
+/*
+** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
+** must be either NO_LOCK or SHARED_LOCK.
+**
+** If the locking level of the file descriptor is already at or below
+** the requested locking level, this routine is a no-op.
+*/
+static int proxyUnlock(sqlite3_file *id, int eFileLock) {
+  unixFile *pFile = (unixFile*)id;
+  int rc = proxyTakeConch(pFile);
+  if( rc==SQLITE_OK ){
+    proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext;
+    if( pCtx->conchHeld>0 ){
+      unixFile *proxy = pCtx->lockProxy;
+      rc = proxy->pMethod->xUnlock((sqlite3_file*)proxy, eFileLock);
+      pFile->eFileLock = proxy->eFileLock;
+    }else{
+      /* conchHeld < 0 is lockless */
+    }
+  }
+  return rc;
+}
+
+/*
+** Close a file that uses proxy locks.
+*/
+static int proxyClose(sqlite3_file *id) {
+  if( id ){
+    unixFile *pFile = (unixFile*)id;
+    proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext;
+    unixFile *lockProxy = pCtx->lockProxy;
+    unixFile *conchFile = pCtx->conchFile;
+    int rc = SQLITE_OK;
+    
+    if( lockProxy ){
+      rc = lockProxy->pMethod->xUnlock((sqlite3_file*)lockProxy, NO_LOCK);
+      if( rc ) return rc;
+      rc = lockProxy->pMethod->xClose((sqlite3_file*)lockProxy);
+      if( rc ) return rc;
+      sqlite3_free(lockProxy);
+      pCtx->lockProxy = 0;
+    }
+    if( conchFile ){
+      if( pCtx->conchHeld ){
+        rc = proxyReleaseConch(pFile);
+        if( rc ) return rc;
+      }
+      rc = conchFile->pMethod->xClose((sqlite3_file*)conchFile);
+      if( rc ) return rc;
+      sqlite3_free(conchFile);
+    }
+    sqlite3DbFree(0, pCtx->lockProxyPath);
+    sqlite3_free(pCtx->conchFilePath);
+    sqlite3DbFree(0, pCtx->dbPath);
+    /* restore the original locking context and pMethod then close it */
+    pFile->lockingContext = pCtx->oldLockingContext;
+    pFile->pMethod = pCtx->pOldMethod;
+    sqlite3_free(pCtx);
+    return pFile->pMethod->xClose(id);
+  }
+  return SQLITE_OK;
+}
+
+
+
+#endif /* defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE */
+/*
+** The proxy locking style is intended for use with AFP filesystems.
+** And since AFP is only supported on MacOSX, the proxy locking is also
+** restricted to MacOSX.
+** 
+**
+******************* End of the proxy lock implementation **********************
+******************************************************************************/
+
+/*
+** Initialize the operating system interface.
+**
+** This routine registers all VFS implementations for unix-like operating
+** systems.  This routine, and the sqlite3_os_end() routine that follows,
+** should be the only routines in this file that are visible from other
+** files.
+**
+** This routine is called once during SQLite initialization and by a
+** single thread.  The memory allocation and mutex subsystems have not
+** necessarily been initialized when this routine is called, and so they
+** should not be used.
+*/
+int sqlite3_os_init(void){ 
+  /* 
+  ** The following macro defines an initializer for an sqlite3_vfs object.
+  ** The name of the VFS is NAME.  The pAppData is a pointer to a pointer
+  ** to the "finder" function.  (pAppData is a pointer to a pointer because
+  ** silly C90 rules prohibit a void* from being cast to a function pointer
+  ** and so we have to go through the intermediate pointer to avoid problems
+  ** when compiling with -pedantic-errors on GCC.)
+  **
+  ** The FINDER parameter to this macro is the name of the pointer to the
+  ** finder-function.  The finder-function returns a pointer to the
+  ** sqlite_io_methods object that implements the desired locking
+  ** behaviors.  See the division above that contains the IOMETHODS
+  ** macro for addition information on finder-functions.
+  **
+  ** Most finders simply return a pointer to a fixed sqlite3_io_methods
+  ** object.  But the "autolockIoFinder" available on MacOSX does a little
+  ** more than that; it looks at the filesystem type that hosts the 
+  ** database file and tries to choose an locking method appropriate for
+  ** that filesystem time.
+  */
+  #define UNIXVFS(VFSNAME, FINDER) {                        \
+    3,                    /* iVersion */                    \
+    sizeof(unixFile),     /* szOsFile */                    \
+    MAX_PATHNAME,         /* mxPathname */                  \
+    0,                    /* pNext */                       \
+    VFSNAME,              /* zName */                       \
+    (void*)&FINDER,       /* pAppData */                    \
+    unixOpen,             /* xOpen */                       \
+    unixDelete,           /* xDelete */                     \
+    unixAccess,           /* xAccess */                     \
+    unixFullPathname,     /* xFullPathname */               \
+    unixDlOpen,           /* xDlOpen */                     \
+    unixDlError,          /* xDlError */                    \
+    unixDlSym,            /* xDlSym */                      \
+    unixDlClose,          /* xDlClose */                    \
+    unixRandomness,       /* xRandomness */                 \
+    unixSleep,            /* xSleep */                      \
+    unixCurrentTime,      /* xCurrentTime */                \
+    unixGetLastError,     /* xGetLastError */               \
+    unixCurrentTimeInt64, /* xCurrentTimeInt64 */           \
+    unixSetSystemCall,    /* xSetSystemCall */              \
+    unixGetSystemCall,    /* xGetSystemCall */              \
+    unixNextSystemCall,   /* xNextSystemCall */             \
+  }
+
+  /*
+  ** All default VFSes for unix are contained in the following array.
+  **
+  ** Note that the sqlite3_vfs.pNext field of the VFS object is modified
+  ** by the SQLite core when the VFS is registered.  So the following
+  ** array cannot be const.
+  */
+  static sqlite3_vfs aVfs[] = {
+#if SQLITE_ENABLE_LOCKING_STYLE && (OS_VXWORKS || defined(__APPLE__))
+    UNIXVFS("unix",          autolockIoFinder ),
+#else
+    UNIXVFS("unix",          posixIoFinder ),
+#endif
+    UNIXVFS("unix-none",     nolockIoFinder ),
+    UNIXVFS("unix-dotfile",  dotlockIoFinder ),
+    UNIXVFS("unix-excl",     posixIoFinder ),
+#if OS_VXWORKS
+    UNIXVFS("unix-namedsem", semIoFinder ),
+#endif
+#if SQLITE_ENABLE_LOCKING_STYLE
+    UNIXVFS("unix-posix",    posixIoFinder ),
+#if !OS_VXWORKS
+    UNIXVFS("unix-flock",    flockIoFinder ),
+#endif
+#endif
+#if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__)
+    UNIXVFS("unix-afp",      afpIoFinder ),
+    UNIXVFS("unix-nfs",      nfsIoFinder ),
+    UNIXVFS("unix-proxy",    proxyIoFinder ),
+#endif
+  };
+  unsigned int i;          /* Loop counter */
+
+  /* Double-check that the aSyscall[] array has been constructed
+  ** correctly.  See ticket [bb3a86e890c8e96ab] */
+  assert( ArraySize(aSyscall)==18 );
+
+  /* Register all VFSes defined in the aVfs[] array */
+  for(i=0; i<(sizeof(aVfs)/sizeof(sqlite3_vfs)); i++){
+    sqlite3_vfs_register(&aVfs[i], i==0);
+  }
+  return SQLITE_OK; 
+}
+
+/*
+** Shutdown the operating system interface.
+**
+** Some operating systems might need to do some cleanup in this routine,
+** to release dynamically allocated objects.  But not on unix.
+** This routine is a no-op for unix.
+*/
+int sqlite3_os_end(void){ 
+  return SQLITE_OK; 
+}
+ 
+#endif /* SQLITE_OS_UNIX */
diff --git a/src/os_win.c b/src/os_win.c
new file mode 100644
index 0000000..4518030
--- /dev/null
+++ b/src/os_win.c
@@ -0,0 +1,3204 @@
+/*
+** 2004 May 22
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains code that is specific to windows.
+*/
+#include "sqliteInt.h"
+#if SQLITE_OS_WIN               /* This file is used for windows only */
+
+
+/*
+** A Note About Memory Allocation:
+**
+** This driver uses malloc()/free() directly rather than going through
+** the SQLite-wrappers sqlite3_malloc()/sqlite3_free().  Those wrappers
+** are designed for use on embedded systems where memory is scarce and
+** malloc failures happen frequently.  Win32 does not typically run on
+** embedded systems, and when it does the developers normally have bigger
+** problems to worry about than running out of memory.  So there is not
+** a compelling need to use the wrappers.
+**
+** But there is a good reason to not use the wrappers.  If we use the
+** wrappers then we will get simulated malloc() failures within this
+** driver.  And that causes all kinds of problems for our tests.  We
+** could enhance SQLite to deal with simulated malloc failures within
+** the OS driver, but the code to deal with those failure would not
+** be exercised on Linux (which does not need to malloc() in the driver)
+** and so we would have difficulty writing coverage tests for that
+** code.  Better to leave the code out, we think.
+**
+** The point of this discussion is as follows:  When creating a new
+** OS layer for an embedded system, if you use this file as an example,
+** avoid the use of malloc()/free().  Those routines work ok on windows
+** desktops but not so well in embedded systems.
+*/
+
+#include <winbase.h>
+
+#ifdef __CYGWIN__
+# include <sys/cygwin.h>
+#endif
+
+/*
+** Macros used to determine whether or not to use threads.
+*/
+#if defined(THREADSAFE) && THREADSAFE
+# define SQLITE_W32_THREADS 1
+#endif
+
+/*
+** Include code that is common to all os_*.c files
+*/
+#include "os_common.h"
+
+/*
+** Some microsoft compilers lack this definition.
+*/
+#ifndef INVALID_FILE_ATTRIBUTES
+# define INVALID_FILE_ATTRIBUTES ((DWORD)-1) 
+#endif
+
+/*
+** Determine if we are dealing with WindowsCE - which has a much
+** reduced API.
+*/
+#if SQLITE_OS_WINCE
+# define AreFileApisANSI() 1
+# define FormatMessageW(a,b,c,d,e,f,g) 0
+#endif
+
+/* Forward references */
+typedef struct winShm winShm;           /* A connection to shared-memory */
+typedef struct winShmNode winShmNode;   /* A region of shared-memory */
+
+/*
+** WinCE lacks native support for file locking so we have to fake it
+** with some code of our own.
+*/
+#if SQLITE_OS_WINCE
+typedef struct winceLock {
+  int nReaders;       /* Number of reader locks obtained */
+  BOOL bPending;      /* Indicates a pending lock has been obtained */
+  BOOL bReserved;     /* Indicates a reserved lock has been obtained */
+  BOOL bExclusive;    /* Indicates an exclusive lock has been obtained */
+} winceLock;
+#endif
+
+/*
+** The winFile structure is a subclass of sqlite3_file* specific to the win32
+** portability layer.
+*/
+typedef struct winFile winFile;
+struct winFile {
+  const sqlite3_io_methods *pMethod; /*** Must be first ***/
+  sqlite3_vfs *pVfs;      /* The VFS used to open this file */
+  HANDLE h;               /* Handle for accessing the file */
+  u8 locktype;            /* Type of lock currently held on this file */
+  short sharedLockByte;   /* Randomly chosen byte used as a shared lock */
+  u8 bPersistWal;         /* True to persist WAL files */
+  DWORD lastErrno;        /* The Windows errno from the last I/O error */
+  DWORD sectorSize;       /* Sector size of the device file is on */
+  winShm *pShm;           /* Instance of shared memory on this file */
+  const char *zPath;      /* Full pathname of this file */
+  int szChunk;            /* Chunk size configured by FCNTL_CHUNK_SIZE */
+#if SQLITE_OS_WINCE
+  WCHAR *zDeleteOnClose;  /* Name of file to delete when closing */
+  HANDLE hMutex;          /* Mutex used to control access to shared lock */  
+  HANDLE hShared;         /* Shared memory segment used for locking */
+  winceLock local;        /* Locks obtained by this instance of winFile */
+  winceLock *shared;      /* Global shared lock memory for the file  */
+#endif
+};
+
+/*
+ * If compiled with SQLITE_WIN32_MALLOC on Windows, we will use the
+ * various Win32 API heap functions instead of our own.
+ */
+#ifdef SQLITE_WIN32_MALLOC
+/*
+ * The initial size of the Win32-specific heap.  This value may be zero.
+ */
+#ifndef SQLITE_WIN32_HEAP_INIT_SIZE
+#  define SQLITE_WIN32_HEAP_INIT_SIZE ((SQLITE_DEFAULT_CACHE_SIZE) * \
+                                       (SQLITE_DEFAULT_PAGE_SIZE) + 4194304)
+#endif
+
+/*
+ * The maximum size of the Win32-specific heap.  This value may be zero.
+ */
+#ifndef SQLITE_WIN32_HEAP_MAX_SIZE
+#  define SQLITE_WIN32_HEAP_MAX_SIZE  (0)
+#endif
+
+/*
+ * The extra flags to use in calls to the Win32 heap APIs.  This value may be
+ * zero for the default behavior.
+ */
+#ifndef SQLITE_WIN32_HEAP_FLAGS
+#  define SQLITE_WIN32_HEAP_FLAGS     (0)
+#endif
+
+/*
+** The winMemData structure stores information required by the Win32-specific
+** sqlite3_mem_methods implementation.
+*/
+typedef struct winMemData winMemData;
+struct winMemData {
+#ifndef NDEBUG
+  u32 magic;    /* Magic number to detect structure corruption. */
+#endif
+  HANDLE hHeap; /* The handle to our heap. */
+  BOOL bOwned;  /* Do we own the heap (i.e. destroy it on shutdown)? */
+};
+
+#ifndef NDEBUG
+#define WINMEM_MAGIC     0x42b2830b
+#endif
+
+static struct winMemData win_mem_data = {
+#ifndef NDEBUG
+  WINMEM_MAGIC,
+#endif
+  NULL, FALSE
+};
+
+#ifndef NDEBUG
+#define winMemAssertMagic() assert( win_mem_data.magic==WINMEM_MAGIC )
+#else
+#define winMemAssertMagic()
+#endif
+
+#define winMemGetHeap() win_mem_data.hHeap
+
+static void *winMemMalloc(int nBytes);
+static void winMemFree(void *pPrior);
+static void *winMemRealloc(void *pPrior, int nBytes);
+static int winMemSize(void *p);
+static int winMemRoundup(int n);
+static int winMemInit(void *pAppData);
+static void winMemShutdown(void *pAppData);
+
+const sqlite3_mem_methods *sqlite3MemGetWin32(void);
+#endif /* SQLITE_WIN32_MALLOC */
+
+/*
+** Forward prototypes.
+*/
+static int getSectorSize(
+    sqlite3_vfs *pVfs,
+    const char *zRelative     /* UTF-8 file name */
+);
+
+/*
+** The following variable is (normally) set once and never changes
+** thereafter.  It records whether the operating system is Win95
+** or WinNT.
+**
+** 0:   Operating system unknown.
+** 1:   Operating system is Win95.
+** 2:   Operating system is WinNT.
+**
+** In order to facilitate testing on a WinNT system, the test fixture
+** can manually set this value to 1 to emulate Win98 behavior.
+*/
+#ifdef SQLITE_TEST
+int sqlite3_os_type = 0;
+#else
+static int sqlite3_os_type = 0;
+#endif
+
+/*
+** Return true (non-zero) if we are running under WinNT, Win2K, WinXP,
+** or WinCE.  Return false (zero) for Win95, Win98, or WinME.
+**
+** Here is an interesting observation:  Win95, Win98, and WinME lack
+** the LockFileEx() API.  But we can still statically link against that
+** API as long as we don't call it when running Win95/98/ME.  A call to
+** this routine is used to determine if the host is Win95/98/ME or
+** WinNT/2K/XP so that we will know whether or not we can safely call
+** the LockFileEx() API.
+*/
+#if SQLITE_OS_WINCE
+# define isNT()  (1)
+#else
+  static int isNT(void){
+    if( sqlite3_os_type==0 ){
+      OSVERSIONINFO sInfo;
+      sInfo.dwOSVersionInfoSize = sizeof(sInfo);
+      GetVersionEx(&sInfo);
+      sqlite3_os_type = sInfo.dwPlatformId==VER_PLATFORM_WIN32_NT ? 2 : 1;
+    }
+    return sqlite3_os_type==2;
+  }
+#endif /* SQLITE_OS_WINCE */
+
+#ifdef SQLITE_WIN32_MALLOC
+/*
+** Allocate nBytes of memory.
+*/
+static void *winMemMalloc(int nBytes){
+  HANDLE hHeap;
+  void *p;
+
+  winMemAssertMagic();
+  hHeap = winMemGetHeap();
+  assert( hHeap!=0 );
+  assert( hHeap!=INVALID_HANDLE_VALUE );
+#ifdef SQLITE_WIN32_MALLOC_VALIDATE
+  assert ( HeapValidate(hHeap, SQLITE_WIN32_HEAP_FLAGS, NULL) );
+#endif
+  assert( nBytes>=0 );
+  p = HeapAlloc(hHeap, SQLITE_WIN32_HEAP_FLAGS, (SIZE_T)nBytes);
+  if( !p ){
+    sqlite3_log(SQLITE_NOMEM, "failed to HeapAlloc %u bytes (%d), heap=%p",
+        nBytes, GetLastError(), (void*)hHeap);
+  }
+  return p;
+}
+
+/*
+** Free memory.
+*/
+static void winMemFree(void *pPrior){
+  HANDLE hHeap;
+
+  winMemAssertMagic();
+  hHeap = winMemGetHeap();
+  assert( hHeap!=0 );
+  assert( hHeap!=INVALID_HANDLE_VALUE );
+#ifdef SQLITE_WIN32_MALLOC_VALIDATE
+  assert ( HeapValidate(hHeap, SQLITE_WIN32_HEAP_FLAGS, pPrior) );
+#endif
+  if( !pPrior ) return; /* Passing NULL to HeapFree is undefined. */
+  if( !HeapFree(hHeap, SQLITE_WIN32_HEAP_FLAGS, pPrior) ){
+    sqlite3_log(SQLITE_NOMEM, "failed to HeapFree block %p (%d), heap=%p",
+        pPrior, GetLastError(), (void*)hHeap);
+  }
+}
+
+/*
+** Change the size of an existing memory allocation
+*/
+static void *winMemRealloc(void *pPrior, int nBytes){
+  HANDLE hHeap;
+  void *p;
+
+  winMemAssertMagic();
+  hHeap = winMemGetHeap();
+  assert( hHeap!=0 );
+  assert( hHeap!=INVALID_HANDLE_VALUE );
+#ifdef SQLITE_WIN32_MALLOC_VALIDATE
+  assert ( HeapValidate(hHeap, SQLITE_WIN32_HEAP_FLAGS, pPrior) );
+#endif
+  assert( nBytes>=0 );
+  if( !pPrior ){
+    p = HeapAlloc(hHeap, SQLITE_WIN32_HEAP_FLAGS, (SIZE_T)nBytes);
+  }else{
+    p = HeapReAlloc(hHeap, SQLITE_WIN32_HEAP_FLAGS, pPrior, (SIZE_T)nBytes);
+  }
+  if( !p ){
+    sqlite3_log(SQLITE_NOMEM, "failed to %s %u bytes (%d), heap=%p",
+        pPrior ? "HeapReAlloc" : "HeapAlloc", nBytes, GetLastError(),
+        (void*)hHeap);
+  }
+  return p;
+}
+
+/*
+** Return the size of an outstanding allocation, in bytes.
+*/
+static int winMemSize(void *p){
+  HANDLE hHeap;
+  SIZE_T n;
+
+  winMemAssertMagic();
+  hHeap = winMemGetHeap();
+  assert( hHeap!=0 );
+  assert( hHeap!=INVALID_HANDLE_VALUE );
+#ifdef SQLITE_WIN32_MALLOC_VALIDATE
+  assert ( HeapValidate(hHeap, SQLITE_WIN32_HEAP_FLAGS, NULL) );
+#endif
+  if( !p ) return 0;
+  n = HeapSize(hHeap, SQLITE_WIN32_HEAP_FLAGS, p);
+  if( n==(SIZE_T)-1 ){
+    sqlite3_log(SQLITE_NOMEM, "failed to HeapSize block %p (%d), heap=%p",
+        p, GetLastError(), (void*)hHeap);
+    return 0;
+  }
+  return (int)n;
+}
+
+/*
+** Round up a request size to the next valid allocation size.
+*/
+static int winMemRoundup(int n){
+  return n;
+}
+
+/*
+** Initialize this module.
+*/
+static int winMemInit(void *pAppData){
+  winMemData *pWinMemData = (winMemData *)pAppData;
+
+  if( !pWinMemData ) return SQLITE_ERROR;
+  assert( pWinMemData->magic==WINMEM_MAGIC );
+  if( !pWinMemData->hHeap ){
+    pWinMemData->hHeap = HeapCreate(SQLITE_WIN32_HEAP_FLAGS,
+                                    SQLITE_WIN32_HEAP_INIT_SIZE,
+                                    SQLITE_WIN32_HEAP_MAX_SIZE);
+    if( !pWinMemData->hHeap ){
+      sqlite3_log(SQLITE_NOMEM,
+          "failed to HeapCreate (%d), flags=%u, initSize=%u, maxSize=%u",
+          GetLastError(), SQLITE_WIN32_HEAP_FLAGS, SQLITE_WIN32_HEAP_INIT_SIZE,
+          SQLITE_WIN32_HEAP_MAX_SIZE);
+      return SQLITE_NOMEM;
+    }
+    pWinMemData->bOwned = TRUE;
+  }
+  assert( pWinMemData->hHeap!=0 );
+  assert( pWinMemData->hHeap!=INVALID_HANDLE_VALUE );
+#ifdef SQLITE_WIN32_MALLOC_VALIDATE
+  assert( HeapValidate(pWinMemData->hHeap, SQLITE_WIN32_HEAP_FLAGS, NULL) );
+#endif
+  return SQLITE_OK;
+}
+
+/*
+** Deinitialize this module.
+*/
+static void winMemShutdown(void *pAppData){
+  winMemData *pWinMemData = (winMemData *)pAppData;
+
+  if( !pWinMemData ) return;
+  if( pWinMemData->hHeap ){
+    assert( pWinMemData->hHeap!=INVALID_HANDLE_VALUE );
+#ifdef SQLITE_WIN32_MALLOC_VALIDATE
+    assert( HeapValidate(pWinMemData->hHeap, SQLITE_WIN32_HEAP_FLAGS, NULL) );
+#endif
+    if( pWinMemData->bOwned ){
+      if( !HeapDestroy(pWinMemData->hHeap) ){
+        sqlite3_log(SQLITE_NOMEM, "failed to HeapDestroy (%d), heap=%p",
+            GetLastError(), (void*)pWinMemData->hHeap);
+      }
+      pWinMemData->bOwned = FALSE;
+    }
+    pWinMemData->hHeap = NULL;
+  }
+}
+
+/*
+** Populate the low-level memory allocation function pointers in
+** sqlite3GlobalConfig.m with pointers to the routines in this file. The
+** arguments specify the block of memory to manage.
+**
+** This routine is only called by sqlite3_config(), and therefore
+** is not required to be threadsafe (it is not).
+*/
+const sqlite3_mem_methods *sqlite3MemGetWin32(void){
+  static const sqlite3_mem_methods winMemMethods = {
+    winMemMalloc,
+    winMemFree,
+    winMemRealloc,
+    winMemSize,
+    winMemRoundup,
+    winMemInit,
+    winMemShutdown,
+    &win_mem_data
+  };
+  return &winMemMethods;
+}
+
+void sqlite3MemSetDefault(void){
+  sqlite3_config(SQLITE_CONFIG_MALLOC, sqlite3MemGetWin32());
+}
+#endif /* SQLITE_WIN32_MALLOC */
+
+/*
+** Convert a UTF-8 string to microsoft unicode (UTF-16?). 
+**
+** Space to hold the returned string is obtained from malloc.
+*/
+static WCHAR *utf8ToUnicode(const char *zFilename){
+  int nChar;
+  WCHAR *zWideFilename;
+
+  nChar = MultiByteToWideChar(CP_UTF8, 0, zFilename, -1, NULL, 0);
+  zWideFilename = malloc( nChar*sizeof(zWideFilename[0]) );
+  if( zWideFilename==0 ){
+    return 0;
+  }
+  nChar = MultiByteToWideChar(CP_UTF8, 0, zFilename, -1, zWideFilename, nChar);
+  if( nChar==0 ){
+    free(zWideFilename);
+    zWideFilename = 0;
+  }
+  return zWideFilename;
+}
+
+/*
+** Convert microsoft unicode to UTF-8.  Space to hold the returned string is
+** obtained from malloc().
+*/
+static char *unicodeToUtf8(const WCHAR *zWideFilename){
+  int nByte;
+  char *zFilename;
+
+  nByte = WideCharToMultiByte(CP_UTF8, 0, zWideFilename, -1, 0, 0, 0, 0);
+  zFilename = malloc( nByte );
+  if( zFilename==0 ){
+    return 0;
+  }
+  nByte = WideCharToMultiByte(CP_UTF8, 0, zWideFilename, -1, zFilename, nByte,
+                              0, 0);
+  if( nByte == 0 ){
+    free(zFilename);
+    zFilename = 0;
+  }
+  return zFilename;
+}
+
+/*
+** Convert an ansi string to microsoft unicode, based on the
+** current codepage settings for file apis.
+** 
+** Space to hold the returned string is obtained
+** from malloc.
+*/
+static WCHAR *mbcsToUnicode(const char *zFilename){
+  int nByte;
+  WCHAR *zMbcsFilename;
+  int codepage = AreFileApisANSI() ? CP_ACP : CP_OEMCP;
+
+  nByte = MultiByteToWideChar(codepage, 0, zFilename, -1, NULL,0)*sizeof(WCHAR);
+  zMbcsFilename = malloc( nByte*sizeof(zMbcsFilename[0]) );
+  if( zMbcsFilename==0 ){
+    return 0;
+  }
+  nByte = MultiByteToWideChar(codepage, 0, zFilename, -1, zMbcsFilename, nByte);
+  if( nByte==0 ){
+    free(zMbcsFilename);
+    zMbcsFilename = 0;
+  }
+  return zMbcsFilename;
+}
+
+/*
+** Convert microsoft unicode to multibyte character string, based on the
+** user's Ansi codepage.
+**
+** Space to hold the returned string is obtained from
+** malloc().
+*/
+static char *unicodeToMbcs(const WCHAR *zWideFilename){
+  int nByte;
+  char *zFilename;
+  int codepage = AreFileApisANSI() ? CP_ACP : CP_OEMCP;
+
+  nByte = WideCharToMultiByte(codepage, 0, zWideFilename, -1, 0, 0, 0, 0);
+  zFilename = malloc( nByte );
+  if( zFilename==0 ){
+    return 0;
+  }
+  nByte = WideCharToMultiByte(codepage, 0, zWideFilename, -1, zFilename, nByte,
+                              0, 0);
+  if( nByte == 0 ){
+    free(zFilename);
+    zFilename = 0;
+  }
+  return zFilename;
+}
+
+/*
+** Convert multibyte character string to UTF-8.  Space to hold the
+** returned string is obtained from malloc().
+*/
+char *sqlite3_win32_mbcs_to_utf8(const char *zFilename){
+  char *zFilenameUtf8;
+  WCHAR *zTmpWide;
+
+  zTmpWide = mbcsToUnicode(zFilename);
+  if( zTmpWide==0 ){
+    return 0;
+  }
+  zFilenameUtf8 = unicodeToUtf8(zTmpWide);
+  free(zTmpWide);
+  return zFilenameUtf8;
+}
+
+/*
+** Convert UTF-8 to multibyte character string.  Space to hold the 
+** returned string is obtained from malloc().
+*/
+char *sqlite3_win32_utf8_to_mbcs(const char *zFilename){
+  char *zFilenameMbcs;
+  WCHAR *zTmpWide;
+
+  zTmpWide = utf8ToUnicode(zFilename);
+  if( zTmpWide==0 ){
+    return 0;
+  }
+  zFilenameMbcs = unicodeToMbcs(zTmpWide);
+  free(zTmpWide);
+  return zFilenameMbcs;
+}
+
+
+/*
+** The return value of getLastErrorMsg
+** is zero if the error message fits in the buffer, or non-zero
+** otherwise (if the message was truncated).
+*/
+static int getLastErrorMsg(int nBuf, char *zBuf){
+  /* FormatMessage returns 0 on failure.  Otherwise it
+  ** returns the number of TCHARs written to the output
+  ** buffer, excluding the terminating null char.
+  */
+  DWORD error = GetLastError();
+  DWORD dwLen = 0;
+  char *zOut = 0;
+
+  if( isNT() ){
+    WCHAR *zTempWide = NULL;
+    dwLen = FormatMessageW(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
+                           NULL,
+                           error,
+                           0,
+                           (LPWSTR) &zTempWide,
+                           0,
+                           0);
+    if( dwLen > 0 ){
+      /* allocate a buffer and convert to UTF8 */
+      zOut = unicodeToUtf8(zTempWide);
+      /* free the system buffer allocated by FormatMessage */
+      LocalFree(zTempWide);
+    }
+/* isNT() is 1 if SQLITE_OS_WINCE==1, so this else is never executed. 
+** Since the ASCII version of these Windows API do not exist for WINCE,
+** it's important to not reference them for WINCE builds.
+*/
+#if SQLITE_OS_WINCE==0
+  }else{
+    char *zTemp = NULL;
+    dwLen = FormatMessageA(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
+                           NULL,
+                           error,
+                           0,
+                           (LPSTR) &zTemp,
+                           0,
+                           0);
+    if( dwLen > 0 ){
+      /* allocate a buffer and convert to UTF8 */
+      zOut = sqlite3_win32_mbcs_to_utf8(zTemp);
+      /* free the system buffer allocated by FormatMessage */
+      LocalFree(zTemp);
+    }
+#endif
+  }
+  if( 0 == dwLen ){
+    sqlite3_snprintf(nBuf, zBuf, "OsError 0x%x (%u)", error, error);
+  }else{
+    /* copy a maximum of nBuf chars to output buffer */
+    sqlite3_snprintf(nBuf, zBuf, "%s", zOut);
+    /* free the UTF8 buffer */
+    free(zOut);
+  }
+  return 0;
+}
+
+/*
+**
+** This function - winLogErrorAtLine() - is only ever called via the macro
+** winLogError().
+**
+** This routine is invoked after an error occurs in an OS function.
+** It logs a message using sqlite3_log() containing the current value of
+** error code and, if possible, the human-readable equivalent from 
+** FormatMessage.
+**
+** The first argument passed to the macro should be the error code that
+** will be returned to SQLite (e.g. SQLITE_IOERR_DELETE, SQLITE_CANTOPEN). 
+** The two subsequent arguments should be the name of the OS function that
+** failed and the the associated file-system path, if any.
+*/
+#define winLogError(a,b,c)     winLogErrorAtLine(a,b,c,__LINE__)
+static int winLogErrorAtLine(
+  int errcode,                    /* SQLite error code */
+  const char *zFunc,              /* Name of OS function that failed */
+  const char *zPath,              /* File path associated with error */
+  int iLine                       /* Source line number where error occurred */
+){
+  char zMsg[500];                 /* Human readable error text */
+  int i;                          /* Loop counter */
+  DWORD iErrno = GetLastError();  /* Error code */
+
+  zMsg[0] = 0;
+  getLastErrorMsg(sizeof(zMsg), zMsg);
+  assert( errcode!=SQLITE_OK );
+  if( zPath==0 ) zPath = "";
+  for(i=0; zMsg[i] && zMsg[i]!='\r' && zMsg[i]!='\n'; i++){}
+  zMsg[i] = 0;
+  sqlite3_log(errcode,
+      "os_win.c:%d: (%d) %s(%s) - %s",
+      iLine, iErrno, zFunc, zPath, zMsg
+  );
+
+  return errcode;
+}
+
+/*
+** The number of times that a ReadFile(), WriteFile(), and DeleteFile()
+** will be retried following a locking error - probably caused by 
+** antivirus software.  Also the initial delay before the first retry.
+** The delay increases linearly with each retry.
+*/
+#ifndef SQLITE_WIN32_IOERR_RETRY
+# define SQLITE_WIN32_IOERR_RETRY 10
+#endif
+#ifndef SQLITE_WIN32_IOERR_RETRY_DELAY
+# define SQLITE_WIN32_IOERR_RETRY_DELAY 25
+#endif
+static int win32IoerrRetry = SQLITE_WIN32_IOERR_RETRY;
+static int win32IoerrRetryDelay = SQLITE_WIN32_IOERR_RETRY_DELAY;
+
+/*
+** If a ReadFile() or WriteFile() error occurs, invoke this routine
+** to see if it should be retried.  Return TRUE to retry.  Return FALSE
+** to give up with an error.
+*/
+static int retryIoerr(int *pnRetry){
+  DWORD e;
+  if( *pnRetry>=win32IoerrRetry ){
+    return 0;
+  }
+  e = GetLastError();
+  if( e==ERROR_ACCESS_DENIED ||
+      e==ERROR_LOCK_VIOLATION ||
+      e==ERROR_SHARING_VIOLATION ){
+    Sleep(win32IoerrRetryDelay*(1+*pnRetry));
+    ++*pnRetry;
+    return 1;
+  }
+  return 0;
+}
+
+/*
+** Log a I/O error retry episode.
+*/
+static void logIoerr(int nRetry){
+  if( nRetry ){
+    sqlite3_log(SQLITE_IOERR, 
+      "delayed %dms for lock/sharing conflict",
+      win32IoerrRetryDelay*nRetry*(nRetry+1)/2
+    );
+  }
+}
+
+#if SQLITE_OS_WINCE
+/*************************************************************************
+** This section contains code for WinCE only.
+*/
+/*
+** WindowsCE does not have a localtime() function.  So create a
+** substitute.
+*/
+#include <time.h>
+struct tm *__cdecl localtime(const time_t *t)
+{
+  static struct tm y;
+  FILETIME uTm, lTm;
+  SYSTEMTIME pTm;
+  sqlite3_int64 t64;
+  t64 = *t;
+  t64 = (t64 + 11644473600)*10000000;
+  uTm.dwLowDateTime = (DWORD)(t64 & 0xFFFFFFFF);
+  uTm.dwHighDateTime= (DWORD)(t64 >> 32);
+  FileTimeToLocalFileTime(&uTm,&lTm);
+  FileTimeToSystemTime(&lTm,&pTm);
+  y.tm_year = pTm.wYear - 1900;
+  y.tm_mon = pTm.wMonth - 1;
+  y.tm_wday = pTm.wDayOfWeek;
+  y.tm_mday = pTm.wDay;
+  y.tm_hour = pTm.wHour;
+  y.tm_min = pTm.wMinute;
+  y.tm_sec = pTm.wSecond;
+  return &y;
+}
+
+/* This will never be called, but defined to make the code compile */
+#define GetTempPathA(a,b)
+
+#define LockFile(a,b,c,d,e)       winceLockFile(&a, b, c, d, e)
+#define UnlockFile(a,b,c,d,e)     winceUnlockFile(&a, b, c, d, e)
+#define LockFileEx(a,b,c,d,e,f)   winceLockFileEx(&a, b, c, d, e, f)
+
+#define HANDLE_TO_WINFILE(a) (winFile*)&((char*)a)[-(int)offsetof(winFile,h)]
+
+/*
+** Acquire a lock on the handle h
+*/
+static void winceMutexAcquire(HANDLE h){
+   DWORD dwErr;
+   do {
+     dwErr = WaitForSingleObject(h, INFINITE);
+   } while (dwErr != WAIT_OBJECT_0 && dwErr != WAIT_ABANDONED);
+}
+/*
+** Release a lock acquired by winceMutexAcquire()
+*/
+#define winceMutexRelease(h) ReleaseMutex(h)
+
+/*
+** Create the mutex and shared memory used for locking in the file
+** descriptor pFile
+*/
+static BOOL winceCreateLock(const char *zFilename, winFile *pFile){
+  WCHAR *zTok;
+  WCHAR *zName = utf8ToUnicode(zFilename);
+  BOOL bInit = TRUE;
+
+  /* Initialize the local lockdata */
+  ZeroMemory(&pFile->local, sizeof(pFile->local));
+
+  /* Replace the backslashes from the filename and lowercase it
+  ** to derive a mutex name. */
+  zTok = CharLowerW(zName);
+  for (;*zTok;zTok++){
+    if (*zTok == '\\') *zTok = '_';
+  }
+
+  /* Create/open the named mutex */
+  pFile->hMutex = CreateMutexW(NULL, FALSE, zName);
+  if (!pFile->hMutex){
+    pFile->lastErrno = GetLastError();
+    winLogError(SQLITE_ERROR, "winceCreateLock1", zFilename);
+    free(zName);
+    return FALSE;
+  }
+
+  /* Acquire the mutex before continuing */
+  winceMutexAcquire(pFile->hMutex);
+  
+  /* Since the names of named mutexes, semaphores, file mappings etc are 
+  ** case-sensitive, take advantage of that by uppercasing the mutex name
+  ** and using that as the shared filemapping name.
+  */
+  CharUpperW(zName);
+  pFile->hShared = CreateFileMappingW(INVALID_HANDLE_VALUE, NULL,
+                                       PAGE_READWRITE, 0, sizeof(winceLock),
+                                       zName);  
+
+  /* Set a flag that indicates we're the first to create the memory so it 
+  ** must be zero-initialized */
+  if (GetLastError() == ERROR_ALREADY_EXISTS){
+    bInit = FALSE;
+  }
+
+  free(zName);
+
+  /* If we succeeded in making the shared memory handle, map it. */
+  if (pFile->hShared){
+    pFile->shared = (winceLock*)MapViewOfFile(pFile->hShared, 
+             FILE_MAP_READ|FILE_MAP_WRITE, 0, 0, sizeof(winceLock));
+    /* If mapping failed, close the shared memory handle and erase it */
+    if (!pFile->shared){
+      pFile->lastErrno = GetLastError();
+      winLogError(SQLITE_ERROR, "winceCreateLock2", zFilename);
+      CloseHandle(pFile->hShared);
+      pFile->hShared = NULL;
+    }
+  }
+
+  /* If shared memory could not be created, then close the mutex and fail */
+  if (pFile->hShared == NULL){
+    winceMutexRelease(pFile->hMutex);
+    CloseHandle(pFile->hMutex);
+    pFile->hMutex = NULL;
+    return FALSE;
+  }
+  
+  /* Initialize the shared memory if we're supposed to */
+  if (bInit) {
+    ZeroMemory(pFile->shared, sizeof(winceLock));
+  }
+
+  winceMutexRelease(pFile->hMutex);
+  return TRUE;
+}
+
+/*
+** Destroy the part of winFile that deals with wince locks
+*/
+static void winceDestroyLock(winFile *pFile){
+  if (pFile->hMutex){
+    /* Acquire the mutex */
+    winceMutexAcquire(pFile->hMutex);
+
+    /* The following blocks should probably assert in debug mode, but they
+       are to cleanup in case any locks remained open */
+    if (pFile->local.nReaders){
+      pFile->shared->nReaders --;
+    }
+    if (pFile->local.bReserved){
+      pFile->shared->bReserved = FALSE;
+    }
+    if (pFile->local.bPending){
+      pFile->shared->bPending = FALSE;
+    }
+    if (pFile->local.bExclusive){
+      pFile->shared->bExclusive = FALSE;
+    }
+
+    /* De-reference and close our copy of the shared memory handle */
+    UnmapViewOfFile(pFile->shared);
+    CloseHandle(pFile->hShared);
+
+    /* Done with the mutex */
+    winceMutexRelease(pFile->hMutex);    
+    CloseHandle(pFile->hMutex);
+    pFile->hMutex = NULL;
+  }
+}
+
+/* 
+** An implementation of the LockFile() API of windows for wince
+*/
+static BOOL winceLockFile(
+  HANDLE *phFile,
+  DWORD dwFileOffsetLow,
+  DWORD dwFileOffsetHigh,
+  DWORD nNumberOfBytesToLockLow,
+  DWORD nNumberOfBytesToLockHigh
+){
+  winFile *pFile = HANDLE_TO_WINFILE(phFile);
+  BOOL bReturn = FALSE;
+
+  UNUSED_PARAMETER(dwFileOffsetHigh);
+  UNUSED_PARAMETER(nNumberOfBytesToLockHigh);
+
+  if (!pFile->hMutex) return TRUE;
+  winceMutexAcquire(pFile->hMutex);
+
+  /* Wanting an exclusive lock? */
+  if (dwFileOffsetLow == (DWORD)SHARED_FIRST
+       && nNumberOfBytesToLockLow == (DWORD)SHARED_SIZE){
+    if (pFile->shared->nReaders == 0 && pFile->shared->bExclusive == 0){
+       pFile->shared->bExclusive = TRUE;
+       pFile->local.bExclusive = TRUE;
+       bReturn = TRUE;
+    }
+  }
+
+  /* Want a read-only lock? */
+  else if (dwFileOffsetLow == (DWORD)SHARED_FIRST &&
+           nNumberOfBytesToLockLow == 1){
+    if (pFile->shared->bExclusive == 0){
+      pFile->local.nReaders ++;
+      if (pFile->local.nReaders == 1){
+        pFile->shared->nReaders ++;
+      }
+      bReturn = TRUE;
+    }
+  }
+
+  /* Want a pending lock? */
+  else if (dwFileOffsetLow == (DWORD)PENDING_BYTE && nNumberOfBytesToLockLow == 1){
+    /* If no pending lock has been acquired, then acquire it */
+    if (pFile->shared->bPending == 0) {
+      pFile->shared->bPending = TRUE;
+      pFile->local.bPending = TRUE;
+      bReturn = TRUE;
+    }
+  }
+
+  /* Want a reserved lock? */
+  else if (dwFileOffsetLow == (DWORD)RESERVED_BYTE && nNumberOfBytesToLockLow == 1){
+    if (pFile->shared->bReserved == 0) {
+      pFile->shared->bReserved = TRUE;
+      pFile->local.bReserved = TRUE;
+      bReturn = TRUE;
+    }
+  }
+
+  winceMutexRelease(pFile->hMutex);
+  return bReturn;
+}
+
+/*
+** An implementation of the UnlockFile API of windows for wince
+*/
+static BOOL winceUnlockFile(
+  HANDLE *phFile,
+  DWORD dwFileOffsetLow,
+  DWORD dwFileOffsetHigh,
+  DWORD nNumberOfBytesToUnlockLow,
+  DWORD nNumberOfBytesToUnlockHigh
+){
+  winFile *pFile = HANDLE_TO_WINFILE(phFile);
+  BOOL bReturn = FALSE;
+
+  UNUSED_PARAMETER(dwFileOffsetHigh);
+  UNUSED_PARAMETER(nNumberOfBytesToUnlockHigh);
+
+  if (!pFile->hMutex) return TRUE;
+  winceMutexAcquire(pFile->hMutex);
+
+  /* Releasing a reader lock or an exclusive lock */
+  if (dwFileOffsetLow == (DWORD)SHARED_FIRST){
+    /* Did we have an exclusive lock? */
+    if (pFile->local.bExclusive){
+      assert(nNumberOfBytesToUnlockLow == (DWORD)SHARED_SIZE);
+      pFile->local.bExclusive = FALSE;
+      pFile->shared->bExclusive = FALSE;
+      bReturn = TRUE;
+    }
+
+    /* Did we just have a reader lock? */
+    else if (pFile->local.nReaders){
+      assert(nNumberOfBytesToUnlockLow == (DWORD)SHARED_SIZE || nNumberOfBytesToUnlockLow == 1);
+      pFile->local.nReaders --;
+      if (pFile->local.nReaders == 0)
+      {
+        pFile->shared->nReaders --;
+      }
+      bReturn = TRUE;
+    }
+  }
+
+  /* Releasing a pending lock */
+  else if (dwFileOffsetLow == (DWORD)PENDING_BYTE && nNumberOfBytesToUnlockLow == 1){
+    if (pFile->local.bPending){
+      pFile->local.bPending = FALSE;
+      pFile->shared->bPending = FALSE;
+      bReturn = TRUE;
+    }
+  }
+  /* Releasing a reserved lock */
+  else if (dwFileOffsetLow == (DWORD)RESERVED_BYTE && nNumberOfBytesToUnlockLow == 1){
+    if (pFile->local.bReserved) {
+      pFile->local.bReserved = FALSE;
+      pFile->shared->bReserved = FALSE;
+      bReturn = TRUE;
+    }
+  }
+
+  winceMutexRelease(pFile->hMutex);
+  return bReturn;
+}
+
+/*
+** An implementation of the LockFileEx() API of windows for wince
+*/
+static BOOL winceLockFileEx(
+  HANDLE *phFile,
+  DWORD dwFlags,
+  DWORD dwReserved,
+  DWORD nNumberOfBytesToLockLow,
+  DWORD nNumberOfBytesToLockHigh,
+  LPOVERLAPPED lpOverlapped
+){
+  UNUSED_PARAMETER(dwReserved);
+  UNUSED_PARAMETER(nNumberOfBytesToLockHigh);
+
+  /* If the caller wants a shared read lock, forward this call
+  ** to winceLockFile */
+  if (lpOverlapped->Offset == (DWORD)SHARED_FIRST &&
+      dwFlags == 1 &&
+      nNumberOfBytesToLockLow == (DWORD)SHARED_SIZE){
+    return winceLockFile(phFile, SHARED_FIRST, 0, 1, 0);
+  }
+  return FALSE;
+}
+/*
+** End of the special code for wince
+*****************************************************************************/
+#endif /* SQLITE_OS_WINCE */
+
+/*****************************************************************************
+** The next group of routines implement the I/O methods specified
+** by the sqlite3_io_methods object.
+******************************************************************************/
+
+/*
+** Some microsoft compilers lack this definition.
+*/
+#ifndef INVALID_SET_FILE_POINTER
+# define INVALID_SET_FILE_POINTER ((DWORD)-1)
+#endif
+
+/*
+** Move the current position of the file handle passed as the first 
+** argument to offset iOffset within the file. If successful, return 0. 
+** Otherwise, set pFile->lastErrno and return non-zero.
+*/
+static int seekWinFile(winFile *pFile, sqlite3_int64 iOffset){
+  LONG upperBits;                 /* Most sig. 32 bits of new offset */
+  LONG lowerBits;                 /* Least sig. 32 bits of new offset */
+  DWORD dwRet;                    /* Value returned by SetFilePointer() */
+
+  upperBits = (LONG)((iOffset>>32) & 0x7fffffff);
+  lowerBits = (LONG)(iOffset & 0xffffffff);
+
+  /* API oddity: If successful, SetFilePointer() returns a dword 
+  ** containing the lower 32-bits of the new file-offset. Or, if it fails,
+  ** it returns INVALID_SET_FILE_POINTER. However according to MSDN, 
+  ** INVALID_SET_FILE_POINTER may also be a valid new offset. So to determine 
+  ** whether an error has actually occured, it is also necessary to call 
+  ** GetLastError().
+  */
+  dwRet = SetFilePointer(pFile->h, lowerBits, &upperBits, FILE_BEGIN);
+  if( (dwRet==INVALID_SET_FILE_POINTER && GetLastError()!=NO_ERROR) ){
+    pFile->lastErrno = GetLastError();
+    winLogError(SQLITE_IOERR_SEEK, "seekWinFile", pFile->zPath);
+    return 1;
+  }
+
+  return 0;
+}
+
+/*
+** Close a file.
+**
+** It is reported that an attempt to close a handle might sometimes
+** fail.  This is a very unreasonable result, but windows is notorious
+** for being unreasonable so I do not doubt that it might happen.  If
+** the close fails, we pause for 100 milliseconds and try again.  As
+** many as MX_CLOSE_ATTEMPT attempts to close the handle are made before
+** giving up and returning an error.
+*/
+#define MX_CLOSE_ATTEMPT 3
+static int winClose(sqlite3_file *id){
+  int rc, cnt = 0;
+  winFile *pFile = (winFile*)id;
+
+  assert( id!=0 );
+  assert( pFile->pShm==0 );
+  OSTRACE(("CLOSE %d\n", pFile->h));
+  do{
+    rc = CloseHandle(pFile->h);
+    /* SimulateIOError( rc=0; cnt=MX_CLOSE_ATTEMPT; ); */
+  }while( rc==0 && ++cnt < MX_CLOSE_ATTEMPT && (Sleep(100), 1) );
+#if SQLITE_OS_WINCE
+#define WINCE_DELETION_ATTEMPTS 3
+  winceDestroyLock(pFile);
+  if( pFile->zDeleteOnClose ){
+    int cnt = 0;
+    while(
+           DeleteFileW(pFile->zDeleteOnClose)==0
+        && GetFileAttributesW(pFile->zDeleteOnClose)!=0xffffffff 
+        && cnt++ < WINCE_DELETION_ATTEMPTS
+    ){
+       Sleep(100);  /* Wait a little before trying again */
+    }
+    free(pFile->zDeleteOnClose);
+  }
+#endif
+  OSTRACE(("CLOSE %d %s\n", pFile->h, rc ? "ok" : "failed"));
+  OpenCounter(-1);
+  return rc ? SQLITE_OK
+            : winLogError(SQLITE_IOERR_CLOSE, "winClose", pFile->zPath);
+}
+
+/*
+** Read data from a file into a buffer.  Return SQLITE_OK if all
+** bytes were read successfully and SQLITE_IOERR if anything goes
+** wrong.
+*/
+static int winRead(
+  sqlite3_file *id,          /* File to read from */
+  void *pBuf,                /* Write content into this buffer */
+  int amt,                   /* Number of bytes to read */
+  sqlite3_int64 offset       /* Begin reading at this offset */
+){
+  winFile *pFile = (winFile*)id;  /* file handle */
+  DWORD nRead;                    /* Number of bytes actually read from file */
+  int nRetry = 0;                 /* Number of retrys */
+
+  assert( id!=0 );
+  SimulateIOError(return SQLITE_IOERR_READ);
+  OSTRACE(("READ %d lock=%d\n", pFile->h, pFile->locktype));
+
+  if( seekWinFile(pFile, offset) ){
+    return SQLITE_FULL;
+  }
+  while( !ReadFile(pFile->h, pBuf, amt, &nRead, 0) ){
+    if( retryIoerr(&nRetry) ) continue;
+    pFile->lastErrno = GetLastError();
+    return winLogError(SQLITE_IOERR_READ, "winRead", pFile->zPath);
+  }
+  logIoerr(nRetry);
+  if( nRead<(DWORD)amt ){
+    /* Unread parts of the buffer must be zero-filled */
+    memset(&((char*)pBuf)[nRead], 0, amt-nRead);
+    return SQLITE_IOERR_SHORT_READ;
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** Write data from a buffer into a file.  Return SQLITE_OK on success
+** or some other error code on failure.
+*/
+static int winWrite(
+  sqlite3_file *id,               /* File to write into */
+  const void *pBuf,               /* The bytes to be written */
+  int amt,                        /* Number of bytes to write */
+  sqlite3_int64 offset            /* Offset into the file to begin writing at */
+){
+  int rc;                         /* True if error has occured, else false */
+  winFile *pFile = (winFile*)id;  /* File handle */
+  int nRetry = 0;                 /* Number of retries */
+
+  assert( amt>0 );
+  assert( pFile );
+  SimulateIOError(return SQLITE_IOERR_WRITE);
+  SimulateDiskfullError(return SQLITE_FULL);
+
+  OSTRACE(("WRITE %d lock=%d\n", pFile->h, pFile->locktype));
+
+  rc = seekWinFile(pFile, offset);
+  if( rc==0 ){
+    u8 *aRem = (u8 *)pBuf;        /* Data yet to be written */
+    int nRem = amt;               /* Number of bytes yet to be written */
+    DWORD nWrite;                 /* Bytes written by each WriteFile() call */
+
+    while( nRem>0 ){
+      if( !WriteFile(pFile->h, aRem, nRem, &nWrite, 0) ){
+        if( retryIoerr(&nRetry) ) continue;
+        break;
+      }
+      if( nWrite<=0 ) break;
+      aRem += nWrite;
+      nRem -= nWrite;
+    }
+    if( nRem>0 ){
+      pFile->lastErrno = GetLastError();
+      rc = 1;
+    }
+  }
+
+  if( rc ){
+    if(   ( pFile->lastErrno==ERROR_HANDLE_DISK_FULL )
+       || ( pFile->lastErrno==ERROR_DISK_FULL )){
+      return SQLITE_FULL;
+    }
+    return winLogError(SQLITE_IOERR_WRITE, "winWrite", pFile->zPath);
+  }else{
+    logIoerr(nRetry);
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Truncate an open file to a specified size
+*/
+static int winTruncate(sqlite3_file *id, sqlite3_int64 nByte){
+  winFile *pFile = (winFile*)id;  /* File handle object */
+  int rc = SQLITE_OK;             /* Return code for this function */
+
+  assert( pFile );
+
+  OSTRACE(("TRUNCATE %d %lld\n", pFile->h, nByte));
+  SimulateIOError(return SQLITE_IOERR_TRUNCATE);
+
+  /* If the user has configured a chunk-size for this file, truncate the
+  ** file so that it consists of an integer number of chunks (i.e. the
+  ** actual file size after the operation may be larger than the requested
+  ** size).
+  */
+  if( pFile->szChunk>0 ){
+    nByte = ((nByte + pFile->szChunk - 1)/pFile->szChunk) * pFile->szChunk;
+  }
+
+  /* SetEndOfFile() returns non-zero when successful, or zero when it fails. */
+  if( seekWinFile(pFile, nByte) ){
+    rc = winLogError(SQLITE_IOERR_TRUNCATE, "winTruncate1", pFile->zPath);
+  }else if( 0==SetEndOfFile(pFile->h) ){
+    pFile->lastErrno = GetLastError();
+    rc = winLogError(SQLITE_IOERR_TRUNCATE, "winTruncate2", pFile->zPath);
+  }
+
+  OSTRACE(("TRUNCATE %d %lld %s\n", pFile->h, nByte, rc ? "failed" : "ok"));
+  return rc;
+}
+
+#ifdef SQLITE_TEST
+/*
+** Count the number of fullsyncs and normal syncs.  This is used to test
+** that syncs and fullsyncs are occuring at the right times.
+*/
+int sqlite3_sync_count = 0;
+int sqlite3_fullsync_count = 0;
+#endif
+
+/*
+** Make sure all writes to a particular file are committed to disk.
+*/
+static int winSync(sqlite3_file *id, int flags){
+#ifndef SQLITE_NO_SYNC
+  /*
+  ** Used only when SQLITE_NO_SYNC is not defined.
+   */
+  BOOL rc;
+#endif
+#if !defined(NDEBUG) || !defined(SQLITE_NO_SYNC) || \
+    (defined(SQLITE_TEST) && defined(SQLITE_DEBUG))
+  /*
+  ** Used when SQLITE_NO_SYNC is not defined and by the assert() and/or
+  ** OSTRACE() macros.
+   */
+  winFile *pFile = (winFile*)id;
+#else
+  UNUSED_PARAMETER(id);
+#endif
+
+  assert( pFile );
+  /* Check that one of SQLITE_SYNC_NORMAL or FULL was passed */
+  assert((flags&0x0F)==SQLITE_SYNC_NORMAL
+      || (flags&0x0F)==SQLITE_SYNC_FULL
+  );
+
+  OSTRACE(("SYNC %d lock=%d\n", pFile->h, pFile->locktype));
+
+  /* Unix cannot, but some systems may return SQLITE_FULL from here. This
+  ** line is to test that doing so does not cause any problems.
+  */
+  SimulateDiskfullError( return SQLITE_FULL );
+
+#ifndef SQLITE_TEST
+  UNUSED_PARAMETER(flags);
+#else
+  if( (flags&0x0F)==SQLITE_SYNC_FULL ){
+    sqlite3_fullsync_count++;
+  }
+  sqlite3_sync_count++;
+#endif
+
+  /* If we compiled with the SQLITE_NO_SYNC flag, then syncing is a
+  ** no-op
+  */
+#ifdef SQLITE_NO_SYNC
+  return SQLITE_OK;
+#else
+  rc = FlushFileBuffers(pFile->h);
+  SimulateIOError( rc=FALSE );
+  if( rc ){
+    return SQLITE_OK;
+  }else{
+    pFile->lastErrno = GetLastError();
+    return winLogError(SQLITE_IOERR_FSYNC, "winSync", pFile->zPath);
+  }
+#endif
+}
+
+/*
+** Determine the current size of a file in bytes
+*/
+static int winFileSize(sqlite3_file *id, sqlite3_int64 *pSize){
+  DWORD upperBits;
+  DWORD lowerBits;
+  winFile *pFile = (winFile*)id;
+  DWORD error;
+
+  assert( id!=0 );
+  SimulateIOError(return SQLITE_IOERR_FSTAT);
+  lowerBits = GetFileSize(pFile->h, &upperBits);
+  if(   (lowerBits == INVALID_FILE_SIZE)
+     && ((error = GetLastError()) != NO_ERROR) )
+  {
+    pFile->lastErrno = error;
+    return winLogError(SQLITE_IOERR_FSTAT, "winFileSize", pFile->zPath);
+  }
+  *pSize = (((sqlite3_int64)upperBits)<<32) + lowerBits;
+  return SQLITE_OK;
+}
+
+/*
+** LOCKFILE_FAIL_IMMEDIATELY is undefined on some Windows systems.
+*/
+#ifndef LOCKFILE_FAIL_IMMEDIATELY
+# define LOCKFILE_FAIL_IMMEDIATELY 1
+#endif
+
+/*
+** Acquire a reader lock.
+** Different API routines are called depending on whether or not this
+** is Win95 or WinNT.
+*/
+static int getReadLock(winFile *pFile){
+  int res;
+  if( isNT() ){
+    OVERLAPPED ovlp;
+    ovlp.Offset = SHARED_FIRST;
+    ovlp.OffsetHigh = 0;
+    ovlp.hEvent = 0;
+    res = LockFileEx(pFile->h, LOCKFILE_FAIL_IMMEDIATELY,
+                     0, SHARED_SIZE, 0, &ovlp);
+/* isNT() is 1 if SQLITE_OS_WINCE==1, so this else is never executed. 
+*/
+#if SQLITE_OS_WINCE==0
+  }else{
+    int lk;
+    sqlite3_randomness(sizeof(lk), &lk);
+    pFile->sharedLockByte = (short)((lk & 0x7fffffff)%(SHARED_SIZE - 1));
+    res = LockFile(pFile->h, SHARED_FIRST+pFile->sharedLockByte, 0, 1, 0);
+#endif
+  }
+  if( res == 0 ){
+    pFile->lastErrno = GetLastError();
+    /* No need to log a failure to lock */
+  }
+  return res;
+}
+
+/*
+** Undo a readlock
+*/
+static int unlockReadLock(winFile *pFile){
+  int res;
+  if( isNT() ){
+    res = UnlockFile(pFile->h, SHARED_FIRST, 0, SHARED_SIZE, 0);
+/* isNT() is 1 if SQLITE_OS_WINCE==1, so this else is never executed. 
+*/
+#if SQLITE_OS_WINCE==0
+  }else{
+    res = UnlockFile(pFile->h, SHARED_FIRST + pFile->sharedLockByte, 0, 1, 0);
+#endif
+  }
+  if( res==0 && GetLastError()!=ERROR_NOT_LOCKED ){
+    pFile->lastErrno = GetLastError();
+    winLogError(SQLITE_IOERR_UNLOCK, "unlockReadLock", pFile->zPath);
+  }
+  return res;
+}
+
+/*
+** Lock the file with the lock specified by parameter locktype - one
+** of the following:
+**
+**     (1) SHARED_LOCK
+**     (2) RESERVED_LOCK
+**     (3) PENDING_LOCK
+**     (4) EXCLUSIVE_LOCK
+**
+** Sometimes when requesting one lock state, additional lock states
+** are inserted in between.  The locking might fail on one of the later
+** transitions leaving the lock state different from what it started but
+** still short of its goal.  The following chart shows the allowed
+** transitions and the inserted intermediate states:
+**
+**    UNLOCKED -> SHARED
+**    SHARED -> RESERVED
+**    SHARED -> (PENDING) -> EXCLUSIVE
+**    RESERVED -> (PENDING) -> EXCLUSIVE
+**    PENDING -> EXCLUSIVE
+**
+** This routine will only increase a lock.  The winUnlock() routine
+** erases all locks at once and returns us immediately to locking level 0.
+** It is not possible to lower the locking level one step at a time.  You
+** must go straight to locking level 0.
+*/
+static int winLock(sqlite3_file *id, int locktype){
+  int rc = SQLITE_OK;    /* Return code from subroutines */
+  int res = 1;           /* Result of a windows lock call */
+  int newLocktype;       /* Set pFile->locktype to this value before exiting */
+  int gotPendingLock = 0;/* True if we acquired a PENDING lock this time */
+  winFile *pFile = (winFile*)id;
+  DWORD error = NO_ERROR;
+
+  assert( id!=0 );
+  OSTRACE(("LOCK %d %d was %d(%d)\n",
+           pFile->h, locktype, pFile->locktype, pFile->sharedLockByte));
+
+  /* If there is already a lock of this type or more restrictive on the
+  ** OsFile, do nothing. Don't use the end_lock: exit path, as
+  ** sqlite3OsEnterMutex() hasn't been called yet.
+  */
+  if( pFile->locktype>=locktype ){
+    return SQLITE_OK;
+  }
+
+  /* Make sure the locking sequence is correct
+  */
+  assert( pFile->locktype!=NO_LOCK || locktype==SHARED_LOCK );
+  assert( locktype!=PENDING_LOCK );
+  assert( locktype!=RESERVED_LOCK || pFile->locktype==SHARED_LOCK );
+
+  /* Lock the PENDING_LOCK byte if we need to acquire a PENDING lock or
+  ** a SHARED lock.  If we are acquiring a SHARED lock, the acquisition of
+  ** the PENDING_LOCK byte is temporary.
+  */
+  newLocktype = pFile->locktype;
+  if(   (pFile->locktype==NO_LOCK)
+     || (   (locktype==EXCLUSIVE_LOCK)
+         && (pFile->locktype==RESERVED_LOCK))
+  ){
+    int cnt = 3;
+    while( cnt-->0 && (res = LockFile(pFile->h, PENDING_BYTE, 0, 1, 0))==0 ){
+      /* Try 3 times to get the pending lock.  The pending lock might be
+      ** held by another reader process who will release it momentarily.
+      */
+      OSTRACE(("could not get a PENDING lock. cnt=%d\n", cnt));
+      Sleep(1);
+    }
+    gotPendingLock = res;
+    if( !res ){
+      error = GetLastError();
+    }
+  }
+
+  /* Acquire a shared lock
+  */
+  if( locktype==SHARED_LOCK && res ){
+    assert( pFile->locktype==NO_LOCK );
+    res = getReadLock(pFile);
+    if( res ){
+      newLocktype = SHARED_LOCK;
+    }else{
+      error = GetLastError();
+    }
+  }
+
+  /* Acquire a RESERVED lock
+  */
+  if( locktype==RESERVED_LOCK && res ){
+    assert( pFile->locktype==SHARED_LOCK );
+    res = LockFile(pFile->h, RESERVED_BYTE, 0, 1, 0);
+    if( res ){
+      newLocktype = RESERVED_LOCK;
+    }else{
+      error = GetLastError();
+    }
+  }
+
+  /* Acquire a PENDING lock
+  */
+  if( locktype==EXCLUSIVE_LOCK && res ){
+    newLocktype = PENDING_LOCK;
+    gotPendingLock = 0;
+  }
+
+  /* Acquire an EXCLUSIVE lock
+  */
+  if( locktype==EXCLUSIVE_LOCK && res ){
+    assert( pFile->locktype>=SHARED_LOCK );
+    res = unlockReadLock(pFile);
+    OSTRACE(("unreadlock = %d\n", res));
+    res = LockFile(pFile->h, SHARED_FIRST, 0, SHARED_SIZE, 0);
+    if( res ){
+      newLocktype = EXCLUSIVE_LOCK;
+    }else{
+      error = GetLastError();
+      OSTRACE(("error-code = %d\n", error));
+      getReadLock(pFile);
+    }
+  }
+
+  /* If we are holding a PENDING lock that ought to be released, then
+  ** release it now.
+  */
+  if( gotPendingLock && locktype==SHARED_LOCK ){
+    UnlockFile(pFile->h, PENDING_BYTE, 0, 1, 0);
+  }
+
+  /* Update the state of the lock has held in the file descriptor then
+  ** return the appropriate result code.
+  */
+  if( res ){
+    rc = SQLITE_OK;
+  }else{
+    OSTRACE(("LOCK FAILED %d trying for %d but got %d\n", pFile->h,
+           locktype, newLocktype));
+    pFile->lastErrno = error;
+    rc = SQLITE_BUSY;
+  }
+  pFile->locktype = (u8)newLocktype;
+  return rc;
+}
+
+/*
+** This routine checks if there is a RESERVED lock held on the specified
+** file by this or any other process. If such a lock is held, return
+** non-zero, otherwise zero.
+*/
+static int winCheckReservedLock(sqlite3_file *id, int *pResOut){
+  int rc;
+  winFile *pFile = (winFile*)id;
+
+  SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
+
+  assert( id!=0 );
+  if( pFile->locktype>=RESERVED_LOCK ){
+    rc = 1;
+    OSTRACE(("TEST WR-LOCK %d %d (local)\n", pFile->h, rc));
+  }else{
+    rc = LockFile(pFile->h, RESERVED_BYTE, 0, 1, 0);
+    if( rc ){
+      UnlockFile(pFile->h, RESERVED_BYTE, 0, 1, 0);
+    }
+    rc = !rc;
+    OSTRACE(("TEST WR-LOCK %d %d (remote)\n", pFile->h, rc));
+  }
+  *pResOut = rc;
+  return SQLITE_OK;
+}
+
+/*
+** Lower the locking level on file descriptor id to locktype.  locktype
+** must be either NO_LOCK or SHARED_LOCK.
+**
+** If the locking level of the file descriptor is already at or below
+** the requested locking level, this routine is a no-op.
+**
+** It is not possible for this routine to fail if the second argument
+** is NO_LOCK.  If the second argument is SHARED_LOCK then this routine
+** might return SQLITE_IOERR;
+*/
+static int winUnlock(sqlite3_file *id, int locktype){
+  int type;
+  winFile *pFile = (winFile*)id;
+  int rc = SQLITE_OK;
+  assert( pFile!=0 );
+  assert( locktype<=SHARED_LOCK );
+  OSTRACE(("UNLOCK %d to %d was %d(%d)\n", pFile->h, locktype,
+          pFile->locktype, pFile->sharedLockByte));
+  type = pFile->locktype;
+  if( type>=EXCLUSIVE_LOCK ){
+    UnlockFile(pFile->h, SHARED_FIRST, 0, SHARED_SIZE, 0);
+    if( locktype==SHARED_LOCK && !getReadLock(pFile) ){
+      /* This should never happen.  We should always be able to
+      ** reacquire the read lock */
+      rc = winLogError(SQLITE_IOERR_UNLOCK, "winUnlock", pFile->zPath);
+    }
+  }
+  if( type>=RESERVED_LOCK ){
+    UnlockFile(pFile->h, RESERVED_BYTE, 0, 1, 0);
+  }
+  if( locktype==NO_LOCK && type>=SHARED_LOCK ){
+    unlockReadLock(pFile);
+  }
+  if( type>=PENDING_LOCK ){
+    UnlockFile(pFile->h, PENDING_BYTE, 0, 1, 0);
+  }
+  pFile->locktype = (u8)locktype;
+  return rc;
+}
+
+/*
+** Control and query of the open file handle.
+*/
+static int winFileControl(sqlite3_file *id, int op, void *pArg){
+  winFile *pFile = (winFile*)id;
+  switch( op ){
+    case SQLITE_FCNTL_LOCKSTATE: {
+      *(int*)pArg = pFile->locktype;
+      return SQLITE_OK;
+    }
+    case SQLITE_LAST_ERRNO: {
+      *(int*)pArg = (int)pFile->lastErrno;
+      return SQLITE_OK;
+    }
+    case SQLITE_FCNTL_CHUNK_SIZE: {
+      pFile->szChunk = *(int *)pArg;
+      return SQLITE_OK;
+    }
+    case SQLITE_FCNTL_SIZE_HINT: {
+      if( pFile->szChunk>0 ){
+        sqlite3_int64 oldSz;
+        int rc = winFileSize(id, &oldSz);
+        if( rc==SQLITE_OK ){
+          sqlite3_int64 newSz = *(sqlite3_int64*)pArg;
+          if( newSz>oldSz ){
+            SimulateIOErrorBenign(1);
+            rc = winTruncate(id, newSz);
+            SimulateIOErrorBenign(0);
+          }
+        }
+        return rc;
+      }
+      return SQLITE_OK;
+    }
+    case SQLITE_FCNTL_PERSIST_WAL: {
+      int bPersist = *(int*)pArg;
+      if( bPersist<0 ){
+        *(int*)pArg = pFile->bPersistWal;
+      }else{
+        pFile->bPersistWal = bPersist!=0;
+      }
+      return SQLITE_OK;
+    }
+    case SQLITE_FCNTL_SYNC_OMITTED: {
+      return SQLITE_OK;
+    }
+    case SQLITE_FCNTL_WIN32_AV_RETRY: {
+      int *a = (int*)pArg;
+      if( a[0]>0 ){
+        win32IoerrRetry = a[0];
+      }else{
+        a[0] = win32IoerrRetry;
+      }
+      if( a[1]>0 ){
+        win32IoerrRetryDelay = a[1];
+      }else{
+        a[1] = win32IoerrRetryDelay;
+      }
+      return SQLITE_OK;
+    }
+  }
+  return SQLITE_NOTFOUND;
+}
+
+/*
+** Return the sector size in bytes of the underlying block device for
+** the specified file. This is almost always 512 bytes, but may be
+** larger for some devices.
+**
+** SQLite code assumes this function cannot fail. It also assumes that
+** if two files are created in the same file-system directory (i.e.
+** a database and its journal file) that the sector size will be the
+** same for both.
+*/
+static int winSectorSize(sqlite3_file *id){
+  assert( id!=0 );
+  return (int)(((winFile*)id)->sectorSize);
+}
+
+/*
+** Return a vector of device characteristics.
+*/
+static int winDeviceCharacteristics(sqlite3_file *id){
+  UNUSED_PARAMETER(id);
+  return SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN;
+}
+
+#ifndef SQLITE_OMIT_WAL
+
+/* 
+** Windows will only let you create file view mappings
+** on allocation size granularity boundaries.
+** During sqlite3_os_init() we do a GetSystemInfo()
+** to get the granularity size.
+*/
+SYSTEM_INFO winSysInfo;
+
+/*
+** Helper functions to obtain and relinquish the global mutex. The
+** global mutex is used to protect the winLockInfo objects used by 
+** this file, all of which may be shared by multiple threads.
+**
+** Function winShmMutexHeld() is used to assert() that the global mutex 
+** is held when required. This function is only used as part of assert() 
+** statements. e.g.
+**
+**   winShmEnterMutex()
+**     assert( winShmMutexHeld() );
+**   winShmLeaveMutex()
+*/
+static void winShmEnterMutex(void){
+  sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
+}
+static void winShmLeaveMutex(void){
+  sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
+}
+#ifdef SQLITE_DEBUG
+static int winShmMutexHeld(void) {
+  return sqlite3_mutex_held(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
+}
+#endif
+
+/*
+** Object used to represent a single file opened and mmapped to provide
+** shared memory.  When multiple threads all reference the same
+** log-summary, each thread has its own winFile object, but they all
+** point to a single instance of this object.  In other words, each
+** log-summary is opened only once per process.
+**
+** winShmMutexHeld() must be true when creating or destroying
+** this object or while reading or writing the following fields:
+**
+**      nRef
+**      pNext 
+**
+** The following fields are read-only after the object is created:
+** 
+**      fid
+**      zFilename
+**
+** Either winShmNode.mutex must be held or winShmNode.nRef==0 and
+** winShmMutexHeld() is true when reading or writing any other field
+** in this structure.
+**
+*/
+struct winShmNode {
+  sqlite3_mutex *mutex;      /* Mutex to access this object */
+  char *zFilename;           /* Name of the file */
+  winFile hFile;             /* File handle from winOpen */
+
+  int szRegion;              /* Size of shared-memory regions */
+  int nRegion;               /* Size of array apRegion */
+  struct ShmRegion {
+    HANDLE hMap;             /* File handle from CreateFileMapping */
+    void *pMap;
+  } *aRegion;
+  DWORD lastErrno;           /* The Windows errno from the last I/O error */
+
+  int nRef;                  /* Number of winShm objects pointing to this */
+  winShm *pFirst;            /* All winShm objects pointing to this */
+  winShmNode *pNext;         /* Next in list of all winShmNode objects */
+#ifdef SQLITE_DEBUG
+  u8 nextShmId;              /* Next available winShm.id value */
+#endif
+};
+
+/*
+** A global array of all winShmNode objects.
+**
+** The winShmMutexHeld() must be true while reading or writing this list.
+*/
+static winShmNode *winShmNodeList = 0;
+
+/*
+** Structure used internally by this VFS to record the state of an
+** open shared memory connection.
+**
+** The following fields are initialized when this object is created and
+** are read-only thereafter:
+**
+**    winShm.pShmNode
+**    winShm.id
+**
+** All other fields are read/write.  The winShm.pShmNode->mutex must be held
+** while accessing any read/write fields.
+*/
+struct winShm {
+  winShmNode *pShmNode;      /* The underlying winShmNode object */
+  winShm *pNext;             /* Next winShm with the same winShmNode */
+  u8 hasMutex;               /* True if holding the winShmNode mutex */
+  u16 sharedMask;            /* Mask of shared locks held */
+  u16 exclMask;              /* Mask of exclusive locks held */
+#ifdef SQLITE_DEBUG
+  u8 id;                     /* Id of this connection with its winShmNode */
+#endif
+};
+
+/*
+** Constants used for locking
+*/
+#define WIN_SHM_BASE   ((22+SQLITE_SHM_NLOCK)*4)        /* first lock byte */
+#define WIN_SHM_DMS    (WIN_SHM_BASE+SQLITE_SHM_NLOCK)  /* deadman switch */
+
+/*
+** Apply advisory locks for all n bytes beginning at ofst.
+*/
+#define _SHM_UNLCK  1
+#define _SHM_RDLCK  2
+#define _SHM_WRLCK  3
+static int winShmSystemLock(
+  winShmNode *pFile,    /* Apply locks to this open shared-memory segment */
+  int lockType,         /* _SHM_UNLCK, _SHM_RDLCK, or _SHM_WRLCK */
+  int ofst,             /* Offset to first byte to be locked/unlocked */
+  int nByte             /* Number of bytes to lock or unlock */
+){
+  OVERLAPPED ovlp;
+  DWORD dwFlags;
+  int rc = 0;           /* Result code form Lock/UnlockFileEx() */
+
+  /* Access to the winShmNode object is serialized by the caller */
+  assert( sqlite3_mutex_held(pFile->mutex) || pFile->nRef==0 );
+
+  /* Initialize the locking parameters */
+  dwFlags = LOCKFILE_FAIL_IMMEDIATELY;
+  if( lockType == _SHM_WRLCK ) dwFlags |= LOCKFILE_EXCLUSIVE_LOCK;
+
+  memset(&ovlp, 0, sizeof(OVERLAPPED));
+  ovlp.Offset = ofst;
+
+  /* Release/Acquire the system-level lock */
+  if( lockType==_SHM_UNLCK ){
+    rc = UnlockFileEx(pFile->hFile.h, 0, nByte, 0, &ovlp);
+  }else{
+    rc = LockFileEx(pFile->hFile.h, dwFlags, 0, nByte, 0, &ovlp);
+  }
+  
+  if( rc!= 0 ){
+    rc = SQLITE_OK;
+  }else{
+    pFile->lastErrno =  GetLastError();
+    rc = SQLITE_BUSY;
+  }
+
+  OSTRACE(("SHM-LOCK %d %s %s 0x%08lx\n", 
+           pFile->hFile.h,
+           rc==SQLITE_OK ? "ok" : "failed",
+           lockType==_SHM_UNLCK ? "UnlockFileEx" : "LockFileEx",
+           pFile->lastErrno));
+
+  return rc;
+}
+
+/* Forward references to VFS methods */
+static int winOpen(sqlite3_vfs*,const char*,sqlite3_file*,int,int*);
+static int winDelete(sqlite3_vfs *,const char*,int);
+
+/*
+** Purge the winShmNodeList list of all entries with winShmNode.nRef==0.
+**
+** This is not a VFS shared-memory method; it is a utility function called
+** by VFS shared-memory methods.
+*/
+static void winShmPurge(sqlite3_vfs *pVfs, int deleteFlag){
+  winShmNode **pp;
+  winShmNode *p;
+  BOOL bRc;
+  assert( winShmMutexHeld() );
+  pp = &winShmNodeList;
+  while( (p = *pp)!=0 ){
+    if( p->nRef==0 ){
+      int i;
+      if( p->mutex ) sqlite3_mutex_free(p->mutex);
+      for(i=0; i<p->nRegion; i++){
+        bRc = UnmapViewOfFile(p->aRegion[i].pMap);
+        OSTRACE(("SHM-PURGE pid-%d unmap region=%d %s\n",
+                 (int)GetCurrentProcessId(), i,
+                 bRc ? "ok" : "failed"));
+        bRc = CloseHandle(p->aRegion[i].hMap);
+        OSTRACE(("SHM-PURGE pid-%d close region=%d %s\n",
+                 (int)GetCurrentProcessId(), i,
+                 bRc ? "ok" : "failed"));
+      }
+      if( p->hFile.h != INVALID_HANDLE_VALUE ){
+        SimulateIOErrorBenign(1);
+        winClose((sqlite3_file *)&p->hFile);
+        SimulateIOErrorBenign(0);
+      }
+      if( deleteFlag ){
+        SimulateIOErrorBenign(1);
+        winDelete(pVfs, p->zFilename, 0);
+        SimulateIOErrorBenign(0);
+      }
+      *pp = p->pNext;
+      sqlite3_free(p->aRegion);
+      sqlite3_free(p);
+    }else{
+      pp = &p->pNext;
+    }
+  }
+}
+
+/*
+** Open the shared-memory area associated with database file pDbFd.
+**
+** When opening a new shared-memory file, if no other instances of that
+** file are currently open, in this process or in other processes, then
+** the file must be truncated to zero length or have its header cleared.
+*/
+static int winOpenSharedMemory(winFile *pDbFd){
+  struct winShm *p;                  /* The connection to be opened */
+  struct winShmNode *pShmNode = 0;   /* The underlying mmapped file */
+  int rc;                            /* Result code */
+  struct winShmNode *pNew;           /* Newly allocated winShmNode */
+  int nName;                         /* Size of zName in bytes */
+
+  assert( pDbFd->pShm==0 );    /* Not previously opened */
+
+  /* Allocate space for the new sqlite3_shm object.  Also speculatively
+  ** allocate space for a new winShmNode and filename.
+  */
+  p = sqlite3_malloc( sizeof(*p) );
+  if( p==0 ) return SQLITE_NOMEM;
+  memset(p, 0, sizeof(*p));
+  nName = sqlite3Strlen30(pDbFd->zPath);
+  pNew = sqlite3_malloc( sizeof(*pShmNode) + nName + 15 );
+  if( pNew==0 ){
+    sqlite3_free(p);
+    return SQLITE_NOMEM;
+  }
+  memset(pNew, 0, sizeof(*pNew));
+  pNew->zFilename = (char*)&pNew[1];
+  sqlite3_snprintf(nName+15, pNew->zFilename, "%s-shm", pDbFd->zPath);
+  sqlite3FileSuffix3(pDbFd->zPath, pNew->zFilename); 
+
+  /* Look to see if there is an existing winShmNode that can be used.
+  ** If no matching winShmNode currently exists, create a new one.
+  */
+  winShmEnterMutex();
+  for(pShmNode = winShmNodeList; pShmNode; pShmNode=pShmNode->pNext){
+    /* TBD need to come up with better match here.  Perhaps
+    ** use FILE_ID_BOTH_DIR_INFO Structure.
+    */
+    if( sqlite3StrICmp(pShmNode->zFilename, pNew->zFilename)==0 ) break;
+  }
+  if( pShmNode ){
+    sqlite3_free(pNew);
+  }else{
+    pShmNode = pNew;
+    pNew = 0;
+    ((winFile*)(&pShmNode->hFile))->h = INVALID_HANDLE_VALUE;
+    pShmNode->pNext = winShmNodeList;
+    winShmNodeList = pShmNode;
+
+    pShmNode->mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_FAST);
+    if( pShmNode->mutex==0 ){
+      rc = SQLITE_NOMEM;
+      goto shm_open_err;
+    }
+
+    rc = winOpen(pDbFd->pVfs,
+                 pShmNode->zFilename,             /* Name of the file (UTF-8) */
+                 (sqlite3_file*)&pShmNode->hFile,  /* File handle here */
+                 SQLITE_OPEN_WAL | SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE, /* Mode flags */
+                 0);
+    if( SQLITE_OK!=rc ){
+      rc = SQLITE_CANTOPEN_BKPT;
+      goto shm_open_err;
+    }
+
+    /* Check to see if another process is holding the dead-man switch.
+    ** If not, truncate the file to zero length. 
+    */
+    if( winShmSystemLock(pShmNode, _SHM_WRLCK, WIN_SHM_DMS, 1)==SQLITE_OK ){
+      rc = winTruncate((sqlite3_file *)&pShmNode->hFile, 0);
+      if( rc!=SQLITE_OK ){
+        rc = winLogError(SQLITE_IOERR_SHMOPEN, "winOpenShm", pDbFd->zPath);
+      }
+    }
+    if( rc==SQLITE_OK ){
+      winShmSystemLock(pShmNode, _SHM_UNLCK, WIN_SHM_DMS, 1);
+      rc = winShmSystemLock(pShmNode, _SHM_RDLCK, WIN_SHM_DMS, 1);
+    }
+    if( rc ) goto shm_open_err;
+  }
+
+  /* Make the new connection a child of the winShmNode */
+  p->pShmNode = pShmNode;
+#ifdef SQLITE_DEBUG
+  p->id = pShmNode->nextShmId++;
+#endif
+  pShmNode->nRef++;
+  pDbFd->pShm = p;
+  winShmLeaveMutex();
+
+  /* The reference count on pShmNode has already been incremented under
+  ** the cover of the winShmEnterMutex() mutex and the pointer from the
+  ** new (struct winShm) object to the pShmNode has been set. All that is
+  ** left to do is to link the new object into the linked list starting
+  ** at pShmNode->pFirst. This must be done while holding the pShmNode->mutex 
+  ** mutex.
+  */
+  sqlite3_mutex_enter(pShmNode->mutex);
+  p->pNext = pShmNode->pFirst;
+  pShmNode->pFirst = p;
+  sqlite3_mutex_leave(pShmNode->mutex);
+  return SQLITE_OK;
+
+  /* Jump here on any error */
+shm_open_err:
+  winShmSystemLock(pShmNode, _SHM_UNLCK, WIN_SHM_DMS, 1);
+  winShmPurge(pDbFd->pVfs, 0);      /* This call frees pShmNode if required */
+  sqlite3_free(p);
+  sqlite3_free(pNew);
+  winShmLeaveMutex();
+  return rc;
+}
+
+/*
+** Close a connection to shared-memory.  Delete the underlying 
+** storage if deleteFlag is true.
+*/
+static int winShmUnmap(
+  sqlite3_file *fd,          /* Database holding shared memory */
+  int deleteFlag             /* Delete after closing if true */
+){
+  winFile *pDbFd;       /* Database holding shared-memory */
+  winShm *p;            /* The connection to be closed */
+  winShmNode *pShmNode; /* The underlying shared-memory file */
+  winShm **pp;          /* For looping over sibling connections */
+
+  pDbFd = (winFile*)fd;
+  p = pDbFd->pShm;
+  if( p==0 ) return SQLITE_OK;
+  pShmNode = p->pShmNode;
+
+  /* Remove connection p from the set of connections associated
+  ** with pShmNode */
+  sqlite3_mutex_enter(pShmNode->mutex);
+  for(pp=&pShmNode->pFirst; (*pp)!=p; pp = &(*pp)->pNext){}
+  *pp = p->pNext;
+
+  /* Free the connection p */
+  sqlite3_free(p);
+  pDbFd->pShm = 0;
+  sqlite3_mutex_leave(pShmNode->mutex);
+
+  /* If pShmNode->nRef has reached 0, then close the underlying
+  ** shared-memory file, too */
+  winShmEnterMutex();
+  assert( pShmNode->nRef>0 );
+  pShmNode->nRef--;
+  if( pShmNode->nRef==0 ){
+    winShmPurge(pDbFd->pVfs, deleteFlag);
+  }
+  winShmLeaveMutex();
+
+  return SQLITE_OK;
+}
+
+/*
+** Change the lock state for a shared-memory segment.
+*/
+static int winShmLock(
+  sqlite3_file *fd,          /* Database file holding the shared memory */
+  int ofst,                  /* First lock to acquire or release */
+  int n,                     /* Number of locks to acquire or release */
+  int flags                  /* What to do with the lock */
+){
+  winFile *pDbFd = (winFile*)fd;        /* Connection holding shared memory */
+  winShm *p = pDbFd->pShm;              /* The shared memory being locked */
+  winShm *pX;                           /* For looping over all siblings */
+  winShmNode *pShmNode = p->pShmNode;
+  int rc = SQLITE_OK;                   /* Result code */
+  u16 mask;                             /* Mask of locks to take or release */
+
+  assert( ofst>=0 && ofst+n<=SQLITE_SHM_NLOCK );
+  assert( n>=1 );
+  assert( flags==(SQLITE_SHM_LOCK | SQLITE_SHM_SHARED)
+       || flags==(SQLITE_SHM_LOCK | SQLITE_SHM_EXCLUSIVE)
+       || flags==(SQLITE_SHM_UNLOCK | SQLITE_SHM_SHARED)
+       || flags==(SQLITE_SHM_UNLOCK | SQLITE_SHM_EXCLUSIVE) );
+  assert( n==1 || (flags & SQLITE_SHM_EXCLUSIVE)!=0 );
+
+  mask = (u16)((1U<<(ofst+n)) - (1U<<ofst));
+  assert( n>1 || mask==(1<<ofst) );
+  sqlite3_mutex_enter(pShmNode->mutex);
+  if( flags & SQLITE_SHM_UNLOCK ){
+    u16 allMask = 0; /* Mask of locks held by siblings */
+
+    /* See if any siblings hold this same lock */
+    for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
+      if( pX==p ) continue;
+      assert( (pX->exclMask & (p->exclMask|p->sharedMask))==0 );
+      allMask |= pX->sharedMask;
+    }
+
+    /* Unlock the system-level locks */
+    if( (mask & allMask)==0 ){
+      rc = winShmSystemLock(pShmNode, _SHM_UNLCK, ofst+WIN_SHM_BASE, n);
+    }else{
+      rc = SQLITE_OK;
+    }
+
+    /* Undo the local locks */
+    if( rc==SQLITE_OK ){
+      p->exclMask &= ~mask;
+      p->sharedMask &= ~mask;
+    } 
+  }else if( flags & SQLITE_SHM_SHARED ){
+    u16 allShared = 0;  /* Union of locks held by connections other than "p" */
+
+    /* Find out which shared locks are already held by sibling connections.
+    ** If any sibling already holds an exclusive lock, go ahead and return
+    ** SQLITE_BUSY.
+    */
+    for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
+      if( (pX->exclMask & mask)!=0 ){
+        rc = SQLITE_BUSY;
+        break;
+      }
+      allShared |= pX->sharedMask;
+    }
+
+    /* Get shared locks at the system level, if necessary */
+    if( rc==SQLITE_OK ){
+      if( (allShared & mask)==0 ){
+        rc = winShmSystemLock(pShmNode, _SHM_RDLCK, ofst+WIN_SHM_BASE, n);
+      }else{
+        rc = SQLITE_OK;
+      }
+    }
+
+    /* Get the local shared locks */
+    if( rc==SQLITE_OK ){
+      p->sharedMask |= mask;
+    }
+  }else{
+    /* Make sure no sibling connections hold locks that will block this
+    ** lock.  If any do, return SQLITE_BUSY right away.
+    */
+    for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
+      if( (pX->exclMask & mask)!=0 || (pX->sharedMask & mask)!=0 ){
+        rc = SQLITE_BUSY;
+        break;
+      }
+    }
+  
+    /* Get the exclusive locks at the system level.  Then if successful
+    ** also mark the local connection as being locked.
+    */
+    if( rc==SQLITE_OK ){
+      rc = winShmSystemLock(pShmNode, _SHM_WRLCK, ofst+WIN_SHM_BASE, n);
+      if( rc==SQLITE_OK ){
+        assert( (p->sharedMask & mask)==0 );
+        p->exclMask |= mask;
+      }
+    }
+  }
+  sqlite3_mutex_leave(pShmNode->mutex);
+  OSTRACE(("SHM-LOCK shmid-%d, pid-%d got %03x,%03x %s\n",
+           p->id, (int)GetCurrentProcessId(), p->sharedMask, p->exclMask,
+           rc ? "failed" : "ok"));
+  return rc;
+}
+
+/*
+** Implement a memory barrier or memory fence on shared memory.  
+**
+** All loads and stores begun before the barrier must complete before
+** any load or store begun after the barrier.
+*/
+static void winShmBarrier(
+  sqlite3_file *fd          /* Database holding the shared memory */
+){
+  UNUSED_PARAMETER(fd);
+  /* MemoryBarrier(); // does not work -- do not know why not */
+  winShmEnterMutex();
+  winShmLeaveMutex();
+}
+
+/*
+** This function is called to obtain a pointer to region iRegion of the 
+** shared-memory associated with the database file fd. Shared-memory regions 
+** are numbered starting from zero. Each shared-memory region is szRegion 
+** bytes in size.
+**
+** If an error occurs, an error code is returned and *pp is set to NULL.
+**
+** Otherwise, if the isWrite parameter is 0 and the requested shared-memory
+** region has not been allocated (by any client, including one running in a
+** separate process), then *pp is set to NULL and SQLITE_OK returned. If 
+** isWrite is non-zero and the requested shared-memory region has not yet 
+** been allocated, it is allocated by this function.
+**
+** If the shared-memory region has already been allocated or is allocated by
+** this call as described above, then it is mapped into this processes 
+** address space (if it is not already), *pp is set to point to the mapped 
+** memory and SQLITE_OK returned.
+*/
+static int winShmMap(
+  sqlite3_file *fd,               /* Handle open on database file */
+  int iRegion,                    /* Region to retrieve */
+  int szRegion,                   /* Size of regions */
+  int isWrite,                    /* True to extend file if necessary */
+  void volatile **pp              /* OUT: Mapped memory */
+){
+  winFile *pDbFd = (winFile*)fd;
+  winShm *p = pDbFd->pShm;
+  winShmNode *pShmNode;
+  int rc = SQLITE_OK;
+
+  if( !p ){
+    rc = winOpenSharedMemory(pDbFd);
+    if( rc!=SQLITE_OK ) return rc;
+    p = pDbFd->pShm;
+  }
+  pShmNode = p->pShmNode;
+
+  sqlite3_mutex_enter(pShmNode->mutex);
+  assert( szRegion==pShmNode->szRegion || pShmNode->nRegion==0 );
+
+  if( pShmNode->nRegion<=iRegion ){
+    struct ShmRegion *apNew;           /* New aRegion[] array */
+    int nByte = (iRegion+1)*szRegion;  /* Minimum required file size */
+    sqlite3_int64 sz;                  /* Current size of wal-index file */
+
+    pShmNode->szRegion = szRegion;
+
+    /* The requested region is not mapped into this processes address space.
+    ** Check to see if it has been allocated (i.e. if the wal-index file is
+    ** large enough to contain the requested region).
+    */
+    rc = winFileSize((sqlite3_file *)&pShmNode->hFile, &sz);
+    if( rc!=SQLITE_OK ){
+      rc = winLogError(SQLITE_IOERR_SHMSIZE, "winShmMap1", pDbFd->zPath);
+      goto shmpage_out;
+    }
+
+    if( sz<nByte ){
+      /* The requested memory region does not exist. If isWrite is set to
+      ** zero, exit early. *pp will be set to NULL and SQLITE_OK returned.
+      **
+      ** Alternatively, if isWrite is non-zero, use ftruncate() to allocate
+      ** the requested memory region.
+      */
+      if( !isWrite ) goto shmpage_out;
+      rc = winTruncate((sqlite3_file *)&pShmNode->hFile, nByte);
+      if( rc!=SQLITE_OK ){
+        rc = winLogError(SQLITE_IOERR_SHMSIZE, "winShmMap2", pDbFd->zPath);
+        goto shmpage_out;
+      }
+    }
+
+    /* Map the requested memory region into this processes address space. */
+    apNew = (struct ShmRegion *)sqlite3_realloc(
+        pShmNode->aRegion, (iRegion+1)*sizeof(apNew[0])
+    );
+    if( !apNew ){
+      rc = SQLITE_IOERR_NOMEM;
+      goto shmpage_out;
+    }
+    pShmNode->aRegion = apNew;
+
+    while( pShmNode->nRegion<=iRegion ){
+      HANDLE hMap;                /* file-mapping handle */
+      void *pMap = 0;             /* Mapped memory region */
+     
+      hMap = CreateFileMapping(pShmNode->hFile.h, 
+          NULL, PAGE_READWRITE, 0, nByte, NULL
+      );
+      OSTRACE(("SHM-MAP pid-%d create region=%d nbyte=%d %s\n",
+               (int)GetCurrentProcessId(), pShmNode->nRegion, nByte,
+               hMap ? "ok" : "failed"));
+      if( hMap ){
+        int iOffset = pShmNode->nRegion*szRegion;
+        int iOffsetShift = iOffset % winSysInfo.dwAllocationGranularity;
+        pMap = MapViewOfFile(hMap, FILE_MAP_WRITE | FILE_MAP_READ,
+            0, iOffset - iOffsetShift, szRegion + iOffsetShift
+        );
+        OSTRACE(("SHM-MAP pid-%d map region=%d offset=%d size=%d %s\n",
+                 (int)GetCurrentProcessId(), pShmNode->nRegion, iOffset, szRegion,
+                 pMap ? "ok" : "failed"));
+      }
+      if( !pMap ){
+        pShmNode->lastErrno = GetLastError();
+        rc = winLogError(SQLITE_IOERR_SHMMAP, "winShmMap3", pDbFd->zPath);
+        if( hMap ) CloseHandle(hMap);
+        goto shmpage_out;
+      }
+
+      pShmNode->aRegion[pShmNode->nRegion].pMap = pMap;
+      pShmNode->aRegion[pShmNode->nRegion].hMap = hMap;
+      pShmNode->nRegion++;
+    }
+  }
+
+shmpage_out:
+  if( pShmNode->nRegion>iRegion ){
+    int iOffset = iRegion*szRegion;
+    int iOffsetShift = iOffset % winSysInfo.dwAllocationGranularity;
+    char *p = (char *)pShmNode->aRegion[iRegion].pMap;
+    *pp = (void *)&p[iOffsetShift];
+  }else{
+    *pp = 0;
+  }
+  sqlite3_mutex_leave(pShmNode->mutex);
+  return rc;
+}
+
+#else
+# define winShmMap     0
+# define winShmLock    0
+# define winShmBarrier 0
+# define winShmUnmap   0
+#endif /* #ifndef SQLITE_OMIT_WAL */
+
+/*
+** Here ends the implementation of all sqlite3_file methods.
+**
+********************** End sqlite3_file Methods *******************************
+******************************************************************************/
+
+/*
+** This vector defines all the methods that can operate on an
+** sqlite3_file for win32.
+*/
+static const sqlite3_io_methods winIoMethod = {
+  2,                              /* iVersion */
+  winClose,                       /* xClose */
+  winRead,                        /* xRead */
+  winWrite,                       /* xWrite */
+  winTruncate,                    /* xTruncate */
+  winSync,                        /* xSync */
+  winFileSize,                    /* xFileSize */
+  winLock,                        /* xLock */
+  winUnlock,                      /* xUnlock */
+  winCheckReservedLock,           /* xCheckReservedLock */
+  winFileControl,                 /* xFileControl */
+  winSectorSize,                  /* xSectorSize */
+  winDeviceCharacteristics,       /* xDeviceCharacteristics */
+  winShmMap,                      /* xShmMap */
+  winShmLock,                     /* xShmLock */
+  winShmBarrier,                  /* xShmBarrier */
+  winShmUnmap                     /* xShmUnmap */
+};
+
+/****************************************************************************
+**************************** sqlite3_vfs methods ****************************
+**
+** This division contains the implementation of methods on the
+** sqlite3_vfs object.
+*/
+
+/*
+** Convert a UTF-8 filename into whatever form the underlying
+** operating system wants filenames in.  Space to hold the result
+** is obtained from malloc and must be freed by the calling
+** function.
+*/
+static void *convertUtf8Filename(const char *zFilename){
+  void *zConverted = 0;
+  if( isNT() ){
+    zConverted = utf8ToUnicode(zFilename);
+/* isNT() is 1 if SQLITE_OS_WINCE==1, so this else is never executed. 
+*/
+#if SQLITE_OS_WINCE==0
+  }else{
+    zConverted = sqlite3_win32_utf8_to_mbcs(zFilename);
+#endif
+  }
+  /* caller will handle out of memory */
+  return zConverted;
+}
+
+/*
+** Create a temporary file name in zBuf.  zBuf must be big enough to
+** hold at pVfs->mxPathname characters.
+*/
+static int getTempname(int nBuf, char *zBuf){
+  static char zChars[] =
+    "abcdefghijklmnopqrstuvwxyz"
+    "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+    "0123456789";
+  size_t i, j;
+  char zTempPath[MAX_PATH+1];
+
+  /* It's odd to simulate an io-error here, but really this is just
+  ** using the io-error infrastructure to test that SQLite handles this
+  ** function failing. 
+  */
+  SimulateIOError( return SQLITE_IOERR );
+
+  if( sqlite3_temp_directory ){
+    sqlite3_snprintf(MAX_PATH-30, zTempPath, "%s", sqlite3_temp_directory);
+  }else if( isNT() ){
+    char *zMulti;
+    WCHAR zWidePath[MAX_PATH];
+    GetTempPathW(MAX_PATH-30, zWidePath);
+    zMulti = unicodeToUtf8(zWidePath);
+    if( zMulti ){
+      sqlite3_snprintf(MAX_PATH-30, zTempPath, "%s", zMulti);
+      free(zMulti);
+    }else{
+      return SQLITE_NOMEM;
+    }
+/* isNT() is 1 if SQLITE_OS_WINCE==1, so this else is never executed. 
+** Since the ASCII version of these Windows API do not exist for WINCE,
+** it's important to not reference them for WINCE builds.
+*/
+#if SQLITE_OS_WINCE==0
+  }else{
+    char *zUtf8;
+    char zMbcsPath[MAX_PATH];
+    GetTempPathA(MAX_PATH-30, zMbcsPath);
+    zUtf8 = sqlite3_win32_mbcs_to_utf8(zMbcsPath);
+    if( zUtf8 ){
+      sqlite3_snprintf(MAX_PATH-30, zTempPath, "%s", zUtf8);
+      free(zUtf8);
+    }else{
+      return SQLITE_NOMEM;
+    }
+#endif
+  }
+
+  /* Check that the output buffer is large enough for the temporary file 
+  ** name. If it is not, return SQLITE_ERROR.
+  */
+  if( (sqlite3Strlen30(zTempPath) + sqlite3Strlen30(SQLITE_TEMP_FILE_PREFIX) + 17) >= nBuf ){
+    return SQLITE_ERROR;
+  }
+
+  for(i=sqlite3Strlen30(zTempPath); i>0 && zTempPath[i-1]=='\\'; i--){}
+  zTempPath[i] = 0;
+
+  sqlite3_snprintf(nBuf-17, zBuf,
+                   "%s\\"SQLITE_TEMP_FILE_PREFIX, zTempPath);
+  j = sqlite3Strlen30(zBuf);
+  sqlite3_randomness(15, &zBuf[j]);
+  for(i=0; i<15; i++, j++){
+    zBuf[j] = (char)zChars[ ((unsigned char)zBuf[j])%(sizeof(zChars)-1) ];
+  }
+  zBuf[j] = 0;
+
+  OSTRACE(("TEMP FILENAME: %s\n", zBuf));
+  return SQLITE_OK; 
+}
+
+/*
+** Open a file.
+*/
+static int winOpen(
+  sqlite3_vfs *pVfs,        /* Not used */
+  const char *zName,        /* Name of the file (UTF-8) */
+  sqlite3_file *id,         /* Write the SQLite file handle here */
+  int flags,                /* Open mode flags */
+  int *pOutFlags            /* Status return flags */
+){
+  HANDLE h;
+  DWORD dwDesiredAccess;
+  DWORD dwShareMode;
+  DWORD dwCreationDisposition;
+  DWORD dwFlagsAndAttributes = 0;
+#if SQLITE_OS_WINCE
+  int isTemp = 0;
+#endif
+  winFile *pFile = (winFile*)id;
+  void *zConverted;              /* Filename in OS encoding */
+  const char *zUtf8Name = zName; /* Filename in UTF-8 encoding */
+  int cnt = 0;
+
+  /* If argument zPath is a NULL pointer, this function is required to open
+  ** a temporary file. Use this buffer to store the file name in.
+  */
+  char zTmpname[MAX_PATH+1];     /* Buffer used to create temp filename */
+
+  int rc = SQLITE_OK;            /* Function Return Code */
+#if !defined(NDEBUG) || SQLITE_OS_WINCE
+  int eType = flags&0xFFFFFF00;  /* Type of file to open */
+#endif
+
+  int isExclusive  = (flags & SQLITE_OPEN_EXCLUSIVE);
+  int isDelete     = (flags & SQLITE_OPEN_DELETEONCLOSE);
+  int isCreate     = (flags & SQLITE_OPEN_CREATE);
+#ifndef NDEBUG
+  int isReadonly   = (flags & SQLITE_OPEN_READONLY);
+#endif
+  int isReadWrite  = (flags & SQLITE_OPEN_READWRITE);
+
+#ifndef NDEBUG
+  int isOpenJournal = (isCreate && (
+        eType==SQLITE_OPEN_MASTER_JOURNAL 
+     || eType==SQLITE_OPEN_MAIN_JOURNAL 
+     || eType==SQLITE_OPEN_WAL
+  ));
+#endif
+
+  /* Check the following statements are true: 
+  **
+  **   (a) Exactly one of the READWRITE and READONLY flags must be set, and 
+  **   (b) if CREATE is set, then READWRITE must also be set, and
+  **   (c) if EXCLUSIVE is set, then CREATE must also be set.
+  **   (d) if DELETEONCLOSE is set, then CREATE must also be set.
+  */
+  assert((isReadonly==0 || isReadWrite==0) && (isReadWrite || isReadonly));
+  assert(isCreate==0 || isReadWrite);
+  assert(isExclusive==0 || isCreate);
+  assert(isDelete==0 || isCreate);
+
+  /* The main DB, main journal, WAL file and master journal are never 
+  ** automatically deleted. Nor are they ever temporary files.  */
+  assert( (!isDelete && zName) || eType!=SQLITE_OPEN_MAIN_DB );
+  assert( (!isDelete && zName) || eType!=SQLITE_OPEN_MAIN_JOURNAL );
+  assert( (!isDelete && zName) || eType!=SQLITE_OPEN_MASTER_JOURNAL );
+  assert( (!isDelete && zName) || eType!=SQLITE_OPEN_WAL );
+
+  /* Assert that the upper layer has set one of the "file-type" flags. */
+  assert( eType==SQLITE_OPEN_MAIN_DB      || eType==SQLITE_OPEN_TEMP_DB 
+       || eType==SQLITE_OPEN_MAIN_JOURNAL || eType==SQLITE_OPEN_TEMP_JOURNAL 
+       || eType==SQLITE_OPEN_SUBJOURNAL   || eType==SQLITE_OPEN_MASTER_JOURNAL 
+       || eType==SQLITE_OPEN_TRANSIENT_DB || eType==SQLITE_OPEN_WAL
+  );
+
+  assert( id!=0 );
+  UNUSED_PARAMETER(pVfs);
+
+  pFile->h = INVALID_HANDLE_VALUE;
+
+  /* If the second argument to this function is NULL, generate a 
+  ** temporary file name to use 
+  */
+  if( !zUtf8Name ){
+    assert(isDelete && !isOpenJournal);
+    rc = getTempname(MAX_PATH+1, zTmpname);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+    zUtf8Name = zTmpname;
+  }
+
+  /* Convert the filename to the system encoding. */
+  zConverted = convertUtf8Filename(zUtf8Name);
+  if( zConverted==0 ){
+    return SQLITE_NOMEM;
+  }
+
+  if( isReadWrite ){
+    dwDesiredAccess = GENERIC_READ | GENERIC_WRITE;
+  }else{
+    dwDesiredAccess = GENERIC_READ;
+  }
+
+  /* SQLITE_OPEN_EXCLUSIVE is used to make sure that a new file is 
+  ** created. SQLite doesn't use it to indicate "exclusive access" 
+  ** as it is usually understood.
+  */
+  if( isExclusive ){
+    /* Creates a new file, only if it does not already exist. */
+    /* If the file exists, it fails. */
+    dwCreationDisposition = CREATE_NEW;
+  }else if( isCreate ){
+    /* Open existing file, or create if it doesn't exist */
+    dwCreationDisposition = OPEN_ALWAYS;
+  }else{
+    /* Opens a file, only if it exists. */
+    dwCreationDisposition = OPEN_EXISTING;
+  }
+
+  dwShareMode = FILE_SHARE_READ | FILE_SHARE_WRITE;
+
+  if( isDelete ){
+#if SQLITE_OS_WINCE
+    dwFlagsAndAttributes = FILE_ATTRIBUTE_HIDDEN;
+    isTemp = 1;
+#else
+    dwFlagsAndAttributes = FILE_ATTRIBUTE_TEMPORARY
+                               | FILE_ATTRIBUTE_HIDDEN
+                               | FILE_FLAG_DELETE_ON_CLOSE;
+#endif
+  }else{
+    dwFlagsAndAttributes = FILE_ATTRIBUTE_NORMAL;
+  }
+  /* Reports from the internet are that performance is always
+  ** better if FILE_FLAG_RANDOM_ACCESS is used.  Ticket #2699. */
+#if SQLITE_OS_WINCE
+  dwFlagsAndAttributes |= FILE_FLAG_RANDOM_ACCESS;
+#endif
+
+  if( isNT() ){
+    while( (h = CreateFileW((WCHAR*)zConverted,
+                            dwDesiredAccess,
+                            dwShareMode, NULL,
+                            dwCreationDisposition,
+                            dwFlagsAndAttributes,
+                            NULL))==INVALID_HANDLE_VALUE &&
+                            retryIoerr(&cnt) ){}
+/* isNT() is 1 if SQLITE_OS_WINCE==1, so this else is never executed. 
+** Since the ASCII version of these Windows API do not exist for WINCE,
+** it's important to not reference them for WINCE builds.
+*/
+#if SQLITE_OS_WINCE==0
+  }else{
+    while( (h = CreateFileA((char*)zConverted,
+                            dwDesiredAccess,
+                            dwShareMode, NULL,
+                            dwCreationDisposition,
+                            dwFlagsAndAttributes,
+                            NULL))==INVALID_HANDLE_VALUE &&
+                            retryIoerr(&cnt) ){}
+#endif
+  }
+
+  logIoerr(cnt);
+
+  OSTRACE(("OPEN %d %s 0x%lx %s\n", 
+           h, zName, dwDesiredAccess, 
+           h==INVALID_HANDLE_VALUE ? "failed" : "ok"));
+
+  if( h==INVALID_HANDLE_VALUE ){
+    pFile->lastErrno = GetLastError();
+    winLogError(SQLITE_CANTOPEN, "winOpen", zUtf8Name);
+    free(zConverted);
+    if( isReadWrite && !isExclusive ){
+      return winOpen(pVfs, zName, id, 
+             ((flags|SQLITE_OPEN_READONLY)&~(SQLITE_OPEN_CREATE|SQLITE_OPEN_READWRITE)), pOutFlags);
+    }else{
+      return SQLITE_CANTOPEN_BKPT;
+    }
+  }
+
+  if( pOutFlags ){
+    if( isReadWrite ){
+      *pOutFlags = SQLITE_OPEN_READWRITE;
+    }else{
+      *pOutFlags = SQLITE_OPEN_READONLY;
+    }
+  }
+
+  memset(pFile, 0, sizeof(*pFile));
+  pFile->pMethod = &winIoMethod;
+  pFile->h = h;
+  pFile->lastErrno = NO_ERROR;
+  pFile->pVfs = pVfs;
+  pFile->pShm = 0;
+  pFile->zPath = zName;
+  pFile->sectorSize = getSectorSize(pVfs, zUtf8Name);
+
+#if SQLITE_OS_WINCE
+  if( isReadWrite && eType==SQLITE_OPEN_MAIN_DB
+       && !winceCreateLock(zName, pFile)
+  ){
+    CloseHandle(h);
+    free(zConverted);
+    return SQLITE_CANTOPEN_BKPT;
+  }
+  if( isTemp ){
+    pFile->zDeleteOnClose = zConverted;
+  }else
+#endif
+  {
+    free(zConverted);
+  }
+
+  OpenCounter(+1);
+  return rc;
+}
+
+/*
+** Delete the named file.
+**
+** Note that windows does not allow a file to be deleted if some other
+** process has it open.  Sometimes a virus scanner or indexing program
+** will open a journal file shortly after it is created in order to do
+** whatever it does.  While this other process is holding the
+** file open, we will be unable to delete it.  To work around this
+** problem, we delay 100 milliseconds and try to delete again.  Up
+** to MX_DELETION_ATTEMPTs deletion attempts are run before giving
+** up and returning an error.
+*/
+static int winDelete(
+  sqlite3_vfs *pVfs,          /* Not used on win32 */
+  const char *zFilename,      /* Name of file to delete */
+  int syncDir                 /* Not used on win32 */
+){
+  int cnt = 0;
+  int rc;
+  void *zConverted;
+  UNUSED_PARAMETER(pVfs);
+  UNUSED_PARAMETER(syncDir);
+
+  SimulateIOError(return SQLITE_IOERR_DELETE);
+  zConverted = convertUtf8Filename(zFilename);
+  if( zConverted==0 ){
+    return SQLITE_NOMEM;
+  }
+  if( isNT() ){
+    rc = 1;
+    while( GetFileAttributesW(zConverted)!=INVALID_FILE_ATTRIBUTES &&
+           (rc = DeleteFileW(zConverted))==0 && retryIoerr(&cnt) ){}
+    rc = rc ? SQLITE_OK : SQLITE_ERROR;
+/* isNT() is 1 if SQLITE_OS_WINCE==1, so this else is never executed. 
+** Since the ASCII version of these Windows API do not exist for WINCE,
+** it's important to not reference them for WINCE builds.
+*/
+#if SQLITE_OS_WINCE==0
+  }else{
+    rc = 1;
+    while( GetFileAttributesA(zConverted)!=INVALID_FILE_ATTRIBUTES &&
+           (rc = DeleteFileA(zConverted))==0 && retryIoerr(&cnt) ){}
+    rc = rc ? SQLITE_OK : SQLITE_ERROR;
+#endif
+  }
+  if( rc ){
+    rc = winLogError(SQLITE_IOERR_DELETE, "winDelete", zFilename);
+  }else{
+    logIoerr(cnt);
+  }
+  free(zConverted);
+  OSTRACE(("DELETE \"%s\" %s\n", zFilename, (rc ? "failed" : "ok" )));
+  return rc;
+}
+
+/*
+** Check the existance and status of a file.
+*/
+static int winAccess(
+  sqlite3_vfs *pVfs,         /* Not used on win32 */
+  const char *zFilename,     /* Name of file to check */
+  int flags,                 /* Type of test to make on this file */
+  int *pResOut               /* OUT: Result */
+){
+  DWORD attr;
+  int rc = 0;
+  void *zConverted;
+  UNUSED_PARAMETER(pVfs);
+
+  SimulateIOError( return SQLITE_IOERR_ACCESS; );
+  zConverted = convertUtf8Filename(zFilename);
+  if( zConverted==0 ){
+    return SQLITE_NOMEM;
+  }
+  if( isNT() ){
+    int cnt = 0;
+    WIN32_FILE_ATTRIBUTE_DATA sAttrData;
+    memset(&sAttrData, 0, sizeof(sAttrData));
+    while( !(rc = GetFileAttributesExW((WCHAR*)zConverted,
+                             GetFileExInfoStandard, 
+                             &sAttrData)) && retryIoerr(&cnt) ){}
+    if( rc ){
+      /* For an SQLITE_ACCESS_EXISTS query, treat a zero-length file
+      ** as if it does not exist.
+      */
+      if(    flags==SQLITE_ACCESS_EXISTS
+          && sAttrData.nFileSizeHigh==0 
+          && sAttrData.nFileSizeLow==0 ){
+        attr = INVALID_FILE_ATTRIBUTES;
+      }else{
+        attr = sAttrData.dwFileAttributes;
+      }
+    }else{
+      logIoerr(cnt);
+      if( GetLastError()!=ERROR_FILE_NOT_FOUND ){
+        winLogError(SQLITE_IOERR_ACCESS, "winAccess", zFilename);
+        free(zConverted);
+        return SQLITE_IOERR_ACCESS;
+      }else{
+        attr = INVALID_FILE_ATTRIBUTES;
+      }
+    }
+/* isNT() is 1 if SQLITE_OS_WINCE==1, so this else is never executed. 
+** Since the ASCII version of these Windows API do not exist for WINCE,
+** it's important to not reference them for WINCE builds.
+*/
+#if SQLITE_OS_WINCE==0
+  }else{
+    attr = GetFileAttributesA((char*)zConverted);
+#endif
+  }
+  free(zConverted);
+  switch( flags ){
+    case SQLITE_ACCESS_READ:
+    case SQLITE_ACCESS_EXISTS:
+      rc = attr!=INVALID_FILE_ATTRIBUTES;
+      break;
+    case SQLITE_ACCESS_READWRITE:
+      rc = attr!=INVALID_FILE_ATTRIBUTES &&
+             (attr & FILE_ATTRIBUTE_READONLY)==0;
+      break;
+    default:
+      assert(!"Invalid flags argument");
+  }
+  *pResOut = rc;
+  return SQLITE_OK;
+}
+
+
+/*
+** Turn a relative pathname into a full pathname.  Write the full
+** pathname into zOut[].  zOut[] will be at least pVfs->mxPathname
+** bytes in size.
+*/
+static int winFullPathname(
+  sqlite3_vfs *pVfs,            /* Pointer to vfs object */
+  const char *zRelative,        /* Possibly relative input path */
+  int nFull,                    /* Size of output buffer in bytes */
+  char *zFull                   /* Output buffer */
+){
+  
+#if defined(__CYGWIN__)
+  SimulateIOError( return SQLITE_ERROR );
+  UNUSED_PARAMETER(nFull);
+  cygwin_conv_to_full_win32_path(zRelative, zFull);
+  return SQLITE_OK;
+#endif
+
+#if SQLITE_OS_WINCE
+  SimulateIOError( return SQLITE_ERROR );
+  UNUSED_PARAMETER(nFull);
+  /* WinCE has no concept of a relative pathname, or so I am told. */
+  sqlite3_snprintf(pVfs->mxPathname, zFull, "%s", zRelative);
+  return SQLITE_OK;
+#endif
+
+#if !SQLITE_OS_WINCE && !defined(__CYGWIN__)
+  int nByte;
+  void *zConverted;
+  char *zOut;
+
+  /* If this path name begins with "/X:", where "X" is any alphabetic
+  ** character, discard the initial "/" from the pathname.
+  */
+  if( zRelative[0]=='/' && sqlite3Isalpha(zRelative[1]) && zRelative[2]==':' ){
+    zRelative++;
+  }
+
+  /* It's odd to simulate an io-error here, but really this is just
+  ** using the io-error infrastructure to test that SQLite handles this
+  ** function failing. This function could fail if, for example, the
+  ** current working directory has been unlinked.
+  */
+  SimulateIOError( return SQLITE_ERROR );
+  UNUSED_PARAMETER(nFull);
+  zConverted = convertUtf8Filename(zRelative);
+  if( isNT() ){
+    WCHAR *zTemp;
+    nByte = GetFullPathNameW((WCHAR*)zConverted, 0, 0, 0) + 3;
+    zTemp = malloc( nByte*sizeof(zTemp[0]) );
+    if( zTemp==0 ){
+      free(zConverted);
+      return SQLITE_NOMEM;
+    }
+    GetFullPathNameW((WCHAR*)zConverted, nByte, zTemp, 0);
+    free(zConverted);
+    zOut = unicodeToUtf8(zTemp);
+    free(zTemp);
+/* isNT() is 1 if SQLITE_OS_WINCE==1, so this else is never executed. 
+** Since the ASCII version of these Windows API do not exist for WINCE,
+** it's important to not reference them for WINCE builds.
+*/
+#if SQLITE_OS_WINCE==0
+  }else{
+    char *zTemp;
+    nByte = GetFullPathNameA((char*)zConverted, 0, 0, 0) + 3;
+    zTemp = malloc( nByte*sizeof(zTemp[0]) );
+    if( zTemp==0 ){
+      free(zConverted);
+      return SQLITE_NOMEM;
+    }
+    GetFullPathNameA((char*)zConverted, nByte, zTemp, 0);
+    free(zConverted);
+    zOut = sqlite3_win32_mbcs_to_utf8(zTemp);
+    free(zTemp);
+#endif
+  }
+  if( zOut ){
+    sqlite3_snprintf(pVfs->mxPathname, zFull, "%s", zOut);
+    free(zOut);
+    return SQLITE_OK;
+  }else{
+    return SQLITE_NOMEM;
+  }
+#endif
+}
+
+/*
+** Get the sector size of the device used to store
+** file.
+*/
+static int getSectorSize(
+    sqlite3_vfs *pVfs,
+    const char *zRelative     /* UTF-8 file name */
+){
+  DWORD bytesPerSector = SQLITE_DEFAULT_SECTOR_SIZE;
+  /* GetDiskFreeSpace is not supported under WINCE */
+#if SQLITE_OS_WINCE
+  UNUSED_PARAMETER(pVfs);
+  UNUSED_PARAMETER(zRelative);
+#else
+  char zFullpath[MAX_PATH+1];
+  int rc;
+  DWORD dwRet = 0;
+  DWORD dwDummy;
+
+  /*
+  ** We need to get the full path name of the file
+  ** to get the drive letter to look up the sector
+  ** size.
+  */
+  SimulateIOErrorBenign(1);
+  rc = winFullPathname(pVfs, zRelative, MAX_PATH, zFullpath);
+  SimulateIOErrorBenign(0);
+  if( rc == SQLITE_OK )
+  {
+    void *zConverted = convertUtf8Filename(zFullpath);
+    if( zConverted ){
+      if( isNT() ){
+        /* trim path to just drive reference */
+        WCHAR *p = zConverted;
+        for(;*p;p++){
+          if( *p == '\\' ){
+            *p = '\0';
+            break;
+          }
+        }
+        dwRet = GetDiskFreeSpaceW((WCHAR*)zConverted,
+                                  &dwDummy,
+                                  &bytesPerSector,
+                                  &dwDummy,
+                                  &dwDummy);
+      }else{
+        /* trim path to just drive reference */
+        char *p = (char *)zConverted;
+        for(;*p;p++){
+          if( *p == '\\' ){
+            *p = '\0';
+            break;
+          }
+        }
+        dwRet = GetDiskFreeSpaceA((char*)zConverted,
+                                  &dwDummy,
+                                  &bytesPerSector,
+                                  &dwDummy,
+                                  &dwDummy);
+      }
+      free(zConverted);
+    }
+    if( !dwRet ){
+      bytesPerSector = SQLITE_DEFAULT_SECTOR_SIZE;
+    }
+  }
+#endif
+  return (int) bytesPerSector; 
+}
+
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+/*
+** Interfaces for opening a shared library, finding entry points
+** within the shared library, and closing the shared library.
+*/
+/*
+** Interfaces for opening a shared library, finding entry points
+** within the shared library, and closing the shared library.
+*/
+static void *winDlOpen(sqlite3_vfs *pVfs, const char *zFilename){
+  HANDLE h;
+  void *zConverted = convertUtf8Filename(zFilename);
+  UNUSED_PARAMETER(pVfs);
+  if( zConverted==0 ){
+    return 0;
+  }
+  if( isNT() ){
+    h = LoadLibraryW((WCHAR*)zConverted);
+/* isNT() is 1 if SQLITE_OS_WINCE==1, so this else is never executed. 
+** Since the ASCII version of these Windows API do not exist for WINCE,
+** it's important to not reference them for WINCE builds.
+*/
+#if SQLITE_OS_WINCE==0
+  }else{
+    h = LoadLibraryA((char*)zConverted);
+#endif
+  }
+  free(zConverted);
+  return (void*)h;
+}
+static void winDlError(sqlite3_vfs *pVfs, int nBuf, char *zBufOut){
+  UNUSED_PARAMETER(pVfs);
+  getLastErrorMsg(nBuf, zBufOut);
+}
+static void (*winDlSym(sqlite3_vfs *pVfs, void *pHandle, const char *zSymbol))(void){
+  UNUSED_PARAMETER(pVfs);
+#if SQLITE_OS_WINCE
+  /* The GetProcAddressA() routine is only available on wince. */
+  return (void(*)(void))GetProcAddressA((HANDLE)pHandle, zSymbol);
+#else
+  /* All other windows platforms expect GetProcAddress() to take
+  ** an Ansi string regardless of the _UNICODE setting */
+  return (void(*)(void))GetProcAddress((HANDLE)pHandle, zSymbol);
+#endif
+}
+static void winDlClose(sqlite3_vfs *pVfs, void *pHandle){
+  UNUSED_PARAMETER(pVfs);
+  FreeLibrary((HANDLE)pHandle);
+}
+#else /* if SQLITE_OMIT_LOAD_EXTENSION is defined: */
+  #define winDlOpen  0
+  #define winDlError 0
+  #define winDlSym   0
+  #define winDlClose 0
+#endif
+
+
+/*
+** Write up to nBuf bytes of randomness into zBuf.
+*/
+static int winRandomness(sqlite3_vfs *pVfs, int nBuf, char *zBuf){
+  int n = 0;
+  UNUSED_PARAMETER(pVfs);
+#if defined(SQLITE_TEST)
+  n = nBuf;
+  memset(zBuf, 0, nBuf);
+#else
+  if( sizeof(SYSTEMTIME)<=nBuf-n ){
+    SYSTEMTIME x;
+    GetSystemTime(&x);
+    memcpy(&zBuf[n], &x, sizeof(x));
+    n += sizeof(x);
+  }
+  if( sizeof(DWORD)<=nBuf-n ){
+    DWORD pid = GetCurrentProcessId();
+    memcpy(&zBuf[n], &pid, sizeof(pid));
+    n += sizeof(pid);
+  }
+  if( sizeof(DWORD)<=nBuf-n ){
+    DWORD cnt = GetTickCount();
+    memcpy(&zBuf[n], &cnt, sizeof(cnt));
+    n += sizeof(cnt);
+  }
+  if( sizeof(LARGE_INTEGER)<=nBuf-n ){
+    LARGE_INTEGER i;
+    QueryPerformanceCounter(&i);
+    memcpy(&zBuf[n], &i, sizeof(i));
+    n += sizeof(i);
+  }
+#endif
+  return n;
+}
+
+
+/*
+** Sleep for a little while.  Return the amount of time slept.
+*/
+static int winSleep(sqlite3_vfs *pVfs, int microsec){
+  Sleep((microsec+999)/1000);
+  UNUSED_PARAMETER(pVfs);
+  return ((microsec+999)/1000)*1000;
+}
+
+/*
+** The following variable, if set to a non-zero value, is interpreted as
+** the number of seconds since 1970 and is used to set the result of
+** sqlite3OsCurrentTime() during testing.
+*/
+#ifdef SQLITE_TEST
+int sqlite3_current_time = 0;  /* Fake system time in seconds since 1970. */
+#endif
+
+/*
+** Find the current time (in Universal Coordinated Time).  Write into *piNow
+** the current time and date as a Julian Day number times 86_400_000.  In
+** other words, write into *piNow the number of milliseconds since the Julian
+** epoch of noon in Greenwich on November 24, 4714 B.C according to the
+** proleptic Gregorian calendar.
+**
+** On success, return SQLITE_OK.  Return SQLITE_ERROR if the time and date 
+** cannot be found.
+*/
+static int winCurrentTimeInt64(sqlite3_vfs *pVfs, sqlite3_int64 *piNow){
+  /* FILETIME structure is a 64-bit value representing the number of 
+     100-nanosecond intervals since January 1, 1601 (= JD 2305813.5). 
+  */
+  FILETIME ft;
+  static const sqlite3_int64 winFiletimeEpoch = 23058135*(sqlite3_int64)8640000;
+#ifdef SQLITE_TEST
+  static const sqlite3_int64 unixEpoch = 24405875*(sqlite3_int64)8640000;
+#endif
+  /* 2^32 - to avoid use of LL and warnings in gcc */
+  static const sqlite3_int64 max32BitValue = 
+      (sqlite3_int64)2000000000 + (sqlite3_int64)2000000000 + (sqlite3_int64)294967296;
+
+#if SQLITE_OS_WINCE
+  SYSTEMTIME time;
+  GetSystemTime(&time);
+  /* if SystemTimeToFileTime() fails, it returns zero. */
+  if (!SystemTimeToFileTime(&time,&ft)){
+    return SQLITE_ERROR;
+  }
+#else
+  GetSystemTimeAsFileTime( &ft );
+#endif
+
+  *piNow = winFiletimeEpoch +
+            ((((sqlite3_int64)ft.dwHighDateTime)*max32BitValue) + 
+               (sqlite3_int64)ft.dwLowDateTime)/(sqlite3_int64)10000;
+
+#ifdef SQLITE_TEST
+  if( sqlite3_current_time ){
+    *piNow = 1000*(sqlite3_int64)sqlite3_current_time + unixEpoch;
+  }
+#endif
+  UNUSED_PARAMETER(pVfs);
+  return SQLITE_OK;
+}
+
+/*
+** Find the current time (in Universal Coordinated Time).  Write the
+** current time and date as a Julian Day number into *prNow and
+** return 0.  Return 1 if the time and date cannot be found.
+*/
+static int winCurrentTime(sqlite3_vfs *pVfs, double *prNow){
+  int rc;
+  sqlite3_int64 i;
+  rc = winCurrentTimeInt64(pVfs, &i);
+  if( !rc ){
+    *prNow = i/86400000.0;
+  }
+  return rc;
+}
+
+/*
+** The idea is that this function works like a combination of
+** GetLastError() and FormatMessage() on windows (or errno and
+** strerror_r() on unix). After an error is returned by an OS
+** function, SQLite calls this function with zBuf pointing to
+** a buffer of nBuf bytes. The OS layer should populate the
+** buffer with a nul-terminated UTF-8 encoded error message
+** describing the last IO error to have occurred within the calling
+** thread.
+**
+** If the error message is too large for the supplied buffer,
+** it should be truncated. The return value of xGetLastError
+** is zero if the error message fits in the buffer, or non-zero
+** otherwise (if the message was truncated). If non-zero is returned,
+** then it is not necessary to include the nul-terminator character
+** in the output buffer.
+**
+** Not supplying an error message will have no adverse effect
+** on SQLite. It is fine to have an implementation that never
+** returns an error message:
+**
+**   int xGetLastError(sqlite3_vfs *pVfs, int nBuf, char *zBuf){
+**     assert(zBuf[0]=='\0');
+**     return 0;
+**   }
+**
+** However if an error message is supplied, it will be incorporated
+** by sqlite into the error message available to the user using
+** sqlite3_errmsg(), possibly making IO errors easier to debug.
+*/
+static int winGetLastError(sqlite3_vfs *pVfs, int nBuf, char *zBuf){
+  UNUSED_PARAMETER(pVfs);
+  return getLastErrorMsg(nBuf, zBuf);
+}
+
+
+
+/*
+** Initialize and deinitialize the operating system interface.
+*/
+int sqlite3_os_init(void){
+  static sqlite3_vfs winVfs = {
+    3,                   /* iVersion */
+    sizeof(winFile),     /* szOsFile */
+    MAX_PATH,            /* mxPathname */
+    0,                   /* pNext */
+    "win32",             /* zName */
+    0,                   /* pAppData */
+    winOpen,             /* xOpen */
+    winDelete,           /* xDelete */
+    winAccess,           /* xAccess */
+    winFullPathname,     /* xFullPathname */
+    winDlOpen,           /* xDlOpen */
+    winDlError,          /* xDlError */
+    winDlSym,            /* xDlSym */
+    winDlClose,          /* xDlClose */
+    winRandomness,       /* xRandomness */
+    winSleep,            /* xSleep */
+    winCurrentTime,      /* xCurrentTime */
+    winGetLastError,     /* xGetLastError */
+    winCurrentTimeInt64, /* xCurrentTimeInt64 */
+    0,                   /* xSetSystemCall */
+    0,                   /* xGetSystemCall */
+    0,                   /* xNextSystemCall */
+  };
+
+#ifndef SQLITE_OMIT_WAL
+  /* get memory map allocation granularity */
+  memset(&winSysInfo, 0, sizeof(SYSTEM_INFO));
+  GetSystemInfo(&winSysInfo);
+  assert(winSysInfo.dwAllocationGranularity > 0);
+#endif
+
+  sqlite3_vfs_register(&winVfs, 1);
+  return SQLITE_OK; 
+}
+int sqlite3_os_end(void){ 
+  return SQLITE_OK;
+}
+
+#endif /* SQLITE_OS_WIN */
diff --git a/src/pager.c b/src/pager.c
new file mode 100644
index 0000000..ad6f831
--- /dev/null
+++ b/src/pager.c
@@ -0,0 +1,6892 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This is the implementation of the page cache subsystem or "pager".
+** 
+** The pager is used to access a database disk file.  It implements
+** atomic commit and rollback through the use of a journal file that
+** is separate from the database file.  The pager also implements file
+** locking to prevent two processes from writing the same database
+** file simultaneously, or one process from reading the database while
+** another is writing.
+*/
+#ifndef SQLITE_OMIT_DISKIO
+#include "sqliteInt.h"
+#include "wal.h"
+
+
+/******************* NOTES ON THE DESIGN OF THE PAGER ************************
+**
+** This comment block describes invariants that hold when using a rollback
+** journal.  These invariants do not apply for journal_mode=WAL,
+** journal_mode=MEMORY, or journal_mode=OFF.
+**
+** Within this comment block, a page is deemed to have been synced
+** automatically as soon as it is written when PRAGMA synchronous=OFF.
+** Otherwise, the page is not synced until the xSync method of the VFS
+** is called successfully on the file containing the page.
+**
+** Definition:  A page of the database file is said to be "overwriteable" if
+** one or more of the following are true about the page:
+** 
+**     (a)  The original content of the page as it was at the beginning of
+**          the transaction has been written into the rollback journal and
+**          synced.
+** 
+**     (b)  The page was a freelist leaf page at the start of the transaction.
+** 
+**     (c)  The page number is greater than the largest page that existed in
+**          the database file at the start of the transaction.
+** 
+** (1) A page of the database file is never overwritten unless one of the
+**     following are true:
+** 
+**     (a) The page and all other pages on the same sector are overwriteable.
+** 
+**     (b) The atomic page write optimization is enabled, and the entire
+**         transaction other than the update of the transaction sequence
+**         number consists of a single page change.
+** 
+** (2) The content of a page written into the rollback journal exactly matches
+**     both the content in the database when the rollback journal was written
+**     and the content in the database at the beginning of the current
+**     transaction.
+** 
+** (3) Writes to the database file are an integer multiple of the page size
+**     in length and are aligned on a page boundary.
+** 
+** (4) Reads from the database file are either aligned on a page boundary and
+**     an integer multiple of the page size in length or are taken from the
+**     first 100 bytes of the database file.
+** 
+** (5) All writes to the database file are synced prior to the rollback journal
+**     being deleted, truncated, or zeroed.
+** 
+** (6) If a master journal file is used, then all writes to the database file
+**     are synced prior to the master journal being deleted.
+** 
+** Definition: Two databases (or the same database at two points it time)
+** are said to be "logically equivalent" if they give the same answer to
+** all queries.  Note in particular the the content of freelist leaf
+** pages can be changed arbitarily without effecting the logical equivalence
+** of the database.
+** 
+** (7) At any time, if any subset, including the empty set and the total set,
+**     of the unsynced changes to a rollback journal are removed and the 
+**     journal is rolled back, the resulting database file will be logical
+**     equivalent to the database file at the beginning of the transaction.
+** 
+** (8) When a transaction is rolled back, the xTruncate method of the VFS
+**     is called to restore the database file to the same size it was at
+**     the beginning of the transaction.  (In some VFSes, the xTruncate
+**     method is a no-op, but that does not change the fact the SQLite will
+**     invoke it.)
+** 
+** (9) Whenever the database file is modified, at least one bit in the range
+**     of bytes from 24 through 39 inclusive will be changed prior to releasing
+**     the EXCLUSIVE lock, thus signaling other connections on the same
+**     database to flush their caches.
+**
+** (10) The pattern of bits in bytes 24 through 39 shall not repeat in less
+**      than one billion transactions.
+**
+** (11) A database file is well-formed at the beginning and at the conclusion
+**      of every transaction.
+**
+** (12) An EXCLUSIVE lock is held on the database file when writing to
+**      the database file.
+**
+** (13) A SHARED lock is held on the database file while reading any
+**      content out of the database file.
+**
+******************************************************************************/
+
+/*
+** Macros for troubleshooting.  Normally turned off
+*/
+#if 0
+int sqlite3PagerTrace=1;  /* True to enable tracing */
+#define sqlite3DebugPrintf printf
+#define PAGERTRACE(X)     if( sqlite3PagerTrace ){ sqlite3DebugPrintf X; }
+#else
+#define PAGERTRACE(X)
+#endif
+
+/*
+** The following two macros are used within the PAGERTRACE() macros above
+** to print out file-descriptors. 
+**
+** PAGERID() takes a pointer to a Pager struct as its argument. The
+** associated file-descriptor is returned. FILEHANDLEID() takes an sqlite3_file
+** struct as its argument.
+*/
+#define PAGERID(p) ((int)(p->fd))
+#define FILEHANDLEID(fd) ((int)fd)
+
+/*
+** The Pager.eState variable stores the current 'state' of a pager. A
+** pager may be in any one of the seven states shown in the following
+** state diagram.
+**
+**                            OPEN <------+------+
+**                              |         |      |
+**                              V         |      |
+**               +---------> READER-------+      |
+**               |              |                |
+**               |              V                |
+**               |<-------WRITER_LOCKED------> ERROR
+**               |              |                ^  
+**               |              V                |
+**               |<------WRITER_CACHEMOD-------->|
+**               |              |                |
+**               |              V                |
+**               |<-------WRITER_DBMOD---------->|
+**               |              |                |
+**               |              V                |
+**               +<------WRITER_FINISHED-------->+
+**
+**
+** List of state transitions and the C [function] that performs each:
+** 
+**   OPEN              -> READER              [sqlite3PagerSharedLock]
+**   READER            -> OPEN                [pager_unlock]
+**
+**   READER            -> WRITER_LOCKED       [sqlite3PagerBegin]
+**   WRITER_LOCKED     -> WRITER_CACHEMOD     [pager_open_journal]
+**   WRITER_CACHEMOD   -> WRITER_DBMOD        [syncJournal]
+**   WRITER_DBMOD      -> WRITER_FINISHED     [sqlite3PagerCommitPhaseOne]
+**   WRITER_***        -> READER              [pager_end_transaction]
+**
+**   WRITER_***        -> ERROR               [pager_error]
+**   ERROR             -> OPEN                [pager_unlock]
+** 
+**
+**  OPEN:
+**
+**    The pager starts up in this state. Nothing is guaranteed in this
+**    state - the file may or may not be locked and the database size is
+**    unknown. The database may not be read or written.
+**
+**    * No read or write transaction is active.
+**    * Any lock, or no lock at all, may be held on the database file.
+**    * The dbSize, dbOrigSize and dbFileSize variables may not be trusted.
+**
+**  READER:
+**
+**    In this state all the requirements for reading the database in 
+**    rollback (non-WAL) mode are met. Unless the pager is (or recently
+**    was) in exclusive-locking mode, a user-level read transaction is 
+**    open. The database size is known in this state.
+**
+**    A connection running with locking_mode=normal enters this state when
+**    it opens a read-transaction on the database and returns to state
+**    OPEN after the read-transaction is completed. However a connection
+**    running in locking_mode=exclusive (including temp databases) remains in
+**    this state even after the read-transaction is closed. The only way
+**    a locking_mode=exclusive connection can transition from READER to OPEN
+**    is via the ERROR state (see below).
+** 
+**    * A read transaction may be active (but a write-transaction cannot).
+**    * A SHARED or greater lock is held on the database file.
+**    * The dbSize variable may be trusted (even if a user-level read 
+**      transaction is not active). The dbOrigSize and dbFileSize variables
+**      may not be trusted at this point.
+**    * If the database is a WAL database, then the WAL connection is open.
+**    * Even if a read-transaction is not open, it is guaranteed that 
+**      there is no hot-journal in the file-system.
+**
+**  WRITER_LOCKED:
+**
+**    The pager moves to this state from READER when a write-transaction
+**    is first opened on the database. In WRITER_LOCKED state, all locks 
+**    required to start a write-transaction are held, but no actual 
+**    modifications to the cache or database have taken place.
+**
+**    In rollback mode, a RESERVED or (if the transaction was opened with 
+**    BEGIN EXCLUSIVE) EXCLUSIVE lock is obtained on the database file when
+**    moving to this state, but the journal file is not written to or opened 
+**    to in this state. If the transaction is committed or rolled back while 
+**    in WRITER_LOCKED state, all that is required is to unlock the database 
+**    file.
+**
+**    IN WAL mode, WalBeginWriteTransaction() is called to lock the log file.
+**    If the connection is running with locking_mode=exclusive, an attempt
+**    is made to obtain an EXCLUSIVE lock on the database file.
+**
+**    * A write transaction is active.
+**    * If the connection is open in rollback-mode, a RESERVED or greater 
+**      lock is held on the database file.
+**    * If the connection is open in WAL-mode, a WAL write transaction
+**      is open (i.e. sqlite3WalBeginWriteTransaction() has been successfully
+**      called).
+**    * The dbSize, dbOrigSize and dbFileSize variables are all valid.
+**    * The contents of the pager cache have not been modified.
+**    * The journal file may or may not be open.
+**    * Nothing (not even the first header) has been written to the journal.
+**
+**  WRITER_CACHEMOD:
+**
+**    A pager moves from WRITER_LOCKED state to this state when a page is
+**    first modified by the upper layer. In rollback mode the journal file
+**    is opened (if it is not already open) and a header written to the
+**    start of it. The database file on disk has not been modified.
+**
+**    * A write transaction is active.
+**    * A RESERVED or greater lock is held on the database file.
+**    * The journal file is open and the first header has been written 
+**      to it, but the header has not been synced to disk.
+**    * The contents of the page cache have been modified.
+**
+**  WRITER_DBMOD:
+**
+**    The pager transitions from WRITER_CACHEMOD into WRITER_DBMOD state
+**    when it modifies the contents of the database file. WAL connections
+**    never enter this state (since they do not modify the database file,
+**    just the log file).
+**
+**    * A write transaction is active.
+**    * An EXCLUSIVE or greater lock is held on the database file.
+**    * The journal file is open and the first header has been written 
+**      and synced to disk.
+**    * The contents of the page cache have been modified (and possibly
+**      written to disk).
+**
+**  WRITER_FINISHED:
+**
+**    It is not possible for a WAL connection to enter this state.
+**
+**    A rollback-mode pager changes to WRITER_FINISHED state from WRITER_DBMOD
+**    state after the entire transaction has been successfully written into the
+**    database file. In this state the transaction may be committed simply
+**    by finalizing the journal file. Once in WRITER_FINISHED state, it is 
+**    not possible to modify the database further. At this point, the upper 
+**    layer must either commit or rollback the transaction.
+**
+**    * A write transaction is active.
+**    * An EXCLUSIVE or greater lock is held on the database file.
+**    * All writing and syncing of journal and database data has finished.
+**      If no error occured, all that remains is to finalize the journal to
+**      commit the transaction. If an error did occur, the caller will need
+**      to rollback the transaction. 
+**
+**  ERROR:
+**
+**    The ERROR state is entered when an IO or disk-full error (including
+**    SQLITE_IOERR_NOMEM) occurs at a point in the code that makes it 
+**    difficult to be sure that the in-memory pager state (cache contents, 
+**    db size etc.) are consistent with the contents of the file-system.
+**
+**    Temporary pager files may enter the ERROR state, but in-memory pagers
+**    cannot.
+**
+**    For example, if an IO error occurs while performing a rollback, 
+**    the contents of the page-cache may be left in an inconsistent state.
+**    At this point it would be dangerous to change back to READER state
+**    (as usually happens after a rollback). Any subsequent readers might
+**    report database corruption (due to the inconsistent cache), and if
+**    they upgrade to writers, they may inadvertently corrupt the database
+**    file. To avoid this hazard, the pager switches into the ERROR state
+**    instead of READER following such an error.
+**
+**    Once it has entered the ERROR state, any attempt to use the pager
+**    to read or write data returns an error. Eventually, once all 
+**    outstanding transactions have been abandoned, the pager is able to
+**    transition back to OPEN state, discarding the contents of the 
+**    page-cache and any other in-memory state at the same time. Everything
+**    is reloaded from disk (and, if necessary, hot-journal rollback peformed)
+**    when a read-transaction is next opened on the pager (transitioning
+**    the pager into READER state). At that point the system has recovered 
+**    from the error.
+**
+**    Specifically, the pager jumps into the ERROR state if:
+**
+**      1. An error occurs while attempting a rollback. This happens in
+**         function sqlite3PagerRollback().
+**
+**      2. An error occurs while attempting to finalize a journal file
+**         following a commit in function sqlite3PagerCommitPhaseTwo().
+**
+**      3. An error occurs while attempting to write to the journal or
+**         database file in function pagerStress() in order to free up
+**         memory.
+**
+**    In other cases, the error is returned to the b-tree layer. The b-tree
+**    layer then attempts a rollback operation. If the error condition 
+**    persists, the pager enters the ERROR state via condition (1) above.
+**
+**    Condition (3) is necessary because it can be triggered by a read-only
+**    statement executed within a transaction. In this case, if the error
+**    code were simply returned to the user, the b-tree layer would not
+**    automatically attempt a rollback, as it assumes that an error in a
+**    read-only statement cannot leave the pager in an internally inconsistent 
+**    state.
+**
+**    * The Pager.errCode variable is set to something other than SQLITE_OK.
+**    * There are one or more outstanding references to pages (after the
+**      last reference is dropped the pager should move back to OPEN state).
+**    * The pager is not an in-memory pager.
+**    
+**
+** Notes:
+**
+**   * A pager is never in WRITER_DBMOD or WRITER_FINISHED state if the
+**     connection is open in WAL mode. A WAL connection is always in one
+**     of the first four states.
+**
+**   * Normally, a connection open in exclusive mode is never in PAGER_OPEN
+**     state. There are two exceptions: immediately after exclusive-mode has
+**     been turned on (and before any read or write transactions are 
+**     executed), and when the pager is leaving the "error state".
+**
+**   * See also: assert_pager_state().
+*/
+#define PAGER_OPEN                  0
+#define PAGER_READER                1
+#define PAGER_WRITER_LOCKED         2
+#define PAGER_WRITER_CACHEMOD       3
+#define PAGER_WRITER_DBMOD          4
+#define PAGER_WRITER_FINISHED       5
+#define PAGER_ERROR                 6
+
+/*
+** The Pager.eLock variable is almost always set to one of the 
+** following locking-states, according to the lock currently held on
+** the database file: NO_LOCK, SHARED_LOCK, RESERVED_LOCK or EXCLUSIVE_LOCK.
+** This variable is kept up to date as locks are taken and released by
+** the pagerLockDb() and pagerUnlockDb() wrappers.
+**
+** If the VFS xLock() or xUnlock() returns an error other than SQLITE_BUSY
+** (i.e. one of the SQLITE_IOERR subtypes), it is not clear whether or not
+** the operation was successful. In these circumstances pagerLockDb() and
+** pagerUnlockDb() take a conservative approach - eLock is always updated
+** when unlocking the file, and only updated when locking the file if the
+** VFS call is successful. This way, the Pager.eLock variable may be set
+** to a less exclusive (lower) value than the lock that is actually held
+** at the system level, but it is never set to a more exclusive value.
+**
+** This is usually safe. If an xUnlock fails or appears to fail, there may 
+** be a few redundant xLock() calls or a lock may be held for longer than
+** required, but nothing really goes wrong.
+**
+** The exception is when the database file is unlocked as the pager moves
+** from ERROR to OPEN state. At this point there may be a hot-journal file 
+** in the file-system that needs to be rolled back (as part of a OPEN->SHARED
+** transition, by the same pager or any other). If the call to xUnlock()
+** fails at this point and the pager is left holding an EXCLUSIVE lock, this
+** can confuse the call to xCheckReservedLock() call made later as part
+** of hot-journal detection.
+**
+** xCheckReservedLock() is defined as returning true "if there is a RESERVED 
+** lock held by this process or any others". So xCheckReservedLock may 
+** return true because the caller itself is holding an EXCLUSIVE lock (but
+** doesn't know it because of a previous error in xUnlock). If this happens
+** a hot-journal may be mistaken for a journal being created by an active
+** transaction in another process, causing SQLite to read from the database
+** without rolling it back.
+**
+** To work around this, if a call to xUnlock() fails when unlocking the
+** database in the ERROR state, Pager.eLock is set to UNKNOWN_LOCK. It
+** is only changed back to a real locking state after a successful call
+** to xLock(EXCLUSIVE). Also, the code to do the OPEN->SHARED state transition
+** omits the check for a hot-journal if Pager.eLock is set to UNKNOWN_LOCK 
+** lock. Instead, it assumes a hot-journal exists and obtains an EXCLUSIVE
+** lock on the database file before attempting to roll it back. See function
+** PagerSharedLock() for more detail.
+**
+** Pager.eLock may only be set to UNKNOWN_LOCK when the pager is in 
+** PAGER_OPEN state.
+*/
+#define UNKNOWN_LOCK                (EXCLUSIVE_LOCK+1)
+
+/*
+** A macro used for invoking the codec if there is one
+*/
+#ifdef SQLITE_HAS_CODEC
+# define CODEC1(P,D,N,X,E) \
+    if( P->xCodec && P->xCodec(P->pCodec,D,N,X)==0 ){ E; }
+# define CODEC2(P,D,N,X,E,O) \
+    if( P->xCodec==0 ){ O=(char*)D; }else \
+    if( (O=(char*)(P->xCodec(P->pCodec,D,N,X)))==0 ){ E; }
+#else
+# define CODEC1(P,D,N,X,E)   /* NO-OP */
+# define CODEC2(P,D,N,X,E,O) O=(char*)D
+#endif
+
+/*
+** The maximum allowed sector size. 64KiB. If the xSectorsize() method 
+** returns a value larger than this, then MAX_SECTOR_SIZE is used instead.
+** This could conceivably cause corruption following a power failure on
+** such a system. This is currently an undocumented limit.
+*/
+#define MAX_SECTOR_SIZE 0x10000
+
+/*
+** An instance of the following structure is allocated for each active
+** savepoint and statement transaction in the system. All such structures
+** are stored in the Pager.aSavepoint[] array, which is allocated and
+** resized using sqlite3Realloc().
+**
+** When a savepoint is created, the PagerSavepoint.iHdrOffset field is
+** set to 0. If a journal-header is written into the main journal while
+** the savepoint is active, then iHdrOffset is set to the byte offset 
+** immediately following the last journal record written into the main
+** journal before the journal-header. This is required during savepoint
+** rollback (see pagerPlaybackSavepoint()).
+*/
+typedef struct PagerSavepoint PagerSavepoint;
+struct PagerSavepoint {
+  i64 iOffset;                 /* Starting offset in main journal */
+  i64 iHdrOffset;              /* See above */
+  Bitvec *pInSavepoint;        /* Set of pages in this savepoint */
+  Pgno nOrig;                  /* Original number of pages in file */
+  Pgno iSubRec;                /* Index of first record in sub-journal */
+#ifndef SQLITE_OMIT_WAL
+  u32 aWalData[WAL_SAVEPOINT_NDATA];        /* WAL savepoint context */
+#endif
+};
+
+/*
+** A open page cache is an instance of struct Pager. A description of
+** some of the more important member variables follows:
+**
+** eState
+**
+**   The current 'state' of the pager object. See the comment and state
+**   diagram above for a description of the pager state.
+**
+** eLock
+**
+**   For a real on-disk database, the current lock held on the database file -
+**   NO_LOCK, SHARED_LOCK, RESERVED_LOCK or EXCLUSIVE_LOCK.
+**
+**   For a temporary or in-memory database (neither of which require any
+**   locks), this variable is always set to EXCLUSIVE_LOCK. Since such
+**   databases always have Pager.exclusiveMode==1, this tricks the pager
+**   logic into thinking that it already has all the locks it will ever
+**   need (and no reason to release them).
+**
+**   In some (obscure) circumstances, this variable may also be set to
+**   UNKNOWN_LOCK. See the comment above the #define of UNKNOWN_LOCK for
+**   details.
+**
+** changeCountDone
+**
+**   This boolean variable is used to make sure that the change-counter 
+**   (the 4-byte header field at byte offset 24 of the database file) is 
+**   not updated more often than necessary. 
+**
+**   It is set to true when the change-counter field is updated, which 
+**   can only happen if an exclusive lock is held on the database file.
+**   It is cleared (set to false) whenever an exclusive lock is 
+**   relinquished on the database file. Each time a transaction is committed,
+**   The changeCountDone flag is inspected. If it is true, the work of
+**   updating the change-counter is omitted for the current transaction.
+**
+**   This mechanism means that when running in exclusive mode, a connection 
+**   need only update the change-counter once, for the first transaction
+**   committed.
+**
+** setMaster
+**
+**   When PagerCommitPhaseOne() is called to commit a transaction, it may
+**   (or may not) specify a master-journal name to be written into the 
+**   journal file before it is synced to disk.
+**
+**   Whether or not a journal file contains a master-journal pointer affects 
+**   the way in which the journal file is finalized after the transaction is 
+**   committed or rolled back when running in "journal_mode=PERSIST" mode.
+**   If a journal file does not contain a master-journal pointer, it is
+**   finalized by overwriting the first journal header with zeroes. If
+**   it does contain a master-journal pointer the journal file is finalized 
+**   by truncating it to zero bytes, just as if the connection were 
+**   running in "journal_mode=truncate" mode.
+**
+**   Journal files that contain master journal pointers cannot be finalized
+**   simply by overwriting the first journal-header with zeroes, as the
+**   master journal pointer could interfere with hot-journal rollback of any
+**   subsequently interrupted transaction that reuses the journal file.
+**
+**   The flag is cleared as soon as the journal file is finalized (either
+**   by PagerCommitPhaseTwo or PagerRollback). If an IO error prevents the
+**   journal file from being successfully finalized, the setMaster flag
+**   is cleared anyway (and the pager will move to ERROR state).
+**
+** doNotSpill, doNotSyncSpill
+**
+**   These two boolean variables control the behaviour of cache-spills
+**   (calls made by the pcache module to the pagerStress() routine to
+**   write cached data to the file-system in order to free up memory).
+**
+**   When doNotSpill is non-zero, writing to the database from pagerStress()
+**   is disabled altogether. This is done in a very obscure case that
+**   comes up during savepoint rollback that requires the pcache module
+**   to allocate a new page to prevent the journal file from being written
+**   while it is being traversed by code in pager_playback().
+** 
+**   If doNotSyncSpill is non-zero, writing to the database from pagerStress()
+**   is permitted, but syncing the journal file is not. This flag is set
+**   by sqlite3PagerWrite() when the file-system sector-size is larger than
+**   the database page-size in order to prevent a journal sync from happening 
+**   in between the journalling of two pages on the same sector. 
+**
+** subjInMemory
+**
+**   This is a boolean variable. If true, then any required sub-journal
+**   is opened as an in-memory journal file. If false, then in-memory
+**   sub-journals are only used for in-memory pager files.
+**
+**   This variable is updated by the upper layer each time a new 
+**   write-transaction is opened.
+**
+** dbSize, dbOrigSize, dbFileSize
+**
+**   Variable dbSize is set to the number of pages in the database file.
+**   It is valid in PAGER_READER and higher states (all states except for
+**   OPEN and ERROR). 
+**
+**   dbSize is set based on the size of the database file, which may be 
+**   larger than the size of the database (the value stored at offset
+**   28 of the database header by the btree). If the size of the file
+**   is not an integer multiple of the page-size, the value stored in
+**   dbSize is rounded down (i.e. a 5KB file with 2K page-size has dbSize==2).
+**   Except, any file that is greater than 0 bytes in size is considered
+**   to have at least one page. (i.e. a 1KB file with 2K page-size leads
+**   to dbSize==1).
+**
+**   During a write-transaction, if pages with page-numbers greater than
+**   dbSize are modified in the cache, dbSize is updated accordingly.
+**   Similarly, if the database is truncated using PagerTruncateImage(), 
+**   dbSize is updated.
+**
+**   Variables dbOrigSize and dbFileSize are valid in states 
+**   PAGER_WRITER_LOCKED and higher. dbOrigSize is a copy of the dbSize
+**   variable at the start of the transaction. It is used during rollback,
+**   and to determine whether or not pages need to be journalled before
+**   being modified.
+**
+**   Throughout a write-transaction, dbFileSize contains the size of
+**   the file on disk in pages. It is set to a copy of dbSize when the
+**   write-transaction is first opened, and updated when VFS calls are made
+**   to write or truncate the database file on disk. 
+**
+**   The only reason the dbFileSize variable is required is to suppress 
+**   unnecessary calls to xTruncate() after committing a transaction. If, 
+**   when a transaction is committed, the dbFileSize variable indicates 
+**   that the database file is larger than the database image (Pager.dbSize), 
+**   pager_truncate() is called. The pager_truncate() call uses xFilesize()
+**   to measure the database file on disk, and then truncates it if required.
+**   dbFileSize is not used when rolling back a transaction. In this case
+**   pager_truncate() is called unconditionally (which means there may be
+**   a call to xFilesize() that is not strictly required). In either case,
+**   pager_truncate() may cause the file to become smaller or larger.
+**
+** dbHintSize
+**
+**   The dbHintSize variable is used to limit the number of calls made to
+**   the VFS xFileControl(FCNTL_SIZE_HINT) method. 
+**
+**   dbHintSize is set to a copy of the dbSize variable when a
+**   write-transaction is opened (at the same time as dbFileSize and
+**   dbOrigSize). If the xFileControl(FCNTL_SIZE_HINT) method is called,
+**   dbHintSize is increased to the number of pages that correspond to the
+**   size-hint passed to the method call. See pager_write_pagelist() for 
+**   details.
+**
+** errCode
+**
+**   The Pager.errCode variable is only ever used in PAGER_ERROR state. It
+**   is set to zero in all other states. In PAGER_ERROR state, Pager.errCode 
+**   is always set to SQLITE_FULL, SQLITE_IOERR or one of the SQLITE_IOERR_XXX 
+**   sub-codes.
+*/
+struct Pager {
+  sqlite3_vfs *pVfs;          /* OS functions to use for IO */
+  u8 exclusiveMode;           /* Boolean. True if locking_mode==EXCLUSIVE */
+  u8 journalMode;             /* One of the PAGER_JOURNALMODE_* values */
+  u8 useJournal;              /* Use a rollback journal on this file */
+  u8 noReadlock;              /* Do not bother to obtain readlocks */
+  u8 noSync;                  /* Do not sync the journal if true */
+  u8 fullSync;                /* Do extra syncs of the journal for robustness */
+  u8 ckptSyncFlags;           /* SYNC_NORMAL or SYNC_FULL for checkpoint */
+  u8 syncFlags;               /* SYNC_NORMAL or SYNC_FULL otherwise */
+  u8 tempFile;                /* zFilename is a temporary file */
+  u8 readOnly;                /* True for a read-only database */
+  u8 memDb;                   /* True to inhibit all file I/O */
+
+  /**************************************************************************
+  ** The following block contains those class members that change during
+  ** routine opertion.  Class members not in this block are either fixed
+  ** when the pager is first created or else only change when there is a
+  ** significant mode change (such as changing the page_size, locking_mode,
+  ** or the journal_mode).  From another view, these class members describe
+  ** the "state" of the pager, while other class members describe the
+  ** "configuration" of the pager.
+  */
+  u8 eState;                  /* Pager state (OPEN, READER, WRITER_LOCKED..) */
+  u8 eLock;                   /* Current lock held on database file */
+  u8 changeCountDone;         /* Set after incrementing the change-counter */
+  u8 setMaster;               /* True if a m-j name has been written to jrnl */
+  u8 doNotSpill;              /* Do not spill the cache when non-zero */
+  u8 doNotSyncSpill;          /* Do not do a spill that requires jrnl sync */
+  u8 subjInMemory;            /* True to use in-memory sub-journals */
+  Pgno dbSize;                /* Number of pages in the database */
+  Pgno dbOrigSize;            /* dbSize before the current transaction */
+  Pgno dbFileSize;            /* Number of pages in the database file */
+  Pgno dbHintSize;            /* Value passed to FCNTL_SIZE_HINT call */
+  int errCode;                /* One of several kinds of errors */
+  int nRec;                   /* Pages journalled since last j-header written */
+  u32 cksumInit;              /* Quasi-random value added to every checksum */
+  u32 nSubRec;                /* Number of records written to sub-journal */
+  Bitvec *pInJournal;         /* One bit for each page in the database file */
+  sqlite3_file *fd;           /* File descriptor for database */
+  sqlite3_file *jfd;          /* File descriptor for main journal */
+  sqlite3_file *sjfd;         /* File descriptor for sub-journal */
+  i64 journalOff;             /* Current write offset in the journal file */
+  i64 journalHdr;             /* Byte offset to previous journal header */
+  sqlite3_backup *pBackup;    /* Pointer to list of ongoing backup processes */
+  PagerSavepoint *aSavepoint; /* Array of active savepoints */
+  int nSavepoint;             /* Number of elements in aSavepoint[] */
+  char dbFileVers[16];        /* Changes whenever database file changes */
+  /*
+  ** End of the routinely-changing class members
+  ***************************************************************************/
+
+  u16 nExtra;                 /* Add this many bytes to each in-memory page */
+  i16 nReserve;               /* Number of unused bytes at end of each page */
+  u32 vfsFlags;               /* Flags for sqlite3_vfs.xOpen() */
+  u32 sectorSize;             /* Assumed sector size during rollback */
+  int pageSize;               /* Number of bytes in a page */
+  Pgno mxPgno;                /* Maximum allowed size of the database */
+  i64 journalSizeLimit;       /* Size limit for persistent journal files */
+  char *zFilename;            /* Name of the database file */
+  char *zJournal;             /* Name of the journal file */
+  int (*xBusyHandler)(void*); /* Function to call when busy */
+  void *pBusyHandlerArg;      /* Context argument for xBusyHandler */
+  int nHit, nMiss;            /* Total cache hits and misses */
+#ifdef SQLITE_TEST
+  int nRead, nWrite;          /* Database pages read/written */
+#endif
+  void (*xReiniter)(DbPage*); /* Call this routine when reloading pages */
+#ifdef SQLITE_HAS_CODEC
+  void *(*xCodec)(void*,void*,Pgno,int); /* Routine for en/decoding data */
+  void (*xCodecSizeChng)(void*,int,int); /* Notify of page size changes */
+  void (*xCodecFree)(void*);             /* Destructor for the codec */
+  void *pCodec;               /* First argument to xCodec... methods */
+#endif
+  char *pTmpSpace;            /* Pager.pageSize bytes of space for tmp use */
+  PCache *pPCache;            /* Pointer to page cache object */
+#ifndef SQLITE_OMIT_WAL
+  Wal *pWal;                  /* Write-ahead log used by "journal_mode=wal" */
+  char *zWal;                 /* File name for write-ahead log */
+#endif
+};
+
+/*
+** The following global variables hold counters used for
+** testing purposes only.  These variables do not exist in
+** a non-testing build.  These variables are not thread-safe.
+*/
+#ifdef SQLITE_TEST
+int sqlite3_pager_readdb_count = 0;    /* Number of full pages read from DB */
+int sqlite3_pager_writedb_count = 0;   /* Number of full pages written to DB */
+int sqlite3_pager_writej_count = 0;    /* Number of pages written to journal */
+# define PAGER_INCR(v)  v++
+#else
+# define PAGER_INCR(v)
+#endif
+
+
+
+/*
+** Journal files begin with the following magic string.  The data
+** was obtained from /dev/random.  It is used only as a sanity check.
+**
+** Since version 2.8.0, the journal format contains additional sanity
+** checking information.  If the power fails while the journal is being
+** written, semi-random garbage data might appear in the journal
+** file after power is restored.  If an attempt is then made
+** to roll the journal back, the database could be corrupted.  The additional
+** sanity checking data is an attempt to discover the garbage in the
+** journal and ignore it.
+**
+** The sanity checking information for the new journal format consists
+** of a 32-bit checksum on each page of data.  The checksum covers both
+** the page number and the pPager->pageSize bytes of data for the page.
+** This cksum is initialized to a 32-bit random value that appears in the
+** journal file right after the header.  The random initializer is important,
+** because garbage data that appears at the end of a journal is likely
+** data that was once in other files that have now been deleted.  If the
+** garbage data came from an obsolete journal file, the checksums might
+** be correct.  But by initializing the checksum to random value which
+** is different for every journal, we minimize that risk.
+*/
+static const unsigned char aJournalMagic[] = {
+  0xd9, 0xd5, 0x05, 0xf9, 0x20, 0xa1, 0x63, 0xd7,
+};
+
+/*
+** The size of the of each page record in the journal is given by
+** the following macro.
+*/
+#define JOURNAL_PG_SZ(pPager)  ((pPager->pageSize) + 8)
+
+/*
+** The journal header size for this pager. This is usually the same 
+** size as a single disk sector. See also setSectorSize().
+*/
+#define JOURNAL_HDR_SZ(pPager) (pPager->sectorSize)
+
+/*
+** The macro MEMDB is true if we are dealing with an in-memory database.
+** We do this as a macro so that if the SQLITE_OMIT_MEMORYDB macro is set,
+** the value of MEMDB will be a constant and the compiler will optimize
+** out code that would never execute.
+*/
+#ifdef SQLITE_OMIT_MEMORYDB
+# define MEMDB 0
+#else
+# define MEMDB pPager->memDb
+#endif
+
+/*
+** The maximum legal page number is (2^31 - 1).
+*/
+#define PAGER_MAX_PGNO 2147483647
+
+/*
+** The argument to this macro is a file descriptor (type sqlite3_file*).
+** Return 0 if it is not open, or non-zero (but not 1) if it is.
+**
+** This is so that expressions can be written as:
+**
+**   if( isOpen(pPager->jfd) ){ ...
+**
+** instead of
+**
+**   if( pPager->jfd->pMethods ){ ...
+*/
+#define isOpen(pFd) ((pFd)->pMethods)
+
+/*
+** Return true if this pager uses a write-ahead log instead of the usual
+** rollback journal. Otherwise false.
+*/
+#ifndef SQLITE_OMIT_WAL
+static int pagerUseWal(Pager *pPager){
+  return (pPager->pWal!=0);
+}
+#else
+# define pagerUseWal(x) 0
+# define pagerRollbackWal(x) 0
+# define pagerWalFrames(v,w,x,y,z) 0
+# define pagerOpenWalIfPresent(z) SQLITE_OK
+# define pagerBeginReadTransaction(z) SQLITE_OK
+#endif
+
+#ifndef NDEBUG 
+/*
+** Usage:
+**
+**   assert( assert_pager_state(pPager) );
+**
+** This function runs many asserts to try to find inconsistencies in
+** the internal state of the Pager object.
+*/
+static int assert_pager_state(Pager *p){
+  Pager *pPager = p;
+
+  /* State must be valid. */
+  assert( p->eState==PAGER_OPEN
+       || p->eState==PAGER_READER
+       || p->eState==PAGER_WRITER_LOCKED
+       || p->eState==PAGER_WRITER_CACHEMOD
+       || p->eState==PAGER_WRITER_DBMOD
+       || p->eState==PAGER_WRITER_FINISHED
+       || p->eState==PAGER_ERROR
+  );
+
+  /* Regardless of the current state, a temp-file connection always behaves
+  ** as if it has an exclusive lock on the database file. It never updates
+  ** the change-counter field, so the changeCountDone flag is always set.
+  */
+  assert( p->tempFile==0 || p->eLock==EXCLUSIVE_LOCK );
+  assert( p->tempFile==0 || pPager->changeCountDone );
+
+  /* If the useJournal flag is clear, the journal-mode must be "OFF". 
+  ** And if the journal-mode is "OFF", the journal file must not be open.
+  */
+  assert( p->journalMode==PAGER_JOURNALMODE_OFF || p->useJournal );
+  assert( p->journalMode!=PAGER_JOURNALMODE_OFF || !isOpen(p->jfd) );
+
+  /* Check that MEMDB implies noSync. And an in-memory journal. Since 
+  ** this means an in-memory pager performs no IO at all, it cannot encounter 
+  ** either SQLITE_IOERR or SQLITE_FULL during rollback or while finalizing 
+  ** a journal file. (although the in-memory journal implementation may 
+  ** return SQLITE_IOERR_NOMEM while the journal file is being written). It 
+  ** is therefore not possible for an in-memory pager to enter the ERROR 
+  ** state.
+  */
+  if( MEMDB ){
+    assert( p->noSync );
+    assert( p->journalMode==PAGER_JOURNALMODE_OFF 
+         || p->journalMode==PAGER_JOURNALMODE_MEMORY 
+    );
+    assert( p->eState!=PAGER_ERROR && p->eState!=PAGER_OPEN );
+    assert( pagerUseWal(p)==0 );
+  }
+
+  /* If changeCountDone is set, a RESERVED lock or greater must be held
+  ** on the file.
+  */
+  assert( pPager->changeCountDone==0 || pPager->eLock>=RESERVED_LOCK );
+  assert( p->eLock!=PENDING_LOCK );
+
+  switch( p->eState ){
+    case PAGER_OPEN:
+      assert( !MEMDB );
+      assert( pPager->errCode==SQLITE_OK );
+      assert( sqlite3PcacheRefCount(pPager->pPCache)==0 || pPager->tempFile );
+      break;
+
+    case PAGER_READER:
+      assert( pPager->errCode==SQLITE_OK );
+      assert( p->eLock!=UNKNOWN_LOCK );
+      assert( p->eLock>=SHARED_LOCK || p->noReadlock );
+      break;
+
+    case PAGER_WRITER_LOCKED:
+      assert( p->eLock!=UNKNOWN_LOCK );
+      assert( pPager->errCode==SQLITE_OK );
+      if( !pagerUseWal(pPager) ){
+        assert( p->eLock>=RESERVED_LOCK );
+      }
+      assert( pPager->dbSize==pPager->dbOrigSize );
+      assert( pPager->dbOrigSize==pPager->dbFileSize );
+      assert( pPager->dbOrigSize==pPager->dbHintSize );
+      assert( pPager->setMaster==0 );
+      break;
+
+    case PAGER_WRITER_CACHEMOD:
+      assert( p->eLock!=UNKNOWN_LOCK );
+      assert( pPager->errCode==SQLITE_OK );
+      if( !pagerUseWal(pPager) ){
+        /* It is possible that if journal_mode=wal here that neither the
+        ** journal file nor the WAL file are open. This happens during
+        ** a rollback transaction that switches from journal_mode=off
+        ** to journal_mode=wal.
+        */
+        assert( p->eLock>=RESERVED_LOCK );
+        assert( isOpen(p->jfd) 
+             || p->journalMode==PAGER_JOURNALMODE_OFF 
+             || p->journalMode==PAGER_JOURNALMODE_WAL 
+        );
+      }
+      assert( pPager->dbOrigSize==pPager->dbFileSize );
+      assert( pPager->dbOrigSize==pPager->dbHintSize );
+      break;
+
+    case PAGER_WRITER_DBMOD:
+      assert( p->eLock==EXCLUSIVE_LOCK );
+      assert( pPager->errCode==SQLITE_OK );
+      assert( !pagerUseWal(pPager) );
+      assert( p->eLock>=EXCLUSIVE_LOCK );
+      assert( isOpen(p->jfd) 
+           || p->journalMode==PAGER_JOURNALMODE_OFF 
+           || p->journalMode==PAGER_JOURNALMODE_WAL 
+      );
+      assert( pPager->dbOrigSize<=pPager->dbHintSize );
+      break;
+
+    case PAGER_WRITER_FINISHED:
+      assert( p->eLock==EXCLUSIVE_LOCK );
+      assert( pPager->errCode==SQLITE_OK );
+      assert( !pagerUseWal(pPager) );
+      assert( isOpen(p->jfd) 
+           || p->journalMode==PAGER_JOURNALMODE_OFF 
+           || p->journalMode==PAGER_JOURNALMODE_WAL 
+      );
+      break;
+
+    case PAGER_ERROR:
+      /* There must be at least one outstanding reference to the pager if
+      ** in ERROR state. Otherwise the pager should have already dropped
+      ** back to OPEN state.
+      */
+      assert( pPager->errCode!=SQLITE_OK );
+      assert( sqlite3PcacheRefCount(pPager->pPCache)>0 );
+      break;
+  }
+
+  return 1;
+}
+#endif /* ifndef NDEBUG */
+
+#ifdef SQLITE_DEBUG 
+/*
+** Return a pointer to a human readable string in a static buffer
+** containing the state of the Pager object passed as an argument. This
+** is intended to be used within debuggers. For example, as an alternative
+** to "print *pPager" in gdb:
+**
+** (gdb) printf "%s", print_pager_state(pPager)
+*/
+static char *print_pager_state(Pager *p){
+  static char zRet[1024];
+
+  sqlite3_snprintf(1024, zRet,
+      "Filename:      %s\n"
+      "State:         %s errCode=%d\n"
+      "Lock:          %s\n"
+      "Locking mode:  locking_mode=%s\n"
+      "Journal mode:  journal_mode=%s\n"
+      "Backing store: tempFile=%d memDb=%d useJournal=%d\n"
+      "Journal:       journalOff=%lld journalHdr=%lld\n"
+      "Size:          dbsize=%d dbOrigSize=%d dbFileSize=%d\n"
+      , p->zFilename
+      , p->eState==PAGER_OPEN            ? "OPEN" :
+        p->eState==PAGER_READER          ? "READER" :
+        p->eState==PAGER_WRITER_LOCKED   ? "WRITER_LOCKED" :
+        p->eState==PAGER_WRITER_CACHEMOD ? "WRITER_CACHEMOD" :
+        p->eState==PAGER_WRITER_DBMOD    ? "WRITER_DBMOD" :
+        p->eState==PAGER_WRITER_FINISHED ? "WRITER_FINISHED" :
+        p->eState==PAGER_ERROR           ? "ERROR" : "?error?"
+      , (int)p->errCode
+      , p->eLock==NO_LOCK         ? "NO_LOCK" :
+        p->eLock==RESERVED_LOCK   ? "RESERVED" :
+        p->eLock==EXCLUSIVE_LOCK  ? "EXCLUSIVE" :
+        p->eLock==SHARED_LOCK     ? "SHARED" :
+        p->eLock==UNKNOWN_LOCK    ? "UNKNOWN" : "?error?"
+      , p->exclusiveMode ? "exclusive" : "normal"
+      , p->journalMode==PAGER_JOURNALMODE_MEMORY   ? "memory" :
+        p->journalMode==PAGER_JOURNALMODE_OFF      ? "off" :
+        p->journalMode==PAGER_JOURNALMODE_DELETE   ? "delete" :
+        p->journalMode==PAGER_JOURNALMODE_PERSIST  ? "persist" :
+        p->journalMode==PAGER_JOURNALMODE_TRUNCATE ? "truncate" :
+        p->journalMode==PAGER_JOURNALMODE_WAL      ? "wal" : "?error?"
+      , (int)p->tempFile, (int)p->memDb, (int)p->useJournal
+      , p->journalOff, p->journalHdr
+      , (int)p->dbSize, (int)p->dbOrigSize, (int)p->dbFileSize
+  );
+
+  return zRet;
+}
+#endif
+
+/*
+** Return true if it is necessary to write page *pPg into the sub-journal.
+** A page needs to be written into the sub-journal if there exists one
+** or more open savepoints for which:
+**
+**   * The page-number is less than or equal to PagerSavepoint.nOrig, and
+**   * The bit corresponding to the page-number is not set in
+**     PagerSavepoint.pInSavepoint.
+*/
+static int subjRequiresPage(PgHdr *pPg){
+  Pgno pgno = pPg->pgno;
+  Pager *pPager = pPg->pPager;
+  int i;
+  for(i=0; i<pPager->nSavepoint; i++){
+    PagerSavepoint *p = &pPager->aSavepoint[i];
+    if( p->nOrig>=pgno && 0==sqlite3BitvecTest(p->pInSavepoint, pgno) ){
+      return 1;
+    }
+  }
+  return 0;
+}
+
+/*
+** Return true if the page is already in the journal file.
+*/
+static int pageInJournal(PgHdr *pPg){
+  return sqlite3BitvecTest(pPg->pPager->pInJournal, pPg->pgno);
+}
+
+/*
+** Read a 32-bit integer from the given file descriptor.  Store the integer
+** that is read in *pRes.  Return SQLITE_OK if everything worked, or an
+** error code is something goes wrong.
+**
+** All values are stored on disk as big-endian.
+*/
+static int read32bits(sqlite3_file *fd, i64 offset, u32 *pRes){
+  unsigned char ac[4];
+  int rc = sqlite3OsRead(fd, ac, sizeof(ac), offset);
+  if( rc==SQLITE_OK ){
+    *pRes = sqlite3Get4byte(ac);
+  }
+  return rc;
+}
+
+/*
+** Write a 32-bit integer into a string buffer in big-endian byte order.
+*/
+#define put32bits(A,B)  sqlite3Put4byte((u8*)A,B)
+
+
+/*
+** Write a 32-bit integer into the given file descriptor.  Return SQLITE_OK
+** on success or an error code is something goes wrong.
+*/
+static int write32bits(sqlite3_file *fd, i64 offset, u32 val){
+  char ac[4];
+  put32bits(ac, val);
+  return sqlite3OsWrite(fd, ac, 4, offset);
+}
+
+/*
+** Unlock the database file to level eLock, which must be either NO_LOCK
+** or SHARED_LOCK. Regardless of whether or not the call to xUnlock()
+** succeeds, set the Pager.eLock variable to match the (attempted) new lock.
+**
+** Except, if Pager.eLock is set to UNKNOWN_LOCK when this function is
+** called, do not modify it. See the comment above the #define of 
+** UNKNOWN_LOCK for an explanation of this.
+*/
+static int pagerUnlockDb(Pager *pPager, int eLock){
+  int rc = SQLITE_OK;
+
+  assert( !pPager->exclusiveMode || pPager->eLock==eLock );
+  assert( eLock==NO_LOCK || eLock==SHARED_LOCK );
+  assert( eLock!=NO_LOCK || pagerUseWal(pPager)==0 );
+  if( isOpen(pPager->fd) ){
+    assert( pPager->eLock>=eLock );
+    rc = sqlite3OsUnlock(pPager->fd, eLock);
+    if( pPager->eLock!=UNKNOWN_LOCK ){
+      pPager->eLock = (u8)eLock;
+    }
+    IOTRACE(("UNLOCK %p %d\n", pPager, eLock))
+  }
+  return rc;
+}
+
+/*
+** Lock the database file to level eLock, which must be either SHARED_LOCK,
+** RESERVED_LOCK or EXCLUSIVE_LOCK. If the caller is successful, set the
+** Pager.eLock variable to the new locking state. 
+**
+** Except, if Pager.eLock is set to UNKNOWN_LOCK when this function is 
+** called, do not modify it unless the new locking state is EXCLUSIVE_LOCK. 
+** See the comment above the #define of UNKNOWN_LOCK for an explanation 
+** of this.
+*/
+static int pagerLockDb(Pager *pPager, int eLock){
+  int rc = SQLITE_OK;
+
+  assert( eLock==SHARED_LOCK || eLock==RESERVED_LOCK || eLock==EXCLUSIVE_LOCK );
+  if( pPager->eLock<eLock || pPager->eLock==UNKNOWN_LOCK ){
+    rc = sqlite3OsLock(pPager->fd, eLock);
+    if( rc==SQLITE_OK && (pPager->eLock!=UNKNOWN_LOCK||eLock==EXCLUSIVE_LOCK) ){
+      pPager->eLock = (u8)eLock;
+      IOTRACE(("LOCK %p %d\n", pPager, eLock))
+    }
+  }
+  return rc;
+}
+
+/*
+** This function determines whether or not the atomic-write optimization
+** can be used with this pager. The optimization can be used if:
+**
+**  (a) the value returned by OsDeviceCharacteristics() indicates that
+**      a database page may be written atomically, and
+**  (b) the value returned by OsSectorSize() is less than or equal
+**      to the page size.
+**
+** The optimization is also always enabled for temporary files. It is
+** an error to call this function if pPager is opened on an in-memory
+** database.
+**
+** If the optimization cannot be used, 0 is returned. If it can be used,
+** then the value returned is the size of the journal file when it
+** contains rollback data for exactly one page.
+*/
+#ifdef SQLITE_ENABLE_ATOMIC_WRITE
+static int jrnlBufferSize(Pager *pPager){
+  assert( !MEMDB );
+  if( !pPager->tempFile ){
+    int dc;                           /* Device characteristics */
+    int nSector;                      /* Sector size */
+    int szPage;                       /* Page size */
+
+    assert( isOpen(pPager->fd) );
+    dc = sqlite3OsDeviceCharacteristics(pPager->fd);
+    nSector = pPager->sectorSize;
+    szPage = pPager->pageSize;
+
+    assert(SQLITE_IOCAP_ATOMIC512==(512>>8));
+    assert(SQLITE_IOCAP_ATOMIC64K==(65536>>8));
+    if( 0==(dc&(SQLITE_IOCAP_ATOMIC|(szPage>>8)) || nSector>szPage) ){
+      return 0;
+    }
+  }
+
+  return JOURNAL_HDR_SZ(pPager) + JOURNAL_PG_SZ(pPager);
+}
+#endif
+
+/*
+** If SQLITE_CHECK_PAGES is defined then we do some sanity checking
+** on the cache using a hash function.  This is used for testing
+** and debugging only.
+*/
+#ifdef SQLITE_CHECK_PAGES
+/*
+** Return a 32-bit hash of the page data for pPage.
+*/
+static u32 pager_datahash(int nByte, unsigned char *pData){
+  u32 hash = 0;
+  int i;
+  for(i=0; i<nByte; i++){
+    hash = (hash*1039) + pData[i];
+  }
+  return hash;
+}
+static u32 pager_pagehash(PgHdr *pPage){
+  return pager_datahash(pPage->pPager->pageSize, (unsigned char *)pPage->pData);
+}
+static void pager_set_pagehash(PgHdr *pPage){
+  pPage->pageHash = pager_pagehash(pPage);
+}
+
+/*
+** The CHECK_PAGE macro takes a PgHdr* as an argument. If SQLITE_CHECK_PAGES
+** is defined, and NDEBUG is not defined, an assert() statement checks
+** that the page is either dirty or still matches the calculated page-hash.
+*/
+#define CHECK_PAGE(x) checkPage(x)
+static void checkPage(PgHdr *pPg){
+  Pager *pPager = pPg->pPager;
+  assert( pPager->eState!=PAGER_ERROR );
+  assert( (pPg->flags&PGHDR_DIRTY) || pPg->pageHash==pager_pagehash(pPg) );
+}
+
+#else
+#define pager_datahash(X,Y)  0
+#define pager_pagehash(X)  0
+#define pager_set_pagehash(X)
+#define CHECK_PAGE(x)
+#endif  /* SQLITE_CHECK_PAGES */
+
+/*
+** When this is called the journal file for pager pPager must be open.
+** This function attempts to read a master journal file name from the 
+** end of the file and, if successful, copies it into memory supplied 
+** by the caller. See comments above writeMasterJournal() for the format
+** used to store a master journal file name at the end of a journal file.
+**
+** zMaster must point to a buffer of at least nMaster bytes allocated by
+** the caller. This should be sqlite3_vfs.mxPathname+1 (to ensure there is
+** enough space to write the master journal name). If the master journal
+** name in the journal is longer than nMaster bytes (including a
+** nul-terminator), then this is handled as if no master journal name
+** were present in the journal.
+**
+** If a master journal file name is present at the end of the journal
+** file, then it is copied into the buffer pointed to by zMaster. A
+** nul-terminator byte is appended to the buffer following the master
+** journal file name.
+**
+** If it is determined that no master journal file name is present 
+** zMaster[0] is set to 0 and SQLITE_OK returned.
+**
+** If an error occurs while reading from the journal file, an SQLite
+** error code is returned.
+*/
+static int readMasterJournal(sqlite3_file *pJrnl, char *zMaster, u32 nMaster){
+  int rc;                    /* Return code */
+  u32 len;                   /* Length in bytes of master journal name */
+  i64 szJ;                   /* Total size in bytes of journal file pJrnl */
+  u32 cksum;                 /* MJ checksum value read from journal */
+  u32 u;                     /* Unsigned loop counter */
+  unsigned char aMagic[8];   /* A buffer to hold the magic header */
+  zMaster[0] = '\0';
+
+  if( SQLITE_OK!=(rc = sqlite3OsFileSize(pJrnl, &szJ))
+   || szJ<16
+   || SQLITE_OK!=(rc = read32bits(pJrnl, szJ-16, &len))
+   || len>=nMaster 
+   || SQLITE_OK!=(rc = read32bits(pJrnl, szJ-12, &cksum))
+   || SQLITE_OK!=(rc = sqlite3OsRead(pJrnl, aMagic, 8, szJ-8))
+   || memcmp(aMagic, aJournalMagic, 8)
+   || SQLITE_OK!=(rc = sqlite3OsRead(pJrnl, zMaster, len, szJ-16-len))
+  ){
+    return rc;
+  }
+
+  /* See if the checksum matches the master journal name */
+  for(u=0; u<len; u++){
+    cksum -= zMaster[u];
+  }
+  if( cksum ){
+    /* If the checksum doesn't add up, then one or more of the disk sectors
+    ** containing the master journal filename is corrupted. This means
+    ** definitely roll back, so just return SQLITE_OK and report a (nul)
+    ** master-journal filename.
+    */
+    len = 0;
+  }
+  zMaster[len] = '\0';
+   
+  return SQLITE_OK;
+}
+
+/*
+** Return the offset of the sector boundary at or immediately 
+** following the value in pPager->journalOff, assuming a sector 
+** size of pPager->sectorSize bytes.
+**
+** i.e for a sector size of 512:
+**
+**   Pager.journalOff          Return value
+**   ---------------------------------------
+**   0                         0
+**   512                       512
+**   100                       512
+**   2000                      2048
+** 
+*/
+static i64 journalHdrOffset(Pager *pPager){
+  i64 offset = 0;
+  i64 c = pPager->journalOff;
+  if( c ){
+    offset = ((c-1)/JOURNAL_HDR_SZ(pPager) + 1) * JOURNAL_HDR_SZ(pPager);
+  }
+  assert( offset%JOURNAL_HDR_SZ(pPager)==0 );
+  assert( offset>=c );
+  assert( (offset-c)<JOURNAL_HDR_SZ(pPager) );
+  return offset;
+}
+
+/*
+** The journal file must be open when this function is called.
+**
+** This function is a no-op if the journal file has not been written to
+** within the current transaction (i.e. if Pager.journalOff==0).
+**
+** If doTruncate is non-zero or the Pager.journalSizeLimit variable is
+** set to 0, then truncate the journal file to zero bytes in size. Otherwise,
+** zero the 28-byte header at the start of the journal file. In either case, 
+** if the pager is not in no-sync mode, sync the journal file immediately 
+** after writing or truncating it.
+**
+** If Pager.journalSizeLimit is set to a positive, non-zero value, and
+** following the truncation or zeroing described above the size of the 
+** journal file in bytes is larger than this value, then truncate the
+** journal file to Pager.journalSizeLimit bytes. The journal file does
+** not need to be synced following this operation.
+**
+** If an IO error occurs, abandon processing and return the IO error code.
+** Otherwise, return SQLITE_OK.
+*/
+static int zeroJournalHdr(Pager *pPager, int doTruncate){
+  int rc = SQLITE_OK;                               /* Return code */
+  assert( isOpen(pPager->jfd) );
+  if( pPager->journalOff ){
+    const i64 iLimit = pPager->journalSizeLimit;    /* Local cache of jsl */
+
+    IOTRACE(("JZEROHDR %p\n", pPager))
+    if( doTruncate || iLimit==0 ){
+      rc = sqlite3OsTruncate(pPager->jfd, 0);
+    }else{
+      static const char zeroHdr[28] = {0};
+      rc = sqlite3OsWrite(pPager->jfd, zeroHdr, sizeof(zeroHdr), 0);
+    }
+    if( rc==SQLITE_OK && !pPager->noSync ){
+      rc = sqlite3OsSync(pPager->jfd, SQLITE_SYNC_DATAONLY|pPager->syncFlags);
+    }
+
+    /* At this point the transaction is committed but the write lock 
+    ** is still held on the file. If there is a size limit configured for 
+    ** the persistent journal and the journal file currently consumes more
+    ** space than that limit allows for, truncate it now. There is no need
+    ** to sync the file following this operation.
+    */
+    if( rc==SQLITE_OK && iLimit>0 ){
+      i64 sz;
+      rc = sqlite3OsFileSize(pPager->jfd, &sz);
+      if( rc==SQLITE_OK && sz>iLimit ){
+        rc = sqlite3OsTruncate(pPager->jfd, iLimit);
+      }
+    }
+  }
+  return rc;
+}
+
+/*
+** The journal file must be open when this routine is called. A journal
+** header (JOURNAL_HDR_SZ bytes) is written into the journal file at the
+** current location.
+**
+** The format for the journal header is as follows:
+** - 8 bytes: Magic identifying journal format.
+** - 4 bytes: Number of records in journal, or -1 no-sync mode is on.
+** - 4 bytes: Random number used for page hash.
+** - 4 bytes: Initial database page count.
+** - 4 bytes: Sector size used by the process that wrote this journal.
+** - 4 bytes: Database page size.
+** 
+** Followed by (JOURNAL_HDR_SZ - 28) bytes of unused space.
+*/
+static int writeJournalHdr(Pager *pPager){
+  int rc = SQLITE_OK;                 /* Return code */
+  char *zHeader = pPager->pTmpSpace;  /* Temporary space used to build header */
+  u32 nHeader = (u32)pPager->pageSize;/* Size of buffer pointed to by zHeader */
+  u32 nWrite;                         /* Bytes of header sector written */
+  int ii;                             /* Loop counter */
+
+  assert( isOpen(pPager->jfd) );      /* Journal file must be open. */
+
+  if( nHeader>JOURNAL_HDR_SZ(pPager) ){
+    nHeader = JOURNAL_HDR_SZ(pPager);
+  }
+
+  /* If there are active savepoints and any of them were created 
+  ** since the most recent journal header was written, update the 
+  ** PagerSavepoint.iHdrOffset fields now.
+  */
+  for(ii=0; ii<pPager->nSavepoint; ii++){
+    if( pPager->aSavepoint[ii].iHdrOffset==0 ){
+      pPager->aSavepoint[ii].iHdrOffset = pPager->journalOff;
+    }
+  }
+
+  pPager->journalHdr = pPager->journalOff = journalHdrOffset(pPager);
+
+  /* 
+  ** Write the nRec Field - the number of page records that follow this
+  ** journal header. Normally, zero is written to this value at this time.
+  ** After the records are added to the journal (and the journal synced, 
+  ** if in full-sync mode), the zero is overwritten with the true number
+  ** of records (see syncJournal()).
+  **
+  ** A faster alternative is to write 0xFFFFFFFF to the nRec field. When
+  ** reading the journal this value tells SQLite to assume that the
+  ** rest of the journal file contains valid page records. This assumption
+  ** is dangerous, as if a failure occurred whilst writing to the journal
+  ** file it may contain some garbage data. There are two scenarios
+  ** where this risk can be ignored:
+  **
+  **   * When the pager is in no-sync mode. Corruption can follow a
+  **     power failure in this case anyway.
+  **
+  **   * When the SQLITE_IOCAP_SAFE_APPEND flag is set. This guarantees
+  **     that garbage data is never appended to the journal file.
+  */
+  assert( isOpen(pPager->fd) || pPager->noSync );
+  if( pPager->noSync || (pPager->journalMode==PAGER_JOURNALMODE_MEMORY)
+   || (sqlite3OsDeviceCharacteristics(pPager->fd)&SQLITE_IOCAP_SAFE_APPEND) 
+  ){
+    memcpy(zHeader, aJournalMagic, sizeof(aJournalMagic));
+    put32bits(&zHeader[sizeof(aJournalMagic)], 0xffffffff);
+  }else{
+    memset(zHeader, 0, sizeof(aJournalMagic)+4);
+  }
+
+  /* The random check-hash initialiser */ 
+  sqlite3_randomness(sizeof(pPager->cksumInit), &pPager->cksumInit);
+  put32bits(&zHeader[sizeof(aJournalMagic)+4], pPager->cksumInit);
+  /* The initial database size */
+  put32bits(&zHeader[sizeof(aJournalMagic)+8], pPager->dbOrigSize);
+  /* The assumed sector size for this process */
+  put32bits(&zHeader[sizeof(aJournalMagic)+12], pPager->sectorSize);
+
+  /* The page size */
+  put32bits(&zHeader[sizeof(aJournalMagic)+16], pPager->pageSize);
+
+  /* Initializing the tail of the buffer is not necessary.  Everything
+  ** works find if the following memset() is omitted.  But initializing
+  ** the memory prevents valgrind from complaining, so we are willing to
+  ** take the performance hit.
+  */
+  memset(&zHeader[sizeof(aJournalMagic)+20], 0,
+         nHeader-(sizeof(aJournalMagic)+20));
+
+  /* In theory, it is only necessary to write the 28 bytes that the 
+  ** journal header consumes to the journal file here. Then increment the 
+  ** Pager.journalOff variable by JOURNAL_HDR_SZ so that the next 
+  ** record is written to the following sector (leaving a gap in the file
+  ** that will be implicitly filled in by the OS).
+  **
+  ** However it has been discovered that on some systems this pattern can 
+  ** be significantly slower than contiguously writing data to the file,
+  ** even if that means explicitly writing data to the block of 
+  ** (JOURNAL_HDR_SZ - 28) bytes that will not be used. So that is what
+  ** is done. 
+  **
+  ** The loop is required here in case the sector-size is larger than the 
+  ** database page size. Since the zHeader buffer is only Pager.pageSize
+  ** bytes in size, more than one call to sqlite3OsWrite() may be required
+  ** to populate the entire journal header sector.
+  */ 
+  for(nWrite=0; rc==SQLITE_OK&&nWrite<JOURNAL_HDR_SZ(pPager); nWrite+=nHeader){
+    IOTRACE(("JHDR %p %lld %d\n", pPager, pPager->journalHdr, nHeader))
+    rc = sqlite3OsWrite(pPager->jfd, zHeader, nHeader, pPager->journalOff);
+    assert( pPager->journalHdr <= pPager->journalOff );
+    pPager->journalOff += nHeader;
+  }
+
+  return rc;
+}
+
+/*
+** The journal file must be open when this is called. A journal header file
+** (JOURNAL_HDR_SZ bytes) is read from the current location in the journal
+** file. The current location in the journal file is given by
+** pPager->journalOff. See comments above function writeJournalHdr() for
+** a description of the journal header format.
+**
+** If the header is read successfully, *pNRec is set to the number of
+** page records following this header and *pDbSize is set to the size of the
+** database before the transaction began, in pages. Also, pPager->cksumInit
+** is set to the value read from the journal header. SQLITE_OK is returned
+** in this case.
+**
+** If the journal header file appears to be corrupted, SQLITE_DONE is
+** returned and *pNRec and *PDbSize are undefined.  If JOURNAL_HDR_SZ bytes
+** cannot be read from the journal file an error code is returned.
+*/
+static int readJournalHdr(
+  Pager *pPager,               /* Pager object */
+  int isHot,
+  i64 journalSize,             /* Size of the open journal file in bytes */
+  u32 *pNRec,                  /* OUT: Value read from the nRec field */
+  u32 *pDbSize                 /* OUT: Value of original database size field */
+){
+  int rc;                      /* Return code */
+  unsigned char aMagic[8];     /* A buffer to hold the magic header */
+  i64 iHdrOff;                 /* Offset of journal header being read */
+
+  assert( isOpen(pPager->jfd) );      /* Journal file must be open. */
+
+  /* Advance Pager.journalOff to the start of the next sector. If the
+  ** journal file is too small for there to be a header stored at this
+  ** point, return SQLITE_DONE.
+  */
+  pPager->journalOff = journalHdrOffset(pPager);
+  if( pPager->journalOff+JOURNAL_HDR_SZ(pPager) > journalSize ){
+    return SQLITE_DONE;
+  }
+  iHdrOff = pPager->journalOff;
+
+  /* Read in the first 8 bytes of the journal header. If they do not match
+  ** the  magic string found at the start of each journal header, return
+  ** SQLITE_DONE. If an IO error occurs, return an error code. Otherwise,
+  ** proceed.
+  */
+  if( isHot || iHdrOff!=pPager->journalHdr ){
+    rc = sqlite3OsRead(pPager->jfd, aMagic, sizeof(aMagic), iHdrOff);
+    if( rc ){
+      return rc;
+    }
+    if( memcmp(aMagic, aJournalMagic, sizeof(aMagic))!=0 ){
+      return SQLITE_DONE;
+    }
+  }
+
+  /* Read the first three 32-bit fields of the journal header: The nRec
+  ** field, the checksum-initializer and the database size at the start
+  ** of the transaction. Return an error code if anything goes wrong.
+  */
+  if( SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+8, pNRec))
+   || SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+12, &pPager->cksumInit))
+   || SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+16, pDbSize))
+  ){
+    return rc;
+  }
+
+  if( pPager->journalOff==0 ){
+    u32 iPageSize;               /* Page-size field of journal header */
+    u32 iSectorSize;             /* Sector-size field of journal header */
+
+    /* Read the page-size and sector-size journal header fields. */
+    if( SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+20, &iSectorSize))
+     || SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+24, &iPageSize))
+    ){
+      return rc;
+    }
+
+    /* Versions of SQLite prior to 3.5.8 set the page-size field of the
+    ** journal header to zero. In this case, assume that the Pager.pageSize
+    ** variable is already set to the correct page size.
+    */
+    if( iPageSize==0 ){
+      iPageSize = pPager->pageSize;
+    }
+
+    /* Check that the values read from the page-size and sector-size fields
+    ** are within range. To be 'in range', both values need to be a power
+    ** of two greater than or equal to 512 or 32, and not greater than their 
+    ** respective compile time maximum limits.
+    */
+    if( iPageSize<512                  || iSectorSize<32
+     || iPageSize>SQLITE_MAX_PAGE_SIZE || iSectorSize>MAX_SECTOR_SIZE
+     || ((iPageSize-1)&iPageSize)!=0   || ((iSectorSize-1)&iSectorSize)!=0 
+    ){
+      /* If the either the page-size or sector-size in the journal-header is 
+      ** invalid, then the process that wrote the journal-header must have 
+      ** crashed before the header was synced. In this case stop reading 
+      ** the journal file here.
+      */
+      return SQLITE_DONE;
+    }
+
+    /* Update the page-size to match the value read from the journal. 
+    ** Use a testcase() macro to make sure that malloc failure within 
+    ** PagerSetPagesize() is tested.
+    */
+    rc = sqlite3PagerSetPagesize(pPager, &iPageSize, -1);
+    testcase( rc!=SQLITE_OK );
+
+    /* Update the assumed sector-size to match the value used by 
+    ** the process that created this journal. If this journal was
+    ** created by a process other than this one, then this routine
+    ** is being called from within pager_playback(). The local value
+    ** of Pager.sectorSize is restored at the end of that routine.
+    */
+    pPager->sectorSize = iSectorSize;
+  }
+
+  pPager->journalOff += JOURNAL_HDR_SZ(pPager);
+  return rc;
+}
+
+
+/*
+** Write the supplied master journal name into the journal file for pager
+** pPager at the current location. The master journal name must be the last
+** thing written to a journal file. If the pager is in full-sync mode, the
+** journal file descriptor is advanced to the next sector boundary before
+** anything is written. The format is:
+**
+**   + 4 bytes: PAGER_MJ_PGNO.
+**   + N bytes: Master journal filename in utf-8.
+**   + 4 bytes: N (length of master journal name in bytes, no nul-terminator).
+**   + 4 bytes: Master journal name checksum.
+**   + 8 bytes: aJournalMagic[].
+**
+** The master journal page checksum is the sum of the bytes in the master
+** journal name, where each byte is interpreted as a signed 8-bit integer.
+**
+** If zMaster is a NULL pointer (occurs for a single database transaction), 
+** this call is a no-op.
+*/
+static int writeMasterJournal(Pager *pPager, const char *zMaster){
+  int rc;                          /* Return code */
+  int nMaster;                     /* Length of string zMaster */
+  i64 iHdrOff;                     /* Offset of header in journal file */
+  i64 jrnlSize;                    /* Size of journal file on disk */
+  u32 cksum = 0;                   /* Checksum of string zMaster */
+
+  assert( pPager->setMaster==0 );
+  assert( !pagerUseWal(pPager) );
+
+  if( !zMaster 
+   || pPager->journalMode==PAGER_JOURNALMODE_MEMORY 
+   || pPager->journalMode==PAGER_JOURNALMODE_OFF 
+  ){
+    return SQLITE_OK;
+  }
+  pPager->setMaster = 1;
+  assert( isOpen(pPager->jfd) );
+  assert( pPager->journalHdr <= pPager->journalOff );
+
+  /* Calculate the length in bytes and the checksum of zMaster */
+  for(nMaster=0; zMaster[nMaster]; nMaster++){
+    cksum += zMaster[nMaster];
+  }
+
+  /* If in full-sync mode, advance to the next disk sector before writing
+  ** the master journal name. This is in case the previous page written to
+  ** the journal has already been synced.
+  */
+  if( pPager->fullSync ){
+    pPager->journalOff = journalHdrOffset(pPager);
+  }
+  iHdrOff = pPager->journalOff;
+
+  /* Write the master journal data to the end of the journal file. If
+  ** an error occurs, return the error code to the caller.
+  */
+  if( (0 != (rc = write32bits(pPager->jfd, iHdrOff, PAGER_MJ_PGNO(pPager))))
+   || (0 != (rc = sqlite3OsWrite(pPager->jfd, zMaster, nMaster, iHdrOff+4)))
+   || (0 != (rc = write32bits(pPager->jfd, iHdrOff+4+nMaster, nMaster)))
+   || (0 != (rc = write32bits(pPager->jfd, iHdrOff+4+nMaster+4, cksum)))
+   || (0 != (rc = sqlite3OsWrite(pPager->jfd, aJournalMagic, 8, iHdrOff+4+nMaster+8)))
+  ){
+    return rc;
+  }
+  pPager->journalOff += (nMaster+20);
+
+  /* If the pager is in peristent-journal mode, then the physical 
+  ** journal-file may extend past the end of the master-journal name
+  ** and 8 bytes of magic data just written to the file. This is 
+  ** dangerous because the code to rollback a hot-journal file
+  ** will not be able to find the master-journal name to determine 
+  ** whether or not the journal is hot. 
+  **
+  ** Easiest thing to do in this scenario is to truncate the journal 
+  ** file to the required size.
+  */ 
+  if( SQLITE_OK==(rc = sqlite3OsFileSize(pPager->jfd, &jrnlSize))
+   && jrnlSize>pPager->journalOff
+  ){
+    rc = sqlite3OsTruncate(pPager->jfd, pPager->journalOff);
+  }
+  return rc;
+}
+
+/*
+** Find a page in the hash table given its page number. Return
+** a pointer to the page or NULL if the requested page is not 
+** already in memory.
+*/
+static PgHdr *pager_lookup(Pager *pPager, Pgno pgno){
+  PgHdr *p;                         /* Return value */
+
+  /* It is not possible for a call to PcacheFetch() with createFlag==0 to
+  ** fail, since no attempt to allocate dynamic memory will be made.
+  */
+  (void)sqlite3PcacheFetch(pPager->pPCache, pgno, 0, &p);
+  return p;
+}
+
+/*
+** Discard the entire contents of the in-memory page-cache.
+*/
+static void pager_reset(Pager *pPager){
+  sqlite3BackupRestart(pPager->pBackup);
+  sqlite3PcacheClear(pPager->pPCache);
+}
+
+/*
+** Free all structures in the Pager.aSavepoint[] array and set both
+** Pager.aSavepoint and Pager.nSavepoint to zero. Close the sub-journal
+** if it is open and the pager is not in exclusive mode.
+*/
+static void releaseAllSavepoints(Pager *pPager){
+  int ii;               /* Iterator for looping through Pager.aSavepoint */
+  for(ii=0; ii<pPager->nSavepoint; ii++){
+    sqlite3BitvecDestroy(pPager->aSavepoint[ii].pInSavepoint);
+  }
+  if( !pPager->exclusiveMode || sqlite3IsMemJournal(pPager->sjfd) ){
+    sqlite3OsClose(pPager->sjfd);
+  }
+  sqlite3_free(pPager->aSavepoint);
+  pPager->aSavepoint = 0;
+  pPager->nSavepoint = 0;
+  pPager->nSubRec = 0;
+}
+
+/*
+** Set the bit number pgno in the PagerSavepoint.pInSavepoint 
+** bitvecs of all open savepoints. Return SQLITE_OK if successful
+** or SQLITE_NOMEM if a malloc failure occurs.
+*/
+static int addToSavepointBitvecs(Pager *pPager, Pgno pgno){
+  int ii;                   /* Loop counter */
+  int rc = SQLITE_OK;       /* Result code */
+
+  for(ii=0; ii<pPager->nSavepoint; ii++){
+    PagerSavepoint *p = &pPager->aSavepoint[ii];
+    if( pgno<=p->nOrig ){
+      rc |= sqlite3BitvecSet(p->pInSavepoint, pgno);
+      testcase( rc==SQLITE_NOMEM );
+      assert( rc==SQLITE_OK || rc==SQLITE_NOMEM );
+    }
+  }
+  return rc;
+}
+
+/*
+** This function is a no-op if the pager is in exclusive mode and not
+** in the ERROR state. Otherwise, it switches the pager to PAGER_OPEN
+** state.
+**
+** If the pager is not in exclusive-access mode, the database file is
+** completely unlocked. If the file is unlocked and the file-system does
+** not exhibit the UNDELETABLE_WHEN_OPEN property, the journal file is
+** closed (if it is open).
+**
+** If the pager is in ERROR state when this function is called, the 
+** contents of the pager cache are discarded before switching back to 
+** the OPEN state. Regardless of whether the pager is in exclusive-mode
+** or not, any journal file left in the file-system will be treated
+** as a hot-journal and rolled back the next time a read-transaction
+** is opened (by this or by any other connection).
+*/
+static void pager_unlock(Pager *pPager){
+
+  assert( pPager->eState==PAGER_READER 
+       || pPager->eState==PAGER_OPEN 
+       || pPager->eState==PAGER_ERROR 
+  );
+
+  sqlite3BitvecDestroy(pPager->pInJournal);
+  pPager->pInJournal = 0;
+  releaseAllSavepoints(pPager);
+
+  if( pagerUseWal(pPager) ){
+    assert( !isOpen(pPager->jfd) );
+    sqlite3WalEndReadTransaction(pPager->pWal);
+    pPager->eState = PAGER_OPEN;
+  }else if( !pPager->exclusiveMode ){
+    int rc;                       /* Error code returned by pagerUnlockDb() */
+    int iDc = isOpen(pPager->fd)?sqlite3OsDeviceCharacteristics(pPager->fd):0;
+
+    /* If the operating system support deletion of open files, then
+    ** close the journal file when dropping the database lock.  Otherwise
+    ** another connection with journal_mode=delete might delete the file
+    ** out from under us.
+    */
+    assert( (PAGER_JOURNALMODE_MEMORY   & 5)!=1 );
+    assert( (PAGER_JOURNALMODE_OFF      & 5)!=1 );
+    assert( (PAGER_JOURNALMODE_WAL      & 5)!=1 );
+    assert( (PAGER_JOURNALMODE_DELETE   & 5)!=1 );
+    assert( (PAGER_JOURNALMODE_TRUNCATE & 5)==1 );
+    assert( (PAGER_JOURNALMODE_PERSIST  & 5)==1 );
+    if( 0==(iDc & SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN)
+     || 1!=(pPager->journalMode & 5)
+    ){
+      sqlite3OsClose(pPager->jfd);
+    }
+
+    /* If the pager is in the ERROR state and the call to unlock the database
+    ** file fails, set the current lock to UNKNOWN_LOCK. See the comment
+    ** above the #define for UNKNOWN_LOCK for an explanation of why this
+    ** is necessary.
+    */
+    rc = pagerUnlockDb(pPager, NO_LOCK);
+    if( rc!=SQLITE_OK && pPager->eState==PAGER_ERROR ){
+      pPager->eLock = UNKNOWN_LOCK;
+    }
+
+    /* The pager state may be changed from PAGER_ERROR to PAGER_OPEN here
+    ** without clearing the error code. This is intentional - the error
+    ** code is cleared and the cache reset in the block below.
+    */
+    assert( pPager->errCode || pPager->eState!=PAGER_ERROR );
+    pPager->changeCountDone = 0;
+    pPager->eState = PAGER_OPEN;
+  }
+
+  /* If Pager.errCode is set, the contents of the pager cache cannot be
+  ** trusted. Now that there are no outstanding references to the pager,
+  ** it can safely move back to PAGER_OPEN state. This happens in both
+  ** normal and exclusive-locking mode.
+  */
+  if( pPager->errCode ){
+    assert( !MEMDB );
+    pager_reset(pPager);
+    pPager->changeCountDone = pPager->tempFile;
+    pPager->eState = PAGER_OPEN;
+    pPager->errCode = SQLITE_OK;
+  }
+
+  pPager->journalOff = 0;
+  pPager->journalHdr = 0;
+  pPager->setMaster = 0;
+}
+
+/*
+** This function is called whenever an IOERR or FULL error that requires
+** the pager to transition into the ERROR state may ahve occurred.
+** The first argument is a pointer to the pager structure, the second 
+** the error-code about to be returned by a pager API function. The 
+** value returned is a copy of the second argument to this function. 
+**
+** If the second argument is SQLITE_FULL, SQLITE_IOERR or one of the
+** IOERR sub-codes, the pager enters the ERROR state and the error code
+** is stored in Pager.errCode. While the pager remains in the ERROR state,
+** all major API calls on the Pager will immediately return Pager.errCode.
+**
+** The ERROR state indicates that the contents of the pager-cache 
+** cannot be trusted. This state can be cleared by completely discarding 
+** the contents of the pager-cache. If a transaction was active when
+** the persistent error occurred, then the rollback journal may need
+** to be replayed to restore the contents of the database file (as if
+** it were a hot-journal).
+*/
+static int pager_error(Pager *pPager, int rc){
+  int rc2 = rc & 0xff;
+  assert( rc==SQLITE_OK || !MEMDB );
+  assert(
+       pPager->errCode==SQLITE_FULL ||
+       pPager->errCode==SQLITE_OK ||
+       (pPager->errCode & 0xff)==SQLITE_IOERR
+  );
+  if( rc2==SQLITE_FULL || rc2==SQLITE_IOERR ){
+    pPager->errCode = rc;
+    pPager->eState = PAGER_ERROR;
+  }
+  return rc;
+}
+
+/*
+** This routine ends a transaction. A transaction is usually ended by 
+** either a COMMIT or a ROLLBACK operation. This routine may be called 
+** after rollback of a hot-journal, or if an error occurs while opening
+** the journal file or writing the very first journal-header of a
+** database transaction.
+** 
+** This routine is never called in PAGER_ERROR state. If it is called
+** in PAGER_NONE or PAGER_SHARED state and the lock held is less
+** exclusive than a RESERVED lock, it is a no-op.
+**
+** Otherwise, any active savepoints are released.
+**
+** If the journal file is open, then it is "finalized". Once a journal 
+** file has been finalized it is not possible to use it to roll back a 
+** transaction. Nor will it be considered to be a hot-journal by this
+** or any other database connection. Exactly how a journal is finalized
+** depends on whether or not the pager is running in exclusive mode and
+** the current journal-mode (Pager.journalMode value), as follows:
+**
+**   journalMode==MEMORY
+**     Journal file descriptor is simply closed. This destroys an 
+**     in-memory journal.
+**
+**   journalMode==TRUNCATE
+**     Journal file is truncated to zero bytes in size.
+**
+**   journalMode==PERSIST
+**     The first 28 bytes of the journal file are zeroed. This invalidates
+**     the first journal header in the file, and hence the entire journal
+**     file. An invalid journal file cannot be rolled back.
+**
+**   journalMode==DELETE
+**     The journal file is closed and deleted using sqlite3OsDelete().
+**
+**     If the pager is running in exclusive mode, this method of finalizing
+**     the journal file is never used. Instead, if the journalMode is
+**     DELETE and the pager is in exclusive mode, the method described under
+**     journalMode==PERSIST is used instead.
+**
+** After the journal is finalized, the pager moves to PAGER_READER state.
+** If running in non-exclusive rollback mode, the lock on the file is 
+** downgraded to a SHARED_LOCK.
+**
+** SQLITE_OK is returned if no error occurs. If an error occurs during
+** any of the IO operations to finalize the journal file or unlock the
+** database then the IO error code is returned to the user. If the 
+** operation to finalize the journal file fails, then the code still
+** tries to unlock the database file if not in exclusive mode. If the
+** unlock operation fails as well, then the first error code related
+** to the first error encountered (the journal finalization one) is
+** returned.
+*/
+static int pager_end_transaction(Pager *pPager, int hasMaster){
+  int rc = SQLITE_OK;      /* Error code from journal finalization operation */
+  int rc2 = SQLITE_OK;     /* Error code from db file unlock operation */
+
+  /* Do nothing if the pager does not have an open write transaction
+  ** or at least a RESERVED lock. This function may be called when there
+  ** is no write-transaction active but a RESERVED or greater lock is
+  ** held under two circumstances:
+  **
+  **   1. After a successful hot-journal rollback, it is called with
+  **      eState==PAGER_NONE and eLock==EXCLUSIVE_LOCK.
+  **
+  **   2. If a connection with locking_mode=exclusive holding an EXCLUSIVE 
+  **      lock switches back to locking_mode=normal and then executes a
+  **      read-transaction, this function is called with eState==PAGER_READER 
+  **      and eLock==EXCLUSIVE_LOCK when the read-transaction is closed.
+  */
+  assert( assert_pager_state(pPager) );
+  assert( pPager->eState!=PAGER_ERROR );
+  if( pPager->eState<PAGER_WRITER_LOCKED && pPager->eLock<RESERVED_LOCK ){
+    return SQLITE_OK;
+  }
+
+  releaseAllSavepoints(pPager);
+  assert( isOpen(pPager->jfd) || pPager->pInJournal==0 );
+  if( isOpen(pPager->jfd) ){
+    assert( !pagerUseWal(pPager) );
+
+    /* Finalize the journal file. */
+    if( sqlite3IsMemJournal(pPager->jfd) ){
+      assert( pPager->journalMode==PAGER_JOURNALMODE_MEMORY );
+      sqlite3OsClose(pPager->jfd);
+    }else if( pPager->journalMode==PAGER_JOURNALMODE_TRUNCATE ){
+      if( pPager->journalOff==0 ){
+        rc = SQLITE_OK;
+      }else{
+        rc = sqlite3OsTruncate(pPager->jfd, 0);
+      }
+      pPager->journalOff = 0;
+    }else if( pPager->journalMode==PAGER_JOURNALMODE_PERSIST
+      || (pPager->exclusiveMode && pPager->journalMode!=PAGER_JOURNALMODE_WAL)
+    ){
+      rc = zeroJournalHdr(pPager, hasMaster);
+      pPager->journalOff = 0;
+    }else{
+      /* This branch may be executed with Pager.journalMode==MEMORY if
+      ** a hot-journal was just rolled back. In this case the journal
+      ** file should be closed and deleted. If this connection writes to
+      ** the database file, it will do so using an in-memory journal. 
+      */
+      assert( pPager->journalMode==PAGER_JOURNALMODE_DELETE 
+           || pPager->journalMode==PAGER_JOURNALMODE_MEMORY 
+           || pPager->journalMode==PAGER_JOURNALMODE_WAL 
+      );
+      sqlite3OsClose(pPager->jfd);
+      if( !pPager->tempFile ){
+        rc = sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0);
+      }
+    }
+  }
+
+#ifdef SQLITE_CHECK_PAGES
+  sqlite3PcacheIterateDirty(pPager->pPCache, pager_set_pagehash);
+  if( pPager->dbSize==0 && sqlite3PcacheRefCount(pPager->pPCache)>0 ){
+    PgHdr *p = pager_lookup(pPager, 1);
+    if( p ){
+      p->pageHash = 0;
+      sqlite3PagerUnref(p);
+    }
+  }
+#endif
+
+  sqlite3BitvecDestroy(pPager->pInJournal);
+  pPager->pInJournal = 0;
+  pPager->nRec = 0;
+  sqlite3PcacheCleanAll(pPager->pPCache);
+  sqlite3PcacheTruncate(pPager->pPCache, pPager->dbSize);
+
+  if( pagerUseWal(pPager) ){
+    /* Drop the WAL write-lock, if any. Also, if the connection was in 
+    ** locking_mode=exclusive mode but is no longer, drop the EXCLUSIVE 
+    ** lock held on the database file.
+    */
+    rc2 = sqlite3WalEndWriteTransaction(pPager->pWal);
+    assert( rc2==SQLITE_OK );
+  }
+  if( !pPager->exclusiveMode 
+   && (!pagerUseWal(pPager) || sqlite3WalExclusiveMode(pPager->pWal, 0))
+  ){
+    rc2 = pagerUnlockDb(pPager, SHARED_LOCK);
+    pPager->changeCountDone = 0;
+  }
+  pPager->eState = PAGER_READER;
+  pPager->setMaster = 0;
+
+  return (rc==SQLITE_OK?rc2:rc);
+}
+
+/*
+** Execute a rollback if a transaction is active and unlock the 
+** database file. 
+**
+** If the pager has already entered the ERROR state, do not attempt 
+** the rollback at this time. Instead, pager_unlock() is called. The
+** call to pager_unlock() will discard all in-memory pages, unlock
+** the database file and move the pager back to OPEN state. If this 
+** means that there is a hot-journal left in the file-system, the next 
+** connection to obtain a shared lock on the pager (which may be this one) 
+** will roll it back.
+**
+** If the pager has not already entered the ERROR state, but an IO or
+** malloc error occurs during a rollback, then this will itself cause 
+** the pager to enter the ERROR state. Which will be cleared by the
+** call to pager_unlock(), as described above.
+*/
+static void pagerUnlockAndRollback(Pager *pPager){
+  if( pPager->eState!=PAGER_ERROR && pPager->eState!=PAGER_OPEN ){
+    assert( assert_pager_state(pPager) );
+    if( pPager->eState>=PAGER_WRITER_LOCKED ){
+      sqlite3BeginBenignMalloc();
+      sqlite3PagerRollback(pPager);
+      sqlite3EndBenignMalloc();
+    }else if( !pPager->exclusiveMode ){
+      assert( pPager->eState==PAGER_READER );
+      pager_end_transaction(pPager, 0);
+    }
+  }
+  pager_unlock(pPager);
+}
+
+/*
+** Parameter aData must point to a buffer of pPager->pageSize bytes
+** of data. Compute and return a checksum based ont the contents of the 
+** page of data and the current value of pPager->cksumInit.
+**
+** This is not a real checksum. It is really just the sum of the 
+** random initial value (pPager->cksumInit) and every 200th byte
+** of the page data, starting with byte offset (pPager->pageSize%200).
+** Each byte is interpreted as an 8-bit unsigned integer.
+**
+** Changing the formula used to compute this checksum results in an
+** incompatible journal file format.
+**
+** If journal corruption occurs due to a power failure, the most likely 
+** scenario is that one end or the other of the record will be changed. 
+** It is much less likely that the two ends of the journal record will be
+** correct and the middle be corrupt.  Thus, this "checksum" scheme,
+** though fast and simple, catches the mostly likely kind of corruption.
+*/
+static u32 pager_cksum(Pager *pPager, const u8 *aData){
+  u32 cksum = pPager->cksumInit;         /* Checksum value to return */
+  int i = pPager->pageSize-200;          /* Loop counter */
+  while( i>0 ){
+    cksum += aData[i];
+    i -= 200;
+  }
+  return cksum;
+}
+
+/*
+** Report the current page size and number of reserved bytes back
+** to the codec.
+*/
+#ifdef SQLITE_HAS_CODEC
+static void pagerReportSize(Pager *pPager){
+  if( pPager->xCodecSizeChng ){
+    pPager->xCodecSizeChng(pPager->pCodec, pPager->pageSize,
+                           (int)pPager->nReserve);
+  }
+}
+#else
+# define pagerReportSize(X)     /* No-op if we do not support a codec */
+#endif
+
+/*
+** Read a single page from either the journal file (if isMainJrnl==1) or
+** from the sub-journal (if isMainJrnl==0) and playback that page.
+** The page begins at offset *pOffset into the file. The *pOffset
+** value is increased to the start of the next page in the journal.
+**
+** The main rollback journal uses checksums - the statement journal does 
+** not.
+**
+** If the page number of the page record read from the (sub-)journal file
+** is greater than the current value of Pager.dbSize, then playback is
+** skipped and SQLITE_OK is returned.
+**
+** If pDone is not NULL, then it is a record of pages that have already
+** been played back.  If the page at *pOffset has already been played back
+** (if the corresponding pDone bit is set) then skip the playback.
+** Make sure the pDone bit corresponding to the *pOffset page is set
+** prior to returning.
+**
+** If the page record is successfully read from the (sub-)journal file
+** and played back, then SQLITE_OK is returned. If an IO error occurs
+** while reading the record from the (sub-)journal file or while writing
+** to the database file, then the IO error code is returned. If data
+** is successfully read from the (sub-)journal file but appears to be
+** corrupted, SQLITE_DONE is returned. Data is considered corrupted in
+** two circumstances:
+** 
+**   * If the record page-number is illegal (0 or PAGER_MJ_PGNO), or
+**   * If the record is being rolled back from the main journal file
+**     and the checksum field does not match the record content.
+**
+** Neither of these two scenarios are possible during a savepoint rollback.
+**
+** If this is a savepoint rollback, then memory may have to be dynamically
+** allocated by this function. If this is the case and an allocation fails,
+** SQLITE_NOMEM is returned.
+*/
+static int pager_playback_one_page(
+  Pager *pPager,                /* The pager being played back */
+  i64 *pOffset,                 /* Offset of record to playback */
+  Bitvec *pDone,                /* Bitvec of pages already played back */
+  int isMainJrnl,               /* 1 -> main journal. 0 -> sub-journal. */
+  int isSavepnt                 /* True for a savepoint rollback */
+){
+  int rc;
+  PgHdr *pPg;                   /* An existing page in the cache */
+  Pgno pgno;                    /* The page number of a page in journal */
+  u32 cksum;                    /* Checksum used for sanity checking */
+  char *aData;                  /* Temporary storage for the page */
+  sqlite3_file *jfd;            /* The file descriptor for the journal file */
+  int isSynced;                 /* True if journal page is synced */
+
+  assert( (isMainJrnl&~1)==0 );      /* isMainJrnl is 0 or 1 */
+  assert( (isSavepnt&~1)==0 );       /* isSavepnt is 0 or 1 */
+  assert( isMainJrnl || pDone );     /* pDone always used on sub-journals */
+  assert( isSavepnt || pDone==0 );   /* pDone never used on non-savepoint */
+
+  aData = pPager->pTmpSpace;
+  assert( aData );         /* Temp storage must have already been allocated */
+  assert( pagerUseWal(pPager)==0 || (!isMainJrnl && isSavepnt) );
+
+  /* Either the state is greater than PAGER_WRITER_CACHEMOD (a transaction 
+  ** or savepoint rollback done at the request of the caller) or this is
+  ** a hot-journal rollback. If it is a hot-journal rollback, the pager
+  ** is in state OPEN and holds an EXCLUSIVE lock. Hot-journal rollback
+  ** only reads from the main journal, not the sub-journal.
+  */
+  assert( pPager->eState>=PAGER_WRITER_CACHEMOD
+       || (pPager->eState==PAGER_OPEN && pPager->eLock==EXCLUSIVE_LOCK)
+  );
+  assert( pPager->eState>=PAGER_WRITER_CACHEMOD || isMainJrnl );
+
+  /* Read the page number and page data from the journal or sub-journal
+  ** file. Return an error code to the caller if an IO error occurs.
+  */
+  jfd = isMainJrnl ? pPager->jfd : pPager->sjfd;
+  rc = read32bits(jfd, *pOffset, &pgno);
+  if( rc!=SQLITE_OK ) return rc;
+  rc = sqlite3OsRead(jfd, (u8*)aData, pPager->pageSize, (*pOffset)+4);
+  if( rc!=SQLITE_OK ) return rc;
+  *pOffset += pPager->pageSize + 4 + isMainJrnl*4;
+
+  /* Sanity checking on the page.  This is more important that I originally
+  ** thought.  If a power failure occurs while the journal is being written,
+  ** it could cause invalid data to be written into the journal.  We need to
+  ** detect this invalid data (with high probability) and ignore it.
+  */
+  if( pgno==0 || pgno==PAGER_MJ_PGNO(pPager) ){
+    assert( !isSavepnt );
+    return SQLITE_DONE;
+  }
+  if( pgno>(Pgno)pPager->dbSize || sqlite3BitvecTest(pDone, pgno) ){
+    return SQLITE_OK;
+  }
+  if( isMainJrnl ){
+    rc = read32bits(jfd, (*pOffset)-4, &cksum);
+    if( rc ) return rc;
+    if( !isSavepnt && pager_cksum(pPager, (u8*)aData)!=cksum ){
+      return SQLITE_DONE;
+    }
+  }
+
+  /* If this page has already been played by before during the current
+  ** rollback, then don't bother to play it back again.
+  */
+  if( pDone && (rc = sqlite3BitvecSet(pDone, pgno))!=SQLITE_OK ){
+    return rc;
+  }
+
+  /* When playing back page 1, restore the nReserve setting
+  */
+  if( pgno==1 && pPager->nReserve!=((u8*)aData)[20] ){
+    pPager->nReserve = ((u8*)aData)[20];
+    pagerReportSize(pPager);
+  }
+
+  /* If the pager is in CACHEMOD state, then there must be a copy of this
+  ** page in the pager cache. In this case just update the pager cache,
+  ** not the database file. The page is left marked dirty in this case.
+  **
+  ** An exception to the above rule: If the database is in no-sync mode
+  ** and a page is moved during an incremental vacuum then the page may
+  ** not be in the pager cache. Later: if a malloc() or IO error occurs
+  ** during a Movepage() call, then the page may not be in the cache
+  ** either. So the condition described in the above paragraph is not
+  ** assert()able.
+  **
+  ** If in WRITER_DBMOD, WRITER_FINISHED or OPEN state, then we update the
+  ** pager cache if it exists and the main file. The page is then marked 
+  ** not dirty. Since this code is only executed in PAGER_OPEN state for
+  ** a hot-journal rollback, it is guaranteed that the page-cache is empty
+  ** if the pager is in OPEN state.
+  **
+  ** Ticket #1171:  The statement journal might contain page content that is
+  ** different from the page content at the start of the transaction.
+  ** This occurs when a page is changed prior to the start of a statement
+  ** then changed again within the statement.  When rolling back such a
+  ** statement we must not write to the original database unless we know
+  ** for certain that original page contents are synced into the main rollback
+  ** journal.  Otherwise, a power loss might leave modified data in the
+  ** database file without an entry in the rollback journal that can
+  ** restore the database to its original form.  Two conditions must be
+  ** met before writing to the database files. (1) the database must be
+  ** locked.  (2) we know that the original page content is fully synced
+  ** in the main journal either because the page is not in cache or else
+  ** the page is marked as needSync==0.
+  **
+  ** 2008-04-14:  When attempting to vacuum a corrupt database file, it
+  ** is possible to fail a statement on a database that does not yet exist.
+  ** Do not attempt to write if database file has never been opened.
+  */
+  if( pagerUseWal(pPager) ){
+    pPg = 0;
+  }else{
+    pPg = pager_lookup(pPager, pgno);
+  }
+  assert( pPg || !MEMDB );
+  assert( pPager->eState!=PAGER_OPEN || pPg==0 );
+  PAGERTRACE(("PLAYBACK %d page %d hash(%08x) %s\n",
+           PAGERID(pPager), pgno, pager_datahash(pPager->pageSize, (u8*)aData),
+           (isMainJrnl?"main-journal":"sub-journal")
+  ));
+  if( isMainJrnl ){
+    isSynced = pPager->noSync || (*pOffset <= pPager->journalHdr);
+  }else{
+    isSynced = (pPg==0 || 0==(pPg->flags & PGHDR_NEED_SYNC));
+  }
+  if( isOpen(pPager->fd)
+   && (pPager->eState>=PAGER_WRITER_DBMOD || pPager->eState==PAGER_OPEN)
+   && isSynced
+  ){
+    i64 ofst = (pgno-1)*(i64)pPager->pageSize;
+    testcase( !isSavepnt && pPg!=0 && (pPg->flags&PGHDR_NEED_SYNC)!=0 );
+    assert( !pagerUseWal(pPager) );
+    rc = sqlite3OsWrite(pPager->fd, (u8*)aData, pPager->pageSize, ofst);
+    if( pgno>pPager->dbFileSize ){
+      pPager->dbFileSize = pgno;
+    }
+    if( pPager->pBackup ){
+      CODEC1(pPager, aData, pgno, 3, rc=SQLITE_NOMEM);
+      sqlite3BackupUpdate(pPager->pBackup, pgno, (u8*)aData);
+      CODEC2(pPager, aData, pgno, 7, rc=SQLITE_NOMEM, aData);
+    }
+  }else if( !isMainJrnl && pPg==0 ){
+    /* If this is a rollback of a savepoint and data was not written to
+    ** the database and the page is not in-memory, there is a potential
+    ** problem. When the page is next fetched by the b-tree layer, it 
+    ** will be read from the database file, which may or may not be 
+    ** current. 
+    **
+    ** There are a couple of different ways this can happen. All are quite
+    ** obscure. When running in synchronous mode, this can only happen 
+    ** if the page is on the free-list at the start of the transaction, then
+    ** populated, then moved using sqlite3PagerMovepage().
+    **
+    ** The solution is to add an in-memory page to the cache containing
+    ** the data just read from the sub-journal. Mark the page as dirty 
+    ** and if the pager requires a journal-sync, then mark the page as 
+    ** requiring a journal-sync before it is written.
+    */
+    assert( isSavepnt );
+    assert( pPager->doNotSpill==0 );
+    pPager->doNotSpill++;
+    rc = sqlite3PagerAcquire(pPager, pgno, &pPg, 1);
+    assert( pPager->doNotSpill==1 );
+    pPager->doNotSpill--;
+    if( rc!=SQLITE_OK ) return rc;
+    pPg->flags &= ~PGHDR_NEED_READ;
+    sqlite3PcacheMakeDirty(pPg);
+  }
+  if( pPg ){
+    /* No page should ever be explicitly rolled back that is in use, except
+    ** for page 1 which is held in use in order to keep the lock on the
+    ** database active. However such a page may be rolled back as a result
+    ** of an internal error resulting in an automatic call to
+    ** sqlite3PagerRollback().
+    */
+    void *pData;
+    pData = pPg->pData;
+    memcpy(pData, (u8*)aData, pPager->pageSize);
+    pPager->xReiniter(pPg);
+    if( isMainJrnl && (!isSavepnt || *pOffset<=pPager->journalHdr) ){
+      /* If the contents of this page were just restored from the main 
+      ** journal file, then its content must be as they were when the 
+      ** transaction was first opened. In this case we can mark the page
+      ** as clean, since there will be no need to write it out to the
+      ** database.
+      **
+      ** There is one exception to this rule. If the page is being rolled
+      ** back as part of a savepoint (or statement) rollback from an 
+      ** unsynced portion of the main journal file, then it is not safe
+      ** to mark the page as clean. This is because marking the page as
+      ** clean will clear the PGHDR_NEED_SYNC flag. Since the page is
+      ** already in the journal file (recorded in Pager.pInJournal) and
+      ** the PGHDR_NEED_SYNC flag is cleared, if the page is written to
+      ** again within this transaction, it will be marked as dirty but
+      ** the PGHDR_NEED_SYNC flag will not be set. It could then potentially
+      ** be written out into the database file before its journal file
+      ** segment is synced. If a crash occurs during or following this,
+      ** database corruption may ensue.
+      */
+      assert( !pagerUseWal(pPager) );
+      sqlite3PcacheMakeClean(pPg);
+    }
+    pager_set_pagehash(pPg);
+
+    /* If this was page 1, then restore the value of Pager.dbFileVers.
+    ** Do this before any decoding. */
+    if( pgno==1 ){
+      memcpy(&pPager->dbFileVers, &((u8*)pData)[24],sizeof(pPager->dbFileVers));
+    }
+
+    /* Decode the page just read from disk */
+    CODEC1(pPager, pData, pPg->pgno, 3, rc=SQLITE_NOMEM);
+    sqlite3PcacheRelease(pPg);
+  }
+  return rc;
+}
+
+/*
+** Parameter zMaster is the name of a master journal file. A single journal
+** file that referred to the master journal file has just been rolled back.
+** This routine checks if it is possible to delete the master journal file,
+** and does so if it is.
+**
+** Argument zMaster may point to Pager.pTmpSpace. So that buffer is not 
+** available for use within this function.
+**
+** When a master journal file is created, it is populated with the names 
+** of all of its child journals, one after another, formatted as utf-8 
+** encoded text. The end of each child journal file is marked with a 
+** nul-terminator byte (0x00). i.e. the entire contents of a master journal
+** file for a transaction involving two databases might be:
+**
+**   "/home/bill/a.db-journal\x00/home/bill/b.db-journal\x00"
+**
+** A master journal file may only be deleted once all of its child 
+** journals have been rolled back.
+**
+** This function reads the contents of the master-journal file into 
+** memory and loops through each of the child journal names. For
+** each child journal, it checks if:
+**
+**   * if the child journal exists, and if so
+**   * if the child journal contains a reference to master journal 
+**     file zMaster
+**
+** If a child journal can be found that matches both of the criteria
+** above, this function returns without doing anything. Otherwise, if
+** no such child journal can be found, file zMaster is deleted from
+** the file-system using sqlite3OsDelete().
+**
+** If an IO error within this function, an error code is returned. This
+** function allocates memory by calling sqlite3Malloc(). If an allocation
+** fails, SQLITE_NOMEM is returned. Otherwise, if no IO or malloc errors 
+** occur, SQLITE_OK is returned.
+**
+** TODO: This function allocates a single block of memory to load
+** the entire contents of the master journal file. This could be
+** a couple of kilobytes or so - potentially larger than the page 
+** size.
+*/
+static int pager_delmaster(Pager *pPager, const char *zMaster){
+  sqlite3_vfs *pVfs = pPager->pVfs;
+  int rc;                   /* Return code */
+  sqlite3_file *pMaster;    /* Malloc'd master-journal file descriptor */
+  sqlite3_file *pJournal;   /* Malloc'd child-journal file descriptor */
+  char *zMasterJournal = 0; /* Contents of master journal file */
+  i64 nMasterJournal;       /* Size of master journal file */
+  char *zJournal;           /* Pointer to one journal within MJ file */
+  char *zMasterPtr;         /* Space to hold MJ filename from a journal file */
+  int nMasterPtr;           /* Amount of space allocated to zMasterPtr[] */
+
+  /* Allocate space for both the pJournal and pMaster file descriptors.
+  ** If successful, open the master journal file for reading.
+  */
+  pMaster = (sqlite3_file *)sqlite3MallocZero(pVfs->szOsFile * 2);
+  pJournal = (sqlite3_file *)(((u8 *)pMaster) + pVfs->szOsFile);
+  if( !pMaster ){
+    rc = SQLITE_NOMEM;
+  }else{
+    const int flags = (SQLITE_OPEN_READONLY|SQLITE_OPEN_MASTER_JOURNAL);
+    rc = sqlite3OsOpen(pVfs, zMaster, pMaster, flags, 0);
+  }
+  if( rc!=SQLITE_OK ) goto delmaster_out;
+
+  /* Load the entire master journal file into space obtained from
+  ** sqlite3_malloc() and pointed to by zMasterJournal.   Also obtain
+  ** sufficient space (in zMasterPtr) to hold the names of master
+  ** journal files extracted from regular rollback-journals.
+  */
+  rc = sqlite3OsFileSize(pMaster, &nMasterJournal);
+  if( rc!=SQLITE_OK ) goto delmaster_out;
+  nMasterPtr = pVfs->mxPathname+1;
+  zMasterJournal = sqlite3Malloc((int)nMasterJournal + nMasterPtr + 1);
+  if( !zMasterJournal ){
+    rc = SQLITE_NOMEM;
+    goto delmaster_out;
+  }
+  zMasterPtr = &zMasterJournal[nMasterJournal+1];
+  rc = sqlite3OsRead(pMaster, zMasterJournal, (int)nMasterJournal, 0);
+  if( rc!=SQLITE_OK ) goto delmaster_out;
+  zMasterJournal[nMasterJournal] = 0;
+
+  zJournal = zMasterJournal;
+  while( (zJournal-zMasterJournal)<nMasterJournal ){
+    int exists;
+    rc = sqlite3OsAccess(pVfs, zJournal, SQLITE_ACCESS_EXISTS, &exists);
+    if( rc!=SQLITE_OK ){
+      goto delmaster_out;
+    }
+    if( exists ){
+      /* One of the journals pointed to by the master journal exists.
+      ** Open it and check if it points at the master journal. If
+      ** so, return without deleting the master journal file.
+      */
+      int c;
+      int flags = (SQLITE_OPEN_READONLY|SQLITE_OPEN_MAIN_JOURNAL);
+      rc = sqlite3OsOpen(pVfs, zJournal, pJournal, flags, 0);
+      if( rc!=SQLITE_OK ){
+        goto delmaster_out;
+      }
+
+      rc = readMasterJournal(pJournal, zMasterPtr, nMasterPtr);
+      sqlite3OsClose(pJournal);
+      if( rc!=SQLITE_OK ){
+        goto delmaster_out;
+      }
+
+      c = zMasterPtr[0]!=0 && strcmp(zMasterPtr, zMaster)==0;
+      if( c ){
+        /* We have a match. Do not delete the master journal file. */
+        goto delmaster_out;
+      }
+    }
+    zJournal += (sqlite3Strlen30(zJournal)+1);
+  }
+ 
+  sqlite3OsClose(pMaster);
+  rc = sqlite3OsDelete(pVfs, zMaster, 0);
+
+delmaster_out:
+  sqlite3_free(zMasterJournal);
+  if( pMaster ){
+    sqlite3OsClose(pMaster);
+    assert( !isOpen(pJournal) );
+    sqlite3_free(pMaster);
+  }
+  return rc;
+}
+
+
+/*
+** This function is used to change the actual size of the database 
+** file in the file-system. This only happens when committing a transaction,
+** or rolling back a transaction (including rolling back a hot-journal).
+**
+** If the main database file is not open, or the pager is not in either
+** DBMOD or OPEN state, this function is a no-op. Otherwise, the size 
+** of the file is changed to nPage pages (nPage*pPager->pageSize bytes). 
+** If the file on disk is currently larger than nPage pages, then use the VFS
+** xTruncate() method to truncate it.
+**
+** Or, it might might be the case that the file on disk is smaller than 
+** nPage pages. Some operating system implementations can get confused if 
+** you try to truncate a file to some size that is larger than it 
+** currently is, so detect this case and write a single zero byte to 
+** the end of the new file instead.
+**
+** If successful, return SQLITE_OK. If an IO error occurs while modifying
+** the database file, return the error code to the caller.
+*/
+static int pager_truncate(Pager *pPager, Pgno nPage){
+  int rc = SQLITE_OK;
+  assert( pPager->eState!=PAGER_ERROR );
+  assert( pPager->eState!=PAGER_READER );
+  
+  if( isOpen(pPager->fd) 
+   && (pPager->eState>=PAGER_WRITER_DBMOD || pPager->eState==PAGER_OPEN) 
+  ){
+    i64 currentSize, newSize;
+    int szPage = pPager->pageSize;
+    assert( pPager->eLock==EXCLUSIVE_LOCK );
+    /* TODO: Is it safe to use Pager.dbFileSize here? */
+    rc = sqlite3OsFileSize(pPager->fd, &currentSize);
+    newSize = szPage*(i64)nPage;
+    if( rc==SQLITE_OK && currentSize!=newSize ){
+      if( currentSize>newSize ){
+        rc = sqlite3OsTruncate(pPager->fd, newSize);
+      }else{
+        char *pTmp = pPager->pTmpSpace;
+        memset(pTmp, 0, szPage);
+        testcase( (newSize-szPage) <  currentSize );
+        testcase( (newSize-szPage) == currentSize );
+        testcase( (newSize-szPage) >  currentSize );
+        rc = sqlite3OsWrite(pPager->fd, pTmp, szPage, newSize-szPage);
+      }
+      if( rc==SQLITE_OK ){
+        pPager->dbFileSize = nPage;
+      }
+    }
+  }
+  return rc;
+}
+
+/*
+** Set the value of the Pager.sectorSize variable for the given
+** pager based on the value returned by the xSectorSize method
+** of the open database file. The sector size will be used used 
+** to determine the size and alignment of journal header and 
+** master journal pointers within created journal files.
+**
+** For temporary files the effective sector size is always 512 bytes.
+**
+** Otherwise, for non-temporary files, the effective sector size is
+** the value returned by the xSectorSize() method rounded up to 32 if
+** it is less than 32, or rounded down to MAX_SECTOR_SIZE if it
+** is greater than MAX_SECTOR_SIZE.
+*/
+static void setSectorSize(Pager *pPager){
+  assert( isOpen(pPager->fd) || pPager->tempFile );
+
+  if( !pPager->tempFile ){
+    /* Sector size doesn't matter for temporary files. Also, the file
+    ** may not have been opened yet, in which case the OsSectorSize()
+    ** call will segfault.
+    */
+    pPager->sectorSize = sqlite3OsSectorSize(pPager->fd);
+  }
+  if( pPager->sectorSize<32 ){
+    pPager->sectorSize = 512;
+  }
+  if( pPager->sectorSize>MAX_SECTOR_SIZE ){
+    assert( MAX_SECTOR_SIZE>=512 );
+    pPager->sectorSize = MAX_SECTOR_SIZE;
+  }
+}
+
+/*
+** Playback the journal and thus restore the database file to
+** the state it was in before we started making changes.  
+**
+** The journal file format is as follows: 
+**
+**  (1)  8 byte prefix.  A copy of aJournalMagic[].
+**  (2)  4 byte big-endian integer which is the number of valid page records
+**       in the journal.  If this value is 0xffffffff, then compute the
+**       number of page records from the journal size.
+**  (3)  4 byte big-endian integer which is the initial value for the 
+**       sanity checksum.
+**  (4)  4 byte integer which is the number of pages to truncate the
+**       database to during a rollback.
+**  (5)  4 byte big-endian integer which is the sector size.  The header
+**       is this many bytes in size.
+**  (6)  4 byte big-endian integer which is the page size.
+**  (7)  zero padding out to the next sector size.
+**  (8)  Zero or more pages instances, each as follows:
+**        +  4 byte page number.
+**        +  pPager->pageSize bytes of data.
+**        +  4 byte checksum
+**
+** When we speak of the journal header, we mean the first 7 items above.
+** Each entry in the journal is an instance of the 8th item.
+**
+** Call the value from the second bullet "nRec".  nRec is the number of
+** valid page entries in the journal.  In most cases, you can compute the
+** value of nRec from the size of the journal file.  But if a power
+** failure occurred while the journal was being written, it could be the
+** case that the size of the journal file had already been increased but
+** the extra entries had not yet made it safely to disk.  In such a case,
+** the value of nRec computed from the file size would be too large.  For
+** that reason, we always use the nRec value in the header.
+**
+** If the nRec value is 0xffffffff it means that nRec should be computed
+** from the file size.  This value is used when the user selects the
+** no-sync option for the journal.  A power failure could lead to corruption
+** in this case.  But for things like temporary table (which will be
+** deleted when the power is restored) we don't care.  
+**
+** If the file opened as the journal file is not a well-formed
+** journal file then all pages up to the first corrupted page are rolled
+** back (or no pages if the journal header is corrupted). The journal file
+** is then deleted and SQLITE_OK returned, just as if no corruption had
+** been encountered.
+**
+** If an I/O or malloc() error occurs, the journal-file is not deleted
+** and an error code is returned.
+**
+** The isHot parameter indicates that we are trying to rollback a journal
+** that might be a hot journal.  Or, it could be that the journal is 
+** preserved because of JOURNALMODE_PERSIST or JOURNALMODE_TRUNCATE.
+** If the journal really is hot, reset the pager cache prior rolling
+** back any content.  If the journal is merely persistent, no reset is
+** needed.
+*/
+static int pager_playback(Pager *pPager, int isHot){
+  sqlite3_vfs *pVfs = pPager->pVfs;
+  i64 szJ;                 /* Size of the journal file in bytes */
+  u32 nRec;                /* Number of Records in the journal */
+  u32 u;                   /* Unsigned loop counter */
+  Pgno mxPg = 0;           /* Size of the original file in pages */
+  int rc;                  /* Result code of a subroutine */
+  int res = 1;             /* Value returned by sqlite3OsAccess() */
+  char *zMaster = 0;       /* Name of master journal file if any */
+  int needPagerReset;      /* True to reset page prior to first page rollback */
+
+  /* Figure out how many records are in the journal.  Abort early if
+  ** the journal is empty.
+  */
+  assert( isOpen(pPager->jfd) );
+  rc = sqlite3OsFileSize(pPager->jfd, &szJ);
+  if( rc!=SQLITE_OK ){
+    goto end_playback;
+  }
+
+  /* Read the master journal name from the journal, if it is present.
+  ** If a master journal file name is specified, but the file is not
+  ** present on disk, then the journal is not hot and does not need to be
+  ** played back.
+  **
+  ** TODO: Technically the following is an error because it assumes that
+  ** buffer Pager.pTmpSpace is (mxPathname+1) bytes or larger. i.e. that
+  ** (pPager->pageSize >= pPager->pVfs->mxPathname+1). Using os_unix.c,
+  **  mxPathname is 512, which is the same as the minimum allowable value
+  ** for pageSize.
+  */
+  zMaster = pPager->pTmpSpace;
+  rc = readMasterJournal(pPager->jfd, zMaster, pPager->pVfs->mxPathname+1);
+  if( rc==SQLITE_OK && zMaster[0] ){
+    rc = sqlite3OsAccess(pVfs, zMaster, SQLITE_ACCESS_EXISTS, &res);
+  }
+  zMaster = 0;
+  if( rc!=SQLITE_OK || !res ){
+    goto end_playback;
+  }
+  pPager->journalOff = 0;
+  needPagerReset = isHot;
+
+  /* This loop terminates either when a readJournalHdr() or 
+  ** pager_playback_one_page() call returns SQLITE_DONE or an IO error 
+  ** occurs. 
+  */
+  while( 1 ){
+    /* Read the next journal header from the journal file.  If there are
+    ** not enough bytes left in the journal file for a complete header, or
+    ** it is corrupted, then a process must have failed while writing it.
+    ** This indicates nothing more needs to be rolled back.
+    */
+    rc = readJournalHdr(pPager, isHot, szJ, &nRec, &mxPg);
+    if( rc!=SQLITE_OK ){ 
+      if( rc==SQLITE_DONE ){
+        rc = SQLITE_OK;
+      }
+      goto end_playback;
+    }
+
+    /* If nRec is 0xffffffff, then this journal was created by a process
+    ** working in no-sync mode. This means that the rest of the journal
+    ** file consists of pages, there are no more journal headers. Compute
+    ** the value of nRec based on this assumption.
+    */
+    if( nRec==0xffffffff ){
+      assert( pPager->journalOff==JOURNAL_HDR_SZ(pPager) );
+      nRec = (int)((szJ - JOURNAL_HDR_SZ(pPager))/JOURNAL_PG_SZ(pPager));
+    }
+
+    /* If nRec is 0 and this rollback is of a transaction created by this
+    ** process and if this is the final header in the journal, then it means
+    ** that this part of the journal was being filled but has not yet been
+    ** synced to disk.  Compute the number of pages based on the remaining
+    ** size of the file.
+    **
+    ** The third term of the test was added to fix ticket #2565.
+    ** When rolling back a hot journal, nRec==0 always means that the next
+    ** chunk of the journal contains zero pages to be rolled back.  But
+    ** when doing a ROLLBACK and the nRec==0 chunk is the last chunk in
+    ** the journal, it means that the journal might contain additional
+    ** pages that need to be rolled back and that the number of pages 
+    ** should be computed based on the journal file size.
+    */
+    if( nRec==0 && !isHot &&
+        pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff ){
+      nRec = (int)((szJ - pPager->journalOff) / JOURNAL_PG_SZ(pPager));
+    }
+
+    /* If this is the first header read from the journal, truncate the
+    ** database file back to its original size.
+    */
+    if( pPager->journalOff==JOURNAL_HDR_SZ(pPager) ){
+      rc = pager_truncate(pPager, mxPg);
+      if( rc!=SQLITE_OK ){
+        goto end_playback;
+      }
+      pPager->dbSize = mxPg;
+    }
+
+    /* Copy original pages out of the journal and back into the 
+    ** database file and/or page cache.
+    */
+    for(u=0; u<nRec; u++){
+      if( needPagerReset ){
+        pager_reset(pPager);
+        needPagerReset = 0;
+      }
+      rc = pager_playback_one_page(pPager,&pPager->journalOff,0,1,0);
+      if( rc!=SQLITE_OK ){
+        if( rc==SQLITE_DONE ){
+          pPager->journalOff = szJ;
+          break;
+        }else if( rc==SQLITE_IOERR_SHORT_READ ){
+          /* If the journal has been truncated, simply stop reading and
+          ** processing the journal. This might happen if the journal was
+          ** not completely written and synced prior to a crash.  In that
+          ** case, the database should have never been written in the
+          ** first place so it is OK to simply abandon the rollback. */
+          rc = SQLITE_OK;
+          goto end_playback;
+        }else{
+          /* If we are unable to rollback, quit and return the error
+          ** code.  This will cause the pager to enter the error state
+          ** so that no further harm will be done.  Perhaps the next
+          ** process to come along will be able to rollback the database.
+          */
+          goto end_playback;
+        }
+      }
+    }
+  }
+  /*NOTREACHED*/
+  assert( 0 );
+
+end_playback:
+  /* Following a rollback, the database file should be back in its original
+  ** state prior to the start of the transaction, so invoke the
+  ** SQLITE_FCNTL_DB_UNCHANGED file-control method to disable the
+  ** assertion that the transaction counter was modified.
+  */
+  assert(
+    pPager->fd->pMethods==0 ||
+    sqlite3OsFileControl(pPager->fd,SQLITE_FCNTL_DB_UNCHANGED,0)>=SQLITE_OK
+  );
+
+  /* If this playback is happening automatically as a result of an IO or 
+  ** malloc error that occurred after the change-counter was updated but 
+  ** before the transaction was committed, then the change-counter 
+  ** modification may just have been reverted. If this happens in exclusive 
+  ** mode, then subsequent transactions performed by the connection will not
+  ** update the change-counter at all. This may lead to cache inconsistency
+  ** problems for other processes at some point in the future. So, just
+  ** in case this has happened, clear the changeCountDone flag now.
+  */
+  pPager->changeCountDone = pPager->tempFile;
+
+  if( rc==SQLITE_OK ){
+    zMaster = pPager->pTmpSpace;
+    rc = readMasterJournal(pPager->jfd, zMaster, pPager->pVfs->mxPathname+1);
+    testcase( rc!=SQLITE_OK );
+  }
+  if( rc==SQLITE_OK
+   && (pPager->eState>=PAGER_WRITER_DBMOD || pPager->eState==PAGER_OPEN)
+  ){
+    rc = sqlite3PagerSync(pPager);
+  }
+  if( rc==SQLITE_OK ){
+    rc = pager_end_transaction(pPager, zMaster[0]!='\0');
+    testcase( rc!=SQLITE_OK );
+  }
+  if( rc==SQLITE_OK && zMaster[0] && res ){
+    /* If there was a master journal and this routine will return success,
+    ** see if it is possible to delete the master journal.
+    */
+    rc = pager_delmaster(pPager, zMaster);
+    testcase( rc!=SQLITE_OK );
+  }
+
+  /* The Pager.sectorSize variable may have been updated while rolling
+  ** back a journal created by a process with a different sector size
+  ** value. Reset it to the correct value for this process.
+  */
+  setSectorSize(pPager);
+  return rc;
+}
+
+
+/*
+** Read the content for page pPg out of the database file and into 
+** pPg->pData. A shared lock or greater must be held on the database
+** file before this function is called.
+**
+** If page 1 is read, then the value of Pager.dbFileVers[] is set to
+** the value read from the database file.
+**
+** If an IO error occurs, then the IO error is returned to the caller.
+** Otherwise, SQLITE_OK is returned.
+*/
+static int readDbPage(PgHdr *pPg){
+  Pager *pPager = pPg->pPager; /* Pager object associated with page pPg */
+  Pgno pgno = pPg->pgno;       /* Page number to read */
+  int rc = SQLITE_OK;          /* Return code */
+  int isInWal = 0;             /* True if page is in log file */
+  int pgsz = pPager->pageSize; /* Number of bytes to read */
+
+  assert( pPager->eState>=PAGER_READER && !MEMDB );
+  assert( isOpen(pPager->fd) );
+
+  if( NEVER(!isOpen(pPager->fd)) ){
+    assert( pPager->tempFile );
+    memset(pPg->pData, 0, pPager->pageSize);
+    return SQLITE_OK;
+  }
+
+  if( pagerUseWal(pPager) ){
+    /* Try to pull the page from the write-ahead log. */
+    rc = sqlite3WalRead(pPager->pWal, pgno, &isInWal, pgsz, pPg->pData);
+  }
+  if( rc==SQLITE_OK && !isInWal ){
+    i64 iOffset = (pgno-1)*(i64)pPager->pageSize;
+    rc = sqlite3OsRead(pPager->fd, pPg->pData, pgsz, iOffset);
+    if( rc==SQLITE_IOERR_SHORT_READ ){
+      rc = SQLITE_OK;
+    }
+  }
+
+  if( pgno==1 ){
+    if( rc ){
+      /* If the read is unsuccessful, set the dbFileVers[] to something
+      ** that will never be a valid file version.  dbFileVers[] is a copy
+      ** of bytes 24..39 of the database.  Bytes 28..31 should always be
+      ** zero or the size of the database in page. Bytes 32..35 and 35..39
+      ** should be page numbers which are never 0xffffffff.  So filling
+      ** pPager->dbFileVers[] with all 0xff bytes should suffice.
+      **
+      ** For an encrypted database, the situation is more complex:  bytes
+      ** 24..39 of the database are white noise.  But the probability of
+      ** white noising equaling 16 bytes of 0xff is vanishingly small so
+      ** we should still be ok.
+      */
+      memset(pPager->dbFileVers, 0xff, sizeof(pPager->dbFileVers));
+    }else{
+      u8 *dbFileVers = &((u8*)pPg->pData)[24];
+      memcpy(&pPager->dbFileVers, dbFileVers, sizeof(pPager->dbFileVers));
+    }
+  }
+  CODEC1(pPager, pPg->pData, pgno, 3, rc = SQLITE_NOMEM);
+
+  PAGER_INCR(sqlite3_pager_readdb_count);
+  PAGER_INCR(pPager->nRead);
+  IOTRACE(("PGIN %p %d\n", pPager, pgno));
+  PAGERTRACE(("FETCH %d page %d hash(%08x)\n",
+               PAGERID(pPager), pgno, pager_pagehash(pPg)));
+
+  return rc;
+}
+
+/*
+** Update the value of the change-counter at offsets 24 and 92 in
+** the header and the sqlite version number at offset 96.
+**
+** This is an unconditional update.  See also the pager_incr_changecounter()
+** routine which only updates the change-counter if the update is actually
+** needed, as determined by the pPager->changeCountDone state variable.
+*/
+static void pager_write_changecounter(PgHdr *pPg){
+  u32 change_counter;
+
+  /* Increment the value just read and write it back to byte 24. */
+  change_counter = sqlite3Get4byte((u8*)pPg->pPager->dbFileVers)+1;
+  put32bits(((char*)pPg->pData)+24, change_counter);
+
+  /* Also store the SQLite version number in bytes 96..99 and in
+  ** bytes 92..95 store the change counter for which the version number
+  ** is valid. */
+  put32bits(((char*)pPg->pData)+92, change_counter);
+  put32bits(((char*)pPg->pData)+96, SQLITE_VERSION_NUMBER);
+}
+
+#ifndef SQLITE_OMIT_WAL
+/*
+** This function is invoked once for each page that has already been 
+** written into the log file when a WAL transaction is rolled back.
+** Parameter iPg is the page number of said page. The pCtx argument 
+** is actually a pointer to the Pager structure.
+**
+** If page iPg is present in the cache, and has no outstanding references,
+** it is discarded. Otherwise, if there are one or more outstanding
+** references, the page content is reloaded from the database. If the
+** attempt to reload content from the database is required and fails, 
+** return an SQLite error code. Otherwise, SQLITE_OK.
+*/
+static int pagerUndoCallback(void *pCtx, Pgno iPg){
+  int rc = SQLITE_OK;
+  Pager *pPager = (Pager *)pCtx;
+  PgHdr *pPg;
+
+  pPg = sqlite3PagerLookup(pPager, iPg);
+  if( pPg ){
+    if( sqlite3PcachePageRefcount(pPg)==1 ){
+      sqlite3PcacheDrop(pPg);
+    }else{
+      rc = readDbPage(pPg);
+      if( rc==SQLITE_OK ){
+        pPager->xReiniter(pPg);
+      }
+      sqlite3PagerUnref(pPg);
+    }
+  }
+
+  /* Normally, if a transaction is rolled back, any backup processes are
+  ** updated as data is copied out of the rollback journal and into the
+  ** database. This is not generally possible with a WAL database, as
+  ** rollback involves simply truncating the log file. Therefore, if one
+  ** or more frames have already been written to the log (and therefore 
+  ** also copied into the backup databases) as part of this transaction,
+  ** the backups must be restarted.
+  */
+  sqlite3BackupRestart(pPager->pBackup);
+
+  return rc;
+}
+
+/*
+** This function is called to rollback a transaction on a WAL database.
+*/
+static int pagerRollbackWal(Pager *pPager){
+  int rc;                         /* Return Code */
+  PgHdr *pList;                   /* List of dirty pages to revert */
+
+  /* For all pages in the cache that are currently dirty or have already
+  ** been written (but not committed) to the log file, do one of the 
+  ** following:
+  **
+  **   + Discard the cached page (if refcount==0), or
+  **   + Reload page content from the database (if refcount>0).
+  */
+  pPager->dbSize = pPager->dbOrigSize;
+  rc = sqlite3WalUndo(pPager->pWal, pagerUndoCallback, (void *)pPager);
+  pList = sqlite3PcacheDirtyList(pPager->pPCache);
+  while( pList && rc==SQLITE_OK ){
+    PgHdr *pNext = pList->pDirty;
+    rc = pagerUndoCallback((void *)pPager, pList->pgno);
+    pList = pNext;
+  }
+
+  return rc;
+}
+
+/*
+** This function is a wrapper around sqlite3WalFrames(). As well as logging
+** the contents of the list of pages headed by pList (connected by pDirty),
+** this function notifies any active backup processes that the pages have
+** changed. 
+**
+** The list of pages passed into this routine is always sorted by page number.
+** Hence, if page 1 appears anywhere on the list, it will be the first page.
+*/ 
+static int pagerWalFrames(
+  Pager *pPager,                  /* Pager object */
+  PgHdr *pList,                   /* List of frames to log */
+  Pgno nTruncate,                 /* Database size after this commit */
+  int isCommit,                   /* True if this is a commit */
+  int syncFlags                   /* Flags to pass to OsSync() (or 0) */
+){
+  int rc;                         /* Return code */
+#if defined(SQLITE_DEBUG) || defined(SQLITE_CHECK_PAGES)
+  PgHdr *p;                       /* For looping over pages */
+#endif
+
+  assert( pPager->pWal );
+  assert( pList );
+#ifdef SQLITE_DEBUG
+  /* Verify that the page list is in accending order */
+  for(p=pList; p && p->pDirty; p=p->pDirty){
+    assert( p->pgno < p->pDirty->pgno );
+  }
+#endif
+
+  if( isCommit ){
+    /* If a WAL transaction is being committed, there is no point in writing
+    ** any pages with page numbers greater than nTruncate into the WAL file.
+    ** They will never be read by any client. So remove them from the pDirty
+    ** list here. */
+    PgHdr *p;
+    PgHdr **ppNext = &pList;
+    for(p=pList; (*ppNext = p); p=p->pDirty){
+      if( p->pgno<=nTruncate ) ppNext = &p->pDirty;
+    }
+    assert( pList );
+  }
+
+  if( pList->pgno==1 ) pager_write_changecounter(pList);
+  rc = sqlite3WalFrames(pPager->pWal, 
+      pPager->pageSize, pList, nTruncate, isCommit, syncFlags
+  );
+  if( rc==SQLITE_OK && pPager->pBackup ){
+    PgHdr *p;
+    for(p=pList; p; p=p->pDirty){
+      sqlite3BackupUpdate(pPager->pBackup, p->pgno, (u8 *)p->pData);
+    }
+  }
+
+#ifdef SQLITE_CHECK_PAGES
+  pList = sqlite3PcacheDirtyList(pPager->pPCache);
+  for(p=pList; p; p=p->pDirty){
+    pager_set_pagehash(p);
+  }
+#endif
+
+  return rc;
+}
+
+/*
+** Begin a read transaction on the WAL.
+**
+** This routine used to be called "pagerOpenSnapshot()" because it essentially
+** makes a snapshot of the database at the current point in time and preserves
+** that snapshot for use by the reader in spite of concurrently changes by
+** other writers or checkpointers.
+*/
+static int pagerBeginReadTransaction(Pager *pPager){
+  int rc;                         /* Return code */
+  int changed = 0;                /* True if cache must be reset */
+
+  assert( pagerUseWal(pPager) );
+  assert( pPager->eState==PAGER_OPEN || pPager->eState==PAGER_READER );
+
+  /* sqlite3WalEndReadTransaction() was not called for the previous
+  ** transaction in locking_mode=EXCLUSIVE.  So call it now.  If we
+  ** are in locking_mode=NORMAL and EndRead() was previously called,
+  ** the duplicate call is harmless.
+  */
+  sqlite3WalEndReadTransaction(pPager->pWal);
+
+  rc = sqlite3WalBeginReadTransaction(pPager->pWal, &changed);
+  if( rc!=SQLITE_OK || changed ){
+    pager_reset(pPager);
+  }
+
+  return rc;
+}
+#endif
+
+/*
+** This function is called as part of the transition from PAGER_OPEN
+** to PAGER_READER state to determine the size of the database file
+** in pages (assuming the page size currently stored in Pager.pageSize).
+**
+** If no error occurs, SQLITE_OK is returned and the size of the database
+** in pages is stored in *pnPage. Otherwise, an error code (perhaps
+** SQLITE_IOERR_FSTAT) is returned and *pnPage is left unmodified.
+*/
+static int pagerPagecount(Pager *pPager, Pgno *pnPage){
+  Pgno nPage;                     /* Value to return via *pnPage */
+
+  /* Query the WAL sub-system for the database size. The WalDbsize()
+  ** function returns zero if the WAL is not open (i.e. Pager.pWal==0), or
+  ** if the database size is not available. The database size is not
+  ** available from the WAL sub-system if the log file is empty or
+  ** contains no valid committed transactions.
+  */
+  assert( pPager->eState==PAGER_OPEN );
+  assert( pPager->eLock>=SHARED_LOCK || pPager->noReadlock );
+  nPage = sqlite3WalDbsize(pPager->pWal);
+
+  /* If the database size was not available from the WAL sub-system,
+  ** determine it based on the size of the database file. If the size
+  ** of the database file is not an integer multiple of the page-size,
+  ** round down to the nearest page. Except, any file larger than 0
+  ** bytes in size is considered to contain at least one page.
+  */
+  if( nPage==0 ){
+    i64 n = 0;                    /* Size of db file in bytes */
+    assert( isOpen(pPager->fd) || pPager->tempFile );
+    if( isOpen(pPager->fd) ){
+      int rc = sqlite3OsFileSize(pPager->fd, &n);
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+    }
+    nPage = (Pgno)(n / pPager->pageSize);
+    if( nPage==0 && n>0 ){
+      nPage = 1;
+    }
+  }
+
+  /* If the current number of pages in the file is greater than the
+  ** configured maximum pager number, increase the allowed limit so
+  ** that the file can be read.
+  */
+  if( nPage>pPager->mxPgno ){
+    pPager->mxPgno = (Pgno)nPage;
+  }
+
+  *pnPage = nPage;
+  return SQLITE_OK;
+}
+
+#ifndef SQLITE_OMIT_WAL
+/*
+** Check if the *-wal file that corresponds to the database opened by pPager
+** exists if the database is not empy, or verify that the *-wal file does
+** not exist (by deleting it) if the database file is empty.
+**
+** If the database is not empty and the *-wal file exists, open the pager
+** in WAL mode.  If the database is empty or if no *-wal file exists and
+** if no error occurs, make sure Pager.journalMode is not set to
+** PAGER_JOURNALMODE_WAL.
+**
+** Return SQLITE_OK or an error code.
+**
+** The caller must hold a SHARED lock on the database file to call this
+** function. Because an EXCLUSIVE lock on the db file is required to delete 
+** a WAL on a none-empty database, this ensures there is no race condition 
+** between the xAccess() below and an xDelete() being executed by some 
+** other connection.
+*/
+static int pagerOpenWalIfPresent(Pager *pPager){
+  int rc = SQLITE_OK;
+  assert( pPager->eState==PAGER_OPEN );
+  assert( pPager->eLock>=SHARED_LOCK || pPager->noReadlock );
+
+  if( !pPager->tempFile ){
+    int isWal;                    /* True if WAL file exists */
+    Pgno nPage;                   /* Size of the database file */
+
+    rc = pagerPagecount(pPager, &nPage);
+    if( rc ) return rc;
+    if( nPage==0 ){
+      rc = sqlite3OsDelete(pPager->pVfs, pPager->zWal, 0);
+      isWal = 0;
+    }else{
+      rc = sqlite3OsAccess(
+          pPager->pVfs, pPager->zWal, SQLITE_ACCESS_EXISTS, &isWal
+      );
+    }
+    if( rc==SQLITE_OK ){
+      if( isWal ){
+        testcase( sqlite3PcachePagecount(pPager->pPCache)==0 );
+        rc = sqlite3PagerOpenWal(pPager, 0);
+      }else if( pPager->journalMode==PAGER_JOURNALMODE_WAL ){
+        pPager->journalMode = PAGER_JOURNALMODE_DELETE;
+      }
+    }
+  }
+  return rc;
+}
+#endif
+
+/*
+** Playback savepoint pSavepoint. Or, if pSavepoint==NULL, then playback
+** the entire master journal file. The case pSavepoint==NULL occurs when 
+** a ROLLBACK TO command is invoked on a SAVEPOINT that is a transaction 
+** savepoint.
+**
+** When pSavepoint is not NULL (meaning a non-transaction savepoint is 
+** being rolled back), then the rollback consists of up to three stages,
+** performed in the order specified:
+**
+**   * Pages are played back from the main journal starting at byte
+**     offset PagerSavepoint.iOffset and continuing to 
+**     PagerSavepoint.iHdrOffset, or to the end of the main journal
+**     file if PagerSavepoint.iHdrOffset is zero.
+**
+**   * If PagerSavepoint.iHdrOffset is not zero, then pages are played
+**     back starting from the journal header immediately following 
+**     PagerSavepoint.iHdrOffset to the end of the main journal file.
+**
+**   * Pages are then played back from the sub-journal file, starting
+**     with the PagerSavepoint.iSubRec and continuing to the end of
+**     the journal file.
+**
+** Throughout the rollback process, each time a page is rolled back, the
+** corresponding bit is set in a bitvec structure (variable pDone in the
+** implementation below). This is used to ensure that a page is only
+** rolled back the first time it is encountered in either journal.
+**
+** If pSavepoint is NULL, then pages are only played back from the main
+** journal file. There is no need for a bitvec in this case.
+**
+** In either case, before playback commences the Pager.dbSize variable
+** is reset to the value that it held at the start of the savepoint 
+** (or transaction). No page with a page-number greater than this value
+** is played back. If one is encountered it is simply skipped.
+*/
+static int pagerPlaybackSavepoint(Pager *pPager, PagerSavepoint *pSavepoint){
+  i64 szJ;                 /* Effective size of the main journal */
+  i64 iHdrOff;             /* End of first segment of main-journal records */
+  int rc = SQLITE_OK;      /* Return code */
+  Bitvec *pDone = 0;       /* Bitvec to ensure pages played back only once */
+
+  assert( pPager->eState!=PAGER_ERROR );
+  assert( pPager->eState>=PAGER_WRITER_LOCKED );
+
+  /* Allocate a bitvec to use to store the set of pages rolled back */
+  if( pSavepoint ){
+    pDone = sqlite3BitvecCreate(pSavepoint->nOrig);
+    if( !pDone ){
+      return SQLITE_NOMEM;
+    }
+  }
+
+  /* Set the database size back to the value it was before the savepoint 
+  ** being reverted was opened.
+  */
+  pPager->dbSize = pSavepoint ? pSavepoint->nOrig : pPager->dbOrigSize;
+  pPager->changeCountDone = pPager->tempFile;
+
+  if( !pSavepoint && pagerUseWal(pPager) ){
+    return pagerRollbackWal(pPager);
+  }
+
+  /* Use pPager->journalOff as the effective size of the main rollback
+  ** journal.  The actual file might be larger than this in
+  ** PAGER_JOURNALMODE_TRUNCATE or PAGER_JOURNALMODE_PERSIST.  But anything
+  ** past pPager->journalOff is off-limits to us.
+  */
+  szJ = pPager->journalOff;
+  assert( pagerUseWal(pPager)==0 || szJ==0 );
+
+  /* Begin by rolling back records from the main journal starting at
+  ** PagerSavepoint.iOffset and continuing to the next journal header.
+  ** There might be records in the main journal that have a page number
+  ** greater than the current database size (pPager->dbSize) but those
+  ** will be skipped automatically.  Pages are added to pDone as they
+  ** are played back.
+  */
+  if( pSavepoint && !pagerUseWal(pPager) ){
+    iHdrOff = pSavepoint->iHdrOffset ? pSavepoint->iHdrOffset : szJ;
+    pPager->journalOff = pSavepoint->iOffset;
+    while( rc==SQLITE_OK && pPager->journalOff<iHdrOff ){
+      rc = pager_playback_one_page(pPager, &pPager->journalOff, pDone, 1, 1);
+    }
+    assert( rc!=SQLITE_DONE );
+  }else{
+    pPager->journalOff = 0;
+  }
+
+  /* Continue rolling back records out of the main journal starting at
+  ** the first journal header seen and continuing until the effective end
+  ** of the main journal file.  Continue to skip out-of-range pages and
+  ** continue adding pages rolled back to pDone.
+  */
+  while( rc==SQLITE_OK && pPager->journalOff<szJ ){
+    u32 ii;            /* Loop counter */
+    u32 nJRec = 0;     /* Number of Journal Records */
+    u32 dummy;
+    rc = readJournalHdr(pPager, 0, szJ, &nJRec, &dummy);
+    assert( rc!=SQLITE_DONE );
+
+    /*
+    ** The "pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff"
+    ** test is related to ticket #2565.  See the discussion in the
+    ** pager_playback() function for additional information.
+    */
+    if( nJRec==0 
+     && pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff
+    ){
+      nJRec = (u32)((szJ - pPager->journalOff)/JOURNAL_PG_SZ(pPager));
+    }
+    for(ii=0; rc==SQLITE_OK && ii<nJRec && pPager->journalOff<szJ; ii++){
+      rc = pager_playback_one_page(pPager, &pPager->journalOff, pDone, 1, 1);
+    }
+    assert( rc!=SQLITE_DONE );
+  }
+  assert( rc!=SQLITE_OK || pPager->journalOff>=szJ );
+
+  /* Finally,  rollback pages from the sub-journal.  Page that were
+  ** previously rolled back out of the main journal (and are hence in pDone)
+  ** will be skipped.  Out-of-range pages are also skipped.
+  */
+  if( pSavepoint ){
+    u32 ii;            /* Loop counter */
+    i64 offset = pSavepoint->iSubRec*(4+pPager->pageSize);
+
+    if( pagerUseWal(pPager) ){
+      rc = sqlite3WalSavepointUndo(pPager->pWal, pSavepoint->aWalData);
+    }
+    for(ii=pSavepoint->iSubRec; rc==SQLITE_OK && ii<pPager->nSubRec; ii++){
+      assert( offset==ii*(4+pPager->pageSize) );
+      rc = pager_playback_one_page(pPager, &offset, pDone, 0, 1);
+    }
+    assert( rc!=SQLITE_DONE );
+  }
+
+  sqlite3BitvecDestroy(pDone);
+  if( rc==SQLITE_OK ){
+    pPager->journalOff = szJ;
+  }
+
+  return rc;
+}
+
+/*
+** Change the maximum number of in-memory pages that are allowed.
+*/
+void sqlite3PagerSetCachesize(Pager *pPager, int mxPage){
+  sqlite3PcacheSetCachesize(pPager->pPCache, mxPage);
+}
+
+/*
+** Adjust the robustness of the database to damage due to OS crashes
+** or power failures by changing the number of syncs()s when writing
+** the rollback journal.  There are three levels:
+**
+**    OFF       sqlite3OsSync() is never called.  This is the default
+**              for temporary and transient files.
+**
+**    NORMAL    The journal is synced once before writes begin on the
+**              database.  This is normally adequate protection, but
+**              it is theoretically possible, though very unlikely,
+**              that an inopertune power failure could leave the journal
+**              in a state which would cause damage to the database
+**              when it is rolled back.
+**
+**    FULL      The journal is synced twice before writes begin on the
+**              database (with some additional information - the nRec field
+**              of the journal header - being written in between the two
+**              syncs).  If we assume that writing a
+**              single disk sector is atomic, then this mode provides
+**              assurance that the journal will not be corrupted to the
+**              point of causing damage to the database during rollback.
+**
+** The above is for a rollback-journal mode.  For WAL mode, OFF continues
+** to mean that no syncs ever occur.  NORMAL means that the WAL is synced
+** prior to the start of checkpoint and that the database file is synced
+** at the conclusion of the checkpoint if the entire content of the WAL
+** was written back into the database.  But no sync operations occur for
+** an ordinary commit in NORMAL mode with WAL.  FULL means that the WAL
+** file is synced following each commit operation, in addition to the
+** syncs associated with NORMAL.
+**
+** Do not confuse synchronous=FULL with SQLITE_SYNC_FULL.  The
+** SQLITE_SYNC_FULL macro means to use the MacOSX-style full-fsync
+** using fcntl(F_FULLFSYNC).  SQLITE_SYNC_NORMAL means to do an
+** ordinary fsync() call.  There is no difference between SQLITE_SYNC_FULL
+** and SQLITE_SYNC_NORMAL on platforms other than MacOSX.  But the
+** synchronous=FULL versus synchronous=NORMAL setting determines when
+** the xSync primitive is called and is relevant to all platforms.
+**
+** Numeric values associated with these states are OFF==1, NORMAL=2,
+** and FULL=3.
+*/
+#ifndef SQLITE_OMIT_PAGER_PRAGMAS
+void sqlite3PagerSetSafetyLevel(
+  Pager *pPager,        /* The pager to set safety level for */
+  int level,            /* PRAGMA synchronous.  1=OFF, 2=NORMAL, 3=FULL */  
+  int bFullFsync,       /* PRAGMA fullfsync */
+  int bCkptFullFsync    /* PRAGMA checkpoint_fullfsync */
+){
+  assert( level>=1 && level<=3 );
+  pPager->noSync =  (level==1 || pPager->tempFile) ?1:0;
+  pPager->fullSync = (level==3 && !pPager->tempFile) ?1:0;
+  if( pPager->noSync ){
+    pPager->syncFlags = 0;
+    pPager->ckptSyncFlags = 0;
+  }else if( bFullFsync ){
+    pPager->syncFlags = SQLITE_SYNC_FULL;
+    pPager->ckptSyncFlags = SQLITE_SYNC_FULL;
+  }else if( bCkptFullFsync ){
+    pPager->syncFlags = SQLITE_SYNC_NORMAL;
+    pPager->ckptSyncFlags = SQLITE_SYNC_FULL;
+  }else{
+    pPager->syncFlags = SQLITE_SYNC_NORMAL;
+    pPager->ckptSyncFlags = SQLITE_SYNC_NORMAL;
+  }
+}
+#endif
+
+/*
+** The following global variable is incremented whenever the library
+** attempts to open a temporary file.  This information is used for
+** testing and analysis only.  
+*/
+#ifdef SQLITE_TEST
+int sqlite3_opentemp_count = 0;
+#endif
+
+/*
+** Open a temporary file.
+**
+** Write the file descriptor into *pFile. Return SQLITE_OK on success 
+** or some other error code if we fail. The OS will automatically 
+** delete the temporary file when it is closed.
+**
+** The flags passed to the VFS layer xOpen() call are those specified
+** by parameter vfsFlags ORed with the following:
+**
+**     SQLITE_OPEN_READWRITE
+**     SQLITE_OPEN_CREATE
+**     SQLITE_OPEN_EXCLUSIVE
+**     SQLITE_OPEN_DELETEONCLOSE
+*/
+static int pagerOpentemp(
+  Pager *pPager,        /* The pager object */
+  sqlite3_file *pFile,  /* Write the file descriptor here */
+  int vfsFlags          /* Flags passed through to the VFS */
+){
+  int rc;               /* Return code */
+
+#ifdef SQLITE_TEST
+  sqlite3_opentemp_count++;  /* Used for testing and analysis only */
+#endif
+
+  vfsFlags |=  SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE |
+            SQLITE_OPEN_EXCLUSIVE | SQLITE_OPEN_DELETEONCLOSE;
+  rc = sqlite3OsOpen(pPager->pVfs, 0, pFile, vfsFlags, 0);
+  assert( rc!=SQLITE_OK || isOpen(pFile) );
+  return rc;
+}
+
+/*
+** Set the busy handler function.
+**
+** The pager invokes the busy-handler if sqlite3OsLock() returns 
+** SQLITE_BUSY when trying to upgrade from no-lock to a SHARED lock,
+** or when trying to upgrade from a RESERVED lock to an EXCLUSIVE 
+** lock. It does *not* invoke the busy handler when upgrading from
+** SHARED to RESERVED, or when upgrading from SHARED to EXCLUSIVE
+** (which occurs during hot-journal rollback). Summary:
+**
+**   Transition                        | Invokes xBusyHandler
+**   --------------------------------------------------------
+**   NO_LOCK       -> SHARED_LOCK      | Yes
+**   SHARED_LOCK   -> RESERVED_LOCK    | No
+**   SHARED_LOCK   -> EXCLUSIVE_LOCK   | No
+**   RESERVED_LOCK -> EXCLUSIVE_LOCK   | Yes
+**
+** If the busy-handler callback returns non-zero, the lock is 
+** retried. If it returns zero, then the SQLITE_BUSY error is
+** returned to the caller of the pager API function.
+*/
+void sqlite3PagerSetBusyhandler(
+  Pager *pPager,                       /* Pager object */
+  int (*xBusyHandler)(void *),         /* Pointer to busy-handler function */
+  void *pBusyHandlerArg                /* Argument to pass to xBusyHandler */
+){  
+  pPager->xBusyHandler = xBusyHandler;
+  pPager->pBusyHandlerArg = pBusyHandlerArg;
+}
+
+/*
+** Change the page size used by the Pager object. The new page size 
+** is passed in *pPageSize.
+**
+** If the pager is in the error state when this function is called, it
+** is a no-op. The value returned is the error state error code (i.e. 
+** one of SQLITE_IOERR, an SQLITE_IOERR_xxx sub-code or SQLITE_FULL).
+**
+** Otherwise, if all of the following are true:
+**
+**   * the new page size (value of *pPageSize) is valid (a power 
+**     of two between 512 and SQLITE_MAX_PAGE_SIZE, inclusive), and
+**
+**   * there are no outstanding page references, and
+**
+**   * the database is either not an in-memory database or it is
+**     an in-memory database that currently consists of zero pages.
+**
+** then the pager object page size is set to *pPageSize.
+**
+** If the page size is changed, then this function uses sqlite3PagerMalloc() 
+** to obtain a new Pager.pTmpSpace buffer. If this allocation attempt 
+** fails, SQLITE_NOMEM is returned and the page size remains unchanged. 
+** In all other cases, SQLITE_OK is returned.
+**
+** If the page size is not changed, either because one of the enumerated
+** conditions above is not true, the pager was in error state when this
+** function was called, or because the memory allocation attempt failed, 
+** then *pPageSize is set to the old, retained page size before returning.
+*/
+int sqlite3PagerSetPagesize(Pager *pPager, u32 *pPageSize, int nReserve){
+  int rc = SQLITE_OK;
+
+  /* It is not possible to do a full assert_pager_state() here, as this
+  ** function may be called from within PagerOpen(), before the state
+  ** of the Pager object is internally consistent.
+  **
+  ** At one point this function returned an error if the pager was in 
+  ** PAGER_ERROR state. But since PAGER_ERROR state guarantees that
+  ** there is at least one outstanding page reference, this function
+  ** is a no-op for that case anyhow.
+  */
+
+  u32 pageSize = *pPageSize;
+  assert( pageSize==0 || (pageSize>=512 && pageSize<=SQLITE_MAX_PAGE_SIZE) );
+  if( (pPager->memDb==0 || pPager->dbSize==0)
+   && sqlite3PcacheRefCount(pPager->pPCache)==0 
+   && pageSize && pageSize!=(u32)pPager->pageSize 
+  ){
+    char *pNew = NULL;             /* New temp space */
+    i64 nByte = 0;
+
+    if( pPager->eState>PAGER_OPEN && isOpen(pPager->fd) ){
+      rc = sqlite3OsFileSize(pPager->fd, &nByte);
+    }
+    if( rc==SQLITE_OK ){
+      pNew = (char *)sqlite3PageMalloc(pageSize);
+      if( !pNew ) rc = SQLITE_NOMEM;
+    }
+
+    if( rc==SQLITE_OK ){
+      pager_reset(pPager);
+      pPager->dbSize = (Pgno)(nByte/pageSize);
+      pPager->pageSize = pageSize;
+      sqlite3PageFree(pPager->pTmpSpace);
+      pPager->pTmpSpace = pNew;
+      sqlite3PcacheSetPageSize(pPager->pPCache, pageSize);
+    }
+  }
+
+  *pPageSize = pPager->pageSize;
+  if( rc==SQLITE_OK ){
+    if( nReserve<0 ) nReserve = pPager->nReserve;
+    assert( nReserve>=0 && nReserve<1000 );
+    pPager->nReserve = (i16)nReserve;
+    pagerReportSize(pPager);
+  }
+  return rc;
+}
+
+/*
+** Return a pointer to the "temporary page" buffer held internally
+** by the pager.  This is a buffer that is big enough to hold the
+** entire content of a database page.  This buffer is used internally
+** during rollback and will be overwritten whenever a rollback
+** occurs.  But other modules are free to use it too, as long as
+** no rollbacks are happening.
+*/
+void *sqlite3PagerTempSpace(Pager *pPager){
+  return pPager->pTmpSpace;
+}
+
+/*
+** Attempt to set the maximum database page count if mxPage is positive. 
+** Make no changes if mxPage is zero or negative.  And never reduce the
+** maximum page count below the current size of the database.
+**
+** Regardless of mxPage, return the current maximum page count.
+*/
+int sqlite3PagerMaxPageCount(Pager *pPager, int mxPage){
+  if( mxPage>0 ){
+    pPager->mxPgno = mxPage;
+  }
+  assert( pPager->eState!=PAGER_OPEN );      /* Called only by OP_MaxPgcnt */
+  assert( pPager->mxPgno>=pPager->dbSize );  /* OP_MaxPgcnt enforces this */
+  return pPager->mxPgno;
+}
+
+/*
+** The following set of routines are used to disable the simulated
+** I/O error mechanism.  These routines are used to avoid simulated
+** errors in places where we do not care about errors.
+**
+** Unless -DSQLITE_TEST=1 is used, these routines are all no-ops
+** and generate no code.
+*/
+#ifdef SQLITE_TEST
+extern int sqlite3_io_error_pending;
+extern int sqlite3_io_error_hit;
+static int saved_cnt;
+void disable_simulated_io_errors(void){
+  saved_cnt = sqlite3_io_error_pending;
+  sqlite3_io_error_pending = -1;
+}
+void enable_simulated_io_errors(void){
+  sqlite3_io_error_pending = saved_cnt;
+}
+#else
+# define disable_simulated_io_errors()
+# define enable_simulated_io_errors()
+#endif
+
+/*
+** Read the first N bytes from the beginning of the file into memory
+** that pDest points to. 
+**
+** If the pager was opened on a transient file (zFilename==""), or
+** opened on a file less than N bytes in size, the output buffer is
+** zeroed and SQLITE_OK returned. The rationale for this is that this 
+** function is used to read database headers, and a new transient or
+** zero sized database has a header than consists entirely of zeroes.
+**
+** If any IO error apart from SQLITE_IOERR_SHORT_READ is encountered,
+** the error code is returned to the caller and the contents of the
+** output buffer undefined.
+*/
+int sqlite3PagerReadFileheader(Pager *pPager, int N, unsigned char *pDest){
+  int rc = SQLITE_OK;
+  memset(pDest, 0, N);
+  assert( isOpen(pPager->fd) || pPager->tempFile );
+
+  /* This routine is only called by btree immediately after creating
+  ** the Pager object.  There has not been an opportunity to transition
+  ** to WAL mode yet.
+  */
+  assert( !pagerUseWal(pPager) );
+
+  if( isOpen(pPager->fd) ){
+    IOTRACE(("DBHDR %p 0 %d\n", pPager, N))
+    rc = sqlite3OsRead(pPager->fd, pDest, N, 0);
+    if( rc==SQLITE_IOERR_SHORT_READ ){
+      rc = SQLITE_OK;
+    }
+  }
+  return rc;
+}
+
+/*
+** This function may only be called when a read-transaction is open on
+** the pager. It returns the total number of pages in the database.
+**
+** However, if the file is between 1 and <page-size> bytes in size, then 
+** this is considered a 1 page file.
+*/
+void sqlite3PagerPagecount(Pager *pPager, int *pnPage){
+  assert( pPager->eState>=PAGER_READER );
+  assert( pPager->eState!=PAGER_WRITER_FINISHED );
+  *pnPage = (int)pPager->dbSize;
+}
+
+
+/*
+** Try to obtain a lock of type locktype on the database file. If
+** a similar or greater lock is already held, this function is a no-op
+** (returning SQLITE_OK immediately).
+**
+** Otherwise, attempt to obtain the lock using sqlite3OsLock(). Invoke 
+** the busy callback if the lock is currently not available. Repeat 
+** until the busy callback returns false or until the attempt to 
+** obtain the lock succeeds.
+**
+** Return SQLITE_OK on success and an error code if we cannot obtain
+** the lock. If the lock is obtained successfully, set the Pager.state 
+** variable to locktype before returning.
+*/
+static int pager_wait_on_lock(Pager *pPager, int locktype){
+  int rc;                              /* Return code */
+
+  /* Check that this is either a no-op (because the requested lock is 
+  ** already held, or one of the transistions that the busy-handler
+  ** may be invoked during, according to the comment above
+  ** sqlite3PagerSetBusyhandler().
+  */
+  assert( (pPager->eLock>=locktype)
+       || (pPager->eLock==NO_LOCK && locktype==SHARED_LOCK)
+       || (pPager->eLock==RESERVED_LOCK && locktype==EXCLUSIVE_LOCK)
+  );
+
+  do {
+    rc = pagerLockDb(pPager, locktype);
+  }while( rc==SQLITE_BUSY && pPager->xBusyHandler(pPager->pBusyHandlerArg) );
+  return rc;
+}
+
+/*
+** Function assertTruncateConstraint(pPager) checks that one of the 
+** following is true for all dirty pages currently in the page-cache:
+**
+**   a) The page number is less than or equal to the size of the 
+**      current database image, in pages, OR
+**
+**   b) if the page content were written at this time, it would not
+**      be necessary to write the current content out to the sub-journal
+**      (as determined by function subjRequiresPage()).
+**
+** If the condition asserted by this function were not true, and the
+** dirty page were to be discarded from the cache via the pagerStress()
+** routine, pagerStress() would not write the current page content to
+** the database file. If a savepoint transaction were rolled back after
+** this happened, the correct behaviour would be to restore the current
+** content of the page. However, since this content is not present in either
+** the database file or the portion of the rollback journal and 
+** sub-journal rolled back the content could not be restored and the
+** database image would become corrupt. It is therefore fortunate that 
+** this circumstance cannot arise.
+*/
+#if defined(SQLITE_DEBUG)
+static void assertTruncateConstraintCb(PgHdr *pPg){
+  assert( pPg->flags&PGHDR_DIRTY );
+  assert( !subjRequiresPage(pPg) || pPg->pgno<=pPg->pPager->dbSize );
+}
+static void assertTruncateConstraint(Pager *pPager){
+  sqlite3PcacheIterateDirty(pPager->pPCache, assertTruncateConstraintCb);
+}
+#else
+# define assertTruncateConstraint(pPager)
+#endif
+
+/*
+** Truncate the in-memory database file image to nPage pages. This 
+** function does not actually modify the database file on disk. It 
+** just sets the internal state of the pager object so that the 
+** truncation will be done when the current transaction is committed.
+*/
+void sqlite3PagerTruncateImage(Pager *pPager, Pgno nPage){
+  assert( pPager->dbSize>=nPage );
+  assert( pPager->eState>=PAGER_WRITER_CACHEMOD );
+  pPager->dbSize = nPage;
+  assertTruncateConstraint(pPager);
+}
+
+
+/*
+** This function is called before attempting a hot-journal rollback. It
+** syncs the journal file to disk, then sets pPager->journalHdr to the
+** size of the journal file so that the pager_playback() routine knows
+** that the entire journal file has been synced.
+**
+** Syncing a hot-journal to disk before attempting to roll it back ensures 
+** that if a power-failure occurs during the rollback, the process that
+** attempts rollback following system recovery sees the same journal
+** content as this process.
+**
+** If everything goes as planned, SQLITE_OK is returned. Otherwise, 
+** an SQLite error code.
+*/
+static int pagerSyncHotJournal(Pager *pPager){
+  int rc = SQLITE_OK;
+  if( !pPager->noSync ){
+    rc = sqlite3OsSync(pPager->jfd, SQLITE_SYNC_NORMAL);
+  }
+  if( rc==SQLITE_OK ){
+    rc = sqlite3OsFileSize(pPager->jfd, &pPager->journalHdr);
+  }
+  return rc;
+}
+
+/*
+** Shutdown the page cache.  Free all memory and close all files.
+**
+** If a transaction was in progress when this routine is called, that
+** transaction is rolled back.  All outstanding pages are invalidated
+** and their memory is freed.  Any attempt to use a page associated
+** with this page cache after this function returns will likely
+** result in a coredump.
+**
+** This function always succeeds. If a transaction is active an attempt
+** is made to roll it back. If an error occurs during the rollback 
+** a hot journal may be left in the filesystem but no error is returned
+** to the caller.
+*/
+int sqlite3PagerClose(Pager *pPager){
+  u8 *pTmp = (u8 *)pPager->pTmpSpace;
+
+  assert( assert_pager_state(pPager) );
+  disable_simulated_io_errors();
+  sqlite3BeginBenignMalloc();
+  /* pPager->errCode = 0; */
+  pPager->exclusiveMode = 0;
+#ifndef SQLITE_OMIT_WAL
+  sqlite3WalClose(pPager->pWal, pPager->ckptSyncFlags, pPager->pageSize, pTmp);
+  pPager->pWal = 0;
+#endif
+  pager_reset(pPager);
+  if( MEMDB ){
+    pager_unlock(pPager);
+  }else{
+    /* If it is open, sync the journal file before calling UnlockAndRollback.
+    ** If this is not done, then an unsynced portion of the open journal 
+    ** file may be played back into the database. If a power failure occurs 
+    ** while this is happening, the database could become corrupt.
+    **
+    ** If an error occurs while trying to sync the journal, shift the pager
+    ** into the ERROR state. This causes UnlockAndRollback to unlock the
+    ** database and close the journal file without attempting to roll it
+    ** back or finalize it. The next database user will have to do hot-journal
+    ** rollback before accessing the database file.
+    */
+    if( isOpen(pPager->jfd) ){
+      pager_error(pPager, pagerSyncHotJournal(pPager));
+    }
+    pagerUnlockAndRollback(pPager);
+  }
+  sqlite3EndBenignMalloc();
+  enable_simulated_io_errors();
+  PAGERTRACE(("CLOSE %d\n", PAGERID(pPager)));
+  IOTRACE(("CLOSE %p\n", pPager))
+  sqlite3OsClose(pPager->jfd);
+  sqlite3OsClose(pPager->fd);
+  sqlite3PageFree(pTmp);
+  sqlite3PcacheClose(pPager->pPCache);
+
+#ifdef SQLITE_HAS_CODEC
+  if( pPager->xCodecFree ) pPager->xCodecFree(pPager->pCodec);
+#endif
+
+  assert( !pPager->aSavepoint && !pPager->pInJournal );
+  assert( !isOpen(pPager->jfd) && !isOpen(pPager->sjfd) );
+
+  sqlite3_free(pPager);
+  return SQLITE_OK;
+}
+
+#if !defined(NDEBUG) || defined(SQLITE_TEST)
+/*
+** Return the page number for page pPg.
+*/
+Pgno sqlite3PagerPagenumber(DbPage *pPg){
+  return pPg->pgno;
+}
+#endif
+
+/*
+** Increment the reference count for page pPg.
+*/
+void sqlite3PagerRef(DbPage *pPg){
+  sqlite3PcacheRef(pPg);
+}
+
+/*
+** Sync the journal. In other words, make sure all the pages that have
+** been written to the journal have actually reached the surface of the
+** disk and can be restored in the event of a hot-journal rollback.
+**
+** If the Pager.noSync flag is set, then this function is a no-op.
+** Otherwise, the actions required depend on the journal-mode and the 
+** device characteristics of the the file-system, as follows:
+**
+**   * If the journal file is an in-memory journal file, no action need
+**     be taken.
+**
+**   * Otherwise, if the device does not support the SAFE_APPEND property,
+**     then the nRec field of the most recently written journal header
+**     is updated to contain the number of journal records that have
+**     been written following it. If the pager is operating in full-sync
+**     mode, then the journal file is synced before this field is updated.
+**
+**   * If the device does not support the SEQUENTIAL property, then 
+**     journal file is synced.
+**
+** Or, in pseudo-code:
+**
+**   if( NOT <in-memory journal> ){
+**     if( NOT SAFE_APPEND ){
+**       if( <full-sync mode> ) xSync(<journal file>);
+**       <update nRec field>
+**     } 
+**     if( NOT SEQUENTIAL ) xSync(<journal file>);
+**   }
+**
+** If successful, this routine clears the PGHDR_NEED_SYNC flag of every 
+** page currently held in memory before returning SQLITE_OK. If an IO
+** error is encountered, then the IO error code is returned to the caller.
+*/
+static int syncJournal(Pager *pPager, int newHdr){
+  int rc;                         /* Return code */
+
+  assert( pPager->eState==PAGER_WRITER_CACHEMOD
+       || pPager->eState==PAGER_WRITER_DBMOD
+  );
+  assert( assert_pager_state(pPager) );
+  assert( !pagerUseWal(pPager) );
+
+  rc = sqlite3PagerExclusiveLock(pPager);
+  if( rc!=SQLITE_OK ) return rc;
+
+  if( !pPager->noSync ){
+    assert( !pPager->tempFile );
+    if( isOpen(pPager->jfd) && pPager->journalMode!=PAGER_JOURNALMODE_MEMORY ){
+      const int iDc = sqlite3OsDeviceCharacteristics(pPager->fd);
+      assert( isOpen(pPager->jfd) );
+
+      if( 0==(iDc&SQLITE_IOCAP_SAFE_APPEND) ){
+        /* This block deals with an obscure problem. If the last connection
+        ** that wrote to this database was operating in persistent-journal
+        ** mode, then the journal file may at this point actually be larger
+        ** than Pager.journalOff bytes. If the next thing in the journal
+        ** file happens to be a journal-header (written as part of the
+        ** previous connection's transaction), and a crash or power-failure 
+        ** occurs after nRec is updated but before this connection writes 
+        ** anything else to the journal file (or commits/rolls back its 
+        ** transaction), then SQLite may become confused when doing the 
+        ** hot-journal rollback following recovery. It may roll back all
+        ** of this connections data, then proceed to rolling back the old,
+        ** out-of-date data that follows it. Database corruption.
+        **
+        ** To work around this, if the journal file does appear to contain
+        ** a valid header following Pager.journalOff, then write a 0x00
+        ** byte to the start of it to prevent it from being recognized.
+        **
+        ** Variable iNextHdrOffset is set to the offset at which this
+        ** problematic header will occur, if it exists. aMagic is used 
+        ** as a temporary buffer to inspect the first couple of bytes of
+        ** the potential journal header.
+        */
+        i64 iNextHdrOffset;
+        u8 aMagic[8];
+        u8 zHeader[sizeof(aJournalMagic)+4];
+
+        memcpy(zHeader, aJournalMagic, sizeof(aJournalMagic));
+        put32bits(&zHeader[sizeof(aJournalMagic)], pPager->nRec);
+
+        iNextHdrOffset = journalHdrOffset(pPager);
+        rc = sqlite3OsRead(pPager->jfd, aMagic, 8, iNextHdrOffset);
+        if( rc==SQLITE_OK && 0==memcmp(aMagic, aJournalMagic, 8) ){
+          static const u8 zerobyte = 0;
+          rc = sqlite3OsWrite(pPager->jfd, &zerobyte, 1, iNextHdrOffset);
+        }
+        if( rc!=SQLITE_OK && rc!=SQLITE_IOERR_SHORT_READ ){
+          return rc;
+        }
+
+        /* Write the nRec value into the journal file header. If in
+        ** full-synchronous mode, sync the journal first. This ensures that
+        ** all data has really hit the disk before nRec is updated to mark
+        ** it as a candidate for rollback.
+        **
+        ** This is not required if the persistent media supports the
+        ** SAFE_APPEND property. Because in this case it is not possible 
+        ** for garbage data to be appended to the file, the nRec field
+        ** is populated with 0xFFFFFFFF when the journal header is written
+        ** and never needs to be updated.
+        */
+        if( pPager->fullSync && 0==(iDc&SQLITE_IOCAP_SEQUENTIAL) ){
+          PAGERTRACE(("SYNC journal of %d\n", PAGERID(pPager)));
+          IOTRACE(("JSYNC %p\n", pPager))
+          rc = sqlite3OsSync(pPager->jfd, pPager->syncFlags);
+          if( rc!=SQLITE_OK ) return rc;
+        }
+        IOTRACE(("JHDR %p %lld\n", pPager, pPager->journalHdr));
+        rc = sqlite3OsWrite(
+            pPager->jfd, zHeader, sizeof(zHeader), pPager->journalHdr
+        );
+        if( rc!=SQLITE_OK ) return rc;
+      }
+      if( 0==(iDc&SQLITE_IOCAP_SEQUENTIAL) ){
+        PAGERTRACE(("SYNC journal of %d\n", PAGERID(pPager)));
+        IOTRACE(("JSYNC %p\n", pPager))
+        rc = sqlite3OsSync(pPager->jfd, pPager->syncFlags| 
+          (pPager->syncFlags==SQLITE_SYNC_FULL?SQLITE_SYNC_DATAONLY:0)
+        );
+        if( rc!=SQLITE_OK ) return rc;
+      }
+
+      pPager->journalHdr = pPager->journalOff;
+      if( newHdr && 0==(iDc&SQLITE_IOCAP_SAFE_APPEND) ){
+        pPager->nRec = 0;
+        rc = writeJournalHdr(pPager);
+        if( rc!=SQLITE_OK ) return rc;
+      }
+    }else{
+      pPager->journalHdr = pPager->journalOff;
+    }
+  }
+
+  /* Unless the pager is in noSync mode, the journal file was just 
+  ** successfully synced. Either way, clear the PGHDR_NEED_SYNC flag on 
+  ** all pages.
+  */
+  sqlite3PcacheClearSyncFlags(pPager->pPCache);
+  pPager->eState = PAGER_WRITER_DBMOD;
+  assert( assert_pager_state(pPager) );
+  return SQLITE_OK;
+}
+
+/*
+** The argument is the first in a linked list of dirty pages connected
+** by the PgHdr.pDirty pointer. This function writes each one of the
+** in-memory pages in the list to the database file. The argument may
+** be NULL, representing an empty list. In this case this function is
+** a no-op.
+**
+** The pager must hold at least a RESERVED lock when this function
+** is called. Before writing anything to the database file, this lock
+** is upgraded to an EXCLUSIVE lock. If the lock cannot be obtained,
+** SQLITE_BUSY is returned and no data is written to the database file.
+** 
+** If the pager is a temp-file pager and the actual file-system file
+** is not yet open, it is created and opened before any data is 
+** written out.
+**
+** Once the lock has been upgraded and, if necessary, the file opened,
+** the pages are written out to the database file in list order. Writing
+** a page is skipped if it meets either of the following criteria:
+**
+**   * The page number is greater than Pager.dbSize, or
+**   * The PGHDR_DONT_WRITE flag is set on the page.
+**
+** If writing out a page causes the database file to grow, Pager.dbFileSize
+** is updated accordingly. If page 1 is written out, then the value cached
+** in Pager.dbFileVers[] is updated to match the new value stored in
+** the database file.
+**
+** If everything is successful, SQLITE_OK is returned. If an IO error 
+** occurs, an IO error code is returned. Or, if the EXCLUSIVE lock cannot
+** be obtained, SQLITE_BUSY is returned.
+*/
+static int pager_write_pagelist(Pager *pPager, PgHdr *pList){
+  int rc = SQLITE_OK;                  /* Return code */
+
+  /* This function is only called for rollback pagers in WRITER_DBMOD state. */
+  assert( !pagerUseWal(pPager) );
+  assert( pPager->eState==PAGER_WRITER_DBMOD );
+  assert( pPager->eLock==EXCLUSIVE_LOCK );
+
+  /* If the file is a temp-file has not yet been opened, open it now. It
+  ** is not possible for rc to be other than SQLITE_OK if this branch
+  ** is taken, as pager_wait_on_lock() is a no-op for temp-files.
+  */
+  if( !isOpen(pPager->fd) ){
+    assert( pPager->tempFile && rc==SQLITE_OK );
+    rc = pagerOpentemp(pPager, pPager->fd, pPager->vfsFlags);
+  }
+
+  /* Before the first write, give the VFS a hint of what the final
+  ** file size will be.
+  */
+  assert( rc!=SQLITE_OK || isOpen(pPager->fd) );
+  if( rc==SQLITE_OK && pPager->dbSize>pPager->dbHintSize ){
+    sqlite3_int64 szFile = pPager->pageSize * (sqlite3_int64)pPager->dbSize;
+    sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_SIZE_HINT, &szFile);
+    pPager->dbHintSize = pPager->dbSize;
+  }
+
+  while( rc==SQLITE_OK && pList ){
+    Pgno pgno = pList->pgno;
+
+    /* If there are dirty pages in the page cache with page numbers greater
+    ** than Pager.dbSize, this means sqlite3PagerTruncateImage() was called to
+    ** make the file smaller (presumably by auto-vacuum code). Do not write
+    ** any such pages to the file.
+    **
+    ** Also, do not write out any page that has the PGHDR_DONT_WRITE flag
+    ** set (set by sqlite3PagerDontWrite()).
+    */
+    if( pgno<=pPager->dbSize && 0==(pList->flags&PGHDR_DONT_WRITE) ){
+      i64 offset = (pgno-1)*(i64)pPager->pageSize;   /* Offset to write */
+      char *pData;                                   /* Data to write */    
+
+      assert( (pList->flags&PGHDR_NEED_SYNC)==0 );
+      if( pList->pgno==1 ) pager_write_changecounter(pList);
+
+      /* Encode the database */
+      CODEC2(pPager, pList->pData, pgno, 6, return SQLITE_NOMEM, pData);
+
+      /* Write out the page data. */
+      rc = sqlite3OsWrite(pPager->fd, pData, pPager->pageSize, offset);
+
+      /* If page 1 was just written, update Pager.dbFileVers to match
+      ** the value now stored in the database file. If writing this 
+      ** page caused the database file to grow, update dbFileSize. 
+      */
+      if( pgno==1 ){
+        memcpy(&pPager->dbFileVers, &pData[24], sizeof(pPager->dbFileVers));
+      }
+      if( pgno>pPager->dbFileSize ){
+        pPager->dbFileSize = pgno;
+      }
+
+      /* Update any backup objects copying the contents of this pager. */
+      sqlite3BackupUpdate(pPager->pBackup, pgno, (u8*)pList->pData);
+
+      PAGERTRACE(("STORE %d page %d hash(%08x)\n",
+                   PAGERID(pPager), pgno, pager_pagehash(pList)));
+      IOTRACE(("PGOUT %p %d\n", pPager, pgno));
+      PAGER_INCR(sqlite3_pager_writedb_count);
+      PAGER_INCR(pPager->nWrite);
+    }else{
+      PAGERTRACE(("NOSTORE %d page %d\n", PAGERID(pPager), pgno));
+    }
+    pager_set_pagehash(pList);
+    pList = pList->pDirty;
+  }
+
+  return rc;
+}
+
+/*
+** Ensure that the sub-journal file is open. If it is already open, this 
+** function is a no-op.
+**
+** SQLITE_OK is returned if everything goes according to plan. An 
+** SQLITE_IOERR_XXX error code is returned if a call to sqlite3OsOpen() 
+** fails.
+*/
+static int openSubJournal(Pager *pPager){
+  int rc = SQLITE_OK;
+  if( !isOpen(pPager->sjfd) ){
+    if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY || pPager->subjInMemory ){
+      sqlite3MemJournalOpen(pPager->sjfd);
+    }else{
+      rc = pagerOpentemp(pPager, pPager->sjfd, SQLITE_OPEN_SUBJOURNAL);
+    }
+  }
+  return rc;
+}
+
+/*
+** Append a record of the current state of page pPg to the sub-journal. 
+** It is the callers responsibility to use subjRequiresPage() to check 
+** that it is really required before calling this function.
+**
+** If successful, set the bit corresponding to pPg->pgno in the bitvecs
+** for all open savepoints before returning.
+**
+** This function returns SQLITE_OK if everything is successful, an IO
+** error code if the attempt to write to the sub-journal fails, or 
+** SQLITE_NOMEM if a malloc fails while setting a bit in a savepoint
+** bitvec.
+*/
+static int subjournalPage(PgHdr *pPg){
+  int rc = SQLITE_OK;
+  Pager *pPager = pPg->pPager;
+  if( pPager->journalMode!=PAGER_JOURNALMODE_OFF ){
+
+    /* Open the sub-journal, if it has not already been opened */
+    assert( pPager->useJournal );
+    assert( isOpen(pPager->jfd) || pagerUseWal(pPager) );
+    assert( isOpen(pPager->sjfd) || pPager->nSubRec==0 );
+    assert( pagerUseWal(pPager) 
+         || pageInJournal(pPg) 
+         || pPg->pgno>pPager->dbOrigSize 
+    );
+    rc = openSubJournal(pPager);
+
+    /* If the sub-journal was opened successfully (or was already open),
+    ** write the journal record into the file.  */
+    if( rc==SQLITE_OK ){
+      void *pData = pPg->pData;
+      i64 offset = pPager->nSubRec*(4+pPager->pageSize);
+      char *pData2;
+  
+      CODEC2(pPager, pData, pPg->pgno, 7, return SQLITE_NOMEM, pData2);
+      PAGERTRACE(("STMT-JOURNAL %d page %d\n", PAGERID(pPager), pPg->pgno));
+      rc = write32bits(pPager->sjfd, offset, pPg->pgno);
+      if( rc==SQLITE_OK ){
+        rc = sqlite3OsWrite(pPager->sjfd, pData2, pPager->pageSize, offset+4);
+      }
+    }
+  }
+  if( rc==SQLITE_OK ){
+    pPager->nSubRec++;
+    assert( pPager->nSavepoint>0 );
+    rc = addToSavepointBitvecs(pPager, pPg->pgno);
+  }
+  return rc;
+}
+
+/*
+** This function is called by the pcache layer when it has reached some
+** soft memory limit. The first argument is a pointer to a Pager object
+** (cast as a void*). The pager is always 'purgeable' (not an in-memory
+** database). The second argument is a reference to a page that is 
+** currently dirty but has no outstanding references. The page
+** is always associated with the Pager object passed as the first 
+** argument.
+**
+** The job of this function is to make pPg clean by writing its contents
+** out to the database file, if possible. This may involve syncing the
+** journal file. 
+**
+** If successful, sqlite3PcacheMakeClean() is called on the page and
+** SQLITE_OK returned. If an IO error occurs while trying to make the
+** page clean, the IO error code is returned. If the page cannot be
+** made clean for some other reason, but no error occurs, then SQLITE_OK
+** is returned by sqlite3PcacheMakeClean() is not called.
+*/
+static int pagerStress(void *p, PgHdr *pPg){
+  Pager *pPager = (Pager *)p;
+  int rc = SQLITE_OK;
+
+  assert( pPg->pPager==pPager );
+  assert( pPg->flags&PGHDR_DIRTY );
+
+  /* The doNotSyncSpill flag is set during times when doing a sync of
+  ** journal (and adding a new header) is not allowed.  This occurs
+  ** during calls to sqlite3PagerWrite() while trying to journal multiple
+  ** pages belonging to the same sector.
+  **
+  ** The doNotSpill flag inhibits all cache spilling regardless of whether
+  ** or not a sync is required.  This is set during a rollback.
+  **
+  ** Spilling is also prohibited when in an error state since that could
+  ** lead to database corruption.   In the current implementaton it 
+  ** is impossible for sqlite3PcacheFetch() to be called with createFlag==1
+  ** while in the error state, hence it is impossible for this routine to
+  ** be called in the error state.  Nevertheless, we include a NEVER()
+  ** test for the error state as a safeguard against future changes.
+  */
+  if( NEVER(pPager->errCode) ) return SQLITE_OK;
+  if( pPager->doNotSpill ) return SQLITE_OK;
+  if( pPager->doNotSyncSpill && (pPg->flags & PGHDR_NEED_SYNC)!=0 ){
+    return SQLITE_OK;
+  }
+
+  pPg->pDirty = 0;
+  if( pagerUseWal(pPager) ){
+    /* Write a single frame for this page to the log. */
+    if( subjRequiresPage(pPg) ){ 
+      rc = subjournalPage(pPg); 
+    }
+    if( rc==SQLITE_OK ){
+      rc = pagerWalFrames(pPager, pPg, 0, 0, 0);
+    }
+  }else{
+  
+    /* Sync the journal file if required. */
+    if( pPg->flags&PGHDR_NEED_SYNC 
+     || pPager->eState==PAGER_WRITER_CACHEMOD
+    ){
+      rc = syncJournal(pPager, 1);
+    }
+  
+    /* If the page number of this page is larger than the current size of
+    ** the database image, it may need to be written to the sub-journal.
+    ** This is because the call to pager_write_pagelist() below will not
+    ** actually write data to the file in this case.
+    **
+    ** Consider the following sequence of events:
+    **
+    **   BEGIN;
+    **     <journal page X>
+    **     <modify page X>
+    **     SAVEPOINT sp;
+    **       <shrink database file to Y pages>
+    **       pagerStress(page X)
+    **     ROLLBACK TO sp;
+    **
+    ** If (X>Y), then when pagerStress is called page X will not be written
+    ** out to the database file, but will be dropped from the cache. Then,
+    ** following the "ROLLBACK TO sp" statement, reading page X will read
+    ** data from the database file. This will be the copy of page X as it
+    ** was when the transaction started, not as it was when "SAVEPOINT sp"
+    ** was executed.
+    **
+    ** The solution is to write the current data for page X into the 
+    ** sub-journal file now (if it is not already there), so that it will
+    ** be restored to its current value when the "ROLLBACK TO sp" is 
+    ** executed.
+    */
+    if( NEVER(
+        rc==SQLITE_OK && pPg->pgno>pPager->dbSize && subjRequiresPage(pPg)
+    ) ){
+      rc = subjournalPage(pPg);
+    }
+  
+    /* Write the contents of the page out to the database file. */
+    if( rc==SQLITE_OK ){
+      assert( (pPg->flags&PGHDR_NEED_SYNC)==0 );
+      rc = pager_write_pagelist(pPager, pPg);
+    }
+  }
+
+  /* Mark the page as clean. */
+  if( rc==SQLITE_OK ){
+    PAGERTRACE(("STRESS %d page %d\n", PAGERID(pPager), pPg->pgno));
+    sqlite3PcacheMakeClean(pPg);
+  }
+
+  return pager_error(pPager, rc); 
+}
+
+
+/*
+** Allocate and initialize a new Pager object and put a pointer to it
+** in *ppPager. The pager should eventually be freed by passing it
+** to sqlite3PagerClose().
+**
+** The zFilename argument is the path to the database file to open.
+** If zFilename is NULL then a randomly-named temporary file is created
+** and used as the file to be cached. Temporary files are be deleted
+** automatically when they are closed. If zFilename is ":memory:" then 
+** all information is held in cache. It is never written to disk. 
+** This can be used to implement an in-memory database.
+**
+** The nExtra parameter specifies the number of bytes of space allocated
+** along with each page reference. This space is available to the user
+** via the sqlite3PagerGetExtra() API.
+**
+** The flags argument is used to specify properties that affect the
+** operation of the pager. It should be passed some bitwise combination
+** of the PAGER_OMIT_JOURNAL and PAGER_NO_READLOCK flags.
+**
+** The vfsFlags parameter is a bitmask to pass to the flags parameter
+** of the xOpen() method of the supplied VFS when opening files. 
+**
+** If the pager object is allocated and the specified file opened 
+** successfully, SQLITE_OK is returned and *ppPager set to point to
+** the new pager object. If an error occurs, *ppPager is set to NULL
+** and error code returned. This function may return SQLITE_NOMEM
+** (sqlite3Malloc() is used to allocate memory), SQLITE_CANTOPEN or 
+** various SQLITE_IO_XXX errors.
+*/
+int sqlite3PagerOpen(
+  sqlite3_vfs *pVfs,       /* The virtual file system to use */
+  Pager **ppPager,         /* OUT: Return the Pager structure here */
+  const char *zFilename,   /* Name of the database file to open */
+  int nExtra,              /* Extra bytes append to each in-memory page */
+  int flags,               /* flags controlling this file */
+  int vfsFlags,            /* flags passed through to sqlite3_vfs.xOpen() */
+  void (*xReinit)(DbPage*) /* Function to reinitialize pages */
+){
+  u8 *pPtr;
+  Pager *pPager = 0;       /* Pager object to allocate and return */
+  int rc = SQLITE_OK;      /* Return code */
+  int tempFile = 0;        /* True for temp files (incl. in-memory files) */
+  int memDb = 0;           /* True if this is an in-memory file */
+  int readOnly = 0;        /* True if this is a read-only file */
+  int journalFileSize;     /* Bytes to allocate for each journal fd */
+  char *zPathname = 0;     /* Full path to database file */
+  int nPathname = 0;       /* Number of bytes in zPathname */
+  int useJournal = (flags & PAGER_OMIT_JOURNAL)==0; /* False to omit journal */
+  int noReadlock = (flags & PAGER_NO_READLOCK)!=0;  /* True to omit read-lock */
+  int pcacheSize = sqlite3PcacheSize();       /* Bytes to allocate for PCache */
+  u32 szPageDflt = SQLITE_DEFAULT_PAGE_SIZE;  /* Default page size */
+  const char *zUri = 0;    /* URI args to copy */
+  int nUri = 0;            /* Number of bytes of URI args at *zUri */
+
+  /* Figure out how much space is required for each journal file-handle
+  ** (there are two of them, the main journal and the sub-journal). This
+  ** is the maximum space required for an in-memory journal file handle 
+  ** and a regular journal file-handle. Note that a "regular journal-handle"
+  ** may be a wrapper capable of caching the first portion of the journal
+  ** file in memory to implement the atomic-write optimization (see 
+  ** source file journal.c).
+  */
+  if( sqlite3JournalSize(pVfs)>sqlite3MemJournalSize() ){
+    journalFileSize = ROUND8(sqlite3JournalSize(pVfs));
+  }else{
+    journalFileSize = ROUND8(sqlite3MemJournalSize());
+  }
+
+  /* Set the output variable to NULL in case an error occurs. */
+  *ppPager = 0;
+
+#ifndef SQLITE_OMIT_MEMORYDB
+  if( flags & PAGER_MEMORY ){
+    memDb = 1;
+    zFilename = 0;
+  }
+#endif
+
+  /* Compute and store the full pathname in an allocated buffer pointed
+  ** to by zPathname, length nPathname. Or, if this is a temporary file,
+  ** leave both nPathname and zPathname set to 0.
+  */
+  if( zFilename && zFilename[0] ){
+    const char *z;
+    nPathname = pVfs->mxPathname+1;
+    zPathname = sqlite3Malloc(nPathname*2);
+    if( zPathname==0 ){
+      return SQLITE_NOMEM;
+    }
+    zPathname[0] = 0; /* Make sure initialized even if FullPathname() fails */
+    rc = sqlite3OsFullPathname(pVfs, zFilename, nPathname, zPathname);
+    nPathname = sqlite3Strlen30(zPathname);
+    z = zUri = &zFilename[sqlite3Strlen30(zFilename)+1];
+    while( *z ){
+      z += sqlite3Strlen30(z)+1;
+      z += sqlite3Strlen30(z)+1;
+    }
+    nUri = &z[1] - zUri;
+    if( rc==SQLITE_OK && nPathname+8>pVfs->mxPathname ){
+      /* This branch is taken when the journal path required by
+      ** the database being opened will be more than pVfs->mxPathname
+      ** bytes in length. This means the database cannot be opened,
+      ** as it will not be possible to open the journal file or even
+      ** check for a hot-journal before reading.
+      */
+      rc = SQLITE_CANTOPEN_BKPT;
+    }
+    if( rc!=SQLITE_OK ){
+      sqlite3_free(zPathname);
+      return rc;
+    }
+  }
+
+  /* Allocate memory for the Pager structure, PCache object, the
+  ** three file descriptors, the database file name and the journal 
+  ** file name. The layout in memory is as follows:
+  **
+  **     Pager object                    (sizeof(Pager) bytes)
+  **     PCache object                   (sqlite3PcacheSize() bytes)
+  **     Database file handle            (pVfs->szOsFile bytes)
+  **     Sub-journal file handle         (journalFileSize bytes)
+  **     Main journal file handle        (journalFileSize bytes)
+  **     Database file name              (nPathname+1 bytes)
+  **     Journal file name               (nPathname+8+1 bytes)
+  */
+  pPtr = (u8 *)sqlite3MallocZero(
+    ROUND8(sizeof(*pPager)) +      /* Pager structure */
+    ROUND8(pcacheSize) +           /* PCache object */
+    ROUND8(pVfs->szOsFile) +       /* The main db file */
+    journalFileSize * 2 +          /* The two journal files */ 
+    nPathname + 1 + nUri +         /* zFilename */
+    nPathname + 8 + 1              /* zJournal */
+#ifndef SQLITE_OMIT_WAL
+    + nPathname + 4 + 1              /* zWal */
+#endif
+  );
+  assert( EIGHT_BYTE_ALIGNMENT(SQLITE_INT_TO_PTR(journalFileSize)) );
+  if( !pPtr ){
+    sqlite3_free(zPathname);
+    return SQLITE_NOMEM;
+  }
+  pPager =              (Pager*)(pPtr);
+  pPager->pPCache =    (PCache*)(pPtr += ROUND8(sizeof(*pPager)));
+  pPager->fd =   (sqlite3_file*)(pPtr += ROUND8(pcacheSize));
+  pPager->sjfd = (sqlite3_file*)(pPtr += ROUND8(pVfs->szOsFile));
+  pPager->jfd =  (sqlite3_file*)(pPtr += journalFileSize);
+  pPager->zFilename =    (char*)(pPtr += journalFileSize);
+  assert( EIGHT_BYTE_ALIGNMENT(pPager->jfd) );
+
+  /* Fill in the Pager.zFilename and Pager.zJournal buffers, if required. */
+  if( zPathname ){
+    assert( nPathname>0 );
+    pPager->zJournal =   (char*)(pPtr += nPathname + 1 + nUri);
+    memcpy(pPager->zFilename, zPathname, nPathname);
+    memcpy(&pPager->zFilename[nPathname+1], zUri, nUri);
+    memcpy(pPager->zJournal, zPathname, nPathname);
+    memcpy(&pPager->zJournal[nPathname], "-journal", 8);
+    sqlite3FileSuffix3(pPager->zFilename, pPager->zJournal);
+#ifndef SQLITE_OMIT_WAL
+    pPager->zWal = &pPager->zJournal[nPathname+8+1];
+    memcpy(pPager->zWal, zPathname, nPathname);
+    memcpy(&pPager->zWal[nPathname], "-wal", 4);
+    sqlite3FileSuffix3(pPager->zFilename, pPager->zWal);
+#endif
+    sqlite3_free(zPathname);
+  }
+  pPager->pVfs = pVfs;
+  pPager->vfsFlags = vfsFlags;
+
+  /* Open the pager file.
+  */
+  if( zFilename && zFilename[0] ){
+    int fout = 0;                    /* VFS flags returned by xOpen() */
+    rc = sqlite3OsOpen(pVfs, pPager->zFilename, pPager->fd, vfsFlags, &fout);
+    assert( !memDb );
+    readOnly = (fout&SQLITE_OPEN_READONLY);
+
+    /* If the file was successfully opened for read/write access,
+    ** choose a default page size in case we have to create the
+    ** database file. The default page size is the maximum of:
+    **
+    **    + SQLITE_DEFAULT_PAGE_SIZE,
+    **    + The value returned by sqlite3OsSectorSize()
+    **    + The largest page size that can be written atomically.
+    */
+    if( rc==SQLITE_OK && !readOnly ){
+      setSectorSize(pPager);
+      assert(SQLITE_DEFAULT_PAGE_SIZE<=SQLITE_MAX_DEFAULT_PAGE_SIZE);
+      if( szPageDflt<pPager->sectorSize ){
+        if( pPager->sectorSize>SQLITE_MAX_DEFAULT_PAGE_SIZE ){
+          szPageDflt = SQLITE_MAX_DEFAULT_PAGE_SIZE;
+        }else{
+          szPageDflt = (u32)pPager->sectorSize;
+        }
+      }
+#ifdef SQLITE_ENABLE_ATOMIC_WRITE
+      {
+        int iDc = sqlite3OsDeviceCharacteristics(pPager->fd);
+        int ii;
+        assert(SQLITE_IOCAP_ATOMIC512==(512>>8));
+        assert(SQLITE_IOCAP_ATOMIC64K==(65536>>8));
+        assert(SQLITE_MAX_DEFAULT_PAGE_SIZE<=65536);
+        for(ii=szPageDflt; ii<=SQLITE_MAX_DEFAULT_PAGE_SIZE; ii=ii*2){
+          if( iDc&(SQLITE_IOCAP_ATOMIC|(ii>>8)) ){
+            szPageDflt = ii;
+          }
+        }
+      }
+#endif
+    }
+  }else{
+    /* If a temporary file is requested, it is not opened immediately.
+    ** In this case we accept the default page size and delay actually
+    ** opening the file until the first call to OsWrite().
+    **
+    ** This branch is also run for an in-memory database. An in-memory
+    ** database is the same as a temp-file that is never written out to
+    ** disk and uses an in-memory rollback journal.
+    */ 
+    tempFile = 1;
+    pPager->eState = PAGER_READER;
+    pPager->eLock = EXCLUSIVE_LOCK;
+    readOnly = (vfsFlags&SQLITE_OPEN_READONLY);
+  }
+
+  /* The following call to PagerSetPagesize() serves to set the value of 
+  ** Pager.pageSize and to allocate the Pager.pTmpSpace buffer.
+  */
+  if( rc==SQLITE_OK ){
+    assert( pPager->memDb==0 );
+    rc = sqlite3PagerSetPagesize(pPager, &szPageDflt, -1);
+    testcase( rc!=SQLITE_OK );
+  }
+
+  /* If an error occurred in either of the blocks above, free the 
+  ** Pager structure and close the file.
+  */
+  if( rc!=SQLITE_OK ){
+    assert( !pPager->pTmpSpace );
+    sqlite3OsClose(pPager->fd);
+    sqlite3_free(pPager);
+    return rc;
+  }
+
+  /* Initialize the PCache object. */
+  assert( nExtra<1000 );
+  nExtra = ROUND8(nExtra);
+  sqlite3PcacheOpen(szPageDflt, nExtra, !memDb,
+                    !memDb?pagerStress:0, (void *)pPager, pPager->pPCache);
+
+  PAGERTRACE(("OPEN %d %s\n", FILEHANDLEID(pPager->fd), pPager->zFilename));
+  IOTRACE(("OPEN %p %s\n", pPager, pPager->zFilename))
+
+  pPager->useJournal = (u8)useJournal;
+  pPager->noReadlock = (noReadlock && readOnly) ?1:0;
+  /* pPager->stmtOpen = 0; */
+  /* pPager->stmtInUse = 0; */
+  /* pPager->nRef = 0; */
+  /* pPager->stmtSize = 0; */
+  /* pPager->stmtJSize = 0; */
+  /* pPager->nPage = 0; */
+  pPager->mxPgno = SQLITE_MAX_PAGE_COUNT;
+  /* pPager->state = PAGER_UNLOCK; */
+#if 0
+  assert( pPager->state == (tempFile ? PAGER_EXCLUSIVE : PAGER_UNLOCK) );
+#endif
+  /* pPager->errMask = 0; */
+  pPager->tempFile = (u8)tempFile;
+  assert( tempFile==PAGER_LOCKINGMODE_NORMAL 
+          || tempFile==PAGER_LOCKINGMODE_EXCLUSIVE );
+  assert( PAGER_LOCKINGMODE_EXCLUSIVE==1 );
+  pPager->exclusiveMode = (u8)tempFile; 
+  pPager->changeCountDone = pPager->tempFile;
+  pPager->memDb = (u8)memDb;
+  pPager->readOnly = (u8)readOnly;
+  assert( useJournal || pPager->tempFile );
+  pPager->noSync = pPager->tempFile;
+  pPager->fullSync = pPager->noSync ?0:1;
+  pPager->syncFlags = pPager->noSync ? 0 : SQLITE_SYNC_NORMAL;
+  pPager->ckptSyncFlags = pPager->syncFlags;
+  /* pPager->pFirst = 0; */
+  /* pPager->pFirstSynced = 0; */
+  /* pPager->pLast = 0; */
+  pPager->nExtra = (u16)nExtra;
+  pPager->journalSizeLimit = SQLITE_DEFAULT_JOURNAL_SIZE_LIMIT;
+  assert( isOpen(pPager->fd) || tempFile );
+  setSectorSize(pPager);
+  if( !useJournal ){
+    pPager->journalMode = PAGER_JOURNALMODE_OFF;
+  }else if( memDb ){
+    pPager->journalMode = PAGER_JOURNALMODE_MEMORY;
+  }
+  /* pPager->xBusyHandler = 0; */
+  /* pPager->pBusyHandlerArg = 0; */
+  pPager->xReiniter = xReinit;
+  /* memset(pPager->aHash, 0, sizeof(pPager->aHash)); */
+
+  *ppPager = pPager;
+  return SQLITE_OK;
+}
+
+
+
+/*
+** This function is called after transitioning from PAGER_UNLOCK to
+** PAGER_SHARED state. It tests if there is a hot journal present in
+** the file-system for the given pager. A hot journal is one that 
+** needs to be played back. According to this function, a hot-journal
+** file exists if the following criteria are met:
+**
+**   * The journal file exists in the file system, and
+**   * No process holds a RESERVED or greater lock on the database file, and
+**   * The database file itself is greater than 0 bytes in size, and
+**   * The first byte of the journal file exists and is not 0x00.
+**
+** If the current size of the database file is 0 but a journal file
+** exists, that is probably an old journal left over from a prior
+** database with the same name. In this case the journal file is
+** just deleted using OsDelete, *pExists is set to 0 and SQLITE_OK
+** is returned.
+**
+** This routine does not check if there is a master journal filename
+** at the end of the file. If there is, and that master journal file
+** does not exist, then the journal file is not really hot. In this
+** case this routine will return a false-positive. The pager_playback()
+** routine will discover that the journal file is not really hot and 
+** will not roll it back. 
+**
+** If a hot-journal file is found to exist, *pExists is set to 1 and 
+** SQLITE_OK returned. If no hot-journal file is present, *pExists is
+** set to 0 and SQLITE_OK returned. If an IO error occurs while trying
+** to determine whether or not a hot-journal file exists, the IO error
+** code is returned and the value of *pExists is undefined.
+*/
+static int hasHotJournal(Pager *pPager, int *pExists){
+  sqlite3_vfs * const pVfs = pPager->pVfs;
+  int rc = SQLITE_OK;           /* Return code */
+  int exists = 1;               /* True if a journal file is present */
+  int jrnlOpen = !!isOpen(pPager->jfd);
+
+  assert( pPager->useJournal );
+  assert( isOpen(pPager->fd) );
+  assert( pPager->eState==PAGER_OPEN );
+
+  assert( jrnlOpen==0 || ( sqlite3OsDeviceCharacteristics(pPager->jfd) &
+    SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN
+  ));
+
+  *pExists = 0;
+  if( !jrnlOpen ){
+    rc = sqlite3OsAccess(pVfs, pPager->zJournal, SQLITE_ACCESS_EXISTS, &exists);
+  }
+  if( rc==SQLITE_OK && exists ){
+    int locked = 0;             /* True if some process holds a RESERVED lock */
+
+    /* Race condition here:  Another process might have been holding the
+    ** the RESERVED lock and have a journal open at the sqlite3OsAccess() 
+    ** call above, but then delete the journal and drop the lock before
+    ** we get to the following sqlite3OsCheckReservedLock() call.  If that
+    ** is the case, this routine might think there is a hot journal when
+    ** in fact there is none.  This results in a false-positive which will
+    ** be dealt with by the playback routine.  Ticket #3883.
+    */
+    rc = sqlite3OsCheckReservedLock(pPager->fd, &locked);
+    if( rc==SQLITE_OK && !locked ){
+      Pgno nPage;                 /* Number of pages in database file */
+
+      /* Check the size of the database file. If it consists of 0 pages,
+      ** then delete the journal file. See the header comment above for 
+      ** the reasoning here.  Delete the obsolete journal file under
+      ** a RESERVED lock to avoid race conditions and to avoid violating
+      ** [H33020].
+      */
+      rc = pagerPagecount(pPager, &nPage);
+      if( rc==SQLITE_OK ){
+        if( nPage==0 ){
+          sqlite3BeginBenignMalloc();
+          if( pagerLockDb(pPager, RESERVED_LOCK)==SQLITE_OK ){
+            sqlite3OsDelete(pVfs, pPager->zJournal, 0);
+            if( !pPager->exclusiveMode ) pagerUnlockDb(pPager, SHARED_LOCK);
+          }
+          sqlite3EndBenignMalloc();
+        }else{
+          /* The journal file exists and no other connection has a reserved
+          ** or greater lock on the database file. Now check that there is
+          ** at least one non-zero bytes at the start of the journal file.
+          ** If there is, then we consider this journal to be hot. If not, 
+          ** it can be ignored.
+          */
+          if( !jrnlOpen ){
+            int f = SQLITE_OPEN_READONLY|SQLITE_OPEN_MAIN_JOURNAL;
+            rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, f, &f);
+          }
+          if( rc==SQLITE_OK ){
+            u8 first = 0;
+            rc = sqlite3OsRead(pPager->jfd, (void *)&first, 1, 0);
+            if( rc==SQLITE_IOERR_SHORT_READ ){
+              rc = SQLITE_OK;
+            }
+            if( !jrnlOpen ){
+              sqlite3OsClose(pPager->jfd);
+            }
+            *pExists = (first!=0);
+          }else if( rc==SQLITE_CANTOPEN ){
+            /* If we cannot open the rollback journal file in order to see if
+            ** its has a zero header, that might be due to an I/O error, or
+            ** it might be due to the race condition described above and in
+            ** ticket #3883.  Either way, assume that the journal is hot.
+            ** This might be a false positive.  But if it is, then the
+            ** automatic journal playback and recovery mechanism will deal
+            ** with it under an EXCLUSIVE lock where we do not need to
+            ** worry so much with race conditions.
+            */
+            *pExists = 1;
+            rc = SQLITE_OK;
+          }
+        }
+      }
+    }
+  }
+
+  return rc;
+}
+
+/*
+** This function is called to obtain a shared lock on the database file.
+** It is illegal to call sqlite3PagerAcquire() until after this function
+** has been successfully called. If a shared-lock is already held when
+** this function is called, it is a no-op.
+**
+** The following operations are also performed by this function.
+**
+**   1) If the pager is currently in PAGER_OPEN state (no lock held
+**      on the database file), then an attempt is made to obtain a
+**      SHARED lock on the database file. Immediately after obtaining
+**      the SHARED lock, the file-system is checked for a hot-journal,
+**      which is played back if present. Following any hot-journal 
+**      rollback, the contents of the cache are validated by checking
+**      the 'change-counter' field of the database file header and
+**      discarded if they are found to be invalid.
+**
+**   2) If the pager is running in exclusive-mode, and there are currently
+**      no outstanding references to any pages, and is in the error state,
+**      then an attempt is made to clear the error state by discarding
+**      the contents of the page cache and rolling back any open journal
+**      file.
+**
+** If everything is successful, SQLITE_OK is returned. If an IO error 
+** occurs while locking the database, checking for a hot-journal file or 
+** rolling back a journal file, the IO error code is returned.
+*/
+int sqlite3PagerSharedLock(Pager *pPager){
+  int rc = SQLITE_OK;                /* Return code */
+
+  /* This routine is only called from b-tree and only when there are no
+  ** outstanding pages. This implies that the pager state should either
+  ** be OPEN or READER. READER is only possible if the pager is or was in 
+  ** exclusive access mode.
+  */
+  assert( sqlite3PcacheRefCount(pPager->pPCache)==0 );
+  assert( assert_pager_state(pPager) );
+  assert( pPager->eState==PAGER_OPEN || pPager->eState==PAGER_READER );
+  if( NEVER(MEMDB && pPager->errCode) ){ return pPager->errCode; }
+
+  if( !pagerUseWal(pPager) && pPager->eState==PAGER_OPEN ){
+    int bHotJournal = 1;          /* True if there exists a hot journal-file */
+
+    assert( !MEMDB );
+    assert( pPager->noReadlock==0 || pPager->readOnly );
+
+    if( pPager->noReadlock==0 ){
+      rc = pager_wait_on_lock(pPager, SHARED_LOCK);
+      if( rc!=SQLITE_OK ){
+        assert( pPager->eLock==NO_LOCK || pPager->eLock==UNKNOWN_LOCK );
+        goto failed;
+      }
+    }
+
+    /* If a journal file exists, and there is no RESERVED lock on the
+    ** database file, then it either needs to be played back or deleted.
+    */
+    if( pPager->eLock<=SHARED_LOCK ){
+      rc = hasHotJournal(pPager, &bHotJournal);
+    }
+    if( rc!=SQLITE_OK ){
+      goto failed;
+    }
+    if( bHotJournal ){
+      /* Get an EXCLUSIVE lock on the database file. At this point it is
+      ** important that a RESERVED lock is not obtained on the way to the
+      ** EXCLUSIVE lock. If it were, another process might open the
+      ** database file, detect the RESERVED lock, and conclude that the
+      ** database is safe to read while this process is still rolling the 
+      ** hot-journal back.
+      ** 
+      ** Because the intermediate RESERVED lock is not requested, any
+      ** other process attempting to access the database file will get to 
+      ** this point in the code and fail to obtain its own EXCLUSIVE lock 
+      ** on the database file.
+      **
+      ** Unless the pager is in locking_mode=exclusive mode, the lock is
+      ** downgraded to SHARED_LOCK before this function returns.
+      */
+      rc = pagerLockDb(pPager, EXCLUSIVE_LOCK);
+      if( rc!=SQLITE_OK ){
+        goto failed;
+      }
+ 
+      /* If it is not already open and the file exists on disk, open the 
+      ** journal for read/write access. Write access is required because 
+      ** in exclusive-access mode the file descriptor will be kept open 
+      ** and possibly used for a transaction later on. Also, write-access 
+      ** is usually required to finalize the journal in journal_mode=persist 
+      ** mode (and also for journal_mode=truncate on some systems).
+      **
+      ** If the journal does not exist, it usually means that some 
+      ** other connection managed to get in and roll it back before 
+      ** this connection obtained the exclusive lock above. Or, it 
+      ** may mean that the pager was in the error-state when this
+      ** function was called and the journal file does not exist.
+      */
+      if( !isOpen(pPager->jfd) ){
+        sqlite3_vfs * const pVfs = pPager->pVfs;
+        int bExists;              /* True if journal file exists */
+        rc = sqlite3OsAccess(
+            pVfs, pPager->zJournal, SQLITE_ACCESS_EXISTS, &bExists);
+        if( rc==SQLITE_OK && bExists ){
+          int fout = 0;
+          int f = SQLITE_OPEN_READWRITE|SQLITE_OPEN_MAIN_JOURNAL;
+          assert( !pPager->tempFile );
+          rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, f, &fout);
+          assert( rc!=SQLITE_OK || isOpen(pPager->jfd) );
+          if( rc==SQLITE_OK && fout&SQLITE_OPEN_READONLY ){
+            rc = SQLITE_CANTOPEN_BKPT;
+            sqlite3OsClose(pPager->jfd);
+          }
+        }
+      }
+ 
+      /* Playback and delete the journal.  Drop the database write
+      ** lock and reacquire the read lock. Purge the cache before
+      ** playing back the hot-journal so that we don't end up with
+      ** an inconsistent cache.  Sync the hot journal before playing
+      ** it back since the process that crashed and left the hot journal
+      ** probably did not sync it and we are required to always sync
+      ** the journal before playing it back.
+      */
+      if( isOpen(pPager->jfd) ){
+        assert( rc==SQLITE_OK );
+        rc = pagerSyncHotJournal(pPager);
+        if( rc==SQLITE_OK ){
+          rc = pager_playback(pPager, 1);
+          pPager->eState = PAGER_OPEN;
+        }
+      }else if( !pPager->exclusiveMode ){
+        pagerUnlockDb(pPager, SHARED_LOCK);
+      }
+
+      if( rc!=SQLITE_OK ){
+        /* This branch is taken if an error occurs while trying to open
+        ** or roll back a hot-journal while holding an EXCLUSIVE lock. The
+        ** pager_unlock() routine will be called before returning to unlock
+        ** the file. If the unlock attempt fails, then Pager.eLock must be
+        ** set to UNKNOWN_LOCK (see the comment above the #define for 
+        ** UNKNOWN_LOCK above for an explanation). 
+        **
+        ** In order to get pager_unlock() to do this, set Pager.eState to
+        ** PAGER_ERROR now. This is not actually counted as a transition
+        ** to ERROR state in the state diagram at the top of this file,
+        ** since we know that the same call to pager_unlock() will very
+        ** shortly transition the pager object to the OPEN state. Calling
+        ** assert_pager_state() would fail now, as it should not be possible
+        ** to be in ERROR state when there are zero outstanding page 
+        ** references.
+        */
+        pager_error(pPager, rc);
+        goto failed;
+      }
+
+      assert( pPager->eState==PAGER_OPEN );
+      assert( (pPager->eLock==SHARED_LOCK)
+           || (pPager->exclusiveMode && pPager->eLock>SHARED_LOCK)
+      );
+    }
+
+    if( !pPager->tempFile 
+     && (pPager->pBackup || sqlite3PcachePagecount(pPager->pPCache)>0) 
+    ){
+      /* The shared-lock has just been acquired on the database file
+      ** and there are already pages in the cache (from a previous
+      ** read or write transaction).  Check to see if the database
+      ** has been modified.  If the database has changed, flush the
+      ** cache.
+      **
+      ** Database changes is detected by looking at 15 bytes beginning
+      ** at offset 24 into the file.  The first 4 of these 16 bytes are
+      ** a 32-bit counter that is incremented with each change.  The
+      ** other bytes change randomly with each file change when
+      ** a codec is in use.
+      ** 
+      ** There is a vanishingly small chance that a change will not be 
+      ** detected.  The chance of an undetected change is so small that
+      ** it can be neglected.
+      */
+      Pgno nPage = 0;
+      char dbFileVers[sizeof(pPager->dbFileVers)];
+
+      rc = pagerPagecount(pPager, &nPage);
+      if( rc ) goto failed;
+
+      if( nPage>0 ){
+        IOTRACE(("CKVERS %p %d\n", pPager, sizeof(dbFileVers)));
+        rc = sqlite3OsRead(pPager->fd, &dbFileVers, sizeof(dbFileVers), 24);
+        if( rc!=SQLITE_OK ){
+          goto failed;
+        }
+      }else{
+        memset(dbFileVers, 0, sizeof(dbFileVers));
+      }
+
+      if( memcmp(pPager->dbFileVers, dbFileVers, sizeof(dbFileVers))!=0 ){
+        pager_reset(pPager);
+      }
+    }
+
+    /* If there is a WAL file in the file-system, open this database in WAL
+    ** mode. Otherwise, the following function call is a no-op.
+    */
+    rc = pagerOpenWalIfPresent(pPager);
+#ifndef SQLITE_OMIT_WAL
+    assert( pPager->pWal==0 || rc==SQLITE_OK );
+#endif
+  }
+
+  if( pagerUseWal(pPager) ){
+    assert( rc==SQLITE_OK );
+    rc = pagerBeginReadTransaction(pPager);
+  }
+
+  if( pPager->eState==PAGER_OPEN && rc==SQLITE_OK ){
+    rc = pagerPagecount(pPager, &pPager->dbSize);
+  }
+
+ failed:
+  if( rc!=SQLITE_OK ){
+    assert( !MEMDB );
+    pager_unlock(pPager);
+    assert( pPager->eState==PAGER_OPEN );
+  }else{
+    pPager->eState = PAGER_READER;
+  }
+  return rc;
+}
+
+/*
+** If the reference count has reached zero, rollback any active
+** transaction and unlock the pager.
+**
+** Except, in locking_mode=EXCLUSIVE when there is nothing to in
+** the rollback journal, the unlock is not performed and there is
+** nothing to rollback, so this routine is a no-op.
+*/ 
+static void pagerUnlockIfUnused(Pager *pPager){
+  if( (sqlite3PcacheRefCount(pPager->pPCache)==0) ){
+    pagerUnlockAndRollback(pPager);
+  }
+}
+
+/*
+** Acquire a reference to page number pgno in pager pPager (a page
+** reference has type DbPage*). If the requested reference is 
+** successfully obtained, it is copied to *ppPage and SQLITE_OK returned.
+**
+** If the requested page is already in the cache, it is returned. 
+** Otherwise, a new page object is allocated and populated with data
+** read from the database file. In some cases, the pcache module may
+** choose not to allocate a new page object and may reuse an existing
+** object with no outstanding references.
+**
+** The extra data appended to a page is always initialized to zeros the 
+** first time a page is loaded into memory. If the page requested is 
+** already in the cache when this function is called, then the extra
+** data is left as it was when the page object was last used.
+**
+** If the database image is smaller than the requested page or if a 
+** non-zero value is passed as the noContent parameter and the 
+** requested page is not already stored in the cache, then no 
+** actual disk read occurs. In this case the memory image of the 
+** page is initialized to all zeros. 
+**
+** If noContent is true, it means that we do not care about the contents
+** of the page. This occurs in two seperate scenarios:
+**
+**   a) When reading a free-list leaf page from the database, and
+**
+**   b) When a savepoint is being rolled back and we need to load
+**      a new page into the cache to be filled with the data read
+**      from the savepoint journal.
+**
+** If noContent is true, then the data returned is zeroed instead of
+** being read from the database. Additionally, the bits corresponding
+** to pgno in Pager.pInJournal (bitvec of pages already written to the
+** journal file) and the PagerSavepoint.pInSavepoint bitvecs of any open
+** savepoints are set. This means if the page is made writable at any
+** point in the future, using a call to sqlite3PagerWrite(), its contents
+** will not be journaled. This saves IO.
+**
+** The acquisition might fail for several reasons.  In all cases,
+** an appropriate error code is returned and *ppPage is set to NULL.
+**
+** See also sqlite3PagerLookup().  Both this routine and Lookup() attempt
+** to find a page in the in-memory cache first.  If the page is not already
+** in memory, this routine goes to disk to read it in whereas Lookup()
+** just returns 0.  This routine acquires a read-lock the first time it
+** has to go to disk, and could also playback an old journal if necessary.
+** Since Lookup() never goes to disk, it never has to deal with locks
+** or journal files.
+*/
+int sqlite3PagerAcquire(
+  Pager *pPager,      /* The pager open on the database file */
+  Pgno pgno,          /* Page number to fetch */
+  DbPage **ppPage,    /* Write a pointer to the page here */
+  int noContent       /* Do not bother reading content from disk if true */
+){
+  int rc;
+  PgHdr *pPg;
+
+  assert( pPager->eState>=PAGER_READER );
+  assert( assert_pager_state(pPager) );
+
+  if( pgno==0 ){
+    return SQLITE_CORRUPT_BKPT;
+  }
+
+  /* If the pager is in the error state, return an error immediately. 
+  ** Otherwise, request the page from the PCache layer. */
+  if( pPager->errCode!=SQLITE_OK ){
+    rc = pPager->errCode;
+  }else{
+    rc = sqlite3PcacheFetch(pPager->pPCache, pgno, 1, ppPage);
+  }
+
+  if( rc!=SQLITE_OK ){
+    /* Either the call to sqlite3PcacheFetch() returned an error or the
+    ** pager was already in the error-state when this function was called.
+    ** Set pPg to 0 and jump to the exception handler.  */
+    pPg = 0;
+    goto pager_acquire_err;
+  }
+  assert( (*ppPage)->pgno==pgno );
+  assert( (*ppPage)->pPager==pPager || (*ppPage)->pPager==0 );
+
+  if( (*ppPage)->pPager && !noContent ){
+    /* In this case the pcache already contains an initialized copy of
+    ** the page. Return without further ado.  */
+    assert( pgno<=PAGER_MAX_PGNO && pgno!=PAGER_MJ_PGNO(pPager) );
+    pPager->nHit++;
+    return SQLITE_OK;
+
+  }else{
+    /* The pager cache has created a new page. Its content needs to 
+    ** be initialized.  */
+
+    pPg = *ppPage;
+    pPg->pPager = pPager;
+
+    /* The maximum page number is 2^31. Return SQLITE_CORRUPT if a page
+    ** number greater than this, or the unused locking-page, is requested. */
+    if( pgno>PAGER_MAX_PGNO || pgno==PAGER_MJ_PGNO(pPager) ){
+      rc = SQLITE_CORRUPT_BKPT;
+      goto pager_acquire_err;
+    }
+
+    if( MEMDB || pPager->dbSize<pgno || noContent || !isOpen(pPager->fd) ){
+      if( pgno>pPager->mxPgno ){
+        rc = SQLITE_FULL;
+        goto pager_acquire_err;
+      }
+      if( noContent ){
+        /* Failure to set the bits in the InJournal bit-vectors is benign.
+        ** It merely means that we might do some extra work to journal a 
+        ** page that does not need to be journaled.  Nevertheless, be sure 
+        ** to test the case where a malloc error occurs while trying to set 
+        ** a bit in a bit vector.
+        */
+        sqlite3BeginBenignMalloc();
+        if( pgno<=pPager->dbOrigSize ){
+          TESTONLY( rc = ) sqlite3BitvecSet(pPager->pInJournal, pgno);
+          testcase( rc==SQLITE_NOMEM );
+        }
+        TESTONLY( rc = ) addToSavepointBitvecs(pPager, pgno);
+        testcase( rc==SQLITE_NOMEM );
+        sqlite3EndBenignMalloc();
+      }
+      memset(pPg->pData, 0, pPager->pageSize);
+      IOTRACE(("ZERO %p %d\n", pPager, pgno));
+    }else{
+      assert( pPg->pPager==pPager );
+      pPager->nMiss++;
+      rc = readDbPage(pPg);
+      if( rc!=SQLITE_OK ){
+        goto pager_acquire_err;
+      }
+    }
+    pager_set_pagehash(pPg);
+  }
+
+  return SQLITE_OK;
+
+pager_acquire_err:
+  assert( rc!=SQLITE_OK );
+  if( pPg ){
+    sqlite3PcacheDrop(pPg);
+  }
+  pagerUnlockIfUnused(pPager);
+
+  *ppPage = 0;
+  return rc;
+}
+
+/*
+** Acquire a page if it is already in the in-memory cache.  Do
+** not read the page from disk.  Return a pointer to the page,
+** or 0 if the page is not in cache. 
+**
+** See also sqlite3PagerGet().  The difference between this routine
+** and sqlite3PagerGet() is that _get() will go to the disk and read
+** in the page if the page is not already in cache.  This routine
+** returns NULL if the page is not in cache or if a disk I/O error 
+** has ever happened.
+*/
+DbPage *sqlite3PagerLookup(Pager *pPager, Pgno pgno){
+  PgHdr *pPg = 0;
+  assert( pPager!=0 );
+  assert( pgno!=0 );
+  assert( pPager->pPCache!=0 );
+  assert( pPager->eState>=PAGER_READER && pPager->eState!=PAGER_ERROR );
+  sqlite3PcacheFetch(pPager->pPCache, pgno, 0, &pPg);
+  return pPg;
+}
+
+/*
+** Release a page reference.
+**
+** If the number of references to the page drop to zero, then the
+** page is added to the LRU list.  When all references to all pages
+** are released, a rollback occurs and the lock on the database is
+** removed.
+*/
+void sqlite3PagerUnref(DbPage *pPg){
+  if( pPg ){
+    Pager *pPager = pPg->pPager;
+    sqlite3PcacheRelease(pPg);
+    pagerUnlockIfUnused(pPager);
+  }
+}
+
+/*
+** This function is called at the start of every write transaction.
+** There must already be a RESERVED or EXCLUSIVE lock on the database 
+** file when this routine is called.
+**
+** Open the journal file for pager pPager and write a journal header
+** to the start of it. If there are active savepoints, open the sub-journal
+** as well. This function is only used when the journal file is being 
+** opened to write a rollback log for a transaction. It is not used 
+** when opening a hot journal file to roll it back.
+**
+** If the journal file is already open (as it may be in exclusive mode),
+** then this function just writes a journal header to the start of the
+** already open file. 
+**
+** Whether or not the journal file is opened by this function, the
+** Pager.pInJournal bitvec structure is allocated.
+**
+** Return SQLITE_OK if everything is successful. Otherwise, return 
+** SQLITE_NOMEM if the attempt to allocate Pager.pInJournal fails, or 
+** an IO error code if opening or writing the journal file fails.
+*/
+static int pager_open_journal(Pager *pPager){
+  int rc = SQLITE_OK;                        /* Return code */
+  sqlite3_vfs * const pVfs = pPager->pVfs;   /* Local cache of vfs pointer */
+
+  assert( pPager->eState==PAGER_WRITER_LOCKED );
+  assert( assert_pager_state(pPager) );
+  assert( pPager->pInJournal==0 );
+  
+  /* If already in the error state, this function is a no-op.  But on
+  ** the other hand, this routine is never called if we are already in
+  ** an error state. */
+  if( NEVER(pPager->errCode) ) return pPager->errCode;
+
+  if( !pagerUseWal(pPager) && pPager->journalMode!=PAGER_JOURNALMODE_OFF ){
+    pPager->pInJournal = sqlite3BitvecCreate(pPager->dbSize);
+    if( pPager->pInJournal==0 ){
+      return SQLITE_NOMEM;
+    }
+  
+    /* Open the journal file if it is not already open. */
+    if( !isOpen(pPager->jfd) ){
+      if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY ){
+        sqlite3MemJournalOpen(pPager->jfd);
+      }else{
+        const int flags =                   /* VFS flags to open journal file */
+          SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE|
+          (pPager->tempFile ? 
+            (SQLITE_OPEN_DELETEONCLOSE|SQLITE_OPEN_TEMP_JOURNAL):
+            (SQLITE_OPEN_MAIN_JOURNAL)
+          );
+  #ifdef SQLITE_ENABLE_ATOMIC_WRITE
+        rc = sqlite3JournalOpen(
+            pVfs, pPager->zJournal, pPager->jfd, flags, jrnlBufferSize(pPager)
+        );
+  #else
+        rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, flags, 0);
+  #endif
+      }
+      assert( rc!=SQLITE_OK || isOpen(pPager->jfd) );
+    }
+  
+  
+    /* Write the first journal header to the journal file and open 
+    ** the sub-journal if necessary.
+    */
+    if( rc==SQLITE_OK ){
+      /* TODO: Check if all of these are really required. */
+      pPager->nRec = 0;
+      pPager->journalOff = 0;
+      pPager->setMaster = 0;
+      pPager->journalHdr = 0;
+      rc = writeJournalHdr(pPager);
+    }
+  }
+
+  if( rc!=SQLITE_OK ){
+    sqlite3BitvecDestroy(pPager->pInJournal);
+    pPager->pInJournal = 0;
+  }else{
+    assert( pPager->eState==PAGER_WRITER_LOCKED );
+    pPager->eState = PAGER_WRITER_CACHEMOD;
+  }
+
+  return rc;
+}
+
+/*
+** Begin a write-transaction on the specified pager object. If a 
+** write-transaction has already been opened, this function is a no-op.
+**
+** If the exFlag argument is false, then acquire at least a RESERVED
+** lock on the database file. If exFlag is true, then acquire at least
+** an EXCLUSIVE lock. If such a lock is already held, no locking 
+** functions need be called.
+**
+** If the subjInMemory argument is non-zero, then any sub-journal opened
+** within this transaction will be opened as an in-memory file. This
+** has no effect if the sub-journal is already opened (as it may be when
+** running in exclusive mode) or if the transaction does not require a
+** sub-journal. If the subjInMemory argument is zero, then any required
+** sub-journal is implemented in-memory if pPager is an in-memory database, 
+** or using a temporary file otherwise.
+*/
+int sqlite3PagerBegin(Pager *pPager, int exFlag, int subjInMemory){
+  int rc = SQLITE_OK;
+
+  if( pPager->errCode ) return pPager->errCode;
+  assert( pPager->eState>=PAGER_READER && pPager->eState<PAGER_ERROR );
+  pPager->subjInMemory = (u8)subjInMemory;
+
+  if( ALWAYS(pPager->eState==PAGER_READER) ){
+    assert( pPager->pInJournal==0 );
+
+    if( pagerUseWal(pPager) ){
+      /* If the pager is configured to use locking_mode=exclusive, and an
+      ** exclusive lock on the database is not already held, obtain it now.
+      */
+      if( pPager->exclusiveMode && sqlite3WalExclusiveMode(pPager->pWal, -1) ){
+        rc = pagerLockDb(pPager, EXCLUSIVE_LOCK);
+        if( rc!=SQLITE_OK ){
+          return rc;
+        }
+        sqlite3WalExclusiveMode(pPager->pWal, 1);
+      }
+
+      /* Grab the write lock on the log file. If successful, upgrade to
+      ** PAGER_RESERVED state. Otherwise, return an error code to the caller.
+      ** The busy-handler is not invoked if another connection already
+      ** holds the write-lock. If possible, the upper layer will call it.
+      */
+      rc = sqlite3WalBeginWriteTransaction(pPager->pWal);
+    }else{
+      /* Obtain a RESERVED lock on the database file. If the exFlag parameter
+      ** is true, then immediately upgrade this to an EXCLUSIVE lock. The
+      ** busy-handler callback can be used when upgrading to the EXCLUSIVE
+      ** lock, but not when obtaining the RESERVED lock.
+      */
+      rc = pagerLockDb(pPager, RESERVED_LOCK);
+      if( rc==SQLITE_OK && exFlag ){
+        rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
+      }
+    }
+
+    if( rc==SQLITE_OK ){
+      /* Change to WRITER_LOCKED state.
+      **
+      ** WAL mode sets Pager.eState to PAGER_WRITER_LOCKED or CACHEMOD
+      ** when it has an open transaction, but never to DBMOD or FINISHED.
+      ** This is because in those states the code to roll back savepoint 
+      ** transactions may copy data from the sub-journal into the database 
+      ** file as well as into the page cache. Which would be incorrect in 
+      ** WAL mode.
+      */
+      pPager->eState = PAGER_WRITER_LOCKED;
+      pPager->dbHintSize = pPager->dbSize;
+      pPager->dbFileSize = pPager->dbSize;
+      pPager->dbOrigSize = pPager->dbSize;
+      pPager->journalOff = 0;
+    }
+
+    assert( rc==SQLITE_OK || pPager->eState==PAGER_READER );
+    assert( rc!=SQLITE_OK || pPager->eState==PAGER_WRITER_LOCKED );
+    assert( assert_pager_state(pPager) );
+  }
+
+  PAGERTRACE(("TRANSACTION %d\n", PAGERID(pPager)));
+  return rc;
+}
+
+/*
+** Mark a single data page as writeable. The page is written into the 
+** main journal or sub-journal as required. If the page is written into
+** one of the journals, the corresponding bit is set in the 
+** Pager.pInJournal bitvec and the PagerSavepoint.pInSavepoint bitvecs
+** of any open savepoints as appropriate.
+*/
+static int pager_write(PgHdr *pPg){
+  void *pData = pPg->pData;
+  Pager *pPager = pPg->pPager;
+  int rc = SQLITE_OK;
+
+  /* This routine is not called unless a write-transaction has already 
+  ** been started. The journal file may or may not be open at this point.
+  ** It is never called in the ERROR state.
+  */
+  assert( pPager->eState==PAGER_WRITER_LOCKED
+       || pPager->eState==PAGER_WRITER_CACHEMOD
+       || pPager->eState==PAGER_WRITER_DBMOD
+  );
+  assert( assert_pager_state(pPager) );
+
+  /* If an error has been previously detected, report the same error
+  ** again. This should not happen, but the check provides robustness. */
+  if( NEVER(pPager->errCode) )  return pPager->errCode;
+
+  /* Higher-level routines never call this function if database is not
+  ** writable.  But check anyway, just for robustness. */
+  if( NEVER(pPager->readOnly) ) return SQLITE_PERM;
+
+  CHECK_PAGE(pPg);
+
+  /* The journal file needs to be opened. Higher level routines have already
+  ** obtained the necessary locks to begin the write-transaction, but the
+  ** rollback journal might not yet be open. Open it now if this is the case.
+  **
+  ** This is done before calling sqlite3PcacheMakeDirty() on the page. 
+  ** Otherwise, if it were done after calling sqlite3PcacheMakeDirty(), then
+  ** an error might occur and the pager would end up in WRITER_LOCKED state
+  ** with pages marked as dirty in the cache.
+  */
+  if( pPager->eState==PAGER_WRITER_LOCKED ){
+    rc = pager_open_journal(pPager);
+    if( rc!=SQLITE_OK ) return rc;
+  }
+  assert( pPager->eState>=PAGER_WRITER_CACHEMOD );
+  assert( assert_pager_state(pPager) );
+
+  /* Mark the page as dirty.  If the page has already been written
+  ** to the journal then we can return right away.
+  */
+  sqlite3PcacheMakeDirty(pPg);
+  if( pageInJournal(pPg) && !subjRequiresPage(pPg) ){
+    assert( !pagerUseWal(pPager) );
+  }else{
+  
+    /* The transaction journal now exists and we have a RESERVED or an
+    ** EXCLUSIVE lock on the main database file.  Write the current page to
+    ** the transaction journal if it is not there already.
+    */
+    if( !pageInJournal(pPg) && !pagerUseWal(pPager) ){
+      assert( pagerUseWal(pPager)==0 );
+      if( pPg->pgno<=pPager->dbOrigSize && isOpen(pPager->jfd) ){
+        u32 cksum;
+        char *pData2;
+        i64 iOff = pPager->journalOff;
+
+        /* We should never write to the journal file the page that
+        ** contains the database locks.  The following assert verifies
+        ** that we do not. */
+        assert( pPg->pgno!=PAGER_MJ_PGNO(pPager) );
+
+        assert( pPager->journalHdr<=pPager->journalOff );
+        CODEC2(pPager, pData, pPg->pgno, 7, return SQLITE_NOMEM, pData2);
+        cksum = pager_cksum(pPager, (u8*)pData2);
+
+        /* Even if an IO or diskfull error occurs while journalling the
+        ** page in the block above, set the need-sync flag for the page.
+        ** Otherwise, when the transaction is rolled back, the logic in
+        ** playback_one_page() will think that the page needs to be restored
+        ** in the database file. And if an IO error occurs while doing so,
+        ** then corruption may follow.
+        */
+        pPg->flags |= PGHDR_NEED_SYNC;
+
+        rc = write32bits(pPager->jfd, iOff, pPg->pgno);
+        if( rc!=SQLITE_OK ) return rc;
+        rc = sqlite3OsWrite(pPager->jfd, pData2, pPager->pageSize, iOff+4);
+        if( rc!=SQLITE_OK ) return rc;
+        rc = write32bits(pPager->jfd, iOff+pPager->pageSize+4, cksum);
+        if( rc!=SQLITE_OK ) return rc;
+
+        IOTRACE(("JOUT %p %d %lld %d\n", pPager, pPg->pgno, 
+                 pPager->journalOff, pPager->pageSize));
+        PAGER_INCR(sqlite3_pager_writej_count);
+        PAGERTRACE(("JOURNAL %d page %d needSync=%d hash(%08x)\n",
+             PAGERID(pPager), pPg->pgno, 
+             ((pPg->flags&PGHDR_NEED_SYNC)?1:0), pager_pagehash(pPg)));
+
+        pPager->journalOff += 8 + pPager->pageSize;
+        pPager->nRec++;
+        assert( pPager->pInJournal!=0 );
+        rc = sqlite3BitvecSet(pPager->pInJournal, pPg->pgno);
+        testcase( rc==SQLITE_NOMEM );
+        assert( rc==SQLITE_OK || rc==SQLITE_NOMEM );
+        rc |= addToSavepointBitvecs(pPager, pPg->pgno);
+        if( rc!=SQLITE_OK ){
+          assert( rc==SQLITE_NOMEM );
+          return rc;
+        }
+      }else{
+        if( pPager->eState!=PAGER_WRITER_DBMOD ){
+          pPg->flags |= PGHDR_NEED_SYNC;
+        }
+        PAGERTRACE(("APPEND %d page %d needSync=%d\n",
+                PAGERID(pPager), pPg->pgno,
+               ((pPg->flags&PGHDR_NEED_SYNC)?1:0)));
+      }
+    }
+  
+    /* If the statement journal is open and the page is not in it,
+    ** then write the current page to the statement journal.  Note that
+    ** the statement journal format differs from the standard journal format
+    ** in that it omits the checksums and the header.
+    */
+    if( subjRequiresPage(pPg) ){
+      rc = subjournalPage(pPg);
+    }
+  }
+
+  /* Update the database size and return.
+  */
+  if( pPager->dbSize<pPg->pgno ){
+    pPager->dbSize = pPg->pgno;
+  }
+  return rc;
+}
+
+/*
+** Mark a data page as writeable. This routine must be called before 
+** making changes to a page. The caller must check the return value 
+** of this function and be careful not to change any page data unless 
+** this routine returns SQLITE_OK.
+**
+** The difference between this function and pager_write() is that this
+** function also deals with the special case where 2 or more pages
+** fit on a single disk sector. In this case all co-resident pages
+** must have been written to the journal file before returning.
+**
+** If an error occurs, SQLITE_NOMEM or an IO error code is returned
+** as appropriate. Otherwise, SQLITE_OK.
+*/
+int sqlite3PagerWrite(DbPage *pDbPage){
+  int rc = SQLITE_OK;
+
+  PgHdr *pPg = pDbPage;
+  Pager *pPager = pPg->pPager;
+  Pgno nPagePerSector = (pPager->sectorSize/pPager->pageSize);
+
+  assert( pPager->eState>=PAGER_WRITER_LOCKED );
+  assert( pPager->eState!=PAGER_ERROR );
+  assert( assert_pager_state(pPager) );
+
+  if( nPagePerSector>1 ){
+    Pgno nPageCount;          /* Total number of pages in database file */
+    Pgno pg1;                 /* First page of the sector pPg is located on. */
+    int nPage = 0;            /* Number of pages starting at pg1 to journal */
+    int ii;                   /* Loop counter */
+    int needSync = 0;         /* True if any page has PGHDR_NEED_SYNC */
+
+    /* Set the doNotSyncSpill flag to 1. This is because we cannot allow
+    ** a journal header to be written between the pages journaled by
+    ** this function.
+    */
+    assert( !MEMDB );
+    assert( pPager->doNotSyncSpill==0 );
+    pPager->doNotSyncSpill++;
+
+    /* This trick assumes that both the page-size and sector-size are
+    ** an integer power of 2. It sets variable pg1 to the identifier
+    ** of the first page of the sector pPg is located on.
+    */
+    pg1 = ((pPg->pgno-1) & ~(nPagePerSector-1)) + 1;
+
+    nPageCount = pPager->dbSize;
+    if( pPg->pgno>nPageCount ){
+      nPage = (pPg->pgno - pg1)+1;
+    }else if( (pg1+nPagePerSector-1)>nPageCount ){
+      nPage = nPageCount+1-pg1;
+    }else{
+      nPage = nPagePerSector;
+    }
+    assert(nPage>0);
+    assert(pg1<=pPg->pgno);
+    assert((pg1+nPage)>pPg->pgno);
+
+    for(ii=0; ii<nPage && rc==SQLITE_OK; ii++){
+      Pgno pg = pg1+ii;
+      PgHdr *pPage;
+      if( pg==pPg->pgno || !sqlite3BitvecTest(pPager->pInJournal, pg) ){
+        if( pg!=PAGER_MJ_PGNO(pPager) ){
+          rc = sqlite3PagerGet(pPager, pg, &pPage);
+          if( rc==SQLITE_OK ){
+            rc = pager_write(pPage);
+            if( pPage->flags&PGHDR_NEED_SYNC ){
+              needSync = 1;
+            }
+            sqlite3PagerUnref(pPage);
+          }
+        }
+      }else if( (pPage = pager_lookup(pPager, pg))!=0 ){
+        if( pPage->flags&PGHDR_NEED_SYNC ){
+          needSync = 1;
+        }
+        sqlite3PagerUnref(pPage);
+      }
+    }
+
+    /* If the PGHDR_NEED_SYNC flag is set for any of the nPage pages 
+    ** starting at pg1, then it needs to be set for all of them. Because
+    ** writing to any of these nPage pages may damage the others, the
+    ** journal file must contain sync()ed copies of all of them
+    ** before any of them can be written out to the database file.
+    */
+    if( rc==SQLITE_OK && needSync ){
+      assert( !MEMDB );
+      for(ii=0; ii<nPage; ii++){
+        PgHdr *pPage = pager_lookup(pPager, pg1+ii);
+        if( pPage ){
+          pPage->flags |= PGHDR_NEED_SYNC;
+          sqlite3PagerUnref(pPage);
+        }
+      }
+    }
+
+    assert( pPager->doNotSyncSpill==1 );
+    pPager->doNotSyncSpill--;
+  }else{
+    rc = pager_write(pDbPage);
+  }
+  return rc;
+}
+
+/*
+** Return TRUE if the page given in the argument was previously passed
+** to sqlite3PagerWrite().  In other words, return TRUE if it is ok
+** to change the content of the page.
+*/
+#ifndef NDEBUG
+int sqlite3PagerIswriteable(DbPage *pPg){
+  return pPg->flags&PGHDR_DIRTY;
+}
+#endif
+
+/*
+** A call to this routine tells the pager that it is not necessary to
+** write the information on page pPg back to the disk, even though
+** that page might be marked as dirty.  This happens, for example, when
+** the page has been added as a leaf of the freelist and so its
+** content no longer matters.
+**
+** The overlying software layer calls this routine when all of the data
+** on the given page is unused. The pager marks the page as clean so
+** that it does not get written to disk.
+**
+** Tests show that this optimization can quadruple the speed of large 
+** DELETE operations.
+*/
+void sqlite3PagerDontWrite(PgHdr *pPg){
+  Pager *pPager = pPg->pPager;
+  if( (pPg->flags&PGHDR_DIRTY) && pPager->nSavepoint==0 ){
+    PAGERTRACE(("DONT_WRITE page %d of %d\n", pPg->pgno, PAGERID(pPager)));
+    IOTRACE(("CLEAN %p %d\n", pPager, pPg->pgno))
+    pPg->flags |= PGHDR_DONT_WRITE;
+    pager_set_pagehash(pPg);
+  }
+}
+
+/*
+** This routine is called to increment the value of the database file 
+** change-counter, stored as a 4-byte big-endian integer starting at 
+** byte offset 24 of the pager file.  The secondary change counter at
+** 92 is also updated, as is the SQLite version number at offset 96.
+**
+** But this only happens if the pPager->changeCountDone flag is false.
+** To avoid excess churning of page 1, the update only happens once.
+** See also the pager_write_changecounter() routine that does an 
+** unconditional update of the change counters.
+**
+** If the isDirectMode flag is zero, then this is done by calling 
+** sqlite3PagerWrite() on page 1, then modifying the contents of the
+** page data. In this case the file will be updated when the current
+** transaction is committed.
+**
+** The isDirectMode flag may only be non-zero if the library was compiled
+** with the SQLITE_ENABLE_ATOMIC_WRITE macro defined. In this case,
+** if isDirect is non-zero, then the database file is updated directly
+** by writing an updated version of page 1 using a call to the 
+** sqlite3OsWrite() function.
+*/
+static int pager_incr_changecounter(Pager *pPager, int isDirectMode){
+  int rc = SQLITE_OK;
+
+  assert( pPager->eState==PAGER_WRITER_CACHEMOD
+       || pPager->eState==PAGER_WRITER_DBMOD
+  );
+  assert( assert_pager_state(pPager) );
+
+  /* Declare and initialize constant integer 'isDirect'. If the
+  ** atomic-write optimization is enabled in this build, then isDirect
+  ** is initialized to the value passed as the isDirectMode parameter
+  ** to this function. Otherwise, it is always set to zero.
+  **
+  ** The idea is that if the atomic-write optimization is not
+  ** enabled at compile time, the compiler can omit the tests of
+  ** 'isDirect' below, as well as the block enclosed in the
+  ** "if( isDirect )" condition.
+  */
+#ifndef SQLITE_ENABLE_ATOMIC_WRITE
+# define DIRECT_MODE 0
+  assert( isDirectMode==0 );
+  UNUSED_PARAMETER(isDirectMode);
+#else
+# define DIRECT_MODE isDirectMode
+#endif
+
+  if( !pPager->changeCountDone && pPager->dbSize>0 ){
+    PgHdr *pPgHdr;                /* Reference to page 1 */
+
+    assert( !pPager->tempFile && isOpen(pPager->fd) );
+
+    /* Open page 1 of the file for writing. */
+    rc = sqlite3PagerGet(pPager, 1, &pPgHdr);
+    assert( pPgHdr==0 || rc==SQLITE_OK );
+
+    /* If page one was fetched successfully, and this function is not
+    ** operating in direct-mode, make page 1 writable.  When not in 
+    ** direct mode, page 1 is always held in cache and hence the PagerGet()
+    ** above is always successful - hence the ALWAYS on rc==SQLITE_OK.
+    */
+    if( !DIRECT_MODE && ALWAYS(rc==SQLITE_OK) ){
+      rc = sqlite3PagerWrite(pPgHdr);
+    }
+
+    if( rc==SQLITE_OK ){
+      /* Actually do the update of the change counter */
+      pager_write_changecounter(pPgHdr);
+
+      /* If running in direct mode, write the contents of page 1 to the file. */
+      if( DIRECT_MODE ){
+        const void *zBuf;
+        assert( pPager->dbFileSize>0 );
+        CODEC2(pPager, pPgHdr->pData, 1, 6, rc=SQLITE_NOMEM, zBuf);
+        if( rc==SQLITE_OK ){
+          rc = sqlite3OsWrite(pPager->fd, zBuf, pPager->pageSize, 0);
+        }
+        if( rc==SQLITE_OK ){
+          pPager->changeCountDone = 1;
+        }
+      }else{
+        pPager->changeCountDone = 1;
+      }
+    }
+
+    /* Release the page reference. */
+    sqlite3PagerUnref(pPgHdr);
+  }
+  return rc;
+}
+
+/*
+** Sync the database file to disk. This is a no-op for in-memory databases
+** or pages with the Pager.noSync flag set.
+**
+** If successful, or if called on a pager for which it is a no-op, this
+** function returns SQLITE_OK. Otherwise, an IO error code is returned.
+*/
+int sqlite3PagerSync(Pager *pPager){
+  int rc = SQLITE_OK;
+  if( !pPager->noSync ){
+    assert( !MEMDB );
+    rc = sqlite3OsSync(pPager->fd, pPager->syncFlags);
+  }else if( isOpen(pPager->fd) ){
+    assert( !MEMDB );
+    sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_SYNC_OMITTED, (void *)&rc);
+  }
+  return rc;
+}
+
+/*
+** This function may only be called while a write-transaction is active in
+** rollback. If the connection is in WAL mode, this call is a no-op. 
+** Otherwise, if the connection does not already have an EXCLUSIVE lock on 
+** the database file, an attempt is made to obtain one.
+**
+** If the EXCLUSIVE lock is already held or the attempt to obtain it is
+** successful, or the connection is in WAL mode, SQLITE_OK is returned.
+** Otherwise, either SQLITE_BUSY or an SQLITE_IOERR_XXX error code is 
+** returned.
+*/
+int sqlite3PagerExclusiveLock(Pager *pPager){
+  int rc = SQLITE_OK;
+  assert( pPager->eState==PAGER_WRITER_CACHEMOD 
+       || pPager->eState==PAGER_WRITER_DBMOD 
+       || pPager->eState==PAGER_WRITER_LOCKED 
+  );
+  assert( assert_pager_state(pPager) );
+  if( 0==pagerUseWal(pPager) ){
+    rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
+  }
+  return rc;
+}
+
+/*
+** Sync the database file for the pager pPager. zMaster points to the name
+** of a master journal file that should be written into the individual
+** journal file. zMaster may be NULL, which is interpreted as no master
+** journal (a single database transaction).
+**
+** This routine ensures that:
+**
+**   * The database file change-counter is updated,
+**   * the journal is synced (unless the atomic-write optimization is used),
+**   * all dirty pages are written to the database file, 
+**   * the database file is truncated (if required), and
+**   * the database file synced. 
+**
+** The only thing that remains to commit the transaction is to finalize 
+** (delete, truncate or zero the first part of) the journal file (or 
+** delete the master journal file if specified).
+**
+** Note that if zMaster==NULL, this does not overwrite a previous value
+** passed to an sqlite3PagerCommitPhaseOne() call.
+**
+** If the final parameter - noSync - is true, then the database file itself
+** is not synced. The caller must call sqlite3PagerSync() directly to
+** sync the database file before calling CommitPhaseTwo() to delete the
+** journal file in this case.
+*/
+int sqlite3PagerCommitPhaseOne(
+  Pager *pPager,                  /* Pager object */
+  const char *zMaster,            /* If not NULL, the master journal name */
+  int noSync                      /* True to omit the xSync on the db file */
+){
+  int rc = SQLITE_OK;             /* Return code */
+
+  assert( pPager->eState==PAGER_WRITER_LOCKED
+       || pPager->eState==PAGER_WRITER_CACHEMOD
+       || pPager->eState==PAGER_WRITER_DBMOD
+       || pPager->eState==PAGER_ERROR
+  );
+  assert( assert_pager_state(pPager) );
+
+  /* If a prior error occurred, report that error again. */
+  if( NEVER(pPager->errCode) ) return pPager->errCode;
+
+  PAGERTRACE(("DATABASE SYNC: File=%s zMaster=%s nSize=%d\n", 
+      pPager->zFilename, zMaster, pPager->dbSize));
+
+  /* If no database changes have been made, return early. */
+  if( pPager->eState<PAGER_WRITER_CACHEMOD ) return SQLITE_OK;
+
+  if( MEMDB ){
+    /* If this is an in-memory db, or no pages have been written to, or this
+    ** function has already been called, it is mostly a no-op.  However, any
+    ** backup in progress needs to be restarted.
+    */
+    sqlite3BackupRestart(pPager->pBackup);
+  }else{
+    if( pagerUseWal(pPager) ){
+      PgHdr *pList = sqlite3PcacheDirtyList(pPager->pPCache);
+      PgHdr *pPageOne = 0;
+      if( pList==0 ){
+        /* Must have at least one page for the WAL commit flag.
+        ** Ticket [2d1a5c67dfc2363e44f29d9bbd57f] 2011-05-18 */
+        rc = sqlite3PagerGet(pPager, 1, &pPageOne);
+        pList = pPageOne;
+        pList->pDirty = 0;
+      }
+      assert( rc==SQLITE_OK );
+      if( ALWAYS(pList) ){
+        rc = pagerWalFrames(pPager, pList, pPager->dbSize, 1, 
+            (pPager->fullSync ? pPager->syncFlags : 0)
+        );
+      }
+      sqlite3PagerUnref(pPageOne);
+      if( rc==SQLITE_OK ){
+        sqlite3PcacheCleanAll(pPager->pPCache);
+      }
+    }else{
+      /* The following block updates the change-counter. Exactly how it
+      ** does this depends on whether or not the atomic-update optimization
+      ** was enabled at compile time, and if this transaction meets the 
+      ** runtime criteria to use the operation: 
+      **
+      **    * The file-system supports the atomic-write property for
+      **      blocks of size page-size, and 
+      **    * This commit is not part of a multi-file transaction, and
+      **    * Exactly one page has been modified and store in the journal file.
+      **
+      ** If the optimization was not enabled at compile time, then the
+      ** pager_incr_changecounter() function is called to update the change
+      ** counter in 'indirect-mode'. If the optimization is compiled in but
+      ** is not applicable to this transaction, call sqlite3JournalCreate()
+      ** to make sure the journal file has actually been created, then call
+      ** pager_incr_changecounter() to update the change-counter in indirect
+      ** mode. 
+      **
+      ** Otherwise, if the optimization is both enabled and applicable,
+      ** then call pager_incr_changecounter() to update the change-counter
+      ** in 'direct' mode. In this case the journal file will never be
+      ** created for this transaction.
+      */
+  #ifdef SQLITE_ENABLE_ATOMIC_WRITE
+      PgHdr *pPg;
+      assert( isOpen(pPager->jfd) 
+           || pPager->journalMode==PAGER_JOURNALMODE_OFF 
+           || pPager->journalMode==PAGER_JOURNALMODE_WAL 
+      );
+      if( !zMaster && isOpen(pPager->jfd) 
+       && pPager->journalOff==jrnlBufferSize(pPager) 
+       && pPager->dbSize>=pPager->dbOrigSize
+       && (0==(pPg = sqlite3PcacheDirtyList(pPager->pPCache)) || 0==pPg->pDirty)
+      ){
+        /* Update the db file change counter via the direct-write method. The 
+        ** following call will modify the in-memory representation of page 1 
+        ** to include the updated change counter and then write page 1 
+        ** directly to the database file. Because of the atomic-write 
+        ** property of the host file-system, this is safe.
+        */
+        rc = pager_incr_changecounter(pPager, 1);
+      }else{
+        rc = sqlite3JournalCreate(pPager->jfd);
+        if( rc==SQLITE_OK ){
+          rc = pager_incr_changecounter(pPager, 0);
+        }
+      }
+  #else
+      rc = pager_incr_changecounter(pPager, 0);
+  #endif
+      if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
+  
+      /* If this transaction has made the database smaller, then all pages
+      ** being discarded by the truncation must be written to the journal
+      ** file. This can only happen in auto-vacuum mode.
+      **
+      ** Before reading the pages with page numbers larger than the 
+      ** current value of Pager.dbSize, set dbSize back to the value
+      ** that it took at the start of the transaction. Otherwise, the
+      ** calls to sqlite3PagerGet() return zeroed pages instead of 
+      ** reading data from the database file.
+      */
+  #ifndef SQLITE_OMIT_AUTOVACUUM
+      if( pPager->dbSize<pPager->dbOrigSize 
+       && pPager->journalMode!=PAGER_JOURNALMODE_OFF
+      ){
+        Pgno i;                                   /* Iterator variable */
+        const Pgno iSkip = PAGER_MJ_PGNO(pPager); /* Pending lock page */
+        const Pgno dbSize = pPager->dbSize;       /* Database image size */ 
+        pPager->dbSize = pPager->dbOrigSize;
+        for( i=dbSize+1; i<=pPager->dbOrigSize; i++ ){
+          if( !sqlite3BitvecTest(pPager->pInJournal, i) && i!=iSkip ){
+            PgHdr *pPage;             /* Page to journal */
+            rc = sqlite3PagerGet(pPager, i, &pPage);
+            if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
+            rc = sqlite3PagerWrite(pPage);
+            sqlite3PagerUnref(pPage);
+            if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
+          }
+        }
+        pPager->dbSize = dbSize;
+      } 
+  #endif
+  
+      /* Write the master journal name into the journal file. If a master 
+      ** journal file name has already been written to the journal file, 
+      ** or if zMaster is NULL (no master journal), then this call is a no-op.
+      */
+      rc = writeMasterJournal(pPager, zMaster);
+      if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
+  
+      /* Sync the journal file and write all dirty pages to the database.
+      ** If the atomic-update optimization is being used, this sync will not 
+      ** create the journal file or perform any real IO.
+      **
+      ** Because the change-counter page was just modified, unless the
+      ** atomic-update optimization is used it is almost certain that the
+      ** journal requires a sync here. However, in locking_mode=exclusive
+      ** on a system under memory pressure it is just possible that this is 
+      ** not the case. In this case it is likely enough that the redundant
+      ** xSync() call will be changed to a no-op by the OS anyhow. 
+      */
+      rc = syncJournal(pPager, 0);
+      if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
+  
+      rc = pager_write_pagelist(pPager,sqlite3PcacheDirtyList(pPager->pPCache));
+      if( rc!=SQLITE_OK ){
+        assert( rc!=SQLITE_IOERR_BLOCKED );
+        goto commit_phase_one_exit;
+      }
+      sqlite3PcacheCleanAll(pPager->pPCache);
+  
+      /* If the file on disk is not the same size as the database image,
+      ** then use pager_truncate to grow or shrink the file here.
+      */
+      if( pPager->dbSize!=pPager->dbFileSize ){
+        Pgno nNew = pPager->dbSize - (pPager->dbSize==PAGER_MJ_PGNO(pPager));
+        assert( pPager->eState==PAGER_WRITER_DBMOD );
+        rc = pager_truncate(pPager, nNew);
+        if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
+      }
+  
+      /* Finally, sync the database file. */
+      if( !noSync ){
+        rc = sqlite3PagerSync(pPager);
+      }
+      IOTRACE(("DBSYNC %p\n", pPager))
+    }
+  }
+
+commit_phase_one_exit:
+  if( rc==SQLITE_OK && !pagerUseWal(pPager) ){
+    pPager->eState = PAGER_WRITER_FINISHED;
+  }
+  return rc;
+}
+
+
+/*
+** When this function is called, the database file has been completely
+** updated to reflect the changes made by the current transaction and
+** synced to disk. The journal file still exists in the file-system 
+** though, and if a failure occurs at this point it will eventually
+** be used as a hot-journal and the current transaction rolled back.
+**
+** This function finalizes the journal file, either by deleting, 
+** truncating or partially zeroing it, so that it cannot be used 
+** for hot-journal rollback. Once this is done the transaction is
+** irrevocably committed.
+**
+** If an error occurs, an IO error code is returned and the pager
+** moves into the error state. Otherwise, SQLITE_OK is returned.
+*/
+int sqlite3PagerCommitPhaseTwo(Pager *pPager){
+  int rc = SQLITE_OK;                  /* Return code */
+
+  /* This routine should not be called if a prior error has occurred.
+  ** But if (due to a coding error elsewhere in the system) it does get
+  ** called, just return the same error code without doing anything. */
+  if( NEVER(pPager->errCode) ) return pPager->errCode;
+
+  assert( pPager->eState==PAGER_WRITER_LOCKED
+       || pPager->eState==PAGER_WRITER_FINISHED
+       || (pagerUseWal(pPager) && pPager->eState==PAGER_WRITER_CACHEMOD)
+  );
+  assert( assert_pager_state(pPager) );
+
+  /* An optimization. If the database was not actually modified during
+  ** this transaction, the pager is running in exclusive-mode and is
+  ** using persistent journals, then this function is a no-op.
+  **
+  ** The start of the journal file currently contains a single journal 
+  ** header with the nRec field set to 0. If such a journal is used as
+  ** a hot-journal during hot-journal rollback, 0 changes will be made
+  ** to the database file. So there is no need to zero the journal 
+  ** header. Since the pager is in exclusive mode, there is no need
+  ** to drop any locks either.
+  */
+  if( pPager->eState==PAGER_WRITER_LOCKED 
+   && pPager->exclusiveMode 
+   && pPager->journalMode==PAGER_JOURNALMODE_PERSIST
+  ){
+    assert( pPager->journalOff==JOURNAL_HDR_SZ(pPager) || !pPager->journalOff );
+    pPager->eState = PAGER_READER;
+    return SQLITE_OK;
+  }
+
+  PAGERTRACE(("COMMIT %d\n", PAGERID(pPager)));
+  rc = pager_end_transaction(pPager, pPager->setMaster);
+  return pager_error(pPager, rc);
+}
+
+/*
+** If a write transaction is open, then all changes made within the 
+** transaction are reverted and the current write-transaction is closed.
+** The pager falls back to PAGER_READER state if successful, or PAGER_ERROR
+** state if an error occurs.
+**
+** If the pager is already in PAGER_ERROR state when this function is called,
+** it returns Pager.errCode immediately. No work is performed in this case.
+**
+** Otherwise, in rollback mode, this function performs two functions:
+**
+**   1) It rolls back the journal file, restoring all database file and 
+**      in-memory cache pages to the state they were in when the transaction
+**      was opened, and
+**
+**   2) It finalizes the journal file, so that it is not used for hot
+**      rollback at any point in the future.
+**
+** Finalization of the journal file (task 2) is only performed if the 
+** rollback is successful.
+**
+** In WAL mode, all cache-entries containing data modified within the
+** current transaction are either expelled from the cache or reverted to
+** their pre-transaction state by re-reading data from the database or
+** WAL files. The WAL transaction is then closed.
+*/
+int sqlite3PagerRollback(Pager *pPager){
+  int rc = SQLITE_OK;                  /* Return code */
+  PAGERTRACE(("ROLLBACK %d\n", PAGERID(pPager)));
+
+  /* PagerRollback() is a no-op if called in READER or OPEN state. If
+  ** the pager is already in the ERROR state, the rollback is not 
+  ** attempted here. Instead, the error code is returned to the caller.
+  */
+  assert( assert_pager_state(pPager) );
+  if( pPager->eState==PAGER_ERROR ) return pPager->errCode;
+  if( pPager->eState<=PAGER_READER ) return SQLITE_OK;
+
+  if( pagerUseWal(pPager) ){
+    int rc2;
+    rc = sqlite3PagerSavepoint(pPager, SAVEPOINT_ROLLBACK, -1);
+    rc2 = pager_end_transaction(pPager, pPager->setMaster);
+    if( rc==SQLITE_OK ) rc = rc2;
+  }else if( !isOpen(pPager->jfd) || pPager->eState==PAGER_WRITER_LOCKED ){
+    int eState = pPager->eState;
+    rc = pager_end_transaction(pPager, 0);
+    if( !MEMDB && eState>PAGER_WRITER_LOCKED ){
+      /* This can happen using journal_mode=off. Move the pager to the error 
+      ** state to indicate that the contents of the cache may not be trusted.
+      ** Any active readers will get SQLITE_ABORT.
+      */
+      pPager->errCode = SQLITE_ABORT;
+      pPager->eState = PAGER_ERROR;
+      return rc;
+    }
+  }else{
+    rc = pager_playback(pPager, 0);
+  }
+
+  assert( pPager->eState==PAGER_READER || rc!=SQLITE_OK );
+  assert( rc==SQLITE_OK || rc==SQLITE_FULL || (rc&0xFF)==SQLITE_IOERR );
+
+  /* If an error occurs during a ROLLBACK, we can no longer trust the pager
+  ** cache. So call pager_error() on the way out to make any error persistent.
+  */
+  return pager_error(pPager, rc);
+}
+
+/*
+** Return TRUE if the database file is opened read-only.  Return FALSE
+** if the database is (in theory) writable.
+*/
+u8 sqlite3PagerIsreadonly(Pager *pPager){
+  return pPager->readOnly;
+}
+
+/*
+** Return the number of references to the pager.
+*/
+int sqlite3PagerRefcount(Pager *pPager){
+  return sqlite3PcacheRefCount(pPager->pPCache);
+}
+
+/*
+** Return the approximate number of bytes of memory currently
+** used by the pager and its associated cache.
+*/
+int sqlite3PagerMemUsed(Pager *pPager){
+  int perPageSize = pPager->pageSize + pPager->nExtra + sizeof(PgHdr)
+                                     + 5*sizeof(void*);
+  return perPageSize*sqlite3PcachePagecount(pPager->pPCache)
+           + sqlite3MallocSize(pPager)
+           + pPager->pageSize;
+}
+
+/*
+** Return the number of references to the specified page.
+*/
+int sqlite3PagerPageRefcount(DbPage *pPage){
+  return sqlite3PcachePageRefcount(pPage);
+}
+
+#ifdef SQLITE_TEST
+/*
+** This routine is used for testing and analysis only.
+*/
+int *sqlite3PagerStats(Pager *pPager){
+  static int a[11];
+  a[0] = sqlite3PcacheRefCount(pPager->pPCache);
+  a[1] = sqlite3PcachePagecount(pPager->pPCache);
+  a[2] = sqlite3PcacheGetCachesize(pPager->pPCache);
+  a[3] = pPager->eState==PAGER_OPEN ? -1 : (int) pPager->dbSize;
+  a[4] = pPager->eState;
+  a[5] = pPager->errCode;
+  a[6] = pPager->nHit;
+  a[7] = pPager->nMiss;
+  a[8] = 0;  /* Used to be pPager->nOvfl */
+  a[9] = pPager->nRead;
+  a[10] = pPager->nWrite;
+  return a;
+}
+#endif
+
+/*
+** Parameter eStat must be either SQLITE_DBSTATUS_CACHE_HIT or
+** SQLITE_DBSTATUS_CACHE_MISS. Before returning, *pnVal is incremented by the
+** current cache hit or miss count, according to the value of eStat. If the 
+** reset parameter is non-zero, the cache hit or miss count is zeroed before 
+** returning.
+*/
+void sqlite3PagerCacheStat(Pager *pPager, int eStat, int reset, int *pnVal){
+  int *piStat;
+
+  assert( eStat==SQLITE_DBSTATUS_CACHE_HIT
+       || eStat==SQLITE_DBSTATUS_CACHE_MISS
+  );
+  if( eStat==SQLITE_DBSTATUS_CACHE_HIT ){
+    piStat = &pPager->nHit;
+  }else{
+    piStat = &pPager->nMiss;
+  }
+
+  *pnVal += *piStat;
+  if( reset ){
+    *piStat = 0;
+  }
+}
+
+/*
+** Return true if this is an in-memory pager.
+*/
+int sqlite3PagerIsMemdb(Pager *pPager){
+  return MEMDB;
+}
+
+/*
+** Check that there are at least nSavepoint savepoints open. If there are
+** currently less than nSavepoints open, then open one or more savepoints
+** to make up the difference. If the number of savepoints is already
+** equal to nSavepoint, then this function is a no-op.
+**
+** If a memory allocation fails, SQLITE_NOMEM is returned. If an error 
+** occurs while opening the sub-journal file, then an IO error code is
+** returned. Otherwise, SQLITE_OK.
+*/
+int sqlite3PagerOpenSavepoint(Pager *pPager, int nSavepoint){
+  int rc = SQLITE_OK;                       /* Return code */
+  int nCurrent = pPager->nSavepoint;        /* Current number of savepoints */
+
+  assert( pPager->eState>=PAGER_WRITER_LOCKED );
+  assert( assert_pager_state(pPager) );
+
+  if( nSavepoint>nCurrent && pPager->useJournal ){
+    int ii;                                 /* Iterator variable */
+    PagerSavepoint *aNew;                   /* New Pager.aSavepoint array */
+
+    /* Grow the Pager.aSavepoint array using realloc(). Return SQLITE_NOMEM
+    ** if the allocation fails. Otherwise, zero the new portion in case a 
+    ** malloc failure occurs while populating it in the for(...) loop below.
+    */
+    aNew = (PagerSavepoint *)sqlite3Realloc(
+        pPager->aSavepoint, sizeof(PagerSavepoint)*nSavepoint
+    );
+    if( !aNew ){
+      return SQLITE_NOMEM;
+    }
+    memset(&aNew[nCurrent], 0, (nSavepoint-nCurrent) * sizeof(PagerSavepoint));
+    pPager->aSavepoint = aNew;
+
+    /* Populate the PagerSavepoint structures just allocated. */
+    for(ii=nCurrent; ii<nSavepoint; ii++){
+      aNew[ii].nOrig = pPager->dbSize;
+      if( isOpen(pPager->jfd) && pPager->journalOff>0 ){
+        aNew[ii].iOffset = pPager->journalOff;
+      }else{
+        aNew[ii].iOffset = JOURNAL_HDR_SZ(pPager);
+      }
+      aNew[ii].iSubRec = pPager->nSubRec;
+      aNew[ii].pInSavepoint = sqlite3BitvecCreate(pPager->dbSize);
+      if( !aNew[ii].pInSavepoint ){
+        return SQLITE_NOMEM;
+      }
+      if( pagerUseWal(pPager) ){
+        sqlite3WalSavepoint(pPager->pWal, aNew[ii].aWalData);
+      }
+      pPager->nSavepoint = ii+1;
+    }
+    assert( pPager->nSavepoint==nSavepoint );
+    assertTruncateConstraint(pPager);
+  }
+
+  return rc;
+}
+
+/*
+** This function is called to rollback or release (commit) a savepoint.
+** The savepoint to release or rollback need not be the most recently 
+** created savepoint.
+**
+** Parameter op is always either SAVEPOINT_ROLLBACK or SAVEPOINT_RELEASE.
+** If it is SAVEPOINT_RELEASE, then release and destroy the savepoint with
+** index iSavepoint. If it is SAVEPOINT_ROLLBACK, then rollback all changes
+** that have occurred since the specified savepoint was created.
+**
+** The savepoint to rollback or release is identified by parameter 
+** iSavepoint. A value of 0 means to operate on the outermost savepoint
+** (the first created). A value of (Pager.nSavepoint-1) means operate
+** on the most recently created savepoint. If iSavepoint is greater than
+** (Pager.nSavepoint-1), then this function is a no-op.
+**
+** If a negative value is passed to this function, then the current
+** transaction is rolled back. This is different to calling 
+** sqlite3PagerRollback() because this function does not terminate
+** the transaction or unlock the database, it just restores the 
+** contents of the database to its original state. 
+**
+** In any case, all savepoints with an index greater than iSavepoint 
+** are destroyed. If this is a release operation (op==SAVEPOINT_RELEASE),
+** then savepoint iSavepoint is also destroyed.
+**
+** This function may return SQLITE_NOMEM if a memory allocation fails,
+** or an IO error code if an IO error occurs while rolling back a 
+** savepoint. If no errors occur, SQLITE_OK is returned.
+*/ 
+int sqlite3PagerSavepoint(Pager *pPager, int op, int iSavepoint){
+  int rc = pPager->errCode;       /* Return code */
+
+  assert( op==SAVEPOINT_RELEASE || op==SAVEPOINT_ROLLBACK );
+  assert( iSavepoint>=0 || op==SAVEPOINT_ROLLBACK );
+
+  if( rc==SQLITE_OK && iSavepoint<pPager->nSavepoint ){
+    int ii;            /* Iterator variable */
+    int nNew;          /* Number of remaining savepoints after this op. */
+
+    /* Figure out how many savepoints will still be active after this
+    ** operation. Store this value in nNew. Then free resources associated 
+    ** with any savepoints that are destroyed by this operation.
+    */
+    nNew = iSavepoint + (( op==SAVEPOINT_RELEASE ) ? 0 : 1);
+    for(ii=nNew; ii<pPager->nSavepoint; ii++){
+      sqlite3BitvecDestroy(pPager->aSavepoint[ii].pInSavepoint);
+    }
+    pPager->nSavepoint = nNew;
+
+    /* If this is a release of the outermost savepoint, truncate 
+    ** the sub-journal to zero bytes in size. */
+    if( op==SAVEPOINT_RELEASE ){
+      if( nNew==0 && isOpen(pPager->sjfd) ){
+        /* Only truncate if it is an in-memory sub-journal. */
+        if( sqlite3IsMemJournal(pPager->sjfd) ){
+          rc = sqlite3OsTruncate(pPager->sjfd, 0);
+          assert( rc==SQLITE_OK );
+        }
+        pPager->nSubRec = 0;
+      }
+    }
+    /* Else this is a rollback operation, playback the specified savepoint.
+    ** If this is a temp-file, it is possible that the journal file has
+    ** not yet been opened. In this case there have been no changes to
+    ** the database file, so the playback operation can be skipped.
+    */
+    else if( pagerUseWal(pPager) || isOpen(pPager->jfd) ){
+      PagerSavepoint *pSavepoint = (nNew==0)?0:&pPager->aSavepoint[nNew-1];
+      rc = pagerPlaybackSavepoint(pPager, pSavepoint);
+      assert(rc!=SQLITE_DONE);
+    }
+  }
+
+  return rc;
+}
+
+/*
+** Return the full pathname of the database file.
+*/
+const char *sqlite3PagerFilename(Pager *pPager){
+  return pPager->zFilename;
+}
+
+/*
+** Return the VFS structure for the pager.
+*/
+const sqlite3_vfs *sqlite3PagerVfs(Pager *pPager){
+  return pPager->pVfs;
+}
+
+/*
+** Return the file handle for the database file associated
+** with the pager.  This might return NULL if the file has
+** not yet been opened.
+*/
+sqlite3_file *sqlite3PagerFile(Pager *pPager){
+  return pPager->fd;
+}
+
+/*
+** Return the full pathname of the journal file.
+*/
+const char *sqlite3PagerJournalname(Pager *pPager){
+  return pPager->zJournal;
+}
+
+/*
+** Return true if fsync() calls are disabled for this pager.  Return FALSE
+** if fsync()s are executed normally.
+*/
+int sqlite3PagerNosync(Pager *pPager){
+  return pPager->noSync;
+}
+
+#ifdef SQLITE_HAS_CODEC
+/*
+** Set or retrieve the codec for this pager
+*/
+void sqlite3PagerSetCodec(
+  Pager *pPager,
+  void *(*xCodec)(void*,void*,Pgno,int),
+  void (*xCodecSizeChng)(void*,int,int),
+  void (*xCodecFree)(void*),
+  void *pCodec
+){
+  if( pPager->xCodecFree ) pPager->xCodecFree(pPager->pCodec);
+  pPager->xCodec = pPager->memDb ? 0 : xCodec;
+  pPager->xCodecSizeChng = xCodecSizeChng;
+  pPager->xCodecFree = xCodecFree;
+  pPager->pCodec = pCodec;
+  pagerReportSize(pPager);
+}
+void *sqlite3PagerGetCodec(Pager *pPager){
+  return pPager->pCodec;
+}
+#endif
+
+#ifndef SQLITE_OMIT_AUTOVACUUM
+/*
+** Move the page pPg to location pgno in the file.
+**
+** There must be no references to the page previously located at
+** pgno (which we call pPgOld) though that page is allowed to be
+** in cache.  If the page previously located at pgno is not already
+** in the rollback journal, it is not put there by by this routine.
+**
+** References to the page pPg remain valid. Updating any
+** meta-data associated with pPg (i.e. data stored in the nExtra bytes
+** allocated along with the page) is the responsibility of the caller.
+**
+** A transaction must be active when this routine is called. It used to be
+** required that a statement transaction was not active, but this restriction
+** has been removed (CREATE INDEX needs to move a page when a statement
+** transaction is active).
+**
+** If the fourth argument, isCommit, is non-zero, then this page is being
+** moved as part of a database reorganization just before the transaction 
+** is being committed. In this case, it is guaranteed that the database page 
+** pPg refers to will not be written to again within this transaction.
+**
+** This function may return SQLITE_NOMEM or an IO error code if an error
+** occurs. Otherwise, it returns SQLITE_OK.
+*/
+int sqlite3PagerMovepage(Pager *pPager, DbPage *pPg, Pgno pgno, int isCommit){
+  PgHdr *pPgOld;               /* The page being overwritten. */
+  Pgno needSyncPgno = 0;       /* Old value of pPg->pgno, if sync is required */
+  int rc;                      /* Return code */
+  Pgno origPgno;               /* The original page number */
+
+  assert( pPg->nRef>0 );
+  assert( pPager->eState==PAGER_WRITER_CACHEMOD
+       || pPager->eState==PAGER_WRITER_DBMOD
+  );
+  assert( assert_pager_state(pPager) );
+
+  /* In order to be able to rollback, an in-memory database must journal
+  ** the page we are moving from.
+  */
+  if( MEMDB ){
+    rc = sqlite3PagerWrite(pPg);
+    if( rc ) return rc;
+  }
+
+  /* If the page being moved is dirty and has not been saved by the latest
+  ** savepoint, then save the current contents of the page into the 
+  ** sub-journal now. This is required to handle the following scenario:
+  **
+  **   BEGIN;
+  **     <journal page X, then modify it in memory>
+  **     SAVEPOINT one;
+  **       <Move page X to location Y>
+  **     ROLLBACK TO one;
+  **
+  ** If page X were not written to the sub-journal here, it would not
+  ** be possible to restore its contents when the "ROLLBACK TO one"
+  ** statement were is processed.
+  **
+  ** subjournalPage() may need to allocate space to store pPg->pgno into
+  ** one or more savepoint bitvecs. This is the reason this function
+  ** may return SQLITE_NOMEM.
+  */
+  if( pPg->flags&PGHDR_DIRTY
+   && subjRequiresPage(pPg)
+   && SQLITE_OK!=(rc = subjournalPage(pPg))
+  ){
+    return rc;
+  }
+
+  PAGERTRACE(("MOVE %d page %d (needSync=%d) moves to %d\n", 
+      PAGERID(pPager), pPg->pgno, (pPg->flags&PGHDR_NEED_SYNC)?1:0, pgno));
+  IOTRACE(("MOVE %p %d %d\n", pPager, pPg->pgno, pgno))
+
+  /* If the journal needs to be sync()ed before page pPg->pgno can
+  ** be written to, store pPg->pgno in local variable needSyncPgno.
+  **
+  ** If the isCommit flag is set, there is no need to remember that
+  ** the journal needs to be sync()ed before database page pPg->pgno 
+  ** can be written to. The caller has already promised not to write to it.
+  */
+  if( (pPg->flags&PGHDR_NEED_SYNC) && !isCommit ){
+    needSyncPgno = pPg->pgno;
+    assert( pageInJournal(pPg) || pPg->pgno>pPager->dbOrigSize );
+    assert( pPg->flags&PGHDR_DIRTY );
+  }
+
+  /* If the cache contains a page with page-number pgno, remove it
+  ** from its hash chain. Also, if the PGHDR_NEED_SYNC flag was set for 
+  ** page pgno before the 'move' operation, it needs to be retained 
+  ** for the page moved there.
+  */
+  pPg->flags &= ~PGHDR_NEED_SYNC;
+  pPgOld = pager_lookup(pPager, pgno);
+  assert( !pPgOld || pPgOld->nRef==1 );
+  if( pPgOld ){
+    pPg->flags |= (pPgOld->flags&PGHDR_NEED_SYNC);
+    if( MEMDB ){
+      /* Do not discard pages from an in-memory database since we might
+      ** need to rollback later.  Just move the page out of the way. */
+      sqlite3PcacheMove(pPgOld, pPager->dbSize+1);
+    }else{
+      sqlite3PcacheDrop(pPgOld);
+    }
+  }
+
+  origPgno = pPg->pgno;
+  sqlite3PcacheMove(pPg, pgno);
+  sqlite3PcacheMakeDirty(pPg);
+
+  /* For an in-memory database, make sure the original page continues
+  ** to exist, in case the transaction needs to roll back.  Use pPgOld
+  ** as the original page since it has already been allocated.
+  */
+  if( MEMDB ){
+    assert( pPgOld );
+    sqlite3PcacheMove(pPgOld, origPgno);
+    sqlite3PagerUnref(pPgOld);
+  }
+
+  if( needSyncPgno ){
+    /* If needSyncPgno is non-zero, then the journal file needs to be 
+    ** sync()ed before any data is written to database file page needSyncPgno.
+    ** Currently, no such page exists in the page-cache and the 
+    ** "is journaled" bitvec flag has been set. This needs to be remedied by
+    ** loading the page into the pager-cache and setting the PGHDR_NEED_SYNC
+    ** flag.
+    **
+    ** If the attempt to load the page into the page-cache fails, (due
+    ** to a malloc() or IO failure), clear the bit in the pInJournal[]
+    ** array. Otherwise, if the page is loaded and written again in
+    ** this transaction, it may be written to the database file before
+    ** it is synced into the journal file. This way, it may end up in
+    ** the journal file twice, but that is not a problem.
+    */
+    PgHdr *pPgHdr;
+    rc = sqlite3PagerGet(pPager, needSyncPgno, &pPgHdr);
+    if( rc!=SQLITE_OK ){
+      if( needSyncPgno<=pPager->dbOrigSize ){
+        assert( pPager->pTmpSpace!=0 );
+        sqlite3BitvecClear(pPager->pInJournal, needSyncPgno, pPager->pTmpSpace);
+      }
+      return rc;
+    }
+    pPgHdr->flags |= PGHDR_NEED_SYNC;
+    sqlite3PcacheMakeDirty(pPgHdr);
+    sqlite3PagerUnref(pPgHdr);
+  }
+
+  return SQLITE_OK;
+}
+#endif
+
+/*
+** Return a pointer to the data for the specified page.
+*/
+void *sqlite3PagerGetData(DbPage *pPg){
+  assert( pPg->nRef>0 || pPg->pPager->memDb );
+  return pPg->pData;
+}
+
+/*
+** Return a pointer to the Pager.nExtra bytes of "extra" space 
+** allocated along with the specified page.
+*/
+void *sqlite3PagerGetExtra(DbPage *pPg){
+  return pPg->pExtra;
+}
+
+/*
+** Get/set the locking-mode for this pager. Parameter eMode must be one
+** of PAGER_LOCKINGMODE_QUERY, PAGER_LOCKINGMODE_NORMAL or 
+** PAGER_LOCKINGMODE_EXCLUSIVE. If the parameter is not _QUERY, then
+** the locking-mode is set to the value specified.
+**
+** The returned value is either PAGER_LOCKINGMODE_NORMAL or
+** PAGER_LOCKINGMODE_EXCLUSIVE, indicating the current (possibly updated)
+** locking-mode.
+*/
+int sqlite3PagerLockingMode(Pager *pPager, int eMode){
+  assert( eMode==PAGER_LOCKINGMODE_QUERY
+            || eMode==PAGER_LOCKINGMODE_NORMAL
+            || eMode==PAGER_LOCKINGMODE_EXCLUSIVE );
+  assert( PAGER_LOCKINGMODE_QUERY<0 );
+  assert( PAGER_LOCKINGMODE_NORMAL>=0 && PAGER_LOCKINGMODE_EXCLUSIVE>=0 );
+  assert( pPager->exclusiveMode || 0==sqlite3WalHeapMemory(pPager->pWal) );
+  if( eMode>=0 && !pPager->tempFile && !sqlite3WalHeapMemory(pPager->pWal) ){
+    pPager->exclusiveMode = (u8)eMode;
+  }
+  return (int)pPager->exclusiveMode;
+}
+
+/*
+** Set the journal-mode for this pager. Parameter eMode must be one of:
+**
+**    PAGER_JOURNALMODE_DELETE
+**    PAGER_JOURNALMODE_TRUNCATE
+**    PAGER_JOURNALMODE_PERSIST
+**    PAGER_JOURNALMODE_OFF
+**    PAGER_JOURNALMODE_MEMORY
+**    PAGER_JOURNALMODE_WAL
+**
+** The journalmode is set to the value specified if the change is allowed.
+** The change may be disallowed for the following reasons:
+**
+**   *  An in-memory database can only have its journal_mode set to _OFF
+**      or _MEMORY.
+**
+**   *  Temporary databases cannot have _WAL journalmode.
+**
+** The returned indicate the current (possibly updated) journal-mode.
+*/
+int sqlite3PagerSetJournalMode(Pager *pPager, int eMode){
+  u8 eOld = pPager->journalMode;    /* Prior journalmode */
+
+#ifdef SQLITE_DEBUG
+  /* The print_pager_state() routine is intended to be used by the debugger
+  ** only.  We invoke it once here to suppress a compiler warning. */
+  print_pager_state(pPager);
+#endif
+
+
+  /* The eMode parameter is always valid */
+  assert(      eMode==PAGER_JOURNALMODE_DELETE
+            || eMode==PAGER_JOURNALMODE_TRUNCATE
+            || eMode==PAGER_JOURNALMODE_PERSIST
+            || eMode==PAGER_JOURNALMODE_OFF 
+            || eMode==PAGER_JOURNALMODE_WAL 
+            || eMode==PAGER_JOURNALMODE_MEMORY );
+
+  /* This routine is only called from the OP_JournalMode opcode, and
+  ** the logic there will never allow a temporary file to be changed
+  ** to WAL mode.
+  */
+  assert( pPager->tempFile==0 || eMode!=PAGER_JOURNALMODE_WAL );
+
+  /* Do allow the journalmode of an in-memory database to be set to
+  ** anything other than MEMORY or OFF
+  */
+  if( MEMDB ){
+    assert( eOld==PAGER_JOURNALMODE_MEMORY || eOld==PAGER_JOURNALMODE_OFF );
+    if( eMode!=PAGER_JOURNALMODE_MEMORY && eMode!=PAGER_JOURNALMODE_OFF ){
+      eMode = eOld;
+    }
+  }
+
+  if( eMode!=eOld ){
+
+    /* Change the journal mode. */
+    assert( pPager->eState!=PAGER_ERROR );
+    pPager->journalMode = (u8)eMode;
+
+    /* When transistioning from TRUNCATE or PERSIST to any other journal
+    ** mode except WAL, unless the pager is in locking_mode=exclusive mode,
+    ** delete the journal file.
+    */
+    assert( (PAGER_JOURNALMODE_TRUNCATE & 5)==1 );
+    assert( (PAGER_JOURNALMODE_PERSIST & 5)==1 );
+    assert( (PAGER_JOURNALMODE_DELETE & 5)==0 );
+    assert( (PAGER_JOURNALMODE_MEMORY & 5)==4 );
+    assert( (PAGER_JOURNALMODE_OFF & 5)==0 );
+    assert( (PAGER_JOURNALMODE_WAL & 5)==5 );
+
+    assert( isOpen(pPager->fd) || pPager->exclusiveMode );
+    if( !pPager->exclusiveMode && (eOld & 5)==1 && (eMode & 1)==0 ){
+
+      /* In this case we would like to delete the journal file. If it is
+      ** not possible, then that is not a problem. Deleting the journal file
+      ** here is an optimization only.
+      **
+      ** Before deleting the journal file, obtain a RESERVED lock on the
+      ** database file. This ensures that the journal file is not deleted
+      ** while it is in use by some other client.
+      */
+      sqlite3OsClose(pPager->jfd);
+      if( pPager->eLock>=RESERVED_LOCK ){
+        sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0);
+      }else{
+        int rc = SQLITE_OK;
+        int state = pPager->eState;
+        assert( state==PAGER_OPEN || state==PAGER_READER );
+        if( state==PAGER_OPEN ){
+          rc = sqlite3PagerSharedLock(pPager);
+        }
+        if( pPager->eState==PAGER_READER ){
+          assert( rc==SQLITE_OK );
+          rc = pagerLockDb(pPager, RESERVED_LOCK);
+        }
+        if( rc==SQLITE_OK ){
+          sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0);
+        }
+        if( rc==SQLITE_OK && state==PAGER_READER ){
+          pagerUnlockDb(pPager, SHARED_LOCK);
+        }else if( state==PAGER_OPEN ){
+          pager_unlock(pPager);
+        }
+        assert( state==pPager->eState );
+      }
+    }
+  }
+
+  /* Return the new journal mode */
+  return (int)pPager->journalMode;
+}
+
+/*
+** Return the current journal mode.
+*/
+int sqlite3PagerGetJournalMode(Pager *pPager){
+  return (int)pPager->journalMode;
+}
+
+/*
+** Return TRUE if the pager is in a state where it is OK to change the
+** journalmode.  Journalmode changes can only happen when the database
+** is unmodified.
+*/
+int sqlite3PagerOkToChangeJournalMode(Pager *pPager){
+  assert( assert_pager_state(pPager) );
+  if( pPager->eState>=PAGER_WRITER_CACHEMOD ) return 0;
+  if( NEVER(isOpen(pPager->jfd) && pPager->journalOff>0) ) return 0;
+  return 1;
+}
+
+/*
+** Get/set the size-limit used for persistent journal files.
+**
+** Setting the size limit to -1 means no limit is enforced.
+** An attempt to set a limit smaller than -1 is a no-op.
+*/
+i64 sqlite3PagerJournalSizeLimit(Pager *pPager, i64 iLimit){
+  if( iLimit>=-1 ){
+    pPager->journalSizeLimit = iLimit;
+    sqlite3WalLimit(pPager->pWal, iLimit);
+  }
+  return pPager->journalSizeLimit;
+}
+
+/*
+** Return a pointer to the pPager->pBackup variable. The backup module
+** in backup.c maintains the content of this variable. This module
+** uses it opaquely as an argument to sqlite3BackupRestart() and
+** sqlite3BackupUpdate() only.
+*/
+sqlite3_backup **sqlite3PagerBackupPtr(Pager *pPager){
+  return &pPager->pBackup;
+}
+
+#ifndef SQLITE_OMIT_WAL
+/*
+** This function is called when the user invokes "PRAGMA wal_checkpoint",
+** "PRAGMA wal_blocking_checkpoint" or calls the sqlite3_wal_checkpoint()
+** or wal_blocking_checkpoint() API functions.
+**
+** Parameter eMode is one of SQLITE_CHECKPOINT_PASSIVE, FULL or RESTART.
+*/
+int sqlite3PagerCheckpoint(Pager *pPager, int eMode, int *pnLog, int *pnCkpt){
+  int rc = SQLITE_OK;
+  if( pPager->pWal ){
+    rc = sqlite3WalCheckpoint(pPager->pWal, eMode,
+        pPager->xBusyHandler, pPager->pBusyHandlerArg,
+        pPager->ckptSyncFlags, pPager->pageSize, (u8 *)pPager->pTmpSpace,
+        pnLog, pnCkpt
+    );
+  }
+  return rc;
+}
+
+int sqlite3PagerWalCallback(Pager *pPager){
+  return sqlite3WalCallback(pPager->pWal);
+}
+
+/*
+** Return true if the underlying VFS for the given pager supports the
+** primitives necessary for write-ahead logging.
+*/
+int sqlite3PagerWalSupported(Pager *pPager){
+  const sqlite3_io_methods *pMethods = pPager->fd->pMethods;
+  return pPager->exclusiveMode || (pMethods->iVersion>=2 && pMethods->xShmMap);
+}
+
+/*
+** Attempt to take an exclusive lock on the database file. If a PENDING lock
+** is obtained instead, immediately release it.
+*/
+static int pagerExclusiveLock(Pager *pPager){
+  int rc;                         /* Return code */
+
+  assert( pPager->eLock==SHARED_LOCK || pPager->eLock==EXCLUSIVE_LOCK );
+  rc = pagerLockDb(pPager, EXCLUSIVE_LOCK);
+  if( rc!=SQLITE_OK ){
+    /* If the attempt to grab the exclusive lock failed, release the 
+    ** pending lock that may have been obtained instead.  */
+    pagerUnlockDb(pPager, SHARED_LOCK);
+  }
+
+  return rc;
+}
+
+/*
+** Call sqlite3WalOpen() to open the WAL handle. If the pager is in 
+** exclusive-locking mode when this function is called, take an EXCLUSIVE
+** lock on the database file and use heap-memory to store the wal-index
+** in. Otherwise, use the normal shared-memory.
+*/
+static int pagerOpenWal(Pager *pPager){
+  int rc = SQLITE_OK;
+
+  assert( pPager->pWal==0 && pPager->tempFile==0 );
+  assert( pPager->eLock==SHARED_LOCK || pPager->eLock==EXCLUSIVE_LOCK || pPager->noReadlock);
+
+  /* If the pager is already in exclusive-mode, the WAL module will use 
+  ** heap-memory for the wal-index instead of the VFS shared-memory 
+  ** implementation. Take the exclusive lock now, before opening the WAL
+  ** file, to make sure this is safe.
+  */
+  if( pPager->exclusiveMode ){
+    rc = pagerExclusiveLock(pPager);
+  }
+
+  /* Open the connection to the log file. If this operation fails, 
+  ** (e.g. due to malloc() failure), return an error code.
+  */
+  if( rc==SQLITE_OK ){
+    rc = sqlite3WalOpen(pPager->pVfs, 
+        pPager->fd, pPager->zWal, pPager->exclusiveMode,
+        pPager->journalSizeLimit, &pPager->pWal
+    );
+  }
+
+  return rc;
+}
+
+
+/*
+** The caller must be holding a SHARED lock on the database file to call
+** this function.
+**
+** If the pager passed as the first argument is open on a real database
+** file (not a temp file or an in-memory database), and the WAL file
+** is not already open, make an attempt to open it now. If successful,
+** return SQLITE_OK. If an error occurs or the VFS used by the pager does 
+** not support the xShmXXX() methods, return an error code. *pbOpen is
+** not modified in either case.
+**
+** If the pager is open on a temp-file (or in-memory database), or if
+** the WAL file is already open, set *pbOpen to 1 and return SQLITE_OK
+** without doing anything.
+*/
+int sqlite3PagerOpenWal(
+  Pager *pPager,                  /* Pager object */
+  int *pbOpen                     /* OUT: Set to true if call is a no-op */
+){
+  int rc = SQLITE_OK;             /* Return code */
+
+  assert( assert_pager_state(pPager) );
+  assert( pPager->eState==PAGER_OPEN   || pbOpen );
+  assert( pPager->eState==PAGER_READER || !pbOpen );
+  assert( pbOpen==0 || *pbOpen==0 );
+  assert( pbOpen!=0 || (!pPager->tempFile && !pPager->pWal) );
+
+  if( !pPager->tempFile && !pPager->pWal ){
+    if( !sqlite3PagerWalSupported(pPager) ) return SQLITE_CANTOPEN;
+
+    /* Close any rollback journal previously open */
+    sqlite3OsClose(pPager->jfd);
+
+    rc = pagerOpenWal(pPager);
+    if( rc==SQLITE_OK ){
+      pPager->journalMode = PAGER_JOURNALMODE_WAL;
+      pPager->eState = PAGER_OPEN;
+    }
+  }else{
+    *pbOpen = 1;
+  }
+
+  return rc;
+}
+
+/*
+** This function is called to close the connection to the log file prior
+** to switching from WAL to rollback mode.
+**
+** Before closing the log file, this function attempts to take an 
+** EXCLUSIVE lock on the database file. If this cannot be obtained, an
+** error (SQLITE_BUSY) is returned and the log connection is not closed.
+** If successful, the EXCLUSIVE lock is not released before returning.
+*/
+int sqlite3PagerCloseWal(Pager *pPager){
+  int rc = SQLITE_OK;
+
+  assert( pPager->journalMode==PAGER_JOURNALMODE_WAL );
+
+  /* If the log file is not already open, but does exist in the file-system,
+  ** it may need to be checkpointed before the connection can switch to
+  ** rollback mode. Open it now so this can happen.
+  */
+  if( !pPager->pWal ){
+    int logexists = 0;
+    rc = pagerLockDb(pPager, SHARED_LOCK);
+    if( rc==SQLITE_OK ){
+      rc = sqlite3OsAccess(
+          pPager->pVfs, pPager->zWal, SQLITE_ACCESS_EXISTS, &logexists
+      );
+    }
+    if( rc==SQLITE_OK && logexists ){
+      rc = pagerOpenWal(pPager);
+    }
+  }
+    
+  /* Checkpoint and close the log. Because an EXCLUSIVE lock is held on
+  ** the database file, the log and log-summary files will be deleted.
+  */
+  if( rc==SQLITE_OK && pPager->pWal ){
+    rc = pagerExclusiveLock(pPager);
+    if( rc==SQLITE_OK ){
+      rc = sqlite3WalClose(pPager->pWal, pPager->ckptSyncFlags,
+                           pPager->pageSize, (u8*)pPager->pTmpSpace);
+      pPager->pWal = 0;
+    }
+  }
+  return rc;
+}
+
+/*
+** Unless this is an in-memory or temporary database, clear the pager cache.
+*/
+void sqlite3PagerClearCache(Pager *pPager){
+  if( !MEMDB && pPager->tempFile==0 ) pager_reset(pPager);
+}
+
+#ifdef SQLITE_HAS_CODEC
+/*
+** This function is called by the wal module when writing page content
+** into the log file.
+**
+** This function returns a pointer to a buffer containing the encrypted
+** page content. If a malloc fails, this function may return NULL.
+*/
+void *sqlite3PagerCodec(PgHdr *pPg){
+  void *aData = 0;
+  CODEC2(pPg->pPager, pPg->pData, pPg->pgno, 6, return 0, aData);
+  return aData;
+}
+#endif /* SQLITE_HAS_CODEC */
+
+#endif /* !SQLITE_OMIT_WAL */
+
+#endif /* SQLITE_OMIT_DISKIO */
+
+/* BEGIN CRYPTO */
+#ifdef SQLITE_HAS_CODEC
+void sqlite3pager_get_codec(Pager *pPager, void **ctx) {
+  *ctx = pPager->pCodec;
+}
+
+int sqlite3pager_is_mj_pgno(Pager *pPager, Pgno pgno) {
+  return (PAGER_MJ_PGNO(pPager) == pgno) ? 1 : 0;
+}
+
+sqlite3_file *sqlite3Pager_get_fd(Pager *pPager) {
+  return (isOpen(pPager->fd)) ? pPager->fd : NULL;
+}
+
+void sqlite3pager_sqlite3PagerSetCodec(
+  Pager *pPager,
+  void *(*xCodec)(void*,void*,Pgno,int),
+  void (*xCodecSizeChng)(void*,int,int),
+  void (*xCodecFree)(void*),
+  void *pCodec
+){
+  sqlite3PagerSetCodec(pPager, xCodec, xCodecSizeChng, xCodecFree, pCodec); 
+}
+
+
+#endif
+/* END CRYPTO */
+
diff --git a/src/pager.h b/src/pager.h
new file mode 100644
index 0000000..e36e6c2
--- /dev/null
+++ b/src/pager.h
@@ -0,0 +1,183 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This header file defines the interface that the sqlite page cache
+** subsystem.  The page cache subsystem reads and writes a file a page
+** at a time and provides a journal for rollback.
+*/
+
+#ifndef _PAGER_H_
+#define _PAGER_H_
+
+/*
+** Default maximum size for persistent journal files. A negative 
+** value means no limit. This value may be overridden using the 
+** sqlite3PagerJournalSizeLimit() API. See also "PRAGMA journal_size_limit".
+*/
+#ifndef SQLITE_DEFAULT_JOURNAL_SIZE_LIMIT
+  #define SQLITE_DEFAULT_JOURNAL_SIZE_LIMIT -1
+#endif
+
+/*
+** The type used to represent a page number.  The first page in a file
+** is called page 1.  0 is used to represent "not a page".
+*/
+typedef u32 Pgno;
+
+/*
+** Each open file is managed by a separate instance of the "Pager" structure.
+*/
+typedef struct Pager Pager;
+
+/*
+** Handle type for pages.
+*/
+typedef struct PgHdr DbPage;
+
+/*
+** Page number PAGER_MJ_PGNO is never used in an SQLite database (it is
+** reserved for working around a windows/posix incompatibility). It is
+** used in the journal to signify that the remainder of the journal file 
+** is devoted to storing a master journal name - there are no more pages to
+** roll back. See comments for function writeMasterJournal() in pager.c 
+** for details.
+*/
+#define PAGER_MJ_PGNO(x) ((Pgno)((PENDING_BYTE/((x)->pageSize))+1))
+
+/*
+** Allowed values for the flags parameter to sqlite3PagerOpen().
+**
+** NOTE: These values must match the corresponding BTREE_ values in btree.h.
+*/
+#define PAGER_OMIT_JOURNAL  0x0001    /* Do not use a rollback journal */
+#define PAGER_NO_READLOCK   0x0002    /* Omit readlocks on readonly files */
+#define PAGER_MEMORY        0x0004    /* In-memory database */
+
+/*
+** Valid values for the second argument to sqlite3PagerLockingMode().
+*/
+#define PAGER_LOCKINGMODE_QUERY      -1
+#define PAGER_LOCKINGMODE_NORMAL      0
+#define PAGER_LOCKINGMODE_EXCLUSIVE   1
+
+/*
+** Numeric constants that encode the journalmode.  
+*/
+#define PAGER_JOURNALMODE_QUERY     (-1)  /* Query the value of journalmode */
+#define PAGER_JOURNALMODE_DELETE      0   /* Commit by deleting journal file */
+#define PAGER_JOURNALMODE_PERSIST     1   /* Commit by zeroing journal header */
+#define PAGER_JOURNALMODE_OFF         2   /* Journal omitted.  */
+#define PAGER_JOURNALMODE_TRUNCATE    3   /* Commit by truncating journal */
+#define PAGER_JOURNALMODE_MEMORY      4   /* In-memory journal file */
+#define PAGER_JOURNALMODE_WAL         5   /* Use write-ahead logging */
+
+/*
+** The remainder of this file contains the declarations of the functions
+** that make up the Pager sub-system API. See source code comments for 
+** a detailed description of each routine.
+*/
+
+/* Open and close a Pager connection. */ 
+int sqlite3PagerOpen(
+  sqlite3_vfs*,
+  Pager **ppPager,
+  const char*,
+  int,
+  int,
+  int,
+  void(*)(DbPage*)
+);
+int sqlite3PagerClose(Pager *pPager);
+int sqlite3PagerReadFileheader(Pager*, int, unsigned char*);
+
+/* Functions used to configure a Pager object. */
+void sqlite3PagerSetBusyhandler(Pager*, int(*)(void *), void *);
+int sqlite3PagerSetPagesize(Pager*, u32*, int);
+int sqlite3PagerMaxPageCount(Pager*, int);
+void sqlite3PagerSetCachesize(Pager*, int);
+void sqlite3PagerSetSafetyLevel(Pager*,int,int,int);
+int sqlite3PagerLockingMode(Pager *, int);
+int sqlite3PagerSetJournalMode(Pager *, int);
+int sqlite3PagerGetJournalMode(Pager*);
+int sqlite3PagerOkToChangeJournalMode(Pager*);
+i64 sqlite3PagerJournalSizeLimit(Pager *, i64);
+sqlite3_backup **sqlite3PagerBackupPtr(Pager*);
+
+/* Functions used to obtain and release page references. */ 
+int sqlite3PagerAcquire(Pager *pPager, Pgno pgno, DbPage **ppPage, int clrFlag);
+#define sqlite3PagerGet(A,B,C) sqlite3PagerAcquire(A,B,C,0)
+DbPage *sqlite3PagerLookup(Pager *pPager, Pgno pgno);
+void sqlite3PagerRef(DbPage*);
+void sqlite3PagerUnref(DbPage*);
+
+/* Operations on page references. */
+int sqlite3PagerWrite(DbPage*);
+void sqlite3PagerDontWrite(DbPage*);
+int sqlite3PagerMovepage(Pager*,DbPage*,Pgno,int);
+int sqlite3PagerPageRefcount(DbPage*);
+void *sqlite3PagerGetData(DbPage *); 
+void *sqlite3PagerGetExtra(DbPage *); 
+
+/* Functions used to manage pager transactions and savepoints. */
+void sqlite3PagerPagecount(Pager*, int*);
+int sqlite3PagerBegin(Pager*, int exFlag, int);
+int sqlite3PagerCommitPhaseOne(Pager*,const char *zMaster, int);
+int sqlite3PagerExclusiveLock(Pager*);
+int sqlite3PagerSync(Pager *pPager);
+int sqlite3PagerCommitPhaseTwo(Pager*);
+int sqlite3PagerRollback(Pager*);
+int sqlite3PagerOpenSavepoint(Pager *pPager, int n);
+int sqlite3PagerSavepoint(Pager *pPager, int op, int iSavepoint);
+int sqlite3PagerSharedLock(Pager *pPager);
+
+int sqlite3PagerCheckpoint(Pager *pPager, int, int*, int*);
+int sqlite3PagerWalSupported(Pager *pPager);
+int sqlite3PagerWalCallback(Pager *pPager);
+int sqlite3PagerOpenWal(Pager *pPager, int *pisOpen);
+int sqlite3PagerCloseWal(Pager *pPager);
+
+/* Functions used to query pager state and configuration. */
+u8 sqlite3PagerIsreadonly(Pager*);
+int sqlite3PagerRefcount(Pager*);
+int sqlite3PagerMemUsed(Pager*);
+const char *sqlite3PagerFilename(Pager*);
+const sqlite3_vfs *sqlite3PagerVfs(Pager*);
+sqlite3_file *sqlite3PagerFile(Pager*);
+const char *sqlite3PagerJournalname(Pager*);
+int sqlite3PagerNosync(Pager*);
+void *sqlite3PagerTempSpace(Pager*);
+int sqlite3PagerIsMemdb(Pager*);
+void sqlite3PagerCacheStat(Pager *, int, int, int *);
+void sqlite3PagerClearCache(Pager *);
+
+/* Functions used to truncate the database file. */
+void sqlite3PagerTruncateImage(Pager*,Pgno);
+
+#if defined(SQLITE_HAS_CODEC) && !defined(SQLITE_OMIT_WAL)
+void *sqlite3PagerCodec(DbPage *);
+#endif
+
+/* Functions to support testing and debugging. */
+#if !defined(NDEBUG) || defined(SQLITE_TEST)
+  Pgno sqlite3PagerPagenumber(DbPage*);
+  int sqlite3PagerIswriteable(DbPage*);
+#endif
+#ifdef SQLITE_TEST
+  int *sqlite3PagerStats(Pager*);
+  void sqlite3PagerRefdump(Pager*);
+  void disable_simulated_io_errors(void);
+  void enable_simulated_io_errors(void);
+#else
+# define disable_simulated_io_errors()
+# define enable_simulated_io_errors()
+#endif
+
+#endif /* _PAGER_H_ */
diff --git a/src/parse.y b/src/parse.y
new file mode 100644
index 0000000..92abd5c
--- /dev/null
+++ b/src/parse.y
@@ -0,0 +1,1371 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains SQLite's grammar for SQL.  Process this file
+** using the lemon parser generator to generate C code that runs
+** the parser.  Lemon will also generate a header file containing
+** numeric codes for all of the tokens.
+*/
+
+// All token codes are small integers with #defines that begin with "TK_"
+%token_prefix TK_
+
+// The type of the data attached to each token is Token.  This is also the
+// default type for non-terminals.
+//
+%token_type {Token}
+%default_type {Token}
+
+// The generated parser function takes a 4th argument as follows:
+%extra_argument {Parse *pParse}
+
+// This code runs whenever there is a syntax error
+//
+%syntax_error {
+  UNUSED_PARAMETER(yymajor);  /* Silence some compiler warnings */
+  assert( TOKEN.z[0] );  /* The tokenizer always gives us a token */
+  sqlite3ErrorMsg(pParse, "near \"%T\": syntax error", &TOKEN);
+  pParse->parseError = 1;
+}
+%stack_overflow {
+  UNUSED_PARAMETER(yypMinor); /* Silence some compiler warnings */
+  sqlite3ErrorMsg(pParse, "parser stack overflow");
+  pParse->parseError = 1;
+}
+
+// The name of the generated procedure that implements the parser
+// is as follows:
+%name sqlite3Parser
+
+// The following text is included near the beginning of the C source
+// code file that implements the parser.
+//
+%include {
+#include "sqliteInt.h"
+
+/*
+** Disable all error recovery processing in the parser push-down
+** automaton.
+*/
+#define YYNOERRORRECOVERY 1
+
+/*
+** Make yytestcase() the same as testcase()
+*/
+#define yytestcase(X) testcase(X)
+
+/*
+** An instance of this structure holds information about the
+** LIMIT clause of a SELECT statement.
+*/
+struct LimitVal {
+  Expr *pLimit;    /* The LIMIT expression.  NULL if there is no limit */
+  Expr *pOffset;   /* The OFFSET expression.  NULL if there is none */
+};
+
+/*
+** An instance of this structure is used to store the LIKE,
+** GLOB, NOT LIKE, and NOT GLOB operators.
+*/
+struct LikeOp {
+  Token eOperator;  /* "like" or "glob" or "regexp" */
+  int not;         /* True if the NOT keyword is present */
+};
+
+/*
+** An instance of the following structure describes the event of a
+** TRIGGER.  "a" is the event type, one of TK_UPDATE, TK_INSERT,
+** TK_DELETE, or TK_INSTEAD.  If the event is of the form
+**
+**      UPDATE ON (a,b,c)
+**
+** Then the "b" IdList records the list "a,b,c".
+*/
+struct TrigEvent { int a; IdList * b; };
+
+/*
+** An instance of this structure holds the ATTACH key and the key type.
+*/
+struct AttachKey { int type;  Token key; };
+
+} // end %include
+
+// Input is a single SQL command
+input ::= cmdlist.
+cmdlist ::= cmdlist ecmd.
+cmdlist ::= ecmd.
+ecmd ::= SEMI.
+ecmd ::= explain cmdx SEMI.
+explain ::= .           { sqlite3BeginParse(pParse, 0); }
+%ifndef SQLITE_OMIT_EXPLAIN
+explain ::= EXPLAIN.              { sqlite3BeginParse(pParse, 1); }
+explain ::= EXPLAIN QUERY PLAN.   { sqlite3BeginParse(pParse, 2); }
+%endif  SQLITE_OMIT_EXPLAIN
+cmdx ::= cmd.           { sqlite3FinishCoding(pParse); }
+
+///////////////////// Begin and end transactions. ////////////////////////////
+//
+
+cmd ::= BEGIN transtype(Y) trans_opt.  {sqlite3BeginTransaction(pParse, Y);}
+trans_opt ::= .
+trans_opt ::= TRANSACTION.
+trans_opt ::= TRANSACTION nm.
+%type transtype {int}
+transtype(A) ::= .             {A = TK_DEFERRED;}
+transtype(A) ::= DEFERRED(X).  {A = @X;}
+transtype(A) ::= IMMEDIATE(X). {A = @X;}
+transtype(A) ::= EXCLUSIVE(X). {A = @X;}
+cmd ::= COMMIT trans_opt.      {sqlite3CommitTransaction(pParse);}
+cmd ::= END trans_opt.         {sqlite3CommitTransaction(pParse);}
+cmd ::= ROLLBACK trans_opt.    {sqlite3RollbackTransaction(pParse);}
+
+savepoint_opt ::= SAVEPOINT.
+savepoint_opt ::= .
+cmd ::= SAVEPOINT nm(X). {
+  sqlite3Savepoint(pParse, SAVEPOINT_BEGIN, &X);
+}
+cmd ::= RELEASE savepoint_opt nm(X). {
+  sqlite3Savepoint(pParse, SAVEPOINT_RELEASE, &X);
+}
+cmd ::= ROLLBACK trans_opt TO savepoint_opt nm(X). {
+  sqlite3Savepoint(pParse, SAVEPOINT_ROLLBACK, &X);
+}
+
+///////////////////// The CREATE TABLE statement ////////////////////////////
+//
+cmd ::= create_table create_table_args.
+create_table ::= createkw temp(T) TABLE ifnotexists(E) nm(Y) dbnm(Z). {
+   sqlite3StartTable(pParse,&Y,&Z,T,0,0,E);
+}
+createkw(A) ::= CREATE(X).  {
+  pParse->db->lookaside.bEnabled = 0;
+  A = X;
+}
+%type ifnotexists {int}
+ifnotexists(A) ::= .              {A = 0;}
+ifnotexists(A) ::= IF NOT EXISTS. {A = 1;}
+%type temp {int}
+%ifndef SQLITE_OMIT_TEMPDB
+temp(A) ::= TEMP.  {A = 1;}
+%endif  SQLITE_OMIT_TEMPDB
+temp(A) ::= .      {A = 0;}
+create_table_args ::= LP columnlist conslist_opt(X) RP(Y). {
+  sqlite3EndTable(pParse,&X,&Y,0);
+}
+create_table_args ::= AS select(S). {
+  sqlite3EndTable(pParse,0,0,S);
+  sqlite3SelectDelete(pParse->db, S);
+}
+columnlist ::= columnlist COMMA column.
+columnlist ::= column.
+
+// A "column" is a complete description of a single column in a
+// CREATE TABLE statement.  This includes the column name, its
+// datatype, and other keywords such as PRIMARY KEY, UNIQUE, REFERENCES,
+// NOT NULL and so forth.
+//
+column(A) ::= columnid(X) type carglist. {
+  A.z = X.z;
+  A.n = (int)(pParse->sLastToken.z-X.z) + pParse->sLastToken.n;
+}
+columnid(A) ::= nm(X). {
+  sqlite3AddColumn(pParse,&X);
+  A = X;
+}
+
+
+// An IDENTIFIER can be a generic identifier, or one of several
+// keywords.  Any non-standard keyword can also be an identifier.
+//
+%type id {Token}
+id(A) ::= ID(X).         {A = X;}
+id(A) ::= INDEXED(X).    {A = X;}
+
+// The following directive causes tokens ABORT, AFTER, ASC, etc. to
+// fallback to ID if they will not parse as their original value.
+// This obviates the need for the "id" nonterminal.
+//
+%fallback ID
+  ABORT ACTION AFTER ANALYZE ASC ATTACH BEFORE BEGIN BY CASCADE CAST COLUMNKW
+  CONFLICT DATABASE DEFERRED DESC DETACH EACH END EXCLUSIVE EXPLAIN FAIL FOR
+  IGNORE IMMEDIATE INITIALLY INSTEAD LIKE_KW MATCH NO PLAN
+  QUERY KEY OF OFFSET PRAGMA RAISE RELEASE REPLACE RESTRICT ROW ROLLBACK
+  SAVEPOINT TEMP TRIGGER VACUUM VIEW VIRTUAL
+%ifdef SQLITE_OMIT_COMPOUND_SELECT
+  EXCEPT INTERSECT UNION
+%endif SQLITE_OMIT_COMPOUND_SELECT
+  REINDEX RENAME CTIME_KW IF
+  .
+%wildcard ANY.
+
+// Define operator precedence early so that this is the first occurance
+// of the operator tokens in the grammer.  Keeping the operators together
+// causes them to be assigned integer values that are close together,
+// which keeps parser tables smaller.
+//
+// The token values assigned to these symbols is determined by the order
+// in which lemon first sees them.  It must be the case that ISNULL/NOTNULL,
+// NE/EQ, GT/LE, and GE/LT are separated by only a single value.  See
+// the sqlite3ExprIfFalse() routine for additional information on this
+// constraint.
+//
+%left OR.
+%left AND.
+%right NOT.
+%left IS MATCH LIKE_KW BETWEEN IN ISNULL NOTNULL NE EQ.
+%left GT LE LT GE.
+%right ESCAPE.
+%left BITAND BITOR LSHIFT RSHIFT.
+%left PLUS MINUS.
+%left STAR SLASH REM.
+%left CONCAT.
+%left COLLATE.
+%right BITNOT.
+
+// And "ids" is an identifer-or-string.
+//
+%type ids {Token}
+ids(A) ::= ID|STRING(X).   {A = X;}
+
+// The name of a column or table can be any of the following:
+//
+%type nm {Token}
+nm(A) ::= id(X).         {A = X;}
+nm(A) ::= STRING(X).     {A = X;}
+nm(A) ::= JOIN_KW(X).    {A = X;}
+
+// A typetoken is really one or more tokens that form a type name such
+// as can be found after the column name in a CREATE TABLE statement.
+// Multiple tokens are concatenated to form the value of the typetoken.
+//
+%type typetoken {Token}
+type ::= .
+type ::= typetoken(X).                   {sqlite3AddColumnType(pParse,&X);}
+typetoken(A) ::= typename(X).   {A = X;}
+typetoken(A) ::= typename(X) LP signed RP(Y). {
+  A.z = X.z;
+  A.n = (int)(&Y.z[Y.n] - X.z);
+}
+typetoken(A) ::= typename(X) LP signed COMMA signed RP(Y). {
+  A.z = X.z;
+  A.n = (int)(&Y.z[Y.n] - X.z);
+}
+%type typename {Token}
+typename(A) ::= ids(X).             {A = X;}
+typename(A) ::= typename(X) ids(Y). {A.z=X.z; A.n=Y.n+(int)(Y.z-X.z);}
+signed ::= plus_num.
+signed ::= minus_num.
+
+// "carglist" is a list of additional constraints that come after the
+// column name and column type in a CREATE TABLE statement.
+//
+carglist ::= carglist carg.
+carglist ::= .
+carg ::= CONSTRAINT nm ccons.
+carg ::= ccons.
+ccons ::= DEFAULT term(X).            {sqlite3AddDefaultValue(pParse,&X);}
+ccons ::= DEFAULT LP expr(X) RP.      {sqlite3AddDefaultValue(pParse,&X);}
+ccons ::= DEFAULT PLUS term(X).       {sqlite3AddDefaultValue(pParse,&X);}
+ccons ::= DEFAULT MINUS(A) term(X).      {
+  ExprSpan v;
+  v.pExpr = sqlite3PExpr(pParse, TK_UMINUS, X.pExpr, 0, 0);
+  v.zStart = A.z;
+  v.zEnd = X.zEnd;
+  sqlite3AddDefaultValue(pParse,&v);
+}
+ccons ::= DEFAULT id(X).              {
+  ExprSpan v;
+  spanExpr(&v, pParse, TK_STRING, &X);
+  sqlite3AddDefaultValue(pParse,&v);
+}
+
+// In addition to the type name, we also care about the primary key and
+// UNIQUE constraints.
+//
+ccons ::= NULL onconf.
+ccons ::= NOT NULL onconf(R).    {sqlite3AddNotNull(pParse, R);}
+ccons ::= PRIMARY KEY sortorder(Z) onconf(R) autoinc(I).
+                                 {sqlite3AddPrimaryKey(pParse,0,R,I,Z);}
+ccons ::= UNIQUE onconf(R).      {sqlite3CreateIndex(pParse,0,0,0,0,R,0,0,0,0);}
+ccons ::= CHECK LP expr(X) RP.   {sqlite3AddCheckConstraint(pParse,X.pExpr);}
+ccons ::= REFERENCES nm(T) idxlist_opt(TA) refargs(R).
+                                 {sqlite3CreateForeignKey(pParse,0,&T,TA,R);}
+ccons ::= defer_subclause(D).    {sqlite3DeferForeignKey(pParse,D);}
+ccons ::= COLLATE ids(C).        {sqlite3AddCollateType(pParse, &C);}
+
+// The optional AUTOINCREMENT keyword
+%type autoinc {int}
+autoinc(X) ::= .          {X = 0;}
+autoinc(X) ::= AUTOINCR.  {X = 1;}
+
+// The next group of rules parses the arguments to a REFERENCES clause
+// that determine if the referential integrity checking is deferred or
+// or immediate and which determine what action to take if a ref-integ
+// check fails.
+//
+%type refargs {int}
+refargs(A) ::= .                  { A = OE_None*0x0101; /* EV: R-19803-45884 */}
+refargs(A) ::= refargs(X) refarg(Y). { A = (X & ~Y.mask) | Y.value; }
+%type refarg {struct {int value; int mask;}}
+refarg(A) ::= MATCH nm.              { A.value = 0;     A.mask = 0x000000; }
+refarg(A) ::= ON INSERT refact.      { A.value = 0;     A.mask = 0x000000; }
+refarg(A) ::= ON DELETE refact(X).   { A.value = X;     A.mask = 0x0000ff; }
+refarg(A) ::= ON UPDATE refact(X).   { A.value = X<<8;  A.mask = 0x00ff00; }
+%type refact {int}
+refact(A) ::= SET NULL.              { A = OE_SetNull;  /* EV: R-33326-45252 */}
+refact(A) ::= SET DEFAULT.           { A = OE_SetDflt;  /* EV: R-33326-45252 */}
+refact(A) ::= CASCADE.               { A = OE_Cascade;  /* EV: R-33326-45252 */}
+refact(A) ::= RESTRICT.              { A = OE_Restrict; /* EV: R-33326-45252 */}
+refact(A) ::= NO ACTION.             { A = OE_None;     /* EV: R-33326-45252 */}
+%type defer_subclause {int}
+defer_subclause(A) ::= NOT DEFERRABLE init_deferred_pred_opt.     {A = 0;}
+defer_subclause(A) ::= DEFERRABLE init_deferred_pred_opt(X).      {A = X;}
+%type init_deferred_pred_opt {int}
+init_deferred_pred_opt(A) ::= .                       {A = 0;}
+init_deferred_pred_opt(A) ::= INITIALLY DEFERRED.     {A = 1;}
+init_deferred_pred_opt(A) ::= INITIALLY IMMEDIATE.    {A = 0;}
+
+// For the time being, the only constraint we care about is the primary
+// key and UNIQUE.  Both create indices.
+//
+conslist_opt(A) ::= .                   {A.n = 0; A.z = 0;}
+conslist_opt(A) ::= COMMA(X) conslist.  {A = X;}
+conslist ::= conslist COMMA tcons.
+conslist ::= conslist tcons.
+conslist ::= tcons.
+tcons ::= CONSTRAINT nm.
+tcons ::= PRIMARY KEY LP idxlist(X) autoinc(I) RP onconf(R).
+                                 {sqlite3AddPrimaryKey(pParse,X,R,I,0);}
+tcons ::= UNIQUE LP idxlist(X) RP onconf(R).
+                                 {sqlite3CreateIndex(pParse,0,0,0,X,R,0,0,0,0);}
+tcons ::= CHECK LP expr(E) RP onconf.
+                                 {sqlite3AddCheckConstraint(pParse,E.pExpr);}
+tcons ::= FOREIGN KEY LP idxlist(FA) RP
+          REFERENCES nm(T) idxlist_opt(TA) refargs(R) defer_subclause_opt(D). {
+    sqlite3CreateForeignKey(pParse, FA, &T, TA, R);
+    sqlite3DeferForeignKey(pParse, D);
+}
+%type defer_subclause_opt {int}
+defer_subclause_opt(A) ::= .                    {A = 0;}
+defer_subclause_opt(A) ::= defer_subclause(X).  {A = X;}
+
+// The following is a non-standard extension that allows us to declare the
+// default behavior when there is a constraint conflict.
+//
+%type onconf {int}
+%type orconf {u8}
+%type resolvetype {int}
+onconf(A) ::= .                              {A = OE_Default;}
+onconf(A) ::= ON CONFLICT resolvetype(X).    {A = X;}
+orconf(A) ::= .                              {A = OE_Default;}
+orconf(A) ::= OR resolvetype(X).             {A = (u8)X;}
+resolvetype(A) ::= raisetype(X).             {A = X;}
+resolvetype(A) ::= IGNORE.                   {A = OE_Ignore;}
+resolvetype(A) ::= REPLACE.                  {A = OE_Replace;}
+
+////////////////////////// The DROP TABLE /////////////////////////////////////
+//
+cmd ::= DROP TABLE ifexists(E) fullname(X). {
+  sqlite3DropTable(pParse, X, 0, E);
+}
+%type ifexists {int}
+ifexists(A) ::= IF EXISTS.   {A = 1;}
+ifexists(A) ::= .            {A = 0;}
+
+///////////////////// The CREATE VIEW statement /////////////////////////////
+//
+%ifndef SQLITE_OMIT_VIEW
+cmd ::= createkw(X) temp(T) VIEW ifnotexists(E) nm(Y) dbnm(Z) AS select(S). {
+  sqlite3CreateView(pParse, &X, &Y, &Z, S, T, E);
+}
+cmd ::= DROP VIEW ifexists(E) fullname(X). {
+  sqlite3DropTable(pParse, X, 1, E);
+}
+%endif  SQLITE_OMIT_VIEW
+
+//////////////////////// The SELECT statement /////////////////////////////////
+//
+cmd ::= select(X).  {
+  SelectDest dest = {SRT_Output, 0, 0, 0, 0};
+  sqlite3Select(pParse, X, &dest);
+  sqlite3SelectDelete(pParse->db, X);
+}
+
+%type select {Select*}
+%destructor select {sqlite3SelectDelete(pParse->db, $$);}
+%type oneselect {Select*}
+%destructor oneselect {sqlite3SelectDelete(pParse->db, $$);}
+
+select(A) ::= oneselect(X).                      {A = X;}
+%ifndef SQLITE_OMIT_COMPOUND_SELECT
+select(A) ::= select(X) multiselect_op(Y) oneselect(Z).  {
+  if( Z ){
+    Z->op = (u8)Y;
+    Z->pPrior = X;
+  }else{
+    sqlite3SelectDelete(pParse->db, X);
+  }
+  A = Z;
+}
+%type multiselect_op {int}
+multiselect_op(A) ::= UNION(OP).             {A = @OP;}
+multiselect_op(A) ::= UNION ALL.             {A = TK_ALL;}
+multiselect_op(A) ::= EXCEPT|INTERSECT(OP).  {A = @OP;}
+%endif SQLITE_OMIT_COMPOUND_SELECT
+oneselect(A) ::= SELECT distinct(D) selcollist(W) from(X) where_opt(Y)
+                 groupby_opt(P) having_opt(Q) orderby_opt(Z) limit_opt(L). {
+  A = sqlite3SelectNew(pParse,W,X,Y,P,Q,Z,D,L.pLimit,L.pOffset);
+}
+
+// The "distinct" nonterminal is true (1) if the DISTINCT keyword is
+// present and false (0) if it is not.
+//
+%type distinct {int}
+distinct(A) ::= DISTINCT.   {A = 1;}
+distinct(A) ::= ALL.        {A = 0;}
+distinct(A) ::= .           {A = 0;}
+
+// selcollist is a list of expressions that are to become the return
+// values of the SELECT statement.  The "*" in statements like
+// "SELECT * FROM ..." is encoded as a special expression with an
+// opcode of TK_ALL.
+//
+%type selcollist {ExprList*}
+%destructor selcollist {sqlite3ExprListDelete(pParse->db, $$);}
+%type sclp {ExprList*}
+%destructor sclp {sqlite3ExprListDelete(pParse->db, $$);}
+sclp(A) ::= selcollist(X) COMMA.             {A = X;}
+sclp(A) ::= .                                {A = 0;}
+selcollist(A) ::= sclp(P) expr(X) as(Y).     {
+   A = sqlite3ExprListAppend(pParse, P, X.pExpr);
+   if( Y.n>0 ) sqlite3ExprListSetName(pParse, A, &Y, 1);
+   sqlite3ExprListSetSpan(pParse,A,&X);
+}
+selcollist(A) ::= sclp(P) STAR. {
+  Expr *p = sqlite3Expr(pParse->db, TK_ALL, 0);
+  A = sqlite3ExprListAppend(pParse, P, p);
+}
+selcollist(A) ::= sclp(P) nm(X) DOT STAR(Y). {
+  Expr *pRight = sqlite3PExpr(pParse, TK_ALL, 0, 0, &Y);
+  Expr *pLeft = sqlite3PExpr(pParse, TK_ID, 0, 0, &X);
+  Expr *pDot = sqlite3PExpr(pParse, TK_DOT, pLeft, pRight, 0);
+  A = sqlite3ExprListAppend(pParse,P, pDot);
+}
+
+// An option "AS <id>" phrase that can follow one of the expressions that
+// define the result set, or one of the tables in the FROM clause.
+//
+%type as {Token}
+as(X) ::= AS nm(Y).    {X = Y;}
+as(X) ::= ids(Y).      {X = Y;}
+as(X) ::= .            {X.n = 0;}
+
+
+%type seltablist {SrcList*}
+%destructor seltablist {sqlite3SrcListDelete(pParse->db, $$);}
+%type stl_prefix {SrcList*}
+%destructor stl_prefix {sqlite3SrcListDelete(pParse->db, $$);}
+%type from {SrcList*}
+%destructor from {sqlite3SrcListDelete(pParse->db, $$);}
+
+// A complete FROM clause.
+//
+from(A) ::= .                {A = sqlite3DbMallocZero(pParse->db, sizeof(*A));}
+from(A) ::= FROM seltablist(X). {
+  A = X;
+  sqlite3SrcListShiftJoinType(A);
+}
+
+// "seltablist" is a "Select Table List" - the content of the FROM clause
+// in a SELECT statement.  "stl_prefix" is a prefix of this list.
+//
+stl_prefix(A) ::= seltablist(X) joinop(Y).    {
+   A = X;
+   if( ALWAYS(A && A->nSrc>0) ) A->a[A->nSrc-1].jointype = (u8)Y;
+}
+stl_prefix(A) ::= .                           {A = 0;}
+seltablist(A) ::= stl_prefix(X) nm(Y) dbnm(D) as(Z) indexed_opt(I) on_opt(N) using_opt(U). {
+  A = sqlite3SrcListAppendFromTerm(pParse,X,&Y,&D,&Z,0,N,U);
+  sqlite3SrcListIndexedBy(pParse, A, &I);
+}
+%ifndef SQLITE_OMIT_SUBQUERY
+  seltablist(A) ::= stl_prefix(X) LP select(S) RP
+                    as(Z) on_opt(N) using_opt(U). {
+    A = sqlite3SrcListAppendFromTerm(pParse,X,0,0,&Z,S,N,U);
+  }
+  seltablist(A) ::= stl_prefix(X) LP seltablist(F) RP
+                    as(Z) on_opt(N) using_opt(U). {
+    if( X==0 && Z.n==0 && N==0 && U==0 ){
+      A = F;
+    }else{
+      Select *pSubquery;
+      sqlite3SrcListShiftJoinType(F);
+      pSubquery = sqlite3SelectNew(pParse,0,F,0,0,0,0,0,0,0);
+      A = sqlite3SrcListAppendFromTerm(pParse,X,0,0,&Z,pSubquery,N,U);
+    }
+  }
+  
+  // A seltablist_paren nonterminal represents anything in a FROM that
+  // is contained inside parentheses.  This can be either a subquery or
+  // a grouping of table and subqueries.
+  //
+//  %type seltablist_paren {Select*}
+//  %destructor seltablist_paren {sqlite3SelectDelete(pParse->db, $$);}
+//  seltablist_paren(A) ::= select(S).      {A = S;}
+//  seltablist_paren(A) ::= seltablist(F).  {
+//     sqlite3SrcListShiftJoinType(F);
+//     A = sqlite3SelectNew(pParse,0,F,0,0,0,0,0,0,0);
+//  }
+%endif  SQLITE_OMIT_SUBQUERY
+
+%type dbnm {Token}
+dbnm(A) ::= .          {A.z=0; A.n=0;}
+dbnm(A) ::= DOT nm(X). {A = X;}
+
+%type fullname {SrcList*}
+%destructor fullname {sqlite3SrcListDelete(pParse->db, $$);}
+fullname(A) ::= nm(X) dbnm(Y).  {A = sqlite3SrcListAppend(pParse->db,0,&X,&Y);}
+
+%type joinop {int}
+%type joinop2 {int}
+joinop(X) ::= COMMA|JOIN.              { X = JT_INNER; }
+joinop(X) ::= JOIN_KW(A) JOIN.         { X = sqlite3JoinType(pParse,&A,0,0); }
+joinop(X) ::= JOIN_KW(A) nm(B) JOIN.   { X = sqlite3JoinType(pParse,&A,&B,0); }
+joinop(X) ::= JOIN_KW(A) nm(B) nm(C) JOIN.
+                                       { X = sqlite3JoinType(pParse,&A,&B,&C); }
+
+%type on_opt {Expr*}
+%destructor on_opt {sqlite3ExprDelete(pParse->db, $$);}
+on_opt(N) ::= ON expr(E).   {N = E.pExpr;}
+on_opt(N) ::= .             {N = 0;}
+
+// Note that this block abuses the Token type just a little. If there is
+// no "INDEXED BY" clause, the returned token is empty (z==0 && n==0). If
+// there is an INDEXED BY clause, then the token is populated as per normal,
+// with z pointing to the token data and n containing the number of bytes
+// in the token.
+//
+// If there is a "NOT INDEXED" clause, then (z==0 && n==1), which is 
+// normally illegal. The sqlite3SrcListIndexedBy() function 
+// recognizes and interprets this as a special case.
+//
+%type indexed_opt {Token}
+indexed_opt(A) ::= .                 {A.z=0; A.n=0;}
+indexed_opt(A) ::= INDEXED BY nm(X). {A = X;}
+indexed_opt(A) ::= NOT INDEXED.      {A.z=0; A.n=1;}
+
+%type using_opt {IdList*}
+%destructor using_opt {sqlite3IdListDelete(pParse->db, $$);}
+using_opt(U) ::= USING LP inscollist(L) RP.  {U = L;}
+using_opt(U) ::= .                        {U = 0;}
+
+
+%type orderby_opt {ExprList*}
+%destructor orderby_opt {sqlite3ExprListDelete(pParse->db, $$);}
+%type sortlist {ExprList*}
+%destructor sortlist {sqlite3ExprListDelete(pParse->db, $$);}
+%type sortitem {Expr*}
+%destructor sortitem {sqlite3ExprDelete(pParse->db, $$);}
+
+orderby_opt(A) ::= .                          {A = 0;}
+orderby_opt(A) ::= ORDER BY sortlist(X).      {A = X;}
+sortlist(A) ::= sortlist(X) COMMA sortitem(Y) sortorder(Z). {
+  A = sqlite3ExprListAppend(pParse,X,Y);
+  if( A ) A->a[A->nExpr-1].sortOrder = (u8)Z;
+}
+sortlist(A) ::= sortitem(Y) sortorder(Z). {
+  A = sqlite3ExprListAppend(pParse,0,Y);
+  if( A && ALWAYS(A->a) ) A->a[0].sortOrder = (u8)Z;
+}
+sortitem(A) ::= expr(X).   {A = X.pExpr;}
+
+%type sortorder {int}
+
+sortorder(A) ::= ASC.           {A = SQLITE_SO_ASC;}
+sortorder(A) ::= DESC.          {A = SQLITE_SO_DESC;}
+sortorder(A) ::= .              {A = SQLITE_SO_ASC;}
+
+%type groupby_opt {ExprList*}
+%destructor groupby_opt {sqlite3ExprListDelete(pParse->db, $$);}
+groupby_opt(A) ::= .                      {A = 0;}
+groupby_opt(A) ::= GROUP BY nexprlist(X). {A = X;}
+
+%type having_opt {Expr*}
+%destructor having_opt {sqlite3ExprDelete(pParse->db, $$);}
+having_opt(A) ::= .                {A = 0;}
+having_opt(A) ::= HAVING expr(X).  {A = X.pExpr;}
+
+%type limit_opt {struct LimitVal}
+
+// The destructor for limit_opt will never fire in the current grammar.
+// The limit_opt non-terminal only occurs at the end of a single production
+// rule for SELECT statements.  As soon as the rule that create the 
+// limit_opt non-terminal reduces, the SELECT statement rule will also
+// reduce.  So there is never a limit_opt non-terminal on the stack 
+// except as a transient.  So there is never anything to destroy.
+//
+//%destructor limit_opt {
+//  sqlite3ExprDelete(pParse->db, $$.pLimit);
+//  sqlite3ExprDelete(pParse->db, $$.pOffset);
+//}
+limit_opt(A) ::= .                    {A.pLimit = 0; A.pOffset = 0;}
+limit_opt(A) ::= LIMIT expr(X).       {A.pLimit = X.pExpr; A.pOffset = 0;}
+limit_opt(A) ::= LIMIT expr(X) OFFSET expr(Y). 
+                                      {A.pLimit = X.pExpr; A.pOffset = Y.pExpr;}
+limit_opt(A) ::= LIMIT expr(X) COMMA expr(Y). 
+                                      {A.pOffset = X.pExpr; A.pLimit = Y.pExpr;}
+
+/////////////////////////// The DELETE statement /////////////////////////////
+//
+%ifdef SQLITE_ENABLE_UPDATE_DELETE_LIMIT
+cmd ::= DELETE FROM fullname(X) indexed_opt(I) where_opt(W) 
+        orderby_opt(O) limit_opt(L). {
+  sqlite3SrcListIndexedBy(pParse, X, &I);
+  W = sqlite3LimitWhere(pParse, X, W, O, L.pLimit, L.pOffset, "DELETE");
+  sqlite3DeleteFrom(pParse,X,W);
+}
+%endif
+%ifndef SQLITE_ENABLE_UPDATE_DELETE_LIMIT
+cmd ::= DELETE FROM fullname(X) indexed_opt(I) where_opt(W). {
+  sqlite3SrcListIndexedBy(pParse, X, &I);
+  sqlite3DeleteFrom(pParse,X,W);
+}
+%endif
+
+%type where_opt {Expr*}
+%destructor where_opt {sqlite3ExprDelete(pParse->db, $$);}
+
+where_opt(A) ::= .                    {A = 0;}
+where_opt(A) ::= WHERE expr(X).       {A = X.pExpr;}
+
+////////////////////////// The UPDATE command ////////////////////////////////
+//
+%ifdef SQLITE_ENABLE_UPDATE_DELETE_LIMIT
+cmd ::= UPDATE orconf(R) fullname(X) indexed_opt(I) SET setlist(Y) where_opt(W) orderby_opt(O) limit_opt(L).  {
+  sqlite3SrcListIndexedBy(pParse, X, &I);
+  sqlite3ExprListCheckLength(pParse,Y,"set list"); 
+  W = sqlite3LimitWhere(pParse, X, W, O, L.pLimit, L.pOffset, "UPDATE");
+  sqlite3Update(pParse,X,Y,W,R);
+}
+%endif
+%ifndef SQLITE_ENABLE_UPDATE_DELETE_LIMIT
+cmd ::= UPDATE orconf(R) fullname(X) indexed_opt(I) SET setlist(Y) where_opt(W).  {
+  sqlite3SrcListIndexedBy(pParse, X, &I);
+  sqlite3ExprListCheckLength(pParse,Y,"set list"); 
+  sqlite3Update(pParse,X,Y,W,R);
+}
+%endif
+
+%type setlist {ExprList*}
+%destructor setlist {sqlite3ExprListDelete(pParse->db, $$);}
+
+setlist(A) ::= setlist(Z) COMMA nm(X) EQ expr(Y). {
+  A = sqlite3ExprListAppend(pParse, Z, Y.pExpr);
+  sqlite3ExprListSetName(pParse, A, &X, 1);
+}
+setlist(A) ::= nm(X) EQ expr(Y). {
+  A = sqlite3ExprListAppend(pParse, 0, Y.pExpr);
+  sqlite3ExprListSetName(pParse, A, &X, 1);
+}
+
+////////////////////////// The INSERT command /////////////////////////////////
+//
+cmd ::= insert_cmd(R) INTO fullname(X) inscollist_opt(F) 
+        VALUES LP itemlist(Y) RP.
+            {sqlite3Insert(pParse, X, Y, 0, F, R);}
+cmd ::= insert_cmd(R) INTO fullname(X) inscollist_opt(F) select(S).
+            {sqlite3Insert(pParse, X, 0, S, F, R);}
+cmd ::= insert_cmd(R) INTO fullname(X) inscollist_opt(F) DEFAULT VALUES.
+            {sqlite3Insert(pParse, X, 0, 0, F, R);}
+
+%type insert_cmd {u8}
+insert_cmd(A) ::= INSERT orconf(R).   {A = R;}
+insert_cmd(A) ::= REPLACE.            {A = OE_Replace;}
+
+
+%type itemlist {ExprList*}
+%destructor itemlist {sqlite3ExprListDelete(pParse->db, $$);}
+
+itemlist(A) ::= itemlist(X) COMMA expr(Y).
+    {A = sqlite3ExprListAppend(pParse,X,Y.pExpr);}
+itemlist(A) ::= expr(X).
+    {A = sqlite3ExprListAppend(pParse,0,X.pExpr);}
+
+%type inscollist_opt {IdList*}
+%destructor inscollist_opt {sqlite3IdListDelete(pParse->db, $$);}
+%type inscollist {IdList*}
+%destructor inscollist {sqlite3IdListDelete(pParse->db, $$);}
+
+inscollist_opt(A) ::= .                       {A = 0;}
+inscollist_opt(A) ::= LP inscollist(X) RP.    {A = X;}
+inscollist(A) ::= inscollist(X) COMMA nm(Y).
+    {A = sqlite3IdListAppend(pParse->db,X,&Y);}
+inscollist(A) ::= nm(Y).
+    {A = sqlite3IdListAppend(pParse->db,0,&Y);}
+
+/////////////////////////// Expression Processing /////////////////////////////
+//
+
+%type expr {ExprSpan}
+%destructor expr {sqlite3ExprDelete(pParse->db, $$.pExpr);}
+%type term {ExprSpan}
+%destructor term {sqlite3ExprDelete(pParse->db, $$.pExpr);}
+
+%include {
+  /* This is a utility routine used to set the ExprSpan.zStart and
+  ** ExprSpan.zEnd values of pOut so that the span covers the complete
+  ** range of text beginning with pStart and going to the end of pEnd.
+  */
+  static void spanSet(ExprSpan *pOut, Token *pStart, Token *pEnd){
+    pOut->zStart = pStart->z;
+    pOut->zEnd = &pEnd->z[pEnd->n];
+  }
+
+  /* Construct a new Expr object from a single identifier.  Use the
+  ** new Expr to populate pOut.  Set the span of pOut to be the identifier
+  ** that created the expression.
+  */
+  static void spanExpr(ExprSpan *pOut, Parse *pParse, int op, Token *pValue){
+    pOut->pExpr = sqlite3PExpr(pParse, op, 0, 0, pValue);
+    pOut->zStart = pValue->z;
+    pOut->zEnd = &pValue->z[pValue->n];
+  }
+}
+
+expr(A) ::= term(X).             {A = X;}
+expr(A) ::= LP(B) expr(X) RP(E). {A.pExpr = X.pExpr; spanSet(&A,&B,&E);}
+term(A) ::= NULL(X).             {spanExpr(&A, pParse, @X, &X);}
+expr(A) ::= id(X).               {spanExpr(&A, pParse, TK_ID, &X);}
+expr(A) ::= JOIN_KW(X).          {spanExpr(&A, pParse, TK_ID, &X);}
+expr(A) ::= nm(X) DOT nm(Y). {
+  Expr *temp1 = sqlite3PExpr(pParse, TK_ID, 0, 0, &X);
+  Expr *temp2 = sqlite3PExpr(pParse, TK_ID, 0, 0, &Y);
+  A.pExpr = sqlite3PExpr(pParse, TK_DOT, temp1, temp2, 0);
+  spanSet(&A,&X,&Y);
+}
+expr(A) ::= nm(X) DOT nm(Y) DOT nm(Z). {
+  Expr *temp1 = sqlite3PExpr(pParse, TK_ID, 0, 0, &X);
+  Expr *temp2 = sqlite3PExpr(pParse, TK_ID, 0, 0, &Y);
+  Expr *temp3 = sqlite3PExpr(pParse, TK_ID, 0, 0, &Z);
+  Expr *temp4 = sqlite3PExpr(pParse, TK_DOT, temp2, temp3, 0);
+  A.pExpr = sqlite3PExpr(pParse, TK_DOT, temp1, temp4, 0);
+  spanSet(&A,&X,&Z);
+}
+term(A) ::= INTEGER|FLOAT|BLOB(X).  {spanExpr(&A, pParse, @X, &X);}
+term(A) ::= STRING(X).              {spanExpr(&A, pParse, @X, &X);}
+expr(A) ::= REGISTER(X).     {
+  /* When doing a nested parse, one can include terms in an expression
+  ** that look like this:   #1 #2 ...  These terms refer to registers
+  ** in the virtual machine.  #N is the N-th register. */
+  if( pParse->nested==0 ){
+    sqlite3ErrorMsg(pParse, "near \"%T\": syntax error", &X);
+    A.pExpr = 0;
+  }else{
+    A.pExpr = sqlite3PExpr(pParse, TK_REGISTER, 0, 0, &X);
+    if( A.pExpr ) sqlite3GetInt32(&X.z[1], &A.pExpr->iTable);
+  }
+  spanSet(&A, &X, &X);
+}
+expr(A) ::= VARIABLE(X).     {
+  spanExpr(&A, pParse, TK_VARIABLE, &X);
+  sqlite3ExprAssignVarNumber(pParse, A.pExpr);
+  spanSet(&A, &X, &X);
+}
+expr(A) ::= expr(E) COLLATE ids(C). {
+  A.pExpr = sqlite3ExprSetCollByToken(pParse, E.pExpr, &C);
+  A.zStart = E.zStart;
+  A.zEnd = &C.z[C.n];
+}
+%ifndef SQLITE_OMIT_CAST
+expr(A) ::= CAST(X) LP expr(E) AS typetoken(T) RP(Y). {
+  A.pExpr = sqlite3PExpr(pParse, TK_CAST, E.pExpr, 0, &T);
+  spanSet(&A,&X,&Y);
+}
+%endif  SQLITE_OMIT_CAST
+expr(A) ::= ID(X) LP distinct(D) exprlist(Y) RP(E). {
+  if( Y && Y->nExpr>pParse->db->aLimit[SQLITE_LIMIT_FUNCTION_ARG] ){
+    sqlite3ErrorMsg(pParse, "too many arguments on function %T", &X);
+  }
+  A.pExpr = sqlite3ExprFunction(pParse, Y, &X);
+  spanSet(&A,&X,&E);
+  if( D && A.pExpr ){
+    A.pExpr->flags |= EP_Distinct;
+  }
+}
+expr(A) ::= ID(X) LP STAR RP(E). {
+  A.pExpr = sqlite3ExprFunction(pParse, 0, &X);
+  spanSet(&A,&X,&E);
+}
+term(A) ::= CTIME_KW(OP). {
+  /* The CURRENT_TIME, CURRENT_DATE, and CURRENT_TIMESTAMP values are
+  ** treated as functions that return constants */
+  A.pExpr = sqlite3ExprFunction(pParse, 0,&OP);
+  if( A.pExpr ){
+    A.pExpr->op = TK_CONST_FUNC;  
+  }
+  spanSet(&A, &OP, &OP);
+}
+
+%include {
+  /* This routine constructs a binary expression node out of two ExprSpan
+  ** objects and uses the result to populate a new ExprSpan object.
+  */
+  static void spanBinaryExpr(
+    ExprSpan *pOut,     /* Write the result here */
+    Parse *pParse,      /* The parsing context.  Errors accumulate here */
+    int op,             /* The binary operation */
+    ExprSpan *pLeft,    /* The left operand */
+    ExprSpan *pRight    /* The right operand */
+  ){
+    pOut->pExpr = sqlite3PExpr(pParse, op, pLeft->pExpr, pRight->pExpr, 0);
+    pOut->zStart = pLeft->zStart;
+    pOut->zEnd = pRight->zEnd;
+  }
+}
+
+expr(A) ::= expr(X) AND(OP) expr(Y).    {spanBinaryExpr(&A,pParse,@OP,&X,&Y);}
+expr(A) ::= expr(X) OR(OP) expr(Y).     {spanBinaryExpr(&A,pParse,@OP,&X,&Y);}
+expr(A) ::= expr(X) LT|GT|GE|LE(OP) expr(Y).
+                                        {spanBinaryExpr(&A,pParse,@OP,&X,&Y);}
+expr(A) ::= expr(X) EQ|NE(OP) expr(Y).  {spanBinaryExpr(&A,pParse,@OP,&X,&Y);}
+expr(A) ::= expr(X) BITAND|BITOR|LSHIFT|RSHIFT(OP) expr(Y).
+                                        {spanBinaryExpr(&A,pParse,@OP,&X,&Y);}
+expr(A) ::= expr(X) PLUS|MINUS(OP) expr(Y).
+                                        {spanBinaryExpr(&A,pParse,@OP,&X,&Y);}
+expr(A) ::= expr(X) STAR|SLASH|REM(OP) expr(Y).
+                                        {spanBinaryExpr(&A,pParse,@OP,&X,&Y);}
+expr(A) ::= expr(X) CONCAT(OP) expr(Y). {spanBinaryExpr(&A,pParse,@OP,&X,&Y);}
+%type likeop {struct LikeOp}
+likeop(A) ::= LIKE_KW(X).     {A.eOperator = X; A.not = 0;}
+likeop(A) ::= NOT LIKE_KW(X). {A.eOperator = X; A.not = 1;}
+likeop(A) ::= MATCH(X).       {A.eOperator = X; A.not = 0;}
+likeop(A) ::= NOT MATCH(X).   {A.eOperator = X; A.not = 1;}
+expr(A) ::= expr(X) likeop(OP) expr(Y).  [LIKE_KW]  {
+  ExprList *pList;
+  pList = sqlite3ExprListAppend(pParse,0, Y.pExpr);
+  pList = sqlite3ExprListAppend(pParse,pList, X.pExpr);
+  A.pExpr = sqlite3ExprFunction(pParse, pList, &OP.eOperator);
+  if( OP.not ) A.pExpr = sqlite3PExpr(pParse, TK_NOT, A.pExpr, 0, 0);
+  A.zStart = X.zStart;
+  A.zEnd = Y.zEnd;
+  if( A.pExpr ) A.pExpr->flags |= EP_InfixFunc;
+}
+expr(A) ::= expr(X) likeop(OP) expr(Y) ESCAPE expr(E).  [LIKE_KW]  {
+  ExprList *pList;
+  pList = sqlite3ExprListAppend(pParse,0, Y.pExpr);
+  pList = sqlite3ExprListAppend(pParse,pList, X.pExpr);
+  pList = sqlite3ExprListAppend(pParse,pList, E.pExpr);
+  A.pExpr = sqlite3ExprFunction(pParse, pList, &OP.eOperator);
+  if( OP.not ) A.pExpr = sqlite3PExpr(pParse, TK_NOT, A.pExpr, 0, 0);
+  A.zStart = X.zStart;
+  A.zEnd = E.zEnd;
+  if( A.pExpr ) A.pExpr->flags |= EP_InfixFunc;
+}
+
+%include {
+  /* Construct an expression node for a unary postfix operator
+  */
+  static void spanUnaryPostfix(
+    ExprSpan *pOut,        /* Write the new expression node here */
+    Parse *pParse,         /* Parsing context to record errors */
+    int op,                /* The operator */
+    ExprSpan *pOperand,    /* The operand */
+    Token *pPostOp         /* The operand token for setting the span */
+  ){
+    pOut->pExpr = sqlite3PExpr(pParse, op, pOperand->pExpr, 0, 0);
+    pOut->zStart = pOperand->zStart;
+    pOut->zEnd = &pPostOp->z[pPostOp->n];
+  }                           
+}
+
+expr(A) ::= expr(X) ISNULL|NOTNULL(E).   {spanUnaryPostfix(&A,pParse,@E,&X,&E);}
+expr(A) ::= expr(X) NOT NULL(E). {spanUnaryPostfix(&A,pParse,TK_NOTNULL,&X,&E);}
+
+%include {
+  /* A routine to convert a binary TK_IS or TK_ISNOT expression into a
+  ** unary TK_ISNULL or TK_NOTNULL expression. */
+  static void binaryToUnaryIfNull(Parse *pParse, Expr *pY, Expr *pA, int op){
+    sqlite3 *db = pParse->db;
+    if( db->mallocFailed==0 && pY->op==TK_NULL ){
+      pA->op = (u8)op;
+      sqlite3ExprDelete(db, pA->pRight);
+      pA->pRight = 0;
+    }
+  }
+}
+
+//    expr1 IS expr2
+//    expr1 IS NOT expr2
+//
+// If expr2 is NULL then code as TK_ISNULL or TK_NOTNULL.  If expr2
+// is any other expression, code as TK_IS or TK_ISNOT.
+// 
+expr(A) ::= expr(X) IS expr(Y).     {
+  spanBinaryExpr(&A,pParse,TK_IS,&X,&Y);
+  binaryToUnaryIfNull(pParse, Y.pExpr, A.pExpr, TK_ISNULL);
+}
+expr(A) ::= expr(X) IS NOT expr(Y). {
+  spanBinaryExpr(&A,pParse,TK_ISNOT,&X,&Y);
+  binaryToUnaryIfNull(pParse, Y.pExpr, A.pExpr, TK_NOTNULL);
+}
+
+%include {
+  /* Construct an expression node for a unary prefix operator
+  */
+  static void spanUnaryPrefix(
+    ExprSpan *pOut,        /* Write the new expression node here */
+    Parse *pParse,         /* Parsing context to record errors */
+    int op,                /* The operator */
+    ExprSpan *pOperand,    /* The operand */
+    Token *pPreOp         /* The operand token for setting the span */
+  ){
+    pOut->pExpr = sqlite3PExpr(pParse, op, pOperand->pExpr, 0, 0);
+    pOut->zStart = pPreOp->z;
+    pOut->zEnd = pOperand->zEnd;
+  }
+}
+
+
+
+expr(A) ::= NOT(B) expr(X).    {spanUnaryPrefix(&A,pParse,@B,&X,&B);}
+expr(A) ::= BITNOT(B) expr(X). {spanUnaryPrefix(&A,pParse,@B,&X,&B);}
+expr(A) ::= MINUS(B) expr(X). [BITNOT]
+                               {spanUnaryPrefix(&A,pParse,TK_UMINUS,&X,&B);}
+expr(A) ::= PLUS(B) expr(X). [BITNOT]
+                               {spanUnaryPrefix(&A,pParse,TK_UPLUS,&X,&B);}
+
+%type between_op {int}
+between_op(A) ::= BETWEEN.     {A = 0;}
+between_op(A) ::= NOT BETWEEN. {A = 1;}
+expr(A) ::= expr(W) between_op(N) expr(X) AND expr(Y). [BETWEEN] {
+  ExprList *pList = sqlite3ExprListAppend(pParse,0, X.pExpr);
+  pList = sqlite3ExprListAppend(pParse,pList, Y.pExpr);
+  A.pExpr = sqlite3PExpr(pParse, TK_BETWEEN, W.pExpr, 0, 0);
+  if( A.pExpr ){
+    A.pExpr->x.pList = pList;
+  }else{
+    sqlite3ExprListDelete(pParse->db, pList);
+  } 
+  if( N ) A.pExpr = sqlite3PExpr(pParse, TK_NOT, A.pExpr, 0, 0);
+  A.zStart = W.zStart;
+  A.zEnd = Y.zEnd;
+}
+%ifndef SQLITE_OMIT_SUBQUERY
+  %type in_op {int}
+  in_op(A) ::= IN.      {A = 0;}
+  in_op(A) ::= NOT IN.  {A = 1;}
+  expr(A) ::= expr(X) in_op(N) LP exprlist(Y) RP(E). [IN] {
+    if( Y==0 ){
+      /* Expressions of the form
+      **
+      **      expr1 IN ()
+      **      expr1 NOT IN ()
+      **
+      ** simplify to constants 0 (false) and 1 (true), respectively,
+      ** regardless of the value of expr1.
+      */
+      A.pExpr = sqlite3PExpr(pParse, TK_INTEGER, 0, 0, &sqlite3IntTokens[N]);
+      sqlite3ExprDelete(pParse->db, X.pExpr);
+    }else{
+      A.pExpr = sqlite3PExpr(pParse, TK_IN, X.pExpr, 0, 0);
+      if( A.pExpr ){
+        A.pExpr->x.pList = Y;
+        sqlite3ExprSetHeight(pParse, A.pExpr);
+      }else{
+        sqlite3ExprListDelete(pParse->db, Y);
+      }
+      if( N ) A.pExpr = sqlite3PExpr(pParse, TK_NOT, A.pExpr, 0, 0);
+    }
+    A.zStart = X.zStart;
+    A.zEnd = &E.z[E.n];
+  }
+  expr(A) ::= LP(B) select(X) RP(E). {
+    A.pExpr = sqlite3PExpr(pParse, TK_SELECT, 0, 0, 0);
+    if( A.pExpr ){
+      A.pExpr->x.pSelect = X;
+      ExprSetProperty(A.pExpr, EP_xIsSelect);
+      sqlite3ExprSetHeight(pParse, A.pExpr);
+    }else{
+      sqlite3SelectDelete(pParse->db, X);
+    }
+    A.zStart = B.z;
+    A.zEnd = &E.z[E.n];
+  }
+  expr(A) ::= expr(X) in_op(N) LP select(Y) RP(E).  [IN] {
+    A.pExpr = sqlite3PExpr(pParse, TK_IN, X.pExpr, 0, 0);
+    if( A.pExpr ){
+      A.pExpr->x.pSelect = Y;
+      ExprSetProperty(A.pExpr, EP_xIsSelect);
+      sqlite3ExprSetHeight(pParse, A.pExpr);
+    }else{
+      sqlite3SelectDelete(pParse->db, Y);
+    }
+    if( N ) A.pExpr = sqlite3PExpr(pParse, TK_NOT, A.pExpr, 0, 0);
+    A.zStart = X.zStart;
+    A.zEnd = &E.z[E.n];
+  }
+  expr(A) ::= expr(X) in_op(N) nm(Y) dbnm(Z). [IN] {
+    SrcList *pSrc = sqlite3SrcListAppend(pParse->db, 0,&Y,&Z);
+    A.pExpr = sqlite3PExpr(pParse, TK_IN, X.pExpr, 0, 0);
+    if( A.pExpr ){
+      A.pExpr->x.pSelect = sqlite3SelectNew(pParse, 0,pSrc,0,0,0,0,0,0,0);
+      ExprSetProperty(A.pExpr, EP_xIsSelect);
+      sqlite3ExprSetHeight(pParse, A.pExpr);
+    }else{
+      sqlite3SrcListDelete(pParse->db, pSrc);
+    }
+    if( N ) A.pExpr = sqlite3PExpr(pParse, TK_NOT, A.pExpr, 0, 0);
+    A.zStart = X.zStart;
+    A.zEnd = Z.z ? &Z.z[Z.n] : &Y.z[Y.n];
+  }
+  expr(A) ::= EXISTS(B) LP select(Y) RP(E). {
+    Expr *p = A.pExpr = sqlite3PExpr(pParse, TK_EXISTS, 0, 0, 0);
+    if( p ){
+      p->x.pSelect = Y;
+      ExprSetProperty(p, EP_xIsSelect);
+      sqlite3ExprSetHeight(pParse, p);
+    }else{
+      sqlite3SelectDelete(pParse->db, Y);
+    }
+    A.zStart = B.z;
+    A.zEnd = &E.z[E.n];
+  }
+%endif SQLITE_OMIT_SUBQUERY
+
+/* CASE expressions */
+expr(A) ::= CASE(C) case_operand(X) case_exprlist(Y) case_else(Z) END(E). {
+  A.pExpr = sqlite3PExpr(pParse, TK_CASE, X, Z, 0);
+  if( A.pExpr ){
+    A.pExpr->x.pList = Y;
+    sqlite3ExprSetHeight(pParse, A.pExpr);
+  }else{
+    sqlite3ExprListDelete(pParse->db, Y);
+  }
+  A.zStart = C.z;
+  A.zEnd = &E.z[E.n];
+}
+%type case_exprlist {ExprList*}
+%destructor case_exprlist {sqlite3ExprListDelete(pParse->db, $$);}
+case_exprlist(A) ::= case_exprlist(X) WHEN expr(Y) THEN expr(Z). {
+  A = sqlite3ExprListAppend(pParse,X, Y.pExpr);
+  A = sqlite3ExprListAppend(pParse,A, Z.pExpr);
+}
+case_exprlist(A) ::= WHEN expr(Y) THEN expr(Z). {
+  A = sqlite3ExprListAppend(pParse,0, Y.pExpr);
+  A = sqlite3ExprListAppend(pParse,A, Z.pExpr);
+}
+%type case_else {Expr*}
+%destructor case_else {sqlite3ExprDelete(pParse->db, $$);}
+case_else(A) ::=  ELSE expr(X).         {A = X.pExpr;}
+case_else(A) ::=  .                     {A = 0;} 
+%type case_operand {Expr*}
+%destructor case_operand {sqlite3ExprDelete(pParse->db, $$);}
+case_operand(A) ::= expr(X).            {A = X.pExpr;} 
+case_operand(A) ::= .                   {A = 0;} 
+
+%type exprlist {ExprList*}
+%destructor exprlist {sqlite3ExprListDelete(pParse->db, $$);}
+%type nexprlist {ExprList*}
+%destructor nexprlist {sqlite3ExprListDelete(pParse->db, $$);}
+
+exprlist(A) ::= nexprlist(X).                {A = X;}
+exprlist(A) ::= .                            {A = 0;}
+nexprlist(A) ::= nexprlist(X) COMMA expr(Y).
+    {A = sqlite3ExprListAppend(pParse,X,Y.pExpr);}
+nexprlist(A) ::= expr(Y).
+    {A = sqlite3ExprListAppend(pParse,0,Y.pExpr);}
+
+
+///////////////////////////// The CREATE INDEX command ///////////////////////
+//
+cmd ::= createkw(S) uniqueflag(U) INDEX ifnotexists(NE) nm(X) dbnm(D)
+        ON nm(Y) LP idxlist(Z) RP(E). {
+  sqlite3CreateIndex(pParse, &X, &D, 
+                     sqlite3SrcListAppend(pParse->db,0,&Y,0), Z, U,
+                      &S, &E, SQLITE_SO_ASC, NE);
+}
+
+%type uniqueflag {int}
+uniqueflag(A) ::= UNIQUE.  {A = OE_Abort;}
+uniqueflag(A) ::= .        {A = OE_None;}
+
+%type idxlist {ExprList*}
+%destructor idxlist {sqlite3ExprListDelete(pParse->db, $$);}
+%type idxlist_opt {ExprList*}
+%destructor idxlist_opt {sqlite3ExprListDelete(pParse->db, $$);}
+
+idxlist_opt(A) ::= .                         {A = 0;}
+idxlist_opt(A) ::= LP idxlist(X) RP.         {A = X;}
+idxlist(A) ::= idxlist(X) COMMA nm(Y) collate(C) sortorder(Z).  {
+  Expr *p = 0;
+  if( C.n>0 ){
+    p = sqlite3Expr(pParse->db, TK_COLUMN, 0);
+    sqlite3ExprSetCollByToken(pParse, p, &C);
+  }
+  A = sqlite3ExprListAppend(pParse,X, p);
+  sqlite3ExprListSetName(pParse,A,&Y,1);
+  sqlite3ExprListCheckLength(pParse, A, "index");
+  if( A ) A->a[A->nExpr-1].sortOrder = (u8)Z;
+}
+idxlist(A) ::= nm(Y) collate(C) sortorder(Z). {
+  Expr *p = 0;
+  if( C.n>0 ){
+    p = sqlite3PExpr(pParse, TK_COLUMN, 0, 0, 0);
+    sqlite3ExprSetCollByToken(pParse, p, &C);
+  }
+  A = sqlite3ExprListAppend(pParse,0, p);
+  sqlite3ExprListSetName(pParse, A, &Y, 1);
+  sqlite3ExprListCheckLength(pParse, A, "index");
+  if( A ) A->a[A->nExpr-1].sortOrder = (u8)Z;
+}
+
+%type collate {Token}
+collate(C) ::= .                 {C.z = 0; C.n = 0;}
+collate(C) ::= COLLATE ids(X).   {C = X;}
+
+
+///////////////////////////// The DROP INDEX command /////////////////////////
+//
+cmd ::= DROP INDEX ifexists(E) fullname(X).   {sqlite3DropIndex(pParse, X, E);}
+
+///////////////////////////// The VACUUM command /////////////////////////////
+//
+%ifndef SQLITE_OMIT_VACUUM
+%ifndef SQLITE_OMIT_ATTACH
+cmd ::= VACUUM.                {sqlite3Vacuum(pParse);}
+cmd ::= VACUUM nm.             {sqlite3Vacuum(pParse);}
+%endif  SQLITE_OMIT_ATTACH
+%endif  SQLITE_OMIT_VACUUM
+
+///////////////////////////// The PRAGMA command /////////////////////////////
+//
+%ifndef SQLITE_OMIT_PRAGMA
+cmd ::= PRAGMA nm(X) dbnm(Z).                {sqlite3Pragma(pParse,&X,&Z,0,0);}
+cmd ::= PRAGMA nm(X) dbnm(Z) EQ nmnum(Y).    {sqlite3Pragma(pParse,&X,&Z,&Y,0);}
+cmd ::= PRAGMA nm(X) dbnm(Z) LP nmnum(Y) RP. {sqlite3Pragma(pParse,&X,&Z,&Y,0);}
+cmd ::= PRAGMA nm(X) dbnm(Z) EQ minus_num(Y). 
+                                             {sqlite3Pragma(pParse,&X,&Z,&Y,1);}
+cmd ::= PRAGMA nm(X) dbnm(Z) LP minus_num(Y) RP.
+                                             {sqlite3Pragma(pParse,&X,&Z,&Y,1);}
+
+nmnum(A) ::= plus_num(X).             {A = X;}
+nmnum(A) ::= nm(X).                   {A = X;}
+nmnum(A) ::= ON(X).                   {A = X;}
+nmnum(A) ::= DELETE(X).               {A = X;}
+nmnum(A) ::= DEFAULT(X).              {A = X;}
+%endif SQLITE_OMIT_PRAGMA
+plus_num(A) ::= plus_opt number(X).   {A = X;}
+minus_num(A) ::= MINUS number(X).     {A = X;}
+number(A) ::= INTEGER|FLOAT(X).       {A = X;}
+plus_opt ::= PLUS.
+plus_opt ::= .
+
+//////////////////////////// The CREATE TRIGGER command /////////////////////
+
+%ifndef SQLITE_OMIT_TRIGGER
+
+cmd ::= createkw trigger_decl(A) BEGIN trigger_cmd_list(S) END(Z). {
+  Token all;
+  all.z = A.z;
+  all.n = (int)(Z.z - A.z) + Z.n;
+  sqlite3FinishTrigger(pParse, S, &all);
+}
+
+trigger_decl(A) ::= temp(T) TRIGGER ifnotexists(NOERR) nm(B) dbnm(Z) 
+                    trigger_time(C) trigger_event(D)
+                    ON fullname(E) foreach_clause when_clause(G). {
+  sqlite3BeginTrigger(pParse, &B, &Z, C, D.a, D.b, E, G, T, NOERR);
+  A = (Z.n==0?B:Z);
+}
+
+%type trigger_time {int}
+trigger_time(A) ::= BEFORE.      { A = TK_BEFORE; }
+trigger_time(A) ::= AFTER.       { A = TK_AFTER;  }
+trigger_time(A) ::= INSTEAD OF.  { A = TK_INSTEAD;}
+trigger_time(A) ::= .            { A = TK_BEFORE; }
+
+%type trigger_event {struct TrigEvent}
+%destructor trigger_event {sqlite3IdListDelete(pParse->db, $$.b);}
+trigger_event(A) ::= DELETE|INSERT(OP).       {A.a = @OP; A.b = 0;}
+trigger_event(A) ::= UPDATE(OP).              {A.a = @OP; A.b = 0;}
+trigger_event(A) ::= UPDATE OF inscollist(X). {A.a = TK_UPDATE; A.b = X;}
+
+foreach_clause ::= .
+foreach_clause ::= FOR EACH ROW.
+
+%type when_clause {Expr*}
+%destructor when_clause {sqlite3ExprDelete(pParse->db, $$);}
+when_clause(A) ::= .             { A = 0; }
+when_clause(A) ::= WHEN expr(X). { A = X.pExpr; }
+
+%type trigger_cmd_list {TriggerStep*}
+%destructor trigger_cmd_list {sqlite3DeleteTriggerStep(pParse->db, $$);}
+trigger_cmd_list(A) ::= trigger_cmd_list(Y) trigger_cmd(X) SEMI. {
+  assert( Y!=0 );
+  Y->pLast->pNext = X;
+  Y->pLast = X;
+  A = Y;
+}
+trigger_cmd_list(A) ::= trigger_cmd(X) SEMI. { 
+  assert( X!=0 );
+  X->pLast = X;
+  A = X;
+}
+
+// Disallow qualified table names on INSERT, UPDATE, and DELETE statements
+// within a trigger.  The table to INSERT, UPDATE, or DELETE is always in 
+// the same database as the table that the trigger fires on.
+//
+%type trnm {Token}
+trnm(A) ::= nm(X).   {A = X;}
+trnm(A) ::= nm DOT nm(X). {
+  A = X;
+  sqlite3ErrorMsg(pParse, 
+        "qualified table names are not allowed on INSERT, UPDATE, and DELETE "
+        "statements within triggers");
+}
+
+// Disallow the INDEX BY and NOT INDEXED clauses on UPDATE and DELETE
+// statements within triggers.  We make a specific error message for this
+// since it is an exception to the default grammar rules.
+//
+tridxby ::= .
+tridxby ::= INDEXED BY nm. {
+  sqlite3ErrorMsg(pParse,
+        "the INDEXED BY clause is not allowed on UPDATE or DELETE statements "
+        "within triggers");
+}
+tridxby ::= NOT INDEXED. {
+  sqlite3ErrorMsg(pParse,
+        "the NOT INDEXED clause is not allowed on UPDATE or DELETE statements "
+        "within triggers");
+}
+
+
+
+%type trigger_cmd {TriggerStep*}
+%destructor trigger_cmd {sqlite3DeleteTriggerStep(pParse->db, $$);}
+// UPDATE 
+trigger_cmd(A) ::=
+   UPDATE orconf(R) trnm(X) tridxby SET setlist(Y) where_opt(Z).  
+   { A = sqlite3TriggerUpdateStep(pParse->db, &X, Y, Z, R); }
+
+// INSERT
+trigger_cmd(A) ::=
+   insert_cmd(R) INTO trnm(X) inscollist_opt(F) VALUES LP itemlist(Y) RP.  
+   {A = sqlite3TriggerInsertStep(pParse->db, &X, F, Y, 0, R);}
+
+trigger_cmd(A) ::= insert_cmd(R) INTO trnm(X) inscollist_opt(F) select(S).
+               {A = sqlite3TriggerInsertStep(pParse->db, &X, F, 0, S, R);}
+
+// DELETE
+trigger_cmd(A) ::= DELETE FROM trnm(X) tridxby where_opt(Y).
+               {A = sqlite3TriggerDeleteStep(pParse->db, &X, Y);}
+
+// SELECT
+trigger_cmd(A) ::= select(X).  {A = sqlite3TriggerSelectStep(pParse->db, X); }
+
+// The special RAISE expression that may occur in trigger programs
+expr(A) ::= RAISE(X) LP IGNORE RP(Y).  {
+  A.pExpr = sqlite3PExpr(pParse, TK_RAISE, 0, 0, 0); 
+  if( A.pExpr ){
+    A.pExpr->affinity = OE_Ignore;
+  }
+  A.zStart = X.z;
+  A.zEnd = &Y.z[Y.n];
+}
+expr(A) ::= RAISE(X) LP raisetype(T) COMMA nm(Z) RP(Y).  {
+  A.pExpr = sqlite3PExpr(pParse, TK_RAISE, 0, 0, &Z); 
+  if( A.pExpr ) {
+    A.pExpr->affinity = (char)T;
+  }
+  A.zStart = X.z;
+  A.zEnd = &Y.z[Y.n];
+}
+%endif  !SQLITE_OMIT_TRIGGER
+
+%type raisetype {int}
+raisetype(A) ::= ROLLBACK.  {A = OE_Rollback;}
+raisetype(A) ::= ABORT.     {A = OE_Abort;}
+raisetype(A) ::= FAIL.      {A = OE_Fail;}
+
+
+////////////////////////  DROP TRIGGER statement //////////////////////////////
+%ifndef SQLITE_OMIT_TRIGGER
+cmd ::= DROP TRIGGER ifexists(NOERR) fullname(X). {
+  sqlite3DropTrigger(pParse,X,NOERR);
+}
+%endif  !SQLITE_OMIT_TRIGGER
+
+//////////////////////// ATTACH DATABASE file AS name /////////////////////////
+%ifndef SQLITE_OMIT_ATTACH
+cmd ::= ATTACH database_kw_opt expr(F) AS expr(D) key_opt(K). {
+  sqlite3Attach(pParse, F.pExpr, D.pExpr, K);
+}
+cmd ::= DETACH database_kw_opt expr(D). {
+  sqlite3Detach(pParse, D.pExpr);
+}
+
+%type key_opt {Expr*}
+%destructor key_opt {sqlite3ExprDelete(pParse->db, $$);}
+key_opt(A) ::= .                     { A = 0; }
+key_opt(A) ::= KEY expr(X).          { A = X.pExpr; }
+
+database_kw_opt ::= DATABASE.
+database_kw_opt ::= .
+%endif SQLITE_OMIT_ATTACH
+
+////////////////////////// REINDEX collation //////////////////////////////////
+%ifndef SQLITE_OMIT_REINDEX
+cmd ::= REINDEX.                {sqlite3Reindex(pParse, 0, 0);}
+cmd ::= REINDEX nm(X) dbnm(Y).  {sqlite3Reindex(pParse, &X, &Y);}
+%endif  SQLITE_OMIT_REINDEX
+
+/////////////////////////////////// ANALYZE ///////////////////////////////////
+%ifndef SQLITE_OMIT_ANALYZE
+cmd ::= ANALYZE.                {sqlite3Analyze(pParse, 0, 0);}
+cmd ::= ANALYZE nm(X) dbnm(Y).  {sqlite3Analyze(pParse, &X, &Y);}
+%endif
+
+//////////////////////// ALTER TABLE table ... ////////////////////////////////
+%ifndef SQLITE_OMIT_ALTERTABLE
+cmd ::= ALTER TABLE fullname(X) RENAME TO nm(Z). {
+  sqlite3AlterRenameTable(pParse,X,&Z);
+}
+cmd ::= ALTER TABLE add_column_fullname ADD kwcolumn_opt column(Y). {
+  sqlite3AlterFinishAddColumn(pParse, &Y);
+}
+add_column_fullname ::= fullname(X). {
+  pParse->db->lookaside.bEnabled = 0;
+  sqlite3AlterBeginAddColumn(pParse, X);
+}
+kwcolumn_opt ::= .
+kwcolumn_opt ::= COLUMNKW.
+%endif  SQLITE_OMIT_ALTERTABLE
+
+//////////////////////// CREATE VIRTUAL TABLE ... /////////////////////////////
+%ifndef SQLITE_OMIT_VIRTUALTABLE
+cmd ::= create_vtab.                       {sqlite3VtabFinishParse(pParse,0);}
+cmd ::= create_vtab LP vtabarglist RP(X).  {sqlite3VtabFinishParse(pParse,&X);}
+create_vtab ::= createkw VIRTUAL TABLE nm(X) dbnm(Y) USING nm(Z). {
+    sqlite3VtabBeginParse(pParse, &X, &Y, &Z);
+}
+vtabarglist ::= vtabarg.
+vtabarglist ::= vtabarglist COMMA vtabarg.
+vtabarg ::= .                       {sqlite3VtabArgInit(pParse);}
+vtabarg ::= vtabarg vtabargtoken.
+vtabargtoken ::= ANY(X).            {sqlite3VtabArgExtend(pParse,&X);}
+vtabargtoken ::= lp anylist RP(X).  {sqlite3VtabArgExtend(pParse,&X);}
+lp ::= LP(X).                       {sqlite3VtabArgExtend(pParse,&X);}
+anylist ::= .
+anylist ::= anylist LP anylist RP.
+anylist ::= anylist ANY.
+%endif  SQLITE_OMIT_VIRTUALTABLE
diff --git a/src/pcache.c b/src/pcache.c
new file mode 100644
index 0000000..f37511e
--- /dev/null
+++ b/src/pcache.c
@@ -0,0 +1,594 @@
+/*
+** 2008 August 05
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file implements that page cache.
+*/
+#include "sqliteInt.h"
+
+/*
+** A complete page cache is an instance of this structure.
+*/
+struct PCache {
+  PgHdr *pDirty, *pDirtyTail;         /* List of dirty pages in LRU order */
+  PgHdr *pSynced;                     /* Last synced page in dirty page list */
+  int nRef;                           /* Number of referenced pages */
+  int nMax;                           /* Configured cache size */
+  int szPage;                         /* Size of every page in this cache */
+  int szExtra;                        /* Size of extra space for each page */
+  int bPurgeable;                     /* True if pages are on backing store */
+  int (*xStress)(void*,PgHdr*);       /* Call to try make a page clean */
+  void *pStress;                      /* Argument to xStress */
+  sqlite3_pcache *pCache;             /* Pluggable cache module */
+  PgHdr *pPage1;                      /* Reference to page 1 */
+};
+
+/*
+** Some of the assert() macros in this code are too expensive to run
+** even during normal debugging.  Use them only rarely on long-running
+** tests.  Enable the expensive asserts using the
+** -DSQLITE_ENABLE_EXPENSIVE_ASSERT=1 compile-time option.
+*/
+#ifdef SQLITE_ENABLE_EXPENSIVE_ASSERT
+# define expensive_assert(X)  assert(X)
+#else
+# define expensive_assert(X)
+#endif
+
+/********************************** Linked List Management ********************/
+
+#if !defined(NDEBUG) && defined(SQLITE_ENABLE_EXPENSIVE_ASSERT)
+/*
+** Check that the pCache->pSynced variable is set correctly. If it
+** is not, either fail an assert or return zero. Otherwise, return
+** non-zero. This is only used in debugging builds, as follows:
+**
+**   expensive_assert( pcacheCheckSynced(pCache) );
+*/
+static int pcacheCheckSynced(PCache *pCache){
+  PgHdr *p;
+  for(p=pCache->pDirtyTail; p!=pCache->pSynced; p=p->pDirtyPrev){
+    assert( p->nRef || (p->flags&PGHDR_NEED_SYNC) );
+  }
+  return (p==0 || p->nRef || (p->flags&PGHDR_NEED_SYNC)==0);
+}
+#endif /* !NDEBUG && SQLITE_ENABLE_EXPENSIVE_ASSERT */
+
+/*
+** Remove page pPage from the list of dirty pages.
+*/
+static void pcacheRemoveFromDirtyList(PgHdr *pPage){
+  PCache *p = pPage->pCache;
+
+  assert( pPage->pDirtyNext || pPage==p->pDirtyTail );
+  assert( pPage->pDirtyPrev || pPage==p->pDirty );
+
+  /* Update the PCache1.pSynced variable if necessary. */
+  if( p->pSynced==pPage ){
+    PgHdr *pSynced = pPage->pDirtyPrev;
+    while( pSynced && (pSynced->flags&PGHDR_NEED_SYNC) ){
+      pSynced = pSynced->pDirtyPrev;
+    }
+    p->pSynced = pSynced;
+  }
+
+  if( pPage->pDirtyNext ){
+    pPage->pDirtyNext->pDirtyPrev = pPage->pDirtyPrev;
+  }else{
+    assert( pPage==p->pDirtyTail );
+    p->pDirtyTail = pPage->pDirtyPrev;
+  }
+  if( pPage->pDirtyPrev ){
+    pPage->pDirtyPrev->pDirtyNext = pPage->pDirtyNext;
+  }else{
+    assert( pPage==p->pDirty );
+    p->pDirty = pPage->pDirtyNext;
+  }
+  pPage->pDirtyNext = 0;
+  pPage->pDirtyPrev = 0;
+
+  expensive_assert( pcacheCheckSynced(p) );
+}
+
+/*
+** Add page pPage to the head of the dirty list (PCache1.pDirty is set to
+** pPage).
+*/
+static void pcacheAddToDirtyList(PgHdr *pPage){
+  PCache *p = pPage->pCache;
+
+  assert( pPage->pDirtyNext==0 && pPage->pDirtyPrev==0 && p->pDirty!=pPage );
+
+  pPage->pDirtyNext = p->pDirty;
+  if( pPage->pDirtyNext ){
+    assert( pPage->pDirtyNext->pDirtyPrev==0 );
+    pPage->pDirtyNext->pDirtyPrev = pPage;
+  }
+  p->pDirty = pPage;
+  if( !p->pDirtyTail ){
+    p->pDirtyTail = pPage;
+  }
+  if( !p->pSynced && 0==(pPage->flags&PGHDR_NEED_SYNC) ){
+    p->pSynced = pPage;
+  }
+  expensive_assert( pcacheCheckSynced(p) );
+}
+
+/*
+** Wrapper around the pluggable caches xUnpin method. If the cache is
+** being used for an in-memory database, this function is a no-op.
+*/
+static void pcacheUnpin(PgHdr *p){
+  PCache *pCache = p->pCache;
+  if( pCache->bPurgeable ){
+    if( p->pgno==1 ){
+      pCache->pPage1 = 0;
+    }
+    sqlite3GlobalConfig.pcache.xUnpin(pCache->pCache, p, 0);
+  }
+}
+
+/*************************************************** General Interfaces ******
+**
+** Initialize and shutdown the page cache subsystem. Neither of these 
+** functions are threadsafe.
+*/
+int sqlite3PcacheInitialize(void){
+  if( sqlite3GlobalConfig.pcache.xInit==0 ){
+    /* IMPLEMENTATION-OF: R-26801-64137 If the xInit() method is NULL, then the
+    ** built-in default page cache is used instead of the application defined
+    ** page cache. */
+    sqlite3PCacheSetDefault();
+  }
+  return sqlite3GlobalConfig.pcache.xInit(sqlite3GlobalConfig.pcache.pArg);
+}
+void sqlite3PcacheShutdown(void){
+  if( sqlite3GlobalConfig.pcache.xShutdown ){
+    /* IMPLEMENTATION-OF: R-26000-56589 The xShutdown() method may be NULL. */
+    sqlite3GlobalConfig.pcache.xShutdown(sqlite3GlobalConfig.pcache.pArg);
+  }
+}
+
+/*
+** Return the size in bytes of a PCache object.
+*/
+int sqlite3PcacheSize(void){ return sizeof(PCache); }
+
+/*
+** Create a new PCache object. Storage space to hold the object
+** has already been allocated and is passed in as the p pointer. 
+** The caller discovers how much space needs to be allocated by 
+** calling sqlite3PcacheSize().
+*/
+void sqlite3PcacheOpen(
+  int szPage,                  /* Size of every page */
+  int szExtra,                 /* Extra space associated with each page */
+  int bPurgeable,              /* True if pages are on backing store */
+  int (*xStress)(void*,PgHdr*),/* Call to try to make pages clean */
+  void *pStress,               /* Argument to xStress */
+  PCache *p                    /* Preallocated space for the PCache */
+){
+  memset(p, 0, sizeof(PCache));
+  p->szPage = szPage;
+  p->szExtra = szExtra;
+  p->bPurgeable = bPurgeable;
+  p->xStress = xStress;
+  p->pStress = pStress;
+  p->nMax = 100;
+}
+
+/*
+** Change the page size for PCache object. The caller must ensure that there
+** are no outstanding page references when this function is called.
+*/
+void sqlite3PcacheSetPageSize(PCache *pCache, int szPage){
+  assert( pCache->nRef==0 && pCache->pDirty==0 );
+  if( pCache->pCache ){
+    sqlite3GlobalConfig.pcache.xDestroy(pCache->pCache);
+    pCache->pCache = 0;
+    pCache->pPage1 = 0;
+  }
+  pCache->szPage = szPage;
+}
+
+/*
+** Try to obtain a page from the cache.
+*/
+int sqlite3PcacheFetch(
+  PCache *pCache,       /* Obtain the page from this cache */
+  Pgno pgno,            /* Page number to obtain */
+  int createFlag,       /* If true, create page if it does not exist already */
+  PgHdr **ppPage        /* Write the page here */
+){
+  PgHdr *pPage = 0;
+  int eCreate;
+
+  assert( pCache!=0 );
+  assert( createFlag==1 || createFlag==0 );
+  assert( pgno>0 );
+
+  /* If the pluggable cache (sqlite3_pcache*) has not been allocated,
+  ** allocate it now.
+  */
+  if( !pCache->pCache && createFlag ){
+    sqlite3_pcache *p;
+    int nByte;
+    nByte = pCache->szPage + pCache->szExtra + sizeof(PgHdr);
+    p = sqlite3GlobalConfig.pcache.xCreate(nByte, pCache->bPurgeable);
+    if( !p ){
+      return SQLITE_NOMEM;
+    }
+    sqlite3GlobalConfig.pcache.xCachesize(p, pCache->nMax);
+    pCache->pCache = p;
+  }
+
+  eCreate = createFlag * (1 + (!pCache->bPurgeable || !pCache->pDirty));
+  if( pCache->pCache ){
+    pPage = sqlite3GlobalConfig.pcache.xFetch(pCache->pCache, pgno, eCreate);
+  }
+
+  if( !pPage && eCreate==1 ){
+    PgHdr *pPg;
+
+    /* Find a dirty page to write-out and recycle. First try to find a 
+    ** page that does not require a journal-sync (one with PGHDR_NEED_SYNC
+    ** cleared), but if that is not possible settle for any other 
+    ** unreferenced dirty page.
+    */
+    expensive_assert( pcacheCheckSynced(pCache) );
+    for(pPg=pCache->pSynced; 
+        pPg && (pPg->nRef || (pPg->flags&PGHDR_NEED_SYNC)); 
+        pPg=pPg->pDirtyPrev
+    );
+    pCache->pSynced = pPg;
+    if( !pPg ){
+      for(pPg=pCache->pDirtyTail; pPg && pPg->nRef; pPg=pPg->pDirtyPrev);
+    }
+    if( pPg ){
+      int rc;
+#ifdef SQLITE_LOG_CACHE_SPILL
+      sqlite3_log(SQLITE_FULL, 
+                  "spill page %d making room for %d - cache used: %d/%d",
+                  pPg->pgno, pgno,
+                  sqlite3GlobalConfig.pcache.xPagecount(pCache->pCache),
+                  pCache->nMax);
+#endif
+      rc = pCache->xStress(pCache->pStress, pPg);
+      if( rc!=SQLITE_OK && rc!=SQLITE_BUSY ){
+        return rc;
+      }
+    }
+
+    pPage = sqlite3GlobalConfig.pcache.xFetch(pCache->pCache, pgno, 2);
+  }
+
+  if( pPage ){
+    if( !pPage->pData ){
+      memset(pPage, 0, sizeof(PgHdr));
+      pPage->pData = (void *)&pPage[1];
+      pPage->pExtra = (void*)&((char *)pPage->pData)[pCache->szPage];
+      memset(pPage->pExtra, 0, pCache->szExtra);
+      pPage->pCache = pCache;
+      pPage->pgno = pgno;
+    }
+    assert( pPage->pCache==pCache );
+    assert( pPage->pgno==pgno );
+    assert( pPage->pData==(void *)&pPage[1] );
+    assert( pPage->pExtra==(void *)&((char *)&pPage[1])[pCache->szPage] );
+
+    if( 0==pPage->nRef ){
+      pCache->nRef++;
+    }
+    pPage->nRef++;
+    if( pgno==1 ){
+      pCache->pPage1 = pPage;
+    }
+  }
+  *ppPage = pPage;
+  return (pPage==0 && eCreate) ? SQLITE_NOMEM : SQLITE_OK;
+}
+
+/*
+** Decrement the reference count on a page. If the page is clean and the
+** reference count drops to 0, then it is made elible for recycling.
+*/
+void sqlite3PcacheRelease(PgHdr *p){
+  assert( p->nRef>0 );
+  p->nRef--;
+  if( p->nRef==0 ){
+    PCache *pCache = p->pCache;
+    pCache->nRef--;
+    if( (p->flags&PGHDR_DIRTY)==0 ){
+      pcacheUnpin(p);
+    }else{
+      /* Move the page to the head of the dirty list. */
+      pcacheRemoveFromDirtyList(p);
+      pcacheAddToDirtyList(p);
+    }
+  }
+}
+
+/*
+** Increase the reference count of a supplied page by 1.
+*/
+void sqlite3PcacheRef(PgHdr *p){
+  assert(p->nRef>0);
+  p->nRef++;
+}
+
+/*
+** Drop a page from the cache. There must be exactly one reference to the
+** page. This function deletes that reference, so after it returns the
+** page pointed to by p is invalid.
+*/
+void sqlite3PcacheDrop(PgHdr *p){
+  PCache *pCache;
+  assert( p->nRef==1 );
+  if( p->flags&PGHDR_DIRTY ){
+    pcacheRemoveFromDirtyList(p);
+  }
+  pCache = p->pCache;
+  pCache->nRef--;
+  if( p->pgno==1 ){
+    pCache->pPage1 = 0;
+  }
+  sqlite3GlobalConfig.pcache.xUnpin(pCache->pCache, p, 1);
+}
+
+/*
+** Make sure the page is marked as dirty. If it isn't dirty already,
+** make it so.
+*/
+void sqlite3PcacheMakeDirty(PgHdr *p){
+  p->flags &= ~PGHDR_DONT_WRITE;
+  assert( p->nRef>0 );
+  if( 0==(p->flags & PGHDR_DIRTY) ){
+    p->flags |= PGHDR_DIRTY;
+    pcacheAddToDirtyList( p);
+  }
+}
+
+/*
+** Make sure the page is marked as clean. If it isn't clean already,
+** make it so.
+*/
+void sqlite3PcacheMakeClean(PgHdr *p){
+  if( (p->flags & PGHDR_DIRTY) ){
+    pcacheRemoveFromDirtyList(p);
+    p->flags &= ~(PGHDR_DIRTY|PGHDR_NEED_SYNC);
+    if( p->nRef==0 ){
+      pcacheUnpin(p);
+    }
+  }
+}
+
+/*
+** Make every page in the cache clean.
+*/
+void sqlite3PcacheCleanAll(PCache *pCache){
+  PgHdr *p;
+  while( (p = pCache->pDirty)!=0 ){
+    sqlite3PcacheMakeClean(p);
+  }
+}
+
+/*
+** Clear the PGHDR_NEED_SYNC flag from all dirty pages.
+*/
+void sqlite3PcacheClearSyncFlags(PCache *pCache){
+  PgHdr *p;
+  for(p=pCache->pDirty; p; p=p->pDirtyNext){
+    p->flags &= ~PGHDR_NEED_SYNC;
+  }
+  pCache->pSynced = pCache->pDirtyTail;
+}
+
+/*
+** Change the page number of page p to newPgno. 
+*/
+void sqlite3PcacheMove(PgHdr *p, Pgno newPgno){
+  PCache *pCache = p->pCache;
+  assert( p->nRef>0 );
+  assert( newPgno>0 );
+  sqlite3GlobalConfig.pcache.xRekey(pCache->pCache, p, p->pgno, newPgno);
+  p->pgno = newPgno;
+  if( (p->flags&PGHDR_DIRTY) && (p->flags&PGHDR_NEED_SYNC) ){
+    pcacheRemoveFromDirtyList(p);
+    pcacheAddToDirtyList(p);
+  }
+}
+
+/*
+** Drop every cache entry whose page number is greater than "pgno". The
+** caller must ensure that there are no outstanding references to any pages
+** other than page 1 with a page number greater than pgno.
+**
+** If there is a reference to page 1 and the pgno parameter passed to this
+** function is 0, then the data area associated with page 1 is zeroed, but
+** the page object is not dropped.
+*/
+void sqlite3PcacheTruncate(PCache *pCache, Pgno pgno){
+  if( pCache->pCache ){
+    PgHdr *p;
+    PgHdr *pNext;
+    for(p=pCache->pDirty; p; p=pNext){
+      pNext = p->pDirtyNext;
+      /* This routine never gets call with a positive pgno except right
+      ** after sqlite3PcacheCleanAll().  So if there are dirty pages,
+      ** it must be that pgno==0.
+      */
+      assert( p->pgno>0 );
+      if( ALWAYS(p->pgno>pgno) ){
+        assert( p->flags&PGHDR_DIRTY );
+        sqlite3PcacheMakeClean(p);
+      }
+    }
+    if( pgno==0 && pCache->pPage1 ){
+      memset(pCache->pPage1->pData, 0, pCache->szPage);
+      pgno = 1;
+    }
+    sqlite3GlobalConfig.pcache.xTruncate(pCache->pCache, pgno+1);
+  }
+}
+
+/*
+** Close a cache.
+*/
+void sqlite3PcacheClose(PCache *pCache){
+  if( pCache->pCache ){
+    sqlite3GlobalConfig.pcache.xDestroy(pCache->pCache);
+  }
+}
+
+/* 
+** Discard the contents of the cache.
+*/
+void sqlite3PcacheClear(PCache *pCache){
+  sqlite3PcacheTruncate(pCache, 0);
+}
+
+/*
+** Merge two lists of pages connected by pDirty and in pgno order.
+** Do not both fixing the pDirtyPrev pointers.
+*/
+static PgHdr *pcacheMergeDirtyList(PgHdr *pA, PgHdr *pB){
+  PgHdr result, *pTail;
+  pTail = &result;
+  while( pA && pB ){
+    if( pA->pgno<pB->pgno ){
+      pTail->pDirty = pA;
+      pTail = pA;
+      pA = pA->pDirty;
+    }else{
+      pTail->pDirty = pB;
+      pTail = pB;
+      pB = pB->pDirty;
+    }
+  }
+  if( pA ){
+    pTail->pDirty = pA;
+  }else if( pB ){
+    pTail->pDirty = pB;
+  }else{
+    pTail->pDirty = 0;
+  }
+  return result.pDirty;
+}
+
+/*
+** Sort the list of pages in accending order by pgno.  Pages are
+** connected by pDirty pointers.  The pDirtyPrev pointers are
+** corrupted by this sort.
+**
+** Since there cannot be more than 2^31 distinct pages in a database,
+** there cannot be more than 31 buckets required by the merge sorter.
+** One extra bucket is added to catch overflow in case something
+** ever changes to make the previous sentence incorrect.
+*/
+#define N_SORT_BUCKET  32
+static PgHdr *pcacheSortDirtyList(PgHdr *pIn){
+  PgHdr *a[N_SORT_BUCKET], *p;
+  int i;
+  memset(a, 0, sizeof(a));
+  while( pIn ){
+    p = pIn;
+    pIn = p->pDirty;
+    p->pDirty = 0;
+    for(i=0; ALWAYS(i<N_SORT_BUCKET-1); i++){
+      if( a[i]==0 ){
+        a[i] = p;
+        break;
+      }else{
+        p = pcacheMergeDirtyList(a[i], p);
+        a[i] = 0;
+      }
+    }
+    if( NEVER(i==N_SORT_BUCKET-1) ){
+      /* To get here, there need to be 2^(N_SORT_BUCKET) elements in
+      ** the input list.  But that is impossible.
+      */
+      a[i] = pcacheMergeDirtyList(a[i], p);
+    }
+  }
+  p = a[0];
+  for(i=1; i<N_SORT_BUCKET; i++){
+    p = pcacheMergeDirtyList(p, a[i]);
+  }
+  return p;
+}
+
+/*
+** Return a list of all dirty pages in the cache, sorted by page number.
+*/
+PgHdr *sqlite3PcacheDirtyList(PCache *pCache){
+  PgHdr *p;
+  for(p=pCache->pDirty; p; p=p->pDirtyNext){
+    p->pDirty = p->pDirtyNext;
+  }
+  return pcacheSortDirtyList(pCache->pDirty);
+}
+
+/* 
+** Return the total number of referenced pages held by the cache.
+*/
+int sqlite3PcacheRefCount(PCache *pCache){
+  return pCache->nRef;
+}
+
+/*
+** Return the number of references to the page supplied as an argument.
+*/
+int sqlite3PcachePageRefcount(PgHdr *p){
+  return p->nRef;
+}
+
+/* 
+** Return the total number of pages in the cache.
+*/
+int sqlite3PcachePagecount(PCache *pCache){
+  int nPage = 0;
+  if( pCache->pCache ){
+    nPage = sqlite3GlobalConfig.pcache.xPagecount(pCache->pCache);
+  }
+  return nPage;
+}
+
+#ifdef SQLITE_TEST
+/*
+** Get the suggested cache-size value.
+*/
+int sqlite3PcacheGetCachesize(PCache *pCache){
+  return pCache->nMax;
+}
+#endif
+
+/*
+** Set the suggested cache-size value.
+*/
+void sqlite3PcacheSetCachesize(PCache *pCache, int mxPage){
+  pCache->nMax = mxPage;
+  if( pCache->pCache ){
+    sqlite3GlobalConfig.pcache.xCachesize(pCache->pCache, mxPage);
+  }
+}
+
+#if defined(SQLITE_CHECK_PAGES) || defined(SQLITE_DEBUG)
+/*
+** For all dirty pages currently in the cache, invoke the specified
+** callback. This is only used if the SQLITE_CHECK_PAGES macro is
+** defined.
+*/
+void sqlite3PcacheIterateDirty(PCache *pCache, void (*xIter)(PgHdr *)){
+  PgHdr *pDirty;
+  for(pDirty=pCache->pDirty; pDirty; pDirty=pDirty->pDirtyNext){
+    xIter(pDirty);
+  }
+}
+#endif
diff --git a/src/pcache.h b/src/pcache.h
new file mode 100644
index 0000000..33735d2
--- /dev/null
+++ b/src/pcache.h
@@ -0,0 +1,155 @@
+/*
+** 2008 August 05
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This header file defines the interface that the sqlite page cache
+** subsystem. 
+*/
+
+#ifndef _PCACHE_H_
+
+typedef struct PgHdr PgHdr;
+typedef struct PCache PCache;
+
+/*
+** Every page in the cache is controlled by an instance of the following
+** structure.
+*/
+struct PgHdr {
+  void *pData;                   /* Content of this page */
+  void *pExtra;                  /* Extra content */
+  PgHdr *pDirty;                 /* Transient list of dirty pages */
+  Pgno pgno;                     /* Page number for this page */
+  Pager *pPager;                 /* The pager this page is part of */
+#ifdef SQLITE_CHECK_PAGES
+  u32 pageHash;                  /* Hash of page content */
+#endif
+  u16 flags;                     /* PGHDR flags defined below */
+
+  /**********************************************************************
+  ** Elements above are public.  All that follows is private to pcache.c
+  ** and should not be accessed by other modules.
+  */
+  i16 nRef;                      /* Number of users of this page */
+  PCache *pCache;                /* Cache that owns this page */
+
+  PgHdr *pDirtyNext;             /* Next element in list of dirty pages */
+  PgHdr *pDirtyPrev;             /* Previous element in list of dirty pages */
+};
+
+/* Bit values for PgHdr.flags */
+#define PGHDR_DIRTY             0x002  /* Page has changed */
+#define PGHDR_NEED_SYNC         0x004  /* Fsync the rollback journal before
+                                       ** writing this page to the database */
+#define PGHDR_NEED_READ         0x008  /* Content is unread */
+#define PGHDR_REUSE_UNLIKELY    0x010  /* A hint that reuse is unlikely */
+#define PGHDR_DONT_WRITE        0x020  /* Do not write content to disk */
+
+/* Initialize and shutdown the page cache subsystem */
+int sqlite3PcacheInitialize(void);
+void sqlite3PcacheShutdown(void);
+
+/* Page cache buffer management:
+** These routines implement SQLITE_CONFIG_PAGECACHE.
+*/
+void sqlite3PCacheBufferSetup(void *, int sz, int n);
+
+/* Create a new pager cache.
+** Under memory stress, invoke xStress to try to make pages clean.
+** Only clean and unpinned pages can be reclaimed.
+*/
+void sqlite3PcacheOpen(
+  int szPage,                    /* Size of every page */
+  int szExtra,                   /* Extra space associated with each page */
+  int bPurgeable,                /* True if pages are on backing store */
+  int (*xStress)(void*, PgHdr*), /* Call to try to make pages clean */
+  void *pStress,                 /* Argument to xStress */
+  PCache *pToInit                /* Preallocated space for the PCache */
+);
+
+/* Modify the page-size after the cache has been created. */
+void sqlite3PcacheSetPageSize(PCache *, int);
+
+/* Return the size in bytes of a PCache object.  Used to preallocate
+** storage space.
+*/
+int sqlite3PcacheSize(void);
+
+/* One release per successful fetch.  Page is pinned until released.
+** Reference counted. 
+*/
+int sqlite3PcacheFetch(PCache*, Pgno, int createFlag, PgHdr**);
+void sqlite3PcacheRelease(PgHdr*);
+
+void sqlite3PcacheDrop(PgHdr*);         /* Remove page from cache */
+void sqlite3PcacheMakeDirty(PgHdr*);    /* Make sure page is marked dirty */
+void sqlite3PcacheMakeClean(PgHdr*);    /* Mark a single page as clean */
+void sqlite3PcacheCleanAll(PCache*);    /* Mark all dirty list pages as clean */
+
+/* Change a page number.  Used by incr-vacuum. */
+void sqlite3PcacheMove(PgHdr*, Pgno);
+
+/* Remove all pages with pgno>x.  Reset the cache if x==0 */
+void sqlite3PcacheTruncate(PCache*, Pgno x);
+
+/* Get a list of all dirty pages in the cache, sorted by page number */
+PgHdr *sqlite3PcacheDirtyList(PCache*);
+
+/* Reset and close the cache object */
+void sqlite3PcacheClose(PCache*);
+
+/* Clear flags from pages of the page cache */
+void sqlite3PcacheClearSyncFlags(PCache *);
+
+/* Discard the contents of the cache */
+void sqlite3PcacheClear(PCache*);
+
+/* Return the total number of outstanding page references */
+int sqlite3PcacheRefCount(PCache*);
+
+/* Increment the reference count of an existing page */
+void sqlite3PcacheRef(PgHdr*);
+
+int sqlite3PcachePageRefcount(PgHdr*);
+
+/* Return the total number of pages stored in the cache */
+int sqlite3PcachePagecount(PCache*);
+
+#if defined(SQLITE_CHECK_PAGES) || defined(SQLITE_DEBUG)
+/* Iterate through all dirty pages currently stored in the cache. This
+** interface is only available if SQLITE_CHECK_PAGES is defined when the 
+** library is built.
+*/
+void sqlite3PcacheIterateDirty(PCache *pCache, void (*xIter)(PgHdr *));
+#endif
+
+/* Set and get the suggested cache-size for the specified pager-cache.
+**
+** If no global maximum is configured, then the system attempts to limit
+** the total number of pages cached by purgeable pager-caches to the sum
+** of the suggested cache-sizes.
+*/
+void sqlite3PcacheSetCachesize(PCache *, int);
+#ifdef SQLITE_TEST
+int sqlite3PcacheGetCachesize(PCache *);
+#endif
+
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
+/* Try to return memory used by the pcache module to the main memory heap */
+int sqlite3PcacheReleaseMemory(int);
+#endif
+
+#ifdef SQLITE_TEST
+void sqlite3PcacheStats(int*,int*,int*,int*);
+#endif
+
+void sqlite3PCacheSetDefault(void);
+
+#endif /* _PCACHE_H_ */
diff --git a/src/pcache1.c b/src/pcache1.c
new file mode 100644
index 0000000..077a7b2
--- /dev/null
+++ b/src/pcache1.c
@@ -0,0 +1,972 @@
+/*
+** 2008 November 05
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file implements the default page cache implementation (the
+** sqlite3_pcache interface). It also contains part of the implementation
+** of the SQLITE_CONFIG_PAGECACHE and sqlite3_release_memory() features.
+** If the default page cache implementation is overriden, then neither of
+** these two features are available.
+*/
+
+#include "sqliteInt.h"
+
+typedef struct PCache1 PCache1;
+typedef struct PgHdr1 PgHdr1;
+typedef struct PgFreeslot PgFreeslot;
+typedef struct PGroup PGroup;
+
+
+/* Each page cache (or PCache) belongs to a PGroup.  A PGroup is a set 
+** of one or more PCaches that are able to recycle each others unpinned
+** pages when they are under memory pressure.  A PGroup is an instance of
+** the following object.
+**
+** This page cache implementation works in one of two modes:
+**
+**   (1)  Every PCache is the sole member of its own PGroup.  There is
+**        one PGroup per PCache.
+**
+**   (2)  There is a single global PGroup that all PCaches are a member
+**        of.
+**
+** Mode 1 uses more memory (since PCache instances are not able to rob
+** unused pages from other PCaches) but it also operates without a mutex,
+** and is therefore often faster.  Mode 2 requires a mutex in order to be
+** threadsafe, but is able recycle pages more efficient.
+**
+** For mode (1), PGroup.mutex is NULL.  For mode (2) there is only a single
+** PGroup which is the pcache1.grp global variable and its mutex is
+** SQLITE_MUTEX_STATIC_LRU.
+*/
+struct PGroup {
+  sqlite3_mutex *mutex;          /* MUTEX_STATIC_LRU or NULL */
+  int nMaxPage;                  /* Sum of nMax for purgeable caches */
+  int nMinPage;                  /* Sum of nMin for purgeable caches */
+  int mxPinned;                  /* nMaxpage + 10 - nMinPage */
+  int nCurrentPage;              /* Number of purgeable pages allocated */
+  PgHdr1 *pLruHead, *pLruTail;   /* LRU list of unpinned pages */
+};
+
+/* Each page cache is an instance of the following object.  Every
+** open database file (including each in-memory database and each
+** temporary or transient database) has a single page cache which
+** is an instance of this object.
+**
+** Pointers to structures of this type are cast and returned as 
+** opaque sqlite3_pcache* handles.
+*/
+struct PCache1 {
+  /* Cache configuration parameters. Page size (szPage) and the purgeable
+  ** flag (bPurgeable) are set when the cache is created. nMax may be 
+  ** modified at any time by a call to the pcache1CacheSize() method.
+  ** The PGroup mutex must be held when accessing nMax.
+  */
+  PGroup *pGroup;                     /* PGroup this cache belongs to */
+  int szPage;                         /* Size of allocated pages in bytes */
+  int bPurgeable;                     /* True if cache is purgeable */
+  unsigned int nMin;                  /* Minimum number of pages reserved */
+  unsigned int nMax;                  /* Configured "cache_size" value */
+  unsigned int n90pct;                /* nMax*9/10 */
+
+  /* Hash table of all pages. The following variables may only be accessed
+  ** when the accessor is holding the PGroup mutex.
+  */
+  unsigned int nRecyclable;           /* Number of pages in the LRU list */
+  unsigned int nPage;                 /* Total number of pages in apHash */
+  unsigned int nHash;                 /* Number of slots in apHash[] */
+  PgHdr1 **apHash;                    /* Hash table for fast lookup by key */
+
+  unsigned int iMaxKey;               /* Largest key seen since xTruncate() */
+};
+
+/*
+** Each cache entry is represented by an instance of the following 
+** structure. A buffer of PgHdr1.pCache->szPage bytes is allocated 
+** directly before this structure in memory (see the PGHDR1_TO_PAGE() 
+** macro below).
+*/
+struct PgHdr1 {
+  unsigned int iKey;             /* Key value (page number) */
+  PgHdr1 *pNext;                 /* Next in hash table chain */
+  PCache1 *pCache;               /* Cache that currently owns this page */
+  PgHdr1 *pLruNext;              /* Next in LRU list of unpinned pages */
+  PgHdr1 *pLruPrev;              /* Previous in LRU list of unpinned pages */
+};
+
+/*
+** Free slots in the allocator used to divide up the buffer provided using
+** the SQLITE_CONFIG_PAGECACHE mechanism.
+*/
+struct PgFreeslot {
+  PgFreeslot *pNext;  /* Next free slot */
+};
+
+/*
+** Global data used by this cache.
+*/
+static SQLITE_WSD struct PCacheGlobal {
+  PGroup grp;                    /* The global PGroup for mode (2) */
+
+  /* Variables related to SQLITE_CONFIG_PAGECACHE settings.  The
+  ** szSlot, nSlot, pStart, pEnd, nReserve, and isInit values are all
+  ** fixed at sqlite3_initialize() time and do not require mutex protection.
+  ** The nFreeSlot and pFree values do require mutex protection.
+  */
+  int isInit;                    /* True if initialized */
+  int szSlot;                    /* Size of each free slot */
+  int nSlot;                     /* The number of pcache slots */
+  int nReserve;                  /* Try to keep nFreeSlot above this */
+  void *pStart, *pEnd;           /* Bounds of pagecache malloc range */
+  /* Above requires no mutex.  Use mutex below for variable that follow. */
+  sqlite3_mutex *mutex;          /* Mutex for accessing the following: */
+  int nFreeSlot;                 /* Number of unused pcache slots */
+  PgFreeslot *pFree;             /* Free page blocks */
+  /* The following value requires a mutex to change.  We skip the mutex on
+  ** reading because (1) most platforms read a 32-bit integer atomically and
+  ** (2) even if an incorrect value is read, no great harm is done since this
+  ** is really just an optimization. */
+  int bUnderPressure;            /* True if low on PAGECACHE memory */
+} pcache1_g;
+
+/*
+** All code in this file should access the global structure above via the
+** alias "pcache1". This ensures that the WSD emulation is used when
+** compiling for systems that do not support real WSD.
+*/
+#define pcache1 (GLOBAL(struct PCacheGlobal, pcache1_g))
+
+/*
+** When a PgHdr1 structure is allocated, the associated PCache1.szPage
+** bytes of data are located directly before it in memory (i.e. the total
+** size of the allocation is sizeof(PgHdr1)+PCache1.szPage byte). The
+** PGHDR1_TO_PAGE() macro takes a pointer to a PgHdr1 structure as
+** an argument and returns a pointer to the associated block of szPage
+** bytes. The PAGE_TO_PGHDR1() macro does the opposite: its argument is
+** a pointer to a block of szPage bytes of data and the return value is
+** a pointer to the associated PgHdr1 structure.
+**
+**   assert( PGHDR1_TO_PAGE(PAGE_TO_PGHDR1(pCache, X))==X );
+*/
+#define PGHDR1_TO_PAGE(p)    (void*)(((char*)p) - p->pCache->szPage)
+#define PAGE_TO_PGHDR1(c, p) (PgHdr1*)(((char*)p) + c->szPage)
+
+/*
+** Macros to enter and leave the PCache LRU mutex.
+*/
+#define pcache1EnterMutex(X) sqlite3_mutex_enter((X)->mutex)
+#define pcache1LeaveMutex(X) sqlite3_mutex_leave((X)->mutex)
+
+/******************************************************************************/
+/******** Page Allocation/SQLITE_CONFIG_PCACHE Related Functions **************/
+
+/*
+** This function is called during initialization if a static buffer is 
+** supplied to use for the page-cache by passing the SQLITE_CONFIG_PAGECACHE
+** verb to sqlite3_config(). Parameter pBuf points to an allocation large
+** enough to contain 'n' buffers of 'sz' bytes each.
+**
+** This routine is called from sqlite3_initialize() and so it is guaranteed
+** to be serialized already.  There is no need for further mutexing.
+*/
+void sqlite3PCacheBufferSetup(void *pBuf, int sz, int n){
+  if( pcache1.isInit ){
+    PgFreeslot *p;
+    sz = ROUNDDOWN8(sz);
+    pcache1.szSlot = sz;
+    pcache1.nSlot = pcache1.nFreeSlot = n;
+    pcache1.nReserve = n>90 ? 10 : (n/10 + 1);
+    pcache1.pStart = pBuf;
+    pcache1.pFree = 0;
+    pcache1.bUnderPressure = 0;
+    while( n-- ){
+      p = (PgFreeslot*)pBuf;
+      p->pNext = pcache1.pFree;
+      pcache1.pFree = p;
+      pBuf = (void*)&((char*)pBuf)[sz];
+    }
+    pcache1.pEnd = pBuf;
+  }
+}
+
+/*
+** Malloc function used within this file to allocate space from the buffer
+** configured using sqlite3_config(SQLITE_CONFIG_PAGECACHE) option. If no 
+** such buffer exists or there is no space left in it, this function falls 
+** back to sqlite3Malloc().
+**
+** Multiple threads can run this routine at the same time.  Global variables
+** in pcache1 need to be protected via mutex.
+*/
+static void *pcache1Alloc(int nByte){
+  void *p = 0;
+  assert( sqlite3_mutex_notheld(pcache1.grp.mutex) );
+  sqlite3StatusSet(SQLITE_STATUS_PAGECACHE_SIZE, nByte);
+  if( nByte<=pcache1.szSlot ){
+    sqlite3_mutex_enter(pcache1.mutex);
+    p = (PgHdr1 *)pcache1.pFree;
+    if( p ){
+      pcache1.pFree = pcache1.pFree->pNext;
+      pcache1.nFreeSlot--;
+      pcache1.bUnderPressure = pcache1.nFreeSlot<pcache1.nReserve;
+      assert( pcache1.nFreeSlot>=0 );
+      sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_USED, 1);
+    }
+    sqlite3_mutex_leave(pcache1.mutex);
+  }
+  if( p==0 ){
+    /* Memory is not available in the SQLITE_CONFIG_PAGECACHE pool.  Get
+    ** it from sqlite3Malloc instead.
+    */
+    p = sqlite3Malloc(nByte);
+    if( p ){
+      int sz = sqlite3MallocSize(p);
+      sqlite3_mutex_enter(pcache1.mutex);
+      sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_OVERFLOW, sz);
+      sqlite3_mutex_leave(pcache1.mutex);
+    }
+    sqlite3MemdebugSetType(p, MEMTYPE_PCACHE);
+  }
+  return p;
+}
+
+/*
+** Free an allocated buffer obtained from pcache1Alloc().
+*/
+static void pcache1Free(void *p){
+  if( p==0 ) return;
+  if( p>=pcache1.pStart && p<pcache1.pEnd ){
+    PgFreeslot *pSlot;
+    sqlite3_mutex_enter(pcache1.mutex);
+    sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_USED, -1);
+    pSlot = (PgFreeslot*)p;
+    pSlot->pNext = pcache1.pFree;
+    pcache1.pFree = pSlot;
+    pcache1.nFreeSlot++;
+    pcache1.bUnderPressure = pcache1.nFreeSlot<pcache1.nReserve;
+    assert( pcache1.nFreeSlot<=pcache1.nSlot );
+    sqlite3_mutex_leave(pcache1.mutex);
+  }else{
+    int iSize;
+    assert( sqlite3MemdebugHasType(p, MEMTYPE_PCACHE) );
+    sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
+    iSize = sqlite3MallocSize(p);
+    sqlite3_mutex_enter(pcache1.mutex);
+    sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_OVERFLOW, -iSize);
+    sqlite3_mutex_leave(pcache1.mutex);
+    sqlite3_free(p);
+  }
+}
+
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
+/*
+** Return the size of a pcache allocation
+*/
+static int pcache1MemSize(void *p){
+  if( p>=pcache1.pStart && p<pcache1.pEnd ){
+    return pcache1.szSlot;
+  }else{
+    int iSize;
+    assert( sqlite3MemdebugHasType(p, MEMTYPE_PCACHE) );
+    sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
+    iSize = sqlite3MallocSize(p);
+    sqlite3MemdebugSetType(p, MEMTYPE_PCACHE);
+    return iSize;
+  }
+}
+#endif /* SQLITE_ENABLE_MEMORY_MANAGEMENT */
+
+/*
+** Allocate a new page object initially associated with cache pCache.
+*/
+static PgHdr1 *pcache1AllocPage(PCache1 *pCache){
+  int nByte = sizeof(PgHdr1) + pCache->szPage;
+  PgHdr1 *p = 0;
+  void *pPg;
+
+  /* The group mutex must be released before pcache1Alloc() is called. This
+  ** is because it may call sqlite3_release_memory(), which assumes that 
+  ** this mutex is not held. */
+  assert( sqlite3_mutex_held(pCache->pGroup->mutex) );
+  pcache1LeaveMutex(pCache->pGroup);
+  pPg = pcache1Alloc(nByte);
+  pcache1EnterMutex(pCache->pGroup);
+
+  if( pPg ){
+    p = PAGE_TO_PGHDR1(pCache, pPg);
+    if( pCache->bPurgeable ){
+      pCache->pGroup->nCurrentPage++;
+    }
+  }
+  return p;
+}
+
+/*
+** Free a page object allocated by pcache1AllocPage().
+**
+** The pointer is allowed to be NULL, which is prudent.  But it turns out
+** that the current implementation happens to never call this routine
+** with a NULL pointer, so we mark the NULL test with ALWAYS().
+*/
+static void pcache1FreePage(PgHdr1 *p){
+  if( ALWAYS(p) ){
+    PCache1 *pCache = p->pCache;
+    assert( sqlite3_mutex_held(p->pCache->pGroup->mutex) );
+    pcache1Free(PGHDR1_TO_PAGE(p));
+    if( pCache->bPurgeable ){
+      pCache->pGroup->nCurrentPage--;
+    }
+  }
+}
+
+/*
+** Malloc function used by SQLite to obtain space from the buffer configured
+** using sqlite3_config(SQLITE_CONFIG_PAGECACHE) option. If no such buffer
+** exists, this function falls back to sqlite3Malloc().
+*/
+void *sqlite3PageMalloc(int sz){
+  return pcache1Alloc(sz);
+}
+
+/*
+** Free an allocated buffer obtained from sqlite3PageMalloc().
+*/
+void sqlite3PageFree(void *p){
+  pcache1Free(p);
+}
+
+
+/*
+** Return true if it desirable to avoid allocating a new page cache
+** entry.
+**
+** If memory was allocated specifically to the page cache using
+** SQLITE_CONFIG_PAGECACHE but that memory has all been used, then
+** it is desirable to avoid allocating a new page cache entry because
+** presumably SQLITE_CONFIG_PAGECACHE was suppose to be sufficient
+** for all page cache needs and we should not need to spill the
+** allocation onto the heap.
+**
+** Or, the heap is used for all page cache memory put the heap is
+** under memory pressure, then again it is desirable to avoid
+** allocating a new page cache entry in order to avoid stressing
+** the heap even further.
+*/
+static int pcache1UnderMemoryPressure(PCache1 *pCache){
+  if( pcache1.nSlot && pCache->szPage<=pcache1.szSlot ){
+    return pcache1.bUnderPressure;
+  }else{
+    return sqlite3HeapNearlyFull();
+  }
+}
+
+/******************************************************************************/
+/******** General Implementation Functions ************************************/
+
+/*
+** This function is used to resize the hash table used by the cache passed
+** as the first argument.
+**
+** The PCache mutex must be held when this function is called.
+*/
+static int pcache1ResizeHash(PCache1 *p){
+  PgHdr1 **apNew;
+  unsigned int nNew;
+  unsigned int i;
+
+  assert( sqlite3_mutex_held(p->pGroup->mutex) );
+
+  nNew = p->nHash*2;
+  if( nNew<256 ){
+    nNew = 256;
+  }
+
+  pcache1LeaveMutex(p->pGroup);
+  if( p->nHash ){ sqlite3BeginBenignMalloc(); }
+  apNew = (PgHdr1 **)sqlite3_malloc(sizeof(PgHdr1 *)*nNew);
+  if( p->nHash ){ sqlite3EndBenignMalloc(); }
+  pcache1EnterMutex(p->pGroup);
+  if( apNew ){
+    memset(apNew, 0, sizeof(PgHdr1 *)*nNew);
+    for(i=0; i<p->nHash; i++){
+      PgHdr1 *pPage;
+      PgHdr1 *pNext = p->apHash[i];
+      while( (pPage = pNext)!=0 ){
+        unsigned int h = pPage->iKey % nNew;
+        pNext = pPage->pNext;
+        pPage->pNext = apNew[h];
+        apNew[h] = pPage;
+      }
+    }
+    sqlite3_free(p->apHash);
+    p->apHash = apNew;
+    p->nHash = nNew;
+  }
+
+  return (p->apHash ? SQLITE_OK : SQLITE_NOMEM);
+}
+
+/*
+** This function is used internally to remove the page pPage from the 
+** PGroup LRU list, if is part of it. If pPage is not part of the PGroup
+** LRU list, then this function is a no-op.
+**
+** The PGroup mutex must be held when this function is called.
+**
+** If pPage is NULL then this routine is a no-op.
+*/
+static void pcache1PinPage(PgHdr1 *pPage){
+  PCache1 *pCache;
+  PGroup *pGroup;
+
+  if( pPage==0 ) return;
+  pCache = pPage->pCache;
+  pGroup = pCache->pGroup;
+  assert( sqlite3_mutex_held(pGroup->mutex) );
+  if( pPage->pLruNext || pPage==pGroup->pLruTail ){
+    if( pPage->pLruPrev ){
+      pPage->pLruPrev->pLruNext = pPage->pLruNext;
+    }
+    if( pPage->pLruNext ){
+      pPage->pLruNext->pLruPrev = pPage->pLruPrev;
+    }
+    if( pGroup->pLruHead==pPage ){
+      pGroup->pLruHead = pPage->pLruNext;
+    }
+    if( pGroup->pLruTail==pPage ){
+      pGroup->pLruTail = pPage->pLruPrev;
+    }
+    pPage->pLruNext = 0;
+    pPage->pLruPrev = 0;
+    pPage->pCache->nRecyclable--;
+  }
+}
+
+
+/*
+** Remove the page supplied as an argument from the hash table 
+** (PCache1.apHash structure) that it is currently stored in.
+**
+** The PGroup mutex must be held when this function is called.
+*/
+static void pcache1RemoveFromHash(PgHdr1 *pPage){
+  unsigned int h;
+  PCache1 *pCache = pPage->pCache;
+  PgHdr1 **pp;
+
+  assert( sqlite3_mutex_held(pCache->pGroup->mutex) );
+  h = pPage->iKey % pCache->nHash;
+  for(pp=&pCache->apHash[h]; (*pp)!=pPage; pp=&(*pp)->pNext);
+  *pp = (*pp)->pNext;
+
+  pCache->nPage--;
+}
+
+/*
+** If there are currently more than nMaxPage pages allocated, try
+** to recycle pages to reduce the number allocated to nMaxPage.
+*/
+static void pcache1EnforceMaxPage(PGroup *pGroup){
+  assert( sqlite3_mutex_held(pGroup->mutex) );
+  while( pGroup->nCurrentPage>pGroup->nMaxPage && pGroup->pLruTail ){
+    PgHdr1 *p = pGroup->pLruTail;
+    assert( p->pCache->pGroup==pGroup );
+    pcache1PinPage(p);
+    pcache1RemoveFromHash(p);
+    pcache1FreePage(p);
+  }
+}
+
+/*
+** Discard all pages from cache pCache with a page number (key value) 
+** greater than or equal to iLimit. Any pinned pages that meet this 
+** criteria are unpinned before they are discarded.
+**
+** The PCache mutex must be held when this function is called.
+*/
+static void pcache1TruncateUnsafe(
+  PCache1 *pCache,             /* The cache to truncate */
+  unsigned int iLimit          /* Drop pages with this pgno or larger */
+){
+  TESTONLY( unsigned int nPage = 0; )  /* To assert pCache->nPage is correct */
+  unsigned int h;
+  assert( sqlite3_mutex_held(pCache->pGroup->mutex) );
+  for(h=0; h<pCache->nHash; h++){
+    PgHdr1 **pp = &pCache->apHash[h]; 
+    PgHdr1 *pPage;
+    while( (pPage = *pp)!=0 ){
+      if( pPage->iKey>=iLimit ){
+        pCache->nPage--;
+        *pp = pPage->pNext;
+        pcache1PinPage(pPage);
+        pcache1FreePage(pPage);
+      }else{
+        pp = &pPage->pNext;
+        TESTONLY( nPage++; )
+      }
+    }
+  }
+  assert( pCache->nPage==nPage );
+}
+
+/******************************************************************************/
+/******** sqlite3_pcache Methods **********************************************/
+
+/*
+** Implementation of the sqlite3_pcache.xInit method.
+*/
+static int pcache1Init(void *NotUsed){
+  UNUSED_PARAMETER(NotUsed);
+  assert( pcache1.isInit==0 );
+  memset(&pcache1, 0, sizeof(pcache1));
+  if( sqlite3GlobalConfig.bCoreMutex ){
+    pcache1.grp.mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_LRU);
+    pcache1.mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_PMEM);
+  }
+  pcache1.grp.mxPinned = 10;
+  pcache1.isInit = 1;
+  return SQLITE_OK;
+}
+
+/*
+** Implementation of the sqlite3_pcache.xShutdown method.
+** Note that the static mutex allocated in xInit does 
+** not need to be freed.
+*/
+static void pcache1Shutdown(void *NotUsed){
+  UNUSED_PARAMETER(NotUsed);
+  assert( pcache1.isInit!=0 );
+  memset(&pcache1, 0, sizeof(pcache1));
+}
+
+/*
+** Implementation of the sqlite3_pcache.xCreate method.
+**
+** Allocate a new cache.
+*/
+static sqlite3_pcache *pcache1Create(int szPage, int bPurgeable){
+  PCache1 *pCache;      /* The newly created page cache */
+  PGroup *pGroup;       /* The group the new page cache will belong to */
+  int sz;               /* Bytes of memory required to allocate the new cache */
+
+  /*
+  ** The seperateCache variable is true if each PCache has its own private
+  ** PGroup.  In other words, separateCache is true for mode (1) where no
+  ** mutexing is required.
+  **
+  **   *  Always use a unified cache (mode-2) if ENABLE_MEMORY_MANAGEMENT
+  **
+  **   *  Always use a unified cache in single-threaded applications
+  **
+  **   *  Otherwise (if multi-threaded and ENABLE_MEMORY_MANAGEMENT is off)
+  **      use separate caches (mode-1)
+  */
+#if defined(SQLITE_ENABLE_MEMORY_MANAGEMENT) || SQLITE_THREADSAFE==0
+  const int separateCache = 0;
+#else
+  int separateCache = sqlite3GlobalConfig.bCoreMutex>0;
+#endif
+
+  sz = sizeof(PCache1) + sizeof(PGroup)*separateCache;
+  pCache = (PCache1 *)sqlite3_malloc(sz);
+  if( pCache ){
+    memset(pCache, 0, sz);
+    if( separateCache ){
+      pGroup = (PGroup*)&pCache[1];
+      pGroup->mxPinned = 10;
+    }else{
+      pGroup = &pcache1.grp;
+    }
+    pCache->pGroup = pGroup;
+    pCache->szPage = szPage;
+    pCache->bPurgeable = (bPurgeable ? 1 : 0);
+    if( bPurgeable ){
+      pCache->nMin = 10;
+      pcache1EnterMutex(pGroup);
+      pGroup->nMinPage += pCache->nMin;
+      pGroup->mxPinned = pGroup->nMaxPage + 10 - pGroup->nMinPage;
+      pcache1LeaveMutex(pGroup);
+    }
+  }
+  return (sqlite3_pcache *)pCache;
+}
+
+/*
+** Implementation of the sqlite3_pcache.xCachesize method. 
+**
+** Configure the cache_size limit for a cache.
+*/
+static void pcache1Cachesize(sqlite3_pcache *p, int nMax){
+  PCache1 *pCache = (PCache1 *)p;
+  if( pCache->bPurgeable ){
+    PGroup *pGroup = pCache->pGroup;
+    pcache1EnterMutex(pGroup);
+    pGroup->nMaxPage += (nMax - pCache->nMax);
+    pGroup->mxPinned = pGroup->nMaxPage + 10 - pGroup->nMinPage;
+    pCache->nMax = nMax;
+    pCache->n90pct = pCache->nMax*9/10;
+    pcache1EnforceMaxPage(pGroup);
+    pcache1LeaveMutex(pGroup);
+  }
+}
+
+/*
+** Implementation of the sqlite3_pcache.xPagecount method. 
+*/
+static int pcache1Pagecount(sqlite3_pcache *p){
+  int n;
+  PCache1 *pCache = (PCache1*)p;
+  pcache1EnterMutex(pCache->pGroup);
+  n = pCache->nPage;
+  pcache1LeaveMutex(pCache->pGroup);
+  return n;
+}
+
+/*
+** Implementation of the sqlite3_pcache.xFetch method. 
+**
+** Fetch a page by key value.
+**
+** Whether or not a new page may be allocated by this function depends on
+** the value of the createFlag argument.  0 means do not allocate a new
+** page.  1 means allocate a new page if space is easily available.  2 
+** means to try really hard to allocate a new page.
+**
+** For a non-purgeable cache (a cache used as the storage for an in-memory
+** database) there is really no difference between createFlag 1 and 2.  So
+** the calling function (pcache.c) will never have a createFlag of 1 on
+** a non-purgable cache.
+**
+** There are three different approaches to obtaining space for a page,
+** depending on the value of parameter createFlag (which may be 0, 1 or 2).
+**
+**   1. Regardless of the value of createFlag, the cache is searched for a 
+**      copy of the requested page. If one is found, it is returned.
+**
+**   2. If createFlag==0 and the page is not already in the cache, NULL is
+**      returned.
+**
+**   3. If createFlag is 1, and the page is not already in the cache, then
+**      return NULL (do not allocate a new page) if any of the following
+**      conditions are true:
+**
+**       (a) the number of pages pinned by the cache is greater than
+**           PCache1.nMax, or
+**
+**       (b) the number of pages pinned by the cache is greater than
+**           the sum of nMax for all purgeable caches, less the sum of 
+**           nMin for all other purgeable caches, or
+**
+**   4. If none of the first three conditions apply and the cache is marked
+**      as purgeable, and if one of the following is true:
+**
+**       (a) The number of pages allocated for the cache is already 
+**           PCache1.nMax, or
+**
+**       (b) The number of pages allocated for all purgeable caches is
+**           already equal to or greater than the sum of nMax for all
+**           purgeable caches,
+**
+**       (c) The system is under memory pressure and wants to avoid
+**           unnecessary pages cache entry allocations
+**
+**      then attempt to recycle a page from the LRU list. If it is the right
+**      size, return the recycled buffer. Otherwise, free the buffer and
+**      proceed to step 5. 
+**
+**   5. Otherwise, allocate and return a new page buffer.
+*/
+static void *pcache1Fetch(sqlite3_pcache *p, unsigned int iKey, int createFlag){
+  int nPinned;
+  PCache1 *pCache = (PCache1 *)p;
+  PGroup *pGroup;
+  PgHdr1 *pPage = 0;
+
+  assert( pCache->bPurgeable || createFlag!=1 );
+  assert( pCache->bPurgeable || pCache->nMin==0 );
+  assert( pCache->bPurgeable==0 || pCache->nMin==10 );
+  assert( pCache->nMin==0 || pCache->bPurgeable );
+  pcache1EnterMutex(pGroup = pCache->pGroup);
+
+  /* Step 1: Search the hash table for an existing entry. */
+  if( pCache->nHash>0 ){
+    unsigned int h = iKey % pCache->nHash;
+    for(pPage=pCache->apHash[h]; pPage&&pPage->iKey!=iKey; pPage=pPage->pNext);
+  }
+
+  /* Step 2: Abort if no existing page is found and createFlag is 0 */
+  if( pPage || createFlag==0 ){
+    pcache1PinPage(pPage);
+    goto fetch_out;
+  }
+
+  /* The pGroup local variable will normally be initialized by the
+  ** pcache1EnterMutex() macro above.  But if SQLITE_MUTEX_OMIT is defined,
+  ** then pcache1EnterMutex() is a no-op, so we have to initialize the
+  ** local variable here.  Delaying the initialization of pGroup is an
+  ** optimization:  The common case is to exit the module before reaching
+  ** this point.
+  */
+#ifdef SQLITE_MUTEX_OMIT
+  pGroup = pCache->pGroup;
+#endif
+
+
+  /* Step 3: Abort if createFlag is 1 but the cache is nearly full */
+  nPinned = pCache->nPage - pCache->nRecyclable;
+  assert( nPinned>=0 );
+  assert( pGroup->mxPinned == pGroup->nMaxPage + 10 - pGroup->nMinPage );
+  assert( pCache->n90pct == pCache->nMax*9/10 );
+  if( createFlag==1 && (
+        nPinned>=pGroup->mxPinned
+     || nPinned>=(int)pCache->n90pct
+     || pcache1UnderMemoryPressure(pCache)
+  )){
+    goto fetch_out;
+  }
+
+  if( pCache->nPage>=pCache->nHash && pcache1ResizeHash(pCache) ){
+    goto fetch_out;
+  }
+
+  /* Step 4. Try to recycle a page. */
+  if( pCache->bPurgeable && pGroup->pLruTail && (
+         (pCache->nPage+1>=pCache->nMax)
+      || pGroup->nCurrentPage>=pGroup->nMaxPage
+      || pcache1UnderMemoryPressure(pCache)
+  )){
+    PCache1 *pOtherCache;
+    pPage = pGroup->pLruTail;
+    pcache1RemoveFromHash(pPage);
+    pcache1PinPage(pPage);
+    if( (pOtherCache = pPage->pCache)->szPage!=pCache->szPage ){
+      pcache1FreePage(pPage);
+      pPage = 0;
+    }else{
+      pGroup->nCurrentPage -= 
+               (pOtherCache->bPurgeable - pCache->bPurgeable);
+    }
+  }
+
+  /* Step 5. If a usable page buffer has still not been found, 
+  ** attempt to allocate a new one. 
+  */
+  if( !pPage ){
+    if( createFlag==1 ) sqlite3BeginBenignMalloc();
+    pPage = pcache1AllocPage(pCache);
+    if( createFlag==1 ) sqlite3EndBenignMalloc();
+  }
+
+  if( pPage ){
+    unsigned int h = iKey % pCache->nHash;
+    pCache->nPage++;
+    pPage->iKey = iKey;
+    pPage->pNext = pCache->apHash[h];
+    pPage->pCache = pCache;
+    pPage->pLruPrev = 0;
+    pPage->pLruNext = 0;
+    *(void **)(PGHDR1_TO_PAGE(pPage)) = 0;
+    pCache->apHash[h] = pPage;
+  }
+
+fetch_out:
+  if( pPage && iKey>pCache->iMaxKey ){
+    pCache->iMaxKey = iKey;
+  }
+  pcache1LeaveMutex(pGroup);
+  return (pPage ? PGHDR1_TO_PAGE(pPage) : 0);
+}
+
+
+/*
+** Implementation of the sqlite3_pcache.xUnpin method.
+**
+** Mark a page as unpinned (eligible for asynchronous recycling).
+*/
+static void pcache1Unpin(sqlite3_pcache *p, void *pPg, int reuseUnlikely){
+  PCache1 *pCache = (PCache1 *)p;
+  PgHdr1 *pPage = PAGE_TO_PGHDR1(pCache, pPg);
+  PGroup *pGroup = pCache->pGroup;
+ 
+  assert( pPage->pCache==pCache );
+  pcache1EnterMutex(pGroup);
+
+  /* It is an error to call this function if the page is already 
+  ** part of the PGroup LRU list.
+  */
+  assert( pPage->pLruPrev==0 && pPage->pLruNext==0 );
+  assert( pGroup->pLruHead!=pPage && pGroup->pLruTail!=pPage );
+
+  if( reuseUnlikely || pGroup->nCurrentPage>pGroup->nMaxPage ){
+    pcache1RemoveFromHash(pPage);
+    pcache1FreePage(pPage);
+  }else{
+    /* Add the page to the PGroup LRU list. */
+    if( pGroup->pLruHead ){
+      pGroup->pLruHead->pLruPrev = pPage;
+      pPage->pLruNext = pGroup->pLruHead;
+      pGroup->pLruHead = pPage;
+    }else{
+      pGroup->pLruTail = pPage;
+      pGroup->pLruHead = pPage;
+    }
+    pCache->nRecyclable++;
+  }
+
+  pcache1LeaveMutex(pCache->pGroup);
+}
+
+/*
+** Implementation of the sqlite3_pcache.xRekey method. 
+*/
+static void pcache1Rekey(
+  sqlite3_pcache *p,
+  void *pPg,
+  unsigned int iOld,
+  unsigned int iNew
+){
+  PCache1 *pCache = (PCache1 *)p;
+  PgHdr1 *pPage = PAGE_TO_PGHDR1(pCache, pPg);
+  PgHdr1 **pp;
+  unsigned int h; 
+  assert( pPage->iKey==iOld );
+  assert( pPage->pCache==pCache );
+
+  pcache1EnterMutex(pCache->pGroup);
+
+  h = iOld%pCache->nHash;
+  pp = &pCache->apHash[h];
+  while( (*pp)!=pPage ){
+    pp = &(*pp)->pNext;
+  }
+  *pp = pPage->pNext;
+
+  h = iNew%pCache->nHash;
+  pPage->iKey = iNew;
+  pPage->pNext = pCache->apHash[h];
+  pCache->apHash[h] = pPage;
+  if( iNew>pCache->iMaxKey ){
+    pCache->iMaxKey = iNew;
+  }
+
+  pcache1LeaveMutex(pCache->pGroup);
+}
+
+/*
+** Implementation of the sqlite3_pcache.xTruncate method. 
+**
+** Discard all unpinned pages in the cache with a page number equal to
+** or greater than parameter iLimit. Any pinned pages with a page number
+** equal to or greater than iLimit are implicitly unpinned.
+*/
+static void pcache1Truncate(sqlite3_pcache *p, unsigned int iLimit){
+  PCache1 *pCache = (PCache1 *)p;
+  pcache1EnterMutex(pCache->pGroup);
+  if( iLimit<=pCache->iMaxKey ){
+    pcache1TruncateUnsafe(pCache, iLimit);
+    pCache->iMaxKey = iLimit-1;
+  }
+  pcache1LeaveMutex(pCache->pGroup);
+}
+
+/*
+** Implementation of the sqlite3_pcache.xDestroy method. 
+**
+** Destroy a cache allocated using pcache1Create().
+*/
+static void pcache1Destroy(sqlite3_pcache *p){
+  PCache1 *pCache = (PCache1 *)p;
+  PGroup *pGroup = pCache->pGroup;
+  assert( pCache->bPurgeable || (pCache->nMax==0 && pCache->nMin==0) );
+  pcache1EnterMutex(pGroup);
+  pcache1TruncateUnsafe(pCache, 0);
+  pGroup->nMaxPage -= pCache->nMax;
+  pGroup->nMinPage -= pCache->nMin;
+  pGroup->mxPinned = pGroup->nMaxPage + 10 - pGroup->nMinPage;
+  pcache1EnforceMaxPage(pGroup);
+  pcache1LeaveMutex(pGroup);
+  sqlite3_free(pCache->apHash);
+  sqlite3_free(pCache);
+}
+
+/*
+** This function is called during initialization (sqlite3_initialize()) to
+** install the default pluggable cache module, assuming the user has not
+** already provided an alternative.
+*/
+void sqlite3PCacheSetDefault(void){
+  static const sqlite3_pcache_methods defaultMethods = {
+    0,                       /* pArg */
+    pcache1Init,             /* xInit */
+    pcache1Shutdown,         /* xShutdown */
+    pcache1Create,           /* xCreate */
+    pcache1Cachesize,        /* xCachesize */
+    pcache1Pagecount,        /* xPagecount */
+    pcache1Fetch,            /* xFetch */
+    pcache1Unpin,            /* xUnpin */
+    pcache1Rekey,            /* xRekey */
+    pcache1Truncate,         /* xTruncate */
+    pcache1Destroy           /* xDestroy */
+  };
+  sqlite3_config(SQLITE_CONFIG_PCACHE, &defaultMethods);
+}
+
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
+/*
+** This function is called to free superfluous dynamically allocated memory
+** held by the pager system. Memory in use by any SQLite pager allocated
+** by the current thread may be sqlite3_free()ed.
+**
+** nReq is the number of bytes of memory required. Once this much has
+** been released, the function returns. The return value is the total number 
+** of bytes of memory released.
+*/
+int sqlite3PcacheReleaseMemory(int nReq){
+  int nFree = 0;
+  assert( sqlite3_mutex_notheld(pcache1.grp.mutex) );
+  assert( sqlite3_mutex_notheld(pcache1.mutex) );
+  if( pcache1.pStart==0 ){
+    PgHdr1 *p;
+    pcache1EnterMutex(&pcache1.grp);
+    while( (nReq<0 || nFree<nReq) && ((p=pcache1.grp.pLruTail)!=0) ){
+      nFree += pcache1MemSize(PGHDR1_TO_PAGE(p));
+      pcache1PinPage(p);
+      pcache1RemoveFromHash(p);
+      pcache1FreePage(p);
+    }
+    pcache1LeaveMutex(&pcache1.grp);
+  }
+  return nFree;
+}
+#endif /* SQLITE_ENABLE_MEMORY_MANAGEMENT */
+
+#ifdef SQLITE_TEST
+/*
+** This function is used by test procedures to inspect the internal state
+** of the global cache.
+*/
+void sqlite3PcacheStats(
+  int *pnCurrent,      /* OUT: Total number of pages cached */
+  int *pnMax,          /* OUT: Global maximum cache size */
+  int *pnMin,          /* OUT: Sum of PCache1.nMin for purgeable caches */
+  int *pnRecyclable    /* OUT: Total number of pages available for recycling */
+){
+  PgHdr1 *p;
+  int nRecyclable = 0;
+  for(p=pcache1.grp.pLruHead; p; p=p->pLruNext){
+    nRecyclable++;
+  }
+  *pnCurrent = pcache1.grp.nCurrentPage;
+  *pnMax = pcache1.grp.nMaxPage;
+  *pnMin = pcache1.grp.nMinPage;
+  *pnRecyclable = nRecyclable;
+}
+#endif
diff --git a/src/pragma.c b/src/pragma.c
new file mode 100644
index 0000000..d9047e1
--- /dev/null
+++ b/src/pragma.c
@@ -0,0 +1,1562 @@
+/*
+** 2003 April 6
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains code used to implement the PRAGMA command.
+*/
+#include "sqliteInt.h"
+
+/*
+** Interpret the given string as a safety level.  Return 0 for OFF,
+** 1 for ON or NORMAL and 2 for FULL.  Return 1 for an empty or 
+** unrecognized string argument.
+**
+** Note that the values returned are one less that the values that
+** should be passed into sqlite3BtreeSetSafetyLevel().  The is done
+** to support legacy SQL code.  The safety level used to be boolean
+** and older scripts may have used numbers 0 for OFF and 1 for ON.
+*/
+static u8 getSafetyLevel(const char *z){
+                             /* 123456789 123456789 */
+  static const char zText[] = "onoffalseyestruefull";
+  static const u8 iOffset[] = {0, 1, 2, 4, 9, 12, 16};
+  static const u8 iLength[] = {2, 2, 3, 5, 3, 4, 4};
+  static const u8 iValue[] =  {1, 0, 0, 0, 1, 1, 2};
+  int i, n;
+  if( sqlite3Isdigit(*z) ){
+    return (u8)sqlite3Atoi(z);
+  }
+  n = sqlite3Strlen30(z);
+  for(i=0; i<ArraySize(iLength); i++){
+    if( iLength[i]==n && sqlite3StrNICmp(&zText[iOffset[i]],z,n)==0 ){
+      return iValue[i];
+    }
+  }
+  return 1;
+}
+
+/*
+** Interpret the given string as a boolean value.
+*/
+u8 sqlite3GetBoolean(const char *z){
+  return getSafetyLevel(z)&1;
+}
+
+/* The sqlite3GetBoolean() function is used by other modules but the
+** remainder of this file is specific to PRAGMA processing.  So omit
+** the rest of the file if PRAGMAs are omitted from the build.
+*/
+#if !defined(SQLITE_OMIT_PRAGMA)
+
+/*
+** Interpret the given string as a locking mode value.
+*/
+static int getLockingMode(const char *z){
+  if( z ){
+    if( 0==sqlite3StrICmp(z, "exclusive") ) return PAGER_LOCKINGMODE_EXCLUSIVE;
+    if( 0==sqlite3StrICmp(z, "normal") ) return PAGER_LOCKINGMODE_NORMAL;
+  }
+  return PAGER_LOCKINGMODE_QUERY;
+}
+
+#ifndef SQLITE_OMIT_AUTOVACUUM
+/*
+** Interpret the given string as an auto-vacuum mode value.
+**
+** The following strings, "none", "full" and "incremental" are 
+** acceptable, as are their numeric equivalents: 0, 1 and 2 respectively.
+*/
+static int getAutoVacuum(const char *z){
+  int i;
+  if( 0==sqlite3StrICmp(z, "none") ) return BTREE_AUTOVACUUM_NONE;
+  if( 0==sqlite3StrICmp(z, "full") ) return BTREE_AUTOVACUUM_FULL;
+  if( 0==sqlite3StrICmp(z, "incremental") ) return BTREE_AUTOVACUUM_INCR;
+  i = sqlite3Atoi(z);
+  return (u8)((i>=0&&i<=2)?i:0);
+}
+#endif /* ifndef SQLITE_OMIT_AUTOVACUUM */
+
+#ifndef SQLITE_OMIT_PAGER_PRAGMAS
+/*
+** Interpret the given string as a temp db location. Return 1 for file
+** backed temporary databases, 2 for the Red-Black tree in memory database
+** and 0 to use the compile-time default.
+*/
+static int getTempStore(const char *z){
+  if( z[0]>='0' && z[0]<='2' ){
+    return z[0] - '0';
+  }else if( sqlite3StrICmp(z, "file")==0 ){
+    return 1;
+  }else if( sqlite3StrICmp(z, "memory")==0 ){
+    return 2;
+  }else{
+    return 0;
+  }
+}
+#endif /* SQLITE_PAGER_PRAGMAS */
+
+#ifndef SQLITE_OMIT_PAGER_PRAGMAS
+/*
+** Invalidate temp storage, either when the temp storage is changed
+** from default, or when 'file' and the temp_store_directory has changed
+*/
+static int invalidateTempStorage(Parse *pParse){
+  sqlite3 *db = pParse->db;
+  if( db->aDb[1].pBt!=0 ){
+    if( !db->autoCommit || sqlite3BtreeIsInReadTrans(db->aDb[1].pBt) ){
+      sqlite3ErrorMsg(pParse, "temporary storage cannot be changed "
+        "from within a transaction");
+      return SQLITE_ERROR;
+    }
+    sqlite3BtreeClose(db->aDb[1].pBt);
+    db->aDb[1].pBt = 0;
+    sqlite3ResetInternalSchema(db, -1);
+  }
+  return SQLITE_OK;
+}
+#endif /* SQLITE_PAGER_PRAGMAS */
+
+#ifndef SQLITE_OMIT_PAGER_PRAGMAS
+/*
+** If the TEMP database is open, close it and mark the database schema
+** as needing reloading.  This must be done when using the SQLITE_TEMP_STORE
+** or DEFAULT_TEMP_STORE pragmas.
+*/
+static int changeTempStorage(Parse *pParse, const char *zStorageType){
+  int ts = getTempStore(zStorageType);
+  sqlite3 *db = pParse->db;
+  if( db->temp_store==ts ) return SQLITE_OK;
+  if( invalidateTempStorage( pParse ) != SQLITE_OK ){
+    return SQLITE_ERROR;
+  }
+  db->temp_store = (u8)ts;
+  return SQLITE_OK;
+}
+#endif /* SQLITE_PAGER_PRAGMAS */
+
+/*
+** Generate code to return a single integer value.
+*/
+static void returnSingleInt(Parse *pParse, const char *zLabel, i64 value){
+  Vdbe *v = sqlite3GetVdbe(pParse);
+  int mem = ++pParse->nMem;
+  i64 *pI64 = sqlite3DbMallocRaw(pParse->db, sizeof(value));
+  if( pI64 ){
+    memcpy(pI64, &value, sizeof(value));
+  }
+  sqlite3VdbeAddOp4(v, OP_Int64, 0, mem, 0, (char*)pI64, P4_INT64);
+  sqlite3VdbeSetNumCols(v, 1);
+  sqlite3VdbeSetColName(v, 0, COLNAME_NAME, zLabel, SQLITE_STATIC);
+  sqlite3VdbeAddOp2(v, OP_ResultRow, mem, 1);
+}
+
+#ifndef SQLITE_OMIT_FLAG_PRAGMAS
+/*
+** Check to see if zRight and zLeft refer to a pragma that queries
+** or changes one of the flags in db->flags.  Return 1 if so and 0 if not.
+** Also, implement the pragma.
+*/
+static int flagPragma(Parse *pParse, const char *zLeft, const char *zRight){
+  static const struct sPragmaType {
+    const char *zName;  /* Name of the pragma */
+    int mask;           /* Mask for the db->flags value */
+  } aPragma[] = {
+    { "full_column_names",        SQLITE_FullColNames  },
+    { "short_column_names",       SQLITE_ShortColNames },
+    { "count_changes",            SQLITE_CountRows     },
+    { "empty_result_callbacks",   SQLITE_NullCallback  },
+    { "legacy_file_format",       SQLITE_LegacyFileFmt },
+    { "fullfsync",                SQLITE_FullFSync     },
+    { "checkpoint_fullfsync",     SQLITE_CkptFullFSync },
+    { "reverse_unordered_selects", SQLITE_ReverseOrder  },
+#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
+    { "automatic_index",          SQLITE_AutoIndex     },
+#endif
+#ifdef SQLITE_DEBUG
+    { "sql_trace",                SQLITE_SqlTrace      },
+    { "vdbe_listing",             SQLITE_VdbeListing   },
+    { "vdbe_trace",               SQLITE_VdbeTrace     },
+#endif
+#ifndef SQLITE_OMIT_CHECK
+    { "ignore_check_constraints", SQLITE_IgnoreChecks  },
+#endif
+    /* The following is VERY experimental */
+    { "writable_schema",          SQLITE_WriteSchema|SQLITE_RecoveryMode },
+    { "omit_readlock",            SQLITE_NoReadlock    },
+
+    /* TODO: Maybe it shouldn't be possible to change the ReadUncommitted
+    ** flag if there are any active statements. */
+    { "read_uncommitted",         SQLITE_ReadUncommitted },
+    { "recursive_triggers",       SQLITE_RecTriggers },
+
+    /* This flag may only be set if both foreign-key and trigger support
+    ** are present in the build.  */
+#if !defined(SQLITE_OMIT_FOREIGN_KEY) && !defined(SQLITE_OMIT_TRIGGER)
+    { "foreign_keys",             SQLITE_ForeignKeys },
+#endif
+  };
+  int i;
+  const struct sPragmaType *p;
+  for(i=0, p=aPragma; i<ArraySize(aPragma); i++, p++){
+    if( sqlite3StrICmp(zLeft, p->zName)==0 ){
+      sqlite3 *db = pParse->db;
+      Vdbe *v;
+      v = sqlite3GetVdbe(pParse);
+      assert( v!=0 );  /* Already allocated by sqlite3Pragma() */
+      if( ALWAYS(v) ){
+        if( zRight==0 ){
+          returnSingleInt(pParse, p->zName, (db->flags & p->mask)!=0 );
+        }else{
+          int mask = p->mask;          /* Mask of bits to set or clear. */
+          if( db->autoCommit==0 ){
+            /* Foreign key support may not be enabled or disabled while not
+            ** in auto-commit mode.  */
+            mask &= ~(SQLITE_ForeignKeys);
+          }
+
+          if( sqlite3GetBoolean(zRight) ){
+            db->flags |= mask;
+          }else{
+            db->flags &= ~mask;
+          }
+
+          /* Many of the flag-pragmas modify the code generated by the SQL 
+          ** compiler (eg. count_changes). So add an opcode to expire all
+          ** compiled SQL statements after modifying a pragma value.
+          */
+          sqlite3VdbeAddOp2(v, OP_Expire, 0, 0);
+        }
+      }
+
+      return 1;
+    }
+  }
+  return 0;
+}
+#endif /* SQLITE_OMIT_FLAG_PRAGMAS */
+
+/*
+** Return a human-readable name for a constraint resolution action.
+*/
+#ifndef SQLITE_OMIT_FOREIGN_KEY
+static const char *actionName(u8 action){
+  const char *zName;
+  switch( action ){
+    case OE_SetNull:  zName = "SET NULL";        break;
+    case OE_SetDflt:  zName = "SET DEFAULT";     break;
+    case OE_Cascade:  zName = "CASCADE";         break;
+    case OE_Restrict: zName = "RESTRICT";        break;
+    default:          zName = "NO ACTION";  
+                      assert( action==OE_None ); break;
+  }
+  return zName;
+}
+#endif
+
+
+/*
+** Parameter eMode must be one of the PAGER_JOURNALMODE_XXX constants
+** defined in pager.h. This function returns the associated lowercase
+** journal-mode name.
+*/
+const char *sqlite3JournalModename(int eMode){
+  static char * const azModeName[] = {
+    "delete", "persist", "off", "truncate", "memory"
+#ifndef SQLITE_OMIT_WAL
+     , "wal"
+#endif
+  };
+  assert( PAGER_JOURNALMODE_DELETE==0 );
+  assert( PAGER_JOURNALMODE_PERSIST==1 );
+  assert( PAGER_JOURNALMODE_OFF==2 );
+  assert( PAGER_JOURNALMODE_TRUNCATE==3 );
+  assert( PAGER_JOURNALMODE_MEMORY==4 );
+  assert( PAGER_JOURNALMODE_WAL==5 );
+  assert( eMode>=0 && eMode<=ArraySize(azModeName) );
+
+  if( eMode==ArraySize(azModeName) ) return 0;
+  return azModeName[eMode];
+}
+
+/*
+** Process a pragma statement.  
+**
+** Pragmas are of this form:
+**
+**      PRAGMA [database.]id [= value]
+**
+** The identifier might also be a string.  The value is a string, and
+** identifier, or a number.  If minusFlag is true, then the value is
+** a number that was preceded by a minus sign.
+**
+** If the left side is "database.id" then pId1 is the database name
+** and pId2 is the id.  If the left side is just "id" then pId1 is the
+** id and pId2 is any empty string.
+*/
+void sqlite3Pragma(
+  Parse *pParse, 
+  Token *pId1,        /* First part of [database.]id field */
+  Token *pId2,        /* Second part of [database.]id field, or NULL */
+  Token *pValue,      /* Token for <value>, or NULL */
+  int minusFlag       /* True if a '-' sign preceded <value> */
+){
+  char *zLeft = 0;       /* Nul-terminated UTF-8 string <id> */
+  char *zRight = 0;      /* Nul-terminated UTF-8 string <value>, or NULL */
+  const char *zDb = 0;   /* The database name */
+  Token *pId;            /* Pointer to <id> token */
+  int iDb;               /* Database index for <database> */
+  sqlite3 *db = pParse->db;
+  Db *pDb;
+  Vdbe *v = pParse->pVdbe = sqlite3VdbeCreate(db);
+  if( v==0 ) return;
+  sqlite3VdbeRunOnlyOnce(v);
+  pParse->nMem = 2;
+
+  /* Interpret the [database.] part of the pragma statement. iDb is the
+  ** index of the database this pragma is being applied to in db.aDb[]. */
+  iDb = sqlite3TwoPartName(pParse, pId1, pId2, &pId);
+  if( iDb<0 ) return;
+  pDb = &db->aDb[iDb];
+
+  /* If the temp database has been explicitly named as part of the 
+  ** pragma, make sure it is open. 
+  */
+  if( iDb==1 && sqlite3OpenTempDatabase(pParse) ){
+    return;
+  }
+
+  zLeft = sqlite3NameFromToken(db, pId);
+  if( !zLeft ) return;
+  if( minusFlag ){
+    zRight = sqlite3MPrintf(db, "-%T", pValue);
+  }else{
+    zRight = sqlite3NameFromToken(db, pValue);
+  }
+
+  assert( pId2 );
+  zDb = pId2->n>0 ? pDb->zName : 0;
+  if( sqlite3AuthCheck(pParse, SQLITE_PRAGMA, zLeft, zRight, zDb) ){
+    goto pragma_out;
+  }
+ 
+#ifndef SQLITE_OMIT_PAGER_PRAGMAS
+  /*
+  **  PRAGMA [database.]default_cache_size
+  **  PRAGMA [database.]default_cache_size=N
+  **
+  ** The first form reports the current persistent setting for the
+  ** page cache size.  The value returned is the maximum number of
+  ** pages in the page cache.  The second form sets both the current
+  ** page cache size value and the persistent page cache size value
+  ** stored in the database file.
+  **
+  ** Older versions of SQLite would set the default cache size to a
+  ** negative number to indicate synchronous=OFF.  These days, synchronous
+  ** is always on by default regardless of the sign of the default cache
+  ** size.  But continue to take the absolute value of the default cache
+  ** size of historical compatibility.
+  */
+  if( sqlite3StrICmp(zLeft,"default_cache_size")==0 ){
+    static const VdbeOpList getCacheSize[] = {
+      { OP_Transaction, 0, 0,        0},                         /* 0 */
+      { OP_ReadCookie,  0, 1,        BTREE_DEFAULT_CACHE_SIZE},  /* 1 */
+      { OP_IfPos,       1, 7,        0},
+      { OP_Integer,     0, 2,        0},
+      { OP_Subtract,    1, 2,        1},
+      { OP_IfPos,       1, 7,        0},
+      { OP_Integer,     0, 1,        0},                         /* 6 */
+      { OP_ResultRow,   1, 1,        0},
+    };
+    int addr;
+    if( sqlite3ReadSchema(pParse) ) goto pragma_out;
+    sqlite3VdbeUsesBtree(v, iDb);
+    if( !zRight ){
+      sqlite3VdbeSetNumCols(v, 1);
+      sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "cache_size", SQLITE_STATIC);
+      pParse->nMem += 2;
+      addr = sqlite3VdbeAddOpList(v, ArraySize(getCacheSize), getCacheSize);
+      sqlite3VdbeChangeP1(v, addr, iDb);
+      sqlite3VdbeChangeP1(v, addr+1, iDb);
+      sqlite3VdbeChangeP1(v, addr+6, SQLITE_DEFAULT_CACHE_SIZE);
+    }else{
+      int size = sqlite3AbsInt32(sqlite3Atoi(zRight));
+      sqlite3BeginWriteOperation(pParse, 0, iDb);
+      sqlite3VdbeAddOp2(v, OP_Integer, size, 1);
+      sqlite3VdbeAddOp3(v, OP_SetCookie, iDb, BTREE_DEFAULT_CACHE_SIZE, 1);
+      assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+      pDb->pSchema->cache_size = size;
+      sqlite3BtreeSetCacheSize(pDb->pBt, pDb->pSchema->cache_size);
+    }
+  }else
+
+  /*
+  **  PRAGMA [database.]page_size
+  **  PRAGMA [database.]page_size=N
+  **
+  ** The first form reports the current setting for the
+  ** database page size in bytes.  The second form sets the
+  ** database page size value.  The value can only be set if
+  ** the database has not yet been created.
+  */
+  if( sqlite3StrICmp(zLeft,"page_size")==0 ){
+    Btree *pBt = pDb->pBt;
+    assert( pBt!=0 );
+    if( !zRight ){
+      int size = ALWAYS(pBt) ? sqlite3BtreeGetPageSize(pBt) : 0;
+      returnSingleInt(pParse, "page_size", size);
+    }else{
+      /* Malloc may fail when setting the page-size, as there is an internal
+      ** buffer that the pager module resizes using sqlite3_realloc().
+      */
+      db->nextPagesize = sqlite3Atoi(zRight);
+      if( SQLITE_NOMEM==sqlite3BtreeSetPageSize(pBt, db->nextPagesize, -1, 0) ){
+        db->mallocFailed = 1;
+      }
+    }
+  }else
+
+  /*
+  **  PRAGMA [database.]secure_delete
+  **  PRAGMA [database.]secure_delete=ON/OFF
+  **
+  ** The first form reports the current setting for the
+  ** secure_delete flag.  The second form changes the secure_delete
+  ** flag setting and reports thenew value.
+  */
+  if( sqlite3StrICmp(zLeft,"secure_delete")==0 ){
+    Btree *pBt = pDb->pBt;
+    int b = -1;
+    assert( pBt!=0 );
+    if( zRight ){
+      b = sqlite3GetBoolean(zRight);
+    }
+    if( pId2->n==0 && b>=0 ){
+      int ii;
+      for(ii=0; ii<db->nDb; ii++){
+        sqlite3BtreeSecureDelete(db->aDb[ii].pBt, b);
+      }
+    }
+    b = sqlite3BtreeSecureDelete(pBt, b);
+    returnSingleInt(pParse, "secure_delete", b);
+  }else
+
+  /*
+  **  PRAGMA [database.]max_page_count
+  **  PRAGMA [database.]max_page_count=N
+  **
+  ** The first form reports the current setting for the
+  ** maximum number of pages in the database file.  The 
+  ** second form attempts to change this setting.  Both
+  ** forms return the current setting.
+  **
+  **  PRAGMA [database.]page_count
+  **
+  ** Return the number of pages in the specified database.
+  */
+  if( sqlite3StrICmp(zLeft,"page_count")==0
+   || sqlite3StrICmp(zLeft,"max_page_count")==0
+  ){
+    int iReg;
+    if( sqlite3ReadSchema(pParse) ) goto pragma_out;
+    sqlite3CodeVerifySchema(pParse, iDb);
+    iReg = ++pParse->nMem;
+    if( sqlite3Tolower(zLeft[0])=='p' ){
+      sqlite3VdbeAddOp2(v, OP_Pagecount, iDb, iReg);
+    }else{
+      sqlite3VdbeAddOp3(v, OP_MaxPgcnt, iDb, iReg, sqlite3Atoi(zRight));
+    }
+    sqlite3VdbeAddOp2(v, OP_ResultRow, iReg, 1);
+    sqlite3VdbeSetNumCols(v, 1);
+    sqlite3VdbeSetColName(v, 0, COLNAME_NAME, zLeft, SQLITE_TRANSIENT);
+  }else
+
+  /*
+  **  PRAGMA [database.]locking_mode
+  **  PRAGMA [database.]locking_mode = (normal|exclusive)
+  */
+  if( sqlite3StrICmp(zLeft,"locking_mode")==0 ){
+    const char *zRet = "normal";
+    int eMode = getLockingMode(zRight);
+
+    if( pId2->n==0 && eMode==PAGER_LOCKINGMODE_QUERY ){
+      /* Simple "PRAGMA locking_mode;" statement. This is a query for
+      ** the current default locking mode (which may be different to
+      ** the locking-mode of the main database).
+      */
+      eMode = db->dfltLockMode;
+    }else{
+      Pager *pPager;
+      if( pId2->n==0 ){
+        /* This indicates that no database name was specified as part
+        ** of the PRAGMA command. In this case the locking-mode must be
+        ** set on all attached databases, as well as the main db file.
+        **
+        ** Also, the sqlite3.dfltLockMode variable is set so that
+        ** any subsequently attached databases also use the specified
+        ** locking mode.
+        */
+        int ii;
+        assert(pDb==&db->aDb[0]);
+        for(ii=2; ii<db->nDb; ii++){
+          pPager = sqlite3BtreePager(db->aDb[ii].pBt);
+          sqlite3PagerLockingMode(pPager, eMode);
+        }
+        db->dfltLockMode = (u8)eMode;
+      }
+      pPager = sqlite3BtreePager(pDb->pBt);
+      eMode = sqlite3PagerLockingMode(pPager, eMode);
+    }
+
+    assert(eMode==PAGER_LOCKINGMODE_NORMAL||eMode==PAGER_LOCKINGMODE_EXCLUSIVE);
+    if( eMode==PAGER_LOCKINGMODE_EXCLUSIVE ){
+      zRet = "exclusive";
+    }
+    sqlite3VdbeSetNumCols(v, 1);
+    sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "locking_mode", SQLITE_STATIC);
+    sqlite3VdbeAddOp4(v, OP_String8, 0, 1, 0, zRet, 0);
+    sqlite3VdbeAddOp2(v, OP_ResultRow, 1, 1);
+  }else
+
+  /*
+  **  PRAGMA [database.]journal_mode
+  **  PRAGMA [database.]journal_mode =
+  **                      (delete|persist|off|truncate|memory|wal|off)
+  */
+  if( sqlite3StrICmp(zLeft,"journal_mode")==0 ){
+    int eMode;        /* One of the PAGER_JOURNALMODE_XXX symbols */
+    int ii;           /* Loop counter */
+
+    /* Force the schema to be loaded on all databases.  This causes all
+    ** database files to be opened and the journal_modes set.  This is
+    ** necessary because subsequent processing must know if the databases
+    ** are in WAL mode. */
+    if( sqlite3ReadSchema(pParse) ){
+      goto pragma_out;
+    }
+
+    sqlite3VdbeSetNumCols(v, 1);
+    sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "journal_mode", SQLITE_STATIC);
+
+    if( zRight==0 ){
+      /* If there is no "=MODE" part of the pragma, do a query for the
+      ** current mode */
+      eMode = PAGER_JOURNALMODE_QUERY;
+    }else{
+      const char *zMode;
+      int n = sqlite3Strlen30(zRight);
+      for(eMode=0; (zMode = sqlite3JournalModename(eMode))!=0; eMode++){
+        if( sqlite3StrNICmp(zRight, zMode, n)==0 ) break;
+      }
+      if( !zMode ){
+        /* If the "=MODE" part does not match any known journal mode,
+        ** then do a query */
+        eMode = PAGER_JOURNALMODE_QUERY;
+      }
+    }
+    if( eMode==PAGER_JOURNALMODE_QUERY && pId2->n==0 ){
+      /* Convert "PRAGMA journal_mode" into "PRAGMA main.journal_mode" */
+      iDb = 0;
+      pId2->n = 1;
+    }
+    for(ii=db->nDb-1; ii>=0; ii--){
+      if( db->aDb[ii].pBt && (ii==iDb || pId2->n==0) ){
+        sqlite3VdbeUsesBtree(v, ii);
+        sqlite3VdbeAddOp3(v, OP_JournalMode, ii, 1, eMode);
+      }
+    }
+    sqlite3VdbeAddOp2(v, OP_ResultRow, 1, 1);
+  }else
+
+  /*
+  **  PRAGMA [database.]journal_size_limit
+  **  PRAGMA [database.]journal_size_limit=N
+  **
+  ** Get or set the size limit on rollback journal files.
+  */
+  if( sqlite3StrICmp(zLeft,"journal_size_limit")==0 ){
+    Pager *pPager = sqlite3BtreePager(pDb->pBt);
+    i64 iLimit = -2;
+    if( zRight ){
+      sqlite3Atoi64(zRight, &iLimit, 1000000, SQLITE_UTF8);
+      if( iLimit<-1 ) iLimit = -1;
+    }
+    iLimit = sqlite3PagerJournalSizeLimit(pPager, iLimit);
+    returnSingleInt(pParse, "journal_size_limit", iLimit);
+  }else
+
+#endif /* SQLITE_OMIT_PAGER_PRAGMAS */
+
+  /*
+  **  PRAGMA [database.]auto_vacuum
+  **  PRAGMA [database.]auto_vacuum=N
+  **
+  ** Get or set the value of the database 'auto-vacuum' parameter.
+  ** The value is one of:  0 NONE 1 FULL 2 INCREMENTAL
+  */
+#ifndef SQLITE_OMIT_AUTOVACUUM
+  if( sqlite3StrICmp(zLeft,"auto_vacuum")==0 ){
+    Btree *pBt = pDb->pBt;
+    assert( pBt!=0 );
+    if( sqlite3ReadSchema(pParse) ){
+      goto pragma_out;
+    }
+    if( !zRight ){
+      int auto_vacuum;
+      if( ALWAYS(pBt) ){
+         auto_vacuum = sqlite3BtreeGetAutoVacuum(pBt);
+      }else{
+         auto_vacuum = SQLITE_DEFAULT_AUTOVACUUM;
+      }
+      returnSingleInt(pParse, "auto_vacuum", auto_vacuum);
+    }else{
+      int eAuto = getAutoVacuum(zRight);
+      assert( eAuto>=0 && eAuto<=2 );
+      db->nextAutovac = (u8)eAuto;
+      if( ALWAYS(eAuto>=0) ){
+        /* Call SetAutoVacuum() to set initialize the internal auto and
+        ** incr-vacuum flags. This is required in case this connection
+        ** creates the database file. It is important that it is created
+        ** as an auto-vacuum capable db.
+        */
+        int rc = sqlite3BtreeSetAutoVacuum(pBt, eAuto);
+        if( rc==SQLITE_OK && (eAuto==1 || eAuto==2) ){
+          /* When setting the auto_vacuum mode to either "full" or 
+          ** "incremental", write the value of meta[6] in the database
+          ** file. Before writing to meta[6], check that meta[3] indicates
+          ** that this really is an auto-vacuum capable database.
+          */
+          static const VdbeOpList setMeta6[] = {
+            { OP_Transaction,    0,         1,                 0},    /* 0 */
+            { OP_ReadCookie,     0,         1,         BTREE_LARGEST_ROOT_PAGE},
+            { OP_If,             1,         0,                 0},    /* 2 */
+            { OP_Halt,           SQLITE_OK, OE_Abort,          0},    /* 3 */
+            { OP_Integer,        0,         1,                 0},    /* 4 */
+            { OP_SetCookie,      0,         BTREE_INCR_VACUUM, 1},    /* 5 */
+          };
+          int iAddr;
+          iAddr = sqlite3VdbeAddOpList(v, ArraySize(setMeta6), setMeta6);
+          sqlite3VdbeChangeP1(v, iAddr, iDb);
+          sqlite3VdbeChangeP1(v, iAddr+1, iDb);
+          sqlite3VdbeChangeP2(v, iAddr+2, iAddr+4);
+          sqlite3VdbeChangeP1(v, iAddr+4, eAuto-1);
+          sqlite3VdbeChangeP1(v, iAddr+5, iDb);
+          sqlite3VdbeUsesBtree(v, iDb);
+        }
+      }
+    }
+  }else
+#endif
+
+  /*
+  **  PRAGMA [database.]incremental_vacuum(N)
+  **
+  ** Do N steps of incremental vacuuming on a database.
+  */
+#ifndef SQLITE_OMIT_AUTOVACUUM
+  if( sqlite3StrICmp(zLeft,"incremental_vacuum")==0 ){
+    int iLimit, addr;
+    if( sqlite3ReadSchema(pParse) ){
+      goto pragma_out;
+    }
+    if( zRight==0 || !sqlite3GetInt32(zRight, &iLimit) || iLimit<=0 ){
+      iLimit = 0x7fffffff;
+    }
+    sqlite3BeginWriteOperation(pParse, 0, iDb);
+    sqlite3VdbeAddOp2(v, OP_Integer, iLimit, 1);
+    addr = sqlite3VdbeAddOp1(v, OP_IncrVacuum, iDb);
+    sqlite3VdbeAddOp1(v, OP_ResultRow, 1);
+    sqlite3VdbeAddOp2(v, OP_AddImm, 1, -1);
+    sqlite3VdbeAddOp2(v, OP_IfPos, 1, addr);
+    sqlite3VdbeJumpHere(v, addr);
+  }else
+#endif
+
+#ifndef SQLITE_OMIT_PAGER_PRAGMAS
+  /*
+  **  PRAGMA [database.]cache_size
+  **  PRAGMA [database.]cache_size=N
+  **
+  ** The first form reports the current local setting for the
+  ** page cache size.  The local setting can be different from
+  ** the persistent cache size value that is stored in the database
+  ** file itself.  The value returned is the maximum number of
+  ** pages in the page cache.  The second form sets the local
+  ** page cache size value.  It does not change the persistent
+  ** cache size stored on the disk so the cache size will revert
+  ** to its default value when the database is closed and reopened.
+  ** N should be a positive integer.
+  */
+  if( sqlite3StrICmp(zLeft,"cache_size")==0 ){
+    if( sqlite3ReadSchema(pParse) ) goto pragma_out;
+    assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+    if( !zRight ){
+      returnSingleInt(pParse, "cache_size", pDb->pSchema->cache_size);
+    }else{
+      int size = sqlite3AbsInt32(sqlite3Atoi(zRight));
+      pDb->pSchema->cache_size = size;
+      sqlite3BtreeSetCacheSize(pDb->pBt, pDb->pSchema->cache_size);
+    }
+  }else
+
+  /*
+  **   PRAGMA temp_store
+  **   PRAGMA temp_store = "default"|"memory"|"file"
+  **
+  ** Return or set the local value of the temp_store flag.  Changing
+  ** the local value does not make changes to the disk file and the default
+  ** value will be restored the next time the database is opened.
+  **
+  ** Note that it is possible for the library compile-time options to
+  ** override this setting
+  */
+  if( sqlite3StrICmp(zLeft, "temp_store")==0 ){
+    if( !zRight ){
+      returnSingleInt(pParse, "temp_store", db->temp_store);
+    }else{
+      changeTempStorage(pParse, zRight);
+    }
+  }else
+
+  /*
+  **   PRAGMA temp_store_directory
+  **   PRAGMA temp_store_directory = ""|"directory_name"
+  **
+  ** Return or set the local value of the temp_store_directory flag.  Changing
+  ** the value sets a specific directory to be used for temporary files.
+  ** Setting to a null string reverts to the default temporary directory search.
+  ** If temporary directory is changed, then invalidateTempStorage.
+  **
+  */
+  if( sqlite3StrICmp(zLeft, "temp_store_directory")==0 ){
+    if( !zRight ){
+      if( sqlite3_temp_directory ){
+        sqlite3VdbeSetNumCols(v, 1);
+        sqlite3VdbeSetColName(v, 0, COLNAME_NAME, 
+            "temp_store_directory", SQLITE_STATIC);
+        sqlite3VdbeAddOp4(v, OP_String8, 0, 1, 0, sqlite3_temp_directory, 0);
+        sqlite3VdbeAddOp2(v, OP_ResultRow, 1, 1);
+      }
+    }else{
+#ifndef SQLITE_OMIT_WSD
+      if( zRight[0] ){
+        int rc;
+        int res;
+        rc = sqlite3OsAccess(db->pVfs, zRight, SQLITE_ACCESS_READWRITE, &res);
+        if( rc!=SQLITE_OK || res==0 ){
+          sqlite3ErrorMsg(pParse, "not a writable directory");
+          goto pragma_out;
+        }
+      }
+      if( SQLITE_TEMP_STORE==0
+       || (SQLITE_TEMP_STORE==1 && db->temp_store<=1)
+       || (SQLITE_TEMP_STORE==2 && db->temp_store==1)
+      ){
+        invalidateTempStorage(pParse);
+      }
+      sqlite3_free(sqlite3_temp_directory);
+      if( zRight[0] ){
+        sqlite3_temp_directory = sqlite3_mprintf("%s", zRight);
+      }else{
+        sqlite3_temp_directory = 0;
+      }
+#endif /* SQLITE_OMIT_WSD */
+    }
+  }else
+
+#if !defined(SQLITE_ENABLE_LOCKING_STYLE)
+#  if defined(__APPLE__)
+#    define SQLITE_ENABLE_LOCKING_STYLE 1
+#  else
+#    define SQLITE_ENABLE_LOCKING_STYLE 0
+#  endif
+#endif
+#if SQLITE_ENABLE_LOCKING_STYLE
+  /*
+   **   PRAGMA [database.]lock_proxy_file
+   **   PRAGMA [database.]lock_proxy_file = ":auto:"|"lock_file_path"
+   **
+   ** Return or set the value of the lock_proxy_file flag.  Changing
+   ** the value sets a specific file to be used for database access locks.
+   **
+   */
+  if( sqlite3StrICmp(zLeft, "lock_proxy_file")==0 ){
+    if( !zRight ){
+      Pager *pPager = sqlite3BtreePager(pDb->pBt);
+      char *proxy_file_path = NULL;
+      sqlite3_file *pFile = sqlite3PagerFile(pPager);
+      sqlite3OsFileControl(pFile, SQLITE_GET_LOCKPROXYFILE, 
+                           &proxy_file_path);
+      
+      if( proxy_file_path ){
+        sqlite3VdbeSetNumCols(v, 1);
+        sqlite3VdbeSetColName(v, 0, COLNAME_NAME, 
+                              "lock_proxy_file", SQLITE_STATIC);
+        sqlite3VdbeAddOp4(v, OP_String8, 0, 1, 0, proxy_file_path, 0);
+        sqlite3VdbeAddOp2(v, OP_ResultRow, 1, 1);
+      }
+    }else{
+      Pager *pPager = sqlite3BtreePager(pDb->pBt);
+      sqlite3_file *pFile = sqlite3PagerFile(pPager);
+      int res;
+      if( zRight[0] ){
+        res=sqlite3OsFileControl(pFile, SQLITE_SET_LOCKPROXYFILE, 
+                                     zRight);
+      } else {
+        res=sqlite3OsFileControl(pFile, SQLITE_SET_LOCKPROXYFILE, 
+                                     NULL);
+      }
+      if( res!=SQLITE_OK ){
+        sqlite3ErrorMsg(pParse, "failed to set lock proxy file");
+        goto pragma_out;
+      }
+    }
+  }else
+#endif /* SQLITE_ENABLE_LOCKING_STYLE */      
+    
+  /*
+  **   PRAGMA [database.]synchronous
+  **   PRAGMA [database.]synchronous=OFF|ON|NORMAL|FULL
+  **
+  ** Return or set the local value of the synchronous flag.  Changing
+  ** the local value does not make changes to the disk file and the
+  ** default value will be restored the next time the database is
+  ** opened.
+  */
+  if( sqlite3StrICmp(zLeft,"synchronous")==0 ){
+    if( sqlite3ReadSchema(pParse) ) goto pragma_out;
+    if( !zRight ){
+      returnSingleInt(pParse, "synchronous", pDb->safety_level-1);
+    }else{
+      if( !db->autoCommit ){
+        sqlite3ErrorMsg(pParse, 
+            "Safety level may not be changed inside a transaction");
+      }else{
+        pDb->safety_level = getSafetyLevel(zRight)+1;
+      }
+    }
+  }else
+#endif /* SQLITE_OMIT_PAGER_PRAGMAS */
+
+#ifndef SQLITE_OMIT_FLAG_PRAGMAS
+  if( flagPragma(pParse, zLeft, zRight) ){
+    /* The flagPragma() subroutine also generates any necessary code
+    ** there is nothing more to do here */
+  }else
+#endif /* SQLITE_OMIT_FLAG_PRAGMAS */
+
+#ifndef SQLITE_OMIT_SCHEMA_PRAGMAS
+  /*
+  **   PRAGMA table_info(<table>)
+  **
+  ** Return a single row for each column of the named table. The columns of
+  ** the returned data set are:
+  **
+  ** cid:        Column id (numbered from left to right, starting at 0)
+  ** name:       Column name
+  ** type:       Column declaration type.
+  ** notnull:    True if 'NOT NULL' is part of column declaration
+  ** dflt_value: The default value for the column, if any.
+  */
+  if( sqlite3StrICmp(zLeft, "table_info")==0 && zRight ){
+    Table *pTab;
+    if( sqlite3ReadSchema(pParse) ) goto pragma_out;
+    pTab = sqlite3FindTable(db, zRight, zDb);
+    if( pTab ){
+      int i;
+      int nHidden = 0;
+      Column *pCol;
+      sqlite3VdbeSetNumCols(v, 6);
+      pParse->nMem = 6;
+      sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "cid", SQLITE_STATIC);
+      sqlite3VdbeSetColName(v, 1, COLNAME_NAME, "name", SQLITE_STATIC);
+      sqlite3VdbeSetColName(v, 2, COLNAME_NAME, "type", SQLITE_STATIC);
+      sqlite3VdbeSetColName(v, 3, COLNAME_NAME, "notnull", SQLITE_STATIC);
+      sqlite3VdbeSetColName(v, 4, COLNAME_NAME, "dflt_value", SQLITE_STATIC);
+      sqlite3VdbeSetColName(v, 5, COLNAME_NAME, "pk", SQLITE_STATIC);
+      sqlite3ViewGetColumnNames(pParse, pTab);
+      for(i=0, pCol=pTab->aCol; i<pTab->nCol; i++, pCol++){
+        if( IsHiddenColumn(pCol) ){
+          nHidden++;
+          continue;
+        }
+        sqlite3VdbeAddOp2(v, OP_Integer, i-nHidden, 1);
+        sqlite3VdbeAddOp4(v, OP_String8, 0, 2, 0, pCol->zName, 0);
+        sqlite3VdbeAddOp4(v, OP_String8, 0, 3, 0,
+           pCol->zType ? pCol->zType : "", 0);
+        sqlite3VdbeAddOp2(v, OP_Integer, (pCol->notNull ? 1 : 0), 4);
+        if( pCol->zDflt ){
+          sqlite3VdbeAddOp4(v, OP_String8, 0, 5, 0, (char*)pCol->zDflt, 0);
+        }else{
+          sqlite3VdbeAddOp2(v, OP_Null, 0, 5);
+        }
+        sqlite3VdbeAddOp2(v, OP_Integer, pCol->isPrimKey, 6);
+        sqlite3VdbeAddOp2(v, OP_ResultRow, 1, 6);
+      }
+    }
+  }else
+
+  if( sqlite3StrICmp(zLeft, "index_info")==0 && zRight ){
+    Index *pIdx;
+    Table *pTab;
+    if( sqlite3ReadSchema(pParse) ) goto pragma_out;
+    pIdx = sqlite3FindIndex(db, zRight, zDb);
+    if( pIdx ){
+      int i;
+      pTab = pIdx->pTable;
+      sqlite3VdbeSetNumCols(v, 3);
+      pParse->nMem = 3;
+      sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "seqno", SQLITE_STATIC);
+      sqlite3VdbeSetColName(v, 1, COLNAME_NAME, "cid", SQLITE_STATIC);
+      sqlite3VdbeSetColName(v, 2, COLNAME_NAME, "name", SQLITE_STATIC);
+      for(i=0; i<pIdx->nColumn; i++){
+        int cnum = pIdx->aiColumn[i];
+        sqlite3VdbeAddOp2(v, OP_Integer, i, 1);
+        sqlite3VdbeAddOp2(v, OP_Integer, cnum, 2);
+        assert( pTab->nCol>cnum );
+        sqlite3VdbeAddOp4(v, OP_String8, 0, 3, 0, pTab->aCol[cnum].zName, 0);
+        sqlite3VdbeAddOp2(v, OP_ResultRow, 1, 3);
+      }
+    }
+  }else
+
+  if( sqlite3StrICmp(zLeft, "index_list")==0 && zRight ){
+    Index *pIdx;
+    Table *pTab;
+    if( sqlite3ReadSchema(pParse) ) goto pragma_out;
+    pTab = sqlite3FindTable(db, zRight, zDb);
+    if( pTab ){
+      v = sqlite3GetVdbe(pParse);
+      pIdx = pTab->pIndex;
+      if( pIdx ){
+        int i = 0; 
+        sqlite3VdbeSetNumCols(v, 3);
+        pParse->nMem = 3;
+        sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "seq", SQLITE_STATIC);
+        sqlite3VdbeSetColName(v, 1, COLNAME_NAME, "name", SQLITE_STATIC);
+        sqlite3VdbeSetColName(v, 2, COLNAME_NAME, "unique", SQLITE_STATIC);
+        while(pIdx){
+          sqlite3VdbeAddOp2(v, OP_Integer, i, 1);
+          sqlite3VdbeAddOp4(v, OP_String8, 0, 2, 0, pIdx->zName, 0);
+          sqlite3VdbeAddOp2(v, OP_Integer, pIdx->onError!=OE_None, 3);
+          sqlite3VdbeAddOp2(v, OP_ResultRow, 1, 3);
+          ++i;
+          pIdx = pIdx->pNext;
+        }
+      }
+    }
+  }else
+
+  if( sqlite3StrICmp(zLeft, "database_list")==0 ){
+    int i;
+    if( sqlite3ReadSchema(pParse) ) goto pragma_out;
+    sqlite3VdbeSetNumCols(v, 3);
+    pParse->nMem = 3;
+    sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "seq", SQLITE_STATIC);
+    sqlite3VdbeSetColName(v, 1, COLNAME_NAME, "name", SQLITE_STATIC);
+    sqlite3VdbeSetColName(v, 2, COLNAME_NAME, "file", SQLITE_STATIC);
+    for(i=0; i<db->nDb; i++){
+      if( db->aDb[i].pBt==0 ) continue;
+      assert( db->aDb[i].zName!=0 );
+      sqlite3VdbeAddOp2(v, OP_Integer, i, 1);
+      sqlite3VdbeAddOp4(v, OP_String8, 0, 2, 0, db->aDb[i].zName, 0);
+      sqlite3VdbeAddOp4(v, OP_String8, 0, 3, 0,
+           sqlite3BtreeGetFilename(db->aDb[i].pBt), 0);
+      sqlite3VdbeAddOp2(v, OP_ResultRow, 1, 3);
+    }
+  }else
+
+  if( sqlite3StrICmp(zLeft, "collation_list")==0 ){
+    int i = 0;
+    HashElem *p;
+    sqlite3VdbeSetNumCols(v, 2);
+    pParse->nMem = 2;
+    sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "seq", SQLITE_STATIC);
+    sqlite3VdbeSetColName(v, 1, COLNAME_NAME, "name", SQLITE_STATIC);
+    for(p=sqliteHashFirst(&db->aCollSeq); p; p=sqliteHashNext(p)){
+      CollSeq *pColl = (CollSeq *)sqliteHashData(p);
+      sqlite3VdbeAddOp2(v, OP_Integer, i++, 1);
+      sqlite3VdbeAddOp4(v, OP_String8, 0, 2, 0, pColl->zName, 0);
+      sqlite3VdbeAddOp2(v, OP_ResultRow, 1, 2);
+    }
+  }else
+#endif /* SQLITE_OMIT_SCHEMA_PRAGMAS */
+
+#ifndef SQLITE_OMIT_FOREIGN_KEY
+  if( sqlite3StrICmp(zLeft, "foreign_key_list")==0 && zRight ){
+    FKey *pFK;
+    Table *pTab;
+    if( sqlite3ReadSchema(pParse) ) goto pragma_out;
+    pTab = sqlite3FindTable(db, zRight, zDb);
+    if( pTab ){
+      v = sqlite3GetVdbe(pParse);
+      pFK = pTab->pFKey;
+      if( pFK ){
+        int i = 0; 
+        sqlite3VdbeSetNumCols(v, 8);
+        pParse->nMem = 8;
+        sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "id", SQLITE_STATIC);
+        sqlite3VdbeSetColName(v, 1, COLNAME_NAME, "seq", SQLITE_STATIC);
+        sqlite3VdbeSetColName(v, 2, COLNAME_NAME, "table", SQLITE_STATIC);
+        sqlite3VdbeSetColName(v, 3, COLNAME_NAME, "from", SQLITE_STATIC);
+        sqlite3VdbeSetColName(v, 4, COLNAME_NAME, "to", SQLITE_STATIC);
+        sqlite3VdbeSetColName(v, 5, COLNAME_NAME, "on_update", SQLITE_STATIC);
+        sqlite3VdbeSetColName(v, 6, COLNAME_NAME, "on_delete", SQLITE_STATIC);
+        sqlite3VdbeSetColName(v, 7, COLNAME_NAME, "match", SQLITE_STATIC);
+        while(pFK){
+          int j;
+          for(j=0; j<pFK->nCol; j++){
+            char *zCol = pFK->aCol[j].zCol;
+            char *zOnDelete = (char *)actionName(pFK->aAction[0]);
+            char *zOnUpdate = (char *)actionName(pFK->aAction[1]);
+            sqlite3VdbeAddOp2(v, OP_Integer, i, 1);
+            sqlite3VdbeAddOp2(v, OP_Integer, j, 2);
+            sqlite3VdbeAddOp4(v, OP_String8, 0, 3, 0, pFK->zTo, 0);
+            sqlite3VdbeAddOp4(v, OP_String8, 0, 4, 0,
+                              pTab->aCol[pFK->aCol[j].iFrom].zName, 0);
+            sqlite3VdbeAddOp4(v, zCol ? OP_String8 : OP_Null, 0, 5, 0, zCol, 0);
+            sqlite3VdbeAddOp4(v, OP_String8, 0, 6, 0, zOnUpdate, 0);
+            sqlite3VdbeAddOp4(v, OP_String8, 0, 7, 0, zOnDelete, 0);
+            sqlite3VdbeAddOp4(v, OP_String8, 0, 8, 0, "NONE", 0);
+            sqlite3VdbeAddOp2(v, OP_ResultRow, 1, 8);
+          }
+          ++i;
+          pFK = pFK->pNextFrom;
+        }
+      }
+    }
+  }else
+#endif /* !defined(SQLITE_OMIT_FOREIGN_KEY) */
+
+#ifndef NDEBUG
+  if( sqlite3StrICmp(zLeft, "parser_trace")==0 ){
+    if( zRight ){
+      if( sqlite3GetBoolean(zRight) ){
+        sqlite3ParserTrace(stderr, "parser: ");
+      }else{
+        sqlite3ParserTrace(0, 0);
+      }
+    }
+  }else
+#endif
+
+  /* Reinstall the LIKE and GLOB functions.  The variant of LIKE
+  ** used will be case sensitive or not depending on the RHS.
+  */
+  if( sqlite3StrICmp(zLeft, "case_sensitive_like")==0 ){
+    if( zRight ){
+      sqlite3RegisterLikeFunctions(db, sqlite3GetBoolean(zRight));
+    }
+  }else
+
+#ifndef SQLITE_INTEGRITY_CHECK_ERROR_MAX
+# define SQLITE_INTEGRITY_CHECK_ERROR_MAX 100
+#endif
+
+#ifndef SQLITE_OMIT_INTEGRITY_CHECK
+  /* Pragma "quick_check" is an experimental reduced version of 
+  ** integrity_check designed to detect most database corruption
+  ** without most of the overhead of a full integrity-check.
+  */
+  if( sqlite3StrICmp(zLeft, "integrity_check")==0
+   || sqlite3StrICmp(zLeft, "quick_check")==0 
+  ){
+    int i, j, addr, mxErr;
+
+    /* Code that appears at the end of the integrity check.  If no error
+    ** messages have been generated, output OK.  Otherwise output the
+    ** error message
+    */
+    static const VdbeOpList endCode[] = {
+      { OP_AddImm,      1, 0,        0},    /* 0 */
+      { OP_IfNeg,       1, 0,        0},    /* 1 */
+      { OP_String8,     0, 3,        0},    /* 2 */
+      { OP_ResultRow,   3, 1,        0},
+    };
+
+    int isQuick = (sqlite3Tolower(zLeft[0])=='q');
+
+    /* Initialize the VDBE program */
+    if( sqlite3ReadSchema(pParse) ) goto pragma_out;
+    pParse->nMem = 6;
+    sqlite3VdbeSetNumCols(v, 1);
+    sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "integrity_check", SQLITE_STATIC);
+
+    /* Set the maximum error count */
+    mxErr = SQLITE_INTEGRITY_CHECK_ERROR_MAX;
+    if( zRight ){
+      sqlite3GetInt32(zRight, &mxErr);
+      if( mxErr<=0 ){
+        mxErr = SQLITE_INTEGRITY_CHECK_ERROR_MAX;
+      }
+    }
+    sqlite3VdbeAddOp2(v, OP_Integer, mxErr, 1);  /* reg[1] holds errors left */
+
+    /* Do an integrity check on each database file */
+    for(i=0; i<db->nDb; i++){
+      HashElem *x;
+      Hash *pTbls;
+      int cnt = 0;
+
+      if( OMIT_TEMPDB && i==1 ) continue;
+
+      sqlite3CodeVerifySchema(pParse, i);
+      addr = sqlite3VdbeAddOp1(v, OP_IfPos, 1); /* Halt if out of errors */
+      sqlite3VdbeAddOp2(v, OP_Halt, 0, 0);
+      sqlite3VdbeJumpHere(v, addr);
+
+      /* Do an integrity check of the B-Tree
+      **
+      ** Begin by filling registers 2, 3, ... with the root pages numbers
+      ** for all tables and indices in the database.
+      */
+      assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+      pTbls = &db->aDb[i].pSchema->tblHash;
+      for(x=sqliteHashFirst(pTbls); x; x=sqliteHashNext(x)){
+        Table *pTab = sqliteHashData(x);
+        Index *pIdx;
+        sqlite3VdbeAddOp2(v, OP_Integer, pTab->tnum, 2+cnt);
+        cnt++;
+        for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+          sqlite3VdbeAddOp2(v, OP_Integer, pIdx->tnum, 2+cnt);
+          cnt++;
+        }
+      }
+
+      /* Make sure sufficient number of registers have been allocated */
+      if( pParse->nMem < cnt+4 ){
+        pParse->nMem = cnt+4;
+      }
+
+      /* Do the b-tree integrity checks */
+      sqlite3VdbeAddOp3(v, OP_IntegrityCk, 2, cnt, 1);
+      sqlite3VdbeChangeP5(v, (u8)i);
+      addr = sqlite3VdbeAddOp1(v, OP_IsNull, 2);
+      sqlite3VdbeAddOp4(v, OP_String8, 0, 3, 0,
+         sqlite3MPrintf(db, "*** in database %s ***\n", db->aDb[i].zName),
+         P4_DYNAMIC);
+      sqlite3VdbeAddOp3(v, OP_Move, 2, 4, 1);
+      sqlite3VdbeAddOp3(v, OP_Concat, 4, 3, 2);
+      sqlite3VdbeAddOp2(v, OP_ResultRow, 2, 1);
+      sqlite3VdbeJumpHere(v, addr);
+
+      /* Make sure all the indices are constructed correctly.
+      */
+      for(x=sqliteHashFirst(pTbls); x && !isQuick; x=sqliteHashNext(x)){
+        Table *pTab = sqliteHashData(x);
+        Index *pIdx;
+        int loopTop;
+
+        if( pTab->pIndex==0 ) continue;
+        addr = sqlite3VdbeAddOp1(v, OP_IfPos, 1);  /* Stop if out of errors */
+        sqlite3VdbeAddOp2(v, OP_Halt, 0, 0);
+        sqlite3VdbeJumpHere(v, addr);
+        sqlite3OpenTableAndIndices(pParse, pTab, 1, OP_OpenRead);
+        sqlite3VdbeAddOp2(v, OP_Integer, 0, 2);  /* reg(2) will count entries */
+        loopTop = sqlite3VdbeAddOp2(v, OP_Rewind, 1, 0);
+        sqlite3VdbeAddOp2(v, OP_AddImm, 2, 1);   /* increment entry count */
+        for(j=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, j++){
+          int jmp2;
+          int r1;
+          static const VdbeOpList idxErr[] = {
+            { OP_AddImm,      1, -1,  0},
+            { OP_String8,     0,  3,  0},    /* 1 */
+            { OP_Rowid,       1,  4,  0},
+            { OP_String8,     0,  5,  0},    /* 3 */
+            { OP_String8,     0,  6,  0},    /* 4 */
+            { OP_Concat,      4,  3,  3},
+            { OP_Concat,      5,  3,  3},
+            { OP_Concat,      6,  3,  3},
+            { OP_ResultRow,   3,  1,  0},
+            { OP_IfPos,       1,  0,  0},    /* 9 */
+            { OP_Halt,        0,  0,  0},
+          };
+          r1 = sqlite3GenerateIndexKey(pParse, pIdx, 1, 3, 0);
+          jmp2 = sqlite3VdbeAddOp4Int(v, OP_Found, j+2, 0, r1, pIdx->nColumn+1);
+          addr = sqlite3VdbeAddOpList(v, ArraySize(idxErr), idxErr);
+          sqlite3VdbeChangeP4(v, addr+1, "rowid ", P4_STATIC);
+          sqlite3VdbeChangeP4(v, addr+3, " missing from index ", P4_STATIC);
+          sqlite3VdbeChangeP4(v, addr+4, pIdx->zName, P4_TRANSIENT);
+          sqlite3VdbeJumpHere(v, addr+9);
+          sqlite3VdbeJumpHere(v, jmp2);
+        }
+        sqlite3VdbeAddOp2(v, OP_Next, 1, loopTop+1);
+        sqlite3VdbeJumpHere(v, loopTop);
+        for(j=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, j++){
+          static const VdbeOpList cntIdx[] = {
+             { OP_Integer,      0,  3,  0},
+             { OP_Rewind,       0,  0,  0},  /* 1 */
+             { OP_AddImm,       3,  1,  0},
+             { OP_Next,         0,  0,  0},  /* 3 */
+             { OP_Eq,           2,  0,  3},  /* 4 */
+             { OP_AddImm,       1, -1,  0},
+             { OP_String8,      0,  2,  0},  /* 6 */
+             { OP_String8,      0,  3,  0},  /* 7 */
+             { OP_Concat,       3,  2,  2},
+             { OP_ResultRow,    2,  1,  0},
+          };
+          addr = sqlite3VdbeAddOp1(v, OP_IfPos, 1);
+          sqlite3VdbeAddOp2(v, OP_Halt, 0, 0);
+          sqlite3VdbeJumpHere(v, addr);
+          addr = sqlite3VdbeAddOpList(v, ArraySize(cntIdx), cntIdx);
+          sqlite3VdbeChangeP1(v, addr+1, j+2);
+          sqlite3VdbeChangeP2(v, addr+1, addr+4);
+          sqlite3VdbeChangeP1(v, addr+3, j+2);
+          sqlite3VdbeChangeP2(v, addr+3, addr+2);
+          sqlite3VdbeJumpHere(v, addr+4);
+          sqlite3VdbeChangeP4(v, addr+6, 
+                     "wrong # of entries in index ", P4_STATIC);
+          sqlite3VdbeChangeP4(v, addr+7, pIdx->zName, P4_TRANSIENT);
+        }
+      } 
+    }
+    addr = sqlite3VdbeAddOpList(v, ArraySize(endCode), endCode);
+    sqlite3VdbeChangeP2(v, addr, -mxErr);
+    sqlite3VdbeJumpHere(v, addr+1);
+    sqlite3VdbeChangeP4(v, addr+2, "ok", P4_STATIC);
+  }else
+#endif /* SQLITE_OMIT_INTEGRITY_CHECK */
+
+#ifndef SQLITE_OMIT_UTF16
+  /*
+  **   PRAGMA encoding
+  **   PRAGMA encoding = "utf-8"|"utf-16"|"utf-16le"|"utf-16be"
+  **
+  ** In its first form, this pragma returns the encoding of the main
+  ** database. If the database is not initialized, it is initialized now.
+  **
+  ** The second form of this pragma is a no-op if the main database file
+  ** has not already been initialized. In this case it sets the default
+  ** encoding that will be used for the main database file if a new file
+  ** is created. If an existing main database file is opened, then the
+  ** default text encoding for the existing database is used.
+  ** 
+  ** In all cases new databases created using the ATTACH command are
+  ** created to use the same default text encoding as the main database. If
+  ** the main database has not been initialized and/or created when ATTACH
+  ** is executed, this is done before the ATTACH operation.
+  **
+  ** In the second form this pragma sets the text encoding to be used in
+  ** new database files created using this database handle. It is only
+  ** useful if invoked immediately after the main database i
+  */
+  if( sqlite3StrICmp(zLeft, "encoding")==0 ){
+    static const struct EncName {
+      char *zName;
+      u8 enc;
+    } encnames[] = {
+      { "UTF8",     SQLITE_UTF8        },
+      { "UTF-8",    SQLITE_UTF8        },  /* Must be element [1] */
+      { "UTF-16le", SQLITE_UTF16LE     },  /* Must be element [2] */
+      { "UTF-16be", SQLITE_UTF16BE     },  /* Must be element [3] */
+      { "UTF16le",  SQLITE_UTF16LE     },
+      { "UTF16be",  SQLITE_UTF16BE     },
+      { "UTF-16",   0                  }, /* SQLITE_UTF16NATIVE */
+      { "UTF16",    0                  }, /* SQLITE_UTF16NATIVE */
+      { 0, 0 }
+    };
+    const struct EncName *pEnc;
+    if( !zRight ){    /* "PRAGMA encoding" */
+      if( sqlite3ReadSchema(pParse) ) goto pragma_out;
+      sqlite3VdbeSetNumCols(v, 1);
+      sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "encoding", SQLITE_STATIC);
+      sqlite3VdbeAddOp2(v, OP_String8, 0, 1);
+      assert( encnames[SQLITE_UTF8].enc==SQLITE_UTF8 );
+      assert( encnames[SQLITE_UTF16LE].enc==SQLITE_UTF16LE );
+      assert( encnames[SQLITE_UTF16BE].enc==SQLITE_UTF16BE );
+      sqlite3VdbeChangeP4(v, -1, encnames[ENC(pParse->db)].zName, P4_STATIC);
+      sqlite3VdbeAddOp2(v, OP_ResultRow, 1, 1);
+    }else{                        /* "PRAGMA encoding = XXX" */
+      /* Only change the value of sqlite.enc if the database handle is not
+      ** initialized. If the main database exists, the new sqlite.enc value
+      ** will be overwritten when the schema is next loaded. If it does not
+      ** already exists, it will be created to use the new encoding value.
+      */
+      if( 
+        !(DbHasProperty(db, 0, DB_SchemaLoaded)) || 
+        DbHasProperty(db, 0, DB_Empty) 
+      ){
+        for(pEnc=&encnames[0]; pEnc->zName; pEnc++){
+          if( 0==sqlite3StrICmp(zRight, pEnc->zName) ){
+            ENC(pParse->db) = pEnc->enc ? pEnc->enc : SQLITE_UTF16NATIVE;
+            break;
+          }
+        }
+        if( !pEnc->zName ){
+          sqlite3ErrorMsg(pParse, "unsupported encoding: %s", zRight);
+        }
+      }
+    }
+  }else
+#endif /* SQLITE_OMIT_UTF16 */
+
+#ifndef SQLITE_OMIT_SCHEMA_VERSION_PRAGMAS
+  /*
+  **   PRAGMA [database.]schema_version
+  **   PRAGMA [database.]schema_version = <integer>
+  **
+  **   PRAGMA [database.]user_version
+  **   PRAGMA [database.]user_version = <integer>
+  **
+  ** The pragma's schema_version and user_version are used to set or get
+  ** the value of the schema-version and user-version, respectively. Both
+  ** the schema-version and the user-version are 32-bit signed integers
+  ** stored in the database header.
+  **
+  ** The schema-cookie is usually only manipulated internally by SQLite. It
+  ** is incremented by SQLite whenever the database schema is modified (by
+  ** creating or dropping a table or index). The schema version is used by
+  ** SQLite each time a query is executed to ensure that the internal cache
+  ** of the schema used when compiling the SQL query matches the schema of
+  ** the database against which the compiled query is actually executed.
+  ** Subverting this mechanism by using "PRAGMA schema_version" to modify
+  ** the schema-version is potentially dangerous and may lead to program
+  ** crashes or database corruption. Use with caution!
+  **
+  ** The user-version is not used internally by SQLite. It may be used by
+  ** applications for any purpose.
+  */
+  if( sqlite3StrICmp(zLeft, "schema_version")==0 
+   || sqlite3StrICmp(zLeft, "user_version")==0 
+   || sqlite3StrICmp(zLeft, "freelist_count")==0 
+  ){
+    int iCookie;   /* Cookie index. 1 for schema-cookie, 6 for user-cookie. */
+    sqlite3VdbeUsesBtree(v, iDb);
+    switch( zLeft[0] ){
+      case 'f': case 'F':
+        iCookie = BTREE_FREE_PAGE_COUNT;
+        break;
+      case 's': case 'S':
+        iCookie = BTREE_SCHEMA_VERSION;
+        break;
+      default:
+        iCookie = BTREE_USER_VERSION;
+        break;
+    }
+
+    if( zRight && iCookie!=BTREE_FREE_PAGE_COUNT ){
+      /* Write the specified cookie value */
+      static const VdbeOpList setCookie[] = {
+        { OP_Transaction,    0,  1,  0},    /* 0 */
+        { OP_Integer,        0,  1,  0},    /* 1 */
+        { OP_SetCookie,      0,  0,  1},    /* 2 */
+      };
+      int addr = sqlite3VdbeAddOpList(v, ArraySize(setCookie), setCookie);
+      sqlite3VdbeChangeP1(v, addr, iDb);
+      sqlite3VdbeChangeP1(v, addr+1, sqlite3Atoi(zRight));
+      sqlite3VdbeChangeP1(v, addr+2, iDb);
+      sqlite3VdbeChangeP2(v, addr+2, iCookie);
+    }else{
+      /* Read the specified cookie value */
+      static const VdbeOpList readCookie[] = {
+        { OP_Transaction,     0,  0,  0},    /* 0 */
+        { OP_ReadCookie,      0,  1,  0},    /* 1 */
+        { OP_ResultRow,       1,  1,  0}
+      };
+      int addr = sqlite3VdbeAddOpList(v, ArraySize(readCookie), readCookie);
+      sqlite3VdbeChangeP1(v, addr, iDb);
+      sqlite3VdbeChangeP1(v, addr+1, iDb);
+      sqlite3VdbeChangeP3(v, addr+1, iCookie);
+      sqlite3VdbeSetNumCols(v, 1);
+      sqlite3VdbeSetColName(v, 0, COLNAME_NAME, zLeft, SQLITE_TRANSIENT);
+    }
+  }else
+#endif /* SQLITE_OMIT_SCHEMA_VERSION_PRAGMAS */
+
+#ifndef SQLITE_OMIT_COMPILEOPTION_DIAGS
+  /*
+  **   PRAGMA compile_options
+  **
+  ** Return the names of all compile-time options used in this build,
+  ** one option per row.
+  */
+  if( sqlite3StrICmp(zLeft, "compile_options")==0 ){
+    int i = 0;
+    const char *zOpt;
+    sqlite3VdbeSetNumCols(v, 1);
+    pParse->nMem = 1;
+    sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "compile_option", SQLITE_STATIC);
+    while( (zOpt = sqlite3_compileoption_get(i++))!=0 ){
+      sqlite3VdbeAddOp4(v, OP_String8, 0, 1, 0, zOpt, 0);
+      sqlite3VdbeAddOp2(v, OP_ResultRow, 1, 1);
+    }
+  }else
+#endif /* SQLITE_OMIT_COMPILEOPTION_DIAGS */
+
+#ifndef SQLITE_OMIT_WAL
+  /*
+  **   PRAGMA [database.]wal_checkpoint = passive|full|restart
+  **
+  ** Checkpoint the database.
+  */
+  if( sqlite3StrICmp(zLeft, "wal_checkpoint")==0 ){
+    int iBt = (pId2->z?iDb:SQLITE_MAX_ATTACHED);
+    int eMode = SQLITE_CHECKPOINT_PASSIVE;
+    if( zRight ){
+      if( sqlite3StrICmp(zRight, "full")==0 ){
+        eMode = SQLITE_CHECKPOINT_FULL;
+      }else if( sqlite3StrICmp(zRight, "restart")==0 ){
+        eMode = SQLITE_CHECKPOINT_RESTART;
+      }
+    }
+    if( sqlite3ReadSchema(pParse) ) goto pragma_out;
+    sqlite3VdbeSetNumCols(v, 3);
+    pParse->nMem = 3;
+    sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "busy", SQLITE_STATIC);
+    sqlite3VdbeSetColName(v, 1, COLNAME_NAME, "log", SQLITE_STATIC);
+    sqlite3VdbeSetColName(v, 2, COLNAME_NAME, "checkpointed", SQLITE_STATIC);
+
+    sqlite3VdbeAddOp3(v, OP_Checkpoint, iBt, eMode, 1);
+    sqlite3VdbeAddOp2(v, OP_ResultRow, 1, 3);
+  }else
+
+  /*
+  **   PRAGMA wal_autocheckpoint
+  **   PRAGMA wal_autocheckpoint = N
+  **
+  ** Configure a database connection to automatically checkpoint a database
+  ** after accumulating N frames in the log. Or query for the current value
+  ** of N.
+  */
+  if( sqlite3StrICmp(zLeft, "wal_autocheckpoint")==0 ){
+    if( zRight ){
+      sqlite3_wal_autocheckpoint(db, sqlite3Atoi(zRight));
+    }
+    returnSingleInt(pParse, "wal_autocheckpoint", 
+       db->xWalCallback==sqlite3WalDefaultHook ? 
+           SQLITE_PTR_TO_INT(db->pWalArg) : 0);
+  }else
+#endif
+
+#if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
+  /*
+  ** Report the current state of file logs for all databases
+  */
+  if( sqlite3StrICmp(zLeft, "lock_status")==0 ){
+    static const char *const azLockName[] = {
+      "unlocked", "shared", "reserved", "pending", "exclusive"
+    };
+    int i;
+    sqlite3VdbeSetNumCols(v, 2);
+    pParse->nMem = 2;
+    sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "database", SQLITE_STATIC);
+    sqlite3VdbeSetColName(v, 1, COLNAME_NAME, "status", SQLITE_STATIC);
+    for(i=0; i<db->nDb; i++){
+      Btree *pBt;
+      Pager *pPager;
+      const char *zState = "unknown";
+      int j;
+      if( db->aDb[i].zName==0 ) continue;
+      sqlite3VdbeAddOp4(v, OP_String8, 0, 1, 0, db->aDb[i].zName, P4_STATIC);
+      pBt = db->aDb[i].pBt;
+      if( pBt==0 || (pPager = sqlite3BtreePager(pBt))==0 ){
+        zState = "closed";
+      }else if( sqlite3_file_control(db, i ? db->aDb[i].zName : 0, 
+                                     SQLITE_FCNTL_LOCKSTATE, &j)==SQLITE_OK ){
+         zState = azLockName[j];
+      }
+      sqlite3VdbeAddOp4(v, OP_String8, 0, 2, 0, zState, P4_STATIC);
+      sqlite3VdbeAddOp2(v, OP_ResultRow, 1, 2);
+    }
+
+  }else
+#endif
+
+#ifdef SQLITE_HAS_CODEC
+  if( sqlite3StrICmp(zLeft, "key")==0 && zRight ){
+    sqlite3_key(db, zRight, sqlite3Strlen30(zRight));
+  }else
+  if( sqlite3StrICmp(zLeft, "rekey")==0 && zRight ){
+    sqlite3_rekey(db, zRight, sqlite3Strlen30(zRight));
+  }else
+  if( zRight && (sqlite3StrICmp(zLeft, "hexkey")==0 ||
+                 sqlite3StrICmp(zLeft, "hexrekey")==0) ){
+    int i, h1, h2;
+    char zKey[40];
+    for(i=0; (h1 = zRight[i])!=0 && (h2 = zRight[i+1])!=0; i+=2){
+      h1 += 9*(1&(h1>>6));
+      h2 += 9*(1&(h2>>6));
+      zKey[i/2] = (h2 & 0x0f) | ((h1 & 0xf)<<4);
+    }
+    if( (zLeft[3] & 0xf)==0xb ){
+      sqlite3_key(db, zKey, i/2);
+    }else{
+      sqlite3_rekey(db, zKey, i/2);
+    }
+  }else
+/** BEGIN CRYPTO **/
+  if( sqlite3StrICmp(zLeft, "cipher")==0 && zRight ){
+    extern int codec_set_cipher_name(sqlite3*, int, const char *, int);
+    codec_set_cipher_name(db, iDb, zRight, 2); // change cipher for both
+  }else
+  if( sqlite3StrICmp(zLeft, "rekey_cipher")==0 && zRight ){
+    extern int codec_set_cipher_name(sqlite3*, int, const char *, int); 
+    codec_set_cipher_name(db, iDb, zRight, 1); // change write cipher only
+  }else
+  if( sqlite3StrICmp(zLeft, "kdf_iter")==0 && zRight ){
+    extern int codec_set_kdf_iter(sqlite3*, int, int, int);
+    codec_set_kdf_iter(db, iDb, atoi(zRight), 2); // change of RW PBKDF2 iteration
+  }else
+  if( sqlite3StrICmp(zLeft, "fast_kdf_iter")==0 && zRight ){
+    extern int codec_set_fast_kdf_iter(sqlite3*, int, int, int);
+    codec_set_fast_kdf_iter(db, iDb, atoi(zRight), 2); // change of RW PBKDF2 iteration
+  }else
+  if( sqlite3StrICmp(zLeft, "rekey_kdf_iter")==0 && zRight ){
+    extern int codec_set_kdf_iter(sqlite3*, int, int, int); 
+    codec_set_kdf_iter(db, iDb, atoi(zRight), 1); // change # if W iterations
+  }else
+  if( sqlite3StrICmp(zLeft,"cipher_page_size")==0 ){
+    extern int codec_set_page_size(sqlite3*, int, int); 
+    codec_set_page_size(db, iDb, atoi(zRight)); // change page size
+  }else
+  if( sqlite3StrICmp(zLeft,"cipher_use_hmac")==0 ){
+    extern int codec_set_use_hmac(sqlite3*, int, int);
+    if(sqlite3GetBoolean(zRight)) {
+      codec_set_use_hmac(db, iDb, 1);
+    } else {
+      codec_set_use_hmac(db, iDb, 0);
+    }
+  }else
+/** END CRYPTO **/
+#endif
+#if defined(SQLITE_HAS_CODEC) || defined(SQLITE_ENABLE_CEROD)
+  if( sqlite3StrICmp(zLeft, "activate_extensions")==0 ){
+#ifdef SQLITE_HAS_CODEC
+    if( sqlite3StrNICmp(zRight, "see-", 4)==0 ){
+      sqlite3_activate_see(&zRight[4]);
+    }
+#endif
+#ifdef SQLITE_ENABLE_CEROD
+    if( sqlite3StrNICmp(zRight, "cerod-", 6)==0 ){
+      sqlite3_activate_cerod(&zRight[6]);
+    }
+#endif
+  }else
+#endif
+
+ 
+  {/* Empty ELSE clause */}
+
+  /*
+  ** Reset the safety level, in case the fullfsync flag or synchronous
+  ** setting changed.
+  */
+#ifndef SQLITE_OMIT_PAGER_PRAGMAS
+  if( db->autoCommit ){
+    sqlite3BtreeSetSafetyLevel(pDb->pBt, pDb->safety_level,
+               (db->flags&SQLITE_FullFSync)!=0,
+               (db->flags&SQLITE_CkptFullFSync)!=0);
+  }
+#endif
+pragma_out:
+  sqlite3DbFree(db, zLeft);
+  sqlite3DbFree(db, zRight);
+}
+
+#endif /* SQLITE_OMIT_PRAGMA */
diff --git a/src/prepare.c b/src/prepare.c
new file mode 100644
index 0000000..fc45b8e
--- /dev/null
+++ b/src/prepare.c
@@ -0,0 +1,858 @@
+/*
+** 2005 May 25
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains the implementation of the sqlite3_prepare()
+** interface, and routines that contribute to loading the database schema
+** from disk.
+*/
+#include "sqliteInt.h"
+
+/*
+** Fill the InitData structure with an error message that indicates
+** that the database is corrupt.
+*/
+static void corruptSchema(
+  InitData *pData,     /* Initialization context */
+  const char *zObj,    /* Object being parsed at the point of error */
+  const char *zExtra   /* Error information */
+){
+  sqlite3 *db = pData->db;
+  if( !db->mallocFailed && (db->flags & SQLITE_RecoveryMode)==0 ){
+    if( zObj==0 ) zObj = "?";
+    sqlite3SetString(pData->pzErrMsg, db,
+      "malformed database schema (%s)", zObj);
+    if( zExtra ){
+      *pData->pzErrMsg = sqlite3MAppendf(db, *pData->pzErrMsg, 
+                                 "%s - %s", *pData->pzErrMsg, zExtra);
+    }
+  }
+  pData->rc = db->mallocFailed ? SQLITE_NOMEM : SQLITE_CORRUPT_BKPT;
+}
+
+/*
+** This is the callback routine for the code that initializes the
+** database.  See sqlite3Init() below for additional information.
+** This routine is also called from the OP_ParseSchema opcode of the VDBE.
+**
+** Each callback contains the following information:
+**
+**     argv[0] = name of thing being created
+**     argv[1] = root page number for table or index. 0 for trigger or view.
+**     argv[2] = SQL text for the CREATE statement.
+**
+*/
+int sqlite3InitCallback(void *pInit, int argc, char **argv, char **NotUsed){
+  InitData *pData = (InitData*)pInit;
+  sqlite3 *db = pData->db;
+  int iDb = pData->iDb;
+
+  assert( argc==3 );
+  UNUSED_PARAMETER2(NotUsed, argc);
+  assert( sqlite3_mutex_held(db->mutex) );
+  DbClearProperty(db, iDb, DB_Empty);
+  if( db->mallocFailed ){
+    corruptSchema(pData, argv[0], 0);
+    return 1;
+  }
+
+  assert( iDb>=0 && iDb<db->nDb );
+  if( argv==0 ) return 0;   /* Might happen if EMPTY_RESULT_CALLBACKS are on */
+  if( argv[1]==0 ){
+    corruptSchema(pData, argv[0], 0);
+  }else if( argv[2] && argv[2][0] ){
+    /* Call the parser to process a CREATE TABLE, INDEX or VIEW.
+    ** But because db->init.busy is set to 1, no VDBE code is generated
+    ** or executed.  All the parser does is build the internal data
+    ** structures that describe the table, index, or view.
+    */
+    int rc;
+    sqlite3_stmt *pStmt;
+    TESTONLY(int rcp);            /* Return code from sqlite3_prepare() */
+
+    assert( db->init.busy );
+    db->init.iDb = iDb;
+    db->init.newTnum = sqlite3Atoi(argv[1]);
+    db->init.orphanTrigger = 0;
+    TESTONLY(rcp = ) sqlite3_prepare(db, argv[2], -1, &pStmt, 0);
+    rc = db->errCode;
+    assert( (rc&0xFF)==(rcp&0xFF) );
+    db->init.iDb = 0;
+    if( SQLITE_OK!=rc ){
+      if( db->init.orphanTrigger ){
+        assert( iDb==1 );
+      }else{
+        pData->rc = rc;
+        if( rc==SQLITE_NOMEM ){
+          db->mallocFailed = 1;
+        }else if( rc!=SQLITE_INTERRUPT && (rc&0xFF)!=SQLITE_LOCKED ){
+          corruptSchema(pData, argv[0], sqlite3_errmsg(db));
+        }
+      }
+    }
+    sqlite3_finalize(pStmt);
+  }else if( argv[0]==0 ){
+    corruptSchema(pData, 0, 0);
+  }else{
+    /* If the SQL column is blank it means this is an index that
+    ** was created to be the PRIMARY KEY or to fulfill a UNIQUE
+    ** constraint for a CREATE TABLE.  The index should have already
+    ** been created when we processed the CREATE TABLE.  All we have
+    ** to do here is record the root page number for that index.
+    */
+    Index *pIndex;
+    pIndex = sqlite3FindIndex(db, argv[0], db->aDb[iDb].zName);
+    if( pIndex==0 ){
+      /* This can occur if there exists an index on a TEMP table which
+      ** has the same name as another index on a permanent index.  Since
+      ** the permanent table is hidden by the TEMP table, we can also
+      ** safely ignore the index on the permanent table.
+      */
+      /* Do Nothing */;
+    }else if( sqlite3GetInt32(argv[1], &pIndex->tnum)==0 ){
+      corruptSchema(pData, argv[0], "invalid rootpage");
+    }
+  }
+  return 0;
+}
+
+/*
+** Attempt to read the database schema and initialize internal
+** data structures for a single database file.  The index of the
+** database file is given by iDb.  iDb==0 is used for the main
+** database.  iDb==1 should never be used.  iDb>=2 is used for
+** auxiliary databases.  Return one of the SQLITE_ error codes to
+** indicate success or failure.
+*/
+static int sqlite3InitOne(sqlite3 *db, int iDb, char **pzErrMsg){
+  int rc;
+  int i;
+  int size;
+  Table *pTab;
+  Db *pDb;
+  char const *azArg[4];
+  int meta[5];
+  InitData initData;
+  char const *zMasterSchema;
+  char const *zMasterName;
+  int openedTransaction = 0;
+
+  /*
+  ** The master database table has a structure like this
+  */
+  static const char master_schema[] = 
+     "CREATE TABLE sqlite_master(\n"
+     "  type text,\n"
+     "  name text,\n"
+     "  tbl_name text,\n"
+     "  rootpage integer,\n"
+     "  sql text\n"
+     ")"
+  ;
+#ifndef SQLITE_OMIT_TEMPDB
+  static const char temp_master_schema[] = 
+     "CREATE TEMP TABLE sqlite_temp_master(\n"
+     "  type text,\n"
+     "  name text,\n"
+     "  tbl_name text,\n"
+     "  rootpage integer,\n"
+     "  sql text\n"
+     ")"
+  ;
+#else
+  #define temp_master_schema 0
+#endif
+
+  assert( iDb>=0 && iDb<db->nDb );
+  assert( db->aDb[iDb].pSchema );
+  assert( sqlite3_mutex_held(db->mutex) );
+  assert( iDb==1 || sqlite3BtreeHoldsMutex(db->aDb[iDb].pBt) );
+
+  /* zMasterSchema and zInitScript are set to point at the master schema
+  ** and initialisation script appropriate for the database being
+  ** initialised. zMasterName is the name of the master table.
+  */
+  if( !OMIT_TEMPDB && iDb==1 ){
+    zMasterSchema = temp_master_schema;
+  }else{
+    zMasterSchema = master_schema;
+  }
+  zMasterName = SCHEMA_TABLE(iDb);
+
+  /* Construct the schema tables.  */
+  azArg[0] = zMasterName;
+  azArg[1] = "1";
+  azArg[2] = zMasterSchema;
+  azArg[3] = 0;
+  initData.db = db;
+  initData.iDb = iDb;
+  initData.rc = SQLITE_OK;
+  initData.pzErrMsg = pzErrMsg;
+  sqlite3InitCallback(&initData, 3, (char **)azArg, 0);
+  if( initData.rc ){
+    rc = initData.rc;
+    goto error_out;
+  }
+  pTab = sqlite3FindTable(db, zMasterName, db->aDb[iDb].zName);
+  if( ALWAYS(pTab) ){
+    pTab->tabFlags |= TF_Readonly;
+  }
+
+  /* Create a cursor to hold the database open
+  */
+  pDb = &db->aDb[iDb];
+  if( pDb->pBt==0 ){
+    if( !OMIT_TEMPDB && ALWAYS(iDb==1) ){
+      DbSetProperty(db, 1, DB_SchemaLoaded);
+    }
+    return SQLITE_OK;
+  }
+
+  /* If there is not already a read-only (or read-write) transaction opened
+  ** on the b-tree database, open one now. If a transaction is opened, it 
+  ** will be closed before this function returns.  */
+  sqlite3BtreeEnter(pDb->pBt);
+  if( !sqlite3BtreeIsInReadTrans(pDb->pBt) ){
+    rc = sqlite3BtreeBeginTrans(pDb->pBt, 0);
+    if( rc!=SQLITE_OK ){
+      sqlite3SetString(pzErrMsg, db, "%s", sqlite3ErrStr(rc));
+      goto initone_error_out;
+    }
+    openedTransaction = 1;
+  }
+
+  /* Get the database meta information.
+  **
+  ** Meta values are as follows:
+  **    meta[0]   Schema cookie.  Changes with each schema change.
+  **    meta[1]   File format of schema layer.
+  **    meta[2]   Size of the page cache.
+  **    meta[3]   Largest rootpage (auto/incr_vacuum mode)
+  **    meta[4]   Db text encoding. 1:UTF-8 2:UTF-16LE 3:UTF-16BE
+  **    meta[5]   User version
+  **    meta[6]   Incremental vacuum mode
+  **    meta[7]   unused
+  **    meta[8]   unused
+  **    meta[9]   unused
+  **
+  ** Note: The #defined SQLITE_UTF* symbols in sqliteInt.h correspond to
+  ** the possible values of meta[4].
+  */
+  for(i=0; i<ArraySize(meta); i++){
+    sqlite3BtreeGetMeta(pDb->pBt, i+1, (u32 *)&meta[i]);
+  }
+  pDb->pSchema->schema_cookie = meta[BTREE_SCHEMA_VERSION-1];
+
+  /* If opening a non-empty database, check the text encoding. For the
+  ** main database, set sqlite3.enc to the encoding of the main database.
+  ** For an attached db, it is an error if the encoding is not the same
+  ** as sqlite3.enc.
+  */
+  if( meta[BTREE_TEXT_ENCODING-1] ){  /* text encoding */
+    if( iDb==0 ){
+      u8 encoding;
+      /* If opening the main database, set ENC(db). */
+      encoding = (u8)meta[BTREE_TEXT_ENCODING-1] & 3;
+      if( encoding==0 ) encoding = SQLITE_UTF8;
+      ENC(db) = encoding;
+      db->pDfltColl = sqlite3FindCollSeq(db, SQLITE_UTF8, "BINARY", 0);
+    }else{
+      /* If opening an attached database, the encoding much match ENC(db) */
+      if( meta[BTREE_TEXT_ENCODING-1]!=ENC(db) ){
+        sqlite3SetString(pzErrMsg, db, "attached databases must use the same"
+            " text encoding as main database");
+        rc = SQLITE_ERROR;
+        goto initone_error_out;
+      }
+    }
+  }else{
+    DbSetProperty(db, iDb, DB_Empty);
+  }
+  pDb->pSchema->enc = ENC(db);
+
+  if( pDb->pSchema->cache_size==0 ){
+    size = sqlite3AbsInt32(meta[BTREE_DEFAULT_CACHE_SIZE-1]);
+    if( size==0 ){ size = SQLITE_DEFAULT_CACHE_SIZE; }
+    pDb->pSchema->cache_size = size;
+    sqlite3BtreeSetCacheSize(pDb->pBt, pDb->pSchema->cache_size);
+  }
+
+  /*
+  ** file_format==1    Version 3.0.0.
+  ** file_format==2    Version 3.1.3.  // ALTER TABLE ADD COLUMN
+  ** file_format==3    Version 3.1.4.  // ditto but with non-NULL defaults
+  ** file_format==4    Version 3.3.0.  // DESC indices.  Boolean constants
+  */
+  pDb->pSchema->file_format = (u8)meta[BTREE_FILE_FORMAT-1];
+  if( pDb->pSchema->file_format==0 ){
+    pDb->pSchema->file_format = 1;
+  }
+  if( pDb->pSchema->file_format>SQLITE_MAX_FILE_FORMAT ){
+    sqlite3SetString(pzErrMsg, db, "unsupported file format");
+    rc = SQLITE_ERROR;
+    goto initone_error_out;
+  }
+
+  /* Ticket #2804:  When we open a database in the newer file format,
+  ** clear the legacy_file_format pragma flag so that a VACUUM will
+  ** not downgrade the database and thus invalidate any descending
+  ** indices that the user might have created.
+  */
+  if( iDb==0 && meta[BTREE_FILE_FORMAT-1]>=4 ){
+    db->flags &= ~SQLITE_LegacyFileFmt;
+  }
+
+  /* Read the schema information out of the schema tables
+  */
+  assert( db->init.busy );
+  {
+    char *zSql;
+    zSql = sqlite3MPrintf(db, 
+        "SELECT name, rootpage, sql FROM '%q'.%s ORDER BY rowid",
+        db->aDb[iDb].zName, zMasterName);
+#ifndef SQLITE_OMIT_AUTHORIZATION
+    {
+      int (*xAuth)(void*,int,const char*,const char*,const char*,const char*);
+      xAuth = db->xAuth;
+      db->xAuth = 0;
+#endif
+      rc = sqlite3_exec(db, zSql, sqlite3InitCallback, &initData, 0);
+#ifndef SQLITE_OMIT_AUTHORIZATION
+      db->xAuth = xAuth;
+    }
+#endif
+    if( rc==SQLITE_OK ) rc = initData.rc;
+    sqlite3DbFree(db, zSql);
+#ifndef SQLITE_OMIT_ANALYZE
+    if( rc==SQLITE_OK ){
+      sqlite3AnalysisLoad(db, iDb);
+    }
+#endif
+  }
+  if( db->mallocFailed ){
+    rc = SQLITE_NOMEM;
+    sqlite3ResetInternalSchema(db, -1);
+  }
+  if( rc==SQLITE_OK || (db->flags&SQLITE_RecoveryMode)){
+    /* Black magic: If the SQLITE_RecoveryMode flag is set, then consider
+    ** the schema loaded, even if errors occurred. In this situation the 
+    ** current sqlite3_prepare() operation will fail, but the following one
+    ** will attempt to compile the supplied statement against whatever subset
+    ** of the schema was loaded before the error occurred. The primary
+    ** purpose of this is to allow access to the sqlite_master table
+    ** even when its contents have been corrupted.
+    */
+    DbSetProperty(db, iDb, DB_SchemaLoaded);
+    rc = SQLITE_OK;
+  }
+
+  /* Jump here for an error that occurs after successfully allocating
+  ** curMain and calling sqlite3BtreeEnter(). For an error that occurs
+  ** before that point, jump to error_out.
+  */
+initone_error_out:
+  if( openedTransaction ){
+    sqlite3BtreeCommit(pDb->pBt);
+  }
+  sqlite3BtreeLeave(pDb->pBt);
+
+error_out:
+  if( rc==SQLITE_NOMEM || rc==SQLITE_IOERR_NOMEM ){
+    db->mallocFailed = 1;
+  }
+  return rc;
+}
+
+/*
+** Initialize all database files - the main database file, the file
+** used to store temporary tables, and any additional database files
+** created using ATTACH statements.  Return a success code.  If an
+** error occurs, write an error message into *pzErrMsg.
+**
+** After a database is initialized, the DB_SchemaLoaded bit is set
+** bit is set in the flags field of the Db structure. If the database
+** file was of zero-length, then the DB_Empty flag is also set.
+*/
+int sqlite3Init(sqlite3 *db, char **pzErrMsg){
+  int i, rc;
+  int commit_internal = !(db->flags&SQLITE_InternChanges);
+  
+  assert( sqlite3_mutex_held(db->mutex) );
+  rc = SQLITE_OK;
+  db->init.busy = 1;
+  for(i=0; rc==SQLITE_OK && i<db->nDb; i++){
+    if( DbHasProperty(db, i, DB_SchemaLoaded) || i==1 ) continue;
+    rc = sqlite3InitOne(db, i, pzErrMsg);
+    if( rc ){
+      sqlite3ResetInternalSchema(db, i);
+    }
+  }
+
+  /* Once all the other databases have been initialised, load the schema
+  ** for the TEMP database. This is loaded last, as the TEMP database
+  ** schema may contain references to objects in other databases.
+  */
+#ifndef SQLITE_OMIT_TEMPDB
+  if( rc==SQLITE_OK && ALWAYS(db->nDb>1)
+                    && !DbHasProperty(db, 1, DB_SchemaLoaded) ){
+    rc = sqlite3InitOne(db, 1, pzErrMsg);
+    if( rc ){
+      sqlite3ResetInternalSchema(db, 1);
+    }
+  }
+#endif
+
+  db->init.busy = 0;
+  if( rc==SQLITE_OK && commit_internal ){
+    sqlite3CommitInternalChanges(db);
+  }
+
+  return rc; 
+}
+
+/*
+** This routine is a no-op if the database schema is already initialised.
+** Otherwise, the schema is loaded. An error code is returned.
+*/
+int sqlite3ReadSchema(Parse *pParse){
+  int rc = SQLITE_OK;
+  sqlite3 *db = pParse->db;
+  assert( sqlite3_mutex_held(db->mutex) );
+  if( !db->init.busy ){
+    rc = sqlite3Init(db, &pParse->zErrMsg);
+  }
+  if( rc!=SQLITE_OK ){
+    pParse->rc = rc;
+    pParse->nErr++;
+  }
+  return rc;
+}
+
+
+/*
+** Check schema cookies in all databases.  If any cookie is out
+** of date set pParse->rc to SQLITE_SCHEMA.  If all schema cookies
+** make no changes to pParse->rc.
+*/
+static void schemaIsValid(Parse *pParse){
+  sqlite3 *db = pParse->db;
+  int iDb;
+  int rc;
+  int cookie;
+
+  assert( pParse->checkSchema );
+  assert( sqlite3_mutex_held(db->mutex) );
+  for(iDb=0; iDb<db->nDb; iDb++){
+    int openedTransaction = 0;         /* True if a transaction is opened */
+    Btree *pBt = db->aDb[iDb].pBt;     /* Btree database to read cookie from */
+    if( pBt==0 ) continue;
+
+    /* If there is not already a read-only (or read-write) transaction opened
+    ** on the b-tree database, open one now. If a transaction is opened, it 
+    ** will be closed immediately after reading the meta-value. */
+    if( !sqlite3BtreeIsInReadTrans(pBt) ){
+      rc = sqlite3BtreeBeginTrans(pBt, 0);
+      if( rc==SQLITE_NOMEM || rc==SQLITE_IOERR_NOMEM ){
+        db->mallocFailed = 1;
+      }
+      if( rc!=SQLITE_OK ) return;
+      openedTransaction = 1;
+    }
+
+    /* Read the schema cookie from the database. If it does not match the 
+    ** value stored as part of the in-memory schema representation,
+    ** set Parse.rc to SQLITE_SCHEMA. */
+    sqlite3BtreeGetMeta(pBt, BTREE_SCHEMA_VERSION, (u32 *)&cookie);
+    assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+    if( cookie!=db->aDb[iDb].pSchema->schema_cookie ){
+      sqlite3ResetInternalSchema(db, iDb);
+      pParse->rc = SQLITE_SCHEMA;
+    }
+
+    /* Close the transaction, if one was opened. */
+    if( openedTransaction ){
+      sqlite3BtreeCommit(pBt);
+    }
+  }
+}
+
+/*
+** Convert a schema pointer into the iDb index that indicates
+** which database file in db->aDb[] the schema refers to.
+**
+** If the same database is attached more than once, the first
+** attached database is returned.
+*/
+int sqlite3SchemaToIndex(sqlite3 *db, Schema *pSchema){
+  int i = -1000000;
+
+  /* If pSchema is NULL, then return -1000000. This happens when code in 
+  ** expr.c is trying to resolve a reference to a transient table (i.e. one
+  ** created by a sub-select). In this case the return value of this 
+  ** function should never be used.
+  **
+  ** We return -1000000 instead of the more usual -1 simply because using
+  ** -1000000 as the incorrect index into db->aDb[] is much 
+  ** more likely to cause a segfault than -1 (of course there are assert()
+  ** statements too, but it never hurts to play the odds).
+  */
+  assert( sqlite3_mutex_held(db->mutex) );
+  if( pSchema ){
+    for(i=0; ALWAYS(i<db->nDb); i++){
+      if( db->aDb[i].pSchema==pSchema ){
+        break;
+      }
+    }
+    assert( i>=0 && i<db->nDb );
+  }
+  return i;
+}
+
+/*
+** Compile the UTF-8 encoded SQL statement zSql into a statement handle.
+*/
+static int sqlite3Prepare(
+  sqlite3 *db,              /* Database handle. */
+  const char *zSql,         /* UTF-8 encoded SQL statement. */
+  int nBytes,               /* Length of zSql in bytes. */
+  int saveSqlFlag,          /* True to copy SQL text into the sqlite3_stmt */
+  Vdbe *pReprepare,         /* VM being reprepared */
+  sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
+  const char **pzTail       /* OUT: End of parsed string */
+){
+  Parse *pParse;            /* Parsing context */
+  char *zErrMsg = 0;        /* Error message */
+  int rc = SQLITE_OK;       /* Result code */
+  int i;                    /* Loop counter */
+
+  /* Allocate the parsing context */
+  pParse = sqlite3StackAllocZero(db, sizeof(*pParse));
+  if( pParse==0 ){
+    rc = SQLITE_NOMEM;
+    goto end_prepare;
+  }
+  pParse->pReprepare = pReprepare;
+  assert( ppStmt && *ppStmt==0 );
+  assert( !db->mallocFailed );
+  assert( sqlite3_mutex_held(db->mutex) );
+
+  /* Check to verify that it is possible to get a read lock on all
+  ** database schemas.  The inability to get a read lock indicates that
+  ** some other database connection is holding a write-lock, which in
+  ** turn means that the other connection has made uncommitted changes
+  ** to the schema.
+  **
+  ** Were we to proceed and prepare the statement against the uncommitted
+  ** schema changes and if those schema changes are subsequently rolled
+  ** back and different changes are made in their place, then when this
+  ** prepared statement goes to run the schema cookie would fail to detect
+  ** the schema change.  Disaster would follow.
+  **
+  ** This thread is currently holding mutexes on all Btrees (because
+  ** of the sqlite3BtreeEnterAll() in sqlite3LockAndPrepare()) so it
+  ** is not possible for another thread to start a new schema change
+  ** while this routine is running.  Hence, we do not need to hold 
+  ** locks on the schema, we just need to make sure nobody else is 
+  ** holding them.
+  **
+  ** Note that setting READ_UNCOMMITTED overrides most lock detection,
+  ** but it does *not* override schema lock detection, so this all still
+  ** works even if READ_UNCOMMITTED is set.
+  */
+  for(i=0; i<db->nDb; i++) {
+    Btree *pBt = db->aDb[i].pBt;
+    if( pBt ){
+      assert( sqlite3BtreeHoldsMutex(pBt) );
+      rc = sqlite3BtreeSchemaLocked(pBt);
+      if( rc ){
+        const char *zDb = db->aDb[i].zName;
+        sqlite3Error(db, rc, "database schema is locked: %s", zDb);
+        testcase( db->flags & SQLITE_ReadUncommitted );
+        goto end_prepare;
+      }
+    }
+  }
+
+  sqlite3VtabUnlockList(db);
+
+  pParse->db = db;
+  pParse->nQueryLoop = (double)1;
+  if( nBytes>=0 && (nBytes==0 || zSql[nBytes-1]!=0) ){
+    char *zSqlCopy;
+    int mxLen = db->aLimit[SQLITE_LIMIT_SQL_LENGTH];
+    testcase( nBytes==mxLen );
+    testcase( nBytes==mxLen+1 );
+    if( nBytes>mxLen ){
+      sqlite3Error(db, SQLITE_TOOBIG, "statement too long");
+      rc = sqlite3ApiExit(db, SQLITE_TOOBIG);
+      goto end_prepare;
+    }
+    zSqlCopy = sqlite3DbStrNDup(db, zSql, nBytes);
+    if( zSqlCopy ){
+      sqlite3RunParser(pParse, zSqlCopy, &zErrMsg);
+      sqlite3DbFree(db, zSqlCopy);
+      pParse->zTail = &zSql[pParse->zTail-zSqlCopy];
+    }else{
+      pParse->zTail = &zSql[nBytes];
+    }
+  }else{
+    sqlite3RunParser(pParse, zSql, &zErrMsg);
+  }
+  assert( 1==(int)pParse->nQueryLoop );
+
+  if( db->mallocFailed ){
+    pParse->rc = SQLITE_NOMEM;
+  }
+  if( pParse->rc==SQLITE_DONE ) pParse->rc = SQLITE_OK;
+  if( pParse->checkSchema ){
+    schemaIsValid(pParse);
+  }
+  if( db->mallocFailed ){
+    pParse->rc = SQLITE_NOMEM;
+  }
+  if( pzTail ){
+    *pzTail = pParse->zTail;
+  }
+  rc = pParse->rc;
+
+#ifndef SQLITE_OMIT_EXPLAIN
+  if( rc==SQLITE_OK && pParse->pVdbe && pParse->explain ){
+    static const char * const azColName[] = {
+       "addr", "opcode", "p1", "p2", "p3", "p4", "p5", "comment",
+       "selectid", "order", "from", "detail"
+    };
+    int iFirst, mx;
+    if( pParse->explain==2 ){
+      sqlite3VdbeSetNumCols(pParse->pVdbe, 4);
+      iFirst = 8;
+      mx = 12;
+    }else{
+      sqlite3VdbeSetNumCols(pParse->pVdbe, 8);
+      iFirst = 0;
+      mx = 8;
+    }
+    for(i=iFirst; i<mx; i++){
+      sqlite3VdbeSetColName(pParse->pVdbe, i-iFirst, COLNAME_NAME,
+                            azColName[i], SQLITE_STATIC);
+    }
+  }
+#endif
+
+  assert( db->init.busy==0 || saveSqlFlag==0 );
+  if( db->init.busy==0 ){
+    Vdbe *pVdbe = pParse->pVdbe;
+    sqlite3VdbeSetSql(pVdbe, zSql, (int)(pParse->zTail-zSql), saveSqlFlag);
+  }
+  if( pParse->pVdbe && (rc!=SQLITE_OK || db->mallocFailed) ){
+    sqlite3VdbeFinalize(pParse->pVdbe);
+    assert(!(*ppStmt));
+  }else{
+    *ppStmt = (sqlite3_stmt*)pParse->pVdbe;
+  }
+
+  if( zErrMsg ){
+    sqlite3Error(db, rc, "%s", zErrMsg);
+    sqlite3DbFree(db, zErrMsg);
+  }else{
+    sqlite3Error(db, rc, 0);
+  }
+
+  /* Delete any TriggerPrg structures allocated while parsing this statement. */
+  while( pParse->pTriggerPrg ){
+    TriggerPrg *pT = pParse->pTriggerPrg;
+    pParse->pTriggerPrg = pT->pNext;
+    sqlite3DbFree(db, pT);
+  }
+
+end_prepare:
+
+  sqlite3StackFree(db, pParse);
+  rc = sqlite3ApiExit(db, rc);
+  assert( (rc&db->errMask)==rc );
+  return rc;
+}
+static int sqlite3LockAndPrepare(
+  sqlite3 *db,              /* Database handle. */
+  const char *zSql,         /* UTF-8 encoded SQL statement. */
+  int nBytes,               /* Length of zSql in bytes. */
+  int saveSqlFlag,          /* True to copy SQL text into the sqlite3_stmt */
+  Vdbe *pOld,               /* VM being reprepared */
+  sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
+  const char **pzTail       /* OUT: End of parsed string */
+){
+  int rc;
+  assert( ppStmt!=0 );
+  *ppStmt = 0;
+  if( !sqlite3SafetyCheckOk(db) ){
+    return SQLITE_MISUSE_BKPT;
+  }
+  sqlite3_mutex_enter(db->mutex);
+  sqlite3BtreeEnterAll(db);
+  rc = sqlite3Prepare(db, zSql, nBytes, saveSqlFlag, pOld, ppStmt, pzTail);
+  if( rc==SQLITE_SCHEMA ){
+    sqlite3_finalize(*ppStmt);
+    rc = sqlite3Prepare(db, zSql, nBytes, saveSqlFlag, pOld, ppStmt, pzTail);
+  }
+  sqlite3BtreeLeaveAll(db);
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+
+/*
+** Rerun the compilation of a statement after a schema change.
+**
+** If the statement is successfully recompiled, return SQLITE_OK. Otherwise,
+** if the statement cannot be recompiled because another connection has
+** locked the sqlite3_master table, return SQLITE_LOCKED. If any other error
+** occurs, return SQLITE_SCHEMA.
+*/
+int sqlite3Reprepare(Vdbe *p){
+  int rc;
+  sqlite3_stmt *pNew;
+  const char *zSql;
+  sqlite3 *db;
+
+  assert( sqlite3_mutex_held(sqlite3VdbeDb(p)->mutex) );
+  zSql = sqlite3_sql((sqlite3_stmt *)p);
+  assert( zSql!=0 );  /* Reprepare only called for prepare_v2() statements */
+  db = sqlite3VdbeDb(p);
+  assert( sqlite3_mutex_held(db->mutex) );
+  rc = sqlite3LockAndPrepare(db, zSql, -1, 0, p, &pNew, 0);
+  if( rc ){
+    if( rc==SQLITE_NOMEM ){
+      db->mallocFailed = 1;
+    }
+    assert( pNew==0 );
+    return rc;
+  }else{
+    assert( pNew!=0 );
+  }
+  sqlite3VdbeSwap((Vdbe*)pNew, p);
+  sqlite3TransferBindings(pNew, (sqlite3_stmt*)p);
+  sqlite3VdbeResetStepResult((Vdbe*)pNew);
+  sqlite3VdbeFinalize((Vdbe*)pNew);
+  return SQLITE_OK;
+}
+
+
+/*
+** Two versions of the official API.  Legacy and new use.  In the legacy
+** version, the original SQL text is not saved in the prepared statement
+** and so if a schema change occurs, SQLITE_SCHEMA is returned by
+** sqlite3_step().  In the new version, the original SQL text is retained
+** and the statement is automatically recompiled if an schema change
+** occurs.
+*/
+int sqlite3_prepare(
+  sqlite3 *db,              /* Database handle. */
+  const char *zSql,         /* UTF-8 encoded SQL statement. */
+  int nBytes,               /* Length of zSql in bytes. */
+  sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
+  const char **pzTail       /* OUT: End of parsed string */
+){
+  int rc;
+  rc = sqlite3LockAndPrepare(db,zSql,nBytes,0,0,ppStmt,pzTail);
+  assert( rc==SQLITE_OK || ppStmt==0 || *ppStmt==0 );  /* VERIFY: F13021 */
+  return rc;
+}
+int sqlite3_prepare_v2(
+  sqlite3 *db,              /* Database handle. */
+  const char *zSql,         /* UTF-8 encoded SQL statement. */
+  int nBytes,               /* Length of zSql in bytes. */
+  sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
+  const char **pzTail       /* OUT: End of parsed string */
+){
+  int rc;
+  rc = sqlite3LockAndPrepare(db,zSql,nBytes,1,0,ppStmt,pzTail);
+  assert( rc==SQLITE_OK || ppStmt==0 || *ppStmt==0 );  /* VERIFY: F13021 */
+  return rc;
+}
+
+
+#ifndef SQLITE_OMIT_UTF16
+/*
+** Compile the UTF-16 encoded SQL statement zSql into a statement handle.
+*/
+static int sqlite3Prepare16(
+  sqlite3 *db,              /* Database handle. */ 
+  const void *zSql,         /* UTF-16 encoded SQL statement. */
+  int nBytes,               /* Length of zSql in bytes. */
+  int saveSqlFlag,          /* True to save SQL text into the sqlite3_stmt */
+  sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
+  const void **pzTail       /* OUT: End of parsed string */
+){
+  /* This function currently works by first transforming the UTF-16
+  ** encoded string to UTF-8, then invoking sqlite3_prepare(). The
+  ** tricky bit is figuring out the pointer to return in *pzTail.
+  */
+  char *zSql8;
+  const char *zTail8 = 0;
+  int rc = SQLITE_OK;
+
+  assert( ppStmt );
+  *ppStmt = 0;
+  if( !sqlite3SafetyCheckOk(db) ){
+    return SQLITE_MISUSE_BKPT;
+  }
+  sqlite3_mutex_enter(db->mutex);
+  zSql8 = sqlite3Utf16to8(db, zSql, nBytes, SQLITE_UTF16NATIVE);
+  if( zSql8 ){
+    rc = sqlite3LockAndPrepare(db, zSql8, -1, saveSqlFlag, 0, ppStmt, &zTail8);
+  }
+
+  if( zTail8 && pzTail ){
+    /* If sqlite3_prepare returns a tail pointer, we calculate the
+    ** equivalent pointer into the UTF-16 string by counting the unicode
+    ** characters between zSql8 and zTail8, and then returning a pointer
+    ** the same number of characters into the UTF-16 string.
+    */
+    int chars_parsed = sqlite3Utf8CharLen(zSql8, (int)(zTail8-zSql8));
+    *pzTail = (u8 *)zSql + sqlite3Utf16ByteLen(zSql, chars_parsed);
+  }
+  sqlite3DbFree(db, zSql8); 
+  rc = sqlite3ApiExit(db, rc);
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+
+/*
+** Two versions of the official API.  Legacy and new use.  In the legacy
+** version, the original SQL text is not saved in the prepared statement
+** and so if a schema change occurs, SQLITE_SCHEMA is returned by
+** sqlite3_step().  In the new version, the original SQL text is retained
+** and the statement is automatically recompiled if an schema change
+** occurs.
+*/
+int sqlite3_prepare16(
+  sqlite3 *db,              /* Database handle. */ 
+  const void *zSql,         /* UTF-16 encoded SQL statement. */
+  int nBytes,               /* Length of zSql in bytes. */
+  sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
+  const void **pzTail       /* OUT: End of parsed string */
+){
+  int rc;
+  rc = sqlite3Prepare16(db,zSql,nBytes,0,ppStmt,pzTail);
+  assert( rc==SQLITE_OK || ppStmt==0 || *ppStmt==0 );  /* VERIFY: F13021 */
+  return rc;
+}
+int sqlite3_prepare16_v2(
+  sqlite3 *db,              /* Database handle. */ 
+  const void *zSql,         /* UTF-16 encoded SQL statement. */
+  int nBytes,               /* Length of zSql in bytes. */
+  sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
+  const void **pzTail       /* OUT: End of parsed string */
+){
+  int rc;
+  rc = sqlite3Prepare16(db,zSql,nBytes,1,ppStmt,pzTail);
+  assert( rc==SQLITE_OK || ppStmt==0 || *ppStmt==0 );  /* VERIFY: F13021 */
+  return rc;
+}
+
+#endif /* SQLITE_OMIT_UTF16 */
diff --git a/src/printf.c b/src/printf.c
new file mode 100644
index 0000000..0babee5
--- /dev/null
+++ b/src/printf.c
@@ -0,0 +1,970 @@
+/*
+** The "printf" code that follows dates from the 1980's.  It is in
+** the public domain.  The original comments are included here for
+** completeness.  They are very out-of-date but might be useful as
+** an historical reference.  Most of the "enhancements" have been backed
+** out so that the functionality is now the same as standard printf().
+**
+**************************************************************************
+**
+** This file contains code for a set of "printf"-like routines.  These
+** routines format strings much like the printf() from the standard C
+** library, though the implementation here has enhancements to support
+** SQLlite.
+*/
+#include "sqliteInt.h"
+
+/*
+** Conversion types fall into various categories as defined by the
+** following enumeration.
+*/
+#define etRADIX       1 /* Integer types.  %d, %x, %o, and so forth */
+#define etFLOAT       2 /* Floating point.  %f */
+#define etEXP         3 /* Exponentional notation. %e and %E */
+#define etGENERIC     4 /* Floating or exponential, depending on exponent. %g */
+#define etSIZE        5 /* Return number of characters processed so far. %n */
+#define etSTRING      6 /* Strings. %s */
+#define etDYNSTRING   7 /* Dynamically allocated strings. %z */
+#define etPERCENT     8 /* Percent symbol. %% */
+#define etCHARX       9 /* Characters. %c */
+/* The rest are extensions, not normally found in printf() */
+#define etSQLESCAPE  10 /* Strings with '\'' doubled.  %q */
+#define etSQLESCAPE2 11 /* Strings with '\'' doubled and enclosed in '',
+                          NULL pointers replaced by SQL NULL.  %Q */
+#define etTOKEN      12 /* a pointer to a Token structure */
+#define etSRCLIST    13 /* a pointer to a SrcList */
+#define etPOINTER    14 /* The %p conversion */
+#define etSQLESCAPE3 15 /* %w -> Strings with '\"' doubled */
+#define etORDINAL    16 /* %r -> 1st, 2nd, 3rd, 4th, etc.  English only */
+
+#define etINVALID     0 /* Any unrecognized conversion type */
+
+
+/*
+** An "etByte" is an 8-bit unsigned value.
+*/
+typedef unsigned char etByte;
+
+/*
+** Each builtin conversion character (ex: the 'd' in "%d") is described
+** by an instance of the following structure
+*/
+typedef struct et_info {   /* Information about each format field */
+  char fmttype;            /* The format field code letter */
+  etByte base;             /* The base for radix conversion */
+  etByte flags;            /* One or more of FLAG_ constants below */
+  etByte type;             /* Conversion paradigm */
+  etByte charset;          /* Offset into aDigits[] of the digits string */
+  etByte prefix;           /* Offset into aPrefix[] of the prefix string */
+} et_info;
+
+/*
+** Allowed values for et_info.flags
+*/
+#define FLAG_SIGNED  1     /* True if the value to convert is signed */
+#define FLAG_INTERN  2     /* True if for internal use only */
+#define FLAG_STRING  4     /* Allow infinity precision */
+
+
+/*
+** The following table is searched linearly, so it is good to put the
+** most frequently used conversion types first.
+*/
+static const char aDigits[] = "0123456789ABCDEF0123456789abcdef";
+static const char aPrefix[] = "-x0\000X0";
+static const et_info fmtinfo[] = {
+  {  'd', 10, 1, etRADIX,      0,  0 },
+  {  's',  0, 4, etSTRING,     0,  0 },
+  {  'g',  0, 1, etGENERIC,    30, 0 },
+  {  'z',  0, 4, etDYNSTRING,  0,  0 },
+  {  'q',  0, 4, etSQLESCAPE,  0,  0 },
+  {  'Q',  0, 4, etSQLESCAPE2, 0,  0 },
+  {  'w',  0, 4, etSQLESCAPE3, 0,  0 },
+  {  'c',  0, 0, etCHARX,      0,  0 },
+  {  'o',  8, 0, etRADIX,      0,  2 },
+  {  'u', 10, 0, etRADIX,      0,  0 },
+  {  'x', 16, 0, etRADIX,      16, 1 },
+  {  'X', 16, 0, etRADIX,      0,  4 },
+#ifndef SQLITE_OMIT_FLOATING_POINT
+  {  'f',  0, 1, etFLOAT,      0,  0 },
+  {  'e',  0, 1, etEXP,        30, 0 },
+  {  'E',  0, 1, etEXP,        14, 0 },
+  {  'G',  0, 1, etGENERIC,    14, 0 },
+#endif
+  {  'i', 10, 1, etRADIX,      0,  0 },
+  {  'n',  0, 0, etSIZE,       0,  0 },
+  {  '%',  0, 0, etPERCENT,    0,  0 },
+  {  'p', 16, 0, etPOINTER,    0,  1 },
+
+/* All the rest have the FLAG_INTERN bit set and are thus for internal
+** use only */
+  {  'T',  0, 2, etTOKEN,      0,  0 },
+  {  'S',  0, 2, etSRCLIST,    0,  0 },
+  {  'r', 10, 3, etORDINAL,    0,  0 },
+};
+
+/*
+** If SQLITE_OMIT_FLOATING_POINT is defined, then none of the floating point
+** conversions will work.
+*/
+#ifndef SQLITE_OMIT_FLOATING_POINT
+/*
+** "*val" is a double such that 0.1 <= *val < 10.0
+** Return the ascii code for the leading digit of *val, then
+** multiply "*val" by 10.0 to renormalize.
+**
+** Example:
+**     input:     *val = 3.14159
+**     output:    *val = 1.4159    function return = '3'
+**
+** The counter *cnt is incremented each time.  After counter exceeds
+** 16 (the number of significant digits in a 64-bit float) '0' is
+** always returned.
+*/
+static char et_getdigit(LONGDOUBLE_TYPE *val, int *cnt){
+  int digit;
+  LONGDOUBLE_TYPE d;
+  if( (*cnt)++ >= 16 ) return '0';
+  digit = (int)*val;
+  d = digit;
+  digit += '0';
+  *val = (*val - d)*10.0;
+  return (char)digit;
+}
+#endif /* SQLITE_OMIT_FLOATING_POINT */
+
+/*
+** Append N space characters to the given string buffer.
+*/
+static void appendSpace(StrAccum *pAccum, int N){
+  static const char zSpaces[] = "                             ";
+  while( N>=(int)sizeof(zSpaces)-1 ){
+    sqlite3StrAccumAppend(pAccum, zSpaces, sizeof(zSpaces)-1);
+    N -= sizeof(zSpaces)-1;
+  }
+  if( N>0 ){
+    sqlite3StrAccumAppend(pAccum, zSpaces, N);
+  }
+}
+
+/*
+** On machines with a small stack size, you can redefine the
+** SQLITE_PRINT_BUF_SIZE to be something smaller, if desired.
+*/
+#ifndef SQLITE_PRINT_BUF_SIZE
+# define SQLITE_PRINT_BUF_SIZE 70
+#endif
+#define etBUFSIZE SQLITE_PRINT_BUF_SIZE  /* Size of the output buffer */
+
+/*
+** Render a string given by "fmt" into the StrAccum object.
+*/
+void sqlite3VXPrintf(
+  StrAccum *pAccum,                  /* Accumulate results here */
+  int useExtended,                   /* Allow extended %-conversions */
+  const char *fmt,                   /* Format string */
+  va_list ap                         /* arguments */
+){
+  int c;                     /* Next character in the format string */
+  char *bufpt;               /* Pointer to the conversion buffer */
+  int precision;             /* Precision of the current field */
+  int length;                /* Length of the field */
+  int idx;                   /* A general purpose loop counter */
+  int width;                 /* Width of the current field */
+  etByte flag_leftjustify;   /* True if "-" flag is present */
+  etByte flag_plussign;      /* True if "+" flag is present */
+  etByte flag_blanksign;     /* True if " " flag is present */
+  etByte flag_alternateform; /* True if "#" flag is present */
+  etByte flag_altform2;      /* True if "!" flag is present */
+  etByte flag_zeropad;       /* True if field width constant starts with zero */
+  etByte flag_long;          /* True if "l" flag is present */
+  etByte flag_longlong;      /* True if the "ll" flag is present */
+  etByte done;               /* Loop termination flag */
+  etByte xtype = 0;          /* Conversion paradigm */
+  char prefix;               /* Prefix character.  "+" or "-" or " " or '\0'. */
+  sqlite_uint64 longvalue;   /* Value for integer types */
+  LONGDOUBLE_TYPE realvalue; /* Value for real types */
+  const et_info *infop;      /* Pointer to the appropriate info structure */
+  char *zOut;                /* Rendering buffer */
+  int nOut;                  /* Size of the rendering buffer */
+  char *zExtra;              /* Malloced memory used by some conversion */
+#ifndef SQLITE_OMIT_FLOATING_POINT
+  int  exp, e2;              /* exponent of real numbers */
+  int nsd;                   /* Number of significant digits returned */
+  double rounder;            /* Used for rounding floating point values */
+  etByte flag_dp;            /* True if decimal point should be shown */
+  etByte flag_rtz;           /* True if trailing zeros should be removed */
+#endif
+  char buf[etBUFSIZE];       /* Conversion buffer */
+
+  bufpt = 0;
+  for(; (c=(*fmt))!=0; ++fmt){
+    if( c!='%' ){
+      int amt;
+      bufpt = (char *)fmt;
+      amt = 1;
+      while( (c=(*++fmt))!='%' && c!=0 ) amt++;
+      sqlite3StrAccumAppend(pAccum, bufpt, amt);
+      if( c==0 ) break;
+    }
+    if( (c=(*++fmt))==0 ){
+      sqlite3StrAccumAppend(pAccum, "%", 1);
+      break;
+    }
+    /* Find out what flags are present */
+    flag_leftjustify = flag_plussign = flag_blanksign = 
+     flag_alternateform = flag_altform2 = flag_zeropad = 0;
+    done = 0;
+    do{
+      switch( c ){
+        case '-':   flag_leftjustify = 1;     break;
+        case '+':   flag_plussign = 1;        break;
+        case ' ':   flag_blanksign = 1;       break;
+        case '#':   flag_alternateform = 1;   break;
+        case '!':   flag_altform2 = 1;        break;
+        case '0':   flag_zeropad = 1;         break;
+        default:    done = 1;                 break;
+      }
+    }while( !done && (c=(*++fmt))!=0 );
+    /* Get the field width */
+    width = 0;
+    if( c=='*' ){
+      width = va_arg(ap,int);
+      if( width<0 ){
+        flag_leftjustify = 1;
+        width = -width;
+      }
+      c = *++fmt;
+    }else{
+      while( c>='0' && c<='9' ){
+        width = width*10 + c - '0';
+        c = *++fmt;
+      }
+    }
+    /* Get the precision */
+    if( c=='.' ){
+      precision = 0;
+      c = *++fmt;
+      if( c=='*' ){
+        precision = va_arg(ap,int);
+        if( precision<0 ) precision = -precision;
+        c = *++fmt;
+      }else{
+        while( c>='0' && c<='9' ){
+          precision = precision*10 + c - '0';
+          c = *++fmt;
+        }
+      }
+    }else{
+      precision = -1;
+    }
+    /* Get the conversion type modifier */
+    if( c=='l' ){
+      flag_long = 1;
+      c = *++fmt;
+      if( c=='l' ){
+        flag_longlong = 1;
+        c = *++fmt;
+      }else{
+        flag_longlong = 0;
+      }
+    }else{
+      flag_long = flag_longlong = 0;
+    }
+    /* Fetch the info entry for the field */
+    infop = &fmtinfo[0];
+    xtype = etINVALID;
+    for(idx=0; idx<ArraySize(fmtinfo); idx++){
+      if( c==fmtinfo[idx].fmttype ){
+        infop = &fmtinfo[idx];
+        if( useExtended || (infop->flags & FLAG_INTERN)==0 ){
+          xtype = infop->type;
+        }else{
+          return;
+        }
+        break;
+      }
+    }
+    zExtra = 0;
+
+    /*
+    ** At this point, variables are initialized as follows:
+    **
+    **   flag_alternateform          TRUE if a '#' is present.
+    **   flag_altform2               TRUE if a '!' is present.
+    **   flag_plussign               TRUE if a '+' is present.
+    **   flag_leftjustify            TRUE if a '-' is present or if the
+    **                               field width was negative.
+    **   flag_zeropad                TRUE if the width began with 0.
+    **   flag_long                   TRUE if the letter 'l' (ell) prefixed
+    **                               the conversion character.
+    **   flag_longlong               TRUE if the letter 'll' (ell ell) prefixed
+    **                               the conversion character.
+    **   flag_blanksign              TRUE if a ' ' is present.
+    **   width                       The specified field width.  This is
+    **                               always non-negative.  Zero is the default.
+    **   precision                   The specified precision.  The default
+    **                               is -1.
+    **   xtype                       The class of the conversion.
+    **   infop                       Pointer to the appropriate info struct.
+    */
+    switch( xtype ){
+      case etPOINTER:
+        flag_longlong = sizeof(char*)==sizeof(i64);
+        flag_long = sizeof(char*)==sizeof(long int);
+        /* Fall through into the next case */
+      case etORDINAL:
+      case etRADIX:
+        if( infop->flags & FLAG_SIGNED ){
+          i64 v;
+          if( flag_longlong ){
+            v = va_arg(ap,i64);
+          }else if( flag_long ){
+            v = va_arg(ap,long int);
+          }else{
+            v = va_arg(ap,int);
+          }
+          if( v<0 ){
+            if( v==SMALLEST_INT64 ){
+              longvalue = ((u64)1)<<63;
+            }else{
+              longvalue = -v;
+            }
+            prefix = '-';
+          }else{
+            longvalue = v;
+            if( flag_plussign )        prefix = '+';
+            else if( flag_blanksign )  prefix = ' ';
+            else                       prefix = 0;
+          }
+        }else{
+          if( flag_longlong ){
+            longvalue = va_arg(ap,u64);
+          }else if( flag_long ){
+            longvalue = va_arg(ap,unsigned long int);
+          }else{
+            longvalue = va_arg(ap,unsigned int);
+          }
+          prefix = 0;
+        }
+        if( longvalue==0 ) flag_alternateform = 0;
+        if( flag_zeropad && precision<width-(prefix!=0) ){
+          precision = width-(prefix!=0);
+        }
+        if( precision<etBUFSIZE-10 ){
+          nOut = etBUFSIZE;
+          zOut = buf;
+        }else{
+          nOut = precision + 10;
+          zOut = zExtra = sqlite3Malloc( nOut );
+          if( zOut==0 ){
+            pAccum->mallocFailed = 1;
+            return;
+          }
+        }
+        bufpt = &zOut[nOut-1];
+        if( xtype==etORDINAL ){
+          static const char zOrd[] = "thstndrd";
+          int x = (int)(longvalue % 10);
+          if( x>=4 || (longvalue/10)%10==1 ){
+            x = 0;
+          }
+          *(--bufpt) = zOrd[x*2+1];
+          *(--bufpt) = zOrd[x*2];
+        }
+        {
+          register const char *cset;      /* Use registers for speed */
+          register int base;
+          cset = &aDigits[infop->charset];
+          base = infop->base;
+          do{                                           /* Convert to ascii */
+            *(--bufpt) = cset[longvalue%base];
+            longvalue = longvalue/base;
+          }while( longvalue>0 );
+        }
+        length = (int)(&zOut[nOut-1]-bufpt);
+        for(idx=precision-length; idx>0; idx--){
+          *(--bufpt) = '0';                             /* Zero pad */
+        }
+        if( prefix ) *(--bufpt) = prefix;               /* Add sign */
+        if( flag_alternateform && infop->prefix ){      /* Add "0" or "0x" */
+          const char *pre;
+          char x;
+          pre = &aPrefix[infop->prefix];
+          for(; (x=(*pre))!=0; pre++) *(--bufpt) = x;
+        }
+        length = (int)(&zOut[nOut-1]-bufpt);
+        break;
+      case etFLOAT:
+      case etEXP:
+      case etGENERIC:
+        realvalue = va_arg(ap,double);
+#ifdef SQLITE_OMIT_FLOATING_POINT
+        length = 0;
+#else
+        if( precision<0 ) precision = 6;         /* Set default precision */
+        if( realvalue<0.0 ){
+          realvalue = -realvalue;
+          prefix = '-';
+        }else{
+          if( flag_plussign )          prefix = '+';
+          else if( flag_blanksign )    prefix = ' ';
+          else                         prefix = 0;
+        }
+        if( xtype==etGENERIC && precision>0 ) precision--;
+#if 0
+        /* Rounding works like BSD when the constant 0.4999 is used.  Wierd! */
+        for(idx=precision, rounder=0.4999; idx>0; idx--, rounder*=0.1);
+#else
+        /* It makes more sense to use 0.5 */
+        for(idx=precision, rounder=0.5; idx>0; idx--, rounder*=0.1){}
+#endif
+        if( xtype==etFLOAT ) realvalue += rounder;
+        /* Normalize realvalue to within 10.0 > realvalue >= 1.0 */
+        exp = 0;
+        if( sqlite3IsNaN((double)realvalue) ){
+          bufpt = "NaN";
+          length = 3;
+          break;
+        }
+        if( realvalue>0.0 ){
+          while( realvalue>=1e32 && exp<=350 ){ realvalue *= 1e-32; exp+=32; }
+          while( realvalue>=1e8 && exp<=350 ){ realvalue *= 1e-8; exp+=8; }
+          while( realvalue>=10.0 && exp<=350 ){ realvalue *= 0.1; exp++; }
+          while( realvalue<1e-8 ){ realvalue *= 1e8; exp-=8; }
+          while( realvalue<1.0 ){ realvalue *= 10.0; exp--; }
+          if( exp>350 ){
+            if( prefix=='-' ){
+              bufpt = "-Inf";
+            }else if( prefix=='+' ){
+              bufpt = "+Inf";
+            }else{
+              bufpt = "Inf";
+            }
+            length = sqlite3Strlen30(bufpt);
+            break;
+          }
+        }
+        bufpt = buf;
+        /*
+        ** If the field type is etGENERIC, then convert to either etEXP
+        ** or etFLOAT, as appropriate.
+        */
+        if( xtype!=etFLOAT ){
+          realvalue += rounder;
+          if( realvalue>=10.0 ){ realvalue *= 0.1; exp++; }
+        }
+        if( xtype==etGENERIC ){
+          flag_rtz = !flag_alternateform;
+          if( exp<-4 || exp>precision ){
+            xtype = etEXP;
+          }else{
+            precision = precision - exp;
+            xtype = etFLOAT;
+          }
+        }else{
+          flag_rtz = 0;
+        }
+        if( xtype==etEXP ){
+          e2 = 0;
+        }else{
+          e2 = exp;
+        }
+        if( e2+precision+width > etBUFSIZE - 15 ){
+          bufpt = zExtra = sqlite3Malloc( e2+precision+width+15 );
+          if( bufpt==0 ){
+            pAccum->mallocFailed = 1;
+            return;
+          }
+        }
+        zOut = bufpt;
+        nsd = 0;
+        flag_dp = (precision>0 ?1:0) | flag_alternateform | flag_altform2;
+        /* The sign in front of the number */
+        if( prefix ){
+          *(bufpt++) = prefix;
+        }
+        /* Digits prior to the decimal point */
+        if( e2<0 ){
+          *(bufpt++) = '0';
+        }else{
+          for(; e2>=0; e2--){
+            *(bufpt++) = et_getdigit(&realvalue,&nsd);
+          }
+        }
+        /* The decimal point */
+        if( flag_dp ){
+          *(bufpt++) = '.';
+        }
+        /* "0" digits after the decimal point but before the first
+        ** significant digit of the number */
+        for(e2++; e2<0; precision--, e2++){
+          assert( precision>0 );
+          *(bufpt++) = '0';
+        }
+        /* Significant digits after the decimal point */
+        while( (precision--)>0 ){
+          *(bufpt++) = et_getdigit(&realvalue,&nsd);
+        }
+        /* Remove trailing zeros and the "." if no digits follow the "." */
+        if( flag_rtz && flag_dp ){
+          while( bufpt[-1]=='0' ) *(--bufpt) = 0;
+          assert( bufpt>zOut );
+          if( bufpt[-1]=='.' ){
+            if( flag_altform2 ){
+              *(bufpt++) = '0';
+            }else{
+              *(--bufpt) = 0;
+            }
+          }
+        }
+        /* Add the "eNNN" suffix */
+        if( xtype==etEXP ){
+          *(bufpt++) = aDigits[infop->charset];
+          if( exp<0 ){
+            *(bufpt++) = '-'; exp = -exp;
+          }else{
+            *(bufpt++) = '+';
+          }
+          if( exp>=100 ){
+            *(bufpt++) = (char)((exp/100)+'0');        /* 100's digit */
+            exp %= 100;
+          }
+          *(bufpt++) = (char)(exp/10+'0');             /* 10's digit */
+          *(bufpt++) = (char)(exp%10+'0');             /* 1's digit */
+        }
+        *bufpt = 0;
+
+        /* The converted number is in buf[] and zero terminated. Output it.
+        ** Note that the number is in the usual order, not reversed as with
+        ** integer conversions. */
+        length = (int)(bufpt-zOut);
+        bufpt = zOut;
+
+        /* Special case:  Add leading zeros if the flag_zeropad flag is
+        ** set and we are not left justified */
+        if( flag_zeropad && !flag_leftjustify && length < width){
+          int i;
+          int nPad = width - length;
+          for(i=width; i>=nPad; i--){
+            bufpt[i] = bufpt[i-nPad];
+          }
+          i = prefix!=0;
+          while( nPad-- ) bufpt[i++] = '0';
+          length = width;
+        }
+#endif /* !defined(SQLITE_OMIT_FLOATING_POINT) */
+        break;
+      case etSIZE:
+        *(va_arg(ap,int*)) = pAccum->nChar;
+        length = width = 0;
+        break;
+      case etPERCENT:
+        buf[0] = '%';
+        bufpt = buf;
+        length = 1;
+        break;
+      case etCHARX:
+        c = va_arg(ap,int);
+        buf[0] = (char)c;
+        if( precision>=0 ){
+          for(idx=1; idx<precision; idx++) buf[idx] = (char)c;
+          length = precision;
+        }else{
+          length =1;
+        }
+        bufpt = buf;
+        break;
+      case etSTRING:
+      case etDYNSTRING:
+        bufpt = va_arg(ap,char*);
+        if( bufpt==0 ){
+          bufpt = "";
+        }else if( xtype==etDYNSTRING ){
+          zExtra = bufpt;
+        }
+        if( precision>=0 ){
+          for(length=0; length<precision && bufpt[length]; length++){}
+        }else{
+          length = sqlite3Strlen30(bufpt);
+        }
+        break;
+      case etSQLESCAPE:
+      case etSQLESCAPE2:
+      case etSQLESCAPE3: {
+        int i, j, k, n, isnull;
+        int needQuote;
+        char ch;
+        char q = ((xtype==etSQLESCAPE3)?'"':'\'');   /* Quote character */
+        char *escarg = va_arg(ap,char*);
+        isnull = escarg==0;
+        if( isnull ) escarg = (xtype==etSQLESCAPE2 ? "NULL" : "(NULL)");
+        k = precision;
+        for(i=n=0; k!=0 && (ch=escarg[i])!=0; i++, k--){
+          if( ch==q )  n++;
+        }
+        needQuote = !isnull && xtype==etSQLESCAPE2;
+        n += i + 1 + needQuote*2;
+        if( n>etBUFSIZE ){
+          bufpt = zExtra = sqlite3Malloc( n );
+          if( bufpt==0 ){
+            pAccum->mallocFailed = 1;
+            return;
+          }
+        }else{
+          bufpt = buf;
+        }
+        j = 0;
+        if( needQuote ) bufpt[j++] = q;
+        k = i;
+        for(i=0; i<k; i++){
+          bufpt[j++] = ch = escarg[i];
+          if( ch==q ) bufpt[j++] = ch;
+        }
+        if( needQuote ) bufpt[j++] = q;
+        bufpt[j] = 0;
+        length = j;
+        /* The precision in %q and %Q means how many input characters to
+        ** consume, not the length of the output...
+        ** if( precision>=0 && precision<length ) length = precision; */
+        break;
+      }
+      case etTOKEN: {
+        Token *pToken = va_arg(ap, Token*);
+        if( pToken ){
+          sqlite3StrAccumAppend(pAccum, (const char*)pToken->z, pToken->n);
+        }
+        length = width = 0;
+        break;
+      }
+      case etSRCLIST: {
+        SrcList *pSrc = va_arg(ap, SrcList*);
+        int k = va_arg(ap, int);
+        struct SrcList_item *pItem = &pSrc->a[k];
+        assert( k>=0 && k<pSrc->nSrc );
+        if( pItem->zDatabase ){
+          sqlite3StrAccumAppend(pAccum, pItem->zDatabase, -1);
+          sqlite3StrAccumAppend(pAccum, ".", 1);
+        }
+        sqlite3StrAccumAppend(pAccum, pItem->zName, -1);
+        length = width = 0;
+        break;
+      }
+      default: {
+        assert( xtype==etINVALID );
+        return;
+      }
+    }/* End switch over the format type */
+    /*
+    ** The text of the conversion is pointed to by "bufpt" and is
+    ** "length" characters long.  The field width is "width".  Do
+    ** the output.
+    */
+    if( !flag_leftjustify ){
+      register int nspace;
+      nspace = width-length;
+      if( nspace>0 ){
+        appendSpace(pAccum, nspace);
+      }
+    }
+    if( length>0 ){
+      sqlite3StrAccumAppend(pAccum, bufpt, length);
+    }
+    if( flag_leftjustify ){
+      register int nspace;
+      nspace = width-length;
+      if( nspace>0 ){
+        appendSpace(pAccum, nspace);
+      }
+    }
+    sqlite3_free(zExtra);
+  }/* End for loop over the format string */
+} /* End of function */
+
+/*
+** Append N bytes of text from z to the StrAccum object.
+*/
+void sqlite3StrAccumAppend(StrAccum *p, const char *z, int N){
+  assert( z!=0 || N==0 );
+  if( p->tooBig | p->mallocFailed ){
+    testcase(p->tooBig);
+    testcase(p->mallocFailed);
+    return;
+  }
+  assert( p->zText!=0 || p->nChar==0 );
+  if( N<0 ){
+    N = sqlite3Strlen30(z);
+  }
+  if( N==0 || NEVER(z==0) ){
+    return;
+  }
+  if( p->nChar+N >= p->nAlloc ){
+    char *zNew;
+    if( !p->useMalloc ){
+      p->tooBig = 1;
+      N = p->nAlloc - p->nChar - 1;
+      if( N<=0 ){
+        return;
+      }
+    }else{
+      char *zOld = (p->zText==p->zBase ? 0 : p->zText);
+      i64 szNew = p->nChar;
+      szNew += N + 1;
+      if( szNew > p->mxAlloc ){
+        sqlite3StrAccumReset(p);
+        p->tooBig = 1;
+        return;
+      }else{
+        p->nAlloc = (int)szNew;
+      }
+      if( p->useMalloc==1 ){
+        zNew = sqlite3DbRealloc(p->db, zOld, p->nAlloc);
+      }else{
+        zNew = sqlite3_realloc(zOld, p->nAlloc);
+      }
+      if( zNew ){
+        if( zOld==0 && p->nChar>0 ) memcpy(zNew, p->zText, p->nChar);
+        p->zText = zNew;
+      }else{
+        p->mallocFailed = 1;
+        sqlite3StrAccumReset(p);
+        return;
+      }
+    }
+  }
+  assert( p->zText );
+  memcpy(&p->zText[p->nChar], z, N);
+  p->nChar += N;
+}
+
+/*
+** Finish off a string by making sure it is zero-terminated.
+** Return a pointer to the resulting string.  Return a NULL
+** pointer if any kind of error was encountered.
+*/
+char *sqlite3StrAccumFinish(StrAccum *p){
+  if( p->zText ){
+    p->zText[p->nChar] = 0;
+    if( p->useMalloc && p->zText==p->zBase ){
+      if( p->useMalloc==1 ){
+        p->zText = sqlite3DbMallocRaw(p->db, p->nChar+1 );
+      }else{
+        p->zText = sqlite3_malloc(p->nChar+1);
+      }
+      if( p->zText ){
+        memcpy(p->zText, p->zBase, p->nChar+1);
+      }else{
+        p->mallocFailed = 1;
+      }
+    }
+  }
+  return p->zText;
+}
+
+/*
+** Reset an StrAccum string.  Reclaim all malloced memory.
+*/
+void sqlite3StrAccumReset(StrAccum *p){
+  if( p->zText!=p->zBase ){
+    if( p->useMalloc==1 ){
+      sqlite3DbFree(p->db, p->zText);
+    }else{
+      sqlite3_free(p->zText);
+    }
+  }
+  p->zText = 0;
+}
+
+/*
+** Initialize a string accumulator
+*/
+void sqlite3StrAccumInit(StrAccum *p, char *zBase, int n, int mx){
+  p->zText = p->zBase = zBase;
+  p->db = 0;
+  p->nChar = 0;
+  p->nAlloc = n;
+  p->mxAlloc = mx;
+  p->useMalloc = 1;
+  p->tooBig = 0;
+  p->mallocFailed = 0;
+}
+
+/*
+** Print into memory obtained from sqliteMalloc().  Use the internal
+** %-conversion extensions.
+*/
+char *sqlite3VMPrintf(sqlite3 *db, const char *zFormat, va_list ap){
+  char *z;
+  char zBase[SQLITE_PRINT_BUF_SIZE];
+  StrAccum acc;
+  assert( db!=0 );
+  sqlite3StrAccumInit(&acc, zBase, sizeof(zBase),
+                      db->aLimit[SQLITE_LIMIT_LENGTH]);
+  acc.db = db;
+  sqlite3VXPrintf(&acc, 1, zFormat, ap);
+  z = sqlite3StrAccumFinish(&acc);
+  if( acc.mallocFailed ){
+    db->mallocFailed = 1;
+  }
+  return z;
+}
+
+/*
+** Print into memory obtained from sqliteMalloc().  Use the internal
+** %-conversion extensions.
+*/
+char *sqlite3MPrintf(sqlite3 *db, const char *zFormat, ...){
+  va_list ap;
+  char *z;
+  va_start(ap, zFormat);
+  z = sqlite3VMPrintf(db, zFormat, ap);
+  va_end(ap);
+  return z;
+}
+
+/*
+** Like sqlite3MPrintf(), but call sqlite3DbFree() on zStr after formatting
+** the string and before returnning.  This routine is intended to be used
+** to modify an existing string.  For example:
+**
+**       x = sqlite3MPrintf(db, x, "prefix %s suffix", x);
+**
+*/
+char *sqlite3MAppendf(sqlite3 *db, char *zStr, const char *zFormat, ...){
+  va_list ap;
+  char *z;
+  va_start(ap, zFormat);
+  z = sqlite3VMPrintf(db, zFormat, ap);
+  va_end(ap);
+  sqlite3DbFree(db, zStr);
+  return z;
+}
+
+/*
+** Print into memory obtained from sqlite3_malloc().  Omit the internal
+** %-conversion extensions.
+*/
+char *sqlite3_vmprintf(const char *zFormat, va_list ap){
+  char *z;
+  char zBase[SQLITE_PRINT_BUF_SIZE];
+  StrAccum acc;
+#ifndef SQLITE_OMIT_AUTOINIT
+  if( sqlite3_initialize() ) return 0;
+#endif
+  sqlite3StrAccumInit(&acc, zBase, sizeof(zBase), SQLITE_MAX_LENGTH);
+  acc.useMalloc = 2;
+  sqlite3VXPrintf(&acc, 0, zFormat, ap);
+  z = sqlite3StrAccumFinish(&acc);
+  return z;
+}
+
+/*
+** Print into memory obtained from sqlite3_malloc()().  Omit the internal
+** %-conversion extensions.
+*/
+char *sqlite3_mprintf(const char *zFormat, ...){
+  va_list ap;
+  char *z;
+#ifndef SQLITE_OMIT_AUTOINIT
+  if( sqlite3_initialize() ) return 0;
+#endif
+  va_start(ap, zFormat);
+  z = sqlite3_vmprintf(zFormat, ap);
+  va_end(ap);
+  return z;
+}
+
+/*
+** sqlite3_snprintf() works like snprintf() except that it ignores the
+** current locale settings.  This is important for SQLite because we
+** are not able to use a "," as the decimal point in place of "." as
+** specified by some locales.
+**
+** Oops:  The first two arguments of sqlite3_snprintf() are backwards
+** from the snprintf() standard.  Unfortunately, it is too late to change
+** this without breaking compatibility, so we just have to live with the
+** mistake.
+**
+** sqlite3_vsnprintf() is the varargs version.
+*/
+char *sqlite3_vsnprintf(int n, char *zBuf, const char *zFormat, va_list ap){
+  StrAccum acc;
+  if( n<=0 ) return zBuf;
+  sqlite3StrAccumInit(&acc, zBuf, n, 0);
+  acc.useMalloc = 0;
+  sqlite3VXPrintf(&acc, 0, zFormat, ap);
+  return sqlite3StrAccumFinish(&acc);
+}
+char *sqlite3_snprintf(int n, char *zBuf, const char *zFormat, ...){
+  char *z;
+  va_list ap;
+  va_start(ap,zFormat);
+  z = sqlite3_vsnprintf(n, zBuf, zFormat, ap);
+  va_end(ap);
+  return z;
+}
+
+/*
+** This is the routine that actually formats the sqlite3_log() message.
+** We house it in a separate routine from sqlite3_log() to avoid using
+** stack space on small-stack systems when logging is disabled.
+**
+** sqlite3_log() must render into a static buffer.  It cannot dynamically
+** allocate memory because it might be called while the memory allocator
+** mutex is held.
+*/
+static void renderLogMsg(int iErrCode, const char *zFormat, va_list ap){
+  StrAccum acc;                          /* String accumulator */
+  char zMsg[SQLITE_PRINT_BUF_SIZE*3];    /* Complete log message */
+
+  sqlite3StrAccumInit(&acc, zMsg, sizeof(zMsg), 0);
+  acc.useMalloc = 0;
+  sqlite3VXPrintf(&acc, 0, zFormat, ap);
+  sqlite3GlobalConfig.xLog(sqlite3GlobalConfig.pLogArg, iErrCode,
+                           sqlite3StrAccumFinish(&acc));
+}
+
+/*
+** Format and write a message to the log if logging is enabled.
+*/
+void sqlite3_log(int iErrCode, const char *zFormat, ...){
+  va_list ap;                             /* Vararg list */
+  if( sqlite3GlobalConfig.xLog ){
+    va_start(ap, zFormat);
+    renderLogMsg(iErrCode, zFormat, ap);
+    va_end(ap);
+  }
+}
+
+#if defined(SQLITE_DEBUG)
+/*
+** A version of printf() that understands %lld.  Used for debugging.
+** The printf() built into some versions of windows does not understand %lld
+** and segfaults if you give it a long long int.
+*/
+void sqlite3DebugPrintf(const char *zFormat, ...){
+  va_list ap;
+  StrAccum acc;
+  char zBuf[500];
+  sqlite3StrAccumInit(&acc, zBuf, sizeof(zBuf), 0);
+  acc.useMalloc = 0;
+  va_start(ap,zFormat);
+  sqlite3VXPrintf(&acc, 0, zFormat, ap);
+  va_end(ap);
+  sqlite3StrAccumFinish(&acc);
+  fprintf(stdout,"%s", zBuf);
+  fflush(stdout);
+}
+#endif
+
+#ifndef SQLITE_OMIT_TRACE
+/*
+** variable-argument wrapper around sqlite3VXPrintf().
+*/
+void sqlite3XPrintf(StrAccum *p, const char *zFormat, ...){
+  va_list ap;
+  va_start(ap,zFormat);
+  sqlite3VXPrintf(p, 1, zFormat, ap);
+  va_end(ap);
+}
+#endif
diff --git a/src/random.c b/src/random.c
new file mode 100644
index 0000000..234ebdf
--- /dev/null
+++ b/src/random.c
@@ -0,0 +1,145 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains code to implement a pseudo-random number
+** generator (PRNG) for SQLite.
+**
+** Random numbers are used by some of the database backends in order
+** to generate random integer keys for tables or random filenames.
+*/
+#include "sqliteInt.h"
+
+
+/* All threads share a single random number generator.
+** This structure is the current state of the generator.
+*/
+static SQLITE_WSD struct sqlite3PrngType {
+  unsigned char isInit;          /* True if initialized */
+  unsigned char i, j;            /* State variables */
+  unsigned char s[256];          /* State variables */
+} sqlite3Prng;
+
+/*
+** Get a single 8-bit random value from the RC4 PRNG.  The Mutex
+** must be held while executing this routine.
+**
+** Why not just use a library random generator like lrand48() for this?
+** Because the OP_NewRowid opcode in the VDBE depends on having a very
+** good source of random numbers.  The lrand48() library function may
+** well be good enough.  But maybe not.  Or maybe lrand48() has some
+** subtle problems on some systems that could cause problems.  It is hard
+** to know.  To minimize the risk of problems due to bad lrand48()
+** implementations, SQLite uses this random number generator based
+** on RC4, which we know works very well.
+**
+** (Later):  Actually, OP_NewRowid does not depend on a good source of
+** randomness any more.  But we will leave this code in all the same.
+*/
+static u8 randomByte(void){
+  unsigned char t;
+
+
+  /* The "wsdPrng" macro will resolve to the pseudo-random number generator
+  ** state vector.  If writable static data is unsupported on the target,
+  ** we have to locate the state vector at run-time.  In the more common
+  ** case where writable static data is supported, wsdPrng can refer directly
+  ** to the "sqlite3Prng" state vector declared above.
+  */
+#ifdef SQLITE_OMIT_WSD
+  struct sqlite3PrngType *p = &GLOBAL(struct sqlite3PrngType, sqlite3Prng);
+# define wsdPrng p[0]
+#else
+# define wsdPrng sqlite3Prng
+#endif
+
+
+  /* Initialize the state of the random number generator once,
+  ** the first time this routine is called.  The seed value does
+  ** not need to contain a lot of randomness since we are not
+  ** trying to do secure encryption or anything like that...
+  **
+  ** Nothing in this file or anywhere else in SQLite does any kind of
+  ** encryption.  The RC4 algorithm is being used as a PRNG (pseudo-random
+  ** number generator) not as an encryption device.
+  */
+  if( !wsdPrng.isInit ){
+    int i;
+    char k[256];
+    wsdPrng.j = 0;
+    wsdPrng.i = 0;
+    sqlite3OsRandomness(sqlite3_vfs_find(0), 256, k);
+    for(i=0; i<256; i++){
+      wsdPrng.s[i] = (u8)i;
+    }
+    for(i=0; i<256; i++){
+      wsdPrng.j += wsdPrng.s[i] + k[i];
+      t = wsdPrng.s[wsdPrng.j];
+      wsdPrng.s[wsdPrng.j] = wsdPrng.s[i];
+      wsdPrng.s[i] = t;
+    }
+    wsdPrng.isInit = 1;
+  }
+
+  /* Generate and return single random byte
+  */
+  wsdPrng.i++;
+  t = wsdPrng.s[wsdPrng.i];
+  wsdPrng.j += t;
+  wsdPrng.s[wsdPrng.i] = wsdPrng.s[wsdPrng.j];
+  wsdPrng.s[wsdPrng.j] = t;
+  t += wsdPrng.s[wsdPrng.i];
+  return wsdPrng.s[t];
+}
+
+/*
+** Return N random bytes.
+*/
+void sqlite3_randomness(int N, void *pBuf){
+  unsigned char *zBuf = pBuf;
+#if SQLITE_THREADSAFE
+  sqlite3_mutex *mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_PRNG);
+#endif
+  sqlite3_mutex_enter(mutex);
+  while( N-- ){
+    *(zBuf++) = randomByte();
+  }
+  sqlite3_mutex_leave(mutex);
+}
+
+#ifndef SQLITE_OMIT_BUILTIN_TEST
+/*
+** For testing purposes, we sometimes want to preserve the state of
+** PRNG and restore the PRNG to its saved state at a later time, or
+** to reset the PRNG to its initial state.  These routines accomplish
+** those tasks.
+**
+** The sqlite3_test_control() interface calls these routines to
+** control the PRNG.
+*/
+static SQLITE_WSD struct sqlite3PrngType sqlite3SavedPrng;
+void sqlite3PrngSaveState(void){
+  memcpy(
+    &GLOBAL(struct sqlite3PrngType, sqlite3SavedPrng),
+    &GLOBAL(struct sqlite3PrngType, sqlite3Prng),
+    sizeof(sqlite3Prng)
+  );
+}
+void sqlite3PrngRestoreState(void){
+  memcpy(
+    &GLOBAL(struct sqlite3PrngType, sqlite3Prng),
+    &GLOBAL(struct sqlite3PrngType, sqlite3SavedPrng),
+    sizeof(sqlite3Prng)
+  );
+}
+void sqlite3PrngResetState(void){
+  GLOBAL(struct sqlite3PrngType, sqlite3Prng).isInit = 0;
+}
+#endif /* SQLITE_OMIT_BUILTIN_TEST */
diff --git a/src/resolve.c b/src/resolve.c
new file mode 100644
index 0000000..6d857f0
--- /dev/null
+++ b/src/resolve.c
@@ -0,0 +1,1223 @@
+/*
+** 2008 August 18
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains routines used for walking the parser tree and
+** resolve all identifiers by associating them with a particular
+** table and column.
+*/
+#include "sqliteInt.h"
+#include <stdlib.h>
+#include <string.h>
+
+/*
+** Turn the pExpr expression into an alias for the iCol-th column of the
+** result set in pEList.
+**
+** If the result set column is a simple column reference, then this routine
+** makes an exact copy.  But for any other kind of expression, this
+** routine make a copy of the result set column as the argument to the
+** TK_AS operator.  The TK_AS operator causes the expression to be
+** evaluated just once and then reused for each alias.
+**
+** The reason for suppressing the TK_AS term when the expression is a simple
+** column reference is so that the column reference will be recognized as
+** usable by indices within the WHERE clause processing logic. 
+**
+** Hack:  The TK_AS operator is inhibited if zType[0]=='G'.  This means
+** that in a GROUP BY clause, the expression is evaluated twice.  Hence:
+**
+**     SELECT random()%5 AS x, count(*) FROM tab GROUP BY x
+**
+** Is equivalent to:
+**
+**     SELECT random()%5 AS x, count(*) FROM tab GROUP BY random()%5
+**
+** The result of random()%5 in the GROUP BY clause is probably different
+** from the result in the result-set.  We might fix this someday.  Or
+** then again, we might not...
+*/
+static void resolveAlias(
+  Parse *pParse,         /* Parsing context */
+  ExprList *pEList,      /* A result set */
+  int iCol,              /* A column in the result set.  0..pEList->nExpr-1 */
+  Expr *pExpr,           /* Transform this into an alias to the result set */
+  const char *zType      /* "GROUP" or "ORDER" or "" */
+){
+  Expr *pOrig;           /* The iCol-th column of the result set */
+  Expr *pDup;            /* Copy of pOrig */
+  sqlite3 *db;           /* The database connection */
+
+  assert( iCol>=0 && iCol<pEList->nExpr );
+  pOrig = pEList->a[iCol].pExpr;
+  assert( pOrig!=0 );
+  assert( pOrig->flags & EP_Resolved );
+  db = pParse->db;
+  if( pOrig->op!=TK_COLUMN && zType[0]!='G' ){
+    pDup = sqlite3ExprDup(db, pOrig, 0);
+    pDup = sqlite3PExpr(pParse, TK_AS, pDup, 0, 0);
+    if( pDup==0 ) return;
+    if( pEList->a[iCol].iAlias==0 ){
+      pEList->a[iCol].iAlias = (u16)(++pParse->nAlias);
+    }
+    pDup->iTable = pEList->a[iCol].iAlias;
+  }else if( ExprHasProperty(pOrig, EP_IntValue) || pOrig->u.zToken==0 ){
+    pDup = sqlite3ExprDup(db, pOrig, 0);
+    if( pDup==0 ) return;
+  }else{
+    char *zToken = pOrig->u.zToken;
+    assert( zToken!=0 );
+    pOrig->u.zToken = 0;
+    pDup = sqlite3ExprDup(db, pOrig, 0);
+    pOrig->u.zToken = zToken;
+    if( pDup==0 ) return;
+    assert( (pDup->flags & (EP_Reduced|EP_TokenOnly))==0 );
+    pDup->flags2 |= EP2_MallocedToken;
+    pDup->u.zToken = sqlite3DbStrDup(db, zToken);
+  }
+  if( pExpr->flags & EP_ExpCollate ){
+    pDup->pColl = pExpr->pColl;
+    pDup->flags |= EP_ExpCollate;
+  }
+
+  /* Before calling sqlite3ExprDelete(), set the EP_Static flag. This 
+  ** prevents ExprDelete() from deleting the Expr structure itself,
+  ** allowing it to be repopulated by the memcpy() on the following line.
+  */
+  ExprSetProperty(pExpr, EP_Static);
+  sqlite3ExprDelete(db, pExpr);
+  memcpy(pExpr, pDup, sizeof(*pExpr));
+  sqlite3DbFree(db, pDup);
+}
+
+
+/*
+** Return TRUE if the name zCol occurs anywhere in the USING clause.
+**
+** Return FALSE if the USING clause is NULL or if it does not contain
+** zCol.
+*/
+static int nameInUsingClause(IdList *pUsing, const char *zCol){
+  if( pUsing ){
+    int k;
+    for(k=0; k<pUsing->nId; k++){
+      if( sqlite3StrICmp(pUsing->a[k].zName, zCol)==0 ) return 1;
+    }
+  }
+  return 0;
+}
+
+
+/*
+** Given the name of a column of the form X.Y.Z or Y.Z or just Z, look up
+** that name in the set of source tables in pSrcList and make the pExpr 
+** expression node refer back to that source column.  The following changes
+** are made to pExpr:
+**
+**    pExpr->iDb           Set the index in db->aDb[] of the database X
+**                         (even if X is implied).
+**    pExpr->iTable        Set to the cursor number for the table obtained
+**                         from pSrcList.
+**    pExpr->pTab          Points to the Table structure of X.Y (even if
+**                         X and/or Y are implied.)
+**    pExpr->iColumn       Set to the column number within the table.
+**    pExpr->op            Set to TK_COLUMN.
+**    pExpr->pLeft         Any expression this points to is deleted
+**    pExpr->pRight        Any expression this points to is deleted.
+**
+** The zDb variable is the name of the database (the "X").  This value may be
+** NULL meaning that name is of the form Y.Z or Z.  Any available database
+** can be used.  The zTable variable is the name of the table (the "Y").  This
+** value can be NULL if zDb is also NULL.  If zTable is NULL it
+** means that the form of the name is Z and that columns from any table
+** can be used.
+**
+** If the name cannot be resolved unambiguously, leave an error message
+** in pParse and return WRC_Abort.  Return WRC_Prune on success.
+*/
+static int lookupName(
+  Parse *pParse,       /* The parsing context */
+  const char *zDb,     /* Name of the database containing table, or NULL */
+  const char *zTab,    /* Name of table containing column, or NULL */
+  const char *zCol,    /* Name of the column. */
+  NameContext *pNC,    /* The name context used to resolve the name */
+  Expr *pExpr          /* Make this EXPR node point to the selected column */
+){
+  int i, j;            /* Loop counters */
+  int cnt = 0;                      /* Number of matching column names */
+  int cntTab = 0;                   /* Number of matching table names */
+  sqlite3 *db = pParse->db;         /* The database connection */
+  struct SrcList_item *pItem;       /* Use for looping over pSrcList items */
+  struct SrcList_item *pMatch = 0;  /* The matching pSrcList item */
+  NameContext *pTopNC = pNC;        /* First namecontext in the list */
+  Schema *pSchema = 0;              /* Schema of the expression */
+  int isTrigger = 0;
+
+  assert( pNC );     /* the name context cannot be NULL. */
+  assert( zCol );    /* The Z in X.Y.Z cannot be NULL */
+  assert( ~ExprHasAnyProperty(pExpr, EP_TokenOnly|EP_Reduced) );
+
+  /* Initialize the node to no-match */
+  pExpr->iTable = -1;
+  pExpr->pTab = 0;
+  ExprSetIrreducible(pExpr);
+
+  /* Start at the inner-most context and move outward until a match is found */
+  while( pNC && cnt==0 ){
+    ExprList *pEList;
+    SrcList *pSrcList = pNC->pSrcList;
+
+    if( pSrcList ){
+      for(i=0, pItem=pSrcList->a; i<pSrcList->nSrc; i++, pItem++){
+        Table *pTab;
+        int iDb;
+        Column *pCol;
+  
+        pTab = pItem->pTab;
+        assert( pTab!=0 && pTab->zName!=0 );
+        iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+        assert( pTab->nCol>0 );
+        if( zTab ){
+          if( pItem->zAlias ){
+            char *zTabName = pItem->zAlias;
+            if( sqlite3StrICmp(zTabName, zTab)!=0 ) continue;
+          }else{
+            char *zTabName = pTab->zName;
+            if( NEVER(zTabName==0) || sqlite3StrICmp(zTabName, zTab)!=0 ){
+              continue;
+            }
+            if( zDb!=0 && sqlite3StrICmp(db->aDb[iDb].zName, zDb)!=0 ){
+              continue;
+            }
+          }
+        }
+        if( 0==(cntTab++) ){
+          pExpr->iTable = pItem->iCursor;
+          pExpr->pTab = pTab;
+          pSchema = pTab->pSchema;
+          pMatch = pItem;
+        }
+        for(j=0, pCol=pTab->aCol; j<pTab->nCol; j++, pCol++){
+          if( sqlite3StrICmp(pCol->zName, zCol)==0 ){
+            /* If there has been exactly one prior match and this match
+            ** is for the right-hand table of a NATURAL JOIN or is in a 
+            ** USING clause, then skip this match.
+            */
+            if( cnt==1 ){
+              if( pItem->jointype & JT_NATURAL ) continue;
+              if( nameInUsingClause(pItem->pUsing, zCol) ) continue;
+            }
+            cnt++;
+            pExpr->iTable = pItem->iCursor;
+            pExpr->pTab = pTab;
+            pMatch = pItem;
+            pSchema = pTab->pSchema;
+            /* Substitute the rowid (column -1) for the INTEGER PRIMARY KEY */
+            pExpr->iColumn = j==pTab->iPKey ? -1 : (i16)j;
+            break;
+          }
+        }
+      }
+    }
+
+#ifndef SQLITE_OMIT_TRIGGER
+    /* If we have not already resolved the name, then maybe 
+    ** it is a new.* or old.* trigger argument reference
+    */
+    if( zDb==0 && zTab!=0 && cnt==0 && pParse->pTriggerTab!=0 ){
+      int op = pParse->eTriggerOp;
+      Table *pTab = 0;
+      assert( op==TK_DELETE || op==TK_UPDATE || op==TK_INSERT );
+      if( op!=TK_DELETE && sqlite3StrICmp("new",zTab) == 0 ){
+        pExpr->iTable = 1;
+        pTab = pParse->pTriggerTab;
+      }else if( op!=TK_INSERT && sqlite3StrICmp("old",zTab)==0 ){
+        pExpr->iTable = 0;
+        pTab = pParse->pTriggerTab;
+      }
+
+      if( pTab ){ 
+        int iCol;
+        pSchema = pTab->pSchema;
+        cntTab++;
+        for(iCol=0; iCol<pTab->nCol; iCol++){
+          Column *pCol = &pTab->aCol[iCol];
+          if( sqlite3StrICmp(pCol->zName, zCol)==0 ){
+            if( iCol==pTab->iPKey ){
+              iCol = -1;
+            }
+            break;
+          }
+        }
+        if( iCol>=pTab->nCol && sqlite3IsRowid(zCol) ){
+          iCol = -1;        /* IMP: R-44911-55124 */
+        }
+        if( iCol<pTab->nCol ){
+          cnt++;
+          if( iCol<0 ){
+            pExpr->affinity = SQLITE_AFF_INTEGER;
+          }else if( pExpr->iTable==0 ){
+            testcase( iCol==31 );
+            testcase( iCol==32 );
+            pParse->oldmask |= (iCol>=32 ? 0xffffffff : (((u32)1)<<iCol));
+          }else{
+            testcase( iCol==31 );
+            testcase( iCol==32 );
+            pParse->newmask |= (iCol>=32 ? 0xffffffff : (((u32)1)<<iCol));
+          }
+          pExpr->iColumn = (i16)iCol;
+          pExpr->pTab = pTab;
+          isTrigger = 1;
+        }
+      }
+    }
+#endif /* !defined(SQLITE_OMIT_TRIGGER) */
+
+    /*
+    ** Perhaps the name is a reference to the ROWID
+    */
+    if( cnt==0 && cntTab==1 && sqlite3IsRowid(zCol) ){
+      cnt = 1;
+      pExpr->iColumn = -1;     /* IMP: R-44911-55124 */
+      pExpr->affinity = SQLITE_AFF_INTEGER;
+    }
+
+    /*
+    ** If the input is of the form Z (not Y.Z or X.Y.Z) then the name Z
+    ** might refer to an result-set alias.  This happens, for example, when
+    ** we are resolving names in the WHERE clause of the following command:
+    **
+    **     SELECT a+b AS x FROM table WHERE x<10;
+    **
+    ** In cases like this, replace pExpr with a copy of the expression that
+    ** forms the result set entry ("a+b" in the example) and return immediately.
+    ** Note that the expression in the result set should have already been
+    ** resolved by the time the WHERE clause is resolved.
+    */
+    if( cnt==0 && (pEList = pNC->pEList)!=0 && zTab==0 ){
+      for(j=0; j<pEList->nExpr; j++){
+        char *zAs = pEList->a[j].zName;
+        if( zAs!=0 && sqlite3StrICmp(zAs, zCol)==0 ){
+          Expr *pOrig;
+          assert( pExpr->pLeft==0 && pExpr->pRight==0 );
+          assert( pExpr->x.pList==0 );
+          assert( pExpr->x.pSelect==0 );
+          pOrig = pEList->a[j].pExpr;
+          if( !pNC->allowAgg && ExprHasProperty(pOrig, EP_Agg) ){
+            sqlite3ErrorMsg(pParse, "misuse of aliased aggregate %s", zAs);
+            return WRC_Abort;
+          }
+          resolveAlias(pParse, pEList, j, pExpr, "");
+          cnt = 1;
+          pMatch = 0;
+          assert( zTab==0 && zDb==0 );
+          goto lookupname_end;
+        }
+      } 
+    }
+
+    /* Advance to the next name context.  The loop will exit when either
+    ** we have a match (cnt>0) or when we run out of name contexts.
+    */
+    if( cnt==0 ){
+      pNC = pNC->pNext;
+    }
+  }
+
+  /*
+  ** If X and Y are NULL (in other words if only the column name Z is
+  ** supplied) and the value of Z is enclosed in double-quotes, then
+  ** Z is a string literal if it doesn't match any column names.  In that
+  ** case, we need to return right away and not make any changes to
+  ** pExpr.
+  **
+  ** Because no reference was made to outer contexts, the pNC->nRef
+  ** fields are not changed in any context.
+  */
+  if( cnt==0 && zTab==0 && ExprHasProperty(pExpr,EP_DblQuoted) ){
+    pExpr->op = TK_STRING;
+    pExpr->pTab = 0;
+    return WRC_Prune;
+  }
+
+  /*
+  ** cnt==0 means there was not match.  cnt>1 means there were two or
+  ** more matches.  Either way, we have an error.
+  */
+  if( cnt!=1 ){
+    const char *zErr;
+    zErr = cnt==0 ? "no such column" : "ambiguous column name";
+    if( zDb ){
+      sqlite3ErrorMsg(pParse, "%s: %s.%s.%s", zErr, zDb, zTab, zCol);
+    }else if( zTab ){
+      sqlite3ErrorMsg(pParse, "%s: %s.%s", zErr, zTab, zCol);
+    }else{
+      sqlite3ErrorMsg(pParse, "%s: %s", zErr, zCol);
+    }
+    pParse->checkSchema = 1;
+    pTopNC->nErr++;
+  }
+
+  /* If a column from a table in pSrcList is referenced, then record
+  ** this fact in the pSrcList.a[].colUsed bitmask.  Column 0 causes
+  ** bit 0 to be set.  Column 1 sets bit 1.  And so forth.  If the
+  ** column number is greater than the number of bits in the bitmask
+  ** then set the high-order bit of the bitmask.
+  */
+  if( pExpr->iColumn>=0 && pMatch!=0 ){
+    int n = pExpr->iColumn;
+    testcase( n==BMS-1 );
+    if( n>=BMS ){
+      n = BMS-1;
+    }
+    assert( pMatch->iCursor==pExpr->iTable );
+    pMatch->colUsed |= ((Bitmask)1)<<n;
+  }
+
+  /* Clean up and return
+  */
+  sqlite3ExprDelete(db, pExpr->pLeft);
+  pExpr->pLeft = 0;
+  sqlite3ExprDelete(db, pExpr->pRight);
+  pExpr->pRight = 0;
+  pExpr->op = (isTrigger ? TK_TRIGGER : TK_COLUMN);
+lookupname_end:
+  if( cnt==1 ){
+    assert( pNC!=0 );
+    sqlite3AuthRead(pParse, pExpr, pSchema, pNC->pSrcList);
+    /* Increment the nRef value on all name contexts from TopNC up to
+    ** the point where the name matched. */
+    for(;;){
+      assert( pTopNC!=0 );
+      pTopNC->nRef++;
+      if( pTopNC==pNC ) break;
+      pTopNC = pTopNC->pNext;
+    }
+    return WRC_Prune;
+  } else {
+    return WRC_Abort;
+  }
+}
+
+/*
+** Allocate and return a pointer to an expression to load the column iCol
+** from datasource iSrc in SrcList pSrc.
+*/
+Expr *sqlite3CreateColumnExpr(sqlite3 *db, SrcList *pSrc, int iSrc, int iCol){
+  Expr *p = sqlite3ExprAlloc(db, TK_COLUMN, 0, 0);
+  if( p ){
+    struct SrcList_item *pItem = &pSrc->a[iSrc];
+    p->pTab = pItem->pTab;
+    p->iTable = pItem->iCursor;
+    if( p->pTab->iPKey==iCol ){
+      p->iColumn = -1;
+    }else{
+      p->iColumn = (ynVar)iCol;
+      testcase( iCol==BMS );
+      testcase( iCol==BMS-1 );
+      pItem->colUsed |= ((Bitmask)1)<<(iCol>=BMS ? BMS-1 : iCol);
+    }
+    ExprSetProperty(p, EP_Resolved);
+  }
+  return p;
+}
+
+/*
+** This routine is callback for sqlite3WalkExpr().
+**
+** Resolve symbolic names into TK_COLUMN operators for the current
+** node in the expression tree.  Return 0 to continue the search down
+** the tree or 2 to abort the tree walk.
+**
+** This routine also does error checking and name resolution for
+** function names.  The operator for aggregate functions is changed
+** to TK_AGG_FUNCTION.
+*/
+static int resolveExprStep(Walker *pWalker, Expr *pExpr){
+  NameContext *pNC;
+  Parse *pParse;
+
+  pNC = pWalker->u.pNC;
+  assert( pNC!=0 );
+  pParse = pNC->pParse;
+  assert( pParse==pWalker->pParse );
+
+  if( ExprHasAnyProperty(pExpr, EP_Resolved) ) return WRC_Prune;
+  ExprSetProperty(pExpr, EP_Resolved);
+#ifndef NDEBUG
+  if( pNC->pSrcList && pNC->pSrcList->nAlloc>0 ){
+    SrcList *pSrcList = pNC->pSrcList;
+    int i;
+    for(i=0; i<pNC->pSrcList->nSrc; i++){
+      assert( pSrcList->a[i].iCursor>=0 && pSrcList->a[i].iCursor<pParse->nTab);
+    }
+  }
+#endif
+  switch( pExpr->op ){
+
+#if defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT) && !defined(SQLITE_OMIT_SUBQUERY)
+    /* The special operator TK_ROW means use the rowid for the first
+    ** column in the FROM clause.  This is used by the LIMIT and ORDER BY
+    ** clause processing on UPDATE and DELETE statements.
+    */
+    case TK_ROW: {
+      SrcList *pSrcList = pNC->pSrcList;
+      struct SrcList_item *pItem;
+      assert( pSrcList && pSrcList->nSrc==1 );
+      pItem = pSrcList->a; 
+      pExpr->op = TK_COLUMN;
+      pExpr->pTab = pItem->pTab;
+      pExpr->iTable = pItem->iCursor;
+      pExpr->iColumn = -1;
+      pExpr->affinity = SQLITE_AFF_INTEGER;
+      break;
+    }
+#endif /* defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT) && !defined(SQLITE_OMIT_SUBQUERY) */
+
+    /* A lone identifier is the name of a column.
+    */
+    case TK_ID: {
+      return lookupName(pParse, 0, 0, pExpr->u.zToken, pNC, pExpr);
+    }
+  
+    /* A table name and column name:     ID.ID
+    ** Or a database, table and column:  ID.ID.ID
+    */
+    case TK_DOT: {
+      const char *zColumn;
+      const char *zTable;
+      const char *zDb;
+      Expr *pRight;
+
+      /* if( pSrcList==0 ) break; */
+      pRight = pExpr->pRight;
+      if( pRight->op==TK_ID ){
+        zDb = 0;
+        zTable = pExpr->pLeft->u.zToken;
+        zColumn = pRight->u.zToken;
+      }else{
+        assert( pRight->op==TK_DOT );
+        zDb = pExpr->pLeft->u.zToken;
+        zTable = pRight->pLeft->u.zToken;
+        zColumn = pRight->pRight->u.zToken;
+      }
+      return lookupName(pParse, zDb, zTable, zColumn, pNC, pExpr);
+    }
+
+    /* Resolve function names
+    */
+    case TK_CONST_FUNC:
+    case TK_FUNCTION: {
+      ExprList *pList = pExpr->x.pList;    /* The argument list */
+      int n = pList ? pList->nExpr : 0;    /* Number of arguments */
+      int no_such_func = 0;       /* True if no such function exists */
+      int wrong_num_args = 0;     /* True if wrong number of arguments */
+      int is_agg = 0;             /* True if is an aggregate function */
+      int auth;                   /* Authorization to use the function */
+      int nId;                    /* Number of characters in function name */
+      const char *zId;            /* The function name. */
+      FuncDef *pDef;              /* Information about the function */
+      u8 enc = ENC(pParse->db);   /* The database encoding */
+
+      testcase( pExpr->op==TK_CONST_FUNC );
+      assert( !ExprHasProperty(pExpr, EP_xIsSelect) );
+      zId = pExpr->u.zToken;
+      nId = sqlite3Strlen30(zId);
+      pDef = sqlite3FindFunction(pParse->db, zId, nId, n, enc, 0);
+      if( pDef==0 ){
+        pDef = sqlite3FindFunction(pParse->db, zId, nId, -1, enc, 0);
+        if( pDef==0 ){
+          no_such_func = 1;
+        }else{
+          wrong_num_args = 1;
+        }
+      }else{
+        is_agg = pDef->xFunc==0;
+      }
+#ifndef SQLITE_OMIT_AUTHORIZATION
+      if( pDef ){
+        auth = sqlite3AuthCheck(pParse, SQLITE_FUNCTION, 0, pDef->zName, 0);
+        if( auth!=SQLITE_OK ){
+          if( auth==SQLITE_DENY ){
+            sqlite3ErrorMsg(pParse, "not authorized to use function: %s",
+                                    pDef->zName);
+            pNC->nErr++;
+          }
+          pExpr->op = TK_NULL;
+          return WRC_Prune;
+        }
+      }
+#endif
+      if( is_agg && !pNC->allowAgg ){
+        sqlite3ErrorMsg(pParse, "misuse of aggregate function %.*s()", nId,zId);
+        pNC->nErr++;
+        is_agg = 0;
+      }else if( no_such_func ){
+        sqlite3ErrorMsg(pParse, "no such function: %.*s", nId, zId);
+        pNC->nErr++;
+      }else if( wrong_num_args ){
+        sqlite3ErrorMsg(pParse,"wrong number of arguments to function %.*s()",
+             nId, zId);
+        pNC->nErr++;
+      }
+      if( is_agg ){
+        pExpr->op = TK_AGG_FUNCTION;
+        pNC->hasAgg = 1;
+      }
+      if( is_agg ) pNC->allowAgg = 0;
+      sqlite3WalkExprList(pWalker, pList);
+      if( is_agg ) pNC->allowAgg = 1;
+      /* FIX ME:  Compute pExpr->affinity based on the expected return
+      ** type of the function 
+      */
+      return WRC_Prune;
+    }
+#ifndef SQLITE_OMIT_SUBQUERY
+    case TK_SELECT:
+    case TK_EXISTS:  testcase( pExpr->op==TK_EXISTS );
+#endif
+    case TK_IN: {
+      testcase( pExpr->op==TK_IN );
+      if( ExprHasProperty(pExpr, EP_xIsSelect) ){
+        int nRef = pNC->nRef;
+#ifndef SQLITE_OMIT_CHECK
+        if( pNC->isCheck ){
+          sqlite3ErrorMsg(pParse,"subqueries prohibited in CHECK constraints");
+        }
+#endif
+        sqlite3WalkSelect(pWalker, pExpr->x.pSelect);
+        assert( pNC->nRef>=nRef );
+        if( nRef!=pNC->nRef ){
+          ExprSetProperty(pExpr, EP_VarSelect);
+        }
+      }
+      break;
+    }
+#ifndef SQLITE_OMIT_CHECK
+    case TK_VARIABLE: {
+      if( pNC->isCheck ){
+        sqlite3ErrorMsg(pParse,"parameters prohibited in CHECK constraints");
+      }
+      break;
+    }
+#endif
+  }
+  return (pParse->nErr || pParse->db->mallocFailed) ? WRC_Abort : WRC_Continue;
+}
+
+/*
+** pEList is a list of expressions which are really the result set of the
+** a SELECT statement.  pE is a term in an ORDER BY or GROUP BY clause.
+** This routine checks to see if pE is a simple identifier which corresponds
+** to the AS-name of one of the terms of the expression list.  If it is,
+** this routine return an integer between 1 and N where N is the number of
+** elements in pEList, corresponding to the matching entry.  If there is
+** no match, or if pE is not a simple identifier, then this routine
+** return 0.
+**
+** pEList has been resolved.  pE has not.
+*/
+static int resolveAsName(
+  Parse *pParse,     /* Parsing context for error messages */
+  ExprList *pEList,  /* List of expressions to scan */
+  Expr *pE           /* Expression we are trying to match */
+){
+  int i;             /* Loop counter */
+
+  UNUSED_PARAMETER(pParse);
+
+  if( pE->op==TK_ID ){
+    char *zCol = pE->u.zToken;
+    for(i=0; i<pEList->nExpr; i++){
+      char *zAs = pEList->a[i].zName;
+      if( zAs!=0 && sqlite3StrICmp(zAs, zCol)==0 ){
+        return i+1;
+      }
+    }
+  }
+  return 0;
+}
+
+/*
+** pE is a pointer to an expression which is a single term in the
+** ORDER BY of a compound SELECT.  The expression has not been
+** name resolved.
+**
+** At the point this routine is called, we already know that the
+** ORDER BY term is not an integer index into the result set.  That
+** case is handled by the calling routine.
+**
+** Attempt to match pE against result set columns in the left-most
+** SELECT statement.  Return the index i of the matching column,
+** as an indication to the caller that it should sort by the i-th column.
+** The left-most column is 1.  In other words, the value returned is the
+** same integer value that would be used in the SQL statement to indicate
+** the column.
+**
+** If there is no match, return 0.  Return -1 if an error occurs.
+*/
+static int resolveOrderByTermToExprList(
+  Parse *pParse,     /* Parsing context for error messages */
+  Select *pSelect,   /* The SELECT statement with the ORDER BY clause */
+  Expr *pE           /* The specific ORDER BY term */
+){
+  int i;             /* Loop counter */
+  ExprList *pEList;  /* The columns of the result set */
+  NameContext nc;    /* Name context for resolving pE */
+  sqlite3 *db;       /* Database connection */
+  int rc;            /* Return code from subprocedures */
+  u8 savedSuppErr;   /* Saved value of db->suppressErr */
+
+  assert( sqlite3ExprIsInteger(pE, &i)==0 );
+  pEList = pSelect->pEList;
+
+  /* Resolve all names in the ORDER BY term expression
+  */
+  memset(&nc, 0, sizeof(nc));
+  nc.pParse = pParse;
+  nc.pSrcList = pSelect->pSrc;
+  nc.pEList = pEList;
+  nc.allowAgg = 1;
+  nc.nErr = 0;
+  db = pParse->db;
+  savedSuppErr = db->suppressErr;
+  db->suppressErr = 1;
+  rc = sqlite3ResolveExprNames(&nc, pE);
+  db->suppressErr = savedSuppErr;
+  if( rc ) return 0;
+
+  /* Try to match the ORDER BY expression against an expression
+  ** in the result set.  Return an 1-based index of the matching
+  ** result-set entry.
+  */
+  for(i=0; i<pEList->nExpr; i++){
+    if( sqlite3ExprCompare(pEList->a[i].pExpr, pE)<2 ){
+      return i+1;
+    }
+  }
+
+  /* If no match, return 0. */
+  return 0;
+}
+
+/*
+** Generate an ORDER BY or GROUP BY term out-of-range error.
+*/
+static void resolveOutOfRangeError(
+  Parse *pParse,         /* The error context into which to write the error */
+  const char *zType,     /* "ORDER" or "GROUP" */
+  int i,                 /* The index (1-based) of the term out of range */
+  int mx                 /* Largest permissible value of i */
+){
+  sqlite3ErrorMsg(pParse, 
+    "%r %s BY term out of range - should be "
+    "between 1 and %d", i, zType, mx);
+}
+
+/*
+** Analyze the ORDER BY clause in a compound SELECT statement.   Modify
+** each term of the ORDER BY clause is a constant integer between 1
+** and N where N is the number of columns in the compound SELECT.
+**
+** ORDER BY terms that are already an integer between 1 and N are
+** unmodified.  ORDER BY terms that are integers outside the range of
+** 1 through N generate an error.  ORDER BY terms that are expressions
+** are matched against result set expressions of compound SELECT
+** beginning with the left-most SELECT and working toward the right.
+** At the first match, the ORDER BY expression is transformed into
+** the integer column number.
+**
+** Return the number of errors seen.
+*/
+static int resolveCompoundOrderBy(
+  Parse *pParse,        /* Parsing context.  Leave error messages here */
+  Select *pSelect       /* The SELECT statement containing the ORDER BY */
+){
+  int i;
+  ExprList *pOrderBy;
+  ExprList *pEList;
+  sqlite3 *db;
+  int moreToDo = 1;
+
+  pOrderBy = pSelect->pOrderBy;
+  if( pOrderBy==0 ) return 0;
+  db = pParse->db;
+#if SQLITE_MAX_COLUMN
+  if( pOrderBy->nExpr>db->aLimit[SQLITE_LIMIT_COLUMN] ){
+    sqlite3ErrorMsg(pParse, "too many terms in ORDER BY clause");
+    return 1;
+  }
+#endif
+  for(i=0; i<pOrderBy->nExpr; i++){
+    pOrderBy->a[i].done = 0;
+  }
+  pSelect->pNext = 0;
+  while( pSelect->pPrior ){
+    pSelect->pPrior->pNext = pSelect;
+    pSelect = pSelect->pPrior;
+  }
+  while( pSelect && moreToDo ){
+    struct ExprList_item *pItem;
+    moreToDo = 0;
+    pEList = pSelect->pEList;
+    assert( pEList!=0 );
+    for(i=0, pItem=pOrderBy->a; i<pOrderBy->nExpr; i++, pItem++){
+      int iCol = -1;
+      Expr *pE, *pDup;
+      if( pItem->done ) continue;
+      pE = pItem->pExpr;
+      if( sqlite3ExprIsInteger(pE, &iCol) ){
+        if( iCol<=0 || iCol>pEList->nExpr ){
+          resolveOutOfRangeError(pParse, "ORDER", i+1, pEList->nExpr);
+          return 1;
+        }
+      }else{
+        iCol = resolveAsName(pParse, pEList, pE);
+        if( iCol==0 ){
+          pDup = sqlite3ExprDup(db, pE, 0);
+          if( !db->mallocFailed ){
+            assert(pDup);
+            iCol = resolveOrderByTermToExprList(pParse, pSelect, pDup);
+          }
+          sqlite3ExprDelete(db, pDup);
+        }
+      }
+      if( iCol>0 ){
+        CollSeq *pColl = pE->pColl;
+        int flags = pE->flags & EP_ExpCollate;
+        sqlite3ExprDelete(db, pE);
+        pItem->pExpr = pE = sqlite3Expr(db, TK_INTEGER, 0);
+        if( pE==0 ) return 1;
+        pE->pColl = pColl;
+        pE->flags |= EP_IntValue | flags;
+        pE->u.iValue = iCol;
+        pItem->iCol = (u16)iCol;
+        pItem->done = 1;
+      }else{
+        moreToDo = 1;
+      }
+    }
+    pSelect = pSelect->pNext;
+  }
+  for(i=0; i<pOrderBy->nExpr; i++){
+    if( pOrderBy->a[i].done==0 ){
+      sqlite3ErrorMsg(pParse, "%r ORDER BY term does not match any "
+            "column in the result set", i+1);
+      return 1;
+    }
+  }
+  return 0;
+}
+
+/*
+** Check every term in the ORDER BY or GROUP BY clause pOrderBy of
+** the SELECT statement pSelect.  If any term is reference to a
+** result set expression (as determined by the ExprList.a.iCol field)
+** then convert that term into a copy of the corresponding result set
+** column.
+**
+** If any errors are detected, add an error message to pParse and
+** return non-zero.  Return zero if no errors are seen.
+*/
+int sqlite3ResolveOrderGroupBy(
+  Parse *pParse,        /* Parsing context.  Leave error messages here */
+  Select *pSelect,      /* The SELECT statement containing the clause */
+  ExprList *pOrderBy,   /* The ORDER BY or GROUP BY clause to be processed */
+  const char *zType     /* "ORDER" or "GROUP" */
+){
+  int i;
+  sqlite3 *db = pParse->db;
+  ExprList *pEList;
+  struct ExprList_item *pItem;
+
+  if( pOrderBy==0 || pParse->db->mallocFailed ) return 0;
+#if SQLITE_MAX_COLUMN
+  if( pOrderBy->nExpr>db->aLimit[SQLITE_LIMIT_COLUMN] ){
+    sqlite3ErrorMsg(pParse, "too many terms in %s BY clause", zType);
+    return 1;
+  }
+#endif
+  pEList = pSelect->pEList;
+  assert( pEList!=0 );  /* sqlite3SelectNew() guarantees this */
+  for(i=0, pItem=pOrderBy->a; i<pOrderBy->nExpr; i++, pItem++){
+    if( pItem->iCol ){
+      if( pItem->iCol>pEList->nExpr ){
+        resolveOutOfRangeError(pParse, zType, i+1, pEList->nExpr);
+        return 1;
+      }
+      resolveAlias(pParse, pEList, pItem->iCol-1, pItem->pExpr, zType);
+    }
+  }
+  return 0;
+}
+
+/*
+** pOrderBy is an ORDER BY or GROUP BY clause in SELECT statement pSelect.
+** The Name context of the SELECT statement is pNC.  zType is either
+** "ORDER" or "GROUP" depending on which type of clause pOrderBy is.
+**
+** This routine resolves each term of the clause into an expression.
+** If the order-by term is an integer I between 1 and N (where N is the
+** number of columns in the result set of the SELECT) then the expression
+** in the resolution is a copy of the I-th result-set expression.  If
+** the order-by term is an identify that corresponds to the AS-name of
+** a result-set expression, then the term resolves to a copy of the
+** result-set expression.  Otherwise, the expression is resolved in
+** the usual way - using sqlite3ResolveExprNames().
+**
+** This routine returns the number of errors.  If errors occur, then
+** an appropriate error message might be left in pParse.  (OOM errors
+** excepted.)
+*/
+static int resolveOrderGroupBy(
+  NameContext *pNC,     /* The name context of the SELECT statement */
+  Select *pSelect,      /* The SELECT statement holding pOrderBy */
+  ExprList *pOrderBy,   /* An ORDER BY or GROUP BY clause to resolve */
+  const char *zType     /* Either "ORDER" or "GROUP", as appropriate */
+){
+  int i;                         /* Loop counter */
+  int iCol;                      /* Column number */
+  struct ExprList_item *pItem;   /* A term of the ORDER BY clause */
+  Parse *pParse;                 /* Parsing context */
+  int nResult;                   /* Number of terms in the result set */
+
+  if( pOrderBy==0 ) return 0;
+  nResult = pSelect->pEList->nExpr;
+  pParse = pNC->pParse;
+  for(i=0, pItem=pOrderBy->a; i<pOrderBy->nExpr; i++, pItem++){
+    Expr *pE = pItem->pExpr;
+    iCol = resolveAsName(pParse, pSelect->pEList, pE);
+    if( iCol>0 ){
+      /* If an AS-name match is found, mark this ORDER BY column as being
+      ** a copy of the iCol-th result-set column.  The subsequent call to
+      ** sqlite3ResolveOrderGroupBy() will convert the expression to a
+      ** copy of the iCol-th result-set expression. */
+      pItem->iCol = (u16)iCol;
+      continue;
+    }
+    if( sqlite3ExprIsInteger(pE, &iCol) ){
+      /* The ORDER BY term is an integer constant.  Again, set the column
+      ** number so that sqlite3ResolveOrderGroupBy() will convert the
+      ** order-by term to a copy of the result-set expression */
+      if( iCol<1 ){
+        resolveOutOfRangeError(pParse, zType, i+1, nResult);
+        return 1;
+      }
+      pItem->iCol = (u16)iCol;
+      continue;
+    }
+
+    /* Otherwise, treat the ORDER BY term as an ordinary expression */
+    pItem->iCol = 0;
+    if( sqlite3ResolveExprNames(pNC, pE) ){
+      return 1;
+    }
+  }
+  return sqlite3ResolveOrderGroupBy(pParse, pSelect, pOrderBy, zType);
+}
+
+/*
+** Resolve names in the SELECT statement p and all of its descendents.
+*/
+static int resolveSelectStep(Walker *pWalker, Select *p){
+  NameContext *pOuterNC;  /* Context that contains this SELECT */
+  NameContext sNC;        /* Name context of this SELECT */
+  int isCompound;         /* True if p is a compound select */
+  int nCompound;          /* Number of compound terms processed so far */
+  Parse *pParse;          /* Parsing context */
+  ExprList *pEList;       /* Result set expression list */
+  int i;                  /* Loop counter */
+  ExprList *pGroupBy;     /* The GROUP BY clause */
+  Select *pLeftmost;      /* Left-most of SELECT of a compound */
+  sqlite3 *db;            /* Database connection */
+  
+
+  assert( p!=0 );
+  if( p->selFlags & SF_Resolved ){
+    return WRC_Prune;
+  }
+  pOuterNC = pWalker->u.pNC;
+  pParse = pWalker->pParse;
+  db = pParse->db;
+
+  /* Normally sqlite3SelectExpand() will be called first and will have
+  ** already expanded this SELECT.  However, if this is a subquery within
+  ** an expression, sqlite3ResolveExprNames() will be called without a
+  ** prior call to sqlite3SelectExpand().  When that happens, let
+  ** sqlite3SelectPrep() do all of the processing for this SELECT.
+  ** sqlite3SelectPrep() will invoke both sqlite3SelectExpand() and
+  ** this routine in the correct order.
+  */
+  if( (p->selFlags & SF_Expanded)==0 ){
+    sqlite3SelectPrep(pParse, p, pOuterNC);
+    return (pParse->nErr || db->mallocFailed) ? WRC_Abort : WRC_Prune;
+  }
+
+  isCompound = p->pPrior!=0;
+  nCompound = 0;
+  pLeftmost = p;
+  while( p ){
+    assert( (p->selFlags & SF_Expanded)!=0 );
+    assert( (p->selFlags & SF_Resolved)==0 );
+    p->selFlags |= SF_Resolved;
+
+    /* Resolve the expressions in the LIMIT and OFFSET clauses. These
+    ** are not allowed to refer to any names, so pass an empty NameContext.
+    */
+    memset(&sNC, 0, sizeof(sNC));
+    sNC.pParse = pParse;
+    if( sqlite3ResolveExprNames(&sNC, p->pLimit) ||
+        sqlite3ResolveExprNames(&sNC, p->pOffset) ){
+      return WRC_Abort;
+    }
+  
+    /* Set up the local name-context to pass to sqlite3ResolveExprNames() to
+    ** resolve the result-set expression list.
+    */
+    sNC.allowAgg = 1;
+    sNC.pSrcList = p->pSrc;
+    sNC.pNext = pOuterNC;
+  
+    /* Resolve names in the result set. */
+    pEList = p->pEList;
+    assert( pEList!=0 );
+    for(i=0; i<pEList->nExpr; i++){
+      Expr *pX = pEList->a[i].pExpr;
+      if( sqlite3ResolveExprNames(&sNC, pX) ){
+        return WRC_Abort;
+      }
+    }
+  
+    /* Recursively resolve names in all subqueries
+    */
+    for(i=0; i<p->pSrc->nSrc; i++){
+      struct SrcList_item *pItem = &p->pSrc->a[i];
+      if( pItem->pSelect ){
+        NameContext *pNC;         /* Used to iterate name contexts */
+        int nRef = 0;             /* Refcount for pOuterNC and outer contexts */
+        const char *zSavedContext = pParse->zAuthContext;
+
+        /* Count the total number of references to pOuterNC and all of its
+        ** parent contexts. After resolving references to expressions in
+        ** pItem->pSelect, check if this value has changed. If so, then
+        ** SELECT statement pItem->pSelect must be correlated. Set the
+        ** pItem->isCorrelated flag if this is the case. */
+        for(pNC=pOuterNC; pNC; pNC=pNC->pNext) nRef += pNC->nRef;
+
+        if( pItem->zName ) pParse->zAuthContext = pItem->zName;
+        sqlite3ResolveSelectNames(pParse, pItem->pSelect, pOuterNC);
+        pParse->zAuthContext = zSavedContext;
+        if( pParse->nErr || db->mallocFailed ) return WRC_Abort;
+
+        for(pNC=pOuterNC; pNC; pNC=pNC->pNext) nRef -= pNC->nRef;
+        assert( pItem->isCorrelated==0 && nRef<=0 );
+        pItem->isCorrelated = (nRef!=0);
+      }
+    }
+  
+    /* If there are no aggregate functions in the result-set, and no GROUP BY 
+    ** expression, do not allow aggregates in any of the other expressions.
+    */
+    assert( (p->selFlags & SF_Aggregate)==0 );
+    pGroupBy = p->pGroupBy;
+    if( pGroupBy || sNC.hasAgg ){
+      p->selFlags |= SF_Aggregate;
+    }else{
+      sNC.allowAgg = 0;
+    }
+  
+    /* If a HAVING clause is present, then there must be a GROUP BY clause.
+    */
+    if( p->pHaving && !pGroupBy ){
+      sqlite3ErrorMsg(pParse, "a GROUP BY clause is required before HAVING");
+      return WRC_Abort;
+    }
+  
+    /* Add the expression list to the name-context before parsing the
+    ** other expressions in the SELECT statement. This is so that
+    ** expressions in the WHERE clause (etc.) can refer to expressions by
+    ** aliases in the result set.
+    **
+    ** Minor point: If this is the case, then the expression will be
+    ** re-evaluated for each reference to it.
+    */
+    sNC.pEList = p->pEList;
+    if( sqlite3ResolveExprNames(&sNC, p->pWhere) ||
+       sqlite3ResolveExprNames(&sNC, p->pHaving)
+    ){
+      return WRC_Abort;
+    }
+
+    /* The ORDER BY and GROUP BY clauses may not refer to terms in
+    ** outer queries 
+    */
+    sNC.pNext = 0;
+    sNC.allowAgg = 1;
+
+    /* Process the ORDER BY clause for singleton SELECT statements.
+    ** The ORDER BY clause for compounds SELECT statements is handled
+    ** below, after all of the result-sets for all of the elements of
+    ** the compound have been resolved.
+    */
+    if( !isCompound && resolveOrderGroupBy(&sNC, p, p->pOrderBy, "ORDER") ){
+      return WRC_Abort;
+    }
+    if( db->mallocFailed ){
+      return WRC_Abort;
+    }
+  
+    /* Resolve the GROUP BY clause.  At the same time, make sure 
+    ** the GROUP BY clause does not contain aggregate functions.
+    */
+    if( pGroupBy ){
+      struct ExprList_item *pItem;
+    
+      if( resolveOrderGroupBy(&sNC, p, pGroupBy, "GROUP") || db->mallocFailed ){
+        return WRC_Abort;
+      }
+      for(i=0, pItem=pGroupBy->a; i<pGroupBy->nExpr; i++, pItem++){
+        if( ExprHasProperty(pItem->pExpr, EP_Agg) ){
+          sqlite3ErrorMsg(pParse, "aggregate functions are not allowed in "
+              "the GROUP BY clause");
+          return WRC_Abort;
+        }
+      }
+    }
+
+    /* Advance to the next term of the compound
+    */
+    p = p->pPrior;
+    nCompound++;
+  }
+
+  /* Resolve the ORDER BY on a compound SELECT after all terms of
+  ** the compound have been resolved.
+  */
+  if( isCompound && resolveCompoundOrderBy(pParse, pLeftmost) ){
+    return WRC_Abort;
+  }
+
+  return WRC_Prune;
+}
+
+/*
+** This routine walks an expression tree and resolves references to
+** table columns and result-set columns.  At the same time, do error
+** checking on function usage and set a flag if any aggregate functions
+** are seen.
+**
+** To resolve table columns references we look for nodes (or subtrees) of the 
+** form X.Y.Z or Y.Z or just Z where
+**
+**      X:   The name of a database.  Ex:  "main" or "temp" or
+**           the symbolic name assigned to an ATTACH-ed database.
+**
+**      Y:   The name of a table in a FROM clause.  Or in a trigger
+**           one of the special names "old" or "new".
+**
+**      Z:   The name of a column in table Y.
+**
+** The node at the root of the subtree is modified as follows:
+**
+**    Expr.op        Changed to TK_COLUMN
+**    Expr.pTab      Points to the Table object for X.Y
+**    Expr.iColumn   The column index in X.Y.  -1 for the rowid.
+**    Expr.iTable    The VDBE cursor number for X.Y
+**
+**
+** To resolve result-set references, look for expression nodes of the
+** form Z (with no X and Y prefix) where the Z matches the right-hand
+** size of an AS clause in the result-set of a SELECT.  The Z expression
+** is replaced by a copy of the left-hand side of the result-set expression.
+** Table-name and function resolution occurs on the substituted expression
+** tree.  For example, in:
+**
+**      SELECT a+b AS x, c+d AS y FROM t1 ORDER BY x;
+**
+** The "x" term of the order by is replaced by "a+b" to render:
+**
+**      SELECT a+b AS x, c+d AS y FROM t1 ORDER BY a+b;
+**
+** Function calls are checked to make sure that the function is 
+** defined and that the correct number of arguments are specified.
+** If the function is an aggregate function, then the pNC->hasAgg is
+** set and the opcode is changed from TK_FUNCTION to TK_AGG_FUNCTION.
+** If an expression contains aggregate functions then the EP_Agg
+** property on the expression is set.
+**
+** An error message is left in pParse if anything is amiss.  The number
+** if errors is returned.
+*/
+int sqlite3ResolveExprNames( 
+  NameContext *pNC,       /* Namespace to resolve expressions in. */
+  Expr *pExpr             /* The expression to be analyzed. */
+){
+  int savedHasAgg;
+  Walker w;
+
+  if( pExpr==0 ) return 0;
+#if SQLITE_MAX_EXPR_DEPTH>0
+  {
+    Parse *pParse = pNC->pParse;
+    if( sqlite3ExprCheckHeight(pParse, pExpr->nHeight+pNC->pParse->nHeight) ){
+      return 1;
+    }
+    pParse->nHeight += pExpr->nHeight;
+  }
+#endif
+  savedHasAgg = pNC->hasAgg;
+  pNC->hasAgg = 0;
+  w.xExprCallback = resolveExprStep;
+  w.xSelectCallback = resolveSelectStep;
+  w.pParse = pNC->pParse;
+  w.u.pNC = pNC;
+  sqlite3WalkExpr(&w, pExpr);
+#if SQLITE_MAX_EXPR_DEPTH>0
+  pNC->pParse->nHeight -= pExpr->nHeight;
+#endif
+  if( pNC->nErr>0 || w.pParse->nErr>0 ){
+    ExprSetProperty(pExpr, EP_Error);
+  }
+  if( pNC->hasAgg ){
+    ExprSetProperty(pExpr, EP_Agg);
+  }else if( savedHasAgg ){
+    pNC->hasAgg = 1;
+  }
+  return ExprHasProperty(pExpr, EP_Error);
+}
+
+
+/*
+** Resolve all names in all expressions of a SELECT and in all
+** decendents of the SELECT, including compounds off of p->pPrior,
+** subqueries in expressions, and subqueries used as FROM clause
+** terms.
+**
+** See sqlite3ResolveExprNames() for a description of the kinds of
+** transformations that occur.
+**
+** All SELECT statements should have been expanded using
+** sqlite3SelectExpand() prior to invoking this routine.
+*/
+void sqlite3ResolveSelectNames(
+  Parse *pParse,         /* The parser context */
+  Select *p,             /* The SELECT statement being coded. */
+  NameContext *pOuterNC  /* Name context for parent SELECT statement */
+){
+  Walker w;
+
+  assert( p!=0 );
+  w.xExprCallback = resolveExprStep;
+  w.xSelectCallback = resolveSelectStep;
+  w.pParse = pParse;
+  w.u.pNC = pOuterNC;
+  sqlite3WalkSelect(&w, p);
+}
diff --git a/src/rowset.c b/src/rowset.c
new file mode 100644
index 0000000..d84bb93
--- /dev/null
+++ b/src/rowset.c
@@ -0,0 +1,422 @@
+/*
+** 2008 December 3
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This module implements an object we call a "RowSet".
+**
+** The RowSet object is a collection of rowids.  Rowids
+** are inserted into the RowSet in an arbitrary order.  Inserts
+** can be intermixed with tests to see if a given rowid has been
+** previously inserted into the RowSet.
+**
+** After all inserts are finished, it is possible to extract the
+** elements of the RowSet in sorted order.  Once this extraction
+** process has started, no new elements may be inserted.
+**
+** Hence, the primitive operations for a RowSet are:
+**
+**    CREATE
+**    INSERT
+**    TEST
+**    SMALLEST
+**    DESTROY
+**
+** The CREATE and DESTROY primitives are the constructor and destructor,
+** obviously.  The INSERT primitive adds a new element to the RowSet.
+** TEST checks to see if an element is already in the RowSet.  SMALLEST
+** extracts the least value from the RowSet.
+**
+** The INSERT primitive might allocate additional memory.  Memory is
+** allocated in chunks so most INSERTs do no allocation.  There is an 
+** upper bound on the size of allocated memory.  No memory is freed
+** until DESTROY.
+**
+** The TEST primitive includes a "batch" number.  The TEST primitive
+** will only see elements that were inserted before the last change
+** in the batch number.  In other words, if an INSERT occurs between
+** two TESTs where the TESTs have the same batch nubmer, then the
+** value added by the INSERT will not be visible to the second TEST.
+** The initial batch number is zero, so if the very first TEST contains
+** a non-zero batch number, it will see all prior INSERTs.
+**
+** No INSERTs may occurs after a SMALLEST.  An assertion will fail if
+** that is attempted.
+**
+** The cost of an INSERT is roughly constant.  (Sometime new memory
+** has to be allocated on an INSERT.)  The cost of a TEST with a new
+** batch number is O(NlogN) where N is the number of elements in the RowSet.
+** The cost of a TEST using the same batch number is O(logN).  The cost
+** of the first SMALLEST is O(NlogN).  Second and subsequent SMALLEST
+** primitives are constant time.  The cost of DESTROY is O(N).
+**
+** There is an added cost of O(N) when switching between TEST and
+** SMALLEST primitives.
+*/
+#include "sqliteInt.h"
+
+
+/*
+** Target size for allocation chunks.
+*/
+#define ROWSET_ALLOCATION_SIZE 1024
+
+/*
+** The number of rowset entries per allocation chunk.
+*/
+#define ROWSET_ENTRY_PER_CHUNK  \
+                       ((ROWSET_ALLOCATION_SIZE-8)/sizeof(struct RowSetEntry))
+
+/*
+** Each entry in a RowSet is an instance of the following object.
+*/
+struct RowSetEntry {            
+  i64 v;                        /* ROWID value for this entry */
+  struct RowSetEntry *pRight;   /* Right subtree (larger entries) or list */
+  struct RowSetEntry *pLeft;    /* Left subtree (smaller entries) */
+};
+
+/*
+** RowSetEntry objects are allocated in large chunks (instances of the
+** following structure) to reduce memory allocation overhead.  The
+** chunks are kept on a linked list so that they can be deallocated
+** when the RowSet is destroyed.
+*/
+struct RowSetChunk {
+  struct RowSetChunk *pNextChunk;        /* Next chunk on list of them all */
+  struct RowSetEntry aEntry[ROWSET_ENTRY_PER_CHUNK]; /* Allocated entries */
+};
+
+/*
+** A RowSet in an instance of the following structure.
+**
+** A typedef of this structure if found in sqliteInt.h.
+*/
+struct RowSet {
+  struct RowSetChunk *pChunk;    /* List of all chunk allocations */
+  sqlite3 *db;                   /* The database connection */
+  struct RowSetEntry *pEntry;    /* List of entries using pRight */
+  struct RowSetEntry *pLast;     /* Last entry on the pEntry list */
+  struct RowSetEntry *pFresh;    /* Source of new entry objects */
+  struct RowSetEntry *pTree;     /* Binary tree of entries */
+  u16 nFresh;                    /* Number of objects on pFresh */
+  u8 isSorted;                   /* True if pEntry is sorted */
+  u8 iBatch;                     /* Current insert batch */
+};
+
+/*
+** Turn bulk memory into a RowSet object.  N bytes of memory
+** are available at pSpace.  The db pointer is used as a memory context
+** for any subsequent allocations that need to occur.
+** Return a pointer to the new RowSet object.
+**
+** It must be the case that N is sufficient to make a Rowset.  If not
+** an assertion fault occurs.
+** 
+** If N is larger than the minimum, use the surplus as an initial
+** allocation of entries available to be filled.
+*/
+RowSet *sqlite3RowSetInit(sqlite3 *db, void *pSpace, unsigned int N){
+  RowSet *p;
+  assert( N >= ROUND8(sizeof(*p)) );
+  p = pSpace;
+  p->pChunk = 0;
+  p->db = db;
+  p->pEntry = 0;
+  p->pLast = 0;
+  p->pTree = 0;
+  p->pFresh = (struct RowSetEntry*)(ROUND8(sizeof(*p)) + (char*)p);
+  p->nFresh = (u16)((N - ROUND8(sizeof(*p)))/sizeof(struct RowSetEntry));
+  p->isSorted = 1;
+  p->iBatch = 0;
+  return p;
+}
+
+/*
+** Deallocate all chunks from a RowSet.  This frees all memory that
+** the RowSet has allocated over its lifetime.  This routine is
+** the destructor for the RowSet.
+*/
+void sqlite3RowSetClear(RowSet *p){
+  struct RowSetChunk *pChunk, *pNextChunk;
+  for(pChunk=p->pChunk; pChunk; pChunk = pNextChunk){
+    pNextChunk = pChunk->pNextChunk;
+    sqlite3DbFree(p->db, pChunk);
+  }
+  p->pChunk = 0;
+  p->nFresh = 0;
+  p->pEntry = 0;
+  p->pLast = 0;
+  p->pTree = 0;
+  p->isSorted = 1;
+}
+
+/*
+** Insert a new value into a RowSet.
+**
+** The mallocFailed flag of the database connection is set if a
+** memory allocation fails.
+*/
+void sqlite3RowSetInsert(RowSet *p, i64 rowid){
+  struct RowSetEntry *pEntry;  /* The new entry */
+  struct RowSetEntry *pLast;   /* The last prior entry */
+  assert( p!=0 );
+  if( p->nFresh==0 ){
+    struct RowSetChunk *pNew;
+    pNew = sqlite3DbMallocRaw(p->db, sizeof(*pNew));
+    if( pNew==0 ){
+      return;
+    }
+    pNew->pNextChunk = p->pChunk;
+    p->pChunk = pNew;
+    p->pFresh = pNew->aEntry;
+    p->nFresh = ROWSET_ENTRY_PER_CHUNK;
+  }
+  pEntry = p->pFresh++;
+  p->nFresh--;
+  pEntry->v = rowid;
+  pEntry->pRight = 0;
+  pLast = p->pLast;
+  if( pLast ){
+    if( p->isSorted && rowid<=pLast->v ){
+      p->isSorted = 0;
+    }
+    pLast->pRight = pEntry;
+  }else{
+    assert( p->pEntry==0 ); /* Fires if INSERT after SMALLEST */
+    p->pEntry = pEntry;
+  }
+  p->pLast = pEntry;
+}
+
+/*
+** Merge two lists of RowSetEntry objects.  Remove duplicates.
+**
+** The input lists are connected via pRight pointers and are 
+** assumed to each already be in sorted order.
+*/
+static struct RowSetEntry *rowSetMerge(
+  struct RowSetEntry *pA,    /* First sorted list to be merged */
+  struct RowSetEntry *pB     /* Second sorted list to be merged */
+){
+  struct RowSetEntry head;
+  struct RowSetEntry *pTail;
+
+  pTail = &head;
+  while( pA && pB ){
+    assert( pA->pRight==0 || pA->v<=pA->pRight->v );
+    assert( pB->pRight==0 || pB->v<=pB->pRight->v );
+    if( pA->v<pB->v ){
+      pTail->pRight = pA;
+      pA = pA->pRight;
+      pTail = pTail->pRight;
+    }else if( pB->v<pA->v ){
+      pTail->pRight = pB;
+      pB = pB->pRight;
+      pTail = pTail->pRight;
+    }else{
+      pA = pA->pRight;
+    }
+  }
+  if( pA ){
+    assert( pA->pRight==0 || pA->v<=pA->pRight->v );
+    pTail->pRight = pA;
+  }else{
+    assert( pB==0 || pB->pRight==0 || pB->v<=pB->pRight->v );
+    pTail->pRight = pB;
+  }
+  return head.pRight;
+}
+
+/*
+** Sort all elements on the pEntry list of the RowSet into ascending order.
+*/ 
+static void rowSetSort(RowSet *p){
+  unsigned int i;
+  struct RowSetEntry *pEntry;
+  struct RowSetEntry *aBucket[40];
+
+  assert( p->isSorted==0 );
+  memset(aBucket, 0, sizeof(aBucket));
+  while( p->pEntry ){
+    pEntry = p->pEntry;
+    p->pEntry = pEntry->pRight;
+    pEntry->pRight = 0;
+    for(i=0; aBucket[i]; i++){
+      pEntry = rowSetMerge(aBucket[i], pEntry);
+      aBucket[i] = 0;
+    }
+    aBucket[i] = pEntry;
+  }
+  pEntry = 0;
+  for(i=0; i<sizeof(aBucket)/sizeof(aBucket[0]); i++){
+    pEntry = rowSetMerge(pEntry, aBucket[i]);
+  }
+  p->pEntry = pEntry;
+  p->pLast = 0;
+  p->isSorted = 1;
+}
+
+
+/*
+** The input, pIn, is a binary tree (or subtree) of RowSetEntry objects.
+** Convert this tree into a linked list connected by the pRight pointers
+** and return pointers to the first and last elements of the new list.
+*/
+static void rowSetTreeToList(
+  struct RowSetEntry *pIn,         /* Root of the input tree */
+  struct RowSetEntry **ppFirst,    /* Write head of the output list here */
+  struct RowSetEntry **ppLast      /* Write tail of the output list here */
+){
+  assert( pIn!=0 );
+  if( pIn->pLeft ){
+    struct RowSetEntry *p;
+    rowSetTreeToList(pIn->pLeft, ppFirst, &p);
+    p->pRight = pIn;
+  }else{
+    *ppFirst = pIn;
+  }
+  if( pIn->pRight ){
+    rowSetTreeToList(pIn->pRight, &pIn->pRight, ppLast);
+  }else{
+    *ppLast = pIn;
+  }
+  assert( (*ppLast)->pRight==0 );
+}
+
+
+/*
+** Convert a sorted list of elements (connected by pRight) into a binary
+** tree with depth of iDepth.  A depth of 1 means the tree contains a single
+** node taken from the head of *ppList.  A depth of 2 means a tree with
+** three nodes.  And so forth.
+**
+** Use as many entries from the input list as required and update the
+** *ppList to point to the unused elements of the list.  If the input
+** list contains too few elements, then construct an incomplete tree
+** and leave *ppList set to NULL.
+**
+** Return a pointer to the root of the constructed binary tree.
+*/
+static struct RowSetEntry *rowSetNDeepTree(
+  struct RowSetEntry **ppList,
+  int iDepth
+){
+  struct RowSetEntry *p;         /* Root of the new tree */
+  struct RowSetEntry *pLeft;     /* Left subtree */
+  if( *ppList==0 ){
+    return 0;
+  }
+  if( iDepth==1 ){
+    p = *ppList;
+    *ppList = p->pRight;
+    p->pLeft = p->pRight = 0;
+    return p;
+  }
+  pLeft = rowSetNDeepTree(ppList, iDepth-1);
+  p = *ppList;
+  if( p==0 ){
+    return pLeft;
+  }
+  p->pLeft = pLeft;
+  *ppList = p->pRight;
+  p->pRight = rowSetNDeepTree(ppList, iDepth-1);
+  return p;
+}
+
+/*
+** Convert a sorted list of elements into a binary tree. Make the tree
+** as deep as it needs to be in order to contain the entire list.
+*/
+static struct RowSetEntry *rowSetListToTree(struct RowSetEntry *pList){
+  int iDepth;           /* Depth of the tree so far */
+  struct RowSetEntry *p;       /* Current tree root */
+  struct RowSetEntry *pLeft;   /* Left subtree */
+
+  assert( pList!=0 );
+  p = pList;
+  pList = p->pRight;
+  p->pLeft = p->pRight = 0;
+  for(iDepth=1; pList; iDepth++){
+    pLeft = p;
+    p = pList;
+    pList = p->pRight;
+    p->pLeft = pLeft;
+    p->pRight = rowSetNDeepTree(&pList, iDepth);
+  }
+  return p;
+}
+
+/*
+** Convert the list in p->pEntry into a sorted list if it is not
+** sorted already.  If there is a binary tree on p->pTree, then
+** convert it into a list too and merge it into the p->pEntry list.
+*/
+static void rowSetToList(RowSet *p){
+  if( !p->isSorted ){
+    rowSetSort(p);
+  }
+  if( p->pTree ){
+    struct RowSetEntry *pHead, *pTail;
+    rowSetTreeToList(p->pTree, &pHead, &pTail);
+    p->pTree = 0;
+    p->pEntry = rowSetMerge(p->pEntry, pHead);
+  }
+}
+
+/*
+** Extract the smallest element from the RowSet.
+** Write the element into *pRowid.  Return 1 on success.  Return
+** 0 if the RowSet is already empty.
+**
+** After this routine has been called, the sqlite3RowSetInsert()
+** routine may not be called again.  
+*/
+int sqlite3RowSetNext(RowSet *p, i64 *pRowid){
+  rowSetToList(p);
+  if( p->pEntry ){
+    *pRowid = p->pEntry->v;
+    p->pEntry = p->pEntry->pRight;
+    if( p->pEntry==0 ){
+      sqlite3RowSetClear(p);
+    }
+    return 1;
+  }else{
+    return 0;
+  }
+}
+
+/*
+** Check to see if element iRowid was inserted into the the rowset as
+** part of any insert batch prior to iBatch.  Return 1 or 0.
+*/
+int sqlite3RowSetTest(RowSet *pRowSet, u8 iBatch, sqlite3_int64 iRowid){
+  struct RowSetEntry *p;
+  if( iBatch!=pRowSet->iBatch ){
+    if( pRowSet->pEntry ){
+      rowSetToList(pRowSet);
+      pRowSet->pTree = rowSetListToTree(pRowSet->pEntry);
+      pRowSet->pEntry = 0;
+      pRowSet->pLast = 0;
+    }
+    pRowSet->iBatch = iBatch;
+  }
+  p = pRowSet->pTree;
+  while( p ){
+    if( p->v<iRowid ){
+      p = p->pRight;
+    }else if( p->v>iRowid ){
+      p = p->pLeft;
+    }else{
+      return 1;
+    }
+  }
+  return 0;
+}
diff --git a/src/select.c b/src/select.c
new file mode 100644
index 0000000..571a778
--- /dev/null
+++ b/src/select.c
@@ -0,0 +1,4591 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains C code routines that are called by the parser
+** to handle SELECT statements in SQLite.
+*/
+#include "sqliteInt.h"
+
+
+/*
+** Delete all the content of a Select structure but do not deallocate
+** the select structure itself.
+*/
+static void clearSelect(sqlite3 *db, Select *p){
+  sqlite3ExprListDelete(db, p->pEList);
+  sqlite3SrcListDelete(db, p->pSrc);
+  sqlite3ExprDelete(db, p->pWhere);
+  sqlite3ExprListDelete(db, p->pGroupBy);
+  sqlite3ExprDelete(db, p->pHaving);
+  sqlite3ExprListDelete(db, p->pOrderBy);
+  sqlite3SelectDelete(db, p->pPrior);
+  sqlite3ExprDelete(db, p->pLimit);
+  sqlite3ExprDelete(db, p->pOffset);
+}
+
+/*
+** Initialize a SelectDest structure.
+*/
+void sqlite3SelectDestInit(SelectDest *pDest, int eDest, int iParm){
+  pDest->eDest = (u8)eDest;
+  pDest->iParm = iParm;
+  pDest->affinity = 0;
+  pDest->iMem = 0;
+  pDest->nMem = 0;
+}
+
+
+/*
+** Allocate a new Select structure and return a pointer to that
+** structure.
+*/
+Select *sqlite3SelectNew(
+  Parse *pParse,        /* Parsing context */
+  ExprList *pEList,     /* which columns to include in the result */
+  SrcList *pSrc,        /* the FROM clause -- which tables to scan */
+  Expr *pWhere,         /* the WHERE clause */
+  ExprList *pGroupBy,   /* the GROUP BY clause */
+  Expr *pHaving,        /* the HAVING clause */
+  ExprList *pOrderBy,   /* the ORDER BY clause */
+  int isDistinct,       /* true if the DISTINCT keyword is present */
+  Expr *pLimit,         /* LIMIT value.  NULL means not used */
+  Expr *pOffset         /* OFFSET value.  NULL means no offset */
+){
+  Select *pNew;
+  Select standin;
+  sqlite3 *db = pParse->db;
+  pNew = sqlite3DbMallocZero(db, sizeof(*pNew) );
+  assert( db->mallocFailed || !pOffset || pLimit ); /* OFFSET implies LIMIT */
+  if( pNew==0 ){
+    assert( db->mallocFailed );
+    pNew = &standin;
+    memset(pNew, 0, sizeof(*pNew));
+  }
+  if( pEList==0 ){
+    pEList = sqlite3ExprListAppend(pParse, 0, sqlite3Expr(db,TK_ALL,0));
+  }
+  pNew->pEList = pEList;
+  pNew->pSrc = pSrc;
+  pNew->pWhere = pWhere;
+  pNew->pGroupBy = pGroupBy;
+  pNew->pHaving = pHaving;
+  pNew->pOrderBy = pOrderBy;
+  pNew->selFlags = isDistinct ? SF_Distinct : 0;
+  pNew->op = TK_SELECT;
+  pNew->pLimit = pLimit;
+  pNew->pOffset = pOffset;
+  assert( pOffset==0 || pLimit!=0 );
+  pNew->addrOpenEphm[0] = -1;
+  pNew->addrOpenEphm[1] = -1;
+  pNew->addrOpenEphm[2] = -1;
+  if( db->mallocFailed ) {
+    clearSelect(db, pNew);
+    if( pNew!=&standin ) sqlite3DbFree(db, pNew);
+    pNew = 0;
+  }else{
+    assert( pNew->pSrc!=0 || pParse->nErr>0 );
+  }
+  assert( pNew!=&standin );
+  return pNew;
+}
+
+/*
+** Delete the given Select structure and all of its substructures.
+*/
+void sqlite3SelectDelete(sqlite3 *db, Select *p){
+  if( p ){
+    clearSelect(db, p);
+    sqlite3DbFree(db, p);
+  }
+}
+
+/*
+** Given 1 to 3 identifiers preceeding the JOIN keyword, determine the
+** type of join.  Return an integer constant that expresses that type
+** in terms of the following bit values:
+**
+**     JT_INNER
+**     JT_CROSS
+**     JT_OUTER
+**     JT_NATURAL
+**     JT_LEFT
+**     JT_RIGHT
+**
+** A full outer join is the combination of JT_LEFT and JT_RIGHT.
+**
+** If an illegal or unsupported join type is seen, then still return
+** a join type, but put an error in the pParse structure.
+*/
+int sqlite3JoinType(Parse *pParse, Token *pA, Token *pB, Token *pC){
+  int jointype = 0;
+  Token *apAll[3];
+  Token *p;
+                             /*   0123456789 123456789 123456789 123 */
+  static const char zKeyText[] = "naturaleftouterightfullinnercross";
+  static const struct {
+    u8 i;        /* Beginning of keyword text in zKeyText[] */
+    u8 nChar;    /* Length of the keyword in characters */
+    u8 code;     /* Join type mask */
+  } aKeyword[] = {
+    /* natural */ { 0,  7, JT_NATURAL                },
+    /* left    */ { 6,  4, JT_LEFT|JT_OUTER          },
+    /* outer   */ { 10, 5, JT_OUTER                  },
+    /* right   */ { 14, 5, JT_RIGHT|JT_OUTER         },
+    /* full    */ { 19, 4, JT_LEFT|JT_RIGHT|JT_OUTER },
+    /* inner   */ { 23, 5, JT_INNER                  },
+    /* cross   */ { 28, 5, JT_INNER|JT_CROSS         },
+  };
+  int i, j;
+  apAll[0] = pA;
+  apAll[1] = pB;
+  apAll[2] = pC;
+  for(i=0; i<3 && apAll[i]; i++){
+    p = apAll[i];
+    for(j=0; j<ArraySize(aKeyword); j++){
+      if( p->n==aKeyword[j].nChar 
+          && sqlite3StrNICmp((char*)p->z, &zKeyText[aKeyword[j].i], p->n)==0 ){
+        jointype |= aKeyword[j].code;
+        break;
+      }
+    }
+    testcase( j==0 || j==1 || j==2 || j==3 || j==4 || j==5 || j==6 );
+    if( j>=ArraySize(aKeyword) ){
+      jointype |= JT_ERROR;
+      break;
+    }
+  }
+  if(
+     (jointype & (JT_INNER|JT_OUTER))==(JT_INNER|JT_OUTER) ||
+     (jointype & JT_ERROR)!=0
+  ){
+    const char *zSp = " ";
+    assert( pB!=0 );
+    if( pC==0 ){ zSp++; }
+    sqlite3ErrorMsg(pParse, "unknown or unsupported join type: "
+       "%T %T%s%T", pA, pB, zSp, pC);
+    jointype = JT_INNER;
+  }else if( (jointype & JT_OUTER)!=0 
+         && (jointype & (JT_LEFT|JT_RIGHT))!=JT_LEFT ){
+    sqlite3ErrorMsg(pParse, 
+      "RIGHT and FULL OUTER JOINs are not currently supported");
+    jointype = JT_INNER;
+  }
+  return jointype;
+}
+
+/*
+** Return the index of a column in a table.  Return -1 if the column
+** is not contained in the table.
+*/
+static int columnIndex(Table *pTab, const char *zCol){
+  int i;
+  for(i=0; i<pTab->nCol; i++){
+    if( sqlite3StrICmp(pTab->aCol[i].zName, zCol)==0 ) return i;
+  }
+  return -1;
+}
+
+/*
+** Search the first N tables in pSrc, from left to right, looking for a
+** table that has a column named zCol.  
+**
+** When found, set *piTab and *piCol to the table index and column index
+** of the matching column and return TRUE.
+**
+** If not found, return FALSE.
+*/
+static int tableAndColumnIndex(
+  SrcList *pSrc,       /* Array of tables to search */
+  int N,               /* Number of tables in pSrc->a[] to search */
+  const char *zCol,    /* Name of the column we are looking for */
+  int *piTab,          /* Write index of pSrc->a[] here */
+  int *piCol           /* Write index of pSrc->a[*piTab].pTab->aCol[] here */
+){
+  int i;               /* For looping over tables in pSrc */
+  int iCol;            /* Index of column matching zCol */
+
+  assert( (piTab==0)==(piCol==0) );  /* Both or neither are NULL */
+  for(i=0; i<N; i++){
+    iCol = columnIndex(pSrc->a[i].pTab, zCol);
+    if( iCol>=0 ){
+      if( piTab ){
+        *piTab = i;
+        *piCol = iCol;
+      }
+      return 1;
+    }
+  }
+  return 0;
+}
+
+/*
+** This function is used to add terms implied by JOIN syntax to the
+** WHERE clause expression of a SELECT statement. The new term, which
+** is ANDed with the existing WHERE clause, is of the form:
+**
+**    (tab1.col1 = tab2.col2)
+**
+** where tab1 is the iSrc'th table in SrcList pSrc and tab2 is the 
+** (iSrc+1)'th. Column col1 is column iColLeft of tab1, and col2 is
+** column iColRight of tab2.
+*/
+static void addWhereTerm(
+  Parse *pParse,                  /* Parsing context */
+  SrcList *pSrc,                  /* List of tables in FROM clause */
+  int iLeft,                      /* Index of first table to join in pSrc */
+  int iColLeft,                   /* Index of column in first table */
+  int iRight,                     /* Index of second table in pSrc */
+  int iColRight,                  /* Index of column in second table */
+  int isOuterJoin,                /* True if this is an OUTER join */
+  Expr **ppWhere                  /* IN/OUT: The WHERE clause to add to */
+){
+  sqlite3 *db = pParse->db;
+  Expr *pE1;
+  Expr *pE2;
+  Expr *pEq;
+
+  assert( iLeft<iRight );
+  assert( pSrc->nSrc>iRight );
+  assert( pSrc->a[iLeft].pTab );
+  assert( pSrc->a[iRight].pTab );
+
+  pE1 = sqlite3CreateColumnExpr(db, pSrc, iLeft, iColLeft);
+  pE2 = sqlite3CreateColumnExpr(db, pSrc, iRight, iColRight);
+
+  pEq = sqlite3PExpr(pParse, TK_EQ, pE1, pE2, 0);
+  if( pEq && isOuterJoin ){
+    ExprSetProperty(pEq, EP_FromJoin);
+    assert( !ExprHasAnyProperty(pEq, EP_TokenOnly|EP_Reduced) );
+    ExprSetIrreducible(pEq);
+    pEq->iRightJoinTable = (i16)pE2->iTable;
+  }
+  *ppWhere = sqlite3ExprAnd(db, *ppWhere, pEq);
+}
+
+/*
+** Set the EP_FromJoin property on all terms of the given expression.
+** And set the Expr.iRightJoinTable to iTable for every term in the
+** expression.
+**
+** The EP_FromJoin property is used on terms of an expression to tell
+** the LEFT OUTER JOIN processing logic that this term is part of the
+** join restriction specified in the ON or USING clause and not a part
+** of the more general WHERE clause.  These terms are moved over to the
+** WHERE clause during join processing but we need to remember that they
+** originated in the ON or USING clause.
+**
+** The Expr.iRightJoinTable tells the WHERE clause processing that the
+** expression depends on table iRightJoinTable even if that table is not
+** explicitly mentioned in the expression.  That information is needed
+** for cases like this:
+**
+**    SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.b AND t1.x=5
+**
+** The where clause needs to defer the handling of the t1.x=5
+** term until after the t2 loop of the join.  In that way, a
+** NULL t2 row will be inserted whenever t1.x!=5.  If we do not
+** defer the handling of t1.x=5, it will be processed immediately
+** after the t1 loop and rows with t1.x!=5 will never appear in
+** the output, which is incorrect.
+*/
+static void setJoinExpr(Expr *p, int iTable){
+  while( p ){
+    ExprSetProperty(p, EP_FromJoin);
+    assert( !ExprHasAnyProperty(p, EP_TokenOnly|EP_Reduced) );
+    ExprSetIrreducible(p);
+    p->iRightJoinTable = (i16)iTable;
+    setJoinExpr(p->pLeft, iTable);
+    p = p->pRight;
+  } 
+}
+
+/*
+** This routine processes the join information for a SELECT statement.
+** ON and USING clauses are converted into extra terms of the WHERE clause.
+** NATURAL joins also create extra WHERE clause terms.
+**
+** The terms of a FROM clause are contained in the Select.pSrc structure.
+** The left most table is the first entry in Select.pSrc.  The right-most
+** table is the last entry.  The join operator is held in the entry to
+** the left.  Thus entry 0 contains the join operator for the join between
+** entries 0 and 1.  Any ON or USING clauses associated with the join are
+** also attached to the left entry.
+**
+** This routine returns the number of errors encountered.
+*/
+static int sqliteProcessJoin(Parse *pParse, Select *p){
+  SrcList *pSrc;                  /* All tables in the FROM clause */
+  int i, j;                       /* Loop counters */
+  struct SrcList_item *pLeft;     /* Left table being joined */
+  struct SrcList_item *pRight;    /* Right table being joined */
+
+  pSrc = p->pSrc;
+  pLeft = &pSrc->a[0];
+  pRight = &pLeft[1];
+  for(i=0; i<pSrc->nSrc-1; i++, pRight++, pLeft++){
+    Table *pLeftTab = pLeft->pTab;
+    Table *pRightTab = pRight->pTab;
+    int isOuter;
+
+    if( NEVER(pLeftTab==0 || pRightTab==0) ) continue;
+    isOuter = (pRight->jointype & JT_OUTER)!=0;
+
+    /* When the NATURAL keyword is present, add WHERE clause terms for
+    ** every column that the two tables have in common.
+    */
+    if( pRight->jointype & JT_NATURAL ){
+      if( pRight->pOn || pRight->pUsing ){
+        sqlite3ErrorMsg(pParse, "a NATURAL join may not have "
+           "an ON or USING clause", 0);
+        return 1;
+      }
+      for(j=0; j<pRightTab->nCol; j++){
+        char *zName;   /* Name of column in the right table */
+        int iLeft;     /* Matching left table */
+        int iLeftCol;  /* Matching column in the left table */
+
+        zName = pRightTab->aCol[j].zName;
+        if( tableAndColumnIndex(pSrc, i+1, zName, &iLeft, &iLeftCol) ){
+          addWhereTerm(pParse, pSrc, iLeft, iLeftCol, i+1, j,
+                       isOuter, &p->pWhere);
+        }
+      }
+    }
+
+    /* Disallow both ON and USING clauses in the same join
+    */
+    if( pRight->pOn && pRight->pUsing ){
+      sqlite3ErrorMsg(pParse, "cannot have both ON and USING "
+        "clauses in the same join");
+      return 1;
+    }
+
+    /* Add the ON clause to the end of the WHERE clause, connected by
+    ** an AND operator.
+    */
+    if( pRight->pOn ){
+      if( isOuter ) setJoinExpr(pRight->pOn, pRight->iCursor);
+      p->pWhere = sqlite3ExprAnd(pParse->db, p->pWhere, pRight->pOn);
+      pRight->pOn = 0;
+    }
+
+    /* Create extra terms on the WHERE clause for each column named
+    ** in the USING clause.  Example: If the two tables to be joined are 
+    ** A and B and the USING clause names X, Y, and Z, then add this
+    ** to the WHERE clause:    A.X=B.X AND A.Y=B.Y AND A.Z=B.Z
+    ** Report an error if any column mentioned in the USING clause is
+    ** not contained in both tables to be joined.
+    */
+    if( pRight->pUsing ){
+      IdList *pList = pRight->pUsing;
+      for(j=0; j<pList->nId; j++){
+        char *zName;     /* Name of the term in the USING clause */
+        int iLeft;       /* Table on the left with matching column name */
+        int iLeftCol;    /* Column number of matching column on the left */
+        int iRightCol;   /* Column number of matching column on the right */
+
+        zName = pList->a[j].zName;
+        iRightCol = columnIndex(pRightTab, zName);
+        if( iRightCol<0
+         || !tableAndColumnIndex(pSrc, i+1, zName, &iLeft, &iLeftCol)
+        ){
+          sqlite3ErrorMsg(pParse, "cannot join using column %s - column "
+            "not present in both tables", zName);
+          return 1;
+        }
+        addWhereTerm(pParse, pSrc, iLeft, iLeftCol, i+1, iRightCol,
+                     isOuter, &p->pWhere);
+      }
+    }
+  }
+  return 0;
+}
+
+/*
+** Insert code into "v" that will push the record on the top of the
+** stack into the sorter.
+*/
+static void pushOntoSorter(
+  Parse *pParse,         /* Parser context */
+  ExprList *pOrderBy,    /* The ORDER BY clause */
+  Select *pSelect,       /* The whole SELECT statement */
+  int regData            /* Register holding data to be sorted */
+){
+  Vdbe *v = pParse->pVdbe;
+  int nExpr = pOrderBy->nExpr;
+  int regBase = sqlite3GetTempRange(pParse, nExpr+2);
+  int regRecord = sqlite3GetTempReg(pParse);
+  int op;
+  sqlite3ExprCacheClear(pParse);
+  sqlite3ExprCodeExprList(pParse, pOrderBy, regBase, 0);
+  sqlite3VdbeAddOp2(v, OP_Sequence, pOrderBy->iECursor, regBase+nExpr);
+  sqlite3ExprCodeMove(pParse, regData, regBase+nExpr+1, 1);
+  sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase, nExpr + 2, regRecord);
+  if( pSelect->selFlags & SF_UseSorter ){
+    op = OP_SorterInsert;
+  }else{
+    op = OP_IdxInsert;
+  }
+  sqlite3VdbeAddOp2(v, op, pOrderBy->iECursor, regRecord);
+  sqlite3ReleaseTempReg(pParse, regRecord);
+  sqlite3ReleaseTempRange(pParse, regBase, nExpr+2);
+  if( pSelect->iLimit ){
+    int addr1, addr2;
+    int iLimit;
+    if( pSelect->iOffset ){
+      iLimit = pSelect->iOffset+1;
+    }else{
+      iLimit = pSelect->iLimit;
+    }
+    addr1 = sqlite3VdbeAddOp1(v, OP_IfZero, iLimit);
+    sqlite3VdbeAddOp2(v, OP_AddImm, iLimit, -1);
+    addr2 = sqlite3VdbeAddOp0(v, OP_Goto);
+    sqlite3VdbeJumpHere(v, addr1);
+    sqlite3VdbeAddOp1(v, OP_Last, pOrderBy->iECursor);
+    sqlite3VdbeAddOp1(v, OP_Delete, pOrderBy->iECursor);
+    sqlite3VdbeJumpHere(v, addr2);
+  }
+}
+
+/*
+** Add code to implement the OFFSET
+*/
+static void codeOffset(
+  Vdbe *v,          /* Generate code into this VM */
+  Select *p,        /* The SELECT statement being coded */
+  int iContinue     /* Jump here to skip the current record */
+){
+  if( p->iOffset && iContinue!=0 ){
+    int addr;
+    sqlite3VdbeAddOp2(v, OP_AddImm, p->iOffset, -1);
+    addr = sqlite3VdbeAddOp1(v, OP_IfNeg, p->iOffset);
+    sqlite3VdbeAddOp2(v, OP_Goto, 0, iContinue);
+    VdbeComment((v, "skip OFFSET records"));
+    sqlite3VdbeJumpHere(v, addr);
+  }
+}
+
+/*
+** Add code that will check to make sure the N registers starting at iMem
+** form a distinct entry.  iTab is a sorting index that holds previously
+** seen combinations of the N values.  A new entry is made in iTab
+** if the current N values are new.
+**
+** A jump to addrRepeat is made and the N+1 values are popped from the
+** stack if the top N elements are not distinct.
+*/
+static void codeDistinct(
+  Parse *pParse,     /* Parsing and code generating context */
+  int iTab,          /* A sorting index used to test for distinctness */
+  int addrRepeat,    /* Jump to here if not distinct */
+  int N,             /* Number of elements */
+  int iMem           /* First element */
+){
+  Vdbe *v;
+  int r1;
+
+  v = pParse->pVdbe;
+  r1 = sqlite3GetTempReg(pParse);
+  sqlite3VdbeAddOp4Int(v, OP_Found, iTab, addrRepeat, iMem, N);
+  sqlite3VdbeAddOp3(v, OP_MakeRecord, iMem, N, r1);
+  sqlite3VdbeAddOp2(v, OP_IdxInsert, iTab, r1);
+  sqlite3ReleaseTempReg(pParse, r1);
+}
+
+#ifndef SQLITE_OMIT_SUBQUERY
+/*
+** Generate an error message when a SELECT is used within a subexpression
+** (example:  "a IN (SELECT * FROM table)") but it has more than 1 result
+** column.  We do this in a subroutine because the error used to occur
+** in multiple places.  (The error only occurs in one place now, but we
+** retain the subroutine to minimize code disruption.)
+*/
+static int checkForMultiColumnSelectError(
+  Parse *pParse,       /* Parse context. */
+  SelectDest *pDest,   /* Destination of SELECT results */
+  int nExpr            /* Number of result columns returned by SELECT */
+){
+  int eDest = pDest->eDest;
+  if( nExpr>1 && (eDest==SRT_Mem || eDest==SRT_Set) ){
+    sqlite3ErrorMsg(pParse, "only a single result allowed for "
+       "a SELECT that is part of an expression");
+    return 1;
+  }else{
+    return 0;
+  }
+}
+#endif
+
+/*
+** This routine generates the code for the inside of the inner loop
+** of a SELECT.
+**
+** If srcTab and nColumn are both zero, then the pEList expressions
+** are evaluated in order to get the data for this row.  If nColumn>0
+** then data is pulled from srcTab and pEList is used only to get the
+** datatypes for each column.
+*/
+static void selectInnerLoop(
+  Parse *pParse,          /* The parser context */
+  Select *p,              /* The complete select statement being coded */
+  ExprList *pEList,       /* List of values being extracted */
+  int srcTab,             /* Pull data from this table */
+  int nColumn,            /* Number of columns in the source table */
+  ExprList *pOrderBy,     /* If not NULL, sort results using this key */
+  int distinct,           /* If >=0, make sure results are distinct */
+  SelectDest *pDest,      /* How to dispose of the results */
+  int iContinue,          /* Jump here to continue with next row */
+  int iBreak              /* Jump here to break out of the inner loop */
+){
+  Vdbe *v = pParse->pVdbe;
+  int i;
+  int hasDistinct;        /* True if the DISTINCT keyword is present */
+  int regResult;              /* Start of memory holding result set */
+  int eDest = pDest->eDest;   /* How to dispose of results */
+  int iParm = pDest->iParm;   /* First argument to disposal method */
+  int nResultCol;             /* Number of result columns */
+
+  assert( v );
+  if( NEVER(v==0) ) return;
+  assert( pEList!=0 );
+  hasDistinct = distinct>=0;
+  if( pOrderBy==0 && !hasDistinct ){
+    codeOffset(v, p, iContinue);
+  }
+
+  /* Pull the requested columns.
+  */
+  if( nColumn>0 ){
+    nResultCol = nColumn;
+  }else{
+    nResultCol = pEList->nExpr;
+  }
+  if( pDest->iMem==0 ){
+    pDest->iMem = pParse->nMem+1;
+    pDest->nMem = nResultCol;
+    pParse->nMem += nResultCol;
+  }else{ 
+    assert( pDest->nMem==nResultCol );
+  }
+  regResult = pDest->iMem;
+  if( nColumn>0 ){
+    for(i=0; i<nColumn; i++){
+      sqlite3VdbeAddOp3(v, OP_Column, srcTab, i, regResult+i);
+    }
+  }else if( eDest!=SRT_Exists ){
+    /* If the destination is an EXISTS(...) expression, the actual
+    ** values returned by the SELECT are not required.
+    */
+    sqlite3ExprCacheClear(pParse);
+    sqlite3ExprCodeExprList(pParse, pEList, regResult, eDest==SRT_Output);
+  }
+  nColumn = nResultCol;
+
+  /* If the DISTINCT keyword was present on the SELECT statement
+  ** and this row has been seen before, then do not make this row
+  ** part of the result.
+  */
+  if( hasDistinct ){
+    assert( pEList!=0 );
+    assert( pEList->nExpr==nColumn );
+    codeDistinct(pParse, distinct, iContinue, nColumn, regResult);
+    if( pOrderBy==0 ){
+      codeOffset(v, p, iContinue);
+    }
+  }
+
+  switch( eDest ){
+    /* In this mode, write each query result to the key of the temporary
+    ** table iParm.
+    */
+#ifndef SQLITE_OMIT_COMPOUND_SELECT
+    case SRT_Union: {
+      int r1;
+      r1 = sqlite3GetTempReg(pParse);
+      sqlite3VdbeAddOp3(v, OP_MakeRecord, regResult, nColumn, r1);
+      sqlite3VdbeAddOp2(v, OP_IdxInsert, iParm, r1);
+      sqlite3ReleaseTempReg(pParse, r1);
+      break;
+    }
+
+    /* Construct a record from the query result, but instead of
+    ** saving that record, use it as a key to delete elements from
+    ** the temporary table iParm.
+    */
+    case SRT_Except: {
+      sqlite3VdbeAddOp3(v, OP_IdxDelete, iParm, regResult, nColumn);
+      break;
+    }
+#endif
+
+    /* Store the result as data using a unique key.
+    */
+    case SRT_Table:
+    case SRT_EphemTab: {
+      int r1 = sqlite3GetTempReg(pParse);
+      testcase( eDest==SRT_Table );
+      testcase( eDest==SRT_EphemTab );
+      sqlite3VdbeAddOp3(v, OP_MakeRecord, regResult, nColumn, r1);
+      if( pOrderBy ){
+        pushOntoSorter(pParse, pOrderBy, p, r1);
+      }else{
+        int r2 = sqlite3GetTempReg(pParse);
+        sqlite3VdbeAddOp2(v, OP_NewRowid, iParm, r2);
+        sqlite3VdbeAddOp3(v, OP_Insert, iParm, r1, r2);
+        sqlite3VdbeChangeP5(v, OPFLAG_APPEND);
+        sqlite3ReleaseTempReg(pParse, r2);
+      }
+      sqlite3ReleaseTempReg(pParse, r1);
+      break;
+    }
+
+#ifndef SQLITE_OMIT_SUBQUERY
+    /* If we are creating a set for an "expr IN (SELECT ...)" construct,
+    ** then there should be a single item on the stack.  Write this
+    ** item into the set table with bogus data.
+    */
+    case SRT_Set: {
+      assert( nColumn==1 );
+      p->affinity = sqlite3CompareAffinity(pEList->a[0].pExpr, pDest->affinity);
+      if( pOrderBy ){
+        /* At first glance you would think we could optimize out the
+        ** ORDER BY in this case since the order of entries in the set
+        ** does not matter.  But there might be a LIMIT clause, in which
+        ** case the order does matter */
+        pushOntoSorter(pParse, pOrderBy, p, regResult);
+      }else{
+        int r1 = sqlite3GetTempReg(pParse);
+        sqlite3VdbeAddOp4(v, OP_MakeRecord, regResult, 1, r1, &p->affinity, 1);
+        sqlite3ExprCacheAffinityChange(pParse, regResult, 1);
+        sqlite3VdbeAddOp2(v, OP_IdxInsert, iParm, r1);
+        sqlite3ReleaseTempReg(pParse, r1);
+      }
+      break;
+    }
+
+    /* If any row exist in the result set, record that fact and abort.
+    */
+    case SRT_Exists: {
+      sqlite3VdbeAddOp2(v, OP_Integer, 1, iParm);
+      /* The LIMIT clause will terminate the loop for us */
+      break;
+    }
+
+    /* If this is a scalar select that is part of an expression, then
+    ** store the results in the appropriate memory cell and break out
+    ** of the scan loop.
+    */
+    case SRT_Mem: {
+      assert( nColumn==1 );
+      if( pOrderBy ){
+        pushOntoSorter(pParse, pOrderBy, p, regResult);
+      }else{
+        sqlite3ExprCodeMove(pParse, regResult, iParm, 1);
+        /* The LIMIT clause will jump out of the loop for us */
+      }
+      break;
+    }
+#endif /* #ifndef SQLITE_OMIT_SUBQUERY */
+
+    /* Send the data to the callback function or to a subroutine.  In the
+    ** case of a subroutine, the subroutine itself is responsible for
+    ** popping the data from the stack.
+    */
+    case SRT_Coroutine:
+    case SRT_Output: {
+      testcase( eDest==SRT_Coroutine );
+      testcase( eDest==SRT_Output );
+      if( pOrderBy ){
+        int r1 = sqlite3GetTempReg(pParse);
+        sqlite3VdbeAddOp3(v, OP_MakeRecord, regResult, nColumn, r1);
+        pushOntoSorter(pParse, pOrderBy, p, r1);
+        sqlite3ReleaseTempReg(pParse, r1);
+      }else if( eDest==SRT_Coroutine ){
+        sqlite3VdbeAddOp1(v, OP_Yield, pDest->iParm);
+      }else{
+        sqlite3VdbeAddOp2(v, OP_ResultRow, regResult, nColumn);
+        sqlite3ExprCacheAffinityChange(pParse, regResult, nColumn);
+      }
+      break;
+    }
+
+#if !defined(SQLITE_OMIT_TRIGGER)
+    /* Discard the results.  This is used for SELECT statements inside
+    ** the body of a TRIGGER.  The purpose of such selects is to call
+    ** user-defined functions that have side effects.  We do not care
+    ** about the actual results of the select.
+    */
+    default: {
+      assert( eDest==SRT_Discard );
+      break;
+    }
+#endif
+  }
+
+  /* Jump to the end of the loop if the LIMIT is reached.  Except, if
+  ** there is a sorter, in which case the sorter has already limited
+  ** the output for us.
+  */
+  if( pOrderBy==0 && p->iLimit ){
+    sqlite3VdbeAddOp3(v, OP_IfZero, p->iLimit, iBreak, -1);
+  }
+}
+
+/*
+** Given an expression list, generate a KeyInfo structure that records
+** the collating sequence for each expression in that expression list.
+**
+** If the ExprList is an ORDER BY or GROUP BY clause then the resulting
+** KeyInfo structure is appropriate for initializing a virtual index to
+** implement that clause.  If the ExprList is the result set of a SELECT
+** then the KeyInfo structure is appropriate for initializing a virtual
+** index to implement a DISTINCT test.
+**
+** Space to hold the KeyInfo structure is obtain from malloc.  The calling
+** function is responsible for seeing that this structure is eventually
+** freed.  Add the KeyInfo structure to the P4 field of an opcode using
+** P4_KEYINFO_HANDOFF is the usual way of dealing with this.
+*/
+static KeyInfo *keyInfoFromExprList(Parse *pParse, ExprList *pList){
+  sqlite3 *db = pParse->db;
+  int nExpr;
+  KeyInfo *pInfo;
+  struct ExprList_item *pItem;
+  int i;
+
+  nExpr = pList->nExpr;
+  pInfo = sqlite3DbMallocZero(db, sizeof(*pInfo) + nExpr*(sizeof(CollSeq*)+1) );
+  if( pInfo ){
+    pInfo->aSortOrder = (u8*)&pInfo->aColl[nExpr];
+    pInfo->nField = (u16)nExpr;
+    pInfo->enc = ENC(db);
+    pInfo->db = db;
+    for(i=0, pItem=pList->a; i<nExpr; i++, pItem++){
+      CollSeq *pColl;
+      pColl = sqlite3ExprCollSeq(pParse, pItem->pExpr);
+      if( !pColl ){
+        pColl = db->pDfltColl;
+      }
+      pInfo->aColl[i] = pColl;
+      pInfo->aSortOrder[i] = pItem->sortOrder;
+    }
+  }
+  return pInfo;
+}
+
+#ifndef SQLITE_OMIT_COMPOUND_SELECT
+/*
+** Name of the connection operator, used for error messages.
+*/
+static const char *selectOpName(int id){
+  char *z;
+  switch( id ){
+    case TK_ALL:       z = "UNION ALL";   break;
+    case TK_INTERSECT: z = "INTERSECT";   break;
+    case TK_EXCEPT:    z = "EXCEPT";      break;
+    default:           z = "UNION";       break;
+  }
+  return z;
+}
+#endif /* SQLITE_OMIT_COMPOUND_SELECT */
+
+#ifndef SQLITE_OMIT_EXPLAIN
+/*
+** Unless an "EXPLAIN QUERY PLAN" command is being processed, this function
+** is a no-op. Otherwise, it adds a single row of output to the EQP result,
+** where the caption is of the form:
+**
+**   "USE TEMP B-TREE FOR xxx"
+**
+** where xxx is one of "DISTINCT", "ORDER BY" or "GROUP BY". Exactly which
+** is determined by the zUsage argument.
+*/
+static void explainTempTable(Parse *pParse, const char *zUsage){
+  if( pParse->explain==2 ){
+    Vdbe *v = pParse->pVdbe;
+    char *zMsg = sqlite3MPrintf(pParse->db, "USE TEMP B-TREE FOR %s", zUsage);
+    sqlite3VdbeAddOp4(v, OP_Explain, pParse->iSelectId, 0, 0, zMsg, P4_DYNAMIC);
+  }
+}
+
+/*
+** Assign expression b to lvalue a. A second, no-op, version of this macro
+** is provided when SQLITE_OMIT_EXPLAIN is defined. This allows the code
+** in sqlite3Select() to assign values to structure member variables that
+** only exist if SQLITE_OMIT_EXPLAIN is not defined without polluting the
+** code with #ifndef directives.
+*/
+# define explainSetInteger(a, b) a = b
+
+#else
+/* No-op versions of the explainXXX() functions and macros. */
+# define explainTempTable(y,z)
+# define explainSetInteger(y,z)
+#endif
+
+#if !defined(SQLITE_OMIT_EXPLAIN) && !defined(SQLITE_OMIT_COMPOUND_SELECT)
+/*
+** Unless an "EXPLAIN QUERY PLAN" command is being processed, this function
+** is a no-op. Otherwise, it adds a single row of output to the EQP result,
+** where the caption is of one of the two forms:
+**
+**   "COMPOSITE SUBQUERIES iSub1 and iSub2 (op)"
+**   "COMPOSITE SUBQUERIES iSub1 and iSub2 USING TEMP B-TREE (op)"
+**
+** where iSub1 and iSub2 are the integers passed as the corresponding
+** function parameters, and op is the text representation of the parameter
+** of the same name. The parameter "op" must be one of TK_UNION, TK_EXCEPT,
+** TK_INTERSECT or TK_ALL. The first form is used if argument bUseTmp is 
+** false, or the second form if it is true.
+*/
+static void explainComposite(
+  Parse *pParse,                  /* Parse context */
+  int op,                         /* One of TK_UNION, TK_EXCEPT etc. */
+  int iSub1,                      /* Subquery id 1 */
+  int iSub2,                      /* Subquery id 2 */
+  int bUseTmp                     /* True if a temp table was used */
+){
+  assert( op==TK_UNION || op==TK_EXCEPT || op==TK_INTERSECT || op==TK_ALL );
+  if( pParse->explain==2 ){
+    Vdbe *v = pParse->pVdbe;
+    char *zMsg = sqlite3MPrintf(
+        pParse->db, "COMPOUND SUBQUERIES %d AND %d %s(%s)", iSub1, iSub2,
+        bUseTmp?"USING TEMP B-TREE ":"", selectOpName(op)
+    );
+    sqlite3VdbeAddOp4(v, OP_Explain, pParse->iSelectId, 0, 0, zMsg, P4_DYNAMIC);
+  }
+}
+#else
+/* No-op versions of the explainXXX() functions and macros. */
+# define explainComposite(v,w,x,y,z)
+#endif
+
+/*
+** If the inner loop was generated using a non-null pOrderBy argument,
+** then the results were placed in a sorter.  After the loop is terminated
+** we need to run the sorter and output the results.  The following
+** routine generates the code needed to do that.
+*/
+static void generateSortTail(
+  Parse *pParse,    /* Parsing context */
+  Select *p,        /* The SELECT statement */
+  Vdbe *v,          /* Generate code into this VDBE */
+  int nColumn,      /* Number of columns of data */
+  SelectDest *pDest /* Write the sorted results here */
+){
+  int addrBreak = sqlite3VdbeMakeLabel(v);     /* Jump here to exit loop */
+  int addrContinue = sqlite3VdbeMakeLabel(v);  /* Jump here for next cycle */
+  int addr;
+  int iTab;
+  int pseudoTab = 0;
+  ExprList *pOrderBy = p->pOrderBy;
+
+  int eDest = pDest->eDest;
+  int iParm = pDest->iParm;
+
+  int regRow;
+  int regRowid;
+
+  iTab = pOrderBy->iECursor;
+  regRow = sqlite3GetTempReg(pParse);
+  if( eDest==SRT_Output || eDest==SRT_Coroutine ){
+    pseudoTab = pParse->nTab++;
+    sqlite3VdbeAddOp3(v, OP_OpenPseudo, pseudoTab, regRow, nColumn);
+    regRowid = 0;
+  }else{
+    regRowid = sqlite3GetTempReg(pParse);
+  }
+  if( p->selFlags & SF_UseSorter ){
+    int regSortOut = ++pParse->nMem;
+    int ptab2 = pParse->nTab++;
+    sqlite3VdbeAddOp3(v, OP_OpenPseudo, ptab2, regSortOut, pOrderBy->nExpr+2);
+    addr = 1 + sqlite3VdbeAddOp2(v, OP_SorterSort, iTab, addrBreak);
+    codeOffset(v, p, addrContinue);
+    sqlite3VdbeAddOp2(v, OP_SorterData, iTab, regSortOut);
+    sqlite3VdbeAddOp3(v, OP_Column, ptab2, pOrderBy->nExpr+1, regRow);
+    sqlite3VdbeChangeP5(v, OPFLAG_CLEARCACHE);
+  }else{
+    addr = 1 + sqlite3VdbeAddOp2(v, OP_Sort, iTab, addrBreak);
+    codeOffset(v, p, addrContinue);
+    sqlite3VdbeAddOp3(v, OP_Column, iTab, pOrderBy->nExpr+1, regRow);
+  }
+  switch( eDest ){
+    case SRT_Table:
+    case SRT_EphemTab: {
+      testcase( eDest==SRT_Table );
+      testcase( eDest==SRT_EphemTab );
+      sqlite3VdbeAddOp2(v, OP_NewRowid, iParm, regRowid);
+      sqlite3VdbeAddOp3(v, OP_Insert, iParm, regRow, regRowid);
+      sqlite3VdbeChangeP5(v, OPFLAG_APPEND);
+      break;
+    }
+#ifndef SQLITE_OMIT_SUBQUERY
+    case SRT_Set: {
+      assert( nColumn==1 );
+      sqlite3VdbeAddOp4(v, OP_MakeRecord, regRow, 1, regRowid, &p->affinity, 1);
+      sqlite3ExprCacheAffinityChange(pParse, regRow, 1);
+      sqlite3VdbeAddOp2(v, OP_IdxInsert, iParm, regRowid);
+      break;
+    }
+    case SRT_Mem: {
+      assert( nColumn==1 );
+      sqlite3ExprCodeMove(pParse, regRow, iParm, 1);
+      /* The LIMIT clause will terminate the loop for us */
+      break;
+    }
+#endif
+    default: {
+      int i;
+      assert( eDest==SRT_Output || eDest==SRT_Coroutine ); 
+      testcase( eDest==SRT_Output );
+      testcase( eDest==SRT_Coroutine );
+      for(i=0; i<nColumn; i++){
+        assert( regRow!=pDest->iMem+i );
+        sqlite3VdbeAddOp3(v, OP_Column, pseudoTab, i, pDest->iMem+i);
+        if( i==0 ){
+          sqlite3VdbeChangeP5(v, OPFLAG_CLEARCACHE);
+        }
+      }
+      if( eDest==SRT_Output ){
+        sqlite3VdbeAddOp2(v, OP_ResultRow, pDest->iMem, nColumn);
+        sqlite3ExprCacheAffinityChange(pParse, pDest->iMem, nColumn);
+      }else{
+        sqlite3VdbeAddOp1(v, OP_Yield, pDest->iParm);
+      }
+      break;
+    }
+  }
+  sqlite3ReleaseTempReg(pParse, regRow);
+  sqlite3ReleaseTempReg(pParse, regRowid);
+
+  /* The bottom of the loop
+  */
+  sqlite3VdbeResolveLabel(v, addrContinue);
+  if( p->selFlags & SF_UseSorter ){
+    sqlite3VdbeAddOp2(v, OP_SorterNext, iTab, addr);
+  }else{
+    sqlite3VdbeAddOp2(v, OP_Next, iTab, addr);
+  }
+  sqlite3VdbeResolveLabel(v, addrBreak);
+  if( eDest==SRT_Output || eDest==SRT_Coroutine ){
+    sqlite3VdbeAddOp2(v, OP_Close, pseudoTab, 0);
+  }
+}
+
+/*
+** Return a pointer to a string containing the 'declaration type' of the
+** expression pExpr. The string may be treated as static by the caller.
+**
+** The declaration type is the exact datatype definition extracted from the
+** original CREATE TABLE statement if the expression is a column. The
+** declaration type for a ROWID field is INTEGER. Exactly when an expression
+** is considered a column can be complex in the presence of subqueries. The
+** result-set expression in all of the following SELECT statements is 
+** considered a column by this function.
+**
+**   SELECT col FROM tbl;
+**   SELECT (SELECT col FROM tbl;
+**   SELECT (SELECT col FROM tbl);
+**   SELECT abc FROM (SELECT col AS abc FROM tbl);
+** 
+** The declaration type for any expression other than a column is NULL.
+*/
+static const char *columnType(
+  NameContext *pNC, 
+  Expr *pExpr,
+  const char **pzOriginDb,
+  const char **pzOriginTab,
+  const char **pzOriginCol
+){
+  char const *zType = 0;
+  char const *zOriginDb = 0;
+  char const *zOriginTab = 0;
+  char const *zOriginCol = 0;
+  int j;
+  if( NEVER(pExpr==0) || pNC->pSrcList==0 ) return 0;
+
+  switch( pExpr->op ){
+    case TK_AGG_COLUMN:
+    case TK_COLUMN: {
+      /* The expression is a column. Locate the table the column is being
+      ** extracted from in NameContext.pSrcList. This table may be real
+      ** database table or a subquery.
+      */
+      Table *pTab = 0;            /* Table structure column is extracted from */
+      Select *pS = 0;             /* Select the column is extracted from */
+      int iCol = pExpr->iColumn;  /* Index of column in pTab */
+      testcase( pExpr->op==TK_AGG_COLUMN );
+      testcase( pExpr->op==TK_COLUMN );
+      while( pNC && !pTab ){
+        SrcList *pTabList = pNC->pSrcList;
+        for(j=0;j<pTabList->nSrc && pTabList->a[j].iCursor!=pExpr->iTable;j++);
+        if( j<pTabList->nSrc ){
+          pTab = pTabList->a[j].pTab;
+          pS = pTabList->a[j].pSelect;
+        }else{
+          pNC = pNC->pNext;
+        }
+      }
+
+      if( pTab==0 ){
+        /* At one time, code such as "SELECT new.x" within a trigger would
+        ** cause this condition to run.  Since then, we have restructured how
+        ** trigger code is generated and so this condition is no longer 
+        ** possible. However, it can still be true for statements like
+        ** the following:
+        **
+        **   CREATE TABLE t1(col INTEGER);
+        **   SELECT (SELECT t1.col) FROM FROM t1;
+        **
+        ** when columnType() is called on the expression "t1.col" in the 
+        ** sub-select. In this case, set the column type to NULL, even
+        ** though it should really be "INTEGER".
+        **
+        ** This is not a problem, as the column type of "t1.col" is never
+        ** used. When columnType() is called on the expression 
+        ** "(SELECT t1.col)", the correct type is returned (see the TK_SELECT
+        ** branch below.  */
+        break;
+      }
+
+      assert( pTab && pExpr->pTab==pTab );
+      if( pS ){
+        /* The "table" is actually a sub-select or a view in the FROM clause
+        ** of the SELECT statement. Return the declaration type and origin
+        ** data for the result-set column of the sub-select.
+        */
+        if( iCol>=0 && ALWAYS(iCol<pS->pEList->nExpr) ){
+          /* If iCol is less than zero, then the expression requests the
+          ** rowid of the sub-select or view. This expression is legal (see 
+          ** test case misc2.2.2) - it always evaluates to NULL.
+          */
+          NameContext sNC;
+          Expr *p = pS->pEList->a[iCol].pExpr;
+          sNC.pSrcList = pS->pSrc;
+          sNC.pNext = pNC;
+          sNC.pParse = pNC->pParse;
+          zType = columnType(&sNC, p, &zOriginDb, &zOriginTab, &zOriginCol); 
+        }
+      }else if( ALWAYS(pTab->pSchema) ){
+        /* A real table */
+        assert( !pS );
+        if( iCol<0 ) iCol = pTab->iPKey;
+        assert( iCol==-1 || (iCol>=0 && iCol<pTab->nCol) );
+        if( iCol<0 ){
+          zType = "INTEGER";
+          zOriginCol = "rowid";
+        }else{
+          zType = pTab->aCol[iCol].zType;
+          zOriginCol = pTab->aCol[iCol].zName;
+        }
+        zOriginTab = pTab->zName;
+        if( pNC->pParse ){
+          int iDb = sqlite3SchemaToIndex(pNC->pParse->db, pTab->pSchema);
+          zOriginDb = pNC->pParse->db->aDb[iDb].zName;
+        }
+      }
+      break;
+    }
+#ifndef SQLITE_OMIT_SUBQUERY
+    case TK_SELECT: {
+      /* The expression is a sub-select. Return the declaration type and
+      ** origin info for the single column in the result set of the SELECT
+      ** statement.
+      */
+      NameContext sNC;
+      Select *pS = pExpr->x.pSelect;
+      Expr *p = pS->pEList->a[0].pExpr;
+      assert( ExprHasProperty(pExpr, EP_xIsSelect) );
+      sNC.pSrcList = pS->pSrc;
+      sNC.pNext = pNC;
+      sNC.pParse = pNC->pParse;
+      zType = columnType(&sNC, p, &zOriginDb, &zOriginTab, &zOriginCol); 
+      break;
+    }
+#endif
+  }
+  
+  if( pzOriginDb ){
+    assert( pzOriginTab && pzOriginCol );
+    *pzOriginDb = zOriginDb;
+    *pzOriginTab = zOriginTab;
+    *pzOriginCol = zOriginCol;
+  }
+  return zType;
+}
+
+/*
+** Generate code that will tell the VDBE the declaration types of columns
+** in the result set.
+*/
+static void generateColumnTypes(
+  Parse *pParse,      /* Parser context */
+  SrcList *pTabList,  /* List of tables */
+  ExprList *pEList    /* Expressions defining the result set */
+){
+#ifndef SQLITE_OMIT_DECLTYPE
+  Vdbe *v = pParse->pVdbe;
+  int i;
+  NameContext sNC;
+  sNC.pSrcList = pTabList;
+  sNC.pParse = pParse;
+  for(i=0; i<pEList->nExpr; i++){
+    Expr *p = pEList->a[i].pExpr;
+    const char *zType;
+#ifdef SQLITE_ENABLE_COLUMN_METADATA
+    const char *zOrigDb = 0;
+    const char *zOrigTab = 0;
+    const char *zOrigCol = 0;
+    zType = columnType(&sNC, p, &zOrigDb, &zOrigTab, &zOrigCol);
+
+    /* The vdbe must make its own copy of the column-type and other 
+    ** column specific strings, in case the schema is reset before this
+    ** virtual machine is deleted.
+    */
+    sqlite3VdbeSetColName(v, i, COLNAME_DATABASE, zOrigDb, SQLITE_TRANSIENT);
+    sqlite3VdbeSetColName(v, i, COLNAME_TABLE, zOrigTab, SQLITE_TRANSIENT);
+    sqlite3VdbeSetColName(v, i, COLNAME_COLUMN, zOrigCol, SQLITE_TRANSIENT);
+#else
+    zType = columnType(&sNC, p, 0, 0, 0);
+#endif
+    sqlite3VdbeSetColName(v, i, COLNAME_DECLTYPE, zType, SQLITE_TRANSIENT);
+  }
+#endif /* SQLITE_OMIT_DECLTYPE */
+}
+
+/*
+** Generate code that will tell the VDBE the names of columns
+** in the result set.  This information is used to provide the
+** azCol[] values in the callback.
+*/
+static void generateColumnNames(
+  Parse *pParse,      /* Parser context */
+  SrcList *pTabList,  /* List of tables */
+  ExprList *pEList    /* Expressions defining the result set */
+){
+  Vdbe *v = pParse->pVdbe;
+  int i, j;
+  sqlite3 *db = pParse->db;
+  int fullNames, shortNames;
+
+#ifndef SQLITE_OMIT_EXPLAIN
+  /* If this is an EXPLAIN, skip this step */
+  if( pParse->explain ){
+    return;
+  }
+#endif
+
+  if( pParse->colNamesSet || NEVER(v==0) || db->mallocFailed ) return;
+  pParse->colNamesSet = 1;
+  fullNames = (db->flags & SQLITE_FullColNames)!=0;
+  shortNames = (db->flags & SQLITE_ShortColNames)!=0;
+  sqlite3VdbeSetNumCols(v, pEList->nExpr);
+  for(i=0; i<pEList->nExpr; i++){
+    Expr *p;
+    p = pEList->a[i].pExpr;
+    if( NEVER(p==0) ) continue;
+    if( pEList->a[i].zName ){
+      char *zName = pEList->a[i].zName;
+      sqlite3VdbeSetColName(v, i, COLNAME_NAME, zName, SQLITE_TRANSIENT);
+    }else if( (p->op==TK_COLUMN || p->op==TK_AGG_COLUMN) && pTabList ){
+      Table *pTab;
+      char *zCol;
+      int iCol = p->iColumn;
+      for(j=0; ALWAYS(j<pTabList->nSrc); j++){
+        if( pTabList->a[j].iCursor==p->iTable ) break;
+      }
+      assert( j<pTabList->nSrc );
+      pTab = pTabList->a[j].pTab;
+      if( iCol<0 ) iCol = pTab->iPKey;
+      assert( iCol==-1 || (iCol>=0 && iCol<pTab->nCol) );
+      if( iCol<0 ){
+        zCol = "rowid";
+      }else{
+        zCol = pTab->aCol[iCol].zName;
+      }
+      if( !shortNames && !fullNames ){
+        sqlite3VdbeSetColName(v, i, COLNAME_NAME, 
+            sqlite3DbStrDup(db, pEList->a[i].zSpan), SQLITE_DYNAMIC);
+      }else if( fullNames ){
+        char *zName = 0;
+        zName = sqlite3MPrintf(db, "%s.%s", pTab->zName, zCol);
+        sqlite3VdbeSetColName(v, i, COLNAME_NAME, zName, SQLITE_DYNAMIC);
+      }else{
+        sqlite3VdbeSetColName(v, i, COLNAME_NAME, zCol, SQLITE_TRANSIENT);
+      }
+    }else{
+      sqlite3VdbeSetColName(v, i, COLNAME_NAME, 
+          sqlite3DbStrDup(db, pEList->a[i].zSpan), SQLITE_DYNAMIC);
+    }
+  }
+  generateColumnTypes(pParse, pTabList, pEList);
+}
+
+/*
+** Given a an expression list (which is really the list of expressions
+** that form the result set of a SELECT statement) compute appropriate
+** column names for a table that would hold the expression list.
+**
+** All column names will be unique.
+**
+** Only the column names are computed.  Column.zType, Column.zColl,
+** and other fields of Column are zeroed.
+**
+** Return SQLITE_OK on success.  If a memory allocation error occurs,
+** store NULL in *paCol and 0 in *pnCol and return SQLITE_NOMEM.
+*/
+static int selectColumnsFromExprList(
+  Parse *pParse,          /* Parsing context */
+  ExprList *pEList,       /* Expr list from which to derive column names */
+  int *pnCol,             /* Write the number of columns here */
+  Column **paCol          /* Write the new column list here */
+){
+  sqlite3 *db = pParse->db;   /* Database connection */
+  int i, j;                   /* Loop counters */
+  int cnt;                    /* Index added to make the name unique */
+  Column *aCol, *pCol;        /* For looping over result columns */
+  int nCol;                   /* Number of columns in the result set */
+  Expr *p;                    /* Expression for a single result column */
+  char *zName;                /* Column name */
+  int nName;                  /* Size of name in zName[] */
+
+  *pnCol = nCol = pEList->nExpr;
+  aCol = *paCol = sqlite3DbMallocZero(db, sizeof(aCol[0])*nCol);
+  if( aCol==0 ) return SQLITE_NOMEM;
+  for(i=0, pCol=aCol; i<nCol; i++, pCol++){
+    /* Get an appropriate name for the column
+    */
+    p = pEList->a[i].pExpr;
+    assert( p->pRight==0 || ExprHasProperty(p->pRight, EP_IntValue)
+               || p->pRight->u.zToken==0 || p->pRight->u.zToken[0]!=0 );
+    if( (zName = pEList->a[i].zName)!=0 ){
+      /* If the column contains an "AS <name>" phrase, use <name> as the name */
+      zName = sqlite3DbStrDup(db, zName);
+    }else{
+      Expr *pColExpr = p;  /* The expression that is the result column name */
+      Table *pTab;         /* Table associated with this expression */
+      while( pColExpr->op==TK_DOT ){
+        pColExpr = pColExpr->pRight;
+        assert( pColExpr!=0 );
+      }
+      if( pColExpr->op==TK_COLUMN && ALWAYS(pColExpr->pTab!=0) ){
+        /* For columns use the column name name */
+        int iCol = pColExpr->iColumn;
+        pTab = pColExpr->pTab;
+        if( iCol<0 ) iCol = pTab->iPKey;
+        zName = sqlite3MPrintf(db, "%s",
+                 iCol>=0 ? pTab->aCol[iCol].zName : "rowid");
+      }else if( pColExpr->op==TK_ID ){
+        assert( !ExprHasProperty(pColExpr, EP_IntValue) );
+        zName = sqlite3MPrintf(db, "%s", pColExpr->u.zToken);
+      }else{
+        /* Use the original text of the column expression as its name */
+        zName = sqlite3MPrintf(db, "%s", pEList->a[i].zSpan);
+      }
+    }
+    if( db->mallocFailed ){
+      sqlite3DbFree(db, zName);
+      break;
+    }
+
+    /* Make sure the column name is unique.  If the name is not unique,
+    ** append a integer to the name so that it becomes unique.
+    */
+    nName = sqlite3Strlen30(zName);
+    for(j=cnt=0; j<i; j++){
+      if( sqlite3StrICmp(aCol[j].zName, zName)==0 ){
+        char *zNewName;
+        zName[nName] = 0;
+        zNewName = sqlite3MPrintf(db, "%s:%d", zName, ++cnt);
+        sqlite3DbFree(db, zName);
+        zName = zNewName;
+        j = -1;
+        if( zName==0 ) break;
+      }
+    }
+    pCol->zName = zName;
+  }
+  if( db->mallocFailed ){
+    for(j=0; j<i; j++){
+      sqlite3DbFree(db, aCol[j].zName);
+    }
+    sqlite3DbFree(db, aCol);
+    *paCol = 0;
+    *pnCol = 0;
+    return SQLITE_NOMEM;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Add type and collation information to a column list based on
+** a SELECT statement.
+** 
+** The column list presumably came from selectColumnNamesFromExprList().
+** The column list has only names, not types or collations.  This
+** routine goes through and adds the types and collations.
+**
+** This routine requires that all identifiers in the SELECT
+** statement be resolved.
+*/
+static void selectAddColumnTypeAndCollation(
+  Parse *pParse,        /* Parsing contexts */
+  int nCol,             /* Number of columns */
+  Column *aCol,         /* List of columns */
+  Select *pSelect       /* SELECT used to determine types and collations */
+){
+  sqlite3 *db = pParse->db;
+  NameContext sNC;
+  Column *pCol;
+  CollSeq *pColl;
+  int i;
+  Expr *p;
+  struct ExprList_item *a;
+
+  assert( pSelect!=0 );
+  assert( (pSelect->selFlags & SF_Resolved)!=0 );
+  assert( nCol==pSelect->pEList->nExpr || db->mallocFailed );
+  if( db->mallocFailed ) return;
+  memset(&sNC, 0, sizeof(sNC));
+  sNC.pSrcList = pSelect->pSrc;
+  a = pSelect->pEList->a;
+  for(i=0, pCol=aCol; i<nCol; i++, pCol++){
+    p = a[i].pExpr;
+    pCol->zType = sqlite3DbStrDup(db, columnType(&sNC, p, 0, 0, 0));
+    pCol->affinity = sqlite3ExprAffinity(p);
+    if( pCol->affinity==0 ) pCol->affinity = SQLITE_AFF_NONE;
+    pColl = sqlite3ExprCollSeq(pParse, p);
+    if( pColl ){
+      pCol->zColl = sqlite3DbStrDup(db, pColl->zName);
+    }
+  }
+}
+
+/*
+** Given a SELECT statement, generate a Table structure that describes
+** the result set of that SELECT.
+*/
+Table *sqlite3ResultSetOfSelect(Parse *pParse, Select *pSelect){
+  Table *pTab;
+  sqlite3 *db = pParse->db;
+  int savedFlags;
+
+  savedFlags = db->flags;
+  db->flags &= ~SQLITE_FullColNames;
+  db->flags |= SQLITE_ShortColNames;
+  sqlite3SelectPrep(pParse, pSelect, 0);
+  if( pParse->nErr ) return 0;
+  while( pSelect->pPrior ) pSelect = pSelect->pPrior;
+  db->flags = savedFlags;
+  pTab = sqlite3DbMallocZero(db, sizeof(Table) );
+  if( pTab==0 ){
+    return 0;
+  }
+  /* The sqlite3ResultSetOfSelect() is only used n contexts where lookaside
+  ** is disabled */
+  assert( db->lookaside.bEnabled==0 );
+  pTab->nRef = 1;
+  pTab->zName = 0;
+  pTab->nRowEst = 1000000;
+  selectColumnsFromExprList(pParse, pSelect->pEList, &pTab->nCol, &pTab->aCol);
+  selectAddColumnTypeAndCollation(pParse, pTab->nCol, pTab->aCol, pSelect);
+  pTab->iPKey = -1;
+  if( db->mallocFailed ){
+    sqlite3DeleteTable(db, pTab);
+    return 0;
+  }
+  return pTab;
+}
+
+/*
+** Get a VDBE for the given parser context.  Create a new one if necessary.
+** If an error occurs, return NULL and leave a message in pParse.
+*/
+Vdbe *sqlite3GetVdbe(Parse *pParse){
+  Vdbe *v = pParse->pVdbe;
+  if( v==0 ){
+    v = pParse->pVdbe = sqlite3VdbeCreate(pParse->db);
+#ifndef SQLITE_OMIT_TRACE
+    if( v ){
+      sqlite3VdbeAddOp0(v, OP_Trace);
+    }
+#endif
+  }
+  return v;
+}
+
+
+/*
+** Compute the iLimit and iOffset fields of the SELECT based on the
+** pLimit and pOffset expressions.  pLimit and pOffset hold the expressions
+** that appear in the original SQL statement after the LIMIT and OFFSET
+** keywords.  Or NULL if those keywords are omitted. iLimit and iOffset 
+** are the integer memory register numbers for counters used to compute 
+** the limit and offset.  If there is no limit and/or offset, then 
+** iLimit and iOffset are negative.
+**
+** This routine changes the values of iLimit and iOffset only if
+** a limit or offset is defined by pLimit and pOffset.  iLimit and
+** iOffset should have been preset to appropriate default values
+** (usually but not always -1) prior to calling this routine.
+** Only if pLimit!=0 or pOffset!=0 do the limit registers get
+** redefined.  The UNION ALL operator uses this property to force
+** the reuse of the same limit and offset registers across multiple
+** SELECT statements.
+*/
+static void computeLimitRegisters(Parse *pParse, Select *p, int iBreak){
+  Vdbe *v = 0;
+  int iLimit = 0;
+  int iOffset;
+  int addr1, n;
+  if( p->iLimit ) return;
+
+  /* 
+  ** "LIMIT -1" always shows all rows.  There is some
+  ** contraversy about what the correct behavior should be.
+  ** The current implementation interprets "LIMIT 0" to mean
+  ** no rows.
+  */
+  sqlite3ExprCacheClear(pParse);
+  assert( p->pOffset==0 || p->pLimit!=0 );
+  if( p->pLimit ){
+    p->iLimit = iLimit = ++pParse->nMem;
+    v = sqlite3GetVdbe(pParse);
+    if( NEVER(v==0) ) return;  /* VDBE should have already been allocated */
+    if( sqlite3ExprIsInteger(p->pLimit, &n) ){
+      sqlite3VdbeAddOp2(v, OP_Integer, n, iLimit);
+      VdbeComment((v, "LIMIT counter"));
+      if( n==0 ){
+        sqlite3VdbeAddOp2(v, OP_Goto, 0, iBreak);
+      }else{
+        if( p->nSelectRow > (double)n ) p->nSelectRow = (double)n;
+      }
+    }else{
+      sqlite3ExprCode(pParse, p->pLimit, iLimit);
+      sqlite3VdbeAddOp1(v, OP_MustBeInt, iLimit);
+      VdbeComment((v, "LIMIT counter"));
+      sqlite3VdbeAddOp2(v, OP_IfZero, iLimit, iBreak);
+    }
+    if( p->pOffset ){
+      p->iOffset = iOffset = ++pParse->nMem;
+      pParse->nMem++;   /* Allocate an extra register for limit+offset */
+      sqlite3ExprCode(pParse, p->pOffset, iOffset);
+      sqlite3VdbeAddOp1(v, OP_MustBeInt, iOffset);
+      VdbeComment((v, "OFFSET counter"));
+      addr1 = sqlite3VdbeAddOp1(v, OP_IfPos, iOffset);
+      sqlite3VdbeAddOp2(v, OP_Integer, 0, iOffset);
+      sqlite3VdbeJumpHere(v, addr1);
+      sqlite3VdbeAddOp3(v, OP_Add, iLimit, iOffset, iOffset+1);
+      VdbeComment((v, "LIMIT+OFFSET"));
+      addr1 = sqlite3VdbeAddOp1(v, OP_IfPos, iLimit);
+      sqlite3VdbeAddOp2(v, OP_Integer, -1, iOffset+1);
+      sqlite3VdbeJumpHere(v, addr1);
+    }
+  }
+}
+
+#ifndef SQLITE_OMIT_COMPOUND_SELECT
+/*
+** Return the appropriate collating sequence for the iCol-th column of
+** the result set for the compound-select statement "p".  Return NULL if
+** the column has no default collating sequence.
+**
+** The collating sequence for the compound select is taken from the
+** left-most term of the select that has a collating sequence.
+*/
+static CollSeq *multiSelectCollSeq(Parse *pParse, Select *p, int iCol){
+  CollSeq *pRet;
+  if( p->pPrior ){
+    pRet = multiSelectCollSeq(pParse, p->pPrior, iCol);
+  }else{
+    pRet = 0;
+  }
+  assert( iCol>=0 );
+  if( pRet==0 && iCol<p->pEList->nExpr ){
+    pRet = sqlite3ExprCollSeq(pParse, p->pEList->a[iCol].pExpr);
+  }
+  return pRet;
+}
+#endif /* SQLITE_OMIT_COMPOUND_SELECT */
+
+/* Forward reference */
+static int multiSelectOrderBy(
+  Parse *pParse,        /* Parsing context */
+  Select *p,            /* The right-most of SELECTs to be coded */
+  SelectDest *pDest     /* What to do with query results */
+);
+
+
+#ifndef SQLITE_OMIT_COMPOUND_SELECT
+/*
+** This routine is called to process a compound query form from
+** two or more separate queries using UNION, UNION ALL, EXCEPT, or
+** INTERSECT
+**
+** "p" points to the right-most of the two queries.  the query on the
+** left is p->pPrior.  The left query could also be a compound query
+** in which case this routine will be called recursively. 
+**
+** The results of the total query are to be written into a destination
+** of type eDest with parameter iParm.
+**
+** Example 1:  Consider a three-way compound SQL statement.
+**
+**     SELECT a FROM t1 UNION SELECT b FROM t2 UNION SELECT c FROM t3
+**
+** This statement is parsed up as follows:
+**
+**     SELECT c FROM t3
+**      |
+**      `----->  SELECT b FROM t2
+**                |
+**                `------>  SELECT a FROM t1
+**
+** The arrows in the diagram above represent the Select.pPrior pointer.
+** So if this routine is called with p equal to the t3 query, then
+** pPrior will be the t2 query.  p->op will be TK_UNION in this case.
+**
+** Notice that because of the way SQLite parses compound SELECTs, the
+** individual selects always group from left to right.
+*/
+static int multiSelect(
+  Parse *pParse,        /* Parsing context */
+  Select *p,            /* The right-most of SELECTs to be coded */
+  SelectDest *pDest     /* What to do with query results */
+){
+  int rc = SQLITE_OK;   /* Success code from a subroutine */
+  Select *pPrior;       /* Another SELECT immediately to our left */
+  Vdbe *v;              /* Generate code to this VDBE */
+  SelectDest dest;      /* Alternative data destination */
+  Select *pDelete = 0;  /* Chain of simple selects to delete */
+  sqlite3 *db;          /* Database connection */
+#ifndef SQLITE_OMIT_EXPLAIN
+  int iSub1;            /* EQP id of left-hand query */
+  int iSub2;            /* EQP id of right-hand query */
+#endif
+
+  /* Make sure there is no ORDER BY or LIMIT clause on prior SELECTs.  Only
+  ** the last (right-most) SELECT in the series may have an ORDER BY or LIMIT.
+  */
+  assert( p && p->pPrior );  /* Calling function guarantees this much */
+  db = pParse->db;
+  pPrior = p->pPrior;
+  assert( pPrior->pRightmost!=pPrior );
+  assert( pPrior->pRightmost==p->pRightmost );
+  dest = *pDest;
+  if( pPrior->pOrderBy ){
+    sqlite3ErrorMsg(pParse,"ORDER BY clause should come after %s not before",
+      selectOpName(p->op));
+    rc = 1;
+    goto multi_select_end;
+  }
+  if( pPrior->pLimit ){
+    sqlite3ErrorMsg(pParse,"LIMIT clause should come after %s not before",
+      selectOpName(p->op));
+    rc = 1;
+    goto multi_select_end;
+  }
+
+  v = sqlite3GetVdbe(pParse);
+  assert( v!=0 );  /* The VDBE already created by calling function */
+
+  /* Create the destination temporary table if necessary
+  */
+  if( dest.eDest==SRT_EphemTab ){
+    assert( p->pEList );
+    sqlite3VdbeAddOp2(v, OP_OpenEphemeral, dest.iParm, p->pEList->nExpr);
+    sqlite3VdbeChangeP5(v, BTREE_UNORDERED);
+    dest.eDest = SRT_Table;
+  }
+
+  /* Make sure all SELECTs in the statement have the same number of elements
+  ** in their result sets.
+  */
+  assert( p->pEList && pPrior->pEList );
+  if( p->pEList->nExpr!=pPrior->pEList->nExpr ){
+    sqlite3ErrorMsg(pParse, "SELECTs to the left and right of %s"
+      " do not have the same number of result columns", selectOpName(p->op));
+    rc = 1;
+    goto multi_select_end;
+  }
+
+  /* Compound SELECTs that have an ORDER BY clause are handled separately.
+  */
+  if( p->pOrderBy ){
+    return multiSelectOrderBy(pParse, p, pDest);
+  }
+
+  /* Generate code for the left and right SELECT statements.
+  */
+  switch( p->op ){
+    case TK_ALL: {
+      int addr = 0;
+      int nLimit;
+      assert( !pPrior->pLimit );
+      pPrior->pLimit = p->pLimit;
+      pPrior->pOffset = p->pOffset;
+      explainSetInteger(iSub1, pParse->iNextSelectId);
+      rc = sqlite3Select(pParse, pPrior, &dest);
+      p->pLimit = 0;
+      p->pOffset = 0;
+      if( rc ){
+        goto multi_select_end;
+      }
+      p->pPrior = 0;
+      p->iLimit = pPrior->iLimit;
+      p->iOffset = pPrior->iOffset;
+      if( p->iLimit ){
+        addr = sqlite3VdbeAddOp1(v, OP_IfZero, p->iLimit);
+        VdbeComment((v, "Jump ahead if LIMIT reached"));
+      }
+      explainSetInteger(iSub2, pParse->iNextSelectId);
+      rc = sqlite3Select(pParse, p, &dest);
+      testcase( rc!=SQLITE_OK );
+      pDelete = p->pPrior;
+      p->pPrior = pPrior;
+      p->nSelectRow += pPrior->nSelectRow;
+      if( pPrior->pLimit
+       && sqlite3ExprIsInteger(pPrior->pLimit, &nLimit)
+       && p->nSelectRow > (double)nLimit 
+      ){
+        p->nSelectRow = (double)nLimit;
+      }
+      if( addr ){
+        sqlite3VdbeJumpHere(v, addr);
+      }
+      break;
+    }
+    case TK_EXCEPT:
+    case TK_UNION: {
+      int unionTab;    /* Cursor number of the temporary table holding result */
+      u8 op = 0;       /* One of the SRT_ operations to apply to self */
+      int priorOp;     /* The SRT_ operation to apply to prior selects */
+      Expr *pLimit, *pOffset; /* Saved values of p->nLimit and p->nOffset */
+      int addr;
+      SelectDest uniondest;
+
+      testcase( p->op==TK_EXCEPT );
+      testcase( p->op==TK_UNION );
+      priorOp = SRT_Union;
+      if( dest.eDest==priorOp && ALWAYS(!p->pLimit &&!p->pOffset) ){
+        /* We can reuse a temporary table generated by a SELECT to our
+        ** right.
+        */
+        assert( p->pRightmost!=p );  /* Can only happen for leftward elements
+                                     ** of a 3-way or more compound */
+        assert( p->pLimit==0 );      /* Not allowed on leftward elements */
+        assert( p->pOffset==0 );     /* Not allowed on leftward elements */
+        unionTab = dest.iParm;
+      }else{
+        /* We will need to create our own temporary table to hold the
+        ** intermediate results.
+        */
+        unionTab = pParse->nTab++;
+        assert( p->pOrderBy==0 );
+        addr = sqlite3VdbeAddOp2(v, OP_OpenEphemeral, unionTab, 0);
+        assert( p->addrOpenEphm[0] == -1 );
+        p->addrOpenEphm[0] = addr;
+        p->pRightmost->selFlags |= SF_UsesEphemeral;
+        assert( p->pEList );
+      }
+
+      /* Code the SELECT statements to our left
+      */
+      assert( !pPrior->pOrderBy );
+      sqlite3SelectDestInit(&uniondest, priorOp, unionTab);
+      explainSetInteger(iSub1, pParse->iNextSelectId);
+      rc = sqlite3Select(pParse, pPrior, &uniondest);
+      if( rc ){
+        goto multi_select_end;
+      }
+
+      /* Code the current SELECT statement
+      */
+      if( p->op==TK_EXCEPT ){
+        op = SRT_Except;
+      }else{
+        assert( p->op==TK_UNION );
+        op = SRT_Union;
+      }
+      p->pPrior = 0;
+      pLimit = p->pLimit;
+      p->pLimit = 0;
+      pOffset = p->pOffset;
+      p->pOffset = 0;
+      uniondest.eDest = op;
+      explainSetInteger(iSub2, pParse->iNextSelectId);
+      rc = sqlite3Select(pParse, p, &uniondest);
+      testcase( rc!=SQLITE_OK );
+      /* Query flattening in sqlite3Select() might refill p->pOrderBy.
+      ** Be sure to delete p->pOrderBy, therefore, to avoid a memory leak. */
+      sqlite3ExprListDelete(db, p->pOrderBy);
+      pDelete = p->pPrior;
+      p->pPrior = pPrior;
+      p->pOrderBy = 0;
+      if( p->op==TK_UNION ) p->nSelectRow += pPrior->nSelectRow;
+      sqlite3ExprDelete(db, p->pLimit);
+      p->pLimit = pLimit;
+      p->pOffset = pOffset;
+      p->iLimit = 0;
+      p->iOffset = 0;
+
+      /* Convert the data in the temporary table into whatever form
+      ** it is that we currently need.
+      */
+      assert( unionTab==dest.iParm || dest.eDest!=priorOp );
+      if( dest.eDest!=priorOp ){
+        int iCont, iBreak, iStart;
+        assert( p->pEList );
+        if( dest.eDest==SRT_Output ){
+          Select *pFirst = p;
+          while( pFirst->pPrior ) pFirst = pFirst->pPrior;
+          generateColumnNames(pParse, 0, pFirst->pEList);
+        }
+        iBreak = sqlite3VdbeMakeLabel(v);
+        iCont = sqlite3VdbeMakeLabel(v);
+        computeLimitRegisters(pParse, p, iBreak);
+        sqlite3VdbeAddOp2(v, OP_Rewind, unionTab, iBreak);
+        iStart = sqlite3VdbeCurrentAddr(v);
+        selectInnerLoop(pParse, p, p->pEList, unionTab, p->pEList->nExpr,
+                        0, -1, &dest, iCont, iBreak);
+        sqlite3VdbeResolveLabel(v, iCont);
+        sqlite3VdbeAddOp2(v, OP_Next, unionTab, iStart);
+        sqlite3VdbeResolveLabel(v, iBreak);
+        sqlite3VdbeAddOp2(v, OP_Close, unionTab, 0);
+      }
+      break;
+    }
+    default: assert( p->op==TK_INTERSECT ); {
+      int tab1, tab2;
+      int iCont, iBreak, iStart;
+      Expr *pLimit, *pOffset;
+      int addr;
+      SelectDest intersectdest;
+      int r1;
+
+      /* INTERSECT is different from the others since it requires
+      ** two temporary tables.  Hence it has its own case.  Begin
+      ** by allocating the tables we will need.
+      */
+      tab1 = pParse->nTab++;
+      tab2 = pParse->nTab++;
+      assert( p->pOrderBy==0 );
+
+      addr = sqlite3VdbeAddOp2(v, OP_OpenEphemeral, tab1, 0);
+      assert( p->addrOpenEphm[0] == -1 );
+      p->addrOpenEphm[0] = addr;
+      p->pRightmost->selFlags |= SF_UsesEphemeral;
+      assert( p->pEList );
+
+      /* Code the SELECTs to our left into temporary table "tab1".
+      */
+      sqlite3SelectDestInit(&intersectdest, SRT_Union, tab1);
+      explainSetInteger(iSub1, pParse->iNextSelectId);
+      rc = sqlite3Select(pParse, pPrior, &intersectdest);
+      if( rc ){
+        goto multi_select_end;
+      }
+
+      /* Code the current SELECT into temporary table "tab2"
+      */
+      addr = sqlite3VdbeAddOp2(v, OP_OpenEphemeral, tab2, 0);
+      assert( p->addrOpenEphm[1] == -1 );
+      p->addrOpenEphm[1] = addr;
+      p->pPrior = 0;
+      pLimit = p->pLimit;
+      p->pLimit = 0;
+      pOffset = p->pOffset;
+      p->pOffset = 0;
+      intersectdest.iParm = tab2;
+      explainSetInteger(iSub2, pParse->iNextSelectId);
+      rc = sqlite3Select(pParse, p, &intersectdest);
+      testcase( rc!=SQLITE_OK );
+      pDelete = p->pPrior;
+      p->pPrior = pPrior;
+      if( p->nSelectRow>pPrior->nSelectRow ) p->nSelectRow = pPrior->nSelectRow;
+      sqlite3ExprDelete(db, p->pLimit);
+      p->pLimit = pLimit;
+      p->pOffset = pOffset;
+
+      /* Generate code to take the intersection of the two temporary
+      ** tables.
+      */
+      assert( p->pEList );
+      if( dest.eDest==SRT_Output ){
+        Select *pFirst = p;
+        while( pFirst->pPrior ) pFirst = pFirst->pPrior;
+        generateColumnNames(pParse, 0, pFirst->pEList);
+      }
+      iBreak = sqlite3VdbeMakeLabel(v);
+      iCont = sqlite3VdbeMakeLabel(v);
+      computeLimitRegisters(pParse, p, iBreak);
+      sqlite3VdbeAddOp2(v, OP_Rewind, tab1, iBreak);
+      r1 = sqlite3GetTempReg(pParse);
+      iStart = sqlite3VdbeAddOp2(v, OP_RowKey, tab1, r1);
+      sqlite3VdbeAddOp4Int(v, OP_NotFound, tab2, iCont, r1, 0);
+      sqlite3ReleaseTempReg(pParse, r1);
+      selectInnerLoop(pParse, p, p->pEList, tab1, p->pEList->nExpr,
+                      0, -1, &dest, iCont, iBreak);
+      sqlite3VdbeResolveLabel(v, iCont);
+      sqlite3VdbeAddOp2(v, OP_Next, tab1, iStart);
+      sqlite3VdbeResolveLabel(v, iBreak);
+      sqlite3VdbeAddOp2(v, OP_Close, tab2, 0);
+      sqlite3VdbeAddOp2(v, OP_Close, tab1, 0);
+      break;
+    }
+  }
+
+  explainComposite(pParse, p->op, iSub1, iSub2, p->op!=TK_ALL);
+
+  /* Compute collating sequences used by 
+  ** temporary tables needed to implement the compound select.
+  ** Attach the KeyInfo structure to all temporary tables.
+  **
+  ** This section is run by the right-most SELECT statement only.
+  ** SELECT statements to the left always skip this part.  The right-most
+  ** SELECT might also skip this part if it has no ORDER BY clause and
+  ** no temp tables are required.
+  */
+  if( p->selFlags & SF_UsesEphemeral ){
+    int i;                        /* Loop counter */
+    KeyInfo *pKeyInfo;            /* Collating sequence for the result set */
+    Select *pLoop;                /* For looping through SELECT statements */
+    CollSeq **apColl;             /* For looping through pKeyInfo->aColl[] */
+    int nCol;                     /* Number of columns in result set */
+
+    assert( p->pRightmost==p );
+    nCol = p->pEList->nExpr;
+    pKeyInfo = sqlite3DbMallocZero(db,
+                       sizeof(*pKeyInfo)+nCol*(sizeof(CollSeq*) + 1));
+    if( !pKeyInfo ){
+      rc = SQLITE_NOMEM;
+      goto multi_select_end;
+    }
+
+    pKeyInfo->enc = ENC(db);
+    pKeyInfo->nField = (u16)nCol;
+
+    for(i=0, apColl=pKeyInfo->aColl; i<nCol; i++, apColl++){
+      *apColl = multiSelectCollSeq(pParse, p, i);
+      if( 0==*apColl ){
+        *apColl = db->pDfltColl;
+      }
+    }
+
+    for(pLoop=p; pLoop; pLoop=pLoop->pPrior){
+      for(i=0; i<2; i++){
+        int addr = pLoop->addrOpenEphm[i];
+        if( addr<0 ){
+          /* If [0] is unused then [1] is also unused.  So we can
+          ** always safely abort as soon as the first unused slot is found */
+          assert( pLoop->addrOpenEphm[1]<0 );
+          break;
+        }
+        sqlite3VdbeChangeP2(v, addr, nCol);
+        sqlite3VdbeChangeP4(v, addr, (char*)pKeyInfo, P4_KEYINFO);
+        pLoop->addrOpenEphm[i] = -1;
+      }
+    }
+    sqlite3DbFree(db, pKeyInfo);
+  }
+
+multi_select_end:
+  pDest->iMem = dest.iMem;
+  pDest->nMem = dest.nMem;
+  sqlite3SelectDelete(db, pDelete);
+  return rc;
+}
+#endif /* SQLITE_OMIT_COMPOUND_SELECT */
+
+/*
+** Code an output subroutine for a coroutine implementation of a
+** SELECT statment.
+**
+** The data to be output is contained in pIn->iMem.  There are
+** pIn->nMem columns to be output.  pDest is where the output should
+** be sent.
+**
+** regReturn is the number of the register holding the subroutine
+** return address.
+**
+** If regPrev>0 then it is the first register in a vector that
+** records the previous output.  mem[regPrev] is a flag that is false
+** if there has been no previous output.  If regPrev>0 then code is
+** generated to suppress duplicates.  pKeyInfo is used for comparing
+** keys.
+**
+** If the LIMIT found in p->iLimit is reached, jump immediately to
+** iBreak.
+*/
+static int generateOutputSubroutine(
+  Parse *pParse,          /* Parsing context */
+  Select *p,              /* The SELECT statement */
+  SelectDest *pIn,        /* Coroutine supplying data */
+  SelectDest *pDest,      /* Where to send the data */
+  int regReturn,          /* The return address register */
+  int regPrev,            /* Previous result register.  No uniqueness if 0 */
+  KeyInfo *pKeyInfo,      /* For comparing with previous entry */
+  int p4type,             /* The p4 type for pKeyInfo */
+  int iBreak              /* Jump here if we hit the LIMIT */
+){
+  Vdbe *v = pParse->pVdbe;
+  int iContinue;
+  int addr;
+
+  addr = sqlite3VdbeCurrentAddr(v);
+  iContinue = sqlite3VdbeMakeLabel(v);
+
+  /* Suppress duplicates for UNION, EXCEPT, and INTERSECT 
+  */
+  if( regPrev ){
+    int j1, j2;
+    j1 = sqlite3VdbeAddOp1(v, OP_IfNot, regPrev);
+    j2 = sqlite3VdbeAddOp4(v, OP_Compare, pIn->iMem, regPrev+1, pIn->nMem,
+                              (char*)pKeyInfo, p4type);
+    sqlite3VdbeAddOp3(v, OP_Jump, j2+2, iContinue, j2+2);
+    sqlite3VdbeJumpHere(v, j1);
+    sqlite3ExprCodeCopy(pParse, pIn->iMem, regPrev+1, pIn->nMem);
+    sqlite3VdbeAddOp2(v, OP_Integer, 1, regPrev);
+  }
+  if( pParse->db->mallocFailed ) return 0;
+
+  /* Suppress the the first OFFSET entries if there is an OFFSET clause
+  */
+  codeOffset(v, p, iContinue);
+
+  switch( pDest->eDest ){
+    /* Store the result as data using a unique key.
+    */
+    case SRT_Table:
+    case SRT_EphemTab: {
+      int r1 = sqlite3GetTempReg(pParse);
+      int r2 = sqlite3GetTempReg(pParse);
+      testcase( pDest->eDest==SRT_Table );
+      testcase( pDest->eDest==SRT_EphemTab );
+      sqlite3VdbeAddOp3(v, OP_MakeRecord, pIn->iMem, pIn->nMem, r1);
+      sqlite3VdbeAddOp2(v, OP_NewRowid, pDest->iParm, r2);
+      sqlite3VdbeAddOp3(v, OP_Insert, pDest->iParm, r1, r2);
+      sqlite3VdbeChangeP5(v, OPFLAG_APPEND);
+      sqlite3ReleaseTempReg(pParse, r2);
+      sqlite3ReleaseTempReg(pParse, r1);
+      break;
+    }
+
+#ifndef SQLITE_OMIT_SUBQUERY
+    /* If we are creating a set for an "expr IN (SELECT ...)" construct,
+    ** then there should be a single item on the stack.  Write this
+    ** item into the set table with bogus data.
+    */
+    case SRT_Set: {
+      int r1;
+      assert( pIn->nMem==1 );
+      p->affinity = 
+         sqlite3CompareAffinity(p->pEList->a[0].pExpr, pDest->affinity);
+      r1 = sqlite3GetTempReg(pParse);
+      sqlite3VdbeAddOp4(v, OP_MakeRecord, pIn->iMem, 1, r1, &p->affinity, 1);
+      sqlite3ExprCacheAffinityChange(pParse, pIn->iMem, 1);
+      sqlite3VdbeAddOp2(v, OP_IdxInsert, pDest->iParm, r1);
+      sqlite3ReleaseTempReg(pParse, r1);
+      break;
+    }
+
+#if 0  /* Never occurs on an ORDER BY query */
+    /* If any row exist in the result set, record that fact and abort.
+    */
+    case SRT_Exists: {
+      sqlite3VdbeAddOp2(v, OP_Integer, 1, pDest->iParm);
+      /* The LIMIT clause will terminate the loop for us */
+      break;
+    }
+#endif
+
+    /* If this is a scalar select that is part of an expression, then
+    ** store the results in the appropriate memory cell and break out
+    ** of the scan loop.
+    */
+    case SRT_Mem: {
+      assert( pIn->nMem==1 );
+      sqlite3ExprCodeMove(pParse, pIn->iMem, pDest->iParm, 1);
+      /* The LIMIT clause will jump out of the loop for us */
+      break;
+    }
+#endif /* #ifndef SQLITE_OMIT_SUBQUERY */
+
+    /* The results are stored in a sequence of registers
+    ** starting at pDest->iMem.  Then the co-routine yields.
+    */
+    case SRT_Coroutine: {
+      if( pDest->iMem==0 ){
+        pDest->iMem = sqlite3GetTempRange(pParse, pIn->nMem);
+        pDest->nMem = pIn->nMem;
+      }
+      sqlite3ExprCodeMove(pParse, pIn->iMem, pDest->iMem, pDest->nMem);
+      sqlite3VdbeAddOp1(v, OP_Yield, pDest->iParm);
+      break;
+    }
+
+    /* If none of the above, then the result destination must be
+    ** SRT_Output.  This routine is never called with any other
+    ** destination other than the ones handled above or SRT_Output.
+    **
+    ** For SRT_Output, results are stored in a sequence of registers.  
+    ** Then the OP_ResultRow opcode is used to cause sqlite3_step() to
+    ** return the next row of result.
+    */
+    default: {
+      assert( pDest->eDest==SRT_Output );
+      sqlite3VdbeAddOp2(v, OP_ResultRow, pIn->iMem, pIn->nMem);
+      sqlite3ExprCacheAffinityChange(pParse, pIn->iMem, pIn->nMem);
+      break;
+    }
+  }
+
+  /* Jump to the end of the loop if the LIMIT is reached.
+  */
+  if( p->iLimit ){
+    sqlite3VdbeAddOp3(v, OP_IfZero, p->iLimit, iBreak, -1);
+  }
+
+  /* Generate the subroutine return
+  */
+  sqlite3VdbeResolveLabel(v, iContinue);
+  sqlite3VdbeAddOp1(v, OP_Return, regReturn);
+
+  return addr;
+}
+
+/*
+** Alternative compound select code generator for cases when there
+** is an ORDER BY clause.
+**
+** We assume a query of the following form:
+**
+**      <selectA>  <operator>  <selectB>  ORDER BY <orderbylist>
+**
+** <operator> is one of UNION ALL, UNION, EXCEPT, or INTERSECT.  The idea
+** is to code both <selectA> and <selectB> with the ORDER BY clause as
+** co-routines.  Then run the co-routines in parallel and merge the results
+** into the output.  In addition to the two coroutines (called selectA and
+** selectB) there are 7 subroutines:
+**
+**    outA:    Move the output of the selectA coroutine into the output
+**             of the compound query.
+**
+**    outB:    Move the output of the selectB coroutine into the output
+**             of the compound query.  (Only generated for UNION and
+**             UNION ALL.  EXCEPT and INSERTSECT never output a row that
+**             appears only in B.)
+**
+**    AltB:    Called when there is data from both coroutines and A<B.
+**
+**    AeqB:    Called when there is data from both coroutines and A==B.
+**
+**    AgtB:    Called when there is data from both coroutines and A>B.
+**
+**    EofA:    Called when data is exhausted from selectA.
+**
+**    EofB:    Called when data is exhausted from selectB.
+**
+** The implementation of the latter five subroutines depend on which 
+** <operator> is used:
+**
+**
+**             UNION ALL         UNION            EXCEPT          INTERSECT
+**          -------------  -----------------  --------------  -----------------
+**   AltB:   outA, nextA      outA, nextA       outA, nextA         nextA
+**
+**   AeqB:   outA, nextA         nextA             nextA         outA, nextA
+**
+**   AgtB:   outB, nextB      outB, nextB          nextB            nextB
+**
+**   EofA:   outB, nextB      outB, nextB          halt             halt
+**
+**   EofB:   outA, nextA      outA, nextA       outA, nextA         halt
+**
+** In the AltB, AeqB, and AgtB subroutines, an EOF on A following nextA
+** causes an immediate jump to EofA and an EOF on B following nextB causes
+** an immediate jump to EofB.  Within EofA and EofB, and EOF on entry or
+** following nextX causes a jump to the end of the select processing.
+**
+** Duplicate removal in the UNION, EXCEPT, and INTERSECT cases is handled
+** within the output subroutine.  The regPrev register set holds the previously
+** output value.  A comparison is made against this value and the output
+** is skipped if the next results would be the same as the previous.
+**
+** The implementation plan is to implement the two coroutines and seven
+** subroutines first, then put the control logic at the bottom.  Like this:
+**
+**          goto Init
+**     coA: coroutine for left query (A)
+**     coB: coroutine for right query (B)
+**    outA: output one row of A
+**    outB: output one row of B (UNION and UNION ALL only)
+**    EofA: ...
+**    EofB: ...
+**    AltB: ...
+**    AeqB: ...
+**    AgtB: ...
+**    Init: initialize coroutine registers
+**          yield coA
+**          if eof(A) goto EofA
+**          yield coB
+**          if eof(B) goto EofB
+**    Cmpr: Compare A, B
+**          Jump AltB, AeqB, AgtB
+**     End: ...
+**
+** We call AltB, AeqB, AgtB, EofA, and EofB "subroutines" but they are not
+** actually called using Gosub and they do not Return.  EofA and EofB loop
+** until all data is exhausted then jump to the "end" labe.  AltB, AeqB,
+** and AgtB jump to either L2 or to one of EofA or EofB.
+*/
+#ifndef SQLITE_OMIT_COMPOUND_SELECT
+static int multiSelectOrderBy(
+  Parse *pParse,        /* Parsing context */
+  Select *p,            /* The right-most of SELECTs to be coded */
+  SelectDest *pDest     /* What to do with query results */
+){
+  int i, j;             /* Loop counters */
+  Select *pPrior;       /* Another SELECT immediately to our left */
+  Vdbe *v;              /* Generate code to this VDBE */
+  SelectDest destA;     /* Destination for coroutine A */
+  SelectDest destB;     /* Destination for coroutine B */
+  int regAddrA;         /* Address register for select-A coroutine */
+  int regEofA;          /* Flag to indicate when select-A is complete */
+  int regAddrB;         /* Address register for select-B coroutine */
+  int regEofB;          /* Flag to indicate when select-B is complete */
+  int addrSelectA;      /* Address of the select-A coroutine */
+  int addrSelectB;      /* Address of the select-B coroutine */
+  int regOutA;          /* Address register for the output-A subroutine */
+  int regOutB;          /* Address register for the output-B subroutine */
+  int addrOutA;         /* Address of the output-A subroutine */
+  int addrOutB = 0;     /* Address of the output-B subroutine */
+  int addrEofA;         /* Address of the select-A-exhausted subroutine */
+  int addrEofB;         /* Address of the select-B-exhausted subroutine */
+  int addrAltB;         /* Address of the A<B subroutine */
+  int addrAeqB;         /* Address of the A==B subroutine */
+  int addrAgtB;         /* Address of the A>B subroutine */
+  int regLimitA;        /* Limit register for select-A */
+  int regLimitB;        /* Limit register for select-A */
+  int regPrev;          /* A range of registers to hold previous output */
+  int savedLimit;       /* Saved value of p->iLimit */
+  int savedOffset;      /* Saved value of p->iOffset */
+  int labelCmpr;        /* Label for the start of the merge algorithm */
+  int labelEnd;         /* Label for the end of the overall SELECT stmt */
+  int j1;               /* Jump instructions that get retargetted */
+  int op;               /* One of TK_ALL, TK_UNION, TK_EXCEPT, TK_INTERSECT */
+  KeyInfo *pKeyDup = 0; /* Comparison information for duplicate removal */
+  KeyInfo *pKeyMerge;   /* Comparison information for merging rows */
+  sqlite3 *db;          /* Database connection */
+  ExprList *pOrderBy;   /* The ORDER BY clause */
+  int nOrderBy;         /* Number of terms in the ORDER BY clause */
+  int *aPermute;        /* Mapping from ORDER BY terms to result set columns */
+#ifndef SQLITE_OMIT_EXPLAIN
+  int iSub1;            /* EQP id of left-hand query */
+  int iSub2;            /* EQP id of right-hand query */
+#endif
+
+  assert( p->pOrderBy!=0 );
+  assert( pKeyDup==0 ); /* "Managed" code needs this.  Ticket #3382. */
+  db = pParse->db;
+  v = pParse->pVdbe;
+  assert( v!=0 );       /* Already thrown the error if VDBE alloc failed */
+  labelEnd = sqlite3VdbeMakeLabel(v);
+  labelCmpr = sqlite3VdbeMakeLabel(v);
+
+
+  /* Patch up the ORDER BY clause
+  */
+  op = p->op;  
+  pPrior = p->pPrior;
+  assert( pPrior->pOrderBy==0 );
+  pOrderBy = p->pOrderBy;
+  assert( pOrderBy );
+  nOrderBy = pOrderBy->nExpr;
+
+  /* For operators other than UNION ALL we have to make sure that
+  ** the ORDER BY clause covers every term of the result set.  Add
+  ** terms to the ORDER BY clause as necessary.
+  */
+  if( op!=TK_ALL ){
+    for(i=1; db->mallocFailed==0 && i<=p->pEList->nExpr; i++){
+      struct ExprList_item *pItem;
+      for(j=0, pItem=pOrderBy->a; j<nOrderBy; j++, pItem++){
+        assert( pItem->iCol>0 );
+        if( pItem->iCol==i ) break;
+      }
+      if( j==nOrderBy ){
+        Expr *pNew = sqlite3Expr(db, TK_INTEGER, 0);
+        if( pNew==0 ) return SQLITE_NOMEM;
+        pNew->flags |= EP_IntValue;
+        pNew->u.iValue = i;
+        pOrderBy = sqlite3ExprListAppend(pParse, pOrderBy, pNew);
+        pOrderBy->a[nOrderBy++].iCol = (u16)i;
+      }
+    }
+  }
+
+  /* Compute the comparison permutation and keyinfo that is used with
+  ** the permutation used to determine if the next
+  ** row of results comes from selectA or selectB.  Also add explicit
+  ** collations to the ORDER BY clause terms so that when the subqueries
+  ** to the right and the left are evaluated, they use the correct
+  ** collation.
+  */
+  aPermute = sqlite3DbMallocRaw(db, sizeof(int)*nOrderBy);
+  if( aPermute ){
+    struct ExprList_item *pItem;
+    for(i=0, pItem=pOrderBy->a; i<nOrderBy; i++, pItem++){
+      assert( pItem->iCol>0  && pItem->iCol<=p->pEList->nExpr );
+      aPermute[i] = pItem->iCol - 1;
+    }
+    pKeyMerge =
+      sqlite3DbMallocRaw(db, sizeof(*pKeyMerge)+nOrderBy*(sizeof(CollSeq*)+1));
+    if( pKeyMerge ){
+      pKeyMerge->aSortOrder = (u8*)&pKeyMerge->aColl[nOrderBy];
+      pKeyMerge->nField = (u16)nOrderBy;
+      pKeyMerge->enc = ENC(db);
+      for(i=0; i<nOrderBy; i++){
+        CollSeq *pColl;
+        Expr *pTerm = pOrderBy->a[i].pExpr;
+        if( pTerm->flags & EP_ExpCollate ){
+          pColl = pTerm->pColl;
+        }else{
+          pColl = multiSelectCollSeq(pParse, p, aPermute[i]);
+          pTerm->flags |= EP_ExpCollate;
+          pTerm->pColl = pColl;
+        }
+        pKeyMerge->aColl[i] = pColl;
+        pKeyMerge->aSortOrder[i] = pOrderBy->a[i].sortOrder;
+      }
+    }
+  }else{
+    pKeyMerge = 0;
+  }
+
+  /* Reattach the ORDER BY clause to the query.
+  */
+  p->pOrderBy = pOrderBy;
+  pPrior->pOrderBy = sqlite3ExprListDup(pParse->db, pOrderBy, 0);
+
+  /* Allocate a range of temporary registers and the KeyInfo needed
+  ** for the logic that removes duplicate result rows when the
+  ** operator is UNION, EXCEPT, or INTERSECT (but not UNION ALL).
+  */
+  if( op==TK_ALL ){
+    regPrev = 0;
+  }else{
+    int nExpr = p->pEList->nExpr;
+    assert( nOrderBy>=nExpr || db->mallocFailed );
+    regPrev = sqlite3GetTempRange(pParse, nExpr+1);
+    sqlite3VdbeAddOp2(v, OP_Integer, 0, regPrev);
+    pKeyDup = sqlite3DbMallocZero(db,
+                  sizeof(*pKeyDup) + nExpr*(sizeof(CollSeq*)+1) );
+    if( pKeyDup ){
+      pKeyDup->aSortOrder = (u8*)&pKeyDup->aColl[nExpr];
+      pKeyDup->nField = (u16)nExpr;
+      pKeyDup->enc = ENC(db);
+      for(i=0; i<nExpr; i++){
+        pKeyDup->aColl[i] = multiSelectCollSeq(pParse, p, i);
+        pKeyDup->aSortOrder[i] = 0;
+      }
+    }
+  }
+ 
+  /* Separate the left and the right query from one another
+  */
+  p->pPrior = 0;
+  sqlite3ResolveOrderGroupBy(pParse, p, p->pOrderBy, "ORDER");
+  if( pPrior->pPrior==0 ){
+    sqlite3ResolveOrderGroupBy(pParse, pPrior, pPrior->pOrderBy, "ORDER");
+  }
+
+  /* Compute the limit registers */
+  computeLimitRegisters(pParse, p, labelEnd);
+  if( p->iLimit && op==TK_ALL ){
+    regLimitA = ++pParse->nMem;
+    regLimitB = ++pParse->nMem;
+    sqlite3VdbeAddOp2(v, OP_Copy, p->iOffset ? p->iOffset+1 : p->iLimit,
+                                  regLimitA);
+    sqlite3VdbeAddOp2(v, OP_Copy, regLimitA, regLimitB);
+  }else{
+    regLimitA = regLimitB = 0;
+  }
+  sqlite3ExprDelete(db, p->pLimit);
+  p->pLimit = 0;
+  sqlite3ExprDelete(db, p->pOffset);
+  p->pOffset = 0;
+
+  regAddrA = ++pParse->nMem;
+  regEofA = ++pParse->nMem;
+  regAddrB = ++pParse->nMem;
+  regEofB = ++pParse->nMem;
+  regOutA = ++pParse->nMem;
+  regOutB = ++pParse->nMem;
+  sqlite3SelectDestInit(&destA, SRT_Coroutine, regAddrA);
+  sqlite3SelectDestInit(&destB, SRT_Coroutine, regAddrB);
+
+  /* Jump past the various subroutines and coroutines to the main
+  ** merge loop
+  */
+  j1 = sqlite3VdbeAddOp0(v, OP_Goto);
+  addrSelectA = sqlite3VdbeCurrentAddr(v);
+
+
+  /* Generate a coroutine to evaluate the SELECT statement to the
+  ** left of the compound operator - the "A" select.
+  */
+  VdbeNoopComment((v, "Begin coroutine for left SELECT"));
+  pPrior->iLimit = regLimitA;
+  explainSetInteger(iSub1, pParse->iNextSelectId);
+  sqlite3Select(pParse, pPrior, &destA);
+  sqlite3VdbeAddOp2(v, OP_Integer, 1, regEofA);
+  sqlite3VdbeAddOp1(v, OP_Yield, regAddrA);
+  VdbeNoopComment((v, "End coroutine for left SELECT"));
+
+  /* Generate a coroutine to evaluate the SELECT statement on 
+  ** the right - the "B" select
+  */
+  addrSelectB = sqlite3VdbeCurrentAddr(v);
+  VdbeNoopComment((v, "Begin coroutine for right SELECT"));
+  savedLimit = p->iLimit;
+  savedOffset = p->iOffset;
+  p->iLimit = regLimitB;
+  p->iOffset = 0;  
+  explainSetInteger(iSub2, pParse->iNextSelectId);
+  sqlite3Select(pParse, p, &destB);
+  p->iLimit = savedLimit;
+  p->iOffset = savedOffset;
+  sqlite3VdbeAddOp2(v, OP_Integer, 1, regEofB);
+  sqlite3VdbeAddOp1(v, OP_Yield, regAddrB);
+  VdbeNoopComment((v, "End coroutine for right SELECT"));
+
+  /* Generate a subroutine that outputs the current row of the A
+  ** select as the next output row of the compound select.
+  */
+  VdbeNoopComment((v, "Output routine for A"));
+  addrOutA = generateOutputSubroutine(pParse,
+                 p, &destA, pDest, regOutA,
+                 regPrev, pKeyDup, P4_KEYINFO_HANDOFF, labelEnd);
+  
+  /* Generate a subroutine that outputs the current row of the B
+  ** select as the next output row of the compound select.
+  */
+  if( op==TK_ALL || op==TK_UNION ){
+    VdbeNoopComment((v, "Output routine for B"));
+    addrOutB = generateOutputSubroutine(pParse,
+                 p, &destB, pDest, regOutB,
+                 regPrev, pKeyDup, P4_KEYINFO_STATIC, labelEnd);
+  }
+
+  /* Generate a subroutine to run when the results from select A
+  ** are exhausted and only data in select B remains.
+  */
+  VdbeNoopComment((v, "eof-A subroutine"));
+  if( op==TK_EXCEPT || op==TK_INTERSECT ){
+    addrEofA = sqlite3VdbeAddOp2(v, OP_Goto, 0, labelEnd);
+  }else{  
+    addrEofA = sqlite3VdbeAddOp2(v, OP_If, regEofB, labelEnd);
+    sqlite3VdbeAddOp2(v, OP_Gosub, regOutB, addrOutB);
+    sqlite3VdbeAddOp1(v, OP_Yield, regAddrB);
+    sqlite3VdbeAddOp2(v, OP_Goto, 0, addrEofA);
+    p->nSelectRow += pPrior->nSelectRow;
+  }
+
+  /* Generate a subroutine to run when the results from select B
+  ** are exhausted and only data in select A remains.
+  */
+  if( op==TK_INTERSECT ){
+    addrEofB = addrEofA;
+    if( p->nSelectRow > pPrior->nSelectRow ) p->nSelectRow = pPrior->nSelectRow;
+  }else{  
+    VdbeNoopComment((v, "eof-B subroutine"));
+    addrEofB = sqlite3VdbeAddOp2(v, OP_If, regEofA, labelEnd);
+    sqlite3VdbeAddOp2(v, OP_Gosub, regOutA, addrOutA);
+    sqlite3VdbeAddOp1(v, OP_Yield, regAddrA);
+    sqlite3VdbeAddOp2(v, OP_Goto, 0, addrEofB);
+  }
+
+  /* Generate code to handle the case of A<B
+  */
+  VdbeNoopComment((v, "A-lt-B subroutine"));
+  addrAltB = sqlite3VdbeAddOp2(v, OP_Gosub, regOutA, addrOutA);
+  sqlite3VdbeAddOp1(v, OP_Yield, regAddrA);
+  sqlite3VdbeAddOp2(v, OP_If, regEofA, addrEofA);
+  sqlite3VdbeAddOp2(v, OP_Goto, 0, labelCmpr);
+
+  /* Generate code to handle the case of A==B
+  */
+  if( op==TK_ALL ){
+    addrAeqB = addrAltB;
+  }else if( op==TK_INTERSECT ){
+    addrAeqB = addrAltB;
+    addrAltB++;
+  }else{
+    VdbeNoopComment((v, "A-eq-B subroutine"));
+    addrAeqB =
+    sqlite3VdbeAddOp1(v, OP_Yield, regAddrA);
+    sqlite3VdbeAddOp2(v, OP_If, regEofA, addrEofA);
+    sqlite3VdbeAddOp2(v, OP_Goto, 0, labelCmpr);
+  }
+
+  /* Generate code to handle the case of A>B
+  */
+  VdbeNoopComment((v, "A-gt-B subroutine"));
+  addrAgtB = sqlite3VdbeCurrentAddr(v);
+  if( op==TK_ALL || op==TK_UNION ){
+    sqlite3VdbeAddOp2(v, OP_Gosub, regOutB, addrOutB);
+  }
+  sqlite3VdbeAddOp1(v, OP_Yield, regAddrB);
+  sqlite3VdbeAddOp2(v, OP_If, regEofB, addrEofB);
+  sqlite3VdbeAddOp2(v, OP_Goto, 0, labelCmpr);
+
+  /* This code runs once to initialize everything.
+  */
+  sqlite3VdbeJumpHere(v, j1);
+  sqlite3VdbeAddOp2(v, OP_Integer, 0, regEofA);
+  sqlite3VdbeAddOp2(v, OP_Integer, 0, regEofB);
+  sqlite3VdbeAddOp2(v, OP_Gosub, regAddrA, addrSelectA);
+  sqlite3VdbeAddOp2(v, OP_Gosub, regAddrB, addrSelectB);
+  sqlite3VdbeAddOp2(v, OP_If, regEofA, addrEofA);
+  sqlite3VdbeAddOp2(v, OP_If, regEofB, addrEofB);
+
+  /* Implement the main merge loop
+  */
+  sqlite3VdbeResolveLabel(v, labelCmpr);
+  sqlite3VdbeAddOp4(v, OP_Permutation, 0, 0, 0, (char*)aPermute, P4_INTARRAY);
+  sqlite3VdbeAddOp4(v, OP_Compare, destA.iMem, destB.iMem, nOrderBy,
+                         (char*)pKeyMerge, P4_KEYINFO_HANDOFF);
+  sqlite3VdbeAddOp3(v, OP_Jump, addrAltB, addrAeqB, addrAgtB);
+
+  /* Release temporary registers
+  */
+  if( regPrev ){
+    sqlite3ReleaseTempRange(pParse, regPrev, nOrderBy+1);
+  }
+
+  /* Jump to the this point in order to terminate the query.
+  */
+  sqlite3VdbeResolveLabel(v, labelEnd);
+
+  /* Set the number of output columns
+  */
+  if( pDest->eDest==SRT_Output ){
+    Select *pFirst = pPrior;
+    while( pFirst->pPrior ) pFirst = pFirst->pPrior;
+    generateColumnNames(pParse, 0, pFirst->pEList);
+  }
+
+  /* Reassembly the compound query so that it will be freed correctly
+  ** by the calling function */
+  if( p->pPrior ){
+    sqlite3SelectDelete(db, p->pPrior);
+  }
+  p->pPrior = pPrior;
+
+  /*** TBD:  Insert subroutine calls to close cursors on incomplete
+  **** subqueries ****/
+  explainComposite(pParse, p->op, iSub1, iSub2, 0);
+  return SQLITE_OK;
+}
+#endif
+
+#if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
+/* Forward Declarations */
+static void substExprList(sqlite3*, ExprList*, int, ExprList*);
+static void substSelect(sqlite3*, Select *, int, ExprList *);
+
+/*
+** Scan through the expression pExpr.  Replace every reference to
+** a column in table number iTable with a copy of the iColumn-th
+** entry in pEList.  (But leave references to the ROWID column 
+** unchanged.)
+**
+** This routine is part of the flattening procedure.  A subquery
+** whose result set is defined by pEList appears as entry in the
+** FROM clause of a SELECT such that the VDBE cursor assigned to that
+** FORM clause entry is iTable.  This routine make the necessary 
+** changes to pExpr so that it refers directly to the source table
+** of the subquery rather the result set of the subquery.
+*/
+static Expr *substExpr(
+  sqlite3 *db,        /* Report malloc errors to this connection */
+  Expr *pExpr,        /* Expr in which substitution occurs */
+  int iTable,         /* Table to be substituted */
+  ExprList *pEList    /* Substitute expressions */
+){
+  if( pExpr==0 ) return 0;
+  if( pExpr->op==TK_COLUMN && pExpr->iTable==iTable ){
+    if( pExpr->iColumn<0 ){
+      pExpr->op = TK_NULL;
+    }else{
+      Expr *pNew;
+      assert( pEList!=0 && pExpr->iColumn<pEList->nExpr );
+      assert( pExpr->pLeft==0 && pExpr->pRight==0 );
+      pNew = sqlite3ExprDup(db, pEList->a[pExpr->iColumn].pExpr, 0);
+      if( pNew && pExpr->pColl ){
+        pNew->pColl = pExpr->pColl;
+      }
+      sqlite3ExprDelete(db, pExpr);
+      pExpr = pNew;
+    }
+  }else{
+    pExpr->pLeft = substExpr(db, pExpr->pLeft, iTable, pEList);
+    pExpr->pRight = substExpr(db, pExpr->pRight, iTable, pEList);
+    if( ExprHasProperty(pExpr, EP_xIsSelect) ){
+      substSelect(db, pExpr->x.pSelect, iTable, pEList);
+    }else{
+      substExprList(db, pExpr->x.pList, iTable, pEList);
+    }
+  }
+  return pExpr;
+}
+static void substExprList(
+  sqlite3 *db,         /* Report malloc errors here */
+  ExprList *pList,     /* List to scan and in which to make substitutes */
+  int iTable,          /* Table to be substituted */
+  ExprList *pEList     /* Substitute values */
+){
+  int i;
+  if( pList==0 ) return;
+  for(i=0; i<pList->nExpr; i++){
+    pList->a[i].pExpr = substExpr(db, pList->a[i].pExpr, iTable, pEList);
+  }
+}
+static void substSelect(
+  sqlite3 *db,         /* Report malloc errors here */
+  Select *p,           /* SELECT statement in which to make substitutions */
+  int iTable,          /* Table to be replaced */
+  ExprList *pEList     /* Substitute values */
+){
+  SrcList *pSrc;
+  struct SrcList_item *pItem;
+  int i;
+  if( !p ) return;
+  substExprList(db, p->pEList, iTable, pEList);
+  substExprList(db, p->pGroupBy, iTable, pEList);
+  substExprList(db, p->pOrderBy, iTable, pEList);
+  p->pHaving = substExpr(db, p->pHaving, iTable, pEList);
+  p->pWhere = substExpr(db, p->pWhere, iTable, pEList);
+  substSelect(db, p->pPrior, iTable, pEList);
+  pSrc = p->pSrc;
+  assert( pSrc );  /* Even for (SELECT 1) we have: pSrc!=0 but pSrc->nSrc==0 */
+  if( ALWAYS(pSrc) ){
+    for(i=pSrc->nSrc, pItem=pSrc->a; i>0; i--, pItem++){
+      substSelect(db, pItem->pSelect, iTable, pEList);
+    }
+  }
+}
+#endif /* !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW) */
+
+#if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
+/*
+** This routine attempts to flatten subqueries in order to speed
+** execution.  It returns 1 if it makes changes and 0 if no flattening
+** occurs.
+**
+** To understand the concept of flattening, consider the following
+** query:
+**
+**     SELECT a FROM (SELECT x+y AS a FROM t1 WHERE z<100) WHERE a>5
+**
+** The default way of implementing this query is to execute the
+** subquery first and store the results in a temporary table, then
+** run the outer query on that temporary table.  This requires two
+** passes over the data.  Furthermore, because the temporary table
+** has no indices, the WHERE clause on the outer query cannot be
+** optimized.
+**
+** This routine attempts to rewrite queries such as the above into
+** a single flat select, like this:
+**
+**     SELECT x+y AS a FROM t1 WHERE z<100 AND a>5
+**
+** The code generated for this simpification gives the same result
+** but only has to scan the data once.  And because indices might 
+** exist on the table t1, a complete scan of the data might be
+** avoided.
+**
+** Flattening is only attempted if all of the following are true:
+**
+**   (1)  The subquery and the outer query do not both use aggregates.
+**
+**   (2)  The subquery is not an aggregate or the outer query is not a join.
+**
+**   (3)  The subquery is not the right operand of a left outer join
+**        (Originally ticket #306.  Strengthened by ticket #3300)
+**
+**   (4)  The subquery is not DISTINCT.
+**
+**  (**)  At one point restrictions (4) and (5) defined a subset of DISTINCT
+**        sub-queries that were excluded from this optimization. Restriction 
+**        (4) has since been expanded to exclude all DISTINCT subqueries.
+**
+**   (6)  The subquery does not use aggregates or the outer query is not
+**        DISTINCT.
+**
+**   (7)  The subquery has a FROM clause.
+**
+**   (8)  The subquery does not use LIMIT or the outer query is not a join.
+**
+**   (9)  The subquery does not use LIMIT or the outer query does not use
+**        aggregates.
+**
+**  (10)  The subquery does not use aggregates or the outer query does not
+**        use LIMIT.
+**
+**  (11)  The subquery and the outer query do not both have ORDER BY clauses.
+**
+**  (**)  Not implemented.  Subsumed into restriction (3).  Was previously
+**        a separate restriction deriving from ticket #350.
+**
+**  (13)  The subquery and outer query do not both use LIMIT.
+**
+**  (14)  The subquery does not use OFFSET.
+**
+**  (15)  The outer query is not part of a compound select or the
+**        subquery does not have a LIMIT clause.
+**        (See ticket #2339 and ticket [02a8e81d44]).
+**
+**  (16)  The outer query is not an aggregate or the subquery does
+**        not contain ORDER BY.  (Ticket #2942)  This used to not matter
+**        until we introduced the group_concat() function.  
+**
+**  (17)  The sub-query is not a compound select, or it is a UNION ALL 
+**        compound clause made up entirely of non-aggregate queries, and 
+**        the parent query:
+**
+**          * is not itself part of a compound select,
+**          * is not an aggregate or DISTINCT query, and
+**          * has no other tables or sub-selects in the FROM clause.
+**
+**        The parent and sub-query may contain WHERE clauses. Subject to
+**        rules (11), (13) and (14), they may also contain ORDER BY,
+**        LIMIT and OFFSET clauses.
+**
+**  (18)  If the sub-query is a compound select, then all terms of the
+**        ORDER by clause of the parent must be simple references to 
+**        columns of the sub-query.
+**
+**  (19)  The subquery does not use LIMIT or the outer query does not
+**        have a WHERE clause.
+**
+**  (20)  If the sub-query is a compound select, then it must not use
+**        an ORDER BY clause.  Ticket #3773.  We could relax this constraint
+**        somewhat by saying that the terms of the ORDER BY clause must
+**        appear as unmodified result columns in the outer query.  But
+**        have other optimizations in mind to deal with that case.
+**
+**  (21)  The subquery does not use LIMIT or the outer query is not
+**        DISTINCT.  (See ticket [752e1646fc]).
+**
+** In this routine, the "p" parameter is a pointer to the outer query.
+** The subquery is p->pSrc->a[iFrom].  isAgg is true if the outer query
+** uses aggregates and subqueryIsAgg is true if the subquery uses aggregates.
+**
+** If flattening is not attempted, this routine is a no-op and returns 0.
+** If flattening is attempted this routine returns 1.
+**
+** All of the expression analysis must occur on both the outer query and
+** the subquery before this routine runs.
+*/
+static int flattenSubquery(
+  Parse *pParse,       /* Parsing context */
+  Select *p,           /* The parent or outer SELECT statement */
+  int iFrom,           /* Index in p->pSrc->a[] of the inner subquery */
+  int isAgg,           /* True if outer SELECT uses aggregate functions */
+  int subqueryIsAgg    /* True if the subquery uses aggregate functions */
+){
+  const char *zSavedAuthContext = pParse->zAuthContext;
+  Select *pParent;
+  Select *pSub;       /* The inner query or "subquery" */
+  Select *pSub1;      /* Pointer to the rightmost select in sub-query */
+  SrcList *pSrc;      /* The FROM clause of the outer query */
+  SrcList *pSubSrc;   /* The FROM clause of the subquery */
+  ExprList *pList;    /* The result set of the outer query */
+  int iParent;        /* VDBE cursor number of the pSub result set temp table */
+  int i;              /* Loop counter */
+  Expr *pWhere;                    /* The WHERE clause */
+  struct SrcList_item *pSubitem;   /* The subquery */
+  sqlite3 *db = pParse->db;
+
+  /* Check to see if flattening is permitted.  Return 0 if not.
+  */
+  assert( p!=0 );
+  assert( p->pPrior==0 );  /* Unable to flatten compound queries */
+  if( db->flags & SQLITE_QueryFlattener ) return 0;
+  pSrc = p->pSrc;
+  assert( pSrc && iFrom>=0 && iFrom<pSrc->nSrc );
+  pSubitem = &pSrc->a[iFrom];
+  iParent = pSubitem->iCursor;
+  pSub = pSubitem->pSelect;
+  assert( pSub!=0 );
+  if( isAgg && subqueryIsAgg ) return 0;                 /* Restriction (1)  */
+  if( subqueryIsAgg && pSrc->nSrc>1 ) return 0;          /* Restriction (2)  */
+  pSubSrc = pSub->pSrc;
+  assert( pSubSrc );
+  /* Prior to version 3.1.2, when LIMIT and OFFSET had to be simple constants,
+  ** not arbitrary expresssions, we allowed some combining of LIMIT and OFFSET
+  ** because they could be computed at compile-time.  But when LIMIT and OFFSET
+  ** became arbitrary expressions, we were forced to add restrictions (13)
+  ** and (14). */
+  if( pSub->pLimit && p->pLimit ) return 0;              /* Restriction (13) */
+  if( pSub->pOffset ) return 0;                          /* Restriction (14) */
+  if( p->pRightmost && pSub->pLimit ){
+    return 0;                                            /* Restriction (15) */
+  }
+  if( pSubSrc->nSrc==0 ) return 0;                       /* Restriction (7)  */
+  if( pSub->selFlags & SF_Distinct ) return 0;           /* Restriction (5)  */
+  if( pSub->pLimit && (pSrc->nSrc>1 || isAgg) ){
+     return 0;         /* Restrictions (8)(9) */
+  }
+  if( (p->selFlags & SF_Distinct)!=0 && subqueryIsAgg ){
+     return 0;         /* Restriction (6)  */
+  }
+  if( p->pOrderBy && pSub->pOrderBy ){
+     return 0;                                           /* Restriction (11) */
+  }
+  if( isAgg && pSub->pOrderBy ) return 0;                /* Restriction (16) */
+  if( pSub->pLimit && p->pWhere ) return 0;              /* Restriction (19) */
+  if( pSub->pLimit && (p->selFlags & SF_Distinct)!=0 ){
+     return 0;         /* Restriction (21) */
+  }
+
+  /* OBSOLETE COMMENT 1:
+  ** Restriction 3:  If the subquery is a join, make sure the subquery is 
+  ** not used as the right operand of an outer join.  Examples of why this
+  ** is not allowed:
+  **
+  **         t1 LEFT OUTER JOIN (t2 JOIN t3)
+  **
+  ** If we flatten the above, we would get
+  **
+  **         (t1 LEFT OUTER JOIN t2) JOIN t3
+  **
+  ** which is not at all the same thing.
+  **
+  ** OBSOLETE COMMENT 2:
+  ** Restriction 12:  If the subquery is the right operand of a left outer
+  ** join, make sure the subquery has no WHERE clause.
+  ** An examples of why this is not allowed:
+  **
+  **         t1 LEFT OUTER JOIN (SELECT * FROM t2 WHERE t2.x>0)
+  **
+  ** If we flatten the above, we would get
+  **
+  **         (t1 LEFT OUTER JOIN t2) WHERE t2.x>0
+  **
+  ** But the t2.x>0 test will always fail on a NULL row of t2, which
+  ** effectively converts the OUTER JOIN into an INNER JOIN.
+  **
+  ** THIS OVERRIDES OBSOLETE COMMENTS 1 AND 2 ABOVE:
+  ** Ticket #3300 shows that flattening the right term of a LEFT JOIN
+  ** is fraught with danger.  Best to avoid the whole thing.  If the
+  ** subquery is the right term of a LEFT JOIN, then do not flatten.
+  */
+  if( (pSubitem->jointype & JT_OUTER)!=0 ){
+    return 0;
+  }
+
+  /* Restriction 17: If the sub-query is a compound SELECT, then it must
+  ** use only the UNION ALL operator. And none of the simple select queries
+  ** that make up the compound SELECT are allowed to be aggregate or distinct
+  ** queries.
+  */
+  if( pSub->pPrior ){
+    if( pSub->pOrderBy ){
+      return 0;  /* Restriction 20 */
+    }
+    if( isAgg || (p->selFlags & SF_Distinct)!=0 || pSrc->nSrc!=1 ){
+      return 0;
+    }
+    for(pSub1=pSub; pSub1; pSub1=pSub1->pPrior){
+      testcase( (pSub1->selFlags & (SF_Distinct|SF_Aggregate))==SF_Distinct );
+      testcase( (pSub1->selFlags & (SF_Distinct|SF_Aggregate))==SF_Aggregate );
+      if( (pSub1->selFlags & (SF_Distinct|SF_Aggregate))!=0
+       || (pSub1->pPrior && pSub1->op!=TK_ALL) 
+       || NEVER(pSub1->pSrc==0) || pSub1->pSrc->nSrc!=1
+      ){
+        return 0;
+      }
+    }
+
+    /* Restriction 18. */
+    if( p->pOrderBy ){
+      int ii;
+      for(ii=0; ii<p->pOrderBy->nExpr; ii++){
+        if( p->pOrderBy->a[ii].iCol==0 ) return 0;
+      }
+    }
+  }
+
+  /***** If we reach this point, flattening is permitted. *****/
+
+  /* Authorize the subquery */
+  pParse->zAuthContext = pSubitem->zName;
+  sqlite3AuthCheck(pParse, SQLITE_SELECT, 0, 0, 0);
+  pParse->zAuthContext = zSavedAuthContext;
+
+  /* If the sub-query is a compound SELECT statement, then (by restrictions
+  ** 17 and 18 above) it must be a UNION ALL and the parent query must 
+  ** be of the form:
+  **
+  **     SELECT <expr-list> FROM (<sub-query>) <where-clause> 
+  **
+  ** followed by any ORDER BY, LIMIT and/or OFFSET clauses. This block
+  ** creates N-1 copies of the parent query without any ORDER BY, LIMIT or 
+  ** OFFSET clauses and joins them to the left-hand-side of the original
+  ** using UNION ALL operators. In this case N is the number of simple
+  ** select statements in the compound sub-query.
+  **
+  ** Example:
+  **
+  **     SELECT a+1 FROM (
+  **        SELECT x FROM tab
+  **        UNION ALL
+  **        SELECT y FROM tab
+  **        UNION ALL
+  **        SELECT abs(z*2) FROM tab2
+  **     ) WHERE a!=5 ORDER BY 1
+  **
+  ** Transformed into:
+  **
+  **     SELECT x+1 FROM tab WHERE x+1!=5
+  **     UNION ALL
+  **     SELECT y+1 FROM tab WHERE y+1!=5
+  **     UNION ALL
+  **     SELECT abs(z*2)+1 FROM tab2 WHERE abs(z*2)+1!=5
+  **     ORDER BY 1
+  **
+  ** We call this the "compound-subquery flattening".
+  */
+  for(pSub=pSub->pPrior; pSub; pSub=pSub->pPrior){
+    Select *pNew;
+    ExprList *pOrderBy = p->pOrderBy;
+    Expr *pLimit = p->pLimit;
+    Select *pPrior = p->pPrior;
+    p->pOrderBy = 0;
+    p->pSrc = 0;
+    p->pPrior = 0;
+    p->pLimit = 0;
+    pNew = sqlite3SelectDup(db, p, 0);
+    p->pLimit = pLimit;
+    p->pOrderBy = pOrderBy;
+    p->pSrc = pSrc;
+    p->op = TK_ALL;
+    p->pRightmost = 0;
+    if( pNew==0 ){
+      pNew = pPrior;
+    }else{
+      pNew->pPrior = pPrior;
+      pNew->pRightmost = 0;
+    }
+    p->pPrior = pNew;
+    if( db->mallocFailed ) return 1;
+  }
+
+  /* Begin flattening the iFrom-th entry of the FROM clause 
+  ** in the outer query.
+  */
+  pSub = pSub1 = pSubitem->pSelect;
+
+  /* Delete the transient table structure associated with the
+  ** subquery
+  */
+  sqlite3DbFree(db, pSubitem->zDatabase);
+  sqlite3DbFree(db, pSubitem->zName);
+  sqlite3DbFree(db, pSubitem->zAlias);
+  pSubitem->zDatabase = 0;
+  pSubitem->zName = 0;
+  pSubitem->zAlias = 0;
+  pSubitem->pSelect = 0;
+
+  /* Defer deleting the Table object associated with the
+  ** subquery until code generation is
+  ** complete, since there may still exist Expr.pTab entries that
+  ** refer to the subquery even after flattening.  Ticket #3346.
+  **
+  ** pSubitem->pTab is always non-NULL by test restrictions and tests above.
+  */
+  if( ALWAYS(pSubitem->pTab!=0) ){
+    Table *pTabToDel = pSubitem->pTab;
+    if( pTabToDel->nRef==1 ){
+      Parse *pToplevel = sqlite3ParseToplevel(pParse);
+      pTabToDel->pNextZombie = pToplevel->pZombieTab;
+      pToplevel->pZombieTab = pTabToDel;
+    }else{
+      pTabToDel->nRef--;
+    }
+    pSubitem->pTab = 0;
+  }
+
+  /* The following loop runs once for each term in a compound-subquery
+  ** flattening (as described above).  If we are doing a different kind
+  ** of flattening - a flattening other than a compound-subquery flattening -
+  ** then this loop only runs once.
+  **
+  ** This loop moves all of the FROM elements of the subquery into the
+  ** the FROM clause of the outer query.  Before doing this, remember
+  ** the cursor number for the original outer query FROM element in
+  ** iParent.  The iParent cursor will never be used.  Subsequent code
+  ** will scan expressions looking for iParent references and replace
+  ** those references with expressions that resolve to the subquery FROM
+  ** elements we are now copying in.
+  */
+  for(pParent=p; pParent; pParent=pParent->pPrior, pSub=pSub->pPrior){
+    int nSubSrc;
+    u8 jointype = 0;
+    pSubSrc = pSub->pSrc;     /* FROM clause of subquery */
+    nSubSrc = pSubSrc->nSrc;  /* Number of terms in subquery FROM clause */
+    pSrc = pParent->pSrc;     /* FROM clause of the outer query */
+
+    if( pSrc ){
+      assert( pParent==p );  /* First time through the loop */
+      jointype = pSubitem->jointype;
+    }else{
+      assert( pParent!=p );  /* 2nd and subsequent times through the loop */
+      pSrc = pParent->pSrc = sqlite3SrcListAppend(db, 0, 0, 0);
+      if( pSrc==0 ){
+        assert( db->mallocFailed );
+        break;
+      }
+    }
+
+    /* The subquery uses a single slot of the FROM clause of the outer
+    ** query.  If the subquery has more than one element in its FROM clause,
+    ** then expand the outer query to make space for it to hold all elements
+    ** of the subquery.
+    **
+    ** Example:
+    **
+    **    SELECT * FROM tabA, (SELECT * FROM sub1, sub2), tabB;
+    **
+    ** The outer query has 3 slots in its FROM clause.  One slot of the
+    ** outer query (the middle slot) is used by the subquery.  The next
+    ** block of code will expand the out query to 4 slots.  The middle
+    ** slot is expanded to two slots in order to make space for the
+    ** two elements in the FROM clause of the subquery.
+    */
+    if( nSubSrc>1 ){
+      pParent->pSrc = pSrc = sqlite3SrcListEnlarge(db, pSrc, nSubSrc-1,iFrom+1);
+      if( db->mallocFailed ){
+        break;
+      }
+    }
+
+    /* Transfer the FROM clause terms from the subquery into the
+    ** outer query.
+    */
+    for(i=0; i<nSubSrc; i++){
+      sqlite3IdListDelete(db, pSrc->a[i+iFrom].pUsing);
+      pSrc->a[i+iFrom] = pSubSrc->a[i];
+      memset(&pSubSrc->a[i], 0, sizeof(pSubSrc->a[i]));
+    }
+    pSrc->a[iFrom].jointype = jointype;
+  
+    /* Now begin substituting subquery result set expressions for 
+    ** references to the iParent in the outer query.
+    ** 
+    ** Example:
+    **
+    **   SELECT a+5, b*10 FROM (SELECT x*3 AS a, y+10 AS b FROM t1) WHERE a>b;
+    **   \                     \_____________ subquery __________/          /
+    **    \_____________________ outer query ______________________________/
+    **
+    ** We look at every expression in the outer query and every place we see
+    ** "a" we substitute "x*3" and every place we see "b" we substitute "y+10".
+    */
+    pList = pParent->pEList;
+    for(i=0; i<pList->nExpr; i++){
+      if( pList->a[i].zName==0 ){
+        const char *zSpan = pList->a[i].zSpan;
+        if( ALWAYS(zSpan) ){
+          pList->a[i].zName = sqlite3DbStrDup(db, zSpan);
+        }
+      }
+    }
+    substExprList(db, pParent->pEList, iParent, pSub->pEList);
+    if( isAgg ){
+      substExprList(db, pParent->pGroupBy, iParent, pSub->pEList);
+      pParent->pHaving = substExpr(db, pParent->pHaving, iParent, pSub->pEList);
+    }
+    if( pSub->pOrderBy ){
+      assert( pParent->pOrderBy==0 );
+      pParent->pOrderBy = pSub->pOrderBy;
+      pSub->pOrderBy = 0;
+    }else if( pParent->pOrderBy ){
+      substExprList(db, pParent->pOrderBy, iParent, pSub->pEList);
+    }
+    if( pSub->pWhere ){
+      pWhere = sqlite3ExprDup(db, pSub->pWhere, 0);
+    }else{
+      pWhere = 0;
+    }
+    if( subqueryIsAgg ){
+      assert( pParent->pHaving==0 );
+      pParent->pHaving = pParent->pWhere;
+      pParent->pWhere = pWhere;
+      pParent->pHaving = substExpr(db, pParent->pHaving, iParent, pSub->pEList);
+      pParent->pHaving = sqlite3ExprAnd(db, pParent->pHaving, 
+                                  sqlite3ExprDup(db, pSub->pHaving, 0));
+      assert( pParent->pGroupBy==0 );
+      pParent->pGroupBy = sqlite3ExprListDup(db, pSub->pGroupBy, 0);
+    }else{
+      pParent->pWhere = substExpr(db, pParent->pWhere, iParent, pSub->pEList);
+      pParent->pWhere = sqlite3ExprAnd(db, pParent->pWhere, pWhere);
+    }
+  
+    /* The flattened query is distinct if either the inner or the
+    ** outer query is distinct. 
+    */
+    pParent->selFlags |= pSub->selFlags & SF_Distinct;
+  
+    /*
+    ** SELECT ... FROM (SELECT ... LIMIT a OFFSET b) LIMIT x OFFSET y;
+    **
+    ** One is tempted to try to add a and b to combine the limits.  But this
+    ** does not work if either limit is negative.
+    */
+    if( pSub->pLimit ){
+      pParent->pLimit = pSub->pLimit;
+      pSub->pLimit = 0;
+    }
+  }
+
+  /* Finially, delete what is left of the subquery and return
+  ** success.
+  */
+  sqlite3SelectDelete(db, pSub1);
+
+  return 1;
+}
+#endif /* !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW) */
+
+/*
+** Analyze the SELECT statement passed as an argument to see if it
+** is a min() or max() query. Return WHERE_ORDERBY_MIN or WHERE_ORDERBY_MAX if 
+** it is, or 0 otherwise. At present, a query is considered to be
+** a min()/max() query if:
+**
+**   1. There is a single object in the FROM clause.
+**
+**   2. There is a single expression in the result set, and it is
+**      either min(x) or max(x), where x is a column reference.
+*/
+static u8 minMaxQuery(Select *p){
+  Expr *pExpr;
+  ExprList *pEList = p->pEList;
+
+  if( pEList->nExpr!=1 ) return WHERE_ORDERBY_NORMAL;
+  pExpr = pEList->a[0].pExpr;
+  if( pExpr->op!=TK_AGG_FUNCTION ) return 0;
+  if( NEVER(ExprHasProperty(pExpr, EP_xIsSelect)) ) return 0;
+  pEList = pExpr->x.pList;
+  if( pEList==0 || pEList->nExpr!=1 ) return 0;
+  if( pEList->a[0].pExpr->op!=TK_AGG_COLUMN ) return WHERE_ORDERBY_NORMAL;
+  assert( !ExprHasProperty(pExpr, EP_IntValue) );
+  if( sqlite3StrICmp(pExpr->u.zToken,"min")==0 ){
+    return WHERE_ORDERBY_MIN;
+  }else if( sqlite3StrICmp(pExpr->u.zToken,"max")==0 ){
+    return WHERE_ORDERBY_MAX;
+  }
+  return WHERE_ORDERBY_NORMAL;
+}
+
+/*
+** The select statement passed as the first argument is an aggregate query.
+** The second argment is the associated aggregate-info object. This 
+** function tests if the SELECT is of the form:
+**
+**   SELECT count(*) FROM <tbl>
+**
+** where table is a database table, not a sub-select or view. If the query
+** does match this pattern, then a pointer to the Table object representing
+** <tbl> is returned. Otherwise, 0 is returned.
+*/
+static Table *isSimpleCount(Select *p, AggInfo *pAggInfo){
+  Table *pTab;
+  Expr *pExpr;
+
+  assert( !p->pGroupBy );
+
+  if( p->pWhere || p->pEList->nExpr!=1 
+   || p->pSrc->nSrc!=1 || p->pSrc->a[0].pSelect
+  ){
+    return 0;
+  }
+  pTab = p->pSrc->a[0].pTab;
+  pExpr = p->pEList->a[0].pExpr;
+  assert( pTab && !pTab->pSelect && pExpr );
+
+  if( IsVirtual(pTab) ) return 0;
+  if( pExpr->op!=TK_AGG_FUNCTION ) return 0;
+  if( (pAggInfo->aFunc[0].pFunc->flags&SQLITE_FUNC_COUNT)==0 ) return 0;
+  if( pExpr->flags&EP_Distinct ) return 0;
+
+  return pTab;
+}
+
+/*
+** If the source-list item passed as an argument was augmented with an
+** INDEXED BY clause, then try to locate the specified index. If there
+** was such a clause and the named index cannot be found, return 
+** SQLITE_ERROR and leave an error in pParse. Otherwise, populate 
+** pFrom->pIndex and return SQLITE_OK.
+*/
+int sqlite3IndexedByLookup(Parse *pParse, struct SrcList_item *pFrom){
+  if( pFrom->pTab && pFrom->zIndex ){
+    Table *pTab = pFrom->pTab;
+    char *zIndex = pFrom->zIndex;
+    Index *pIdx;
+    for(pIdx=pTab->pIndex; 
+        pIdx && sqlite3StrICmp(pIdx->zName, zIndex); 
+        pIdx=pIdx->pNext
+    );
+    if( !pIdx ){
+      sqlite3ErrorMsg(pParse, "no such index: %s", zIndex, 0);
+      pParse->checkSchema = 1;
+      return SQLITE_ERROR;
+    }
+    pFrom->pIndex = pIdx;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** This routine is a Walker callback for "expanding" a SELECT statement.
+** "Expanding" means to do the following:
+**
+**    (1)  Make sure VDBE cursor numbers have been assigned to every
+**         element of the FROM clause.
+**
+**    (2)  Fill in the pTabList->a[].pTab fields in the SrcList that 
+**         defines FROM clause.  When views appear in the FROM clause,
+**         fill pTabList->a[].pSelect with a copy of the SELECT statement
+**         that implements the view.  A copy is made of the view's SELECT
+**         statement so that we can freely modify or delete that statement
+**         without worrying about messing up the presistent representation
+**         of the view.
+**
+**    (3)  Add terms to the WHERE clause to accomodate the NATURAL keyword
+**         on joins and the ON and USING clause of joins.
+**
+**    (4)  Scan the list of columns in the result set (pEList) looking
+**         for instances of the "*" operator or the TABLE.* operator.
+**         If found, expand each "*" to be every column in every table
+**         and TABLE.* to be every column in TABLE.
+**
+*/
+static int selectExpander(Walker *pWalker, Select *p){
+  Parse *pParse = pWalker->pParse;
+  int i, j, k;
+  SrcList *pTabList;
+  ExprList *pEList;
+  struct SrcList_item *pFrom;
+  sqlite3 *db = pParse->db;
+
+  if( db->mallocFailed  ){
+    return WRC_Abort;
+  }
+  if( NEVER(p->pSrc==0) || (p->selFlags & SF_Expanded)!=0 ){
+    return WRC_Prune;
+  }
+  p->selFlags |= SF_Expanded;
+  pTabList = p->pSrc;
+  pEList = p->pEList;
+
+  /* Make sure cursor numbers have been assigned to all entries in
+  ** the FROM clause of the SELECT statement.
+  */
+  sqlite3SrcListAssignCursors(pParse, pTabList);
+
+  /* Look up every table named in the FROM clause of the select.  If
+  ** an entry of the FROM clause is a subquery instead of a table or view,
+  ** then create a transient table structure to describe the subquery.
+  */
+  for(i=0, pFrom=pTabList->a; i<pTabList->nSrc; i++, pFrom++){
+    Table *pTab;
+    if( pFrom->pTab!=0 ){
+      /* This statement has already been prepared.  There is no need
+      ** to go further. */
+      assert( i==0 );
+      return WRC_Prune;
+    }
+    if( pFrom->zName==0 ){
+#ifndef SQLITE_OMIT_SUBQUERY
+      Select *pSel = pFrom->pSelect;
+      /* A sub-query in the FROM clause of a SELECT */
+      assert( pSel!=0 );
+      assert( pFrom->pTab==0 );
+      sqlite3WalkSelect(pWalker, pSel);
+      pFrom->pTab = pTab = sqlite3DbMallocZero(db, sizeof(Table));
+      if( pTab==0 ) return WRC_Abort;
+      pTab->nRef = 1;
+      pTab->zName = sqlite3MPrintf(db, "sqlite_subquery_%p_", (void*)pTab);
+      while( pSel->pPrior ){ pSel = pSel->pPrior; }
+      selectColumnsFromExprList(pParse, pSel->pEList, &pTab->nCol, &pTab->aCol);
+      pTab->iPKey = -1;
+      pTab->nRowEst = 1000000;
+      pTab->tabFlags |= TF_Ephemeral;
+#endif
+    }else{
+      /* An ordinary table or view name in the FROM clause */
+      assert( pFrom->pTab==0 );
+      pFrom->pTab = pTab = 
+        sqlite3LocateTable(pParse,0,pFrom->zName,pFrom->zDatabase);
+      if( pTab==0 ) return WRC_Abort;
+      pTab->nRef++;
+#if !defined(SQLITE_OMIT_VIEW) || !defined (SQLITE_OMIT_VIRTUALTABLE)
+      if( pTab->pSelect || IsVirtual(pTab) ){
+        /* We reach here if the named table is a really a view */
+        if( sqlite3ViewGetColumnNames(pParse, pTab) ) return WRC_Abort;
+        assert( pFrom->pSelect==0 );
+        pFrom->pSelect = sqlite3SelectDup(db, pTab->pSelect, 0);
+        sqlite3WalkSelect(pWalker, pFrom->pSelect);
+      }
+#endif
+    }
+
+    /* Locate the index named by the INDEXED BY clause, if any. */
+    if( sqlite3IndexedByLookup(pParse, pFrom) ){
+      return WRC_Abort;
+    }
+  }
+
+  /* Process NATURAL keywords, and ON and USING clauses of joins.
+  */
+  if( db->mallocFailed || sqliteProcessJoin(pParse, p) ){
+    return WRC_Abort;
+  }
+
+  /* For every "*" that occurs in the column list, insert the names of
+  ** all columns in all tables.  And for every TABLE.* insert the names
+  ** of all columns in TABLE.  The parser inserted a special expression
+  ** with the TK_ALL operator for each "*" that it found in the column list.
+  ** The following code just has to locate the TK_ALL expressions and expand
+  ** each one to the list of all columns in all tables.
+  **
+  ** The first loop just checks to see if there are any "*" operators
+  ** that need expanding.
+  */
+  for(k=0; k<pEList->nExpr; k++){
+    Expr *pE = pEList->a[k].pExpr;
+    if( pE->op==TK_ALL ) break;
+    assert( pE->op!=TK_DOT || pE->pRight!=0 );
+    assert( pE->op!=TK_DOT || (pE->pLeft!=0 && pE->pLeft->op==TK_ID) );
+    if( pE->op==TK_DOT && pE->pRight->op==TK_ALL ) break;
+  }
+  if( k<pEList->nExpr ){
+    /*
+    ** If we get here it means the result set contains one or more "*"
+    ** operators that need to be expanded.  Loop through each expression
+    ** in the result set and expand them one by one.
+    */
+    struct ExprList_item *a = pEList->a;
+    ExprList *pNew = 0;
+    int flags = pParse->db->flags;
+    int longNames = (flags & SQLITE_FullColNames)!=0
+                      && (flags & SQLITE_ShortColNames)==0;
+
+    for(k=0; k<pEList->nExpr; k++){
+      Expr *pE = a[k].pExpr;
+      assert( pE->op!=TK_DOT || pE->pRight!=0 );
+      if( pE->op!=TK_ALL && (pE->op!=TK_DOT || pE->pRight->op!=TK_ALL) ){
+        /* This particular expression does not need to be expanded.
+        */
+        pNew = sqlite3ExprListAppend(pParse, pNew, a[k].pExpr);
+        if( pNew ){
+          pNew->a[pNew->nExpr-1].zName = a[k].zName;
+          pNew->a[pNew->nExpr-1].zSpan = a[k].zSpan;
+          a[k].zName = 0;
+          a[k].zSpan = 0;
+        }
+        a[k].pExpr = 0;
+      }else{
+        /* This expression is a "*" or a "TABLE.*" and needs to be
+        ** expanded. */
+        int tableSeen = 0;      /* Set to 1 when TABLE matches */
+        char *zTName;            /* text of name of TABLE */
+        if( pE->op==TK_DOT ){
+          assert( pE->pLeft!=0 );
+          assert( !ExprHasProperty(pE->pLeft, EP_IntValue) );
+          zTName = pE->pLeft->u.zToken;
+        }else{
+          zTName = 0;
+        }
+        for(i=0, pFrom=pTabList->a; i<pTabList->nSrc; i++, pFrom++){
+          Table *pTab = pFrom->pTab;
+          char *zTabName = pFrom->zAlias;
+          if( zTabName==0 ){
+            zTabName = pTab->zName;
+          }
+          if( db->mallocFailed ) break;
+          if( zTName && sqlite3StrICmp(zTName, zTabName)!=0 ){
+            continue;
+          }
+          tableSeen = 1;
+          for(j=0; j<pTab->nCol; j++){
+            Expr *pExpr, *pRight;
+            char *zName = pTab->aCol[j].zName;
+            char *zColname;  /* The computed column name */
+            char *zToFree;   /* Malloced string that needs to be freed */
+            Token sColname;  /* Computed column name as a token */
+
+            /* If a column is marked as 'hidden' (currently only possible
+            ** for virtual tables), do not include it in the expanded
+            ** result-set list.
+            */
+            if( IsHiddenColumn(&pTab->aCol[j]) ){
+              assert(IsVirtual(pTab));
+              continue;
+            }
+
+            if( i>0 && zTName==0 ){
+              if( (pFrom->jointype & JT_NATURAL)!=0
+                && tableAndColumnIndex(pTabList, i, zName, 0, 0)
+              ){
+                /* In a NATURAL join, omit the join columns from the 
+                ** table to the right of the join */
+                continue;
+              }
+              if( sqlite3IdListIndex(pFrom->pUsing, zName)>=0 ){
+                /* In a join with a USING clause, omit columns in the
+                ** using clause from the table on the right. */
+                continue;
+              }
+            }
+            pRight = sqlite3Expr(db, TK_ID, zName);
+            zColname = zName;
+            zToFree = 0;
+            if( longNames || pTabList->nSrc>1 ){
+              Expr *pLeft;
+              pLeft = sqlite3Expr(db, TK_ID, zTabName);
+              pExpr = sqlite3PExpr(pParse, TK_DOT, pLeft, pRight, 0);
+              if( longNames ){
+                zColname = sqlite3MPrintf(db, "%s.%s", zTabName, zName);
+                zToFree = zColname;
+              }
+            }else{
+              pExpr = pRight;
+            }
+            pNew = sqlite3ExprListAppend(pParse, pNew, pExpr);
+            sColname.z = zColname;
+            sColname.n = sqlite3Strlen30(zColname);
+            sqlite3ExprListSetName(pParse, pNew, &sColname, 0);
+            sqlite3DbFree(db, zToFree);
+          }
+        }
+        if( !tableSeen ){
+          if( zTName ){
+            sqlite3ErrorMsg(pParse, "no such table: %s", zTName);
+          }else{
+            sqlite3ErrorMsg(pParse, "no tables specified");
+          }
+        }
+      }
+    }
+    sqlite3ExprListDelete(db, pEList);
+    p->pEList = pNew;
+  }
+#if SQLITE_MAX_COLUMN
+  if( p->pEList && p->pEList->nExpr>db->aLimit[SQLITE_LIMIT_COLUMN] ){
+    sqlite3ErrorMsg(pParse, "too many columns in result set");
+  }
+#endif
+  return WRC_Continue;
+}
+
+/*
+** No-op routine for the parse-tree walker.
+**
+** When this routine is the Walker.xExprCallback then expression trees
+** are walked without any actions being taken at each node.  Presumably,
+** when this routine is used for Walker.xExprCallback then 
+** Walker.xSelectCallback is set to do something useful for every 
+** subquery in the parser tree.
+*/
+static int exprWalkNoop(Walker *NotUsed, Expr *NotUsed2){
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  return WRC_Continue;
+}
+
+/*
+** This routine "expands" a SELECT statement and all of its subqueries.
+** For additional information on what it means to "expand" a SELECT
+** statement, see the comment on the selectExpand worker callback above.
+**
+** Expanding a SELECT statement is the first step in processing a
+** SELECT statement.  The SELECT statement must be expanded before
+** name resolution is performed.
+**
+** If anything goes wrong, an error message is written into pParse.
+** The calling function can detect the problem by looking at pParse->nErr
+** and/or pParse->db->mallocFailed.
+*/
+static void sqlite3SelectExpand(Parse *pParse, Select *pSelect){
+  Walker w;
+  w.xSelectCallback = selectExpander;
+  w.xExprCallback = exprWalkNoop;
+  w.pParse = pParse;
+  sqlite3WalkSelect(&w, pSelect);
+}
+
+
+#ifndef SQLITE_OMIT_SUBQUERY
+/*
+** This is a Walker.xSelectCallback callback for the sqlite3SelectTypeInfo()
+** interface.
+**
+** For each FROM-clause subquery, add Column.zType and Column.zColl
+** information to the Table structure that represents the result set
+** of that subquery.
+**
+** The Table structure that represents the result set was constructed
+** by selectExpander() but the type and collation information was omitted
+** at that point because identifiers had not yet been resolved.  This
+** routine is called after identifier resolution.
+*/
+static int selectAddSubqueryTypeInfo(Walker *pWalker, Select *p){
+  Parse *pParse;
+  int i;
+  SrcList *pTabList;
+  struct SrcList_item *pFrom;
+
+  assert( p->selFlags & SF_Resolved );
+  if( (p->selFlags & SF_HasTypeInfo)==0 ){
+    p->selFlags |= SF_HasTypeInfo;
+    pParse = pWalker->pParse;
+    pTabList = p->pSrc;
+    for(i=0, pFrom=pTabList->a; i<pTabList->nSrc; i++, pFrom++){
+      Table *pTab = pFrom->pTab;
+      if( ALWAYS(pTab!=0) && (pTab->tabFlags & TF_Ephemeral)!=0 ){
+        /* A sub-query in the FROM clause of a SELECT */
+        Select *pSel = pFrom->pSelect;
+        assert( pSel );
+        while( pSel->pPrior ) pSel = pSel->pPrior;
+        selectAddColumnTypeAndCollation(pParse, pTab->nCol, pTab->aCol, pSel);
+      }
+    }
+  }
+  return WRC_Continue;
+}
+#endif
+
+
+/*
+** This routine adds datatype and collating sequence information to
+** the Table structures of all FROM-clause subqueries in a
+** SELECT statement.
+**
+** Use this routine after name resolution.
+*/
+static void sqlite3SelectAddTypeInfo(Parse *pParse, Select *pSelect){
+#ifndef SQLITE_OMIT_SUBQUERY
+  Walker w;
+  w.xSelectCallback = selectAddSubqueryTypeInfo;
+  w.xExprCallback = exprWalkNoop;
+  w.pParse = pParse;
+  sqlite3WalkSelect(&w, pSelect);
+#endif
+}
+
+
+/*
+** This routine sets of a SELECT statement for processing.  The
+** following is accomplished:
+**
+**     *  VDBE Cursor numbers are assigned to all FROM-clause terms.
+**     *  Ephemeral Table objects are created for all FROM-clause subqueries.
+**     *  ON and USING clauses are shifted into WHERE statements
+**     *  Wildcards "*" and "TABLE.*" in result sets are expanded.
+**     *  Identifiers in expression are matched to tables.
+**
+** This routine acts recursively on all subqueries within the SELECT.
+*/
+void sqlite3SelectPrep(
+  Parse *pParse,         /* The parser context */
+  Select *p,             /* The SELECT statement being coded. */
+  NameContext *pOuterNC  /* Name context for container */
+){
+  sqlite3 *db;
+  if( NEVER(p==0) ) return;
+  db = pParse->db;
+  if( p->selFlags & SF_HasTypeInfo ) return;
+  sqlite3SelectExpand(pParse, p);
+  if( pParse->nErr || db->mallocFailed ) return;
+  sqlite3ResolveSelectNames(pParse, p, pOuterNC);
+  if( pParse->nErr || db->mallocFailed ) return;
+  sqlite3SelectAddTypeInfo(pParse, p);
+}
+
+/*
+** Reset the aggregate accumulator.
+**
+** The aggregate accumulator is a set of memory cells that hold
+** intermediate results while calculating an aggregate.  This
+** routine simply stores NULLs in all of those memory cells.
+*/
+static void resetAccumulator(Parse *pParse, AggInfo *pAggInfo){
+  Vdbe *v = pParse->pVdbe;
+  int i;
+  struct AggInfo_func *pFunc;
+  if( pAggInfo->nFunc+pAggInfo->nColumn==0 ){
+    return;
+  }
+  for(i=0; i<pAggInfo->nColumn; i++){
+    sqlite3VdbeAddOp2(v, OP_Null, 0, pAggInfo->aCol[i].iMem);
+  }
+  for(pFunc=pAggInfo->aFunc, i=0; i<pAggInfo->nFunc; i++, pFunc++){
+    sqlite3VdbeAddOp2(v, OP_Null, 0, pFunc->iMem);
+    if( pFunc->iDistinct>=0 ){
+      Expr *pE = pFunc->pExpr;
+      assert( !ExprHasProperty(pE, EP_xIsSelect) );
+      if( pE->x.pList==0 || pE->x.pList->nExpr!=1 ){
+        sqlite3ErrorMsg(pParse, "DISTINCT aggregates must have exactly one "
+           "argument");
+        pFunc->iDistinct = -1;
+      }else{
+        KeyInfo *pKeyInfo = keyInfoFromExprList(pParse, pE->x.pList);
+        sqlite3VdbeAddOp4(v, OP_OpenEphemeral, pFunc->iDistinct, 0, 0,
+                          (char*)pKeyInfo, P4_KEYINFO_HANDOFF);
+      }
+    }
+  }
+}
+
+/*
+** Invoke the OP_AggFinalize opcode for every aggregate function
+** in the AggInfo structure.
+*/
+static void finalizeAggFunctions(Parse *pParse, AggInfo *pAggInfo){
+  Vdbe *v = pParse->pVdbe;
+  int i;
+  struct AggInfo_func *pF;
+  for(i=0, pF=pAggInfo->aFunc; i<pAggInfo->nFunc; i++, pF++){
+    ExprList *pList = pF->pExpr->x.pList;
+    assert( !ExprHasProperty(pF->pExpr, EP_xIsSelect) );
+    sqlite3VdbeAddOp4(v, OP_AggFinal, pF->iMem, pList ? pList->nExpr : 0, 0,
+                      (void*)pF->pFunc, P4_FUNCDEF);
+  }
+}
+
+/*
+** Update the accumulator memory cells for an aggregate based on
+** the current cursor position.
+*/
+static void updateAccumulator(Parse *pParse, AggInfo *pAggInfo){
+  Vdbe *v = pParse->pVdbe;
+  int i;
+  struct AggInfo_func *pF;
+  struct AggInfo_col *pC;
+
+  pAggInfo->directMode = 1;
+  sqlite3ExprCacheClear(pParse);
+  for(i=0, pF=pAggInfo->aFunc; i<pAggInfo->nFunc; i++, pF++){
+    int nArg;
+    int addrNext = 0;
+    int regAgg;
+    ExprList *pList = pF->pExpr->x.pList;
+    assert( !ExprHasProperty(pF->pExpr, EP_xIsSelect) );
+    if( pList ){
+      nArg = pList->nExpr;
+      regAgg = sqlite3GetTempRange(pParse, nArg);
+      sqlite3ExprCodeExprList(pParse, pList, regAgg, 1);
+    }else{
+      nArg = 0;
+      regAgg = 0;
+    }
+    if( pF->iDistinct>=0 ){
+      addrNext = sqlite3VdbeMakeLabel(v);
+      assert( nArg==1 );
+      codeDistinct(pParse, pF->iDistinct, addrNext, 1, regAgg);
+    }
+    if( pF->pFunc->flags & SQLITE_FUNC_NEEDCOLL ){
+      CollSeq *pColl = 0;
+      struct ExprList_item *pItem;
+      int j;
+      assert( pList!=0 );  /* pList!=0 if pF->pFunc has NEEDCOLL */
+      for(j=0, pItem=pList->a; !pColl && j<nArg; j++, pItem++){
+        pColl = sqlite3ExprCollSeq(pParse, pItem->pExpr);
+      }
+      if( !pColl ){
+        pColl = pParse->db->pDfltColl;
+      }
+      sqlite3VdbeAddOp4(v, OP_CollSeq, 0, 0, 0, (char *)pColl, P4_COLLSEQ);
+    }
+    sqlite3VdbeAddOp4(v, OP_AggStep, 0, regAgg, pF->iMem,
+                      (void*)pF->pFunc, P4_FUNCDEF);
+    sqlite3VdbeChangeP5(v, (u8)nArg);
+    sqlite3ExprCacheAffinityChange(pParse, regAgg, nArg);
+    sqlite3ReleaseTempRange(pParse, regAgg, nArg);
+    if( addrNext ){
+      sqlite3VdbeResolveLabel(v, addrNext);
+      sqlite3ExprCacheClear(pParse);
+    }
+  }
+
+  /* Before populating the accumulator registers, clear the column cache.
+  ** Otherwise, if any of the required column values are already present 
+  ** in registers, sqlite3ExprCode() may use OP_SCopy to copy the value
+  ** to pC->iMem. But by the time the value is used, the original register
+  ** may have been used, invalidating the underlying buffer holding the
+  ** text or blob value. See ticket [883034dcb5].
+  **
+  ** Another solution would be to change the OP_SCopy used to copy cached
+  ** values to an OP_Copy.
+  */
+  sqlite3ExprCacheClear(pParse);
+  for(i=0, pC=pAggInfo->aCol; i<pAggInfo->nAccumulator; i++, pC++){
+    sqlite3ExprCode(pParse, pC->pExpr, pC->iMem);
+  }
+  pAggInfo->directMode = 0;
+  sqlite3ExprCacheClear(pParse);
+}
+
+/*
+** Add a single OP_Explain instruction to the VDBE to explain a simple
+** count(*) query ("SELECT count(*) FROM pTab").
+*/
+#ifndef SQLITE_OMIT_EXPLAIN
+static void explainSimpleCount(
+  Parse *pParse,                  /* Parse context */
+  Table *pTab,                    /* Table being queried */
+  Index *pIdx                     /* Index used to optimize scan, or NULL */
+){
+  if( pParse->explain==2 ){
+    char *zEqp = sqlite3MPrintf(pParse->db, "SCAN TABLE %s %s%s(~%d rows)",
+        pTab->zName, 
+        pIdx ? "USING COVERING INDEX " : "",
+        pIdx ? pIdx->zName : "",
+        pTab->nRowEst
+    );
+    sqlite3VdbeAddOp4(
+        pParse->pVdbe, OP_Explain, pParse->iSelectId, 0, 0, zEqp, P4_DYNAMIC
+    );
+  }
+}
+#else
+# define explainSimpleCount(a,b,c)
+#endif
+
+/*
+** Generate code for the SELECT statement given in the p argument.  
+**
+** The results are distributed in various ways depending on the
+** contents of the SelectDest structure pointed to by argument pDest
+** as follows:
+**
+**     pDest->eDest    Result
+**     ------------    -------------------------------------------
+**     SRT_Output      Generate a row of output (using the OP_ResultRow
+**                     opcode) for each row in the result set.
+**
+**     SRT_Mem         Only valid if the result is a single column.
+**                     Store the first column of the first result row
+**                     in register pDest->iParm then abandon the rest
+**                     of the query.  This destination implies "LIMIT 1".
+**
+**     SRT_Set         The result must be a single column.  Store each
+**                     row of result as the key in table pDest->iParm. 
+**                     Apply the affinity pDest->affinity before storing
+**                     results.  Used to implement "IN (SELECT ...)".
+**
+**     SRT_Union       Store results as a key in a temporary table pDest->iParm.
+**
+**     SRT_Except      Remove results from the temporary table pDest->iParm.
+**
+**     SRT_Table       Store results in temporary table pDest->iParm.
+**                     This is like SRT_EphemTab except that the table
+**                     is assumed to already be open.
+**
+**     SRT_EphemTab    Create an temporary table pDest->iParm and store
+**                     the result there. The cursor is left open after
+**                     returning.  This is like SRT_Table except that
+**                     this destination uses OP_OpenEphemeral to create
+**                     the table first.
+**
+**     SRT_Coroutine   Generate a co-routine that returns a new row of
+**                     results each time it is invoked.  The entry point
+**                     of the co-routine is stored in register pDest->iParm.
+**
+**     SRT_Exists      Store a 1 in memory cell pDest->iParm if the result
+**                     set is not empty.
+**
+**     SRT_Discard     Throw the results away.  This is used by SELECT
+**                     statements within triggers whose only purpose is
+**                     the side-effects of functions.
+**
+** This routine returns the number of errors.  If any errors are
+** encountered, then an appropriate error message is left in
+** pParse->zErrMsg.
+**
+** This routine does NOT free the Select structure passed in.  The
+** calling function needs to do that.
+*/
+int sqlite3Select(
+  Parse *pParse,         /* The parser context */
+  Select *p,             /* The SELECT statement being coded. */
+  SelectDest *pDest      /* What to do with the query results */
+){
+  int i, j;              /* Loop counters */
+  WhereInfo *pWInfo;     /* Return from sqlite3WhereBegin() */
+  Vdbe *v;               /* The virtual machine under construction */
+  int isAgg;             /* True for select lists like "count(*)" */
+  ExprList *pEList;      /* List of columns to extract. */
+  SrcList *pTabList;     /* List of tables to select from */
+  Expr *pWhere;          /* The WHERE clause.  May be NULL */
+  ExprList *pOrderBy;    /* The ORDER BY clause.  May be NULL */
+  ExprList *pGroupBy;    /* The GROUP BY clause.  May be NULL */
+  Expr *pHaving;         /* The HAVING clause.  May be NULL */
+  int isDistinct;        /* True if the DISTINCT keyword is present */
+  int distinct;          /* Table to use for the distinct set */
+  int rc = 1;            /* Value to return from this function */
+  int addrSortIndex;     /* Address of an OP_OpenEphemeral instruction */
+  int addrDistinctIndex; /* Address of an OP_OpenEphemeral instruction */
+  AggInfo sAggInfo;      /* Information used by aggregate queries */
+  int iEnd;              /* Address of the end of the query */
+  sqlite3 *db;           /* The database connection */
+
+#ifndef SQLITE_OMIT_EXPLAIN
+  int iRestoreSelectId = pParse->iSelectId;
+  pParse->iSelectId = pParse->iNextSelectId++;
+#endif
+
+  db = pParse->db;
+  if( p==0 || db->mallocFailed || pParse->nErr ){
+    return 1;
+  }
+  if( sqlite3AuthCheck(pParse, SQLITE_SELECT, 0, 0, 0) ) return 1;
+  memset(&sAggInfo, 0, sizeof(sAggInfo));
+
+  if( IgnorableOrderby(pDest) ){
+    assert(pDest->eDest==SRT_Exists || pDest->eDest==SRT_Union || 
+           pDest->eDest==SRT_Except || pDest->eDest==SRT_Discard);
+    /* If ORDER BY makes no difference in the output then neither does
+    ** DISTINCT so it can be removed too. */
+    sqlite3ExprListDelete(db, p->pOrderBy);
+    p->pOrderBy = 0;
+    p->selFlags &= ~SF_Distinct;
+  }
+  sqlite3SelectPrep(pParse, p, 0);
+  pOrderBy = p->pOrderBy;
+  pTabList = p->pSrc;
+  pEList = p->pEList;
+  if( pParse->nErr || db->mallocFailed ){
+    goto select_end;
+  }
+  isAgg = (p->selFlags & SF_Aggregate)!=0;
+  assert( pEList!=0 );
+
+  /* Begin generating code.
+  */
+  v = sqlite3GetVdbe(pParse);
+  if( v==0 ) goto select_end;
+
+  /* If writing to memory or generating a set
+  ** only a single column may be output.
+  */
+#ifndef SQLITE_OMIT_SUBQUERY
+  if( checkForMultiColumnSelectError(pParse, pDest, pEList->nExpr) ){
+    goto select_end;
+  }
+#endif
+
+  /* Generate code for all sub-queries in the FROM clause
+  */
+#if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
+  for(i=0; !p->pPrior && i<pTabList->nSrc; i++){
+    struct SrcList_item *pItem = &pTabList->a[i];
+    SelectDest dest;
+    Select *pSub = pItem->pSelect;
+    int isAggSub;
+
+    if( pSub==0 ) continue;
+    if( pItem->addrFillSub ){
+      sqlite3VdbeAddOp2(v, OP_Gosub, pItem->regReturn, pItem->addrFillSub);
+      continue;
+    }
+
+    /* Increment Parse.nHeight by the height of the largest expression
+    ** tree refered to by this, the parent select. The child select
+    ** may contain expression trees of at most
+    ** (SQLITE_MAX_EXPR_DEPTH-Parse.nHeight) height. This is a bit
+    ** more conservative than necessary, but much easier than enforcing
+    ** an exact limit.
+    */
+    pParse->nHeight += sqlite3SelectExprHeight(p);
+
+    isAggSub = (pSub->selFlags & SF_Aggregate)!=0;
+    if( flattenSubquery(pParse, p, i, isAgg, isAggSub) ){
+      /* This subquery can be absorbed into its parent. */
+      if( isAggSub ){
+        isAgg = 1;
+        p->selFlags |= SF_Aggregate;
+      }
+      i = -1;
+    }else{
+      /* Generate a subroutine that will fill an ephemeral table with
+      ** the content of this subquery.  pItem->addrFillSub will point
+      ** to the address of the generated subroutine.  pItem->regReturn
+      ** is a register allocated to hold the subroutine return address
+      */
+      int topAddr;
+      int onceAddr = 0;
+      int retAddr;
+      assert( pItem->addrFillSub==0 );
+      pItem->regReturn = ++pParse->nMem;
+      topAddr = sqlite3VdbeAddOp2(v, OP_Integer, 0, pItem->regReturn);
+      pItem->addrFillSub = topAddr+1;
+      VdbeNoopComment((v, "materialize %s", pItem->pTab->zName));
+      if( pItem->isCorrelated==0 && pParse->pTriggerTab==0 ){
+        /* If the subquery is no correlated and if we are not inside of
+        ** a trigger, then we only need to compute the value of the subquery
+        ** once. */
+        int regOnce = ++pParse->nMem;
+        onceAddr = sqlite3VdbeAddOp1(v, OP_Once, regOnce);
+      }
+      sqlite3SelectDestInit(&dest, SRT_EphemTab, pItem->iCursor);
+      explainSetInteger(pItem->iSelectId, (u8)pParse->iNextSelectId);
+      sqlite3Select(pParse, pSub, &dest);
+      pItem->pTab->nRowEst = (unsigned)pSub->nSelectRow;
+      if( onceAddr ) sqlite3VdbeJumpHere(v, onceAddr);
+      retAddr = sqlite3VdbeAddOp1(v, OP_Return, pItem->regReturn);
+      VdbeComment((v, "end %s", pItem->pTab->zName));
+      sqlite3VdbeChangeP1(v, topAddr, retAddr);
+
+    }
+    if( /*pParse->nErr ||*/ db->mallocFailed ){
+      goto select_end;
+    }
+    pParse->nHeight -= sqlite3SelectExprHeight(p);
+    pTabList = p->pSrc;
+    if( !IgnorableOrderby(pDest) ){
+      pOrderBy = p->pOrderBy;
+    }
+  }
+  pEList = p->pEList;
+#endif
+  pWhere = p->pWhere;
+  pGroupBy = p->pGroupBy;
+  pHaving = p->pHaving;
+  isDistinct = (p->selFlags & SF_Distinct)!=0;
+
+#ifndef SQLITE_OMIT_COMPOUND_SELECT
+  /* If there is are a sequence of queries, do the earlier ones first.
+  */
+  if( p->pPrior ){
+    if( p->pRightmost==0 ){
+      Select *pLoop, *pRight = 0;
+      int cnt = 0;
+      int mxSelect;
+      for(pLoop=p; pLoop; pLoop=pLoop->pPrior, cnt++){
+        pLoop->pRightmost = p;
+        pLoop->pNext = pRight;
+        pRight = pLoop;
+      }
+      mxSelect = db->aLimit[SQLITE_LIMIT_COMPOUND_SELECT];
+      if( mxSelect && cnt>mxSelect ){
+        sqlite3ErrorMsg(pParse, "too many terms in compound SELECT");
+        goto select_end;
+      }
+    }
+    rc = multiSelect(pParse, p, pDest);
+    explainSetInteger(pParse->iSelectId, iRestoreSelectId);
+    return rc;
+  }
+#endif
+
+  /* If there is both a GROUP BY and an ORDER BY clause and they are
+  ** identical, then disable the ORDER BY clause since the GROUP BY
+  ** will cause elements to come out in the correct order.  This is
+  ** an optimization - the correct answer should result regardless.
+  ** Use the SQLITE_GroupByOrder flag with SQLITE_TESTCTRL_OPTIMIZER
+  ** to disable this optimization for testing purposes.
+  */
+  if( sqlite3ExprListCompare(p->pGroupBy, pOrderBy)==0
+         && (db->flags & SQLITE_GroupByOrder)==0 ){
+    pOrderBy = 0;
+  }
+
+  /* If the query is DISTINCT with an ORDER BY but is not an aggregate, and 
+  ** if the select-list is the same as the ORDER BY list, then this query
+  ** can be rewritten as a GROUP BY. In other words, this:
+  **
+  **     SELECT DISTINCT xyz FROM ... ORDER BY xyz
+  **
+  ** is transformed to:
+  **
+  **     SELECT xyz FROM ... GROUP BY xyz
+  **
+  ** The second form is preferred as a single index (or temp-table) may be 
+  ** used for both the ORDER BY and DISTINCT processing. As originally 
+  ** written the query must use a temp-table for at least one of the ORDER 
+  ** BY and DISTINCT, and an index or separate temp-table for the other.
+  */
+  if( (p->selFlags & (SF_Distinct|SF_Aggregate))==SF_Distinct 
+   && sqlite3ExprListCompare(pOrderBy, p->pEList)==0
+  ){
+    p->selFlags &= ~SF_Distinct;
+    p->pGroupBy = sqlite3ExprListDup(db, p->pEList, 0);
+    pGroupBy = p->pGroupBy;
+    pOrderBy = 0;
+  }
+
+  /* If there is an ORDER BY clause, then this sorting
+  ** index might end up being unused if the data can be 
+  ** extracted in pre-sorted order.  If that is the case, then the
+  ** OP_OpenEphemeral instruction will be changed to an OP_Noop once
+  ** we figure out that the sorting index is not needed.  The addrSortIndex
+  ** variable is used to facilitate that change.
+  */
+  if( pOrderBy ){
+    KeyInfo *pKeyInfo;
+    pKeyInfo = keyInfoFromExprList(pParse, pOrderBy);
+    pOrderBy->iECursor = pParse->nTab++;
+    p->addrOpenEphm[2] = addrSortIndex =
+      sqlite3VdbeAddOp4(v, OP_OpenEphemeral,
+                           pOrderBy->iECursor, pOrderBy->nExpr+2, 0,
+                           (char*)pKeyInfo, P4_KEYINFO_HANDOFF);
+  }else{
+    addrSortIndex = -1;
+  }
+
+  /* If the output is destined for a temporary table, open that table.
+  */
+  if( pDest->eDest==SRT_EphemTab ){
+    sqlite3VdbeAddOp2(v, OP_OpenEphemeral, pDest->iParm, pEList->nExpr);
+  }
+
+  /* Set the limiter.
+  */
+  iEnd = sqlite3VdbeMakeLabel(v);
+  p->nSelectRow = (double)LARGEST_INT64;
+  computeLimitRegisters(pParse, p, iEnd);
+  if( p->iLimit==0 && addrSortIndex>=0 ){
+    sqlite3VdbeGetOp(v, addrSortIndex)->opcode = OP_SorterOpen;
+    p->selFlags |= SF_UseSorter;
+  }
+
+  /* Open a virtual index to use for the distinct set.
+  */
+  if( p->selFlags & SF_Distinct ){
+    KeyInfo *pKeyInfo;
+    distinct = pParse->nTab++;
+    pKeyInfo = keyInfoFromExprList(pParse, p->pEList);
+    addrDistinctIndex = sqlite3VdbeAddOp4(v, OP_OpenEphemeral, distinct, 0, 0,
+        (char*)pKeyInfo, P4_KEYINFO_HANDOFF);
+    sqlite3VdbeChangeP5(v, BTREE_UNORDERED);
+  }else{
+    distinct = addrDistinctIndex = -1;
+  }
+
+  /* Aggregate and non-aggregate queries are handled differently */
+  if( !isAgg && pGroupBy==0 ){
+    ExprList *pDist = (isDistinct ? p->pEList : 0);
+
+    /* Begin the database scan. */
+    pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, &pOrderBy, pDist, 0);
+    if( pWInfo==0 ) goto select_end;
+    if( pWInfo->nRowOut < p->nSelectRow ) p->nSelectRow = pWInfo->nRowOut;
+
+    /* If sorting index that was created by a prior OP_OpenEphemeral 
+    ** instruction ended up not being needed, then change the OP_OpenEphemeral
+    ** into an OP_Noop.
+    */
+    if( addrSortIndex>=0 && pOrderBy==0 ){
+      sqlite3VdbeChangeToNoop(v, addrSortIndex);
+      p->addrOpenEphm[2] = -1;
+    }
+
+    if( pWInfo->eDistinct ){
+      VdbeOp *pOp;                /* No longer required OpenEphemeral instr. */
+     
+      assert( addrDistinctIndex>=0 );
+      pOp = sqlite3VdbeGetOp(v, addrDistinctIndex);
+
+      assert( isDistinct );
+      assert( pWInfo->eDistinct==WHERE_DISTINCT_ORDERED 
+           || pWInfo->eDistinct==WHERE_DISTINCT_UNIQUE 
+      );
+      distinct = -1;
+      if( pWInfo->eDistinct==WHERE_DISTINCT_ORDERED ){
+        int iJump;
+        int iExpr;
+        int iFlag = ++pParse->nMem;
+        int iBase = pParse->nMem+1;
+        int iBase2 = iBase + pEList->nExpr;
+        pParse->nMem += (pEList->nExpr*2);
+
+        /* Change the OP_OpenEphemeral coded earlier to an OP_Integer. The
+        ** OP_Integer initializes the "first row" flag.  */
+        pOp->opcode = OP_Integer;
+        pOp->p1 = 1;
+        pOp->p2 = iFlag;
+
+        sqlite3ExprCodeExprList(pParse, pEList, iBase, 1);
+        iJump = sqlite3VdbeCurrentAddr(v) + 1 + pEList->nExpr + 1 + 1;
+        sqlite3VdbeAddOp2(v, OP_If, iFlag, iJump-1);
+        for(iExpr=0; iExpr<pEList->nExpr; iExpr++){
+          CollSeq *pColl = sqlite3ExprCollSeq(pParse, pEList->a[iExpr].pExpr);
+          sqlite3VdbeAddOp3(v, OP_Ne, iBase+iExpr, iJump, iBase2+iExpr);
+          sqlite3VdbeChangeP4(v, -1, (const char *)pColl, P4_COLLSEQ);
+          sqlite3VdbeChangeP5(v, SQLITE_NULLEQ);
+        }
+        sqlite3VdbeAddOp2(v, OP_Goto, 0, pWInfo->iContinue);
+
+        sqlite3VdbeAddOp2(v, OP_Integer, 0, iFlag);
+        assert( sqlite3VdbeCurrentAddr(v)==iJump );
+        sqlite3VdbeAddOp3(v, OP_Move, iBase, iBase2, pEList->nExpr);
+      }else{
+        pOp->opcode = OP_Noop;
+      }
+    }
+
+    /* Use the standard inner loop. */
+    selectInnerLoop(pParse, p, pEList, 0, 0, pOrderBy, distinct, pDest,
+                    pWInfo->iContinue, pWInfo->iBreak);
+
+    /* End the database scan loop.
+    */
+    sqlite3WhereEnd(pWInfo);
+  }else{
+    /* This is the processing for aggregate queries */
+    NameContext sNC;    /* Name context for processing aggregate information */
+    int iAMem;          /* First Mem address for storing current GROUP BY */
+    int iBMem;          /* First Mem address for previous GROUP BY */
+    int iUseFlag;       /* Mem address holding flag indicating that at least
+                        ** one row of the input to the aggregator has been
+                        ** processed */
+    int iAbortFlag;     /* Mem address which causes query abort if positive */
+    int groupBySort;    /* Rows come from source in GROUP BY order */
+    int addrEnd;        /* End of processing for this SELECT */
+    int sortPTab = 0;   /* Pseudotable used to decode sorting results */
+    int sortOut = 0;    /* Output register from the sorter */
+
+    /* Remove any and all aliases between the result set and the
+    ** GROUP BY clause.
+    */
+    if( pGroupBy ){
+      int k;                        /* Loop counter */
+      struct ExprList_item *pItem;  /* For looping over expression in a list */
+
+      for(k=p->pEList->nExpr, pItem=p->pEList->a; k>0; k--, pItem++){
+        pItem->iAlias = 0;
+      }
+      for(k=pGroupBy->nExpr, pItem=pGroupBy->a; k>0; k--, pItem++){
+        pItem->iAlias = 0;
+      }
+      if( p->nSelectRow>(double)100 ) p->nSelectRow = (double)100;
+    }else{
+      p->nSelectRow = (double)1;
+    }
+
+ 
+    /* Create a label to jump to when we want to abort the query */
+    addrEnd = sqlite3VdbeMakeLabel(v);
+
+    /* Convert TK_COLUMN nodes into TK_AGG_COLUMN and make entries in
+    ** sAggInfo for all TK_AGG_FUNCTION nodes in expressions of the
+    ** SELECT statement.
+    */
+    memset(&sNC, 0, sizeof(sNC));
+    sNC.pParse = pParse;
+    sNC.pSrcList = pTabList;
+    sNC.pAggInfo = &sAggInfo;
+    sAggInfo.nSortingColumn = pGroupBy ? pGroupBy->nExpr+1 : 0;
+    sAggInfo.pGroupBy = pGroupBy;
+    sqlite3ExprAnalyzeAggList(&sNC, pEList);
+    sqlite3ExprAnalyzeAggList(&sNC, pOrderBy);
+    if( pHaving ){
+      sqlite3ExprAnalyzeAggregates(&sNC, pHaving);
+    }
+    sAggInfo.nAccumulator = sAggInfo.nColumn;
+    for(i=0; i<sAggInfo.nFunc; i++){
+      assert( !ExprHasProperty(sAggInfo.aFunc[i].pExpr, EP_xIsSelect) );
+      sqlite3ExprAnalyzeAggList(&sNC, sAggInfo.aFunc[i].pExpr->x.pList);
+    }
+    if( db->mallocFailed ) goto select_end;
+
+    /* Processing for aggregates with GROUP BY is very different and
+    ** much more complex than aggregates without a GROUP BY.
+    */
+    if( pGroupBy ){
+      KeyInfo *pKeyInfo;  /* Keying information for the group by clause */
+      int j1;             /* A-vs-B comparision jump */
+      int addrOutputRow;  /* Start of subroutine that outputs a result row */
+      int regOutputRow;   /* Return address register for output subroutine */
+      int addrSetAbort;   /* Set the abort flag and return */
+      int addrTopOfLoop;  /* Top of the input loop */
+      int addrSortingIdx; /* The OP_OpenEphemeral for the sorting index */
+      int addrReset;      /* Subroutine for resetting the accumulator */
+      int regReset;       /* Return address register for reset subroutine */
+
+      /* If there is a GROUP BY clause we might need a sorting index to
+      ** implement it.  Allocate that sorting index now.  If it turns out
+      ** that we do not need it after all, the OP_SorterOpen instruction
+      ** will be converted into a Noop.  
+      */
+      sAggInfo.sortingIdx = pParse->nTab++;
+      pKeyInfo = keyInfoFromExprList(pParse, pGroupBy);
+      addrSortingIdx = sqlite3VdbeAddOp4(v, OP_SorterOpen, 
+          sAggInfo.sortingIdx, sAggInfo.nSortingColumn, 
+          0, (char*)pKeyInfo, P4_KEYINFO_HANDOFF);
+
+      /* Initialize memory locations used by GROUP BY aggregate processing
+      */
+      iUseFlag = ++pParse->nMem;
+      iAbortFlag = ++pParse->nMem;
+      regOutputRow = ++pParse->nMem;
+      addrOutputRow = sqlite3VdbeMakeLabel(v);
+      regReset = ++pParse->nMem;
+      addrReset = sqlite3VdbeMakeLabel(v);
+      iAMem = pParse->nMem + 1;
+      pParse->nMem += pGroupBy->nExpr;
+      iBMem = pParse->nMem + 1;
+      pParse->nMem += pGroupBy->nExpr;
+      sqlite3VdbeAddOp2(v, OP_Integer, 0, iAbortFlag);
+      VdbeComment((v, "clear abort flag"));
+      sqlite3VdbeAddOp2(v, OP_Integer, 0, iUseFlag);
+      VdbeComment((v, "indicate accumulator empty"));
+
+      /* Begin a loop that will extract all source rows in GROUP BY order.
+      ** This might involve two separate loops with an OP_Sort in between, or
+      ** it might be a single loop that uses an index to extract information
+      ** in the right order to begin with.
+      */
+      sqlite3VdbeAddOp2(v, OP_Gosub, regReset, addrReset);
+      pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, &pGroupBy, 0, 0);
+      if( pWInfo==0 ) goto select_end;
+      if( pGroupBy==0 ){
+        /* The optimizer is able to deliver rows in group by order so
+        ** we do not have to sort.  The OP_OpenEphemeral table will be
+        ** cancelled later because we still need to use the pKeyInfo
+        */
+        pGroupBy = p->pGroupBy;
+        groupBySort = 0;
+      }else{
+        /* Rows are coming out in undetermined order.  We have to push
+        ** each row into a sorting index, terminate the first loop,
+        ** then loop over the sorting index in order to get the output
+        ** in sorted order
+        */
+        int regBase;
+        int regRecord;
+        int nCol;
+        int nGroupBy;
+
+        explainTempTable(pParse, 
+            isDistinct && !(p->selFlags&SF_Distinct)?"DISTINCT":"GROUP BY");
+
+        groupBySort = 1;
+        nGroupBy = pGroupBy->nExpr;
+        nCol = nGroupBy + 1;
+        j = nGroupBy+1;
+        for(i=0; i<sAggInfo.nColumn; i++){
+          if( sAggInfo.aCol[i].iSorterColumn>=j ){
+            nCol++;
+            j++;
+          }
+        }
+        regBase = sqlite3GetTempRange(pParse, nCol);
+        sqlite3ExprCacheClear(pParse);
+        sqlite3ExprCodeExprList(pParse, pGroupBy, regBase, 0);
+        sqlite3VdbeAddOp2(v, OP_Sequence, sAggInfo.sortingIdx,regBase+nGroupBy);
+        j = nGroupBy+1;
+        for(i=0; i<sAggInfo.nColumn; i++){
+          struct AggInfo_col *pCol = &sAggInfo.aCol[i];
+          if( pCol->iSorterColumn>=j ){
+            int r1 = j + regBase;
+            int r2;
+
+            r2 = sqlite3ExprCodeGetColumn(pParse, 
+                               pCol->pTab, pCol->iColumn, pCol->iTable, r1);
+            if( r1!=r2 ){
+              sqlite3VdbeAddOp2(v, OP_SCopy, r2, r1);
+            }
+            j++;
+          }
+        }
+        regRecord = sqlite3GetTempReg(pParse);
+        sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase, nCol, regRecord);
+        sqlite3VdbeAddOp2(v, OP_SorterInsert, sAggInfo.sortingIdx, regRecord);
+        sqlite3ReleaseTempReg(pParse, regRecord);
+        sqlite3ReleaseTempRange(pParse, regBase, nCol);
+        sqlite3WhereEnd(pWInfo);
+        sAggInfo.sortingIdxPTab = sortPTab = pParse->nTab++;
+        sortOut = sqlite3GetTempReg(pParse);
+        sqlite3VdbeAddOp3(v, OP_OpenPseudo, sortPTab, sortOut, nCol);
+        sqlite3VdbeAddOp2(v, OP_SorterSort, sAggInfo.sortingIdx, addrEnd);
+        VdbeComment((v, "GROUP BY sort"));
+        sAggInfo.useSortingIdx = 1;
+        sqlite3ExprCacheClear(pParse);
+      }
+
+      /* Evaluate the current GROUP BY terms and store in b0, b1, b2...
+      ** (b0 is memory location iBMem+0, b1 is iBMem+1, and so forth)
+      ** Then compare the current GROUP BY terms against the GROUP BY terms
+      ** from the previous row currently stored in a0, a1, a2...
+      */
+      addrTopOfLoop = sqlite3VdbeCurrentAddr(v);
+      sqlite3ExprCacheClear(pParse);
+      if( groupBySort ){
+        sqlite3VdbeAddOp2(v, OP_SorterData, sAggInfo.sortingIdx, sortOut);
+      }
+      for(j=0; j<pGroupBy->nExpr; j++){
+        if( groupBySort ){
+          sqlite3VdbeAddOp3(v, OP_Column, sortPTab, j, iBMem+j);
+          if( j==0 ) sqlite3VdbeChangeP5(v, OPFLAG_CLEARCACHE);
+        }else{
+          sAggInfo.directMode = 1;
+          sqlite3ExprCode(pParse, pGroupBy->a[j].pExpr, iBMem+j);
+        }
+      }
+      sqlite3VdbeAddOp4(v, OP_Compare, iAMem, iBMem, pGroupBy->nExpr,
+                          (char*)pKeyInfo, P4_KEYINFO);
+      j1 = sqlite3VdbeCurrentAddr(v);
+      sqlite3VdbeAddOp3(v, OP_Jump, j1+1, 0, j1+1);
+
+      /* Generate code that runs whenever the GROUP BY changes.
+      ** Changes in the GROUP BY are detected by the previous code
+      ** block.  If there were no changes, this block is skipped.
+      **
+      ** This code copies current group by terms in b0,b1,b2,...
+      ** over to a0,a1,a2.  It then calls the output subroutine
+      ** and resets the aggregate accumulator registers in preparation
+      ** for the next GROUP BY batch.
+      */
+      sqlite3ExprCodeMove(pParse, iBMem, iAMem, pGroupBy->nExpr);
+      sqlite3VdbeAddOp2(v, OP_Gosub, regOutputRow, addrOutputRow);
+      VdbeComment((v, "output one row"));
+      sqlite3VdbeAddOp2(v, OP_IfPos, iAbortFlag, addrEnd);
+      VdbeComment((v, "check abort flag"));
+      sqlite3VdbeAddOp2(v, OP_Gosub, regReset, addrReset);
+      VdbeComment((v, "reset accumulator"));
+
+      /* Update the aggregate accumulators based on the content of
+      ** the current row
+      */
+      sqlite3VdbeJumpHere(v, j1);
+      updateAccumulator(pParse, &sAggInfo);
+      sqlite3VdbeAddOp2(v, OP_Integer, 1, iUseFlag);
+      VdbeComment((v, "indicate data in accumulator"));
+
+      /* End of the loop
+      */
+      if( groupBySort ){
+        sqlite3VdbeAddOp2(v, OP_SorterNext, sAggInfo.sortingIdx, addrTopOfLoop);
+      }else{
+        sqlite3WhereEnd(pWInfo);
+        sqlite3VdbeChangeToNoop(v, addrSortingIdx);
+      }
+
+      /* Output the final row of result
+      */
+      sqlite3VdbeAddOp2(v, OP_Gosub, regOutputRow, addrOutputRow);
+      VdbeComment((v, "output final row"));
+
+      /* Jump over the subroutines
+      */
+      sqlite3VdbeAddOp2(v, OP_Goto, 0, addrEnd);
+
+      /* Generate a subroutine that outputs a single row of the result
+      ** set.  This subroutine first looks at the iUseFlag.  If iUseFlag
+      ** is less than or equal to zero, the subroutine is a no-op.  If
+      ** the processing calls for the query to abort, this subroutine
+      ** increments the iAbortFlag memory location before returning in
+      ** order to signal the caller to abort.
+      */
+      addrSetAbort = sqlite3VdbeCurrentAddr(v);
+      sqlite3VdbeAddOp2(v, OP_Integer, 1, iAbortFlag);
+      VdbeComment((v, "set abort flag"));
+      sqlite3VdbeAddOp1(v, OP_Return, regOutputRow);
+      sqlite3VdbeResolveLabel(v, addrOutputRow);
+      addrOutputRow = sqlite3VdbeCurrentAddr(v);
+      sqlite3VdbeAddOp2(v, OP_IfPos, iUseFlag, addrOutputRow+2);
+      VdbeComment((v, "Groupby result generator entry point"));
+      sqlite3VdbeAddOp1(v, OP_Return, regOutputRow);
+      finalizeAggFunctions(pParse, &sAggInfo);
+      sqlite3ExprIfFalse(pParse, pHaving, addrOutputRow+1, SQLITE_JUMPIFNULL);
+      selectInnerLoop(pParse, p, p->pEList, 0, 0, pOrderBy,
+                      distinct, pDest,
+                      addrOutputRow+1, addrSetAbort);
+      sqlite3VdbeAddOp1(v, OP_Return, regOutputRow);
+      VdbeComment((v, "end groupby result generator"));
+
+      /* Generate a subroutine that will reset the group-by accumulator
+      */
+      sqlite3VdbeResolveLabel(v, addrReset);
+      resetAccumulator(pParse, &sAggInfo);
+      sqlite3VdbeAddOp1(v, OP_Return, regReset);
+     
+    } /* endif pGroupBy.  Begin aggregate queries without GROUP BY: */
+    else {
+      ExprList *pDel = 0;
+#ifndef SQLITE_OMIT_BTREECOUNT
+      Table *pTab;
+      if( (pTab = isSimpleCount(p, &sAggInfo))!=0 ){
+        /* If isSimpleCount() returns a pointer to a Table structure, then
+        ** the SQL statement is of the form:
+        **
+        **   SELECT count(*) FROM <tbl>
+        **
+        ** where the Table structure returned represents table <tbl>.
+        **
+        ** This statement is so common that it is optimized specially. The
+        ** OP_Count instruction is executed either on the intkey table that
+        ** contains the data for table <tbl> or on one of its indexes. It
+        ** is better to execute the op on an index, as indexes are almost
+        ** always spread across less pages than their corresponding tables.
+        */
+        const int iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
+        const int iCsr = pParse->nTab++;     /* Cursor to scan b-tree */
+        Index *pIdx;                         /* Iterator variable */
+        KeyInfo *pKeyInfo = 0;               /* Keyinfo for scanned index */
+        Index *pBest = 0;                    /* Best index found so far */
+        int iRoot = pTab->tnum;              /* Root page of scanned b-tree */
+
+        sqlite3CodeVerifySchema(pParse, iDb);
+        sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);
+
+        /* Search for the index that has the least amount of columns. If
+        ** there is such an index, and it has less columns than the table
+        ** does, then we can assume that it consumes less space on disk and
+        ** will therefore be cheaper to scan to determine the query result.
+        ** In this case set iRoot to the root page number of the index b-tree
+        ** and pKeyInfo to the KeyInfo structure required to navigate the
+        ** index.
+        **
+        ** (2011-04-15) Do not do a full scan of an unordered index.
+        **
+        ** In practice the KeyInfo structure will not be used. It is only 
+        ** passed to keep OP_OpenRead happy.
+        */
+        for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+          if( pIdx->bUnordered==0 && (!pBest || pIdx->nColumn<pBest->nColumn) ){
+            pBest = pIdx;
+          }
+        }
+        if( pBest && pBest->nColumn<pTab->nCol ){
+          iRoot = pBest->tnum;
+          pKeyInfo = sqlite3IndexKeyinfo(pParse, pBest);
+        }
+
+        /* Open a read-only cursor, execute the OP_Count, close the cursor. */
+        sqlite3VdbeAddOp3(v, OP_OpenRead, iCsr, iRoot, iDb);
+        if( pKeyInfo ){
+          sqlite3VdbeChangeP4(v, -1, (char *)pKeyInfo, P4_KEYINFO_HANDOFF);
+        }
+        sqlite3VdbeAddOp2(v, OP_Count, iCsr, sAggInfo.aFunc[0].iMem);
+        sqlite3VdbeAddOp1(v, OP_Close, iCsr);
+        explainSimpleCount(pParse, pTab, pBest);
+      }else
+#endif /* SQLITE_OMIT_BTREECOUNT */
+      {
+        /* Check if the query is of one of the following forms:
+        **
+        **   SELECT min(x) FROM ...
+        **   SELECT max(x) FROM ...
+        **
+        ** If it is, then ask the code in where.c to attempt to sort results
+        ** as if there was an "ORDER ON x" or "ORDER ON x DESC" clause. 
+        ** If where.c is able to produce results sorted in this order, then
+        ** add vdbe code to break out of the processing loop after the 
+        ** first iteration (since the first iteration of the loop is 
+        ** guaranteed to operate on the row with the minimum or maximum 
+        ** value of x, the only row required).
+        **
+        ** A special flag must be passed to sqlite3WhereBegin() to slightly
+        ** modify behaviour as follows:
+        **
+        **   + If the query is a "SELECT min(x)", then the loop coded by
+        **     where.c should not iterate over any values with a NULL value
+        **     for x.
+        **
+        **   + The optimizer code in where.c (the thing that decides which
+        **     index or indices to use) should place a different priority on 
+        **     satisfying the 'ORDER BY' clause than it does in other cases.
+        **     Refer to code and comments in where.c for details.
+        */
+        ExprList *pMinMax = 0;
+        u8 flag = minMaxQuery(p);
+        if( flag ){
+          assert( !ExprHasProperty(p->pEList->a[0].pExpr, EP_xIsSelect) );
+          pMinMax = sqlite3ExprListDup(db, p->pEList->a[0].pExpr->x.pList,0);
+          pDel = pMinMax;
+          if( pMinMax && !db->mallocFailed ){
+            pMinMax->a[0].sortOrder = flag!=WHERE_ORDERBY_MIN ?1:0;
+            pMinMax->a[0].pExpr->op = TK_COLUMN;
+          }
+        }
+  
+        /* This case runs if the aggregate has no GROUP BY clause.  The
+        ** processing is much simpler since there is only a single row
+        ** of output.
+        */
+        resetAccumulator(pParse, &sAggInfo);
+        pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, &pMinMax, 0, flag);
+        if( pWInfo==0 ){
+          sqlite3ExprListDelete(db, pDel);
+          goto select_end;
+        }
+        updateAccumulator(pParse, &sAggInfo);
+        if( !pMinMax && flag ){
+          sqlite3VdbeAddOp2(v, OP_Goto, 0, pWInfo->iBreak);
+          VdbeComment((v, "%s() by index",
+                (flag==WHERE_ORDERBY_MIN?"min":"max")));
+        }
+        sqlite3WhereEnd(pWInfo);
+        finalizeAggFunctions(pParse, &sAggInfo);
+      }
+
+      pOrderBy = 0;
+      sqlite3ExprIfFalse(pParse, pHaving, addrEnd, SQLITE_JUMPIFNULL);
+      selectInnerLoop(pParse, p, p->pEList, 0, 0, 0, -1, 
+                      pDest, addrEnd, addrEnd);
+      sqlite3ExprListDelete(db, pDel);
+    }
+    sqlite3VdbeResolveLabel(v, addrEnd);
+    
+  } /* endif aggregate query */
+
+  if( distinct>=0 ){
+    explainTempTable(pParse, "DISTINCT");
+  }
+
+  /* If there is an ORDER BY clause, then we need to sort the results
+  ** and send them to the callback one by one.
+  */
+  if( pOrderBy ){
+    explainTempTable(pParse, "ORDER BY");
+    generateSortTail(pParse, p, v, pEList->nExpr, pDest);
+  }
+
+  /* Jump here to skip this query
+  */
+  sqlite3VdbeResolveLabel(v, iEnd);
+
+  /* The SELECT was successfully coded.   Set the return code to 0
+  ** to indicate no errors.
+  */
+  rc = 0;
+
+  /* Control jumps to here if an error is encountered above, or upon
+  ** successful coding of the SELECT.
+  */
+select_end:
+  explainSetInteger(pParse->iSelectId, iRestoreSelectId);
+
+  /* Identify column names if results of the SELECT are to be output.
+  */
+  if( rc==SQLITE_OK && pDest->eDest==SRT_Output ){
+    generateColumnNames(pParse, pTabList, pEList);
+  }
+
+  sqlite3DbFree(db, sAggInfo.aCol);
+  sqlite3DbFree(db, sAggInfo.aFunc);
+  return rc;
+}
+
+#if defined(SQLITE_DEBUG)
+/*
+*******************************************************************************
+** The following code is used for testing and debugging only.  The code
+** that follows does not appear in normal builds.
+**
+** These routines are used to print out the content of all or part of a 
+** parse structures such as Select or Expr.  Such printouts are useful
+** for helping to understand what is happening inside the code generator
+** during the execution of complex SELECT statements.
+**
+** These routine are not called anywhere from within the normal
+** code base.  Then are intended to be called from within the debugger
+** or from temporary "printf" statements inserted for debugging.
+*/
+void sqlite3PrintExpr(Expr *p){
+  if( !ExprHasProperty(p, EP_IntValue) && p->u.zToken ){
+    sqlite3DebugPrintf("(%s", p->u.zToken);
+  }else{
+    sqlite3DebugPrintf("(%d", p->op);
+  }
+  if( p->pLeft ){
+    sqlite3DebugPrintf(" ");
+    sqlite3PrintExpr(p->pLeft);
+  }
+  if( p->pRight ){
+    sqlite3DebugPrintf(" ");
+    sqlite3PrintExpr(p->pRight);
+  }
+  sqlite3DebugPrintf(")");
+}
+void sqlite3PrintExprList(ExprList *pList){
+  int i;
+  for(i=0; i<pList->nExpr; i++){
+    sqlite3PrintExpr(pList->a[i].pExpr);
+    if( i<pList->nExpr-1 ){
+      sqlite3DebugPrintf(", ");
+    }
+  }
+}
+void sqlite3PrintSelect(Select *p, int indent){
+  sqlite3DebugPrintf("%*sSELECT(%p) ", indent, "", p);
+  sqlite3PrintExprList(p->pEList);
+  sqlite3DebugPrintf("\n");
+  if( p->pSrc ){
+    char *zPrefix;
+    int i;
+    zPrefix = "FROM";
+    for(i=0; i<p->pSrc->nSrc; i++){
+      struct SrcList_item *pItem = &p->pSrc->a[i];
+      sqlite3DebugPrintf("%*s ", indent+6, zPrefix);
+      zPrefix = "";
+      if( pItem->pSelect ){
+        sqlite3DebugPrintf("(\n");
+        sqlite3PrintSelect(pItem->pSelect, indent+10);
+        sqlite3DebugPrintf("%*s)", indent+8, "");
+      }else if( pItem->zName ){
+        sqlite3DebugPrintf("%s", pItem->zName);
+      }
+      if( pItem->pTab ){
+        sqlite3DebugPrintf("(table: %s)", pItem->pTab->zName);
+      }
+      if( pItem->zAlias ){
+        sqlite3DebugPrintf(" AS %s", pItem->zAlias);
+      }
+      if( i<p->pSrc->nSrc-1 ){
+        sqlite3DebugPrintf(",");
+      }
+      sqlite3DebugPrintf("\n");
+    }
+  }
+  if( p->pWhere ){
+    sqlite3DebugPrintf("%*s WHERE ", indent, "");
+    sqlite3PrintExpr(p->pWhere);
+    sqlite3DebugPrintf("\n");
+  }
+  if( p->pGroupBy ){
+    sqlite3DebugPrintf("%*s GROUP BY ", indent, "");
+    sqlite3PrintExprList(p->pGroupBy);
+    sqlite3DebugPrintf("\n");
+  }
+  if( p->pHaving ){
+    sqlite3DebugPrintf("%*s HAVING ", indent, "");
+    sqlite3PrintExpr(p->pHaving);
+    sqlite3DebugPrintf("\n");
+  }
+  if( p->pOrderBy ){
+    sqlite3DebugPrintf("%*s ORDER BY ", indent, "");
+    sqlite3PrintExprList(p->pOrderBy);
+    sqlite3DebugPrintf("\n");
+  }
+}
+/* End of the structure debug printing code
+*****************************************************************************/
+#endif /* defined(SQLITE_TEST) || defined(SQLITE_DEBUG) */
diff --git a/src/shell.c b/src/shell.c
new file mode 100644
index 0000000..07623e5
--- /dev/null
+++ b/src/shell.c
@@ -0,0 +1,2967 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains code to implement the "sqlite" command line
+** utility for accessing SQLite databases.
+*/
+#if (defined(_WIN32) || defined(WIN32)) && !defined(_CRT_SECURE_NO_WARNINGS)
+/* This needs to come before any includes for MSVC compiler */
+#define _CRT_SECURE_NO_WARNINGS
+#endif
+
+/*
+** Enable large-file support for fopen() and friends on unix.
+*/
+#ifndef SQLITE_DISABLE_LFS
+# define _LARGE_FILE       1
+# ifndef _FILE_OFFSET_BITS
+#   define _FILE_OFFSET_BITS 64
+# endif
+# define _LARGEFILE_SOURCE 1
+#endif
+
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include <assert.h>
+#include "sqlite3.h"
+#include <ctype.h>
+#include <stdarg.h>
+
+#if !defined(_WIN32) && !defined(WIN32) && !defined(__OS2__)
+# include <signal.h>
+# if !defined(__RTP__) && !defined(_WRS_KERNEL)
+#  include <pwd.h>
+# endif
+# include <unistd.h>
+# include <sys/types.h>
+#endif
+
+#ifdef __OS2__
+# include <unistd.h>
+#endif
+
+#ifdef HAVE_EDITLINE
+# include <editline/editline.h>
+#endif
+#if defined(HAVE_READLINE) && HAVE_READLINE==1
+# include <readline/readline.h>
+# include <readline/history.h>
+#endif
+#if !defined(HAVE_EDITLINE) && (!defined(HAVE_READLINE) || HAVE_READLINE!=1)
+# define readline(p) local_getline(p,stdin)
+# define add_history(X)
+# define read_history(X)
+# define write_history(X)
+# define stifle_history(X)
+#endif
+
+#if defined(_WIN32) || defined(WIN32)
+# include <io.h>
+#define isatty(h) _isatty(h)
+#define access(f,m) _access((f),(m))
+#else
+/* Make sure isatty() has a prototype.
+*/
+extern int isatty(int);
+#endif
+
+#if defined(_WIN32_WCE)
+/* Windows CE (arm-wince-mingw32ce-gcc) does not provide isatty()
+ * thus we always assume that we have a console. That can be
+ * overridden with the -batch command line option.
+ */
+#define isatty(x) 1
+#endif
+
+/* True if the timer is enabled */
+static int enableTimer = 0;
+
+/* ctype macros that work with signed characters */
+#define IsSpace(X)  isspace((unsigned char)X)
+#define IsDigit(X)  isdigit((unsigned char)X)
+#define ToLower(X)  (char)tolower((unsigned char)X)
+
+#if !defined(_WIN32) && !defined(WIN32) && !defined(__OS2__) && !defined(__RTP__) && !defined(_WRS_KERNEL)
+#include <sys/time.h>
+#include <sys/resource.h>
+
+/* Saved resource information for the beginning of an operation */
+static struct rusage sBegin;
+
+/*
+** Begin timing an operation
+*/
+static void beginTimer(void){
+  if( enableTimer ){
+    getrusage(RUSAGE_SELF, &sBegin);
+  }
+}
+
+/* Return the difference of two time_structs in seconds */
+static double timeDiff(struct timeval *pStart, struct timeval *pEnd){
+  return (pEnd->tv_usec - pStart->tv_usec)*0.000001 + 
+         (double)(pEnd->tv_sec - pStart->tv_sec);
+}
+
+/*
+** Print the timing results.
+*/
+static void endTimer(void){
+  if( enableTimer ){
+    struct rusage sEnd;
+    getrusage(RUSAGE_SELF, &sEnd);
+    printf("CPU Time: user %f sys %f\n",
+       timeDiff(&sBegin.ru_utime, &sEnd.ru_utime),
+       timeDiff(&sBegin.ru_stime, &sEnd.ru_stime));
+  }
+}
+
+#define BEGIN_TIMER beginTimer()
+#define END_TIMER endTimer()
+#define HAS_TIMER 1
+
+#elif (defined(_WIN32) || defined(WIN32))
+
+#include <windows.h>
+
+/* Saved resource information for the beginning of an operation */
+static HANDLE hProcess;
+static FILETIME ftKernelBegin;
+static FILETIME ftUserBegin;
+typedef BOOL (WINAPI *GETPROCTIMES)(HANDLE, LPFILETIME, LPFILETIME, LPFILETIME, LPFILETIME);
+static GETPROCTIMES getProcessTimesAddr = NULL;
+
+/*
+** Check to see if we have timer support.  Return 1 if necessary
+** support found (or found previously).
+*/
+static int hasTimer(void){
+  if( getProcessTimesAddr ){
+    return 1;
+  } else {
+    /* GetProcessTimes() isn't supported in WIN95 and some other Windows versions.
+    ** See if the version we are running on has it, and if it does, save off
+    ** a pointer to it and the current process handle.
+    */
+    hProcess = GetCurrentProcess();
+    if( hProcess ){
+      HINSTANCE hinstLib = LoadLibrary(TEXT("Kernel32.dll"));
+      if( NULL != hinstLib ){
+        getProcessTimesAddr = (GETPROCTIMES) GetProcAddress(hinstLib, "GetProcessTimes");
+        if( NULL != getProcessTimesAddr ){
+          return 1;
+        }
+        FreeLibrary(hinstLib); 
+      }
+    }
+  }
+  return 0;
+}
+
+/*
+** Begin timing an operation
+*/
+static void beginTimer(void){
+  if( enableTimer && getProcessTimesAddr ){
+    FILETIME ftCreation, ftExit;
+    getProcessTimesAddr(hProcess, &ftCreation, &ftExit, &ftKernelBegin, &ftUserBegin);
+  }
+}
+
+/* Return the difference of two FILETIME structs in seconds */
+static double timeDiff(FILETIME *pStart, FILETIME *pEnd){
+  sqlite_int64 i64Start = *((sqlite_int64 *) pStart);
+  sqlite_int64 i64End = *((sqlite_int64 *) pEnd);
+  return (double) ((i64End - i64Start) / 10000000.0);
+}
+
+/*
+** Print the timing results.
+*/
+static void endTimer(void){
+  if( enableTimer && getProcessTimesAddr){
+    FILETIME ftCreation, ftExit, ftKernelEnd, ftUserEnd;
+    getProcessTimesAddr(hProcess, &ftCreation, &ftExit, &ftKernelEnd, &ftUserEnd);
+    printf("CPU Time: user %f sys %f\n",
+       timeDiff(&ftUserBegin, &ftUserEnd),
+       timeDiff(&ftKernelBegin, &ftKernelEnd));
+  }
+}
+
+#define BEGIN_TIMER beginTimer()
+#define END_TIMER endTimer()
+#define HAS_TIMER hasTimer()
+
+#else
+#define BEGIN_TIMER 
+#define END_TIMER
+#define HAS_TIMER 0
+#endif
+
+/*
+** Used to prevent warnings about unused parameters
+*/
+#define UNUSED_PARAMETER(x) (void)(x)
+
+/*
+** If the following flag is set, then command execution stops
+** at an error if we are not interactive.
+*/
+static int bail_on_error = 0;
+
+/*
+** Threat stdin as an interactive input if the following variable
+** is true.  Otherwise, assume stdin is connected to a file or pipe.
+*/
+static int stdin_is_interactive = 1;
+
+/*
+** The following is the open SQLite database.  We make a pointer
+** to this database a static variable so that it can be accessed
+** by the SIGINT handler to interrupt database processing.
+*/
+static sqlite3 *db = 0;
+
+/*
+** True if an interrupt (Control-C) has been received.
+*/
+static volatile int seenInterrupt = 0;
+
+/*
+** This is the name of our program. It is set in main(), used
+** in a number of other places, mostly for error messages.
+*/
+static char *Argv0;
+
+/*
+** Prompt strings. Initialized in main. Settable with
+**   .prompt main continue
+*/
+static char mainPrompt[20];     /* First line prompt. default: "sqlite> "*/
+static char continuePrompt[20]; /* Continuation prompt. default: "   ...> " */
+
+/*
+** Write I/O traces to the following stream.
+*/
+#ifdef SQLITE_ENABLE_IOTRACE
+static FILE *iotrace = 0;
+#endif
+
+/*
+** This routine works like printf in that its first argument is a
+** format string and subsequent arguments are values to be substituted
+** in place of % fields.  The result of formatting this string
+** is written to iotrace.
+*/
+#ifdef SQLITE_ENABLE_IOTRACE
+static void iotracePrintf(const char *zFormat, ...){
+  va_list ap;
+  char *z;
+  if( iotrace==0 ) return;
+  va_start(ap, zFormat);
+  z = sqlite3_vmprintf(zFormat, ap);
+  va_end(ap);
+  fprintf(iotrace, "%s", z);
+  sqlite3_free(z);
+}
+#endif
+
+
+/*
+** Determines if a string is a number of not.
+*/
+static int isNumber(const char *z, int *realnum){
+  if( *z=='-' || *z=='+' ) z++;
+  if( !IsDigit(*z) ){
+    return 0;
+  }
+  z++;
+  if( realnum ) *realnum = 0;
+  while( IsDigit(*z) ){ z++; }
+  if( *z=='.' ){
+    z++;
+    if( !IsDigit(*z) ) return 0;
+    while( IsDigit(*z) ){ z++; }
+    if( realnum ) *realnum = 1;
+  }
+  if( *z=='e' || *z=='E' ){
+    z++;
+    if( *z=='+' || *z=='-' ) z++;
+    if( !IsDigit(*z) ) return 0;
+    while( IsDigit(*z) ){ z++; }
+    if( realnum ) *realnum = 1;
+  }
+  return *z==0;
+}
+
+/*
+** A global char* and an SQL function to access its current value 
+** from within an SQL statement. This program used to use the 
+** sqlite_exec_printf() API to substitue a string into an SQL statement.
+** The correct way to do this with sqlite3 is to use the bind API, but
+** since the shell is built around the callback paradigm it would be a lot
+** of work. Instead just use this hack, which is quite harmless.
+*/
+static const char *zShellStatic = 0;
+static void shellstaticFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  assert( 0==argc );
+  assert( zShellStatic );
+  UNUSED_PARAMETER(argc);
+  UNUSED_PARAMETER(argv);
+  sqlite3_result_text(context, zShellStatic, -1, SQLITE_STATIC);
+}
+
+
+/*
+** This routine reads a line of text from FILE in, stores
+** the text in memory obtained from malloc() and returns a pointer
+** to the text.  NULL is returned at end of file, or if malloc()
+** fails.
+**
+** The interface is like "readline" but no command-line editing
+** is done.
+*/
+static char *local_getline(char *zPrompt, FILE *in){
+  char *zLine;
+  int nLine;
+  int n;
+
+  if( zPrompt && *zPrompt ){
+    printf("%s",zPrompt);
+    fflush(stdout);
+  }
+  nLine = 100;
+  zLine = malloc( nLine );
+  if( zLine==0 ) return 0;
+  n = 0;
+  while( 1 ){
+    if( n+100>nLine ){
+      nLine = nLine*2 + 100;
+      zLine = realloc(zLine, nLine);
+      if( zLine==0 ) return 0;
+    }
+    if( fgets(&zLine[n], nLine - n, in)==0 ){
+      if( n==0 ){
+        free(zLine);
+        return 0;
+      }
+      zLine[n] = 0;
+      break;
+    }
+    while( zLine[n] ){ n++; }
+    if( n>0 && zLine[n-1]=='\n' ){
+      n--;
+      if( n>0 && zLine[n-1]=='\r' ) n--;
+      zLine[n] = 0;
+      break;
+    }
+  }
+  zLine = realloc( zLine, n+1 );
+  return zLine;
+}
+
+/*
+** Retrieve a single line of input text.
+**
+** zPrior is a string of prior text retrieved.  If not the empty
+** string, then issue a continuation prompt.
+*/
+static char *one_input_line(const char *zPrior, FILE *in){
+  char *zPrompt;
+  char *zResult;
+  if( in!=0 ){
+    return local_getline(0, in);
+  }
+  if( zPrior && zPrior[0] ){
+    zPrompt = continuePrompt;
+  }else{
+    zPrompt = mainPrompt;
+  }
+  zResult = readline(zPrompt);
+#if defined(HAVE_READLINE) && HAVE_READLINE==1
+  if( zResult && *zResult ) add_history(zResult);
+#endif
+  return zResult;
+}
+
+struct previous_mode_data {
+  int valid;        /* Is there legit data in here? */
+  int mode;
+  int showHeader;
+  int colWidth[100];
+};
+
+/*
+** An pointer to an instance of this structure is passed from
+** the main program to the callback.  This is used to communicate
+** state and mode information.
+*/
+struct callback_data {
+  sqlite3 *db;           /* The database */
+  int echoOn;            /* True to echo input commands */
+  int statsOn;           /* True to display memory stats before each finalize */
+  int cnt;               /* Number of records displayed so far */
+  FILE *out;             /* Write results here */
+  int nErr;              /* Number of errors seen */
+  int mode;              /* An output mode setting */
+  int writableSchema;    /* True if PRAGMA writable_schema=ON */
+  int showHeader;        /* True to show column names in List or Column mode */
+  char *zDestTable;      /* Name of destination table when MODE_Insert */
+  char separator[20];    /* Separator character for MODE_List */
+  int colWidth[100];     /* Requested width of each column when in column mode*/
+  int actualWidth[100];  /* Actual width of each column */
+  char nullvalue[20];    /* The text to print when a NULL comes back from
+                         ** the database */
+  struct previous_mode_data explainPrev;
+                         /* Holds the mode information just before
+                         ** .explain ON */
+  char outfile[FILENAME_MAX]; /* Filename for *out */
+  const char *zDbFilename;    /* name of the database file */
+  const char *zVfs;           /* Name of VFS to use */
+  sqlite3_stmt *pStmt;   /* Current statement if any. */
+  FILE *pLog;            /* Write log output here */
+};
+
+/*
+** These are the allowed modes.
+*/
+#define MODE_Line     0  /* One column per line.  Blank line between records */
+#define MODE_Column   1  /* One record per line in neat columns */
+#define MODE_List     2  /* One record per line with a separator */
+#define MODE_Semi     3  /* Same as MODE_List but append ";" to each line */
+#define MODE_Html     4  /* Generate an XHTML table */
+#define MODE_Insert   5  /* Generate SQL "insert" statements */
+#define MODE_Tcl      6  /* Generate ANSI-C or TCL quoted elements */
+#define MODE_Csv      7  /* Quote strings, numbers are plain */
+#define MODE_Explain  8  /* Like MODE_Column, but do not truncate data */
+
+static const char *modeDescr[] = {
+  "line",
+  "column",
+  "list",
+  "semi",
+  "html",
+  "insert",
+  "tcl",
+  "csv",
+  "explain",
+};
+
+/*
+** Number of elements in an array
+*/
+#define ArraySize(X)  (int)(sizeof(X)/sizeof(X[0]))
+
+/*
+** Compute a string length that is limited to what can be stored in
+** lower 30 bits of a 32-bit signed integer.
+*/
+static int strlen30(const char *z){
+  const char *z2 = z;
+  while( *z2 ){ z2++; }
+  return 0x3fffffff & (int)(z2 - z);
+}
+
+/*
+** A callback for the sqlite3_log() interface.
+*/
+static void shellLog(void *pArg, int iErrCode, const char *zMsg){
+  struct callback_data *p = (struct callback_data*)pArg;
+  if( p->pLog==0 ) return;
+  fprintf(p->pLog, "(%d) %s\n", iErrCode, zMsg);
+  fflush(p->pLog);
+}
+
+/*
+** Output the given string as a hex-encoded blob (eg. X'1234' )
+*/
+static void output_hex_blob(FILE *out, const void *pBlob, int nBlob){
+  int i;
+  char *zBlob = (char *)pBlob;
+  fprintf(out,"X'");
+  for(i=0; i<nBlob; i++){ fprintf(out,"%02x",zBlob[i]); }
+  fprintf(out,"'");
+}
+
+/*
+** Output the given string as a quoted string using SQL quoting conventions.
+*/
+static void output_quoted_string(FILE *out, const char *z){
+  int i;
+  int nSingle = 0;
+  for(i=0; z[i]; i++){
+    if( z[i]=='\'' ) nSingle++;
+  }
+  if( nSingle==0 ){
+    fprintf(out,"'%s'",z);
+  }else{
+    fprintf(out,"'");
+    while( *z ){
+      for(i=0; z[i] && z[i]!='\''; i++){}
+      if( i==0 ){
+        fprintf(out,"''");
+        z++;
+      }else if( z[i]=='\'' ){
+        fprintf(out,"%.*s''",i,z);
+        z += i+1;
+      }else{
+        fprintf(out,"%s",z);
+        break;
+      }
+    }
+    fprintf(out,"'");
+  }
+}
+
+/*
+** Output the given string as a quoted according to C or TCL quoting rules.
+*/
+static void output_c_string(FILE *out, const char *z){
+  unsigned int c;
+  fputc('"', out);
+  while( (c = *(z++))!=0 ){
+    if( c=='\\' ){
+      fputc(c, out);
+      fputc(c, out);
+    }else if( c=='\t' ){
+      fputc('\\', out);
+      fputc('t', out);
+    }else if( c=='\n' ){
+      fputc('\\', out);
+      fputc('n', out);
+    }else if( c=='\r' ){
+      fputc('\\', out);
+      fputc('r', out);
+    }else if( !isprint(c) ){
+      fprintf(out, "\\%03o", c&0xff);
+    }else{
+      fputc(c, out);
+    }
+  }
+  fputc('"', out);
+}
+
+/*
+** Output the given string with characters that are special to
+** HTML escaped.
+*/
+static void output_html_string(FILE *out, const char *z){
+  int i;
+  while( *z ){
+    for(i=0;   z[i] 
+            && z[i]!='<' 
+            && z[i]!='&' 
+            && z[i]!='>' 
+            && z[i]!='\"' 
+            && z[i]!='\'';
+        i++){}
+    if( i>0 ){
+      fprintf(out,"%.*s",i,z);
+    }
+    if( z[i]=='<' ){
+      fprintf(out,"&lt;");
+    }else if( z[i]=='&' ){
+      fprintf(out,"&amp;");
+    }else if( z[i]=='>' ){
+      fprintf(out,"&gt;");
+    }else if( z[i]=='\"' ){
+      fprintf(out,"&quot;");
+    }else if( z[i]=='\'' ){
+      fprintf(out,"&#39;");
+    }else{
+      break;
+    }
+    z += i + 1;
+  }
+}
+
+/*
+** If a field contains any character identified by a 1 in the following
+** array, then the string must be quoted for CSV.
+*/
+static const char needCsvQuote[] = {
+  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,   
+  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,   
+  1, 0, 1, 0, 0, 0, 0, 1,   0, 0, 0, 0, 0, 0, 0, 0, 
+  0, 0, 0, 0, 0, 0, 0, 0,   0, 0, 0, 0, 0, 0, 0, 0, 
+  0, 0, 0, 0, 0, 0, 0, 0,   0, 0, 0, 0, 0, 0, 0, 0, 
+  0, 0, 0, 0, 0, 0, 0, 0,   0, 0, 0, 0, 0, 0, 0, 0, 
+  0, 0, 0, 0, 0, 0, 0, 0,   0, 0, 0, 0, 0, 0, 0, 0, 
+  0, 0, 0, 0, 0, 0, 0, 0,   0, 0, 0, 0, 0, 0, 0, 1, 
+  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,   
+  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,   
+  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,   
+  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,   
+  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,   
+  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,   
+  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,   
+  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,   
+};
+
+/*
+** Output a single term of CSV.  Actually, p->separator is used for
+** the separator, which may or may not be a comma.  p->nullvalue is
+** the null value.  Strings are quoted using ANSI-C rules.  Numbers
+** appear outside of quotes.
+*/
+static void output_csv(struct callback_data *p, const char *z, int bSep){
+  FILE *out = p->out;
+  if( z==0 ){
+    fprintf(out,"%s",p->nullvalue);
+  }else{
+    int i;
+    int nSep = strlen30(p->separator);
+    for(i=0; z[i]; i++){
+      if( needCsvQuote[((unsigned char*)z)[i]] 
+         || (z[i]==p->separator[0] && 
+             (nSep==1 || memcmp(z, p->separator, nSep)==0)) ){
+        i = 0;
+        break;
+      }
+    }
+    if( i==0 ){
+      putc('"', out);
+      for(i=0; z[i]; i++){
+        if( z[i]=='"' ) putc('"', out);
+        putc(z[i], out);
+      }
+      putc('"', out);
+    }else{
+      fprintf(out, "%s", z);
+    }
+  }
+  if( bSep ){
+    fprintf(p->out, "%s", p->separator);
+  }
+}
+
+#ifdef SIGINT
+/*
+** This routine runs when the user presses Ctrl-C
+*/
+static void interrupt_handler(int NotUsed){
+  UNUSED_PARAMETER(NotUsed);
+  seenInterrupt = 1;
+  if( db ) sqlite3_interrupt(db);
+}
+#endif
+
+/*
+** This is the callback routine that the shell
+** invokes for each row of a query result.
+*/
+static int shell_callback(void *pArg, int nArg, char **azArg, char **azCol, int *aiType){
+  int i;
+  struct callback_data *p = (struct callback_data*)pArg;
+
+  switch( p->mode ){
+    case MODE_Line: {
+      int w = 5;
+      if( azArg==0 ) break;
+      for(i=0; i<nArg; i++){
+        int len = strlen30(azCol[i] ? azCol[i] : "");
+        if( len>w ) w = len;
+      }
+      if( p->cnt++>0 ) fprintf(p->out,"\n");
+      for(i=0; i<nArg; i++){
+        fprintf(p->out,"%*s = %s\n", w, azCol[i],
+                azArg[i] ? azArg[i] : p->nullvalue);
+      }
+      break;
+    }
+    case MODE_Explain:
+    case MODE_Column: {
+      if( p->cnt++==0 ){
+        for(i=0; i<nArg; i++){
+          int w, n;
+          if( i<ArraySize(p->colWidth) ){
+            w = p->colWidth[i];
+          }else{
+            w = 0;
+          }
+          if( w<=0 ){
+            w = strlen30(azCol[i] ? azCol[i] : "");
+            if( w<10 ) w = 10;
+            n = strlen30(azArg && azArg[i] ? azArg[i] : p->nullvalue);
+            if( w<n ) w = n;
+          }
+          if( i<ArraySize(p->actualWidth) ){
+            p->actualWidth[i] = w;
+          }
+          if( p->showHeader ){
+            fprintf(p->out,"%-*.*s%s",w,w,azCol[i], i==nArg-1 ? "\n": "  ");
+          }
+        }
+        if( p->showHeader ){
+          for(i=0; i<nArg; i++){
+            int w;
+            if( i<ArraySize(p->actualWidth) ){
+               w = p->actualWidth[i];
+            }else{
+               w = 10;
+            }
+            fprintf(p->out,"%-*.*s%s",w,w,"-----------------------------------"
+                   "----------------------------------------------------------",
+                    i==nArg-1 ? "\n": "  ");
+          }
+        }
+      }
+      if( azArg==0 ) break;
+      for(i=0; i<nArg; i++){
+        int w;
+        if( i<ArraySize(p->actualWidth) ){
+           w = p->actualWidth[i];
+        }else{
+           w = 10;
+        }
+        if( p->mode==MODE_Explain && azArg[i] && 
+           strlen30(azArg[i])>w ){
+          w = strlen30(azArg[i]);
+        }
+        fprintf(p->out,"%-*.*s%s",w,w,
+            azArg[i] ? azArg[i] : p->nullvalue, i==nArg-1 ? "\n": "  ");
+      }
+      break;
+    }
+    case MODE_Semi:
+    case MODE_List: {
+      if( p->cnt++==0 && p->showHeader ){
+        for(i=0; i<nArg; i++){
+          fprintf(p->out,"%s%s",azCol[i], i==nArg-1 ? "\n" : p->separator);
+        }
+      }
+      if( azArg==0 ) break;
+      for(i=0; i<nArg; i++){
+        char *z = azArg[i];
+        if( z==0 ) z = p->nullvalue;
+        fprintf(p->out, "%s", z);
+        if( i<nArg-1 ){
+          fprintf(p->out, "%s", p->separator);
+        }else if( p->mode==MODE_Semi ){
+          fprintf(p->out, ";\n");
+        }else{
+          fprintf(p->out, "\n");
+        }
+      }
+      break;
+    }
+    case MODE_Html: {
+      if( p->cnt++==0 && p->showHeader ){
+        fprintf(p->out,"<TR>");
+        for(i=0; i<nArg; i++){
+          fprintf(p->out,"<TH>");
+          output_html_string(p->out, azCol[i]);
+          fprintf(p->out,"</TH>\n");
+        }
+        fprintf(p->out,"</TR>\n");
+      }
+      if( azArg==0 ) break;
+      fprintf(p->out,"<TR>");
+      for(i=0; i<nArg; i++){
+        fprintf(p->out,"<TD>");
+        output_html_string(p->out, azArg[i] ? azArg[i] : p->nullvalue);
+        fprintf(p->out,"</TD>\n");
+      }
+      fprintf(p->out,"</TR>\n");
+      break;
+    }
+    case MODE_Tcl: {
+      if( p->cnt++==0 && p->showHeader ){
+        for(i=0; i<nArg; i++){
+          output_c_string(p->out,azCol[i] ? azCol[i] : "");
+          fprintf(p->out, "%s", p->separator);
+        }
+        fprintf(p->out,"\n");
+      }
+      if( azArg==0 ) break;
+      for(i=0; i<nArg; i++){
+        output_c_string(p->out, azArg[i] ? azArg[i] : p->nullvalue);
+        fprintf(p->out, "%s", p->separator);
+      }
+      fprintf(p->out,"\n");
+      break;
+    }
+    case MODE_Csv: {
+      if( p->cnt++==0 && p->showHeader ){
+        for(i=0; i<nArg; i++){
+          output_csv(p, azCol[i] ? azCol[i] : "", i<nArg-1);
+        }
+        fprintf(p->out,"\n");
+      }
+      if( azArg==0 ) break;
+      for(i=0; i<nArg; i++){
+        output_csv(p, azArg[i], i<nArg-1);
+      }
+      fprintf(p->out,"\n");
+      break;
+    }
+    case MODE_Insert: {
+      p->cnt++;
+      if( azArg==0 ) break;
+      fprintf(p->out,"INSERT INTO %s VALUES(",p->zDestTable);
+      for(i=0; i<nArg; i++){
+        char *zSep = i>0 ? ",": "";
+        if( (azArg[i]==0) || (aiType && aiType[i]==SQLITE_NULL) ){
+          fprintf(p->out,"%sNULL",zSep);
+        }else if( aiType && aiType[i]==SQLITE_TEXT ){
+          if( zSep[0] ) fprintf(p->out,"%s",zSep);
+          output_quoted_string(p->out, azArg[i]);
+        }else if( aiType && (aiType[i]==SQLITE_INTEGER || aiType[i]==SQLITE_FLOAT) ){
+          fprintf(p->out,"%s%s",zSep, azArg[i]);
+        }else if( aiType && aiType[i]==SQLITE_BLOB && p->pStmt ){
+          const void *pBlob = sqlite3_column_blob(p->pStmt, i);
+          int nBlob = sqlite3_column_bytes(p->pStmt, i);
+          if( zSep[0] ) fprintf(p->out,"%s",zSep);
+          output_hex_blob(p->out, pBlob, nBlob);
+        }else if( isNumber(azArg[i], 0) ){
+          fprintf(p->out,"%s%s",zSep, azArg[i]);
+        }else{
+          if( zSep[0] ) fprintf(p->out,"%s",zSep);
+          output_quoted_string(p->out, azArg[i]);
+        }
+      }
+      fprintf(p->out,");\n");
+      break;
+    }
+  }
+  return 0;
+}
+
+/*
+** This is the callback routine that the SQLite library
+** invokes for each row of a query result.
+*/
+static int callback(void *pArg, int nArg, char **azArg, char **azCol){
+  /* since we don't have type info, call the shell_callback with a NULL value */
+  return shell_callback(pArg, nArg, azArg, azCol, NULL);
+}
+
+/*
+** Set the destination table field of the callback_data structure to
+** the name of the table given.  Escape any quote characters in the
+** table name.
+*/
+static void set_table_name(struct callback_data *p, const char *zName){
+  int i, n;
+  int needQuote;
+  char *z;
+
+  if( p->zDestTable ){
+    free(p->zDestTable);
+    p->zDestTable = 0;
+  }
+  if( zName==0 ) return;
+  needQuote = !isalpha((unsigned char)*zName) && *zName!='_';
+  for(i=n=0; zName[i]; i++, n++){
+    if( !isalnum((unsigned char)zName[i]) && zName[i]!='_' ){
+      needQuote = 1;
+      if( zName[i]=='\'' ) n++;
+    }
+  }
+  if( needQuote ) n += 2;
+  z = p->zDestTable = malloc( n+1 );
+  if( z==0 ){
+    fprintf(stderr,"Error: out of memory\n");
+    exit(1);
+  }
+  n = 0;
+  if( needQuote ) z[n++] = '\'';
+  for(i=0; zName[i]; i++){
+    z[n++] = zName[i];
+    if( zName[i]=='\'' ) z[n++] = '\'';
+  }
+  if( needQuote ) z[n++] = '\'';
+  z[n] = 0;
+}
+
+/* zIn is either a pointer to a NULL-terminated string in memory obtained
+** from malloc(), or a NULL pointer. The string pointed to by zAppend is
+** added to zIn, and the result returned in memory obtained from malloc().
+** zIn, if it was not NULL, is freed.
+**
+** If the third argument, quote, is not '\0', then it is used as a 
+** quote character for zAppend.
+*/
+static char *appendText(char *zIn, char const *zAppend, char quote){
+  int len;
+  int i;
+  int nAppend = strlen30(zAppend);
+  int nIn = (zIn?strlen30(zIn):0);
+
+  len = nAppend+nIn+1;
+  if( quote ){
+    len += 2;
+    for(i=0; i<nAppend; i++){
+      if( zAppend[i]==quote ) len++;
+    }
+  }
+
+  zIn = (char *)realloc(zIn, len);
+  if( !zIn ){
+    return 0;
+  }
+
+  if( quote ){
+    char *zCsr = &zIn[nIn];
+    *zCsr++ = quote;
+    for(i=0; i<nAppend; i++){
+      *zCsr++ = zAppend[i];
+      if( zAppend[i]==quote ) *zCsr++ = quote;
+    }
+    *zCsr++ = quote;
+    *zCsr++ = '\0';
+    assert( (zCsr-zIn)==len );
+  }else{
+    memcpy(&zIn[nIn], zAppend, nAppend);
+    zIn[len-1] = '\0';
+  }
+
+  return zIn;
+}
+
+
+/*
+** Execute a query statement that has a single result column.  Print
+** that result column on a line by itself with a semicolon terminator.
+**
+** This is used, for example, to show the schema of the database by
+** querying the SQLITE_MASTER table.
+*/
+static int run_table_dump_query(
+  struct callback_data *p, /* Query context */
+  const char *zSelect,     /* SELECT statement to extract content */
+  const char *zFirstRow    /* Print before first row, if not NULL */
+){
+  sqlite3_stmt *pSelect;
+  int rc;
+  rc = sqlite3_prepare(p->db, zSelect, -1, &pSelect, 0);
+  if( rc!=SQLITE_OK || !pSelect ){
+    fprintf(p->out, "/**** ERROR: (%d) %s *****/\n", rc, sqlite3_errmsg(p->db));
+    p->nErr++;
+    return rc;
+  }
+  rc = sqlite3_step(pSelect);
+  while( rc==SQLITE_ROW ){
+    if( zFirstRow ){
+      fprintf(p->out, "%s", zFirstRow);
+      zFirstRow = 0;
+    }
+    fprintf(p->out, "%s;\n", sqlite3_column_text(pSelect, 0));
+    rc = sqlite3_step(pSelect);
+  }
+  rc = sqlite3_finalize(pSelect);
+  if( rc!=SQLITE_OK ){
+    fprintf(p->out, "/**** ERROR: (%d) %s *****/\n", rc, sqlite3_errmsg(p->db));
+    p->nErr++;
+  }
+  return rc;
+}
+
+/*
+** Allocate space and save off current error string.
+*/
+static char *save_err_msg(
+  sqlite3 *db            /* Database to query */
+){
+  int nErrMsg = 1+strlen30(sqlite3_errmsg(db));
+  char *zErrMsg = sqlite3_malloc(nErrMsg);
+  if( zErrMsg ){
+    memcpy(zErrMsg, sqlite3_errmsg(db), nErrMsg);
+  }
+  return zErrMsg;
+}
+
+/*
+** Display memory stats.
+*/
+static int display_stats(
+  sqlite3 *db,                /* Database to query */
+  struct callback_data *pArg, /* Pointer to struct callback_data */
+  int bReset                  /* True to reset the stats */
+){
+  int iCur;
+  int iHiwtr;
+
+  if( pArg && pArg->out ){
+    
+    iHiwtr = iCur = -1;
+    sqlite3_status(SQLITE_STATUS_MEMORY_USED, &iCur, &iHiwtr, bReset);
+    fprintf(pArg->out, "Memory Used:                         %d (max %d) bytes\n", iCur, iHiwtr);
+    iHiwtr = iCur = -1;
+    sqlite3_status(SQLITE_STATUS_MALLOC_COUNT, &iCur, &iHiwtr, bReset);
+    fprintf(pArg->out, "Number of Outstanding Allocations:   %d (max %d)\n", iCur, iHiwtr);
+/*
+** Not currently used by the CLI.
+**    iHiwtr = iCur = -1;
+**    sqlite3_status(SQLITE_STATUS_PAGECACHE_USED, &iCur, &iHiwtr, bReset);
+**    fprintf(pArg->out, "Number of Pcache Pages Used:         %d (max %d) pages\n", iCur, iHiwtr);
+*/
+    iHiwtr = iCur = -1;
+    sqlite3_status(SQLITE_STATUS_PAGECACHE_OVERFLOW, &iCur, &iHiwtr, bReset);
+    fprintf(pArg->out, "Number of Pcache Overflow Bytes:     %d (max %d) bytes\n", iCur, iHiwtr);
+/*
+** Not currently used by the CLI.
+**    iHiwtr = iCur = -1;
+**    sqlite3_status(SQLITE_STATUS_SCRATCH_USED, &iCur, &iHiwtr, bReset);
+**    fprintf(pArg->out, "Number of Scratch Allocations Used:  %d (max %d)\n", iCur, iHiwtr);
+*/
+    iHiwtr = iCur = -1;
+    sqlite3_status(SQLITE_STATUS_SCRATCH_OVERFLOW, &iCur, &iHiwtr, bReset);
+    fprintf(pArg->out, "Number of Scratch Overflow Bytes:    %d (max %d) bytes\n", iCur, iHiwtr);
+    iHiwtr = iCur = -1;
+    sqlite3_status(SQLITE_STATUS_MALLOC_SIZE, &iCur, &iHiwtr, bReset);
+    fprintf(pArg->out, "Largest Allocation:                  %d bytes\n", iHiwtr);
+    iHiwtr = iCur = -1;
+    sqlite3_status(SQLITE_STATUS_PAGECACHE_SIZE, &iCur, &iHiwtr, bReset);
+    fprintf(pArg->out, "Largest Pcache Allocation:           %d bytes\n", iHiwtr);
+    iHiwtr = iCur = -1;
+    sqlite3_status(SQLITE_STATUS_SCRATCH_SIZE, &iCur, &iHiwtr, bReset);
+    fprintf(pArg->out, "Largest Scratch Allocation:          %d bytes\n", iHiwtr);
+#ifdef YYTRACKMAXSTACKDEPTH
+    iHiwtr = iCur = -1;
+    sqlite3_status(SQLITE_STATUS_PARSER_STACK, &iCur, &iHiwtr, bReset);
+    fprintf(pArg->out, "Deepest Parser Stack:                %d (max %d)\n", iCur, iHiwtr);
+#endif
+  }
+
+  if( pArg && pArg->out && db ){
+    iHiwtr = iCur = -1;
+    sqlite3_db_status(db, SQLITE_DBSTATUS_LOOKASIDE_USED, &iCur, &iHiwtr, bReset);
+    fprintf(pArg->out, "Lookaside Slots Used:                %d (max %d)\n", iCur, iHiwtr);
+    sqlite3_db_status(db, SQLITE_DBSTATUS_LOOKASIDE_HIT, &iCur, &iHiwtr, bReset);
+    fprintf(pArg->out, "Successful lookaside attempts:       %d\n", iHiwtr);
+    sqlite3_db_status(db, SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE, &iCur, &iHiwtr, bReset);
+    fprintf(pArg->out, "Lookaside failures due to size:      %d\n", iHiwtr);
+    sqlite3_db_status(db, SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL, &iCur, &iHiwtr, bReset);
+    fprintf(pArg->out, "Lookaside failures due to OOM:       %d\n", iHiwtr);
+    iHiwtr = iCur = -1;
+    sqlite3_db_status(db, SQLITE_DBSTATUS_CACHE_USED, &iCur, &iHiwtr, bReset);
+    fprintf(pArg->out, "Pager Heap Usage:                    %d bytes\n", iCur);    iHiwtr = iCur = -1;
+    sqlite3_db_status(db, SQLITE_DBSTATUS_CACHE_HIT, &iCur, &iHiwtr, 1);
+    fprintf(pArg->out, "Page cache hits:                     %d\n", iCur);
+    iHiwtr = iCur = -1;
+    sqlite3_db_status(db, SQLITE_DBSTATUS_CACHE_MISS, &iCur, &iHiwtr, 1);
+    fprintf(pArg->out, "Page cache misses:                   %d\n", iCur); 
+    iHiwtr = iCur = -1;
+    sqlite3_db_status(db, SQLITE_DBSTATUS_SCHEMA_USED, &iCur, &iHiwtr, bReset);
+    fprintf(pArg->out, "Schema Heap Usage:                   %d bytes\n", iCur); 
+    iHiwtr = iCur = -1;
+    sqlite3_db_status(db, SQLITE_DBSTATUS_STMT_USED, &iCur, &iHiwtr, bReset);
+    fprintf(pArg->out, "Statement Heap/Lookaside Usage:      %d bytes\n", iCur); 
+  }
+
+  if( pArg && pArg->out && db && pArg->pStmt ){
+    iCur = sqlite3_stmt_status(pArg->pStmt, SQLITE_STMTSTATUS_FULLSCAN_STEP, bReset);
+    fprintf(pArg->out, "Fullscan Steps:                      %d\n", iCur);
+    iCur = sqlite3_stmt_status(pArg->pStmt, SQLITE_STMTSTATUS_SORT, bReset);
+    fprintf(pArg->out, "Sort Operations:                     %d\n", iCur);
+    iCur = sqlite3_stmt_status(pArg->pStmt, SQLITE_STMTSTATUS_AUTOINDEX, bReset);
+    fprintf(pArg->out, "Autoindex Inserts:                   %d\n", iCur);
+  }
+
+  return 0;
+}
+
+/*
+** Execute a statement or set of statements.  Print 
+** any result rows/columns depending on the current mode 
+** set via the supplied callback.
+**
+** This is very similar to SQLite's built-in sqlite3_exec() 
+** function except it takes a slightly different callback 
+** and callback data argument.
+*/
+static int shell_exec(
+  sqlite3 *db,                                /* An open database */
+  const char *zSql,                           /* SQL to be evaluated */
+  int (*xCallback)(void*,int,char**,char**,int*),   /* Callback function */
+                                              /* (not the same as sqlite3_exec) */
+  struct callback_data *pArg,                 /* Pointer to struct callback_data */
+  char **pzErrMsg                             /* Error msg written here */
+){
+  sqlite3_stmt *pStmt = NULL;     /* Statement to execute. */
+  int rc = SQLITE_OK;             /* Return Code */
+  int rc2;
+  const char *zLeftover;          /* Tail of unprocessed SQL */
+
+  if( pzErrMsg ){
+    *pzErrMsg = NULL;
+  }
+
+  while( zSql[0] && (SQLITE_OK == rc) ){
+    rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, &zLeftover);
+    if( SQLITE_OK != rc ){
+      if( pzErrMsg ){
+        *pzErrMsg = save_err_msg(db);
+      }
+    }else{
+      if( !pStmt ){
+        /* this happens for a comment or white-space */
+        zSql = zLeftover;
+        while( IsSpace(zSql[0]) ) zSql++;
+        continue;
+      }
+
+      /* save off the prepared statment handle and reset row count */
+      if( pArg ){
+        pArg->pStmt = pStmt;
+        pArg->cnt = 0;
+      }
+
+      /* echo the sql statement if echo on */
+      if( pArg && pArg->echoOn ){
+        const char *zStmtSql = sqlite3_sql(pStmt);
+        fprintf(pArg->out, "%s\n", zStmtSql ? zStmtSql : zSql);
+      }
+
+      /* perform the first step.  this will tell us if we
+      ** have a result set or not and how wide it is.
+      */
+      rc = sqlite3_step(pStmt);
+      /* if we have a result set... */
+      if( SQLITE_ROW == rc ){
+        /* if we have a callback... */
+        if( xCallback ){
+          /* allocate space for col name ptr, value ptr, and type */
+          int nCol = sqlite3_column_count(pStmt);
+          void *pData = sqlite3_malloc(3*nCol*sizeof(const char*) + 1);
+          if( !pData ){
+            rc = SQLITE_NOMEM;
+          }else{
+            char **azCols = (char **)pData;      /* Names of result columns */
+            char **azVals = &azCols[nCol];       /* Results */
+            int *aiTypes = (int *)&azVals[nCol]; /* Result types */
+            int i;
+            assert(sizeof(int) <= sizeof(char *)); 
+            /* save off ptrs to column names */
+            for(i=0; i<nCol; i++){
+              azCols[i] = (char *)sqlite3_column_name(pStmt, i);
+            }
+            do{
+              /* extract the data and data types */
+              for(i=0; i<nCol; i++){
+                azVals[i] = (char *)sqlite3_column_text(pStmt, i);
+                aiTypes[i] = sqlite3_column_type(pStmt, i);
+                if( !azVals[i] && (aiTypes[i]!=SQLITE_NULL) ){
+                  rc = SQLITE_NOMEM;
+                  break; /* from for */
+                }
+              } /* end for */
+
+              /* if data and types extracted successfully... */
+              if( SQLITE_ROW == rc ){ 
+                /* call the supplied callback with the result row data */
+                if( xCallback(pArg, nCol, azVals, azCols, aiTypes) ){
+                  rc = SQLITE_ABORT;
+                }else{
+                  rc = sqlite3_step(pStmt);
+                }
+              }
+            } while( SQLITE_ROW == rc );
+            sqlite3_free(pData);
+          }
+        }else{
+          do{
+            rc = sqlite3_step(pStmt);
+          } while( rc == SQLITE_ROW );
+        }
+      }
+
+      /* print usage stats if stats on */
+      if( pArg && pArg->statsOn ){
+        display_stats(db, pArg, 0);
+      }
+
+      /* Finalize the statement just executed. If this fails, save a 
+      ** copy of the error message. Otherwise, set zSql to point to the
+      ** next statement to execute. */
+      rc2 = sqlite3_finalize(pStmt);
+      if( rc!=SQLITE_NOMEM ) rc = rc2;
+      if( rc==SQLITE_OK ){
+        zSql = zLeftover;
+        while( IsSpace(zSql[0]) ) zSql++;
+      }else if( pzErrMsg ){
+        *pzErrMsg = save_err_msg(db);
+      }
+
+      /* clear saved stmt handle */
+      if( pArg ){
+        pArg->pStmt = NULL;
+      }
+    }
+  } /* end while */
+
+  return rc;
+}
+
+
+/*
+** This is a different callback routine used for dumping the database.
+** Each row received by this callback consists of a table name,
+** the table type ("index" or "table") and SQL to create the table.
+** This routine should print text sufficient to recreate the table.
+*/
+static int dump_callback(void *pArg, int nArg, char **azArg, char **azCol){
+  int rc;
+  const char *zTable;
+  const char *zType;
+  const char *zSql;
+  const char *zPrepStmt = 0;
+  struct callback_data *p = (struct callback_data *)pArg;
+
+  UNUSED_PARAMETER(azCol);
+  if( nArg!=3 ) return 1;
+  zTable = azArg[0];
+  zType = azArg[1];
+  zSql = azArg[2];
+  
+  if( strcmp(zTable, "sqlite_sequence")==0 ){
+    zPrepStmt = "DELETE FROM sqlite_sequence;\n";
+  }else if( strcmp(zTable, "sqlite_stat1")==0 ){
+    fprintf(p->out, "ANALYZE sqlite_master;\n");
+  }else if( strncmp(zTable, "sqlite_", 7)==0 ){
+    return 0;
+  }else if( strncmp(zSql, "CREATE VIRTUAL TABLE", 20)==0 ){
+    char *zIns;
+    if( !p->writableSchema ){
+      fprintf(p->out, "PRAGMA writable_schema=ON;\n");
+      p->writableSchema = 1;
+    }
+    zIns = sqlite3_mprintf(
+       "INSERT INTO sqlite_master(type,name,tbl_name,rootpage,sql)"
+       "VALUES('table','%q','%q',0,'%q');",
+       zTable, zTable, zSql);
+    fprintf(p->out, "%s\n", zIns);
+    sqlite3_free(zIns);
+    return 0;
+  }else{
+    fprintf(p->out, "%s;\n", zSql);
+  }
+
+  if( strcmp(zType, "table")==0 ){
+    sqlite3_stmt *pTableInfo = 0;
+    char *zSelect = 0;
+    char *zTableInfo = 0;
+    char *zTmp = 0;
+    int nRow = 0;
+   
+    zTableInfo = appendText(zTableInfo, "PRAGMA table_info(", 0);
+    zTableInfo = appendText(zTableInfo, zTable, '"');
+    zTableInfo = appendText(zTableInfo, ");", 0);
+
+    rc = sqlite3_prepare(p->db, zTableInfo, -1, &pTableInfo, 0);
+    free(zTableInfo);
+    if( rc!=SQLITE_OK || !pTableInfo ){
+      return 1;
+    }
+
+    zSelect = appendText(zSelect, "SELECT 'INSERT INTO ' || ", 0);
+    zTmp = appendText(zTmp, zTable, '"');
+    if( zTmp ){
+      zSelect = appendText(zSelect, zTmp, '\'');
+    }
+    zSelect = appendText(zSelect, " || ' VALUES(' || ", 0);
+    rc = sqlite3_step(pTableInfo);
+    while( rc==SQLITE_ROW ){
+      const char *zText = (const char *)sqlite3_column_text(pTableInfo, 1);
+      zSelect = appendText(zSelect, "quote(", 0);
+      zSelect = appendText(zSelect, zText, '"');
+      rc = sqlite3_step(pTableInfo);
+      if( rc==SQLITE_ROW ){
+        zSelect = appendText(zSelect, ") || ',' || ", 0);
+      }else{
+        zSelect = appendText(zSelect, ") ", 0);
+      }
+      nRow++;
+    }
+    rc = sqlite3_finalize(pTableInfo);
+    if( rc!=SQLITE_OK || nRow==0 ){
+      free(zSelect);
+      return 1;
+    }
+    zSelect = appendText(zSelect, "|| ')' FROM  ", 0);
+    zSelect = appendText(zSelect, zTable, '"');
+
+    rc = run_table_dump_query(p, zSelect, zPrepStmt);
+    if( rc==SQLITE_CORRUPT ){
+      zSelect = appendText(zSelect, " ORDER BY rowid DESC", 0);
+      run_table_dump_query(p, zSelect, 0);
+    }
+    if( zSelect ) free(zSelect);
+  }
+  return 0;
+}
+
+/*
+** Run zQuery.  Use dump_callback() as the callback routine so that
+** the contents of the query are output as SQL statements.
+**
+** If we get a SQLITE_CORRUPT error, rerun the query after appending
+** "ORDER BY rowid DESC" to the end.
+*/
+static int run_schema_dump_query(
+  struct callback_data *p, 
+  const char *zQuery
+){
+  int rc;
+  char *zErr = 0;
+  rc = sqlite3_exec(p->db, zQuery, dump_callback, p, &zErr);
+  if( rc==SQLITE_CORRUPT ){
+    char *zQ2;
+    int len = strlen30(zQuery);
+    fprintf(p->out, "/****** CORRUPTION ERROR *******/\n");
+    if( zErr ){
+      fprintf(p->out, "/****** %s ******/\n", zErr);
+      sqlite3_free(zErr);
+      zErr = 0;
+    }
+    zQ2 = malloc( len+100 );
+    if( zQ2==0 ) return rc;
+    sqlite3_snprintf(sizeof(zQ2), zQ2, "%s ORDER BY rowid DESC", zQuery);
+    rc = sqlite3_exec(p->db, zQ2, dump_callback, p, &zErr);
+    if( rc ){
+      fprintf(p->out, "/****** ERROR: %s ******/\n", zErr);
+    }else{
+      rc = SQLITE_CORRUPT;
+    }
+    sqlite3_free(zErr);
+    free(zQ2);
+  }
+  return rc;
+}
+
+/*
+** Text of a help message
+*/
+static char zHelp[] =
+  ".backup ?DB? FILE      Backup DB (default \"main\") to FILE\n"
+  ".bail ON|OFF           Stop after hitting an error.  Default OFF\n"
+  ".databases             List names and files of attached databases\n"
+  ".dump ?TABLE? ...      Dump the database in an SQL text format\n"
+  "                         If TABLE specified, only dump tables matching\n"
+  "                         LIKE pattern TABLE.\n"
+  ".echo ON|OFF           Turn command echo on or off\n"
+  ".exit                  Exit this program\n"
+  ".explain ?ON|OFF?      Turn output mode suitable for EXPLAIN on or off.\n"
+  "                         With no args, it turns EXPLAIN on.\n"
+  ".header(s) ON|OFF      Turn display of headers on or off\n"
+  ".help                  Show this message\n"
+  ".import FILE TABLE     Import data from FILE into TABLE\n"
+  ".indices ?TABLE?       Show names of all indices\n"
+  "                         If TABLE specified, only show indices for tables\n"
+  "                         matching LIKE pattern TABLE.\n"
+#ifdef SQLITE_ENABLE_IOTRACE
+  ".iotrace FILE          Enable I/O diagnostic logging to FILE\n"
+#endif
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+  ".load FILE ?ENTRY?     Load an extension library\n"
+#endif
+  ".log FILE|off          Turn logging on or off.  FILE can be stderr/stdout\n"
+  ".mode MODE ?TABLE?     Set output mode where MODE is one of:\n"
+  "                         csv      Comma-separated values\n"
+  "                         column   Left-aligned columns.  (See .width)\n"
+  "                         html     HTML <table> code\n"
+  "                         insert   SQL insert statements for TABLE\n"
+  "                         line     One value per line\n"
+  "                         list     Values delimited by .separator string\n"
+  "                         tabs     Tab-separated values\n"
+  "                         tcl      TCL list elements\n"
+  ".nullvalue STRING      Print STRING in place of NULL values\n"
+  ".output FILENAME       Send output to FILENAME\n"
+  ".output stdout         Send output to the screen\n"
+  ".prompt MAIN CONTINUE  Replace the standard prompts\n"
+  ".quit                  Exit this program\n"
+  ".read FILENAME         Execute SQL in FILENAME\n"
+  ".restore ?DB? FILE     Restore content of DB (default \"main\") from FILE\n"
+  ".schema ?TABLE?        Show the CREATE statements\n"
+  "                         If TABLE specified, only show tables matching\n"
+  "                         LIKE pattern TABLE.\n"
+  ".separator STRING      Change separator used by output mode and .import\n"
+  ".show                  Show the current values for various settings\n"
+  ".stats ON|OFF          Turn stats on or off\n"
+  ".tables ?TABLE?        List names of tables\n"
+  "                         If TABLE specified, only list tables matching\n"
+  "                         LIKE pattern TABLE.\n"
+  ".timeout MS            Try opening locked tables for MS milliseconds\n"
+  ".width NUM1 NUM2 ...   Set column widths for \"column\" mode\n"
+;
+
+static char zTimerHelp[] =
+  ".timer ON|OFF          Turn the CPU timer measurement on or off\n"
+;
+
+/* Forward reference */
+static int process_input(struct callback_data *p, FILE *in);
+
+/*
+** Make sure the database is open.  If it is not, then open it.  If
+** the database fails to open, print an error message and exit.
+*/
+static void open_db(struct callback_data *p){
+  if( p->db==0 ){
+    sqlite3_open(p->zDbFilename, &p->db);
+    db = p->db;
+    if( db && sqlite3_errcode(db)==SQLITE_OK ){
+      sqlite3_create_function(db, "shellstatic", 0, SQLITE_UTF8, 0,
+          shellstaticFunc, 0, 0);
+    }
+    if( db==0 || SQLITE_OK!=sqlite3_errcode(db) ){
+      fprintf(stderr,"Error: unable to open database \"%s\": %s\n", 
+          p->zDbFilename, sqlite3_errmsg(db));
+      exit(1);
+    }
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+    sqlite3_enable_load_extension(p->db, 1);
+#endif
+  }
+}
+
+/*
+** Do C-language style dequoting.
+**
+**    \t    -> tab
+**    \n    -> newline
+**    \r    -> carriage return
+**    \NNN  -> ascii character NNN in octal
+**    \\    -> backslash
+*/
+static void resolve_backslashes(char *z){
+  int i, j;
+  char c;
+  for(i=j=0; (c = z[i])!=0; i++, j++){
+    if( c=='\\' ){
+      c = z[++i];
+      if( c=='n' ){
+        c = '\n';
+      }else if( c=='t' ){
+        c = '\t';
+      }else if( c=='r' ){
+        c = '\r';
+      }else if( c>='0' && c<='7' ){
+        c -= '0';
+        if( z[i+1]>='0' && z[i+1]<='7' ){
+          i++;
+          c = (c<<3) + z[i] - '0';
+          if( z[i+1]>='0' && z[i+1]<='7' ){
+            i++;
+            c = (c<<3) + z[i] - '0';
+          }
+        }
+      }
+    }
+    z[j] = c;
+  }
+  z[j] = 0;
+}
+
+/*
+** Interpret zArg as a boolean value.  Return either 0 or 1.
+*/
+static int booleanValue(char *zArg){
+  int val = atoi(zArg);
+  int j;
+  for(j=0; zArg[j]; j++){
+    zArg[j] = ToLower(zArg[j]);
+  }
+  if( strcmp(zArg,"on")==0 ){
+    val = 1;
+  }else if( strcmp(zArg,"yes")==0 ){
+    val = 1;
+  }
+  return val;
+}
+
+/*
+** If an input line begins with "." then invoke this routine to
+** process that line.
+**
+** Return 1 on error, 2 to exit, and 0 otherwise.
+*/
+static int do_meta_command(char *zLine, struct callback_data *p){
+  int i = 1;
+  int nArg = 0;
+  int n, c;
+  int rc = 0;
+  char *azArg[50];
+
+  /* Parse the input line into tokens.
+  */
+  while( zLine[i] && nArg<ArraySize(azArg) ){
+    while( IsSpace(zLine[i]) ){ i++; }
+    if( zLine[i]==0 ) break;
+    if( zLine[i]=='\'' || zLine[i]=='"' ){
+      int delim = zLine[i++];
+      azArg[nArg++] = &zLine[i];
+      while( zLine[i] && zLine[i]!=delim ){ i++; }
+      if( zLine[i]==delim ){
+        zLine[i++] = 0;
+      }
+      if( delim=='"' ) resolve_backslashes(azArg[nArg-1]);
+    }else{
+      azArg[nArg++] = &zLine[i];
+      while( zLine[i] && !IsSpace(zLine[i]) ){ i++; }
+      if( zLine[i] ) zLine[i++] = 0;
+      resolve_backslashes(azArg[nArg-1]);
+    }
+  }
+
+  /* Process the input line.
+  */
+  if( nArg==0 ) return 0; /* no tokens, no error */
+  n = strlen30(azArg[0]);
+  c = azArg[0][0];
+  if( c=='b' && n>=3 && strncmp(azArg[0], "backup", n)==0 && nArg>1 && nArg<4){
+    const char *zDestFile;
+    const char *zDb;
+    sqlite3 *pDest;
+    sqlite3_backup *pBackup;
+    if( nArg==2 ){
+      zDestFile = azArg[1];
+      zDb = "main";
+    }else{
+      zDestFile = azArg[2];
+      zDb = azArg[1];
+    }
+    rc = sqlite3_open(zDestFile, &pDest);
+    if( rc!=SQLITE_OK ){
+      fprintf(stderr, "Error: cannot open \"%s\"\n", zDestFile);
+      sqlite3_close(pDest);
+      return 1;
+    }
+    open_db(p);
+    pBackup = sqlite3_backup_init(pDest, "main", p->db, zDb);
+    if( pBackup==0 ){
+      fprintf(stderr, "Error: %s\n", sqlite3_errmsg(pDest));
+      sqlite3_close(pDest);
+      return 1;
+    }
+    while(  (rc = sqlite3_backup_step(pBackup,100))==SQLITE_OK ){}
+    sqlite3_backup_finish(pBackup);
+    if( rc==SQLITE_DONE ){
+      rc = 0;
+    }else{
+      fprintf(stderr, "Error: %s\n", sqlite3_errmsg(pDest));
+      rc = 1;
+    }
+    sqlite3_close(pDest);
+  }else
+
+  if( c=='b' && n>=3 && strncmp(azArg[0], "bail", n)==0 && nArg>1 && nArg<3 ){
+    bail_on_error = booleanValue(azArg[1]);
+  }else
+
+  if( c=='d' && n>1 && strncmp(azArg[0], "databases", n)==0 && nArg==1 ){
+    struct callback_data data;
+    char *zErrMsg = 0;
+    open_db(p);
+    memcpy(&data, p, sizeof(data));
+    data.showHeader = 1;
+    data.mode = MODE_Column;
+    data.colWidth[0] = 3;
+    data.colWidth[1] = 15;
+    data.colWidth[2] = 58;
+    data.cnt = 0;
+    sqlite3_exec(p->db, "PRAGMA database_list; ", callback, &data, &zErrMsg);
+    if( zErrMsg ){
+      fprintf(stderr,"Error: %s\n", zErrMsg);
+      sqlite3_free(zErrMsg);
+      rc = 1;
+    }
+  }else
+
+  if( c=='d' && strncmp(azArg[0], "dump", n)==0 && nArg<3 ){
+    open_db(p);
+    /* When playing back a "dump", the content might appear in an order
+    ** which causes immediate foreign key constraints to be violated.
+    ** So disable foreign-key constraint enforcement to prevent problems. */
+    fprintf(p->out, "PRAGMA foreign_keys=OFF;\n");
+    fprintf(p->out, "BEGIN TRANSACTION;\n");
+    p->writableSchema = 0;
+    sqlite3_exec(p->db, "SAVEPOINT dump; PRAGMA writable_schema=ON", 0, 0, 0);
+    p->nErr = 0;
+    if( nArg==1 ){
+      run_schema_dump_query(p, 
+        "SELECT name, type, sql FROM sqlite_master "
+        "WHERE sql NOT NULL AND type=='table' AND name!='sqlite_sequence'"
+      );
+      run_schema_dump_query(p, 
+        "SELECT name, type, sql FROM sqlite_master "
+        "WHERE name=='sqlite_sequence'"
+      );
+      run_table_dump_query(p,
+        "SELECT sql FROM sqlite_master "
+        "WHERE sql NOT NULL AND type IN ('index','trigger','view')", 0
+      );
+    }else{
+      int i;
+      for(i=1; i<nArg; i++){
+        zShellStatic = azArg[i];
+        run_schema_dump_query(p,
+          "SELECT name, type, sql FROM sqlite_master "
+          "WHERE tbl_name LIKE shellstatic() AND type=='table'"
+          "  AND sql NOT NULL");
+        run_table_dump_query(p,
+          "SELECT sql FROM sqlite_master "
+          "WHERE sql NOT NULL"
+          "  AND type IN ('index','trigger','view')"
+          "  AND tbl_name LIKE shellstatic()", 0
+        );
+        zShellStatic = 0;
+      }
+    }
+    if( p->writableSchema ){
+      fprintf(p->out, "PRAGMA writable_schema=OFF;\n");
+      p->writableSchema = 0;
+    }
+    sqlite3_exec(p->db, "PRAGMA writable_schema=OFF;", 0, 0, 0);
+    sqlite3_exec(p->db, "RELEASE dump;", 0, 0, 0);
+    fprintf(p->out, p->nErr ? "ROLLBACK; -- due to errors\n" : "COMMIT;\n");
+  }else
+
+  if( c=='e' && strncmp(azArg[0], "echo", n)==0 && nArg>1 && nArg<3 ){
+    p->echoOn = booleanValue(azArg[1]);
+  }else
+
+  if( c=='e' && strncmp(azArg[0], "exit", n)==0  && nArg==1 ){
+    rc = 2;
+  }else
+
+  if( c=='e' && strncmp(azArg[0], "explain", n)==0 && nArg<3 ){
+    int val = nArg>=2 ? booleanValue(azArg[1]) : 1;
+    if(val == 1) {
+      if(!p->explainPrev.valid) {
+        p->explainPrev.valid = 1;
+        p->explainPrev.mode = p->mode;
+        p->explainPrev.showHeader = p->showHeader;
+        memcpy(p->explainPrev.colWidth,p->colWidth,sizeof(p->colWidth));
+      }
+      /* We could put this code under the !p->explainValid
+      ** condition so that it does not execute if we are already in
+      ** explain mode. However, always executing it allows us an easy
+      ** was to reset to explain mode in case the user previously
+      ** did an .explain followed by a .width, .mode or .header
+      ** command.
+      */
+      p->mode = MODE_Explain;
+      p->showHeader = 1;
+      memset(p->colWidth,0,ArraySize(p->colWidth));
+      p->colWidth[0] = 4;                  /* addr */
+      p->colWidth[1] = 13;                 /* opcode */
+      p->colWidth[2] = 4;                  /* P1 */
+      p->colWidth[3] = 4;                  /* P2 */
+      p->colWidth[4] = 4;                  /* P3 */
+      p->colWidth[5] = 13;                 /* P4 */
+      p->colWidth[6] = 2;                  /* P5 */
+      p->colWidth[7] = 13;                  /* Comment */
+    }else if (p->explainPrev.valid) {
+      p->explainPrev.valid = 0;
+      p->mode = p->explainPrev.mode;
+      p->showHeader = p->explainPrev.showHeader;
+      memcpy(p->colWidth,p->explainPrev.colWidth,sizeof(p->colWidth));
+    }
+  }else
+
+  if( c=='h' && (strncmp(azArg[0], "header", n)==0 ||
+                 strncmp(azArg[0], "headers", n)==0) && nArg>1 && nArg<3 ){
+    p->showHeader = booleanValue(azArg[1]);
+  }else
+
+  if( c=='h' && strncmp(azArg[0], "help", n)==0 ){
+    fprintf(stderr,"%s",zHelp);
+    if( HAS_TIMER ){
+      fprintf(stderr,"%s",zTimerHelp);
+    }
+  }else
+
+  if( c=='i' && strncmp(azArg[0], "import", n)==0 && nArg==3 ){
+    char *zTable = azArg[2];    /* Insert data into this table */
+    char *zFile = azArg[1];     /* The file from which to extract data */
+    sqlite3_stmt *pStmt = NULL; /* A statement */
+    int nCol;                   /* Number of columns in the table */
+    int nByte;                  /* Number of bytes in an SQL string */
+    int i, j;                   /* Loop counters */
+    int nSep;                   /* Number of bytes in p->separator[] */
+    char *zSql;                 /* An SQL statement */
+    char *zLine;                /* A single line of input from the file */
+    char **azCol;               /* zLine[] broken up into columns */
+    char *zCommit;              /* How to commit changes */   
+    FILE *in;                   /* The input file */
+    int lineno = 0;             /* Line number of input file */
+
+    open_db(p);
+    nSep = strlen30(p->separator);
+    if( nSep==0 ){
+      fprintf(stderr, "Error: non-null separator required for import\n");
+      return 1;
+    }
+    zSql = sqlite3_mprintf("SELECT * FROM %s", zTable);
+    if( zSql==0 ){
+      fprintf(stderr, "Error: out of memory\n");
+      return 1;
+    }
+    nByte = strlen30(zSql);
+    rc = sqlite3_prepare(p->db, zSql, -1, &pStmt, 0);
+    sqlite3_free(zSql);
+    if( rc ){
+      if (pStmt) sqlite3_finalize(pStmt);
+      fprintf(stderr,"Error: %s\n", sqlite3_errmsg(db));
+      return 1;
+    }
+    nCol = sqlite3_column_count(pStmt);
+    sqlite3_finalize(pStmt);
+    pStmt = 0;
+    if( nCol==0 ) return 0; /* no columns, no error */
+    zSql = malloc( nByte + 20 + nCol*2 );
+    if( zSql==0 ){
+      fprintf(stderr, "Error: out of memory\n");
+      return 1;
+    }
+    sqlite3_snprintf(nByte+20, zSql, "INSERT INTO %s VALUES(?", zTable);
+    j = strlen30(zSql);
+    for(i=1; i<nCol; i++){
+      zSql[j++] = ',';
+      zSql[j++] = '?';
+    }
+    zSql[j++] = ')';
+    zSql[j] = 0;
+    rc = sqlite3_prepare(p->db, zSql, -1, &pStmt, 0);
+    free(zSql);
+    if( rc ){
+      fprintf(stderr, "Error: %s\n", sqlite3_errmsg(db));
+      if (pStmt) sqlite3_finalize(pStmt);
+      return 1;
+    }
+    in = fopen(zFile, "rb");
+    if( in==0 ){
+      fprintf(stderr, "Error: cannot open \"%s\"\n", zFile);
+      sqlite3_finalize(pStmt);
+      return 1;
+    }
+    azCol = malloc( sizeof(azCol[0])*(nCol+1) );
+    if( azCol==0 ){
+      fprintf(stderr, "Error: out of memory\n");
+      fclose(in);
+      sqlite3_finalize(pStmt);
+      return 1;
+    }
+    sqlite3_exec(p->db, "BEGIN", 0, 0, 0);
+    zCommit = "COMMIT";
+    while( (zLine = local_getline(0, in))!=0 ){
+      char *z;
+      lineno++;
+      azCol[0] = zLine;
+      for(i=0, z=zLine; *z && *z!='\n' && *z!='\r'; z++){
+        if( *z==p->separator[0] && strncmp(z, p->separator, nSep)==0 ){
+          *z = 0;
+          i++;
+          if( i<nCol ){
+            azCol[i] = &z[nSep];
+            z += nSep-1;
+          }
+        }
+      } /* end for */
+      *z = 0;
+      if( i+1!=nCol ){
+        fprintf(stderr,
+                "Error: %s line %d: expected %d columns of data but found %d\n",
+                zFile, lineno, nCol, i+1);
+        zCommit = "ROLLBACK";
+        free(zLine);
+        rc = 1;
+        break; /* from while */
+      }
+      for(i=0; i<nCol; i++){
+        sqlite3_bind_text(pStmt, i+1, azCol[i], -1, SQLITE_STATIC);
+      }
+      sqlite3_step(pStmt);
+      rc = sqlite3_reset(pStmt);
+      free(zLine);
+      if( rc!=SQLITE_OK ){
+        fprintf(stderr,"Error: %s\n", sqlite3_errmsg(db));
+        zCommit = "ROLLBACK";
+        rc = 1;
+        break; /* from while */
+      }
+    } /* end while */
+    free(azCol);
+    fclose(in);
+    sqlite3_finalize(pStmt);
+    sqlite3_exec(p->db, zCommit, 0, 0, 0);
+  }else
+
+  if( c=='i' && strncmp(azArg[0], "indices", n)==0 && nArg<3 ){
+    struct callback_data data;
+    char *zErrMsg = 0;
+    open_db(p);
+    memcpy(&data, p, sizeof(data));
+    data.showHeader = 0;
+    data.mode = MODE_List;
+    if( nArg==1 ){
+      rc = sqlite3_exec(p->db,
+        "SELECT name FROM sqlite_master "
+        "WHERE type='index' AND name NOT LIKE 'sqlite_%' "
+        "UNION ALL "
+        "SELECT name FROM sqlite_temp_master "
+        "WHERE type='index' "
+        "ORDER BY 1",
+        callback, &data, &zErrMsg
+      );
+    }else{
+      zShellStatic = azArg[1];
+      rc = sqlite3_exec(p->db,
+        "SELECT name FROM sqlite_master "
+        "WHERE type='index' AND tbl_name LIKE shellstatic() "
+        "UNION ALL "
+        "SELECT name FROM sqlite_temp_master "
+        "WHERE type='index' AND tbl_name LIKE shellstatic() "
+        "ORDER BY 1",
+        callback, &data, &zErrMsg
+      );
+      zShellStatic = 0;
+    }
+    if( zErrMsg ){
+      fprintf(stderr,"Error: %s\n", zErrMsg);
+      sqlite3_free(zErrMsg);
+      rc = 1;
+    }else if( rc != SQLITE_OK ){
+      fprintf(stderr,"Error: querying sqlite_master and sqlite_temp_master\n");
+      rc = 1;
+    }
+  }else
+
+#ifdef SQLITE_ENABLE_IOTRACE
+  if( c=='i' && strncmp(azArg[0], "iotrace", n)==0 ){
+    extern void (*sqlite3IoTrace)(const char*, ...);
+    if( iotrace && iotrace!=stdout ) fclose(iotrace);
+    iotrace = 0;
+    if( nArg<2 ){
+      sqlite3IoTrace = 0;
+    }else if( strcmp(azArg[1], "-")==0 ){
+      sqlite3IoTrace = iotracePrintf;
+      iotrace = stdout;
+    }else{
+      iotrace = fopen(azArg[1], "w");
+      if( iotrace==0 ){
+        fprintf(stderr, "Error: cannot open \"%s\"\n", azArg[1]);
+        sqlite3IoTrace = 0;
+        rc = 1;
+      }else{
+        sqlite3IoTrace = iotracePrintf;
+      }
+    }
+  }else
+#endif
+
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+  if( c=='l' && strncmp(azArg[0], "load", n)==0 && nArg>=2 ){
+    const char *zFile, *zProc;
+    char *zErrMsg = 0;
+    zFile = azArg[1];
+    zProc = nArg>=3 ? azArg[2] : 0;
+    open_db(p);
+    rc = sqlite3_load_extension(p->db, zFile, zProc, &zErrMsg);
+    if( rc!=SQLITE_OK ){
+      fprintf(stderr, "Error: %s\n", zErrMsg);
+      sqlite3_free(zErrMsg);
+      rc = 1;
+    }
+  }else
+#endif
+
+  if( c=='l' && strncmp(azArg[0], "log", n)==0 && nArg>=2 ){
+    const char *zFile = azArg[1];
+    if( p->pLog && p->pLog!=stdout && p->pLog!=stderr ){
+      fclose(p->pLog);
+      p->pLog = 0;
+    }
+    if( strcmp(zFile,"stdout")==0 ){
+      p->pLog = stdout;
+    }else if( strcmp(zFile, "stderr")==0 ){
+      p->pLog = stderr;
+    }else if( strcmp(zFile, "off")==0 ){
+      p->pLog = 0;
+    }else{
+      p->pLog = fopen(zFile, "w");
+      if( p->pLog==0 ){
+        fprintf(stderr, "Error: cannot open \"%s\"\n", zFile);
+      }
+    }
+  }else
+
+  if( c=='m' && strncmp(azArg[0], "mode", n)==0 && nArg==2 ){
+    int n2 = strlen30(azArg[1]);
+    if( (n2==4 && strncmp(azArg[1],"line",n2)==0)
+        ||
+        (n2==5 && strncmp(azArg[1],"lines",n2)==0) ){
+      p->mode = MODE_Line;
+    }else if( (n2==6 && strncmp(azArg[1],"column",n2)==0)
+              ||
+              (n2==7 && strncmp(azArg[1],"columns",n2)==0) ){
+      p->mode = MODE_Column;
+    }else if( n2==4 && strncmp(azArg[1],"list",n2)==0 ){
+      p->mode = MODE_List;
+    }else if( n2==4 && strncmp(azArg[1],"html",n2)==0 ){
+      p->mode = MODE_Html;
+    }else if( n2==3 && strncmp(azArg[1],"tcl",n2)==0 ){
+      p->mode = MODE_Tcl;
+    }else if( n2==3 && strncmp(azArg[1],"csv",n2)==0 ){
+      p->mode = MODE_Csv;
+      sqlite3_snprintf(sizeof(p->separator), p->separator, ",");
+    }else if( n2==4 && strncmp(azArg[1],"tabs",n2)==0 ){
+      p->mode = MODE_List;
+      sqlite3_snprintf(sizeof(p->separator), p->separator, "\t");
+    }else if( n2==6 && strncmp(azArg[1],"insert",n2)==0 ){
+      p->mode = MODE_Insert;
+      set_table_name(p, "table");
+    }else {
+      fprintf(stderr,"Error: mode should be one of: "
+         "column csv html insert line list tabs tcl\n");
+      rc = 1;
+    }
+  }else
+
+  if( c=='m' && strncmp(azArg[0], "mode", n)==0 && nArg==3 ){
+    int n2 = strlen30(azArg[1]);
+    if( n2==6 && strncmp(azArg[1],"insert",n2)==0 ){
+      p->mode = MODE_Insert;
+      set_table_name(p, azArg[2]);
+    }else {
+      fprintf(stderr, "Error: invalid arguments: "
+        " \"%s\". Enter \".help\" for help\n", azArg[2]);
+      rc = 1;
+    }
+  }else
+
+  if( c=='n' && strncmp(azArg[0], "nullvalue", n)==0 && nArg==2 ) {
+    sqlite3_snprintf(sizeof(p->nullvalue), p->nullvalue,
+                     "%.*s", (int)ArraySize(p->nullvalue)-1, azArg[1]);
+  }else
+
+  if( c=='o' && strncmp(azArg[0], "output", n)==0 && nArg==2 ){
+    if( p->out!=stdout ){
+      fclose(p->out);
+    }
+    if( strcmp(azArg[1],"stdout")==0 ){
+      p->out = stdout;
+      sqlite3_snprintf(sizeof(p->outfile), p->outfile, "stdout");
+    }else{
+      p->out = fopen(azArg[1], "wb");
+      if( p->out==0 ){
+        fprintf(stderr,"Error: cannot write to \"%s\"\n", azArg[1]);
+        p->out = stdout;
+        rc = 1;
+      } else {
+         sqlite3_snprintf(sizeof(p->outfile), p->outfile, "%s", azArg[1]);
+      }
+    }
+  }else
+
+  if( c=='p' && strncmp(azArg[0], "prompt", n)==0 && (nArg==2 || nArg==3)){
+    if( nArg >= 2) {
+      strncpy(mainPrompt,azArg[1],(int)ArraySize(mainPrompt)-1);
+    }
+    if( nArg >= 3) {
+      strncpy(continuePrompt,azArg[2],(int)ArraySize(continuePrompt)-1);
+    }
+  }else
+
+  if( c=='q' && strncmp(azArg[0], "quit", n)==0 && nArg==1 ){
+    rc = 2;
+  }else
+
+  if( c=='r' && n>=3 && strncmp(azArg[0], "read", n)==0 && nArg==2 ){
+    FILE *alt = fopen(azArg[1], "rb");
+    if( alt==0 ){
+      fprintf(stderr,"Error: cannot open \"%s\"\n", azArg[1]);
+      rc = 1;
+    }else{
+      rc = process_input(p, alt);
+      fclose(alt);
+    }
+  }else
+
+  if( c=='r' && n>=3 && strncmp(azArg[0], "restore", n)==0 && nArg>1 && nArg<4){
+    const char *zSrcFile;
+    const char *zDb;
+    sqlite3 *pSrc;
+    sqlite3_backup *pBackup;
+    int nTimeout = 0;
+
+    if( nArg==2 ){
+      zSrcFile = azArg[1];
+      zDb = "main";
+    }else{
+      zSrcFile = azArg[2];
+      zDb = azArg[1];
+    }
+    rc = sqlite3_open(zSrcFile, &pSrc);
+    if( rc!=SQLITE_OK ){
+      fprintf(stderr, "Error: cannot open \"%s\"\n", zSrcFile);
+      sqlite3_close(pSrc);
+      return 1;
+    }
+    open_db(p);
+    pBackup = sqlite3_backup_init(p->db, zDb, pSrc, "main");
+    if( pBackup==0 ){
+      fprintf(stderr, "Error: %s\n", sqlite3_errmsg(p->db));
+      sqlite3_close(pSrc);
+      return 1;
+    }
+    while( (rc = sqlite3_backup_step(pBackup,100))==SQLITE_OK
+          || rc==SQLITE_BUSY  ){
+      if( rc==SQLITE_BUSY ){
+        if( nTimeout++ >= 3 ) break;
+        sqlite3_sleep(100);
+      }
+    }
+    sqlite3_backup_finish(pBackup);
+    if( rc==SQLITE_DONE ){
+      rc = 0;
+    }else if( rc==SQLITE_BUSY || rc==SQLITE_LOCKED ){
+      fprintf(stderr, "Error: source database is busy\n");
+      rc = 1;
+    }else{
+      fprintf(stderr, "Error: %s\n", sqlite3_errmsg(p->db));
+      rc = 1;
+    }
+    sqlite3_close(pSrc);
+  }else
+
+  if( c=='s' && strncmp(azArg[0], "schema", n)==0 && nArg<3 ){
+    struct callback_data data;
+    char *zErrMsg = 0;
+    open_db(p);
+    memcpy(&data, p, sizeof(data));
+    data.showHeader = 0;
+    data.mode = MODE_Semi;
+    if( nArg>1 ){
+      int i;
+      for(i=0; azArg[1][i]; i++) azArg[1][i] = ToLower(azArg[1][i]);
+      if( strcmp(azArg[1],"sqlite_master")==0 ){
+        char *new_argv[2], *new_colv[2];
+        new_argv[0] = "CREATE TABLE sqlite_master (\n"
+                      "  type text,\n"
+                      "  name text,\n"
+                      "  tbl_name text,\n"
+                      "  rootpage integer,\n"
+                      "  sql text\n"
+                      ")";
+        new_argv[1] = 0;
+        new_colv[0] = "sql";
+        new_colv[1] = 0;
+        callback(&data, 1, new_argv, new_colv);
+        rc = SQLITE_OK;
+      }else if( strcmp(azArg[1],"sqlite_temp_master")==0 ){
+        char *new_argv[2], *new_colv[2];
+        new_argv[0] = "CREATE TEMP TABLE sqlite_temp_master (\n"
+                      "  type text,\n"
+                      "  name text,\n"
+                      "  tbl_name text,\n"
+                      "  rootpage integer,\n"
+                      "  sql text\n"
+                      ")";
+        new_argv[1] = 0;
+        new_colv[0] = "sql";
+        new_colv[1] = 0;
+        callback(&data, 1, new_argv, new_colv);
+        rc = SQLITE_OK;
+      }else{
+        zShellStatic = azArg[1];
+        rc = sqlite3_exec(p->db,
+          "SELECT sql FROM "
+          "  (SELECT sql sql, type type, tbl_name tbl_name, name name"
+          "     FROM sqlite_master UNION ALL"
+          "   SELECT sql, type, tbl_name, name FROM sqlite_temp_master) "
+          "WHERE tbl_name LIKE shellstatic() AND type!='meta' AND sql NOTNULL "
+          "ORDER BY substr(type,2,1), name",
+          callback, &data, &zErrMsg);
+        zShellStatic = 0;
+      }
+    }else{
+      rc = sqlite3_exec(p->db,
+         "SELECT sql FROM "
+         "  (SELECT sql sql, type type, tbl_name tbl_name, name name"
+         "     FROM sqlite_master UNION ALL"
+         "   SELECT sql, type, tbl_name, name FROM sqlite_temp_master) "
+         "WHERE type!='meta' AND sql NOTNULL AND name NOT LIKE 'sqlite_%'"
+         "ORDER BY substr(type,2,1), name",
+         callback, &data, &zErrMsg
+      );
+    }
+    if( zErrMsg ){
+      fprintf(stderr,"Error: %s\n", zErrMsg);
+      sqlite3_free(zErrMsg);
+      rc = 1;
+    }else if( rc != SQLITE_OK ){
+      fprintf(stderr,"Error: querying schema information\n");
+      rc = 1;
+    }else{
+      rc = 0;
+    }
+  }else
+
+  if( c=='s' && strncmp(azArg[0], "separator", n)==0 && nArg==2 ){
+    sqlite3_snprintf(sizeof(p->separator), p->separator,
+                     "%.*s", (int)sizeof(p->separator)-1, azArg[1]);
+  }else
+
+  if( c=='s' && strncmp(azArg[0], "show", n)==0 && nArg==1 ){
+    int i;
+    fprintf(p->out,"%9.9s: %s\n","echo", p->echoOn ? "on" : "off");
+    fprintf(p->out,"%9.9s: %s\n","explain", p->explainPrev.valid ? "on" :"off");
+    fprintf(p->out,"%9.9s: %s\n","headers", p->showHeader ? "on" : "off");
+    fprintf(p->out,"%9.9s: %s\n","mode", modeDescr[p->mode]);
+    fprintf(p->out,"%9.9s: ", "nullvalue");
+      output_c_string(p->out, p->nullvalue);
+      fprintf(p->out, "\n");
+    fprintf(p->out,"%9.9s: %s\n","output",
+            strlen30(p->outfile) ? p->outfile : "stdout");
+    fprintf(p->out,"%9.9s: ", "separator");
+      output_c_string(p->out, p->separator);
+      fprintf(p->out, "\n");
+    fprintf(p->out,"%9.9s: %s\n","stats", p->statsOn ? "on" : "off");
+    fprintf(p->out,"%9.9s: ","width");
+    for (i=0;i<(int)ArraySize(p->colWidth) && p->colWidth[i] != 0;i++) {
+      fprintf(p->out,"%d ",p->colWidth[i]);
+    }
+    fprintf(p->out,"\n");
+  }else
+
+  if( c=='s' && strncmp(azArg[0], "stats", n)==0 && nArg>1 && nArg<3 ){
+    p->statsOn = booleanValue(azArg[1]);
+  }else
+
+  if( c=='t' && n>1 && strncmp(azArg[0], "tables", n)==0 && nArg<3 ){
+    char **azResult;
+    int nRow;
+    char *zErrMsg;
+    open_db(p);
+    if( nArg==1 ){
+      rc = sqlite3_get_table(p->db,
+        "SELECT name FROM sqlite_master "
+        "WHERE type IN ('table','view') AND name NOT LIKE 'sqlite_%' "
+        "UNION ALL "
+        "SELECT name FROM sqlite_temp_master "
+        "WHERE type IN ('table','view') "
+        "ORDER BY 1",
+        &azResult, &nRow, 0, &zErrMsg
+      );
+    }else{
+      zShellStatic = azArg[1];
+      rc = sqlite3_get_table(p->db,
+        "SELECT name FROM sqlite_master "
+        "WHERE type IN ('table','view') AND name LIKE shellstatic() "
+        "UNION ALL "
+        "SELECT name FROM sqlite_temp_master "
+        "WHERE type IN ('table','view') AND name LIKE shellstatic() "
+        "ORDER BY 1",
+        &azResult, &nRow, 0, &zErrMsg
+      );
+      zShellStatic = 0;
+    }
+    if( zErrMsg ){
+      fprintf(stderr,"Error: %s\n", zErrMsg);
+      sqlite3_free(zErrMsg);
+      rc = 1;
+    }else if( rc != SQLITE_OK ){
+      fprintf(stderr,"Error: querying sqlite_master and sqlite_temp_master\n");
+      rc = 1;
+    }else{
+      int len, maxlen = 0;
+      int i, j;
+      int nPrintCol, nPrintRow;
+      for(i=1; i<=nRow; i++){
+        if( azResult[i]==0 ) continue;
+        len = strlen30(azResult[i]);
+        if( len>maxlen ) maxlen = len;
+      }
+      nPrintCol = 80/(maxlen+2);
+      if( nPrintCol<1 ) nPrintCol = 1;
+      nPrintRow = (nRow + nPrintCol - 1)/nPrintCol;
+      for(i=0; i<nPrintRow; i++){
+        for(j=i+1; j<=nRow; j+=nPrintRow){
+          char *zSp = j<=nPrintRow ? "" : "  ";
+          printf("%s%-*s", zSp, maxlen, azResult[j] ? azResult[j] : "");
+        }
+        printf("\n");
+      }
+    }
+    sqlite3_free_table(azResult);
+  }else
+
+  if( c=='t' && n>=8 && strncmp(azArg[0], "testctrl", n)==0 && nArg>=2 ){
+    static const struct {
+       const char *zCtrlName;   /* Name of a test-control option */
+       int ctrlCode;            /* Integer code for that option */
+    } aCtrl[] = {
+      { "prng_save",             SQLITE_TESTCTRL_PRNG_SAVE              },
+      { "prng_restore",          SQLITE_TESTCTRL_PRNG_RESTORE           },
+      { "prng_reset",            SQLITE_TESTCTRL_PRNG_RESET             },
+      { "bitvec_test",           SQLITE_TESTCTRL_BITVEC_TEST            },
+      { "fault_install",         SQLITE_TESTCTRL_FAULT_INSTALL          },
+      { "benign_malloc_hooks",   SQLITE_TESTCTRL_BENIGN_MALLOC_HOOKS    },
+      { "pending_byte",          SQLITE_TESTCTRL_PENDING_BYTE           },
+      { "assert",                SQLITE_TESTCTRL_ASSERT                 },
+      { "always",                SQLITE_TESTCTRL_ALWAYS                 },
+      { "reserve",               SQLITE_TESTCTRL_RESERVE                },
+      { "optimizations",         SQLITE_TESTCTRL_OPTIMIZATIONS          },
+      { "iskeyword",             SQLITE_TESTCTRL_ISKEYWORD              },
+      { "pghdrsz",               SQLITE_TESTCTRL_PGHDRSZ                },
+      { "scratchmalloc",         SQLITE_TESTCTRL_SCRATCHMALLOC          },
+    };
+    int testctrl = -1;
+    int rc = 0;
+    int i, n;
+    open_db(p);
+
+    /* convert testctrl text option to value. allow any unique prefix
+    ** of the option name, or a numerical value. */
+    n = strlen30(azArg[1]);
+    for(i=0; i<(int)(sizeof(aCtrl)/sizeof(aCtrl[0])); i++){
+      if( strncmp(azArg[1], aCtrl[i].zCtrlName, n)==0 ){
+        if( testctrl<0 ){
+          testctrl = aCtrl[i].ctrlCode;
+        }else{
+          fprintf(stderr, "ambiguous option name: \"%s\"\n", azArg[1]);
+          testctrl = -1;
+          break;
+        }
+      }
+    }
+    if( testctrl<0 ) testctrl = atoi(azArg[1]);
+    if( (testctrl<SQLITE_TESTCTRL_FIRST) || (testctrl>SQLITE_TESTCTRL_LAST) ){
+      fprintf(stderr,"Error: invalid testctrl option: %s\n", azArg[1]);
+    }else{
+      switch(testctrl){
+
+        /* sqlite3_test_control(int, db, int) */
+        case SQLITE_TESTCTRL_OPTIMIZATIONS:
+        case SQLITE_TESTCTRL_RESERVE:             
+          if( nArg==3 ){
+            int opt = (int)strtol(azArg[2], 0, 0);        
+            rc = sqlite3_test_control(testctrl, p->db, opt);
+            printf("%d (0x%08x)\n", rc, rc);
+          } else {
+            fprintf(stderr,"Error: testctrl %s takes a single int option\n",
+                    azArg[1]);
+          }
+          break;
+
+        /* sqlite3_test_control(int) */
+        case SQLITE_TESTCTRL_PRNG_SAVE:           
+        case SQLITE_TESTCTRL_PRNG_RESTORE:        
+        case SQLITE_TESTCTRL_PRNG_RESET:
+        case SQLITE_TESTCTRL_PGHDRSZ:             
+          if( nArg==2 ){
+            rc = sqlite3_test_control(testctrl);
+            printf("%d (0x%08x)\n", rc, rc);
+          } else {
+            fprintf(stderr,"Error: testctrl %s takes no options\n", azArg[1]);
+          }
+          break;
+
+        /* sqlite3_test_control(int, uint) */
+        case SQLITE_TESTCTRL_PENDING_BYTE:        
+          if( nArg==3 ){
+            unsigned int opt = (unsigned int)atoi(azArg[2]);        
+            rc = sqlite3_test_control(testctrl, opt);
+            printf("%d (0x%08x)\n", rc, rc);
+          } else {
+            fprintf(stderr,"Error: testctrl %s takes a single unsigned"
+                           " int option\n", azArg[1]);
+          }
+          break;
+          
+        /* sqlite3_test_control(int, int) */
+        case SQLITE_TESTCTRL_ASSERT:              
+        case SQLITE_TESTCTRL_ALWAYS:              
+          if( nArg==3 ){
+            int opt = atoi(azArg[2]);        
+            rc = sqlite3_test_control(testctrl, opt);
+            printf("%d (0x%08x)\n", rc, rc);
+          } else {
+            fprintf(stderr,"Error: testctrl %s takes a single int option\n",
+                            azArg[1]);
+          }
+          break;
+
+        /* sqlite3_test_control(int, char *) */
+#ifdef SQLITE_N_KEYWORD
+        case SQLITE_TESTCTRL_ISKEYWORD:           
+          if( nArg==3 ){
+            const char *opt = azArg[2];        
+            rc = sqlite3_test_control(testctrl, opt);
+            printf("%d (0x%08x)\n", rc, rc);
+          } else {
+            fprintf(stderr,"Error: testctrl %s takes a single char * option\n",
+                            azArg[1]);
+          }
+          break;
+#endif
+
+        case SQLITE_TESTCTRL_BITVEC_TEST:         
+        case SQLITE_TESTCTRL_FAULT_INSTALL:       
+        case SQLITE_TESTCTRL_BENIGN_MALLOC_HOOKS: 
+        case SQLITE_TESTCTRL_SCRATCHMALLOC:       
+        default:
+          fprintf(stderr,"Error: CLI support for testctrl %s not implemented\n",
+                  azArg[1]);
+          break;
+      }
+    }
+  }else
+
+  if( c=='t' && n>4 && strncmp(azArg[0], "timeout", n)==0 && nArg==2 ){
+    open_db(p);
+    sqlite3_busy_timeout(p->db, atoi(azArg[1]));
+  }else
+    
+  if( HAS_TIMER && c=='t' && n>=5 && strncmp(azArg[0], "timer", n)==0
+   && nArg==2
+  ){
+    enableTimer = booleanValue(azArg[1]);
+  }else
+  
+  if( c=='v' && strncmp(azArg[0], "version", n)==0 ){
+    printf("SQLite %s %s\n",
+        sqlite3_libversion(), sqlite3_sourceid());
+  }else
+
+  if( c=='w' && strncmp(azArg[0], "width", n)==0 && nArg>1 ){
+    int j;
+    assert( nArg<=ArraySize(azArg) );
+    for(j=1; j<nArg && j<ArraySize(p->colWidth); j++){
+      p->colWidth[j-1] = atoi(azArg[j]);
+    }
+  }else
+
+  {
+    fprintf(stderr, "Error: unknown command or invalid arguments: "
+      " \"%s\". Enter \".help\" for help\n", azArg[0]);
+    rc = 1;
+  }
+
+  return rc;
+}
+
+/*
+** Return TRUE if a semicolon occurs anywhere in the first N characters
+** of string z[].
+*/
+static int _contains_semicolon(const char *z, int N){
+  int i;
+  for(i=0; i<N; i++){  if( z[i]==';' ) return 1; }
+  return 0;
+}
+
+/*
+** Test to see if a line consists entirely of whitespace.
+*/
+static int _all_whitespace(const char *z){
+  for(; *z; z++){
+    if( IsSpace(z[0]) ) continue;
+    if( *z=='/' && z[1]=='*' ){
+      z += 2;
+      while( *z && (*z!='*' || z[1]!='/') ){ z++; }
+      if( *z==0 ) return 0;
+      z++;
+      continue;
+    }
+    if( *z=='-' && z[1]=='-' ){
+      z += 2;
+      while( *z && *z!='\n' ){ z++; }
+      if( *z==0 ) return 1;
+      continue;
+    }
+    return 0;
+  }
+  return 1;
+}
+
+/*
+** Return TRUE if the line typed in is an SQL command terminator other
+** than a semi-colon.  The SQL Server style "go" command is understood
+** as is the Oracle "/".
+*/
+static int _is_command_terminator(const char *zLine){
+  while( IsSpace(zLine[0]) ){ zLine++; };
+  if( zLine[0]=='/' && _all_whitespace(&zLine[1]) ){
+    return 1;  /* Oracle */
+  }
+  if( ToLower(zLine[0])=='g' && ToLower(zLine[1])=='o'
+         && _all_whitespace(&zLine[2]) ){
+    return 1;  /* SQL Server */
+  }
+  return 0;
+}
+
+/*
+** Return true if zSql is a complete SQL statement.  Return false if it
+** ends in the middle of a string literal or C-style comment.
+*/
+static int _is_complete(char *zSql, int nSql){
+  int rc;
+  if( zSql==0 ) return 1;
+  zSql[nSql] = ';';
+  zSql[nSql+1] = 0;
+  rc = sqlite3_complete(zSql);
+  zSql[nSql] = 0;
+  return rc;
+}
+
+/*
+** Read input from *in and process it.  If *in==0 then input
+** is interactive - the user is typing it it.  Otherwise, input
+** is coming from a file or device.  A prompt is issued and history
+** is saved only if input is interactive.  An interrupt signal will
+** cause this routine to exit immediately, unless input is interactive.
+**
+** Return the number of errors.
+*/
+static int process_input(struct callback_data *p, FILE *in){
+  char *zLine = 0;
+  char *zSql = 0;
+  int nSql = 0;
+  int nSqlPrior = 0;
+  char *zErrMsg;
+  int rc;
+  int errCnt = 0;
+  int lineno = 0;
+  int startline = 0;
+
+  while( errCnt==0 || !bail_on_error || (in==0 && stdin_is_interactive) ){
+    fflush(p->out);
+    free(zLine);
+    zLine = one_input_line(zSql, in);
+    if( zLine==0 ){
+      break;  /* We have reached EOF */
+    }
+    if( seenInterrupt ){
+      if( in!=0 ) break;
+      seenInterrupt = 0;
+    }
+    lineno++;
+    if( (zSql==0 || zSql[0]==0) && _all_whitespace(zLine) ) continue;
+    if( zLine && zLine[0]=='.' && nSql==0 ){
+      if( p->echoOn ) printf("%s\n", zLine);
+      rc = do_meta_command(zLine, p);
+      if( rc==2 ){ /* exit requested */
+        break;
+      }else if( rc ){
+        errCnt++;
+      }
+      continue;
+    }
+    if( _is_command_terminator(zLine) && _is_complete(zSql, nSql) ){
+      memcpy(zLine,";",2);
+    }
+    nSqlPrior = nSql;
+    if( zSql==0 ){
+      int i;
+      for(i=0; zLine[i] && IsSpace(zLine[i]); i++){}
+      if( zLine[i]!=0 ){
+        nSql = strlen30(zLine);
+        zSql = malloc( nSql+3 );
+        if( zSql==0 ){
+          fprintf(stderr, "Error: out of memory\n");
+          exit(1);
+        }
+        memcpy(zSql, zLine, nSql+1);
+        startline = lineno;
+      }
+    }else{
+      int len = strlen30(zLine);
+      zSql = realloc( zSql, nSql + len + 4 );
+      if( zSql==0 ){
+        fprintf(stderr,"Error: out of memory\n");
+        exit(1);
+      }
+      zSql[nSql++] = '\n';
+      memcpy(&zSql[nSql], zLine, len+1);
+      nSql += len;
+    }
+    if( zSql && _contains_semicolon(&zSql[nSqlPrior], nSql-nSqlPrior)
+                && sqlite3_complete(zSql) ){
+      p->cnt = 0;
+      open_db(p);
+      BEGIN_TIMER;
+      rc = shell_exec(p->db, zSql, shell_callback, p, &zErrMsg);
+      END_TIMER;
+      if( rc || zErrMsg ){
+        char zPrefix[100];
+        if( in!=0 || !stdin_is_interactive ){
+          sqlite3_snprintf(sizeof(zPrefix), zPrefix, 
+                           "Error: near line %d:", startline);
+        }else{
+          sqlite3_snprintf(sizeof(zPrefix), zPrefix, "Error:");
+        }
+        if( zErrMsg!=0 ){
+          fprintf(stderr, "%s %s\n", zPrefix, zErrMsg);
+          sqlite3_free(zErrMsg);
+          zErrMsg = 0;
+        }else{
+          fprintf(stderr, "%s %s\n", zPrefix, sqlite3_errmsg(p->db));
+        }
+        errCnt++;
+      }
+      free(zSql);
+      zSql = 0;
+      nSql = 0;
+    }
+  }
+  if( zSql ){
+    if( !_all_whitespace(zSql) ){
+      fprintf(stderr, "Error: incomplete SQL: %s\n", zSql);
+    }
+    free(zSql);
+  }
+  free(zLine);
+  return errCnt;
+}
+
+/*
+** Return a pathname which is the user's home directory.  A
+** 0 return indicates an error of some kind.  Space to hold the
+** resulting string is obtained from malloc().  The calling
+** function should free the result.
+*/
+static char *find_home_dir(void){
+  char *home_dir = NULL;
+
+#if !defined(_WIN32) && !defined(WIN32) && !defined(__OS2__) && !defined(_WIN32_WCE) && !defined(__RTP__) && !defined(_WRS_KERNEL)
+  struct passwd *pwent;
+  uid_t uid = getuid();
+  if( (pwent=getpwuid(uid)) != NULL) {
+    home_dir = pwent->pw_dir;
+  }
+#endif
+
+#if defined(_WIN32_WCE)
+  /* Windows CE (arm-wince-mingw32ce-gcc) does not provide getenv()
+   */
+  home_dir = strdup("/");
+#else
+
+#if defined(_WIN32) || defined(WIN32) || defined(__OS2__)
+  if (!home_dir) {
+    home_dir = getenv("USERPROFILE");
+  }
+#endif
+
+  if (!home_dir) {
+    home_dir = getenv("HOME");
+  }
+
+#if defined(_WIN32) || defined(WIN32) || defined(__OS2__)
+  if (!home_dir) {
+    char *zDrive, *zPath;
+    int n;
+    zDrive = getenv("HOMEDRIVE");
+    zPath = getenv("HOMEPATH");
+    if( zDrive && zPath ){
+      n = strlen30(zDrive) + strlen30(zPath) + 1;
+      home_dir = malloc( n );
+      if( home_dir==0 ) return 0;
+      sqlite3_snprintf(n, home_dir, "%s%s", zDrive, zPath);
+      return home_dir;
+    }
+    home_dir = "c:\\";
+  }
+#endif
+
+#endif /* !_WIN32_WCE */
+
+  if( home_dir ){
+    int n = strlen30(home_dir) + 1;
+    char *z = malloc( n );
+    if( z ) memcpy(z, home_dir, n);
+    home_dir = z;
+  }
+
+  return home_dir;
+}
+
+/*
+** Read input from the file given by sqliterc_override.  Or if that
+** parameter is NULL, take input from ~/.sqliterc
+**
+** Returns the number of errors.
+*/
+static int process_sqliterc(
+  struct callback_data *p,        /* Configuration data */
+  const char *sqliterc_override   /* Name of config file. NULL to use default */
+){
+  char *home_dir = NULL;
+  const char *sqliterc = sqliterc_override;
+  char *zBuf = 0;
+  FILE *in = NULL;
+  int nBuf;
+  int rc = 0;
+
+  if (sqliterc == NULL) {
+    home_dir = find_home_dir();
+    if( home_dir==0 ){
+#if !defined(__RTP__) && !defined(_WRS_KERNEL)
+      fprintf(stderr,"%s: Error: cannot locate your home directory\n", Argv0);
+#endif
+      return 1;
+    }
+    nBuf = strlen30(home_dir) + 16;
+    zBuf = malloc( nBuf );
+    if( zBuf==0 ){
+      fprintf(stderr,"%s: Error: out of memory\n",Argv0);
+      return 1;
+    }
+    sqlite3_snprintf(nBuf, zBuf,"%s/.sqliterc",home_dir);
+    free(home_dir);
+    sqliterc = (const char*)zBuf;
+  }
+  in = fopen(sqliterc,"rb");
+  if( in ){
+    if( stdin_is_interactive ){
+      fprintf(stderr,"-- Loading resources from %s\n",sqliterc);
+    }
+    rc = process_input(p,in);
+    fclose(in);
+  }
+  free(zBuf);
+  return rc;
+}
+
+/*
+** Show available command line options
+*/
+static const char zOptions[] = 
+  "   -help                show this message\n"
+  "   -init filename       read/process named file\n"
+  "   -echo                print commands before execution\n"
+  "   -[no]header          turn headers on or off\n"
+  "   -bail                stop after hitting an error\n"
+  "   -interactive         force interactive I/O\n"
+  "   -batch               force batch I/O\n"
+  "   -column              set output mode to 'column'\n"
+  "   -csv                 set output mode to 'csv'\n"
+  "   -html                set output mode to HTML\n"
+  "   -line                set output mode to 'line'\n"
+  "   -list                set output mode to 'list'\n"
+  "   -separator 'x'       set output field separator (|)\n"
+  "   -stats               print memory stats before each finalize\n"
+  "   -nullvalue 'text'    set text string for NULL values\n"
+  "   -version             show SQLite version\n"
+  "   -vfs NAME            use NAME as the default VFS\n"
+#ifdef SQLITE_ENABLE_VFSTRACE
+  "   -vfstrace            enable tracing of all VFS calls\n"
+#endif
+#ifdef SQLITE_ENABLE_MULTIPLEX
+  "   -multiplex           enable the multiplexor VFS\n"
+#endif
+;
+static void usage(int showDetail){
+  fprintf(stderr,
+      "Usage: %s [OPTIONS] FILENAME [SQL]\n"  
+      "FILENAME is the name of an SQLite database. A new database is created\n"
+      "if the file does not previously exist.\n", Argv0);
+  if( showDetail ){
+    fprintf(stderr, "OPTIONS include:\n%s", zOptions);
+  }else{
+    fprintf(stderr, "Use the -help option for additional information\n");
+  }
+  exit(1);
+}
+
+/*
+** Initialize the state information in data
+*/
+static void main_init(struct callback_data *data) {
+  memset(data, 0, sizeof(*data));
+  data->mode = MODE_List;
+  memcpy(data->separator,"|", 2);
+  data->showHeader = 0;
+  sqlite3_config(SQLITE_CONFIG_URI, 1);
+  sqlite3_config(SQLITE_CONFIG_LOG, shellLog, data);
+  sqlite3_snprintf(sizeof(mainPrompt), mainPrompt,"sqlite> ");
+  sqlite3_snprintf(sizeof(continuePrompt), continuePrompt,"   ...> ");
+  sqlite3_config(SQLITE_CONFIG_SINGLETHREAD);
+}
+
+int main(int argc, char **argv){
+  char *zErrMsg = 0;
+  struct callback_data data;
+  const char *zInitFile = 0;
+  char *zFirstCmd = 0;
+  int i;
+  int rc = 0;
+
+  if( strcmp(sqlite3_sourceid(),SQLITE_SOURCE_ID)!=0 ){
+    fprintf(stderr, "SQLite header and source version mismatch\n%s\n%s\n",
+            sqlite3_sourceid(), SQLITE_SOURCE_ID);
+    exit(1);
+  }
+  Argv0 = argv[0];
+  main_init(&data);
+  stdin_is_interactive = isatty(0);
+
+  /* Make sure we have a valid signal handler early, before anything
+  ** else is done.
+  */
+#ifdef SIGINT
+  signal(SIGINT, interrupt_handler);
+#endif
+
+  /* Do an initial pass through the command-line argument to locate
+  ** the name of the database file, the name of the initialization file,
+  ** the size of the alternative malloc heap,
+  ** and the first command to execute.
+  */
+  for(i=1; i<argc-1; i++){
+    char *z;
+    if( argv[i][0]!='-' ) break;
+    z = argv[i];
+    if( z[0]=='-' && z[1]=='-' ) z++;
+    if( strcmp(argv[i],"-separator")==0 || strcmp(argv[i],"-nullvalue")==0 ){
+      i++;
+    }else if( strcmp(argv[i],"-init")==0 ){
+      i++;
+      zInitFile = argv[i];
+    /* Need to check for batch mode here to so we can avoid printing
+    ** informational messages (like from process_sqliterc) before 
+    ** we do the actual processing of arguments later in a second pass.
+    */
+    }else if( strcmp(argv[i],"-batch")==0 ){
+      stdin_is_interactive = 0;
+    }else if( strcmp(argv[i],"-heap")==0 ){
+#if defined(SQLITE_ENABLE_MEMSYS3) || defined(SQLITE_ENABLE_MEMSYS5)
+      int j, c;
+      const char *zSize;
+      sqlite3_int64 szHeap;
+
+      zSize = argv[++i];
+      szHeap = atoi(zSize);
+      for(j=0; (c = zSize[j])!=0; j++){
+        if( c=='M' ){ szHeap *= 1000000; break; }
+        if( c=='K' ){ szHeap *= 1000; break; }
+        if( c=='G' ){ szHeap *= 1000000000; break; }
+      }
+      if( szHeap>0x7fff0000 ) szHeap = 0x7fff0000;
+      sqlite3_config(SQLITE_CONFIG_HEAP, malloc((int)szHeap), (int)szHeap, 64);
+#endif
+#ifdef SQLITE_ENABLE_VFSTRACE
+    }else if( strcmp(argv[i],"-vfstrace")==0 ){
+      extern int vfstrace_register(
+         const char *zTraceName,
+         const char *zOldVfsName,
+         int (*xOut)(const char*,void*),
+         void *pOutArg,
+         int makeDefault
+      );
+      vfstrace_register("trace",0,(int(*)(const char*,void*))fputs,stderr,1);
+#endif
+#ifdef SQLITE_ENABLE_MULTIPLEX
+    }else if( strcmp(argv[i],"-multiplex")==0 ){
+      extern int sqlite3_multiple_initialize(const char*,int);
+      sqlite3_multiplex_initialize(0, 1);
+#endif
+    }else if( strcmp(argv[i],"-vfs")==0 ){
+      sqlite3_vfs *pVfs = sqlite3_vfs_find(argv[++i]);
+      if( pVfs ){
+        sqlite3_vfs_register(pVfs, 1);
+      }else{
+        fprintf(stderr, "no such VFS: \"%s\"\n", argv[i]);
+        exit(1);
+      }
+    }
+  }
+  if( i<argc ){
+#if defined(SQLITE_OS_OS2) && SQLITE_OS_OS2
+    data.zDbFilename = (const char *)convertCpPathToUtf8( argv[i++] );
+#else
+    data.zDbFilename = argv[i++];
+#endif
+  }else{
+#ifndef SQLITE_OMIT_MEMORYDB
+    data.zDbFilename = ":memory:";
+#else
+    data.zDbFilename = 0;
+#endif
+  }
+  if( i<argc ){
+    zFirstCmd = argv[i++];
+  }
+  if( i<argc ){
+    fprintf(stderr,"%s: Error: too many options: \"%s\"\n", Argv0, argv[i]);
+    fprintf(stderr,"Use -help for a list of options.\n");
+    return 1;
+  }
+  data.out = stdout;
+
+#ifdef SQLITE_OMIT_MEMORYDB
+  if( data.zDbFilename==0 ){
+    fprintf(stderr,"%s: Error: no database filename specified\n", Argv0);
+    return 1;
+  }
+#endif
+
+  /* Go ahead and open the database file if it already exists.  If the
+  ** file does not exist, delay opening it.  This prevents empty database
+  ** files from being created if a user mistypes the database name argument
+  ** to the sqlite command-line tool.
+  */
+  if( access(data.zDbFilename, 0)==0 ){
+    open_db(&data);
+  }
+
+  /* Process the initialization file if there is one.  If no -init option
+  ** is given on the command line, look for a file named ~/.sqliterc and
+  ** try to process it.
+  */
+  rc = process_sqliterc(&data,zInitFile);
+  if( rc>0 ){
+    return rc;
+  }
+
+  /* Make a second pass through the command-line argument and set
+  ** options.  This second pass is delayed until after the initialization
+  ** file is processed so that the command-line arguments will override
+  ** settings in the initialization file.
+  */
+  for(i=1; i<argc && argv[i][0]=='-'; i++){
+    char *z = argv[i];
+    if( z[1]=='-' ){ z++; }
+    if( strcmp(z,"-init")==0 ){
+      i++;
+    }else if( strcmp(z,"-html")==0 ){
+      data.mode = MODE_Html;
+    }else if( strcmp(z,"-list")==0 ){
+      data.mode = MODE_List;
+    }else if( strcmp(z,"-line")==0 ){
+      data.mode = MODE_Line;
+    }else if( strcmp(z,"-column")==0 ){
+      data.mode = MODE_Column;
+    }else if( strcmp(z,"-csv")==0 ){
+      data.mode = MODE_Csv;
+      memcpy(data.separator,",",2);
+    }else if( strcmp(z,"-separator")==0 ){
+      i++;
+      if(i>=argc){
+        fprintf(stderr,"%s: Error: missing argument for option: %s\n", Argv0, z);
+        fprintf(stderr,"Use -help for a list of options.\n");
+        return 1;
+      }
+      sqlite3_snprintf(sizeof(data.separator), data.separator,
+                       "%.*s",(int)sizeof(data.separator)-1,argv[i]);
+    }else if( strcmp(z,"-nullvalue")==0 ){
+      i++;
+      if(i>=argc){
+        fprintf(stderr,"%s: Error: missing argument for option: %s\n", Argv0, z);
+        fprintf(stderr,"Use -help for a list of options.\n");
+        return 1;
+      }
+      sqlite3_snprintf(sizeof(data.nullvalue), data.nullvalue,
+                       "%.*s",(int)sizeof(data.nullvalue)-1,argv[i]);
+    }else if( strcmp(z,"-header")==0 ){
+      data.showHeader = 1;
+    }else if( strcmp(z,"-noheader")==0 ){
+      data.showHeader = 0;
+    }else if( strcmp(z,"-echo")==0 ){
+      data.echoOn = 1;
+    }else if( strcmp(z,"-stats")==0 ){
+      data.statsOn = 1;
+    }else if( strcmp(z,"-bail")==0 ){
+      bail_on_error = 1;
+    }else if( strcmp(z,"-version")==0 ){
+      printf("%s %s\n", sqlite3_libversion(), sqlite3_sourceid());
+      return 0;
+    }else if( strcmp(z,"-interactive")==0 ){
+      stdin_is_interactive = 1;
+    }else if( strcmp(z,"-batch")==0 ){
+      stdin_is_interactive = 0;
+    }else if( strcmp(z,"-heap")==0 ){
+      i++;
+    }else if( strcmp(z,"-vfs")==0 ){
+      i++;
+#ifdef SQLITE_ENABLE_VFSTRACE
+    }else if( strcmp(z,"-vfstrace")==0 ){
+      i++;
+#endif
+#ifdef SQLITE_ENABLE_MULTIPLEX
+    }else if( strcmp(z,"-multiplex")==0 ){
+      i++;
+#endif
+    }else if( strcmp(z,"-help")==0 || strcmp(z, "--help")==0 ){
+      usage(1);
+    }else{
+      fprintf(stderr,"%s: Error: unknown option: %s\n", Argv0, z);
+      fprintf(stderr,"Use -help for a list of options.\n");
+      return 1;
+    }
+  }
+
+  if( zFirstCmd ){
+    /* Run just the command that follows the database name
+    */
+    if( zFirstCmd[0]=='.' ){
+      rc = do_meta_command(zFirstCmd, &data);
+    }else{
+      open_db(&data);
+      rc = shell_exec(data.db, zFirstCmd, shell_callback, &data, &zErrMsg);
+      if( zErrMsg!=0 ){
+        fprintf(stderr,"Error: %s\n", zErrMsg);
+        return rc!=0 ? rc : 1;
+      }else if( rc!=0 ){
+        fprintf(stderr,"Error: unable to process SQL \"%s\"\n", zFirstCmd);
+        return rc;
+      }
+    }
+  }else{
+    /* Run commands received from standard input
+    */
+    if( stdin_is_interactive ){
+      char *zHome;
+      char *zHistory = 0;
+      int nHistory;
+      printf(
+        "SQLite version %s %.19s\n"
+        "Enter \".help\" for instructions\n"
+        "Enter SQL statements terminated with a \";\"\n",
+        sqlite3_libversion(), sqlite3_sourceid()
+      );
+      zHome = find_home_dir();
+      if( zHome ){
+        nHistory = strlen30(zHome) + 20;
+        if( (zHistory = malloc(nHistory))!=0 ){
+          sqlite3_snprintf(nHistory, zHistory,"%s/.sqlite_history", zHome);
+        }
+      }
+#if defined(HAVE_READLINE) && HAVE_READLINE==1
+      if( zHistory ) read_history(zHistory);
+#endif
+      rc = process_input(&data, 0);
+      if( zHistory ){
+        stifle_history(100);
+        write_history(zHistory);
+        free(zHistory);
+      }
+      free(zHome);
+    }else{
+      rc = process_input(&data, stdin);
+    }
+  }
+  set_table_name(&data, 0);
+  if( data.db ){
+    sqlite3_close(data.db);
+  }
+  return rc;
+}
diff --git a/src/sqlite.h.in b/src/sqlite.h.in
new file mode 100644
index 0000000..ed18330
--- /dev/null
+++ b/src/sqlite.h.in
@@ -0,0 +1,6732 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This header file defines the interface that the SQLite library
+** presents to client programs.  If a C-function, structure, datatype,
+** or constant definition does not appear in this file, then it is
+** not a published API of SQLite, is subject to change without
+** notice, and should not be referenced by programs that use SQLite.
+**
+** Some of the definitions that are in this file are marked as
+** "experimental".  Experimental interfaces are normally new
+** features recently added to SQLite.  We do not anticipate changes
+** to experimental interfaces but reserve the right to make minor changes
+** if experience from use "in the wild" suggest such changes are prudent.
+**
+** The official C-language API documentation for SQLite is derived
+** from comments in this file.  This file is the authoritative source
+** on how SQLite interfaces are suppose to operate.
+**
+** The name of this file under configuration management is "sqlite.h.in".
+** The makefile makes some minor changes to this file (such as inserting
+** the version number) and changes its name to "sqlite3.h" as
+** part of the build process.
+*/
+#ifndef _SQLITE3_H_
+#define _SQLITE3_H_
+#include <stdarg.h>     /* Needed for the definition of va_list */
+
+/*
+** Make sure we can call this stuff from C++.
+*/
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+/*
+** Add the ability to override 'extern'
+*/
+#ifndef SQLITE_EXTERN
+# define SQLITE_EXTERN extern
+#endif
+
+/*
+** These no-op macros are used in front of interfaces to mark those
+** interfaces as either deprecated or experimental.  New applications
+** should not use deprecated interfaces - they are support for backwards
+** compatibility only.  Application writers should be aware that
+** experimental interfaces are subject to change in point releases.
+**
+** These macros used to resolve to various kinds of compiler magic that
+** would generate warning messages when they were used.  But that
+** compiler magic ended up generating such a flurry of bug reports
+** that we have taken it all out and gone back to using simple
+** noop macros.
+*/
+#define SQLITE_DEPRECATED
+#define SQLITE_EXPERIMENTAL
+
+/*
+** Ensure these symbols were not defined by some previous header file.
+*/
+#ifdef SQLITE_VERSION
+# undef SQLITE_VERSION
+#endif
+#ifdef SQLITE_VERSION_NUMBER
+# undef SQLITE_VERSION_NUMBER
+#endif
+
+/*
+** CAPI3REF: Compile-Time Library Version Numbers
+**
+** ^(The [SQLITE_VERSION] C preprocessor macro in the sqlite3.h header
+** evaluates to a string literal that is the SQLite version in the
+** format "X.Y.Z" where X is the major version number (always 3 for
+** SQLite3) and Y is the minor version number and Z is the release number.)^
+** ^(The [SQLITE_VERSION_NUMBER] C preprocessor macro resolves to an integer
+** with the value (X*1000000 + Y*1000 + Z) where X, Y, and Z are the same
+** numbers used in [SQLITE_VERSION].)^
+** The SQLITE_VERSION_NUMBER for any given release of SQLite will also
+** be larger than the release from which it is derived.  Either Y will
+** be held constant and Z will be incremented or else Y will be incremented
+** and Z will be reset to zero.
+**
+** Since version 3.6.18, SQLite source code has been stored in the
+** <a href="http://www.fossil-scm.org/">Fossil configuration management
+** system</a>.  ^The SQLITE_SOURCE_ID macro evaluates to
+** a string which identifies a particular check-in of SQLite
+** within its configuration management system.  ^The SQLITE_SOURCE_ID
+** string contains the date and time of the check-in (UTC) and an SHA1
+** hash of the entire source tree.
+**
+** See also: [sqlite3_libversion()],
+** [sqlite3_libversion_number()], [sqlite3_sourceid()],
+** [sqlite_version()] and [sqlite_source_id()].
+*/
+#define SQLITE_VERSION        "--VERS--"
+#define SQLITE_VERSION_NUMBER --VERSION-NUMBER--
+#define SQLITE_SOURCE_ID      "--SOURCE-ID--"
+
+/*
+** CAPI3REF: Run-Time Library Version Numbers
+** KEYWORDS: sqlite3_version, sqlite3_sourceid
+**
+** These interfaces provide the same information as the [SQLITE_VERSION],
+** [SQLITE_VERSION_NUMBER], and [SQLITE_SOURCE_ID] C preprocessor macros
+** but are associated with the library instead of the header file.  ^(Cautious
+** programmers might include assert() statements in their application to
+** verify that values returned by these interfaces match the macros in
+** the header, and thus insure that the application is
+** compiled with matching library and header files.
+**
+** <blockquote><pre>
+** assert( sqlite3_libversion_number()==SQLITE_VERSION_NUMBER );
+** assert( strcmp(sqlite3_sourceid(),SQLITE_SOURCE_ID)==0 );
+** assert( strcmp(sqlite3_libversion(),SQLITE_VERSION)==0 );
+** </pre></blockquote>)^
+**
+** ^The sqlite3_version[] string constant contains the text of [SQLITE_VERSION]
+** macro.  ^The sqlite3_libversion() function returns a pointer to the
+** to the sqlite3_version[] string constant.  The sqlite3_libversion()
+** function is provided for use in DLLs since DLL users usually do not have
+** direct access to string constants within the DLL.  ^The
+** sqlite3_libversion_number() function returns an integer equal to
+** [SQLITE_VERSION_NUMBER].  ^The sqlite3_sourceid() function returns 
+** a pointer to a string constant whose value is the same as the 
+** [SQLITE_SOURCE_ID] C preprocessor macro.
+**
+** See also: [sqlite_version()] and [sqlite_source_id()].
+*/
+SQLITE_EXTERN const char sqlite3_version[];
+const char *sqlite3_libversion(void);
+const char *sqlite3_sourceid(void);
+int sqlite3_libversion_number(void);
+
+/*
+** CAPI3REF: Run-Time Library Compilation Options Diagnostics
+**
+** ^The sqlite3_compileoption_used() function returns 0 or 1 
+** indicating whether the specified option was defined at 
+** compile time.  ^The SQLITE_ prefix may be omitted from the 
+** option name passed to sqlite3_compileoption_used().  
+**
+** ^The sqlite3_compileoption_get() function allows iterating
+** over the list of options that were defined at compile time by
+** returning the N-th compile time option string.  ^If N is out of range,
+** sqlite3_compileoption_get() returns a NULL pointer.  ^The SQLITE_ 
+** prefix is omitted from any strings returned by 
+** sqlite3_compileoption_get().
+**
+** ^Support for the diagnostic functions sqlite3_compileoption_used()
+** and sqlite3_compileoption_get() may be omitted by specifying the 
+** [SQLITE_OMIT_COMPILEOPTION_DIAGS] option at compile time.
+**
+** See also: SQL functions [sqlite_compileoption_used()] and
+** [sqlite_compileoption_get()] and the [compile_options pragma].
+*/
+#ifndef SQLITE_OMIT_COMPILEOPTION_DIAGS
+int sqlite3_compileoption_used(const char *zOptName);
+const char *sqlite3_compileoption_get(int N);
+#endif
+
+/*
+** CAPI3REF: Test To See If The Library Is Threadsafe
+**
+** ^The sqlite3_threadsafe() function returns zero if and only if
+** SQLite was compiled mutexing code omitted due to the
+** [SQLITE_THREADSAFE] compile-time option being set to 0.
+**
+** SQLite can be compiled with or without mutexes.  When
+** the [SQLITE_THREADSAFE] C preprocessor macro is 1 or 2, mutexes
+** are enabled and SQLite is threadsafe.  When the
+** [SQLITE_THREADSAFE] macro is 0, 
+** the mutexes are omitted.  Without the mutexes, it is not safe
+** to use SQLite concurrently from more than one thread.
+**
+** Enabling mutexes incurs a measurable performance penalty.
+** So if speed is of utmost importance, it makes sense to disable
+** the mutexes.  But for maximum safety, mutexes should be enabled.
+** ^The default behavior is for mutexes to be enabled.
+**
+** This interface can be used by an application to make sure that the
+** version of SQLite that it is linking against was compiled with
+** the desired setting of the [SQLITE_THREADSAFE] macro.
+**
+** This interface only reports on the compile-time mutex setting
+** of the [SQLITE_THREADSAFE] flag.  If SQLite is compiled with
+** SQLITE_THREADSAFE=1 or =2 then mutexes are enabled by default but
+** can be fully or partially disabled using a call to [sqlite3_config()]
+** with the verbs [SQLITE_CONFIG_SINGLETHREAD], [SQLITE_CONFIG_MULTITHREAD],
+** or [SQLITE_CONFIG_MUTEX].  ^(The return value of the
+** sqlite3_threadsafe() function shows only the compile-time setting of
+** thread safety, not any run-time changes to that setting made by
+** sqlite3_config(). In other words, the return value from sqlite3_threadsafe()
+** is unchanged by calls to sqlite3_config().)^
+**
+** See the [threading mode] documentation for additional information.
+*/
+int sqlite3_threadsafe(void);
+
+/*
+** CAPI3REF: Database Connection Handle
+** KEYWORDS: {database connection} {database connections}
+**
+** Each open SQLite database is represented by a pointer to an instance of
+** the opaque structure named "sqlite3".  It is useful to think of an sqlite3
+** pointer as an object.  The [sqlite3_open()], [sqlite3_open16()], and
+** [sqlite3_open_v2()] interfaces are its constructors, and [sqlite3_close()]
+** is its destructor.  There are many other interfaces (such as
+** [sqlite3_prepare_v2()], [sqlite3_create_function()], and
+** [sqlite3_busy_timeout()] to name but three) that are methods on an
+** sqlite3 object.
+*/
+typedef struct sqlite3 sqlite3;
+
+/*
+** CAPI3REF: 64-Bit Integer Types
+** KEYWORDS: sqlite_int64 sqlite_uint64
+**
+** Because there is no cross-platform way to specify 64-bit integer types
+** SQLite includes typedefs for 64-bit signed and unsigned integers.
+**
+** The sqlite3_int64 and sqlite3_uint64 are the preferred type definitions.
+** The sqlite_int64 and sqlite_uint64 types are supported for backwards
+** compatibility only.
+**
+** ^The sqlite3_int64 and sqlite_int64 types can store integer values
+** between -9223372036854775808 and +9223372036854775807 inclusive.  ^The
+** sqlite3_uint64 and sqlite_uint64 types can store integer values 
+** between 0 and +18446744073709551615 inclusive.
+*/
+#ifdef SQLITE_INT64_TYPE
+  typedef SQLITE_INT64_TYPE sqlite_int64;
+  typedef unsigned SQLITE_INT64_TYPE sqlite_uint64;
+#elif defined(_MSC_VER) || defined(__BORLANDC__)
+  typedef __int64 sqlite_int64;
+  typedef unsigned __int64 sqlite_uint64;
+#else
+  typedef long long int sqlite_int64;
+  typedef unsigned long long int sqlite_uint64;
+#endif
+typedef sqlite_int64 sqlite3_int64;
+typedef sqlite_uint64 sqlite3_uint64;
+
+/*
+** If compiling for a processor that lacks floating point support,
+** substitute integer for floating-point.
+*/
+#ifdef SQLITE_OMIT_FLOATING_POINT
+# define double sqlite3_int64
+#endif
+
+/*
+** CAPI3REF: Closing A Database Connection
+**
+** ^The sqlite3_close() routine is the destructor for the [sqlite3] object.
+** ^Calls to sqlite3_close() return SQLITE_OK if the [sqlite3] object is
+** successfully destroyed and all associated resources are deallocated.
+**
+** Applications must [sqlite3_finalize | finalize] all [prepared statements]
+** and [sqlite3_blob_close | close] all [BLOB handles] associated with
+** the [sqlite3] object prior to attempting to close the object.  ^If
+** sqlite3_close() is called on a [database connection] that still has
+** outstanding [prepared statements] or [BLOB handles], then it returns
+** SQLITE_BUSY.
+**
+** ^If [sqlite3_close()] is invoked while a transaction is open,
+** the transaction is automatically rolled back.
+**
+** The C parameter to [sqlite3_close(C)] must be either a NULL
+** pointer or an [sqlite3] object pointer obtained
+** from [sqlite3_open()], [sqlite3_open16()], or
+** [sqlite3_open_v2()], and not previously closed.
+** ^Calling sqlite3_close() with a NULL pointer argument is a 
+** harmless no-op.
+*/
+int sqlite3_close(sqlite3 *);
+
+/*
+** The type for a callback function.
+** This is legacy and deprecated.  It is included for historical
+** compatibility and is not documented.
+*/
+typedef int (*sqlite3_callback)(void*,int,char**, char**);
+
+/*
+** CAPI3REF: One-Step Query Execution Interface
+**
+** The sqlite3_exec() interface is a convenience wrapper around
+** [sqlite3_prepare_v2()], [sqlite3_step()], and [sqlite3_finalize()],
+** that allows an application to run multiple statements of SQL
+** without having to use a lot of C code. 
+**
+** ^The sqlite3_exec() interface runs zero or more UTF-8 encoded,
+** semicolon-separate SQL statements passed into its 2nd argument,
+** in the context of the [database connection] passed in as its 1st
+** argument.  ^If the callback function of the 3rd argument to
+** sqlite3_exec() is not NULL, then it is invoked for each result row
+** coming out of the evaluated SQL statements.  ^The 4th argument to
+** sqlite3_exec() is relayed through to the 1st argument of each
+** callback invocation.  ^If the callback pointer to sqlite3_exec()
+** is NULL, then no callback is ever invoked and result rows are
+** ignored.
+**
+** ^If an error occurs while evaluating the SQL statements passed into
+** sqlite3_exec(), then execution of the current statement stops and
+** subsequent statements are skipped.  ^If the 5th parameter to sqlite3_exec()
+** is not NULL then any error message is written into memory obtained
+** from [sqlite3_malloc()] and passed back through the 5th parameter.
+** To avoid memory leaks, the application should invoke [sqlite3_free()]
+** on error message strings returned through the 5th parameter of
+** of sqlite3_exec() after the error message string is no longer needed.
+** ^If the 5th parameter to sqlite3_exec() is not NULL and no errors
+** occur, then sqlite3_exec() sets the pointer in its 5th parameter to
+** NULL before returning.
+**
+** ^If an sqlite3_exec() callback returns non-zero, the sqlite3_exec()
+** routine returns SQLITE_ABORT without invoking the callback again and
+** without running any subsequent SQL statements.
+**
+** ^The 2nd argument to the sqlite3_exec() callback function is the
+** number of columns in the result.  ^The 3rd argument to the sqlite3_exec()
+** callback is an array of pointers to strings obtained as if from
+** [sqlite3_column_text()], one for each column.  ^If an element of a
+** result row is NULL then the corresponding string pointer for the
+** sqlite3_exec() callback is a NULL pointer.  ^The 4th argument to the
+** sqlite3_exec() callback is an array of pointers to strings where each
+** entry represents the name of corresponding result column as obtained
+** from [sqlite3_column_name()].
+**
+** ^If the 2nd parameter to sqlite3_exec() is a NULL pointer, a pointer
+** to an empty string, or a pointer that contains only whitespace and/or 
+** SQL comments, then no SQL statements are evaluated and the database
+** is not changed.
+**
+** Restrictions:
+**
+** <ul>
+** <li> The application must insure that the 1st parameter to sqlite3_exec()
+**      is a valid and open [database connection].
+** <li> The application must not close [database connection] specified by
+**      the 1st parameter to sqlite3_exec() while sqlite3_exec() is running.
+** <li> The application must not modify the SQL statement text passed into
+**      the 2nd parameter of sqlite3_exec() while sqlite3_exec() is running.
+** </ul>
+*/
+int sqlite3_exec(
+  sqlite3*,                                  /* An open database */
+  const char *sql,                           /* SQL to be evaluated */
+  int (*callback)(void*,int,char**,char**),  /* Callback function */
+  void *,                                    /* 1st argument to callback */
+  char **errmsg                              /* Error msg written here */
+);
+
+/*
+** CAPI3REF: Result Codes
+** KEYWORDS: SQLITE_OK {error code} {error codes}
+** KEYWORDS: {result code} {result codes}
+**
+** Many SQLite functions return an integer result code from the set shown
+** here in order to indicates success or failure.
+**
+** New error codes may be added in future versions of SQLite.
+**
+** See also: [SQLITE_IOERR_READ | extended result codes],
+** [sqlite3_vtab_on_conflict()] [SQLITE_ROLLBACK | result codes].
+*/
+#define SQLITE_OK           0   /* Successful result */
+/* beginning-of-error-codes */
+#define SQLITE_ERROR        1   /* SQL error or missing database */
+#define SQLITE_INTERNAL     2   /* Internal logic error in SQLite */
+#define SQLITE_PERM         3   /* Access permission denied */
+#define SQLITE_ABORT        4   /* Callback routine requested an abort */
+#define SQLITE_BUSY         5   /* The database file is locked */
+#define SQLITE_LOCKED       6   /* A table in the database is locked */
+#define SQLITE_NOMEM        7   /* A malloc() failed */
+#define SQLITE_READONLY     8   /* Attempt to write a readonly database */
+#define SQLITE_INTERRUPT    9   /* Operation terminated by sqlite3_interrupt()*/
+#define SQLITE_IOERR       10   /* Some kind of disk I/O error occurred */
+#define SQLITE_CORRUPT     11   /* The database disk image is malformed */
+#define SQLITE_NOTFOUND    12   /* Unknown opcode in sqlite3_file_control() */
+#define SQLITE_FULL        13   /* Insertion failed because database is full */
+#define SQLITE_CANTOPEN    14   /* Unable to open the database file */
+#define SQLITE_PROTOCOL    15   /* Database lock protocol error */
+#define SQLITE_EMPTY       16   /* Database is empty */
+#define SQLITE_SCHEMA      17   /* The database schema changed */
+#define SQLITE_TOOBIG      18   /* String or BLOB exceeds size limit */
+#define SQLITE_CONSTRAINT  19   /* Abort due to constraint violation */
+#define SQLITE_MISMATCH    20   /* Data type mismatch */
+#define SQLITE_MISUSE      21   /* Library used incorrectly */
+#define SQLITE_NOLFS       22   /* Uses OS features not supported on host */
+#define SQLITE_AUTH        23   /* Authorization denied */
+#define SQLITE_FORMAT      24   /* Auxiliary database format error */
+#define SQLITE_RANGE       25   /* 2nd parameter to sqlite3_bind out of range */
+#define SQLITE_NOTADB      26   /* File opened that is not a database file */
+#define SQLITE_ROW         100  /* sqlite3_step() has another row ready */
+#define SQLITE_DONE        101  /* sqlite3_step() has finished executing */
+/* end-of-error-codes */
+
+/*
+** CAPI3REF: Extended Result Codes
+** KEYWORDS: {extended error code} {extended error codes}
+** KEYWORDS: {extended result code} {extended result codes}
+**
+** In its default configuration, SQLite API routines return one of 26 integer
+** [SQLITE_OK | result codes].  However, experience has shown that many of
+** these result codes are too coarse-grained.  They do not provide as
+** much information about problems as programmers might like.  In an effort to
+** address this, newer versions of SQLite (version 3.3.8 and later) include
+** support for additional result codes that provide more detailed information
+** about errors. The extended result codes are enabled or disabled
+** on a per database connection basis using the
+** [sqlite3_extended_result_codes()] API.
+**
+** Some of the available extended result codes are listed here.
+** One may expect the number of extended result codes will be expand
+** over time.  Software that uses extended result codes should expect
+** to see new result codes in future releases of SQLite.
+**
+** The SQLITE_OK result code will never be extended.  It will always
+** be exactly zero.
+*/
+#define SQLITE_IOERR_READ              (SQLITE_IOERR | (1<<8))
+#define SQLITE_IOERR_SHORT_READ        (SQLITE_IOERR | (2<<8))
+#define SQLITE_IOERR_WRITE             (SQLITE_IOERR | (3<<8))
+#define SQLITE_IOERR_FSYNC             (SQLITE_IOERR | (4<<8))
+#define SQLITE_IOERR_DIR_FSYNC         (SQLITE_IOERR | (5<<8))
+#define SQLITE_IOERR_TRUNCATE          (SQLITE_IOERR | (6<<8))
+#define SQLITE_IOERR_FSTAT             (SQLITE_IOERR | (7<<8))
+#define SQLITE_IOERR_UNLOCK            (SQLITE_IOERR | (8<<8))
+#define SQLITE_IOERR_RDLOCK            (SQLITE_IOERR | (9<<8))
+#define SQLITE_IOERR_DELETE            (SQLITE_IOERR | (10<<8))
+#define SQLITE_IOERR_BLOCKED           (SQLITE_IOERR | (11<<8))
+#define SQLITE_IOERR_NOMEM             (SQLITE_IOERR | (12<<8))
+#define SQLITE_IOERR_ACCESS            (SQLITE_IOERR | (13<<8))
+#define SQLITE_IOERR_CHECKRESERVEDLOCK (SQLITE_IOERR | (14<<8))
+#define SQLITE_IOERR_LOCK              (SQLITE_IOERR | (15<<8))
+#define SQLITE_IOERR_CLOSE             (SQLITE_IOERR | (16<<8))
+#define SQLITE_IOERR_DIR_CLOSE         (SQLITE_IOERR | (17<<8))
+#define SQLITE_IOERR_SHMOPEN           (SQLITE_IOERR | (18<<8))
+#define SQLITE_IOERR_SHMSIZE           (SQLITE_IOERR | (19<<8))
+#define SQLITE_IOERR_SHMLOCK           (SQLITE_IOERR | (20<<8))
+#define SQLITE_IOERR_SHMMAP            (SQLITE_IOERR | (21<<8))
+#define SQLITE_IOERR_SEEK              (SQLITE_IOERR | (22<<8))
+#define SQLITE_LOCKED_SHAREDCACHE      (SQLITE_LOCKED |  (1<<8))
+#define SQLITE_BUSY_RECOVERY           (SQLITE_BUSY   |  (1<<8))
+#define SQLITE_CANTOPEN_NOTEMPDIR      (SQLITE_CANTOPEN | (1<<8))
+#define SQLITE_CORRUPT_VTAB            (SQLITE_CORRUPT | (1<<8))
+#define SQLITE_READONLY_RECOVERY       (SQLITE_READONLY | (1<<8))
+#define SQLITE_READONLY_CANTLOCK       (SQLITE_READONLY | (2<<8))
+
+/*
+** CAPI3REF: Flags For File Open Operations
+**
+** These bit values are intended for use in the
+** 3rd parameter to the [sqlite3_open_v2()] interface and
+** in the 4th parameter to the [sqlite3_vfs.xOpen] method.
+*/
+#define SQLITE_OPEN_READONLY         0x00000001  /* Ok for sqlite3_open_v2() */
+#define SQLITE_OPEN_READWRITE        0x00000002  /* Ok for sqlite3_open_v2() */
+#define SQLITE_OPEN_CREATE           0x00000004  /* Ok for sqlite3_open_v2() */
+#define SQLITE_OPEN_DELETEONCLOSE    0x00000008  /* VFS only */
+#define SQLITE_OPEN_EXCLUSIVE        0x00000010  /* VFS only */
+#define SQLITE_OPEN_AUTOPROXY        0x00000020  /* VFS only */
+#define SQLITE_OPEN_URI              0x00000040  /* Ok for sqlite3_open_v2() */
+#define SQLITE_OPEN_MAIN_DB          0x00000100  /* VFS only */
+#define SQLITE_OPEN_TEMP_DB          0x00000200  /* VFS only */
+#define SQLITE_OPEN_TRANSIENT_DB     0x00000400  /* VFS only */
+#define SQLITE_OPEN_MAIN_JOURNAL     0x00000800  /* VFS only */
+#define SQLITE_OPEN_TEMP_JOURNAL     0x00001000  /* VFS only */
+#define SQLITE_OPEN_SUBJOURNAL       0x00002000  /* VFS only */
+#define SQLITE_OPEN_MASTER_JOURNAL   0x00004000  /* VFS only */
+#define SQLITE_OPEN_NOMUTEX          0x00008000  /* Ok for sqlite3_open_v2() */
+#define SQLITE_OPEN_FULLMUTEX        0x00010000  /* Ok for sqlite3_open_v2() */
+#define SQLITE_OPEN_SHAREDCACHE      0x00020000  /* Ok for sqlite3_open_v2() */
+#define SQLITE_OPEN_PRIVATECACHE     0x00040000  /* Ok for sqlite3_open_v2() */
+#define SQLITE_OPEN_WAL              0x00080000  /* VFS only */
+
+/* Reserved:                         0x00F00000 */
+
+/*
+** CAPI3REF: Device Characteristics
+**
+** The xDeviceCharacteristics method of the [sqlite3_io_methods]
+** object returns an integer which is a vector of the these
+** bit values expressing I/O characteristics of the mass storage
+** device that holds the file that the [sqlite3_io_methods]
+** refers to.
+**
+** The SQLITE_IOCAP_ATOMIC property means that all writes of
+** any size are atomic.  The SQLITE_IOCAP_ATOMICnnn values
+** mean that writes of blocks that are nnn bytes in size and
+** are aligned to an address which is an integer multiple of
+** nnn are atomic.  The SQLITE_IOCAP_SAFE_APPEND value means
+** that when data is appended to a file, the data is appended
+** first then the size of the file is extended, never the other
+** way around.  The SQLITE_IOCAP_SEQUENTIAL property means that
+** information is written to disk in the same order as calls
+** to xWrite().
+*/
+#define SQLITE_IOCAP_ATOMIC                 0x00000001
+#define SQLITE_IOCAP_ATOMIC512              0x00000002
+#define SQLITE_IOCAP_ATOMIC1K               0x00000004
+#define SQLITE_IOCAP_ATOMIC2K               0x00000008
+#define SQLITE_IOCAP_ATOMIC4K               0x00000010
+#define SQLITE_IOCAP_ATOMIC8K               0x00000020
+#define SQLITE_IOCAP_ATOMIC16K              0x00000040
+#define SQLITE_IOCAP_ATOMIC32K              0x00000080
+#define SQLITE_IOCAP_ATOMIC64K              0x00000100
+#define SQLITE_IOCAP_SAFE_APPEND            0x00000200
+#define SQLITE_IOCAP_SEQUENTIAL             0x00000400
+#define SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN  0x00000800
+
+/*
+** CAPI3REF: File Locking Levels
+**
+** SQLite uses one of these integer values as the second
+** argument to calls it makes to the xLock() and xUnlock() methods
+** of an [sqlite3_io_methods] object.
+*/
+#define SQLITE_LOCK_NONE          0
+#define SQLITE_LOCK_SHARED        1
+#define SQLITE_LOCK_RESERVED      2
+#define SQLITE_LOCK_PENDING       3
+#define SQLITE_LOCK_EXCLUSIVE     4
+
+/*
+** CAPI3REF: Synchronization Type Flags
+**
+** When SQLite invokes the xSync() method of an
+** [sqlite3_io_methods] object it uses a combination of
+** these integer values as the second argument.
+**
+** When the SQLITE_SYNC_DATAONLY flag is used, it means that the
+** sync operation only needs to flush data to mass storage.  Inode
+** information need not be flushed. If the lower four bits of the flag
+** equal SQLITE_SYNC_NORMAL, that means to use normal fsync() semantics.
+** If the lower four bits equal SQLITE_SYNC_FULL, that means
+** to use Mac OS X style fullsync instead of fsync().
+**
+** Do not confuse the SQLITE_SYNC_NORMAL and SQLITE_SYNC_FULL flags
+** with the [PRAGMA synchronous]=NORMAL and [PRAGMA synchronous]=FULL
+** settings.  The [synchronous pragma] determines when calls to the
+** xSync VFS method occur and applies uniformly across all platforms.
+** The SQLITE_SYNC_NORMAL and SQLITE_SYNC_FULL flags determine how
+** energetic or rigorous or forceful the sync operations are and
+** only make a difference on Mac OSX for the default SQLite code.
+** (Third-party VFS implementations might also make the distinction
+** between SQLITE_SYNC_NORMAL and SQLITE_SYNC_FULL, but among the
+** operating systems natively supported by SQLite, only Mac OSX
+** cares about the difference.)
+*/
+#define SQLITE_SYNC_NORMAL        0x00002
+#define SQLITE_SYNC_FULL          0x00003
+#define SQLITE_SYNC_DATAONLY      0x00010
+
+/*
+** CAPI3REF: OS Interface Open File Handle
+**
+** An [sqlite3_file] object represents an open file in the 
+** [sqlite3_vfs | OS interface layer].  Individual OS interface
+** implementations will
+** want to subclass this object by appending additional fields
+** for their own use.  The pMethods entry is a pointer to an
+** [sqlite3_io_methods] object that defines methods for performing
+** I/O operations on the open file.
+*/
+typedef struct sqlite3_file sqlite3_file;
+struct sqlite3_file {
+  const struct sqlite3_io_methods *pMethods;  /* Methods for an open file */
+};
+
+/*
+** CAPI3REF: OS Interface File Virtual Methods Object
+**
+** Every file opened by the [sqlite3_vfs.xOpen] method populates an
+** [sqlite3_file] object (or, more commonly, a subclass of the
+** [sqlite3_file] object) with a pointer to an instance of this object.
+** This object defines the methods used to perform various operations
+** against the open file represented by the [sqlite3_file] object.
+**
+** If the [sqlite3_vfs.xOpen] method sets the sqlite3_file.pMethods element 
+** to a non-NULL pointer, then the sqlite3_io_methods.xClose method
+** may be invoked even if the [sqlite3_vfs.xOpen] reported that it failed.  The
+** only way to prevent a call to xClose following a failed [sqlite3_vfs.xOpen]
+** is for the [sqlite3_vfs.xOpen] to set the sqlite3_file.pMethods element
+** to NULL.
+**
+** The flags argument to xSync may be one of [SQLITE_SYNC_NORMAL] or
+** [SQLITE_SYNC_FULL].  The first choice is the normal fsync().
+** The second choice is a Mac OS X style fullsync.  The [SQLITE_SYNC_DATAONLY]
+** flag may be ORed in to indicate that only the data of the file
+** and not its inode needs to be synced.
+**
+** The integer values to xLock() and xUnlock() are one of
+** <ul>
+** <li> [SQLITE_LOCK_NONE],
+** <li> [SQLITE_LOCK_SHARED],
+** <li> [SQLITE_LOCK_RESERVED],
+** <li> [SQLITE_LOCK_PENDING], or
+** <li> [SQLITE_LOCK_EXCLUSIVE].
+** </ul>
+** xLock() increases the lock. xUnlock() decreases the lock.
+** The xCheckReservedLock() method checks whether any database connection,
+** either in this process or in some other process, is holding a RESERVED,
+** PENDING, or EXCLUSIVE lock on the file.  It returns true
+** if such a lock exists and false otherwise.
+**
+** The xFileControl() method is a generic interface that allows custom
+** VFS implementations to directly control an open file using the
+** [sqlite3_file_control()] interface.  The second "op" argument is an
+** integer opcode.  The third argument is a generic pointer intended to
+** point to a structure that may contain arguments or space in which to
+** write return values.  Potential uses for xFileControl() might be
+** functions to enable blocking locks with timeouts, to change the
+** locking strategy (for example to use dot-file locks), to inquire
+** about the status of a lock, or to break stale locks.  The SQLite
+** core reserves all opcodes less than 100 for its own use.
+** A [SQLITE_FCNTL_LOCKSTATE | list of opcodes] less than 100 is available.
+** Applications that define a custom xFileControl method should use opcodes
+** greater than 100 to avoid conflicts.  VFS implementations should
+** return [SQLITE_NOTFOUND] for file control opcodes that they do not
+** recognize.
+**
+** The xSectorSize() method returns the sector size of the
+** device that underlies the file.  The sector size is the
+** minimum write that can be performed without disturbing
+** other bytes in the file.  The xDeviceCharacteristics()
+** method returns a bit vector describing behaviors of the
+** underlying device:
+**
+** <ul>
+** <li> [SQLITE_IOCAP_ATOMIC]
+** <li> [SQLITE_IOCAP_ATOMIC512]
+** <li> [SQLITE_IOCAP_ATOMIC1K]
+** <li> [SQLITE_IOCAP_ATOMIC2K]
+** <li> [SQLITE_IOCAP_ATOMIC4K]
+** <li> [SQLITE_IOCAP_ATOMIC8K]
+** <li> [SQLITE_IOCAP_ATOMIC16K]
+** <li> [SQLITE_IOCAP_ATOMIC32K]
+** <li> [SQLITE_IOCAP_ATOMIC64K]
+** <li> [SQLITE_IOCAP_SAFE_APPEND]
+** <li> [SQLITE_IOCAP_SEQUENTIAL]
+** </ul>
+**
+** The SQLITE_IOCAP_ATOMIC property means that all writes of
+** any size are atomic.  The SQLITE_IOCAP_ATOMICnnn values
+** mean that writes of blocks that are nnn bytes in size and
+** are aligned to an address which is an integer multiple of
+** nnn are atomic.  The SQLITE_IOCAP_SAFE_APPEND value means
+** that when data is appended to a file, the data is appended
+** first then the size of the file is extended, never the other
+** way around.  The SQLITE_IOCAP_SEQUENTIAL property means that
+** information is written to disk in the same order as calls
+** to xWrite().
+**
+** If xRead() returns SQLITE_IOERR_SHORT_READ it must also fill
+** in the unread portions of the buffer with zeros.  A VFS that
+** fails to zero-fill short reads might seem to work.  However,
+** failure to zero-fill short reads will eventually lead to
+** database corruption.
+*/
+typedef struct sqlite3_io_methods sqlite3_io_methods;
+struct sqlite3_io_methods {
+  int iVersion;
+  int (*xClose)(sqlite3_file*);
+  int (*xRead)(sqlite3_file*, void*, int iAmt, sqlite3_int64 iOfst);
+  int (*xWrite)(sqlite3_file*, const void*, int iAmt, sqlite3_int64 iOfst);
+  int (*xTruncate)(sqlite3_file*, sqlite3_int64 size);
+  int (*xSync)(sqlite3_file*, int flags);
+  int (*xFileSize)(sqlite3_file*, sqlite3_int64 *pSize);
+  int (*xLock)(sqlite3_file*, int);
+  int (*xUnlock)(sqlite3_file*, int);
+  int (*xCheckReservedLock)(sqlite3_file*, int *pResOut);
+  int (*xFileControl)(sqlite3_file*, int op, void *pArg);
+  int (*xSectorSize)(sqlite3_file*);
+  int (*xDeviceCharacteristics)(sqlite3_file*);
+  /* Methods above are valid for version 1 */
+  int (*xShmMap)(sqlite3_file*, int iPg, int pgsz, int, void volatile**);
+  int (*xShmLock)(sqlite3_file*, int offset, int n, int flags);
+  void (*xShmBarrier)(sqlite3_file*);
+  int (*xShmUnmap)(sqlite3_file*, int deleteFlag);
+  /* Methods above are valid for version 2 */
+  /* Additional methods may be added in future releases */
+};
+
+/*
+** CAPI3REF: Standard File Control Opcodes
+**
+** These integer constants are opcodes for the xFileControl method
+** of the [sqlite3_io_methods] object and for the [sqlite3_file_control()]
+** interface.
+**
+** The [SQLITE_FCNTL_LOCKSTATE] opcode is used for debugging.  This
+** opcode causes the xFileControl method to write the current state of
+** the lock (one of [SQLITE_LOCK_NONE], [SQLITE_LOCK_SHARED],
+** [SQLITE_LOCK_RESERVED], [SQLITE_LOCK_PENDING], or [SQLITE_LOCK_EXCLUSIVE])
+** into an integer that the pArg argument points to. This capability
+** is used during testing and only needs to be supported when SQLITE_TEST
+** is defined.
+**
+** The [SQLITE_FCNTL_SIZE_HINT] opcode is used by SQLite to give the VFS
+** layer a hint of how large the database file will grow to be during the
+** current transaction.  This hint is not guaranteed to be accurate but it
+** is often close.  The underlying VFS might choose to preallocate database
+** file space based on this hint in order to help writes to the database
+** file run faster.
+**
+** The [SQLITE_FCNTL_CHUNK_SIZE] opcode is used to request that the VFS
+** extends and truncates the database file in chunks of a size specified
+** by the user. The fourth argument to [sqlite3_file_control()] should 
+** point to an integer (type int) containing the new chunk-size to use
+** for the nominated database. Allocating database file space in large
+** chunks (say 1MB at a time), may reduce file-system fragmentation and
+** improve performance on some systems.
+**
+** The [SQLITE_FCNTL_FILE_POINTER] opcode is used to obtain a pointer
+** to the [sqlite3_file] object associated with a particular database
+** connection.  See the [sqlite3_file_control()] documentation for
+** additional information.
+**
+** ^(The [SQLITE_FCNTL_SYNC_OMITTED] opcode is generated internally by
+** SQLite and sent to all VFSes in place of a call to the xSync method
+** when the database connection has [PRAGMA synchronous] set to OFF.)^
+** Some specialized VFSes need this signal in order to operate correctly
+** when [PRAGMA synchronous | PRAGMA synchronous=OFF] is set, but most 
+** VFSes do not need this signal and should silently ignore this opcode.
+** Applications should not call [sqlite3_file_control()] with this
+** opcode as doing so may disrupt the operation of the specialized VFSes
+** that do require it.  
+**
+** ^The [SQLITE_FCNTL_WIN32_AV_RETRY] opcode is used to configure automatic
+** retry counts and intervals for certain disk I/O operations for the
+** windows [VFS] in order to work to provide robustness against
+** anti-virus programs.  By default, the windows VFS will retry file read,
+** file write, and file delete operations up to 10 times, with a delay
+** of 25 milliseconds before the first retry and with the delay increasing
+** by an additional 25 milliseconds with each subsequent retry.  This
+** opcode allows those to values (10 retries and 25 milliseconds of delay)
+** to be adjusted.  The values are changed for all database connections
+** within the same process.  The argument is a pointer to an array of two
+** integers where the first integer i the new retry count and the second
+** integer is the delay.  If either integer is negative, then the setting
+** is not changed but instead the prior value of that setting is written
+** into the array entry, allowing the current retry settings to be
+** interrogated.  The zDbName parameter is ignored.
+**
+** ^The [SQLITE_FCNTL_PERSIST_WAL] opcode is used to set or query the
+** persistent [WAL | Write AHead Log] setting.  By default, the auxiliary
+** write ahead log and shared memory files used for transaction control
+** are automatically deleted when the latest connection to the database
+** closes.  Setting persistent WAL mode causes those files to persist after
+** close.  Persisting the files is useful when other processes that do not
+** have write permission on the directory containing the database file want
+** to read the database file, as the WAL and shared memory files must exist
+** in order for the database to be readable.  The fourth parameter to
+** [sqlite3_file_control()] for this opcode should be a pointer to an integer.
+** That integer is 0 to disable persistent WAL mode or 1 to enable persistent
+** WAL mode.  If the integer is -1, then it is overwritten with the current
+** WAL persistence setting.
+**
+** ^The [SQLITE_FCNTL_OVERWRITE] opcode is invoked by SQLite after opening
+** a write transaction to indicate that, unless it is rolled back for some
+** reason, the entire database file will be overwritten by the current 
+** transaction. This is used by VACUUM operations.
+*/
+#define SQLITE_FCNTL_LOCKSTATE        1
+#define SQLITE_GET_LOCKPROXYFILE      2
+#define SQLITE_SET_LOCKPROXYFILE      3
+#define SQLITE_LAST_ERRNO             4
+#define SQLITE_FCNTL_SIZE_HINT        5
+#define SQLITE_FCNTL_CHUNK_SIZE       6
+#define SQLITE_FCNTL_FILE_POINTER     7
+#define SQLITE_FCNTL_SYNC_OMITTED     8
+#define SQLITE_FCNTL_WIN32_AV_RETRY   9
+#define SQLITE_FCNTL_PERSIST_WAL     10
+#define SQLITE_FCNTL_OVERWRITE       11
+
+/*
+** CAPI3REF: Mutex Handle
+**
+** The mutex module within SQLite defines [sqlite3_mutex] to be an
+** abstract type for a mutex object.  The SQLite core never looks
+** at the internal representation of an [sqlite3_mutex].  It only
+** deals with pointers to the [sqlite3_mutex] object.
+**
+** Mutexes are created using [sqlite3_mutex_alloc()].
+*/
+typedef struct sqlite3_mutex sqlite3_mutex;
+
+/*
+** CAPI3REF: OS Interface Object
+**
+** An instance of the sqlite3_vfs object defines the interface between
+** the SQLite core and the underlying operating system.  The "vfs"
+** in the name of the object stands for "virtual file system".  See
+** the [VFS | VFS documentation] for further information.
+**
+** The value of the iVersion field is initially 1 but may be larger in
+** future versions of SQLite.  Additional fields may be appended to this
+** object when the iVersion value is increased.  Note that the structure
+** of the sqlite3_vfs object changes in the transaction between
+** SQLite version 3.5.9 and 3.6.0 and yet the iVersion field was not
+** modified.
+**
+** The szOsFile field is the size of the subclassed [sqlite3_file]
+** structure used by this VFS.  mxPathname is the maximum length of
+** a pathname in this VFS.
+**
+** Registered sqlite3_vfs objects are kept on a linked list formed by
+** the pNext pointer.  The [sqlite3_vfs_register()]
+** and [sqlite3_vfs_unregister()] interfaces manage this list
+** in a thread-safe way.  The [sqlite3_vfs_find()] interface
+** searches the list.  Neither the application code nor the VFS
+** implementation should use the pNext pointer.
+**
+** The pNext field is the only field in the sqlite3_vfs
+** structure that SQLite will ever modify.  SQLite will only access
+** or modify this field while holding a particular static mutex.
+** The application should never modify anything within the sqlite3_vfs
+** object once the object has been registered.
+**
+** The zName field holds the name of the VFS module.  The name must
+** be unique across all VFS modules.
+**
+** [[sqlite3_vfs.xOpen]]
+** ^SQLite guarantees that the zFilename parameter to xOpen
+** is either a NULL pointer or string obtained
+** from xFullPathname() with an optional suffix added.
+** ^If a suffix is added to the zFilename parameter, it will
+** consist of a single "-" character followed by no more than
+** 10 alphanumeric and/or "-" characters.
+** ^SQLite further guarantees that
+** the string will be valid and unchanged until xClose() is
+** called. Because of the previous sentence,
+** the [sqlite3_file] can safely store a pointer to the
+** filename if it needs to remember the filename for some reason.
+** If the zFilename parameter to xOpen is a NULL pointer then xOpen
+** must invent its own temporary name for the file.  ^Whenever the 
+** xFilename parameter is NULL it will also be the case that the
+** flags parameter will include [SQLITE_OPEN_DELETEONCLOSE].
+**
+** The flags argument to xOpen() includes all bits set in
+** the flags argument to [sqlite3_open_v2()].  Or if [sqlite3_open()]
+** or [sqlite3_open16()] is used, then flags includes at least
+** [SQLITE_OPEN_READWRITE] | [SQLITE_OPEN_CREATE]. 
+** If xOpen() opens a file read-only then it sets *pOutFlags to
+** include [SQLITE_OPEN_READONLY].  Other bits in *pOutFlags may be set.
+**
+** ^(SQLite will also add one of the following flags to the xOpen()
+** call, depending on the object being opened:
+**
+** <ul>
+** <li>  [SQLITE_OPEN_MAIN_DB]
+** <li>  [SQLITE_OPEN_MAIN_JOURNAL]
+** <li>  [SQLITE_OPEN_TEMP_DB]
+** <li>  [SQLITE_OPEN_TEMP_JOURNAL]
+** <li>  [SQLITE_OPEN_TRANSIENT_DB]
+** <li>  [SQLITE_OPEN_SUBJOURNAL]
+** <li>  [SQLITE_OPEN_MASTER_JOURNAL]
+** <li>  [SQLITE_OPEN_WAL]
+** </ul>)^
+**
+** The file I/O implementation can use the object type flags to
+** change the way it deals with files.  For example, an application
+** that does not care about crash recovery or rollback might make
+** the open of a journal file a no-op.  Writes to this journal would
+** also be no-ops, and any attempt to read the journal would return
+** SQLITE_IOERR.  Or the implementation might recognize that a database
+** file will be doing page-aligned sector reads and writes in a random
+** order and set up its I/O subsystem accordingly.
+**
+** SQLite might also add one of the following flags to the xOpen method:
+**
+** <ul>
+** <li> [SQLITE_OPEN_DELETEONCLOSE]
+** <li> [SQLITE_OPEN_EXCLUSIVE]
+** </ul>
+**
+** The [SQLITE_OPEN_DELETEONCLOSE] flag means the file should be
+** deleted when it is closed.  ^The [SQLITE_OPEN_DELETEONCLOSE]
+** will be set for TEMP databases and their journals, transient
+** databases, and subjournals.
+**
+** ^The [SQLITE_OPEN_EXCLUSIVE] flag is always used in conjunction
+** with the [SQLITE_OPEN_CREATE] flag, which are both directly
+** analogous to the O_EXCL and O_CREAT flags of the POSIX open()
+** API.  The SQLITE_OPEN_EXCLUSIVE flag, when paired with the 
+** SQLITE_OPEN_CREATE, is used to indicate that file should always
+** be created, and that it is an error if it already exists.
+** It is <i>not</i> used to indicate the file should be opened 
+** for exclusive access.
+**
+** ^At least szOsFile bytes of memory are allocated by SQLite
+** to hold the  [sqlite3_file] structure passed as the third
+** argument to xOpen.  The xOpen method does not have to
+** allocate the structure; it should just fill it in.  Note that
+** the xOpen method must set the sqlite3_file.pMethods to either
+** a valid [sqlite3_io_methods] object or to NULL.  xOpen must do
+** this even if the open fails.  SQLite expects that the sqlite3_file.pMethods
+** element will be valid after xOpen returns regardless of the success
+** or failure of the xOpen call.
+**
+** [[sqlite3_vfs.xAccess]]
+** ^The flags argument to xAccess() may be [SQLITE_ACCESS_EXISTS]
+** to test for the existence of a file, or [SQLITE_ACCESS_READWRITE] to
+** test whether a file is readable and writable, or [SQLITE_ACCESS_READ]
+** to test whether a file is at least readable.   The file can be a
+** directory.
+**
+** ^SQLite will always allocate at least mxPathname+1 bytes for the
+** output buffer xFullPathname.  The exact size of the output buffer
+** is also passed as a parameter to both  methods. If the output buffer
+** is not large enough, [SQLITE_CANTOPEN] should be returned. Since this is
+** handled as a fatal error by SQLite, vfs implementations should endeavor
+** to prevent this by setting mxPathname to a sufficiently large value.
+**
+** The xRandomness(), xSleep(), xCurrentTime(), and xCurrentTimeInt64()
+** interfaces are not strictly a part of the filesystem, but they are
+** included in the VFS structure for completeness.
+** The xRandomness() function attempts to return nBytes bytes
+** of good-quality randomness into zOut.  The return value is
+** the actual number of bytes of randomness obtained.
+** The xSleep() method causes the calling thread to sleep for at
+** least the number of microseconds given.  ^The xCurrentTime()
+** method returns a Julian Day Number for the current date and time as
+** a floating point value.
+** ^The xCurrentTimeInt64() method returns, as an integer, the Julian
+** Day Number multiplied by 86400000 (the number of milliseconds in 
+** a 24-hour day).  
+** ^SQLite will use the xCurrentTimeInt64() method to get the current
+** date and time if that method is available (if iVersion is 2 or 
+** greater and the function pointer is not NULL) and will fall back
+** to xCurrentTime() if xCurrentTimeInt64() is unavailable.
+**
+** ^The xSetSystemCall(), xGetSystemCall(), and xNestSystemCall() interfaces
+** are not used by the SQLite core.  These optional interfaces are provided
+** by some VFSes to facilitate testing of the VFS code. By overriding 
+** system calls with functions under its control, a test program can
+** simulate faults and error conditions that would otherwise be difficult
+** or impossible to induce.  The set of system calls that can be overridden
+** varies from one VFS to another, and from one version of the same VFS to the
+** next.  Applications that use these interfaces must be prepared for any
+** or all of these interfaces to be NULL or for their behavior to change
+** from one release to the next.  Applications must not attempt to access
+** any of these methods if the iVersion of the VFS is less than 3.
+*/
+typedef struct sqlite3_vfs sqlite3_vfs;
+typedef void (*sqlite3_syscall_ptr)(void);
+struct sqlite3_vfs {
+  int iVersion;            /* Structure version number (currently 3) */
+  int szOsFile;            /* Size of subclassed sqlite3_file */
+  int mxPathname;          /* Maximum file pathname length */
+  sqlite3_vfs *pNext;      /* Next registered VFS */
+  const char *zName;       /* Name of this virtual file system */
+  void *pAppData;          /* Pointer to application-specific data */
+  int (*xOpen)(sqlite3_vfs*, const char *zName, sqlite3_file*,
+               int flags, int *pOutFlags);
+  int (*xDelete)(sqlite3_vfs*, const char *zName, int syncDir);
+  int (*xAccess)(sqlite3_vfs*, const char *zName, int flags, int *pResOut);
+  int (*xFullPathname)(sqlite3_vfs*, const char *zName, int nOut, char *zOut);
+  void *(*xDlOpen)(sqlite3_vfs*, const char *zFilename);
+  void (*xDlError)(sqlite3_vfs*, int nByte, char *zErrMsg);
+  void (*(*xDlSym)(sqlite3_vfs*,void*, const char *zSymbol))(void);
+  void (*xDlClose)(sqlite3_vfs*, void*);
+  int (*xRandomness)(sqlite3_vfs*, int nByte, char *zOut);
+  int (*xSleep)(sqlite3_vfs*, int microseconds);
+  int (*xCurrentTime)(sqlite3_vfs*, double*);
+  int (*xGetLastError)(sqlite3_vfs*, int, char *);
+  /*
+  ** The methods above are in version 1 of the sqlite_vfs object
+  ** definition.  Those that follow are added in version 2 or later
+  */
+  int (*xCurrentTimeInt64)(sqlite3_vfs*, sqlite3_int64*);
+  /*
+  ** The methods above are in versions 1 and 2 of the sqlite_vfs object.
+  ** Those below are for version 3 and greater.
+  */
+  int (*xSetSystemCall)(sqlite3_vfs*, const char *zName, sqlite3_syscall_ptr);
+  sqlite3_syscall_ptr (*xGetSystemCall)(sqlite3_vfs*, const char *zName);
+  const char *(*xNextSystemCall)(sqlite3_vfs*, const char *zName);
+  /*
+  ** The methods above are in versions 1 through 3 of the sqlite_vfs object.
+  ** New fields may be appended in figure versions.  The iVersion
+  ** value will increment whenever this happens. 
+  */
+};
+
+/*
+** CAPI3REF: Flags for the xAccess VFS method
+**
+** These integer constants can be used as the third parameter to
+** the xAccess method of an [sqlite3_vfs] object.  They determine
+** what kind of permissions the xAccess method is looking for.
+** With SQLITE_ACCESS_EXISTS, the xAccess method
+** simply checks whether the file exists.
+** With SQLITE_ACCESS_READWRITE, the xAccess method
+** checks whether the named directory is both readable and writable
+** (in other words, if files can be added, removed, and renamed within
+** the directory).
+** The SQLITE_ACCESS_READWRITE constant is currently used only by the
+** [temp_store_directory pragma], though this could change in a future
+** release of SQLite.
+** With SQLITE_ACCESS_READ, the xAccess method
+** checks whether the file is readable.  The SQLITE_ACCESS_READ constant is
+** currently unused, though it might be used in a future release of
+** SQLite.
+*/
+#define SQLITE_ACCESS_EXISTS    0
+#define SQLITE_ACCESS_READWRITE 1   /* Used by PRAGMA temp_store_directory */
+#define SQLITE_ACCESS_READ      2   /* Unused */
+
+/*
+** CAPI3REF: Flags for the xShmLock VFS method
+**
+** These integer constants define the various locking operations
+** allowed by the xShmLock method of [sqlite3_io_methods].  The
+** following are the only legal combinations of flags to the
+** xShmLock method:
+**
+** <ul>
+** <li>  SQLITE_SHM_LOCK | SQLITE_SHM_SHARED
+** <li>  SQLITE_SHM_LOCK | SQLITE_SHM_EXCLUSIVE
+** <li>  SQLITE_SHM_UNLOCK | SQLITE_SHM_SHARED
+** <li>  SQLITE_SHM_UNLOCK | SQLITE_SHM_EXCLUSIVE
+** </ul>
+**
+** When unlocking, the same SHARED or EXCLUSIVE flag must be supplied as
+** was given no the corresponding lock.  
+**
+** The xShmLock method can transition between unlocked and SHARED or
+** between unlocked and EXCLUSIVE.  It cannot transition between SHARED
+** and EXCLUSIVE.
+*/
+#define SQLITE_SHM_UNLOCK       1
+#define SQLITE_SHM_LOCK         2
+#define SQLITE_SHM_SHARED       4
+#define SQLITE_SHM_EXCLUSIVE    8
+
+/*
+** CAPI3REF: Maximum xShmLock index
+**
+** The xShmLock method on [sqlite3_io_methods] may use values
+** between 0 and this upper bound as its "offset" argument.
+** The SQLite core will never attempt to acquire or release a
+** lock outside of this range
+*/
+#define SQLITE_SHM_NLOCK        8
+
+
+/*
+** CAPI3REF: Initialize The SQLite Library
+**
+** ^The sqlite3_initialize() routine initializes the
+** SQLite library.  ^The sqlite3_shutdown() routine
+** deallocates any resources that were allocated by sqlite3_initialize().
+** These routines are designed to aid in process initialization and
+** shutdown on embedded systems.  Workstation applications using
+** SQLite normally do not need to invoke either of these routines.
+**
+** A call to sqlite3_initialize() is an "effective" call if it is
+** the first time sqlite3_initialize() is invoked during the lifetime of
+** the process, or if it is the first time sqlite3_initialize() is invoked
+** following a call to sqlite3_shutdown().  ^(Only an effective call
+** of sqlite3_initialize() does any initialization.  All other calls
+** are harmless no-ops.)^
+**
+** A call to sqlite3_shutdown() is an "effective" call if it is the first
+** call to sqlite3_shutdown() since the last sqlite3_initialize().  ^(Only
+** an effective call to sqlite3_shutdown() does any deinitialization.
+** All other valid calls to sqlite3_shutdown() are harmless no-ops.)^
+**
+** The sqlite3_initialize() interface is threadsafe, but sqlite3_shutdown()
+** is not.  The sqlite3_shutdown() interface must only be called from a
+** single thread.  All open [database connections] must be closed and all
+** other SQLite resources must be deallocated prior to invoking
+** sqlite3_shutdown().
+**
+** Among other things, ^sqlite3_initialize() will invoke
+** sqlite3_os_init().  Similarly, ^sqlite3_shutdown()
+** will invoke sqlite3_os_end().
+**
+** ^The sqlite3_initialize() routine returns [SQLITE_OK] on success.
+** ^If for some reason, sqlite3_initialize() is unable to initialize
+** the library (perhaps it is unable to allocate a needed resource such
+** as a mutex) it returns an [error code] other than [SQLITE_OK].
+**
+** ^The sqlite3_initialize() routine is called internally by many other
+** SQLite interfaces so that an application usually does not need to
+** invoke sqlite3_initialize() directly.  For example, [sqlite3_open()]
+** calls sqlite3_initialize() so the SQLite library will be automatically
+** initialized when [sqlite3_open()] is called if it has not be initialized
+** already.  ^However, if SQLite is compiled with the [SQLITE_OMIT_AUTOINIT]
+** compile-time option, then the automatic calls to sqlite3_initialize()
+** are omitted and the application must call sqlite3_initialize() directly
+** prior to using any other SQLite interface.  For maximum portability,
+** it is recommended that applications always invoke sqlite3_initialize()
+** directly prior to using any other SQLite interface.  Future releases
+** of SQLite may require this.  In other words, the behavior exhibited
+** when SQLite is compiled with [SQLITE_OMIT_AUTOINIT] might become the
+** default behavior in some future release of SQLite.
+**
+** The sqlite3_os_init() routine does operating-system specific
+** initialization of the SQLite library.  The sqlite3_os_end()
+** routine undoes the effect of sqlite3_os_init().  Typical tasks
+** performed by these routines include allocation or deallocation
+** of static resources, initialization of global variables,
+** setting up a default [sqlite3_vfs] module, or setting up
+** a default configuration using [sqlite3_config()].
+**
+** The application should never invoke either sqlite3_os_init()
+** or sqlite3_os_end() directly.  The application should only invoke
+** sqlite3_initialize() and sqlite3_shutdown().  The sqlite3_os_init()
+** interface is called automatically by sqlite3_initialize() and
+** sqlite3_os_end() is called by sqlite3_shutdown().  Appropriate
+** implementations for sqlite3_os_init() and sqlite3_os_end()
+** are built into SQLite when it is compiled for Unix, Windows, or OS/2.
+** When [custom builds | built for other platforms]
+** (using the [SQLITE_OS_OTHER=1] compile-time
+** option) the application must supply a suitable implementation for
+** sqlite3_os_init() and sqlite3_os_end().  An application-supplied
+** implementation of sqlite3_os_init() or sqlite3_os_end()
+** must return [SQLITE_OK] on success and some other [error code] upon
+** failure.
+*/
+int sqlite3_initialize(void);
+int sqlite3_shutdown(void);
+int sqlite3_os_init(void);
+int sqlite3_os_end(void);
+
+/*
+** CAPI3REF: Configuring The SQLite Library
+**
+** The sqlite3_config() interface is used to make global configuration
+** changes to SQLite in order to tune SQLite to the specific needs of
+** the application.  The default configuration is recommended for most
+** applications and so this routine is usually not necessary.  It is
+** provided to support rare applications with unusual needs.
+**
+** The sqlite3_config() interface is not threadsafe.  The application
+** must insure that no other SQLite interfaces are invoked by other
+** threads while sqlite3_config() is running.  Furthermore, sqlite3_config()
+** may only be invoked prior to library initialization using
+** [sqlite3_initialize()] or after shutdown by [sqlite3_shutdown()].
+** ^If sqlite3_config() is called after [sqlite3_initialize()] and before
+** [sqlite3_shutdown()] then it will return SQLITE_MISUSE.
+** Note, however, that ^sqlite3_config() can be called as part of the
+** implementation of an application-defined [sqlite3_os_init()].
+**
+** The first argument to sqlite3_config() is an integer
+** [configuration option] that determines
+** what property of SQLite is to be configured.  Subsequent arguments
+** vary depending on the [configuration option]
+** in the first argument.
+**
+** ^When a configuration option is set, sqlite3_config() returns [SQLITE_OK].
+** ^If the option is unknown or SQLite is unable to set the option
+** then this routine returns a non-zero [error code].
+*/
+int sqlite3_config(int, ...);
+
+/*
+** CAPI3REF: Configure database connections
+**
+** The sqlite3_db_config() interface is used to make configuration
+** changes to a [database connection].  The interface is similar to
+** [sqlite3_config()] except that the changes apply to a single
+** [database connection] (specified in the first argument).
+**
+** The second argument to sqlite3_db_config(D,V,...)  is the
+** [SQLITE_DBCONFIG_LOOKASIDE | configuration verb] - an integer code 
+** that indicates what aspect of the [database connection] is being configured.
+** Subsequent arguments vary depending on the configuration verb.
+**
+** ^Calls to sqlite3_db_config() return SQLITE_OK if and only if
+** the call is considered successful.
+*/
+int sqlite3_db_config(sqlite3*, int op, ...);
+
+/*
+** CAPI3REF: Memory Allocation Routines
+**
+** An instance of this object defines the interface between SQLite
+** and low-level memory allocation routines.
+**
+** This object is used in only one place in the SQLite interface.
+** A pointer to an instance of this object is the argument to
+** [sqlite3_config()] when the configuration option is
+** [SQLITE_CONFIG_MALLOC] or [SQLITE_CONFIG_GETMALLOC].  
+** By creating an instance of this object
+** and passing it to [sqlite3_config]([SQLITE_CONFIG_MALLOC])
+** during configuration, an application can specify an alternative
+** memory allocation subsystem for SQLite to use for all of its
+** dynamic memory needs.
+**
+** Note that SQLite comes with several [built-in memory allocators]
+** that are perfectly adequate for the overwhelming majority of applications
+** and that this object is only useful to a tiny minority of applications
+** with specialized memory allocation requirements.  This object is
+** also used during testing of SQLite in order to specify an alternative
+** memory allocator that simulates memory out-of-memory conditions in
+** order to verify that SQLite recovers gracefully from such
+** conditions.
+**
+** The xMalloc, xRealloc, and xFree methods must work like the
+** malloc(), realloc() and free() functions from the standard C library.
+** ^SQLite guarantees that the second argument to
+** xRealloc is always a value returned by a prior call to xRoundup.
+**
+** xSize should return the allocated size of a memory allocation
+** previously obtained from xMalloc or xRealloc.  The allocated size
+** is always at least as big as the requested size but may be larger.
+**
+** The xRoundup method returns what would be the allocated size of
+** a memory allocation given a particular requested size.  Most memory
+** allocators round up memory allocations at least to the next multiple
+** of 8.  Some allocators round up to a larger multiple or to a power of 2.
+** Every memory allocation request coming in through [sqlite3_malloc()]
+** or [sqlite3_realloc()] first calls xRoundup.  If xRoundup returns 0, 
+** that causes the corresponding memory allocation to fail.
+**
+** The xInit method initializes the memory allocator.  (For example,
+** it might allocate any require mutexes or initialize internal data
+** structures.  The xShutdown method is invoked (indirectly) by
+** [sqlite3_shutdown()] and should deallocate any resources acquired
+** by xInit.  The pAppData pointer is used as the only parameter to
+** xInit and xShutdown.
+**
+** SQLite holds the [SQLITE_MUTEX_STATIC_MASTER] mutex when it invokes
+** the xInit method, so the xInit method need not be threadsafe.  The
+** xShutdown method is only called from [sqlite3_shutdown()] so it does
+** not need to be threadsafe either.  For all other methods, SQLite
+** holds the [SQLITE_MUTEX_STATIC_MEM] mutex as long as the
+** [SQLITE_CONFIG_MEMSTATUS] configuration option is turned on (which
+** it is by default) and so the methods are automatically serialized.
+** However, if [SQLITE_CONFIG_MEMSTATUS] is disabled, then the other
+** methods must be threadsafe or else make their own arrangements for
+** serialization.
+**
+** SQLite will never invoke xInit() more than once without an intervening
+** call to xShutdown().
+*/
+typedef struct sqlite3_mem_methods sqlite3_mem_methods;
+struct sqlite3_mem_methods {
+  void *(*xMalloc)(int);         /* Memory allocation function */
+  void (*xFree)(void*);          /* Free a prior allocation */
+  void *(*xRealloc)(void*,int);  /* Resize an allocation */
+  int (*xSize)(void*);           /* Return the size of an allocation */
+  int (*xRoundup)(int);          /* Round up request size to allocation size */
+  int (*xInit)(void*);           /* Initialize the memory allocator */
+  void (*xShutdown)(void*);      /* Deinitialize the memory allocator */
+  void *pAppData;                /* Argument to xInit() and xShutdown() */
+};
+
+/*
+** CAPI3REF: Configuration Options
+** KEYWORDS: {configuration option}
+**
+** These constants are the available integer configuration options that
+** can be passed as the first argument to the [sqlite3_config()] interface.
+**
+** New configuration options may be added in future releases of SQLite.
+** Existing configuration options might be discontinued.  Applications
+** should check the return code from [sqlite3_config()] to make sure that
+** the call worked.  The [sqlite3_config()] interface will return a
+** non-zero [error code] if a discontinued or unsupported configuration option
+** is invoked.
+**
+** <dl>
+** [[SQLITE_CONFIG_SINGLETHREAD]] <dt>SQLITE_CONFIG_SINGLETHREAD</dt>
+** <dd>There are no arguments to this option.  ^This option sets the
+** [threading mode] to Single-thread.  In other words, it disables
+** all mutexing and puts SQLite into a mode where it can only be used
+** by a single thread.   ^If SQLite is compiled with
+** the [SQLITE_THREADSAFE | SQLITE_THREADSAFE=0] compile-time option then
+** it is not possible to change the [threading mode] from its default
+** value of Single-thread and so [sqlite3_config()] will return 
+** [SQLITE_ERROR] if called with the SQLITE_CONFIG_SINGLETHREAD
+** configuration option.</dd>
+**
+** [[SQLITE_CONFIG_MULTITHREAD]] <dt>SQLITE_CONFIG_MULTITHREAD</dt>
+** <dd>There are no arguments to this option.  ^This option sets the
+** [threading mode] to Multi-thread.  In other words, it disables
+** mutexing on [database connection] and [prepared statement] objects.
+** The application is responsible for serializing access to
+** [database connections] and [prepared statements].  But other mutexes
+** are enabled so that SQLite will be safe to use in a multi-threaded
+** environment as long as no two threads attempt to use the same
+** [database connection] at the same time.  ^If SQLite is compiled with
+** the [SQLITE_THREADSAFE | SQLITE_THREADSAFE=0] compile-time option then
+** it is not possible to set the Multi-thread [threading mode] and
+** [sqlite3_config()] will return [SQLITE_ERROR] if called with the
+** SQLITE_CONFIG_MULTITHREAD configuration option.</dd>
+**
+** [[SQLITE_CONFIG_SERIALIZED]] <dt>SQLITE_CONFIG_SERIALIZED</dt>
+** <dd>There are no arguments to this option.  ^This option sets the
+** [threading mode] to Serialized. In other words, this option enables
+** all mutexes including the recursive
+** mutexes on [database connection] and [prepared statement] objects.
+** In this mode (which is the default when SQLite is compiled with
+** [SQLITE_THREADSAFE=1]) the SQLite library will itself serialize access
+** to [database connections] and [prepared statements] so that the
+** application is free to use the same [database connection] or the
+** same [prepared statement] in different threads at the same time.
+** ^If SQLite is compiled with
+** the [SQLITE_THREADSAFE | SQLITE_THREADSAFE=0] compile-time option then
+** it is not possible to set the Serialized [threading mode] and
+** [sqlite3_config()] will return [SQLITE_ERROR] if called with the
+** SQLITE_CONFIG_SERIALIZED configuration option.</dd>
+**
+** [[SQLITE_CONFIG_MALLOC]] <dt>SQLITE_CONFIG_MALLOC</dt>
+** <dd> ^(This option takes a single argument which is a pointer to an
+** instance of the [sqlite3_mem_methods] structure.  The argument specifies
+** alternative low-level memory allocation routines to be used in place of
+** the memory allocation routines built into SQLite.)^ ^SQLite makes
+** its own private copy of the content of the [sqlite3_mem_methods] structure
+** before the [sqlite3_config()] call returns.</dd>
+**
+** [[SQLITE_CONFIG_GETMALLOC]] <dt>SQLITE_CONFIG_GETMALLOC</dt>
+** <dd> ^(This option takes a single argument which is a pointer to an
+** instance of the [sqlite3_mem_methods] structure.  The [sqlite3_mem_methods]
+** structure is filled with the currently defined memory allocation routines.)^
+** This option can be used to overload the default memory allocation
+** routines with a wrapper that simulations memory allocation failure or
+** tracks memory usage, for example. </dd>
+**
+** [[SQLITE_CONFIG_MEMSTATUS]] <dt>SQLITE_CONFIG_MEMSTATUS</dt>
+** <dd> ^This option takes single argument of type int, interpreted as a 
+** boolean, which enables or disables the collection of memory allocation 
+** statistics. ^(When memory allocation statistics are disabled, the 
+** following SQLite interfaces become non-operational:
+**   <ul>
+**   <li> [sqlite3_memory_used()]
+**   <li> [sqlite3_memory_highwater()]
+**   <li> [sqlite3_soft_heap_limit64()]
+**   <li> [sqlite3_status()]
+**   </ul>)^
+** ^Memory allocation statistics are enabled by default unless SQLite is
+** compiled with [SQLITE_DEFAULT_MEMSTATUS]=0 in which case memory
+** allocation statistics are disabled by default.
+** </dd>
+**
+** [[SQLITE_CONFIG_SCRATCH]] <dt>SQLITE_CONFIG_SCRATCH</dt>
+** <dd> ^This option specifies a static memory buffer that SQLite can use for
+** scratch memory.  There are three arguments:  A pointer an 8-byte
+** aligned memory buffer from which the scratch allocations will be
+** drawn, the size of each scratch allocation (sz),
+** and the maximum number of scratch allocations (N).  The sz
+** argument must be a multiple of 16.
+** The first argument must be a pointer to an 8-byte aligned buffer
+** of at least sz*N bytes of memory.
+** ^SQLite will use no more than two scratch buffers per thread.  So
+** N should be set to twice the expected maximum number of threads.
+** ^SQLite will never require a scratch buffer that is more than 6
+** times the database page size. ^If SQLite needs needs additional
+** scratch memory beyond what is provided by this configuration option, then 
+** [sqlite3_malloc()] will be used to obtain the memory needed.</dd>
+**
+** [[SQLITE_CONFIG_PAGECACHE]] <dt>SQLITE_CONFIG_PAGECACHE</dt>
+** <dd> ^This option specifies a static memory buffer that SQLite can use for
+** the database page cache with the default page cache implementation.  
+** This configuration should not be used if an application-define page
+** cache implementation is loaded using the SQLITE_CONFIG_PCACHE option.
+** There are three arguments to this option: A pointer to 8-byte aligned
+** memory, the size of each page buffer (sz), and the number of pages (N).
+** The sz argument should be the size of the largest database page
+** (a power of two between 512 and 32768) plus a little extra for each
+** page header.  ^The page header size is 20 to 40 bytes depending on
+** the host architecture.  ^It is harmless, apart from the wasted memory,
+** to make sz a little too large.  The first
+** argument should point to an allocation of at least sz*N bytes of memory.
+** ^SQLite will use the memory provided by the first argument to satisfy its
+** memory needs for the first N pages that it adds to cache.  ^If additional
+** page cache memory is needed beyond what is provided by this option, then
+** SQLite goes to [sqlite3_malloc()] for the additional storage space.
+** The pointer in the first argument must
+** be aligned to an 8-byte boundary or subsequent behavior of SQLite
+** will be undefined.</dd>
+**
+** [[SQLITE_CONFIG_HEAP]] <dt>SQLITE_CONFIG_HEAP</dt>
+** <dd> ^This option specifies a static memory buffer that SQLite will use
+** for all of its dynamic memory allocation needs beyond those provided
+** for by [SQLITE_CONFIG_SCRATCH] and [SQLITE_CONFIG_PAGECACHE].
+** There are three arguments: An 8-byte aligned pointer to the memory,
+** the number of bytes in the memory buffer, and the minimum allocation size.
+** ^If the first pointer (the memory pointer) is NULL, then SQLite reverts
+** to using its default memory allocator (the system malloc() implementation),
+** undoing any prior invocation of [SQLITE_CONFIG_MALLOC].  ^If the
+** memory pointer is not NULL and either [SQLITE_ENABLE_MEMSYS3] or
+** [SQLITE_ENABLE_MEMSYS5] are defined, then the alternative memory
+** allocator is engaged to handle all of SQLites memory allocation needs.
+** The first pointer (the memory pointer) must be aligned to an 8-byte
+** boundary or subsequent behavior of SQLite will be undefined.
+** The minimum allocation size is capped at 2**12. Reasonable values
+** for the minimum allocation size are 2**5 through 2**8.</dd>
+**
+** [[SQLITE_CONFIG_MUTEX]] <dt>SQLITE_CONFIG_MUTEX</dt>
+** <dd> ^(This option takes a single argument which is a pointer to an
+** instance of the [sqlite3_mutex_methods] structure.  The argument specifies
+** alternative low-level mutex routines to be used in place
+** the mutex routines built into SQLite.)^  ^SQLite makes a copy of the
+** content of the [sqlite3_mutex_methods] structure before the call to
+** [sqlite3_config()] returns. ^If SQLite is compiled with
+** the [SQLITE_THREADSAFE | SQLITE_THREADSAFE=0] compile-time option then
+** the entire mutexing subsystem is omitted from the build and hence calls to
+** [sqlite3_config()] with the SQLITE_CONFIG_MUTEX configuration option will
+** return [SQLITE_ERROR].</dd>
+**
+** [[SQLITE_CONFIG_GETMUTEX]] <dt>SQLITE_CONFIG_GETMUTEX</dt>
+** <dd> ^(This option takes a single argument which is a pointer to an
+** instance of the [sqlite3_mutex_methods] structure.  The
+** [sqlite3_mutex_methods]
+** structure is filled with the currently defined mutex routines.)^
+** This option can be used to overload the default mutex allocation
+** routines with a wrapper used to track mutex usage for performance
+** profiling or testing, for example.   ^If SQLite is compiled with
+** the [SQLITE_THREADSAFE | SQLITE_THREADSAFE=0] compile-time option then
+** the entire mutexing subsystem is omitted from the build and hence calls to
+** [sqlite3_config()] with the SQLITE_CONFIG_GETMUTEX configuration option will
+** return [SQLITE_ERROR].</dd>
+**
+** [[SQLITE_CONFIG_LOOKASIDE]] <dt>SQLITE_CONFIG_LOOKASIDE</dt>
+** <dd> ^(This option takes two arguments that determine the default
+** memory allocation for the lookaside memory allocator on each
+** [database connection].  The first argument is the
+** size of each lookaside buffer slot and the second is the number of
+** slots allocated to each database connection.)^  ^(This option sets the
+** <i>default</i> lookaside size. The [SQLITE_DBCONFIG_LOOKASIDE]
+** verb to [sqlite3_db_config()] can be used to change the lookaside
+** configuration on individual connections.)^ </dd>
+**
+** [[SQLITE_CONFIG_PCACHE]] <dt>SQLITE_CONFIG_PCACHE</dt>
+** <dd> ^(This option takes a single argument which is a pointer to
+** an [sqlite3_pcache_methods] object.  This object specifies the interface
+** to a custom page cache implementation.)^  ^SQLite makes a copy of the
+** object and uses it for page cache memory allocations.</dd>
+**
+** [[SQLITE_CONFIG_GETPCACHE]] <dt>SQLITE_CONFIG_GETPCACHE</dt>
+** <dd> ^(This option takes a single argument which is a pointer to an
+** [sqlite3_pcache_methods] object.  SQLite copies of the current
+** page cache implementation into that object.)^ </dd>
+**
+** [[SQLITE_CONFIG_LOG]] <dt>SQLITE_CONFIG_LOG</dt>
+** <dd> ^The SQLITE_CONFIG_LOG option takes two arguments: a pointer to a
+** function with a call signature of void(*)(void*,int,const char*), 
+** and a pointer to void. ^If the function pointer is not NULL, it is
+** invoked by [sqlite3_log()] to process each logging event.  ^If the
+** function pointer is NULL, the [sqlite3_log()] interface becomes a no-op.
+** ^The void pointer that is the second argument to SQLITE_CONFIG_LOG is
+** passed through as the first parameter to the application-defined logger
+** function whenever that function is invoked.  ^The second parameter to
+** the logger function is a copy of the first parameter to the corresponding
+** [sqlite3_log()] call and is intended to be a [result code] or an
+** [extended result code].  ^The third parameter passed to the logger is
+** log message after formatting via [sqlite3_snprintf()].
+** The SQLite logging interface is not reentrant; the logger function
+** supplied by the application must not invoke any SQLite interface.
+** In a multi-threaded application, the application-defined logger
+** function must be threadsafe. </dd>
+**
+** [[SQLITE_CONFIG_URI]] <dt>SQLITE_CONFIG_URI
+** <dd> This option takes a single argument of type int. If non-zero, then
+** URI handling is globally enabled. If the parameter is zero, then URI handling
+** is globally disabled. If URI handling is globally enabled, all filenames
+** passed to [sqlite3_open()], [sqlite3_open_v2()], [sqlite3_open16()] or
+** specified as part of [ATTACH] commands are interpreted as URIs, regardless
+** of whether or not the [SQLITE_OPEN_URI] flag is set when the database
+** connection is opened. If it is globally disabled, filenames are
+** only interpreted as URIs if the SQLITE_OPEN_URI flag is set when the
+** database connection is opened. By default, URI handling is globally
+** disabled. The default value may be changed by compiling with the
+** [SQLITE_USE_URI] symbol defined.
+** </dl>
+*/
+#define SQLITE_CONFIG_SINGLETHREAD  1  /* nil */
+#define SQLITE_CONFIG_MULTITHREAD   2  /* nil */
+#define SQLITE_CONFIG_SERIALIZED    3  /* nil */
+#define SQLITE_CONFIG_MALLOC        4  /* sqlite3_mem_methods* */
+#define SQLITE_CONFIG_GETMALLOC     5  /* sqlite3_mem_methods* */
+#define SQLITE_CONFIG_SCRATCH       6  /* void*, int sz, int N */
+#define SQLITE_CONFIG_PAGECACHE     7  /* void*, int sz, int N */
+#define SQLITE_CONFIG_HEAP          8  /* void*, int nByte, int min */
+#define SQLITE_CONFIG_MEMSTATUS     9  /* boolean */
+#define SQLITE_CONFIG_MUTEX        10  /* sqlite3_mutex_methods* */
+#define SQLITE_CONFIG_GETMUTEX     11  /* sqlite3_mutex_methods* */
+/* previously SQLITE_CONFIG_CHUNKALLOC 12 which is now unused. */ 
+#define SQLITE_CONFIG_LOOKASIDE    13  /* int int */
+#define SQLITE_CONFIG_PCACHE       14  /* sqlite3_pcache_methods* */
+#define SQLITE_CONFIG_GETPCACHE    15  /* sqlite3_pcache_methods* */
+#define SQLITE_CONFIG_LOG          16  /* xFunc, void* */
+#define SQLITE_CONFIG_URI          17  /* int */
+
+/*
+** CAPI3REF: Database Connection Configuration Options
+**
+** These constants are the available integer configuration options that
+** can be passed as the second argument to the [sqlite3_db_config()] interface.
+**
+** New configuration options may be added in future releases of SQLite.
+** Existing configuration options might be discontinued.  Applications
+** should check the return code from [sqlite3_db_config()] to make sure that
+** the call worked.  ^The [sqlite3_db_config()] interface will return a
+** non-zero [error code] if a discontinued or unsupported configuration option
+** is invoked.
+**
+** <dl>
+** <dt>SQLITE_DBCONFIG_LOOKASIDE</dt>
+** <dd> ^This option takes three additional arguments that determine the 
+** [lookaside memory allocator] configuration for the [database connection].
+** ^The first argument (the third parameter to [sqlite3_db_config()] is a
+** pointer to a memory buffer to use for lookaside memory.
+** ^The first argument after the SQLITE_DBCONFIG_LOOKASIDE verb
+** may be NULL in which case SQLite will allocate the
+** lookaside buffer itself using [sqlite3_malloc()]. ^The second argument is the
+** size of each lookaside buffer slot.  ^The third argument is the number of
+** slots.  The size of the buffer in the first argument must be greater than
+** or equal to the product of the second and third arguments.  The buffer
+** must be aligned to an 8-byte boundary.  ^If the second argument to
+** SQLITE_DBCONFIG_LOOKASIDE is not a multiple of 8, it is internally
+** rounded down to the next smaller multiple of 8.  ^(The lookaside memory
+** configuration for a database connection can only be changed when that
+** connection is not currently using lookaside memory, or in other words
+** when the "current value" returned by
+** [sqlite3_db_status](D,[SQLITE_CONFIG_LOOKASIDE],...) is zero.
+** Any attempt to change the lookaside memory configuration when lookaside
+** memory is in use leaves the configuration unchanged and returns 
+** [SQLITE_BUSY].)^</dd>
+**
+** <dt>SQLITE_DBCONFIG_ENABLE_FKEY</dt>
+** <dd> ^This option is used to enable or disable the enforcement of
+** [foreign key constraints].  There should be two additional arguments.
+** The first argument is an integer which is 0 to disable FK enforcement,
+** positive to enable FK enforcement or negative to leave FK enforcement
+** unchanged.  The second parameter is a pointer to an integer into which
+** is written 0 or 1 to indicate whether FK enforcement is off or on
+** following this call.  The second parameter may be a NULL pointer, in
+** which case the FK enforcement setting is not reported back. </dd>
+**
+** <dt>SQLITE_DBCONFIG_ENABLE_TRIGGER</dt>
+** <dd> ^This option is used to enable or disable [CREATE TRIGGER | triggers].
+** There should be two additional arguments.
+** The first argument is an integer which is 0 to disable triggers,
+** positive to enable triggers or negative to leave the setting unchanged.
+** The second parameter is a pointer to an integer into which
+** is written 0 or 1 to indicate whether triggers are disabled or enabled
+** following this call.  The second parameter may be a NULL pointer, in
+** which case the trigger setting is not reported back. </dd>
+**
+** </dl>
+*/
+#define SQLITE_DBCONFIG_LOOKASIDE       1001  /* void* int int */
+#define SQLITE_DBCONFIG_ENABLE_FKEY     1002  /* int int* */
+#define SQLITE_DBCONFIG_ENABLE_TRIGGER  1003  /* int int* */
+
+
+/*
+** CAPI3REF: Enable Or Disable Extended Result Codes
+**
+** ^The sqlite3_extended_result_codes() routine enables or disables the
+** [extended result codes] feature of SQLite. ^The extended result
+** codes are disabled by default for historical compatibility.
+*/
+int sqlite3_extended_result_codes(sqlite3*, int onoff);
+
+/*
+** CAPI3REF: Last Insert Rowid
+**
+** ^Each entry in an SQLite table has a unique 64-bit signed
+** integer key called the [ROWID | "rowid"]. ^The rowid is always available
+** as an undeclared column named ROWID, OID, or _ROWID_ as long as those
+** names are not also used by explicitly declared columns. ^If
+** the table has a column of type [INTEGER PRIMARY KEY] then that column
+** is another alias for the rowid.
+**
+** ^This routine returns the [rowid] of the most recent
+** successful [INSERT] into the database from the [database connection]
+** in the first argument.  ^As of SQLite version 3.7.7, this routines
+** records the last insert rowid of both ordinary tables and [virtual tables].
+** ^If no successful [INSERT]s
+** have ever occurred on that database connection, zero is returned.
+**
+** ^(If an [INSERT] occurs within a trigger or within a [virtual table]
+** method, then this routine will return the [rowid] of the inserted
+** row as long as the trigger or virtual table method is running.
+** But once the trigger or virtual table method ends, the value returned 
+** by this routine reverts to what it was before the trigger or virtual
+** table method began.)^
+**
+** ^An [INSERT] that fails due to a constraint violation is not a
+** successful [INSERT] and does not change the value returned by this
+** routine.  ^Thus INSERT OR FAIL, INSERT OR IGNORE, INSERT OR ROLLBACK,
+** and INSERT OR ABORT make no changes to the return value of this
+** routine when their insertion fails.  ^(When INSERT OR REPLACE
+** encounters a constraint violation, it does not fail.  The
+** INSERT continues to completion after deleting rows that caused
+** the constraint problem so INSERT OR REPLACE will always change
+** the return value of this interface.)^
+**
+** ^For the purposes of this routine, an [INSERT] is considered to
+** be successful even if it is subsequently rolled back.
+**
+** This function is accessible to SQL statements via the
+** [last_insert_rowid() SQL function].
+**
+** If a separate thread performs a new [INSERT] on the same
+** database connection while the [sqlite3_last_insert_rowid()]
+** function is running and thus changes the last insert [rowid],
+** then the value returned by [sqlite3_last_insert_rowid()] is
+** unpredictable and might not equal either the old or the new
+** last insert [rowid].
+*/
+sqlite3_int64 sqlite3_last_insert_rowid(sqlite3*);
+
+/*
+** CAPI3REF: Count The Number Of Rows Modified
+**
+** ^This function returns the number of database rows that were changed
+** or inserted or deleted by the most recently completed SQL statement
+** on the [database connection] specified by the first parameter.
+** ^(Only changes that are directly specified by the [INSERT], [UPDATE],
+** or [DELETE] statement are counted.  Auxiliary changes caused by
+** triggers or [foreign key actions] are not counted.)^ Use the
+** [sqlite3_total_changes()] function to find the total number of changes
+** including changes caused by triggers and foreign key actions.
+**
+** ^Changes to a view that are simulated by an [INSTEAD OF trigger]
+** are not counted.  Only real table changes are counted.
+**
+** ^(A "row change" is a change to a single row of a single table
+** caused by an INSERT, DELETE, or UPDATE statement.  Rows that
+** are changed as side effects of [REPLACE] constraint resolution,
+** rollback, ABORT processing, [DROP TABLE], or by any other
+** mechanisms do not count as direct row changes.)^
+**
+** A "trigger context" is a scope of execution that begins and
+** ends with the script of a [CREATE TRIGGER | trigger]. 
+** Most SQL statements are
+** evaluated outside of any trigger.  This is the "top level"
+** trigger context.  If a trigger fires from the top level, a
+** new trigger context is entered for the duration of that one
+** trigger.  Subtriggers create subcontexts for their duration.
+**
+** ^Calling [sqlite3_exec()] or [sqlite3_step()] recursively does
+** not create a new trigger context.
+**
+** ^This function returns the number of direct row changes in the
+** most recent INSERT, UPDATE, or DELETE statement within the same
+** trigger context.
+**
+** ^Thus, when called from the top level, this function returns the
+** number of changes in the most recent INSERT, UPDATE, or DELETE
+** that also occurred at the top level.  ^(Within the body of a trigger,
+** the sqlite3_changes() interface can be called to find the number of
+** changes in the most recently completed INSERT, UPDATE, or DELETE
+** statement within the body of the same trigger.
+** However, the number returned does not include changes
+** caused by subtriggers since those have their own context.)^
+**
+** See also the [sqlite3_total_changes()] interface, the
+** [count_changes pragma], and the [changes() SQL function].
+**
+** If a separate thread makes changes on the same database connection
+** while [sqlite3_changes()] is running then the value returned
+** is unpredictable and not meaningful.
+*/
+int sqlite3_changes(sqlite3*);
+
+/*
+** CAPI3REF: Total Number Of Rows Modified
+**
+** ^This function returns the number of row changes caused by [INSERT],
+** [UPDATE] or [DELETE] statements since the [database connection] was opened.
+** ^(The count returned by sqlite3_total_changes() includes all changes
+** from all [CREATE TRIGGER | trigger] contexts and changes made by
+** [foreign key actions]. However,
+** the count does not include changes used to implement [REPLACE] constraints,
+** do rollbacks or ABORT processing, or [DROP TABLE] processing.  The
+** count does not include rows of views that fire an [INSTEAD OF trigger],
+** though if the INSTEAD OF trigger makes changes of its own, those changes 
+** are counted.)^
+** ^The sqlite3_total_changes() function counts the changes as soon as
+** the statement that makes them is completed (when the statement handle
+** is passed to [sqlite3_reset()] or [sqlite3_finalize()]).
+**
+** See also the [sqlite3_changes()] interface, the
+** [count_changes pragma], and the [total_changes() SQL function].
+**
+** If a separate thread makes changes on the same database connection
+** while [sqlite3_total_changes()] is running then the value
+** returned is unpredictable and not meaningful.
+*/
+int sqlite3_total_changes(sqlite3*);
+
+/*
+** CAPI3REF: Interrupt A Long-Running Query
+**
+** ^This function causes any pending database operation to abort and
+** return at its earliest opportunity. This routine is typically
+** called in response to a user action such as pressing "Cancel"
+** or Ctrl-C where the user wants a long query operation to halt
+** immediately.
+**
+** ^It is safe to call this routine from a thread different from the
+** thread that is currently running the database operation.  But it
+** is not safe to call this routine with a [database connection] that
+** is closed or might close before sqlite3_interrupt() returns.
+**
+** ^If an SQL operation is very nearly finished at the time when
+** sqlite3_interrupt() is called, then it might not have an opportunity
+** to be interrupted and might continue to completion.
+**
+** ^An SQL operation that is interrupted will return [SQLITE_INTERRUPT].
+** ^If the interrupted SQL operation is an INSERT, UPDATE, or DELETE
+** that is inside an explicit transaction, then the entire transaction
+** will be rolled back automatically.
+**
+** ^The sqlite3_interrupt(D) call is in effect until all currently running
+** SQL statements on [database connection] D complete.  ^Any new SQL statements
+** that are started after the sqlite3_interrupt() call and before the 
+** running statements reaches zero are interrupted as if they had been
+** running prior to the sqlite3_interrupt() call.  ^New SQL statements
+** that are started after the running statement count reaches zero are
+** not effected by the sqlite3_interrupt().
+** ^A call to sqlite3_interrupt(D) that occurs when there are no running
+** SQL statements is a no-op and has no effect on SQL statements
+** that are started after the sqlite3_interrupt() call returns.
+**
+** If the database connection closes while [sqlite3_interrupt()]
+** is running then bad things will likely happen.
+*/
+void sqlite3_interrupt(sqlite3*);
+
+/*
+** CAPI3REF: Determine If An SQL Statement Is Complete
+**
+** These routines are useful during command-line input to determine if the
+** currently entered text seems to form a complete SQL statement or
+** if additional input is needed before sending the text into
+** SQLite for parsing.  ^These routines return 1 if the input string
+** appears to be a complete SQL statement.  ^A statement is judged to be
+** complete if it ends with a semicolon token and is not a prefix of a
+** well-formed CREATE TRIGGER statement.  ^Semicolons that are embedded within
+** string literals or quoted identifier names or comments are not
+** independent tokens (they are part of the token in which they are
+** embedded) and thus do not count as a statement terminator.  ^Whitespace
+** and comments that follow the final semicolon are ignored.
+**
+** ^These routines return 0 if the statement is incomplete.  ^If a
+** memory allocation fails, then SQLITE_NOMEM is returned.
+**
+** ^These routines do not parse the SQL statements thus
+** will not detect syntactically incorrect SQL.
+**
+** ^(If SQLite has not been initialized using [sqlite3_initialize()] prior 
+** to invoking sqlite3_complete16() then sqlite3_initialize() is invoked
+** automatically by sqlite3_complete16().  If that initialization fails,
+** then the return value from sqlite3_complete16() will be non-zero
+** regardless of whether or not the input SQL is complete.)^
+**
+** The input to [sqlite3_complete()] must be a zero-terminated
+** UTF-8 string.
+**
+** The input to [sqlite3_complete16()] must be a zero-terminated
+** UTF-16 string in native byte order.
+*/
+int sqlite3_complete(const char *sql);
+int sqlite3_complete16(const void *sql);
+
+/*
+** CAPI3REF: Register A Callback To Handle SQLITE_BUSY Errors
+**
+** ^This routine sets a callback function that might be invoked whenever
+** an attempt is made to open a database table that another thread
+** or process has locked.
+**
+** ^If the busy callback is NULL, then [SQLITE_BUSY] or [SQLITE_IOERR_BLOCKED]
+** is returned immediately upon encountering the lock.  ^If the busy callback
+** is not NULL, then the callback might be invoked with two arguments.
+**
+** ^The first argument to the busy handler is a copy of the void* pointer which
+** is the third argument to sqlite3_busy_handler().  ^The second argument to
+** the busy handler callback is the number of times that the busy handler has
+** been invoked for this locking event.  ^If the
+** busy callback returns 0, then no additional attempts are made to
+** access the database and [SQLITE_BUSY] or [SQLITE_IOERR_BLOCKED] is returned.
+** ^If the callback returns non-zero, then another attempt
+** is made to open the database for reading and the cycle repeats.
+**
+** The presence of a busy handler does not guarantee that it will be invoked
+** when there is lock contention. ^If SQLite determines that invoking the busy
+** handler could result in a deadlock, it will go ahead and return [SQLITE_BUSY]
+** or [SQLITE_IOERR_BLOCKED] instead of invoking the busy handler.
+** Consider a scenario where one process is holding a read lock that
+** it is trying to promote to a reserved lock and
+** a second process is holding a reserved lock that it is trying
+** to promote to an exclusive lock.  The first process cannot proceed
+** because it is blocked by the second and the second process cannot
+** proceed because it is blocked by the first.  If both processes
+** invoke the busy handlers, neither will make any progress.  Therefore,
+** SQLite returns [SQLITE_BUSY] for the first process, hoping that this
+** will induce the first process to release its read lock and allow
+** the second process to proceed.
+**
+** ^The default busy callback is NULL.
+**
+** ^The [SQLITE_BUSY] error is converted to [SQLITE_IOERR_BLOCKED]
+** when SQLite is in the middle of a large transaction where all the
+** changes will not fit into the in-memory cache.  SQLite will
+** already hold a RESERVED lock on the database file, but it needs
+** to promote this lock to EXCLUSIVE so that it can spill cache
+** pages into the database file without harm to concurrent
+** readers.  ^If it is unable to promote the lock, then the in-memory
+** cache will be left in an inconsistent state and so the error
+** code is promoted from the relatively benign [SQLITE_BUSY] to
+** the more severe [SQLITE_IOERR_BLOCKED].  ^This error code promotion
+** forces an automatic rollback of the changes.  See the
+** <a href="/cvstrac/wiki?p=CorruptionFollowingBusyError">
+** CorruptionFollowingBusyError</a> wiki page for a discussion of why
+** this is important.
+**
+** ^(There can only be a single busy handler defined for each
+** [database connection].  Setting a new busy handler clears any
+** previously set handler.)^  ^Note that calling [sqlite3_busy_timeout()]
+** will also set or clear the busy handler.
+**
+** The busy callback should not take any actions which modify the
+** database connection that invoked the busy handler.  Any such actions
+** result in undefined behavior.
+** 
+** A busy handler must not close the database connection
+** or [prepared statement] that invoked the busy handler.
+*/
+int sqlite3_busy_handler(sqlite3*, int(*)(void*,int), void*);
+
+/*
+** CAPI3REF: Set A Busy Timeout
+**
+** ^This routine sets a [sqlite3_busy_handler | busy handler] that sleeps
+** for a specified amount of time when a table is locked.  ^The handler
+** will sleep multiple times until at least "ms" milliseconds of sleeping
+** have accumulated.  ^After at least "ms" milliseconds of sleeping,
+** the handler returns 0 which causes [sqlite3_step()] to return
+** [SQLITE_BUSY] or [SQLITE_IOERR_BLOCKED].
+**
+** ^Calling this routine with an argument less than or equal to zero
+** turns off all busy handlers.
+**
+** ^(There can only be a single busy handler for a particular
+** [database connection] any any given moment.  If another busy handler
+** was defined  (using [sqlite3_busy_handler()]) prior to calling
+** this routine, that other busy handler is cleared.)^
+*/
+int sqlite3_busy_timeout(sqlite3*, int ms);
+
+/*
+** CAPI3REF: Convenience Routines For Running Queries
+**
+** This is a legacy interface that is preserved for backwards compatibility.
+** Use of this interface is not recommended.
+**
+** Definition: A <b>result table</b> is memory data structure created by the
+** [sqlite3_get_table()] interface.  A result table records the
+** complete query results from one or more queries.
+**
+** The table conceptually has a number of rows and columns.  But
+** these numbers are not part of the result table itself.  These
+** numbers are obtained separately.  Let N be the number of rows
+** and M be the number of columns.
+**
+** A result table is an array of pointers to zero-terminated UTF-8 strings.
+** There are (N+1)*M elements in the array.  The first M pointers point
+** to zero-terminated strings that  contain the names of the columns.
+** The remaining entries all point to query results.  NULL values result
+** in NULL pointers.  All other values are in their UTF-8 zero-terminated
+** string representation as returned by [sqlite3_column_text()].
+**
+** A result table might consist of one or more memory allocations.
+** It is not safe to pass a result table directly to [sqlite3_free()].
+** A result table should be deallocated using [sqlite3_free_table()].
+**
+** ^(As an example of the result table format, suppose a query result
+** is as follows:
+**
+** <blockquote><pre>
+**        Name        | Age
+**        -----------------------
+**        Alice       | 43
+**        Bob         | 28
+**        Cindy       | 21
+** </pre></blockquote>
+**
+** There are two column (M==2) and three rows (N==3).  Thus the
+** result table has 8 entries.  Suppose the result table is stored
+** in an array names azResult.  Then azResult holds this content:
+**
+** <blockquote><pre>
+**        azResult&#91;0] = "Name";
+**        azResult&#91;1] = "Age";
+**        azResult&#91;2] = "Alice";
+**        azResult&#91;3] = "43";
+**        azResult&#91;4] = "Bob";
+**        azResult&#91;5] = "28";
+**        azResult&#91;6] = "Cindy";
+**        azResult&#91;7] = "21";
+** </pre></blockquote>)^
+**
+** ^The sqlite3_get_table() function evaluates one or more
+** semicolon-separated SQL statements in the zero-terminated UTF-8
+** string of its 2nd parameter and returns a result table to the
+** pointer given in its 3rd parameter.
+**
+** After the application has finished with the result from sqlite3_get_table(),
+** it must pass the result table pointer to sqlite3_free_table() in order to
+** release the memory that was malloced.  Because of the way the
+** [sqlite3_malloc()] happens within sqlite3_get_table(), the calling
+** function must not try to call [sqlite3_free()] directly.  Only
+** [sqlite3_free_table()] is able to release the memory properly and safely.
+**
+** The sqlite3_get_table() interface is implemented as a wrapper around
+** [sqlite3_exec()].  The sqlite3_get_table() routine does not have access
+** to any internal data structures of SQLite.  It uses only the public
+** interface defined here.  As a consequence, errors that occur in the
+** wrapper layer outside of the internal [sqlite3_exec()] call are not
+** reflected in subsequent calls to [sqlite3_errcode()] or
+** [sqlite3_errmsg()].
+*/
+int sqlite3_get_table(
+  sqlite3 *db,          /* An open database */
+  const char *zSql,     /* SQL to be evaluated */
+  char ***pazResult,    /* Results of the query */
+  int *pnRow,           /* Number of result rows written here */
+  int *pnColumn,        /* Number of result columns written here */
+  char **pzErrmsg       /* Error msg written here */
+);
+void sqlite3_free_table(char **result);
+
+/*
+** CAPI3REF: Formatted String Printing Functions
+**
+** These routines are work-alikes of the "printf()" family of functions
+** from the standard C library.
+**
+** ^The sqlite3_mprintf() and sqlite3_vmprintf() routines write their
+** results into memory obtained from [sqlite3_malloc()].
+** The strings returned by these two routines should be
+** released by [sqlite3_free()].  ^Both routines return a
+** NULL pointer if [sqlite3_malloc()] is unable to allocate enough
+** memory to hold the resulting string.
+**
+** ^(The sqlite3_snprintf() routine is similar to "snprintf()" from
+** the standard C library.  The result is written into the
+** buffer supplied as the second parameter whose size is given by
+** the first parameter. Note that the order of the
+** first two parameters is reversed from snprintf().)^  This is an
+** historical accident that cannot be fixed without breaking
+** backwards compatibility.  ^(Note also that sqlite3_snprintf()
+** returns a pointer to its buffer instead of the number of
+** characters actually written into the buffer.)^  We admit that
+** the number of characters written would be a more useful return
+** value but we cannot change the implementation of sqlite3_snprintf()
+** now without breaking compatibility.
+**
+** ^As long as the buffer size is greater than zero, sqlite3_snprintf()
+** guarantees that the buffer is always zero-terminated.  ^The first
+** parameter "n" is the total size of the buffer, including space for
+** the zero terminator.  So the longest string that can be completely
+** written will be n-1 characters.
+**
+** ^The sqlite3_vsnprintf() routine is a varargs version of sqlite3_snprintf().
+**
+** These routines all implement some additional formatting
+** options that are useful for constructing SQL statements.
+** All of the usual printf() formatting options apply.  In addition, there
+** is are "%q", "%Q", and "%z" options.
+**
+** ^(The %q option works like %s in that it substitutes a null-terminated
+** string from the argument list.  But %q also doubles every '\'' character.
+** %q is designed for use inside a string literal.)^  By doubling each '\''
+** character it escapes that character and allows it to be inserted into
+** the string.
+**
+** For example, assume the string variable zText contains text as follows:
+**
+** <blockquote><pre>
+**  char *zText = "It's a happy day!";
+** </pre></blockquote>
+**
+** One can use this text in an SQL statement as follows:
+**
+** <blockquote><pre>
+**  char *zSQL = sqlite3_mprintf("INSERT INTO table VALUES('%q')", zText);
+**  sqlite3_exec(db, zSQL, 0, 0, 0);
+**  sqlite3_free(zSQL);
+** </pre></blockquote>
+**
+** Because the %q format string is used, the '\'' character in zText
+** is escaped and the SQL generated is as follows:
+**
+** <blockquote><pre>
+**  INSERT INTO table1 VALUES('It''s a happy day!')
+** </pre></blockquote>
+**
+** This is correct.  Had we used %s instead of %q, the generated SQL
+** would have looked like this:
+**
+** <blockquote><pre>
+**  INSERT INTO table1 VALUES('It's a happy day!');
+** </pre></blockquote>
+**
+** This second example is an SQL syntax error.  As a general rule you should
+** always use %q instead of %s when inserting text into a string literal.
+**
+** ^(The %Q option works like %q except it also adds single quotes around
+** the outside of the total string.  Additionally, if the parameter in the
+** argument list is a NULL pointer, %Q substitutes the text "NULL" (without
+** single quotes).)^  So, for example, one could say:
+**
+** <blockquote><pre>
+**  char *zSQL = sqlite3_mprintf("INSERT INTO table VALUES(%Q)", zText);
+**  sqlite3_exec(db, zSQL, 0, 0, 0);
+**  sqlite3_free(zSQL);
+** </pre></blockquote>
+**
+** The code above will render a correct SQL statement in the zSQL
+** variable even if the zText variable is a NULL pointer.
+**
+** ^(The "%z" formatting option works like "%s" but with the
+** addition that after the string has been read and copied into
+** the result, [sqlite3_free()] is called on the input string.)^
+*/
+char *sqlite3_mprintf(const char*,...);
+char *sqlite3_vmprintf(const char*, va_list);
+char *sqlite3_snprintf(int,char*,const char*, ...);
+char *sqlite3_vsnprintf(int,char*,const char*, va_list);
+
+/*
+** CAPI3REF: Memory Allocation Subsystem
+**
+** The SQLite core uses these three routines for all of its own
+** internal memory allocation needs. "Core" in the previous sentence
+** does not include operating-system specific VFS implementation.  The
+** Windows VFS uses native malloc() and free() for some operations.
+**
+** ^The sqlite3_malloc() routine returns a pointer to a block
+** of memory at least N bytes in length, where N is the parameter.
+** ^If sqlite3_malloc() is unable to obtain sufficient free
+** memory, it returns a NULL pointer.  ^If the parameter N to
+** sqlite3_malloc() is zero or negative then sqlite3_malloc() returns
+** a NULL pointer.
+**
+** ^Calling sqlite3_free() with a pointer previously returned
+** by sqlite3_malloc() or sqlite3_realloc() releases that memory so
+** that it might be reused.  ^The sqlite3_free() routine is
+** a no-op if is called with a NULL pointer.  Passing a NULL pointer
+** to sqlite3_free() is harmless.  After being freed, memory
+** should neither be read nor written.  Even reading previously freed
+** memory might result in a segmentation fault or other severe error.
+** Memory corruption, a segmentation fault, or other severe error
+** might result if sqlite3_free() is called with a non-NULL pointer that
+** was not obtained from sqlite3_malloc() or sqlite3_realloc().
+**
+** ^(The sqlite3_realloc() interface attempts to resize a
+** prior memory allocation to be at least N bytes, where N is the
+** second parameter.  The memory allocation to be resized is the first
+** parameter.)^ ^ If the first parameter to sqlite3_realloc()
+** is a NULL pointer then its behavior is identical to calling
+** sqlite3_malloc(N) where N is the second parameter to sqlite3_realloc().
+** ^If the second parameter to sqlite3_realloc() is zero or
+** negative then the behavior is exactly the same as calling
+** sqlite3_free(P) where P is the first parameter to sqlite3_realloc().
+** ^sqlite3_realloc() returns a pointer to a memory allocation
+** of at least N bytes in size or NULL if sufficient memory is unavailable.
+** ^If M is the size of the prior allocation, then min(N,M) bytes
+** of the prior allocation are copied into the beginning of buffer returned
+** by sqlite3_realloc() and the prior allocation is freed.
+** ^If sqlite3_realloc() returns NULL, then the prior allocation
+** is not freed.
+**
+** ^The memory returned by sqlite3_malloc() and sqlite3_realloc()
+** is always aligned to at least an 8 byte boundary, or to a
+** 4 byte boundary if the [SQLITE_4_BYTE_ALIGNED_MALLOC] compile-time
+** option is used.
+**
+** In SQLite version 3.5.0 and 3.5.1, it was possible to define
+** the SQLITE_OMIT_MEMORY_ALLOCATION which would cause the built-in
+** implementation of these routines to be omitted.  That capability
+** is no longer provided.  Only built-in memory allocators can be used.
+**
+** The Windows OS interface layer calls
+** the system malloc() and free() directly when converting
+** filenames between the UTF-8 encoding used by SQLite
+** and whatever filename encoding is used by the particular Windows
+** installation.  Memory allocation errors are detected, but
+** they are reported back as [SQLITE_CANTOPEN] or
+** [SQLITE_IOERR] rather than [SQLITE_NOMEM].
+**
+** The pointer arguments to [sqlite3_free()] and [sqlite3_realloc()]
+** must be either NULL or else pointers obtained from a prior
+** invocation of [sqlite3_malloc()] or [sqlite3_realloc()] that have
+** not yet been released.
+**
+** The application must not read or write any part of
+** a block of memory after it has been released using
+** [sqlite3_free()] or [sqlite3_realloc()].
+*/
+void *sqlite3_malloc(int);
+void *sqlite3_realloc(void*, int);
+void sqlite3_free(void*);
+
+/*
+** CAPI3REF: Memory Allocator Statistics
+**
+** SQLite provides these two interfaces for reporting on the status
+** of the [sqlite3_malloc()], [sqlite3_free()], and [sqlite3_realloc()]
+** routines, which form the built-in memory allocation subsystem.
+**
+** ^The [sqlite3_memory_used()] routine returns the number of bytes
+** of memory currently outstanding (malloced but not freed).
+** ^The [sqlite3_memory_highwater()] routine returns the maximum
+** value of [sqlite3_memory_used()] since the high-water mark
+** was last reset.  ^The values returned by [sqlite3_memory_used()] and
+** [sqlite3_memory_highwater()] include any overhead
+** added by SQLite in its implementation of [sqlite3_malloc()],
+** but not overhead added by the any underlying system library
+** routines that [sqlite3_malloc()] may call.
+**
+** ^The memory high-water mark is reset to the current value of
+** [sqlite3_memory_used()] if and only if the parameter to
+** [sqlite3_memory_highwater()] is true.  ^The value returned
+** by [sqlite3_memory_highwater(1)] is the high-water mark
+** prior to the reset.
+*/
+sqlite3_int64 sqlite3_memory_used(void);
+sqlite3_int64 sqlite3_memory_highwater(int resetFlag);
+
+/*
+** CAPI3REF: Pseudo-Random Number Generator
+**
+** SQLite contains a high-quality pseudo-random number generator (PRNG) used to
+** select random [ROWID | ROWIDs] when inserting new records into a table that
+** already uses the largest possible [ROWID].  The PRNG is also used for
+** the build-in random() and randomblob() SQL functions.  This interface allows
+** applications to access the same PRNG for other purposes.
+**
+** ^A call to this routine stores N bytes of randomness into buffer P.
+**
+** ^The first time this routine is invoked (either internally or by
+** the application) the PRNG is seeded using randomness obtained
+** from the xRandomness method of the default [sqlite3_vfs] object.
+** ^On all subsequent invocations, the pseudo-randomness is generated
+** internally and without recourse to the [sqlite3_vfs] xRandomness
+** method.
+*/
+void sqlite3_randomness(int N, void *P);
+
+/*
+** CAPI3REF: Compile-Time Authorization Callbacks
+**
+** ^This routine registers an authorizer callback with a particular
+** [database connection], supplied in the first argument.
+** ^The authorizer callback is invoked as SQL statements are being compiled
+** by [sqlite3_prepare()] or its variants [sqlite3_prepare_v2()],
+** [sqlite3_prepare16()] and [sqlite3_prepare16_v2()].  ^At various
+** points during the compilation process, as logic is being created
+** to perform various actions, the authorizer callback is invoked to
+** see if those actions are allowed.  ^The authorizer callback should
+** return [SQLITE_OK] to allow the action, [SQLITE_IGNORE] to disallow the
+** specific action but allow the SQL statement to continue to be
+** compiled, or [SQLITE_DENY] to cause the entire SQL statement to be
+** rejected with an error.  ^If the authorizer callback returns
+** any value other than [SQLITE_IGNORE], [SQLITE_OK], or [SQLITE_DENY]
+** then the [sqlite3_prepare_v2()] or equivalent call that triggered
+** the authorizer will fail with an error message.
+**
+** When the callback returns [SQLITE_OK], that means the operation
+** requested is ok.  ^When the callback returns [SQLITE_DENY], the
+** [sqlite3_prepare_v2()] or equivalent call that triggered the
+** authorizer will fail with an error message explaining that
+** access is denied. 
+**
+** ^The first parameter to the authorizer callback is a copy of the third
+** parameter to the sqlite3_set_authorizer() interface. ^The second parameter
+** to the callback is an integer [SQLITE_COPY | action code] that specifies
+** the particular action to be authorized. ^The third through sixth parameters
+** to the callback are zero-terminated strings that contain additional
+** details about the action to be authorized.
+**
+** ^If the action code is [SQLITE_READ]
+** and the callback returns [SQLITE_IGNORE] then the
+** [prepared statement] statement is constructed to substitute
+** a NULL value in place of the table column that would have
+** been read if [SQLITE_OK] had been returned.  The [SQLITE_IGNORE]
+** return can be used to deny an untrusted user access to individual
+** columns of a table.
+** ^If the action code is [SQLITE_DELETE] and the callback returns
+** [SQLITE_IGNORE] then the [DELETE] operation proceeds but the
+** [truncate optimization] is disabled and all rows are deleted individually.
+**
+** An authorizer is used when [sqlite3_prepare | preparing]
+** SQL statements from an untrusted source, to ensure that the SQL statements
+** do not try to access data they are not allowed to see, or that they do not
+** try to execute malicious statements that damage the database.  For
+** example, an application may allow a user to enter arbitrary
+** SQL queries for evaluation by a database.  But the application does
+** not want the user to be able to make arbitrary changes to the
+** database.  An authorizer could then be put in place while the
+** user-entered SQL is being [sqlite3_prepare | prepared] that
+** disallows everything except [SELECT] statements.
+**
+** Applications that need to process SQL from untrusted sources
+** might also consider lowering resource limits using [sqlite3_limit()]
+** and limiting database size using the [max_page_count] [PRAGMA]
+** in addition to using an authorizer.
+**
+** ^(Only a single authorizer can be in place on a database connection
+** at a time.  Each call to sqlite3_set_authorizer overrides the
+** previous call.)^  ^Disable the authorizer by installing a NULL callback.
+** The authorizer is disabled by default.
+**
+** The authorizer callback must not do anything that will modify
+** the database connection that invoked the authorizer callback.
+** Note that [sqlite3_prepare_v2()] and [sqlite3_step()] both modify their
+** database connections for the meaning of "modify" in this paragraph.
+**
+** ^When [sqlite3_prepare_v2()] is used to prepare a statement, the
+** statement might be re-prepared during [sqlite3_step()] due to a 
+** schema change.  Hence, the application should ensure that the
+** correct authorizer callback remains in place during the [sqlite3_step()].
+**
+** ^Note that the authorizer callback is invoked only during
+** [sqlite3_prepare()] or its variants.  Authorization is not
+** performed during statement evaluation in [sqlite3_step()], unless
+** as stated in the previous paragraph, sqlite3_step() invokes
+** sqlite3_prepare_v2() to reprepare a statement after a schema change.
+*/
+int sqlite3_set_authorizer(
+  sqlite3*,
+  int (*xAuth)(void*,int,const char*,const char*,const char*,const char*),
+  void *pUserData
+);
+
+/*
+** CAPI3REF: Authorizer Return Codes
+**
+** The [sqlite3_set_authorizer | authorizer callback function] must
+** return either [SQLITE_OK] or one of these two constants in order
+** to signal SQLite whether or not the action is permitted.  See the
+** [sqlite3_set_authorizer | authorizer documentation] for additional
+** information.
+**
+** Note that SQLITE_IGNORE is also used as a [SQLITE_ROLLBACK | return code]
+** from the [sqlite3_vtab_on_conflict()] interface.
+*/
+#define SQLITE_DENY   1   /* Abort the SQL statement with an error */
+#define SQLITE_IGNORE 2   /* Don't allow access, but don't generate an error */
+
+/*
+** CAPI3REF: Authorizer Action Codes
+**
+** The [sqlite3_set_authorizer()] interface registers a callback function
+** that is invoked to authorize certain SQL statement actions.  The
+** second parameter to the callback is an integer code that specifies
+** what action is being authorized.  These are the integer action codes that
+** the authorizer callback may be passed.
+**
+** These action code values signify what kind of operation is to be
+** authorized.  The 3rd and 4th parameters to the authorization
+** callback function will be parameters or NULL depending on which of these
+** codes is used as the second parameter.  ^(The 5th parameter to the
+** authorizer callback is the name of the database ("main", "temp",
+** etc.) if applicable.)^  ^The 6th parameter to the authorizer callback
+** is the name of the inner-most trigger or view that is responsible for
+** the access attempt or NULL if this access attempt is directly from
+** top-level SQL code.
+*/
+/******************************************* 3rd ************ 4th ***********/
+#define SQLITE_CREATE_INDEX          1   /* Index Name      Table Name      */
+#define SQLITE_CREATE_TABLE          2   /* Table Name      NULL            */
+#define SQLITE_CREATE_TEMP_INDEX     3   /* Index Name      Table Name      */
+#define SQLITE_CREATE_TEMP_TABLE     4   /* Table Name      NULL            */
+#define SQLITE_CREATE_TEMP_TRIGGER   5   /* Trigger Name    Table Name      */
+#define SQLITE_CREATE_TEMP_VIEW      6   /* View Name       NULL            */
+#define SQLITE_CREATE_TRIGGER        7   /* Trigger Name    Table Name      */
+#define SQLITE_CREATE_VIEW           8   /* View Name       NULL            */
+#define SQLITE_DELETE                9   /* Table Name      NULL            */
+#define SQLITE_DROP_INDEX           10   /* Index Name      Table Name      */
+#define SQLITE_DROP_TABLE           11   /* Table Name      NULL            */
+#define SQLITE_DROP_TEMP_INDEX      12   /* Index Name      Table Name      */
+#define SQLITE_DROP_TEMP_TABLE      13   /* Table Name      NULL            */
+#define SQLITE_DROP_TEMP_TRIGGER    14   /* Trigger Name    Table Name      */
+#define SQLITE_DROP_TEMP_VIEW       15   /* View Name       NULL            */
+#define SQLITE_DROP_TRIGGER         16   /* Trigger Name    Table Name      */
+#define SQLITE_DROP_VIEW            17   /* View Name       NULL            */
+#define SQLITE_INSERT               18   /* Table Name      NULL            */
+#define SQLITE_PRAGMA               19   /* Pragma Name     1st arg or NULL */
+#define SQLITE_READ                 20   /* Table Name      Column Name     */
+#define SQLITE_SELECT               21   /* NULL            NULL            */
+#define SQLITE_TRANSACTION          22   /* Operation       NULL            */
+#define SQLITE_UPDATE               23   /* Table Name      Column Name     */
+#define SQLITE_ATTACH               24   /* Filename        NULL            */
+#define SQLITE_DETACH               25   /* Database Name   NULL            */
+#define SQLITE_ALTER_TABLE          26   /* Database Name   Table Name      */
+#define SQLITE_REINDEX              27   /* Index Name      NULL            */
+#define SQLITE_ANALYZE              28   /* Table Name      NULL            */
+#define SQLITE_CREATE_VTABLE        29   /* Table Name      Module Name     */
+#define SQLITE_DROP_VTABLE          30   /* Table Name      Module Name     */
+#define SQLITE_FUNCTION             31   /* NULL            Function Name   */
+#define SQLITE_SAVEPOINT            32   /* Operation       Savepoint Name  */
+#define SQLITE_COPY                  0   /* No longer used */
+
+/*
+** CAPI3REF: Tracing And Profiling Functions
+**
+** These routines register callback functions that can be used for
+** tracing and profiling the execution of SQL statements.
+**
+** ^The callback function registered by sqlite3_trace() is invoked at
+** various times when an SQL statement is being run by [sqlite3_step()].
+** ^The sqlite3_trace() callback is invoked with a UTF-8 rendering of the
+** SQL statement text as the statement first begins executing.
+** ^(Additional sqlite3_trace() callbacks might occur
+** as each triggered subprogram is entered.  The callbacks for triggers
+** contain a UTF-8 SQL comment that identifies the trigger.)^
+**
+** ^The callback function registered by sqlite3_profile() is invoked
+** as each SQL statement finishes.  ^The profile callback contains
+** the original statement text and an estimate of wall-clock time
+** of how long that statement took to run.  ^The profile callback
+** time is in units of nanoseconds, however the current implementation
+** is only capable of millisecond resolution so the six least significant
+** digits in the time are meaningless.  Future versions of SQLite
+** might provide greater resolution on the profiler callback.  The
+** sqlite3_profile() function is considered experimental and is
+** subject to change in future versions of SQLite.
+*/
+void *sqlite3_trace(sqlite3*, void(*xTrace)(void*,const char*), void*);
+SQLITE_EXPERIMENTAL void *sqlite3_profile(sqlite3*,
+   void(*xProfile)(void*,const char*,sqlite3_uint64), void*);
+
+/*
+** CAPI3REF: Query Progress Callbacks
+**
+** ^The sqlite3_progress_handler(D,N,X,P) interface causes the callback
+** function X to be invoked periodically during long running calls to
+** [sqlite3_exec()], [sqlite3_step()] and [sqlite3_get_table()] for
+** database connection D.  An example use for this
+** interface is to keep a GUI updated during a large query.
+**
+** ^The parameter P is passed through as the only parameter to the 
+** callback function X.  ^The parameter N is the number of 
+** [virtual machine instructions] that are evaluated between successive
+** invocations of the callback X.
+**
+** ^Only a single progress handler may be defined at one time per
+** [database connection]; setting a new progress handler cancels the
+** old one.  ^Setting parameter X to NULL disables the progress handler.
+** ^The progress handler is also disabled by setting N to a value less
+** than 1.
+**
+** ^If the progress callback returns non-zero, the operation is
+** interrupted.  This feature can be used to implement a
+** "Cancel" button on a GUI progress dialog box.
+**
+** The progress handler callback must not do anything that will modify
+** the database connection that invoked the progress handler.
+** Note that [sqlite3_prepare_v2()] and [sqlite3_step()] both modify their
+** database connections for the meaning of "modify" in this paragraph.
+**
+*/
+void sqlite3_progress_handler(sqlite3*, int, int(*)(void*), void*);
+
+/*
+** CAPI3REF: Opening A New Database Connection
+**
+** ^These routines open an SQLite database file as specified by the 
+** filename argument. ^The filename argument is interpreted as UTF-8 for
+** sqlite3_open() and sqlite3_open_v2() and as UTF-16 in the native byte
+** order for sqlite3_open16(). ^(A [database connection] handle is usually
+** returned in *ppDb, even if an error occurs.  The only exception is that
+** if SQLite is unable to allocate memory to hold the [sqlite3] object,
+** a NULL will be written into *ppDb instead of a pointer to the [sqlite3]
+** object.)^ ^(If the database is opened (and/or created) successfully, then
+** [SQLITE_OK] is returned.  Otherwise an [error code] is returned.)^ ^The
+** [sqlite3_errmsg()] or [sqlite3_errmsg16()] routines can be used to obtain
+** an English language description of the error following a failure of any
+** of the sqlite3_open() routines.
+**
+** ^The default encoding for the database will be UTF-8 if
+** sqlite3_open() or sqlite3_open_v2() is called and
+** UTF-16 in the native byte order if sqlite3_open16() is used.
+**
+** Whether or not an error occurs when it is opened, resources
+** associated with the [database connection] handle should be released by
+** passing it to [sqlite3_close()] when it is no longer required.
+**
+** The sqlite3_open_v2() interface works like sqlite3_open()
+** except that it accepts two additional parameters for additional control
+** over the new database connection.  ^(The flags parameter to
+** sqlite3_open_v2() can take one of
+** the following three values, optionally combined with the 
+** [SQLITE_OPEN_NOMUTEX], [SQLITE_OPEN_FULLMUTEX], [SQLITE_OPEN_SHAREDCACHE],
+** [SQLITE_OPEN_PRIVATECACHE], and/or [SQLITE_OPEN_URI] flags:)^
+**
+** <dl>
+** ^(<dt>[SQLITE_OPEN_READONLY]</dt>
+** <dd>The database is opened in read-only mode.  If the database does not
+** already exist, an error is returned.</dd>)^
+**
+** ^(<dt>[SQLITE_OPEN_READWRITE]</dt>
+** <dd>The database is opened for reading and writing if possible, or reading
+** only if the file is write protected by the operating system.  In either
+** case the database must already exist, otherwise an error is returned.</dd>)^
+**
+** ^(<dt>[SQLITE_OPEN_READWRITE] | [SQLITE_OPEN_CREATE]</dt>
+** <dd>The database is opened for reading and writing, and is created if
+** it does not already exist. This is the behavior that is always used for
+** sqlite3_open() and sqlite3_open16().</dd>)^
+** </dl>
+**
+** If the 3rd parameter to sqlite3_open_v2() is not one of the
+** combinations shown above optionally combined with other
+** [SQLITE_OPEN_READONLY | SQLITE_OPEN_* bits]
+** then the behavior is undefined.
+**
+** ^If the [SQLITE_OPEN_NOMUTEX] flag is set, then the database connection
+** opens in the multi-thread [threading mode] as long as the single-thread
+** mode has not been set at compile-time or start-time.  ^If the
+** [SQLITE_OPEN_FULLMUTEX] flag is set then the database connection opens
+** in the serialized [threading mode] unless single-thread was
+** previously selected at compile-time or start-time.
+** ^The [SQLITE_OPEN_SHAREDCACHE] flag causes the database connection to be
+** eligible to use [shared cache mode], regardless of whether or not shared
+** cache is enabled using [sqlite3_enable_shared_cache()].  ^The
+** [SQLITE_OPEN_PRIVATECACHE] flag causes the database connection to not
+** participate in [shared cache mode] even if it is enabled.
+**
+** ^The fourth parameter to sqlite3_open_v2() is the name of the
+** [sqlite3_vfs] object that defines the operating system interface that
+** the new database connection should use.  ^If the fourth parameter is
+** a NULL pointer then the default [sqlite3_vfs] object is used.
+**
+** ^If the filename is ":memory:", then a private, temporary in-memory database
+** is created for the connection.  ^This in-memory database will vanish when
+** the database connection is closed.  Future versions of SQLite might
+** make use of additional special filenames that begin with the ":" character.
+** It is recommended that when a database filename actually does begin with
+** a ":" character you should prefix the filename with a pathname such as
+** "./" to avoid ambiguity.
+**
+** ^If the filename is an empty string, then a private, temporary
+** on-disk database will be created.  ^This private database will be
+** automatically deleted as soon as the database connection is closed.
+**
+** [[URI filenames in sqlite3_open()]] <h3>URI Filenames</h3>
+**
+** ^If [URI filename] interpretation is enabled, and the filename argument
+** begins with "file:", then the filename is interpreted as a URI. ^URI
+** filename interpretation is enabled if the [SQLITE_OPEN_URI] flag is
+** set in the fourth argument to sqlite3_open_v2(), or if it has
+** been enabled globally using the [SQLITE_CONFIG_URI] option with the
+** [sqlite3_config()] method or by the [SQLITE_USE_URI] compile-time option.
+** As of SQLite version 3.7.7, URI filename interpretation is turned off
+** by default, but future releases of SQLite might enable URI filename
+** interpretation by default.  See "[URI filenames]" for additional
+** information.
+**
+** URI filenames are parsed according to RFC 3986. ^If the URI contains an
+** authority, then it must be either an empty string or the string 
+** "localhost". ^If the authority is not an empty string or "localhost", an 
+** error is returned to the caller. ^The fragment component of a URI, if 
+** present, is ignored.
+**
+** ^SQLite uses the path component of the URI as the name of the disk file
+** which contains the database. ^If the path begins with a '/' character, 
+** then it is interpreted as an absolute path. ^If the path does not begin 
+** with a '/' (meaning that the authority section is omitted from the URI)
+** then the path is interpreted as a relative path. 
+** ^On windows, the first component of an absolute path 
+** is a drive specification (e.g. "C:").
+**
+** [[core URI query parameters]]
+** The query component of a URI may contain parameters that are interpreted
+** either by SQLite itself, or by a [VFS | custom VFS implementation].
+** SQLite interprets the following three query parameters:
+**
+** <ul>
+**   <li> <b>vfs</b>: ^The "vfs" parameter may be used to specify the name of
+**     a VFS object that provides the operating system interface that should
+**     be used to access the database file on disk. ^If this option is set to
+**     an empty string the default VFS object is used. ^Specifying an unknown
+**     VFS is an error. ^If sqlite3_open_v2() is used and the vfs option is
+**     present, then the VFS specified by the option takes precedence over
+**     the value passed as the fourth parameter to sqlite3_open_v2().
+**
+**   <li> <b>mode</b>: ^(The mode parameter may be set to either "ro", "rw" or
+**     "rwc". Attempting to set it to any other value is an error)^. 
+**     ^If "ro" is specified, then the database is opened for read-only 
+**     access, just as if the [SQLITE_OPEN_READONLY] flag had been set in the 
+**     third argument to sqlite3_prepare_v2(). ^If the mode option is set to 
+**     "rw", then the database is opened for read-write (but not create) 
+**     access, as if SQLITE_OPEN_READWRITE (but not SQLITE_OPEN_CREATE) had 
+**     been set. ^Value "rwc" is equivalent to setting both 
+**     SQLITE_OPEN_READWRITE and SQLITE_OPEN_CREATE. ^If sqlite3_open_v2() is 
+**     used, it is an error to specify a value for the mode parameter that is 
+**     less restrictive than that specified by the flags passed as the third 
+**     parameter.
+**
+**   <li> <b>cache</b>: ^The cache parameter may be set to either "shared" or
+**     "private". ^Setting it to "shared" is equivalent to setting the
+**     SQLITE_OPEN_SHAREDCACHE bit in the flags argument passed to
+**     sqlite3_open_v2(). ^Setting the cache parameter to "private" is 
+**     equivalent to setting the SQLITE_OPEN_PRIVATECACHE bit.
+**     ^If sqlite3_open_v2() is used and the "cache" parameter is present in
+**     a URI filename, its value overrides any behaviour requested by setting
+**     SQLITE_OPEN_PRIVATECACHE or SQLITE_OPEN_SHAREDCACHE flag.
+** </ul>
+**
+** ^Specifying an unknown parameter in the query component of a URI is not an
+** error.  Future versions of SQLite might understand additional query
+** parameters.  See "[query parameters with special meaning to SQLite]" for
+** additional information.
+**
+** [[URI filename examples]] <h3>URI filename examples</h3>
+**
+** <table border="1" align=center cellpadding=5>
+** <tr><th> URI filenames <th> Results
+** <tr><td> file:data.db <td> 
+**          Open the file "data.db" in the current directory.
+** <tr><td> file:/home/fred/data.db<br>
+**          file:///home/fred/data.db <br> 
+**          file://localhost/home/fred/data.db <br> <td> 
+**          Open the database file "/home/fred/data.db".
+** <tr><td> file://darkstar/home/fred/data.db <td> 
+**          An error. "darkstar" is not a recognized authority.
+** <tr><td style="white-space:nowrap"> 
+**          file:///C:/Documents%20and%20Settings/fred/Desktop/data.db
+**     <td> Windows only: Open the file "data.db" on fred's desktop on drive
+**          C:. Note that the %20 escaping in this example is not strictly 
+**          necessary - space characters can be used literally
+**          in URI filenames.
+** <tr><td> file:data.db?mode=ro&cache=private <td> 
+**          Open file "data.db" in the current directory for read-only access.
+**          Regardless of whether or not shared-cache mode is enabled by
+**          default, use a private cache.
+** <tr><td> file:/home/fred/data.db?vfs=unix-nolock <td>
+**          Open file "/home/fred/data.db". Use the special VFS "unix-nolock".
+** <tr><td> file:data.db?mode=readonly <td> 
+**          An error. "readonly" is not a valid option for the "mode" parameter.
+** </table>
+**
+** ^URI hexadecimal escape sequences (%HH) are supported within the path and
+** query components of a URI. A hexadecimal escape sequence consists of a
+** percent sign - "%" - followed by exactly two hexadecimal digits 
+** specifying an octet value. ^Before the path or query components of a
+** URI filename are interpreted, they are encoded using UTF-8 and all 
+** hexadecimal escape sequences replaced by a single byte containing the
+** corresponding octet. If this process generates an invalid UTF-8 encoding,
+** the results are undefined.
+**
+** <b>Note to Windows users:</b>  The encoding used for the filename argument
+** of sqlite3_open() and sqlite3_open_v2() must be UTF-8, not whatever
+** codepage is currently defined.  Filenames containing international
+** characters must be converted to UTF-8 prior to passing them into
+** sqlite3_open() or sqlite3_open_v2().
+*/
+int sqlite3_open(
+  const char *filename,   /* Database filename (UTF-8) */
+  sqlite3 **ppDb          /* OUT: SQLite db handle */
+);
+int sqlite3_open16(
+  const void *filename,   /* Database filename (UTF-16) */
+  sqlite3 **ppDb          /* OUT: SQLite db handle */
+);
+int sqlite3_open_v2(
+  const char *filename,   /* Database filename (UTF-8) */
+  sqlite3 **ppDb,         /* OUT: SQLite db handle */
+  int flags,              /* Flags */
+  const char *zVfs        /* Name of VFS module to use */
+);
+
+/*
+** CAPI3REF: Obtain Values For URI Parameters
+**
+** This is a utility routine, useful to VFS implementations, that checks
+** to see if a database file was a URI that contained a specific query 
+** parameter, and if so obtains the value of the query parameter.
+**
+** The zFilename argument is the filename pointer passed into the xOpen()
+** method of a VFS implementation.  The zParam argument is the name of the
+** query parameter we seek.  This routine returns the value of the zParam
+** parameter if it exists.  If the parameter does not exist, this routine
+** returns a NULL pointer.
+**
+** If the zFilename argument to this function is not a pointer that SQLite
+** passed into the xOpen VFS method, then the behavior of this routine
+** is undefined and probably undesirable.
+*/
+const char *sqlite3_uri_parameter(const char *zFilename, const char *zParam);
+
+
+/*
+** CAPI3REF: Error Codes And Messages
+**
+** ^The sqlite3_errcode() interface returns the numeric [result code] or
+** [extended result code] for the most recent failed sqlite3_* API call
+** associated with a [database connection]. If a prior API call failed
+** but the most recent API call succeeded, the return value from
+** sqlite3_errcode() is undefined.  ^The sqlite3_extended_errcode()
+** interface is the same except that it always returns the 
+** [extended result code] even when extended result codes are
+** disabled.
+**
+** ^The sqlite3_errmsg() and sqlite3_errmsg16() return English-language
+** text that describes the error, as either UTF-8 or UTF-16 respectively.
+** ^(Memory to hold the error message string is managed internally.
+** The application does not need to worry about freeing the result.
+** However, the error string might be overwritten or deallocated by
+** subsequent calls to other SQLite interface functions.)^
+**
+** When the serialized [threading mode] is in use, it might be the
+** case that a second error occurs on a separate thread in between
+** the time of the first error and the call to these interfaces.
+** When that happens, the second error will be reported since these
+** interfaces always report the most recent result.  To avoid
+** this, each thread can obtain exclusive use of the [database connection] D
+** by invoking [sqlite3_mutex_enter]([sqlite3_db_mutex](D)) before beginning
+** to use D and invoking [sqlite3_mutex_leave]([sqlite3_db_mutex](D)) after
+** all calls to the interfaces listed here are completed.
+**
+** If an interface fails with SQLITE_MISUSE, that means the interface
+** was invoked incorrectly by the application.  In that case, the
+** error code and message may or may not be set.
+*/
+int sqlite3_errcode(sqlite3 *db);
+int sqlite3_extended_errcode(sqlite3 *db);
+const char *sqlite3_errmsg(sqlite3*);
+const void *sqlite3_errmsg16(sqlite3*);
+
+/*
+** CAPI3REF: SQL Statement Object
+** KEYWORDS: {prepared statement} {prepared statements}
+**
+** An instance of this object represents a single SQL statement.
+** This object is variously known as a "prepared statement" or a
+** "compiled SQL statement" or simply as a "statement".
+**
+** The life of a statement object goes something like this:
+**
+** <ol>
+** <li> Create the object using [sqlite3_prepare_v2()] or a related
+**      function.
+** <li> Bind values to [host parameters] using the sqlite3_bind_*()
+**      interfaces.
+** <li> Run the SQL by calling [sqlite3_step()] one or more times.
+** <li> Reset the statement using [sqlite3_reset()] then go back
+**      to step 2.  Do this zero or more times.
+** <li> Destroy the object using [sqlite3_finalize()].
+** </ol>
+**
+** Refer to documentation on individual methods above for additional
+** information.
+*/
+typedef struct sqlite3_stmt sqlite3_stmt;
+
+/*
+** CAPI3REF: Run-time Limits
+**
+** ^(This interface allows the size of various constructs to be limited
+** on a connection by connection basis.  The first parameter is the
+** [database connection] whose limit is to be set or queried.  The
+** second parameter is one of the [limit categories] that define a
+** class of constructs to be size limited.  The third parameter is the
+** new limit for that construct.)^
+**
+** ^If the new limit is a negative number, the limit is unchanged.
+** ^(For each limit category SQLITE_LIMIT_<i>NAME</i> there is a 
+** [limits | hard upper bound]
+** set at compile-time by a C preprocessor macro called
+** [limits | SQLITE_MAX_<i>NAME</i>].
+** (The "_LIMIT_" in the name is changed to "_MAX_".))^
+** ^Attempts to increase a limit above its hard upper bound are
+** silently truncated to the hard upper bound.
+**
+** ^Regardless of whether or not the limit was changed, the 
+** [sqlite3_limit()] interface returns the prior value of the limit.
+** ^Hence, to find the current value of a limit without changing it,
+** simply invoke this interface with the third parameter set to -1.
+**
+** Run-time limits are intended for use in applications that manage
+** both their own internal database and also databases that are controlled
+** by untrusted external sources.  An example application might be a
+** web browser that has its own databases for storing history and
+** separate databases controlled by JavaScript applications downloaded
+** off the Internet.  The internal databases can be given the
+** large, default limits.  Databases managed by external sources can
+** be given much smaller limits designed to prevent a denial of service
+** attack.  Developers might also want to use the [sqlite3_set_authorizer()]
+** interface to further control untrusted SQL.  The size of the database
+** created by an untrusted script can be contained using the
+** [max_page_count] [PRAGMA].
+**
+** New run-time limit categories may be added in future releases.
+*/
+int sqlite3_limit(sqlite3*, int id, int newVal);
+
+/*
+** CAPI3REF: Run-Time Limit Categories
+** KEYWORDS: {limit category} {*limit categories}
+**
+** These constants define various performance limits
+** that can be lowered at run-time using [sqlite3_limit()].
+** The synopsis of the meanings of the various limits is shown below.
+** Additional information is available at [limits | Limits in SQLite].
+**
+** <dl>
+** [[SQLITE_LIMIT_LENGTH]] ^(<dt>SQLITE_LIMIT_LENGTH</dt>
+** <dd>The maximum size of any string or BLOB or table row, in bytes.<dd>)^
+**
+** [[SQLITE_LIMIT_SQL_LENGTH]] ^(<dt>SQLITE_LIMIT_SQL_LENGTH</dt>
+** <dd>The maximum length of an SQL statement, in bytes.</dd>)^
+**
+** [[SQLITE_LIMIT_COLUMN]] ^(<dt>SQLITE_LIMIT_COLUMN</dt>
+** <dd>The maximum number of columns in a table definition or in the
+** result set of a [SELECT] or the maximum number of columns in an index
+** or in an ORDER BY or GROUP BY clause.</dd>)^
+**
+** [[SQLITE_LIMIT_EXPR_DEPTH]] ^(<dt>SQLITE_LIMIT_EXPR_DEPTH</dt>
+** <dd>The maximum depth of the parse tree on any expression.</dd>)^
+**
+** [[SQLITE_LIMIT_COMPOUND_SELECT]] ^(<dt>SQLITE_LIMIT_COMPOUND_SELECT</dt>
+** <dd>The maximum number of terms in a compound SELECT statement.</dd>)^
+**
+** [[SQLITE_LIMIT_VDBE_OP]] ^(<dt>SQLITE_LIMIT_VDBE_OP</dt>
+** <dd>The maximum number of instructions in a virtual machine program
+** used to implement an SQL statement.  This limit is not currently
+** enforced, though that might be added in some future release of
+** SQLite.</dd>)^
+**
+** [[SQLITE_LIMIT_FUNCTION_ARG]] ^(<dt>SQLITE_LIMIT_FUNCTION_ARG</dt>
+** <dd>The maximum number of arguments on a function.</dd>)^
+**
+** [[SQLITE_LIMIT_ATTACHED]] ^(<dt>SQLITE_LIMIT_ATTACHED</dt>
+** <dd>The maximum number of [ATTACH | attached databases].)^</dd>
+**
+** [[SQLITE_LIMIT_LIKE_PATTERN_LENGTH]]
+** ^(<dt>SQLITE_LIMIT_LIKE_PATTERN_LENGTH</dt>
+** <dd>The maximum length of the pattern argument to the [LIKE] or
+** [GLOB] operators.</dd>)^
+**
+** [[SQLITE_LIMIT_VARIABLE_NUMBER]]
+** ^(<dt>SQLITE_LIMIT_VARIABLE_NUMBER</dt>
+** <dd>The maximum index number of any [parameter] in an SQL statement.)^
+**
+** [[SQLITE_LIMIT_TRIGGER_DEPTH]] ^(<dt>SQLITE_LIMIT_TRIGGER_DEPTH</dt>
+** <dd>The maximum depth of recursion for triggers.</dd>)^
+** </dl>
+*/
+#define SQLITE_LIMIT_LENGTH                    0
+#define SQLITE_LIMIT_SQL_LENGTH                1
+#define SQLITE_LIMIT_COLUMN                    2
+#define SQLITE_LIMIT_EXPR_DEPTH                3
+#define SQLITE_LIMIT_COMPOUND_SELECT           4
+#define SQLITE_LIMIT_VDBE_OP                   5
+#define SQLITE_LIMIT_FUNCTION_ARG              6
+#define SQLITE_LIMIT_ATTACHED                  7
+#define SQLITE_LIMIT_LIKE_PATTERN_LENGTH       8
+#define SQLITE_LIMIT_VARIABLE_NUMBER           9
+#define SQLITE_LIMIT_TRIGGER_DEPTH            10
+
+/*
+** CAPI3REF: Compiling An SQL Statement
+** KEYWORDS: {SQL statement compiler}
+**
+** To execute an SQL query, it must first be compiled into a byte-code
+** program using one of these routines.
+**
+** The first argument, "db", is a [database connection] obtained from a
+** prior successful call to [sqlite3_open()], [sqlite3_open_v2()] or
+** [sqlite3_open16()].  The database connection must not have been closed.
+**
+** The second argument, "zSql", is the statement to be compiled, encoded
+** as either UTF-8 or UTF-16.  The sqlite3_prepare() and sqlite3_prepare_v2()
+** interfaces use UTF-8, and sqlite3_prepare16() and sqlite3_prepare16_v2()
+** use UTF-16.
+**
+** ^If the nByte argument is less than zero, then zSql is read up to the
+** first zero terminator. ^If nByte is non-negative, then it is the maximum
+** number of  bytes read from zSql.  ^When nByte is non-negative, the
+** zSql string ends at either the first '\000' or '\u0000' character or
+** the nByte-th byte, whichever comes first. If the caller knows
+** that the supplied string is nul-terminated, then there is a small
+** performance advantage to be gained by passing an nByte parameter that
+** is equal to the number of bytes in the input string <i>including</i>
+** the nul-terminator bytes as this saves SQLite from having to
+** make a copy of the input string.
+**
+** ^If pzTail is not NULL then *pzTail is made to point to the first byte
+** past the end of the first SQL statement in zSql.  These routines only
+** compile the first statement in zSql, so *pzTail is left pointing to
+** what remains uncompiled.
+**
+** ^*ppStmt is left pointing to a compiled [prepared statement] that can be
+** executed using [sqlite3_step()].  ^If there is an error, *ppStmt is set
+** to NULL.  ^If the input text contains no SQL (if the input is an empty
+** string or a comment) then *ppStmt is set to NULL.
+** The calling procedure is responsible for deleting the compiled
+** SQL statement using [sqlite3_finalize()] after it has finished with it.
+** ppStmt may not be NULL.
+**
+** ^On success, the sqlite3_prepare() family of routines return [SQLITE_OK];
+** otherwise an [error code] is returned.
+**
+** The sqlite3_prepare_v2() and sqlite3_prepare16_v2() interfaces are
+** recommended for all new programs. The two older interfaces are retained
+** for backwards compatibility, but their use is discouraged.
+** ^In the "v2" interfaces, the prepared statement
+** that is returned (the [sqlite3_stmt] object) contains a copy of the
+** original SQL text. This causes the [sqlite3_step()] interface to
+** behave differently in three ways:
+**
+** <ol>
+** <li>
+** ^If the database schema changes, instead of returning [SQLITE_SCHEMA] as it
+** always used to do, [sqlite3_step()] will automatically recompile the SQL
+** statement and try to run it again.
+** </li>
+**
+** <li>
+** ^When an error occurs, [sqlite3_step()] will return one of the detailed
+** [error codes] or [extended error codes].  ^The legacy behavior was that
+** [sqlite3_step()] would only return a generic [SQLITE_ERROR] result code
+** and the application would have to make a second call to [sqlite3_reset()]
+** in order to find the underlying cause of the problem. With the "v2" prepare
+** interfaces, the underlying reason for the error is returned immediately.
+** </li>
+**
+** <li>
+** ^If the specific value bound to [parameter | host parameter] in the 
+** WHERE clause might influence the choice of query plan for a statement,
+** then the statement will be automatically recompiled, as if there had been 
+** a schema change, on the first  [sqlite3_step()] call following any change
+** to the [sqlite3_bind_text | bindings] of that [parameter]. 
+** ^The specific value of WHERE-clause [parameter] might influence the 
+** choice of query plan if the parameter is the left-hand side of a [LIKE]
+** or [GLOB] operator or if the parameter is compared to an indexed column
+** and the [SQLITE_ENABLE_STAT3] compile-time option is enabled.
+** the 
+** </li>
+** </ol>
+*/
+int sqlite3_prepare(
+  sqlite3 *db,            /* Database handle */
+  const char *zSql,       /* SQL statement, UTF-8 encoded */
+  int nByte,              /* Maximum length of zSql in bytes. */
+  sqlite3_stmt **ppStmt,  /* OUT: Statement handle */
+  const char **pzTail     /* OUT: Pointer to unused portion of zSql */
+);
+int sqlite3_prepare_v2(
+  sqlite3 *db,            /* Database handle */
+  const char *zSql,       /* SQL statement, UTF-8 encoded */
+  int nByte,              /* Maximum length of zSql in bytes. */
+  sqlite3_stmt **ppStmt,  /* OUT: Statement handle */
+  const char **pzTail     /* OUT: Pointer to unused portion of zSql */
+);
+int sqlite3_prepare16(
+  sqlite3 *db,            /* Database handle */
+  const void *zSql,       /* SQL statement, UTF-16 encoded */
+  int nByte,              /* Maximum length of zSql in bytes. */
+  sqlite3_stmt **ppStmt,  /* OUT: Statement handle */
+  const void **pzTail     /* OUT: Pointer to unused portion of zSql */
+);
+int sqlite3_prepare16_v2(
+  sqlite3 *db,            /* Database handle */
+  const void *zSql,       /* SQL statement, UTF-16 encoded */
+  int nByte,              /* Maximum length of zSql in bytes. */
+  sqlite3_stmt **ppStmt,  /* OUT: Statement handle */
+  const void **pzTail     /* OUT: Pointer to unused portion of zSql */
+);
+
+/*
+** CAPI3REF: Retrieving Statement SQL
+**
+** ^This interface can be used to retrieve a saved copy of the original
+** SQL text used to create a [prepared statement] if that statement was
+** compiled using either [sqlite3_prepare_v2()] or [sqlite3_prepare16_v2()].
+*/
+const char *sqlite3_sql(sqlite3_stmt *pStmt);
+
+/*
+** CAPI3REF: Determine If An SQL Statement Writes The Database
+**
+** ^The sqlite3_stmt_readonly(X) interface returns true (non-zero) if
+** and only if the [prepared statement] X makes no direct changes to
+** the content of the database file.
+**
+** Note that [application-defined SQL functions] or
+** [virtual tables] might change the database indirectly as a side effect.  
+** ^(For example, if an application defines a function "eval()" that 
+** calls [sqlite3_exec()], then the following SQL statement would
+** change the database file through side-effects:
+**
+** <blockquote><pre>
+**    SELECT eval('DELETE FROM t1') FROM t2;
+** </pre></blockquote>
+**
+** But because the [SELECT] statement does not change the database file
+** directly, sqlite3_stmt_readonly() would still return true.)^
+**
+** ^Transaction control statements such as [BEGIN], [COMMIT], [ROLLBACK],
+** [SAVEPOINT], and [RELEASE] cause sqlite3_stmt_readonly() to return true,
+** since the statements themselves do not actually modify the database but
+** rather they control the timing of when other statements modify the 
+** database.  ^The [ATTACH] and [DETACH] statements also cause
+** sqlite3_stmt_readonly() to return true since, while those statements
+** change the configuration of a database connection, they do not make 
+** changes to the content of the database files on disk.
+*/
+int sqlite3_stmt_readonly(sqlite3_stmt *pStmt);
+
+/*
+** CAPI3REF: Dynamically Typed Value Object
+** KEYWORDS: {protected sqlite3_value} {unprotected sqlite3_value}
+**
+** SQLite uses the sqlite3_value object to represent all values
+** that can be stored in a database table. SQLite uses dynamic typing
+** for the values it stores.  ^Values stored in sqlite3_value objects
+** can be integers, floating point values, strings, BLOBs, or NULL.
+**
+** An sqlite3_value object may be either "protected" or "unprotected".
+** Some interfaces require a protected sqlite3_value.  Other interfaces
+** will accept either a protected or an unprotected sqlite3_value.
+** Every interface that accepts sqlite3_value arguments specifies
+** whether or not it requires a protected sqlite3_value.
+**
+** The terms "protected" and "unprotected" refer to whether or not
+** a mutex is held.  An internal mutex is held for a protected
+** sqlite3_value object but no mutex is held for an unprotected
+** sqlite3_value object.  If SQLite is compiled to be single-threaded
+** (with [SQLITE_THREADSAFE=0] and with [sqlite3_threadsafe()] returning 0)
+** or if SQLite is run in one of reduced mutex modes 
+** [SQLITE_CONFIG_SINGLETHREAD] or [SQLITE_CONFIG_MULTITHREAD]
+** then there is no distinction between protected and unprotected
+** sqlite3_value objects and they can be used interchangeably.  However,
+** for maximum code portability it is recommended that applications
+** still make the distinction between protected and unprotected
+** sqlite3_value objects even when not strictly required.
+**
+** ^The sqlite3_value objects that are passed as parameters into the
+** implementation of [application-defined SQL functions] are protected.
+** ^The sqlite3_value object returned by
+** [sqlite3_column_value()] is unprotected.
+** Unprotected sqlite3_value objects may only be used with
+** [sqlite3_result_value()] and [sqlite3_bind_value()].
+** The [sqlite3_value_blob | sqlite3_value_type()] family of
+** interfaces require protected sqlite3_value objects.
+*/
+typedef struct Mem sqlite3_value;
+
+/*
+** CAPI3REF: SQL Function Context Object
+**
+** The context in which an SQL function executes is stored in an
+** sqlite3_context object.  ^A pointer to an sqlite3_context object
+** is always first parameter to [application-defined SQL functions].
+** The application-defined SQL function implementation will pass this
+** pointer through into calls to [sqlite3_result_int | sqlite3_result()],
+** [sqlite3_aggregate_context()], [sqlite3_user_data()],
+** [sqlite3_context_db_handle()], [sqlite3_get_auxdata()],
+** and/or [sqlite3_set_auxdata()].
+*/
+typedef struct sqlite3_context sqlite3_context;
+
+/*
+** CAPI3REF: Binding Values To Prepared Statements
+** KEYWORDS: {host parameter} {host parameters} {host parameter name}
+** KEYWORDS: {SQL parameter} {SQL parameters} {parameter binding}
+**
+** ^(In the SQL statement text input to [sqlite3_prepare_v2()] and its variants,
+** literals may be replaced by a [parameter] that matches one of following
+** templates:
+**
+** <ul>
+** <li>  ?
+** <li>  ?NNN
+** <li>  :VVV
+** <li>  @VVV
+** <li>  $VVV
+** </ul>
+**
+** In the templates above, NNN represents an integer literal,
+** and VVV represents an alphanumeric identifier.)^  ^The values of these
+** parameters (also called "host parameter names" or "SQL parameters")
+** can be set using the sqlite3_bind_*() routines defined here.
+**
+** ^The first argument to the sqlite3_bind_*() routines is always
+** a pointer to the [sqlite3_stmt] object returned from
+** [sqlite3_prepare_v2()] or its variants.
+**
+** ^The second argument is the index of the SQL parameter to be set.
+** ^The leftmost SQL parameter has an index of 1.  ^When the same named
+** SQL parameter is used more than once, second and subsequent
+** occurrences have the same index as the first occurrence.
+** ^The index for named parameters can be looked up using the
+** [sqlite3_bind_parameter_index()] API if desired.  ^The index
+** for "?NNN" parameters is the value of NNN.
+** ^The NNN value must be between 1 and the [sqlite3_limit()]
+** parameter [SQLITE_LIMIT_VARIABLE_NUMBER] (default value: 999).
+**
+** ^The third argument is the value to bind to the parameter.
+**
+** ^(In those routines that have a fourth argument, its value is the
+** number of bytes in the parameter.  To be clear: the value is the
+** number of <u>bytes</u> in the value, not the number of characters.)^
+** ^If the fourth parameter is negative, the length of the string is
+** the number of bytes up to the first zero terminator.
+** If a non-negative fourth parameter is provided to sqlite3_bind_text()
+** or sqlite3_bind_text16() then that parameter must be the byte offset
+** where the NUL terminator would occur assuming the string were NUL
+** terminated.  If any NUL characters occur at byte offsets less than 
+** the value of the fourth parameter then the resulting string value will
+** contain embedded NULs.  The result of expressions involving strings
+** with embedded NULs is undefined.
+**
+** ^The fifth argument to sqlite3_bind_blob(), sqlite3_bind_text(), and
+** sqlite3_bind_text16() is a destructor used to dispose of the BLOB or
+** string after SQLite has finished with it.  ^The destructor is called
+** to dispose of the BLOB or string even if the call to sqlite3_bind_blob(),
+** sqlite3_bind_text(), or sqlite3_bind_text16() fails.  
+** ^If the fifth argument is
+** the special value [SQLITE_STATIC], then SQLite assumes that the
+** information is in static, unmanaged space and does not need to be freed.
+** ^If the fifth argument has the value [SQLITE_TRANSIENT], then
+** SQLite makes its own private copy of the data immediately, before
+** the sqlite3_bind_*() routine returns.
+**
+** ^The sqlite3_bind_zeroblob() routine binds a BLOB of length N that
+** is filled with zeroes.  ^A zeroblob uses a fixed amount of memory
+** (just an integer to hold its size) while it is being processed.
+** Zeroblobs are intended to serve as placeholders for BLOBs whose
+** content is later written using
+** [sqlite3_blob_open | incremental BLOB I/O] routines.
+** ^A negative value for the zeroblob results in a zero-length BLOB.
+**
+** ^If any of the sqlite3_bind_*() routines are called with a NULL pointer
+** for the [prepared statement] or with a prepared statement for which
+** [sqlite3_step()] has been called more recently than [sqlite3_reset()],
+** then the call will return [SQLITE_MISUSE].  If any sqlite3_bind_()
+** routine is passed a [prepared statement] that has been finalized, the
+** result is undefined and probably harmful.
+**
+** ^Bindings are not cleared by the [sqlite3_reset()] routine.
+** ^Unbound parameters are interpreted as NULL.
+**
+** ^The sqlite3_bind_* routines return [SQLITE_OK] on success or an
+** [error code] if anything goes wrong.
+** ^[SQLITE_RANGE] is returned if the parameter
+** index is out of range.  ^[SQLITE_NOMEM] is returned if malloc() fails.
+**
+** See also: [sqlite3_bind_parameter_count()],
+** [sqlite3_bind_parameter_name()], and [sqlite3_bind_parameter_index()].
+*/
+int sqlite3_bind_blob(sqlite3_stmt*, int, const void*, int n, void(*)(void*));
+int sqlite3_bind_double(sqlite3_stmt*, int, double);
+int sqlite3_bind_int(sqlite3_stmt*, int, int);
+int sqlite3_bind_int64(sqlite3_stmt*, int, sqlite3_int64);
+int sqlite3_bind_null(sqlite3_stmt*, int);
+int sqlite3_bind_text(sqlite3_stmt*, int, const char*, int n, void(*)(void*));
+int sqlite3_bind_text16(sqlite3_stmt*, int, const void*, int, void(*)(void*));
+int sqlite3_bind_value(sqlite3_stmt*, int, const sqlite3_value*);
+int sqlite3_bind_zeroblob(sqlite3_stmt*, int, int n);
+
+/*
+** CAPI3REF: Number Of SQL Parameters
+**
+** ^This routine can be used to find the number of [SQL parameters]
+** in a [prepared statement].  SQL parameters are tokens of the
+** form "?", "?NNN", ":AAA", "$AAA", or "@AAA" that serve as
+** placeholders for values that are [sqlite3_bind_blob | bound]
+** to the parameters at a later time.
+**
+** ^(This routine actually returns the index of the largest (rightmost)
+** parameter. For all forms except ?NNN, this will correspond to the
+** number of unique parameters.  If parameters of the ?NNN form are used,
+** there may be gaps in the list.)^
+**
+** See also: [sqlite3_bind_blob|sqlite3_bind()],
+** [sqlite3_bind_parameter_name()], and
+** [sqlite3_bind_parameter_index()].
+*/
+int sqlite3_bind_parameter_count(sqlite3_stmt*);
+
+/*
+** CAPI3REF: Name Of A Host Parameter
+**
+** ^The sqlite3_bind_parameter_name(P,N) interface returns
+** the name of the N-th [SQL parameter] in the [prepared statement] P.
+** ^(SQL parameters of the form "?NNN" or ":AAA" or "@AAA" or "$AAA"
+** have a name which is the string "?NNN" or ":AAA" or "@AAA" or "$AAA"
+** respectively.
+** In other words, the initial ":" or "$" or "@" or "?"
+** is included as part of the name.)^
+** ^Parameters of the form "?" without a following integer have no name
+** and are referred to as "nameless" or "anonymous parameters".
+**
+** ^The first host parameter has an index of 1, not 0.
+**
+** ^If the value N is out of range or if the N-th parameter is
+** nameless, then NULL is returned.  ^The returned string is
+** always in UTF-8 encoding even if the named parameter was
+** originally specified as UTF-16 in [sqlite3_prepare16()] or
+** [sqlite3_prepare16_v2()].
+**
+** See also: [sqlite3_bind_blob|sqlite3_bind()],
+** [sqlite3_bind_parameter_count()], and
+** [sqlite3_bind_parameter_index()].
+*/
+const char *sqlite3_bind_parameter_name(sqlite3_stmt*, int);
+
+/*
+** CAPI3REF: Index Of A Parameter With A Given Name
+**
+** ^Return the index of an SQL parameter given its name.  ^The
+** index value returned is suitable for use as the second
+** parameter to [sqlite3_bind_blob|sqlite3_bind()].  ^A zero
+** is returned if no matching parameter is found.  ^The parameter
+** name must be given in UTF-8 even if the original statement
+** was prepared from UTF-16 text using [sqlite3_prepare16_v2()].
+**
+** See also: [sqlite3_bind_blob|sqlite3_bind()],
+** [sqlite3_bind_parameter_count()], and
+** [sqlite3_bind_parameter_index()].
+*/
+int sqlite3_bind_parameter_index(sqlite3_stmt*, const char *zName);
+
+/*
+** CAPI3REF: Reset All Bindings On A Prepared Statement
+**
+** ^Contrary to the intuition of many, [sqlite3_reset()] does not reset
+** the [sqlite3_bind_blob | bindings] on a [prepared statement].
+** ^Use this routine to reset all host parameters to NULL.
+*/
+int sqlite3_clear_bindings(sqlite3_stmt*);
+
+/*
+** CAPI3REF: Number Of Columns In A Result Set
+**
+** ^Return the number of columns in the result set returned by the
+** [prepared statement]. ^This routine returns 0 if pStmt is an SQL
+** statement that does not return data (for example an [UPDATE]).
+**
+** See also: [sqlite3_data_count()]
+*/
+int sqlite3_column_count(sqlite3_stmt *pStmt);
+
+/*
+** CAPI3REF: Column Names In A Result Set
+**
+** ^These routines return the name assigned to a particular column
+** in the result set of a [SELECT] statement.  ^The sqlite3_column_name()
+** interface returns a pointer to a zero-terminated UTF-8 string
+** and sqlite3_column_name16() returns a pointer to a zero-terminated
+** UTF-16 string.  ^The first parameter is the [prepared statement]
+** that implements the [SELECT] statement. ^The second parameter is the
+** column number.  ^The leftmost column is number 0.
+**
+** ^The returned string pointer is valid until either the [prepared statement]
+** is destroyed by [sqlite3_finalize()] or until the statement is automatically
+** reprepared by the first call to [sqlite3_step()] for a particular run
+** or until the next call to
+** sqlite3_column_name() or sqlite3_column_name16() on the same column.
+**
+** ^If sqlite3_malloc() fails during the processing of either routine
+** (for example during a conversion from UTF-8 to UTF-16) then a
+** NULL pointer is returned.
+**
+** ^The name of a result column is the value of the "AS" clause for
+** that column, if there is an AS clause.  If there is no AS clause
+** then the name of the column is unspecified and may change from
+** one release of SQLite to the next.
+*/
+const char *sqlite3_column_name(sqlite3_stmt*, int N);
+const void *sqlite3_column_name16(sqlite3_stmt*, int N);
+
+/*
+** CAPI3REF: Source Of Data In A Query Result
+**
+** ^These routines provide a means to determine the database, table, and
+** table column that is the origin of a particular result column in
+** [SELECT] statement.
+** ^The name of the database or table or column can be returned as
+** either a UTF-8 or UTF-16 string.  ^The _database_ routines return
+** the database name, the _table_ routines return the table name, and
+** the origin_ routines return the column name.
+** ^The returned string is valid until the [prepared statement] is destroyed
+** using [sqlite3_finalize()] or until the statement is automatically
+** reprepared by the first call to [sqlite3_step()] for a particular run
+** or until the same information is requested
+** again in a different encoding.
+**
+** ^The names returned are the original un-aliased names of the
+** database, table, and column.
+**
+** ^The first argument to these interfaces is a [prepared statement].
+** ^These functions return information about the Nth result column returned by
+** the statement, where N is the second function argument.
+** ^The left-most column is column 0 for these routines.
+**
+** ^If the Nth column returned by the statement is an expression or
+** subquery and is not a column value, then all of these functions return
+** NULL.  ^These routine might also return NULL if a memory allocation error
+** occurs.  ^Otherwise, they return the name of the attached database, table,
+** or column that query result column was extracted from.
+**
+** ^As with all other SQLite APIs, those whose names end with "16" return
+** UTF-16 encoded strings and the other functions return UTF-8.
+**
+** ^These APIs are only available if the library was compiled with the
+** [SQLITE_ENABLE_COLUMN_METADATA] C-preprocessor symbol.
+**
+** If two or more threads call one or more of these routines against the same
+** prepared statement and column at the same time then the results are
+** undefined.
+**
+** If two or more threads call one or more
+** [sqlite3_column_database_name | column metadata interfaces]
+** for the same [prepared statement] and result column
+** at the same time then the results are undefined.
+*/
+const char *sqlite3_column_database_name(sqlite3_stmt*,int);
+const void *sqlite3_column_database_name16(sqlite3_stmt*,int);
+const char *sqlite3_column_table_name(sqlite3_stmt*,int);
+const void *sqlite3_column_table_name16(sqlite3_stmt*,int);
+const char *sqlite3_column_origin_name(sqlite3_stmt*,int);
+const void *sqlite3_column_origin_name16(sqlite3_stmt*,int);
+
+/*
+** CAPI3REF: Declared Datatype Of A Query Result
+**
+** ^(The first parameter is a [prepared statement].
+** If this statement is a [SELECT] statement and the Nth column of the
+** returned result set of that [SELECT] is a table column (not an
+** expression or subquery) then the declared type of the table
+** column is returned.)^  ^If the Nth column of the result set is an
+** expression or subquery, then a NULL pointer is returned.
+** ^The returned string is always UTF-8 encoded.
+**
+** ^(For example, given the database schema:
+**
+** CREATE TABLE t1(c1 VARIANT);
+**
+** and the following statement to be compiled:
+**
+** SELECT c1 + 1, c1 FROM t1;
+**
+** this routine would return the string "VARIANT" for the second result
+** column (i==1), and a NULL pointer for the first result column (i==0).)^
+**
+** ^SQLite uses dynamic run-time typing.  ^So just because a column
+** is declared to contain a particular type does not mean that the
+** data stored in that column is of the declared type.  SQLite is
+** strongly typed, but the typing is dynamic not static.  ^Type
+** is associated with individual values, not with the containers
+** used to hold those values.
+*/
+const char *sqlite3_column_decltype(sqlite3_stmt*,int);
+const void *sqlite3_column_decltype16(sqlite3_stmt*,int);
+
+/*
+** CAPI3REF: Evaluate An SQL Statement
+**
+** After a [prepared statement] has been prepared using either
+** [sqlite3_prepare_v2()] or [sqlite3_prepare16_v2()] or one of the legacy
+** interfaces [sqlite3_prepare()] or [sqlite3_prepare16()], this function
+** must be called one or more times to evaluate the statement.
+**
+** The details of the behavior of the sqlite3_step() interface depend
+** on whether the statement was prepared using the newer "v2" interface
+** [sqlite3_prepare_v2()] and [sqlite3_prepare16_v2()] or the older legacy
+** interface [sqlite3_prepare()] and [sqlite3_prepare16()].  The use of the
+** new "v2" interface is recommended for new applications but the legacy
+** interface will continue to be supported.
+**
+** ^In the legacy interface, the return value will be either [SQLITE_BUSY],
+** [SQLITE_DONE], [SQLITE_ROW], [SQLITE_ERROR], or [SQLITE_MISUSE].
+** ^With the "v2" interface, any of the other [result codes] or
+** [extended result codes] might be returned as well.
+**
+** ^[SQLITE_BUSY] means that the database engine was unable to acquire the
+** database locks it needs to do its job.  ^If the statement is a [COMMIT]
+** or occurs outside of an explicit transaction, then you can retry the
+** statement.  If the statement is not a [COMMIT] and occurs within an
+** explicit transaction then you should rollback the transaction before
+** continuing.
+**
+** ^[SQLITE_DONE] means that the statement has finished executing
+** successfully.  sqlite3_step() should not be called again on this virtual
+** machine without first calling [sqlite3_reset()] to reset the virtual
+** machine back to its initial state.
+**
+** ^If the SQL statement being executed returns any data, then [SQLITE_ROW]
+** is returned each time a new row of data is ready for processing by the
+** caller. The values may be accessed using the [column access functions].
+** sqlite3_step() is called again to retrieve the next row of data.
+**
+** ^[SQLITE_ERROR] means that a run-time error (such as a constraint
+** violation) has occurred.  sqlite3_step() should not be called again on
+** the VM. More information may be found by calling [sqlite3_errmsg()].
+** ^With the legacy interface, a more specific error code (for example,
+** [SQLITE_INTERRUPT], [SQLITE_SCHEMA], [SQLITE_CORRUPT], and so forth)
+** can be obtained by calling [sqlite3_reset()] on the
+** [prepared statement].  ^In the "v2" interface,
+** the more specific error code is returned directly by sqlite3_step().
+**
+** [SQLITE_MISUSE] means that the this routine was called inappropriately.
+** Perhaps it was called on a [prepared statement] that has
+** already been [sqlite3_finalize | finalized] or on one that had
+** previously returned [SQLITE_ERROR] or [SQLITE_DONE].  Or it could
+** be the case that the same database connection is being used by two or
+** more threads at the same moment in time.
+**
+** For all versions of SQLite up to and including 3.6.23.1, a call to
+** [sqlite3_reset()] was required after sqlite3_step() returned anything
+** other than [SQLITE_ROW] before any subsequent invocation of
+** sqlite3_step().  Failure to reset the prepared statement using 
+** [sqlite3_reset()] would result in an [SQLITE_MISUSE] return from
+** sqlite3_step().  But after version 3.6.23.1, sqlite3_step() began
+** calling [sqlite3_reset()] automatically in this circumstance rather
+** than returning [SQLITE_MISUSE].  This is not considered a compatibility
+** break because any application that ever receives an SQLITE_MISUSE error
+** is broken by definition.  The [SQLITE_OMIT_AUTORESET] compile-time option
+** can be used to restore the legacy behavior.
+**
+** <b>Goofy Interface Alert:</b> In the legacy interface, the sqlite3_step()
+** API always returns a generic error code, [SQLITE_ERROR], following any
+** error other than [SQLITE_BUSY] and [SQLITE_MISUSE].  You must call
+** [sqlite3_reset()] or [sqlite3_finalize()] in order to find one of the
+** specific [error codes] that better describes the error.
+** We admit that this is a goofy design.  The problem has been fixed
+** with the "v2" interface.  If you prepare all of your SQL statements
+** using either [sqlite3_prepare_v2()] or [sqlite3_prepare16_v2()] instead
+** of the legacy [sqlite3_prepare()] and [sqlite3_prepare16()] interfaces,
+** then the more specific [error codes] are returned directly
+** by sqlite3_step().  The use of the "v2" interface is recommended.
+*/
+int sqlite3_step(sqlite3_stmt*);
+
+/*
+** CAPI3REF: Number of columns in a result set
+**
+** ^The sqlite3_data_count(P) interface returns the number of columns in the
+** current row of the result set of [prepared statement] P.
+** ^If prepared statement P does not have results ready to return
+** (via calls to the [sqlite3_column_int | sqlite3_column_*()] of
+** interfaces) then sqlite3_data_count(P) returns 0.
+** ^The sqlite3_data_count(P) routine also returns 0 if P is a NULL pointer.
+** ^The sqlite3_data_count(P) routine returns 0 if the previous call to
+** [sqlite3_step](P) returned [SQLITE_DONE].  ^The sqlite3_data_count(P)
+** will return non-zero if previous call to [sqlite3_step](P) returned
+** [SQLITE_ROW], except in the case of the [PRAGMA incremental_vacuum]
+** where it always returns zero since each step of that multi-step
+** pragma returns 0 columns of data.
+**
+** See also: [sqlite3_column_count()]
+*/
+int sqlite3_data_count(sqlite3_stmt *pStmt);
+
+/*
+** CAPI3REF: Fundamental Datatypes
+** KEYWORDS: SQLITE_TEXT
+**
+** ^(Every value in SQLite has one of five fundamental datatypes:
+**
+** <ul>
+** <li> 64-bit signed integer
+** <li> 64-bit IEEE floating point number
+** <li> string
+** <li> BLOB
+** <li> NULL
+** </ul>)^
+**
+** These constants are codes for each of those types.
+**
+** Note that the SQLITE_TEXT constant was also used in SQLite version 2
+** for a completely different meaning.  Software that links against both
+** SQLite version 2 and SQLite version 3 should use SQLITE3_TEXT, not
+** SQLITE_TEXT.
+*/
+#define SQLITE_INTEGER  1
+#define SQLITE_FLOAT    2
+#define SQLITE_BLOB     4
+#define SQLITE_NULL     5
+#ifdef SQLITE_TEXT
+# undef SQLITE_TEXT
+#else
+# define SQLITE_TEXT     3
+#endif
+#define SQLITE3_TEXT     3
+
+/*
+** CAPI3REF: Result Values From A Query
+** KEYWORDS: {column access functions}
+**
+** These routines form the "result set" interface.
+**
+** ^These routines return information about a single column of the current
+** result row of a query.  ^In every case the first argument is a pointer
+** to the [prepared statement] that is being evaluated (the [sqlite3_stmt*]
+** that was returned from [sqlite3_prepare_v2()] or one of its variants)
+** and the second argument is the index of the column for which information
+** should be returned. ^The leftmost column of the result set has the index 0.
+** ^The number of columns in the result can be determined using
+** [sqlite3_column_count()].
+**
+** If the SQL statement does not currently point to a valid row, or if the
+** column index is out of range, the result is undefined.
+** These routines may only be called when the most recent call to
+** [sqlite3_step()] has returned [SQLITE_ROW] and neither
+** [sqlite3_reset()] nor [sqlite3_finalize()] have been called subsequently.
+** If any of these routines are called after [sqlite3_reset()] or
+** [sqlite3_finalize()] or after [sqlite3_step()] has returned
+** something other than [SQLITE_ROW], the results are undefined.
+** If [sqlite3_step()] or [sqlite3_reset()] or [sqlite3_finalize()]
+** are called from a different thread while any of these routines
+** are pending, then the results are undefined.
+**
+** ^The sqlite3_column_type() routine returns the
+** [SQLITE_INTEGER | datatype code] for the initial data type
+** of the result column.  ^The returned value is one of [SQLITE_INTEGER],
+** [SQLITE_FLOAT], [SQLITE_TEXT], [SQLITE_BLOB], or [SQLITE_NULL].  The value
+** returned by sqlite3_column_type() is only meaningful if no type
+** conversions have occurred as described below.  After a type conversion,
+** the value returned by sqlite3_column_type() is undefined.  Future
+** versions of SQLite may change the behavior of sqlite3_column_type()
+** following a type conversion.
+**
+** ^If the result is a BLOB or UTF-8 string then the sqlite3_column_bytes()
+** routine returns the number of bytes in that BLOB or string.
+** ^If the result is a UTF-16 string, then sqlite3_column_bytes() converts
+** the string to UTF-8 and then returns the number of bytes.
+** ^If the result is a numeric value then sqlite3_column_bytes() uses
+** [sqlite3_snprintf()] to convert that value to a UTF-8 string and returns
+** the number of bytes in that string.
+** ^If the result is NULL, then sqlite3_column_bytes() returns zero.
+**
+** ^If the result is a BLOB or UTF-16 string then the sqlite3_column_bytes16()
+** routine returns the number of bytes in that BLOB or string.
+** ^If the result is a UTF-8 string, then sqlite3_column_bytes16() converts
+** the string to UTF-16 and then returns the number of bytes.
+** ^If the result is a numeric value then sqlite3_column_bytes16() uses
+** [sqlite3_snprintf()] to convert that value to a UTF-16 string and returns
+** the number of bytes in that string.
+** ^If the result is NULL, then sqlite3_column_bytes16() returns zero.
+**
+** ^The values returned by [sqlite3_column_bytes()] and 
+** [sqlite3_column_bytes16()] do not include the zero terminators at the end
+** of the string.  ^For clarity: the values returned by
+** [sqlite3_column_bytes()] and [sqlite3_column_bytes16()] are the number of
+** bytes in the string, not the number of characters.
+**
+** ^Strings returned by sqlite3_column_text() and sqlite3_column_text16(),
+** even empty strings, are always zero terminated.  ^The return
+** value from sqlite3_column_blob() for a zero-length BLOB is a NULL pointer.
+**
+** ^The object returned by [sqlite3_column_value()] is an
+** [unprotected sqlite3_value] object.  An unprotected sqlite3_value object
+** may only be used with [sqlite3_bind_value()] and [sqlite3_result_value()].
+** If the [unprotected sqlite3_value] object returned by
+** [sqlite3_column_value()] is used in any other way, including calls
+** to routines like [sqlite3_value_int()], [sqlite3_value_text()],
+** or [sqlite3_value_bytes()], then the behavior is undefined.
+**
+** These routines attempt to convert the value where appropriate.  ^For
+** example, if the internal representation is FLOAT and a text result
+** is requested, [sqlite3_snprintf()] is used internally to perform the
+** conversion automatically.  ^(The following table details the conversions
+** that are applied:
+**
+** <blockquote>
+** <table border="1">
+** <tr><th> Internal<br>Type <th> Requested<br>Type <th>  Conversion
+**
+** <tr><td>  NULL    <td> INTEGER   <td> Result is 0
+** <tr><td>  NULL    <td>  FLOAT    <td> Result is 0.0
+** <tr><td>  NULL    <td>   TEXT    <td> Result is NULL pointer
+** <tr><td>  NULL    <td>   BLOB    <td> Result is NULL pointer
+** <tr><td> INTEGER  <td>  FLOAT    <td> Convert from integer to float
+** <tr><td> INTEGER  <td>   TEXT    <td> ASCII rendering of the integer
+** <tr><td> INTEGER  <td>   BLOB    <td> Same as INTEGER->TEXT
+** <tr><td>  FLOAT   <td> INTEGER   <td> Convert from float to integer
+** <tr><td>  FLOAT   <td>   TEXT    <td> ASCII rendering of the float
+** <tr><td>  FLOAT   <td>   BLOB    <td> Same as FLOAT->TEXT
+** <tr><td>  TEXT    <td> INTEGER   <td> Use atoi()
+** <tr><td>  TEXT    <td>  FLOAT    <td> Use atof()
+** <tr><td>  TEXT    <td>   BLOB    <td> No change
+** <tr><td>  BLOB    <td> INTEGER   <td> Convert to TEXT then use atoi()
+** <tr><td>  BLOB    <td>  FLOAT    <td> Convert to TEXT then use atof()
+** <tr><td>  BLOB    <td>   TEXT    <td> Add a zero terminator if needed
+** </table>
+** </blockquote>)^
+**
+** The table above makes reference to standard C library functions atoi()
+** and atof().  SQLite does not really use these functions.  It has its
+** own equivalent internal routines.  The atoi() and atof() names are
+** used in the table for brevity and because they are familiar to most
+** C programmers.
+**
+** Note that when type conversions occur, pointers returned by prior
+** calls to sqlite3_column_blob(), sqlite3_column_text(), and/or
+** sqlite3_column_text16() may be invalidated.
+** Type conversions and pointer invalidations might occur
+** in the following cases:
+**
+** <ul>
+** <li> The initial content is a BLOB and sqlite3_column_text() or
+**      sqlite3_column_text16() is called.  A zero-terminator might
+**      need to be added to the string.</li>
+** <li> The initial content is UTF-8 text and sqlite3_column_bytes16() or
+**      sqlite3_column_text16() is called.  The content must be converted
+**      to UTF-16.</li>
+** <li> The initial content is UTF-16 text and sqlite3_column_bytes() or
+**      sqlite3_column_text() is called.  The content must be converted
+**      to UTF-8.</li>
+** </ul>
+**
+** ^Conversions between UTF-16be and UTF-16le are always done in place and do
+** not invalidate a prior pointer, though of course the content of the buffer
+** that the prior pointer references will have been modified.  Other kinds
+** of conversion are done in place when it is possible, but sometimes they
+** are not possible and in those cases prior pointers are invalidated.
+**
+** The safest and easiest to remember policy is to invoke these routines
+** in one of the following ways:
+**
+** <ul>
+**  <li>sqlite3_column_text() followed by sqlite3_column_bytes()</li>
+**  <li>sqlite3_column_blob() followed by sqlite3_column_bytes()</li>
+**  <li>sqlite3_column_text16() followed by sqlite3_column_bytes16()</li>
+** </ul>
+**
+** In other words, you should call sqlite3_column_text(),
+** sqlite3_column_blob(), or sqlite3_column_text16() first to force the result
+** into the desired format, then invoke sqlite3_column_bytes() or
+** sqlite3_column_bytes16() to find the size of the result.  Do not mix calls
+** to sqlite3_column_text() or sqlite3_column_blob() with calls to
+** sqlite3_column_bytes16(), and do not mix calls to sqlite3_column_text16()
+** with calls to sqlite3_column_bytes().
+**
+** ^The pointers returned are valid until a type conversion occurs as
+** described above, or until [sqlite3_step()] or [sqlite3_reset()] or
+** [sqlite3_finalize()] is called.  ^The memory space used to hold strings
+** and BLOBs is freed automatically.  Do <b>not</b> pass the pointers returned
+** [sqlite3_column_blob()], [sqlite3_column_text()], etc. into
+** [sqlite3_free()].
+**
+** ^(If a memory allocation error occurs during the evaluation of any
+** of these routines, a default value is returned.  The default value
+** is either the integer 0, the floating point number 0.0, or a NULL
+** pointer.  Subsequent calls to [sqlite3_errcode()] will return
+** [SQLITE_NOMEM].)^
+*/
+const void *sqlite3_column_blob(sqlite3_stmt*, int iCol);
+int sqlite3_column_bytes(sqlite3_stmt*, int iCol);
+int sqlite3_column_bytes16(sqlite3_stmt*, int iCol);
+double sqlite3_column_double(sqlite3_stmt*, int iCol);
+int sqlite3_column_int(sqlite3_stmt*, int iCol);
+sqlite3_int64 sqlite3_column_int64(sqlite3_stmt*, int iCol);
+const unsigned char *sqlite3_column_text(sqlite3_stmt*, int iCol);
+const void *sqlite3_column_text16(sqlite3_stmt*, int iCol);
+int sqlite3_column_type(sqlite3_stmt*, int iCol);
+sqlite3_value *sqlite3_column_value(sqlite3_stmt*, int iCol);
+
+/*
+** CAPI3REF: Destroy A Prepared Statement Object
+**
+** ^The sqlite3_finalize() function is called to delete a [prepared statement].
+** ^If the most recent evaluation of the statement encountered no errors
+** or if the statement is never been evaluated, then sqlite3_finalize() returns
+** SQLITE_OK.  ^If the most recent evaluation of statement S failed, then
+** sqlite3_finalize(S) returns the appropriate [error code] or
+** [extended error code].
+**
+** ^The sqlite3_finalize(S) routine can be called at any point during
+** the life cycle of [prepared statement] S:
+** before statement S is ever evaluated, after
+** one or more calls to [sqlite3_reset()], or after any call
+** to [sqlite3_step()] regardless of whether or not the statement has
+** completed execution.
+**
+** ^Invoking sqlite3_finalize() on a NULL pointer is a harmless no-op.
+**
+** The application must finalize every [prepared statement] in order to avoid
+** resource leaks.  It is a grievous error for the application to try to use
+** a prepared statement after it has been finalized.  Any use of a prepared
+** statement after it has been finalized can result in undefined and
+** undesirable behavior such as segfaults and heap corruption.
+*/
+int sqlite3_finalize(sqlite3_stmt *pStmt);
+
+/*
+** CAPI3REF: Reset A Prepared Statement Object
+**
+** The sqlite3_reset() function is called to reset a [prepared statement]
+** object back to its initial state, ready to be re-executed.
+** ^Any SQL statement variables that had values bound to them using
+** the [sqlite3_bind_blob | sqlite3_bind_*() API] retain their values.
+** Use [sqlite3_clear_bindings()] to reset the bindings.
+**
+** ^The [sqlite3_reset(S)] interface resets the [prepared statement] S
+** back to the beginning of its program.
+**
+** ^If the most recent call to [sqlite3_step(S)] for the
+** [prepared statement] S returned [SQLITE_ROW] or [SQLITE_DONE],
+** or if [sqlite3_step(S)] has never before been called on S,
+** then [sqlite3_reset(S)] returns [SQLITE_OK].
+**
+** ^If the most recent call to [sqlite3_step(S)] for the
+** [prepared statement] S indicated an error, then
+** [sqlite3_reset(S)] returns an appropriate [error code].
+**
+** ^The [sqlite3_reset(S)] interface does not change the values
+** of any [sqlite3_bind_blob|bindings] on the [prepared statement] S.
+*/
+int sqlite3_reset(sqlite3_stmt *pStmt);
+
+/*
+** CAPI3REF: Create Or Redefine SQL Functions
+** KEYWORDS: {function creation routines}
+** KEYWORDS: {application-defined SQL function}
+** KEYWORDS: {application-defined SQL functions}
+**
+** ^These functions (collectively known as "function creation routines")
+** are used to add SQL functions or aggregates or to redefine the behavior
+** of existing SQL functions or aggregates.  The only differences between
+** these routines are the text encoding expected for
+** the second parameter (the name of the function being created)
+** and the presence or absence of a destructor callback for
+** the application data pointer.
+**
+** ^The first parameter is the [database connection] to which the SQL
+** function is to be added.  ^If an application uses more than one database
+** connection then application-defined SQL functions must be added
+** to each database connection separately.
+**
+** ^The second parameter is the name of the SQL function to be created or
+** redefined.  ^The length of the name is limited to 255 bytes in a UTF-8
+** representation, exclusive of the zero-terminator.  ^Note that the name
+** length limit is in UTF-8 bytes, not characters nor UTF-16 bytes.  
+** ^Any attempt to create a function with a longer name
+** will result in [SQLITE_MISUSE] being returned.
+**
+** ^The third parameter (nArg)
+** is the number of arguments that the SQL function or
+** aggregate takes. ^If this parameter is -1, then the SQL function or
+** aggregate may take any number of arguments between 0 and the limit
+** set by [sqlite3_limit]([SQLITE_LIMIT_FUNCTION_ARG]).  If the third
+** parameter is less than -1 or greater than 127 then the behavior is
+** undefined.
+**
+** ^The fourth parameter, eTextRep, specifies what
+** [SQLITE_UTF8 | text encoding] this SQL function prefers for
+** its parameters.  Every SQL function implementation must be able to work
+** with UTF-8, UTF-16le, or UTF-16be.  But some implementations may be
+** more efficient with one encoding than another.  ^An application may
+** invoke sqlite3_create_function() or sqlite3_create_function16() multiple
+** times with the same function but with different values of eTextRep.
+** ^When multiple implementations of the same function are available, SQLite
+** will pick the one that involves the least amount of data conversion.
+** If there is only a single implementation which does not care what text
+** encoding is used, then the fourth argument should be [SQLITE_ANY].
+**
+** ^(The fifth parameter is an arbitrary pointer.  The implementation of the
+** function can gain access to this pointer using [sqlite3_user_data()].)^
+**
+** ^The sixth, seventh and eighth parameters, xFunc, xStep and xFinal, are
+** pointers to C-language functions that implement the SQL function or
+** aggregate. ^A scalar SQL function requires an implementation of the xFunc
+** callback only; NULL pointers must be passed as the xStep and xFinal
+** parameters. ^An aggregate SQL function requires an implementation of xStep
+** and xFinal and NULL pointer must be passed for xFunc. ^To delete an existing
+** SQL function or aggregate, pass NULL pointers for all three function
+** callbacks.
+**
+** ^(If the ninth parameter to sqlite3_create_function_v2() is not NULL,
+** then it is destructor for the application data pointer. 
+** The destructor is invoked when the function is deleted, either by being
+** overloaded or when the database connection closes.)^
+** ^The destructor is also invoked if the call to
+** sqlite3_create_function_v2() fails.
+** ^When the destructor callback of the tenth parameter is invoked, it
+** is passed a single argument which is a copy of the application data 
+** pointer which was the fifth parameter to sqlite3_create_function_v2().
+**
+** ^It is permitted to register multiple implementations of the same
+** functions with the same name but with either differing numbers of
+** arguments or differing preferred text encodings.  ^SQLite will use
+** the implementation that most closely matches the way in which the
+** SQL function is used.  ^A function implementation with a non-negative
+** nArg parameter is a better match than a function implementation with
+** a negative nArg.  ^A function where the preferred text encoding
+** matches the database encoding is a better
+** match than a function where the encoding is different.  
+** ^A function where the encoding difference is between UTF16le and UTF16be
+** is a closer match than a function where the encoding difference is
+** between UTF8 and UTF16.
+**
+** ^Built-in functions may be overloaded by new application-defined functions.
+**
+** ^An application-defined function is permitted to call other
+** SQLite interfaces.  However, such calls must not
+** close the database connection nor finalize or reset the prepared
+** statement in which the function is running.
+*/
+int sqlite3_create_function(
+  sqlite3 *db,
+  const char *zFunctionName,
+  int nArg,
+  int eTextRep,
+  void *pApp,
+  void (*xFunc)(sqlite3_context*,int,sqlite3_value**),
+  void (*xStep)(sqlite3_context*,int,sqlite3_value**),
+  void (*xFinal)(sqlite3_context*)
+);
+int sqlite3_create_function16(
+  sqlite3 *db,
+  const void *zFunctionName,
+  int nArg,
+  int eTextRep,
+  void *pApp,
+  void (*xFunc)(sqlite3_context*,int,sqlite3_value**),
+  void (*xStep)(sqlite3_context*,int,sqlite3_value**),
+  void (*xFinal)(sqlite3_context*)
+);
+int sqlite3_create_function_v2(
+  sqlite3 *db,
+  const char *zFunctionName,
+  int nArg,
+  int eTextRep,
+  void *pApp,
+  void (*xFunc)(sqlite3_context*,int,sqlite3_value**),
+  void (*xStep)(sqlite3_context*,int,sqlite3_value**),
+  void (*xFinal)(sqlite3_context*),
+  void(*xDestroy)(void*)
+);
+
+/*
+** CAPI3REF: Text Encodings
+**
+** These constant define integer codes that represent the various
+** text encodings supported by SQLite.
+*/
+#define SQLITE_UTF8           1
+#define SQLITE_UTF16LE        2
+#define SQLITE_UTF16BE        3
+#define SQLITE_UTF16          4    /* Use native byte order */
+#define SQLITE_ANY            5    /* sqlite3_create_function only */
+#define SQLITE_UTF16_ALIGNED  8    /* sqlite3_create_collation only */
+
+/*
+** CAPI3REF: Deprecated Functions
+** DEPRECATED
+**
+** These functions are [deprecated].  In order to maintain
+** backwards compatibility with older code, these functions continue 
+** to be supported.  However, new applications should avoid
+** the use of these functions.  To help encourage people to avoid
+** using these functions, we are not going to tell you what they do.
+*/
+#ifndef SQLITE_OMIT_DEPRECATED
+SQLITE_DEPRECATED int sqlite3_aggregate_count(sqlite3_context*);
+SQLITE_DEPRECATED int sqlite3_expired(sqlite3_stmt*);
+SQLITE_DEPRECATED int sqlite3_transfer_bindings(sqlite3_stmt*, sqlite3_stmt*);
+SQLITE_DEPRECATED int sqlite3_global_recover(void);
+SQLITE_DEPRECATED void sqlite3_thread_cleanup(void);
+SQLITE_DEPRECATED int sqlite3_memory_alarm(void(*)(void*,sqlite3_int64,int),void*,sqlite3_int64);
+#endif
+
+/*
+** CAPI3REF: Obtaining SQL Function Parameter Values
+**
+** The C-language implementation of SQL functions and aggregates uses
+** this set of interface routines to access the parameter values on
+** the function or aggregate.
+**
+** The xFunc (for scalar functions) or xStep (for aggregates) parameters
+** to [sqlite3_create_function()] and [sqlite3_create_function16()]
+** define callbacks that implement the SQL functions and aggregates.
+** The 3rd parameter to these callbacks is an array of pointers to
+** [protected sqlite3_value] objects.  There is one [sqlite3_value] object for
+** each parameter to the SQL function.  These routines are used to
+** extract values from the [sqlite3_value] objects.
+**
+** These routines work only with [protected sqlite3_value] objects.
+** Any attempt to use these routines on an [unprotected sqlite3_value]
+** object results in undefined behavior.
+**
+** ^These routines work just like the corresponding [column access functions]
+** except that  these routines take a single [protected sqlite3_value] object
+** pointer instead of a [sqlite3_stmt*] pointer and an integer column number.
+**
+** ^The sqlite3_value_text16() interface extracts a UTF-16 string
+** in the native byte-order of the host machine.  ^The
+** sqlite3_value_text16be() and sqlite3_value_text16le() interfaces
+** extract UTF-16 strings as big-endian and little-endian respectively.
+**
+** ^(The sqlite3_value_numeric_type() interface attempts to apply
+** numeric affinity to the value.  This means that an attempt is
+** made to convert the value to an integer or floating point.  If
+** such a conversion is possible without loss of information (in other
+** words, if the value is a string that looks like a number)
+** then the conversion is performed.  Otherwise no conversion occurs.
+** The [SQLITE_INTEGER | datatype] after conversion is returned.)^
+**
+** Please pay particular attention to the fact that the pointer returned
+** from [sqlite3_value_blob()], [sqlite3_value_text()], or
+** [sqlite3_value_text16()] can be invalidated by a subsequent call to
+** [sqlite3_value_bytes()], [sqlite3_value_bytes16()], [sqlite3_value_text()],
+** or [sqlite3_value_text16()].
+**
+** These routines must be called from the same thread as
+** the SQL function that supplied the [sqlite3_value*] parameters.
+*/
+const void *sqlite3_value_blob(sqlite3_value*);
+int sqlite3_value_bytes(sqlite3_value*);
+int sqlite3_value_bytes16(sqlite3_value*);
+double sqlite3_value_double(sqlite3_value*);
+int sqlite3_value_int(sqlite3_value*);
+sqlite3_int64 sqlite3_value_int64(sqlite3_value*);
+const unsigned char *sqlite3_value_text(sqlite3_value*);
+const void *sqlite3_value_text16(sqlite3_value*);
+const void *sqlite3_value_text16le(sqlite3_value*);
+const void *sqlite3_value_text16be(sqlite3_value*);
+int sqlite3_value_type(sqlite3_value*);
+int sqlite3_value_numeric_type(sqlite3_value*);
+
+/*
+** CAPI3REF: Obtain Aggregate Function Context
+**
+** Implementations of aggregate SQL functions use this
+** routine to allocate memory for storing their state.
+**
+** ^The first time the sqlite3_aggregate_context(C,N) routine is called 
+** for a particular aggregate function, SQLite
+** allocates N of memory, zeroes out that memory, and returns a pointer
+** to the new memory. ^On second and subsequent calls to
+** sqlite3_aggregate_context() for the same aggregate function instance,
+** the same buffer is returned.  Sqlite3_aggregate_context() is normally
+** called once for each invocation of the xStep callback and then one
+** last time when the xFinal callback is invoked.  ^(When no rows match
+** an aggregate query, the xStep() callback of the aggregate function
+** implementation is never called and xFinal() is called exactly once.
+** In those cases, sqlite3_aggregate_context() might be called for the
+** first time from within xFinal().)^
+**
+** ^The sqlite3_aggregate_context(C,N) routine returns a NULL pointer if N is
+** less than or equal to zero or if a memory allocate error occurs.
+**
+** ^(The amount of space allocated by sqlite3_aggregate_context(C,N) is
+** determined by the N parameter on first successful call.  Changing the
+** value of N in subsequent call to sqlite3_aggregate_context() within
+** the same aggregate function instance will not resize the memory
+** allocation.)^
+**
+** ^SQLite automatically frees the memory allocated by 
+** sqlite3_aggregate_context() when the aggregate query concludes.
+**
+** The first parameter must be a copy of the
+** [sqlite3_context | SQL function context] that is the first parameter
+** to the xStep or xFinal callback routine that implements the aggregate
+** function.
+**
+** This routine must be called from the same thread in which
+** the aggregate SQL function is running.
+*/
+void *sqlite3_aggregate_context(sqlite3_context*, int nBytes);
+
+/*
+** CAPI3REF: User Data For Functions
+**
+** ^The sqlite3_user_data() interface returns a copy of
+** the pointer that was the pUserData parameter (the 5th parameter)
+** of the [sqlite3_create_function()]
+** and [sqlite3_create_function16()] routines that originally
+** registered the application defined function.
+**
+** This routine must be called from the same thread in which
+** the application-defined function is running.
+*/
+void *sqlite3_user_data(sqlite3_context*);
+
+/*
+** CAPI3REF: Database Connection For Functions
+**
+** ^The sqlite3_context_db_handle() interface returns a copy of
+** the pointer to the [database connection] (the 1st parameter)
+** of the [sqlite3_create_function()]
+** and [sqlite3_create_function16()] routines that originally
+** registered the application defined function.
+*/
+sqlite3 *sqlite3_context_db_handle(sqlite3_context*);
+
+/*
+** CAPI3REF: Function Auxiliary Data
+**
+** The following two functions may be used by scalar SQL functions to
+** associate metadata with argument values. If the same value is passed to
+** multiple invocations of the same SQL function during query execution, under
+** some circumstances the associated metadata may be preserved. This may
+** be used, for example, to add a regular-expression matching scalar
+** function. The compiled version of the regular expression is stored as
+** metadata associated with the SQL value passed as the regular expression
+** pattern.  The compiled regular expression can be reused on multiple
+** invocations of the same function so that the original pattern string
+** does not need to be recompiled on each invocation.
+**
+** ^The sqlite3_get_auxdata() interface returns a pointer to the metadata
+** associated by the sqlite3_set_auxdata() function with the Nth argument
+** value to the application-defined function. ^If no metadata has been ever
+** been set for the Nth argument of the function, or if the corresponding
+** function parameter has changed since the meta-data was set,
+** then sqlite3_get_auxdata() returns a NULL pointer.
+**
+** ^The sqlite3_set_auxdata() interface saves the metadata
+** pointed to by its 3rd parameter as the metadata for the N-th
+** argument of the application-defined function.  Subsequent
+** calls to sqlite3_get_auxdata() might return this data, if it has
+** not been destroyed.
+** ^If it is not NULL, SQLite will invoke the destructor
+** function given by the 4th parameter to sqlite3_set_auxdata() on
+** the metadata when the corresponding function parameter changes
+** or when the SQL statement completes, whichever comes first.
+**
+** SQLite is free to call the destructor and drop metadata on any
+** parameter of any function at any time.  ^The only guarantee is that
+** the destructor will be called before the metadata is dropped.
+**
+** ^(In practice, metadata is preserved between function calls for
+** expressions that are constant at compile time. This includes literal
+** values and [parameters].)^
+**
+** These routines must be called from the same thread in which
+** the SQL function is running.
+*/
+void *sqlite3_get_auxdata(sqlite3_context*, int N);
+void sqlite3_set_auxdata(sqlite3_context*, int N, void*, void (*)(void*));
+
+
+/*
+** CAPI3REF: Constants Defining Special Destructor Behavior
+**
+** These are special values for the destructor that is passed in as the
+** final argument to routines like [sqlite3_result_blob()].  ^If the destructor
+** argument is SQLITE_STATIC, it means that the content pointer is constant
+** and will never change.  It does not need to be destroyed.  ^The
+** SQLITE_TRANSIENT value means that the content will likely change in
+** the near future and that SQLite should make its own private copy of
+** the content before returning.
+**
+** The typedef is necessary to work around problems in certain
+** C++ compilers.  See ticket #2191.
+*/
+typedef void (*sqlite3_destructor_type)(void*);
+#define SQLITE_STATIC      ((sqlite3_destructor_type)0)
+#define SQLITE_TRANSIENT   ((sqlite3_destructor_type)-1)
+
+/*
+** CAPI3REF: Setting The Result Of An SQL Function
+**
+** These routines are used by the xFunc or xFinal callbacks that
+** implement SQL functions and aggregates.  See
+** [sqlite3_create_function()] and [sqlite3_create_function16()]
+** for additional information.
+**
+** These functions work very much like the [parameter binding] family of
+** functions used to bind values to host parameters in prepared statements.
+** Refer to the [SQL parameter] documentation for additional information.
+**
+** ^The sqlite3_result_blob() interface sets the result from
+** an application-defined function to be the BLOB whose content is pointed
+** to by the second parameter and which is N bytes long where N is the
+** third parameter.
+**
+** ^The sqlite3_result_zeroblob() interfaces set the result of
+** the application-defined function to be a BLOB containing all zero
+** bytes and N bytes in size, where N is the value of the 2nd parameter.
+**
+** ^The sqlite3_result_double() interface sets the result from
+** an application-defined function to be a floating point value specified
+** by its 2nd argument.
+**
+** ^The sqlite3_result_error() and sqlite3_result_error16() functions
+** cause the implemented SQL function to throw an exception.
+** ^SQLite uses the string pointed to by the
+** 2nd parameter of sqlite3_result_error() or sqlite3_result_error16()
+** as the text of an error message.  ^SQLite interprets the error
+** message string from sqlite3_result_error() as UTF-8. ^SQLite
+** interprets the string from sqlite3_result_error16() as UTF-16 in native
+** byte order.  ^If the third parameter to sqlite3_result_error()
+** or sqlite3_result_error16() is negative then SQLite takes as the error
+** message all text up through the first zero character.
+** ^If the third parameter to sqlite3_result_error() or
+** sqlite3_result_error16() is non-negative then SQLite takes that many
+** bytes (not characters) from the 2nd parameter as the error message.
+** ^The sqlite3_result_error() and sqlite3_result_error16()
+** routines make a private copy of the error message text before
+** they return.  Hence, the calling function can deallocate or
+** modify the text after they return without harm.
+** ^The sqlite3_result_error_code() function changes the error code
+** returned by SQLite as a result of an error in a function.  ^By default,
+** the error code is SQLITE_ERROR.  ^A subsequent call to sqlite3_result_error()
+** or sqlite3_result_error16() resets the error code to SQLITE_ERROR.
+**
+** ^The sqlite3_result_toobig() interface causes SQLite to throw an error
+** indicating that a string or BLOB is too long to represent.
+**
+** ^The sqlite3_result_nomem() interface causes SQLite to throw an error
+** indicating that a memory allocation failed.
+**
+** ^The sqlite3_result_int() interface sets the return value
+** of the application-defined function to be the 32-bit signed integer
+** value given in the 2nd argument.
+** ^The sqlite3_result_int64() interface sets the return value
+** of the application-defined function to be the 64-bit signed integer
+** value given in the 2nd argument.
+**
+** ^The sqlite3_result_null() interface sets the return value
+** of the application-defined function to be NULL.
+**
+** ^The sqlite3_result_text(), sqlite3_result_text16(),
+** sqlite3_result_text16le(), and sqlite3_result_text16be() interfaces
+** set the return value of the application-defined function to be
+** a text string which is represented as UTF-8, UTF-16 native byte order,
+** UTF-16 little endian, or UTF-16 big endian, respectively.
+** ^SQLite takes the text result from the application from
+** the 2nd parameter of the sqlite3_result_text* interfaces.
+** ^If the 3rd parameter to the sqlite3_result_text* interfaces
+** is negative, then SQLite takes result text from the 2nd parameter
+** through the first zero character.
+** ^If the 3rd parameter to the sqlite3_result_text* interfaces
+** is non-negative, then as many bytes (not characters) of the text
+** pointed to by the 2nd parameter are taken as the application-defined
+** function result.  If the 3rd parameter is non-negative, then it
+** must be the byte offset into the string where the NUL terminator would
+** appear if the string where NUL terminated.  If any NUL characters occur
+** in the string at a byte offset that is less than the value of the 3rd
+** parameter, then the resulting string will contain embedded NULs and the
+** result of expressions operating on strings with embedded NULs is undefined.
+** ^If the 4th parameter to the sqlite3_result_text* interfaces
+** or sqlite3_result_blob is a non-NULL pointer, then SQLite calls that
+** function as the destructor on the text or BLOB result when it has
+** finished using that result.
+** ^If the 4th parameter to the sqlite3_result_text* interfaces or to
+** sqlite3_result_blob is the special constant SQLITE_STATIC, then SQLite
+** assumes that the text or BLOB result is in constant space and does not
+** copy the content of the parameter nor call a destructor on the content
+** when it has finished using that result.
+** ^If the 4th parameter to the sqlite3_result_text* interfaces
+** or sqlite3_result_blob is the special constant SQLITE_TRANSIENT
+** then SQLite makes a copy of the result into space obtained from
+** from [sqlite3_malloc()] before it returns.
+**
+** ^The sqlite3_result_value() interface sets the result of
+** the application-defined function to be a copy the
+** [unprotected sqlite3_value] object specified by the 2nd parameter.  ^The
+** sqlite3_result_value() interface makes a copy of the [sqlite3_value]
+** so that the [sqlite3_value] specified in the parameter may change or
+** be deallocated after sqlite3_result_value() returns without harm.
+** ^A [protected sqlite3_value] object may always be used where an
+** [unprotected sqlite3_value] object is required, so either
+** kind of [sqlite3_value] object can be used with this interface.
+**
+** If these routines are called from within the different thread
+** than the one containing the application-defined function that received
+** the [sqlite3_context] pointer, the results are undefined.
+*/
+void sqlite3_result_blob(sqlite3_context*, const void*, int, void(*)(void*));
+void sqlite3_result_double(sqlite3_context*, double);
+void sqlite3_result_error(sqlite3_context*, const char*, int);
+void sqlite3_result_error16(sqlite3_context*, const void*, int);
+void sqlite3_result_error_toobig(sqlite3_context*);
+void sqlite3_result_error_nomem(sqlite3_context*);
+void sqlite3_result_error_code(sqlite3_context*, int);
+void sqlite3_result_int(sqlite3_context*, int);
+void sqlite3_result_int64(sqlite3_context*, sqlite3_int64);
+void sqlite3_result_null(sqlite3_context*);
+void sqlite3_result_text(sqlite3_context*, const char*, int, void(*)(void*));
+void sqlite3_result_text16(sqlite3_context*, const void*, int, void(*)(void*));
+void sqlite3_result_text16le(sqlite3_context*, const void*, int,void(*)(void*));
+void sqlite3_result_text16be(sqlite3_context*, const void*, int,void(*)(void*));
+void sqlite3_result_value(sqlite3_context*, sqlite3_value*);
+void sqlite3_result_zeroblob(sqlite3_context*, int n);
+
+/*
+** CAPI3REF: Define New Collating Sequences
+**
+** ^These functions add, remove, or modify a [collation] associated
+** with the [database connection] specified as the first argument.
+**
+** ^The name of the collation is a UTF-8 string
+** for sqlite3_create_collation() and sqlite3_create_collation_v2()
+** and a UTF-16 string in native byte order for sqlite3_create_collation16().
+** ^Collation names that compare equal according to [sqlite3_strnicmp()] are
+** considered to be the same name.
+**
+** ^(The third argument (eTextRep) must be one of the constants:
+** <ul>
+** <li> [SQLITE_UTF8],
+** <li> [SQLITE_UTF16LE],
+** <li> [SQLITE_UTF16BE],
+** <li> [SQLITE_UTF16], or
+** <li> [SQLITE_UTF16_ALIGNED].
+** </ul>)^
+** ^The eTextRep argument determines the encoding of strings passed
+** to the collating function callback, xCallback.
+** ^The [SQLITE_UTF16] and [SQLITE_UTF16_ALIGNED] values for eTextRep
+** force strings to be UTF16 with native byte order.
+** ^The [SQLITE_UTF16_ALIGNED] value for eTextRep forces strings to begin
+** on an even byte address.
+**
+** ^The fourth argument, pArg, is an application data pointer that is passed
+** through as the first argument to the collating function callback.
+**
+** ^The fifth argument, xCallback, is a pointer to the collating function.
+** ^Multiple collating functions can be registered using the same name but
+** with different eTextRep parameters and SQLite will use whichever
+** function requires the least amount of data transformation.
+** ^If the xCallback argument is NULL then the collating function is
+** deleted.  ^When all collating functions having the same name are deleted,
+** that collation is no longer usable.
+**
+** ^The collating function callback is invoked with a copy of the pArg 
+** application data pointer and with two strings in the encoding specified
+** by the eTextRep argument.  The collating function must return an
+** integer that is negative, zero, or positive
+** if the first string is less than, equal to, or greater than the second,
+** respectively.  A collating function must always return the same answer
+** given the same inputs.  If two or more collating functions are registered
+** to the same collation name (using different eTextRep values) then all
+** must give an equivalent answer when invoked with equivalent strings.
+** The collating function must obey the following properties for all
+** strings A, B, and C:
+**
+** <ol>
+** <li> If A==B then B==A.
+** <li> If A==B and B==C then A==C.
+** <li> If A&lt;B THEN B&gt;A.
+** <li> If A&lt;B and B&lt;C then A&lt;C.
+** </ol>
+**
+** If a collating function fails any of the above constraints and that
+** collating function is  registered and used, then the behavior of SQLite
+** is undefined.
+**
+** ^The sqlite3_create_collation_v2() works like sqlite3_create_collation()
+** with the addition that the xDestroy callback is invoked on pArg when
+** the collating function is deleted.
+** ^Collating functions are deleted when they are overridden by later
+** calls to the collation creation functions or when the
+** [database connection] is closed using [sqlite3_close()].
+**
+** ^The xDestroy callback is <u>not</u> called if the 
+** sqlite3_create_collation_v2() function fails.  Applications that invoke
+** sqlite3_create_collation_v2() with a non-NULL xDestroy argument should 
+** check the return code and dispose of the application data pointer
+** themselves rather than expecting SQLite to deal with it for them.
+** This is different from every other SQLite interface.  The inconsistency 
+** is unfortunate but cannot be changed without breaking backwards 
+** compatibility.
+**
+** See also:  [sqlite3_collation_needed()] and [sqlite3_collation_needed16()].
+*/
+int sqlite3_create_collation(
+  sqlite3*, 
+  const char *zName, 
+  int eTextRep, 
+  void *pArg,
+  int(*xCompare)(void*,int,const void*,int,const void*)
+);
+int sqlite3_create_collation_v2(
+  sqlite3*, 
+  const char *zName, 
+  int eTextRep, 
+  void *pArg,
+  int(*xCompare)(void*,int,const void*,int,const void*),
+  void(*xDestroy)(void*)
+);
+int sqlite3_create_collation16(
+  sqlite3*, 
+  const void *zName,
+  int eTextRep, 
+  void *pArg,
+  int(*xCompare)(void*,int,const void*,int,const void*)
+);
+
+/*
+** CAPI3REF: Collation Needed Callbacks
+**
+** ^To avoid having to register all collation sequences before a database
+** can be used, a single callback function may be registered with the
+** [database connection] to be invoked whenever an undefined collation
+** sequence is required.
+**
+** ^If the function is registered using the sqlite3_collation_needed() API,
+** then it is passed the names of undefined collation sequences as strings
+** encoded in UTF-8. ^If sqlite3_collation_needed16() is used,
+** the names are passed as UTF-16 in machine native byte order.
+** ^A call to either function replaces the existing collation-needed callback.
+**
+** ^(When the callback is invoked, the first argument passed is a copy
+** of the second argument to sqlite3_collation_needed() or
+** sqlite3_collation_needed16().  The second argument is the database
+** connection.  The third argument is one of [SQLITE_UTF8], [SQLITE_UTF16BE],
+** or [SQLITE_UTF16LE], indicating the most desirable form of the collation
+** sequence function required.  The fourth parameter is the name of the
+** required collation sequence.)^
+**
+** The callback function should register the desired collation using
+** [sqlite3_create_collation()], [sqlite3_create_collation16()], or
+** [sqlite3_create_collation_v2()].
+*/
+int sqlite3_collation_needed(
+  sqlite3*, 
+  void*, 
+  void(*)(void*,sqlite3*,int eTextRep,const char*)
+);
+int sqlite3_collation_needed16(
+  sqlite3*, 
+  void*,
+  void(*)(void*,sqlite3*,int eTextRep,const void*)
+);
+
+#ifdef SQLITE_HAS_CODEC
+/*
+** Specify the key for an encrypted database.  This routine should be
+** called right after sqlite3_open().
+**
+** The code to implement this API is not available in the public release
+** of SQLite.
+*/
+int sqlite3_key(
+  sqlite3 *db,                   /* Database to be rekeyed */
+  const void *pKey, int nKey     /* The key */
+);
+
+/*
+** Change the key on an open database.  If the current database is not
+** encrypted, this routine will encrypt it.  If pNew==0 or nNew==0, the
+** database is decrypted.
+**
+** The code to implement this API is not available in the public release
+** of SQLite.
+*/
+int sqlite3_rekey(
+  sqlite3 *db,                   /* Database to be rekeyed */
+  const void *pKey, int nKey     /* The new key */
+);
+
+/*
+** Specify the activation key for a SEE database.  Unless 
+** activated, none of the SEE routines will work.
+*/
+void sqlite3_activate_see(
+  const char *zPassPhrase        /* Activation phrase */
+);
+#endif
+
+#ifdef SQLITE_ENABLE_CEROD
+/*
+** Specify the activation key for a CEROD database.  Unless 
+** activated, none of the CEROD routines will work.
+*/
+void sqlite3_activate_cerod(
+  const char *zPassPhrase        /* Activation phrase */
+);
+#endif
+
+/*
+** CAPI3REF: Suspend Execution For A Short Time
+**
+** The sqlite3_sleep() function causes the current thread to suspend execution
+** for at least a number of milliseconds specified in its parameter.
+**
+** If the operating system does not support sleep requests with
+** millisecond time resolution, then the time will be rounded up to
+** the nearest second. The number of milliseconds of sleep actually
+** requested from the operating system is returned.
+**
+** ^SQLite implements this interface by calling the xSleep()
+** method of the default [sqlite3_vfs] object.  If the xSleep() method
+** of the default VFS is not implemented correctly, or not implemented at
+** all, then the behavior of sqlite3_sleep() may deviate from the description
+** in the previous paragraphs.
+*/
+int sqlite3_sleep(int);
+
+/*
+** CAPI3REF: Name Of The Folder Holding Temporary Files
+**
+** ^(If this global variable is made to point to a string which is
+** the name of a folder (a.k.a. directory), then all temporary files
+** created by SQLite when using a built-in [sqlite3_vfs | VFS]
+** will be placed in that directory.)^  ^If this variable
+** is a NULL pointer, then SQLite performs a search for an appropriate
+** temporary file directory.
+**
+** It is not safe to read or modify this variable in more than one
+** thread at a time.  It is not safe to read or modify this variable
+** if a [database connection] is being used at the same time in a separate
+** thread.
+** It is intended that this variable be set once
+** as part of process initialization and before any SQLite interface
+** routines have been called and that this variable remain unchanged
+** thereafter.
+**
+** ^The [temp_store_directory pragma] may modify this variable and cause
+** it to point to memory obtained from [sqlite3_malloc].  ^Furthermore,
+** the [temp_store_directory pragma] always assumes that any string
+** that this variable points to is held in memory obtained from 
+** [sqlite3_malloc] and the pragma may attempt to free that memory
+** using [sqlite3_free].
+** Hence, if this variable is modified directly, either it should be
+** made NULL or made to point to memory obtained from [sqlite3_malloc]
+** or else the use of the [temp_store_directory pragma] should be avoided.
+*/
+SQLITE_EXTERN char *sqlite3_temp_directory;
+
+/*
+** CAPI3REF: Test For Auto-Commit Mode
+** KEYWORDS: {autocommit mode}
+**
+** ^The sqlite3_get_autocommit() interface returns non-zero or
+** zero if the given database connection is or is not in autocommit mode,
+** respectively.  ^Autocommit mode is on by default.
+** ^Autocommit mode is disabled by a [BEGIN] statement.
+** ^Autocommit mode is re-enabled by a [COMMIT] or [ROLLBACK].
+**
+** If certain kinds of errors occur on a statement within a multi-statement
+** transaction (errors including [SQLITE_FULL], [SQLITE_IOERR],
+** [SQLITE_NOMEM], [SQLITE_BUSY], and [SQLITE_INTERRUPT]) then the
+** transaction might be rolled back automatically.  The only way to
+** find out whether SQLite automatically rolled back the transaction after
+** an error is to use this function.
+**
+** If another thread changes the autocommit status of the database
+** connection while this routine is running, then the return value
+** is undefined.
+*/
+int sqlite3_get_autocommit(sqlite3*);
+
+/*
+** CAPI3REF: Find The Database Handle Of A Prepared Statement
+**
+** ^The sqlite3_db_handle interface returns the [database connection] handle
+** to which a [prepared statement] belongs.  ^The [database connection]
+** returned by sqlite3_db_handle is the same [database connection]
+** that was the first argument
+** to the [sqlite3_prepare_v2()] call (or its variants) that was used to
+** create the statement in the first place.
+*/
+sqlite3 *sqlite3_db_handle(sqlite3_stmt*);
+
+/*
+** CAPI3REF: Find the next prepared statement
+**
+** ^This interface returns a pointer to the next [prepared statement] after
+** pStmt associated with the [database connection] pDb.  ^If pStmt is NULL
+** then this interface returns a pointer to the first prepared statement
+** associated with the database connection pDb.  ^If no prepared statement
+** satisfies the conditions of this routine, it returns NULL.
+**
+** The [database connection] pointer D in a call to
+** [sqlite3_next_stmt(D,S)] must refer to an open database
+** connection and in particular must not be a NULL pointer.
+*/
+sqlite3_stmt *sqlite3_next_stmt(sqlite3 *pDb, sqlite3_stmt *pStmt);
+
+/*
+** CAPI3REF: Commit And Rollback Notification Callbacks
+**
+** ^The sqlite3_commit_hook() interface registers a callback
+** function to be invoked whenever a transaction is [COMMIT | committed].
+** ^Any callback set by a previous call to sqlite3_commit_hook()
+** for the same database connection is overridden.
+** ^The sqlite3_rollback_hook() interface registers a callback
+** function to be invoked whenever a transaction is [ROLLBACK | rolled back].
+** ^Any callback set by a previous call to sqlite3_rollback_hook()
+** for the same database connection is overridden.
+** ^The pArg argument is passed through to the callback.
+** ^If the callback on a commit hook function returns non-zero,
+** then the commit is converted into a rollback.
+**
+** ^The sqlite3_commit_hook(D,C,P) and sqlite3_rollback_hook(D,C,P) functions
+** return the P argument from the previous call of the same function
+** on the same [database connection] D, or NULL for
+** the first call for each function on D.
+**
+** The callback implementation must not do anything that will modify
+** the database connection that invoked the callback.  Any actions
+** to modify the database connection must be deferred until after the
+** completion of the [sqlite3_step()] call that triggered the commit
+** or rollback hook in the first place.
+** Note that [sqlite3_prepare_v2()] and [sqlite3_step()] both modify their
+** database connections for the meaning of "modify" in this paragraph.
+**
+** ^Registering a NULL function disables the callback.
+**
+** ^When the commit hook callback routine returns zero, the [COMMIT]
+** operation is allowed to continue normally.  ^If the commit hook
+** returns non-zero, then the [COMMIT] is converted into a [ROLLBACK].
+** ^The rollback hook is invoked on a rollback that results from a commit
+** hook returning non-zero, just as it would be with any other rollback.
+**
+** ^For the purposes of this API, a transaction is said to have been
+** rolled back if an explicit "ROLLBACK" statement is executed, or
+** an error or constraint causes an implicit rollback to occur.
+** ^The rollback callback is not invoked if a transaction is
+** automatically rolled back because the database connection is closed.
+**
+** See also the [sqlite3_update_hook()] interface.
+*/
+void *sqlite3_commit_hook(sqlite3*, int(*)(void*), void*);
+void *sqlite3_rollback_hook(sqlite3*, void(*)(void *), void*);
+
+/*
+** CAPI3REF: Data Change Notification Callbacks
+**
+** ^The sqlite3_update_hook() interface registers a callback function
+** with the [database connection] identified by the first argument
+** to be invoked whenever a row is updated, inserted or deleted.
+** ^Any callback set by a previous call to this function
+** for the same database connection is overridden.
+**
+** ^The second argument is a pointer to the function to invoke when a
+** row is updated, inserted or deleted.
+** ^The first argument to the callback is a copy of the third argument
+** to sqlite3_update_hook().
+** ^The second callback argument is one of [SQLITE_INSERT], [SQLITE_DELETE],
+** or [SQLITE_UPDATE], depending on the operation that caused the callback
+** to be invoked.
+** ^The third and fourth arguments to the callback contain pointers to the
+** database and table name containing the affected row.
+** ^The final callback parameter is the [rowid] of the row.
+** ^In the case of an update, this is the [rowid] after the update takes place.
+**
+** ^(The update hook is not invoked when internal system tables are
+** modified (i.e. sqlite_master and sqlite_sequence).)^
+**
+** ^In the current implementation, the update hook
+** is not invoked when duplication rows are deleted because of an
+** [ON CONFLICT | ON CONFLICT REPLACE] clause.  ^Nor is the update hook
+** invoked when rows are deleted using the [truncate optimization].
+** The exceptions defined in this paragraph might change in a future
+** release of SQLite.
+**
+** The update hook implementation must not do anything that will modify
+** the database connection that invoked the update hook.  Any actions
+** to modify the database connection must be deferred until after the
+** completion of the [sqlite3_step()] call that triggered the update hook.
+** Note that [sqlite3_prepare_v2()] and [sqlite3_step()] both modify their
+** database connections for the meaning of "modify" in this paragraph.
+**
+** ^The sqlite3_update_hook(D,C,P) function
+** returns the P argument from the previous call
+** on the same [database connection] D, or NULL for
+** the first call on D.
+**
+** See also the [sqlite3_commit_hook()] and [sqlite3_rollback_hook()]
+** interfaces.
+*/
+void *sqlite3_update_hook(
+  sqlite3*, 
+  void(*)(void *,int ,char const *,char const *,sqlite3_int64),
+  void*
+);
+
+/*
+** CAPI3REF: Enable Or Disable Shared Pager Cache
+** KEYWORDS: {shared cache}
+**
+** ^(This routine enables or disables the sharing of the database cache
+** and schema data structures between [database connection | connections]
+** to the same database. Sharing is enabled if the argument is true
+** and disabled if the argument is false.)^
+**
+** ^Cache sharing is enabled and disabled for an entire process.
+** This is a change as of SQLite version 3.5.0. In prior versions of SQLite,
+** sharing was enabled or disabled for each thread separately.
+**
+** ^(The cache sharing mode set by this interface effects all subsequent
+** calls to [sqlite3_open()], [sqlite3_open_v2()], and [sqlite3_open16()].
+** Existing database connections continue use the sharing mode
+** that was in effect at the time they were opened.)^
+**
+** ^(This routine returns [SQLITE_OK] if shared cache was enabled or disabled
+** successfully.  An [error code] is returned otherwise.)^
+**
+** ^Shared cache is disabled by default. But this might change in
+** future releases of SQLite.  Applications that care about shared
+** cache setting should set it explicitly.
+**
+** See Also:  [SQLite Shared-Cache Mode]
+*/
+int sqlite3_enable_shared_cache(int);
+
+/*
+** CAPI3REF: Attempt To Free Heap Memory
+**
+** ^The sqlite3_release_memory() interface attempts to free N bytes
+** of heap memory by deallocating non-essential memory allocations
+** held by the database library.   Memory used to cache database
+** pages to improve performance is an example of non-essential memory.
+** ^sqlite3_release_memory() returns the number of bytes actually freed,
+** which might be more or less than the amount requested.
+** ^The sqlite3_release_memory() routine is a no-op returning zero
+** if SQLite is not compiled with [SQLITE_ENABLE_MEMORY_MANAGEMENT].
+*/
+int sqlite3_release_memory(int);
+
+/*
+** CAPI3REF: Impose A Limit On Heap Size
+**
+** ^The sqlite3_soft_heap_limit64() interface sets and/or queries the
+** soft limit on the amount of heap memory that may be allocated by SQLite.
+** ^SQLite strives to keep heap memory utilization below the soft heap
+** limit by reducing the number of pages held in the page cache
+** as heap memory usages approaches the limit.
+** ^The soft heap limit is "soft" because even though SQLite strives to stay
+** below the limit, it will exceed the limit rather than generate
+** an [SQLITE_NOMEM] error.  In other words, the soft heap limit 
+** is advisory only.
+**
+** ^The return value from sqlite3_soft_heap_limit64() is the size of
+** the soft heap limit prior to the call.  ^If the argument N is negative
+** then no change is made to the soft heap limit.  Hence, the current
+** size of the soft heap limit can be determined by invoking
+** sqlite3_soft_heap_limit64() with a negative argument.
+**
+** ^If the argument N is zero then the soft heap limit is disabled.
+**
+** ^(The soft heap limit is not enforced in the current implementation
+** if one or more of following conditions are true:
+**
+** <ul>
+** <li> The soft heap limit is set to zero.
+** <li> Memory accounting is disabled using a combination of the
+**      [sqlite3_config]([SQLITE_CONFIG_MEMSTATUS],...) start-time option and
+**      the [SQLITE_DEFAULT_MEMSTATUS] compile-time option.
+** <li> An alternative page cache implementation is specified using
+**      [sqlite3_config]([SQLITE_CONFIG_PCACHE],...).
+** <li> The page cache allocates from its own memory pool supplied
+**      by [sqlite3_config]([SQLITE_CONFIG_PAGECACHE],...) rather than
+**      from the heap.
+** </ul>)^
+**
+** Beginning with SQLite version 3.7.3, the soft heap limit is enforced
+** regardless of whether or not the [SQLITE_ENABLE_MEMORY_MANAGEMENT]
+** compile-time option is invoked.  With [SQLITE_ENABLE_MEMORY_MANAGEMENT],
+** the soft heap limit is enforced on every memory allocation.  Without
+** [SQLITE_ENABLE_MEMORY_MANAGEMENT], the soft heap limit is only enforced
+** when memory is allocated by the page cache.  Testing suggests that because
+** the page cache is the predominate memory user in SQLite, most
+** applications will achieve adequate soft heap limit enforcement without
+** the use of [SQLITE_ENABLE_MEMORY_MANAGEMENT].
+**
+** The circumstances under which SQLite will enforce the soft heap limit may
+** changes in future releases of SQLite.
+*/
+sqlite3_int64 sqlite3_soft_heap_limit64(sqlite3_int64 N);
+
+/*
+** CAPI3REF: Deprecated Soft Heap Limit Interface
+** DEPRECATED
+**
+** This is a deprecated version of the [sqlite3_soft_heap_limit64()]
+** interface.  This routine is provided for historical compatibility
+** only.  All new applications should use the
+** [sqlite3_soft_heap_limit64()] interface rather than this one.
+*/
+SQLITE_DEPRECATED void sqlite3_soft_heap_limit(int N);
+
+
+/*
+** CAPI3REF: Extract Metadata About A Column Of A Table
+**
+** ^This routine returns metadata about a specific column of a specific
+** database table accessible using the [database connection] handle
+** passed as the first function argument.
+**
+** ^The column is identified by the second, third and fourth parameters to
+** this function. ^The second parameter is either the name of the database
+** (i.e. "main", "temp", or an attached database) containing the specified
+** table or NULL. ^If it is NULL, then all attached databases are searched
+** for the table using the same algorithm used by the database engine to
+** resolve unqualified table references.
+**
+** ^The third and fourth parameters to this function are the table and column
+** name of the desired column, respectively. Neither of these parameters
+** may be NULL.
+**
+** ^Metadata is returned by writing to the memory locations passed as the 5th
+** and subsequent parameters to this function. ^Any of these arguments may be
+** NULL, in which case the corresponding element of metadata is omitted.
+**
+** ^(<blockquote>
+** <table border="1">
+** <tr><th> Parameter <th> Output<br>Type <th>  Description
+**
+** <tr><td> 5th <td> const char* <td> Data type
+** <tr><td> 6th <td> const char* <td> Name of default collation sequence
+** <tr><td> 7th <td> int         <td> True if column has a NOT NULL constraint
+** <tr><td> 8th <td> int         <td> True if column is part of the PRIMARY KEY
+** <tr><td> 9th <td> int         <td> True if column is [AUTOINCREMENT]
+** </table>
+** </blockquote>)^
+**
+** ^The memory pointed to by the character pointers returned for the
+** declaration type and collation sequence is valid only until the next
+** call to any SQLite API function.
+**
+** ^If the specified table is actually a view, an [error code] is returned.
+**
+** ^If the specified column is "rowid", "oid" or "_rowid_" and an
+** [INTEGER PRIMARY KEY] column has been explicitly declared, then the output
+** parameters are set for the explicitly declared column. ^(If there is no
+** explicitly declared [INTEGER PRIMARY KEY] column, then the output
+** parameters are set as follows:
+**
+** <pre>
+**     data type: "INTEGER"
+**     collation sequence: "BINARY"
+**     not null: 0
+**     primary key: 1
+**     auto increment: 0
+** </pre>)^
+**
+** ^(This function may load one or more schemas from database files. If an
+** error occurs during this process, or if the requested table or column
+** cannot be found, an [error code] is returned and an error message left
+** in the [database connection] (to be retrieved using sqlite3_errmsg()).)^
+**
+** ^This API is only available if the library was compiled with the
+** [SQLITE_ENABLE_COLUMN_METADATA] C-preprocessor symbol defined.
+*/
+int sqlite3_table_column_metadata(
+  sqlite3 *db,                /* Connection handle */
+  const char *zDbName,        /* Database name or NULL */
+  const char *zTableName,     /* Table name */
+  const char *zColumnName,    /* Column name */
+  char const **pzDataType,    /* OUTPUT: Declared data type */
+  char const **pzCollSeq,     /* OUTPUT: Collation sequence name */
+  int *pNotNull,              /* OUTPUT: True if NOT NULL constraint exists */
+  int *pPrimaryKey,           /* OUTPUT: True if column part of PK */
+  int *pAutoinc               /* OUTPUT: True if column is auto-increment */
+);
+
+/*
+** CAPI3REF: Load An Extension
+**
+** ^This interface loads an SQLite extension library from the named file.
+**
+** ^The sqlite3_load_extension() interface attempts to load an
+** SQLite extension library contained in the file zFile.
+**
+** ^The entry point is zProc.
+** ^zProc may be 0, in which case the name of the entry point
+** defaults to "sqlite3_extension_init".
+** ^The sqlite3_load_extension() interface returns
+** [SQLITE_OK] on success and [SQLITE_ERROR] if something goes wrong.
+** ^If an error occurs and pzErrMsg is not 0, then the
+** [sqlite3_load_extension()] interface shall attempt to
+** fill *pzErrMsg with error message text stored in memory
+** obtained from [sqlite3_malloc()]. The calling function
+** should free this memory by calling [sqlite3_free()].
+**
+** ^Extension loading must be enabled using
+** [sqlite3_enable_load_extension()] prior to calling this API,
+** otherwise an error will be returned.
+**
+** See also the [load_extension() SQL function].
+*/
+int sqlite3_load_extension(
+  sqlite3 *db,          /* Load the extension into this database connection */
+  const char *zFile,    /* Name of the shared library containing extension */
+  const char *zProc,    /* Entry point.  Derived from zFile if 0 */
+  char **pzErrMsg       /* Put error message here if not 0 */
+);
+
+/*
+** CAPI3REF: Enable Or Disable Extension Loading
+**
+** ^So as not to open security holes in older applications that are
+** unprepared to deal with extension loading, and as a means of disabling
+** extension loading while evaluating user-entered SQL, the following API
+** is provided to turn the [sqlite3_load_extension()] mechanism on and off.
+**
+** ^Extension loading is off by default. See ticket #1863.
+** ^Call the sqlite3_enable_load_extension() routine with onoff==1
+** to turn extension loading on and call it with onoff==0 to turn
+** it back off again.
+*/
+int sqlite3_enable_load_extension(sqlite3 *db, int onoff);
+
+/*
+** CAPI3REF: Automatically Load Statically Linked Extensions
+**
+** ^This interface causes the xEntryPoint() function to be invoked for
+** each new [database connection] that is created.  The idea here is that
+** xEntryPoint() is the entry point for a statically linked SQLite extension
+** that is to be automatically loaded into all new database connections.
+**
+** ^(Even though the function prototype shows that xEntryPoint() takes
+** no arguments and returns void, SQLite invokes xEntryPoint() with three
+** arguments and expects and integer result as if the signature of the
+** entry point where as follows:
+**
+** <blockquote><pre>
+** &nbsp;  int xEntryPoint(
+** &nbsp;    sqlite3 *db,
+** &nbsp;    const char **pzErrMsg,
+** &nbsp;    const struct sqlite3_api_routines *pThunk
+** &nbsp;  );
+** </pre></blockquote>)^
+**
+** If the xEntryPoint routine encounters an error, it should make *pzErrMsg
+** point to an appropriate error message (obtained from [sqlite3_mprintf()])
+** and return an appropriate [error code].  ^SQLite ensures that *pzErrMsg
+** is NULL before calling the xEntryPoint().  ^SQLite will invoke
+** [sqlite3_free()] on *pzErrMsg after xEntryPoint() returns.  ^If any
+** xEntryPoint() returns an error, the [sqlite3_open()], [sqlite3_open16()],
+** or [sqlite3_open_v2()] call that provoked the xEntryPoint() will fail.
+**
+** ^Calling sqlite3_auto_extension(X) with an entry point X that is already
+** on the list of automatic extensions is a harmless no-op. ^No entry point
+** will be called more than once for each database connection that is opened.
+**
+** See also: [sqlite3_reset_auto_extension()].
+*/
+int sqlite3_auto_extension(void (*xEntryPoint)(void));
+
+/*
+** CAPI3REF: Reset Automatic Extension Loading
+**
+** ^This interface disables all automatic extensions previously
+** registered using [sqlite3_auto_extension()].
+*/
+void sqlite3_reset_auto_extension(void);
+
+/*
+** The interface to the virtual-table mechanism is currently considered
+** to be experimental.  The interface might change in incompatible ways.
+** If this is a problem for you, do not use the interface at this time.
+**
+** When the virtual-table mechanism stabilizes, we will declare the
+** interface fixed, support it indefinitely, and remove this comment.
+*/
+
+/*
+** Structures used by the virtual table interface
+*/
+typedef struct sqlite3_vtab sqlite3_vtab;
+typedef struct sqlite3_index_info sqlite3_index_info;
+typedef struct sqlite3_vtab_cursor sqlite3_vtab_cursor;
+typedef struct sqlite3_module sqlite3_module;
+
+/*
+** CAPI3REF: Virtual Table Object
+** KEYWORDS: sqlite3_module {virtual table module}
+**
+** This structure, sometimes called a "virtual table module", 
+** defines the implementation of a [virtual tables].  
+** This structure consists mostly of methods for the module.
+**
+** ^A virtual table module is created by filling in a persistent
+** instance of this structure and passing a pointer to that instance
+** to [sqlite3_create_module()] or [sqlite3_create_module_v2()].
+** ^The registration remains valid until it is replaced by a different
+** module or until the [database connection] closes.  The content
+** of this structure must not change while it is registered with
+** any database connection.
+*/
+struct sqlite3_module {
+  int iVersion;
+  int (*xCreate)(sqlite3*, void *pAux,
+               int argc, const char *const*argv,
+               sqlite3_vtab **ppVTab, char**);
+  int (*xConnect)(sqlite3*, void *pAux,
+               int argc, const char *const*argv,
+               sqlite3_vtab **ppVTab, char**);
+  int (*xBestIndex)(sqlite3_vtab *pVTab, sqlite3_index_info*);
+  int (*xDisconnect)(sqlite3_vtab *pVTab);
+  int (*xDestroy)(sqlite3_vtab *pVTab);
+  int (*xOpen)(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor);
+  int (*xClose)(sqlite3_vtab_cursor*);
+  int (*xFilter)(sqlite3_vtab_cursor*, int idxNum, const char *idxStr,
+                int argc, sqlite3_value **argv);
+  int (*xNext)(sqlite3_vtab_cursor*);
+  int (*xEof)(sqlite3_vtab_cursor*);
+  int (*xColumn)(sqlite3_vtab_cursor*, sqlite3_context*, int);
+  int (*xRowid)(sqlite3_vtab_cursor*, sqlite3_int64 *pRowid);
+  int (*xUpdate)(sqlite3_vtab *, int, sqlite3_value **, sqlite3_int64 *);
+  int (*xBegin)(sqlite3_vtab *pVTab);
+  int (*xSync)(sqlite3_vtab *pVTab);
+  int (*xCommit)(sqlite3_vtab *pVTab);
+  int (*xRollback)(sqlite3_vtab *pVTab);
+  int (*xFindFunction)(sqlite3_vtab *pVtab, int nArg, const char *zName,
+                       void (**pxFunc)(sqlite3_context*,int,sqlite3_value**),
+                       void **ppArg);
+  int (*xRename)(sqlite3_vtab *pVtab, const char *zNew);
+  /* The methods above are in version 1 of the sqlite_module object. Those 
+  ** below are for version 2 and greater. */
+  int (*xSavepoint)(sqlite3_vtab *pVTab, int);
+  int (*xRelease)(sqlite3_vtab *pVTab, int);
+  int (*xRollbackTo)(sqlite3_vtab *pVTab, int);
+};
+
+/*
+** CAPI3REF: Virtual Table Indexing Information
+** KEYWORDS: sqlite3_index_info
+**
+** The sqlite3_index_info structure and its substructures is used as part
+** of the [virtual table] interface to
+** pass information into and receive the reply from the [xBestIndex]
+** method of a [virtual table module].  The fields under **Inputs** are the
+** inputs to xBestIndex and are read-only.  xBestIndex inserts its
+** results into the **Outputs** fields.
+**
+** ^(The aConstraint[] array records WHERE clause constraints of the form:
+**
+** <blockquote>column OP expr</blockquote>
+**
+** where OP is =, &lt;, &lt;=, &gt;, or &gt;=.)^  ^(The particular operator is
+** stored in aConstraint[].op using one of the
+** [SQLITE_INDEX_CONSTRAINT_EQ | SQLITE_INDEX_CONSTRAINT_ values].)^
+** ^(The index of the column is stored in
+** aConstraint[].iColumn.)^  ^(aConstraint[].usable is TRUE if the
+** expr on the right-hand side can be evaluated (and thus the constraint
+** is usable) and false if it cannot.)^
+**
+** ^The optimizer automatically inverts terms of the form "expr OP column"
+** and makes other simplifications to the WHERE clause in an attempt to
+** get as many WHERE clause terms into the form shown above as possible.
+** ^The aConstraint[] array only reports WHERE clause terms that are
+** relevant to the particular virtual table being queried.
+**
+** ^Information about the ORDER BY clause is stored in aOrderBy[].
+** ^Each term of aOrderBy records a column of the ORDER BY clause.
+**
+** The [xBestIndex] method must fill aConstraintUsage[] with information
+** about what parameters to pass to xFilter.  ^If argvIndex>0 then
+** the right-hand side of the corresponding aConstraint[] is evaluated
+** and becomes the argvIndex-th entry in argv.  ^(If aConstraintUsage[].omit
+** is true, then the constraint is assumed to be fully handled by the
+** virtual table and is not checked again by SQLite.)^
+**
+** ^The idxNum and idxPtr values are recorded and passed into the
+** [xFilter] method.
+** ^[sqlite3_free()] is used to free idxPtr if and only if
+** needToFreeIdxPtr is true.
+**
+** ^The orderByConsumed means that output from [xFilter]/[xNext] will occur in
+** the correct order to satisfy the ORDER BY clause so that no separate
+** sorting step is required.
+**
+** ^The estimatedCost value is an estimate of the cost of doing the
+** particular lookup.  A full scan of a table with N entries should have
+** a cost of N.  A binary search of a table of N entries should have a
+** cost of approximately log(N).
+*/
+struct sqlite3_index_info {
+  /* Inputs */
+  int nConstraint;           /* Number of entries in aConstraint */
+  struct sqlite3_index_constraint {
+     int iColumn;              /* Column on left-hand side of constraint */
+     unsigned char op;         /* Constraint operator */
+     unsigned char usable;     /* True if this constraint is usable */
+     int iTermOffset;          /* Used internally - xBestIndex should ignore */
+  } *aConstraint;            /* Table of WHERE clause constraints */
+  int nOrderBy;              /* Number of terms in the ORDER BY clause */
+  struct sqlite3_index_orderby {
+     int iColumn;              /* Column number */
+     unsigned char desc;       /* True for DESC.  False for ASC. */
+  } *aOrderBy;               /* The ORDER BY clause */
+  /* Outputs */
+  struct sqlite3_index_constraint_usage {
+    int argvIndex;           /* if >0, constraint is part of argv to xFilter */
+    unsigned char omit;      /* Do not code a test for this constraint */
+  } *aConstraintUsage;
+  int idxNum;                /* Number used to identify the index */
+  char *idxStr;              /* String, possibly obtained from sqlite3_malloc */
+  int needToFreeIdxStr;      /* Free idxStr using sqlite3_free() if true */
+  int orderByConsumed;       /* True if output is already ordered */
+  double estimatedCost;      /* Estimated cost of using this index */
+};
+
+/*
+** CAPI3REF: Virtual Table Constraint Operator Codes
+**
+** These macros defined the allowed values for the
+** [sqlite3_index_info].aConstraint[].op field.  Each value represents
+** an operator that is part of a constraint term in the wHERE clause of
+** a query that uses a [virtual table].
+*/
+#define SQLITE_INDEX_CONSTRAINT_EQ    2
+#define SQLITE_INDEX_CONSTRAINT_GT    4
+#define SQLITE_INDEX_CONSTRAINT_LE    8
+#define SQLITE_INDEX_CONSTRAINT_LT    16
+#define SQLITE_INDEX_CONSTRAINT_GE    32
+#define SQLITE_INDEX_CONSTRAINT_MATCH 64
+
+/*
+** CAPI3REF: Register A Virtual Table Implementation
+**
+** ^These routines are used to register a new [virtual table module] name.
+** ^Module names must be registered before
+** creating a new [virtual table] using the module and before using a
+** preexisting [virtual table] for the module.
+**
+** ^The module name is registered on the [database connection] specified
+** by the first parameter.  ^The name of the module is given by the 
+** second parameter.  ^The third parameter is a pointer to
+** the implementation of the [virtual table module].   ^The fourth
+** parameter is an arbitrary client data pointer that is passed through
+** into the [xCreate] and [xConnect] methods of the virtual table module
+** when a new virtual table is be being created or reinitialized.
+**
+** ^The sqlite3_create_module_v2() interface has a fifth parameter which
+** is a pointer to a destructor for the pClientData.  ^SQLite will
+** invoke the destructor function (if it is not NULL) when SQLite
+** no longer needs the pClientData pointer.  ^The destructor will also
+** be invoked if the call to sqlite3_create_module_v2() fails.
+** ^The sqlite3_create_module()
+** interface is equivalent to sqlite3_create_module_v2() with a NULL
+** destructor.
+*/
+int sqlite3_create_module(
+  sqlite3 *db,               /* SQLite connection to register module with */
+  const char *zName,         /* Name of the module */
+  const sqlite3_module *p,   /* Methods for the module */
+  void *pClientData          /* Client data for xCreate/xConnect */
+);
+int sqlite3_create_module_v2(
+  sqlite3 *db,               /* SQLite connection to register module with */
+  const char *zName,         /* Name of the module */
+  const sqlite3_module *p,   /* Methods for the module */
+  void *pClientData,         /* Client data for xCreate/xConnect */
+  void(*xDestroy)(void*)     /* Module destructor function */
+);
+
+/*
+** CAPI3REF: Virtual Table Instance Object
+** KEYWORDS: sqlite3_vtab
+**
+** Every [virtual table module] implementation uses a subclass
+** of this object to describe a particular instance
+** of the [virtual table].  Each subclass will
+** be tailored to the specific needs of the module implementation.
+** The purpose of this superclass is to define certain fields that are
+** common to all module implementations.
+**
+** ^Virtual tables methods can set an error message by assigning a
+** string obtained from [sqlite3_mprintf()] to zErrMsg.  The method should
+** take care that any prior string is freed by a call to [sqlite3_free()]
+** prior to assigning a new string to zErrMsg.  ^After the error message
+** is delivered up to the client application, the string will be automatically
+** freed by sqlite3_free() and the zErrMsg field will be zeroed.
+*/
+struct sqlite3_vtab {
+  const sqlite3_module *pModule;  /* The module for this virtual table */
+  int nRef;                       /* NO LONGER USED */
+  char *zErrMsg;                  /* Error message from sqlite3_mprintf() */
+  /* Virtual table implementations will typically add additional fields */
+};
+
+/*
+** CAPI3REF: Virtual Table Cursor Object
+** KEYWORDS: sqlite3_vtab_cursor {virtual table cursor}
+**
+** Every [virtual table module] implementation uses a subclass of the
+** following structure to describe cursors that point into the
+** [virtual table] and are used
+** to loop through the virtual table.  Cursors are created using the
+** [sqlite3_module.xOpen | xOpen] method of the module and are destroyed
+** by the [sqlite3_module.xClose | xClose] method.  Cursors are used
+** by the [xFilter], [xNext], [xEof], [xColumn], and [xRowid] methods
+** of the module.  Each module implementation will define
+** the content of a cursor structure to suit its own needs.
+**
+** This superclass exists in order to define fields of the cursor that
+** are common to all implementations.
+*/
+struct sqlite3_vtab_cursor {
+  sqlite3_vtab *pVtab;      /* Virtual table of this cursor */
+  /* Virtual table implementations will typically add additional fields */
+};
+
+/*
+** CAPI3REF: Declare The Schema Of A Virtual Table
+**
+** ^The [xCreate] and [xConnect] methods of a
+** [virtual table module] call this interface
+** to declare the format (the names and datatypes of the columns) of
+** the virtual tables they implement.
+*/
+int sqlite3_declare_vtab(sqlite3*, const char *zSQL);
+
+/*
+** CAPI3REF: Overload A Function For A Virtual Table
+**
+** ^(Virtual tables can provide alternative implementations of functions
+** using the [xFindFunction] method of the [virtual table module].  
+** But global versions of those functions
+** must exist in order to be overloaded.)^
+**
+** ^(This API makes sure a global version of a function with a particular
+** name and number of parameters exists.  If no such function exists
+** before this API is called, a new function is created.)^  ^The implementation
+** of the new function always causes an exception to be thrown.  So
+** the new function is not good for anything by itself.  Its only
+** purpose is to be a placeholder function that can be overloaded
+** by a [virtual table].
+*/
+int sqlite3_overload_function(sqlite3*, const char *zFuncName, int nArg);
+
+/*
+** The interface to the virtual-table mechanism defined above (back up
+** to a comment remarkably similar to this one) is currently considered
+** to be experimental.  The interface might change in incompatible ways.
+** If this is a problem for you, do not use the interface at this time.
+**
+** When the virtual-table mechanism stabilizes, we will declare the
+** interface fixed, support it indefinitely, and remove this comment.
+*/
+
+/*
+** CAPI3REF: A Handle To An Open BLOB
+** KEYWORDS: {BLOB handle} {BLOB handles}
+**
+** An instance of this object represents an open BLOB on which
+** [sqlite3_blob_open | incremental BLOB I/O] can be performed.
+** ^Objects of this type are created by [sqlite3_blob_open()]
+** and destroyed by [sqlite3_blob_close()].
+** ^The [sqlite3_blob_read()] and [sqlite3_blob_write()] interfaces
+** can be used to read or write small subsections of the BLOB.
+** ^The [sqlite3_blob_bytes()] interface returns the size of the BLOB in bytes.
+*/
+typedef struct sqlite3_blob sqlite3_blob;
+
+/*
+** CAPI3REF: Open A BLOB For Incremental I/O
+**
+** ^(This interfaces opens a [BLOB handle | handle] to the BLOB located
+** in row iRow, column zColumn, table zTable in database zDb;
+** in other words, the same BLOB that would be selected by:
+**
+** <pre>
+**     SELECT zColumn FROM zDb.zTable WHERE [rowid] = iRow;
+** </pre>)^
+**
+** ^If the flags parameter is non-zero, then the BLOB is opened for read
+** and write access. ^If it is zero, the BLOB is opened for read access.
+** ^It is not possible to open a column that is part of an index or primary 
+** key for writing. ^If [foreign key constraints] are enabled, it is 
+** not possible to open a column that is part of a [child key] for writing.
+**
+** ^Note that the database name is not the filename that contains
+** the database but rather the symbolic name of the database that
+** appears after the AS keyword when the database is connected using [ATTACH].
+** ^For the main database file, the database name is "main".
+** ^For TEMP tables, the database name is "temp".
+**
+** ^(On success, [SQLITE_OK] is returned and the new [BLOB handle] is written
+** to *ppBlob. Otherwise an [error code] is returned and *ppBlob is set
+** to be a null pointer.)^
+** ^This function sets the [database connection] error code and message
+** accessible via [sqlite3_errcode()] and [sqlite3_errmsg()] and related
+** functions. ^Note that the *ppBlob variable is always initialized in a
+** way that makes it safe to invoke [sqlite3_blob_close()] on *ppBlob
+** regardless of the success or failure of this routine.
+**
+** ^(If the row that a BLOB handle points to is modified by an
+** [UPDATE], [DELETE], or by [ON CONFLICT] side-effects
+** then the BLOB handle is marked as "expired".
+** This is true if any column of the row is changed, even a column
+** other than the one the BLOB handle is open on.)^
+** ^Calls to [sqlite3_blob_read()] and [sqlite3_blob_write()] for
+** an expired BLOB handle fail with a return code of [SQLITE_ABORT].
+** ^(Changes written into a BLOB prior to the BLOB expiring are not
+** rolled back by the expiration of the BLOB.  Such changes will eventually
+** commit if the transaction continues to completion.)^
+**
+** ^Use the [sqlite3_blob_bytes()] interface to determine the size of
+** the opened blob.  ^The size of a blob may not be changed by this
+** interface.  Use the [UPDATE] SQL command to change the size of a
+** blob.
+**
+** ^The [sqlite3_bind_zeroblob()] and [sqlite3_result_zeroblob()] interfaces
+** and the built-in [zeroblob] SQL function can be used, if desired,
+** to create an empty, zero-filled blob in which to read or write using
+** this interface.
+**
+** To avoid a resource leak, every open [BLOB handle] should eventually
+** be released by a call to [sqlite3_blob_close()].
+*/
+int sqlite3_blob_open(
+  sqlite3*,
+  const char *zDb,
+  const char *zTable,
+  const char *zColumn,
+  sqlite3_int64 iRow,
+  int flags,
+  sqlite3_blob **ppBlob
+);
+
+/*
+** CAPI3REF: Move a BLOB Handle to a New Row
+**
+** ^This function is used to move an existing blob handle so that it points
+** to a different row of the same database table. ^The new row is identified
+** by the rowid value passed as the second argument. Only the row can be
+** changed. ^The database, table and column on which the blob handle is open
+** remain the same. Moving an existing blob handle to a new row can be
+** faster than closing the existing handle and opening a new one.
+**
+** ^(The new row must meet the same criteria as for [sqlite3_blob_open()] -
+** it must exist and there must be either a blob or text value stored in
+** the nominated column.)^ ^If the new row is not present in the table, or if
+** it does not contain a blob or text value, or if another error occurs, an
+** SQLite error code is returned and the blob handle is considered aborted.
+** ^All subsequent calls to [sqlite3_blob_read()], [sqlite3_blob_write()] or
+** [sqlite3_blob_reopen()] on an aborted blob handle immediately return
+** SQLITE_ABORT. ^Calling [sqlite3_blob_bytes()] on an aborted blob handle
+** always returns zero.
+**
+** ^This function sets the database handle error code and message.
+*/
+SQLITE_EXPERIMENTAL int sqlite3_blob_reopen(sqlite3_blob *, sqlite3_int64);
+
+/*
+** CAPI3REF: Close A BLOB Handle
+**
+** ^Closes an open [BLOB handle].
+**
+** ^Closing a BLOB shall cause the current transaction to commit
+** if there are no other BLOBs, no pending prepared statements, and the
+** database connection is in [autocommit mode].
+** ^If any writes were made to the BLOB, they might be held in cache
+** until the close operation if they will fit.
+**
+** ^(Closing the BLOB often forces the changes
+** out to disk and so if any I/O errors occur, they will likely occur
+** at the time when the BLOB is closed.  Any errors that occur during
+** closing are reported as a non-zero return value.)^
+**
+** ^(The BLOB is closed unconditionally.  Even if this routine returns
+** an error code, the BLOB is still closed.)^
+**
+** ^Calling this routine with a null pointer (such as would be returned
+** by a failed call to [sqlite3_blob_open()]) is a harmless no-op.
+*/
+int sqlite3_blob_close(sqlite3_blob *);
+
+/*
+** CAPI3REF: Return The Size Of An Open BLOB
+**
+** ^Returns the size in bytes of the BLOB accessible via the 
+** successfully opened [BLOB handle] in its only argument.  ^The
+** incremental blob I/O routines can only read or overwriting existing
+** blob content; they cannot change the size of a blob.
+**
+** This routine only works on a [BLOB handle] which has been created
+** by a prior successful call to [sqlite3_blob_open()] and which has not
+** been closed by [sqlite3_blob_close()].  Passing any other pointer in
+** to this routine results in undefined and probably undesirable behavior.
+*/
+int sqlite3_blob_bytes(sqlite3_blob *);
+
+/*
+** CAPI3REF: Read Data From A BLOB Incrementally
+**
+** ^(This function is used to read data from an open [BLOB handle] into a
+** caller-supplied buffer. N bytes of data are copied into buffer Z
+** from the open BLOB, starting at offset iOffset.)^
+**
+** ^If offset iOffset is less than N bytes from the end of the BLOB,
+** [SQLITE_ERROR] is returned and no data is read.  ^If N or iOffset is
+** less than zero, [SQLITE_ERROR] is returned and no data is read.
+** ^The size of the blob (and hence the maximum value of N+iOffset)
+** can be determined using the [sqlite3_blob_bytes()] interface.
+**
+** ^An attempt to read from an expired [BLOB handle] fails with an
+** error code of [SQLITE_ABORT].
+**
+** ^(On success, sqlite3_blob_read() returns SQLITE_OK.
+** Otherwise, an [error code] or an [extended error code] is returned.)^
+**
+** This routine only works on a [BLOB handle] which has been created
+** by a prior successful call to [sqlite3_blob_open()] and which has not
+** been closed by [sqlite3_blob_close()].  Passing any other pointer in
+** to this routine results in undefined and probably undesirable behavior.
+**
+** See also: [sqlite3_blob_write()].
+*/
+int sqlite3_blob_read(sqlite3_blob *, void *Z, int N, int iOffset);
+
+/*
+** CAPI3REF: Write Data Into A BLOB Incrementally
+**
+** ^This function is used to write data into an open [BLOB handle] from a
+** caller-supplied buffer. ^N bytes of data are copied from the buffer Z
+** into the open BLOB, starting at offset iOffset.
+**
+** ^If the [BLOB handle] passed as the first argument was not opened for
+** writing (the flags parameter to [sqlite3_blob_open()] was zero),
+** this function returns [SQLITE_READONLY].
+**
+** ^This function may only modify the contents of the BLOB; it is
+** not possible to increase the size of a BLOB using this API.
+** ^If offset iOffset is less than N bytes from the end of the BLOB,
+** [SQLITE_ERROR] is returned and no data is written.  ^If N is
+** less than zero [SQLITE_ERROR] is returned and no data is written.
+** The size of the BLOB (and hence the maximum value of N+iOffset)
+** can be determined using the [sqlite3_blob_bytes()] interface.
+**
+** ^An attempt to write to an expired [BLOB handle] fails with an
+** error code of [SQLITE_ABORT].  ^Writes to the BLOB that occurred
+** before the [BLOB handle] expired are not rolled back by the
+** expiration of the handle, though of course those changes might
+** have been overwritten by the statement that expired the BLOB handle
+** or by other independent statements.
+**
+** ^(On success, sqlite3_blob_write() returns SQLITE_OK.
+** Otherwise, an  [error code] or an [extended error code] is returned.)^
+**
+** This routine only works on a [BLOB handle] which has been created
+** by a prior successful call to [sqlite3_blob_open()] and which has not
+** been closed by [sqlite3_blob_close()].  Passing any other pointer in
+** to this routine results in undefined and probably undesirable behavior.
+**
+** See also: [sqlite3_blob_read()].
+*/
+int sqlite3_blob_write(sqlite3_blob *, const void *z, int n, int iOffset);
+
+/*
+** CAPI3REF: Virtual File System Objects
+**
+** A virtual filesystem (VFS) is an [sqlite3_vfs] object
+** that SQLite uses to interact
+** with the underlying operating system.  Most SQLite builds come with a
+** single default VFS that is appropriate for the host computer.
+** New VFSes can be registered and existing VFSes can be unregistered.
+** The following interfaces are provided.
+**
+** ^The sqlite3_vfs_find() interface returns a pointer to a VFS given its name.
+** ^Names are case sensitive.
+** ^Names are zero-terminated UTF-8 strings.
+** ^If there is no match, a NULL pointer is returned.
+** ^If zVfsName is NULL then the default VFS is returned.
+**
+** ^New VFSes are registered with sqlite3_vfs_register().
+** ^Each new VFS becomes the default VFS if the makeDflt flag is set.
+** ^The same VFS can be registered multiple times without injury.
+** ^To make an existing VFS into the default VFS, register it again
+** with the makeDflt flag set.  If two different VFSes with the
+** same name are registered, the behavior is undefined.  If a
+** VFS is registered with a name that is NULL or an empty string,
+** then the behavior is undefined.
+**
+** ^Unregister a VFS with the sqlite3_vfs_unregister() interface.
+** ^(If the default VFS is unregistered, another VFS is chosen as
+** the default.  The choice for the new VFS is arbitrary.)^
+*/
+sqlite3_vfs *sqlite3_vfs_find(const char *zVfsName);
+int sqlite3_vfs_register(sqlite3_vfs*, int makeDflt);
+int sqlite3_vfs_unregister(sqlite3_vfs*);
+
+/*
+** CAPI3REF: Mutexes
+**
+** The SQLite core uses these routines for thread
+** synchronization. Though they are intended for internal
+** use by SQLite, code that links against SQLite is
+** permitted to use any of these routines.
+**
+** The SQLite source code contains multiple implementations
+** of these mutex routines.  An appropriate implementation
+** is selected automatically at compile-time.  ^(The following
+** implementations are available in the SQLite core:
+**
+** <ul>
+** <li>   SQLITE_MUTEX_OS2
+** <li>   SQLITE_MUTEX_PTHREAD
+** <li>   SQLITE_MUTEX_W32
+** <li>   SQLITE_MUTEX_NOOP
+** </ul>)^
+**
+** ^The SQLITE_MUTEX_NOOP implementation is a set of routines
+** that does no real locking and is appropriate for use in
+** a single-threaded application.  ^The SQLITE_MUTEX_OS2,
+** SQLITE_MUTEX_PTHREAD, and SQLITE_MUTEX_W32 implementations
+** are appropriate for use on OS/2, Unix, and Windows.
+**
+** ^(If SQLite is compiled with the SQLITE_MUTEX_APPDEF preprocessor
+** macro defined (with "-DSQLITE_MUTEX_APPDEF=1"), then no mutex
+** implementation is included with the library. In this case the
+** application must supply a custom mutex implementation using the
+** [SQLITE_CONFIG_MUTEX] option of the sqlite3_config() function
+** before calling sqlite3_initialize() or any other public sqlite3_
+** function that calls sqlite3_initialize().)^
+**
+** ^The sqlite3_mutex_alloc() routine allocates a new
+** mutex and returns a pointer to it. ^If it returns NULL
+** that means that a mutex could not be allocated.  ^SQLite
+** will unwind its stack and return an error.  ^(The argument
+** to sqlite3_mutex_alloc() is one of these integer constants:
+**
+** <ul>
+** <li>  SQLITE_MUTEX_FAST
+** <li>  SQLITE_MUTEX_RECURSIVE
+** <li>  SQLITE_MUTEX_STATIC_MASTER
+** <li>  SQLITE_MUTEX_STATIC_MEM
+** <li>  SQLITE_MUTEX_STATIC_MEM2
+** <li>  SQLITE_MUTEX_STATIC_PRNG
+** <li>  SQLITE_MUTEX_STATIC_LRU
+** <li>  SQLITE_MUTEX_STATIC_LRU2
+** </ul>)^
+**
+** ^The first two constants (SQLITE_MUTEX_FAST and SQLITE_MUTEX_RECURSIVE)
+** cause sqlite3_mutex_alloc() to create
+** a new mutex.  ^The new mutex is recursive when SQLITE_MUTEX_RECURSIVE
+** is used but not necessarily so when SQLITE_MUTEX_FAST is used.
+** The mutex implementation does not need to make a distinction
+** between SQLITE_MUTEX_RECURSIVE and SQLITE_MUTEX_FAST if it does
+** not want to.  ^SQLite will only request a recursive mutex in
+** cases where it really needs one.  ^If a faster non-recursive mutex
+** implementation is available on the host platform, the mutex subsystem
+** might return such a mutex in response to SQLITE_MUTEX_FAST.
+**
+** ^The other allowed parameters to sqlite3_mutex_alloc() (anything other
+** than SQLITE_MUTEX_FAST and SQLITE_MUTEX_RECURSIVE) each return
+** a pointer to a static preexisting mutex.  ^Six static mutexes are
+** used by the current version of SQLite.  Future versions of SQLite
+** may add additional static mutexes.  Static mutexes are for internal
+** use by SQLite only.  Applications that use SQLite mutexes should
+** use only the dynamic mutexes returned by SQLITE_MUTEX_FAST or
+** SQLITE_MUTEX_RECURSIVE.
+**
+** ^Note that if one of the dynamic mutex parameters (SQLITE_MUTEX_FAST
+** or SQLITE_MUTEX_RECURSIVE) is used then sqlite3_mutex_alloc()
+** returns a different mutex on every call.  ^But for the static
+** mutex types, the same mutex is returned on every call that has
+** the same type number.
+**
+** ^The sqlite3_mutex_free() routine deallocates a previously
+** allocated dynamic mutex.  ^SQLite is careful to deallocate every
+** dynamic mutex that it allocates.  The dynamic mutexes must not be in
+** use when they are deallocated.  Attempting to deallocate a static
+** mutex results in undefined behavior.  ^SQLite never deallocates
+** a static mutex.
+**
+** ^The sqlite3_mutex_enter() and sqlite3_mutex_try() routines attempt
+** to enter a mutex.  ^If another thread is already within the mutex,
+** sqlite3_mutex_enter() will block and sqlite3_mutex_try() will return
+** SQLITE_BUSY.  ^The sqlite3_mutex_try() interface returns [SQLITE_OK]
+** upon successful entry.  ^(Mutexes created using
+** SQLITE_MUTEX_RECURSIVE can be entered multiple times by the same thread.
+** In such cases the,
+** mutex must be exited an equal number of times before another thread
+** can enter.)^  ^(If the same thread tries to enter any other
+** kind of mutex more than once, the behavior is undefined.
+** SQLite will never exhibit
+** such behavior in its own use of mutexes.)^
+**
+** ^(Some systems (for example, Windows 95) do not support the operation
+** implemented by sqlite3_mutex_try().  On those systems, sqlite3_mutex_try()
+** will always return SQLITE_BUSY.  The SQLite core only ever uses
+** sqlite3_mutex_try() as an optimization so this is acceptable behavior.)^
+**
+** ^The sqlite3_mutex_leave() routine exits a mutex that was
+** previously entered by the same thread.   ^(The behavior
+** is undefined if the mutex is not currently entered by the
+** calling thread or is not currently allocated.  SQLite will
+** never do either.)^
+**
+** ^If the argument to sqlite3_mutex_enter(), sqlite3_mutex_try(), or
+** sqlite3_mutex_leave() is a NULL pointer, then all three routines
+** behave as no-ops.
+**
+** See also: [sqlite3_mutex_held()] and [sqlite3_mutex_notheld()].
+*/
+sqlite3_mutex *sqlite3_mutex_alloc(int);
+void sqlite3_mutex_free(sqlite3_mutex*);
+void sqlite3_mutex_enter(sqlite3_mutex*);
+int sqlite3_mutex_try(sqlite3_mutex*);
+void sqlite3_mutex_leave(sqlite3_mutex*);
+
+/*
+** CAPI3REF: Mutex Methods Object
+**
+** An instance of this structure defines the low-level routines
+** used to allocate and use mutexes.
+**
+** Usually, the default mutex implementations provided by SQLite are
+** sufficient, however the user has the option of substituting a custom
+** implementation for specialized deployments or systems for which SQLite
+** does not provide a suitable implementation. In this case, the user
+** creates and populates an instance of this structure to pass
+** to sqlite3_config() along with the [SQLITE_CONFIG_MUTEX] option.
+** Additionally, an instance of this structure can be used as an
+** output variable when querying the system for the current mutex
+** implementation, using the [SQLITE_CONFIG_GETMUTEX] option.
+**
+** ^The xMutexInit method defined by this structure is invoked as
+** part of system initialization by the sqlite3_initialize() function.
+** ^The xMutexInit routine is called by SQLite exactly once for each
+** effective call to [sqlite3_initialize()].
+**
+** ^The xMutexEnd method defined by this structure is invoked as
+** part of system shutdown by the sqlite3_shutdown() function. The
+** implementation of this method is expected to release all outstanding
+** resources obtained by the mutex methods implementation, especially
+** those obtained by the xMutexInit method.  ^The xMutexEnd()
+** interface is invoked exactly once for each call to [sqlite3_shutdown()].
+**
+** ^(The remaining seven methods defined by this structure (xMutexAlloc,
+** xMutexFree, xMutexEnter, xMutexTry, xMutexLeave, xMutexHeld and
+** xMutexNotheld) implement the following interfaces (respectively):
+**
+** <ul>
+**   <li>  [sqlite3_mutex_alloc()] </li>
+**   <li>  [sqlite3_mutex_free()] </li>
+**   <li>  [sqlite3_mutex_enter()] </li>
+**   <li>  [sqlite3_mutex_try()] </li>
+**   <li>  [sqlite3_mutex_leave()] </li>
+**   <li>  [sqlite3_mutex_held()] </li>
+**   <li>  [sqlite3_mutex_notheld()] </li>
+** </ul>)^
+**
+** The only difference is that the public sqlite3_XXX functions enumerated
+** above silently ignore any invocations that pass a NULL pointer instead
+** of a valid mutex handle. The implementations of the methods defined
+** by this structure are not required to handle this case, the results
+** of passing a NULL pointer instead of a valid mutex handle are undefined
+** (i.e. it is acceptable to provide an implementation that segfaults if
+** it is passed a NULL pointer).
+**
+** The xMutexInit() method must be threadsafe.  ^It must be harmless to
+** invoke xMutexInit() multiple times within the same process and without
+** intervening calls to xMutexEnd().  Second and subsequent calls to
+** xMutexInit() must be no-ops.
+**
+** ^xMutexInit() must not use SQLite memory allocation ([sqlite3_malloc()]
+** and its associates).  ^Similarly, xMutexAlloc() must not use SQLite memory
+** allocation for a static mutex.  ^However xMutexAlloc() may use SQLite
+** memory allocation for a fast or recursive mutex.
+**
+** ^SQLite will invoke the xMutexEnd() method when [sqlite3_shutdown()] is
+** called, but only if the prior call to xMutexInit returned SQLITE_OK.
+** If xMutexInit fails in any way, it is expected to clean up after itself
+** prior to returning.
+*/
+typedef struct sqlite3_mutex_methods sqlite3_mutex_methods;
+struct sqlite3_mutex_methods {
+  int (*xMutexInit)(void);
+  int (*xMutexEnd)(void);
+  sqlite3_mutex *(*xMutexAlloc)(int);
+  void (*xMutexFree)(sqlite3_mutex *);
+  void (*xMutexEnter)(sqlite3_mutex *);
+  int (*xMutexTry)(sqlite3_mutex *);
+  void (*xMutexLeave)(sqlite3_mutex *);
+  int (*xMutexHeld)(sqlite3_mutex *);
+  int (*xMutexNotheld)(sqlite3_mutex *);
+};
+
+/*
+** CAPI3REF: Mutex Verification Routines
+**
+** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routines
+** are intended for use inside assert() statements.  ^The SQLite core
+** never uses these routines except inside an assert() and applications
+** are advised to follow the lead of the core.  ^The SQLite core only
+** provides implementations for these routines when it is compiled
+** with the SQLITE_DEBUG flag.  ^External mutex implementations
+** are only required to provide these routines if SQLITE_DEBUG is
+** defined and if NDEBUG is not defined.
+**
+** ^These routines should return true if the mutex in their argument
+** is held or not held, respectively, by the calling thread.
+**
+** ^The implementation is not required to provided versions of these
+** routines that actually work. If the implementation does not provide working
+** versions of these routines, it should at least provide stubs that always
+** return true so that one does not get spurious assertion failures.
+**
+** ^If the argument to sqlite3_mutex_held() is a NULL pointer then
+** the routine should return 1.   This seems counter-intuitive since
+** clearly the mutex cannot be held if it does not exist.  But
+** the reason the mutex does not exist is because the build is not
+** using mutexes.  And we do not want the assert() containing the
+** call to sqlite3_mutex_held() to fail, so a non-zero return is
+** the appropriate thing to do.  ^The sqlite3_mutex_notheld()
+** interface should also return 1 when given a NULL pointer.
+*/
+#ifndef NDEBUG
+int sqlite3_mutex_held(sqlite3_mutex*);
+int sqlite3_mutex_notheld(sqlite3_mutex*);
+#endif
+
+/*
+** CAPI3REF: Mutex Types
+**
+** The [sqlite3_mutex_alloc()] interface takes a single argument
+** which is one of these integer constants.
+**
+** The set of static mutexes may change from one SQLite release to the
+** next.  Applications that override the built-in mutex logic must be
+** prepared to accommodate additional static mutexes.
+*/
+#define SQLITE_MUTEX_FAST             0
+#define SQLITE_MUTEX_RECURSIVE        1
+#define SQLITE_MUTEX_STATIC_MASTER    2
+#define SQLITE_MUTEX_STATIC_MEM       3  /* sqlite3_malloc() */
+#define SQLITE_MUTEX_STATIC_MEM2      4  /* NOT USED */
+#define SQLITE_MUTEX_STATIC_OPEN      4  /* sqlite3BtreeOpen() */
+#define SQLITE_MUTEX_STATIC_PRNG      5  /* sqlite3_random() */
+#define SQLITE_MUTEX_STATIC_LRU       6  /* lru page list */
+#define SQLITE_MUTEX_STATIC_LRU2      7  /* NOT USED */
+#define SQLITE_MUTEX_STATIC_PMEM      7  /* sqlite3PageMalloc() */
+
+/*
+** CAPI3REF: Retrieve the mutex for a database connection
+**
+** ^This interface returns a pointer the [sqlite3_mutex] object that 
+** serializes access to the [database connection] given in the argument
+** when the [threading mode] is Serialized.
+** ^If the [threading mode] is Single-thread or Multi-thread then this
+** routine returns a NULL pointer.
+*/
+sqlite3_mutex *sqlite3_db_mutex(sqlite3*);
+
+/*
+** CAPI3REF: Low-Level Control Of Database Files
+**
+** ^The [sqlite3_file_control()] interface makes a direct call to the
+** xFileControl method for the [sqlite3_io_methods] object associated
+** with a particular database identified by the second argument. ^The
+** name of the database is "main" for the main database or "temp" for the
+** TEMP database, or the name that appears after the AS keyword for
+** databases that are added using the [ATTACH] SQL command.
+** ^A NULL pointer can be used in place of "main" to refer to the
+** main database file.
+** ^The third and fourth parameters to this routine
+** are passed directly through to the second and third parameters of
+** the xFileControl method.  ^The return value of the xFileControl
+** method becomes the return value of this routine.
+**
+** ^The SQLITE_FCNTL_FILE_POINTER value for the op parameter causes
+** a pointer to the underlying [sqlite3_file] object to be written into
+** the space pointed to by the 4th parameter.  ^The SQLITE_FCNTL_FILE_POINTER
+** case is a short-circuit path which does not actually invoke the
+** underlying sqlite3_io_methods.xFileControl method.
+**
+** ^If the second parameter (zDbName) does not match the name of any
+** open database file, then SQLITE_ERROR is returned.  ^This error
+** code is not remembered and will not be recalled by [sqlite3_errcode()]
+** or [sqlite3_errmsg()].  The underlying xFileControl method might
+** also return SQLITE_ERROR.  There is no way to distinguish between
+** an incorrect zDbName and an SQLITE_ERROR return from the underlying
+** xFileControl method.
+**
+** See also: [SQLITE_FCNTL_LOCKSTATE]
+*/
+int sqlite3_file_control(sqlite3*, const char *zDbName, int op, void*);
+
+/*
+** CAPI3REF: Testing Interface
+**
+** ^The sqlite3_test_control() interface is used to read out internal
+** state of SQLite and to inject faults into SQLite for testing
+** purposes.  ^The first parameter is an operation code that determines
+** the number, meaning, and operation of all subsequent parameters.
+**
+** This interface is not for use by applications.  It exists solely
+** for verifying the correct operation of the SQLite library.  Depending
+** on how the SQLite library is compiled, this interface might not exist.
+**
+** The details of the operation codes, their meanings, the parameters
+** they take, and what they do are all subject to change without notice.
+** Unlike most of the SQLite API, this function is not guaranteed to
+** operate consistently from one release to the next.
+*/
+int sqlite3_test_control(int op, ...);
+
+/*
+** CAPI3REF: Testing Interface Operation Codes
+**
+** These constants are the valid operation code parameters used
+** as the first argument to [sqlite3_test_control()].
+**
+** These parameters and their meanings are subject to change
+** without notice.  These values are for testing purposes only.
+** Applications should not use any of these parameters or the
+** [sqlite3_test_control()] interface.
+*/
+#define SQLITE_TESTCTRL_FIRST                    5
+#define SQLITE_TESTCTRL_PRNG_SAVE                5
+#define SQLITE_TESTCTRL_PRNG_RESTORE             6
+#define SQLITE_TESTCTRL_PRNG_RESET               7
+#define SQLITE_TESTCTRL_BITVEC_TEST              8
+#define SQLITE_TESTCTRL_FAULT_INSTALL            9
+#define SQLITE_TESTCTRL_BENIGN_MALLOC_HOOKS     10
+#define SQLITE_TESTCTRL_PENDING_BYTE            11
+#define SQLITE_TESTCTRL_ASSERT                  12
+#define SQLITE_TESTCTRL_ALWAYS                  13
+#define SQLITE_TESTCTRL_RESERVE                 14
+#define SQLITE_TESTCTRL_OPTIMIZATIONS           15
+#define SQLITE_TESTCTRL_ISKEYWORD               16
+#define SQLITE_TESTCTRL_PGHDRSZ                 17
+#define SQLITE_TESTCTRL_SCRATCHMALLOC           18
+#define SQLITE_TESTCTRL_LOCALTIME_FAULT         19
+#define SQLITE_TESTCTRL_LAST                    19
+
+/*
+** CAPI3REF: SQLite Runtime Status
+**
+** ^This interface is used to retrieve runtime status information
+** about the performance of SQLite, and optionally to reset various
+** highwater marks.  ^The first argument is an integer code for
+** the specific parameter to measure.  ^(Recognized integer codes
+** are of the form [status parameters | SQLITE_STATUS_...].)^
+** ^The current value of the parameter is returned into *pCurrent.
+** ^The highest recorded value is returned in *pHighwater.  ^If the
+** resetFlag is true, then the highest record value is reset after
+** *pHighwater is written.  ^(Some parameters do not record the highest
+** value.  For those parameters
+** nothing is written into *pHighwater and the resetFlag is ignored.)^
+** ^(Other parameters record only the highwater mark and not the current
+** value.  For these latter parameters nothing is written into *pCurrent.)^
+**
+** ^The sqlite3_status() routine returns SQLITE_OK on success and a
+** non-zero [error code] on failure.
+**
+** This routine is threadsafe but is not atomic.  This routine can be
+** called while other threads are running the same or different SQLite
+** interfaces.  However the values returned in *pCurrent and
+** *pHighwater reflect the status of SQLite at different points in time
+** and it is possible that another thread might change the parameter
+** in between the times when *pCurrent and *pHighwater are written.
+**
+** See also: [sqlite3_db_status()]
+*/
+int sqlite3_status(int op, int *pCurrent, int *pHighwater, int resetFlag);
+
+
+/*
+** CAPI3REF: Status Parameters
+** KEYWORDS: {status parameters}
+**
+** These integer constants designate various run-time status parameters
+** that can be returned by [sqlite3_status()].
+**
+** <dl>
+** [[SQLITE_STATUS_MEMORY_USED]] ^(<dt>SQLITE_STATUS_MEMORY_USED</dt>
+** <dd>This parameter is the current amount of memory checked out
+** using [sqlite3_malloc()], either directly or indirectly.  The
+** figure includes calls made to [sqlite3_malloc()] by the application
+** and internal memory usage by the SQLite library.  Scratch memory
+** controlled by [SQLITE_CONFIG_SCRATCH] and auxiliary page-cache
+** memory controlled by [SQLITE_CONFIG_PAGECACHE] is not included in
+** this parameter.  The amount returned is the sum of the allocation
+** sizes as reported by the xSize method in [sqlite3_mem_methods].</dd>)^
+**
+** [[SQLITE_STATUS_MALLOC_SIZE]] ^(<dt>SQLITE_STATUS_MALLOC_SIZE</dt>
+** <dd>This parameter records the largest memory allocation request
+** handed to [sqlite3_malloc()] or [sqlite3_realloc()] (or their
+** internal equivalents).  Only the value returned in the
+** *pHighwater parameter to [sqlite3_status()] is of interest.  
+** The value written into the *pCurrent parameter is undefined.</dd>)^
+**
+** [[SQLITE_STATUS_MALLOC_COUNT]] ^(<dt>SQLITE_STATUS_MALLOC_COUNT</dt>
+** <dd>This parameter records the number of separate memory allocations
+** currently checked out.</dd>)^
+**
+** [[SQLITE_STATUS_PAGECACHE_USED]] ^(<dt>SQLITE_STATUS_PAGECACHE_USED</dt>
+** <dd>This parameter returns the number of pages used out of the
+** [pagecache memory allocator] that was configured using 
+** [SQLITE_CONFIG_PAGECACHE].  The
+** value returned is in pages, not in bytes.</dd>)^
+**
+** [[SQLITE_STATUS_PAGECACHE_OVERFLOW]] 
+** ^(<dt>SQLITE_STATUS_PAGECACHE_OVERFLOW</dt>
+** <dd>This parameter returns the number of bytes of page cache
+** allocation which could not be satisfied by the [SQLITE_CONFIG_PAGECACHE]
+** buffer and where forced to overflow to [sqlite3_malloc()].  The
+** returned value includes allocations that overflowed because they
+** where too large (they were larger than the "sz" parameter to
+** [SQLITE_CONFIG_PAGECACHE]) and allocations that overflowed because
+** no space was left in the page cache.</dd>)^
+**
+** [[SQLITE_STATUS_PAGECACHE_SIZE]] ^(<dt>SQLITE_STATUS_PAGECACHE_SIZE</dt>
+** <dd>This parameter records the largest memory allocation request
+** handed to [pagecache memory allocator].  Only the value returned in the
+** *pHighwater parameter to [sqlite3_status()] is of interest.  
+** The value written into the *pCurrent parameter is undefined.</dd>)^
+**
+** [[SQLITE_STATUS_SCRATCH_USED]] ^(<dt>SQLITE_STATUS_SCRATCH_USED</dt>
+** <dd>This parameter returns the number of allocations used out of the
+** [scratch memory allocator] configured using
+** [SQLITE_CONFIG_SCRATCH].  The value returned is in allocations, not
+** in bytes.  Since a single thread may only have one scratch allocation
+** outstanding at time, this parameter also reports the number of threads
+** using scratch memory at the same time.</dd>)^
+**
+** [[SQLITE_STATUS_SCRATCH_OVERFLOW]] ^(<dt>SQLITE_STATUS_SCRATCH_OVERFLOW</dt>
+** <dd>This parameter returns the number of bytes of scratch memory
+** allocation which could not be satisfied by the [SQLITE_CONFIG_SCRATCH]
+** buffer and where forced to overflow to [sqlite3_malloc()].  The values
+** returned include overflows because the requested allocation was too
+** larger (that is, because the requested allocation was larger than the
+** "sz" parameter to [SQLITE_CONFIG_SCRATCH]) and because no scratch buffer
+** slots were available.
+** </dd>)^
+**
+** [[SQLITE_STATUS_SCRATCH_SIZE]] ^(<dt>SQLITE_STATUS_SCRATCH_SIZE</dt>
+** <dd>This parameter records the largest memory allocation request
+** handed to [scratch memory allocator].  Only the value returned in the
+** *pHighwater parameter to [sqlite3_status()] is of interest.  
+** The value written into the *pCurrent parameter is undefined.</dd>)^
+**
+** [[SQLITE_STATUS_PARSER_STACK]] ^(<dt>SQLITE_STATUS_PARSER_STACK</dt>
+** <dd>This parameter records the deepest parser stack.  It is only
+** meaningful if SQLite is compiled with [YYTRACKMAXSTACKDEPTH].</dd>)^
+** </dl>
+**
+** New status parameters may be added from time to time.
+*/
+#define SQLITE_STATUS_MEMORY_USED          0
+#define SQLITE_STATUS_PAGECACHE_USED       1
+#define SQLITE_STATUS_PAGECACHE_OVERFLOW   2
+#define SQLITE_STATUS_SCRATCH_USED         3
+#define SQLITE_STATUS_SCRATCH_OVERFLOW     4
+#define SQLITE_STATUS_MALLOC_SIZE          5
+#define SQLITE_STATUS_PARSER_STACK         6
+#define SQLITE_STATUS_PAGECACHE_SIZE       7
+#define SQLITE_STATUS_SCRATCH_SIZE         8
+#define SQLITE_STATUS_MALLOC_COUNT         9
+
+/*
+** CAPI3REF: Database Connection Status
+**
+** ^This interface is used to retrieve runtime status information 
+** about a single [database connection].  ^The first argument is the
+** database connection object to be interrogated.  ^The second argument
+** is an integer constant, taken from the set of
+** [SQLITE_DBSTATUS options], that
+** determines the parameter to interrogate.  The set of 
+** [SQLITE_DBSTATUS options] is likely
+** to grow in future releases of SQLite.
+**
+** ^The current value of the requested parameter is written into *pCur
+** and the highest instantaneous value is written into *pHiwtr.  ^If
+** the resetFlg is true, then the highest instantaneous value is
+** reset back down to the current value.
+**
+** ^The sqlite3_db_status() routine returns SQLITE_OK on success and a
+** non-zero [error code] on failure.
+**
+** See also: [sqlite3_status()] and [sqlite3_stmt_status()].
+*/
+int sqlite3_db_status(sqlite3*, int op, int *pCur, int *pHiwtr, int resetFlg);
+
+/*
+** CAPI3REF: Status Parameters for database connections
+** KEYWORDS: {SQLITE_DBSTATUS options}
+**
+** These constants are the available integer "verbs" that can be passed as
+** the second argument to the [sqlite3_db_status()] interface.
+**
+** New verbs may be added in future releases of SQLite. Existing verbs
+** might be discontinued. Applications should check the return code from
+** [sqlite3_db_status()] to make sure that the call worked.
+** The [sqlite3_db_status()] interface will return a non-zero error code
+** if a discontinued or unsupported verb is invoked.
+**
+** <dl>
+** [[SQLITE_DBSTATUS_LOOKASIDE_USED]] ^(<dt>SQLITE_DBSTATUS_LOOKASIDE_USED</dt>
+** <dd>This parameter returns the number of lookaside memory slots currently
+** checked out.</dd>)^
+**
+** [[SQLITE_DBSTATUS_LOOKASIDE_HIT]] ^(<dt>SQLITE_DBSTATUS_LOOKASIDE_HIT</dt>
+** <dd>This parameter returns the number malloc attempts that were 
+** satisfied using lookaside memory. Only the high-water value is meaningful;
+** the current value is always zero.)^
+**
+** [[SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE]]
+** ^(<dt>SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE</dt>
+** <dd>This parameter returns the number malloc attempts that might have
+** been satisfied using lookaside memory but failed due to the amount of
+** memory requested being larger than the lookaside slot size.
+** Only the high-water value is meaningful;
+** the current value is always zero.)^
+**
+** [[SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL]]
+** ^(<dt>SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL</dt>
+** <dd>This parameter returns the number malloc attempts that might have
+** been satisfied using lookaside memory but failed due to all lookaside
+** memory already being in use.
+** Only the high-water value is meaningful;
+** the current value is always zero.)^
+**
+** [[SQLITE_DBSTATUS_CACHE_USED]] ^(<dt>SQLITE_DBSTATUS_CACHE_USED</dt>
+** <dd>This parameter returns the approximate number of of bytes of heap
+** memory used by all pager caches associated with the database connection.)^
+** ^The highwater mark associated with SQLITE_DBSTATUS_CACHE_USED is always 0.
+**
+** [[SQLITE_DBSTATUS_SCHEMA_USED]] ^(<dt>SQLITE_DBSTATUS_SCHEMA_USED</dt>
+** <dd>This parameter returns the approximate number of of bytes of heap
+** memory used to store the schema for all databases associated
+** with the connection - main, temp, and any [ATTACH]-ed databases.)^ 
+** ^The full amount of memory used by the schemas is reported, even if the
+** schema memory is shared with other database connections due to
+** [shared cache mode] being enabled.
+** ^The highwater mark associated with SQLITE_DBSTATUS_SCHEMA_USED is always 0.
+**
+** [[SQLITE_DBSTATUS_STMT_USED]] ^(<dt>SQLITE_DBSTATUS_STMT_USED</dt>
+** <dd>This parameter returns the approximate number of of bytes of heap
+** and lookaside memory used by all prepared statements associated with
+** the database connection.)^
+** ^The highwater mark associated with SQLITE_DBSTATUS_STMT_USED is always 0.
+** </dd>
+**
+** [[SQLITE_DBSTATUS_CACHE_HIT]] ^(<dt>SQLITE_DBSTATUS_CACHE_HIT</dt>
+** <dd>This parameter returns the number of pager cache hits that have
+** occurred.)^ ^The highwater mark associated with SQLITE_DBSTATUS_CACHE_HIT 
+** is always 0.
+** </dd>
+**
+** [[SQLITE_DBSTATUS_CACHE_MISS]] ^(<dt>SQLITE_DBSTATUS_CACHE_MISS</dt>
+** <dd>This parameter returns the number of pager cache misses that have
+** occurred.)^ ^The highwater mark associated with SQLITE_DBSTATUS_CACHE_MISS 
+** is always 0.
+** </dd>
+** </dl>
+*/
+#define SQLITE_DBSTATUS_LOOKASIDE_USED       0
+#define SQLITE_DBSTATUS_CACHE_USED           1
+#define SQLITE_DBSTATUS_SCHEMA_USED          2
+#define SQLITE_DBSTATUS_STMT_USED            3
+#define SQLITE_DBSTATUS_LOOKASIDE_HIT        4
+#define SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE  5
+#define SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL  6
+#define SQLITE_DBSTATUS_CACHE_HIT            7
+#define SQLITE_DBSTATUS_CACHE_MISS           8
+#define SQLITE_DBSTATUS_MAX                  8   /* Largest defined DBSTATUS */
+
+
+/*
+** CAPI3REF: Prepared Statement Status
+**
+** ^(Each prepared statement maintains various
+** [SQLITE_STMTSTATUS counters] that measure the number
+** of times it has performed specific operations.)^  These counters can
+** be used to monitor the performance characteristics of the prepared
+** statements.  For example, if the number of table steps greatly exceeds
+** the number of table searches or result rows, that would tend to indicate
+** that the prepared statement is using a full table scan rather than
+** an index.  
+**
+** ^(This interface is used to retrieve and reset counter values from
+** a [prepared statement].  The first argument is the prepared statement
+** object to be interrogated.  The second argument
+** is an integer code for a specific [SQLITE_STMTSTATUS counter]
+** to be interrogated.)^
+** ^The current value of the requested counter is returned.
+** ^If the resetFlg is true, then the counter is reset to zero after this
+** interface call returns.
+**
+** See also: [sqlite3_status()] and [sqlite3_db_status()].
+*/
+int sqlite3_stmt_status(sqlite3_stmt*, int op,int resetFlg);
+
+/*
+** CAPI3REF: Status Parameters for prepared statements
+** KEYWORDS: {SQLITE_STMTSTATUS counter} {SQLITE_STMTSTATUS counters}
+**
+** These preprocessor macros define integer codes that name counter
+** values associated with the [sqlite3_stmt_status()] interface.
+** The meanings of the various counters are as follows:
+**
+** <dl>
+** [[SQLITE_STMTSTATUS_FULLSCAN_STEP]] <dt>SQLITE_STMTSTATUS_FULLSCAN_STEP</dt>
+** <dd>^This is the number of times that SQLite has stepped forward in
+** a table as part of a full table scan.  Large numbers for this counter
+** may indicate opportunities for performance improvement through 
+** careful use of indices.</dd>
+**
+** [[SQLITE_STMTSTATUS_SORT]] <dt>SQLITE_STMTSTATUS_SORT</dt>
+** <dd>^This is the number of sort operations that have occurred.
+** A non-zero value in this counter may indicate an opportunity to
+** improvement performance through careful use of indices.</dd>
+**
+** [[SQLITE_STMTSTATUS_AUTOINDEX]] <dt>SQLITE_STMTSTATUS_AUTOINDEX</dt>
+** <dd>^This is the number of rows inserted into transient indices that
+** were created automatically in order to help joins run faster.
+** A non-zero value in this counter may indicate an opportunity to
+** improvement performance by adding permanent indices that do not
+** need to be reinitialized each time the statement is run.</dd>
+** </dl>
+*/
+#define SQLITE_STMTSTATUS_FULLSCAN_STEP     1
+#define SQLITE_STMTSTATUS_SORT              2
+#define SQLITE_STMTSTATUS_AUTOINDEX         3
+
+/*
+** CAPI3REF: Custom Page Cache Object
+**
+** The sqlite3_pcache type is opaque.  It is implemented by
+** the pluggable module.  The SQLite core has no knowledge of
+** its size or internal structure and never deals with the
+** sqlite3_pcache object except by holding and passing pointers
+** to the object.
+**
+** See [sqlite3_pcache_methods] for additional information.
+*/
+typedef struct sqlite3_pcache sqlite3_pcache;
+
+/*
+** CAPI3REF: Application Defined Page Cache.
+** KEYWORDS: {page cache}
+**
+** ^(The [sqlite3_config]([SQLITE_CONFIG_PCACHE], ...) interface can
+** register an alternative page cache implementation by passing in an 
+** instance of the sqlite3_pcache_methods structure.)^
+** In many applications, most of the heap memory allocated by 
+** SQLite is used for the page cache.
+** By implementing a 
+** custom page cache using this API, an application can better control
+** the amount of memory consumed by SQLite, the way in which 
+** that memory is allocated and released, and the policies used to 
+** determine exactly which parts of a database file are cached and for 
+** how long.
+**
+** The alternative page cache mechanism is an
+** extreme measure that is only needed by the most demanding applications.
+** The built-in page cache is recommended for most uses.
+**
+** ^(The contents of the sqlite3_pcache_methods structure are copied to an
+** internal buffer by SQLite within the call to [sqlite3_config].  Hence
+** the application may discard the parameter after the call to
+** [sqlite3_config()] returns.)^
+**
+** [[the xInit() page cache method]]
+** ^(The xInit() method is called once for each effective 
+** call to [sqlite3_initialize()])^
+** (usually only once during the lifetime of the process). ^(The xInit()
+** method is passed a copy of the sqlite3_pcache_methods.pArg value.)^
+** The intent of the xInit() method is to set up global data structures 
+** required by the custom page cache implementation. 
+** ^(If the xInit() method is NULL, then the 
+** built-in default page cache is used instead of the application defined
+** page cache.)^
+**
+** [[the xShutdown() page cache method]]
+** ^The xShutdown() method is called by [sqlite3_shutdown()].
+** It can be used to clean up 
+** any outstanding resources before process shutdown, if required.
+** ^The xShutdown() method may be NULL.
+**
+** ^SQLite automatically serializes calls to the xInit method,
+** so the xInit method need not be threadsafe.  ^The
+** xShutdown method is only called from [sqlite3_shutdown()] so it does
+** not need to be threadsafe either.  All other methods must be threadsafe
+** in multithreaded applications.
+**
+** ^SQLite will never invoke xInit() more than once without an intervening
+** call to xShutdown().
+**
+** [[the xCreate() page cache methods]]
+** ^SQLite invokes the xCreate() method to construct a new cache instance.
+** SQLite will typically create one cache instance for each open database file,
+** though this is not guaranteed. ^The
+** first parameter, szPage, is the size in bytes of the pages that must
+** be allocated by the cache.  ^szPage will not be a power of two.  ^szPage
+** will the page size of the database file that is to be cached plus an
+** increment (here called "R") of less than 250.  SQLite will use the
+** extra R bytes on each page to store metadata about the underlying
+** database page on disk.  The value of R depends
+** on the SQLite version, the target platform, and how SQLite was compiled.
+** ^(R is constant for a particular build of SQLite. Except, there are two
+** distinct values of R when SQLite is compiled with the proprietary
+** ZIPVFS extension.)^  ^The second argument to
+** xCreate(), bPurgeable, is true if the cache being created will
+** be used to cache database pages of a file stored on disk, or
+** false if it is used for an in-memory database. The cache implementation
+** does not have to do anything special based with the value of bPurgeable;
+** it is purely advisory.  ^On a cache where bPurgeable is false, SQLite will
+** never invoke xUnpin() except to deliberately delete a page.
+** ^In other words, calls to xUnpin() on a cache with bPurgeable set to
+** false will always have the "discard" flag set to true.  
+** ^Hence, a cache created with bPurgeable false will
+** never contain any unpinned pages.
+**
+** [[the xCachesize() page cache method]]
+** ^(The xCachesize() method may be called at any time by SQLite to set the
+** suggested maximum cache-size (number of pages stored by) the cache
+** instance passed as the first argument. This is the value configured using
+** the SQLite "[PRAGMA cache_size]" command.)^  As with the bPurgeable
+** parameter, the implementation is not required to do anything with this
+** value; it is advisory only.
+**
+** [[the xPagecount() page cache methods]]
+** The xPagecount() method must return the number of pages currently
+** stored in the cache, both pinned and unpinned.
+** 
+** [[the xFetch() page cache methods]]
+** The xFetch() method locates a page in the cache and returns a pointer to 
+** the page, or a NULL pointer.
+** A "page", in this context, means a buffer of szPage bytes aligned at an
+** 8-byte boundary. The page to be fetched is determined by the key. ^The
+** minimum key value is 1.  After it has been retrieved using xFetch, the page 
+** is considered to be "pinned".
+**
+** If the requested page is already in the page cache, then the page cache
+** implementation must return a pointer to the page buffer with its content
+** intact.  If the requested page is not already in the cache, then the
+** cache implementation should use the value of the createFlag
+** parameter to help it determined what action to take:
+**
+** <table border=1 width=85% align=center>
+** <tr><th> createFlag <th> Behaviour when page is not already in cache
+** <tr><td> 0 <td> Do not allocate a new page.  Return NULL.
+** <tr><td> 1 <td> Allocate a new page if it easy and convenient to do so.
+**                 Otherwise return NULL.
+** <tr><td> 2 <td> Make every effort to allocate a new page.  Only return
+**                 NULL if allocating a new page is effectively impossible.
+** </table>
+**
+** ^(SQLite will normally invoke xFetch() with a createFlag of 0 or 1.  SQLite
+** will only use a createFlag of 2 after a prior call with a createFlag of 1
+** failed.)^  In between the to xFetch() calls, SQLite may
+** attempt to unpin one or more cache pages by spilling the content of
+** pinned pages to disk and synching the operating system disk cache.
+**
+** [[the xUnpin() page cache method]]
+** ^xUnpin() is called by SQLite with a pointer to a currently pinned page
+** as its second argument.  If the third parameter, discard, is non-zero,
+** then the page must be evicted from the cache.
+** ^If the discard parameter is
+** zero, then the page may be discarded or retained at the discretion of
+** page cache implementation. ^The page cache implementation
+** may choose to evict unpinned pages at any time.
+**
+** The cache must not perform any reference counting. A single 
+** call to xUnpin() unpins the page regardless of the number of prior calls 
+** to xFetch().
+**
+** [[the xRekey() page cache methods]]
+** The xRekey() method is used to change the key value associated with the
+** page passed as the second argument. If the cache
+** previously contains an entry associated with newKey, it must be
+** discarded. ^Any prior cache entry associated with newKey is guaranteed not
+** to be pinned.
+**
+** When SQLite calls the xTruncate() method, the cache must discard all
+** existing cache entries with page numbers (keys) greater than or equal
+** to the value of the iLimit parameter passed to xTruncate(). If any
+** of these pages are pinned, they are implicitly unpinned, meaning that
+** they can be safely discarded.
+**
+** [[the xDestroy() page cache method]]
+** ^The xDestroy() method is used to delete a cache allocated by xCreate().
+** All resources associated with the specified cache should be freed. ^After
+** calling the xDestroy() method, SQLite considers the [sqlite3_pcache*]
+** handle invalid, and will not use it with any other sqlite3_pcache_methods
+** functions.
+*/
+typedef struct sqlite3_pcache_methods sqlite3_pcache_methods;
+struct sqlite3_pcache_methods {
+  void *pArg;
+  int (*xInit)(void*);
+  void (*xShutdown)(void*);
+  sqlite3_pcache *(*xCreate)(int szPage, int bPurgeable);
+  void (*xCachesize)(sqlite3_pcache*, int nCachesize);
+  int (*xPagecount)(sqlite3_pcache*);
+  void *(*xFetch)(sqlite3_pcache*, unsigned key, int createFlag);
+  void (*xUnpin)(sqlite3_pcache*, void*, int discard);
+  void (*xRekey)(sqlite3_pcache*, void*, unsigned oldKey, unsigned newKey);
+  void (*xTruncate)(sqlite3_pcache*, unsigned iLimit);
+  void (*xDestroy)(sqlite3_pcache*);
+};
+
+/*
+** CAPI3REF: Online Backup Object
+**
+** The sqlite3_backup object records state information about an ongoing
+** online backup operation.  ^The sqlite3_backup object is created by
+** a call to [sqlite3_backup_init()] and is destroyed by a call to
+** [sqlite3_backup_finish()].
+**
+** See Also: [Using the SQLite Online Backup API]
+*/
+typedef struct sqlite3_backup sqlite3_backup;
+
+/*
+** CAPI3REF: Online Backup API.
+**
+** The backup API copies the content of one database into another.
+** It is useful either for creating backups of databases or
+** for copying in-memory databases to or from persistent files. 
+**
+** See Also: [Using the SQLite Online Backup API]
+**
+** ^SQLite holds a write transaction open on the destination database file
+** for the duration of the backup operation.
+** ^The source database is read-locked only while it is being read;
+** it is not locked continuously for the entire backup operation.
+** ^Thus, the backup may be performed on a live source database without
+** preventing other database connections from
+** reading or writing to the source database while the backup is underway.
+** 
+** ^(To perform a backup operation: 
+**   <ol>
+**     <li><b>sqlite3_backup_init()</b> is called once to initialize the
+**         backup, 
+**     <li><b>sqlite3_backup_step()</b> is called one or more times to transfer 
+**         the data between the two databases, and finally
+**     <li><b>sqlite3_backup_finish()</b> is called to release all resources 
+**         associated with the backup operation. 
+**   </ol>)^
+** There should be exactly one call to sqlite3_backup_finish() for each
+** successful call to sqlite3_backup_init().
+**
+** [[sqlite3_backup_init()]] <b>sqlite3_backup_init()</b>
+**
+** ^The D and N arguments to sqlite3_backup_init(D,N,S,M) are the 
+** [database connection] associated with the destination database 
+** and the database name, respectively.
+** ^The database name is "main" for the main database, "temp" for the
+** temporary database, or the name specified after the AS keyword in
+** an [ATTACH] statement for an attached database.
+** ^The S and M arguments passed to 
+** sqlite3_backup_init(D,N,S,M) identify the [database connection]
+** and database name of the source database, respectively.
+** ^The source and destination [database connections] (parameters S and D)
+** must be different or else sqlite3_backup_init(D,N,S,M) will fail with
+** an error.
+**
+** ^If an error occurs within sqlite3_backup_init(D,N,S,M), then NULL is
+** returned and an error code and error message are stored in the
+** destination [database connection] D.
+** ^The error code and message for the failed call to sqlite3_backup_init()
+** can be retrieved using the [sqlite3_errcode()], [sqlite3_errmsg()], and/or
+** [sqlite3_errmsg16()] functions.
+** ^A successful call to sqlite3_backup_init() returns a pointer to an
+** [sqlite3_backup] object.
+** ^The [sqlite3_backup] object may be used with the sqlite3_backup_step() and
+** sqlite3_backup_finish() functions to perform the specified backup 
+** operation.
+**
+** [[sqlite3_backup_step()]] <b>sqlite3_backup_step()</b>
+**
+** ^Function sqlite3_backup_step(B,N) will copy up to N pages between 
+** the source and destination databases specified by [sqlite3_backup] object B.
+** ^If N is negative, all remaining source pages are copied. 
+** ^If sqlite3_backup_step(B,N) successfully copies N pages and there
+** are still more pages to be copied, then the function returns [SQLITE_OK].
+** ^If sqlite3_backup_step(B,N) successfully finishes copying all pages
+** from source to destination, then it returns [SQLITE_DONE].
+** ^If an error occurs while running sqlite3_backup_step(B,N),
+** then an [error code] is returned. ^As well as [SQLITE_OK] and
+** [SQLITE_DONE], a call to sqlite3_backup_step() may return [SQLITE_READONLY],
+** [SQLITE_NOMEM], [SQLITE_BUSY], [SQLITE_LOCKED], or an
+** [SQLITE_IOERR_ACCESS | SQLITE_IOERR_XXX] extended error code.
+**
+** ^(The sqlite3_backup_step() might return [SQLITE_READONLY] if
+** <ol>
+** <li> the destination database was opened read-only, or
+** <li> the destination database is using write-ahead-log journaling
+** and the destination and source page sizes differ, or
+** <li> the destination database is an in-memory database and the
+** destination and source page sizes differ.
+** </ol>)^
+**
+** ^If sqlite3_backup_step() cannot obtain a required file-system lock, then
+** the [sqlite3_busy_handler | busy-handler function]
+** is invoked (if one is specified). ^If the 
+** busy-handler returns non-zero before the lock is available, then 
+** [SQLITE_BUSY] is returned to the caller. ^In this case the call to
+** sqlite3_backup_step() can be retried later. ^If the source
+** [database connection]
+** is being used to write to the source database when sqlite3_backup_step()
+** is called, then [SQLITE_LOCKED] is returned immediately. ^Again, in this
+** case the call to sqlite3_backup_step() can be retried later on. ^(If
+** [SQLITE_IOERR_ACCESS | SQLITE_IOERR_XXX], [SQLITE_NOMEM], or
+** [SQLITE_READONLY] is returned, then 
+** there is no point in retrying the call to sqlite3_backup_step(). These 
+** errors are considered fatal.)^  The application must accept 
+** that the backup operation has failed and pass the backup operation handle 
+** to the sqlite3_backup_finish() to release associated resources.
+**
+** ^The first call to sqlite3_backup_step() obtains an exclusive lock
+** on the destination file. ^The exclusive lock is not released until either 
+** sqlite3_backup_finish() is called or the backup operation is complete 
+** and sqlite3_backup_step() returns [SQLITE_DONE].  ^Every call to
+** sqlite3_backup_step() obtains a [shared lock] on the source database that
+** lasts for the duration of the sqlite3_backup_step() call.
+** ^Because the source database is not locked between calls to
+** sqlite3_backup_step(), the source database may be modified mid-way
+** through the backup process.  ^If the source database is modified by an
+** external process or via a database connection other than the one being
+** used by the backup operation, then the backup will be automatically
+** restarted by the next call to sqlite3_backup_step(). ^If the source 
+** database is modified by the using the same database connection as is used
+** by the backup operation, then the backup database is automatically
+** updated at the same time.
+**
+** [[sqlite3_backup_finish()]] <b>sqlite3_backup_finish()</b>
+**
+** When sqlite3_backup_step() has returned [SQLITE_DONE], or when the 
+** application wishes to abandon the backup operation, the application
+** should destroy the [sqlite3_backup] by passing it to sqlite3_backup_finish().
+** ^The sqlite3_backup_finish() interfaces releases all
+** resources associated with the [sqlite3_backup] object. 
+** ^If sqlite3_backup_step() has not yet returned [SQLITE_DONE], then any
+** active write-transaction on the destination database is rolled back.
+** The [sqlite3_backup] object is invalid
+** and may not be used following a call to sqlite3_backup_finish().
+**
+** ^The value returned by sqlite3_backup_finish is [SQLITE_OK] if no
+** sqlite3_backup_step() errors occurred, regardless or whether or not
+** sqlite3_backup_step() completed.
+** ^If an out-of-memory condition or IO error occurred during any prior
+** sqlite3_backup_step() call on the same [sqlite3_backup] object, then
+** sqlite3_backup_finish() returns the corresponding [error code].
+**
+** ^A return of [SQLITE_BUSY] or [SQLITE_LOCKED] from sqlite3_backup_step()
+** is not a permanent error and does not affect the return value of
+** sqlite3_backup_finish().
+**
+** [[sqlite3_backup__remaining()]] [[sqlite3_backup_pagecount()]]
+** <b>sqlite3_backup_remaining() and sqlite3_backup_pagecount()</b>
+**
+** ^Each call to sqlite3_backup_step() sets two values inside
+** the [sqlite3_backup] object: the number of pages still to be backed
+** up and the total number of pages in the source database file.
+** The sqlite3_backup_remaining() and sqlite3_backup_pagecount() interfaces
+** retrieve these two values, respectively.
+**
+** ^The values returned by these functions are only updated by
+** sqlite3_backup_step(). ^If the source database is modified during a backup
+** operation, then the values are not updated to account for any extra
+** pages that need to be updated or the size of the source database file
+** changing.
+**
+** <b>Concurrent Usage of Database Handles</b>
+**
+** ^The source [database connection] may be used by the application for other
+** purposes while a backup operation is underway or being initialized.
+** ^If SQLite is compiled and configured to support threadsafe database
+** connections, then the source database connection may be used concurrently
+** from within other threads.
+**
+** However, the application must guarantee that the destination 
+** [database connection] is not passed to any other API (by any thread) after 
+** sqlite3_backup_init() is called and before the corresponding call to
+** sqlite3_backup_finish().  SQLite does not currently check to see
+** if the application incorrectly accesses the destination [database connection]
+** and so no error code is reported, but the operations may malfunction
+** nevertheless.  Use of the destination database connection while a
+** backup is in progress might also also cause a mutex deadlock.
+**
+** If running in [shared cache mode], the application must
+** guarantee that the shared cache used by the destination database
+** is not accessed while the backup is running. In practice this means
+** that the application must guarantee that the disk file being 
+** backed up to is not accessed by any connection within the process,
+** not just the specific connection that was passed to sqlite3_backup_init().
+**
+** The [sqlite3_backup] object itself is partially threadsafe. Multiple 
+** threads may safely make multiple concurrent calls to sqlite3_backup_step().
+** However, the sqlite3_backup_remaining() and sqlite3_backup_pagecount()
+** APIs are not strictly speaking threadsafe. If they are invoked at the
+** same time as another thread is invoking sqlite3_backup_step() it is
+** possible that they return invalid values.
+*/
+sqlite3_backup *sqlite3_backup_init(
+  sqlite3 *pDest,                        /* Destination database handle */
+  const char *zDestName,                 /* Destination database name */
+  sqlite3 *pSource,                      /* Source database handle */
+  const char *zSourceName                /* Source database name */
+);
+int sqlite3_backup_step(sqlite3_backup *p, int nPage);
+int sqlite3_backup_finish(sqlite3_backup *p);
+int sqlite3_backup_remaining(sqlite3_backup *p);
+int sqlite3_backup_pagecount(sqlite3_backup *p);
+
+/*
+** CAPI3REF: Unlock Notification
+**
+** ^When running in shared-cache mode, a database operation may fail with
+** an [SQLITE_LOCKED] error if the required locks on the shared-cache or
+** individual tables within the shared-cache cannot be obtained. See
+** [SQLite Shared-Cache Mode] for a description of shared-cache locking. 
+** ^This API may be used to register a callback that SQLite will invoke 
+** when the connection currently holding the required lock relinquishes it.
+** ^This API is only available if the library was compiled with the
+** [SQLITE_ENABLE_UNLOCK_NOTIFY] C-preprocessor symbol defined.
+**
+** See Also: [Using the SQLite Unlock Notification Feature].
+**
+** ^Shared-cache locks are released when a database connection concludes
+** its current transaction, either by committing it or rolling it back. 
+**
+** ^When a connection (known as the blocked connection) fails to obtain a
+** shared-cache lock and SQLITE_LOCKED is returned to the caller, the
+** identity of the database connection (the blocking connection) that
+** has locked the required resource is stored internally. ^After an 
+** application receives an SQLITE_LOCKED error, it may call the
+** sqlite3_unlock_notify() method with the blocked connection handle as 
+** the first argument to register for a callback that will be invoked
+** when the blocking connections current transaction is concluded. ^The
+** callback is invoked from within the [sqlite3_step] or [sqlite3_close]
+** call that concludes the blocking connections transaction.
+**
+** ^(If sqlite3_unlock_notify() is called in a multi-threaded application,
+** there is a chance that the blocking connection will have already
+** concluded its transaction by the time sqlite3_unlock_notify() is invoked.
+** If this happens, then the specified callback is invoked immediately,
+** from within the call to sqlite3_unlock_notify().)^
+**
+** ^If the blocked connection is attempting to obtain a write-lock on a
+** shared-cache table, and more than one other connection currently holds
+** a read-lock on the same table, then SQLite arbitrarily selects one of 
+** the other connections to use as the blocking connection.
+**
+** ^(There may be at most one unlock-notify callback registered by a 
+** blocked connection. If sqlite3_unlock_notify() is called when the
+** blocked connection already has a registered unlock-notify callback,
+** then the new callback replaces the old.)^ ^If sqlite3_unlock_notify() is
+** called with a NULL pointer as its second argument, then any existing
+** unlock-notify callback is canceled. ^The blocked connections 
+** unlock-notify callback may also be canceled by closing the blocked
+** connection using [sqlite3_close()].
+**
+** The unlock-notify callback is not reentrant. If an application invokes
+** any sqlite3_xxx API functions from within an unlock-notify callback, a
+** crash or deadlock may be the result.
+**
+** ^Unless deadlock is detected (see below), sqlite3_unlock_notify() always
+** returns SQLITE_OK.
+**
+** <b>Callback Invocation Details</b>
+**
+** When an unlock-notify callback is registered, the application provides a 
+** single void* pointer that is passed to the callback when it is invoked.
+** However, the signature of the callback function allows SQLite to pass
+** it an array of void* context pointers. The first argument passed to
+** an unlock-notify callback is a pointer to an array of void* pointers,
+** and the second is the number of entries in the array.
+**
+** When a blocking connections transaction is concluded, there may be
+** more than one blocked connection that has registered for an unlock-notify
+** callback. ^If two or more such blocked connections have specified the
+** same callback function, then instead of invoking the callback function
+** multiple times, it is invoked once with the set of void* context pointers
+** specified by the blocked connections bundled together into an array.
+** This gives the application an opportunity to prioritize any actions 
+** related to the set of unblocked database connections.
+**
+** <b>Deadlock Detection</b>
+**
+** Assuming that after registering for an unlock-notify callback a 
+** database waits for the callback to be issued before taking any further
+** action (a reasonable assumption), then using this API may cause the
+** application to deadlock. For example, if connection X is waiting for
+** connection Y's transaction to be concluded, and similarly connection
+** Y is waiting on connection X's transaction, then neither connection
+** will proceed and the system may remain deadlocked indefinitely.
+**
+** To avoid this scenario, the sqlite3_unlock_notify() performs deadlock
+** detection. ^If a given call to sqlite3_unlock_notify() would put the
+** system in a deadlocked state, then SQLITE_LOCKED is returned and no
+** unlock-notify callback is registered. The system is said to be in
+** a deadlocked state if connection A has registered for an unlock-notify
+** callback on the conclusion of connection B's transaction, and connection
+** B has itself registered for an unlock-notify callback when connection
+** A's transaction is concluded. ^Indirect deadlock is also detected, so
+** the system is also considered to be deadlocked if connection B has
+** registered for an unlock-notify callback on the conclusion of connection
+** C's transaction, where connection C is waiting on connection A. ^Any
+** number of levels of indirection are allowed.
+**
+** <b>The "DROP TABLE" Exception</b>
+**
+** When a call to [sqlite3_step()] returns SQLITE_LOCKED, it is almost 
+** always appropriate to call sqlite3_unlock_notify(). There is however,
+** one exception. When executing a "DROP TABLE" or "DROP INDEX" statement,
+** SQLite checks if there are any currently executing SELECT statements
+** that belong to the same connection. If there are, SQLITE_LOCKED is
+** returned. In this case there is no "blocking connection", so invoking
+** sqlite3_unlock_notify() results in the unlock-notify callback being
+** invoked immediately. If the application then re-attempts the "DROP TABLE"
+** or "DROP INDEX" query, an infinite loop might be the result.
+**
+** One way around this problem is to check the extended error code returned
+** by an sqlite3_step() call. ^(If there is a blocking connection, then the
+** extended error code is set to SQLITE_LOCKED_SHAREDCACHE. Otherwise, in
+** the special "DROP TABLE/INDEX" case, the extended error code is just 
+** SQLITE_LOCKED.)^
+*/
+int sqlite3_unlock_notify(
+  sqlite3 *pBlocked,                          /* Waiting connection */
+  void (*xNotify)(void **apArg, int nArg),    /* Callback function to invoke */
+  void *pNotifyArg                            /* Argument to pass to xNotify */
+);
+
+
+/*
+** CAPI3REF: String Comparison
+**
+** ^The [sqlite3_strnicmp()] API allows applications and extensions to
+** compare the contents of two buffers containing UTF-8 strings in a
+** case-independent fashion, using the same definition of case independence 
+** that SQLite uses internally when comparing identifiers.
+*/
+int sqlite3_strnicmp(const char *, const char *, int);
+
+/*
+** CAPI3REF: Error Logging Interface
+**
+** ^The [sqlite3_log()] interface writes a message into the error log
+** established by the [SQLITE_CONFIG_LOG] option to [sqlite3_config()].
+** ^If logging is enabled, the zFormat string and subsequent arguments are
+** used with [sqlite3_snprintf()] to generate the final output string.
+**
+** The sqlite3_log() interface is intended for use by extensions such as
+** virtual tables, collating functions, and SQL functions.  While there is
+** nothing to prevent an application from calling sqlite3_log(), doing so
+** is considered bad form.
+**
+** The zFormat string must not be NULL.
+**
+** To avoid deadlocks and other threading problems, the sqlite3_log() routine
+** will not use dynamically allocated memory.  The log message is stored in
+** a fixed-length buffer on the stack.  If the log message is longer than
+** a few hundred characters, it will be truncated to the length of the
+** buffer.
+*/
+void sqlite3_log(int iErrCode, const char *zFormat, ...);
+
+/*
+** CAPI3REF: Write-Ahead Log Commit Hook
+**
+** ^The [sqlite3_wal_hook()] function is used to register a callback that
+** will be invoked each time a database connection commits data to a
+** [write-ahead log] (i.e. whenever a transaction is committed in
+** [journal_mode | journal_mode=WAL mode]). 
+**
+** ^The callback is invoked by SQLite after the commit has taken place and 
+** the associated write-lock on the database released, so the implementation 
+** may read, write or [checkpoint] the database as required.
+**
+** ^The first parameter passed to the callback function when it is invoked
+** is a copy of the third parameter passed to sqlite3_wal_hook() when
+** registering the callback. ^The second is a copy of the database handle.
+** ^The third parameter is the name of the database that was written to -
+** either "main" or the name of an [ATTACH]-ed database. ^The fourth parameter
+** is the number of pages currently in the write-ahead log file,
+** including those that were just committed.
+**
+** The callback function should normally return [SQLITE_OK].  ^If an error
+** code is returned, that error will propagate back up through the
+** SQLite code base to cause the statement that provoked the callback
+** to report an error, though the commit will have still occurred. If the
+** callback returns [SQLITE_ROW] or [SQLITE_DONE], or if it returns a value
+** that does not correspond to any valid SQLite error code, the results
+** are undefined.
+**
+** A single database handle may have at most a single write-ahead log callback 
+** registered at one time. ^Calling [sqlite3_wal_hook()] replaces any
+** previously registered write-ahead log callback. ^Note that the
+** [sqlite3_wal_autocheckpoint()] interface and the
+** [wal_autocheckpoint pragma] both invoke [sqlite3_wal_hook()] and will
+** those overwrite any prior [sqlite3_wal_hook()] settings.
+*/
+void *sqlite3_wal_hook(
+  sqlite3*, 
+  int(*)(void *,sqlite3*,const char*,int),
+  void*
+);
+
+/*
+** CAPI3REF: Configure an auto-checkpoint
+**
+** ^The [sqlite3_wal_autocheckpoint(D,N)] is a wrapper around
+** [sqlite3_wal_hook()] that causes any database on [database connection] D
+** to automatically [checkpoint]
+** after committing a transaction if there are N or
+** more frames in the [write-ahead log] file.  ^Passing zero or 
+** a negative value as the nFrame parameter disables automatic
+** checkpoints entirely.
+**
+** ^The callback registered by this function replaces any existing callback
+** registered using [sqlite3_wal_hook()].  ^Likewise, registering a callback
+** using [sqlite3_wal_hook()] disables the automatic checkpoint mechanism
+** configured by this function.
+**
+** ^The [wal_autocheckpoint pragma] can be used to invoke this interface
+** from SQL.
+**
+** ^Every new [database connection] defaults to having the auto-checkpoint
+** enabled with a threshold of 1000 or [SQLITE_DEFAULT_WAL_AUTOCHECKPOINT]
+** pages.  The use of this interface
+** is only necessary if the default setting is found to be suboptimal
+** for a particular application.
+*/
+int sqlite3_wal_autocheckpoint(sqlite3 *db, int N);
+
+/*
+** CAPI3REF: Checkpoint a database
+**
+** ^The [sqlite3_wal_checkpoint(D,X)] interface causes database named X
+** on [database connection] D to be [checkpointed].  ^If X is NULL or an
+** empty string, then a checkpoint is run on all databases of
+** connection D.  ^If the database connection D is not in
+** [WAL | write-ahead log mode] then this interface is a harmless no-op.
+**
+** ^The [wal_checkpoint pragma] can be used to invoke this interface
+** from SQL.  ^The [sqlite3_wal_autocheckpoint()] interface and the
+** [wal_autocheckpoint pragma] can be used to cause this interface to be
+** run whenever the WAL reaches a certain size threshold.
+**
+** See also: [sqlite3_wal_checkpoint_v2()]
+*/
+int sqlite3_wal_checkpoint(sqlite3 *db, const char *zDb);
+
+/*
+** CAPI3REF: Checkpoint a database
+**
+** Run a checkpoint operation on WAL database zDb attached to database 
+** handle db. The specific operation is determined by the value of the 
+** eMode parameter:
+**
+** <dl>
+** <dt>SQLITE_CHECKPOINT_PASSIVE<dd>
+**   Checkpoint as many frames as possible without waiting for any database 
+**   readers or writers to finish. Sync the db file if all frames in the log
+**   are checkpointed. This mode is the same as calling 
+**   sqlite3_wal_checkpoint(). The busy-handler callback is never invoked.
+**
+** <dt>SQLITE_CHECKPOINT_FULL<dd>
+**   This mode blocks (calls the busy-handler callback) until there is no
+**   database writer and all readers are reading from the most recent database
+**   snapshot. It then checkpoints all frames in the log file and syncs the
+**   database file. This call blocks database writers while it is running,
+**   but not database readers.
+**
+** <dt>SQLITE_CHECKPOINT_RESTART<dd>
+**   This mode works the same way as SQLITE_CHECKPOINT_FULL, except after 
+**   checkpointing the log file it blocks (calls the busy-handler callback)
+**   until all readers are reading from the database file only. This ensures 
+**   that the next client to write to the database file restarts the log file 
+**   from the beginning. This call blocks database writers while it is running,
+**   but not database readers.
+** </dl>
+**
+** If pnLog is not NULL, then *pnLog is set to the total number of frames in
+** the log file before returning. If pnCkpt is not NULL, then *pnCkpt is set to
+** the total number of checkpointed frames (including any that were already
+** checkpointed when this function is called). *pnLog and *pnCkpt may be
+** populated even if sqlite3_wal_checkpoint_v2() returns other than SQLITE_OK.
+** If no values are available because of an error, they are both set to -1
+** before returning to communicate this to the caller.
+**
+** All calls obtain an exclusive "checkpoint" lock on the database file. If
+** any other process is running a checkpoint operation at the same time, the 
+** lock cannot be obtained and SQLITE_BUSY is returned. Even if there is a 
+** busy-handler configured, it will not be invoked in this case.
+**
+** The SQLITE_CHECKPOINT_FULL and RESTART modes also obtain the exclusive 
+** "writer" lock on the database file. If the writer lock cannot be obtained
+** immediately, and a busy-handler is configured, it is invoked and the writer
+** lock retried until either the busy-handler returns 0 or the lock is
+** successfully obtained. The busy-handler is also invoked while waiting for
+** database readers as described above. If the busy-handler returns 0 before
+** the writer lock is obtained or while waiting for database readers, the
+** checkpoint operation proceeds from that point in the same way as 
+** SQLITE_CHECKPOINT_PASSIVE - checkpointing as many frames as possible 
+** without blocking any further. SQLITE_BUSY is returned in this case.
+**
+** If parameter zDb is NULL or points to a zero length string, then the
+** specified operation is attempted on all WAL databases. In this case the
+** values written to output parameters *pnLog and *pnCkpt are undefined. If 
+** an SQLITE_BUSY error is encountered when processing one or more of the 
+** attached WAL databases, the operation is still attempted on any remaining 
+** attached databases and SQLITE_BUSY is returned to the caller. If any other 
+** error occurs while processing an attached database, processing is abandoned 
+** and the error code returned to the caller immediately. If no error 
+** (SQLITE_BUSY or otherwise) is encountered while processing the attached 
+** databases, SQLITE_OK is returned.
+**
+** If database zDb is the name of an attached database that is not in WAL
+** mode, SQLITE_OK is returned and both *pnLog and *pnCkpt set to -1. If
+** zDb is not NULL (or a zero length string) and is not the name of any
+** attached database, SQLITE_ERROR is returned to the caller.
+*/
+int sqlite3_wal_checkpoint_v2(
+  sqlite3 *db,                    /* Database handle */
+  const char *zDb,                /* Name of attached database (or NULL) */
+  int eMode,                      /* SQLITE_CHECKPOINT_* value */
+  int *pnLog,                     /* OUT: Size of WAL log in frames */
+  int *pnCkpt                     /* OUT: Total number of frames checkpointed */
+);
+
+/*
+** CAPI3REF: Checkpoint operation parameters
+**
+** These constants can be used as the 3rd parameter to
+** [sqlite3_wal_checkpoint_v2()].  See the [sqlite3_wal_checkpoint_v2()]
+** documentation for additional information about the meaning and use of
+** each of these values.
+*/
+#define SQLITE_CHECKPOINT_PASSIVE 0
+#define SQLITE_CHECKPOINT_FULL    1
+#define SQLITE_CHECKPOINT_RESTART 2
+
+/*
+** CAPI3REF: Virtual Table Interface Configuration
+**
+** This function may be called by either the [xConnect] or [xCreate] method
+** of a [virtual table] implementation to configure
+** various facets of the virtual table interface.
+**
+** If this interface is invoked outside the context of an xConnect or
+** xCreate virtual table method then the behavior is undefined.
+**
+** At present, there is only one option that may be configured using
+** this function. (See [SQLITE_VTAB_CONSTRAINT_SUPPORT].)  Further options
+** may be added in the future.
+*/
+int sqlite3_vtab_config(sqlite3*, int op, ...);
+
+/*
+** CAPI3REF: Virtual Table Configuration Options
+**
+** These macros define the various options to the
+** [sqlite3_vtab_config()] interface that [virtual table] implementations
+** can use to customize and optimize their behavior.
+**
+** <dl>
+** <dt>SQLITE_VTAB_CONSTRAINT_SUPPORT
+** <dd>Calls of the form
+** [sqlite3_vtab_config](db,SQLITE_VTAB_CONSTRAINT_SUPPORT,X) are supported,
+** where X is an integer.  If X is zero, then the [virtual table] whose
+** [xCreate] or [xConnect] method invoked [sqlite3_vtab_config()] does not
+** support constraints.  In this configuration (which is the default) if
+** a call to the [xUpdate] method returns [SQLITE_CONSTRAINT], then the entire
+** statement is rolled back as if [ON CONFLICT | OR ABORT] had been
+** specified as part of the users SQL statement, regardless of the actual
+** ON CONFLICT mode specified.
+**
+** If X is non-zero, then the virtual table implementation guarantees
+** that if [xUpdate] returns [SQLITE_CONSTRAINT], it will do so before
+** any modifications to internal or persistent data structures have been made.
+** If the [ON CONFLICT] mode is ABORT, FAIL, IGNORE or ROLLBACK, SQLite 
+** is able to roll back a statement or database transaction, and abandon
+** or continue processing the current SQL statement as appropriate. 
+** If the ON CONFLICT mode is REPLACE and the [xUpdate] method returns
+** [SQLITE_CONSTRAINT], SQLite handles this as if the ON CONFLICT mode
+** had been ABORT.
+**
+** Virtual table implementations that are required to handle OR REPLACE
+** must do so within the [xUpdate] method. If a call to the 
+** [sqlite3_vtab_on_conflict()] function indicates that the current ON 
+** CONFLICT policy is REPLACE, the virtual table implementation should 
+** silently replace the appropriate rows within the xUpdate callback and
+** return SQLITE_OK. Or, if this is not possible, it may return
+** SQLITE_CONSTRAINT, in which case SQLite falls back to OR ABORT 
+** constraint handling.
+** </dl>
+*/
+#define SQLITE_VTAB_CONSTRAINT_SUPPORT 1
+
+/*
+** CAPI3REF: Determine The Virtual Table Conflict Policy
+**
+** This function may only be called from within a call to the [xUpdate] method
+** of a [virtual table] implementation for an INSERT or UPDATE operation. ^The
+** value returned is one of [SQLITE_ROLLBACK], [SQLITE_IGNORE], [SQLITE_FAIL],
+** [SQLITE_ABORT], or [SQLITE_REPLACE], according to the [ON CONFLICT] mode
+** of the SQL statement that triggered the call to the [xUpdate] method of the
+** [virtual table].
+*/
+int sqlite3_vtab_on_conflict(sqlite3 *);
+
+/*
+** CAPI3REF: Conflict resolution modes
+**
+** These constants are returned by [sqlite3_vtab_on_conflict()] to
+** inform a [virtual table] implementation what the [ON CONFLICT] mode
+** is for the SQL statement being evaluated.
+**
+** Note that the [SQLITE_IGNORE] constant is also used as a potential
+** return value from the [sqlite3_set_authorizer()] callback and that
+** [SQLITE_ABORT] is also a [result code].
+*/
+#define SQLITE_ROLLBACK 1
+/* #define SQLITE_IGNORE 2 // Also used by sqlite3_authorizer() callback */
+#define SQLITE_FAIL     3
+/* #define SQLITE_ABORT 4  // Also an error code */
+#define SQLITE_REPLACE  5
+
+
+
+/*
+** Undo the hack that converts floating point types to integer for
+** builds on processors without floating point support.
+*/
+#ifdef SQLITE_OMIT_FLOATING_POINT
+# undef double
+#endif
+
+#ifdef __cplusplus
+}  /* End of the 'extern "C"' block */
+#endif
+#endif
diff --git a/src/sqlite3ext.h b/src/sqlite3ext.h
new file mode 100644
index 0000000..5abcde2
--- /dev/null
+++ b/src/sqlite3ext.h
@@ -0,0 +1,447 @@
+/*
+** 2006 June 7
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This header file defines the SQLite interface for use by
+** shared libraries that want to be imported as extensions into
+** an SQLite instance.  Shared libraries that intend to be loaded
+** as extensions by SQLite should #include this file instead of 
+** sqlite3.h.
+*/
+#ifndef _SQLITE3EXT_H_
+#define _SQLITE3EXT_H_
+#include "sqlite3.h"
+
+typedef struct sqlite3_api_routines sqlite3_api_routines;
+
+/*
+** The following structure holds pointers to all of the SQLite API
+** routines.
+**
+** WARNING:  In order to maintain backwards compatibility, add new
+** interfaces to the end of this structure only.  If you insert new
+** interfaces in the middle of this structure, then older different
+** versions of SQLite will not be able to load each others' shared
+** libraries!
+*/
+struct sqlite3_api_routines {
+  void * (*aggregate_context)(sqlite3_context*,int nBytes);
+  int  (*aggregate_count)(sqlite3_context*);
+  int  (*bind_blob)(sqlite3_stmt*,int,const void*,int n,void(*)(void*));
+  int  (*bind_double)(sqlite3_stmt*,int,double);
+  int  (*bind_int)(sqlite3_stmt*,int,int);
+  int  (*bind_int64)(sqlite3_stmt*,int,sqlite_int64);
+  int  (*bind_null)(sqlite3_stmt*,int);
+  int  (*bind_parameter_count)(sqlite3_stmt*);
+  int  (*bind_parameter_index)(sqlite3_stmt*,const char*zName);
+  const char * (*bind_parameter_name)(sqlite3_stmt*,int);
+  int  (*bind_text)(sqlite3_stmt*,int,const char*,int n,void(*)(void*));
+  int  (*bind_text16)(sqlite3_stmt*,int,const void*,int,void(*)(void*));
+  int  (*bind_value)(sqlite3_stmt*,int,const sqlite3_value*);
+  int  (*busy_handler)(sqlite3*,int(*)(void*,int),void*);
+  int  (*busy_timeout)(sqlite3*,int ms);
+  int  (*changes)(sqlite3*);
+  int  (*close)(sqlite3*);
+  int  (*collation_needed)(sqlite3*,void*,void(*)(void*,sqlite3*,
+                           int eTextRep,const char*));
+  int  (*collation_needed16)(sqlite3*,void*,void(*)(void*,sqlite3*,
+                             int eTextRep,const void*));
+  const void * (*column_blob)(sqlite3_stmt*,int iCol);
+  int  (*column_bytes)(sqlite3_stmt*,int iCol);
+  int  (*column_bytes16)(sqlite3_stmt*,int iCol);
+  int  (*column_count)(sqlite3_stmt*pStmt);
+  const char * (*column_database_name)(sqlite3_stmt*,int);
+  const void * (*column_database_name16)(sqlite3_stmt*,int);
+  const char * (*column_decltype)(sqlite3_stmt*,int i);
+  const void * (*column_decltype16)(sqlite3_stmt*,int);
+  double  (*column_double)(sqlite3_stmt*,int iCol);
+  int  (*column_int)(sqlite3_stmt*,int iCol);
+  sqlite_int64  (*column_int64)(sqlite3_stmt*,int iCol);
+  const char * (*column_name)(sqlite3_stmt*,int);
+  const void * (*column_name16)(sqlite3_stmt*,int);
+  const char * (*column_origin_name)(sqlite3_stmt*,int);
+  const void * (*column_origin_name16)(sqlite3_stmt*,int);
+  const char * (*column_table_name)(sqlite3_stmt*,int);
+  const void * (*column_table_name16)(sqlite3_stmt*,int);
+  const unsigned char * (*column_text)(sqlite3_stmt*,int iCol);
+  const void * (*column_text16)(sqlite3_stmt*,int iCol);
+  int  (*column_type)(sqlite3_stmt*,int iCol);
+  sqlite3_value* (*column_value)(sqlite3_stmt*,int iCol);
+  void * (*commit_hook)(sqlite3*,int(*)(void*),void*);
+  int  (*complete)(const char*sql);
+  int  (*complete16)(const void*sql);
+  int  (*create_collation)(sqlite3*,const char*,int,void*,
+                           int(*)(void*,int,const void*,int,const void*));
+  int  (*create_collation16)(sqlite3*,const void*,int,void*,
+                             int(*)(void*,int,const void*,int,const void*));
+  int  (*create_function)(sqlite3*,const char*,int,int,void*,
+                          void (*xFunc)(sqlite3_context*,int,sqlite3_value**),
+                          void (*xStep)(sqlite3_context*,int,sqlite3_value**),
+                          void (*xFinal)(sqlite3_context*));
+  int  (*create_function16)(sqlite3*,const void*,int,int,void*,
+                            void (*xFunc)(sqlite3_context*,int,sqlite3_value**),
+                            void (*xStep)(sqlite3_context*,int,sqlite3_value**),
+                            void (*xFinal)(sqlite3_context*));
+  int (*create_module)(sqlite3*,const char*,const sqlite3_module*,void*);
+  int  (*data_count)(sqlite3_stmt*pStmt);
+  sqlite3 * (*db_handle)(sqlite3_stmt*);
+  int (*declare_vtab)(sqlite3*,const char*);
+  int  (*enable_shared_cache)(int);
+  int  (*errcode)(sqlite3*db);
+  const char * (*errmsg)(sqlite3*);
+  const void * (*errmsg16)(sqlite3*);
+  int  (*exec)(sqlite3*,const char*,sqlite3_callback,void*,char**);
+  int  (*expired)(sqlite3_stmt*);
+  int  (*finalize)(sqlite3_stmt*pStmt);
+  void  (*free)(void*);
+  void  (*free_table)(char**result);
+  int  (*get_autocommit)(sqlite3*);
+  void * (*get_auxdata)(sqlite3_context*,int);
+  int  (*get_table)(sqlite3*,const char*,char***,int*,int*,char**);
+  int  (*global_recover)(void);
+  void  (*interruptx)(sqlite3*);
+  sqlite_int64  (*last_insert_rowid)(sqlite3*);
+  const char * (*libversion)(void);
+  int  (*libversion_number)(void);
+  void *(*malloc)(int);
+  char * (*mprintf)(const char*,...);
+  int  (*open)(const char*,sqlite3**);
+  int  (*open16)(const void*,sqlite3**);
+  int  (*prepare)(sqlite3*,const char*,int,sqlite3_stmt**,const char**);
+  int  (*prepare16)(sqlite3*,const void*,int,sqlite3_stmt**,const void**);
+  void * (*profile)(sqlite3*,void(*)(void*,const char*,sqlite_uint64),void*);
+  void  (*progress_handler)(sqlite3*,int,int(*)(void*),void*);
+  void *(*realloc)(void*,int);
+  int  (*reset)(sqlite3_stmt*pStmt);
+  void  (*result_blob)(sqlite3_context*,const void*,int,void(*)(void*));
+  void  (*result_double)(sqlite3_context*,double);
+  void  (*result_error)(sqlite3_context*,const char*,int);
+  void  (*result_error16)(sqlite3_context*,const void*,int);
+  void  (*result_int)(sqlite3_context*,int);
+  void  (*result_int64)(sqlite3_context*,sqlite_int64);
+  void  (*result_null)(sqlite3_context*);
+  void  (*result_text)(sqlite3_context*,const char*,int,void(*)(void*));
+  void  (*result_text16)(sqlite3_context*,const void*,int,void(*)(void*));
+  void  (*result_text16be)(sqlite3_context*,const void*,int,void(*)(void*));
+  void  (*result_text16le)(sqlite3_context*,const void*,int,void(*)(void*));
+  void  (*result_value)(sqlite3_context*,sqlite3_value*);
+  void * (*rollback_hook)(sqlite3*,void(*)(void*),void*);
+  int  (*set_authorizer)(sqlite3*,int(*)(void*,int,const char*,const char*,
+                         const char*,const char*),void*);
+  void  (*set_auxdata)(sqlite3_context*,int,void*,void (*)(void*));
+  char * (*snprintf)(int,char*,const char*,...);
+  int  (*step)(sqlite3_stmt*);
+  int  (*table_column_metadata)(sqlite3*,const char*,const char*,const char*,
+                                char const**,char const**,int*,int*,int*);
+  void  (*thread_cleanup)(void);
+  int  (*total_changes)(sqlite3*);
+  void * (*trace)(sqlite3*,void(*xTrace)(void*,const char*),void*);
+  int  (*transfer_bindings)(sqlite3_stmt*,sqlite3_stmt*);
+  void * (*update_hook)(sqlite3*,void(*)(void*,int ,char const*,char const*,
+                                         sqlite_int64),void*);
+  void * (*user_data)(sqlite3_context*);
+  const void * (*value_blob)(sqlite3_value*);
+  int  (*value_bytes)(sqlite3_value*);
+  int  (*value_bytes16)(sqlite3_value*);
+  double  (*value_double)(sqlite3_value*);
+  int  (*value_int)(sqlite3_value*);
+  sqlite_int64  (*value_int64)(sqlite3_value*);
+  int  (*value_numeric_type)(sqlite3_value*);
+  const unsigned char * (*value_text)(sqlite3_value*);
+  const void * (*value_text16)(sqlite3_value*);
+  const void * (*value_text16be)(sqlite3_value*);
+  const void * (*value_text16le)(sqlite3_value*);
+  int  (*value_type)(sqlite3_value*);
+  char *(*vmprintf)(const char*,va_list);
+  /* Added ??? */
+  int (*overload_function)(sqlite3*, const char *zFuncName, int nArg);
+  /* Added by 3.3.13 */
+  int (*prepare_v2)(sqlite3*,const char*,int,sqlite3_stmt**,const char**);
+  int (*prepare16_v2)(sqlite3*,const void*,int,sqlite3_stmt**,const void**);
+  int (*clear_bindings)(sqlite3_stmt*);
+  /* Added by 3.4.1 */
+  int (*create_module_v2)(sqlite3*,const char*,const sqlite3_module*,void*,
+                          void (*xDestroy)(void *));
+  /* Added by 3.5.0 */
+  int (*bind_zeroblob)(sqlite3_stmt*,int,int);
+  int (*blob_bytes)(sqlite3_blob*);
+  int (*blob_close)(sqlite3_blob*);
+  int (*blob_open)(sqlite3*,const char*,const char*,const char*,sqlite3_int64,
+                   int,sqlite3_blob**);
+  int (*blob_read)(sqlite3_blob*,void*,int,int);
+  int (*blob_write)(sqlite3_blob*,const void*,int,int);
+  int (*create_collation_v2)(sqlite3*,const char*,int,void*,
+                             int(*)(void*,int,const void*,int,const void*),
+                             void(*)(void*));
+  int (*file_control)(sqlite3*,const char*,int,void*);
+  sqlite3_int64 (*memory_highwater)(int);
+  sqlite3_int64 (*memory_used)(void);
+  sqlite3_mutex *(*mutex_alloc)(int);
+  void (*mutex_enter)(sqlite3_mutex*);
+  void (*mutex_free)(sqlite3_mutex*);
+  void (*mutex_leave)(sqlite3_mutex*);
+  int (*mutex_try)(sqlite3_mutex*);
+  int (*open_v2)(const char*,sqlite3**,int,const char*);
+  int (*release_memory)(int);
+  void (*result_error_nomem)(sqlite3_context*);
+  void (*result_error_toobig)(sqlite3_context*);
+  int (*sleep)(int);
+  void (*soft_heap_limit)(int);
+  sqlite3_vfs *(*vfs_find)(const char*);
+  int (*vfs_register)(sqlite3_vfs*,int);
+  int (*vfs_unregister)(sqlite3_vfs*);
+  int (*xthreadsafe)(void);
+  void (*result_zeroblob)(sqlite3_context*,int);
+  void (*result_error_code)(sqlite3_context*,int);
+  int (*test_control)(int, ...);
+  void (*randomness)(int,void*);
+  sqlite3 *(*context_db_handle)(sqlite3_context*);
+  int (*extended_result_codes)(sqlite3*,int);
+  int (*limit)(sqlite3*,int,int);
+  sqlite3_stmt *(*next_stmt)(sqlite3*,sqlite3_stmt*);
+  const char *(*sql)(sqlite3_stmt*);
+  int (*status)(int,int*,int*,int);
+  int (*backup_finish)(sqlite3_backup*);
+  sqlite3_backup *(*backup_init)(sqlite3*,const char*,sqlite3*,const char*);
+  int (*backup_pagecount)(sqlite3_backup*);
+  int (*backup_remaining)(sqlite3_backup*);
+  int (*backup_step)(sqlite3_backup*,int);
+  const char *(*compileoption_get)(int);
+  int (*compileoption_used)(const char*);
+  int (*create_function_v2)(sqlite3*,const char*,int,int,void*,
+                            void (*xFunc)(sqlite3_context*,int,sqlite3_value**),
+                            void (*xStep)(sqlite3_context*,int,sqlite3_value**),
+                            void (*xFinal)(sqlite3_context*),
+                            void(*xDestroy)(void*));
+  int (*db_config)(sqlite3*,int,...);
+  sqlite3_mutex *(*db_mutex)(sqlite3*);
+  int (*db_status)(sqlite3*,int,int*,int*,int);
+  int (*extended_errcode)(sqlite3*);
+  void (*log)(int,const char*,...);
+  sqlite3_int64 (*soft_heap_limit64)(sqlite3_int64);
+  const char *(*sourceid)(void);
+  int (*stmt_status)(sqlite3_stmt*,int,int);
+  int (*strnicmp)(const char*,const char*,int);
+  int (*unlock_notify)(sqlite3*,void(*)(void**,int),void*);
+  int (*wal_autocheckpoint)(sqlite3*,int);
+  int (*wal_checkpoint)(sqlite3*,const char*);
+  void *(*wal_hook)(sqlite3*,int(*)(void*,sqlite3*,const char*,int),void*);
+  int (*blob_reopen)(sqlite3_blob*,sqlite3_int64);
+  int (*vtab_config)(sqlite3*,int op,...);
+  int (*vtab_on_conflict)(sqlite3*);
+};
+
+/*
+** The following macros redefine the API routines so that they are
+** redirected throught the global sqlite3_api structure.
+**
+** This header file is also used by the loadext.c source file
+** (part of the main SQLite library - not an extension) so that
+** it can get access to the sqlite3_api_routines structure
+** definition.  But the main library does not want to redefine
+** the API.  So the redefinition macros are only valid if the
+** SQLITE_CORE macros is undefined.
+*/
+#ifndef SQLITE_CORE
+#define sqlite3_aggregate_context      sqlite3_api->aggregate_context
+#ifndef SQLITE_OMIT_DEPRECATED
+#define sqlite3_aggregate_count        sqlite3_api->aggregate_count
+#endif
+#define sqlite3_bind_blob              sqlite3_api->bind_blob
+#define sqlite3_bind_double            sqlite3_api->bind_double
+#define sqlite3_bind_int               sqlite3_api->bind_int
+#define sqlite3_bind_int64             sqlite3_api->bind_int64
+#define sqlite3_bind_null              sqlite3_api->bind_null
+#define sqlite3_bind_parameter_count   sqlite3_api->bind_parameter_count
+#define sqlite3_bind_parameter_index   sqlite3_api->bind_parameter_index
+#define sqlite3_bind_parameter_name    sqlite3_api->bind_parameter_name
+#define sqlite3_bind_text              sqlite3_api->bind_text
+#define sqlite3_bind_text16            sqlite3_api->bind_text16
+#define sqlite3_bind_value             sqlite3_api->bind_value
+#define sqlite3_busy_handler           sqlite3_api->busy_handler
+#define sqlite3_busy_timeout           sqlite3_api->busy_timeout
+#define sqlite3_changes                sqlite3_api->changes
+#define sqlite3_close                  sqlite3_api->close
+#define sqlite3_collation_needed       sqlite3_api->collation_needed
+#define sqlite3_collation_needed16     sqlite3_api->collation_needed16
+#define sqlite3_column_blob            sqlite3_api->column_blob
+#define sqlite3_column_bytes           sqlite3_api->column_bytes
+#define sqlite3_column_bytes16         sqlite3_api->column_bytes16
+#define sqlite3_column_count           sqlite3_api->column_count
+#define sqlite3_column_database_name   sqlite3_api->column_database_name
+#define sqlite3_column_database_name16 sqlite3_api->column_database_name16
+#define sqlite3_column_decltype        sqlite3_api->column_decltype
+#define sqlite3_column_decltype16      sqlite3_api->column_decltype16
+#define sqlite3_column_double          sqlite3_api->column_double
+#define sqlite3_column_int             sqlite3_api->column_int
+#define sqlite3_column_int64           sqlite3_api->column_int64
+#define sqlite3_column_name            sqlite3_api->column_name
+#define sqlite3_column_name16          sqlite3_api->column_name16
+#define sqlite3_column_origin_name     sqlite3_api->column_origin_name
+#define sqlite3_column_origin_name16   sqlite3_api->column_origin_name16
+#define sqlite3_column_table_name      sqlite3_api->column_table_name
+#define sqlite3_column_table_name16    sqlite3_api->column_table_name16
+#define sqlite3_column_text            sqlite3_api->column_text
+#define sqlite3_column_text16          sqlite3_api->column_text16
+#define sqlite3_column_type            sqlite3_api->column_type
+#define sqlite3_column_value           sqlite3_api->column_value
+#define sqlite3_commit_hook            sqlite3_api->commit_hook
+#define sqlite3_complete               sqlite3_api->complete
+#define sqlite3_complete16             sqlite3_api->complete16
+#define sqlite3_create_collation       sqlite3_api->create_collation
+#define sqlite3_create_collation16     sqlite3_api->create_collation16
+#define sqlite3_create_function        sqlite3_api->create_function
+#define sqlite3_create_function16      sqlite3_api->create_function16
+#define sqlite3_create_module          sqlite3_api->create_module
+#define sqlite3_create_module_v2       sqlite3_api->create_module_v2
+#define sqlite3_data_count             sqlite3_api->data_count
+#define sqlite3_db_handle              sqlite3_api->db_handle
+#define sqlite3_declare_vtab           sqlite3_api->declare_vtab
+#define sqlite3_enable_shared_cache    sqlite3_api->enable_shared_cache
+#define sqlite3_errcode                sqlite3_api->errcode
+#define sqlite3_errmsg                 sqlite3_api->errmsg
+#define sqlite3_errmsg16               sqlite3_api->errmsg16
+#define sqlite3_exec                   sqlite3_api->exec
+#ifndef SQLITE_OMIT_DEPRECATED
+#define sqlite3_expired                sqlite3_api->expired
+#endif
+#define sqlite3_finalize               sqlite3_api->finalize
+#define sqlite3_free                   sqlite3_api->free
+#define sqlite3_free_table             sqlite3_api->free_table
+#define sqlite3_get_autocommit         sqlite3_api->get_autocommit
+#define sqlite3_get_auxdata            sqlite3_api->get_auxdata
+#define sqlite3_get_table              sqlite3_api->get_table
+#ifndef SQLITE_OMIT_DEPRECATED
+#define sqlite3_global_recover         sqlite3_api->global_recover
+#endif
+#define sqlite3_interrupt              sqlite3_api->interruptx
+#define sqlite3_last_insert_rowid      sqlite3_api->last_insert_rowid
+#define sqlite3_libversion             sqlite3_api->libversion
+#define sqlite3_libversion_number      sqlite3_api->libversion_number
+#define sqlite3_malloc                 sqlite3_api->malloc
+#define sqlite3_mprintf                sqlite3_api->mprintf
+#define sqlite3_open                   sqlite3_api->open
+#define sqlite3_open16                 sqlite3_api->open16
+#define sqlite3_prepare                sqlite3_api->prepare
+#define sqlite3_prepare16              sqlite3_api->prepare16
+#define sqlite3_prepare_v2             sqlite3_api->prepare_v2
+#define sqlite3_prepare16_v2           sqlite3_api->prepare16_v2
+#define sqlite3_profile                sqlite3_api->profile
+#define sqlite3_progress_handler       sqlite3_api->progress_handler
+#define sqlite3_realloc                sqlite3_api->realloc
+#define sqlite3_reset                  sqlite3_api->reset
+#define sqlite3_result_blob            sqlite3_api->result_blob
+#define sqlite3_result_double          sqlite3_api->result_double
+#define sqlite3_result_error           sqlite3_api->result_error
+#define sqlite3_result_error16         sqlite3_api->result_error16
+#define sqlite3_result_int             sqlite3_api->result_int
+#define sqlite3_result_int64           sqlite3_api->result_int64
+#define sqlite3_result_null            sqlite3_api->result_null
+#define sqlite3_result_text            sqlite3_api->result_text
+#define sqlite3_result_text16          sqlite3_api->result_text16
+#define sqlite3_result_text16be        sqlite3_api->result_text16be
+#define sqlite3_result_text16le        sqlite3_api->result_text16le
+#define sqlite3_result_value           sqlite3_api->result_value
+#define sqlite3_rollback_hook          sqlite3_api->rollback_hook
+#define sqlite3_set_authorizer         sqlite3_api->set_authorizer
+#define sqlite3_set_auxdata            sqlite3_api->set_auxdata
+#define sqlite3_snprintf               sqlite3_api->snprintf
+#define sqlite3_step                   sqlite3_api->step
+#define sqlite3_table_column_metadata  sqlite3_api->table_column_metadata
+#define sqlite3_thread_cleanup         sqlite3_api->thread_cleanup
+#define sqlite3_total_changes          sqlite3_api->total_changes
+#define sqlite3_trace                  sqlite3_api->trace
+#ifndef SQLITE_OMIT_DEPRECATED
+#define sqlite3_transfer_bindings      sqlite3_api->transfer_bindings
+#endif
+#define sqlite3_update_hook            sqlite3_api->update_hook
+#define sqlite3_user_data              sqlite3_api->user_data
+#define sqlite3_value_blob             sqlite3_api->value_blob
+#define sqlite3_value_bytes            sqlite3_api->value_bytes
+#define sqlite3_value_bytes16          sqlite3_api->value_bytes16
+#define sqlite3_value_double           sqlite3_api->value_double
+#define sqlite3_value_int              sqlite3_api->value_int
+#define sqlite3_value_int64            sqlite3_api->value_int64
+#define sqlite3_value_numeric_type     sqlite3_api->value_numeric_type
+#define sqlite3_value_text             sqlite3_api->value_text
+#define sqlite3_value_text16           sqlite3_api->value_text16
+#define sqlite3_value_text16be         sqlite3_api->value_text16be
+#define sqlite3_value_text16le         sqlite3_api->value_text16le
+#define sqlite3_value_type             sqlite3_api->value_type
+#define sqlite3_vmprintf               sqlite3_api->vmprintf
+#define sqlite3_overload_function      sqlite3_api->overload_function
+#define sqlite3_prepare_v2             sqlite3_api->prepare_v2
+#define sqlite3_prepare16_v2           sqlite3_api->prepare16_v2
+#define sqlite3_clear_bindings         sqlite3_api->clear_bindings
+#define sqlite3_bind_zeroblob          sqlite3_api->bind_zeroblob
+#define sqlite3_blob_bytes             sqlite3_api->blob_bytes
+#define sqlite3_blob_close             sqlite3_api->blob_close
+#define sqlite3_blob_open              sqlite3_api->blob_open
+#define sqlite3_blob_read              sqlite3_api->blob_read
+#define sqlite3_blob_write             sqlite3_api->blob_write
+#define sqlite3_create_collation_v2    sqlite3_api->create_collation_v2
+#define sqlite3_file_control           sqlite3_api->file_control
+#define sqlite3_memory_highwater       sqlite3_api->memory_highwater
+#define sqlite3_memory_used            sqlite3_api->memory_used
+#define sqlite3_mutex_alloc            sqlite3_api->mutex_alloc
+#define sqlite3_mutex_enter            sqlite3_api->mutex_enter
+#define sqlite3_mutex_free             sqlite3_api->mutex_free
+#define sqlite3_mutex_leave            sqlite3_api->mutex_leave
+#define sqlite3_mutex_try              sqlite3_api->mutex_try
+#define sqlite3_open_v2                sqlite3_api->open_v2
+#define sqlite3_release_memory         sqlite3_api->release_memory
+#define sqlite3_result_error_nomem     sqlite3_api->result_error_nomem
+#define sqlite3_result_error_toobig    sqlite3_api->result_error_toobig
+#define sqlite3_sleep                  sqlite3_api->sleep
+#define sqlite3_soft_heap_limit        sqlite3_api->soft_heap_limit
+#define sqlite3_vfs_find               sqlite3_api->vfs_find
+#define sqlite3_vfs_register           sqlite3_api->vfs_register
+#define sqlite3_vfs_unregister         sqlite3_api->vfs_unregister
+#define sqlite3_threadsafe             sqlite3_api->xthreadsafe
+#define sqlite3_result_zeroblob        sqlite3_api->result_zeroblob
+#define sqlite3_result_error_code      sqlite3_api->result_error_code
+#define sqlite3_test_control           sqlite3_api->test_control
+#define sqlite3_randomness             sqlite3_api->randomness
+#define sqlite3_context_db_handle      sqlite3_api->context_db_handle
+#define sqlite3_extended_result_codes  sqlite3_api->extended_result_codes
+#define sqlite3_limit                  sqlite3_api->limit
+#define sqlite3_next_stmt              sqlite3_api->next_stmt
+#define sqlite3_sql                    sqlite3_api->sql
+#define sqlite3_status                 sqlite3_api->status
+#define sqlite3_backup_finish          sqlite3_api->backup_finish
+#define sqlite3_backup_init            sqlite3_api->backup_init
+#define sqlite3_backup_pagecount       sqlite3_api->backup_pagecount
+#define sqlite3_backup_remaining       sqlite3_api->backup_remaining
+#define sqlite3_backup_step            sqlite3_api->backup_step
+#define sqlite3_compileoption_get      sqlite3_api->compileoption_get
+#define sqlite3_compileoption_used     sqlite3_api->compileoption_used
+#define sqlite3_create_function_v2     sqlite3_api->create_function_v2
+#define sqlite3_db_config              sqlite3_api->db_config
+#define sqlite3_db_mutex               sqlite3_api->db_mutex
+#define sqlite3_db_status              sqlite3_api->db_status
+#define sqlite3_extended_errcode       sqlite3_api->extended_errcode
+#define sqlite3_log                    sqlite3_api->log
+#define sqlite3_soft_heap_limit64      sqlite3_api->soft_heap_limit64
+#define sqlite3_sourceid               sqlite3_api->sourceid
+#define sqlite3_stmt_status            sqlite3_api->stmt_status
+#define sqlite3_strnicmp               sqlite3_api->strnicmp
+#define sqlite3_unlock_notify          sqlite3_api->unlock_notify
+#define sqlite3_wal_autocheckpoint     sqlite3_api->wal_autocheckpoint
+#define sqlite3_wal_checkpoint         sqlite3_api->wal_checkpoint
+#define sqlite3_wal_hook               sqlite3_api->wal_hook
+#define sqlite3_blob_reopen            sqlite3_api->blob_reopen
+#define sqlite3_vtab_config            sqlite3_api->vtab_config
+#define sqlite3_vtab_on_conflict       sqlite3_api->vtab_on_conflict
+#endif /* SQLITE_CORE */
+
+#define SQLITE_EXTENSION_INIT1     const sqlite3_api_routines *sqlite3_api = 0;
+#define SQLITE_EXTENSION_INIT2(v)  sqlite3_api = v;
+
+#endif /* _SQLITE3EXT_H_ */
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
new file mode 100644
index 0000000..9e27654
--- /dev/null
+++ b/src/sqliteInt.h
@@ -0,0 +1,3274 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Internal interface definitions for SQLite.
+**
+*/
+#ifndef _SQLITEINT_H_
+#define _SQLITEINT_H_
+
+/*
+** These #defines should enable >2GB file support on POSIX if the
+** underlying operating system supports it.  If the OS lacks
+** large file support, or if the OS is windows, these should be no-ops.
+**
+** Ticket #2739:  The _LARGEFILE_SOURCE macro must appear before any
+** system #includes.  Hence, this block of code must be the very first
+** code in all source files.
+**
+** Large file support can be disabled using the -DSQLITE_DISABLE_LFS switch
+** on the compiler command line.  This is necessary if you are compiling
+** on a recent machine (ex: Red Hat 7.2) but you want your code to work
+** on an older machine (ex: Red Hat 6.0).  If you compile on Red Hat 7.2
+** without this option, LFS is enable.  But LFS does not exist in the kernel
+** in Red Hat 6.0, so the code won't work.  Hence, for maximum binary
+** portability you should omit LFS.
+**
+** Similar is true for Mac OS X.  LFS is only supported on Mac OS X 9 and later.
+*/
+#ifndef SQLITE_DISABLE_LFS
+# define _LARGE_FILE       1
+# ifndef _FILE_OFFSET_BITS
+#   define _FILE_OFFSET_BITS 64
+# endif
+# define _LARGEFILE_SOURCE 1
+#endif
+
+/*
+** Include the configuration header output by 'configure' if we're using the
+** autoconf-based build
+*/
+#ifdef _HAVE_SQLITE_CONFIG_H
+#include "config.h"
+#endif
+
+#include "sqliteLimit.h"
+
+/* Disable nuisance warnings on Borland compilers */
+#if defined(__BORLANDC__)
+#pragma warn -rch /* unreachable code */
+#pragma warn -ccc /* Condition is always true or false */
+#pragma warn -aus /* Assigned value is never used */
+#pragma warn -csu /* Comparing signed and unsigned */
+#pragma warn -spa /* Suspicious pointer arithmetic */
+#endif
+
+/* Needed for various definitions... */
+#ifndef _GNU_SOURCE
+# define _GNU_SOURCE
+#endif
+
+/*
+** Include standard header files as necessary
+*/
+#ifdef HAVE_STDINT_H
+#include <stdint.h>
+#endif
+#ifdef HAVE_INTTYPES_H
+#include <inttypes.h>
+#endif
+
+/*
+** The following macros are used to cast pointers to integers and
+** integers to pointers.  The way you do this varies from one compiler
+** to the next, so we have developed the following set of #if statements
+** to generate appropriate macros for a wide range of compilers.
+**
+** The correct "ANSI" way to do this is to use the intptr_t type. 
+** Unfortunately, that typedef is not available on all compilers, or
+** if it is available, it requires an #include of specific headers
+** that vary from one machine to the next.
+**
+** Ticket #3860:  The llvm-gcc-4.2 compiler from Apple chokes on
+** the ((void*)&((char*)0)[X]) construct.  But MSVC chokes on ((void*)(X)).
+** So we have to define the macros in different ways depending on the
+** compiler.
+*/
+#if defined(__PTRDIFF_TYPE__)  /* This case should work for GCC */
+# define SQLITE_INT_TO_PTR(X)  ((void*)(__PTRDIFF_TYPE__)(X))
+# define SQLITE_PTR_TO_INT(X)  ((int)(__PTRDIFF_TYPE__)(X))
+#elif !defined(__GNUC__)       /* Works for compilers other than LLVM */
+# define SQLITE_INT_TO_PTR(X)  ((void*)&((char*)0)[X])
+# define SQLITE_PTR_TO_INT(X)  ((int)(((char*)X)-(char*)0))
+#elif defined(HAVE_STDINT_H)   /* Use this case if we have ANSI headers */
+# define SQLITE_INT_TO_PTR(X)  ((void*)(intptr_t)(X))
+# define SQLITE_PTR_TO_INT(X)  ((int)(intptr_t)(X))
+#else                          /* Generates a warning - but it always works */
+# define SQLITE_INT_TO_PTR(X)  ((void*)(X))
+# define SQLITE_PTR_TO_INT(X)  ((int)(X))
+#endif
+
+/*
+** The SQLITE_THREADSAFE macro must be defined as 0, 1, or 2.
+** 0 means mutexes are permanently disable and the library is never
+** threadsafe.  1 means the library is serialized which is the highest
+** level of threadsafety.  2 means the libary is multithreaded - multiple
+** threads can use SQLite as long as no two threads try to use the same
+** database connection at the same time.
+**
+** Older versions of SQLite used an optional THREADSAFE macro.
+** We support that for legacy.
+*/
+#if !defined(SQLITE_THREADSAFE)
+#if defined(THREADSAFE)
+# define SQLITE_THREADSAFE THREADSAFE
+#else
+# define SQLITE_THREADSAFE 1 /* IMP: R-07272-22309 */
+#endif
+#endif
+
+/*
+** The SQLITE_DEFAULT_MEMSTATUS macro must be defined as either 0 or 1.
+** It determines whether or not the features related to 
+** SQLITE_CONFIG_MEMSTATUS are available by default or not. This value can
+** be overridden at runtime using the sqlite3_config() API.
+*/
+#if !defined(SQLITE_DEFAULT_MEMSTATUS)
+# define SQLITE_DEFAULT_MEMSTATUS 1
+#endif
+
+/*
+** Exactly one of the following macros must be defined in order to
+** specify which memory allocation subsystem to use.
+**
+**     SQLITE_SYSTEM_MALLOC          // Use normal system malloc()
+**     SQLITE_WIN32_MALLOC           // Use Win32 native heap API
+**     SQLITE_MEMDEBUG               // Debugging version of system malloc()
+**
+** On Windows, if the SQLITE_WIN32_MALLOC_VALIDATE macro is defined and the
+** assert() macro is enabled, each call into the Win32 native heap subsystem
+** will cause HeapValidate to be called.  If heap validation should fail, an
+** assertion will be triggered.
+**
+** (Historical note:  There used to be several other options, but we've
+** pared it down to just these three.)
+**
+** If none of the above are defined, then set SQLITE_SYSTEM_MALLOC as
+** the default.
+*/
+#if defined(SQLITE_SYSTEM_MALLOC)+defined(SQLITE_WIN32_MALLOC)+defined(SQLITE_MEMDEBUG)>1
+# error "At most one of the following compile-time configuration options\
+ is allows: SQLITE_SYSTEM_MALLOC, SQLITE_WIN32_MALLOC, SQLITE_MEMDEBUG"
+#endif
+#if defined(SQLITE_SYSTEM_MALLOC)+defined(SQLITE_WIN32_MALLOC)+defined(SQLITE_MEMDEBUG)==0
+# define SQLITE_SYSTEM_MALLOC 1
+#endif
+
+/*
+** If SQLITE_MALLOC_SOFT_LIMIT is not zero, then try to keep the
+** sizes of memory allocations below this value where possible.
+*/
+#if !defined(SQLITE_MALLOC_SOFT_LIMIT)
+# define SQLITE_MALLOC_SOFT_LIMIT 1024
+#endif
+
+/*
+** We need to define _XOPEN_SOURCE as follows in order to enable
+** recursive mutexes on most Unix systems.  But Mac OS X is different.
+** The _XOPEN_SOURCE define causes problems for Mac OS X we are told,
+** so it is omitted there.  See ticket #2673.
+**
+** Later we learn that _XOPEN_SOURCE is poorly or incorrectly
+** implemented on some systems.  So we avoid defining it at all
+** if it is already defined or if it is unneeded because we are
+** not doing a threadsafe build.  Ticket #2681.
+**
+** See also ticket #2741.
+*/
+#if !defined(_XOPEN_SOURCE) && !defined(__DARWIN__) && !defined(__APPLE__) && SQLITE_THREADSAFE
+#  define _XOPEN_SOURCE 500  /* Needed to enable pthread recursive mutexes */
+#endif
+
+/*
+** The TCL headers are only needed when compiling the TCL bindings.
+*/
+#if defined(SQLITE_TCL) || defined(TCLSH)
+# include <tcl.h>
+#endif
+
+/*
+** Many people are failing to set -DNDEBUG=1 when compiling SQLite.
+** Setting NDEBUG makes the code smaller and run faster.  So the following
+** lines are added to automatically set NDEBUG unless the -DSQLITE_DEBUG=1
+** option is set.  Thus NDEBUG becomes an opt-in rather than an opt-out
+** feature.
+*/
+#if !defined(NDEBUG) && !defined(SQLITE_DEBUG) 
+# define NDEBUG 1
+#endif
+
+/*
+** The testcase() macro is used to aid in coverage testing.  When 
+** doing coverage testing, the condition inside the argument to
+** testcase() must be evaluated both true and false in order to
+** get full branch coverage.  The testcase() macro is inserted
+** to help ensure adequate test coverage in places where simple
+** condition/decision coverage is inadequate.  For example, testcase()
+** can be used to make sure boundary values are tested.  For
+** bitmask tests, testcase() can be used to make sure each bit
+** is significant and used at least once.  On switch statements
+** where multiple cases go to the same block of code, testcase()
+** can insure that all cases are evaluated.
+**
+*/
+#ifdef SQLITE_COVERAGE_TEST
+  void sqlite3Coverage(int);
+# define testcase(X)  if( X ){ sqlite3Coverage(__LINE__); }
+#else
+# define testcase(X)
+#endif
+
+/*
+** The TESTONLY macro is used to enclose variable declarations or
+** other bits of code that are needed to support the arguments
+** within testcase() and assert() macros.
+*/
+#if !defined(NDEBUG) || defined(SQLITE_COVERAGE_TEST)
+# define TESTONLY(X)  X
+#else
+# define TESTONLY(X)
+#endif
+
+/*
+** Sometimes we need a small amount of code such as a variable initialization
+** to setup for a later assert() statement.  We do not want this code to
+** appear when assert() is disabled.  The following macro is therefore
+** used to contain that setup code.  The "VVA" acronym stands for
+** "Verification, Validation, and Accreditation".  In other words, the
+** code within VVA_ONLY() will only run during verification processes.
+*/
+#ifndef NDEBUG
+# define VVA_ONLY(X)  X
+#else
+# define VVA_ONLY(X)
+#endif
+
+/*
+** The ALWAYS and NEVER macros surround boolean expressions which 
+** are intended to always be true or false, respectively.  Such
+** expressions could be omitted from the code completely.  But they
+** are included in a few cases in order to enhance the resilience
+** of SQLite to unexpected behavior - to make the code "self-healing"
+** or "ductile" rather than being "brittle" and crashing at the first
+** hint of unplanned behavior.
+**
+** In other words, ALWAYS and NEVER are added for defensive code.
+**
+** When doing coverage testing ALWAYS and NEVER are hard-coded to
+** be true and false so that the unreachable code then specify will
+** not be counted as untested code.
+*/
+#if defined(SQLITE_COVERAGE_TEST)
+# define ALWAYS(X)      (1)
+# define NEVER(X)       (0)
+#elif !defined(NDEBUG)
+# define ALWAYS(X)      ((X)?1:(assert(0),0))
+# define NEVER(X)       ((X)?(assert(0),1):0)
+#else
+# define ALWAYS(X)      (X)
+# define NEVER(X)       (X)
+#endif
+
+/*
+** Return true (non-zero) if the input is a integer that is too large
+** to fit in 32-bits.  This macro is used inside of various testcase()
+** macros to verify that we have tested SQLite for large-file support.
+*/
+#define IS_BIG_INT(X)  (((X)&~(i64)0xffffffff)!=0)
+
+/*
+** The macro unlikely() is a hint that surrounds a boolean
+** expression that is usually false.  Macro likely() surrounds
+** a boolean expression that is usually true.  GCC is able to
+** use these hints to generate better code, sometimes.
+*/
+#if defined(__GNUC__) && 0
+# define likely(X)    __builtin_expect((X),1)
+# define unlikely(X)  __builtin_expect((X),0)
+#else
+# define likely(X)    !!(X)
+# define unlikely(X)  !!(X)
+#endif
+
+#include "sqlite3.h"
+#include "hash.h"
+#include "parse.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include <stddef.h>
+
+/*
+** If compiling for a processor that lacks floating point support,
+** substitute integer for floating-point
+*/
+#ifdef SQLITE_OMIT_FLOATING_POINT
+# define double sqlite_int64
+# define float sqlite_int64
+# define LONGDOUBLE_TYPE sqlite_int64
+# ifndef SQLITE_BIG_DBL
+#   define SQLITE_BIG_DBL (((sqlite3_int64)1)<<50)
+# endif
+# define SQLITE_OMIT_DATETIME_FUNCS 1
+# define SQLITE_OMIT_TRACE 1
+# undef SQLITE_MIXED_ENDIAN_64BIT_FLOAT
+# undef SQLITE_HAVE_ISNAN
+#endif
+#ifndef SQLITE_BIG_DBL
+# define SQLITE_BIG_DBL (1e99)
+#endif
+
+/*
+** OMIT_TEMPDB is set to 1 if SQLITE_OMIT_TEMPDB is defined, or 0
+** afterward. Having this macro allows us to cause the C compiler 
+** to omit code used by TEMP tables without messy #ifndef statements.
+*/
+#ifdef SQLITE_OMIT_TEMPDB
+#define OMIT_TEMPDB 1
+#else
+#define OMIT_TEMPDB 0
+#endif
+
+/*
+** The "file format" number is an integer that is incremented whenever
+** the VDBE-level file format changes.  The following macros define the
+** the default file format for new databases and the maximum file format
+** that the library can read.
+*/
+#define SQLITE_MAX_FILE_FORMAT 4
+#ifndef SQLITE_DEFAULT_FILE_FORMAT
+# define SQLITE_DEFAULT_FILE_FORMAT 1
+#endif
+
+/*
+** Determine whether triggers are recursive by default.  This can be
+** changed at run-time using a pragma.
+*/
+#ifndef SQLITE_DEFAULT_RECURSIVE_TRIGGERS
+# define SQLITE_DEFAULT_RECURSIVE_TRIGGERS 0
+#endif
+
+/*
+** Provide a default value for SQLITE_TEMP_STORE in case it is not specified
+** on the command-line
+*/
+#ifndef SQLITE_TEMP_STORE
+# define SQLITE_TEMP_STORE 1
+#endif
+
+/*
+** GCC does not define the offsetof() macro so we'll have to do it
+** ourselves.
+*/
+#ifndef offsetof
+#define offsetof(STRUCTURE,FIELD) ((int)((char*)&((STRUCTURE*)0)->FIELD))
+#endif
+
+/*
+** Check to see if this machine uses EBCDIC.  (Yes, believe it or
+** not, there are still machines out there that use EBCDIC.)
+*/
+#if 'A' == '\301'
+# define SQLITE_EBCDIC 1
+#else
+# define SQLITE_ASCII 1
+#endif
+
+/*
+** Integers of known sizes.  These typedefs might change for architectures
+** where the sizes very.  Preprocessor macros are available so that the
+** types can be conveniently redefined at compile-type.  Like this:
+**
+**         cc '-DUINTPTR_TYPE=long long int' ...
+*/
+#ifndef UINT32_TYPE
+# ifdef HAVE_UINT32_T
+#  define UINT32_TYPE uint32_t
+# else
+#  define UINT32_TYPE unsigned int
+# endif
+#endif
+#ifndef UINT16_TYPE
+# ifdef HAVE_UINT16_T
+#  define UINT16_TYPE uint16_t
+# else
+#  define UINT16_TYPE unsigned short int
+# endif
+#endif
+#ifndef INT16_TYPE
+# ifdef HAVE_INT16_T
+#  define INT16_TYPE int16_t
+# else
+#  define INT16_TYPE short int
+# endif
+#endif
+#ifndef UINT8_TYPE
+# ifdef HAVE_UINT8_T
+#  define UINT8_TYPE uint8_t
+# else
+#  define UINT8_TYPE unsigned char
+# endif
+#endif
+#ifndef INT8_TYPE
+# ifdef HAVE_INT8_T
+#  define INT8_TYPE int8_t
+# else
+#  define INT8_TYPE signed char
+# endif
+#endif
+#ifndef LONGDOUBLE_TYPE
+# define LONGDOUBLE_TYPE long double
+#endif
+typedef sqlite_int64 i64;          /* 8-byte signed integer */
+typedef sqlite_uint64 u64;         /* 8-byte unsigned integer */
+typedef UINT32_TYPE u32;           /* 4-byte unsigned integer */
+typedef UINT16_TYPE u16;           /* 2-byte unsigned integer */
+typedef INT16_TYPE i16;            /* 2-byte signed integer */
+typedef UINT8_TYPE u8;             /* 1-byte unsigned integer */
+typedef INT8_TYPE i8;              /* 1-byte signed integer */
+
+/*
+** SQLITE_MAX_U32 is a u64 constant that is the maximum u64 value
+** that can be stored in a u32 without loss of data.  The value
+** is 0x00000000ffffffff.  But because of quirks of some compilers, we
+** have to specify the value in the less intuitive manner shown:
+*/
+#define SQLITE_MAX_U32  ((((u64)1)<<32)-1)
+
+/*
+** The datatype used to store estimates of the number of rows in a
+** table or index.  This is an unsigned integer type.  For 99.9% of
+** the world, a 32-bit integer is sufficient.  But a 64-bit integer
+** can be used at compile-time if desired.
+*/
+#ifdef SQLITE_64BIT_STATS
+ typedef u64 tRowcnt;    /* 64-bit only if requested at compile-time */
+#else
+ typedef u32 tRowcnt;    /* 32-bit is the default */
+#endif
+
+/*
+** Macros to determine whether the machine is big or little endian,
+** evaluated at runtime.
+*/
+#ifdef SQLITE_AMALGAMATION
+const int sqlite3one = 1;
+#else
+extern const int sqlite3one;
+#endif
+#if defined(i386) || defined(__i386__) || defined(_M_IX86)\
+                             || defined(__x86_64) || defined(__x86_64__)
+# define SQLITE_BIGENDIAN    0
+# define SQLITE_LITTLEENDIAN 1
+# define SQLITE_UTF16NATIVE  SQLITE_UTF16LE
+#else
+# define SQLITE_BIGENDIAN    (*(char *)(&sqlite3one)==0)
+# define SQLITE_LITTLEENDIAN (*(char *)(&sqlite3one)==1)
+# define SQLITE_UTF16NATIVE (SQLITE_BIGENDIAN?SQLITE_UTF16BE:SQLITE_UTF16LE)
+#endif
+
+/*
+** Constants for the largest and smallest possible 64-bit signed integers.
+** These macros are designed to work correctly on both 32-bit and 64-bit
+** compilers.
+*/
+#define LARGEST_INT64  (0xffffffff|(((i64)0x7fffffff)<<32))
+#define SMALLEST_INT64 (((i64)-1) - LARGEST_INT64)
+
+/* 
+** Round up a number to the next larger multiple of 8.  This is used
+** to force 8-byte alignment on 64-bit architectures.
+*/
+#define ROUND8(x)     (((x)+7)&~7)
+
+/*
+** Round down to the nearest multiple of 8
+*/
+#define ROUNDDOWN8(x) ((x)&~7)
+
+/*
+** Assert that the pointer X is aligned to an 8-byte boundary.  This
+** macro is used only within assert() to verify that the code gets
+** all alignment restrictions correct.
+**
+** Except, if SQLITE_4_BYTE_ALIGNED_MALLOC is defined, then the
+** underlying malloc() implemention might return us 4-byte aligned
+** pointers.  In that case, only verify 4-byte alignment.
+*/
+#ifdef SQLITE_4_BYTE_ALIGNED_MALLOC
+# define EIGHT_BYTE_ALIGNMENT(X)   ((((char*)(X) - (char*)0)&3)==0)
+#else
+# define EIGHT_BYTE_ALIGNMENT(X)   ((((char*)(X) - (char*)0)&7)==0)
+#endif
+
+
+/*
+** An instance of the following structure is used to store the busy-handler
+** callback for a given sqlite handle. 
+**
+** The sqlite.busyHandler member of the sqlite struct contains the busy
+** callback for the database handle. Each pager opened via the sqlite
+** handle is passed a pointer to sqlite.busyHandler. The busy-handler
+** callback is currently invoked only from within pager.c.
+*/
+typedef struct BusyHandler BusyHandler;
+struct BusyHandler {
+  int (*xFunc)(void *,int);  /* The busy callback */
+  void *pArg;                /* First arg to busy callback */
+  int nBusy;                 /* Incremented with each busy call */
+};
+
+/*
+** Name of the master database table.  The master database table
+** is a special table that holds the names and attributes of all
+** user tables and indices.
+*/
+#define MASTER_NAME       "sqlite_master"
+#define TEMP_MASTER_NAME  "sqlite_temp_master"
+
+/*
+** The root-page of the master database table.
+*/
+#define MASTER_ROOT       1
+
+/*
+** The name of the schema table.
+*/
+#define SCHEMA_TABLE(x)  ((!OMIT_TEMPDB)&&(x==1)?TEMP_MASTER_NAME:MASTER_NAME)
+
+/*
+** A convenience macro that returns the number of elements in
+** an array.
+*/
+#define ArraySize(X)    ((int)(sizeof(X)/sizeof(X[0])))
+
+/*
+** The following value as a destructor means to use sqlite3DbFree().
+** This is an internal extension to SQLITE_STATIC and SQLITE_TRANSIENT.
+*/
+#define SQLITE_DYNAMIC   ((sqlite3_destructor_type)sqlite3DbFree)
+
+/*
+** When SQLITE_OMIT_WSD is defined, it means that the target platform does
+** not support Writable Static Data (WSD) such as global and static variables.
+** All variables must either be on the stack or dynamically allocated from
+** the heap.  When WSD is unsupported, the variable declarations scattered
+** throughout the SQLite code must become constants instead.  The SQLITE_WSD
+** macro is used for this purpose.  And instead of referencing the variable
+** directly, we use its constant as a key to lookup the run-time allocated
+** buffer that holds real variable.  The constant is also the initializer
+** for the run-time allocated buffer.
+**
+** In the usual case where WSD is supported, the SQLITE_WSD and GLOBAL
+** macros become no-ops and have zero performance impact.
+*/
+#ifdef SQLITE_OMIT_WSD
+  #define SQLITE_WSD const
+  #define GLOBAL(t,v) (*(t*)sqlite3_wsd_find((void*)&(v), sizeof(v)))
+  #define sqlite3GlobalConfig GLOBAL(struct Sqlite3Config, sqlite3Config)
+  int sqlite3_wsd_init(int N, int J);
+  void *sqlite3_wsd_find(void *K, int L);
+#else
+  #define SQLITE_WSD 
+  #define GLOBAL(t,v) v
+  #define sqlite3GlobalConfig sqlite3Config
+#endif
+
+/*
+** The following macros are used to suppress compiler warnings and to
+** make it clear to human readers when a function parameter is deliberately 
+** left unused within the body of a function. This usually happens when
+** a function is called via a function pointer. For example the 
+** implementation of an SQL aggregate step callback may not use the
+** parameter indicating the number of arguments passed to the aggregate,
+** if it knows that this is enforced elsewhere.
+**
+** When a function parameter is not used at all within the body of a function,
+** it is generally named "NotUsed" or "NotUsed2" to make things even clearer.
+** However, these macros may also be used to suppress warnings related to
+** parameters that may or may not be used depending on compilation options.
+** For example those parameters only used in assert() statements. In these
+** cases the parameters are named as per the usual conventions.
+*/
+#define UNUSED_PARAMETER(x) (void)(x)
+#define UNUSED_PARAMETER2(x,y) UNUSED_PARAMETER(x),UNUSED_PARAMETER(y)
+
+/*
+** Forward references to structures
+*/
+typedef struct AggInfo AggInfo;
+typedef struct AuthContext AuthContext;
+typedef struct AutoincInfo AutoincInfo;
+typedef struct Bitvec Bitvec;
+typedef struct CollSeq CollSeq;
+typedef struct Column Column;
+typedef struct Db Db;
+typedef struct Schema Schema;
+typedef struct Expr Expr;
+typedef struct ExprList ExprList;
+typedef struct ExprSpan ExprSpan;
+typedef struct FKey FKey;
+typedef struct FuncDestructor FuncDestructor;
+typedef struct FuncDef FuncDef;
+typedef struct FuncDefHash FuncDefHash;
+typedef struct IdList IdList;
+typedef struct Index Index;
+typedef struct IndexSample IndexSample;
+typedef struct KeyClass KeyClass;
+typedef struct KeyInfo KeyInfo;
+typedef struct Lookaside Lookaside;
+typedef struct LookasideSlot LookasideSlot;
+typedef struct Module Module;
+typedef struct NameContext NameContext;
+typedef struct Parse Parse;
+typedef struct RowSet RowSet;
+typedef struct Savepoint Savepoint;
+typedef struct Select Select;
+typedef struct SrcList SrcList;
+typedef struct StrAccum StrAccum;
+typedef struct Table Table;
+typedef struct TableLock TableLock;
+typedef struct Token Token;
+typedef struct Trigger Trigger;
+typedef struct TriggerPrg TriggerPrg;
+typedef struct TriggerStep TriggerStep;
+typedef struct UnpackedRecord UnpackedRecord;
+typedef struct VTable VTable;
+typedef struct VtabCtx VtabCtx;
+typedef struct Walker Walker;
+typedef struct WherePlan WherePlan;
+typedef struct WhereInfo WhereInfo;
+typedef struct WhereLevel WhereLevel;
+
+/*
+** Defer sourcing vdbe.h and btree.h until after the "u8" and 
+** "BusyHandler" typedefs. vdbe.h also requires a few of the opaque
+** pointer types (i.e. FuncDef) defined above.
+*/
+#include "btree.h"
+#include "vdbe.h"
+#include "pager.h"
+#include "pcache.h"
+
+#include "os.h"
+#include "mutex.h"
+
+
+/*
+** Each database file to be accessed by the system is an instance
+** of the following structure.  There are normally two of these structures
+** in the sqlite.aDb[] array.  aDb[0] is the main database file and
+** aDb[1] is the database file used to hold temporary tables.  Additional
+** databases may be attached.
+*/
+struct Db {
+  char *zName;         /* Name of this database */
+  Btree *pBt;          /* The B*Tree structure for this database file */
+  u8 inTrans;          /* 0: not writable.  1: Transaction.  2: Checkpoint */
+  u8 safety_level;     /* How aggressive at syncing data to disk */
+  Schema *pSchema;     /* Pointer to database schema (possibly shared) */
+};
+
+/*
+** An instance of the following structure stores a database schema.
+**
+** Most Schema objects are associated with a Btree.  The exception is
+** the Schema for the TEMP databaes (sqlite3.aDb[1]) which is free-standing.
+** In shared cache mode, a single Schema object can be shared by multiple
+** Btrees that refer to the same underlying BtShared object.
+** 
+** Schema objects are automatically deallocated when the last Btree that
+** references them is destroyed.   The TEMP Schema is manually freed by
+** sqlite3_close().
+*
+** A thread must be holding a mutex on the corresponding Btree in order
+** to access Schema content.  This implies that the thread must also be
+** holding a mutex on the sqlite3 connection pointer that owns the Btree.
+** For a TEMP Schema, only the connection mutex is required.
+*/
+struct Schema {
+  int schema_cookie;   /* Database schema version number for this file */
+  int iGeneration;     /* Generation counter.  Incremented with each change */
+  Hash tblHash;        /* All tables indexed by name */
+  Hash idxHash;        /* All (named) indices indexed by name */
+  Hash trigHash;       /* All triggers indexed by name */
+  Hash fkeyHash;       /* All foreign keys by referenced table name */
+  Table *pSeqTab;      /* The sqlite_sequence table used by AUTOINCREMENT */
+  u8 file_format;      /* Schema format version for this file */
+  u8 enc;              /* Text encoding used by this database */
+  u16 flags;           /* Flags associated with this schema */
+  int cache_size;      /* Number of pages to use in the cache */
+};
+
+/*
+** These macros can be used to test, set, or clear bits in the 
+** Db.pSchema->flags field.
+*/
+#define DbHasProperty(D,I,P)     (((D)->aDb[I].pSchema->flags&(P))==(P))
+#define DbHasAnyProperty(D,I,P)  (((D)->aDb[I].pSchema->flags&(P))!=0)
+#define DbSetProperty(D,I,P)     (D)->aDb[I].pSchema->flags|=(P)
+#define DbClearProperty(D,I,P)   (D)->aDb[I].pSchema->flags&=~(P)
+
+/*
+** Allowed values for the DB.pSchema->flags field.
+**
+** The DB_SchemaLoaded flag is set after the database schema has been
+** read into internal hash tables.
+**
+** DB_UnresetViews means that one or more views have column names that
+** have been filled out.  If the schema changes, these column names might
+** changes and so the view will need to be reset.
+*/
+#define DB_SchemaLoaded    0x0001  /* The schema has been loaded */
+#define DB_UnresetViews    0x0002  /* Some views have defined column names */
+#define DB_Empty           0x0004  /* The file is empty (length 0 bytes) */
+
+/*
+** The number of different kinds of things that can be limited
+** using the sqlite3_limit() interface.
+*/
+#define SQLITE_N_LIMIT (SQLITE_LIMIT_TRIGGER_DEPTH+1)
+
+/*
+** Lookaside malloc is a set of fixed-size buffers that can be used
+** to satisfy small transient memory allocation requests for objects
+** associated with a particular database connection.  The use of
+** lookaside malloc provides a significant performance enhancement
+** (approx 10%) by avoiding numerous malloc/free requests while parsing
+** SQL statements.
+**
+** The Lookaside structure holds configuration information about the
+** lookaside malloc subsystem.  Each available memory allocation in
+** the lookaside subsystem is stored on a linked list of LookasideSlot
+** objects.
+**
+** Lookaside allocations are only allowed for objects that are associated
+** with a particular database connection.  Hence, schema information cannot
+** be stored in lookaside because in shared cache mode the schema information
+** is shared by multiple database connections.  Therefore, while parsing
+** schema information, the Lookaside.bEnabled flag is cleared so that
+** lookaside allocations are not used to construct the schema objects.
+*/
+struct Lookaside {
+  u16 sz;                 /* Size of each buffer in bytes */
+  u8 bEnabled;            /* False to disable new lookaside allocations */
+  u8 bMalloced;           /* True if pStart obtained from sqlite3_malloc() */
+  int nOut;               /* Number of buffers currently checked out */
+  int mxOut;              /* Highwater mark for nOut */
+  int anStat[3];          /* 0: hits.  1: size misses.  2: full misses */
+  LookasideSlot *pFree;   /* List of available buffers */
+  void *pStart;           /* First byte of available memory space */
+  void *pEnd;             /* First byte past end of available space */
+};
+struct LookasideSlot {
+  LookasideSlot *pNext;    /* Next buffer in the list of free buffers */
+};
+
+/*
+** A hash table for function definitions.
+**
+** Hash each FuncDef structure into one of the FuncDefHash.a[] slots.
+** Collisions are on the FuncDef.pHash chain.
+*/
+struct FuncDefHash {
+  FuncDef *a[23];       /* Hash table for functions */
+};
+
+/*
+** Each database connection is an instance of the following structure.
+**
+** The sqlite.lastRowid records the last insert rowid generated by an
+** insert statement.  Inserts on views do not affect its value.  Each
+** trigger has its own context, so that lastRowid can be updated inside
+** triggers as usual.  The previous value will be restored once the trigger
+** exits.  Upon entering a before or instead of trigger, lastRowid is no
+** longer (since after version 2.8.12) reset to -1.
+**
+** The sqlite.nChange does not count changes within triggers and keeps no
+** context.  It is reset at start of sqlite3_exec.
+** The sqlite.lsChange represents the number of changes made by the last
+** insert, update, or delete statement.  It remains constant throughout the
+** length of a statement and is then updated by OP_SetCounts.  It keeps a
+** context stack just like lastRowid so that the count of changes
+** within a trigger is not seen outside the trigger.  Changes to views do not
+** affect the value of lsChange.
+** The sqlite.csChange keeps track of the number of current changes (since
+** the last statement) and is used to update sqlite_lsChange.
+**
+** The member variables sqlite.errCode, sqlite.zErrMsg and sqlite.zErrMsg16
+** store the most recent error code and, if applicable, string. The
+** internal function sqlite3Error() is used to set these variables
+** consistently.
+*/
+struct sqlite3 {
+  sqlite3_vfs *pVfs;            /* OS Interface */
+  int nDb;                      /* Number of backends currently in use */
+  Db *aDb;                      /* All backends */
+  int flags;                    /* Miscellaneous flags. See below */
+  unsigned int openFlags;       /* Flags passed to sqlite3_vfs.xOpen() */
+  int errCode;                  /* Most recent error code (SQLITE_*) */
+  int errMask;                  /* & result codes with this before returning */
+  u8 autoCommit;                /* The auto-commit flag. */
+  u8 temp_store;                /* 1: file 2: memory 0: default */
+  u8 mallocFailed;              /* True if we have seen a malloc failure */
+  u8 dfltLockMode;              /* Default locking-mode for attached dbs */
+  signed char nextAutovac;      /* Autovac setting after VACUUM if >=0 */
+  u8 suppressErr;               /* Do not issue error messages if true */
+  u8 vtabOnConflict;            /* Value to return for s3_vtab_on_conflict() */
+  int nextPagesize;             /* Pagesize after VACUUM if >0 */
+  int nTable;                   /* Number of tables in the database */
+  CollSeq *pDfltColl;           /* The default collating sequence (BINARY) */
+  i64 lastRowid;                /* ROWID of most recent insert (see above) */
+  u32 magic;                    /* Magic number for detect library misuse */
+  int nChange;                  /* Value returned by sqlite3_changes() */
+  int nTotalChange;             /* Value returned by sqlite3_total_changes() */
+  sqlite3_mutex *mutex;         /* Connection mutex */
+  int aLimit[SQLITE_N_LIMIT];   /* Limits */
+  struct sqlite3InitInfo {      /* Information used during initialization */
+    int iDb;                    /* When back is being initialized */
+    int newTnum;                /* Rootpage of table being initialized */
+    u8 busy;                    /* TRUE if currently initializing */
+    u8 orphanTrigger;           /* Last statement is orphaned TEMP trigger */
+  } init;
+  int nExtension;               /* Number of loaded extensions */
+  void **aExtension;            /* Array of shared library handles */
+  struct Vdbe *pVdbe;           /* List of active virtual machines */
+  int activeVdbeCnt;            /* Number of VDBEs currently executing */
+  int writeVdbeCnt;             /* Number of active VDBEs that are writing */
+  int vdbeExecCnt;              /* Number of nested calls to VdbeExec() */
+  void (*xTrace)(void*,const char*);        /* Trace function */
+  void *pTraceArg;                          /* Argument to the trace function */
+  void (*xProfile)(void*,const char*,u64);  /* Profiling function */
+  void *pProfileArg;                        /* Argument to profile function */
+  void *pCommitArg;                 /* Argument to xCommitCallback() */   
+  int (*xCommitCallback)(void*);    /* Invoked at every commit. */
+  void *pRollbackArg;               /* Argument to xRollbackCallback() */   
+  void (*xRollbackCallback)(void*); /* Invoked at every commit. */
+  void *pUpdateArg;
+  void (*xUpdateCallback)(void*,int, const char*,const char*,sqlite_int64);
+#ifndef SQLITE_OMIT_WAL
+  int (*xWalCallback)(void *, sqlite3 *, const char *, int);
+  void *pWalArg;
+#endif
+  void(*xCollNeeded)(void*,sqlite3*,int eTextRep,const char*);
+  void(*xCollNeeded16)(void*,sqlite3*,int eTextRep,const void*);
+  void *pCollNeededArg;
+  sqlite3_value *pErr;          /* Most recent error message */
+  char *zErrMsg;                /* Most recent error message (UTF-8 encoded) */
+  char *zErrMsg16;              /* Most recent error message (UTF-16 encoded) */
+  union {
+    volatile int isInterrupted; /* True if sqlite3_interrupt has been called */
+    double notUsed1;            /* Spacer */
+  } u1;
+  Lookaside lookaside;          /* Lookaside malloc configuration */
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  int (*xAuth)(void*,int,const char*,const char*,const char*,const char*);
+                                /* Access authorization function */
+  void *pAuthArg;               /* 1st argument to the access auth function */
+#endif
+#ifndef SQLITE_OMIT_PROGRESS_CALLBACK
+  int (*xProgress)(void *);     /* The progress callback */
+  void *pProgressArg;           /* Argument to the progress callback */
+  int nProgressOps;             /* Number of opcodes for progress callback */
+#endif
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  Hash aModule;                 /* populated by sqlite3_create_module() */
+  VtabCtx *pVtabCtx;            /* Context for active vtab connect/create */
+  VTable **aVTrans;             /* Virtual tables with open transactions */
+  int nVTrans;                  /* Allocated size of aVTrans */
+  VTable *pDisconnect;    /* Disconnect these in next sqlite3_prepare() */
+#endif
+  FuncDefHash aFunc;            /* Hash table of connection functions */
+  Hash aCollSeq;                /* All collating sequences */
+  BusyHandler busyHandler;      /* Busy callback */
+  int busyTimeout;              /* Busy handler timeout, in msec */
+  Db aDbStatic[2];              /* Static space for the 2 default backends */
+  Savepoint *pSavepoint;        /* List of active savepoints */
+  int nSavepoint;               /* Number of non-transaction savepoints */
+  int nStatement;               /* Number of nested statement-transactions  */
+  u8 isTransactionSavepoint;    /* True if the outermost savepoint is a TS */
+  i64 nDeferredCons;            /* Net deferred constraints this transaction. */
+  int *pnBytesFreed;            /* If not NULL, increment this in DbFree() */
+
+#ifdef SQLITE_ENABLE_UNLOCK_NOTIFY
+  /* The following variables are all protected by the STATIC_MASTER 
+  ** mutex, not by sqlite3.mutex. They are used by code in notify.c. 
+  **
+  ** When X.pUnlockConnection==Y, that means that X is waiting for Y to
+  ** unlock so that it can proceed.
+  **
+  ** When X.pBlockingConnection==Y, that means that something that X tried
+  ** tried to do recently failed with an SQLITE_LOCKED error due to locks
+  ** held by Y.
+  */
+  sqlite3 *pBlockingConnection; /* Connection that caused SQLITE_LOCKED */
+  sqlite3 *pUnlockConnection;           /* Connection to watch for unlock */
+  void *pUnlockArg;                     /* Argument to xUnlockNotify */
+  void (*xUnlockNotify)(void **, int);  /* Unlock notify callback */
+  sqlite3 *pNextBlocked;        /* Next in list of all blocked connections */
+#endif
+};
+
+/*
+** A macro to discover the encoding of a database.
+*/
+#define ENC(db) ((db)->aDb[0].pSchema->enc)
+
+/*
+** Possible values for the sqlite3.flags.
+*/
+#define SQLITE_VdbeTrace      0x00000100  /* True to trace VDBE execution */
+#define SQLITE_InternChanges  0x00000200  /* Uncommitted Hash table changes */
+#define SQLITE_FullColNames   0x00000400  /* Show full column names on SELECT */
+#define SQLITE_ShortColNames  0x00000800  /* Show short columns names */
+#define SQLITE_CountRows      0x00001000  /* Count rows changed by INSERT, */
+                                          /*   DELETE, or UPDATE and return */
+                                          /*   the count using a callback. */
+#define SQLITE_NullCallback   0x00002000  /* Invoke the callback once if the */
+                                          /*   result set is empty */
+#define SQLITE_SqlTrace       0x00004000  /* Debug print SQL as it executes */
+#define SQLITE_VdbeListing    0x00008000  /* Debug listings of VDBE programs */
+#define SQLITE_WriteSchema    0x00010000  /* OK to update SQLITE_MASTER */
+#define SQLITE_NoReadlock     0x00020000  /* Readlocks are omitted when 
+                                          ** accessing read-only databases */
+#define SQLITE_IgnoreChecks   0x00040000  /* Do not enforce check constraints */
+#define SQLITE_ReadUncommitted 0x0080000  /* For shared-cache mode */
+#define SQLITE_LegacyFileFmt  0x00100000  /* Create new databases in format 1 */
+#define SQLITE_FullFSync      0x00200000  /* Use full fsync on the backend */
+#define SQLITE_CkptFullFSync  0x00400000  /* Use full fsync for checkpoint */
+#define SQLITE_RecoveryMode   0x00800000  /* Ignore schema errors */
+#define SQLITE_ReverseOrder   0x01000000  /* Reverse unordered SELECTs */
+#define SQLITE_RecTriggers    0x02000000  /* Enable recursive triggers */
+#define SQLITE_ForeignKeys    0x04000000  /* Enforce foreign key constraints  */
+#define SQLITE_AutoIndex      0x08000000  /* Enable automatic indexes */
+#define SQLITE_PreferBuiltin  0x10000000  /* Preference to built-in funcs */
+#define SQLITE_LoadExtension  0x20000000  /* Enable load_extension */
+#define SQLITE_EnableTrigger  0x40000000  /* True to enable triggers */
+
+/*
+** Bits of the sqlite3.flags field that are used by the
+** sqlite3_test_control(SQLITE_TESTCTRL_OPTIMIZATIONS,...) interface.
+** These must be the low-order bits of the flags field.
+*/
+#define SQLITE_QueryFlattener 0x01        /* Disable query flattening */
+#define SQLITE_ColumnCache    0x02        /* Disable the column cache */
+#define SQLITE_IndexSort      0x04        /* Disable indexes for sorting */
+#define SQLITE_IndexSearch    0x08        /* Disable indexes for searching */
+#define SQLITE_IndexCover     0x10        /* Disable index covering table */
+#define SQLITE_GroupByOrder   0x20        /* Disable GROUPBY cover of ORDERBY */
+#define SQLITE_FactorOutConst 0x40        /* Disable factoring out constants */
+#define SQLITE_IdxRealAsInt   0x80        /* Store REAL as INT in indices */
+#define SQLITE_DistinctOpt    0x80        /* DISTINCT using indexes */
+#define SQLITE_OptMask        0xff        /* Mask of all disablable opts */
+
+/*
+** Possible values for the sqlite.magic field.
+** The numbers are obtained at random and have no special meaning, other
+** than being distinct from one another.
+*/
+#define SQLITE_MAGIC_OPEN     0xa029a697  /* Database is open */
+#define SQLITE_MAGIC_CLOSED   0x9f3c2d33  /* Database is closed */
+#define SQLITE_MAGIC_SICK     0x4b771290  /* Error and awaiting close */
+#define SQLITE_MAGIC_BUSY     0xf03b7906  /* Database currently in use */
+#define SQLITE_MAGIC_ERROR    0xb5357930  /* An SQLITE_MISUSE error occurred */
+
+/*
+** Each SQL function is defined by an instance of the following
+** structure.  A pointer to this structure is stored in the sqlite.aFunc
+** hash table.  When multiple functions have the same name, the hash table
+** points to a linked list of these structures.
+*/
+struct FuncDef {
+  i16 nArg;            /* Number of arguments.  -1 means unlimited */
+  u8 iPrefEnc;         /* Preferred text encoding (SQLITE_UTF8, 16LE, 16BE) */
+  u8 flags;            /* Some combination of SQLITE_FUNC_* */
+  void *pUserData;     /* User data parameter */
+  FuncDef *pNext;      /* Next function with same name */
+  void (*xFunc)(sqlite3_context*,int,sqlite3_value**); /* Regular function */
+  void (*xStep)(sqlite3_context*,int,sqlite3_value**); /* Aggregate step */
+  void (*xFinalize)(sqlite3_context*);                /* Aggregate finalizer */
+  char *zName;         /* SQL name of the function. */
+  FuncDef *pHash;      /* Next with a different name but the same hash */
+  FuncDestructor *pDestructor;   /* Reference counted destructor function */
+};
+
+/*
+** This structure encapsulates a user-function destructor callback (as
+** configured using create_function_v2()) and a reference counter. When
+** create_function_v2() is called to create a function with a destructor,
+** a single object of this type is allocated. FuncDestructor.nRef is set to 
+** the number of FuncDef objects created (either 1 or 3, depending on whether
+** or not the specified encoding is SQLITE_ANY). The FuncDef.pDestructor
+** member of each of the new FuncDef objects is set to point to the allocated
+** FuncDestructor.
+**
+** Thereafter, when one of the FuncDef objects is deleted, the reference
+** count on this object is decremented. When it reaches 0, the destructor
+** is invoked and the FuncDestructor structure freed.
+*/
+struct FuncDestructor {
+  int nRef;
+  void (*xDestroy)(void *);
+  void *pUserData;
+};
+
+/*
+** Possible values for FuncDef.flags
+*/
+#define SQLITE_FUNC_LIKE     0x01 /* Candidate for the LIKE optimization */
+#define SQLITE_FUNC_CASE     0x02 /* Case-sensitive LIKE-type function */
+#define SQLITE_FUNC_EPHEM    0x04 /* Ephemeral.  Delete with VDBE */
+#define SQLITE_FUNC_NEEDCOLL 0x08 /* sqlite3GetFuncCollSeq() might be called */
+#define SQLITE_FUNC_PRIVATE  0x10 /* Allowed for internal use only */
+#define SQLITE_FUNC_COUNT    0x20 /* Built-in count(*) aggregate */
+#define SQLITE_FUNC_COALESCE 0x40 /* Built-in coalesce() or ifnull() function */
+
+/*
+** The following three macros, FUNCTION(), LIKEFUNC() and AGGREGATE() are
+** used to create the initializers for the FuncDef structures.
+**
+**   FUNCTION(zName, nArg, iArg, bNC, xFunc)
+**     Used to create a scalar function definition of a function zName 
+**     implemented by C function xFunc that accepts nArg arguments. The
+**     value passed as iArg is cast to a (void*) and made available
+**     as the user-data (sqlite3_user_data()) for the function. If 
+**     argument bNC is true, then the SQLITE_FUNC_NEEDCOLL flag is set.
+**
+**   AGGREGATE(zName, nArg, iArg, bNC, xStep, xFinal)
+**     Used to create an aggregate function definition implemented by
+**     the C functions xStep and xFinal. The first four parameters
+**     are interpreted in the same way as the first 4 parameters to
+**     FUNCTION().
+**
+**   LIKEFUNC(zName, nArg, pArg, flags)
+**     Used to create a scalar function definition of a function zName 
+**     that accepts nArg arguments and is implemented by a call to C 
+**     function likeFunc. Argument pArg is cast to a (void *) and made
+**     available as the function user-data (sqlite3_user_data()). The
+**     FuncDef.flags variable is set to the value passed as the flags
+**     parameter.
+*/
+#define FUNCTION(zName, nArg, iArg, bNC, xFunc) \
+  {nArg, SQLITE_UTF8, bNC*SQLITE_FUNC_NEEDCOLL, \
+   SQLITE_INT_TO_PTR(iArg), 0, xFunc, 0, 0, #zName, 0, 0}
+#define STR_FUNCTION(zName, nArg, pArg, bNC, xFunc) \
+  {nArg, SQLITE_UTF8, bNC*SQLITE_FUNC_NEEDCOLL, \
+   pArg, 0, xFunc, 0, 0, #zName, 0, 0}
+#define LIKEFUNC(zName, nArg, arg, flags) \
+  {nArg, SQLITE_UTF8, flags, (void *)arg, 0, likeFunc, 0, 0, #zName, 0, 0}
+#define AGGREGATE(zName, nArg, arg, nc, xStep, xFinal) \
+  {nArg, SQLITE_UTF8, nc*SQLITE_FUNC_NEEDCOLL, \
+   SQLITE_INT_TO_PTR(arg), 0, 0, xStep,xFinal,#zName,0,0}
+
+/*
+** All current savepoints are stored in a linked list starting at
+** sqlite3.pSavepoint. The first element in the list is the most recently
+** opened savepoint. Savepoints are added to the list by the vdbe
+** OP_Savepoint instruction.
+*/
+struct Savepoint {
+  char *zName;                        /* Savepoint name (nul-terminated) */
+  i64 nDeferredCons;                  /* Number of deferred fk violations */
+  Savepoint *pNext;                   /* Parent savepoint (if any) */
+};
+
+/*
+** The following are used as the second parameter to sqlite3Savepoint(),
+** and as the P1 argument to the OP_Savepoint instruction.
+*/
+#define SAVEPOINT_BEGIN      0
+#define SAVEPOINT_RELEASE    1
+#define SAVEPOINT_ROLLBACK   2
+
+
+/*
+** Each SQLite module (virtual table definition) is defined by an
+** instance of the following structure, stored in the sqlite3.aModule
+** hash table.
+*/
+struct Module {
+  const sqlite3_module *pModule;       /* Callback pointers */
+  const char *zName;                   /* Name passed to create_module() */
+  void *pAux;                          /* pAux passed to create_module() */
+  void (*xDestroy)(void *);            /* Module destructor function */
+};
+
+/*
+** information about each column of an SQL table is held in an instance
+** of this structure.
+*/
+struct Column {
+  char *zName;     /* Name of this column */
+  Expr *pDflt;     /* Default value of this column */
+  char *zDflt;     /* Original text of the default value */
+  char *zType;     /* Data type for this column */
+  char *zColl;     /* Collating sequence.  If NULL, use the default */
+  u8 notNull;      /* True if there is a NOT NULL constraint */
+  u8 isPrimKey;    /* True if this column is part of the PRIMARY KEY */
+  char affinity;   /* One of the SQLITE_AFF_... values */
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  u8 isHidden;     /* True if this column is 'hidden' */
+#endif
+};
+
+/*
+** A "Collating Sequence" is defined by an instance of the following
+** structure. Conceptually, a collating sequence consists of a name and
+** a comparison routine that defines the order of that sequence.
+**
+** There may two separate implementations of the collation function, one
+** that processes text in UTF-8 encoding (CollSeq.xCmp) and another that
+** processes text encoded in UTF-16 (CollSeq.xCmp16), using the machine
+** native byte order. When a collation sequence is invoked, SQLite selects
+** the version that will require the least expensive encoding
+** translations, if any.
+**
+** The CollSeq.pUser member variable is an extra parameter that passed in
+** as the first argument to the UTF-8 comparison function, xCmp.
+** CollSeq.pUser16 is the equivalent for the UTF-16 comparison function,
+** xCmp16.
+**
+** If both CollSeq.xCmp and CollSeq.xCmp16 are NULL, it means that the
+** collating sequence is undefined.  Indices built on an undefined
+** collating sequence may not be read or written.
+*/
+struct CollSeq {
+  char *zName;          /* Name of the collating sequence, UTF-8 encoded */
+  u8 enc;               /* Text encoding handled by xCmp() */
+  u8 type;              /* One of the SQLITE_COLL_... values below */
+  void *pUser;          /* First argument to xCmp() */
+  int (*xCmp)(void*,int, const void*, int, const void*);
+  void (*xDel)(void*);  /* Destructor for pUser */
+};
+
+/*
+** Allowed values of CollSeq.type:
+*/
+#define SQLITE_COLL_BINARY  1  /* The default memcmp() collating sequence */
+#define SQLITE_COLL_NOCASE  2  /* The built-in NOCASE collating sequence */
+#define SQLITE_COLL_REVERSE 3  /* The built-in REVERSE collating sequence */
+#define SQLITE_COLL_USER    0  /* Any other user-defined collating sequence */
+
+/*
+** A sort order can be either ASC or DESC.
+*/
+#define SQLITE_SO_ASC       0  /* Sort in ascending order */
+#define SQLITE_SO_DESC      1  /* Sort in ascending order */
+
+/*
+** Column affinity types.
+**
+** These used to have mnemonic name like 'i' for SQLITE_AFF_INTEGER and
+** 't' for SQLITE_AFF_TEXT.  But we can save a little space and improve
+** the speed a little by numbering the values consecutively.  
+**
+** But rather than start with 0 or 1, we begin with 'a'.  That way,
+** when multiple affinity types are concatenated into a string and
+** used as the P4 operand, they will be more readable.
+**
+** Note also that the numeric types are grouped together so that testing
+** for a numeric type is a single comparison.
+*/
+#define SQLITE_AFF_TEXT     'a'
+#define SQLITE_AFF_NONE     'b'
+#define SQLITE_AFF_NUMERIC  'c'
+#define SQLITE_AFF_INTEGER  'd'
+#define SQLITE_AFF_REAL     'e'
+
+#define sqlite3IsNumericAffinity(X)  ((X)>=SQLITE_AFF_NUMERIC)
+
+/*
+** The SQLITE_AFF_MASK values masks off the significant bits of an
+** affinity value. 
+*/
+#define SQLITE_AFF_MASK     0x67
+
+/*
+** Additional bit values that can be ORed with an affinity without
+** changing the affinity.
+*/
+#define SQLITE_JUMPIFNULL   0x08  /* jumps if either operand is NULL */
+#define SQLITE_STOREP2      0x10  /* Store result in reg[P2] rather than jump */
+#define SQLITE_NULLEQ       0x80  /* NULL=NULL */
+
+/*
+** An object of this type is created for each virtual table present in
+** the database schema. 
+**
+** If the database schema is shared, then there is one instance of this
+** structure for each database connection (sqlite3*) that uses the shared
+** schema. This is because each database connection requires its own unique
+** instance of the sqlite3_vtab* handle used to access the virtual table 
+** implementation. sqlite3_vtab* handles can not be shared between 
+** database connections, even when the rest of the in-memory database 
+** schema is shared, as the implementation often stores the database
+** connection handle passed to it via the xConnect() or xCreate() method
+** during initialization internally. This database connection handle may
+** then be used by the virtual table implementation to access real tables 
+** within the database. So that they appear as part of the callers 
+** transaction, these accesses need to be made via the same database 
+** connection as that used to execute SQL operations on the virtual table.
+**
+** All VTable objects that correspond to a single table in a shared
+** database schema are initially stored in a linked-list pointed to by
+** the Table.pVTable member variable of the corresponding Table object.
+** When an sqlite3_prepare() operation is required to access the virtual
+** table, it searches the list for the VTable that corresponds to the
+** database connection doing the preparing so as to use the correct
+** sqlite3_vtab* handle in the compiled query.
+**
+** When an in-memory Table object is deleted (for example when the
+** schema is being reloaded for some reason), the VTable objects are not 
+** deleted and the sqlite3_vtab* handles are not xDisconnect()ed 
+** immediately. Instead, they are moved from the Table.pVTable list to
+** another linked list headed by the sqlite3.pDisconnect member of the
+** corresponding sqlite3 structure. They are then deleted/xDisconnected 
+** next time a statement is prepared using said sqlite3*. This is done
+** to avoid deadlock issues involving multiple sqlite3.mutex mutexes.
+** Refer to comments above function sqlite3VtabUnlockList() for an
+** explanation as to why it is safe to add an entry to an sqlite3.pDisconnect
+** list without holding the corresponding sqlite3.mutex mutex.
+**
+** The memory for objects of this type is always allocated by 
+** sqlite3DbMalloc(), using the connection handle stored in VTable.db as 
+** the first argument.
+*/
+struct VTable {
+  sqlite3 *db;              /* Database connection associated with this table */
+  Module *pMod;             /* Pointer to module implementation */
+  sqlite3_vtab *pVtab;      /* Pointer to vtab instance */
+  int nRef;                 /* Number of pointers to this structure */
+  u8 bConstraint;           /* True if constraints are supported */
+  int iSavepoint;           /* Depth of the SAVEPOINT stack */
+  VTable *pNext;            /* Next in linked list (see above) */
+};
+
+/*
+** Each SQL table is represented in memory by an instance of the
+** following structure.
+**
+** Table.zName is the name of the table.  The case of the original
+** CREATE TABLE statement is stored, but case is not significant for
+** comparisons.
+**
+** Table.nCol is the number of columns in this table.  Table.aCol is a
+** pointer to an array of Column structures, one for each column.
+**
+** If the table has an INTEGER PRIMARY KEY, then Table.iPKey is the index of
+** the column that is that key.   Otherwise Table.iPKey is negative.  Note
+** that the datatype of the PRIMARY KEY must be INTEGER for this field to
+** be set.  An INTEGER PRIMARY KEY is used as the rowid for each row of
+** the table.  If a table has no INTEGER PRIMARY KEY, then a random rowid
+** is generated for each row of the table.  TF_HasPrimaryKey is set if
+** the table has any PRIMARY KEY, INTEGER or otherwise.
+**
+** Table.tnum is the page number for the root BTree page of the table in the
+** database file.  If Table.iDb is the index of the database table backend
+** in sqlite.aDb[].  0 is for the main database and 1 is for the file that
+** holds temporary tables and indices.  If TF_Ephemeral is set
+** then the table is stored in a file that is automatically deleted
+** when the VDBE cursor to the table is closed.  In this case Table.tnum 
+** refers VDBE cursor number that holds the table open, not to the root
+** page number.  Transient tables are used to hold the results of a
+** sub-query that appears instead of a real table name in the FROM clause 
+** of a SELECT statement.
+*/
+struct Table {
+  char *zName;         /* Name of the table or view */
+  int iPKey;           /* If not negative, use aCol[iPKey] as the primary key */
+  int nCol;            /* Number of columns in this table */
+  Column *aCol;        /* Information about each column */
+  Index *pIndex;       /* List of SQL indexes on this table. */
+  int tnum;            /* Root BTree node for this table (see note above) */
+  tRowcnt nRowEst;     /* Estimated rows in table - from sqlite_stat1 table */
+  Select *pSelect;     /* NULL for tables.  Points to definition if a view. */
+  u16 nRef;            /* Number of pointers to this Table */
+  u8 tabFlags;         /* Mask of TF_* values */
+  u8 keyConf;          /* What to do in case of uniqueness conflict on iPKey */
+  FKey *pFKey;         /* Linked list of all foreign keys in this table */
+  char *zColAff;       /* String defining the affinity of each column */
+#ifndef SQLITE_OMIT_CHECK
+  Expr *pCheck;        /* The AND of all CHECK constraints */
+#endif
+#ifndef SQLITE_OMIT_ALTERTABLE
+  int addColOffset;    /* Offset in CREATE TABLE stmt to add a new column */
+#endif
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  VTable *pVTable;     /* List of VTable objects. */
+  int nModuleArg;      /* Number of arguments to the module */
+  char **azModuleArg;  /* Text of all module args. [0] is module name */
+#endif
+  Trigger *pTrigger;   /* List of triggers stored in pSchema */
+  Schema *pSchema;     /* Schema that contains this table */
+  Table *pNextZombie;  /* Next on the Parse.pZombieTab list */
+};
+
+/*
+** Allowed values for Tabe.tabFlags.
+*/
+#define TF_Readonly        0x01    /* Read-only system table */
+#define TF_Ephemeral       0x02    /* An ephemeral table */
+#define TF_HasPrimaryKey   0x04    /* Table has a primary key */
+#define TF_Autoincrement   0x08    /* Integer primary key is autoincrement */
+#define TF_Virtual         0x10    /* Is a virtual table */
+#define TF_NeedMetadata    0x20    /* aCol[].zType and aCol[].pColl missing */
+
+
+
+/*
+** Test to see whether or not a table is a virtual table.  This is
+** done as a macro so that it will be optimized out when virtual
+** table support is omitted from the build.
+*/
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+#  define IsVirtual(X)      (((X)->tabFlags & TF_Virtual)!=0)
+#  define IsHiddenColumn(X) ((X)->isHidden)
+#else
+#  define IsVirtual(X)      0
+#  define IsHiddenColumn(X) 0
+#endif
+
+/*
+** Each foreign key constraint is an instance of the following structure.
+**
+** A foreign key is associated with two tables.  The "from" table is
+** the table that contains the REFERENCES clause that creates the foreign
+** key.  The "to" table is the table that is named in the REFERENCES clause.
+** Consider this example:
+**
+**     CREATE TABLE ex1(
+**       a INTEGER PRIMARY KEY,
+**       b INTEGER CONSTRAINT fk1 REFERENCES ex2(x)
+**     );
+**
+** For foreign key "fk1", the from-table is "ex1" and the to-table is "ex2".
+**
+** Each REFERENCES clause generates an instance of the following structure
+** which is attached to the from-table.  The to-table need not exist when
+** the from-table is created.  The existence of the to-table is not checked.
+*/
+struct FKey {
+  Table *pFrom;     /* Table containing the REFERENCES clause (aka: Child) */
+  FKey *pNextFrom;  /* Next foreign key in pFrom */
+  char *zTo;        /* Name of table that the key points to (aka: Parent) */
+  FKey *pNextTo;    /* Next foreign key on table named zTo */
+  FKey *pPrevTo;    /* Previous foreign key on table named zTo */
+  int nCol;         /* Number of columns in this key */
+  /* EV: R-30323-21917 */
+  u8 isDeferred;    /* True if constraint checking is deferred till COMMIT */
+  u8 aAction[2];          /* ON DELETE and ON UPDATE actions, respectively */
+  Trigger *apTrigger[2];  /* Triggers for aAction[] actions */
+  struct sColMap {  /* Mapping of columns in pFrom to columns in zTo */
+    int iFrom;         /* Index of column in pFrom */
+    char *zCol;        /* Name of column in zTo.  If 0 use PRIMARY KEY */
+  } aCol[1];        /* One entry for each of nCol column s */
+};
+
+/*
+** SQLite supports many different ways to resolve a constraint
+** error.  ROLLBACK processing means that a constraint violation
+** causes the operation in process to fail and for the current transaction
+** to be rolled back.  ABORT processing means the operation in process
+** fails and any prior changes from that one operation are backed out,
+** but the transaction is not rolled back.  FAIL processing means that
+** the operation in progress stops and returns an error code.  But prior
+** changes due to the same operation are not backed out and no rollback
+** occurs.  IGNORE means that the particular row that caused the constraint
+** error is not inserted or updated.  Processing continues and no error
+** is returned.  REPLACE means that preexisting database rows that caused
+** a UNIQUE constraint violation are removed so that the new insert or
+** update can proceed.  Processing continues and no error is reported.
+**
+** RESTRICT, SETNULL, and CASCADE actions apply only to foreign keys.
+** RESTRICT is the same as ABORT for IMMEDIATE foreign keys and the
+** same as ROLLBACK for DEFERRED keys.  SETNULL means that the foreign
+** key is set to NULL.  CASCADE means that a DELETE or UPDATE of the
+** referenced table row is propagated into the row that holds the
+** foreign key.
+** 
+** The following symbolic values are used to record which type
+** of action to take.
+*/
+#define OE_None     0   /* There is no constraint to check */
+#define OE_Rollback 1   /* Fail the operation and rollback the transaction */
+#define OE_Abort    2   /* Back out changes but do no rollback transaction */
+#define OE_Fail     3   /* Stop the operation but leave all prior changes */
+#define OE_Ignore   4   /* Ignore the error. Do not do the INSERT or UPDATE */
+#define OE_Replace  5   /* Delete existing record, then do INSERT or UPDATE */
+
+#define OE_Restrict 6   /* OE_Abort for IMMEDIATE, OE_Rollback for DEFERRED */
+#define OE_SetNull  7   /* Set the foreign key value to NULL */
+#define OE_SetDflt  8   /* Set the foreign key value to its default */
+#define OE_Cascade  9   /* Cascade the changes */
+
+#define OE_Default  99  /* Do whatever the default action is */
+
+
+/*
+** An instance of the following structure is passed as the first
+** argument to sqlite3VdbeKeyCompare and is used to control the 
+** comparison of the two index keys.
+*/
+struct KeyInfo {
+  sqlite3 *db;        /* The database connection */
+  u8 enc;             /* Text encoding - one of the SQLITE_UTF* values */
+  u16 nField;         /* Number of entries in aColl[] */
+  u8 *aSortOrder;     /* Sort order for each column.  May be NULL */
+  CollSeq *aColl[1];  /* Collating sequence for each term of the key */
+};
+
+/*
+** An instance of the following structure holds information about a
+** single index record that has already been parsed out into individual
+** values.
+**
+** A record is an object that contains one or more fields of data.
+** Records are used to store the content of a table row and to store
+** the key of an index.  A blob encoding of a record is created by
+** the OP_MakeRecord opcode of the VDBE and is disassembled by the
+** OP_Column opcode.
+**
+** This structure holds a record that has already been disassembled
+** into its constituent fields.
+*/
+struct UnpackedRecord {
+  KeyInfo *pKeyInfo;  /* Collation and sort-order information */
+  u16 nField;         /* Number of entries in apMem[] */
+  u16 flags;          /* Boolean settings.  UNPACKED_... below */
+  i64 rowid;          /* Used by UNPACKED_PREFIX_SEARCH */
+  Mem *aMem;          /* Values */
+};
+
+/*
+** Allowed values of UnpackedRecord.flags
+*/
+#define UNPACKED_NEED_FREE     0x0001  /* Memory is from sqlite3Malloc() */
+#define UNPACKED_NEED_DESTROY  0x0002  /* apMem[]s should all be destroyed */
+#define UNPACKED_IGNORE_ROWID  0x0004  /* Ignore trailing rowid on key1 */
+#define UNPACKED_INCRKEY       0x0008  /* Make this key an epsilon larger */
+#define UNPACKED_PREFIX_MATCH  0x0010  /* A prefix match is considered OK */
+#define UNPACKED_PREFIX_SEARCH 0x0020  /* A prefix match is considered OK */
+
+/*
+** Each SQL index is represented in memory by an
+** instance of the following structure.
+**
+** The columns of the table that are to be indexed are described
+** by the aiColumn[] field of this structure.  For example, suppose
+** we have the following table and index:
+**
+**     CREATE TABLE Ex1(c1 int, c2 int, c3 text);
+**     CREATE INDEX Ex2 ON Ex1(c3,c1);
+**
+** In the Table structure describing Ex1, nCol==3 because there are
+** three columns in the table.  In the Index structure describing
+** Ex2, nColumn==2 since 2 of the 3 columns of Ex1 are indexed.
+** The value of aiColumn is {2, 0}.  aiColumn[0]==2 because the 
+** first column to be indexed (c3) has an index of 2 in Ex1.aCol[].
+** The second column to be indexed (c1) has an index of 0 in
+** Ex1.aCol[], hence Ex2.aiColumn[1]==0.
+**
+** The Index.onError field determines whether or not the indexed columns
+** must be unique and what to do if they are not.  When Index.onError=OE_None,
+** it means this is not a unique index.  Otherwise it is a unique index
+** and the value of Index.onError indicate the which conflict resolution 
+** algorithm to employ whenever an attempt is made to insert a non-unique
+** element.
+*/
+struct Index {
+  char *zName;     /* Name of this index */
+  int nColumn;     /* Number of columns in the table used by this index */
+  int *aiColumn;   /* Which columns are used by this index.  1st is 0 */
+  tRowcnt *aiRowEst; /* Result of ANALYZE: Est. rows selected by each column */
+  Table *pTable;   /* The SQL table being indexed */
+  int tnum;        /* Page containing root of this index in database file */
+  u8 onError;      /* OE_Abort, OE_Ignore, OE_Replace, or OE_None */
+  u8 autoIndex;    /* True if is automatically created (ex: by UNIQUE) */
+  u8 bUnordered;   /* Use this index for == or IN queries only */
+  char *zColAff;   /* String defining the affinity of each column */
+  Index *pNext;    /* The next index associated with the same table */
+  Schema *pSchema; /* Schema containing this index */
+  u8 *aSortOrder;  /* Array of size Index.nColumn. True==DESC, False==ASC */
+  char **azColl;   /* Array of collation sequence names for index */
+#ifdef SQLITE_ENABLE_STAT3
+  int nSample;             /* Number of elements in aSample[] */
+  tRowcnt avgEq;           /* Average nEq value for key values not in aSample */
+  IndexSample *aSample;    /* Samples of the left-most key */
+#endif
+};
+
+/*
+** Each sample stored in the sqlite_stat3 table is represented in memory 
+** using a structure of this type.  See documentation at the top of the
+** analyze.c source file for additional information.
+*/
+struct IndexSample {
+  union {
+    char *z;        /* Value if eType is SQLITE_TEXT or SQLITE_BLOB */
+    double r;       /* Value if eType is SQLITE_FLOAT */
+    i64 i;          /* Value if eType is SQLITE_INTEGER */
+  } u;
+  u8 eType;         /* SQLITE_NULL, SQLITE_INTEGER ... etc. */
+  int nByte;        /* Size in byte of text or blob. */
+  tRowcnt nEq;      /* Est. number of rows where the key equals this sample */
+  tRowcnt nLt;      /* Est. number of rows where key is less than this sample */
+  tRowcnt nDLt;     /* Est. number of distinct keys less than this sample */
+};
+
+/*
+** Each token coming out of the lexer is an instance of
+** this structure.  Tokens are also used as part of an expression.
+**
+** Note if Token.z==0 then Token.dyn and Token.n are undefined and
+** may contain random values.  Do not make any assumptions about Token.dyn
+** and Token.n when Token.z==0.
+*/
+struct Token {
+  const char *z;     /* Text of the token.  Not NULL-terminated! */
+  unsigned int n;    /* Number of characters in this token */
+};
+
+/*
+** An instance of this structure contains information needed to generate
+** code for a SELECT that contains aggregate functions.
+**
+** If Expr.op==TK_AGG_COLUMN or TK_AGG_FUNCTION then Expr.pAggInfo is a
+** pointer to this structure.  The Expr.iColumn field is the index in
+** AggInfo.aCol[] or AggInfo.aFunc[] of information needed to generate
+** code for that node.
+**
+** AggInfo.pGroupBy and AggInfo.aFunc.pExpr point to fields within the
+** original Select structure that describes the SELECT statement.  These
+** fields do not need to be freed when deallocating the AggInfo structure.
+*/
+struct AggInfo {
+  u8 directMode;          /* Direct rendering mode means take data directly
+                          ** from source tables rather than from accumulators */
+  u8 useSortingIdx;       /* In direct mode, reference the sorting index rather
+                          ** than the source table */
+  int sortingIdx;         /* Cursor number of the sorting index */
+  int sortingIdxPTab;     /* Cursor number of pseudo-table */
+  ExprList *pGroupBy;     /* The group by clause */
+  int nSortingColumn;     /* Number of columns in the sorting index */
+  struct AggInfo_col {    /* For each column used in source tables */
+    Table *pTab;             /* Source table */
+    int iTable;              /* Cursor number of the source table */
+    int iColumn;             /* Column number within the source table */
+    int iSorterColumn;       /* Column number in the sorting index */
+    int iMem;                /* Memory location that acts as accumulator */
+    Expr *pExpr;             /* The original expression */
+  } *aCol;
+  int nColumn;            /* Number of used entries in aCol[] */
+  int nColumnAlloc;       /* Number of slots allocated for aCol[] */
+  int nAccumulator;       /* Number of columns that show through to the output.
+                          ** Additional columns are used only as parameters to
+                          ** aggregate functions */
+  struct AggInfo_func {   /* For each aggregate function */
+    Expr *pExpr;             /* Expression encoding the function */
+    FuncDef *pFunc;          /* The aggregate function implementation */
+    int iMem;                /* Memory location that acts as accumulator */
+    int iDistinct;           /* Ephemeral table used to enforce DISTINCT */
+  } *aFunc;
+  int nFunc;              /* Number of entries in aFunc[] */
+  int nFuncAlloc;         /* Number of slots allocated for aFunc[] */
+};
+
+/*
+** The datatype ynVar is a signed integer, either 16-bit or 32-bit.
+** Usually it is 16-bits.  But if SQLITE_MAX_VARIABLE_NUMBER is greater
+** than 32767 we have to make it 32-bit.  16-bit is preferred because
+** it uses less memory in the Expr object, which is a big memory user
+** in systems with lots of prepared statements.  And few applications
+** need more than about 10 or 20 variables.  But some extreme users want
+** to have prepared statements with over 32767 variables, and for them
+** the option is available (at compile-time).
+*/
+#if SQLITE_MAX_VARIABLE_NUMBER<=32767
+typedef i16 ynVar;
+#else
+typedef int ynVar;
+#endif
+
+/*
+** Each node of an expression in the parse tree is an instance
+** of this structure.
+**
+** Expr.op is the opcode. The integer parser token codes are reused
+** as opcodes here. For example, the parser defines TK_GE to be an integer
+** code representing the ">=" operator. This same integer code is reused
+** to represent the greater-than-or-equal-to operator in the expression
+** tree.
+**
+** If the expression is an SQL literal (TK_INTEGER, TK_FLOAT, TK_BLOB, 
+** or TK_STRING), then Expr.token contains the text of the SQL literal. If
+** the expression is a variable (TK_VARIABLE), then Expr.token contains the 
+** variable name. Finally, if the expression is an SQL function (TK_FUNCTION),
+** then Expr.token contains the name of the function.
+**
+** Expr.pRight and Expr.pLeft are the left and right subexpressions of a
+** binary operator. Either or both may be NULL.
+**
+** Expr.x.pList is a list of arguments if the expression is an SQL function,
+** a CASE expression or an IN expression of the form "<lhs> IN (<y>, <z>...)".
+** Expr.x.pSelect is used if the expression is a sub-select or an expression of
+** the form "<lhs> IN (SELECT ...)". If the EP_xIsSelect bit is set in the
+** Expr.flags mask, then Expr.x.pSelect is valid. Otherwise, Expr.x.pList is 
+** valid.
+**
+** An expression of the form ID or ID.ID refers to a column in a table.
+** For such expressions, Expr.op is set to TK_COLUMN and Expr.iTable is
+** the integer cursor number of a VDBE cursor pointing to that table and
+** Expr.iColumn is the column number for the specific column.  If the
+** expression is used as a result in an aggregate SELECT, then the
+** value is also stored in the Expr.iAgg column in the aggregate so that
+** it can be accessed after all aggregates are computed.
+**
+** If the expression is an unbound variable marker (a question mark 
+** character '?' in the original SQL) then the Expr.iTable holds the index 
+** number for that variable.
+**
+** If the expression is a subquery then Expr.iColumn holds an integer
+** register number containing the result of the subquery.  If the
+** subquery gives a constant result, then iTable is -1.  If the subquery
+** gives a different answer at different times during statement processing
+** then iTable is the address of a subroutine that computes the subquery.
+**
+** If the Expr is of type OP_Column, and the table it is selecting from
+** is a disk table or the "old.*" pseudo-table, then pTab points to the
+** corresponding table definition.
+**
+** ALLOCATION NOTES:
+**
+** Expr objects can use a lot of memory space in database schema.  To
+** help reduce memory requirements, sometimes an Expr object will be
+** truncated.  And to reduce the number of memory allocations, sometimes
+** two or more Expr objects will be stored in a single memory allocation,
+** together with Expr.zToken strings.
+**
+** If the EP_Reduced and EP_TokenOnly flags are set when
+** an Expr object is truncated.  When EP_Reduced is set, then all
+** the child Expr objects in the Expr.pLeft and Expr.pRight subtrees
+** are contained within the same memory allocation.  Note, however, that
+** the subtrees in Expr.x.pList or Expr.x.pSelect are always separately
+** allocated, regardless of whether or not EP_Reduced is set.
+*/
+struct Expr {
+  u8 op;                 /* Operation performed by this node */
+  char affinity;         /* The affinity of the column or 0 if not a column */
+  u16 flags;             /* Various flags.  EP_* See below */
+  union {
+    char *zToken;          /* Token value. Zero terminated and dequoted */
+    int iValue;            /* Non-negative integer value if EP_IntValue */
+  } u;
+
+  /* If the EP_TokenOnly flag is set in the Expr.flags mask, then no
+  ** space is allocated for the fields below this point. An attempt to
+  ** access them will result in a segfault or malfunction. 
+  *********************************************************************/
+
+  Expr *pLeft;           /* Left subnode */
+  Expr *pRight;          /* Right subnode */
+  union {
+    ExprList *pList;     /* Function arguments or in "<expr> IN (<expr-list)" */
+    Select *pSelect;     /* Used for sub-selects and "<expr> IN (<select>)" */
+  } x;
+  CollSeq *pColl;        /* The collation type of the column or 0 */
+
+  /* If the EP_Reduced flag is set in the Expr.flags mask, then no
+  ** space is allocated for the fields below this point. An attempt to
+  ** access them will result in a segfault or malfunction.
+  *********************************************************************/
+
+  int iTable;            /* TK_COLUMN: cursor number of table holding column
+                         ** TK_REGISTER: register number
+                         ** TK_TRIGGER: 1 -> new, 0 -> old */
+  ynVar iColumn;         /* TK_COLUMN: column index.  -1 for rowid.
+                         ** TK_VARIABLE: variable number (always >= 1). */
+  i16 iAgg;              /* Which entry in pAggInfo->aCol[] or ->aFunc[] */
+  i16 iRightJoinTable;   /* If EP_FromJoin, the right table of the join */
+  u8 flags2;             /* Second set of flags.  EP2_... */
+  u8 op2;                /* If a TK_REGISTER, the original value of Expr.op */
+  AggInfo *pAggInfo;     /* Used by TK_AGG_COLUMN and TK_AGG_FUNCTION */
+  Table *pTab;           /* Table for TK_COLUMN expressions. */
+#if SQLITE_MAX_EXPR_DEPTH>0
+  int nHeight;           /* Height of the tree headed by this node */
+#endif
+};
+
+/*
+** The following are the meanings of bits in the Expr.flags field.
+*/
+#define EP_FromJoin   0x0001  /* Originated in ON or USING clause of a join */
+#define EP_Agg        0x0002  /* Contains one or more aggregate functions */
+#define EP_Resolved   0x0004  /* IDs have been resolved to COLUMNs */
+#define EP_Error      0x0008  /* Expression contains one or more errors */
+#define EP_Distinct   0x0010  /* Aggregate function with DISTINCT keyword */
+#define EP_VarSelect  0x0020  /* pSelect is correlated, not constant */
+#define EP_DblQuoted  0x0040  /* token.z was originally in "..." */
+#define EP_InfixFunc  0x0080  /* True for an infix function: LIKE, GLOB, etc */
+#define EP_ExpCollate 0x0100  /* Collating sequence specified explicitly */
+#define EP_FixedDest  0x0200  /* Result needed in a specific register */
+#define EP_IntValue   0x0400  /* Integer value contained in u.iValue */
+#define EP_xIsSelect  0x0800  /* x.pSelect is valid (otherwise x.pList is) */
+
+#define EP_Reduced    0x1000  /* Expr struct is EXPR_REDUCEDSIZE bytes only */
+#define EP_TokenOnly  0x2000  /* Expr struct is EXPR_TOKENONLYSIZE bytes only */
+#define EP_Static     0x4000  /* Held in memory not obtained from malloc() */
+
+/*
+** The following are the meanings of bits in the Expr.flags2 field.
+*/
+#define EP2_MallocedToken  0x0001  /* Need to sqlite3DbFree() Expr.zToken */
+#define EP2_Irreducible    0x0002  /* Cannot EXPRDUP_REDUCE this Expr */
+
+/*
+** The pseudo-routine sqlite3ExprSetIrreducible sets the EP2_Irreducible
+** flag on an expression structure.  This flag is used for VV&A only.  The
+** routine is implemented as a macro that only works when in debugging mode,
+** so as not to burden production code.
+*/
+#ifdef SQLITE_DEBUG
+# define ExprSetIrreducible(X)  (X)->flags2 |= EP2_Irreducible
+#else
+# define ExprSetIrreducible(X)
+#endif
+
+/*
+** These macros can be used to test, set, or clear bits in the 
+** Expr.flags field.
+*/
+#define ExprHasProperty(E,P)     (((E)->flags&(P))==(P))
+#define ExprHasAnyProperty(E,P)  (((E)->flags&(P))!=0)
+#define ExprSetProperty(E,P)     (E)->flags|=(P)
+#define ExprClearProperty(E,P)   (E)->flags&=~(P)
+
+/*
+** Macros to determine the number of bytes required by a normal Expr 
+** struct, an Expr struct with the EP_Reduced flag set in Expr.flags 
+** and an Expr struct with the EP_TokenOnly flag set.
+*/
+#define EXPR_FULLSIZE           sizeof(Expr)           /* Full size */
+#define EXPR_REDUCEDSIZE        offsetof(Expr,iTable)  /* Common features */
+#define EXPR_TOKENONLYSIZE      offsetof(Expr,pLeft)   /* Fewer features */
+
+/*
+** Flags passed to the sqlite3ExprDup() function. See the header comment 
+** above sqlite3ExprDup() for details.
+*/
+#define EXPRDUP_REDUCE         0x0001  /* Used reduced-size Expr nodes */
+
+/*
+** A list of expressions.  Each expression may optionally have a
+** name.  An expr/name combination can be used in several ways, such
+** as the list of "expr AS ID" fields following a "SELECT" or in the
+** list of "ID = expr" items in an UPDATE.  A list of expressions can
+** also be used as the argument to a function, in which case the a.zName
+** field is not used.
+*/
+struct ExprList {
+  int nExpr;             /* Number of expressions on the list */
+  int nAlloc;            /* Number of entries allocated below */
+  int iECursor;          /* VDBE Cursor associated with this ExprList */
+  struct ExprList_item {
+    Expr *pExpr;           /* The list of expressions */
+    char *zName;           /* Token associated with this expression */
+    char *zSpan;           /* Original text of the expression */
+    u8 sortOrder;          /* 1 for DESC or 0 for ASC */
+    u8 done;               /* A flag to indicate when processing is finished */
+    u16 iCol;              /* For ORDER BY, column number in result set */
+    u16 iAlias;            /* Index into Parse.aAlias[] for zName */
+  } *a;                  /* One entry for each expression */
+};
+
+/*
+** An instance of this structure is used by the parser to record both
+** the parse tree for an expression and the span of input text for an
+** expression.
+*/
+struct ExprSpan {
+  Expr *pExpr;          /* The expression parse tree */
+  const char *zStart;   /* First character of input text */
+  const char *zEnd;     /* One character past the end of input text */
+};
+
+/*
+** An instance of this structure can hold a simple list of identifiers,
+** such as the list "a,b,c" in the following statements:
+**
+**      INSERT INTO t(a,b,c) VALUES ...;
+**      CREATE INDEX idx ON t(a,b,c);
+**      CREATE TRIGGER trig BEFORE UPDATE ON t(a,b,c) ...;
+**
+** The IdList.a.idx field is used when the IdList represents the list of
+** column names after a table name in an INSERT statement.  In the statement
+**
+**     INSERT INTO t(a,b,c) ...
+**
+** If "a" is the k-th column of table "t", then IdList.a[0].idx==k.
+*/
+struct IdList {
+  struct IdList_item {
+    char *zName;      /* Name of the identifier */
+    int idx;          /* Index in some Table.aCol[] of a column named zName */
+  } *a;
+  int nId;         /* Number of identifiers on the list */
+  int nAlloc;      /* Number of entries allocated for a[] below */
+};
+
+/*
+** The bitmask datatype defined below is used for various optimizations.
+**
+** Changing this from a 64-bit to a 32-bit type limits the number of
+** tables in a join to 32 instead of 64.  But it also reduces the size
+** of the library by 738 bytes on ix86.
+*/
+typedef u64 Bitmask;
+
+/*
+** The number of bits in a Bitmask.  "BMS" means "BitMask Size".
+*/
+#define BMS  ((int)(sizeof(Bitmask)*8))
+
+/*
+** The following structure describes the FROM clause of a SELECT statement.
+** Each table or subquery in the FROM clause is a separate element of
+** the SrcList.a[] array.
+**
+** With the addition of multiple database support, the following structure
+** can also be used to describe a particular table such as the table that
+** is modified by an INSERT, DELETE, or UPDATE statement.  In standard SQL,
+** such a table must be a simple name: ID.  But in SQLite, the table can
+** now be identified by a database name, a dot, then the table name: ID.ID.
+**
+** The jointype starts out showing the join type between the current table
+** and the next table on the list.  The parser builds the list this way.
+** But sqlite3SrcListShiftJoinType() later shifts the jointypes so that each
+** jointype expresses the join between the table and the previous table.
+**
+** In the colUsed field, the high-order bit (bit 63) is set if the table
+** contains more than 63 columns and the 64-th or later column is used.
+*/
+struct SrcList {
+  i16 nSrc;        /* Number of tables or subqueries in the FROM clause */
+  i16 nAlloc;      /* Number of entries allocated in a[] below */
+  struct SrcList_item {
+    char *zDatabase;  /* Name of database holding this table */
+    char *zName;      /* Name of the table */
+    char *zAlias;     /* The "B" part of a "A AS B" phrase.  zName is the "A" */
+    Table *pTab;      /* An SQL table corresponding to zName */
+    Select *pSelect;  /* A SELECT statement used in place of a table name */
+    int addrFillSub;  /* Address of subroutine to manifest a subquery */
+    int regReturn;    /* Register holding return address of addrFillSub */
+    u8 jointype;      /* Type of join between this able and the previous */
+    u8 notIndexed;    /* True if there is a NOT INDEXED clause */
+    u8 isCorrelated;  /* True if sub-query is correlated */
+#ifndef SQLITE_OMIT_EXPLAIN
+    u8 iSelectId;     /* If pSelect!=0, the id of the sub-select in EQP */
+#endif
+    int iCursor;      /* The VDBE cursor number used to access this table */
+    Expr *pOn;        /* The ON clause of a join */
+    IdList *pUsing;   /* The USING clause of a join */
+    Bitmask colUsed;  /* Bit N (1<<N) set if column N of pTab is used */
+    char *zIndex;     /* Identifier from "INDEXED BY <zIndex>" clause */
+    Index *pIndex;    /* Index structure corresponding to zIndex, if any */
+  } a[1];             /* One entry for each identifier on the list */
+};
+
+/*
+** Permitted values of the SrcList.a.jointype field
+*/
+#define JT_INNER     0x0001    /* Any kind of inner or cross join */
+#define JT_CROSS     0x0002    /* Explicit use of the CROSS keyword */
+#define JT_NATURAL   0x0004    /* True for a "natural" join */
+#define JT_LEFT      0x0008    /* Left outer join */
+#define JT_RIGHT     0x0010    /* Right outer join */
+#define JT_OUTER     0x0020    /* The "OUTER" keyword is present */
+#define JT_ERROR     0x0040    /* unknown or unsupported join type */
+
+
+/*
+** A WherePlan object holds information that describes a lookup
+** strategy.
+**
+** This object is intended to be opaque outside of the where.c module.
+** It is included here only so that that compiler will know how big it
+** is.  None of the fields in this object should be used outside of
+** the where.c module.
+**
+** Within the union, pIdx is only used when wsFlags&WHERE_INDEXED is true.
+** pTerm is only used when wsFlags&WHERE_MULTI_OR is true.  And pVtabIdx
+** is only used when wsFlags&WHERE_VIRTUALTABLE is true.  It is never the
+** case that more than one of these conditions is true.
+*/
+struct WherePlan {
+  u32 wsFlags;                   /* WHERE_* flags that describe the strategy */
+  u32 nEq;                       /* Number of == constraints */
+  double nRow;                   /* Estimated number of rows (for EQP) */
+  union {
+    Index *pIdx;                   /* Index when WHERE_INDEXED is true */
+    struct WhereTerm *pTerm;       /* WHERE clause term for OR-search */
+    sqlite3_index_info *pVtabIdx;  /* Virtual table index to use */
+  } u;
+};
+
+/*
+** For each nested loop in a WHERE clause implementation, the WhereInfo
+** structure contains a single instance of this structure.  This structure
+** is intended to be private the the where.c module and should not be
+** access or modified by other modules.
+**
+** The pIdxInfo field is used to help pick the best index on a
+** virtual table.  The pIdxInfo pointer contains indexing
+** information for the i-th table in the FROM clause before reordering.
+** All the pIdxInfo pointers are freed by whereInfoFree() in where.c.
+** All other information in the i-th WhereLevel object for the i-th table
+** after FROM clause ordering.
+*/
+struct WhereLevel {
+  WherePlan plan;       /* query plan for this element of the FROM clause */
+  int iLeftJoin;        /* Memory cell used to implement LEFT OUTER JOIN */
+  int iTabCur;          /* The VDBE cursor used to access the table */
+  int iIdxCur;          /* The VDBE cursor used to access pIdx */
+  int addrBrk;          /* Jump here to break out of the loop */
+  int addrNxt;          /* Jump here to start the next IN combination */
+  int addrCont;         /* Jump here to continue with the next loop cycle */
+  int addrFirst;        /* First instruction of interior of the loop */
+  u8 iFrom;             /* Which entry in the FROM clause */
+  u8 op, p5;            /* Opcode and P5 of the opcode that ends the loop */
+  int p1, p2;           /* Operands of the opcode used to ends the loop */
+  union {               /* Information that depends on plan.wsFlags */
+    struct {
+      int nIn;              /* Number of entries in aInLoop[] */
+      struct InLoop {
+        int iCur;              /* The VDBE cursor used by this IN operator */
+        int addrInTop;         /* Top of the IN loop */
+      } *aInLoop;           /* Information about each nested IN operator */
+    } in;                 /* Used when plan.wsFlags&WHERE_IN_ABLE */
+  } u;
+
+  /* The following field is really not part of the current level.  But
+  ** we need a place to cache virtual table index information for each
+  ** virtual table in the FROM clause and the WhereLevel structure is
+  ** a convenient place since there is one WhereLevel for each FROM clause
+  ** element.
+  */
+  sqlite3_index_info *pIdxInfo;  /* Index info for n-th source table */
+};
+
+/*
+** Flags appropriate for the wctrlFlags parameter of sqlite3WhereBegin()
+** and the WhereInfo.wctrlFlags member.
+*/
+#define WHERE_ORDERBY_NORMAL   0x0000 /* No-op */
+#define WHERE_ORDERBY_MIN      0x0001 /* ORDER BY processing for min() func */
+#define WHERE_ORDERBY_MAX      0x0002 /* ORDER BY processing for max() func */
+#define WHERE_ONEPASS_DESIRED  0x0004 /* Want to do one-pass UPDATE/DELETE */
+#define WHERE_DUPLICATES_OK    0x0008 /* Ok to return a row more than once */
+#define WHERE_OMIT_OPEN_CLOSE  0x0010 /* Table cursors are already open */
+#define WHERE_FORCE_TABLE      0x0020 /* Do not use an index-only search */
+#define WHERE_ONETABLE_ONLY    0x0040 /* Only code the 1st table in pTabList */
+#define WHERE_AND_ONLY         0x0080 /* Don't use indices for OR terms */
+
+/*
+** The WHERE clause processing routine has two halves.  The
+** first part does the start of the WHERE loop and the second
+** half does the tail of the WHERE loop.  An instance of
+** this structure is returned by the first half and passed
+** into the second half to give some continuity.
+*/
+struct WhereInfo {
+  Parse *pParse;       /* Parsing and code generating context */
+  u16 wctrlFlags;      /* Flags originally passed to sqlite3WhereBegin() */
+  u8 okOnePass;        /* Ok to use one-pass algorithm for UPDATE or DELETE */
+  u8 untestedTerms;    /* Not all WHERE terms resolved by outer loop */
+  u8 eDistinct;
+  SrcList *pTabList;             /* List of tables in the join */
+  int iTop;                      /* The very beginning of the WHERE loop */
+  int iContinue;                 /* Jump here to continue with next record */
+  int iBreak;                    /* Jump here to break out of the loop */
+  int nLevel;                    /* Number of nested loop */
+  struct WhereClause *pWC;       /* Decomposition of the WHERE clause */
+  double savedNQueryLoop;        /* pParse->nQueryLoop outside the WHERE loop */
+  double nRowOut;                /* Estimated number of output rows */
+  WhereLevel a[1];               /* Information about each nest loop in WHERE */
+};
+
+#define WHERE_DISTINCT_UNIQUE 1
+#define WHERE_DISTINCT_ORDERED 2
+
+/*
+** A NameContext defines a context in which to resolve table and column
+** names.  The context consists of a list of tables (the pSrcList) field and
+** a list of named expression (pEList).  The named expression list may
+** be NULL.  The pSrc corresponds to the FROM clause of a SELECT or
+** to the table being operated on by INSERT, UPDATE, or DELETE.  The
+** pEList corresponds to the result set of a SELECT and is NULL for
+** other statements.
+**
+** NameContexts can be nested.  When resolving names, the inner-most 
+** context is searched first.  If no match is found, the next outer
+** context is checked.  If there is still no match, the next context
+** is checked.  This process continues until either a match is found
+** or all contexts are check.  When a match is found, the nRef member of
+** the context containing the match is incremented. 
+**
+** Each subquery gets a new NameContext.  The pNext field points to the
+** NameContext in the parent query.  Thus the process of scanning the
+** NameContext list corresponds to searching through successively outer
+** subqueries looking for a match.
+*/
+struct NameContext {
+  Parse *pParse;       /* The parser */
+  SrcList *pSrcList;   /* One or more tables used to resolve names */
+  ExprList *pEList;    /* Optional list of named expressions */
+  int nRef;            /* Number of names resolved by this context */
+  int nErr;            /* Number of errors encountered while resolving names */
+  u8 allowAgg;         /* Aggregate functions allowed here */
+  u8 hasAgg;           /* True if aggregates are seen */
+  u8 isCheck;          /* True if resolving names in a CHECK constraint */
+  int nDepth;          /* Depth of subquery recursion. 1 for no recursion */
+  AggInfo *pAggInfo;   /* Information about aggregates at this level */
+  NameContext *pNext;  /* Next outer name context.  NULL for outermost */
+};
+
+/*
+** An instance of the following structure contains all information
+** needed to generate code for a single SELECT statement.
+**
+** nLimit is set to -1 if there is no LIMIT clause.  nOffset is set to 0.
+** If there is a LIMIT clause, the parser sets nLimit to the value of the
+** limit and nOffset to the value of the offset (or 0 if there is not
+** offset).  But later on, nLimit and nOffset become the memory locations
+** in the VDBE that record the limit and offset counters.
+**
+** addrOpenEphm[] entries contain the address of OP_OpenEphemeral opcodes.
+** These addresses must be stored so that we can go back and fill in
+** the P4_KEYINFO and P2 parameters later.  Neither the KeyInfo nor
+** the number of columns in P2 can be computed at the same time
+** as the OP_OpenEphm instruction is coded because not
+** enough information about the compound query is known at that point.
+** The KeyInfo for addrOpenTran[0] and [1] contains collating sequences
+** for the result set.  The KeyInfo for addrOpenTran[2] contains collating
+** sequences for the ORDER BY clause.
+*/
+struct Select {
+  ExprList *pEList;      /* The fields of the result */
+  u8 op;                 /* One of: TK_UNION TK_ALL TK_INTERSECT TK_EXCEPT */
+  char affinity;         /* MakeRecord with this affinity for SRT_Set */
+  u16 selFlags;          /* Various SF_* values */
+  SrcList *pSrc;         /* The FROM clause */
+  Expr *pWhere;          /* The WHERE clause */
+  ExprList *pGroupBy;    /* The GROUP BY clause */
+  Expr *pHaving;         /* The HAVING clause */
+  ExprList *pOrderBy;    /* The ORDER BY clause */
+  Select *pPrior;        /* Prior select in a compound select statement */
+  Select *pNext;         /* Next select to the left in a compound */
+  Select *pRightmost;    /* Right-most select in a compound select statement */
+  Expr *pLimit;          /* LIMIT expression. NULL means not used. */
+  Expr *pOffset;         /* OFFSET expression. NULL means not used. */
+  int iLimit, iOffset;   /* Memory registers holding LIMIT & OFFSET counters */
+  int addrOpenEphm[3];   /* OP_OpenEphem opcodes related to this select */
+  double nSelectRow;     /* Estimated number of result rows */
+};
+
+/*
+** Allowed values for Select.selFlags.  The "SF" prefix stands for
+** "Select Flag".
+*/
+#define SF_Distinct        0x0001  /* Output should be DISTINCT */
+#define SF_Resolved        0x0002  /* Identifiers have been resolved */
+#define SF_Aggregate       0x0004  /* Contains aggregate functions */
+#define SF_UsesEphemeral   0x0008  /* Uses the OpenEphemeral opcode */
+#define SF_Expanded        0x0010  /* sqlite3SelectExpand() called on this */
+#define SF_HasTypeInfo     0x0020  /* FROM subqueries have Table metadata */
+#define SF_UseSorter       0x0040  /* Sort using a sorter */
+
+
+/*
+** The results of a select can be distributed in several ways.  The
+** "SRT" prefix means "SELECT Result Type".
+*/
+#define SRT_Union        1  /* Store result as keys in an index */
+#define SRT_Except       2  /* Remove result from a UNION index */
+#define SRT_Exists       3  /* Store 1 if the result is not empty */
+#define SRT_Discard      4  /* Do not save the results anywhere */
+
+/* The ORDER BY clause is ignored for all of the above */
+#define IgnorableOrderby(X) ((X->eDest)<=SRT_Discard)
+
+#define SRT_Output       5  /* Output each row of result */
+#define SRT_Mem          6  /* Store result in a memory cell */
+#define SRT_Set          7  /* Store results as keys in an index */
+#define SRT_Table        8  /* Store result as data with an automatic rowid */
+#define SRT_EphemTab     9  /* Create transient tab and store like SRT_Table */
+#define SRT_Coroutine   10  /* Generate a single row of result */
+
+/*
+** A structure used to customize the behavior of sqlite3Select(). See
+** comments above sqlite3Select() for details.
+*/
+typedef struct SelectDest SelectDest;
+struct SelectDest {
+  u8 eDest;         /* How to dispose of the results */
+  u8 affinity;      /* Affinity used when eDest==SRT_Set */
+  int iParm;        /* A parameter used by the eDest disposal method */
+  int iMem;         /* Base register where results are written */
+  int nMem;         /* Number of registers allocated */
+};
+
+/*
+** During code generation of statements that do inserts into AUTOINCREMENT 
+** tables, the following information is attached to the Table.u.autoInc.p
+** pointer of each autoincrement table to record some side information that
+** the code generator needs.  We have to keep per-table autoincrement
+** information in case inserts are down within triggers.  Triggers do not
+** normally coordinate their activities, but we do need to coordinate the
+** loading and saving of autoincrement information.
+*/
+struct AutoincInfo {
+  AutoincInfo *pNext;   /* Next info block in a list of them all */
+  Table *pTab;          /* Table this info block refers to */
+  int iDb;              /* Index in sqlite3.aDb[] of database holding pTab */
+  int regCtr;           /* Memory register holding the rowid counter */
+};
+
+/*
+** Size of the column cache
+*/
+#ifndef SQLITE_N_COLCACHE
+# define SQLITE_N_COLCACHE 10
+#endif
+
+/*
+** At least one instance of the following structure is created for each 
+** trigger that may be fired while parsing an INSERT, UPDATE or DELETE
+** statement. All such objects are stored in the linked list headed at
+** Parse.pTriggerPrg and deleted once statement compilation has been
+** completed.
+**
+** A Vdbe sub-program that implements the body and WHEN clause of trigger
+** TriggerPrg.pTrigger, assuming a default ON CONFLICT clause of
+** TriggerPrg.orconf, is stored in the TriggerPrg.pProgram variable.
+** The Parse.pTriggerPrg list never contains two entries with the same
+** values for both pTrigger and orconf.
+**
+** The TriggerPrg.aColmask[0] variable is set to a mask of old.* columns
+** accessed (or set to 0 for triggers fired as a result of INSERT 
+** statements). Similarly, the TriggerPrg.aColmask[1] variable is set to
+** a mask of new.* columns used by the program.
+*/
+struct TriggerPrg {
+  Trigger *pTrigger;      /* Trigger this program was coded from */
+  int orconf;             /* Default ON CONFLICT policy */
+  SubProgram *pProgram;   /* Program implementing pTrigger/orconf */
+  u32 aColmask[2];        /* Masks of old.*, new.* columns accessed */
+  TriggerPrg *pNext;      /* Next entry in Parse.pTriggerPrg list */
+};
+
+/*
+** The yDbMask datatype for the bitmask of all attached databases.
+*/
+#if SQLITE_MAX_ATTACHED>30
+  typedef sqlite3_uint64 yDbMask;
+#else
+  typedef unsigned int yDbMask;
+#endif
+
+/*
+** An SQL parser context.  A copy of this structure is passed through
+** the parser and down into all the parser action routine in order to
+** carry around information that is global to the entire parse.
+**
+** The structure is divided into two parts.  When the parser and code
+** generate call themselves recursively, the first part of the structure
+** is constant but the second part is reset at the beginning and end of
+** each recursion.
+**
+** The nTableLock and aTableLock variables are only used if the shared-cache 
+** feature is enabled (if sqlite3Tsd()->useSharedData is true). They are
+** used to store the set of table-locks required by the statement being
+** compiled. Function sqlite3TableLock() is used to add entries to the
+** list.
+*/
+struct Parse {
+  sqlite3 *db;         /* The main database structure */
+  int rc;              /* Return code from execution */
+  char *zErrMsg;       /* An error message */
+  Vdbe *pVdbe;         /* An engine for executing database bytecode */
+  u8 colNamesSet;      /* TRUE after OP_ColumnName has been issued to pVdbe */
+  u8 nameClash;        /* A permanent table name clashes with temp table name */
+  u8 checkSchema;      /* Causes schema cookie check after an error */
+  u8 nested;           /* Number of nested calls to the parser/code generator */
+  u8 parseError;       /* True after a parsing error.  Ticket #1794 */
+  u8 nTempReg;         /* Number of temporary registers in aTempReg[] */
+  u8 nTempInUse;       /* Number of aTempReg[] currently checked out */
+  int aTempReg[8];     /* Holding area for temporary registers */
+  int nRangeReg;       /* Size of the temporary register block */
+  int iRangeReg;       /* First register in temporary register block */
+  int nErr;            /* Number of errors seen */
+  int nTab;            /* Number of previously allocated VDBE cursors */
+  int nMem;            /* Number of memory cells used so far */
+  int nSet;            /* Number of sets used so far */
+  int ckBase;          /* Base register of data during check constraints */
+  int iCacheLevel;     /* ColCache valid when aColCache[].iLevel<=iCacheLevel */
+  int iCacheCnt;       /* Counter used to generate aColCache[].lru values */
+  u8 nColCache;        /* Number of entries in the column cache */
+  u8 iColCache;        /* Next entry of the cache to replace */
+  struct yColCache {
+    int iTable;           /* Table cursor number */
+    int iColumn;          /* Table column number */
+    u8 tempReg;           /* iReg is a temp register that needs to be freed */
+    int iLevel;           /* Nesting level */
+    int iReg;             /* Reg with value of this column. 0 means none. */
+    int lru;              /* Least recently used entry has the smallest value */
+  } aColCache[SQLITE_N_COLCACHE];  /* One for each column cache entry */
+  yDbMask writeMask;   /* Start a write transaction on these databases */
+  yDbMask cookieMask;  /* Bitmask of schema verified databases */
+  u8 isMultiWrite;     /* True if statement may affect/insert multiple rows */
+  u8 mayAbort;         /* True if statement may throw an ABORT exception */
+  int cookieGoto;      /* Address of OP_Goto to cookie verifier subroutine */
+  int cookieValue[SQLITE_MAX_ATTACHED+2];  /* Values of cookies to verify */
+#ifndef SQLITE_OMIT_SHARED_CACHE
+  int nTableLock;        /* Number of locks in aTableLock */
+  TableLock *aTableLock; /* Required table locks for shared-cache mode */
+#endif
+  int regRowid;        /* Register holding rowid of CREATE TABLE entry */
+  int regRoot;         /* Register holding root page number for new objects */
+  AutoincInfo *pAinc;  /* Information about AUTOINCREMENT counters */
+  int nMaxArg;         /* Max args passed to user function by sub-program */
+
+  /* Information used while coding trigger programs. */
+  Parse *pToplevel;    /* Parse structure for main program (or NULL) */
+  Table *pTriggerTab;  /* Table triggers are being coded for */
+  u32 oldmask;         /* Mask of old.* columns referenced */
+  u32 newmask;         /* Mask of new.* columns referenced */
+  u8 eTriggerOp;       /* TK_UPDATE, TK_INSERT or TK_DELETE */
+  u8 eOrconf;          /* Default ON CONFLICT policy for trigger steps */
+  u8 disableTriggers;  /* True to disable triggers */
+  double nQueryLoop;   /* Estimated number of iterations of a query */
+
+  /* Above is constant between recursions.  Below is reset before and after
+  ** each recursion */
+
+  int nVar;            /* Number of '?' variables seen in the SQL so far */
+  int nzVar;           /* Number of available slots in azVar[] */
+  char **azVar;        /* Pointers to names of parameters */
+  Vdbe *pReprepare;    /* VM being reprepared (sqlite3Reprepare()) */
+  int nAlias;          /* Number of aliased result set columns */
+  int nAliasAlloc;     /* Number of allocated slots for aAlias[] */
+  int *aAlias;         /* Register used to hold aliased result */
+  u8 explain;          /* True if the EXPLAIN flag is found on the query */
+  Token sNameToken;    /* Token with unqualified schema object name */
+  Token sLastToken;    /* The last token parsed */
+  const char *zTail;   /* All SQL text past the last semicolon parsed */
+  Table *pNewTable;    /* A table being constructed by CREATE TABLE */
+  Trigger *pNewTrigger;     /* Trigger under construct by a CREATE TRIGGER */
+  const char *zAuthContext; /* The 6th parameter to db->xAuth callbacks */
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  Token sArg;                /* Complete text of a module argument */
+  u8 declareVtab;            /* True if inside sqlite3_declare_vtab() */
+  int nVtabLock;             /* Number of virtual tables to lock */
+  Table **apVtabLock;        /* Pointer to virtual tables needing locking */
+#endif
+  int nHeight;            /* Expression tree height of current sub-select */
+  Table *pZombieTab;      /* List of Table objects to delete after code gen */
+  TriggerPrg *pTriggerPrg;    /* Linked list of coded triggers */
+
+#ifndef SQLITE_OMIT_EXPLAIN
+  int iSelectId;
+  int iNextSelectId;
+#endif
+};
+
+#ifdef SQLITE_OMIT_VIRTUALTABLE
+  #define IN_DECLARE_VTAB 0
+#else
+  #define IN_DECLARE_VTAB (pParse->declareVtab)
+#endif
+
+/*
+** An instance of the following structure can be declared on a stack and used
+** to save the Parse.zAuthContext value so that it can be restored later.
+*/
+struct AuthContext {
+  const char *zAuthContext;   /* Put saved Parse.zAuthContext here */
+  Parse *pParse;              /* The Parse structure */
+};
+
+/*
+** Bitfield flags for P5 value in OP_Insert and OP_Delete
+*/
+#define OPFLAG_NCHANGE       0x01    /* Set to update db->nChange */
+#define OPFLAG_LASTROWID     0x02    /* Set to update db->lastRowid */
+#define OPFLAG_ISUPDATE      0x04    /* This OP_Insert is an sql UPDATE */
+#define OPFLAG_APPEND        0x08    /* This is likely to be an append */
+#define OPFLAG_USESEEKRESULT 0x10    /* Try to avoid a seek in BtreeInsert() */
+#define OPFLAG_CLEARCACHE    0x20    /* Clear pseudo-table cache in OP_Column */
+
+/*
+ * Each trigger present in the database schema is stored as an instance of
+ * struct Trigger. 
+ *
+ * Pointers to instances of struct Trigger are stored in two ways.
+ * 1. In the "trigHash" hash table (part of the sqlite3* that represents the 
+ *    database). This allows Trigger structures to be retrieved by name.
+ * 2. All triggers associated with a single table form a linked list, using the
+ *    pNext member of struct Trigger. A pointer to the first element of the
+ *    linked list is stored as the "pTrigger" member of the associated
+ *    struct Table.
+ *
+ * The "step_list" member points to the first element of a linked list
+ * containing the SQL statements specified as the trigger program.
+ */
+struct Trigger {
+  char *zName;            /* The name of the trigger                        */
+  char *table;            /* The table or view to which the trigger applies */
+  u8 op;                  /* One of TK_DELETE, TK_UPDATE, TK_INSERT         */
+  u8 tr_tm;               /* One of TRIGGER_BEFORE, TRIGGER_AFTER */
+  Expr *pWhen;            /* The WHEN clause of the expression (may be NULL) */
+  IdList *pColumns;       /* If this is an UPDATE OF <column-list> trigger,
+                             the <column-list> is stored here */
+  Schema *pSchema;        /* Schema containing the trigger */
+  Schema *pTabSchema;     /* Schema containing the table */
+  TriggerStep *step_list; /* Link list of trigger program steps             */
+  Trigger *pNext;         /* Next trigger associated with the table */
+};
+
+/*
+** A trigger is either a BEFORE or an AFTER trigger.  The following constants
+** determine which. 
+**
+** If there are multiple triggers, you might of some BEFORE and some AFTER.
+** In that cases, the constants below can be ORed together.
+*/
+#define TRIGGER_BEFORE  1
+#define TRIGGER_AFTER   2
+
+/*
+ * An instance of struct TriggerStep is used to store a single SQL statement
+ * that is a part of a trigger-program. 
+ *
+ * Instances of struct TriggerStep are stored in a singly linked list (linked
+ * using the "pNext" member) referenced by the "step_list" member of the 
+ * associated struct Trigger instance. The first element of the linked list is
+ * the first step of the trigger-program.
+ * 
+ * The "op" member indicates whether this is a "DELETE", "INSERT", "UPDATE" or
+ * "SELECT" statement. The meanings of the other members is determined by the 
+ * value of "op" as follows:
+ *
+ * (op == TK_INSERT)
+ * orconf    -> stores the ON CONFLICT algorithm
+ * pSelect   -> If this is an INSERT INTO ... SELECT ... statement, then
+ *              this stores a pointer to the SELECT statement. Otherwise NULL.
+ * target    -> A token holding the quoted name of the table to insert into.
+ * pExprList -> If this is an INSERT INTO ... VALUES ... statement, then
+ *              this stores values to be inserted. Otherwise NULL.
+ * pIdList   -> If this is an INSERT INTO ... (<column-names>) VALUES ... 
+ *              statement, then this stores the column-names to be
+ *              inserted into.
+ *
+ * (op == TK_DELETE)
+ * target    -> A token holding the quoted name of the table to delete from.
+ * pWhere    -> The WHERE clause of the DELETE statement if one is specified.
+ *              Otherwise NULL.
+ * 
+ * (op == TK_UPDATE)
+ * target    -> A token holding the quoted name of the table to update rows of.
+ * pWhere    -> The WHERE clause of the UPDATE statement if one is specified.
+ *              Otherwise NULL.
+ * pExprList -> A list of the columns to update and the expressions to update
+ *              them to. See sqlite3Update() documentation of "pChanges"
+ *              argument.
+ * 
+ */
+struct TriggerStep {
+  u8 op;               /* One of TK_DELETE, TK_UPDATE, TK_INSERT, TK_SELECT */
+  u8 orconf;           /* OE_Rollback etc. */
+  Trigger *pTrig;      /* The trigger that this step is a part of */
+  Select *pSelect;     /* SELECT statment or RHS of INSERT INTO .. SELECT ... */
+  Token target;        /* Target table for DELETE, UPDATE, INSERT */
+  Expr *pWhere;        /* The WHERE clause for DELETE or UPDATE steps */
+  ExprList *pExprList; /* SET clause for UPDATE.  VALUES clause for INSERT */
+  IdList *pIdList;     /* Column names for INSERT */
+  TriggerStep *pNext;  /* Next in the link-list */
+  TriggerStep *pLast;  /* Last element in link-list. Valid for 1st elem only */
+};
+
+/*
+** The following structure contains information used by the sqliteFix...
+** routines as they walk the parse tree to make database references
+** explicit.  
+*/
+typedef struct DbFixer DbFixer;
+struct DbFixer {
+  Parse *pParse;      /* The parsing context.  Error messages written here */
+  const char *zDb;    /* Make sure all objects are contained in this database */
+  const char *zType;  /* Type of the container - used for error messages */
+  const Token *pName; /* Name of the container - used for error messages */
+};
+
+/*
+** An objected used to accumulate the text of a string where we
+** do not necessarily know how big the string will be in the end.
+*/
+struct StrAccum {
+  sqlite3 *db;         /* Optional database for lookaside.  Can be NULL */
+  char *zBase;         /* A base allocation.  Not from malloc. */
+  char *zText;         /* The string collected so far */
+  int  nChar;          /* Length of the string so far */
+  int  nAlloc;         /* Amount of space allocated in zText */
+  int  mxAlloc;        /* Maximum allowed string length */
+  u8   mallocFailed;   /* Becomes true if any memory allocation fails */
+  u8   useMalloc;      /* 0: none,  1: sqlite3DbMalloc,  2: sqlite3_malloc */
+  u8   tooBig;         /* Becomes true if string size exceeds limits */
+};
+
+/*
+** A pointer to this structure is used to communicate information
+** from sqlite3Init and OP_ParseSchema into the sqlite3InitCallback.
+*/
+typedef struct {
+  sqlite3 *db;        /* The database being initialized */
+  int iDb;            /* 0 for main database.  1 for TEMP, 2.. for ATTACHed */
+  char **pzErrMsg;    /* Error message stored here */
+  int rc;             /* Result code stored here */
+} InitData;
+
+/*
+** Structure containing global configuration data for the SQLite library.
+**
+** This structure also contains some state information.
+*/
+struct Sqlite3Config {
+  int bMemstat;                     /* True to enable memory status */
+  int bCoreMutex;                   /* True to enable core mutexing */
+  int bFullMutex;                   /* True to enable full mutexing */
+  int bOpenUri;                     /* True to interpret filenames as URIs */
+  int mxStrlen;                     /* Maximum string length */
+  int szLookaside;                  /* Default lookaside buffer size */
+  int nLookaside;                   /* Default lookaside buffer count */
+  sqlite3_mem_methods m;            /* Low-level memory allocation interface */
+  sqlite3_mutex_methods mutex;      /* Low-level mutex interface */
+  sqlite3_pcache_methods pcache;    /* Low-level page-cache interface */
+  void *pHeap;                      /* Heap storage space */
+  int nHeap;                        /* Size of pHeap[] */
+  int mnReq, mxReq;                 /* Min and max heap requests sizes */
+  void *pScratch;                   /* Scratch memory */
+  int szScratch;                    /* Size of each scratch buffer */
+  int nScratch;                     /* Number of scratch buffers */
+  void *pPage;                      /* Page cache memory */
+  int szPage;                       /* Size of each page in pPage[] */
+  int nPage;                        /* Number of pages in pPage[] */
+  int mxParserStack;                /* maximum depth of the parser stack */
+  int sharedCacheEnabled;           /* true if shared-cache mode enabled */
+  /* The above might be initialized to non-zero.  The following need to always
+  ** initially be zero, however. */
+  int isInit;                       /* True after initialization has finished */
+  int inProgress;                   /* True while initialization in progress */
+  int isMutexInit;                  /* True after mutexes are initialized */
+  int isMallocInit;                 /* True after malloc is initialized */
+  int isPCacheInit;                 /* True after malloc is initialized */
+  sqlite3_mutex *pInitMutex;        /* Mutex used by sqlite3_initialize() */
+  int nRefInitMutex;                /* Number of users of pInitMutex */
+  void (*xLog)(void*,int,const char*); /* Function for logging */
+  void *pLogArg;                       /* First argument to xLog() */
+  int bLocaltimeFault;              /* True to fail localtime() calls */
+};
+
+/*
+** Context pointer passed down through the tree-walk.
+*/
+struct Walker {
+  int (*xExprCallback)(Walker*, Expr*);     /* Callback for expressions */
+  int (*xSelectCallback)(Walker*,Select*);  /* Callback for SELECTs */
+  Parse *pParse;                            /* Parser context.  */
+  union {                                   /* Extra data for callback */
+    NameContext *pNC;                          /* Naming context */
+    int i;                                     /* Integer value */
+  } u;
+};
+
+/* Forward declarations */
+int sqlite3WalkExpr(Walker*, Expr*);
+int sqlite3WalkExprList(Walker*, ExprList*);
+int sqlite3WalkSelect(Walker*, Select*);
+int sqlite3WalkSelectExpr(Walker*, Select*);
+int sqlite3WalkSelectFrom(Walker*, Select*);
+
+/*
+** Return code from the parse-tree walking primitives and their
+** callbacks.
+*/
+#define WRC_Continue    0   /* Continue down into children */
+#define WRC_Prune       1   /* Omit children but continue walking siblings */
+#define WRC_Abort       2   /* Abandon the tree walk */
+
+/*
+** Assuming zIn points to the first byte of a UTF-8 character,
+** advance zIn to point to the first byte of the next UTF-8 character.
+*/
+#define SQLITE_SKIP_UTF8(zIn) {                        \
+  if( (*(zIn++))>=0xc0 ){                              \
+    while( (*zIn & 0xc0)==0x80 ){ zIn++; }             \
+  }                                                    \
+}
+
+/*
+** The SQLITE_*_BKPT macros are substitutes for the error codes with
+** the same name but without the _BKPT suffix.  These macros invoke
+** routines that report the line-number on which the error originated
+** using sqlite3_log().  The routines also provide a convenient place
+** to set a debugger breakpoint.
+*/
+int sqlite3CorruptError(int);
+int sqlite3MisuseError(int);
+int sqlite3CantopenError(int);
+#define SQLITE_CORRUPT_BKPT sqlite3CorruptError(__LINE__)
+#define SQLITE_MISUSE_BKPT sqlite3MisuseError(__LINE__)
+#define SQLITE_CANTOPEN_BKPT sqlite3CantopenError(__LINE__)
+
+
+/*
+** FTS4 is really an extension for FTS3.  It is enabled using the
+** SQLITE_ENABLE_FTS3 macro.  But to avoid confusion we also all
+** the SQLITE_ENABLE_FTS4 macro to serve as an alisse for SQLITE_ENABLE_FTS3.
+*/
+#if defined(SQLITE_ENABLE_FTS4) && !defined(SQLITE_ENABLE_FTS3)
+# define SQLITE_ENABLE_FTS3
+#endif
+
+/*
+** The ctype.h header is needed for non-ASCII systems.  It is also
+** needed by FTS3 when FTS3 is included in the amalgamation.
+*/
+#if !defined(SQLITE_ASCII) || \
+    (defined(SQLITE_ENABLE_FTS3) && defined(SQLITE_AMALGAMATION))
+# include <ctype.h>
+#endif
+
+/*
+** The following macros mimic the standard library functions toupper(),
+** isspace(), isalnum(), isdigit() and isxdigit(), respectively. The
+** sqlite versions only work for ASCII characters, regardless of locale.
+*/
+#ifdef SQLITE_ASCII
+# define sqlite3Toupper(x)  ((x)&~(sqlite3CtypeMap[(unsigned char)(x)]&0x20))
+# define sqlite3Isspace(x)   (sqlite3CtypeMap[(unsigned char)(x)]&0x01)
+# define sqlite3Isalnum(x)   (sqlite3CtypeMap[(unsigned char)(x)]&0x06)
+# define sqlite3Isalpha(x)   (sqlite3CtypeMap[(unsigned char)(x)]&0x02)
+# define sqlite3Isdigit(x)   (sqlite3CtypeMap[(unsigned char)(x)]&0x04)
+# define sqlite3Isxdigit(x)  (sqlite3CtypeMap[(unsigned char)(x)]&0x08)
+# define sqlite3Tolower(x)   (sqlite3UpperToLower[(unsigned char)(x)])
+#else
+# define sqlite3Toupper(x)   toupper((unsigned char)(x))
+# define sqlite3Isspace(x)   isspace((unsigned char)(x))
+# define sqlite3Isalnum(x)   isalnum((unsigned char)(x))
+# define sqlite3Isalpha(x)   isalpha((unsigned char)(x))
+# define sqlite3Isdigit(x)   isdigit((unsigned char)(x))
+# define sqlite3Isxdigit(x)  isxdigit((unsigned char)(x))
+# define sqlite3Tolower(x)   tolower((unsigned char)(x))
+#endif
+
+/*
+** Internal function prototypes
+*/
+int sqlite3StrICmp(const char *, const char *);
+int sqlite3Strlen30(const char*);
+#define sqlite3StrNICmp sqlite3_strnicmp
+
+int sqlite3MallocInit(void);
+void sqlite3MallocEnd(void);
+void *sqlite3Malloc(int);
+void *sqlite3MallocZero(int);
+void *sqlite3DbMallocZero(sqlite3*, int);
+void *sqlite3DbMallocRaw(sqlite3*, int);
+char *sqlite3DbStrDup(sqlite3*,const char*);
+char *sqlite3DbStrNDup(sqlite3*,const char*, int);
+void *sqlite3Realloc(void*, int);
+void *sqlite3DbReallocOrFree(sqlite3 *, void *, int);
+void *sqlite3DbRealloc(sqlite3 *, void *, int);
+void sqlite3DbFree(sqlite3*, void*);
+int sqlite3MallocSize(void*);
+int sqlite3DbMallocSize(sqlite3*, void*);
+void *sqlite3ScratchMalloc(int);
+void sqlite3ScratchFree(void*);
+void *sqlite3PageMalloc(int);
+void sqlite3PageFree(void*);
+void sqlite3MemSetDefault(void);
+void sqlite3BenignMallocHooks(void (*)(void), void (*)(void));
+int sqlite3HeapNearlyFull(void);
+
+/*
+** On systems with ample stack space and that support alloca(), make
+** use of alloca() to obtain space for large automatic objects.  By default,
+** obtain space from malloc().
+**
+** The alloca() routine never returns NULL.  This will cause code paths
+** that deal with sqlite3StackAlloc() failures to be unreachable.
+*/
+#ifdef SQLITE_USE_ALLOCA
+# define sqlite3StackAllocRaw(D,N)   alloca(N)
+# define sqlite3StackAllocZero(D,N)  memset(alloca(N), 0, N)
+# define sqlite3StackFree(D,P)       
+#else
+# define sqlite3StackAllocRaw(D,N)   sqlite3DbMallocRaw(D,N)
+# define sqlite3StackAllocZero(D,N)  sqlite3DbMallocZero(D,N)
+# define sqlite3StackFree(D,P)       sqlite3DbFree(D,P)
+#endif
+
+#ifdef SQLITE_ENABLE_MEMSYS3
+const sqlite3_mem_methods *sqlite3MemGetMemsys3(void);
+#endif
+#ifdef SQLITE_ENABLE_MEMSYS5
+const sqlite3_mem_methods *sqlite3MemGetMemsys5(void);
+#endif
+
+
+#ifndef SQLITE_MUTEX_OMIT
+  sqlite3_mutex_methods const *sqlite3DefaultMutex(void);
+  sqlite3_mutex_methods const *sqlite3NoopMutex(void);
+  sqlite3_mutex *sqlite3MutexAlloc(int);
+  int sqlite3MutexInit(void);
+  int sqlite3MutexEnd(void);
+#endif
+
+int sqlite3StatusValue(int);
+void sqlite3StatusAdd(int, int);
+void sqlite3StatusSet(int, int);
+
+#ifndef SQLITE_OMIT_FLOATING_POINT
+  int sqlite3IsNaN(double);
+#else
+# define sqlite3IsNaN(X)  0
+#endif
+
+void sqlite3VXPrintf(StrAccum*, int, const char*, va_list);
+#ifndef SQLITE_OMIT_TRACE
+void sqlite3XPrintf(StrAccum*, const char*, ...);
+#endif
+char *sqlite3MPrintf(sqlite3*,const char*, ...);
+char *sqlite3VMPrintf(sqlite3*,const char*, va_list);
+char *sqlite3MAppendf(sqlite3*,char*,const char*,...);
+#if defined(SQLITE_TEST) || defined(SQLITE_DEBUG)
+  void sqlite3DebugPrintf(const char*, ...);
+#endif
+#if defined(SQLITE_TEST)
+  void *sqlite3TestTextToPtr(const char*);
+#endif
+void sqlite3SetString(char **, sqlite3*, const char*, ...);
+void sqlite3ErrorMsg(Parse*, const char*, ...);
+int sqlite3Dequote(char*);
+int sqlite3KeywordCode(const unsigned char*, int);
+int sqlite3RunParser(Parse*, const char*, char **);
+void sqlite3FinishCoding(Parse*);
+int sqlite3GetTempReg(Parse*);
+void sqlite3ReleaseTempReg(Parse*,int);
+int sqlite3GetTempRange(Parse*,int);
+void sqlite3ReleaseTempRange(Parse*,int,int);
+Expr *sqlite3ExprAlloc(sqlite3*,int,const Token*,int);
+Expr *sqlite3Expr(sqlite3*,int,const char*);
+void sqlite3ExprAttachSubtrees(sqlite3*,Expr*,Expr*,Expr*);
+Expr *sqlite3PExpr(Parse*, int, Expr*, Expr*, const Token*);
+Expr *sqlite3ExprAnd(sqlite3*,Expr*, Expr*);
+Expr *sqlite3ExprFunction(Parse*,ExprList*, Token*);
+void sqlite3ExprAssignVarNumber(Parse*, Expr*);
+void sqlite3ExprDelete(sqlite3*, Expr*);
+ExprList *sqlite3ExprListAppend(Parse*,ExprList*,Expr*);
+void sqlite3ExprListSetName(Parse*,ExprList*,Token*,int);
+void sqlite3ExprListSetSpan(Parse*,ExprList*,ExprSpan*);
+void sqlite3ExprListDelete(sqlite3*, ExprList*);
+int sqlite3Init(sqlite3*, char**);
+int sqlite3InitCallback(void*, int, char**, char**);
+void sqlite3Pragma(Parse*,Token*,Token*,Token*,int);
+void sqlite3ResetInternalSchema(sqlite3*, int);
+void sqlite3BeginParse(Parse*,int);
+void sqlite3CommitInternalChanges(sqlite3*);
+Table *sqlite3ResultSetOfSelect(Parse*,Select*);
+void sqlite3OpenMasterTable(Parse *, int);
+void sqlite3StartTable(Parse*,Token*,Token*,int,int,int,int);
+void sqlite3AddColumn(Parse*,Token*);
+void sqlite3AddNotNull(Parse*, int);
+void sqlite3AddPrimaryKey(Parse*, ExprList*, int, int, int);
+void sqlite3AddCheckConstraint(Parse*, Expr*);
+void sqlite3AddColumnType(Parse*,Token*);
+void sqlite3AddDefaultValue(Parse*,ExprSpan*);
+void sqlite3AddCollateType(Parse*, Token*);
+void sqlite3EndTable(Parse*,Token*,Token*,Select*);
+int sqlite3ParseUri(const char*,const char*,unsigned int*,
+                    sqlite3_vfs**,char**,char **);
+
+Bitvec *sqlite3BitvecCreate(u32);
+int sqlite3BitvecTest(Bitvec*, u32);
+int sqlite3BitvecSet(Bitvec*, u32);
+void sqlite3BitvecClear(Bitvec*, u32, void*);
+void sqlite3BitvecDestroy(Bitvec*);
+u32 sqlite3BitvecSize(Bitvec*);
+int sqlite3BitvecBuiltinTest(int,int*);
+
+RowSet *sqlite3RowSetInit(sqlite3*, void*, unsigned int);
+void sqlite3RowSetClear(RowSet*);
+void sqlite3RowSetInsert(RowSet*, i64);
+int sqlite3RowSetTest(RowSet*, u8 iBatch, i64);
+int sqlite3RowSetNext(RowSet*, i64*);
+
+void sqlite3CreateView(Parse*,Token*,Token*,Token*,Select*,int,int);
+
+#if !defined(SQLITE_OMIT_VIEW) || !defined(SQLITE_OMIT_VIRTUALTABLE)
+  int sqlite3ViewGetColumnNames(Parse*,Table*);
+#else
+# define sqlite3ViewGetColumnNames(A,B) 0
+#endif
+
+void sqlite3DropTable(Parse*, SrcList*, int, int);
+void sqlite3CodeDropTable(Parse*, Table*, int, int);
+void sqlite3DeleteTable(sqlite3*, Table*);
+#ifndef SQLITE_OMIT_AUTOINCREMENT
+  void sqlite3AutoincrementBegin(Parse *pParse);
+  void sqlite3AutoincrementEnd(Parse *pParse);
+#else
+# define sqlite3AutoincrementBegin(X)
+# define sqlite3AutoincrementEnd(X)
+#endif
+void sqlite3Insert(Parse*, SrcList*, ExprList*, Select*, IdList*, int);
+void *sqlite3ArrayAllocate(sqlite3*,void*,int,int,int*,int*,int*);
+IdList *sqlite3IdListAppend(sqlite3*, IdList*, Token*);
+int sqlite3IdListIndex(IdList*,const char*);
+SrcList *sqlite3SrcListEnlarge(sqlite3*, SrcList*, int, int);
+SrcList *sqlite3SrcListAppend(sqlite3*, SrcList*, Token*, Token*);
+SrcList *sqlite3SrcListAppendFromTerm(Parse*, SrcList*, Token*, Token*,
+                                      Token*, Select*, Expr*, IdList*);
+void sqlite3SrcListIndexedBy(Parse *, SrcList *, Token *);
+int sqlite3IndexedByLookup(Parse *, struct SrcList_item *);
+void sqlite3SrcListShiftJoinType(SrcList*);
+void sqlite3SrcListAssignCursors(Parse*, SrcList*);
+void sqlite3IdListDelete(sqlite3*, IdList*);
+void sqlite3SrcListDelete(sqlite3*, SrcList*);
+Index *sqlite3CreateIndex(Parse*,Token*,Token*,SrcList*,ExprList*,int,Token*,
+                        Token*, int, int);
+void sqlite3DropIndex(Parse*, SrcList*, int);
+int sqlite3Select(Parse*, Select*, SelectDest*);
+Select *sqlite3SelectNew(Parse*,ExprList*,SrcList*,Expr*,ExprList*,
+                         Expr*,ExprList*,int,Expr*,Expr*);
+void sqlite3SelectDelete(sqlite3*, Select*);
+Table *sqlite3SrcListLookup(Parse*, SrcList*);
+int sqlite3IsReadOnly(Parse*, Table*, int);
+void sqlite3OpenTable(Parse*, int iCur, int iDb, Table*, int);
+#if defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT) && !defined(SQLITE_OMIT_SUBQUERY)
+Expr *sqlite3LimitWhere(Parse *, SrcList *, Expr *, ExprList *, Expr *, Expr *, char *);
+#endif
+void sqlite3DeleteFrom(Parse*, SrcList*, Expr*);
+void sqlite3Update(Parse*, SrcList*, ExprList*, Expr*, int);
+WhereInfo *sqlite3WhereBegin(Parse*, SrcList*, Expr*, ExprList**,ExprList*,u16);
+void sqlite3WhereEnd(WhereInfo*);
+int sqlite3ExprCodeGetColumn(Parse*, Table*, int, int, int);
+void sqlite3ExprCodeGetColumnOfTable(Vdbe*, Table*, int, int, int);
+void sqlite3ExprCodeMove(Parse*, int, int, int);
+void sqlite3ExprCodeCopy(Parse*, int, int, int);
+void sqlite3ExprCacheStore(Parse*, int, int, int);
+void sqlite3ExprCachePush(Parse*);
+void sqlite3ExprCachePop(Parse*, int);
+void sqlite3ExprCacheRemove(Parse*, int, int);
+void sqlite3ExprCacheClear(Parse*);
+void sqlite3ExprCacheAffinityChange(Parse*, int, int);
+int sqlite3ExprCode(Parse*, Expr*, int);
+int sqlite3ExprCodeTemp(Parse*, Expr*, int*);
+int sqlite3ExprCodeTarget(Parse*, Expr*, int);
+int sqlite3ExprCodeAndCache(Parse*, Expr*, int);
+void sqlite3ExprCodeConstants(Parse*, Expr*);
+int sqlite3ExprCodeExprList(Parse*, ExprList*, int, int);
+void sqlite3ExprIfTrue(Parse*, Expr*, int, int);
+void sqlite3ExprIfFalse(Parse*, Expr*, int, int);
+Table *sqlite3FindTable(sqlite3*,const char*, const char*);
+Table *sqlite3LocateTable(Parse*,int isView,const char*, const char*);
+Index *sqlite3FindIndex(sqlite3*,const char*, const char*);
+void sqlite3UnlinkAndDeleteTable(sqlite3*,int,const char*);
+void sqlite3UnlinkAndDeleteIndex(sqlite3*,int,const char*);
+void sqlite3Vacuum(Parse*);
+int sqlite3RunVacuum(char**, sqlite3*);
+char *sqlite3NameFromToken(sqlite3*, Token*);
+int sqlite3ExprCompare(Expr*, Expr*);
+int sqlite3ExprListCompare(ExprList*, ExprList*);
+void sqlite3ExprAnalyzeAggregates(NameContext*, Expr*);
+void sqlite3ExprAnalyzeAggList(NameContext*,ExprList*);
+Vdbe *sqlite3GetVdbe(Parse*);
+void sqlite3PrngSaveState(void);
+void sqlite3PrngRestoreState(void);
+void sqlite3PrngResetState(void);
+void sqlite3RollbackAll(sqlite3*);
+void sqlite3CodeVerifySchema(Parse*, int);
+void sqlite3CodeVerifyNamedSchema(Parse*, const char *zDb);
+void sqlite3BeginTransaction(Parse*, int);
+void sqlite3CommitTransaction(Parse*);
+void sqlite3RollbackTransaction(Parse*);
+void sqlite3Savepoint(Parse*, int, Token*);
+void sqlite3CloseSavepoints(sqlite3 *);
+int sqlite3ExprIsConstant(Expr*);
+int sqlite3ExprIsConstantNotJoin(Expr*);
+int sqlite3ExprIsConstantOrFunction(Expr*);
+int sqlite3ExprIsInteger(Expr*, int*);
+int sqlite3ExprCanBeNull(const Expr*);
+void sqlite3ExprCodeIsNullJump(Vdbe*, const Expr*, int, int);
+int sqlite3ExprNeedsNoAffinityChange(const Expr*, char);
+int sqlite3IsRowid(const char*);
+void sqlite3GenerateRowDelete(Parse*, Table*, int, int, int, Trigger *, int);
+void sqlite3GenerateRowIndexDelete(Parse*, Table*, int, int*);
+int sqlite3GenerateIndexKey(Parse*, Index*, int, int, int);
+void sqlite3GenerateConstraintChecks(Parse*,Table*,int,int,
+                                     int*,int,int,int,int,int*);
+void sqlite3CompleteInsertion(Parse*, Table*, int, int, int*, int, int, int);
+int sqlite3OpenTableAndIndices(Parse*, Table*, int, int);
+void sqlite3BeginWriteOperation(Parse*, int, int);
+void sqlite3MultiWrite(Parse*);
+void sqlite3MayAbort(Parse*);
+void sqlite3HaltConstraint(Parse*, int, char*, int);
+Expr *sqlite3ExprDup(sqlite3*,Expr*,int);
+ExprList *sqlite3ExprListDup(sqlite3*,ExprList*,int);
+SrcList *sqlite3SrcListDup(sqlite3*,SrcList*,int);
+IdList *sqlite3IdListDup(sqlite3*,IdList*);
+Select *sqlite3SelectDup(sqlite3*,Select*,int);
+void sqlite3FuncDefInsert(FuncDefHash*, FuncDef*);
+FuncDef *sqlite3FindFunction(sqlite3*,const char*,int,int,u8,int);
+void sqlite3RegisterBuiltinFunctions(sqlite3*);
+void sqlite3RegisterDateTimeFunctions(void);
+void sqlite3RegisterGlobalFunctions(void);
+int sqlite3SafetyCheckOk(sqlite3*);
+int sqlite3SafetyCheckSickOrOk(sqlite3*);
+void sqlite3ChangeCookie(Parse*, int);
+
+#if !defined(SQLITE_OMIT_VIEW) && !defined(SQLITE_OMIT_TRIGGER)
+void sqlite3MaterializeView(Parse*, Table*, Expr*, int);
+#endif
+
+#ifndef SQLITE_OMIT_TRIGGER
+  void sqlite3BeginTrigger(Parse*, Token*,Token*,int,int,IdList*,SrcList*,
+                           Expr*,int, int);
+  void sqlite3FinishTrigger(Parse*, TriggerStep*, Token*);
+  void sqlite3DropTrigger(Parse*, SrcList*, int);
+  void sqlite3DropTriggerPtr(Parse*, Trigger*);
+  Trigger *sqlite3TriggersExist(Parse *, Table*, int, ExprList*, int *pMask);
+  Trigger *sqlite3TriggerList(Parse *, Table *);
+  void sqlite3CodeRowTrigger(Parse*, Trigger *, int, ExprList*, int, Table *,
+                            int, int, int);
+  void sqlite3CodeRowTriggerDirect(Parse *, Trigger *, Table *, int, int, int);
+  void sqliteViewTriggers(Parse*, Table*, Expr*, int, ExprList*);
+  void sqlite3DeleteTriggerStep(sqlite3*, TriggerStep*);
+  TriggerStep *sqlite3TriggerSelectStep(sqlite3*,Select*);
+  TriggerStep *sqlite3TriggerInsertStep(sqlite3*,Token*, IdList*,
+                                        ExprList*,Select*,u8);
+  TriggerStep *sqlite3TriggerUpdateStep(sqlite3*,Token*,ExprList*, Expr*, u8);
+  TriggerStep *sqlite3TriggerDeleteStep(sqlite3*,Token*, Expr*);
+  void sqlite3DeleteTrigger(sqlite3*, Trigger*);
+  void sqlite3UnlinkAndDeleteTrigger(sqlite3*,int,const char*);
+  u32 sqlite3TriggerColmask(Parse*,Trigger*,ExprList*,int,int,Table*,int);
+# define sqlite3ParseToplevel(p) ((p)->pToplevel ? (p)->pToplevel : (p))
+#else
+# define sqlite3TriggersExist(B,C,D,E,F) 0
+# define sqlite3DeleteTrigger(A,B)
+# define sqlite3DropTriggerPtr(A,B)
+# define sqlite3UnlinkAndDeleteTrigger(A,B,C)
+# define sqlite3CodeRowTrigger(A,B,C,D,E,F,G,H,I)
+# define sqlite3CodeRowTriggerDirect(A,B,C,D,E,F)
+# define sqlite3TriggerList(X, Y) 0
+# define sqlite3ParseToplevel(p) p
+# define sqlite3TriggerColmask(A,B,C,D,E,F,G) 0
+#endif
+
+int sqlite3JoinType(Parse*, Token*, Token*, Token*);
+void sqlite3CreateForeignKey(Parse*, ExprList*, Token*, ExprList*, int);
+void sqlite3DeferForeignKey(Parse*, int);
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  void sqlite3AuthRead(Parse*,Expr*,Schema*,SrcList*);
+  int sqlite3AuthCheck(Parse*,int, const char*, const char*, const char*);
+  void sqlite3AuthContextPush(Parse*, AuthContext*, const char*);
+  void sqlite3AuthContextPop(AuthContext*);
+  int sqlite3AuthReadCol(Parse*, const char *, const char *, int);
+#else
+# define sqlite3AuthRead(a,b,c,d)
+# define sqlite3AuthCheck(a,b,c,d,e)    SQLITE_OK
+# define sqlite3AuthContextPush(a,b,c)
+# define sqlite3AuthContextPop(a)  ((void)(a))
+#endif
+void sqlite3Attach(Parse*, Expr*, Expr*, Expr*);
+void sqlite3Detach(Parse*, Expr*);
+int sqlite3FixInit(DbFixer*, Parse*, int, const char*, const Token*);
+int sqlite3FixSrcList(DbFixer*, SrcList*);
+int sqlite3FixSelect(DbFixer*, Select*);
+int sqlite3FixExpr(DbFixer*, Expr*);
+int sqlite3FixExprList(DbFixer*, ExprList*);
+int sqlite3FixTriggerStep(DbFixer*, TriggerStep*);
+int sqlite3AtoF(const char *z, double*, int, u8);
+int sqlite3GetInt32(const char *, int*);
+int sqlite3Atoi(const char*);
+int sqlite3Utf16ByteLen(const void *pData, int nChar);
+int sqlite3Utf8CharLen(const char *pData, int nByte);
+u32 sqlite3Utf8Read(const u8*, const u8**);
+
+/*
+** Routines to read and write variable-length integers.  These used to
+** be defined locally, but now we use the varint routines in the util.c
+** file.  Code should use the MACRO forms below, as the Varint32 versions
+** are coded to assume the single byte case is already handled (which 
+** the MACRO form does).
+*/
+int sqlite3PutVarint(unsigned char*, u64);
+int sqlite3PutVarint32(unsigned char*, u32);
+u8 sqlite3GetVarint(const unsigned char *, u64 *);
+u8 sqlite3GetVarint32(const unsigned char *, u32 *);
+int sqlite3VarintLen(u64 v);
+
+/*
+** The header of a record consists of a sequence variable-length integers.
+** These integers are almost always small and are encoded as a single byte.
+** The following macros take advantage this fact to provide a fast encode
+** and decode of the integers in a record header.  It is faster for the common
+** case where the integer is a single byte.  It is a little slower when the
+** integer is two or more bytes.  But overall it is faster.
+**
+** The following expressions are equivalent:
+**
+**     x = sqlite3GetVarint32( A, &B );
+**     x = sqlite3PutVarint32( A, B );
+**
+**     x = getVarint32( A, B );
+**     x = putVarint32( A, B );
+**
+*/
+#define getVarint32(A,B)  (u8)((*(A)<(u8)0x80) ? ((B) = (u32)*(A)),1 : sqlite3GetVarint32((A), (u32 *)&(B)))
+#define putVarint32(A,B)  (u8)(((u32)(B)<(u32)0x80) ? (*(A) = (unsigned char)(B)),1 : sqlite3PutVarint32((A), (B)))
+#define getVarint    sqlite3GetVarint
+#define putVarint    sqlite3PutVarint
+
+
+const char *sqlite3IndexAffinityStr(Vdbe *, Index *);
+void sqlite3TableAffinityStr(Vdbe *, Table *);
+char sqlite3CompareAffinity(Expr *pExpr, char aff2);
+int sqlite3IndexAffinityOk(Expr *pExpr, char idx_affinity);
+char sqlite3ExprAffinity(Expr *pExpr);
+int sqlite3Atoi64(const char*, i64*, int, u8);
+void sqlite3Error(sqlite3*, int, const char*,...);
+void *sqlite3HexToBlob(sqlite3*, const char *z, int n);
+u8 sqlite3HexToInt(int h);
+int sqlite3TwoPartName(Parse *, Token *, Token *, Token **);
+const char *sqlite3ErrStr(int);
+int sqlite3ReadSchema(Parse *pParse);
+CollSeq *sqlite3FindCollSeq(sqlite3*,u8 enc, const char*,int);
+CollSeq *sqlite3LocateCollSeq(Parse *pParse, const char*zName);
+CollSeq *sqlite3ExprCollSeq(Parse *pParse, Expr *pExpr);
+Expr *sqlite3ExprSetColl(Expr*, CollSeq*);
+Expr *sqlite3ExprSetCollByToken(Parse *pParse, Expr*, Token*);
+int sqlite3CheckCollSeq(Parse *, CollSeq *);
+int sqlite3CheckObjectName(Parse *, const char *);
+void sqlite3VdbeSetChanges(sqlite3 *, int);
+int sqlite3AddInt64(i64*,i64);
+int sqlite3SubInt64(i64*,i64);
+int sqlite3MulInt64(i64*,i64);
+int sqlite3AbsInt32(int);
+#ifdef SQLITE_ENABLE_8_3_NAMES
+void sqlite3FileSuffix3(const char*, char*);
+#else
+# define sqlite3FileSuffix3(X,Y)
+#endif
+u8 sqlite3GetBoolean(const char *z);
+
+const void *sqlite3ValueText(sqlite3_value*, u8);
+int sqlite3ValueBytes(sqlite3_value*, u8);
+void sqlite3ValueSetStr(sqlite3_value*, int, const void *,u8, 
+                        void(*)(void*));
+void sqlite3ValueFree(sqlite3_value*);
+sqlite3_value *sqlite3ValueNew(sqlite3 *);
+char *sqlite3Utf16to8(sqlite3 *, const void*, int, u8);
+#ifdef SQLITE_ENABLE_STAT3
+char *sqlite3Utf8to16(sqlite3 *, u8, char *, int, int *);
+#endif
+int sqlite3ValueFromExpr(sqlite3 *, Expr *, u8, u8, sqlite3_value **);
+void sqlite3ValueApplyAffinity(sqlite3_value *, u8, u8);
+#ifndef SQLITE_AMALGAMATION
+extern const unsigned char sqlite3OpcodeProperty[];
+extern const unsigned char sqlite3UpperToLower[];
+extern const unsigned char sqlite3CtypeMap[];
+extern const Token sqlite3IntTokens[];
+extern SQLITE_WSD struct Sqlite3Config sqlite3Config;
+extern SQLITE_WSD FuncDefHash sqlite3GlobalFunctions;
+#ifndef SQLITE_OMIT_WSD
+extern int sqlite3PendingByte;
+#endif
+#endif
+void sqlite3RootPageMoved(sqlite3*, int, int, int);
+void sqlite3Reindex(Parse*, Token*, Token*);
+void sqlite3AlterFunctions(void);
+void sqlite3AlterRenameTable(Parse*, SrcList*, Token*);
+int sqlite3GetToken(const unsigned char *, int *);
+void sqlite3NestedParse(Parse*, const char*, ...);
+void sqlite3ExpirePreparedStatements(sqlite3*);
+int sqlite3CodeSubselect(Parse *, Expr *, int, int);
+void sqlite3SelectPrep(Parse*, Select*, NameContext*);
+int sqlite3ResolveExprNames(NameContext*, Expr*);
+void sqlite3ResolveSelectNames(Parse*, Select*, NameContext*);
+int sqlite3ResolveOrderGroupBy(Parse*, Select*, ExprList*, const char*);
+void sqlite3ColumnDefault(Vdbe *, Table *, int, int);
+void sqlite3AlterFinishAddColumn(Parse *, Token *);
+void sqlite3AlterBeginAddColumn(Parse *, SrcList *);
+CollSeq *sqlite3GetCollSeq(sqlite3*, u8, CollSeq *, const char*);
+char sqlite3AffinityType(const char*);
+void sqlite3Analyze(Parse*, Token*, Token*);
+int sqlite3InvokeBusyHandler(BusyHandler*);
+int sqlite3FindDb(sqlite3*, Token*);
+int sqlite3FindDbName(sqlite3 *, const char *);
+int sqlite3AnalysisLoad(sqlite3*,int iDB);
+void sqlite3DeleteIndexSamples(sqlite3*,Index*);
+void sqlite3DefaultRowEst(Index*);
+void sqlite3RegisterLikeFunctions(sqlite3*, int);
+int sqlite3IsLikeFunction(sqlite3*,Expr*,int*,char*);
+void sqlite3MinimumFileFormat(Parse*, int, int);
+void sqlite3SchemaClear(void *);
+Schema *sqlite3SchemaGet(sqlite3 *, Btree *);
+int sqlite3SchemaToIndex(sqlite3 *db, Schema *);
+KeyInfo *sqlite3IndexKeyinfo(Parse *, Index *);
+int sqlite3CreateFunc(sqlite3 *, const char *, int, int, void *, 
+  void (*)(sqlite3_context*,int,sqlite3_value **),
+  void (*)(sqlite3_context*,int,sqlite3_value **), void (*)(sqlite3_context*),
+  FuncDestructor *pDestructor
+);
+int sqlite3ApiExit(sqlite3 *db, int);
+int sqlite3OpenTempDatabase(Parse *);
+
+void sqlite3StrAccumInit(StrAccum*, char*, int, int);
+void sqlite3StrAccumAppend(StrAccum*,const char*,int);
+char *sqlite3StrAccumFinish(StrAccum*);
+void sqlite3StrAccumReset(StrAccum*);
+void sqlite3SelectDestInit(SelectDest*,int,int);
+Expr *sqlite3CreateColumnExpr(sqlite3 *, SrcList *, int, int);
+
+void sqlite3BackupRestart(sqlite3_backup *);
+void sqlite3BackupUpdate(sqlite3_backup *, Pgno, const u8 *);
+
+/*
+** The interface to the LEMON-generated parser
+*/
+void *sqlite3ParserAlloc(void*(*)(size_t));
+void sqlite3ParserFree(void*, void(*)(void*));
+void sqlite3Parser(void*, int, Token, Parse*);
+#ifdef YYTRACKMAXSTACKDEPTH
+  int sqlite3ParserStackPeak(void*);
+#endif
+
+void sqlite3AutoLoadExtensions(sqlite3*);
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+  void sqlite3CloseExtensions(sqlite3*);
+#else
+# define sqlite3CloseExtensions(X)
+#endif
+
+#ifndef SQLITE_OMIT_SHARED_CACHE
+  void sqlite3TableLock(Parse *, int, int, u8, const char *);
+#else
+  #define sqlite3TableLock(v,w,x,y,z)
+#endif
+
+#ifdef SQLITE_TEST
+  int sqlite3Utf8To8(unsigned char*);
+#endif
+
+#ifdef SQLITE_OMIT_VIRTUALTABLE
+#  define sqlite3VtabClear(Y)
+#  define sqlite3VtabSync(X,Y) SQLITE_OK
+#  define sqlite3VtabRollback(X)
+#  define sqlite3VtabCommit(X)
+#  define sqlite3VtabInSync(db) 0
+#  define sqlite3VtabLock(X) 
+#  define sqlite3VtabUnlock(X)
+#  define sqlite3VtabUnlockList(X)
+#  define sqlite3VtabSavepoint(X, Y, Z) SQLITE_OK
+#  define sqlite3GetVTable(X,Y)  ((VTable*)0)
+#else
+   void sqlite3VtabClear(sqlite3 *db, Table*);
+   int sqlite3VtabSync(sqlite3 *db, char **);
+   int sqlite3VtabRollback(sqlite3 *db);
+   int sqlite3VtabCommit(sqlite3 *db);
+   void sqlite3VtabLock(VTable *);
+   void sqlite3VtabUnlock(VTable *);
+   void sqlite3VtabUnlockList(sqlite3*);
+   int sqlite3VtabSavepoint(sqlite3 *, int, int);
+   VTable *sqlite3GetVTable(sqlite3*, Table*);
+#  define sqlite3VtabInSync(db) ((db)->nVTrans>0 && (db)->aVTrans==0)
+#endif
+void sqlite3VtabMakeWritable(Parse*,Table*);
+void sqlite3VtabBeginParse(Parse*, Token*, Token*, Token*);
+void sqlite3VtabFinishParse(Parse*, Token*);
+void sqlite3VtabArgInit(Parse*);
+void sqlite3VtabArgExtend(Parse*, Token*);
+int sqlite3VtabCallCreate(sqlite3*, int, const char *, char **);
+int sqlite3VtabCallConnect(Parse*, Table*);
+int sqlite3VtabCallDestroy(sqlite3*, int, const char *);
+int sqlite3VtabBegin(sqlite3 *, VTable *);
+FuncDef *sqlite3VtabOverloadFunction(sqlite3 *,FuncDef*, int nArg, Expr*);
+void sqlite3InvalidFunction(sqlite3_context*,int,sqlite3_value**);
+int sqlite3VdbeParameterIndex(Vdbe*, const char*, int);
+int sqlite3TransferBindings(sqlite3_stmt *, sqlite3_stmt *);
+int sqlite3Reprepare(Vdbe*);
+void sqlite3ExprListCheckLength(Parse*, ExprList*, const char*);
+CollSeq *sqlite3BinaryCompareCollSeq(Parse *, Expr *, Expr *);
+int sqlite3TempInMemory(const sqlite3*);
+const char *sqlite3JournalModename(int);
+int sqlite3Checkpoint(sqlite3*, int, int, int*, int*);
+int sqlite3WalDefaultHook(void*,sqlite3*,const char*,int);
+
+/* Declarations for functions in fkey.c. All of these are replaced by
+** no-op macros if OMIT_FOREIGN_KEY is defined. In this case no foreign
+** key functionality is available. If OMIT_TRIGGER is defined but
+** OMIT_FOREIGN_KEY is not, only some of the functions are no-oped. In
+** this case foreign keys are parsed, but no other functionality is 
+** provided (enforcement of FK constraints requires the triggers sub-system).
+*/
+#if !defined(SQLITE_OMIT_FOREIGN_KEY) && !defined(SQLITE_OMIT_TRIGGER)
+  void sqlite3FkCheck(Parse*, Table*, int, int);
+  void sqlite3FkDropTable(Parse*, SrcList *, Table*);
+  void sqlite3FkActions(Parse*, Table*, ExprList*, int);
+  int sqlite3FkRequired(Parse*, Table*, int*, int);
+  u32 sqlite3FkOldmask(Parse*, Table*);
+  FKey *sqlite3FkReferences(Table *);
+#else
+  #define sqlite3FkActions(a,b,c,d)
+  #define sqlite3FkCheck(a,b,c,d)
+  #define sqlite3FkDropTable(a,b,c)
+  #define sqlite3FkOldmask(a,b)      0
+  #define sqlite3FkRequired(a,b,c,d) 0
+#endif
+#ifndef SQLITE_OMIT_FOREIGN_KEY
+  void sqlite3FkDelete(sqlite3 *, Table*);
+#else
+  #define sqlite3FkDelete(a,b)
+#endif
+
+
+/*
+** Available fault injectors.  Should be numbered beginning with 0.
+*/
+#define SQLITE_FAULTINJECTOR_MALLOC     0
+#define SQLITE_FAULTINJECTOR_COUNT      1
+
+/*
+** The interface to the code in fault.c used for identifying "benign"
+** malloc failures. This is only present if SQLITE_OMIT_BUILTIN_TEST
+** is not defined.
+*/
+#ifndef SQLITE_OMIT_BUILTIN_TEST
+  void sqlite3BeginBenignMalloc(void);
+  void sqlite3EndBenignMalloc(void);
+#else
+  #define sqlite3BeginBenignMalloc()
+  #define sqlite3EndBenignMalloc()
+#endif
+
+#define IN_INDEX_ROWID           1
+#define IN_INDEX_EPH             2
+#define IN_INDEX_INDEX           3
+int sqlite3FindInIndex(Parse *, Expr *, int*);
+
+#ifdef SQLITE_ENABLE_ATOMIC_WRITE
+  int sqlite3JournalOpen(sqlite3_vfs *, const char *, sqlite3_file *, int, int);
+  int sqlite3JournalSize(sqlite3_vfs *);
+  int sqlite3JournalCreate(sqlite3_file *);
+#else
+  #define sqlite3JournalSize(pVfs) ((pVfs)->szOsFile)
+#endif
+
+void sqlite3MemJournalOpen(sqlite3_file *);
+int sqlite3MemJournalSize(void);
+int sqlite3IsMemJournal(sqlite3_file *);
+
+#if SQLITE_MAX_EXPR_DEPTH>0
+  void sqlite3ExprSetHeight(Parse *pParse, Expr *p);
+  int sqlite3SelectExprHeight(Select *);
+  int sqlite3ExprCheckHeight(Parse*, int);
+#else
+  #define sqlite3ExprSetHeight(x,y)
+  #define sqlite3SelectExprHeight(x) 0
+  #define sqlite3ExprCheckHeight(x,y)
+#endif
+
+u32 sqlite3Get4byte(const u8*);
+void sqlite3Put4byte(u8*, u32);
+
+#ifdef SQLITE_ENABLE_UNLOCK_NOTIFY
+  void sqlite3ConnectionBlocked(sqlite3 *, sqlite3 *);
+  void sqlite3ConnectionUnlocked(sqlite3 *db);
+  void sqlite3ConnectionClosed(sqlite3 *db);
+#else
+  #define sqlite3ConnectionBlocked(x,y)
+  #define sqlite3ConnectionUnlocked(x)
+  #define sqlite3ConnectionClosed(x)
+#endif
+
+#ifdef SQLITE_DEBUG
+  void sqlite3ParserTrace(FILE*, char *);
+#endif
+
+/*
+** If the SQLITE_ENABLE IOTRACE exists then the global variable
+** sqlite3IoTrace is a pointer to a printf-like routine used to
+** print I/O tracing messages. 
+*/
+#ifdef SQLITE_ENABLE_IOTRACE
+# define IOTRACE(A)  if( sqlite3IoTrace ){ sqlite3IoTrace A; }
+  void sqlite3VdbeIOTraceSql(Vdbe*);
+SQLITE_EXTERN void (*sqlite3IoTrace)(const char*,...);
+#else
+# define IOTRACE(A)
+# define sqlite3VdbeIOTraceSql(X)
+#endif
+
+/*
+** These routines are available for the mem2.c debugging memory allocator
+** only.  They are used to verify that different "types" of memory
+** allocations are properly tracked by the system.
+**
+** sqlite3MemdebugSetType() sets the "type" of an allocation to one of
+** the MEMTYPE_* macros defined below.  The type must be a bitmask with
+** a single bit set.
+**
+** sqlite3MemdebugHasType() returns true if any of the bits in its second
+** argument match the type set by the previous sqlite3MemdebugSetType().
+** sqlite3MemdebugHasType() is intended for use inside assert() statements.
+**
+** sqlite3MemdebugNoType() returns true if none of the bits in its second
+** argument match the type set by the previous sqlite3MemdebugSetType().
+**
+** Perhaps the most important point is the difference between MEMTYPE_HEAP
+** and MEMTYPE_LOOKASIDE.  If an allocation is MEMTYPE_LOOKASIDE, that means
+** it might have been allocated by lookaside, except the allocation was
+** too large or lookaside was already full.  It is important to verify
+** that allocations that might have been satisfied by lookaside are not
+** passed back to non-lookaside free() routines.  Asserts such as the
+** example above are placed on the non-lookaside free() routines to verify
+** this constraint. 
+**
+** All of this is no-op for a production build.  It only comes into
+** play when the SQLITE_MEMDEBUG compile-time option is used.
+*/
+#ifdef SQLITE_MEMDEBUG
+  void sqlite3MemdebugSetType(void*,u8);
+  int sqlite3MemdebugHasType(void*,u8);
+  int sqlite3MemdebugNoType(void*,u8);
+#else
+# define sqlite3MemdebugSetType(X,Y)  /* no-op */
+# define sqlite3MemdebugHasType(X,Y)  1
+# define sqlite3MemdebugNoType(X,Y)   1
+#endif
+#define MEMTYPE_HEAP       0x01  /* General heap allocations */
+#define MEMTYPE_LOOKASIDE  0x02  /* Might have been lookaside memory */
+#define MEMTYPE_SCRATCH    0x04  /* Scratch allocations */
+#define MEMTYPE_PCACHE     0x08  /* Page cache allocations */
+#define MEMTYPE_DB         0x10  /* Uses sqlite3DbMalloc, not sqlite_malloc */
+
+#endif /* _SQLITEINT_H_ */
diff --git a/src/sqliteLimit.h b/src/sqliteLimit.h
new file mode 100644
index 0000000..c7aee53
--- /dev/null
+++ b/src/sqliteLimit.h
@@ -0,0 +1,208 @@
+/*
+** 2007 May 7
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** 
+** This file defines various limits of what SQLite can process.
+*/
+
+/*
+** The maximum length of a TEXT or BLOB in bytes.   This also
+** limits the size of a row in a table or index.
+**
+** The hard limit is the ability of a 32-bit signed integer
+** to count the size: 2^31-1 or 2147483647.
+*/
+#ifndef SQLITE_MAX_LENGTH
+# define SQLITE_MAX_LENGTH 1000000000
+#endif
+
+/*
+** This is the maximum number of
+**
+**    * Columns in a table
+**    * Columns in an index
+**    * Columns in a view
+**    * Terms in the SET clause of an UPDATE statement
+**    * Terms in the result set of a SELECT statement
+**    * Terms in the GROUP BY or ORDER BY clauses of a SELECT statement.
+**    * Terms in the VALUES clause of an INSERT statement
+**
+** The hard upper limit here is 32676.  Most database people will
+** tell you that in a well-normalized database, you usually should
+** not have more than a dozen or so columns in any table.  And if
+** that is the case, there is no point in having more than a few
+** dozen values in any of the other situations described above.
+*/
+#ifndef SQLITE_MAX_COLUMN
+# define SQLITE_MAX_COLUMN 2000
+#endif
+
+/*
+** The maximum length of a single SQL statement in bytes.
+**
+** It used to be the case that setting this value to zero would
+** turn the limit off.  That is no longer true.  It is not possible
+** to turn this limit off.
+*/
+#ifndef SQLITE_MAX_SQL_LENGTH
+# define SQLITE_MAX_SQL_LENGTH 1000000000
+#endif
+
+/*
+** The maximum depth of an expression tree. This is limited to 
+** some extent by SQLITE_MAX_SQL_LENGTH. But sometime you might 
+** want to place more severe limits on the complexity of an 
+** expression.
+**
+** A value of 0 used to mean that the limit was not enforced.
+** But that is no longer true.  The limit is now strictly enforced
+** at all times.
+*/
+#ifndef SQLITE_MAX_EXPR_DEPTH
+# define SQLITE_MAX_EXPR_DEPTH 1000
+#endif
+
+/*
+** The maximum number of terms in a compound SELECT statement.
+** The code generator for compound SELECT statements does one
+** level of recursion for each term.  A stack overflow can result
+** if the number of terms is too large.  In practice, most SQL
+** never has more than 3 or 4 terms.  Use a value of 0 to disable
+** any limit on the number of terms in a compount SELECT.
+*/
+#ifndef SQLITE_MAX_COMPOUND_SELECT
+# define SQLITE_MAX_COMPOUND_SELECT 500
+#endif
+
+/*
+** The maximum number of opcodes in a VDBE program.
+** Not currently enforced.
+*/
+#ifndef SQLITE_MAX_VDBE_OP
+# define SQLITE_MAX_VDBE_OP 25000
+#endif
+
+/*
+** The maximum number of arguments to an SQL function.
+*/
+#ifndef SQLITE_MAX_FUNCTION_ARG
+# define SQLITE_MAX_FUNCTION_ARG 127
+#endif
+
+/*
+** The maximum number of in-memory pages to use for the main database
+** table and for temporary tables.  The SQLITE_DEFAULT_CACHE_SIZE
+*/
+#ifndef SQLITE_DEFAULT_CACHE_SIZE
+# define SQLITE_DEFAULT_CACHE_SIZE  2000
+#endif
+#ifndef SQLITE_DEFAULT_TEMP_CACHE_SIZE
+# define SQLITE_DEFAULT_TEMP_CACHE_SIZE  500
+#endif
+
+/*
+** The default number of frames to accumulate in the log file before
+** checkpointing the database in WAL mode.
+*/
+#ifndef SQLITE_DEFAULT_WAL_AUTOCHECKPOINT
+# define SQLITE_DEFAULT_WAL_AUTOCHECKPOINT  1000
+#endif
+
+/*
+** The maximum number of attached databases.  This must be between 0
+** and 62.  The upper bound on 62 is because a 64-bit integer bitmap
+** is used internally to track attached databases.
+*/
+#ifndef SQLITE_MAX_ATTACHED
+# define SQLITE_MAX_ATTACHED 10
+#endif
+
+
+/*
+** The maximum value of a ?nnn wildcard that the parser will accept.
+*/
+#ifndef SQLITE_MAX_VARIABLE_NUMBER
+# define SQLITE_MAX_VARIABLE_NUMBER 999
+#endif
+
+/* Maximum page size.  The upper bound on this value is 65536.  This a limit
+** imposed by the use of 16-bit offsets within each page.
+**
+** Earlier versions of SQLite allowed the user to change this value at
+** compile time. This is no longer permitted, on the grounds that it creates
+** a library that is technically incompatible with an SQLite library 
+** compiled with a different limit. If a process operating on a database 
+** with a page-size of 65536 bytes crashes, then an instance of SQLite 
+** compiled with the default page-size limit will not be able to rollback 
+** the aborted transaction. This could lead to database corruption.
+*/
+#ifdef SQLITE_MAX_PAGE_SIZE
+# undef SQLITE_MAX_PAGE_SIZE
+#endif
+#define SQLITE_MAX_PAGE_SIZE 65536
+
+
+/*
+** The default size of a database page.
+*/
+#ifndef SQLITE_DEFAULT_PAGE_SIZE
+# define SQLITE_DEFAULT_PAGE_SIZE 1024
+#endif
+#if SQLITE_DEFAULT_PAGE_SIZE>SQLITE_MAX_PAGE_SIZE
+# undef SQLITE_DEFAULT_PAGE_SIZE
+# define SQLITE_DEFAULT_PAGE_SIZE SQLITE_MAX_PAGE_SIZE
+#endif
+
+/*
+** Ordinarily, if no value is explicitly provided, SQLite creates databases
+** with page size SQLITE_DEFAULT_PAGE_SIZE. However, based on certain
+** device characteristics (sector-size and atomic write() support),
+** SQLite may choose a larger value. This constant is the maximum value
+** SQLite will choose on its own.
+*/
+#ifndef SQLITE_MAX_DEFAULT_PAGE_SIZE
+# define SQLITE_MAX_DEFAULT_PAGE_SIZE 8192
+#endif
+#if SQLITE_MAX_DEFAULT_PAGE_SIZE>SQLITE_MAX_PAGE_SIZE
+# undef SQLITE_MAX_DEFAULT_PAGE_SIZE
+# define SQLITE_MAX_DEFAULT_PAGE_SIZE SQLITE_MAX_PAGE_SIZE
+#endif
+
+
+/*
+** Maximum number of pages in one database file.
+**
+** This is really just the default value for the max_page_count pragma.
+** This value can be lowered (or raised) at run-time using that the
+** max_page_count macro.
+*/
+#ifndef SQLITE_MAX_PAGE_COUNT
+# define SQLITE_MAX_PAGE_COUNT 1073741823
+#endif
+
+/*
+** Maximum length (in bytes) of the pattern in a LIKE or GLOB
+** operator.
+*/
+#ifndef SQLITE_MAX_LIKE_PATTERN_LENGTH
+# define SQLITE_MAX_LIKE_PATTERN_LENGTH 50000
+#endif
+
+/*
+** Maximum depth of recursion for triggers.
+**
+** A value of 1 means that a trigger program will not be able to itself
+** fire any triggers. A value of 0 means that no trigger programs at all 
+** may be executed.
+*/
+#ifndef SQLITE_MAX_TRIGGER_DEPTH
+# define SQLITE_MAX_TRIGGER_DEPTH 1000
+#endif
diff --git a/src/status.c b/src/status.c
new file mode 100644
index 0000000..b23238b
--- /dev/null
+++ b/src/status.c
@@ -0,0 +1,249 @@
+/*
+** 2008 June 18
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This module implements the sqlite3_status() interface and related
+** functionality.
+*/
+#include "sqliteInt.h"
+#include "vdbeInt.h"
+
+/*
+** Variables in which to record status information.
+*/
+typedef struct sqlite3StatType sqlite3StatType;
+static SQLITE_WSD struct sqlite3StatType {
+  int nowValue[10];         /* Current value */
+  int mxValue[10];          /* Maximum value */
+} sqlite3Stat = { {0,}, {0,} };
+
+
+/* The "wsdStat" macro will resolve to the status information
+** state vector.  If writable static data is unsupported on the target,
+** we have to locate the state vector at run-time.  In the more common
+** case where writable static data is supported, wsdStat can refer directly
+** to the "sqlite3Stat" state vector declared above.
+*/
+#ifdef SQLITE_OMIT_WSD
+# define wsdStatInit  sqlite3StatType *x = &GLOBAL(sqlite3StatType,sqlite3Stat)
+# define wsdStat x[0]
+#else
+# define wsdStatInit
+# define wsdStat sqlite3Stat
+#endif
+
+/*
+** Return the current value of a status parameter.
+*/
+int sqlite3StatusValue(int op){
+  wsdStatInit;
+  assert( op>=0 && op<ArraySize(wsdStat.nowValue) );
+  return wsdStat.nowValue[op];
+}
+
+/*
+** Add N to the value of a status record.  It is assumed that the
+** caller holds appropriate locks.
+*/
+void sqlite3StatusAdd(int op, int N){
+  wsdStatInit;
+  assert( op>=0 && op<ArraySize(wsdStat.nowValue) );
+  wsdStat.nowValue[op] += N;
+  if( wsdStat.nowValue[op]>wsdStat.mxValue[op] ){
+    wsdStat.mxValue[op] = wsdStat.nowValue[op];
+  }
+}
+
+/*
+** Set the value of a status to X.
+*/
+void sqlite3StatusSet(int op, int X){
+  wsdStatInit;
+  assert( op>=0 && op<ArraySize(wsdStat.nowValue) );
+  wsdStat.nowValue[op] = X;
+  if( wsdStat.nowValue[op]>wsdStat.mxValue[op] ){
+    wsdStat.mxValue[op] = wsdStat.nowValue[op];
+  }
+}
+
+/*
+** Query status information.
+**
+** This implementation assumes that reading or writing an aligned
+** 32-bit integer is an atomic operation.  If that assumption is not true,
+** then this routine is not threadsafe.
+*/
+int sqlite3_status(int op, int *pCurrent, int *pHighwater, int resetFlag){
+  wsdStatInit;
+  if( op<0 || op>=ArraySize(wsdStat.nowValue) ){
+    return SQLITE_MISUSE_BKPT;
+  }
+  *pCurrent = wsdStat.nowValue[op];
+  *pHighwater = wsdStat.mxValue[op];
+  if( resetFlag ){
+    wsdStat.mxValue[op] = wsdStat.nowValue[op];
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Query status information for a single database connection
+*/
+int sqlite3_db_status(
+  sqlite3 *db,          /* The database connection whose status is desired */
+  int op,               /* Status verb */
+  int *pCurrent,        /* Write current value here */
+  int *pHighwater,      /* Write high-water mark here */
+  int resetFlag         /* Reset high-water mark if true */
+){
+  int rc = SQLITE_OK;   /* Return code */
+  sqlite3_mutex_enter(db->mutex);
+  switch( op ){
+    case SQLITE_DBSTATUS_LOOKASIDE_USED: {
+      *pCurrent = db->lookaside.nOut;
+      *pHighwater = db->lookaside.mxOut;
+      if( resetFlag ){
+        db->lookaside.mxOut = db->lookaside.nOut;
+      }
+      break;
+    }
+
+    case SQLITE_DBSTATUS_LOOKASIDE_HIT:
+    case SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE:
+    case SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL: {
+      testcase( op==SQLITE_DBSTATUS_LOOKASIDE_HIT );
+      testcase( op==SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE );
+      testcase( op==SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL );
+      assert( (op-SQLITE_DBSTATUS_LOOKASIDE_HIT)>=0 );
+      assert( (op-SQLITE_DBSTATUS_LOOKASIDE_HIT)<3 );
+      *pCurrent = 0;
+      *pHighwater = db->lookaside.anStat[op - SQLITE_DBSTATUS_LOOKASIDE_HIT];
+      if( resetFlag ){
+        db->lookaside.anStat[op - SQLITE_DBSTATUS_LOOKASIDE_HIT] = 0;
+      }
+      break;
+    }
+
+    /* 
+    ** Return an approximation for the amount of memory currently used
+    ** by all pagers associated with the given database connection.  The
+    ** highwater mark is meaningless and is returned as zero.
+    */
+    case SQLITE_DBSTATUS_CACHE_USED: {
+      int totalUsed = 0;
+      int i;
+      sqlite3BtreeEnterAll(db);
+      for(i=0; i<db->nDb; i++){
+        Btree *pBt = db->aDb[i].pBt;
+        if( pBt ){
+          Pager *pPager = sqlite3BtreePager(pBt);
+          totalUsed += sqlite3PagerMemUsed(pPager);
+        }
+      }
+      sqlite3BtreeLeaveAll(db);
+      *pCurrent = totalUsed;
+      *pHighwater = 0;
+      break;
+    }
+
+    /*
+    ** *pCurrent gets an accurate estimate of the amount of memory used
+    ** to store the schema for all databases (main, temp, and any ATTACHed
+    ** databases.  *pHighwater is set to zero.
+    */
+    case SQLITE_DBSTATUS_SCHEMA_USED: {
+      int i;                      /* Used to iterate through schemas */
+      int nByte = 0;              /* Used to accumulate return value */
+
+      sqlite3BtreeEnterAll(db);
+      db->pnBytesFreed = &nByte;
+      for(i=0; i<db->nDb; i++){
+        Schema *pSchema = db->aDb[i].pSchema;
+        if( ALWAYS(pSchema!=0) ){
+          HashElem *p;
+
+          nByte += sqlite3GlobalConfig.m.xRoundup(sizeof(HashElem)) * (
+              pSchema->tblHash.count 
+            + pSchema->trigHash.count
+            + pSchema->idxHash.count
+            + pSchema->fkeyHash.count
+          );
+          nByte += sqlite3MallocSize(pSchema->tblHash.ht);
+          nByte += sqlite3MallocSize(pSchema->trigHash.ht);
+          nByte += sqlite3MallocSize(pSchema->idxHash.ht);
+          nByte += sqlite3MallocSize(pSchema->fkeyHash.ht);
+
+          for(p=sqliteHashFirst(&pSchema->trigHash); p; p=sqliteHashNext(p)){
+            sqlite3DeleteTrigger(db, (Trigger*)sqliteHashData(p));
+          }
+          for(p=sqliteHashFirst(&pSchema->tblHash); p; p=sqliteHashNext(p)){
+            sqlite3DeleteTable(db, (Table *)sqliteHashData(p));
+          }
+        }
+      }
+      db->pnBytesFreed = 0;
+      sqlite3BtreeLeaveAll(db);
+
+      *pHighwater = 0;
+      *pCurrent = nByte;
+      break;
+    }
+
+    /*
+    ** *pCurrent gets an accurate estimate of the amount of memory used
+    ** to store all prepared statements.
+    ** *pHighwater is set to zero.
+    */
+    case SQLITE_DBSTATUS_STMT_USED: {
+      struct Vdbe *pVdbe;         /* Used to iterate through VMs */
+      int nByte = 0;              /* Used to accumulate return value */
+
+      db->pnBytesFreed = &nByte;
+      for(pVdbe=db->pVdbe; pVdbe; pVdbe=pVdbe->pNext){
+        sqlite3VdbeDeleteObject(db, pVdbe);
+      }
+      db->pnBytesFreed = 0;
+
+      *pHighwater = 0;
+      *pCurrent = nByte;
+
+      break;
+    }
+
+    /*
+    ** Set *pCurrent to the total cache hits or misses encountered by all
+    ** pagers the database handle is connected to. *pHighwater is always set 
+    ** to zero.
+    */
+    case SQLITE_DBSTATUS_CACHE_HIT:
+    case SQLITE_DBSTATUS_CACHE_MISS: {
+      int i;
+      int nRet = 0;
+      assert( SQLITE_DBSTATUS_CACHE_MISS==SQLITE_DBSTATUS_CACHE_HIT+1 );
+
+      for(i=0; i<db->nDb; i++){
+        if( db->aDb[i].pBt ){
+          Pager *pPager = sqlite3BtreePager(db->aDb[i].pBt);
+          sqlite3PagerCacheStat(pPager, op, resetFlag, &nRet);
+        }
+      }
+      *pHighwater = 0;
+      *pCurrent = nRet;
+      break;
+    }
+
+    default: {
+      rc = SQLITE_ERROR;
+    }
+  }
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
diff --git a/src/table.c b/src/table.c
new file mode 100644
index 0000000..26bbfb4
--- /dev/null
+++ b/src/table.c
@@ -0,0 +1,197 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains the sqlite3_get_table() and sqlite3_free_table()
+** interface routines.  These are just wrappers around the main
+** interface routine of sqlite3_exec().
+**
+** These routines are in a separate files so that they will not be linked
+** if they are not used.
+*/
+#include "sqliteInt.h"
+#include <stdlib.h>
+#include <string.h>
+
+#ifndef SQLITE_OMIT_GET_TABLE
+
+/*
+** This structure is used to pass data from sqlite3_get_table() through
+** to the callback function is uses to build the result.
+*/
+typedef struct TabResult {
+  char **azResult;   /* Accumulated output */
+  char *zErrMsg;     /* Error message text, if an error occurs */
+  int nAlloc;        /* Slots allocated for azResult[] */
+  int nRow;          /* Number of rows in the result */
+  int nColumn;       /* Number of columns in the result */
+  int nData;         /* Slots used in azResult[].  (nRow+1)*nColumn */
+  int rc;            /* Return code from sqlite3_exec() */
+} TabResult;
+
+/*
+** This routine is called once for each row in the result table.  Its job
+** is to fill in the TabResult structure appropriately, allocating new
+** memory as necessary.
+*/
+static int sqlite3_get_table_cb(void *pArg, int nCol, char **argv, char **colv){
+  TabResult *p = (TabResult*)pArg;  /* Result accumulator */
+  int need;                         /* Slots needed in p->azResult[] */
+  int i;                            /* Loop counter */
+  char *z;                          /* A single column of result */
+
+  /* Make sure there is enough space in p->azResult to hold everything
+  ** we need to remember from this invocation of the callback.
+  */
+  if( p->nRow==0 && argv!=0 ){
+    need = nCol*2;
+  }else{
+    need = nCol;
+  }
+  if( p->nData + need > p->nAlloc ){
+    char **azNew;
+    p->nAlloc = p->nAlloc*2 + need;
+    azNew = sqlite3_realloc( p->azResult, sizeof(char*)*p->nAlloc );
+    if( azNew==0 ) goto malloc_failed;
+    p->azResult = azNew;
+  }
+
+  /* If this is the first row, then generate an extra row containing
+  ** the names of all columns.
+  */
+  if( p->nRow==0 ){
+    p->nColumn = nCol;
+    for(i=0; i<nCol; i++){
+      z = sqlite3_mprintf("%s", colv[i]);
+      if( z==0 ) goto malloc_failed;
+      p->azResult[p->nData++] = z;
+    }
+  }else if( p->nColumn!=nCol ){
+    sqlite3_free(p->zErrMsg);
+    p->zErrMsg = sqlite3_mprintf(
+       "sqlite3_get_table() called with two or more incompatible queries"
+    );
+    p->rc = SQLITE_ERROR;
+    return 1;
+  }
+
+  /* Copy over the row data
+  */
+  if( argv!=0 ){
+    for(i=0; i<nCol; i++){
+      if( argv[i]==0 ){
+        z = 0;
+      }else{
+        int n = sqlite3Strlen30(argv[i])+1;
+        z = sqlite3_malloc( n );
+        if( z==0 ) goto malloc_failed;
+        memcpy(z, argv[i], n);
+      }
+      p->azResult[p->nData++] = z;
+    }
+    p->nRow++;
+  }
+  return 0;
+
+malloc_failed:
+  p->rc = SQLITE_NOMEM;
+  return 1;
+}
+
+/*
+** Query the database.  But instead of invoking a callback for each row,
+** malloc() for space to hold the result and return the entire results
+** at the conclusion of the call.
+**
+** The result that is written to ***pazResult is held in memory obtained
+** from malloc().  But the caller cannot free this memory directly.  
+** Instead, the entire table should be passed to sqlite3_free_table() when
+** the calling procedure is finished using it.
+*/
+int sqlite3_get_table(
+  sqlite3 *db,                /* The database on which the SQL executes */
+  const char *zSql,           /* The SQL to be executed */
+  char ***pazResult,          /* Write the result table here */
+  int *pnRow,                 /* Write the number of rows in the result here */
+  int *pnColumn,              /* Write the number of columns of result here */
+  char **pzErrMsg             /* Write error messages here */
+){
+  int rc;
+  TabResult res;
+
+  *pazResult = 0;
+  if( pnColumn ) *pnColumn = 0;
+  if( pnRow ) *pnRow = 0;
+  if( pzErrMsg ) *pzErrMsg = 0;
+  res.zErrMsg = 0;
+  res.nRow = 0;
+  res.nColumn = 0;
+  res.nData = 1;
+  res.nAlloc = 20;
+  res.rc = SQLITE_OK;
+  res.azResult = sqlite3_malloc(sizeof(char*)*res.nAlloc );
+  if( res.azResult==0 ){
+     db->errCode = SQLITE_NOMEM;
+     return SQLITE_NOMEM;
+  }
+  res.azResult[0] = 0;
+  rc = sqlite3_exec(db, zSql, sqlite3_get_table_cb, &res, pzErrMsg);
+  assert( sizeof(res.azResult[0])>= sizeof(res.nData) );
+  res.azResult[0] = SQLITE_INT_TO_PTR(res.nData);
+  if( (rc&0xff)==SQLITE_ABORT ){
+    sqlite3_free_table(&res.azResult[1]);
+    if( res.zErrMsg ){
+      if( pzErrMsg ){
+        sqlite3_free(*pzErrMsg);
+        *pzErrMsg = sqlite3_mprintf("%s",res.zErrMsg);
+      }
+      sqlite3_free(res.zErrMsg);
+    }
+    db->errCode = res.rc;  /* Assume 32-bit assignment is atomic */
+    return res.rc;
+  }
+  sqlite3_free(res.zErrMsg);
+  if( rc!=SQLITE_OK ){
+    sqlite3_free_table(&res.azResult[1]);
+    return rc;
+  }
+  if( res.nAlloc>res.nData ){
+    char **azNew;
+    azNew = sqlite3_realloc( res.azResult, sizeof(char*)*res.nData );
+    if( azNew==0 ){
+      sqlite3_free_table(&res.azResult[1]);
+      db->errCode = SQLITE_NOMEM;
+      return SQLITE_NOMEM;
+    }
+    res.azResult = azNew;
+  }
+  *pazResult = &res.azResult[1];
+  if( pnColumn ) *pnColumn = res.nColumn;
+  if( pnRow ) *pnRow = res.nRow;
+  return rc;
+}
+
+/*
+** This routine frees the space the sqlite3_get_table() malloced.
+*/
+void sqlite3_free_table(
+  char **azResult            /* Result returned from from sqlite3_get_table() */
+){
+  if( azResult ){
+    int i, n;
+    azResult--;
+    assert( azResult!=0 );
+    n = SQLITE_PTR_TO_INT(azResult[0]);
+    for(i=1; i<n; i++){ if( azResult[i] ) sqlite3_free(azResult[i]); }
+    sqlite3_free(azResult);
+  }
+}
+
+#endif /* SQLITE_OMIT_GET_TABLE */
diff --git a/src/tclsqlite.c b/src/tclsqlite.c
new file mode 100644
index 0000000..c8f0fbd
--- /dev/null
+++ b/src/tclsqlite.c
@@ -0,0 +1,3804 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** A TCL Interface to SQLite.  Append this file to sqlite3.c and
+** compile the whole thing to build a TCL-enabled version of SQLite.
+**
+** Compile-time options:
+**
+**  -DTCLSH=1             Add a "main()" routine that works as a tclsh.
+**
+**  -DSQLITE_TCLMD5       When used in conjuction with -DTCLSH=1, add
+**                        four new commands to the TCL interpreter for
+**                        generating MD5 checksums:  md5, md5file,
+**                        md5-10x8, and md5file-10x8.
+**
+**  -DSQLITE_TEST         When used in conjuction with -DTCLSH=1, add
+**                        hundreds of new commands used for testing
+**                        SQLite.  This option implies -DSQLITE_TCLMD5.
+*/
+#include "tcl.h"
+#include <errno.h>
+
+/*
+** Some additional include files are needed if this file is not
+** appended to the amalgamation.
+*/
+#ifndef SQLITE_AMALGAMATION
+# include "sqlite3.h"
+# include <stdlib.h>
+# include <string.h>
+# include <assert.h>
+  typedef unsigned char u8;
+#endif
+#include <ctype.h>
+
+/*
+ * Windows needs to know which symbols to export.  Unix does not.
+ * BUILD_sqlite should be undefined for Unix.
+ */
+#ifdef BUILD_sqlite
+#undef TCL_STORAGE_CLASS
+#define TCL_STORAGE_CLASS DLLEXPORT
+#endif /* BUILD_sqlite */
+
+#define NUM_PREPARED_STMTS 10
+#define MAX_PREPARED_STMTS 100
+
+/*
+** If TCL uses UTF-8 and SQLite is configured to use iso8859, then we
+** have to do a translation when going between the two.  Set the 
+** UTF_TRANSLATION_NEEDED macro to indicate that we need to do
+** this translation.  
+*/
+#if defined(TCL_UTF_MAX) && !defined(SQLITE_UTF8)
+# define UTF_TRANSLATION_NEEDED 1
+#endif
+
+/*
+** New SQL functions can be created as TCL scripts.  Each such function
+** is described by an instance of the following structure.
+*/
+typedef struct SqlFunc SqlFunc;
+struct SqlFunc {
+  Tcl_Interp *interp;   /* The TCL interpret to execute the function */
+  Tcl_Obj *pScript;     /* The Tcl_Obj representation of the script */
+  int useEvalObjv;      /* True if it is safe to use Tcl_EvalObjv */
+  char *zName;          /* Name of this function */
+  SqlFunc *pNext;       /* Next function on the list of them all */
+};
+
+/*
+** New collation sequences function can be created as TCL scripts.  Each such
+** function is described by an instance of the following structure.
+*/
+typedef struct SqlCollate SqlCollate;
+struct SqlCollate {
+  Tcl_Interp *interp;   /* The TCL interpret to execute the function */
+  char *zScript;        /* The script to be run */
+  SqlCollate *pNext;    /* Next function on the list of them all */
+};
+
+/*
+** Prepared statements are cached for faster execution.  Each prepared
+** statement is described by an instance of the following structure.
+*/
+typedef struct SqlPreparedStmt SqlPreparedStmt;
+struct SqlPreparedStmt {
+  SqlPreparedStmt *pNext;  /* Next in linked list */
+  SqlPreparedStmt *pPrev;  /* Previous on the list */
+  sqlite3_stmt *pStmt;     /* The prepared statement */
+  int nSql;                /* chars in zSql[] */
+  const char *zSql;        /* Text of the SQL statement */
+  int nParm;               /* Size of apParm array */
+  Tcl_Obj **apParm;        /* Array of referenced object pointers */
+};
+
+typedef struct IncrblobChannel IncrblobChannel;
+
+/*
+** There is one instance of this structure for each SQLite database
+** that has been opened by the SQLite TCL interface.
+**
+** If this module is built with SQLITE_TEST defined (to create the SQLite
+** testfixture executable), then it may be configured to use either
+** sqlite3_prepare_v2() or sqlite3_prepare() to prepare SQL statements.
+** If SqliteDb.bLegacyPrepare is true, sqlite3_prepare() is used.
+*/
+typedef struct SqliteDb SqliteDb;
+struct SqliteDb {
+  sqlite3 *db;               /* The "real" database structure. MUST BE FIRST */
+  Tcl_Interp *interp;        /* The interpreter used for this database */
+  char *zBusy;               /* The busy callback routine */
+  char *zCommit;             /* The commit hook callback routine */
+  char *zTrace;              /* The trace callback routine */
+  char *zProfile;            /* The profile callback routine */
+  char *zProgress;           /* The progress callback routine */
+  char *zAuth;               /* The authorization callback routine */
+  int disableAuth;           /* Disable the authorizer if it exists */
+  char *zNull;               /* Text to substitute for an SQL NULL value */
+  SqlFunc *pFunc;            /* List of SQL functions */
+  Tcl_Obj *pUpdateHook;      /* Update hook script (if any) */
+  Tcl_Obj *pRollbackHook;    /* Rollback hook script (if any) */
+  Tcl_Obj *pWalHook;         /* WAL hook script (if any) */
+  Tcl_Obj *pUnlockNotify;    /* Unlock notify script (if any) */
+  SqlCollate *pCollate;      /* List of SQL collation functions */
+  int rc;                    /* Return code of most recent sqlite3_exec() */
+  Tcl_Obj *pCollateNeeded;   /* Collation needed script */
+  SqlPreparedStmt *stmtList; /* List of prepared statements*/
+  SqlPreparedStmt *stmtLast; /* Last statement in the list */
+  int maxStmt;               /* The next maximum number of stmtList */
+  int nStmt;                 /* Number of statements in stmtList */
+  IncrblobChannel *pIncrblob;/* Linked list of open incrblob channels */
+  int nStep, nSort, nIndex;  /* Statistics for most recent operation */
+  int nTransaction;          /* Number of nested [transaction] methods */
+#ifdef SQLITE_TEST
+  int bLegacyPrepare;        /* True to use sqlite3_prepare() */
+#endif
+};
+
+struct IncrblobChannel {
+  sqlite3_blob *pBlob;      /* sqlite3 blob handle */
+  SqliteDb *pDb;            /* Associated database connection */
+  int iSeek;                /* Current seek offset */
+  Tcl_Channel channel;      /* Channel identifier */
+  IncrblobChannel *pNext;   /* Linked list of all open incrblob channels */
+  IncrblobChannel *pPrev;   /* Linked list of all open incrblob channels */
+};
+
+/*
+** Compute a string length that is limited to what can be stored in
+** lower 30 bits of a 32-bit signed integer.
+*/
+static int strlen30(const char *z){
+  const char *z2 = z;
+  while( *z2 ){ z2++; }
+  return 0x3fffffff & (int)(z2 - z);
+}
+
+
+#ifndef SQLITE_OMIT_INCRBLOB
+/*
+** Close all incrblob channels opened using database connection pDb.
+** This is called when shutting down the database connection.
+*/
+static void closeIncrblobChannels(SqliteDb *pDb){
+  IncrblobChannel *p;
+  IncrblobChannel *pNext;
+
+  for(p=pDb->pIncrblob; p; p=pNext){
+    pNext = p->pNext;
+
+    /* Note: Calling unregister here call Tcl_Close on the incrblob channel, 
+    ** which deletes the IncrblobChannel structure at *p. So do not
+    ** call Tcl_Free() here.
+    */
+    Tcl_UnregisterChannel(pDb->interp, p->channel);
+  }
+}
+
+/*
+** Close an incremental blob channel.
+*/
+static int incrblobClose(ClientData instanceData, Tcl_Interp *interp){
+  IncrblobChannel *p = (IncrblobChannel *)instanceData;
+  int rc = sqlite3_blob_close(p->pBlob);
+  sqlite3 *db = p->pDb->db;
+
+  /* Remove the channel from the SqliteDb.pIncrblob list. */
+  if( p->pNext ){
+    p->pNext->pPrev = p->pPrev;
+  }
+  if( p->pPrev ){
+    p->pPrev->pNext = p->pNext;
+  }
+  if( p->pDb->pIncrblob==p ){
+    p->pDb->pIncrblob = p->pNext;
+  }
+
+  /* Free the IncrblobChannel structure */
+  Tcl_Free((char *)p);
+
+  if( rc!=SQLITE_OK ){
+    Tcl_SetResult(interp, (char *)sqlite3_errmsg(db), TCL_VOLATILE);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
+/*
+** Read data from an incremental blob channel.
+*/
+static int incrblobInput(
+  ClientData instanceData, 
+  char *buf, 
+  int bufSize,
+  int *errorCodePtr
+){
+  IncrblobChannel *p = (IncrblobChannel *)instanceData;
+  int nRead = bufSize;         /* Number of bytes to read */
+  int nBlob;                   /* Total size of the blob */
+  int rc;                      /* sqlite error code */
+
+  nBlob = sqlite3_blob_bytes(p->pBlob);
+  if( (p->iSeek+nRead)>nBlob ){
+    nRead = nBlob-p->iSeek;
+  }
+  if( nRead<=0 ){
+    return 0;
+  }
+
+  rc = sqlite3_blob_read(p->pBlob, (void *)buf, nRead, p->iSeek);
+  if( rc!=SQLITE_OK ){
+    *errorCodePtr = rc;
+    return -1;
+  }
+
+  p->iSeek += nRead;
+  return nRead;
+}
+
+/*
+** Write data to an incremental blob channel.
+*/
+static int incrblobOutput(
+  ClientData instanceData, 
+  CONST char *buf, 
+  int toWrite,
+  int *errorCodePtr
+){
+  IncrblobChannel *p = (IncrblobChannel *)instanceData;
+  int nWrite = toWrite;        /* Number of bytes to write */
+  int nBlob;                   /* Total size of the blob */
+  int rc;                      /* sqlite error code */
+
+  nBlob = sqlite3_blob_bytes(p->pBlob);
+  if( (p->iSeek+nWrite)>nBlob ){
+    *errorCodePtr = EINVAL;
+    return -1;
+  }
+  if( nWrite<=0 ){
+    return 0;
+  }
+
+  rc = sqlite3_blob_write(p->pBlob, (void *)buf, nWrite, p->iSeek);
+  if( rc!=SQLITE_OK ){
+    *errorCodePtr = EIO;
+    return -1;
+  }
+
+  p->iSeek += nWrite;
+  return nWrite;
+}
+
+/*
+** Seek an incremental blob channel.
+*/
+static int incrblobSeek(
+  ClientData instanceData, 
+  long offset,
+  int seekMode,
+  int *errorCodePtr
+){
+  IncrblobChannel *p = (IncrblobChannel *)instanceData;
+
+  switch( seekMode ){
+    case SEEK_SET:
+      p->iSeek = offset;
+      break;
+    case SEEK_CUR:
+      p->iSeek += offset;
+      break;
+    case SEEK_END:
+      p->iSeek = sqlite3_blob_bytes(p->pBlob) + offset;
+      break;
+
+    default: assert(!"Bad seekMode");
+  }
+
+  return p->iSeek;
+}
+
+
+static void incrblobWatch(ClientData instanceData, int mode){ 
+  /* NO-OP */ 
+}
+static int incrblobHandle(ClientData instanceData, int dir, ClientData *hPtr){
+  return TCL_ERROR;
+}
+
+static Tcl_ChannelType IncrblobChannelType = {
+  "incrblob",                        /* typeName                             */
+  TCL_CHANNEL_VERSION_2,             /* version                              */
+  incrblobClose,                     /* closeProc                            */
+  incrblobInput,                     /* inputProc                            */
+  incrblobOutput,                    /* outputProc                           */
+  incrblobSeek,                      /* seekProc                             */
+  0,                                 /* setOptionProc                        */
+  0,                                 /* getOptionProc                        */
+  incrblobWatch,                     /* watchProc (this is a no-op)          */
+  incrblobHandle,                    /* getHandleProc (always returns error) */
+  0,                                 /* close2Proc                           */
+  0,                                 /* blockModeProc                        */
+  0,                                 /* flushProc                            */
+  0,                                 /* handlerProc                          */
+  0,                                 /* wideSeekProc                         */
+};
+
+/*
+** Create a new incrblob channel.
+*/
+static int createIncrblobChannel(
+  Tcl_Interp *interp, 
+  SqliteDb *pDb, 
+  const char *zDb,
+  const char *zTable, 
+  const char *zColumn, 
+  sqlite_int64 iRow,
+  int isReadonly
+){
+  IncrblobChannel *p;
+  sqlite3 *db = pDb->db;
+  sqlite3_blob *pBlob;
+  int rc;
+  int flags = TCL_READABLE|(isReadonly ? 0 : TCL_WRITABLE);
+
+  /* This variable is used to name the channels: "incrblob_[incr count]" */
+  static int count = 0;
+  char zChannel[64];
+
+  rc = sqlite3_blob_open(db, zDb, zTable, zColumn, iRow, !isReadonly, &pBlob);
+  if( rc!=SQLITE_OK ){
+    Tcl_SetResult(interp, (char *)sqlite3_errmsg(pDb->db), TCL_VOLATILE);
+    return TCL_ERROR;
+  }
+
+  p = (IncrblobChannel *)Tcl_Alloc(sizeof(IncrblobChannel));
+  p->iSeek = 0;
+  p->pBlob = pBlob;
+
+  sqlite3_snprintf(sizeof(zChannel), zChannel, "incrblob_%d", ++count);
+  p->channel = Tcl_CreateChannel(&IncrblobChannelType, zChannel, p, flags);
+  Tcl_RegisterChannel(interp, p->channel);
+
+  /* Link the new channel into the SqliteDb.pIncrblob list. */
+  p->pNext = pDb->pIncrblob;
+  p->pPrev = 0;
+  if( p->pNext ){
+    p->pNext->pPrev = p;
+  }
+  pDb->pIncrblob = p;
+  p->pDb = pDb;
+
+  Tcl_SetResult(interp, (char *)Tcl_GetChannelName(p->channel), TCL_VOLATILE);
+  return TCL_OK;
+}
+#else  /* else clause for "#ifndef SQLITE_OMIT_INCRBLOB" */
+  #define closeIncrblobChannels(pDb)
+#endif
+
+/*
+** Look at the script prefix in pCmd.  We will be executing this script
+** after first appending one or more arguments.  This routine analyzes
+** the script to see if it is safe to use Tcl_EvalObjv() on the script
+** rather than the more general Tcl_EvalEx().  Tcl_EvalObjv() is much
+** faster.
+**
+** Scripts that are safe to use with Tcl_EvalObjv() consists of a
+** command name followed by zero or more arguments with no [...] or $
+** or {...} or ; to be seen anywhere.  Most callback scripts consist
+** of just a single procedure name and they meet this requirement.
+*/
+static int safeToUseEvalObjv(Tcl_Interp *interp, Tcl_Obj *pCmd){
+  /* We could try to do something with Tcl_Parse().  But we will instead
+  ** just do a search for forbidden characters.  If any of the forbidden
+  ** characters appear in pCmd, we will report the string as unsafe.
+  */
+  const char *z;
+  int n;
+  z = Tcl_GetStringFromObj(pCmd, &n);
+  while( n-- > 0 ){
+    int c = *(z++);
+    if( c=='$' || c=='[' || c==';' ) return 0;
+  }
+  return 1;
+}
+
+/*
+** Find an SqlFunc structure with the given name.  Or create a new
+** one if an existing one cannot be found.  Return a pointer to the
+** structure.
+*/
+static SqlFunc *findSqlFunc(SqliteDb *pDb, const char *zName){
+  SqlFunc *p, *pNew;
+  int i;
+  pNew = (SqlFunc*)Tcl_Alloc( sizeof(*pNew) + strlen30(zName) + 1 );
+  pNew->zName = (char*)&pNew[1];
+  for(i=0; zName[i]; i++){ pNew->zName[i] = tolower(zName[i]); }
+  pNew->zName[i] = 0;
+  for(p=pDb->pFunc; p; p=p->pNext){ 
+    if( strcmp(p->zName, pNew->zName)==0 ){
+      Tcl_Free((char*)pNew);
+      return p;
+    }
+  }
+  pNew->interp = pDb->interp;
+  pNew->pScript = 0;
+  pNew->pNext = pDb->pFunc;
+  pDb->pFunc = pNew;
+  return pNew;
+}
+
+/*
+** Free a single SqlPreparedStmt object.
+*/
+static void dbFreeStmt(SqlPreparedStmt *pStmt){
+#ifdef SQLITE_TEST
+  if( sqlite3_sql(pStmt->pStmt)==0 ){
+    Tcl_Free((char *)pStmt->zSql);
+  }
+#endif
+  sqlite3_finalize(pStmt->pStmt);
+  Tcl_Free((char *)pStmt);
+}
+
+/*
+** Finalize and free a list of prepared statements
+*/
+static void flushStmtCache(SqliteDb *pDb){
+  SqlPreparedStmt *pPreStmt;
+  SqlPreparedStmt *pNext;
+
+  for(pPreStmt = pDb->stmtList; pPreStmt; pPreStmt=pNext){
+    pNext = pPreStmt->pNext;
+    dbFreeStmt(pPreStmt);
+  }
+  pDb->nStmt = 0;
+  pDb->stmtLast = 0;
+  pDb->stmtList = 0;
+}
+
+/*
+** TCL calls this procedure when an sqlite3 database command is
+** deleted.
+*/
+static void DbDeleteCmd(void *db){
+  SqliteDb *pDb = (SqliteDb*)db;
+  flushStmtCache(pDb);
+  closeIncrblobChannels(pDb);
+  sqlite3_close(pDb->db);
+  while( pDb->pFunc ){
+    SqlFunc *pFunc = pDb->pFunc;
+    pDb->pFunc = pFunc->pNext;
+    Tcl_DecrRefCount(pFunc->pScript);
+    Tcl_Free((char*)pFunc);
+  }
+  while( pDb->pCollate ){
+    SqlCollate *pCollate = pDb->pCollate;
+    pDb->pCollate = pCollate->pNext;
+    Tcl_Free((char*)pCollate);
+  }
+  if( pDb->zBusy ){
+    Tcl_Free(pDb->zBusy);
+  }
+  if( pDb->zTrace ){
+    Tcl_Free(pDb->zTrace);
+  }
+  if( pDb->zProfile ){
+    Tcl_Free(pDb->zProfile);
+  }
+  if( pDb->zAuth ){
+    Tcl_Free(pDb->zAuth);
+  }
+  if( pDb->zNull ){
+    Tcl_Free(pDb->zNull);
+  }
+  if( pDb->pUpdateHook ){
+    Tcl_DecrRefCount(pDb->pUpdateHook);
+  }
+  if( pDb->pRollbackHook ){
+    Tcl_DecrRefCount(pDb->pRollbackHook);
+  }
+  if( pDb->pWalHook ){
+    Tcl_DecrRefCount(pDb->pWalHook);
+  }
+  if( pDb->pCollateNeeded ){
+    Tcl_DecrRefCount(pDb->pCollateNeeded);
+  }
+  Tcl_Free((char*)pDb);
+}
+
+/*
+** This routine is called when a database file is locked while trying
+** to execute SQL.
+*/
+static int DbBusyHandler(void *cd, int nTries){
+  SqliteDb *pDb = (SqliteDb*)cd;
+  int rc;
+  char zVal[30];
+
+  sqlite3_snprintf(sizeof(zVal), zVal, "%d", nTries);
+  rc = Tcl_VarEval(pDb->interp, pDb->zBusy, " ", zVal, (char*)0);
+  if( rc!=TCL_OK || atoi(Tcl_GetStringResult(pDb->interp)) ){
+    return 0;
+  }
+  return 1;
+}
+
+#ifndef SQLITE_OMIT_PROGRESS_CALLBACK
+/*
+** This routine is invoked as the 'progress callback' for the database.
+*/
+static int DbProgressHandler(void *cd){
+  SqliteDb *pDb = (SqliteDb*)cd;
+  int rc;
+
+  assert( pDb->zProgress );
+  rc = Tcl_Eval(pDb->interp, pDb->zProgress);
+  if( rc!=TCL_OK || atoi(Tcl_GetStringResult(pDb->interp)) ){
+    return 1;
+  }
+  return 0;
+}
+#endif
+
+#ifndef SQLITE_OMIT_TRACE
+/*
+** This routine is called by the SQLite trace handler whenever a new
+** block of SQL is executed.  The TCL script in pDb->zTrace is executed.
+*/
+static void DbTraceHandler(void *cd, const char *zSql){
+  SqliteDb *pDb = (SqliteDb*)cd;
+  Tcl_DString str;
+
+  Tcl_DStringInit(&str);
+  Tcl_DStringAppend(&str, pDb->zTrace, -1);
+  Tcl_DStringAppendElement(&str, zSql);
+  Tcl_Eval(pDb->interp, Tcl_DStringValue(&str));
+  Tcl_DStringFree(&str);
+  Tcl_ResetResult(pDb->interp);
+}
+#endif
+
+#ifndef SQLITE_OMIT_TRACE
+/*
+** This routine is called by the SQLite profile handler after a statement
+** SQL has executed.  The TCL script in pDb->zProfile is evaluated.
+*/
+static void DbProfileHandler(void *cd, const char *zSql, sqlite_uint64 tm){
+  SqliteDb *pDb = (SqliteDb*)cd;
+  Tcl_DString str;
+  char zTm[100];
+
+  sqlite3_snprintf(sizeof(zTm)-1, zTm, "%lld", tm);
+  Tcl_DStringInit(&str);
+  Tcl_DStringAppend(&str, pDb->zProfile, -1);
+  Tcl_DStringAppendElement(&str, zSql);
+  Tcl_DStringAppendElement(&str, zTm);
+  Tcl_Eval(pDb->interp, Tcl_DStringValue(&str));
+  Tcl_DStringFree(&str);
+  Tcl_ResetResult(pDb->interp);
+}
+#endif
+
+/*
+** This routine is called when a transaction is committed.  The
+** TCL script in pDb->zCommit is executed.  If it returns non-zero or
+** if it throws an exception, the transaction is rolled back instead
+** of being committed.
+*/
+static int DbCommitHandler(void *cd){
+  SqliteDb *pDb = (SqliteDb*)cd;
+  int rc;
+
+  rc = Tcl_Eval(pDb->interp, pDb->zCommit);
+  if( rc!=TCL_OK || atoi(Tcl_GetStringResult(pDb->interp)) ){
+    return 1;
+  }
+  return 0;
+}
+
+static void DbRollbackHandler(void *clientData){
+  SqliteDb *pDb = (SqliteDb*)clientData;
+  assert(pDb->pRollbackHook);
+  if( TCL_OK!=Tcl_EvalObjEx(pDb->interp, pDb->pRollbackHook, 0) ){
+    Tcl_BackgroundError(pDb->interp);
+  }
+}
+
+/*
+** This procedure handles wal_hook callbacks.
+*/
+static int DbWalHandler(
+  void *clientData, 
+  sqlite3 *db, 
+  const char *zDb, 
+  int nEntry
+){
+  int ret = SQLITE_OK;
+  Tcl_Obj *p;
+  SqliteDb *pDb = (SqliteDb*)clientData;
+  Tcl_Interp *interp = pDb->interp;
+  assert(pDb->pWalHook);
+
+  p = Tcl_DuplicateObj(pDb->pWalHook);
+  Tcl_IncrRefCount(p);
+  Tcl_ListObjAppendElement(interp, p, Tcl_NewStringObj(zDb, -1));
+  Tcl_ListObjAppendElement(interp, p, Tcl_NewIntObj(nEntry));
+  if( TCL_OK!=Tcl_EvalObjEx(interp, p, 0) 
+   || TCL_OK!=Tcl_GetIntFromObj(interp, Tcl_GetObjResult(interp), &ret)
+  ){
+    Tcl_BackgroundError(interp);
+  }
+  Tcl_DecrRefCount(p);
+
+  return ret;
+}
+
+#if defined(SQLITE_TEST) && defined(SQLITE_ENABLE_UNLOCK_NOTIFY)
+static void setTestUnlockNotifyVars(Tcl_Interp *interp, int iArg, int nArg){
+  char zBuf[64];
+  sprintf(zBuf, "%d", iArg);
+  Tcl_SetVar(interp, "sqlite_unlock_notify_arg", zBuf, TCL_GLOBAL_ONLY);
+  sprintf(zBuf, "%d", nArg);
+  Tcl_SetVar(interp, "sqlite_unlock_notify_argcount", zBuf, TCL_GLOBAL_ONLY);
+}
+#else
+# define setTestUnlockNotifyVars(x,y,z)
+#endif
+
+#ifdef SQLITE_ENABLE_UNLOCK_NOTIFY
+static void DbUnlockNotify(void **apArg, int nArg){
+  int i;
+  for(i=0; i<nArg; i++){
+    const int flags = (TCL_EVAL_GLOBAL|TCL_EVAL_DIRECT);
+    SqliteDb *pDb = (SqliteDb *)apArg[i];
+    setTestUnlockNotifyVars(pDb->interp, i, nArg);
+    assert( pDb->pUnlockNotify);
+    Tcl_EvalObjEx(pDb->interp, pDb->pUnlockNotify, flags);
+    Tcl_DecrRefCount(pDb->pUnlockNotify);
+    pDb->pUnlockNotify = 0;
+  }
+}
+#endif
+
+static void DbUpdateHandler(
+  void *p, 
+  int op,
+  const char *zDb, 
+  const char *zTbl, 
+  sqlite_int64 rowid
+){
+  SqliteDb *pDb = (SqliteDb *)p;
+  Tcl_Obj *pCmd;
+
+  assert( pDb->pUpdateHook );
+  assert( op==SQLITE_INSERT || op==SQLITE_UPDATE || op==SQLITE_DELETE );
+
+  pCmd = Tcl_DuplicateObj(pDb->pUpdateHook);
+  Tcl_IncrRefCount(pCmd);
+  Tcl_ListObjAppendElement(0, pCmd, Tcl_NewStringObj(
+    ( (op==SQLITE_INSERT)?"INSERT":(op==SQLITE_UPDATE)?"UPDATE":"DELETE"), -1));
+  Tcl_ListObjAppendElement(0, pCmd, Tcl_NewStringObj(zDb, -1));
+  Tcl_ListObjAppendElement(0, pCmd, Tcl_NewStringObj(zTbl, -1));
+  Tcl_ListObjAppendElement(0, pCmd, Tcl_NewWideIntObj(rowid));
+  Tcl_EvalObjEx(pDb->interp, pCmd, TCL_EVAL_DIRECT);
+  Tcl_DecrRefCount(pCmd);
+}
+
+static void tclCollateNeeded(
+  void *pCtx,
+  sqlite3 *db,
+  int enc,
+  const char *zName
+){
+  SqliteDb *pDb = (SqliteDb *)pCtx;
+  Tcl_Obj *pScript = Tcl_DuplicateObj(pDb->pCollateNeeded);
+  Tcl_IncrRefCount(pScript);
+  Tcl_ListObjAppendElement(0, pScript, Tcl_NewStringObj(zName, -1));
+  Tcl_EvalObjEx(pDb->interp, pScript, 0);
+  Tcl_DecrRefCount(pScript);
+}
+
+/*
+** This routine is called to evaluate an SQL collation function implemented
+** using TCL script.
+*/
+static int tclSqlCollate(
+  void *pCtx,
+  int nA,
+  const void *zA,
+  int nB,
+  const void *zB
+){
+  SqlCollate *p = (SqlCollate *)pCtx;
+  Tcl_Obj *pCmd;
+
+  pCmd = Tcl_NewStringObj(p->zScript, -1);
+  Tcl_IncrRefCount(pCmd);
+  Tcl_ListObjAppendElement(p->interp, pCmd, Tcl_NewStringObj(zA, nA));
+  Tcl_ListObjAppendElement(p->interp, pCmd, Tcl_NewStringObj(zB, nB));
+  Tcl_EvalObjEx(p->interp, pCmd, TCL_EVAL_DIRECT);
+  Tcl_DecrRefCount(pCmd);
+  return (atoi(Tcl_GetStringResult(p->interp)));
+}
+
+/*
+** This routine is called to evaluate an SQL function implemented
+** using TCL script.
+*/
+static void tclSqlFunc(sqlite3_context *context, int argc, sqlite3_value**argv){
+  SqlFunc *p = sqlite3_user_data(context);
+  Tcl_Obj *pCmd;
+  int i;
+  int rc;
+
+  if( argc==0 ){
+    /* If there are no arguments to the function, call Tcl_EvalObjEx on the
+    ** script object directly.  This allows the TCL compiler to generate
+    ** bytecode for the command on the first invocation and thus make
+    ** subsequent invocations much faster. */
+    pCmd = p->pScript;
+    Tcl_IncrRefCount(pCmd);
+    rc = Tcl_EvalObjEx(p->interp, pCmd, 0);
+    Tcl_DecrRefCount(pCmd);
+  }else{
+    /* If there are arguments to the function, make a shallow copy of the
+    ** script object, lappend the arguments, then evaluate the copy.
+    **
+    ** By "shallow" copy, we mean a only the outer list Tcl_Obj is duplicated.
+    ** The new Tcl_Obj contains pointers to the original list elements. 
+    ** That way, when Tcl_EvalObjv() is run and shimmers the first element
+    ** of the list to tclCmdNameType, that alternate representation will
+    ** be preserved and reused on the next invocation.
+    */
+    Tcl_Obj **aArg;
+    int nArg;
+    if( Tcl_ListObjGetElements(p->interp, p->pScript, &nArg, &aArg) ){
+      sqlite3_result_error(context, Tcl_GetStringResult(p->interp), -1); 
+      return;
+    }     
+    pCmd = Tcl_NewListObj(nArg, aArg);
+    Tcl_IncrRefCount(pCmd);
+    for(i=0; i<argc; i++){
+      sqlite3_value *pIn = argv[i];
+      Tcl_Obj *pVal;
+            
+      /* Set pVal to contain the i'th column of this row. */
+      switch( sqlite3_value_type(pIn) ){
+        case SQLITE_BLOB: {
+          int bytes = sqlite3_value_bytes(pIn);
+          pVal = Tcl_NewByteArrayObj(sqlite3_value_blob(pIn), bytes);
+          break;
+        }
+        case SQLITE_INTEGER: {
+          sqlite_int64 v = sqlite3_value_int64(pIn);
+          if( v>=-2147483647 && v<=2147483647 ){
+            pVal = Tcl_NewIntObj((int)v);
+          }else{
+            pVal = Tcl_NewWideIntObj(v);
+          }
+          break;
+        }
+        case SQLITE_FLOAT: {
+          double r = sqlite3_value_double(pIn);
+          pVal = Tcl_NewDoubleObj(r);
+          break;
+        }
+        case SQLITE_NULL: {
+          pVal = Tcl_NewStringObj("", 0);
+          break;
+        }
+        default: {
+          int bytes = sqlite3_value_bytes(pIn);
+          pVal = Tcl_NewStringObj((char *)sqlite3_value_text(pIn), bytes);
+          break;
+        }
+      }
+      rc = Tcl_ListObjAppendElement(p->interp, pCmd, pVal);
+      if( rc ){
+        Tcl_DecrRefCount(pCmd);
+        sqlite3_result_error(context, Tcl_GetStringResult(p->interp), -1); 
+        return;
+      }
+    }
+    if( !p->useEvalObjv ){
+      /* Tcl_EvalObjEx() will automatically call Tcl_EvalObjv() if pCmd
+      ** is a list without a string representation.  To prevent this from
+      ** happening, make sure pCmd has a valid string representation */
+      Tcl_GetString(pCmd);
+    }
+    rc = Tcl_EvalObjEx(p->interp, pCmd, TCL_EVAL_DIRECT);
+    Tcl_DecrRefCount(pCmd);
+  }
+
+  if( rc && rc!=TCL_RETURN ){
+    sqlite3_result_error(context, Tcl_GetStringResult(p->interp), -1); 
+  }else{
+    Tcl_Obj *pVar = Tcl_GetObjResult(p->interp);
+    int n;
+    u8 *data;
+    const char *zType = (pVar->typePtr ? pVar->typePtr->name : "");
+    char c = zType[0];
+    if( c=='b' && strcmp(zType,"bytearray")==0 && pVar->bytes==0 ){
+      /* Only return a BLOB type if the Tcl variable is a bytearray and
+      ** has no string representation. */
+      data = Tcl_GetByteArrayFromObj(pVar, &n);
+      sqlite3_result_blob(context, data, n, SQLITE_TRANSIENT);
+    }else if( c=='b' && strcmp(zType,"boolean")==0 ){
+      Tcl_GetIntFromObj(0, pVar, &n);
+      sqlite3_result_int(context, n);
+    }else if( c=='d' && strcmp(zType,"double")==0 ){
+      double r;
+      Tcl_GetDoubleFromObj(0, pVar, &r);
+      sqlite3_result_double(context, r);
+    }else if( (c=='w' && strcmp(zType,"wideInt")==0) ||
+          (c=='i' && strcmp(zType,"int")==0) ){
+      Tcl_WideInt v;
+      Tcl_GetWideIntFromObj(0, pVar, &v);
+      sqlite3_result_int64(context, v);
+    }else{
+      data = (unsigned char *)Tcl_GetStringFromObj(pVar, &n);
+      sqlite3_result_text(context, (char *)data, n, SQLITE_TRANSIENT);
+    }
+  }
+}
+
+#ifndef SQLITE_OMIT_AUTHORIZATION
+/*
+** This is the authentication function.  It appends the authentication
+** type code and the two arguments to zCmd[] then invokes the result
+** on the interpreter.  The reply is examined to determine if the
+** authentication fails or succeeds.
+*/
+static int auth_callback(
+  void *pArg,
+  int code,
+  const char *zArg1,
+  const char *zArg2,
+  const char *zArg3,
+  const char *zArg4
+){
+  char *zCode;
+  Tcl_DString str;
+  int rc;
+  const char *zReply;
+  SqliteDb *pDb = (SqliteDb*)pArg;
+  if( pDb->disableAuth ) return SQLITE_OK;
+
+  switch( code ){
+    case SQLITE_COPY              : zCode="SQLITE_COPY"; break;
+    case SQLITE_CREATE_INDEX      : zCode="SQLITE_CREATE_INDEX"; break;
+    case SQLITE_CREATE_TABLE      : zCode="SQLITE_CREATE_TABLE"; break;
+    case SQLITE_CREATE_TEMP_INDEX : zCode="SQLITE_CREATE_TEMP_INDEX"; break;
+    case SQLITE_CREATE_TEMP_TABLE : zCode="SQLITE_CREATE_TEMP_TABLE"; break;
+    case SQLITE_CREATE_TEMP_TRIGGER: zCode="SQLITE_CREATE_TEMP_TRIGGER"; break;
+    case SQLITE_CREATE_TEMP_VIEW  : zCode="SQLITE_CREATE_TEMP_VIEW"; break;
+    case SQLITE_CREATE_TRIGGER    : zCode="SQLITE_CREATE_TRIGGER"; break;
+    case SQLITE_CREATE_VIEW       : zCode="SQLITE_CREATE_VIEW"; break;
+    case SQLITE_DELETE            : zCode="SQLITE_DELETE"; break;
+    case SQLITE_DROP_INDEX        : zCode="SQLITE_DROP_INDEX"; break;
+    case SQLITE_DROP_TABLE        : zCode="SQLITE_DROP_TABLE"; break;
+    case SQLITE_DROP_TEMP_INDEX   : zCode="SQLITE_DROP_TEMP_INDEX"; break;
+    case SQLITE_DROP_TEMP_TABLE   : zCode="SQLITE_DROP_TEMP_TABLE"; break;
+    case SQLITE_DROP_TEMP_TRIGGER : zCode="SQLITE_DROP_TEMP_TRIGGER"; break;
+    case SQLITE_DROP_TEMP_VIEW    : zCode="SQLITE_DROP_TEMP_VIEW"; break;
+    case SQLITE_DROP_TRIGGER      : zCode="SQLITE_DROP_TRIGGER"; break;
+    case SQLITE_DROP_VIEW         : zCode="SQLITE_DROP_VIEW"; break;
+    case SQLITE_INSERT            : zCode="SQLITE_INSERT"; break;
+    case SQLITE_PRAGMA            : zCode="SQLITE_PRAGMA"; break;
+    case SQLITE_READ              : zCode="SQLITE_READ"; break;
+    case SQLITE_SELECT            : zCode="SQLITE_SELECT"; break;
+    case SQLITE_TRANSACTION       : zCode="SQLITE_TRANSACTION"; break;
+    case SQLITE_UPDATE            : zCode="SQLITE_UPDATE"; break;
+    case SQLITE_ATTACH            : zCode="SQLITE_ATTACH"; break;
+    case SQLITE_DETACH            : zCode="SQLITE_DETACH"; break;
+    case SQLITE_ALTER_TABLE       : zCode="SQLITE_ALTER_TABLE"; break;
+    case SQLITE_REINDEX           : zCode="SQLITE_REINDEX"; break;
+    case SQLITE_ANALYZE           : zCode="SQLITE_ANALYZE"; break;
+    case SQLITE_CREATE_VTABLE     : zCode="SQLITE_CREATE_VTABLE"; break;
+    case SQLITE_DROP_VTABLE       : zCode="SQLITE_DROP_VTABLE"; break;
+    case SQLITE_FUNCTION          : zCode="SQLITE_FUNCTION"; break;
+    case SQLITE_SAVEPOINT         : zCode="SQLITE_SAVEPOINT"; break;
+    default                       : zCode="????"; break;
+  }
+  Tcl_DStringInit(&str);
+  Tcl_DStringAppend(&str, pDb->zAuth, -1);
+  Tcl_DStringAppendElement(&str, zCode);
+  Tcl_DStringAppendElement(&str, zArg1 ? zArg1 : "");
+  Tcl_DStringAppendElement(&str, zArg2 ? zArg2 : "");
+  Tcl_DStringAppendElement(&str, zArg3 ? zArg3 : "");
+  Tcl_DStringAppendElement(&str, zArg4 ? zArg4 : "");
+  rc = Tcl_GlobalEval(pDb->interp, Tcl_DStringValue(&str));
+  Tcl_DStringFree(&str);
+  zReply = rc==TCL_OK ? Tcl_GetStringResult(pDb->interp) : "SQLITE_DENY";
+  if( strcmp(zReply,"SQLITE_OK")==0 ){
+    rc = SQLITE_OK;
+  }else if( strcmp(zReply,"SQLITE_DENY")==0 ){
+    rc = SQLITE_DENY;
+  }else if( strcmp(zReply,"SQLITE_IGNORE")==0 ){
+    rc = SQLITE_IGNORE;
+  }else{
+    rc = 999;
+  }
+  return rc;
+}
+#endif /* SQLITE_OMIT_AUTHORIZATION */
+
+/*
+** zText is a pointer to text obtained via an sqlite3_result_text()
+** or similar interface. This routine returns a Tcl string object, 
+** reference count set to 0, containing the text. If a translation
+** between iso8859 and UTF-8 is required, it is preformed.
+*/
+static Tcl_Obj *dbTextToObj(char const *zText){
+  Tcl_Obj *pVal;
+#ifdef UTF_TRANSLATION_NEEDED
+  Tcl_DString dCol;
+  Tcl_DStringInit(&dCol);
+  Tcl_ExternalToUtfDString(NULL, zText, -1, &dCol);
+  pVal = Tcl_NewStringObj(Tcl_DStringValue(&dCol), -1);
+  Tcl_DStringFree(&dCol);
+#else
+  pVal = Tcl_NewStringObj(zText, -1);
+#endif
+  return pVal;
+}
+
+/*
+** This routine reads a line of text from FILE in, stores
+** the text in memory obtained from malloc() and returns a pointer
+** to the text.  NULL is returned at end of file, or if malloc()
+** fails.
+**
+** The interface is like "readline" but no command-line editing
+** is done.
+**
+** copied from shell.c from '.import' command
+*/
+static char *local_getline(char *zPrompt, FILE *in){
+  char *zLine;
+  int nLine;
+  int n;
+
+  nLine = 100;
+  zLine = malloc( nLine );
+  if( zLine==0 ) return 0;
+  n = 0;
+  while( 1 ){
+    if( n+100>nLine ){
+      nLine = nLine*2 + 100;
+      zLine = realloc(zLine, nLine);
+      if( zLine==0 ) return 0;
+    }
+    if( fgets(&zLine[n], nLine - n, in)==0 ){
+      if( n==0 ){
+        free(zLine);
+        return 0;
+      }
+      zLine[n] = 0;
+      break;
+    }
+    while( zLine[n] ){ n++; }
+    if( n>0 && zLine[n-1]=='\n' ){
+      n--;
+      zLine[n] = 0;
+      break;
+    }
+  }
+  zLine = realloc( zLine, n+1 );
+  return zLine;
+}
+
+
+/*
+** This function is part of the implementation of the command:
+**
+**   $db transaction [-deferred|-immediate|-exclusive] SCRIPT
+**
+** It is invoked after evaluating the script SCRIPT to commit or rollback
+** the transaction or savepoint opened by the [transaction] command.
+*/
+static int DbTransPostCmd(
+  ClientData data[],                   /* data[0] is the Sqlite3Db* for $db */
+  Tcl_Interp *interp,                  /* Tcl interpreter */
+  int result                           /* Result of evaluating SCRIPT */
+){
+  static const char *azEnd[] = {
+    "RELEASE _tcl_transaction",        /* rc==TCL_ERROR, nTransaction!=0 */
+    "COMMIT",                          /* rc!=TCL_ERROR, nTransaction==0 */
+    "ROLLBACK TO _tcl_transaction ; RELEASE _tcl_transaction",
+    "ROLLBACK"                         /* rc==TCL_ERROR, nTransaction==0 */
+  };
+  SqliteDb *pDb = (SqliteDb*)data[0];
+  int rc = result;
+  const char *zEnd;
+
+  pDb->nTransaction--;
+  zEnd = azEnd[(rc==TCL_ERROR)*2 + (pDb->nTransaction==0)];
+
+  pDb->disableAuth++;
+  if( sqlite3_exec(pDb->db, zEnd, 0, 0, 0) ){
+      /* This is a tricky scenario to handle. The most likely cause of an
+      ** error is that the exec() above was an attempt to commit the 
+      ** top-level transaction that returned SQLITE_BUSY. Or, less likely,
+      ** that an IO-error has occured. In either case, throw a Tcl exception
+      ** and try to rollback the transaction.
+      **
+      ** But it could also be that the user executed one or more BEGIN, 
+      ** COMMIT, SAVEPOINT, RELEASE or ROLLBACK commands that are confusing
+      ** this method's logic. Not clear how this would be best handled.
+      */
+    if( rc!=TCL_ERROR ){
+      Tcl_AppendResult(interp, sqlite3_errmsg(pDb->db), 0);
+      rc = TCL_ERROR;
+    }
+    sqlite3_exec(pDb->db, "ROLLBACK", 0, 0, 0);
+  }
+  pDb->disableAuth--;
+
+  return rc;
+}
+
+/*
+** Unless SQLITE_TEST is defined, this function is a simple wrapper around
+** sqlite3_prepare_v2(). If SQLITE_TEST is defined, then it uses either
+** sqlite3_prepare_v2() or legacy interface sqlite3_prepare(), depending
+** on whether or not the [db_use_legacy_prepare] command has been used to 
+** configure the connection.
+*/
+static int dbPrepare(
+  SqliteDb *pDb,                  /* Database object */
+  const char *zSql,               /* SQL to compile */
+  sqlite3_stmt **ppStmt,          /* OUT: Prepared statement */
+  const char **pzOut              /* OUT: Pointer to next SQL statement */
+){
+#ifdef SQLITE_TEST
+  if( pDb->bLegacyPrepare ){
+    return sqlite3_prepare(pDb->db, zSql, -1, ppStmt, pzOut);
+  }
+#endif
+  return sqlite3_prepare_v2(pDb->db, zSql, -1, ppStmt, pzOut);
+}
+
+/*
+** Search the cache for a prepared-statement object that implements the
+** first SQL statement in the buffer pointed to by parameter zIn. If
+** no such prepared-statement can be found, allocate and prepare a new
+** one. In either case, bind the current values of the relevant Tcl
+** variables to any $var, :var or @var variables in the statement. Before
+** returning, set *ppPreStmt to point to the prepared-statement object.
+**
+** Output parameter *pzOut is set to point to the next SQL statement in
+** buffer zIn, or to the '\0' byte at the end of zIn if there is no
+** next statement.
+**
+** If successful, TCL_OK is returned. Otherwise, TCL_ERROR is returned
+** and an error message loaded into interpreter pDb->interp.
+*/
+static int dbPrepareAndBind(
+  SqliteDb *pDb,                  /* Database object */
+  char const *zIn,                /* SQL to compile */
+  char const **pzOut,             /* OUT: Pointer to next SQL statement */
+  SqlPreparedStmt **ppPreStmt     /* OUT: Object used to cache statement */
+){
+  const char *zSql = zIn;         /* Pointer to first SQL statement in zIn */
+  sqlite3_stmt *pStmt;            /* Prepared statement object */
+  SqlPreparedStmt *pPreStmt;      /* Pointer to cached statement */
+  int nSql;                       /* Length of zSql in bytes */
+  int nVar;                       /* Number of variables in statement */
+  int iParm = 0;                  /* Next free entry in apParm */
+  int i;
+  Tcl_Interp *interp = pDb->interp;
+
+  *ppPreStmt = 0;
+
+  /* Trim spaces from the start of zSql and calculate the remaining length. */
+  while( isspace(zSql[0]) ){ zSql++; }
+  nSql = strlen30(zSql);
+
+  for(pPreStmt = pDb->stmtList; pPreStmt; pPreStmt=pPreStmt->pNext){
+    int n = pPreStmt->nSql;
+    if( nSql>=n 
+        && memcmp(pPreStmt->zSql, zSql, n)==0
+        && (zSql[n]==0 || zSql[n-1]==';')
+    ){
+      pStmt = pPreStmt->pStmt;
+      *pzOut = &zSql[pPreStmt->nSql];
+
+      /* When a prepared statement is found, unlink it from the
+      ** cache list.  It will later be added back to the beginning
+      ** of the cache list in order to implement LRU replacement.
+      */
+      if( pPreStmt->pPrev ){
+        pPreStmt->pPrev->pNext = pPreStmt->pNext;
+      }else{
+        pDb->stmtList = pPreStmt->pNext;
+      }
+      if( pPreStmt->pNext ){
+        pPreStmt->pNext->pPrev = pPreStmt->pPrev;
+      }else{
+        pDb->stmtLast = pPreStmt->pPrev;
+      }
+      pDb->nStmt--;
+      nVar = sqlite3_bind_parameter_count(pStmt);
+      break;
+    }
+  }
+  
+  /* If no prepared statement was found. Compile the SQL text. Also allocate
+  ** a new SqlPreparedStmt structure.  */
+  if( pPreStmt==0 ){
+    int nByte;
+
+    if( SQLITE_OK!=dbPrepare(pDb, zSql, &pStmt, pzOut) ){
+      Tcl_SetObjResult(interp, dbTextToObj(sqlite3_errmsg(pDb->db)));
+      return TCL_ERROR;
+    }
+    if( pStmt==0 ){
+      if( SQLITE_OK!=sqlite3_errcode(pDb->db) ){
+        /* A compile-time error in the statement. */
+        Tcl_SetObjResult(interp, dbTextToObj(sqlite3_errmsg(pDb->db)));
+        return TCL_ERROR;
+      }else{
+        /* The statement was a no-op.  Continue to the next statement
+        ** in the SQL string.
+        */
+        return TCL_OK;
+      }
+    }
+
+    assert( pPreStmt==0 );
+    nVar = sqlite3_bind_parameter_count(pStmt);
+    nByte = sizeof(SqlPreparedStmt) + nVar*sizeof(Tcl_Obj *);
+    pPreStmt = (SqlPreparedStmt*)Tcl_Alloc(nByte);
+    memset(pPreStmt, 0, nByte);
+
+    pPreStmt->pStmt = pStmt;
+    pPreStmt->nSql = (*pzOut - zSql);
+    pPreStmt->zSql = sqlite3_sql(pStmt);
+    pPreStmt->apParm = (Tcl_Obj **)&pPreStmt[1];
+#ifdef SQLITE_TEST
+    if( pPreStmt->zSql==0 ){
+      char *zCopy = Tcl_Alloc(pPreStmt->nSql + 1);
+      memcpy(zCopy, zSql, pPreStmt->nSql);
+      zCopy[pPreStmt->nSql] = '\0';
+      pPreStmt->zSql = zCopy;
+    }
+#endif
+  }
+  assert( pPreStmt );
+  assert( strlen30(pPreStmt->zSql)==pPreStmt->nSql );
+  assert( 0==memcmp(pPreStmt->zSql, zSql, pPreStmt->nSql) );
+
+  /* Bind values to parameters that begin with $ or : */  
+  for(i=1; i<=nVar; i++){
+    const char *zVar = sqlite3_bind_parameter_name(pStmt, i);
+    if( zVar!=0 && (zVar[0]=='$' || zVar[0]==':' || zVar[0]=='@') ){
+      Tcl_Obj *pVar = Tcl_GetVar2Ex(interp, &zVar[1], 0, 0);
+      if( pVar ){
+        int n;
+        u8 *data;
+        const char *zType = (pVar->typePtr ? pVar->typePtr->name : "");
+        char c = zType[0];
+        if( zVar[0]=='@' ||
+           (c=='b' && strcmp(zType,"bytearray")==0 && pVar->bytes==0) ){
+          /* Load a BLOB type if the Tcl variable is a bytearray and
+          ** it has no string representation or the host
+          ** parameter name begins with "@". */
+          data = Tcl_GetByteArrayFromObj(pVar, &n);
+          sqlite3_bind_blob(pStmt, i, data, n, SQLITE_STATIC);
+          Tcl_IncrRefCount(pVar);
+          pPreStmt->apParm[iParm++] = pVar;
+        }else if( c=='b' && strcmp(zType,"boolean")==0 ){
+          Tcl_GetIntFromObj(interp, pVar, &n);
+          sqlite3_bind_int(pStmt, i, n);
+        }else if( c=='d' && strcmp(zType,"double")==0 ){
+          double r;
+          Tcl_GetDoubleFromObj(interp, pVar, &r);
+          sqlite3_bind_double(pStmt, i, r);
+        }else if( (c=='w' && strcmp(zType,"wideInt")==0) ||
+              (c=='i' && strcmp(zType,"int")==0) ){
+          Tcl_WideInt v;
+          Tcl_GetWideIntFromObj(interp, pVar, &v);
+          sqlite3_bind_int64(pStmt, i, v);
+        }else{
+          data = (unsigned char *)Tcl_GetStringFromObj(pVar, &n);
+          sqlite3_bind_text(pStmt, i, (char *)data, n, SQLITE_STATIC);
+          Tcl_IncrRefCount(pVar);
+          pPreStmt->apParm[iParm++] = pVar;
+        }
+      }else{
+        sqlite3_bind_null(pStmt, i);
+      }
+    }
+  }
+  pPreStmt->nParm = iParm;
+  *ppPreStmt = pPreStmt;
+
+  return TCL_OK;
+}
+
+/*
+** Release a statement reference obtained by calling dbPrepareAndBind().
+** There should be exactly one call to this function for each call to
+** dbPrepareAndBind().
+**
+** If the discard parameter is non-zero, then the statement is deleted
+** immediately. Otherwise it is added to the LRU list and may be returned
+** by a subsequent call to dbPrepareAndBind().
+*/
+static void dbReleaseStmt(
+  SqliteDb *pDb,                  /* Database handle */
+  SqlPreparedStmt *pPreStmt,      /* Prepared statement handle to release */
+  int discard                     /* True to delete (not cache) the pPreStmt */
+){
+  int i;
+
+  /* Free the bound string and blob parameters */
+  for(i=0; i<pPreStmt->nParm; i++){
+    Tcl_DecrRefCount(pPreStmt->apParm[i]);
+  }
+  pPreStmt->nParm = 0;
+
+  if( pDb->maxStmt<=0 || discard ){
+    /* If the cache is turned off, deallocated the statement */
+    dbFreeStmt(pPreStmt);
+  }else{
+    /* Add the prepared statement to the beginning of the cache list. */
+    pPreStmt->pNext = pDb->stmtList;
+    pPreStmt->pPrev = 0;
+    if( pDb->stmtList ){
+     pDb->stmtList->pPrev = pPreStmt;
+    }
+    pDb->stmtList = pPreStmt;
+    if( pDb->stmtLast==0 ){
+      assert( pDb->nStmt==0 );
+      pDb->stmtLast = pPreStmt;
+    }else{
+      assert( pDb->nStmt>0 );
+    }
+    pDb->nStmt++;
+   
+    /* If we have too many statement in cache, remove the surplus from 
+    ** the end of the cache list.  */
+    while( pDb->nStmt>pDb->maxStmt ){
+      SqlPreparedStmt *pLast = pDb->stmtLast;
+      pDb->stmtLast = pLast->pPrev;
+      pDb->stmtLast->pNext = 0;
+      pDb->nStmt--;
+      dbFreeStmt(pLast);
+    }
+  }
+}
+
+/*
+** Structure used with dbEvalXXX() functions:
+**
+**   dbEvalInit()
+**   dbEvalStep()
+**   dbEvalFinalize()
+**   dbEvalRowInfo()
+**   dbEvalColumnValue()
+*/
+typedef struct DbEvalContext DbEvalContext;
+struct DbEvalContext {
+  SqliteDb *pDb;                  /* Database handle */
+  Tcl_Obj *pSql;                  /* Object holding string zSql */
+  const char *zSql;               /* Remaining SQL to execute */
+  SqlPreparedStmt *pPreStmt;      /* Current statement */
+  int nCol;                       /* Number of columns returned by pStmt */
+  Tcl_Obj *pArray;                /* Name of array variable */
+  Tcl_Obj **apColName;            /* Array of column names */
+};
+
+/*
+** Release any cache of column names currently held as part of
+** the DbEvalContext structure passed as the first argument.
+*/
+static void dbReleaseColumnNames(DbEvalContext *p){
+  if( p->apColName ){
+    int i;
+    for(i=0; i<p->nCol; i++){
+      Tcl_DecrRefCount(p->apColName[i]);
+    }
+    Tcl_Free((char *)p->apColName);
+    p->apColName = 0;
+  }
+  p->nCol = 0;
+}
+
+/*
+** Initialize a DbEvalContext structure.
+**
+** If pArray is not NULL, then it contains the name of a Tcl array
+** variable. The "*" member of this array is set to a list containing
+** the names of the columns returned by the statement as part of each
+** call to dbEvalStep(), in order from left to right. e.g. if the names 
+** of the returned columns are a, b and c, it does the equivalent of the 
+** tcl command:
+**
+**     set ${pArray}(*) {a b c}
+*/
+static void dbEvalInit(
+  DbEvalContext *p,               /* Pointer to structure to initialize */
+  SqliteDb *pDb,                  /* Database handle */
+  Tcl_Obj *pSql,                  /* Object containing SQL script */
+  Tcl_Obj *pArray                 /* Name of Tcl array to set (*) element of */
+){
+  memset(p, 0, sizeof(DbEvalContext));
+  p->pDb = pDb;
+  p->zSql = Tcl_GetString(pSql);
+  p->pSql = pSql;
+  Tcl_IncrRefCount(pSql);
+  if( pArray ){
+    p->pArray = pArray;
+    Tcl_IncrRefCount(pArray);
+  }
+}
+
+/*
+** Obtain information about the row that the DbEvalContext passed as the
+** first argument currently points to.
+*/
+static void dbEvalRowInfo(
+  DbEvalContext *p,               /* Evaluation context */
+  int *pnCol,                     /* OUT: Number of column names */
+  Tcl_Obj ***papColName           /* OUT: Array of column names */
+){
+  /* Compute column names */
+  if( 0==p->apColName ){
+    sqlite3_stmt *pStmt = p->pPreStmt->pStmt;
+    int i;                        /* Iterator variable */
+    int nCol;                     /* Number of columns returned by pStmt */
+    Tcl_Obj **apColName = 0;      /* Array of column names */
+
+    p->nCol = nCol = sqlite3_column_count(pStmt);
+    if( nCol>0 && (papColName || p->pArray) ){
+      apColName = (Tcl_Obj**)Tcl_Alloc( sizeof(Tcl_Obj*)*nCol );
+      for(i=0; i<nCol; i++){
+        apColName[i] = dbTextToObj(sqlite3_column_name(pStmt,i));
+        Tcl_IncrRefCount(apColName[i]);
+      }
+      p->apColName = apColName;
+    }
+
+    /* If results are being stored in an array variable, then create
+    ** the array(*) entry for that array
+    */
+    if( p->pArray ){
+      Tcl_Interp *interp = p->pDb->interp;
+      Tcl_Obj *pColList = Tcl_NewObj();
+      Tcl_Obj *pStar = Tcl_NewStringObj("*", -1);
+
+      for(i=0; i<nCol; i++){
+        Tcl_ListObjAppendElement(interp, pColList, apColName[i]);
+      }
+      Tcl_IncrRefCount(pStar);
+      Tcl_ObjSetVar2(interp, p->pArray, pStar, pColList, 0);
+      Tcl_DecrRefCount(pStar);
+    }
+  }
+
+  if( papColName ){
+    *papColName = p->apColName;
+  }
+  if( pnCol ){
+    *pnCol = p->nCol;
+  }
+}
+
+/*
+** Return one of TCL_OK, TCL_BREAK or TCL_ERROR. If TCL_ERROR is
+** returned, then an error message is stored in the interpreter before
+** returning.
+**
+** A return value of TCL_OK means there is a row of data available. The
+** data may be accessed using dbEvalRowInfo() and dbEvalColumnValue(). This
+** is analogous to a return of SQLITE_ROW from sqlite3_step(). If TCL_BREAK
+** is returned, then the SQL script has finished executing and there are
+** no further rows available. This is similar to SQLITE_DONE.
+*/
+static int dbEvalStep(DbEvalContext *p){
+  const char *zPrevSql = 0;       /* Previous value of p->zSql */
+
+  while( p->zSql[0] || p->pPreStmt ){
+    int rc;
+    if( p->pPreStmt==0 ){
+      zPrevSql = (p->zSql==zPrevSql ? 0 : p->zSql);
+      rc = dbPrepareAndBind(p->pDb, p->zSql, &p->zSql, &p->pPreStmt);
+      if( rc!=TCL_OK ) return rc;
+    }else{
+      int rcs;
+      SqliteDb *pDb = p->pDb;
+      SqlPreparedStmt *pPreStmt = p->pPreStmt;
+      sqlite3_stmt *pStmt = pPreStmt->pStmt;
+
+      rcs = sqlite3_step(pStmt);
+      if( rcs==SQLITE_ROW ){
+        return TCL_OK;
+      }
+      if( p->pArray ){
+        dbEvalRowInfo(p, 0, 0);
+      }
+      rcs = sqlite3_reset(pStmt);
+
+      pDb->nStep = sqlite3_stmt_status(pStmt,SQLITE_STMTSTATUS_FULLSCAN_STEP,1);
+      pDb->nSort = sqlite3_stmt_status(pStmt,SQLITE_STMTSTATUS_SORT,1);
+      pDb->nIndex = sqlite3_stmt_status(pStmt,SQLITE_STMTSTATUS_AUTOINDEX,1);
+      dbReleaseColumnNames(p);
+      p->pPreStmt = 0;
+
+      if( rcs!=SQLITE_OK ){
+        /* If a run-time error occurs, report the error and stop reading
+        ** the SQL.  */
+        dbReleaseStmt(pDb, pPreStmt, 1);
+#if SQLITE_TEST
+        if( p->pDb->bLegacyPrepare && rcs==SQLITE_SCHEMA && zPrevSql ){
+          /* If the runtime error was an SQLITE_SCHEMA, and the database
+          ** handle is configured to use the legacy sqlite3_prepare() 
+          ** interface, retry prepare()/step() on the same SQL statement.
+          ** This only happens once. If there is a second SQLITE_SCHEMA
+          ** error, the error will be returned to the caller. */
+          p->zSql = zPrevSql;
+          continue;
+        }
+#endif
+        Tcl_SetObjResult(pDb->interp, dbTextToObj(sqlite3_errmsg(pDb->db)));
+        return TCL_ERROR;
+      }else{
+        dbReleaseStmt(pDb, pPreStmt, 0);
+      }
+    }
+  }
+
+  /* Finished */
+  return TCL_BREAK;
+}
+
+/*
+** Free all resources currently held by the DbEvalContext structure passed
+** as the first argument. There should be exactly one call to this function
+** for each call to dbEvalInit().
+*/
+static void dbEvalFinalize(DbEvalContext *p){
+  if( p->pPreStmt ){
+    sqlite3_reset(p->pPreStmt->pStmt);
+    dbReleaseStmt(p->pDb, p->pPreStmt, 0);
+    p->pPreStmt = 0;
+  }
+  if( p->pArray ){
+    Tcl_DecrRefCount(p->pArray);
+    p->pArray = 0;
+  }
+  Tcl_DecrRefCount(p->pSql);
+  dbReleaseColumnNames(p);
+}
+
+/*
+** Return a pointer to a Tcl_Obj structure with ref-count 0 that contains
+** the value for the iCol'th column of the row currently pointed to by
+** the DbEvalContext structure passed as the first argument.
+*/
+static Tcl_Obj *dbEvalColumnValue(DbEvalContext *p, int iCol){
+  sqlite3_stmt *pStmt = p->pPreStmt->pStmt;
+  switch( sqlite3_column_type(pStmt, iCol) ){
+    case SQLITE_BLOB: {
+      int bytes = sqlite3_column_bytes(pStmt, iCol);
+      const char *zBlob = sqlite3_column_blob(pStmt, iCol);
+      if( !zBlob ) bytes = 0;
+      return Tcl_NewByteArrayObj((u8*)zBlob, bytes);
+    }
+    case SQLITE_INTEGER: {
+      sqlite_int64 v = sqlite3_column_int64(pStmt, iCol);
+      if( v>=-2147483647 && v<=2147483647 ){
+        return Tcl_NewIntObj((int)v);
+      }else{
+        return Tcl_NewWideIntObj(v);
+      }
+    }
+    case SQLITE_FLOAT: {
+      return Tcl_NewDoubleObj(sqlite3_column_double(pStmt, iCol));
+    }
+    case SQLITE_NULL: {
+      return dbTextToObj(p->pDb->zNull);
+    }
+  }
+
+  return dbTextToObj((char *)sqlite3_column_text(pStmt, iCol));
+}
+
+/*
+** If using Tcl version 8.6 or greater, use the NR functions to avoid
+** recursive evalution of scripts by the [db eval] and [db trans]
+** commands. Even if the headers used while compiling the extension
+** are 8.6 or newer, the code still tests the Tcl version at runtime.
+** This allows stubs-enabled builds to be used with older Tcl libraries.
+*/
+#if TCL_MAJOR_VERSION>8 || (TCL_MAJOR_VERSION==8 && TCL_MINOR_VERSION>=6)
+# define SQLITE_TCL_NRE 1
+static int DbUseNre(void){
+  int major, minor;
+  Tcl_GetVersion(&major, &minor, 0, 0);
+  return( (major==8 && minor>=6) || major>8 );
+}
+#else
+/* 
+** Compiling using headers earlier than 8.6. In this case NR cannot be
+** used, so DbUseNre() to always return zero. Add #defines for the other
+** Tcl_NRxxx() functions to prevent them from causing compilation errors,
+** even though the only invocations of them are within conditional blocks 
+** of the form:
+**
+**   if( DbUseNre() ) { ... }
+*/
+# define SQLITE_TCL_NRE 0
+# define DbUseNre() 0
+# define Tcl_NRAddCallback(a,b,c,d,e,f) 0
+# define Tcl_NREvalObj(a,b,c) 0
+# define Tcl_NRCreateCommand(a,b,c,d,e,f) 0
+#endif
+
+/*
+** This function is part of the implementation of the command:
+**
+**   $db eval SQL ?ARRAYNAME? SCRIPT
+*/
+static int DbEvalNextCmd(
+  ClientData data[],                   /* data[0] is the (DbEvalContext*) */
+  Tcl_Interp *interp,                  /* Tcl interpreter */
+  int result                           /* Result so far */
+){
+  int rc = result;                     /* Return code */
+
+  /* The first element of the data[] array is a pointer to a DbEvalContext
+  ** structure allocated using Tcl_Alloc(). The second element of data[]
+  ** is a pointer to a Tcl_Obj containing the script to run for each row
+  ** returned by the queries encapsulated in data[0]. */
+  DbEvalContext *p = (DbEvalContext *)data[0];
+  Tcl_Obj *pScript = (Tcl_Obj *)data[1];
+  Tcl_Obj *pArray = p->pArray;
+
+  while( (rc==TCL_OK || rc==TCL_CONTINUE) && TCL_OK==(rc = dbEvalStep(p)) ){
+    int i;
+    int nCol;
+    Tcl_Obj **apColName;
+    dbEvalRowInfo(p, &nCol, &apColName);
+    for(i=0; i<nCol; i++){
+      Tcl_Obj *pVal = dbEvalColumnValue(p, i);
+      if( pArray==0 ){
+        Tcl_ObjSetVar2(interp, apColName[i], 0, pVal, 0);
+      }else{
+        Tcl_ObjSetVar2(interp, pArray, apColName[i], pVal, 0);
+      }
+    }
+
+    /* The required interpreter variables are now populated with the data 
+    ** from the current row. If using NRE, schedule callbacks to evaluate
+    ** script pScript, then to invoke this function again to fetch the next
+    ** row (or clean up if there is no next row or the script throws an
+    ** exception). After scheduling the callbacks, return control to the 
+    ** caller.
+    **
+    ** If not using NRE, evaluate pScript directly and continue with the
+    ** next iteration of this while(...) loop.  */
+    if( DbUseNre() ){
+      Tcl_NRAddCallback(interp, DbEvalNextCmd, (void*)p, (void*)pScript, 0, 0);
+      return Tcl_NREvalObj(interp, pScript, 0);
+    }else{
+      rc = Tcl_EvalObjEx(interp, pScript, 0);
+    }
+  }
+
+  Tcl_DecrRefCount(pScript);
+  dbEvalFinalize(p);
+  Tcl_Free((char *)p);
+
+  if( rc==TCL_OK || rc==TCL_BREAK ){
+    Tcl_ResetResult(interp);
+    rc = TCL_OK;
+  }
+  return rc;
+}
+
+/*
+** The "sqlite" command below creates a new Tcl command for each
+** connection it opens to an SQLite database.  This routine is invoked
+** whenever one of those connection-specific commands is executed
+** in Tcl.  For example, if you run Tcl code like this:
+**
+**       sqlite3 db1  "my_database"
+**       db1 close
+**
+** The first command opens a connection to the "my_database" database
+** and calls that connection "db1".  The second command causes this
+** subroutine to be invoked.
+*/
+static int DbObjCmd(void *cd, Tcl_Interp *interp, int objc,Tcl_Obj *const*objv){
+  SqliteDb *pDb = (SqliteDb*)cd;
+  int choice;
+  int rc = TCL_OK;
+  static const char *DB_strs[] = {
+    "authorizer",         "backup",            "busy",
+    "cache",              "changes",           "close",
+    "collate",            "collation_needed",  "commit_hook",
+    "complete",           "copy",              "enable_load_extension",
+    "errorcode",          "eval",              "exists",
+    "function",           "incrblob",          "interrupt",
+    "last_insert_rowid",  "nullvalue",         "onecolumn",
+    "profile",            "progress",          "rekey",
+    "restore",            "rollback_hook",     "status",
+    "timeout",            "total_changes",     "trace",
+    "transaction",        "unlock_notify",     "update_hook",
+    "version",            "wal_hook",          0
+  };
+  enum DB_enum {
+    DB_AUTHORIZER,        DB_BACKUP,           DB_BUSY,
+    DB_CACHE,             DB_CHANGES,          DB_CLOSE,
+    DB_COLLATE,           DB_COLLATION_NEEDED, DB_COMMIT_HOOK,
+    DB_COMPLETE,          DB_COPY,             DB_ENABLE_LOAD_EXTENSION,
+    DB_ERRORCODE,         DB_EVAL,             DB_EXISTS,
+    DB_FUNCTION,          DB_INCRBLOB,         DB_INTERRUPT,
+    DB_LAST_INSERT_ROWID, DB_NULLVALUE,        DB_ONECOLUMN,
+    DB_PROFILE,           DB_PROGRESS,         DB_REKEY,
+    DB_RESTORE,           DB_ROLLBACK_HOOK,    DB_STATUS,
+    DB_TIMEOUT,           DB_TOTAL_CHANGES,    DB_TRACE,
+    DB_TRANSACTION,       DB_UNLOCK_NOTIFY,    DB_UPDATE_HOOK,
+    DB_VERSION,           DB_WAL_HOOK
+  };
+  /* don't leave trailing commas on DB_enum, it confuses the AIX xlc compiler */
+
+  if( objc<2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "SUBCOMMAND ...");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIndexFromObj(interp, objv[1], DB_strs, "option", 0, &choice) ){
+    return TCL_ERROR;
+  }
+
+  switch( (enum DB_enum)choice ){
+
+  /*    $db authorizer ?CALLBACK?
+  **
+  ** Invoke the given callback to authorize each SQL operation as it is
+  ** compiled.  5 arguments are appended to the callback before it is
+  ** invoked:
+  **
+  **   (1) The authorization type (ex: SQLITE_CREATE_TABLE, SQLITE_INSERT, ...)
+  **   (2) First descriptive name (depends on authorization type)
+  **   (3) Second descriptive name
+  **   (4) Name of the database (ex: "main", "temp")
+  **   (5) Name of trigger that is doing the access
+  **
+  ** The callback should return on of the following strings: SQLITE_OK,
+  ** SQLITE_IGNORE, or SQLITE_DENY.  Any other return value is an error.
+  **
+  ** If this method is invoked with no arguments, the current authorization
+  ** callback string is returned.
+  */
+  case DB_AUTHORIZER: {
+#ifdef SQLITE_OMIT_AUTHORIZATION
+    Tcl_AppendResult(interp, "authorization not available in this build", 0);
+    return TCL_ERROR;
+#else
+    if( objc>3 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "?CALLBACK?");
+      return TCL_ERROR;
+    }else if( objc==2 ){
+      if( pDb->zAuth ){
+        Tcl_AppendResult(interp, pDb->zAuth, 0);
+      }
+    }else{
+      char *zAuth;
+      int len;
+      if( pDb->zAuth ){
+        Tcl_Free(pDb->zAuth);
+      }
+      zAuth = Tcl_GetStringFromObj(objv[2], &len);
+      if( zAuth && len>0 ){
+        pDb->zAuth = Tcl_Alloc( len + 1 );
+        memcpy(pDb->zAuth, zAuth, len+1);
+      }else{
+        pDb->zAuth = 0;
+      }
+      if( pDb->zAuth ){
+        pDb->interp = interp;
+        sqlite3_set_authorizer(pDb->db, auth_callback, pDb);
+      }else{
+        sqlite3_set_authorizer(pDb->db, 0, 0);
+      }
+    }
+#endif
+    break;
+  }
+
+  /*    $db backup ?DATABASE? FILENAME
+  **
+  ** Open or create a database file named FILENAME.  Transfer the
+  ** content of local database DATABASE (default: "main") into the
+  ** FILENAME database.
+  */
+  case DB_BACKUP: {
+    const char *zDestFile;
+    const char *zSrcDb;
+    sqlite3 *pDest;
+    sqlite3_backup *pBackup;
+
+    if( objc==3 ){
+      zSrcDb = "main";
+      zDestFile = Tcl_GetString(objv[2]);
+    }else if( objc==4 ){
+      zSrcDb = Tcl_GetString(objv[2]);
+      zDestFile = Tcl_GetString(objv[3]);
+    }else{
+      Tcl_WrongNumArgs(interp, 2, objv, "?DATABASE? FILENAME");
+      return TCL_ERROR;
+    }
+    rc = sqlite3_open(zDestFile, &pDest);
+    if( rc!=SQLITE_OK ){
+      Tcl_AppendResult(interp, "cannot open target database: ",
+           sqlite3_errmsg(pDest), (char*)0);
+      sqlite3_close(pDest);
+      return TCL_ERROR;
+    }
+    pBackup = sqlite3_backup_init(pDest, "main", pDb->db, zSrcDb);
+    if( pBackup==0 ){
+      Tcl_AppendResult(interp, "backup failed: ",
+           sqlite3_errmsg(pDest), (char*)0);
+      sqlite3_close(pDest);
+      return TCL_ERROR;
+    }
+    while(  (rc = sqlite3_backup_step(pBackup,100))==SQLITE_OK ){}
+    sqlite3_backup_finish(pBackup);
+    if( rc==SQLITE_DONE ){
+      rc = TCL_OK;
+    }else{
+      Tcl_AppendResult(interp, "backup failed: ",
+           sqlite3_errmsg(pDest), (char*)0);
+      rc = TCL_ERROR;
+    }
+    sqlite3_close(pDest);
+    break;
+  }
+
+  /*    $db busy ?CALLBACK?
+  **
+  ** Invoke the given callback if an SQL statement attempts to open
+  ** a locked database file.
+  */
+  case DB_BUSY: {
+    if( objc>3 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "CALLBACK");
+      return TCL_ERROR;
+    }else if( objc==2 ){
+      if( pDb->zBusy ){
+        Tcl_AppendResult(interp, pDb->zBusy, 0);
+      }
+    }else{
+      char *zBusy;
+      int len;
+      if( pDb->zBusy ){
+        Tcl_Free(pDb->zBusy);
+      }
+      zBusy = Tcl_GetStringFromObj(objv[2], &len);
+      if( zBusy && len>0 ){
+        pDb->zBusy = Tcl_Alloc( len + 1 );
+        memcpy(pDb->zBusy, zBusy, len+1);
+      }else{
+        pDb->zBusy = 0;
+      }
+      if( pDb->zBusy ){
+        pDb->interp = interp;
+        sqlite3_busy_handler(pDb->db, DbBusyHandler, pDb);
+      }else{
+        sqlite3_busy_handler(pDb->db, 0, 0);
+      }
+    }
+    break;
+  }
+
+  /*     $db cache flush
+  **     $db cache size n
+  **
+  ** Flush the prepared statement cache, or set the maximum number of
+  ** cached statements.
+  */
+  case DB_CACHE: {
+    char *subCmd;
+    int n;
+
+    if( objc<=2 ){
+      Tcl_WrongNumArgs(interp, 1, objv, "cache option ?arg?");
+      return TCL_ERROR;
+    }
+    subCmd = Tcl_GetStringFromObj( objv[2], 0 );
+    if( *subCmd=='f' && strcmp(subCmd,"flush")==0 ){
+      if( objc!=3 ){
+        Tcl_WrongNumArgs(interp, 2, objv, "flush");
+        return TCL_ERROR;
+      }else{
+        flushStmtCache( pDb );
+      }
+    }else if( *subCmd=='s' && strcmp(subCmd,"size")==0 ){
+      if( objc!=4 ){
+        Tcl_WrongNumArgs(interp, 2, objv, "size n");
+        return TCL_ERROR;
+      }else{
+        if( TCL_ERROR==Tcl_GetIntFromObj(interp, objv[3], &n) ){
+          Tcl_AppendResult( interp, "cannot convert \"", 
+               Tcl_GetStringFromObj(objv[3],0), "\" to integer", 0);
+          return TCL_ERROR;
+        }else{
+          if( n<0 ){
+            flushStmtCache( pDb );
+            n = 0;
+          }else if( n>MAX_PREPARED_STMTS ){
+            n = MAX_PREPARED_STMTS;
+          }
+          pDb->maxStmt = n;
+        }
+      }
+    }else{
+      Tcl_AppendResult( interp, "bad option \"", 
+          Tcl_GetStringFromObj(objv[2],0), "\": must be flush or size", 0);
+      return TCL_ERROR;
+    }
+    break;
+  }
+
+  /*     $db changes
+  **
+  ** Return the number of rows that were modified, inserted, or deleted by
+  ** the most recent INSERT, UPDATE or DELETE statement, not including 
+  ** any changes made by trigger programs.
+  */
+  case DB_CHANGES: {
+    Tcl_Obj *pResult;
+    if( objc!=2 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "");
+      return TCL_ERROR;
+    }
+    pResult = Tcl_GetObjResult(interp);
+    Tcl_SetIntObj(pResult, sqlite3_changes(pDb->db));
+    break;
+  }
+
+  /*    $db close
+  **
+  ** Shutdown the database
+  */
+  case DB_CLOSE: {
+    Tcl_DeleteCommand(interp, Tcl_GetStringFromObj(objv[0], 0));
+    break;
+  }
+
+  /*
+  **     $db collate NAME SCRIPT
+  **
+  ** Create a new SQL collation function called NAME.  Whenever
+  ** that function is called, invoke SCRIPT to evaluate the function.
+  */
+  case DB_COLLATE: {
+    SqlCollate *pCollate;
+    char *zName;
+    char *zScript;
+    int nScript;
+    if( objc!=4 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "NAME SCRIPT");
+      return TCL_ERROR;
+    }
+    zName = Tcl_GetStringFromObj(objv[2], 0);
+    zScript = Tcl_GetStringFromObj(objv[3], &nScript);
+    pCollate = (SqlCollate*)Tcl_Alloc( sizeof(*pCollate) + nScript + 1 );
+    if( pCollate==0 ) return TCL_ERROR;
+    pCollate->interp = interp;
+    pCollate->pNext = pDb->pCollate;
+    pCollate->zScript = (char*)&pCollate[1];
+    pDb->pCollate = pCollate;
+    memcpy(pCollate->zScript, zScript, nScript+1);
+    if( sqlite3_create_collation(pDb->db, zName, SQLITE_UTF8, 
+        pCollate, tclSqlCollate) ){
+      Tcl_SetResult(interp, (char *)sqlite3_errmsg(pDb->db), TCL_VOLATILE);
+      return TCL_ERROR;
+    }
+    break;
+  }
+
+  /*
+  **     $db collation_needed SCRIPT
+  **
+  ** Create a new SQL collation function called NAME.  Whenever
+  ** that function is called, invoke SCRIPT to evaluate the function.
+  */
+  case DB_COLLATION_NEEDED: {
+    if( objc!=3 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "SCRIPT");
+      return TCL_ERROR;
+    }
+    if( pDb->pCollateNeeded ){
+      Tcl_DecrRefCount(pDb->pCollateNeeded);
+    }
+    pDb->pCollateNeeded = Tcl_DuplicateObj(objv[2]);
+    Tcl_IncrRefCount(pDb->pCollateNeeded);
+    sqlite3_collation_needed(pDb->db, pDb, tclCollateNeeded);
+    break;
+  }
+
+  /*    $db commit_hook ?CALLBACK?
+  **
+  ** Invoke the given callback just before committing every SQL transaction.
+  ** If the callback throws an exception or returns non-zero, then the
+  ** transaction is aborted.  If CALLBACK is an empty string, the callback
+  ** is disabled.
+  */
+  case DB_COMMIT_HOOK: {
+    if( objc>3 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "?CALLBACK?");
+      return TCL_ERROR;
+    }else if( objc==2 ){
+      if( pDb->zCommit ){
+        Tcl_AppendResult(interp, pDb->zCommit, 0);
+      }
+    }else{
+      char *zCommit;
+      int len;
+      if( pDb->zCommit ){
+        Tcl_Free(pDb->zCommit);
+      }
+      zCommit = Tcl_GetStringFromObj(objv[2], &len);
+      if( zCommit && len>0 ){
+        pDb->zCommit = Tcl_Alloc( len + 1 );
+        memcpy(pDb->zCommit, zCommit, len+1);
+      }else{
+        pDb->zCommit = 0;
+      }
+      if( pDb->zCommit ){
+        pDb->interp = interp;
+        sqlite3_commit_hook(pDb->db, DbCommitHandler, pDb);
+      }else{
+        sqlite3_commit_hook(pDb->db, 0, 0);
+      }
+    }
+    break;
+  }
+
+  /*    $db complete SQL
+  **
+  ** Return TRUE if SQL is a complete SQL statement.  Return FALSE if
+  ** additional lines of input are needed.  This is similar to the
+  ** built-in "info complete" command of Tcl.
+  */
+  case DB_COMPLETE: {
+#ifndef SQLITE_OMIT_COMPLETE
+    Tcl_Obj *pResult;
+    int isComplete;
+    if( objc!=3 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "SQL");
+      return TCL_ERROR;
+    }
+    isComplete = sqlite3_complete( Tcl_GetStringFromObj(objv[2], 0) );
+    pResult = Tcl_GetObjResult(interp);
+    Tcl_SetBooleanObj(pResult, isComplete);
+#endif
+    break;
+  }
+
+  /*    $db copy conflict-algorithm table filename ?SEPARATOR? ?NULLINDICATOR?
+  **
+  ** Copy data into table from filename, optionally using SEPARATOR
+  ** as column separators.  If a column contains a null string, or the
+  ** value of NULLINDICATOR, a NULL is inserted for the column.
+  ** conflict-algorithm is one of the sqlite conflict algorithms:
+  **    rollback, abort, fail, ignore, replace
+  ** On success, return the number of lines processed, not necessarily same
+  ** as 'db changes' due to conflict-algorithm selected.
+  **
+  ** This code is basically an implementation/enhancement of
+  ** the sqlite3 shell.c ".import" command.
+  **
+  ** This command usage is equivalent to the sqlite2.x COPY statement,
+  ** which imports file data into a table using the PostgreSQL COPY file format:
+  **   $db copy $conflit_algo $table_name $filename \t \\N
+  */
+  case DB_COPY: {
+    char *zTable;               /* Insert data into this table */
+    char *zFile;                /* The file from which to extract data */
+    char *zConflict;            /* The conflict algorithm to use */
+    sqlite3_stmt *pStmt;        /* A statement */
+    int nCol;                   /* Number of columns in the table */
+    int nByte;                  /* Number of bytes in an SQL string */
+    int i, j;                   /* Loop counters */
+    int nSep;                   /* Number of bytes in zSep[] */
+    int nNull;                  /* Number of bytes in zNull[] */
+    char *zSql;                 /* An SQL statement */
+    char *zLine;                /* A single line of input from the file */
+    char **azCol;               /* zLine[] broken up into columns */
+    char *zCommit;              /* How to commit changes */
+    FILE *in;                   /* The input file */
+    int lineno = 0;             /* Line number of input file */
+    char zLineNum[80];          /* Line number print buffer */
+    Tcl_Obj *pResult;           /* interp result */
+
+    char *zSep;
+    char *zNull;
+    if( objc<5 || objc>7 ){
+      Tcl_WrongNumArgs(interp, 2, objv, 
+         "CONFLICT-ALGORITHM TABLE FILENAME ?SEPARATOR? ?NULLINDICATOR?");
+      return TCL_ERROR;
+    }
+    if( objc>=6 ){
+      zSep = Tcl_GetStringFromObj(objv[5], 0);
+    }else{
+      zSep = "\t";
+    }
+    if( objc>=7 ){
+      zNull = Tcl_GetStringFromObj(objv[6], 0);
+    }else{
+      zNull = "";
+    }
+    zConflict = Tcl_GetStringFromObj(objv[2], 0);
+    zTable = Tcl_GetStringFromObj(objv[3], 0);
+    zFile = Tcl_GetStringFromObj(objv[4], 0);
+    nSep = strlen30(zSep);
+    nNull = strlen30(zNull);
+    if( nSep==0 ){
+      Tcl_AppendResult(interp,"Error: non-null separator required for copy",0);
+      return TCL_ERROR;
+    }
+    if(strcmp(zConflict, "rollback") != 0 &&
+       strcmp(zConflict, "abort"   ) != 0 &&
+       strcmp(zConflict, "fail"    ) != 0 &&
+       strcmp(zConflict, "ignore"  ) != 0 &&
+       strcmp(zConflict, "replace" ) != 0 ) {
+      Tcl_AppendResult(interp, "Error: \"", zConflict, 
+            "\", conflict-algorithm must be one of: rollback, "
+            "abort, fail, ignore, or replace", 0);
+      return TCL_ERROR;
+    }
+    zSql = sqlite3_mprintf("SELECT * FROM '%q'", zTable);
+    if( zSql==0 ){
+      Tcl_AppendResult(interp, "Error: no such table: ", zTable, 0);
+      return TCL_ERROR;
+    }
+    nByte = strlen30(zSql);
+    rc = sqlite3_prepare(pDb->db, zSql, -1, &pStmt, 0);
+    sqlite3_free(zSql);
+    if( rc ){
+      Tcl_AppendResult(interp, "Error: ", sqlite3_errmsg(pDb->db), 0);
+      nCol = 0;
+    }else{
+      nCol = sqlite3_column_count(pStmt);
+    }
+    sqlite3_finalize(pStmt);
+    if( nCol==0 ) {
+      return TCL_ERROR;
+    }
+    zSql = malloc( nByte + 50 + nCol*2 );
+    if( zSql==0 ) {
+      Tcl_AppendResult(interp, "Error: can't malloc()", 0);
+      return TCL_ERROR;
+    }
+    sqlite3_snprintf(nByte+50, zSql, "INSERT OR %q INTO '%q' VALUES(?",
+         zConflict, zTable);
+    j = strlen30(zSql);
+    for(i=1; i<nCol; i++){
+      zSql[j++] = ',';
+      zSql[j++] = '?';
+    }
+    zSql[j++] = ')';
+    zSql[j] = 0;
+    rc = sqlite3_prepare(pDb->db, zSql, -1, &pStmt, 0);
+    free(zSql);
+    if( rc ){
+      Tcl_AppendResult(interp, "Error: ", sqlite3_errmsg(pDb->db), 0);
+      sqlite3_finalize(pStmt);
+      return TCL_ERROR;
+    }
+    in = fopen(zFile, "rb");
+    if( in==0 ){
+      Tcl_AppendResult(interp, "Error: cannot open file: ", zFile, NULL);
+      sqlite3_finalize(pStmt);
+      return TCL_ERROR;
+    }
+    azCol = malloc( sizeof(azCol[0])*(nCol+1) );
+    if( azCol==0 ) {
+      Tcl_AppendResult(interp, "Error: can't malloc()", 0);
+      fclose(in);
+      return TCL_ERROR;
+    }
+    (void)sqlite3_exec(pDb->db, "BEGIN", 0, 0, 0);
+    zCommit = "COMMIT";
+    while( (zLine = local_getline(0, in))!=0 ){
+      char *z;
+      lineno++;
+      azCol[0] = zLine;
+      for(i=0, z=zLine; *z; z++){
+        if( *z==zSep[0] && strncmp(z, zSep, nSep)==0 ){
+          *z = 0;
+          i++;
+          if( i<nCol ){
+            azCol[i] = &z[nSep];
+            z += nSep-1;
+          }
+        }
+      }
+      if( i+1!=nCol ){
+        char *zErr;
+        int nErr = strlen30(zFile) + 200;
+        zErr = malloc(nErr);
+        if( zErr ){
+          sqlite3_snprintf(nErr, zErr,
+             "Error: %s line %d: expected %d columns of data but found %d",
+             zFile, lineno, nCol, i+1);
+          Tcl_AppendResult(interp, zErr, 0);
+          free(zErr);
+        }
+        zCommit = "ROLLBACK";
+        break;
+      }
+      for(i=0; i<nCol; i++){
+        /* check for null data, if so, bind as null */
+        if( (nNull>0 && strcmp(azCol[i], zNull)==0)
+          || strlen30(azCol[i])==0 
+        ){
+          sqlite3_bind_null(pStmt, i+1);
+        }else{
+          sqlite3_bind_text(pStmt, i+1, azCol[i], -1, SQLITE_STATIC);
+        }
+      }
+      sqlite3_step(pStmt);
+      rc = sqlite3_reset(pStmt);
+      free(zLine);
+      if( rc!=SQLITE_OK ){
+        Tcl_AppendResult(interp,"Error: ", sqlite3_errmsg(pDb->db), 0);
+        zCommit = "ROLLBACK";
+        break;
+      }
+    }
+    free(azCol);
+    fclose(in);
+    sqlite3_finalize(pStmt);
+    (void)sqlite3_exec(pDb->db, zCommit, 0, 0, 0);
+
+    if( zCommit[0] == 'C' ){
+      /* success, set result as number of lines processed */
+      pResult = Tcl_GetObjResult(interp);
+      Tcl_SetIntObj(pResult, lineno);
+      rc = TCL_OK;
+    }else{
+      /* failure, append lineno where failed */
+      sqlite3_snprintf(sizeof(zLineNum), zLineNum,"%d",lineno);
+      Tcl_AppendResult(interp,", failed while processing line: ",zLineNum,0);
+      rc = TCL_ERROR;
+    }
+    break;
+  }
+
+  /*
+  **    $db enable_load_extension BOOLEAN
+  **
+  ** Turn the extension loading feature on or off.  It if off by
+  ** default.
+  */
+  case DB_ENABLE_LOAD_EXTENSION: {
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+    int onoff;
+    if( objc!=3 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "BOOLEAN");
+      return TCL_ERROR;
+    }
+    if( Tcl_GetBooleanFromObj(interp, objv[2], &onoff) ){
+      return TCL_ERROR;
+    }
+    sqlite3_enable_load_extension(pDb->db, onoff);
+    break;
+#else
+    Tcl_AppendResult(interp, "extension loading is turned off at compile-time",
+                     0);
+    return TCL_ERROR;
+#endif
+  }
+
+  /*
+  **    $db errorcode
+  **
+  ** Return the numeric error code that was returned by the most recent
+  ** call to sqlite3_exec().
+  */
+  case DB_ERRORCODE: {
+    Tcl_SetObjResult(interp, Tcl_NewIntObj(sqlite3_errcode(pDb->db)));
+    break;
+  }
+
+  /*
+  **    $db exists $sql
+  **    $db onecolumn $sql
+  **
+  ** The onecolumn method is the equivalent of:
+  **     lindex [$db eval $sql] 0
+  */
+  case DB_EXISTS: 
+  case DB_ONECOLUMN: {
+    DbEvalContext sEval;
+    if( objc!=3 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "SQL");
+      return TCL_ERROR;
+    }
+
+    dbEvalInit(&sEval, pDb, objv[2], 0);
+    rc = dbEvalStep(&sEval);
+    if( choice==DB_ONECOLUMN ){
+      if( rc==TCL_OK ){
+        Tcl_SetObjResult(interp, dbEvalColumnValue(&sEval, 0));
+      }else if( rc==TCL_BREAK ){
+        Tcl_ResetResult(interp);
+      }
+    }else if( rc==TCL_BREAK || rc==TCL_OK ){
+      Tcl_SetObjResult(interp, Tcl_NewBooleanObj(rc==TCL_OK));
+    }
+    dbEvalFinalize(&sEval);
+
+    if( rc==TCL_BREAK ){
+      rc = TCL_OK;
+    }
+    break;
+  }
+   
+  /*
+  **    $db eval $sql ?array? ?{  ...code... }?
+  **
+  ** The SQL statement in $sql is evaluated.  For each row, the values are
+  ** placed in elements of the array named "array" and ...code... is executed.
+  ** If "array" and "code" are omitted, then no callback is every invoked.
+  ** If "array" is an empty string, then the values are placed in variables
+  ** that have the same name as the fields extracted by the query.
+  */
+  case DB_EVAL: {
+    if( objc<3 || objc>5 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "SQL ?ARRAY-NAME? ?SCRIPT?");
+      return TCL_ERROR;
+    }
+
+    if( objc==3 ){
+      DbEvalContext sEval;
+      Tcl_Obj *pRet = Tcl_NewObj();
+      Tcl_IncrRefCount(pRet);
+      dbEvalInit(&sEval, pDb, objv[2], 0);
+      while( TCL_OK==(rc = dbEvalStep(&sEval)) ){
+        int i;
+        int nCol;
+        dbEvalRowInfo(&sEval, &nCol, 0);
+        for(i=0; i<nCol; i++){
+          Tcl_ListObjAppendElement(interp, pRet, dbEvalColumnValue(&sEval, i));
+        }
+      }
+      dbEvalFinalize(&sEval);
+      if( rc==TCL_BREAK ){
+        Tcl_SetObjResult(interp, pRet);
+        rc = TCL_OK;
+      }
+      Tcl_DecrRefCount(pRet);
+    }else{
+      ClientData cd[2];
+      DbEvalContext *p;
+      Tcl_Obj *pArray = 0;
+      Tcl_Obj *pScript;
+
+      if( objc==5 && *(char *)Tcl_GetString(objv[3]) ){
+        pArray = objv[3];
+      }
+      pScript = objv[objc-1];
+      Tcl_IncrRefCount(pScript);
+      
+      p = (DbEvalContext *)Tcl_Alloc(sizeof(DbEvalContext));
+      dbEvalInit(p, pDb, objv[2], pArray);
+
+      cd[0] = (void *)p;
+      cd[1] = (void *)pScript;
+      rc = DbEvalNextCmd(cd, interp, TCL_OK);
+    }
+    break;
+  }
+
+  /*
+  **     $db function NAME [-argcount N] SCRIPT
+  **
+  ** Create a new SQL function called NAME.  Whenever that function is
+  ** called, invoke SCRIPT to evaluate the function.
+  */
+  case DB_FUNCTION: {
+    SqlFunc *pFunc;
+    Tcl_Obj *pScript;
+    char *zName;
+    int nArg = -1;
+    if( objc==6 ){
+      const char *z = Tcl_GetString(objv[3]);
+      int n = strlen30(z);
+      if( n>2 && strncmp(z, "-argcount",n)==0 ){
+        if( Tcl_GetIntFromObj(interp, objv[4], &nArg) ) return TCL_ERROR;
+        if( nArg<0 ){
+          Tcl_AppendResult(interp, "number of arguments must be non-negative",
+                           (char*)0);
+          return TCL_ERROR;
+        }
+      }
+      pScript = objv[5];
+    }else if( objc!=4 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "NAME [-argcount N] SCRIPT");
+      return TCL_ERROR;
+    }else{
+      pScript = objv[3];
+    }
+    zName = Tcl_GetStringFromObj(objv[2], 0);
+    pFunc = findSqlFunc(pDb, zName);
+    if( pFunc==0 ) return TCL_ERROR;
+    if( pFunc->pScript ){
+      Tcl_DecrRefCount(pFunc->pScript);
+    }
+    pFunc->pScript = pScript;
+    Tcl_IncrRefCount(pScript);
+    pFunc->useEvalObjv = safeToUseEvalObjv(interp, pScript);
+    rc = sqlite3_create_function(pDb->db, zName, nArg, SQLITE_UTF8,
+        pFunc, tclSqlFunc, 0, 0);
+    if( rc!=SQLITE_OK ){
+      rc = TCL_ERROR;
+      Tcl_SetResult(interp, (char *)sqlite3_errmsg(pDb->db), TCL_VOLATILE);
+    }
+    break;
+  }
+
+  /*
+  **     $db incrblob ?-readonly? ?DB? TABLE COLUMN ROWID
+  */
+  case DB_INCRBLOB: {
+#ifdef SQLITE_OMIT_INCRBLOB
+    Tcl_AppendResult(interp, "incrblob not available in this build", 0);
+    return TCL_ERROR;
+#else
+    int isReadonly = 0;
+    const char *zDb = "main";
+    const char *zTable;
+    const char *zColumn;
+    sqlite_int64 iRow;
+
+    /* Check for the -readonly option */
+    if( objc>3 && strcmp(Tcl_GetString(objv[2]), "-readonly")==0 ){
+      isReadonly = 1;
+    }
+
+    if( objc!=(5+isReadonly) && objc!=(6+isReadonly) ){
+      Tcl_WrongNumArgs(interp, 2, objv, "?-readonly? ?DB? TABLE COLUMN ROWID");
+      return TCL_ERROR;
+    }
+
+    if( objc==(6+isReadonly) ){
+      zDb = Tcl_GetString(objv[2]);
+    }
+    zTable = Tcl_GetString(objv[objc-3]);
+    zColumn = Tcl_GetString(objv[objc-2]);
+    rc = Tcl_GetWideIntFromObj(interp, objv[objc-1], &iRow);
+
+    if( rc==TCL_OK ){
+      rc = createIncrblobChannel(
+          interp, pDb, zDb, zTable, zColumn, iRow, isReadonly
+      );
+    }
+#endif
+    break;
+  }
+
+  /*
+  **     $db interrupt
+  **
+  ** Interrupt the execution of the inner-most SQL interpreter.  This
+  ** causes the SQL statement to return an error of SQLITE_INTERRUPT.
+  */
+  case DB_INTERRUPT: {
+    sqlite3_interrupt(pDb->db);
+    break;
+  }
+
+  /*
+  **     $db nullvalue ?STRING?
+  **
+  ** Change text used when a NULL comes back from the database. If ?STRING?
+  ** is not present, then the current string used for NULL is returned.
+  ** If STRING is present, then STRING is returned.
+  **
+  */
+  case DB_NULLVALUE: {
+    if( objc!=2 && objc!=3 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "NULLVALUE");
+      return TCL_ERROR;
+    }
+    if( objc==3 ){
+      int len;
+      char *zNull = Tcl_GetStringFromObj(objv[2], &len);
+      if( pDb->zNull ){
+        Tcl_Free(pDb->zNull);
+      }
+      if( zNull && len>0 ){
+        pDb->zNull = Tcl_Alloc( len + 1 );
+        memcpy(pDb->zNull, zNull, len);
+        pDb->zNull[len] = '\0';
+      }else{
+        pDb->zNull = 0;
+      }
+    }
+    Tcl_SetObjResult(interp, dbTextToObj(pDb->zNull));
+    break;
+  }
+
+  /*
+  **     $db last_insert_rowid 
+  **
+  ** Return an integer which is the ROWID for the most recent insert.
+  */
+  case DB_LAST_INSERT_ROWID: {
+    Tcl_Obj *pResult;
+    Tcl_WideInt rowid;
+    if( objc!=2 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "");
+      return TCL_ERROR;
+    }
+    rowid = sqlite3_last_insert_rowid(pDb->db);
+    pResult = Tcl_GetObjResult(interp);
+    Tcl_SetWideIntObj(pResult, rowid);
+    break;
+  }
+
+  /*
+  ** The DB_ONECOLUMN method is implemented together with DB_EXISTS.
+  */
+
+  /*    $db progress ?N CALLBACK?
+  ** 
+  ** Invoke the given callback every N virtual machine opcodes while executing
+  ** queries.
+  */
+  case DB_PROGRESS: {
+    if( objc==2 ){
+      if( pDb->zProgress ){
+        Tcl_AppendResult(interp, pDb->zProgress, 0);
+      }
+    }else if( objc==4 ){
+      char *zProgress;
+      int len;
+      int N;
+      if( TCL_OK!=Tcl_GetIntFromObj(interp, objv[2], &N) ){
+        return TCL_ERROR;
+      };
+      if( pDb->zProgress ){
+        Tcl_Free(pDb->zProgress);
+      }
+      zProgress = Tcl_GetStringFromObj(objv[3], &len);
+      if( zProgress && len>0 ){
+        pDb->zProgress = Tcl_Alloc( len + 1 );
+        memcpy(pDb->zProgress, zProgress, len+1);
+      }else{
+        pDb->zProgress = 0;
+      }
+#ifndef SQLITE_OMIT_PROGRESS_CALLBACK
+      if( pDb->zProgress ){
+        pDb->interp = interp;
+        sqlite3_progress_handler(pDb->db, N, DbProgressHandler, pDb);
+      }else{
+        sqlite3_progress_handler(pDb->db, 0, 0, 0);
+      }
+#endif
+    }else{
+      Tcl_WrongNumArgs(interp, 2, objv, "N CALLBACK");
+      return TCL_ERROR;
+    }
+    break;
+  }
+
+  /*    $db profile ?CALLBACK?
+  **
+  ** Make arrangements to invoke the CALLBACK routine after each SQL statement
+  ** that has run.  The text of the SQL and the amount of elapse time are
+  ** appended to CALLBACK before the script is run.
+  */
+  case DB_PROFILE: {
+    if( objc>3 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "?CALLBACK?");
+      return TCL_ERROR;
+    }else if( objc==2 ){
+      if( pDb->zProfile ){
+        Tcl_AppendResult(interp, pDb->zProfile, 0);
+      }
+    }else{
+      char *zProfile;
+      int len;
+      if( pDb->zProfile ){
+        Tcl_Free(pDb->zProfile);
+      }
+      zProfile = Tcl_GetStringFromObj(objv[2], &len);
+      if( zProfile && len>0 ){
+        pDb->zProfile = Tcl_Alloc( len + 1 );
+        memcpy(pDb->zProfile, zProfile, len+1);
+      }else{
+        pDb->zProfile = 0;
+      }
+#if !defined(SQLITE_OMIT_TRACE) && !defined(SQLITE_OMIT_FLOATING_POINT)
+      if( pDb->zProfile ){
+        pDb->interp = interp;
+        sqlite3_profile(pDb->db, DbProfileHandler, pDb);
+      }else{
+        sqlite3_profile(pDb->db, 0, 0);
+      }
+#endif
+    }
+    break;
+  }
+
+  /*
+  **     $db rekey KEY
+  **
+  ** Change the encryption key on the currently open database.
+  */
+  case DB_REKEY: {
+#ifdef SQLITE_HAS_CODEC
+    int nKey;
+    void *pKey;
+#endif
+    if( objc!=3 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "KEY");
+      return TCL_ERROR;
+    }
+#ifdef SQLITE_HAS_CODEC
+    pKey = Tcl_GetByteArrayFromObj(objv[2], &nKey);
+    rc = sqlite3_rekey(pDb->db, pKey, nKey);
+    if( rc ){
+      Tcl_AppendResult(interp, sqlite3ErrStr(rc), 0);
+      rc = TCL_ERROR;
+    }
+#endif
+    break;
+  }
+
+  /*    $db restore ?DATABASE? FILENAME
+  **
+  ** Open a database file named FILENAME.  Transfer the content 
+  ** of FILENAME into the local database DATABASE (default: "main").
+  */
+  case DB_RESTORE: {
+    const char *zSrcFile;
+    const char *zDestDb;
+    sqlite3 *pSrc;
+    sqlite3_backup *pBackup;
+    int nTimeout = 0;
+
+    if( objc==3 ){
+      zDestDb = "main";
+      zSrcFile = Tcl_GetString(objv[2]);
+    }else if( objc==4 ){
+      zDestDb = Tcl_GetString(objv[2]);
+      zSrcFile = Tcl_GetString(objv[3]);
+    }else{
+      Tcl_WrongNumArgs(interp, 2, objv, "?DATABASE? FILENAME");
+      return TCL_ERROR;
+    }
+    rc = sqlite3_open_v2(zSrcFile, &pSrc, SQLITE_OPEN_READONLY, 0);
+    if( rc!=SQLITE_OK ){
+      Tcl_AppendResult(interp, "cannot open source database: ",
+           sqlite3_errmsg(pSrc), (char*)0);
+      sqlite3_close(pSrc);
+      return TCL_ERROR;
+    }
+    pBackup = sqlite3_backup_init(pDb->db, zDestDb, pSrc, "main");
+    if( pBackup==0 ){
+      Tcl_AppendResult(interp, "restore failed: ",
+           sqlite3_errmsg(pDb->db), (char*)0);
+      sqlite3_close(pSrc);
+      return TCL_ERROR;
+    }
+    while( (rc = sqlite3_backup_step(pBackup,100))==SQLITE_OK
+              || rc==SQLITE_BUSY ){
+      if( rc==SQLITE_BUSY ){
+        if( nTimeout++ >= 3 ) break;
+        sqlite3_sleep(100);
+      }
+    }
+    sqlite3_backup_finish(pBackup);
+    if( rc==SQLITE_DONE ){
+      rc = TCL_OK;
+    }else if( rc==SQLITE_BUSY || rc==SQLITE_LOCKED ){
+      Tcl_AppendResult(interp, "restore failed: source database busy",
+                       (char*)0);
+      rc = TCL_ERROR;
+    }else{
+      Tcl_AppendResult(interp, "restore failed: ",
+           sqlite3_errmsg(pDb->db), (char*)0);
+      rc = TCL_ERROR;
+    }
+    sqlite3_close(pSrc);
+    break;
+  }
+
+  /*
+  **     $db status (step|sort|autoindex)
+  **
+  ** Display SQLITE_STMTSTATUS_FULLSCAN_STEP or 
+  ** SQLITE_STMTSTATUS_SORT for the most recent eval.
+  */
+  case DB_STATUS: {
+    int v;
+    const char *zOp;
+    if( objc!=3 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "(step|sort|autoindex)");
+      return TCL_ERROR;
+    }
+    zOp = Tcl_GetString(objv[2]);
+    if( strcmp(zOp, "step")==0 ){
+      v = pDb->nStep;
+    }else if( strcmp(zOp, "sort")==0 ){
+      v = pDb->nSort;
+    }else if( strcmp(zOp, "autoindex")==0 ){
+      v = pDb->nIndex;
+    }else{
+      Tcl_AppendResult(interp, 
+            "bad argument: should be autoindex, step, or sort", 
+            (char*)0);
+      return TCL_ERROR;
+    }
+    Tcl_SetObjResult(interp, Tcl_NewIntObj(v));
+    break;
+  }
+  
+  /*
+  **     $db timeout MILLESECONDS
+  **
+  ** Delay for the number of milliseconds specified when a file is locked.
+  */
+  case DB_TIMEOUT: {
+    int ms;
+    if( objc!=3 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "MILLISECONDS");
+      return TCL_ERROR;
+    }
+    if( Tcl_GetIntFromObj(interp, objv[2], &ms) ) return TCL_ERROR;
+    sqlite3_busy_timeout(pDb->db, ms);
+    break;
+  }
+  
+  /*
+  **     $db total_changes
+  **
+  ** Return the number of rows that were modified, inserted, or deleted 
+  ** since the database handle was created.
+  */
+  case DB_TOTAL_CHANGES: {
+    Tcl_Obj *pResult;
+    if( objc!=2 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "");
+      return TCL_ERROR;
+    }
+    pResult = Tcl_GetObjResult(interp);
+    Tcl_SetIntObj(pResult, sqlite3_total_changes(pDb->db));
+    break;
+  }
+
+  /*    $db trace ?CALLBACK?
+  **
+  ** Make arrangements to invoke the CALLBACK routine for each SQL statement
+  ** that is executed.  The text of the SQL is appended to CALLBACK before
+  ** it is executed.
+  */
+  case DB_TRACE: {
+    if( objc>3 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "?CALLBACK?");
+      return TCL_ERROR;
+    }else if( objc==2 ){
+      if( pDb->zTrace ){
+        Tcl_AppendResult(interp, pDb->zTrace, 0);
+      }
+    }else{
+      char *zTrace;
+      int len;
+      if( pDb->zTrace ){
+        Tcl_Free(pDb->zTrace);
+      }
+      zTrace = Tcl_GetStringFromObj(objv[2], &len);
+      if( zTrace && len>0 ){
+        pDb->zTrace = Tcl_Alloc( len + 1 );
+        memcpy(pDb->zTrace, zTrace, len+1);
+      }else{
+        pDb->zTrace = 0;
+      }
+#if !defined(SQLITE_OMIT_TRACE) && !defined(SQLITE_OMIT_FLOATING_POINT)
+      if( pDb->zTrace ){
+        pDb->interp = interp;
+        sqlite3_trace(pDb->db, DbTraceHandler, pDb);
+      }else{
+        sqlite3_trace(pDb->db, 0, 0);
+      }
+#endif
+    }
+    break;
+  }
+
+  /*    $db transaction [-deferred|-immediate|-exclusive] SCRIPT
+  **
+  ** Start a new transaction (if we are not already in the midst of a
+  ** transaction) and execute the TCL script SCRIPT.  After SCRIPT
+  ** completes, either commit the transaction or roll it back if SCRIPT
+  ** throws an exception.  Or if no new transation was started, do nothing.
+  ** pass the exception on up the stack.
+  **
+  ** This command was inspired by Dave Thomas's talk on Ruby at the
+  ** 2005 O'Reilly Open Source Convention (OSCON).
+  */
+  case DB_TRANSACTION: {
+    Tcl_Obj *pScript;
+    const char *zBegin = "SAVEPOINT _tcl_transaction";
+    if( objc!=3 && objc!=4 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "[TYPE] SCRIPT");
+      return TCL_ERROR;
+    }
+
+    if( pDb->nTransaction==0 && objc==4 ){
+      static const char *TTYPE_strs[] = {
+        "deferred",   "exclusive",  "immediate", 0
+      };
+      enum TTYPE_enum {
+        TTYPE_DEFERRED, TTYPE_EXCLUSIVE, TTYPE_IMMEDIATE
+      };
+      int ttype;
+      if( Tcl_GetIndexFromObj(interp, objv[2], TTYPE_strs, "transaction type",
+                              0, &ttype) ){
+        return TCL_ERROR;
+      }
+      switch( (enum TTYPE_enum)ttype ){
+        case TTYPE_DEFERRED:    /* no-op */;                 break;
+        case TTYPE_EXCLUSIVE:   zBegin = "BEGIN EXCLUSIVE";  break;
+        case TTYPE_IMMEDIATE:   zBegin = "BEGIN IMMEDIATE";  break;
+      }
+    }
+    pScript = objv[objc-1];
+
+    /* Run the SQLite BEGIN command to open a transaction or savepoint. */
+    pDb->disableAuth++;
+    rc = sqlite3_exec(pDb->db, zBegin, 0, 0, 0);
+    pDb->disableAuth--;
+    if( rc!=SQLITE_OK ){
+      Tcl_AppendResult(interp, sqlite3_errmsg(pDb->db), 0);
+      return TCL_ERROR;
+    }
+    pDb->nTransaction++;
+
+    /* If using NRE, schedule a callback to invoke the script pScript, then
+    ** a second callback to commit (or rollback) the transaction or savepoint
+    ** opened above. If not using NRE, evaluate the script directly, then
+    ** call function DbTransPostCmd() to commit (or rollback) the transaction 
+    ** or savepoint.  */
+    if( DbUseNre() ){
+      Tcl_NRAddCallback(interp, DbTransPostCmd, cd, 0, 0, 0);
+      Tcl_NREvalObj(interp, pScript, 0);
+    }else{
+      rc = DbTransPostCmd(&cd, interp, Tcl_EvalObjEx(interp, pScript, 0));
+    }
+    break;
+  }
+
+  /*
+  **    $db unlock_notify ?script?
+  */
+  case DB_UNLOCK_NOTIFY: {
+#ifndef SQLITE_ENABLE_UNLOCK_NOTIFY
+    Tcl_AppendResult(interp, "unlock_notify not available in this build", 0);
+    rc = TCL_ERROR;
+#else
+    if( objc!=2 && objc!=3 ){
+      Tcl_WrongNumArgs(interp, 2, objv, "?SCRIPT?");
+      rc = TCL_ERROR;
+    }else{
+      void (*xNotify)(void **, int) = 0;
+      void *pNotifyArg = 0;
+
+      if( pDb->pUnlockNotify ){
+        Tcl_DecrRefCount(pDb->pUnlockNotify);
+        pDb->pUnlockNotify = 0;
+      }
+  
+      if( objc==3 ){
+        xNotify = DbUnlockNotify;
+        pNotifyArg = (void *)pDb;
+        pDb->pUnlockNotify = objv[2];
+        Tcl_IncrRefCount(pDb->pUnlockNotify);
+      }
+  
+      if( sqlite3_unlock_notify(pDb->db, xNotify, pNotifyArg) ){
+        Tcl_AppendResult(interp, sqlite3_errmsg(pDb->db), 0);
+        rc = TCL_ERROR;
+      }
+    }
+#endif
+    break;
+  }
+
+  /*
+  **    $db wal_hook ?script?
+  **    $db update_hook ?script?
+  **    $db rollback_hook ?script?
+  */
+  case DB_WAL_HOOK: 
+  case DB_UPDATE_HOOK: 
+  case DB_ROLLBACK_HOOK: {
+
+    /* set ppHook to point at pUpdateHook or pRollbackHook, depending on 
+    ** whether [$db update_hook] or [$db rollback_hook] was invoked.
+    */
+    Tcl_Obj **ppHook; 
+    if( choice==DB_UPDATE_HOOK ){
+      ppHook = &pDb->pUpdateHook;
+    }else if( choice==DB_WAL_HOOK ){
+      ppHook = &pDb->pWalHook;
+    }else{
+      ppHook = &pDb->pRollbackHook;
+    }
+
+    if( objc!=2 && objc!=3 ){
+       Tcl_WrongNumArgs(interp, 2, objv, "?SCRIPT?");
+       return TCL_ERROR;
+    }
+    if( *ppHook ){
+      Tcl_SetObjResult(interp, *ppHook);
+      if( objc==3 ){
+        Tcl_DecrRefCount(*ppHook);
+        *ppHook = 0;
+      }
+    }
+    if( objc==3 ){
+      assert( !(*ppHook) );
+      if( Tcl_GetCharLength(objv[2])>0 ){
+        *ppHook = objv[2];
+        Tcl_IncrRefCount(*ppHook);
+      }
+    }
+
+    sqlite3_update_hook(pDb->db, (pDb->pUpdateHook?DbUpdateHandler:0), pDb);
+    sqlite3_rollback_hook(pDb->db,(pDb->pRollbackHook?DbRollbackHandler:0),pDb);
+    sqlite3_wal_hook(pDb->db,(pDb->pWalHook?DbWalHandler:0),pDb);
+
+    break;
+  }
+
+  /*    $db version
+  **
+  ** Return the version string for this database.
+  */
+  case DB_VERSION: {
+    Tcl_SetResult(interp, (char *)sqlite3_libversion(), TCL_STATIC);
+    break;
+  }
+
+
+  } /* End of the SWITCH statement */
+  return rc;
+}
+
+#if SQLITE_TCL_NRE
+/*
+** Adaptor that provides an objCmd interface to the NRE-enabled
+** interface implementation.
+*/
+static int DbObjCmdAdaptor(
+  void *cd,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *const*objv
+){
+  return Tcl_NRCallObjProc(interp, DbObjCmd, cd, objc, objv);
+}
+#endif /* SQLITE_TCL_NRE */
+
+/*
+**   sqlite3 DBNAME FILENAME ?-vfs VFSNAME? ?-key KEY? ?-readonly BOOLEAN?
+**                           ?-create BOOLEAN? ?-nomutex BOOLEAN?
+**
+** This is the main Tcl command.  When the "sqlite" Tcl command is
+** invoked, this routine runs to process that command.
+**
+** The first argument, DBNAME, is an arbitrary name for a new
+** database connection.  This command creates a new command named
+** DBNAME that is used to control that connection.  The database
+** connection is deleted when the DBNAME command is deleted.
+**
+** The second argument is the name of the database file.
+**
+*/
+static int DbMain(void *cd, Tcl_Interp *interp, int objc,Tcl_Obj *const*objv){
+  SqliteDb *p;
+  const char *zArg;
+  char *zErrMsg;
+  int i;
+  const char *zFile;
+  const char *zVfs = 0;
+  int flags;
+  Tcl_DString translatedFilename;
+#ifdef SQLITE_HAS_CODEC
+  void *pKey = 0;
+  int nKey = 0;
+#endif
+
+  /* In normal use, each TCL interpreter runs in a single thread.  So
+  ** by default, we can turn of mutexing on SQLite database connections.
+  ** However, for testing purposes it is useful to have mutexes turned
+  ** on.  So, by default, mutexes default off.  But if compiled with
+  ** SQLITE_TCL_DEFAULT_FULLMUTEX then mutexes default on.
+  */
+#ifdef SQLITE_TCL_DEFAULT_FULLMUTEX
+  flags = SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE | SQLITE_OPEN_FULLMUTEX;
+#else
+  flags = SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE | SQLITE_OPEN_NOMUTEX;
+#endif
+
+  if( objc==2 ){
+    zArg = Tcl_GetStringFromObj(objv[1], 0);
+    if( strcmp(zArg,"-version")==0 ){
+      Tcl_AppendResult(interp,sqlite3_version,0);
+      return TCL_OK;
+    }
+    if( strcmp(zArg,"-has-codec")==0 ){
+#ifdef SQLITE_HAS_CODEC
+      Tcl_AppendResult(interp,"1",0);
+#else
+      Tcl_AppendResult(interp,"0",0);
+#endif
+      return TCL_OK;
+    }
+  }
+  for(i=3; i+1<objc; i+=2){
+    zArg = Tcl_GetString(objv[i]);
+    if( strcmp(zArg,"-key")==0 ){
+#ifdef SQLITE_HAS_CODEC
+      pKey = Tcl_GetByteArrayFromObj(objv[i+1], &nKey);
+#endif
+    }else if( strcmp(zArg, "-vfs")==0 ){
+      zVfs = Tcl_GetString(objv[i+1]);
+    }else if( strcmp(zArg, "-readonly")==0 ){
+      int b;
+      if( Tcl_GetBooleanFromObj(interp, objv[i+1], &b) ) return TCL_ERROR;
+      if( b ){
+        flags &= ~(SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE);
+        flags |= SQLITE_OPEN_READONLY;
+      }else{
+        flags &= ~SQLITE_OPEN_READONLY;
+        flags |= SQLITE_OPEN_READWRITE;
+      }
+    }else if( strcmp(zArg, "-create")==0 ){
+      int b;
+      if( Tcl_GetBooleanFromObj(interp, objv[i+1], &b) ) return TCL_ERROR;
+      if( b && (flags & SQLITE_OPEN_READONLY)==0 ){
+        flags |= SQLITE_OPEN_CREATE;
+      }else{
+        flags &= ~SQLITE_OPEN_CREATE;
+      }
+    }else if( strcmp(zArg, "-nomutex")==0 ){
+      int b;
+      if( Tcl_GetBooleanFromObj(interp, objv[i+1], &b) ) return TCL_ERROR;
+      if( b ){
+        flags |= SQLITE_OPEN_NOMUTEX;
+        flags &= ~SQLITE_OPEN_FULLMUTEX;
+      }else{
+        flags &= ~SQLITE_OPEN_NOMUTEX;
+      }
+    }else if( strcmp(zArg, "-fullmutex")==0 ){
+      int b;
+      if( Tcl_GetBooleanFromObj(interp, objv[i+1], &b) ) return TCL_ERROR;
+      if( b ){
+        flags |= SQLITE_OPEN_FULLMUTEX;
+        flags &= ~SQLITE_OPEN_NOMUTEX;
+      }else{
+        flags &= ~SQLITE_OPEN_FULLMUTEX;
+      }
+    }else{
+      Tcl_AppendResult(interp, "unknown option: ", zArg, (char*)0);
+      return TCL_ERROR;
+    }
+  }
+  if( objc<3 || (objc&1)!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, 
+      "HANDLE FILENAME ?-vfs VFSNAME? ?-readonly BOOLEAN? ?-create BOOLEAN?"
+      " ?-nomutex BOOLEAN? ?-fullmutex BOOLEAN?"
+#ifdef SQLITE_HAS_CODEC
+      " ?-key CODECKEY?"
+#endif
+    );
+    return TCL_ERROR;
+  }
+  zErrMsg = 0;
+  p = (SqliteDb*)Tcl_Alloc( sizeof(*p) );
+  if( p==0 ){
+    Tcl_SetResult(interp, "malloc failed", TCL_STATIC);
+    return TCL_ERROR;
+  }
+  memset(p, 0, sizeof(*p));
+  zFile = Tcl_GetStringFromObj(objv[2], 0);
+  zFile = Tcl_TranslateFileName(interp, zFile, &translatedFilename);
+  sqlite3_open_v2(zFile, &p->db, flags, zVfs);
+  Tcl_DStringFree(&translatedFilename);
+  if( SQLITE_OK!=sqlite3_errcode(p->db) ){
+    zErrMsg = sqlite3_mprintf("%s", sqlite3_errmsg(p->db));
+    sqlite3_close(p->db);
+    p->db = 0;
+  }
+#ifdef SQLITE_HAS_CODEC
+  if( p->db ){
+    sqlite3_key(p->db, pKey, nKey);
+  }
+#endif
+  if( p->db==0 ){
+    Tcl_SetResult(interp, zErrMsg, TCL_VOLATILE);
+    Tcl_Free((char*)p);
+    sqlite3_free(zErrMsg);
+    return TCL_ERROR;
+  }
+  p->maxStmt = NUM_PREPARED_STMTS;
+  p->interp = interp;
+  zArg = Tcl_GetStringFromObj(objv[1], 0);
+  if( DbUseNre() ){
+    Tcl_NRCreateCommand(interp, zArg, DbObjCmdAdaptor, DbObjCmd,
+                        (char*)p, DbDeleteCmd);
+  }else{
+    Tcl_CreateObjCommand(interp, zArg, DbObjCmd, (char*)p, DbDeleteCmd);
+  }
+  return TCL_OK;
+}
+
+/*
+** Provide a dummy Tcl_InitStubs if we are using this as a static
+** library.
+*/
+#ifndef USE_TCL_STUBS
+# undef  Tcl_InitStubs
+# define Tcl_InitStubs(a,b,c)
+#endif
+
+/*
+** Make sure we have a PACKAGE_VERSION macro defined.  This will be
+** defined automatically by the TEA makefile.  But other makefiles
+** do not define it.
+*/
+#ifndef PACKAGE_VERSION
+# define PACKAGE_VERSION SQLITE_VERSION
+#endif
+
+/*
+** Initialize this module.
+**
+** This Tcl module contains only a single new Tcl command named "sqlite".
+** (Hence there is no namespace.  There is no point in using a namespace
+** if the extension only supplies one new name!)  The "sqlite" command is
+** used to open a new SQLite database.  See the DbMain() routine above
+** for additional information.
+**
+** The EXTERN macros are required by TCL in order to work on windows.
+*/
+EXTERN int Sqlite3_Init(Tcl_Interp *interp){
+  Tcl_InitStubs(interp, "8.4", 0);
+  Tcl_CreateObjCommand(interp, "sqlite3", (Tcl_ObjCmdProc*)DbMain, 0, 0);
+  Tcl_PkgProvide(interp, "sqlite3", PACKAGE_VERSION);
+
+#ifndef SQLITE_3_SUFFIX_ONLY
+  /* The "sqlite" alias is undocumented.  It is here only to support
+  ** legacy scripts.  All new scripts should use only the "sqlite3"
+  ** command.
+  */
+  Tcl_CreateObjCommand(interp, "sqlite", (Tcl_ObjCmdProc*)DbMain, 0, 0);
+#endif
+
+  return TCL_OK;
+}
+EXTERN int Tclsqlite3_Init(Tcl_Interp *interp){ return Sqlite3_Init(interp); }
+EXTERN int Sqlite3_SafeInit(Tcl_Interp *interp){ return TCL_OK; }
+EXTERN int Tclsqlite3_SafeInit(Tcl_Interp *interp){ return TCL_OK; }
+EXTERN int Sqlite3_Unload(Tcl_Interp *interp, int flags){ return TCL_OK; }
+EXTERN int Tclsqlite3_Unload(Tcl_Interp *interp, int flags){ return TCL_OK; }
+EXTERN int Sqlite3_SafeUnload(Tcl_Interp *interp, int flags){ return TCL_OK; }
+EXTERN int Tclsqlite3_SafeUnload(Tcl_Interp *interp, int flags){ return TCL_OK;}
+
+
+#ifndef SQLITE_3_SUFFIX_ONLY
+int Sqlite_Init(Tcl_Interp *interp){ return Sqlite3_Init(interp); }
+int Tclsqlite_Init(Tcl_Interp *interp){ return Sqlite3_Init(interp); }
+int Sqlite_SafeInit(Tcl_Interp *interp){ return TCL_OK; }
+int Tclsqlite_SafeInit(Tcl_Interp *interp){ return TCL_OK; }
+int Sqlite_Unload(Tcl_Interp *interp, int flags){ return TCL_OK; }
+int Tclsqlite_Unload(Tcl_Interp *interp, int flags){ return TCL_OK; }
+int Sqlite_SafeUnload(Tcl_Interp *interp, int flags){ return TCL_OK; }
+int Tclsqlite_SafeUnload(Tcl_Interp *interp, int flags){ return TCL_OK;}
+#endif
+
+#ifdef TCLSH
+/*****************************************************************************
+** All of the code that follows is used to build standalone TCL interpreters
+** that are statically linked with SQLite.  Enable these by compiling
+** with -DTCLSH=n where n can be 1 or 2.  An n of 1 generates a standard
+** tclsh but with SQLite built in.  An n of 2 generates the SQLite space
+** analysis program.
+*/
+
+#if defined(SQLITE_TEST) || defined(SQLITE_TCLMD5)
+/*
+ * This code implements the MD5 message-digest algorithm.
+ * The algorithm is due to Ron Rivest.  This code was
+ * written by Colin Plumb in 1993, no copyright is claimed.
+ * This code is in the public domain; do with it what you wish.
+ *
+ * Equivalent code is available from RSA Data Security, Inc.
+ * This code has been tested against that, and is equivalent,
+ * except that you don't need to include two pages of legalese
+ * with every copy.
+ *
+ * To compute the message digest of a chunk of bytes, declare an
+ * MD5Context structure, pass it to MD5Init, call MD5Update as
+ * needed on buffers full of bytes, and then call MD5Final, which
+ * will fill a supplied 16-byte array with the digest.
+ */
+
+/*
+ * If compiled on a machine that doesn't have a 32-bit integer,
+ * you just set "uint32" to the appropriate datatype for an
+ * unsigned 32-bit integer.  For example:
+ *
+ *       cc -Duint32='unsigned long' md5.c
+ *
+ */
+#ifndef uint32
+#  define uint32 unsigned int
+#endif
+
+struct MD5Context {
+  int isInit;
+  uint32 buf[4];
+  uint32 bits[2];
+  unsigned char in[64];
+};
+typedef struct MD5Context MD5Context;
+
+/*
+ * Note: this code is harmless on little-endian machines.
+ */
+static void byteReverse (unsigned char *buf, unsigned longs){
+        uint32 t;
+        do {
+                t = (uint32)((unsigned)buf[3]<<8 | buf[2]) << 16 |
+                            ((unsigned)buf[1]<<8 | buf[0]);
+                *(uint32 *)buf = t;
+                buf += 4;
+        } while (--longs);
+}
+/* The four core functions - F1 is optimized somewhat */
+
+/* #define F1(x, y, z) (x & y | ~x & z) */
+#define F1(x, y, z) (z ^ (x & (y ^ z)))
+#define F2(x, y, z) F1(z, x, y)
+#define F3(x, y, z) (x ^ y ^ z)
+#define F4(x, y, z) (y ^ (x | ~z))
+
+/* This is the central step in the MD5 algorithm. */
+#define MD5STEP(f, w, x, y, z, data, s) \
+        ( w += f(x, y, z) + data,  w = w<<s | w>>(32-s),  w += x )
+
+/*
+ * The core of the MD5 algorithm, this alters an existing MD5 hash to
+ * reflect the addition of 16 longwords of new data.  MD5Update blocks
+ * the data and converts bytes into longwords for this routine.
+ */
+static void MD5Transform(uint32 buf[4], const uint32 in[16]){
+        register uint32 a, b, c, d;
+
+        a = buf[0];
+        b = buf[1];
+        c = buf[2];
+        d = buf[3];
+
+        MD5STEP(F1, a, b, c, d, in[ 0]+0xd76aa478,  7);
+        MD5STEP(F1, d, a, b, c, in[ 1]+0xe8c7b756, 12);
+        MD5STEP(F1, c, d, a, b, in[ 2]+0x242070db, 17);
+        MD5STEP(F1, b, c, d, a, in[ 3]+0xc1bdceee, 22);
+        MD5STEP(F1, a, b, c, d, in[ 4]+0xf57c0faf,  7);
+        MD5STEP(F1, d, a, b, c, in[ 5]+0x4787c62a, 12);
+        MD5STEP(F1, c, d, a, b, in[ 6]+0xa8304613, 17);
+        MD5STEP(F1, b, c, d, a, in[ 7]+0xfd469501, 22);
+        MD5STEP(F1, a, b, c, d, in[ 8]+0x698098d8,  7);
+        MD5STEP(F1, d, a, b, c, in[ 9]+0x8b44f7af, 12);
+        MD5STEP(F1, c, d, a, b, in[10]+0xffff5bb1, 17);
+        MD5STEP(F1, b, c, d, a, in[11]+0x895cd7be, 22);
+        MD5STEP(F1, a, b, c, d, in[12]+0x6b901122,  7);
+        MD5STEP(F1, d, a, b, c, in[13]+0xfd987193, 12);
+        MD5STEP(F1, c, d, a, b, in[14]+0xa679438e, 17);
+        MD5STEP(F1, b, c, d, a, in[15]+0x49b40821, 22);
+
+        MD5STEP(F2, a, b, c, d, in[ 1]+0xf61e2562,  5);
+        MD5STEP(F2, d, a, b, c, in[ 6]+0xc040b340,  9);
+        MD5STEP(F2, c, d, a, b, in[11]+0x265e5a51, 14);
+        MD5STEP(F2, b, c, d, a, in[ 0]+0xe9b6c7aa, 20);
+        MD5STEP(F2, a, b, c, d, in[ 5]+0xd62f105d,  5);
+        MD5STEP(F2, d, a, b, c, in[10]+0x02441453,  9);
+        MD5STEP(F2, c, d, a, b, in[15]+0xd8a1e681, 14);
+        MD5STEP(F2, b, c, d, a, in[ 4]+0xe7d3fbc8, 20);
+        MD5STEP(F2, a, b, c, d, in[ 9]+0x21e1cde6,  5);
+        MD5STEP(F2, d, a, b, c, in[14]+0xc33707d6,  9);
+        MD5STEP(F2, c, d, a, b, in[ 3]+0xf4d50d87, 14);
+        MD5STEP(F2, b, c, d, a, in[ 8]+0x455a14ed, 20);
+        MD5STEP(F2, a, b, c, d, in[13]+0xa9e3e905,  5);
+        MD5STEP(F2, d, a, b, c, in[ 2]+0xfcefa3f8,  9);
+        MD5STEP(F2, c, d, a, b, in[ 7]+0x676f02d9, 14);
+        MD5STEP(F2, b, c, d, a, in[12]+0x8d2a4c8a, 20);
+
+        MD5STEP(F3, a, b, c, d, in[ 5]+0xfffa3942,  4);
+        MD5STEP(F3, d, a, b, c, in[ 8]+0x8771f681, 11);
+        MD5STEP(F3, c, d, a, b, in[11]+0x6d9d6122, 16);
+        MD5STEP(F3, b, c, d, a, in[14]+0xfde5380c, 23);
+        MD5STEP(F3, a, b, c, d, in[ 1]+0xa4beea44,  4);
+        MD5STEP(F3, d, a, b, c, in[ 4]+0x4bdecfa9, 11);
+        MD5STEP(F3, c, d, a, b, in[ 7]+0xf6bb4b60, 16);
+        MD5STEP(F3, b, c, d, a, in[10]+0xbebfbc70, 23);
+        MD5STEP(F3, a, b, c, d, in[13]+0x289b7ec6,  4);
+        MD5STEP(F3, d, a, b, c, in[ 0]+0xeaa127fa, 11);
+        MD5STEP(F3, c, d, a, b, in[ 3]+0xd4ef3085, 16);
+        MD5STEP(F3, b, c, d, a, in[ 6]+0x04881d05, 23);
+        MD5STEP(F3, a, b, c, d, in[ 9]+0xd9d4d039,  4);
+        MD5STEP(F3, d, a, b, c, in[12]+0xe6db99e5, 11);
+        MD5STEP(F3, c, d, a, b, in[15]+0x1fa27cf8, 16);
+        MD5STEP(F3, b, c, d, a, in[ 2]+0xc4ac5665, 23);
+
+        MD5STEP(F4, a, b, c, d, in[ 0]+0xf4292244,  6);
+        MD5STEP(F4, d, a, b, c, in[ 7]+0x432aff97, 10);
+        MD5STEP(F4, c, d, a, b, in[14]+0xab9423a7, 15);
+        MD5STEP(F4, b, c, d, a, in[ 5]+0xfc93a039, 21);
+        MD5STEP(F4, a, b, c, d, in[12]+0x655b59c3,  6);
+        MD5STEP(F4, d, a, b, c, in[ 3]+0x8f0ccc92, 10);
+        MD5STEP(F4, c, d, a, b, in[10]+0xffeff47d, 15);
+        MD5STEP(F4, b, c, d, a, in[ 1]+0x85845dd1, 21);
+        MD5STEP(F4, a, b, c, d, in[ 8]+0x6fa87e4f,  6);
+        MD5STEP(F4, d, a, b, c, in[15]+0xfe2ce6e0, 10);
+        MD5STEP(F4, c, d, a, b, in[ 6]+0xa3014314, 15);
+        MD5STEP(F4, b, c, d, a, in[13]+0x4e0811a1, 21);
+        MD5STEP(F4, a, b, c, d, in[ 4]+0xf7537e82,  6);
+        MD5STEP(F4, d, a, b, c, in[11]+0xbd3af235, 10);
+        MD5STEP(F4, c, d, a, b, in[ 2]+0x2ad7d2bb, 15);
+        MD5STEP(F4, b, c, d, a, in[ 9]+0xeb86d391, 21);
+
+        buf[0] += a;
+        buf[1] += b;
+        buf[2] += c;
+        buf[3] += d;
+}
+
+/*
+ * Start MD5 accumulation.  Set bit count to 0 and buffer to mysterious
+ * initialization constants.
+ */
+static void MD5Init(MD5Context *ctx){
+        ctx->isInit = 1;
+        ctx->buf[0] = 0x67452301;
+        ctx->buf[1] = 0xefcdab89;
+        ctx->buf[2] = 0x98badcfe;
+        ctx->buf[3] = 0x10325476;
+        ctx->bits[0] = 0;
+        ctx->bits[1] = 0;
+}
+
+/*
+ * Update context to reflect the concatenation of another buffer full
+ * of bytes.
+ */
+static 
+void MD5Update(MD5Context *ctx, const unsigned char *buf, unsigned int len){
+        uint32 t;
+
+        /* Update bitcount */
+
+        t = ctx->bits[0];
+        if ((ctx->bits[0] = t + ((uint32)len << 3)) < t)
+                ctx->bits[1]++; /* Carry from low to high */
+        ctx->bits[1] += len >> 29;
+
+        t = (t >> 3) & 0x3f;    /* Bytes already in shsInfo->data */
+
+        /* Handle any leading odd-sized chunks */
+
+        if ( t ) {
+                unsigned char *p = (unsigned char *)ctx->in + t;
+
+                t = 64-t;
+                if (len < t) {
+                        memcpy(p, buf, len);
+                        return;
+                }
+                memcpy(p, buf, t);
+                byteReverse(ctx->in, 16);
+                MD5Transform(ctx->buf, (uint32 *)ctx->in);
+                buf += t;
+                len -= t;
+        }
+
+        /* Process data in 64-byte chunks */
+
+        while (len >= 64) {
+                memcpy(ctx->in, buf, 64);
+                byteReverse(ctx->in, 16);
+                MD5Transform(ctx->buf, (uint32 *)ctx->in);
+                buf += 64;
+                len -= 64;
+        }
+
+        /* Handle any remaining bytes of data. */
+
+        memcpy(ctx->in, buf, len);
+}
+
+/*
+ * Final wrapup - pad to 64-byte boundary with the bit pattern 
+ * 1 0* (64-bit count of bits processed, MSB-first)
+ */
+static void MD5Final(unsigned char digest[16], MD5Context *ctx){
+        unsigned count;
+        unsigned char *p;
+
+        /* Compute number of bytes mod 64 */
+        count = (ctx->bits[0] >> 3) & 0x3F;
+
+        /* Set the first char of padding to 0x80.  This is safe since there is
+           always at least one byte free */
+        p = ctx->in + count;
+        *p++ = 0x80;
+
+        /* Bytes of padding needed to make 64 bytes */
+        count = 64 - 1 - count;
+
+        /* Pad out to 56 mod 64 */
+        if (count < 8) {
+                /* Two lots of padding:  Pad the first block to 64 bytes */
+                memset(p, 0, count);
+                byteReverse(ctx->in, 16);
+                MD5Transform(ctx->buf, (uint32 *)ctx->in);
+
+                /* Now fill the next block with 56 bytes */
+                memset(ctx->in, 0, 56);
+        } else {
+                /* Pad block to 56 bytes */
+                memset(p, 0, count-8);
+        }
+        byteReverse(ctx->in, 14);
+
+        /* Append length in bits and transform */
+        ((uint32 *)ctx->in)[ 14 ] = ctx->bits[0];
+        ((uint32 *)ctx->in)[ 15 ] = ctx->bits[1];
+
+        MD5Transform(ctx->buf, (uint32 *)ctx->in);
+        byteReverse((unsigned char *)ctx->buf, 4);
+        memcpy(digest, ctx->buf, 16);
+        memset(ctx, 0, sizeof(ctx));    /* In case it is sensitive */
+}
+
+/*
+** Convert a 128-bit MD5 digest into a 32-digit base-16 number.
+*/
+static void MD5DigestToBase16(unsigned char *digest, char *zBuf){
+  static char const zEncode[] = "0123456789abcdef";
+  int i, j;
+
+  for(j=i=0; i<16; i++){
+    int a = digest[i];
+    zBuf[j++] = zEncode[(a>>4)&0xf];
+    zBuf[j++] = zEncode[a & 0xf];
+  }
+  zBuf[j] = 0;
+}
+
+
+/*
+** Convert a 128-bit MD5 digest into sequency of eight 5-digit integers
+** each representing 16 bits of the digest and separated from each
+** other by a "-" character.
+*/
+static void MD5DigestToBase10x8(unsigned char digest[16], char zDigest[50]){
+  int i, j;
+  unsigned int x;
+  for(i=j=0; i<16; i+=2){
+    x = digest[i]*256 + digest[i+1];
+    if( i>0 ) zDigest[j++] = '-';
+    sprintf(&zDigest[j], "%05u", x);
+    j += 5;
+  }
+  zDigest[j] = 0;
+}
+
+/*
+** A TCL command for md5.  The argument is the text to be hashed.  The
+** Result is the hash in base64.  
+*/
+static int md5_cmd(void*cd, Tcl_Interp *interp, int argc, const char **argv){
+  MD5Context ctx;
+  unsigned char digest[16];
+  char zBuf[50];
+  void (*converter)(unsigned char*, char*);
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp,"wrong # args: should be \"", argv[0], 
+        " TEXT\"", 0);
+    return TCL_ERROR;
+  }
+  MD5Init(&ctx);
+  MD5Update(&ctx, (unsigned char*)argv[1], (unsigned)strlen(argv[1]));
+  MD5Final(digest, &ctx);
+  converter = (void(*)(unsigned char*,char*))cd;
+  converter(digest, zBuf);
+  Tcl_AppendResult(interp, zBuf, (char*)0);
+  return TCL_OK;
+}
+
+/*
+** A TCL command to take the md5 hash of a file.  The argument is the
+** name of the file.
+*/
+static int md5file_cmd(void*cd, Tcl_Interp*interp, int argc, const char **argv){
+  FILE *in;
+  MD5Context ctx;
+  void (*converter)(unsigned char*, char*);
+  unsigned char digest[16];
+  char zBuf[10240];
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp,"wrong # args: should be \"", argv[0], 
+        " FILENAME\"", 0);
+    return TCL_ERROR;
+  }
+  in = fopen(argv[1],"rb");
+  if( in==0 ){
+    Tcl_AppendResult(interp,"unable to open file \"", argv[1], 
+         "\" for reading", 0);
+    return TCL_ERROR;
+  }
+  MD5Init(&ctx);
+  for(;;){
+    int n;
+    n = fread(zBuf, 1, sizeof(zBuf), in);
+    if( n<=0 ) break;
+    MD5Update(&ctx, (unsigned char*)zBuf, (unsigned)n);
+  }
+  fclose(in);
+  MD5Final(digest, &ctx);
+  converter = (void(*)(unsigned char*,char*))cd;
+  converter(digest, zBuf);
+  Tcl_AppendResult(interp, zBuf, (char*)0);
+  return TCL_OK;
+}
+
+/*
+** Register the four new TCL commands for generating MD5 checksums
+** with the TCL interpreter.
+*/
+int Md5_Init(Tcl_Interp *interp){
+  Tcl_CreateCommand(interp, "md5", (Tcl_CmdProc*)md5_cmd,
+                    MD5DigestToBase16, 0);
+  Tcl_CreateCommand(interp, "md5-10x8", (Tcl_CmdProc*)md5_cmd,
+                    MD5DigestToBase10x8, 0);
+  Tcl_CreateCommand(interp, "md5file", (Tcl_CmdProc*)md5file_cmd,
+                    MD5DigestToBase16, 0);
+  Tcl_CreateCommand(interp, "md5file-10x8", (Tcl_CmdProc*)md5file_cmd,
+                    MD5DigestToBase10x8, 0);
+  return TCL_OK;
+}
+#endif /* defined(SQLITE_TEST) || defined(SQLITE_TCLMD5) */
+
+#if defined(SQLITE_TEST)
+/*
+** During testing, the special md5sum() aggregate function is available.
+** inside SQLite.  The following routines implement that function.
+*/
+static void md5step(sqlite3_context *context, int argc, sqlite3_value **argv){
+  MD5Context *p;
+  int i;
+  if( argc<1 ) return;
+  p = sqlite3_aggregate_context(context, sizeof(*p));
+  if( p==0 ) return;
+  if( !p->isInit ){
+    MD5Init(p);
+  }
+  for(i=0; i<argc; i++){
+    const char *zData = (char*)sqlite3_value_text(argv[i]);
+    if( zData ){
+      MD5Update(p, (unsigned char*)zData, strlen(zData));
+    }
+  }
+}
+static void md5finalize(sqlite3_context *context){
+  MD5Context *p;
+  unsigned char digest[16];
+  char zBuf[33];
+  p = sqlite3_aggregate_context(context, sizeof(*p));
+  MD5Final(digest,p);
+  MD5DigestToBase16(digest, zBuf);
+  sqlite3_result_text(context, zBuf, -1, SQLITE_TRANSIENT);
+}
+int Md5_Register(sqlite3 *db){
+  int rc = sqlite3_create_function(db, "md5sum", -1, SQLITE_UTF8, 0, 0, 
+                                 md5step, md5finalize);
+  sqlite3_overload_function(db, "md5sum", -1);  /* To exercise this API */
+  return rc;
+}
+#endif /* defined(SQLITE_TEST) */
+
+
+/*
+** If the macro TCLSH is one, then put in code this for the
+** "main" routine that will initialize Tcl and take input from
+** standard input, or if a file is named on the command line
+** the TCL interpreter reads and evaluates that file.
+*/
+#if TCLSH==1
+static const char *tclsh_main_loop(void){
+  static const char zMainloop[] =
+    "set line {}\n"
+    "while {![eof stdin]} {\n"
+      "if {$line!=\"\"} {\n"
+        "puts -nonewline \"> \"\n"
+      "} else {\n"
+        "puts -nonewline \"% \"\n"
+      "}\n"
+      "flush stdout\n"
+      "append line [gets stdin]\n"
+      "if {[info complete $line]} {\n"
+        "if {[catch {uplevel #0 $line} result]} {\n"
+          "puts stderr \"Error: $result\"\n"
+        "} elseif {$result!=\"\"} {\n"
+          "puts $result\n"
+        "}\n"
+        "set line {}\n"
+      "} else {\n"
+        "append line \\n\n"
+      "}\n"
+    "}\n"
+  ;
+  return zMainloop;
+}
+#endif
+#if TCLSH==2
+static const char *tclsh_main_loop(void);
+#endif
+
+#ifdef SQLITE_TEST
+static void init_all(Tcl_Interp *);
+static int init_all_cmd(
+  ClientData cd,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+
+  Tcl_Interp *slave;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "SLAVE");
+    return TCL_ERROR;
+  }
+
+  slave = Tcl_GetSlave(interp, Tcl_GetString(objv[1]));
+  if( !slave ){
+    return TCL_ERROR;
+  }
+
+  init_all(slave);
+  return TCL_OK;
+}
+
+/*
+** Tclcmd: db_use_legacy_prepare DB BOOLEAN
+**
+**   The first argument to this command must be a database command created by
+**   [sqlite3]. If the second argument is true, then the handle is configured
+**   to use the sqlite3_prepare_v2() function to prepare statements. If it
+**   is false, sqlite3_prepare().
+*/
+static int db_use_legacy_prepare_cmd(
+  ClientData cd,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  Tcl_CmdInfo cmdInfo;
+  SqliteDb *pDb;
+  int bPrepare;
+
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB BOOLEAN");
+    return TCL_ERROR;
+  }
+
+  if( !Tcl_GetCommandInfo(interp, Tcl_GetString(objv[1]), &cmdInfo) ){
+    Tcl_AppendResult(interp, "no such db: ", Tcl_GetString(objv[1]), (char*)0);
+    return TCL_ERROR;
+  }
+  pDb = (SqliteDb*)cmdInfo.objClientData;
+  if( Tcl_GetBooleanFromObj(interp, objv[2], &bPrepare) ){
+    return TCL_ERROR;
+  }
+
+  pDb->bLegacyPrepare = bPrepare;
+
+  Tcl_ResetResult(interp);
+  return TCL_OK;
+}
+#endif
+
+/*
+** Configure the interpreter passed as the first argument to have access
+** to the commands and linked variables that make up:
+**
+**   * the [sqlite3] extension itself, 
+**
+**   * If SQLITE_TCLMD5 or SQLITE_TEST is defined, the Md5 commands, and
+**
+**   * If SQLITE_TEST is set, the various test interfaces used by the Tcl
+**     test suite.
+*/
+static void init_all(Tcl_Interp *interp){
+  Sqlite3_Init(interp);
+
+#if defined(SQLITE_TEST) || defined(SQLITE_TCLMD5)
+  Md5_Init(interp);
+#endif
+
+  /* Install the [register_dbstat_vtab] command to access the implementation
+  ** of virtual table dbstat (source file test_stat.c). This command is
+  ** required for testfixture and sqlite3_analyzer, but not by the production
+  ** Tcl extension.  */
+#if defined(SQLITE_TEST) || TCLSH==2
+  {
+    extern int SqlitetestStat_Init(Tcl_Interp*);
+    SqlitetestStat_Init(interp);
+  }
+#endif
+
+#ifdef SQLITE_TEST
+  {
+    extern int Sqliteconfig_Init(Tcl_Interp*);
+    extern int Sqlitetest1_Init(Tcl_Interp*);
+    extern int Sqlitetest2_Init(Tcl_Interp*);
+    extern int Sqlitetest3_Init(Tcl_Interp*);
+    extern int Sqlitetest4_Init(Tcl_Interp*);
+    extern int Sqlitetest5_Init(Tcl_Interp*);
+    extern int Sqlitetest6_Init(Tcl_Interp*);
+    extern int Sqlitetest7_Init(Tcl_Interp*);
+    extern int Sqlitetest8_Init(Tcl_Interp*);
+    extern int Sqlitetest9_Init(Tcl_Interp*);
+    extern int Sqlitetestasync_Init(Tcl_Interp*);
+    extern int Sqlitetest_autoext_Init(Tcl_Interp*);
+    extern int Sqlitetest_demovfs_Init(Tcl_Interp *);
+    extern int Sqlitetest_func_Init(Tcl_Interp*);
+    extern int Sqlitetest_hexio_Init(Tcl_Interp*);
+    extern int Sqlitetest_init_Init(Tcl_Interp*);
+    extern int Sqlitetest_malloc_Init(Tcl_Interp*);
+    extern int Sqlitetest_mutex_Init(Tcl_Interp*);
+    extern int Sqlitetestschema_Init(Tcl_Interp*);
+    extern int Sqlitetestsse_Init(Tcl_Interp*);
+    extern int Sqlitetesttclvar_Init(Tcl_Interp*);
+    extern int SqlitetestThread_Init(Tcl_Interp*);
+    extern int SqlitetestOnefile_Init();
+    extern int SqlitetestOsinst_Init(Tcl_Interp*);
+    extern int Sqlitetestbackup_Init(Tcl_Interp*);
+    extern int Sqlitetestintarray_Init(Tcl_Interp*);
+    extern int Sqlitetestvfs_Init(Tcl_Interp *);
+    extern int Sqlitetestrtree_Init(Tcl_Interp*);
+    extern int Sqlitequota_Init(Tcl_Interp*);
+    extern int Sqlitemultiplex_Init(Tcl_Interp*);
+    extern int SqliteSuperlock_Init(Tcl_Interp*);
+    extern int SqlitetestSyscall_Init(Tcl_Interp*);
+    extern int Sqlitetestfuzzer_Init(Tcl_Interp*);
+    extern int Sqlitetestwholenumber_Init(Tcl_Interp*);
+
+#if defined(SQLITE_ENABLE_FTS3) || defined(SQLITE_ENABLE_FTS4)
+    extern int Sqlitetestfts3_Init(Tcl_Interp *interp);
+#endif
+
+#ifdef SQLITE_ENABLE_ZIPVFS
+    extern int Zipvfs_Init(Tcl_Interp*);
+    Zipvfs_Init(interp);
+#endif
+
+    Sqliteconfig_Init(interp);
+    Sqlitetest1_Init(interp);
+    Sqlitetest2_Init(interp);
+    Sqlitetest3_Init(interp);
+    Sqlitetest4_Init(interp);
+    Sqlitetest5_Init(interp);
+    Sqlitetest6_Init(interp);
+    Sqlitetest7_Init(interp);
+    Sqlitetest8_Init(interp);
+    Sqlitetest9_Init(interp);
+    Sqlitetestasync_Init(interp);
+    Sqlitetest_autoext_Init(interp);
+    Sqlitetest_demovfs_Init(interp);
+    Sqlitetest_func_Init(interp);
+    Sqlitetest_hexio_Init(interp);
+    Sqlitetest_init_Init(interp);
+    Sqlitetest_malloc_Init(interp);
+    Sqlitetest_mutex_Init(interp);
+    Sqlitetestschema_Init(interp);
+    Sqlitetesttclvar_Init(interp);
+    SqlitetestThread_Init(interp);
+    SqlitetestOnefile_Init(interp);
+    SqlitetestOsinst_Init(interp);
+    Sqlitetestbackup_Init(interp);
+    Sqlitetestintarray_Init(interp);
+    Sqlitetestvfs_Init(interp);
+    Sqlitetestrtree_Init(interp);
+    Sqlitequota_Init(interp);
+    Sqlitemultiplex_Init(interp);
+    SqliteSuperlock_Init(interp);
+    SqlitetestSyscall_Init(interp);
+    Sqlitetestfuzzer_Init(interp);
+    Sqlitetestwholenumber_Init(interp);
+
+#if defined(SQLITE_ENABLE_FTS3) || defined(SQLITE_ENABLE_FTS4)
+    Sqlitetestfts3_Init(interp);
+#endif
+
+    Tcl_CreateObjCommand(
+        interp, "load_testfixture_extensions", init_all_cmd, 0, 0
+    );
+    Tcl_CreateObjCommand(
+        interp, "db_use_legacy_prepare", db_use_legacy_prepare_cmd, 0, 0
+    );
+
+#ifdef SQLITE_SSE
+    Sqlitetestsse_Init(interp);
+#endif
+  }
+#endif
+}
+
+#define TCLSH_MAIN main   /* Needed to fake out mktclapp */
+int TCLSH_MAIN(int argc, char **argv){
+  Tcl_Interp *interp;
+  
+  /* Call sqlite3_shutdown() once before doing anything else. This is to
+  ** test that sqlite3_shutdown() can be safely called by a process before
+  ** sqlite3_initialize() is. */
+  sqlite3_shutdown();
+
+  Tcl_FindExecutable(argv[0]);
+  interp = Tcl_CreateInterp();
+
+#if TCLSH==2
+  sqlite3_config(SQLITE_CONFIG_SINGLETHREAD);
+#endif
+
+  init_all(interp);
+  if( argc>=2 ){
+    int i;
+    char zArgc[32];
+    sqlite3_snprintf(sizeof(zArgc), zArgc, "%d", argc-(3-TCLSH));
+    Tcl_SetVar(interp,"argc", zArgc, TCL_GLOBAL_ONLY);
+    Tcl_SetVar(interp,"argv0",argv[1],TCL_GLOBAL_ONLY);
+    Tcl_SetVar(interp,"argv", "", TCL_GLOBAL_ONLY);
+    for(i=3-TCLSH; i<argc; i++){
+      Tcl_SetVar(interp, "argv", argv[i],
+          TCL_GLOBAL_ONLY | TCL_LIST_ELEMENT | TCL_APPEND_VALUE);
+    }
+    if( TCLSH==1 && Tcl_EvalFile(interp, argv[1])!=TCL_OK ){
+      const char *zInfo = Tcl_GetVar(interp, "errorInfo", TCL_GLOBAL_ONLY);
+      if( zInfo==0 ) zInfo = Tcl_GetStringResult(interp);
+      fprintf(stderr,"%s: %s\n", *argv, zInfo);
+      return 1;
+    }
+  }
+  if( TCLSH==2 || argc<=1 ){
+    Tcl_GlobalEval(interp, tclsh_main_loop());
+  }
+  return 0;
+}
+#endif /* TCLSH */
diff --git a/src/test1.c b/src/test1.c
new file mode 100644
index 0000000..2634252
--- /dev/null
+++ b/src/test1.c
@@ -0,0 +1,6133 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Code for testing all sorts of SQLite interfaces.  This code
+** is not included in the SQLite library.  It is used for automated
+** testing of the SQLite library.
+*/
+#include "sqliteInt.h"
+#include "vdbeInt.h"
+#include "tcl.h"
+#include <stdlib.h>
+#include <string.h>
+
+/*
+** This is a copy of the first part of the SqliteDb structure in 
+** tclsqlite.c.  We need it here so that the get_sqlite_pointer routine
+** can extract the sqlite3* pointer from an existing Tcl SQLite
+** connection.
+*/
+struct SqliteDb {
+  sqlite3 *db;
+};
+
+/*
+** Convert text generated by the "%p" conversion format back into
+** a pointer.
+*/
+static int testHexToInt(int h){
+  if( h>='0' && h<='9' ){
+    return h - '0';
+  }else if( h>='a' && h<='f' ){
+    return h - 'a' + 10;
+  }else{
+    assert( h>='A' && h<='F' );
+    return h - 'A' + 10;
+  }
+}
+void *sqlite3TestTextToPtr(const char *z){
+  void *p;
+  u64 v;
+  u32 v2;
+  if( z[0]=='0' && z[1]=='x' ){
+    z += 2;
+  }
+  v = 0;
+  while( *z ){
+    v = (v<<4) + testHexToInt(*z);
+    z++;
+  }
+  if( sizeof(p)==sizeof(v) ){
+    memcpy(&p, &v, sizeof(p));
+  }else{
+    assert( sizeof(p)==sizeof(v2) );
+    v2 = (u32)v;
+    memcpy(&p, &v2, sizeof(p));
+  }
+  return p;
+}
+
+
+/*
+** A TCL command that returns the address of the sqlite* pointer
+** for an sqlite connection instance.  Bad things happen if the
+** input is not an sqlite connection.
+*/
+static int get_sqlite_pointer(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  struct SqliteDb *p;
+  Tcl_CmdInfo cmdInfo;
+  char zBuf[100];
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "SQLITE-CONNECTION");
+    return TCL_ERROR;
+  }
+  if( !Tcl_GetCommandInfo(interp, Tcl_GetString(objv[1]), &cmdInfo) ){
+    Tcl_AppendResult(interp, "command not found: ",
+           Tcl_GetString(objv[1]), (char*)0);
+    return TCL_ERROR;
+  }
+  p = (struct SqliteDb*)cmdInfo.objClientData;
+  sprintf(zBuf, "%p", p->db);
+  if( strncmp(zBuf,"0x",2) ){
+    sprintf(zBuf, "0x%p", p->db);
+  }
+  Tcl_AppendResult(interp, zBuf, 0);
+  return TCL_OK;
+}
+
+/*
+** Decode a pointer to an sqlite3 object.
+*/
+int getDbPointer(Tcl_Interp *interp, const char *zA, sqlite3 **ppDb){
+  struct SqliteDb *p;
+  Tcl_CmdInfo cmdInfo;
+  if( Tcl_GetCommandInfo(interp, zA, &cmdInfo) ){
+    p = (struct SqliteDb*)cmdInfo.objClientData;
+    *ppDb = p->db;
+  }else{
+    *ppDb = (sqlite3*)sqlite3TestTextToPtr(zA);
+  }
+  return TCL_OK;
+}
+
+
+const char *sqlite3TestErrorName(int rc){
+  const char *zName = 0;
+  switch( rc ){
+    case SQLITE_OK:                  zName = "SQLITE_OK";                break;
+    case SQLITE_ERROR:               zName = "SQLITE_ERROR";             break;
+    case SQLITE_INTERNAL:            zName = "SQLITE_INTERNAL";          break;
+    case SQLITE_PERM:                zName = "SQLITE_PERM";              break;
+    case SQLITE_ABORT:               zName = "SQLITE_ABORT";             break;
+    case SQLITE_BUSY:                zName = "SQLITE_BUSY";              break;
+    case SQLITE_LOCKED:              zName = "SQLITE_LOCKED";            break;
+    case SQLITE_LOCKED_SHAREDCACHE:  zName = "SQLITE_LOCKED_SHAREDCACHE";break;
+    case SQLITE_NOMEM:               zName = "SQLITE_NOMEM";             break;
+    case SQLITE_READONLY:            zName = "SQLITE_READONLY";          break;
+    case SQLITE_INTERRUPT:           zName = "SQLITE_INTERRUPT";         break;
+    case SQLITE_IOERR:               zName = "SQLITE_IOERR";             break;
+    case SQLITE_CORRUPT:             zName = "SQLITE_CORRUPT";           break;
+    case SQLITE_NOTFOUND:            zName = "SQLITE_NOTFOUND";          break;
+    case SQLITE_FULL:                zName = "SQLITE_FULL";              break;
+    case SQLITE_CANTOPEN:            zName = "SQLITE_CANTOPEN";          break;
+    case SQLITE_PROTOCOL:            zName = "SQLITE_PROTOCOL";          break;
+    case SQLITE_EMPTY:               zName = "SQLITE_EMPTY";             break;
+    case SQLITE_SCHEMA:              zName = "SQLITE_SCHEMA";            break;
+    case SQLITE_TOOBIG:              zName = "SQLITE_TOOBIG";            break;
+    case SQLITE_CONSTRAINT:          zName = "SQLITE_CONSTRAINT";        break;
+    case SQLITE_MISMATCH:            zName = "SQLITE_MISMATCH";          break;
+    case SQLITE_MISUSE:              zName = "SQLITE_MISUSE";            break;
+    case SQLITE_NOLFS:               zName = "SQLITE_NOLFS";             break;
+    case SQLITE_AUTH:                zName = "SQLITE_AUTH";              break;
+    case SQLITE_FORMAT:              zName = "SQLITE_FORMAT";            break;
+    case SQLITE_RANGE:               zName = "SQLITE_RANGE";             break;
+    case SQLITE_NOTADB:              zName = "SQLITE_NOTADB";            break;
+    case SQLITE_ROW:                 zName = "SQLITE_ROW";               break;
+    case SQLITE_DONE:                zName = "SQLITE_DONE";              break;
+    case SQLITE_IOERR_READ:          zName = "SQLITE_IOERR_READ";        break;
+    case SQLITE_IOERR_SHORT_READ:    zName = "SQLITE_IOERR_SHORT_READ";  break;
+    case SQLITE_IOERR_WRITE:         zName = "SQLITE_IOERR_WRITE";       break;
+    case SQLITE_IOERR_FSYNC:         zName = "SQLITE_IOERR_FSYNC";       break;
+    case SQLITE_IOERR_DIR_FSYNC:     zName = "SQLITE_IOERR_DIR_FSYNC";   break;
+    case SQLITE_IOERR_TRUNCATE:      zName = "SQLITE_IOERR_TRUNCATE";    break;
+    case SQLITE_IOERR_FSTAT:         zName = "SQLITE_IOERR_FSTAT";       break;
+    case SQLITE_IOERR_UNLOCK:        zName = "SQLITE_IOERR_UNLOCK";      break;
+    case SQLITE_IOERR_RDLOCK:        zName = "SQLITE_IOERR_RDLOCK";      break;
+    case SQLITE_IOERR_DELETE:        zName = "SQLITE_IOERR_DELETE";      break;
+    case SQLITE_IOERR_BLOCKED:       zName = "SQLITE_IOERR_BLOCKED";     break;
+    case SQLITE_IOERR_NOMEM:         zName = "SQLITE_IOERR_NOMEM";       break;
+    case SQLITE_IOERR_ACCESS:        zName = "SQLITE_IOERR_ACCESS";      break;
+    case SQLITE_IOERR_CHECKRESERVEDLOCK:
+                               zName = "SQLITE_IOERR_CHECKRESERVEDLOCK"; break;
+    case SQLITE_IOERR_LOCK:          zName = "SQLITE_IOERR_LOCK";        break;
+    case SQLITE_CORRUPT_VTAB:        zName = "SQLITE_CORRUPT_VTAB";      break;
+    case SQLITE_READONLY_RECOVERY:   zName = "SQLITE_READONLY_RECOVERY"; break;
+    case SQLITE_READONLY_CANTLOCK:   zName = "SQLITE_READONLY_CANTLOCK"; break;
+    default:                         zName = "SQLITE_Unknown";           break;
+  }
+  return zName;
+}
+#define t1ErrorName sqlite3TestErrorName
+
+/*
+** Convert an sqlite3_stmt* into an sqlite3*.  This depends on the
+** fact that the sqlite3* is the first field in the Vdbe structure.
+*/
+#define StmtToDb(X)   sqlite3_db_handle(X)
+
+/*
+** Check a return value to make sure it agrees with the results
+** from sqlite3_errcode.
+*/
+int sqlite3TestErrCode(Tcl_Interp *interp, sqlite3 *db, int rc){
+  if( sqlite3_threadsafe()==0 && rc!=SQLITE_MISUSE && rc!=SQLITE_OK
+   && sqlite3_errcode(db)!=rc ){
+    char zBuf[200];
+    int r2 = sqlite3_errcode(db);
+    sprintf(zBuf, "error code %s (%d) does not match sqlite3_errcode %s (%d)",
+       t1ErrorName(rc), rc, t1ErrorName(r2), r2);
+    Tcl_ResetResult(interp);
+    Tcl_AppendResult(interp, zBuf, 0);
+    return 1;
+  }
+  return 0;
+}
+
+/*
+** Decode a pointer to an sqlite3_stmt object.
+*/
+static int getStmtPointer(
+  Tcl_Interp *interp, 
+  const char *zArg,  
+  sqlite3_stmt **ppStmt
+){
+  *ppStmt = (sqlite3_stmt*)sqlite3TestTextToPtr(zArg);
+  return TCL_OK;
+}
+
+/*
+** Generate a text representation of a pointer that can be understood
+** by the getDbPointer and getVmPointer routines above.
+**
+** The problem is, on some machines (Solaris) if you do a printf with
+** "%p" you cannot turn around and do a scanf with the same "%p" and
+** get your pointer back.  You have to prepend a "0x" before it will
+** work.  Or at least that is what is reported to me (drh).  But this
+** behavior varies from machine to machine.  The solution used her is
+** to test the string right after it is generated to see if it can be
+** understood by scanf, and if not, try prepending an "0x" to see if
+** that helps.  If nothing works, a fatal error is generated.
+*/
+int sqlite3TestMakePointerStr(Tcl_Interp *interp, char *zPtr, void *p){
+  sqlite3_snprintf(100, zPtr, "%p", p);
+  return TCL_OK;
+}
+
+/*
+** The callback routine for sqlite3_exec_printf().
+*/
+static int exec_printf_cb(void *pArg, int argc, char **argv, char **name){
+  Tcl_DString *str = (Tcl_DString*)pArg;
+  int i;
+
+  if( Tcl_DStringLength(str)==0 ){
+    for(i=0; i<argc; i++){
+      Tcl_DStringAppendElement(str, name[i] ? name[i] : "NULL");
+    }
+  }
+  for(i=0; i<argc; i++){
+    Tcl_DStringAppendElement(str, argv[i] ? argv[i] : "NULL");
+  }
+  return 0;
+}
+
+/*
+** The I/O tracing callback.
+*/
+#if !defined(SQLITE_OMIT_TRACE) && defined(SQLITE_ENABLE_IOTRACE)
+static FILE *iotrace_file = 0;
+static void io_trace_callback(const char *zFormat, ...){
+  va_list ap;
+  va_start(ap, zFormat);
+  vfprintf(iotrace_file, zFormat, ap);
+  va_end(ap);
+  fflush(iotrace_file);
+}
+#endif
+
+/*
+** Usage:  io_trace FILENAME
+**
+** Turn I/O tracing on or off.  If FILENAME is not an empty string,
+** I/O tracing begins going into FILENAME. If FILENAME is an empty
+** string, I/O tracing is turned off.
+*/
+static int test_io_trace(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+#if !defined(SQLITE_OMIT_TRACE) && defined(SQLITE_ENABLE_IOTRACE)
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+          " FILENAME\"", 0);
+    return TCL_ERROR;
+  }
+  if( iotrace_file ){
+    if( iotrace_file!=stdout && iotrace_file!=stderr ){
+      fclose(iotrace_file);
+    }
+    iotrace_file = 0;
+    sqlite3IoTrace = 0;
+  }
+  if( argv[1][0] ){
+    if( strcmp(argv[1],"stdout")==0 ){
+      iotrace_file = stdout;
+    }else if( strcmp(argv[1],"stderr")==0 ){
+      iotrace_file = stderr;
+    }else{
+      iotrace_file = fopen(argv[1], "w");
+    }
+    sqlite3IoTrace = io_trace_callback;
+  }
+#endif
+  return TCL_OK;
+}
+
+
+/*
+** Usage:  sqlite3_exec_printf  DB  FORMAT  STRING
+**
+** Invoke the sqlite3_exec_printf() interface using the open database
+** DB.  The SQL is the string FORMAT.  The format string should contain
+** one %s or %q.  STRING is the value inserted into %s or %q.
+*/
+static int test_exec_printf(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  sqlite3 *db;
+  Tcl_DString str;
+  int rc;
+  char *zErr = 0;
+  char *zSql;
+  char zBuf[30];
+  if( argc!=4 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], 
+       " DB FORMAT STRING", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  Tcl_DStringInit(&str);
+  zSql = sqlite3_mprintf(argv[2], argv[3]);
+  rc = sqlite3_exec(db, zSql, exec_printf_cb, &str, &zErr);
+  sqlite3_free(zSql);
+  sprintf(zBuf, "%d", rc);
+  Tcl_AppendElement(interp, zBuf);
+  Tcl_AppendElement(interp, rc==SQLITE_OK ? Tcl_DStringValue(&str) : zErr);
+  Tcl_DStringFree(&str);
+  if( zErr ) sqlite3_free(zErr);
+  if( sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_exec_hex  DB  HEX
+**
+** Invoke the sqlite3_exec() on a string that is obtained by translating
+** HEX into ASCII.  Most characters are translated as is.  %HH becomes
+** a hex character.
+*/
+static int test_exec_hex(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  sqlite3 *db;
+  Tcl_DString str;
+  int rc, i, j;
+  char *zErr = 0;
+  char *zHex;
+  char zSql[500];
+  char zBuf[30];
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], 
+       " DB HEX", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  zHex = argv[2];
+  for(i=j=0; i<sizeof(zSql) && zHex[j]; i++, j++){
+    if( zHex[j]=='%' && zHex[j+2] && zHex[j+2] ){
+      zSql[i] = (testHexToInt(zHex[j+1])<<4) + testHexToInt(zHex[j+2]);
+      j += 2;
+    }else{
+      zSql[i] = zHex[j];
+    }
+  }
+  zSql[i] = 0;
+  Tcl_DStringInit(&str);
+  rc = sqlite3_exec(db, zSql, exec_printf_cb, &str, &zErr);
+  sprintf(zBuf, "%d", rc);
+  Tcl_AppendElement(interp, zBuf);
+  Tcl_AppendElement(interp, rc==SQLITE_OK ? Tcl_DStringValue(&str) : zErr);
+  Tcl_DStringFree(&str);
+  if( zErr ) sqlite3_free(zErr);
+  if( sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
+  return TCL_OK;
+}
+
+/*
+** Usage:  db_enter DB
+**         db_leave DB
+**
+** Enter or leave the mutex on a database connection.
+*/
+static int db_enter(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  sqlite3 *db;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], 
+       " DB", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  sqlite3_mutex_enter(db->mutex);
+  return TCL_OK;
+}
+static int db_leave(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  sqlite3 *db;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], 
+       " DB", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  sqlite3_mutex_leave(db->mutex);
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_exec  DB  SQL
+**
+** Invoke the sqlite3_exec interface using the open database DB
+*/
+static int test_exec(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  sqlite3 *db;
+  Tcl_DString str;
+  int rc;
+  char *zErr = 0;
+  char *zSql;
+  int i, j;
+  char zBuf[30];
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], 
+       " DB SQL", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  Tcl_DStringInit(&str);
+  zSql = sqlite3_mprintf("%s", argv[2]);
+  for(i=j=0; zSql[i];){
+    if( zSql[i]=='%' ){
+      zSql[j++] = (testHexToInt(zSql[i+1])<<4) + testHexToInt(zSql[i+2]);
+      i += 3;
+    }else{
+      zSql[j++] = zSql[i++];
+    }
+  }
+  zSql[j] = 0;
+  rc = sqlite3_exec(db, zSql, exec_printf_cb, &str, &zErr);
+  sqlite3_free(zSql);
+  sprintf(zBuf, "%d", rc);
+  Tcl_AppendElement(interp, zBuf);
+  Tcl_AppendElement(interp, rc==SQLITE_OK ? Tcl_DStringValue(&str) : zErr);
+  Tcl_DStringFree(&str);
+  if( zErr ) sqlite3_free(zErr);
+  if( sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_exec_nr  DB  SQL
+**
+** Invoke the sqlite3_exec interface using the open database DB.  Discard
+** all results
+*/
+static int test_exec_nr(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  sqlite3 *db;
+  int rc;
+  char *zErr = 0;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], 
+       " DB SQL", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  rc = sqlite3_exec(db, argv[2], 0, 0, &zErr);
+  if( sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_mprintf_z_test  SEPARATOR  ARG0  ARG1 ...
+**
+** Test the %z format of sqlite_mprintf().  Use multiple mprintf() calls to 
+** concatenate arg0 through argn using separator as the separator.
+** Return the result.
+*/
+static int test_mprintf_z(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  char *zResult = 0;
+  int i;
+
+  for(i=2; i<argc && (i==2 || zResult); i++){
+    zResult = sqlite3_mprintf("%z%s%s", zResult, argv[1], argv[i]);
+  }
+  Tcl_AppendResult(interp, zResult, 0);
+  sqlite3_free(zResult);
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_mprintf_n_test  STRING
+**
+** Test the %n format of sqlite_mprintf().  Return the length of the
+** input string.
+*/
+static int test_mprintf_n(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  char *zStr;
+  int n = 0;
+  zStr = sqlite3_mprintf("%s%n", argv[1], &n);
+  sqlite3_free(zStr);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(n));
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_snprintf_int  SIZE FORMAT  INT
+**
+** Test the of sqlite3_snprintf() routine.  SIZE is the size of the
+** output buffer in bytes.  The maximum size is 100.  FORMAT is the
+** format string.  INT is a single integer argument.  The FORMAT
+** string must require no more than this one integer argument.  If
+** You pass in a format string that requires more than one argument,
+** bad things will happen.
+*/
+static int test_snprintf_int(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  char zStr[100];
+  int n = atoi(argv[1]);
+  const char *zFormat = argv[2];
+  int a1 = atoi(argv[3]);
+  if( n>sizeof(zStr) ) n = sizeof(zStr);
+  sqlite3_snprintf(sizeof(zStr), zStr, "abcdefghijklmnopqrstuvwxyz");
+  sqlite3_snprintf(n, zStr, zFormat, a1);
+  Tcl_AppendResult(interp, zStr, 0);
+  return TCL_OK;
+}
+
+#ifndef SQLITE_OMIT_GET_TABLE
+
+/*
+** Usage:  sqlite3_get_table_printf  DB  FORMAT  STRING  ?--no-counts?
+**
+** Invoke the sqlite3_get_table_printf() interface using the open database
+** DB.  The SQL is the string FORMAT.  The format string should contain
+** one %s or %q.  STRING is the value inserted into %s or %q.
+*/
+static int test_get_table_printf(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  sqlite3 *db;
+  Tcl_DString str;
+  int rc;
+  char *zErr = 0;
+  int nRow, nCol;
+  char **aResult;
+  int i;
+  char zBuf[30];
+  char *zSql;
+  int resCount = -1;
+  if( argc==5 ){
+    if( Tcl_GetInt(interp, argv[4], &resCount) ) return TCL_ERROR;
+  }
+  if( argc!=4 && argc!=5 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], 
+       " DB FORMAT STRING ?COUNT?", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  Tcl_DStringInit(&str);
+  zSql = sqlite3_mprintf(argv[2],argv[3]);
+  if( argc==5 ){
+    rc = sqlite3_get_table(db, zSql, &aResult, 0, 0, &zErr);
+  }else{
+    rc = sqlite3_get_table(db, zSql, &aResult, &nRow, &nCol, &zErr);
+    resCount = (nRow+1)*nCol;
+  }
+  sqlite3_free(zSql);
+  sprintf(zBuf, "%d", rc);
+  Tcl_AppendElement(interp, zBuf);
+  if( rc==SQLITE_OK ){
+    if( argc==4 ){
+      sprintf(zBuf, "%d", nRow);
+      Tcl_AppendElement(interp, zBuf);
+      sprintf(zBuf, "%d", nCol);
+      Tcl_AppendElement(interp, zBuf);
+    }
+    for(i=0; i<resCount; i++){
+      Tcl_AppendElement(interp, aResult[i] ? aResult[i] : "NULL");
+    }
+  }else{
+    Tcl_AppendElement(interp, zErr);
+  }
+  sqlite3_free_table(aResult);
+  if( zErr ) sqlite3_free(zErr);
+  if( sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
+  return TCL_OK;
+}
+
+#endif /* SQLITE_OMIT_GET_TABLE */
+
+
+/*
+** Usage:  sqlite3_last_insert_rowid DB
+**
+** Returns the integer ROWID of the most recent insert.
+*/
+static int test_last_rowid(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  sqlite3 *db;
+  char zBuf[30];
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], " DB\"", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  sprintf(zBuf, "%lld", sqlite3_last_insert_rowid(db));
+  Tcl_AppendResult(interp, zBuf, 0);
+  return SQLITE_OK;
+}
+
+/*
+** Usage:  sqlite3_key DB KEY
+**
+** Set the codec key.
+*/
+static int test_key(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  sqlite3 *db;
+  const char *zKey;
+  int nKey;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " FILENAME\"", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  zKey = argv[2];
+  nKey = strlen(zKey);
+#ifdef SQLITE_HAS_CODEC
+  sqlite3_key(db, zKey, nKey);
+#endif
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_rekey DB KEY
+**
+** Change the codec key.
+*/
+static int test_rekey(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  sqlite3 *db;
+  const char *zKey;
+  int nKey;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " FILENAME\"", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  zKey = argv[2];
+  nKey = strlen(zKey);
+#ifdef SQLITE_HAS_CODEC
+  sqlite3_rekey(db, zKey, nKey);
+#endif
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_close DB
+**
+** Closes the database opened by sqlite3_open.
+*/
+static int sqlite_test_close(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  sqlite3 *db;
+  int rc;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " FILENAME\"", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  rc = sqlite3_close(db);
+  Tcl_SetResult(interp, (char *)t1ErrorName(rc), TCL_STATIC);
+  return TCL_OK;
+}
+
+/*
+** Implementation of the x_coalesce() function.
+** Return the first argument non-NULL argument.
+*/
+static void t1_ifnullFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  int i;
+  for(i=0; i<argc; i++){
+    if( SQLITE_NULL!=sqlite3_value_type(argv[i]) ){
+      int n = sqlite3_value_bytes(argv[i]);
+      sqlite3_result_text(context, (char*)sqlite3_value_text(argv[i]),
+          n, SQLITE_TRANSIENT);
+      break;
+    }
+  }
+}
+
+/*
+** These are test functions.    hex8() interprets its argument as
+** UTF8 and returns a hex encoding.  hex16le() interprets its argument
+** as UTF16le and returns a hex encoding.
+*/
+static void hex8Func(sqlite3_context *p, int argc, sqlite3_value **argv){
+  const unsigned char *z;
+  int i;
+  char zBuf[200];
+  z = sqlite3_value_text(argv[0]);
+  for(i=0; i<sizeof(zBuf)/2 - 2 && z[i]; i++){
+    sprintf(&zBuf[i*2], "%02x", z[i]&0xff);
+  }
+  zBuf[i*2] = 0;
+  sqlite3_result_text(p, (char*)zBuf, -1, SQLITE_TRANSIENT);
+}
+#ifndef SQLITE_OMIT_UTF16
+static void hex16Func(sqlite3_context *p, int argc, sqlite3_value **argv){
+  const unsigned short int *z;
+  int i;
+  char zBuf[400];
+  z = sqlite3_value_text16(argv[0]);
+  for(i=0; i<sizeof(zBuf)/4 - 4 && z[i]; i++){
+    sprintf(&zBuf[i*4], "%04x", z[i]&0xff);
+  }
+  zBuf[i*4] = 0;
+  sqlite3_result_text(p, (char*)zBuf, -1, SQLITE_TRANSIENT);
+}
+#endif
+
+/*
+** A structure into which to accumulate text.
+*/
+struct dstr {
+  int nAlloc;  /* Space allocated */
+  int nUsed;   /* Space used */
+  char *z;     /* The space */
+};
+
+/*
+** Append text to a dstr
+*/
+static void dstrAppend(struct dstr *p, const char *z, int divider){
+  int n = strlen(z);
+  if( p->nUsed + n + 2 > p->nAlloc ){
+    char *zNew;
+    p->nAlloc = p->nAlloc*2 + n + 200;
+    zNew = sqlite3_realloc(p->z, p->nAlloc);
+    if( zNew==0 ){
+      sqlite3_free(p->z);
+      memset(p, 0, sizeof(*p));
+      return;
+    }
+    p->z = zNew;
+  }
+  if( divider && p->nUsed>0 ){
+    p->z[p->nUsed++] = divider;
+  }
+  memcpy(&p->z[p->nUsed], z, n+1);
+  p->nUsed += n;
+}
+
+/*
+** Invoked for each callback from sqlite3ExecFunc
+*/
+static int execFuncCallback(void *pData, int argc, char **argv, char **NotUsed){
+  struct dstr *p = (struct dstr*)pData;
+  int i;
+  for(i=0; i<argc; i++){
+    if( argv[i]==0 ){
+      dstrAppend(p, "NULL", ' ');
+    }else{
+      dstrAppend(p, argv[i], ' ');
+    }
+  }
+  return 0;
+}
+
+/*
+** Implementation of the x_sqlite_exec() function.  This function takes
+** a single argument and attempts to execute that argument as SQL code.
+** This is illegal and should set the SQLITE_MISUSE flag on the database.
+**
+** 2004-Jan-07:  We have changed this to make it legal to call sqlite3_exec()
+** from within a function call.  
+** 
+** This routine simulates the effect of having two threads attempt to
+** use the same database at the same time.
+*/
+static void sqlite3ExecFunc(
+  sqlite3_context *context, 
+  int argc,  
+  sqlite3_value **argv
+){
+  struct dstr x;
+  memset(&x, 0, sizeof(x));
+  (void)sqlite3_exec((sqlite3*)sqlite3_user_data(context),
+      (char*)sqlite3_value_text(argv[0]),
+      execFuncCallback, &x, 0);
+  sqlite3_result_text(context, x.z, x.nUsed, SQLITE_TRANSIENT);
+  sqlite3_free(x.z);
+}
+
+/*
+** Implementation of tkt2213func(), a scalar function that takes exactly
+** one argument. It has two interesting features:
+**
+** * It calls sqlite3_value_text() 3 times on the argument sqlite3_value*.
+**   If the three pointers returned are not the same an SQL error is raised.
+**
+** * Otherwise it returns a copy of the text representation of its 
+**   argument in such a way as the VDBE representation is a Mem* cell 
+**   with the MEM_Term flag clear. 
+**
+** Ticket #2213 can therefore be tested by evaluating the following
+** SQL expression:
+**
+**   tkt2213func(tkt2213func('a string'));
+*/
+static void tkt2213Function(
+  sqlite3_context *context, 
+  int argc,  
+  sqlite3_value **argv
+){
+  int nText;
+  unsigned char const *zText1;
+  unsigned char const *zText2;
+  unsigned char const *zText3;
+
+  nText = sqlite3_value_bytes(argv[0]);
+  zText1 = sqlite3_value_text(argv[0]);
+  zText2 = sqlite3_value_text(argv[0]);
+  zText3 = sqlite3_value_text(argv[0]);
+
+  if( zText1!=zText2 || zText2!=zText3 ){
+    sqlite3_result_error(context, "tkt2213 is not fixed", -1);
+  }else{
+    char *zCopy = (char *)sqlite3_malloc(nText);
+    memcpy(zCopy, zText1, nText);
+    sqlite3_result_text(context, zCopy, nText, sqlite3_free);
+  }
+}
+
+/*
+** The following SQL function takes 4 arguments.  The 2nd and
+** 4th argument must be one of these strings:  'text', 'text16',
+** or 'blob' corresponding to API functions
+**
+**      sqlite3_value_text()
+**      sqlite3_value_text16()
+**      sqlite3_value_blob()
+**
+** The third argument is a string, either 'bytes' or 'bytes16' or 'noop',
+** corresponding to APIs:
+**
+**      sqlite3_value_bytes()
+**      sqlite3_value_bytes16()
+**      noop
+**
+** The APIs designated by the 2nd through 4th arguments are applied
+** to the first argument in order.  If the pointers returned by the
+** second and fourth are different, this routine returns 1.  Otherwise,
+** this routine returns 0.
+**
+** This function is used to test to see when returned pointers from
+** the _text(), _text16() and _blob() APIs become invalidated.
+*/
+static void ptrChngFunction(
+  sqlite3_context *context, 
+  int argc,  
+  sqlite3_value **argv
+){
+  const void *p1, *p2;
+  const char *zCmd;
+  if( argc!=4 ) return;
+  zCmd = (const char*)sqlite3_value_text(argv[1]);
+  if( zCmd==0 ) return;
+  if( strcmp(zCmd,"text")==0 ){
+    p1 = (const void*)sqlite3_value_text(argv[0]);
+#ifndef SQLITE_OMIT_UTF16
+  }else if( strcmp(zCmd, "text16")==0 ){
+    p1 = (const void*)sqlite3_value_text16(argv[0]);
+#endif
+  }else if( strcmp(zCmd, "blob")==0 ){
+    p1 = (const void*)sqlite3_value_blob(argv[0]);
+  }else{
+    return;
+  }
+  zCmd = (const char*)sqlite3_value_text(argv[2]);
+  if( zCmd==0 ) return;
+  if( strcmp(zCmd,"bytes")==0 ){
+    sqlite3_value_bytes(argv[0]);
+#ifndef SQLITE_OMIT_UTF16
+  }else if( strcmp(zCmd, "bytes16")==0 ){
+    sqlite3_value_bytes16(argv[0]);
+#endif
+  }else if( strcmp(zCmd, "noop")==0 ){
+    /* do nothing */
+  }else{
+    return;
+  }
+  zCmd = (const char*)sqlite3_value_text(argv[3]);
+  if( zCmd==0 ) return;
+  if( strcmp(zCmd,"text")==0 ){
+    p2 = (const void*)sqlite3_value_text(argv[0]);
+#ifndef SQLITE_OMIT_UTF16
+  }else if( strcmp(zCmd, "text16")==0 ){
+    p2 = (const void*)sqlite3_value_text16(argv[0]);
+#endif
+  }else if( strcmp(zCmd, "blob")==0 ){
+    p2 = (const void*)sqlite3_value_blob(argv[0]);
+  }else{
+    return;
+  }
+  sqlite3_result_int(context, p1!=p2);
+}
+
+
+/*
+** Usage:  sqlite_test_create_function DB
+**
+** Call the sqlite3_create_function API on the given database in order
+** to create a function named "x_coalesce".  This function does the same thing
+** as the "coalesce" function.  This function also registers an SQL function
+** named "x_sqlite_exec" that invokes sqlite3_exec().  Invoking sqlite3_exec()
+** in this way is illegal recursion and should raise an SQLITE_MISUSE error.
+** The effect is similar to trying to use the same database connection from
+** two threads at the same time.
+**
+** The original motivation for this routine was to be able to call the
+** sqlite3_create_function function while a query is in progress in order
+** to test the SQLITE_MISUSE detection logic.
+*/
+static int test_create_function(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  int rc;
+  sqlite3 *db;
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " DB\"", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  rc = sqlite3_create_function(db, "x_coalesce", -1, SQLITE_ANY, 0, 
+        t1_ifnullFunc, 0, 0);
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_create_function(db, "hex8", 1, SQLITE_ANY, 0, 
+          hex8Func, 0, 0);
+  }
+#ifndef SQLITE_OMIT_UTF16
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_create_function(db, "hex16", 1, SQLITE_ANY, 0, 
+          hex16Func, 0, 0);
+  }
+#endif
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_create_function(db, "tkt2213func", 1, SQLITE_ANY, 0, 
+          tkt2213Function, 0, 0);
+  }
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_create_function(db, "pointer_change", 4, SQLITE_ANY, 0, 
+          ptrChngFunction, 0, 0);
+  }
+
+#ifndef SQLITE_OMIT_UTF16
+  /* Use the sqlite3_create_function16() API here. Mainly for fun, but also 
+  ** because it is not tested anywhere else. */
+  if( rc==SQLITE_OK ){
+    const void *zUtf16;
+    sqlite3_value *pVal;
+    sqlite3_mutex_enter(db->mutex);
+    pVal = sqlite3ValueNew(db);
+    sqlite3ValueSetStr(pVal, -1, "x_sqlite_exec", SQLITE_UTF8, SQLITE_STATIC);
+    zUtf16 = sqlite3ValueText(pVal, SQLITE_UTF16NATIVE);
+    if( db->mallocFailed ){
+      rc = SQLITE_NOMEM;
+    }else{
+      rc = sqlite3_create_function16(db, zUtf16, 
+                1, SQLITE_UTF16, db, sqlite3ExecFunc, 0, 0);
+    }
+    sqlite3ValueFree(pVal);
+    sqlite3_mutex_leave(db->mutex);
+  }
+#endif
+
+  if( sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
+  Tcl_SetResult(interp, (char *)t1ErrorName(rc), 0);
+  return TCL_OK;
+}
+
+/*
+** Routines to implement the x_count() aggregate function.
+**
+** x_count() counts the number of non-null arguments.  But there are
+** some twists for testing purposes.
+**
+** If the argument to x_count() is 40 then a UTF-8 error is reported
+** on the step function.  If x_count(41) is seen, then a UTF-16 error
+** is reported on the step function.  If the total count is 42, then
+** a UTF-8 error is reported on the finalize function.
+*/
+typedef struct t1CountCtx t1CountCtx;
+struct t1CountCtx {
+  int n;
+};
+static void t1CountStep(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  t1CountCtx *p;
+  p = sqlite3_aggregate_context(context, sizeof(*p));
+  if( (argc==0 || SQLITE_NULL!=sqlite3_value_type(argv[0]) ) && p ){
+    p->n++;
+  }
+  if( argc>0 ){
+    int v = sqlite3_value_int(argv[0]);
+    if( v==40 ){
+      sqlite3_result_error(context, "value of 40 handed to x_count", -1);
+#ifndef SQLITE_OMIT_UTF16
+    }else if( v==41 ){
+      const char zUtf16ErrMsg[] = { 0, 0x61, 0, 0x62, 0, 0x63, 0, 0, 0};
+      sqlite3_result_error16(context, &zUtf16ErrMsg[1-SQLITE_BIGENDIAN], -1);
+#endif
+    }
+  }
+}   
+static void t1CountFinalize(sqlite3_context *context){
+  t1CountCtx *p;
+  p = sqlite3_aggregate_context(context, sizeof(*p));
+  if( p ){
+    if( p->n==42 ){
+      sqlite3_result_error(context, "x_count totals to 42", -1);
+    }else{
+      sqlite3_result_int(context, p ? p->n : 0);
+    }
+  }
+}
+
+#ifndef SQLITE_OMIT_DEPRECATED
+static void legacyCountStep(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  /* no-op */
+}
+
+static void legacyCountFinalize(sqlite3_context *context){
+  sqlite3_result_int(context, sqlite3_aggregate_count(context));
+}
+#endif
+
+/*
+** Usage:  sqlite3_create_aggregate DB
+**
+** Call the sqlite3_create_function API on the given database in order
+** to create a function named "x_count".  This function is similar
+** to the built-in count() function, with a few special quirks
+** for testing the sqlite3_result_error() APIs.
+**
+** The original motivation for this routine was to be able to call the
+** sqlite3_create_aggregate function while a query is in progress in order
+** to test the SQLITE_MISUSE detection logic.  See misuse.test.
+**
+** This routine was later extended to test the use of sqlite3_result_error()
+** within aggregate functions.
+**
+** Later: It is now also extended to register the aggregate function
+** "legacy_count()" with the supplied database handle. This is used
+** to test the deprecated sqlite3_aggregate_count() API.
+*/
+static int test_create_aggregate(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  sqlite3 *db;
+  int rc;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " FILENAME\"", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  rc = sqlite3_create_function(db, "x_count", 0, SQLITE_UTF8, 0, 0,
+      t1CountStep,t1CountFinalize);
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_create_function(db, "x_count", 1, SQLITE_UTF8, 0, 0,
+        t1CountStep,t1CountFinalize);
+  }
+#ifndef SQLITE_OMIT_DEPRECATED
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_create_function(db, "legacy_count", 0, SQLITE_ANY, 0, 0,
+        legacyCountStep, legacyCountFinalize
+    );
+  }
+#endif
+  if( sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
+  Tcl_SetResult(interp, (char *)t1ErrorName(rc), 0);
+  return TCL_OK;
+}
+
+
+/*
+** Usage:  printf TEXT
+**
+** Send output to printf.  Use this rather than puts to merge the output
+** in the correct sequence with debugging printfs inserted into C code.
+** Puts uses a separate buffer and debugging statements will be out of
+** sequence if it is used.
+*/
+static int test_printf(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " TEXT\"", 0);
+    return TCL_ERROR;
+  }
+  printf("%s\n", argv[1]);
+  return TCL_OK;
+}
+
+
+
+/*
+** Usage:  sqlite3_mprintf_int FORMAT INTEGER INTEGER INTEGER
+**
+** Call mprintf with three integer arguments
+*/
+static int sqlite3_mprintf_int(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  int a[3], i;
+  char *z;
+  if( argc!=5 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " FORMAT INT INT INT\"", 0);
+    return TCL_ERROR;
+  }
+  for(i=2; i<5; i++){
+    if( Tcl_GetInt(interp, argv[i], &a[i-2]) ) return TCL_ERROR;
+  }
+  z = sqlite3_mprintf(argv[1], a[0], a[1], a[2]);
+  Tcl_AppendResult(interp, z, 0);
+  sqlite3_free(z);
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_mprintf_int64 FORMAT INTEGER INTEGER INTEGER
+**
+** Call mprintf with three 64-bit integer arguments
+*/
+static int sqlite3_mprintf_int64(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  int i;
+  sqlite_int64 a[3];
+  char *z;
+  if( argc!=5 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " FORMAT INT INT INT\"", 0);
+    return TCL_ERROR;
+  }
+  for(i=2; i<5; i++){
+    if( sqlite3Atoi64(argv[i], &a[i-2], 1000000, SQLITE_UTF8) ){
+      Tcl_AppendResult(interp, "argument is not a valid 64-bit integer", 0);
+      return TCL_ERROR;
+    }
+  }
+  z = sqlite3_mprintf(argv[1], a[0], a[1], a[2]);
+  Tcl_AppendResult(interp, z, 0);
+  sqlite3_free(z);
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_mprintf_long FORMAT INTEGER INTEGER INTEGER
+**
+** Call mprintf with three long integer arguments.   This might be the
+** same as sqlite3_mprintf_int or sqlite3_mprintf_int64, depending on
+** platform.
+*/
+static int sqlite3_mprintf_long(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  int i;
+  long int a[3];
+  int b[3];
+  char *z;
+  if( argc!=5 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " FORMAT INT INT INT\"", 0);
+    return TCL_ERROR;
+  }
+  for(i=2; i<5; i++){
+    if( Tcl_GetInt(interp, argv[i], &b[i-2]) ) return TCL_ERROR;
+    a[i-2] = (long int)b[i-2];
+    a[i-2] &= (((u64)1)<<(sizeof(int)*8))-1;
+  }
+  z = sqlite3_mprintf(argv[1], a[0], a[1], a[2]);
+  Tcl_AppendResult(interp, z, 0);
+  sqlite3_free(z);
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_mprintf_str FORMAT INTEGER INTEGER STRING
+**
+** Call mprintf with two integer arguments and one string argument
+*/
+static int sqlite3_mprintf_str(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  int a[3], i;
+  char *z;
+  if( argc<4 || argc>5 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " FORMAT INT INT ?STRING?\"", 0);
+    return TCL_ERROR;
+  }
+  for(i=2; i<4; i++){
+    if( Tcl_GetInt(interp, argv[i], &a[i-2]) ) return TCL_ERROR;
+  }
+  z = sqlite3_mprintf(argv[1], a[0], a[1], argc>4 ? argv[4] : NULL);
+  Tcl_AppendResult(interp, z, 0);
+  sqlite3_free(z);
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_snprintf_str INTEGER FORMAT INTEGER INTEGER STRING
+**
+** Call mprintf with two integer arguments and one string argument
+*/
+static int sqlite3_snprintf_str(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  int a[3], i;
+  int n;
+  char *z;
+  if( argc<5 || argc>6 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " INT FORMAT INT INT ?STRING?\"", 0);
+    return TCL_ERROR;
+  }
+  if( Tcl_GetInt(interp, argv[1], &n) ) return TCL_ERROR;
+  if( n<0 ){
+    Tcl_AppendResult(interp, "N must be non-negative", 0);
+    return TCL_ERROR;
+  }
+  for(i=3; i<5; i++){
+    if( Tcl_GetInt(interp, argv[i], &a[i-3]) ) return TCL_ERROR;
+  }
+  z = sqlite3_malloc( n+1 );
+  sqlite3_snprintf(n, z, argv[2], a[0], a[1], argc>4 ? argv[5] : NULL);
+  Tcl_AppendResult(interp, z, 0);
+  sqlite3_free(z);
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_mprintf_double FORMAT INTEGER INTEGER DOUBLE
+**
+** Call mprintf with two integer arguments and one double argument
+*/
+static int sqlite3_mprintf_double(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  int a[3], i;
+  double r;
+  char *z;
+  if( argc!=5 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " FORMAT INT INT DOUBLE\"", 0);
+    return TCL_ERROR;
+  }
+  for(i=2; i<4; i++){
+    if( Tcl_GetInt(interp, argv[i], &a[i-2]) ) return TCL_ERROR;
+  }
+  if( Tcl_GetDouble(interp, argv[4], &r) ) return TCL_ERROR;
+  z = sqlite3_mprintf(argv[1], a[0], a[1], r);
+  Tcl_AppendResult(interp, z, 0);
+  sqlite3_free(z);
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_mprintf_scaled FORMAT DOUBLE DOUBLE
+**
+** Call mprintf with a single double argument which is the product of the
+** two arguments given above.  This is used to generate overflow and underflow
+** doubles to test that they are converted properly.
+*/
+static int sqlite3_mprintf_scaled(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  int i;
+  double r[2];
+  char *z;
+  if( argc!=4 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " FORMAT DOUBLE DOUBLE\"", 0);
+    return TCL_ERROR;
+  }
+  for(i=2; i<4; i++){
+    if( Tcl_GetDouble(interp, argv[i], &r[i-2]) ) return TCL_ERROR;
+  }
+  z = sqlite3_mprintf(argv[1], r[0]*r[1]);
+  Tcl_AppendResult(interp, z, 0);
+  sqlite3_free(z);
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_mprintf_stronly FORMAT STRING
+**
+** Call mprintf with a single double argument which is the product of the
+** two arguments given above.  This is used to generate overflow and underflow
+** doubles to test that they are converted properly.
+*/
+static int sqlite3_mprintf_stronly(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  char *z;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " FORMAT STRING\"", 0);
+    return TCL_ERROR;
+  }
+  z = sqlite3_mprintf(argv[1], argv[2]);
+  Tcl_AppendResult(interp, z, 0);
+  sqlite3_free(z);
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_mprintf_hexdouble FORMAT HEX
+**
+** Call mprintf with a single double argument which is derived from the
+** hexadecimal encoding of an IEEE double.
+*/
+static int sqlite3_mprintf_hexdouble(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  char *z;
+  double r;
+  unsigned int x1, x2;
+  sqlite_uint64 d;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " FORMAT STRING\"", 0);
+    return TCL_ERROR;
+  }
+  if( sscanf(argv[2], "%08x%08x", &x2, &x1)!=2 ){
+    Tcl_AppendResult(interp, "2nd argument should be 16-characters of hex", 0);
+    return TCL_ERROR;
+  }
+  d = x2;
+  d = (d<<32) + x1;
+  memcpy(&r, &d, sizeof(r));
+  z = sqlite3_mprintf(argv[1], r);
+  Tcl_AppendResult(interp, z, 0);
+  sqlite3_free(z);
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_enable_shared_cache ?BOOLEAN?
+**
+*/
+#if !defined(SQLITE_OMIT_SHARED_CACHE)
+static int test_enable_shared(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  int rc;
+  int enable;
+  int ret = 0;
+
+  if( objc!=2 && objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "?BOOLEAN?");
+    return TCL_ERROR;
+  }
+  ret = sqlite3GlobalConfig.sharedCacheEnabled;
+
+  if( objc==2 ){
+    if( Tcl_GetBooleanFromObj(interp, objv[1], &enable) ){
+      return TCL_ERROR;
+    }
+    rc = sqlite3_enable_shared_cache(enable);
+    if( rc!=SQLITE_OK ){
+      Tcl_SetResult(interp, (char *)sqlite3ErrStr(rc), TCL_STATIC);
+      return TCL_ERROR;
+    }
+  }
+  Tcl_SetObjResult(interp, Tcl_NewBooleanObj(ret));
+  return TCL_OK;
+}
+#endif
+
+
+
+/*
+** Usage: sqlite3_extended_result_codes   DB    BOOLEAN
+**
+*/
+static int test_extended_result_codes(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  int enable;
+  sqlite3 *db;
+
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB BOOLEAN");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  if( Tcl_GetBooleanFromObj(interp, objv[2], &enable) ) return TCL_ERROR;
+  sqlite3_extended_result_codes(db, enable);
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_libversion_number
+**
+*/
+static int test_libversion_number(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(sqlite3_libversion_number()));
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_table_column_metadata DB dbname tblname colname
+**
+*/
+#ifdef SQLITE_ENABLE_COLUMN_METADATA
+static int test_table_column_metadata(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3 *db;
+  const char *zDb;
+  const char *zTbl;
+  const char *zCol;
+  int rc;
+  Tcl_Obj *pRet;
+
+  const char *zDatatype;
+  const char *zCollseq;
+  int notnull;
+  int primarykey;
+  int autoincrement;
+
+  if( objc!=5 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB dbname tblname colname");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zDb = Tcl_GetString(objv[2]);
+  zTbl = Tcl_GetString(objv[3]);
+  zCol = Tcl_GetString(objv[4]);
+
+  if( strlen(zDb)==0 ) zDb = 0;
+
+  rc = sqlite3_table_column_metadata(db, zDb, zTbl, zCol, 
+      &zDatatype, &zCollseq, &notnull, &primarykey, &autoincrement);
+
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, sqlite3_errmsg(db), 0);
+    return TCL_ERROR;
+  }
+
+  pRet = Tcl_NewObj();
+  Tcl_ListObjAppendElement(0, pRet, Tcl_NewStringObj(zDatatype, -1));
+  Tcl_ListObjAppendElement(0, pRet, Tcl_NewStringObj(zCollseq, -1));
+  Tcl_ListObjAppendElement(0, pRet, Tcl_NewIntObj(notnull));
+  Tcl_ListObjAppendElement(0, pRet, Tcl_NewIntObj(primarykey));
+  Tcl_ListObjAppendElement(0, pRet, Tcl_NewIntObj(autoincrement));
+  Tcl_SetObjResult(interp, pRet);
+
+  return TCL_OK;
+}
+#endif
+
+#ifndef SQLITE_OMIT_INCRBLOB
+
+static int blobHandleFromObj(
+  Tcl_Interp *interp, 
+  Tcl_Obj *pObj,
+  sqlite3_blob **ppBlob
+){
+  char *z;
+  int n;
+
+  z = Tcl_GetStringFromObj(pObj, &n);
+  if( n==0 ){
+    *ppBlob = 0;
+  }else{
+    int notUsed;
+    Tcl_Channel channel;
+    ClientData instanceData;
+    
+    channel = Tcl_GetChannel(interp, z, &notUsed);
+    if( !channel ) return TCL_ERROR;
+
+    Tcl_Flush(channel);
+    Tcl_Seek(channel, 0, SEEK_SET);
+
+    instanceData = Tcl_GetChannelInstanceData(channel);
+    *ppBlob = *((sqlite3_blob **)instanceData);
+  }
+
+  return TCL_OK;
+}
+
+/*
+** sqlite3_blob_bytes  CHANNEL
+*/
+static int test_blob_bytes(
+  ClientData clientData, /* Not used */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3_blob *pBlob;
+  int nByte;
+  
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "CHANNEL");
+    return TCL_ERROR;
+  }
+
+  if( blobHandleFromObj(interp, objv[1], &pBlob) ) return TCL_ERROR;
+  nByte = sqlite3_blob_bytes(pBlob);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(nByte));
+
+  return TCL_OK;
+}
+
+/*
+** sqlite3_blob_close  CHANNEL
+*/
+static int test_blob_close(
+  ClientData clientData, /* Not used */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3_blob *pBlob;
+  
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "CHANNEL");
+    return TCL_ERROR;
+  }
+
+  if( blobHandleFromObj(interp, objv[1], &pBlob) ) return TCL_ERROR;
+  sqlite3_blob_close(pBlob);
+
+  return TCL_OK;
+}
+
+/*
+** sqlite3_blob_read  CHANNEL OFFSET N
+**
+**   This command is used to test the sqlite3_blob_read() in ways that
+**   the Tcl channel interface does not. The first argument should
+**   be the name of a valid channel created by the [incrblob] method
+**   of a database handle. This function calls sqlite3_blob_read()
+**   to read N bytes from offset OFFSET from the underlying SQLite
+**   blob handle.
+**
+**   On success, a byte-array object containing the read data is 
+**   returned. On failure, the interpreter result is set to the
+**   text representation of the returned error code (i.e. "SQLITE_NOMEM")
+**   and a Tcl exception is thrown.
+*/
+static int test_blob_read(
+  ClientData clientData, /* Not used */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3_blob *pBlob;
+  int nByte;
+  int iOffset;
+  unsigned char *zBuf = 0;
+  int rc;
+  
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "CHANNEL OFFSET N");
+    return TCL_ERROR;
+  }
+
+  if( blobHandleFromObj(interp, objv[1], &pBlob) ) return TCL_ERROR;
+  if( TCL_OK!=Tcl_GetIntFromObj(interp, objv[2], &iOffset)
+   || TCL_OK!=Tcl_GetIntFromObj(interp, objv[3], &nByte)
+  ){ 
+    return TCL_ERROR;
+  }
+
+  if( nByte>0 ){
+    zBuf = (unsigned char *)Tcl_Alloc(nByte);
+  }
+  rc = sqlite3_blob_read(pBlob, zBuf, nByte, iOffset);
+  if( rc==SQLITE_OK ){
+    Tcl_SetObjResult(interp, Tcl_NewByteArrayObj(zBuf, nByte));
+  }else{
+    Tcl_SetResult(interp, (char *)sqlite3TestErrorName(rc), TCL_VOLATILE);
+  }
+  Tcl_Free((char *)zBuf);
+
+  return (rc==SQLITE_OK ? TCL_OK : TCL_ERROR);
+}
+
+/*
+** sqlite3_blob_write CHANNEL OFFSET DATA ?NDATA?
+**
+**   This command is used to test the sqlite3_blob_write() in ways that
+**   the Tcl channel interface does not. The first argument should
+**   be the name of a valid channel created by the [incrblob] method
+**   of a database handle. This function calls sqlite3_blob_write()
+**   to write the DATA byte-array to the underlying SQLite blob handle.
+**   at offset OFFSET.
+**
+**   On success, an empty string is returned. On failure, the interpreter
+**   result is set to the text representation of the returned error code 
+**   (i.e. "SQLITE_NOMEM") and a Tcl exception is thrown.
+*/
+static int test_blob_write(
+  ClientData clientData, /* Not used */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3_blob *pBlob;
+  int iOffset;
+  int rc;
+
+  unsigned char *zBuf;
+  int nBuf;
+  
+  if( objc!=4 && objc!=5 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "CHANNEL OFFSET DATA ?NDATA?");
+    return TCL_ERROR;
+  }
+
+  if( blobHandleFromObj(interp, objv[1], &pBlob) ) return TCL_ERROR;
+  if( TCL_OK!=Tcl_GetIntFromObj(interp, objv[2], &iOffset) ){ 
+    return TCL_ERROR;
+  }
+
+  zBuf = Tcl_GetByteArrayFromObj(objv[3], &nBuf);
+  if( objc==5 && Tcl_GetIntFromObj(interp, objv[4], &nBuf) ){
+    return TCL_ERROR;
+  }
+  rc = sqlite3_blob_write(pBlob, zBuf, nBuf, iOffset);
+  if( rc!=SQLITE_OK ){
+    Tcl_SetResult(interp, (char *)sqlite3TestErrorName(rc), TCL_VOLATILE);
+  }
+
+  return (rc==SQLITE_OK ? TCL_OK : TCL_ERROR);
+}
+
+static int test_blob_reopen(
+  ClientData clientData, /* Not used */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  Tcl_WideInt iRowid;
+  sqlite3_blob *pBlob;
+  int rc;
+
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "CHANNEL ROWID");
+    return TCL_ERROR;
+  }
+
+  if( blobHandleFromObj(interp, objv[1], &pBlob) ) return TCL_ERROR;
+  if( Tcl_GetWideIntFromObj(interp, objv[2], &iRowid) ) return TCL_ERROR;
+
+  rc = sqlite3_blob_reopen(pBlob, iRowid);
+  if( rc!=SQLITE_OK ){
+    Tcl_SetResult(interp, (char *)sqlite3TestErrorName(rc), TCL_VOLATILE);
+  }
+
+  return (rc==SQLITE_OK ? TCL_OK : TCL_ERROR);
+}
+
+#endif
+
+/*
+** Usage: sqlite3_create_collation_v2 DB-HANDLE NAME CMP-PROC DEL-PROC
+**
+**   This Tcl proc is used for testing the experimental
+**   sqlite3_create_collation_v2() interface.
+*/
+struct TestCollationX {
+  Tcl_Interp *interp;
+  Tcl_Obj *pCmp;
+  Tcl_Obj *pDel;
+};
+typedef struct TestCollationX TestCollationX;
+static void testCreateCollationDel(void *pCtx){
+  TestCollationX *p = (TestCollationX *)pCtx;
+
+  int rc = Tcl_EvalObjEx(p->interp, p->pDel, TCL_EVAL_DIRECT|TCL_EVAL_GLOBAL);
+  if( rc!=TCL_OK ){
+    Tcl_BackgroundError(p->interp);
+  }
+
+  Tcl_DecrRefCount(p->pCmp);
+  Tcl_DecrRefCount(p->pDel);
+  sqlite3_free((void *)p);
+}
+static int testCreateCollationCmp(
+  void *pCtx,
+  int nLeft,
+  const void *zLeft,
+  int nRight,
+  const void *zRight
+){
+  TestCollationX *p = (TestCollationX *)pCtx;
+  Tcl_Obj *pScript = Tcl_DuplicateObj(p->pCmp);
+  int iRes = 0;
+
+  Tcl_IncrRefCount(pScript);
+  Tcl_ListObjAppendElement(0, pScript, Tcl_NewStringObj((char *)zLeft, nLeft));
+  Tcl_ListObjAppendElement(0, pScript, Tcl_NewStringObj((char *)zRight,nRight));
+
+  if( TCL_OK!=Tcl_EvalObjEx(p->interp, pScript, TCL_EVAL_DIRECT|TCL_EVAL_GLOBAL)
+   || TCL_OK!=Tcl_GetIntFromObj(p->interp, Tcl_GetObjResult(p->interp), &iRes)
+  ){
+    Tcl_BackgroundError(p->interp);
+  }
+  Tcl_DecrRefCount(pScript);
+
+  return iRes;
+}
+static int test_create_collation_v2(
+  ClientData clientData, /* Not used */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  TestCollationX *p;
+  sqlite3 *db;
+  int rc;
+
+  if( objc!=5 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB-HANDLE NAME CMP-PROC DEL-PROC");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+
+  p = (TestCollationX *)sqlite3_malloc(sizeof(TestCollationX));
+  p->pCmp = objv[3];
+  p->pDel = objv[4];
+  p->interp = interp;
+  Tcl_IncrRefCount(p->pCmp);
+  Tcl_IncrRefCount(p->pDel);
+
+  rc = sqlite3_create_collation_v2(db, Tcl_GetString(objv[2]), 16, 
+      (void *)p, testCreateCollationCmp, testCreateCollationDel
+  );
+  if( rc!=SQLITE_MISUSE ){
+    Tcl_AppendResult(interp, "sqlite3_create_collate_v2() failed to detect "
+      "an invalid encoding", (char*)0);
+    return TCL_ERROR;
+  }
+  rc = sqlite3_create_collation_v2(db, Tcl_GetString(objv[2]), SQLITE_UTF8, 
+      (void *)p, testCreateCollationCmp, testCreateCollationDel
+  );
+  return TCL_OK;
+}
+
+/*
+** USAGE: sqlite3_create_function_v2 DB NAME NARG ENC ?SWITCHES?
+**
+** Available switches are:
+**
+**   -func    SCRIPT
+**   -step    SCRIPT
+**   -final   SCRIPT
+**   -destroy SCRIPT
+*/
+typedef struct CreateFunctionV2 CreateFunctionV2;
+struct CreateFunctionV2 {
+  Tcl_Interp *interp;
+  Tcl_Obj *pFunc;                 /* Script for function invocation */
+  Tcl_Obj *pStep;                 /* Script for agg. step invocation */
+  Tcl_Obj *pFinal;                /* Script for agg. finalization invocation */
+  Tcl_Obj *pDestroy;              /* Destructor script */
+};
+static void cf2Func(sqlite3_context *ctx, int nArg, sqlite3_value **aArg){
+}
+static void cf2Step(sqlite3_context *ctx, int nArg, sqlite3_value **aArg){
+}
+static void cf2Final(sqlite3_context *ctx){
+}
+static void cf2Destroy(void *pUser){
+  CreateFunctionV2 *p = (CreateFunctionV2 *)pUser;
+
+  if( p->interp && p->pDestroy ){
+    int rc = Tcl_EvalObjEx(p->interp, p->pDestroy, 0);
+    if( rc!=TCL_OK ) Tcl_BackgroundError(p->interp);
+  }
+
+  if( p->pFunc ) Tcl_DecrRefCount(p->pFunc); 
+  if( p->pStep ) Tcl_DecrRefCount(p->pStep); 
+  if( p->pFinal ) Tcl_DecrRefCount(p->pFinal); 
+  if( p->pDestroy ) Tcl_DecrRefCount(p->pDestroy); 
+  sqlite3_free(p);
+}
+static int test_create_function_v2(
+  ClientData clientData,          /* Not used */
+  Tcl_Interp *interp,             /* The invoking TCL interpreter */
+  int objc,                       /* Number of arguments */
+  Tcl_Obj *CONST objv[]           /* Command arguments */
+){
+  sqlite3 *db;
+  const char *zFunc;
+  int nArg;
+  int enc;
+  CreateFunctionV2 *p;
+  int i;
+  int rc;
+
+  struct EncTable {
+    const char *zEnc;
+    int enc;
+  } aEnc[] = {
+    {"utf8",    SQLITE_UTF8 },
+    {"utf16",   SQLITE_UTF16 },
+    {"utf16le", SQLITE_UTF16LE },
+    {"utf16be", SQLITE_UTF16BE },
+    {"any",     SQLITE_ANY },
+    {"0", 0 }
+  };
+
+  if( objc<5 || (objc%2)==0 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB NAME NARG ENC SWITCHES...");
+    return TCL_ERROR;
+  }
+
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zFunc = Tcl_GetString(objv[2]);
+  if( Tcl_GetIntFromObj(interp, objv[3], &nArg) ) return TCL_ERROR;
+  if( Tcl_GetIndexFromObjStruct(interp, objv[4], aEnc, sizeof(aEnc[0]), 
+          "encoding", 0, &enc)
+  ){
+    return TCL_ERROR;
+  }
+  enc = aEnc[enc].enc;
+
+  p = sqlite3_malloc(sizeof(CreateFunctionV2));
+  assert( p );
+  memset(p, 0, sizeof(CreateFunctionV2));
+  p->interp = interp;
+
+  for(i=5; i<objc; i+=2){
+    int iSwitch;
+    const char *azSwitch[] = {"-func", "-step", "-final", "-destroy", 0};
+    if( Tcl_GetIndexFromObj(interp, objv[i], azSwitch, "switch", 0, &iSwitch) ){
+      sqlite3_free(p);
+      return TCL_ERROR;
+    }
+
+    switch( iSwitch ){
+      case 0: p->pFunc = objv[i+1];      break;
+      case 1: p->pStep = objv[i+1];      break;
+      case 2: p->pFinal = objv[i+1];     break;
+      case 3: p->pDestroy = objv[i+1];   break;
+    }
+  }
+  if( p->pFunc ) p->pFunc = Tcl_DuplicateObj(p->pFunc); 
+  if( p->pStep ) p->pStep = Tcl_DuplicateObj(p->pStep); 
+  if( p->pFinal ) p->pFinal = Tcl_DuplicateObj(p->pFinal); 
+  if( p->pDestroy ) p->pDestroy = Tcl_DuplicateObj(p->pDestroy); 
+
+  if( p->pFunc ) Tcl_IncrRefCount(p->pFunc); 
+  if( p->pStep ) Tcl_IncrRefCount(p->pStep); 
+  if( p->pFinal ) Tcl_IncrRefCount(p->pFinal); 
+  if( p->pDestroy ) Tcl_IncrRefCount(p->pDestroy); 
+
+  rc = sqlite3_create_function_v2(db, zFunc, nArg, enc, (void *)p, 
+      (p->pFunc ? cf2Func : 0),
+      (p->pStep ? cf2Step : 0),
+      (p->pFinal ? cf2Final : 0),
+      cf2Destroy
+  );
+  if( rc!=SQLITE_OK ){
+    Tcl_ResetResult(interp);
+    Tcl_AppendResult(interp, sqlite3TestErrorName(rc), 0);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_load_extension DB-HANDLE FILE ?PROC?
+*/
+static int test_load_extension(
+  ClientData clientData, /* Not used */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  Tcl_CmdInfo cmdInfo;
+  sqlite3 *db;
+  int rc;
+  char *zDb;
+  char *zFile;
+  char *zProc = 0;
+  char *zErr = 0;
+
+  if( objc!=4 && objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB-HANDLE FILE ?PROC?");
+    return TCL_ERROR;
+  }
+  zDb = Tcl_GetString(objv[1]);
+  zFile = Tcl_GetString(objv[2]);
+  if( objc==4 ){
+    zProc = Tcl_GetString(objv[3]);
+  }
+
+  /* Extract the C database handle from the Tcl command name */
+  if( !Tcl_GetCommandInfo(interp, zDb, &cmdInfo) ){
+    Tcl_AppendResult(interp, "command not found: ", zDb, (char*)0);
+    return TCL_ERROR;
+  }
+  db = ((struct SqliteDb*)cmdInfo.objClientData)->db;
+  assert(db);
+
+  /* Call the underlying C function. If an error occurs, set rc to 
+  ** TCL_ERROR and load any error string into the interpreter. If no 
+  ** error occurs, set rc to TCL_OK.
+  */
+#ifdef SQLITE_OMIT_LOAD_EXTENSION
+  rc = SQLITE_ERROR;
+  zErr = sqlite3_mprintf("this build omits sqlite3_load_extension()");
+#else
+  rc = sqlite3_load_extension(db, zFile, zProc, &zErr);
+#endif
+  if( rc!=SQLITE_OK ){
+    Tcl_SetResult(interp, zErr ? zErr : "", TCL_VOLATILE);
+    rc = TCL_ERROR;
+  }else{
+    rc = TCL_OK;
+  }
+  sqlite3_free(zErr);
+
+  return rc;
+}
+
+/*
+** Usage: sqlite3_enable_load_extension DB-HANDLE ONOFF
+*/
+static int test_enable_load(
+  ClientData clientData, /* Not used */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  Tcl_CmdInfo cmdInfo;
+  sqlite3 *db;
+  char *zDb;
+  int onoff;
+
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB-HANDLE ONOFF");
+    return TCL_ERROR;
+  }
+  zDb = Tcl_GetString(objv[1]);
+
+  /* Extract the C database handle from the Tcl command name */
+  if( !Tcl_GetCommandInfo(interp, zDb, &cmdInfo) ){
+    Tcl_AppendResult(interp, "command not found: ", zDb, (char*)0);
+    return TCL_ERROR;
+  }
+  db = ((struct SqliteDb*)cmdInfo.objClientData)->db;
+  assert(db);
+
+  /* Get the onoff parameter */
+  if( Tcl_GetBooleanFromObj(interp, objv[2], &onoff) ){
+    return TCL_ERROR;
+  }
+
+#ifdef SQLITE_OMIT_LOAD_EXTENSION
+  Tcl_AppendResult(interp, "this build omits sqlite3_load_extension()");
+  return TCL_ERROR;
+#else
+  sqlite3_enable_load_extension(db, onoff);
+  return TCL_OK;
+#endif
+}
+
+/*
+** Usage:  sqlite_abort
+**
+** Shutdown the process immediately.  This is not a clean shutdown.
+** This command is used to test the recoverability of a database in
+** the event of a program crash.
+*/
+static int sqlite_abort(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+#if defined(_MSC_VER)
+  /* We do this, otherwise the test will halt with a popup message
+   * that we have to click away before the test will continue.
+   */
+  _set_abort_behavior( 0, _CALL_REPORTFAULT );
+#endif
+  exit(255);
+  assert( interp==0 );   /* This will always fail */
+  return TCL_OK;
+}
+
+/*
+** The following routine is a user-defined SQL function whose purpose
+** is to test the sqlite_set_result() API.
+*/
+static void testFunc(sqlite3_context *context, int argc, sqlite3_value **argv){
+  while( argc>=2 ){
+    const char *zArg0 = (char*)sqlite3_value_text(argv[0]);
+    if( zArg0 ){
+      if( 0==sqlite3StrICmp(zArg0, "int") ){
+        sqlite3_result_int(context, sqlite3_value_int(argv[1]));
+      }else if( sqlite3StrICmp(zArg0,"int64")==0 ){
+        sqlite3_result_int64(context, sqlite3_value_int64(argv[1]));
+      }else if( sqlite3StrICmp(zArg0,"string")==0 ){
+        sqlite3_result_text(context, (char*)sqlite3_value_text(argv[1]), -1,
+            SQLITE_TRANSIENT);
+      }else if( sqlite3StrICmp(zArg0,"double")==0 ){
+        sqlite3_result_double(context, sqlite3_value_double(argv[1]));
+      }else if( sqlite3StrICmp(zArg0,"null")==0 ){
+        sqlite3_result_null(context);
+      }else if( sqlite3StrICmp(zArg0,"value")==0 ){
+        sqlite3_result_value(context, argv[sqlite3_value_int(argv[1])]);
+      }else{
+        goto error_out;
+      }
+    }else{
+      goto error_out;
+    }
+    argc -= 2;
+    argv += 2;
+  }
+  return;
+
+error_out:
+  sqlite3_result_error(context,"first argument should be one of: "
+      "int int64 string double null value", -1);
+}
+
+/*
+** Usage:   sqlite_register_test_function  DB  NAME
+**
+** Register the test SQL function on the database DB under the name NAME.
+*/
+static int test_register_func(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  sqlite3 *db;
+  int rc;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], 
+       " DB FUNCTION-NAME", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  rc = sqlite3_create_function(db, argv[2], -1, SQLITE_UTF8, 0, 
+      testFunc, 0, 0);
+  if( rc!=0 ){
+    Tcl_AppendResult(interp, sqlite3ErrStr(rc), 0);
+    return TCL_ERROR;
+  }
+  if( sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_finalize  STMT 
+**
+** Finalize a statement handle.
+*/
+static int test_finalize(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int rc;
+  sqlite3 *db = 0;
+
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " <STMT>", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+
+  if( pStmt ){
+    db = StmtToDb(pStmt);
+  }
+  rc = sqlite3_finalize(pStmt);
+  Tcl_SetResult(interp, (char *)t1ErrorName(rc), TCL_STATIC);
+  if( db && sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_stmt_status  STMT  CODE  RESETFLAG
+**
+** Get the value of a status counter from a statement.
+*/
+static int test_stmt_status(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int iValue;
+  int i, op, resetFlag;
+  const char *zOpName;
+  sqlite3_stmt *pStmt;
+
+  static const struct {
+    const char *zName;
+    int op;
+  } aOp[] = {
+    { "SQLITE_STMTSTATUS_FULLSCAN_STEP",   SQLITE_STMTSTATUS_FULLSCAN_STEP   },
+    { "SQLITE_STMTSTATUS_SORT",            SQLITE_STMTSTATUS_SORT            },
+    { "SQLITE_STMTSTATUS_AUTOINDEX",       SQLITE_STMTSTATUS_AUTOINDEX       },
+  };
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "STMT PARAMETER RESETFLAG");
+    return TCL_ERROR;
+  }
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  zOpName = Tcl_GetString(objv[2]);
+  for(i=0; i<ArraySize(aOp); i++){
+    if( strcmp(aOp[i].zName, zOpName)==0 ){
+      op = aOp[i].op;
+      break;
+    }
+  }
+  if( i>=ArraySize(aOp) ){
+    if( Tcl_GetIntFromObj(interp, objv[2], &op) ) return TCL_ERROR;
+  }
+  if( Tcl_GetBooleanFromObj(interp, objv[3], &resetFlag) ) return TCL_ERROR;
+  iValue = sqlite3_stmt_status(pStmt, op, resetFlag);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(iValue));
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_next_stmt  DB  STMT
+**
+** Return the next statment in sequence after STMT.
+*/
+static int test_next_stmt(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  sqlite3 *db = 0;
+  char zBuf[50];
+
+  if( objc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " DB STMT", 0);
+    return TCL_ERROR;
+  }
+
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  if( getStmtPointer(interp, Tcl_GetString(objv[2]), &pStmt) ) return TCL_ERROR;
+  pStmt = sqlite3_next_stmt(db, pStmt);
+  if( pStmt ){
+    if( sqlite3TestMakePointerStr(interp, zBuf, pStmt) ) return TCL_ERROR;
+    Tcl_AppendResult(interp, zBuf, 0);
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_stmt_readonly  STMT
+**
+** Return true if STMT is a NULL pointer or a pointer to a statement
+** that is guaranteed to leave the database unmodified.
+*/
+static int test_stmt_readonly(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int rc;
+
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " STMT", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  rc = sqlite3_stmt_readonly(pStmt);
+  Tcl_SetObjResult(interp, Tcl_NewBooleanObj(rc));
+  return TCL_OK;
+}
+
+/*
+** Usage:  uses_stmt_journal  STMT
+**
+** Return true if STMT uses a statement journal.
+*/
+static int uses_stmt_journal(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int rc;
+
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " STMT", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  rc = sqlite3_stmt_readonly(pStmt);
+  Tcl_SetObjResult(interp, Tcl_NewBooleanObj(((Vdbe *)pStmt)->usesStmtJournal));
+  return TCL_OK;
+}
+
+
+/*
+** Usage:  sqlite3_reset  STMT 
+**
+** Reset a statement handle.
+*/
+static int test_reset(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int rc;
+
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " <STMT>", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+
+  rc = sqlite3_reset(pStmt);
+  if( pStmt && sqlite3TestErrCode(interp, StmtToDb(pStmt), rc) ){
+    return TCL_ERROR;
+  }
+  Tcl_SetResult(interp, (char *)t1ErrorName(rc), TCL_STATIC);
+/*
+  if( rc ){
+    return TCL_ERROR;
+  }
+*/
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_expired STMT 
+**
+** Return TRUE if a recompilation of the statement is recommended.
+*/
+static int test_expired(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#ifndef SQLITE_OMIT_DEPRECATED
+  sqlite3_stmt *pStmt;
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " <STMT>", 0);
+    return TCL_ERROR;
+  }
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  Tcl_SetObjResult(interp, Tcl_NewBooleanObj(sqlite3_expired(pStmt)));
+#endif
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_transfer_bindings FROMSTMT TOSTMT
+**
+** Transfer all bindings from FROMSTMT over to TOSTMT
+*/
+static int test_transfer_bind(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#ifndef SQLITE_OMIT_DEPRECATED
+  sqlite3_stmt *pStmt1, *pStmt2;
+  if( objc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " FROM-STMT TO-STMT", 0);
+    return TCL_ERROR;
+  }
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt1)) return TCL_ERROR;
+  if( getStmtPointer(interp, Tcl_GetString(objv[2]), &pStmt2)) return TCL_ERROR;
+  Tcl_SetObjResult(interp, 
+     Tcl_NewIntObj(sqlite3_transfer_bindings(pStmt1,pStmt2)));
+#endif
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_changes DB
+**
+** Return the number of changes made to the database by the last SQL
+** execution.
+*/
+static int test_changes(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+       Tcl_GetString(objv[0]), " DB", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(sqlite3_changes(db)));
+  return TCL_OK;
+}
+
+/*
+** This is the "static_bind_value" that variables are bound to when
+** the FLAG option of sqlite3_bind is "static"
+*/
+static char *sqlite_static_bind_value = 0;
+static int sqlite_static_bind_nbyte = 0;
+
+/*
+** Usage:  sqlite3_bind  VM  IDX  VALUE  FLAGS
+**
+** Sets the value of the IDX-th occurance of "?" in the original SQL
+** string.  VALUE is the new value.  If FLAGS=="null" then VALUE is
+** ignored and the value is set to NULL.  If FLAGS=="static" then
+** the value is set to the value of a static variable named
+** "sqlite_static_bind_value".  If FLAGS=="normal" then a copy
+** of the VALUE is made.  If FLAGS=="blob10" then a VALUE is ignored
+** an a 10-byte blob "abc\000xyz\000pq" is inserted.
+*/
+static int test_bind(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  sqlite3_stmt *pStmt;
+  int rc;
+  int idx;
+  if( argc!=5 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], 
+       " VM IDX VALUE (null|static|normal)\"", 0);
+    return TCL_ERROR;
+  }
+  if( getStmtPointer(interp, argv[1], &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetInt(interp, argv[2], &idx) ) return TCL_ERROR;
+  if( strcmp(argv[4],"null")==0 ){
+    rc = sqlite3_bind_null(pStmt, idx);
+  }else if( strcmp(argv[4],"static")==0 ){
+    rc = sqlite3_bind_text(pStmt, idx, sqlite_static_bind_value, -1, 0);
+  }else if( strcmp(argv[4],"static-nbytes")==0 ){
+    rc = sqlite3_bind_text(pStmt, idx, sqlite_static_bind_value,
+                                       sqlite_static_bind_nbyte, 0);
+  }else if( strcmp(argv[4],"normal")==0 ){
+    rc = sqlite3_bind_text(pStmt, idx, argv[3], -1, SQLITE_TRANSIENT);
+  }else if( strcmp(argv[4],"blob10")==0 ){
+    rc = sqlite3_bind_text(pStmt, idx, "abc\000xyz\000pq", 10, SQLITE_STATIC);
+  }else{
+    Tcl_AppendResult(interp, "4th argument should be "
+        "\"null\" or \"static\" or \"normal\"", 0);
+    return TCL_ERROR;
+  }
+  if( sqlite3TestErrCode(interp, StmtToDb(pStmt), rc) ) return TCL_ERROR;
+  if( rc ){
+    char zBuf[50];
+    sprintf(zBuf, "(%d) ", rc);
+    Tcl_AppendResult(interp, zBuf, sqlite3ErrStr(rc), 0);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
+#ifndef SQLITE_OMIT_UTF16
+/*
+** Usage: add_test_collate <db ptr> <utf8> <utf16le> <utf16be>
+**
+** This function is used to test that SQLite selects the correct collation
+** sequence callback when multiple versions (for different text encodings)
+** are available.
+**
+** Calling this routine registers the collation sequence "test_collate"
+** with database handle <db>. The second argument must be a list of three
+** boolean values. If the first is true, then a version of test_collate is
+** registered for UTF-8, if the second is true, a version is registered for
+** UTF-16le, if the third is true, a UTF-16be version is available.
+** Previous versions of test_collate are deleted.
+**
+** The collation sequence test_collate is implemented by calling the
+** following TCL script:
+**
+**   "test_collate <enc> <lhs> <rhs>"
+**
+** The <lhs> and <rhs> are the two values being compared, encoded in UTF-8.
+** The <enc> parameter is the encoding of the collation function that
+** SQLite selected to call. The TCL test script implements the
+** "test_collate" proc.
+**
+** Note that this will only work with one intepreter at a time, as the
+** interp pointer to use when evaluating the TCL script is stored in
+** pTestCollateInterp.
+*/
+static Tcl_Interp* pTestCollateInterp;
+static int test_collate_func(
+  void *pCtx, 
+  int nA, const void *zA,
+  int nB, const void *zB
+){
+  Tcl_Interp *i = pTestCollateInterp;
+  int encin = SQLITE_PTR_TO_INT(pCtx);
+  int res;
+  int n;
+
+  sqlite3_value *pVal;
+  Tcl_Obj *pX;
+
+  pX = Tcl_NewStringObj("test_collate", -1);
+  Tcl_IncrRefCount(pX);
+
+  switch( encin ){
+    case SQLITE_UTF8:
+      Tcl_ListObjAppendElement(i,pX,Tcl_NewStringObj("UTF-8",-1));
+      break;
+    case SQLITE_UTF16LE:
+      Tcl_ListObjAppendElement(i,pX,Tcl_NewStringObj("UTF-16LE",-1));
+      break;
+    case SQLITE_UTF16BE:
+      Tcl_ListObjAppendElement(i,pX,Tcl_NewStringObj("UTF-16BE",-1));
+      break;
+    default:
+      assert(0);
+  }
+
+  sqlite3BeginBenignMalloc();
+  pVal = sqlite3ValueNew(0);
+  if( pVal ){
+    sqlite3ValueSetStr(pVal, nA, zA, encin, SQLITE_STATIC);
+    n = sqlite3_value_bytes(pVal);
+    Tcl_ListObjAppendElement(i,pX,
+        Tcl_NewStringObj((char*)sqlite3_value_text(pVal),n));
+    sqlite3ValueSetStr(pVal, nB, zB, encin, SQLITE_STATIC);
+    n = sqlite3_value_bytes(pVal);
+    Tcl_ListObjAppendElement(i,pX,
+        Tcl_NewStringObj((char*)sqlite3_value_text(pVal),n));
+    sqlite3ValueFree(pVal);
+  }
+  sqlite3EndBenignMalloc();
+
+  Tcl_EvalObjEx(i, pX, 0);
+  Tcl_DecrRefCount(pX);
+  Tcl_GetIntFromObj(i, Tcl_GetObjResult(i), &res);
+  return res;
+}
+static int test_collate(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  int val;
+  sqlite3_value *pVal;
+  int rc;
+
+  if( objc!=5 ) goto bad_args;
+  pTestCollateInterp = interp;
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+
+  if( TCL_OK!=Tcl_GetBooleanFromObj(interp, objv[2], &val) ) return TCL_ERROR;
+  rc = sqlite3_create_collation(db, "test_collate", SQLITE_UTF8, 
+          (void *)SQLITE_UTF8, val?test_collate_func:0);
+  if( rc==SQLITE_OK ){
+    const void *zUtf16;
+    if( TCL_OK!=Tcl_GetBooleanFromObj(interp, objv[3], &val) ) return TCL_ERROR;
+    rc = sqlite3_create_collation(db, "test_collate", SQLITE_UTF16LE, 
+            (void *)SQLITE_UTF16LE, val?test_collate_func:0);
+    if( TCL_OK!=Tcl_GetBooleanFromObj(interp, objv[4], &val) ) return TCL_ERROR;
+
+#if 0
+    if( sqlite3_iMallocFail>0 ){
+      sqlite3_iMallocFail++;
+    }
+#endif
+    sqlite3_mutex_enter(db->mutex);
+    pVal = sqlite3ValueNew(db);
+    sqlite3ValueSetStr(pVal, -1, "test_collate", SQLITE_UTF8, SQLITE_STATIC);
+    zUtf16 = sqlite3ValueText(pVal, SQLITE_UTF16NATIVE);
+    if( db->mallocFailed ){
+      rc = SQLITE_NOMEM;
+    }else{
+      rc = sqlite3_create_collation16(db, zUtf16, SQLITE_UTF16BE, 
+          (void *)SQLITE_UTF16BE, val?test_collate_func:0);
+    }
+    sqlite3ValueFree(pVal);
+    sqlite3_mutex_leave(db->mutex);
+  }
+  if( sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
+  
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, sqlite3TestErrorName(rc), 0);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+
+bad_args:
+  Tcl_AppendResult(interp, "wrong # args: should be \"",
+      Tcl_GetStringFromObj(objv[0], 0), " <DB> <utf8> <utf16le> <utf16be>", 0);
+  return TCL_ERROR;
+}
+
+/*
+** When the collation needed callback is invoked, record the name of 
+** the requested collating function here.  The recorded name is linked
+** to a TCL variable and used to make sure that the requested collation
+** name is correct.
+*/
+static char zNeededCollation[200];
+static char *pzNeededCollation = zNeededCollation;
+
+
+/*
+** Called when a collating sequence is needed.  Registered using
+** sqlite3_collation_needed16().
+*/
+static void test_collate_needed_cb(
+  void *pCtx, 
+  sqlite3 *db,
+  int eTextRep,
+  const void *pName
+){
+  int enc = ENC(db);
+  int i;
+  char *z;
+  for(z = (char*)pName, i=0; *z || z[1]; z++){
+    if( *z ) zNeededCollation[i++] = *z;
+  }
+  zNeededCollation[i] = 0;
+  sqlite3_create_collation(
+      db, "test_collate", ENC(db), SQLITE_INT_TO_PTR(enc), test_collate_func);
+}
+
+/*
+** Usage: add_test_collate_needed DB
+*/
+static int test_collate_needed(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  int rc;
+
+  if( objc!=2 ) goto bad_args;
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  rc = sqlite3_collation_needed16(db, 0, test_collate_needed_cb);
+  zNeededCollation[0] = 0;
+  if( sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
+  return TCL_OK;
+
+bad_args:
+  Tcl_WrongNumArgs(interp, 1, objv, "DB");
+  return TCL_ERROR;
+}
+
+/*
+** tclcmd:   add_alignment_test_collations  DB
+**
+** Add two new collating sequences to the database DB
+**
+**     utf16_aligned
+**     utf16_unaligned
+**
+** Both collating sequences use the same sort order as BINARY.
+** The only difference is that the utf16_aligned collating
+** sequence is declared with the SQLITE_UTF16_ALIGNED flag.
+** Both collating functions increment the unaligned utf16 counter
+** whenever they see a string that begins on an odd byte boundary.
+*/
+static int unaligned_string_counter = 0;
+static int alignmentCollFunc(
+  void *NotUsed,
+  int nKey1, const void *pKey1,
+  int nKey2, const void *pKey2
+){
+  int rc, n;
+  n = nKey1<nKey2 ? nKey1 : nKey2;
+  if( nKey1>0 && 1==(1&(SQLITE_PTR_TO_INT(pKey1))) ) unaligned_string_counter++;
+  if( nKey2>0 && 1==(1&(SQLITE_PTR_TO_INT(pKey2))) ) unaligned_string_counter++;
+  rc = memcmp(pKey1, pKey2, n);
+  if( rc==0 ){
+    rc = nKey1 - nKey2;
+  }
+  return rc;
+}
+static int add_alignment_test_collations(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  if( objc>=2 ){
+    if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+    sqlite3_create_collation(db, "utf16_unaligned", SQLITE_UTF16, 
+        0, alignmentCollFunc);
+    sqlite3_create_collation(db, "utf16_aligned", SQLITE_UTF16_ALIGNED, 
+        0, alignmentCollFunc);
+  }
+  return SQLITE_OK;
+}
+#endif /* !defined(SQLITE_OMIT_UTF16) */
+
+/*
+** Usage: add_test_function <db ptr> <utf8> <utf16le> <utf16be>
+**
+** This function is used to test that SQLite selects the correct user
+** function callback when multiple versions (for different text encodings)
+** are available.
+**
+** Calling this routine registers up to three versions of the user function
+** "test_function" with database handle <db>.  If the second argument is
+** true, then a version of test_function is registered for UTF-8, if the
+** third is true, a version is registered for UTF-16le, if the fourth is
+** true, a UTF-16be version is available.  Previous versions of
+** test_function are deleted.
+**
+** The user function is implemented by calling the following TCL script:
+**
+**   "test_function <enc> <arg>"
+**
+** Where <enc> is one of UTF-8, UTF-16LE or UTF16BE, and <arg> is the
+** single argument passed to the SQL function. The value returned by
+** the TCL script is used as the return value of the SQL function. It
+** is passed to SQLite using UTF-16BE for a UTF-8 test_function(), UTF-8
+** for a UTF-16LE test_function(), and UTF-16LE for an implementation that
+** prefers UTF-16BE.
+*/
+#ifndef SQLITE_OMIT_UTF16
+static void test_function_utf8(
+  sqlite3_context *pCtx, 
+  int nArg,
+  sqlite3_value **argv
+){
+  Tcl_Interp *interp;
+  Tcl_Obj *pX;
+  sqlite3_value *pVal;
+  interp = (Tcl_Interp *)sqlite3_user_data(pCtx);
+  pX = Tcl_NewStringObj("test_function", -1);
+  Tcl_IncrRefCount(pX);
+  Tcl_ListObjAppendElement(interp, pX, Tcl_NewStringObj("UTF-8", -1));
+  Tcl_ListObjAppendElement(interp, pX, 
+      Tcl_NewStringObj((char*)sqlite3_value_text(argv[0]), -1));
+  Tcl_EvalObjEx(interp, pX, 0);
+  Tcl_DecrRefCount(pX);
+  sqlite3_result_text(pCtx, Tcl_GetStringResult(interp), -1, SQLITE_TRANSIENT);
+  pVal = sqlite3ValueNew(0);
+  sqlite3ValueSetStr(pVal, -1, Tcl_GetStringResult(interp), 
+      SQLITE_UTF8, SQLITE_STATIC);
+  sqlite3_result_text16be(pCtx, sqlite3_value_text16be(pVal),
+      -1, SQLITE_TRANSIENT);
+  sqlite3ValueFree(pVal);
+}
+static void test_function_utf16le(
+  sqlite3_context *pCtx, 
+  int nArg,
+  sqlite3_value **argv
+){
+  Tcl_Interp *interp;
+  Tcl_Obj *pX;
+  sqlite3_value *pVal;
+  interp = (Tcl_Interp *)sqlite3_user_data(pCtx);
+  pX = Tcl_NewStringObj("test_function", -1);
+  Tcl_IncrRefCount(pX);
+  Tcl_ListObjAppendElement(interp, pX, Tcl_NewStringObj("UTF-16LE", -1));
+  Tcl_ListObjAppendElement(interp, pX, 
+      Tcl_NewStringObj((char*)sqlite3_value_text(argv[0]), -1));
+  Tcl_EvalObjEx(interp, pX, 0);
+  Tcl_DecrRefCount(pX);
+  pVal = sqlite3ValueNew(0);
+  sqlite3ValueSetStr(pVal, -1, Tcl_GetStringResult(interp), 
+      SQLITE_UTF8, SQLITE_STATIC);
+  sqlite3_result_text(pCtx,(char*)sqlite3_value_text(pVal),-1,SQLITE_TRANSIENT);
+  sqlite3ValueFree(pVal);
+}
+static void test_function_utf16be(
+  sqlite3_context *pCtx, 
+  int nArg,
+  sqlite3_value **argv
+){
+  Tcl_Interp *interp;
+  Tcl_Obj *pX;
+  sqlite3_value *pVal;
+  interp = (Tcl_Interp *)sqlite3_user_data(pCtx);
+  pX = Tcl_NewStringObj("test_function", -1);
+  Tcl_IncrRefCount(pX);
+  Tcl_ListObjAppendElement(interp, pX, Tcl_NewStringObj("UTF-16BE", -1));
+  Tcl_ListObjAppendElement(interp, pX, 
+      Tcl_NewStringObj((char*)sqlite3_value_text(argv[0]), -1));
+  Tcl_EvalObjEx(interp, pX, 0);
+  Tcl_DecrRefCount(pX);
+  pVal = sqlite3ValueNew(0);
+  sqlite3ValueSetStr(pVal, -1, Tcl_GetStringResult(interp), 
+      SQLITE_UTF8, SQLITE_STATIC);
+  sqlite3_result_text16(pCtx, sqlite3_value_text16le(pVal),
+      -1, SQLITE_TRANSIENT);
+  sqlite3_result_text16be(pCtx, sqlite3_value_text16le(pVal),
+      -1, SQLITE_TRANSIENT);
+  sqlite3_result_text16le(pCtx, sqlite3_value_text16le(pVal),
+      -1, SQLITE_TRANSIENT);
+  sqlite3ValueFree(pVal);
+}
+#endif /* SQLITE_OMIT_UTF16 */
+static int test_function(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#ifndef SQLITE_OMIT_UTF16
+  sqlite3 *db;
+  int val;
+
+  if( objc!=5 ) goto bad_args;
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+
+  if( TCL_OK!=Tcl_GetBooleanFromObj(interp, objv[2], &val) ) return TCL_ERROR;
+  if( val ){
+    sqlite3_create_function(db, "test_function", 1, SQLITE_UTF8, 
+        interp, test_function_utf8, 0, 0);
+  }
+  if( TCL_OK!=Tcl_GetBooleanFromObj(interp, objv[3], &val) ) return TCL_ERROR;
+  if( val ){
+    sqlite3_create_function(db, "test_function", 1, SQLITE_UTF16LE, 
+        interp, test_function_utf16le, 0, 0);
+  }
+  if( TCL_OK!=Tcl_GetBooleanFromObj(interp, objv[4], &val) ) return TCL_ERROR;
+  if( val ){
+    sqlite3_create_function(db, "test_function", 1, SQLITE_UTF16BE, 
+        interp, test_function_utf16be, 0, 0);
+  }
+
+  return TCL_OK;
+bad_args:
+  Tcl_AppendResult(interp, "wrong # args: should be \"",
+      Tcl_GetStringFromObj(objv[0], 0), " <DB> <utf8> <utf16le> <utf16be>", 0);
+#endif /* SQLITE_OMIT_UTF16 */
+  return TCL_ERROR;
+}
+
+/*
+** Usage:         sqlite3_test_errstr <err code>
+**
+** Test that the english language string equivalents for sqlite error codes
+** are sane. The parameter is an integer representing an sqlite error code.
+** The result is a list of two elements, the string representation of the
+** error code and the english language explanation.
+*/
+static int test_errstr(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  char *zCode;
+  int i;
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "<error code>");
+  }
+
+  zCode = Tcl_GetString(objv[1]);
+  for(i=0; i<200; i++){
+    if( 0==strcmp(t1ErrorName(i), zCode) ) break;
+  }
+  Tcl_SetResult(interp, (char *)sqlite3ErrStr(i), 0);
+  return TCL_OK;
+}
+
+/*
+** Usage:    breakpoint
+**
+** This routine exists for one purpose - to provide a place to put a
+** breakpoint with GDB that can be triggered using TCL code.  The use
+** for this is when a particular test fails on (say) the 1485th iteration.
+** In the TCL test script, we can add code like this:
+**
+**     if {$i==1485} breakpoint
+**
+** Then run testfixture in the debugger and wait for the breakpoint to
+** fire.  Then additional breakpoints can be set to trace down the bug.
+*/
+static int test_breakpoint(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  char **argv            /* Text of each argument */
+){
+  return TCL_OK;         /* Do nothing */
+}
+
+/*
+** Usage:   sqlite3_bind_zeroblob  STMT IDX N
+**
+** Test the sqlite3_bind_zeroblob interface.  STMT is a prepared statement.
+** IDX is the index of a wildcard in the prepared statement.  This command
+** binds a N-byte zero-filled BLOB to the wildcard.
+*/
+static int test_bind_zeroblob(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int idx;
+  int n;
+  int rc;
+
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "STMT IDX N");
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &idx) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[3], &n) ) return TCL_ERROR;
+
+  rc = sqlite3_bind_zeroblob(pStmt, idx, n);
+  if( sqlite3TestErrCode(interp, StmtToDb(pStmt), rc) ) return TCL_ERROR;
+  if( rc!=SQLITE_OK ){
+    return TCL_ERROR;
+  }
+
+  return TCL_OK;
+}
+
+/*
+** Usage:   sqlite3_bind_int  STMT N VALUE
+**
+** Test the sqlite3_bind_int interface.  STMT is a prepared statement.
+** N is the index of a wildcard in the prepared statement.  This command
+** binds a 32-bit integer VALUE to that wildcard.
+*/
+static int test_bind_int(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int idx;
+  int value;
+  int rc;
+
+  if( objc!=4 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " STMT N VALUE", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &idx) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[3], &value) ) return TCL_ERROR;
+
+  rc = sqlite3_bind_int(pStmt, idx, value);
+  if( sqlite3TestErrCode(interp, StmtToDb(pStmt), rc) ) return TCL_ERROR;
+  if( rc!=SQLITE_OK ){
+    return TCL_ERROR;
+  }
+
+  return TCL_OK;
+}
+
+
+/*
+** Usage:   sqlite3_bind_int64  STMT N VALUE
+**
+** Test the sqlite3_bind_int64 interface.  STMT is a prepared statement.
+** N is the index of a wildcard in the prepared statement.  This command
+** binds a 64-bit integer VALUE to that wildcard.
+*/
+static int test_bind_int64(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int idx;
+  i64 value;
+  int rc;
+
+  if( objc!=4 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " STMT N VALUE", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &idx) ) return TCL_ERROR;
+  if( Tcl_GetWideIntFromObj(interp, objv[3], &value) ) return TCL_ERROR;
+
+  rc = sqlite3_bind_int64(pStmt, idx, value);
+  if( sqlite3TestErrCode(interp, StmtToDb(pStmt), rc) ) return TCL_ERROR;
+  if( rc!=SQLITE_OK ){
+    return TCL_ERROR;
+  }
+
+  return TCL_OK;
+}
+
+
+/*
+** Usage:   sqlite3_bind_double  STMT N VALUE
+**
+** Test the sqlite3_bind_double interface.  STMT is a prepared statement.
+** N is the index of a wildcard in the prepared statement.  This command
+** binds a 64-bit integer VALUE to that wildcard.
+*/
+static int test_bind_double(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int idx;
+  double value;
+  int rc;
+  const char *zVal;
+  int i;
+  static const struct {
+    const char *zName;     /* Name of the special floating point value */
+    unsigned int iUpper;   /* Upper 32 bits */
+    unsigned int iLower;   /* Lower 32 bits */
+  } aSpecialFp[] = {
+    {  "NaN",      0x7fffffff, 0xffffffff },
+    {  "SNaN",     0x7ff7ffff, 0xffffffff },
+    {  "-NaN",     0xffffffff, 0xffffffff },
+    {  "-SNaN",    0xfff7ffff, 0xffffffff },
+    {  "+Inf",     0x7ff00000, 0x00000000 },
+    {  "-Inf",     0xfff00000, 0x00000000 },
+    {  "Epsilon",  0x00000000, 0x00000001 },
+    {  "-Epsilon", 0x80000000, 0x00000001 },
+    {  "NaN0",     0x7ff80000, 0x00000000 },
+    {  "-NaN0",    0xfff80000, 0x00000000 },
+  };
+
+  if( objc!=4 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " STMT N VALUE", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &idx) ) return TCL_ERROR;
+
+  /* Intercept the string "NaN" and generate a NaN value for it.
+  ** All other strings are passed through to Tcl_GetDoubleFromObj().
+  ** Tcl_GetDoubleFromObj() should understand "NaN" but some versions
+  ** contain a bug.
+  */
+  zVal = Tcl_GetString(objv[3]);
+  for(i=0; i<sizeof(aSpecialFp)/sizeof(aSpecialFp[0]); i++){
+    if( strcmp(aSpecialFp[i].zName, zVal)==0 ){
+      sqlite3_uint64 x;
+      x = aSpecialFp[i].iUpper;
+      x <<= 32;
+      x |= aSpecialFp[i].iLower;
+      assert( sizeof(value)==8 );
+      assert( sizeof(x)==8 );
+      memcpy(&value, &x, 8);
+      break;
+    }
+  }
+  if( i>=sizeof(aSpecialFp)/sizeof(aSpecialFp[0]) &&
+         Tcl_GetDoubleFromObj(interp, objv[3], &value) ){
+    return TCL_ERROR;
+  }
+  rc = sqlite3_bind_double(pStmt, idx, value);
+  if( sqlite3TestErrCode(interp, StmtToDb(pStmt), rc) ) return TCL_ERROR;
+  if( rc!=SQLITE_OK ){
+    return TCL_ERROR;
+  }
+
+  return TCL_OK;
+}
+
+/*
+** Usage:   sqlite3_bind_null  STMT N
+**
+** Test the sqlite3_bind_null interface.  STMT is a prepared statement.
+** N is the index of a wildcard in the prepared statement.  This command
+** binds a NULL to the wildcard.
+*/
+static int test_bind_null(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int idx;
+  int rc;
+
+  if( objc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " STMT N", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &idx) ) return TCL_ERROR;
+
+  rc = sqlite3_bind_null(pStmt, idx);
+  if( sqlite3TestErrCode(interp, StmtToDb(pStmt), rc) ) return TCL_ERROR;
+  if( rc!=SQLITE_OK ){
+    return TCL_ERROR;
+  }
+
+  return TCL_OK;
+}
+
+/*
+** Usage:   sqlite3_bind_text  STMT N STRING BYTES
+**
+** Test the sqlite3_bind_text interface.  STMT is a prepared statement.
+** N is the index of a wildcard in the prepared statement.  This command
+** binds a UTF-8 string STRING to the wildcard.  The string is BYTES bytes
+** long.
+*/
+static int test_bind_text(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int idx;
+  int bytes;
+  char *value;
+  int rc;
+
+  if( objc!=5 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " STMT N VALUE BYTES", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &idx) ) return TCL_ERROR;
+  value = (char*)Tcl_GetByteArrayFromObj(objv[3], &bytes);
+  if( Tcl_GetIntFromObj(interp, objv[4], &bytes) ) return TCL_ERROR;
+
+  rc = sqlite3_bind_text(pStmt, idx, value, bytes, SQLITE_TRANSIENT);
+  if( sqlite3TestErrCode(interp, StmtToDb(pStmt), rc) ) return TCL_ERROR;
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, sqlite3TestErrorName(rc), 0);
+    return TCL_ERROR;
+  }
+
+  return TCL_OK;
+}
+
+/*
+** Usage:   sqlite3_bind_text16 ?-static? STMT N STRING BYTES
+**
+** Test the sqlite3_bind_text16 interface.  STMT is a prepared statement.
+** N is the index of a wildcard in the prepared statement.  This command
+** binds a UTF-16 string STRING to the wildcard.  The string is BYTES bytes
+** long.
+*/
+static int test_bind_text16(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#ifndef SQLITE_OMIT_UTF16
+  sqlite3_stmt *pStmt;
+  int idx;
+  int bytes;
+  char *value;
+  int rc;
+
+  void (*xDel)() = (objc==6?SQLITE_STATIC:SQLITE_TRANSIENT);
+  Tcl_Obj *oStmt    = objv[objc-4];
+  Tcl_Obj *oN       = objv[objc-3];
+  Tcl_Obj *oString  = objv[objc-2];
+  Tcl_Obj *oBytes   = objv[objc-1];
+
+  if( objc!=5 && objc!=6){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " STMT N VALUE BYTES", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(oStmt), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, oN, &idx) ) return TCL_ERROR;
+  value = (char*)Tcl_GetByteArrayFromObj(oString, 0);
+  if( Tcl_GetIntFromObj(interp, oBytes, &bytes) ) return TCL_ERROR;
+
+  rc = sqlite3_bind_text16(pStmt, idx, (void *)value, bytes, xDel);
+  if( sqlite3TestErrCode(interp, StmtToDb(pStmt), rc) ) return TCL_ERROR;
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, sqlite3TestErrorName(rc), 0);
+    return TCL_ERROR;
+  }
+
+#endif /* SQLITE_OMIT_UTF16 */
+  return TCL_OK;
+}
+
+/*
+** Usage:   sqlite3_bind_blob ?-static? STMT N DATA BYTES
+**
+** Test the sqlite3_bind_blob interface.  STMT is a prepared statement.
+** N is the index of a wildcard in the prepared statement.  This command
+** binds a BLOB to the wildcard.  The BLOB is BYTES bytes in size.
+*/
+static int test_bind_blob(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int idx;
+  int bytes;
+  char *value;
+  int rc;
+  sqlite3_destructor_type xDestructor = SQLITE_TRANSIENT;
+
+  if( objc!=5 && objc!=6 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " STMT N DATA BYTES", 0);
+    return TCL_ERROR;
+  }
+
+  if( objc==6 ){
+    xDestructor = SQLITE_STATIC;
+    objv++;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &idx) ) return TCL_ERROR;
+  value = Tcl_GetString(objv[3]);
+  if( Tcl_GetIntFromObj(interp, objv[4], &bytes) ) return TCL_ERROR;
+
+  rc = sqlite3_bind_blob(pStmt, idx, value, bytes, xDestructor);
+  if( sqlite3TestErrCode(interp, StmtToDb(pStmt), rc) ) return TCL_ERROR;
+  if( rc!=SQLITE_OK ){
+    return TCL_ERROR;
+  }
+
+  return TCL_OK;
+}
+
+/*
+** Usage:   sqlite3_bind_parameter_count  STMT
+**
+** Return the number of wildcards in the given statement.
+*/
+static int test_bind_parameter_count(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "STMT");
+    return TCL_ERROR;
+  }
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(sqlite3_bind_parameter_count(pStmt)));
+  return TCL_OK;
+}
+
+/*
+** Usage:   sqlite3_bind_parameter_name  STMT  N
+**
+** Return the name of the Nth wildcard.  The first wildcard is 1.
+** An empty string is returned if N is out of range or if the wildcard
+** is nameless.
+*/
+static int test_bind_parameter_name(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int i;
+
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "STMT N");
+    return TCL_ERROR;
+  }
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &i) ) return TCL_ERROR;
+  Tcl_SetObjResult(interp, 
+     Tcl_NewStringObj(sqlite3_bind_parameter_name(pStmt,i),-1)
+  );
+  return TCL_OK;
+}
+
+/*
+** Usage:   sqlite3_bind_parameter_index  STMT  NAME
+**
+** Return the index of the wildcard called NAME.  Return 0 if there is
+** no such wildcard.
+*/
+static int test_bind_parameter_index(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "STMT NAME");
+    return TCL_ERROR;
+  }
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  Tcl_SetObjResult(interp, 
+     Tcl_NewIntObj(
+       sqlite3_bind_parameter_index(pStmt,Tcl_GetString(objv[2]))
+     )
+  );
+  return TCL_OK;
+}
+
+/*
+** Usage:   sqlite3_clear_bindings STMT
+**
+*/
+static int test_clear_bindings(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "STMT");
+    return TCL_ERROR;
+  }
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(sqlite3_clear_bindings(pStmt)));
+  return TCL_OK;
+}
+
+/*
+** Usage:   sqlite3_sleep MILLISECONDS
+*/
+static int test_sleep(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int ms;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "MILLISECONDS");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[1], &ms) ){
+    return TCL_ERROR;
+  }
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(sqlite3_sleep(ms)));
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_extended_errcode DB
+**
+** Return the string representation of the most recent sqlite3_* API
+** error code. e.g. "SQLITE_ERROR".
+*/
+static int test_ex_errcode(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  int rc;
+
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " DB", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  rc = sqlite3_extended_errcode(db);
+  Tcl_AppendResult(interp, (char *)t1ErrorName(rc), 0);
+  return TCL_OK;
+}
+
+
+/*
+** Usage: sqlite3_errcode DB
+**
+** Return the string representation of the most recent sqlite3_* API
+** error code. e.g. "SQLITE_ERROR".
+*/
+static int test_errcode(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  int rc;
+
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " DB", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  rc = sqlite3_errcode(db);
+  Tcl_AppendResult(interp, (char *)t1ErrorName(rc), 0);
+  return TCL_OK;
+}
+
+/*
+** Usage:   sqlite3_errmsg DB
+**
+** Returns the UTF-8 representation of the error message string for the
+** most recent sqlite3_* API call.
+*/
+static int test_errmsg(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  const char *zErr;
+
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " DB", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+
+  zErr = sqlite3_errmsg(db);
+  Tcl_SetObjResult(interp, Tcl_NewStringObj(zErr, -1));
+  return TCL_OK;
+}
+
+/*
+** Usage:   test_errmsg16 DB
+**
+** Returns the UTF-16 representation of the error message string for the
+** most recent sqlite3_* API call. This is a byte array object at the TCL 
+** level, and it includes the 0x00 0x00 terminator bytes at the end of the
+** UTF-16 string.
+*/
+static int test_errmsg16(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#ifndef SQLITE_OMIT_UTF16
+  sqlite3 *db;
+  const void *zErr;
+  const char *z;
+  int bytes = 0;
+
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " DB", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+
+  zErr = sqlite3_errmsg16(db);
+  if( zErr ){
+    z = zErr;
+    for(bytes=0; z[bytes] || z[bytes+1]; bytes+=2){}
+  }
+  Tcl_SetObjResult(interp, Tcl_NewByteArrayObj(zErr, bytes));
+#endif /* SQLITE_OMIT_UTF16 */
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_prepare DB sql bytes ?tailvar?
+**
+** Compile up to <bytes> bytes of the supplied SQL string <sql> using
+** database handle <DB>. The parameter <tailval> is the name of a global
+** variable that is set to the unused portion of <sql> (if any). A
+** STMT handle is returned.
+*/
+static int test_prepare(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  const char *zSql;
+  int bytes;
+  const char *zTail = 0;
+  sqlite3_stmt *pStmt = 0;
+  char zBuf[50];
+  int rc;
+
+  if( objc!=5 && objc!=4 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " DB sql bytes ?tailvar?", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zSql = Tcl_GetString(objv[2]);
+  if( Tcl_GetIntFromObj(interp, objv[3], &bytes) ) return TCL_ERROR;
+
+  rc = sqlite3_prepare(db, zSql, bytes, &pStmt, objc>=5 ? &zTail : 0);
+  Tcl_ResetResult(interp);
+  if( sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
+  if( zTail && objc>=5 ){
+    if( bytes>=0 ){
+      bytes = bytes - (zTail-zSql);
+    }
+    if( strlen(zTail)<bytes ){
+      bytes = strlen(zTail);
+    }
+    Tcl_ObjSetVar2(interp, objv[4], 0, Tcl_NewStringObj(zTail, bytes), 0);
+  }
+  if( rc!=SQLITE_OK ){
+    assert( pStmt==0 );
+    sprintf(zBuf, "(%d) ", rc);
+    Tcl_AppendResult(interp, zBuf, sqlite3_errmsg(db), 0);
+    return TCL_ERROR;
+  }
+
+  if( pStmt ){
+    if( sqlite3TestMakePointerStr(interp, zBuf, pStmt) ) return TCL_ERROR;
+    Tcl_AppendResult(interp, zBuf, 0);
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_prepare_v2 DB sql bytes ?tailvar?
+**
+** Compile up to <bytes> bytes of the supplied SQL string <sql> using
+** database handle <DB>. The parameter <tailval> is the name of a global
+** variable that is set to the unused portion of <sql> (if any). A
+** STMT handle is returned.
+*/
+static int test_prepare_v2(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  const char *zSql;
+  int bytes;
+  const char *zTail = 0;
+  sqlite3_stmt *pStmt = 0;
+  char zBuf[50];
+  int rc;
+
+  if( objc!=5 && objc!=4 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " DB sql bytes tailvar", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zSql = Tcl_GetString(objv[2]);
+  if( Tcl_GetIntFromObj(interp, objv[3], &bytes) ) return TCL_ERROR;
+
+  rc = sqlite3_prepare_v2(db, zSql, bytes, &pStmt, objc>=5 ? &zTail : 0);
+  assert(rc==SQLITE_OK || pStmt==0);
+  Tcl_ResetResult(interp);
+  if( sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
+  if( zTail && objc>=5 ){
+    if( bytes>=0 ){
+      bytes = bytes - (zTail-zSql);
+    }
+    Tcl_ObjSetVar2(interp, objv[4], 0, Tcl_NewStringObj(zTail, bytes), 0);
+  }
+  if( rc!=SQLITE_OK ){
+    assert( pStmt==0 );
+    sprintf(zBuf, "(%d) ", rc);
+    Tcl_AppendResult(interp, zBuf, sqlite3_errmsg(db), 0);
+    return TCL_ERROR;
+  }
+
+  if( pStmt ){
+    if( sqlite3TestMakePointerStr(interp, zBuf, pStmt) ) return TCL_ERROR;
+    Tcl_AppendResult(interp, zBuf, 0);
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_prepare_tkt3134 DB
+**
+** Generate a prepared statement for a zero-byte string as a test
+** for ticket #3134.  The string should be preceeded by a zero byte.
+*/
+static int test_prepare_tkt3134(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  static const char zSql[] = "\000SELECT 1";
+  sqlite3_stmt *pStmt = 0;
+  char zBuf[50];
+  int rc;
+
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " DB sql bytes tailvar", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  rc = sqlite3_prepare_v2(db, &zSql[1], 0, &pStmt, 0);
+  assert(rc==SQLITE_OK || pStmt==0);
+  if( sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
+  if( rc!=SQLITE_OK ){
+    assert( pStmt==0 );
+    sprintf(zBuf, "(%d) ", rc);
+    Tcl_AppendResult(interp, zBuf, sqlite3_errmsg(db), 0);
+    return TCL_ERROR;
+  }
+
+  if( pStmt ){
+    if( sqlite3TestMakePointerStr(interp, zBuf, pStmt) ) return TCL_ERROR;
+    Tcl_AppendResult(interp, zBuf, 0);
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_prepare16 DB sql bytes tailvar
+**
+** Compile up to <bytes> bytes of the supplied SQL string <sql> using
+** database handle <DB>. The parameter <tailval> is the name of a global
+** variable that is set to the unused portion of <sql> (if any). A
+** STMT handle is returned.
+*/
+static int test_prepare16(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#ifndef SQLITE_OMIT_UTF16
+  sqlite3 *db;
+  const void *zSql;
+  const void *zTail = 0;
+  Tcl_Obj *pTail = 0;
+  sqlite3_stmt *pStmt = 0;
+  char zBuf[50]; 
+  int rc;
+  int bytes;                /* The integer specified as arg 3 */
+  int objlen;               /* The byte-array length of arg 2 */
+
+  if( objc!=5 && objc!=4 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " DB sql bytes ?tailvar?", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zSql = Tcl_GetByteArrayFromObj(objv[2], &objlen);
+  if( Tcl_GetIntFromObj(interp, objv[3], &bytes) ) return TCL_ERROR;
+
+  rc = sqlite3_prepare16(db, zSql, bytes, &pStmt, objc>=5 ? &zTail : 0);
+  if( sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
+  if( rc ){
+    return TCL_ERROR;
+  }
+
+  if( objc>=5 ){
+    if( zTail ){
+      objlen = objlen - ((u8 *)zTail-(u8 *)zSql);
+    }else{
+      objlen = 0;
+    }
+    pTail = Tcl_NewByteArrayObj((u8 *)zTail, objlen);
+    Tcl_IncrRefCount(pTail);
+    Tcl_ObjSetVar2(interp, objv[4], 0, pTail, 0);
+    Tcl_DecrRefCount(pTail);
+  }
+
+  if( pStmt ){
+    if( sqlite3TestMakePointerStr(interp, zBuf, pStmt) ) return TCL_ERROR;
+  }
+  Tcl_AppendResult(interp, zBuf, 0);
+#endif /* SQLITE_OMIT_UTF16 */
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_prepare16_v2 DB sql bytes ?tailvar?
+**
+** Compile up to <bytes> bytes of the supplied SQL string <sql> using
+** database handle <DB>. The parameter <tailval> is the name of a global
+** variable that is set to the unused portion of <sql> (if any). A
+** STMT handle is returned.
+*/
+static int test_prepare16_v2(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#ifndef SQLITE_OMIT_UTF16
+  sqlite3 *db;
+  const void *zSql;
+  const void *zTail = 0;
+  Tcl_Obj *pTail = 0;
+  sqlite3_stmt *pStmt = 0;
+  char zBuf[50]; 
+  int rc;
+  int bytes;                /* The integer specified as arg 3 */
+  int objlen;               /* The byte-array length of arg 2 */
+
+  if( objc!=5 && objc!=4 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " DB sql bytes ?tailvar?", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zSql = Tcl_GetByteArrayFromObj(objv[2], &objlen);
+  if( Tcl_GetIntFromObj(interp, objv[3], &bytes) ) return TCL_ERROR;
+
+  rc = sqlite3_prepare16_v2(db, zSql, bytes, &pStmt, objc>=5 ? &zTail : 0);
+  if( sqlite3TestErrCode(interp, db, rc) ) return TCL_ERROR;
+  if( rc ){
+    return TCL_ERROR;
+  }
+
+  if( objc>=5 ){
+    if( zTail ){
+      objlen = objlen - ((u8 *)zTail-(u8 *)zSql);
+    }else{
+      objlen = 0;
+    }
+    pTail = Tcl_NewByteArrayObj((u8 *)zTail, objlen);
+    Tcl_IncrRefCount(pTail);
+    Tcl_ObjSetVar2(interp, objv[4], 0, pTail, 0);
+    Tcl_DecrRefCount(pTail);
+  }
+
+  if( pStmt ){
+    if( sqlite3TestMakePointerStr(interp, zBuf, pStmt) ) return TCL_ERROR;
+  }
+  Tcl_AppendResult(interp, zBuf, 0);
+#endif /* SQLITE_OMIT_UTF16 */
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_open filename ?options-list?
+*/
+static int test_open(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  const char *zFilename;
+  sqlite3 *db;
+  int rc;
+  char zBuf[100];
+
+  if( objc!=3 && objc!=2 && objc!=1 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " filename options-list", 0);
+    return TCL_ERROR;
+  }
+
+  zFilename = objc>1 ? Tcl_GetString(objv[1]) : 0;
+  rc = sqlite3_open(zFilename, &db);
+  
+  if( sqlite3TestMakePointerStr(interp, zBuf, db) ) return TCL_ERROR;
+  Tcl_AppendResult(interp, zBuf, 0);
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_open_v2 FILENAME FLAGS VFS
+*/
+static int test_open_v2(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  const char *zFilename;
+  const char *zVfs;
+  int flags = 0;
+  sqlite3 *db;
+  int rc;
+  char zBuf[100];
+
+  int nFlag;
+  Tcl_Obj **apFlag;
+  int i;
+
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "FILENAME FLAGS VFS");
+    return TCL_ERROR;
+  }
+  zFilename = Tcl_GetString(objv[1]);
+  zVfs = Tcl_GetString(objv[3]);
+  if( zVfs[0]==0x00 ) zVfs = 0;
+
+  rc = Tcl_ListObjGetElements(interp, objv[2], &nFlag, &apFlag);
+  if( rc!=TCL_OK ) return rc;
+  for(i=0; i<nFlag; i++){
+    int iFlag;
+    struct OpenFlag {
+      const char *zFlag;
+      int flag;
+    } aFlag[] = {
+      { "SQLITE_OPEN_READONLY", SQLITE_OPEN_READONLY },
+      { "SQLITE_OPEN_READWRITE", SQLITE_OPEN_READWRITE },
+      { "SQLITE_OPEN_CREATE", SQLITE_OPEN_CREATE },
+      { "SQLITE_OPEN_DELETEONCLOSE", SQLITE_OPEN_DELETEONCLOSE },
+      { "SQLITE_OPEN_EXCLUSIVE", SQLITE_OPEN_EXCLUSIVE },
+      { "SQLITE_OPEN_AUTOPROXY", SQLITE_OPEN_AUTOPROXY },
+      { "SQLITE_OPEN_MAIN_DB", SQLITE_OPEN_MAIN_DB },
+      { "SQLITE_OPEN_TEMP_DB", SQLITE_OPEN_TEMP_DB },
+      { "SQLITE_OPEN_TRANSIENT_DB", SQLITE_OPEN_TRANSIENT_DB },
+      { "SQLITE_OPEN_MAIN_JOURNAL", SQLITE_OPEN_MAIN_JOURNAL },
+      { "SQLITE_OPEN_TEMP_JOURNAL", SQLITE_OPEN_TEMP_JOURNAL },
+      { "SQLITE_OPEN_SUBJOURNAL", SQLITE_OPEN_SUBJOURNAL },
+      { "SQLITE_OPEN_MASTER_JOURNAL", SQLITE_OPEN_MASTER_JOURNAL },
+      { "SQLITE_OPEN_NOMUTEX", SQLITE_OPEN_NOMUTEX },
+      { "SQLITE_OPEN_FULLMUTEX", SQLITE_OPEN_FULLMUTEX },
+      { "SQLITE_OPEN_SHAREDCACHE", SQLITE_OPEN_SHAREDCACHE },
+      { "SQLITE_OPEN_PRIVATECACHE", SQLITE_OPEN_PRIVATECACHE },
+      { "SQLITE_OPEN_WAL", SQLITE_OPEN_WAL },
+      { "SQLITE_OPEN_URI", SQLITE_OPEN_URI },
+      { 0, 0 }
+    };
+    rc = Tcl_GetIndexFromObjStruct(interp, apFlag[i], aFlag, sizeof(aFlag[0]), 
+        "flag", 0, &iFlag
+    );
+    if( rc!=TCL_OK ) return rc;
+    flags |= aFlag[iFlag].flag;
+  }
+
+  rc = sqlite3_open_v2(zFilename, &db, flags, zVfs);
+  if( sqlite3TestMakePointerStr(interp, zBuf, db) ) return TCL_ERROR;
+  Tcl_AppendResult(interp, zBuf, 0);
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_open16 filename options
+*/
+static int test_open16(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#ifndef SQLITE_OMIT_UTF16
+  const void *zFilename;
+  sqlite3 *db;
+  int rc;
+  char zBuf[100];
+
+  if( objc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " filename options-list", 0);
+    return TCL_ERROR;
+  }
+
+  zFilename = Tcl_GetByteArrayFromObj(objv[1], 0);
+  rc = sqlite3_open16(zFilename, &db);
+  
+  if( sqlite3TestMakePointerStr(interp, zBuf, db) ) return TCL_ERROR;
+  Tcl_AppendResult(interp, zBuf, 0);
+#endif /* SQLITE_OMIT_UTF16 */
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_complete16 <UTF-16 string>
+**
+** Return 1 if the supplied argument is a complete SQL statement, or zero
+** otherwise.
+*/
+static int test_complete16(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#if !defined(SQLITE_OMIT_COMPLETE) && !defined(SQLITE_OMIT_UTF16)
+  char *zBuf;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "<utf-16 sql>");
+    return TCL_ERROR;
+  }
+
+  zBuf = (char*)Tcl_GetByteArrayFromObj(objv[1], 0);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(sqlite3_complete16(zBuf)));
+#endif /* SQLITE_OMIT_COMPLETE && SQLITE_OMIT_UTF16 */
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_step STMT
+**
+** Advance the statement to the next row.
+*/
+static int test_step(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int rc;
+
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " STMT", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  rc = sqlite3_step(pStmt);
+
+  /* if( rc!=SQLITE_DONE && rc!=SQLITE_ROW ) return TCL_ERROR; */
+  Tcl_SetResult(interp, (char *)t1ErrorName(rc), 0);
+  return TCL_OK;
+}
+
+static int test_sql(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "STMT");
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  Tcl_SetResult(interp, (char *)sqlite3_sql(pStmt), TCL_VOLATILE);
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_column_count STMT 
+**
+** Return the number of columns returned by the sql statement STMT.
+*/
+static int test_column_count(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " STMT column", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(sqlite3_column_count(pStmt)));
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_column_type STMT column
+**
+** Return the type of the data in column 'column' of the current row.
+*/
+static int test_column_type(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int col;
+  int tp;
+
+  if( objc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " STMT column", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &col) ) return TCL_ERROR;
+
+  tp = sqlite3_column_type(pStmt, col);
+  switch( tp ){
+    case SQLITE_INTEGER: 
+      Tcl_SetResult(interp, "INTEGER", TCL_STATIC); 
+      break;
+    case SQLITE_NULL:
+      Tcl_SetResult(interp, "NULL", TCL_STATIC); 
+      break;
+    case SQLITE_FLOAT:
+      Tcl_SetResult(interp, "FLOAT", TCL_STATIC); 
+      break;
+    case SQLITE_TEXT:
+      Tcl_SetResult(interp, "TEXT", TCL_STATIC); 
+      break;
+    case SQLITE_BLOB:
+      Tcl_SetResult(interp, "BLOB", TCL_STATIC); 
+      break;
+    default:
+      assert(0);
+  }
+
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_column_int64 STMT column
+**
+** Return the data in column 'column' of the current row cast as an
+** wide (64-bit) integer.
+*/
+static int test_column_int64(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int col;
+  i64 iVal;
+
+  if( objc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " STMT column", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &col) ) return TCL_ERROR;
+
+  iVal = sqlite3_column_int64(pStmt, col);
+  Tcl_SetObjResult(interp, Tcl_NewWideIntObj(iVal));
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_column_blob STMT column
+*/
+static int test_column_blob(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int col;
+
+  int len;
+  const void *pBlob;
+
+  if( objc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " STMT column", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &col) ) return TCL_ERROR;
+
+  len = sqlite3_column_bytes(pStmt, col);
+  pBlob = sqlite3_column_blob(pStmt, col);
+  Tcl_SetObjResult(interp, Tcl_NewByteArrayObj(pBlob, len));
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_column_double STMT column
+**
+** Return the data in column 'column' of the current row cast as a double.
+*/
+static int test_column_double(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int col;
+  double rVal;
+
+  if( objc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " STMT column", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &col) ) return TCL_ERROR;
+
+  rVal = sqlite3_column_double(pStmt, col);
+  Tcl_SetObjResult(interp, Tcl_NewDoubleObj(rVal));
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_data_count STMT 
+**
+** Return the number of columns returned by the sql statement STMT.
+*/
+static int test_data_count(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " STMT column", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(sqlite3_data_count(pStmt)));
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_column_text STMT column
+**
+** Usage: sqlite3_column_decltype STMT column
+**
+** Usage: sqlite3_column_name STMT column
+*/
+static int test_stmt_utf8(
+  void * clientData,        /* Pointer to SQLite API function to be invoke */
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int col;
+  const char *(*xFunc)(sqlite3_stmt*, int);
+  const char *zRet;
+
+  xFunc = (const char *(*)(sqlite3_stmt*, int))clientData;
+  if( objc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " STMT column", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &col) ) return TCL_ERROR;
+  zRet = xFunc(pStmt, col);
+  if( zRet ){
+    Tcl_SetResult(interp, (char *)zRet, 0);
+  }
+  return TCL_OK;
+}
+
+static int test_global_recover(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#ifndef SQLITE_OMIT_DEPRECATED
+  int rc;
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+  rc = sqlite3_global_recover();
+  Tcl_SetResult(interp, (char *)t1ErrorName(rc), TCL_STATIC);
+#endif
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_column_text STMT column
+**
+** Usage: sqlite3_column_decltype STMT column
+**
+** Usage: sqlite3_column_name STMT column
+*/
+static int test_stmt_utf16(
+  void * clientData,     /* Pointer to SQLite API function to be invoked */
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#ifndef SQLITE_OMIT_UTF16
+  sqlite3_stmt *pStmt;
+  int col;
+  Tcl_Obj *pRet;
+  const void *zName16;
+  const void *(*xFunc)(sqlite3_stmt*, int);
+
+  xFunc = (const void *(*)(sqlite3_stmt*, int))clientData;
+  if( objc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " STMT column", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &col) ) return TCL_ERROR;
+
+  zName16 = xFunc(pStmt, col);
+  if( zName16 ){
+    int n;
+    const char *z = zName16;
+    for(n=0; z[n] || z[n+1]; n+=2){}
+    pRet = Tcl_NewByteArrayObj(zName16, n+2);
+    Tcl_SetObjResult(interp, pRet);
+  }
+#endif /* SQLITE_OMIT_UTF16 */
+
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_column_int STMT column
+**
+** Usage: sqlite3_column_bytes STMT column
+**
+** Usage: sqlite3_column_bytes16 STMT column
+**
+*/
+static int test_stmt_int(
+  void * clientData,    /* Pointer to SQLite API function to be invoked */
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_stmt *pStmt;
+  int col;
+  int (*xFunc)(sqlite3_stmt*, int);
+
+  xFunc = (int (*)(sqlite3_stmt*, int))clientData;
+  if( objc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " STMT column", 0);
+    return TCL_ERROR;
+  }
+
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &col) ) return TCL_ERROR;
+
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(xFunc(pStmt, col)));
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite_set_magic  DB  MAGIC-NUMBER
+**
+** Set the db->magic value.  This is used to test error recovery logic.
+*/
+static int sqlite_set_magic(
+  void * clientData,
+  Tcl_Interp *interp,
+  int argc,
+  char **argv
+){
+  sqlite3 *db;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+         " DB MAGIC", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  if( strcmp(argv[2], "SQLITE_MAGIC_OPEN")==0 ){
+    db->magic = SQLITE_MAGIC_OPEN;
+  }else if( strcmp(argv[2], "SQLITE_MAGIC_CLOSED")==0 ){
+    db->magic = SQLITE_MAGIC_CLOSED;
+  }else if( strcmp(argv[2], "SQLITE_MAGIC_BUSY")==0 ){
+    db->magic = SQLITE_MAGIC_BUSY;
+  }else if( strcmp(argv[2], "SQLITE_MAGIC_ERROR")==0 ){
+    db->magic = SQLITE_MAGIC_ERROR;
+  }else if( Tcl_GetInt(interp, argv[2], (int*)&db->magic) ){
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_interrupt  DB 
+**
+** Trigger an interrupt on DB
+*/
+static int test_interrupt(
+  void * clientData,
+  Tcl_Interp *interp,
+  int argc,
+  char **argv
+){
+  sqlite3 *db;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], " DB", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  sqlite3_interrupt(db);
+  return TCL_OK;
+}
+
+static u8 *sqlite3_stack_baseline = 0;
+
+/*
+** Fill the stack with a known bitpattern.
+*/
+static void prepStack(void){
+  int i;
+  u32 bigBuf[65536];
+  for(i=0; i<sizeof(bigBuf)/sizeof(bigBuf[0]); i++) bigBuf[i] = 0xdeadbeef;
+  sqlite3_stack_baseline = (u8*)&bigBuf[65536];
+}
+
+/*
+** Get the current stack depth.  Used for debugging only.
+*/
+u64 sqlite3StackDepth(void){
+  u8 x;
+  return (u64)(sqlite3_stack_baseline - &x);
+}
+
+/*
+** Usage:  sqlite3_stack_used DB SQL
+**
+** Try to measure the amount of stack space used by a call to sqlite3_exec
+*/
+static int test_stack_used(
+  void * clientData,
+  Tcl_Interp *interp,
+  int argc,
+  char **argv
+){
+  sqlite3 *db;
+  int i;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], 
+        " DB SQL", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  prepStack();
+  (void)sqlite3_exec(db, argv[2], 0, 0, 0);
+  for(i=65535; i>=0 && ((u32*)sqlite3_stack_baseline)[-i]==0xdeadbeef; i--){}
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(i*4));
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite_delete_function DB function-name
+**
+** Delete the user function 'function-name' from database handle DB. It
+** is assumed that the user function was created as UTF8, any number of
+** arguments (the way the TCL interface does it).
+*/
+static int delete_function(
+  void * clientData,
+  Tcl_Interp *interp,
+  int argc,
+  char **argv
+){
+  int rc;
+  sqlite3 *db;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], 
+        " DB function-name", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  rc = sqlite3_create_function(db, argv[2], -1, SQLITE_UTF8, 0, 0, 0, 0);
+  Tcl_SetResult(interp, (char *)t1ErrorName(rc), TCL_STATIC);
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite_delete_collation DB collation-name
+**
+** Delete the collation sequence 'collation-name' from database handle 
+** DB. It is assumed that the collation sequence was created as UTF8 (the 
+** way the TCL interface does it).
+*/
+static int delete_collation(
+  void * clientData,
+  Tcl_Interp *interp,
+  int argc,
+  char **argv
+){
+  int rc;
+  sqlite3 *db;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], 
+        " DB function-name", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  rc = sqlite3_create_collation(db, argv[2], SQLITE_UTF8, 0, 0);
+  Tcl_SetResult(interp, (char *)t1ErrorName(rc), TCL_STATIC);
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_get_autocommit DB
+**
+** Return true if the database DB is currently in auto-commit mode.
+** Return false if not.
+*/
+static int get_autocommit(
+  void * clientData,
+  Tcl_Interp *interp,
+  int argc,
+  char **argv
+){
+  char zBuf[30];
+  sqlite3 *db;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], 
+        " DB", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  sprintf(zBuf, "%d", sqlite3_get_autocommit(db));
+  Tcl_AppendResult(interp, zBuf, 0);
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_busy_timeout DB MS
+**
+** Set the busy timeout.  This is more easily done using the timeout
+** method of the TCL interface.  But we need a way to test the case
+** where it returns SQLITE_MISUSE.
+*/
+static int test_busy_timeout(
+  void * clientData,
+  Tcl_Interp *interp,
+  int argc,
+  char **argv
+){
+  int rc, ms;
+  sqlite3 *db;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0], 
+        " DB", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, argv[1], &db) ) return TCL_ERROR;
+  if( Tcl_GetInt(interp, argv[2], &ms) ) return TCL_ERROR;
+  rc = sqlite3_busy_timeout(db, ms);
+  Tcl_AppendResult(interp, sqlite3TestErrorName(rc), 0);
+  return TCL_OK;
+}
+
+/*
+** Usage:  tcl_variable_type VARIABLENAME
+**
+** Return the name of the internal representation for the
+** value of the given variable.
+*/
+static int tcl_variable_type(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  Tcl_Obj *pVar;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "VARIABLE");
+    return TCL_ERROR;
+  }
+  pVar = Tcl_GetVar2Ex(interp, Tcl_GetString(objv[1]), 0, TCL_LEAVE_ERR_MSG);
+  if( pVar==0 ) return TCL_ERROR;
+  if( pVar->typePtr ){
+    Tcl_SetObjResult(interp, Tcl_NewStringObj(pVar->typePtr->name, -1));
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_release_memory ?N?
+**
+** Attempt to release memory currently held but not actually required.
+** The integer N is the number of bytes we are trying to release.  The 
+** return value is the amount of memory actually released.
+*/
+static int test_release_memory(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#if defined(SQLITE_ENABLE_MEMORY_MANAGEMENT) && !defined(SQLITE_OMIT_DISKIO)
+  int N;
+  int amt;
+  if( objc!=1 && objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "?N?");
+    return TCL_ERROR;
+  }
+  if( objc==2 ){
+    if( Tcl_GetIntFromObj(interp, objv[1], &N) ) return TCL_ERROR;
+  }else{
+    N = -1;
+  }
+  amt = sqlite3_release_memory(N);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(amt));
+#endif
+  return TCL_OK;
+}
+
+/*
+** Usage:  sqlite3_soft_heap_limit ?N?
+**
+** Query or set the soft heap limit for the current thread.  The
+** limit is only changed if the N is present.  The previous limit
+** is returned.
+*/
+static int test_soft_heap_limit(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_int64 amt;
+  sqlite3_int64 N = -1;
+  if( objc!=1 && objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "?N?");
+    return TCL_ERROR;
+  }
+  if( objc==2 ){
+    if( Tcl_GetWideIntFromObj(interp, objv[1], &N) ) return TCL_ERROR;
+  }
+  amt = sqlite3_soft_heap_limit64(N);
+  Tcl_SetObjResult(interp, Tcl_NewWideIntObj(amt));
+  return TCL_OK;
+}
+
+/*
+** Usage:   sqlite3_thread_cleanup
+**
+** Call the sqlite3_thread_cleanup API.
+*/
+static int test_thread_cleanup(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#ifndef SQLITE_OMIT_DEPRECATED
+  sqlite3_thread_cleanup();
+#endif
+  return TCL_OK;
+}
+
+/*
+** Usage:   sqlite3_pager_refcounts  DB
+**
+** Return a list of numbers which are the PagerRefcount for all
+** pagers on each database connection.
+*/
+static int test_pager_refcounts(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  int i;
+  int v, *a;
+  Tcl_Obj *pResult;
+
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " DB", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  pResult = Tcl_NewObj();
+  for(i=0; i<db->nDb; i++){
+    if( db->aDb[i].pBt==0 ){
+      v = -1;
+    }else{
+      sqlite3_mutex_enter(db->mutex);
+      a = sqlite3PagerStats(sqlite3BtreePager(db->aDb[i].pBt));
+      v = a[0];
+      sqlite3_mutex_leave(db->mutex);
+    }
+    Tcl_ListObjAppendElement(0, pResult, Tcl_NewIntObj(v));
+  }
+  Tcl_SetObjResult(interp, pResult);
+  return TCL_OK;
+}
+
+
+/*
+** tclcmd:   working_64bit_int
+**
+** Some TCL builds (ex: cygwin) do not support 64-bit integers.  This
+** leads to a number of test failures.  The present command checks the
+** TCL build to see whether or not it supports 64-bit integers.  It
+** returns TRUE if it does and FALSE if not.
+**
+** This command is used to warn users that their TCL build is defective
+** and that the errors they are seeing in the test scripts might be
+** a result of their defective TCL rather than problems in SQLite.
+*/
+static int working_64bit_int(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  Tcl_Obj *pTestObj;
+  int working = 0;
+
+  pTestObj = Tcl_NewWideIntObj(1000000*(i64)1234567890);
+  working = strcmp(Tcl_GetString(pTestObj), "1234567890000000")==0;
+  Tcl_DecrRefCount(pTestObj);
+  Tcl_SetObjResult(interp, Tcl_NewBooleanObj(working));
+  return TCL_OK;
+}
+
+
+/*
+** tclcmd:   vfs_unlink_test
+**
+** This TCL command unregisters the primary VFS and then registers
+** it back again.  This is used to test the ability to register a
+** VFS when none are previously registered, and the ability to 
+** unregister the only available VFS.  Ticket #2738
+*/
+static int vfs_unlink_test(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  int i;
+  sqlite3_vfs *pMain;
+  sqlite3_vfs *apVfs[20];
+  sqlite3_vfs one, two;
+
+  sqlite3_vfs_unregister(0);   /* Unregister of NULL is harmless */
+  one.zName = "__one";
+  two.zName = "__two";
+
+  /* Calling sqlite3_vfs_register with 2nd argument of 0 does not
+  ** change the default VFS
+  */
+  pMain = sqlite3_vfs_find(0);
+  sqlite3_vfs_register(&one, 0);
+  assert( pMain==0 || pMain==sqlite3_vfs_find(0) );
+  sqlite3_vfs_register(&two, 0);
+  assert( pMain==0 || pMain==sqlite3_vfs_find(0) );
+
+  /* We can find a VFS by its name */
+  assert( sqlite3_vfs_find("__one")==&one );
+  assert( sqlite3_vfs_find("__two")==&two );
+
+  /* Calling sqlite_vfs_register with non-zero second parameter changes the
+  ** default VFS, even if the 1st parameter is an existig VFS that is
+  ** previously registered as the non-default.
+  */
+  sqlite3_vfs_register(&one, 1);
+  assert( sqlite3_vfs_find("__one")==&one );
+  assert( sqlite3_vfs_find("__two")==&two );
+  assert( sqlite3_vfs_find(0)==&one );
+  sqlite3_vfs_register(&two, 1);
+  assert( sqlite3_vfs_find("__one")==&one );
+  assert( sqlite3_vfs_find("__two")==&two );
+  assert( sqlite3_vfs_find(0)==&two );
+  if( pMain ){
+    sqlite3_vfs_register(pMain, 1);
+    assert( sqlite3_vfs_find("__one")==&one );
+    assert( sqlite3_vfs_find("__two")==&two );
+    assert( sqlite3_vfs_find(0)==pMain );
+  }
+  
+  /* Unlink the default VFS.  Repeat until there are no more VFSes
+  ** registered.
+  */
+  for(i=0; i<sizeof(apVfs)/sizeof(apVfs[0]); i++){
+    apVfs[i] = sqlite3_vfs_find(0);
+    if( apVfs[i] ){
+      assert( apVfs[i]==sqlite3_vfs_find(apVfs[i]->zName) );
+      sqlite3_vfs_unregister(apVfs[i]);
+      assert( 0==sqlite3_vfs_find(apVfs[i]->zName) );
+    }
+  }
+  assert( 0==sqlite3_vfs_find(0) );
+  
+  /* Register the main VFS as non-default (will be made default, since
+  ** it'll be the only one in existence).
+  */
+  sqlite3_vfs_register(pMain, 0);
+  assert( sqlite3_vfs_find(0)==pMain );
+  
+  /* Un-register the main VFS again to restore an empty VFS list */
+  sqlite3_vfs_unregister(pMain);
+  assert( 0==sqlite3_vfs_find(0) );
+
+  /* Relink all VFSes in reverse order. */  
+  for(i=sizeof(apVfs)/sizeof(apVfs[0])-1; i>=0; i--){
+    if( apVfs[i] ){
+      sqlite3_vfs_register(apVfs[i], 1);
+      assert( apVfs[i]==sqlite3_vfs_find(0) );
+      assert( apVfs[i]==sqlite3_vfs_find(apVfs[i]->zName) );
+    }
+  }
+
+  /* Unregister out sample VFSes. */
+  sqlite3_vfs_unregister(&one);
+  sqlite3_vfs_unregister(&two);
+
+  /* Unregistering a VFS that is not currently registered is harmless */
+  sqlite3_vfs_unregister(&one);
+  sqlite3_vfs_unregister(&two);
+  assert( sqlite3_vfs_find("__one")==0 );
+  assert( sqlite3_vfs_find("__two")==0 );
+
+  /* We should be left with the original default VFS back as the
+  ** original */
+  assert( sqlite3_vfs_find(0)==pMain );
+
+  return TCL_OK;
+}
+
+/*
+** tclcmd:   vfs_initfail_test
+**
+** This TCL command attempts to vfs_find and vfs_register when the
+** sqlite3_initialize() interface is failing.  All calls should fail.
+*/
+static int vfs_initfail_test(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3_vfs one;
+  one.zName = "__one";
+
+  if( sqlite3_vfs_find(0) ) return TCL_ERROR;
+  sqlite3_vfs_register(&one, 0);
+  if( sqlite3_vfs_find(0) ) return TCL_ERROR;
+  sqlite3_vfs_register(&one, 1);
+  if( sqlite3_vfs_find(0) ) return TCL_ERROR;
+  return TCL_OK;
+}
+
+/*
+** Saved VFSes
+*/
+static sqlite3_vfs *apVfs[20];
+static int nVfs = 0;
+
+/*
+** tclcmd:   vfs_unregister_all
+**
+** Unregister all VFSes.
+*/
+static int vfs_unregister_all(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  int i;
+  for(i=0; i<ArraySize(apVfs); i++){
+    apVfs[i] = sqlite3_vfs_find(0);
+    if( apVfs[i]==0 ) break;
+    sqlite3_vfs_unregister(apVfs[i]);
+  }
+  nVfs = i;
+  return TCL_OK;
+}
+/*
+** tclcmd:   vfs_reregister_all
+**
+** Restore all VFSes that were removed using vfs_unregister_all
+*/
+static int vfs_reregister_all(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  int i;
+  for(i=0; i<nVfs; i++){
+    sqlite3_vfs_register(apVfs[i], i==0);
+  }
+  return TCL_OK;
+}
+
+
+/*
+** tclcmd:   file_control_test DB
+**
+** This TCL command runs the sqlite3_file_control interface and
+** verifies correct operation of the same.
+*/
+static int file_control_test(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  int iArg = 0;
+  sqlite3 *db;
+  int rc;
+
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " DB", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  rc = sqlite3_file_control(db, 0, 0, &iArg);
+  assert( rc==SQLITE_NOTFOUND );
+  rc = sqlite3_file_control(db, "notadatabase", SQLITE_FCNTL_LOCKSTATE, &iArg);
+  assert( rc==SQLITE_ERROR );
+  rc = sqlite3_file_control(db, "main", -1, &iArg);
+  assert( rc==SQLITE_NOTFOUND );
+  rc = sqlite3_file_control(db, "temp", -1, &iArg);
+  assert( rc==SQLITE_NOTFOUND || rc==SQLITE_ERROR );
+
+  return TCL_OK;
+}
+
+
+/*
+** tclcmd:   file_control_lasterrno_test DB
+**
+** This TCL command runs the sqlite3_file_control interface and
+** verifies correct operation of the SQLITE_LAST_ERRNO verb.
+*/
+static int file_control_lasterrno_test(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  int iArg = 0;
+  sqlite3 *db;
+  int rc;
+
+  if( objc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " DB", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ){
+    return TCL_ERROR;
+  }
+  rc = sqlite3_file_control(db, NULL, SQLITE_LAST_ERRNO, &iArg);
+  if( rc ){ 
+    Tcl_SetObjResult(interp, Tcl_NewIntObj(rc)); 
+    return TCL_ERROR; 
+  }
+  if( iArg!=0 ) {
+    Tcl_AppendResult(interp, "Unexpected non-zero errno: ",
+                     Tcl_GetStringFromObj(Tcl_NewIntObj(iArg), 0), " ", 0);
+    return TCL_ERROR;
+  }
+  return TCL_OK;  
+}
+
+/*
+** tclcmd:   file_control_chunksize_test DB DBNAME SIZE
+**
+** This TCL command runs the sqlite3_file_control interface and
+** verifies correct operation of the SQLITE_GET_LOCKPROXYFILE and
+** SQLITE_SET_LOCKPROXYFILE verbs.
+*/
+static int file_control_chunksize_test(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  int nSize;                      /* New chunk size */
+  char *zDb;                      /* Db name ("main", "temp" etc.) */
+  sqlite3 *db;                    /* Database handle */
+  int rc;                         /* file_control() return code */
+
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB DBNAME SIZE");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) 
+   || Tcl_GetIntFromObj(interp, objv[3], &nSize)
+  ){
+   return TCL_ERROR;
+  }
+  zDb = Tcl_GetString(objv[2]);
+  if( zDb[0]=='\0' ) zDb = NULL;
+
+  rc = sqlite3_file_control(db, zDb, SQLITE_FCNTL_CHUNK_SIZE, (void *)&nSize);
+  if( rc ){
+    Tcl_SetResult(interp, (char *)sqlite3TestErrorName(rc), TCL_STATIC);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
+/*
+** tclcmd:   file_control_sizehint_test DB DBNAME SIZE
+**
+** This TCL command runs the sqlite3_file_control interface 
+** with SQLITE_FCNTL_SIZE_HINT
+*/
+static int file_control_sizehint_test(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3_int64 nSize;            /* Hinted size */
+  char *zDb;                      /* Db name ("main", "temp" etc.) */
+  sqlite3 *db;                    /* Database handle */
+  int rc;                         /* file_control() return code */
+
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB DBNAME SIZE");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) 
+   || Tcl_GetWideIntFromObj(interp, objv[3], &nSize)
+  ){
+   return TCL_ERROR;
+  }
+  zDb = Tcl_GetString(objv[2]);
+  if( zDb[0]=='\0' ) zDb = NULL;
+
+  rc = sqlite3_file_control(db, zDb, SQLITE_FCNTL_SIZE_HINT, (void *)&nSize);
+  if( rc ){
+    Tcl_SetResult(interp, (char *)sqlite3TestErrorName(rc), TCL_STATIC);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
+/*
+** tclcmd:   file_control_lockproxy_test DB PWD
+**
+** This TCL command runs the sqlite3_file_control interface and
+** verifies correct operation of the SQLITE_GET_LOCKPROXYFILE and
+** SQLITE_SET_LOCKPROXYFILE verbs.
+*/
+static int file_control_lockproxy_test(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3 *db;
+  const char *zPwd;
+  int nPwd;
+  
+  if( objc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+                     Tcl_GetStringFromObj(objv[0], 0), " DB PWD", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ){
+   return TCL_ERROR;
+  }
+  zPwd = Tcl_GetStringFromObj(objv[2], &nPwd);
+  
+#if !defined(SQLITE_ENABLE_LOCKING_STYLE)
+#  if defined(__APPLE__)
+#    define SQLITE_ENABLE_LOCKING_STYLE 1
+#  else
+#    define SQLITE_ENABLE_LOCKING_STYLE 0
+#  endif
+#endif
+#if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__)
+  {
+    char *testPath;
+    int rc;
+    char proxyPath[400];
+    
+    if( sizeof(proxyPath)<nPwd+20 ){
+      Tcl_AppendResult(interp, "PWD too big", (void*)0);
+      return TCL_ERROR;
+    }
+    sprintf(proxyPath, "%s/test.proxy", zPwd);
+    rc = sqlite3_file_control(db, NULL, SQLITE_SET_LOCKPROXYFILE, proxyPath);
+    if( rc ){
+      Tcl_SetObjResult(interp, Tcl_NewIntObj(rc)); 
+      return TCL_ERROR;
+    }
+    rc = sqlite3_file_control(db, NULL, SQLITE_GET_LOCKPROXYFILE, &testPath);
+    if( strncmp(proxyPath,testPath,11) ){
+      Tcl_AppendResult(interp, "Lock proxy file did not match the "
+                               "previously assigned value", 0);
+      return TCL_ERROR;
+    }
+    if( rc ){
+      Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+      return TCL_ERROR;
+    }
+    rc = sqlite3_file_control(db, NULL, SQLITE_SET_LOCKPROXYFILE, proxyPath);
+    if( rc ){
+      Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+      return TCL_ERROR;
+    }
+  }
+#endif
+  return TCL_OK;  
+}
+
+/*
+** tclcmd:   file_control_win32_av_retry DB  NRETRY  DELAY
+**
+** This TCL command runs the sqlite3_file_control interface with
+** the SQLITE_FCNTL_WIN32_AV_RETRY opcode.
+*/
+static int file_control_win32_av_retry(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3 *db;
+  int rc;
+  int a[2];
+  char z[100];
+
+  if( objc!=4 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " DB NRETRY DELAY", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ){
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[2], &a[0]) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[3], &a[1]) ) return TCL_ERROR;
+  rc = sqlite3_file_control(db, NULL, SQLITE_FCNTL_WIN32_AV_RETRY, (void*)a);
+  sqlite3_snprintf(sizeof(z), z, "%d %d %d", rc, a[0], a[1]);
+  Tcl_AppendResult(interp, z, (char*)0);
+  return TCL_OK;  
+}
+
+/*
+** tclcmd:   file_control_persist_wal DB PERSIST-FLAG
+**
+** This TCL command runs the sqlite3_file_control interface with
+** the SQLITE_FCNTL_PERSIST_WAL opcode.
+*/
+static int file_control_persist_wal(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3 *db;
+  int rc;
+  int bPersist;
+  char z[100];
+
+  if( objc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " DB FLAG", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ){
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[2], &bPersist) ) return TCL_ERROR;
+  rc = sqlite3_file_control(db, NULL, SQLITE_FCNTL_PERSIST_WAL, (void*)&bPersist);
+  sqlite3_snprintf(sizeof(z), z, "%d %d", rc, bPersist);
+  Tcl_AppendResult(interp, z, (char*)0);
+  return TCL_OK;  
+}
+
+
+/*
+** tclcmd:   sqlite3_vfs_list
+**
+**   Return a tcl list containing the names of all registered vfs's.
+*/
+static int vfs_list(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3_vfs *pVfs;
+  Tcl_Obj *pRet = Tcl_NewObj();
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+  for(pVfs=sqlite3_vfs_find(0); pVfs; pVfs=pVfs->pNext){
+    Tcl_ListObjAppendElement(interp, pRet, Tcl_NewStringObj(pVfs->zName, -1));
+  }
+  Tcl_SetObjResult(interp, pRet);
+  return TCL_OK;  
+}
+
+/*
+** tclcmd:   sqlite3_limit DB ID VALUE
+**
+** This TCL command runs the sqlite3_limit interface and
+** verifies correct operation of the same.
+*/
+static int test_limit(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3 *db;
+  int rc;
+  static const struct {
+     char *zName;
+     int id;
+  } aId[] = {
+    { "SQLITE_LIMIT_LENGTH",              SQLITE_LIMIT_LENGTH               },
+    { "SQLITE_LIMIT_SQL_LENGTH",          SQLITE_LIMIT_SQL_LENGTH           },
+    { "SQLITE_LIMIT_COLUMN",              SQLITE_LIMIT_COLUMN               },
+    { "SQLITE_LIMIT_EXPR_DEPTH",          SQLITE_LIMIT_EXPR_DEPTH           },
+    { "SQLITE_LIMIT_COMPOUND_SELECT",     SQLITE_LIMIT_COMPOUND_SELECT      },
+    { "SQLITE_LIMIT_VDBE_OP",             SQLITE_LIMIT_VDBE_OP              },
+    { "SQLITE_LIMIT_FUNCTION_ARG",        SQLITE_LIMIT_FUNCTION_ARG         },
+    { "SQLITE_LIMIT_ATTACHED",            SQLITE_LIMIT_ATTACHED             },
+    { "SQLITE_LIMIT_LIKE_PATTERN_LENGTH", SQLITE_LIMIT_LIKE_PATTERN_LENGTH  },
+    { "SQLITE_LIMIT_VARIABLE_NUMBER",     SQLITE_LIMIT_VARIABLE_NUMBER      },
+    { "SQLITE_LIMIT_TRIGGER_DEPTH",       SQLITE_LIMIT_TRIGGER_DEPTH        },
+    
+    /* Out of range test cases */
+    { "SQLITE_LIMIT_TOOSMALL",            -1,                               },
+    { "SQLITE_LIMIT_TOOBIG",              SQLITE_LIMIT_TRIGGER_DEPTH+1      },
+  };
+  int i, id;
+  int val;
+  const char *zId;
+
+  if( objc!=4 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " DB ID VALUE", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zId = Tcl_GetString(objv[2]);
+  for(i=0; i<sizeof(aId)/sizeof(aId[0]); i++){
+    if( strcmp(zId, aId[i].zName)==0 ){
+      id = aId[i].id;
+      break;
+    }
+  }
+  if( i>=sizeof(aId)/sizeof(aId[0]) ){
+    Tcl_AppendResult(interp, "unknown limit type: ", zId, (char*)0);
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[3], &val) ) return TCL_ERROR;
+  rc = sqlite3_limit(db, id, val);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+  return TCL_OK;  
+}
+
+/*
+** tclcmd:  save_prng_state
+**
+** Save the state of the pseudo-random number generator.
+** At the same time, verify that sqlite3_test_control works even when
+** called with an out-of-range opcode.
+*/
+static int save_prng_state(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  int rc = sqlite3_test_control(9999);
+  assert( rc==0 );
+  rc = sqlite3_test_control(-1);
+  assert( rc==0 );
+  sqlite3_test_control(SQLITE_TESTCTRL_PRNG_SAVE);
+  return TCL_OK;
+}
+/*
+** tclcmd:  restore_prng_state
+*/
+static int restore_prng_state(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3_test_control(SQLITE_TESTCTRL_PRNG_RESTORE);
+  return TCL_OK;
+}
+/*
+** tclcmd:  reset_prng_state
+*/
+static int reset_prng_state(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3_test_control(SQLITE_TESTCTRL_PRNG_RESET);
+  return TCL_OK;
+}
+
+/*
+** tclcmd:  pcache_stats
+*/
+static int test_pcache_stats(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  int nMin;
+  int nMax;
+  int nCurrent;
+  int nRecyclable;
+  Tcl_Obj *pRet;
+
+  sqlite3PcacheStats(&nCurrent, &nMax, &nMin, &nRecyclable);
+
+  pRet = Tcl_NewObj();
+  Tcl_ListObjAppendElement(interp, pRet, Tcl_NewStringObj("current", -1));
+  Tcl_ListObjAppendElement(interp, pRet, Tcl_NewIntObj(nCurrent));
+  Tcl_ListObjAppendElement(interp, pRet, Tcl_NewStringObj("max", -1));
+  Tcl_ListObjAppendElement(interp, pRet, Tcl_NewIntObj(nMax));
+  Tcl_ListObjAppendElement(interp, pRet, Tcl_NewStringObj("min", -1));
+  Tcl_ListObjAppendElement(interp, pRet, Tcl_NewIntObj(nMin));
+  Tcl_ListObjAppendElement(interp, pRet, Tcl_NewStringObj("recyclable", -1));
+  Tcl_ListObjAppendElement(interp, pRet, Tcl_NewIntObj(nRecyclable));
+
+  Tcl_SetObjResult(interp, pRet);
+
+  return TCL_OK;
+}
+
+#ifdef SQLITE_ENABLE_UNLOCK_NOTIFY
+static void test_unlock_notify_cb(void **aArg, int nArg){
+  int ii;
+  for(ii=0; ii<nArg; ii++){
+    Tcl_EvalEx((Tcl_Interp *)aArg[ii], "unlock_notify", -1, TCL_EVAL_GLOBAL);
+  }
+}
+#endif /* SQLITE_ENABLE_UNLOCK_NOTIFY */
+
+/*
+** tclcmd:  sqlite3_unlock_notify db
+*/
+#ifdef SQLITE_ENABLE_UNLOCK_NOTIFY
+static int test_unlock_notify(
+  ClientData clientData, /* Unused */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3 *db;
+  int rc;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB");
+    return TCL_ERROR;
+  }
+
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ){
+    return TCL_ERROR;
+  }
+  rc = sqlite3_unlock_notify(db, test_unlock_notify_cb, (void *)interp);
+  Tcl_SetResult(interp, (char *)t1ErrorName(rc), TCL_STATIC);
+  return TCL_OK;
+}
+#endif
+
+/*
+** tclcmd:  sqlite3_wal_checkpoint db ?NAME?
+*/
+static int test_wal_checkpoint(
+  ClientData clientData, /* Unused */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  char *zDb = 0;
+  sqlite3 *db;
+  int rc;
+
+  if( objc!=3 && objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB ?NAME?");
+    return TCL_ERROR;
+  }
+
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ){
+    return TCL_ERROR;
+  }
+  if( objc==3 ){
+    zDb = Tcl_GetString(objv[2]);
+  }
+  rc = sqlite3_wal_checkpoint(db, zDb);
+  Tcl_SetResult(interp, (char *)t1ErrorName(rc), TCL_STATIC);
+  return TCL_OK;
+}
+
+/*
+** tclcmd:  sqlite3_wal_checkpoint_v2 db MODE ?NAME?
+**
+** This command calls the wal_checkpoint_v2() function with the specified
+** mode argument (passive, full or restart). If present, the database name
+** NAME is passed as the second argument to wal_checkpoint_v2(). If it the
+** NAME argument is not present, a NULL pointer is passed instead.
+**
+** If wal_checkpoint_v2() returns any value other than SQLITE_BUSY or
+** SQLITE_OK, then this command returns TCL_ERROR. The Tcl result is set
+** to the error message obtained from sqlite3_errmsg().
+**
+** Otherwise, this command returns a list of three integers. The first integer
+** is 1 if SQLITE_BUSY was returned, or 0 otherwise. The following two integers
+** are the values returned via the output paramaters by wal_checkpoint_v2() -
+** the number of frames in the log and the number of frames in the log
+** that have been checkpointed.
+*/
+static int test_wal_checkpoint_v2(
+  ClientData clientData, /* Unused */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  char *zDb = 0;
+  sqlite3 *db;
+  int rc;
+
+  int eMode;
+  int nLog = -555;
+  int nCkpt = -555;
+  Tcl_Obj *pRet;
+
+  const char * aMode[] = { "passive", "full", "restart", 0 };
+  assert( SQLITE_CHECKPOINT_PASSIVE==0 );
+  assert( SQLITE_CHECKPOINT_FULL==1 );
+  assert( SQLITE_CHECKPOINT_RESTART==2 );
+
+  if( objc!=3 && objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB MODE ?NAME?");
+    return TCL_ERROR;
+  }
+
+  if( objc==4 ){
+    zDb = Tcl_GetString(objv[3]);
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db)
+   || Tcl_GetIndexFromObj(interp, objv[2], aMode, "mode", 0, &eMode) 
+  ){
+    return TCL_ERROR;
+  }
+
+  rc = sqlite3_wal_checkpoint_v2(db, zDb, eMode, &nLog, &nCkpt);
+  if( rc!=SQLITE_OK && rc!=SQLITE_BUSY ){
+    Tcl_SetResult(interp, (char *)sqlite3_errmsg(db), TCL_VOLATILE);
+    return TCL_ERROR;
+  }
+
+  pRet = Tcl_NewObj();
+  Tcl_ListObjAppendElement(interp, pRet, Tcl_NewIntObj(rc==SQLITE_BUSY?1:0));
+  Tcl_ListObjAppendElement(interp, pRet, Tcl_NewIntObj(nLog));
+  Tcl_ListObjAppendElement(interp, pRet, Tcl_NewIntObj(nCkpt));
+  Tcl_SetObjResult(interp, pRet);
+
+  return TCL_OK;
+}
+
+/*
+** tclcmd:  test_sqlite3_log ?SCRIPT?
+*/
+static struct LogCallback {
+  Tcl_Interp *pInterp;
+  Tcl_Obj *pObj;
+} logcallback = {0, 0};
+static void xLogcallback(void *unused, int err, char *zMsg){
+  Tcl_Obj *pNew = Tcl_DuplicateObj(logcallback.pObj);
+  Tcl_IncrRefCount(pNew);
+  Tcl_ListObjAppendElement(
+      0, pNew, Tcl_NewStringObj(sqlite3TestErrorName(err), -1)
+  );
+  Tcl_ListObjAppendElement(0, pNew, Tcl_NewStringObj(zMsg, -1));
+  Tcl_EvalObjEx(logcallback.pInterp, pNew, TCL_EVAL_GLOBAL|TCL_EVAL_DIRECT);
+  Tcl_DecrRefCount(pNew);
+}
+static int test_sqlite3_log(
+  ClientData clientData,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  if( objc>2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "SCRIPT");
+    return TCL_ERROR;
+  }
+  if( logcallback.pObj ){
+    Tcl_DecrRefCount(logcallback.pObj);
+    logcallback.pObj = 0;
+    logcallback.pInterp = 0;
+    sqlite3_config(SQLITE_CONFIG_LOG, 0, 0);
+  }
+  if( objc>1 ){
+    logcallback.pObj = objv[1];
+    Tcl_IncrRefCount(logcallback.pObj);
+    logcallback.pInterp = interp;
+    sqlite3_config(SQLITE_CONFIG_LOG, xLogcallback, 0);
+  }
+  return TCL_OK;
+}
+
+/*
+**     tcl_objproc COMMANDNAME ARGS...
+**
+** Run a TCL command using its objProc interface.  Throw an error if
+** the command has no objProc interface.
+*/
+static int runAsObjProc(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  Tcl_CmdInfo cmdInfo;
+  if( objc<2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "COMMAND ...");
+    return TCL_ERROR;
+  }
+  if( !Tcl_GetCommandInfo(interp, Tcl_GetString(objv[1]), &cmdInfo) ){
+    Tcl_AppendResult(interp, "command not found: ",
+           Tcl_GetString(objv[1]), (char*)0);
+    return TCL_ERROR;
+  }
+  if( cmdInfo.objProc==0 ){
+    Tcl_AppendResult(interp, "command has no objProc: ",
+           Tcl_GetString(objv[1]), (char*)0);
+    return TCL_ERROR;
+  }
+  return cmdInfo.objProc(cmdInfo.objClientData, interp, objc-1, objv+1);
+}
+
+#ifndef SQLITE_OMIT_EXPLAIN
+/*
+** WARNING: The following function, printExplainQueryPlan() is an exact
+** copy of example code from eqp.in (eqp.html). If this code is modified,
+** then the documentation copy needs to be modified as well.
+*/
+/*
+** Argument pStmt is a prepared SQL statement. This function compiles
+** an EXPLAIN QUERY PLAN command to report on the prepared statement,
+** and prints the report to stdout using printf().
+*/
+int printExplainQueryPlan(sqlite3_stmt *pStmt){
+  const char *zSql;               /* Input SQL */
+  char *zExplain;                 /* SQL with EXPLAIN QUERY PLAN prepended */
+  sqlite3_stmt *pExplain;         /* Compiled EXPLAIN QUERY PLAN command */
+  int rc;                         /* Return code from sqlite3_prepare_v2() */
+
+  zSql = sqlite3_sql(pStmt);
+  if( zSql==0 ) return SQLITE_ERROR;
+
+  zExplain = sqlite3_mprintf("EXPLAIN QUERY PLAN %s", zSql);
+  if( zExplain==0 ) return SQLITE_NOMEM;
+
+  rc = sqlite3_prepare_v2(sqlite3_db_handle(pStmt), zExplain, -1, &pExplain, 0);
+  sqlite3_free(zExplain);
+  if( rc!=SQLITE_OK ) return rc;
+
+  while( SQLITE_ROW==sqlite3_step(pExplain) ){
+    int iSelectid = sqlite3_column_int(pExplain, 0);
+    int iOrder = sqlite3_column_int(pExplain, 1);
+    int iFrom = sqlite3_column_int(pExplain, 2);
+    const char *zDetail = (const char *)sqlite3_column_text(pExplain, 3);
+
+    printf("%d %d %d %s\n", iSelectid, iOrder, iFrom, zDetail);
+  }
+
+  return sqlite3_finalize(pExplain);
+}
+
+static int test_print_eqp(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc;
+  sqlite3_stmt *pStmt;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "STMT");
+    return TCL_ERROR;
+  }
+  if( getStmtPointer(interp, Tcl_GetString(objv[1]), &pStmt) ) return TCL_ERROR;
+  rc = printExplainQueryPlan(pStmt);
+  /* This is needed on Windows so that a test case using this 
+  ** function can open a read pipe and get the output of
+  ** printExplainQueryPlan() immediately.
+  */
+  fflush(stdout);
+  Tcl_SetResult(interp, (char *)t1ErrorName(rc), 0);
+  return TCL_OK;
+}
+#endif /* SQLITE_OMIT_EXPLAIN */
+
+/*
+** sqlite3_test_control VERB ARGS...
+*/
+static int test_test_control(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  struct Verb {
+    const char *zName;
+    int i;
+  } aVerb[] = {
+    { "SQLITE_TESTCTRL_LOCALTIME_FAULT", SQLITE_TESTCTRL_LOCALTIME_FAULT }, 
+  };
+  int iVerb;
+  int iFlag;
+  int rc;
+
+  if( objc<2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "VERB ARGS...");
+    return TCL_ERROR;
+  }
+
+  rc = Tcl_GetIndexFromObjStruct(
+      interp, objv[1], aVerb, sizeof(aVerb[0]), "VERB", 0, &iVerb
+  );
+  if( rc!=TCL_OK ) return rc;
+
+  iFlag = aVerb[iVerb].i;
+  switch( iFlag ){
+    case SQLITE_TESTCTRL_LOCALTIME_FAULT: {
+      int val;
+      if( objc!=3 ){
+        Tcl_WrongNumArgs(interp, 2, objv, "ONOFF");
+        return TCL_ERROR;
+      }
+      if( Tcl_GetBooleanFromObj(interp, objv[2], &val) ) return TCL_ERROR;
+      sqlite3_test_control(SQLITE_TESTCTRL_LOCALTIME_FAULT, val);
+      break;
+    }
+  }
+
+  Tcl_ResetResult(interp);
+  return TCL_OK;
+}
+
+#if SQLITE_OS_WIN
+/*
+** Information passed from the main thread into the windows file locker
+** background thread.
+*/
+struct win32FileLocker {
+  char *evName;       /* Name of event to signal thread startup */
+  HANDLE h;           /* Handle of the file to be locked */
+  int delay1;         /* Delay before locking */
+  int delay2;         /* Delay before unlocking */
+  int ok;             /* Finished ok */
+  int err;            /* True if an error occurs */
+};
+#endif
+
+
+#if SQLITE_OS_WIN
+/*
+** The background thread that does file locking.
+*/
+static void win32_file_locker(void *pAppData){
+  struct win32FileLocker *p = (struct win32FileLocker*)pAppData;
+  if( p->evName ){
+    HANDLE ev = OpenEvent(EVENT_MODIFY_STATE, FALSE, p->evName);
+    if ( ev ){
+      SetEvent(ev);
+      CloseHandle(ev);
+    }
+  }
+  if( p->delay1 ) Sleep(p->delay1);
+  if( LockFile(p->h, 0, 0, 100000000, 0) ){
+    Sleep(p->delay2);
+    UnlockFile(p->h, 0, 0, 100000000, 0);
+    p->ok = 1;
+  }else{
+    p->err = 1;
+  }
+  CloseHandle(p->h);
+  p->h = 0;
+  p->delay1 = 0;
+  p->delay2 = 0;
+}
+#endif
+
+#if SQLITE_OS_WIN
+/*
+**      lock_win32_file FILENAME DELAY1 DELAY2
+**
+** Get an exclusive manditory lock on file for DELAY2 milliseconds.
+** Wait DELAY1 milliseconds before acquiring the lock.
+*/
+static int win32_file_lock(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  static struct win32FileLocker x = { "win32_file_lock", 0, 0, 0, 0, 0 };
+  const char *zFilename;
+  char zBuf[200];
+  int retry = 0;
+  HANDLE ev;
+  DWORD wResult;
+  
+  if( objc!=4 && objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "FILENAME DELAY1 DELAY2");
+    return TCL_ERROR;
+  }
+  if( objc==1 ){
+    sqlite3_snprintf(sizeof(zBuf), zBuf, "%d %d %d %d %d",
+                     x.ok, x.err, x.delay1, x.delay2, x.h);
+    Tcl_AppendResult(interp, zBuf, (char*)0);
+    return TCL_OK;
+  }
+  while( x.h && retry<30 ){
+    retry++;
+    Sleep(100);
+  }
+  if( x.h ){
+    Tcl_AppendResult(interp, "busy", (char*)0);
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[2], &x.delay1) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[3], &x.delay2) ) return TCL_ERROR;
+  zFilename = Tcl_GetString(objv[1]);
+  x.h = CreateFile(zFilename, GENERIC_READ|GENERIC_WRITE,
+              FILE_SHARE_READ|FILE_SHARE_WRITE, 0, OPEN_ALWAYS,
+              FILE_ATTRIBUTE_NORMAL, 0);
+  if( !x.h ){
+    Tcl_AppendResult(interp, "cannot open file: ", zFilename, (char*)0);
+    return TCL_ERROR;
+  }
+  ev = CreateEvent(NULL, TRUE, FALSE, x.evName);
+  if ( !ev ){
+    Tcl_AppendResult(interp, "cannot create event: ", x.evName, (char*)0);
+    return TCL_ERROR;
+  }
+  _beginthread(win32_file_locker, 0, (void*)&x);
+  Sleep(0);
+  if ( (wResult = WaitForSingleObject(ev, 10000))!=WAIT_OBJECT_0 ){
+    sqlite3_snprintf(sizeof(zBuf), zBuf, "0x%x", wResult);
+    Tcl_AppendResult(interp, "wait failed: ", zBuf, (char*)0);
+    CloseHandle(ev);
+    return TCL_ERROR;
+  }
+  CloseHandle(ev);
+  return TCL_OK;
+}
+#endif
+
+
+/*
+**      optimization_control DB OPT BOOLEAN
+**
+** Enable or disable query optimizations using the sqlite3_test_control()
+** interface.  Disable if BOOLEAN is false and enable if BOOLEAN is true.
+** OPT is the name of the optimization to be disabled.
+*/
+static int optimization_control(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int i;
+  sqlite3 *db;
+  const char *zOpt;
+  int onoff;
+  int mask;
+  static const struct {
+    const char *zOptName;
+    int mask;
+  } aOpt[] = {
+    { "all",              SQLITE_OptMask        },
+    { "query-flattener",  SQLITE_QueryFlattener },
+    { "column-cache",     SQLITE_ColumnCache    },
+    { "index-sort",       SQLITE_IndexSort      },
+    { "index-search",     SQLITE_IndexSearch    },
+    { "index-cover",      SQLITE_IndexCover     },
+    { "groupby-order",    SQLITE_GroupByOrder   },
+    { "factor-constants", SQLITE_FactorOutConst },
+    { "real-as-int",      SQLITE_IdxRealAsInt   },
+  };
+
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB OPT BOOLEAN");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  if( Tcl_GetBooleanFromObj(interp, objv[3], &onoff) ) return TCL_ERROR;
+  zOpt = Tcl_GetString(objv[2]);
+  for(i=0; i<sizeof(aOpt)/sizeof(aOpt[0]); i++){
+    if( strcmp(zOpt, aOpt[i].zOptName)==0 ){
+      mask = aOpt[i].mask;
+      break;
+    }
+  }
+  if( onoff ) mask = ~mask;
+  if( i>=sizeof(aOpt)/sizeof(aOpt[0]) ){
+    Tcl_AppendResult(interp, "unknown optimization - should be one of:",
+                     (char*)0);
+    for(i=0; i<sizeof(aOpt)/sizeof(aOpt[0]); i++){
+      Tcl_AppendResult(interp, " ", aOpt[i].zOptName);
+    }
+    return TCL_ERROR;
+  }
+  sqlite3_test_control(SQLITE_TESTCTRL_OPTIMIZATIONS, db, mask);
+  return TCL_OK;
+}
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetest1_Init(Tcl_Interp *interp){
+  extern int sqlite3_search_count;
+  extern int sqlite3_found_count;
+  extern int sqlite3_interrupt_count;
+  extern int sqlite3_open_file_count;
+  extern int sqlite3_sort_count;
+  extern int sqlite3_current_time;
+#if SQLITE_OS_UNIX && defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
+  extern int sqlite3_hostid_num;
+#endif
+  extern int sqlite3_max_blobsize;
+  extern int sqlite3BtreeSharedCacheReport(void*,
+                                          Tcl_Interp*,int,Tcl_Obj*CONST*);
+  static struct {
+     char *zName;
+     Tcl_CmdProc *xProc;
+  } aCmd[] = {
+     { "db_enter",                      (Tcl_CmdProc*)db_enter               },
+     { "db_leave",                      (Tcl_CmdProc*)db_leave               },
+     { "sqlite3_mprintf_int",           (Tcl_CmdProc*)sqlite3_mprintf_int    },
+     { "sqlite3_mprintf_int64",         (Tcl_CmdProc*)sqlite3_mprintf_int64  },
+     { "sqlite3_mprintf_long",          (Tcl_CmdProc*)sqlite3_mprintf_long   },
+     { "sqlite3_mprintf_str",           (Tcl_CmdProc*)sqlite3_mprintf_str    },
+     { "sqlite3_snprintf_str",          (Tcl_CmdProc*)sqlite3_snprintf_str   },
+     { "sqlite3_mprintf_stronly",       (Tcl_CmdProc*)sqlite3_mprintf_stronly},
+     { "sqlite3_mprintf_double",        (Tcl_CmdProc*)sqlite3_mprintf_double },
+     { "sqlite3_mprintf_scaled",        (Tcl_CmdProc*)sqlite3_mprintf_scaled },
+     { "sqlite3_mprintf_hexdouble",   (Tcl_CmdProc*)sqlite3_mprintf_hexdouble},
+     { "sqlite3_mprintf_z_test",        (Tcl_CmdProc*)test_mprintf_z        },
+     { "sqlite3_mprintf_n_test",        (Tcl_CmdProc*)test_mprintf_n        },
+     { "sqlite3_snprintf_int",          (Tcl_CmdProc*)test_snprintf_int     },
+     { "sqlite3_last_insert_rowid",     (Tcl_CmdProc*)test_last_rowid       },
+     { "sqlite3_exec_printf",           (Tcl_CmdProc*)test_exec_printf      },
+     { "sqlite3_exec_hex",              (Tcl_CmdProc*)test_exec_hex         },
+     { "sqlite3_exec",                  (Tcl_CmdProc*)test_exec             },
+     { "sqlite3_exec_nr",               (Tcl_CmdProc*)test_exec_nr          },
+#ifndef SQLITE_OMIT_GET_TABLE
+     { "sqlite3_get_table_printf",      (Tcl_CmdProc*)test_get_table_printf },
+#endif
+     { "sqlite3_close",                 (Tcl_CmdProc*)sqlite_test_close     },
+     { "sqlite3_create_function",       (Tcl_CmdProc*)test_create_function  },
+     { "sqlite3_create_aggregate",      (Tcl_CmdProc*)test_create_aggregate },
+     { "sqlite_register_test_function", (Tcl_CmdProc*)test_register_func    },
+     { "sqlite_abort",                  (Tcl_CmdProc*)sqlite_abort          },
+     { "sqlite_bind",                   (Tcl_CmdProc*)test_bind             },
+     { "breakpoint",                    (Tcl_CmdProc*)test_breakpoint       },
+     { "sqlite3_key",                   (Tcl_CmdProc*)test_key              },
+     { "sqlite3_rekey",                 (Tcl_CmdProc*)test_rekey            },
+     { "sqlite_set_magic",              (Tcl_CmdProc*)sqlite_set_magic      },
+     { "sqlite3_interrupt",             (Tcl_CmdProc*)test_interrupt        },
+     { "sqlite_delete_function",        (Tcl_CmdProc*)delete_function       },
+     { "sqlite_delete_collation",       (Tcl_CmdProc*)delete_collation      },
+     { "sqlite3_get_autocommit",        (Tcl_CmdProc*)get_autocommit        },
+     { "sqlite3_stack_used",            (Tcl_CmdProc*)test_stack_used       },
+     { "sqlite3_busy_timeout",          (Tcl_CmdProc*)test_busy_timeout     },
+     { "printf",                        (Tcl_CmdProc*)test_printf           },
+     { "sqlite3IoTrace",              (Tcl_CmdProc*)test_io_trace         },
+  };
+  static struct {
+     char *zName;
+     Tcl_ObjCmdProc *xProc;
+     void *clientData;
+  } aObjCmd[] = {
+     { "sqlite3_connection_pointer",    get_sqlite_pointer, 0 },
+     { "sqlite3_bind_int",              test_bind_int,      0 },
+     { "sqlite3_bind_zeroblob",         test_bind_zeroblob, 0 },
+     { "sqlite3_bind_int64",            test_bind_int64,    0 },
+     { "sqlite3_bind_double",           test_bind_double,   0 },
+     { "sqlite3_bind_null",             test_bind_null     ,0 },
+     { "sqlite3_bind_text",             test_bind_text     ,0 },
+     { "sqlite3_bind_text16",           test_bind_text16   ,0 },
+     { "sqlite3_bind_blob",             test_bind_blob     ,0 },
+     { "sqlite3_bind_parameter_count",  test_bind_parameter_count, 0},
+     { "sqlite3_bind_parameter_name",   test_bind_parameter_name,  0},
+     { "sqlite3_bind_parameter_index",  test_bind_parameter_index, 0},
+     { "sqlite3_clear_bindings",        test_clear_bindings, 0},
+     { "sqlite3_sleep",                 test_sleep,          0},
+     { "sqlite3_errcode",               test_errcode       ,0 },
+     { "sqlite3_extended_errcode",      test_ex_errcode    ,0 },
+     { "sqlite3_errmsg",                test_errmsg        ,0 },
+     { "sqlite3_errmsg16",              test_errmsg16      ,0 },
+     { "sqlite3_open",                  test_open          ,0 },
+     { "sqlite3_open16",                test_open16        ,0 },
+     { "sqlite3_open_v2",               test_open_v2       ,0 },
+     { "sqlite3_complete16",            test_complete16    ,0 },
+
+     { "sqlite3_prepare",               test_prepare       ,0 },
+     { "sqlite3_prepare16",             test_prepare16     ,0 },
+     { "sqlite3_prepare_v2",            test_prepare_v2    ,0 },
+     { "sqlite3_prepare_tkt3134",       test_prepare_tkt3134, 0},
+     { "sqlite3_prepare16_v2",          test_prepare16_v2  ,0 },
+     { "sqlite3_finalize",              test_finalize      ,0 },
+     { "sqlite3_stmt_status",           test_stmt_status   ,0 },
+     { "sqlite3_reset",                 test_reset         ,0 },
+     { "sqlite3_expired",               test_expired       ,0 },
+     { "sqlite3_transfer_bindings",     test_transfer_bind ,0 },
+     { "sqlite3_changes",               test_changes       ,0 },
+     { "sqlite3_step",                  test_step          ,0 },
+     { "sqlite3_sql",                   test_sql           ,0 },
+     { "sqlite3_next_stmt",             test_next_stmt     ,0 },
+     { "sqlite3_stmt_readonly",         test_stmt_readonly ,0 },
+     { "uses_stmt_journal",             uses_stmt_journal ,0 },
+
+     { "sqlite3_release_memory",        test_release_memory,     0},
+     { "sqlite3_soft_heap_limit",       test_soft_heap_limit,    0},
+     { "sqlite3_thread_cleanup",        test_thread_cleanup,     0},
+     { "sqlite3_pager_refcounts",       test_pager_refcounts,    0},
+
+     { "sqlite3_load_extension",        test_load_extension,     0},
+     { "sqlite3_enable_load_extension", test_enable_load,        0},
+     { "sqlite3_extended_result_codes", test_extended_result_codes, 0},
+     { "sqlite3_limit",                 test_limit,                 0},
+
+     { "save_prng_state",               save_prng_state,    0 },
+     { "restore_prng_state",            restore_prng_state, 0 },
+     { "reset_prng_state",              reset_prng_state,   0 },
+     { "optimization_control",          optimization_control,0},
+#if SQLITE_OS_WIN
+     { "lock_win32_file",               win32_file_lock,    0 },
+#endif
+     { "tcl_objproc",                   runAsObjProc,       0 },
+
+     /* sqlite3_column_*() API */
+     { "sqlite3_column_count",          test_column_count  ,0 },
+     { "sqlite3_data_count",            test_data_count    ,0 },
+     { "sqlite3_column_type",           test_column_type   ,0 },
+     { "sqlite3_column_blob",           test_column_blob   ,0 },
+     { "sqlite3_column_double",         test_column_double ,0 },
+     { "sqlite3_column_int64",          test_column_int64  ,0 },
+     { "sqlite3_column_text",   test_stmt_utf8,  (void*)sqlite3_column_text },
+     { "sqlite3_column_name",   test_stmt_utf8,  (void*)sqlite3_column_name },
+     { "sqlite3_column_int",    test_stmt_int,   (void*)sqlite3_column_int  },
+     { "sqlite3_column_bytes",  test_stmt_int,   (void*)sqlite3_column_bytes},
+#ifndef SQLITE_OMIT_DECLTYPE
+     { "sqlite3_column_decltype",test_stmt_utf8,(void*)sqlite3_column_decltype},
+#endif
+#ifdef SQLITE_ENABLE_COLUMN_METADATA
+{ "sqlite3_column_database_name",test_stmt_utf8,(void*)sqlite3_column_database_name},
+{ "sqlite3_column_table_name",test_stmt_utf8,(void*)sqlite3_column_table_name},
+{ "sqlite3_column_origin_name",test_stmt_utf8,(void*)sqlite3_column_origin_name},
+#endif
+
+#ifndef SQLITE_OMIT_UTF16
+     { "sqlite3_column_bytes16", test_stmt_int, (void*)sqlite3_column_bytes16 },
+     { "sqlite3_column_text16",  test_stmt_utf16, (void*)sqlite3_column_text16},
+     { "sqlite3_column_name16",  test_stmt_utf16, (void*)sqlite3_column_name16},
+     { "add_alignment_test_collations", add_alignment_test_collations, 0      },
+#ifndef SQLITE_OMIT_DECLTYPE
+     { "sqlite3_column_decltype16",test_stmt_utf16,(void*)sqlite3_column_decltype16},
+#endif
+#ifdef SQLITE_ENABLE_COLUMN_METADATA
+{"sqlite3_column_database_name16",
+  test_stmt_utf16, sqlite3_column_database_name16},
+{"sqlite3_column_table_name16", test_stmt_utf16, (void*)sqlite3_column_table_name16},
+{"sqlite3_column_origin_name16", test_stmt_utf16, (void*)sqlite3_column_origin_name16},
+#endif
+#endif
+     { "sqlite3_create_collation_v2", test_create_collation_v2, 0 },
+     { "sqlite3_global_recover",     test_global_recover, 0   },
+     { "working_64bit_int",          working_64bit_int,   0   },
+     { "vfs_unlink_test",            vfs_unlink_test,     0   },
+     { "vfs_initfail_test",          vfs_initfail_test,   0   },
+     { "vfs_unregister_all",         vfs_unregister_all,  0   },
+     { "vfs_reregister_all",         vfs_reregister_all,  0   },
+     { "file_control_test",          file_control_test,   0   },
+     { "file_control_lasterrno_test", file_control_lasterrno_test,  0   },
+     { "file_control_lockproxy_test", file_control_lockproxy_test,  0   },
+     { "file_control_chunksize_test", file_control_chunksize_test,  0   },
+     { "file_control_sizehint_test",  file_control_sizehint_test,   0   },
+     { "file_control_win32_av_retry", file_control_win32_av_retry,  0   },
+     { "file_control_persist_wal",    file_control_persist_wal,     0   },
+     { "sqlite3_vfs_list",           vfs_list,     0   },
+     { "sqlite3_create_function_v2", test_create_function_v2, 0 },
+
+     /* Functions from os.h */
+#ifndef SQLITE_OMIT_UTF16
+     { "add_test_collate",        test_collate, 0            },
+     { "add_test_collate_needed", test_collate_needed, 0     },
+     { "add_test_function",       test_function, 0           },
+#endif
+     { "sqlite3_test_errstr",     test_errstr, 0             },
+     { "tcl_variable_type",       tcl_variable_type, 0       },
+#ifndef SQLITE_OMIT_SHARED_CACHE
+     { "sqlite3_enable_shared_cache", test_enable_shared, 0  },
+     { "sqlite3_shared_cache_report", sqlite3BtreeSharedCacheReport, 0},
+#endif
+     { "sqlite3_libversion_number", test_libversion_number, 0  },
+#ifdef SQLITE_ENABLE_COLUMN_METADATA
+     { "sqlite3_table_column_metadata", test_table_column_metadata, 0  },
+#endif
+#ifndef SQLITE_OMIT_INCRBLOB
+     { "sqlite3_blob_read",   test_blob_read, 0  },
+     { "sqlite3_blob_write",  test_blob_write, 0  },
+     { "sqlite3_blob_reopen", test_blob_reopen, 0  },
+     { "sqlite3_blob_bytes",  test_blob_bytes, 0  },
+     { "sqlite3_blob_close",  test_blob_close, 0  },
+#endif
+     { "pcache_stats",       test_pcache_stats, 0  },
+#ifdef SQLITE_ENABLE_UNLOCK_NOTIFY
+     { "sqlite3_unlock_notify", test_unlock_notify, 0  },
+#endif
+     { "sqlite3_wal_checkpoint",   test_wal_checkpoint, 0  },
+     { "sqlite3_wal_checkpoint_v2",test_wal_checkpoint_v2, 0  },
+     { "test_sqlite3_log",         test_sqlite3_log, 0  },
+#ifndef SQLITE_OMIT_EXPLAIN
+     { "print_explain_query_plan", test_print_eqp, 0  },
+#endif
+     { "sqlite3_test_control", test_test_control },
+  };
+  static int bitmask_size = sizeof(Bitmask)*8;
+  int i;
+  extern int sqlite3_sync_count, sqlite3_fullsync_count;
+  extern int sqlite3_opentemp_count;
+  extern int sqlite3_like_count;
+  extern int sqlite3_xferopt_count;
+  extern int sqlite3_pager_readdb_count;
+  extern int sqlite3_pager_writedb_count;
+  extern int sqlite3_pager_writej_count;
+#if SQLITE_OS_WIN
+  extern int sqlite3_os_type;
+#endif
+#ifdef SQLITE_DEBUG
+  extern int sqlite3WhereTrace;
+  extern int sqlite3OSTrace;
+  extern int sqlite3VdbeAddopTrace;
+  extern int sqlite3WalTrace;
+#endif
+#ifdef SQLITE_TEST
+  extern char sqlite3_query_plan[];
+  static char *query_plan = sqlite3_query_plan;
+#ifdef SQLITE_ENABLE_FTS3
+  extern int sqlite3_fts3_enable_parentheses;
+#endif
+#endif
+
+  for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){
+    Tcl_CreateCommand(interp, aCmd[i].zName, aCmd[i].xProc, 0, 0);
+  }
+  for(i=0; i<sizeof(aObjCmd)/sizeof(aObjCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aObjCmd[i].zName, 
+        aObjCmd[i].xProc, aObjCmd[i].clientData, 0);
+  }
+  Tcl_LinkVar(interp, "sqlite_search_count", 
+      (char*)&sqlite3_search_count, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite_found_count", 
+      (char*)&sqlite3_found_count, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite_sort_count", 
+      (char*)&sqlite3_sort_count, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite3_max_blobsize", 
+      (char*)&sqlite3_max_blobsize, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite_like_count", 
+      (char*)&sqlite3_like_count, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite_interrupt_count", 
+      (char*)&sqlite3_interrupt_count, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite_open_file_count", 
+      (char*)&sqlite3_open_file_count, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite_current_time", 
+      (char*)&sqlite3_current_time, TCL_LINK_INT);
+#if SQLITE_OS_UNIX && defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
+  Tcl_LinkVar(interp, "sqlite_hostid_num", 
+      (char*)&sqlite3_hostid_num, TCL_LINK_INT);
+#endif
+  Tcl_LinkVar(interp, "sqlite3_xferopt_count",
+      (char*)&sqlite3_xferopt_count, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite3_pager_readdb_count",
+      (char*)&sqlite3_pager_readdb_count, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite3_pager_writedb_count",
+      (char*)&sqlite3_pager_writedb_count, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite3_pager_writej_count",
+      (char*)&sqlite3_pager_writej_count, TCL_LINK_INT);
+#ifndef SQLITE_OMIT_UTF16
+  Tcl_LinkVar(interp, "unaligned_string_counter",
+      (char*)&unaligned_string_counter, TCL_LINK_INT);
+#endif
+#ifndef SQLITE_OMIT_UTF16
+  Tcl_LinkVar(interp, "sqlite_last_needed_collation",
+      (char*)&pzNeededCollation, TCL_LINK_STRING|TCL_LINK_READ_ONLY);
+#endif
+#if SQLITE_OS_WIN
+  Tcl_LinkVar(interp, "sqlite_os_type",
+      (char*)&sqlite3_os_type, TCL_LINK_INT);
+#endif
+#ifdef SQLITE_TEST
+  Tcl_LinkVar(interp, "sqlite_query_plan",
+      (char*)&query_plan, TCL_LINK_STRING|TCL_LINK_READ_ONLY);
+#endif
+#ifdef SQLITE_DEBUG
+  Tcl_LinkVar(interp, "sqlite_addop_trace",
+      (char*)&sqlite3VdbeAddopTrace, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite_where_trace",
+      (char*)&sqlite3WhereTrace, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite_os_trace",
+      (char*)&sqlite3OSTrace, TCL_LINK_INT);
+#ifndef SQLITE_OMIT_WAL
+  Tcl_LinkVar(interp, "sqlite_wal_trace",
+      (char*)&sqlite3WalTrace, TCL_LINK_INT);
+#endif
+#endif
+#ifndef SQLITE_OMIT_DISKIO
+  Tcl_LinkVar(interp, "sqlite_opentemp_count",
+      (char*)&sqlite3_opentemp_count, TCL_LINK_INT);
+#endif
+  Tcl_LinkVar(interp, "sqlite_static_bind_value",
+      (char*)&sqlite_static_bind_value, TCL_LINK_STRING);
+  Tcl_LinkVar(interp, "sqlite_static_bind_nbyte",
+      (char*)&sqlite_static_bind_nbyte, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite_temp_directory",
+      (char*)&sqlite3_temp_directory, TCL_LINK_STRING);
+  Tcl_LinkVar(interp, "bitmask_size",
+      (char*)&bitmask_size, TCL_LINK_INT|TCL_LINK_READ_ONLY);
+  Tcl_LinkVar(interp, "sqlite_sync_count",
+      (char*)&sqlite3_sync_count, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite_fullsync_count",
+      (char*)&sqlite3_fullsync_count, TCL_LINK_INT);
+#if defined(SQLITE_ENABLE_FTS3) && defined(SQLITE_TEST)
+  Tcl_LinkVar(interp, "sqlite_fts3_enable_parentheses",
+      (char*)&sqlite3_fts3_enable_parentheses, TCL_LINK_INT);
+#endif
+  return TCL_OK;
+}
diff --git a/src/test2.c b/src/test2.c
new file mode 100644
index 0000000..fa7dd76
--- /dev/null
+++ b/src/test2.c
@@ -0,0 +1,683 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Code for testing the pager.c module in SQLite.  This code
+** is not included in the SQLite library.  It is used for automated
+** testing of the SQLite library.
+*/
+#include "sqliteInt.h"
+#include "tcl.h"
+#include <stdlib.h>
+#include <string.h>
+#include <ctype.h>
+
+/*
+** Interpret an SQLite error number
+*/
+static char *errorName(int rc){
+  char *zName;
+  switch( rc ){
+    case SQLITE_OK:         zName = "SQLITE_OK";          break;
+    case SQLITE_ERROR:      zName = "SQLITE_ERROR";       break;
+    case SQLITE_PERM:       zName = "SQLITE_PERM";        break;
+    case SQLITE_ABORT:      zName = "SQLITE_ABORT";       break;
+    case SQLITE_BUSY:       zName = "SQLITE_BUSY";        break;
+    case SQLITE_NOMEM:      zName = "SQLITE_NOMEM";       break;
+    case SQLITE_READONLY:   zName = "SQLITE_READONLY";    break;
+    case SQLITE_INTERRUPT:  zName = "SQLITE_INTERRUPT";   break;
+    case SQLITE_IOERR:      zName = "SQLITE_IOERR";       break;
+    case SQLITE_CORRUPT:    zName = "SQLITE_CORRUPT";     break;
+    case SQLITE_FULL:       zName = "SQLITE_FULL";        break;
+    case SQLITE_CANTOPEN:   zName = "SQLITE_CANTOPEN";    break;
+    case SQLITE_PROTOCOL:   zName = "SQLITE_PROTOCOL";    break;
+    case SQLITE_EMPTY:      zName = "SQLITE_EMPTY";       break;
+    case SQLITE_SCHEMA:     zName = "SQLITE_SCHEMA";      break;
+    case SQLITE_CONSTRAINT: zName = "SQLITE_CONSTRAINT";  break;
+    case SQLITE_MISMATCH:   zName = "SQLITE_MISMATCH";    break;
+    case SQLITE_MISUSE:     zName = "SQLITE_MISUSE";      break;
+    case SQLITE_NOLFS:      zName = "SQLITE_NOLFS";       break;
+    default:                zName = "SQLITE_Unknown";     break;
+  }
+  return zName;
+}
+
+/*
+** Page size and reserved size used for testing.
+*/
+static int test_pagesize = 1024;
+
+/*
+** Dummy page reinitializer
+*/
+static void pager_test_reiniter(DbPage *pNotUsed){
+  return;
+}
+
+/*
+** Usage:   pager_open FILENAME N-PAGE
+**
+** Open a new pager
+*/
+static int pager_open(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  u32 pageSize;
+  Pager *pPager;
+  int nPage;
+  int rc;
+  char zBuf[100];
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " FILENAME N-PAGE\"", 0);
+    return TCL_ERROR;
+  }
+  if( Tcl_GetInt(interp, argv[2], &nPage) ) return TCL_ERROR;
+  rc = sqlite3PagerOpen(sqlite3_vfs_find(0), &pPager, argv[1], 0, 0,
+      SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE | SQLITE_OPEN_MAIN_DB,
+      pager_test_reiniter);
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, errorName(rc), 0);
+    return TCL_ERROR;
+  }
+  sqlite3PagerSetCachesize(pPager, nPage);
+  pageSize = test_pagesize;
+  sqlite3PagerSetPagesize(pPager, &pageSize, -1);
+  sqlite3_snprintf(sizeof(zBuf),zBuf,"%p",pPager);
+  Tcl_AppendResult(interp, zBuf, 0);
+  return TCL_OK;
+}
+
+/*
+** Usage:   pager_close ID
+**
+** Close the given pager.
+*/
+static int pager_close(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  Pager *pPager;
+  int rc;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID\"", 0);
+    return TCL_ERROR;
+  }
+  pPager = sqlite3TestTextToPtr(argv[1]);
+  rc = sqlite3PagerClose(pPager);
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, errorName(rc), 0);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:   pager_rollback ID
+**
+** Rollback changes
+*/
+static int pager_rollback(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  Pager *pPager;
+  int rc;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID\"", 0);
+    return TCL_ERROR;
+  }
+  pPager = sqlite3TestTextToPtr(argv[1]);
+  rc = sqlite3PagerRollback(pPager);
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, errorName(rc), 0);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:   pager_commit ID
+**
+** Commit all changes
+*/
+static int pager_commit(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  Pager *pPager;
+  int rc;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID\"", 0);
+    return TCL_ERROR;
+  }
+  pPager = sqlite3TestTextToPtr(argv[1]);
+  rc = sqlite3PagerCommitPhaseOne(pPager, 0, 0);
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, errorName(rc), 0);
+    return TCL_ERROR;
+  }
+  rc = sqlite3PagerCommitPhaseTwo(pPager);
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, errorName(rc), 0);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:   pager_stmt_begin ID
+**
+** Start a new checkpoint.
+*/
+static int pager_stmt_begin(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  Pager *pPager;
+  int rc;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID\"", 0);
+    return TCL_ERROR;
+  }
+  pPager = sqlite3TestTextToPtr(argv[1]);
+  rc = sqlite3PagerOpenSavepoint(pPager, 1);
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, errorName(rc), 0);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:   pager_stmt_rollback ID
+**
+** Rollback changes to a checkpoint
+*/
+static int pager_stmt_rollback(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  Pager *pPager;
+  int rc;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID\"", 0);
+    return TCL_ERROR;
+  }
+  pPager = sqlite3TestTextToPtr(argv[1]);
+  rc = sqlite3PagerSavepoint(pPager, SAVEPOINT_ROLLBACK, 0);
+  sqlite3PagerSavepoint(pPager, SAVEPOINT_RELEASE, 0);
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, errorName(rc), 0);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:   pager_stmt_commit ID
+**
+** Commit changes to a checkpoint
+*/
+static int pager_stmt_commit(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  Pager *pPager;
+  int rc;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID\"", 0);
+    return TCL_ERROR;
+  }
+  pPager = sqlite3TestTextToPtr(argv[1]);
+  rc = sqlite3PagerSavepoint(pPager, SAVEPOINT_RELEASE, 0);
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, errorName(rc), 0);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:   pager_stats ID
+**
+** Return pager statistics.
+*/
+static int pager_stats(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  Pager *pPager;
+  int i, *a;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID\"", 0);
+    return TCL_ERROR;
+  }
+  pPager = sqlite3TestTextToPtr(argv[1]);
+  a = sqlite3PagerStats(pPager);
+  for(i=0; i<9; i++){
+    static char *zName[] = {
+      "ref", "page", "max", "size", "state", "err",
+      "hit", "miss", "ovfl",
+    };
+    char zBuf[100];
+    Tcl_AppendElement(interp, zName[i]);
+    sqlite3_snprintf(sizeof(zBuf),zBuf,"%d",a[i]);
+    Tcl_AppendElement(interp, zBuf);
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:   pager_pagecount ID
+**
+** Return the size of the database file.
+*/
+static int pager_pagecount(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  Pager *pPager;
+  char zBuf[100];
+  int nPage;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID\"", 0);
+    return TCL_ERROR;
+  }
+  pPager = sqlite3TestTextToPtr(argv[1]);
+  sqlite3PagerPagecount(pPager, &nPage);
+  sqlite3_snprintf(sizeof(zBuf), zBuf, "%d", nPage);
+  Tcl_AppendResult(interp, zBuf, 0);
+  return TCL_OK;
+}
+
+/*
+** Usage:   page_get ID PGNO
+**
+** Return a pointer to a page from the database.
+*/
+static int page_get(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  Pager *pPager;
+  char zBuf[100];
+  DbPage *pPage;
+  int pgno;
+  int rc;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID PGNO\"", 0);
+    return TCL_ERROR;
+  }
+  pPager = sqlite3TestTextToPtr(argv[1]);
+  if( Tcl_GetInt(interp, argv[2], &pgno) ) return TCL_ERROR;
+  rc = sqlite3PagerSharedLock(pPager);
+  if( rc==SQLITE_OK ){
+    rc = sqlite3PagerGet(pPager, pgno, &pPage);
+  }
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, errorName(rc), 0);
+    return TCL_ERROR;
+  }
+  sqlite3_snprintf(sizeof(zBuf),zBuf,"%p",pPage);
+  Tcl_AppendResult(interp, zBuf, 0);
+  return TCL_OK;
+}
+
+/*
+** Usage:   page_lookup ID PGNO
+**
+** Return a pointer to a page if the page is already in cache.
+** If not in cache, return an empty string.
+*/
+static int page_lookup(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  Pager *pPager;
+  char zBuf[100];
+  DbPage *pPage;
+  int pgno;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID PGNO\"", 0);
+    return TCL_ERROR;
+  }
+  pPager = sqlite3TestTextToPtr(argv[1]);
+  if( Tcl_GetInt(interp, argv[2], &pgno) ) return TCL_ERROR;
+  pPage = sqlite3PagerLookup(pPager, pgno);
+  if( pPage ){
+    sqlite3_snprintf(sizeof(zBuf),zBuf,"%p",pPage);
+    Tcl_AppendResult(interp, zBuf, 0);
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:   pager_truncate ID PGNO
+*/
+static int pager_truncate(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  Pager *pPager;
+  int pgno;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID PGNO\"", 0);
+    return TCL_ERROR;
+  }
+  pPager = sqlite3TestTextToPtr(argv[1]);
+  if( Tcl_GetInt(interp, argv[2], &pgno) ) return TCL_ERROR;
+  sqlite3PagerTruncateImage(pPager, pgno);
+  return TCL_OK;
+}
+
+
+/*
+** Usage:   page_unref PAGE
+**
+** Drop a pointer to a page.
+*/
+static int page_unref(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  DbPage *pPage;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " PAGE\"", 0);
+    return TCL_ERROR;
+  }
+  pPage = (DbPage *)sqlite3TestTextToPtr(argv[1]);
+  sqlite3PagerUnref(pPage);
+  return TCL_OK;
+}
+
+/*
+** Usage:   page_read PAGE
+**
+** Return the content of a page
+*/
+static int page_read(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  char zBuf[100];
+  DbPage *pPage;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " PAGE\"", 0);
+    return TCL_ERROR;
+  }
+  pPage = sqlite3TestTextToPtr(argv[1]);
+  memcpy(zBuf, sqlite3PagerGetData(pPage), sizeof(zBuf));
+  Tcl_AppendResult(interp, zBuf, 0);
+  return TCL_OK;
+}
+
+/*
+** Usage:   page_number PAGE
+**
+** Return the page number for a page.
+*/
+static int page_number(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  char zBuf[100];
+  DbPage *pPage;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " PAGE\"", 0);
+    return TCL_ERROR;
+  }
+  pPage = (DbPage *)sqlite3TestTextToPtr(argv[1]);
+  sqlite3_snprintf(sizeof(zBuf), zBuf, "%d", sqlite3PagerPagenumber(pPage));
+  Tcl_AppendResult(interp, zBuf, 0);
+  return TCL_OK;
+}
+
+/*
+** Usage:   page_write PAGE DATA
+**
+** Write something into a page.
+*/
+static int page_write(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  DbPage *pPage;
+  char *pData;
+  int rc;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " PAGE DATA\"", 0);
+    return TCL_ERROR;
+  }
+  pPage = (DbPage *)sqlite3TestTextToPtr(argv[1]);
+  rc = sqlite3PagerWrite(pPage);
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, errorName(rc), 0);
+    return TCL_ERROR;
+  }
+  pData = sqlite3PagerGetData(pPage);
+  strncpy(pData, argv[2], test_pagesize-1);
+  pData[test_pagesize-1] = 0;
+  return TCL_OK;
+}
+
+#ifndef SQLITE_OMIT_DISKIO
+/*
+** Usage:   fake_big_file  N  FILENAME
+**
+** Write a few bytes at the N megabyte point of FILENAME.  This will
+** create a large file.  If the file was a valid SQLite database, then
+** the next time the database is opened, SQLite will begin allocating
+** new pages after N.  If N is 2096 or bigger, this will test the
+** ability of SQLite to write to large files.
+*/
+static int fake_big_file(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  sqlite3_vfs *pVfs;
+  sqlite3_file *fd = 0;
+  int rc;
+  int n;
+  i64 offset;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " N-MEGABYTES FILE\"", 0);
+    return TCL_ERROR;
+  }
+  if( Tcl_GetInt(interp, argv[1], &n) ) return TCL_ERROR;
+
+  pVfs = sqlite3_vfs_find(0);
+  rc = sqlite3OsOpenMalloc(pVfs, argv[2], &fd, 
+      (SQLITE_OPEN_CREATE|SQLITE_OPEN_READWRITE|SQLITE_OPEN_MAIN_DB), 0
+  );
+  if( rc ){
+    Tcl_AppendResult(interp, "open failed: ", errorName(rc), 0);
+    return TCL_ERROR;
+  }
+  offset = n;
+  offset *= 1024*1024;
+  rc = sqlite3OsWrite(fd, "Hello, World!", 14, offset);
+  sqlite3OsCloseFree(fd);
+  if( rc ){
+    Tcl_AppendResult(interp, "write failed: ", errorName(rc), 0);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+#endif
+
+
+/*
+** test_control_pending_byte  PENDING_BYTE
+**
+** Set the PENDING_BYTE using the sqlite3_test_control() interface.
+*/
+static int testPendingByte(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int pbyte;
+  int rc;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+                     " PENDING-BYTE\"", (void*)0);
+    return TCL_ERROR;
+  }
+  if( Tcl_GetInt(interp, argv[1], &pbyte) ) return TCL_ERROR;
+  rc = sqlite3_test_control(SQLITE_TESTCTRL_PENDING_BYTE, pbyte);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+  return TCL_OK;
+}  
+
+/*
+** sqlite3BitvecBuiltinTest SIZE PROGRAM
+**
+** Invoke the SQLITE_TESTCTRL_BITVEC_TEST operator on test_control.
+** See comments on sqlite3BitvecBuiltinTest() for additional information.
+*/
+static int testBitvecBuiltinTest(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int sz, rc;
+  int nProg = 0;
+  int aProg[100];
+  const char *z;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+                     " SIZE PROGRAM\"", (void*)0);
+  }
+  if( Tcl_GetInt(interp, argv[1], &sz) ) return TCL_ERROR;
+  z = argv[2];
+  while( nProg<99 && *z ){
+    while( *z && !sqlite3Isdigit(*z) ){ z++; }
+    if( *z==0 ) break;
+    aProg[nProg++] = atoi(z);
+    while( sqlite3Isdigit(*z) ){ z++; }
+  }
+  aProg[nProg] = 0;
+  rc = sqlite3_test_control(SQLITE_TESTCTRL_BITVEC_TEST, sz, aProg);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+  return TCL_OK;
+}  
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetest2_Init(Tcl_Interp *interp){
+  extern int sqlite3_io_error_persist;
+  extern int sqlite3_io_error_pending;
+  extern int sqlite3_io_error_hit;
+  extern int sqlite3_io_error_hardhit;
+  extern int sqlite3_diskfull_pending;
+  extern int sqlite3_diskfull;
+  static struct {
+    char *zName;
+    Tcl_CmdProc *xProc;
+  } aCmd[] = {
+    { "pager_open",              (Tcl_CmdProc*)pager_open          },
+    { "pager_close",             (Tcl_CmdProc*)pager_close         },
+    { "pager_commit",            (Tcl_CmdProc*)pager_commit        },
+    { "pager_rollback",          (Tcl_CmdProc*)pager_rollback      },
+    { "pager_stmt_begin",        (Tcl_CmdProc*)pager_stmt_begin    },
+    { "pager_stmt_commit",       (Tcl_CmdProc*)pager_stmt_commit   },
+    { "pager_stmt_rollback",     (Tcl_CmdProc*)pager_stmt_rollback },
+    { "pager_stats",             (Tcl_CmdProc*)pager_stats         },
+    { "pager_pagecount",         (Tcl_CmdProc*)pager_pagecount     },
+    { "page_get",                (Tcl_CmdProc*)page_get            },
+    { "page_lookup",             (Tcl_CmdProc*)page_lookup         },
+    { "page_unref",              (Tcl_CmdProc*)page_unref          },
+    { "page_read",               (Tcl_CmdProc*)page_read           },
+    { "page_write",              (Tcl_CmdProc*)page_write          },
+    { "page_number",             (Tcl_CmdProc*)page_number         },
+    { "pager_truncate",          (Tcl_CmdProc*)pager_truncate      },
+#ifndef SQLITE_OMIT_DISKIO
+    { "fake_big_file",           (Tcl_CmdProc*)fake_big_file       },
+#endif
+    { "sqlite3BitvecBuiltinTest",(Tcl_CmdProc*)testBitvecBuiltinTest     },
+    { "sqlite3_test_control_pending_byte", (Tcl_CmdProc*)testPendingByte },
+  };
+  int i;
+  for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){
+    Tcl_CreateCommand(interp, aCmd[i].zName, aCmd[i].xProc, 0, 0);
+  }
+  Tcl_LinkVar(interp, "sqlite_io_error_pending",
+     (char*)&sqlite3_io_error_pending, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite_io_error_persist",
+     (char*)&sqlite3_io_error_persist, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite_io_error_hit",
+     (char*)&sqlite3_io_error_hit, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite_io_error_hardhit",
+     (char*)&sqlite3_io_error_hardhit, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite_diskfull_pending",
+     (char*)&sqlite3_diskfull_pending, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "sqlite_diskfull",
+     (char*)&sqlite3_diskfull, TCL_LINK_INT);
+#ifndef SQLITE_OMIT_WSD
+  Tcl_LinkVar(interp, "sqlite_pending_byte",
+     (char*)&sqlite3PendingByte, TCL_LINK_INT | TCL_LINK_READ_ONLY);
+#endif
+  return TCL_OK;
+}
diff --git a/src/test3.c b/src/test3.c
new file mode 100644
index 0000000..4eabdcc
--- /dev/null
+++ b/src/test3.c
@@ -0,0 +1,644 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Code for testing the btree.c module in SQLite.  This code
+** is not included in the SQLite library.  It is used for automated
+** testing of the SQLite library.
+*/
+#include "sqliteInt.h"
+#include "btreeInt.h"
+#include "tcl.h"
+#include <stdlib.h>
+#include <string.h>
+
+/*
+** Interpret an SQLite error number
+*/
+static char *errorName(int rc){
+  char *zName;
+  switch( rc ){
+    case SQLITE_OK:         zName = "SQLITE_OK";          break;
+    case SQLITE_ERROR:      zName = "SQLITE_ERROR";       break;
+    case SQLITE_PERM:       zName = "SQLITE_PERM";        break;
+    case SQLITE_ABORT:      zName = "SQLITE_ABORT";       break;
+    case SQLITE_BUSY:       zName = "SQLITE_BUSY";        break;
+    case SQLITE_NOMEM:      zName = "SQLITE_NOMEM";       break;
+    case SQLITE_READONLY:   zName = "SQLITE_READONLY";    break;
+    case SQLITE_INTERRUPT:  zName = "SQLITE_INTERRUPT";   break;
+    case SQLITE_IOERR:      zName = "SQLITE_IOERR";       break;
+    case SQLITE_CORRUPT:    zName = "SQLITE_CORRUPT";     break;
+    case SQLITE_FULL:       zName = "SQLITE_FULL";        break;
+    case SQLITE_CANTOPEN:   zName = "SQLITE_CANTOPEN";    break;
+    case SQLITE_PROTOCOL:   zName = "SQLITE_PROTOCOL";    break;
+    case SQLITE_EMPTY:      zName = "SQLITE_EMPTY";       break;
+    case SQLITE_LOCKED:     zName = "SQLITE_LOCKED";      break;
+    default:                zName = "SQLITE_Unknown";     break;
+  }
+  return zName;
+}
+
+/*
+** A bogus sqlite3 connection structure for use in the btree
+** tests.
+*/
+static sqlite3 sDb;
+static int nRefSqlite3 = 0;
+
+/*
+** Usage:   btree_open FILENAME NCACHE
+**
+** Open a new database
+*/
+static int btree_open(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  Btree *pBt;
+  int rc, nCache;
+  char zBuf[100];
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " FILENAME NCACHE FLAGS\"", 0);
+    return TCL_ERROR;
+  }
+  if( Tcl_GetInt(interp, argv[2], &nCache) ) return TCL_ERROR;
+  nRefSqlite3++;
+  if( nRefSqlite3==1 ){
+    sDb.pVfs = sqlite3_vfs_find(0);
+    sDb.mutex = sqlite3MutexAlloc(SQLITE_MUTEX_RECURSIVE);
+    sqlite3_mutex_enter(sDb.mutex);
+  }
+  rc = sqlite3BtreeOpen(sDb.pVfs, argv[1], &sDb, &pBt, 0, 
+     SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE | SQLITE_OPEN_MAIN_DB);
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, errorName(rc), 0);
+    return TCL_ERROR;
+  }
+  sqlite3BtreeSetCacheSize(pBt, nCache);
+  sqlite3_snprintf(sizeof(zBuf), zBuf,"%p", pBt);
+  Tcl_AppendResult(interp, zBuf, 0);
+  return TCL_OK;
+}
+
+/*
+** Usage:   btree_close ID
+**
+** Close the given database.
+*/
+static int btree_close(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  Btree *pBt;
+  int rc;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID\"", 0);
+    return TCL_ERROR;
+  }
+  pBt = sqlite3TestTextToPtr(argv[1]);
+  rc = sqlite3BtreeClose(pBt);
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, errorName(rc), 0);
+    return TCL_ERROR;
+  }
+  nRefSqlite3--;
+  if( nRefSqlite3==0 ){
+    sqlite3_mutex_leave(sDb.mutex);
+    sqlite3_mutex_free(sDb.mutex);
+    sDb.mutex = 0;
+    sDb.pVfs = 0;
+  }
+  return TCL_OK;
+}
+
+
+/*
+** Usage:   btree_begin_transaction ID
+**
+** Start a new transaction
+*/
+static int btree_begin_transaction(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  Btree *pBt;
+  int rc;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID\"", 0);
+    return TCL_ERROR;
+  }
+  pBt = sqlite3TestTextToPtr(argv[1]);
+  sqlite3BtreeEnter(pBt);
+  rc = sqlite3BtreeBeginTrans(pBt, 1);
+  sqlite3BtreeLeave(pBt);
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, errorName(rc), 0);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:   btree_pager_stats ID
+**
+** Returns pager statistics
+*/
+static int btree_pager_stats(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  Btree *pBt;
+  int i;
+  int *a;
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID\"", 0);
+    return TCL_ERROR;
+  }
+  pBt = sqlite3TestTextToPtr(argv[1]);
+ 
+  /* Normally in this file, with a b-tree handle opened using the 
+  ** [btree_open] command it is safe to call sqlite3BtreeEnter() directly.
+  ** But this function is sometimes called with a btree handle obtained
+  ** from an open SQLite connection (using [btree_from_db]). In this case
+  ** we need to obtain the mutex for the controlling SQLite handle before
+  ** it is safe to call sqlite3BtreeEnter().
+  */
+  sqlite3_mutex_enter(pBt->db->mutex);
+
+  sqlite3BtreeEnter(pBt);
+  a = sqlite3PagerStats(sqlite3BtreePager(pBt));
+  for(i=0; i<11; i++){
+    static char *zName[] = {
+      "ref", "page", "max", "size", "state", "err",
+      "hit", "miss", "ovfl", "read", "write"
+    };
+    char zBuf[100];
+    Tcl_AppendElement(interp, zName[i]);
+    sqlite3_snprintf(sizeof(zBuf), zBuf,"%d",a[i]);
+    Tcl_AppendElement(interp, zBuf);
+  }
+  sqlite3BtreeLeave(pBt);
+
+  /* Release the mutex on the SQLite handle that controls this b-tree */
+  sqlite3_mutex_leave(pBt->db->mutex);
+  return TCL_OK;
+}
+
+/*
+** Usage:   btree_cursor ID TABLENUM WRITEABLE
+**
+** Create a new cursor.  Return the ID for the cursor.
+*/
+static int btree_cursor(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  Btree *pBt;
+  int iTable;
+  BtCursor *pCur;
+  int rc = SQLITE_OK;
+  int wrFlag;
+  char zBuf[30];
+
+  if( argc!=4 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID TABLENUM WRITEABLE\"", 0);
+    return TCL_ERROR;
+  }
+  pBt = sqlite3TestTextToPtr(argv[1]);
+  if( Tcl_GetInt(interp, argv[2], &iTable) ) return TCL_ERROR;
+  if( Tcl_GetBoolean(interp, argv[3], &wrFlag) ) return TCL_ERROR;
+  pCur = (BtCursor *)ckalloc(sqlite3BtreeCursorSize());
+  memset(pCur, 0, sqlite3BtreeCursorSize());
+  sqlite3BtreeEnter(pBt);
+#ifndef SQLITE_OMIT_SHARED_CACHE
+  rc = sqlite3BtreeLockTable(pBt, iTable, wrFlag);
+#endif
+  if( rc==SQLITE_OK ){
+    rc = sqlite3BtreeCursor(pBt, iTable, wrFlag, 0, pCur);
+  }
+  sqlite3BtreeLeave(pBt);
+  if( rc ){
+    ckfree((char *)pCur);
+    Tcl_AppendResult(interp, errorName(rc), 0);
+    return TCL_ERROR;
+  }
+  sqlite3_snprintf(sizeof(zBuf), zBuf,"%p", pCur);
+  Tcl_AppendResult(interp, zBuf, 0);
+  return SQLITE_OK;
+}
+
+/*
+** Usage:   btree_close_cursor ID
+**
+** Close a cursor opened using btree_cursor.
+*/
+static int btree_close_cursor(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  BtCursor *pCur;
+  Btree *pBt;
+  int rc;
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID\"", 0);
+    return TCL_ERROR;
+  }
+  pCur = sqlite3TestTextToPtr(argv[1]);
+  pBt = pCur->pBtree;
+  sqlite3BtreeEnter(pBt);
+  rc = sqlite3BtreeCloseCursor(pCur);
+  sqlite3BtreeLeave(pBt);
+  ckfree((char *)pCur);
+  if( rc ){
+    Tcl_AppendResult(interp, errorName(rc), 0);
+    return TCL_ERROR;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Usage:   btree_next ID
+**
+** Move the cursor to the next entry in the table.  Return 0 on success
+** or 1 if the cursor was already on the last entry in the table or if
+** the table is empty.
+*/
+static int btree_next(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  BtCursor *pCur;
+  int rc;
+  int res = 0;
+  char zBuf[100];
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID\"", 0);
+    return TCL_ERROR;
+  }
+  pCur = sqlite3TestTextToPtr(argv[1]);
+  sqlite3BtreeEnter(pCur->pBtree);
+  rc = sqlite3BtreeNext(pCur, &res);
+  sqlite3BtreeLeave(pCur->pBtree);
+  if( rc ){
+    Tcl_AppendResult(interp, errorName(rc), 0);
+    return TCL_ERROR;
+  }
+  sqlite3_snprintf(sizeof(zBuf),zBuf,"%d",res);
+  Tcl_AppendResult(interp, zBuf, 0);
+  return SQLITE_OK;
+}
+
+/*
+** Usage:   btree_first ID
+**
+** Move the cursor to the first entry in the table.  Return 0 if the
+** cursor was left point to something and 1 if the table is empty.
+*/
+static int btree_first(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  BtCursor *pCur;
+  int rc;
+  int res = 0;
+  char zBuf[100];
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID\"", 0);
+    return TCL_ERROR;
+  }
+  pCur = sqlite3TestTextToPtr(argv[1]);
+  sqlite3BtreeEnter(pCur->pBtree);
+  rc = sqlite3BtreeFirst(pCur, &res);
+  sqlite3BtreeLeave(pCur->pBtree);
+  if( rc ){
+    Tcl_AppendResult(interp, errorName(rc), 0);
+    return TCL_ERROR;
+  }
+  sqlite3_snprintf(sizeof(zBuf),zBuf,"%d",res);
+  Tcl_AppendResult(interp, zBuf, 0);
+  return SQLITE_OK;
+}
+
+/*
+** Usage:   btree_eof ID
+**
+** Return TRUE if the given cursor is not pointing at a valid entry.
+** Return FALSE if the cursor does point to a valid entry.
+*/
+static int btree_eof(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  BtCursor *pCur;
+  int rc;
+  char zBuf[50];
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID\"", 0);
+    return TCL_ERROR;
+  }
+  pCur = sqlite3TestTextToPtr(argv[1]);
+  sqlite3BtreeEnter(pCur->pBtree);
+  rc = sqlite3BtreeEof(pCur);
+  sqlite3BtreeLeave(pCur->pBtree);
+  sqlite3_snprintf(sizeof(zBuf),zBuf, "%d", rc);
+  Tcl_AppendResult(interp, zBuf, 0);
+  return SQLITE_OK;
+}
+
+/*
+** Usage:   btree_payload_size ID
+**
+** Return the number of bytes of payload
+*/
+static int btree_payload_size(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  BtCursor *pCur;
+  int n2;
+  u64 n1;
+  char zBuf[50];
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID\"", 0);
+    return TCL_ERROR;
+  }
+  pCur = sqlite3TestTextToPtr(argv[1]);
+  sqlite3BtreeEnter(pCur->pBtree);
+
+  /* The cursor may be in "require-seek" state. If this is the case, the
+  ** call to BtreeDataSize() will fix it. */
+  sqlite3BtreeDataSize(pCur, (u32*)&n2);
+  if( pCur->apPage[pCur->iPage]->intKey ){
+    n1 = 0;
+  }else{
+    sqlite3BtreeKeySize(pCur, (i64*)&n1);
+  }
+  sqlite3BtreeLeave(pCur->pBtree);
+  sqlite3_snprintf(sizeof(zBuf),zBuf, "%d", (int)(n1+n2));
+  Tcl_AppendResult(interp, zBuf, 0);
+  return SQLITE_OK;
+}
+
+/*
+** usage:   varint_test  START  MULTIPLIER  COUNT  INCREMENT
+**
+** This command tests the putVarint() and getVarint()
+** routines, both for accuracy and for speed.
+**
+** An integer is written using putVarint() and read back with
+** getVarint() and varified to be unchanged.  This repeats COUNT
+** times.  The first integer is START*MULTIPLIER.  Each iteration
+** increases the integer by INCREMENT.
+**
+** This command returns nothing if it works.  It returns an error message
+** if something goes wrong.
+*/
+static int btree_varint_test(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  u32 start, mult, count, incr;
+  u64 in, out;
+  int n1, n2, i, j;
+  unsigned char zBuf[100];
+  if( argc!=5 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " START MULTIPLIER COUNT INCREMENT\"", 0);
+    return TCL_ERROR;
+  }
+  if( Tcl_GetInt(interp, argv[1], (int*)&start) ) return TCL_ERROR;
+  if( Tcl_GetInt(interp, argv[2], (int*)&mult) ) return TCL_ERROR;
+  if( Tcl_GetInt(interp, argv[3], (int*)&count) ) return TCL_ERROR;
+  if( Tcl_GetInt(interp, argv[4], (int*)&incr) ) return TCL_ERROR;
+  in = start;
+  in *= mult;
+  for(i=0; i<count; i++){
+    char zErr[200];
+    n1 = putVarint(zBuf, in);
+    if( n1>9 || n1<1 ){
+      sprintf(zErr, "putVarint returned %d - should be between 1 and 9", n1);
+      Tcl_AppendResult(interp, zErr, 0);
+      return TCL_ERROR;
+    }
+    n2 = getVarint(zBuf, &out);
+    if( n1!=n2 ){
+      sprintf(zErr, "putVarint returned %d and getVarint returned %d", n1, n2);
+      Tcl_AppendResult(interp, zErr, 0);
+      return TCL_ERROR;
+    }
+    if( in!=out ){
+      sprintf(zErr, "Wrote 0x%016llx and got back 0x%016llx", in, out);
+      Tcl_AppendResult(interp, zErr, 0);
+      return TCL_ERROR;
+    }
+    if( (in & 0xffffffff)==in ){
+      u32 out32;
+      n2 = getVarint32(zBuf, out32);
+      out = out32;
+      if( n1!=n2 ){
+        sprintf(zErr, "putVarint returned %d and GetVarint32 returned %d", 
+                  n1, n2);
+        Tcl_AppendResult(interp, zErr, 0);
+        return TCL_ERROR;
+      }
+      if( in!=out ){
+        sprintf(zErr, "Wrote 0x%016llx and got back 0x%016llx from GetVarint32",
+            in, out);
+        Tcl_AppendResult(interp, zErr, 0);
+        return TCL_ERROR;
+      }
+    }
+
+    /* In order to get realistic timings, run getVarint 19 more times.
+    ** This is because getVarint is called about 20 times more often
+    ** than putVarint.
+    */
+    for(j=0; j<19; j++){
+      getVarint(zBuf, &out);
+    }
+    in += incr;
+  }
+  return TCL_OK;
+}
+
+/*
+** usage:   btree_from_db  DB-HANDLE
+**
+** This command returns the btree handle for the main database associated
+** with the database-handle passed as the argument. Example usage:
+**
+** sqlite3 db test.db
+** set bt [btree_from_db db]
+*/
+static int btree_from_db(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  char zBuf[100];
+  Tcl_CmdInfo info;
+  sqlite3 *db;
+  Btree *pBt;
+  int iDb = 0;
+
+  if( argc!=2 && argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " DB-HANDLE ?N?\"", 0);
+    return TCL_ERROR;
+  }
+
+  if( 1!=Tcl_GetCommandInfo(interp, argv[1], &info) ){
+    Tcl_AppendResult(interp, "No such db-handle: \"", argv[1], "\"", 0);
+    return TCL_ERROR;
+  }
+  if( argc==3 ){
+    iDb = atoi(argv[2]);
+  }
+
+  db = *((sqlite3 **)info.objClientData);
+  assert( db );
+
+  pBt = db->aDb[iDb].pBt;
+  sqlite3_snprintf(sizeof(zBuf), zBuf, "%p", pBt);
+  Tcl_SetResult(interp, zBuf, TCL_VOLATILE);
+  return TCL_OK;
+}
+
+/*
+** Usage:   btree_ismemdb ID
+**
+** Return true if the B-Tree is in-memory.
+*/
+static int btree_ismemdb(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  Btree *pBt;
+  int res;
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID\"", 0);
+    return TCL_ERROR;
+  }
+  pBt = sqlite3TestTextToPtr(argv[1]);
+  sqlite3_mutex_enter(pBt->db->mutex);
+  sqlite3BtreeEnter(pBt);
+  res = sqlite3PagerIsMemdb(sqlite3BtreePager(pBt));
+  sqlite3BtreeLeave(pBt);
+  sqlite3_mutex_leave(pBt->db->mutex);
+  Tcl_SetObjResult(interp, Tcl_NewBooleanObj(res));
+  return SQLITE_OK;
+}
+
+/*
+** usage:   btree_set_cache_size ID NCACHE
+**
+** Set the size of the cache used by btree $ID.
+*/
+static int btree_set_cache_size(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int nCache;
+  Btree *pBt;
+  
+  if( argc!=3 ){
+    Tcl_AppendResult(
+        interp, "wrong # args: should be \"", argv[0], " BT NCACHE\"", 0);
+    return TCL_ERROR;
+  }
+  pBt = sqlite3TestTextToPtr(argv[1]);
+  if( Tcl_GetInt(interp, argv[2], &nCache) ) return TCL_ERROR;
+
+  sqlite3_mutex_enter(pBt->db->mutex);
+  sqlite3BtreeEnter(pBt);
+  sqlite3BtreeSetCacheSize(pBt, nCache);
+  sqlite3BtreeLeave(pBt);
+  sqlite3_mutex_leave(pBt->db->mutex);
+  return TCL_OK;
+}      
+
+
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetest3_Init(Tcl_Interp *interp){
+  static struct {
+     char *zName;
+     Tcl_CmdProc *xProc;
+  } aCmd[] = {
+     { "btree_open",               (Tcl_CmdProc*)btree_open               },
+     { "btree_close",              (Tcl_CmdProc*)btree_close              },
+     { "btree_begin_transaction",  (Tcl_CmdProc*)btree_begin_transaction  },
+     { "btree_pager_stats",        (Tcl_CmdProc*)btree_pager_stats        },
+     { "btree_cursor",             (Tcl_CmdProc*)btree_cursor             },
+     { "btree_close_cursor",       (Tcl_CmdProc*)btree_close_cursor       },
+     { "btree_next",               (Tcl_CmdProc*)btree_next               },
+     { "btree_eof",                (Tcl_CmdProc*)btree_eof                },
+     { "btree_payload_size",       (Tcl_CmdProc*)btree_payload_size       },
+     { "btree_first",              (Tcl_CmdProc*)btree_first              },
+     { "btree_varint_test",        (Tcl_CmdProc*)btree_varint_test        },
+     { "btree_from_db",            (Tcl_CmdProc*)btree_from_db            },
+     { "btree_ismemdb",            (Tcl_CmdProc*)btree_ismemdb            },
+     { "btree_set_cache_size",     (Tcl_CmdProc*)btree_set_cache_size     }
+  };
+  int i;
+
+  for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){
+    Tcl_CreateCommand(interp, aCmd[i].zName, aCmd[i].xProc, 0, 0);
+  }
+
+  return TCL_OK;
+}
diff --git a/src/test4.c b/src/test4.c
new file mode 100644
index 0000000..5c94370
--- /dev/null
+++ b/src/test4.c
@@ -0,0 +1,747 @@
+/*
+** 2003 December 18
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Code for testing the the SQLite library in a multithreaded environment.
+*/
+#include "sqliteInt.h"
+#include "tcl.h"
+#if SQLITE_OS_UNIX && SQLITE_THREADSAFE
+#include <stdlib.h>
+#include <string.h>
+#include <pthread.h>
+#include <sched.h>
+#include <ctype.h>
+
+/*
+** Each thread is controlled by an instance of the following
+** structure.
+*/
+typedef struct Thread Thread;
+struct Thread {
+  /* The first group of fields are writable by the master and read-only
+  ** to the thread. */
+  char *zFilename;       /* Name of database file */
+  void (*xOp)(Thread*);  /* next operation to do */
+  char *zArg;            /* argument usable by xOp */
+  int opnum;             /* Operation number */
+  int busy;              /* True if this thread is in use */
+
+  /* The next group of fields are writable by the thread but read-only to the
+  ** master. */
+  int completed;        /* Number of operations completed */
+  sqlite3 *db;           /* Open database */
+  sqlite3_stmt *pStmt;     /* Pending operation */
+  char *zErr;           /* operation error */
+  char *zStaticErr;     /* Static error message */
+  int rc;               /* operation return code */
+  int argc;             /* number of columns in result */
+  const char *argv[100];    /* result columns */
+  const char *colv[100];    /* result column names */
+};
+
+/*
+** There can be as many as 26 threads running at once.  Each is named
+** by a capital letter: A, B, C, ..., Y, Z.
+*/
+#define N_THREAD 26
+static Thread threadset[N_THREAD];
+
+
+/*
+** The main loop for a thread.  Threads use busy waiting. 
+*/
+static void *thread_main(void *pArg){
+  Thread *p = (Thread*)pArg;
+  if( p->db ){
+    sqlite3_close(p->db);
+  }
+  sqlite3_open(p->zFilename, &p->db);
+  if( SQLITE_OK!=sqlite3_errcode(p->db) ){
+    p->zErr = strdup(sqlite3_errmsg(p->db));
+    sqlite3_close(p->db);
+    p->db = 0;
+  }
+  p->pStmt = 0;
+  p->completed = 1;
+  while( p->opnum<=p->completed ) sched_yield();
+  while( p->xOp ){
+    if( p->zErr && p->zErr!=p->zStaticErr ){
+      sqlite3_free(p->zErr);
+      p->zErr = 0;
+    }
+    (*p->xOp)(p);
+    p->completed++;
+    while( p->opnum<=p->completed ) sched_yield();
+  }
+  if( p->pStmt ){
+    sqlite3_finalize(p->pStmt);
+    p->pStmt = 0;
+  }
+  if( p->db ){
+    sqlite3_close(p->db);
+    p->db = 0;
+  }
+  if( p->zErr && p->zErr!=p->zStaticErr ){
+    sqlite3_free(p->zErr);
+    p->zErr = 0;
+  }
+  p->completed++;
+#ifndef SQLITE_OMIT_DEPRECATED
+  sqlite3_thread_cleanup();
+#endif
+  return 0;
+}
+
+/*
+** Get a thread ID which is an upper case letter.  Return the index.
+** If the argument is not a valid thread ID put an error message in
+** the interpreter and return -1.
+*/
+static int parse_thread_id(Tcl_Interp *interp, const char *zArg){
+  if( zArg==0 || zArg[0]==0 || zArg[1]!=0 || !isupper((unsigned char)zArg[0]) ){
+    Tcl_AppendResult(interp, "thread ID must be an upper case letter", 0);
+    return -1;
+  }
+  return zArg[0] - 'A';
+}
+
+/*
+** Usage:    thread_create NAME  FILENAME
+**
+** NAME should be an upper case letter.  Start the thread running with
+** an open connection to the given database.
+*/
+static int tcl_thread_create(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+  pthread_t x;
+  int rc;
+
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID FILENAME", 0);
+    return TCL_ERROR;
+  }
+  i = parse_thread_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( threadset[i].busy ){
+    Tcl_AppendResult(interp, "thread ", argv[1], " is already running", 0);
+    return TCL_ERROR;
+  }
+  threadset[i].busy = 1;
+  sqlite3_free(threadset[i].zFilename);
+  threadset[i].zFilename = sqlite3_mprintf("%s", argv[2]);
+  threadset[i].opnum = 1;
+  threadset[i].completed = 0;
+  rc = pthread_create(&x, 0, thread_main, &threadset[i]);
+  if( rc ){
+    Tcl_AppendResult(interp, "failed to create the thread", 0);
+    sqlite3_free(threadset[i].zFilename);
+    threadset[i].busy = 0;
+    return TCL_ERROR;
+  }
+  pthread_detach(x);
+  return TCL_OK;
+}
+
+/*
+** Wait for a thread to reach its idle state.
+*/
+static void thread_wait(Thread *p){
+  while( p->opnum>p->completed ) sched_yield();
+}
+
+/*
+** Usage:  thread_wait ID
+**
+** Wait on thread ID to reach its idle state.
+*/
+static int tcl_thread_wait(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID", 0);
+    return TCL_ERROR;
+  }
+  i = parse_thread_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  thread_wait(&threadset[i]);
+  return TCL_OK;
+}
+
+/*
+** Stop a thread.
+*/
+static void stop_thread(Thread *p){
+  thread_wait(p);
+  p->xOp = 0;
+  p->opnum++;
+  thread_wait(p);
+  sqlite3_free(p->zArg);
+  p->zArg = 0;
+  sqlite3_free(p->zFilename);
+  p->zFilename = 0;
+  p->busy = 0;
+}
+
+/*
+** Usage:  thread_halt ID
+**
+** Cause a thread to shut itself down.  Wait for the shutdown to be
+** completed.  If ID is "*" then stop all threads.
+*/
+static int tcl_thread_halt(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID", 0);
+    return TCL_ERROR;
+  }
+  if( argv[1][0]=='*' && argv[1][1]==0 ){
+    for(i=0; i<N_THREAD; i++){
+      if( threadset[i].busy ) stop_thread(&threadset[i]);
+    }
+  }else{
+    i = parse_thread_id(interp, argv[1]);
+    if( i<0 ) return TCL_ERROR;
+    if( !threadset[i].busy ){
+      Tcl_AppendResult(interp, "no such thread", 0);
+      return TCL_ERROR;
+    }
+    stop_thread(&threadset[i]);
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage: thread_argc  ID
+**
+** Wait on the most recent thread_step to complete, then return the
+** number of columns in the result set.
+*/
+static int tcl_thread_argc(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+  char zBuf[100];
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID", 0);
+    return TCL_ERROR;
+  }
+  i = parse_thread_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  thread_wait(&threadset[i]);
+  sprintf(zBuf, "%d", threadset[i].argc);
+  Tcl_AppendResult(interp, zBuf, 0);
+  return TCL_OK;
+}
+
+/*
+** Usage: thread_argv  ID   N
+**
+** Wait on the most recent thread_step to complete, then return the
+** value of the N-th columns in the result set.
+*/
+static int tcl_thread_argv(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+  int n;
+
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID N", 0);
+    return TCL_ERROR;
+  }
+  i = parse_thread_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  if( Tcl_GetInt(interp, argv[2], &n) ) return TCL_ERROR;
+  thread_wait(&threadset[i]);
+  if( n<0 || n>=threadset[i].argc ){
+    Tcl_AppendResult(interp, "column number out of range", 0);
+    return TCL_ERROR;
+  }
+  Tcl_AppendResult(interp, threadset[i].argv[n], 0);
+  return TCL_OK;
+}
+
+/*
+** Usage: thread_colname  ID   N
+**
+** Wait on the most recent thread_step to complete, then return the
+** name of the N-th columns in the result set.
+*/
+static int tcl_thread_colname(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+  int n;
+
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID N", 0);
+    return TCL_ERROR;
+  }
+  i = parse_thread_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  if( Tcl_GetInt(interp, argv[2], &n) ) return TCL_ERROR;
+  thread_wait(&threadset[i]);
+  if( n<0 || n>=threadset[i].argc ){
+    Tcl_AppendResult(interp, "column number out of range", 0);
+    return TCL_ERROR;
+  }
+  Tcl_AppendResult(interp, threadset[i].colv[n], 0);
+  return TCL_OK;
+}
+
+/*
+** Usage: thread_result  ID
+**
+** Wait on the most recent operation to complete, then return the
+** result code from that operation.
+*/
+static int tcl_thread_result(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+  const char *zName;
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID", 0);
+    return TCL_ERROR;
+  }
+  i = parse_thread_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  thread_wait(&threadset[i]);
+  switch( threadset[i].rc ){
+    case SQLITE_OK:         zName = "SQLITE_OK";          break;
+    case SQLITE_ERROR:      zName = "SQLITE_ERROR";       break;
+    case SQLITE_PERM:       zName = "SQLITE_PERM";        break;
+    case SQLITE_ABORT:      zName = "SQLITE_ABORT";       break;
+    case SQLITE_BUSY:       zName = "SQLITE_BUSY";        break;
+    case SQLITE_LOCKED:     zName = "SQLITE_LOCKED";      break;
+    case SQLITE_NOMEM:      zName = "SQLITE_NOMEM";       break;
+    case SQLITE_READONLY:   zName = "SQLITE_READONLY";    break;
+    case SQLITE_INTERRUPT:  zName = "SQLITE_INTERRUPT";   break;
+    case SQLITE_IOERR:      zName = "SQLITE_IOERR";       break;
+    case SQLITE_CORRUPT:    zName = "SQLITE_CORRUPT";     break;
+    case SQLITE_FULL:       zName = "SQLITE_FULL";        break;
+    case SQLITE_CANTOPEN:   zName = "SQLITE_CANTOPEN";    break;
+    case SQLITE_PROTOCOL:   zName = "SQLITE_PROTOCOL";    break;
+    case SQLITE_EMPTY:      zName = "SQLITE_EMPTY";       break;
+    case SQLITE_SCHEMA:     zName = "SQLITE_SCHEMA";      break;
+    case SQLITE_CONSTRAINT: zName = "SQLITE_CONSTRAINT";  break;
+    case SQLITE_MISMATCH:   zName = "SQLITE_MISMATCH";    break;
+    case SQLITE_MISUSE:     zName = "SQLITE_MISUSE";      break;
+    case SQLITE_NOLFS:      zName = "SQLITE_NOLFS";       break;
+    case SQLITE_AUTH:       zName = "SQLITE_AUTH";        break;
+    case SQLITE_FORMAT:     zName = "SQLITE_FORMAT";      break;
+    case SQLITE_RANGE:      zName = "SQLITE_RANGE";       break;
+    case SQLITE_ROW:        zName = "SQLITE_ROW";         break;
+    case SQLITE_DONE:       zName = "SQLITE_DONE";        break;
+    default:                zName = "SQLITE_Unknown";     break;
+  }
+  Tcl_AppendResult(interp, zName, 0);
+  return TCL_OK;
+}
+
+/*
+** Usage: thread_error  ID
+**
+** Wait on the most recent operation to complete, then return the
+** error string.
+*/
+static int tcl_thread_error(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID", 0);
+    return TCL_ERROR;
+  }
+  i = parse_thread_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  thread_wait(&threadset[i]);
+  Tcl_AppendResult(interp, threadset[i].zErr, 0);
+  return TCL_OK;
+}
+
+/*
+** This procedure runs in the thread to compile an SQL statement.
+*/
+static void do_compile(Thread *p){
+  if( p->db==0 ){
+    p->zErr = p->zStaticErr = "no database is open";
+    p->rc = SQLITE_ERROR;
+    return;
+  }
+  if( p->pStmt ){
+    sqlite3_finalize(p->pStmt);
+    p->pStmt = 0;
+  }
+  p->rc = sqlite3_prepare(p->db, p->zArg, -1, &p->pStmt, 0);
+}
+
+/*
+** Usage: thread_compile ID SQL
+**
+** Compile a new virtual machine.
+*/
+static int tcl_thread_compile(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID SQL", 0);
+    return TCL_ERROR;
+  }
+  i = parse_thread_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  thread_wait(&threadset[i]);
+  threadset[i].xOp = do_compile;
+  sqlite3_free(threadset[i].zArg);
+  threadset[i].zArg = sqlite3_mprintf("%s", argv[2]);
+  threadset[i].opnum++;
+  return TCL_OK;
+}
+
+/*
+** This procedure runs in the thread to step the virtual machine.
+*/
+static void do_step(Thread *p){
+  int i;
+  if( p->pStmt==0 ){
+    p->zErr = p->zStaticErr = "no virtual machine available";
+    p->rc = SQLITE_ERROR;
+    return;
+  }
+  p->rc = sqlite3_step(p->pStmt);
+  if( p->rc==SQLITE_ROW ){
+    p->argc = sqlite3_column_count(p->pStmt);
+    for(i=0; i<sqlite3_data_count(p->pStmt); i++){
+      p->argv[i] = (char*)sqlite3_column_text(p->pStmt, i);
+    }
+    for(i=0; i<p->argc; i++){
+      p->colv[i] = sqlite3_column_name(p->pStmt, i);
+    }
+  }
+}
+
+/*
+** Usage: thread_step ID
+**
+** Advance the virtual machine by one step
+*/
+static int tcl_thread_step(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " IDL", 0);
+    return TCL_ERROR;
+  }
+  i = parse_thread_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  thread_wait(&threadset[i]);
+  threadset[i].xOp = do_step;
+  threadset[i].opnum++;
+  return TCL_OK;
+}
+
+/*
+** This procedure runs in the thread to finalize a virtual machine.
+*/
+static void do_finalize(Thread *p){
+  if( p->pStmt==0 ){
+    p->zErr = p->zStaticErr = "no virtual machine available";
+    p->rc = SQLITE_ERROR;
+    return;
+  }
+  p->rc = sqlite3_finalize(p->pStmt);
+  p->pStmt = 0;
+}
+
+/*
+** Usage: thread_finalize ID
+**
+** Finalize the virtual machine.
+*/
+static int tcl_thread_finalize(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " IDL", 0);
+    return TCL_ERROR;
+  }
+  i = parse_thread_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  thread_wait(&threadset[i]);
+  threadset[i].xOp = do_finalize;
+  sqlite3_free(threadset[i].zArg);
+  threadset[i].zArg = 0;
+  threadset[i].opnum++;
+  return TCL_OK;
+}
+
+/*
+** Usage: thread_swap ID ID
+**
+** Interchange the sqlite* pointer between two threads.
+*/
+static int tcl_thread_swap(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i, j;
+  sqlite3 *temp;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID1 ID2", 0);
+    return TCL_ERROR;
+  }
+  i = parse_thread_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  thread_wait(&threadset[i]);
+  j = parse_thread_id(interp, argv[2]);
+  if( j<0 ) return TCL_ERROR;
+  if( !threadset[j].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  thread_wait(&threadset[j]);
+  temp = threadset[i].db;
+  threadset[i].db = threadset[j].db;
+  threadset[j].db = temp;
+  return TCL_OK;
+}
+
+/*
+** Usage: thread_db_get ID
+**
+** Return the database connection pointer for the given thread.  Then
+** remove the pointer from the thread itself.  Afterwards, the thread
+** can be stopped and the connection can be used by the main thread.
+*/
+static int tcl_thread_db_get(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+  char zBuf[100];
+  extern int sqlite3TestMakePointerStr(Tcl_Interp*, char*, void*);
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID", 0);
+    return TCL_ERROR;
+  }
+  i = parse_thread_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  thread_wait(&threadset[i]);
+  sqlite3TestMakePointerStr(interp, zBuf, threadset[i].db);
+  threadset[i].db = 0;
+  Tcl_AppendResult(interp, zBuf, (char*)0);
+  return TCL_OK;
+}
+
+/*
+** Usage: thread_db_put ID DB
+**
+*/
+static int tcl_thread_db_put(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+  extern int sqlite3TestMakePointerStr(Tcl_Interp*, char*, void*);
+  extern void *sqlite3TestTextToPtr(const char *);
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID DB", 0);
+    return TCL_ERROR;
+  }
+  i = parse_thread_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  thread_wait(&threadset[i]);
+  assert( !threadset[i].db );
+  threadset[i].db = (sqlite3*)sqlite3TestTextToPtr(argv[2]);
+  return TCL_OK;
+}
+
+/*
+** Usage: thread_stmt_get ID
+**
+** Return the database stmt pointer for the given thread.  Then
+** remove the pointer from the thread itself. 
+*/
+static int tcl_thread_stmt_get(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+  char zBuf[100];
+  extern int sqlite3TestMakePointerStr(Tcl_Interp*, char*, void*);
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID", 0);
+    return TCL_ERROR;
+  }
+  i = parse_thread_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  thread_wait(&threadset[i]);
+  sqlite3TestMakePointerStr(interp, zBuf, threadset[i].pStmt);
+  threadset[i].pStmt = 0;
+  Tcl_AppendResult(interp, zBuf, (char*)0);
+  return TCL_OK;
+}
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetest4_Init(Tcl_Interp *interp){
+  static struct {
+     char *zName;
+     Tcl_CmdProc *xProc;
+  } aCmd[] = {
+     { "thread_create",     (Tcl_CmdProc*)tcl_thread_create     },
+     { "thread_wait",       (Tcl_CmdProc*)tcl_thread_wait       },
+     { "thread_halt",       (Tcl_CmdProc*)tcl_thread_halt       },
+     { "thread_argc",       (Tcl_CmdProc*)tcl_thread_argc       },
+     { "thread_argv",       (Tcl_CmdProc*)tcl_thread_argv       },
+     { "thread_colname",    (Tcl_CmdProc*)tcl_thread_colname    },
+     { "thread_result",     (Tcl_CmdProc*)tcl_thread_result     },
+     { "thread_error",      (Tcl_CmdProc*)tcl_thread_error      },
+     { "thread_compile",    (Tcl_CmdProc*)tcl_thread_compile    },
+     { "thread_step",       (Tcl_CmdProc*)tcl_thread_step       },
+     { "thread_finalize",   (Tcl_CmdProc*)tcl_thread_finalize   },
+     { "thread_swap",       (Tcl_CmdProc*)tcl_thread_swap       },
+     { "thread_db_get",     (Tcl_CmdProc*)tcl_thread_db_get     },
+     { "thread_db_put",     (Tcl_CmdProc*)tcl_thread_db_put     },
+     { "thread_stmt_get",   (Tcl_CmdProc*)tcl_thread_stmt_get   },
+  };
+  int i;
+
+  for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){
+    Tcl_CreateCommand(interp, aCmd[i].zName, aCmd[i].xProc, 0, 0);
+  }
+  return TCL_OK;
+}
+#else
+int Sqlitetest4_Init(Tcl_Interp *interp){ return TCL_OK; }
+#endif /* SQLITE_OS_UNIX */
diff --git a/src/test5.c b/src/test5.c
new file mode 100644
index 0000000..504fdb8
--- /dev/null
+++ b/src/test5.c
@@ -0,0 +1,218 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Code for testing the utf.c module in SQLite.  This code
+** is not included in the SQLite library.  It is used for automated
+** testing of the SQLite library. Specifically, the code in this file
+** is used for testing the SQLite routines for converting between
+** the various supported unicode encodings.
+*/
+#include "sqliteInt.h"
+#include "vdbeInt.h"
+#include "tcl.h"
+#include <stdlib.h>
+#include <string.h>
+
+/*
+** The first argument is a TCL UTF-8 string. Return the byte array
+** object with the encoded representation of the string, including
+** the NULL terminator.
+*/
+static int binarize(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int len;
+  char *bytes;
+  Tcl_Obj *pRet;
+  assert(objc==2);
+
+  bytes = Tcl_GetStringFromObj(objv[1], &len);
+  pRet = Tcl_NewByteArrayObj((u8*)bytes, len+1);
+  Tcl_SetObjResult(interp, pRet);
+  return TCL_OK;
+}
+
+/*
+** Usage: test_value_overhead <repeat-count> <do-calls>.
+**
+** This routine is used to test the overhead of calls to
+** sqlite3_value_text(), on a value that contains a UTF-8 string. The idea
+** is to figure out whether or not it is a problem to use sqlite3_value
+** structures with collation sequence functions.
+**
+** If <do-calls> is 0, then the calls to sqlite3_value_text() are not
+** actually made.
+*/
+static int test_value_overhead(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int do_calls;
+  int repeat_count;
+  int i;
+  Mem val;
+  const char *zVal;
+
+  if( objc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), " <repeat-count> <do-calls>", 0);
+    return TCL_ERROR;
+  }
+
+  if( Tcl_GetIntFromObj(interp, objv[1], &repeat_count) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &do_calls) ) return TCL_ERROR;
+
+  val.flags = MEM_Str|MEM_Term|MEM_Static;
+  val.z = "hello world";
+  val.type = SQLITE_TEXT;
+  val.enc = SQLITE_UTF8;
+
+  for(i=0; i<repeat_count; i++){
+    if( do_calls ){
+      zVal = (char*)sqlite3_value_text(&val);
+    }
+  }
+
+  return TCL_OK;
+}
+
+static u8 name_to_enc(Tcl_Interp *interp, Tcl_Obj *pObj){
+  struct EncName {
+    char *zName;
+    u8 enc;
+  } encnames[] = {
+    { "UTF8", SQLITE_UTF8 },
+    { "UTF16LE", SQLITE_UTF16LE },
+    { "UTF16BE", SQLITE_UTF16BE },
+    { "UTF16", SQLITE_UTF16 },
+    { 0, 0 }
+  };
+  struct EncName *pEnc;
+  char *z = Tcl_GetString(pObj);
+  for(pEnc=&encnames[0]; pEnc->zName; pEnc++){
+    if( 0==sqlite3StrICmp(z, pEnc->zName) ){
+      break;
+    }
+  }
+  if( !pEnc->enc ){
+    Tcl_AppendResult(interp, "No such encoding: ", z, 0);
+  }
+  if( pEnc->enc==SQLITE_UTF16 ){
+    return SQLITE_UTF16NATIVE;
+  }
+  return pEnc->enc;
+}
+
+/*
+** Usage:   test_translate <string/blob> <from enc> <to enc> ?<transient>?
+**
+*/
+static int test_translate(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  u8 enc_from;
+  u8 enc_to;
+  sqlite3_value *pVal;
+
+  char *z;
+  int len;
+  void (*xDel)(void *p) = SQLITE_STATIC;
+
+  if( objc!=4 && objc!=5 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"",
+        Tcl_GetStringFromObj(objv[0], 0), 
+        " <string/blob> <from enc> <to enc>", 0
+    );
+    return TCL_ERROR;
+  }
+  if( objc==5 ){
+    xDel = sqlite3_free;
+  }
+
+  enc_from = name_to_enc(interp, objv[2]);
+  if( !enc_from ) return TCL_ERROR;
+  enc_to = name_to_enc(interp, objv[3]);
+  if( !enc_to ) return TCL_ERROR;
+
+  pVal = sqlite3ValueNew(0);
+
+  if( enc_from==SQLITE_UTF8 ){
+    z = Tcl_GetString(objv[1]);
+    if( objc==5 ){
+      z = sqlite3_mprintf("%s", z);
+    }
+    sqlite3ValueSetStr(pVal, -1, z, enc_from, xDel);
+  }else{
+    z = (char*)Tcl_GetByteArrayFromObj(objv[1], &len);
+    if( objc==5 ){
+      char *zTmp = z;
+      z = sqlite3_malloc(len);
+      memcpy(z, zTmp, len);
+    }
+    sqlite3ValueSetStr(pVal, -1, z, enc_from, xDel);
+  }
+
+  z = (char *)sqlite3ValueText(pVal, enc_to);
+  len = sqlite3ValueBytes(pVal, enc_to) + (enc_to==SQLITE_UTF8?1:2);
+  Tcl_SetObjResult(interp, Tcl_NewByteArrayObj((u8*)z, len));
+
+  sqlite3ValueFree(pVal);
+
+  return TCL_OK;
+}
+
+/*
+** Usage: translate_selftest
+**
+** Call sqlite3UtfSelfTest() to run the internal tests for unicode
+** translation. If there is a problem an assert() will fail.
+**/
+void sqlite3UtfSelfTest(void);
+static int test_translate_selftest(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#ifndef SQLITE_OMIT_UTF16
+  sqlite3UtfSelfTest();
+#endif
+  return SQLITE_OK;
+}
+
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetest5_Init(Tcl_Interp *interp){
+  static struct {
+    char *zName;
+    Tcl_ObjCmdProc *xProc;
+  } aCmd[] = {
+    { "binarize",                (Tcl_ObjCmdProc*)binarize },
+    { "test_value_overhead",     (Tcl_ObjCmdProc*)test_value_overhead },
+    { "test_translate",          (Tcl_ObjCmdProc*)test_translate     },
+    { "translate_selftest",      (Tcl_ObjCmdProc*)test_translate_selftest},
+  };
+  int i;
+  for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aCmd[i].zName, aCmd[i].xProc, 0, 0);
+  }
+  return SQLITE_OK;
+}
diff --git a/src/test6.c b/src/test6.c
new file mode 100644
index 0000000..23fb14c
--- /dev/null
+++ b/src/test6.c
@@ -0,0 +1,1010 @@
+/*
+** 2004 May 22
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains code that modified the OS layer in order to simulate
+** the effect on the database file of an OS crash or power failure.  This
+** is used to test the ability of SQLite to recover from those situations.
+*/
+#if SQLITE_TEST          /* This file is used for testing only */
+#include "sqliteInt.h"
+#include "tcl.h"
+
+#ifndef SQLITE_OMIT_DISKIO  /* This file is a no-op if disk I/O is disabled */
+
+/* #define TRACE_CRASHTEST */
+
+typedef struct CrashFile CrashFile;
+typedef struct CrashGlobal CrashGlobal;
+typedef struct WriteBuffer WriteBuffer;
+
+/*
+** Method:
+**
+**   This layer is implemented as a wrapper around the "real" 
+**   sqlite3_file object for the host system. Each time data is 
+**   written to the file object, instead of being written to the
+**   underlying file, the write operation is stored in an in-memory 
+**   structure (type WriteBuffer). This structure is placed at the
+**   end of a global ordered list (the write-list).
+**
+**   When data is read from a file object, the requested region is
+**   first retrieved from the real file. The write-list is then 
+**   traversed and data copied from any overlapping WriteBuffer 
+**   structures to the output buffer. i.e. a read() operation following
+**   one or more write() operations works as expected, even if no
+**   data has actually been written out to the real file.
+**
+**   When a fsync() operation is performed, an operating system crash 
+**   may be simulated, in which case exit(-1) is called (the call to 
+**   xSync() never returns). Whether or not a crash is simulated,
+**   the data associated with a subset of the WriteBuffer structures 
+**   stored in the write-list is written to the real underlying files 
+**   and the entries removed from the write-list. If a crash is simulated,
+**   a subset of the buffers may be corrupted before the data is written.
+**
+**   The exact subset of the write-list written and/or corrupted is
+**   determined by the simulated device characteristics and sector-size.
+**
+** "Normal" mode:
+**
+**   Normal mode is used when the simulated device has none of the
+**   SQLITE_IOCAP_XXX flags set.
+**
+**   In normal mode, if the fsync() is not a simulated crash, the 
+**   write-list is traversed from beginning to end. Each WriteBuffer
+**   structure associated with the file handle used to call xSync()
+**   is written to the real file and removed from the write-list.
+**
+**   If a crash is simulated, one of the following takes place for 
+**   each WriteBuffer in the write-list, regardless of which 
+**   file-handle it is associated with:
+**
+**     1. The buffer is correctly written to the file, just as if
+**        a crash were not being simulated.
+**
+**     2. Nothing is done.
+**
+**     3. Garbage data is written to all sectors of the file that 
+**        overlap the region specified by the WriteBuffer. Or garbage
+**        data is written to some contiguous section within the 
+**        overlapped sectors.
+**
+** Device Characteristic flag handling:
+**
+**   If the IOCAP_ATOMIC flag is set, then option (3) above is 
+**   never selected.
+**
+**   If the IOCAP_ATOMIC512 flag is set, and the WriteBuffer represents
+**   an aligned write() of an integer number of 512 byte regions, then
+**   option (3) above is never selected. Instead, each 512 byte region
+**   is either correctly written or left completely untouched. Similar
+**   logic governs the behaviour if any of the other ATOMICXXX flags
+**   is set.
+**
+**   If either the IOCAP_SAFEAPPEND or IOCAP_SEQUENTIAL flags are set
+**   and a crash is being simulated, then an entry of the write-list is
+**   selected at random. Everything in the list after the selected entry 
+**   is discarded before processing begins.
+**
+**   If IOCAP_SEQUENTIAL is set and a crash is being simulated, option 
+**   (1) is selected for all write-list entries except the last. If a 
+**   crash is not being simulated, then all entries in the write-list
+**   that occur before at least one write() on the file-handle specified
+**   as part of the xSync() are written to their associated real files.
+**
+**   If IOCAP_SAFEAPPEND is set and the first byte written by the write()
+**   operation is one byte past the current end of the file, then option
+**   (1) is always selected.
+*/
+
+/*
+** Each write operation in the write-list is represented by an instance
+** of the following structure.
+**
+** If zBuf is 0, then this structure represents a call to xTruncate(), 
+** not xWrite(). In that case, iOffset is the size that the file is
+** truncated to.
+*/
+struct WriteBuffer {
+  i64 iOffset;                 /* Byte offset of the start of this write() */
+  int nBuf;                    /* Number of bytes written */
+  u8 *zBuf;                    /* Pointer to copy of written data */
+  CrashFile *pFile;            /* File this write() applies to */
+
+  WriteBuffer *pNext;          /* Next in CrashGlobal.pWriteList */
+};
+
+struct CrashFile {
+  const sqlite3_io_methods *pMethod;   /* Must be first */
+  sqlite3_file *pRealFile;             /* Underlying "real" file handle */
+  char *zName;
+  int flags;                           /* Flags the file was opened with */
+
+  /* Cache of the entire file. This is used to speed up OsRead() and 
+  ** OsFileSize() calls. Although both could be done by traversing the
+  ** write-list, in practice this is impractically slow.
+  */
+  int iSize;                           /* Size of file in bytes */
+  int nData;                           /* Size of buffer allocated at zData */
+  u8 *zData;                           /* Buffer containing file contents */
+};
+
+struct CrashGlobal {
+  WriteBuffer *pWriteList;     /* Head of write-list */
+  WriteBuffer *pWriteListEnd;  /* End of write-list */
+
+  int iSectorSize;             /* Value of simulated sector size */
+  int iDeviceCharacteristics;  /* Value of simulated device characteristics */
+
+  int iCrash;                  /* Crash on the iCrash'th call to xSync() */
+  char zCrashFile[500];        /* Crash during an xSync() on this file */ 
+};
+
+static CrashGlobal g = {0, 0, SQLITE_DEFAULT_SECTOR_SIZE, 0, 0};
+
+/*
+** Set this global variable to 1 to enable crash testing.
+*/
+static int sqlite3CrashTestEnable = 0;
+
+static void *crash_malloc(int nByte){
+  return (void *)Tcl_Alloc((size_t)nByte);
+}
+static void crash_free(void *p){
+  Tcl_Free(p);
+}
+static void *crash_realloc(void *p, int n){
+  return (void *)Tcl_Realloc(p, (size_t)n);
+}
+
+/*
+** Wrapper around the sqlite3OsWrite() function that avoids writing to the
+** 512 byte block begining at offset PENDING_BYTE.
+*/
+static int writeDbFile(CrashFile *p, u8 *z, i64 iAmt, i64 iOff){
+  int rc = SQLITE_OK;
+  int iSkip = 0;
+  if( iOff==PENDING_BYTE && (p->flags&SQLITE_OPEN_MAIN_DB) ){
+    iSkip = 512;
+  }
+  if( (iAmt-iSkip)>0 ){
+    rc = sqlite3OsWrite(p->pRealFile, &z[iSkip], iAmt-iSkip, iOff+iSkip);
+  }
+  return rc;
+}
+
+/*
+** Flush the write-list as if xSync() had been called on file handle
+** pFile. If isCrash is true, simulate a crash.
+*/
+static int writeListSync(CrashFile *pFile, int isCrash){
+  int rc = SQLITE_OK;
+  int iDc = g.iDeviceCharacteristics;
+
+  WriteBuffer *pWrite;
+  WriteBuffer **ppPtr;
+
+  /* If this is not a crash simulation, set pFinal to point to the 
+  ** last element of the write-list that is associated with file handle
+  ** pFile.
+  **
+  ** If this is a crash simulation, set pFinal to an arbitrarily selected
+  ** element of the write-list.
+  */
+  WriteBuffer *pFinal = 0;
+  if( !isCrash ){
+    for(pWrite=g.pWriteList; pWrite; pWrite=pWrite->pNext){
+      if( pWrite->pFile==pFile ){
+        pFinal = pWrite;
+      }
+    }
+  }else if( iDc&(SQLITE_IOCAP_SEQUENTIAL|SQLITE_IOCAP_SAFE_APPEND) ){
+    int nWrite = 0;
+    int iFinal;
+    for(pWrite=g.pWriteList; pWrite; pWrite=pWrite->pNext) nWrite++;
+    sqlite3_randomness(sizeof(int), &iFinal);
+    iFinal = ((iFinal<0)?-1*iFinal:iFinal)%nWrite;
+    for(pWrite=g.pWriteList; iFinal>0; pWrite=pWrite->pNext) iFinal--;
+    pFinal = pWrite;
+  }
+
+#ifdef TRACE_CRASHTEST
+  printf("Sync %s (is %s crash)\n", pFile->zName, (isCrash?"a":"not a"));
+#endif
+
+  ppPtr = &g.pWriteList;
+  for(pWrite=*ppPtr; rc==SQLITE_OK && pWrite; pWrite=*ppPtr){
+    sqlite3_file *pRealFile = pWrite->pFile->pRealFile;
+
+    /* (eAction==1)      -> write block out normally,
+    ** (eAction==2)      -> do nothing,
+    ** (eAction==3)      -> trash sectors.
+    */
+    int eAction = 0;
+    if( !isCrash ){
+      eAction = 2;
+      if( (pWrite->pFile==pFile || iDc&SQLITE_IOCAP_SEQUENTIAL) ){
+        eAction = 1;
+      }
+    }else{
+      char random;
+      sqlite3_randomness(1, &random);
+
+      /* Do not select option 3 (sector trashing) if the IOCAP_ATOMIC flag 
+      ** is set or this is an OsTruncate(), not an Oswrite().
+      */
+      if( (iDc&SQLITE_IOCAP_ATOMIC) || (pWrite->zBuf==0) ){
+        random &= 0x01;
+      }
+
+      /* If IOCAP_SEQUENTIAL is set and this is not the final entry
+      ** in the truncated write-list, always select option 1 (write
+      ** out correctly).
+      */
+      if( (iDc&SQLITE_IOCAP_SEQUENTIAL && pWrite!=pFinal) ){
+        random = 0;
+      }
+
+      /* If IOCAP_SAFE_APPEND is set and this OsWrite() operation is
+      ** an append (first byte of the written region is 1 byte past the
+      ** current EOF), always select option 1 (write out correctly).
+      */
+      if( iDc&SQLITE_IOCAP_SAFE_APPEND && pWrite->zBuf ){
+        i64 iSize;
+        sqlite3OsFileSize(pRealFile, &iSize);
+        if( iSize==pWrite->iOffset ){
+          random = 0;
+        }
+      }
+
+      if( (random&0x06)==0x06 ){
+        eAction = 3;
+      }else{
+        eAction = ((random&0x01)?2:1);
+      }
+    }
+
+    switch( eAction ){
+      case 1: {               /* Write out correctly */
+        if( pWrite->zBuf ){
+          rc = writeDbFile(
+              pWrite->pFile, pWrite->zBuf, pWrite->nBuf, pWrite->iOffset
+          );
+        }else{
+          rc = sqlite3OsTruncate(pRealFile, pWrite->iOffset);
+        }
+        *ppPtr = pWrite->pNext;
+#ifdef TRACE_CRASHTEST
+        if( isCrash ){
+          printf("Writing %d bytes @ %d (%s)\n", 
+            pWrite->nBuf, (int)pWrite->iOffset, pWrite->pFile->zName
+          );
+        }
+#endif
+        crash_free(pWrite);
+        break;
+      }
+      case 2: {               /* Do nothing */
+        ppPtr = &pWrite->pNext;
+#ifdef TRACE_CRASHTEST
+        if( isCrash ){
+          printf("Omiting %d bytes @ %d (%s)\n", 
+            pWrite->nBuf, (int)pWrite->iOffset, pWrite->pFile->zName
+          );
+        }
+#endif
+        break;
+      }
+      case 3: {               /* Trash sectors */
+        u8 *zGarbage;
+        int iFirst = (pWrite->iOffset/g.iSectorSize);
+        int iLast = (pWrite->iOffset+pWrite->nBuf-1)/g.iSectorSize;
+
+        assert(pWrite->zBuf);
+
+#ifdef TRACE_CRASHTEST
+        printf("Trashing %d sectors @ sector %d (%s)\n", 
+            1+iLast-iFirst, iFirst, pWrite->pFile->zName
+        );
+#endif
+
+        zGarbage = crash_malloc(g.iSectorSize);
+        if( zGarbage ){
+          sqlite3_int64 i;
+          for(i=iFirst; rc==SQLITE_OK && i<=iLast; i++){
+            sqlite3_randomness(g.iSectorSize, zGarbage); 
+            rc = writeDbFile(
+              pWrite->pFile, zGarbage, g.iSectorSize, i*g.iSectorSize
+            );
+          }
+          crash_free(zGarbage);
+        }else{
+          rc = SQLITE_NOMEM;
+        }
+
+        ppPtr = &pWrite->pNext;
+        break;
+      }
+
+      default:
+        assert(!"Cannot happen");
+    }
+
+    if( pWrite==pFinal ) break;
+  }
+
+  if( rc==SQLITE_OK && isCrash ){
+    exit(-1);
+  }
+
+  for(pWrite=g.pWriteList; pWrite && pWrite->pNext; pWrite=pWrite->pNext);
+  g.pWriteListEnd = pWrite;
+
+  return rc;
+}
+
+/*
+** Add an entry to the end of the write-list.
+*/
+static int writeListAppend(
+  sqlite3_file *pFile,
+  sqlite3_int64 iOffset,
+  const u8 *zBuf,
+  int nBuf
+){
+  WriteBuffer *pNew;
+
+  assert((zBuf && nBuf) || (!nBuf && !zBuf));
+
+  pNew = (WriteBuffer *)crash_malloc(sizeof(WriteBuffer) + nBuf);
+  if( pNew==0 ){
+    fprintf(stderr, "out of memory in the crash simulator\n");
+  }
+  memset(pNew, 0, sizeof(WriteBuffer)+nBuf);
+  pNew->iOffset = iOffset;
+  pNew->nBuf = nBuf;
+  pNew->pFile = (CrashFile *)pFile;
+  if( zBuf ){
+    pNew->zBuf = (u8 *)&pNew[1];
+    memcpy(pNew->zBuf, zBuf, nBuf);
+  }
+
+  if( g.pWriteList ){
+    assert(g.pWriteListEnd);
+    g.pWriteListEnd->pNext = pNew;
+  }else{
+    g.pWriteList = pNew;
+  }
+  g.pWriteListEnd = pNew;
+  
+  return SQLITE_OK;
+}
+
+/*
+** Close a crash-file.
+*/
+static int cfClose(sqlite3_file *pFile){
+  CrashFile *pCrash = (CrashFile *)pFile;
+  writeListSync(pCrash, 0);
+  sqlite3OsClose(pCrash->pRealFile);
+  return SQLITE_OK;
+}
+
+/*
+** Read data from a crash-file.
+*/
+static int cfRead(
+  sqlite3_file *pFile, 
+  void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  CrashFile *pCrash = (CrashFile *)pFile;
+
+  /* Check the file-size to see if this is a short-read */
+  if( pCrash->iSize<(iOfst+iAmt) ){
+    return SQLITE_IOERR_SHORT_READ;
+  }
+
+  memcpy(zBuf, &pCrash->zData[iOfst], iAmt);
+  return SQLITE_OK;
+}
+
+/*
+** Write data to a crash-file.
+*/
+static int cfWrite(
+  sqlite3_file *pFile, 
+  const void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  CrashFile *pCrash = (CrashFile *)pFile;
+  if( iAmt+iOfst>pCrash->iSize ){
+    pCrash->iSize = iAmt+iOfst;
+  }
+  while( pCrash->iSize>pCrash->nData ){
+    u8 *zNew;
+    int nNew = (pCrash->nData*2) + 4096;
+    zNew = crash_realloc(pCrash->zData, nNew);
+    if( !zNew ){
+      return SQLITE_NOMEM;
+    }
+    memset(&zNew[pCrash->nData], 0, nNew-pCrash->nData);
+    pCrash->nData = nNew;
+    pCrash->zData = zNew;
+  }
+  memcpy(&pCrash->zData[iOfst], zBuf, iAmt);
+  return writeListAppend(pFile, iOfst, zBuf, iAmt);
+}
+
+/*
+** Truncate a crash-file.
+*/
+static int cfTruncate(sqlite3_file *pFile, sqlite_int64 size){
+  CrashFile *pCrash = (CrashFile *)pFile;
+  assert(size>=0);
+  if( pCrash->iSize>size ){
+    pCrash->iSize = size;
+  }
+  return writeListAppend(pFile, size, 0, 0);
+}
+
+/*
+** Sync a crash-file.
+*/
+static int cfSync(sqlite3_file *pFile, int flags){
+  CrashFile *pCrash = (CrashFile *)pFile;
+  int isCrash = 0;
+
+  const char *zName = pCrash->zName;
+  const char *zCrashFile = g.zCrashFile;
+  int nName = strlen(zName);
+  int nCrashFile = strlen(zCrashFile);
+
+  if( nCrashFile>0 && zCrashFile[nCrashFile-1]=='*' ){
+    nCrashFile--;
+    if( nName>nCrashFile ) nName = nCrashFile;
+  }
+
+  if( nName==nCrashFile && 0==memcmp(zName, zCrashFile, nName) ){
+    if( (--g.iCrash)==0 ) isCrash = 1;
+  }
+
+  return writeListSync(pCrash, isCrash);
+}
+
+/*
+** Return the current file-size of the crash-file.
+*/
+static int cfFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
+  CrashFile *pCrash = (CrashFile *)pFile;
+  *pSize = (i64)pCrash->iSize;
+  return SQLITE_OK;
+}
+
+/*
+** Calls related to file-locks are passed on to the real file handle.
+*/
+static int cfLock(sqlite3_file *pFile, int eLock){
+  return sqlite3OsLock(((CrashFile *)pFile)->pRealFile, eLock);
+}
+static int cfUnlock(sqlite3_file *pFile, int eLock){
+  return sqlite3OsUnlock(((CrashFile *)pFile)->pRealFile, eLock);
+}
+static int cfCheckReservedLock(sqlite3_file *pFile, int *pResOut){
+  return sqlite3OsCheckReservedLock(((CrashFile *)pFile)->pRealFile, pResOut);
+}
+static int cfFileControl(sqlite3_file *pFile, int op, void *pArg){
+  if( op==SQLITE_FCNTL_SIZE_HINT ){
+    CrashFile *pCrash = (CrashFile *)pFile;
+    i64 nByte = *(i64 *)pArg;
+    if( nByte>pCrash->iSize ){
+      if( SQLITE_OK==writeListAppend(pFile, nByte, 0, 0) ){
+        pCrash->iSize = nByte;
+      }
+    }
+    return SQLITE_OK;
+  }
+  return sqlite3OsFileControl(((CrashFile *)pFile)->pRealFile, op, pArg);
+}
+
+/*
+** The xSectorSize() and xDeviceCharacteristics() functions return
+** the global values configured by the [sqlite_crashparams] tcl
+*  interface.
+*/
+static int cfSectorSize(sqlite3_file *pFile){
+  return g.iSectorSize;
+}
+static int cfDeviceCharacteristics(sqlite3_file *pFile){
+  return g.iDeviceCharacteristics;
+}
+
+/*
+** Pass-throughs for WAL support.
+*/
+static int cfShmLock(sqlite3_file *pFile, int ofst, int n, int flags){
+  return sqlite3OsShmLock(((CrashFile*)pFile)->pRealFile, ofst, n, flags);
+}
+static void cfShmBarrier(sqlite3_file *pFile){
+  sqlite3OsShmBarrier(((CrashFile*)pFile)->pRealFile);
+}
+static int cfShmUnmap(sqlite3_file *pFile, int delFlag){
+  return sqlite3OsShmUnmap(((CrashFile*)pFile)->pRealFile, delFlag);
+}
+static int cfShmMap(
+  sqlite3_file *pFile,            /* Handle open on database file */
+  int iRegion,                    /* Region to retrieve */
+  int sz,                         /* Size of regions */
+  int w,                          /* True to extend file if necessary */
+  void volatile **pp              /* OUT: Mapped memory */
+){
+  return sqlite3OsShmMap(((CrashFile*)pFile)->pRealFile, iRegion, sz, w, pp);
+}
+
+static const sqlite3_io_methods CrashFileVtab = {
+  2,                            /* iVersion */
+  cfClose,                      /* xClose */
+  cfRead,                       /* xRead */
+  cfWrite,                      /* xWrite */
+  cfTruncate,                   /* xTruncate */
+  cfSync,                       /* xSync */
+  cfFileSize,                   /* xFileSize */
+  cfLock,                       /* xLock */
+  cfUnlock,                     /* xUnlock */
+  cfCheckReservedLock,          /* xCheckReservedLock */
+  cfFileControl,                /* xFileControl */
+  cfSectorSize,                 /* xSectorSize */
+  cfDeviceCharacteristics,      /* xDeviceCharacteristics */
+  cfShmMap,                     /* xShmMap */
+  cfShmLock,                    /* xShmLock */
+  cfShmBarrier,                 /* xShmBarrier */
+  cfShmUnmap                    /* xShmUnmap */
+};
+
+/*
+** Application data for the crash VFS
+*/
+struct crashAppData {
+  sqlite3_vfs *pOrig;                   /* Wrapped vfs structure */
+};
+
+/*
+** Open a crash-file file handle.
+**
+** The caller will have allocated pVfs->szOsFile bytes of space
+** at pFile. This file uses this space for the CrashFile structure
+** and allocates space for the "real" file structure using 
+** sqlite3_malloc(). The assumption here is (pVfs->szOsFile) is
+** equal or greater than sizeof(CrashFile).
+*/
+static int cfOpen(
+  sqlite3_vfs *pCfVfs,
+  const char *zName,
+  sqlite3_file *pFile,
+  int flags,
+  int *pOutFlags
+){
+  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
+  int rc;
+  CrashFile *pWrapper = (CrashFile *)pFile;
+  sqlite3_file *pReal = (sqlite3_file*)&pWrapper[1];
+
+  memset(pWrapper, 0, sizeof(CrashFile));
+  rc = sqlite3OsOpen(pVfs, zName, pReal, flags, pOutFlags);
+
+  if( rc==SQLITE_OK ){
+    i64 iSize;
+    pWrapper->pMethod = &CrashFileVtab;
+    pWrapper->zName = (char *)zName;
+    pWrapper->pRealFile = pReal;
+    rc = sqlite3OsFileSize(pReal, &iSize);
+    pWrapper->iSize = (int)iSize;
+    pWrapper->flags = flags;
+  }
+  if( rc==SQLITE_OK ){
+    pWrapper->nData = (4096 + pWrapper->iSize);
+    pWrapper->zData = crash_malloc(pWrapper->nData);
+    if( pWrapper->zData ){
+      /* os_unix.c contains an assert() that fails if the caller attempts
+      ** to read data from the 512-byte locking region of a file opened
+      ** with the SQLITE_OPEN_MAIN_DB flag. This region of a database file
+      ** never contains valid data anyhow. So avoid doing such a read here.
+      */
+      const int isDb = (flags&SQLITE_OPEN_MAIN_DB);
+      i64 iChunk = pWrapper->iSize;
+      if( iChunk>PENDING_BYTE && isDb ){
+        iChunk = PENDING_BYTE;
+      }
+      memset(pWrapper->zData, 0, pWrapper->nData);
+      rc = sqlite3OsRead(pReal, pWrapper->zData, iChunk, 0); 
+      if( SQLITE_OK==rc && pWrapper->iSize>(PENDING_BYTE+512) && isDb ){
+        i64 iOff = PENDING_BYTE+512;
+        iChunk = pWrapper->iSize - iOff;
+        rc = sqlite3OsRead(pReal, &pWrapper->zData[iOff], iChunk, iOff);
+      }
+    }else{
+      rc = SQLITE_NOMEM;
+    }
+  }
+  if( rc!=SQLITE_OK && pWrapper->pMethod ){
+    sqlite3OsClose(pFile);
+  }
+  return rc;
+}
+
+static int cfDelete(sqlite3_vfs *pCfVfs, const char *zPath, int dirSync){
+  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
+  return pVfs->xDelete(pVfs, zPath, dirSync);
+}
+static int cfAccess(
+  sqlite3_vfs *pCfVfs, 
+  const char *zPath, 
+  int flags, 
+  int *pResOut
+){
+  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
+  return pVfs->xAccess(pVfs, zPath, flags, pResOut);
+}
+static int cfFullPathname(
+  sqlite3_vfs *pCfVfs, 
+  const char *zPath, 
+  int nPathOut,
+  char *zPathOut
+){
+  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
+  return pVfs->xFullPathname(pVfs, zPath, nPathOut, zPathOut);
+}
+static void *cfDlOpen(sqlite3_vfs *pCfVfs, const char *zPath){
+  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
+  return pVfs->xDlOpen(pVfs, zPath);
+}
+static void cfDlError(sqlite3_vfs *pCfVfs, int nByte, char *zErrMsg){
+  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
+  pVfs->xDlError(pVfs, nByte, zErrMsg);
+}
+static void (*cfDlSym(sqlite3_vfs *pCfVfs, void *pH, const char *zSym))(void){
+  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
+  return pVfs->xDlSym(pVfs, pH, zSym);
+}
+static void cfDlClose(sqlite3_vfs *pCfVfs, void *pHandle){
+  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
+  pVfs->xDlClose(pVfs, pHandle);
+}
+static int cfRandomness(sqlite3_vfs *pCfVfs, int nByte, char *zBufOut){
+  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
+  return pVfs->xRandomness(pVfs, nByte, zBufOut);
+}
+static int cfSleep(sqlite3_vfs *pCfVfs, int nMicro){
+  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
+  return pVfs->xSleep(pVfs, nMicro);
+}
+static int cfCurrentTime(sqlite3_vfs *pCfVfs, double *pTimeOut){
+  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
+  return pVfs->xCurrentTime(pVfs, pTimeOut);
+}
+
+static int processDevSymArgs(
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[],
+  int *piDeviceChar,
+  int *piSectorSize
+){
+  struct DeviceFlag {
+    char *zName;
+    int iValue;
+  } aFlag[] = {
+    { "atomic",      SQLITE_IOCAP_ATOMIC      },
+    { "atomic512",   SQLITE_IOCAP_ATOMIC512   },
+    { "atomic1k",    SQLITE_IOCAP_ATOMIC1K    },
+    { "atomic2k",    SQLITE_IOCAP_ATOMIC2K    },
+    { "atomic4k",    SQLITE_IOCAP_ATOMIC4K    },
+    { "atomic8k",    SQLITE_IOCAP_ATOMIC8K    },
+    { "atomic16k",   SQLITE_IOCAP_ATOMIC16K   },
+    { "atomic32k",   SQLITE_IOCAP_ATOMIC32K   },
+    { "atomic64k",   SQLITE_IOCAP_ATOMIC64K   },
+    { "sequential",  SQLITE_IOCAP_SEQUENTIAL  },
+    { "safe_append", SQLITE_IOCAP_SAFE_APPEND },
+    { 0, 0 }
+  };
+
+  int i;
+  int iDc = 0;
+  int iSectorSize = 0;
+  int setSectorsize = 0;
+  int setDeviceChar = 0;
+
+  for(i=0; i<objc; i+=2){
+    int nOpt;
+    char *zOpt = Tcl_GetStringFromObj(objv[i], &nOpt);
+
+    if( (nOpt>11 || nOpt<2 || strncmp("-sectorsize", zOpt, nOpt)) 
+     && (nOpt>16 || nOpt<2 || strncmp("-characteristics", zOpt, nOpt))
+    ){
+      Tcl_AppendResult(interp, 
+        "Bad option: \"", zOpt, 
+        "\" - must be \"-characteristics\" or \"-sectorsize\"", 0
+      );
+      return TCL_ERROR;
+    }
+    if( i==objc-1 ){
+      Tcl_AppendResult(interp, "Option requires an argument: \"", zOpt, "\"",0);
+      return TCL_ERROR;
+    }
+
+    if( zOpt[1]=='s' ){
+      if( Tcl_GetIntFromObj(interp, objv[i+1], &iSectorSize) ){
+        return TCL_ERROR;
+      }
+      setSectorsize = 1;
+    }else{
+      int j;
+      Tcl_Obj **apObj;
+      int nObj;
+      if( Tcl_ListObjGetElements(interp, objv[i+1], &nObj, &apObj) ){
+        return TCL_ERROR;
+      }
+      for(j=0; j<nObj; j++){
+        int rc;
+        int iChoice;
+        Tcl_Obj *pFlag = Tcl_DuplicateObj(apObj[j]);
+        Tcl_IncrRefCount(pFlag);
+        Tcl_UtfToLower(Tcl_GetString(pFlag));
+ 
+        rc = Tcl_GetIndexFromObjStruct(
+            interp, pFlag, aFlag, sizeof(aFlag[0]), "no such flag", 0, &iChoice
+        );
+        Tcl_DecrRefCount(pFlag);
+        if( rc ){
+          return TCL_ERROR;
+        }
+
+        iDc |= aFlag[iChoice].iValue;
+      }
+      setDeviceChar = 1;
+    }
+  }
+
+  if( setDeviceChar ){
+    *piDeviceChar = iDc;
+  }
+  if( setSectorsize ){
+    *piSectorSize = iSectorSize;
+  }
+
+  return TCL_OK;
+}
+
+/*
+** tclcmd:   sqlite_crash_enable ENABLE
+**
+** Parameter ENABLE must be a boolean value. If true, then the "crash"
+** vfs is added to the system. If false, it is removed.
+*/
+static int crashEnableCmd(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int isEnable;
+  static sqlite3_vfs crashVfs = {
+    2,                  /* iVersion */
+    0,                  /* szOsFile */
+    0,                  /* mxPathname */
+    0,                  /* pNext */
+    "crash",            /* zName */
+    0,                  /* pAppData */
+  
+    cfOpen,               /* xOpen */
+    cfDelete,             /* xDelete */
+    cfAccess,             /* xAccess */
+    cfFullPathname,       /* xFullPathname */
+    cfDlOpen,             /* xDlOpen */
+    cfDlError,            /* xDlError */
+    cfDlSym,              /* xDlSym */
+    cfDlClose,            /* xDlClose */
+    cfRandomness,         /* xRandomness */
+    cfSleep,              /* xSleep */
+    cfCurrentTime,        /* xCurrentTime */
+    0,                    /* xGetlastError */
+    0,                    /* xCurrentTimeInt64 */
+  };
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "ENABLE");
+    return TCL_ERROR;
+  }
+
+  if( Tcl_GetBooleanFromObj(interp, objv[1], &isEnable) ){
+    return TCL_ERROR;
+  }
+
+  if( (isEnable && crashVfs.pAppData) || (!isEnable && !crashVfs.pAppData) ){
+    return TCL_OK;
+  }
+
+  if( crashVfs.pAppData==0 ){
+    sqlite3_vfs *pOriginalVfs = sqlite3_vfs_find(0);
+    crashVfs.mxPathname = pOriginalVfs->mxPathname;
+    crashVfs.pAppData = (void *)pOriginalVfs;
+    crashVfs.szOsFile = sizeof(CrashFile) + pOriginalVfs->szOsFile;
+    sqlite3_vfs_register(&crashVfs, 0);
+  }else{
+    crashVfs.pAppData = 0;
+    sqlite3_vfs_unregister(&crashVfs);
+  }
+
+  return TCL_OK;
+}
+
+/*
+** tclcmd:   sqlite_crashparams ?OPTIONS? DELAY CRASHFILE
+**
+** This procedure implements a TCL command that enables crash testing
+** in testfixture.  Once enabled, crash testing cannot be disabled.
+**
+** Available options are "-characteristics" and "-sectorsize". Both require
+** an argument. For -sectorsize, this is the simulated sector size in
+** bytes. For -characteristics, the argument must be a list of io-capability
+** flags to simulate. Valid flags are "atomic", "atomic512", "atomic1K",
+** "atomic2K", "atomic4K", "atomic8K", "atomic16K", "atomic32K", 
+** "atomic64K", "sequential" and "safe_append".
+**
+** Example:
+**
+**   sqlite_crashparams -sect 1024 -char {atomic sequential} ./test.db 1
+**
+*/
+static int crashParamsObjCmd(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int iDelay;
+  const char *zCrashFile;
+  int nCrashFile, iDc, iSectorSize;
+
+  iDc = -1;
+  iSectorSize = -1;
+
+  if( objc<3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "?OPTIONS? DELAY CRASHFILE");
+    goto error;
+  }
+
+  zCrashFile = Tcl_GetStringFromObj(objv[objc-1], &nCrashFile);
+  if( nCrashFile>=sizeof(g.zCrashFile) ){
+    Tcl_AppendResult(interp, "Filename is too long: \"", zCrashFile, "\"", 0);
+    goto error;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[objc-2], &iDelay) ){
+    goto error;
+  }
+
+  if( processDevSymArgs(interp, objc-3, &objv[1], &iDc, &iSectorSize) ){
+    return TCL_ERROR;
+  }
+
+  if( iDc>=0 ){
+    g.iDeviceCharacteristics = iDc;
+  }
+  if( iSectorSize>=0 ){
+    g.iSectorSize = iSectorSize;
+  }
+
+  g.iCrash = iDelay;
+  memcpy(g.zCrashFile, zCrashFile, nCrashFile+1);
+  sqlite3CrashTestEnable = 1;
+  return TCL_OK;
+
+error:
+  return TCL_ERROR;
+}
+
+static int devSymObjCmd(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  void devsym_register(int iDeviceChar, int iSectorSize);
+
+  int iDc = -1;
+  int iSectorSize = -1;
+
+  if( processDevSymArgs(interp, objc-1, &objv[1], &iDc, &iSectorSize) ){
+    return TCL_ERROR;
+  }
+  devsym_register(iDc, iSectorSize);
+
+  return TCL_OK;
+}
+
+/*
+** tclcmd: register_jt_vfs ?-default? PARENT-VFS
+*/
+static int jtObjCmd(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int jt_register(char *, int);
+  char *zParent = 0;
+
+  if( objc!=2 && objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "?-default? PARENT-VFS");
+    return TCL_ERROR;
+  }
+  zParent = Tcl_GetString(objv[1]);
+  if( objc==3 ){
+    if( strcmp(zParent, "-default") ){
+      Tcl_AppendResult(interp, 
+          "bad option \"", zParent, "\": must be -default", 0
+      );
+      return TCL_ERROR;
+    }
+    zParent = Tcl_GetString(objv[2]);
+  }
+
+  if( !(*zParent) ){
+    zParent = 0;
+  }
+  if( jt_register(zParent, objc==3) ){
+    Tcl_AppendResult(interp, "Error in jt_register", 0);
+    return TCL_ERROR;
+  }
+
+  return TCL_OK;
+}
+
+/*
+** tclcmd: unregister_jt_vfs
+*/
+static int jtUnregisterObjCmd(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  void jt_unregister(void);
+
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+
+  jt_unregister();
+  return TCL_OK;
+}
+
+#endif /* SQLITE_OMIT_DISKIO */
+
+/*
+** This procedure registers the TCL procedures defined in this file.
+*/
+int Sqlitetest6_Init(Tcl_Interp *interp){
+#ifndef SQLITE_OMIT_DISKIO
+  Tcl_CreateObjCommand(interp, "sqlite3_crash_enable", crashEnableCmd, 0, 0);
+  Tcl_CreateObjCommand(interp, "sqlite3_crashparams", crashParamsObjCmd, 0, 0);
+  Tcl_CreateObjCommand(interp, "sqlite3_simulate_device", devSymObjCmd, 0, 0);
+  Tcl_CreateObjCommand(interp, "register_jt_vfs", jtObjCmd, 0, 0);
+  Tcl_CreateObjCommand(interp, "unregister_jt_vfs", jtUnregisterObjCmd, 0, 0);
+#endif
+  return TCL_OK;
+}
+
+#endif /* SQLITE_TEST */
diff --git a/src/test7.c b/src/test7.c
new file mode 100644
index 0000000..852cd1d
--- /dev/null
+++ b/src/test7.c
@@ -0,0 +1,723 @@
+/*
+** 2006 January 09
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Code for testing the client/server version of the SQLite library.
+** Derived from test4.c.
+*/
+#include "sqliteInt.h"
+#include "tcl.h"
+
+/*
+** This test only works on UNIX with a SQLITE_THREADSAFE build that includes
+** the SQLITE_SERVER option.
+*/
+#if defined(SQLITE_SERVER) && !defined(SQLITE_OMIT_SHARED_CACHE) && \
+    SQLITE_OS_UNIX && SQLITE_THREADSAFE
+
+#include <stdlib.h>
+#include <string.h>
+#include <pthread.h>
+#include <sched.h>
+#include <ctype.h>
+
+/*
+** Interfaces defined in server.c
+*/
+int sqlite3_client_open(const char*, sqlite3**);
+int sqlite3_client_prepare(sqlite3*,const char*,int,
+                           sqlite3_stmt**,const char**);
+int sqlite3_client_step(sqlite3_stmt*);
+int sqlite3_client_reset(sqlite3_stmt*);
+int sqlite3_client_finalize(sqlite3_stmt*);
+int sqlite3_client_close(sqlite3*);
+int sqlite3_server_start(void);
+int sqlite3_server_stop(void);
+
+/*
+** Each thread is controlled by an instance of the following
+** structure.
+*/
+typedef struct Thread Thread;
+struct Thread {
+  /* The first group of fields are writable by the supervisor thread
+  ** and read-only to the client threads
+  */
+  char *zFilename;         /* Name of database file */
+  void (*xOp)(Thread*);    /* next operation to do */
+  char *zArg;              /* argument usable by xOp */
+  volatile int opnum;      /* Operation number */
+  volatile int busy;       /* True if this thread is in use */
+
+  /* The next group of fields are writable by the client threads 
+  ** but read-only to the superviser thread.
+  */
+  volatile int completed;  /* Number of operations completed */
+  sqlite3 *db;             /* Open database */
+  sqlite3_stmt *pStmt;     /* Pending operation */
+  char *zErr;              /* operation error */
+  char *zStaticErr;        /* Static error message */
+  int rc;                  /* operation return code */
+  int argc;                /* number of columns in result */
+  const char *argv[100];   /* result columns */
+  const char *colv[100];   /* result column names */
+};
+
+/*
+** There can be as many as 26 threads running at once.  Each is named
+** by a capital letter: A, B, C, ..., Y, Z.
+*/
+#define N_THREAD 26
+static Thread threadset[N_THREAD];
+
+/*
+** The main loop for a thread.  Threads use busy waiting. 
+*/
+static void *client_main(void *pArg){
+  Thread *p = (Thread*)pArg;
+  if( p->db ){
+    sqlite3_client_close(p->db);
+  }
+  sqlite3_client_open(p->zFilename, &p->db);
+  if( SQLITE_OK!=sqlite3_errcode(p->db) ){
+    p->zErr = strdup(sqlite3_errmsg(p->db));
+    sqlite3_client_close(p->db);
+    p->db = 0;
+  }
+  p->pStmt = 0;
+  p->completed = 1;
+  while( p->opnum<=p->completed ) sched_yield();
+  while( p->xOp ){
+    if( p->zErr && p->zErr!=p->zStaticErr ){
+      sqlite3_free(p->zErr);
+      p->zErr = 0;
+    }
+    (*p->xOp)(p);
+    p->completed++;
+    while( p->opnum<=p->completed ) sched_yield();
+  }
+  if( p->pStmt ){
+    sqlite3_client_finalize(p->pStmt);
+    p->pStmt = 0;
+  }
+  if( p->db ){
+    sqlite3_client_close(p->db);
+    p->db = 0;
+  }
+  if( p->zErr && p->zErr!=p->zStaticErr ){
+    sqlite3_free(p->zErr);
+    p->zErr = 0;
+  }
+  p->completed++;
+#ifndef SQLITE_OMIT_DEPRECATED
+  sqlite3_thread_cleanup();
+#endif
+  return 0;
+}
+
+/*
+** Get a thread ID which is an upper case letter.  Return the index.
+** If the argument is not a valid thread ID put an error message in
+** the interpreter and return -1.
+*/
+static int parse_client_id(Tcl_Interp *interp, const char *zArg){
+  if( zArg==0 || zArg[0]==0 || zArg[1]!=0 || !isupper((unsigned char)zArg[0]) ){
+    Tcl_AppendResult(interp, "thread ID must be an upper case letter", 0);
+    return -1;
+  }
+  return zArg[0] - 'A';
+}
+
+/*
+** Usage:    client_create NAME  FILENAME
+**
+** NAME should be an upper case letter.  Start the thread running with
+** an open connection to the given database.
+*/
+static int tcl_client_create(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+  pthread_t x;
+  int rc;
+
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID FILENAME", 0);
+    return TCL_ERROR;
+  }
+  i = parse_client_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( threadset[i].busy ){
+    Tcl_AppendResult(interp, "thread ", argv[1], " is already running", 0);
+    return TCL_ERROR;
+  }
+  threadset[i].busy = 1;
+  sqlite3_free(threadset[i].zFilename);
+  threadset[i].zFilename = sqlite3_mprintf("%s", argv[2]);
+  threadset[i].opnum = 1;
+  threadset[i].completed = 0;
+  rc = pthread_create(&x, 0, client_main, &threadset[i]);
+  if( rc ){
+    Tcl_AppendResult(interp, "failed to create the thread", 0);
+    sqlite3_free(threadset[i].zFilename);
+    threadset[i].busy = 0;
+    return TCL_ERROR;
+  }
+  pthread_detach(x);
+  sqlite3_server_start();
+  return TCL_OK;
+}
+
+/*
+** Wait for a thread to reach its idle state.
+*/
+static void client_wait(Thread *p){
+  while( p->opnum>p->completed ) sched_yield();
+}
+
+/*
+** Usage:  client_wait ID
+**
+** Wait on thread ID to reach its idle state.
+*/
+static int tcl_client_wait(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID", 0);
+    return TCL_ERROR;
+  }
+  i = parse_client_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  client_wait(&threadset[i]);
+  return TCL_OK;
+}
+
+/*
+** Stop a thread.
+*/
+static void stop_thread(Thread *p){
+  client_wait(p);
+  p->xOp = 0;
+  p->opnum++;
+  client_wait(p);
+  sqlite3_free(p->zArg);
+  p->zArg = 0;
+  sqlite3_free(p->zFilename);
+  p->zFilename = 0;
+  p->busy = 0;
+}
+
+/*
+** Usage:  client_halt ID
+**
+** Cause a client thread to shut itself down.  Wait for the shutdown to be
+** completed.  If ID is "*" then stop all client threads.
+*/
+static int tcl_client_halt(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID", 0);
+    return TCL_ERROR;
+  }
+  if( argv[1][0]=='*' && argv[1][1]==0 ){
+    for(i=0; i<N_THREAD; i++){
+      if( threadset[i].busy ){
+        stop_thread(&threadset[i]);
+      }
+    }
+  }else{
+    i = parse_client_id(interp, argv[1]);
+    if( i<0 ) return TCL_ERROR;
+    if( !threadset[i].busy ){
+      Tcl_AppendResult(interp, "no such thread", 0);
+      return TCL_ERROR;
+    }
+    stop_thread(&threadset[i]);
+  }
+
+  /* If no client threads are still running, also stop the server */
+  for(i=0; i<N_THREAD && threadset[i].busy==0; i++){}
+  if( i>=N_THREAD ){
+    sqlite3_server_stop();
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage: client_argc  ID
+**
+** Wait on the most recent client_step to complete, then return the
+** number of columns in the result set.
+*/
+static int tcl_client_argc(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+  char zBuf[100];
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID", 0);
+    return TCL_ERROR;
+  }
+  i = parse_client_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  client_wait(&threadset[i]);
+  sprintf(zBuf, "%d", threadset[i].argc);
+  Tcl_AppendResult(interp, zBuf, 0);
+  return TCL_OK;
+}
+
+/*
+** Usage: client_argv  ID   N
+**
+** Wait on the most recent client_step to complete, then return the
+** value of the N-th columns in the result set.
+*/
+static int tcl_client_argv(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+  int n;
+
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID N", 0);
+    return TCL_ERROR;
+  }
+  i = parse_client_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  if( Tcl_GetInt(interp, argv[2], &n) ) return TCL_ERROR;
+  client_wait(&threadset[i]);
+  if( n<0 || n>=threadset[i].argc ){
+    Tcl_AppendResult(interp, "column number out of range", 0);
+    return TCL_ERROR;
+  }
+  Tcl_AppendResult(interp, threadset[i].argv[n], 0);
+  return TCL_OK;
+}
+
+/*
+** Usage: client_colname  ID   N
+**
+** Wait on the most recent client_step to complete, then return the
+** name of the N-th columns in the result set.
+*/
+static int tcl_client_colname(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+  int n;
+
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID N", 0);
+    return TCL_ERROR;
+  }
+  i = parse_client_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  if( Tcl_GetInt(interp, argv[2], &n) ) return TCL_ERROR;
+  client_wait(&threadset[i]);
+  if( n<0 || n>=threadset[i].argc ){
+    Tcl_AppendResult(interp, "column number out of range", 0);
+    return TCL_ERROR;
+  }
+  Tcl_AppendResult(interp, threadset[i].colv[n], 0);
+  return TCL_OK;
+}
+
+/*
+** Usage: client_result  ID
+**
+** Wait on the most recent operation to complete, then return the
+** result code from that operation.
+*/
+static int tcl_client_result(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+  const char *zName;
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID", 0);
+    return TCL_ERROR;
+  }
+  i = parse_client_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  client_wait(&threadset[i]);
+  switch( threadset[i].rc ){
+    case SQLITE_OK:         zName = "SQLITE_OK";          break;
+    case SQLITE_ERROR:      zName = "SQLITE_ERROR";       break;
+    case SQLITE_PERM:       zName = "SQLITE_PERM";        break;
+    case SQLITE_ABORT:      zName = "SQLITE_ABORT";       break;
+    case SQLITE_BUSY:       zName = "SQLITE_BUSY";        break;
+    case SQLITE_LOCKED:     zName = "SQLITE_LOCKED";      break;
+    case SQLITE_NOMEM:      zName = "SQLITE_NOMEM";       break;
+    case SQLITE_READONLY:   zName = "SQLITE_READONLY";    break;
+    case SQLITE_INTERRUPT:  zName = "SQLITE_INTERRUPT";   break;
+    case SQLITE_IOERR:      zName = "SQLITE_IOERR";       break;
+    case SQLITE_CORRUPT:    zName = "SQLITE_CORRUPT";     break;
+    case SQLITE_FULL:       zName = "SQLITE_FULL";        break;
+    case SQLITE_CANTOPEN:   zName = "SQLITE_CANTOPEN";    break;
+    case SQLITE_PROTOCOL:   zName = "SQLITE_PROTOCOL";    break;
+    case SQLITE_EMPTY:      zName = "SQLITE_EMPTY";       break;
+    case SQLITE_SCHEMA:     zName = "SQLITE_SCHEMA";      break;
+    case SQLITE_CONSTRAINT: zName = "SQLITE_CONSTRAINT";  break;
+    case SQLITE_MISMATCH:   zName = "SQLITE_MISMATCH";    break;
+    case SQLITE_MISUSE:     zName = "SQLITE_MISUSE";      break;
+    case SQLITE_NOLFS:      zName = "SQLITE_NOLFS";       break;
+    case SQLITE_AUTH:       zName = "SQLITE_AUTH";        break;
+    case SQLITE_FORMAT:     zName = "SQLITE_FORMAT";      break;
+    case SQLITE_RANGE:      zName = "SQLITE_RANGE";       break;
+    case SQLITE_ROW:        zName = "SQLITE_ROW";         break;
+    case SQLITE_DONE:       zName = "SQLITE_DONE";        break;
+    default:                zName = "SQLITE_Unknown";     break;
+  }
+  Tcl_AppendResult(interp, zName, 0);
+  return TCL_OK;
+}
+
+/*
+** Usage: client_error  ID
+**
+** Wait on the most recent operation to complete, then return the
+** error string.
+*/
+static int tcl_client_error(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID", 0);
+    return TCL_ERROR;
+  }
+  i = parse_client_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  client_wait(&threadset[i]);
+  Tcl_AppendResult(interp, threadset[i].zErr, 0);
+  return TCL_OK;
+}
+
+/*
+** This procedure runs in the thread to compile an SQL statement.
+*/
+static void do_compile(Thread *p){
+  if( p->db==0 ){
+    p->zErr = p->zStaticErr = "no database is open";
+    p->rc = SQLITE_ERROR;
+    return;
+  }
+  if( p->pStmt ){
+    sqlite3_client_finalize(p->pStmt);
+    p->pStmt = 0;
+  }
+  p->rc = sqlite3_client_prepare(p->db, p->zArg, -1, &p->pStmt, 0);
+}
+
+/*
+** Usage: client_compile ID SQL
+**
+** Compile a new virtual machine.
+*/
+static int tcl_client_compile(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID SQL", 0);
+    return TCL_ERROR;
+  }
+  i = parse_client_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  client_wait(&threadset[i]);
+  threadset[i].xOp = do_compile;
+  sqlite3_free(threadset[i].zArg);
+  threadset[i].zArg = sqlite3_mprintf("%s", argv[2]);
+  threadset[i].opnum++;
+  return TCL_OK;
+}
+
+/*
+** This procedure runs in the thread to step the virtual machine.
+*/
+static void do_step(Thread *p){
+  int i;
+  if( p->pStmt==0 ){
+    p->zErr = p->zStaticErr = "no virtual machine available";
+    p->rc = SQLITE_ERROR;
+    return;
+  }
+  p->rc = sqlite3_client_step(p->pStmt);
+  if( p->rc==SQLITE_ROW ){
+    p->argc = sqlite3_column_count(p->pStmt);
+    for(i=0; i<sqlite3_data_count(p->pStmt); i++){
+      p->argv[i] = (char*)sqlite3_column_text(p->pStmt, i);
+    }
+    for(i=0; i<p->argc; i++){
+      p->colv[i] = sqlite3_column_name(p->pStmt, i);
+    }
+  }
+}
+
+/*
+** Usage: client_step ID
+**
+** Advance the virtual machine by one step
+*/
+static int tcl_client_step(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " IDL", 0);
+    return TCL_ERROR;
+  }
+  i = parse_client_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  client_wait(&threadset[i]);
+  threadset[i].xOp = do_step;
+  threadset[i].opnum++;
+  return TCL_OK;
+}
+
+/*
+** This procedure runs in the thread to finalize a virtual machine.
+*/
+static void do_finalize(Thread *p){
+  if( p->pStmt==0 ){
+    p->zErr = p->zStaticErr = "no virtual machine available";
+    p->rc = SQLITE_ERROR;
+    return;
+  }
+  p->rc = sqlite3_client_finalize(p->pStmt);
+  p->pStmt = 0;
+}
+
+/*
+** Usage: client_finalize ID
+**
+** Finalize the virtual machine.
+*/
+static int tcl_client_finalize(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " IDL", 0);
+    return TCL_ERROR;
+  }
+  i = parse_client_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  client_wait(&threadset[i]);
+  threadset[i].xOp = do_finalize;
+  sqlite3_free(threadset[i].zArg);
+  threadset[i].zArg = 0;
+  threadset[i].opnum++;
+  return TCL_OK;
+}
+
+/*
+** This procedure runs in the thread to reset a virtual machine.
+*/
+static void do_reset(Thread *p){
+  if( p->pStmt==0 ){
+    p->zErr = p->zStaticErr = "no virtual machine available";
+    p->rc = SQLITE_ERROR;
+    return;
+  }
+  p->rc = sqlite3_client_reset(p->pStmt);
+  p->pStmt = 0;
+}
+
+/*
+** Usage: client_reset ID
+**
+** Finalize the virtual machine.
+*/
+static int tcl_client_reset(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i;
+  if( argc!=2 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " IDL", 0);
+    return TCL_ERROR;
+  }
+  i = parse_client_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  client_wait(&threadset[i]);
+  threadset[i].xOp = do_reset;
+  sqlite3_free(threadset[i].zArg);
+  threadset[i].zArg = 0;
+  threadset[i].opnum++;
+  return TCL_OK;
+}
+
+/*
+** Usage: client_swap ID ID
+**
+** Interchange the sqlite* pointer between two threads.
+*/
+static int tcl_client_swap(
+  void *NotUsed,
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int argc,              /* Number of arguments */
+  const char **argv      /* Text of each argument */
+){
+  int i, j;
+  sqlite3 *temp;
+  if( argc!=3 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
+       " ID1 ID2", 0);
+    return TCL_ERROR;
+  }
+  i = parse_client_id(interp, argv[1]);
+  if( i<0 ) return TCL_ERROR;
+  if( !threadset[i].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  client_wait(&threadset[i]);
+  j = parse_client_id(interp, argv[2]);
+  if( j<0 ) return TCL_ERROR;
+  if( !threadset[j].busy ){
+    Tcl_AppendResult(interp, "no such thread", 0);
+    return TCL_ERROR;
+  }
+  client_wait(&threadset[j]);
+  temp = threadset[i].db;
+  threadset[i].db = threadset[j].db;
+  threadset[j].db = temp;
+  return TCL_OK;
+}
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetest7_Init(Tcl_Interp *interp){
+  static struct {
+     char *zName;
+     Tcl_CmdProc *xProc;
+  } aCmd[] = {
+     { "client_create",     (Tcl_CmdProc*)tcl_client_create     },
+     { "client_wait",       (Tcl_CmdProc*)tcl_client_wait       },
+     { "client_halt",       (Tcl_CmdProc*)tcl_client_halt       },
+     { "client_argc",       (Tcl_CmdProc*)tcl_client_argc       },
+     { "client_argv",       (Tcl_CmdProc*)tcl_client_argv       },
+     { "client_colname",    (Tcl_CmdProc*)tcl_client_colname    },
+     { "client_result",     (Tcl_CmdProc*)tcl_client_result     },
+     { "client_error",      (Tcl_CmdProc*)tcl_client_error      },
+     { "client_compile",    (Tcl_CmdProc*)tcl_client_compile    },
+     { "client_step",       (Tcl_CmdProc*)tcl_client_step       },
+     { "client_reset",      (Tcl_CmdProc*)tcl_client_reset      },
+     { "client_finalize",   (Tcl_CmdProc*)tcl_client_finalize   },
+     { "client_swap",       (Tcl_CmdProc*)tcl_client_swap       },
+  };
+  int i;
+
+  for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){
+    Tcl_CreateCommand(interp, aCmd[i].zName, aCmd[i].xProc, 0, 0);
+  }
+  return TCL_OK;
+}
+#else
+int Sqlitetest7_Init(Tcl_Interp *interp){ return TCL_OK; }
+#endif /* SQLITE_OS_UNIX */
diff --git a/src/test8.c b/src/test8.c
new file mode 100644
index 0000000..283d790
--- /dev/null
+++ b/src/test8.c
@@ -0,0 +1,1391 @@
+/*
+** 2006 June 10
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Code for testing the virtual table interfaces.  This code
+** is not included in the SQLite library.  It is used for automated
+** testing of the SQLite library.
+*/
+#include "sqliteInt.h"
+#include "tcl.h"
+#include <stdlib.h>
+#include <string.h>
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+
+typedef struct echo_vtab echo_vtab;
+typedef struct echo_cursor echo_cursor;
+
+/*
+** The test module defined in this file uses four global Tcl variables to
+** commicate with test-scripts:
+**
+**     $::echo_module
+**     $::echo_module_sync_fail
+**     $::echo_module_begin_fail
+**     $::echo_module_cost
+**
+** The variable ::echo_module is a list. Each time one of the following
+** methods is called, one or more elements are appended to the list.
+** This is used for automated testing of virtual table modules.
+**
+** The ::echo_module_sync_fail variable is set by test scripts and read
+** by code in this file. If it is set to the name of a real table in the
+** the database, then all xSync operations on echo virtual tables that
+** use the named table as a backing store will fail.
+*/
+
+/*
+** Errors can be provoked within the following echo virtual table methods:
+**
+**   xBestIndex   xOpen     xFilter   xNext   
+**   xColumn      xRowid    xUpdate   xSync   
+**   xBegin       xRename
+**
+** This is done by setting the global tcl variable:
+**
+**   echo_module_fail($method,$tbl)
+**
+** where $method is set to the name of the virtual table method to fail
+** (i.e. "xBestIndex") and $tbl is the name of the table being echoed (not
+** the name of the virtual table, the name of the underlying real table).
+*/
+
+/* 
+** An echo virtual-table object.
+**
+** echo.vtab.aIndex is an array of booleans. The nth entry is true if 
+** the nth column of the real table is the left-most column of an index
+** (implicit or otherwise). In other words, if SQLite can optimize
+** a query like "SELECT * FROM real_table WHERE col = ?".
+**
+** Member variable aCol[] contains copies of the column names of the real
+** table.
+*/
+struct echo_vtab {
+  sqlite3_vtab base;
+  Tcl_Interp *interp;     /* Tcl interpreter containing debug variables */
+  sqlite3 *db;            /* Database connection */
+
+  int isPattern;
+  int inTransaction;      /* True if within a transaction */
+  char *zThis;            /* Name of the echo table */
+  char *zTableName;       /* Name of the real table */
+  char *zLogName;         /* Name of the log table */
+  int nCol;               /* Number of columns in the real table */
+  int *aIndex;            /* Array of size nCol. True if column has an index */
+  char **aCol;            /* Array of size nCol. Column names */
+};
+
+/* An echo cursor object */
+struct echo_cursor {
+  sqlite3_vtab_cursor base;
+  sqlite3_stmt *pStmt;
+};
+
+static int simulateVtabError(echo_vtab *p, const char *zMethod){
+  const char *zErr;
+  char zVarname[128];
+  zVarname[127] = '\0';
+  sqlite3_snprintf(127, zVarname, "echo_module_fail(%s,%s)", zMethod, p->zTableName);
+  zErr = Tcl_GetVar(p->interp, zVarname, TCL_GLOBAL_ONLY);
+  if( zErr ){
+    p->base.zErrMsg = sqlite3_mprintf("echo-vtab-error: %s", zErr);
+  }
+  return (zErr!=0);
+}
+
+/*
+** Convert an SQL-style quoted string into a normal string by removing
+** the quote characters.  The conversion is done in-place.  If the
+** input does not begin with a quote character, then this routine
+** is a no-op.
+**
+** Examples:
+**
+**     "abc"   becomes   abc
+**     'xyz'   becomes   xyz
+**     [pqr]   becomes   pqr
+**     `mno`   becomes   mno
+*/
+static void dequoteString(char *z){
+  int quote;
+  int i, j;
+  if( z==0 ) return;
+  quote = z[0];
+  switch( quote ){
+    case '\'':  break;
+    case '"':   break;
+    case '`':   break;                /* For MySQL compatibility */
+    case '[':   quote = ']';  break;  /* For MS SqlServer compatibility */
+    default:    return;
+  }
+  for(i=1, j=0; z[i]; i++){
+    if( z[i]==quote ){
+      if( z[i+1]==quote ){
+        z[j++] = quote;
+        i++;
+      }else{
+        z[j++] = 0;
+        break;
+      }
+    }else{
+      z[j++] = z[i];
+    }
+  }
+}
+
+/*
+** Retrieve the column names for the table named zTab via database
+** connection db. SQLITE_OK is returned on success, or an sqlite error
+** code otherwise.
+**
+** If successful, the number of columns is written to *pnCol. *paCol is
+** set to point at sqlite3_malloc()'d space containing the array of
+** nCol column names. The caller is responsible for calling sqlite3_free
+** on *paCol.
+*/
+static int getColumnNames(
+  sqlite3 *db, 
+  const char *zTab,
+  char ***paCol, 
+  int *pnCol
+){
+  char **aCol = 0;
+  char *zSql;
+  sqlite3_stmt *pStmt = 0;
+  int rc = SQLITE_OK;
+  int nCol = 0;
+
+  /* Prepare the statement "SELECT * FROM <tbl>". The column names
+  ** of the result set of the compiled SELECT will be the same as
+  ** the column names of table <tbl>.
+  */
+  zSql = sqlite3_mprintf("SELECT * FROM %Q", zTab);
+  if( !zSql ){
+    rc = SQLITE_NOMEM;
+    goto out;
+  }
+  rc = sqlite3_prepare(db, zSql, -1, &pStmt, 0);
+  sqlite3_free(zSql);
+
+  if( rc==SQLITE_OK ){
+    int ii;
+    int nBytes;
+    char *zSpace;
+    nCol = sqlite3_column_count(pStmt);
+
+    /* Figure out how much space to allocate for the array of column names 
+    ** (including space for the strings themselves). Then allocate it.
+    */
+    nBytes = sizeof(char *) * nCol;
+    for(ii=0; ii<nCol; ii++){
+      const char *zName = sqlite3_column_name(pStmt, ii);
+      if( !zName ){
+        rc = SQLITE_NOMEM;
+        goto out;
+      }
+      nBytes += strlen(zName)+1;
+    }
+    aCol = (char **)sqlite3MallocZero(nBytes);
+    if( !aCol ){
+      rc = SQLITE_NOMEM;
+      goto out;
+    }
+
+    /* Copy the column names into the allocated space and set up the
+    ** pointers in the aCol[] array.
+    */
+    zSpace = (char *)(&aCol[nCol]);
+    for(ii=0; ii<nCol; ii++){
+      aCol[ii] = zSpace;
+      zSpace += sprintf(zSpace, "%s", sqlite3_column_name(pStmt, ii));
+      zSpace++;
+    }
+    assert( (zSpace-nBytes)==(char *)aCol );
+  }
+
+  *paCol = aCol;
+  *pnCol = nCol;
+
+out:
+  sqlite3_finalize(pStmt);
+  return rc;
+}
+
+/*
+** Parameter zTab is the name of a table in database db with nCol 
+** columns. This function allocates an array of integers nCol in 
+** size and populates it according to any implicit or explicit 
+** indices on table zTab.
+**
+** If successful, SQLITE_OK is returned and *paIndex set to point 
+** at the allocated array. Otherwise, an error code is returned.
+**
+** See comments associated with the member variable aIndex above 
+** "struct echo_vtab" for details of the contents of the array.
+*/
+static int getIndexArray(
+  sqlite3 *db,             /* Database connection */
+  const char *zTab,        /* Name of table in database db */
+  int nCol,
+  int **paIndex
+){
+  sqlite3_stmt *pStmt = 0;
+  int *aIndex = 0;
+  int rc;
+  char *zSql;
+
+  /* Allocate space for the index array */
+  aIndex = (int *)sqlite3MallocZero(sizeof(int) * nCol);
+  if( !aIndex ){
+    rc = SQLITE_NOMEM;
+    goto get_index_array_out;
+  }
+
+  /* Compile an sqlite pragma to loop through all indices on table zTab */
+  zSql = sqlite3_mprintf("PRAGMA index_list(%s)", zTab);
+  if( !zSql ){
+    rc = SQLITE_NOMEM;
+    goto get_index_array_out;
+  }
+  rc = sqlite3_prepare(db, zSql, -1, &pStmt, 0);
+  sqlite3_free(zSql);
+
+  /* For each index, figure out the left-most column and set the 
+  ** corresponding entry in aIndex[] to 1.
+  */
+  while( pStmt && sqlite3_step(pStmt)==SQLITE_ROW ){
+    const char *zIdx = (const char *)sqlite3_column_text(pStmt, 1);
+    sqlite3_stmt *pStmt2 = 0;
+    zSql = sqlite3_mprintf("PRAGMA index_info(%s)", zIdx);
+    if( !zSql ){
+      rc = SQLITE_NOMEM;
+      goto get_index_array_out;
+    }
+    rc = sqlite3_prepare(db, zSql, -1, &pStmt2, 0);
+    sqlite3_free(zSql);
+    if( pStmt2 && sqlite3_step(pStmt2)==SQLITE_ROW ){
+      int cid = sqlite3_column_int(pStmt2, 1);
+      assert( cid>=0 && cid<nCol );
+      aIndex[cid] = 1;
+    }
+    if( pStmt2 ){
+      rc = sqlite3_finalize(pStmt2);
+    }
+    if( rc!=SQLITE_OK ){
+      goto get_index_array_out;
+    }
+  }
+
+
+get_index_array_out:
+  if( pStmt ){
+    int rc2 = sqlite3_finalize(pStmt);
+    if( rc==SQLITE_OK ){
+      rc = rc2;
+    }
+  }
+  if( rc!=SQLITE_OK ){
+    sqlite3_free(aIndex);
+    aIndex = 0;
+  }
+  *paIndex = aIndex;
+  return rc;
+}
+
+/*
+** Global Tcl variable $echo_module is a list. This routine appends
+** the string element zArg to that list in interpreter interp.
+*/
+static void appendToEchoModule(Tcl_Interp *interp, const char *zArg){
+  int flags = (TCL_APPEND_VALUE | TCL_LIST_ELEMENT | TCL_GLOBAL_ONLY);
+  Tcl_SetVar(interp, "echo_module", (zArg?zArg:""), flags);
+}
+
+/*
+** This function is called from within the echo-modules xCreate and
+** xConnect methods. The argc and argv arguments are copies of those 
+** passed to the calling method. This function is responsible for
+** calling sqlite3_declare_vtab() to declare the schema of the virtual
+** table being created or connected.
+**
+** If the constructor was passed just one argument, i.e.:
+**
+**   CREATE TABLE t1 AS echo(t2);
+**
+** Then t2 is assumed to be the name of a *real* database table. The
+** schema of the virtual table is declared by passing a copy of the 
+** CREATE TABLE statement for the real table to sqlite3_declare_vtab().
+** Hence, the virtual table should have exactly the same column names and 
+** types as the real table.
+*/
+static int echoDeclareVtab(
+  echo_vtab *pVtab, 
+  sqlite3 *db 
+){
+  int rc = SQLITE_OK;
+
+  if( pVtab->zTableName ){
+    sqlite3_stmt *pStmt = 0;
+    rc = sqlite3_prepare(db, 
+        "SELECT sql FROM sqlite_master WHERE type = 'table' AND name = ?",
+        -1, &pStmt, 0);
+    if( rc==SQLITE_OK ){
+      sqlite3_bind_text(pStmt, 1, pVtab->zTableName, -1, 0);
+      if( sqlite3_step(pStmt)==SQLITE_ROW ){
+        int rc2;
+        const char *zCreateTable = (const char *)sqlite3_column_text(pStmt, 0);
+        rc = sqlite3_declare_vtab(db, zCreateTable);
+        rc2 = sqlite3_finalize(pStmt);
+        if( rc==SQLITE_OK ){
+          rc = rc2;
+        }
+      } else {
+        rc = sqlite3_finalize(pStmt);
+        if( rc==SQLITE_OK ){ 
+          rc = SQLITE_ERROR;
+        }
+      }
+      if( rc==SQLITE_OK ){
+        rc = getColumnNames(db, pVtab->zTableName, &pVtab->aCol, &pVtab->nCol);
+      }
+      if( rc==SQLITE_OK ){
+        rc = getIndexArray(db, pVtab->zTableName, pVtab->nCol, &pVtab->aIndex);
+      }
+    }
+  }
+
+  return rc;
+}
+
+/*
+** This function frees all runtime structures associated with the virtual
+** table pVtab.
+*/
+static int echoDestructor(sqlite3_vtab *pVtab){
+  echo_vtab *p = (echo_vtab*)pVtab;
+  sqlite3_free(p->aIndex);
+  sqlite3_free(p->aCol);
+  sqlite3_free(p->zThis);
+  sqlite3_free(p->zTableName);
+  sqlite3_free(p->zLogName);
+  sqlite3_free(p);
+  return 0;
+}
+
+typedef struct EchoModule EchoModule;
+struct EchoModule {
+  Tcl_Interp *interp;
+};
+
+/*
+** This function is called to do the work of the xConnect() method -
+** to allocate the required in-memory structures for a newly connected
+** virtual table.
+*/
+static int echoConstructor(
+  sqlite3 *db,
+  void *pAux,
+  int argc, const char *const*argv,
+  sqlite3_vtab **ppVtab,
+  char **pzErr
+){
+  int rc;
+  int i;
+  echo_vtab *pVtab;
+
+  /* Allocate the sqlite3_vtab/echo_vtab structure itself */
+  pVtab = sqlite3MallocZero( sizeof(*pVtab) );
+  if( !pVtab ){
+    return SQLITE_NOMEM;
+  }
+  pVtab->interp = ((EchoModule *)pAux)->interp;
+  pVtab->db = db;
+
+  /* Allocate echo_vtab.zThis */
+  pVtab->zThis = sqlite3_mprintf("%s", argv[2]);
+  if( !pVtab->zThis ){
+    echoDestructor((sqlite3_vtab *)pVtab);
+    return SQLITE_NOMEM;
+  }
+
+  /* Allocate echo_vtab.zTableName */
+  if( argc>3 ){
+    pVtab->zTableName = sqlite3_mprintf("%s", argv[3]);
+    dequoteString(pVtab->zTableName);
+    if( pVtab->zTableName && pVtab->zTableName[0]=='*' ){
+      char *z = sqlite3_mprintf("%s%s", argv[2], &(pVtab->zTableName[1]));
+      sqlite3_free(pVtab->zTableName);
+      pVtab->zTableName = z;
+      pVtab->isPattern = 1;
+    }
+    if( !pVtab->zTableName ){
+      echoDestructor((sqlite3_vtab *)pVtab);
+      return SQLITE_NOMEM;
+    }
+  }
+
+  /* Log the arguments to this function to Tcl var ::echo_module */
+  for(i=0; i<argc; i++){
+    appendToEchoModule(pVtab->interp, argv[i]);
+  }
+
+  /* Invoke sqlite3_declare_vtab and set up other members of the echo_vtab
+  ** structure. If an error occurs, delete the sqlite3_vtab structure and
+  ** return an error code.
+  */
+  rc = echoDeclareVtab(pVtab, db);
+  if( rc!=SQLITE_OK ){
+    echoDestructor((sqlite3_vtab *)pVtab);
+    return rc;
+  }
+
+  /* Success. Set *ppVtab and return */
+  *ppVtab = &pVtab->base;
+  return SQLITE_OK;
+}
+
+/* 
+** Echo virtual table module xCreate method.
+*/
+static int echoCreate(
+  sqlite3 *db,
+  void *pAux,
+  int argc, const char *const*argv,
+  sqlite3_vtab **ppVtab,
+  char **pzErr
+){
+  int rc = SQLITE_OK;
+  appendToEchoModule(((EchoModule *)pAux)->interp, "xCreate");
+  rc = echoConstructor(db, pAux, argc, argv, ppVtab, pzErr);
+
+  /* If there were two arguments passed to the module at the SQL level 
+  ** (i.e. "CREATE VIRTUAL TABLE tbl USING echo(arg1, arg2)"), then 
+  ** the second argument is used as a table name. Attempt to create
+  ** such a table with a single column, "logmsg". This table will
+  ** be used to log calls to the xUpdate method. It will be deleted
+  ** when the virtual table is DROPed.
+  **
+  ** Note: The main point of this is to test that we can drop tables
+  ** from within an xDestroy method call.
+  */
+  if( rc==SQLITE_OK && argc==5 ){
+    char *zSql;
+    echo_vtab *pVtab = *(echo_vtab **)ppVtab;
+    pVtab->zLogName = sqlite3_mprintf("%s", argv[4]);
+    zSql = sqlite3_mprintf("CREATE TABLE %Q(logmsg)", pVtab->zLogName);
+    rc = sqlite3_exec(db, zSql, 0, 0, 0);
+    sqlite3_free(zSql);
+    if( rc!=SQLITE_OK ){
+      *pzErr = sqlite3_mprintf("%s", sqlite3_errmsg(db));
+    }
+  }
+
+  if( *ppVtab && rc!=SQLITE_OK ){
+    echoDestructor(*ppVtab);
+    *ppVtab = 0;
+  }
+
+  if( rc==SQLITE_OK ){
+    (*(echo_vtab**)ppVtab)->inTransaction = 1;
+  }
+
+  return rc;
+}
+
+/* 
+** Echo virtual table module xConnect method.
+*/
+static int echoConnect(
+  sqlite3 *db,
+  void *pAux,
+  int argc, const char *const*argv,
+  sqlite3_vtab **ppVtab,
+  char **pzErr
+){
+  appendToEchoModule(((EchoModule *)pAux)->interp, "xConnect");
+  return echoConstructor(db, pAux, argc, argv, ppVtab, pzErr);
+}
+
+/* 
+** Echo virtual table module xDisconnect method.
+*/
+static int echoDisconnect(sqlite3_vtab *pVtab){
+  appendToEchoModule(((echo_vtab *)pVtab)->interp, "xDisconnect");
+  return echoDestructor(pVtab);
+}
+
+/* 
+** Echo virtual table module xDestroy method.
+*/
+static int echoDestroy(sqlite3_vtab *pVtab){
+  int rc = SQLITE_OK;
+  echo_vtab *p = (echo_vtab *)pVtab;
+  appendToEchoModule(((echo_vtab *)pVtab)->interp, "xDestroy");
+
+  /* Drop the "log" table, if one exists (see echoCreate() for details) */
+  if( p && p->zLogName ){
+    char *zSql;
+    zSql = sqlite3_mprintf("DROP TABLE %Q", p->zLogName);
+    rc = sqlite3_exec(p->db, zSql, 0, 0, 0);
+    sqlite3_free(zSql);
+  }
+
+  if( rc==SQLITE_OK ){
+    rc = echoDestructor(pVtab);
+  }
+  return rc;
+}
+
+/* 
+** Echo virtual table module xOpen method.
+*/
+static int echoOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
+  echo_cursor *pCur;
+  if( simulateVtabError((echo_vtab *)pVTab, "xOpen") ){
+    return SQLITE_ERROR;
+  }
+  pCur = sqlite3MallocZero(sizeof(echo_cursor));
+  *ppCursor = (sqlite3_vtab_cursor *)pCur;
+  return (pCur ? SQLITE_OK : SQLITE_NOMEM);
+}
+
+/* 
+** Echo virtual table module xClose method.
+*/
+static int echoClose(sqlite3_vtab_cursor *cur){
+  int rc;
+  echo_cursor *pCur = (echo_cursor *)cur;
+  sqlite3_stmt *pStmt = pCur->pStmt;
+  pCur->pStmt = 0;
+  sqlite3_free(pCur);
+  rc = sqlite3_finalize(pStmt);
+  return rc;
+}
+
+/*
+** Return non-zero if the cursor does not currently point to a valid record
+** (i.e if the scan has finished), or zero otherwise.
+*/
+static int echoEof(sqlite3_vtab_cursor *cur){
+  return (((echo_cursor *)cur)->pStmt ? 0 : 1);
+}
+
+/* 
+** Echo virtual table module xNext method.
+*/
+static int echoNext(sqlite3_vtab_cursor *cur){
+  int rc = SQLITE_OK;
+  echo_cursor *pCur = (echo_cursor *)cur;
+
+  if( simulateVtabError((echo_vtab *)(cur->pVtab), "xNext") ){
+    return SQLITE_ERROR;
+  }
+
+  if( pCur->pStmt ){
+    rc = sqlite3_step(pCur->pStmt);
+    if( rc==SQLITE_ROW ){
+      rc = SQLITE_OK;
+    }else{
+      rc = sqlite3_finalize(pCur->pStmt);
+      pCur->pStmt = 0;
+    }
+  }
+
+  return rc;
+}
+
+/* 
+** Echo virtual table module xColumn method.
+*/
+static int echoColumn(sqlite3_vtab_cursor *cur, sqlite3_context *ctx, int i){
+  int iCol = i + 1;
+  sqlite3_stmt *pStmt = ((echo_cursor *)cur)->pStmt;
+
+  if( simulateVtabError((echo_vtab *)(cur->pVtab), "xColumn") ){
+    return SQLITE_ERROR;
+  }
+
+  if( !pStmt ){
+    sqlite3_result_null(ctx);
+  }else{
+    assert( sqlite3_data_count(pStmt)>iCol );
+    sqlite3_result_value(ctx, sqlite3_column_value(pStmt, iCol));
+  }
+  return SQLITE_OK;
+}
+
+/* 
+** Echo virtual table module xRowid method.
+*/
+static int echoRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
+  sqlite3_stmt *pStmt = ((echo_cursor *)cur)->pStmt;
+
+  if( simulateVtabError((echo_vtab *)(cur->pVtab), "xRowid") ){
+    return SQLITE_ERROR;
+  }
+
+  *pRowid = sqlite3_column_int64(pStmt, 0);
+  return SQLITE_OK;
+}
+
+/*
+** Compute a simple hash of the null terminated string zString.
+**
+** This module uses only sqlite3_index_info.idxStr, not 
+** sqlite3_index_info.idxNum. So to test idxNum, when idxStr is set
+** in echoBestIndex(), idxNum is set to the corresponding hash value.
+** In echoFilter(), code assert()s that the supplied idxNum value is
+** indeed the hash of the supplied idxStr.
+*/
+static int hashString(const char *zString){
+  int val = 0;
+  int ii;
+  for(ii=0; zString[ii]; ii++){
+    val = (val << 3) + (int)zString[ii];
+  }
+  return val;
+}
+
+/* 
+** Echo virtual table module xFilter method.
+*/
+static int echoFilter(
+  sqlite3_vtab_cursor *pVtabCursor, 
+  int idxNum, const char *idxStr,
+  int argc, sqlite3_value **argv
+){
+  int rc;
+  int i;
+
+  echo_cursor *pCur = (echo_cursor *)pVtabCursor;
+  echo_vtab *pVtab = (echo_vtab *)pVtabCursor->pVtab;
+  sqlite3 *db = pVtab->db;
+
+  if( simulateVtabError(pVtab, "xFilter") ){
+    return SQLITE_ERROR;
+  }
+
+  /* Check that idxNum matches idxStr */
+  assert( idxNum==hashString(idxStr) );
+
+  /* Log arguments to the ::echo_module Tcl variable */
+  appendToEchoModule(pVtab->interp, "xFilter");
+  appendToEchoModule(pVtab->interp, idxStr);
+  for(i=0; i<argc; i++){
+    appendToEchoModule(pVtab->interp, (const char*)sqlite3_value_text(argv[i]));
+  }
+
+  sqlite3_finalize(pCur->pStmt);
+  pCur->pStmt = 0;
+
+  /* Prepare the SQL statement created by echoBestIndex and bind the
+  ** runtime parameters passed to this function to it.
+  */
+  rc = sqlite3_prepare(db, idxStr, -1, &pCur->pStmt, 0);
+  assert( pCur->pStmt || rc!=SQLITE_OK );
+  for(i=0; rc==SQLITE_OK && i<argc; i++){
+    rc = sqlite3_bind_value(pCur->pStmt, i+1, argv[i]);
+  }
+
+  /* If everything was successful, advance to the first row of the scan */
+  if( rc==SQLITE_OK ){
+    rc = echoNext(pVtabCursor);
+  }
+
+  return rc;
+}
+
+
+/*
+** A helper function used by echoUpdate() and echoBestIndex() for
+** manipulating strings in concert with the sqlite3_mprintf() function.
+**
+** Parameter pzStr points to a pointer to a string allocated with
+** sqlite3_mprintf. The second parameter, zAppend, points to another
+** string. The two strings are concatenated together and *pzStr
+** set to point at the result. The initial buffer pointed to by *pzStr
+** is deallocated via sqlite3_free().
+**
+** If the third argument, doFree, is true, then sqlite3_free() is
+** also called to free the buffer pointed to by zAppend.
+*/
+static void string_concat(char **pzStr, char *zAppend, int doFree, int *pRc){
+  char *zIn = *pzStr;
+  if( !zAppend && doFree && *pRc==SQLITE_OK ){
+    *pRc = SQLITE_NOMEM;
+  }
+  if( *pRc!=SQLITE_OK ){
+    sqlite3_free(zIn);
+    zIn = 0;
+  }else{
+    if( zIn ){
+      char *zTemp = zIn;
+      zIn = sqlite3_mprintf("%s%s", zIn, zAppend);
+      sqlite3_free(zTemp);
+    }else{
+      zIn = sqlite3_mprintf("%s", zAppend);
+    }
+    if( !zIn ){
+      *pRc = SQLITE_NOMEM;
+    }
+  }
+  *pzStr = zIn;
+  if( doFree ){
+    sqlite3_free(zAppend);
+  }
+}
+
+/*
+** The echo module implements the subset of query constraints and sort
+** orders that may take advantage of SQLite indices on the underlying
+** real table. For example, if the real table is declared as:
+**
+**     CREATE TABLE real(a, b, c);
+**     CREATE INDEX real_index ON real(b);
+**
+** then the echo module handles WHERE or ORDER BY clauses that refer
+** to the column "b", but not "a" or "c". If a multi-column index is
+** present, only its left most column is considered. 
+**
+** This xBestIndex method encodes the proposed search strategy as
+** an SQL query on the real table underlying the virtual echo module 
+** table and stores the query in sqlite3_index_info.idxStr. The SQL
+** statement is of the form:
+**
+**   SELECT rowid, * FROM <real-table> ?<where-clause>? ?<order-by-clause>?
+**
+** where the <where-clause> and <order-by-clause> are determined
+** by the contents of the structure pointed to by the pIdxInfo argument.
+*/
+static int echoBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
+  int ii;
+  char *zQuery = 0;
+  char *zNew;
+  int nArg = 0;
+  const char *zSep = "WHERE";
+  echo_vtab *pVtab = (echo_vtab *)tab;
+  sqlite3_stmt *pStmt = 0;
+  Tcl_Interp *interp = pVtab->interp;
+
+  int nRow;
+  int useIdx = 0;
+  int rc = SQLITE_OK;
+  int useCost = 0;
+  double cost;
+  int isIgnoreUsable = 0;
+  if( Tcl_GetVar(interp, "echo_module_ignore_usable", TCL_GLOBAL_ONLY) ){
+    isIgnoreUsable = 1;
+  }
+
+  if( simulateVtabError(pVtab, "xBestIndex") ){
+    return SQLITE_ERROR;
+  }
+
+  /* Determine the number of rows in the table and store this value in local
+  ** variable nRow. The 'estimated-cost' of the scan will be the number of
+  ** rows in the table for a linear scan, or the log (base 2) of the 
+  ** number of rows if the proposed scan uses an index.  
+  */
+  if( Tcl_GetVar(interp, "echo_module_cost", TCL_GLOBAL_ONLY) ){
+    cost = atof(Tcl_GetVar(interp, "echo_module_cost", TCL_GLOBAL_ONLY));
+    useCost = 1;
+  } else {
+    zQuery = sqlite3_mprintf("SELECT count(*) FROM %Q", pVtab->zTableName);
+    if( !zQuery ){
+      return SQLITE_NOMEM;
+    }
+    rc = sqlite3_prepare(pVtab->db, zQuery, -1, &pStmt, 0);
+    sqlite3_free(zQuery);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+    sqlite3_step(pStmt);
+    nRow = sqlite3_column_int(pStmt, 0);
+    rc = sqlite3_finalize(pStmt);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+  }
+
+  zQuery = sqlite3_mprintf("SELECT rowid, * FROM %Q", pVtab->zTableName);
+  if( !zQuery ){
+    return SQLITE_NOMEM;
+  }
+  for(ii=0; ii<pIdxInfo->nConstraint; ii++){
+    const struct sqlite3_index_constraint *pConstraint;
+    struct sqlite3_index_constraint_usage *pUsage;
+    int iCol;
+
+    pConstraint = &pIdxInfo->aConstraint[ii];
+    pUsage = &pIdxInfo->aConstraintUsage[ii];
+
+    if( !isIgnoreUsable && !pConstraint->usable ) continue;
+
+    iCol = pConstraint->iColumn;
+    if( pVtab->aIndex[iCol] || iCol<0 ){
+      char *zCol = pVtab->aCol[iCol];
+      char *zOp = 0;
+      useIdx = 1;
+      if( iCol<0 ){
+        zCol = "rowid";
+      }
+      switch( pConstraint->op ){
+        case SQLITE_INDEX_CONSTRAINT_EQ:
+          zOp = "="; break;
+        case SQLITE_INDEX_CONSTRAINT_LT:
+          zOp = "<"; break;
+        case SQLITE_INDEX_CONSTRAINT_GT:
+          zOp = ">"; break;
+        case SQLITE_INDEX_CONSTRAINT_LE:
+          zOp = "<="; break;
+        case SQLITE_INDEX_CONSTRAINT_GE:
+          zOp = ">="; break;
+        case SQLITE_INDEX_CONSTRAINT_MATCH:
+          zOp = "LIKE"; break;
+      }
+      if( zOp[0]=='L' ){
+        zNew = sqlite3_mprintf(" %s %s LIKE (SELECT '%%'||?||'%%')", 
+                               zSep, zCol);
+      } else {
+        zNew = sqlite3_mprintf(" %s %s %s ?", zSep, zCol, zOp);
+      }
+      string_concat(&zQuery, zNew, 1, &rc);
+
+      zSep = "AND";
+      pUsage->argvIndex = ++nArg;
+      pUsage->omit = 1;
+    }
+  }
+
+  /* If there is only one term in the ORDER BY clause, and it is
+  ** on a column that this virtual table has an index for, then consume 
+  ** the ORDER BY clause.
+  */
+  if( pIdxInfo->nOrderBy==1 && pVtab->aIndex[pIdxInfo->aOrderBy->iColumn] ){
+    int iCol = pIdxInfo->aOrderBy->iColumn;
+    char *zCol = pVtab->aCol[iCol];
+    char *zDir = pIdxInfo->aOrderBy->desc?"DESC":"ASC";
+    if( iCol<0 ){
+      zCol = "rowid";
+    }
+    zNew = sqlite3_mprintf(" ORDER BY %s %s", zCol, zDir);
+    string_concat(&zQuery, zNew, 1, &rc);
+    pIdxInfo->orderByConsumed = 1;
+  }
+
+  appendToEchoModule(pVtab->interp, "xBestIndex");;
+  appendToEchoModule(pVtab->interp, zQuery);
+
+  if( !zQuery ){
+    return rc;
+  }
+  pIdxInfo->idxNum = hashString(zQuery);
+  pIdxInfo->idxStr = zQuery;
+  pIdxInfo->needToFreeIdxStr = 1;
+  if( useCost ){
+    pIdxInfo->estimatedCost = cost;
+  }else if( useIdx ){
+    /* Approximation of log2(nRow). */
+    for( ii=0; ii<(sizeof(int)*8); ii++ ){
+      if( nRow & (1<<ii) ){
+        pIdxInfo->estimatedCost = (double)ii;
+      }
+    }
+  }else{
+    pIdxInfo->estimatedCost = (double)nRow;
+  }
+  return rc;
+}
+
+/*
+** The xUpdate method for echo module virtual tables.
+** 
+**    apData[0]  apData[1]  apData[2..]
+**
+**    INTEGER                              DELETE            
+**
+**    INTEGER    NULL       (nCol args)    UPDATE (do not set rowid)
+**    INTEGER    INTEGER    (nCol args)    UPDATE (with SET rowid = <arg1>)
+**
+**    NULL       NULL       (nCol args)    INSERT INTO (automatic rowid value)
+**    NULL       INTEGER    (nCol args)    INSERT (incl. rowid value)
+**
+*/
+int echoUpdate(
+  sqlite3_vtab *tab, 
+  int nData, 
+  sqlite3_value **apData, 
+  sqlite_int64 *pRowid
+){
+  echo_vtab *pVtab = (echo_vtab *)tab;
+  sqlite3 *db = pVtab->db;
+  int rc = SQLITE_OK;
+
+  sqlite3_stmt *pStmt;
+  char *z = 0;               /* SQL statement to execute */
+  int bindArgZero = 0;       /* True to bind apData[0] to sql var no. nData */
+  int bindArgOne = 0;        /* True to bind apData[1] to sql var no. 1 */
+  int i;                     /* Counter variable used by for loops */
+
+  assert( nData==pVtab->nCol+2 || nData==1 );
+
+  /* Ticket #3083 - make sure we always start a transaction prior to
+  ** making any changes to a virtual table */
+  assert( pVtab->inTransaction );
+
+  if( simulateVtabError(pVtab, "xUpdate") ){
+    return SQLITE_ERROR;
+  }
+
+  /* If apData[0] is an integer and nData>1 then do an UPDATE */
+  if( nData>1 && sqlite3_value_type(apData[0])==SQLITE_INTEGER ){
+    char *zSep = " SET";
+    z = sqlite3_mprintf("UPDATE %Q", pVtab->zTableName);
+    if( !z ){
+      rc = SQLITE_NOMEM;
+    }
+
+    bindArgOne = (apData[1] && sqlite3_value_type(apData[1])==SQLITE_INTEGER);
+    bindArgZero = 1;
+
+    if( bindArgOne ){
+       string_concat(&z, " SET rowid=?1 ", 0, &rc);
+       zSep = ",";
+    }
+    for(i=2; i<nData; i++){
+      if( apData[i]==0 ) continue;
+      string_concat(&z, sqlite3_mprintf(
+          "%s %Q=?%d", zSep, pVtab->aCol[i-2], i), 1, &rc);
+      zSep = ",";
+    }
+    string_concat(&z, sqlite3_mprintf(" WHERE rowid=?%d", nData), 1, &rc);
+  }
+
+  /* If apData[0] is an integer and nData==1 then do a DELETE */
+  else if( nData==1 && sqlite3_value_type(apData[0])==SQLITE_INTEGER ){
+    z = sqlite3_mprintf("DELETE FROM %Q WHERE rowid = ?1", pVtab->zTableName);
+    if( !z ){
+      rc = SQLITE_NOMEM;
+    }
+    bindArgZero = 1;
+  }
+
+  /* If the first argument is NULL and there are more than two args, INSERT */
+  else if( nData>2 && sqlite3_value_type(apData[0])==SQLITE_NULL ){
+    int ii;
+    char *zInsert = 0;
+    char *zValues = 0;
+  
+    zInsert = sqlite3_mprintf("INSERT INTO %Q (", pVtab->zTableName);
+    if( !zInsert ){
+      rc = SQLITE_NOMEM;
+    }
+    if( sqlite3_value_type(apData[1])==SQLITE_INTEGER ){
+      bindArgOne = 1;
+      zValues = sqlite3_mprintf("?");
+      string_concat(&zInsert, "rowid", 0, &rc);
+    }
+
+    assert((pVtab->nCol+2)==nData);
+    for(ii=2; ii<nData; ii++){
+      string_concat(&zInsert, 
+          sqlite3_mprintf("%s%Q", zValues?", ":"", pVtab->aCol[ii-2]), 1, &rc);
+      string_concat(&zValues, 
+          sqlite3_mprintf("%s?%d", zValues?", ":"", ii), 1, &rc);
+    }
+
+    string_concat(&z, zInsert, 1, &rc);
+    string_concat(&z, ") VALUES(", 0, &rc);
+    string_concat(&z, zValues, 1, &rc);
+    string_concat(&z, ")", 0, &rc);
+  }
+
+  /* Anything else is an error */
+  else{
+    assert(0);
+    return SQLITE_ERROR;
+  }
+
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_prepare(db, z, -1, &pStmt, 0);
+  }
+  assert( rc!=SQLITE_OK || pStmt );
+  sqlite3_free(z);
+  if( rc==SQLITE_OK ) {
+    if( bindArgZero ){
+      sqlite3_bind_value(pStmt, nData, apData[0]);
+    }
+    if( bindArgOne ){
+      sqlite3_bind_value(pStmt, 1, apData[1]);
+    }
+    for(i=2; i<nData && rc==SQLITE_OK; i++){
+      if( apData[i] ) rc = sqlite3_bind_value(pStmt, i, apData[i]);
+    }
+    if( rc==SQLITE_OK ){
+      sqlite3_step(pStmt);
+      rc = sqlite3_finalize(pStmt);
+    }else{
+      sqlite3_finalize(pStmt);
+    }
+  }
+
+  if( pRowid && rc==SQLITE_OK ){
+    *pRowid = sqlite3_last_insert_rowid(db);
+  }
+  if( rc!=SQLITE_OK ){
+    tab->zErrMsg = sqlite3_mprintf("echo-vtab-error: %s", sqlite3_errmsg(db));
+  }
+
+  return rc;
+}
+
+/*
+** xBegin, xSync, xCommit and xRollback callbacks for echo module
+** virtual tables. Do nothing other than add the name of the callback
+** to the $::echo_module Tcl variable.
+*/
+static int echoTransactionCall(sqlite3_vtab *tab, const char *zCall){
+  char *z;
+  echo_vtab *pVtab = (echo_vtab *)tab;
+  z = sqlite3_mprintf("echo(%s)", pVtab->zTableName);
+  if( z==0 ) return SQLITE_NOMEM;
+  appendToEchoModule(pVtab->interp, zCall);
+  appendToEchoModule(pVtab->interp, z);
+  sqlite3_free(z);
+  return SQLITE_OK;
+}
+static int echoBegin(sqlite3_vtab *tab){
+  int rc;
+  echo_vtab *pVtab = (echo_vtab *)tab;
+  Tcl_Interp *interp = pVtab->interp;
+  const char *zVal; 
+
+  /* Ticket #3083 - do not start a transaction if we are already in
+  ** a transaction */
+  assert( !pVtab->inTransaction );
+
+  if( simulateVtabError(pVtab, "xBegin") ){
+    return SQLITE_ERROR;
+  }
+
+  rc = echoTransactionCall(tab, "xBegin");
+
+  if( rc==SQLITE_OK ){
+    /* Check if the $::echo_module_begin_fail variable is defined. If it is,
+    ** and it is set to the name of the real table underlying this virtual
+    ** echo module table, then cause this xSync operation to fail.
+    */
+    zVal = Tcl_GetVar(interp, "echo_module_begin_fail", TCL_GLOBAL_ONLY);
+    if( zVal && 0==strcmp(zVal, pVtab->zTableName) ){
+      rc = SQLITE_ERROR;
+    }
+  }
+  if( rc==SQLITE_OK ){
+    pVtab->inTransaction = 1;
+  }
+  return rc;
+}
+static int echoSync(sqlite3_vtab *tab){
+  int rc;
+  echo_vtab *pVtab = (echo_vtab *)tab;
+  Tcl_Interp *interp = pVtab->interp;
+  const char *zVal; 
+
+  /* Ticket #3083 - Only call xSync if we have previously started a
+  ** transaction */
+  assert( pVtab->inTransaction );
+
+  if( simulateVtabError(pVtab, "xSync") ){
+    return SQLITE_ERROR;
+  }
+
+  rc = echoTransactionCall(tab, "xSync");
+
+  if( rc==SQLITE_OK ){
+    /* Check if the $::echo_module_sync_fail variable is defined. If it is,
+    ** and it is set to the name of the real table underlying this virtual
+    ** echo module table, then cause this xSync operation to fail.
+    */
+    zVal = Tcl_GetVar(interp, "echo_module_sync_fail", TCL_GLOBAL_ONLY);
+    if( zVal && 0==strcmp(zVal, pVtab->zTableName) ){
+      rc = -1;
+    }
+  }
+  return rc;
+}
+static int echoCommit(sqlite3_vtab *tab){
+  echo_vtab *pVtab = (echo_vtab*)tab;
+  int rc;
+
+  /* Ticket #3083 - Only call xCommit if we have previously started
+  ** a transaction */
+  assert( pVtab->inTransaction );
+
+  if( simulateVtabError(pVtab, "xCommit") ){
+    return SQLITE_ERROR;
+  }
+
+  sqlite3BeginBenignMalloc();
+  rc = echoTransactionCall(tab, "xCommit");
+  sqlite3EndBenignMalloc();
+  pVtab->inTransaction = 0;
+  return rc;
+}
+static int echoRollback(sqlite3_vtab *tab){
+  int rc;
+  echo_vtab *pVtab = (echo_vtab*)tab;
+
+  /* Ticket #3083 - Only call xRollback if we have previously started
+  ** a transaction */
+  assert( pVtab->inTransaction );
+
+  rc = echoTransactionCall(tab, "xRollback");
+  pVtab->inTransaction = 0;
+  return rc;
+}
+
+/*
+** Implementation of "GLOB" function on the echo module.  Pass
+** all arguments to the ::echo_glob_overload procedure of TCL
+** and return the result of that procedure as a string.
+*/
+static void overloadedGlobFunction(
+  sqlite3_context *pContext,
+  int nArg,
+  sqlite3_value **apArg
+){
+  Tcl_Interp *interp = sqlite3_user_data(pContext);
+  Tcl_DString str;
+  int i;
+  int rc;
+  Tcl_DStringInit(&str);
+  Tcl_DStringAppendElement(&str, "::echo_glob_overload");
+  for(i=0; i<nArg; i++){
+    Tcl_DStringAppendElement(&str, (char*)sqlite3_value_text(apArg[i]));
+  }
+  rc = Tcl_Eval(interp, Tcl_DStringValue(&str));
+  Tcl_DStringFree(&str);
+  if( rc ){
+    sqlite3_result_error(pContext, Tcl_GetStringResult(interp), -1);
+  }else{
+    sqlite3_result_text(pContext, Tcl_GetStringResult(interp),
+                        -1, SQLITE_TRANSIENT);
+  }
+  Tcl_ResetResult(interp);
+}
+
+/*
+** This is the xFindFunction implementation for the echo module.
+** SQLite calls this routine when the first argument of a function
+** is a column of an echo virtual table.  This routine can optionally
+** override the implementation of that function.  It will choose to
+** do so if the function is named "glob", and a TCL command named
+** ::echo_glob_overload exists.
+*/
+static int echoFindFunction(
+  sqlite3_vtab *vtab,
+  int nArg,
+  const char *zFuncName,
+  void (**pxFunc)(sqlite3_context*,int,sqlite3_value**),
+  void **ppArg
+){
+  echo_vtab *pVtab = (echo_vtab *)vtab;
+  Tcl_Interp *interp = pVtab->interp;
+  Tcl_CmdInfo info;
+  if( strcmp(zFuncName,"glob")!=0 ){
+    return 0;
+  }
+  if( Tcl_GetCommandInfo(interp, "::echo_glob_overload", &info)==0 ){
+    return 0;
+  }
+  *pxFunc = overloadedGlobFunction;
+  *ppArg = interp;
+  return 1;
+}
+
+static int echoRename(sqlite3_vtab *vtab, const char *zNewName){
+  int rc = SQLITE_OK;
+  echo_vtab *p = (echo_vtab *)vtab;
+
+  if( simulateVtabError(p, "xRename") ){
+    return SQLITE_ERROR;
+  }
+
+  if( p->isPattern ){
+    int nThis = strlen(p->zThis);
+    char *zSql = sqlite3_mprintf("ALTER TABLE %s RENAME TO %s%s", 
+        p->zTableName, zNewName, &p->zTableName[nThis]
+    );
+    rc = sqlite3_exec(p->db, zSql, 0, 0, 0);
+    sqlite3_free(zSql);
+  }
+
+  return rc;
+}
+
+static int echoSavepoint(sqlite3_vtab *pVTab, int iSavepoint){
+  assert( pVTab );
+  return SQLITE_OK;
+}
+
+static int echoRelease(sqlite3_vtab *pVTab, int iSavepoint){
+  assert( pVTab );
+  return SQLITE_OK;
+}
+
+static int echoRollbackTo(sqlite3_vtab *pVTab, int iSavepoint){
+  assert( pVTab );
+  return SQLITE_OK;
+}
+
+/*
+** A virtual table module that merely "echos" the contents of another
+** table (like an SQL VIEW).
+*/
+static sqlite3_module echoModule = {
+  1,                         /* iVersion */
+  echoCreate,
+  echoConnect,
+  echoBestIndex,
+  echoDisconnect, 
+  echoDestroy,
+  echoOpen,                  /* xOpen - open a cursor */
+  echoClose,                 /* xClose - close a cursor */
+  echoFilter,                /* xFilter - configure scan constraints */
+  echoNext,                  /* xNext - advance a cursor */
+  echoEof,                   /* xEof */
+  echoColumn,                /* xColumn - read data */
+  echoRowid,                 /* xRowid - read data */
+  echoUpdate,                /* xUpdate - write data */
+  echoBegin,                 /* xBegin - begin transaction */
+  echoSync,                  /* xSync - sync transaction */
+  echoCommit,                /* xCommit - commit transaction */
+  echoRollback,              /* xRollback - rollback transaction */
+  echoFindFunction,          /* xFindFunction - function overloading */
+  echoRename                 /* xRename - rename the table */
+};
+
+static sqlite3_module echoModuleV2 = {
+  2,                         /* iVersion */
+  echoCreate,
+  echoConnect,
+  echoBestIndex,
+  echoDisconnect, 
+  echoDestroy,
+  echoOpen,                  /* xOpen - open a cursor */
+  echoClose,                 /* xClose - close a cursor */
+  echoFilter,                /* xFilter - configure scan constraints */
+  echoNext,                  /* xNext - advance a cursor */
+  echoEof,                   /* xEof */
+  echoColumn,                /* xColumn - read data */
+  echoRowid,                 /* xRowid - read data */
+  echoUpdate,                /* xUpdate - write data */
+  echoBegin,                 /* xBegin - begin transaction */
+  echoSync,                  /* xSync - sync transaction */
+  echoCommit,                /* xCommit - commit transaction */
+  echoRollback,              /* xRollback - rollback transaction */
+  echoFindFunction,          /* xFindFunction - function overloading */
+  echoRename,                /* xRename - rename the table */
+  echoSavepoint,
+  echoRelease,
+  echoRollbackTo
+};
+
+/*
+** Decode a pointer to an sqlite3 object.
+*/
+extern int getDbPointer(Tcl_Interp *interp, const char *zA, sqlite3 **ppDb);
+
+static void moduleDestroy(void *p){
+  sqlite3_free(p);
+}
+
+/*
+** Register the echo virtual table module.
+*/
+static int register_echo_module(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3 *db;
+  EchoModule *pMod;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+
+  /* Virtual table module "echo" */
+  pMod = sqlite3_malloc(sizeof(EchoModule));
+  pMod->interp = interp;
+  sqlite3_create_module_v2(db, "echo", &echoModule, (void*)pMod, moduleDestroy);
+
+  /* Virtual table module "echo_v2" */
+  pMod = sqlite3_malloc(sizeof(EchoModule));
+  pMod->interp = interp;
+  sqlite3_create_module_v2(db, "echo_v2", 
+      &echoModuleV2, (void*)pMod, moduleDestroy
+  );
+  return TCL_OK;
+}
+
+/*
+** Tcl interface to sqlite3_declare_vtab, invoked as follows from Tcl:
+**
+** sqlite3_declare_vtab DB SQL
+*/
+static int declare_vtab(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3 *db;
+  int rc;
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB SQL");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  rc = sqlite3_declare_vtab(db, Tcl_GetString(objv[2]));
+  if( rc!=SQLITE_OK ){
+    Tcl_SetResult(interp, (char *)sqlite3_errmsg(db), TCL_VOLATILE);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
+#endif /* ifndef SQLITE_OMIT_VIRTUALTABLE */
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetest8_Init(Tcl_Interp *interp){
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  static struct {
+     char *zName;
+     Tcl_ObjCmdProc *xProc;
+     void *clientData;
+  } aObjCmd[] = {
+     { "register_echo_module",   register_echo_module, 0 },
+     { "sqlite3_declare_vtab",   declare_vtab, 0 },
+  };
+  int i;
+  for(i=0; i<sizeof(aObjCmd)/sizeof(aObjCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aObjCmd[i].zName, 
+        aObjCmd[i].xProc, aObjCmd[i].clientData, 0);
+  }
+#endif
+  return TCL_OK;
+}
diff --git a/src/test9.c b/src/test9.c
new file mode 100644
index 0000000..e5993e8
--- /dev/null
+++ b/src/test9.c
@@ -0,0 +1,200 @@
+/*
+** 2007 March 29
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains obscure tests of the C-interface required
+** for completeness. Test code is written in C for these cases
+** as there is not much point in binding to Tcl.
+*/
+#include "sqliteInt.h"
+#include "tcl.h"
+#include <stdlib.h>
+#include <string.h>
+
+/*
+** c_collation_test
+*/
+static int c_collation_test(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  const char *zErrFunction = "N/A";
+  sqlite3 *db;
+
+  int rc;
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+
+  /* Open a database. */
+  rc = sqlite3_open(":memory:", &db);
+  if( rc!=SQLITE_OK ){
+    zErrFunction = "sqlite3_open";
+    goto error_out;
+  }
+
+  rc = sqlite3_create_collation(db, "collate", 456, 0, 0);
+  if( rc!=SQLITE_MISUSE ){
+    sqlite3_close(db);
+    zErrFunction = "sqlite3_create_collation";
+    goto error_out;
+  }
+
+  sqlite3_close(db);
+  return TCL_OK;
+
+error_out:
+  Tcl_ResetResult(interp);
+  Tcl_AppendResult(interp, "Error testing function: ", zErrFunction, 0);
+  return TCL_ERROR;
+}
+
+/*
+** c_realloc_test
+*/
+static int c_realloc_test(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  void *p;
+  const char *zErrFunction = "N/A";
+
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+
+  p = sqlite3_malloc(5);
+  if( !p ){
+    zErrFunction = "sqlite3_malloc";
+    goto error_out;
+  }
+
+  /* Test that realloc()ing a block of memory to a negative size is
+  ** the same as free()ing that memory.
+  */
+  p = sqlite3_realloc(p, -1);
+  if( p ){
+    zErrFunction = "sqlite3_realloc";
+    goto error_out;
+  }
+
+  return TCL_OK;
+
+error_out:
+  Tcl_ResetResult(interp);
+  Tcl_AppendResult(interp, "Error testing function: ", zErrFunction, 0);
+  return TCL_ERROR;
+}
+
+
+/*
+** c_misuse_test
+*/
+static int c_misuse_test(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  const char *zErrFunction = "N/A";
+  sqlite3 *db = 0;
+  sqlite3_stmt *pStmt;
+  int rc;
+
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+
+  /* Open a database. Then close it again. We need to do this so that
+  ** we have a "closed database handle" to pass to various API functions.
+  */
+  rc = sqlite3_open(":memory:", &db);
+  if( rc!=SQLITE_OK ){
+    zErrFunction = "sqlite3_open";
+    goto error_out;
+  }
+  sqlite3_close(db);
+
+
+  rc = sqlite3_errcode(db);
+  if( rc!=SQLITE_MISUSE ){
+    zErrFunction = "sqlite3_errcode";
+    goto error_out;
+  }
+
+  pStmt = (sqlite3_stmt*)1234;
+  rc = sqlite3_prepare(db, 0, 0, &pStmt, 0);
+  if( rc!=SQLITE_MISUSE ){
+    zErrFunction = "sqlite3_prepare";
+    goto error_out;
+  }
+  assert( pStmt==0 ); /* Verify that pStmt is zeroed even on a MISUSE error */
+
+  pStmt = (sqlite3_stmt*)1234;
+  rc = sqlite3_prepare_v2(db, 0, 0, &pStmt, 0);
+  if( rc!=SQLITE_MISUSE ){
+    zErrFunction = "sqlite3_prepare_v2";
+    goto error_out;
+  }
+  assert( pStmt==0 );
+
+#ifndef SQLITE_OMIT_UTF16
+  pStmt = (sqlite3_stmt*)1234;
+  rc = sqlite3_prepare16(db, 0, 0, &pStmt, 0);
+  if( rc!=SQLITE_MISUSE ){
+    zErrFunction = "sqlite3_prepare16";
+    goto error_out;
+  }
+  assert( pStmt==0 );
+  pStmt = (sqlite3_stmt*)1234;
+  rc = sqlite3_prepare16_v2(db, 0, 0, &pStmt, 0);
+  if( rc!=SQLITE_MISUSE ){
+    zErrFunction = "sqlite3_prepare16_v2";
+    goto error_out;
+  }
+  assert( pStmt==0 );
+#endif
+
+  return TCL_OK;
+
+error_out:
+  Tcl_ResetResult(interp);
+  Tcl_AppendResult(interp, "Error testing function: ", zErrFunction, 0);
+  return TCL_ERROR;
+}
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetest9_Init(Tcl_Interp *interp){
+  static struct {
+     char *zName;
+     Tcl_ObjCmdProc *xProc;
+     void *clientData;
+  } aObjCmd[] = {
+     { "c_misuse_test",    c_misuse_test, 0 },
+     { "c_realloc_test",   c_realloc_test, 0 },
+     { "c_collation_test", c_collation_test, 0 },
+  };
+  int i;
+  for(i=0; i<sizeof(aObjCmd)/sizeof(aObjCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aObjCmd[i].zName, 
+        aObjCmd[i].xProc, aObjCmd[i].clientData, 0);
+  }
+  return TCL_OK;
+}
diff --git a/src/test_async.c b/src/test_async.c
new file mode 100644
index 0000000..c760eea
--- /dev/null
+++ b/src/test_async.c
@@ -0,0 +1,241 @@
+/*
+** 2005 December 14
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains a binding of the asynchronous IO extension interface
+** (defined in ext/async/sqlite3async.h) to Tcl.
+*/
+
+#define TCL_THREADS 
+#include <tcl.h>
+
+#ifdef SQLITE_ENABLE_ASYNCIO
+
+#include "sqlite3async.h"
+#include "sqlite3.h"
+#include <assert.h>
+
+/* From test1.c */
+const char *sqlite3TestErrorName(int);
+
+
+struct TestAsyncGlobal {
+  int isInstalled;                     /* True when async VFS is installed */
+} testasync_g = { 0 };
+
+TCL_DECLARE_MUTEX(testasync_g_writerMutex);
+
+/*
+** sqlite3async_initialize PARENT-VFS ISDEFAULT
+*/
+static int testAsyncInit(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  const char *zParent;
+  int isDefault;
+  int rc;
+
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "PARENT-VFS ISDEFAULT");
+    return TCL_ERROR;
+  }
+  zParent = Tcl_GetString(objv[1]);
+  if( !*zParent ) {
+    zParent = 0;
+  }
+  if( Tcl_GetBooleanFromObj(interp, objv[2], &isDefault) ){
+    return TCL_ERROR;
+  }
+
+  rc = sqlite3async_initialize(zParent, isDefault);
+  if( rc!=SQLITE_OK ){
+    Tcl_SetObjResult(interp, Tcl_NewStringObj(sqlite3TestErrorName(rc), -1));
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
+/*
+** sqlite3async_shutdown
+*/
+static int testAsyncShutdown(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3async_shutdown();
+  return TCL_OK;
+}
+
+static Tcl_ThreadCreateType tclWriterThread(ClientData pIsStarted){
+  Tcl_MutexLock(&testasync_g_writerMutex);
+  *((int *)pIsStarted) = 1;
+  sqlite3async_run();
+  Tcl_MutexUnlock(&testasync_g_writerMutex);
+  Tcl_ExitThread(0);
+  TCL_THREAD_CREATE_RETURN;
+}
+
+/*
+** sqlite3async_start
+**
+** Start a new writer thread.
+*/
+static int testAsyncStart(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  volatile int isStarted = 0;
+  ClientData threadData = (ClientData)&isStarted;
+
+  Tcl_ThreadId x;
+  const int nStack = TCL_THREAD_STACK_DEFAULT;
+  const int flags = TCL_THREAD_NOFLAGS;
+  int rc;
+
+  rc = Tcl_CreateThread(&x, tclWriterThread, threadData, nStack, flags);
+  if( rc!=TCL_OK ){
+    Tcl_AppendResult(interp, "Tcl_CreateThread() failed", 0);
+    return TCL_ERROR;
+  }
+
+  while( isStarted==0 ) { /* Busy loop */ }
+  return TCL_OK;
+}
+
+/*
+** sqlite3async_wait
+**
+** Wait for the current writer thread to terminate.
+**
+** If the current writer thread is set to run forever then this
+** command would block forever.  To prevent that, an error is returned. 
+*/
+static int testAsyncWait(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int eCond;
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+
+  sqlite3async_control(SQLITEASYNC_GET_HALT, &eCond);
+  if( eCond==SQLITEASYNC_HALT_NEVER ){
+    Tcl_AppendResult(interp, "would block forever", (char*)0);
+    return TCL_ERROR;
+  }
+
+  Tcl_MutexLock(&testasync_g_writerMutex);
+  Tcl_MutexUnlock(&testasync_g_writerMutex);
+  return TCL_OK;
+}
+
+/*
+** sqlite3async_control OPTION ?VALUE?
+*/
+static int testAsyncControl(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc = SQLITE_OK;
+  int aeOpt[] = { SQLITEASYNC_HALT, SQLITEASYNC_DELAY, SQLITEASYNC_LOCKFILES };
+  const char *azOpt[] = { "halt", "delay", "lockfiles", 0 };
+  const char *az[] = { "never", "now", "idle", 0 };
+  int iVal;
+  int eOpt;
+
+  if( objc!=2 && objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "OPTION ?VALUE?");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIndexFromObj(interp, objv[1], azOpt, "option", 0, &eOpt) ){
+    return TCL_ERROR;
+  }
+  eOpt = aeOpt[eOpt];
+
+  if( objc==3 ){
+    switch( eOpt ){
+      case SQLITEASYNC_HALT: {
+        assert( SQLITEASYNC_HALT_NEVER==0 );
+        assert( SQLITEASYNC_HALT_NOW==1 );
+        assert( SQLITEASYNC_HALT_IDLE==2 );
+        if( Tcl_GetIndexFromObj(interp, objv[2], az, "value", 0, &iVal) ){
+          return TCL_ERROR;
+        }
+        break;
+      }
+      case SQLITEASYNC_DELAY:
+        if( Tcl_GetIntFromObj(interp, objv[2], &iVal) ){
+          return TCL_ERROR;
+        }
+        break;
+
+      case SQLITEASYNC_LOCKFILES:
+        if( Tcl_GetBooleanFromObj(interp, objv[2], &iVal) ){
+          return TCL_ERROR;
+        }
+        break;
+    }
+
+    rc = sqlite3async_control(eOpt, iVal);
+  }
+
+  if( rc==SQLITE_OK ){
+    rc = sqlite3async_control(
+        eOpt==SQLITEASYNC_HALT ? SQLITEASYNC_GET_HALT :
+        eOpt==SQLITEASYNC_DELAY ? SQLITEASYNC_GET_DELAY :
+        SQLITEASYNC_GET_LOCKFILES, &iVal);
+  }
+
+  if( rc!=SQLITE_OK ){
+    Tcl_SetObjResult(interp, Tcl_NewStringObj(sqlite3TestErrorName(rc), -1));
+    return TCL_ERROR;
+  }
+
+  if( eOpt==SQLITEASYNC_HALT ){
+    Tcl_SetObjResult(interp, Tcl_NewStringObj(az[iVal], -1));
+  }else{
+    Tcl_SetObjResult(interp, Tcl_NewIntObj(iVal));
+  }
+
+  return TCL_OK;
+}
+
+#endif  /* SQLITE_ENABLE_ASYNCIO */
+
+/*
+** This routine registers the custom TCL commands defined in this
+** module.  This should be the only procedure visible from outside
+** of this module.
+*/
+int Sqlitetestasync_Init(Tcl_Interp *interp){
+#ifdef SQLITE_ENABLE_ASYNCIO
+  Tcl_CreateObjCommand(interp,"sqlite3async_start",testAsyncStart,0,0);
+  Tcl_CreateObjCommand(interp,"sqlite3async_wait",testAsyncWait,0,0);
+
+  Tcl_CreateObjCommand(interp,"sqlite3async_control",testAsyncControl,0,0);
+  Tcl_CreateObjCommand(interp,"sqlite3async_initialize",testAsyncInit,0,0);
+  Tcl_CreateObjCommand(interp,"sqlite3async_shutdown",testAsyncShutdown,0,0);
+#endif  /* SQLITE_ENABLE_ASYNCIO */
+  return TCL_OK;
+}
diff --git a/src/test_autoext.c b/src/test_autoext.c
new file mode 100644
index 0000000..6b1e297
--- /dev/null
+++ b/src/test_autoext.c
@@ -0,0 +1,167 @@
+/*
+** 2006 August 23
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Test extension for testing the sqlite3_auto_extension() function.
+*/
+#include "tcl.h"
+#include "sqlite3ext.h"
+
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+static SQLITE_EXTENSION_INIT1
+
+/*
+** The sqr() SQL function returns the square of its input value.
+*/
+static void sqrFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  double r = sqlite3_value_double(argv[0]);
+  sqlite3_result_double(context, r*r);
+}
+
+/*
+** This is the entry point to register the extension for the sqr() function.
+*/
+static int sqr_init(
+  sqlite3 *db, 
+  char **pzErrMsg, 
+  const sqlite3_api_routines *pApi
+){
+  SQLITE_EXTENSION_INIT2(pApi);
+  sqlite3_create_function(db, "sqr", 1, SQLITE_ANY, 0, sqrFunc, 0, 0);
+  return 0;
+}
+
+/*
+** The cube() SQL function returns the cube of its input value.
+*/
+static void cubeFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  double r = sqlite3_value_double(argv[0]);
+  sqlite3_result_double(context, r*r*r);
+}
+
+/*
+** This is the entry point to register the extension for the cube() function.
+*/
+static int cube_init(
+  sqlite3 *db, 
+  char **pzErrMsg, 
+  const sqlite3_api_routines *pApi
+){
+  SQLITE_EXTENSION_INIT2(pApi);
+  sqlite3_create_function(db, "cube", 1, SQLITE_ANY, 0, cubeFunc, 0, 0);
+  return 0;
+}
+
+/*
+** This is a broken extension entry point
+*/
+static int broken_init(
+  sqlite3 *db, 
+  char **pzErrMsg, 
+  const sqlite3_api_routines *pApi
+){
+  char *zErr;
+  SQLITE_EXTENSION_INIT2(pApi);
+  zErr = sqlite3_mprintf("broken autoext!");
+  *pzErrMsg = zErr;
+  return 1;
+}
+
+/*
+** tclcmd:   sqlite3_auto_extension_sqr
+**
+** Register the "sqr" extension to be loaded automatically.
+*/
+static int autoExtSqrObjCmd(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc = sqlite3_auto_extension((void*)sqr_init);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+  return SQLITE_OK;
+}
+
+/*
+** tclcmd:   sqlite3_auto_extension_cube
+**
+** Register the "cube" extension to be loaded automatically.
+*/
+static int autoExtCubeObjCmd(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc = sqlite3_auto_extension((void*)cube_init);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+  return SQLITE_OK;
+}
+
+/*
+** tclcmd:   sqlite3_auto_extension_broken
+**
+** Register the broken extension to be loaded automatically.
+*/
+static int autoExtBrokenObjCmd(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc = sqlite3_auto_extension((void*)broken_init);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+  return SQLITE_OK;
+}
+
+#endif /* SQLITE_OMIT_LOAD_EXTENSION */
+
+
+/*
+** tclcmd:   sqlite3_reset_auto_extension
+**
+** Reset all auto-extensions
+*/
+static int resetAutoExtObjCmd(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_reset_auto_extension();
+  return SQLITE_OK;
+}
+
+
+/*
+** This procedure registers the TCL procs defined in this file.
+*/
+int Sqlitetest_autoext_Init(Tcl_Interp *interp){
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+  Tcl_CreateObjCommand(interp, "sqlite3_auto_extension_sqr",
+          autoExtSqrObjCmd, 0, 0);
+  Tcl_CreateObjCommand(interp, "sqlite3_auto_extension_cube",
+          autoExtCubeObjCmd, 0, 0);
+  Tcl_CreateObjCommand(interp, "sqlite3_auto_extension_broken",
+          autoExtBrokenObjCmd, 0, 0);
+#endif
+  Tcl_CreateObjCommand(interp, "sqlite3_reset_auto_extension",
+          resetAutoExtObjCmd, 0, 0);
+  return TCL_OK;
+}
diff --git a/src/test_backup.c b/src/test_backup.c
new file mode 100644
index 0000000..2727137
--- /dev/null
+++ b/src/test_backup.c
@@ -0,0 +1,148 @@
+/*
+** 2009 January 28
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains test logic for the sqlite3_backup() interface.
+**
+*/
+
+#include "tcl.h"
+#include <sqlite3.h>
+#include <assert.h>
+
+/* These functions are implemented in test1.c. */
+int getDbPointer(Tcl_Interp *, const char *, sqlite3 **);
+const char *sqlite3TestErrorName(int);
+
+static int backupTestCmd(
+  ClientData clientData, 
+  Tcl_Interp *interp, 
+  int objc,
+  Tcl_Obj *const*objv
+){
+  enum BackupSubCommandEnum {
+    BACKUP_STEP, BACKUP_FINISH, BACKUP_REMAINING, BACKUP_PAGECOUNT
+  };
+  struct BackupSubCommand {
+    const char *zCmd;
+    enum BackupSubCommandEnum eCmd;
+    int nArg;
+    const char *zArg;
+  } aSub[] = {
+    {"step",      BACKUP_STEP      , 1, "npage" },
+    {"finish",    BACKUP_FINISH    , 0, ""      },
+    {"remaining", BACKUP_REMAINING , 0, ""      },
+    {"pagecount", BACKUP_PAGECOUNT , 0, ""      },
+    {0, 0, 0, 0}
+  };
+
+  sqlite3_backup *p = (sqlite3_backup *)clientData;
+  int iCmd;
+  int rc;
+
+  rc = Tcl_GetIndexFromObjStruct(
+      interp, objv[1], aSub, sizeof(aSub[0]), "option", 0, &iCmd
+  );
+  if( rc!=TCL_OK ){
+    return rc;
+  }
+  if( objc!=(2 + aSub[iCmd].nArg) ){
+    Tcl_WrongNumArgs(interp, 2, objv, aSub[iCmd].zArg);
+    return TCL_ERROR;
+  }
+
+  switch( aSub[iCmd].eCmd ){
+
+    case BACKUP_FINISH: {
+      const char *zCmdName;
+      Tcl_CmdInfo cmdInfo;
+      zCmdName = Tcl_GetString(objv[0]);
+      Tcl_GetCommandInfo(interp, zCmdName, &cmdInfo);
+      cmdInfo.deleteProc = 0;
+      Tcl_SetCommandInfo(interp, zCmdName, &cmdInfo);
+      Tcl_DeleteCommand(interp, zCmdName);
+
+      rc = sqlite3_backup_finish(p);
+      Tcl_SetResult(interp, (char *)sqlite3TestErrorName(rc), TCL_STATIC);
+      break;
+    }
+
+    case BACKUP_STEP: {
+      int nPage;
+      if( TCL_OK!=Tcl_GetIntFromObj(interp, objv[2], &nPage) ){
+        return TCL_ERROR;
+      }
+      rc = sqlite3_backup_step(p, nPage);
+      Tcl_SetResult(interp, (char *)sqlite3TestErrorName(rc), TCL_STATIC);
+      break;
+    }
+
+    case BACKUP_REMAINING:
+      Tcl_SetObjResult(interp, Tcl_NewIntObj(sqlite3_backup_remaining(p)));
+      break;
+
+    case BACKUP_PAGECOUNT:
+      Tcl_SetObjResult(interp, Tcl_NewIntObj(sqlite3_backup_pagecount(p)));
+      break;
+  }
+
+  return TCL_OK;
+}
+
+static void backupTestFinish(ClientData clientData){
+  sqlite3_backup *pBackup = (sqlite3_backup *)clientData;
+  sqlite3_backup_finish(pBackup);
+}
+
+/*
+**     sqlite3_backup CMDNAME DESTHANDLE DESTNAME SRCHANDLE SRCNAME
+**
+*/
+static int backupTestInit(
+  ClientData clientData, 
+  Tcl_Interp *interp, 
+  int objc,
+  Tcl_Obj *const*objv
+){
+  sqlite3_backup *pBackup;
+  sqlite3 *pDestDb;
+  sqlite3 *pSrcDb;
+  const char *zDestName;
+  const char *zSrcName;
+  const char *zCmd;
+
+  if( objc!=6 ){
+    Tcl_WrongNumArgs(
+      interp, 1, objv, "CMDNAME DESTHANDLE DESTNAME SRCHANDLE SRCNAME"
+    );
+    return TCL_ERROR;
+  }
+
+  zCmd = Tcl_GetString(objv[1]);
+  getDbPointer(interp, Tcl_GetString(objv[2]), &pDestDb);
+  zDestName = Tcl_GetString(objv[3]);
+  getDbPointer(interp, Tcl_GetString(objv[4]), &pSrcDb);
+  zSrcName = Tcl_GetString(objv[5]);
+
+  pBackup = sqlite3_backup_init(pDestDb, zDestName, pSrcDb, zSrcName);
+  if( !pBackup ){
+    Tcl_AppendResult(interp, "sqlite3_backup_init() failed", 0);
+    return TCL_ERROR;
+  }
+
+  Tcl_CreateObjCommand(interp, zCmd, backupTestCmd, pBackup, backupTestFinish);
+  Tcl_SetObjResult(interp, objv[1]);
+  return TCL_OK;
+}
+
+int Sqlitetestbackup_Init(Tcl_Interp *interp){
+  Tcl_CreateObjCommand(interp, "sqlite3_backup", backupTestInit, 0, 0);
+  return TCL_OK;
+}
diff --git a/src/test_btree.c b/src/test_btree.c
new file mode 100644
index 0000000..0048397
--- /dev/null
+++ b/src/test_btree.c
@@ -0,0 +1,62 @@
+/*
+** 2007 May 05
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Code for testing the btree.c module in SQLite.  This code
+** is not included in the SQLite library.  It is used for automated
+** testing of the SQLite library.
+*/
+#include "btreeInt.h"
+#include <tcl.h>
+
+/*
+** Usage: sqlite3_shared_cache_report
+**
+** Return a list of file that are shared and the number of
+** references to each file.
+*/
+int sqlite3BtreeSharedCacheReport(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#ifndef SQLITE_OMIT_SHARED_CACHE
+  extern BtShared *sqlite3SharedCacheList;
+  BtShared *pBt;
+  Tcl_Obj *pRet = Tcl_NewObj();
+  for(pBt=GLOBAL(BtShared*,sqlite3SharedCacheList); pBt; pBt=pBt->pNext){
+    const char *zFile = sqlite3PagerFilename(pBt->pPager);
+    Tcl_ListObjAppendElement(interp, pRet, Tcl_NewStringObj(zFile, -1));
+    Tcl_ListObjAppendElement(interp, pRet, Tcl_NewIntObj(pBt->nRef));
+  }
+  Tcl_SetObjResult(interp, pRet);
+#endif
+  return TCL_OK;
+}
+
+/*
+** Print debugging information about all cursors to standard output.
+*/
+void sqlite3BtreeCursorList(Btree *p){
+#ifdef SQLITE_DEBUG
+  BtCursor *pCur;
+  BtShared *pBt = p->pBt;
+  for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
+    MemPage *pPage = pCur->apPage[pCur->iPage];
+    char *zMode = pCur->wrFlag ? "rw" : "ro";
+    sqlite3DebugPrintf("CURSOR %p rooted at %4d(%s) currently at %d.%d%s\n",
+       pCur, pCur->pgnoRoot, zMode,
+       pPage ? pPage->pgno : 0, pCur->aiIdx[pCur->iPage],
+       (pCur->eState==CURSOR_VALID) ? "" : " eof"
+    );
+  }
+#endif
+}
diff --git a/src/test_config.c b/src/test_config.c
new file mode 100644
index 0000000..ce72f87
--- /dev/null
+++ b/src/test_config.c
@@ -0,0 +1,602 @@
+/*
+** 2007 May 7
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** 
+** This file contains code used for testing the SQLite system.
+** None of the code in this file goes into a deliverable build.
+** 
+** The focus of this file is providing the TCL testing layer
+** access to compile-time constants.
+*/
+
+#include "sqliteLimit.h"
+
+#include "sqliteInt.h"
+#include "tcl.h"
+#include <stdlib.h>
+#include <string.h>
+
+/*
+** Macro to stringify the results of the evaluation a pre-processor
+** macro. i.e. so that STRINGVALUE(SQLITE_NOMEM) -> "7".
+*/
+#define STRINGVALUE2(x) #x
+#define STRINGVALUE(x) STRINGVALUE2(x)
+
+/*
+** This routine sets entries in the global ::sqlite_options() array variable
+** according to the compile-time configuration of the database.  Test
+** procedures use this to determine when tests should be omitted.
+*/
+static void set_options(Tcl_Interp *interp){
+#ifdef SQLITE_32BIT_ROWID
+  Tcl_SetVar2(interp, "sqlite_options", "rowid32", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "rowid32", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_CASE_SENSITIVE_LIKE
+  Tcl_SetVar2(interp, "sqlite_options","casesensitivelike","1",TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options","casesensitivelike","0",TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_DEBUG
+  Tcl_SetVar2(interp, "sqlite_options", "debug", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "debug", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_DIRECT_OVERFLOW_READ
+  Tcl_SetVar2(interp, "sqlite_options", "direct_read", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "direct_read", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_DISABLE_DIRSYNC
+  Tcl_SetVar2(interp, "sqlite_options", "dirsync", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "dirsync", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_DISABLE_LFS
+  Tcl_SetVar2(interp, "sqlite_options", "lfs", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "lfs", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#if 1 /* def SQLITE_MEMDEBUG */
+  Tcl_SetVar2(interp, "sqlite_options", "memdebug", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "memdebug", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_8_3_NAMES
+  Tcl_SetVar2(interp, "sqlite_options", "8_3_names", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "8_3_names", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_MEMSYS3
+  Tcl_SetVar2(interp, "sqlite_options", "mem3", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "mem3", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_MEMSYS5
+  Tcl_SetVar2(interp, "sqlite_options", "mem5", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "mem5", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_MUTEX_OMIT
+  Tcl_SetVar2(interp, "sqlite_options", "mutex", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "mutex", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_MUTEX_NOOP
+  Tcl_SetVar2(interp, "sqlite_options", "mutex_noop", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "mutex_noop", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_ALTERTABLE
+  Tcl_SetVar2(interp, "sqlite_options", "altertable", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "altertable", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_ANALYZE
+  Tcl_SetVar2(interp, "sqlite_options", "analyze", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "analyze", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_ATOMIC_WRITE
+  Tcl_SetVar2(interp, "sqlite_options", "atomicwrite", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "atomicwrite", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_ATTACH
+  Tcl_SetVar2(interp, "sqlite_options", "attach", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "attach", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_AUTHORIZATION
+  Tcl_SetVar2(interp, "sqlite_options", "auth", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "auth", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_AUTOINCREMENT
+  Tcl_SetVar2(interp, "sqlite_options", "autoinc", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "autoinc", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_AUTOMATIC_INDEX
+  Tcl_SetVar2(interp, "sqlite_options", "autoindex", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "autoindex", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_AUTORESET
+  Tcl_SetVar2(interp, "sqlite_options", "autoreset", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "autoreset", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_AUTOVACUUM
+  Tcl_SetVar2(interp, "sqlite_options", "autovacuum", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "autovacuum", "1", TCL_GLOBAL_ONLY);
+#endif /* SQLITE_OMIT_AUTOVACUUM */
+#if !defined(SQLITE_DEFAULT_AUTOVACUUM)
+  Tcl_SetVar2(interp,"sqlite_options","default_autovacuum","0",TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "default_autovacuum", 
+      STRINGVALUE(SQLITE_DEFAULT_AUTOVACUUM), TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_BETWEEN_OPTIMIZATION
+  Tcl_SetVar2(interp, "sqlite_options", "between_opt", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "between_opt", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_BUILTIN_TEST
+  Tcl_SetVar2(interp, "sqlite_options", "builtin_test", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "builtin_test", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_BLOB_LITERAL
+  Tcl_SetVar2(interp, "sqlite_options", "bloblit", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "bloblit", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_CAST
+  Tcl_SetVar2(interp, "sqlite_options", "cast", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "cast", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_CHECK
+  Tcl_SetVar2(interp, "sqlite_options", "check", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "check", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_COLUMN_METADATA
+  Tcl_SetVar2(interp, "sqlite_options", "columnmetadata", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "columnmetadata", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_OVERSIZE_CELL_CHECK
+  Tcl_SetVar2(interp, "sqlite_options", "oversize_cell_check", "1",
+              TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "oversize_cell_check", "0",
+              TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_COMPILEOPTION_DIAGS
+  Tcl_SetVar2(interp, "sqlite_options", "compileoption_diags", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "compileoption_diags", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_COMPLETE
+  Tcl_SetVar2(interp, "sqlite_options", "complete", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "complete", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_COMPOUND_SELECT
+  Tcl_SetVar2(interp, "sqlite_options", "compound", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "compound", "1", TCL_GLOBAL_ONLY);
+#endif
+
+  Tcl_SetVar2(interp, "sqlite_options", "conflict", "1", TCL_GLOBAL_ONLY);
+
+#if SQLITE_OS_UNIX
+  Tcl_SetVar2(interp, "sqlite_options", "crashtest", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "crashtest", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_DATETIME_FUNCS
+  Tcl_SetVar2(interp, "sqlite_options", "datetime", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "datetime", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_DECLTYPE
+  Tcl_SetVar2(interp, "sqlite_options", "decltype", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "decltype", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_DEPRECATED
+  Tcl_SetVar2(interp, "sqlite_options", "deprecated", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "deprecated", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_DISKIO
+  Tcl_SetVar2(interp, "sqlite_options", "diskio", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "diskio", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_EXPLAIN
+  Tcl_SetVar2(interp, "sqlite_options", "explain", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "explain", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_FLOATING_POINT
+  Tcl_SetVar2(interp, "sqlite_options", "floatingpoint", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "floatingpoint", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_FOREIGN_KEY
+  Tcl_SetVar2(interp, "sqlite_options", "foreignkey", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "foreignkey", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_FTS1
+  Tcl_SetVar2(interp, "sqlite_options", "fts1", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "fts1", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_FTS2
+  Tcl_SetVar2(interp, "sqlite_options", "fts2", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "fts2", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_FTS3
+  Tcl_SetVar2(interp, "sqlite_options", "fts3", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "fts3", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_GET_TABLE
+  Tcl_SetVar2(interp, "sqlite_options", "gettable", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "gettable", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_ICU
+  Tcl_SetVar2(interp, "sqlite_options", "icu", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "icu", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_INCRBLOB
+  Tcl_SetVar2(interp, "sqlite_options", "incrblob", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "incrblob", "1", TCL_GLOBAL_ONLY);
+#endif /* SQLITE_OMIT_AUTOVACUUM */
+
+#ifdef SQLITE_OMIT_INTEGRITY_CHECK
+  Tcl_SetVar2(interp, "sqlite_options", "integrityck", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "integrityck", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#if defined(SQLITE_DEFAULT_FILE_FORMAT) && SQLITE_DEFAULT_FILE_FORMAT==1
+  Tcl_SetVar2(interp, "sqlite_options", "legacyformat", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "legacyformat", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_LIKE_OPTIMIZATION
+  Tcl_SetVar2(interp, "sqlite_options", "like_opt", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "like_opt", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_LOAD_EXTENSION
+  Tcl_SetVar2(interp, "sqlite_options", "load_ext", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "load_ext", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_LOCALTIME
+  Tcl_SetVar2(interp, "sqlite_options", "localtime", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "localtime", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_LOOKASIDE
+  Tcl_SetVar2(interp, "sqlite_options", "lookaside", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "lookaside", "1", TCL_GLOBAL_ONLY);
+#endif
+
+Tcl_SetVar2(interp, "sqlite_options", "long_double",
+              sizeof(LONGDOUBLE_TYPE)>sizeof(double) ? "1" : "0",
+              TCL_GLOBAL_ONLY);
+
+#ifdef SQLITE_OMIT_MEMORYDB
+  Tcl_SetVar2(interp, "sqlite_options", "memorydb", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "memorydb", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
+  Tcl_SetVar2(interp, "sqlite_options", "memorymanage", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "memorymanage", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_MERGE_SORT
+  Tcl_SetVar2(interp, "sqlite_options", "mergesort", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "mergesort", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_OR_OPTIMIZATION
+  Tcl_SetVar2(interp, "sqlite_options", "or_opt", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "or_opt", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_PAGER_PRAGMAS
+  Tcl_SetVar2(interp, "sqlite_options", "pager_pragmas", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "pager_pragmas", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#if defined(SQLITE_OMIT_PRAGMA) || defined(SQLITE_OMIT_FLAG_PRAGMAS)
+  Tcl_SetVar2(interp, "sqlite_options", "pragma", "0", TCL_GLOBAL_ONLY);
+  Tcl_SetVar2(interp, "sqlite_options", "integrityck", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "pragma", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_PROGRESS_CALLBACK
+  Tcl_SetVar2(interp, "sqlite_options", "progress", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "progress", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_REINDEX
+  Tcl_SetVar2(interp, "sqlite_options", "reindex", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "reindex", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_RTREE
+  Tcl_SetVar2(interp, "sqlite_options", "rtree", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "rtree", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_SCHEMA_PRAGMAS
+  Tcl_SetVar2(interp, "sqlite_options", "schema_pragmas", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "schema_pragmas", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_SCHEMA_VERSION_PRAGMAS
+  Tcl_SetVar2(interp, "sqlite_options", "schema_version", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "schema_version", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_ENABLE_STAT3
+  Tcl_SetVar2(interp, "sqlite_options", "stat3", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "stat3", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#if !defined(SQLITE_ENABLE_LOCKING_STYLE)
+#  if defined(__APPLE__)
+#    define SQLITE_ENABLE_LOCKING_STYLE 1
+#  else
+#    define SQLITE_ENABLE_LOCKING_STYLE 0
+#  endif
+#endif
+#if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__)
+  Tcl_SetVar2(interp,"sqlite_options","lock_proxy_pragmas","1",TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp,"sqlite_options","lock_proxy_pragmas","0",TCL_GLOBAL_ONLY);
+#endif
+#if defined(SQLITE_PREFER_PROXY_LOCKING) && defined(__APPLE__)
+  Tcl_SetVar2(interp,"sqlite_options","prefer_proxy_locking","1",TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp,"sqlite_options","prefer_proxy_locking","0",TCL_GLOBAL_ONLY);
+#endif
+    
+    
+#ifdef SQLITE_OMIT_SHARED_CACHE
+  Tcl_SetVar2(interp, "sqlite_options", "shared_cache", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "shared_cache", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_SUBQUERY
+  Tcl_SetVar2(interp, "sqlite_options", "subquery", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "subquery", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_TCL_VARIABLE
+  Tcl_SetVar2(interp, "sqlite_options", "tclvar", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "tclvar", "1", TCL_GLOBAL_ONLY);
+#endif
+
+  Tcl_SetVar2(interp, "sqlite_options", "threadsafe", 
+      STRINGVALUE(SQLITE_THREADSAFE), TCL_GLOBAL_ONLY);
+  assert( sqlite3_threadsafe()==SQLITE_THREADSAFE );
+
+#ifdef SQLITE_OMIT_TEMPDB
+  Tcl_SetVar2(interp, "sqlite_options", "tempdb", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "tempdb", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_TRACE
+  Tcl_SetVar2(interp, "sqlite_options", "trace", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "trace", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_TRIGGER
+  Tcl_SetVar2(interp, "sqlite_options", "trigger", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "trigger", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_TRUNCATE_OPTIMIZATION
+  Tcl_SetVar2(interp, "sqlite_options", "truncate_opt", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "truncate_opt", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_UTF16
+  Tcl_SetVar2(interp, "sqlite_options", "utf16", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "utf16", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#if defined(SQLITE_OMIT_VACUUM) || defined(SQLITE_OMIT_ATTACH)
+  Tcl_SetVar2(interp, "sqlite_options", "vacuum", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "vacuum", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_VIEW
+  Tcl_SetVar2(interp, "sqlite_options", "view", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "view", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_VIRTUALTABLE
+  Tcl_SetVar2(interp, "sqlite_options", "vtab", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "vtab", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_WAL
+  Tcl_SetVar2(interp, "sqlite_options", "wal", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "wal", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_OMIT_WSD
+  Tcl_SetVar2(interp, "sqlite_options", "wsd", "0", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "wsd", "1", TCL_GLOBAL_ONLY);
+#endif
+
+#if defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT) && !defined(SQLITE_OMIT_SUBQUERY)
+  Tcl_SetVar2(interp, "sqlite_options", "update_delete_limit", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "update_delete_limit", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#if defined(SQLITE_ENABLE_UNLOCK_NOTIFY)
+  Tcl_SetVar2(interp, "sqlite_options", "unlock_notify", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "unlock_notify", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_SECURE_DELETE
+  Tcl_SetVar2(interp, "sqlite_options", "secure_delete", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "secure_delete", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef SQLITE_MULTIPLEX_EXT_OVWR
+  Tcl_SetVar2(interp, "sqlite_options", "multiplex_ext_overwrite", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "multiplex_ext_overwrite", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#ifdef YYTRACKMAXSTACKDEPTH
+  Tcl_SetVar2(interp, "sqlite_options", "yytrackmaxstackdepth", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "yytrackmaxstackdepth", "0", TCL_GLOBAL_ONLY);
+#endif
+
+#define LINKVAR(x) { \
+    static const int cv_ ## x = SQLITE_ ## x; \
+    Tcl_LinkVar(interp, "SQLITE_" #x, (char *)&(cv_ ## x), \
+                TCL_LINK_INT | TCL_LINK_READ_ONLY); }
+
+  LINKVAR( MAX_LENGTH );
+  LINKVAR( MAX_COLUMN );
+  LINKVAR( MAX_SQL_LENGTH );
+  LINKVAR( MAX_EXPR_DEPTH );
+  LINKVAR( MAX_COMPOUND_SELECT );
+  LINKVAR( MAX_VDBE_OP );
+  LINKVAR( MAX_FUNCTION_ARG );
+  LINKVAR( MAX_VARIABLE_NUMBER );
+  LINKVAR( MAX_PAGE_SIZE );
+  LINKVAR( MAX_PAGE_COUNT );
+  LINKVAR( MAX_LIKE_PATTERN_LENGTH );
+  LINKVAR( MAX_TRIGGER_DEPTH );
+  LINKVAR( DEFAULT_TEMP_CACHE_SIZE );
+  LINKVAR( DEFAULT_CACHE_SIZE );
+  LINKVAR( DEFAULT_PAGE_SIZE );
+  LINKVAR( DEFAULT_FILE_FORMAT );
+  LINKVAR( MAX_ATTACHED );
+  LINKVAR( MAX_DEFAULT_PAGE_SIZE );
+
+  {
+    static const int cv_TEMP_STORE = SQLITE_TEMP_STORE;
+    Tcl_LinkVar(interp, "TEMP_STORE", (char *)&(cv_TEMP_STORE),
+                TCL_LINK_INT | TCL_LINK_READ_ONLY);
+  }
+}
+
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqliteconfig_Init(Tcl_Interp *interp){
+  set_options(interp);
+  return TCL_OK;
+}
diff --git a/src/test_demovfs.c b/src/test_demovfs.c
new file mode 100644
index 0000000..6376270
--- /dev/null
+++ b/src/test_demovfs.c
@@ -0,0 +1,679 @@
+/*
+** 2010 April 7
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file implements an example of a simple VFS implementation that 
+** omits complex features often not required or not possible on embedded
+** platforms.  Code is included to buffer writes to the journal file, 
+** which can be a significant performance improvement on some embedded
+** platforms.
+**
+** OVERVIEW
+**
+**   The code in this file implements a minimal SQLite VFS that can be 
+**   used on Linux and other posix-like operating systems. The following 
+**   system calls are used:
+**
+**    File-system: access(), unlink(), getcwd()
+**    File IO:     open(), read(), write(), fsync(), close(), fstat()
+**    Other:       sleep(), usleep(), time()
+**
+**   The following VFS features are omitted:
+**
+**     1. File locking. The user must ensure that there is at most one
+**        connection to each database when using this VFS. Multiple
+**        connections to a single shared-cache count as a single connection
+**        for the purposes of the previous statement.
+**
+**     2. The loading of dynamic extensions (shared libraries).
+**
+**     3. Temporary files. The user must configure SQLite to use in-memory
+**        temp files when using this VFS. The easiest way to do this is to
+**        compile with:
+**
+**          -DSQLITE_TEMP_STORE=3
+**
+**     4. File truncation. As of version 3.6.24, SQLite may run without
+**        a working xTruncate() call, providing the user does not configure
+**        SQLite to use "journal_mode=truncate", or use both
+**        "journal_mode=persist" and ATTACHed databases.
+**
+**   It is assumed that the system uses UNIX-like path-names. Specifically,
+**   that '/' characters are used to separate path components and that
+**   a path-name is a relative path unless it begins with a '/'. And that
+**   no UTF-8 encoded paths are greater than 512 bytes in length.
+**
+** JOURNAL WRITE-BUFFERING
+**
+**   To commit a transaction to the database, SQLite first writes rollback
+**   information into the journal file. This usually consists of 4 steps:
+**
+**     1. The rollback information is sequentially written into the journal
+**        file, starting at the start of the file.
+**     2. The journal file is synced to disk.
+**     3. A modification is made to the first few bytes of the journal file.
+**     4. The journal file is synced to disk again.
+**
+**   Most of the data is written in step 1 using a series of calls to the
+**   VFS xWrite() method. The buffers passed to the xWrite() calls are of
+**   various sizes. For example, as of version 3.6.24, when committing a 
+**   transaction that modifies 3 pages of a database file that uses 4096 
+**   byte pages residing on a media with 512 byte sectors, SQLite makes 
+**   eleven calls to the xWrite() method to create the rollback journal, 
+**   as follows:
+**
+**             Write offset | Bytes written
+**             ----------------------------
+**                        0            512
+**                      512              4
+**                      516           4096
+**                     4612              4
+**                     4616              4
+**                     4620           4096
+**                     8716              4
+**                     8720              4
+**                     8724           4096
+**                    12820              4
+**             ++++++++++++SYNC+++++++++++
+**                        0             12
+**             ++++++++++++SYNC+++++++++++
+**
+**   On many operating systems, this is an efficient way to write to a file.
+**   However, on some embedded systems that do not cache writes in OS 
+**   buffers it is much more efficient to write data in blocks that are
+**   an integer multiple of the sector-size in size and aligned at the
+**   start of a sector.
+**
+**   To work around this, the code in this file allocates a fixed size
+**   buffer of SQLITE_DEMOVFS_BUFFERSZ using sqlite3_malloc() whenever a 
+**   journal file is opened. It uses the buffer to coalesce sequential
+**   writes into aligned SQLITE_DEMOVFS_BUFFERSZ blocks. When SQLite
+**   invokes the xSync() method to sync the contents of the file to disk,
+**   all accumulated data is written out, even if it does not constitute
+**   a complete block. This means the actual IO to create the rollback 
+**   journal for the example transaction above is this:
+**
+**             Write offset | Bytes written
+**             ----------------------------
+**                        0           8192
+**                     8192           4632
+**             ++++++++++++SYNC+++++++++++
+**                        0             12
+**             ++++++++++++SYNC+++++++++++
+**
+**   Much more efficient if the underlying OS is not caching write 
+**   operations.
+*/
+
+#if !defined(SQLITE_TEST) || SQLITE_OS_UNIX
+
+#include <sqlite3.h>
+
+#include <assert.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/file.h>
+#include <sys/param.h>
+#include <unistd.h>
+#include <time.h>
+#include <errno.h>
+#include <fcntl.h>
+
+/*
+** Size of the write buffer used by journal files in bytes.
+*/
+#ifndef SQLITE_DEMOVFS_BUFFERSZ
+# define SQLITE_DEMOVFS_BUFFERSZ 8192
+#endif
+
+/*
+** The maximum pathname length supported by this VFS.
+*/
+#define MAXPATHNAME 512
+
+/*
+** When using this VFS, the sqlite3_file* handles that SQLite uses are
+** actually pointers to instances of type DemoFile.
+*/
+typedef struct DemoFile DemoFile;
+struct DemoFile {
+  sqlite3_file base;              /* Base class. Must be first. */
+  int fd;                         /* File descriptor */
+
+  char *aBuffer;                  /* Pointer to malloc'd buffer */
+  int nBuffer;                    /* Valid bytes of data in zBuffer */
+  sqlite3_int64 iBufferOfst;      /* Offset in file of zBuffer[0] */
+};
+
+/*
+** Write directly to the file passed as the first argument. Even if the
+** file has a write-buffer (DemoFile.aBuffer), ignore it.
+*/
+static int demoDirectWrite(
+  DemoFile *p,                    /* File handle */
+  const void *zBuf,               /* Buffer containing data to write */
+  int iAmt,                       /* Size of data to write in bytes */
+  sqlite_int64 iOfst              /* File offset to write to */
+){
+  off_t ofst;                     /* Return value from lseek() */
+  size_t nWrite;                  /* Return value from write() */
+
+  ofst = lseek(p->fd, iOfst, SEEK_SET);
+  if( ofst!=iOfst ){
+    return SQLITE_IOERR_WRITE;
+  }
+
+  nWrite = write(p->fd, zBuf, iAmt);
+  if( nWrite!=iAmt ){
+    return SQLITE_IOERR_WRITE;
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** Flush the contents of the DemoFile.aBuffer buffer to disk. This is a
+** no-op if this particular file does not have a buffer (i.e. it is not
+** a journal file) or if the buffer is currently empty.
+*/
+static int demoFlushBuffer(DemoFile *p){
+  int rc = SQLITE_OK;
+  if( p->nBuffer ){
+    rc = demoDirectWrite(p, p->aBuffer, p->nBuffer, p->iBufferOfst);
+    p->nBuffer = 0;
+  }
+  return rc;
+}
+
+/*
+** Close a file.
+*/
+static int demoClose(sqlite3_file *pFile){
+  int rc;
+  DemoFile *p = (DemoFile*)pFile;
+  rc = demoFlushBuffer(p);
+  sqlite3_free(p->aBuffer);
+  close(p->fd);
+  return rc;
+}
+
+/*
+** Read data from a file.
+*/
+static int demoRead(
+  sqlite3_file *pFile, 
+  void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  DemoFile *p = (DemoFile*)pFile;
+  off_t ofst;                     /* Return value from lseek() */
+  int nRead;                      /* Return value from read() */
+  int rc;                         /* Return code from demoFlushBuffer() */
+
+  /* Flush any data in the write buffer to disk in case this operation
+  ** is trying to read data the file-region currently cached in the buffer.
+  ** It would be possible to detect this case and possibly save an 
+  ** unnecessary write here, but in practice SQLite will rarely read from
+  ** a journal file when there is data cached in the write-buffer.
+  */
+  rc = demoFlushBuffer(p);
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+
+  ofst = lseek(p->fd, iOfst, SEEK_SET);
+  if( ofst!=iOfst ){
+    return SQLITE_IOERR_READ;
+  }
+  nRead = read(p->fd, zBuf, iAmt);
+
+  if( nRead==iAmt ){
+    return SQLITE_OK;
+  }else if( nRead>=0 ){
+    return SQLITE_IOERR_SHORT_READ;
+  }
+
+  return SQLITE_IOERR_READ;
+}
+
+/*
+** Write data to a crash-file.
+*/
+static int demoWrite(
+  sqlite3_file *pFile, 
+  const void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  DemoFile *p = (DemoFile*)pFile;
+  
+  if( p->aBuffer ){
+    char *z = (char *)zBuf;       /* Pointer to remaining data to write */
+    int n = iAmt;                 /* Number of bytes at z */
+    sqlite3_int64 i = iOfst;      /* File offset to write to */
+
+    while( n>0 ){
+      int nCopy;                  /* Number of bytes to copy into buffer */
+
+      /* If the buffer is full, or if this data is not being written directly
+      ** following the data already buffered, flush the buffer. Flushing
+      ** the buffer is a no-op if it is empty.  
+      */
+      if( p->nBuffer==SQLITE_DEMOVFS_BUFFERSZ || p->iBufferOfst+p->nBuffer!=i ){
+        int rc = demoFlushBuffer(p);
+        if( rc!=SQLITE_OK ){
+          return rc;
+        }
+      }
+      assert( p->nBuffer==0 || p->iBufferOfst+p->nBuffer==i );
+      p->iBufferOfst = i - p->nBuffer;
+
+      /* Copy as much data as possible into the buffer. */
+      nCopy = SQLITE_DEMOVFS_BUFFERSZ - p->nBuffer;
+      if( nCopy>n ){
+        nCopy = n;
+      }
+      memcpy(&p->aBuffer[p->nBuffer], z, nCopy);
+      p->nBuffer += nCopy;
+
+      n -= nCopy;
+      i += nCopy;
+      z += nCopy;
+    }
+  }else{
+    return demoDirectWrite(p, zBuf, iAmt, iOfst);
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** Truncate a file. This is a no-op for this VFS (see header comments at
+** the top of the file).
+*/
+static int demoTruncate(sqlite3_file *pFile, sqlite_int64 size){
+#if 0
+  if( ftruncate(((DemoFile *)pFile)->fd, size) ) return SQLITE_IOERR_TRUNCATE;
+#endif
+  return SQLITE_OK;
+}
+
+/*
+** Sync the contents of the file to the persistent media.
+*/
+static int demoSync(sqlite3_file *pFile, int flags){
+  DemoFile *p = (DemoFile*)pFile;
+  int rc;
+
+  rc = demoFlushBuffer(p);
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+
+  rc = fsync(p->fd);
+  return (rc==0 ? SQLITE_OK : SQLITE_IOERR_FSYNC);
+}
+
+/*
+** Write the size of the file in bytes to *pSize.
+*/
+static int demoFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
+  DemoFile *p = (DemoFile*)pFile;
+  int rc;                         /* Return code from fstat() call */
+  struct stat sStat;              /* Output of fstat() call */
+
+  /* Flush the contents of the buffer to disk. As with the flush in the
+  ** demoRead() method, it would be possible to avoid this and save a write
+  ** here and there. But in practice this comes up so infrequently it is
+  ** not worth the trouble.
+  */
+  rc = demoFlushBuffer(p);
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+
+  rc = fstat(p->fd, &sStat);
+  if( rc!=0 ) return SQLITE_IOERR_FSTAT;
+  *pSize = sStat.st_size;
+  return SQLITE_OK;
+}
+
+/*
+** Locking functions. The xLock() and xUnlock() methods are both no-ops.
+** The xCheckReservedLock() always indicates that no other process holds
+** a reserved lock on the database file. This ensures that if a hot-journal
+** file is found in the file-system it is rolled back.
+*/
+static int demoLock(sqlite3_file *pFile, int eLock){
+  return SQLITE_OK;
+}
+static int demoUnlock(sqlite3_file *pFile, int eLock){
+  return SQLITE_OK;
+}
+static int demoCheckReservedLock(sqlite3_file *pFile, int *pResOut){
+  *pResOut = 0;
+  return SQLITE_OK;
+}
+
+/*
+** No xFileControl() verbs are implemented by this VFS.
+*/
+static int demoFileControl(sqlite3_file *pFile, int op, void *pArg){
+  return SQLITE_OK;
+}
+
+/*
+** The xSectorSize() and xDeviceCharacteristics() methods. These two
+** may return special values allowing SQLite to optimize file-system 
+** access to some extent. But it is also safe to simply return 0.
+*/
+static int demoSectorSize(sqlite3_file *pFile){
+  return 0;
+}
+static int demoDeviceCharacteristics(sqlite3_file *pFile){
+  return 0;
+}
+
+/*
+** Open a file handle.
+*/
+static int demoOpen(
+  sqlite3_vfs *pVfs,              /* VFS */
+  const char *zName,              /* File to open, or 0 for a temp file */
+  sqlite3_file *pFile,            /* Pointer to DemoFile struct to populate */
+  int flags,                      /* Input SQLITE_OPEN_XXX flags */
+  int *pOutFlags                  /* Output SQLITE_OPEN_XXX flags (or NULL) */
+){
+  static const sqlite3_io_methods demoio = {
+    1,                            /* iVersion */
+    demoClose,                    /* xClose */
+    demoRead,                     /* xRead */
+    demoWrite,                    /* xWrite */
+    demoTruncate,                 /* xTruncate */
+    demoSync,                     /* xSync */
+    demoFileSize,                 /* xFileSize */
+    demoLock,                     /* xLock */
+    demoUnlock,                   /* xUnlock */
+    demoCheckReservedLock,        /* xCheckReservedLock */
+    demoFileControl,              /* xFileControl */
+    demoSectorSize,               /* xSectorSize */
+    demoDeviceCharacteristics     /* xDeviceCharacteristics */
+  };
+
+  DemoFile *p = (DemoFile*)pFile; /* Populate this structure */
+  int oflags = 0;                 /* flags to pass to open() call */
+  char *aBuf = 0;
+
+  if( zName==0 ){
+    return SQLITE_IOERR;
+  }
+
+  if( flags&SQLITE_OPEN_MAIN_JOURNAL ){
+    aBuf = (char *)sqlite3_malloc(SQLITE_DEMOVFS_BUFFERSZ);
+    if( !aBuf ){
+      return SQLITE_NOMEM;
+    }
+  }
+
+  if( flags&SQLITE_OPEN_EXCLUSIVE ) oflags |= O_EXCL;
+  if( flags&SQLITE_OPEN_CREATE )    oflags |= O_CREAT;
+  if( flags&SQLITE_OPEN_READONLY )  oflags |= O_RDONLY;
+  if( flags&SQLITE_OPEN_READWRITE ) oflags |= O_RDWR;
+
+  memset(p, 0, sizeof(DemoFile));
+  p->fd = open(zName, oflags, 0600);
+  if( p->fd<0 ){
+    sqlite3_free(aBuf);
+    return SQLITE_CANTOPEN;
+  }
+  p->aBuffer = aBuf;
+
+  if( pOutFlags ){
+    *pOutFlags = flags;
+  }
+  p->base.pMethods = &demoio;
+  return SQLITE_OK;
+}
+
+/*
+** Delete the file identified by argument zPath. If the dirSync parameter
+** is non-zero, then ensure the file-system modification to delete the
+** file has been synced to disk before returning.
+*/
+static int demoDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
+  int rc;                         /* Return code */
+
+  rc = unlink(zPath);
+  if( rc!=0 && errno==ENOENT ) return SQLITE_OK;
+
+  if( rc==0 && dirSync ){
+    int dfd;                      /* File descriptor open on directory */
+    int i;                        /* Iterator variable */
+    char zDir[MAXPATHNAME+1];     /* Name of directory containing file zPath */
+
+    /* Figure out the directory name from the path of the file deleted. */
+    sqlite3_snprintf(MAXPATHNAME, zDir, "%s", zPath);
+    zDir[MAXPATHNAME] = '\0';
+    for(i=strlen(zDir); i>1 && zDir[i]!='/'; i++);
+    zDir[i] = '\0';
+
+    /* Open a file-descriptor on the directory. Sync. Close. */
+    dfd = open(zDir, O_RDONLY, 0);
+    if( dfd<0 ){
+      rc = -1;
+    }else{
+      rc = fsync(dfd);
+      close(dfd);
+    }
+  }
+  return (rc==0 ? SQLITE_OK : SQLITE_IOERR_DELETE);
+}
+
+#ifndef F_OK
+# define F_OK 0
+#endif
+#ifndef R_OK
+# define R_OK 4
+#endif
+#ifndef W_OK
+# define W_OK 2
+#endif
+
+/*
+** Query the file-system to see if the named file exists, is readable or
+** is both readable and writable.
+*/
+static int demoAccess(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  int flags, 
+  int *pResOut
+){
+  int rc;                         /* access() return code */
+  int eAccess = F_OK;             /* Second argument to access() */
+
+  assert( flags==SQLITE_ACCESS_EXISTS       /* access(zPath, F_OK) */
+       || flags==SQLITE_ACCESS_READ         /* access(zPath, R_OK) */
+       || flags==SQLITE_ACCESS_READWRITE    /* access(zPath, R_OK|W_OK) */
+  );
+
+  if( flags==SQLITE_ACCESS_READWRITE ) eAccess = R_OK|W_OK;
+  if( flags==SQLITE_ACCESS_READ )      eAccess = R_OK;
+
+  rc = access(zPath, eAccess);
+  *pResOut = (rc==0);
+  return SQLITE_OK;
+}
+
+/*
+** Argument zPath points to a nul-terminated string containing a file path.
+** If zPath is an absolute path, then it is copied as is into the output 
+** buffer. Otherwise, if it is a relative path, then the equivalent full
+** path is written to the output buffer.
+**
+** This function assumes that paths are UNIX style. Specifically, that:
+**
+**   1. Path components are separated by a '/'. and 
+**   2. Full paths begin with a '/' character.
+*/
+static int demoFullPathname(
+  sqlite3_vfs *pVfs,              /* VFS */
+  const char *zPath,              /* Input path (possibly a relative path) */
+  int nPathOut,                   /* Size of output buffer in bytes */
+  char *zPathOut                  /* Pointer to output buffer */
+){
+  char zDir[MAXPATHNAME+1];
+  if( zPath[0]=='/' ){
+    zDir[0] = '\0';
+  }else{
+    getcwd(zDir, sizeof(zDir));
+  }
+  zDir[MAXPATHNAME] = '\0';
+
+  sqlite3_snprintf(nPathOut, zPathOut, "%s/%s", zDir, zPath);
+  zPathOut[nPathOut-1] = '\0';
+
+  return SQLITE_OK;
+}
+
+/*
+** The following four VFS methods:
+**
+**   xDlOpen
+**   xDlError
+**   xDlSym
+**   xDlClose
+**
+** are supposed to implement the functionality needed by SQLite to load
+** extensions compiled as shared objects. This simple VFS does not support
+** this functionality, so the following functions are no-ops.
+*/
+static void *demoDlOpen(sqlite3_vfs *pVfs, const char *zPath){
+  return 0;
+}
+static void demoDlError(sqlite3_vfs *pVfs, int nByte, char *zErrMsg){
+  sqlite3_snprintf(nByte, zErrMsg, "Loadable extensions are not supported");
+  zErrMsg[nByte-1] = '\0';
+}
+static void (*demoDlSym(sqlite3_vfs *pVfs, void *pH, const char *z))(void){
+  return 0;
+}
+static void demoDlClose(sqlite3_vfs *pVfs, void *pHandle){
+  return;
+}
+
+/*
+** Parameter zByte points to a buffer nByte bytes in size. Populate this
+** buffer with pseudo-random data.
+*/
+static int demoRandomness(sqlite3_vfs *pVfs, int nByte, char *zByte){
+  return SQLITE_OK;
+}
+
+/*
+** Sleep for at least nMicro microseconds. Return the (approximate) number 
+** of microseconds slept for.
+*/
+static int demoSleep(sqlite3_vfs *pVfs, int nMicro){
+  sleep(nMicro / 1000000);
+  usleep(nMicro % 1000000);
+  return nMicro;
+}
+
+/*
+** Set *pTime to the current UTC time expressed as a Julian day. Return
+** SQLITE_OK if successful, or an error code otherwise.
+**
+**   http://en.wikipedia.org/wiki/Julian_day
+**
+** This implementation is not very good. The current time is rounded to
+** an integer number of seconds. Also, assuming time_t is a signed 32-bit 
+** value, it will stop working some time in the year 2038 AD (the so-called
+** "year 2038" problem that afflicts systems that store time this way). 
+*/
+static int demoCurrentTime(sqlite3_vfs *pVfs, double *pTime){
+  time_t t = time(0);
+  *pTime = t/86400.0 + 2440587.5; 
+  return SQLITE_OK;
+}
+
+/*
+** This function returns a pointer to the VFS implemented in this file.
+** To make the VFS available to SQLite:
+**
+**   sqlite3_vfs_register(sqlite3_demovfs(), 0);
+*/
+sqlite3_vfs *sqlite3_demovfs(void){
+  static sqlite3_vfs demovfs = {
+    1,                            /* iVersion */
+    sizeof(DemoFile),             /* szOsFile */
+    MAXPATHNAME,                  /* mxPathname */
+    0,                            /* pNext */
+    "demo",                       /* zName */
+    0,                            /* pAppData */
+    demoOpen,                     /* xOpen */
+    demoDelete,                   /* xDelete */
+    demoAccess,                   /* xAccess */
+    demoFullPathname,             /* xFullPathname */
+    demoDlOpen,                   /* xDlOpen */
+    demoDlError,                  /* xDlError */
+    demoDlSym,                    /* xDlSym */
+    demoDlClose,                  /* xDlClose */
+    demoRandomness,               /* xRandomness */
+    demoSleep,                    /* xSleep */
+    demoCurrentTime,              /* xCurrentTime */
+  };
+  return &demovfs;
+}
+
+#endif /* !defined(SQLITE_TEST) || SQLITE_OS_UNIX */
+
+
+#ifdef SQLITE_TEST
+
+#include <tcl.h>
+
+#if SQLITE_OS_UNIX
+static int register_demovfs(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3_vfs_register(sqlite3_demovfs(), 1);
+  return TCL_OK;
+}
+static int unregister_demovfs(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3_vfs_unregister(sqlite3_demovfs());
+  return TCL_OK;
+}
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetest_demovfs_Init(Tcl_Interp *interp){
+  Tcl_CreateObjCommand(interp, "register_demovfs", register_demovfs, 0, 0);
+  Tcl_CreateObjCommand(interp, "unregister_demovfs", unregister_demovfs, 0, 0);
+  return TCL_OK;
+}
+
+#else
+int Sqlitetest_demovfs_Init(Tcl_Interp *interp){ return TCL_OK; }
+#endif
+
+#endif /* SQLITE_TEST */
diff --git a/src/test_devsym.c b/src/test_devsym.c
new file mode 100644
index 0000000..21f0f68
--- /dev/null
+++ b/src/test_devsym.c
@@ -0,0 +1,398 @@
+/*
+** 2008 Jan 22
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains code that modified the OS layer in order to simulate
+** different device types (by overriding the return values of the 
+** xDeviceCharacteristics() and xSectorSize() methods).
+*/
+#if SQLITE_TEST          /* This file is used for testing only */
+
+#include "sqlite3.h"
+#include "sqliteInt.h"
+
+/*
+** Maximum pathname length supported by the devsym backend.
+*/
+#define DEVSYM_MAX_PATHNAME 512
+
+/*
+** Name used to identify this VFS.
+*/
+#define DEVSYM_VFS_NAME "devsym"
+
+typedef struct devsym_file devsym_file;
+struct devsym_file {
+  sqlite3_file base;
+  sqlite3_file *pReal;
+};
+
+/*
+** Method declarations for devsym_file.
+*/
+static int devsymClose(sqlite3_file*);
+static int devsymRead(sqlite3_file*, void*, int iAmt, sqlite3_int64 iOfst);
+static int devsymWrite(sqlite3_file*,const void*,int iAmt, sqlite3_int64 iOfst);
+static int devsymTruncate(sqlite3_file*, sqlite3_int64 size);
+static int devsymSync(sqlite3_file*, int flags);
+static int devsymFileSize(sqlite3_file*, sqlite3_int64 *pSize);
+static int devsymLock(sqlite3_file*, int);
+static int devsymUnlock(sqlite3_file*, int);
+static int devsymCheckReservedLock(sqlite3_file*, int *);
+static int devsymFileControl(sqlite3_file*, int op, void *pArg);
+static int devsymSectorSize(sqlite3_file*);
+static int devsymDeviceCharacteristics(sqlite3_file*);
+static int devsymShmLock(sqlite3_file*,int,int,int);
+static int devsymShmMap(sqlite3_file*,int,int,int, void volatile **);
+static void devsymShmBarrier(sqlite3_file*);
+static int devsymShmUnmap(sqlite3_file*,int);
+
+/*
+** Method declarations for devsym_vfs.
+*/
+static int devsymOpen(sqlite3_vfs*, const char *, sqlite3_file*, int , int *);
+static int devsymDelete(sqlite3_vfs*, const char *zName, int syncDir);
+static int devsymAccess(sqlite3_vfs*, const char *zName, int flags, int *);
+static int devsymFullPathname(sqlite3_vfs*, const char *zName, int, char *zOut);
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+static void *devsymDlOpen(sqlite3_vfs*, const char *zFilename);
+static void devsymDlError(sqlite3_vfs*, int nByte, char *zErrMsg);
+static void (*devsymDlSym(sqlite3_vfs*,void*, const char *zSymbol))(void);
+static void devsymDlClose(sqlite3_vfs*, void*);
+#endif /* SQLITE_OMIT_LOAD_EXTENSION */
+static int devsymRandomness(sqlite3_vfs*, int nByte, char *zOut);
+static int devsymSleep(sqlite3_vfs*, int microseconds);
+static int devsymCurrentTime(sqlite3_vfs*, double*);
+
+static sqlite3_vfs devsym_vfs = {
+  2,                     /* iVersion */
+  sizeof(devsym_file),      /* szOsFile */
+  DEVSYM_MAX_PATHNAME,      /* mxPathname */
+  0,                     /* pNext */
+  DEVSYM_VFS_NAME,          /* zName */
+  0,                     /* pAppData */
+  devsymOpen,               /* xOpen */
+  devsymDelete,             /* xDelete */
+  devsymAccess,             /* xAccess */
+  devsymFullPathname,       /* xFullPathname */
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+  devsymDlOpen,             /* xDlOpen */
+  devsymDlError,            /* xDlError */
+  devsymDlSym,              /* xDlSym */
+  devsymDlClose,            /* xDlClose */
+#else
+  0,                        /* xDlOpen */
+  0,                        /* xDlError */
+  0,                        /* xDlSym */
+  0,                        /* xDlClose */
+#endif /* SQLITE_OMIT_LOAD_EXTENSION */
+  devsymRandomness,         /* xRandomness */
+  devsymSleep,              /* xSleep */
+  devsymCurrentTime,        /* xCurrentTime */
+  0,                        /* xGetLastError */
+  0                         /* xCurrentTimeInt64 */
+};
+
+static sqlite3_io_methods devsym_io_methods = {
+  2,                                /* iVersion */
+  devsymClose,                      /* xClose */
+  devsymRead,                       /* xRead */
+  devsymWrite,                      /* xWrite */
+  devsymTruncate,                   /* xTruncate */
+  devsymSync,                       /* xSync */
+  devsymFileSize,                   /* xFileSize */
+  devsymLock,                       /* xLock */
+  devsymUnlock,                     /* xUnlock */
+  devsymCheckReservedLock,          /* xCheckReservedLock */
+  devsymFileControl,                /* xFileControl */
+  devsymSectorSize,                 /* xSectorSize */
+  devsymDeviceCharacteristics,      /* xDeviceCharacteristics */
+  devsymShmMap,                     /* xShmMap */
+  devsymShmLock,                    /* xShmLock */
+  devsymShmBarrier,                 /* xShmBarrier */
+  devsymShmUnmap                    /* xShmUnmap */
+};
+
+struct DevsymGlobal {
+  sqlite3_vfs *pVfs;
+  int iDeviceChar;
+  int iSectorSize;
+};
+struct DevsymGlobal g = {0, 0, 512};
+
+/*
+** Close an devsym-file.
+*/
+static int devsymClose(sqlite3_file *pFile){
+  devsym_file *p = (devsym_file *)pFile;
+  return sqlite3OsClose(p->pReal);
+}
+
+/*
+** Read data from an devsym-file.
+*/
+static int devsymRead(
+  sqlite3_file *pFile, 
+  void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  devsym_file *p = (devsym_file *)pFile;
+  return sqlite3OsRead(p->pReal, zBuf, iAmt, iOfst);
+}
+
+/*
+** Write data to an devsym-file.
+*/
+static int devsymWrite(
+  sqlite3_file *pFile, 
+  const void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  devsym_file *p = (devsym_file *)pFile;
+  return sqlite3OsWrite(p->pReal, zBuf, iAmt, iOfst);
+}
+
+/*
+** Truncate an devsym-file.
+*/
+static int devsymTruncate(sqlite3_file *pFile, sqlite_int64 size){
+  devsym_file *p = (devsym_file *)pFile;
+  return sqlite3OsTruncate(p->pReal, size);
+}
+
+/*
+** Sync an devsym-file.
+*/
+static int devsymSync(sqlite3_file *pFile, int flags){
+  devsym_file *p = (devsym_file *)pFile;
+  return sqlite3OsSync(p->pReal, flags);
+}
+
+/*
+** Return the current file-size of an devsym-file.
+*/
+static int devsymFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
+  devsym_file *p = (devsym_file *)pFile;
+  return sqlite3OsFileSize(p->pReal, pSize);
+}
+
+/*
+** Lock an devsym-file.
+*/
+static int devsymLock(sqlite3_file *pFile, int eLock){
+  devsym_file *p = (devsym_file *)pFile;
+  return sqlite3OsLock(p->pReal, eLock);
+}
+
+/*
+** Unlock an devsym-file.
+*/
+static int devsymUnlock(sqlite3_file *pFile, int eLock){
+  devsym_file *p = (devsym_file *)pFile;
+  return sqlite3OsUnlock(p->pReal, eLock);
+}
+
+/*
+** Check if another file-handle holds a RESERVED lock on an devsym-file.
+*/
+static int devsymCheckReservedLock(sqlite3_file *pFile, int *pResOut){
+  devsym_file *p = (devsym_file *)pFile;
+  return sqlite3OsCheckReservedLock(p->pReal, pResOut);
+}
+
+/*
+** File control method. For custom operations on an devsym-file.
+*/
+static int devsymFileControl(sqlite3_file *pFile, int op, void *pArg){
+  devsym_file *p = (devsym_file *)pFile;
+  return sqlite3OsFileControl(p->pReal, op, pArg);
+}
+
+/*
+** Return the sector-size in bytes for an devsym-file.
+*/
+static int devsymSectorSize(sqlite3_file *pFile){
+  return g.iSectorSize;
+}
+
+/*
+** Return the device characteristic flags supported by an devsym-file.
+*/
+static int devsymDeviceCharacteristics(sqlite3_file *pFile){
+  return g.iDeviceChar;
+}
+
+/*
+** Shared-memory methods are all pass-thrus.
+*/
+static int devsymShmLock(sqlite3_file *pFile, int ofst, int n, int flags){
+  devsym_file *p = (devsym_file *)pFile;
+  return sqlite3OsShmLock(p->pReal, ofst, n, flags);
+}
+static int devsymShmMap(
+  sqlite3_file *pFile, 
+  int iRegion, 
+  int szRegion, 
+  int isWrite, 
+  void volatile **pp
+){
+  devsym_file *p = (devsym_file *)pFile;
+  return sqlite3OsShmMap(p->pReal, iRegion, szRegion, isWrite, pp);
+}
+static void devsymShmBarrier(sqlite3_file *pFile){
+  devsym_file *p = (devsym_file *)pFile;
+  sqlite3OsShmBarrier(p->pReal);
+}
+static int devsymShmUnmap(sqlite3_file *pFile, int delFlag){
+  devsym_file *p = (devsym_file *)pFile;
+  return sqlite3OsShmUnmap(p->pReal, delFlag);
+}
+
+
+
+/*
+** Open an devsym file handle.
+*/
+static int devsymOpen(
+  sqlite3_vfs *pVfs,
+  const char *zName,
+  sqlite3_file *pFile,
+  int flags,
+  int *pOutFlags
+){
+  int rc;
+  devsym_file *p = (devsym_file *)pFile;
+  p->pReal = (sqlite3_file *)&p[1];
+  rc = sqlite3OsOpen(g.pVfs, zName, p->pReal, flags, pOutFlags);
+  if( p->pReal->pMethods ){
+    pFile->pMethods = &devsym_io_methods;
+  }
+  return rc;
+}
+
+/*
+** Delete the file located at zPath. If the dirSync argument is true,
+** ensure the file-system modifications are synced to disk before
+** returning.
+*/
+static int devsymDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
+  return sqlite3OsDelete(g.pVfs, zPath, dirSync);
+}
+
+/*
+** Test for access permissions. Return true if the requested permission
+** is available, or false otherwise.
+*/
+static int devsymAccess(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  int flags, 
+  int *pResOut
+){
+  return sqlite3OsAccess(g.pVfs, zPath, flags, pResOut);
+}
+
+/*
+** Populate buffer zOut with the full canonical pathname corresponding
+** to the pathname in zPath. zOut is guaranteed to point to a buffer
+** of at least (DEVSYM_MAX_PATHNAME+1) bytes.
+*/
+static int devsymFullPathname(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  int nOut, 
+  char *zOut
+){
+  return sqlite3OsFullPathname(g.pVfs, zPath, nOut, zOut);
+}
+
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+/*
+** Open the dynamic library located at zPath and return a handle.
+*/
+static void *devsymDlOpen(sqlite3_vfs *pVfs, const char *zPath){
+  return sqlite3OsDlOpen(g.pVfs, zPath);
+}
+
+/*
+** Populate the buffer zErrMsg (size nByte bytes) with a human readable
+** utf-8 string describing the most recent error encountered associated 
+** with dynamic libraries.
+*/
+static void devsymDlError(sqlite3_vfs *pVfs, int nByte, char *zErrMsg){
+  sqlite3OsDlError(g.pVfs, nByte, zErrMsg);
+}
+
+/*
+** Return a pointer to the symbol zSymbol in the dynamic library pHandle.
+*/
+static void (*devsymDlSym(sqlite3_vfs *pVfs, void *p, const char *zSym))(void){
+  return sqlite3OsDlSym(g.pVfs, p, zSym);
+}
+
+/*
+** Close the dynamic library handle pHandle.
+*/
+static void devsymDlClose(sqlite3_vfs *pVfs, void *pHandle){
+  sqlite3OsDlClose(g.pVfs, pHandle);
+}
+#endif /* SQLITE_OMIT_LOAD_EXTENSION */
+
+/*
+** Populate the buffer pointed to by zBufOut with nByte bytes of 
+** random data.
+*/
+static int devsymRandomness(sqlite3_vfs *pVfs, int nByte, char *zBufOut){
+  return sqlite3OsRandomness(g.pVfs, nByte, zBufOut);
+}
+
+/*
+** Sleep for nMicro microseconds. Return the number of microseconds 
+** actually slept.
+*/
+static int devsymSleep(sqlite3_vfs *pVfs, int nMicro){
+  return sqlite3OsSleep(g.pVfs, nMicro);
+}
+
+/*
+** Return the current time as a Julian Day number in *pTimeOut.
+*/
+static int devsymCurrentTime(sqlite3_vfs *pVfs, double *pTimeOut){
+  return g.pVfs->xCurrentTime(g.pVfs, pTimeOut);
+}
+
+
+/*
+** This procedure registers the devsym vfs with SQLite. If the argument is
+** true, the devsym vfs becomes the new default vfs. It is the only publicly
+** available function in this file.
+*/
+void devsym_register(int iDeviceChar, int iSectorSize){
+  if( g.pVfs==0 ){
+    g.pVfs = sqlite3_vfs_find(0);
+    devsym_vfs.szOsFile += g.pVfs->szOsFile;
+    sqlite3_vfs_register(&devsym_vfs, 0);
+  }
+  if( iDeviceChar>=0 ){
+    g.iDeviceChar = iDeviceChar;
+  }else{
+    g.iDeviceChar = 0;
+  }
+  if( iSectorSize>=0 ){
+    g.iSectorSize = iSectorSize;
+  }else{
+    g.iSectorSize = 512;
+  }
+}
+
+#endif
diff --git a/src/test_func.c b/src/test_func.c
new file mode 100644
index 0000000..a123943
--- /dev/null
+++ b/src/test_func.c
@@ -0,0 +1,583 @@
+/*
+** 2008 March 19
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Code for testing all sorts of SQLite interfaces.  This code
+** implements new SQL functions used by the test scripts.
+*/
+#include "sqlite3.h"
+#include "tcl.h"
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+
+
+/*
+** Allocate nByte bytes of space using sqlite3_malloc(). If the
+** allocation fails, call sqlite3_result_error_nomem() to notify
+** the database handle that malloc() has failed.
+*/
+static void *testContextMalloc(sqlite3_context *context, int nByte){
+  char *z = sqlite3_malloc(nByte);
+  if( !z && nByte>0 ){
+    sqlite3_result_error_nomem(context);
+  }
+  return z;
+}
+
+/*
+** This function generates a string of random characters.  Used for
+** generating test data.
+*/
+static void randStr(sqlite3_context *context, int argc, sqlite3_value **argv){
+  static const unsigned char zSrc[] = 
+     "abcdefghijklmnopqrstuvwxyz"
+     "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+     "0123456789"
+     ".-!,:*^+=_|?/<> ";
+  int iMin, iMax, n, r, i;
+  unsigned char zBuf[1000];
+
+  /* It used to be possible to call randstr() with any number of arguments,
+  ** but now it is registered with SQLite as requiring exactly 2.
+  */
+  assert(argc==2);
+
+  iMin = sqlite3_value_int(argv[0]);
+  if( iMin<0 ) iMin = 0;
+  if( iMin>=sizeof(zBuf) ) iMin = sizeof(zBuf)-1;
+  iMax = sqlite3_value_int(argv[1]);
+  if( iMax<iMin ) iMax = iMin;
+  if( iMax>=sizeof(zBuf) ) iMax = sizeof(zBuf)-1;
+  n = iMin;
+  if( iMax>iMin ){
+    sqlite3_randomness(sizeof(r), &r);
+    r &= 0x7fffffff;
+    n += r%(iMax + 1 - iMin);
+  }
+  assert( n<sizeof(zBuf) );
+  sqlite3_randomness(n, zBuf);
+  for(i=0; i<n; i++){
+    zBuf[i] = zSrc[zBuf[i]%(sizeof(zSrc)-1)];
+  }
+  zBuf[n] = 0;
+  sqlite3_result_text(context, (char*)zBuf, n, SQLITE_TRANSIENT);
+}
+
+/*
+** The following two SQL functions are used to test returning a text
+** result with a destructor. Function 'test_destructor' takes one argument
+** and returns the same argument interpreted as TEXT. A destructor is
+** passed with the sqlite3_result_text() call.
+**
+** SQL function 'test_destructor_count' returns the number of outstanding 
+** allocations made by 'test_destructor';
+**
+** WARNING: Not threadsafe.
+*/
+static int test_destructor_count_var = 0;
+static void destructor(void *p){
+  char *zVal = (char *)p;
+  assert(zVal);
+  zVal--;
+  sqlite3_free(zVal);
+  test_destructor_count_var--;
+}
+static void test_destructor(
+  sqlite3_context *pCtx, 
+  int nArg,
+  sqlite3_value **argv
+){
+  char *zVal;
+  int len;
+  
+  test_destructor_count_var++;
+  assert( nArg==1 );
+  if( sqlite3_value_type(argv[0])==SQLITE_NULL ) return;
+  len = sqlite3_value_bytes(argv[0]); 
+  zVal = testContextMalloc(pCtx, len+3);
+  if( !zVal ){
+    return;
+  }
+  zVal[len+1] = 0;
+  zVal[len+2] = 0;
+  zVal++;
+  memcpy(zVal, sqlite3_value_text(argv[0]), len);
+  sqlite3_result_text(pCtx, zVal, -1, destructor);
+}
+#ifndef SQLITE_OMIT_UTF16
+static void test_destructor16(
+  sqlite3_context *pCtx, 
+  int nArg,
+  sqlite3_value **argv
+){
+  char *zVal;
+  int len;
+  
+  test_destructor_count_var++;
+  assert( nArg==1 );
+  if( sqlite3_value_type(argv[0])==SQLITE_NULL ) return;
+  len = sqlite3_value_bytes16(argv[0]); 
+  zVal = testContextMalloc(pCtx, len+3);
+  if( !zVal ){
+    return;
+  }
+  zVal[len+1] = 0;
+  zVal[len+2] = 0;
+  zVal++;
+  memcpy(zVal, sqlite3_value_text16(argv[0]), len);
+  sqlite3_result_text16(pCtx, zVal, -1, destructor);
+}
+#endif
+static void test_destructor_count(
+  sqlite3_context *pCtx, 
+  int nArg,
+  sqlite3_value **argv
+){
+  sqlite3_result_int(pCtx, test_destructor_count_var);
+}
+
+/*
+** The following aggregate function, test_agg_errmsg16(), takes zero 
+** arguments. It returns the text value returned by the sqlite3_errmsg16()
+** API function.
+*/
+#ifndef SQLITE_OMIT_BUILTIN_TEST

+void sqlite3BeginBenignMalloc(void);
+void sqlite3EndBenignMalloc(void);
+#else

+  #define sqlite3BeginBenignMalloc()

+  #define sqlite3EndBenignMalloc()

+#endif

+static void test_agg_errmsg16_step(sqlite3_context *a, int b,sqlite3_value **c){
+}
+static void test_agg_errmsg16_final(sqlite3_context *ctx){
+#ifndef SQLITE_OMIT_UTF16
+  const void *z;
+  sqlite3 * db = sqlite3_context_db_handle(ctx);
+  sqlite3_aggregate_context(ctx, 2048);
+  sqlite3BeginBenignMalloc();
+  z = sqlite3_errmsg16(db);
+  sqlite3EndBenignMalloc();
+  sqlite3_result_text16(ctx, z, -1, SQLITE_TRANSIENT);
+#endif
+}
+
+/*
+** Routines for testing the sqlite3_get_auxdata() and sqlite3_set_auxdata()
+** interface.
+**
+** The test_auxdata() SQL function attempts to register each of its arguments
+** as auxiliary data.  If there are no prior registrations of aux data for
+** that argument (meaning the argument is not a constant or this is its first
+** call) then the result for that argument is 0.  If there is a prior
+** registration, the result for that argument is 1.  The overall result
+** is the individual argument results separated by spaces.
+*/
+static void free_test_auxdata(void *p) {sqlite3_free(p);}
+static void test_auxdata(
+  sqlite3_context *pCtx, 
+  int nArg,
+  sqlite3_value **argv
+){
+  int i;
+  char *zRet = testContextMalloc(pCtx, nArg*2);
+  if( !zRet ) return;
+  memset(zRet, 0, nArg*2);
+  for(i=0; i<nArg; i++){
+    char const *z = (char*)sqlite3_value_text(argv[i]);
+    if( z ){
+      int n;
+      char *zAux = sqlite3_get_auxdata(pCtx, i);
+      if( zAux ){
+        zRet[i*2] = '1';
+        assert( strcmp(zAux,z)==0 );
+      }else {
+        zRet[i*2] = '0';
+      }
+      n = strlen(z) + 1;
+      zAux = testContextMalloc(pCtx, n);
+      if( zAux ){
+        memcpy(zAux, z, n);
+        sqlite3_set_auxdata(pCtx, i, zAux, free_test_auxdata);
+      }
+      zRet[i*2+1] = ' ';
+    }
+  }
+  sqlite3_result_text(pCtx, zRet, 2*nArg-1, free_test_auxdata);
+}
+
+/*
+** A function to test error reporting from user functions. This function
+** returns a copy of its first argument as the error message.  If the
+** second argument exists, it becomes the error code.
+*/
+static void test_error(
+  sqlite3_context *pCtx, 
+  int nArg,
+  sqlite3_value **argv
+){
+  sqlite3_result_error(pCtx, (char*)sqlite3_value_text(argv[0]), -1);
+  if( nArg==2 ){
+    sqlite3_result_error_code(pCtx, sqlite3_value_int(argv[1]));
+  }
+}
+
+/*
+** Implementation of the counter(X) function.  If X is an integer
+** constant, then the first invocation will return X.  The second X+1.
+** and so forth.  Can be used (for example) to provide a sequence number
+** in a result set.
+*/
+static void counterFunc(
+  sqlite3_context *pCtx,   /* Function context */
+  int nArg,                /* Number of function arguments */
+  sqlite3_value **argv     /* Values for all function arguments */
+){
+  int *pCounter = (int*)sqlite3_get_auxdata(pCtx, 0);
+  if( pCounter==0 ){
+    pCounter = sqlite3_malloc( sizeof(*pCounter) );
+    if( pCounter==0 ){
+      sqlite3_result_error_nomem(pCtx);
+      return;
+    }
+    *pCounter = sqlite3_value_int(argv[0]);
+    sqlite3_set_auxdata(pCtx, 0, pCounter, sqlite3_free);
+  }else{
+    ++*pCounter;
+  }
+  sqlite3_result_int(pCtx, *pCounter);
+}
+
+
+/*
+** This function takes two arguments.  It performance UTF-8/16 type
+** conversions on the first argument then returns a copy of the second
+** argument.
+**
+** This function is used in cases such as the following:
+**
+**      SELECT test_isolation(x,x) FROM t1;
+**
+** We want to verify that the type conversions that occur on the
+** first argument do not invalidate the second argument.
+*/
+static void test_isolation(
+  sqlite3_context *pCtx, 
+  int nArg,
+  sqlite3_value **argv
+){
+#ifndef SQLITE_OMIT_UTF16
+  sqlite3_value_text16(argv[0]);
+  sqlite3_value_text(argv[0]);
+  sqlite3_value_text16(argv[0]);
+  sqlite3_value_text(argv[0]);
+#endif
+  sqlite3_result_value(pCtx, argv[1]);
+}
+
+/*
+** Invoke an SQL statement recursively.  The function result is the 
+** first column of the first row of the result set.
+*/
+static void test_eval(
+  sqlite3_context *pCtx, 
+  int nArg,
+  sqlite3_value **argv
+){
+  sqlite3_stmt *pStmt;
+  int rc;
+  sqlite3 *db = sqlite3_context_db_handle(pCtx);
+  const char *zSql;
+
+  zSql = (char*)sqlite3_value_text(argv[0]);
+  rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_step(pStmt);
+    if( rc==SQLITE_ROW ){
+      sqlite3_result_value(pCtx, sqlite3_column_value(pStmt, 0));
+    }
+    rc = sqlite3_finalize(pStmt);
+  }
+  if( rc ){
+    char *zErr;
+    assert( pStmt==0 );
+    zErr = sqlite3_mprintf("sqlite3_prepare_v2() error: %s",sqlite3_errmsg(db));
+    sqlite3_result_text(pCtx, zErr, -1, sqlite3_free);
+    sqlite3_result_error_code(pCtx, rc);
+  }
+}
+
+
+/*
+** convert one character from hex to binary
+*/
+static int testHexChar(char c){
+  if( c>='0' && c<='9' ){
+    return c - '0';
+  }else if( c>='a' && c<='f' ){
+    return c - 'a' + 10;
+  }else if( c>='A' && c<='F' ){
+    return c - 'A' + 10;
+  }
+  return 0;
+}
+
+/*
+** Convert hex to binary.
+*/
+static void testHexToBin(const char *zIn, char *zOut){
+  while( zIn[0] && zIn[1] ){
+    *(zOut++) = (testHexChar(zIn[0])<<4) + testHexChar(zIn[1]);
+    zIn += 2;
+  }
+}
+
+/*
+**      hex_to_utf16be(HEX)
+**
+** Convert the input string from HEX into binary.  Then return the
+** result using sqlite3_result_text16le().
+*/
+#ifndef SQLITE_OMIT_UTF16
+static void testHexToUtf16be(
+  sqlite3_context *pCtx, 
+  int nArg,
+  sqlite3_value **argv
+){
+  int n;
+  const char *zIn;
+  char *zOut;
+  assert( nArg==1 );
+  n = sqlite3_value_bytes(argv[0]);
+  zIn = (const char*)sqlite3_value_text(argv[0]);
+  zOut = sqlite3_malloc( n/2 );
+  if( zOut==0 ){
+    sqlite3_result_error_nomem(pCtx);
+  }else{
+    testHexToBin(zIn, zOut);
+    sqlite3_result_text16be(pCtx, zOut, n/2, sqlite3_free);
+  }
+}
+#endif
+
+/*
+**      hex_to_utf8(HEX)
+**
+** Convert the input string from HEX into binary.  Then return the
+** result using sqlite3_result_text16le().
+*/
+static void testHexToUtf8(
+  sqlite3_context *pCtx, 
+  int nArg,
+  sqlite3_value **argv
+){
+  int n;
+  const char *zIn;
+  char *zOut;
+  assert( nArg==1 );
+  n = sqlite3_value_bytes(argv[0]);
+  zIn = (const char*)sqlite3_value_text(argv[0]);
+  zOut = sqlite3_malloc( n/2 );
+  if( zOut==0 ){
+    sqlite3_result_error_nomem(pCtx);
+  }else{
+    testHexToBin(zIn, zOut);
+    sqlite3_result_text(pCtx, zOut, n/2, sqlite3_free);
+  }
+}
+
+/*
+**      hex_to_utf16le(HEX)
+**
+** Convert the input string from HEX into binary.  Then return the
+** result using sqlite3_result_text16le().
+*/
+#ifndef SQLITE_OMIT_UTF16
+static void testHexToUtf16le(
+  sqlite3_context *pCtx, 
+  int nArg,
+  sqlite3_value **argv
+){
+  int n;
+  const char *zIn;
+  char *zOut;
+  assert( nArg==1 );
+  n = sqlite3_value_bytes(argv[0]);
+  zIn = (const char*)sqlite3_value_text(argv[0]);
+  zOut = sqlite3_malloc( n/2 );
+  if( zOut==0 ){
+    sqlite3_result_error_nomem(pCtx);
+  }else{
+    testHexToBin(zIn, zOut);
+    sqlite3_result_text16le(pCtx, zOut, n/2, sqlite3_free);
+  }
+}
+#endif
+
+static int registerTestFunctions(sqlite3 *db){
+  static const struct {
+     char *zName;
+     signed char nArg;
+     unsigned char eTextRep; /* 1: UTF-16.  0: UTF-8 */
+     void (*xFunc)(sqlite3_context*,int,sqlite3_value **);
+  } aFuncs[] = {
+    { "randstr",               2, SQLITE_UTF8, randStr    },
+    { "test_destructor",       1, SQLITE_UTF8, test_destructor},
+#ifndef SQLITE_OMIT_UTF16
+    { "test_destructor16",     1, SQLITE_UTF8, test_destructor16},
+    { "hex_to_utf16be",        1, SQLITE_UTF8, testHexToUtf16be},
+    { "hex_to_utf16le",        1, SQLITE_UTF8, testHexToUtf16le},
+#endif
+    { "hex_to_utf8",           1, SQLITE_UTF8, testHexToUtf8},
+    { "test_destructor_count", 0, SQLITE_UTF8, test_destructor_count},
+    { "test_auxdata",         -1, SQLITE_UTF8, test_auxdata},
+    { "test_error",            1, SQLITE_UTF8, test_error},
+    { "test_error",            2, SQLITE_UTF8, test_error},
+    { "test_eval",             1, SQLITE_UTF8, test_eval},
+    { "test_isolation",        2, SQLITE_UTF8, test_isolation},
+    { "test_counter",          1, SQLITE_UTF8, counterFunc},
+  };
+  int i;
+
+  for(i=0; i<sizeof(aFuncs)/sizeof(aFuncs[0]); i++){
+    sqlite3_create_function(db, aFuncs[i].zName, aFuncs[i].nArg,
+        aFuncs[i].eTextRep, 0, aFuncs[i].xFunc, 0, 0);
+  }
+
+  sqlite3_create_function(db, "test_agg_errmsg16", 0, SQLITE_ANY, 0, 0, 
+      test_agg_errmsg16_step, test_agg_errmsg16_final);
+      
+  return SQLITE_OK;
+}
+
+/*
+** TCLCMD:  autoinstall_test_functions
+**
+** Invoke this TCL command to use sqlite3_auto_extension() to cause
+** the standard set of test functions to be loaded into each new
+** database connection.
+*/
+static int autoinstall_test_funcs(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  extern int Md5_Register(sqlite3*);
+  int rc = sqlite3_auto_extension((void*)registerTestFunctions);
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_auto_extension((void*)Md5_Register);
+  }
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+  return TCL_OK;
+}
+
+/*
+** A bogus step function and finalizer function.
+*/
+static void tStep(sqlite3_context *a, int b, sqlite3_value **c){}
+static void tFinal(sqlite3_context *a){}
+
+
+/*
+** tclcmd:  abuse_create_function
+**
+** Make various calls to sqlite3_create_function that do not have valid
+** parameters.  Verify that the error condition is detected and reported.
+*/
+static int abuse_create_function(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  extern int getDbPointer(Tcl_Interp*, const char*, sqlite3**);
+  sqlite3 *db;
+  int rc;
+  int mxArg;
+
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+
+  rc = sqlite3_create_function(db, "tx", 1, SQLITE_UTF8, 0, tStep,tStep,tFinal);
+  if( rc!=SQLITE_MISUSE ) goto abuse_err;
+
+  rc = sqlite3_create_function(db, "tx", 1, SQLITE_UTF8, 0, tStep, tStep, 0);
+  if( rc!=SQLITE_MISUSE ) goto abuse_err;
+
+  rc = sqlite3_create_function(db, "tx", 1, SQLITE_UTF8, 0, tStep, 0, tFinal);
+  if( rc!=SQLITE_MISUSE) goto abuse_err;
+
+  rc = sqlite3_create_function(db, "tx", 1, SQLITE_UTF8, 0, 0, 0, tFinal);
+  if( rc!=SQLITE_MISUSE ) goto abuse_err;
+
+  rc = sqlite3_create_function(db, "tx", 1, SQLITE_UTF8, 0, 0, tStep, 0);
+  if( rc!=SQLITE_MISUSE ) goto abuse_err;
+
+  rc = sqlite3_create_function(db, "tx", -2, SQLITE_UTF8, 0, tStep, 0, 0);
+  if( rc!=SQLITE_MISUSE ) goto abuse_err;
+
+  rc = sqlite3_create_function(db, "tx", 128, SQLITE_UTF8, 0, tStep, 0, 0);
+  if( rc!=SQLITE_MISUSE ) goto abuse_err;
+
+  rc = sqlite3_create_function(db, "funcxx"
+       "_123456789_123456789_123456789_123456789_123456789"
+       "_123456789_123456789_123456789_123456789_123456789"
+       "_123456789_123456789_123456789_123456789_123456789"
+       "_123456789_123456789_123456789_123456789_123456789"
+       "_123456789_123456789_123456789_123456789_123456789",
+       1, SQLITE_UTF8, 0, tStep, 0, 0);
+  if( rc!=SQLITE_MISUSE ) goto abuse_err;
+
+  /* This last function registration should actually work.  Generate
+  ** a no-op function (that always returns NULL) and which has the
+  ** maximum-length function name and the maximum number of parameters.
+  */
+  sqlite3_limit(db, SQLITE_LIMIT_FUNCTION_ARG, 10000);
+  mxArg = sqlite3_limit(db, SQLITE_LIMIT_FUNCTION_ARG, -1);
+  rc = sqlite3_create_function(db, "nullx"
+       "_123456789_123456789_123456789_123456789_123456789"
+       "_123456789_123456789_123456789_123456789_123456789"
+       "_123456789_123456789_123456789_123456789_123456789"
+       "_123456789_123456789_123456789_123456789_123456789"
+       "_123456789_123456789_123456789_123456789_123456789",
+       mxArg, SQLITE_UTF8, 0, tStep, 0, 0);
+  if( rc!=SQLITE_OK ) goto abuse_err;
+                                
+  return TCL_OK;
+
+abuse_err:
+  Tcl_AppendResult(interp, "sqlite3_create_function abused test failed", 
+                   (char*)0);
+  return TCL_ERROR;
+}
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetest_func_Init(Tcl_Interp *interp){
+  static struct {
+     char *zName;
+     Tcl_ObjCmdProc *xProc;
+  } aObjCmd[] = {
+     { "autoinstall_test_functions",    autoinstall_test_funcs },
+     { "abuse_create_function",         abuse_create_function  },
+  };
+  int i;
+  extern int Md5_Register(sqlite3*);
+
+  for(i=0; i<sizeof(aObjCmd)/sizeof(aObjCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aObjCmd[i].zName, aObjCmd[i].xProc, 0, 0);
+  }
+  sqlite3_initialize();
+  sqlite3_auto_extension((void*)registerTestFunctions);
+  sqlite3_auto_extension((void*)Md5_Register);
+  return TCL_OK;
+}
diff --git a/src/test_fuzzer.c b/src/test_fuzzer.c
new file mode 100644
index 0000000..cf59257
--- /dev/null
+++ b/src/test_fuzzer.c
@@ -0,0 +1,944 @@
+/*
+** 2011 March 24
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** Code for demonstartion virtual table that generates variations
+** on an input word at increasing edit distances from the original.
+**
+** A fuzzer virtual table is created like this:
+**
+**     CREATE VIRTUAL TABLE temp.f USING fuzzer;
+**
+** The name of the new virtual table in the example above is "f".
+** Note that all fuzzer virtual tables must be TEMP tables.  The
+** "temp." prefix in front of the table name is required when the
+** table is being created.  The "temp." prefix can be omitted when
+** using the table as long as the name is unambiguous.
+**
+** Before being used, the fuzzer needs to be programmed by giving it
+** character transformations and a cost associated with each transformation.
+** Examples:
+**
+**    INSERT INTO f(cFrom,cTo,Cost) VALUES('','a',100);
+**
+** The above statement says that the cost of inserting a letter 'a' is
+** 100.  (All costs are integers.  We recommend that costs be scaled so
+** that the average cost is around 100.)
+**
+**    INSERT INTO f(cFrom,cTo,Cost) VALUES('b','',87);
+**
+** The above statement says that the cost of deleting a single letter
+** 'b' is 87.
+**
+**    INSERT INTO f(cFrom,cTo,Cost) VALUES('o','oe',38);
+**    INSERT INTO f(cFrom,cTo,Cost) VALUES('oe','o',40);
+**
+** This third example says that the cost of transforming the single
+** letter "o" into the two-letter sequence "oe" is 38 and that the
+** cost of transforming "oe" back into "o" is 40.
+**
+** After all the transformation costs have been set, the fuzzer table
+** can be queried as follows:
+**
+**    SELECT word, distance FROM f
+**     WHERE word MATCH 'abcdefg'
+**       AND distance<200;
+**
+** This first query outputs the string "abcdefg" and all strings that
+** can be derived from that string by appling the specified transformations.
+** The strings are output together with their total transformation cost
+** (called "distance") and appear in order of increasing cost.  No string
+** is output more than once.  If there are multiple ways to transform the
+** target string into the output string then the lowest cost transform is
+** the one that is returned.  In the example, the search is limited to 
+** strings with a total distance of less than 200.
+**
+** It is important to put some kind of a limit on the fuzzer output.  This
+** can be either in the form of a LIMIT clause at the end of the query,
+** or better, a "distance<NNN" constraint where NNN is some number.  The
+** running time and memory requirement is exponential in the value of NNN 
+** so you want to make sure that NNN is not too big.  A value of NNN that
+** is about twice the average transformation cost seems to give good results.
+**
+** The fuzzer table can be useful for tasks such as spelling correction.
+** Suppose there is a second table vocabulary(w) where the w column contains
+** all correctly spelled words.   Let $word be a word you want to look up.
+**
+**   SELECT vocabulary.w FROM f, vocabulary
+**    WHERE f.word MATCH $word
+**      AND f.distance<=200
+**      AND f.word=vocabulary.w
+**    LIMIT 20
+**
+** The query above gives the 20 closest words to the $word being tested.
+** (Note that for good performance, the vocubulary.w column should be
+** indexed.)
+**
+** A similar query can be used to find all words in the dictionary that
+** begin with some prefix $prefix:
+**
+**   SELECT vocabulary.w FROM f, vocabulary
+**    WHERE f.word MATCH $prefix
+**      AND f.distance<=200
+**      AND vocabulary.w BETWEEN f.word AND (f.word || x'F7BFBFBF')
+**    LIMIT 50
+**
+** This last query will show up to 50 words out of the vocabulary that
+** match or nearly match the $prefix.
+*/
+#include "sqlite3.h"
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include <stdio.h>
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+
+/*
+** Forward declaration of objects used by this implementation
+*/
+typedef struct fuzzer_vtab fuzzer_vtab;
+typedef struct fuzzer_cursor fuzzer_cursor;
+typedef struct fuzzer_rule fuzzer_rule;
+typedef struct fuzzer_seen fuzzer_seen;
+typedef struct fuzzer_stem fuzzer_stem;
+
+/*
+** Type of the "cost" of an edit operation.  Might be changed to
+** "float" or "double" or "sqlite3_int64" in the future.
+*/
+typedef int fuzzer_cost;
+
+
+/*
+** Each transformation rule is stored as an instance of this object.
+** All rules are kept on a linked list sorted by rCost.
+*/
+struct fuzzer_rule {
+  fuzzer_rule *pNext;        /* Next rule in order of increasing rCost */
+  fuzzer_cost rCost;         /* Cost of this transformation */
+  int nFrom, nTo;            /* Length of the zFrom and zTo strings */
+  char *zFrom;               /* Transform from */
+  char zTo[4];               /* Transform to (extra space appended) */
+};
+
+/*
+** A stem object is used to generate variants.  It is also used to record
+** previously generated outputs.
+**
+** Every stem is added to a hash table as it is output.  Generation of
+** duplicate stems is suppressed.
+**
+** Active stems (those that might generate new outputs) are kepts on a linked
+** list sorted by increasing cost.  The cost is the sum of rBaseCost and
+** pRule->rCost.
+*/
+struct fuzzer_stem {
+  char *zBasis;              /* Word being fuzzed */
+  int nBasis;                /* Length of the zBasis string */
+  const fuzzer_rule *pRule;  /* Current rule to apply */
+  int n;                     /* Apply pRule at this character offset */
+  fuzzer_cost rBaseCost;     /* Base cost of getting to zBasis */
+  fuzzer_cost rCostX;        /* Precomputed rBaseCost + pRule->rCost */
+  fuzzer_stem *pNext;        /* Next stem in rCost order */
+  fuzzer_stem *pHash;        /* Next stem with same hash on zBasis */
+};
+
+/* 
+** A fuzzer virtual-table object 
+*/
+struct fuzzer_vtab {
+  sqlite3_vtab base;         /* Base class - must be first */
+  char *zClassName;          /* Name of this class.  Default: "fuzzer" */
+  fuzzer_rule *pRule;        /* All active rules in this fuzzer */
+  fuzzer_rule *pNewRule;     /* New rules to add when last cursor expires */
+  int nCursor;               /* Number of active cursors */
+};
+
+#define FUZZER_HASH  4001    /* Hash table size */
+#define FUZZER_NQUEUE  20    /* Number of slots on the stem queue */
+
+/* A fuzzer cursor object */
+struct fuzzer_cursor {
+  sqlite3_vtab_cursor base;  /* Base class - must be first */
+  sqlite3_int64 iRowid;      /* The rowid of the current word */
+  fuzzer_vtab *pVtab;        /* The virtual table this cursor belongs to */
+  fuzzer_cost rLimit;        /* Maximum cost of any term */
+  fuzzer_stem *pStem;        /* Stem with smallest rCostX */
+  fuzzer_stem *pDone;        /* Stems already processed to completion */
+  fuzzer_stem *aQueue[FUZZER_NQUEUE];  /* Queue of stems with higher rCostX */
+  int mxQueue;               /* Largest used index in aQueue[] */
+  char *zBuf;                /* Temporary use buffer */
+  int nBuf;                  /* Bytes allocated for zBuf */
+  int nStem;                 /* Number of stems allocated */
+  fuzzer_rule nullRule;      /* Null rule used first */
+  fuzzer_stem *apHash[FUZZER_HASH]; /* Hash of previously generated terms */
+};
+
+/* Methods for the fuzzer module */
+static int fuzzerConnect(
+  sqlite3 *db,
+  void *pAux,
+  int argc, const char *const*argv,
+  sqlite3_vtab **ppVtab,
+  char **pzErr
+){
+  fuzzer_vtab *pNew;
+  int n;
+  if( strcmp(argv[1],"temp")!=0 ){
+    *pzErr = sqlite3_mprintf("%s virtual tables must be TEMP", argv[0]);
+    return SQLITE_ERROR;
+  }
+  n = strlen(argv[0]) + 1;
+  pNew = sqlite3_malloc( sizeof(*pNew) + n );
+  if( pNew==0 ) return SQLITE_NOMEM;
+  pNew->zClassName = (char*)&pNew[1];
+  memcpy(pNew->zClassName, argv[0], n);
+  sqlite3_declare_vtab(db, "CREATE TABLE x(word,distance,cFrom,cTo,cost)");
+  memset(pNew, 0, sizeof(*pNew));
+  *ppVtab = &pNew->base;
+  return SQLITE_OK;
+}
+/* Note that for this virtual table, the xCreate and xConnect
+** methods are identical. */
+
+static int fuzzerDisconnect(sqlite3_vtab *pVtab){
+  fuzzer_vtab *p = (fuzzer_vtab*)pVtab;
+  assert( p->nCursor==0 );
+  do{
+    while( p->pRule ){
+      fuzzer_rule *pRule = p->pRule;
+      p->pRule = pRule->pNext;
+      sqlite3_free(pRule);
+    }
+    p->pRule = p->pNewRule;
+    p->pNewRule = 0;
+  }while( p->pRule );
+  sqlite3_free(p);
+  return SQLITE_OK;
+}
+/* The xDisconnect and xDestroy methods are also the same */
+
+/*
+** The two input rule lists are both sorted in order of increasing
+** cost.  Merge them together into a single list, sorted by cost, and
+** return a pointer to the head of that list.
+*/
+static fuzzer_rule *fuzzerMergeRules(fuzzer_rule *pA, fuzzer_rule *pB){
+  fuzzer_rule head;
+  fuzzer_rule *pTail;
+
+  pTail =  &head;
+  while( pA && pB ){
+    if( pA->rCost<=pB->rCost ){
+      pTail->pNext = pA;
+      pTail = pA;
+      pA = pA->pNext;
+    }else{
+      pTail->pNext = pB;
+      pTail = pB;
+      pB = pB->pNext;
+    }
+  }
+  if( pA==0 ){
+    pTail->pNext = pB;
+  }else{
+    pTail->pNext = pA;
+  }
+  return head.pNext;
+}
+
+
+/*
+** Open a new fuzzer cursor.
+*/
+static int fuzzerOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
+  fuzzer_vtab *p = (fuzzer_vtab*)pVTab;
+  fuzzer_cursor *pCur;
+  pCur = sqlite3_malloc( sizeof(*pCur) );
+  if( pCur==0 ) return SQLITE_NOMEM;
+  memset(pCur, 0, sizeof(*pCur));
+  pCur->pVtab = p;
+  *ppCursor = &pCur->base;
+  if( p->nCursor==0 && p->pNewRule ){
+    unsigned int i;
+    fuzzer_rule *pX;
+    fuzzer_rule *a[15];
+    for(i=0; i<sizeof(a)/sizeof(a[0]); i++) a[i] = 0;
+    while( (pX = p->pNewRule)!=0 ){
+      p->pNewRule = pX->pNext;
+      pX->pNext = 0;
+      for(i=0; a[i] && i<sizeof(a)/sizeof(a[0])-1; i++){
+        pX = fuzzerMergeRules(a[i], pX);
+        a[i] = 0;
+      }
+      a[i] = fuzzerMergeRules(a[i], pX);
+    }
+    for(pX=a[0], i=1; i<sizeof(a)/sizeof(a[0]); i++){
+      pX = fuzzerMergeRules(a[i], pX);
+    }
+    p->pRule = fuzzerMergeRules(p->pRule, pX);
+  }
+  p->nCursor++;
+  return SQLITE_OK;
+}
+
+/*
+** Free all stems in a list.
+*/
+static void fuzzerClearStemList(fuzzer_stem *pStem){
+  while( pStem ){
+    fuzzer_stem *pNext = pStem->pNext;
+    sqlite3_free(pStem);
+    pStem = pNext;
+  }
+}
+
+/*
+** Free up all the memory allocated by a cursor.  Set it rLimit to 0
+** to indicate that it is at EOF.
+*/
+static void fuzzerClearCursor(fuzzer_cursor *pCur, int clearHash){
+  int i;
+  fuzzerClearStemList(pCur->pStem);
+  fuzzerClearStemList(pCur->pDone);
+  for(i=0; i<FUZZER_NQUEUE; i++) fuzzerClearStemList(pCur->aQueue[i]);
+  pCur->rLimit = (fuzzer_cost)0;
+  if( clearHash && pCur->nStem ){
+    pCur->mxQueue = 0;
+    pCur->pStem = 0;
+    pCur->pDone = 0;
+    memset(pCur->aQueue, 0, sizeof(pCur->aQueue));
+    memset(pCur->apHash, 0, sizeof(pCur->apHash));
+  }
+  pCur->nStem = 0;
+}
+
+/*
+** Close a fuzzer cursor.
+*/
+static int fuzzerClose(sqlite3_vtab_cursor *cur){
+  fuzzer_cursor *pCur = (fuzzer_cursor *)cur;
+  fuzzerClearCursor(pCur, 0);
+  sqlite3_free(pCur->zBuf);
+  pCur->pVtab->nCursor--;
+  sqlite3_free(pCur);
+  return SQLITE_OK;
+}
+
+/*
+** Compute the current output term for a fuzzer_stem.
+*/
+static int fuzzerRender(
+  fuzzer_stem *pStem,   /* The stem to be rendered */
+  char **pzBuf,         /* Write results into this buffer.  realloc if needed */
+  int *pnBuf            /* Size of the buffer */
+){
+  const fuzzer_rule *pRule = pStem->pRule;
+  int n;
+  char *z;
+
+  n = pStem->nBasis + pRule->nTo - pRule->nFrom;
+  if( (*pnBuf)<n+1 ){
+    (*pzBuf) = sqlite3_realloc((*pzBuf), n+100);
+    if( (*pzBuf)==0 ) return SQLITE_NOMEM;
+    (*pnBuf) = n+100;
+  }
+  n = pStem->n;
+  z = *pzBuf;
+  if( n<0 ){
+    memcpy(z, pStem->zBasis, pStem->nBasis+1);
+  }else{
+    memcpy(z, pStem->zBasis, n);
+    memcpy(&z[n], pRule->zTo, pRule->nTo);
+    memcpy(&z[n+pRule->nTo], &pStem->zBasis[n+pRule->nFrom], 
+           pStem->nBasis-n-pRule->nFrom+1);
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Compute a hash on zBasis.
+*/
+static unsigned int fuzzerHash(const char *z){
+  unsigned int h = 0;
+  while( *z ){ h = (h<<3) ^ (h>>29) ^ *(z++); }
+  return h % FUZZER_HASH;
+}
+
+/*
+** Current cost of a stem
+*/
+static fuzzer_cost fuzzerCost(fuzzer_stem *pStem){
+  return pStem->rCostX = pStem->rBaseCost + pStem->pRule->rCost;
+}
+
+#if 0
+/*
+** Print a description of a fuzzer_stem on stderr.
+*/
+static void fuzzerStemPrint(
+  const char *zPrefix,
+  fuzzer_stem *pStem,
+  const char *zSuffix
+){
+  if( pStem->n<0 ){
+    fprintf(stderr, "%s[%s](%d)-->self%s",
+       zPrefix,
+       pStem->zBasis, pStem->rBaseCost,
+       zSuffix
+    );
+  }else{
+    char *zBuf = 0;
+    int nBuf = 0;
+    if( fuzzerRender(pStem, &zBuf, &nBuf)!=SQLITE_OK ) return;
+    fprintf(stderr, "%s[%s](%d)-->{%s}(%d)%s",
+      zPrefix,
+      pStem->zBasis, pStem->rBaseCost, zBuf, pStem->,
+      zSuffix
+    );
+    sqlite3_free(zBuf);
+  }
+}
+#endif
+
+/*
+** Return 1 if the string to which the cursor is point has already
+** been emitted.  Return 0 if not.  Return -1 on a memory allocation
+** failures.
+*/
+static int fuzzerSeen(fuzzer_cursor *pCur, fuzzer_stem *pStem){
+  unsigned int h;
+  fuzzer_stem *pLookup;
+
+  if( fuzzerRender(pStem, &pCur->zBuf, &pCur->nBuf)==SQLITE_NOMEM ){
+    return -1;
+  }
+  h = fuzzerHash(pCur->zBuf);
+  pLookup = pCur->apHash[h];
+    while( pLookup && strcmp(pLookup->zBasis, pCur->zBuf)!=0 ){
+    pLookup = pLookup->pHash;
+  }
+  return pLookup!=0;
+}
+
+/*
+** Advance a fuzzer_stem to its next value.   Return 0 if there are
+** no more values that can be generated by this fuzzer_stem.  Return
+** -1 on a memory allocation failure.
+*/
+static int fuzzerAdvance(fuzzer_cursor *pCur, fuzzer_stem *pStem){
+  const fuzzer_rule *pRule;
+  while( (pRule = pStem->pRule)!=0 ){
+    while( pStem->n < pStem->nBasis - pRule->nFrom ){
+      pStem->n++;
+      if( pRule->nFrom==0
+       || memcmp(&pStem->zBasis[pStem->n], pRule->zFrom, pRule->nFrom)==0
+      ){
+        /* Found a rewrite case.  Make sure it is not a duplicate */
+        int rc = fuzzerSeen(pCur, pStem);
+        if( rc<0 ) return -1;
+        if( rc==0 ){
+          fuzzerCost(pStem);
+          return 1;
+        }
+      }
+    }
+    pStem->n = -1;
+    pStem->pRule = pRule->pNext;
+    if( pStem->pRule && fuzzerCost(pStem)>pCur->rLimit ) pStem->pRule = 0;
+  }
+  return 0;
+}
+
+/*
+** The two input stem lists are both sorted in order of increasing
+** rCostX.  Merge them together into a single list, sorted by rCostX, and
+** return a pointer to the head of that new list.
+*/
+static fuzzer_stem *fuzzerMergeStems(fuzzer_stem *pA, fuzzer_stem *pB){
+  fuzzer_stem head;
+  fuzzer_stem *pTail;
+
+  pTail =  &head;
+  while( pA && pB ){
+    if( pA->rCostX<=pB->rCostX ){
+      pTail->pNext = pA;
+      pTail = pA;
+      pA = pA->pNext;
+    }else{
+      pTail->pNext = pB;
+      pTail = pB;
+      pB = pB->pNext;
+    }
+  }
+  if( pA==0 ){
+    pTail->pNext = pB;
+  }else{
+    pTail->pNext = pA;
+  }
+  return head.pNext;
+}
+
+/*
+** Load pCur->pStem with the lowest-cost stem.  Return a pointer
+** to the lowest-cost stem.
+*/
+static fuzzer_stem *fuzzerLowestCostStem(fuzzer_cursor *pCur){
+  fuzzer_stem *pBest, *pX;
+  int iBest;
+  int i;
+
+  if( pCur->pStem==0 ){
+    iBest = -1;
+    pBest = 0;
+    for(i=0; i<=pCur->mxQueue; i++){
+      pX = pCur->aQueue[i];
+      if( pX==0 ) continue;
+      if( pBest==0 || pBest->rCostX>pX->rCostX ){
+        pBest = pX;
+        iBest = i;
+      }
+    } 
+    if( pBest ){
+      pCur->aQueue[iBest] = pBest->pNext;
+      pBest->pNext = 0;
+      pCur->pStem = pBest;
+    }
+  }
+  return pCur->pStem;
+}
+
+/*
+** Insert pNew into queue of pending stems.  Then find the stem
+** with the lowest rCostX and move it into pCur->pStem.
+** list.  The insert is done such the pNew is in the correct order
+** according to fuzzer_stem.zBaseCost+fuzzer_stem.pRule->rCost.
+*/
+static fuzzer_stem *fuzzerInsert(fuzzer_cursor *pCur, fuzzer_stem *pNew){
+  fuzzer_stem *pX;
+  int i;
+
+  /* If pCur->pStem exists and is greater than pNew, then make pNew
+  ** the new pCur->pStem and insert the old pCur->pStem instead.
+  */
+  if( (pX = pCur->pStem)!=0 && pX->rCostX>pNew->rCostX ){
+    pNew->pNext = 0;
+    pCur->pStem = pNew;
+    pNew = pX;
+  }
+
+  /* Insert the new value */
+  pNew->pNext = 0;
+  pX = pNew;
+  for(i=0; i<=pCur->mxQueue; i++){
+    if( pCur->aQueue[i] ){
+      pX = fuzzerMergeStems(pX, pCur->aQueue[i]);
+      pCur->aQueue[i] = 0;
+    }else{
+      pCur->aQueue[i] = pX;
+      break;
+    }
+  }
+  if( i>pCur->mxQueue ){
+    if( i<FUZZER_NQUEUE ){
+      pCur->mxQueue = i;
+      pCur->aQueue[i] = pX;
+    }else{
+      assert( pCur->mxQueue==FUZZER_NQUEUE-1 );
+      pX = fuzzerMergeStems(pX, pCur->aQueue[FUZZER_NQUEUE-1]);
+      pCur->aQueue[FUZZER_NQUEUE-1] = pX;
+    }
+  }
+
+  return fuzzerLowestCostStem(pCur);
+}
+
+/*
+** Allocate a new fuzzer_stem.  Add it to the hash table but do not
+** link it into either the pCur->pStem or pCur->pDone lists.
+*/
+static fuzzer_stem *fuzzerNewStem(
+  fuzzer_cursor *pCur,
+  const char *zWord,
+  fuzzer_cost rBaseCost
+){
+  fuzzer_stem *pNew;
+  unsigned int h;
+
+  pNew = sqlite3_malloc( sizeof(*pNew) + strlen(zWord) + 1 );
+  if( pNew==0 ) return 0;
+  memset(pNew, 0, sizeof(*pNew));
+  pNew->zBasis = (char*)&pNew[1];
+  pNew->nBasis = strlen(zWord);
+  memcpy(pNew->zBasis, zWord, pNew->nBasis+1);
+  pNew->pRule = pCur->pVtab->pRule;
+  pNew->n = -1;
+  pNew->rBaseCost = pNew->rCostX = rBaseCost;
+  h = fuzzerHash(pNew->zBasis);
+  pNew->pHash = pCur->apHash[h];
+  pCur->apHash[h] = pNew;
+  pCur->nStem++;
+  return pNew;
+}
+
+
+/*
+** Advance a cursor to its next row of output
+*/
+static int fuzzerNext(sqlite3_vtab_cursor *cur){
+  fuzzer_cursor *pCur = (fuzzer_cursor*)cur;
+  int rc;
+  fuzzer_stem *pStem, *pNew;
+
+  pCur->iRowid++;
+
+  /* Use the element the cursor is currently point to to create
+  ** a new stem and insert the new stem into the priority queue.
+  */
+  pStem = pCur->pStem;
+  if( pStem->rCostX>0 ){
+    rc = fuzzerRender(pStem, &pCur->zBuf, &pCur->nBuf);
+    if( rc==SQLITE_NOMEM ) return SQLITE_NOMEM;
+    pNew = fuzzerNewStem(pCur, pCur->zBuf, pStem->rCostX);
+    if( pNew ){
+      if( fuzzerAdvance(pCur, pNew)==0 ){
+        pNew->pNext = pCur->pDone;
+        pCur->pDone = pNew;
+      }else{
+        if( fuzzerInsert(pCur, pNew)==pNew ){
+          return SQLITE_OK;
+        }
+      }
+    }else{
+      return SQLITE_NOMEM;
+    }
+  }
+
+  /* Adjust the priority queue so that the first element of the
+  ** stem list is the next lowest cost word.
+  */
+  while( (pStem = pCur->pStem)!=0 ){
+    if( fuzzerAdvance(pCur, pStem) ){
+      pCur->pStem = 0;
+      pStem = fuzzerInsert(pCur, pStem);
+      if( (rc = fuzzerSeen(pCur, pStem))!=0 ){
+        if( rc<0 ) return SQLITE_NOMEM;
+        continue;
+      }
+      return SQLITE_OK;  /* New word found */
+    }
+    pCur->pStem = 0;
+    pStem->pNext = pCur->pDone;
+    pCur->pDone = pStem;
+    if( fuzzerLowestCostStem(pCur) ){
+      rc = fuzzerSeen(pCur, pCur->pStem);
+      if( rc<0 ) return SQLITE_NOMEM;
+      if( rc==0 ){
+        return SQLITE_OK;
+      }
+    }
+  }
+
+  /* Reach this point only if queue has been exhausted and there is
+  ** nothing left to be output. */
+  pCur->rLimit = (fuzzer_cost)0;
+  return SQLITE_OK;
+}
+
+/*
+** Called to "rewind" a cursor back to the beginning so that
+** it starts its output over again.  Always called at least once
+** prior to any fuzzerColumn, fuzzerRowid, or fuzzerEof call.
+*/
+static int fuzzerFilter(
+  sqlite3_vtab_cursor *pVtabCursor, 
+  int idxNum, const char *idxStr,
+  int argc, sqlite3_value **argv
+){
+  fuzzer_cursor *pCur = (fuzzer_cursor *)pVtabCursor;
+  const char *zWord = 0;
+  fuzzer_stem *pStem;
+
+  fuzzerClearCursor(pCur, 1);
+  pCur->rLimit = 2147483647;
+  if( idxNum==1 ){
+    zWord = (const char*)sqlite3_value_text(argv[0]);
+  }else if( idxNum==2 ){
+    pCur->rLimit = (fuzzer_cost)sqlite3_value_int(argv[0]);
+  }else if( idxNum==3 ){
+    zWord = (const char*)sqlite3_value_text(argv[0]);
+    pCur->rLimit = (fuzzer_cost)sqlite3_value_int(argv[1]);
+  }
+  if( zWord==0 ) zWord = "";
+  pCur->pStem = pStem = fuzzerNewStem(pCur, zWord, (fuzzer_cost)0);
+  if( pStem==0 ) return SQLITE_NOMEM;
+  pCur->nullRule.pNext = pCur->pVtab->pRule;
+  pCur->nullRule.rCost = 0;
+  pCur->nullRule.nFrom = 0;
+  pCur->nullRule.nTo = 0;
+  pCur->nullRule.zFrom = "";
+  pStem->pRule = &pCur->nullRule;
+  pStem->n = pStem->nBasis;
+  pCur->iRowid = 1;
+  return SQLITE_OK;
+}
+
+/*
+** Only the word and distance columns have values.  All other columns
+** return NULL
+*/
+static int fuzzerColumn(sqlite3_vtab_cursor *cur, sqlite3_context *ctx, int i){
+  fuzzer_cursor *pCur = (fuzzer_cursor*)cur;
+  if( i==0 ){
+    /* the "word" column */
+    if( fuzzerRender(pCur->pStem, &pCur->zBuf, &pCur->nBuf)==SQLITE_NOMEM ){
+      return SQLITE_NOMEM;
+    }
+    sqlite3_result_text(ctx, pCur->zBuf, -1, SQLITE_TRANSIENT);
+  }else if( i==1 ){
+    /* the "distance" column */
+    sqlite3_result_int(ctx, pCur->pStem->rCostX);
+  }else{
+    /* All other columns are NULL */
+    sqlite3_result_null(ctx);
+  }
+  return SQLITE_OK;
+}
+
+/*
+** The rowid.
+*/
+static int fuzzerRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
+  fuzzer_cursor *pCur = (fuzzer_cursor*)cur;
+  *pRowid = pCur->iRowid;
+  return SQLITE_OK;
+}
+
+/*
+** When the fuzzer_cursor.rLimit value is 0 or less, that is a signal
+** that the cursor has nothing more to output.
+*/
+static int fuzzerEof(sqlite3_vtab_cursor *cur){
+  fuzzer_cursor *pCur = (fuzzer_cursor*)cur;
+  return pCur->rLimit<=(fuzzer_cost)0;
+}
+
+/*
+** Search for terms of these forms:
+**
+**       word MATCH $str
+**       distance < $value
+**       distance <= $value
+**
+** The distance< and distance<= are both treated as distance<=.
+** The query plan number is as follows:
+**
+**   0:    None of the terms above are found
+**   1:    There is a "word MATCH" term with $str in filter.argv[0].
+**   2:    There is a "distance<" term with $value in filter.argv[0].
+**   3:    Both "word MATCH" and "distance<" with $str in argv[0] and
+**         $value in argv[1].
+*/
+static int fuzzerBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
+  int iPlan = 0;
+  int iDistTerm = -1;
+  int i;
+  const struct sqlite3_index_constraint *pConstraint;
+  pConstraint = pIdxInfo->aConstraint;
+  for(i=0; i<pIdxInfo->nConstraint; i++, pConstraint++){
+    if( pConstraint->usable==0 ) continue;
+    if( (iPlan & 1)==0 
+     && pConstraint->iColumn==0
+     && pConstraint->op==SQLITE_INDEX_CONSTRAINT_MATCH
+    ){
+      iPlan |= 1;
+      pIdxInfo->aConstraintUsage[i].argvIndex = 1;
+      pIdxInfo->aConstraintUsage[i].omit = 1;
+    }
+    if( (iPlan & 2)==0
+     && pConstraint->iColumn==1
+     && (pConstraint->op==SQLITE_INDEX_CONSTRAINT_LT
+           || pConstraint->op==SQLITE_INDEX_CONSTRAINT_LE)
+    ){
+      iPlan |= 2;
+      iDistTerm = i;
+    }
+  }
+  if( iPlan==2 ){
+    pIdxInfo->aConstraintUsage[iDistTerm].argvIndex = 1;
+  }else if( iPlan==3 ){
+    pIdxInfo->aConstraintUsage[iDistTerm].argvIndex = 2;
+  }
+  pIdxInfo->idxNum = iPlan;
+  if( pIdxInfo->nOrderBy==1
+   && pIdxInfo->aOrderBy[0].iColumn==1
+   && pIdxInfo->aOrderBy[0].desc==0
+  ){
+    pIdxInfo->orderByConsumed = 1;
+  }
+  pIdxInfo->estimatedCost = (double)10000;
+   
+  return SQLITE_OK;
+}
+
+/*
+** Disallow all attempts to DELETE or UPDATE.  Only INSERTs are allowed.
+**
+** On an insert, the cFrom, cTo, and cost columns are used to construct
+** a new rule.   All other columns are ignored.  The rule is ignored
+** if cFrom and cTo are identical.  A NULL value for cFrom or cTo is
+** interpreted as an empty string.  The cost must be positive.
+*/
+static int fuzzerUpdate(
+  sqlite3_vtab *pVTab,
+  int argc,
+  sqlite3_value **argv,
+  sqlite_int64 *pRowid
+){
+  fuzzer_vtab *p = (fuzzer_vtab*)pVTab;
+  fuzzer_rule *pRule;
+  const char *zFrom;
+  int nFrom;
+  const char *zTo;
+  int nTo;
+  fuzzer_cost rCost;
+  if( argc!=7 ){
+    sqlite3_free(pVTab->zErrMsg);
+    pVTab->zErrMsg = sqlite3_mprintf("cannot delete from a %s virtual table",
+                                     p->zClassName);
+    return SQLITE_CONSTRAINT;
+  }
+  if( sqlite3_value_type(argv[0])!=SQLITE_NULL ){
+    sqlite3_free(pVTab->zErrMsg);
+    pVTab->zErrMsg = sqlite3_mprintf("cannot update a %s virtual table",
+                                     p->zClassName);
+    return SQLITE_CONSTRAINT;
+  }
+  zFrom = (char*)sqlite3_value_text(argv[4]);
+  if( zFrom==0 ) zFrom = "";
+  zTo = (char*)sqlite3_value_text(argv[5]);
+  if( zTo==0 ) zTo = "";
+  if( strcmp(zFrom,zTo)==0 ){
+    /* Silently ignore null transformations */
+    return SQLITE_OK;
+  }
+  rCost = sqlite3_value_int(argv[6]);
+  if( rCost<=0 ){
+    sqlite3_free(pVTab->zErrMsg);
+    pVTab->zErrMsg = sqlite3_mprintf("cost must be positive");
+    return SQLITE_CONSTRAINT;    
+  }
+  nFrom = strlen(zFrom);
+  nTo = strlen(zTo);
+  pRule = sqlite3_malloc( sizeof(*pRule) + nFrom + nTo );
+  if( pRule==0 ){
+    return SQLITE_NOMEM;
+  }
+  pRule->zFrom = &pRule->zTo[nTo+1];
+  pRule->nFrom = nFrom;
+  memcpy(pRule->zFrom, zFrom, nFrom+1);
+  memcpy(pRule->zTo, zTo, nTo+1);
+  pRule->nTo = nTo;
+  pRule->rCost = rCost;
+  pRule->pNext = p->pNewRule;
+  p->pNewRule = pRule;
+  return SQLITE_OK;
+}
+
+/*
+** A virtual table module that provides read-only access to a
+** Tcl global variable namespace.
+*/
+static sqlite3_module fuzzerModule = {
+  0,                           /* iVersion */
+  fuzzerConnect,
+  fuzzerConnect,
+  fuzzerBestIndex,
+  fuzzerDisconnect, 
+  fuzzerDisconnect,
+  fuzzerOpen,                  /* xOpen - open a cursor */
+  fuzzerClose,                 /* xClose - close a cursor */
+  fuzzerFilter,                /* xFilter - configure scan constraints */
+  fuzzerNext,                  /* xNext - advance a cursor */
+  fuzzerEof,                   /* xEof - check for end of scan */
+  fuzzerColumn,                /* xColumn - read data */
+  fuzzerRowid,                 /* xRowid - read data */
+  fuzzerUpdate,                /* xUpdate - INSERT */
+  0,                           /* xBegin */
+  0,                           /* xSync */
+  0,                           /* xCommit */
+  0,                           /* xRollback */
+  0,                           /* xFindMethod */
+  0,                           /* xRename */
+};
+
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+
+/*
+** Register the fuzzer virtual table
+*/
+int fuzzer_register(sqlite3 *db){
+  int rc = SQLITE_OK;
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  rc = sqlite3_create_module(db, "fuzzer", &fuzzerModule, 0);
+#endif
+  return rc;
+}
+
+#ifdef SQLITE_TEST
+#include <tcl.h>
+/*
+** Decode a pointer to an sqlite3 object.
+*/
+extern int getDbPointer(Tcl_Interp *interp, const char *zA, sqlite3 **ppDb);
+
+/*
+** Register the echo virtual table module.
+*/
+static int register_fuzzer_module(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3 *db;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  fuzzer_register(db);
+  return TCL_OK;
+}
+
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetestfuzzer_Init(Tcl_Interp *interp){
+  static struct {
+     char *zName;
+     Tcl_ObjCmdProc *xProc;
+     void *clientData;
+  } aObjCmd[] = {
+     { "register_fuzzer_module",   register_fuzzer_module, 0 },
+  };
+  int i;
+  for(i=0; i<sizeof(aObjCmd)/sizeof(aObjCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aObjCmd[i].zName, 
+        aObjCmd[i].xProc, aObjCmd[i].clientData, 0);
+  }
+  return TCL_OK;
+}
+
+#endif /* SQLITE_TEST */
diff --git a/src/test_hexio.c b/src/test_hexio.c
new file mode 100644
index 0000000..e3258e8
--- /dev/null
+++ b/src/test_hexio.c
@@ -0,0 +1,388 @@
+/*
+** 2007 April 6
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Code for testing all sorts of SQLite interfaces.  This code
+** implements TCL commands for reading and writing the binary
+** database files and displaying the content of those files as
+** hexadecimal.  We could, in theory, use the built-in "binary"
+** command of TCL to do a lot of this, but there are some issues
+** with historical versions of the "binary" command.  So it seems
+** easier and safer to build our own mechanism.
+*/
+#include "sqliteInt.h"
+#include "tcl.h"
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+
+
+/*
+** Convert binary to hex.  The input zBuf[] contains N bytes of
+** binary data.  zBuf[] is 2*n+1 bytes long.  Overwrite zBuf[]
+** with a hexadecimal representation of its original binary input.
+*/
+void sqlite3TestBinToHex(unsigned char *zBuf, int N){
+  const unsigned char zHex[] = "0123456789ABCDEF";
+  int i, j;
+  unsigned char c;
+  i = N*2;
+  zBuf[i--] = 0;
+  for(j=N-1; j>=0; j--){
+    c = zBuf[j];
+    zBuf[i--] = zHex[c&0xf];
+    zBuf[i--] = zHex[c>>4];
+  }
+  assert( i==-1 );
+}
+
+/*
+** Convert hex to binary.  The input zIn[] contains N bytes of
+** hexadecimal.  Convert this into binary and write aOut[] with
+** the binary data.  Spaces in the original input are ignored.
+** Return the number of bytes of binary rendered.
+*/
+int sqlite3TestHexToBin(const unsigned char *zIn, int N, unsigned char *aOut){
+  const unsigned char aMap[] = {
+     0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+     0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+     0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+     1, 2, 3, 4, 5, 6, 7, 8,  9,10, 0, 0, 0, 0, 0, 0,
+     0,11,12,13,14,15,16, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+     0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+     0,11,12,13,14,15,16, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+     0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+     0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+     0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+     0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+     0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+     0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+     0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+     0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+     0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+  };
+  int i, j;
+  int hi=1;
+  unsigned char c;
+
+  for(i=j=0; i<N; i++){
+    c = aMap[zIn[i]];
+    if( c==0 ) continue;
+    if( hi ){
+      aOut[j] = (c-1)<<4;
+      hi = 0;
+    }else{
+      aOut[j++] |= c-1;
+      hi = 1;
+    }
+  }
+  return j;
+}
+
+
+/*
+** Usage:   hexio_read  FILENAME  OFFSET  AMT
+**
+** Read AMT bytes from file FILENAME beginning at OFFSET from the
+** beginning of the file.  Convert that information to hexadecimal
+** and return the resulting HEX string.
+*/
+static int hexio_read(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int offset;
+  int amt, got;
+  const char *zFile;
+  unsigned char *zBuf;
+  FILE *in;
+
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "FILENAME OFFSET AMT");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[2], &offset) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[3], &amt) ) return TCL_ERROR;
+  zFile = Tcl_GetString(objv[1]);
+  zBuf = sqlite3_malloc( amt*2+1 );
+  if( zBuf==0 ){
+    return TCL_ERROR;
+  }
+  in = fopen(zFile, "rb");
+  if( in==0 ){
+    in = fopen(zFile, "r");
+  }
+  if( in==0 ){
+    Tcl_AppendResult(interp, "cannot open input file ", zFile, 0);
+    return TCL_ERROR;
+  }
+  fseek(in, offset, SEEK_SET);
+  got = fread(zBuf, 1, amt, in);
+  fclose(in);
+  if( got<0 ){
+    got = 0;
+  }
+  sqlite3TestBinToHex(zBuf, got);
+  Tcl_AppendResult(interp, zBuf, 0);
+  sqlite3_free(zBuf);
+  return TCL_OK;
+}
+
+
+/*
+** Usage:   hexio_write  FILENAME  OFFSET  DATA
+**
+** Write DATA into file FILENAME beginning at OFFSET from the
+** beginning of the file.  DATA is expressed in hexadecimal.
+*/
+static int hexio_write(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int offset;
+  int nIn, nOut, written;
+  const char *zFile;
+  const unsigned char *zIn;
+  unsigned char *aOut;
+  FILE *out;
+
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "FILENAME OFFSET HEXDATA");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[2], &offset) ) return TCL_ERROR;
+  zFile = Tcl_GetString(objv[1]);
+  zIn = (const unsigned char *)Tcl_GetStringFromObj(objv[3], &nIn);
+  aOut = sqlite3_malloc( nIn/2 );
+  if( aOut==0 ){
+    return TCL_ERROR;
+  }
+  nOut = sqlite3TestHexToBin(zIn, nIn, aOut);
+  out = fopen(zFile, "r+b");
+  if( out==0 ){
+    out = fopen(zFile, "r+");
+  }
+  if( out==0 ){
+    Tcl_AppendResult(interp, "cannot open output file ", zFile, 0);
+    return TCL_ERROR;
+  }
+  fseek(out, offset, SEEK_SET);
+  written = fwrite(aOut, 1, nOut, out);
+  sqlite3_free(aOut);
+  fclose(out);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(written));
+  return TCL_OK;
+}
+
+/*
+** USAGE:   hexio_get_int   HEXDATA
+**
+** Interpret the HEXDATA argument as a big-endian integer.  Return
+** the value of that integer.  HEXDATA can contain between 2 and 8
+** hexadecimal digits.
+*/
+static int hexio_get_int(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int val;
+  int nIn, nOut;
+  const unsigned char *zIn;
+  unsigned char *aOut;
+  unsigned char aNum[4];
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "HEXDATA");
+    return TCL_ERROR;
+  }
+  zIn = (const unsigned char *)Tcl_GetStringFromObj(objv[1], &nIn);
+  aOut = sqlite3_malloc( nIn/2 );
+  if( aOut==0 ){
+    return TCL_ERROR;
+  }
+  nOut = sqlite3TestHexToBin(zIn, nIn, aOut);
+  if( nOut>=4 ){
+    memcpy(aNum, aOut, 4);
+  }else{
+    memset(aNum, 0, sizeof(aNum));
+    memcpy(&aNum[4-nOut], aOut, nOut);
+  }
+  sqlite3_free(aOut);
+  val = (aNum[0]<<24) | (aNum[1]<<16) | (aNum[2]<<8) | aNum[3];
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(val));
+  return TCL_OK;
+}
+
+
+/*
+** USAGE:   hexio_render_int16   INTEGER
+**
+** Render INTEGER has a 16-bit big-endian integer in hexadecimal.
+*/
+static int hexio_render_int16(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int val;
+  unsigned char aNum[10];
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "INTEGER");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[1], &val) ) return TCL_ERROR;
+  aNum[0] = val>>8;
+  aNum[1] = val;
+  sqlite3TestBinToHex(aNum, 2);
+  Tcl_SetObjResult(interp, Tcl_NewStringObj((char*)aNum, 4));
+  return TCL_OK;
+}
+
+
+/*
+** USAGE:   hexio_render_int32   INTEGER
+**
+** Render INTEGER has a 32-bit big-endian integer in hexadecimal.
+*/
+static int hexio_render_int32(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int val;
+  unsigned char aNum[10];
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "INTEGER");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[1], &val) ) return TCL_ERROR;
+  aNum[0] = val>>24;
+  aNum[1] = val>>16;
+  aNum[2] = val>>8;
+  aNum[3] = val;
+  sqlite3TestBinToHex(aNum, 4);
+  Tcl_SetObjResult(interp, Tcl_NewStringObj((char*)aNum, 8));
+  return TCL_OK;
+}
+
+/*
+** USAGE:  utf8_to_utf8  HEX
+**
+** The argument is a UTF8 string represented in hexadecimal.
+** The UTF8 might not be well-formed.  Run this string through
+** sqlite3Utf8to8() convert it back to hex and return the result.
+*/
+static int utf8_to_utf8(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#ifdef SQLITE_DEBUG
+  int n;
+  int nOut;
+  const unsigned char *zOrig;
+  unsigned char *z;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "HEX");
+    return TCL_ERROR;
+  }
+  zOrig = (unsigned char *)Tcl_GetStringFromObj(objv[1], &n);
+  z = sqlite3_malloc( n+3 );
+  n = sqlite3TestHexToBin(zOrig, n, z);
+  z[n] = 0;
+  nOut = sqlite3Utf8To8(z);
+  sqlite3TestBinToHex(z,nOut);
+  Tcl_AppendResult(interp, (char*)z, 0);
+  sqlite3_free(z);
+  return TCL_OK;
+#else
+  Tcl_AppendResult(interp, 
+      "[utf8_to_utf8] unavailable - SQLITE_DEBUG not defined", 0
+  );
+  return TCL_ERROR;
+#endif
+}
+
+static int getFts3Varint(const char *p, sqlite_int64 *v){
+  const unsigned char *q = (const unsigned char *) p;
+  sqlite_uint64 x = 0, y = 1;
+  while( (*q & 0x80) == 0x80 ){
+    x += y * (*q++ & 0x7f);
+    y <<= 7;
+  }
+  x += y * (*q++);
+  *v = (sqlite_int64) x;
+  return (int) (q - (unsigned char *)p);
+}
+
+
+/*
+** USAGE:  read_fts3varint BLOB VARNAME
+**
+** Read a varint from the start of BLOB. Set variable VARNAME to contain
+** the interpreted value. Return the number of bytes of BLOB consumed.
+*/
+static int read_fts3varint(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int nBlob;
+  unsigned char *zBlob;
+  sqlite3_int64 iVal;
+  int nVal;
+
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "BLOB VARNAME");
+    return TCL_ERROR;
+  }
+  zBlob = Tcl_GetByteArrayFromObj(objv[1], &nBlob);
+
+  nVal = getFts3Varint((char*)zBlob, (sqlite3_int64 *)(&iVal));
+  Tcl_ObjSetVar2(interp, objv[2], 0, Tcl_NewWideIntObj(iVal), 0);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(nVal));
+  return TCL_OK;
+}
+
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetest_hexio_Init(Tcl_Interp *interp){
+  static struct {
+     char *zName;
+     Tcl_ObjCmdProc *xProc;
+  } aObjCmd[] = {
+     { "hexio_read",                   hexio_read            },
+     { "hexio_write",                  hexio_write           },
+     { "hexio_get_int",                hexio_get_int         },
+     { "hexio_render_int16",           hexio_render_int16    },
+     { "hexio_render_int32",           hexio_render_int32    },
+     { "utf8_to_utf8",                 utf8_to_utf8          },
+     { "read_fts3varint",              read_fts3varint       },
+  };
+  int i;
+  for(i=0; i<sizeof(aObjCmd)/sizeof(aObjCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aObjCmd[i].zName, aObjCmd[i].xProc, 0, 0);
+  }
+  return TCL_OK;
+}
diff --git a/src/test_init.c b/src/test_init.c
new file mode 100644
index 0000000..a67b678
--- /dev/null
+++ b/src/test_init.c
@@ -0,0 +1,287 @@
+/*
+** 2009 August 17
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** The code in this file is used for testing SQLite. It is not part of
+** the source code used in production systems.
+**
+** Specifically, this file tests the effect of errors while initializing
+** the various pluggable sub-systems from within sqlite3_initialize().
+** If an error occurs in sqlite3_initialize() the following should be
+** true:
+**
+**   1) An error code is returned to the user, and
+**   2) A subsequent call to sqlite3_shutdown() calls the shutdown method
+**      of those subsystems that were initialized, and
+**   3) A subsequent call to sqlite3_initialize() attempts to initialize
+**      the remaining, uninitialized, subsystems.
+*/
+
+#include "sqliteInt.h"
+#include <string.h>
+#include <tcl.h>
+
+static struct Wrapped {
+  sqlite3_pcache_methods pcache;
+  sqlite3_mem_methods    mem;
+  sqlite3_mutex_methods  mutex;
+
+  int mem_init;                /* True if mem subsystem is initalized */
+  int mem_fail;                /* True to fail mem subsystem inialization */
+  int mutex_init;              /* True if mutex subsystem is initalized */
+  int mutex_fail;              /* True to fail mutex subsystem inialization */
+  int pcache_init;             /* True if pcache subsystem is initalized */
+  int pcache_fail;             /* True to fail pcache subsystem inialization */
+} wrapped;
+
+static int wrMemInit(void *pAppData){
+  int rc;
+  if( wrapped.mem_fail ){
+    rc = SQLITE_ERROR;
+  }else{
+    rc = wrapped.mem.xInit(wrapped.mem.pAppData);
+  }
+  if( rc==SQLITE_OK ){
+    wrapped.mem_init = 1;
+  }
+  return rc;
+}
+static void wrMemShutdown(void *pAppData){
+  wrapped.mem.xShutdown(wrapped.mem.pAppData);
+  wrapped.mem_init = 0;
+}
+static void *wrMemMalloc(int n)           {return wrapped.mem.xMalloc(n);}
+static void wrMemFree(void *p)            {wrapped.mem.xFree(p);}
+static void *wrMemRealloc(void *p, int n) {return wrapped.mem.xRealloc(p, n);}
+static int wrMemSize(void *p)             {return wrapped.mem.xSize(p);}
+static int wrMemRoundup(int n)            {return wrapped.mem.xRoundup(n);}
+
+
+static int wrMutexInit(void){
+  int rc;
+  if( wrapped.mutex_fail ){
+    rc = SQLITE_ERROR;
+  }else{
+    rc = wrapped.mutex.xMutexInit();
+  }
+  if( rc==SQLITE_OK ){
+    wrapped.mutex_init = 1;
+  }
+  return rc;
+}
+static int wrMutexEnd(void){
+  wrapped.mutex.xMutexEnd();
+  wrapped.mutex_init = 0;
+  return SQLITE_OK;
+}
+static sqlite3_mutex *wrMutexAlloc(int e){
+  return wrapped.mutex.xMutexAlloc(e);
+}
+static void wrMutexFree(sqlite3_mutex *p){
+  wrapped.mutex.xMutexFree(p);
+}
+static void wrMutexEnter(sqlite3_mutex *p){
+  wrapped.mutex.xMutexEnter(p);
+}
+static int wrMutexTry(sqlite3_mutex *p){
+  return wrapped.mutex.xMutexTry(p);
+}
+static void wrMutexLeave(sqlite3_mutex *p){
+  wrapped.mutex.xMutexLeave(p);
+}
+static int wrMutexHeld(sqlite3_mutex *p){
+  return wrapped.mutex.xMutexHeld(p);
+}
+static int wrMutexNotheld(sqlite3_mutex *p){
+  return wrapped.mutex.xMutexNotheld(p);
+}
+
+
+
+static int wrPCacheInit(void *pArg){
+  int rc;
+  if( wrapped.pcache_fail ){
+    rc = SQLITE_ERROR;
+  }else{
+    rc = wrapped.pcache.xInit(wrapped.pcache.pArg);
+  }
+  if( rc==SQLITE_OK ){
+    wrapped.pcache_init = 1;
+  }
+  return rc;
+}
+static void wrPCacheShutdown(void *pArg){
+  wrapped.pcache.xShutdown(wrapped.pcache.pArg);
+  wrapped.pcache_init = 0;
+}
+
+static sqlite3_pcache *wrPCacheCreate(int a, int b){
+  return wrapped.pcache.xCreate(a, b);
+}  
+static void wrPCacheCachesize(sqlite3_pcache *p, int n){
+  wrapped.pcache.xCachesize(p, n);
+}  
+static int wrPCachePagecount(sqlite3_pcache *p){
+  return wrapped.pcache.xPagecount(p);
+}  
+static void *wrPCacheFetch(sqlite3_pcache *p, unsigned a, int b){
+  return wrapped.pcache.xFetch(p, a, b);
+}  
+static void wrPCacheUnpin(sqlite3_pcache *p, void *a, int b){
+  wrapped.pcache.xUnpin(p, a, b);
+}  
+static void wrPCacheRekey(sqlite3_pcache *p, void *a, unsigned b, unsigned c){
+  wrapped.pcache.xRekey(p, a, b, c);
+}  
+static void wrPCacheTruncate(sqlite3_pcache *p, unsigned a){
+  wrapped.pcache.xTruncate(p, a);
+}  
+static void wrPCacheDestroy(sqlite3_pcache *p){
+  wrapped.pcache.xDestroy(p);
+}  
+
+static void installInitWrappers(void){
+  sqlite3_mutex_methods mutexmethods = {
+    wrMutexInit,  wrMutexEnd,   wrMutexAlloc,
+    wrMutexFree,  wrMutexEnter, wrMutexTry,
+    wrMutexLeave, wrMutexHeld,  wrMutexNotheld
+  };
+  sqlite3_pcache_methods pcachemethods = {
+    0,
+    wrPCacheInit,      wrPCacheShutdown,  wrPCacheCreate, 
+    wrPCacheCachesize, wrPCachePagecount, wrPCacheFetch,
+    wrPCacheUnpin,     wrPCacheRekey,     wrPCacheTruncate,  
+    wrPCacheDestroy
+  };
+  sqlite3_mem_methods memmethods = {
+    wrMemMalloc,   wrMemFree,    wrMemRealloc,
+    wrMemSize,     wrMemRoundup, wrMemInit,
+    wrMemShutdown,
+    0
+  };
+
+  memset(&wrapped, 0, sizeof(wrapped));
+
+  sqlite3_shutdown();
+  sqlite3_config(SQLITE_CONFIG_GETMUTEX, &wrapped.mutex);
+  sqlite3_config(SQLITE_CONFIG_GETMALLOC, &wrapped.mem);
+  sqlite3_config(SQLITE_CONFIG_GETPCACHE, &wrapped.pcache);
+  sqlite3_config(SQLITE_CONFIG_MUTEX, &mutexmethods);
+  sqlite3_config(SQLITE_CONFIG_MALLOC, &memmethods);
+  sqlite3_config(SQLITE_CONFIG_PCACHE, &pcachemethods);
+}
+
+static int init_wrapper_install(
+  ClientData clientData, /* Unused */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  int i;
+  installInitWrappers();
+  for(i=1; i<objc; i++){
+    char *z = Tcl_GetString(objv[i]);
+    if( strcmp(z, "mem")==0 ){
+      wrapped.mem_fail = 1;
+    }else if( strcmp(z, "mutex")==0 ){
+      wrapped.mutex_fail = 1;
+    }else if( strcmp(z, "pcache")==0 ){
+      wrapped.pcache_fail = 1;
+    }else{
+      Tcl_AppendResult(interp, "Unknown argument: \"", z, "\"");
+      return TCL_ERROR;
+    }
+  }
+  return TCL_OK;
+}
+
+static int init_wrapper_uninstall(
+  ClientData clientData, /* Unused */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+
+  memset(&wrapped, 0, sizeof(&wrapped));
+  sqlite3_shutdown();
+  sqlite3_config(SQLITE_CONFIG_MUTEX, &wrapped.mutex);
+  sqlite3_config(SQLITE_CONFIG_MALLOC, &wrapped.mem);
+  sqlite3_config(SQLITE_CONFIG_PCACHE, &wrapped.pcache);
+  return TCL_OK;
+}
+
+static int init_wrapper_clear(
+  ClientData clientData, /* Unused */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+
+  wrapped.mem_fail = 0;
+  wrapped.mutex_fail = 0;
+  wrapped.pcache_fail = 0;
+  return TCL_OK;
+}
+
+static int init_wrapper_query(
+  ClientData clientData, /* Unused */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  Tcl_Obj *pRet;
+
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+
+  pRet = Tcl_NewObj();
+  if( wrapped.mutex_init ){
+    Tcl_ListObjAppendElement(interp, pRet, Tcl_NewStringObj("mutex", -1));
+  }
+  if( wrapped.mem_init ){
+    Tcl_ListObjAppendElement(interp, pRet, Tcl_NewStringObj("mem", -1));
+  }
+  if( wrapped.pcache_init ){
+    Tcl_ListObjAppendElement(interp, pRet, Tcl_NewStringObj("pcache", -1));
+  }
+
+  Tcl_SetObjResult(interp, pRet);
+  return TCL_OK;
+}
+
+int Sqlitetest_init_Init(Tcl_Interp *interp){
+  static struct {
+     char *zName;
+     Tcl_ObjCmdProc *xProc;
+  } aObjCmd[] = {
+    {"init_wrapper_install",   init_wrapper_install},
+    {"init_wrapper_query",     init_wrapper_query  },
+    {"init_wrapper_uninstall", init_wrapper_uninstall},
+    {"init_wrapper_clear",     init_wrapper_clear}
+  };
+  int i;
+
+  for(i=0; i<sizeof(aObjCmd)/sizeof(aObjCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aObjCmd[i].zName, aObjCmd[i].xProc, 0, 0);
+  }
+
+  return TCL_OK;
+}
diff --git a/src/test_intarray.c b/src/test_intarray.c
new file mode 100644
index 0000000..8651d01
--- /dev/null
+++ b/src/test_intarray.c
@@ -0,0 +1,381 @@
+/*
+** 2009 November 10
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file implements a read-only VIRTUAL TABLE that contains the
+** content of a C-language array of integer values.  See the corresponding
+** header file for full details.
+*/
+#include "test_intarray.h"
+#include <string.h>
+#include <assert.h>
+
+
+/*
+** Definition of the sqlite3_intarray object.
+**
+** The internal representation of an intarray object is subject
+** to change, is not externally visible, and should be used by
+** the implementation of intarray only.  This object is opaque
+** to users.
+*/
+struct sqlite3_intarray {
+  int n;                    /* Number of elements in the array */
+  sqlite3_int64 *a;         /* Contents of the array */
+  void (*xFree)(void*);     /* Function used to free a[] */
+};
+
+/* Objects used internally by the virtual table implementation */
+typedef struct intarray_vtab intarray_vtab;
+typedef struct intarray_cursor intarray_cursor;
+
+/* A intarray table object */
+struct intarray_vtab {
+  sqlite3_vtab base;            /* Base class */
+  sqlite3_intarray *pContent;   /* Content of the integer array */
+};
+
+/* A intarray cursor object */
+struct intarray_cursor {
+  sqlite3_vtab_cursor base;    /* Base class */
+  int i;                       /* Current cursor position */
+};
+
+/*
+** None of this works unless we have virtual tables.
+*/
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+
+/*
+** Free an sqlite3_intarray object.
+*/
+static void intarrayFree(sqlite3_intarray *p){
+  if( p->xFree ){
+    p->xFree(p->a);
+  }
+  sqlite3_free(p);
+}
+
+/*
+** Table destructor for the intarray module.
+*/
+static int intarrayDestroy(sqlite3_vtab *p){
+  intarray_vtab *pVtab = (intarray_vtab*)p;
+  sqlite3_free(pVtab);
+  return 0;
+}
+
+/*
+** Table constructor for the intarray module.
+*/
+static int intarrayCreate(
+  sqlite3 *db,              /* Database where module is created */
+  void *pAux,               /* clientdata for the module */
+  int argc,                 /* Number of arguments */
+  const char *const*argv,   /* Value for all arguments */
+  sqlite3_vtab **ppVtab,    /* Write the new virtual table object here */
+  char **pzErr              /* Put error message text here */
+){
+  int rc = SQLITE_NOMEM;
+  intarray_vtab *pVtab = sqlite3_malloc(sizeof(intarray_vtab));
+
+  if( pVtab ){
+    memset(pVtab, 0, sizeof(intarray_vtab));
+    pVtab->pContent = (sqlite3_intarray*)pAux;
+    rc = sqlite3_declare_vtab(db, "CREATE TABLE x(value INTEGER PRIMARY KEY)");
+  }
+  *ppVtab = (sqlite3_vtab *)pVtab;
+  return rc;
+}
+
+/*
+** Open a new cursor on the intarray table.
+*/
+static int intarrayOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
+  int rc = SQLITE_NOMEM;
+  intarray_cursor *pCur;
+  pCur = sqlite3_malloc(sizeof(intarray_cursor));
+  if( pCur ){
+    memset(pCur, 0, sizeof(intarray_cursor));
+    *ppCursor = (sqlite3_vtab_cursor *)pCur;
+    rc = SQLITE_OK;
+  }
+  return rc;
+}
+
+/*
+** Close a intarray table cursor.
+*/
+static int intarrayClose(sqlite3_vtab_cursor *cur){
+  intarray_cursor *pCur = (intarray_cursor *)cur;
+  sqlite3_free(pCur);
+  return SQLITE_OK;
+}
+
+/*
+** Retrieve a column of data.
+*/
+static int intarrayColumn(sqlite3_vtab_cursor *cur, sqlite3_context *ctx, int i){
+  intarray_cursor *pCur = (intarray_cursor*)cur;
+  intarray_vtab *pVtab = (intarray_vtab*)cur->pVtab;
+  if( pCur->i>=0 && pCur->i<pVtab->pContent->n ){
+    sqlite3_result_int64(ctx, pVtab->pContent->a[pCur->i]);
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Retrieve the current rowid.
+*/
+static int intarrayRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
+  intarray_cursor *pCur = (intarray_cursor *)cur;
+  *pRowid = pCur->i;
+  return SQLITE_OK;
+}
+
+static int intarrayEof(sqlite3_vtab_cursor *cur){
+  intarray_cursor *pCur = (intarray_cursor *)cur;
+  intarray_vtab *pVtab = (intarray_vtab *)cur->pVtab;
+  return pCur->i>=pVtab->pContent->n;
+}
+
+/*
+** Advance the cursor to the next row.
+*/
+static int intarrayNext(sqlite3_vtab_cursor *cur){
+  intarray_cursor *pCur = (intarray_cursor *)cur;
+  pCur->i++;
+  return SQLITE_OK;
+}
+
+/*
+** Reset a intarray table cursor.
+*/
+static int intarrayFilter(
+  sqlite3_vtab_cursor *pVtabCursor, 
+  int idxNum, const char *idxStr,
+  int argc, sqlite3_value **argv
+){
+  intarray_cursor *pCur = (intarray_cursor *)pVtabCursor;
+  pCur->i = 0;
+  return SQLITE_OK;
+}
+
+/*
+** Analyse the WHERE condition.
+*/
+static int intarrayBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
+  return SQLITE_OK;
+}
+
+/*
+** A virtual table module that merely echos method calls into TCL
+** variables.
+*/
+static sqlite3_module intarrayModule = {
+  0,                           /* iVersion */
+  intarrayCreate,              /* xCreate - create a new virtual table */
+  intarrayCreate,              /* xConnect - connect to an existing vtab */
+  intarrayBestIndex,           /* xBestIndex - find the best query index */
+  intarrayDestroy,             /* xDisconnect - disconnect a vtab */
+  intarrayDestroy,             /* xDestroy - destroy a vtab */
+  intarrayOpen,                /* xOpen - open a cursor */
+  intarrayClose,               /* xClose - close a cursor */
+  intarrayFilter,              /* xFilter - configure scan constraints */
+  intarrayNext,                /* xNext - advance a cursor */
+  intarrayEof,                 /* xEof */
+  intarrayColumn,              /* xColumn - read data */
+  intarrayRowid,               /* xRowid - read data */
+  0,                           /* xUpdate */
+  0,                           /* xBegin */
+  0,                           /* xSync */
+  0,                           /* xCommit */
+  0,                           /* xRollback */
+  0,                           /* xFindMethod */
+  0,                           /* xRename */
+};
+
+#endif /* !defined(SQLITE_OMIT_VIRTUALTABLE) */
+
+/*
+** Invoke this routine to create a specific instance of an intarray object.
+** The new intarray object is returned by the 3rd parameter.
+**
+** Each intarray object corresponds to a virtual table in the TEMP table
+** with a name of zName.
+**
+** Destroy the intarray object by dropping the virtual table.  If not done
+** explicitly by the application, the virtual table will be dropped implicitly
+** by the system when the database connection is closed.
+*/
+int sqlite3_intarray_create(
+  sqlite3 *db,
+  const char *zName,
+  sqlite3_intarray **ppReturn
+){
+  int rc = SQLITE_OK;
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  sqlite3_intarray *p;
+
+  *ppReturn = p = sqlite3_malloc( sizeof(*p) );
+  if( p==0 ){
+    return SQLITE_NOMEM;
+  }
+  memset(p, 0, sizeof(*p));
+  rc = sqlite3_create_module_v2(db, zName, &intarrayModule, p,
+                                (void(*)(void*))intarrayFree);
+  if( rc==SQLITE_OK ){
+    char *zSql;
+    zSql = sqlite3_mprintf("CREATE VIRTUAL TABLE temp.%Q USING %Q",
+                           zName, zName);
+    rc = sqlite3_exec(db, zSql, 0, 0, 0);
+    sqlite3_free(zSql);
+  }
+#endif
+  return rc;
+}
+
+/*
+** Bind a new array array of integers to a specific intarray object.
+**
+** The array of integers bound must be unchanged for the duration of
+** any query against the corresponding virtual table.  If the integer
+** array does change or is deallocated undefined behavior will result.
+*/
+int sqlite3_intarray_bind(
+  sqlite3_intarray *pIntArray,   /* The intarray object to bind to */
+  int nElements,                 /* Number of elements in the intarray */
+  sqlite3_int64 *aElements,      /* Content of the intarray */
+  void (*xFree)(void*)           /* How to dispose of the intarray when done */
+){
+  if( pIntArray->xFree ){
+    pIntArray->xFree(pIntArray->a);
+  }
+  pIntArray->n = nElements;
+  pIntArray->a = aElements;
+  pIntArray->xFree = xFree;
+  return SQLITE_OK;
+}
+
+
+/*****************************************************************************
+** Everything below is interface for testing this module.
+*/
+#ifdef SQLITE_TEST
+#include <tcl.h>
+
+/*
+** Routines to encode and decode pointers
+*/
+extern int getDbPointer(Tcl_Interp *interp, const char *zA, sqlite3 **ppDb);
+extern void *sqlite3TestTextToPtr(const char*);
+extern int sqlite3TestMakePointerStr(Tcl_Interp*, char *zPtr, void*);
+extern const char *sqlite3TestErrorName(int);
+
+/*
+**    sqlite3_intarray_create  DB  NAME
+**
+** Invoke the sqlite3_intarray_create interface.  A string that becomes
+** the first parameter to sqlite3_intarray_bind.
+*/
+static int test_intarray_create(
+  ClientData clientData, /* Not used */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3 *db;
+  const char *zName;
+  sqlite3_intarray *pArray;
+  int rc = SQLITE_OK;
+  char zPtr[100];
+
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zName = Tcl_GetString(objv[2]);
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  rc = sqlite3_intarray_create(db, zName, &pArray);
+#endif
+  if( rc!=SQLITE_OK ){
+    assert( pArray==0 );
+    Tcl_AppendResult(interp, sqlite3TestErrorName(rc), (char*)0);
+    return TCL_ERROR;
+  }
+  sqlite3TestMakePointerStr(interp, zPtr, pArray);
+  Tcl_AppendResult(interp, zPtr, (char*)0);
+  return TCL_OK;
+}
+
+/*
+**    sqlite3_intarray_bind  INTARRAY  ?VALUE ...?
+**
+** Invoke the sqlite3_intarray_bind interface on the given array of integers.
+*/
+static int test_intarray_bind(
+  ClientData clientData, /* Not used */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3_intarray *pArray;
+  int rc = SQLITE_OK;
+  int i, n;
+  sqlite3_int64 *a;
+
+  if( objc<2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "INTARRAY");
+    return TCL_ERROR;
+  }
+  pArray = (sqlite3_intarray*)sqlite3TestTextToPtr(Tcl_GetString(objv[1]));
+  n = objc - 2;
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  a = sqlite3_malloc( sizeof(a[0])*n );
+  if( a==0 ){
+    Tcl_AppendResult(interp, "SQLITE_NOMEM", (char*)0);
+    return TCL_ERROR;
+  }
+  for(i=0; i<n; i++){
+    a[i] = 0;
+    Tcl_GetWideIntFromObj(0, objv[i+2], &a[i]);
+  }
+  rc = sqlite3_intarray_bind(pArray, n, a, sqlite3_free);
+  if( rc!=SQLITE_OK ){
+    Tcl_AppendResult(interp, sqlite3TestErrorName(rc), (char*)0);
+    return TCL_ERROR;
+  }
+#endif
+  return TCL_OK;
+}
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetestintarray_Init(Tcl_Interp *interp){
+  static struct {
+     char *zName;
+     Tcl_ObjCmdProc *xProc;
+     void *clientData;
+  } aObjCmd[] = {
+     { "sqlite3_intarray_create", test_intarray_create, 0 },
+     { "sqlite3_intarray_bind", test_intarray_bind, 0 },
+  };
+  int i;
+  for(i=0; i<sizeof(aObjCmd)/sizeof(aObjCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aObjCmd[i].zName, 
+        aObjCmd[i].xProc, aObjCmd[i].clientData, 0);
+  }
+  return TCL_OK;
+}
+
+#endif /* SQLITE_TEST */
diff --git a/src/test_intarray.h b/src/test_intarray.h
new file mode 100644
index 0000000..e994367
--- /dev/null
+++ b/src/test_intarray.h
@@ -0,0 +1,114 @@
+/*
+** 2009 November 10
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This is the C-language interface definition for the "intarray" or
+** integer array virtual table for SQLite.
+**
+** The intarray virtual table is designed to facilitate using an
+** array of integers as the right-hand side of an IN operator.  So
+** instead of doing a prepared statement like this:
+**
+**     SELECT * FROM table WHERE x IN (?,?,?,...,?);
+**
+** And then binding indivdual integers to each of ? slots, a C-language
+** application can create an intarray object (named "ex1" in the following
+** example), prepare a statement like this:
+**
+**     SELECT * FROM table WHERE x IN ex1;
+**
+** Then bind an ordinary C/C++ array of integer values to the ex1 object
+** to run the statement.
+**
+** USAGE:
+**
+** One or more intarray objects can be created as follows:
+**
+**      sqlite3_intarray *p1, *p2, *p3;
+**      sqlite3_intarray_create(db, "ex1", &p1);
+**      sqlite3_intarray_create(db, "ex2", &p2);
+**      sqlite3_intarray_create(db, "ex3", &p3);
+**
+** Each call to sqlite3_intarray_create() generates a new virtual table
+** module and a singleton of that virtual table module in the TEMP
+** database.  Both the module and the virtual table instance use the
+** name given by the second parameter.  The virtual tables can then be
+** used in prepared statements:
+**
+**      SELECT * FROM t1, t2, t3
+**       WHERE t1.x IN ex1
+**         AND t2.y IN ex2
+**         AND t3.z IN ex3;
+**
+** Each integer array is initially empty.  New arrays can be bound to
+** an integer array as follows:
+**
+**     sqlite3_int64 a1[] = { 1, 2, 3, 4 };
+**     sqlite3_int64 a2[] = { 5, 6, 7, 8, 9, 10, 11 };
+**     sqlite3_int64 *a3 = sqlite3_malloc( 100*sizeof(sqlite3_int64) );
+**     // Fill in content of a3[]
+**     sqlite3_intarray_bind(p1, 4, a1, 0);
+**     sqlite3_intarray_bind(p2, 7, a2, 0);
+**     sqlite3_intarray_bind(p3, 100, a3, sqlite3_free);
+**
+** A single intarray object can be rebound multiple times.  But do not
+** attempt to change the bindings of an intarray while it is in the middle
+** of a query.
+**
+** The array that holds the integers is automatically freed by the function
+** in the fourth parameter to sqlite3_intarray_bind() when the array is no
+** longer needed.  The application must not change the intarray values
+** while an intarray is in the middle of a query.
+**
+** The intarray object is automatically destroyed when its corresponding
+** virtual table is dropped.  Since the virtual tables are created in the
+** TEMP database, they are automatically dropped when the database connection
+** closes so the application does not normally need to take any special
+** action to free the intarray objects.
+*/
+#include "sqlite3.h"
+
+/*
+** An sqlite3_intarray is an abstract type to stores an instance of
+** an integer array.
+*/
+typedef struct sqlite3_intarray sqlite3_intarray;
+
+/*
+** Invoke this routine to create a specific instance of an intarray object.
+** The new intarray object is returned by the 3rd parameter.
+**
+** Each intarray object corresponds to a virtual table in the TEMP table
+** with a name of zName.
+**
+** Destroy the intarray object by dropping the virtual table.  If not done
+** explicitly by the application, the virtual table will be dropped implicitly
+** by the system when the database connection is closed.
+*/
+int sqlite3_intarray_create(
+  sqlite3 *db,
+  const char *zName,
+  sqlite3_intarray **ppReturn
+);
+
+/*
+** Bind a new array array of integers to a specific intarray object.
+**
+** The array of integers bound must be unchanged for the duration of
+** any query against the corresponding virtual table.  If the integer
+** array does change or is deallocated undefined behavior will result.
+*/
+int sqlite3_intarray_bind(
+  sqlite3_intarray *pIntArray,   /* The intarray object to bind to */
+  int nElements,                 /* Number of elements in the intarray */
+  sqlite3_int64 *aElements,      /* Content of the intarray */
+  void (*xFree)(void*)           /* How to dispose of the intarray when done */
+);
diff --git a/src/test_journal.c b/src/test_journal.c
new file mode 100644
index 0000000..6886972
--- /dev/null
+++ b/src/test_journal.c
@@ -0,0 +1,856 @@
+/*
+** 2008 Jan 22
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains code for a VFS layer that acts as a wrapper around
+** an existing VFS. The code in this file attempts to verify that SQLite
+** correctly populates and syncs a journal file before writing to a
+** corresponding database file.
+**
+** INTERFACE
+**
+**   The public interface to this wrapper VFS is two functions:
+**
+**     jt_register()
+**     jt_unregister()
+**
+**   See header comments associated with those two functions below for 
+**   details.
+**
+** LIMITATIONS
+**
+**   This wrapper will not work if "PRAGMA synchronous = off" is used.
+**
+** OPERATION
+**
+**  Starting a Transaction:
+**
+**   When a write-transaction is started, the contents of the database is
+**   inspected and the following data stored as part of the database file 
+**   handle (type struct jt_file):
+**
+**     a) The page-size of the database file.
+**     b) The number of pages that are in the database file.
+**     c) The set of page numbers corresponding to free-list leaf pages.
+**     d) A check-sum for every page in the database file.
+**
+**   The start of a write-transaction is deemed to have occurred when a 
+**   28-byte journal header is written to byte offset 0 of the journal 
+**   file.
+**
+**  Syncing the Journal File:
+**
+**   Whenever the xSync method is invoked to sync a journal-file, the
+**   contents of the journal file are read. For each page written to
+**   the journal file, a check-sum is calculated and compared to the  
+**   check-sum calculated for the corresponding database page when the
+**   write-transaction was initialized. The success of the comparison
+**   is assert()ed. So if SQLite has written something other than the
+**   original content to the database file, an assert() will fail.
+**
+**   Additionally, the set of page numbers for which records exist in
+**   the journal file is added to (unioned with) the set of page numbers
+**   corresponding to free-list leaf pages collected when the 
+**   write-transaction was initialized. This set comprises the page-numbers 
+**   corresponding to those pages that SQLite may now safely modify.
+**
+**  Writing to the Database File:
+**
+**   When a block of data is written to a database file, the following
+**   invariants are asserted:
+**
+**     a) That the block of data is an aligned block of page-size bytes.
+**
+**     b) That if the page being written did not exist when the 
+**        transaction was started (i.e. the database file is growing), then
+**        the journal-file must have been synced at least once since
+**        the start of the transaction.
+**
+**     c) That if the page being written did exist when the transaction 
+**        was started, then the page must have either been a free-list
+**        leaf page at the start of the transaction, or else must have
+**        been stored in the journal file prior to the most recent sync.
+**
+**  Closing a Transaction:
+**
+**   When a transaction is closed, all data collected at the start of
+**   the transaction, or following an xSync of a journal-file, is 
+**   discarded. The end of a transaction is recognized when any one 
+**   of the following occur:
+**
+**     a) A block of zeroes (or anything else that is not a valid 
+**        journal-header) is written to the start of the journal file.
+**
+**     b) A journal file is truncated to zero bytes in size using xTruncate.
+**
+**     c) The journal file is deleted using xDelete.
+*/
+#if SQLITE_TEST          /* This file is used for testing only */
+
+#include "sqlite3.h"
+#include "sqliteInt.h"
+
+/*
+** Maximum pathname length supported by the jt backend.
+*/
+#define JT_MAX_PATHNAME 512
+
+/*
+** Name used to identify this VFS.
+*/
+#define JT_VFS_NAME "jt"
+
+typedef struct jt_file jt_file;
+struct jt_file {
+  sqlite3_file base;
+  const char *zName;       /* Name of open file */
+  int flags;               /* Flags the file was opened with */
+
+  /* The following are only used by database file file handles */
+  int eLock;               /* Current lock held on the file */
+  u32 nPage;               /* Size of file in pages when transaction started */
+  u32 nPagesize;           /* Page size when transaction started */
+  Bitvec *pWritable;       /* Bitvec of pages that may be written to the file */
+  u32 *aCksum;             /* Checksum for first nPage pages */
+  int nSync;               /* Number of times journal file has been synced */
+
+  /* Only used by journal file-handles */
+  sqlite3_int64 iMaxOff;   /* Maximum offset written to this transaction */
+
+  jt_file *pNext;          /* All files are stored in a linked list */
+  sqlite3_file *pReal;     /* The file handle for the underlying vfs */
+};
+
+/*
+** Method declarations for jt_file.
+*/
+static int jtClose(sqlite3_file*);
+static int jtRead(sqlite3_file*, void*, int iAmt, sqlite3_int64 iOfst);
+static int jtWrite(sqlite3_file*,const void*,int iAmt, sqlite3_int64 iOfst);
+static int jtTruncate(sqlite3_file*, sqlite3_int64 size);
+static int jtSync(sqlite3_file*, int flags);
+static int jtFileSize(sqlite3_file*, sqlite3_int64 *pSize);
+static int jtLock(sqlite3_file*, int);
+static int jtUnlock(sqlite3_file*, int);
+static int jtCheckReservedLock(sqlite3_file*, int *);
+static int jtFileControl(sqlite3_file*, int op, void *pArg);
+static int jtSectorSize(sqlite3_file*);
+static int jtDeviceCharacteristics(sqlite3_file*);
+
+/*
+** Method declarations for jt_vfs.
+*/
+static int jtOpen(sqlite3_vfs*, const char *, sqlite3_file*, int , int *);
+static int jtDelete(sqlite3_vfs*, const char *zName, int syncDir);
+static int jtAccess(sqlite3_vfs*, const char *zName, int flags, int *);
+static int jtFullPathname(sqlite3_vfs*, const char *zName, int, char *zOut);
+static void *jtDlOpen(sqlite3_vfs*, const char *zFilename);
+static void jtDlError(sqlite3_vfs*, int nByte, char *zErrMsg);
+static void (*jtDlSym(sqlite3_vfs*,void*, const char *zSymbol))(void);
+static void jtDlClose(sqlite3_vfs*, void*);
+static int jtRandomness(sqlite3_vfs*, int nByte, char *zOut);
+static int jtSleep(sqlite3_vfs*, int microseconds);
+static int jtCurrentTime(sqlite3_vfs*, double*);
+static int jtCurrentTimeInt64(sqlite3_vfs*, sqlite3_int64*);
+
+static sqlite3_vfs jt_vfs = {
+  2,                             /* iVersion */
+  sizeof(jt_file),               /* szOsFile */
+  JT_MAX_PATHNAME,               /* mxPathname */
+  0,                             /* pNext */
+  JT_VFS_NAME,                   /* zName */
+  0,                             /* pAppData */
+  jtOpen,                        /* xOpen */
+  jtDelete,                      /* xDelete */
+  jtAccess,                      /* xAccess */
+  jtFullPathname,                /* xFullPathname */
+  jtDlOpen,                      /* xDlOpen */
+  jtDlError,                     /* xDlError */
+  jtDlSym,                       /* xDlSym */
+  jtDlClose,                     /* xDlClose */
+  jtRandomness,                  /* xRandomness */
+  jtSleep,                       /* xSleep */
+  jtCurrentTime,                 /* xCurrentTime */
+  0,                             /* xGetLastError */
+  jtCurrentTimeInt64             /* xCurrentTimeInt64 */
+};
+
+static sqlite3_io_methods jt_io_methods = {
+  1,                             /* iVersion */
+  jtClose,                       /* xClose */
+  jtRead,                        /* xRead */
+  jtWrite,                       /* xWrite */
+  jtTruncate,                    /* xTruncate */
+  jtSync,                        /* xSync */
+  jtFileSize,                    /* xFileSize */
+  jtLock,                        /* xLock */
+  jtUnlock,                      /* xUnlock */
+  jtCheckReservedLock,           /* xCheckReservedLock */
+  jtFileControl,                 /* xFileControl */
+  jtSectorSize,                  /* xSectorSize */
+  jtDeviceCharacteristics        /* xDeviceCharacteristics */
+};
+
+struct JtGlobal {
+  sqlite3_vfs *pVfs;             /* Parent VFS */
+  jt_file *pList;                /* List of all open files */
+};
+static struct JtGlobal g = {0, 0};
+
+/*
+** Functions to obtain and relinquish a mutex to protect g.pList. The
+** STATIC_PRNG mutex is reused, purely for the sake of convenience.
+*/
+static void enterJtMutex(void){
+  sqlite3_mutex_enter(sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_PRNG));
+}
+static void leaveJtMutex(void){
+  sqlite3_mutex_leave(sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_PRNG));
+}
+
+extern int sqlite3_io_error_pending;
+extern int sqlite3_io_error_hit;
+static void stop_ioerr_simulation(int *piSave, int *piSave2){
+  *piSave = sqlite3_io_error_pending;
+  *piSave2 = sqlite3_io_error_hit;
+  sqlite3_io_error_pending = -1;
+  sqlite3_io_error_hit = 0;
+}
+static void start_ioerr_simulation(int iSave, int iSave2){
+  sqlite3_io_error_pending = iSave;
+  sqlite3_io_error_hit = iSave2;
+}
+
+/*
+** The jt_file pointed to by the argument may or may not be a file-handle
+** open on a main database file. If it is, and a transaction is currently
+** opened on the file, then discard all transaction related data.
+*/
+static void closeTransaction(jt_file *p){
+  sqlite3BitvecDestroy(p->pWritable);
+  sqlite3_free(p->aCksum);
+  p->pWritable = 0;
+  p->aCksum = 0;
+  p->nSync = 0;
+}
+
+/*
+** Close an jt-file.
+*/
+static int jtClose(sqlite3_file *pFile){
+  jt_file **pp;
+  jt_file *p = (jt_file *)pFile;
+
+  closeTransaction(p);
+  enterJtMutex();
+  if( p->zName ){
+    for(pp=&g.pList; *pp!=p; pp=&(*pp)->pNext);
+    *pp = p->pNext;
+  }
+  leaveJtMutex();
+  return sqlite3OsClose(p->pReal);
+}
+
+/*
+** Read data from an jt-file.
+*/
+static int jtRead(
+  sqlite3_file *pFile, 
+  void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  jt_file *p = (jt_file *)pFile;
+  return sqlite3OsRead(p->pReal, zBuf, iAmt, iOfst);
+}
+
+/*
+** Parameter zJournal is the name of a journal file that is currently 
+** open. This function locates and returns the handle opened on the
+** corresponding database file by the pager that currently has the
+** journal file opened. This file-handle is identified by the 
+** following properties:
+**
+**   a) SQLITE_OPEN_MAIN_DB was specified when the file was opened.
+**
+**   b) The file-name specified when the file was opened matches
+**      all but the final 8 characters of the journal file name.
+**
+**   c) There is currently a reserved lock on the file.
+**/
+static jt_file *locateDatabaseHandle(const char *zJournal){
+  jt_file *pMain = 0;
+  enterJtMutex();
+  for(pMain=g.pList; pMain; pMain=pMain->pNext){
+    int nName = strlen(zJournal) - strlen("-journal");
+    if( (pMain->flags&SQLITE_OPEN_MAIN_DB)
+     && (strlen(pMain->zName)==nName)
+     && 0==memcmp(pMain->zName, zJournal, nName)
+     && (pMain->eLock>=SQLITE_LOCK_RESERVED)
+    ){
+      break;
+    }
+  }
+  leaveJtMutex();
+  return pMain;
+}
+
+/*
+** Parameter z points to a buffer of 4 bytes in size containing a 
+** unsigned 32-bit integer stored in big-endian format. Decode the 
+** integer and return its value.
+*/
+static u32 decodeUint32(const unsigned char *z){
+  return (z[0]<<24) + (z[1]<<16) + (z[2]<<8) + z[3];
+}
+
+/*
+** Calculate a checksum from the buffer of length n bytes pointed to
+** by parameter z.
+*/
+static u32 genCksum(const unsigned char *z, int n){
+  int i;
+  u32 cksum = 0;
+  for(i=0; i<n; i++){
+    cksum = cksum + z[i] + (cksum<<3);
+  }
+  return cksum;
+}
+
+/*
+** The first argument, zBuf, points to a buffer containing a 28 byte
+** serialized journal header. This function deserializes four of the
+** integer fields contained in the journal header and writes their
+** values to the output variables.
+**
+** SQLITE_OK is returned if the journal-header is successfully 
+** decoded. Otherwise, SQLITE_ERROR.
+*/
+static int decodeJournalHdr(
+  const unsigned char *zBuf,         /* Input: 28 byte journal header */
+  u32 *pnRec,                        /* Out: Number of journalled records */
+  u32 *pnPage,                       /* Out: Original database page count */
+  u32 *pnSector,                     /* Out: Sector size in bytes */
+  u32 *pnPagesize                    /* Out: Page size in bytes */
+){
+  unsigned char aMagic[] = { 0xd9, 0xd5, 0x05, 0xf9, 0x20, 0xa1, 0x63, 0xd7 };
+  if( memcmp(aMagic, zBuf, 8) ) return SQLITE_ERROR;
+  if( pnRec ) *pnRec = decodeUint32(&zBuf[8]);
+  if( pnPage ) *pnPage = decodeUint32(&zBuf[16]);
+  if( pnSector ) *pnSector = decodeUint32(&zBuf[20]);
+  if( pnPagesize ) *pnPagesize = decodeUint32(&zBuf[24]);
+  return SQLITE_OK;
+}
+
+/*
+** This function is called when a new transaction is opened, just after
+** the first journal-header is written to the journal file.
+*/
+static int openTransaction(jt_file *pMain, jt_file *pJournal){
+  unsigned char *aData;
+  sqlite3_file *p = pMain->pReal;
+  int rc = SQLITE_OK;
+
+  closeTransaction(pMain);
+  aData = sqlite3_malloc(pMain->nPagesize);
+  pMain->pWritable = sqlite3BitvecCreate(pMain->nPage);
+  pMain->aCksum = sqlite3_malloc(sizeof(u32) * (pMain->nPage + 1));
+  pJournal->iMaxOff = 0;
+
+  if( !pMain->pWritable || !pMain->aCksum || !aData ){
+    rc = SQLITE_IOERR_NOMEM;
+  }else if( pMain->nPage>0 ){
+    u32 iTrunk;
+    int iSave;
+    int iSave2;
+
+    stop_ioerr_simulation(&iSave, &iSave2);
+
+    /* Read the database free-list. Add the page-number for each free-list
+    ** leaf to the jt_file.pWritable bitvec.
+    */
+    rc = sqlite3OsRead(p, aData, pMain->nPagesize, 0);
+    if( rc==SQLITE_OK ){
+      u32 nDbsize = decodeUint32(&aData[28]);
+      if( nDbsize>0 && memcmp(&aData[24], &aData[92], 4)==0 ){
+        u32 iPg;
+        for(iPg=nDbsize+1; iPg<=pMain->nPage; iPg++){
+          sqlite3BitvecSet(pMain->pWritable, iPg);
+        }
+      }
+    }
+    iTrunk = decodeUint32(&aData[32]);
+    while( rc==SQLITE_OK && iTrunk>0 ){
+      u32 nLeaf;
+      u32 iLeaf;
+      sqlite3_int64 iOff = (iTrunk-1)*pMain->nPagesize;
+      rc = sqlite3OsRead(p, aData, pMain->nPagesize, iOff);
+      nLeaf = decodeUint32(&aData[4]);
+      for(iLeaf=0; rc==SQLITE_OK && iLeaf<nLeaf; iLeaf++){
+        u32 pgno = decodeUint32(&aData[8+4*iLeaf]);
+        sqlite3BitvecSet(pMain->pWritable, pgno);
+      }
+      iTrunk = decodeUint32(aData);
+    }
+
+    /* Calculate and store a checksum for each page in the database file. */
+    if( rc==SQLITE_OK ){
+      int ii;
+      for(ii=0; rc==SQLITE_OK && ii<pMain->nPage; ii++){
+        i64 iOff = (i64)(pMain->nPagesize) * (i64)ii;
+        if( iOff==PENDING_BYTE ) continue;
+        rc = sqlite3OsRead(pMain->pReal, aData, pMain->nPagesize, iOff);
+        pMain->aCksum[ii] = genCksum(aData, pMain->nPagesize);
+      }
+    }
+
+    start_ioerr_simulation(iSave, iSave2);
+  }
+
+  sqlite3_free(aData);
+  return rc;
+}
+
+/*
+** The first argument to this function is a handle open on a journal file.
+** This function reads the journal file and adds the page number for each
+** page in the journal to the Bitvec object passed as the second argument.
+*/
+static int readJournalFile(jt_file *p, jt_file *pMain){
+  int rc = SQLITE_OK;
+  unsigned char zBuf[28];
+  sqlite3_file *pReal = p->pReal;
+  sqlite3_int64 iOff = 0;
+  sqlite3_int64 iSize = p->iMaxOff;
+  unsigned char *aPage;
+  int iSave;
+  int iSave2;
+
+  aPage = sqlite3_malloc(pMain->nPagesize);
+  if( !aPage ){
+    return SQLITE_IOERR_NOMEM;
+  }
+
+  stop_ioerr_simulation(&iSave, &iSave2);
+
+  while( rc==SQLITE_OK && iOff<iSize ){
+    u32 nRec, nPage, nSector, nPagesize;
+    u32 ii;
+
+    /* Read and decode the next journal-header from the journal file. */
+    rc = sqlite3OsRead(pReal, zBuf, 28, iOff);
+    if( rc!=SQLITE_OK 
+     || decodeJournalHdr(zBuf, &nRec, &nPage, &nSector, &nPagesize) 
+    ){
+      goto finish_rjf;
+    }
+    iOff += nSector;
+
+    if( nRec==0 ){
+      /* A trick. There might be another journal-header immediately 
+      ** following this one. In this case, 0 records means 0 records, 
+      ** not "read until the end of the file". See also ticket #2565.
+      */
+      if( iSize>=(iOff+nSector) ){
+        rc = sqlite3OsRead(pReal, zBuf, 28, iOff);
+        if( rc!=SQLITE_OK || 0==decodeJournalHdr(zBuf, 0, 0, 0, 0) ){
+          continue;
+        }
+      }
+      nRec = (iSize-iOff) / (pMain->nPagesize+8);
+    }
+
+    /* Read all the records that follow the journal-header just read. */
+    for(ii=0; rc==SQLITE_OK && ii<nRec && iOff<iSize; ii++){
+      u32 pgno;
+      rc = sqlite3OsRead(pReal, zBuf, 4, iOff);
+      if( rc==SQLITE_OK ){
+        pgno = decodeUint32(zBuf);
+        if( pgno>0 && pgno<=pMain->nPage ){
+          if( 0==sqlite3BitvecTest(pMain->pWritable, pgno) ){
+            rc = sqlite3OsRead(pReal, aPage, pMain->nPagesize, iOff+4);
+            if( rc==SQLITE_OK ){
+              u32 cksum = genCksum(aPage, pMain->nPagesize);
+              assert( cksum==pMain->aCksum[pgno-1] );
+            }
+          }
+          sqlite3BitvecSet(pMain->pWritable, pgno);
+        }
+        iOff += (8 + pMain->nPagesize);
+      }
+    }
+
+    iOff = ((iOff + (nSector-1)) / nSector) * nSector;
+  }
+
+finish_rjf:
+  start_ioerr_simulation(iSave, iSave2);
+  sqlite3_free(aPage);
+  if( rc==SQLITE_IOERR_SHORT_READ ){
+    rc = SQLITE_OK;
+  }
+  return rc;
+}
+
+/*
+** Write data to an jt-file.
+*/
+static int jtWrite(
+  sqlite3_file *pFile, 
+  const void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  int rc;
+  jt_file *p = (jt_file *)pFile;
+  if( p->flags&SQLITE_OPEN_MAIN_JOURNAL ){
+    if( iOfst==0 ){
+      jt_file *pMain = locateDatabaseHandle(p->zName);
+      assert( pMain );
+  
+      if( iAmt==28 ){
+        /* Zeroing the first journal-file header. This is the end of a
+        ** transaction. */
+        closeTransaction(pMain);
+      }else if( iAmt!=12 ){
+        /* Writing the first journal header to a journal file. This happens
+        ** when a transaction is first started.  */
+        u8 *z = (u8 *)zBuf;
+        pMain->nPage = decodeUint32(&z[16]);
+        pMain->nPagesize = decodeUint32(&z[24]);
+        if( SQLITE_OK!=(rc=openTransaction(pMain, p)) ){
+          return rc;
+        }
+      }
+    }
+    if( p->iMaxOff<(iOfst + iAmt) ){
+      p->iMaxOff = iOfst + iAmt;
+    }
+  }
+
+  if( p->flags&SQLITE_OPEN_MAIN_DB && p->pWritable ){
+    if( iAmt<p->nPagesize 
+     && p->nPagesize%iAmt==0 
+     && iOfst>=(PENDING_BYTE+512) 
+     && iOfst+iAmt<=PENDING_BYTE+p->nPagesize
+    ){
+      /* No-op. This special case is hit when the backup code is copying a
+      ** to a database with a larger page-size than the source database and
+      ** it needs to fill in the non-locking-region part of the original
+      ** pending-byte page.
+      */
+    }else{
+      u32 pgno = iOfst/p->nPagesize + 1;
+      assert( (iAmt==1||iAmt==p->nPagesize) && ((iOfst+iAmt)%p->nPagesize)==0 );
+      assert( pgno<=p->nPage || p->nSync>0 );
+      assert( pgno>p->nPage || sqlite3BitvecTest(p->pWritable, pgno) );
+    }
+  }
+
+  rc = sqlite3OsWrite(p->pReal, zBuf, iAmt, iOfst);
+  if( (p->flags&SQLITE_OPEN_MAIN_JOURNAL) && iAmt==12 ){
+    jt_file *pMain = locateDatabaseHandle(p->zName);
+    int rc2 = readJournalFile(p, pMain);
+    if( rc==SQLITE_OK ) rc = rc2;
+  }
+  return rc;
+}
+
+/*
+** Truncate an jt-file.
+*/
+static int jtTruncate(sqlite3_file *pFile, sqlite_int64 size){
+  jt_file *p = (jt_file *)pFile;
+  if( p->flags&SQLITE_OPEN_MAIN_JOURNAL && size==0 ){
+    /* Truncating a journal file. This is the end of a transaction. */
+    jt_file *pMain = locateDatabaseHandle(p->zName);
+    closeTransaction(pMain);
+  }
+  if( p->flags&SQLITE_OPEN_MAIN_DB && p->pWritable ){
+    u32 pgno;
+    u32 locking_page = (u32)(PENDING_BYTE/p->nPagesize+1);
+    for(pgno=size/p->nPagesize+1; pgno<=p->nPage; pgno++){
+      assert( pgno==locking_page || sqlite3BitvecTest(p->pWritable, pgno) );
+    }
+  }
+  return sqlite3OsTruncate(p->pReal, size);
+}
+
+/*
+** Sync an jt-file.
+*/
+static int jtSync(sqlite3_file *pFile, int flags){
+  jt_file *p = (jt_file *)pFile;
+
+  if( p->flags&SQLITE_OPEN_MAIN_JOURNAL ){
+    int rc;
+    jt_file *pMain;                   /* The associated database file */
+
+    /* The journal file is being synced. At this point, we inspect the 
+    ** contents of the file up to this point and set each bit in the 
+    ** jt_file.pWritable bitvec of the main database file associated with
+    ** this journal file.
+    */
+    pMain = locateDatabaseHandle(p->zName);
+    assert(pMain);
+
+    /* Set the bitvec values */
+    if( pMain->pWritable ){
+      pMain->nSync++;
+      rc = readJournalFile(p, pMain);
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+    }
+  }
+
+  return sqlite3OsSync(p->pReal, flags);
+}
+
+/*
+** Return the current file-size of an jt-file.
+*/
+static int jtFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
+  jt_file *p = (jt_file *)pFile;
+  return sqlite3OsFileSize(p->pReal, pSize);
+}
+
+/*
+** Lock an jt-file.
+*/
+static int jtLock(sqlite3_file *pFile, int eLock){
+  int rc;
+  jt_file *p = (jt_file *)pFile;
+  rc = sqlite3OsLock(p->pReal, eLock);
+  if( rc==SQLITE_OK && eLock>p->eLock ){
+    p->eLock = eLock;
+  }
+  return rc;
+}
+
+/*
+** Unlock an jt-file.
+*/
+static int jtUnlock(sqlite3_file *pFile, int eLock){
+  int rc;
+  jt_file *p = (jt_file *)pFile;
+  rc = sqlite3OsUnlock(p->pReal, eLock);
+  if( rc==SQLITE_OK && eLock<p->eLock ){
+    p->eLock = eLock;
+  }
+  return rc;
+}
+
+/*
+** Check if another file-handle holds a RESERVED lock on an jt-file.
+*/
+static int jtCheckReservedLock(sqlite3_file *pFile, int *pResOut){
+  jt_file *p = (jt_file *)pFile;
+  return sqlite3OsCheckReservedLock(p->pReal, pResOut);
+}
+
+/*
+** File control method. For custom operations on an jt-file.
+*/
+static int jtFileControl(sqlite3_file *pFile, int op, void *pArg){
+  jt_file *p = (jt_file *)pFile;
+  return sqlite3OsFileControl(p->pReal, op, pArg);
+}
+
+/*
+** Return the sector-size in bytes for an jt-file.
+*/
+static int jtSectorSize(sqlite3_file *pFile){
+  jt_file *p = (jt_file *)pFile;
+  return sqlite3OsSectorSize(p->pReal);
+}
+
+/*
+** Return the device characteristic flags supported by an jt-file.
+*/
+static int jtDeviceCharacteristics(sqlite3_file *pFile){
+  jt_file *p = (jt_file *)pFile;
+  return sqlite3OsDeviceCharacteristics(p->pReal);
+}
+
+/*
+** Open an jt file handle.
+*/
+static int jtOpen(
+  sqlite3_vfs *pVfs,
+  const char *zName,
+  sqlite3_file *pFile,
+  int flags,
+  int *pOutFlags
+){
+  int rc;
+  jt_file *p = (jt_file *)pFile;
+  pFile->pMethods = 0;
+  p->pReal = (sqlite3_file *)&p[1];
+  p->pReal->pMethods = 0;
+  rc = sqlite3OsOpen(g.pVfs, zName, p->pReal, flags, pOutFlags);
+  assert( rc==SQLITE_OK || p->pReal->pMethods==0 );
+  if( rc==SQLITE_OK ){
+    pFile->pMethods = &jt_io_methods;
+    p->eLock = 0;
+    p->zName = zName;
+    p->flags = flags;
+    p->pNext = 0;
+    p->pWritable = 0;
+    p->aCksum = 0;
+    enterJtMutex();
+    if( zName ){
+      p->pNext = g.pList;
+      g.pList = p;
+    }
+    leaveJtMutex();
+  }
+  return rc;
+}
+
+/*
+** Delete the file located at zPath. If the dirSync argument is true,
+** ensure the file-system modifications are synced to disk before
+** returning.
+*/
+static int jtDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
+  int nPath = strlen(zPath);
+  if( nPath>8 && 0==strcmp("-journal", &zPath[nPath-8]) ){
+    /* Deleting a journal file. The end of a transaction. */
+    jt_file *pMain = locateDatabaseHandle(zPath);
+    if( pMain ){
+      closeTransaction(pMain);
+    }
+  }
+
+  return sqlite3OsDelete(g.pVfs, zPath, dirSync);
+}
+
+/*
+** Test for access permissions. Return true if the requested permission
+** is available, or false otherwise.
+*/
+static int jtAccess(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  int flags, 
+  int *pResOut
+){
+  return sqlite3OsAccess(g.pVfs, zPath, flags, pResOut);
+}
+
+/*
+** Populate buffer zOut with the full canonical pathname corresponding
+** to the pathname in zPath. zOut is guaranteed to point to a buffer
+** of at least (JT_MAX_PATHNAME+1) bytes.
+*/
+static int jtFullPathname(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  int nOut, 
+  char *zOut
+){
+  return sqlite3OsFullPathname(g.pVfs, zPath, nOut, zOut);
+}
+
+/*
+** Open the dynamic library located at zPath and return a handle.
+*/
+static void *jtDlOpen(sqlite3_vfs *pVfs, const char *zPath){
+  return g.pVfs->xDlOpen(g.pVfs, zPath);
+}
+
+/*
+** Populate the buffer zErrMsg (size nByte bytes) with a human readable
+** utf-8 string describing the most recent error encountered associated 
+** with dynamic libraries.
+*/
+static void jtDlError(sqlite3_vfs *pVfs, int nByte, char *zErrMsg){
+  g.pVfs->xDlError(g.pVfs, nByte, zErrMsg);
+}
+
+/*
+** Return a pointer to the symbol zSymbol in the dynamic library pHandle.
+*/
+static void (*jtDlSym(sqlite3_vfs *pVfs, void *p, const char *zSym))(void){
+  return g.pVfs->xDlSym(g.pVfs, p, zSym);
+}
+
+/*
+** Close the dynamic library handle pHandle.
+*/
+static void jtDlClose(sqlite3_vfs *pVfs, void *pHandle){
+  g.pVfs->xDlClose(g.pVfs, pHandle);
+}
+
+/*
+** Populate the buffer pointed to by zBufOut with nByte bytes of 
+** random data.
+*/
+static int jtRandomness(sqlite3_vfs *pVfs, int nByte, char *zBufOut){
+  return sqlite3OsRandomness(g.pVfs, nByte, zBufOut);
+}
+
+/*
+** Sleep for nMicro microseconds. Return the number of microseconds 
+** actually slept.
+*/
+static int jtSleep(sqlite3_vfs *pVfs, int nMicro){
+  return sqlite3OsSleep(g.pVfs, nMicro);
+}
+
+/*
+** Return the current time as a Julian Day number in *pTimeOut.
+*/
+static int jtCurrentTime(sqlite3_vfs *pVfs, double *pTimeOut){
+  return g.pVfs->xCurrentTime(g.pVfs, pTimeOut);
+}
+/*
+** Return the current time as a Julian Day number in *pTimeOut.
+*/
+static int jtCurrentTimeInt64(sqlite3_vfs *pVfs, sqlite3_int64 *pTimeOut){
+  return g.pVfs->xCurrentTimeInt64(g.pVfs, pTimeOut);
+}
+
+/**************************************************************************
+** Start of public API.
+*/
+
+/*
+** Configure the jt VFS as a wrapper around the VFS named by parameter 
+** zWrap. If the isDefault parameter is true, then the jt VFS is installed
+** as the new default VFS for SQLite connections. If isDefault is not
+** true, then the jt VFS is installed as non-default. In this case it
+** is available via its name, "jt".
+*/
+int jt_register(char *zWrap, int isDefault){
+  g.pVfs = sqlite3_vfs_find(zWrap);
+  if( g.pVfs==0 ){
+    return SQLITE_ERROR;
+  }
+  jt_vfs.szOsFile = sizeof(jt_file) + g.pVfs->szOsFile;
+  if( g.pVfs->iVersion==1 ){
+    jt_vfs.iVersion = 1;
+  }else if( g.pVfs->xCurrentTimeInt64==0 ){
+    jt_vfs.xCurrentTimeInt64 = 0;
+  }
+  sqlite3_vfs_register(&jt_vfs, isDefault);
+  return SQLITE_OK;
+}
+
+/*
+** Uninstall the jt VFS, if it is installed.
+*/
+void jt_unregister(void){
+  sqlite3_vfs_unregister(&jt_vfs);
+}
+
+#endif
diff --git a/src/test_loadext.c b/src/test_loadext.c
new file mode 100644
index 0000000..1137e3a
--- /dev/null
+++ b/src/test_loadext.c
@@ -0,0 +1,122 @@
+/*
+** 2006 June 14
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Test extension for testing the sqlite3_load_extension() function.
+*/
+#include <string.h>
+#include "sqlite3ext.h"
+SQLITE_EXTENSION_INIT1
+
+/*
+** The half() SQL function returns half of its input value.
+*/
+static void halfFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  sqlite3_result_double(context, 0.5*sqlite3_value_double(argv[0]));
+}
+
+/*
+** SQL functions to call the sqlite3_status function and return results.
+*/
+static void statusFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  int op, mx, cur, resetFlag, rc;
+  if( sqlite3_value_type(argv[0])==SQLITE_INTEGER ){
+    op = sqlite3_value_int(argv[0]);
+  }else if( sqlite3_value_type(argv[0])==SQLITE_TEXT ){
+    int i;
+    const char *zName;
+    static const struct {
+      const char *zName;
+      int op;
+    } aOp[] = {
+      { "MEMORY_USED",         SQLITE_STATUS_MEMORY_USED         },
+      { "PAGECACHE_USED",      SQLITE_STATUS_PAGECACHE_USED      },
+      { "PAGECACHE_OVERFLOW",  SQLITE_STATUS_PAGECACHE_OVERFLOW  },
+      { "SCRATCH_USED",        SQLITE_STATUS_SCRATCH_USED        },
+      { "SCRATCH_OVERFLOW",    SQLITE_STATUS_SCRATCH_OVERFLOW    },
+      { "MALLOC_SIZE",         SQLITE_STATUS_MALLOC_SIZE         },
+    };
+    int nOp = sizeof(aOp)/sizeof(aOp[0]);
+    zName = (const char*)sqlite3_value_text(argv[0]);
+    for(i=0; i<nOp; i++){
+      if( strcmp(aOp[i].zName, zName)==0 ){
+        op = aOp[i].op;
+        break;
+      }
+    }
+    if( i>=nOp ){
+      char *zMsg = sqlite3_mprintf("unknown status property: %s", zName);
+      sqlite3_result_error(context, zMsg, -1);
+      sqlite3_free(zMsg);
+      return;
+    }
+  }else{
+    sqlite3_result_error(context, "unknown status type", -1);
+    return;
+  }
+  if( argc==2 ){
+    resetFlag = sqlite3_value_int(argv[1]);
+  }else{
+    resetFlag = 0;
+  }
+  rc = sqlite3_status(op, &cur, &mx, resetFlag);
+  if( rc!=SQLITE_OK ){
+    char *zMsg = sqlite3_mprintf("sqlite3_status(%d,...) returns %d", op, rc);
+    sqlite3_result_error(context, zMsg, -1);
+    sqlite3_free(zMsg);
+    return;
+  } 
+  if( argc==2 ){
+    sqlite3_result_int(context, mx);
+  }else{
+    sqlite3_result_int(context, cur);
+  }
+}
+
+/*
+** Extension load function.
+*/
+int testloadext_init(
+  sqlite3 *db, 
+  char **pzErrMsg, 
+  const sqlite3_api_routines *pApi
+){
+  int nErr = 0;
+  SQLITE_EXTENSION_INIT2(pApi);
+  nErr |= sqlite3_create_function(db, "half", 1, SQLITE_ANY, 0, halfFunc, 0, 0);
+  nErr |= sqlite3_create_function(db, "sqlite3_status", 1, SQLITE_ANY, 0,
+                          statusFunc, 0, 0);
+  nErr |= sqlite3_create_function(db, "sqlite3_status", 2, SQLITE_ANY, 0,
+                          statusFunc, 0, 0);
+  return nErr ? SQLITE_ERROR : SQLITE_OK;
+}
+
+/*
+** Another extension entry point. This one always fails.
+*/
+int testbrokenext_init(
+  sqlite3 *db, 
+  char **pzErrMsg, 
+  const sqlite3_api_routines *pApi
+){
+  char *zErr;
+  SQLITE_EXTENSION_INIT2(pApi);
+  zErr = sqlite3_mprintf("broken!");
+  *pzErrMsg = zErr;
+  return 1;
+}
diff --git a/src/test_malloc.c b/src/test_malloc.c
new file mode 100644
index 0000000..e955d57
--- /dev/null
+++ b/src/test_malloc.c
@@ -0,0 +1,1470 @@
+/*
+** 2007 August 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains code used to implement test interfaces to the
+** memory allocation subsystem.
+*/
+#include "sqliteInt.h"
+#include "tcl.h"
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+
+/*
+** This structure is used to encapsulate the global state variables used 
+** by malloc() fault simulation.
+*/
+static struct MemFault {
+  int iCountdown;         /* Number of pending successes before a failure */
+  int nRepeat;            /* Number of times to repeat the failure */
+  int nBenign;            /* Number of benign failures seen since last config */
+  int nFail;              /* Number of failures seen since last config */
+  u8 enable;              /* True if enabled */
+  int isInstalled;        /* True if the fault simulation layer is installed */
+  int isBenignMode;       /* True if malloc failures are considered benign */
+  sqlite3_mem_methods m;  /* 'Real' malloc implementation */
+} memfault;
+
+/*
+** This routine exists as a place to set a breakpoint that will
+** fire on any simulated malloc() failure.
+*/
+static void sqlite3Fault(void){
+  static int cnt = 0;
+  cnt++;
+}
+
+/*
+** Check to see if a fault should be simulated.  Return true to simulate
+** the fault.  Return false if the fault should not be simulated.
+*/
+static int faultsimStep(void){
+  if( likely(!memfault.enable) ){
+    return 0;
+  }
+  if( memfault.iCountdown>0 ){
+    memfault.iCountdown--;
+    return 0;
+  }
+  sqlite3Fault();
+  memfault.nFail++;
+  if( memfault.isBenignMode>0 ){
+    memfault.nBenign++;
+  }
+  memfault.nRepeat--;
+  if( memfault.nRepeat<=0 ){
+    memfault.enable = 0;
+  }
+  return 1;  
+}
+
+/*
+** A version of sqlite3_mem_methods.xMalloc() that includes fault simulation
+** logic.
+*/
+static void *faultsimMalloc(int n){
+  void *p = 0;
+  if( !faultsimStep() ){
+    p = memfault.m.xMalloc(n);
+  }
+  return p;
+}
+
+
+/*
+** A version of sqlite3_mem_methods.xRealloc() that includes fault simulation
+** logic.
+*/
+static void *faultsimRealloc(void *pOld, int n){
+  void *p = 0;
+  if( !faultsimStep() ){
+    p = memfault.m.xRealloc(pOld, n);
+  }
+  return p;
+}
+
+/* 
+** The following method calls are passed directly through to the underlying
+** malloc system:
+**
+**     xFree
+**     xSize
+**     xRoundup
+**     xInit
+**     xShutdown
+*/
+static void faultsimFree(void *p){
+  memfault.m.xFree(p);
+}
+static int faultsimSize(void *p){
+  return memfault.m.xSize(p);
+}
+static int faultsimRoundup(int n){
+  return memfault.m.xRoundup(n);
+}
+static int faultsimInit(void *p){
+  return memfault.m.xInit(memfault.m.pAppData);
+}
+static void faultsimShutdown(void *p){
+  memfault.m.xShutdown(memfault.m.pAppData);
+}
+
+/*
+** This routine configures the malloc failure simulation.  After
+** calling this routine, the next nDelay mallocs will succeed, followed
+** by a block of nRepeat failures, after which malloc() calls will begin
+** to succeed again.
+*/
+static void faultsimConfig(int nDelay, int nRepeat){
+  memfault.iCountdown = nDelay;
+  memfault.nRepeat = nRepeat;
+  memfault.nBenign = 0;
+  memfault.nFail = 0;
+  memfault.enable = nDelay>=0;
+
+  /* Sometimes, when running multi-threaded tests, the isBenignMode 
+  ** variable is not properly incremented/decremented so that it is
+  ** 0 when not inside a benign malloc block. This doesn't affect
+  ** the multi-threaded tests, as they do not use this system. But
+  ** it does affect OOM tests run later in the same process. So
+  ** zero the variable here, just to be sure.
+  */
+  memfault.isBenignMode = 0;
+}
+
+/*
+** Return the number of faults (both hard and benign faults) that have
+** occurred since the injector was last configured.
+*/
+static int faultsimFailures(void){
+  return memfault.nFail;
+}
+
+/*
+** Return the number of benign faults that have occurred since the
+** injector was last configured.
+*/
+static int faultsimBenignFailures(void){
+  return memfault.nBenign;
+}
+
+/*
+** Return the number of successes that will occur before the next failure.
+** If no failures are scheduled, return -1.
+*/
+static int faultsimPending(void){
+  if( memfault.enable ){
+    return memfault.iCountdown;
+  }else{
+    return -1;
+  }
+}
+
+
+static void faultsimBeginBenign(void){
+  memfault.isBenignMode++;
+}
+static void faultsimEndBenign(void){
+  memfault.isBenignMode--;
+}
+
+/*
+** Add or remove the fault-simulation layer using sqlite3_config(). If
+** the argument is non-zero, the 
+*/
+static int faultsimInstall(int install){
+  static struct sqlite3_mem_methods m = {
+    faultsimMalloc,                   /* xMalloc */
+    faultsimFree,                     /* xFree */
+    faultsimRealloc,                  /* xRealloc */
+    faultsimSize,                     /* xSize */
+    faultsimRoundup,                  /* xRoundup */
+    faultsimInit,                     /* xInit */
+    faultsimShutdown,                 /* xShutdown */
+    0                                 /* pAppData */
+  };
+  int rc;
+
+  install = (install ? 1 : 0);
+  assert(memfault.isInstalled==1 || memfault.isInstalled==0);
+
+  if( install==memfault.isInstalled ){
+    return SQLITE_ERROR;
+  }
+
+  if( install ){
+    rc = sqlite3_config(SQLITE_CONFIG_GETMALLOC, &memfault.m);
+    assert(memfault.m.xMalloc);
+    if( rc==SQLITE_OK ){
+      rc = sqlite3_config(SQLITE_CONFIG_MALLOC, &m);
+    }
+    sqlite3_test_control(SQLITE_TESTCTRL_BENIGN_MALLOC_HOOKS, 
+        faultsimBeginBenign, faultsimEndBenign
+    );
+  }else{
+    sqlite3_mem_methods m;
+    assert(memfault.m.xMalloc);
+
+    /* One should be able to reset the default memory allocator by storing
+    ** a zeroed allocator then calling GETMALLOC. */
+    memset(&m, 0, sizeof(m));
+    sqlite3_config(SQLITE_CONFIG_MALLOC, &m);
+    sqlite3_config(SQLITE_CONFIG_GETMALLOC, &m);
+    assert( memcmp(&m, &memfault.m, sizeof(m))==0 );
+
+    rc = sqlite3_config(SQLITE_CONFIG_MALLOC, &memfault.m);
+    sqlite3_test_control(SQLITE_TESTCTRL_BENIGN_MALLOC_HOOKS, 0, 0);
+  }
+
+  if( rc==SQLITE_OK ){
+    memfault.isInstalled = 1;
+  }
+  return rc;
+}
+
+#ifdef SQLITE_TEST
+
+/*
+** This function is implemented in test1.c. Returns a pointer to a static
+** buffer containing the symbolic SQLite error code that corresponds to
+** the least-significant 8-bits of the integer passed as an argument.
+** For example:
+**
+**   sqlite3TestErrorName(1) -> "SQLITE_ERROR"
+*/
+const char *sqlite3TestErrorName(int);
+
+/*
+** Transform pointers to text and back again
+*/
+static void pointerToText(void *p, char *z){
+  static const char zHex[] = "0123456789abcdef";
+  int i, k;
+  unsigned int u;
+  sqlite3_uint64 n;
+  if( p==0 ){
+    strcpy(z, "0");
+    return;
+  }
+  if( sizeof(n)==sizeof(p) ){
+    memcpy(&n, &p, sizeof(p));
+  }else if( sizeof(u)==sizeof(p) ){
+    memcpy(&u, &p, sizeof(u));
+    n = u;
+  }else{
+    assert( 0 );
+  }
+  for(i=0, k=sizeof(p)*2-1; i<sizeof(p)*2; i++, k--){
+    z[k] = zHex[n&0xf];
+    n >>= 4;
+  }
+  z[sizeof(p)*2] = 0;
+}
+static int hexToInt(int h){
+  if( h>='0' && h<='9' ){
+    return h - '0';
+  }else if( h>='a' && h<='f' ){
+    return h - 'a' + 10;
+  }else{
+    return -1;
+  }
+}
+static int textToPointer(const char *z, void **pp){
+  sqlite3_uint64 n = 0;
+  int i;
+  unsigned int u;
+  for(i=0; i<sizeof(void*)*2 && z[0]; i++){
+    int v;
+    v = hexToInt(*z++);
+    if( v<0 ) return TCL_ERROR;
+    n = n*16 + v;
+  }
+  if( *z!=0 ) return TCL_ERROR;
+  if( sizeof(n)==sizeof(*pp) ){
+    memcpy(pp, &n, sizeof(n));
+  }else if( sizeof(u)==sizeof(*pp) ){
+    u = (unsigned int)n;
+    memcpy(pp, &u, sizeof(u));
+  }else{
+    assert( 0 );
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_malloc  NBYTES
+**
+** Raw test interface for sqlite3_malloc().
+*/
+static int test_malloc(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int nByte;
+  void *p;
+  char zOut[100];
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "NBYTES");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[1], &nByte) ) return TCL_ERROR;
+  p = sqlite3_malloc((unsigned)nByte);
+  pointerToText(p, zOut);
+  Tcl_AppendResult(interp, zOut, NULL);
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_realloc  PRIOR  NBYTES
+**
+** Raw test interface for sqlite3_realloc().
+*/
+static int test_realloc(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int nByte;
+  void *pPrior, *p;
+  char zOut[100];
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "PRIOR NBYTES");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[2], &nByte) ) return TCL_ERROR;
+  if( textToPointer(Tcl_GetString(objv[1]), &pPrior) ){
+    Tcl_AppendResult(interp, "bad pointer: ", Tcl_GetString(objv[1]), (char*)0);
+    return TCL_ERROR;
+  }
+  p = sqlite3_realloc(pPrior, (unsigned)nByte);
+  pointerToText(p, zOut);
+  Tcl_AppendResult(interp, zOut, NULL);
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_free  PRIOR
+**
+** Raw test interface for sqlite3_free().
+*/
+static int test_free(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  void *pPrior;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "PRIOR");
+    return TCL_ERROR;
+  }
+  if( textToPointer(Tcl_GetString(objv[1]), &pPrior) ){
+    Tcl_AppendResult(interp, "bad pointer: ", Tcl_GetString(objv[1]), (char*)0);
+    return TCL_ERROR;
+  }
+  sqlite3_free(pPrior);
+  return TCL_OK;
+}
+
+/*
+** These routines are in test_hexio.c
+*/
+int sqlite3TestHexToBin(const char *, int, char *);
+int sqlite3TestBinToHex(char*,int);
+
+/*
+** Usage:    memset  ADDRESS  SIZE  HEX
+**
+** Set a chunk of memory (obtained from malloc, probably) to a
+** specified hex pattern.
+*/
+static int test_memset(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  void *p;
+  int size, n, i;
+  char *zHex;
+  char *zOut;
+  char zBin[100];
+
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "ADDRESS SIZE HEX");
+    return TCL_ERROR;
+  }
+  if( textToPointer(Tcl_GetString(objv[1]), &p) ){
+    Tcl_AppendResult(interp, "bad pointer: ", Tcl_GetString(objv[1]), (char*)0);
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[2], &size) ){
+    return TCL_ERROR;
+  }
+  if( size<=0 ){
+    Tcl_AppendResult(interp, "size must be positive", (char*)0);
+    return TCL_ERROR;
+  }
+  zHex = Tcl_GetStringFromObj(objv[3], &n);
+  if( n>sizeof(zBin)*2 ) n = sizeof(zBin)*2;
+  n = sqlite3TestHexToBin(zHex, n, zBin);
+  if( n==0 ){
+    Tcl_AppendResult(interp, "no data", (char*)0);
+    return TCL_ERROR;
+  }
+  zOut = p;
+  for(i=0; i<size; i++){
+    zOut[i] = zBin[i%n];
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:    memget  ADDRESS  SIZE
+**
+** Return memory as hexadecimal text.
+*/
+static int test_memget(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  void *p;
+  int size, n;
+  char *zBin;
+  char zHex[100];
+
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "ADDRESS SIZE");
+    return TCL_ERROR;
+  }
+  if( textToPointer(Tcl_GetString(objv[1]), &p) ){
+    Tcl_AppendResult(interp, "bad pointer: ", Tcl_GetString(objv[1]), (char*)0);
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[2], &size) ){
+    return TCL_ERROR;
+  }
+  if( size<=0 ){
+    Tcl_AppendResult(interp, "size must be positive", (char*)0);
+    return TCL_ERROR;
+  }
+  zBin = p;
+  while( size>0 ){
+    if( size>(sizeof(zHex)-1)/2 ){
+      n = (sizeof(zHex)-1)/2;
+    }else{
+      n = size;
+    }
+    memcpy(zHex, zBin, n);
+    zBin += n;
+    size -= n;
+    sqlite3TestBinToHex(zHex, n);
+    Tcl_AppendResult(interp, zHex, (char*)0);
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_memory_used
+**
+** Raw test interface for sqlite3_memory_used().
+*/
+static int test_memory_used(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  Tcl_SetObjResult(interp, Tcl_NewWideIntObj(sqlite3_memory_used()));
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_memory_highwater ?RESETFLAG?
+**
+** Raw test interface for sqlite3_memory_highwater().
+*/
+static int test_memory_highwater(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int resetFlag = 0;
+  if( objc!=1 && objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "?RESET?");
+    return TCL_ERROR;
+  }
+  if( objc==2 ){
+    if( Tcl_GetBooleanFromObj(interp, objv[1], &resetFlag) ) return TCL_ERROR;
+  } 
+  Tcl_SetObjResult(interp, 
+     Tcl_NewWideIntObj(sqlite3_memory_highwater(resetFlag)));
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_memdebug_backtrace DEPTH
+**
+** Set the depth of backtracing.  If SQLITE_MEMDEBUG is not defined
+** then this routine is a no-op.
+*/
+static int test_memdebug_backtrace(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int depth;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DEPT");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[1], &depth) ) return TCL_ERROR;
+#ifdef SQLITE_MEMDEBUG
+  {
+    extern void sqlite3MemdebugBacktrace(int);
+    sqlite3MemdebugBacktrace(depth);
+  }
+#endif
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_memdebug_dump  FILENAME
+**
+** Write a summary of unfreed memory to FILENAME.
+*/
+static int test_memdebug_dump(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "FILENAME");
+    return TCL_ERROR;
+  }
+#if defined(SQLITE_MEMDEBUG) || defined(SQLITE_MEMORY_SIZE) \
+     || defined(SQLITE_POW2_MEMORY_SIZE)
+  {
+    extern void sqlite3MemdebugDump(const char*);
+    sqlite3MemdebugDump(Tcl_GetString(objv[1]));
+  }
+#endif
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_memdebug_malloc_count
+**
+** Return the total number of times malloc() has been called.
+*/
+static int test_memdebug_malloc_count(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int nMalloc = -1;
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+#if defined(SQLITE_MEMDEBUG)
+  {
+    extern int sqlite3MemdebugMallocCount();
+    nMalloc = sqlite3MemdebugMallocCount();
+  }
+#endif
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(nMalloc));
+  return TCL_OK;
+}
+
+
+/*
+** Usage:    sqlite3_memdebug_fail  COUNTER  ?OPTIONS?
+**
+** where options are:
+**
+**     -repeat    <count>
+**     -benigncnt <varname>
+**
+** Arrange for a simulated malloc() failure after COUNTER successes.
+** If a repeat count is specified, the fault is repeated that many
+** times.
+**
+** Each call to this routine overrides the prior counter value.
+** This routine returns the number of simulated failures that have
+** happened since the previous call to this routine.
+**
+** To disable simulated failures, use a COUNTER of -1.
+*/
+static int test_memdebug_fail(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int ii;
+  int iFail;
+  int nRepeat = 1;
+  Tcl_Obj *pBenignCnt = 0;
+  int nBenign;
+  int nFail = 0;
+
+  if( objc<2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "COUNTER ?OPTIONS?");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[1], &iFail) ) return TCL_ERROR;
+
+  for(ii=2; ii<objc; ii+=2){
+    int nOption;
+    char *zOption = Tcl_GetStringFromObj(objv[ii], &nOption);
+    char *zErr = 0;
+
+    if( nOption>1 && strncmp(zOption, "-repeat", nOption)==0 ){
+      if( ii==(objc-1) ){
+        zErr = "option requires an argument: ";
+      }else{
+        if( Tcl_GetIntFromObj(interp, objv[ii+1], &nRepeat) ){
+          return TCL_ERROR;
+        }
+      }
+    }else if( nOption>1 && strncmp(zOption, "-benigncnt", nOption)==0 ){
+      if( ii==(objc-1) ){
+        zErr = "option requires an argument: ";
+      }else{
+        pBenignCnt = objv[ii+1];
+      }
+    }else{
+      zErr = "unknown option: ";
+    }
+
+    if( zErr ){
+      Tcl_AppendResult(interp, zErr, zOption, 0);
+      return TCL_ERROR;
+    }
+  }
+  
+  nBenign = faultsimBenignFailures();
+  nFail = faultsimFailures();
+  faultsimConfig(iFail, nRepeat);
+
+  if( pBenignCnt ){
+    Tcl_ObjSetVar2(interp, pBenignCnt, 0, Tcl_NewIntObj(nBenign), 0);
+  }
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(nFail));
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_memdebug_pending
+**
+** Return the number of malloc() calls that will succeed before a 
+** simulated failure occurs. A negative return value indicates that
+** no malloc() failure is scheduled.
+*/
+static int test_memdebug_pending(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int nPending;
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+  nPending = faultsimPending();
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(nPending));
+  return TCL_OK;
+}
+
+
+/*
+** Usage:    sqlite3_memdebug_settitle TITLE
+**
+** Set a title string stored with each allocation.  The TITLE is
+** typically the name of the test that was running when the
+** allocation occurred.  The TITLE is stored with the allocation
+** and can be used to figure out which tests are leaking memory.
+**
+** Each title overwrite the previous.
+*/
+static int test_memdebug_settitle(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  const char *zTitle;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "TITLE");
+    return TCL_ERROR;
+  }
+  zTitle = Tcl_GetString(objv[1]);
+#ifdef SQLITE_MEMDEBUG
+  {
+    extern int sqlite3MemdebugSettitle(const char*);
+    sqlite3MemdebugSettitle(zTitle);
+  }
+#endif
+  return TCL_OK;
+}
+
+#define MALLOC_LOG_FRAMES  10 
+#define MALLOC_LOG_KEYINTS (                                              \
+    10 * ((sizeof(int)>=sizeof(void*)) ? 1 : sizeof(void*)/sizeof(int))   \
+)
+static Tcl_HashTable aMallocLog;
+static int mallocLogEnabled = 0;
+
+typedef struct MallocLog MallocLog;
+struct MallocLog {
+  int nCall;
+  int nByte;
+};
+
+#ifdef SQLITE_MEMDEBUG
+static void test_memdebug_callback(int nByte, int nFrame, void **aFrame){
+  if( mallocLogEnabled ){
+    MallocLog *pLog;
+    Tcl_HashEntry *pEntry;
+    int isNew;
+
+    int aKey[MALLOC_LOG_KEYINTS];
+    int nKey = sizeof(int)*MALLOC_LOG_KEYINTS;
+
+    memset(aKey, 0, nKey);
+    if( (sizeof(void*)*nFrame)<nKey ){
+      nKey = nFrame*sizeof(void*);
+    }
+    memcpy(aKey, aFrame, nKey);
+
+    pEntry = Tcl_CreateHashEntry(&aMallocLog, (const char *)aKey, &isNew);
+    if( isNew ){
+      pLog = (MallocLog *)Tcl_Alloc(sizeof(MallocLog));
+      memset(pLog, 0, sizeof(MallocLog));
+      Tcl_SetHashValue(pEntry, (ClientData)pLog);
+    }else{
+      pLog = (MallocLog *)Tcl_GetHashValue(pEntry);
+    }
+
+    pLog->nCall++;
+    pLog->nByte += nByte;
+  }
+}
+#endif /* SQLITE_MEMDEBUG */
+
+static void test_memdebug_log_clear(void){
+  Tcl_HashSearch search;
+  Tcl_HashEntry *pEntry;
+  for(
+    pEntry=Tcl_FirstHashEntry(&aMallocLog, &search);
+    pEntry;
+    pEntry=Tcl_NextHashEntry(&search)
+  ){
+    MallocLog *pLog = (MallocLog *)Tcl_GetHashValue(pEntry);
+    Tcl_Free((char *)pLog);
+  }
+  Tcl_DeleteHashTable(&aMallocLog);
+  Tcl_InitHashTable(&aMallocLog, MALLOC_LOG_KEYINTS);
+}
+
+static int test_memdebug_log(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  static int isInit = 0;
+  int iSub;
+
+  static const char *MB_strs[] = { "start", "stop", "dump", "clear", "sync" };
+  enum MB_enum { 
+      MB_LOG_START, MB_LOG_STOP, MB_LOG_DUMP, MB_LOG_CLEAR, MB_LOG_SYNC 
+  };
+
+  if( !isInit ){
+#ifdef SQLITE_MEMDEBUG
+    extern void sqlite3MemdebugBacktraceCallback(
+        void (*xBacktrace)(int, int, void **));
+    sqlite3MemdebugBacktraceCallback(test_memdebug_callback);
+#endif
+    Tcl_InitHashTable(&aMallocLog, MALLOC_LOG_KEYINTS);
+    isInit = 1;
+  }
+
+  if( objc<2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "SUB-COMMAND ...");
+  }
+  if( Tcl_GetIndexFromObj(interp, objv[1], MB_strs, "sub-command", 0, &iSub) ){
+    return TCL_ERROR;
+  }
+
+  switch( (enum MB_enum)iSub ){
+    case MB_LOG_START:
+      mallocLogEnabled = 1;
+      break;
+    case MB_LOG_STOP:
+      mallocLogEnabled = 0;
+      break;
+    case MB_LOG_DUMP: {
+      Tcl_HashSearch search;
+      Tcl_HashEntry *pEntry;
+      Tcl_Obj *pRet = Tcl_NewObj();
+
+      assert(sizeof(Tcl_WideInt)>=sizeof(void*));
+
+      for(
+        pEntry=Tcl_FirstHashEntry(&aMallocLog, &search);
+        pEntry;
+        pEntry=Tcl_NextHashEntry(&search)
+      ){
+        Tcl_Obj *apElem[MALLOC_LOG_FRAMES+2];
+        MallocLog *pLog = (MallocLog *)Tcl_GetHashValue(pEntry);
+        Tcl_WideInt *aKey = (Tcl_WideInt *)Tcl_GetHashKey(&aMallocLog, pEntry);
+        int ii;
+  
+        apElem[0] = Tcl_NewIntObj(pLog->nCall);
+        apElem[1] = Tcl_NewIntObj(pLog->nByte);
+        for(ii=0; ii<MALLOC_LOG_FRAMES; ii++){
+          apElem[ii+2] = Tcl_NewWideIntObj(aKey[ii]);
+        }
+
+        Tcl_ListObjAppendElement(interp, pRet,
+            Tcl_NewListObj(MALLOC_LOG_FRAMES+2, apElem)
+        );
+      }
+
+      Tcl_SetObjResult(interp, pRet);
+      break;
+    }
+    case MB_LOG_CLEAR: {
+      test_memdebug_log_clear();
+      break;
+    }
+
+    case MB_LOG_SYNC: {
+#ifdef SQLITE_MEMDEBUG
+      extern void sqlite3MemdebugSync();
+      test_memdebug_log_clear();
+      mallocLogEnabled = 1;
+      sqlite3MemdebugSync();
+#endif
+      break;
+    }
+  }
+
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_config_scratch SIZE N
+**
+** Set the scratch memory buffer using SQLITE_CONFIG_SCRATCH.
+** The buffer is static and is of limited size.  N might be
+** adjusted downward as needed to accomodate the requested size.
+** The revised value of N is returned.
+**
+** A negative SIZE causes the buffer pointer to be NULL.
+*/
+static int test_config_scratch(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int sz, N, rc;
+  Tcl_Obj *pResult;
+  static char *buf = 0;
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "SIZE N");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[1], &sz) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &N) ) return TCL_ERROR;
+  free(buf);
+  if( sz<0 ){
+    buf = 0;
+    rc = sqlite3_config(SQLITE_CONFIG_SCRATCH, 0, 0, 0);
+  }else{
+    buf = malloc( sz*N + 1 );
+    rc = sqlite3_config(SQLITE_CONFIG_SCRATCH, buf, sz, N);
+  }
+  pResult = Tcl_NewObj();
+  Tcl_ListObjAppendElement(0, pResult, Tcl_NewIntObj(rc));
+  Tcl_ListObjAppendElement(0, pResult, Tcl_NewIntObj(N));
+  Tcl_SetObjResult(interp, pResult);
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_config_pagecache SIZE N
+**
+** Set the page-cache memory buffer using SQLITE_CONFIG_PAGECACHE.
+** The buffer is static and is of limited size.  N might be
+** adjusted downward as needed to accomodate the requested size.
+** The revised value of N is returned.
+**
+** A negative SIZE causes the buffer pointer to be NULL.
+*/
+static int test_config_pagecache(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int sz, N, rc;
+  Tcl_Obj *pResult;
+  static char *buf = 0;
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "SIZE N");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[1], &sz) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &N) ) return TCL_ERROR;
+  free(buf);
+  if( sz<0 ){
+    buf = 0;
+    rc = sqlite3_config(SQLITE_CONFIG_PAGECACHE, 0, 0, 0);
+  }else{
+    buf = malloc( sz*N );
+    rc = sqlite3_config(SQLITE_CONFIG_PAGECACHE, buf, sz, N);
+  }
+  pResult = Tcl_NewObj();
+  Tcl_ListObjAppendElement(0, pResult, Tcl_NewIntObj(rc));
+  Tcl_ListObjAppendElement(0, pResult, Tcl_NewIntObj(N));
+  Tcl_SetObjResult(interp, pResult);
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_config_alt_pcache INSTALL_FLAG DISCARD_CHANCE PRNG_SEED
+**
+** Set up the alternative test page cache.  Install if INSTALL_FLAG is
+** true and uninstall (reverting to the default page cache) if INSTALL_FLAG
+** is false.  DISCARD_CHANGE is an integer between 0 and 100 inclusive
+** which determines the chance of discarding a page when unpinned.  100
+** is certainty.  0 is never.  PRNG_SEED is the pseudo-random number generator
+** seed.
+*/
+static int test_alt_pcache(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int installFlag;
+  int discardChance = 0;
+  int prngSeed = 0;
+  int highStress = 0;
+  extern void installTestPCache(int,unsigned,unsigned,unsigned);
+  if( objc<2 || objc>5 ){
+    Tcl_WrongNumArgs(interp, 1, objv, 
+        "INSTALLFLAG DISCARDCHANCE PRNGSEEED HIGHSTRESS");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[1], &installFlag) ) return TCL_ERROR;
+  if( objc>=3 && Tcl_GetIntFromObj(interp, objv[2], &discardChance) ){
+     return TCL_ERROR;
+  }
+  if( objc>=4 && Tcl_GetIntFromObj(interp, objv[3], &prngSeed) ){
+     return TCL_ERROR;
+  }
+  if( objc>=5 && Tcl_GetIntFromObj(interp, objv[4], &highStress) ){
+    return TCL_ERROR;
+  }
+  if( discardChance<0 || discardChance>100 ){
+    Tcl_AppendResult(interp, "discard-chance should be between 0 and 100",
+                     (char*)0);
+    return TCL_ERROR;
+  }
+  installTestPCache(installFlag, (unsigned)discardChance, (unsigned)prngSeed,
+                    (unsigned)highStress);
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_config_memstatus BOOLEAN
+**
+** Enable or disable memory status reporting using SQLITE_CONFIG_MEMSTATUS.
+*/
+static int test_config_memstatus(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int enable, rc;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "BOOLEAN");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetBooleanFromObj(interp, objv[1], &enable) ) return TCL_ERROR;
+  rc = sqlite3_config(SQLITE_CONFIG_MEMSTATUS, enable);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_config_lookaside  SIZE  COUNT
+**
+*/
+static int test_config_lookaside(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc;
+  int sz, cnt;
+  Tcl_Obj *pRet;
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "SIZE COUNT");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[1], &sz) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &cnt) ) return TCL_ERROR;
+  pRet = Tcl_NewObj();
+  Tcl_ListObjAppendElement(
+      interp, pRet, Tcl_NewIntObj(sqlite3GlobalConfig.szLookaside)
+  );
+  Tcl_ListObjAppendElement(
+      interp, pRet, Tcl_NewIntObj(sqlite3GlobalConfig.nLookaside)
+  );
+  rc = sqlite3_config(SQLITE_CONFIG_LOOKASIDE, sz, cnt);
+  Tcl_SetObjResult(interp, pRet);
+  return TCL_OK;
+}
+
+
+/*
+** Usage:    sqlite3_db_config_lookaside  CONNECTION  BUFID  SIZE  COUNT
+**
+** There are two static buffers with BUFID 1 and 2.   Each static buffer
+** is 10KB in size.  A BUFID of 0 indicates that the buffer should be NULL
+** which will cause sqlite3_db_config() to allocate space on its own.
+*/
+static int test_db_config_lookaside(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc;
+  int sz, cnt;
+  sqlite3 *db;
+  int bufid;
+  static char azBuf[2][10000];
+  int getDbPointer(Tcl_Interp*, const char*, sqlite3**);
+  if( objc!=5 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "BUFID SIZE COUNT");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[2], &bufid) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[3], &sz) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, objv[4], &cnt) ) return TCL_ERROR;
+  if( bufid==0 ){
+    rc = sqlite3_db_config(db, SQLITE_DBCONFIG_LOOKASIDE, 0, sz, cnt);
+  }else if( bufid>=1 && bufid<=2 && sz*cnt<=sizeof(azBuf[0]) ){
+    rc = sqlite3_db_config(db, SQLITE_DBCONFIG_LOOKASIDE, azBuf[bufid], sz,cnt);
+  }else{
+    Tcl_AppendResult(interp, "illegal arguments - see documentation", (char*)0);
+    return TCL_ERROR;
+  }
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(rc));
+  return TCL_OK;
+}
+
+/*
+** Usage:
+**
+**   sqlite3_config_heap NBYTE NMINALLOC
+*/
+static int test_config_heap(
+  void * clientData, 
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  static char *zBuf; /* Use this memory */
+  static int szBuf;  /* Bytes allocated for zBuf */
+  int nByte;         /* Size of buffer to pass to sqlite3_config() */
+  int nMinAlloc;     /* Size of minimum allocation */
+  int rc;            /* Return code of sqlite3_config() */
+
+  Tcl_Obj * CONST *aArg = &objv[1];
+  int nArg = objc-1;
+
+  if( nArg!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "NBYTE NMINALLOC");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, aArg[0], &nByte) ) return TCL_ERROR;
+  if( Tcl_GetIntFromObj(interp, aArg[1], &nMinAlloc) ) return TCL_ERROR;
+
+  if( nByte==0 ){
+    free( zBuf );
+    zBuf = 0;
+    szBuf = 0;
+    rc = sqlite3_config(SQLITE_CONFIG_HEAP, (void*)0, 0, 0);
+  }else{
+    zBuf = realloc(zBuf, nByte);
+    szBuf = nByte;
+    rc = sqlite3_config(SQLITE_CONFIG_HEAP, zBuf, nByte, nMinAlloc);
+  }
+
+  Tcl_SetResult(interp, (char *)sqlite3TestErrorName(rc), TCL_VOLATILE);
+  return TCL_OK;
+}
+
+/*
+** tclcmd:     sqlite3_config_error  [DB]
+**
+** Invoke sqlite3_config() or sqlite3_db_config() with invalid
+** opcodes and verify that they return errors.
+*/
+static int test_config_error(
+  void * clientData, 
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  int getDbPointer(Tcl_Interp*, const char*, sqlite3**);
+
+  if( objc!=2 && objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "[DB]");
+    return TCL_ERROR;
+  }
+  if( objc==2 ){
+    if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+    if( sqlite3_db_config(db, 99999)!=SQLITE_ERROR ){
+      Tcl_AppendResult(interp, 
+            "sqlite3_db_config(db, 99999) does not return SQLITE_ERROR",
+            (char*)0);
+      return TCL_ERROR;
+    }
+  }else{
+    if( sqlite3_config(99999)!=SQLITE_ERROR ){
+      Tcl_AppendResult(interp, 
+          "sqlite3_config(99999) does not return SQLITE_ERROR",
+          (char*)0);
+      return TCL_ERROR;
+    }
+  }
+  return TCL_OK;
+}
+
+/*
+** tclcmd:     sqlite3_config_uri  BOOLEAN
+**
+** Invoke sqlite3_config() or sqlite3_db_config() with invalid
+** opcodes and verify that they return errors.
+*/
+static int test_config_uri(
+  void * clientData, 
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc;
+  int bOpenUri;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "BOOL");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetBooleanFromObj(interp, objv[1], &bOpenUri) ){
+    return TCL_ERROR;
+  }
+
+  rc = sqlite3_config(SQLITE_CONFIG_URI, bOpenUri);
+  Tcl_SetResult(interp, (char *)sqlite3TestErrorName(rc), TCL_VOLATILE);
+
+  return TCL_OK;
+}
+
+/*
+** Usage:    
+**
+**   sqlite3_dump_memsys3  FILENAME
+**   sqlite3_dump_memsys5  FILENAME
+**
+** Write a summary of unfreed memsys3 allocations to FILENAME.
+*/
+static int test_dump_memsys3(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "FILENAME");
+    return TCL_ERROR;
+  }
+
+  switch( SQLITE_PTR_TO_INT(clientData) ){
+    case 3: {
+#ifdef SQLITE_ENABLE_MEMSYS3
+      extern void sqlite3Memsys3Dump(const char*);
+      sqlite3Memsys3Dump(Tcl_GetString(objv[1]));
+      break;
+#endif
+    }
+    case 5: {
+#ifdef SQLITE_ENABLE_MEMSYS5
+      extern void sqlite3Memsys5Dump(const char*);
+      sqlite3Memsys5Dump(Tcl_GetString(objv[1]));
+      break;
+#endif
+    }
+  }
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_status  OPCODE  RESETFLAG
+**
+** Return a list of three elements which are the sqlite3_status() return
+** code, the current value, and the high-water mark value.
+*/
+static int test_status(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc, iValue, mxValue;
+  int i, op, resetFlag;
+  const char *zOpName;
+  static const struct {
+    const char *zName;
+    int op;
+  } aOp[] = {
+    { "SQLITE_STATUS_MEMORY_USED",         SQLITE_STATUS_MEMORY_USED         },
+    { "SQLITE_STATUS_MALLOC_SIZE",         SQLITE_STATUS_MALLOC_SIZE         },
+    { "SQLITE_STATUS_PAGECACHE_USED",      SQLITE_STATUS_PAGECACHE_USED      },
+    { "SQLITE_STATUS_PAGECACHE_OVERFLOW",  SQLITE_STATUS_PAGECACHE_OVERFLOW  },
+    { "SQLITE_STATUS_PAGECACHE_SIZE",      SQLITE_STATUS_PAGECACHE_SIZE      },
+    { "SQLITE_STATUS_SCRATCH_USED",        SQLITE_STATUS_SCRATCH_USED        },
+    { "SQLITE_STATUS_SCRATCH_OVERFLOW",    SQLITE_STATUS_SCRATCH_OVERFLOW    },
+    { "SQLITE_STATUS_SCRATCH_SIZE",        SQLITE_STATUS_SCRATCH_SIZE        },
+    { "SQLITE_STATUS_PARSER_STACK",        SQLITE_STATUS_PARSER_STACK        },
+    { "SQLITE_STATUS_MALLOC_COUNT",        SQLITE_STATUS_MALLOC_COUNT        },
+  };
+  Tcl_Obj *pResult;
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "PARAMETER RESETFLAG");
+    return TCL_ERROR;
+  }
+  zOpName = Tcl_GetString(objv[1]);
+  for(i=0; i<ArraySize(aOp); i++){
+    if( strcmp(aOp[i].zName, zOpName)==0 ){
+      op = aOp[i].op;
+      break;
+    }
+  }
+  if( i>=ArraySize(aOp) ){
+    if( Tcl_GetIntFromObj(interp, objv[1], &op) ) return TCL_ERROR;
+  }
+  if( Tcl_GetBooleanFromObj(interp, objv[2], &resetFlag) ) return TCL_ERROR;
+  iValue = 0;
+  mxValue = 0;
+  rc = sqlite3_status(op, &iValue, &mxValue, resetFlag);
+  pResult = Tcl_NewObj();
+  Tcl_ListObjAppendElement(0, pResult, Tcl_NewIntObj(rc));
+  Tcl_ListObjAppendElement(0, pResult, Tcl_NewIntObj(iValue));
+  Tcl_ListObjAppendElement(0, pResult, Tcl_NewIntObj(mxValue));
+  Tcl_SetObjResult(interp, pResult);
+  return TCL_OK;
+}
+
+/*
+** Usage:    sqlite3_db_status  DATABASE  OPCODE  RESETFLAG
+**
+** Return a list of three elements which are the sqlite3_db_status() return
+** code, the current value, and the high-water mark value.
+*/
+static int test_db_status(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc, iValue, mxValue;
+  int i, op, resetFlag;
+  const char *zOpName;
+  sqlite3 *db;
+  int getDbPointer(Tcl_Interp*, const char*, sqlite3**);
+  static const struct {
+    const char *zName;
+    int op;
+  } aOp[] = {
+    { "LOOKASIDE_USED",      SQLITE_DBSTATUS_LOOKASIDE_USED      },
+    { "CACHE_USED",          SQLITE_DBSTATUS_CACHE_USED          },
+    { "SCHEMA_USED",         SQLITE_DBSTATUS_SCHEMA_USED         },
+    { "STMT_USED",           SQLITE_DBSTATUS_STMT_USED           },
+    { "LOOKASIDE_HIT",       SQLITE_DBSTATUS_LOOKASIDE_HIT       },
+    { "LOOKASIDE_MISS_SIZE", SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE },
+    { "LOOKASIDE_MISS_FULL", SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL },
+    { "CACHE_HIT",           SQLITE_DBSTATUS_CACHE_HIT           },
+    { "CACHE_MISS",          SQLITE_DBSTATUS_CACHE_MISS          }
+  };
+  Tcl_Obj *pResult;
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB PARAMETER RESETFLAG");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zOpName = Tcl_GetString(objv[2]);
+  if( memcmp(zOpName, "SQLITE_", 7)==0 ) zOpName += 7;
+  if( memcmp(zOpName, "DBSTATUS_", 9)==0 ) zOpName += 9;
+  for(i=0; i<ArraySize(aOp); i++){
+    if( strcmp(aOp[i].zName, zOpName)==0 ){
+      op = aOp[i].op;
+      break;
+    }
+  }
+  if( i>=ArraySize(aOp) ){
+    if( Tcl_GetIntFromObj(interp, objv[2], &op) ) return TCL_ERROR;
+  }
+  if( Tcl_GetBooleanFromObj(interp, objv[3], &resetFlag) ) return TCL_ERROR;
+  iValue = 0;
+  mxValue = 0;
+  rc = sqlite3_db_status(db, op, &iValue, &mxValue, resetFlag);
+  pResult = Tcl_NewObj();
+  Tcl_ListObjAppendElement(0, pResult, Tcl_NewIntObj(rc));
+  Tcl_ListObjAppendElement(0, pResult, Tcl_NewIntObj(iValue));
+  Tcl_ListObjAppendElement(0, pResult, Tcl_NewIntObj(mxValue));
+  Tcl_SetObjResult(interp, pResult);
+  return TCL_OK;
+}
+
+/*
+** install_malloc_faultsim BOOLEAN
+*/
+static int test_install_malloc_faultsim(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc;
+  int isInstall;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "BOOLEAN");
+    return TCL_ERROR;
+  }
+  if( TCL_OK!=Tcl_GetBooleanFromObj(interp, objv[1], &isInstall) ){
+    return TCL_ERROR;
+  }
+  rc = faultsimInstall(isInstall);
+  Tcl_SetResult(interp, (char *)sqlite3TestErrorName(rc), TCL_VOLATILE);
+  return TCL_OK;
+}
+
+/*
+** sqlite3_install_memsys3
+*/
+static int test_install_memsys3(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc = SQLITE_MISUSE;
+#ifdef SQLITE_ENABLE_MEMSYS3
+  const sqlite3_mem_methods *sqlite3MemGetMemsys3(void);
+  rc = sqlite3_config(SQLITE_CONFIG_MALLOC, sqlite3MemGetMemsys3());
+#endif
+  Tcl_SetResult(interp, (char *)sqlite3TestErrorName(rc), TCL_VOLATILE);
+  return TCL_OK;
+}
+
+static int test_vfs_oom_test(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  extern int sqlite3_memdebug_vfs_oom_test;
+  if( objc>2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "?INTEGER?");
+    return TCL_ERROR;
+  }else if( objc==2 ){
+    int iNew;
+    if( Tcl_GetIntFromObj(interp, objv[1], &iNew) ) return TCL_ERROR;
+    sqlite3_memdebug_vfs_oom_test = iNew;
+  }
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(sqlite3_memdebug_vfs_oom_test));
+  return TCL_OK;
+}
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetest_malloc_Init(Tcl_Interp *interp){
+  static struct {
+     char *zName;
+     Tcl_ObjCmdProc *xProc;
+     int clientData;
+  } aObjCmd[] = {
+     { "sqlite3_malloc",             test_malloc                   ,0 },
+     { "sqlite3_realloc",            test_realloc                  ,0 },
+     { "sqlite3_free",               test_free                     ,0 },
+     { "memset",                     test_memset                   ,0 },
+     { "memget",                     test_memget                   ,0 },
+     { "sqlite3_memory_used",        test_memory_used              ,0 },
+     { "sqlite3_memory_highwater",   test_memory_highwater         ,0 },
+     { "sqlite3_memdebug_backtrace", test_memdebug_backtrace       ,0 },
+     { "sqlite3_memdebug_dump",      test_memdebug_dump            ,0 },
+     { "sqlite3_memdebug_fail",      test_memdebug_fail            ,0 },
+     { "sqlite3_memdebug_pending",   test_memdebug_pending         ,0 },
+     { "sqlite3_memdebug_settitle",  test_memdebug_settitle        ,0 },
+     { "sqlite3_memdebug_malloc_count", test_memdebug_malloc_count ,0 },
+     { "sqlite3_memdebug_log",       test_memdebug_log             ,0 },
+     { "sqlite3_config_scratch",     test_config_scratch           ,0 },
+     { "sqlite3_config_pagecache",   test_config_pagecache         ,0 },
+     { "sqlite3_config_alt_pcache",  test_alt_pcache               ,0 },
+     { "sqlite3_status",             test_status                   ,0 },
+     { "sqlite3_db_status",          test_db_status                ,0 },
+     { "install_malloc_faultsim",    test_install_malloc_faultsim  ,0 },
+     { "sqlite3_config_heap",        test_config_heap              ,0 },
+     { "sqlite3_config_memstatus",   test_config_memstatus         ,0 },
+     { "sqlite3_config_lookaside",   test_config_lookaside         ,0 },
+     { "sqlite3_config_error",       test_config_error             ,0 },
+     { "sqlite3_config_uri",         test_config_uri               ,0 },
+     { "sqlite3_db_config_lookaside",test_db_config_lookaside      ,0 },
+     { "sqlite3_dump_memsys3",       test_dump_memsys3             ,3 },
+     { "sqlite3_dump_memsys5",       test_dump_memsys3             ,5 },
+     { "sqlite3_install_memsys3",    test_install_memsys3          ,0 },
+     { "sqlite3_memdebug_vfs_oom_test", test_vfs_oom_test          ,0 },
+  };
+  int i;
+  for(i=0; i<sizeof(aObjCmd)/sizeof(aObjCmd[0]); i++){
+    ClientData c = (ClientData)SQLITE_INT_TO_PTR(aObjCmd[i].clientData);
+    Tcl_CreateObjCommand(interp, aObjCmd[i].zName, aObjCmd[i].xProc, c, 0);
+  }
+  return TCL_OK;
+}
+#endif
diff --git a/src/test_multiplex.c b/src/test_multiplex.c
new file mode 100644
index 0000000..5d29607
--- /dev/null
+++ b/src/test_multiplex.c
@@ -0,0 +1,1306 @@
+/*
+** 2010 October 28
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains a VFS "shim" - a layer that sits in between the
+** pager and the real VFS - that breaks up a very large database file
+** into two or more smaller files on disk.  This is useful, for example,
+** in order to support large, multi-gigabyte databases on older filesystems
+** that limit the maximum file size to 2 GiB.
+**
+** USAGE:
+**
+** Compile this source file and link it with your application.  Then
+** at start-time, invoke the following procedure:
+**
+**   int sqlite3_multiplex_initialize(
+**      const char *zOrigVfsName,    // The underlying real VFS
+**      int makeDefault              // True to make multiplex the default VFS
+**   );
+**
+** The procedure call above will create and register a new VFS shim named
+** "multiplex".  The multiplex VFS will use the VFS named by zOrigVfsName to
+** do the actual disk I/O.  (The zOrigVfsName parameter may be NULL, in 
+** which case the default VFS at the moment sqlite3_multiplex_initialize()
+** is called will be used as the underlying real VFS.)  
+**
+** If the makeDefault parameter is TRUE then multiplex becomes the new
+** default VFS.  Otherwise, you can use the multiplex VFS by specifying
+** "multiplex" as the 4th parameter to sqlite3_open_v2() or by employing
+** URI filenames and adding "vfs=multiplex" as a parameter to the filename
+** URI.
+**
+** The multiplex VFS allows databases up to 32 GiB in size.  But it splits
+** the files up into smaller pieces, so that they will work even on 
+** filesystems that do not support large files.  The default chunk size
+** is 2147418112 bytes (which is 64KiB less than 2GiB) but this can be
+** changed at compile-time by defining the SQLITE_MULTIPLEX_CHUNK_SIZE
+** macro.  Use the "chunksize=NNNN" query parameter with a URI filename
+** in order to select an alternative chunk size for individual connections
+** at run-time.
+*/
+#include "sqlite3.h"
+#include <string.h>
+#include <assert.h>
+#include <stdlib.h>
+#include "test_multiplex.h"
+
+#ifndef SQLITE_CORE
+  #define SQLITE_CORE 1  /* Disable the API redefinition in sqlite3ext.h */
+#endif
+#include "sqlite3ext.h"
+
+/* 
+** These should be defined to be the same as the values in 
+** sqliteInt.h.  They are defined seperately here so that
+** the multiplex VFS shim can be built as a loadable 
+** module.
+*/
+#define UNUSED_PARAMETER(x) (void)(x)
+#define MAX_PAGE_SIZE       0x10000
+#define DEFAULT_SECTOR_SIZE 0x1000
+
+/*
+** For a build without mutexes, no-op the mutex calls.
+*/
+#if defined(SQLITE_THREADSAFE) && SQLITE_THREADSAFE==0
+#define sqlite3_mutex_alloc(X)    ((sqlite3_mutex*)8)
+#define sqlite3_mutex_free(X)
+#define sqlite3_mutex_enter(X)
+#define sqlite3_mutex_try(X)      SQLITE_OK
+#define sqlite3_mutex_leave(X)
+#define sqlite3_mutex_held(X)     ((void)(X),1)
+#define sqlite3_mutex_notheld(X)  ((void)(X),1)
+#endif /* SQLITE_THREADSAFE==0 */
+
+
+/************************ Shim Definitions ******************************/
+
+#ifndef SQLITE_MULTIPLEX_VFS_NAME
+# define SQLITE_MULTIPLEX_VFS_NAME "multiplex"
+#endif
+
+/* This is the limit on the chunk size.  It may be changed by calling
+** the xFileControl() interface.  It will be rounded up to a 
+** multiple of MAX_PAGE_SIZE.  We default it here to 2GiB less 64KiB.
+*/
+#ifndef SQLITE_MULTIPLEX_CHUNK_SIZE
+# define SQLITE_MULTIPLEX_CHUNK_SIZE 2147418112
+#endif
+
+/* Default limit on number of chunks.  Care should be taken
+** so that values for chunks numbers fit in the SQLITE_MULTIPLEX_EXT_FMT
+** format specifier. It may be changed by calling
+** the xFileControl() interface.
+*/
+#ifndef SQLITE_MULTIPLEX_MAX_CHUNKS
+# define SQLITE_MULTIPLEX_MAX_CHUNKS 32
+#endif
+
+/* If SQLITE_MULTIPLEX_EXT_OVWR is defined, the 
+** last SQLITE_MULTIPLEX_EXT_SZ characters of the 
+** filename will be overwritten, otherwise, the 
+** multiplex extension is simply appended to the filename.
+** Ex.  (undefined) test.db -> test.db01
+**      (defined)   test.db -> test.01
+** Chunk 0 does not have a modified extension.
+*/
+#define SQLITE_MULTIPLEX_EXT_FMT    "%02d"
+#define SQLITE_MULTIPLEX_EXT_SZ     2
+
+/************************ Object Definitions ******************************/
+
+/* Forward declaration of all object types */
+typedef struct multiplexGroup multiplexGroup;
+typedef struct multiplexConn multiplexConn;
+
+/*
+** A "multiplex group" is a collection of files that collectively
+** makeup a single SQLite DB file.  This allows the size of the DB
+** to exceed the limits imposed by the file system.
+**
+** There is an instance of the following object for each defined multiplex
+** group.
+*/
+struct multiplexGroup {
+  struct multiplexReal {           /* For each chunk */
+    sqlite3_file *p;                  /* Handle for the chunk */
+    char *z;                          /* Name of this chunk */
+  } *aReal;                        /* list of all chunks */
+  int nReal;                       /* Number of chunks */
+  char *zName;                     /* Base filename of this group */
+  int nName;                       /* Length of base filename */
+  int flags;                       /* Flags used for original opening */
+  unsigned int szChunk;            /* Chunk size used for this group */
+  int bEnabled;                    /* TRUE to use Multiplex VFS for this file */
+  multiplexGroup *pNext, *pPrev;   /* Doubly linked list of all group objects */
+};
+
+/*
+** An instance of the following object represents each open connection
+** to a file that is multiplex'ed.  This object is a 
+** subclass of sqlite3_file.  The sqlite3_file object for the underlying
+** VFS is appended to this structure.
+*/
+struct multiplexConn {
+  sqlite3_file base;              /* Base class - must be first */
+  multiplexGroup *pGroup;         /* The underlying group of files */
+};
+
+/************************* Global Variables **********************************/
+/*
+** All global variables used by this file are containing within the following
+** gMultiplex structure.
+*/
+static struct {
+  /* The pOrigVfs is the real, original underlying VFS implementation.
+  ** Most operations pass-through to the real VFS.  This value is read-only
+  ** during operation.  It is only modified at start-time and thus does not
+  ** require a mutex.
+  */
+  sqlite3_vfs *pOrigVfs;
+
+  /* The sThisVfs is the VFS structure used by this shim.  It is initialized
+  ** at start-time and thus does not require a mutex
+  */
+  sqlite3_vfs sThisVfs;
+
+  /* The sIoMethods defines the methods used by sqlite3_file objects 
+  ** associated with this shim.  It is initialized at start-time and does
+  ** not require a mutex.
+  **
+  ** When the underlying VFS is called to open a file, it might return 
+  ** either a version 1 or a version 2 sqlite3_file object.  This shim
+  ** has to create a wrapper sqlite3_file of the same version.  Hence
+  ** there are two I/O method structures, one for version 1 and the other
+  ** for version 2.
+  */
+  sqlite3_io_methods sIoMethodsV1;
+  sqlite3_io_methods sIoMethodsV2;
+
+  /* True when this shim has been initialized.
+  */
+  int isInitialized;
+
+  /* For run-time access any of the other global data structures in this
+  ** shim, the following mutex must be held.
+  */
+  sqlite3_mutex *pMutex;
+
+  /* List of multiplexGroup objects.
+  */
+  multiplexGroup *pGroups;
+} gMultiplex;
+
+/************************* Utility Routines *********************************/
+/*
+** Acquire and release the mutex used to serialize access to the
+** list of multiplexGroups.
+*/
+static void multiplexEnter(void){ sqlite3_mutex_enter(gMultiplex.pMutex); }
+static void multiplexLeave(void){ sqlite3_mutex_leave(gMultiplex.pMutex); }
+
+/*
+** Compute a string length that is limited to what can be stored in
+** lower 30 bits of a 32-bit signed integer.
+**
+** The value returned will never be negative.  Nor will it ever be greater
+** than the actual length of the string.  For very long strings (greater
+** than 1GiB) the value returned might be less than the true string length.
+*/
+static int multiplexStrlen30(const char *z){
+  const char *z2 = z;
+  if( z==0 ) return 0;
+  while( *z2 ){ z2++; }
+  return 0x3fffffff & (int)(z2 - z);
+}
+
+/*
+** Create a temporary file name in zBuf.  zBuf must be big enough to
+** hold at pOrigVfs->mxPathname characters.  This function departs
+** from the traditional temporary name generation in the os_win
+** and os_unix VFS in several ways, but is necessary so that 
+** the file name is known for temporary files (like those used 
+** during vacuum.)
+**
+** N.B. This routine assumes your underlying VFS is ok with using
+** "/" as a directory seperator.  This is the default for UNIXs
+** and is allowed (even mixed) for most versions of Windows.
+*/
+static int multiplexGetTempname(sqlite3_vfs *pOrigVfs, int nBuf, char *zBuf){
+  static char zChars[] =
+    "abcdefghijklmnopqrstuvwxyz"
+    "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+    "0123456789";
+  int i,j;
+  int attempts = 0;
+  int exists = 0;
+  int rc = SQLITE_ERROR;
+
+  /* Check that the output buffer is large enough for 
+  ** pVfs->mxPathname characters.
+  */
+  if( pOrigVfs->mxPathname <= nBuf ){
+    char *zTmp = sqlite3_malloc(pOrigVfs->mxPathname);
+    if( zTmp==0 ) return SQLITE_NOMEM;
+
+    /* sqlite3_temp_directory should always be less than
+    ** pVfs->mxPathname characters.
+    */
+    sqlite3_snprintf(pOrigVfs->mxPathname,
+                     zTmp,
+                     "%s/",
+                     sqlite3_temp_directory ? sqlite3_temp_directory : ".");
+    rc = pOrigVfs->xFullPathname(pOrigVfs, zTmp, nBuf, zBuf);
+    sqlite3_free(zTmp);
+    if( rc ) return rc;
+
+    /* Check that the output buffer is large enough for the temporary file 
+    ** name.
+    */
+    j = multiplexStrlen30(zBuf);
+    if( (j + 8 + 1 + 3 + 1) <= nBuf ){
+      /* Make 3 attempts to generate a unique name. */
+      do {
+        attempts++;
+        sqlite3_randomness(8, &zBuf[j]);
+        for(i=0; i<8; i++){
+          unsigned char uc = (unsigned char)zBuf[j+i];
+          zBuf[j+i] = (char)zChars[uc%(sizeof(zChars)-1)];
+        }
+        memcpy(&zBuf[j+i], ".tmp", 5);
+        rc = pOrigVfs->xAccess(pOrigVfs, zBuf, SQLITE_ACCESS_EXISTS, &exists);
+      } while ( (rc==SQLITE_OK) && exists && (attempts<3) );
+      if( rc==SQLITE_OK && exists ){
+        rc = SQLITE_ERROR;
+      }
+    }
+  }
+
+  return rc;
+}
+
+/* Compute the filename for the iChunk-th chunk
+*/
+static int multiplexSubFilename(multiplexGroup *pGroup, int iChunk){
+  if( iChunk>=pGroup->nReal ){
+    struct multiplexReal *p;
+    p = sqlite3_realloc(pGroup->aReal, (iChunk+1)*sizeof(*p));
+    if( p==0 ){
+      return SQLITE_NOMEM;
+    }
+    memset(&p[pGroup->nReal], 0, sizeof(p[0])*(iChunk+1-pGroup->nReal));
+    pGroup->aReal = p;
+    pGroup->nReal = iChunk+1;
+  }
+  if( pGroup->aReal[iChunk].z==0 ){
+    char *z;
+    int n = pGroup->nName;
+    pGroup->aReal[iChunk].z = z = sqlite3_malloc( n+3 );
+    if( z==0 ){
+      return SQLITE_NOMEM;
+    }
+    memcpy(z, pGroup->zName, n+1);
+    if( iChunk>0 ){
+#ifdef SQLITE_ENABLE_8_3_NAMES
+      if( n>3 && z[n-3]=='.' ){
+        n--;
+      }else if( n>4 && z[n-4]=='.' ){
+        n -= 2;
+      }
+#endif
+      sqlite3_snprintf(3,&z[n],"%02d",iChunk);
+    }
+  }
+  return SQLITE_OK;
+}
+
+/* Translate an sqlite3_file* that is really a multiplexGroup* into
+** the sqlite3_file* for the underlying original VFS.
+*/
+static sqlite3_file *multiplexSubOpen(
+  multiplexGroup *pGroup,
+  int iChunk,
+  int *rc,
+  int *pOutFlags
+){
+  sqlite3_file *pSubOpen = 0;
+  sqlite3_vfs *pOrigVfs = gMultiplex.pOrigVfs;        /* Real VFS */
+  *rc = multiplexSubFilename(pGroup, iChunk);
+  if( (*rc)==SQLITE_OK && (pSubOpen = pGroup->aReal[iChunk].p)==0 ){
+    pSubOpen = sqlite3_malloc( pOrigVfs->szOsFile );
+    if( pSubOpen==0 ){
+      *rc = SQLITE_NOMEM;
+      return 0;
+    }
+    pGroup->aReal[iChunk].p = pSubOpen;
+    *rc = pOrigVfs->xOpen(pOrigVfs, pGroup->aReal[iChunk].z, pSubOpen,
+                          pGroup->flags, pOutFlags);
+    if( *rc!=SQLITE_OK ){
+      sqlite3_free(pSubOpen);
+      pGroup->aReal[iChunk].p = 0;
+      return 0;
+    }
+  }
+  return pSubOpen;
+}
+
+/*
+** This is the implementation of the multiplex_control() SQL function.
+*/
+static void multiplexControlFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  int rc = SQLITE_OK;
+  sqlite3 *db = sqlite3_context_db_handle(context);
+  int op;
+  int iVal;
+
+  if( !db || argc!=2 ){ 
+    rc = SQLITE_ERROR; 
+  }else{
+    /* extract params */
+    op = sqlite3_value_int(argv[0]);
+    iVal = sqlite3_value_int(argv[1]);
+    /* map function op to file_control op */
+    switch( op ){
+      case 1: 
+        op = MULTIPLEX_CTRL_ENABLE; 
+        break;
+      case 2: 
+        op = MULTIPLEX_CTRL_SET_CHUNK_SIZE; 
+        break;
+      case 3: 
+        op = MULTIPLEX_CTRL_SET_MAX_CHUNKS; 
+        break;
+      default:
+        rc = SQLITE_NOTFOUND;
+        break;
+    }
+  }
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_file_control(db, 0, op, &iVal);
+  }
+  sqlite3_result_error_code(context, rc);
+}
+
+/*
+** This is the entry point to register the auto-extension for the 
+** multiplex_control() function.
+*/
+static int multiplexFuncInit(
+  sqlite3 *db, 
+  char **pzErrMsg, 
+  const sqlite3_api_routines *pApi
+){
+  int rc;
+  rc = sqlite3_create_function(db, "multiplex_control", 2, SQLITE_ANY, 
+      0, multiplexControlFunc, 0, 0);
+  return rc;
+}
+
+/*
+** Close a single sub-file in the connection group.
+*/
+static void multiplexSubClose(
+  multiplexGroup *pGroup,
+  int iChunk,
+  sqlite3_vfs *pOrigVfs
+){
+  sqlite3_file *pSubOpen = pGroup->aReal[iChunk].p;
+  if( pSubOpen ){
+    pSubOpen->pMethods->xClose(pSubOpen);
+    if( pOrigVfs ) pOrigVfs->xDelete(pOrigVfs, pGroup->aReal[iChunk].z, 0);
+    sqlite3_free(pGroup->aReal[iChunk].p);
+  }
+  sqlite3_free(pGroup->aReal[iChunk].z);
+  memset(&pGroup->aReal[iChunk], 0, sizeof(pGroup->aReal[iChunk]));
+}
+
+/*
+** Deallocate memory held by a multiplexGroup
+*/
+static void multiplexFreeComponents(multiplexGroup *pGroup){
+  int i;
+  for(i=0; i<pGroup->nReal; i++){ multiplexSubClose(pGroup, i, 0); }
+  sqlite3_free(pGroup->aReal);
+  pGroup->aReal = 0;
+  pGroup->nReal = 0;
+}
+
+
+/************************* VFS Method Wrappers *****************************/
+
+/*
+** This is the xOpen method used for the "multiplex" VFS.
+**
+** Most of the work is done by the underlying original VFS.  This method
+** simply links the new file into the appropriate multiplex group if it is a
+** file that needs to be tracked.
+*/
+static int multiplexOpen(
+  sqlite3_vfs *pVfs,         /* The multiplex VFS */
+  const char *zName,         /* Name of file to be opened */
+  sqlite3_file *pConn,       /* Fill in this file descriptor */
+  int flags,                 /* Flags to control the opening */
+  int *pOutFlags             /* Flags showing results of opening */
+){
+  int rc = SQLITE_OK;                  /* Result code */
+  multiplexConn *pMultiplexOpen;       /* The new multiplex file descriptor */
+  multiplexGroup *pGroup;              /* Corresponding multiplexGroup object */
+  sqlite3_file *pSubOpen = 0;                    /* Real file descriptor */
+  sqlite3_vfs *pOrigVfs = gMultiplex.pOrigVfs;   /* Real VFS */
+  int nName;
+  int sz;
+  char *zToFree = 0;
+
+  UNUSED_PARAMETER(pVfs);
+  memset(pConn, 0, pVfs->szOsFile);
+
+  /* We need to create a group structure and manage
+  ** access to this group of files.
+  */
+  multiplexEnter();
+  pMultiplexOpen = (multiplexConn*)pConn;
+
+  /* If the second argument to this function is NULL, generate a 
+  ** temporary file name to use.  This will be handled by the
+  ** original xOpen method.  We just need to allocate space for
+  ** it.
+  */
+  if( !zName ){
+    zName = zToFree = sqlite3_malloc( pOrigVfs->mxPathname + 10 );
+    if( zName==0 ){
+      rc = SQLITE_NOMEM;
+    }else{
+      rc = multiplexGetTempname(pOrigVfs, pOrigVfs->mxPathname, zToFree);
+    }
+  }
+
+  if( rc==SQLITE_OK ){
+    /* allocate space for group */
+    nName = multiplexStrlen30(zName);
+    sz = sizeof(multiplexGroup)                             /* multiplexGroup */
+       + nName + 1;                                         /* zName */
+    pGroup = sqlite3_malloc( sz );
+    if( pGroup==0 ){
+      rc = SQLITE_NOMEM;
+    }
+  }
+
+  if( rc==SQLITE_OK ){
+    /* assign pointers to extra space allocated */
+    char *p = (char *)&pGroup[1];
+    pMultiplexOpen->pGroup = pGroup;
+    memset(pGroup, 0, sz);
+    pGroup->bEnabled = -1;
+    pGroup->szChunk = SQLITE_MULTIPLEX_CHUNK_SIZE;
+    if( flags & SQLITE_OPEN_URI ){
+      const char *zChunkSize;
+      zChunkSize = sqlite3_uri_parameter(zName, "chunksize");
+      if( zChunkSize ){
+        unsigned int n = 0;
+        int i;
+        for(i=0; zChunkSize[i]>='0' && zChunkSize[i]<='9'; i++){
+          n = n*10 + zChunkSize[i] - '0';
+        }
+        if( n>0 ){
+          pGroup->szChunk = (n+0xffff)&~0xffff;
+        }else{
+          /* A zero or negative chunksize disabled the multiplexor */
+          pGroup->bEnabled = 0;
+        }
+      }
+    }
+    pGroup->zName = p;
+    /* save off base filename, name length, and original open flags  */
+    memcpy(pGroup->zName, zName, nName+1);
+    pGroup->nName = nName;
+    pGroup->flags = flags;
+    rc = multiplexSubFilename(pGroup, 1);
+    if( rc==SQLITE_OK ){
+      pSubOpen = multiplexSubOpen(pGroup, 0, &rc, pOutFlags);
+    }
+    if( pSubOpen ){
+      int exists, rc2, rc3;
+      sqlite3_int64 sz;
+
+      rc2 = pSubOpen->pMethods->xFileSize(pSubOpen, &sz);
+      if( rc2==SQLITE_OK ){
+        /* If the first overflow file exists and if the size of the main file
+        ** is different from the chunk size, that means the chunk size is set
+        ** set incorrectly.  So fix it.
+        **
+        ** Or, if the first overflow file does not exist and the main file is
+        ** larger than the chunk size, that means the chunk size is too small.
+        ** But we have no way of determining the intended chunk size, so 
+        ** just disable the multiplexor all togethre.
+        */
+        rc3 = pOrigVfs->xAccess(pOrigVfs, pGroup->aReal[1].z,
+            SQLITE_ACCESS_EXISTS, &exists);
+        if( rc3==SQLITE_OK && exists && sz==(sz&0xffff0000) && sz>0
+            && sz!=pGroup->szChunk ){
+          pGroup->szChunk = sz;
+        }else if( rc3==SQLITE_OK && !exists && sz>pGroup->szChunk ){
+          pGroup->bEnabled = 0;
+        }
+      }
+
+      if( pSubOpen->pMethods->iVersion==1 ){
+        pMultiplexOpen->base.pMethods = &gMultiplex.sIoMethodsV1;
+      }else{
+        pMultiplexOpen->base.pMethods = &gMultiplex.sIoMethodsV2;
+      }
+      /* place this group at the head of our list */
+      pGroup->pNext = gMultiplex.pGroups;
+      if( gMultiplex.pGroups ) gMultiplex.pGroups->pPrev = pGroup;
+      gMultiplex.pGroups = pGroup;
+    }else{
+      multiplexFreeComponents(pGroup);
+      sqlite3_free(pGroup);
+    }
+  }
+  multiplexLeave();
+  sqlite3_free(zToFree);
+  return rc;
+}
+
+/*
+** This is the xDelete method used for the "multiplex" VFS.
+** It attempts to delete the filename specified.
+*/
+static int multiplexDelete(
+  sqlite3_vfs *pVfs,         /* The multiplex VFS */
+  const char *zName,         /* Name of file to delete */
+  int syncDir
+){
+  sqlite3_vfs *pOrigVfs = gMultiplex.pOrigVfs;   /* Real VFS */
+  return pOrigVfs->xDelete(pOrigVfs, zName, syncDir);
+}
+
+static int multiplexAccess(sqlite3_vfs *a, const char *b, int c, int *d){
+  return gMultiplex.pOrigVfs->xAccess(gMultiplex.pOrigVfs, b, c, d);
+}
+static int multiplexFullPathname(sqlite3_vfs *a, const char *b, int c, char *d){
+  return gMultiplex.pOrigVfs->xFullPathname(gMultiplex.pOrigVfs, b, c, d);
+}
+static void *multiplexDlOpen(sqlite3_vfs *a, const char *b){
+  return gMultiplex.pOrigVfs->xDlOpen(gMultiplex.pOrigVfs, b);
+}
+static void multiplexDlError(sqlite3_vfs *a, int b, char *c){
+  gMultiplex.pOrigVfs->xDlError(gMultiplex.pOrigVfs, b, c);
+}
+static void (*multiplexDlSym(sqlite3_vfs *a, void *b, const char *c))(void){
+  return gMultiplex.pOrigVfs->xDlSym(gMultiplex.pOrigVfs, b, c);
+}
+static void multiplexDlClose(sqlite3_vfs *a, void *b){
+  gMultiplex.pOrigVfs->xDlClose(gMultiplex.pOrigVfs, b);
+}
+static int multiplexRandomness(sqlite3_vfs *a, int b, char *c){
+  return gMultiplex.pOrigVfs->xRandomness(gMultiplex.pOrigVfs, b, c);
+}
+static int multiplexSleep(sqlite3_vfs *a, int b){
+  return gMultiplex.pOrigVfs->xSleep(gMultiplex.pOrigVfs, b);
+}
+static int multiplexCurrentTime(sqlite3_vfs *a, double *b){
+  return gMultiplex.pOrigVfs->xCurrentTime(gMultiplex.pOrigVfs, b);
+}
+static int multiplexGetLastError(sqlite3_vfs *a, int b, char *c){
+  return gMultiplex.pOrigVfs->xGetLastError(gMultiplex.pOrigVfs, b, c);
+}
+static int multiplexCurrentTimeInt64(sqlite3_vfs *a, sqlite3_int64 *b){
+  return gMultiplex.pOrigVfs->xCurrentTimeInt64(gMultiplex.pOrigVfs, b);
+}
+
+/************************ I/O Method Wrappers *******************************/
+
+/* xClose requests get passed through to the original VFS.
+** We loop over all open chunk handles and close them.
+** The group structure for this file is unlinked from 
+** our list of groups and freed.
+*/
+static int multiplexClose(sqlite3_file *pConn){
+  multiplexConn *p = (multiplexConn*)pConn;
+  multiplexGroup *pGroup = p->pGroup;
+  int rc = SQLITE_OK;
+  multiplexEnter();
+  multiplexFreeComponents(pGroup);
+  /* remove from linked list */
+  if( pGroup->pNext ) pGroup->pNext->pPrev = pGroup->pPrev;
+  if( pGroup->pPrev ){
+    pGroup->pPrev->pNext = pGroup->pNext;
+  }else{
+    gMultiplex.pGroups = pGroup->pNext;
+  }
+  sqlite3_free(pGroup);
+  multiplexLeave();
+  return rc;
+}
+
+/* Pass xRead requests thru to the original VFS after
+** determining the correct chunk to operate on.
+** Break up reads across chunk boundaries.
+*/
+static int multiplexRead(
+  sqlite3_file *pConn,
+  void *pBuf,
+  int iAmt,
+  sqlite3_int64 iOfst
+){
+  multiplexConn *p = (multiplexConn*)pConn;
+  multiplexGroup *pGroup = p->pGroup;
+  int rc = SQLITE_OK;
+  multiplexEnter();
+  if( !pGroup->bEnabled ){
+    sqlite3_file *pSubOpen = multiplexSubOpen(pGroup, 0, &rc, NULL);
+    if( pSubOpen==0 ){
+      rc = SQLITE_IOERR_READ;
+    }else{
+      rc = pSubOpen->pMethods->xRead(pSubOpen, pBuf, iAmt, iOfst);
+    }
+  }else{
+    while( iAmt > 0 ){
+      int i = (int)(iOfst / pGroup->szChunk);
+      sqlite3_file *pSubOpen = multiplexSubOpen(pGroup, i, &rc, NULL);
+      if( pSubOpen ){
+        int extra = ((int)(iOfst % pGroup->szChunk) + iAmt) - pGroup->szChunk;
+        if( extra<0 ) extra = 0;
+        iAmt -= extra;
+        rc = pSubOpen->pMethods->xRead(pSubOpen, pBuf, iAmt,
+                                       iOfst % pGroup->szChunk);
+        if( rc!=SQLITE_OK ) break;
+        pBuf = (char *)pBuf + iAmt;
+        iOfst += iAmt;
+        iAmt = extra;
+      }else{
+        rc = SQLITE_IOERR_READ;
+        break;
+      }
+    }
+  }
+  multiplexLeave();
+  return rc;
+}
+
+/* Pass xWrite requests thru to the original VFS after
+** determining the correct chunk to operate on.
+** Break up writes across chunk boundaries.
+*/
+static int multiplexWrite(
+  sqlite3_file *pConn,
+  const void *pBuf,
+  int iAmt,
+  sqlite3_int64 iOfst
+){
+  multiplexConn *p = (multiplexConn*)pConn;
+  multiplexGroup *pGroup = p->pGroup;
+  int rc = SQLITE_OK;
+  multiplexEnter();
+  if( !pGroup->bEnabled ){
+    sqlite3_file *pSubOpen = multiplexSubOpen(pGroup, 0, &rc, NULL);
+    if( pSubOpen==0 ){
+      rc = SQLITE_IOERR_WRITE;
+    }else{
+      rc = pSubOpen->pMethods->xWrite(pSubOpen, pBuf, iAmt, iOfst);
+    }
+  }else{
+    while( iAmt > 0 ){
+      int i = (int)(iOfst / pGroup->szChunk);
+      sqlite3_file *pSubOpen = multiplexSubOpen(pGroup, i, &rc, NULL);
+      if( pSubOpen ){
+        int extra = ((int)(iOfst % pGroup->szChunk) + iAmt) -
+                    pGroup->szChunk;
+        if( extra<0 ) extra = 0;
+        iAmt -= extra;
+        rc = pSubOpen->pMethods->xWrite(pSubOpen, pBuf, iAmt,
+                                        iOfst % pGroup->szChunk);
+        if( rc!=SQLITE_OK ) break;
+        pBuf = (char *)pBuf + iAmt;
+        iOfst += iAmt;
+        iAmt = extra;
+      }else{
+        rc = SQLITE_IOERR_WRITE;
+        break;
+      }
+    }
+  }
+  multiplexLeave();
+  return rc;
+}
+
+/* Pass xTruncate requests thru to the original VFS after
+** determining the correct chunk to operate on.  Delete any
+** chunks above the truncate mark.
+*/
+static int multiplexTruncate(sqlite3_file *pConn, sqlite3_int64 size){
+  multiplexConn *p = (multiplexConn*)pConn;
+  multiplexGroup *pGroup = p->pGroup;
+  int rc = SQLITE_OK;
+  multiplexEnter();
+  if( !pGroup->bEnabled ){
+    sqlite3_file *pSubOpen = multiplexSubOpen(pGroup, 0, &rc, NULL);
+    if( pSubOpen==0 ){
+      rc = SQLITE_IOERR_TRUNCATE;
+    }else{
+      rc = pSubOpen->pMethods->xTruncate(pSubOpen, size);
+    }
+  }else{
+    int rc2;
+    int i;
+    sqlite3_file *pSubOpen;
+    sqlite3_vfs *pOrigVfs = gMultiplex.pOrigVfs;   /* Real VFS */
+    /* delete the chunks above the truncate limit */
+    for(i=(int)(size / pGroup->szChunk)+1; i<pGroup->nReal; i++){
+      multiplexSubClose(pGroup, i, pOrigVfs);
+    }
+    pSubOpen = multiplexSubOpen(pGroup, (int)(size/pGroup->szChunk), &rc2,0);
+    if( pSubOpen ){
+      rc2 = pSubOpen->pMethods->xTruncate(pSubOpen, size % pGroup->szChunk);
+      if( rc2!=SQLITE_OK ) rc = rc2;
+    }else{
+      rc = SQLITE_IOERR_TRUNCATE;
+    }
+  }
+  multiplexLeave();
+  return rc;
+}
+
+/* Pass xSync requests through to the original VFS without change
+*/
+static int multiplexSync(sqlite3_file *pConn, int flags){
+  multiplexConn *p = (multiplexConn*)pConn;
+  multiplexGroup *pGroup = p->pGroup;
+  int rc = SQLITE_OK;
+  int i;
+  multiplexEnter();
+  for(i=0; i<pGroup->nReal; i++){
+    sqlite3_file *pSubOpen = pGroup->aReal[i].p;
+    if( pSubOpen ){
+      int rc2 = pSubOpen->pMethods->xSync(pSubOpen, flags);
+      if( rc2!=SQLITE_OK ) rc = rc2;
+    }
+  }
+  multiplexLeave();
+  return rc;
+}
+
+/* Pass xFileSize requests through to the original VFS.
+** Aggregate the size of all the chunks before returning.
+*/
+static int multiplexFileSize(sqlite3_file *pConn, sqlite3_int64 *pSize){
+  multiplexConn *p = (multiplexConn*)pConn;
+  multiplexGroup *pGroup = p->pGroup;
+  int rc = SQLITE_OK;
+  int rc2;
+  int i;
+  multiplexEnter();
+  if( !pGroup->bEnabled ){
+    sqlite3_file *pSubOpen = multiplexSubOpen(pGroup, 0, &rc, NULL);
+    if( pSubOpen==0 ){
+      rc = SQLITE_IOERR_FSTAT;
+    }else{
+      rc = pSubOpen->pMethods->xFileSize(pSubOpen, pSize);
+    }
+  }else{
+    sqlite3_vfs *pOrigVfs = gMultiplex.pOrigVfs;
+    *pSize = 0;
+    for(i=0; 1; i++){
+      sqlite3_file *pSubOpen = 0;
+      int exists = 0;
+      rc = multiplexSubFilename(pGroup, i);
+      if( rc ) break;
+      rc2 = pOrigVfs->xAccess(pOrigVfs, pGroup->aReal[i].z,
+          SQLITE_ACCESS_EXISTS, &exists);
+      if( rc2==SQLITE_OK && exists){
+        /* if it exists, open it */
+        pSubOpen = multiplexSubOpen(pGroup, i, &rc, NULL);
+      }else{
+        /* stop at first "gap" */
+        break;
+      }
+      if( pSubOpen ){
+        sqlite3_int64 sz;
+        rc2 = pSubOpen->pMethods->xFileSize(pSubOpen, &sz);
+        if( rc2!=SQLITE_OK ){
+          rc = rc2;
+        }else{
+          if( sz>pGroup->szChunk ){
+            rc = SQLITE_IOERR_FSTAT;
+          }
+          *pSize += sz;
+        }
+      }else{
+        break;
+      }
+    }
+  }
+  multiplexLeave();
+  return rc;
+}
+
+/* Pass xLock requests through to the original VFS unchanged.
+*/
+static int multiplexLock(sqlite3_file *pConn, int lock){
+  multiplexConn *p = (multiplexConn*)pConn;
+  int rc;
+  sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL);
+  if( pSubOpen ){
+    return pSubOpen->pMethods->xLock(pSubOpen, lock);
+  }
+  return SQLITE_BUSY;
+}
+
+/* Pass xUnlock requests through to the original VFS unchanged.
+*/
+static int multiplexUnlock(sqlite3_file *pConn, int lock){
+  multiplexConn *p = (multiplexConn*)pConn;
+  int rc;
+  sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL);
+  if( pSubOpen ){
+    return pSubOpen->pMethods->xUnlock(pSubOpen, lock);
+  }
+  return SQLITE_IOERR_UNLOCK;
+}
+
+/* Pass xCheckReservedLock requests through to the original VFS unchanged.
+*/
+static int multiplexCheckReservedLock(sqlite3_file *pConn, int *pResOut){
+  multiplexConn *p = (multiplexConn*)pConn;
+  int rc;
+  sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL);
+  if( pSubOpen ){
+    return pSubOpen->pMethods->xCheckReservedLock(pSubOpen, pResOut);
+  }
+  return SQLITE_IOERR_CHECKRESERVEDLOCK;
+}
+
+/* Pass xFileControl requests through to the original VFS unchanged,
+** except for any MULTIPLEX_CTRL_* requests here.
+*/
+static int multiplexFileControl(sqlite3_file *pConn, int op, void *pArg){
+  multiplexConn *p = (multiplexConn*)pConn;
+  multiplexGroup *pGroup = p->pGroup;
+  int rc = SQLITE_ERROR;
+  sqlite3_file *pSubOpen;
+
+  if( !gMultiplex.isInitialized ) return SQLITE_MISUSE;
+  switch( op ){
+    case MULTIPLEX_CTRL_ENABLE:
+      if( pArg ) {
+        int bEnabled = *(int *)pArg;
+        pGroup->bEnabled = bEnabled;
+        rc = SQLITE_OK;
+      }
+      break;
+    case MULTIPLEX_CTRL_SET_CHUNK_SIZE:
+      if( pArg ) {
+        unsigned int szChunk = *(unsigned*)pArg;
+        if( szChunk<1 ){
+          rc = SQLITE_MISUSE;
+        }else{
+          /* Round up to nearest multiple of MAX_PAGE_SIZE. */
+          szChunk = (szChunk + (MAX_PAGE_SIZE-1));
+          szChunk &= ~(MAX_PAGE_SIZE-1);
+          pGroup->szChunk = szChunk;
+          rc = SQLITE_OK;
+        }
+      }
+      break;
+    case MULTIPLEX_CTRL_SET_MAX_CHUNKS:
+      rc = SQLITE_OK;
+      break;
+    case SQLITE_FCNTL_SIZE_HINT:
+    case SQLITE_FCNTL_CHUNK_SIZE:
+      /* no-op these */
+      rc = SQLITE_OK;
+      break;
+    default:
+      pSubOpen = multiplexSubOpen(pGroup, 0, &rc, NULL);
+      if( pSubOpen ){
+        rc = pSubOpen->pMethods->xFileControl(pSubOpen, op, pArg);
+      }
+      break;
+  }
+  return rc;
+}
+
+/* Pass xSectorSize requests through to the original VFS unchanged.
+*/
+static int multiplexSectorSize(sqlite3_file *pConn){
+  multiplexConn *p = (multiplexConn*)pConn;
+  int rc;
+  sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL);
+  if( pSubOpen ){
+    return pSubOpen->pMethods->xSectorSize(pSubOpen);
+  }
+  return DEFAULT_SECTOR_SIZE;
+}
+
+/* Pass xDeviceCharacteristics requests through to the original VFS unchanged.
+*/
+static int multiplexDeviceCharacteristics(sqlite3_file *pConn){
+  multiplexConn *p = (multiplexConn*)pConn;
+  int rc;
+  sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL);
+  if( pSubOpen ){
+    return pSubOpen->pMethods->xDeviceCharacteristics(pSubOpen);
+  }
+  return 0;
+}
+
+/* Pass xShmMap requests through to the original VFS unchanged.
+*/
+static int multiplexShmMap(
+  sqlite3_file *pConn,            /* Handle open on database file */
+  int iRegion,                    /* Region to retrieve */
+  int szRegion,                   /* Size of regions */
+  int bExtend,                    /* True to extend file if necessary */
+  void volatile **pp              /* OUT: Mapped memory */
+){
+  multiplexConn *p = (multiplexConn*)pConn;
+  int rc;
+  sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL);
+  if( pSubOpen ){
+    return pSubOpen->pMethods->xShmMap(pSubOpen, iRegion, szRegion, bExtend,pp);
+  }
+  return SQLITE_IOERR;
+}
+
+/* Pass xShmLock requests through to the original VFS unchanged.
+*/
+static int multiplexShmLock(
+  sqlite3_file *pConn,       /* Database file holding the shared memory */
+  int ofst,                  /* First lock to acquire or release */
+  int n,                     /* Number of locks to acquire or release */
+  int flags                  /* What to do with the lock */
+){
+  multiplexConn *p = (multiplexConn*)pConn;
+  int rc;
+  sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL);
+  if( pSubOpen ){
+    return pSubOpen->pMethods->xShmLock(pSubOpen, ofst, n, flags);
+  }
+  return SQLITE_BUSY;
+}
+
+/* Pass xShmBarrier requests through to the original VFS unchanged.
+*/
+static void multiplexShmBarrier(sqlite3_file *pConn){
+  multiplexConn *p = (multiplexConn*)pConn;
+  int rc;
+  sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL);
+  if( pSubOpen ){
+    pSubOpen->pMethods->xShmBarrier(pSubOpen);
+  }
+}
+
+/* Pass xShmUnmap requests through to the original VFS unchanged.
+*/
+static int multiplexShmUnmap(sqlite3_file *pConn, int deleteFlag){
+  multiplexConn *p = (multiplexConn*)pConn;
+  int rc;
+  sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL);
+  if( pSubOpen ){
+    return pSubOpen->pMethods->xShmUnmap(pSubOpen, deleteFlag);
+  }
+  return SQLITE_OK;
+}
+
+/************************** Public Interfaces *****************************/
+/*
+** CAPI: Initialize the multiplex VFS shim - sqlite3_multiplex_initialize()
+**
+** Use the VFS named zOrigVfsName as the VFS that does the actual work.  
+** Use the default if zOrigVfsName==NULL.  
+**
+** The multiplex VFS shim is named "multiplex".  It will become the default
+** VFS if makeDefault is non-zero.
+**
+** THIS ROUTINE IS NOT THREADSAFE.  Call this routine exactly once
+** during start-up.
+*/
+int sqlite3_multiplex_initialize(const char *zOrigVfsName, int makeDefault){
+  sqlite3_vfs *pOrigVfs;
+  if( gMultiplex.isInitialized ) return SQLITE_MISUSE;
+  pOrigVfs = sqlite3_vfs_find(zOrigVfsName);
+  if( pOrigVfs==0 ) return SQLITE_ERROR;
+  assert( pOrigVfs!=&gMultiplex.sThisVfs );
+  gMultiplex.pMutex = sqlite3_mutex_alloc(SQLITE_MUTEX_FAST);
+  if( !gMultiplex.pMutex ){
+    return SQLITE_NOMEM;
+  }
+  gMultiplex.pGroups = NULL;
+  gMultiplex.isInitialized = 1;
+  gMultiplex.pOrigVfs = pOrigVfs;
+  gMultiplex.sThisVfs = *pOrigVfs;
+  gMultiplex.sThisVfs.szOsFile += sizeof(multiplexConn);
+  gMultiplex.sThisVfs.zName = SQLITE_MULTIPLEX_VFS_NAME;
+  gMultiplex.sThisVfs.xOpen = multiplexOpen;
+  gMultiplex.sThisVfs.xDelete = multiplexDelete;
+  gMultiplex.sThisVfs.xAccess = multiplexAccess;
+  gMultiplex.sThisVfs.xFullPathname = multiplexFullPathname;
+  gMultiplex.sThisVfs.xDlOpen = multiplexDlOpen;
+  gMultiplex.sThisVfs.xDlError = multiplexDlError;
+  gMultiplex.sThisVfs.xDlSym = multiplexDlSym;
+  gMultiplex.sThisVfs.xDlClose = multiplexDlClose;
+  gMultiplex.sThisVfs.xRandomness = multiplexRandomness;
+  gMultiplex.sThisVfs.xSleep = multiplexSleep;
+  gMultiplex.sThisVfs.xCurrentTime = multiplexCurrentTime;
+  gMultiplex.sThisVfs.xGetLastError = multiplexGetLastError;
+  gMultiplex.sThisVfs.xCurrentTimeInt64 = multiplexCurrentTimeInt64;
+
+  gMultiplex.sIoMethodsV1.iVersion = 1;
+  gMultiplex.sIoMethodsV1.xClose = multiplexClose;
+  gMultiplex.sIoMethodsV1.xRead = multiplexRead;
+  gMultiplex.sIoMethodsV1.xWrite = multiplexWrite;
+  gMultiplex.sIoMethodsV1.xTruncate = multiplexTruncate;
+  gMultiplex.sIoMethodsV1.xSync = multiplexSync;
+  gMultiplex.sIoMethodsV1.xFileSize = multiplexFileSize;
+  gMultiplex.sIoMethodsV1.xLock = multiplexLock;
+  gMultiplex.sIoMethodsV1.xUnlock = multiplexUnlock;
+  gMultiplex.sIoMethodsV1.xCheckReservedLock = multiplexCheckReservedLock;
+  gMultiplex.sIoMethodsV1.xFileControl = multiplexFileControl;
+  gMultiplex.sIoMethodsV1.xSectorSize = multiplexSectorSize;
+  gMultiplex.sIoMethodsV1.xDeviceCharacteristics =
+                                            multiplexDeviceCharacteristics;
+  gMultiplex.sIoMethodsV2 = gMultiplex.sIoMethodsV1;
+  gMultiplex.sIoMethodsV2.iVersion = 2;
+  gMultiplex.sIoMethodsV2.xShmMap = multiplexShmMap;
+  gMultiplex.sIoMethodsV2.xShmLock = multiplexShmLock;
+  gMultiplex.sIoMethodsV2.xShmBarrier = multiplexShmBarrier;
+  gMultiplex.sIoMethodsV2.xShmUnmap = multiplexShmUnmap;
+  sqlite3_vfs_register(&gMultiplex.sThisVfs, makeDefault);
+
+  sqlite3_auto_extension((void*)multiplexFuncInit);
+
+  return SQLITE_OK;
+}
+
+/*
+** CAPI: Shutdown the multiplex system - sqlite3_multiplex_shutdown()
+**
+** All SQLite database connections must be closed before calling this
+** routine.
+**
+** THIS ROUTINE IS NOT THREADSAFE.  Call this routine exactly once while
+** shutting down in order to free all remaining multiplex groups.
+*/
+int sqlite3_multiplex_shutdown(void){
+  if( gMultiplex.isInitialized==0 ) return SQLITE_MISUSE;
+  if( gMultiplex.pGroups ) return SQLITE_MISUSE;
+  gMultiplex.isInitialized = 0;
+  sqlite3_mutex_free(gMultiplex.pMutex);
+  sqlite3_vfs_unregister(&gMultiplex.sThisVfs);
+  memset(&gMultiplex, 0, sizeof(gMultiplex));
+  return SQLITE_OK;
+}
+
+/***************************** Test Code ***********************************/
+#ifdef SQLITE_TEST
+#include <tcl.h>
+extern const char *sqlite3TestErrorName(int);
+
+
+/*
+** tclcmd: sqlite3_multiplex_initialize NAME MAKEDEFAULT
+*/
+static int test_multiplex_initialize(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  const char *zName;              /* Name of new multiplex VFS */
+  int makeDefault;                /* True to make the new VFS the default */
+  int rc;                         /* Value returned by multiplex_initialize() */
+
+  UNUSED_PARAMETER(clientData);
+
+  /* Process arguments */
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "NAME MAKEDEFAULT");
+    return TCL_ERROR;
+  }
+  zName = Tcl_GetString(objv[1]);
+  if( Tcl_GetBooleanFromObj(interp, objv[2], &makeDefault) ) return TCL_ERROR;
+  if( zName[0]=='\0' ) zName = 0;
+
+  /* Call sqlite3_multiplex_initialize() */
+  rc = sqlite3_multiplex_initialize(zName, makeDefault);
+  Tcl_SetResult(interp, (char *)sqlite3TestErrorName(rc), TCL_STATIC);
+
+  return TCL_OK;
+}
+
+/*
+** tclcmd: sqlite3_multiplex_shutdown
+*/
+static int test_multiplex_shutdown(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc;                         /* Value returned by multiplex_shutdown() */
+
+  UNUSED_PARAMETER(clientData);
+
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+
+  /* Call sqlite3_multiplex_shutdown() */
+  rc = sqlite3_multiplex_shutdown();
+  Tcl_SetResult(interp, (char *)sqlite3TestErrorName(rc), TCL_STATIC);
+
+  return TCL_OK;
+}
+
+/*
+** tclcmd:  sqlite3_multiplex_dump
+*/
+static int test_multiplex_dump(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  Tcl_Obj *pResult;
+  Tcl_Obj *pGroupTerm;
+  multiplexGroup *pGroup;
+  int i;
+  int nChunks = 0;
+
+  UNUSED_PARAMETER(clientData);
+  UNUSED_PARAMETER(objc);
+  UNUSED_PARAMETER(objv);
+
+  pResult = Tcl_NewObj();
+  multiplexEnter();
+  for(pGroup=gMultiplex.pGroups; pGroup; pGroup=pGroup->pNext){
+    pGroupTerm = Tcl_NewObj();
+
+    pGroup->zName[pGroup->nName] = '\0';
+    Tcl_ListObjAppendElement(interp, pGroupTerm,
+          Tcl_NewStringObj(pGroup->zName, -1));
+    Tcl_ListObjAppendElement(interp, pGroupTerm,
+          Tcl_NewIntObj(pGroup->nName));
+    Tcl_ListObjAppendElement(interp, pGroupTerm,
+          Tcl_NewIntObj(pGroup->flags));
+
+    /* count number of chunks with open handles */
+    for(i=0; i<pGroup->nReal; i++){
+      if( pGroup->aReal[i].p!=0 ) nChunks++;
+    }
+    Tcl_ListObjAppendElement(interp, pGroupTerm,
+          Tcl_NewIntObj(nChunks));
+
+    Tcl_ListObjAppendElement(interp, pGroupTerm,
+          Tcl_NewIntObj(pGroup->szChunk));
+    Tcl_ListObjAppendElement(interp, pGroupTerm,
+          Tcl_NewIntObj(pGroup->nReal));
+
+    Tcl_ListObjAppendElement(interp, pResult, pGroupTerm);
+  }
+  multiplexLeave();
+  Tcl_SetObjResult(interp, pResult);
+  return TCL_OK;
+}
+
+/*
+** Tclcmd: test_multiplex_control HANDLE DBNAME SUB-COMMAND ?INT-VALUE?
+*/
+static int test_multiplex_control(
+  ClientData cd,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc;                         /* Return code from file_control() */
+  int idx;                        /* Index in aSub[] */
+  Tcl_CmdInfo cmdInfo;            /* Command info structure for HANDLE */
+  sqlite3 *db;                    /* Underlying db handle for HANDLE */
+  int iValue = 0;
+  void *pArg = 0;
+
+  struct SubCommand {
+    const char *zName;
+    int op;
+    int argtype;
+  } aSub[] = {
+    { "enable",       MULTIPLEX_CTRL_ENABLE,           1 },
+    { "chunk_size",   MULTIPLEX_CTRL_SET_CHUNK_SIZE,   1 },
+    { "max_chunks",   MULTIPLEX_CTRL_SET_MAX_CHUNKS,   1 },
+    { 0, 0, 0 }
+  };
+
+  if( objc!=5 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "HANDLE DBNAME SUB-COMMAND INT-VALUE");
+    return TCL_ERROR;
+  }
+
+  if( 0==Tcl_GetCommandInfo(interp, Tcl_GetString(objv[1]), &cmdInfo) ){
+    Tcl_AppendResult(interp, "expected database handle, got \"", 0);
+    Tcl_AppendResult(interp, Tcl_GetString(objv[1]), "\"", 0);
+    return TCL_ERROR;
+  }else{
+    db = *(sqlite3 **)cmdInfo.objClientData;
+  }
+
+  rc = Tcl_GetIndexFromObjStruct(
+      interp, objv[3], aSub, sizeof(aSub[0]), "sub-command", 0, &idx
+  );
+  if( rc!=TCL_OK ) return rc;
+
+  switch( aSub[idx].argtype ){
+    case 1:
+      if( Tcl_GetIntFromObj(interp, objv[4], &iValue) ){
+        return TCL_ERROR;
+      }
+      pArg = (void *)&iValue;
+      break;
+    default:
+      Tcl_WrongNumArgs(interp, 4, objv, "SUB-COMMAND");
+      return TCL_ERROR;
+  }
+
+  rc = sqlite3_file_control(db, Tcl_GetString(objv[2]), aSub[idx].op, pArg);
+  Tcl_SetResult(interp, (char *)sqlite3TestErrorName(rc), TCL_STATIC);
+  return (rc==SQLITE_OK) ? TCL_OK : TCL_ERROR;
+}
+
+/*
+** This routine registers the custom TCL commands defined in this
+** module.  This should be the only procedure visible from outside
+** of this module.
+*/
+int Sqlitemultiplex_Init(Tcl_Interp *interp){
+  static struct {
+     char *zName;
+     Tcl_ObjCmdProc *xProc;
+  } aCmd[] = {
+    { "sqlite3_multiplex_initialize", test_multiplex_initialize },
+    { "sqlite3_multiplex_shutdown", test_multiplex_shutdown },
+    { "sqlite3_multiplex_dump", test_multiplex_dump },
+    { "sqlite3_multiplex_control", test_multiplex_control },
+  };
+  int i;
+
+  for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aCmd[i].zName, aCmd[i].xProc, 0, 0);
+  }
+
+  return TCL_OK;
+}
+#endif
diff --git a/src/test_multiplex.h b/src/test_multiplex.h
new file mode 100644
index 0000000..ec1ba9b
--- /dev/null
+++ b/src/test_multiplex.h
@@ -0,0 +1,91 @@
+/*
+** 2011 March 18
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains a VFS "shim" - a layer that sits in between the
+** pager and the real VFS.
+**
+** This particular shim enforces a multiplex system on DB files.  
+** This shim shards/partitions a single DB file into smaller 
+** "chunks" such that the total DB file size may exceed the maximum
+** file size of the underlying file system.
+**
+*/
+
+#ifndef _TEST_MULTIPLEX_H
+#define _TEST_MULTIPLEX_H
+
+/*
+** CAPI: File-control Operations Supported by Multiplex VFS
+**
+** Values interpreted by the xFileControl method of a Multiplex VFS db file-handle.
+**
+** MULTIPLEX_CTRL_ENABLE:
+**   This file control is used to enable or disable the multiplex
+**   shim.
+**
+** MULTIPLEX_CTRL_SET_CHUNK_SIZE:
+**   This file control is used to set the maximum allowed chunk 
+**   size for a multiplex file set.  The chunk size should be 
+**   a multiple of SQLITE_MAX_PAGE_SIZE, and will be rounded up
+**   if not.
+**
+** MULTIPLEX_CTRL_SET_MAX_CHUNKS:
+**   This file control is used to set the maximum number of chunks
+**   allowed to be used for a mutliplex file set.
+*/
+#define MULTIPLEX_CTRL_ENABLE          214014
+#define MULTIPLEX_CTRL_SET_CHUNK_SIZE  214015
+#define MULTIPLEX_CTRL_SET_MAX_CHUNKS  214016
+
+/*
+** CAPI: Initialize the multiplex VFS shim - sqlite3_multiplex_initialize()
+**
+** Use the VFS named zOrigVfsName as the VFS that does the actual work.  
+** Use the default if zOrigVfsName==NULL.  
+**
+** The multiplex VFS shim is named "multiplex".  It will become the default
+** VFS if makeDefault is non-zero.
+**
+** An auto-extension is registered which will make the function 
+** multiplex_control() available to database connections.  This
+** function gives access to the xFileControl interface of the 
+** multiplex VFS shim.
+**
+** SELECT multiplex_control(<op>,<val>);
+** 
+**   <op>=1 MULTIPLEX_CTRL_ENABLE
+**   <val>=0 disable
+**   <val>=1 enable
+** 
+**   <op>=2 MULTIPLEX_CTRL_SET_CHUNK_SIZE
+**   <val> int, chunk size
+** 
+**   <op>=3 MULTIPLEX_CTRL_SET_MAX_CHUNKS
+**   <val> int, max chunks
+**
+** THIS ROUTINE IS NOT THREADSAFE.  Call this routine exactly once
+** during start-up.
+*/
+extern int sqlite3_multiplex_initialize(const char *zOrigVfsName, int makeDefault);
+
+/*
+** CAPI: Shutdown the multiplex system - sqlite3_multiplex_shutdown()
+**
+** All SQLite database connections must be closed before calling this
+** routine.
+**
+** THIS ROUTINE IS NOT THREADSAFE.  Call this routine exactly once while
+** shutting down in order to free all remaining multiplex groups.
+*/
+extern int sqlite3_multiplex_shutdown(void);
+
+#endif
diff --git a/src/test_mutex.c b/src/test_mutex.c
new file mode 100644
index 0000000..0bb7437
--- /dev/null
+++ b/src/test_mutex.c
@@ -0,0 +1,439 @@
+/*
+** 2008 June 18
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains test logic for the sqlite3_mutex interfaces.
+*/
+
+#include "tcl.h"
+#include "sqlite3.h"
+#include "sqliteInt.h"
+#include <stdlib.h>
+#include <assert.h>
+#include <string.h>
+
+/* defined in test1.c */
+const char *sqlite3TestErrorName(int);
+
+/* A countable mutex */
+struct sqlite3_mutex {
+  sqlite3_mutex *pReal;
+  int eType;
+};
+
+/* State variables */
+static struct test_mutex_globals {
+  int isInstalled;              /* True if installed */
+  int disableInit;              /* True to cause sqlite3_initalize() to fail */
+  int disableTry;               /* True to force sqlite3_mutex_try() to fail */
+  int isInit;                   /* True if initialized */
+  sqlite3_mutex_methods m;      /* Interface to "real" mutex system */
+  int aCounter[8];              /* Number of grabs of each type of mutex */
+  sqlite3_mutex aStatic[6];     /* The six static mutexes */
+} g = {0};
+
+/* Return true if the countable mutex is currently held */
+static int counterMutexHeld(sqlite3_mutex *p){
+  return g.m.xMutexHeld(p->pReal);
+}
+
+/* Return true if the countable mutex is not currently held */
+static int counterMutexNotheld(sqlite3_mutex *p){
+  return g.m.xMutexNotheld(p->pReal);
+}
+
+/* Initialize the countable mutex interface
+** Or, if g.disableInit is non-zero, then do not initialize but instead
+** return the value of g.disableInit as the result code.  This can be used
+** to simulate an initialization failure.
+*/
+static int counterMutexInit(void){ 
+  int rc;
+  if( g.disableInit ) return g.disableInit;
+  rc = g.m.xMutexInit();
+  g.isInit = 1;
+  return rc;
+}
+
+/*
+** Uninitialize the mutex subsystem
+*/
+static int counterMutexEnd(void){ 
+  g.isInit = 0;
+  return g.m.xMutexEnd();
+}
+
+/*
+** Allocate a countable mutex
+*/
+static sqlite3_mutex *counterMutexAlloc(int eType){
+  sqlite3_mutex *pReal;
+  sqlite3_mutex *pRet = 0;
+
+  assert( g.isInit );
+  assert(eType<8 && eType>=0);
+
+  pReal = g.m.xMutexAlloc(eType);
+  if( !pReal ) return 0;
+
+  if( eType==SQLITE_MUTEX_FAST || eType==SQLITE_MUTEX_RECURSIVE ){
+    pRet = (sqlite3_mutex *)malloc(sizeof(sqlite3_mutex));
+  }else{
+    pRet = &g.aStatic[eType-2];
+  }
+
+  pRet->eType = eType;
+  pRet->pReal = pReal;
+  return pRet;
+}
+
+/*
+** Free a countable mutex
+*/
+static void counterMutexFree(sqlite3_mutex *p){
+  assert( g.isInit );
+  g.m.xMutexFree(p->pReal);
+  if( p->eType==SQLITE_MUTEX_FAST || p->eType==SQLITE_MUTEX_RECURSIVE ){
+    free(p);
+  }
+}
+
+/*
+** Enter a countable mutex.  Block until entry is safe.
+*/
+static void counterMutexEnter(sqlite3_mutex *p){
+  assert( g.isInit );
+  g.aCounter[p->eType]++;
+  g.m.xMutexEnter(p->pReal);
+}
+
+/*
+** Try to enter a mutex.  Return true on success.
+*/
+static int counterMutexTry(sqlite3_mutex *p){
+  assert( g.isInit );
+  g.aCounter[p->eType]++;
+  if( g.disableTry ) return SQLITE_BUSY;
+  return g.m.xMutexTry(p->pReal);
+}
+
+/* Leave a mutex
+*/
+static void counterMutexLeave(sqlite3_mutex *p){
+  assert( g.isInit );
+  g.m.xMutexLeave(p->pReal);
+}
+
+/*
+** sqlite3_shutdown
+*/
+static int test_shutdown(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc;
+
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+
+  rc = sqlite3_shutdown();
+  Tcl_SetResult(interp, (char *)sqlite3TestErrorName(rc), TCL_VOLATILE);
+  return TCL_OK;
+}
+
+/*
+** sqlite3_initialize
+*/
+static int test_initialize(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc;
+
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+
+  rc = sqlite3_initialize();
+  Tcl_SetResult(interp, (char *)sqlite3TestErrorName(rc), TCL_VOLATILE);
+  return TCL_OK;
+}
+
+/*
+** install_mutex_counters BOOLEAN
+*/
+static int test_install_mutex_counters(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc = SQLITE_OK;
+  int isInstall;
+
+  sqlite3_mutex_methods counter_methods = {
+    counterMutexInit,
+    counterMutexEnd,
+    counterMutexAlloc,
+    counterMutexFree,
+    counterMutexEnter,
+    counterMutexTry,
+    counterMutexLeave,
+    counterMutexHeld,
+    counterMutexNotheld
+  };
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "BOOLEAN");
+    return TCL_ERROR;
+  }
+  if( TCL_OK!=Tcl_GetBooleanFromObj(interp, objv[1], &isInstall) ){
+    return TCL_ERROR;
+  }
+
+  assert(isInstall==0 || isInstall==1);
+  assert(g.isInstalled==0 || g.isInstalled==1);
+  if( isInstall==g.isInstalled ){
+    Tcl_AppendResult(interp, "mutex counters are ", 0);
+    Tcl_AppendResult(interp, isInstall?"already installed":"not installed", 0);
+    return TCL_ERROR;
+  }
+
+  if( isInstall ){
+    assert( g.m.xMutexAlloc==0 );
+    rc = sqlite3_config(SQLITE_CONFIG_GETMUTEX, &g.m);
+    if( rc==SQLITE_OK ){
+      sqlite3_config(SQLITE_CONFIG_MUTEX, &counter_methods);
+    }
+    g.disableTry = 0;
+  }else{
+    assert( g.m.xMutexAlloc );
+    rc = sqlite3_config(SQLITE_CONFIG_MUTEX, &g.m);
+    memset(&g.m, 0, sizeof(sqlite3_mutex_methods));
+  }
+
+  if( rc==SQLITE_OK ){
+    g.isInstalled = isInstall;
+  }
+
+  Tcl_SetResult(interp, (char *)sqlite3TestErrorName(rc), TCL_VOLATILE);
+  return TCL_OK;
+}
+
+/*
+** read_mutex_counters
+*/
+static int test_read_mutex_counters(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  Tcl_Obj *pRet;
+  int ii;
+  char *aName[8] = {
+    "fast",        "recursive",   "static_master", "static_mem", 
+    "static_open", "static_prng", "static_lru",    "static_pmem"
+  };
+
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+
+  pRet = Tcl_NewObj();
+  Tcl_IncrRefCount(pRet);
+  for(ii=0; ii<8; ii++){
+    Tcl_ListObjAppendElement(interp, pRet, Tcl_NewStringObj(aName[ii], -1));
+    Tcl_ListObjAppendElement(interp, pRet, Tcl_NewIntObj(g.aCounter[ii]));
+  }
+  Tcl_SetObjResult(interp, pRet);
+  Tcl_DecrRefCount(pRet);
+
+  return TCL_OK;
+}
+
+/*
+** clear_mutex_counters
+*/
+static int test_clear_mutex_counters(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int ii;
+
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+
+  for(ii=0; ii<8; ii++){
+    g.aCounter[ii] = 0;
+  }
+  return TCL_OK;
+}
+
+/*
+** Create and free a mutex.  Return the mutex pointer.  The pointer
+** will be invalid since the mutex has already been freed.  The
+** return pointer just checks to see if the mutex really was allocated.
+*/
+static int test_alloc_mutex(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#if SQLITE_THREADSAFE
+  sqlite3_mutex *p = sqlite3_mutex_alloc(SQLITE_MUTEX_FAST);
+  char zBuf[100];
+  sqlite3_mutex_free(p);
+  sqlite3_snprintf(sizeof(zBuf), zBuf, "%p", p);
+  Tcl_AppendResult(interp, zBuf, (char*)0);
+#endif
+  return TCL_OK;
+}
+
+/*
+** sqlite3_config OPTION
+**
+** OPTION can be either one of the keywords:
+**
+**            SQLITE_CONFIG_SINGLETHREAD
+**            SQLITE_CONFIG_MULTITHREAD
+**            SQLITE_CONFIG_SERIALIZED
+**
+** Or OPTION can be an raw integer.
+*/
+static int test_config(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  struct ConfigOption {
+    const char *zName;
+    int iValue;
+  } aOpt[] = {
+    {"singlethread", SQLITE_CONFIG_SINGLETHREAD},
+    {"multithread",  SQLITE_CONFIG_MULTITHREAD},
+    {"serialized",   SQLITE_CONFIG_SERIALIZED},
+    {0, 0}
+  };
+  int s = sizeof(struct ConfigOption);
+  int i;
+  int rc;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+
+  if( Tcl_GetIndexFromObjStruct(interp, objv[1], aOpt, s, "flag", 0, &i) ){
+    if( Tcl_GetIntFromObj(interp, objv[1], &i) ){
+      return TCL_ERROR;
+    }
+  }else{
+    i = aOpt[i].iValue;
+  }
+
+  rc = sqlite3_config(i);
+  Tcl_SetResult(interp, (char *)sqlite3TestErrorName(rc), TCL_VOLATILE);
+  return TCL_OK;
+}
+
+static sqlite3 *getDbPointer(Tcl_Interp *pInterp, Tcl_Obj *pObj){
+  sqlite3 *db;
+  Tcl_CmdInfo info;
+  char *zCmd = Tcl_GetString(pObj);
+  if( Tcl_GetCommandInfo(pInterp, zCmd, &info) ){
+    db = *((sqlite3 **)info.objClientData);
+  }else{
+    db = (sqlite3*)sqlite3TestTextToPtr(zCmd);
+  }
+  assert( db );
+  return db;
+}
+
+static int test_enter_db_mutex(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB");
+    return TCL_ERROR;
+  }
+  db = getDbPointer(interp, objv[1]);
+  if( !db ){
+    return TCL_ERROR;
+  }
+  sqlite3_mutex_enter(sqlite3_db_mutex(db));
+  return TCL_OK;
+}
+
+static int test_leave_db_mutex(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB");
+    return TCL_ERROR;
+  }
+  db = getDbPointer(interp, objv[1]);
+  if( !db ){
+    return TCL_ERROR;
+  }
+  sqlite3_mutex_leave(sqlite3_db_mutex(db));
+  return TCL_OK;
+}
+
+int Sqlitetest_mutex_Init(Tcl_Interp *interp){
+  static struct {
+    char *zName;
+    Tcl_ObjCmdProc *xProc;
+  } aCmd[] = {
+    { "sqlite3_shutdown",        (Tcl_ObjCmdProc*)test_shutdown },
+    { "sqlite3_initialize",      (Tcl_ObjCmdProc*)test_initialize },
+    { "sqlite3_config",          (Tcl_ObjCmdProc*)test_config },
+
+    { "enter_db_mutex",          (Tcl_ObjCmdProc*)test_enter_db_mutex },
+    { "leave_db_mutex",          (Tcl_ObjCmdProc*)test_leave_db_mutex },
+
+    { "alloc_dealloc_mutex",     (Tcl_ObjCmdProc*)test_alloc_mutex },
+    { "install_mutex_counters",  (Tcl_ObjCmdProc*)test_install_mutex_counters },
+    { "read_mutex_counters",     (Tcl_ObjCmdProc*)test_read_mutex_counters },
+    { "clear_mutex_counters",    (Tcl_ObjCmdProc*)test_clear_mutex_counters },
+  };
+  int i;
+  for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aCmd[i].zName, aCmd[i].xProc, 0, 0);
+  }
+
+  Tcl_LinkVar(interp, "disable_mutex_init", 
+              (char*)&g.disableInit, TCL_LINK_INT);
+  Tcl_LinkVar(interp, "disable_mutex_try", 
+              (char*)&g.disableTry, TCL_LINK_INT);
+  return SQLITE_OK;
+}
diff --git a/src/test_onefile.c b/src/test_onefile.c
new file mode 100644
index 0000000..cd7db00
--- /dev/null
+++ b/src/test_onefile.c
@@ -0,0 +1,830 @@
+/*
+** 2007 September 14
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** OVERVIEW:
+**
+**   This file contains some example code demonstrating how the SQLite 
+**   vfs feature can be used to have SQLite operate directly on an 
+**   embedded media, without using an intermediate file system.
+**
+**   Because this is only a demo designed to run on a workstation, the
+**   underlying media is simulated using a regular file-system file. The
+**   size of the file is fixed when it is first created (default size 10 MB).
+**   From SQLite's point of view, this space is used to store a single
+**   database file and the journal file. 
+**
+**   Any statement journal created is stored in volatile memory obtained 
+**   from sqlite3_malloc(). Any attempt to create a temporary database file 
+**   will fail (SQLITE_IOERR). To prevent SQLite from attempting this,
+**   it should be configured to store all temporary database files in 
+**   main memory (see pragma "temp_store" or the SQLITE_TEMP_STORE compile 
+**   time option).
+**
+** ASSUMPTIONS:
+**
+**   After it has been created, the blob file is accessed using the
+**   following three functions only:
+**
+**       mediaRead();            - Read a 512 byte block from the file.
+**       mediaWrite();           - Write a 512 byte block to the file.
+**       mediaSync();            - Tell the media hardware to sync.
+**
+**   It is assumed that these can be easily implemented by any "real"
+**   media vfs driver adapting this code.
+**
+** FILE FORMAT:
+**
+**   The basic principle is that the "database file" is stored at the
+**   beginning of the 10 MB blob and grows in a forward direction. The 
+**   "journal file" is stored at the end of the 10MB blob and grows
+**   in the reverse direction. If, during a transaction, insufficient
+**   space is available to expand either the journal or database file,
+**   an SQLITE_FULL error is returned. The database file is never allowed
+**   to consume more than 90% of the blob space. If SQLite tries to
+**   create a file larger than this, SQLITE_FULL is returned.
+**
+**   No allowance is made for "wear-leveling", as is required by.
+**   embedded devices in the absence of equivalent hardware features.
+**
+**   The first 512 block byte of the file is reserved for storing the
+**   size of the "database file". It is updated as part of the sync()
+**   operation. On startup, it can only be trusted if no journal file
+**   exists. If a journal-file does exist, then it stores the real size
+**   of the database region. The second and subsequent blocks store the 
+**   actual database content.
+**
+**   The size of the "journal file" is not stored persistently in the 
+**   file. When the system is running, the size of the journal file is
+**   stored in volatile memory. When recovering from a crash, this vfs
+**   reports a very large size for the journal file. The normal journal
+**   header and checksum mechanisms serve to prevent SQLite from 
+**   processing any data that lies past the logical end of the journal.
+**
+**   When SQLite calls OsDelete() to delete the journal file, the final
+**   512 bytes of the blob (the area containing the first journal header)
+**   are zeroed.
+**
+** LOCKING:
+**
+**   File locking is a no-op. Only one connection may be open at any one
+**   time using this demo vfs.
+*/
+
+#include "sqlite3.h"
+#include <assert.h>
+#include <string.h>
+
+/*
+** Maximum pathname length supported by the fs backend.
+*/
+#define BLOCKSIZE 512
+#define BLOBSIZE 10485760
+
+/*
+** Name used to identify this VFS.
+*/
+#define FS_VFS_NAME "fs"
+
+typedef struct fs_real_file fs_real_file;
+struct fs_real_file {
+  sqlite3_file *pFile;
+  const char *zName;
+  int nDatabase;              /* Current size of database region */
+  int nJournal;               /* Current size of journal region */
+  int nBlob;                  /* Total size of allocated blob */
+  int nRef;                   /* Number of pointers to this structure */
+  fs_real_file *pNext;
+  fs_real_file **ppThis;
+};
+
+typedef struct fs_file fs_file;
+struct fs_file {
+  sqlite3_file base;
+  int eType;
+  fs_real_file *pReal;
+};
+
+typedef struct tmp_file tmp_file;
+struct tmp_file {
+  sqlite3_file base;
+  int nSize;
+  int nAlloc;
+  char *zAlloc;
+};
+
+/* Values for fs_file.eType. */
+#define DATABASE_FILE   1
+#define JOURNAL_FILE    2
+
+/*
+** Method declarations for fs_file.
+*/
+static int fsClose(sqlite3_file*);
+static int fsRead(sqlite3_file*, void*, int iAmt, sqlite3_int64 iOfst);
+static int fsWrite(sqlite3_file*, const void*, int iAmt, sqlite3_int64 iOfst);
+static int fsTruncate(sqlite3_file*, sqlite3_int64 size);
+static int fsSync(sqlite3_file*, int flags);
+static int fsFileSize(sqlite3_file*, sqlite3_int64 *pSize);
+static int fsLock(sqlite3_file*, int);
+static int fsUnlock(sqlite3_file*, int);
+static int fsCheckReservedLock(sqlite3_file*, int *pResOut);
+static int fsFileControl(sqlite3_file*, int op, void *pArg);
+static int fsSectorSize(sqlite3_file*);
+static int fsDeviceCharacteristics(sqlite3_file*);
+
+/*
+** Method declarations for tmp_file.
+*/
+static int tmpClose(sqlite3_file*);
+static int tmpRead(sqlite3_file*, void*, int iAmt, sqlite3_int64 iOfst);
+static int tmpWrite(sqlite3_file*, const void*, int iAmt, sqlite3_int64 iOfst);
+static int tmpTruncate(sqlite3_file*, sqlite3_int64 size);
+static int tmpSync(sqlite3_file*, int flags);
+static int tmpFileSize(sqlite3_file*, sqlite3_int64 *pSize);
+static int tmpLock(sqlite3_file*, int);
+static int tmpUnlock(sqlite3_file*, int);
+static int tmpCheckReservedLock(sqlite3_file*, int *pResOut);
+static int tmpFileControl(sqlite3_file*, int op, void *pArg);
+static int tmpSectorSize(sqlite3_file*);
+static int tmpDeviceCharacteristics(sqlite3_file*);
+
+/*
+** Method declarations for fs_vfs.
+*/
+static int fsOpen(sqlite3_vfs*, const char *, sqlite3_file*, int , int *);
+static int fsDelete(sqlite3_vfs*, const char *zName, int syncDir);
+static int fsAccess(sqlite3_vfs*, const char *zName, int flags, int *);
+static int fsFullPathname(sqlite3_vfs*, const char *zName, int nOut,char *zOut);
+static void *fsDlOpen(sqlite3_vfs*, const char *zFilename);
+static void fsDlError(sqlite3_vfs*, int nByte, char *zErrMsg);
+static void (*fsDlSym(sqlite3_vfs*,void*, const char *zSymbol))(void);
+static void fsDlClose(sqlite3_vfs*, void*);
+static int fsRandomness(sqlite3_vfs*, int nByte, char *zOut);
+static int fsSleep(sqlite3_vfs*, int microseconds);
+static int fsCurrentTime(sqlite3_vfs*, double*);
+
+
+typedef struct fs_vfs_t fs_vfs_t;
+struct fs_vfs_t {
+  sqlite3_vfs base;
+  fs_real_file *pFileList;
+  sqlite3_vfs *pParent;
+};
+
+static fs_vfs_t fs_vfs = {
+  {
+    1,                                          /* iVersion */
+    0,                                          /* szOsFile */
+    0,                                          /* mxPathname */
+    0,                                          /* pNext */
+    FS_VFS_NAME,                                /* zName */
+    0,                                          /* pAppData */
+    fsOpen,                                     /* xOpen */
+    fsDelete,                                   /* xDelete */
+    fsAccess,                                   /* xAccess */
+    fsFullPathname,                             /* xFullPathname */
+    fsDlOpen,                                   /* xDlOpen */
+    fsDlError,                                  /* xDlError */
+    fsDlSym,                                    /* xDlSym */
+    fsDlClose,                                  /* xDlClose */
+    fsRandomness,                               /* xRandomness */
+    fsSleep,                                    /* xSleep */
+    fsCurrentTime,                              /* xCurrentTime */
+    0                                           /* xCurrentTimeInt64 */
+  }, 
+  0,                                            /* pFileList */
+  0                                             /* pParent */
+};
+
+static sqlite3_io_methods fs_io_methods = {
+  1,                            /* iVersion */
+  fsClose,                      /* xClose */
+  fsRead,                       /* xRead */
+  fsWrite,                      /* xWrite */
+  fsTruncate,                   /* xTruncate */
+  fsSync,                       /* xSync */
+  fsFileSize,                   /* xFileSize */
+  fsLock,                       /* xLock */
+  fsUnlock,                     /* xUnlock */
+  fsCheckReservedLock,          /* xCheckReservedLock */
+  fsFileControl,                /* xFileControl */
+  fsSectorSize,                 /* xSectorSize */
+  fsDeviceCharacteristics,      /* xDeviceCharacteristics */
+  0,                            /* xShmMap */
+  0,                            /* xShmLock */
+  0,                            /* xShmBarrier */
+  0                             /* xShmUnmap */
+};
+
+
+static sqlite3_io_methods tmp_io_methods = {
+  1,                            /* iVersion */
+  tmpClose,                     /* xClose */
+  tmpRead,                      /* xRead */
+  tmpWrite,                     /* xWrite */
+  tmpTruncate,                  /* xTruncate */
+  tmpSync,                      /* xSync */
+  tmpFileSize,                  /* xFileSize */
+  tmpLock,                      /* xLock */
+  tmpUnlock,                    /* xUnlock */
+  tmpCheckReservedLock,         /* xCheckReservedLock */
+  tmpFileControl,               /* xFileControl */
+  tmpSectorSize,                /* xSectorSize */
+  tmpDeviceCharacteristics,     /* xDeviceCharacteristics */
+  0,                            /* xShmMap */
+  0,                            /* xShmLock */
+  0,                            /* xShmBarrier */
+  0                             /* xShmUnmap */
+};
+
+/* Useful macros used in several places */
+#define MIN(x,y) ((x)<(y)?(x):(y))
+#define MAX(x,y) ((x)>(y)?(x):(y))
+
+
+/*
+** Close a tmp-file.
+*/
+static int tmpClose(sqlite3_file *pFile){
+  tmp_file *pTmp = (tmp_file *)pFile;
+  sqlite3_free(pTmp->zAlloc);
+  return SQLITE_OK;
+}
+
+/*
+** Read data from a tmp-file.
+*/
+static int tmpRead(
+  sqlite3_file *pFile, 
+  void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  tmp_file *pTmp = (tmp_file *)pFile;
+  if( (iAmt+iOfst)>pTmp->nSize ){
+    return SQLITE_IOERR_SHORT_READ;
+  }
+  memcpy(zBuf, &pTmp->zAlloc[iOfst], iAmt);
+  return SQLITE_OK;
+}
+
+/*
+** Write data to a tmp-file.
+*/
+static int tmpWrite(
+  sqlite3_file *pFile, 
+  const void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  tmp_file *pTmp = (tmp_file *)pFile;
+  if( (iAmt+iOfst)>pTmp->nAlloc ){
+    int nNew = 2*(iAmt+iOfst+pTmp->nAlloc);
+    char *zNew = sqlite3_realloc(pTmp->zAlloc, nNew);
+    if( !zNew ){
+      return SQLITE_NOMEM;
+    }
+    pTmp->zAlloc = zNew;
+    pTmp->nAlloc = nNew;
+  }
+  memcpy(&pTmp->zAlloc[iOfst], zBuf, iAmt);
+  pTmp->nSize = MAX(pTmp->nSize, iOfst+iAmt);
+  return SQLITE_OK;
+}
+
+/*
+** Truncate a tmp-file.
+*/
+static int tmpTruncate(sqlite3_file *pFile, sqlite_int64 size){
+  tmp_file *pTmp = (tmp_file *)pFile;
+  pTmp->nSize = MIN(pTmp->nSize, size);
+  return SQLITE_OK;
+}
+
+/*
+** Sync a tmp-file.
+*/
+static int tmpSync(sqlite3_file *pFile, int flags){
+  return SQLITE_OK;
+}
+
+/*
+** Return the current file-size of a tmp-file.
+*/
+static int tmpFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
+  tmp_file *pTmp = (tmp_file *)pFile;
+  *pSize = pTmp->nSize;
+  return SQLITE_OK;
+}
+
+/*
+** Lock a tmp-file.
+*/
+static int tmpLock(sqlite3_file *pFile, int eLock){
+  return SQLITE_OK;
+}
+
+/*
+** Unlock a tmp-file.
+*/
+static int tmpUnlock(sqlite3_file *pFile, int eLock){
+  return SQLITE_OK;
+}
+
+/*
+** Check if another file-handle holds a RESERVED lock on a tmp-file.
+*/
+static int tmpCheckReservedLock(sqlite3_file *pFile, int *pResOut){
+  *pResOut = 0;
+  return SQLITE_OK;
+}
+
+/*
+** File control method. For custom operations on a tmp-file.
+*/
+static int tmpFileControl(sqlite3_file *pFile, int op, void *pArg){
+  return SQLITE_OK;
+}
+
+/*
+** Return the sector-size in bytes for a tmp-file.
+*/
+static int tmpSectorSize(sqlite3_file *pFile){
+  return 0;
+}
+
+/*
+** Return the device characteristic flags supported by a tmp-file.
+*/
+static int tmpDeviceCharacteristics(sqlite3_file *pFile){
+  return 0;
+}
+
+/*
+** Close an fs-file.
+*/
+static int fsClose(sqlite3_file *pFile){
+  int rc = SQLITE_OK;
+  fs_file *p = (fs_file *)pFile;
+  fs_real_file *pReal = p->pReal;
+
+  /* Decrement the real_file ref-count. */
+  pReal->nRef--;
+  assert(pReal->nRef>=0);
+
+  /* When the ref-count reaches 0, destroy the structure */
+  if( pReal->nRef==0 ){
+    *pReal->ppThis = pReal->pNext;
+    if( pReal->pNext ){
+      pReal->pNext->ppThis = pReal->ppThis;
+    }
+    rc = pReal->pFile->pMethods->xClose(pReal->pFile);
+    sqlite3_free(pReal);
+  }
+
+  return rc;
+}
+
+/*
+** Read data from an fs-file.
+*/
+static int fsRead(
+  sqlite3_file *pFile, 
+  void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  int rc = SQLITE_OK;
+  fs_file *p = (fs_file *)pFile;
+  fs_real_file *pReal = p->pReal;
+  sqlite3_file *pF = pReal->pFile;
+
+  if( (p->eType==DATABASE_FILE && (iAmt+iOfst)>pReal->nDatabase)
+   || (p->eType==JOURNAL_FILE && (iAmt+iOfst)>pReal->nJournal)
+  ){
+    rc = SQLITE_IOERR_SHORT_READ;
+  }else if( p->eType==DATABASE_FILE ){
+    rc = pF->pMethods->xRead(pF, zBuf, iAmt, iOfst+BLOCKSIZE);
+  }else{
+    /* Journal file. */
+    int iRem = iAmt;
+    int iBuf = 0;
+    int ii = iOfst;
+    while( iRem>0 && rc==SQLITE_OK ){
+      int iRealOff = pReal->nBlob - BLOCKSIZE*((ii/BLOCKSIZE)+1) + ii%BLOCKSIZE;
+      int iRealAmt = MIN(iRem, BLOCKSIZE - (iRealOff%BLOCKSIZE));
+
+      rc = pF->pMethods->xRead(pF, &((char *)zBuf)[iBuf], iRealAmt, iRealOff);
+      ii += iRealAmt;
+      iBuf += iRealAmt;
+      iRem -= iRealAmt;
+    }
+  }
+
+  return rc;
+}
+
+/*
+** Write data to an fs-file.
+*/
+static int fsWrite(
+  sqlite3_file *pFile, 
+  const void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  int rc = SQLITE_OK;
+  fs_file *p = (fs_file *)pFile;
+  fs_real_file *pReal = p->pReal;
+  sqlite3_file *pF = pReal->pFile;
+
+  if( p->eType==DATABASE_FILE ){
+    if( (iAmt+iOfst+BLOCKSIZE)>(pReal->nBlob-pReal->nJournal) ){
+      rc = SQLITE_FULL;
+    }else{
+      rc = pF->pMethods->xWrite(pF, zBuf, iAmt, iOfst+BLOCKSIZE);
+      if( rc==SQLITE_OK ){
+        pReal->nDatabase = MAX(pReal->nDatabase, iAmt+iOfst);
+      }
+    }
+  }else{
+    /* Journal file. */
+    int iRem = iAmt;
+    int iBuf = 0;
+    int ii = iOfst;
+    while( iRem>0 && rc==SQLITE_OK ){
+      int iRealOff = pReal->nBlob - BLOCKSIZE*((ii/BLOCKSIZE)+1) + ii%BLOCKSIZE;
+      int iRealAmt = MIN(iRem, BLOCKSIZE - (iRealOff%BLOCKSIZE));
+
+      if( iRealOff<(pReal->nDatabase+BLOCKSIZE) ){
+        rc = SQLITE_FULL;
+      }else{
+        rc = pF->pMethods->xWrite(pF, &((char *)zBuf)[iBuf], iRealAmt,iRealOff);
+        ii += iRealAmt;
+        iBuf += iRealAmt;
+        iRem -= iRealAmt;
+      }
+    }
+    if( rc==SQLITE_OK ){
+      pReal->nJournal = MAX(pReal->nJournal, iAmt+iOfst);
+    }
+  }
+
+  return rc;
+}
+
+/*
+** Truncate an fs-file.
+*/
+static int fsTruncate(sqlite3_file *pFile, sqlite_int64 size){
+  fs_file *p = (fs_file *)pFile;
+  fs_real_file *pReal = p->pReal;
+  if( p->eType==DATABASE_FILE ){
+    pReal->nDatabase = MIN(pReal->nDatabase, size);
+  }else{
+    pReal->nJournal = MIN(pReal->nJournal, size);
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Sync an fs-file.
+*/
+static int fsSync(sqlite3_file *pFile, int flags){
+  fs_file *p = (fs_file *)pFile;
+  fs_real_file *pReal = p->pReal;
+  sqlite3_file *pRealFile = pReal->pFile;
+  int rc = SQLITE_OK;
+
+  if( p->eType==DATABASE_FILE ){
+    unsigned char zSize[4];
+    zSize[0] = (pReal->nDatabase&0xFF000000)>>24;
+    zSize[1] = (pReal->nDatabase&0x00FF0000)>>16;
+    zSize[2] = (pReal->nDatabase&0x0000FF00)>>8;
+    zSize[3] = (pReal->nDatabase&0x000000FF);
+    rc = pRealFile->pMethods->xWrite(pRealFile, zSize, 4, 0);
+  }
+  if( rc==SQLITE_OK ){
+    rc = pRealFile->pMethods->xSync(pRealFile, flags&(~SQLITE_SYNC_DATAONLY));
+  }
+
+  return rc;
+}
+
+/*
+** Return the current file-size of an fs-file.
+*/
+static int fsFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
+  fs_file *p = (fs_file *)pFile;
+  fs_real_file *pReal = p->pReal;
+  if( p->eType==DATABASE_FILE ){
+    *pSize = pReal->nDatabase;
+  }else{
+    *pSize = pReal->nJournal;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Lock an fs-file.
+*/
+static int fsLock(sqlite3_file *pFile, int eLock){
+  return SQLITE_OK;
+}
+
+/*
+** Unlock an fs-file.
+*/
+static int fsUnlock(sqlite3_file *pFile, int eLock){
+  return SQLITE_OK;
+}
+
+/*
+** Check if another file-handle holds a RESERVED lock on an fs-file.
+*/
+static int fsCheckReservedLock(sqlite3_file *pFile, int *pResOut){
+  *pResOut = 0;
+  return SQLITE_OK;
+}
+
+/*
+** File control method. For custom operations on an fs-file.
+*/
+static int fsFileControl(sqlite3_file *pFile, int op, void *pArg){
+  return SQLITE_OK;
+}
+
+/*
+** Return the sector-size in bytes for an fs-file.
+*/
+static int fsSectorSize(sqlite3_file *pFile){
+  return BLOCKSIZE;
+}
+
+/*
+** Return the device characteristic flags supported by an fs-file.
+*/
+static int fsDeviceCharacteristics(sqlite3_file *pFile){
+  return 0;
+}
+
+/*
+** Open an fs file handle.
+*/
+static int fsOpen(
+  sqlite3_vfs *pVfs,
+  const char *zName,
+  sqlite3_file *pFile,
+  int flags,
+  int *pOutFlags
+){
+  fs_vfs_t *pFsVfs = (fs_vfs_t *)pVfs;
+  fs_file *p = (fs_file *)pFile;
+  fs_real_file *pReal = 0;
+  int eType;
+  int nName;
+  int rc = SQLITE_OK;
+
+  if( 0==(flags&(SQLITE_OPEN_MAIN_DB|SQLITE_OPEN_MAIN_JOURNAL)) ){
+    tmp_file *p = (tmp_file *)pFile;
+    memset(p, 0, sizeof(*p));
+    p->base.pMethods = &tmp_io_methods;
+    return SQLITE_OK;
+  }
+
+  eType = ((flags&(SQLITE_OPEN_MAIN_DB))?DATABASE_FILE:JOURNAL_FILE);
+  p->base.pMethods = &fs_io_methods;
+  p->eType = eType;
+
+  assert(strlen("-journal")==8);
+  nName = strlen(zName)-((eType==JOURNAL_FILE)?8:0);
+  pReal=pFsVfs->pFileList; 
+  for(; pReal && strncmp(pReal->zName, zName, nName); pReal=pReal->pNext);
+
+  if( !pReal ){
+    int real_flags = (flags&~(SQLITE_OPEN_MAIN_DB))|SQLITE_OPEN_TEMP_DB;
+    sqlite3_int64 size;
+    sqlite3_file *pRealFile;
+    sqlite3_vfs *pParent = pFsVfs->pParent;
+    assert(eType==DATABASE_FILE);
+
+    pReal = (fs_real_file *)sqlite3_malloc(sizeof(*pReal)+pParent->szOsFile);
+    if( !pReal ){
+      rc = SQLITE_NOMEM;
+      goto open_out;
+    }
+    memset(pReal, 0, sizeof(*pReal)+pParent->szOsFile);
+    pReal->zName = zName;
+    pReal->pFile = (sqlite3_file *)(&pReal[1]);
+
+    rc = pParent->xOpen(pParent, zName, pReal->pFile, real_flags, pOutFlags);
+    if( rc!=SQLITE_OK ){
+      goto open_out;
+    }
+    pRealFile = pReal->pFile;
+
+    rc = pRealFile->pMethods->xFileSize(pRealFile, &size);
+    if( rc!=SQLITE_OK ){
+      goto open_out;
+    }
+    if( size==0 ){
+      rc = pRealFile->pMethods->xWrite(pRealFile, "\0", 1, BLOBSIZE-1);
+      pReal->nBlob = BLOBSIZE;
+    }else{
+      unsigned char zS[4];
+      pReal->nBlob = size;
+      rc = pRealFile->pMethods->xRead(pRealFile, zS, 4, 0);
+      pReal->nDatabase = (zS[0]<<24)+(zS[1]<<16)+(zS[2]<<8)+zS[3];
+      if( rc==SQLITE_OK ){
+        rc = pRealFile->pMethods->xRead(pRealFile, zS, 4, pReal->nBlob-4);
+        if( zS[0] || zS[1] || zS[2] || zS[3] ){
+          pReal->nJournal = pReal->nBlob;
+        }
+      }
+    }
+
+    if( rc==SQLITE_OK ){
+      pReal->pNext = pFsVfs->pFileList;
+      if( pReal->pNext ){
+        pReal->pNext->ppThis = &pReal->pNext;
+      }
+      pReal->ppThis = &pFsVfs->pFileList;
+      pFsVfs->pFileList = pReal;
+    }
+  }
+
+open_out:
+  if( pReal ){
+    if( rc==SQLITE_OK ){
+      p->pReal = pReal;
+      pReal->nRef++;
+    }else{
+      if( pReal->pFile->pMethods ){
+        pReal->pFile->pMethods->xClose(pReal->pFile);
+      }
+      sqlite3_free(pReal);
+    }
+  }
+  return rc;
+}
+
+/*
+** Delete the file located at zPath. If the dirSync argument is true,
+** ensure the file-system modifications are synced to disk before
+** returning.
+*/
+static int fsDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
+  int rc = SQLITE_OK;
+  fs_vfs_t *pFsVfs = (fs_vfs_t *)pVfs;
+  fs_real_file *pReal;
+  sqlite3_file *pF;
+  int nName = strlen(zPath) - 8;
+
+  assert(strlen("-journal")==8);
+  assert(strcmp("-journal", &zPath[nName])==0);
+
+  pReal = pFsVfs->pFileList; 
+  for(; pReal && strncmp(pReal->zName, zPath, nName); pReal=pReal->pNext);
+  if( pReal ){
+    pF = pReal->pFile;
+    rc = pF->pMethods->xWrite(pF, "\0\0\0\0", 4, pReal->nBlob-BLOCKSIZE);
+    if( rc==SQLITE_OK ){
+      pReal->nJournal = 0;
+    }
+  }
+  return rc;
+}
+
+/*
+** Test for access permissions. Return true if the requested permission
+** is available, or false otherwise.
+*/
+static int fsAccess(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  int flags, 
+  int *pResOut
+){
+  fs_vfs_t *pFsVfs = (fs_vfs_t *)pVfs;
+  fs_real_file *pReal;
+  int isJournal = 0;
+  int nName = strlen(zPath);
+
+  if( flags!=SQLITE_ACCESS_EXISTS ){
+    sqlite3_vfs *pParent = ((fs_vfs_t *)pVfs)->pParent;
+    return pParent->xAccess(pParent, zPath, flags, pResOut);
+  }
+
+  assert(strlen("-journal")==8);
+  if( nName>8 && strcmp("-journal", &zPath[nName-8])==0 ){
+    nName -= 8;
+    isJournal = 1;
+  }
+
+  pReal = pFsVfs->pFileList; 
+  for(; pReal && strncmp(pReal->zName, zPath, nName); pReal=pReal->pNext);
+
+  *pResOut = (pReal && (!isJournal || pReal->nJournal>0));
+  return SQLITE_OK;
+}
+
+/*
+** Populate buffer zOut with the full canonical pathname corresponding
+** to the pathname in zPath. zOut is guaranteed to point to a buffer
+** of at least (FS_MAX_PATHNAME+1) bytes.
+*/
+static int fsFullPathname(
+  sqlite3_vfs *pVfs,            /* Pointer to vfs object */
+  const char *zPath,            /* Possibly relative input path */
+  int nOut,                     /* Size of output buffer in bytes */
+  char *zOut                    /* Output buffer */
+){
+  sqlite3_vfs *pParent = ((fs_vfs_t *)pVfs)->pParent;
+  return pParent->xFullPathname(pParent, zPath, nOut, zOut);
+}
+
+/*
+** Open the dynamic library located at zPath and return a handle.
+*/
+static void *fsDlOpen(sqlite3_vfs *pVfs, const char *zPath){
+  sqlite3_vfs *pParent = ((fs_vfs_t *)pVfs)->pParent;
+  return pParent->xDlOpen(pParent, zPath);
+}
+
+/*
+** Populate the buffer zErrMsg (size nByte bytes) with a human readable
+** utf-8 string describing the most recent error encountered associated 
+** with dynamic libraries.
+*/
+static void fsDlError(sqlite3_vfs *pVfs, int nByte, char *zErrMsg){
+  sqlite3_vfs *pParent = ((fs_vfs_t *)pVfs)->pParent;
+  pParent->xDlError(pParent, nByte, zErrMsg);
+}
+
+/*
+** Return a pointer to the symbol zSymbol in the dynamic library pHandle.
+*/
+static void (*fsDlSym(sqlite3_vfs *pVfs, void *pH, const char *zSym))(void){
+  sqlite3_vfs *pParent = ((fs_vfs_t *)pVfs)->pParent;
+  return pParent->xDlSym(pParent, pH, zSym);
+}
+
+/*
+** Close the dynamic library handle pHandle.
+*/
+static void fsDlClose(sqlite3_vfs *pVfs, void *pHandle){
+  sqlite3_vfs *pParent = ((fs_vfs_t *)pVfs)->pParent;
+  pParent->xDlClose(pParent, pHandle);
+}
+
+/*
+** Populate the buffer pointed to by zBufOut with nByte bytes of 
+** random data.
+*/
+static int fsRandomness(sqlite3_vfs *pVfs, int nByte, char *zBufOut){
+  sqlite3_vfs *pParent = ((fs_vfs_t *)pVfs)->pParent;
+  return pParent->xRandomness(pParent, nByte, zBufOut);
+}
+
+/*
+** Sleep for nMicro microseconds. Return the number of microseconds 
+** actually slept.
+*/
+static int fsSleep(sqlite3_vfs *pVfs, int nMicro){
+  sqlite3_vfs *pParent = ((fs_vfs_t *)pVfs)->pParent;
+  return pParent->xSleep(pParent, nMicro);
+}
+
+/*
+** Return the current time as a Julian Day number in *pTimeOut.
+*/
+static int fsCurrentTime(sqlite3_vfs *pVfs, double *pTimeOut){
+  sqlite3_vfs *pParent = ((fs_vfs_t *)pVfs)->pParent;
+  return pParent->xCurrentTime(pParent, pTimeOut);
+}
+
+/*
+** This procedure registers the fs vfs with SQLite. If the argument is
+** true, the fs vfs becomes the new default vfs. It is the only publicly
+** available function in this file.
+*/
+int fs_register(void){
+  if( fs_vfs.pParent ) return SQLITE_OK;
+  fs_vfs.pParent = sqlite3_vfs_find(0);
+  fs_vfs.base.mxPathname = fs_vfs.pParent->mxPathname;
+  fs_vfs.base.szOsFile = MAX(sizeof(tmp_file), sizeof(fs_file));
+  return sqlite3_vfs_register(&fs_vfs.base, 0);
+}
+
+#ifdef SQLITE_TEST
+  int SqlitetestOnefile_Init() {return fs_register();}
+#endif
diff --git a/src/test_osinst.c b/src/test_osinst.c
new file mode 100644
index 0000000..50d6250
--- /dev/null
+++ b/src/test_osinst.c
@@ -0,0 +1,1211 @@
+/*
+** 2008 April 10
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains the implementation of an SQLite vfs wrapper that
+** adds instrumentation to all vfs and file methods. C and Tcl interfaces
+** are provided to control the instrumentation.
+*/
+
+/*
+** This module contains code for a wrapper VFS that causes a log of
+** most VFS calls to be written into a nominated file on disk. The log 
+** is stored in a compressed binary format to reduce the amount of IO 
+** overhead introduced into the application by logging.
+**
+** All calls on sqlite3_file objects except xFileControl() are logged.
+** Additionally, calls to the xAccess(), xOpen(), and xDelete()
+** methods are logged. The other sqlite3_vfs object methods (xDlXXX,
+** xRandomness, xSleep, xCurrentTime, xGetLastError and xCurrentTimeInt64) 
+** are not logged.
+**
+** The binary log files are read using a virtual table implementation
+** also contained in this file. 
+**
+** CREATING LOG FILES:
+**
+**       int sqlite3_vfslog_new(
+**         const char *zVfs,          // Name of new VFS
+**         const char *zParentVfs,    // Name of parent VFS (or NULL)
+**         const char *zLog           // Name of log file to write to
+**       );
+**
+**       int sqlite3_vfslog_finalize(const char *zVfs);
+**
+** ANNOTATING LOG FILES:
+**
+**   To write an arbitrary message into a log file:
+**
+**       int sqlite3_vfslog_annotate(const char *zVfs, const char *zMsg);
+**
+** READING LOG FILES:
+**
+**   Log files are read using the "vfslog" virtual table implementation
+**   in this file. To register the virtual table with SQLite, use:
+**
+**       int sqlite3_vfslog_register(sqlite3 *db);
+**
+**   Then, if the log file is named "vfs.log", the following SQL command:
+**
+**       CREATE VIRTUAL TABLE v USING vfslog('vfs.log');
+**
+**   creates a virtual table with 6 columns, as follows:
+**
+**       CREATE TABLE v(
+**         event    TEXT,             // "xOpen", "xRead" etc.
+**         file     TEXT,             // Name of file this call applies to
+**         clicks   INTEGER,          // Time spent in call
+**         rc       INTEGER,          // Return value
+**         size     INTEGER,          // Bytes read or written
+**         offset   INTEGER           // File offset read or written
+**       );
+*/
+
+#include "sqlite3.h"
+#include <string.h>
+#include <assert.h>
+
+
+/*
+** Maximum pathname length supported by the vfslog backend.
+*/
+#define INST_MAX_PATHNAME 512
+
+#define OS_ACCESS            1
+#define OS_CHECKRESERVEDLOCK 2
+#define OS_CLOSE             3
+#define OS_CURRENTTIME       4
+#define OS_DELETE            5
+#define OS_DEVCHAR           6
+#define OS_FILECONTROL       7
+#define OS_FILESIZE          8
+#define OS_FULLPATHNAME      9
+#define OS_LOCK              11
+#define OS_OPEN              12
+#define OS_RANDOMNESS        13
+#define OS_READ              14 
+#define OS_SECTORSIZE        15
+#define OS_SLEEP             16
+#define OS_SYNC              17
+#define OS_TRUNCATE          18
+#define OS_UNLOCK            19
+#define OS_WRITE             20
+#define OS_SHMUNMAP          22
+#define OS_SHMMAP            23
+#define OS_SHMLOCK           25
+#define OS_SHMBARRIER        26
+#define OS_ANNOTATE          28
+
+#define OS_NUMEVENTS         29
+
+#define VFSLOG_BUFFERSIZE 8192
+
+typedef struct VfslogVfs VfslogVfs;
+typedef struct VfslogFile VfslogFile;
+
+struct VfslogVfs {
+  sqlite3_vfs base;               /* VFS methods */
+  sqlite3_vfs *pVfs;              /* Parent VFS */
+  int iNextFileId;                /* Next file id */
+  sqlite3_file *pLog;             /* Log file handle */
+  sqlite3_int64 iOffset;          /* Log file offset of start of write buffer */
+  int nBuf;                       /* Number of valid bytes in aBuf[] */
+  char aBuf[VFSLOG_BUFFERSIZE];   /* Write buffer */
+};
+
+struct VfslogFile {
+  sqlite3_file base;              /* IO methods */
+  sqlite3_file *pReal;            /* Underlying file handle */
+  sqlite3_vfs *pVfslog;           /* Associated VsflogVfs object */
+  int iFileId;                    /* File id number */
+};
+
+#define REALVFS(p) (((VfslogVfs *)(p))->pVfs)
+
+
+
+/*
+** Method declarations for vfslog_file.
+*/
+static int vfslogClose(sqlite3_file*);
+static int vfslogRead(sqlite3_file*, void*, int iAmt, sqlite3_int64 iOfst);
+static int vfslogWrite(sqlite3_file*,const void*,int iAmt, sqlite3_int64 iOfst);
+static int vfslogTruncate(sqlite3_file*, sqlite3_int64 size);
+static int vfslogSync(sqlite3_file*, int flags);
+static int vfslogFileSize(sqlite3_file*, sqlite3_int64 *pSize);
+static int vfslogLock(sqlite3_file*, int);
+static int vfslogUnlock(sqlite3_file*, int);
+static int vfslogCheckReservedLock(sqlite3_file*, int *pResOut);
+static int vfslogFileControl(sqlite3_file*, int op, void *pArg);
+static int vfslogSectorSize(sqlite3_file*);
+static int vfslogDeviceCharacteristics(sqlite3_file*);
+
+static int vfslogShmLock(sqlite3_file *pFile, int ofst, int n, int flags);
+static int vfslogShmMap(sqlite3_file *pFile,int,int,int,volatile void **);
+static void vfslogShmBarrier(sqlite3_file*);
+static int vfslogShmUnmap(sqlite3_file *pFile, int deleteFlag);
+
+/*
+** Method declarations for vfslog_vfs.
+*/
+static int vfslogOpen(sqlite3_vfs*, const char *, sqlite3_file*, int , int *);
+static int vfslogDelete(sqlite3_vfs*, const char *zName, int syncDir);
+static int vfslogAccess(sqlite3_vfs*, const char *zName, int flags, int *);
+static int vfslogFullPathname(sqlite3_vfs*, const char *zName, int, char *zOut);
+static void *vfslogDlOpen(sqlite3_vfs*, const char *zFilename);
+static void vfslogDlError(sqlite3_vfs*, int nByte, char *zErrMsg);
+static void (*vfslogDlSym(sqlite3_vfs *pVfs, void *p, const char*zSym))(void);
+static void vfslogDlClose(sqlite3_vfs*, void*);
+static int vfslogRandomness(sqlite3_vfs*, int nByte, char *zOut);
+static int vfslogSleep(sqlite3_vfs*, int microseconds);
+static int vfslogCurrentTime(sqlite3_vfs*, double*);
+
+static int vfslogGetLastError(sqlite3_vfs*, int, char *);
+static int vfslogCurrentTimeInt64(sqlite3_vfs*, sqlite3_int64*);
+
+static sqlite3_vfs vfslog_vfs = {
+  1,                              /* iVersion */
+  sizeof(VfslogFile),             /* szOsFile */
+  INST_MAX_PATHNAME,              /* mxPathname */
+  0,                              /* pNext */
+  0,                              /* zName */
+  0,                              /* pAppData */
+  vfslogOpen,                     /* xOpen */
+  vfslogDelete,                   /* xDelete */
+  vfslogAccess,                   /* xAccess */
+  vfslogFullPathname,             /* xFullPathname */
+  vfslogDlOpen,                   /* xDlOpen */
+  vfslogDlError,                  /* xDlError */
+  vfslogDlSym,                    /* xDlSym */
+  vfslogDlClose,                  /* xDlClose */
+  vfslogRandomness,               /* xRandomness */
+  vfslogSleep,                    /* xSleep */
+  vfslogCurrentTime,              /* xCurrentTime */
+  vfslogGetLastError,             /* xGetLastError */
+  vfslogCurrentTimeInt64          /* xCurrentTime */
+};
+
+static sqlite3_io_methods vfslog_io_methods = {
+  2,                              /* iVersion */
+  vfslogClose,                    /* xClose */
+  vfslogRead,                     /* xRead */
+  vfslogWrite,                    /* xWrite */
+  vfslogTruncate,                 /* xTruncate */
+  vfslogSync,                     /* xSync */
+  vfslogFileSize,                 /* xFileSize */
+  vfslogLock,                     /* xLock */
+  vfslogUnlock,                   /* xUnlock */
+  vfslogCheckReservedLock,        /* xCheckReservedLock */
+  vfslogFileControl,              /* xFileControl */
+  vfslogSectorSize,               /* xSectorSize */
+  vfslogDeviceCharacteristics,    /* xDeviceCharacteristics */
+  vfslogShmMap,                   /* xShmMap */
+  vfslogShmLock,                  /* xShmLock */
+  vfslogShmBarrier,               /* xShmBarrier */
+  vfslogShmUnmap                  /* xShmUnmap */
+};
+
+#if SQLITE_OS_UNIX && !defined(NO_GETTOD)
+#include <sys/time.h>
+static sqlite3_uint64 vfslog_time(){
+  struct timeval sTime;
+  gettimeofday(&sTime, 0);
+  return sTime.tv_usec + (sqlite3_uint64)sTime.tv_sec * 1000000;
+}
+#elif SQLITE_OS_WIN
+#include <windows.h>
+#include <time.h>
+static sqlite3_uint64 vfslog_time(){
+  FILETIME ft;
+  sqlite3_uint64 u64time = 0;
+ 
+  GetSystemTimeAsFileTime(&ft);
+
+  u64time |= ft.dwHighDateTime;
+  u64time <<= 32;
+  u64time |= ft.dwLowDateTime;
+
+  /* ft is 100-nanosecond intervals, we want microseconds */
+  return u64time /(sqlite3_uint64)10;
+}
+#else
+static sqlite3_uint64 vfslog_time(){
+  return 0;
+}
+#endif
+
+static void vfslog_call(sqlite3_vfs *, int, int, int, int, int, int);
+static void vfslog_string(sqlite3_vfs *, const char *);
+
+/*
+** Close an vfslog-file.
+*/
+static int vfslogClose(sqlite3_file *pFile){
+  sqlite3_uint64 t;
+  int rc = SQLITE_OK;
+  VfslogFile *p = (VfslogFile *)pFile;
+
+  t = vfslog_time();
+  if( p->pReal->pMethods ){
+    rc = p->pReal->pMethods->xClose(p->pReal);
+  }
+  t = vfslog_time() - t;
+  vfslog_call(p->pVfslog, OS_CLOSE, p->iFileId, t, rc, 0, 0);
+  return rc;
+}
+
+/*
+** Read data from an vfslog-file.
+*/
+static int vfslogRead(
+  sqlite3_file *pFile, 
+  void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  int rc;
+  sqlite3_uint64 t;
+  VfslogFile *p = (VfslogFile *)pFile;
+  t = vfslog_time();
+  rc = p->pReal->pMethods->xRead(p->pReal, zBuf, iAmt, iOfst);
+  t = vfslog_time() - t;
+  vfslog_call(p->pVfslog, OS_READ, p->iFileId, t, rc, iAmt, (int)iOfst);
+  return rc;
+}
+
+/*
+** Write data to an vfslog-file.
+*/
+static int vfslogWrite(
+  sqlite3_file *pFile,
+  const void *z,
+  int iAmt,
+  sqlite_int64 iOfst
+){
+  int rc;
+  sqlite3_uint64 t;
+  VfslogFile *p = (VfslogFile *)pFile;
+  t = vfslog_time();
+  rc = p->pReal->pMethods->xWrite(p->pReal, z, iAmt, iOfst);
+  t = vfslog_time() - t;
+  vfslog_call(p->pVfslog, OS_WRITE, p->iFileId, t, rc, iAmt, (int)iOfst);
+  return rc;
+}
+
+/*
+** Truncate an vfslog-file.
+*/
+static int vfslogTruncate(sqlite3_file *pFile, sqlite_int64 size){
+  int rc;
+  sqlite3_uint64 t;
+  VfslogFile *p = (VfslogFile *)pFile;
+  t = vfslog_time();
+  rc = p->pReal->pMethods->xTruncate(p->pReal, size);
+  t = vfslog_time() - t;
+  vfslog_call(p->pVfslog, OS_TRUNCATE, p->iFileId, t, rc, 0, (int)size);
+  return rc;
+}
+
+/*
+** Sync an vfslog-file.
+*/
+static int vfslogSync(sqlite3_file *pFile, int flags){
+  int rc;
+  sqlite3_uint64 t;
+  VfslogFile *p = (VfslogFile *)pFile;
+  t = vfslog_time();
+  rc = p->pReal->pMethods->xSync(p->pReal, flags);
+  t = vfslog_time() - t;
+  vfslog_call(p->pVfslog, OS_SYNC, p->iFileId, t, rc, flags, 0);
+  return rc;
+}
+
+/*
+** Return the current file-size of an vfslog-file.
+*/
+static int vfslogFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
+  int rc;
+  sqlite3_uint64 t;
+  VfslogFile *p = (VfslogFile *)pFile;
+  t = vfslog_time();
+  rc = p->pReal->pMethods->xFileSize(p->pReal, pSize);
+  t = vfslog_time() - t;
+  vfslog_call(p->pVfslog, OS_FILESIZE, p->iFileId, t, rc, 0, (int)*pSize);
+  return rc;
+}
+
+/*
+** Lock an vfslog-file.
+*/
+static int vfslogLock(sqlite3_file *pFile, int eLock){
+  int rc;
+  sqlite3_uint64 t;
+  VfslogFile *p = (VfslogFile *)pFile;
+  t = vfslog_time();
+  rc = p->pReal->pMethods->xLock(p->pReal, eLock);
+  t = vfslog_time() - t;
+  vfslog_call(p->pVfslog, OS_LOCK, p->iFileId, t, rc, eLock, 0);
+  return rc;
+}
+
+/*
+** Unlock an vfslog-file.
+*/
+static int vfslogUnlock(sqlite3_file *pFile, int eLock){
+  int rc;
+  sqlite3_uint64 t;
+  VfslogFile *p = (VfslogFile *)pFile;
+  t = vfslog_time();
+  rc = p->pReal->pMethods->xUnlock(p->pReal, eLock);
+  t = vfslog_time() - t;
+  vfslog_call(p->pVfslog, OS_UNLOCK, p->iFileId, t, rc, eLock, 0);
+  return rc;
+}
+
+/*
+** Check if another file-handle holds a RESERVED lock on an vfslog-file.
+*/
+static int vfslogCheckReservedLock(sqlite3_file *pFile, int *pResOut){
+  int rc;
+  sqlite3_uint64 t;
+  VfslogFile *p = (VfslogFile *)pFile;
+  t = vfslog_time();
+  rc = p->pReal->pMethods->xCheckReservedLock(p->pReal, pResOut);
+  t = vfslog_time() - t;
+  vfslog_call(p->pVfslog, OS_CHECKRESERVEDLOCK, p->iFileId, t, rc, *pResOut, 0);
+  return rc;
+}
+
+/*
+** File control method. For custom operations on an vfslog-file.
+*/
+static int vfslogFileControl(sqlite3_file *pFile, int op, void *pArg){
+  VfslogFile *p = (VfslogFile *)pFile;
+  return p->pReal->pMethods->xFileControl(p->pReal, op, pArg);
+}
+
+/*
+** Return the sector-size in bytes for an vfslog-file.
+*/
+static int vfslogSectorSize(sqlite3_file *pFile){
+  int rc;
+  sqlite3_uint64 t;
+  VfslogFile *p = (VfslogFile *)pFile;
+  t = vfslog_time();
+  rc = p->pReal->pMethods->xSectorSize(p->pReal);
+  t = vfslog_time() - t;
+  vfslog_call(p->pVfslog, OS_SECTORSIZE, p->iFileId, t, rc, 0, 0);
+  return rc;
+}
+
+/*
+** Return the device characteristic flags supported by an vfslog-file.
+*/
+static int vfslogDeviceCharacteristics(sqlite3_file *pFile){
+  int rc;
+  sqlite3_uint64 t;
+  VfslogFile *p = (VfslogFile *)pFile;
+  t = vfslog_time();
+  rc = p->pReal->pMethods->xDeviceCharacteristics(p->pReal);
+  t = vfslog_time() - t;
+  vfslog_call(p->pVfslog, OS_DEVCHAR, p->iFileId, t, rc, 0, 0);
+  return rc;
+}
+
+static int vfslogShmLock(sqlite3_file *pFile, int ofst, int n, int flags){
+  int rc;
+  sqlite3_uint64 t;
+  VfslogFile *p = (VfslogFile *)pFile;
+  t = vfslog_time();
+  rc = p->pReal->pMethods->xShmLock(p->pReal, ofst, n, flags);
+  t = vfslog_time() - t;
+  vfslog_call(p->pVfslog, OS_SHMLOCK, p->iFileId, t, rc, 0, 0);
+  return rc;
+}
+static int vfslogShmMap(
+  sqlite3_file *pFile, 
+  int iRegion, 
+  int szRegion, 
+  int isWrite, 
+  volatile void **pp
+){
+  int rc;
+  sqlite3_uint64 t;
+  VfslogFile *p = (VfslogFile *)pFile;
+  t = vfslog_time();
+  rc = p->pReal->pMethods->xShmMap(p->pReal, iRegion, szRegion, isWrite, pp);
+  t = vfslog_time() - t;
+  vfslog_call(p->pVfslog, OS_SHMMAP, p->iFileId, t, rc, 0, 0);
+  return rc;
+}
+static void vfslogShmBarrier(sqlite3_file *pFile){
+  sqlite3_uint64 t;
+  VfslogFile *p = (VfslogFile *)pFile;
+  t = vfslog_time();
+  p->pReal->pMethods->xShmBarrier(p->pReal);
+  t = vfslog_time() - t;
+  vfslog_call(p->pVfslog, OS_SHMBARRIER, p->iFileId, t, SQLITE_OK, 0, 0);
+}
+static int vfslogShmUnmap(sqlite3_file *pFile, int deleteFlag){
+  int rc;
+  sqlite3_uint64 t;
+  VfslogFile *p = (VfslogFile *)pFile;
+  t = vfslog_time();
+  rc = p->pReal->pMethods->xShmUnmap(p->pReal, deleteFlag);
+  t = vfslog_time() - t;
+  vfslog_call(p->pVfslog, OS_SHMUNMAP, p->iFileId, t, rc, 0, 0);
+  return rc;
+}
+
+
+/*
+** Open an vfslog file handle.
+*/
+static int vfslogOpen(
+  sqlite3_vfs *pVfs,
+  const char *zName,
+  sqlite3_file *pFile,
+  int flags,
+  int *pOutFlags
+){
+  int rc;
+  sqlite3_uint64 t;
+  VfslogFile *p = (VfslogFile *)pFile;
+  VfslogVfs *pLog = (VfslogVfs *)pVfs;
+
+  pFile->pMethods = &vfslog_io_methods;
+  p->pReal = (sqlite3_file *)&p[1];
+  p->pVfslog = pVfs;
+  p->iFileId = ++pLog->iNextFileId;
+
+  t = vfslog_time();
+  rc = REALVFS(pVfs)->xOpen(REALVFS(pVfs), zName, p->pReal, flags, pOutFlags);
+  t = vfslog_time() - t;
+
+  vfslog_call(pVfs, OS_OPEN, p->iFileId, t, rc, 0, 0);
+  vfslog_string(pVfs, zName);
+  return rc;
+}
+
+/*
+** Delete the file located at zPath. If the dirSync argument is true,
+** ensure the file-system modifications are synced to disk before
+** returning.
+*/
+static int vfslogDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
+  int rc;
+  sqlite3_uint64 t;
+  t = vfslog_time();
+  rc = REALVFS(pVfs)->xDelete(REALVFS(pVfs), zPath, dirSync);
+  t = vfslog_time() - t;
+  vfslog_call(pVfs, OS_DELETE, 0, t, rc, dirSync, 0);
+  vfslog_string(pVfs, zPath);
+  return rc;
+}
+
+/*
+** Test for access permissions. Return true if the requested permission
+** is available, or false otherwise.
+*/
+static int vfslogAccess(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  int flags, 
+  int *pResOut
+){
+  int rc;
+  sqlite3_uint64 t;
+  t = vfslog_time();
+  rc = REALVFS(pVfs)->xAccess(REALVFS(pVfs), zPath, flags, pResOut);
+  t = vfslog_time() - t;
+  vfslog_call(pVfs, OS_ACCESS, 0, t, rc, flags, *pResOut);
+  vfslog_string(pVfs, zPath);
+  return rc;
+}
+
+/*
+** Populate buffer zOut with the full canonical pathname corresponding
+** to the pathname in zPath. zOut is guaranteed to point to a buffer
+** of at least (INST_MAX_PATHNAME+1) bytes.
+*/
+static int vfslogFullPathname(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  int nOut, 
+  char *zOut
+){
+  return REALVFS(pVfs)->xFullPathname(REALVFS(pVfs), zPath, nOut, zOut);
+}
+
+/*
+** Open the dynamic library located at zPath and return a handle.
+*/
+static void *vfslogDlOpen(sqlite3_vfs *pVfs, const char *zPath){
+  return REALVFS(pVfs)->xDlOpen(REALVFS(pVfs), zPath);
+}
+
+/*
+** Populate the buffer zErrMsg (size nByte bytes) with a human readable
+** utf-8 string describing the most recent error encountered associated 
+** with dynamic libraries.
+*/
+static void vfslogDlError(sqlite3_vfs *pVfs, int nByte, char *zErrMsg){
+  REALVFS(pVfs)->xDlError(REALVFS(pVfs), nByte, zErrMsg);
+}
+
+/*
+** Return a pointer to the symbol zSymbol in the dynamic library pHandle.
+*/
+static void (*vfslogDlSym(sqlite3_vfs *pVfs, void *p, const char *zSym))(void){
+  return REALVFS(pVfs)->xDlSym(REALVFS(pVfs), p, zSym);
+}
+
+/*
+** Close the dynamic library handle pHandle.
+*/
+static void vfslogDlClose(sqlite3_vfs *pVfs, void *pHandle){
+  REALVFS(pVfs)->xDlClose(REALVFS(pVfs), pHandle);
+}
+
+/*
+** Populate the buffer pointed to by zBufOut with nByte bytes of 
+** random data.
+*/
+static int vfslogRandomness(sqlite3_vfs *pVfs, int nByte, char *zBufOut){
+  return REALVFS(pVfs)->xRandomness(REALVFS(pVfs), nByte, zBufOut);
+}
+
+/*
+** Sleep for nMicro microseconds. Return the number of microseconds 
+** actually slept.
+*/
+static int vfslogSleep(sqlite3_vfs *pVfs, int nMicro){
+  return REALVFS(pVfs)->xSleep(REALVFS(pVfs), nMicro);
+}
+
+/*
+** Return the current time as a Julian Day number in *pTimeOut.
+*/
+static int vfslogCurrentTime(sqlite3_vfs *pVfs, double *pTimeOut){
+  return REALVFS(pVfs)->xCurrentTime(REALVFS(pVfs), pTimeOut);
+}
+
+static int vfslogGetLastError(sqlite3_vfs *pVfs, int a, char *b){
+  return REALVFS(pVfs)->xGetLastError(REALVFS(pVfs), a, b);
+}
+static int vfslogCurrentTimeInt64(sqlite3_vfs *pVfs, sqlite3_int64 *p){
+  return REALVFS(pVfs)->xCurrentTimeInt64(REALVFS(pVfs), p);
+}
+
+static void vfslog_flush(VfslogVfs *p){
+#ifdef SQLITE_TEST
+  extern int sqlite3_io_error_pending;
+  extern int sqlite3_io_error_persist;
+  extern int sqlite3_diskfull_pending;
+
+  int pending = sqlite3_io_error_pending;
+  int persist = sqlite3_io_error_persist;
+  int diskfull = sqlite3_diskfull_pending;
+
+  sqlite3_io_error_pending = 0;
+  sqlite3_io_error_persist = 0;
+  sqlite3_diskfull_pending = 0;
+#endif
+
+  if( p->nBuf ){
+    p->pLog->pMethods->xWrite(p->pLog, p->aBuf, p->nBuf, p->iOffset);
+    p->iOffset += p->nBuf;
+    p->nBuf = 0;
+  }
+
+#ifdef SQLITE_TEST
+  sqlite3_io_error_pending = pending;
+  sqlite3_io_error_persist = persist;
+  sqlite3_diskfull_pending = diskfull;
+#endif
+}
+
+static void put32bits(unsigned char *p, unsigned int v){
+  p[0] = v>>24;
+  p[1] = v>>16;
+  p[2] = v>>8;
+  p[3] = v;
+}
+
+static void vfslog_call(
+  sqlite3_vfs *pVfs,
+  int eEvent,
+  int iFileid,
+  int nClick,
+  int return_code,
+  int size,
+  int offset
+){
+  VfslogVfs *p = (VfslogVfs *)pVfs;
+  unsigned char *zRec;
+  if( (24+p->nBuf)>sizeof(p->aBuf) ){
+    vfslog_flush(p);
+  }
+  zRec = (unsigned char *)&p->aBuf[p->nBuf];
+  put32bits(&zRec[0], eEvent);
+  put32bits(&zRec[4], iFileid);
+  put32bits(&zRec[8], nClick);
+  put32bits(&zRec[12], return_code);
+  put32bits(&zRec[16], size);
+  put32bits(&zRec[20], offset);
+  p->nBuf += 24;
+}
+
+static void vfslog_string(sqlite3_vfs *pVfs, const char *zStr){
+  VfslogVfs *p = (VfslogVfs *)pVfs;
+  unsigned char *zRec;
+  int nStr = zStr ? strlen(zStr) : 0;
+  if( (4+nStr+p->nBuf)>sizeof(p->aBuf) ){
+    vfslog_flush(p);
+  }
+  zRec = (unsigned char *)&p->aBuf[p->nBuf];
+  put32bits(&zRec[0], nStr);
+  if( zStr ){
+    memcpy(&zRec[4], zStr, nStr);
+  }
+  p->nBuf += (4 + nStr);
+}
+
+static void vfslog_finalize(VfslogVfs *p){
+  if( p->pLog->pMethods ){
+    vfslog_flush(p);
+    p->pLog->pMethods->xClose(p->pLog);
+  }
+  sqlite3_free(p);
+}
+
+int sqlite3_vfslog_finalize(const char *zVfs){
+  sqlite3_vfs *pVfs;
+  pVfs = sqlite3_vfs_find(zVfs);
+  if( !pVfs || pVfs->xOpen!=vfslogOpen ){
+    return SQLITE_ERROR;
+  } 
+  sqlite3_vfs_unregister(pVfs);
+  vfslog_finalize((VfslogVfs *)pVfs);
+  return SQLITE_OK;
+}
+
+int sqlite3_vfslog_new(
+  const char *zVfs,               /* New VFS name */
+  const char *zParentVfs,         /* Parent VFS name (or NULL) */
+  const char *zLog                /* Log file name */
+){
+  VfslogVfs *p;
+  sqlite3_vfs *pParent;
+  int nByte;
+  int flags;
+  int rc;
+  char *zFile;
+  int nVfs;
+
+  pParent = sqlite3_vfs_find(zParentVfs);
+  if( !pParent ){
+    return SQLITE_ERROR;
+  }
+
+  nVfs = strlen(zVfs);
+  nByte = sizeof(VfslogVfs) + pParent->szOsFile + nVfs+1+pParent->mxPathname+1;
+  p = (VfslogVfs *)sqlite3_malloc(nByte);
+  memset(p, 0, nByte);
+
+  p->pVfs = pParent;
+  p->pLog = (sqlite3_file *)&p[1];
+  memcpy(&p->base, &vfslog_vfs, sizeof(sqlite3_vfs));
+  p->base.zName = &((char *)p->pLog)[pParent->szOsFile];
+  p->base.szOsFile += pParent->szOsFile;
+  memcpy((char *)p->base.zName, zVfs, nVfs);
+
+  zFile = (char *)&p->base.zName[nVfs+1];
+  pParent->xFullPathname(pParent, zLog, pParent->mxPathname, zFile);
+
+  flags = SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE|SQLITE_OPEN_MASTER_JOURNAL;
+  pParent->xDelete(pParent, zFile, 0);
+  rc = pParent->xOpen(pParent, zFile, p->pLog, flags, &flags);
+  if( rc==SQLITE_OK ){
+    memcpy(p->aBuf, "sqlite_ostrace1.....", 20);
+    p->iOffset = 0;
+    p->nBuf = 20;
+    rc = sqlite3_vfs_register((sqlite3_vfs *)p, 1);
+  }
+  if( rc ){
+    vfslog_finalize(p);
+  }
+  return rc;
+}
+
+int sqlite3_vfslog_annotate(const char *zVfs, const char *zMsg){
+  sqlite3_vfs *pVfs;
+  pVfs = sqlite3_vfs_find(zVfs);
+  if( !pVfs || pVfs->xOpen!=vfslogOpen ){
+    return SQLITE_ERROR;
+  } 
+  vfslog_call(pVfs, OS_ANNOTATE, 0, 0, 0, 0, 0);
+  vfslog_string(pVfs, zMsg);
+  return SQLITE_OK;
+}
+
+static const char *vfslog_eventname(int eEvent){
+  const char *zEvent = 0;
+
+  switch( eEvent ){
+    case OS_CLOSE:             zEvent = "xClose"; break;
+    case OS_READ:              zEvent = "xRead"; break;
+    case OS_WRITE:             zEvent = "xWrite"; break;
+    case OS_TRUNCATE:          zEvent = "xTruncate"; break;
+    case OS_SYNC:              zEvent = "xSync"; break;
+    case OS_FILESIZE:          zEvent = "xFilesize"; break;
+    case OS_LOCK:              zEvent = "xLock"; break;
+    case OS_UNLOCK:            zEvent = "xUnlock"; break;
+    case OS_CHECKRESERVEDLOCK: zEvent = "xCheckResLock"; break;
+    case OS_FILECONTROL:       zEvent = "xFileControl"; break;
+    case OS_SECTORSIZE:        zEvent = "xSectorSize"; break;
+    case OS_DEVCHAR:           zEvent = "xDeviceChar"; break;
+    case OS_OPEN:              zEvent = "xOpen"; break;
+    case OS_DELETE:            zEvent = "xDelete"; break;
+    case OS_ACCESS:            zEvent = "xAccess"; break;
+    case OS_FULLPATHNAME:      zEvent = "xFullPathname"; break;
+    case OS_RANDOMNESS:        zEvent = "xRandomness"; break;
+    case OS_SLEEP:             zEvent = "xSleep"; break;
+    case OS_CURRENTTIME:       zEvent = "xCurrentTime"; break;
+
+    case OS_SHMUNMAP:          zEvent = "xShmUnmap"; break;
+    case OS_SHMLOCK:           zEvent = "xShmLock"; break;
+    case OS_SHMBARRIER:        zEvent = "xShmBarrier"; break;
+    case OS_SHMMAP:            zEvent = "xShmMap"; break;
+
+    case OS_ANNOTATE:          zEvent = "annotation"; break;
+  }
+
+  return zEvent;
+}
+
+typedef struct VfslogVtab VfslogVtab;
+typedef struct VfslogCsr VfslogCsr;
+
+/*
+** Virtual table type for the vfslog reader module.
+*/
+struct VfslogVtab {
+  sqlite3_vtab base;              /* Base class */
+  sqlite3_file *pFd;              /* File descriptor open on vfslog file */
+  sqlite3_int64 nByte;            /* Size of file in bytes */
+  char *zFile;                    /* File name for pFd */
+};
+
+/*
+** Virtual table cursor type for the vfslog reader module.
+*/
+struct VfslogCsr {
+  sqlite3_vtab_cursor base;       /* Base class */
+  sqlite3_int64 iRowid;           /* Current rowid. */
+  sqlite3_int64 iOffset;          /* Offset of next record in file */
+  char *zTransient;               /* Transient 'file' string */
+  int nFile;                      /* Size of array azFile[] */
+  char **azFile;                  /* File strings */
+  unsigned char aBuf[1024];       /* Current vfs log entry (read from file) */
+};
+
+static unsigned int get32bits(unsigned char *p){
+  return (p[0]<<24) + (p[1]<<16) + (p[2]<<8) + p[3];
+}
+
+/*
+** The argument must point to a buffer containing a nul-terminated string.
+** If the string begins with an SQL quote character it is overwritten by
+** the dequoted version. Otherwise the buffer is left unmodified.
+*/
+static void dequote(char *z){
+  char quote;                     /* Quote character (if any ) */
+  quote = z[0];
+  if( quote=='[' || quote=='\'' || quote=='"' || quote=='`' ){
+    int iIn = 1;                  /* Index of next byte to read from input */
+    int iOut = 0;                 /* Index of next byte to write to output */
+    if( quote=='[' ) quote = ']';  
+    while( z[iIn] ){
+      if( z[iIn]==quote ){
+        if( z[iIn+1]!=quote ) break;
+        z[iOut++] = quote;
+        iIn += 2;
+      }else{
+        z[iOut++] = z[iIn++];
+      }
+    }
+    z[iOut] = '\0';
+  }
+}
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/*
+** Connect to or create a vfslog virtual table.
+*/
+static int vlogConnect(
+  sqlite3 *db,
+  void *pAux,
+  int argc, const char *const*argv,
+  sqlite3_vtab **ppVtab,
+  char **pzErr
+){
+  sqlite3_vfs *pVfs;              /* VFS used to read log file */
+  int flags;                      /* flags passed to pVfs->xOpen() */
+  VfslogVtab *p;
+  int rc;
+  int nByte;
+  char *zFile;
+
+  *ppVtab = 0;
+  pVfs = sqlite3_vfs_find(0);
+  nByte = sizeof(VfslogVtab) + pVfs->szOsFile + pVfs->mxPathname;
+  p = sqlite3_malloc(nByte);
+  if( p==0 ) return SQLITE_NOMEM;
+  memset(p, 0, nByte);
+
+  p->pFd = (sqlite3_file *)&p[1];
+  p->zFile = &((char *)p->pFd)[pVfs->szOsFile];
+
+  zFile = sqlite3_mprintf("%s", argv[3]);
+  if( !zFile ){
+    sqlite3_free(p);
+    return SQLITE_NOMEM;
+  }
+  dequote(zFile);
+  pVfs->xFullPathname(pVfs, zFile, pVfs->mxPathname, p->zFile);
+  sqlite3_free(zFile);
+
+  flags = SQLITE_OPEN_READWRITE|SQLITE_OPEN_MASTER_JOURNAL;
+  rc = pVfs->xOpen(pVfs, p->zFile, p->pFd, flags, &flags);
+
+  if( rc==SQLITE_OK ){
+    p->pFd->pMethods->xFileSize(p->pFd, &p->nByte);
+    sqlite3_declare_vtab(db, 
+        "CREATE TABLE xxx(event, file, click, rc, size, offset)"
+    );
+    *ppVtab = &p->base;
+  }else{
+    sqlite3_free(p);
+  }
+
+  return rc;
+}
+
+/*
+** There is no "best-index". This virtual table always does a linear
+** scan of the binary VFS log file.
+*/
+static int vlogBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
+  pIdxInfo->estimatedCost = 10.0;
+  return SQLITE_OK;
+}
+
+/*
+** Disconnect from or destroy a vfslog virtual table.
+*/
+static int vlogDisconnect(sqlite3_vtab *pVtab){
+  VfslogVtab *p = (VfslogVtab *)pVtab;
+  if( p->pFd->pMethods ){
+    p->pFd->pMethods->xClose(p->pFd);
+    p->pFd->pMethods = 0;
+  }
+  sqlite3_free(p);
+  return SQLITE_OK;
+}
+
+/*
+** Open a new vfslog cursor.
+*/
+static int vlogOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
+  VfslogCsr *pCsr;                /* Newly allocated cursor object */
+
+  pCsr = sqlite3_malloc(sizeof(VfslogCsr));
+  if( !pCsr ) return SQLITE_NOMEM;
+  memset(pCsr, 0, sizeof(VfslogCsr));
+  *ppCursor = &pCsr->base;
+  return SQLITE_OK;
+}
+
+/*
+** Close a vfslog cursor.
+*/
+static int vlogClose(sqlite3_vtab_cursor *pCursor){
+  VfslogCsr *p = (VfslogCsr *)pCursor;
+  int i;
+  for(i=0; i<p->nFile; i++){
+    sqlite3_free(p->azFile[i]);
+  }
+  sqlite3_free(p->azFile);
+  sqlite3_free(p->zTransient);
+  sqlite3_free(p);
+  return SQLITE_OK;
+}
+
+/*
+** Move a vfslog cursor to the next entry in the file.
+*/
+static int vlogNext(sqlite3_vtab_cursor *pCursor){
+  VfslogCsr *pCsr = (VfslogCsr *)pCursor;
+  VfslogVtab *p = (VfslogVtab *)pCursor->pVtab;
+  int rc = SQLITE_OK;
+  int nRead;
+
+  sqlite3_free(pCsr->zTransient);
+  pCsr->zTransient = 0;
+
+  nRead = 24;
+  if( pCsr->iOffset+nRead<=p->nByte ){
+    int eEvent;
+    rc = p->pFd->pMethods->xRead(p->pFd, pCsr->aBuf, nRead, pCsr->iOffset);
+
+    eEvent = get32bits(pCsr->aBuf);
+    if( (rc==SQLITE_OK)
+     && (eEvent==OS_OPEN || eEvent==OS_DELETE || eEvent==OS_ACCESS) 
+    ){
+      char buf[4];
+      rc = p->pFd->pMethods->xRead(p->pFd, buf, 4, pCsr->iOffset+nRead);
+      nRead += 4;
+      if( rc==SQLITE_OK ){
+        int nStr = get32bits((unsigned char *)buf);
+        char *zStr = sqlite3_malloc(nStr+1);
+        rc = p->pFd->pMethods->xRead(p->pFd, zStr, nStr, pCsr->iOffset+nRead);
+        zStr[nStr] = '\0';
+        nRead += nStr;
+
+        if( eEvent==OS_OPEN ){
+          int iFileid = get32bits(&pCsr->aBuf[4]);
+          if( iFileid>=pCsr->nFile ){
+            int nNew = sizeof(pCsr->azFile[0])*(iFileid+1);
+            pCsr->azFile = (char **)sqlite3_realloc(pCsr->azFile, nNew);
+            nNew -= sizeof(pCsr->azFile[0])*pCsr->nFile;
+            memset(&pCsr->azFile[pCsr->nFile], 0, nNew);
+            pCsr->nFile = iFileid+1;
+          }
+          sqlite3_free(pCsr->azFile[iFileid]);
+          pCsr->azFile[iFileid] = zStr;
+        }else{
+          pCsr->zTransient = zStr;
+        }
+      }
+    }
+  }
+
+  pCsr->iRowid += 1;
+  pCsr->iOffset += nRead;
+  return rc;
+}
+
+static int vlogEof(sqlite3_vtab_cursor *pCursor){
+  VfslogCsr *pCsr = (VfslogCsr *)pCursor;
+  VfslogVtab *p = (VfslogVtab *)pCursor->pVtab;
+  return (pCsr->iOffset>=p->nByte);
+}
+
+static int vlogFilter(
+  sqlite3_vtab_cursor *pCursor, 
+  int idxNum, const char *idxStr,
+  int argc, sqlite3_value **argv
+){
+  VfslogCsr *pCsr = (VfslogCsr *)pCursor;
+  pCsr->iRowid = 0;
+  pCsr->iOffset = 20;
+  return vlogNext(pCursor);
+}
+
+static int vlogColumn(
+  sqlite3_vtab_cursor *pCursor, 
+  sqlite3_context *ctx, 
+  int i
+){
+  unsigned int val;
+  VfslogCsr *pCsr = (VfslogCsr *)pCursor;
+
+  assert( i<7 );
+  val = get32bits(&pCsr->aBuf[4*i]);
+
+  switch( i ){
+    case 0: {
+      sqlite3_result_text(ctx, vfslog_eventname(val), -1, SQLITE_STATIC);
+      break;
+    }
+    case 1: {
+      char *zStr = pCsr->zTransient;
+      if( val!=0 && val<pCsr->nFile ){
+        zStr = pCsr->azFile[val];
+      }
+      sqlite3_result_text(ctx, zStr, -1, SQLITE_TRANSIENT);
+      break;
+    }
+    default:
+      sqlite3_result_int(ctx, val);
+      break;
+  }
+
+  return SQLITE_OK;
+}
+
+static int vlogRowid(sqlite3_vtab_cursor *pCursor, sqlite_int64 *pRowid){
+  VfslogCsr *pCsr = (VfslogCsr *)pCursor;
+  *pRowid = pCsr->iRowid;
+  return SQLITE_OK;
+}
+
+int sqlite3_vfslog_register(sqlite3 *db){
+  static sqlite3_module vfslog_module = {
+    0,                            /* iVersion */
+    vlogConnect,                /* xCreate */
+    vlogConnect,                /* xConnect */
+    vlogBestIndex,              /* xBestIndex */
+    vlogDisconnect,             /* xDisconnect */
+    vlogDisconnect,             /* xDestroy */
+    vlogOpen,                   /* xOpen - open a cursor */
+    vlogClose,                  /* xClose - close a cursor */
+    vlogFilter,                 /* xFilter - configure scan constraints */
+    vlogNext,                   /* xNext - advance a cursor */
+    vlogEof,                    /* xEof - check for end of scan */
+    vlogColumn,                 /* xColumn - read data */
+    vlogRowid,                  /* xRowid - read data */
+    0,                            /* xUpdate */
+    0,                            /* xBegin */
+    0,                            /* xSync */
+    0,                            /* xCommit */
+    0,                            /* xRollback */
+    0,                            /* xFindMethod */
+    0,                            /* xRename */
+  };
+
+  sqlite3_create_module(db, "vfslog", &vfslog_module, 0);
+  return SQLITE_OK;
+}
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+/**************************************************************************
+***************************************************************************
+** Tcl interface starts here.
+*/
+
+#if defined(SQLITE_TEST) || defined(TCLSH)
+
+#include <tcl.h>
+
+static int test_vfslog(
+  void *clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  struct SqliteDb { sqlite3 *db; };
+  sqlite3 *db;
+  Tcl_CmdInfo cmdInfo;
+  int rc = SQLITE_ERROR;
+
+  static const char *strs[] = { "annotate", "finalize", "new",  "register", 0 };
+  enum VL_enum { VL_ANNOTATE, VL_FINALIZE, VL_NEW, VL_REGISTER };
+  int iSub;
+
+  if( objc<2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "SUB-COMMAND ...");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIndexFromObj(interp, objv[1], strs, "sub-command", 0, &iSub) ){
+    return TCL_ERROR;
+  }
+
+  switch( (enum VL_enum)iSub ){
+    case VL_ANNOTATE: {
+      int rc;
+      char *zVfs;
+      char *zMsg;
+      if( objc!=4 ){
+        Tcl_WrongNumArgs(interp, 3, objv, "VFS");
+        return TCL_ERROR;
+      }
+      zVfs = Tcl_GetString(objv[2]);
+      zMsg = Tcl_GetString(objv[3]);
+      rc = sqlite3_vfslog_annotate(zVfs, zMsg);
+      if( rc!=SQLITE_OK ){
+        Tcl_AppendResult(interp, "failed", 0);
+        return TCL_ERROR;
+      }
+      break;
+    }
+    case VL_FINALIZE: {
+      int rc;
+      char *zVfs;
+      if( objc!=3 ){
+        Tcl_WrongNumArgs(interp, 2, objv, "VFS");
+        return TCL_ERROR;
+      }
+      zVfs = Tcl_GetString(objv[2]);
+      rc = sqlite3_vfslog_finalize(zVfs);
+      if( rc!=SQLITE_OK ){
+        Tcl_AppendResult(interp, "failed", 0);
+        return TCL_ERROR;
+      }
+      break;
+    };
+
+    case VL_NEW: {
+      int rc;
+      char *zVfs;
+      char *zParent;
+      char *zLog;
+      if( objc!=5 ){
+        Tcl_WrongNumArgs(interp, 2, objv, "VFS PARENT LOGFILE");
+        return TCL_ERROR;
+      }
+      zVfs = Tcl_GetString(objv[2]);
+      zParent = Tcl_GetString(objv[3]);
+      zLog = Tcl_GetString(objv[4]);
+      if( *zParent=='\0' ) zParent = 0;
+      rc = sqlite3_vfslog_new(zVfs, zParent, zLog);
+      if( rc!=SQLITE_OK ){
+        Tcl_AppendResult(interp, "failed", 0);
+        return TCL_ERROR;
+      }
+      break;
+    };
+
+    case VL_REGISTER: {
+      char *zDb;
+      if( objc!=3 ){
+        Tcl_WrongNumArgs(interp, 2, objv, "DB");
+        return TCL_ERROR;
+      }
+#ifdef SQLITE_OMIT_VIRTUALTABLE
+      Tcl_AppendResult(interp, "vfslog not available because of "
+                               "SQLITE_OMIT_VIRTUALTABLE", (void*)0);
+      return TCL_ERROR;
+#else
+      zDb = Tcl_GetString(objv[2]);
+      if( Tcl_GetCommandInfo(interp, zDb, &cmdInfo) ){
+        db = ((struct SqliteDb*)cmdInfo.objClientData)->db;
+        rc = sqlite3_vfslog_register(db);
+      }
+      if( rc!=SQLITE_OK ){
+        Tcl_AppendResult(interp, "bad sqlite3 handle: ", zDb, (void*)0);
+        return TCL_ERROR;
+      }
+      break;
+#endif
+    }
+  }
+
+  return TCL_OK;
+}
+
+int SqlitetestOsinst_Init(Tcl_Interp *interp){
+  Tcl_CreateObjCommand(interp, "vfslog", test_vfslog, 0, 0);
+  return TCL_OK;
+}
+
+#endif /* SQLITE_TEST */
diff --git a/src/test_pcache.c b/src/test_pcache.c
new file mode 100644
index 0000000..98aa136
--- /dev/null
+++ b/src/test_pcache.c
@@ -0,0 +1,458 @@
+/*
+** 2008 November 18
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** 
+** This file contains code used for testing the SQLite system.
+** None of the code in this file goes into a deliverable build.
+** 
+** This file contains an application-defined pager cache
+** implementation that can be plugged in in place of the
+** default pcache.  This alternative pager cache will throw
+** some errors that the default cache does not.
+**
+** This pagecache implementation is designed for simplicity
+** not speed.  
+*/
+#include "sqlite3.h"
+#include <string.h>
+#include <assert.h>
+
+/*
+** Global data used by this test implementation.  There is no
+** mutexing, which means this page cache will not work in a
+** multi-threaded test.
+*/
+typedef struct testpcacheGlobalType testpcacheGlobalType;
+struct testpcacheGlobalType {
+  void *pDummy;             /* Dummy allocation to simulate failures */
+  int nInstance;            /* Number of current instances */
+  unsigned discardChance;   /* Chance of discarding on an unpin (0-100) */
+  unsigned prngSeed;        /* Seed for the PRNG */
+  unsigned highStress;      /* Call xStress agressively */
+};
+static testpcacheGlobalType testpcacheGlobal;
+
+/*
+** Initializer.
+**
+** Verify that the initializer is only called when the system is
+** uninitialized.  Allocate some memory and report SQLITE_NOMEM if
+** the allocation fails.  This provides a means to test the recovery
+** from a failed initialization attempt.  It also verifies that the
+** the destructor always gets call - otherwise there would be a
+** memory leak.
+*/
+static int testpcacheInit(void *pArg){
+  assert( pArg==(void*)&testpcacheGlobal );
+  assert( testpcacheGlobal.pDummy==0 );
+  assert( testpcacheGlobal.nInstance==0 );
+  testpcacheGlobal.pDummy = sqlite3_malloc(10);
+  return testpcacheGlobal.pDummy==0 ? SQLITE_NOMEM : SQLITE_OK;
+}
+
+/*
+** Destructor
+**
+** Verify that this is only called after initialization.
+** Free the memory allocated by the initializer.
+*/
+static void testpcacheShutdown(void *pArg){
+  assert( pArg==(void*)&testpcacheGlobal );
+  assert( testpcacheGlobal.pDummy!=0 );
+  assert( testpcacheGlobal.nInstance==0 );
+  sqlite3_free( testpcacheGlobal.pDummy );
+  testpcacheGlobal.pDummy = 0;
+}
+
+/*
+** Number of pages in a cache.
+**
+** The number of pages is a hard upper bound in this test module.
+** If more pages are requested, sqlite3PcacheFetch() returns NULL.
+**
+** If testing with in-memory temp tables, provide a larger pcache.
+** Some of the test cases need this.
+*/
+#if defined(SQLITE_TEMP_STORE) && SQLITE_TEMP_STORE>=2
+# define TESTPCACHE_NPAGE    499
+#else
+# define TESTPCACHE_NPAGE    217
+#endif
+#define TESTPCACHE_RESERVE   17
+
+/*
+** Magic numbers used to determine validity of the page cache.
+*/
+#define TESTPCACHE_VALID  0x364585fd
+#define TESTPCACHE_CLEAR  0xd42670d4
+
+/*
+** Private implementation of a page cache.
+*/
+typedef struct testpcache testpcache;
+struct testpcache {
+  int szPage;               /* Size of each page.  Multiple of 8. */
+  int bPurgeable;           /* True if the page cache is purgeable */
+  int nFree;                /* Number of unused slots in a[] */
+  int nPinned;              /* Number of pinned slots in a[] */
+  unsigned iRand;           /* State of the PRNG */
+  unsigned iMagic;          /* Magic number for sanity checking */
+  struct testpcachePage {
+    unsigned key;              /* The key for this page. 0 means unallocated */
+    int isPinned;              /* True if the page is pinned */
+    void *pData;               /* Data for this page */
+  } a[TESTPCACHE_NPAGE];    /* All pages in the cache */
+};
+
+/*
+** Get a random number using the PRNG in the given page cache.
+*/
+static unsigned testpcacheRandom(testpcache *p){
+  unsigned x = 0;
+  int i;
+  for(i=0; i<4; i++){
+    p->iRand = (p->iRand*69069 + 5);
+    x = (x<<8) | ((p->iRand>>16)&0xff);
+  }
+  return x;
+}
+
+
+/*
+** Allocate a new page cache instance.
+*/
+static sqlite3_pcache *testpcacheCreate(int szPage, int bPurgeable){
+  int nMem;
+  char *x;
+  testpcache *p;
+  int i;
+  assert( testpcacheGlobal.pDummy!=0 );
+  szPage = (szPage+7)&~7;
+  nMem = sizeof(testpcache) + TESTPCACHE_NPAGE*szPage;
+  p = sqlite3_malloc( nMem );
+  if( p==0 ) return 0;
+  x = (char*)&p[1];
+  p->szPage = szPage;
+  p->nFree = TESTPCACHE_NPAGE;
+  p->nPinned = 0;
+  p->iRand = testpcacheGlobal.prngSeed;
+  p->bPurgeable = bPurgeable;
+  p->iMagic = TESTPCACHE_VALID;
+  for(i=0; i<TESTPCACHE_NPAGE; i++, x += szPage){
+    p->a[i].key = 0;
+    p->a[i].isPinned = 0;
+    p->a[i].pData = (void*)x;
+  }
+  testpcacheGlobal.nInstance++;
+  return (sqlite3_pcache*)p;
+}
+
+/*
+** Set the cache size
+*/
+static void testpcacheCachesize(sqlite3_pcache *pCache, int newSize){
+  testpcache *p = (testpcache*)pCache;
+  assert( p->iMagic==TESTPCACHE_VALID );
+  assert( newSize>=1 );
+  assert( testpcacheGlobal.pDummy!=0 );
+  assert( testpcacheGlobal.nInstance>0 );
+}
+
+/*
+** Return the number of pages in the cache that are being used.
+** This includes both pinned and unpinned pages.
+*/
+static int testpcachePagecount(sqlite3_pcache *pCache){
+  testpcache *p = (testpcache*)pCache;
+  assert( p->iMagic==TESTPCACHE_VALID );
+  assert( testpcacheGlobal.pDummy!=0 );
+  assert( testpcacheGlobal.nInstance>0 );
+  return TESTPCACHE_NPAGE - p->nFree;
+}
+
+/*
+** Fetch a page.
+*/
+static void *testpcacheFetch(
+  sqlite3_pcache *pCache,
+  unsigned key,
+  int createFlag
+){
+  testpcache *p = (testpcache*)pCache;
+  int i, j;
+  assert( p->iMagic==TESTPCACHE_VALID );
+  assert( testpcacheGlobal.pDummy!=0 );
+  assert( testpcacheGlobal.nInstance>0 );
+
+  /* See if the page is already in cache.  Return immediately if it is */
+  for(i=0; i<TESTPCACHE_NPAGE; i++){
+    if( p->a[i].key==key ){
+      if( !p->a[i].isPinned ){
+        p->nPinned++;
+        assert( p->nPinned <= TESTPCACHE_NPAGE - p->nFree );
+        p->a[i].isPinned = 1;
+      }
+      return p->a[i].pData;
+    }
+  }
+
+  /* If createFlag is 0, never allocate a new page */
+  if( createFlag==0 ){
+    return 0;
+  }
+
+  /* If no pages are available, always fail */
+  if( p->nPinned==TESTPCACHE_NPAGE ){
+    return 0;
+  }
+
+  /* Do not allocate the last TESTPCACHE_RESERVE pages unless createFlag is 2 */
+  if( p->nPinned>=TESTPCACHE_NPAGE-TESTPCACHE_RESERVE && createFlag<2 ){
+    return 0;
+  }
+
+  /* Do not allocate if highStress is enabled and createFlag is not 2.  
+  **
+  ** The highStress setting causes pagerStress() to be called much more
+  ** often, which exercises the pager logic more intensely.
+  */
+  if( testpcacheGlobal.highStress && createFlag<2 ){
+    return 0;
+  }
+
+  /* Find a free page to allocate if there are any free pages.
+  ** Withhold TESTPCACHE_RESERVE free pages until createFlag is 2.
+  */
+  if( p->nFree>TESTPCACHE_RESERVE || (createFlag==2 && p->nFree>0) ){
+    j = testpcacheRandom(p) % TESTPCACHE_NPAGE;
+    for(i=0; i<TESTPCACHE_NPAGE; i++, j = (j+1)%TESTPCACHE_NPAGE){
+      if( p->a[j].key==0 ){
+        p->a[j].key = key;
+        p->a[j].isPinned = 1;
+        memset(p->a[j].pData, 0, p->szPage);
+        p->nPinned++;
+        p->nFree--;
+        assert( p->nPinned <= TESTPCACHE_NPAGE - p->nFree );
+        return p->a[j].pData;
+      }
+    }
+
+    /* The prior loop always finds a freepage to allocate */
+    assert( 0 );
+  }
+
+  /* If this cache is not purgeable then we have to fail.
+  */
+  if( p->bPurgeable==0 ){
+    return 0;
+  }
+
+  /* If there are no free pages, recycle a page.  The page to
+  ** recycle is selected at random from all unpinned pages.
+  */
+  j = testpcacheRandom(p) % TESTPCACHE_NPAGE;
+  for(i=0; i<TESTPCACHE_NPAGE; i++, j = (j+1)%TESTPCACHE_NPAGE){
+    if( p->a[j].key>0 && p->a[j].isPinned==0 ){
+      p->a[j].key = key;
+      p->a[j].isPinned = 1;
+      memset(p->a[j].pData, 0, p->szPage);
+      p->nPinned++;
+      assert( p->nPinned <= TESTPCACHE_NPAGE - p->nFree );
+      return p->a[j].pData;
+    }
+  }
+
+  /* The previous loop always finds a page to recycle. */
+  assert(0);
+  return 0;
+}
+
+/*
+** Unpin a page.
+*/
+static void testpcacheUnpin(
+  sqlite3_pcache *pCache,
+  void *pOldPage,
+  int discard
+){
+  testpcache *p = (testpcache*)pCache;
+  int i;
+  assert( p->iMagic==TESTPCACHE_VALID );
+  assert( testpcacheGlobal.pDummy!=0 );
+  assert( testpcacheGlobal.nInstance>0 );
+
+  /* Randomly discard pages as they are unpinned according to the
+  ** discardChance setting.  If discardChance is 0, the random discard
+  ** never happens.  If discardChance is 100, it always happens.
+  */
+  if( p->bPurgeable
+  && (100-testpcacheGlobal.discardChance) <= (testpcacheRandom(p)%100)
+  ){
+    discard = 1;
+  }
+
+  for(i=0; i<TESTPCACHE_NPAGE; i++){
+    if( p->a[i].pData==pOldPage ){
+      /* The pOldPage pointer always points to a pinned page */
+      assert( p->a[i].isPinned );
+      p->a[i].isPinned = 0;
+      p->nPinned--;
+      assert( p->nPinned>=0 );
+      if( discard ){
+        p->a[i].key = 0;
+        p->nFree++;
+        assert( p->nFree<=TESTPCACHE_NPAGE );
+      }
+      return;
+    }
+  }
+
+  /* The pOldPage pointer always points to a valid page */
+  assert( 0 );
+}
+
+
+/*
+** Rekey a single page.
+*/
+static void testpcacheRekey(
+  sqlite3_pcache *pCache,
+  void *pOldPage,
+  unsigned oldKey,
+  unsigned newKey
+){
+  testpcache *p = (testpcache*)pCache;
+  int i;
+  assert( p->iMagic==TESTPCACHE_VALID );
+  assert( testpcacheGlobal.pDummy!=0 );
+  assert( testpcacheGlobal.nInstance>0 );
+
+  /* If there already exists another page at newKey, verify that
+  ** the other page is unpinned and discard it.
+  */
+  for(i=0; i<TESTPCACHE_NPAGE; i++){
+    if( p->a[i].key==newKey ){
+      /* The new key is never a page that is already pinned */
+      assert( p->a[i].isPinned==0 );
+      p->a[i].key = 0;
+      p->nFree++;
+      assert( p->nFree<=TESTPCACHE_NPAGE );
+      break;
+    }
+  }
+
+  /* Find the page to be rekeyed and rekey it.
+  */
+  for(i=0; i<TESTPCACHE_NPAGE; i++){
+    if( p->a[i].key==oldKey ){
+      /* The oldKey and pOldPage parameters match */
+      assert( p->a[i].pData==pOldPage );
+      /* Page to be rekeyed must be pinned */
+      assert( p->a[i].isPinned );
+      p->a[i].key = newKey;
+      return;
+    }
+  }
+
+  /* Rekey is always given a valid page to work with */
+  assert( 0 );
+}
+
+
+/*
+** Truncate the page cache.  Every page with a key of iLimit or larger
+** is discarded.
+*/
+static void testpcacheTruncate(sqlite3_pcache *pCache, unsigned iLimit){
+  testpcache *p = (testpcache*)pCache;
+  unsigned int i;
+  assert( p->iMagic==TESTPCACHE_VALID );
+  assert( testpcacheGlobal.pDummy!=0 );
+  assert( testpcacheGlobal.nInstance>0 );
+  for(i=0; i<TESTPCACHE_NPAGE; i++){
+    if( p->a[i].key>=iLimit ){
+      p->a[i].key = 0;
+      if( p->a[i].isPinned ){
+        p->nPinned--;
+        assert( p->nPinned>=0 );
+      }
+      p->nFree++;
+      assert( p->nFree<=TESTPCACHE_NPAGE );
+    }
+  }
+}
+
+/*
+** Destroy a page cache.
+*/
+static void testpcacheDestroy(sqlite3_pcache *pCache){
+  testpcache *p = (testpcache*)pCache;
+  assert( p->iMagic==TESTPCACHE_VALID );
+  assert( testpcacheGlobal.pDummy!=0 );
+  assert( testpcacheGlobal.nInstance>0 );
+  p->iMagic = TESTPCACHE_CLEAR;
+  sqlite3_free(p);
+  testpcacheGlobal.nInstance--;
+}
+
+
+/*
+** Invoke this routine to register or unregister the testing pager cache
+** implemented by this file.
+**
+** Install the test pager cache if installFlag is 1 and uninstall it if
+** installFlag is 0.
+**
+** When installing, discardChance is a number between 0 and 100 that
+** indicates the probability of discarding a page when unpinning the
+** page.  0 means never discard (unless the discard flag is set).
+** 100 means always discard.
+*/
+void installTestPCache(
+  int installFlag,            /* True to install.  False to uninstall. */
+  unsigned discardChance,     /* 0-100.  Chance to discard on unpin */
+  unsigned prngSeed,          /* Seed for the PRNG */
+  unsigned highStress         /* Call xStress agressively */
+){
+  static const sqlite3_pcache_methods testPcache = {
+    (void*)&testpcacheGlobal,
+    testpcacheInit,
+    testpcacheShutdown,
+    testpcacheCreate,
+    testpcacheCachesize,
+    testpcachePagecount,
+    testpcacheFetch,
+    testpcacheUnpin,
+    testpcacheRekey,
+    testpcacheTruncate,
+    testpcacheDestroy,
+  };
+  static sqlite3_pcache_methods defaultPcache;
+  static int isInstalled = 0;
+
+  assert( testpcacheGlobal.nInstance==0 );
+  assert( testpcacheGlobal.pDummy==0 );
+  assert( discardChance<=100 );
+  testpcacheGlobal.discardChance = discardChance;
+  testpcacheGlobal.prngSeed = prngSeed ^ (prngSeed<<16);
+  testpcacheGlobal.highStress = highStress;
+  if( installFlag!=isInstalled ){
+    if( installFlag ){
+      sqlite3_config(SQLITE_CONFIG_GETPCACHE, &defaultPcache);
+      assert( defaultPcache.xCreate!=testpcacheCreate );
+      sqlite3_config(SQLITE_CONFIG_PCACHE, &testPcache);
+    }else{
+      assert( defaultPcache.xCreate!=0 );
+      sqlite3_config(SQLITE_CONFIG_PCACHE, &defaultPcache);
+    }
+    isInstalled = installFlag;
+  }
+}
diff --git a/src/test_quota.c b/src/test_quota.c
new file mode 100644
index 0000000..74d1a6d
--- /dev/null
+++ b/src/test_quota.c
@@ -0,0 +1,1105 @@
+/*
+** 2010 September 31
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains a VFS "shim" - a layer that sits in between the
+** pager and the real VFS.
+**
+** This particular shim enforces a quota system on files.  One or more
+** database files are in a "quota group" that is defined by a GLOB
+** pattern.  A quota is set for the combined size of all files in the
+** the group.  A quota of zero means "no limit".  If the total size
+** of all files in the quota group is greater than the limit, then
+** write requests that attempt to enlarge a file fail with SQLITE_FULL.
+**
+** However, before returning SQLITE_FULL, the write requests invoke
+** a callback function that is configurable for each quota group.
+** This callback has the opportunity to enlarge the quota.  If the
+** callback does enlarge the quota such that the total size of all
+** files within the group is less than the new quota, then the write
+** continues as if nothing had happened.
+*/
+#include "sqlite3.h"
+#include <string.h>
+#include <assert.h>
+
+/*
+** For an build without mutexes, no-op the mutex calls.
+*/
+#if defined(SQLITE_THREADSAFE) && SQLITE_THREADSAFE==0
+#define sqlite3_mutex_alloc(X)    ((sqlite3_mutex*)8)
+#define sqlite3_mutex_free(X)
+#define sqlite3_mutex_enter(X)
+#define sqlite3_mutex_try(X)      SQLITE_OK
+#define sqlite3_mutex_leave(X)
+#define sqlite3_mutex_held(X)     ((void)(X),1)
+#define sqlite3_mutex_notheld(X)  ((void)(X),1)
+#endif /* SQLITE_THREADSAFE==0 */
+
+
+/************************ Object Definitions ******************************/
+
+/* Forward declaration of all object types */
+typedef struct quotaGroup quotaGroup;
+typedef struct quotaConn quotaConn;
+typedef struct quotaFile quotaFile;
+
+/*
+** A "quota group" is a collection of files whose collective size we want
+** to limit.  Each quota group is defined by a GLOB pattern.
+**
+** There is an instance of the following object for each defined quota
+** group.  This object records the GLOB pattern that defines which files
+** belong to the quota group.  The object also remembers the size limit
+** for the group (the quota) and the callback to be invoked when the
+** sum of the sizes of the files within the group goes over the limit.
+**
+** A quota group must be established (using sqlite3_quota_set(...))
+** prior to opening any of the database connections that access files
+** within the quota group.
+*/
+struct quotaGroup {
+  const char *zPattern;          /* Filename pattern to be quotaed */
+  sqlite3_int64 iLimit;          /* Upper bound on total file size */
+  sqlite3_int64 iSize;           /* Current size of all files */
+  void (*xCallback)(             /* Callback invoked when going over quota */
+     const char *zFilename,         /* Name of file whose size increases */
+     sqlite3_int64 *piLimit,        /* IN/OUT: The current limit */
+     sqlite3_int64 iSize,           /* Total size of all files in the group */
+     void *pArg                     /* Client data */
+  );
+  void *pArg;                    /* Third argument to the xCallback() */
+  void (*xDestroy)(void*);       /* Optional destructor for pArg */
+  quotaGroup *pNext, **ppPrev;   /* Doubly linked list of all quota objects */
+  quotaFile *pFiles;             /* Files within this group */
+};
+
+/*
+** An instance of this structure represents a single file that is part
+** of a quota group.  A single file can be opened multiple times.  In
+** order keep multiple openings of the same file from causing the size
+** of the file to count against the quota multiple times, each file
+** has a unique instance of this object and multiple open connections
+** to the same file each point to a single instance of this object.
+*/
+struct quotaFile {
+  char *zFilename;                /* Name of this file */
+  quotaGroup *pGroup;             /* Quota group to which this file belongs */
+  sqlite3_int64 iSize;            /* Current size of this file */
+  int nRef;                       /* Number of times this file is open */
+  int deleteOnClose;              /* True to delete this file when it closes */
+  quotaFile *pNext, **ppPrev;     /* Linked list of files in the same group */
+};
+
+/*
+** An instance of the following object represents each open connection
+** to a file that participates in quota tracking.  This object is a 
+** subclass of sqlite3_file.  The sqlite3_file object for the underlying
+** VFS is appended to this structure.
+*/
+struct quotaConn {
+  sqlite3_file base;              /* Base class - must be first */
+  quotaFile *pFile;               /* The underlying file */
+  /* The underlying VFS sqlite3_file is appended to this object */
+};
+
+/************************* Global Variables **********************************/
+/*
+** All global variables used by this file are containing within the following
+** gQuota structure.
+*/
+static struct {
+  /* The pOrigVfs is the real, original underlying VFS implementation.
+  ** Most operations pass-through to the real VFS.  This value is read-only
+  ** during operation.  It is only modified at start-time and thus does not
+  ** require a mutex.
+  */
+  sqlite3_vfs *pOrigVfs;
+
+  /* The sThisVfs is the VFS structure used by this shim.  It is initialized
+  ** at start-time and thus does not require a mutex
+  */
+  sqlite3_vfs sThisVfs;
+
+  /* The sIoMethods defines the methods used by sqlite3_file objects 
+  ** associated with this shim.  It is initialized at start-time and does
+  ** not require a mutex.
+  **
+  ** When the underlying VFS is called to open a file, it might return 
+  ** either a version 1 or a version 2 sqlite3_file object.  This shim
+  ** has to create a wrapper sqlite3_file of the same version.  Hence
+  ** there are two I/O method structures, one for version 1 and the other
+  ** for version 2.
+  */
+  sqlite3_io_methods sIoMethodsV1;
+  sqlite3_io_methods sIoMethodsV2;
+
+  /* True when this shim as been initialized.
+  */
+  int isInitialized;
+
+  /* For run-time access any of the other global data structures in this
+  ** shim, the following mutex must be held.
+  */
+  sqlite3_mutex *pMutex;
+
+  /* List of quotaGroup objects.
+  */
+  quotaGroup *pGroup;
+
+} gQuota;
+
+/************************* Utility Routines *********************************/
+/*
+** Acquire and release the mutex used to serialize access to the
+** list of quotaGroups.
+*/
+static void quotaEnter(void){ sqlite3_mutex_enter(gQuota.pMutex); }
+static void quotaLeave(void){ sqlite3_mutex_leave(gQuota.pMutex); }
+
+/* Count the number of open files in a quotaGroup 
+*/
+static int quotaGroupOpenFileCount(quotaGroup *pGroup){
+  int N = 0;
+  quotaFile *pFile = pGroup->pFiles;
+  while( pFile ){
+    if( pFile->nRef ) N++;
+    pFile = pFile->pNext;
+  }
+  return N;
+}
+
+/* Remove a file from a quota group.
+*/
+static void quotaRemoveFile(quotaFile *pFile){
+  quotaGroup *pGroup = pFile->pGroup;
+  pGroup->iSize -= pFile->iSize;
+  *pFile->ppPrev = pFile->pNext;
+  if( pFile->pNext ) pFile->pNext->ppPrev = pFile->ppPrev;
+  sqlite3_free(pFile);
+}
+
+/* Remove all files from a quota group.  It is always the case that
+** all files will be closed when this routine is called.
+*/
+static void quotaRemoveAllFiles(quotaGroup *pGroup){
+  while( pGroup->pFiles ){
+    assert( pGroup->pFiles->nRef==0 );
+    quotaRemoveFile(pGroup->pFiles);
+  }
+}
+
+
+/* If the reference count and threshold for a quotaGroup are both
+** zero, then destroy the quotaGroup.
+*/
+static void quotaGroupDeref(quotaGroup *pGroup){
+  if( pGroup->iLimit==0 && quotaGroupOpenFileCount(pGroup)==0 ){
+    quotaRemoveAllFiles(pGroup);
+    *pGroup->ppPrev = pGroup->pNext;
+    if( pGroup->pNext ) pGroup->pNext->ppPrev = pGroup->ppPrev;
+    if( pGroup->xDestroy ) pGroup->xDestroy(pGroup->pArg);
+    sqlite3_free(pGroup);
+  }
+}
+
+/*
+** Return TRUE if string z matches glob pattern zGlob.
+**
+** Globbing rules:
+**
+**      '*'       Matches any sequence of zero or more characters.
+**
+**      '?'       Matches exactly one character.
+**
+**     [...]      Matches one character from the enclosed list of
+**                characters.
+**
+**     [^...]     Matches one character not in the enclosed list.
+**
+*/
+static int quotaStrglob(const char *zGlob, const char *z){
+  int c, c2;
+  int invert;
+  int seen;
+
+  while( (c = (*(zGlob++)))!=0 ){
+    if( c=='*' ){
+      while( (c=(*(zGlob++))) == '*' || c=='?' ){
+        if( c=='?' && (*(z++))==0 ) return 0;
+      }
+      if( c==0 ){
+        return 1;
+      }else if( c=='[' ){
+        while( *z && quotaStrglob(zGlob-1,z)==0 ){
+          z++;
+        }
+        return (*z)!=0;
+      }
+      while( (c2 = (*(z++)))!=0 ){
+        while( c2!=c ){
+          c2 = *(z++);
+          if( c2==0 ) return 0;
+        }
+        if( quotaStrglob(zGlob,z) ) return 1;
+      }
+      return 0;
+    }else if( c=='?' ){
+      if( (*(z++))==0 ) return 0;
+    }else if( c=='[' ){
+      int prior_c = 0;
+      seen = 0;
+      invert = 0;
+      c = *(z++);
+      if( c==0 ) return 0;
+      c2 = *(zGlob++);
+      if( c2=='^' ){
+        invert = 1;
+        c2 = *(zGlob++);
+      }
+      if( c2==']' ){
+        if( c==']' ) seen = 1;
+        c2 = *(zGlob++);
+      }
+      while( c2 && c2!=']' ){
+        if( c2=='-' && zGlob[0]!=']' && zGlob[0]!=0 && prior_c>0 ){
+          c2 = *(zGlob++);
+          if( c>=prior_c && c<=c2 ) seen = 1;
+          prior_c = 0;
+        }else{
+          if( c==c2 ){
+            seen = 1;
+          }
+          prior_c = c2;
+        }
+        c2 = *(zGlob++);
+      }
+      if( c2==0 || (seen ^ invert)==0 ) return 0;
+    }else{
+      if( c!=(*(z++)) ) return 0;
+    }
+  }
+  return *z==0;
+}
+
+
+/* Find a quotaGroup given the filename.
+**
+** Return a pointer to the quotaGroup object. Return NULL if not found.
+*/
+static quotaGroup *quotaGroupFind(const char *zFilename){
+  quotaGroup *p;
+  for(p=gQuota.pGroup; p && quotaStrglob(p->zPattern, zFilename)==0;
+      p=p->pNext){}
+  return p;
+}
+
+/* Translate an sqlite3_file* that is really a quotaConn* into
+** the sqlite3_file* for the underlying original VFS.
+*/
+static sqlite3_file *quotaSubOpen(sqlite3_file *pConn){
+  quotaConn *p = (quotaConn*)pConn;
+  return (sqlite3_file*)&p[1];
+}
+
+/* Find a file in a quota group and return a pointer to that file.
+** Return NULL if the file is not in the group.
+*/
+static quotaFile *quotaFindFile(quotaGroup *pGroup, const char *zName){
+  quotaFile *pFile = pGroup->pFiles;
+  while( pFile && strcmp(pFile->zFilename, zName)!=0 ){
+    pFile = pFile->pNext;
+  }
+  return pFile;
+}
+
+/************************* VFS Method Wrappers *****************************/
+/*
+** This is the xOpen method used for the "quota" VFS.
+**
+** Most of the work is done by the underlying original VFS.  This method
+** simply links the new file into the appropriate quota group if it is a
+** file that needs to be tracked.
+*/
+static int quotaOpen(
+  sqlite3_vfs *pVfs,          /* The quota VFS */
+  const char *zName,          /* Name of file to be opened */
+  sqlite3_file *pConn,        /* Fill in this file descriptor */
+  int flags,                  /* Flags to control the opening */
+  int *pOutFlags              /* Flags showing results of opening */
+){
+  int rc;                                    /* Result code */         
+  quotaConn *pQuotaOpen;                     /* The new quota file descriptor */
+  quotaFile *pFile;                          /* Corresponding quotaFile obj */
+  quotaGroup *pGroup;                        /* The group file belongs to */
+  sqlite3_file *pSubOpen;                    /* Real file descriptor */
+  sqlite3_vfs *pOrigVfs = gQuota.pOrigVfs;   /* Real VFS */
+
+  /* If the file is not a main database file or a WAL, then use the
+  ** normal xOpen method.
+  */
+  if( (flags & (SQLITE_OPEN_MAIN_DB|SQLITE_OPEN_WAL))==0 ){
+    return pOrigVfs->xOpen(pOrigVfs, zName, pConn, flags, pOutFlags);
+  }
+
+  /* If the name of the file does not match any quota group, then
+  ** use the normal xOpen method.
+  */
+  quotaEnter();
+  pGroup = quotaGroupFind(zName);
+  if( pGroup==0 ){
+    rc = pOrigVfs->xOpen(pOrigVfs, zName, pConn, flags, pOutFlags);
+  }else{
+    /* If we get to this point, it means the file needs to be quota tracked.
+    */
+    pQuotaOpen = (quotaConn*)pConn;
+    pSubOpen = quotaSubOpen(pConn);
+    rc = pOrigVfs->xOpen(pOrigVfs, zName, pSubOpen, flags, pOutFlags);
+    if( rc==SQLITE_OK ){
+      pFile = quotaFindFile(pGroup, zName);
+      if( pFile==0 ){
+        int nName = strlen(zName);
+        pFile = (quotaFile *)sqlite3_malloc( sizeof(*pFile) + nName + 1 );
+        if( pFile==0 ){
+          quotaLeave();
+          pSubOpen->pMethods->xClose(pSubOpen);
+          return SQLITE_NOMEM;
+        }
+        memset(pFile, 0, sizeof(*pFile));
+        pFile->zFilename = (char*)&pFile[1];
+        memcpy(pFile->zFilename, zName, nName+1);
+        pFile->pNext = pGroup->pFiles;
+        if( pGroup->pFiles ) pGroup->pFiles->ppPrev = &pFile->pNext;
+        pFile->ppPrev = &pGroup->pFiles;
+        pGroup->pFiles = pFile;
+        pFile->pGroup = pGroup;
+        pFile->deleteOnClose = (flags & SQLITE_OPEN_DELETEONCLOSE)!=0;
+      }
+      pFile->nRef++;
+      pQuotaOpen->pFile = pFile;
+      if( pSubOpen->pMethods->iVersion==1 ){
+        pQuotaOpen->base.pMethods = &gQuota.sIoMethodsV1;
+      }else{
+        pQuotaOpen->base.pMethods = &gQuota.sIoMethodsV2;
+      }
+    }
+  }
+  quotaLeave();
+  return rc;
+}
+
+/*
+** This is the xDelete method used for the "quota" VFS.
+**
+** If the file being deleted is part of the quota group, then reduce
+** the size of the quota group accordingly.  And remove the file from
+** the set of files in the quota group.
+*/
+static int quotaDelete(
+  sqlite3_vfs *pVfs,          /* The quota VFS */
+  const char *zName,          /* Name of file to be deleted */
+  int syncDir                 /* Do a directory sync after deleting */
+){
+  int rc;                                    /* Result code */         
+  quotaFile *pFile;                          /* Files in the quota */
+  quotaGroup *pGroup;                        /* The group file belongs to */
+  sqlite3_vfs *pOrigVfs = gQuota.pOrigVfs;   /* Real VFS */
+
+  /* Do the actual file delete */
+  rc = pOrigVfs->xDelete(pOrigVfs, zName, syncDir);
+
+  /* If the file just deleted is a member of a quota group, then remove
+  ** it from that quota group.
+  */
+  if( rc==SQLITE_OK ){
+    quotaEnter();
+    pGroup = quotaGroupFind(zName);
+    if( pGroup ){
+      pFile = quotaFindFile(pGroup, zName);
+      if( pFile ){
+        if( pFile->nRef ){
+          pFile->deleteOnClose = 1;
+        }else{
+          quotaRemoveFile(pFile);
+          quotaGroupDeref(pGroup);
+        }
+      }
+    }
+    quotaLeave();
+  }
+  return rc;
+}
+
+
+/************************ I/O Method Wrappers *******************************/
+
+/* xClose requests get passed through to the original VFS.  But we
+** also have to unlink the quotaConn from the quotaFile and quotaGroup.
+** The quotaFile and/or quotaGroup are freed if they are no longer in use.
+*/
+static int quotaClose(sqlite3_file *pConn){
+  quotaConn *p = (quotaConn*)pConn;
+  quotaFile *pFile = p->pFile;
+  sqlite3_file *pSubOpen = quotaSubOpen(pConn);
+  int rc;
+  rc = pSubOpen->pMethods->xClose(pSubOpen);
+  quotaEnter();
+  pFile->nRef--;
+  if( pFile->nRef==0 ){
+    quotaGroup *pGroup = pFile->pGroup;
+    if( pFile->deleteOnClose ) quotaRemoveFile(pFile);
+    quotaGroupDeref(pGroup);
+  }
+  quotaLeave();
+  return rc;
+}
+
+/* Pass xRead requests directory thru to the original VFS without
+** further processing.
+*/
+static int quotaRead(
+  sqlite3_file *pConn,
+  void *pBuf,
+  int iAmt,
+  sqlite3_int64 iOfst
+){
+  sqlite3_file *pSubOpen = quotaSubOpen(pConn);
+  return pSubOpen->pMethods->xRead(pSubOpen, pBuf, iAmt, iOfst);
+}
+
+/* Check xWrite requests to see if they expand the file.  If they do,
+** the perform a quota check before passing them through to the
+** original VFS.
+*/
+static int quotaWrite(
+  sqlite3_file *pConn,
+  const void *pBuf,
+  int iAmt,
+  sqlite3_int64 iOfst
+){
+  quotaConn *p = (quotaConn*)pConn;
+  sqlite3_file *pSubOpen = quotaSubOpen(pConn);
+  sqlite3_int64 iEnd = iOfst+iAmt;
+  quotaGroup *pGroup;
+  quotaFile *pFile = p->pFile;
+  sqlite3_int64 szNew;
+
+  if( pFile->iSize<iEnd ){
+    pGroup = pFile->pGroup;
+    quotaEnter();
+    szNew = pGroup->iSize - pFile->iSize + iEnd;
+    if( szNew>pGroup->iLimit && pGroup->iLimit>0 ){
+      if( pGroup->xCallback ){
+        pGroup->xCallback(pFile->zFilename, &pGroup->iLimit, szNew, 
+                          pGroup->pArg);
+      }
+      if( szNew>pGroup->iLimit && pGroup->iLimit>0 ){
+        quotaLeave();
+        return SQLITE_FULL;
+      }
+    }
+    pGroup->iSize = szNew;
+    pFile->iSize = iEnd;
+    quotaLeave();
+  }
+  return pSubOpen->pMethods->xWrite(pSubOpen, pBuf, iAmt, iOfst);
+}
+
+/* Pass xTruncate requests thru to the original VFS.  If the
+** success, update the file size.
+*/
+static int quotaTruncate(sqlite3_file *pConn, sqlite3_int64 size){
+  quotaConn *p = (quotaConn*)pConn;
+  sqlite3_file *pSubOpen = quotaSubOpen(pConn);
+  int rc = pSubOpen->pMethods->xTruncate(pSubOpen, size);
+  quotaFile *pFile = p->pFile;
+  quotaGroup *pGroup;
+  if( rc==SQLITE_OK ){
+    quotaEnter();
+    pGroup = pFile->pGroup;
+    pGroup->iSize -= pFile->iSize;
+    pFile->iSize = size;
+    pGroup->iSize += size;
+    quotaLeave();
+  }
+  return rc;
+}
+
+/* Pass xSync requests through to the original VFS without change
+*/
+static int quotaSync(sqlite3_file *pConn, int flags){
+  sqlite3_file *pSubOpen = quotaSubOpen(pConn);
+  return pSubOpen->pMethods->xSync(pSubOpen, flags);
+}
+
+/* Pass xFileSize requests through to the original VFS but then
+** update the quotaGroup with the new size before returning.
+*/
+static int quotaFileSize(sqlite3_file *pConn, sqlite3_int64 *pSize){
+  quotaConn *p = (quotaConn*)pConn;
+  sqlite3_file *pSubOpen = quotaSubOpen(pConn);
+  quotaFile *pFile = p->pFile;
+  quotaGroup *pGroup;
+  sqlite3_int64 sz;
+  int rc;
+
+  rc = pSubOpen->pMethods->xFileSize(pSubOpen, &sz);
+  if( rc==SQLITE_OK ){
+    quotaEnter();
+    pGroup = pFile->pGroup;
+    pGroup->iSize -= pFile->iSize;
+    pFile->iSize = sz;
+    pGroup->iSize += sz;
+    quotaLeave();
+    *pSize = sz;
+  }
+  return rc;
+}
+
+/* Pass xLock requests through to the original VFS unchanged.
+*/
+static int quotaLock(sqlite3_file *pConn, int lock){
+  sqlite3_file *pSubOpen = quotaSubOpen(pConn);
+  return pSubOpen->pMethods->xLock(pSubOpen, lock);
+}
+
+/* Pass xUnlock requests through to the original VFS unchanged.
+*/
+static int quotaUnlock(sqlite3_file *pConn, int lock){
+  sqlite3_file *pSubOpen = quotaSubOpen(pConn);
+  return pSubOpen->pMethods->xUnlock(pSubOpen, lock);
+}
+
+/* Pass xCheckReservedLock requests through to the original VFS unchanged.
+*/
+static int quotaCheckReservedLock(sqlite3_file *pConn, int *pResOut){
+  sqlite3_file *pSubOpen = quotaSubOpen(pConn);
+  return pSubOpen->pMethods->xCheckReservedLock(pSubOpen, pResOut);
+}
+
+/* Pass xFileControl requests through to the original VFS unchanged.
+*/
+static int quotaFileControl(sqlite3_file *pConn, int op, void *pArg){
+  sqlite3_file *pSubOpen = quotaSubOpen(pConn);
+  return pSubOpen->pMethods->xFileControl(pSubOpen, op, pArg);
+}
+
+/* Pass xSectorSize requests through to the original VFS unchanged.
+*/
+static int quotaSectorSize(sqlite3_file *pConn){
+  sqlite3_file *pSubOpen = quotaSubOpen(pConn);
+  return pSubOpen->pMethods->xSectorSize(pSubOpen);
+}
+
+/* Pass xDeviceCharacteristics requests through to the original VFS unchanged.
+*/
+static int quotaDeviceCharacteristics(sqlite3_file *pConn){
+  sqlite3_file *pSubOpen = quotaSubOpen(pConn);
+  return pSubOpen->pMethods->xDeviceCharacteristics(pSubOpen);
+}
+
+/* Pass xShmMap requests through to the original VFS unchanged.
+*/
+static int quotaShmMap(
+  sqlite3_file *pConn,            /* Handle open on database file */
+  int iRegion,                    /* Region to retrieve */
+  int szRegion,                   /* Size of regions */
+  int bExtend,                    /* True to extend file if necessary */
+  void volatile **pp              /* OUT: Mapped memory */
+){
+  sqlite3_file *pSubOpen = quotaSubOpen(pConn);
+  return pSubOpen->pMethods->xShmMap(pSubOpen, iRegion, szRegion, bExtend, pp);
+}
+
+/* Pass xShmLock requests through to the original VFS unchanged.
+*/
+static int quotaShmLock(
+  sqlite3_file *pConn,       /* Database file holding the shared memory */
+  int ofst,                  /* First lock to acquire or release */
+  int n,                     /* Number of locks to acquire or release */
+  int flags                  /* What to do with the lock */
+){
+  sqlite3_file *pSubOpen = quotaSubOpen(pConn);
+  return pSubOpen->pMethods->xShmLock(pSubOpen, ofst, n, flags);
+}
+
+/* Pass xShmBarrier requests through to the original VFS unchanged.
+*/
+static void quotaShmBarrier(sqlite3_file *pConn){
+  sqlite3_file *pSubOpen = quotaSubOpen(pConn);
+  pSubOpen->pMethods->xShmBarrier(pSubOpen);
+}
+
+/* Pass xShmUnmap requests through to the original VFS unchanged.
+*/
+static int quotaShmUnmap(sqlite3_file *pConn, int deleteFlag){
+  sqlite3_file *pSubOpen = quotaSubOpen(pConn);
+  return pSubOpen->pMethods->xShmUnmap(pSubOpen, deleteFlag);
+}
+
+/************************** Public Interfaces *****************************/
+/*
+** Initialize the quota VFS shim.  Use the VFS named zOrigVfsName
+** as the VFS that does the actual work.  Use the default if
+** zOrigVfsName==NULL.  
+**
+** The quota VFS shim is named "quota".  It will become the default
+** VFS if makeDefault is non-zero.
+**
+** THIS ROUTINE IS NOT THREADSAFE.  Call this routine exactly once
+** during start-up.
+*/
+int sqlite3_quota_initialize(const char *zOrigVfsName, int makeDefault){
+  sqlite3_vfs *pOrigVfs;
+  if( gQuota.isInitialized ) return SQLITE_MISUSE;
+  pOrigVfs = sqlite3_vfs_find(zOrigVfsName);
+  if( pOrigVfs==0 ) return SQLITE_ERROR;
+  assert( pOrigVfs!=&gQuota.sThisVfs );
+  gQuota.pMutex = sqlite3_mutex_alloc(SQLITE_MUTEX_FAST);
+  if( !gQuota.pMutex ){
+    return SQLITE_NOMEM;
+  }
+  gQuota.isInitialized = 1;
+  gQuota.pOrigVfs = pOrigVfs;
+  gQuota.sThisVfs = *pOrigVfs;
+  gQuota.sThisVfs.xOpen = quotaOpen;
+  gQuota.sThisVfs.xDelete = quotaDelete;
+  gQuota.sThisVfs.szOsFile += sizeof(quotaConn);
+  gQuota.sThisVfs.zName = "quota";
+  gQuota.sIoMethodsV1.iVersion = 1;
+  gQuota.sIoMethodsV1.xClose = quotaClose;
+  gQuota.sIoMethodsV1.xRead = quotaRead;
+  gQuota.sIoMethodsV1.xWrite = quotaWrite;
+  gQuota.sIoMethodsV1.xTruncate = quotaTruncate;
+  gQuota.sIoMethodsV1.xSync = quotaSync;
+  gQuota.sIoMethodsV1.xFileSize = quotaFileSize;
+  gQuota.sIoMethodsV1.xLock = quotaLock;
+  gQuota.sIoMethodsV1.xUnlock = quotaUnlock;
+  gQuota.sIoMethodsV1.xCheckReservedLock = quotaCheckReservedLock;
+  gQuota.sIoMethodsV1.xFileControl = quotaFileControl;
+  gQuota.sIoMethodsV1.xSectorSize = quotaSectorSize;
+  gQuota.sIoMethodsV1.xDeviceCharacteristics = quotaDeviceCharacteristics;
+  gQuota.sIoMethodsV2 = gQuota.sIoMethodsV1;
+  gQuota.sIoMethodsV2.iVersion = 2;
+  gQuota.sIoMethodsV2.xShmMap = quotaShmMap;
+  gQuota.sIoMethodsV2.xShmLock = quotaShmLock;
+  gQuota.sIoMethodsV2.xShmBarrier = quotaShmBarrier;
+  gQuota.sIoMethodsV2.xShmUnmap = quotaShmUnmap;
+  sqlite3_vfs_register(&gQuota.sThisVfs, makeDefault);
+  return SQLITE_OK;
+}
+
+/*
+** Shutdown the quota system.
+**
+** All SQLite database connections must be closed before calling this
+** routine.
+**
+** THIS ROUTINE IS NOT THREADSAFE.  Call this routine exactly once while
+** shutting down in order to free all remaining quota groups.
+*/
+int sqlite3_quota_shutdown(void){
+  quotaGroup *pGroup;
+  if( gQuota.isInitialized==0 ) return SQLITE_MISUSE;
+  for(pGroup=gQuota.pGroup; pGroup; pGroup=pGroup->pNext){
+    if( quotaGroupOpenFileCount(pGroup)>0 ) return SQLITE_MISUSE;
+  }
+  while( gQuota.pGroup ){
+    pGroup = gQuota.pGroup;
+    gQuota.pGroup = pGroup->pNext;
+    pGroup->iLimit = 0;
+    assert( quotaGroupOpenFileCount(pGroup)==0 );
+    quotaGroupDeref(pGroup);
+  }
+  gQuota.isInitialized = 0;
+  sqlite3_mutex_free(gQuota.pMutex);
+  sqlite3_vfs_unregister(&gQuota.sThisVfs);
+  memset(&gQuota, 0, sizeof(gQuota));
+  return SQLITE_OK;
+}
+
+/*
+** Create or destroy a quota group.
+**
+** The quota group is defined by the zPattern.  When calling this routine
+** with a zPattern for a quota group that already exists, this routine
+** merely updates the iLimit, xCallback, and pArg values for that quota
+** group.  If zPattern is new, then a new quota group is created.
+**
+** If the iLimit for a quota group is set to zero, then the quota group
+** is disabled and will be deleted when the last database connection using
+** the quota group is closed.
+**
+** Calling this routine on a zPattern that does not exist and with a
+** zero iLimit is a no-op.
+**
+** A quota group must exist with a non-zero iLimit prior to opening
+** database connections if those connections are to participate in the
+** quota group.  Creating a quota group does not affect database connections
+** that are already open.
+*/
+int sqlite3_quota_set(
+  const char *zPattern,           /* The filename pattern */
+  sqlite3_int64 iLimit,           /* New quota to set for this quota group */
+  void (*xCallback)(              /* Callback invoked when going over quota */
+     const char *zFilename,         /* Name of file whose size increases */
+     sqlite3_int64 *piLimit,        /* IN/OUT: The current limit */
+     sqlite3_int64 iSize,           /* Total size of all files in the group */
+     void *pArg                     /* Client data */
+  ),
+  void *pArg,                     /* client data passed thru to callback */
+  void (*xDestroy)(void*)         /* Optional destructor for pArg */
+){
+  quotaGroup *pGroup;
+  quotaEnter();
+  pGroup = gQuota.pGroup;
+  while( pGroup && strcmp(pGroup->zPattern, zPattern)!=0 ){
+    pGroup = pGroup->pNext;
+  }
+  if( pGroup==0 ){
+    int nPattern = strlen(zPattern);
+    if( iLimit<=0 ){
+      quotaLeave();
+      return SQLITE_OK;
+    }
+    pGroup = (quotaGroup *)sqlite3_malloc( sizeof(*pGroup) + nPattern + 1 );
+    if( pGroup==0 ){
+      quotaLeave();
+      return SQLITE_NOMEM;
+    }
+    memset(pGroup, 0, sizeof(*pGroup));
+    pGroup->zPattern = (char*)&pGroup[1];
+    memcpy((char *)pGroup->zPattern, zPattern, nPattern+1);
+    if( gQuota.pGroup ) gQuota.pGroup->ppPrev = &pGroup->pNext;
+    pGroup->pNext = gQuota.pGroup;
+    pGroup->ppPrev = &gQuota.pGroup;
+    gQuota.pGroup = pGroup;
+  }
+  pGroup->iLimit = iLimit;
+  pGroup->xCallback = xCallback;
+  if( pGroup->xDestroy && pGroup->pArg!=pArg ){
+    pGroup->xDestroy(pGroup->pArg);
+  }
+  pGroup->pArg = pArg;
+  pGroup->xDestroy = xDestroy;
+  quotaGroupDeref(pGroup);
+  quotaLeave();
+  return SQLITE_OK;
+}
+
+/*
+** Bring the named file under quota management.  Or if it is already under
+** management, update its size.
+*/
+int sqlite3_quota_file(const char *zFilename){
+  char *zFull;
+  sqlite3_file *fd;
+  int rc;
+  int outFlags = 0;
+  sqlite3_int64 iSize;
+  fd = sqlite3_malloc(gQuota.sThisVfs.szOsFile + gQuota.sThisVfs.mxPathname+1);
+  if( fd==0 ) return SQLITE_NOMEM;
+  zFull = gQuota.sThisVfs.szOsFile + (char*)fd;
+  rc = gQuota.pOrigVfs->xFullPathname(gQuota.pOrigVfs, zFilename,
+                                      gQuota.sThisVfs.mxPathname+1, zFull);
+  if( rc==SQLITE_OK ){
+    rc = quotaOpen(&gQuota.sThisVfs, zFull, fd, 
+                   SQLITE_OPEN_READONLY | SQLITE_OPEN_MAIN_DB, &outFlags);
+  }
+  if( rc==SQLITE_OK ){
+    fd->pMethods->xFileSize(fd, &iSize);
+    fd->pMethods->xClose(fd);
+  }else if( rc==SQLITE_CANTOPEN ){
+    quotaGroup *pGroup;
+    quotaFile *pFile;
+    quotaEnter();
+    pGroup = quotaGroupFind(zFull);
+    if( pGroup ){
+      pFile = quotaFindFile(pGroup, zFull);
+      if( pFile ) quotaRemoveFile(pFile);
+    }
+    quotaLeave();
+  }
+  sqlite3_free(fd);
+  return rc;
+}
+
+  
+/***************************** Test Code ***********************************/
+#ifdef SQLITE_TEST
+#include <tcl.h>
+
+/*
+** Argument passed to a TCL quota-over-limit callback.
+*/
+typedef struct TclQuotaCallback TclQuotaCallback;
+struct TclQuotaCallback {
+  Tcl_Interp *interp;    /* Interpreter in which to run the script */
+  Tcl_Obj *pScript;      /* Script to be run */
+};
+
+extern const char *sqlite3TestErrorName(int);
+
+
+/*
+** This is the callback from a quota-over-limit.
+*/
+static void tclQuotaCallback(
+  const char *zFilename,          /* Name of file whose size increases */
+  sqlite3_int64 *piLimit,         /* IN/OUT: The current limit */
+  sqlite3_int64 iSize,            /* Total size of all files in the group */
+  void *pArg                      /* Client data */
+){
+  TclQuotaCallback *p;            /* Callback script object */
+  Tcl_Obj *pEval;                 /* Script to evaluate */
+  Tcl_Obj *pVarname;              /* Name of variable to pass as 2nd arg */
+  unsigned int rnd;               /* Random part of pVarname */
+  int rc;                         /* Tcl error code */
+
+  p = (TclQuotaCallback *)pArg;
+  if( p==0 ) return;
+
+  pVarname = Tcl_NewStringObj("::piLimit_", -1);
+  Tcl_IncrRefCount(pVarname);
+  sqlite3_randomness(sizeof(rnd), (void *)&rnd);
+  Tcl_AppendObjToObj(pVarname, Tcl_NewIntObj((int)(rnd&0x7FFFFFFF)));
+  Tcl_ObjSetVar2(p->interp, pVarname, 0, Tcl_NewWideIntObj(*piLimit), 0);
+
+  pEval = Tcl_DuplicateObj(p->pScript);
+  Tcl_IncrRefCount(pEval);
+  Tcl_ListObjAppendElement(0, pEval, Tcl_NewStringObj(zFilename, -1));
+  Tcl_ListObjAppendElement(0, pEval, pVarname);
+  Tcl_ListObjAppendElement(0, pEval, Tcl_NewWideIntObj(iSize));
+  rc = Tcl_EvalObjEx(p->interp, pEval, TCL_EVAL_GLOBAL);
+
+  if( rc==TCL_OK ){
+    Tcl_Obj *pLimit = Tcl_ObjGetVar2(p->interp, pVarname, 0, 0);
+    rc = Tcl_GetWideIntFromObj(p->interp, pLimit, piLimit);
+    Tcl_UnsetVar(p->interp, Tcl_GetString(pVarname), 0);
+  }
+
+  Tcl_DecrRefCount(pEval);
+  Tcl_DecrRefCount(pVarname);
+  if( rc!=TCL_OK ) Tcl_BackgroundError(p->interp);
+}
+
+/*
+** Destructor for a TCL quota-over-limit callback.
+*/
+static void tclCallbackDestructor(void *pObj){
+  TclQuotaCallback *p = (TclQuotaCallback*)pObj;
+  if( p ){
+    Tcl_DecrRefCount(p->pScript);
+    sqlite3_free((char *)p);
+  }
+}
+
+/*
+** tclcmd: sqlite3_quota_initialize NAME MAKEDEFAULT
+*/
+static int test_quota_initialize(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  const char *zName;              /* Name of new quota VFS */
+  int makeDefault;                /* True to make the new VFS the default */
+  int rc;                         /* Value returned by quota_initialize() */
+
+  /* Process arguments */
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "NAME MAKEDEFAULT");
+    return TCL_ERROR;
+  }
+  zName = Tcl_GetString(objv[1]);
+  if( Tcl_GetBooleanFromObj(interp, objv[2], &makeDefault) ) return TCL_ERROR;
+  if( zName[0]=='\0' ) zName = 0;
+
+  /* Call sqlite3_quota_initialize() */
+  rc = sqlite3_quota_initialize(zName, makeDefault);
+  Tcl_SetResult(interp, (char *)sqlite3TestErrorName(rc), TCL_STATIC);
+
+  return TCL_OK;
+}
+
+/*
+** tclcmd: sqlite3_quota_shutdown
+*/
+static int test_quota_shutdown(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int rc;                         /* Value returned by quota_shutdown() */
+
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+
+  /* Call sqlite3_quota_shutdown() */
+  rc = sqlite3_quota_shutdown();
+  Tcl_SetResult(interp, (char *)sqlite3TestErrorName(rc), TCL_STATIC);
+
+  return TCL_OK;
+}
+
+/*
+** tclcmd: sqlite3_quota_set PATTERN LIMIT SCRIPT
+*/
+static int test_quota_set(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  const char *zPattern;           /* File pattern to configure */
+  sqlite3_int64 iLimit;           /* Initial quota in bytes */
+  Tcl_Obj *pScript;               /* Tcl script to invoke to increase quota */
+  int rc;                         /* Value returned by quota_set() */
+  TclQuotaCallback *p;            /* Callback object */
+  int nScript;                    /* Length of callback script */
+  void (*xDestroy)(void*);        /* Optional destructor for pArg */
+  void (*xCallback)(const char *, sqlite3_int64 *, sqlite3_int64, void *);
+
+  /* Process arguments */
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "PATTERN LIMIT SCRIPT");
+    return TCL_ERROR;
+  }
+  zPattern = Tcl_GetString(objv[1]);
+  if( Tcl_GetWideIntFromObj(interp, objv[2], &iLimit) ) return TCL_ERROR;
+  pScript = objv[3];
+  Tcl_GetStringFromObj(pScript, &nScript);
+
+  if( nScript>0 ){
+    /* Allocate a TclQuotaCallback object */
+    p = (TclQuotaCallback *)sqlite3_malloc(sizeof(TclQuotaCallback));
+    if( !p ){
+      Tcl_SetResult(interp, (char *)"SQLITE_NOMEM", TCL_STATIC);
+      return TCL_OK;
+    }
+    memset(p, 0, sizeof(TclQuotaCallback));
+    p->interp = interp;
+    Tcl_IncrRefCount(pScript);
+    p->pScript = pScript;
+    xDestroy = tclCallbackDestructor;
+    xCallback = tclQuotaCallback;
+  }else{
+    p = 0;
+    xDestroy = 0;
+    xCallback = 0;
+  }
+
+  /* Invoke sqlite3_quota_set() */
+  rc = sqlite3_quota_set(zPattern, iLimit, xCallback, (void*)p, xDestroy);
+
+  Tcl_SetResult(interp, (char *)sqlite3TestErrorName(rc), TCL_STATIC);
+  return TCL_OK;
+}
+
+/*
+** tclcmd: sqlite3_quota_file FILENAME
+*/
+static int test_quota_file(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  const char *zFilename;          /* File pattern to configure */
+  int rc;                         /* Value returned by quota_file() */
+
+  /* Process arguments */
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "FILENAME");
+    return TCL_ERROR;
+  }
+  zFilename = Tcl_GetString(objv[1]);
+
+  /* Invoke sqlite3_quota_file() */
+  rc = sqlite3_quota_file(zFilename);
+
+  Tcl_SetResult(interp, (char *)sqlite3TestErrorName(rc), TCL_STATIC);
+  return TCL_OK;
+}
+
+/*
+** tclcmd:  sqlite3_quota_dump
+*/
+static int test_quota_dump(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  Tcl_Obj *pResult;
+  Tcl_Obj *pGroupTerm;
+  Tcl_Obj *pFileTerm;
+  quotaGroup *pGroup;
+  quotaFile *pFile;
+
+  pResult = Tcl_NewObj();
+  quotaEnter();
+  for(pGroup=gQuota.pGroup; pGroup; pGroup=pGroup->pNext){
+    pGroupTerm = Tcl_NewObj();
+    Tcl_ListObjAppendElement(interp, pGroupTerm,
+          Tcl_NewStringObj(pGroup->zPattern, -1));
+    Tcl_ListObjAppendElement(interp, pGroupTerm,
+          Tcl_NewWideIntObj(pGroup->iLimit));
+    Tcl_ListObjAppendElement(interp, pGroupTerm,
+          Tcl_NewWideIntObj(pGroup->iSize));
+    for(pFile=pGroup->pFiles; pFile; pFile=pFile->pNext){
+      pFileTerm = Tcl_NewObj();
+      Tcl_ListObjAppendElement(interp, pFileTerm,
+            Tcl_NewStringObj(pFile->zFilename, -1));
+      Tcl_ListObjAppendElement(interp, pFileTerm,
+            Tcl_NewWideIntObj(pFile->iSize));
+      Tcl_ListObjAppendElement(interp, pFileTerm,
+            Tcl_NewWideIntObj(pFile->nRef));
+      Tcl_ListObjAppendElement(interp, pFileTerm,
+            Tcl_NewWideIntObj(pFile->deleteOnClose));
+      Tcl_ListObjAppendElement(interp, pGroupTerm, pFileTerm);
+    }
+    Tcl_ListObjAppendElement(interp, pResult, pGroupTerm);
+  }
+  quotaLeave();
+  Tcl_SetObjResult(interp, pResult);
+  return TCL_OK;
+}
+
+/*
+** This routine registers the custom TCL commands defined in this
+** module.  This should be the only procedure visible from outside
+** of this module.
+*/
+int Sqlitequota_Init(Tcl_Interp *interp){
+  static struct {
+     char *zName;
+     Tcl_ObjCmdProc *xProc;
+  } aCmd[] = {
+    { "sqlite3_quota_initialize", test_quota_initialize },
+    { "sqlite3_quota_shutdown", test_quota_shutdown },
+    { "sqlite3_quota_set", test_quota_set },
+    { "sqlite3_quota_file", test_quota_file },
+    { "sqlite3_quota_dump", test_quota_dump },
+  };
+  int i;
+
+  for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aCmd[i].zName, aCmd[i].xProc, 0, 0);
+  }
+
+  return TCL_OK;
+}
+#endif
diff --git a/src/test_rtree.c b/src/test_rtree.c
new file mode 100644
index 0000000..9745b00
--- /dev/null
+++ b/src/test_rtree.c
@@ -0,0 +1,296 @@
+/*
+** 2010 August 28
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Code for testing all sorts of SQLite interfaces. This code
+** is not included in the SQLite library. 
+*/
+
+#include <sqlite3.h>
+
+/* Solely for the UNUSED_PARAMETER() macro. */
+#include "sqliteInt.h"
+
+#ifdef SQLITE_ENABLE_RTREE
+/* 
+** Type used to cache parameter information for the "circle" r-tree geometry
+** callback.
+*/
+typedef struct Circle Circle;
+struct Circle {
+  struct Box {
+    double xmin;
+    double xmax;
+    double ymin;
+    double ymax;
+  } aBox[2];
+  double centerx;
+  double centery;
+  double radius;
+};
+
+/*
+** Destructor function for Circle objects allocated by circle_geom().
+*/
+static void circle_del(void *p){
+  sqlite3_free(p);
+}
+
+/*
+** Implementation of "circle" r-tree geometry callback.
+*/
+static int circle_geom(
+  sqlite3_rtree_geometry *p,
+  int nCoord, 
+  double *aCoord, 
+  int *pRes
+){
+  int i;                          /* Iterator variable */
+  Circle *pCircle;                /* Structure defining circular region */
+  double xmin, xmax;              /* X dimensions of box being tested */
+  double ymin, ymax;              /* X dimensions of box being tested */
+
+  if( p->pUser==0 ){
+    /* If pUser is still 0, then the parameter values have not been tested
+    ** for correctness or stored into a Circle structure yet. Do this now. */
+
+    /* This geometry callback is for use with a 2-dimensional r-tree table.
+    ** Return an error if the table does not have exactly 2 dimensions. */
+    if( nCoord!=4 ) return SQLITE_ERROR;
+
+    /* Test that the correct number of parameters (3) have been supplied,
+    ** and that the parameters are in range (that the radius of the circle 
+    ** radius is greater than zero). */
+    if( p->nParam!=3 || p->aParam[2]<0.0 ) return SQLITE_ERROR;
+
+    /* Allocate a structure to cache parameter data in. Return SQLITE_NOMEM
+    ** if the allocation fails. */
+    pCircle = (Circle *)(p->pUser = sqlite3_malloc(sizeof(Circle)));
+    if( !pCircle ) return SQLITE_NOMEM;
+    p->xDelUser = circle_del;
+
+    /* Record the center and radius of the circular region. One way that
+    ** tested bounding boxes that intersect the circular region are detected
+    ** is by testing if each corner of the bounding box lies within radius
+    ** units of the center of the circle. */
+    pCircle->centerx = p->aParam[0];
+    pCircle->centery = p->aParam[1];
+    pCircle->radius = p->aParam[2];
+
+    /* Define two bounding box regions. The first, aBox[0], extends to
+    ** infinity in the X dimension. It covers the same range of the Y dimension
+    ** as the circular region. The second, aBox[1], extends to infinity in
+    ** the Y dimension and is constrained to the range of the circle in the
+    ** X dimension.
+    **
+    ** Then imagine each box is split in half along its short axis by a line
+    ** that intersects the center of the circular region. A bounding box
+    ** being tested can be said to intersect the circular region if it contains
+    ** points from each half of either of the two infinite bounding boxes.
+    */
+    pCircle->aBox[0].xmin = pCircle->centerx;
+    pCircle->aBox[0].xmax = pCircle->centerx;
+    pCircle->aBox[0].ymin = pCircle->centery + pCircle->radius;
+    pCircle->aBox[0].ymax = pCircle->centery - pCircle->radius;
+    pCircle->aBox[1].xmin = pCircle->centerx + pCircle->radius;
+    pCircle->aBox[1].xmax = pCircle->centerx - pCircle->radius;
+    pCircle->aBox[1].ymin = pCircle->centery;
+    pCircle->aBox[1].ymax = pCircle->centery;
+  }
+
+  pCircle = (Circle *)p->pUser;
+  xmin = aCoord[0];
+  xmax = aCoord[1];
+  ymin = aCoord[2];
+  ymax = aCoord[3];
+
+  /* Check if any of the 4 corners of the bounding-box being tested lie 
+  ** inside the circular region. If they do, then the bounding-box does
+  ** intersect the region of interest. Set the output variable to true and
+  ** return SQLITE_OK in this case. */
+  for(i=0; i<4; i++){
+    double x = (i&0x01) ? xmax : xmin;
+    double y = (i&0x02) ? ymax : ymin;
+    double d2;
+    
+    d2  = (x-pCircle->centerx)*(x-pCircle->centerx);
+    d2 += (y-pCircle->centery)*(y-pCircle->centery);
+    if( d2<(pCircle->radius*pCircle->radius) ){
+      *pRes = 1;
+      return SQLITE_OK;
+    }
+  }
+
+  /* Check if the bounding box covers any other part of the circular region.
+  ** See comments above for a description of how this test works. If it does
+  ** cover part of the circular region, set the output variable to true
+  ** and return SQLITE_OK. */
+  for(i=0; i<2; i++){
+    if( xmin<=pCircle->aBox[i].xmin 
+     && xmax>=pCircle->aBox[i].xmax 
+     && ymin<=pCircle->aBox[i].ymin 
+     && ymax>=pCircle->aBox[i].ymax 
+    ){
+      *pRes = 1;
+      return SQLITE_OK;
+    }
+  }
+
+  /* The specified bounding box does not intersect the circular region. Set
+  ** the output variable to zero and return SQLITE_OK. */
+  *pRes = 0;
+  return SQLITE_OK;
+}
+
+/* END of implementation of "circle" geometry callback.
+**************************************************************************
+*************************************************************************/
+
+#include <assert.h>
+#include "tcl.h"
+
+typedef struct Cube Cube;
+struct Cube {
+  double x;
+  double y;
+  double z;
+  double width;
+  double height;
+  double depth;
+};
+
+static void cube_context_free(void *p){
+  sqlite3_free(p);
+}
+
+/*
+** The context pointer registered along with the 'cube' callback is
+** always ((void *)&gHere). This is just to facilitate testing, it is not
+** actually used for anything.
+*/
+static int gHere = 42;
+
+/*
+** Implementation of a simple r-tree geom callback to test for intersection
+** of r-tree rows with a "cube" shape. Cubes are defined by six scalar
+** coordinates as follows:
+**
+**   cube(x, y, z, width, height, depth)
+**
+** The width, height and depth parameters must all be greater than zero.
+*/
+static int cube_geom(
+  sqlite3_rtree_geometry *p,
+  int nCoord, 
+  double *aCoord, 
+  int *piRes
+){
+  Cube *pCube = (Cube *)p->pUser;
+
+  assert( p->pContext==(void *)&gHere );
+
+  if( pCube==0 ){
+    if( p->nParam!=6 || nCoord!=6
+     || p->aParam[3]<=0.0 || p->aParam[4]<=0.0 || p->aParam[5]<=0.0
+    ){
+      return SQLITE_ERROR;
+    }
+    pCube = (Cube *)sqlite3_malloc(sizeof(Cube));
+    if( !pCube ){
+      return SQLITE_NOMEM;
+    }
+    pCube->x = p->aParam[0];
+    pCube->y = p->aParam[1];
+    pCube->z = p->aParam[2];
+    pCube->width = p->aParam[3];
+    pCube->height = p->aParam[4];
+    pCube->depth = p->aParam[5];
+
+    p->pUser = (void *)pCube;
+    p->xDelUser = cube_context_free;
+  }
+
+  assert( nCoord==6 );
+  *piRes = 0;
+  if( aCoord[0]<=(pCube->x+pCube->width)
+   && aCoord[1]>=pCube->x
+   && aCoord[2]<=(pCube->y+pCube->height)
+   && aCoord[3]>=pCube->y
+   && aCoord[4]<=(pCube->z+pCube->depth)
+   && aCoord[5]>=pCube->z
+  ){
+    *piRes = 1;
+  }
+
+  return SQLITE_OK;
+}
+#endif /* SQLITE_ENABLE_RTREE */
+
+static int register_cube_geom(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#ifndef SQLITE_ENABLE_RTREE
+  UNUSED_PARAMETER(clientData);
+  UNUSED_PARAMETER(interp);
+  UNUSED_PARAMETER(objc);
+  UNUSED_PARAMETER(objv);
+#else
+  extern int getDbPointer(Tcl_Interp*, const char*, sqlite3**);
+  extern const char *sqlite3TestErrorName(int);
+  sqlite3 *db;
+  int rc;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  rc = sqlite3_rtree_geometry_callback(db, "cube", cube_geom, (void *)&gHere);
+  Tcl_SetResult(interp, (char *)sqlite3TestErrorName(rc), TCL_STATIC);
+#endif
+  return TCL_OK;
+}
+
+static int register_circle_geom(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#ifndef SQLITE_ENABLE_RTREE
+  UNUSED_PARAMETER(clientData);
+  UNUSED_PARAMETER(interp);
+  UNUSED_PARAMETER(objc);
+  UNUSED_PARAMETER(objv);
+#else
+  extern int getDbPointer(Tcl_Interp*, const char*, sqlite3**);
+  extern const char *sqlite3TestErrorName(int);
+  sqlite3 *db;
+  int rc;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  rc = sqlite3_rtree_geometry_callback(db, "circle", circle_geom, 0);
+  Tcl_SetResult(interp, (char *)sqlite3TestErrorName(rc), TCL_STATIC);
+#endif
+  return TCL_OK;
+}
+
+int Sqlitetestrtree_Init(Tcl_Interp *interp){
+  Tcl_CreateObjCommand(interp, "register_cube_geom", register_cube_geom, 0, 0);
+  Tcl_CreateObjCommand(interp, "register_circle_geom",register_circle_geom,0,0);
+  return TCL_OK;
+}
diff --git a/src/test_schema.c b/src/test_schema.c
new file mode 100644
index 0000000..1264446
--- /dev/null
+++ b/src/test_schema.c
@@ -0,0 +1,359 @@
+/*
+** 2006 June 10
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Code for testing the virtual table interfaces.  This code
+** is not included in the SQLite library.  It is used for automated
+** testing of the SQLite library.
+*/
+
+/* The code in this file defines a sqlite3 virtual-table module that
+** provides a read-only view of the current database schema. There is one
+** row in the schema table for each column in the database schema.
+*/
+#define SCHEMA \
+"CREATE TABLE x("                                                            \
+  "database,"          /* Name of database (i.e. main, temp etc.) */         \
+  "tablename,"         /* Name of table */                                   \
+  "cid,"               /* Column number (from left-to-right, 0 upward) */    \
+  "name,"              /* Column name */                                     \
+  "type,"              /* Specified type (i.e. VARCHAR(32)) */               \
+  "not_null,"          /* Boolean. True if NOT NULL was specified */         \
+  "dflt_value,"        /* Default value for this column */                   \
+  "pk"                 /* True if this column is part of the primary key */  \
+")"
+
+/* If SQLITE_TEST is defined this code is preprocessed for use as part
+** of the sqlite test binary "testfixture". Otherwise it is preprocessed
+** to be compiled into an sqlite dynamic extension.
+*/
+#ifdef SQLITE_TEST
+  #include "sqliteInt.h"
+  #include "tcl.h"
+#else
+  #include "sqlite3ext.h"
+  SQLITE_EXTENSION_INIT1
+#endif
+
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+
+typedef struct schema_vtab schema_vtab;
+typedef struct schema_cursor schema_cursor;
+
+/* A schema table object */
+struct schema_vtab {
+  sqlite3_vtab base;
+  sqlite3 *db;
+};
+
+/* A schema table cursor object */
+struct schema_cursor {
+  sqlite3_vtab_cursor base;
+  sqlite3_stmt *pDbList;
+  sqlite3_stmt *pTableList;
+  sqlite3_stmt *pColumnList;
+  int rowid;
+};
+
+/*
+** None of this works unless we have virtual tables.
+*/
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+
+/*
+** Table destructor for the schema module.
+*/
+static int schemaDestroy(sqlite3_vtab *pVtab){
+  sqlite3_free(pVtab);
+  return 0;
+}
+
+/*
+** Table constructor for the schema module.
+*/
+static int schemaCreate(
+  sqlite3 *db,
+  void *pAux,
+  int argc, const char *const*argv,
+  sqlite3_vtab **ppVtab,
+  char **pzErr
+){
+  int rc = SQLITE_NOMEM;
+  schema_vtab *pVtab = sqlite3_malloc(sizeof(schema_vtab));
+  if( pVtab ){
+    memset(pVtab, 0, sizeof(schema_vtab));
+    pVtab->db = db;
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+    rc = sqlite3_declare_vtab(db, SCHEMA);
+#endif
+  }
+  *ppVtab = (sqlite3_vtab *)pVtab;
+  return rc;
+}
+
+/*
+** Open a new cursor on the schema table.
+*/
+static int schemaOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
+  int rc = SQLITE_NOMEM;
+  schema_cursor *pCur;
+  pCur = sqlite3_malloc(sizeof(schema_cursor));
+  if( pCur ){
+    memset(pCur, 0, sizeof(schema_cursor));
+    *ppCursor = (sqlite3_vtab_cursor *)pCur;
+    rc = SQLITE_OK;
+  }
+  return rc;
+}
+
+/*
+** Close a schema table cursor.
+*/
+static int schemaClose(sqlite3_vtab_cursor *cur){
+  schema_cursor *pCur = (schema_cursor *)cur;
+  sqlite3_finalize(pCur->pDbList);
+  sqlite3_finalize(pCur->pTableList);
+  sqlite3_finalize(pCur->pColumnList);
+  sqlite3_free(pCur);
+  return SQLITE_OK;
+}
+
+/*
+** Retrieve a column of data.
+*/
+static int schemaColumn(sqlite3_vtab_cursor *cur, sqlite3_context *ctx, int i){
+  schema_cursor *pCur = (schema_cursor *)cur;
+  switch( i ){
+    case 0:
+      sqlite3_result_value(ctx, sqlite3_column_value(pCur->pDbList, 1));
+      break;
+    case 1:
+      sqlite3_result_value(ctx, sqlite3_column_value(pCur->pTableList, 0));
+      break;
+    default:
+      sqlite3_result_value(ctx, sqlite3_column_value(pCur->pColumnList, i-2));
+      break;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Retrieve the current rowid.
+*/
+static int schemaRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
+  schema_cursor *pCur = (schema_cursor *)cur;
+  *pRowid = pCur->rowid;
+  return SQLITE_OK;
+}
+
+static int finalize(sqlite3_stmt **ppStmt){
+  int rc = sqlite3_finalize(*ppStmt);
+  *ppStmt = 0;
+  return rc;
+}
+
+static int schemaEof(sqlite3_vtab_cursor *cur){
+  schema_cursor *pCur = (schema_cursor *)cur;
+  return (pCur->pDbList ? 0 : 1);
+}
+
+/*
+** Advance the cursor to the next row.
+*/
+static int schemaNext(sqlite3_vtab_cursor *cur){
+  int rc = SQLITE_OK;
+  schema_cursor *pCur = (schema_cursor *)cur;
+  schema_vtab *pVtab = (schema_vtab *)(cur->pVtab);
+  char *zSql = 0;
+
+  while( !pCur->pColumnList || SQLITE_ROW!=sqlite3_step(pCur->pColumnList) ){
+    if( SQLITE_OK!=(rc = finalize(&pCur->pColumnList)) ) goto next_exit;
+
+    while( !pCur->pTableList || SQLITE_ROW!=sqlite3_step(pCur->pTableList) ){
+      if( SQLITE_OK!=(rc = finalize(&pCur->pTableList)) ) goto next_exit;
+
+      assert(pCur->pDbList);
+      while( SQLITE_ROW!=sqlite3_step(pCur->pDbList) ){
+        rc = finalize(&pCur->pDbList);
+        goto next_exit;
+      }
+
+      /* Set zSql to the SQL to pull the list of tables from the 
+      ** sqlite_master (or sqlite_temp_master) table of the database
+      ** identfied by the row pointed to by the SQL statement pCur->pDbList
+      ** (iterating through a "PRAGMA database_list;" statement).
+      */
+      if( sqlite3_column_int(pCur->pDbList, 0)==1 ){
+        zSql = sqlite3_mprintf(
+            "SELECT name FROM sqlite_temp_master WHERE type='table'"
+        );
+      }else{
+        sqlite3_stmt *pDbList = pCur->pDbList;
+        zSql = sqlite3_mprintf(
+            "SELECT name FROM %Q.sqlite_master WHERE type='table'",
+             sqlite3_column_text(pDbList, 1)
+        );
+      }
+      if( !zSql ){
+        rc = SQLITE_NOMEM;
+        goto next_exit;
+      }
+
+      rc = sqlite3_prepare(pVtab->db, zSql, -1, &pCur->pTableList, 0);
+      sqlite3_free(zSql);
+      if( rc!=SQLITE_OK ) goto next_exit;
+    }
+
+    /* Set zSql to the SQL to the table_info pragma for the table currently
+    ** identified by the rows pointed to by statements pCur->pDbList and
+    ** pCur->pTableList.
+    */
+    zSql = sqlite3_mprintf("PRAGMA %Q.table_info(%Q)", 
+        sqlite3_column_text(pCur->pDbList, 1),
+        sqlite3_column_text(pCur->pTableList, 0)
+    );
+
+    if( !zSql ){
+      rc = SQLITE_NOMEM;
+      goto next_exit;
+    }
+    rc = sqlite3_prepare(pVtab->db, zSql, -1, &pCur->pColumnList, 0);
+    sqlite3_free(zSql);
+    if( rc!=SQLITE_OK ) goto next_exit;
+  }
+  pCur->rowid++;
+
+next_exit:
+  /* TODO: Handle rc */
+  return rc;
+}
+
+/*
+** Reset a schema table cursor.
+*/
+static int schemaFilter(
+  sqlite3_vtab_cursor *pVtabCursor, 
+  int idxNum, const char *idxStr,
+  int argc, sqlite3_value **argv
+){
+  int rc;
+  schema_vtab *pVtab = (schema_vtab *)(pVtabCursor->pVtab);
+  schema_cursor *pCur = (schema_cursor *)pVtabCursor;
+  pCur->rowid = 0;
+  finalize(&pCur->pTableList);
+  finalize(&pCur->pColumnList);
+  finalize(&pCur->pDbList);
+  rc = sqlite3_prepare(pVtab->db,"PRAGMA database_list", -1, &pCur->pDbList, 0);
+  return (rc==SQLITE_OK ? schemaNext(pVtabCursor) : rc);
+}
+
+/*
+** Analyse the WHERE condition.
+*/
+static int schemaBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
+  return SQLITE_OK;
+}
+
+/*
+** A virtual table module that merely echos method calls into TCL
+** variables.
+*/
+static sqlite3_module schemaModule = {
+  0,                           /* iVersion */
+  schemaCreate,
+  schemaCreate,
+  schemaBestIndex,
+  schemaDestroy,
+  schemaDestroy,
+  schemaOpen,                  /* xOpen - open a cursor */
+  schemaClose,                 /* xClose - close a cursor */
+  schemaFilter,                /* xFilter - configure scan constraints */
+  schemaNext,                  /* xNext - advance a cursor */
+  schemaEof,                   /* xEof */
+  schemaColumn,                /* xColumn - read data */
+  schemaRowid,                 /* xRowid - read data */
+  0,                           /* xUpdate */
+  0,                           /* xBegin */
+  0,                           /* xSync */
+  0,                           /* xCommit */
+  0,                           /* xRollback */
+  0,                           /* xFindMethod */
+  0,                           /* xRename */
+};
+
+#endif /* !defined(SQLITE_OMIT_VIRTUALTABLE) */
+
+#ifdef SQLITE_TEST
+
+/*
+** Decode a pointer to an sqlite3 object.
+*/
+extern int getDbPointer(Tcl_Interp *interp, const char *zA, sqlite3 **ppDb);
+
+/*
+** Register the schema virtual table module.
+*/
+static int register_schema_module(
+  ClientData clientData, /* Not used */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3 *db;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  sqlite3_create_module(db, "schema", &schemaModule, 0);
+#endif
+  return TCL_OK;
+}
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetestschema_Init(Tcl_Interp *interp){
+  static struct {
+     char *zName;
+     Tcl_ObjCmdProc *xProc;
+     void *clientData;
+  } aObjCmd[] = {
+     { "register_schema_module", register_schema_module, 0 },
+  };
+  int i;
+  for(i=0; i<sizeof(aObjCmd)/sizeof(aObjCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aObjCmd[i].zName, 
+        aObjCmd[i].xProc, aObjCmd[i].clientData, 0);
+  }
+  return TCL_OK;
+}
+
+#else
+
+/*
+** Extension load function.
+*/
+int sqlite3_extension_init(
+  sqlite3 *db, 
+  char **pzErrMsg, 
+  const sqlite3_api_routines *pApi
+){
+  SQLITE_EXTENSION_INIT2(pApi);
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  sqlite3_create_module(db, "schema", &schemaModule, 0);
+#endif
+  return 0;
+}
+
+#endif
diff --git a/src/test_server.c b/src/test_server.c
new file mode 100644
index 0000000..ed0818e
--- /dev/null
+++ b/src/test_server.c
@@ -0,0 +1,490 @@
+/*
+** 2006 January 07
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains demonstration code.  Nothing in this file gets compiled
+** or linked into the SQLite library unless you use a non-standard option:
+**
+**      -DSQLITE_SERVER=1
+**
+** The configure script will never generate a Makefile with the option
+** above.  You will need to manually modify the Makefile if you want to
+** include any of the code from this file in your project.  Or, at your
+** option, you may copy and paste the code from this file and
+** thereby avoiding a recompile of SQLite.
+**
+**
+** This source file demonstrates how to use SQLite to create an SQL database 
+** server thread in a multiple-threaded program.  One or more client threads
+** send messages to the server thread and the server thread processes those
+** messages in the order received and returns the results to the client.
+**
+** One might ask:  "Why bother?  Why not just let each thread connect
+** to the database directly?"  There are a several of reasons to
+** prefer the client/server approach.
+**
+**    (1)  Some systems (ex: Redhat9) have broken threading implementations
+**         that prevent SQLite database connections from being used in
+**         a thread different from the one where they were created.  With
+**         the client/server approach, all database connections are created
+**         and used within the server thread.  Client calls to the database
+**         can be made from multiple threads (though not at the same time!)
+**
+**    (2)  Beginning with SQLite version 3.3.0, when two or more 
+**         connections to the same database occur within the same thread,
+**         they can optionally share their database cache.  This reduces
+**         I/O and memory requirements.  Cache shared is controlled using
+**         the sqlite3_enable_shared_cache() API.
+**
+**    (3)  Database connections on a shared cache use table-level locking
+**         instead of file-level locking for improved concurrency.
+**
+**    (4)  Database connections on a shared cache can by optionally
+**         set to READ UNCOMMITTED isolation.  (The default isolation for
+**         SQLite is SERIALIZABLE.)  When this occurs, readers will
+**         never be blocked by a writer and writers will not be
+**         blocked by readers.  There can still only be a single writer
+**         at a time, but multiple readers can simultaneously exist with
+**         that writer.  This is a huge increase in concurrency.
+**
+** To summarize the rational for using a client/server approach: prior
+** to SQLite version 3.3.0 it probably was not worth the trouble.  But
+** with SQLite version 3.3.0 and beyond you can get significant performance
+** and concurrency improvements and memory usage reductions by going
+** client/server.
+**
+** Note:  The extra features of version 3.3.0 described by points (2)
+** through (4) above are only available if you compile without the
+** option -DSQLITE_OMIT_SHARED_CACHE. 
+**
+** Here is how the client/server approach works:  The database server
+** thread is started on this procedure:
+**
+**       void *sqlite3_server(void *NotUsed);
+**
+** The sqlite_server procedure runs as long as the g.serverHalt variable
+** is false.  A mutex is used to make sure no more than one server runs
+** at a time.  The server waits for messages to arrive on a message
+** queue and processes the messages in order.
+**
+** Two convenience routines are provided for starting and stopping the
+** server thread:
+**
+**       void sqlite3_server_start(void);
+**       void sqlite3_server_stop(void);
+**
+** Both of the convenience routines return immediately.  Neither will
+** ever give an error.  If a server is already started or already halted,
+** then the routines are effectively no-ops.
+**
+** Clients use the following interfaces:
+**
+**       sqlite3_client_open
+**       sqlite3_client_prepare
+**       sqlite3_client_step
+**       sqlite3_client_reset
+**       sqlite3_client_finalize
+**       sqlite3_client_close
+**
+** These interfaces work exactly like the standard core SQLite interfaces
+** having the same names without the "_client_" infix.  Many other SQLite
+** interfaces can be used directly without having to send messages to the
+** server as long as SQLITE_ENABLE_MEMORY_MANAGEMENT is not defined.
+** The following interfaces fall into this second category:
+**
+**       sqlite3_bind_*
+**       sqlite3_changes
+**       sqlite3_clear_bindings
+**       sqlite3_column_*
+**       sqlite3_complete
+**       sqlite3_create_collation
+**       sqlite3_create_function
+**       sqlite3_data_count
+**       sqlite3_db_handle
+**       sqlite3_errcode
+**       sqlite3_errmsg
+**       sqlite3_last_insert_rowid
+**       sqlite3_total_changes
+**       sqlite3_transfer_bindings
+**
+** A single SQLite connection (an sqlite3* object) or an SQLite statement
+** (an sqlite3_stmt* object) should only be passed to a single interface
+** function at a time.  The connections and statements can be passed from
+** any thread to any of the functions listed in the second group above as
+** long as the same connection is not in use by two threads at once and
+** as long as SQLITE_ENABLE_MEMORY_MANAGEMENT is not defined.  Additional
+** information about the SQLITE_ENABLE_MEMORY_MANAGEMENT constraint is
+** below.
+**
+** The busy handler for all database connections should remain turned
+** off.  That means that any lock contention will cause the associated
+** sqlite3_client_step() call to return immediately with an SQLITE_BUSY
+** error code.  If a busy handler is enabled and lock contention occurs,
+** then the entire server thread will block.  This will cause not only
+** the requesting client to block but every other database client as
+** well.  It is possible to enhance the code below so that lock
+** contention will cause the message to be placed back on the top of
+** the queue to be tried again later.  But such enhanced processing is
+** not included here, in order to keep the example simple.
+**
+** This example code assumes the use of pthreads.  Pthreads
+** implementations are available for windows.  (See, for example
+** http://sourceware.org/pthreads-win32/announcement.html.)  Or, you
+** can translate the locking and thread synchronization code to use
+** windows primitives easily enough.  The details are left as an
+** exercise to the reader.
+**
+**** Restrictions Associated With SQLITE_ENABLE_MEMORY_MANAGEMENT ****
+**
+** If you compile with SQLITE_ENABLE_MEMORY_MANAGEMENT defined, then
+** SQLite includes code that tracks how much memory is being used by
+** each thread.  These memory counts can become confused if memory
+** is allocated by one thread and then freed by another.  For that
+** reason, when SQLITE_ENABLE_MEMORY_MANAGEMENT is used, all operations
+** that might allocate or free memory should be performanced in the same
+** thread that originally created the database connection.  In that case,
+** many of the operations that are listed above as safe to be performed
+** in separate threads would need to be sent over to the server to be
+** done there.  If SQLITE_ENABLE_MEMORY_MANAGEMENT is defined, then
+** the following functions can be used safely from different threads
+** without messing up the allocation counts:
+**
+**       sqlite3_bind_parameter_name
+**       sqlite3_bind_parameter_index
+**       sqlite3_changes
+**       sqlite3_column_blob
+**       sqlite3_column_count
+**       sqlite3_complete
+**       sqlite3_data_count
+**       sqlite3_db_handle
+**       sqlite3_errcode
+**       sqlite3_errmsg
+**       sqlite3_last_insert_rowid
+**       sqlite3_total_changes
+**
+** The remaining functions are not thread-safe when memory management
+** is enabled.  So one would have to define some new interface routines
+** along the following lines:
+**
+**       sqlite3_client_bind_*
+**       sqlite3_client_clear_bindings
+**       sqlite3_client_column_*
+**       sqlite3_client_create_collation
+**       sqlite3_client_create_function
+**       sqlite3_client_transfer_bindings
+**
+** The example code in this file is intended for use with memory
+** management turned off.  So the implementation of these additional
+** client interfaces is left as an exercise to the reader.
+**
+** It may seem surprising to the reader that the list of safe functions
+** above does not include things like sqlite3_bind_int() or
+** sqlite3_column_int().  But those routines might, in fact, allocate
+** or deallocate memory.  In the case of sqlite3_bind_int(), if the
+** parameter was previously bound to a string that string might need
+** to be deallocated before the new integer value is inserted.  In
+** the case of sqlite3_column_int(), the value of the column might be
+** a UTF-16 string which will need to be converted to UTF-8 then into
+** an integer.
+*/
+
+/* Include this to get the definition of SQLITE_THREADSAFE, in the
+** case that default values are used.
+*/
+#include "sqliteInt.h"
+
+/*
+** Only compile the code in this file on UNIX with a SQLITE_THREADSAFE build
+** and only if the SQLITE_SERVER macro is defined.
+*/
+#if defined(SQLITE_SERVER) && !defined(SQLITE_OMIT_SHARED_CACHE)
+#if SQLITE_OS_UNIX && SQLITE_THREADSAFE
+
+/*
+** We require only pthreads and the public interface of SQLite.
+*/
+#include <pthread.h>
+#include "sqlite3.h"
+
+/*
+** Messages are passed from client to server and back again as 
+** instances of the following structure.
+*/
+typedef struct SqlMessage SqlMessage;
+struct SqlMessage {
+  int op;                      /* Opcode for the message */
+  sqlite3 *pDb;                /* The SQLite connection */
+  sqlite3_stmt *pStmt;         /* A specific statement */
+  int errCode;                 /* Error code returned */
+  const char *zIn;             /* Input filename or SQL statement */
+  int nByte;                   /* Size of the zIn parameter for prepare() */
+  const char *zOut;            /* Tail of the SQL statement */
+  SqlMessage *pNext;           /* Next message in the queue */
+  SqlMessage *pPrev;           /* Previous message in the queue */
+  pthread_mutex_t clientMutex; /* Hold this mutex to access the message */
+  pthread_cond_t clientWakeup; /* Signal to wake up the client */
+};
+
+/*
+** Legal values for SqlMessage.op
+*/
+#define MSG_Open       1  /* sqlite3_open(zIn, &pDb) */
+#define MSG_Prepare    2  /* sqlite3_prepare(pDb, zIn, nByte, &pStmt, &zOut) */
+#define MSG_Step       3  /* sqlite3_step(pStmt) */
+#define MSG_Reset      4  /* sqlite3_reset(pStmt) */
+#define MSG_Finalize   5  /* sqlite3_finalize(pStmt) */
+#define MSG_Close      6  /* sqlite3_close(pDb) */
+#define MSG_Done       7  /* Server has finished with this message */
+
+
+/*
+** State information about the server is stored in a static variable
+** named "g" as follows:
+*/
+static struct ServerState {
+  pthread_mutex_t queueMutex;   /* Hold this mutex to access the msg queue */
+  pthread_mutex_t serverMutex;  /* Held by the server while it is running */
+  pthread_cond_t serverWakeup;  /* Signal this condvar to wake up the server */
+  volatile int serverHalt;      /* Server halts itself when true */
+  SqlMessage *pQueueHead;       /* Head of the message queue */
+  SqlMessage *pQueueTail;       /* Tail of the message queue */
+} g = {
+  PTHREAD_MUTEX_INITIALIZER,
+  PTHREAD_MUTEX_INITIALIZER,
+  PTHREAD_COND_INITIALIZER,
+};
+
+/*
+** Send a message to the server.  Block until we get a reply.
+**
+** The mutex and condition variable in the message are uninitialized
+** when this routine is called.  This routine takes care of 
+** initializing them and destroying them when it has finished.
+*/
+static void sendToServer(SqlMessage *pMsg){
+  /* Initialize the mutex and condition variable on the message
+  */
+  pthread_mutex_init(&pMsg->clientMutex, 0);
+  pthread_cond_init(&pMsg->clientWakeup, 0);
+
+  /* Add the message to the head of the server's message queue.
+  */
+  pthread_mutex_lock(&g.queueMutex);
+  pMsg->pNext = g.pQueueHead;
+  if( g.pQueueHead==0 ){
+    g.pQueueTail = pMsg;
+  }else{
+    g.pQueueHead->pPrev = pMsg;
+  }
+  pMsg->pPrev = 0;
+  g.pQueueHead = pMsg;
+  pthread_mutex_unlock(&g.queueMutex);
+
+  /* Signal the server that the new message has be queued, then
+  ** block waiting for the server to process the message.
+  */
+  pthread_mutex_lock(&pMsg->clientMutex);
+  pthread_cond_signal(&g.serverWakeup);
+  while( pMsg->op!=MSG_Done ){
+    pthread_cond_wait(&pMsg->clientWakeup, &pMsg->clientMutex);
+  }
+  pthread_mutex_unlock(&pMsg->clientMutex);
+
+  /* Destroy the mutex and condition variable of the message.
+  */
+  pthread_mutex_destroy(&pMsg->clientMutex);
+  pthread_cond_destroy(&pMsg->clientWakeup);
+}
+
+/*
+** The following 6 routines are client-side implementations of the
+** core SQLite interfaces:
+**
+**        sqlite3_open
+**        sqlite3_prepare
+**        sqlite3_step
+**        sqlite3_reset
+**        sqlite3_finalize
+**        sqlite3_close
+**
+** Clients should use the following client-side routines instead of 
+** the core routines above.
+**
+**        sqlite3_client_open
+**        sqlite3_client_prepare
+**        sqlite3_client_step
+**        sqlite3_client_reset
+**        sqlite3_client_finalize
+**        sqlite3_client_close
+**
+** Each of these routines creates a message for the desired operation,
+** sends that message to the server, waits for the server to process
+** then message and return a response.
+*/
+int sqlite3_client_open(const char *zDatabaseName, sqlite3 **ppDb){
+  SqlMessage msg;
+  msg.op = MSG_Open;
+  msg.zIn = zDatabaseName;
+  sendToServer(&msg);
+  *ppDb = msg.pDb;
+  return msg.errCode;
+}
+int sqlite3_client_prepare(
+  sqlite3 *pDb,
+  const char *zSql,
+  int nByte,
+  sqlite3_stmt **ppStmt,
+  const char **pzTail
+){
+  SqlMessage msg;
+  msg.op = MSG_Prepare;
+  msg.pDb = pDb;
+  msg.zIn = zSql;
+  msg.nByte = nByte;
+  sendToServer(&msg);
+  *ppStmt = msg.pStmt;
+  if( pzTail ) *pzTail = msg.zOut;
+  return msg.errCode;
+}
+int sqlite3_client_step(sqlite3_stmt *pStmt){
+  SqlMessage msg;
+  msg.op = MSG_Step;
+  msg.pStmt = pStmt;
+  sendToServer(&msg);
+  return msg.errCode;
+}
+int sqlite3_client_reset(sqlite3_stmt *pStmt){
+  SqlMessage msg;
+  msg.op = MSG_Reset;
+  msg.pStmt = pStmt;
+  sendToServer(&msg);
+  return msg.errCode;
+}
+int sqlite3_client_finalize(sqlite3_stmt *pStmt){
+  SqlMessage msg;
+  msg.op = MSG_Finalize;
+  msg.pStmt = pStmt;
+  sendToServer(&msg);
+  return msg.errCode;
+}
+int sqlite3_client_close(sqlite3 *pDb){
+  SqlMessage msg;
+  msg.op = MSG_Close;
+  msg.pDb = pDb;
+  sendToServer(&msg);
+  return msg.errCode;
+}
+
+/*
+** This routine implements the server.  To start the server, first
+** make sure g.serverHalt is false, then create a new detached thread
+** on this procedure.  See the sqlite3_server_start() routine below
+** for an example.  This procedure loops until g.serverHalt becomes
+** true.
+*/
+void *sqlite3_server(void *NotUsed){
+  if( pthread_mutex_trylock(&g.serverMutex) ){
+    return 0;  /* Another server is already running */
+  }
+  sqlite3_enable_shared_cache(1);
+  while( !g.serverHalt ){
+    SqlMessage *pMsg;
+
+    /* Remove the last message from the message queue.
+    */
+    pthread_mutex_lock(&g.queueMutex);
+    while( g.pQueueTail==0 && g.serverHalt==0 ){
+      pthread_cond_wait(&g.serverWakeup, &g.queueMutex);
+    }
+    pMsg = g.pQueueTail;
+    if( pMsg ){
+      if( pMsg->pPrev ){
+        pMsg->pPrev->pNext = 0;
+      }else{
+        g.pQueueHead = 0;
+      }
+      g.pQueueTail = pMsg->pPrev;
+    }
+    pthread_mutex_unlock(&g.queueMutex);
+    if( pMsg==0 ) break;
+
+    /* Process the message just removed
+    */
+    pthread_mutex_lock(&pMsg->clientMutex);
+    switch( pMsg->op ){
+      case MSG_Open: {
+        pMsg->errCode = sqlite3_open(pMsg->zIn, &pMsg->pDb);
+        break;
+      }
+      case MSG_Prepare: {
+        pMsg->errCode = sqlite3_prepare(pMsg->pDb, pMsg->zIn, pMsg->nByte,
+                                        &pMsg->pStmt, &pMsg->zOut);
+        break;
+      }
+      case MSG_Step: {
+        pMsg->errCode = sqlite3_step(pMsg->pStmt);
+        break;
+      }
+      case MSG_Reset: {
+        pMsg->errCode = sqlite3_reset(pMsg->pStmt);
+        break;
+      }
+      case MSG_Finalize: {
+        pMsg->errCode = sqlite3_finalize(pMsg->pStmt);
+        break;
+      }
+      case MSG_Close: {
+        pMsg->errCode = sqlite3_close(pMsg->pDb);
+        break;
+      }
+    }
+
+    /* Signal the client that the message has been processed.
+    */
+    pMsg->op = MSG_Done;
+    pthread_mutex_unlock(&pMsg->clientMutex);
+    pthread_cond_signal(&pMsg->clientWakeup);
+  }
+  pthread_mutex_unlock(&g.serverMutex);
+  return 0;
+}
+
+/*
+** Start a server thread if one is not already running.  If there
+** is aleady a server thread running, the new thread will quickly
+** die and this routine is effectively a no-op.
+*/
+void sqlite3_server_start(void){
+  pthread_t x;
+  int rc;
+  g.serverHalt = 0;
+  rc = pthread_create(&x, 0, sqlite3_server, 0);
+  if( rc==0 ){
+    pthread_detach(x);
+  }
+}
+
+/*
+** If a server thread is running, then stop it.  If no server is
+** running, this routine is effectively a no-op.
+**
+** This routine waits until the server has actually stopped before
+** returning.
+*/
+void sqlite3_server_stop(void){
+  g.serverHalt = 1;
+  pthread_cond_broadcast(&g.serverWakeup);
+  pthread_mutex_lock(&g.serverMutex);
+  pthread_mutex_unlock(&g.serverMutex);
+}
+
+#endif /* SQLITE_OS_UNIX && SQLITE_THREADSAFE */
+#endif /* defined(SQLITE_SERVER) */
diff --git a/src/test_stat.c b/src/test_stat.c
new file mode 100644
index 0000000..ef81769
--- /dev/null
+++ b/src/test_stat.c
@@ -0,0 +1,638 @@
+/*
+** 2010 July 12
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains an implementation of the "dbstat" virtual table.
+**
+** The dbstat virtual table is used to extract low-level formatting
+** information from an SQLite database in order to implement the
+** "sqlite3_analyzer" utility.  See the ../tool/spaceanal.tcl script
+** for an example implementation.
+*/
+
+#ifndef SQLITE_AMALGAMATION
+# include "sqliteInt.h"
+#endif
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+
+/*
+** Page paths:
+** 
+**   The value of the 'path' column describes the path taken from the 
+**   root-node of the b-tree structure to each page. The value of the 
+**   root-node path is '/'.
+**
+**   The value of the path for the left-most child page of the root of
+**   a b-tree is '/000/'. (Btrees store content ordered from left to right
+**   so the pages to the left have smaller keys than the pages to the right.)
+**   The next to left-most child of the root page is
+**   '/001', and so on, each sibling page identified by a 3-digit hex 
+**   value. The children of the 451st left-most sibling have paths such
+**   as '/1c2/000/, '/1c2/001/' etc.
+**
+**   Overflow pages are specified by appending a '+' character and a 
+**   six-digit hexadecimal value to the path to the cell they are linked
+**   from. For example, the three overflow pages in a chain linked from 
+**   the left-most cell of the 450th child of the root page are identified
+**   by the paths:
+**
+**      '/1c2/000+000000'         // First page in overflow chain
+**      '/1c2/000+000001'         // Second page in overflow chain
+**      '/1c2/000+000002'         // Third page in overflow chain
+**
+**   If the paths are sorted using the BINARY collation sequence, then
+**   the overflow pages associated with a cell will appear earlier in the
+**   sort-order than its child page:
+**
+**      '/1c2/000/'               // Left-most child of 451st child of root
+*/
+#define VTAB_SCHEMA                                                         \
+  "CREATE TABLE xx( "                                                       \
+  "  name       STRING,           /* Name of table or index */"             \
+  "  path       INTEGER,          /* Path to page from root */"             \
+  "  pageno     INTEGER,          /* Page number */"                        \
+  "  pagetype   STRING,           /* 'internal', 'leaf' or 'overflow' */"   \
+  "  ncell      INTEGER,          /* Cells on page (0 for overflow) */"     \
+  "  payload    INTEGER,          /* Bytes of payload on this page */"      \
+  "  unused     INTEGER,          /* Bytes of unused space on this page */" \
+  "  mx_payload INTEGER,          /* Largest payload size of all cells */"  \
+  "  pgoffset   INTEGER,          /* Offset of page in file */"             \
+  "  pgsize     INTEGER           /* Size of the page */"                   \
+  ");"
+
+
+typedef struct StatTable StatTable;
+typedef struct StatCursor StatCursor;
+typedef struct StatPage StatPage;
+typedef struct StatCell StatCell;
+
+struct StatCell {
+  int nLocal;                     /* Bytes of local payload */
+  u32 iChildPg;                   /* Child node (or 0 if this is a leaf) */
+  int nOvfl;                      /* Entries in aOvfl[] */
+  u32 *aOvfl;                     /* Array of overflow page numbers */
+  int nLastOvfl;                  /* Bytes of payload on final overflow page */
+  int iOvfl;                      /* Iterates through aOvfl[] */
+};
+
+struct StatPage {
+  u32 iPgno;
+  DbPage *pPg;
+  int iCell;
+
+  char *zPath;                    /* Path to this page */
+
+  /* Variables populated by statDecodePage(): */
+  u8 flags;                       /* Copy of flags byte */
+  int nCell;                      /* Number of cells on page */
+  int nUnused;                    /* Number of unused bytes on page */
+  StatCell *aCell;                /* Array of parsed cells */
+  u32 iRightChildPg;              /* Right-child page number (or 0) */
+  int nMxPayload;                 /* Largest payload of any cell on this page */
+};
+
+struct StatCursor {
+  sqlite3_vtab_cursor base;
+  sqlite3_stmt *pStmt;            /* Iterates through set of root pages */
+  int isEof;                      /* After pStmt has returned SQLITE_DONE */
+
+  StatPage aPage[32];
+  int iPage;                      /* Current entry in aPage[] */
+
+  /* Values to return. */
+  char *zName;                    /* Value of 'name' column */
+  char *zPath;                    /* Value of 'path' column */
+  u32 iPageno;                    /* Value of 'pageno' column */
+  char *zPagetype;                /* Value of 'pagetype' column */
+  int nCell;                      /* Value of 'ncell' column */
+  int nPayload;                   /* Value of 'payload' column */
+  int nUnused;                    /* Value of 'unused' column */
+  int nMxPayload;                 /* Value of 'mx_payload' column */
+  i64 iOffset;                    /* Value of 'pgOffset' column */
+  int szPage;                     /* Value of 'pgSize' column */
+};
+
+struct StatTable {
+  sqlite3_vtab base;
+  sqlite3 *db;
+};
+
+#ifndef get2byte
+# define get2byte(x)   ((x)[0]<<8 | (x)[1])
+#endif
+
+/*
+** Connect to or create a statvfs virtual table.
+*/
+static int statConnect(
+  sqlite3 *db,
+  void *pAux,
+  int argc, const char *const*argv,
+  sqlite3_vtab **ppVtab,
+  char **pzErr
+){
+  StatTable *pTab;
+
+  pTab = (StatTable *)sqlite3_malloc(sizeof(StatTable));
+  memset(pTab, 0, sizeof(StatTable));
+  pTab->db = db;
+
+  sqlite3_declare_vtab(db, VTAB_SCHEMA);
+  *ppVtab = &pTab->base;
+  return SQLITE_OK;
+}
+
+/*
+** Disconnect from or destroy a statvfs virtual table.
+*/
+static int statDisconnect(sqlite3_vtab *pVtab){
+  sqlite3_free(pVtab);
+  return SQLITE_OK;
+}
+
+/*
+** There is no "best-index". This virtual table always does a linear
+** scan of the binary VFS log file.
+*/
+static int statBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
+
+  /* Records are always returned in ascending order of (name, path). 
+  ** If this will satisfy the client, set the orderByConsumed flag so that 
+  ** SQLite does not do an external sort.
+  */
+  if( ( pIdxInfo->nOrderBy==1
+     && pIdxInfo->aOrderBy[0].iColumn==0
+     && pIdxInfo->aOrderBy[0].desc==0
+     ) ||
+      ( pIdxInfo->nOrderBy==2
+     && pIdxInfo->aOrderBy[0].iColumn==0
+     && pIdxInfo->aOrderBy[0].desc==0
+     && pIdxInfo->aOrderBy[1].iColumn==1
+     && pIdxInfo->aOrderBy[1].desc==0
+     )
+  ){
+    pIdxInfo->orderByConsumed = 1;
+  }
+
+  pIdxInfo->estimatedCost = 10.0;
+  return SQLITE_OK;
+}
+
+/*
+** Open a new statvfs cursor.
+*/
+static int statOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
+  StatTable *pTab = (StatTable *)pVTab;
+  StatCursor *pCsr;
+  int rc;
+
+  pCsr = (StatCursor *)sqlite3_malloc(sizeof(StatCursor));
+  memset(pCsr, 0, sizeof(StatCursor));
+  pCsr->base.pVtab = pVTab;
+
+  rc = sqlite3_prepare_v2(pTab->db, 
+      "SELECT 'sqlite_master' AS name, 1 AS rootpage, 'table' AS type"
+      "  UNION ALL  "
+      "SELECT name, rootpage, type FROM sqlite_master WHERE rootpage!=0"
+      "  ORDER BY name", -1,
+      &pCsr->pStmt, 0
+  );
+  if( rc!=SQLITE_OK ){
+    sqlite3_free(pCsr);
+    return rc;
+  }
+
+  *ppCursor = (sqlite3_vtab_cursor *)pCsr;
+  return SQLITE_OK;
+}
+
+static void statClearPage(StatPage *p){
+  int i;
+  for(i=0; i<p->nCell; i++){
+    sqlite3_free(p->aCell[i].aOvfl);
+  }
+  sqlite3PagerUnref(p->pPg);
+  sqlite3_free(p->aCell);
+  sqlite3_free(p->zPath);
+  memset(p, 0, sizeof(StatPage));
+}
+
+static void statResetCsr(StatCursor *pCsr){
+  int i;
+  sqlite3_reset(pCsr->pStmt);
+  for(i=0; i<ArraySize(pCsr->aPage); i++){
+    statClearPage(&pCsr->aPage[i]);
+  }
+  pCsr->iPage = 0;
+  sqlite3_free(pCsr->zPath);
+  pCsr->zPath = 0;
+}
+
+/*
+** Close a statvfs cursor.
+*/
+static int statClose(sqlite3_vtab_cursor *pCursor){
+  StatCursor *pCsr = (StatCursor *)pCursor;
+  statResetCsr(pCsr);
+  sqlite3_finalize(pCsr->pStmt);
+  sqlite3_free(pCsr);
+  return SQLITE_OK;
+}
+
+static void getLocalPayload(
+  int nUsable,                    /* Usable bytes per page */
+  u8 flags,                       /* Page flags */
+  int nTotal,                     /* Total record (payload) size */
+  int *pnLocal                    /* OUT: Bytes stored locally */
+){
+  int nLocal;
+  int nMinLocal;
+  int nMaxLocal;
+ 
+  if( flags==0x0D ){              /* Table leaf node */
+    nMinLocal = (nUsable - 12) * 32 / 255 - 23;
+    nMaxLocal = nUsable - 35;
+  }else{                          /* Index interior and leaf nodes */
+    nMinLocal = (nUsable - 12) * 32 / 255 - 23;
+    nMaxLocal = (nUsable - 12) * 64 / 255 - 23;
+  }
+
+  nLocal = nMinLocal + (nTotal - nMinLocal) % (nUsable - 4);
+  if( nLocal>nMaxLocal ) nLocal = nMinLocal;
+  *pnLocal = nLocal;
+}
+
+static int statDecodePage(Btree *pBt, StatPage *p){
+  int nUnused;
+  int iOff;
+  int nHdr;
+  int isLeaf;
+  int szPage;
+
+  u8 *aData = sqlite3PagerGetData(p->pPg);
+  u8 *aHdr = &aData[p->iPgno==1 ? 100 : 0];
+
+  p->flags = aHdr[0];
+  p->nCell = get2byte(&aHdr[3]);
+  p->nMxPayload = 0;
+
+  isLeaf = (p->flags==0x0A || p->flags==0x0D);
+  nHdr = 12 - isLeaf*4 + (p->iPgno==1)*100;
+
+  nUnused = get2byte(&aHdr[5]) - nHdr - 2*p->nCell;
+  nUnused += (int)aHdr[7];
+  iOff = get2byte(&aHdr[1]);
+  while( iOff ){
+    nUnused += get2byte(&aData[iOff+2]);
+    iOff = get2byte(&aData[iOff]);
+  }
+  p->nUnused = nUnused;
+  p->iRightChildPg = isLeaf ? 0 : sqlite3Get4byte(&aHdr[8]);
+  szPage = sqlite3BtreeGetPageSize(pBt);
+
+  if( p->nCell ){
+    int i;                        /* Used to iterate through cells */
+    int nUsable = szPage - sqlite3BtreeGetReserve(pBt);
+
+    p->aCell = sqlite3_malloc((p->nCell+1) * sizeof(StatCell));
+    memset(p->aCell, 0, (p->nCell+1) * sizeof(StatCell));
+
+    for(i=0; i<p->nCell; i++){
+      StatCell *pCell = &p->aCell[i];
+
+      iOff = get2byte(&aData[nHdr+i*2]);
+      if( !isLeaf ){
+        pCell->iChildPg = sqlite3Get4byte(&aData[iOff]);
+        iOff += 4;
+      }
+      if( p->flags==0x05 ){
+        /* A table interior node. nPayload==0. */
+      }else{
+        u32 nPayload;             /* Bytes of payload total (local+overflow) */
+        int nLocal;               /* Bytes of payload stored locally */
+        iOff += getVarint32(&aData[iOff], nPayload);
+        if( p->flags==0x0D ){
+          u64 dummy;
+          iOff += sqlite3GetVarint(&aData[iOff], &dummy);
+        }
+        if( nPayload>p->nMxPayload ) p->nMxPayload = nPayload;
+        getLocalPayload(nUsable, p->flags, nPayload, &nLocal);
+        pCell->nLocal = nLocal;
+        assert( nPayload>=nLocal );
+        assert( nLocal<=(nUsable-35) );
+        if( nPayload>nLocal ){
+          int j;
+          int nOvfl = ((nPayload - nLocal) + nUsable-4 - 1) / (nUsable - 4);
+          pCell->nLastOvfl = (nPayload-nLocal) - (nOvfl-1) * (nUsable-4);
+          pCell->nOvfl = nOvfl;
+          pCell->aOvfl = sqlite3_malloc(sizeof(u32)*nOvfl);
+          pCell->aOvfl[0] = sqlite3Get4byte(&aData[iOff+nLocal]);
+          for(j=1; j<nOvfl; j++){
+            int rc;
+            u32 iPrev = pCell->aOvfl[j-1];
+            DbPage *pPg = 0;
+            rc = sqlite3PagerGet(sqlite3BtreePager(pBt), iPrev, &pPg);
+            if( rc!=SQLITE_OK ){
+              assert( pPg==0 );
+              return rc;
+            } 
+            pCell->aOvfl[j] = sqlite3Get4byte(sqlite3PagerGetData(pPg));
+            sqlite3PagerUnref(pPg);
+          }
+        }
+      }
+    }
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** Populate the pCsr->iOffset and pCsr->szPage member variables. Based on
+** the current value of pCsr->iPageno.
+*/
+static void statSizeAndOffset(StatCursor *pCsr){
+  StatTable *pTab = (StatTable *)((sqlite3_vtab_cursor *)pCsr)->pVtab;
+  Btree *pBt = pTab->db->aDb[0].pBt;
+  Pager *pPager = sqlite3BtreePager(pBt);
+  sqlite3_file *fd;
+  sqlite3_int64 x[2];
+
+  /* The default page size and offset */
+  pCsr->szPage = sqlite3BtreeGetPageSize(pBt);
+  pCsr->iOffset = pCsr->szPage * (pCsr->iPageno - 1);
+
+  /* If connected to a ZIPVFS backend, override the page size and
+  ** offset with actual values obtained from ZIPVFS.
+  */
+  fd = sqlite3PagerFile(pPager);
+  x[0] = pCsr->iPageno;
+  if( sqlite3OsFileControl(fd, 230440, &x)==SQLITE_OK ){
+    pCsr->iOffset = x[0];
+    pCsr->szPage = x[1];
+  }
+}
+
+/*
+** Move a statvfs cursor to the next entry in the file.
+*/
+static int statNext(sqlite3_vtab_cursor *pCursor){
+  int rc;
+  int nPayload;
+  StatCursor *pCsr = (StatCursor *)pCursor;
+  StatTable *pTab = (StatTable *)pCursor->pVtab;
+  Btree *pBt = pTab->db->aDb[0].pBt;
+  Pager *pPager = sqlite3BtreePager(pBt);
+
+  sqlite3_free(pCsr->zPath);
+  pCsr->zPath = 0;
+
+  if( pCsr->aPage[0].pPg==0 ){
+    rc = sqlite3_step(pCsr->pStmt);
+    if( rc==SQLITE_ROW ){
+      int nPage;
+      u32 iRoot = sqlite3_column_int64(pCsr->pStmt, 1);
+      sqlite3PagerPagecount(pPager, &nPage);
+      if( nPage==0 ){
+        pCsr->isEof = 1;
+        return sqlite3_reset(pCsr->pStmt);
+      }
+      rc = sqlite3PagerGet(pPager, iRoot, &pCsr->aPage[0].pPg);
+      pCsr->aPage[0].iPgno = iRoot;
+      pCsr->aPage[0].iCell = 0;
+      pCsr->aPage[0].zPath = sqlite3_mprintf("/");
+      pCsr->iPage = 0;
+    }else{
+      pCsr->isEof = 1;
+      return sqlite3_reset(pCsr->pStmt);
+    }
+  }else{
+
+    /* Page p itself has already been visited. */
+    StatPage *p = &pCsr->aPage[pCsr->iPage];
+
+    while( p->iCell<p->nCell ){
+      StatCell *pCell = &p->aCell[p->iCell];
+      if( pCell->iOvfl<pCell->nOvfl ){
+        int nUsable = sqlite3BtreeGetPageSize(pBt)-sqlite3BtreeGetReserve(pBt);
+        pCsr->zName = (char *)sqlite3_column_text(pCsr->pStmt, 0);
+        pCsr->iPageno = pCell->aOvfl[pCell->iOvfl];
+        pCsr->zPagetype = "overflow";
+        pCsr->nCell = 0;
+        pCsr->nMxPayload = 0;
+        pCsr->zPath = sqlite3_mprintf(
+            "%s%.3x+%.6x", p->zPath, p->iCell, pCell->iOvfl
+        );
+        if( pCell->iOvfl<pCell->nOvfl-1 ){
+          pCsr->nUnused = 0;
+          pCsr->nPayload = nUsable - 4;
+        }else{
+          pCsr->nPayload = pCell->nLastOvfl;
+          pCsr->nUnused = nUsable - 4 - pCsr->nPayload;
+        }
+        pCell->iOvfl++;
+        statSizeAndOffset(pCsr);
+        return SQLITE_OK;
+      }
+      if( p->iRightChildPg ) break;
+      p->iCell++;
+    }
+
+    while( !p->iRightChildPg || p->iCell>p->nCell ){
+      statClearPage(p);
+      if( pCsr->iPage==0 ) return statNext(pCursor);
+      pCsr->iPage--;
+      p = &pCsr->aPage[pCsr->iPage];
+    }
+    pCsr->iPage++;
+    assert( p==&pCsr->aPage[pCsr->iPage-1] );
+
+    if( p->iCell==p->nCell ){
+      p[1].iPgno = p->iRightChildPg;
+    }else{
+      p[1].iPgno = p->aCell[p->iCell].iChildPg;
+    }
+    rc = sqlite3PagerGet(pPager, p[1].iPgno, &p[1].pPg);
+    p[1].iCell = 0;
+    p[1].zPath = sqlite3_mprintf("%s%.3x/", p->zPath, p->iCell);
+    p->iCell++;
+  }
+
+
+  /* Populate the StatCursor fields with the values to be returned
+  ** by the xColumn() and xRowid() methods.
+  */
+  if( rc==SQLITE_OK ){
+    int i;
+    StatPage *p = &pCsr->aPage[pCsr->iPage];
+    pCsr->zName = (char *)sqlite3_column_text(pCsr->pStmt, 0);
+    pCsr->iPageno = p->iPgno;
+
+    statDecodePage(pBt, p);
+    statSizeAndOffset(pCsr);
+
+    switch( p->flags ){
+      case 0x05:             /* table internal */
+      case 0x02:             /* index internal */
+        pCsr->zPagetype = "internal";
+        break;
+      case 0x0D:             /* table leaf */
+      case 0x0A:             /* index leaf */
+        pCsr->zPagetype = "leaf";
+        break;
+      default:
+        pCsr->zPagetype = "corrupted";
+        break;
+    }
+    pCsr->nCell = p->nCell;
+    pCsr->nUnused = p->nUnused;
+    pCsr->nMxPayload = p->nMxPayload;
+    pCsr->zPath = sqlite3_mprintf("%s", p->zPath);
+    nPayload = 0;
+    for(i=0; i<p->nCell; i++){
+      nPayload += p->aCell[i].nLocal;
+    }
+    pCsr->nPayload = nPayload;
+  }
+
+  return rc;
+}
+
+static int statEof(sqlite3_vtab_cursor *pCursor){
+  StatCursor *pCsr = (StatCursor *)pCursor;
+  return pCsr->isEof;
+}
+
+static int statFilter(
+  sqlite3_vtab_cursor *pCursor, 
+  int idxNum, const char *idxStr,
+  int argc, sqlite3_value **argv
+){
+  StatCursor *pCsr = (StatCursor *)pCursor;
+
+  statResetCsr(pCsr);
+  return statNext(pCursor);
+}
+
+static int statColumn(
+  sqlite3_vtab_cursor *pCursor, 
+  sqlite3_context *ctx, 
+  int i
+){
+  StatCursor *pCsr = (StatCursor *)pCursor;
+  switch( i ){
+    case 0:            /* name */
+      sqlite3_result_text(ctx, pCsr->zName, -1, SQLITE_STATIC);
+      break;
+    case 1:            /* path */
+      sqlite3_result_text(ctx, pCsr->zPath, -1, SQLITE_TRANSIENT);
+      break;
+    case 2:            /* pageno */
+      sqlite3_result_int64(ctx, pCsr->iPageno);
+      break;
+    case 3:            /* pagetype */
+      sqlite3_result_text(ctx, pCsr->zPagetype, -1, SQLITE_STATIC);
+      break;
+    case 4:            /* ncell */
+      sqlite3_result_int(ctx, pCsr->nCell);
+      break;
+    case 5:            /* payload */
+      sqlite3_result_int(ctx, pCsr->nPayload);
+      break;
+    case 6:            /* unused */
+      sqlite3_result_int(ctx, pCsr->nUnused);
+      break;
+    case 7:            /* mx_payload */
+      sqlite3_result_int(ctx, pCsr->nMxPayload);
+      break;
+    case 8:            /* pgoffset */
+      sqlite3_result_int64(ctx, pCsr->iOffset);
+      break;
+    case 9:            /* pgsize */
+      sqlite3_result_int(ctx, pCsr->szPage);
+      break;
+  }
+  return SQLITE_OK;
+}
+
+static int statRowid(sqlite3_vtab_cursor *pCursor, sqlite_int64 *pRowid){
+  StatCursor *pCsr = (StatCursor *)pCursor;
+  *pRowid = pCsr->iPageno;
+  return SQLITE_OK;
+}
+
+int sqlite3_dbstat_register(sqlite3 *db){
+  static sqlite3_module dbstat_module = {
+    0,                            /* iVersion */
+    statConnect,                  /* xCreate */
+    statConnect,                  /* xConnect */
+    statBestIndex,                /* xBestIndex */
+    statDisconnect,               /* xDisconnect */
+    statDisconnect,               /* xDestroy */
+    statOpen,                     /* xOpen - open a cursor */
+    statClose,                    /* xClose - close a cursor */
+    statFilter,                   /* xFilter - configure scan constraints */
+    statNext,                     /* xNext - advance a cursor */
+    statEof,                      /* xEof - check for end of scan */
+    statColumn,                   /* xColumn - read data */
+    statRowid,                    /* xRowid - read data */
+    0,                            /* xUpdate */
+    0,                            /* xBegin */
+    0,                            /* xSync */
+    0,                            /* xCommit */
+    0,                            /* xRollback */
+    0,                            /* xFindMethod */
+    0,                            /* xRename */
+  };
+  sqlite3_create_module(db, "dbstat", &dbstat_module, 0);
+  return SQLITE_OK;
+}
+
+#endif
+
+#if defined(SQLITE_TEST) || TCLSH==2
+#include <tcl.h>
+
+static int test_dbstat(
+  void *clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+#ifdef SQLITE_OMIT_VIRTUALTABLE
+  Tcl_AppendResult(interp, "dbstat not available because of "
+                           "SQLITE_OMIT_VIRTUALTABLE", (void*)0);
+  return TCL_ERROR;
+#else
+  struct SqliteDb { sqlite3 *db; };
+  char *zDb;
+  Tcl_CmdInfo cmdInfo;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB");
+    return TCL_ERROR;
+  }
+
+  zDb = Tcl_GetString(objv[1]);
+  if( Tcl_GetCommandInfo(interp, zDb, &cmdInfo) ){
+    sqlite3* db = ((struct SqliteDb*)cmdInfo.objClientData)->db;
+    sqlite3_dbstat_register(db);
+  }
+  return TCL_OK;
+#endif
+}
+
+int SqlitetestStat_Init(Tcl_Interp *interp){
+  Tcl_CreateObjCommand(interp, "register_dbstat_vtab", test_dbstat, 0, 0);
+  return TCL_OK;
+}
+#endif /* if defined(SQLITE_TEST) || TCLSH==2 */
diff --git a/src/test_superlock.c b/src/test_superlock.c
new file mode 100644
index 0000000..936fcad
--- /dev/null
+++ b/src/test_superlock.c
@@ -0,0 +1,356 @@
+/*
+** 2010 November 19
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Example code for obtaining an exclusive lock on an SQLite database
+** file. This method is complicated, but works for both WAL and rollback
+** mode database files. The interface to the example code in this file 
+** consists of the following two functions:
+**
+**   sqlite3demo_superlock()
+**   sqlite3demo_superunlock()
+*/
+
+#include <sqlite3.h>
+#include <string.h>               /* memset(), strlen() */
+#include <assert.h>               /* assert() */
+
+/*
+** A structure to collect a busy-handler callback and argument and a count
+** of the number of times it has been invoked.
+*/
+struct SuperlockBusy {
+  int (*xBusy)(void*,int);        /* Pointer to busy-handler function */
+  void *pBusyArg;                 /* First arg to pass to xBusy */
+  int nBusy;                      /* Number of times xBusy has been invoked */
+};
+typedef struct SuperlockBusy SuperlockBusy;
+
+/*
+** An instance of the following structure is allocated for each active
+** superlock. The opaque handle returned by sqlite3demo_superlock() is
+** actually a pointer to an instance of this structure.
+*/
+struct Superlock {
+  sqlite3 *db;                    /* Database handle used to lock db */
+  int bWal;                       /* True if db is a WAL database */
+};
+typedef struct Superlock Superlock;
+
+/*
+** The pCtx pointer passed to this function is actually a pointer to a
+** SuperlockBusy structure. Invoke the busy-handler function encapsulated
+** by the structure and return the result.
+*/
+static int superlockBusyHandler(void *pCtx, int UNUSED){
+  SuperlockBusy *pBusy = (SuperlockBusy *)pCtx;
+  if( pBusy->xBusy==0 ) return 0;
+  return pBusy->xBusy(pBusy->pBusyArg, pBusy->nBusy++);
+}
+
+/*
+** This function is used to determine if the main database file for 
+** connection db is open in WAL mode or not. If no error occurs and the
+** database file is in WAL mode, set *pbWal to true and return SQLITE_OK.
+** If it is not in WAL mode, set *pbWal to false.
+**
+** If an error occurs, return an SQLite error code. The value of *pbWal
+** is undefined in this case.
+*/
+static int superlockIsWal(Superlock *pLock){
+  int rc;                         /* Return Code */
+  sqlite3_stmt *pStmt;            /* Compiled PRAGMA journal_mode statement */
+
+  rc = sqlite3_prepare(pLock->db, "PRAGMA main.journal_mode", -1, &pStmt, 0);
+  if( rc!=SQLITE_OK ) return rc;
+
+  pLock->bWal = 0;
+  if( SQLITE_ROW==sqlite3_step(pStmt) ){
+    const char *zMode = (const char *)sqlite3_column_text(pStmt, 0);
+    if( zMode && strlen(zMode)==3 && sqlite3_strnicmp("wal", zMode, 3)==0 ){
+      pLock->bWal = 1;
+    }
+  }
+
+  return sqlite3_finalize(pStmt);
+}
+
+/*
+** Obtain an exclusive shm-lock on nByte bytes starting at offset idx
+** of the file fd. If the lock cannot be obtained immediately, invoke
+** the busy-handler until either it is obtained or the busy-handler
+** callback returns 0.
+*/
+static int superlockShmLock(
+  sqlite3_file *fd,               /* Database file handle */
+  int idx,                        /* Offset of shm-lock to obtain */
+  int nByte,                      /* Number of consective bytes to lock */
+  SuperlockBusy *pBusy            /* Busy-handler wrapper object */
+){
+  int rc;
+  int (*xShmLock)(sqlite3_file*, int, int, int) = fd->pMethods->xShmLock;
+  do {
+    rc = xShmLock(fd, idx, nByte, SQLITE_SHM_LOCK|SQLITE_SHM_EXCLUSIVE);
+  }while( rc==SQLITE_BUSY && superlockBusyHandler((void *)pBusy, 0) );
+  return rc;
+}
+
+/*
+** Obtain the extra locks on the database file required for WAL databases.
+** Invoke the supplied busy-handler as required.
+*/
+static int superlockWalLock(
+  sqlite3 *db,                    /* Database handle open on WAL database */
+  SuperlockBusy *pBusy            /* Busy handler wrapper object */
+){
+  int rc;                         /* Return code */
+  sqlite3_file *fd = 0;           /* Main database file handle */
+  void volatile *p = 0;           /* Pointer to first page of shared memory */
+
+  /* Obtain a pointer to the sqlite3_file object open on the main db file. */
+  rc = sqlite3_file_control(db, "main", SQLITE_FCNTL_FILE_POINTER, (void *)&fd);
+  if( rc!=SQLITE_OK ) return rc;
+
+  /* Obtain the "recovery" lock. Normally, this lock is only obtained by
+  ** clients running database recovery.  
+  */
+  rc = superlockShmLock(fd, 2, 1, pBusy);
+  if( rc!=SQLITE_OK ) return rc;
+
+  /* Zero the start of the first shared-memory page. This means that any
+  ** clients that open read or write transactions from this point on will
+  ** have to run recovery before proceeding. Since they need the "recovery"
+  ** lock that this process is holding to do that, no new read or write
+  ** transactions may now be opened. Nor can a checkpoint be run, for the
+  ** same reason.
+  */
+  rc = fd->pMethods->xShmMap(fd, 0, 32*1024, 1, &p);
+  if( rc!=SQLITE_OK ) return rc;
+  memset((void *)p, 0, 32);
+
+  /* Obtain exclusive locks on all the "read-lock" slots. Once these locks
+  ** are held, it is guaranteed that there are no active reader, writer or 
+  ** checkpointer clients.
+  */
+  rc = superlockShmLock(fd, 3, SQLITE_SHM_NLOCK-3, pBusy);
+  return rc;
+}
+
+/*
+** Release a superlock held on a database file. The argument passed to 
+** this function must have been obtained from a successful call to
+** sqlite3demo_superlock().
+*/
+void sqlite3demo_superunlock(void *pLock){
+  Superlock *p = (Superlock *)pLock;
+  if( p->bWal ){
+    int rc;                         /* Return code */
+    int flags = SQLITE_SHM_UNLOCK | SQLITE_SHM_EXCLUSIVE;
+    sqlite3_file *fd = 0;
+    rc = sqlite3_file_control(p->db, "main", SQLITE_FCNTL_FILE_POINTER, (void *)&fd);
+    if( rc==SQLITE_OK ){
+      fd->pMethods->xShmLock(fd, 2, 1, flags);
+      fd->pMethods->xShmLock(fd, 3, SQLITE_SHM_NLOCK-3, flags);
+    }
+  }
+  sqlite3_close(p->db);
+  sqlite3_free(p);
+}
+
+/*
+** Obtain a superlock on the database file identified by zPath, using the
+** locking primitives provided by VFS zVfs. If successful, SQLITE_OK is
+** returned and output variable *ppLock is populated with an opaque handle
+** that may be used with sqlite3demo_superunlock() to release the lock.
+**
+** If an error occurs, *ppLock is set to 0 and an SQLite error code 
+** (e.g. SQLITE_BUSY) is returned.
+**
+** If a required lock cannot be obtained immediately and the xBusy parameter
+** to this function is not NULL, then xBusy is invoked in the same way
+** as a busy-handler registered with SQLite (using sqlite3_busy_handler())
+** until either the lock can be obtained or the busy-handler function returns
+** 0 (indicating "give up").
+*/
+int sqlite3demo_superlock(
+  const char *zPath,              /* Path to database file to lock */
+  const char *zVfs,               /* VFS to use to access database file */
+  int (*xBusy)(void*,int),        /* Busy handler callback */
+  void *pBusyArg,                 /* Context arg for busy handler */
+  void **ppLock                   /* OUT: Context to pass to superunlock() */
+){
+  SuperlockBusy busy = {0, 0, 0}; /* Busy handler wrapper object */
+  int rc;                         /* Return code */
+  Superlock *pLock;
+
+  pLock = sqlite3_malloc(sizeof(Superlock));
+  if( !pLock ) return SQLITE_NOMEM;
+  memset(pLock, 0, sizeof(Superlock));
+
+  /* Open a database handle on the file to superlock. */
+  rc = sqlite3_open_v2(
+      zPath, &pLock->db, SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE, zVfs
+  );
+
+  /* Install a busy-handler and execute a BEGIN EXCLUSIVE. If this is not
+  ** a WAL database, this is all we need to do.  
+  **
+  ** A wrapper function is used to invoke the busy-handler instead of
+  ** registering the busy-handler function supplied by the user directly
+  ** with SQLite. This is because the same busy-handler function may be
+  ** invoked directly later on when attempting to obtain the extra locks
+  ** required in WAL mode. By using the wrapper, we are able to guarantee
+  ** that the "nBusy" integer parameter passed to the users busy-handler
+  ** represents the total number of busy-handler invocations made within
+  ** this call to sqlite3demo_superlock(), including any made during the
+  ** "BEGIN EXCLUSIVE".
+  */
+  if( rc==SQLITE_OK ){
+    busy.xBusy = xBusy;
+    busy.pBusyArg = pBusyArg;
+    sqlite3_busy_handler(pLock->db, superlockBusyHandler, (void *)&busy);
+    rc = sqlite3_exec(pLock->db, "BEGIN EXCLUSIVE", 0, 0, 0);
+  }
+
+  /* If the BEGIN EXCLUSIVE was executed successfully and this is a WAL
+  ** database, call superlockWalLock() to obtain the extra locks required
+  ** to prevent readers, writers and/or checkpointers from accessing the
+  ** db while this process is holding the superlock.
+  **
+  ** Before attempting any WAL locks, commit the transaction started above
+  ** to drop the WAL read and write locks currently held. Otherwise, the
+  ** new WAL locks may conflict with the old.
+  */
+  if( rc==SQLITE_OK ){
+    if( SQLITE_OK==(rc = superlockIsWal(pLock)) && pLock->bWal ){
+      rc = sqlite3_exec(pLock->db, "COMMIT", 0, 0, 0);
+      if( rc==SQLITE_OK ){
+        rc = superlockWalLock(pLock->db, &busy);
+      }
+    }
+  }
+
+  if( rc!=SQLITE_OK ){
+    sqlite3demo_superunlock(pLock);
+    *ppLock = 0;
+  }else{
+    *ppLock = pLock;
+  }
+
+  return rc;
+}
+
+/*
+** End of example code. Everything below here is the test harness.
+**************************************************************************
+**************************************************************************
+*************************************************************************/
+
+
+#ifdef SQLITE_TEST
+
+#include <tcl.h>
+
+struct InterpAndScript {
+  Tcl_Interp *interp;
+  Tcl_Obj *pScript;
+};
+typedef struct InterpAndScript InterpAndScript;
+
+static void superunlock_del(ClientData cd){
+  sqlite3demo_superunlock((void *)cd);
+}
+
+static int superunlock_cmd(
+  ClientData cd,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  if( objc!=1 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "");
+    return TCL_ERROR;
+  }
+  Tcl_DeleteCommand(interp, Tcl_GetString(objv[0]));
+  return TCL_OK;
+}
+
+static int superlock_busy(void *pCtx, int nBusy){
+  InterpAndScript *p = (InterpAndScript *)pCtx;
+  Tcl_Obj *pEval;                 /* Script to evaluate */
+  int iVal = 0;                   /* Value to return */
+
+  pEval = Tcl_DuplicateObj(p->pScript);
+  Tcl_IncrRefCount(pEval);
+  Tcl_ListObjAppendElement(p->interp, pEval, Tcl_NewIntObj(nBusy));
+  Tcl_EvalObjEx(p->interp, pEval, TCL_EVAL_GLOBAL);
+  Tcl_GetIntFromObj(p->interp, Tcl_GetObjResult(p->interp), &iVal);
+  Tcl_DecrRefCount(pEval);
+
+  return iVal;
+}
+
+/*
+** Tclcmd: sqlite3demo_superlock CMDNAME PATH VFS BUSY-HANDLER-SCRIPT
+*/
+static int superlock_cmd(
+  ClientData cd,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  void *pLock;                    /* Lock context */
+  char *zPath;
+  char *zVfs = 0;
+  InterpAndScript busy = {0, 0};
+  int (*xBusy)(void*,int) = 0;    /* Busy handler callback */
+  int rc;                         /* Return code from sqlite3demo_superlock() */
+
+  if( objc<3 || objc>5 ){
+    Tcl_WrongNumArgs(
+        interp, 1, objv, "CMDNAME PATH ?VFS? ?BUSY-HANDLER-SCRIPT?");
+    return TCL_ERROR;
+  }
+
+  zPath = Tcl_GetString(objv[2]);
+
+  if( objc>3 ){
+    zVfs = Tcl_GetString(objv[3]);
+    if( strlen(zVfs)==0 ) zVfs = 0;
+  }
+  if( objc>4 ){
+    busy.interp = interp;
+    busy.pScript = objv[4];
+    xBusy = superlock_busy;
+  }
+
+  rc = sqlite3demo_superlock(zPath, zVfs, xBusy, &busy, &pLock);
+  assert( rc==SQLITE_OK || pLock==0 );
+  assert( rc!=SQLITE_OK || pLock!=0 );
+
+  if( rc!=SQLITE_OK ){
+    extern const char *sqlite3ErrStr(int);
+    Tcl_ResetResult(interp);
+    Tcl_AppendResult(interp, sqlite3ErrStr(rc), 0);
+    return TCL_ERROR;
+  }
+
+  Tcl_CreateObjCommand(
+      interp, Tcl_GetString(objv[1]), superunlock_cmd, pLock, superunlock_del
+  );
+  Tcl_SetObjResult(interp, objv[1]);
+  return TCL_OK;
+}
+
+int SqliteSuperlock_Init(Tcl_Interp *interp){
+  Tcl_CreateObjCommand(interp, "sqlite3demo_superlock", superlock_cmd, 0, 0);
+  return TCL_OK;
+}
+#endif
diff --git a/src/test_syscall.c b/src/test_syscall.c
new file mode 100644
index 0000000..d484f22
--- /dev/null
+++ b/src/test_syscall.c
@@ -0,0 +1,674 @@
+/*
+** 2011 March 28
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** The code in this file implements a Tcl interface used to test error
+** handling in the os_unix.c module. Wrapper functions that support fault
+** injection are registered as the low-level OS functions using the 
+** xSetSystemCall() method of the VFS. The Tcl interface is as follows:
+**
+**
+**   test_syscall install LIST
+**     Install wrapper functions for all system calls in argument LIST.
+**     LIST must be a list consisting of zero or more of the following
+**     literal values:
+**
+**         open        close      access   getcwd   stat      fstat    
+**         ftruncate   fcntl      read     pread    pread64   write
+**         pwrite      pwrite64   fchmod   fallocate
+**
+**   test_syscall uninstall
+**     Uninstall all wrapper functions.
+**
+**   test_syscall fault ?COUNT PERSIST?
+**     If [test_syscall fault] is invoked without the two arguments, fault
+**     injection is disabled. Otherwise, fault injection is configured to
+**     cause a failure on the COUNT'th next call to a system call with a
+**     wrapper function installed. A COUNT value of 1 means fail the next
+**     system call. 
+** 
+**     Argument PERSIST is interpreted as a boolean. If true, the all
+**     system calls following the initial failure also fail. Otherwise, only
+**     the single transient failure is injected.
+**
+**   test_syscall errno CALL ERRNO
+**     Set the value that the global "errno" is set to following a fault
+**     in call CALL. Argument CALL must be one of the system call names
+**     listed above (under [test_syscall install]). ERRNO is a symbolic
+**     name (i.e. "EACCES"). Not all errno codes are supported. Add extra
+**     to the aErrno table in function test_syscall_errno() below as 
+**     required.
+**
+**   test_syscall reset ?SYSTEM-CALL?
+**     With no argument, this is an alias for the [uninstall] command. However,
+**     this command uses a VFS call of the form:
+**
+**       xSetSystemCall(pVfs, 0, 0);
+**
+**     To restore the default system calls. The [uninstall] command restores
+**     each system call individually by calling (i.e.):
+**
+**       xSetSystemCall(pVfs, "open", 0);
+**
+**     With an argument, this command attempts to reset the system call named
+**     by the parameter using the same method as [uninstall].
+**
+**   test_syscall exists SYSTEM-CALL
+**     Return true if the named system call exists. Or false otherwise.
+**
+**   test_syscall list
+**     Return a list of all system calls. The list is constructed using
+**     the xNextSystemCall() VFS method.
+*/
+
+#include "sqlite3.h"
+#include "tcl.h"
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+
+#include "sqliteInt.h"
+#if SQLITE_OS_UNIX
+
+/* From test1.c */
+extern const char *sqlite3TestErrorName(int);
+
+#include <sys/types.h>
+#include <errno.h>
+
+static struct TestSyscallGlobal {
+  int bPersist;                   /* 1 for persistent errors, 0 for transient */
+  int nCount;                     /* Fail after this many more calls */
+  int nFail;                      /* Number of failures that have occurred */
+} gSyscall = { 0, 0 };
+
+static int ts_open(const char *, int, int);
+static int ts_close(int fd);
+static int ts_access(const char *zPath, int mode);
+static char *ts_getcwd(char *zPath, size_t nPath);
+static int ts_stat(const char *zPath, struct stat *p);
+static int ts_fstat(int fd, struct stat *p);
+static int ts_ftruncate(int fd, off_t n);
+static int ts_fcntl(int fd, int cmd, ... );
+static int ts_read(int fd, void *aBuf, size_t nBuf);
+static int ts_pread(int fd, void *aBuf, size_t nBuf, off_t off);
+static int ts_pread64(int fd, void *aBuf, size_t nBuf, off_t off);
+static int ts_write(int fd, const void *aBuf, size_t nBuf);
+static int ts_pwrite(int fd, const void *aBuf, size_t nBuf, off_t off);
+static int ts_pwrite64(int fd, const void *aBuf, size_t nBuf, off_t off);
+static int ts_fchmod(int fd, mode_t mode);
+static int ts_fallocate(int fd, off_t off, off_t len);
+
+
+struct TestSyscallArray {
+  const char *zName;
+  sqlite3_syscall_ptr xTest;
+  sqlite3_syscall_ptr xOrig;
+  int default_errno;              /* Default value for errno following errors */
+  int custom_errno;               /* Current value for errno if error */
+} aSyscall[] = {
+  /*  0 */ { "open",      (sqlite3_syscall_ptr)ts_open,      0, EACCES, 0 },
+  /*  1 */ { "close",     (sqlite3_syscall_ptr)ts_close,     0, 0, 0 },
+  /*  2 */ { "access",    (sqlite3_syscall_ptr)ts_access,    0, 0, 0 },
+  /*  3 */ { "getcwd",    (sqlite3_syscall_ptr)ts_getcwd,    0, 0, 0 },
+  /*  4 */ { "stat",      (sqlite3_syscall_ptr)ts_stat,      0, 0, 0 },
+  /*  5 */ { "fstat",     (sqlite3_syscall_ptr)ts_fstat,     0, 0, 0 },
+  /*  6 */ { "ftruncate", (sqlite3_syscall_ptr)ts_ftruncate, 0, EIO, 0 },
+  /*  7 */ { "fcntl",     (sqlite3_syscall_ptr)ts_fcntl,     0, EACCES, 0 },
+  /*  8 */ { "read",      (sqlite3_syscall_ptr)ts_read,      0, 0, 0 },
+  /*  9 */ { "pread",     (sqlite3_syscall_ptr)ts_pread,     0, 0, 0 },
+  /* 10 */ { "pread64",   (sqlite3_syscall_ptr)ts_pread64,   0, 0, 0 },
+  /* 11 */ { "write",     (sqlite3_syscall_ptr)ts_write,     0, 0, 0 },
+  /* 12 */ { "pwrite",    (sqlite3_syscall_ptr)ts_pwrite,    0, 0, 0 },
+  /* 13 */ { "pwrite64",  (sqlite3_syscall_ptr)ts_pwrite64,  0, 0, 0 },
+  /* 14 */ { "fchmod",    (sqlite3_syscall_ptr)ts_fchmod,    0, 0, 0 },
+  /* 15 */ { "fallocate", (sqlite3_syscall_ptr)ts_fallocate, 0, 0, 0 },
+           { 0, 0, 0, 0, 0 }
+};
+
+#define orig_open      ((int(*)(const char *, int, int))aSyscall[0].xOrig)
+#define orig_close     ((int(*)(int))aSyscall[1].xOrig)
+#define orig_access    ((int(*)(const char*,int))aSyscall[2].xOrig)
+#define orig_getcwd    ((char*(*)(char*,size_t))aSyscall[3].xOrig)
+#define orig_stat      ((int(*)(const char*,struct stat*))aSyscall[4].xOrig)
+#define orig_fstat     ((int(*)(int,struct stat*))aSyscall[5].xOrig)
+#define orig_ftruncate ((int(*)(int,off_t))aSyscall[6].xOrig)
+#define orig_fcntl     ((int(*)(int,int,...))aSyscall[7].xOrig)
+#define orig_read      ((ssize_t(*)(int,void*,size_t))aSyscall[8].xOrig)
+#define orig_pread     ((ssize_t(*)(int,void*,size_t,off_t))aSyscall[9].xOrig)
+#define orig_pread64   ((ssize_t(*)(int,void*,size_t,off_t))aSyscall[10].xOrig)
+#define orig_write     ((ssize_t(*)(int,const void*,size_t))aSyscall[11].xOrig)
+#define orig_pwrite    ((ssize_t(*)(int,const void*,size_t,off_t))\
+                       aSyscall[12].xOrig)
+#define orig_pwrite64  ((ssize_t(*)(int,const void*,size_t,off_t))\
+                       aSyscall[13].xOrig)
+#define orig_fchmod    ((int(*)(int,mode_t))aSyscall[14].xOrig)
+#define orig_fallocate ((int(*)(int,off_t,off_t))aSyscall[15].xOrig)
+
+/*
+** This function is called exactly once from within each invocation of a
+** system call wrapper in this file. It returns 1 if the function should
+** fail, or 0 if it should succeed.
+*/
+static int tsIsFail(void){
+  gSyscall.nCount--;
+  if( gSyscall.nCount==0 || (gSyscall.nFail && gSyscall.bPersist) ){
+    gSyscall.nFail++;
+    return 1;
+  }
+  return 0;
+}
+
+/*
+** Return the current error-number value for function zFunc. zFunc must be
+** the name of a system call in the aSyscall[] table.
+**
+** Usually, the current error-number is the value that errno should be set
+** to if the named system call fails. The exception is "fallocate". See 
+** comments above the implementation of ts_fallocate() for details.
+*/
+static int tsErrno(const char *zFunc){
+  int i;
+  int nFunc = strlen(zFunc);
+  for(i=0; aSyscall[i].zName; i++){
+    if( strlen(aSyscall[i].zName)!=nFunc ) continue;
+    if( memcmp(aSyscall[i].zName, zFunc, nFunc) ) continue;
+    return aSyscall[i].custom_errno;
+  }
+
+  assert(0);
+  return 0;
+}
+
+/*
+** A wrapper around tsIsFail(). If tsIsFail() returns non-zero, set the
+** value of errno before returning.
+*/ 
+static int tsIsFailErrno(const char *zFunc){
+  if( tsIsFail() ){
+    errno = tsErrno(zFunc);
+    return 1;
+  }
+  return 0;
+}
+
+/*
+** A wrapper around open().
+*/
+static int ts_open(const char *zFile, int flags, int mode){
+  if( tsIsFailErrno("open") ){
+    return -1;
+  }
+  return orig_open(zFile, flags, mode);
+}
+
+/*
+** A wrapper around close().
+*/
+static int ts_close(int fd){
+  if( tsIsFail() ){
+    /* Even if simulating an error, close the original file-descriptor. 
+    ** This is to stop the test process from running out of file-descriptors
+    ** when running a long test. If a call to close() appears to fail, SQLite
+    ** never attempts to use the file-descriptor afterwards (or even to close
+    ** it a second time).  */
+    orig_close(fd);
+    return -1;
+  }
+  return orig_close(fd);
+}
+
+/*
+** A wrapper around access().
+*/
+static int ts_access(const char *zPath, int mode){
+  if( tsIsFail() ){
+    return -1;
+  }
+  return orig_access(zPath, mode);
+}
+
+/*
+** A wrapper around getcwd().
+*/
+static char *ts_getcwd(char *zPath, size_t nPath){
+  if( tsIsFail() ){
+    return NULL;
+  }
+  return orig_getcwd(zPath, nPath);
+}
+
+/*
+** A wrapper around stat().
+*/
+static int ts_stat(const char *zPath, struct stat *p){
+  if( tsIsFail() ){
+    return -1;
+  }
+  return orig_stat(zPath, p);
+}
+
+/*
+** A wrapper around fstat().
+*/
+static int ts_fstat(int fd, struct stat *p){
+  if( tsIsFailErrno("fstat") ){
+    return -1;
+  }
+  return orig_fstat(fd, p);
+}
+
+/*
+** A wrapper around ftruncate().
+*/
+static int ts_ftruncate(int fd, off_t n){
+  if( tsIsFailErrno("ftruncate") ){
+    return -1;
+  }
+  return orig_ftruncate(fd, n);
+}
+
+/*
+** A wrapper around fcntl().
+*/
+static int ts_fcntl(int fd, int cmd, ... ){
+  va_list ap;
+  void *pArg;
+  if( tsIsFailErrno("fcntl") ){
+    return -1;
+  }
+  va_start(ap, cmd);
+  pArg = va_arg(ap, void *);
+  return orig_fcntl(fd, cmd, pArg);
+}
+
+/*
+** A wrapper around read().
+*/
+static int ts_read(int fd, void *aBuf, size_t nBuf){
+  if( tsIsFailErrno("read") ){
+    return -1;
+  }
+  return orig_read(fd, aBuf, nBuf);
+}
+
+/*
+** A wrapper around pread().
+*/
+static int ts_pread(int fd, void *aBuf, size_t nBuf, off_t off){
+  if( tsIsFailErrno("pread") ){
+    return -1;
+  }
+  return orig_pread(fd, aBuf, nBuf, off);
+}
+
+/*
+** A wrapper around pread64().
+*/
+static int ts_pread64(int fd, void *aBuf, size_t nBuf, off_t off){
+  if( tsIsFailErrno("pread64") ){
+    return -1;
+  }
+  return orig_pread64(fd, aBuf, nBuf, off);
+}
+
+/*
+** A wrapper around write().
+*/
+static int ts_write(int fd, const void *aBuf, size_t nBuf){
+  if( tsIsFailErrno("write") ){
+    if( tsErrno("write")==EINTR ) orig_write(fd, aBuf, nBuf/2);
+    return -1;
+  }
+  return orig_write(fd, aBuf, nBuf);
+}
+
+/*
+** A wrapper around pwrite().
+*/
+static int ts_pwrite(int fd, const void *aBuf, size_t nBuf, off_t off){
+  if( tsIsFailErrno("pwrite") ){
+    return -1;
+  }
+  return orig_pwrite(fd, aBuf, nBuf, off);
+}
+
+/*
+** A wrapper around pwrite64().
+*/
+static int ts_pwrite64(int fd, const void *aBuf, size_t nBuf, off_t off){
+  if( tsIsFailErrno("pwrite64") ){
+    return -1;
+  }
+  return orig_pwrite64(fd, aBuf, nBuf, off);
+}
+
+/*
+** A wrapper around fchmod().
+*/
+static int ts_fchmod(int fd, mode_t mode){
+  if( tsIsFail() ){
+    return -1;
+  }
+  return orig_fchmod(fd, mode);
+}
+
+/*
+** A wrapper around fallocate().
+**
+** SQLite assumes that the fallocate() function is compatible with
+** posix_fallocate(). According to the Linux man page (2009-09-30):
+**
+**   posix_fallocate() returns  zero on success, or an error number on
+**   failure. Note that errno is not set.
+*/
+static int ts_fallocate(int fd, off_t off, off_t len){
+  if( tsIsFail() ){
+    return tsErrno("fallocate");
+  }
+  return orig_fallocate(fd, off, len);
+}
+
+static int test_syscall_install(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_vfs *pVfs; 
+  int nElem;
+  int i;
+  Tcl_Obj **apElem;
+
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 2, objv, "SYSCALL-LIST");
+    return TCL_ERROR;
+  }
+  if( Tcl_ListObjGetElements(interp, objv[2], &nElem, &apElem) ){
+    return TCL_ERROR;
+  }
+  pVfs = sqlite3_vfs_find(0);
+
+  for(i=0; i<nElem; i++){
+    int iCall;
+    int rc = Tcl_GetIndexFromObjStruct(interp, 
+        apElem[i], aSyscall, sizeof(aSyscall[0]), "system-call", 0, &iCall
+    );
+    if( rc ) return rc;
+    if( aSyscall[iCall].xOrig==0 ){
+      aSyscall[iCall].xOrig = pVfs->xGetSystemCall(pVfs, aSyscall[iCall].zName);
+      pVfs->xSetSystemCall(pVfs, aSyscall[iCall].zName, aSyscall[iCall].xTest);
+    }
+    aSyscall[iCall].custom_errno = aSyscall[iCall].default_errno;
+  }
+
+  return TCL_OK;
+}
+
+static int test_syscall_uninstall(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_vfs *pVfs; 
+  int i;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 2, objv, "");
+    return TCL_ERROR;
+  }
+
+  pVfs = sqlite3_vfs_find(0);
+  for(i=0; aSyscall[i].zName; i++){
+    if( aSyscall[i].xOrig ){
+      pVfs->xSetSystemCall(pVfs, aSyscall[i].zName, 0);
+      aSyscall[i].xOrig = 0;
+    }
+  }
+  return TCL_OK;
+}
+
+static int test_syscall_reset(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_vfs *pVfs; 
+  int i;
+  int rc;
+
+  if( objc!=2 && objc!=3 ){
+    Tcl_WrongNumArgs(interp, 2, objv, "");
+    return TCL_ERROR;
+  }
+
+  pVfs = sqlite3_vfs_find(0);
+  if( objc==2 ){
+    rc = pVfs->xSetSystemCall(pVfs, 0, 0);
+    for(i=0; aSyscall[i].zName; i++) aSyscall[i].xOrig = 0;
+  }else{
+    int nFunc;
+    char *zFunc = Tcl_GetStringFromObj(objv[2], &nFunc);
+    rc = pVfs->xSetSystemCall(pVfs, Tcl_GetString(objv[2]), 0);
+    for(i=0; rc==SQLITE_OK && aSyscall[i].zName; i++){
+      if( strlen(aSyscall[i].zName)!=nFunc ) continue;
+      if( memcmp(aSyscall[i].zName, zFunc, nFunc) ) continue;
+      aSyscall[i].xOrig = 0;
+    }
+  }
+  if( rc!=SQLITE_OK ){
+    Tcl_SetObjResult(interp, Tcl_NewStringObj(sqlite3TestErrorName(rc), -1));
+    return TCL_ERROR;
+  }
+
+  Tcl_ResetResult(interp);
+  return TCL_OK;
+}
+
+static int test_syscall_exists(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_vfs *pVfs; 
+  sqlite3_syscall_ptr x;
+
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 2, objv, "");
+    return TCL_ERROR;
+  }
+
+  pVfs = sqlite3_vfs_find(0);
+  x = pVfs->xGetSystemCall(pVfs, Tcl_GetString(objv[2]));
+
+  Tcl_SetObjResult(interp, Tcl_NewBooleanObj(x!=0));
+  return TCL_OK;
+}
+
+static int test_syscall_fault(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int nCount = 0;
+  int bPersist = 0;
+
+  if( objc!=2 && objc!=4 ){
+    Tcl_WrongNumArgs(interp, 2, objv, "?COUNT PERSIST?");
+    return TCL_ERROR;
+  }
+
+  if( objc==4 ){
+    if( Tcl_GetIntFromObj(interp, objv[2], &nCount)
+     || Tcl_GetBooleanFromObj(interp, objv[3], &bPersist)
+    ){
+      return TCL_ERROR;
+    }
+  }
+
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(gSyscall.nFail));
+  gSyscall.nCount = nCount;
+  gSyscall.bPersist = bPersist;
+  gSyscall.nFail = 0;
+  return TCL_OK;
+}
+
+static int test_syscall_errno(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int iCall;
+  int iErrno;
+  int rc;
+
+  struct Errno {
+    const char *z;
+    int i;
+  } aErrno[] = {
+    { "EACCES",    EACCES },
+    { "EINTR",     EINTR },
+    { "EIO",       EIO },
+    { "EOVERFLOW", EOVERFLOW },
+    { "ENOMEM",    ENOMEM },
+    { "EAGAIN",    EAGAIN },
+    { "ETIMEDOUT", ETIMEDOUT },
+    { "EBUSY",     EBUSY },
+    { "EPERM",     EPERM },
+    { "EDEADLK",   EDEADLK },
+    { "ENOLCK",    ENOLCK },
+    { 0, 0 }
+  };
+
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 2, objv, "SYSCALL ERRNO");
+    return TCL_ERROR;
+  }
+
+  rc = Tcl_GetIndexFromObjStruct(interp, 
+      objv[2], aSyscall, sizeof(aSyscall[0]), "system-call", 0, &iCall
+  );
+  if( rc!=TCL_OK ) return rc;
+  rc = Tcl_GetIndexFromObjStruct(interp, 
+      objv[3], aErrno, sizeof(aErrno[0]), "errno", 0, &iErrno
+  );
+  if( rc!=TCL_OK ) return rc;
+
+  aSyscall[iCall].custom_errno = aErrno[iErrno].i;
+  return TCL_OK;
+}
+
+static int test_syscall_list(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  const char *zSys;
+  sqlite3_vfs *pVfs; 
+  Tcl_Obj *pList;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 2, objv, "");
+    return TCL_ERROR;
+  }
+
+  pVfs = sqlite3_vfs_find(0);
+  pList = Tcl_NewObj();
+  Tcl_IncrRefCount(pList);
+  for(zSys = pVfs->xNextSystemCall(pVfs, 0); 
+      zSys!=0;
+      zSys = pVfs->xNextSystemCall(pVfs, zSys)
+  ){
+    Tcl_ListObjAppendElement(interp, pList, Tcl_NewStringObj(zSys, -1));
+  }
+
+  Tcl_SetObjResult(interp, pList);
+  Tcl_DecrRefCount(pList);
+  return TCL_OK;
+}
+
+static int test_syscall_defaultvfs(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_vfs *pVfs; 
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 2, objv, "");
+    return TCL_ERROR;
+  }
+
+  pVfs = sqlite3_vfs_find(0);
+  Tcl_SetObjResult(interp, Tcl_NewStringObj(pVfs->zName, -1));
+  return TCL_OK;
+}
+
+static int test_syscall(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  struct SyscallCmd {
+    const char *zName;
+    Tcl_ObjCmdProc *xCmd;
+  } aCmd[] = {
+    { "fault",      test_syscall_fault },
+    { "install",    test_syscall_install },
+    { "uninstall",  test_syscall_uninstall },
+    { "reset",      test_syscall_reset },
+    { "errno",      test_syscall_errno },
+    { "exists",     test_syscall_exists },
+    { "list",       test_syscall_list },
+    { "defaultvfs", test_syscall_defaultvfs },
+    { 0, 0 }
+  };
+  int iCmd;
+  int rc;
+
+  if( objc<2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "SUB-COMMAND ...");
+    return TCL_ERROR;
+  }
+  rc = Tcl_GetIndexFromObjStruct(interp, 
+      objv[1], aCmd, sizeof(aCmd[0]), "sub-command", 0, &iCmd
+  );
+  if( rc!=TCL_OK ) return rc;
+  return aCmd[iCmd].xCmd(clientData, interp, objc, objv);
+}
+
+int SqlitetestSyscall_Init(Tcl_Interp *interp){
+  struct SyscallCmd {
+    const char *zName;
+    Tcl_ObjCmdProc *xCmd;
+  } aCmd[] = {
+    { "test_syscall",     test_syscall},
+  };
+  int i;
+
+  for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aCmd[i].zName, aCmd[i].xCmd, 0, 0);
+  }
+  return TCL_OK;
+}
+#else
+int SqlitetestSyscall_Init(Tcl_Interp *interp){
+  return TCL_OK;
+}
+#endif
diff --git a/src/test_tclvar.c b/src/test_tclvar.c
new file mode 100644
index 0000000..1219190
--- /dev/null
+++ b/src/test_tclvar.c
@@ -0,0 +1,332 @@
+/*
+** 2006 June 13
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Code for testing the virtual table interfaces.  This code
+** is not included in the SQLite library.  It is used for automated
+** testing of the SQLite library.
+**
+** The emphasis of this file is a virtual table that provides
+** access to TCL variables.
+*/
+#include "sqliteInt.h"
+#include "tcl.h"
+#include <stdlib.h>
+#include <string.h>
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+
+typedef struct tclvar_vtab tclvar_vtab;
+typedef struct tclvar_cursor tclvar_cursor;
+
+/* 
+** A tclvar virtual-table object 
+*/
+struct tclvar_vtab {
+  sqlite3_vtab base;
+  Tcl_Interp *interp;
+};
+
+/* A tclvar cursor object */
+struct tclvar_cursor {
+  sqlite3_vtab_cursor base;
+
+  Tcl_Obj *pList1;     /* Result of [info vars ?pattern?] */
+  Tcl_Obj *pList2;     /* Result of [array names [lindex $pList1 $i1]] */
+  int i1;              /* Current item in pList1 */
+  int i2;              /* Current item (if any) in pList2 */
+};
+
+/* Methods for the tclvar module */
+static int tclvarConnect(
+  sqlite3 *db,
+  void *pAux,
+  int argc, const char *const*argv,
+  sqlite3_vtab **ppVtab,
+  char **pzErr
+){
+  tclvar_vtab *pVtab;
+  static const char zSchema[] = 
+     "CREATE TABLE whatever(name TEXT, arrayname TEXT, value TEXT)";
+  pVtab = sqlite3MallocZero( sizeof(*pVtab) );
+  if( pVtab==0 ) return SQLITE_NOMEM;
+  *ppVtab = &pVtab->base;
+  pVtab->interp = (Tcl_Interp *)pAux;
+  sqlite3_declare_vtab(db, zSchema);
+  return SQLITE_OK;
+}
+/* Note that for this virtual table, the xCreate and xConnect
+** methods are identical. */
+
+static int tclvarDisconnect(sqlite3_vtab *pVtab){
+  sqlite3_free(pVtab);
+  return SQLITE_OK;
+}
+/* The xDisconnect and xDestroy methods are also the same */
+
+/*
+** Open a new tclvar cursor.
+*/
+static int tclvarOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
+  tclvar_cursor *pCur;
+  pCur = sqlite3MallocZero(sizeof(tclvar_cursor));
+  *ppCursor = &pCur->base;
+  return SQLITE_OK;
+}
+
+/*
+** Close a tclvar cursor.
+*/
+static int tclvarClose(sqlite3_vtab_cursor *cur){
+  tclvar_cursor *pCur = (tclvar_cursor *)cur;
+  if( pCur->pList1 ){
+    Tcl_DecrRefCount(pCur->pList1);
+  }
+  if( pCur->pList2 ){
+    Tcl_DecrRefCount(pCur->pList2);
+  }
+  sqlite3_free(pCur);
+  return SQLITE_OK;
+}
+
+/*
+** Returns 1 if data is ready, or 0 if not.
+*/
+static int next2(Tcl_Interp *interp, tclvar_cursor *pCur, Tcl_Obj *pObj){
+  Tcl_Obj *p;
+
+  if( pObj ){
+    if( !pCur->pList2 ){
+      p = Tcl_NewStringObj("array names", -1);
+      Tcl_IncrRefCount(p);
+      Tcl_ListObjAppendElement(0, p, pObj);
+      Tcl_EvalObjEx(interp, p, TCL_EVAL_GLOBAL);
+      Tcl_DecrRefCount(p);
+      pCur->pList2 = Tcl_GetObjResult(interp);
+      Tcl_IncrRefCount(pCur->pList2);
+      assert( pCur->i2==0 );
+    }else{
+      int n = 0;
+      pCur->i2++;
+      Tcl_ListObjLength(0, pCur->pList2, &n);
+      if( pCur->i2>=n ){
+        Tcl_DecrRefCount(pCur->pList2);
+        pCur->pList2 = 0;
+        pCur->i2 = 0;
+        return 0;
+      }
+    }
+  }
+
+  return 1;
+}
+
+static int tclvarNext(sqlite3_vtab_cursor *cur){
+  Tcl_Obj *pObj;
+  int n = 0;
+  int ok = 0;
+
+  tclvar_cursor *pCur = (tclvar_cursor *)cur;
+  Tcl_Interp *interp = ((tclvar_vtab *)(cur->pVtab))->interp;
+
+  Tcl_ListObjLength(0, pCur->pList1, &n);
+  while( !ok && pCur->i1<n ){
+    Tcl_ListObjIndex(0, pCur->pList1, pCur->i1, &pObj);
+    ok = next2(interp, pCur, pObj);
+    if( !ok ){
+      pCur->i1++;
+    }
+  }
+
+  return 0;
+}
+
+static int tclvarFilter(
+  sqlite3_vtab_cursor *pVtabCursor, 
+  int idxNum, const char *idxStr,
+  int argc, sqlite3_value **argv
+){
+  tclvar_cursor *pCur = (tclvar_cursor *)pVtabCursor;
+  Tcl_Interp *interp = ((tclvar_vtab *)(pVtabCursor->pVtab))->interp;
+
+  Tcl_Obj *p = Tcl_NewStringObj("info vars", -1);
+  Tcl_IncrRefCount(p);
+
+  assert( argc==0 || argc==1 );
+  if( argc==1 ){
+    Tcl_Obj *pArg = Tcl_NewStringObj((char*)sqlite3_value_text(argv[0]), -1);
+    Tcl_ListObjAppendElement(0, p, pArg);
+  }
+  Tcl_EvalObjEx(interp, p, TCL_EVAL_GLOBAL);
+  if( pCur->pList1 ){
+    Tcl_DecrRefCount(pCur->pList1);
+  }
+  if( pCur->pList2 ){
+    Tcl_DecrRefCount(pCur->pList2);
+    pCur->pList2 = 0;
+  }
+  pCur->i1 = 0;
+  pCur->i2 = 0;
+  pCur->pList1 = Tcl_GetObjResult(interp);
+  Tcl_IncrRefCount(pCur->pList1);
+  assert( pCur->i1==0 && pCur->i2==0 && pCur->pList2==0 );
+
+  Tcl_DecrRefCount(p);
+  return tclvarNext(pVtabCursor);
+}
+
+static int tclvarColumn(sqlite3_vtab_cursor *cur, sqlite3_context *ctx, int i){
+  Tcl_Obj *p1;
+  Tcl_Obj *p2;
+  const char *z1; 
+  const char *z2 = "";
+  tclvar_cursor *pCur = (tclvar_cursor*)cur;
+  Tcl_Interp *interp = ((tclvar_vtab *)cur->pVtab)->interp;
+
+  Tcl_ListObjIndex(interp, pCur->pList1, pCur->i1, &p1);
+  Tcl_ListObjIndex(interp, pCur->pList2, pCur->i2, &p2);
+  z1 = Tcl_GetString(p1);
+  if( p2 ){
+    z2 = Tcl_GetString(p2);
+  }
+  switch (i) {
+    case 0: {
+      sqlite3_result_text(ctx, z1, -1, SQLITE_TRANSIENT);
+      break;
+    }
+    case 1: {
+      sqlite3_result_text(ctx, z2, -1, SQLITE_TRANSIENT);
+      break;
+    }
+    case 2: {
+      Tcl_Obj *pVal = Tcl_GetVar2Ex(interp, z1, *z2?z2:0, TCL_GLOBAL_ONLY);
+      sqlite3_result_text(ctx, Tcl_GetString(pVal), -1, SQLITE_TRANSIENT);
+      break;
+    }
+  }
+  return SQLITE_OK;
+}
+
+static int tclvarRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
+  *pRowid = 0;
+  return SQLITE_OK;
+}
+
+static int tclvarEof(sqlite3_vtab_cursor *cur){
+  tclvar_cursor *pCur = (tclvar_cursor*)cur;
+  return (pCur->pList2?0:1);
+}
+
+static int tclvarBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
+  int ii;
+
+  for(ii=0; ii<pIdxInfo->nConstraint; ii++){
+    struct sqlite3_index_constraint const *pCons = &pIdxInfo->aConstraint[ii];
+    if( pCons->iColumn==0 && pCons->usable
+           && pCons->op==SQLITE_INDEX_CONSTRAINT_EQ ){
+      struct sqlite3_index_constraint_usage *pUsage;
+      pUsage = &pIdxInfo->aConstraintUsage[ii];
+      pUsage->omit = 0;
+      pUsage->argvIndex = 1;
+      return SQLITE_OK;
+    }
+  }
+
+  for(ii=0; ii<pIdxInfo->nConstraint; ii++){
+    struct sqlite3_index_constraint const *pCons = &pIdxInfo->aConstraint[ii];
+    if( pCons->iColumn==0 && pCons->usable
+           && pCons->op==SQLITE_INDEX_CONSTRAINT_MATCH ){
+      struct sqlite3_index_constraint_usage *pUsage;
+      pUsage = &pIdxInfo->aConstraintUsage[ii];
+      pUsage->omit = 1;
+      pUsage->argvIndex = 1;
+      return SQLITE_OK;
+    }
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** A virtual table module that provides read-only access to a
+** Tcl global variable namespace.
+*/
+static sqlite3_module tclvarModule = {
+  0,                         /* iVersion */
+  tclvarConnect,
+  tclvarConnect,
+  tclvarBestIndex,
+  tclvarDisconnect, 
+  tclvarDisconnect,
+  tclvarOpen,                  /* xOpen - open a cursor */
+  tclvarClose,                 /* xClose - close a cursor */
+  tclvarFilter,                /* xFilter - configure scan constraints */
+  tclvarNext,                  /* xNext - advance a cursor */
+  tclvarEof,                   /* xEof - check for end of scan */
+  tclvarColumn,                /* xColumn - read data */
+  tclvarRowid,                 /* xRowid - read data */
+  0,                           /* xUpdate */
+  0,                           /* xBegin */
+  0,                           /* xSync */
+  0,                           /* xCommit */
+  0,                           /* xRollback */
+  0,                           /* xFindMethod */
+  0,                           /* xRename */
+};
+
+/*
+** Decode a pointer to an sqlite3 object.
+*/
+extern int getDbPointer(Tcl_Interp *interp, const char *zA, sqlite3 **ppDb);
+
+/*
+** Register the echo virtual table module.
+*/
+static int register_tclvar_module(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3 *db;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  sqlite3_create_module(db, "tclvar", &tclvarModule, (void *)interp);
+#endif
+  return TCL_OK;
+}
+
+#endif
+
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetesttclvar_Init(Tcl_Interp *interp){
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  static struct {
+     char *zName;
+     Tcl_ObjCmdProc *xProc;
+     void *clientData;
+  } aObjCmd[] = {
+     { "register_tclvar_module",   register_tclvar_module, 0 },
+  };
+  int i;
+  for(i=0; i<sizeof(aObjCmd)/sizeof(aObjCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aObjCmd[i].zName, 
+        aObjCmd[i].xProc, aObjCmd[i].clientData, 0);
+  }
+#endif
+  return TCL_OK;
+}
diff --git a/src/test_thread.c b/src/test_thread.c
new file mode 100644
index 0000000..aa89467
--- /dev/null
+++ b/src/test_thread.c
@@ -0,0 +1,645 @@
+/*
+** 2007 September 9
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains the implementation of some Tcl commands used to
+** test that sqlite3 database handles may be concurrently accessed by 
+** multiple threads. Right now this only works on unix.
+*/
+
+#include "sqliteInt.h"
+#include <tcl.h>
+
+#if SQLITE_THREADSAFE
+
+#include <errno.h>
+
+#if !defined(_MSC_VER)
+#include <unistd.h>
+#endif
+
+/*
+** One of these is allocated for each thread created by [sqlthread spawn].
+*/
+typedef struct SqlThread SqlThread;
+struct SqlThread {
+  Tcl_ThreadId parent;     /* Thread id of parent thread */
+  Tcl_Interp *interp;      /* Parent interpreter */
+  char *zScript;           /* The script to execute. */
+  char *zVarname;          /* Varname in parent script */
+};
+
+/*
+** A custom Tcl_Event type used by this module. When the event is
+** handled, script zScript is evaluated in interpreter interp. If
+** the evaluation throws an exception (returns TCL_ERROR), then the
+** error is handled by Tcl_BackgroundError(). If no error occurs,
+** the result is simply discarded.
+*/
+typedef struct EvalEvent EvalEvent;
+struct EvalEvent {
+  Tcl_Event base;          /* Base class of type Tcl_Event */
+  char *zScript;           /* The script to execute. */
+  Tcl_Interp *interp;      /* The interpreter to execute it in. */
+};
+
+static Tcl_ObjCmdProc sqlthread_proc;
+static Tcl_ObjCmdProc clock_seconds_proc;
+#if SQLITE_OS_UNIX && defined(SQLITE_ENABLE_UNLOCK_NOTIFY)
+static Tcl_ObjCmdProc blocking_step_proc;
+static Tcl_ObjCmdProc blocking_prepare_v2_proc;
+#endif
+int Sqlitetest1_Init(Tcl_Interp *);
+int Sqlite3_Init(Tcl_Interp *);
+
+/* Functions from test1.c */
+void *sqlite3TestTextToPtr(const char *);
+const char *sqlite3TestErrorName(int);
+int getDbPointer(Tcl_Interp *, const char *, sqlite3 **);
+int sqlite3TestMakePointerStr(Tcl_Interp *, char *, void *);
+int sqlite3TestErrCode(Tcl_Interp *, sqlite3 *, int);
+
+/*
+** Handler for events of type EvalEvent.
+*/
+static int tclScriptEvent(Tcl_Event *evPtr, int flags){
+  int rc;
+  EvalEvent *p = (EvalEvent *)evPtr;
+  rc = Tcl_Eval(p->interp, p->zScript);
+  if( rc!=TCL_OK ){
+    Tcl_BackgroundError(p->interp);
+  }
+  UNUSED_PARAMETER(flags);
+  return 1;
+}
+
+/*
+** Register an EvalEvent to evaluate the script pScript in the
+** parent interpreter/thread of SqlThread p.
+*/
+static void postToParent(SqlThread *p, Tcl_Obj *pScript){
+  EvalEvent *pEvent;
+  char *zMsg;
+  int nMsg;
+
+  zMsg = Tcl_GetStringFromObj(pScript, &nMsg); 
+  pEvent = (EvalEvent *)ckalloc(sizeof(EvalEvent)+nMsg+1);
+  pEvent->base.nextPtr = 0;
+  pEvent->base.proc = tclScriptEvent;
+  pEvent->zScript = (char *)&pEvent[1];
+  memcpy(pEvent->zScript, zMsg, nMsg+1);
+  pEvent->interp = p->interp;
+
+  Tcl_ThreadQueueEvent(p->parent, (Tcl_Event *)pEvent, TCL_QUEUE_TAIL);
+  Tcl_ThreadAlert(p->parent);
+}
+
+/*
+** The main function for threads created with [sqlthread spawn].
+*/
+static Tcl_ThreadCreateType tclScriptThread(ClientData pSqlThread){
+  Tcl_Interp *interp;
+  Tcl_Obj *pRes;
+  Tcl_Obj *pList;
+  int rc;
+  SqlThread *p = (SqlThread *)pSqlThread;
+  extern int Sqlitetest_mutex_Init(Tcl_Interp*);
+
+  interp = Tcl_CreateInterp();
+  Tcl_CreateObjCommand(interp, "clock_seconds", clock_seconds_proc, 0, 0);
+  Tcl_CreateObjCommand(interp, "sqlthread", sqlthread_proc, pSqlThread, 0);
+#if SQLITE_OS_UNIX && defined(SQLITE_ENABLE_UNLOCK_NOTIFY)
+  Tcl_CreateObjCommand(interp, "sqlite3_blocking_step", blocking_step_proc,0,0);
+  Tcl_CreateObjCommand(interp, 
+      "sqlite3_blocking_prepare_v2", blocking_prepare_v2_proc, (void *)1, 0);
+  Tcl_CreateObjCommand(interp, 
+      "sqlite3_nonblocking_prepare_v2", blocking_prepare_v2_proc, 0, 0);
+#endif
+  Sqlitetest1_Init(interp);
+  Sqlitetest_mutex_Init(interp);
+  Sqlite3_Init(interp);
+
+  rc = Tcl_Eval(interp, p->zScript);
+  pRes = Tcl_GetObjResult(interp);
+  pList = Tcl_NewObj();
+  Tcl_IncrRefCount(pList);
+  Tcl_IncrRefCount(pRes);
+
+  if( rc!=TCL_OK ){
+    Tcl_ListObjAppendElement(interp, pList, Tcl_NewStringObj("error", -1));
+    Tcl_ListObjAppendElement(interp, pList, pRes);
+    postToParent(p, pList);
+    Tcl_DecrRefCount(pList);
+    pList = Tcl_NewObj();
+  }
+
+  Tcl_ListObjAppendElement(interp, pList, Tcl_NewStringObj("set", -1));
+  Tcl_ListObjAppendElement(interp, pList, Tcl_NewStringObj(p->zVarname, -1));
+  Tcl_ListObjAppendElement(interp, pList, pRes);
+  postToParent(p, pList);
+
+  ckfree((void *)p);
+  Tcl_DecrRefCount(pList);
+  Tcl_DecrRefCount(pRes);
+  Tcl_DeleteInterp(interp);
+  while( Tcl_DoOneEvent(TCL_ALL_EVENTS|TCL_DONT_WAIT) );
+  Tcl_ExitThread(0);
+  TCL_THREAD_CREATE_RETURN;
+}
+
+/*
+** sqlthread spawn VARNAME SCRIPT
+**
+**     Spawn a new thread with its own Tcl interpreter and run the
+**     specified SCRIPT(s) in it. The thread terminates after running
+**     the script. The result of the script is stored in the variable
+**     VARNAME.
+**
+**     The caller can wait for the script to terminate using [vwait VARNAME].
+*/
+static int sqlthread_spawn(
+  ClientData clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  Tcl_ThreadId x;
+  SqlThread *pNew;
+  int rc;
+
+  int nVarname; char *zVarname;
+  int nScript; char *zScript;
+
+  /* Parameters for thread creation */
+  const int nStack = TCL_THREAD_STACK_DEFAULT;
+  const int flags = TCL_THREAD_NOFLAGS;
+
+  assert(objc==4);
+  UNUSED_PARAMETER(clientData);
+  UNUSED_PARAMETER(objc);
+
+  zVarname = Tcl_GetStringFromObj(objv[2], &nVarname);
+  zScript = Tcl_GetStringFromObj(objv[3], &nScript);
+
+  pNew = (SqlThread *)ckalloc(sizeof(SqlThread)+nVarname+nScript+2);
+  pNew->zVarname = (char *)&pNew[1];
+  pNew->zScript = (char *)&pNew->zVarname[nVarname+1];
+  memcpy(pNew->zVarname, zVarname, nVarname+1);
+  memcpy(pNew->zScript, zScript, nScript+1);
+  pNew->parent = Tcl_GetCurrentThread();
+  pNew->interp = interp;
+
+  rc = Tcl_CreateThread(&x, tclScriptThread, (void *)pNew, nStack, flags);
+  if( rc!=TCL_OK ){
+    Tcl_AppendResult(interp, "Error in Tcl_CreateThread()", 0);
+    ckfree((char *)pNew);
+    return TCL_ERROR;
+  }
+
+  return TCL_OK;
+}
+
+/*
+** sqlthread parent SCRIPT
+**
+**     This can be called by spawned threads only. It sends the specified
+**     script back to the parent thread for execution. The result of
+**     evaluating the SCRIPT is returned. The parent thread must enter
+**     the event loop for this to work - otherwise the caller will
+**     block indefinitely.
+**
+**     NOTE: At the moment, this doesn't work. FIXME.
+*/
+static int sqlthread_parent(
+  ClientData clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  EvalEvent *pEvent;
+  char *zMsg;
+  int nMsg;
+  SqlThread *p = (SqlThread *)clientData;
+
+  assert(objc==3);
+  UNUSED_PARAMETER(objc);
+
+  if( p==0 ){
+    Tcl_AppendResult(interp, "no parent thread", 0);
+    return TCL_ERROR;
+  }
+
+  zMsg = Tcl_GetStringFromObj(objv[2], &nMsg);
+  pEvent = (EvalEvent *)ckalloc(sizeof(EvalEvent)+nMsg+1);
+  pEvent->base.nextPtr = 0;
+  pEvent->base.proc = tclScriptEvent;
+  pEvent->zScript = (char *)&pEvent[1];
+  memcpy(pEvent->zScript, zMsg, nMsg+1);
+  pEvent->interp = p->interp;
+  Tcl_ThreadQueueEvent(p->parent, (Tcl_Event *)pEvent, TCL_QUEUE_TAIL);
+  Tcl_ThreadAlert(p->parent);
+
+  return TCL_OK;
+}
+
+static int xBusy(void *pArg, int nBusy){
+  UNUSED_PARAMETER(pArg);
+  UNUSED_PARAMETER(nBusy);
+  sqlite3_sleep(50);
+  return 1;             /* Try again... */
+}
+
+/*
+** sqlthread open
+**
+**     Open a database handle and return the string representation of
+**     the pointer value.
+*/
+static int sqlthread_open(
+  ClientData clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int sqlite3TestMakePointerStr(Tcl_Interp *interp, char *zPtr, void *p);
+
+  const char *zFilename;
+  sqlite3 *db;
+  int rc;
+  char zBuf[100];
+  extern void Md5_Register(sqlite3*);
+
+  UNUSED_PARAMETER(clientData);
+  UNUSED_PARAMETER(objc);
+
+  zFilename = Tcl_GetString(objv[2]);
+  rc = sqlite3_open(zFilename, &db);
+#ifdef SQLITE_HAS_CODEC
+  if( db && objc>=4 ){
+    const char *zKey;
+    int nKey;
+    zKey = Tcl_GetStringFromObj(objv[3], &nKey);
+    rc = sqlite3_key(db, zKey, nKey);
+    if( rc!=SQLITE_OK ){
+      char *zErrMsg = sqlite3_mprintf("error %d: %s", rc, sqlite3_errmsg(db));
+      sqlite3_close(db);
+      Tcl_AppendResult(interp, zErrMsg, (char*)0);
+      sqlite3_free(zErrMsg);
+      return TCL_ERROR;
+    }
+  }
+#endif
+  Md5_Register(db);
+  sqlite3_busy_handler(db, xBusy, 0);
+  
+  if( sqlite3TestMakePointerStr(interp, zBuf, db) ) return TCL_ERROR;
+  Tcl_AppendResult(interp, zBuf, 0);
+
+  return TCL_OK;
+}
+
+
+/*
+** sqlthread open
+**
+**     Return the current thread-id (Tcl_GetCurrentThread()) cast to
+**     an integer.
+*/
+static int sqlthread_id(
+  ClientData clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  Tcl_ThreadId id = Tcl_GetCurrentThread();
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(SQLITE_PTR_TO_INT(id)));
+  UNUSED_PARAMETER(clientData);
+  UNUSED_PARAMETER(objc);
+  UNUSED_PARAMETER(objv);
+  return TCL_OK;
+}
+
+
+/*
+** Dispatch routine for the sub-commands of [sqlthread].
+*/
+static int sqlthread_proc(
+  ClientData clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  struct SubCommand {
+    char *zName;
+    Tcl_ObjCmdProc *xProc;
+    int nArg;
+    char *zUsage;
+  } aSub[] = {
+    {"parent", sqlthread_parent, 1, "SCRIPT"},
+    {"spawn",  sqlthread_spawn,  2, "VARNAME SCRIPT"},
+    {"open",   sqlthread_open,   1, "DBNAME"},
+    {"id",     sqlthread_id,     0, ""},
+    {0, 0, 0}
+  };
+  struct SubCommand *pSub;
+  int rc;
+  int iIndex;
+
+  if( objc<2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "SUB-COMMAND");
+    return TCL_ERROR;
+  }
+
+  rc = Tcl_GetIndexFromObjStruct(
+      interp, objv[1], aSub, sizeof(aSub[0]), "sub-command", 0, &iIndex
+  );
+  if( rc!=TCL_OK ) return rc;
+  pSub = &aSub[iIndex];
+
+  if( objc<(pSub->nArg+2) ){
+    Tcl_WrongNumArgs(interp, 2, objv, pSub->zUsage);
+    return TCL_ERROR;
+  }
+
+  return pSub->xProc(clientData, interp, objc, objv);
+}
+
+/*
+** The [clock_seconds] command. This is more or less the same as the
+** regular tcl [clock seconds], except that it is available in testfixture
+** when linked against both Tcl 8.4 and 8.5. Because [clock seconds] is
+** implemented as a script in Tcl 8.5, it is not usually available to
+** testfixture.
+*/ 
+static int clock_seconds_proc(
+  ClientData clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  Tcl_Time now;
+  Tcl_GetTime(&now);
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(now.sec));
+  UNUSED_PARAMETER(clientData);
+  UNUSED_PARAMETER(objc);
+  UNUSED_PARAMETER(objv);
+  return TCL_OK;
+}
+
+/*************************************************************************
+** This block contains the implementation of the [sqlite3_blocking_step]
+** command available to threads created by [sqlthread spawn] commands. It
+** is only available on UNIX for now. This is because pthread condition
+** variables are used.
+**
+** The source code for the C functions sqlite3_blocking_step(),
+** blocking_step_notify() and the structure UnlockNotification is
+** automatically extracted from this file and used as part of the
+** documentation for the sqlite3_unlock_notify() API function. This
+** should be considered if these functions are to be extended (i.e. to 
+** support windows) in the future.
+*/ 
+#if SQLITE_OS_UNIX && defined(SQLITE_ENABLE_UNLOCK_NOTIFY)
+
+/* BEGIN_SQLITE_BLOCKING_STEP */
+/* This example uses the pthreads API */
+#include <pthread.h>
+
+/*
+** A pointer to an instance of this structure is passed as the user-context
+** pointer when registering for an unlock-notify callback.
+*/
+typedef struct UnlockNotification UnlockNotification;
+struct UnlockNotification {
+  int fired;                         /* True after unlock event has occurred */
+  pthread_cond_t cond;               /* Condition variable to wait on */
+  pthread_mutex_t mutex;             /* Mutex to protect structure */
+};
+
+/*
+** This function is an unlock-notify callback registered with SQLite.
+*/
+static void unlock_notify_cb(void **apArg, int nArg){
+  int i;
+  for(i=0; i<nArg; i++){
+    UnlockNotification *p = (UnlockNotification *)apArg[i];
+    pthread_mutex_lock(&p->mutex);
+    p->fired = 1;
+    pthread_cond_signal(&p->cond);
+    pthread_mutex_unlock(&p->mutex);
+  }
+}
+
+/*
+** This function assumes that an SQLite API call (either sqlite3_prepare_v2() 
+** or sqlite3_step()) has just returned SQLITE_LOCKED. The argument is the
+** associated database connection.
+**
+** This function calls sqlite3_unlock_notify() to register for an 
+** unlock-notify callback, then blocks until that callback is delivered 
+** and returns SQLITE_OK. The caller should then retry the failed operation.
+**
+** Or, if sqlite3_unlock_notify() indicates that to block would deadlock 
+** the system, then this function returns SQLITE_LOCKED immediately. In 
+** this case the caller should not retry the operation and should roll 
+** back the current transaction (if any).
+*/
+static int wait_for_unlock_notify(sqlite3 *db){
+  int rc;
+  UnlockNotification un;
+
+  /* Initialize the UnlockNotification structure. */
+  un.fired = 0;
+  pthread_mutex_init(&un.mutex, 0);
+  pthread_cond_init(&un.cond, 0);
+
+  /* Register for an unlock-notify callback. */
+  rc = sqlite3_unlock_notify(db, unlock_notify_cb, (void *)&un);
+  assert( rc==SQLITE_LOCKED || rc==SQLITE_OK );
+
+  /* The call to sqlite3_unlock_notify() always returns either SQLITE_LOCKED 
+  ** or SQLITE_OK. 
+  **
+  ** If SQLITE_LOCKED was returned, then the system is deadlocked. In this
+  ** case this function needs to return SQLITE_LOCKED to the caller so 
+  ** that the current transaction can be rolled back. Otherwise, block
+  ** until the unlock-notify callback is invoked, then return SQLITE_OK.
+  */
+  if( rc==SQLITE_OK ){
+    pthread_mutex_lock(&un.mutex);
+    if( !un.fired ){
+      pthread_cond_wait(&un.cond, &un.mutex);
+    }
+    pthread_mutex_unlock(&un.mutex);
+  }
+
+  /* Destroy the mutex and condition variables. */
+  pthread_cond_destroy(&un.cond);
+  pthread_mutex_destroy(&un.mutex);
+
+  return rc;
+}
+
+/*
+** This function is a wrapper around the SQLite function sqlite3_step().
+** It functions in the same way as step(), except that if a required
+** shared-cache lock cannot be obtained, this function may block waiting for
+** the lock to become available. In this scenario the normal API step()
+** function always returns SQLITE_LOCKED.
+**
+** If this function returns SQLITE_LOCKED, the caller should rollback
+** the current transaction (if any) and try again later. Otherwise, the
+** system may become deadlocked.
+*/
+int sqlite3_blocking_step(sqlite3_stmt *pStmt){
+  int rc;
+  while( SQLITE_LOCKED==(rc = sqlite3_step(pStmt)) ){
+    rc = wait_for_unlock_notify(sqlite3_db_handle(pStmt));
+    if( rc!=SQLITE_OK ) break;
+    sqlite3_reset(pStmt);
+  }
+  return rc;
+}
+
+/*
+** This function is a wrapper around the SQLite function sqlite3_prepare_v2().
+** It functions in the same way as prepare_v2(), except that if a required
+** shared-cache lock cannot be obtained, this function may block waiting for
+** the lock to become available. In this scenario the normal API prepare_v2()
+** function always returns SQLITE_LOCKED.
+**
+** If this function returns SQLITE_LOCKED, the caller should rollback
+** the current transaction (if any) and try again later. Otherwise, the
+** system may become deadlocked.
+*/
+int sqlite3_blocking_prepare_v2(
+  sqlite3 *db,              /* Database handle. */
+  const char *zSql,         /* UTF-8 encoded SQL statement. */
+  int nSql,                 /* Length of zSql in bytes. */
+  sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
+  const char **pz           /* OUT: End of parsed string */
+){
+  int rc;
+  while( SQLITE_LOCKED==(rc = sqlite3_prepare_v2(db, zSql, nSql, ppStmt, pz)) ){
+    rc = wait_for_unlock_notify(db);
+    if( rc!=SQLITE_OK ) break;
+  }
+  return rc;
+}
+/* END_SQLITE_BLOCKING_STEP */
+
+/*
+** Usage: sqlite3_blocking_step STMT
+**
+** Advance the statement to the next row.
+*/
+static int blocking_step_proc(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+
+  sqlite3_stmt *pStmt;
+  int rc;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "STMT");
+    return TCL_ERROR;
+  }
+
+  pStmt = (sqlite3_stmt*)sqlite3TestTextToPtr(Tcl_GetString(objv[1]));
+  rc = sqlite3_blocking_step(pStmt);
+
+  Tcl_SetResult(interp, (char *)sqlite3TestErrorName(rc), 0);
+  return TCL_OK;
+}
+
+/*
+** Usage: sqlite3_blocking_prepare_v2 DB sql bytes ?tailvar?
+** Usage: sqlite3_nonblocking_prepare_v2 DB sql bytes ?tailvar?
+*/
+static int blocking_prepare_v2_proc(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3 *db;
+  const char *zSql;
+  int bytes;
+  const char *zTail = 0;
+  sqlite3_stmt *pStmt = 0;
+  char zBuf[50];
+  int rc;
+  int isBlocking = !(clientData==0);
+
+  if( objc!=5 && objc!=4 ){
+    Tcl_AppendResult(interp, "wrong # args: should be \"", 
+       Tcl_GetString(objv[0]), " DB sql bytes tailvar", 0);
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  zSql = Tcl_GetString(objv[2]);
+  if( Tcl_GetIntFromObj(interp, objv[3], &bytes) ) return TCL_ERROR;
+
+  if( isBlocking ){
+    rc = sqlite3_blocking_prepare_v2(db, zSql, bytes, &pStmt, &zTail);
+  }else{
+    rc = sqlite3_prepare_v2(db, zSql, bytes, &pStmt, &zTail);
+  }
+
+  assert(rc==SQLITE_OK || pStmt==0);
+  if( zTail && objc>=5 ){
+    if( bytes>=0 ){
+      bytes = bytes - (zTail-zSql);
+    }
+    Tcl_ObjSetVar2(interp, objv[4], 0, Tcl_NewStringObj(zTail, bytes), 0);
+  }
+  if( rc!=SQLITE_OK ){
+    assert( pStmt==0 );
+    sprintf(zBuf, "%s ", (char *)sqlite3TestErrorName(rc));
+    Tcl_AppendResult(interp, zBuf, sqlite3_errmsg(db), 0);
+    return TCL_ERROR;
+  }
+
+  if( pStmt ){
+    if( sqlite3TestMakePointerStr(interp, zBuf, pStmt) ) return TCL_ERROR;
+    Tcl_AppendResult(interp, zBuf, 0);
+  }
+  return TCL_OK;
+}
+
+#endif /* SQLITE_OS_UNIX && SQLITE_ENABLE_UNLOCK_NOTIFY */
+/*
+** End of implementation of [sqlite3_blocking_step].
+************************************************************************/
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int SqlitetestThread_Init(Tcl_Interp *interp){
+  Tcl_CreateObjCommand(interp, "sqlthread", sqlthread_proc, 0, 0);
+  Tcl_CreateObjCommand(interp, "clock_seconds", clock_seconds_proc, 0, 0);
+#if SQLITE_OS_UNIX && defined(SQLITE_ENABLE_UNLOCK_NOTIFY)
+  Tcl_CreateObjCommand(interp, "sqlite3_blocking_step", blocking_step_proc,0,0);
+  Tcl_CreateObjCommand(interp, 
+      "sqlite3_blocking_prepare_v2", blocking_prepare_v2_proc, (void *)1, 0);
+  Tcl_CreateObjCommand(interp, 
+      "sqlite3_nonblocking_prepare_v2", blocking_prepare_v2_proc, 0, 0);
+#endif
+  return TCL_OK;
+}
+#else
+int SqlitetestThread_Init(Tcl_Interp *interp){
+  return TCL_OK;
+}
+#endif
diff --git a/src/test_vfs.c b/src/test_vfs.c
new file mode 100644
index 0000000..546cb7c
--- /dev/null
+++ b/src/test_vfs.c
@@ -0,0 +1,1418 @@
+/*
+** 2010 May 05
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains the implementation of the Tcl [testvfs] command,
+** used to create SQLite VFS implementations with various properties and
+** instrumentation to support testing SQLite.
+**
+**   testvfs VFSNAME ?OPTIONS?
+**
+** Available options are:
+**
+**   -noshm      BOOLEAN        (True to omit shm methods. Default false)
+**   -default    BOOLEAN        (True to make the vfs default. Default false)
+**   -szosfile   INTEGER        (Value for sqlite3_vfs.szOsFile)
+**   -mxpathname INTEGER        (Value for sqlite3_vfs.mxPathname)
+**   -iversion   INTEGER        (Value for sqlite3_vfs.iVersion)
+*/
+#if SQLITE_TEST          /* This file is used for testing only */
+
+#include "sqlite3.h"
+#include "sqliteInt.h"
+
+typedef struct Testvfs Testvfs;
+typedef struct TestvfsShm TestvfsShm;
+typedef struct TestvfsBuffer TestvfsBuffer;
+typedef struct TestvfsFile TestvfsFile;
+typedef struct TestvfsFd TestvfsFd;
+
+/*
+** An open file handle.
+*/
+struct TestvfsFile {
+  sqlite3_file base;              /* Base class.  Must be first */
+  TestvfsFd *pFd;                 /* File data */
+};
+#define tvfsGetFd(pFile) (((TestvfsFile *)pFile)->pFd)
+
+struct TestvfsFd {
+  sqlite3_vfs *pVfs;              /* The VFS */
+  const char *zFilename;          /* Filename as passed to xOpen() */
+  sqlite3_file *pReal;            /* The real, underlying file descriptor */
+  Tcl_Obj *pShmId;                /* Shared memory id for Tcl callbacks */
+
+  TestvfsBuffer *pShm;            /* Shared memory buffer */
+  u32 excllock;                   /* Mask of exclusive locks */
+  u32 sharedlock;                 /* Mask of shared locks */
+  TestvfsFd *pNext;               /* Next handle opened on the same file */
+};
+
+
+#define FAULT_INJECT_NONE       0
+#define FAULT_INJECT_TRANSIENT  1
+#define FAULT_INJECT_PERSISTENT 2
+
+typedef struct TestFaultInject TestFaultInject;
+struct TestFaultInject {
+  int iCnt;                       /* Remaining calls before fault injection */
+  int eFault;                     /* A FAULT_INJECT_* value */
+  int nFail;                      /* Number of faults injected */
+};
+
+/*
+** An instance of this structure is allocated for each VFS created. The
+** sqlite3_vfs.pAppData field of the VFS structure registered with SQLite
+** is set to point to it.
+*/
+struct Testvfs {
+  char *zName;                    /* Name of this VFS */
+  sqlite3_vfs *pParent;           /* The VFS to use for file IO */
+  sqlite3_vfs *pVfs;              /* The testvfs registered with SQLite */
+  Tcl_Interp *interp;             /* Interpreter to run script in */
+  Tcl_Obj *pScript;               /* Script to execute */
+  TestvfsBuffer *pBuffer;         /* List of shared buffers */
+  int isNoshm;
+
+  int mask;                       /* Mask controlling [script] and [ioerr] */
+
+  TestFaultInject ioerr_err;
+  TestFaultInject full_err;
+  TestFaultInject cantopen_err;
+
+#if 0
+  int iIoerrCnt;
+  int ioerr;
+  int nIoerrFail;
+  int iFullCnt;
+  int fullerr;
+  int nFullFail;
+#endif
+
+  int iDevchar;
+  int iSectorsize;
+};
+
+/*
+** The Testvfs.mask variable is set to a combination of the following.
+** If a bit is clear in Testvfs.mask, then calls made by SQLite to the 
+** corresponding VFS method is ignored for purposes of:
+**
+**   + Simulating IO errors, and
+**   + Invoking the Tcl callback script.
+*/
+#define TESTVFS_SHMOPEN_MASK      0x00000001
+#define TESTVFS_SHMLOCK_MASK      0x00000010
+#define TESTVFS_SHMMAP_MASK       0x00000020
+#define TESTVFS_SHMBARRIER_MASK   0x00000040
+#define TESTVFS_SHMCLOSE_MASK     0x00000080
+
+#define TESTVFS_OPEN_MASK         0x00000100
+#define TESTVFS_SYNC_MASK         0x00000200
+#define TESTVFS_DELETE_MASK       0x00000400
+#define TESTVFS_CLOSE_MASK        0x00000800
+#define TESTVFS_WRITE_MASK        0x00001000
+#define TESTVFS_TRUNCATE_MASK     0x00002000
+#define TESTVFS_ACCESS_MASK       0x00004000
+#define TESTVFS_FULLPATHNAME_MASK 0x00008000
+#define TESTVFS_READ_MASK         0x00010000
+
+#define TESTVFS_ALL_MASK          0x0001FFFF
+
+
+#define TESTVFS_MAX_PAGES 1024
+
+/*
+** A shared-memory buffer. There is one of these objects for each shared
+** memory region opened by clients. If two clients open the same file,
+** there are two TestvfsFile structures but only one TestvfsBuffer structure.
+*/
+struct TestvfsBuffer {
+  char *zFile;                    /* Associated file name */
+  int pgsz;                       /* Page size */
+  u8 *aPage[TESTVFS_MAX_PAGES];   /* Array of ckalloc'd pages */
+  TestvfsFd *pFile;               /* List of open handles */
+  TestvfsBuffer *pNext;           /* Next in linked list of all buffers */
+};
+
+
+#define PARENTVFS(x) (((Testvfs *)((x)->pAppData))->pParent)
+
+#define TESTVFS_MAX_ARGS 12
+
+
+/*
+** Method declarations for TestvfsFile.
+*/
+static int tvfsClose(sqlite3_file*);
+static int tvfsRead(sqlite3_file*, void*, int iAmt, sqlite3_int64 iOfst);
+static int tvfsWrite(sqlite3_file*,const void*,int iAmt, sqlite3_int64 iOfst);
+static int tvfsTruncate(sqlite3_file*, sqlite3_int64 size);
+static int tvfsSync(sqlite3_file*, int flags);
+static int tvfsFileSize(sqlite3_file*, sqlite3_int64 *pSize);
+static int tvfsLock(sqlite3_file*, int);
+static int tvfsUnlock(sqlite3_file*, int);
+static int tvfsCheckReservedLock(sqlite3_file*, int *);
+static int tvfsFileControl(sqlite3_file*, int op, void *pArg);
+static int tvfsSectorSize(sqlite3_file*);
+static int tvfsDeviceCharacteristics(sqlite3_file*);
+
+/*
+** Method declarations for tvfs_vfs.
+*/
+static int tvfsOpen(sqlite3_vfs*, const char *, sqlite3_file*, int , int *);
+static int tvfsDelete(sqlite3_vfs*, const char *zName, int syncDir);
+static int tvfsAccess(sqlite3_vfs*, const char *zName, int flags, int *);
+static int tvfsFullPathname(sqlite3_vfs*, const char *zName, int, char *zOut);
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+static void *tvfsDlOpen(sqlite3_vfs*, const char *zFilename);
+static void tvfsDlError(sqlite3_vfs*, int nByte, char *zErrMsg);
+static void (*tvfsDlSym(sqlite3_vfs*,void*, const char *zSymbol))(void);
+static void tvfsDlClose(sqlite3_vfs*, void*);
+#endif /* SQLITE_OMIT_LOAD_EXTENSION */
+static int tvfsRandomness(sqlite3_vfs*, int nByte, char *zOut);
+static int tvfsSleep(sqlite3_vfs*, int microseconds);
+static int tvfsCurrentTime(sqlite3_vfs*, double*);
+
+static int tvfsShmOpen(sqlite3_file*);
+static int tvfsShmLock(sqlite3_file*, int , int, int);
+static int tvfsShmMap(sqlite3_file*,int,int,int, void volatile **);
+static void tvfsShmBarrier(sqlite3_file*);
+static int tvfsShmUnmap(sqlite3_file*, int);
+
+static sqlite3_io_methods tvfs_io_methods = {
+  2,                              /* iVersion */
+  tvfsClose,                      /* xClose */
+  tvfsRead,                       /* xRead */
+  tvfsWrite,                      /* xWrite */
+  tvfsTruncate,                   /* xTruncate */
+  tvfsSync,                       /* xSync */
+  tvfsFileSize,                   /* xFileSize */
+  tvfsLock,                       /* xLock */
+  tvfsUnlock,                     /* xUnlock */
+  tvfsCheckReservedLock,          /* xCheckReservedLock */
+  tvfsFileControl,                /* xFileControl */
+  tvfsSectorSize,                 /* xSectorSize */
+  tvfsDeviceCharacteristics,      /* xDeviceCharacteristics */
+  tvfsShmMap,                     /* xShmMap */
+  tvfsShmLock,                    /* xShmLock */
+  tvfsShmBarrier,                 /* xShmBarrier */
+  tvfsShmUnmap                    /* xShmUnmap */
+};
+
+static int tvfsResultCode(Testvfs *p, int *pRc){
+  struct errcode {
+    int eCode;
+    const char *zCode;
+  } aCode[] = {
+    { SQLITE_OK,     "SQLITE_OK"     },
+    { SQLITE_ERROR,  "SQLITE_ERROR"  },
+    { SQLITE_IOERR,  "SQLITE_IOERR"  },
+    { SQLITE_LOCKED, "SQLITE_LOCKED" },
+    { SQLITE_BUSY,   "SQLITE_BUSY"   },
+  };
+
+  const char *z;
+  int i;
+
+  z = Tcl_GetStringResult(p->interp);
+  for(i=0; i<ArraySize(aCode); i++){
+    if( 0==strcmp(z, aCode[i].zCode) ){
+      *pRc = aCode[i].eCode;
+      return 1;
+    }
+  }
+
+  return 0;
+}
+
+static int tvfsInjectFault(TestFaultInject *p){
+  int ret = 0;
+  if( p->eFault ){
+    p->iCnt--;
+    if( p->iCnt==0 || (p->iCnt<0 && p->eFault==FAULT_INJECT_PERSISTENT ) ){
+      ret = 1;
+      p->nFail++;
+    }
+  }
+  return ret;
+}
+
+
+static int tvfsInjectIoerr(Testvfs *p){
+  return tvfsInjectFault(&p->ioerr_err);
+}
+
+static int tvfsInjectFullerr(Testvfs *p){
+  return tvfsInjectFault(&p->full_err);
+}
+static int tvfsInjectCantopenerr(Testvfs *p){
+  return tvfsInjectFault(&p->cantopen_err);
+}
+
+
+static void tvfsExecTcl(
+  Testvfs *p, 
+  const char *zMethod,
+  Tcl_Obj *arg1,
+  Tcl_Obj *arg2,
+  Tcl_Obj *arg3
+){
+  int rc;                         /* Return code from Tcl_EvalObj() */
+  Tcl_Obj *pEval;
+  assert( p->pScript );
+
+  assert( zMethod );
+  assert( p );
+  assert( arg2==0 || arg1!=0 );
+  assert( arg3==0 || arg2!=0 );
+
+  pEval = Tcl_DuplicateObj(p->pScript);
+  Tcl_IncrRefCount(p->pScript);
+  Tcl_ListObjAppendElement(p->interp, pEval, Tcl_NewStringObj(zMethod, -1));
+  if( arg1 ) Tcl_ListObjAppendElement(p->interp, pEval, arg1);
+  if( arg2 ) Tcl_ListObjAppendElement(p->interp, pEval, arg2);
+  if( arg3 ) Tcl_ListObjAppendElement(p->interp, pEval, arg3);
+
+  rc = Tcl_EvalObjEx(p->interp, pEval, TCL_EVAL_GLOBAL);
+  if( rc!=TCL_OK ){
+    Tcl_BackgroundError(p->interp);
+    Tcl_ResetResult(p->interp);
+  }
+}
+
+
+/*
+** Close an tvfs-file.
+*/
+static int tvfsClose(sqlite3_file *pFile){
+  int rc;
+  TestvfsFile *pTestfile = (TestvfsFile *)pFile;
+  TestvfsFd *pFd = pTestfile->pFd;
+  Testvfs *p = (Testvfs *)pFd->pVfs->pAppData;
+
+  if( p->pScript && p->mask&TESTVFS_CLOSE_MASK ){
+    tvfsExecTcl(p, "xClose", 
+        Tcl_NewStringObj(pFd->zFilename, -1), pFd->pShmId, 0
+    );
+  }
+
+  if( pFd->pShmId ){
+    Tcl_DecrRefCount(pFd->pShmId);
+    pFd->pShmId = 0;
+  }
+  if( pFile->pMethods ){
+    ckfree((char *)pFile->pMethods);
+  }
+  rc = sqlite3OsClose(pFd->pReal);
+  ckfree((char *)pFd);
+  pTestfile->pFd = 0;
+  return rc;
+}
+
+/*
+** Read data from an tvfs-file.
+*/
+static int tvfsRead(
+  sqlite3_file *pFile, 
+  void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  int rc = SQLITE_OK;
+  TestvfsFd *pFd = tvfsGetFd(pFile);
+  Testvfs *p = (Testvfs *)pFd->pVfs->pAppData;
+  if( p->pScript && p->mask&TESTVFS_READ_MASK ){
+    tvfsExecTcl(p, "xRead", 
+        Tcl_NewStringObj(pFd->zFilename, -1), pFd->pShmId, 0
+    );
+    tvfsResultCode(p, &rc);
+  }
+  if( rc==SQLITE_OK && p->mask&TESTVFS_READ_MASK && tvfsInjectIoerr(p) ){
+    rc = SQLITE_IOERR;
+  }
+  if( rc==SQLITE_OK ){
+    rc = sqlite3OsRead(pFd->pReal, zBuf, iAmt, iOfst);
+  }
+  return rc;
+}
+
+/*
+** Write data to an tvfs-file.
+*/
+static int tvfsWrite(
+  sqlite3_file *pFile, 
+  const void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  int rc = SQLITE_OK;
+  TestvfsFd *pFd = tvfsGetFd(pFile);
+  Testvfs *p = (Testvfs *)pFd->pVfs->pAppData;
+
+  if( p->pScript && p->mask&TESTVFS_WRITE_MASK ){
+    tvfsExecTcl(p, "xWrite", 
+        Tcl_NewStringObj(pFd->zFilename, -1), pFd->pShmId, 0
+    );
+    tvfsResultCode(p, &rc);
+  }
+
+  if( rc==SQLITE_OK && tvfsInjectFullerr(p) ){
+    rc = SQLITE_FULL;
+  }
+  if( rc==SQLITE_OK && p->mask&TESTVFS_WRITE_MASK && tvfsInjectIoerr(p) ){
+    rc = SQLITE_IOERR;
+  }
+  
+  if( rc==SQLITE_OK ){
+    rc = sqlite3OsWrite(pFd->pReal, zBuf, iAmt, iOfst);
+  }
+  return rc;
+}
+
+/*
+** Truncate an tvfs-file.
+*/
+static int tvfsTruncate(sqlite3_file *pFile, sqlite_int64 size){
+  int rc = SQLITE_OK;
+  TestvfsFd *pFd = tvfsGetFd(pFile);
+  Testvfs *p = (Testvfs *)pFd->pVfs->pAppData;
+
+  if( p->pScript && p->mask&TESTVFS_TRUNCATE_MASK ){
+    tvfsExecTcl(p, "xTruncate", 
+        Tcl_NewStringObj(pFd->zFilename, -1), pFd->pShmId, 0
+    );
+    tvfsResultCode(p, &rc);
+  }
+  
+  if( rc==SQLITE_OK ){
+    rc = sqlite3OsTruncate(pFd->pReal, size);
+  }
+  return rc;
+}
+
+/*
+** Sync an tvfs-file.
+*/
+static int tvfsSync(sqlite3_file *pFile, int flags){
+  int rc = SQLITE_OK;
+  TestvfsFd *pFd = tvfsGetFd(pFile);
+  Testvfs *p = (Testvfs *)pFd->pVfs->pAppData;
+
+  if( p->pScript && p->mask&TESTVFS_SYNC_MASK ){
+    char *zFlags;
+
+    switch( flags ){
+      case SQLITE_SYNC_NORMAL:
+        zFlags = "normal";
+        break;
+      case SQLITE_SYNC_FULL:
+        zFlags = "full";
+        break;
+      case SQLITE_SYNC_NORMAL|SQLITE_SYNC_DATAONLY:
+        zFlags = "normal|dataonly";
+        break;
+      case SQLITE_SYNC_FULL|SQLITE_SYNC_DATAONLY:
+        zFlags = "full|dataonly";
+        break;
+      default:
+        assert(0);
+    }
+
+    tvfsExecTcl(p, "xSync", 
+        Tcl_NewStringObj(pFd->zFilename, -1), pFd->pShmId,
+        Tcl_NewStringObj(zFlags, -1)
+    );
+    tvfsResultCode(p, &rc);
+  }
+
+  if( rc==SQLITE_OK && tvfsInjectFullerr(p) ) rc = SQLITE_FULL;
+
+  if( rc==SQLITE_OK ){
+    rc = sqlite3OsSync(pFd->pReal, flags);
+  }
+
+  return rc;
+}
+
+/*
+** Return the current file-size of an tvfs-file.
+*/
+static int tvfsFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
+  TestvfsFd *p = tvfsGetFd(pFile);
+  return sqlite3OsFileSize(p->pReal, pSize);
+}
+
+/*
+** Lock an tvfs-file.
+*/
+static int tvfsLock(sqlite3_file *pFile, int eLock){
+  TestvfsFd *p = tvfsGetFd(pFile);
+  return sqlite3OsLock(p->pReal, eLock);
+}
+
+/*
+** Unlock an tvfs-file.
+*/
+static int tvfsUnlock(sqlite3_file *pFile, int eLock){
+  TestvfsFd *p = tvfsGetFd(pFile);
+  return sqlite3OsUnlock(p->pReal, eLock);
+}
+
+/*
+** Check if another file-handle holds a RESERVED lock on an tvfs-file.
+*/
+static int tvfsCheckReservedLock(sqlite3_file *pFile, int *pResOut){
+  TestvfsFd *p = tvfsGetFd(pFile);
+  return sqlite3OsCheckReservedLock(p->pReal, pResOut);
+}
+
+/*
+** File control method. For custom operations on an tvfs-file.
+*/
+static int tvfsFileControl(sqlite3_file *pFile, int op, void *pArg){
+  TestvfsFd *p = tvfsGetFd(pFile);
+  return sqlite3OsFileControl(p->pReal, op, pArg);
+}
+
+/*
+** Return the sector-size in bytes for an tvfs-file.
+*/
+static int tvfsSectorSize(sqlite3_file *pFile){
+  TestvfsFd *pFd = tvfsGetFd(pFile);
+  Testvfs *p = (Testvfs *)pFd->pVfs->pAppData;
+  if( p->iSectorsize>=0 ){
+    return p->iSectorsize;
+  }
+  return sqlite3OsSectorSize(pFd->pReal);
+}
+
+/*
+** Return the device characteristic flags supported by an tvfs-file.
+*/
+static int tvfsDeviceCharacteristics(sqlite3_file *pFile){
+  TestvfsFd *pFd = tvfsGetFd(pFile);
+  Testvfs *p = (Testvfs *)pFd->pVfs->pAppData;
+  if( p->iDevchar>=0 ){
+    return p->iDevchar;
+  }
+  return sqlite3OsDeviceCharacteristics(pFd->pReal);
+}
+
+/*
+** Open an tvfs file handle.
+*/
+static int tvfsOpen(
+  sqlite3_vfs *pVfs,
+  const char *zName,
+  sqlite3_file *pFile,
+  int flags,
+  int *pOutFlags
+){
+  int rc;
+  TestvfsFile *pTestfile = (TestvfsFile *)pFile;
+  TestvfsFd *pFd;
+  Tcl_Obj *pId = 0;
+  Testvfs *p = (Testvfs *)pVfs->pAppData;
+
+  pFd = (TestvfsFd *)ckalloc(sizeof(TestvfsFd) + PARENTVFS(pVfs)->szOsFile);
+  memset(pFd, 0, sizeof(TestvfsFd) + PARENTVFS(pVfs)->szOsFile);
+  pFd->pShm = 0;
+  pFd->pShmId = 0;
+  pFd->zFilename = zName;
+  pFd->pVfs = pVfs;
+  pFd->pReal = (sqlite3_file *)&pFd[1];
+  memset(pTestfile, 0, sizeof(TestvfsFile));
+  pTestfile->pFd = pFd;
+
+  /* Evaluate the Tcl script: 
+  **
+  **   SCRIPT xOpen FILENAME KEY-VALUE-ARGS
+  **
+  ** If the script returns an SQLite error code other than SQLITE_OK, an
+  ** error is returned to the caller. If it returns SQLITE_OK, the new
+  ** connection is named "anon". Otherwise, the value returned by the
+  ** script is used as the connection name.
+  */
+  Tcl_ResetResult(p->interp);
+  if( p->pScript && p->mask&TESTVFS_OPEN_MASK ){
+    Tcl_Obj *pArg = Tcl_NewObj();
+    Tcl_IncrRefCount(pArg);
+    if( flags&SQLITE_OPEN_MAIN_DB ){
+      const char *z = &zName[strlen(zName)+1];
+      while( *z ){
+        Tcl_ListObjAppendElement(0, pArg, Tcl_NewStringObj(z, -1));
+        z += strlen(z) + 1;
+        Tcl_ListObjAppendElement(0, pArg, Tcl_NewStringObj(z, -1));
+        z += strlen(z) + 1;
+      }
+    }
+    tvfsExecTcl(p, "xOpen", Tcl_NewStringObj(pFd->zFilename, -1), pArg, 0);
+    Tcl_DecrRefCount(pArg);
+    if( tvfsResultCode(p, &rc) ){
+      if( rc!=SQLITE_OK ) return rc;
+    }else{
+      pId = Tcl_GetObjResult(p->interp);
+    }
+  }
+
+  if( (p->mask&TESTVFS_OPEN_MASK) &&  tvfsInjectIoerr(p) ) return SQLITE_IOERR;
+  if( tvfsInjectCantopenerr(p) ) return SQLITE_CANTOPEN;
+  if( tvfsInjectFullerr(p) ) return SQLITE_FULL;
+
+  if( !pId ){
+    pId = Tcl_NewStringObj("anon", -1);
+  }
+  Tcl_IncrRefCount(pId);
+  pFd->pShmId = pId;
+  Tcl_ResetResult(p->interp);
+
+  rc = sqlite3OsOpen(PARENTVFS(pVfs), zName, pFd->pReal, flags, pOutFlags);
+  if( pFd->pReal->pMethods ){
+    sqlite3_io_methods *pMethods;
+    int nByte;
+
+    if( pVfs->iVersion>1 ){
+      nByte = sizeof(sqlite3_io_methods);
+    }else{
+      nByte = offsetof(sqlite3_io_methods, xShmMap);
+    }
+
+    pMethods = (sqlite3_io_methods *)ckalloc(nByte);
+    memcpy(pMethods, &tvfs_io_methods, nByte);
+    pMethods->iVersion = pVfs->iVersion;
+    if( pVfs->iVersion>1 && ((Testvfs *)pVfs->pAppData)->isNoshm ){
+      pMethods->xShmUnmap = 0;
+      pMethods->xShmLock = 0;
+      pMethods->xShmBarrier = 0;
+      pMethods->xShmMap = 0;
+    }
+    pFile->pMethods = pMethods;
+  }
+
+  return rc;
+}
+
+/*
+** Delete the file located at zPath. If the dirSync argument is true,
+** ensure the file-system modifications are synced to disk before
+** returning.
+*/
+static int tvfsDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
+  int rc = SQLITE_OK;
+  Testvfs *p = (Testvfs *)pVfs->pAppData;
+
+  if( p->pScript && p->mask&TESTVFS_DELETE_MASK ){
+    tvfsExecTcl(p, "xDelete", 
+        Tcl_NewStringObj(zPath, -1), Tcl_NewIntObj(dirSync), 0
+    );
+    tvfsResultCode(p, &rc);
+  }
+  if( rc==SQLITE_OK ){
+    rc = sqlite3OsDelete(PARENTVFS(pVfs), zPath, dirSync);
+  }
+  return rc;
+}
+
+/*
+** Test for access permissions. Return true if the requested permission
+** is available, or false otherwise.
+*/
+static int tvfsAccess(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  int flags, 
+  int *pResOut
+){
+  Testvfs *p = (Testvfs *)pVfs->pAppData;
+  if( p->pScript && p->mask&TESTVFS_ACCESS_MASK ){
+    int rc;
+    char *zArg = 0;
+    if( flags==SQLITE_ACCESS_EXISTS ) zArg = "SQLITE_ACCESS_EXISTS";
+    if( flags==SQLITE_ACCESS_READWRITE ) zArg = "SQLITE_ACCESS_READWRITE";
+    if( flags==SQLITE_ACCESS_READ ) zArg = "SQLITE_ACCESS_READ";
+    tvfsExecTcl(p, "xAccess", 
+        Tcl_NewStringObj(zPath, -1), Tcl_NewStringObj(zArg, -1), 0
+    );
+    if( tvfsResultCode(p, &rc) ){
+      if( rc!=SQLITE_OK ) return rc;
+    }else{
+      Tcl_Interp *interp = p->interp;
+      if( TCL_OK==Tcl_GetBooleanFromObj(0, Tcl_GetObjResult(interp), pResOut) ){
+        return SQLITE_OK;
+      }
+    }
+  }
+  return sqlite3OsAccess(PARENTVFS(pVfs), zPath, flags, pResOut);
+}
+
+/*
+** Populate buffer zOut with the full canonical pathname corresponding
+** to the pathname in zPath. zOut is guaranteed to point to a buffer
+** of at least (DEVSYM_MAX_PATHNAME+1) bytes.
+*/
+static int tvfsFullPathname(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  int nOut, 
+  char *zOut
+){
+  Testvfs *p = (Testvfs *)pVfs->pAppData;
+  if( p->pScript && p->mask&TESTVFS_FULLPATHNAME_MASK ){
+    int rc;
+    tvfsExecTcl(p, "xFullPathname", Tcl_NewStringObj(zPath, -1), 0, 0);
+    if( tvfsResultCode(p, &rc) ){
+      if( rc!=SQLITE_OK ) return rc;
+    }
+  }
+  return sqlite3OsFullPathname(PARENTVFS(pVfs), zPath, nOut, zOut);
+}
+
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+/*
+** Open the dynamic library located at zPath and return a handle.
+*/
+static void *tvfsDlOpen(sqlite3_vfs *pVfs, const char *zPath){
+  return sqlite3OsDlOpen(PARENTVFS(pVfs), zPath);
+}
+
+/*
+** Populate the buffer zErrMsg (size nByte bytes) with a human readable
+** utf-8 string describing the most recent error encountered associated 
+** with dynamic libraries.
+*/
+static void tvfsDlError(sqlite3_vfs *pVfs, int nByte, char *zErrMsg){
+  sqlite3OsDlError(PARENTVFS(pVfs), nByte, zErrMsg);
+}
+
+/*
+** Return a pointer to the symbol zSymbol in the dynamic library pHandle.
+*/
+static void (*tvfsDlSym(sqlite3_vfs *pVfs, void *p, const char *zSym))(void){
+  return sqlite3OsDlSym(PARENTVFS(pVfs), p, zSym);
+}
+
+/*
+** Close the dynamic library handle pHandle.
+*/
+static void tvfsDlClose(sqlite3_vfs *pVfs, void *pHandle){
+  sqlite3OsDlClose(PARENTVFS(pVfs), pHandle);
+}
+#endif /* SQLITE_OMIT_LOAD_EXTENSION */
+
+/*
+** Populate the buffer pointed to by zBufOut with nByte bytes of 
+** random data.
+*/
+static int tvfsRandomness(sqlite3_vfs *pVfs, int nByte, char *zBufOut){
+  return sqlite3OsRandomness(PARENTVFS(pVfs), nByte, zBufOut);
+}
+
+/*
+** Sleep for nMicro microseconds. Return the number of microseconds 
+** actually slept.
+*/
+static int tvfsSleep(sqlite3_vfs *pVfs, int nMicro){
+  return sqlite3OsSleep(PARENTVFS(pVfs), nMicro);
+}
+
+/*
+** Return the current time as a Julian Day number in *pTimeOut.
+*/
+static int tvfsCurrentTime(sqlite3_vfs *pVfs, double *pTimeOut){
+  return PARENTVFS(pVfs)->xCurrentTime(PARENTVFS(pVfs), pTimeOut);
+}
+
+static int tvfsShmOpen(sqlite3_file *pFile){
+  Testvfs *p;
+  int rc = SQLITE_OK;             /* Return code */
+  TestvfsBuffer *pBuffer;         /* Buffer to open connection to */
+  TestvfsFd *pFd;                 /* The testvfs file structure */
+
+  pFd = tvfsGetFd(pFile);
+  p = (Testvfs *)pFd->pVfs->pAppData;
+  assert( pFd->pShmId && pFd->pShm==0 && pFd->pNext==0 );
+
+  /* Evaluate the Tcl script: 
+  **
+  **   SCRIPT xShmOpen FILENAME
+  */
+  Tcl_ResetResult(p->interp);
+  if( p->pScript && p->mask&TESTVFS_SHMOPEN_MASK ){
+    tvfsExecTcl(p, "xShmOpen", Tcl_NewStringObj(pFd->zFilename, -1), 0, 0);
+    if( tvfsResultCode(p, &rc) ){
+      if( rc!=SQLITE_OK ) return rc;
+    }
+  }
+
+  assert( rc==SQLITE_OK );
+  if( p->mask&TESTVFS_SHMOPEN_MASK && tvfsInjectIoerr(p) ){
+    return SQLITE_IOERR;
+  }
+
+  /* Search for a TestvfsBuffer. Create a new one if required. */
+  for(pBuffer=p->pBuffer; pBuffer; pBuffer=pBuffer->pNext){
+    if( 0==strcmp(pFd->zFilename, pBuffer->zFile) ) break;
+  }
+  if( !pBuffer ){
+    int nByte = sizeof(TestvfsBuffer) + strlen(pFd->zFilename) + 1;
+    pBuffer = (TestvfsBuffer *)ckalloc(nByte);
+    memset(pBuffer, 0, nByte);
+    pBuffer->zFile = (char *)&pBuffer[1];
+    strcpy(pBuffer->zFile, pFd->zFilename);
+    pBuffer->pNext = p->pBuffer;
+    p->pBuffer = pBuffer;
+  }
+
+  /* Connect the TestvfsBuffer to the new TestvfsShm handle and return. */
+  pFd->pNext = pBuffer->pFile;
+  pBuffer->pFile = pFd;
+  pFd->pShm = pBuffer;
+  return SQLITE_OK;
+}
+
+static void tvfsAllocPage(TestvfsBuffer *p, int iPage, int pgsz){
+  assert( iPage<TESTVFS_MAX_PAGES );
+  if( p->aPage[iPage]==0 ){
+    p->aPage[iPage] = (u8 *)ckalloc(pgsz);
+    memset(p->aPage[iPage], 0, pgsz);
+    p->pgsz = pgsz;
+  }
+}
+
+static int tvfsShmMap(
+  sqlite3_file *pFile,            /* Handle open on database file */
+  int iPage,                      /* Page to retrieve */
+  int pgsz,                       /* Size of pages */
+  int isWrite,                    /* True to extend file if necessary */
+  void volatile **pp              /* OUT: Mapped memory */
+){
+  int rc = SQLITE_OK;
+  TestvfsFd *pFd = tvfsGetFd(pFile);
+  Testvfs *p = (Testvfs *)(pFd->pVfs->pAppData);
+
+  if( 0==pFd->pShm ){
+    rc = tvfsShmOpen(pFile);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+  }
+
+  if( p->pScript && p->mask&TESTVFS_SHMMAP_MASK ){
+    Tcl_Obj *pArg = Tcl_NewObj();
+    Tcl_IncrRefCount(pArg);
+    Tcl_ListObjAppendElement(p->interp, pArg, Tcl_NewIntObj(iPage));
+    Tcl_ListObjAppendElement(p->interp, pArg, Tcl_NewIntObj(pgsz));
+    Tcl_ListObjAppendElement(p->interp, pArg, Tcl_NewIntObj(isWrite));
+    tvfsExecTcl(p, "xShmMap", 
+        Tcl_NewStringObj(pFd->pShm->zFile, -1), pFd->pShmId, pArg
+    );
+    tvfsResultCode(p, &rc);
+    Tcl_DecrRefCount(pArg);
+  }
+  if( rc==SQLITE_OK && p->mask&TESTVFS_SHMMAP_MASK && tvfsInjectIoerr(p) ){
+    rc = SQLITE_IOERR;
+  }
+
+  if( rc==SQLITE_OK && isWrite && !pFd->pShm->aPage[iPage] ){
+    tvfsAllocPage(pFd->pShm, iPage, pgsz);
+  }
+  *pp = (void volatile *)pFd->pShm->aPage[iPage];
+
+  return rc;
+}
+
+
+static int tvfsShmLock(
+  sqlite3_file *pFile,
+  int ofst,
+  int n,
+  int flags
+){
+  int rc = SQLITE_OK;
+  TestvfsFd *pFd = tvfsGetFd(pFile);
+  Testvfs *p = (Testvfs *)(pFd->pVfs->pAppData);
+  int nLock;
+  char zLock[80];
+
+  if( p->pScript && p->mask&TESTVFS_SHMLOCK_MASK ){
+    sqlite3_snprintf(sizeof(zLock), zLock, "%d %d", ofst, n);
+    nLock = strlen(zLock);
+    if( flags & SQLITE_SHM_LOCK ){
+      strcpy(&zLock[nLock], " lock");
+    }else{
+      strcpy(&zLock[nLock], " unlock");
+    }
+    nLock += strlen(&zLock[nLock]);
+    if( flags & SQLITE_SHM_SHARED ){
+      strcpy(&zLock[nLock], " shared");
+    }else{
+      strcpy(&zLock[nLock], " exclusive");
+    }
+    tvfsExecTcl(p, "xShmLock", 
+        Tcl_NewStringObj(pFd->pShm->zFile, -1), pFd->pShmId,
+        Tcl_NewStringObj(zLock, -1)
+    );
+    tvfsResultCode(p, &rc);
+  }
+
+  if( rc==SQLITE_OK && p->mask&TESTVFS_SHMLOCK_MASK && tvfsInjectIoerr(p) ){
+    rc = SQLITE_IOERR;
+  }
+
+  if( rc==SQLITE_OK ){
+    int isLock = (flags & SQLITE_SHM_LOCK);
+    int isExcl = (flags & SQLITE_SHM_EXCLUSIVE);
+    u32 mask = (((1<<n)-1) << ofst);
+    if( isLock ){
+      TestvfsFd *p2;
+      for(p2=pFd->pShm->pFile; p2; p2=p2->pNext){
+        if( p2==pFd ) continue;
+        if( (p2->excllock&mask) || (isExcl && p2->sharedlock&mask) ){
+          rc = SQLITE_BUSY;
+          break;
+        }
+      }
+      if( rc==SQLITE_OK ){
+        if( isExcl )  pFd->excllock |= mask;
+        if( !isExcl ) pFd->sharedlock |= mask;
+      }
+    }else{
+      if( isExcl )  pFd->excllock &= (~mask);
+      if( !isExcl ) pFd->sharedlock &= (~mask);
+    }
+  }
+
+  return rc;
+}
+
+static void tvfsShmBarrier(sqlite3_file *pFile){
+  TestvfsFd *pFd = tvfsGetFd(pFile);
+  Testvfs *p = (Testvfs *)(pFd->pVfs->pAppData);
+
+  if( p->pScript && p->mask&TESTVFS_SHMBARRIER_MASK ){
+    tvfsExecTcl(p, "xShmBarrier", 
+        Tcl_NewStringObj(pFd->pShm->zFile, -1), pFd->pShmId, 0
+    );
+  }
+}
+
+static int tvfsShmUnmap(
+  sqlite3_file *pFile,
+  int deleteFlag
+){
+  int rc = SQLITE_OK;
+  TestvfsFd *pFd = tvfsGetFd(pFile);
+  Testvfs *p = (Testvfs *)(pFd->pVfs->pAppData);
+  TestvfsBuffer *pBuffer = pFd->pShm;
+  TestvfsFd **ppFd;
+
+  if( !pBuffer ) return SQLITE_OK;
+  assert( pFd->pShmId && pFd->pShm );
+
+  if( p->pScript && p->mask&TESTVFS_SHMCLOSE_MASK ){
+    tvfsExecTcl(p, "xShmUnmap", 
+        Tcl_NewStringObj(pFd->pShm->zFile, -1), pFd->pShmId, 0
+    );
+    tvfsResultCode(p, &rc);
+  }
+
+  for(ppFd=&pBuffer->pFile; *ppFd!=pFd; ppFd=&((*ppFd)->pNext));
+  assert( (*ppFd)==pFd );
+  *ppFd = pFd->pNext;
+  pFd->pNext = 0;
+
+  if( pBuffer->pFile==0 ){
+    int i;
+    TestvfsBuffer **pp;
+    for(pp=&p->pBuffer; *pp!=pBuffer; pp=&((*pp)->pNext));
+    *pp = (*pp)->pNext;
+    for(i=0; pBuffer->aPage[i]; i++){
+      ckfree((char *)pBuffer->aPage[i]);
+    }
+    ckfree((char *)pBuffer);
+  }
+  pFd->pShm = 0;
+
+  return rc;
+}
+
+static int testvfs_obj_cmd(
+  ClientData cd,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  Testvfs *p = (Testvfs *)cd;
+
+  enum DB_enum { 
+    CMD_SHM, CMD_DELETE, CMD_FILTER, CMD_IOERR, CMD_SCRIPT, 
+    CMD_DEVCHAR, CMD_SECTORSIZE, CMD_FULLERR, CMD_CANTOPENERR
+  };
+  struct TestvfsSubcmd {
+    char *zName;
+    enum DB_enum eCmd;
+  } aSubcmd[] = {
+    { "shm",         CMD_SHM         },
+    { "delete",      CMD_DELETE      },
+    { "filter",      CMD_FILTER      },
+    { "ioerr",       CMD_IOERR       },
+    { "fullerr",     CMD_FULLERR     },
+    { "cantopenerr", CMD_CANTOPENERR },
+    { "script",      CMD_SCRIPT      },
+    { "devchar",     CMD_DEVCHAR     },
+    { "sectorsize",  CMD_SECTORSIZE  },
+    { 0, 0 }
+  };
+  int i;
+  
+  if( objc<2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "SUBCOMMAND ...");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIndexFromObjStruct(
+        interp, objv[1], aSubcmd, sizeof(aSubcmd[0]), "subcommand", 0, &i) 
+  ){
+    return TCL_ERROR;
+  }
+  Tcl_ResetResult(interp);
+
+  switch( aSubcmd[i].eCmd ){
+    case CMD_SHM: {
+      Tcl_Obj *pObj;
+      int i;
+      TestvfsBuffer *pBuffer;
+      char *zName;
+      if( objc!=3 && objc!=4 ){
+        Tcl_WrongNumArgs(interp, 2, objv, "FILE ?VALUE?");
+        return TCL_ERROR;
+      }
+      zName = ckalloc(p->pParent->mxPathname);
+      p->pParent->xFullPathname(
+          p->pParent, Tcl_GetString(objv[2]), 
+          p->pParent->mxPathname, zName
+      );
+      for(pBuffer=p->pBuffer; pBuffer; pBuffer=pBuffer->pNext){
+        if( 0==strcmp(pBuffer->zFile, zName) ) break;
+      }
+      ckfree(zName);
+      if( !pBuffer ){
+        Tcl_AppendResult(interp, "no such file: ", Tcl_GetString(objv[2]), 0);
+        return TCL_ERROR;
+      }
+      if( objc==4 ){
+        int n;
+        u8 *a = Tcl_GetByteArrayFromObj(objv[3], &n);
+        int pgsz = pBuffer->pgsz;
+        if( pgsz==0 ) pgsz = 65536;
+        for(i=0; i*pgsz<n; i++){
+          int nByte = pgsz;
+          tvfsAllocPage(pBuffer, i, pgsz);
+          if( n-i*pgsz<pgsz ){
+            nByte = n;
+          }
+          memcpy(pBuffer->aPage[i], &a[i*pgsz], nByte);
+        }
+      }
+
+      pObj = Tcl_NewObj();
+      for(i=0; pBuffer->aPage[i]; i++){
+        int pgsz = pBuffer->pgsz;
+        if( pgsz==0 ) pgsz = 65536;
+        Tcl_AppendObjToObj(pObj, Tcl_NewByteArrayObj(pBuffer->aPage[i], pgsz));
+      }
+      Tcl_SetObjResult(interp, pObj);
+      break;
+    }
+
+    case CMD_FILTER: {
+      static struct VfsMethod {
+        char *zName;
+        int mask;
+      } vfsmethod [] = {
+        { "xShmOpen",      TESTVFS_SHMOPEN_MASK },
+        { "xShmLock",      TESTVFS_SHMLOCK_MASK },
+        { "xShmBarrier",   TESTVFS_SHMBARRIER_MASK },
+        { "xShmUnmap",     TESTVFS_SHMCLOSE_MASK },
+        { "xShmMap",       TESTVFS_SHMMAP_MASK },
+        { "xSync",         TESTVFS_SYNC_MASK },
+        { "xDelete",       TESTVFS_DELETE_MASK },
+        { "xWrite",        TESTVFS_WRITE_MASK },
+        { "xRead",         TESTVFS_READ_MASK },
+        { "xTruncate",     TESTVFS_TRUNCATE_MASK },
+        { "xOpen",         TESTVFS_OPEN_MASK },
+        { "xClose",        TESTVFS_CLOSE_MASK },
+        { "xAccess",       TESTVFS_ACCESS_MASK },
+        { "xFullPathname", TESTVFS_FULLPATHNAME_MASK },
+      };
+      Tcl_Obj **apElem = 0;
+      int nElem = 0;
+      int i;
+      int mask = 0;
+      if( objc!=3 ){
+        Tcl_WrongNumArgs(interp, 2, objv, "LIST");
+        return TCL_ERROR;
+      }
+      if( Tcl_ListObjGetElements(interp, objv[2], &nElem, &apElem) ){
+        return TCL_ERROR;
+      }
+      Tcl_ResetResult(interp);
+      for(i=0; i<nElem; i++){
+        int iMethod;
+        char *zElem = Tcl_GetString(apElem[i]);
+        for(iMethod=0; iMethod<ArraySize(vfsmethod); iMethod++){
+          if( strcmp(zElem, vfsmethod[iMethod].zName)==0 ){
+            mask |= vfsmethod[iMethod].mask;
+            break;
+          }
+        }
+        if( iMethod==ArraySize(vfsmethod) ){
+          Tcl_AppendResult(interp, "unknown method: ", zElem, 0);
+          return TCL_ERROR;
+        }
+      }
+      p->mask = mask;
+      break;
+    }
+
+    case CMD_SCRIPT: {
+      if( objc==3 ){
+        int nByte;
+        if( p->pScript ){
+          Tcl_DecrRefCount(p->pScript);
+          p->pScript = 0;
+        }
+        Tcl_GetStringFromObj(objv[2], &nByte);
+        if( nByte>0 ){
+          p->pScript = Tcl_DuplicateObj(objv[2]);
+          Tcl_IncrRefCount(p->pScript);
+        }
+      }else if( objc!=2 ){
+        Tcl_WrongNumArgs(interp, 2, objv, "?SCRIPT?");
+        return TCL_ERROR;
+      }
+
+      Tcl_ResetResult(interp);
+      if( p->pScript ) Tcl_SetObjResult(interp, p->pScript);
+
+      break;
+    }
+
+    /*
+    ** TESTVFS ioerr ?IFAIL PERSIST?
+    **
+    **   Where IFAIL is an integer and PERSIST is boolean.
+    */
+    case CMD_CANTOPENERR:
+    case CMD_IOERR:
+    case CMD_FULLERR: {
+      TestFaultInject *pTest;
+      int iRet;
+
+      switch( aSubcmd[i].eCmd ){
+        case CMD_IOERR: pTest = &p->ioerr_err; break;
+        case CMD_FULLERR: pTest = &p->full_err; break;
+        case CMD_CANTOPENERR: pTest = &p->cantopen_err; break;
+        default: assert(0);
+      }
+      iRet = pTest->nFail;
+      pTest->nFail = 0;
+      pTest->eFault = 0;
+      pTest->iCnt = 0;
+
+      if( objc==4 ){
+        int iCnt, iPersist;
+        if( TCL_OK!=Tcl_GetIntFromObj(interp, objv[2], &iCnt)
+         || TCL_OK!=Tcl_GetBooleanFromObj(interp, objv[3], &iPersist)
+        ){
+          return TCL_ERROR;
+        }
+        pTest->eFault = iPersist?FAULT_INJECT_PERSISTENT:FAULT_INJECT_TRANSIENT;
+        pTest->iCnt = iCnt;
+      }else if( objc!=2 ){
+        Tcl_WrongNumArgs(interp, 2, objv, "?CNT PERSIST?");
+        return TCL_ERROR;
+      }
+      Tcl_SetObjResult(interp, Tcl_NewIntObj(iRet));
+      break;
+    }
+
+    case CMD_DELETE: {
+      Tcl_DeleteCommand(interp, Tcl_GetString(objv[0]));
+      break;
+    }
+
+    case CMD_DEVCHAR: {
+      struct DeviceFlag {
+        char *zName;
+        int iValue;
+      } aFlag[] = {
+        { "default",               -1 },
+        { "atomic",                SQLITE_IOCAP_ATOMIC      },
+        { "atomic512",             SQLITE_IOCAP_ATOMIC512   },
+        { "atomic1k",              SQLITE_IOCAP_ATOMIC1K    },
+        { "atomic2k",              SQLITE_IOCAP_ATOMIC2K    },
+        { "atomic4k",              SQLITE_IOCAP_ATOMIC4K    },
+        { "atomic8k",              SQLITE_IOCAP_ATOMIC8K    },
+        { "atomic16k",             SQLITE_IOCAP_ATOMIC16K   },
+        { "atomic32k",             SQLITE_IOCAP_ATOMIC32K   },
+        { "atomic64k",             SQLITE_IOCAP_ATOMIC64K   },
+        { "sequential",            SQLITE_IOCAP_SEQUENTIAL  },
+        { "safe_append",           SQLITE_IOCAP_SAFE_APPEND },
+        { "undeletable_when_open", SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN },
+        { 0, 0 }
+      };
+      Tcl_Obj *pRet;
+      int iFlag;
+
+      if( objc>3 ){
+        Tcl_WrongNumArgs(interp, 2, objv, "?ATTR-LIST?");
+        return TCL_ERROR;
+      }
+      if( objc==3 ){
+        int j;
+        int iNew = 0;
+        Tcl_Obj **flags = 0;
+        int nFlags = 0;
+
+        if( Tcl_ListObjGetElements(interp, objv[2], &nFlags, &flags) ){
+          return TCL_ERROR;
+        }
+
+        for(j=0; j<nFlags; j++){
+          int idx = 0;
+          if( Tcl_GetIndexFromObjStruct(interp, flags[j], aFlag, 
+                sizeof(aFlag[0]), "flag", 0, &idx) 
+          ){
+            return TCL_ERROR;
+          }
+          if( aFlag[idx].iValue<0 && nFlags>1 ){
+            Tcl_AppendResult(interp, "bad flags: ", Tcl_GetString(objv[2]), 0);
+            return TCL_ERROR;
+          }
+          iNew |= aFlag[idx].iValue;
+        }
+
+        p->iDevchar = iNew;
+      }
+
+      pRet = Tcl_NewObj();
+      for(iFlag=0; iFlag<sizeof(aFlag)/sizeof(aFlag[0]); iFlag++){
+        if( p->iDevchar & aFlag[iFlag].iValue ){
+          Tcl_ListObjAppendElement(
+              interp, pRet, Tcl_NewStringObj(aFlag[iFlag].zName, -1)
+          );
+        }
+      }
+      Tcl_SetObjResult(interp, pRet);
+
+      break;
+    }
+
+    case CMD_SECTORSIZE: {
+      if( objc>3 ){
+        Tcl_WrongNumArgs(interp, 2, objv, "?VALUE?");
+        return TCL_ERROR;
+      }
+      if( objc==3 ){
+        int iNew = 0;
+        if( Tcl_GetIntFromObj(interp, objv[2], &iNew) ){
+          return TCL_ERROR;
+        }
+        p->iSectorsize = iNew;
+      }
+      Tcl_SetObjResult(interp, Tcl_NewIntObj(p->iSectorsize));
+      break;
+    }
+  }
+
+  return TCL_OK;
+}
+
+static void testvfs_obj_del(ClientData cd){
+  Testvfs *p = (Testvfs *)cd;
+  if( p->pScript ) Tcl_DecrRefCount(p->pScript);
+  sqlite3_vfs_unregister(p->pVfs);
+  ckfree((char *)p->pVfs);
+  ckfree((char *)p);
+}
+
+/*
+** Usage:  testvfs VFSNAME ?SWITCHES?
+**
+** Switches are:
+**
+**   -noshm   BOOLEAN             (True to omit shm methods. Default false)
+**   -default BOOLEAN             (True to make the vfs default. Default false)
+**
+** This command creates two things when it is invoked: an SQLite VFS, and
+** a Tcl command. Both are named VFSNAME. The VFS is installed. It is not
+** installed as the default VFS.
+**
+** The VFS passes all file I/O calls through to the underlying VFS.
+**
+** Whenever the xShmMap method of the VFS
+** is invoked, the SCRIPT is executed as follows:
+**
+**   SCRIPT xShmMap    FILENAME ID
+**
+** The value returned by the invocation of SCRIPT above is interpreted as
+** an SQLite error code and returned to SQLite. Either a symbolic 
+** "SQLITE_OK" or numeric "0" value may be returned.
+**
+** The contents of the shared-memory buffer associated with a given file
+** may be read and set using the following command:
+**
+**   VFSNAME shm FILENAME ?NEWVALUE?
+**
+** When the xShmLock method is invoked by SQLite, the following script is
+** run:
+**
+**   SCRIPT xShmLock    FILENAME ID LOCK
+**
+** where LOCK is of the form "OFFSET NBYTE lock/unlock shared/exclusive"
+*/
+static int testvfs_cmd(
+  ClientData cd,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  static sqlite3_vfs tvfs_vfs = {
+    2,                            /* iVersion */
+    0,                            /* szOsFile */
+    0,                            /* mxPathname */
+    0,                            /* pNext */
+    0,                            /* zName */
+    0,                            /* pAppData */
+    tvfsOpen,                     /* xOpen */
+    tvfsDelete,                   /* xDelete */
+    tvfsAccess,                   /* xAccess */
+    tvfsFullPathname,             /* xFullPathname */
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+    tvfsDlOpen,                   /* xDlOpen */
+    tvfsDlError,                  /* xDlError */
+    tvfsDlSym,                    /* xDlSym */
+    tvfsDlClose,                  /* xDlClose */
+#else
+    0,                            /* xDlOpen */
+    0,                            /* xDlError */
+    0,                            /* xDlSym */
+    0,                            /* xDlClose */
+#endif /* SQLITE_OMIT_LOAD_EXTENSION */
+    tvfsRandomness,               /* xRandomness */
+    tvfsSleep,                    /* xSleep */
+    tvfsCurrentTime,              /* xCurrentTime */
+    0,                            /* xGetLastError */
+    0,                            /* xCurrentTimeInt64 */
+  };
+
+  Testvfs *p;                     /* New object */
+  sqlite3_vfs *pVfs;              /* New VFS */
+  char *zVfs;
+  int nByte;                      /* Bytes of space to allocate at p */
+
+  int i;
+  int isNoshm = 0;                /* True if -noshm is passed */
+  int isDefault = 0;              /* True if -default is passed */
+  int szOsFile = 0;               /* Value passed to -szosfile */
+  int mxPathname = -1;            /* Value passed to -mxpathname */
+  int iVersion = 2;               /* Value passed to -iversion */
+
+  if( objc<2 || 0!=(objc%2) ) goto bad_args;
+  for(i=2; i<objc; i += 2){
+    int nSwitch;
+    char *zSwitch;
+    zSwitch = Tcl_GetStringFromObj(objv[i], &nSwitch); 
+
+    if( nSwitch>2 && 0==strncmp("-noshm", zSwitch, nSwitch) ){
+      if( Tcl_GetBooleanFromObj(interp, objv[i+1], &isNoshm) ){
+        return TCL_ERROR;
+      }
+    }
+    else if( nSwitch>2 && 0==strncmp("-default", zSwitch, nSwitch) ){
+      if( Tcl_GetBooleanFromObj(interp, objv[i+1], &isDefault) ){
+        return TCL_ERROR;
+      }
+    }
+    else if( nSwitch>2 && 0==strncmp("-szosfile", zSwitch, nSwitch) ){
+      if( Tcl_GetIntFromObj(interp, objv[i+1], &szOsFile) ){
+        return TCL_ERROR;
+      }
+    }
+    else if( nSwitch>2 && 0==strncmp("-mxpathname", zSwitch, nSwitch) ){
+      if( Tcl_GetIntFromObj(interp, objv[i+1], &mxPathname) ){
+        return TCL_ERROR;
+      }
+    }
+    else if( nSwitch>2 && 0==strncmp("-iversion", zSwitch, nSwitch) ){
+      if( Tcl_GetIntFromObj(interp, objv[i+1], &iVersion) ){
+        return TCL_ERROR;
+      }
+    }
+    else{
+      goto bad_args;
+    }
+  }
+
+  if( szOsFile<sizeof(TestvfsFile) ){
+    szOsFile = sizeof(TestvfsFile);
+  }
+
+  zVfs = Tcl_GetString(objv[1]);
+  nByte = sizeof(Testvfs) + strlen(zVfs)+1;
+  p = (Testvfs *)ckalloc(nByte);
+  memset(p, 0, nByte);
+  p->iDevchar = -1;
+  p->iSectorsize = -1;
+
+  /* Create the new object command before querying SQLite for a default VFS
+  ** to use for 'real' IO operations. This is because creating the new VFS
+  ** may delete an existing [testvfs] VFS of the same name. If such a VFS
+  ** is currently the default, the new [testvfs] may end up calling the 
+  ** methods of a deleted object.
+  */
+  Tcl_CreateObjCommand(interp, zVfs, testvfs_obj_cmd, p, testvfs_obj_del);
+  p->pParent = sqlite3_vfs_find(0);
+  p->interp = interp;
+
+  p->zName = (char *)&p[1];
+  memcpy(p->zName, zVfs, strlen(zVfs)+1);
+
+  pVfs = (sqlite3_vfs *)ckalloc(sizeof(sqlite3_vfs));
+  memcpy(pVfs, &tvfs_vfs, sizeof(sqlite3_vfs));
+  pVfs->pAppData = (void *)p;
+  pVfs->iVersion = iVersion;
+  pVfs->zName = p->zName;
+  pVfs->mxPathname = p->pParent->mxPathname;
+  if( mxPathname>=0 && mxPathname<pVfs->mxPathname ){
+    pVfs->mxPathname = mxPathname;
+  }
+  pVfs->szOsFile = szOsFile;
+  p->pVfs = pVfs;
+  p->isNoshm = isNoshm;
+  p->mask = TESTVFS_ALL_MASK;
+
+  sqlite3_vfs_register(pVfs, isDefault);
+
+  return TCL_OK;
+
+ bad_args:
+  Tcl_WrongNumArgs(interp, 1, objv, "VFSNAME ?-noshm BOOL? ?-default BOOL? ?-mxpathname INT? ?-szosfile INT? ?-iversion INT?");
+  return TCL_ERROR;
+}
+
+int Sqlitetestvfs_Init(Tcl_Interp *interp){
+  Tcl_CreateObjCommand(interp, "testvfs", testvfs_cmd, 0, 0);
+  return TCL_OK;
+}
+
+#endif
diff --git a/src/test_vfstrace.c b/src/test_vfstrace.c
new file mode 100644
index 0000000..5e94f5c
--- /dev/null
+++ b/src/test_vfstrace.c
@@ -0,0 +1,867 @@
+/*
+** 2011 March 16
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains code implements a VFS shim that writes diagnostic
+** output for each VFS call, similar to "strace".
+**
+** USAGE:
+**
+** This source file exports a single symbol which is the name of a
+** function:
+**
+**   int vfstrace_register(
+**     const char *zTraceName,         // Name of the newly constructed VFS
+**     const char *zOldVfsName,        // Name of the underlying VFS
+**     int (*xOut)(const char*,void*), // Output routine.  ex: fputs
+**     void *pOutArg,                  // 2nd argument to xOut.  ex: stderr
+**     int makeDefault                 // Make the new VFS the default
+**   );
+**
+** Applications that want to trace their VFS usage must provide a callback
+** function with this prototype:
+**
+**   int traceOutput(const char *zMessage, void *pAppData);
+**
+** This function will "output" the trace messages, where "output" can
+** mean different things to different applications.  The traceOutput function
+** for the command-line shell (see shell.c) is "fputs" from the standard
+** library, which means that all trace output is written on the stream
+** specified by the second argument.  In the case of the command-line shell
+** the second argument is stderr.  Other applications might choose to output
+** trace information to a file, over a socket, or write it into a buffer.
+**
+** The vfstrace_register() function creates a new "shim" VFS named by
+** the zTraceName parameter.  A "shim" VFS is an SQLite backend that does
+** not really perform the duties of a true backend, but simply filters or
+** interprets VFS calls before passing them off to another VFS which does
+** the actual work.  In this case the other VFS - the one that does the
+** real work - is identified by the second parameter, zOldVfsName.  If
+** the the 2nd parameter is NULL then the default VFS is used.  The common
+** case is for the 2nd parameter to be NULL.
+**
+** The third and fourth parameters are the pointer to the output function
+** and the second argument to the output function.  For the SQLite
+** command-line shell, when the -vfstrace option is used, these parameters
+** are fputs and stderr, respectively.
+**
+** The fifth argument is true (non-zero) to cause the newly created VFS
+** to become the default VFS.  The common case is for the fifth parameter
+** to be true.
+**
+** The call to vfstrace_register() simply creates the shim VFS that does
+** tracing.  The application must also arrange to use the new VFS for
+** all database connections that are created and for which tracing is 
+** desired.  This can be done by specifying the trace VFS using URI filename
+** notation, or by specifying the trace VFS as the 4th parameter to
+** sqlite3_open_v2() or by making the trace VFS be the default (by setting
+** the 5th parameter of vfstrace_register() to 1).
+**
+**
+** ENABLING VFSTRACE IN A COMMAND-LINE SHELL
+**
+** The SQLite command line shell implemented by the shell.c source file
+** can be used with this module.  To compile in -vfstrace support, first
+** gather this file (test_vfstrace.c), the shell source file (shell.c),
+** and the SQLite amalgamation source files (sqlite3.c, sqlite3.h) into
+** the working directory.  Then compile using a command like the following:
+**
+**    gcc -o sqlite3 -Os -I. -DSQLITE_ENABLE_VFSTRACE \
+**        -DSQLITE_THREADSAFE=0 -DSQLITE_ENABLE_FTS3 -DSQLITE_ENABLE_RTREE \
+**        -DHAVE_READLINE -DHAVE_USLEEP=1 \
+**        shell.c test_vfstrace.c sqlite3.c -ldl -lreadline -lncurses
+**
+** The gcc command above works on Linux and provides (in addition to the
+** -vfstrace option) support for FTS3 and FTS4, RTREE, and command-line
+** editing using the readline library.  The command-line shell does not
+** use threads so we added -DSQLITE_THREADSAFE=0 just to make the code
+** run a little faster.   For compiling on a Mac, you'll probably need
+** to omit the -DHAVE_READLINE, the -lreadline, and the -lncurses options.
+** The compilation could be simplified to just this:
+**
+**    gcc -DSQLITE_ENABLE_VFSTRACE \
+**         shell.c test_vfstrace.c sqlite3.c -ldl -lpthread
+**
+** In this second example, all unnecessary options have been removed
+** Note that since the code is now threadsafe, we had to add the -lpthread
+** option to pull in the pthreads library.
+**
+** To cross-compile for windows using MinGW, a command like this might
+** work:
+**
+**    /opt/mingw/bin/i386-mingw32msvc-gcc -o sqlite3.exe -Os -I \
+**         -DSQLITE_THREADSAFE=0 -DSQLITE_ENABLE_VFSTRACE \
+**         shell.c test_vfstrace.c sqlite3.c
+**
+** Similar compiler commands will work on different systems.  The key
+** invariants are (1) you must have -DSQLITE_ENABLE_VFSTRACE so that
+** the shell.c source file will know to include the -vfstrace command-line
+** option and (2) you must compile and link the three source files
+** shell,c, test_vfstrace.c, and sqlite3.c.  
+*/
+#include <stdlib.h>
+#include <string.h>
+#include "sqlite3.h"
+
+/*
+** An instance of this structure is attached to the each trace VFS to
+** provide auxiliary information.
+*/
+typedef struct vfstrace_info vfstrace_info;
+struct vfstrace_info {
+  sqlite3_vfs *pRootVfs;              /* The underlying real VFS */
+  int (*xOut)(const char*, void*);    /* Send output here */
+  void *pOutArg;                      /* First argument to xOut */
+  const char *zVfsName;               /* Name of this trace-VFS */
+  sqlite3_vfs *pTraceVfs;             /* Pointer back to the trace VFS */
+};
+
+/*
+** The sqlite3_file object for the trace VFS
+*/
+typedef struct vfstrace_file vfstrace_file;
+struct vfstrace_file {
+  sqlite3_file base;        /* Base class.  Must be first */
+  vfstrace_info *pInfo;     /* The trace-VFS to which this file belongs */
+  const char *zFName;       /* Base name of the file */
+  sqlite3_file *pReal;      /* The real underlying file */
+};
+
+/*
+** Method declarations for vfstrace_file.
+*/
+static int vfstraceClose(sqlite3_file*);
+static int vfstraceRead(sqlite3_file*, void*, int iAmt, sqlite3_int64 iOfst);
+static int vfstraceWrite(sqlite3_file*,const void*,int iAmt, sqlite3_int64);
+static int vfstraceTruncate(sqlite3_file*, sqlite3_int64 size);
+static int vfstraceSync(sqlite3_file*, int flags);
+static int vfstraceFileSize(sqlite3_file*, sqlite3_int64 *pSize);
+static int vfstraceLock(sqlite3_file*, int);
+static int vfstraceUnlock(sqlite3_file*, int);
+static int vfstraceCheckReservedLock(sqlite3_file*, int *);
+static int vfstraceFileControl(sqlite3_file*, int op, void *pArg);
+static int vfstraceSectorSize(sqlite3_file*);
+static int vfstraceDeviceCharacteristics(sqlite3_file*);
+static int vfstraceShmLock(sqlite3_file*,int,int,int);
+static int vfstraceShmMap(sqlite3_file*,int,int,int, void volatile **);
+static void vfstraceShmBarrier(sqlite3_file*);
+static int vfstraceShmUnmap(sqlite3_file*,int);
+
+/*
+** Method declarations for vfstrace_vfs.
+*/
+static int vfstraceOpen(sqlite3_vfs*, const char *, sqlite3_file*, int , int *);
+static int vfstraceDelete(sqlite3_vfs*, const char *zName, int syncDir);
+static int vfstraceAccess(sqlite3_vfs*, const char *zName, int flags, int *);
+static int vfstraceFullPathname(sqlite3_vfs*, const char *zName, int, char *);
+static void *vfstraceDlOpen(sqlite3_vfs*, const char *zFilename);
+static void vfstraceDlError(sqlite3_vfs*, int nByte, char *zErrMsg);
+static void (*vfstraceDlSym(sqlite3_vfs*,void*, const char *zSymbol))(void);
+static void vfstraceDlClose(sqlite3_vfs*, void*);
+static int vfstraceRandomness(sqlite3_vfs*, int nByte, char *zOut);
+static int vfstraceSleep(sqlite3_vfs*, int microseconds);
+static int vfstraceCurrentTime(sqlite3_vfs*, double*);
+static int vfstraceGetLastError(sqlite3_vfs*, int, char*);
+static int vfstraceCurrentTimeInt64(sqlite3_vfs*, sqlite3_int64*);
+static int vfstraceSetSystemCall(sqlite3_vfs*,const char*, sqlite3_syscall_ptr);
+static sqlite3_syscall_ptr vfstraceGetSystemCall(sqlite3_vfs*, const char *);
+static const char *vfstraceNextSystemCall(sqlite3_vfs*, const char *zName);
+
+/*
+** Return a pointer to the tail of the pathname.  Examples:
+**
+**     /home/drh/xyzzy.txt -> xyzzy.txt
+**     xyzzy.txt           -> xyzzy.txt
+*/
+static const char *fileTail(const char *z){
+  int i;
+  if( z==0 ) return 0;
+  i = strlen(z)-1;
+  while( i>0 && z[i-1]!='/' ){ i--; }
+  return &z[i];
+}
+
+/*
+** Send trace output defined by zFormat and subsequent arguments.
+*/
+static void vfstrace_printf(
+  vfstrace_info *pInfo,
+  const char *zFormat,
+  ...
+){
+  va_list ap;
+  char *zMsg;
+  va_start(ap, zFormat);
+  zMsg = sqlite3_vmprintf(zFormat, ap);
+  va_end(ap);
+  pInfo->xOut(zMsg, pInfo->pOutArg);
+  sqlite3_free(zMsg);
+}
+
+/*
+** Convert value rc into a string and print it using zFormat.  zFormat
+** should have exactly one %s
+*/
+static void vfstrace_print_errcode(
+  vfstrace_info *pInfo,
+  const char *zFormat,
+  int rc
+){
+  char zBuf[50];
+  char *zVal;
+  switch( rc ){
+    case SQLITE_OK:         zVal = "SQLITE_OK";          break;
+    case SQLITE_ERROR:      zVal = "SQLITE_ERROR";       break;
+    case SQLITE_PERM:       zVal = "SQLITE_PERM";        break;
+    case SQLITE_ABORT:      zVal = "SQLITE_ABORT";       break;
+    case SQLITE_BUSY:       zVal = "SQLITE_BUSY";        break;
+    case SQLITE_NOMEM:      zVal = "SQLITE_NOMEM";       break;
+    case SQLITE_READONLY:   zVal = "SQLITE_READONLY";    break;
+    case SQLITE_INTERRUPT:  zVal = "SQLITE_INTERRUPT";   break;
+    case SQLITE_IOERR:      zVal = "SQLITE_IOERR";       break;
+    case SQLITE_CORRUPT:    zVal = "SQLITE_CORRUPT";     break;
+    case SQLITE_FULL:       zVal = "SQLITE_FULL";        break;
+    case SQLITE_CANTOPEN:   zVal = "SQLITE_CANTOPEN";    break;
+    case SQLITE_PROTOCOL:   zVal = "SQLITE_PROTOCOL";    break;
+    case SQLITE_EMPTY:      zVal = "SQLITE_EMPTY";       break;
+    case SQLITE_SCHEMA:     zVal = "SQLITE_SCHEMA";      break;
+    case SQLITE_CONSTRAINT: zVal = "SQLITE_CONSTRAINT";  break;
+    case SQLITE_MISMATCH:   zVal = "SQLITE_MISMATCH";    break;
+    case SQLITE_MISUSE:     zVal = "SQLITE_MISUSE";      break;
+    case SQLITE_NOLFS:      zVal = "SQLITE_NOLFS";       break;
+    case SQLITE_IOERR_READ:         zVal = "SQLITE_IOERR_READ";         break;
+    case SQLITE_IOERR_SHORT_READ:   zVal = "SQLITE_IOERR_SHORT_READ";   break;
+    case SQLITE_IOERR_WRITE:        zVal = "SQLITE_IOERR_WRITE";        break;
+    case SQLITE_IOERR_FSYNC:        zVal = "SQLITE_IOERR_FSYNC";        break;
+    case SQLITE_IOERR_DIR_FSYNC:    zVal = "SQLITE_IOERR_DIR_FSYNC";    break;
+    case SQLITE_IOERR_TRUNCATE:     zVal = "SQLITE_IOERR_TRUNCATE";     break;
+    case SQLITE_IOERR_FSTAT:        zVal = "SQLITE_IOERR_FSTAT";        break;
+    case SQLITE_IOERR_UNLOCK:       zVal = "SQLITE_IOERR_UNLOCK";       break;
+    case SQLITE_IOERR_RDLOCK:       zVal = "SQLITE_IOERR_RDLOCK";       break;
+    case SQLITE_IOERR_DELETE:       zVal = "SQLITE_IOERR_DELETE";       break;
+    case SQLITE_IOERR_BLOCKED:      zVal = "SQLITE_IOERR_BLOCKED";      break;
+    case SQLITE_IOERR_NOMEM:        zVal = "SQLITE_IOERR_NOMEM";        break;
+    case SQLITE_IOERR_ACCESS:       zVal = "SQLITE_IOERR_ACCESS";       break;
+    case SQLITE_IOERR_CHECKRESERVEDLOCK:
+                               zVal = "SQLITE_IOERR_CHECKRESERVEDLOCK"; break;
+    case SQLITE_IOERR_LOCK:         zVal = "SQLITE_IOERR_LOCK";         break;
+    case SQLITE_IOERR_CLOSE:        zVal = "SQLITE_IOERR_CLOSE";        break;
+    case SQLITE_IOERR_DIR_CLOSE:    zVal = "SQLITE_IOERR_DIR_CLOSE";    break;
+    case SQLITE_IOERR_SHMOPEN:      zVal = "SQLITE_IOERR_SHMOPEN";      break;
+    case SQLITE_IOERR_SHMSIZE:      zVal = "SQLITE_IOERR_SHMSIZE";      break;
+    case SQLITE_IOERR_SHMLOCK:      zVal = "SQLITE_IOERR_SHMLOCK";      break;
+    case SQLITE_LOCKED_SHAREDCACHE: zVal = "SQLITE_LOCKED_SHAREDCACHE"; break;
+    case SQLITE_BUSY_RECOVERY:      zVal = "SQLITE_BUSY_RECOVERY";      break;
+    case SQLITE_CANTOPEN_NOTEMPDIR: zVal = "SQLITE_CANTOPEN_NOTEMPDIR"; break;
+    default: {
+       sqlite3_snprintf(sizeof(zBuf), zBuf, "%d", rc);
+       zVal = zBuf;
+       break;
+    }
+  }
+  vfstrace_printf(pInfo, zFormat, zVal);
+}
+
+/*
+** Append to a buffer.
+*/
+static void strappend(char *z, int *pI, const char *zAppend){
+  int i = *pI;
+  while( zAppend[0] ){ z[i++] = *(zAppend++); }
+  z[i] = 0;
+  *pI = i;
+}
+
+/*
+** Close an vfstrace-file.
+*/
+static int vfstraceClose(sqlite3_file *pFile){
+  vfstrace_file *p = (vfstrace_file *)pFile;
+  vfstrace_info *pInfo = p->pInfo;
+  int rc;
+  vfstrace_printf(pInfo, "%s.xClose(%s)", pInfo->zVfsName, p->zFName);
+  rc = p->pReal->pMethods->xClose(p->pReal);
+  vfstrace_print_errcode(pInfo, " -> %s\n", rc);
+  if( rc==SQLITE_OK ){
+    sqlite3_free((void*)p->base.pMethods);
+    p->base.pMethods = 0;
+  }
+  return rc;
+}
+
+/*
+** Read data from an vfstrace-file.
+*/
+static int vfstraceRead(
+  sqlite3_file *pFile, 
+  void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  vfstrace_file *p = (vfstrace_file *)pFile;
+  vfstrace_info *pInfo = p->pInfo;
+  int rc;
+  vfstrace_printf(pInfo, "%s.xRead(%s,n=%d,ofst=%lld)",
+                  pInfo->zVfsName, p->zFName, iAmt, iOfst);
+  rc = p->pReal->pMethods->xRead(p->pReal, zBuf, iAmt, iOfst);
+  vfstrace_print_errcode(pInfo, " -> %s\n", rc);
+  return rc;
+}
+
+/*
+** Write data to an vfstrace-file.
+*/
+static int vfstraceWrite(
+  sqlite3_file *pFile, 
+  const void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  vfstrace_file *p = (vfstrace_file *)pFile;
+  vfstrace_info *pInfo = p->pInfo;
+  int rc;
+  vfstrace_printf(pInfo, "%s.xWrite(%s,n=%d,ofst=%lld)",
+                  pInfo->zVfsName, p->zFName, iAmt, iOfst);
+  rc = p->pReal->pMethods->xWrite(p->pReal, zBuf, iAmt, iOfst);
+  vfstrace_print_errcode(pInfo, " -> %s\n", rc);
+  return rc;
+}
+
+/*
+** Truncate an vfstrace-file.
+*/
+static int vfstraceTruncate(sqlite3_file *pFile, sqlite_int64 size){
+  vfstrace_file *p = (vfstrace_file *)pFile;
+  vfstrace_info *pInfo = p->pInfo;
+  int rc;
+  vfstrace_printf(pInfo, "%s.xTruncate(%s,%lld)", pInfo->zVfsName, p->zFName,
+                  size);
+  rc = p->pReal->pMethods->xTruncate(p->pReal, size);
+  vfstrace_printf(pInfo, " -> %d\n", rc);
+  return rc;
+}
+
+/*
+** Sync an vfstrace-file.
+*/
+static int vfstraceSync(sqlite3_file *pFile, int flags){
+  vfstrace_file *p = (vfstrace_file *)pFile;
+  vfstrace_info *pInfo = p->pInfo;
+  int rc;
+  int i;
+  char zBuf[100];
+  memcpy(zBuf, "|0", 3);
+  i = 0;
+  if( flags & SQLITE_SYNC_FULL )        strappend(zBuf, &i, "|FULL");
+  else if( flags & SQLITE_SYNC_NORMAL ) strappend(zBuf, &i, "|NORMAL");
+  if( flags & SQLITE_SYNC_DATAONLY )    strappend(zBuf, &i, "|DATAONLY");
+  if( flags & ~(SQLITE_SYNC_FULL|SQLITE_SYNC_DATAONLY) ){
+    sqlite3_snprintf(sizeof(zBuf)-i, &zBuf[i], "|0x%x", flags);
+  }
+  vfstrace_printf(pInfo, "%s.xSync(%s,%s)", pInfo->zVfsName, p->zFName,
+                  &zBuf[1]);
+  rc = p->pReal->pMethods->xSync(p->pReal, flags);
+  vfstrace_printf(pInfo, " -> %d\n", rc);
+  return rc;
+}
+
+/*
+** Return the current file-size of an vfstrace-file.
+*/
+static int vfstraceFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
+  vfstrace_file *p = (vfstrace_file *)pFile;
+  vfstrace_info *pInfo = p->pInfo;
+  int rc;
+  vfstrace_printf(pInfo, "%s.xFileSize(%s)", pInfo->zVfsName, p->zFName);
+  rc = p->pReal->pMethods->xFileSize(p->pReal, pSize);
+  vfstrace_print_errcode(pInfo, " -> %s,", rc);
+  vfstrace_printf(pInfo, " size=%lld\n", *pSize);
+  return rc;
+}
+
+/*
+** Return the name of a lock.
+*/
+static const char *lockName(int eLock){
+  const char *azLockNames[] = {
+     "NONE", "SHARED", "RESERVED", "PENDING", "EXCLUSIVE"
+  };
+  if( eLock<0 || eLock>=sizeof(azLockNames)/sizeof(azLockNames[0]) ){
+    return "???";
+  }else{
+    return azLockNames[eLock];
+  }
+}
+
+/*
+** Lock an vfstrace-file.
+*/
+static int vfstraceLock(sqlite3_file *pFile, int eLock){
+  vfstrace_file *p = (vfstrace_file *)pFile;
+  vfstrace_info *pInfo = p->pInfo;
+  int rc;
+  vfstrace_printf(pInfo, "%s.xLock(%s,%s)", pInfo->zVfsName, p->zFName,
+                  lockName(eLock));
+  rc = p->pReal->pMethods->xLock(p->pReal, eLock);
+  vfstrace_print_errcode(pInfo, " -> %s\n", rc);
+  return rc;
+}
+
+/*
+** Unlock an vfstrace-file.
+*/
+static int vfstraceUnlock(sqlite3_file *pFile, int eLock){
+  vfstrace_file *p = (vfstrace_file *)pFile;
+  vfstrace_info *pInfo = p->pInfo;
+  int rc;
+  vfstrace_printf(pInfo, "%s.xUnlock(%s,%s)", pInfo->zVfsName, p->zFName,
+                  lockName(eLock));
+  rc = p->pReal->pMethods->xUnlock(p->pReal, eLock);
+  vfstrace_print_errcode(pInfo, " -> %s\n", rc);
+  return rc;
+}
+
+/*
+** Check if another file-handle holds a RESERVED lock on an vfstrace-file.
+*/
+static int vfstraceCheckReservedLock(sqlite3_file *pFile, int *pResOut){
+  vfstrace_file *p = (vfstrace_file *)pFile;
+  vfstrace_info *pInfo = p->pInfo;
+  int rc;
+  vfstrace_printf(pInfo, "%s.xCheckReservedLock(%s,%d)", 
+                  pInfo->zVfsName, p->zFName);
+  rc = p->pReal->pMethods->xCheckReservedLock(p->pReal, pResOut);
+  vfstrace_print_errcode(pInfo, " -> %s", rc);
+  vfstrace_printf(pInfo, ", out=%d\n", *pResOut);
+  return rc;
+}
+
+/*
+** File control method. For custom operations on an vfstrace-file.
+*/
+static int vfstraceFileControl(sqlite3_file *pFile, int op, void *pArg){
+  vfstrace_file *p = (vfstrace_file *)pFile;
+  vfstrace_info *pInfo = p->pInfo;
+  int rc;
+  char zBuf[100];
+  char *zOp;
+  switch( op ){
+    case SQLITE_FCNTL_LOCKSTATE:    zOp = "LOCKSTATE";          break;
+    case SQLITE_GET_LOCKPROXYFILE:  zOp = "GET_LOCKPROXYFILE";  break;
+    case SQLITE_SET_LOCKPROXYFILE:  zOp = "SET_LOCKPROXYFILE";  break;
+    case SQLITE_LAST_ERRNO:         zOp = "LAST_ERRNO";         break;
+    case SQLITE_FCNTL_SIZE_HINT: {
+      sqlite3_snprintf(sizeof(zBuf), zBuf, "SIZE_HINT,%lld",
+                       *(sqlite3_int64*)pArg);
+      zOp = zBuf;
+      break;
+    }
+    case SQLITE_FCNTL_CHUNK_SIZE: {
+      sqlite3_snprintf(sizeof(zBuf), zBuf, "CHUNK_SIZE,%d", *(int*)pArg);
+      zOp = zBuf;
+      break;
+    }
+    case SQLITE_FCNTL_FILE_POINTER: zOp = "FILE_POINTER";       break;
+    case SQLITE_FCNTL_SYNC_OMITTED: zOp = "SYNC_OMITTED";       break;
+    case 0xca093fa0:                zOp = "DB_UNCHANGED";       break;
+    default: {
+      sqlite3_snprintf(sizeof zBuf, zBuf, "%d", op);
+      zOp = zBuf;
+      break;
+    }
+  }
+  vfstrace_printf(pInfo, "%s.xFileControl(%s,%s)",
+                  pInfo->zVfsName, p->zFName, zOp);
+  rc = p->pReal->pMethods->xFileControl(p->pReal, op, pArg);
+  vfstrace_print_errcode(pInfo, " -> %s\n", rc);
+  return rc;
+}
+
+/*
+** Return the sector-size in bytes for an vfstrace-file.
+*/
+static int vfstraceSectorSize(sqlite3_file *pFile){
+  vfstrace_file *p = (vfstrace_file *)pFile;
+  vfstrace_info *pInfo = p->pInfo;
+  int rc;
+  vfstrace_printf(pInfo, "%s.xSectorSize(%s)", pInfo->zVfsName, p->zFName);
+  rc = p->pReal->pMethods->xSectorSize(p->pReal);
+  vfstrace_printf(pInfo, " -> %d\n", rc);
+  return rc;
+}
+
+/*
+** Return the device characteristic flags supported by an vfstrace-file.
+*/
+static int vfstraceDeviceCharacteristics(sqlite3_file *pFile){
+  vfstrace_file *p = (vfstrace_file *)pFile;
+  vfstrace_info *pInfo = p->pInfo;
+  int rc;
+  vfstrace_printf(pInfo, "%s.xDeviceCharacteristics(%s)",
+                  pInfo->zVfsName, p->zFName);
+  rc = p->pReal->pMethods->xDeviceCharacteristics(p->pReal);
+  vfstrace_printf(pInfo, " -> 0x%08x\n", rc);
+  return rc;
+}
+
+/*
+** Shared-memory operations.
+*/
+static int vfstraceShmLock(sqlite3_file *pFile, int ofst, int n, int flags){
+  vfstrace_file *p = (vfstrace_file *)pFile;
+  vfstrace_info *pInfo = p->pInfo;
+  int rc;
+  char zLck[100];
+  int i = 0;
+  memcpy(zLck, "|0", 3);
+  if( flags & SQLITE_SHM_UNLOCK )    strappend(zLck, &i, "|UNLOCK");
+  if( flags & SQLITE_SHM_LOCK )      strappend(zLck, &i, "|LOCK");
+  if( flags & SQLITE_SHM_SHARED )    strappend(zLck, &i, "|SHARED");
+  if( flags & SQLITE_SHM_EXCLUSIVE ) strappend(zLck, &i, "|EXCLUSIVE");
+  if( flags & ~(0xf) ){
+     sqlite3_snprintf(sizeof(zLck)-i, &zLck[i], "|0x%x", flags);
+  }
+  vfstrace_printf(pInfo, "%s.xShmLock(%s,ofst=%d,n=%d,%s)",
+                  pInfo->zVfsName, p->zFName, ofst, n, &zLck[1]);
+  rc = p->pReal->pMethods->xShmLock(p->pReal, ofst, n, flags);
+  vfstrace_print_errcode(pInfo, " -> %s\n", rc);
+  return rc;
+}
+static int vfstraceShmMap(
+  sqlite3_file *pFile, 
+  int iRegion, 
+  int szRegion, 
+  int isWrite, 
+  void volatile **pp
+){
+  vfstrace_file *p = (vfstrace_file *)pFile;
+  vfstrace_info *pInfo = p->pInfo;
+  int rc;
+  vfstrace_printf(pInfo, "%s.xShmMap(%s,iRegion=%d,szRegion=%d,isWrite=%d,*)",
+                  pInfo->zVfsName, p->zFName, iRegion, szRegion, isWrite);
+  rc = p->pReal->pMethods->xShmMap(p->pReal, iRegion, szRegion, isWrite, pp);
+  vfstrace_print_errcode(pInfo, " -> %s\n", rc);
+  return rc;
+}
+static void vfstraceShmBarrier(sqlite3_file *pFile){
+  vfstrace_file *p = (vfstrace_file *)pFile;
+  vfstrace_info *pInfo = p->pInfo;
+  vfstrace_printf(pInfo, "%s.xShmBarrier(%s)\n", pInfo->zVfsName, p->zFName);
+  p->pReal->pMethods->xShmBarrier(p->pReal);
+}
+static int vfstraceShmUnmap(sqlite3_file *pFile, int delFlag){
+  vfstrace_file *p = (vfstrace_file *)pFile;
+  vfstrace_info *pInfo = p->pInfo;
+  int rc;
+  vfstrace_printf(pInfo, "%s.xShmUnmap(%s,delFlag=%d)",
+                  pInfo->zVfsName, p->zFName, delFlag);
+  rc = p->pReal->pMethods->xShmUnmap(p->pReal, delFlag);
+  vfstrace_print_errcode(pInfo, " -> %s\n", rc);
+  return rc;
+}
+
+
+
+/*
+** Open an vfstrace file handle.
+*/
+static int vfstraceOpen(
+  sqlite3_vfs *pVfs,
+  const char *zName,
+  sqlite3_file *pFile,
+  int flags,
+  int *pOutFlags
+){
+  int rc;
+  vfstrace_file *p = (vfstrace_file *)pFile;
+  vfstrace_info *pInfo = (vfstrace_info*)pVfs->pAppData;
+  sqlite3_vfs *pRoot = pInfo->pRootVfs;
+  p->pInfo = pInfo;
+  p->zFName = zName ? fileTail(zName) : "<temp>";
+  p->pReal = (sqlite3_file *)&p[1];
+  rc = pRoot->xOpen(pRoot, zName, p->pReal, flags, pOutFlags);
+  vfstrace_printf(pInfo, "%s.xOpen(%s,flags=0x%x)",
+                  pInfo->zVfsName, p->zFName, flags);
+  if( p->pReal->pMethods ){
+    sqlite3_io_methods *pNew = sqlite3_malloc( sizeof(*pNew) );
+    const sqlite3_io_methods *pSub = p->pReal->pMethods;
+    memset(pNew, 0, sizeof(*pNew));
+    pNew->iVersion = pSub->iVersion;
+    pNew->xClose = vfstraceClose;
+    pNew->xRead = vfstraceRead;
+    pNew->xWrite = vfstraceWrite;
+    pNew->xTruncate = vfstraceTruncate;
+    pNew->xSync = vfstraceSync;
+    pNew->xFileSize = vfstraceFileSize;
+    pNew->xLock = vfstraceLock;
+    pNew->xUnlock = vfstraceUnlock;
+    pNew->xCheckReservedLock = vfstraceCheckReservedLock;
+    pNew->xFileControl = vfstraceFileControl;
+    pNew->xSectorSize = vfstraceSectorSize;
+    pNew->xDeviceCharacteristics = vfstraceDeviceCharacteristics;
+    if( pNew->iVersion>=2 ){
+      pNew->xShmMap = pSub->xShmMap ? vfstraceShmMap : 0;
+      pNew->xShmLock = pSub->xShmLock ? vfstraceShmLock : 0;
+      pNew->xShmBarrier = pSub->xShmBarrier ? vfstraceShmBarrier : 0;
+      pNew->xShmUnmap = pSub->xShmUnmap ? vfstraceShmUnmap : 0;
+    }
+    pFile->pMethods = pNew;
+  }
+  vfstrace_print_errcode(pInfo, " -> %s", rc);
+  if( pOutFlags ){
+    vfstrace_printf(pInfo, ", outFlags=0x%x\n", *pOutFlags);
+  }else{
+    vfstrace_printf(pInfo, "\n");
+  }
+  return rc;
+}
+
+/*
+** Delete the file located at zPath. If the dirSync argument is true,
+** ensure the file-system modifications are synced to disk before
+** returning.
+*/
+static int vfstraceDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
+  vfstrace_info *pInfo = (vfstrace_info*)pVfs->pAppData;
+  sqlite3_vfs *pRoot = pInfo->pRootVfs;
+  int rc;
+  vfstrace_printf(pInfo, "%s.xDelete(\"%s\",%d)",
+                  pInfo->zVfsName, zPath, dirSync);
+  rc = pRoot->xDelete(pRoot, zPath, dirSync);
+  vfstrace_print_errcode(pInfo, " -> %s\n", rc);
+  return rc;
+}
+
+/*
+** Test for access permissions. Return true if the requested permission
+** is available, or false otherwise.
+*/
+static int vfstraceAccess(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  int flags, 
+  int *pResOut
+){
+  vfstrace_info *pInfo = (vfstrace_info*)pVfs->pAppData;
+  sqlite3_vfs *pRoot = pInfo->pRootVfs;
+  int rc;
+  vfstrace_printf(pInfo, "%s.xDelete(\"%s\",%d)",
+                  pInfo->zVfsName, zPath, flags);
+  rc = pRoot->xAccess(pRoot, zPath, flags, pResOut);
+  vfstrace_print_errcode(pInfo, " -> %s", rc);
+  vfstrace_printf(pInfo, ", out=%d\n", *pResOut);
+  return rc;
+}
+
+/*
+** Populate buffer zOut with the full canonical pathname corresponding
+** to the pathname in zPath. zOut is guaranteed to point to a buffer
+** of at least (DEVSYM_MAX_PATHNAME+1) bytes.
+*/
+static int vfstraceFullPathname(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  int nOut, 
+  char *zOut
+){
+  vfstrace_info *pInfo = (vfstrace_info*)pVfs->pAppData;
+  sqlite3_vfs *pRoot = pInfo->pRootVfs;
+  int rc;
+  vfstrace_printf(pInfo, "%s.xFullPathname(\"%s\")",
+                  pInfo->zVfsName, zPath);
+  rc = pRoot->xFullPathname(pRoot, zPath, nOut, zOut);
+  vfstrace_print_errcode(pInfo, " -> %s", rc);
+  vfstrace_printf(pInfo, ", out=\"%.*s\"\n", nOut, zOut);
+  return rc;
+}
+
+/*
+** Open the dynamic library located at zPath and return a handle.
+*/
+static void *vfstraceDlOpen(sqlite3_vfs *pVfs, const char *zPath){
+  vfstrace_info *pInfo = (vfstrace_info*)pVfs->pAppData;
+  sqlite3_vfs *pRoot = pInfo->pRootVfs;
+  vfstrace_printf(pInfo, "%s.xDlOpen(\"%s\")\n", pInfo->zVfsName, zPath);
+  return pRoot->xDlOpen(pRoot, zPath);
+}
+
+/*
+** Populate the buffer zErrMsg (size nByte bytes) with a human readable
+** utf-8 string describing the most recent error encountered associated 
+** with dynamic libraries.
+*/
+static void vfstraceDlError(sqlite3_vfs *pVfs, int nByte, char *zErrMsg){
+  vfstrace_info *pInfo = (vfstrace_info*)pVfs->pAppData;
+  sqlite3_vfs *pRoot = pInfo->pRootVfs;
+  vfstrace_printf(pInfo, "%s.xDlError(%d)", pInfo->zVfsName, nByte);
+  pRoot->xDlError(pRoot, nByte, zErrMsg);
+  vfstrace_printf(pInfo, " -> \"%s\"", zErrMsg);
+}
+
+/*
+** Return a pointer to the symbol zSymbol in the dynamic library pHandle.
+*/
+static void (*vfstraceDlSym(sqlite3_vfs *pVfs,void *p,const char *zSym))(void){
+  vfstrace_info *pInfo = (vfstrace_info*)pVfs->pAppData;
+  sqlite3_vfs *pRoot = pInfo->pRootVfs;
+  vfstrace_printf(pInfo, "%s.xDlSym(\"%s\")\n", pInfo->zVfsName, zSym);
+  return pRoot->xDlSym(pRoot, p, zSym);
+}
+
+/*
+** Close the dynamic library handle pHandle.
+*/
+static void vfstraceDlClose(sqlite3_vfs *pVfs, void *pHandle){
+  vfstrace_info *pInfo = (vfstrace_info*)pVfs->pAppData;
+  sqlite3_vfs *pRoot = pInfo->pRootVfs;
+  vfstrace_printf(pInfo, "%s.xDlOpen()\n", pInfo->zVfsName);
+  pRoot->xDlClose(pRoot, pHandle);
+}
+
+/*
+** Populate the buffer pointed to by zBufOut with nByte bytes of 
+** random data.
+*/
+static int vfstraceRandomness(sqlite3_vfs *pVfs, int nByte, char *zBufOut){
+  vfstrace_info *pInfo = (vfstrace_info*)pVfs->pAppData;
+  sqlite3_vfs *pRoot = pInfo->pRootVfs;
+  vfstrace_printf(pInfo, "%s.xRandomness(%d)\n", pInfo->zVfsName, nByte);
+  return pRoot->xRandomness(pRoot, nByte, zBufOut);
+}
+
+/*
+** Sleep for nMicro microseconds. Return the number of microseconds 
+** actually slept.
+*/
+static int vfstraceSleep(sqlite3_vfs *pVfs, int nMicro){
+  vfstrace_info *pInfo = (vfstrace_info*)pVfs->pAppData;
+  sqlite3_vfs *pRoot = pInfo->pRootVfs;
+  return pRoot->xSleep(pRoot, nMicro);
+}
+
+/*
+** Return the current time as a Julian Day number in *pTimeOut.
+*/
+static int vfstraceCurrentTime(sqlite3_vfs *pVfs, double *pTimeOut){
+  vfstrace_info *pInfo = (vfstrace_info*)pVfs->pAppData;
+  sqlite3_vfs *pRoot = pInfo->pRootVfs;
+  return pRoot->xCurrentTime(pRoot, pTimeOut);
+}
+static int vfstraceCurrentTimeInt64(sqlite3_vfs *pVfs, sqlite3_int64 *pTimeOut){
+  vfstrace_info *pInfo = (vfstrace_info*)pVfs->pAppData;
+  sqlite3_vfs *pRoot = pInfo->pRootVfs;
+  return pRoot->xCurrentTimeInt64(pRoot, pTimeOut);
+}
+
+/*
+** Return th3 emost recent error code and message
+*/
+static int vfstraceGetLastError(sqlite3_vfs *pVfs, int iErr, char *zErr){
+  vfstrace_info *pInfo = (vfstrace_info*)pVfs->pAppData;
+  sqlite3_vfs *pRoot = pInfo->pRootVfs;
+  return pRoot->xGetLastError(pRoot, iErr, zErr);
+}
+
+/*
+** Override system calls.
+*/
+static int vfstraceSetSystemCall(
+  sqlite3_vfs *pVfs,
+  const char *zName,
+  sqlite3_syscall_ptr pFunc
+){
+  vfstrace_info *pInfo = (vfstrace_info*)pVfs->pAppData;
+  sqlite3_vfs *pRoot = pInfo->pRootVfs;
+  return pRoot->xSetSystemCall(pRoot, zName, pFunc);
+}
+static sqlite3_syscall_ptr vfstraceGetSystemCall(
+  sqlite3_vfs *pVfs,
+  const char *zName
+){
+  vfstrace_info *pInfo = (vfstrace_info*)pVfs->pAppData;
+  sqlite3_vfs *pRoot = pInfo->pRootVfs;
+  return pRoot->xGetSystemCall(pRoot, zName);
+}
+static const char *vfstraceNextSystemCall(sqlite3_vfs *pVfs, const char *zName){
+  vfstrace_info *pInfo = (vfstrace_info*)pVfs->pAppData;
+  sqlite3_vfs *pRoot = pInfo->pRootVfs;
+  return pRoot->xNextSystemCall(pRoot, zName);
+}
+
+
+/*
+** Clients invoke this routine to construct a new trace-vfs shim.
+**
+** Return SQLITE_OK on success.  
+**
+** SQLITE_NOMEM is returned in the case of a memory allocation error.
+** SQLITE_NOTFOUND is returned if zOldVfsName does not exist.
+*/
+int vfstrace_register(
+   const char *zTraceName,           /* Name of the newly constructed VFS */
+   const char *zOldVfsName,          /* Name of the underlying VFS */
+   int (*xOut)(const char*,void*),   /* Output routine.  ex: fputs */
+   void *pOutArg,                    /* 2nd argument to xOut.  ex: stderr */
+   int makeDefault                   /* True to make the new VFS the default */
+){
+  sqlite3_vfs *pNew;
+  sqlite3_vfs *pRoot;
+  vfstrace_info *pInfo;
+  int nName;
+  int nByte;
+
+  pRoot = sqlite3_vfs_find(zOldVfsName);
+  if( pRoot==0 ) return SQLITE_NOTFOUND;
+  nName = strlen(zTraceName);
+  nByte = sizeof(*pNew) + sizeof(*pInfo) + nName + 1;
+  pNew = sqlite3_malloc( nByte );
+  if( pNew==0 ) return SQLITE_NOMEM;
+  memset(pNew, 0, nByte);
+  pInfo = (vfstrace_info*)&pNew[1];
+  pNew->iVersion = pRoot->iVersion;
+  pNew->szOsFile = pRoot->szOsFile + sizeof(vfstrace_file);
+  pNew->mxPathname = pRoot->mxPathname;
+  pNew->zName = (char*)&pInfo[1];
+  memcpy((char*)&pInfo[1], zTraceName, nName+1);
+  pNew->pAppData = pInfo;
+  pNew->xOpen = vfstraceOpen;
+  pNew->xDelete = vfstraceDelete;
+  pNew->xAccess = vfstraceAccess;
+  pNew->xFullPathname = vfstraceFullPathname;
+  pNew->xDlOpen = pRoot->xDlOpen==0 ? 0 : vfstraceDlOpen;
+  pNew->xDlError = pRoot->xDlError==0 ? 0 : vfstraceDlError;
+  pNew->xDlSym = pRoot->xDlSym==0 ? 0 : vfstraceDlSym;
+  pNew->xDlClose = pRoot->xDlClose==0 ? 0 : vfstraceDlClose;
+  pNew->xRandomness = vfstraceRandomness;
+  pNew->xSleep = vfstraceSleep;
+  pNew->xCurrentTime = vfstraceCurrentTime;
+  pNew->xGetLastError = pRoot->xGetLastError==0 ? 0 : vfstraceGetLastError;
+  if( pNew->iVersion>=2 ){
+    pNew->xCurrentTimeInt64 = pRoot->xCurrentTimeInt64==0 ? 0 :
+                                   vfstraceCurrentTimeInt64;
+    if( pNew->iVersion>=3 ){
+      pNew->xSetSystemCall = pRoot->xSetSystemCall==0 ? 0 : 
+                                   vfstraceSetSystemCall;
+      pNew->xGetSystemCall = pRoot->xGetSystemCall==0 ? 0 : 
+                                   vfstraceGetSystemCall;
+      pNew->xNextSystemCall = pRoot->xNextSystemCall==0 ? 0 : 
+                                   vfstraceNextSystemCall;
+    }
+  }
+  pInfo->pRootVfs = pRoot;
+  pInfo->xOut = xOut;
+  pInfo->pOutArg = pOutArg;
+  pInfo->zVfsName = pNew->zName;
+  pInfo->pTraceVfs = pNew;
+  vfstrace_printf(pInfo, "%s.enabled_for(\"%s\")\n",
+       pInfo->zVfsName, pRoot->zName);
+  return sqlite3_vfs_register(pNew, makeDefault);
+}
diff --git a/src/test_wholenumber.c b/src/test_wholenumber.c
new file mode 100644
index 0000000..150dc95
--- /dev/null
+++ b/src/test_wholenumber.c
@@ -0,0 +1,311 @@
+/*
+** 2011 April 02
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file implements a virtual table that returns the whole numbers
+** between 1 and 4294967295, inclusive.
+**
+** Example:
+**
+**     CREATE VIRTUAL TABLE nums USING wholenumber;
+**     SELECT value FROM nums WHERE value<10;
+**
+** Results in:
+**
+**     1 2 3 4 5 6 7 8 9
+*/
+#include "sqlite3.h"
+#include <assert.h>
+#include <string.h>
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+
+
+/* A wholenumber cursor object */
+typedef struct wholenumber_cursor wholenumber_cursor;
+struct wholenumber_cursor {
+  sqlite3_vtab_cursor base;  /* Base class - must be first */
+  unsigned iValue;           /* Current value */
+  unsigned mxValue;          /* Maximum value */
+};
+
+/* Methods for the wholenumber module */
+static int wholenumberConnect(
+  sqlite3 *db,
+  void *pAux,
+  int argc, const char *const*argv,
+  sqlite3_vtab **ppVtab,
+  char **pzErr
+){
+  sqlite3_vtab *pNew;
+  pNew = *ppVtab = sqlite3_malloc( sizeof(*pNew) );
+  if( pNew==0 ) return SQLITE_NOMEM;
+  sqlite3_declare_vtab(db, "CREATE TABLE x(value)");
+  memset(pNew, 0, sizeof(*pNew));
+  return SQLITE_OK;
+}
+/* Note that for this virtual table, the xCreate and xConnect
+** methods are identical. */
+
+static int wholenumberDisconnect(sqlite3_vtab *pVtab){
+  sqlite3_free(pVtab);
+  return SQLITE_OK;
+}
+/* The xDisconnect and xDestroy methods are also the same */
+
+
+/*
+** Open a new wholenumber cursor.
+*/
+static int wholenumberOpen(sqlite3_vtab *p, sqlite3_vtab_cursor **ppCursor){
+  wholenumber_cursor *pCur;
+  pCur = sqlite3_malloc( sizeof(*pCur) );
+  if( pCur==0 ) return SQLITE_NOMEM;
+  memset(pCur, 0, sizeof(*pCur));
+  *ppCursor = &pCur->base;
+  return SQLITE_OK;
+}
+
+/*
+** Close a wholenumber cursor.
+*/
+static int wholenumberClose(sqlite3_vtab_cursor *cur){
+  sqlite3_free(cur);
+  return SQLITE_OK;
+}
+
+
+/*
+** Advance a cursor to its next row of output
+*/
+static int wholenumberNext(sqlite3_vtab_cursor *cur){
+  wholenumber_cursor *pCur = (wholenumber_cursor*)cur;
+  pCur->iValue++;
+  return SQLITE_OK;
+}
+
+/*
+** Return the value associated with a wholenumber.
+*/
+static int wholenumberColumn(
+  sqlite3_vtab_cursor *cur,
+  sqlite3_context *ctx,
+  int i
+){
+  wholenumber_cursor *pCur = (wholenumber_cursor*)cur;
+  sqlite3_result_int64(ctx, pCur->iValue);
+  return SQLITE_OK;
+}
+
+/*
+** The rowid.
+*/
+static int wholenumberRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
+  wholenumber_cursor *pCur = (wholenumber_cursor*)cur;
+  *pRowid = pCur->iValue;
+  return SQLITE_OK;
+}
+
+/*
+** When the wholenumber_cursor.rLimit value is 0 or less, that is a signal
+** that the cursor has nothing more to output.
+*/
+static int wholenumberEof(sqlite3_vtab_cursor *cur){
+  wholenumber_cursor *pCur = (wholenumber_cursor*)cur;
+  return pCur->iValue>pCur->mxValue || pCur->iValue==0;
+}
+
+/*
+** Called to "rewind" a cursor back to the beginning so that
+** it starts its output over again.  Always called at least once
+** prior to any wholenumberColumn, wholenumberRowid, or wholenumberEof call.
+**
+**    idxNum   Constraints
+**    ------   ---------------------
+**      0      (none)
+**      1      value > $argv0
+**      2      value >= $argv0
+**      4      value < $argv0
+**      8      value <= $argv0
+**
+**      5      value > $argv0 AND value < $argv1
+**      6      value >= $argv0 AND value < $argv1
+**      9      value > $argv0 AND value <= $argv1
+**     10      value >= $argv0 AND value <= $argv1
+*/
+static int wholenumberFilter(
+  sqlite3_vtab_cursor *pVtabCursor, 
+  int idxNum, const char *idxStr,
+  int argc, sqlite3_value **argv
+){
+  wholenumber_cursor *pCur = (wholenumber_cursor *)pVtabCursor;
+  sqlite3_int64 v;
+  int i = 0;
+  pCur->iValue = 1;
+  pCur->mxValue = 0xffffffff;  /* 4294967295 */
+  if( idxNum & 3 ){
+    v = sqlite3_value_int64(argv[0]) + (idxNum&1);
+    if( v>pCur->iValue && v<=pCur->mxValue ) pCur->iValue = v;
+    i++;
+  }
+  if( idxNum & 12 ){
+    v = sqlite3_value_int64(argv[i]) - ((idxNum>>2)&1);
+    if( v>=pCur->iValue && v<pCur->mxValue ) pCur->mxValue = v;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Search for terms of these forms:
+**
+**  (1)  value > $value
+**  (2)  value >= $value
+**  (4)  value < $value
+**  (8)  value <= $value
+**
+** idxNum is an ORed combination of 1 or 2 with 4 or 8.
+*/
+static int wholenumberBestIndex(
+  sqlite3_vtab *tab,
+  sqlite3_index_info *pIdxInfo
+){
+  int i;
+  int idxNum = 0;
+  int argvIdx = 1;
+  int ltIdx = -1;
+  int gtIdx = -1;
+  const struct sqlite3_index_constraint *pConstraint;
+  pConstraint = pIdxInfo->aConstraint;
+  for(i=0; i<pIdxInfo->nConstraint; i++, pConstraint++){
+    if( pConstraint->usable==0 ) continue;
+    if( (idxNum & 3)==0 && pConstraint->op==SQLITE_INDEX_CONSTRAINT_GT ){
+      idxNum |= 1;
+      ltIdx = i;
+    }
+    if( (idxNum & 3)==0 && pConstraint->op==SQLITE_INDEX_CONSTRAINT_GE ){
+      idxNum |= 2;
+      ltIdx = i;
+    }
+    if( (idxNum & 12)==0 && pConstraint->op==SQLITE_INDEX_CONSTRAINT_LT ){
+      idxNum |= 4;
+      gtIdx = i;
+    }
+    if( (idxNum & 12)==0 && pConstraint->op==SQLITE_INDEX_CONSTRAINT_LE ){
+      idxNum |= 8;
+      gtIdx = i;
+    }
+  }
+  pIdxInfo->idxNum = idxNum;
+  if( ltIdx>=0 ){
+    pIdxInfo->aConstraintUsage[ltIdx].argvIndex = argvIdx++;
+    pIdxInfo->aConstraintUsage[ltIdx].omit = 1;
+  }
+  if( gtIdx>=0 ){
+    pIdxInfo->aConstraintUsage[gtIdx].argvIndex = argvIdx;
+    pIdxInfo->aConstraintUsage[gtIdx].omit = 1;
+  }
+  if( pIdxInfo->nOrderBy==1
+   && pIdxInfo->aOrderBy[0].desc==0
+  ){
+    pIdxInfo->orderByConsumed = 1;
+  }
+  pIdxInfo->estimatedCost = (double)1;
+  return SQLITE_OK;
+}
+
+/*
+** A virtual table module that provides read-only access to a
+** Tcl global variable namespace.
+*/
+static sqlite3_module wholenumberModule = {
+  0,                         /* iVersion */
+  wholenumberConnect,
+  wholenumberConnect,
+  wholenumberBestIndex,
+  wholenumberDisconnect, 
+  wholenumberDisconnect,
+  wholenumberOpen,           /* xOpen - open a cursor */
+  wholenumberClose,          /* xClose - close a cursor */
+  wholenumberFilter,         /* xFilter - configure scan constraints */
+  wholenumberNext,           /* xNext - advance a cursor */
+  wholenumberEof,            /* xEof - check for end of scan */
+  wholenumberColumn,         /* xColumn - read data */
+  wholenumberRowid,          /* xRowid - read data */
+  0,                         /* xUpdate */
+  0,                         /* xBegin */
+  0,                         /* xSync */
+  0,                         /* xCommit */
+  0,                         /* xRollback */
+  0,                         /* xFindMethod */
+  0,                         /* xRename */
+};
+
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+
+/*
+** Register the wholenumber virtual table
+*/
+int wholenumber_register(sqlite3 *db){
+  int rc = SQLITE_OK;
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  rc = sqlite3_create_module(db, "wholenumber", &wholenumberModule, 0);
+#endif
+  return rc;
+}
+
+#ifdef SQLITE_TEST
+#include <tcl.h>
+/*
+** Decode a pointer to an sqlite3 object.
+*/
+extern int getDbPointer(Tcl_Interp *interp, const char *zA, sqlite3 **ppDb);
+
+/*
+** Register the echo virtual table module.
+*/
+static int register_wholenumber_module(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3 *db;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  wholenumber_register(db);
+  return TCL_OK;
+}
+
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetestwholenumber_Init(Tcl_Interp *interp){
+  static struct {
+     char *zName;
+     Tcl_ObjCmdProc *xProc;
+     void *clientData;
+  } aObjCmd[] = {
+     { "register_wholenumber_module",   register_wholenumber_module, 0 },
+  };
+  int i;
+  for(i=0; i<sizeof(aObjCmd)/sizeof(aObjCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aObjCmd[i].zName, 
+        aObjCmd[i].xProc, aObjCmd[i].clientData, 0);
+  }
+  return TCL_OK;
+}
+
+#endif /* SQLITE_TEST */
diff --git a/src/test_wsd.c b/src/test_wsd.c
new file mode 100644
index 0000000..99e4a05
--- /dev/null
+++ b/src/test_wsd.c
@@ -0,0 +1,84 @@
+/*
+** 2008 September 1
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** The code in this file contains sample implementations of the 
+** sqlite3_wsd_init() and sqlite3_wsd_find() functions required if the
+** SQLITE_OMIT_WSD symbol is defined at build time.
+*/
+
+#if defined(SQLITE_OMIT_WSD) && defined(SQLITE_TEST)
+
+#include "sqliteInt.h"
+
+#define PLS_HASHSIZE 43
+
+typedef struct ProcessLocalStorage ProcessLocalStorage;
+typedef struct ProcessLocalVar ProcessLocalVar;
+
+struct ProcessLocalStorage {
+  ProcessLocalVar *aData[PLS_HASHSIZE];
+  int nFree;
+  u8 *pFree;
+};
+
+struct ProcessLocalVar {
+  void *pKey;
+  ProcessLocalVar *pNext;
+};
+
+static ProcessLocalStorage *pGlobal = 0;
+
+int sqlite3_wsd_init(int N, int J){
+  if( !pGlobal ){
+    int nMalloc = N + sizeof(ProcessLocalStorage) + J*sizeof(ProcessLocalVar);
+    pGlobal = (ProcessLocalStorage *)malloc(nMalloc);
+    if( pGlobal ){
+      memset(pGlobal, 0, sizeof(ProcessLocalStorage));
+      pGlobal->nFree = nMalloc - sizeof(ProcessLocalStorage);
+      pGlobal->pFree = (u8 *)&pGlobal[1];
+    }
+  }
+
+  return pGlobal ? SQLITE_OK : SQLITE_NOMEM;
+}
+
+void *sqlite3_wsd_find(void *K, int L){
+  int i;
+  int iHash = 0;
+  ProcessLocalVar *pVar;
+
+  /* Calculate a hash of K */
+  for(i=0; i<sizeof(void*); i++){
+    iHash = (iHash<<3) + ((unsigned char *)&K)[i];
+  }
+  iHash = iHash%PLS_HASHSIZE;
+
+  /* Search the hash table for K. */
+  for(pVar=pGlobal->aData[iHash]; pVar && pVar->pKey!=K; pVar=pVar->pNext);
+
+  /* If no entry for K was found, create and populate a new one. */
+  if( !pVar ){
+    int nByte = ROUND8(sizeof(ProcessLocalVar) + L);
+    assert( pGlobal->nFree>=nByte );
+    pVar = (ProcessLocalVar *)pGlobal->pFree;
+    pVar->pKey = K;
+    pVar->pNext = pGlobal->aData[iHash];
+    pGlobal->aData[iHash] = pVar;
+    pGlobal->nFree -= nByte;
+    pGlobal->pFree += nByte;
+    memcpy(&pVar[1], K, L);
+  }
+
+  return (void *)&pVar[1];
+}
+
+#endif
diff --git a/src/tokenize.c b/src/tokenize.c
new file mode 100644
index 0000000..b329892
--- /dev/null
+++ b/src/tokenize.c
@@ -0,0 +1,526 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** An tokenizer for SQL
+**
+** This file contains C code that splits an SQL input string up into
+** individual tokens and sends those tokens one-by-one over to the
+** parser for analysis.
+*/
+#include "sqliteInt.h"
+#include <stdlib.h>
+
+/*
+** The charMap() macro maps alphabetic characters into their
+** lower-case ASCII equivalent.  On ASCII machines, this is just
+** an upper-to-lower case map.  On EBCDIC machines we also need
+** to adjust the encoding.  Only alphabetic characters and underscores
+** need to be translated.
+*/
+#ifdef SQLITE_ASCII
+# define charMap(X) sqlite3UpperToLower[(unsigned char)X]
+#endif
+#ifdef SQLITE_EBCDIC
+# define charMap(X) ebcdicToAscii[(unsigned char)X]
+const unsigned char ebcdicToAscii[] = {
+/* 0   1   2   3   4   5   6   7   8   9   A   B   C   D   E   F */
+   0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  /* 0x */
+   0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  /* 1x */
+   0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  /* 2x */
+   0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  /* 3x */
+   0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  /* 4x */
+   0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  /* 5x */
+   0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0, 95,  0,  0,  /* 6x */
+   0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  /* 7x */
+   0, 97, 98, 99,100,101,102,103,104,105,  0,  0,  0,  0,  0,  0,  /* 8x */
+   0,106,107,108,109,110,111,112,113,114,  0,  0,  0,  0,  0,  0,  /* 9x */
+   0,  0,115,116,117,118,119,120,121,122,  0,  0,  0,  0,  0,  0,  /* Ax */
+   0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  /* Bx */
+   0, 97, 98, 99,100,101,102,103,104,105,  0,  0,  0,  0,  0,  0,  /* Cx */
+   0,106,107,108,109,110,111,112,113,114,  0,  0,  0,  0,  0,  0,  /* Dx */
+   0,  0,115,116,117,118,119,120,121,122,  0,  0,  0,  0,  0,  0,  /* Ex */
+   0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  /* Fx */
+};
+#endif
+
+/*
+** The sqlite3KeywordCode function looks up an identifier to determine if
+** it is a keyword.  If it is a keyword, the token code of that keyword is 
+** returned.  If the input is not a keyword, TK_ID is returned.
+**
+** The implementation of this routine was generated by a program,
+** mkkeywordhash.h, located in the tool subdirectory of the distribution.
+** The output of the mkkeywordhash.c program is written into a file
+** named keywordhash.h and then included into this source file by
+** the #include below.
+*/
+#include "keywordhash.h"
+
+
+/*
+** If X is a character that can be used in an identifier then
+** IdChar(X) will be true.  Otherwise it is false.
+**
+** For ASCII, any character with the high-order bit set is
+** allowed in an identifier.  For 7-bit characters, 
+** sqlite3IsIdChar[X] must be 1.
+**
+** For EBCDIC, the rules are more complex but have the same
+** end result.
+**
+** Ticket #1066.  the SQL standard does not allow '$' in the
+** middle of identfiers.  But many SQL implementations do. 
+** SQLite will allow '$' in identifiers for compatibility.
+** But the feature is undocumented.
+*/
+#ifdef SQLITE_ASCII
+#define IdChar(C)  ((sqlite3CtypeMap[(unsigned char)C]&0x46)!=0)
+#endif
+#ifdef SQLITE_EBCDIC
+const char sqlite3IsEbcdicIdChar[] = {
+/* x0 x1 x2 x3 x4 x5 x6 x7 x8 x9 xA xB xC xD xE xF */
+    0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0,  /* 4x */
+    0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 0, 0, 0, 0,  /* 5x */
+    0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1, 0, 0,  /* 6x */
+    0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0,  /* 7x */
+    0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 0,  /* 8x */
+    0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 0, 1, 0,  /* 9x */
+    1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 0,  /* Ax */
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  /* Bx */
+    0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1,  /* Cx */
+    0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1,  /* Dx */
+    0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1,  /* Ex */
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 0,  /* Fx */
+};
+#define IdChar(C)  (((c=C)>=0x42 && sqlite3IsEbcdicIdChar[c-0x40]))
+#endif
+
+
+/*
+** Return the length of the token that begins at z[0]. 
+** Store the token type in *tokenType before returning.
+*/
+int sqlite3GetToken(const unsigned char *z, int *tokenType){
+  int i, c;
+  switch( *z ){
+    case ' ': case '\t': case '\n': case '\f': case '\r': {
+      testcase( z[0]==' ' );
+      testcase( z[0]=='\t' );
+      testcase( z[0]=='\n' );
+      testcase( z[0]=='\f' );
+      testcase( z[0]=='\r' );
+      for(i=1; sqlite3Isspace(z[i]); i++){}
+      *tokenType = TK_SPACE;
+      return i;
+    }
+    case '-': {
+      if( z[1]=='-' ){
+        /* IMP: R-15891-05542 -- syntax diagram for comments */
+        for(i=2; (c=z[i])!=0 && c!='\n'; i++){}
+        *tokenType = TK_SPACE;   /* IMP: R-22934-25134 */
+        return i;
+      }
+      *tokenType = TK_MINUS;
+      return 1;
+    }
+    case '(': {
+      *tokenType = TK_LP;
+      return 1;
+    }
+    case ')': {
+      *tokenType = TK_RP;
+      return 1;
+    }
+    case ';': {
+      *tokenType = TK_SEMI;
+      return 1;
+    }
+    case '+': {
+      *tokenType = TK_PLUS;
+      return 1;
+    }
+    case '*': {
+      *tokenType = TK_STAR;
+      return 1;
+    }
+    case '/': {
+      if( z[1]!='*' || z[2]==0 ){
+        *tokenType = TK_SLASH;
+        return 1;
+      }
+      /* IMP: R-15891-05542 -- syntax diagram for comments */
+      for(i=3, c=z[2]; (c!='*' || z[i]!='/') && (c=z[i])!=0; i++){}
+      if( c ) i++;
+      *tokenType = TK_SPACE;   /* IMP: R-22934-25134 */
+      return i;
+    }
+    case '%': {
+      *tokenType = TK_REM;
+      return 1;
+    }
+    case '=': {
+      *tokenType = TK_EQ;
+      return 1 + (z[1]=='=');
+    }
+    case '<': {
+      if( (c=z[1])=='=' ){
+        *tokenType = TK_LE;
+        return 2;
+      }else if( c=='>' ){
+        *tokenType = TK_NE;
+        return 2;
+      }else if( c=='<' ){
+        *tokenType = TK_LSHIFT;
+        return 2;
+      }else{
+        *tokenType = TK_LT;
+        return 1;
+      }
+    }
+    case '>': {
+      if( (c=z[1])=='=' ){
+        *tokenType = TK_GE;
+        return 2;
+      }else if( c=='>' ){
+        *tokenType = TK_RSHIFT;
+        return 2;
+      }else{
+        *tokenType = TK_GT;
+        return 1;
+      }
+    }
+    case '!': {
+      if( z[1]!='=' ){
+        *tokenType = TK_ILLEGAL;
+        return 2;
+      }else{
+        *tokenType = TK_NE;
+        return 2;
+      }
+    }
+    case '|': {
+      if( z[1]!='|' ){
+        *tokenType = TK_BITOR;
+        return 1;
+      }else{
+        *tokenType = TK_CONCAT;
+        return 2;
+      }
+    }
+    case ',': {
+      *tokenType = TK_COMMA;
+      return 1;
+    }
+    case '&': {
+      *tokenType = TK_BITAND;
+      return 1;
+    }
+    case '~': {
+      *tokenType = TK_BITNOT;
+      return 1;
+    }
+    case '`':
+    case '\'':
+    case '"': {
+      int delim = z[0];
+      testcase( delim=='`' );
+      testcase( delim=='\'' );
+      testcase( delim=='"' );
+      for(i=1; (c=z[i])!=0; i++){
+        if( c==delim ){
+          if( z[i+1]==delim ){
+            i++;
+          }else{
+            break;
+          }
+        }
+      }
+      if( c=='\'' ){
+        *tokenType = TK_STRING;
+        return i+1;
+      }else if( c!=0 ){
+        *tokenType = TK_ID;
+        return i+1;
+      }else{
+        *tokenType = TK_ILLEGAL;
+        return i;
+      }
+    }
+    case '.': {
+#ifndef SQLITE_OMIT_FLOATING_POINT
+      if( !sqlite3Isdigit(z[1]) )
+#endif
+      {
+        *tokenType = TK_DOT;
+        return 1;
+      }
+      /* If the next character is a digit, this is a floating point
+      ** number that begins with ".".  Fall thru into the next case */
+    }
+    case '0': case '1': case '2': case '3': case '4':
+    case '5': case '6': case '7': case '8': case '9': {
+      testcase( z[0]=='0' );  testcase( z[0]=='1' );  testcase( z[0]=='2' );
+      testcase( z[0]=='3' );  testcase( z[0]=='4' );  testcase( z[0]=='5' );
+      testcase( z[0]=='6' );  testcase( z[0]=='7' );  testcase( z[0]=='8' );
+      testcase( z[0]=='9' );
+      *tokenType = TK_INTEGER;
+      for(i=0; sqlite3Isdigit(z[i]); i++){}
+#ifndef SQLITE_OMIT_FLOATING_POINT
+      if( z[i]=='.' ){
+        i++;
+        while( sqlite3Isdigit(z[i]) ){ i++; }
+        *tokenType = TK_FLOAT;
+      }
+      if( (z[i]=='e' || z[i]=='E') &&
+           ( sqlite3Isdigit(z[i+1]) 
+            || ((z[i+1]=='+' || z[i+1]=='-') && sqlite3Isdigit(z[i+2]))
+           )
+      ){
+        i += 2;
+        while( sqlite3Isdigit(z[i]) ){ i++; }
+        *tokenType = TK_FLOAT;
+      }
+#endif
+      while( IdChar(z[i]) ){
+        *tokenType = TK_ILLEGAL;
+        i++;
+      }
+      return i;
+    }
+    case '[': {
+      for(i=1, c=z[0]; c!=']' && (c=z[i])!=0; i++){}
+      *tokenType = c==']' ? TK_ID : TK_ILLEGAL;
+      return i;
+    }
+    case '?': {
+      *tokenType = TK_VARIABLE;
+      for(i=1; sqlite3Isdigit(z[i]); i++){}
+      return i;
+    }
+    case '#': {
+      for(i=1; sqlite3Isdigit(z[i]); i++){}
+      if( i>1 ){
+        /* Parameters of the form #NNN (where NNN is a number) are used
+        ** internally by sqlite3NestedParse.  */
+        *tokenType = TK_REGISTER;
+        return i;
+      }
+      /* Fall through into the next case if the '#' is not followed by
+      ** a digit. Try to match #AAAA where AAAA is a parameter name. */
+    }
+#ifndef SQLITE_OMIT_TCL_VARIABLE
+    case '$':
+#endif
+    case '@':  /* For compatibility with MS SQL Server */
+    case ':': {
+      int n = 0;
+      testcase( z[0]=='$' );  testcase( z[0]=='@' );  testcase( z[0]==':' );
+      *tokenType = TK_VARIABLE;
+      for(i=1; (c=z[i])!=0; i++){
+        if( IdChar(c) ){
+          n++;
+#ifndef SQLITE_OMIT_TCL_VARIABLE
+        }else if( c=='(' && n>0 ){
+          do{
+            i++;
+          }while( (c=z[i])!=0 && !sqlite3Isspace(c) && c!=')' );
+          if( c==')' ){
+            i++;
+          }else{
+            *tokenType = TK_ILLEGAL;
+          }
+          break;
+        }else if( c==':' && z[i+1]==':' ){
+          i++;
+#endif
+        }else{
+          break;
+        }
+      }
+      if( n==0 ) *tokenType = TK_ILLEGAL;
+      return i;
+    }
+#ifndef SQLITE_OMIT_BLOB_LITERAL
+    case 'x': case 'X': {
+      testcase( z[0]=='x' ); testcase( z[0]=='X' );
+      if( z[1]=='\'' ){
+        *tokenType = TK_BLOB;
+        for(i=2; sqlite3Isxdigit(z[i]); i++){}
+        if( z[i]!='\'' || i%2 ){
+          *tokenType = TK_ILLEGAL;
+          while( z[i] && z[i]!='\'' ){ i++; }
+        }
+        if( z[i] ) i++;
+        return i;
+      }
+      /* Otherwise fall through to the next case */
+    }
+#endif
+    default: {
+      if( !IdChar(*z) ){
+        break;
+      }
+      for(i=1; IdChar(z[i]); i++){}
+      *tokenType = keywordCode((char*)z, i);
+      return i;
+    }
+  }
+  *tokenType = TK_ILLEGAL;
+  return 1;
+}
+
+/*
+** Run the parser on the given SQL string.  The parser structure is
+** passed in.  An SQLITE_ status code is returned.  If an error occurs
+** then an and attempt is made to write an error message into 
+** memory obtained from sqlite3_malloc() and to make *pzErrMsg point to that
+** error message.
+*/
+int sqlite3RunParser(Parse *pParse, const char *zSql, char **pzErrMsg){
+  int nErr = 0;                   /* Number of errors encountered */
+  int i;                          /* Loop counter */
+  void *pEngine;                  /* The LEMON-generated LALR(1) parser */
+  int tokenType;                  /* type of the next token */
+  int lastTokenParsed = -1;       /* type of the previous token */
+  u8 enableLookaside;             /* Saved value of db->lookaside.bEnabled */
+  sqlite3 *db = pParse->db;       /* The database connection */
+  int mxSqlLen;                   /* Max length of an SQL string */
+
+
+  mxSqlLen = db->aLimit[SQLITE_LIMIT_SQL_LENGTH];
+  if( db->activeVdbeCnt==0 ){
+    db->u1.isInterrupted = 0;
+  }
+  pParse->rc = SQLITE_OK;
+  pParse->zTail = zSql;
+  i = 0;
+  assert( pzErrMsg!=0 );
+  pEngine = sqlite3ParserAlloc((void*(*)(size_t))sqlite3Malloc);
+  if( pEngine==0 ){
+    db->mallocFailed = 1;
+    return SQLITE_NOMEM;
+  }
+  assert( pParse->pNewTable==0 );
+  assert( pParse->pNewTrigger==0 );
+  assert( pParse->nVar==0 );
+  assert( pParse->nzVar==0 );
+  assert( pParse->azVar==0 );
+  enableLookaside = db->lookaside.bEnabled;
+  if( db->lookaside.pStart ) db->lookaside.bEnabled = 1;
+  while( !db->mallocFailed && zSql[i]!=0 ){
+    assert( i>=0 );
+    pParse->sLastToken.z = &zSql[i];
+    pParse->sLastToken.n = sqlite3GetToken((unsigned char*)&zSql[i],&tokenType);
+    i += pParse->sLastToken.n;
+    if( i>mxSqlLen ){
+      pParse->rc = SQLITE_TOOBIG;
+      break;
+    }
+    switch( tokenType ){
+      case TK_SPACE: {
+        if( db->u1.isInterrupted ){
+          sqlite3ErrorMsg(pParse, "interrupt");
+          pParse->rc = SQLITE_INTERRUPT;
+          goto abort_parse;
+        }
+        break;
+      }
+      case TK_ILLEGAL: {
+        sqlite3DbFree(db, *pzErrMsg);
+        *pzErrMsg = sqlite3MPrintf(db, "unrecognized token: \"%T\"",
+                        &pParse->sLastToken);
+        nErr++;
+        goto abort_parse;
+      }
+      case TK_SEMI: {
+        pParse->zTail = &zSql[i];
+        /* Fall thru into the default case */
+      }
+      default: {
+        sqlite3Parser(pEngine, tokenType, pParse->sLastToken, pParse);
+        lastTokenParsed = tokenType;
+        if( pParse->rc!=SQLITE_OK ){
+          goto abort_parse;
+        }
+        break;
+      }
+    }
+  }
+abort_parse:
+  if( zSql[i]==0 && nErr==0 && pParse->rc==SQLITE_OK ){
+    if( lastTokenParsed!=TK_SEMI ){
+      sqlite3Parser(pEngine, TK_SEMI, pParse->sLastToken, pParse);
+      pParse->zTail = &zSql[i];
+    }
+    sqlite3Parser(pEngine, 0, pParse->sLastToken, pParse);
+  }
+#ifdef YYTRACKMAXSTACKDEPTH
+  sqlite3StatusSet(SQLITE_STATUS_PARSER_STACK,
+      sqlite3ParserStackPeak(pEngine)
+  );
+#endif /* YYDEBUG */
+  sqlite3ParserFree(pEngine, sqlite3_free);
+  db->lookaside.bEnabled = enableLookaside;
+  if( db->mallocFailed ){
+    pParse->rc = SQLITE_NOMEM;
+  }
+  if( pParse->rc!=SQLITE_OK && pParse->rc!=SQLITE_DONE && pParse->zErrMsg==0 ){
+    sqlite3SetString(&pParse->zErrMsg, db, "%s", sqlite3ErrStr(pParse->rc));
+  }
+  assert( pzErrMsg!=0 );
+  if( pParse->zErrMsg ){
+    *pzErrMsg = pParse->zErrMsg;
+    sqlite3_log(pParse->rc, "%s", *pzErrMsg);
+    pParse->zErrMsg = 0;
+    nErr++;
+  }
+  if( pParse->pVdbe && pParse->nErr>0 && pParse->nested==0 ){
+    sqlite3VdbeDelete(pParse->pVdbe);
+    pParse->pVdbe = 0;
+  }
+#ifndef SQLITE_OMIT_SHARED_CACHE
+  if( pParse->nested==0 ){
+    sqlite3DbFree(db, pParse->aTableLock);
+    pParse->aTableLock = 0;
+    pParse->nTableLock = 0;
+  }
+#endif
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  sqlite3_free(pParse->apVtabLock);
+#endif
+
+  if( !IN_DECLARE_VTAB ){
+    /* If the pParse->declareVtab flag is set, do not delete any table 
+    ** structure built up in pParse->pNewTable. The calling code (see vtab.c)
+    ** will take responsibility for freeing the Table structure.
+    */
+    sqlite3DeleteTable(db, pParse->pNewTable);
+  }
+
+  sqlite3DeleteTrigger(db, pParse->pNewTrigger);
+  for(i=pParse->nzVar-1; i>=0; i--) sqlite3DbFree(db, pParse->azVar[i]);
+  sqlite3DbFree(db, pParse->azVar);
+  sqlite3DbFree(db, pParse->aAlias);
+  while( pParse->pAinc ){
+    AutoincInfo *p = pParse->pAinc;
+    pParse->pAinc = p->pNext;
+    sqlite3DbFree(db, p);
+  }
+  while( pParse->pZombieTab ){
+    Table *p = pParse->pZombieTab;
+    pParse->pZombieTab = p->pNextZombie;
+    sqlite3DeleteTable(db, p);
+  }
+  if( nErr>0 && pParse->rc==SQLITE_OK ){
+    pParse->rc = SQLITE_ERROR;
+  }
+  return nErr;
+}
diff --git a/src/trigger.c b/src/trigger.c
new file mode 100644
index 0000000..22c4877
--- /dev/null
+++ b/src/trigger.c
@@ -0,0 +1,1123 @@
+/*
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains the implementation for TRIGGERs
+*/
+#include "sqliteInt.h"
+
+#ifndef SQLITE_OMIT_TRIGGER
+/*
+** Delete a linked list of TriggerStep structures.
+*/
+void sqlite3DeleteTriggerStep(sqlite3 *db, TriggerStep *pTriggerStep){
+  while( pTriggerStep ){
+    TriggerStep * pTmp = pTriggerStep;
+    pTriggerStep = pTriggerStep->pNext;
+
+    sqlite3ExprDelete(db, pTmp->pWhere);
+    sqlite3ExprListDelete(db, pTmp->pExprList);
+    sqlite3SelectDelete(db, pTmp->pSelect);
+    sqlite3IdListDelete(db, pTmp->pIdList);
+
+    sqlite3DbFree(db, pTmp);
+  }
+}
+
+/*
+** Given table pTab, return a list of all the triggers attached to 
+** the table. The list is connected by Trigger.pNext pointers.
+**
+** All of the triggers on pTab that are in the same database as pTab
+** are already attached to pTab->pTrigger.  But there might be additional
+** triggers on pTab in the TEMP schema.  This routine prepends all
+** TEMP triggers on pTab to the beginning of the pTab->pTrigger list
+** and returns the combined list.
+**
+** To state it another way:  This routine returns a list of all triggers
+** that fire off of pTab.  The list will include any TEMP triggers on
+** pTab as well as the triggers lised in pTab->pTrigger.
+*/
+Trigger *sqlite3TriggerList(Parse *pParse, Table *pTab){
+  Schema * const pTmpSchema = pParse->db->aDb[1].pSchema;
+  Trigger *pList = 0;                  /* List of triggers to return */
+
+  if( pParse->disableTriggers ){
+    return 0;
+  }
+
+  if( pTmpSchema!=pTab->pSchema ){
+    HashElem *p;
+    assert( sqlite3SchemaMutexHeld(pParse->db, 0, pTmpSchema) );
+    for(p=sqliteHashFirst(&pTmpSchema->trigHash); p; p=sqliteHashNext(p)){
+      Trigger *pTrig = (Trigger *)sqliteHashData(p);
+      if( pTrig->pTabSchema==pTab->pSchema
+       && 0==sqlite3StrICmp(pTrig->table, pTab->zName) 
+      ){
+        pTrig->pNext = (pList ? pList : pTab->pTrigger);
+        pList = pTrig;
+      }
+    }
+  }
+
+  return (pList ? pList : pTab->pTrigger);
+}
+
+/*
+** This is called by the parser when it sees a CREATE TRIGGER statement
+** up to the point of the BEGIN before the trigger actions.  A Trigger
+** structure is generated based on the information available and stored
+** in pParse->pNewTrigger.  After the trigger actions have been parsed, the
+** sqlite3FinishTrigger() function is called to complete the trigger
+** construction process.
+*/
+void sqlite3BeginTrigger(
+  Parse *pParse,      /* The parse context of the CREATE TRIGGER statement */
+  Token *pName1,      /* The name of the trigger */
+  Token *pName2,      /* The name of the trigger */
+  int tr_tm,          /* One of TK_BEFORE, TK_AFTER, TK_INSTEAD */
+  int op,             /* One of TK_INSERT, TK_UPDATE, TK_DELETE */
+  IdList *pColumns,   /* column list if this is an UPDATE OF trigger */
+  SrcList *pTableName,/* The name of the table/view the trigger applies to */
+  Expr *pWhen,        /* WHEN clause */
+  int isTemp,         /* True if the TEMPORARY keyword is present */
+  int noErr           /* Suppress errors if the trigger already exists */
+){
+  Trigger *pTrigger = 0;  /* The new trigger */
+  Table *pTab;            /* Table that the trigger fires off of */
+  char *zName = 0;        /* Name of the trigger */
+  sqlite3 *db = pParse->db;  /* The database connection */
+  int iDb;                /* The database to store the trigger in */
+  Token *pName;           /* The unqualified db name */
+  DbFixer sFix;           /* State vector for the DB fixer */
+  int iTabDb;             /* Index of the database holding pTab */
+
+  assert( pName1!=0 );   /* pName1->z might be NULL, but not pName1 itself */
+  assert( pName2!=0 );
+  assert( op==TK_INSERT || op==TK_UPDATE || op==TK_DELETE );
+  assert( op>0 && op<0xff );
+  if( isTemp ){
+    /* If TEMP was specified, then the trigger name may not be qualified. */
+    if( pName2->n>0 ){
+      sqlite3ErrorMsg(pParse, "temporary trigger may not have qualified name");
+      goto trigger_cleanup;
+    }
+    iDb = 1;
+    pName = pName1;
+  }else{
+    /* Figure out the db that the the trigger will be created in */
+    iDb = sqlite3TwoPartName(pParse, pName1, pName2, &pName);
+    if( iDb<0 ){
+      goto trigger_cleanup;
+    }
+  }
+  if( !pTableName || db->mallocFailed ){
+    goto trigger_cleanup;
+  }
+
+  /* A long-standing parser bug is that this syntax was allowed:
+  **
+  **    CREATE TRIGGER attached.demo AFTER INSERT ON attached.tab ....
+  **                                                 ^^^^^^^^
+  **
+  ** To maintain backwards compatibility, ignore the database
+  ** name on pTableName if we are reparsing our of SQLITE_MASTER.
+  */
+  if( db->init.busy && iDb!=1 ){
+    sqlite3DbFree(db, pTableName->a[0].zDatabase);
+    pTableName->a[0].zDatabase = 0;
+  }
+
+  /* If the trigger name was unqualified, and the table is a temp table,
+  ** then set iDb to 1 to create the trigger in the temporary database.
+  ** If sqlite3SrcListLookup() returns 0, indicating the table does not
+  ** exist, the error is caught by the block below.
+  */
+  pTab = sqlite3SrcListLookup(pParse, pTableName);
+  if( db->init.busy==0 && pName2->n==0 && pTab
+        && pTab->pSchema==db->aDb[1].pSchema ){
+    iDb = 1;
+  }
+
+  /* Ensure the table name matches database name and that the table exists */
+  if( db->mallocFailed ) goto trigger_cleanup;
+  assert( pTableName->nSrc==1 );
+  if( sqlite3FixInit(&sFix, pParse, iDb, "trigger", pName) && 
+      sqlite3FixSrcList(&sFix, pTableName) ){
+    goto trigger_cleanup;
+  }
+  pTab = sqlite3SrcListLookup(pParse, pTableName);
+  if( !pTab ){
+    /* The table does not exist. */
+    if( db->init.iDb==1 ){
+      /* Ticket #3810.
+      ** Normally, whenever a table is dropped, all associated triggers are
+      ** dropped too.  But if a TEMP trigger is created on a non-TEMP table
+      ** and the table is dropped by a different database connection, the
+      ** trigger is not visible to the database connection that does the
+      ** drop so the trigger cannot be dropped.  This results in an
+      ** "orphaned trigger" - a trigger whose associated table is missing.
+      */
+      db->init.orphanTrigger = 1;
+    }
+    goto trigger_cleanup;
+  }
+  if( IsVirtual(pTab) ){
+    sqlite3ErrorMsg(pParse, "cannot create triggers on virtual tables");
+    goto trigger_cleanup;
+  }
+
+  /* Check that the trigger name is not reserved and that no trigger of the
+  ** specified name exists */
+  zName = sqlite3NameFromToken(db, pName);
+  if( !zName || SQLITE_OK!=sqlite3CheckObjectName(pParse, zName) ){
+    goto trigger_cleanup;
+  }
+  assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+  if( sqlite3HashFind(&(db->aDb[iDb].pSchema->trigHash),
+                      zName, sqlite3Strlen30(zName)) ){
+    if( !noErr ){
+      sqlite3ErrorMsg(pParse, "trigger %T already exists", pName);
+    }else{
+      assert( !db->init.busy );
+      sqlite3CodeVerifySchema(pParse, iDb);
+    }
+    goto trigger_cleanup;
+  }
+
+  /* Do not create a trigger on a system table */
+  if( sqlite3StrNICmp(pTab->zName, "sqlite_", 7)==0 ){
+    sqlite3ErrorMsg(pParse, "cannot create trigger on system table");
+    pParse->nErr++;
+    goto trigger_cleanup;
+  }
+
+  /* INSTEAD of triggers are only for views and views only support INSTEAD
+  ** of triggers.
+  */
+  if( pTab->pSelect && tr_tm!=TK_INSTEAD ){
+    sqlite3ErrorMsg(pParse, "cannot create %s trigger on view: %S", 
+        (tr_tm == TK_BEFORE)?"BEFORE":"AFTER", pTableName, 0);
+    goto trigger_cleanup;
+  }
+  if( !pTab->pSelect && tr_tm==TK_INSTEAD ){
+    sqlite3ErrorMsg(pParse, "cannot create INSTEAD OF"
+        " trigger on table: %S", pTableName, 0);
+    goto trigger_cleanup;
+  }
+  iTabDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  {
+    int code = SQLITE_CREATE_TRIGGER;
+    const char *zDb = db->aDb[iTabDb].zName;
+    const char *zDbTrig = isTemp ? db->aDb[1].zName : zDb;
+    if( iTabDb==1 || isTemp ) code = SQLITE_CREATE_TEMP_TRIGGER;
+    if( sqlite3AuthCheck(pParse, code, zName, pTab->zName, zDbTrig) ){
+      goto trigger_cleanup;
+    }
+    if( sqlite3AuthCheck(pParse, SQLITE_INSERT, SCHEMA_TABLE(iTabDb),0,zDb)){
+      goto trigger_cleanup;
+    }
+  }
+#endif
+
+  /* INSTEAD OF triggers can only appear on views and BEFORE triggers
+  ** cannot appear on views.  So we might as well translate every
+  ** INSTEAD OF trigger into a BEFORE trigger.  It simplifies code
+  ** elsewhere.
+  */
+  if (tr_tm == TK_INSTEAD){
+    tr_tm = TK_BEFORE;
+  }
+
+  /* Build the Trigger object */
+  pTrigger = (Trigger*)sqlite3DbMallocZero(db, sizeof(Trigger));
+  if( pTrigger==0 ) goto trigger_cleanup;
+  pTrigger->zName = zName;
+  zName = 0;
+  pTrigger->table = sqlite3DbStrDup(db, pTableName->a[0].zName);
+  pTrigger->pSchema = db->aDb[iDb].pSchema;
+  pTrigger->pTabSchema = pTab->pSchema;
+  pTrigger->op = (u8)op;
+  pTrigger->tr_tm = tr_tm==TK_BEFORE ? TRIGGER_BEFORE : TRIGGER_AFTER;
+  pTrigger->pWhen = sqlite3ExprDup(db, pWhen, EXPRDUP_REDUCE);
+  pTrigger->pColumns = sqlite3IdListDup(db, pColumns);
+  assert( pParse->pNewTrigger==0 );
+  pParse->pNewTrigger = pTrigger;
+
+trigger_cleanup:
+  sqlite3DbFree(db, zName);
+  sqlite3SrcListDelete(db, pTableName);
+  sqlite3IdListDelete(db, pColumns);
+  sqlite3ExprDelete(db, pWhen);
+  if( !pParse->pNewTrigger ){
+    sqlite3DeleteTrigger(db, pTrigger);
+  }else{
+    assert( pParse->pNewTrigger==pTrigger );
+  }
+}
+
+/*
+** This routine is called after all of the trigger actions have been parsed
+** in order to complete the process of building the trigger.
+*/
+void sqlite3FinishTrigger(
+  Parse *pParse,          /* Parser context */
+  TriggerStep *pStepList, /* The triggered program */
+  Token *pAll             /* Token that describes the complete CREATE TRIGGER */
+){
+  Trigger *pTrig = pParse->pNewTrigger;   /* Trigger being finished */
+  char *zName;                            /* Name of trigger */
+  sqlite3 *db = pParse->db;               /* The database */
+  DbFixer sFix;                           /* Fixer object */
+  int iDb;                                /* Database containing the trigger */
+  Token nameToken;                        /* Trigger name for error reporting */
+
+  pParse->pNewTrigger = 0;
+  if( NEVER(pParse->nErr) || !pTrig ) goto triggerfinish_cleanup;
+  zName = pTrig->zName;
+  iDb = sqlite3SchemaToIndex(pParse->db, pTrig->pSchema);
+  pTrig->step_list = pStepList;
+  while( pStepList ){
+    pStepList->pTrig = pTrig;
+    pStepList = pStepList->pNext;
+  }
+  nameToken.z = pTrig->zName;
+  nameToken.n = sqlite3Strlen30(nameToken.z);
+  if( sqlite3FixInit(&sFix, pParse, iDb, "trigger", &nameToken) 
+          && sqlite3FixTriggerStep(&sFix, pTrig->step_list) ){
+    goto triggerfinish_cleanup;
+  }
+
+  /* if we are not initializing,
+  ** build the sqlite_master entry
+  */
+  if( !db->init.busy ){
+    Vdbe *v;
+    char *z;
+
+    /* Make an entry in the sqlite_master table */
+    v = sqlite3GetVdbe(pParse);
+    if( v==0 ) goto triggerfinish_cleanup;
+    sqlite3BeginWriteOperation(pParse, 0, iDb);
+    z = sqlite3DbStrNDup(db, (char*)pAll->z, pAll->n);
+    sqlite3NestedParse(pParse,
+       "INSERT INTO %Q.%s VALUES('trigger',%Q,%Q,0,'CREATE TRIGGER %q')",
+       db->aDb[iDb].zName, SCHEMA_TABLE(iDb), zName,
+       pTrig->table, z);
+    sqlite3DbFree(db, z);
+    sqlite3ChangeCookie(pParse, iDb);
+    sqlite3VdbeAddParseSchemaOp(v, iDb,
+        sqlite3MPrintf(db, "type='trigger' AND name='%q'", zName));
+  }
+
+  if( db->init.busy ){
+    Trigger *pLink = pTrig;
+    Hash *pHash = &db->aDb[iDb].pSchema->trigHash;
+    assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+    pTrig = sqlite3HashInsert(pHash, zName, sqlite3Strlen30(zName), pTrig);
+    if( pTrig ){
+      db->mallocFailed = 1;
+    }else if( pLink->pSchema==pLink->pTabSchema ){
+      Table *pTab;
+      int n = sqlite3Strlen30(pLink->table);
+      pTab = sqlite3HashFind(&pLink->pTabSchema->tblHash, pLink->table, n);
+      assert( pTab!=0 );
+      pLink->pNext = pTab->pTrigger;
+      pTab->pTrigger = pLink;
+    }
+  }
+
+triggerfinish_cleanup:
+  sqlite3DeleteTrigger(db, pTrig);
+  assert( !pParse->pNewTrigger );
+  sqlite3DeleteTriggerStep(db, pStepList);
+}
+
+/*
+** Turn a SELECT statement (that the pSelect parameter points to) into
+** a trigger step.  Return a pointer to a TriggerStep structure.
+**
+** The parser calls this routine when it finds a SELECT statement in
+** body of a TRIGGER.  
+*/
+TriggerStep *sqlite3TriggerSelectStep(sqlite3 *db, Select *pSelect){
+  TriggerStep *pTriggerStep = sqlite3DbMallocZero(db, sizeof(TriggerStep));
+  if( pTriggerStep==0 ) {
+    sqlite3SelectDelete(db, pSelect);
+    return 0;
+  }
+  pTriggerStep->op = TK_SELECT;
+  pTriggerStep->pSelect = pSelect;
+  pTriggerStep->orconf = OE_Default;
+  return pTriggerStep;
+}
+
+/*
+** Allocate space to hold a new trigger step.  The allocated space
+** holds both the TriggerStep object and the TriggerStep.target.z string.
+**
+** If an OOM error occurs, NULL is returned and db->mallocFailed is set.
+*/
+static TriggerStep *triggerStepAllocate(
+  sqlite3 *db,                /* Database connection */
+  u8 op,                      /* Trigger opcode */
+  Token *pName                /* The target name */
+){
+  TriggerStep *pTriggerStep;
+
+  pTriggerStep = sqlite3DbMallocZero(db, sizeof(TriggerStep) + pName->n);
+  if( pTriggerStep ){
+    char *z = (char*)&pTriggerStep[1];
+    memcpy(z, pName->z, pName->n);
+    pTriggerStep->target.z = z;
+    pTriggerStep->target.n = pName->n;
+    pTriggerStep->op = op;
+  }
+  return pTriggerStep;
+}
+
+/*
+** Build a trigger step out of an INSERT statement.  Return a pointer
+** to the new trigger step.
+**
+** The parser calls this routine when it sees an INSERT inside the
+** body of a trigger.
+*/
+TriggerStep *sqlite3TriggerInsertStep(
+  sqlite3 *db,        /* The database connection */
+  Token *pTableName,  /* Name of the table into which we insert */
+  IdList *pColumn,    /* List of columns in pTableName to insert into */
+  ExprList *pEList,   /* The VALUE clause: a list of values to be inserted */
+  Select *pSelect,    /* A SELECT statement that supplies values */
+  u8 orconf           /* The conflict algorithm (OE_Abort, OE_Replace, etc.) */
+){
+  TriggerStep *pTriggerStep;
+
+  assert(pEList == 0 || pSelect == 0);
+  assert(pEList != 0 || pSelect != 0 || db->mallocFailed);
+
+  pTriggerStep = triggerStepAllocate(db, TK_INSERT, pTableName);
+  if( pTriggerStep ){
+    pTriggerStep->pSelect = sqlite3SelectDup(db, pSelect, EXPRDUP_REDUCE);
+    pTriggerStep->pIdList = pColumn;
+    pTriggerStep->pExprList = sqlite3ExprListDup(db, pEList, EXPRDUP_REDUCE);
+    pTriggerStep->orconf = orconf;
+  }else{
+    sqlite3IdListDelete(db, pColumn);
+  }
+  sqlite3ExprListDelete(db, pEList);
+  sqlite3SelectDelete(db, pSelect);
+
+  return pTriggerStep;
+}
+
+/*
+** Construct a trigger step that implements an UPDATE statement and return
+** a pointer to that trigger step.  The parser calls this routine when it
+** sees an UPDATE statement inside the body of a CREATE TRIGGER.
+*/
+TriggerStep *sqlite3TriggerUpdateStep(
+  sqlite3 *db,         /* The database connection */
+  Token *pTableName,   /* Name of the table to be updated */
+  ExprList *pEList,    /* The SET clause: list of column and new values */
+  Expr *pWhere,        /* The WHERE clause */
+  u8 orconf            /* The conflict algorithm. (OE_Abort, OE_Ignore, etc) */
+){
+  TriggerStep *pTriggerStep;
+
+  pTriggerStep = triggerStepAllocate(db, TK_UPDATE, pTableName);
+  if( pTriggerStep ){
+    pTriggerStep->pExprList = sqlite3ExprListDup(db, pEList, EXPRDUP_REDUCE);
+    pTriggerStep->pWhere = sqlite3ExprDup(db, pWhere, EXPRDUP_REDUCE);
+    pTriggerStep->orconf = orconf;
+  }
+  sqlite3ExprListDelete(db, pEList);
+  sqlite3ExprDelete(db, pWhere);
+  return pTriggerStep;
+}
+
+/*
+** Construct a trigger step that implements a DELETE statement and return
+** a pointer to that trigger step.  The parser calls this routine when it
+** sees a DELETE statement inside the body of a CREATE TRIGGER.
+*/
+TriggerStep *sqlite3TriggerDeleteStep(
+  sqlite3 *db,            /* Database connection */
+  Token *pTableName,      /* The table from which rows are deleted */
+  Expr *pWhere            /* The WHERE clause */
+){
+  TriggerStep *pTriggerStep;
+
+  pTriggerStep = triggerStepAllocate(db, TK_DELETE, pTableName);
+  if( pTriggerStep ){
+    pTriggerStep->pWhere = sqlite3ExprDup(db, pWhere, EXPRDUP_REDUCE);
+    pTriggerStep->orconf = OE_Default;
+  }
+  sqlite3ExprDelete(db, pWhere);
+  return pTriggerStep;
+}
+
+/* 
+** Recursively delete a Trigger structure
+*/
+void sqlite3DeleteTrigger(sqlite3 *db, Trigger *pTrigger){
+  if( pTrigger==0 ) return;
+  sqlite3DeleteTriggerStep(db, pTrigger->step_list);
+  sqlite3DbFree(db, pTrigger->zName);
+  sqlite3DbFree(db, pTrigger->table);
+  sqlite3ExprDelete(db, pTrigger->pWhen);
+  sqlite3IdListDelete(db, pTrigger->pColumns);
+  sqlite3DbFree(db, pTrigger);
+}
+
+/*
+** This function is called to drop a trigger from the database schema. 
+**
+** This may be called directly from the parser and therefore identifies
+** the trigger by name.  The sqlite3DropTriggerPtr() routine does the
+** same job as this routine except it takes a pointer to the trigger
+** instead of the trigger name.
+**/
+void sqlite3DropTrigger(Parse *pParse, SrcList *pName, int noErr){
+  Trigger *pTrigger = 0;
+  int i;
+  const char *zDb;
+  const char *zName;
+  int nName;
+  sqlite3 *db = pParse->db;
+
+  if( db->mallocFailed ) goto drop_trigger_cleanup;
+  if( SQLITE_OK!=sqlite3ReadSchema(pParse) ){
+    goto drop_trigger_cleanup;
+  }
+
+  assert( pName->nSrc==1 );
+  zDb = pName->a[0].zDatabase;
+  zName = pName->a[0].zName;
+  nName = sqlite3Strlen30(zName);
+  assert( zDb!=0 || sqlite3BtreeHoldsAllMutexes(db) );
+  for(i=OMIT_TEMPDB; i<db->nDb; i++){
+    int j = (i<2) ? i^1 : i;  /* Search TEMP before MAIN */
+    if( zDb && sqlite3StrICmp(db->aDb[j].zName, zDb) ) continue;
+    assert( sqlite3SchemaMutexHeld(db, j, 0) );
+    pTrigger = sqlite3HashFind(&(db->aDb[j].pSchema->trigHash), zName, nName);
+    if( pTrigger ) break;
+  }
+  if( !pTrigger ){
+    if( !noErr ){
+      sqlite3ErrorMsg(pParse, "no such trigger: %S", pName, 0);
+    }else{
+      sqlite3CodeVerifyNamedSchema(pParse, zDb);
+    }
+    pParse->checkSchema = 1;
+    goto drop_trigger_cleanup;
+  }
+  sqlite3DropTriggerPtr(pParse, pTrigger);
+
+drop_trigger_cleanup:
+  sqlite3SrcListDelete(db, pName);
+}
+
+/*
+** Return a pointer to the Table structure for the table that a trigger
+** is set on.
+*/
+static Table *tableOfTrigger(Trigger *pTrigger){
+  int n = sqlite3Strlen30(pTrigger->table);
+  return sqlite3HashFind(&pTrigger->pTabSchema->tblHash, pTrigger->table, n);
+}
+
+
+/*
+** Drop a trigger given a pointer to that trigger. 
+*/
+void sqlite3DropTriggerPtr(Parse *pParse, Trigger *pTrigger){
+  Table   *pTable;
+  Vdbe *v;
+  sqlite3 *db = pParse->db;
+  int iDb;
+
+  iDb = sqlite3SchemaToIndex(pParse->db, pTrigger->pSchema);
+  assert( iDb>=0 && iDb<db->nDb );
+  pTable = tableOfTrigger(pTrigger);
+  assert( pTable );
+  assert( pTable->pSchema==pTrigger->pSchema || iDb==1 );
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  {
+    int code = SQLITE_DROP_TRIGGER;
+    const char *zDb = db->aDb[iDb].zName;
+    const char *zTab = SCHEMA_TABLE(iDb);
+    if( iDb==1 ) code = SQLITE_DROP_TEMP_TRIGGER;
+    if( sqlite3AuthCheck(pParse, code, pTrigger->zName, pTable->zName, zDb) ||
+      sqlite3AuthCheck(pParse, SQLITE_DELETE, zTab, 0, zDb) ){
+      return;
+    }
+  }
+#endif
+
+  /* Generate code to destroy the database record of the trigger.
+  */
+  assert( pTable!=0 );
+  if( (v = sqlite3GetVdbe(pParse))!=0 ){
+    int base;
+    static const VdbeOpList dropTrigger[] = {
+      { OP_Rewind,     0, ADDR(9),  0},
+      { OP_String8,    0, 1,        0}, /* 1 */
+      { OP_Column,     0, 1,        2},
+      { OP_Ne,         2, ADDR(8),  1},
+      { OP_String8,    0, 1,        0}, /* 4: "trigger" */
+      { OP_Column,     0, 0,        2},
+      { OP_Ne,         2, ADDR(8),  1},
+      { OP_Delete,     0, 0,        0},
+      { OP_Next,       0, ADDR(1),  0}, /* 8 */
+    };
+
+    sqlite3BeginWriteOperation(pParse, 0, iDb);
+    sqlite3OpenMasterTable(pParse, iDb);
+    base = sqlite3VdbeAddOpList(v,  ArraySize(dropTrigger), dropTrigger);
+    sqlite3VdbeChangeP4(v, base+1, pTrigger->zName, P4_TRANSIENT);
+    sqlite3VdbeChangeP4(v, base+4, "trigger", P4_STATIC);
+    sqlite3ChangeCookie(pParse, iDb);
+    sqlite3VdbeAddOp2(v, OP_Close, 0, 0);
+    sqlite3VdbeAddOp4(v, OP_DropTrigger, iDb, 0, 0, pTrigger->zName, 0);
+    if( pParse->nMem<3 ){
+      pParse->nMem = 3;
+    }
+  }
+}
+
+/*
+** Remove a trigger from the hash tables of the sqlite* pointer.
+*/
+void sqlite3UnlinkAndDeleteTrigger(sqlite3 *db, int iDb, const char *zName){
+  Trigger *pTrigger;
+  Hash *pHash;
+
+  assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+  pHash = &(db->aDb[iDb].pSchema->trigHash);
+  pTrigger = sqlite3HashInsert(pHash, zName, sqlite3Strlen30(zName), 0);
+  if( ALWAYS(pTrigger) ){
+    if( pTrigger->pSchema==pTrigger->pTabSchema ){
+      Table *pTab = tableOfTrigger(pTrigger);
+      Trigger **pp;
+      for(pp=&pTab->pTrigger; *pp!=pTrigger; pp=&((*pp)->pNext));
+      *pp = (*pp)->pNext;
+    }
+    sqlite3DeleteTrigger(db, pTrigger);
+    db->flags |= SQLITE_InternChanges;
+  }
+}
+
+/*
+** pEList is the SET clause of an UPDATE statement.  Each entry
+** in pEList is of the format <id>=<expr>.  If any of the entries
+** in pEList have an <id> which matches an identifier in pIdList,
+** then return TRUE.  If pIdList==NULL, then it is considered a
+** wildcard that matches anything.  Likewise if pEList==NULL then
+** it matches anything so always return true.  Return false only
+** if there is no match.
+*/
+static int checkColumnOverlap(IdList *pIdList, ExprList *pEList){
+  int e;
+  if( pIdList==0 || NEVER(pEList==0) ) return 1;
+  for(e=0; e<pEList->nExpr; e++){
+    if( sqlite3IdListIndex(pIdList, pEList->a[e].zName)>=0 ) return 1;
+  }
+  return 0; 
+}
+
+/*
+** Return a list of all triggers on table pTab if there exists at least
+** one trigger that must be fired when an operation of type 'op' is 
+** performed on the table, and, if that operation is an UPDATE, if at
+** least one of the columns in pChanges is being modified.
+*/
+Trigger *sqlite3TriggersExist(
+  Parse *pParse,          /* Parse context */
+  Table *pTab,            /* The table the contains the triggers */
+  int op,                 /* one of TK_DELETE, TK_INSERT, TK_UPDATE */
+  ExprList *pChanges,     /* Columns that change in an UPDATE statement */
+  int *pMask              /* OUT: Mask of TRIGGER_BEFORE|TRIGGER_AFTER */
+){
+  int mask = 0;
+  Trigger *pList = 0;
+  Trigger *p;
+
+  if( (pParse->db->flags & SQLITE_EnableTrigger)!=0 ){
+    pList = sqlite3TriggerList(pParse, pTab);
+  }
+  assert( pList==0 || IsVirtual(pTab)==0 );
+  for(p=pList; p; p=p->pNext){
+    if( p->op==op && checkColumnOverlap(p->pColumns, pChanges) ){
+      mask |= p->tr_tm;
+    }
+  }
+  if( pMask ){
+    *pMask = mask;
+  }
+  return (mask ? pList : 0);
+}
+
+/*
+** Convert the pStep->target token into a SrcList and return a pointer
+** to that SrcList.
+**
+** This routine adds a specific database name, if needed, to the target when
+** forming the SrcList.  This prevents a trigger in one database from
+** referring to a target in another database.  An exception is when the
+** trigger is in TEMP in which case it can refer to any other database it
+** wants.
+*/
+static SrcList *targetSrcList(
+  Parse *pParse,       /* The parsing context */
+  TriggerStep *pStep   /* The trigger containing the target token */
+){
+  int iDb;             /* Index of the database to use */
+  SrcList *pSrc;       /* SrcList to be returned */
+
+  pSrc = sqlite3SrcListAppend(pParse->db, 0, &pStep->target, 0);
+  if( pSrc ){
+    assert( pSrc->nSrc>0 );
+    assert( pSrc->a!=0 );
+    iDb = sqlite3SchemaToIndex(pParse->db, pStep->pTrig->pSchema);
+    if( iDb==0 || iDb>=2 ){
+      sqlite3 *db = pParse->db;
+      assert( iDb<pParse->db->nDb );
+      pSrc->a[pSrc->nSrc-1].zDatabase = sqlite3DbStrDup(db, db->aDb[iDb].zName);
+    }
+  }
+  return pSrc;
+}
+
+/*
+** Generate VDBE code for the statements inside the body of a single 
+** trigger.
+*/
+static int codeTriggerProgram(
+  Parse *pParse,            /* The parser context */
+  TriggerStep *pStepList,   /* List of statements inside the trigger body */
+  int orconf                /* Conflict algorithm. (OE_Abort, etc) */  
+){
+  TriggerStep *pStep;
+  Vdbe *v = pParse->pVdbe;
+  sqlite3 *db = pParse->db;
+
+  assert( pParse->pTriggerTab && pParse->pToplevel );
+  assert( pStepList );
+  assert( v!=0 );
+  for(pStep=pStepList; pStep; pStep=pStep->pNext){
+    /* Figure out the ON CONFLICT policy that will be used for this step
+    ** of the trigger program. If the statement that caused this trigger
+    ** to fire had an explicit ON CONFLICT, then use it. Otherwise, use
+    ** the ON CONFLICT policy that was specified as part of the trigger
+    ** step statement. Example:
+    **
+    **   CREATE TRIGGER AFTER INSERT ON t1 BEGIN;
+    **     INSERT OR REPLACE INTO t2 VALUES(new.a, new.b);
+    **   END;
+    **
+    **   INSERT INTO t1 ... ;            -- insert into t2 uses REPLACE policy
+    **   INSERT OR IGNORE INTO t1 ... ;  -- insert into t2 uses IGNORE policy
+    */
+    pParse->eOrconf = (orconf==OE_Default)?pStep->orconf:(u8)orconf;
+
+    switch( pStep->op ){
+      case TK_UPDATE: {
+        sqlite3Update(pParse, 
+          targetSrcList(pParse, pStep),
+          sqlite3ExprListDup(db, pStep->pExprList, 0), 
+          sqlite3ExprDup(db, pStep->pWhere, 0), 
+          pParse->eOrconf
+        );
+        break;
+      }
+      case TK_INSERT: {
+        sqlite3Insert(pParse, 
+          targetSrcList(pParse, pStep),
+          sqlite3ExprListDup(db, pStep->pExprList, 0), 
+          sqlite3SelectDup(db, pStep->pSelect, 0), 
+          sqlite3IdListDup(db, pStep->pIdList), 
+          pParse->eOrconf
+        );
+        break;
+      }
+      case TK_DELETE: {
+        sqlite3DeleteFrom(pParse, 
+          targetSrcList(pParse, pStep),
+          sqlite3ExprDup(db, pStep->pWhere, 0)
+        );
+        break;
+      }
+      default: assert( pStep->op==TK_SELECT ); {
+        SelectDest sDest;
+        Select *pSelect = sqlite3SelectDup(db, pStep->pSelect, 0);
+        sqlite3SelectDestInit(&sDest, SRT_Discard, 0);
+        sqlite3Select(pParse, pSelect, &sDest);
+        sqlite3SelectDelete(db, pSelect);
+        break;
+      }
+    } 
+    if( pStep->op!=TK_SELECT ){
+      sqlite3VdbeAddOp0(v, OP_ResetCount);
+    }
+  }
+
+  return 0;
+}
+
+#ifdef SQLITE_DEBUG
+/*
+** This function is used to add VdbeComment() annotations to a VDBE
+** program. It is not used in production code, only for debugging.
+*/
+static const char *onErrorText(int onError){
+  switch( onError ){
+    case OE_Abort:    return "abort";
+    case OE_Rollback: return "rollback";
+    case OE_Fail:     return "fail";
+    case OE_Replace:  return "replace";
+    case OE_Ignore:   return "ignore";
+    case OE_Default:  return "default";
+  }
+  return "n/a";
+}
+#endif
+
+/*
+** Parse context structure pFrom has just been used to create a sub-vdbe
+** (trigger program). If an error has occurred, transfer error information
+** from pFrom to pTo.
+*/
+static void transferParseError(Parse *pTo, Parse *pFrom){
+  assert( pFrom->zErrMsg==0 || pFrom->nErr );
+  assert( pTo->zErrMsg==0 || pTo->nErr );
+  if( pTo->nErr==0 ){
+    pTo->zErrMsg = pFrom->zErrMsg;
+    pTo->nErr = pFrom->nErr;
+  }else{
+    sqlite3DbFree(pFrom->db, pFrom->zErrMsg);
+  }
+}
+
+/*
+** Create and populate a new TriggerPrg object with a sub-program 
+** implementing trigger pTrigger with ON CONFLICT policy orconf.
+*/
+static TriggerPrg *codeRowTrigger(
+  Parse *pParse,       /* Current parse context */
+  Trigger *pTrigger,   /* Trigger to code */
+  Table *pTab,         /* The table pTrigger is attached to */
+  int orconf           /* ON CONFLICT policy to code trigger program with */
+){
+  Parse *pTop = sqlite3ParseToplevel(pParse);
+  sqlite3 *db = pParse->db;   /* Database handle */
+  TriggerPrg *pPrg;           /* Value to return */
+  Expr *pWhen = 0;            /* Duplicate of trigger WHEN expression */
+  Vdbe *v;                    /* Temporary VM */
+  NameContext sNC;            /* Name context for sub-vdbe */
+  SubProgram *pProgram = 0;   /* Sub-vdbe for trigger program */
+  Parse *pSubParse;           /* Parse context for sub-vdbe */
+  int iEndTrigger = 0;        /* Label to jump to if WHEN is false */
+
+  assert( pTrigger->zName==0 || pTab==tableOfTrigger(pTrigger) );
+  assert( pTop->pVdbe );
+
+  /* Allocate the TriggerPrg and SubProgram objects. To ensure that they
+  ** are freed if an error occurs, link them into the Parse.pTriggerPrg 
+  ** list of the top-level Parse object sooner rather than later.  */
+  pPrg = sqlite3DbMallocZero(db, sizeof(TriggerPrg));
+  if( !pPrg ) return 0;
+  pPrg->pNext = pTop->pTriggerPrg;
+  pTop->pTriggerPrg = pPrg;
+  pPrg->pProgram = pProgram = sqlite3DbMallocZero(db, sizeof(SubProgram));
+  if( !pProgram ) return 0;
+  sqlite3VdbeLinkSubProgram(pTop->pVdbe, pProgram);
+  pPrg->pTrigger = pTrigger;
+  pPrg->orconf = orconf;
+  pPrg->aColmask[0] = 0xffffffff;
+  pPrg->aColmask[1] = 0xffffffff;
+
+  /* Allocate and populate a new Parse context to use for coding the 
+  ** trigger sub-program.  */
+  pSubParse = sqlite3StackAllocZero(db, sizeof(Parse));
+  if( !pSubParse ) return 0;
+  memset(&sNC, 0, sizeof(sNC));
+  sNC.pParse = pSubParse;
+  pSubParse->db = db;
+  pSubParse->pTriggerTab = pTab;
+  pSubParse->pToplevel = pTop;
+  pSubParse->zAuthContext = pTrigger->zName;
+  pSubParse->eTriggerOp = pTrigger->op;
+  pSubParse->nQueryLoop = pParse->nQueryLoop;
+
+  v = sqlite3GetVdbe(pSubParse);
+  if( v ){
+    VdbeComment((v, "Start: %s.%s (%s %s%s%s ON %s)", 
+      pTrigger->zName, onErrorText(orconf),
+      (pTrigger->tr_tm==TRIGGER_BEFORE ? "BEFORE" : "AFTER"),
+        (pTrigger->op==TK_UPDATE ? "UPDATE" : ""),
+        (pTrigger->op==TK_INSERT ? "INSERT" : ""),
+        (pTrigger->op==TK_DELETE ? "DELETE" : ""),
+      pTab->zName
+    ));
+#ifndef SQLITE_OMIT_TRACE
+    sqlite3VdbeChangeP4(v, -1, 
+      sqlite3MPrintf(db, "-- TRIGGER %s", pTrigger->zName), P4_DYNAMIC
+    );
+#endif
+
+    /* If one was specified, code the WHEN clause. If it evaluates to false
+    ** (or NULL) the sub-vdbe is immediately halted by jumping to the 
+    ** OP_Halt inserted at the end of the program.  */
+    if( pTrigger->pWhen ){
+      pWhen = sqlite3ExprDup(db, pTrigger->pWhen, 0);
+      if( SQLITE_OK==sqlite3ResolveExprNames(&sNC, pWhen) 
+       && db->mallocFailed==0 
+      ){
+        iEndTrigger = sqlite3VdbeMakeLabel(v);
+        sqlite3ExprIfFalse(pSubParse, pWhen, iEndTrigger, SQLITE_JUMPIFNULL);
+      }
+      sqlite3ExprDelete(db, pWhen);
+    }
+
+    /* Code the trigger program into the sub-vdbe. */
+    codeTriggerProgram(pSubParse, pTrigger->step_list, orconf);
+
+    /* Insert an OP_Halt at the end of the sub-program. */
+    if( iEndTrigger ){
+      sqlite3VdbeResolveLabel(v, iEndTrigger);
+    }
+    sqlite3VdbeAddOp0(v, OP_Halt);
+    VdbeComment((v, "End: %s.%s", pTrigger->zName, onErrorText(orconf)));
+
+    transferParseError(pParse, pSubParse);
+    if( db->mallocFailed==0 ){
+      pProgram->aOp = sqlite3VdbeTakeOpArray(v, &pProgram->nOp, &pTop->nMaxArg);
+    }
+    pProgram->nMem = pSubParse->nMem;
+    pProgram->nCsr = pSubParse->nTab;
+    pProgram->token = (void *)pTrigger;
+    pPrg->aColmask[0] = pSubParse->oldmask;
+    pPrg->aColmask[1] = pSubParse->newmask;
+    sqlite3VdbeDelete(v);
+  }
+
+  assert( !pSubParse->pAinc       && !pSubParse->pZombieTab );
+  assert( !pSubParse->pTriggerPrg && !pSubParse->nMaxArg );
+  sqlite3StackFree(db, pSubParse);
+
+  return pPrg;
+}
+    
+/*
+** Return a pointer to a TriggerPrg object containing the sub-program for
+** trigger pTrigger with default ON CONFLICT algorithm orconf. If no such
+** TriggerPrg object exists, a new object is allocated and populated before
+** being returned.
+*/
+static TriggerPrg *getRowTrigger(
+  Parse *pParse,       /* Current parse context */
+  Trigger *pTrigger,   /* Trigger to code */
+  Table *pTab,         /* The table trigger pTrigger is attached to */
+  int orconf           /* ON CONFLICT algorithm. */
+){
+  Parse *pRoot = sqlite3ParseToplevel(pParse);
+  TriggerPrg *pPrg;
+
+  assert( pTrigger->zName==0 || pTab==tableOfTrigger(pTrigger) );
+
+  /* It may be that this trigger has already been coded (or is in the
+  ** process of being coded). If this is the case, then an entry with
+  ** a matching TriggerPrg.pTrigger field will be present somewhere
+  ** in the Parse.pTriggerPrg list. Search for such an entry.  */
+  for(pPrg=pRoot->pTriggerPrg; 
+      pPrg && (pPrg->pTrigger!=pTrigger || pPrg->orconf!=orconf); 
+      pPrg=pPrg->pNext
+  );
+
+  /* If an existing TriggerPrg could not be located, create a new one. */
+  if( !pPrg ){
+    pPrg = codeRowTrigger(pParse, pTrigger, pTab, orconf);
+  }
+
+  return pPrg;
+}
+
+/*
+** Generate code for the trigger program associated with trigger p on 
+** table pTab. The reg, orconf and ignoreJump parameters passed to this
+** function are the same as those described in the header function for
+** sqlite3CodeRowTrigger()
+*/
+void sqlite3CodeRowTriggerDirect(
+  Parse *pParse,       /* Parse context */
+  Trigger *p,          /* Trigger to code */
+  Table *pTab,         /* The table to code triggers from */
+  int reg,             /* Reg array containing OLD.* and NEW.* values */
+  int orconf,          /* ON CONFLICT policy */
+  int ignoreJump       /* Instruction to jump to for RAISE(IGNORE) */
+){
+  Vdbe *v = sqlite3GetVdbe(pParse); /* Main VM */
+  TriggerPrg *pPrg;
+  pPrg = getRowTrigger(pParse, p, pTab, orconf);
+  assert( pPrg || pParse->nErr || pParse->db->mallocFailed );
+
+  /* Code the OP_Program opcode in the parent VDBE. P4 of the OP_Program 
+  ** is a pointer to the sub-vdbe containing the trigger program.  */
+  if( pPrg ){
+    int bRecursive = (p->zName && 0==(pParse->db->flags&SQLITE_RecTriggers));
+
+    sqlite3VdbeAddOp3(v, OP_Program, reg, ignoreJump, ++pParse->nMem);
+    sqlite3VdbeChangeP4(v, -1, (const char *)pPrg->pProgram, P4_SUBPROGRAM);
+    VdbeComment(
+        (v, "Call: %s.%s", (p->zName?p->zName:"fkey"), onErrorText(orconf)));
+
+    /* Set the P5 operand of the OP_Program instruction to non-zero if
+    ** recursive invocation of this trigger program is disallowed. Recursive
+    ** invocation is disallowed if (a) the sub-program is really a trigger,
+    ** not a foreign key action, and (b) the flag to enable recursive triggers
+    ** is clear.  */
+    sqlite3VdbeChangeP5(v, (u8)bRecursive);
+  }
+}
+
+/*
+** This is called to code the required FOR EACH ROW triggers for an operation
+** on table pTab. The operation to code triggers for (INSERT, UPDATE or DELETE)
+** is given by the op paramater. The tr_tm parameter determines whether the
+** BEFORE or AFTER triggers are coded. If the operation is an UPDATE, then
+** parameter pChanges is passed the list of columns being modified.
+**
+** If there are no triggers that fire at the specified time for the specified
+** operation on pTab, this function is a no-op.
+**
+** The reg argument is the address of the first in an array of registers 
+** that contain the values substituted for the new.* and old.* references
+** in the trigger program. If N is the number of columns in table pTab
+** (a copy of pTab->nCol), then registers are populated as follows:
+**
+**   Register       Contains
+**   ------------------------------------------------------
+**   reg+0          OLD.rowid
+**   reg+1          OLD.* value of left-most column of pTab
+**   ...            ...
+**   reg+N          OLD.* value of right-most column of pTab
+**   reg+N+1        NEW.rowid
+**   reg+N+2        OLD.* value of left-most column of pTab
+**   ...            ...
+**   reg+N+N+1      NEW.* value of right-most column of pTab
+**
+** For ON DELETE triggers, the registers containing the NEW.* values will
+** never be accessed by the trigger program, so they are not allocated or 
+** populated by the caller (there is no data to populate them with anyway). 
+** Similarly, for ON INSERT triggers the values stored in the OLD.* registers
+** are never accessed, and so are not allocated by the caller. So, for an
+** ON INSERT trigger, the value passed to this function as parameter reg
+** is not a readable register, although registers (reg+N) through 
+** (reg+N+N+1) are.
+**
+** Parameter orconf is the default conflict resolution algorithm for the
+** trigger program to use (REPLACE, IGNORE etc.). Parameter ignoreJump
+** is the instruction that control should jump to if a trigger program
+** raises an IGNORE exception.
+*/
+void sqlite3CodeRowTrigger(
+  Parse *pParse,       /* Parse context */
+  Trigger *pTrigger,   /* List of triggers on table pTab */
+  int op,              /* One of TK_UPDATE, TK_INSERT, TK_DELETE */
+  ExprList *pChanges,  /* Changes list for any UPDATE OF triggers */
+  int tr_tm,           /* One of TRIGGER_BEFORE, TRIGGER_AFTER */
+  Table *pTab,         /* The table to code triggers from */
+  int reg,             /* The first in an array of registers (see above) */
+  int orconf,          /* ON CONFLICT policy */
+  int ignoreJump       /* Instruction to jump to for RAISE(IGNORE) */
+){
+  Trigger *p;          /* Used to iterate through pTrigger list */
+
+  assert( op==TK_UPDATE || op==TK_INSERT || op==TK_DELETE );
+  assert( tr_tm==TRIGGER_BEFORE || tr_tm==TRIGGER_AFTER );
+  assert( (op==TK_UPDATE)==(pChanges!=0) );
+
+  for(p=pTrigger; p; p=p->pNext){
+
+    /* Sanity checking:  The schema for the trigger and for the table are
+    ** always defined.  The trigger must be in the same schema as the table
+    ** or else it must be a TEMP trigger. */
+    assert( p->pSchema!=0 );
+    assert( p->pTabSchema!=0 );
+    assert( p->pSchema==p->pTabSchema 
+         || p->pSchema==pParse->db->aDb[1].pSchema );
+
+    /* Determine whether we should code this trigger */
+    if( p->op==op 
+     && p->tr_tm==tr_tm 
+     && checkColumnOverlap(p->pColumns, pChanges)
+    ){
+      sqlite3CodeRowTriggerDirect(pParse, p, pTab, reg, orconf, ignoreJump);
+    }
+  }
+}
+
+/*
+** Triggers may access values stored in the old.* or new.* pseudo-table. 
+** This function returns a 32-bit bitmask indicating which columns of the 
+** old.* or new.* tables actually are used by triggers. This information 
+** may be used by the caller, for example, to avoid having to load the entire
+** old.* record into memory when executing an UPDATE or DELETE command.
+**
+** Bit 0 of the returned mask is set if the left-most column of the
+** table may be accessed using an [old|new].<col> reference. Bit 1 is set if
+** the second leftmost column value is required, and so on. If there
+** are more than 32 columns in the table, and at least one of the columns
+** with an index greater than 32 may be accessed, 0xffffffff is returned.
+**
+** It is not possible to determine if the old.rowid or new.rowid column is 
+** accessed by triggers. The caller must always assume that it is.
+**
+** Parameter isNew must be either 1 or 0. If it is 0, then the mask returned
+** applies to the old.* table. If 1, the new.* table.
+**
+** Parameter tr_tm must be a mask with one or both of the TRIGGER_BEFORE
+** and TRIGGER_AFTER bits set. Values accessed by BEFORE triggers are only
+** included in the returned mask if the TRIGGER_BEFORE bit is set in the
+** tr_tm parameter. Similarly, values accessed by AFTER triggers are only
+** included in the returned mask if the TRIGGER_AFTER bit is set in tr_tm.
+*/
+u32 sqlite3TriggerColmask(
+  Parse *pParse,       /* Parse context */
+  Trigger *pTrigger,   /* List of triggers on table pTab */
+  ExprList *pChanges,  /* Changes list for any UPDATE OF triggers */
+  int isNew,           /* 1 for new.* ref mask, 0 for old.* ref mask */
+  int tr_tm,           /* Mask of TRIGGER_BEFORE|TRIGGER_AFTER */
+  Table *pTab,         /* The table to code triggers from */
+  int orconf           /* Default ON CONFLICT policy for trigger steps */
+){
+  const int op = pChanges ? TK_UPDATE : TK_DELETE;
+  u32 mask = 0;
+  Trigger *p;
+
+  assert( isNew==1 || isNew==0 );
+  for(p=pTrigger; p; p=p->pNext){
+    if( p->op==op && (tr_tm&p->tr_tm)
+     && checkColumnOverlap(p->pColumns,pChanges)
+    ){
+      TriggerPrg *pPrg;
+      pPrg = getRowTrigger(pParse, p, pTab, orconf);
+      if( pPrg ){
+        mask |= pPrg->aColmask[isNew];
+      }
+    }
+  }
+
+  return mask;
+}
+
+#endif /* !defined(SQLITE_OMIT_TRIGGER) */
diff --git a/src/update.c b/src/update.c
new file mode 100644
index 0000000..1e30522
--- /dev/null
+++ b/src/update.c
@@ -0,0 +1,672 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains C code routines that are called by the parser
+** to handle UPDATE statements.
+*/
+#include "sqliteInt.h"
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/* Forward declaration */
+static void updateVirtualTable(
+  Parse *pParse,       /* The parsing context */
+  SrcList *pSrc,       /* The virtual table to be modified */
+  Table *pTab,         /* The virtual table */
+  ExprList *pChanges,  /* The columns to change in the UPDATE statement */
+  Expr *pRowidExpr,    /* Expression used to recompute the rowid */
+  int *aXRef,          /* Mapping from columns of pTab to entries in pChanges */
+  Expr *pWhere,        /* WHERE clause of the UPDATE statement */
+  int onError          /* ON CONFLICT strategy */
+);
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+/*
+** The most recently coded instruction was an OP_Column to retrieve the
+** i-th column of table pTab. This routine sets the P4 parameter of the 
+** OP_Column to the default value, if any.
+**
+** The default value of a column is specified by a DEFAULT clause in the 
+** column definition. This was either supplied by the user when the table
+** was created, or added later to the table definition by an ALTER TABLE
+** command. If the latter, then the row-records in the table btree on disk
+** may not contain a value for the column and the default value, taken
+** from the P4 parameter of the OP_Column instruction, is returned instead.
+** If the former, then all row-records are guaranteed to include a value
+** for the column and the P4 value is not required.
+**
+** Column definitions created by an ALTER TABLE command may only have 
+** literal default values specified: a number, null or a string. (If a more
+** complicated default expression value was provided, it is evaluated 
+** when the ALTER TABLE is executed and one of the literal values written
+** into the sqlite_master table.)
+**
+** Therefore, the P4 parameter is only required if the default value for
+** the column is a literal number, string or null. The sqlite3ValueFromExpr()
+** function is capable of transforming these types of expressions into
+** sqlite3_value objects.
+**
+** If parameter iReg is not negative, code an OP_RealAffinity instruction
+** on register iReg. This is used when an equivalent integer value is 
+** stored in place of an 8-byte floating point value in order to save 
+** space.
+*/
+void sqlite3ColumnDefault(Vdbe *v, Table *pTab, int i, int iReg){
+  assert( pTab!=0 );
+  if( !pTab->pSelect ){
+    sqlite3_value *pValue;
+    u8 enc = ENC(sqlite3VdbeDb(v));
+    Column *pCol = &pTab->aCol[i];
+    VdbeComment((v, "%s.%s", pTab->zName, pCol->zName));
+    assert( i<pTab->nCol );
+    sqlite3ValueFromExpr(sqlite3VdbeDb(v), pCol->pDflt, enc, 
+                         pCol->affinity, &pValue);
+    if( pValue ){
+      sqlite3VdbeChangeP4(v, -1, (const char *)pValue, P4_MEM);
+    }
+#ifndef SQLITE_OMIT_FLOATING_POINT
+    if( iReg>=0 && pTab->aCol[i].affinity==SQLITE_AFF_REAL ){
+      sqlite3VdbeAddOp1(v, OP_RealAffinity, iReg);
+    }
+#endif
+  }
+}
+
+/*
+** Process an UPDATE statement.
+**
+**   UPDATE OR IGNORE table_wxyz SET a=b, c=d WHERE e<5 AND f NOT NULL;
+**          \_______/ \________/     \______/       \________________/
+*            onError   pTabList      pChanges             pWhere
+*/
+void sqlite3Update(
+  Parse *pParse,         /* The parser context */
+  SrcList *pTabList,     /* The table in which we should change things */
+  ExprList *pChanges,    /* Things to be changed */
+  Expr *pWhere,          /* The WHERE clause.  May be null */
+  int onError            /* How to handle constraint errors */
+){
+  int i, j;              /* Loop counters */
+  Table *pTab;           /* The table to be updated */
+  int addr = 0;          /* VDBE instruction address of the start of the loop */
+  WhereInfo *pWInfo;     /* Information about the WHERE clause */
+  Vdbe *v;               /* The virtual database engine */
+  Index *pIdx;           /* For looping over indices */
+  int nIdx;              /* Number of indices that need updating */
+  int iCur;              /* VDBE Cursor number of pTab */
+  sqlite3 *db;           /* The database structure */
+  int *aRegIdx = 0;      /* One register assigned to each index to be updated */
+  int *aXRef = 0;        /* aXRef[i] is the index in pChanges->a[] of the
+                         ** an expression for the i-th column of the table.
+                         ** aXRef[i]==-1 if the i-th column is not changed. */
+  int chngRowid;         /* True if the record number is being changed */
+  Expr *pRowidExpr = 0;  /* Expression defining the new record number */
+  int openAll = 0;       /* True if all indices need to be opened */
+  AuthContext sContext;  /* The authorization context */
+  NameContext sNC;       /* The name-context to resolve expressions in */
+  int iDb;               /* Database containing the table being updated */
+  int okOnePass;         /* True for one-pass algorithm without the FIFO */
+  int hasFK;             /* True if foreign key processing is required */
+
+#ifndef SQLITE_OMIT_TRIGGER
+  int isView;            /* True when updating a view (INSTEAD OF trigger) */
+  Trigger *pTrigger;     /* List of triggers on pTab, if required */
+  int tmask;             /* Mask of TRIGGER_BEFORE|TRIGGER_AFTER */
+#endif
+  int newmask;           /* Mask of NEW.* columns accessed by BEFORE triggers */
+
+  /* Register Allocations */
+  int regRowCount = 0;   /* A count of rows changed */
+  int regOldRowid;       /* The old rowid */
+  int regNewRowid;       /* The new rowid */
+  int regNew;
+  int regOld = 0;
+  int regRowSet = 0;     /* Rowset of rows to be updated */
+
+  memset(&sContext, 0, sizeof(sContext));
+  db = pParse->db;
+  if( pParse->nErr || db->mallocFailed ){
+    goto update_cleanup;
+  }
+  assert( pTabList->nSrc==1 );
+
+  /* Locate the table which we want to update. 
+  */
+  pTab = sqlite3SrcListLookup(pParse, pTabList);
+  if( pTab==0 ) goto update_cleanup;
+  iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
+
+  /* Figure out if we have any triggers and if the table being
+  ** updated is a view.
+  */
+#ifndef SQLITE_OMIT_TRIGGER
+  pTrigger = sqlite3TriggersExist(pParse, pTab, TK_UPDATE, pChanges, &tmask);
+  isView = pTab->pSelect!=0;
+  assert( pTrigger || tmask==0 );
+#else
+# define pTrigger 0
+# define isView 0
+# define tmask 0
+#endif
+#ifdef SQLITE_OMIT_VIEW
+# undef isView
+# define isView 0
+#endif
+
+  if( sqlite3ViewGetColumnNames(pParse, pTab) ){
+    goto update_cleanup;
+  }
+  if( sqlite3IsReadOnly(pParse, pTab, tmask) ){
+    goto update_cleanup;
+  }
+  aXRef = sqlite3DbMallocRaw(db, sizeof(int) * pTab->nCol );
+  if( aXRef==0 ) goto update_cleanup;
+  for(i=0; i<pTab->nCol; i++) aXRef[i] = -1;
+
+  /* Allocate a cursors for the main database table and for all indices.
+  ** The index cursors might not be used, but if they are used they
+  ** need to occur right after the database cursor.  So go ahead and
+  ** allocate enough space, just in case.
+  */
+  pTabList->a[0].iCursor = iCur = pParse->nTab++;
+  for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+    pParse->nTab++;
+  }
+
+  /* Initialize the name-context */
+  memset(&sNC, 0, sizeof(sNC));
+  sNC.pParse = pParse;
+  sNC.pSrcList = pTabList;
+
+  /* Resolve the column names in all the expressions of the
+  ** of the UPDATE statement.  Also find the column index
+  ** for each column to be updated in the pChanges array.  For each
+  ** column to be updated, make sure we have authorization to change
+  ** that column.
+  */
+  chngRowid = 0;
+  for(i=0; i<pChanges->nExpr; i++){
+    if( sqlite3ResolveExprNames(&sNC, pChanges->a[i].pExpr) ){
+      goto update_cleanup;
+    }
+    for(j=0; j<pTab->nCol; j++){
+      if( sqlite3StrICmp(pTab->aCol[j].zName, pChanges->a[i].zName)==0 ){
+        if( j==pTab->iPKey ){
+          chngRowid = 1;
+          pRowidExpr = pChanges->a[i].pExpr;
+        }
+        aXRef[j] = i;
+        break;
+      }
+    }
+    if( j>=pTab->nCol ){
+      if( sqlite3IsRowid(pChanges->a[i].zName) ){
+        chngRowid = 1;
+        pRowidExpr = pChanges->a[i].pExpr;
+      }else{
+        sqlite3ErrorMsg(pParse, "no such column: %s", pChanges->a[i].zName);
+        pParse->checkSchema = 1;
+        goto update_cleanup;
+      }
+    }
+#ifndef SQLITE_OMIT_AUTHORIZATION
+    {
+      int rc;
+      rc = sqlite3AuthCheck(pParse, SQLITE_UPDATE, pTab->zName,
+                           pTab->aCol[j].zName, db->aDb[iDb].zName);
+      if( rc==SQLITE_DENY ){
+        goto update_cleanup;
+      }else if( rc==SQLITE_IGNORE ){
+        aXRef[j] = -1;
+      }
+    }
+#endif
+  }
+
+  hasFK = sqlite3FkRequired(pParse, pTab, aXRef, chngRowid);
+
+  /* Allocate memory for the array aRegIdx[].  There is one entry in the
+  ** array for each index associated with table being updated.  Fill in
+  ** the value with a register number for indices that are to be used
+  ** and with zero for unused indices.
+  */
+  for(nIdx=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, nIdx++){}
+  if( nIdx>0 ){
+    aRegIdx = sqlite3DbMallocRaw(db, sizeof(Index*) * nIdx );
+    if( aRegIdx==0 ) goto update_cleanup;
+  }
+  for(j=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, j++){
+    int reg;
+    if( hasFK || chngRowid ){
+      reg = ++pParse->nMem;
+    }else{
+      reg = 0;
+      for(i=0; i<pIdx->nColumn; i++){
+        if( aXRef[pIdx->aiColumn[i]]>=0 ){
+          reg = ++pParse->nMem;
+          break;
+        }
+      }
+    }
+    aRegIdx[j] = reg;
+  }
+
+  /* Begin generating code. */
+  v = sqlite3GetVdbe(pParse);
+  if( v==0 ) goto update_cleanup;
+  if( pParse->nested==0 ) sqlite3VdbeCountChanges(v);
+  sqlite3BeginWriteOperation(pParse, 1, iDb);
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  /* Virtual tables must be handled separately */
+  if( IsVirtual(pTab) ){
+    updateVirtualTable(pParse, pTabList, pTab, pChanges, pRowidExpr, aXRef,
+                       pWhere, onError);
+    pWhere = 0;
+    pTabList = 0;
+    goto update_cleanup;
+  }
+#endif
+
+  /* Allocate required registers. */
+  regOldRowid = regNewRowid = ++pParse->nMem;
+  if( pTrigger || hasFK ){
+    regOld = pParse->nMem + 1;
+    pParse->nMem += pTab->nCol;
+  }
+  if( chngRowid || pTrigger || hasFK ){
+    regNewRowid = ++pParse->nMem;
+  }
+  regNew = pParse->nMem + 1;
+  pParse->nMem += pTab->nCol;
+
+  /* Start the view context. */
+  if( isView ){
+    sqlite3AuthContextPush(pParse, &sContext, pTab->zName);
+  }
+
+  /* If we are trying to update a view, realize that view into
+  ** a ephemeral table.
+  */
+#if !defined(SQLITE_OMIT_VIEW) && !defined(SQLITE_OMIT_TRIGGER)
+  if( isView ){
+    sqlite3MaterializeView(pParse, pTab, pWhere, iCur);
+  }
+#endif
+
+  /* Resolve the column names in all the expressions in the
+  ** WHERE clause.
+  */
+  if( sqlite3ResolveExprNames(&sNC, pWhere) ){
+    goto update_cleanup;
+  }
+
+  /* Begin the database scan
+  */
+  sqlite3VdbeAddOp2(v, OP_Null, 0, regOldRowid);
+  pWInfo = sqlite3WhereBegin(
+      pParse, pTabList, pWhere, 0, 0, WHERE_ONEPASS_DESIRED
+  );
+  if( pWInfo==0 ) goto update_cleanup;
+  okOnePass = pWInfo->okOnePass;
+
+  /* Remember the rowid of every item to be updated.
+  */
+  sqlite3VdbeAddOp2(v, OP_Rowid, iCur, regOldRowid);
+  if( !okOnePass ){
+    regRowSet = ++pParse->nMem;
+    sqlite3VdbeAddOp2(v, OP_RowSetAdd, regRowSet, regOldRowid);
+  }
+
+  /* End the database scan loop.
+  */
+  sqlite3WhereEnd(pWInfo);
+
+  /* Initialize the count of updated rows
+  */
+  if( (db->flags & SQLITE_CountRows) && !pParse->pTriggerTab ){
+    regRowCount = ++pParse->nMem;
+    sqlite3VdbeAddOp2(v, OP_Integer, 0, regRowCount);
+  }
+
+  if( !isView ){
+    /* 
+    ** Open every index that needs updating.  Note that if any
+    ** index could potentially invoke a REPLACE conflict resolution 
+    ** action, then we need to open all indices because we might need
+    ** to be deleting some records.
+    */
+    if( !okOnePass ) sqlite3OpenTable(pParse, iCur, iDb, pTab, OP_OpenWrite); 
+    if( onError==OE_Replace ){
+      openAll = 1;
+    }else{
+      openAll = 0;
+      for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+        if( pIdx->onError==OE_Replace ){
+          openAll = 1;
+          break;
+        }
+      }
+    }
+    for(i=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, i++){
+      assert( aRegIdx );
+      if( openAll || aRegIdx[i]>0 ){
+        KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIdx);
+        sqlite3VdbeAddOp4(v, OP_OpenWrite, iCur+i+1, pIdx->tnum, iDb,
+                       (char*)pKey, P4_KEYINFO_HANDOFF);
+        assert( pParse->nTab>iCur+i+1 );
+      }
+    }
+  }
+
+  /* Top of the update loop */
+  if( okOnePass ){
+    int a1 = sqlite3VdbeAddOp1(v, OP_NotNull, regOldRowid);
+    addr = sqlite3VdbeAddOp0(v, OP_Goto);
+    sqlite3VdbeJumpHere(v, a1);
+  }else{
+    addr = sqlite3VdbeAddOp3(v, OP_RowSetRead, regRowSet, 0, regOldRowid);
+  }
+
+  /* Make cursor iCur point to the record that is being updated. If
+  ** this record does not exist for some reason (deleted by a trigger,
+  ** for example, then jump to the next iteration of the RowSet loop.  */
+  sqlite3VdbeAddOp3(v, OP_NotExists, iCur, addr, regOldRowid);
+
+  /* If the record number will change, set register regNewRowid to
+  ** contain the new value. If the record number is not being modified,
+  ** then regNewRowid is the same register as regOldRowid, which is
+  ** already populated.  */
+  assert( chngRowid || pTrigger || hasFK || regOldRowid==regNewRowid );
+  if( chngRowid ){
+    sqlite3ExprCode(pParse, pRowidExpr, regNewRowid);
+    sqlite3VdbeAddOp1(v, OP_MustBeInt, regNewRowid);
+  }
+
+  /* If there are triggers on this table, populate an array of registers 
+  ** with the required old.* column data.  */
+  if( hasFK || pTrigger ){
+    u32 oldmask = (hasFK ? sqlite3FkOldmask(pParse, pTab) : 0);
+    oldmask |= sqlite3TriggerColmask(pParse, 
+        pTrigger, pChanges, 0, TRIGGER_BEFORE|TRIGGER_AFTER, pTab, onError
+    );
+    for(i=0; i<pTab->nCol; i++){
+      if( aXRef[i]<0 || oldmask==0xffffffff || (i<32 && (oldmask & (1<<i))) ){
+        sqlite3ExprCodeGetColumnOfTable(v, pTab, iCur, i, regOld+i);
+      }else{
+        sqlite3VdbeAddOp2(v, OP_Null, 0, regOld+i);
+      }
+    }
+    if( chngRowid==0 ){
+      sqlite3VdbeAddOp2(v, OP_Copy, regOldRowid, regNewRowid);
+    }
+  }
+
+  /* Populate the array of registers beginning at regNew with the new
+  ** row data. This array is used to check constaints, create the new
+  ** table and index records, and as the values for any new.* references
+  ** made by triggers.
+  **
+  ** If there are one or more BEFORE triggers, then do not populate the
+  ** registers associated with columns that are (a) not modified by
+  ** this UPDATE statement and (b) not accessed by new.* references. The
+  ** values for registers not modified by the UPDATE must be reloaded from 
+  ** the database after the BEFORE triggers are fired anyway (as the trigger 
+  ** may have modified them). So not loading those that are not going to
+  ** be used eliminates some redundant opcodes.
+  */
+  newmask = sqlite3TriggerColmask(
+      pParse, pTrigger, pChanges, 1, TRIGGER_BEFORE, pTab, onError
+  );
+  for(i=0; i<pTab->nCol; i++){
+    if( i==pTab->iPKey ){
+      sqlite3VdbeAddOp2(v, OP_Null, 0, regNew+i);
+    }else{
+      j = aXRef[i];
+      if( j>=0 ){
+        sqlite3ExprCode(pParse, pChanges->a[j].pExpr, regNew+i);
+      }else if( 0==(tmask&TRIGGER_BEFORE) || i>31 || (newmask&(1<<i)) ){
+        /* This branch loads the value of a column that will not be changed 
+        ** into a register. This is done if there are no BEFORE triggers, or
+        ** if there are one or more BEFORE triggers that use this value via
+        ** a new.* reference in a trigger program.
+        */
+        testcase( i==31 );
+        testcase( i==32 );
+        sqlite3VdbeAddOp3(v, OP_Column, iCur, i, regNew+i);
+        sqlite3ColumnDefault(v, pTab, i, regNew+i);
+      }
+    }
+  }
+
+  /* Fire any BEFORE UPDATE triggers. This happens before constraints are
+  ** verified. One could argue that this is wrong.
+  */
+  if( tmask&TRIGGER_BEFORE ){
+    sqlite3VdbeAddOp2(v, OP_Affinity, regNew, pTab->nCol);
+    sqlite3TableAffinityStr(v, pTab);
+    sqlite3CodeRowTrigger(pParse, pTrigger, TK_UPDATE, pChanges, 
+        TRIGGER_BEFORE, pTab, regOldRowid, onError, addr);
+
+    /* The row-trigger may have deleted the row being updated. In this
+    ** case, jump to the next row. No updates or AFTER triggers are 
+    ** required. This behaviour - what happens when the row being updated
+    ** is deleted or renamed by a BEFORE trigger - is left undefined in the
+    ** documentation.
+    */
+    sqlite3VdbeAddOp3(v, OP_NotExists, iCur, addr, regOldRowid);
+
+    /* If it did not delete it, the row-trigger may still have modified 
+    ** some of the columns of the row being updated. Load the values for 
+    ** all columns not modified by the update statement into their 
+    ** registers in case this has happened.
+    */
+    for(i=0; i<pTab->nCol; i++){
+      if( aXRef[i]<0 && i!=pTab->iPKey ){
+        sqlite3VdbeAddOp3(v, OP_Column, iCur, i, regNew+i);
+        sqlite3ColumnDefault(v, pTab, i, regNew+i);
+      }
+    }
+  }
+
+  if( !isView ){
+    int j1;                       /* Address of jump instruction */
+
+    /* Do constraint checks. */
+    sqlite3GenerateConstraintChecks(pParse, pTab, iCur, regNewRowid,
+        aRegIdx, (chngRowid?regOldRowid:0), 1, onError, addr, 0);
+
+    /* Do FK constraint checks. */
+    if( hasFK ){
+      sqlite3FkCheck(pParse, pTab, regOldRowid, 0);
+    }
+
+    /* Delete the index entries associated with the current record.  */
+    j1 = sqlite3VdbeAddOp3(v, OP_NotExists, iCur, 0, regOldRowid);
+    sqlite3GenerateRowIndexDelete(pParse, pTab, iCur, aRegIdx);
+  
+    /* If changing the record number, delete the old record.  */
+    if( hasFK || chngRowid ){
+      sqlite3VdbeAddOp2(v, OP_Delete, iCur, 0);
+    }
+    sqlite3VdbeJumpHere(v, j1);
+
+    if( hasFK ){
+      sqlite3FkCheck(pParse, pTab, 0, regNewRowid);
+    }
+  
+    /* Insert the new index entries and the new record. */
+    sqlite3CompleteInsertion(pParse, pTab, iCur, regNewRowid, aRegIdx, 1, 0, 0);
+
+    /* Do any ON CASCADE, SET NULL or SET DEFAULT operations required to
+    ** handle rows (possibly in other tables) that refer via a foreign key
+    ** to the row just updated. */ 
+    if( hasFK ){
+      sqlite3FkActions(pParse, pTab, pChanges, regOldRowid);
+    }
+  }
+
+  /* Increment the row counter 
+  */
+  if( (db->flags & SQLITE_CountRows) && !pParse->pTriggerTab){
+    sqlite3VdbeAddOp2(v, OP_AddImm, regRowCount, 1);
+  }
+
+  sqlite3CodeRowTrigger(pParse, pTrigger, TK_UPDATE, pChanges, 
+      TRIGGER_AFTER, pTab, regOldRowid, onError, addr);
+
+  /* Repeat the above with the next record to be updated, until
+  ** all record selected by the WHERE clause have been updated.
+  */
+  sqlite3VdbeAddOp2(v, OP_Goto, 0, addr);
+  sqlite3VdbeJumpHere(v, addr);
+
+  /* Close all tables */
+  for(i=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, i++){
+    assert( aRegIdx );
+    if( openAll || aRegIdx[i]>0 ){
+      sqlite3VdbeAddOp2(v, OP_Close, iCur+i+1, 0);
+    }
+  }
+  sqlite3VdbeAddOp2(v, OP_Close, iCur, 0);
+
+  /* Update the sqlite_sequence table by storing the content of the
+  ** maximum rowid counter values recorded while inserting into
+  ** autoincrement tables.
+  */
+  if( pParse->nested==0 && pParse->pTriggerTab==0 ){
+    sqlite3AutoincrementEnd(pParse);
+  }
+
+  /*
+  ** Return the number of rows that were changed. If this routine is 
+  ** generating code because of a call to sqlite3NestedParse(), do not
+  ** invoke the callback function.
+  */
+  if( (db->flags&SQLITE_CountRows) && !pParse->pTriggerTab && !pParse->nested ){
+    sqlite3VdbeAddOp2(v, OP_ResultRow, regRowCount, 1);
+    sqlite3VdbeSetNumCols(v, 1);
+    sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "rows updated", SQLITE_STATIC);
+  }
+
+update_cleanup:
+  sqlite3AuthContextPop(&sContext);
+  sqlite3DbFree(db, aRegIdx);
+  sqlite3DbFree(db, aXRef);
+  sqlite3SrcListDelete(db, pTabList);
+  sqlite3ExprListDelete(db, pChanges);
+  sqlite3ExprDelete(db, pWhere);
+  return;
+}
+/* Make sure "isView" and other macros defined above are undefined. Otherwise
+** thely may interfere with compilation of other functions in this file
+** (or in another file, if this file becomes part of the amalgamation).  */
+#ifdef isView
+ #undef isView
+#endif
+#ifdef pTrigger
+ #undef pTrigger
+#endif
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/*
+** Generate code for an UPDATE of a virtual table.
+**
+** The strategy is that we create an ephemerial table that contains
+** for each row to be changed:
+**
+**   (A)  The original rowid of that row.
+**   (B)  The revised rowid for the row. (note1)
+**   (C)  The content of every column in the row.
+**
+** Then we loop over this ephemeral table and for each row in
+** the ephermeral table call VUpdate.
+**
+** When finished, drop the ephemeral table.
+**
+** (note1) Actually, if we know in advance that (A) is always the same
+** as (B) we only store (A), then duplicate (A) when pulling
+** it out of the ephemeral table before calling VUpdate.
+*/
+static void updateVirtualTable(
+  Parse *pParse,       /* The parsing context */
+  SrcList *pSrc,       /* The virtual table to be modified */
+  Table *pTab,         /* The virtual table */
+  ExprList *pChanges,  /* The columns to change in the UPDATE statement */
+  Expr *pRowid,        /* Expression used to recompute the rowid */
+  int *aXRef,          /* Mapping from columns of pTab to entries in pChanges */
+  Expr *pWhere,        /* WHERE clause of the UPDATE statement */
+  int onError          /* ON CONFLICT strategy */
+){
+  Vdbe *v = pParse->pVdbe;  /* Virtual machine under construction */
+  ExprList *pEList = 0;     /* The result set of the SELECT statement */
+  Select *pSelect = 0;      /* The SELECT statement */
+  Expr *pExpr;              /* Temporary expression */
+  int ephemTab;             /* Table holding the result of the SELECT */
+  int i;                    /* Loop counter */
+  int addr;                 /* Address of top of loop */
+  int iReg;                 /* First register in set passed to OP_VUpdate */
+  sqlite3 *db = pParse->db; /* Database connection */
+  const char *pVTab = (const char*)sqlite3GetVTable(db, pTab);
+  SelectDest dest;
+
+  /* Construct the SELECT statement that will find the new values for
+  ** all updated rows. 
+  */
+  pEList = sqlite3ExprListAppend(pParse, 0, sqlite3Expr(db, TK_ID, "_rowid_"));
+  if( pRowid ){
+    pEList = sqlite3ExprListAppend(pParse, pEList,
+                                   sqlite3ExprDup(db, pRowid, 0));
+  }
+  assert( pTab->iPKey<0 );
+  for(i=0; i<pTab->nCol; i++){
+    if( aXRef[i]>=0 ){
+      pExpr = sqlite3ExprDup(db, pChanges->a[aXRef[i]].pExpr, 0);
+    }else{
+      pExpr = sqlite3Expr(db, TK_ID, pTab->aCol[i].zName);
+    }
+    pEList = sqlite3ExprListAppend(pParse, pEList, pExpr);
+  }
+  pSelect = sqlite3SelectNew(pParse, pEList, pSrc, pWhere, 0, 0, 0, 0, 0, 0);
+  
+  /* Create the ephemeral table into which the update results will
+  ** be stored.
+  */
+  assert( v );
+  ephemTab = pParse->nTab++;
+  sqlite3VdbeAddOp2(v, OP_OpenEphemeral, ephemTab, pTab->nCol+1+(pRowid!=0));
+  sqlite3VdbeChangeP5(v, BTREE_UNORDERED);
+
+  /* fill the ephemeral table 
+  */
+  sqlite3SelectDestInit(&dest, SRT_Table, ephemTab);
+  sqlite3Select(pParse, pSelect, &dest);
+
+  /* Generate code to scan the ephemeral table and call VUpdate. */
+  iReg = ++pParse->nMem;
+  pParse->nMem += pTab->nCol+1;
+  addr = sqlite3VdbeAddOp2(v, OP_Rewind, ephemTab, 0);
+  sqlite3VdbeAddOp3(v, OP_Column,  ephemTab, 0, iReg);
+  sqlite3VdbeAddOp3(v, OP_Column, ephemTab, (pRowid?1:0), iReg+1);
+  for(i=0; i<pTab->nCol; i++){
+    sqlite3VdbeAddOp3(v, OP_Column, ephemTab, i+1+(pRowid!=0), iReg+2+i);
+  }
+  sqlite3VtabMakeWritable(pParse, pTab);
+  sqlite3VdbeAddOp4(v, OP_VUpdate, 0, pTab->nCol+2, iReg, pVTab, P4_VTAB);
+  sqlite3VdbeChangeP5(v, onError==OE_Default ? OE_Abort : onError);
+  sqlite3MayAbort(pParse);
+  sqlite3VdbeAddOp2(v, OP_Next, ephemTab, addr+1);
+  sqlite3VdbeJumpHere(v, addr);
+  sqlite3VdbeAddOp2(v, OP_Close, ephemTab, 0);
+
+  /* Cleanup */
+  sqlite3SelectDelete(db, pSelect);  
+}
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
diff --git a/src/utf.c b/src/utf.c
new file mode 100644
index 0000000..e94815b
--- /dev/null
+++ b/src/utf.c
@@ -0,0 +1,560 @@
+/*
+** 2004 April 13
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains routines used to translate between UTF-8, 
+** UTF-16, UTF-16BE, and UTF-16LE.
+**
+** Notes on UTF-8:
+**
+**   Byte-0    Byte-1    Byte-2    Byte-3    Value
+**  0xxxxxxx                                 00000000 00000000 0xxxxxxx
+**  110yyyyy  10xxxxxx                       00000000 00000yyy yyxxxxxx
+**  1110zzzz  10yyyyyy  10xxxxxx             00000000 zzzzyyyy yyxxxxxx
+**  11110uuu  10uuzzzz  10yyyyyy  10xxxxxx   000uuuuu zzzzyyyy yyxxxxxx
+**
+**
+** Notes on UTF-16:  (with wwww+1==uuuuu)
+**
+**      Word-0               Word-1          Value
+**  110110ww wwzzzzyy   110111yy yyxxxxxx    000uuuuu zzzzyyyy yyxxxxxx
+**  zzzzyyyy yyxxxxxx                        00000000 zzzzyyyy yyxxxxxx
+**
+**
+** BOM or Byte Order Mark:
+**     0xff 0xfe   little-endian utf-16 follows
+**     0xfe 0xff   big-endian utf-16 follows
+**
+*/
+#include "sqliteInt.h"
+#include <assert.h>
+#include "vdbeInt.h"
+
+#ifndef SQLITE_AMALGAMATION
+/*
+** The following constant value is used by the SQLITE_BIGENDIAN and
+** SQLITE_LITTLEENDIAN macros.
+*/
+const int sqlite3one = 1;
+#endif /* SQLITE_AMALGAMATION */
+
+/*
+** This lookup table is used to help decode the first byte of
+** a multi-byte UTF8 character.
+*/
+static const unsigned char sqlite3Utf8Trans1[] = {
+  0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+  0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
+  0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
+  0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f,
+  0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+  0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
+  0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+  0x00, 0x01, 0x02, 0x03, 0x00, 0x01, 0x00, 0x00,
+};
+
+
+#define WRITE_UTF8(zOut, c) {                          \
+  if( c<0x00080 ){                                     \
+    *zOut++ = (u8)(c&0xFF);                            \
+  }                                                    \
+  else if( c<0x00800 ){                                \
+    *zOut++ = 0xC0 + (u8)((c>>6)&0x1F);                \
+    *zOut++ = 0x80 + (u8)(c & 0x3F);                   \
+  }                                                    \
+  else if( c<0x10000 ){                                \
+    *zOut++ = 0xE0 + (u8)((c>>12)&0x0F);               \
+    *zOut++ = 0x80 + (u8)((c>>6) & 0x3F);              \
+    *zOut++ = 0x80 + (u8)(c & 0x3F);                   \
+  }else{                                               \
+    *zOut++ = 0xF0 + (u8)((c>>18) & 0x07);             \
+    *zOut++ = 0x80 + (u8)((c>>12) & 0x3F);             \
+    *zOut++ = 0x80 + (u8)((c>>6) & 0x3F);              \
+    *zOut++ = 0x80 + (u8)(c & 0x3F);                   \
+  }                                                    \
+}
+
+#define WRITE_UTF16LE(zOut, c) {                                    \
+  if( c<=0xFFFF ){                                                  \
+    *zOut++ = (u8)(c&0x00FF);                                       \
+    *zOut++ = (u8)((c>>8)&0x00FF);                                  \
+  }else{                                                            \
+    *zOut++ = (u8)(((c>>10)&0x003F) + (((c-0x10000)>>10)&0x00C0));  \
+    *zOut++ = (u8)(0x00D8 + (((c-0x10000)>>18)&0x03));              \
+    *zOut++ = (u8)(c&0x00FF);                                       \
+    *zOut++ = (u8)(0x00DC + ((c>>8)&0x03));                         \
+  }                                                                 \
+}
+
+#define WRITE_UTF16BE(zOut, c) {                                    \
+  if( c<=0xFFFF ){                                                  \
+    *zOut++ = (u8)((c>>8)&0x00FF);                                  \
+    *zOut++ = (u8)(c&0x00FF);                                       \
+  }else{                                                            \
+    *zOut++ = (u8)(0x00D8 + (((c-0x10000)>>18)&0x03));              \
+    *zOut++ = (u8)(((c>>10)&0x003F) + (((c-0x10000)>>10)&0x00C0));  \
+    *zOut++ = (u8)(0x00DC + ((c>>8)&0x03));                         \
+    *zOut++ = (u8)(c&0x00FF);                                       \
+  }                                                                 \
+}
+
+#define READ_UTF16LE(zIn, TERM, c){                                   \
+  c = (*zIn++);                                                       \
+  c += ((*zIn++)<<8);                                                 \
+  if( c>=0xD800 && c<0xE000 && TERM ){                                \
+    int c2 = (*zIn++);                                                \
+    c2 += ((*zIn++)<<8);                                              \
+    c = (c2&0x03FF) + ((c&0x003F)<<10) + (((c&0x03C0)+0x0040)<<10);   \
+  }                                                                   \
+}
+
+#define READ_UTF16BE(zIn, TERM, c){                                   \
+  c = ((*zIn++)<<8);                                                  \
+  c += (*zIn++);                                                      \
+  if( c>=0xD800 && c<0xE000 && TERM ){                                \
+    int c2 = ((*zIn++)<<8);                                           \
+    c2 += (*zIn++);                                                   \
+    c = (c2&0x03FF) + ((c&0x003F)<<10) + (((c&0x03C0)+0x0040)<<10);   \
+  }                                                                   \
+}
+
+/*
+** Translate a single UTF-8 character.  Return the unicode value.
+**
+** During translation, assume that the byte that zTerm points
+** is a 0x00.
+**
+** Write a pointer to the next unread byte back into *pzNext.
+**
+** Notes On Invalid UTF-8:
+**
+**  *  This routine never allows a 7-bit character (0x00 through 0x7f) to
+**     be encoded as a multi-byte character.  Any multi-byte character that
+**     attempts to encode a value between 0x00 and 0x7f is rendered as 0xfffd.
+**
+**  *  This routine never allows a UTF16 surrogate value to be encoded.
+**     If a multi-byte character attempts to encode a value between
+**     0xd800 and 0xe000 then it is rendered as 0xfffd.
+**
+**  *  Bytes in the range of 0x80 through 0xbf which occur as the first
+**     byte of a character are interpreted as single-byte characters
+**     and rendered as themselves even though they are technically
+**     invalid characters.
+**
+**  *  This routine accepts an infinite number of different UTF8 encodings
+**     for unicode values 0x80 and greater.  It do not change over-length
+**     encodings to 0xfffd as some systems recommend.
+*/
+#define READ_UTF8(zIn, zTerm, c)                           \
+  c = *(zIn++);                                            \
+  if( c>=0xc0 ){                                           \
+    c = sqlite3Utf8Trans1[c-0xc0];                         \
+    while( zIn!=zTerm && (*zIn & 0xc0)==0x80 ){            \
+      c = (c<<6) + (0x3f & *(zIn++));                      \
+    }                                                      \
+    if( c<0x80                                             \
+        || (c&0xFFFFF800)==0xD800                          \
+        || (c&0xFFFFFFFE)==0xFFFE ){  c = 0xFFFD; }        \
+  }
+u32 sqlite3Utf8Read(
+  const unsigned char *zIn,       /* First byte of UTF-8 character */
+  const unsigned char **pzNext    /* Write first byte past UTF-8 char here */
+){
+  unsigned int c;
+
+  /* Same as READ_UTF8() above but without the zTerm parameter.
+  ** For this routine, we assume the UTF8 string is always zero-terminated.
+  */
+  c = *(zIn++);
+  if( c>=0xc0 ){
+    c = sqlite3Utf8Trans1[c-0xc0];
+    while( (*zIn & 0xc0)==0x80 ){
+      c = (c<<6) + (0x3f & *(zIn++));
+    }
+    if( c<0x80
+        || (c&0xFFFFF800)==0xD800
+        || (c&0xFFFFFFFE)==0xFFFE ){  c = 0xFFFD; }
+  }
+  *pzNext = zIn;
+  return c;
+}
+
+
+
+
+/*
+** If the TRANSLATE_TRACE macro is defined, the value of each Mem is
+** printed on stderr on the way into and out of sqlite3VdbeMemTranslate().
+*/ 
+/* #define TRANSLATE_TRACE 1 */
+
+#ifndef SQLITE_OMIT_UTF16
+/*
+** This routine transforms the internal text encoding used by pMem to
+** desiredEnc. It is an error if the string is already of the desired
+** encoding, or if *pMem does not contain a string value.
+*/
+int sqlite3VdbeMemTranslate(Mem *pMem, u8 desiredEnc){
+  int len;                    /* Maximum length of output string in bytes */
+  unsigned char *zOut;                  /* Output buffer */
+  unsigned char *zIn;                   /* Input iterator */
+  unsigned char *zTerm;                 /* End of input */
+  unsigned char *z;                     /* Output iterator */
+  unsigned int c;
+
+  assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+  assert( pMem->flags&MEM_Str );
+  assert( pMem->enc!=desiredEnc );
+  assert( pMem->enc!=0 );
+  assert( pMem->n>=0 );
+
+#if defined(TRANSLATE_TRACE) && defined(SQLITE_DEBUG)
+  {
+    char zBuf[100];
+    sqlite3VdbeMemPrettyPrint(pMem, zBuf);
+    fprintf(stderr, "INPUT:  %s\n", zBuf);
+  }
+#endif
+
+  /* If the translation is between UTF-16 little and big endian, then 
+  ** all that is required is to swap the byte order. This case is handled
+  ** differently from the others.
+  */
+  if( pMem->enc!=SQLITE_UTF8 && desiredEnc!=SQLITE_UTF8 ){
+    u8 temp;
+    int rc;
+    rc = sqlite3VdbeMemMakeWriteable(pMem);
+    if( rc!=SQLITE_OK ){
+      assert( rc==SQLITE_NOMEM );
+      return SQLITE_NOMEM;
+    }
+    zIn = (u8*)pMem->z;
+    zTerm = &zIn[pMem->n&~1];
+    while( zIn<zTerm ){
+      temp = *zIn;
+      *zIn = *(zIn+1);
+      zIn++;
+      *zIn++ = temp;
+    }
+    pMem->enc = desiredEnc;
+    goto translate_out;
+  }
+
+  /* Set len to the maximum number of bytes required in the output buffer. */
+  if( desiredEnc==SQLITE_UTF8 ){
+    /* When converting from UTF-16, the maximum growth results from
+    ** translating a 2-byte character to a 4-byte UTF-8 character.
+    ** A single byte is required for the output string
+    ** nul-terminator.
+    */
+    pMem->n &= ~1;
+    len = pMem->n * 2 + 1;
+  }else{
+    /* When converting from UTF-8 to UTF-16 the maximum growth is caused
+    ** when a 1-byte UTF-8 character is translated into a 2-byte UTF-16
+    ** character. Two bytes are required in the output buffer for the
+    ** nul-terminator.
+    */
+    len = pMem->n * 2 + 2;
+  }
+
+  /* Set zIn to point at the start of the input buffer and zTerm to point 1
+  ** byte past the end.
+  **
+  ** Variable zOut is set to point at the output buffer, space obtained
+  ** from sqlite3_malloc().
+  */
+  zIn = (u8*)pMem->z;
+  zTerm = &zIn[pMem->n];
+  zOut = sqlite3DbMallocRaw(pMem->db, len);
+  if( !zOut ){
+    return SQLITE_NOMEM;
+  }
+  z = zOut;
+
+  if( pMem->enc==SQLITE_UTF8 ){
+    if( desiredEnc==SQLITE_UTF16LE ){
+      /* UTF-8 -> UTF-16 Little-endian */
+      while( zIn<zTerm ){
+        /* c = sqlite3Utf8Read(zIn, zTerm, (const u8**)&zIn); */
+        READ_UTF8(zIn, zTerm, c);
+        WRITE_UTF16LE(z, c);
+      }
+    }else{
+      assert( desiredEnc==SQLITE_UTF16BE );
+      /* UTF-8 -> UTF-16 Big-endian */
+      while( zIn<zTerm ){
+        /* c = sqlite3Utf8Read(zIn, zTerm, (const u8**)&zIn); */
+        READ_UTF8(zIn, zTerm, c);
+        WRITE_UTF16BE(z, c);
+      }
+    }
+    pMem->n = (int)(z - zOut);
+    *z++ = 0;
+  }else{
+    assert( desiredEnc==SQLITE_UTF8 );
+    if( pMem->enc==SQLITE_UTF16LE ){
+      /* UTF-16 Little-endian -> UTF-8 */
+      while( zIn<zTerm ){
+        READ_UTF16LE(zIn, zIn<zTerm, c); 
+        WRITE_UTF8(z, c);
+      }
+    }else{
+      /* UTF-16 Big-endian -> UTF-8 */
+      while( zIn<zTerm ){
+        READ_UTF16BE(zIn, zIn<zTerm, c); 
+        WRITE_UTF8(z, c);
+      }
+    }
+    pMem->n = (int)(z - zOut);
+  }
+  *z = 0;
+  assert( (pMem->n+(desiredEnc==SQLITE_UTF8?1:2))<=len );
+
+  sqlite3VdbeMemRelease(pMem);
+  pMem->flags &= ~(MEM_Static|MEM_Dyn|MEM_Ephem);
+  pMem->enc = desiredEnc;
+  pMem->flags |= (MEM_Term|MEM_Dyn);
+  pMem->z = (char*)zOut;
+  pMem->zMalloc = pMem->z;
+
+translate_out:
+#if defined(TRANSLATE_TRACE) && defined(SQLITE_DEBUG)
+  {
+    char zBuf[100];
+    sqlite3VdbeMemPrettyPrint(pMem, zBuf);
+    fprintf(stderr, "OUTPUT: %s\n", zBuf);
+  }
+#endif
+  return SQLITE_OK;
+}
+
+/*
+** This routine checks for a byte-order mark at the beginning of the 
+** UTF-16 string stored in *pMem. If one is present, it is removed and
+** the encoding of the Mem adjusted. This routine does not do any
+** byte-swapping, it just sets Mem.enc appropriately.
+**
+** The allocation (static, dynamic etc.) and encoding of the Mem may be
+** changed by this function.
+*/
+int sqlite3VdbeMemHandleBom(Mem *pMem){
+  int rc = SQLITE_OK;
+  u8 bom = 0;
+
+  assert( pMem->n>=0 );
+  if( pMem->n>1 ){
+    u8 b1 = *(u8 *)pMem->z;
+    u8 b2 = *(((u8 *)pMem->z) + 1);
+    if( b1==0xFE && b2==0xFF ){
+      bom = SQLITE_UTF16BE;
+    }
+    if( b1==0xFF && b2==0xFE ){
+      bom = SQLITE_UTF16LE;
+    }
+  }
+  
+  if( bom ){
+    rc = sqlite3VdbeMemMakeWriteable(pMem);
+    if( rc==SQLITE_OK ){
+      pMem->n -= 2;
+      memmove(pMem->z, &pMem->z[2], pMem->n);
+      pMem->z[pMem->n] = '\0';
+      pMem->z[pMem->n+1] = '\0';
+      pMem->flags |= MEM_Term;
+      pMem->enc = bom;
+    }
+  }
+  return rc;
+}
+#endif /* SQLITE_OMIT_UTF16 */
+
+/*
+** pZ is a UTF-8 encoded unicode string. If nByte is less than zero,
+** return the number of unicode characters in pZ up to (but not including)
+** the first 0x00 byte. If nByte is not less than zero, return the
+** number of unicode characters in the first nByte of pZ (or up to 
+** the first 0x00, whichever comes first).
+*/
+int sqlite3Utf8CharLen(const char *zIn, int nByte){
+  int r = 0;
+  const u8 *z = (const u8*)zIn;
+  const u8 *zTerm;
+  if( nByte>=0 ){
+    zTerm = &z[nByte];
+  }else{
+    zTerm = (const u8*)(-1);
+  }
+  assert( z<=zTerm );
+  while( *z!=0 && z<zTerm ){
+    SQLITE_SKIP_UTF8(z);
+    r++;
+  }
+  return r;
+}
+
+/* This test function is not currently used by the automated test-suite. 
+** Hence it is only available in debug builds.
+*/
+#if defined(SQLITE_TEST) && defined(SQLITE_DEBUG)
+/*
+** Translate UTF-8 to UTF-8.
+**
+** This has the effect of making sure that the string is well-formed
+** UTF-8.  Miscoded characters are removed.
+**
+** The translation is done in-place and aborted if the output
+** overruns the input.
+*/
+int sqlite3Utf8To8(unsigned char *zIn){
+  unsigned char *zOut = zIn;
+  unsigned char *zStart = zIn;
+  u32 c;
+
+  while( zIn[0] && zOut<=zIn ){
+    c = sqlite3Utf8Read(zIn, (const u8**)&zIn);
+    if( c!=0xfffd ){
+      WRITE_UTF8(zOut, c);
+    }
+  }
+  *zOut = 0;
+  return (int)(zOut - zStart);
+}
+#endif
+
+#ifndef SQLITE_OMIT_UTF16
+/*
+** Convert a UTF-16 string in the native encoding into a UTF-8 string.
+** Memory to hold the UTF-8 string is obtained from sqlite3_malloc and must
+** be freed by the calling function.
+**
+** NULL is returned if there is an allocation error.
+*/
+char *sqlite3Utf16to8(sqlite3 *db, const void *z, int nByte, u8 enc){
+  Mem m;
+  memset(&m, 0, sizeof(m));
+  m.db = db;
+  sqlite3VdbeMemSetStr(&m, z, nByte, enc, SQLITE_STATIC);
+  sqlite3VdbeChangeEncoding(&m, SQLITE_UTF8);
+  if( db->mallocFailed ){
+    sqlite3VdbeMemRelease(&m);
+    m.z = 0;
+  }
+  assert( (m.flags & MEM_Term)!=0 || db->mallocFailed );
+  assert( (m.flags & MEM_Str)!=0 || db->mallocFailed );
+  assert( (m.flags & MEM_Dyn)!=0 || db->mallocFailed );
+  assert( m.z || db->mallocFailed );
+  return m.z;
+}
+
+/*
+** Convert a UTF-8 string to the UTF-16 encoding specified by parameter
+** enc. A pointer to the new string is returned, and the value of *pnOut
+** is set to the length of the returned string in bytes. The call should
+** arrange to call sqlite3DbFree() on the returned pointer when it is
+** no longer required.
+** 
+** If a malloc failure occurs, NULL is returned and the db.mallocFailed
+** flag set.
+*/
+#ifdef SQLITE_ENABLE_STAT3
+char *sqlite3Utf8to16(sqlite3 *db, u8 enc, char *z, int n, int *pnOut){
+  Mem m;
+  memset(&m, 0, sizeof(m));
+  m.db = db;
+  sqlite3VdbeMemSetStr(&m, z, n, SQLITE_UTF8, SQLITE_STATIC);
+  if( sqlite3VdbeMemTranslate(&m, enc) ){
+    assert( db->mallocFailed );
+    return 0;
+  }
+  assert( m.z==m.zMalloc );
+  *pnOut = m.n;
+  return m.z;
+}
+#endif
+
+/*
+** zIn is a UTF-16 encoded unicode string at least nChar characters long.
+** Return the number of bytes in the first nChar unicode characters
+** in pZ.  nChar must be non-negative.
+*/
+int sqlite3Utf16ByteLen(const void *zIn, int nChar){
+  int c;
+  unsigned char const *z = zIn;
+  int n = 0;
+  
+  if( SQLITE_UTF16NATIVE==SQLITE_UTF16BE ){
+    while( n<nChar ){
+      READ_UTF16BE(z, 1, c);
+      n++;
+    }
+  }else{
+    while( n<nChar ){
+      READ_UTF16LE(z, 1, c);
+      n++;
+    }
+  }
+  return (int)(z-(unsigned char const *)zIn);
+}
+
+#if defined(SQLITE_TEST)
+/*
+** This routine is called from the TCL test function "translate_selftest".
+** It checks that the primitives for serializing and deserializing
+** characters in each encoding are inverses of each other.
+*/
+void sqlite3UtfSelfTest(void){
+  unsigned int i, t;
+  unsigned char zBuf[20];
+  unsigned char *z;
+  int n;
+  unsigned int c;
+
+  for(i=0; i<0x00110000; i++){
+    z = zBuf;
+    WRITE_UTF8(z, i);
+    n = (int)(z-zBuf);
+    assert( n>0 && n<=4 );
+    z[0] = 0;
+    z = zBuf;
+    c = sqlite3Utf8Read(z, (const u8**)&z);
+    t = i;
+    if( i>=0xD800 && i<=0xDFFF ) t = 0xFFFD;
+    if( (i&0xFFFFFFFE)==0xFFFE ) t = 0xFFFD;
+    assert( c==t );
+    assert( (z-zBuf)==n );
+  }
+  for(i=0; i<0x00110000; i++){
+    if( i>=0xD800 && i<0xE000 ) continue;
+    z = zBuf;
+    WRITE_UTF16LE(z, i);
+    n = (int)(z-zBuf);
+    assert( n>0 && n<=4 );
+    z[0] = 0;
+    z = zBuf;
+    READ_UTF16LE(z, 1, c);
+    assert( c==i );
+    assert( (z-zBuf)==n );
+  }
+  for(i=0; i<0x00110000; i++){
+    if( i>=0xD800 && i<0xE000 ) continue;
+    z = zBuf;
+    WRITE_UTF16BE(z, i);
+    n = (int)(z-zBuf);
+    assert( n>0 && n<=4 );
+    z[0] = 0;
+    z = zBuf;
+    READ_UTF16BE(z, 1, c);
+    assert( c==i );
+    assert( (z-zBuf)==n );
+  }
+}
+#endif /* SQLITE_TEST */
+#endif /* SQLITE_OMIT_UTF16 */
diff --git a/src/util.c b/src/util.c
new file mode 100644
index 0000000..3356417
--- /dev/null
+++ b/src/util.c
@@ -0,0 +1,1186 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Utility functions used throughout sqlite.
+**
+** This file contains functions for allocating memory, comparing
+** strings, and stuff like that.
+**
+*/
+#include "sqliteInt.h"
+#include <stdarg.h>
+#ifdef SQLITE_HAVE_ISNAN
+# include <math.h>
+#endif
+
+/*
+** Routine needed to support the testcase() macro.
+*/
+#ifdef SQLITE_COVERAGE_TEST
+void sqlite3Coverage(int x){
+  static unsigned dummy = 0;
+  dummy += (unsigned)x;
+}
+#endif
+
+#ifndef SQLITE_OMIT_FLOATING_POINT
+/*
+** Return true if the floating point value is Not a Number (NaN).
+**
+** Use the math library isnan() function if compiled with SQLITE_HAVE_ISNAN.
+** Otherwise, we have our own implementation that works on most systems.
+*/
+int sqlite3IsNaN(double x){
+  int rc;   /* The value return */
+#if !defined(SQLITE_HAVE_ISNAN)
+  /*
+  ** Systems that support the isnan() library function should probably
+  ** make use of it by compiling with -DSQLITE_HAVE_ISNAN.  But we have
+  ** found that many systems do not have a working isnan() function so
+  ** this implementation is provided as an alternative.
+  **
+  ** This NaN test sometimes fails if compiled on GCC with -ffast-math.
+  ** On the other hand, the use of -ffast-math comes with the following
+  ** warning:
+  **
+  **      This option [-ffast-math] should never be turned on by any
+  **      -O option since it can result in incorrect output for programs
+  **      which depend on an exact implementation of IEEE or ISO 
+  **      rules/specifications for math functions.
+  **
+  ** Under MSVC, this NaN test may fail if compiled with a floating-
+  ** point precision mode other than /fp:precise.  From the MSDN 
+  ** documentation:
+  **
+  **      The compiler [with /fp:precise] will properly handle comparisons 
+  **      involving NaN. For example, x != x evaluates to true if x is NaN 
+  **      ...
+  */
+#ifdef __FAST_MATH__
+# error SQLite will not work correctly with the -ffast-math option of GCC.
+#endif
+  volatile double y = x;
+  volatile double z = y;
+  rc = (y!=z);
+#else  /* if defined(SQLITE_HAVE_ISNAN) */
+  rc = isnan(x);
+#endif /* SQLITE_HAVE_ISNAN */
+  testcase( rc );
+  return rc;
+}
+#endif /* SQLITE_OMIT_FLOATING_POINT */
+
+/*
+** Compute a string length that is limited to what can be stored in
+** lower 30 bits of a 32-bit signed integer.
+**
+** The value returned will never be negative.  Nor will it ever be greater
+** than the actual length of the string.  For very long strings (greater
+** than 1GiB) the value returned might be less than the true string length.
+*/
+int sqlite3Strlen30(const char *z){
+  const char *z2 = z;
+  if( z==0 ) return 0;
+  while( *z2 ){ z2++; }
+  return 0x3fffffff & (int)(z2 - z);
+}
+
+/*
+** Set the most recent error code and error string for the sqlite
+** handle "db". The error code is set to "err_code".
+**
+** If it is not NULL, string zFormat specifies the format of the
+** error string in the style of the printf functions: The following
+** format characters are allowed:
+**
+**      %s      Insert a string
+**      %z      A string that should be freed after use
+**      %d      Insert an integer
+**      %T      Insert a token
+**      %S      Insert the first element of a SrcList
+**
+** zFormat and any string tokens that follow it are assumed to be
+** encoded in UTF-8.
+**
+** To clear the most recent error for sqlite handle "db", sqlite3Error
+** should be called with err_code set to SQLITE_OK and zFormat set
+** to NULL.
+*/
+void sqlite3Error(sqlite3 *db, int err_code, const char *zFormat, ...){
+  if( db && (db->pErr || (db->pErr = sqlite3ValueNew(db))!=0) ){
+    db->errCode = err_code;
+    if( zFormat ){
+      char *z;
+      va_list ap;
+      va_start(ap, zFormat);
+      z = sqlite3VMPrintf(db, zFormat, ap);
+      va_end(ap);
+      sqlite3ValueSetStr(db->pErr, -1, z, SQLITE_UTF8, SQLITE_DYNAMIC);
+    }else{
+      sqlite3ValueSetStr(db->pErr, 0, 0, SQLITE_UTF8, SQLITE_STATIC);
+    }
+  }
+}
+
+/*
+** Add an error message to pParse->zErrMsg and increment pParse->nErr.
+** The following formatting characters are allowed:
+**
+**      %s      Insert a string
+**      %z      A string that should be freed after use
+**      %d      Insert an integer
+**      %T      Insert a token
+**      %S      Insert the first element of a SrcList
+**
+** This function should be used to report any error that occurs whilst
+** compiling an SQL statement (i.e. within sqlite3_prepare()). The
+** last thing the sqlite3_prepare() function does is copy the error
+** stored by this function into the database handle using sqlite3Error().
+** Function sqlite3Error() should be used during statement execution
+** (sqlite3_step() etc.).
+*/
+void sqlite3ErrorMsg(Parse *pParse, const char *zFormat, ...){
+  char *zMsg;
+  va_list ap;
+  sqlite3 *db = pParse->db;
+  va_start(ap, zFormat);
+  zMsg = sqlite3VMPrintf(db, zFormat, ap);
+  va_end(ap);
+  if( db->suppressErr ){
+    sqlite3DbFree(db, zMsg);
+  }else{
+    pParse->nErr++;
+    sqlite3DbFree(db, pParse->zErrMsg);
+    pParse->zErrMsg = zMsg;
+    pParse->rc = SQLITE_ERROR;
+  }
+}
+
+/*
+** Convert an SQL-style quoted string into a normal string by removing
+** the quote characters.  The conversion is done in-place.  If the
+** input does not begin with a quote character, then this routine
+** is a no-op.
+**
+** The input string must be zero-terminated.  A new zero-terminator
+** is added to the dequoted string.
+**
+** The return value is -1 if no dequoting occurs or the length of the
+** dequoted string, exclusive of the zero terminator, if dequoting does
+** occur.
+**
+** 2002-Feb-14: This routine is extended to remove MS-Access style
+** brackets from around identifers.  For example:  "[a-b-c]" becomes
+** "a-b-c".
+*/
+int sqlite3Dequote(char *z){
+  char quote;
+  int i, j;
+  if( z==0 ) return -1;
+  quote = z[0];
+  switch( quote ){
+    case '\'':  break;
+    case '"':   break;
+    case '`':   break;                /* For MySQL compatibility */
+    case '[':   quote = ']';  break;  /* For MS SqlServer compatibility */
+    default:    return -1;
+  }
+  for(i=1, j=0; ALWAYS(z[i]); i++){
+    if( z[i]==quote ){
+      if( z[i+1]==quote ){
+        z[j++] = quote;
+        i++;
+      }else{
+        break;
+      }
+    }else{
+      z[j++] = z[i];
+    }
+  }
+  z[j] = 0;
+  return j;
+}
+
+/* Convenient short-hand */
+#define UpperToLower sqlite3UpperToLower
+
+/*
+** Some systems have stricmp().  Others have strcasecmp().  Because
+** there is no consistency, we will define our own.
+**
+** IMPLEMENTATION-OF: R-20522-24639 The sqlite3_strnicmp() API allows
+** applications and extensions to compare the contents of two buffers
+** containing UTF-8 strings in a case-independent fashion, using the same
+** definition of case independence that SQLite uses internally when
+** comparing identifiers.
+*/
+int sqlite3StrICmp(const char *zLeft, const char *zRight){
+  register unsigned char *a, *b;
+  a = (unsigned char *)zLeft;
+  b = (unsigned char *)zRight;
+  while( *a!=0 && UpperToLower[*a]==UpperToLower[*b]){ a++; b++; }
+  return UpperToLower[*a] - UpperToLower[*b];
+}
+int sqlite3_strnicmp(const char *zLeft, const char *zRight, int N){
+  register unsigned char *a, *b;
+  a = (unsigned char *)zLeft;
+  b = (unsigned char *)zRight;
+  while( N-- > 0 && *a!=0 && UpperToLower[*a]==UpperToLower[*b]){ a++; b++; }
+  return N<0 ? 0 : UpperToLower[*a] - UpperToLower[*b];
+}
+
+/*
+** The string z[] is an text representation of a real number.
+** Convert this string to a double and write it into *pResult.
+**
+** The string z[] is length bytes in length (bytes, not characters) and
+** uses the encoding enc.  The string is not necessarily zero-terminated.
+**
+** Return TRUE if the result is a valid real number (or integer) and FALSE
+** if the string is empty or contains extraneous text.  Valid numbers
+** are in one of these formats:
+**
+**    [+-]digits[E[+-]digits]
+**    [+-]digits.[digits][E[+-]digits]
+**    [+-].digits[E[+-]digits]
+**
+** Leading and trailing whitespace is ignored for the purpose of determining
+** validity.
+**
+** If some prefix of the input string is a valid number, this routine
+** returns FALSE but it still converts the prefix and writes the result
+** into *pResult.
+*/
+int sqlite3AtoF(const char *z, double *pResult, int length, u8 enc){
+#ifndef SQLITE_OMIT_FLOATING_POINT
+  int incr = (enc==SQLITE_UTF8?1:2);
+  const char *zEnd = z + length;
+  /* sign * significand * (10 ^ (esign * exponent)) */
+  int sign = 1;    /* sign of significand */
+  i64 s = 0;       /* significand */
+  int d = 0;       /* adjust exponent for shifting decimal point */
+  int esign = 1;   /* sign of exponent */
+  int e = 0;       /* exponent */
+  int eValid = 1;  /* True exponent is either not used or is well-formed */
+  double result;
+  int nDigits = 0;
+
+  *pResult = 0.0;   /* Default return value, in case of an error */
+
+  if( enc==SQLITE_UTF16BE ) z++;
+
+  /* skip leading spaces */
+  while( z<zEnd && sqlite3Isspace(*z) ) z+=incr;
+  if( z>=zEnd ) return 0;
+
+  /* get sign of significand */
+  if( *z=='-' ){
+    sign = -1;
+    z+=incr;
+  }else if( *z=='+' ){
+    z+=incr;
+  }
+
+  /* skip leading zeroes */
+  while( z<zEnd && z[0]=='0' ) z+=incr, nDigits++;
+
+  /* copy max significant digits to significand */
+  while( z<zEnd && sqlite3Isdigit(*z) && s<((LARGEST_INT64-9)/10) ){
+    s = s*10 + (*z - '0');
+    z+=incr, nDigits++;
+  }
+
+  /* skip non-significant significand digits
+  ** (increase exponent by d to shift decimal left) */
+  while( z<zEnd && sqlite3Isdigit(*z) ) z+=incr, nDigits++, d++;
+  if( z>=zEnd ) goto do_atof_calc;
+
+  /* if decimal point is present */
+  if( *z=='.' ){
+    z+=incr;
+    /* copy digits from after decimal to significand
+    ** (decrease exponent by d to shift decimal right) */
+    while( z<zEnd && sqlite3Isdigit(*z) && s<((LARGEST_INT64-9)/10) ){
+      s = s*10 + (*z - '0');
+      z+=incr, nDigits++, d--;
+    }
+    /* skip non-significant digits */
+    while( z<zEnd && sqlite3Isdigit(*z) ) z+=incr, nDigits++;
+  }
+  if( z>=zEnd ) goto do_atof_calc;
+
+  /* if exponent is present */
+  if( *z=='e' || *z=='E' ){
+    z+=incr;
+    eValid = 0;
+    if( z>=zEnd ) goto do_atof_calc;
+    /* get sign of exponent */
+    if( *z=='-' ){
+      esign = -1;
+      z+=incr;
+    }else if( *z=='+' ){
+      z+=incr;
+    }
+    /* copy digits to exponent */
+    while( z<zEnd && sqlite3Isdigit(*z) ){
+      e = e<10000 ? (e*10 + (*z - '0')) : 10000;
+      z+=incr;
+      eValid = 1;
+    }
+  }
+
+  /* skip trailing spaces */
+  if( nDigits && eValid ){
+    while( z<zEnd && sqlite3Isspace(*z) ) z+=incr;
+  }
+
+do_atof_calc:
+  /* adjust exponent by d, and update sign */
+  e = (e*esign) + d;
+  if( e<0 ) {
+    esign = -1;
+    e *= -1;
+  } else {
+    esign = 1;
+  }
+
+  /* if 0 significand */
+  if( !s ) {
+    /* In the IEEE 754 standard, zero is signed.
+    ** Add the sign if we've seen at least one digit */
+    result = (sign<0 && nDigits) ? -(double)0 : (double)0;
+  } else {
+    /* attempt to reduce exponent */
+    if( esign>0 ){
+      while( s<(LARGEST_INT64/10) && e>0 ) e--,s*=10;
+    }else{
+      while( !(s%10) && e>0 ) e--,s/=10;
+    }
+
+    /* adjust the sign of significand */
+    s = sign<0 ? -s : s;
+
+    /* if exponent, scale significand as appropriate
+    ** and store in result. */
+    if( e ){
+      double scale = 1.0;
+      /* attempt to handle extremely small/large numbers better */
+      if( e>307 && e<342 ){
+        while( e%308 ) { scale *= 1.0e+1; e -= 1; }
+        if( esign<0 ){
+          result = s / scale;
+          result /= 1.0e+308;
+        }else{
+          result = s * scale;
+          result *= 1.0e+308;
+        }
+      }else if( e>=342 ){
+        if( esign<0 ){
+          result = 0.0*s;
+        }else{
+          result = 1e308*1e308*s;  /* Infinity */
+        }
+      }else{
+        /* 1.0e+22 is the largest power of 10 than can be 
+        ** represented exactly. */
+        while( e%22 ) { scale *= 1.0e+1; e -= 1; }
+        while( e>0 ) { scale *= 1.0e+22; e -= 22; }
+        if( esign<0 ){
+          result = s / scale;
+        }else{
+          result = s * scale;
+        }
+      }
+    } else {
+      result = (double)s;
+    }
+  }
+
+  /* store the result */
+  *pResult = result;
+
+  /* return true if number and no extra non-whitespace chracters after */
+  return z>=zEnd && nDigits>0 && eValid;
+#else
+  return !sqlite3Atoi64(z, pResult, length, enc);
+#endif /* SQLITE_OMIT_FLOATING_POINT */
+}
+
+/*
+** Compare the 19-character string zNum against the text representation
+** value 2^63:  9223372036854775808.  Return negative, zero, or positive
+** if zNum is less than, equal to, or greater than the string.
+** Note that zNum must contain exactly 19 characters.
+**
+** Unlike memcmp() this routine is guaranteed to return the difference
+** in the values of the last digit if the only difference is in the
+** last digit.  So, for example,
+**
+**      compare2pow63("9223372036854775800", 1)
+**
+** will return -8.
+*/
+static int compare2pow63(const char *zNum, int incr){
+  int c = 0;
+  int i;
+                    /* 012345678901234567 */
+  const char *pow63 = "922337203685477580";
+  for(i=0; c==0 && i<18; i++){
+    c = (zNum[i*incr]-pow63[i])*10;
+  }
+  if( c==0 ){
+    c = zNum[18*incr] - '8';
+    testcase( c==(-1) );
+    testcase( c==0 );
+    testcase( c==(+1) );
+  }
+  return c;
+}
+
+
+/*
+** Convert zNum to a 64-bit signed integer.
+**
+** If the zNum value is representable as a 64-bit twos-complement 
+** integer, then write that value into *pNum and return 0.
+**
+** If zNum is exactly 9223372036854665808, return 2.  This special
+** case is broken out because while 9223372036854665808 cannot be a 
+** signed 64-bit integer, its negative -9223372036854665808 can be.
+**
+** If zNum is too big for a 64-bit integer and is not
+** 9223372036854665808 then return 1.
+**
+** length is the number of bytes in the string (bytes, not characters).
+** The string is not necessarily zero-terminated.  The encoding is
+** given by enc.
+*/
+int sqlite3Atoi64(const char *zNum, i64 *pNum, int length, u8 enc){
+  int incr = (enc==SQLITE_UTF8?1:2);
+  u64 u = 0;
+  int neg = 0; /* assume positive */
+  int i;
+  int c = 0;
+  const char *zStart;
+  const char *zEnd = zNum + length;
+  if( enc==SQLITE_UTF16BE ) zNum++;
+  while( zNum<zEnd && sqlite3Isspace(*zNum) ) zNum+=incr;
+  if( zNum<zEnd ){
+    if( *zNum=='-' ){
+      neg = 1;
+      zNum+=incr;
+    }else if( *zNum=='+' ){
+      zNum+=incr;
+    }
+  }
+  zStart = zNum;
+  while( zNum<zEnd && zNum[0]=='0' ){ zNum+=incr; } /* Skip leading zeros. */
+  for(i=0; &zNum[i]<zEnd && (c=zNum[i])>='0' && c<='9'; i+=incr){
+    u = u*10 + c - '0';
+  }
+  if( u>LARGEST_INT64 ){
+    *pNum = SMALLEST_INT64;
+  }else if( neg ){
+    *pNum = -(i64)u;
+  }else{
+    *pNum = (i64)u;
+  }
+  testcase( i==18 );
+  testcase( i==19 );
+  testcase( i==20 );
+  if( (c!=0 && &zNum[i]<zEnd) || (i==0 && zStart==zNum) || i>19*incr ){
+    /* zNum is empty or contains non-numeric text or is longer
+    ** than 19 digits (thus guaranteeing that it is too large) */
+    return 1;
+  }else if( i<19*incr ){
+    /* Less than 19 digits, so we know that it fits in 64 bits */
+    assert( u<=LARGEST_INT64 );
+    return 0;
+  }else{
+    /* zNum is a 19-digit numbers.  Compare it against 9223372036854775808. */
+    c = compare2pow63(zNum, incr);
+    if( c<0 ){
+      /* zNum is less than 9223372036854775808 so it fits */
+      assert( u<=LARGEST_INT64 );
+      return 0;
+    }else if( c>0 ){
+      /* zNum is greater than 9223372036854775808 so it overflows */
+      return 1;
+    }else{
+      /* zNum is exactly 9223372036854775808.  Fits if negative.  The
+      ** special case 2 overflow if positive */
+      assert( u-1==LARGEST_INT64 );
+      assert( (*pNum)==SMALLEST_INT64 );
+      return neg ? 0 : 2;
+    }
+  }
+}
+
+/*
+** If zNum represents an integer that will fit in 32-bits, then set
+** *pValue to that integer and return true.  Otherwise return false.
+**
+** Any non-numeric characters that following zNum are ignored.
+** This is different from sqlite3Atoi64() which requires the
+** input number to be zero-terminated.
+*/
+int sqlite3GetInt32(const char *zNum, int *pValue){
+  sqlite_int64 v = 0;
+  int i, c;
+  int neg = 0;
+  if( zNum[0]=='-' ){
+    neg = 1;
+    zNum++;
+  }else if( zNum[0]=='+' ){
+    zNum++;
+  }
+  while( zNum[0]=='0' ) zNum++;
+  for(i=0; i<11 && (c = zNum[i] - '0')>=0 && c<=9; i++){
+    v = v*10 + c;
+  }
+
+  /* The longest decimal representation of a 32 bit integer is 10 digits:
+  **
+  **             1234567890
+  **     2^31 -> 2147483648
+  */
+  testcase( i==10 );
+  if( i>10 ){
+    return 0;
+  }
+  testcase( v-neg==2147483647 );
+  if( v-neg>2147483647 ){
+    return 0;
+  }
+  if( neg ){
+    v = -v;
+  }
+  *pValue = (int)v;
+  return 1;
+}
+
+/*
+** Return a 32-bit integer value extracted from a string.  If the
+** string is not an integer, just return 0.
+*/
+int sqlite3Atoi(const char *z){
+  int x = 0;
+  if( z ) sqlite3GetInt32(z, &x);
+  return x;
+}
+
+/*
+** The variable-length integer encoding is as follows:
+**
+** KEY:
+**         A = 0xxxxxxx    7 bits of data and one flag bit
+**         B = 1xxxxxxx    7 bits of data and one flag bit
+**         C = xxxxxxxx    8 bits of data
+**
+**  7 bits - A
+** 14 bits - BA
+** 21 bits - BBA
+** 28 bits - BBBA
+** 35 bits - BBBBA
+** 42 bits - BBBBBA
+** 49 bits - BBBBBBA
+** 56 bits - BBBBBBBA
+** 64 bits - BBBBBBBBC
+*/
+
+/*
+** Write a 64-bit variable-length integer to memory starting at p[0].
+** The length of data write will be between 1 and 9 bytes.  The number
+** of bytes written is returned.
+**
+** A variable-length integer consists of the lower 7 bits of each byte
+** for all bytes that have the 8th bit set and one byte with the 8th
+** bit clear.  Except, if we get to the 9th byte, it stores the full
+** 8 bits and is the last byte.
+*/
+int sqlite3PutVarint(unsigned char *p, u64 v){
+  int i, j, n;
+  u8 buf[10];
+  if( v & (((u64)0xff000000)<<32) ){
+    p[8] = (u8)v;
+    v >>= 8;
+    for(i=7; i>=0; i--){
+      p[i] = (u8)((v & 0x7f) | 0x80);
+      v >>= 7;
+    }
+    return 9;
+  }    
+  n = 0;
+  do{
+    buf[n++] = (u8)((v & 0x7f) | 0x80);
+    v >>= 7;
+  }while( v!=0 );
+  buf[0] &= 0x7f;
+  assert( n<=9 );
+  for(i=0, j=n-1; j>=0; j--, i++){
+    p[i] = buf[j];
+  }
+  return n;
+}
+
+/*
+** This routine is a faster version of sqlite3PutVarint() that only
+** works for 32-bit positive integers and which is optimized for
+** the common case of small integers.  A MACRO version, putVarint32,
+** is provided which inlines the single-byte case.  All code should use
+** the MACRO version as this function assumes the single-byte case has
+** already been handled.
+*/
+int sqlite3PutVarint32(unsigned char *p, u32 v){
+#ifndef putVarint32
+  if( (v & ~0x7f)==0 ){
+    p[0] = v;
+    return 1;
+  }
+#endif
+  if( (v & ~0x3fff)==0 ){
+    p[0] = (u8)((v>>7) | 0x80);
+    p[1] = (u8)(v & 0x7f);
+    return 2;
+  }
+  return sqlite3PutVarint(p, v);
+}
+
+/*
+** Bitmasks used by sqlite3GetVarint().  These precomputed constants
+** are defined here rather than simply putting the constant expressions
+** inline in order to work around bugs in the RVT compiler.
+**
+** SLOT_2_0     A mask for  (0x7f<<14) | 0x7f
+**
+** SLOT_4_2_0   A mask for  (0x7f<<28) | SLOT_2_0
+*/
+#define SLOT_2_0     0x001fc07f
+#define SLOT_4_2_0   0xf01fc07f
+
+
+/*
+** Read a 64-bit variable-length integer from memory starting at p[0].
+** Return the number of bytes read.  The value is stored in *v.
+*/
+u8 sqlite3GetVarint(const unsigned char *p, u64 *v){
+  u32 a,b,s;
+
+  a = *p;
+  /* a: p0 (unmasked) */
+  if (!(a&0x80))
+  {
+    *v = a;
+    return 1;
+  }
+
+  p++;
+  b = *p;
+  /* b: p1 (unmasked) */
+  if (!(b&0x80))
+  {
+    a &= 0x7f;
+    a = a<<7;
+    a |= b;
+    *v = a;
+    return 2;
+  }
+
+  /* Verify that constants are precomputed correctly */
+  assert( SLOT_2_0 == ((0x7f<<14) | (0x7f)) );
+  assert( SLOT_4_2_0 == ((0xfU<<28) | (0x7f<<14) | (0x7f)) );
+
+  p++;
+  a = a<<14;
+  a |= *p;
+  /* a: p0<<14 | p2 (unmasked) */
+  if (!(a&0x80))
+  {
+    a &= SLOT_2_0;
+    b &= 0x7f;
+    b = b<<7;
+    a |= b;
+    *v = a;
+    return 3;
+  }
+
+  /* CSE1 from below */
+  a &= SLOT_2_0;
+  p++;
+  b = b<<14;
+  b |= *p;
+  /* b: p1<<14 | p3 (unmasked) */
+  if (!(b&0x80))
+  {
+    b &= SLOT_2_0;
+    /* moved CSE1 up */
+    /* a &= (0x7f<<14)|(0x7f); */
+    a = a<<7;
+    a |= b;
+    *v = a;
+    return 4;
+  }
+
+  /* a: p0<<14 | p2 (masked) */
+  /* b: p1<<14 | p3 (unmasked) */
+  /* 1:save off p0<<21 | p1<<14 | p2<<7 | p3 (masked) */
+  /* moved CSE1 up */
+  /* a &= (0x7f<<14)|(0x7f); */
+  b &= SLOT_2_0;
+  s = a;
+  /* s: p0<<14 | p2 (masked) */
+
+  p++;
+  a = a<<14;
+  a |= *p;
+  /* a: p0<<28 | p2<<14 | p4 (unmasked) */
+  if (!(a&0x80))
+  {
+    /* we can skip these cause they were (effectively) done above in calc'ing s */
+    /* a &= (0x7f<<28)|(0x7f<<14)|(0x7f); */
+    /* b &= (0x7f<<14)|(0x7f); */
+    b = b<<7;
+    a |= b;
+    s = s>>18;
+    *v = ((u64)s)<<32 | a;
+    return 5;
+  }
+
+  /* 2:save off p0<<21 | p1<<14 | p2<<7 | p3 (masked) */
+  s = s<<7;
+  s |= b;
+  /* s: p0<<21 | p1<<14 | p2<<7 | p3 (masked) */
+
+  p++;
+  b = b<<14;
+  b |= *p;
+  /* b: p1<<28 | p3<<14 | p5 (unmasked) */
+  if (!(b&0x80))
+  {
+    /* we can skip this cause it was (effectively) done above in calc'ing s */
+    /* b &= (0x7f<<28)|(0x7f<<14)|(0x7f); */
+    a &= SLOT_2_0;
+    a = a<<7;
+    a |= b;
+    s = s>>18;
+    *v = ((u64)s)<<32 | a;
+    return 6;
+  }
+
+  p++;
+  a = a<<14;
+  a |= *p;
+  /* a: p2<<28 | p4<<14 | p6 (unmasked) */
+  if (!(a&0x80))
+  {
+    a &= SLOT_4_2_0;
+    b &= SLOT_2_0;
+    b = b<<7;
+    a |= b;
+    s = s>>11;
+    *v = ((u64)s)<<32 | a;
+    return 7;
+  }
+
+  /* CSE2 from below */
+  a &= SLOT_2_0;
+  p++;
+  b = b<<14;
+  b |= *p;
+  /* b: p3<<28 | p5<<14 | p7 (unmasked) */
+  if (!(b&0x80))
+  {
+    b &= SLOT_4_2_0;
+    /* moved CSE2 up */
+    /* a &= (0x7f<<14)|(0x7f); */
+    a = a<<7;
+    a |= b;
+    s = s>>4;
+    *v = ((u64)s)<<32 | a;
+    return 8;
+  }
+
+  p++;
+  a = a<<15;
+  a |= *p;
+  /* a: p4<<29 | p6<<15 | p8 (unmasked) */
+
+  /* moved CSE2 up */
+  /* a &= (0x7f<<29)|(0x7f<<15)|(0xff); */
+  b &= SLOT_2_0;
+  b = b<<8;
+  a |= b;
+
+  s = s<<4;
+  b = p[-4];
+  b &= 0x7f;
+  b = b>>3;
+  s |= b;
+
+  *v = ((u64)s)<<32 | a;
+
+  return 9;
+}
+
+/*
+** Read a 32-bit variable-length integer from memory starting at p[0].
+** Return the number of bytes read.  The value is stored in *v.
+**
+** If the varint stored in p[0] is larger than can fit in a 32-bit unsigned
+** integer, then set *v to 0xffffffff.
+**
+** A MACRO version, getVarint32, is provided which inlines the 
+** single-byte case.  All code should use the MACRO version as 
+** this function assumes the single-byte case has already been handled.
+*/
+u8 sqlite3GetVarint32(const unsigned char *p, u32 *v){
+  u32 a,b;
+
+  /* The 1-byte case.  Overwhelmingly the most common.  Handled inline
+  ** by the getVarin32() macro */
+  a = *p;
+  /* a: p0 (unmasked) */
+#ifndef getVarint32
+  if (!(a&0x80))
+  {
+    /* Values between 0 and 127 */
+    *v = a;
+    return 1;
+  }
+#endif
+
+  /* The 2-byte case */
+  p++;
+  b = *p;
+  /* b: p1 (unmasked) */
+  if (!(b&0x80))
+  {
+    /* Values between 128 and 16383 */
+    a &= 0x7f;
+    a = a<<7;
+    *v = a | b;
+    return 2;
+  }
+
+  /* The 3-byte case */
+  p++;
+  a = a<<14;
+  a |= *p;
+  /* a: p0<<14 | p2 (unmasked) */
+  if (!(a&0x80))
+  {
+    /* Values between 16384 and 2097151 */
+    a &= (0x7f<<14)|(0x7f);
+    b &= 0x7f;
+    b = b<<7;
+    *v = a | b;
+    return 3;
+  }
+
+  /* A 32-bit varint is used to store size information in btrees.
+  ** Objects are rarely larger than 2MiB limit of a 3-byte varint.
+  ** A 3-byte varint is sufficient, for example, to record the size
+  ** of a 1048569-byte BLOB or string.
+  **
+  ** We only unroll the first 1-, 2-, and 3- byte cases.  The very
+  ** rare larger cases can be handled by the slower 64-bit varint
+  ** routine.
+  */
+#if 1
+  {
+    u64 v64;
+    u8 n;
+
+    p -= 2;
+    n = sqlite3GetVarint(p, &v64);
+    assert( n>3 && n<=9 );
+    if( (v64 & SQLITE_MAX_U32)!=v64 ){
+      *v = 0xffffffff;
+    }else{
+      *v = (u32)v64;
+    }
+    return n;
+  }
+
+#else
+  /* For following code (kept for historical record only) shows an
+  ** unrolling for the 3- and 4-byte varint cases.  This code is
+  ** slightly faster, but it is also larger and much harder to test.
+  */
+  p++;
+  b = b<<14;
+  b |= *p;
+  /* b: p1<<14 | p3 (unmasked) */
+  if (!(b&0x80))
+  {
+    /* Values between 2097152 and 268435455 */
+    b &= (0x7f<<14)|(0x7f);
+    a &= (0x7f<<14)|(0x7f);
+    a = a<<7;
+    *v = a | b;
+    return 4;
+  }
+
+  p++;
+  a = a<<14;
+  a |= *p;
+  /* a: p0<<28 | p2<<14 | p4 (unmasked) */
+  if (!(a&0x80))
+  {
+    /* Values  between 268435456 and 34359738367 */
+    a &= SLOT_4_2_0;
+    b &= SLOT_4_2_0;
+    b = b<<7;
+    *v = a | b;
+    return 5;
+  }
+
+  /* We can only reach this point when reading a corrupt database
+  ** file.  In that case we are not in any hurry.  Use the (relatively
+  ** slow) general-purpose sqlite3GetVarint() routine to extract the
+  ** value. */
+  {
+    u64 v64;
+    u8 n;
+
+    p -= 4;
+    n = sqlite3GetVarint(p, &v64);
+    assert( n>5 && n<=9 );
+    *v = (u32)v64;
+    return n;
+  }
+#endif
+}
+
+/*
+** Return the number of bytes that will be needed to store the given
+** 64-bit integer.
+*/
+int sqlite3VarintLen(u64 v){
+  int i = 0;
+  do{
+    i++;
+    v >>= 7;
+  }while( v!=0 && ALWAYS(i<9) );
+  return i;
+}
+
+
+/*
+** Read or write a four-byte big-endian integer value.
+*/
+u32 sqlite3Get4byte(const u8 *p){
+  return (p[0]<<24) | (p[1]<<16) | (p[2]<<8) | p[3];
+}
+void sqlite3Put4byte(unsigned char *p, u32 v){
+  p[0] = (u8)(v>>24);
+  p[1] = (u8)(v>>16);
+  p[2] = (u8)(v>>8);
+  p[3] = (u8)v;
+}
+
+
+
+/*
+** Translate a single byte of Hex into an integer.
+** This routine only works if h really is a valid hexadecimal
+** character:  0..9a..fA..F
+*/
+u8 sqlite3HexToInt(int h){
+  assert( (h>='0' && h<='9') ||  (h>='a' && h<='f') ||  (h>='A' && h<='F') );
+#ifdef SQLITE_ASCII
+  h += 9*(1&(h>>6));
+#endif
+#ifdef SQLITE_EBCDIC
+  h += 9*(1&~(h>>4));
+#endif
+  return (u8)(h & 0xf);
+}
+
+#if !defined(SQLITE_OMIT_BLOB_LITERAL) || defined(SQLITE_HAS_CODEC)
+/*
+** Convert a BLOB literal of the form "x'hhhhhh'" into its binary
+** value.  Return a pointer to its binary value.  Space to hold the
+** binary value has been obtained from malloc and must be freed by
+** the calling routine.
+*/
+void *sqlite3HexToBlob(sqlite3 *db, const char *z, int n){
+  char *zBlob;
+  int i;
+
+  zBlob = (char *)sqlite3DbMallocRaw(db, n/2 + 1);
+  n--;
+  if( zBlob ){
+    for(i=0; i<n; i+=2){
+      zBlob[i/2] = (sqlite3HexToInt(z[i])<<4) | sqlite3HexToInt(z[i+1]);
+    }
+    zBlob[i/2] = 0;
+  }
+  return zBlob;
+}
+#endif /* !SQLITE_OMIT_BLOB_LITERAL || SQLITE_HAS_CODEC */
+
+/*
+** Log an error that is an API call on a connection pointer that should
+** not have been used.  The "type" of connection pointer is given as the
+** argument.  The zType is a word like "NULL" or "closed" or "invalid".
+*/
+static void logBadConnection(const char *zType){
+  sqlite3_log(SQLITE_MISUSE, 
+     "API call with %s database connection pointer",
+     zType
+  );
+}
+
+/*
+** Check to make sure we have a valid db pointer.  This test is not
+** foolproof but it does provide some measure of protection against
+** misuse of the interface such as passing in db pointers that are
+** NULL or which have been previously closed.  If this routine returns
+** 1 it means that the db pointer is valid and 0 if it should not be
+** dereferenced for any reason.  The calling function should invoke
+** SQLITE_MISUSE immediately.
+**
+** sqlite3SafetyCheckOk() requires that the db pointer be valid for
+** use.  sqlite3SafetyCheckSickOrOk() allows a db pointer that failed to
+** open properly and is not fit for general use but which can be
+** used as an argument to sqlite3_errmsg() or sqlite3_close().
+*/
+int sqlite3SafetyCheckOk(sqlite3 *db){
+  u32 magic;
+  if( db==0 ){
+    logBadConnection("NULL");
+    return 0;
+  }
+  magic = db->magic;
+  if( magic!=SQLITE_MAGIC_OPEN ){
+    if( sqlite3SafetyCheckSickOrOk(db) ){
+      testcase( sqlite3GlobalConfig.xLog!=0 );
+      logBadConnection("unopened");
+    }
+    return 0;
+  }else{
+    return 1;
+  }
+}
+int sqlite3SafetyCheckSickOrOk(sqlite3 *db){
+  u32 magic;
+  magic = db->magic;
+  if( magic!=SQLITE_MAGIC_SICK &&
+      magic!=SQLITE_MAGIC_OPEN &&
+      magic!=SQLITE_MAGIC_BUSY ){
+    testcase( sqlite3GlobalConfig.xLog!=0 );
+    logBadConnection("invalid");
+    return 0;
+  }else{
+    return 1;
+  }
+}
+
+/*
+** Attempt to add, substract, or multiply the 64-bit signed value iB against
+** the other 64-bit signed integer at *pA and store the result in *pA.
+** Return 0 on success.  Or if the operation would have resulted in an
+** overflow, leave *pA unchanged and return 1.
+*/
+int sqlite3AddInt64(i64 *pA, i64 iB){
+  i64 iA = *pA;
+  testcase( iA==0 ); testcase( iA==1 );
+  testcase( iB==-1 ); testcase( iB==0 );
+  if( iB>=0 ){
+    testcase( iA>0 && LARGEST_INT64 - iA == iB );
+    testcase( iA>0 && LARGEST_INT64 - iA == iB - 1 );
+    if( iA>0 && LARGEST_INT64 - iA < iB ) return 1;
+    *pA += iB;
+  }else{
+    testcase( iA<0 && -(iA + LARGEST_INT64) == iB + 1 );
+    testcase( iA<0 && -(iA + LARGEST_INT64) == iB + 2 );
+    if( iA<0 && -(iA + LARGEST_INT64) > iB + 1 ) return 1;
+    *pA += iB;
+  }
+  return 0; 
+}
+int sqlite3SubInt64(i64 *pA, i64 iB){
+  testcase( iB==SMALLEST_INT64+1 );
+  if( iB==SMALLEST_INT64 ){
+    testcase( (*pA)==(-1) ); testcase( (*pA)==0 );
+    if( (*pA)>=0 ) return 1;
+    *pA -= iB;
+    return 0;
+  }else{
+    return sqlite3AddInt64(pA, -iB);
+  }
+}
+#define TWOPOWER32 (((i64)1)<<32)
+#define TWOPOWER31 (((i64)1)<<31)
+int sqlite3MulInt64(i64 *pA, i64 iB){
+  i64 iA = *pA;
+  i64 iA1, iA0, iB1, iB0, r;
+
+  iA1 = iA/TWOPOWER32;
+  iA0 = iA % TWOPOWER32;
+  iB1 = iB/TWOPOWER32;
+  iB0 = iB % TWOPOWER32;
+  if( iA1*iB1 != 0 ) return 1;
+  assert( iA1*iB0==0 || iA0*iB1==0 );
+  r = iA1*iB0 + iA0*iB1;
+  testcase( r==(-TWOPOWER31)-1 );
+  testcase( r==(-TWOPOWER31) );
+  testcase( r==TWOPOWER31 );
+  testcase( r==TWOPOWER31-1 );
+  if( r<(-TWOPOWER31) || r>=TWOPOWER31 ) return 1;
+  r *= TWOPOWER32;
+  if( sqlite3AddInt64(&r, iA0*iB0) ) return 1;
+  *pA = r;
+  return 0;
+}
+
+/*
+** Compute the absolute value of a 32-bit signed integer, of possible.  Or 
+** if the integer has a value of -2147483648, return +2147483647
+*/
+int sqlite3AbsInt32(int x){
+  if( x>=0 ) return x;
+  if( x==(int)0x80000000 ) return 0x7fffffff;
+  return -x;
+}
+
+#ifdef SQLITE_ENABLE_8_3_NAMES
+/*
+** If SQLITE_ENABLE_8_3_NAMES is set at compile-time and if the database
+** filename in zBaseFilename is a URI with the "8_3_names=1" parameter and
+** if filename in z[] has a suffix (a.k.a. "extension") that is longer than
+** three characters, then shorten the suffix on z[] to be the last three
+** characters of the original suffix.
+**
+** If SQLITE_ENABLE_8_3_NAMES is set to 2 at compile-time, then always
+** do the suffix shortening regardless of URI parameter.
+**
+** Examples:
+**
+**     test.db-journal    =>   test.nal
+**     test.db-wal        =>   test.wal
+**     test.db-shm        =>   test.shm
+*/
+void sqlite3FileSuffix3(const char *zBaseFilename, char *z){
+#if SQLITE_ENABLE_8_3_NAMES<2
+  const char *zOk;
+  zOk = sqlite3_uri_parameter(zBaseFilename, "8_3_names");
+  if( zOk && sqlite3GetBoolean(zOk) )
+#endif
+  {
+    int i, sz;
+    sz = sqlite3Strlen30(z);
+    for(i=sz-1; i>0 && z[i]!='/' && z[i]!='.'; i--){}
+    if( z[i]=='.' && ALWAYS(sz>i+4) ) memcpy(&z[i+1], &z[sz-3], 4);
+  }
+}
+#endif
diff --git a/src/vacuum.c b/src/vacuum.c
new file mode 100644
index 0000000..58a3c9d
--- /dev/null
+++ b/src/vacuum.c
@@ -0,0 +1,343 @@
+/*
+** 2003 April 6
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains code used to implement the VACUUM command.
+**
+** Most of the code in this file may be omitted by defining the
+** SQLITE_OMIT_VACUUM macro.
+*/
+#include "sqliteInt.h"
+#include "vdbeInt.h"
+
+#if !defined(SQLITE_OMIT_VACUUM) && !defined(SQLITE_OMIT_ATTACH)
+/*
+** Finalize a prepared statement.  If there was an error, store the
+** text of the error message in *pzErrMsg.  Return the result code.
+*/
+static int vacuumFinalize(sqlite3 *db, sqlite3_stmt *pStmt, char **pzErrMsg){
+  int rc;
+  rc = sqlite3VdbeFinalize((Vdbe*)pStmt);
+  if( rc ){
+    sqlite3SetString(pzErrMsg, db, sqlite3_errmsg(db));
+  }
+  return rc;
+}
+
+/*
+** Execute zSql on database db. Return an error code.
+*/
+static int execSql(sqlite3 *db, char **pzErrMsg, const char *zSql){
+  sqlite3_stmt *pStmt;
+  VVA_ONLY( int rc; )
+  if( !zSql ){
+    return SQLITE_NOMEM;
+  }
+  if( SQLITE_OK!=sqlite3_prepare(db, zSql, -1, &pStmt, 0) ){
+    sqlite3SetString(pzErrMsg, db, sqlite3_errmsg(db));
+    return sqlite3_errcode(db);
+  }
+  VVA_ONLY( rc = ) sqlite3_step(pStmt);
+  assert( rc!=SQLITE_ROW || (db->flags&SQLITE_CountRows) );
+  return vacuumFinalize(db, pStmt, pzErrMsg);
+}
+
+/*
+** Execute zSql on database db. The statement returns exactly
+** one column. Execute this as SQL on the same database.
+*/
+static int execExecSql(sqlite3 *db, char **pzErrMsg, const char *zSql){
+  sqlite3_stmt *pStmt;
+  int rc;
+
+  rc = sqlite3_prepare(db, zSql, -1, &pStmt, 0);
+  if( rc!=SQLITE_OK ) return rc;
+
+  while( SQLITE_ROW==sqlite3_step(pStmt) ){
+    rc = execSql(db, pzErrMsg, (char*)sqlite3_column_text(pStmt, 0));
+    if( rc!=SQLITE_OK ){
+      vacuumFinalize(db, pStmt, pzErrMsg);
+      return rc;
+    }
+  }
+
+  return vacuumFinalize(db, pStmt, pzErrMsg);
+}
+
+/*
+** The non-standard VACUUM command is used to clean up the database,
+** collapse free space, etc.  It is modelled after the VACUUM command
+** in PostgreSQL.
+**
+** In version 1.0.x of SQLite, the VACUUM command would call
+** gdbm_reorganize() on all the database tables.  But beginning
+** with 2.0.0, SQLite no longer uses GDBM so this command has
+** become a no-op.
+*/
+void sqlite3Vacuum(Parse *pParse){
+  Vdbe *v = sqlite3GetVdbe(pParse);
+  if( v ){
+    sqlite3VdbeAddOp2(v, OP_Vacuum, 0, 0);
+  }
+  return;
+}
+
+/*
+** This routine implements the OP_Vacuum opcode of the VDBE.
+*/
+int sqlite3RunVacuum(char **pzErrMsg, sqlite3 *db){
+  int rc = SQLITE_OK;     /* Return code from service routines */
+  Btree *pMain;           /* The database being vacuumed */
+  Btree *pTemp;           /* The temporary database we vacuum into */
+  char *zSql = 0;         /* SQL statements */
+  int saved_flags;        /* Saved value of the db->flags */
+  int saved_nChange;      /* Saved value of db->nChange */
+  int saved_nTotalChange; /* Saved value of db->nTotalChange */
+  void (*saved_xTrace)(void*,const char*);  /* Saved db->xTrace */
+  Db *pDb = 0;            /* Database to detach at end of vacuum */
+  int isMemDb;            /* True if vacuuming a :memory: database */
+  int nRes;               /* Bytes of reserved space at the end of each page */
+  int nDb;                /* Number of attached databases */
+
+  if( !db->autoCommit ){
+    sqlite3SetString(pzErrMsg, db, "cannot VACUUM from within a transaction");
+    return SQLITE_ERROR;
+  }
+  if( db->activeVdbeCnt>1 ){
+    sqlite3SetString(pzErrMsg, db,"cannot VACUUM - SQL statements in progress");
+    return SQLITE_ERROR;
+  }
+
+  /* Save the current value of the database flags so that it can be 
+  ** restored before returning. Then set the writable-schema flag, and
+  ** disable CHECK and foreign key constraints.  */
+  saved_flags = db->flags;
+  saved_nChange = db->nChange;
+  saved_nTotalChange = db->nTotalChange;
+  saved_xTrace = db->xTrace;
+  db->flags |= SQLITE_WriteSchema | SQLITE_IgnoreChecks | SQLITE_PreferBuiltin;
+  db->flags &= ~(SQLITE_ForeignKeys | SQLITE_ReverseOrder);
+  db->xTrace = 0;
+
+  pMain = db->aDb[0].pBt;
+  isMemDb = sqlite3PagerIsMemdb(sqlite3BtreePager(pMain));
+
+  /* Attach the temporary database as 'vacuum_db'. The synchronous pragma
+  ** can be set to 'off' for this file, as it is not recovered if a crash
+  ** occurs anyway. The integrity of the database is maintained by a
+  ** (possibly synchronous) transaction opened on the main database before
+  ** sqlite3BtreeCopyFile() is called.
+  **
+  ** An optimisation would be to use a non-journaled pager.
+  ** (Later:) I tried setting "PRAGMA vacuum_db.journal_mode=OFF" but
+  ** that actually made the VACUUM run slower.  Very little journalling
+  ** actually occurs when doing a vacuum since the vacuum_db is initially
+  ** empty.  Only the journal header is written.  Apparently it takes more
+  ** time to parse and run the PRAGMA to turn journalling off than it does
+  ** to write the journal header file.
+  */
+  nDb = db->nDb;
+  if( sqlite3TempInMemory(db) ){
+    zSql = "ATTACH ':memory:' AS vacuum_db;";
+  }else{
+    zSql = "ATTACH '' AS vacuum_db;";
+  }
+  rc = execSql(db, pzErrMsg, zSql);
+  if( db->nDb>nDb ){
+    pDb = &db->aDb[db->nDb-1];
+    assert( strcmp(pDb->zName,"vacuum_db")==0 );
+  }
+  if( rc!=SQLITE_OK ) goto end_of_vacuum;
+  pTemp = db->aDb[db->nDb-1].pBt;
+
+  /* The call to execSql() to attach the temp database has left the file
+  ** locked (as there was more than one active statement when the transaction
+  ** to read the schema was concluded. Unlock it here so that this doesn't
+  ** cause problems for the call to BtreeSetPageSize() below.  */
+  sqlite3BtreeCommit(pTemp);
+
+  nRes = sqlite3BtreeGetReserve(pMain);
+
+  /* A VACUUM cannot change the pagesize of an encrypted database. */
+#ifdef SQLITE_HAS_CODEC
+  if( db->nextPagesize ){
+    extern void sqlite3CodecGetKey(sqlite3*, int, void**, int*);
+    int nKey;
+    char *zKey;
+    sqlite3CodecGetKey(db, 0, (void**)&zKey, &nKey);
+    if( nKey ) db->nextPagesize = 0;
+  }
+#endif
+
+  /* Do not attempt to change the page size for a WAL database */
+  if( sqlite3PagerGetJournalMode(sqlite3BtreePager(pMain))
+                                               ==PAGER_JOURNALMODE_WAL ){
+    db->nextPagesize = 0;
+  }
+
+  if( sqlite3BtreeSetPageSize(pTemp, sqlite3BtreeGetPageSize(pMain), nRes, 0)
+   || (!isMemDb && sqlite3BtreeSetPageSize(pTemp, db->nextPagesize, nRes, 0))
+   || NEVER(db->mallocFailed)
+  ){
+    rc = SQLITE_NOMEM;
+    goto end_of_vacuum;
+  }
+  rc = execSql(db, pzErrMsg, "PRAGMA vacuum_db.synchronous=OFF");
+  if( rc!=SQLITE_OK ){
+    goto end_of_vacuum;
+  }
+
+#ifndef SQLITE_OMIT_AUTOVACUUM
+  sqlite3BtreeSetAutoVacuum(pTemp, db->nextAutovac>=0 ? db->nextAutovac :
+                                           sqlite3BtreeGetAutoVacuum(pMain));
+#endif
+
+  /* Begin a transaction */
+  rc = execSql(db, pzErrMsg, "BEGIN EXCLUSIVE;");
+  if( rc!=SQLITE_OK ) goto end_of_vacuum;
+
+  /* Query the schema of the main database. Create a mirror schema
+  ** in the temporary database.
+  */
+  rc = execExecSql(db, pzErrMsg,
+      "SELECT 'CREATE TABLE vacuum_db.' || substr(sql,14) "
+      "  FROM sqlite_master WHERE type='table' AND name!='sqlite_sequence'"
+      "   AND rootpage>0"
+  );
+  if( rc!=SQLITE_OK ) goto end_of_vacuum;
+  rc = execExecSql(db, pzErrMsg,
+      "SELECT 'CREATE INDEX vacuum_db.' || substr(sql,14)"
+      "  FROM sqlite_master WHERE sql LIKE 'CREATE INDEX %' ");
+  if( rc!=SQLITE_OK ) goto end_of_vacuum;
+  rc = execExecSql(db, pzErrMsg,
+      "SELECT 'CREATE UNIQUE INDEX vacuum_db.' || substr(sql,21) "
+      "  FROM sqlite_master WHERE sql LIKE 'CREATE UNIQUE INDEX %'");
+  if( rc!=SQLITE_OK ) goto end_of_vacuum;
+
+  /* Loop through the tables in the main database. For each, do
+  ** an "INSERT INTO vacuum_db.xxx SELECT * FROM main.xxx;" to copy
+  ** the contents to the temporary database.
+  */
+  rc = execExecSql(db, pzErrMsg,
+      "SELECT 'INSERT INTO vacuum_db.' || quote(name) "
+      "|| ' SELECT * FROM main.' || quote(name) || ';'"
+      "FROM main.sqlite_master "
+      "WHERE type = 'table' AND name!='sqlite_sequence' "
+      "  AND rootpage>0"
+  );
+  if( rc!=SQLITE_OK ) goto end_of_vacuum;
+
+  /* Copy over the sequence table
+  */
+  rc = execExecSql(db, pzErrMsg,
+      "SELECT 'DELETE FROM vacuum_db.' || quote(name) || ';' "
+      "FROM vacuum_db.sqlite_master WHERE name='sqlite_sequence' "
+  );
+  if( rc!=SQLITE_OK ) goto end_of_vacuum;
+  rc = execExecSql(db, pzErrMsg,
+      "SELECT 'INSERT INTO vacuum_db.' || quote(name) "
+      "|| ' SELECT * FROM main.' || quote(name) || ';' "
+      "FROM vacuum_db.sqlite_master WHERE name=='sqlite_sequence';"
+  );
+  if( rc!=SQLITE_OK ) goto end_of_vacuum;
+
+
+  /* Copy the triggers, views, and virtual tables from the main database
+  ** over to the temporary database.  None of these objects has any
+  ** associated storage, so all we have to do is copy their entries
+  ** from the SQLITE_MASTER table.
+  */
+  rc = execSql(db, pzErrMsg,
+      "INSERT INTO vacuum_db.sqlite_master "
+      "  SELECT type, name, tbl_name, rootpage, sql"
+      "    FROM main.sqlite_master"
+      "   WHERE type='view' OR type='trigger'"
+      "      OR (type='table' AND rootpage=0)"
+  );
+  if( rc ) goto end_of_vacuum;
+
+  /* At this point, there is a write transaction open on both the 
+  ** vacuum database and the main database. Assuming no error occurs,
+  ** both transactions are closed by this block - the main database
+  ** transaction by sqlite3BtreeCopyFile() and the other by an explicit
+  ** call to sqlite3BtreeCommit().
+  */
+  {
+    u32 meta;
+    int i;
+
+    /* This array determines which meta meta values are preserved in the
+    ** vacuum.  Even entries are the meta value number and odd entries
+    ** are an increment to apply to the meta value after the vacuum.
+    ** The increment is used to increase the schema cookie so that other
+    ** connections to the same database will know to reread the schema.
+    */
+    static const unsigned char aCopy[] = {
+       BTREE_SCHEMA_VERSION,     1,  /* Add one to the old schema cookie */
+       BTREE_DEFAULT_CACHE_SIZE, 0,  /* Preserve the default page cache size */
+       BTREE_TEXT_ENCODING,      0,  /* Preserve the text encoding */
+       BTREE_USER_VERSION,       0,  /* Preserve the user version */
+    };
+
+    assert( 1==sqlite3BtreeIsInTrans(pTemp) );
+    assert( 1==sqlite3BtreeIsInTrans(pMain) );
+
+    /* Copy Btree meta values */
+    for(i=0; i<ArraySize(aCopy); i+=2){
+      /* GetMeta() and UpdateMeta() cannot fail in this context because
+      ** we already have page 1 loaded into cache and marked dirty. */
+      sqlite3BtreeGetMeta(pMain, aCopy[i], &meta);
+      rc = sqlite3BtreeUpdateMeta(pTemp, aCopy[i], meta+aCopy[i+1]);
+      if( NEVER(rc!=SQLITE_OK) ) goto end_of_vacuum;
+    }
+
+    rc = sqlite3BtreeCopyFile(pMain, pTemp);
+    if( rc!=SQLITE_OK ) goto end_of_vacuum;
+    rc = sqlite3BtreeCommit(pTemp);
+    if( rc!=SQLITE_OK ) goto end_of_vacuum;
+#ifndef SQLITE_OMIT_AUTOVACUUM
+    sqlite3BtreeSetAutoVacuum(pMain, sqlite3BtreeGetAutoVacuum(pTemp));
+#endif
+  }
+
+  assert( rc==SQLITE_OK );
+  rc = sqlite3BtreeSetPageSize(pMain, sqlite3BtreeGetPageSize(pTemp), nRes,1);
+
+end_of_vacuum:
+  /* Restore the original value of db->flags */
+  db->flags = saved_flags;
+  db->nChange = saved_nChange;
+  db->nTotalChange = saved_nTotalChange;
+  db->xTrace = saved_xTrace;
+  sqlite3BtreeSetPageSize(pMain, -1, -1, 1);
+
+  /* Currently there is an SQL level transaction open on the vacuum
+  ** database. No locks are held on any other files (since the main file
+  ** was committed at the btree level). So it safe to end the transaction
+  ** by manually setting the autoCommit flag to true and detaching the
+  ** vacuum database. The vacuum_db journal file is deleted when the pager
+  ** is closed by the DETACH.
+  */
+  db->autoCommit = 1;
+
+  if( pDb ){
+    sqlite3BtreeClose(pDb->pBt);
+    pDb->pBt = 0;
+    pDb->pSchema = 0;
+  }
+
+  /* This both clears the schemas and reduces the size of the db->aDb[]
+  ** array. */ 
+  sqlite3ResetInternalSchema(db, -1);
+
+  return rc;
+}
+
+#endif  /* SQLITE_OMIT_VACUUM && SQLITE_OMIT_ATTACH */
diff --git a/src/vdbe.c b/src/vdbe.c
new file mode 100644
index 0000000..22e6d9c
--- /dev/null
+++ b/src/vdbe.c
@@ -0,0 +1,6158 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** The code in this file implements execution method of the 
+** Virtual Database Engine (VDBE).  A separate file ("vdbeaux.c")
+** handles housekeeping details such as creating and deleting
+** VDBE instances.  This file is solely interested in executing
+** the VDBE program.
+**
+** In the external interface, an "sqlite3_stmt*" is an opaque pointer
+** to a VDBE.
+**
+** The SQL parser generates a program which is then executed by
+** the VDBE to do the work of the SQL statement.  VDBE programs are 
+** similar in form to assembly language.  The program consists of
+** a linear sequence of operations.  Each operation has an opcode 
+** and 5 operands.  Operands P1, P2, and P3 are integers.  Operand P4 
+** is a null-terminated string.  Operand P5 is an unsigned character.
+** Few opcodes use all 5 operands.
+**
+** Computation results are stored on a set of registers numbered beginning
+** with 1 and going up to Vdbe.nMem.  Each register can store
+** either an integer, a null-terminated string, a floating point
+** number, or the SQL "NULL" value.  An implicit conversion from one
+** type to the other occurs as necessary.
+** 
+** Most of the code in this file is taken up by the sqlite3VdbeExec()
+** function which does the work of interpreting a VDBE program.
+** But other routines are also provided to help in building up
+** a program instruction by instruction.
+**
+** Various scripts scan this source file in order to generate HTML
+** documentation, headers files, or other derived files.  The formatting
+** of the code in this file is, therefore, important.  See other comments
+** in this file for details.  If in doubt, do not deviate from existing
+** commenting and indentation practices when changing or adding code.
+*/
+#include "sqliteInt.h"
+#include "vdbeInt.h"
+
+/*
+** Invoke this macro on memory cells just prior to changing the
+** value of the cell.  This macro verifies that shallow copies are
+** not misused.
+*/
+#ifdef SQLITE_DEBUG
+# define memAboutToChange(P,M) sqlite3VdbeMemPrepareToChange(P,M)
+#else
+# define memAboutToChange(P,M)
+#endif
+
+/*
+** The following global variable is incremented every time a cursor
+** moves, either by the OP_SeekXX, OP_Next, or OP_Prev opcodes.  The test
+** procedures use this information to make sure that indices are
+** working correctly.  This variable has no function other than to
+** help verify the correct operation of the library.
+*/
+#ifdef SQLITE_TEST
+int sqlite3_search_count = 0;
+#endif
+
+/*
+** When this global variable is positive, it gets decremented once before
+** each instruction in the VDBE.  When reaches zero, the u1.isInterrupted
+** field of the sqlite3 structure is set in order to simulate and interrupt.
+**
+** This facility is used for testing purposes only.  It does not function
+** in an ordinary build.
+*/
+#ifdef SQLITE_TEST
+int sqlite3_interrupt_count = 0;
+#endif
+
+/*
+** The next global variable is incremented each type the OP_Sort opcode
+** is executed.  The test procedures use this information to make sure that
+** sorting is occurring or not occurring at appropriate times.   This variable
+** has no function other than to help verify the correct operation of the
+** library.
+*/
+#ifdef SQLITE_TEST
+int sqlite3_sort_count = 0;
+#endif
+
+/*
+** The next global variable records the size of the largest MEM_Blob
+** or MEM_Str that has been used by a VDBE opcode.  The test procedures
+** use this information to make sure that the zero-blob functionality
+** is working correctly.   This variable has no function other than to
+** help verify the correct operation of the library.
+*/
+#ifdef SQLITE_TEST
+int sqlite3_max_blobsize = 0;
+static void updateMaxBlobsize(Mem *p){
+  if( (p->flags & (MEM_Str|MEM_Blob))!=0 && p->n>sqlite3_max_blobsize ){
+    sqlite3_max_blobsize = p->n;
+  }
+}
+#endif
+
+/*
+** The next global variable is incremented each type the OP_Found opcode
+** is executed. This is used to test whether or not the foreign key
+** operation implemented using OP_FkIsZero is working. This variable
+** has no function other than to help verify the correct operation of the
+** library.
+*/
+#ifdef SQLITE_TEST
+int sqlite3_found_count = 0;
+#endif
+
+/*
+** Test a register to see if it exceeds the current maximum blob size.
+** If it does, record the new maximum blob size.
+*/
+#if defined(SQLITE_TEST) && !defined(SQLITE_OMIT_BUILTIN_TEST)
+# define UPDATE_MAX_BLOBSIZE(P)  updateMaxBlobsize(P)
+#else
+# define UPDATE_MAX_BLOBSIZE(P)
+#endif
+
+/*
+** Convert the given register into a string if it isn't one
+** already. Return non-zero if a malloc() fails.
+*/
+#define Stringify(P, enc) \
+   if(((P)->flags&(MEM_Str|MEM_Blob))==0 && sqlite3VdbeMemStringify(P,enc)) \
+     { goto no_mem; }
+
+/*
+** An ephemeral string value (signified by the MEM_Ephem flag) contains
+** a pointer to a dynamically allocated string where some other entity
+** is responsible for deallocating that string.  Because the register
+** does not control the string, it might be deleted without the register
+** knowing it.
+**
+** This routine converts an ephemeral string into a dynamically allocated
+** string that the register itself controls.  In other words, it
+** converts an MEM_Ephem string into an MEM_Dyn string.
+*/
+#define Deephemeralize(P) \
+   if( ((P)->flags&MEM_Ephem)!=0 \
+       && sqlite3VdbeMemMakeWriteable(P) ){ goto no_mem;}
+
+/*
+** Call sqlite3VdbeMemExpandBlob() on the supplied value (type Mem*)
+** P if required.
+*/
+#define ExpandBlob(P) (((P)->flags&MEM_Zero)?sqlite3VdbeMemExpandBlob(P):0)
+
+/* Return true if the cursor was opened using the OP_OpenSorter opcode. */
+#ifdef SQLITE_OMIT_MERGE_SORT
+# define isSorter(x) 0
+#else
+# define isSorter(x) ((x)->pSorter!=0)
+#endif
+
+/*
+** Argument pMem points at a register that will be passed to a
+** user-defined function or returned to the user as the result of a query.
+** This routine sets the pMem->type variable used by the sqlite3_value_*() 
+** routines.
+*/
+void sqlite3VdbeMemStoreType(Mem *pMem){
+  int flags = pMem->flags;
+  if( flags & MEM_Null ){
+    pMem->type = SQLITE_NULL;
+  }
+  else if( flags & MEM_Int ){
+    pMem->type = SQLITE_INTEGER;
+  }
+  else if( flags & MEM_Real ){
+    pMem->type = SQLITE_FLOAT;
+  }
+  else if( flags & MEM_Str ){
+    pMem->type = SQLITE_TEXT;
+  }else{
+    pMem->type = SQLITE_BLOB;
+  }
+}
+
+/*
+** Allocate VdbeCursor number iCur.  Return a pointer to it.  Return NULL
+** if we run out of memory.
+*/
+static VdbeCursor *allocateCursor(
+  Vdbe *p,              /* The virtual machine */
+  int iCur,             /* Index of the new VdbeCursor */
+  int nField,           /* Number of fields in the table or index */
+  int iDb,              /* When database the cursor belongs to, or -1 */
+  int isBtreeCursor     /* True for B-Tree.  False for pseudo-table or vtab */
+){
+  /* Find the memory cell that will be used to store the blob of memory
+  ** required for this VdbeCursor structure. It is convenient to use a 
+  ** vdbe memory cell to manage the memory allocation required for a
+  ** VdbeCursor structure for the following reasons:
+  **
+  **   * Sometimes cursor numbers are used for a couple of different
+  **     purposes in a vdbe program. The different uses might require
+  **     different sized allocations. Memory cells provide growable
+  **     allocations.
+  **
+  **   * When using ENABLE_MEMORY_MANAGEMENT, memory cell buffers can
+  **     be freed lazily via the sqlite3_release_memory() API. This
+  **     minimizes the number of malloc calls made by the system.
+  **
+  ** Memory cells for cursors are allocated at the top of the address
+  ** space. Memory cell (p->nMem) corresponds to cursor 0. Space for
+  ** cursor 1 is managed by memory cell (p->nMem-1), etc.
+  */
+  Mem *pMem = &p->aMem[p->nMem-iCur];
+
+  int nByte;
+  VdbeCursor *pCx = 0;
+  nByte = 
+      ROUND8(sizeof(VdbeCursor)) + 
+      (isBtreeCursor?sqlite3BtreeCursorSize():0) + 
+      2*nField*sizeof(u32);
+
+  assert( iCur<p->nCursor );
+  if( p->apCsr[iCur] ){
+    sqlite3VdbeFreeCursor(p, p->apCsr[iCur]);
+    p->apCsr[iCur] = 0;
+  }
+  if( SQLITE_OK==sqlite3VdbeMemGrow(pMem, nByte, 0) ){
+    p->apCsr[iCur] = pCx = (VdbeCursor*)pMem->z;
+    memset(pCx, 0, sizeof(VdbeCursor));
+    pCx->iDb = iDb;
+    pCx->nField = nField;
+    if( nField ){
+      pCx->aType = (u32 *)&pMem->z[ROUND8(sizeof(VdbeCursor))];
+    }
+    if( isBtreeCursor ){
+      pCx->pCursor = (BtCursor*)
+          &pMem->z[ROUND8(sizeof(VdbeCursor))+2*nField*sizeof(u32)];
+      sqlite3BtreeCursorZero(pCx->pCursor);
+    }
+  }
+  return pCx;
+}
+
+/*
+** Try to convert a value into a numeric representation if we can
+** do so without loss of information.  In other words, if the string
+** looks like a number, convert it into a number.  If it does not
+** look like a number, leave it alone.
+*/
+static void applyNumericAffinity(Mem *pRec){
+  if( (pRec->flags & (MEM_Real|MEM_Int))==0 ){
+    double rValue;
+    i64 iValue;
+    u8 enc = pRec->enc;
+    if( (pRec->flags&MEM_Str)==0 ) return;
+    if( sqlite3AtoF(pRec->z, &rValue, pRec->n, enc)==0 ) return;
+    if( 0==sqlite3Atoi64(pRec->z, &iValue, pRec->n, enc) ){
+      pRec->u.i = iValue;
+      pRec->flags |= MEM_Int;
+    }else{
+      pRec->r = rValue;
+      pRec->flags |= MEM_Real;
+    }
+  }
+}
+
+/*
+** Processing is determine by the affinity parameter:
+**
+** SQLITE_AFF_INTEGER:
+** SQLITE_AFF_REAL:
+** SQLITE_AFF_NUMERIC:
+**    Try to convert pRec to an integer representation or a 
+**    floating-point representation if an integer representation
+**    is not possible.  Note that the integer representation is
+**    always preferred, even if the affinity is REAL, because
+**    an integer representation is more space efficient on disk.
+**
+** SQLITE_AFF_TEXT:
+**    Convert pRec to a text representation.
+**
+** SQLITE_AFF_NONE:
+**    No-op.  pRec is unchanged.
+*/
+static void applyAffinity(
+  Mem *pRec,          /* The value to apply affinity to */
+  char affinity,      /* The affinity to be applied */
+  u8 enc              /* Use this text encoding */
+){
+  if( affinity==SQLITE_AFF_TEXT ){
+    /* Only attempt the conversion to TEXT if there is an integer or real
+    ** representation (blob and NULL do not get converted) but no string
+    ** representation.
+    */
+    if( 0==(pRec->flags&MEM_Str) && (pRec->flags&(MEM_Real|MEM_Int)) ){
+      sqlite3VdbeMemStringify(pRec, enc);
+    }
+    pRec->flags &= ~(MEM_Real|MEM_Int);
+  }else if( affinity!=SQLITE_AFF_NONE ){
+    assert( affinity==SQLITE_AFF_INTEGER || affinity==SQLITE_AFF_REAL
+             || affinity==SQLITE_AFF_NUMERIC );
+    applyNumericAffinity(pRec);
+    if( pRec->flags & MEM_Real ){
+      sqlite3VdbeIntegerAffinity(pRec);
+    }
+  }
+}
+
+/*
+** Try to convert the type of a function argument or a result column
+** into a numeric representation.  Use either INTEGER or REAL whichever
+** is appropriate.  But only do the conversion if it is possible without
+** loss of information and return the revised type of the argument.
+*/
+int sqlite3_value_numeric_type(sqlite3_value *pVal){
+  Mem *pMem = (Mem*)pVal;
+  if( pMem->type==SQLITE_TEXT ){
+    applyNumericAffinity(pMem);
+    sqlite3VdbeMemStoreType(pMem);
+  }
+  return pMem->type;
+}
+
+/*
+** Exported version of applyAffinity(). This one works on sqlite3_value*, 
+** not the internal Mem* type.
+*/
+void sqlite3ValueApplyAffinity(
+  sqlite3_value *pVal, 
+  u8 affinity, 
+  u8 enc
+){
+  applyAffinity((Mem *)pVal, affinity, enc);
+}
+
+#ifdef SQLITE_DEBUG
+/*
+** Write a nice string representation of the contents of cell pMem
+** into buffer zBuf, length nBuf.
+*/
+void sqlite3VdbeMemPrettyPrint(Mem *pMem, char *zBuf){
+  char *zCsr = zBuf;
+  int f = pMem->flags;
+
+  static const char *const encnames[] = {"(X)", "(8)", "(16LE)", "(16BE)"};
+
+  if( f&MEM_Blob ){
+    int i;
+    char c;
+    if( f & MEM_Dyn ){
+      c = 'z';
+      assert( (f & (MEM_Static|MEM_Ephem))==0 );
+    }else if( f & MEM_Static ){
+      c = 't';
+      assert( (f & (MEM_Dyn|MEM_Ephem))==0 );
+    }else if( f & MEM_Ephem ){
+      c = 'e';
+      assert( (f & (MEM_Static|MEM_Dyn))==0 );
+    }else{
+      c = 's';
+    }
+
+    sqlite3_snprintf(100, zCsr, "%c", c);
+    zCsr += sqlite3Strlen30(zCsr);
+    sqlite3_snprintf(100, zCsr, "%d[", pMem->n);
+    zCsr += sqlite3Strlen30(zCsr);
+    for(i=0; i<16 && i<pMem->n; i++){
+      sqlite3_snprintf(100, zCsr, "%02X", ((int)pMem->z[i] & 0xFF));
+      zCsr += sqlite3Strlen30(zCsr);
+    }
+    for(i=0; i<16 && i<pMem->n; i++){
+      char z = pMem->z[i];
+      if( z<32 || z>126 ) *zCsr++ = '.';
+      else *zCsr++ = z;
+    }
+
+    sqlite3_snprintf(100, zCsr, "]%s", encnames[pMem->enc]);
+    zCsr += sqlite3Strlen30(zCsr);
+    if( f & MEM_Zero ){
+      sqlite3_snprintf(100, zCsr,"+%dz",pMem->u.nZero);
+      zCsr += sqlite3Strlen30(zCsr);
+    }
+    *zCsr = '\0';
+  }else if( f & MEM_Str ){
+    int j, k;
+    zBuf[0] = ' ';
+    if( f & MEM_Dyn ){
+      zBuf[1] = 'z';
+      assert( (f & (MEM_Static|MEM_Ephem))==0 );
+    }else if( f & MEM_Static ){
+      zBuf[1] = 't';
+      assert( (f & (MEM_Dyn|MEM_Ephem))==0 );
+    }else if( f & MEM_Ephem ){
+      zBuf[1] = 'e';
+      assert( (f & (MEM_Static|MEM_Dyn))==0 );
+    }else{
+      zBuf[1] = 's';
+    }
+    k = 2;
+    sqlite3_snprintf(100, &zBuf[k], "%d", pMem->n);
+    k += sqlite3Strlen30(&zBuf[k]);
+    zBuf[k++] = '[';
+    for(j=0; j<15 && j<pMem->n; j++){
+      u8 c = pMem->z[j];
+      if( c>=0x20 && c<0x7f ){
+        zBuf[k++] = c;
+      }else{
+        zBuf[k++] = '.';
+      }
+    }
+    zBuf[k++] = ']';
+    sqlite3_snprintf(100,&zBuf[k], encnames[pMem->enc]);
+    k += sqlite3Strlen30(&zBuf[k]);
+    zBuf[k++] = 0;
+  }
+}
+#endif
+
+#ifdef SQLITE_DEBUG
+/*
+** Print the value of a register for tracing purposes:
+*/
+static void memTracePrint(FILE *out, Mem *p){
+  if( p->flags & MEM_Null ){
+    fprintf(out, " NULL");
+  }else if( (p->flags & (MEM_Int|MEM_Str))==(MEM_Int|MEM_Str) ){
+    fprintf(out, " si:%lld", p->u.i);
+  }else if( p->flags & MEM_Int ){
+    fprintf(out, " i:%lld", p->u.i);
+#ifndef SQLITE_OMIT_FLOATING_POINT
+  }else if( p->flags & MEM_Real ){
+    fprintf(out, " r:%g", p->r);
+#endif
+  }else if( p->flags & MEM_RowSet ){
+    fprintf(out, " (rowset)");
+  }else{
+    char zBuf[200];
+    sqlite3VdbeMemPrettyPrint(p, zBuf);
+    fprintf(out, " ");
+    fprintf(out, "%s", zBuf);
+  }
+}
+static void registerTrace(FILE *out, int iReg, Mem *p){
+  fprintf(out, "REG[%d] = ", iReg);
+  memTracePrint(out, p);
+  fprintf(out, "\n");
+}
+#endif
+
+#ifdef SQLITE_DEBUG
+#  define REGISTER_TRACE(R,M) if(p->trace)registerTrace(p->trace,R,M)
+#else
+#  define REGISTER_TRACE(R,M)
+#endif
+
+
+#ifdef VDBE_PROFILE
+
+/* 
+** hwtime.h contains inline assembler code for implementing 
+** high-performance timing routines.
+*/
+#include "hwtime.h"
+
+#endif
+
+/*
+** The CHECK_FOR_INTERRUPT macro defined here looks to see if the
+** sqlite3_interrupt() routine has been called.  If it has been, then
+** processing of the VDBE program is interrupted.
+**
+** This macro added to every instruction that does a jump in order to
+** implement a loop.  This test used to be on every single instruction,
+** but that meant we more testing that we needed.  By only testing the
+** flag on jump instructions, we get a (small) speed improvement.
+*/
+#define CHECK_FOR_INTERRUPT \
+   if( db->u1.isInterrupted ) goto abort_due_to_interrupt;
+
+
+#ifndef NDEBUG
+/*
+** This function is only called from within an assert() expression. It
+** checks that the sqlite3.nTransaction variable is correctly set to
+** the number of non-transaction savepoints currently in the 
+** linked list starting at sqlite3.pSavepoint.
+** 
+** Usage:
+**
+**     assert( checkSavepointCount(db) );
+*/
+static int checkSavepointCount(sqlite3 *db){
+  int n = 0;
+  Savepoint *p;
+  for(p=db->pSavepoint; p; p=p->pNext) n++;
+  assert( n==(db->nSavepoint + db->isTransactionSavepoint) );
+  return 1;
+}
+#endif
+
+/*
+** Transfer error message text from an sqlite3_vtab.zErrMsg (text stored
+** in memory obtained from sqlite3_malloc) into a Vdbe.zErrMsg (text stored
+** in memory obtained from sqlite3DbMalloc).
+*/
+static void importVtabErrMsg(Vdbe *p, sqlite3_vtab *pVtab){
+  sqlite3 *db = p->db;
+  sqlite3DbFree(db, p->zErrMsg);
+  p->zErrMsg = sqlite3DbStrDup(db, pVtab->zErrMsg);
+  sqlite3_free(pVtab->zErrMsg);
+  pVtab->zErrMsg = 0;
+}
+
+
+/*
+** Execute as much of a VDBE program as we can then return.
+**
+** sqlite3VdbeMakeReady() must be called before this routine in order to
+** close the program with a final OP_Halt and to set up the callbacks
+** and the error message pointer.
+**
+** Whenever a row or result data is available, this routine will either
+** invoke the result callback (if there is one) or return with
+** SQLITE_ROW.
+**
+** If an attempt is made to open a locked database, then this routine
+** will either invoke the busy callback (if there is one) or it will
+** return SQLITE_BUSY.
+**
+** If an error occurs, an error message is written to memory obtained
+** from sqlite3_malloc() and p->zErrMsg is made to point to that memory.
+** The error code is stored in p->rc and this routine returns SQLITE_ERROR.
+**
+** If the callback ever returns non-zero, then the program exits
+** immediately.  There will be no error message but the p->rc field is
+** set to SQLITE_ABORT and this routine will return SQLITE_ERROR.
+**
+** A memory allocation error causes p->rc to be set to SQLITE_NOMEM and this
+** routine to return SQLITE_ERROR.
+**
+** Other fatal errors return SQLITE_ERROR.
+**
+** After this routine has finished, sqlite3VdbeFinalize() should be
+** used to clean up the mess that was left behind.
+*/
+int sqlite3VdbeExec(
+  Vdbe *p                    /* The VDBE */
+){
+  int pc=0;                  /* The program counter */
+  Op *aOp = p->aOp;          /* Copy of p->aOp */
+  Op *pOp;                   /* Current operation */
+  int rc = SQLITE_OK;        /* Value to return */
+  sqlite3 *db = p->db;       /* The database */
+  u8 resetSchemaOnFault = 0; /* Reset schema after an error if positive */
+  u8 encoding = ENC(db);     /* The database encoding */
+#ifndef SQLITE_OMIT_PROGRESS_CALLBACK
+  int checkProgress;         /* True if progress callbacks are enabled */
+  int nProgressOps = 0;      /* Opcodes executed since progress callback. */
+#endif
+  Mem *aMem = p->aMem;       /* Copy of p->aMem */
+  Mem *pIn1 = 0;             /* 1st input operand */
+  Mem *pIn2 = 0;             /* 2nd input operand */
+  Mem *pIn3 = 0;             /* 3rd input operand */
+  Mem *pOut = 0;             /* Output operand */
+  int iCompare = 0;          /* Result of last OP_Compare operation */
+  int *aPermute = 0;         /* Permutation of columns for OP_Compare */
+  i64 lastRowid = db->lastRowid;  /* Saved value of the last insert ROWID */
+#ifdef VDBE_PROFILE
+  u64 start;                 /* CPU clock count at start of opcode */
+  int origPc;                /* Program counter at start of opcode */
+#endif
+  /*** INSERT STACK UNION HERE ***/
+
+  assert( p->magic==VDBE_MAGIC_RUN );  /* sqlite3_step() verifies this */
+  sqlite3VdbeEnter(p);
+  if( p->rc==SQLITE_NOMEM ){
+    /* This happens if a malloc() inside a call to sqlite3_column_text() or
+    ** sqlite3_column_text16() failed.  */
+    goto no_mem;
+  }
+  assert( p->rc==SQLITE_OK || p->rc==SQLITE_BUSY );
+  p->rc = SQLITE_OK;
+  assert( p->explain==0 );
+  p->pResultSet = 0;
+  db->busyHandler.nBusy = 0;
+  CHECK_FOR_INTERRUPT;
+  sqlite3VdbeIOTraceSql(p);
+#ifndef SQLITE_OMIT_PROGRESS_CALLBACK
+  checkProgress = db->xProgress!=0;
+#endif
+#ifdef SQLITE_DEBUG
+  sqlite3BeginBenignMalloc();
+  if( p->pc==0  && (p->db->flags & SQLITE_VdbeListing)!=0 ){
+    int i;
+    printf("VDBE Program Listing:\n");
+    sqlite3VdbePrintSql(p);
+    for(i=0; i<p->nOp; i++){
+      sqlite3VdbePrintOp(stdout, i, &aOp[i]);
+    }
+  }
+  sqlite3EndBenignMalloc();
+#endif
+  for(pc=p->pc; rc==SQLITE_OK; pc++){
+    assert( pc>=0 && pc<p->nOp );
+    if( db->mallocFailed ) goto no_mem;
+#ifdef VDBE_PROFILE
+    origPc = pc;
+    start = sqlite3Hwtime();
+#endif
+    pOp = &aOp[pc];
+
+    /* Only allow tracing if SQLITE_DEBUG is defined.
+    */
+#ifdef SQLITE_DEBUG
+    if( p->trace ){
+      if( pc==0 ){
+        printf("VDBE Execution Trace:\n");
+        sqlite3VdbePrintSql(p);
+      }
+      sqlite3VdbePrintOp(p->trace, pc, pOp);
+    }
+#endif
+      
+
+    /* Check to see if we need to simulate an interrupt.  This only happens
+    ** if we have a special test build.
+    */
+#ifdef SQLITE_TEST
+    if( sqlite3_interrupt_count>0 ){
+      sqlite3_interrupt_count--;
+      if( sqlite3_interrupt_count==0 ){
+        sqlite3_interrupt(db);
+      }
+    }
+#endif
+
+#ifndef SQLITE_OMIT_PROGRESS_CALLBACK
+    /* Call the progress callback if it is configured and the required number
+    ** of VDBE ops have been executed (either since this invocation of
+    ** sqlite3VdbeExec() or since last time the progress callback was called).
+    ** If the progress callback returns non-zero, exit the virtual machine with
+    ** a return code SQLITE_ABORT.
+    */
+    if( checkProgress ){
+      if( db->nProgressOps==nProgressOps ){
+        int prc;
+        prc = db->xProgress(db->pProgressArg);
+        if( prc!=0 ){
+          rc = SQLITE_INTERRUPT;
+          goto vdbe_error_halt;
+        }
+        nProgressOps = 0;
+      }
+      nProgressOps++;
+    }
+#endif
+
+    /* On any opcode with the "out2-prerelase" tag, free any
+    ** external allocations out of mem[p2] and set mem[p2] to be
+    ** an undefined integer.  Opcodes will either fill in the integer
+    ** value or convert mem[p2] to a different type.
+    */
+    assert( pOp->opflags==sqlite3OpcodeProperty[pOp->opcode] );
+    if( pOp->opflags & OPFLG_OUT2_PRERELEASE ){
+      assert( pOp->p2>0 );
+      assert( pOp->p2<=p->nMem );
+      pOut = &aMem[pOp->p2];
+      memAboutToChange(p, pOut);
+      MemReleaseExt(pOut);
+      pOut->flags = MEM_Int;
+    }
+
+    /* Sanity checking on other operands */
+#ifdef SQLITE_DEBUG
+    if( (pOp->opflags & OPFLG_IN1)!=0 ){
+      assert( pOp->p1>0 );
+      assert( pOp->p1<=p->nMem );
+      assert( memIsValid(&aMem[pOp->p1]) );
+      REGISTER_TRACE(pOp->p1, &aMem[pOp->p1]);
+    }
+    if( (pOp->opflags & OPFLG_IN2)!=0 ){
+      assert( pOp->p2>0 );
+      assert( pOp->p2<=p->nMem );
+      assert( memIsValid(&aMem[pOp->p2]) );
+      REGISTER_TRACE(pOp->p2, &aMem[pOp->p2]);
+    }
+    if( (pOp->opflags & OPFLG_IN3)!=0 ){
+      assert( pOp->p3>0 );
+      assert( pOp->p3<=p->nMem );
+      assert( memIsValid(&aMem[pOp->p3]) );
+      REGISTER_TRACE(pOp->p3, &aMem[pOp->p3]);
+    }
+    if( (pOp->opflags & OPFLG_OUT2)!=0 ){
+      assert( pOp->p2>0 );
+      assert( pOp->p2<=p->nMem );
+      memAboutToChange(p, &aMem[pOp->p2]);
+    }
+    if( (pOp->opflags & OPFLG_OUT3)!=0 ){
+      assert( pOp->p3>0 );
+      assert( pOp->p3<=p->nMem );
+      memAboutToChange(p, &aMem[pOp->p3]);
+    }
+#endif
+  
+    switch( pOp->opcode ){
+
+/*****************************************************************************
+** What follows is a massive switch statement where each case implements a
+** separate instruction in the virtual machine.  If we follow the usual
+** indentation conventions, each case should be indented by 6 spaces.  But
+** that is a lot of wasted space on the left margin.  So the code within
+** the switch statement will break with convention and be flush-left. Another
+** big comment (similar to this one) will mark the point in the code where
+** we transition back to normal indentation.
+**
+** The formatting of each case is important.  The makefile for SQLite
+** generates two C files "opcodes.h" and "opcodes.c" by scanning this
+** file looking for lines that begin with "case OP_".  The opcodes.h files
+** will be filled with #defines that give unique integer values to each
+** opcode and the opcodes.c file is filled with an array of strings where
+** each string is the symbolic name for the corresponding opcode.  If the
+** case statement is followed by a comment of the form "/# same as ... #/"
+** that comment is used to determine the particular value of the opcode.
+**
+** Other keywords in the comment that follows each case are used to
+** construct the OPFLG_INITIALIZER value that initializes opcodeProperty[].
+** Keywords include: in1, in2, in3, out2_prerelease, out2, out3.  See
+** the mkopcodeh.awk script for additional information.
+**
+** Documentation about VDBE opcodes is generated by scanning this file
+** for lines of that contain "Opcode:".  That line and all subsequent
+** comment lines are used in the generation of the opcode.html documentation
+** file.
+**
+** SUMMARY:
+**
+**     Formatting is important to scripts that scan this file.
+**     Do not deviate from the formatting style currently in use.
+**
+*****************************************************************************/
+
+/* Opcode:  Goto * P2 * * *
+**
+** An unconditional jump to address P2.
+** The next instruction executed will be 
+** the one at index P2 from the beginning of
+** the program.
+*/
+case OP_Goto: {             /* jump */
+  CHECK_FOR_INTERRUPT;
+  pc = pOp->p2 - 1;
+  break;
+}
+
+/* Opcode:  Gosub P1 P2 * * *
+**
+** Write the current address onto register P1
+** and then jump to address P2.
+*/
+case OP_Gosub: {            /* jump, in1 */
+  pIn1 = &aMem[pOp->p1];
+  assert( (pIn1->flags & MEM_Dyn)==0 );
+  memAboutToChange(p, pIn1);
+  pIn1->flags = MEM_Int;
+  pIn1->u.i = pc;
+  REGISTER_TRACE(pOp->p1, pIn1);
+  pc = pOp->p2 - 1;
+  break;
+}
+
+/* Opcode:  Return P1 * * * *
+**
+** Jump to the next instruction after the address in register P1.
+*/
+case OP_Return: {           /* in1 */
+  pIn1 = &aMem[pOp->p1];
+  assert( pIn1->flags & MEM_Int );
+  pc = (int)pIn1->u.i;
+  break;
+}
+
+/* Opcode:  Yield P1 * * * *
+**
+** Swap the program counter with the value in register P1.
+*/
+case OP_Yield: {            /* in1 */
+  int pcDest;
+  pIn1 = &aMem[pOp->p1];
+  assert( (pIn1->flags & MEM_Dyn)==0 );
+  pIn1->flags = MEM_Int;
+  pcDest = (int)pIn1->u.i;
+  pIn1->u.i = pc;
+  REGISTER_TRACE(pOp->p1, pIn1);
+  pc = pcDest;
+  break;
+}
+
+/* Opcode:  HaltIfNull  P1 P2 P3 P4 *
+**
+** Check the value in register P3.  If it is NULL then Halt using
+** parameter P1, P2, and P4 as if this were a Halt instruction.  If the
+** value in register P3 is not NULL, then this routine is a no-op.
+*/
+case OP_HaltIfNull: {      /* in3 */
+  pIn3 = &aMem[pOp->p3];
+  if( (pIn3->flags & MEM_Null)==0 ) break;
+  /* Fall through into OP_Halt */
+}
+
+/* Opcode:  Halt P1 P2 * P4 *
+**
+** Exit immediately.  All open cursors, etc are closed
+** automatically.
+**
+** P1 is the result code returned by sqlite3_exec(), sqlite3_reset(),
+** or sqlite3_finalize().  For a normal halt, this should be SQLITE_OK (0).
+** For errors, it can be some other value.  If P1!=0 then P2 will determine
+** whether or not to rollback the current transaction.  Do not rollback
+** if P2==OE_Fail. Do the rollback if P2==OE_Rollback.  If P2==OE_Abort,
+** then back out all changes that have occurred during this execution of the
+** VDBE, but do not rollback the transaction. 
+**
+** If P4 is not null then it is an error message string.
+**
+** There is an implied "Halt 0 0 0" instruction inserted at the very end of
+** every program.  So a jump past the last instruction of the program
+** is the same as executing Halt.
+*/
+case OP_Halt: {
+  if( pOp->p1==SQLITE_OK && p->pFrame ){
+    /* Halt the sub-program. Return control to the parent frame. */
+    VdbeFrame *pFrame = p->pFrame;
+    p->pFrame = pFrame->pParent;
+    p->nFrame--;
+    sqlite3VdbeSetChanges(db, p->nChange);
+    pc = sqlite3VdbeFrameRestore(pFrame);
+    lastRowid = db->lastRowid;
+    if( pOp->p2==OE_Ignore ){
+      /* Instruction pc is the OP_Program that invoked the sub-program 
+      ** currently being halted. If the p2 instruction of this OP_Halt
+      ** instruction is set to OE_Ignore, then the sub-program is throwing
+      ** an IGNORE exception. In this case jump to the address specified
+      ** as the p2 of the calling OP_Program.  */
+      pc = p->aOp[pc].p2-1;
+    }
+    aOp = p->aOp;
+    aMem = p->aMem;
+    break;
+  }
+
+  p->rc = pOp->p1;
+  p->errorAction = (u8)pOp->p2;
+  p->pc = pc;
+  if( pOp->p4.z ){
+    assert( p->rc!=SQLITE_OK );
+    sqlite3SetString(&p->zErrMsg, db, "%s", pOp->p4.z);
+    testcase( sqlite3GlobalConfig.xLog!=0 );
+    sqlite3_log(pOp->p1, "abort at %d in [%s]: %s", pc, p->zSql, pOp->p4.z);
+  }else if( p->rc ){
+    testcase( sqlite3GlobalConfig.xLog!=0 );
+    sqlite3_log(pOp->p1, "constraint failed at %d in [%s]", pc, p->zSql);
+  }
+  rc = sqlite3VdbeHalt(p);
+  assert( rc==SQLITE_BUSY || rc==SQLITE_OK || rc==SQLITE_ERROR );
+  if( rc==SQLITE_BUSY ){
+    p->rc = rc = SQLITE_BUSY;
+  }else{
+    assert( rc==SQLITE_OK || p->rc==SQLITE_CONSTRAINT );
+    assert( rc==SQLITE_OK || db->nDeferredCons>0 );
+    rc = p->rc ? SQLITE_ERROR : SQLITE_DONE;
+  }
+  goto vdbe_return;
+}
+
+/* Opcode: Integer P1 P2 * * *
+**
+** The 32-bit integer value P1 is written into register P2.
+*/
+case OP_Integer: {         /* out2-prerelease */
+  pOut->u.i = pOp->p1;
+  break;
+}
+
+/* Opcode: Int64 * P2 * P4 *
+**
+** P4 is a pointer to a 64-bit integer value.
+** Write that value into register P2.
+*/
+case OP_Int64: {           /* out2-prerelease */
+  assert( pOp->p4.pI64!=0 );
+  pOut->u.i = *pOp->p4.pI64;
+  break;
+}
+
+#ifndef SQLITE_OMIT_FLOATING_POINT
+/* Opcode: Real * P2 * P4 *
+**
+** P4 is a pointer to a 64-bit floating point value.
+** Write that value into register P2.
+*/
+case OP_Real: {            /* same as TK_FLOAT, out2-prerelease */
+  pOut->flags = MEM_Real;
+  assert( !sqlite3IsNaN(*pOp->p4.pReal) );
+  pOut->r = *pOp->p4.pReal;
+  break;
+}
+#endif
+
+/* Opcode: String8 * P2 * P4 *
+**
+** P4 points to a nul terminated UTF-8 string. This opcode is transformed 
+** into an OP_String before it is executed for the first time.
+*/
+case OP_String8: {         /* same as TK_STRING, out2-prerelease */
+  assert( pOp->p4.z!=0 );
+  pOp->opcode = OP_String;
+  pOp->p1 = sqlite3Strlen30(pOp->p4.z);
+
+#ifndef SQLITE_OMIT_UTF16
+  if( encoding!=SQLITE_UTF8 ){
+    rc = sqlite3VdbeMemSetStr(pOut, pOp->p4.z, -1, SQLITE_UTF8, SQLITE_STATIC);
+    if( rc==SQLITE_TOOBIG ) goto too_big;
+    if( SQLITE_OK!=sqlite3VdbeChangeEncoding(pOut, encoding) ) goto no_mem;
+    assert( pOut->zMalloc==pOut->z );
+    assert( pOut->flags & MEM_Dyn );
+    pOut->zMalloc = 0;
+    pOut->flags |= MEM_Static;
+    pOut->flags &= ~MEM_Dyn;
+    if( pOp->p4type==P4_DYNAMIC ){
+      sqlite3DbFree(db, pOp->p4.z);
+    }
+    pOp->p4type = P4_DYNAMIC;
+    pOp->p4.z = pOut->z;
+    pOp->p1 = pOut->n;
+  }
+#endif
+  if( pOp->p1>db->aLimit[SQLITE_LIMIT_LENGTH] ){
+    goto too_big;
+  }
+  /* Fall through to the next case, OP_String */
+}
+  
+/* Opcode: String P1 P2 * P4 *
+**
+** The string value P4 of length P1 (bytes) is stored in register P2.
+*/
+case OP_String: {          /* out2-prerelease */
+  assert( pOp->p4.z!=0 );
+  pOut->flags = MEM_Str|MEM_Static|MEM_Term;
+  pOut->z = pOp->p4.z;
+  pOut->n = pOp->p1;
+  pOut->enc = encoding;
+  UPDATE_MAX_BLOBSIZE(pOut);
+  break;
+}
+
+/* Opcode: Null * P2 * * *
+**
+** Write a NULL into register P2.
+*/
+case OP_Null: {           /* out2-prerelease */
+  pOut->flags = MEM_Null;
+  break;
+}
+
+
+/* Opcode: Blob P1 P2 * P4
+**
+** P4 points to a blob of data P1 bytes long.  Store this
+** blob in register P2.
+*/
+case OP_Blob: {                /* out2-prerelease */
+  assert( pOp->p1 <= SQLITE_MAX_LENGTH );
+  sqlite3VdbeMemSetStr(pOut, pOp->p4.z, pOp->p1, 0, 0);
+  pOut->enc = encoding;
+  UPDATE_MAX_BLOBSIZE(pOut);
+  break;
+}
+
+/* Opcode: Variable P1 P2 * P4 *
+**
+** Transfer the values of bound parameter P1 into register P2
+**
+** If the parameter is named, then its name appears in P4 and P3==1.
+** The P4 value is used by sqlite3_bind_parameter_name().
+*/
+case OP_Variable: {            /* out2-prerelease */
+  Mem *pVar;       /* Value being transferred */
+
+  assert( pOp->p1>0 && pOp->p1<=p->nVar );
+  assert( pOp->p4.z==0 || pOp->p4.z==p->azVar[pOp->p1-1] );
+  pVar = &p->aVar[pOp->p1 - 1];
+  if( sqlite3VdbeMemTooBig(pVar) ){
+    goto too_big;
+  }
+  sqlite3VdbeMemShallowCopy(pOut, pVar, MEM_Static);
+  UPDATE_MAX_BLOBSIZE(pOut);
+  break;
+}
+
+/* Opcode: Move P1 P2 P3 * *
+**
+** Move the values in register P1..P1+P3-1 over into
+** registers P2..P2+P3-1.  Registers P1..P1+P1-1 are
+** left holding a NULL.  It is an error for register ranges
+** P1..P1+P3-1 and P2..P2+P3-1 to overlap.
+*/
+case OP_Move: {
+  char *zMalloc;   /* Holding variable for allocated memory */
+  int n;           /* Number of registers left to copy */
+  int p1;          /* Register to copy from */
+  int p2;          /* Register to copy to */
+
+  n = pOp->p3;
+  p1 = pOp->p1;
+  p2 = pOp->p2;
+  assert( n>0 && p1>0 && p2>0 );
+  assert( p1+n<=p2 || p2+n<=p1 );
+
+  pIn1 = &aMem[p1];
+  pOut = &aMem[p2];
+  while( n-- ){
+    assert( pOut<=&aMem[p->nMem] );
+    assert( pIn1<=&aMem[p->nMem] );
+    assert( memIsValid(pIn1) );
+    memAboutToChange(p, pOut);
+    zMalloc = pOut->zMalloc;
+    pOut->zMalloc = 0;
+    sqlite3VdbeMemMove(pOut, pIn1);
+#ifdef SQLITE_DEBUG
+    if( pOut->pScopyFrom>=&aMem[p1] && pOut->pScopyFrom<&aMem[p1+pOp->p3] ){
+      pOut->pScopyFrom += p1 - pOp->p2;
+    }
+#endif
+    pIn1->zMalloc = zMalloc;
+    REGISTER_TRACE(p2++, pOut);
+    pIn1++;
+    pOut++;
+  }
+  break;
+}
+
+/* Opcode: Copy P1 P2 * * *
+**
+** Make a copy of register P1 into register P2.
+**
+** This instruction makes a deep copy of the value.  A duplicate
+** is made of any string or blob constant.  See also OP_SCopy.
+*/
+case OP_Copy: {             /* in1, out2 */
+  pIn1 = &aMem[pOp->p1];
+  pOut = &aMem[pOp->p2];
+  assert( pOut!=pIn1 );
+  sqlite3VdbeMemShallowCopy(pOut, pIn1, MEM_Ephem);
+  Deephemeralize(pOut);
+  REGISTER_TRACE(pOp->p2, pOut);
+  break;
+}
+
+/* Opcode: SCopy P1 P2 * * *
+**
+** Make a shallow copy of register P1 into register P2.
+**
+** This instruction makes a shallow copy of the value.  If the value
+** is a string or blob, then the copy is only a pointer to the
+** original and hence if the original changes so will the copy.
+** Worse, if the original is deallocated, the copy becomes invalid.
+** Thus the program must guarantee that the original will not change
+** during the lifetime of the copy.  Use OP_Copy to make a complete
+** copy.
+*/
+case OP_SCopy: {            /* in1, out2 */
+  pIn1 = &aMem[pOp->p1];
+  pOut = &aMem[pOp->p2];
+  assert( pOut!=pIn1 );
+  sqlite3VdbeMemShallowCopy(pOut, pIn1, MEM_Ephem);
+#ifdef SQLITE_DEBUG
+  if( pOut->pScopyFrom==0 ) pOut->pScopyFrom = pIn1;
+#endif
+  REGISTER_TRACE(pOp->p2, pOut);
+  break;
+}
+
+/* Opcode: ResultRow P1 P2 * * *
+**
+** The registers P1 through P1+P2-1 contain a single row of
+** results. This opcode causes the sqlite3_step() call to terminate
+** with an SQLITE_ROW return code and it sets up the sqlite3_stmt
+** structure to provide access to the top P1 values as the result
+** row.
+*/
+case OP_ResultRow: {
+  Mem *pMem;
+  int i;
+  assert( p->nResColumn==pOp->p2 );
+  assert( pOp->p1>0 );
+  assert( pOp->p1+pOp->p2<=p->nMem+1 );
+
+  /* If this statement has violated immediate foreign key constraints, do
+  ** not return the number of rows modified. And do not RELEASE the statement
+  ** transaction. It needs to be rolled back.  */
+  if( SQLITE_OK!=(rc = sqlite3VdbeCheckFk(p, 0)) ){
+    assert( db->flags&SQLITE_CountRows );
+    assert( p->usesStmtJournal );
+    break;
+  }
+
+  /* If the SQLITE_CountRows flag is set in sqlite3.flags mask, then 
+  ** DML statements invoke this opcode to return the number of rows 
+  ** modified to the user. This is the only way that a VM that
+  ** opens a statement transaction may invoke this opcode.
+  **
+  ** In case this is such a statement, close any statement transaction
+  ** opened by this VM before returning control to the user. This is to
+  ** ensure that statement-transactions are always nested, not overlapping.
+  ** If the open statement-transaction is not closed here, then the user
+  ** may step another VM that opens its own statement transaction. This
+  ** may lead to overlapping statement transactions.
+  **
+  ** The statement transaction is never a top-level transaction.  Hence
+  ** the RELEASE call below can never fail.
+  */
+  assert( p->iStatement==0 || db->flags&SQLITE_CountRows );
+  rc = sqlite3VdbeCloseStatement(p, SAVEPOINT_RELEASE);
+  if( NEVER(rc!=SQLITE_OK) ){
+    break;
+  }
+
+  /* Invalidate all ephemeral cursor row caches */
+  p->cacheCtr = (p->cacheCtr + 2)|1;
+
+  /* Make sure the results of the current row are \000 terminated
+  ** and have an assigned type.  The results are de-ephemeralized as
+  ** as side effect.
+  */
+  pMem = p->pResultSet = &aMem[pOp->p1];
+  for(i=0; i<pOp->p2; i++){
+    assert( memIsValid(&pMem[i]) );
+    Deephemeralize(&pMem[i]);
+    assert( (pMem[i].flags & MEM_Ephem)==0
+            || (pMem[i].flags & (MEM_Str|MEM_Blob))==0 );
+    sqlite3VdbeMemNulTerminate(&pMem[i]);
+    sqlite3VdbeMemStoreType(&pMem[i]);
+    REGISTER_TRACE(pOp->p1+i, &pMem[i]);
+  }
+  if( db->mallocFailed ) goto no_mem;
+
+  /* Return SQLITE_ROW
+  */
+  p->pc = pc + 1;
+  rc = SQLITE_ROW;
+  goto vdbe_return;
+}
+
+/* Opcode: Concat P1 P2 P3 * *
+**
+** Add the text in register P1 onto the end of the text in
+** register P2 and store the result in register P3.
+** If either the P1 or P2 text are NULL then store NULL in P3.
+**
+**   P3 = P2 || P1
+**
+** It is illegal for P1 and P3 to be the same register. Sometimes,
+** if P3 is the same register as P2, the implementation is able
+** to avoid a memcpy().
+*/
+case OP_Concat: {           /* same as TK_CONCAT, in1, in2, out3 */
+  i64 nByte;
+
+  pIn1 = &aMem[pOp->p1];
+  pIn2 = &aMem[pOp->p2];
+  pOut = &aMem[pOp->p3];
+  assert( pIn1!=pOut );
+  if( (pIn1->flags | pIn2->flags) & MEM_Null ){
+    sqlite3VdbeMemSetNull(pOut);
+    break;
+  }
+  if( ExpandBlob(pIn1) || ExpandBlob(pIn2) ) goto no_mem;
+  Stringify(pIn1, encoding);
+  Stringify(pIn2, encoding);
+  nByte = pIn1->n + pIn2->n;
+  if( nByte>db->aLimit[SQLITE_LIMIT_LENGTH] ){
+    goto too_big;
+  }
+  MemSetTypeFlag(pOut, MEM_Str);
+  if( sqlite3VdbeMemGrow(pOut, (int)nByte+2, pOut==pIn2) ){
+    goto no_mem;
+  }
+  if( pOut!=pIn2 ){
+    memcpy(pOut->z, pIn2->z, pIn2->n);
+  }
+  memcpy(&pOut->z[pIn2->n], pIn1->z, pIn1->n);
+  pOut->z[nByte] = 0;
+  pOut->z[nByte+1] = 0;
+  pOut->flags |= MEM_Term;
+  pOut->n = (int)nByte;
+  pOut->enc = encoding;
+  UPDATE_MAX_BLOBSIZE(pOut);
+  break;
+}
+
+/* Opcode: Add P1 P2 P3 * *
+**
+** Add the value in register P1 to the value in register P2
+** and store the result in register P3.
+** If either input is NULL, the result is NULL.
+*/
+/* Opcode: Multiply P1 P2 P3 * *
+**
+**
+** Multiply the value in register P1 by the value in register P2
+** and store the result in register P3.
+** If either input is NULL, the result is NULL.
+*/
+/* Opcode: Subtract P1 P2 P3 * *
+**
+** Subtract the value in register P1 from the value in register P2
+** and store the result in register P3.
+** If either input is NULL, the result is NULL.
+*/
+/* Opcode: Divide P1 P2 P3 * *
+**
+** Divide the value in register P1 by the value in register P2
+** and store the result in register P3 (P3=P2/P1). If the value in 
+** register P1 is zero, then the result is NULL. If either input is 
+** NULL, the result is NULL.
+*/
+/* Opcode: Remainder P1 P2 P3 * *
+**
+** Compute the remainder after integer division of the value in
+** register P1 by the value in register P2 and store the result in P3. 
+** If the value in register P2 is zero the result is NULL.
+** If either operand is NULL, the result is NULL.
+*/
+case OP_Add:                   /* same as TK_PLUS, in1, in2, out3 */
+case OP_Subtract:              /* same as TK_MINUS, in1, in2, out3 */
+case OP_Multiply:              /* same as TK_STAR, in1, in2, out3 */
+case OP_Divide:                /* same as TK_SLASH, in1, in2, out3 */
+case OP_Remainder: {           /* same as TK_REM, in1, in2, out3 */
+  int flags;      /* Combined MEM_* flags from both inputs */
+  i64 iA;         /* Integer value of left operand */
+  i64 iB;         /* Integer value of right operand */
+  double rA;      /* Real value of left operand */
+  double rB;      /* Real value of right operand */
+
+  pIn1 = &aMem[pOp->p1];
+  applyNumericAffinity(pIn1);
+  pIn2 = &aMem[pOp->p2];
+  applyNumericAffinity(pIn2);
+  pOut = &aMem[pOp->p3];
+  flags = pIn1->flags | pIn2->flags;
+  if( (flags & MEM_Null)!=0 ) goto arithmetic_result_is_null;
+  if( (pIn1->flags & pIn2->flags & MEM_Int)==MEM_Int ){
+    iA = pIn1->u.i;
+    iB = pIn2->u.i;
+    switch( pOp->opcode ){
+      case OP_Add:       if( sqlite3AddInt64(&iB,iA) ) goto fp_math;  break;
+      case OP_Subtract:  if( sqlite3SubInt64(&iB,iA) ) goto fp_math;  break;
+      case OP_Multiply:  if( sqlite3MulInt64(&iB,iA) ) goto fp_math;  break;
+      case OP_Divide: {
+        if( iA==0 ) goto arithmetic_result_is_null;
+        if( iA==-1 && iB==SMALLEST_INT64 ) goto fp_math;
+        iB /= iA;
+        break;
+      }
+      default: {
+        if( iA==0 ) goto arithmetic_result_is_null;
+        if( iA==-1 ) iA = 1;
+        iB %= iA;
+        break;
+      }
+    }
+    pOut->u.i = iB;
+    MemSetTypeFlag(pOut, MEM_Int);
+  }else{
+fp_math:
+    rA = sqlite3VdbeRealValue(pIn1);
+    rB = sqlite3VdbeRealValue(pIn2);
+    switch( pOp->opcode ){
+      case OP_Add:         rB += rA;       break;
+      case OP_Subtract:    rB -= rA;       break;
+      case OP_Multiply:    rB *= rA;       break;
+      case OP_Divide: {
+        /* (double)0 In case of SQLITE_OMIT_FLOATING_POINT... */
+        if( rA==(double)0 ) goto arithmetic_result_is_null;
+        rB /= rA;
+        break;
+      }
+      default: {
+        iA = (i64)rA;
+        iB = (i64)rB;
+        if( iA==0 ) goto arithmetic_result_is_null;
+        if( iA==-1 ) iA = 1;
+        rB = (double)(iB % iA);
+        break;
+      }
+    }
+#ifdef SQLITE_OMIT_FLOATING_POINT
+    pOut->u.i = rB;
+    MemSetTypeFlag(pOut, MEM_Int);
+#else
+    if( sqlite3IsNaN(rB) ){
+      goto arithmetic_result_is_null;
+    }
+    pOut->r = rB;
+    MemSetTypeFlag(pOut, MEM_Real);
+    if( (flags & MEM_Real)==0 ){
+      sqlite3VdbeIntegerAffinity(pOut);
+    }
+#endif
+  }
+  break;
+
+arithmetic_result_is_null:
+  sqlite3VdbeMemSetNull(pOut);
+  break;
+}
+
+/* Opcode: CollSeq * * P4
+**
+** P4 is a pointer to a CollSeq struct. If the next call to a user function
+** or aggregate calls sqlite3GetFuncCollSeq(), this collation sequence will
+** be returned. This is used by the built-in min(), max() and nullif()
+** functions.
+**
+** The interface used by the implementation of the aforementioned functions
+** to retrieve the collation sequence set by this opcode is not available
+** publicly, only to user functions defined in func.c.
+*/
+case OP_CollSeq: {
+  assert( pOp->p4type==P4_COLLSEQ );
+  break;
+}
+
+/* Opcode: Function P1 P2 P3 P4 P5
+**
+** Invoke a user function (P4 is a pointer to a Function structure that
+** defines the function) with P5 arguments taken from register P2 and
+** successors.  The result of the function is stored in register P3.
+** Register P3 must not be one of the function inputs.
+**
+** P1 is a 32-bit bitmask indicating whether or not each argument to the 
+** function was determined to be constant at compile time. If the first
+** argument was constant then bit 0 of P1 is set. This is used to determine
+** whether meta data associated with a user function argument using the
+** sqlite3_set_auxdata() API may be safely retained until the next
+** invocation of this opcode.
+**
+** See also: AggStep and AggFinal
+*/
+case OP_Function: {
+  int i;
+  Mem *pArg;
+  sqlite3_context ctx;
+  sqlite3_value **apVal;
+  int n;
+
+  n = pOp->p5;
+  apVal = p->apArg;
+  assert( apVal || n==0 );
+  assert( pOp->p3>0 && pOp->p3<=p->nMem );
+  pOut = &aMem[pOp->p3];
+  memAboutToChange(p, pOut);
+
+  assert( n==0 || (pOp->p2>0 && pOp->p2+n<=p->nMem+1) );
+  assert( pOp->p3<pOp->p2 || pOp->p3>=pOp->p2+n );
+  pArg = &aMem[pOp->p2];
+  for(i=0; i<n; i++, pArg++){
+    assert( memIsValid(pArg) );
+    apVal[i] = pArg;
+    Deephemeralize(pArg);
+    sqlite3VdbeMemStoreType(pArg);
+    REGISTER_TRACE(pOp->p2+i, pArg);
+  }
+
+  assert( pOp->p4type==P4_FUNCDEF || pOp->p4type==P4_VDBEFUNC );
+  if( pOp->p4type==P4_FUNCDEF ){
+    ctx.pFunc = pOp->p4.pFunc;
+    ctx.pVdbeFunc = 0;
+  }else{
+    ctx.pVdbeFunc = (VdbeFunc*)pOp->p4.pVdbeFunc;
+    ctx.pFunc = ctx.pVdbeFunc->pFunc;
+  }
+
+  ctx.s.flags = MEM_Null;
+  ctx.s.db = db;
+  ctx.s.xDel = 0;
+  ctx.s.zMalloc = 0;
+
+  /* The output cell may already have a buffer allocated. Move
+  ** the pointer to ctx.s so in case the user-function can use
+  ** the already allocated buffer instead of allocating a new one.
+  */
+  sqlite3VdbeMemMove(&ctx.s, pOut);
+  MemSetTypeFlag(&ctx.s, MEM_Null);
+
+  ctx.isError = 0;
+  if( ctx.pFunc->flags & SQLITE_FUNC_NEEDCOLL ){
+    assert( pOp>aOp );
+    assert( pOp[-1].p4type==P4_COLLSEQ );
+    assert( pOp[-1].opcode==OP_CollSeq );
+    ctx.pColl = pOp[-1].p4.pColl;
+  }
+  db->lastRowid = lastRowid;
+  (*ctx.pFunc->xFunc)(&ctx, n, apVal); /* IMP: R-24505-23230 */
+  lastRowid = db->lastRowid;
+
+  /* If any auxiliary data functions have been called by this user function,
+  ** immediately call the destructor for any non-static values.
+  */
+  if( ctx.pVdbeFunc ){
+    sqlite3VdbeDeleteAuxData(ctx.pVdbeFunc, pOp->p1);
+    pOp->p4.pVdbeFunc = ctx.pVdbeFunc;
+    pOp->p4type = P4_VDBEFUNC;
+  }
+
+  if( db->mallocFailed ){
+    /* Even though a malloc() has failed, the implementation of the
+    ** user function may have called an sqlite3_result_XXX() function
+    ** to return a value. The following call releases any resources
+    ** associated with such a value.
+    */
+    sqlite3VdbeMemRelease(&ctx.s);
+    goto no_mem;
+  }
+
+  /* If the function returned an error, throw an exception */
+  if( ctx.isError ){
+    sqlite3SetString(&p->zErrMsg, db, "%s", sqlite3_value_text(&ctx.s));
+    rc = ctx.isError;
+  }
+
+  /* Copy the result of the function into register P3 */
+  sqlite3VdbeChangeEncoding(&ctx.s, encoding);
+  sqlite3VdbeMemMove(pOut, &ctx.s);
+  if( sqlite3VdbeMemTooBig(pOut) ){
+    goto too_big;
+  }
+
+#if 0
+  /* The app-defined function has done something that as caused this
+  ** statement to expire.  (Perhaps the function called sqlite3_exec()
+  ** with a CREATE TABLE statement.)
+  */
+  if( p->expired ) rc = SQLITE_ABORT;
+#endif
+
+  REGISTER_TRACE(pOp->p3, pOut);
+  UPDATE_MAX_BLOBSIZE(pOut);
+  break;
+}
+
+/* Opcode: BitAnd P1 P2 P3 * *
+**
+** Take the bit-wise AND of the values in register P1 and P2 and
+** store the result in register P3.
+** If either input is NULL, the result is NULL.
+*/
+/* Opcode: BitOr P1 P2 P3 * *
+**
+** Take the bit-wise OR of the values in register P1 and P2 and
+** store the result in register P3.
+** If either input is NULL, the result is NULL.
+*/
+/* Opcode: ShiftLeft P1 P2 P3 * *
+**
+** Shift the integer value in register P2 to the left by the
+** number of bits specified by the integer in register P1.
+** Store the result in register P3.
+** If either input is NULL, the result is NULL.
+*/
+/* Opcode: ShiftRight P1 P2 P3 * *
+**
+** Shift the integer value in register P2 to the right by the
+** number of bits specified by the integer in register P1.
+** Store the result in register P3.
+** If either input is NULL, the result is NULL.
+*/
+case OP_BitAnd:                 /* same as TK_BITAND, in1, in2, out3 */
+case OP_BitOr:                  /* same as TK_BITOR, in1, in2, out3 */
+case OP_ShiftLeft:              /* same as TK_LSHIFT, in1, in2, out3 */
+case OP_ShiftRight: {           /* same as TK_RSHIFT, in1, in2, out3 */
+  i64 iA;
+  u64 uA;
+  i64 iB;
+  u8 op;
+
+  pIn1 = &aMem[pOp->p1];
+  pIn2 = &aMem[pOp->p2];
+  pOut = &aMem[pOp->p3];
+  if( (pIn1->flags | pIn2->flags) & MEM_Null ){
+    sqlite3VdbeMemSetNull(pOut);
+    break;
+  }
+  iA = sqlite3VdbeIntValue(pIn2);
+  iB = sqlite3VdbeIntValue(pIn1);
+  op = pOp->opcode;
+  if( op==OP_BitAnd ){
+    iA &= iB;
+  }else if( op==OP_BitOr ){
+    iA |= iB;
+  }else if( iB!=0 ){
+    assert( op==OP_ShiftRight || op==OP_ShiftLeft );
+
+    /* If shifting by a negative amount, shift in the other direction */
+    if( iB<0 ){
+      assert( OP_ShiftRight==OP_ShiftLeft+1 );
+      op = 2*OP_ShiftLeft + 1 - op;
+      iB = iB>(-64) ? -iB : 64;
+    }
+
+    if( iB>=64 ){
+      iA = (iA>=0 || op==OP_ShiftLeft) ? 0 : -1;
+    }else{
+      memcpy(&uA, &iA, sizeof(uA));
+      if( op==OP_ShiftLeft ){
+        uA <<= iB;
+      }else{
+        uA >>= iB;
+        /* Sign-extend on a right shift of a negative number */
+        if( iA<0 ) uA |= ((((u64)0xffffffff)<<32)|0xffffffff) << (64-iB);
+      }
+      memcpy(&iA, &uA, sizeof(iA));
+    }
+  }
+  pOut->u.i = iA;
+  MemSetTypeFlag(pOut, MEM_Int);
+  break;
+}
+
+/* Opcode: AddImm  P1 P2 * * *
+** 
+** Add the constant P2 to the value in register P1.
+** The result is always an integer.
+**
+** To force any register to be an integer, just add 0.
+*/
+case OP_AddImm: {            /* in1 */
+  pIn1 = &aMem[pOp->p1];
+  memAboutToChange(p, pIn1);
+  sqlite3VdbeMemIntegerify(pIn1);
+  pIn1->u.i += pOp->p2;
+  break;
+}
+
+/* Opcode: MustBeInt P1 P2 * * *
+** 
+** Force the value in register P1 to be an integer.  If the value
+** in P1 is not an integer and cannot be converted into an integer
+** without data loss, then jump immediately to P2, or if P2==0
+** raise an SQLITE_MISMATCH exception.
+*/
+case OP_MustBeInt: {            /* jump, in1 */
+  pIn1 = &aMem[pOp->p1];
+  applyAffinity(pIn1, SQLITE_AFF_NUMERIC, encoding);
+  if( (pIn1->flags & MEM_Int)==0 ){
+    if( pOp->p2==0 ){
+      rc = SQLITE_MISMATCH;
+      goto abort_due_to_error;
+    }else{
+      pc = pOp->p2 - 1;
+    }
+  }else{
+    MemSetTypeFlag(pIn1, MEM_Int);
+  }
+  break;
+}
+
+#ifndef SQLITE_OMIT_FLOATING_POINT
+/* Opcode: RealAffinity P1 * * * *
+**
+** If register P1 holds an integer convert it to a real value.
+**
+** This opcode is used when extracting information from a column that
+** has REAL affinity.  Such column values may still be stored as
+** integers, for space efficiency, but after extraction we want them
+** to have only a real value.
+*/
+case OP_RealAffinity: {                  /* in1 */
+  pIn1 = &aMem[pOp->p1];
+  if( pIn1->flags & MEM_Int ){
+    sqlite3VdbeMemRealify(pIn1);
+  }
+  break;
+}
+#endif
+
+#ifndef SQLITE_OMIT_CAST
+/* Opcode: ToText P1 * * * *
+**
+** Force the value in register P1 to be text.
+** If the value is numeric, convert it to a string using the
+** equivalent of printf().  Blob values are unchanged and
+** are afterwards simply interpreted as text.
+**
+** A NULL value is not changed by this routine.  It remains NULL.
+*/
+case OP_ToText: {                  /* same as TK_TO_TEXT, in1 */
+  pIn1 = &aMem[pOp->p1];
+  memAboutToChange(p, pIn1);
+  if( pIn1->flags & MEM_Null ) break;
+  assert( MEM_Str==(MEM_Blob>>3) );
+  pIn1->flags |= (pIn1->flags&MEM_Blob)>>3;
+  applyAffinity(pIn1, SQLITE_AFF_TEXT, encoding);
+  rc = ExpandBlob(pIn1);
+  assert( pIn1->flags & MEM_Str || db->mallocFailed );
+  pIn1->flags &= ~(MEM_Int|MEM_Real|MEM_Blob|MEM_Zero);
+  UPDATE_MAX_BLOBSIZE(pIn1);
+  break;
+}
+
+/* Opcode: ToBlob P1 * * * *
+**
+** Force the value in register P1 to be a BLOB.
+** If the value is numeric, convert it to a string first.
+** Strings are simply reinterpreted as blobs with no change
+** to the underlying data.
+**
+** A NULL value is not changed by this routine.  It remains NULL.
+*/
+case OP_ToBlob: {                  /* same as TK_TO_BLOB, in1 */
+  pIn1 = &aMem[pOp->p1];
+  if( pIn1->flags & MEM_Null ) break;
+  if( (pIn1->flags & MEM_Blob)==0 ){
+    applyAffinity(pIn1, SQLITE_AFF_TEXT, encoding);
+    assert( pIn1->flags & MEM_Str || db->mallocFailed );
+    MemSetTypeFlag(pIn1, MEM_Blob);
+  }else{
+    pIn1->flags &= ~(MEM_TypeMask&~MEM_Blob);
+  }
+  UPDATE_MAX_BLOBSIZE(pIn1);
+  break;
+}
+
+/* Opcode: ToNumeric P1 * * * *
+**
+** Force the value in register P1 to be numeric (either an
+** integer or a floating-point number.)
+** If the value is text or blob, try to convert it to an using the
+** equivalent of atoi() or atof() and store 0 if no such conversion 
+** is possible.
+**
+** A NULL value is not changed by this routine.  It remains NULL.
+*/
+case OP_ToNumeric: {                  /* same as TK_TO_NUMERIC, in1 */
+  pIn1 = &aMem[pOp->p1];
+  sqlite3VdbeMemNumerify(pIn1);
+  break;
+}
+#endif /* SQLITE_OMIT_CAST */
+
+/* Opcode: ToInt P1 * * * *
+**
+** Force the value in register P1 to be an integer.  If
+** The value is currently a real number, drop its fractional part.
+** If the value is text or blob, try to convert it to an integer using the
+** equivalent of atoi() and store 0 if no such conversion is possible.
+**
+** A NULL value is not changed by this routine.  It remains NULL.
+*/
+case OP_ToInt: {                  /* same as TK_TO_INT, in1 */
+  pIn1 = &aMem[pOp->p1];
+  if( (pIn1->flags & MEM_Null)==0 ){
+    sqlite3VdbeMemIntegerify(pIn1);
+  }
+  break;
+}
+
+#if !defined(SQLITE_OMIT_CAST) && !defined(SQLITE_OMIT_FLOATING_POINT)
+/* Opcode: ToReal P1 * * * *
+**
+** Force the value in register P1 to be a floating point number.
+** If The value is currently an integer, convert it.
+** If the value is text or blob, try to convert it to an integer using the
+** equivalent of atoi() and store 0.0 if no such conversion is possible.
+**
+** A NULL value is not changed by this routine.  It remains NULL.
+*/
+case OP_ToReal: {                  /* same as TK_TO_REAL, in1 */
+  pIn1 = &aMem[pOp->p1];
+  memAboutToChange(p, pIn1);
+  if( (pIn1->flags & MEM_Null)==0 ){
+    sqlite3VdbeMemRealify(pIn1);
+  }
+  break;
+}
+#endif /* !defined(SQLITE_OMIT_CAST) && !defined(SQLITE_OMIT_FLOATING_POINT) */
+
+/* Opcode: Lt P1 P2 P3 P4 P5
+**
+** Compare the values in register P1 and P3.  If reg(P3)<reg(P1) then
+** jump to address P2.  
+**
+** If the SQLITE_JUMPIFNULL bit of P5 is set and either reg(P1) or
+** reg(P3) is NULL then take the jump.  If the SQLITE_JUMPIFNULL 
+** bit is clear then fall through if either operand is NULL.
+**
+** The SQLITE_AFF_MASK portion of P5 must be an affinity character -
+** SQLITE_AFF_TEXT, SQLITE_AFF_INTEGER, and so forth. An attempt is made 
+** to coerce both inputs according to this affinity before the
+** comparison is made. If the SQLITE_AFF_MASK is 0x00, then numeric
+** affinity is used. Note that the affinity conversions are stored
+** back into the input registers P1 and P3.  So this opcode can cause
+** persistent changes to registers P1 and P3.
+**
+** Once any conversions have taken place, and neither value is NULL, 
+** the values are compared. If both values are blobs then memcmp() is
+** used to determine the results of the comparison.  If both values
+** are text, then the appropriate collating function specified in
+** P4 is  used to do the comparison.  If P4 is not specified then
+** memcmp() is used to compare text string.  If both values are
+** numeric, then a numeric comparison is used. If the two values
+** are of different types, then numbers are considered less than
+** strings and strings are considered less than blobs.
+**
+** If the SQLITE_STOREP2 bit of P5 is set, then do not jump.  Instead,
+** store a boolean result (either 0, or 1, or NULL) in register P2.
+*/
+/* Opcode: Ne P1 P2 P3 P4 P5
+**
+** This works just like the Lt opcode except that the jump is taken if
+** the operands in registers P1 and P3 are not equal.  See the Lt opcode for
+** additional information.
+**
+** If SQLITE_NULLEQ is set in P5 then the result of comparison is always either
+** true or false and is never NULL.  If both operands are NULL then the result
+** of comparison is false.  If either operand is NULL then the result is true.
+** If neither operand is NULL the result is the same as it would be if
+** the SQLITE_NULLEQ flag were omitted from P5.
+*/
+/* Opcode: Eq P1 P2 P3 P4 P5
+**
+** This works just like the Lt opcode except that the jump is taken if
+** the operands in registers P1 and P3 are equal.
+** See the Lt opcode for additional information.
+**
+** If SQLITE_NULLEQ is set in P5 then the result of comparison is always either
+** true or false and is never NULL.  If both operands are NULL then the result
+** of comparison is true.  If either operand is NULL then the result is false.
+** If neither operand is NULL the result is the same as it would be if
+** the SQLITE_NULLEQ flag were omitted from P5.
+*/
+/* Opcode: Le P1 P2 P3 P4 P5
+**
+** This works just like the Lt opcode except that the jump is taken if
+** the content of register P3 is less than or equal to the content of
+** register P1.  See the Lt opcode for additional information.
+*/
+/* Opcode: Gt P1 P2 P3 P4 P5
+**
+** This works just like the Lt opcode except that the jump is taken if
+** the content of register P3 is greater than the content of
+** register P1.  See the Lt opcode for additional information.
+*/
+/* Opcode: Ge P1 P2 P3 P4 P5
+**
+** This works just like the Lt opcode except that the jump is taken if
+** the content of register P3 is greater than or equal to the content of
+** register P1.  See the Lt opcode for additional information.
+*/
+case OP_Eq:               /* same as TK_EQ, jump, in1, in3 */
+case OP_Ne:               /* same as TK_NE, jump, in1, in3 */
+case OP_Lt:               /* same as TK_LT, jump, in1, in3 */
+case OP_Le:               /* same as TK_LE, jump, in1, in3 */
+case OP_Gt:               /* same as TK_GT, jump, in1, in3 */
+case OP_Ge: {             /* same as TK_GE, jump, in1, in3 */
+  int res;            /* Result of the comparison of pIn1 against pIn3 */
+  char affinity;      /* Affinity to use for comparison */
+  u16 flags1;         /* Copy of initial value of pIn1->flags */
+  u16 flags3;         /* Copy of initial value of pIn3->flags */
+
+  pIn1 = &aMem[pOp->p1];
+  pIn3 = &aMem[pOp->p3];
+  flags1 = pIn1->flags;
+  flags3 = pIn3->flags;
+  if( (flags1 | flags3)&MEM_Null ){
+    /* One or both operands are NULL */
+    if( pOp->p5 & SQLITE_NULLEQ ){
+      /* If SQLITE_NULLEQ is set (which will only happen if the operator is
+      ** OP_Eq or OP_Ne) then take the jump or not depending on whether
+      ** or not both operands are null.
+      */
+      assert( pOp->opcode==OP_Eq || pOp->opcode==OP_Ne );
+      res = (flags1 & flags3 & MEM_Null)==0;
+    }else{
+      /* SQLITE_NULLEQ is clear and at least one operand is NULL,
+      ** then the result is always NULL.
+      ** The jump is taken if the SQLITE_JUMPIFNULL bit is set.
+      */
+      if( pOp->p5 & SQLITE_STOREP2 ){
+        pOut = &aMem[pOp->p2];
+        MemSetTypeFlag(pOut, MEM_Null);
+        REGISTER_TRACE(pOp->p2, pOut);
+      }else if( pOp->p5 & SQLITE_JUMPIFNULL ){
+        pc = pOp->p2-1;
+      }
+      break;
+    }
+  }else{
+    /* Neither operand is NULL.  Do a comparison. */
+    affinity = pOp->p5 & SQLITE_AFF_MASK;
+    if( affinity ){
+      applyAffinity(pIn1, affinity, encoding);
+      applyAffinity(pIn3, affinity, encoding);
+      if( db->mallocFailed ) goto no_mem;
+    }
+
+    assert( pOp->p4type==P4_COLLSEQ || pOp->p4.pColl==0 );
+    ExpandBlob(pIn1);
+    ExpandBlob(pIn3);
+    res = sqlite3MemCompare(pIn3, pIn1, pOp->p4.pColl);
+  }
+  switch( pOp->opcode ){
+    case OP_Eq:    res = res==0;     break;
+    case OP_Ne:    res = res!=0;     break;
+    case OP_Lt:    res = res<0;      break;
+    case OP_Le:    res = res<=0;     break;
+    case OP_Gt:    res = res>0;      break;
+    default:       res = res>=0;     break;
+  }
+
+  if( pOp->p5 & SQLITE_STOREP2 ){
+    pOut = &aMem[pOp->p2];
+    memAboutToChange(p, pOut);
+    MemSetTypeFlag(pOut, MEM_Int);
+    pOut->u.i = res;
+    REGISTER_TRACE(pOp->p2, pOut);
+  }else if( res ){
+    pc = pOp->p2-1;
+  }
+
+  /* Undo any changes made by applyAffinity() to the input registers. */
+  pIn1->flags = (pIn1->flags&~MEM_TypeMask) | (flags1&MEM_TypeMask);
+  pIn3->flags = (pIn3->flags&~MEM_TypeMask) | (flags3&MEM_TypeMask);
+  break;
+}
+
+/* Opcode: Permutation * * * P4 *
+**
+** Set the permutation used by the OP_Compare operator to be the array
+** of integers in P4.
+**
+** The permutation is only valid until the next OP_Permutation, OP_Compare,
+** OP_Halt, or OP_ResultRow.  Typically the OP_Permutation should occur
+** immediately prior to the OP_Compare.
+*/
+case OP_Permutation: {
+  assert( pOp->p4type==P4_INTARRAY );
+  assert( pOp->p4.ai );
+  aPermute = pOp->p4.ai;
+  break;
+}
+
+/* Opcode: Compare P1 P2 P3 P4 *
+**
+** Compare two vectors of registers in reg(P1)..reg(P1+P3-1) (call this
+** vector "A") and in reg(P2)..reg(P2+P3-1) ("B").  Save the result of
+** the comparison for use by the next OP_Jump instruct.
+**
+** P4 is a KeyInfo structure that defines collating sequences and sort
+** orders for the comparison.  The permutation applies to registers
+** only.  The KeyInfo elements are used sequentially.
+**
+** The comparison is a sort comparison, so NULLs compare equal,
+** NULLs are less than numbers, numbers are less than strings,
+** and strings are less than blobs.
+*/
+case OP_Compare: {
+  int n;
+  int i;
+  int p1;
+  int p2;
+  const KeyInfo *pKeyInfo;
+  int idx;
+  CollSeq *pColl;    /* Collating sequence to use on this term */
+  int bRev;          /* True for DESCENDING sort order */
+
+  n = pOp->p3;
+  pKeyInfo = pOp->p4.pKeyInfo;
+  assert( n>0 );
+  assert( pKeyInfo!=0 );
+  p1 = pOp->p1;
+  p2 = pOp->p2;
+#if SQLITE_DEBUG
+  if( aPermute ){
+    int k, mx = 0;
+    for(k=0; k<n; k++) if( aPermute[k]>mx ) mx = aPermute[k];
+    assert( p1>0 && p1+mx<=p->nMem+1 );
+    assert( p2>0 && p2+mx<=p->nMem+1 );
+  }else{
+    assert( p1>0 && p1+n<=p->nMem+1 );
+    assert( p2>0 && p2+n<=p->nMem+1 );
+  }
+#endif /* SQLITE_DEBUG */
+  for(i=0; i<n; i++){
+    idx = aPermute ? aPermute[i] : i;
+    assert( memIsValid(&aMem[p1+idx]) );
+    assert( memIsValid(&aMem[p2+idx]) );
+    REGISTER_TRACE(p1+idx, &aMem[p1+idx]);
+    REGISTER_TRACE(p2+idx, &aMem[p2+idx]);
+    assert( i<pKeyInfo->nField );
+    pColl = pKeyInfo->aColl[i];
+    bRev = pKeyInfo->aSortOrder[i];
+    iCompare = sqlite3MemCompare(&aMem[p1+idx], &aMem[p2+idx], pColl);
+    if( iCompare ){
+      if( bRev ) iCompare = -iCompare;
+      break;
+    }
+  }
+  aPermute = 0;
+  break;
+}
+
+/* Opcode: Jump P1 P2 P3 * *
+**
+** Jump to the instruction at address P1, P2, or P3 depending on whether
+** in the most recent OP_Compare instruction the P1 vector was less than
+** equal to, or greater than the P2 vector, respectively.
+*/
+case OP_Jump: {             /* jump */
+  if( iCompare<0 ){
+    pc = pOp->p1 - 1;
+  }else if( iCompare==0 ){
+    pc = pOp->p2 - 1;
+  }else{
+    pc = pOp->p3 - 1;
+  }
+  break;
+}
+
+/* Opcode: And P1 P2 P3 * *
+**
+** Take the logical AND of the values in registers P1 and P2 and
+** write the result into register P3.
+**
+** If either P1 or P2 is 0 (false) then the result is 0 even if
+** the other input is NULL.  A NULL and true or two NULLs give
+** a NULL output.
+*/
+/* Opcode: Or P1 P2 P3 * *
+**
+** Take the logical OR of the values in register P1 and P2 and
+** store the answer in register P3.
+**
+** If either P1 or P2 is nonzero (true) then the result is 1 (true)
+** even if the other input is NULL.  A NULL and false or two NULLs
+** give a NULL output.
+*/
+case OP_And:              /* same as TK_AND, in1, in2, out3 */
+case OP_Or: {             /* same as TK_OR, in1, in2, out3 */
+  int v1;    /* Left operand:  0==FALSE, 1==TRUE, 2==UNKNOWN or NULL */
+  int v2;    /* Right operand: 0==FALSE, 1==TRUE, 2==UNKNOWN or NULL */
+
+  pIn1 = &aMem[pOp->p1];
+  if( pIn1->flags & MEM_Null ){
+    v1 = 2;
+  }else{
+    v1 = sqlite3VdbeIntValue(pIn1)!=0;
+  }
+  pIn2 = &aMem[pOp->p2];
+  if( pIn2->flags & MEM_Null ){
+    v2 = 2;
+  }else{
+    v2 = sqlite3VdbeIntValue(pIn2)!=0;
+  }
+  if( pOp->opcode==OP_And ){
+    static const unsigned char and_logic[] = { 0, 0, 0, 0, 1, 2, 0, 2, 2 };
+    v1 = and_logic[v1*3+v2];
+  }else{
+    static const unsigned char or_logic[] = { 0, 1, 2, 1, 1, 1, 2, 1, 2 };
+    v1 = or_logic[v1*3+v2];
+  }
+  pOut = &aMem[pOp->p3];
+  if( v1==2 ){
+    MemSetTypeFlag(pOut, MEM_Null);
+  }else{
+    pOut->u.i = v1;
+    MemSetTypeFlag(pOut, MEM_Int);
+  }
+  break;
+}
+
+/* Opcode: Not P1 P2 * * *
+**
+** Interpret the value in register P1 as a boolean value.  Store the
+** boolean complement in register P2.  If the value in register P1 is 
+** NULL, then a NULL is stored in P2.
+*/
+case OP_Not: {                /* same as TK_NOT, in1, out2 */
+  pIn1 = &aMem[pOp->p1];
+  pOut = &aMem[pOp->p2];
+  if( pIn1->flags & MEM_Null ){
+    sqlite3VdbeMemSetNull(pOut);
+  }else{
+    sqlite3VdbeMemSetInt64(pOut, !sqlite3VdbeIntValue(pIn1));
+  }
+  break;
+}
+
+/* Opcode: BitNot P1 P2 * * *
+**
+** Interpret the content of register P1 as an integer.  Store the
+** ones-complement of the P1 value into register P2.  If P1 holds
+** a NULL then store a NULL in P2.
+*/
+case OP_BitNot: {             /* same as TK_BITNOT, in1, out2 */
+  pIn1 = &aMem[pOp->p1];
+  pOut = &aMem[pOp->p2];
+  if( pIn1->flags & MEM_Null ){
+    sqlite3VdbeMemSetNull(pOut);
+  }else{
+    sqlite3VdbeMemSetInt64(pOut, ~sqlite3VdbeIntValue(pIn1));
+  }
+  break;
+}
+
+/* Opcode: Once P1 P2 * * *
+**
+** Jump to P2 if the value in register P1 is a not null or zero.  If
+** the value is NULL or zero, fall through and change the P1 register
+** to an integer 1.
+**
+** When P1 is not used otherwise in a program, this opcode falls through
+** once and jumps on all subsequent invocations.  It is the equivalent
+** of "OP_If P1 P2", followed by "OP_Integer 1 P1".
+*/
+/* Opcode: If P1 P2 P3 * *
+**
+** Jump to P2 if the value in register P1 is true.  The value
+** is considered true if it is numeric and non-zero.  If the value
+** in P1 is NULL then take the jump if P3 is true.
+*/
+/* Opcode: IfNot P1 P2 P3 * *
+**
+** Jump to P2 if the value in register P1 is False.  The value
+** is considered true if it has a numeric value of zero.  If the value
+** in P1 is NULL then take the jump if P3 is true.
+*/
+case OP_Once:               /* jump, in1 */
+case OP_If:                 /* jump, in1 */
+case OP_IfNot: {            /* jump, in1 */
+  int c;
+  pIn1 = &aMem[pOp->p1];
+  if( pIn1->flags & MEM_Null ){
+    c = pOp->p3;
+  }else{
+#ifdef SQLITE_OMIT_FLOATING_POINT
+    c = sqlite3VdbeIntValue(pIn1)!=0;
+#else
+    c = sqlite3VdbeRealValue(pIn1)!=0.0;
+#endif
+    if( pOp->opcode==OP_IfNot ) c = !c;
+  }
+  if( c ){
+    pc = pOp->p2-1;
+  }else if( pOp->opcode==OP_Once ){
+    assert( (pIn1->flags & (MEM_Agg|MEM_Dyn|MEM_RowSet|MEM_Frame))==0 );
+    memAboutToChange(p, pIn1);
+    pIn1->flags = MEM_Int;
+    pIn1->u.i = 1;
+    REGISTER_TRACE(pOp->p1, pIn1);
+  }
+  break;
+}
+
+/* Opcode: IsNull P1 P2 * * *
+**
+** Jump to P2 if the value in register P1 is NULL.
+*/
+case OP_IsNull: {            /* same as TK_ISNULL, jump, in1 */
+  pIn1 = &aMem[pOp->p1];
+  if( (pIn1->flags & MEM_Null)!=0 ){
+    pc = pOp->p2 - 1;
+  }
+  break;
+}
+
+/* Opcode: NotNull P1 P2 * * *
+**
+** Jump to P2 if the value in register P1 is not NULL.  
+*/
+case OP_NotNull: {            /* same as TK_NOTNULL, jump, in1 */
+  pIn1 = &aMem[pOp->p1];
+  if( (pIn1->flags & MEM_Null)==0 ){
+    pc = pOp->p2 - 1;
+  }
+  break;
+}
+
+/* Opcode: Column P1 P2 P3 P4 P5
+**
+** Interpret the data that cursor P1 points to as a structure built using
+** the MakeRecord instruction.  (See the MakeRecord opcode for additional
+** information about the format of the data.)  Extract the P2-th column
+** from this record.  If there are less that (P2+1) 
+** values in the record, extract a NULL.
+**
+** The value extracted is stored in register P3.
+**
+** If the column contains fewer than P2 fields, then extract a NULL.  Or,
+** if the P4 argument is a P4_MEM use the value of the P4 argument as
+** the result.
+**
+** If the OPFLAG_CLEARCACHE bit is set on P5 and P1 is a pseudo-table cursor,
+** then the cache of the cursor is reset prior to extracting the column.
+** The first OP_Column against a pseudo-table after the value of the content
+** register has changed should have this bit set.
+*/
+case OP_Column: {
+  u32 payloadSize;   /* Number of bytes in the record */
+  i64 payloadSize64; /* Number of bytes in the record */
+  int p1;            /* P1 value of the opcode */
+  int p2;            /* column number to retrieve */
+  VdbeCursor *pC;    /* The VDBE cursor */
+  char *zRec;        /* Pointer to complete record-data */
+  BtCursor *pCrsr;   /* The BTree cursor */
+  u32 *aType;        /* aType[i] holds the numeric type of the i-th column */
+  u32 *aOffset;      /* aOffset[i] is offset to start of data for i-th column */
+  int nField;        /* number of fields in the record */
+  int len;           /* The length of the serialized data for the column */
+  int i;             /* Loop counter */
+  char *zData;       /* Part of the record being decoded */
+  Mem *pDest;        /* Where to write the extracted value */
+  Mem sMem;          /* For storing the record being decoded */
+  u8 *zIdx;          /* Index into header */
+  u8 *zEndHdr;       /* Pointer to first byte after the header */
+  u32 offset;        /* Offset into the data */
+  u32 szField;       /* Number of bytes in the content of a field */
+  int szHdr;         /* Size of the header size field at start of record */
+  int avail;         /* Number of bytes of available data */
+  u32 t;             /* A type code from the record header */
+  Mem *pReg;         /* PseudoTable input register */
+
+
+  p1 = pOp->p1;
+  p2 = pOp->p2;
+  pC = 0;
+  memset(&sMem, 0, sizeof(sMem));
+  assert( p1<p->nCursor );
+  assert( pOp->p3>0 && pOp->p3<=p->nMem );
+  pDest = &aMem[pOp->p3];
+  memAboutToChange(p, pDest);
+  zRec = 0;
+
+  /* This block sets the variable payloadSize to be the total number of
+  ** bytes in the record.
+  **
+  ** zRec is set to be the complete text of the record if it is available.
+  ** The complete record text is always available for pseudo-tables
+  ** If the record is stored in a cursor, the complete record text
+  ** might be available in the  pC->aRow cache.  Or it might not be.
+  ** If the data is unavailable,  zRec is set to NULL.
+  **
+  ** We also compute the number of columns in the record.  For cursors,
+  ** the number of columns is stored in the VdbeCursor.nField element.
+  */
+  pC = p->apCsr[p1];
+  assert( pC!=0 );
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  assert( pC->pVtabCursor==0 );
+#endif
+  pCrsr = pC->pCursor;
+  if( pCrsr!=0 ){
+    /* The record is stored in a B-Tree */
+    rc = sqlite3VdbeCursorMoveto(pC);
+    if( rc ) goto abort_due_to_error;
+    if( pC->nullRow ){
+      payloadSize = 0;
+    }else if( pC->cacheStatus==p->cacheCtr ){
+      payloadSize = pC->payloadSize;
+      zRec = (char*)pC->aRow;
+    }else if( pC->isIndex ){
+      assert( sqlite3BtreeCursorIsValid(pCrsr) );
+      VVA_ONLY(rc =) sqlite3BtreeKeySize(pCrsr, &payloadSize64);
+      assert( rc==SQLITE_OK );   /* True because of CursorMoveto() call above */
+      /* sqlite3BtreeParseCellPtr() uses getVarint32() to extract the
+      ** payload size, so it is impossible for payloadSize64 to be
+      ** larger than 32 bits. */
+      assert( (payloadSize64 & SQLITE_MAX_U32)==(u64)payloadSize64 );
+      payloadSize = (u32)payloadSize64;
+    }else{
+      assert( sqlite3BtreeCursorIsValid(pCrsr) );
+      VVA_ONLY(rc =) sqlite3BtreeDataSize(pCrsr, &payloadSize);
+      assert( rc==SQLITE_OK );   /* DataSize() cannot fail */
+    }
+  }else if( ALWAYS(pC->pseudoTableReg>0) ){
+    pReg = &aMem[pC->pseudoTableReg];
+    assert( pReg->flags & MEM_Blob );
+    assert( memIsValid(pReg) );
+    payloadSize = pReg->n;
+    zRec = pReg->z;
+    pC->cacheStatus = (pOp->p5&OPFLAG_CLEARCACHE) ? CACHE_STALE : p->cacheCtr;
+    assert( payloadSize==0 || zRec!=0 );
+  }else{
+    /* Consider the row to be NULL */
+    payloadSize = 0;
+  }
+
+  /* If payloadSize is 0, then just store a NULL.  This can happen because of
+  ** nullRow or because of a corrupt database. */
+  if( payloadSize==0 ){
+    MemSetTypeFlag(pDest, MEM_Null);
+    goto op_column_out;
+  }
+  assert( db->aLimit[SQLITE_LIMIT_LENGTH]>=0 );
+  if( payloadSize > (u32)db->aLimit[SQLITE_LIMIT_LENGTH] ){
+    goto too_big;
+  }
+
+  nField = pC->nField;
+  assert( p2<nField );
+
+  /* Read and parse the table header.  Store the results of the parse
+  ** into the record header cache fields of the cursor.
+  */
+  aType = pC->aType;
+  if( pC->cacheStatus==p->cacheCtr ){
+    aOffset = pC->aOffset;
+  }else{
+    assert(aType);
+    avail = 0;
+    pC->aOffset = aOffset = &aType[nField];
+    pC->payloadSize = payloadSize;
+    pC->cacheStatus = p->cacheCtr;
+
+    /* Figure out how many bytes are in the header */
+    if( zRec ){
+      zData = zRec;
+    }else{
+      if( pC->isIndex ){
+        zData = (char*)sqlite3BtreeKeyFetch(pCrsr, &avail);
+      }else{
+        zData = (char*)sqlite3BtreeDataFetch(pCrsr, &avail);
+      }
+      /* If KeyFetch()/DataFetch() managed to get the entire payload,
+      ** save the payload in the pC->aRow cache.  That will save us from
+      ** having to make additional calls to fetch the content portion of
+      ** the record.
+      */
+      assert( avail>=0 );
+      if( payloadSize <= (u32)avail ){
+        zRec = zData;
+        pC->aRow = (u8*)zData;
+      }else{
+        pC->aRow = 0;
+      }
+    }
+    /* The following assert is true in all cases accept when
+    ** the database file has been corrupted externally.
+    **    assert( zRec!=0 || avail>=payloadSize || avail>=9 ); */
+    szHdr = getVarint32((u8*)zData, offset);
+
+    /* Make sure a corrupt database has not given us an oversize header.
+    ** Do this now to avoid an oversize memory allocation.
+    **
+    ** Type entries can be between 1 and 5 bytes each.  But 4 and 5 byte
+    ** types use so much data space that there can only be 4096 and 32 of
+    ** them, respectively.  So the maximum header length results from a
+    ** 3-byte type for each of the maximum of 32768 columns plus three
+    ** extra bytes for the header length itself.  32768*3 + 3 = 98307.
+    */
+    if( offset > 98307 ){
+      rc = SQLITE_CORRUPT_BKPT;
+      goto op_column_out;
+    }
+
+    /* Compute in len the number of bytes of data we need to read in order
+    ** to get nField type values.  offset is an upper bound on this.  But
+    ** nField might be significantly less than the true number of columns
+    ** in the table, and in that case, 5*nField+3 might be smaller than offset.
+    ** We want to minimize len in order to limit the size of the memory
+    ** allocation, especially if a corrupt database file has caused offset
+    ** to be oversized. Offset is limited to 98307 above.  But 98307 might
+    ** still exceed Robson memory allocation limits on some configurations.
+    ** On systems that cannot tolerate large memory allocations, nField*5+3
+    ** will likely be much smaller since nField will likely be less than
+    ** 20 or so.  This insures that Robson memory allocation limits are
+    ** not exceeded even for corrupt database files.
+    */
+    len = nField*5 + 3;
+    if( len > (int)offset ) len = (int)offset;
+
+    /* The KeyFetch() or DataFetch() above are fast and will get the entire
+    ** record header in most cases.  But they will fail to get the complete
+    ** record header if the record header does not fit on a single page
+    ** in the B-Tree.  When that happens, use sqlite3VdbeMemFromBtree() to
+    ** acquire the complete header text.
+    */
+    if( !zRec && avail<len ){
+      sMem.flags = 0;
+      sMem.db = 0;
+      rc = sqlite3VdbeMemFromBtree(pCrsr, 0, len, pC->isIndex, &sMem);
+      if( rc!=SQLITE_OK ){
+        goto op_column_out;
+      }
+      zData = sMem.z;
+    }
+    zEndHdr = (u8 *)&zData[len];
+    zIdx = (u8 *)&zData[szHdr];
+
+    /* Scan the header and use it to fill in the aType[] and aOffset[]
+    ** arrays.  aType[i] will contain the type integer for the i-th
+    ** column and aOffset[i] will contain the offset from the beginning
+    ** of the record to the start of the data for the i-th column
+    */
+    for(i=0; i<nField; i++){
+      if( zIdx<zEndHdr ){
+        aOffset[i] = offset;
+        if( zIdx[0]<0x80 ){
+          t = zIdx[0];
+          zIdx++;
+        }else{
+          zIdx += sqlite3GetVarint32(zIdx, &t);
+        }
+        aType[i] = t;
+        szField = sqlite3VdbeSerialTypeLen(t);
+        offset += szField;
+        if( offset<szField ){  /* True if offset overflows */
+          zIdx = &zEndHdr[1];  /* Forces SQLITE_CORRUPT return below */
+          break;
+        }
+      }else{
+        /* If i is less that nField, then there are less fields in this
+        ** record than SetNumColumns indicated there are columns in the
+        ** table. Set the offset for any extra columns not present in
+        ** the record to 0. This tells code below to store a NULL
+        ** instead of deserializing a value from the record.
+        */
+        aOffset[i] = 0;
+      }
+    }
+    sqlite3VdbeMemRelease(&sMem);
+    sMem.flags = MEM_Null;
+
+    /* If we have read more header data than was contained in the header,
+    ** or if the end of the last field appears to be past the end of the
+    ** record, or if the end of the last field appears to be before the end
+    ** of the record (when all fields present), then we must be dealing 
+    ** with a corrupt database.
+    */
+    if( (zIdx > zEndHdr) || (offset > payloadSize)
+         || (zIdx==zEndHdr && offset!=payloadSize) ){
+      rc = SQLITE_CORRUPT_BKPT;
+      goto op_column_out;
+    }
+  }
+
+  /* Get the column information. If aOffset[p2] is non-zero, then 
+  ** deserialize the value from the record. If aOffset[p2] is zero,
+  ** then there are not enough fields in the record to satisfy the
+  ** request.  In this case, set the value NULL or to P4 if P4 is
+  ** a pointer to a Mem object.
+  */
+  if( aOffset[p2] ){
+    assert( rc==SQLITE_OK );
+    if( zRec ){
+      MemReleaseExt(pDest);
+      sqlite3VdbeSerialGet((u8 *)&zRec[aOffset[p2]], aType[p2], pDest);
+    }else{
+      len = sqlite3VdbeSerialTypeLen(aType[p2]);
+      sqlite3VdbeMemMove(&sMem, pDest);
+      rc = sqlite3VdbeMemFromBtree(pCrsr, aOffset[p2], len, pC->isIndex, &sMem);
+      if( rc!=SQLITE_OK ){
+        goto op_column_out;
+      }
+      zData = sMem.z;
+      sqlite3VdbeSerialGet((u8*)zData, aType[p2], pDest);
+    }
+    pDest->enc = encoding;
+  }else{
+    if( pOp->p4type==P4_MEM ){
+      sqlite3VdbeMemShallowCopy(pDest, pOp->p4.pMem, MEM_Static);
+    }else{
+      MemSetTypeFlag(pDest, MEM_Null);
+    }
+  }
+
+  /* If we dynamically allocated space to hold the data (in the
+  ** sqlite3VdbeMemFromBtree() call above) then transfer control of that
+  ** dynamically allocated space over to the pDest structure.
+  ** This prevents a memory copy.
+  */
+  if( sMem.zMalloc ){
+    assert( sMem.z==sMem.zMalloc );
+    assert( !(pDest->flags & MEM_Dyn) );
+    assert( !(pDest->flags & (MEM_Blob|MEM_Str)) || pDest->z==sMem.z );
+    pDest->flags &= ~(MEM_Ephem|MEM_Static);
+    pDest->flags |= MEM_Term;
+    pDest->z = sMem.z;
+    pDest->zMalloc = sMem.zMalloc;
+  }
+
+  rc = sqlite3VdbeMemMakeWriteable(pDest);
+
+op_column_out:
+  UPDATE_MAX_BLOBSIZE(pDest);
+  REGISTER_TRACE(pOp->p3, pDest);
+  break;
+}
+
+/* Opcode: Affinity P1 P2 * P4 *
+**
+** Apply affinities to a range of P2 registers starting with P1.
+**
+** P4 is a string that is P2 characters long. The nth character of the
+** string indicates the column affinity that should be used for the nth
+** memory cell in the range.
+*/
+case OP_Affinity: {
+  const char *zAffinity;   /* The affinity to be applied */
+  char cAff;               /* A single character of affinity */
+
+  zAffinity = pOp->p4.z;
+  assert( zAffinity!=0 );
+  assert( zAffinity[pOp->p2]==0 );
+  pIn1 = &aMem[pOp->p1];
+  while( (cAff = *(zAffinity++))!=0 ){
+    assert( pIn1 <= &p->aMem[p->nMem] );
+    assert( memIsValid(pIn1) );
+    ExpandBlob(pIn1);
+    applyAffinity(pIn1, cAff, encoding);
+    pIn1++;
+  }
+  break;
+}
+
+/* Opcode: MakeRecord P1 P2 P3 P4 *
+**
+** Convert P2 registers beginning with P1 into the [record format]
+** use as a data record in a database table or as a key
+** in an index.  The OP_Column opcode can decode the record later.
+**
+** P4 may be a string that is P2 characters long.  The nth character of the
+** string indicates the column affinity that should be used for the nth
+** field of the index key.
+**
+** The mapping from character to affinity is given by the SQLITE_AFF_
+** macros defined in sqliteInt.h.
+**
+** If P4 is NULL then all index fields have the affinity NONE.
+*/
+case OP_MakeRecord: {
+  u8 *zNewRecord;        /* A buffer to hold the data for the new record */
+  Mem *pRec;             /* The new record */
+  u64 nData;             /* Number of bytes of data space */
+  int nHdr;              /* Number of bytes of header space */
+  i64 nByte;             /* Data space required for this record */
+  int nZero;             /* Number of zero bytes at the end of the record */
+  int nVarint;           /* Number of bytes in a varint */
+  u32 serial_type;       /* Type field */
+  Mem *pData0;           /* First field to be combined into the record */
+  Mem *pLast;            /* Last field of the record */
+  int nField;            /* Number of fields in the record */
+  char *zAffinity;       /* The affinity string for the record */
+  int file_format;       /* File format to use for encoding */
+  int i;                 /* Space used in zNewRecord[] */
+  int len;               /* Length of a field */
+
+  /* Assuming the record contains N fields, the record format looks
+  ** like this:
+  **
+  ** ------------------------------------------------------------------------
+  ** | hdr-size | type 0 | type 1 | ... | type N-1 | data0 | ... | data N-1 | 
+  ** ------------------------------------------------------------------------
+  **
+  ** Data(0) is taken from register P1.  Data(1) comes from register P1+1
+  ** and so froth.
+  **
+  ** Each type field is a varint representing the serial type of the 
+  ** corresponding data element (see sqlite3VdbeSerialType()). The
+  ** hdr-size field is also a varint which is the offset from the beginning
+  ** of the record to data0.
+  */
+  nData = 0;         /* Number of bytes of data space */
+  nHdr = 0;          /* Number of bytes of header space */
+  nZero = 0;         /* Number of zero bytes at the end of the record */
+  nField = pOp->p1;
+  zAffinity = pOp->p4.z;
+  assert( nField>0 && pOp->p2>0 && pOp->p2+nField<=p->nMem+1 );
+  pData0 = &aMem[nField];
+  nField = pOp->p2;
+  pLast = &pData0[nField-1];
+  file_format = p->minWriteFileFormat;
+
+  /* Identify the output register */
+  assert( pOp->p3<pOp->p1 || pOp->p3>=pOp->p1+pOp->p2 );
+  pOut = &aMem[pOp->p3];
+  memAboutToChange(p, pOut);
+
+  /* Loop through the elements that will make up the record to figure
+  ** out how much space is required for the new record.
+  */
+  for(pRec=pData0; pRec<=pLast; pRec++){
+    assert( memIsValid(pRec) );
+    if( zAffinity ){
+      applyAffinity(pRec, zAffinity[pRec-pData0], encoding);
+    }
+    if( pRec->flags&MEM_Zero && pRec->n>0 ){
+      sqlite3VdbeMemExpandBlob(pRec);
+    }
+    serial_type = sqlite3VdbeSerialType(pRec, file_format);
+    len = sqlite3VdbeSerialTypeLen(serial_type);
+    nData += len;
+    nHdr += sqlite3VarintLen(serial_type);
+    if( pRec->flags & MEM_Zero ){
+      /* Only pure zero-filled BLOBs can be input to this Opcode.
+      ** We do not allow blobs with a prefix and a zero-filled tail. */
+      nZero += pRec->u.nZero;
+    }else if( len ){
+      nZero = 0;
+    }
+  }
+
+  /* Add the initial header varint and total the size */
+  nHdr += nVarint = sqlite3VarintLen(nHdr);
+  if( nVarint<sqlite3VarintLen(nHdr) ){
+    nHdr++;
+  }
+  nByte = nHdr+nData-nZero;
+  if( nByte>db->aLimit[SQLITE_LIMIT_LENGTH] ){
+    goto too_big;
+  }
+
+  /* Make sure the output register has a buffer large enough to store 
+  ** the new record. The output register (pOp->p3) is not allowed to
+  ** be one of the input registers (because the following call to
+  ** sqlite3VdbeMemGrow() could clobber the value before it is used).
+  */
+  if( sqlite3VdbeMemGrow(pOut, (int)nByte, 0) ){
+    goto no_mem;
+  }
+  zNewRecord = (u8 *)pOut->z;
+
+  /* Write the record */
+  i = putVarint32(zNewRecord, nHdr);
+  for(pRec=pData0; pRec<=pLast; pRec++){
+    serial_type = sqlite3VdbeSerialType(pRec, file_format);
+    i += putVarint32(&zNewRecord[i], serial_type);      /* serial type */
+  }
+  for(pRec=pData0; pRec<=pLast; pRec++){  /* serial data */
+    i += sqlite3VdbeSerialPut(&zNewRecord[i], (int)(nByte-i), pRec,file_format);
+  }
+  assert( i==nByte );
+
+  assert( pOp->p3>0 && pOp->p3<=p->nMem );
+  pOut->n = (int)nByte;
+  pOut->flags = MEM_Blob | MEM_Dyn;
+  pOut->xDel = 0;
+  if( nZero ){
+    pOut->u.nZero = nZero;
+    pOut->flags |= MEM_Zero;
+  }
+  pOut->enc = SQLITE_UTF8;  /* In case the blob is ever converted to text */
+  REGISTER_TRACE(pOp->p3, pOut);
+  UPDATE_MAX_BLOBSIZE(pOut);
+  break;
+}
+
+/* Opcode: Count P1 P2 * * *
+**
+** Store the number of entries (an integer value) in the table or index 
+** opened by cursor P1 in register P2
+*/
+#ifndef SQLITE_OMIT_BTREECOUNT
+case OP_Count: {         /* out2-prerelease */
+  i64 nEntry;
+  BtCursor *pCrsr;
+
+  pCrsr = p->apCsr[pOp->p1]->pCursor;
+  if( ALWAYS(pCrsr) ){
+    rc = sqlite3BtreeCount(pCrsr, &nEntry);
+  }else{
+    nEntry = 0;
+  }
+  pOut->u.i = nEntry;
+  break;
+}
+#endif
+
+/* Opcode: Savepoint P1 * * P4 *
+**
+** Open, release or rollback the savepoint named by parameter P4, depending
+** on the value of P1. To open a new savepoint, P1==0. To release (commit) an
+** existing savepoint, P1==1, or to rollback an existing savepoint P1==2.
+*/
+case OP_Savepoint: {
+  int p1;                         /* Value of P1 operand */
+  char *zName;                    /* Name of savepoint */
+  int nName;
+  Savepoint *pNew;
+  Savepoint *pSavepoint;
+  Savepoint *pTmp;
+  int iSavepoint;
+  int ii;
+
+  p1 = pOp->p1;
+  zName = pOp->p4.z;
+
+  /* Assert that the p1 parameter is valid. Also that if there is no open
+  ** transaction, then there cannot be any savepoints. 
+  */
+  assert( db->pSavepoint==0 || db->autoCommit==0 );
+  assert( p1==SAVEPOINT_BEGIN||p1==SAVEPOINT_RELEASE||p1==SAVEPOINT_ROLLBACK );
+  assert( db->pSavepoint || db->isTransactionSavepoint==0 );
+  assert( checkSavepointCount(db) );
+
+  if( p1==SAVEPOINT_BEGIN ){
+    if( db->writeVdbeCnt>0 ){
+      /* A new savepoint cannot be created if there are active write 
+      ** statements (i.e. open read/write incremental blob handles).
+      */
+      sqlite3SetString(&p->zErrMsg, db, "cannot open savepoint - "
+        "SQL statements in progress");
+      rc = SQLITE_BUSY;
+    }else{
+      nName = sqlite3Strlen30(zName);
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+      /* This call is Ok even if this savepoint is actually a transaction
+      ** savepoint (and therefore should not prompt xSavepoint()) callbacks.
+      ** If this is a transaction savepoint being opened, it is guaranteed
+      ** that the db->aVTrans[] array is empty.  */
+      assert( db->autoCommit==0 || db->nVTrans==0 );
+      rc = sqlite3VtabSavepoint(db, SAVEPOINT_BEGIN,
+                                db->nStatement+db->nSavepoint);
+      if( rc!=SQLITE_OK ) goto abort_due_to_error;
+#endif
+
+      /* Create a new savepoint structure. */
+      pNew = sqlite3DbMallocRaw(db, sizeof(Savepoint)+nName+1);
+      if( pNew ){
+        pNew->zName = (char *)&pNew[1];
+        memcpy(pNew->zName, zName, nName+1);
+    
+        /* If there is no open transaction, then mark this as a special
+        ** "transaction savepoint". */
+        if( db->autoCommit ){
+          db->autoCommit = 0;
+          db->isTransactionSavepoint = 1;
+        }else{
+          db->nSavepoint++;
+        }
+    
+        /* Link the new savepoint into the database handle's list. */
+        pNew->pNext = db->pSavepoint;
+        db->pSavepoint = pNew;
+        pNew->nDeferredCons = db->nDeferredCons;
+      }
+    }
+  }else{
+    iSavepoint = 0;
+
+    /* Find the named savepoint. If there is no such savepoint, then an
+    ** an error is returned to the user.  */
+    for(
+      pSavepoint = db->pSavepoint; 
+      pSavepoint && sqlite3StrICmp(pSavepoint->zName, zName);
+      pSavepoint = pSavepoint->pNext
+    ){
+      iSavepoint++;
+    }
+    if( !pSavepoint ){
+      sqlite3SetString(&p->zErrMsg, db, "no such savepoint: %s", zName);
+      rc = SQLITE_ERROR;
+    }else if( 
+        db->writeVdbeCnt>0 || (p1==SAVEPOINT_ROLLBACK && db->activeVdbeCnt>1) 
+    ){
+      /* It is not possible to release (commit) a savepoint if there are 
+      ** active write statements. It is not possible to rollback a savepoint
+      ** if there are any active statements at all.
+      */
+      sqlite3SetString(&p->zErrMsg, db, 
+        "cannot %s savepoint - SQL statements in progress",
+        (p1==SAVEPOINT_ROLLBACK ? "rollback": "release")
+      );
+      rc = SQLITE_BUSY;
+    }else{
+
+      /* Determine whether or not this is a transaction savepoint. If so,
+      ** and this is a RELEASE command, then the current transaction 
+      ** is committed. 
+      */
+      int isTransaction = pSavepoint->pNext==0 && db->isTransactionSavepoint;
+      if( isTransaction && p1==SAVEPOINT_RELEASE ){
+        if( (rc = sqlite3VdbeCheckFk(p, 1))!=SQLITE_OK ){
+          goto vdbe_return;
+        }
+        db->autoCommit = 1;
+        if( sqlite3VdbeHalt(p)==SQLITE_BUSY ){
+          p->pc = pc;
+          db->autoCommit = 0;
+          p->rc = rc = SQLITE_BUSY;
+          goto vdbe_return;
+        }
+        db->isTransactionSavepoint = 0;
+        rc = p->rc;
+      }else{
+        iSavepoint = db->nSavepoint - iSavepoint - 1;
+        for(ii=0; ii<db->nDb; ii++){
+          rc = sqlite3BtreeSavepoint(db->aDb[ii].pBt, p1, iSavepoint);
+          if( rc!=SQLITE_OK ){
+            goto abort_due_to_error;
+          }
+        }
+        if( p1==SAVEPOINT_ROLLBACK && (db->flags&SQLITE_InternChanges)!=0 ){
+          sqlite3ExpirePreparedStatements(db);
+          sqlite3ResetInternalSchema(db, -1);
+          db->flags = (db->flags | SQLITE_InternChanges);
+        }
+      }
+  
+      /* Regardless of whether this is a RELEASE or ROLLBACK, destroy all 
+      ** savepoints nested inside of the savepoint being operated on. */
+      while( db->pSavepoint!=pSavepoint ){
+        pTmp = db->pSavepoint;
+        db->pSavepoint = pTmp->pNext;
+        sqlite3DbFree(db, pTmp);
+        db->nSavepoint--;
+      }
+
+      /* If it is a RELEASE, then destroy the savepoint being operated on 
+      ** too. If it is a ROLLBACK TO, then set the number of deferred 
+      ** constraint violations present in the database to the value stored
+      ** when the savepoint was created.  */
+      if( p1==SAVEPOINT_RELEASE ){
+        assert( pSavepoint==db->pSavepoint );
+        db->pSavepoint = pSavepoint->pNext;
+        sqlite3DbFree(db, pSavepoint);
+        if( !isTransaction ){
+          db->nSavepoint--;
+        }
+      }else{
+        db->nDeferredCons = pSavepoint->nDeferredCons;
+      }
+
+      if( !isTransaction ){
+        rc = sqlite3VtabSavepoint(db, p1, iSavepoint);
+        if( rc!=SQLITE_OK ) goto abort_due_to_error;
+      }
+    }
+  }
+
+  break;
+}
+
+/* Opcode: AutoCommit P1 P2 * * *
+**
+** Set the database auto-commit flag to P1 (1 or 0). If P2 is true, roll
+** back any currently active btree transactions. If there are any active
+** VMs (apart from this one), then a ROLLBACK fails.  A COMMIT fails if
+** there are active writing VMs or active VMs that use shared cache.
+**
+** This instruction causes the VM to halt.
+*/
+case OP_AutoCommit: {
+  int desiredAutoCommit;
+  int iRollback;
+  int turnOnAC;
+
+  desiredAutoCommit = pOp->p1;
+  iRollback = pOp->p2;
+  turnOnAC = desiredAutoCommit && !db->autoCommit;
+  assert( desiredAutoCommit==1 || desiredAutoCommit==0 );
+  assert( desiredAutoCommit==1 || iRollback==0 );
+  assert( db->activeVdbeCnt>0 );  /* At least this one VM is active */
+
+  if( turnOnAC && iRollback && db->activeVdbeCnt>1 ){
+    /* If this instruction implements a ROLLBACK and other VMs are
+    ** still running, and a transaction is active, return an error indicating
+    ** that the other VMs must complete first. 
+    */
+    sqlite3SetString(&p->zErrMsg, db, "cannot rollback transaction - "
+        "SQL statements in progress");
+    rc = SQLITE_BUSY;
+  }else if( turnOnAC && !iRollback && db->writeVdbeCnt>0 ){
+    /* If this instruction implements a COMMIT and other VMs are writing
+    ** return an error indicating that the other VMs must complete first. 
+    */
+    sqlite3SetString(&p->zErrMsg, db, "cannot commit transaction - "
+        "SQL statements in progress");
+    rc = SQLITE_BUSY;
+  }else if( desiredAutoCommit!=db->autoCommit ){
+    if( iRollback ){
+      assert( desiredAutoCommit==1 );
+      sqlite3RollbackAll(db);
+      db->autoCommit = 1;
+    }else if( (rc = sqlite3VdbeCheckFk(p, 1))!=SQLITE_OK ){
+      goto vdbe_return;
+    }else{
+      db->autoCommit = (u8)desiredAutoCommit;
+      if( sqlite3VdbeHalt(p)==SQLITE_BUSY ){
+        p->pc = pc;
+        db->autoCommit = (u8)(1-desiredAutoCommit);
+        p->rc = rc = SQLITE_BUSY;
+        goto vdbe_return;
+      }
+    }
+    assert( db->nStatement==0 );
+    sqlite3CloseSavepoints(db);
+    if( p->rc==SQLITE_OK ){
+      rc = SQLITE_DONE;
+    }else{
+      rc = SQLITE_ERROR;
+    }
+    goto vdbe_return;
+  }else{
+    sqlite3SetString(&p->zErrMsg, db,
+        (!desiredAutoCommit)?"cannot start a transaction within a transaction":(
+        (iRollback)?"cannot rollback - no transaction is active":
+                   "cannot commit - no transaction is active"));
+         
+    rc = SQLITE_ERROR;
+  }
+  break;
+}
+
+/* Opcode: Transaction P1 P2 * * *
+**
+** Begin a transaction.  The transaction ends when a Commit or Rollback
+** opcode is encountered.  Depending on the ON CONFLICT setting, the
+** transaction might also be rolled back if an error is encountered.
+**
+** P1 is the index of the database file on which the transaction is
+** started.  Index 0 is the main database file and index 1 is the
+** file used for temporary tables.  Indices of 2 or more are used for
+** attached databases.
+**
+** If P2 is non-zero, then a write-transaction is started.  A RESERVED lock is
+** obtained on the database file when a write-transaction is started.  No
+** other process can start another write transaction while this transaction is
+** underway.  Starting a write transaction also creates a rollback journal. A
+** write transaction must be started before any changes can be made to the
+** database.  If P2 is 2 or greater then an EXCLUSIVE lock is also obtained
+** on the file.
+**
+** If a write-transaction is started and the Vdbe.usesStmtJournal flag is
+** true (this flag is set if the Vdbe may modify more than one row and may
+** throw an ABORT exception), a statement transaction may also be opened.
+** More specifically, a statement transaction is opened iff the database
+** connection is currently not in autocommit mode, or if there are other
+** active statements. A statement transaction allows the affects of this
+** VDBE to be rolled back after an error without having to roll back the
+** entire transaction. If no error is encountered, the statement transaction
+** will automatically commit when the VDBE halts.
+**
+** If P2 is zero, then a read-lock is obtained on the database file.
+*/
+case OP_Transaction: {
+  Btree *pBt;
+
+  assert( pOp->p1>=0 && pOp->p1<db->nDb );
+  assert( (p->btreeMask & (((yDbMask)1)<<pOp->p1))!=0 );
+  pBt = db->aDb[pOp->p1].pBt;
+
+  if( pBt ){
+    rc = sqlite3BtreeBeginTrans(pBt, pOp->p2);
+    if( rc==SQLITE_BUSY ){
+      p->pc = pc;
+      p->rc = rc = SQLITE_BUSY;
+      goto vdbe_return;
+    }
+    if( rc!=SQLITE_OK ){
+      goto abort_due_to_error;
+    }
+
+    if( pOp->p2 && p->usesStmtJournal 
+     && (db->autoCommit==0 || db->activeVdbeCnt>1) 
+    ){
+      assert( sqlite3BtreeIsInTrans(pBt) );
+      if( p->iStatement==0 ){
+        assert( db->nStatement>=0 && db->nSavepoint>=0 );
+        db->nStatement++; 
+        p->iStatement = db->nSavepoint + db->nStatement;
+      }
+
+      rc = sqlite3VtabSavepoint(db, SAVEPOINT_BEGIN, p->iStatement-1);
+      if( rc==SQLITE_OK ){
+        rc = sqlite3BtreeBeginStmt(pBt, p->iStatement);
+      }
+
+      /* Store the current value of the database handles deferred constraint
+      ** counter. If the statement transaction needs to be rolled back,
+      ** the value of this counter needs to be restored too.  */
+      p->nStmtDefCons = db->nDeferredCons;
+    }
+  }
+  break;
+}
+
+/* Opcode: ReadCookie P1 P2 P3 * *
+**
+** Read cookie number P3 from database P1 and write it into register P2.
+** P3==1 is the schema version.  P3==2 is the database format.
+** P3==3 is the recommended pager cache size, and so forth.  P1==0 is
+** the main database file and P1==1 is the database file used to store
+** temporary tables.
+**
+** There must be a read-lock on the database (either a transaction
+** must be started or there must be an open cursor) before
+** executing this instruction.
+*/
+case OP_ReadCookie: {               /* out2-prerelease */
+  int iMeta;
+  int iDb;
+  int iCookie;
+
+  iDb = pOp->p1;
+  iCookie = pOp->p3;
+  assert( pOp->p3<SQLITE_N_BTREE_META );
+  assert( iDb>=0 && iDb<db->nDb );
+  assert( db->aDb[iDb].pBt!=0 );
+  assert( (p->btreeMask & (((yDbMask)1)<<iDb))!=0 );
+
+  sqlite3BtreeGetMeta(db->aDb[iDb].pBt, iCookie, (u32 *)&iMeta);
+  pOut->u.i = iMeta;
+  break;
+}
+
+/* Opcode: SetCookie P1 P2 P3 * *
+**
+** Write the content of register P3 (interpreted as an integer)
+** into cookie number P2 of database P1.  P2==1 is the schema version.  
+** P2==2 is the database format. P2==3 is the recommended pager cache 
+** size, and so forth.  P1==0 is the main database file and P1==1 is the 
+** database file used to store temporary tables.
+**
+** A transaction must be started before executing this opcode.
+*/
+case OP_SetCookie: {       /* in3 */
+  Db *pDb;
+  assert( pOp->p2<SQLITE_N_BTREE_META );
+  assert( pOp->p1>=0 && pOp->p1<db->nDb );
+  assert( (p->btreeMask & (((yDbMask)1)<<pOp->p1))!=0 );
+  pDb = &db->aDb[pOp->p1];
+  assert( pDb->pBt!=0 );
+  assert( sqlite3SchemaMutexHeld(db, pOp->p1, 0) );
+  pIn3 = &aMem[pOp->p3];
+  sqlite3VdbeMemIntegerify(pIn3);
+  /* See note about index shifting on OP_ReadCookie */
+  rc = sqlite3BtreeUpdateMeta(pDb->pBt, pOp->p2, (int)pIn3->u.i);
+  if( pOp->p2==BTREE_SCHEMA_VERSION ){
+    /* When the schema cookie changes, record the new cookie internally */
+    pDb->pSchema->schema_cookie = (int)pIn3->u.i;
+    db->flags |= SQLITE_InternChanges;
+  }else if( pOp->p2==BTREE_FILE_FORMAT ){
+    /* Record changes in the file format */
+    pDb->pSchema->file_format = (u8)pIn3->u.i;
+  }
+  if( pOp->p1==1 ){
+    /* Invalidate all prepared statements whenever the TEMP database
+    ** schema is changed.  Ticket #1644 */
+    sqlite3ExpirePreparedStatements(db);
+    p->expired = 0;
+  }
+  break;
+}
+
+/* Opcode: VerifyCookie P1 P2 P3 * *
+**
+** Check the value of global database parameter number 0 (the
+** schema version) and make sure it is equal to P2 and that the
+** generation counter on the local schema parse equals P3.
+**
+** P1 is the database number which is 0 for the main database file
+** and 1 for the file holding temporary tables and some higher number
+** for auxiliary databases.
+**
+** The cookie changes its value whenever the database schema changes.
+** This operation is used to detect when that the cookie has changed
+** and that the current process needs to reread the schema.
+**
+** Either a transaction needs to have been started or an OP_Open needs
+** to be executed (to establish a read lock) before this opcode is
+** invoked.
+*/
+case OP_VerifyCookie: {
+  int iMeta;
+  int iGen;
+  Btree *pBt;
+
+  assert( pOp->p1>=0 && pOp->p1<db->nDb );
+  assert( (p->btreeMask & (((yDbMask)1)<<pOp->p1))!=0 );
+  assert( sqlite3SchemaMutexHeld(db, pOp->p1, 0) );
+  pBt = db->aDb[pOp->p1].pBt;
+  if( pBt ){
+    sqlite3BtreeGetMeta(pBt, BTREE_SCHEMA_VERSION, (u32 *)&iMeta);
+    iGen = db->aDb[pOp->p1].pSchema->iGeneration;
+  }else{
+    iGen = iMeta = 0;
+  }
+  if( iMeta!=pOp->p2 || iGen!=pOp->p3 ){
+    sqlite3DbFree(db, p->zErrMsg);
+    p->zErrMsg = sqlite3DbStrDup(db, "database schema has changed");
+    /* If the schema-cookie from the database file matches the cookie 
+    ** stored with the in-memory representation of the schema, do
+    ** not reload the schema from the database file.
+    **
+    ** If virtual-tables are in use, this is not just an optimization.
+    ** Often, v-tables store their data in other SQLite tables, which
+    ** are queried from within xNext() and other v-table methods using
+    ** prepared queries. If such a query is out-of-date, we do not want to
+    ** discard the database schema, as the user code implementing the
+    ** v-table would have to be ready for the sqlite3_vtab structure itself
+    ** to be invalidated whenever sqlite3_step() is called from within 
+    ** a v-table method.
+    */
+    if( db->aDb[pOp->p1].pSchema->schema_cookie!=iMeta ){
+      sqlite3ResetInternalSchema(db, pOp->p1);
+    }
+
+    p->expired = 1;
+    rc = SQLITE_SCHEMA;
+  }
+  break;
+}
+
+/* Opcode: OpenRead P1 P2 P3 P4 P5
+**
+** Open a read-only cursor for the database table whose root page is
+** P2 in a database file.  The database file is determined by P3. 
+** P3==0 means the main database, P3==1 means the database used for 
+** temporary tables, and P3>1 means used the corresponding attached
+** database.  Give the new cursor an identifier of P1.  The P1
+** values need not be contiguous but all P1 values should be small integers.
+** It is an error for P1 to be negative.
+**
+** If P5!=0 then use the content of register P2 as the root page, not
+** the value of P2 itself.
+**
+** There will be a read lock on the database whenever there is an
+** open cursor.  If the database was unlocked prior to this instruction
+** then a read lock is acquired as part of this instruction.  A read
+** lock allows other processes to read the database but prohibits
+** any other process from modifying the database.  The read lock is
+** released when all cursors are closed.  If this instruction attempts
+** to get a read lock but fails, the script terminates with an
+** SQLITE_BUSY error code.
+**
+** The P4 value may be either an integer (P4_INT32) or a pointer to
+** a KeyInfo structure (P4_KEYINFO). If it is a pointer to a KeyInfo 
+** structure, then said structure defines the content and collating 
+** sequence of the index being opened. Otherwise, if P4 is an integer 
+** value, it is set to the number of columns in the table.
+**
+** See also OpenWrite.
+*/
+/* Opcode: OpenWrite P1 P2 P3 P4 P5
+**
+** Open a read/write cursor named P1 on the table or index whose root
+** page is P2.  Or if P5!=0 use the content of register P2 to find the
+** root page.
+**
+** The P4 value may be either an integer (P4_INT32) or a pointer to
+** a KeyInfo structure (P4_KEYINFO). If it is a pointer to a KeyInfo 
+** structure, then said structure defines the content and collating 
+** sequence of the index being opened. Otherwise, if P4 is an integer 
+** value, it is set to the number of columns in the table, or to the
+** largest index of any column of the table that is actually used.
+**
+** This instruction works just like OpenRead except that it opens the cursor
+** in read/write mode.  For a given table, there can be one or more read-only
+** cursors or a single read/write cursor but not both.
+**
+** See also OpenRead.
+*/
+case OP_OpenRead:
+case OP_OpenWrite: {
+  int nField;
+  KeyInfo *pKeyInfo;
+  int p2;
+  int iDb;
+  int wrFlag;
+  Btree *pX;
+  VdbeCursor *pCur;
+  Db *pDb;
+
+  if( p->expired ){
+    rc = SQLITE_ABORT;
+    break;
+  }
+
+  nField = 0;
+  pKeyInfo = 0;
+  p2 = pOp->p2;
+  iDb = pOp->p3;
+  assert( iDb>=0 && iDb<db->nDb );
+  assert( (p->btreeMask & (((yDbMask)1)<<iDb))!=0 );
+  pDb = &db->aDb[iDb];
+  pX = pDb->pBt;
+  assert( pX!=0 );
+  if( pOp->opcode==OP_OpenWrite ){
+    wrFlag = 1;
+    assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+    if( pDb->pSchema->file_format < p->minWriteFileFormat ){
+      p->minWriteFileFormat = pDb->pSchema->file_format;
+    }
+  }else{
+    wrFlag = 0;
+  }
+  if( pOp->p5 ){
+    assert( p2>0 );
+    assert( p2<=p->nMem );
+    pIn2 = &aMem[p2];
+    assert( memIsValid(pIn2) );
+    assert( (pIn2->flags & MEM_Int)!=0 );
+    sqlite3VdbeMemIntegerify(pIn2);
+    p2 = (int)pIn2->u.i;
+    /* The p2 value always comes from a prior OP_CreateTable opcode and
+    ** that opcode will always set the p2 value to 2 or more or else fail.
+    ** If there were a failure, the prepared statement would have halted
+    ** before reaching this instruction. */
+    if( NEVER(p2<2) ) {
+      rc = SQLITE_CORRUPT_BKPT;
+      goto abort_due_to_error;
+    }
+  }
+  if( pOp->p4type==P4_KEYINFO ){
+    pKeyInfo = pOp->p4.pKeyInfo;
+    pKeyInfo->enc = ENC(p->db);
+    nField = pKeyInfo->nField+1;
+  }else if( pOp->p4type==P4_INT32 ){
+    nField = pOp->p4.i;
+  }
+  assert( pOp->p1>=0 );
+  pCur = allocateCursor(p, pOp->p1, nField, iDb, 1);
+  if( pCur==0 ) goto no_mem;
+  pCur->nullRow = 1;
+  pCur->isOrdered = 1;
+  rc = sqlite3BtreeCursor(pX, p2, wrFlag, pKeyInfo, pCur->pCursor);
+  pCur->pKeyInfo = pKeyInfo;
+
+  /* Since it performs no memory allocation or IO, the only value that
+  ** sqlite3BtreeCursor() may return is SQLITE_OK. */
+  assert( rc==SQLITE_OK );
+
+  /* Set the VdbeCursor.isTable and isIndex variables. Previous versions of
+  ** SQLite used to check if the root-page flags were sane at this point
+  ** and report database corruption if they were not, but this check has
+  ** since moved into the btree layer.  */  
+  pCur->isTable = pOp->p4type!=P4_KEYINFO;
+  pCur->isIndex = !pCur->isTable;
+  break;
+}
+
+/* Opcode: OpenEphemeral P1 P2 * P4 P5
+**
+** Open a new cursor P1 to a transient table.
+** The cursor is always opened read/write even if 
+** the main database is read-only.  The ephemeral
+** table is deleted automatically when the cursor is closed.
+**
+** P2 is the number of columns in the ephemeral table.
+** The cursor points to a BTree table if P4==0 and to a BTree index
+** if P4 is not 0.  If P4 is not NULL, it points to a KeyInfo structure
+** that defines the format of keys in the index.
+**
+** This opcode was once called OpenTemp.  But that created
+** confusion because the term "temp table", might refer either
+** to a TEMP table at the SQL level, or to a table opened by
+** this opcode.  Then this opcode was call OpenVirtual.  But
+** that created confusion with the whole virtual-table idea.
+**
+** The P5 parameter can be a mask of the BTREE_* flags defined
+** in btree.h.  These flags control aspects of the operation of
+** the btree.  The BTREE_OMIT_JOURNAL and BTREE_SINGLE flags are
+** added automatically.
+*/
+/* Opcode: OpenAutoindex P1 P2 * P4 *
+**
+** This opcode works the same as OP_OpenEphemeral.  It has a
+** different name to distinguish its use.  Tables created using
+** by this opcode will be used for automatically created transient
+** indices in joins.
+*/
+case OP_OpenAutoindex: 
+case OP_OpenEphemeral: {
+  VdbeCursor *pCx;
+  static const int vfsFlags = 
+      SQLITE_OPEN_READWRITE |
+      SQLITE_OPEN_CREATE |
+      SQLITE_OPEN_EXCLUSIVE |
+      SQLITE_OPEN_DELETEONCLOSE |
+      SQLITE_OPEN_TRANSIENT_DB;
+
+  assert( pOp->p1>=0 );
+  pCx = allocateCursor(p, pOp->p1, pOp->p2, -1, 1);
+  if( pCx==0 ) goto no_mem;
+  pCx->nullRow = 1;
+  rc = sqlite3BtreeOpen(db->pVfs, 0, db, &pCx->pBt, 
+                        BTREE_OMIT_JOURNAL | BTREE_SINGLE | pOp->p5, vfsFlags);
+  if( rc==SQLITE_OK ){
+    rc = sqlite3BtreeBeginTrans(pCx->pBt, 1);
+  }
+  if( rc==SQLITE_OK ){
+    /* If a transient index is required, create it by calling
+    ** sqlite3BtreeCreateTable() with the BTREE_BLOBKEY flag before
+    ** opening it. If a transient table is required, just use the
+    ** automatically created table with root-page 1 (an BLOB_INTKEY table).
+    */
+    if( pOp->p4.pKeyInfo ){
+      int pgno;
+      assert( pOp->p4type==P4_KEYINFO );
+      rc = sqlite3BtreeCreateTable(pCx->pBt, &pgno, BTREE_BLOBKEY | pOp->p5); 
+      if( rc==SQLITE_OK ){
+        assert( pgno==MASTER_ROOT+1 );
+        rc = sqlite3BtreeCursor(pCx->pBt, pgno, 1, 
+                                (KeyInfo*)pOp->p4.z, pCx->pCursor);
+        pCx->pKeyInfo = pOp->p4.pKeyInfo;
+        pCx->pKeyInfo->enc = ENC(p->db);
+      }
+      pCx->isTable = 0;
+    }else{
+      rc = sqlite3BtreeCursor(pCx->pBt, MASTER_ROOT, 1, 0, pCx->pCursor);
+      pCx->isTable = 1;
+    }
+  }
+  pCx->isOrdered = (pOp->p5!=BTREE_UNORDERED);
+  pCx->isIndex = !pCx->isTable;
+  break;
+}
+
+/* Opcode: OpenSorter P1 P2 * P4 *
+**
+** This opcode works like OP_OpenEphemeral except that it opens
+** a transient index that is specifically designed to sort large
+** tables using an external merge-sort algorithm.
+*/
+case OP_SorterOpen: {
+  VdbeCursor *pCx;
+#ifndef SQLITE_OMIT_MERGE_SORT
+  pCx = allocateCursor(p, pOp->p1, pOp->p2, -1, 1);
+  if( pCx==0 ) goto no_mem;
+  pCx->pKeyInfo = pOp->p4.pKeyInfo;
+  pCx->pKeyInfo->enc = ENC(p->db);
+  pCx->isSorter = 1;
+  rc = sqlite3VdbeSorterInit(db, pCx);
+#else
+  pOp->opcode = OP_OpenEphemeral;
+  pc--;
+#endif
+  break;
+}
+
+/* Opcode: OpenPseudo P1 P2 P3 * *
+**
+** Open a new cursor that points to a fake table that contains a single
+** row of data.  The content of that one row in the content of memory
+** register P2.  In other words, cursor P1 becomes an alias for the 
+** MEM_Blob content contained in register P2.
+**
+** A pseudo-table created by this opcode is used to hold a single
+** row output from the sorter so that the row can be decomposed into
+** individual columns using the OP_Column opcode.  The OP_Column opcode
+** is the only cursor opcode that works with a pseudo-table.
+**
+** P3 is the number of fields in the records that will be stored by
+** the pseudo-table.
+*/
+case OP_OpenPseudo: {
+  VdbeCursor *pCx;
+
+  assert( pOp->p1>=0 );
+  pCx = allocateCursor(p, pOp->p1, pOp->p3, -1, 0);
+  if( pCx==0 ) goto no_mem;
+  pCx->nullRow = 1;
+  pCx->pseudoTableReg = pOp->p2;
+  pCx->isTable = 1;
+  pCx->isIndex = 0;
+  break;
+}
+
+/* Opcode: Close P1 * * * *
+**
+** Close a cursor previously opened as P1.  If P1 is not
+** currently open, this instruction is a no-op.
+*/
+case OP_Close: {
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  sqlite3VdbeFreeCursor(p, p->apCsr[pOp->p1]);
+  p->apCsr[pOp->p1] = 0;
+  break;
+}
+
+/* Opcode: SeekGe P1 P2 P3 P4 *
+**
+** If cursor P1 refers to an SQL table (B-Tree that uses integer keys), 
+** use the value in register P3 as the key.  If cursor P1 refers 
+** to an SQL index, then P3 is the first in an array of P4 registers 
+** that are used as an unpacked index key. 
+**
+** Reposition cursor P1 so that  it points to the smallest entry that 
+** is greater than or equal to the key value. If there are no records 
+** greater than or equal to the key and P2 is not zero, then jump to P2.
+**
+** See also: Found, NotFound, Distinct, SeekLt, SeekGt, SeekLe
+*/
+/* Opcode: SeekGt P1 P2 P3 P4 *
+**
+** If cursor P1 refers to an SQL table (B-Tree that uses integer keys), 
+** use the value in register P3 as a key. If cursor P1 refers 
+** to an SQL index, then P3 is the first in an array of P4 registers 
+** that are used as an unpacked index key. 
+**
+** Reposition cursor P1 so that  it points to the smallest entry that 
+** is greater than the key value. If there are no records greater than 
+** the key and P2 is not zero, then jump to P2.
+**
+** See also: Found, NotFound, Distinct, SeekLt, SeekGe, SeekLe
+*/
+/* Opcode: SeekLt P1 P2 P3 P4 * 
+**
+** If cursor P1 refers to an SQL table (B-Tree that uses integer keys), 
+** use the value in register P3 as a key. If cursor P1 refers 
+** to an SQL index, then P3 is the first in an array of P4 registers 
+** that are used as an unpacked index key. 
+**
+** Reposition cursor P1 so that  it points to the largest entry that 
+** is less than the key value. If there are no records less than 
+** the key and P2 is not zero, then jump to P2.
+**
+** See also: Found, NotFound, Distinct, SeekGt, SeekGe, SeekLe
+*/
+/* Opcode: SeekLe P1 P2 P3 P4 *
+**
+** If cursor P1 refers to an SQL table (B-Tree that uses integer keys), 
+** use the value in register P3 as a key. If cursor P1 refers 
+** to an SQL index, then P3 is the first in an array of P4 registers 
+** that are used as an unpacked index key. 
+**
+** Reposition cursor P1 so that it points to the largest entry that 
+** is less than or equal to the key value. If there are no records 
+** less than or equal to the key and P2 is not zero, then jump to P2.
+**
+** See also: Found, NotFound, Distinct, SeekGt, SeekGe, SeekLt
+*/
+case OP_SeekLt:         /* jump, in3 */
+case OP_SeekLe:         /* jump, in3 */
+case OP_SeekGe:         /* jump, in3 */
+case OP_SeekGt: {       /* jump, in3 */
+  int res;
+  int oc;
+  VdbeCursor *pC;
+  UnpackedRecord r;
+  int nField;
+  i64 iKey;      /* The rowid we are to seek to */
+
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  assert( pOp->p2!=0 );
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  assert( pC->pseudoTableReg==0 );
+  assert( OP_SeekLe == OP_SeekLt+1 );
+  assert( OP_SeekGe == OP_SeekLt+2 );
+  assert( OP_SeekGt == OP_SeekLt+3 );
+  assert( pC->isOrdered );
+  if( ALWAYS(pC->pCursor!=0) ){
+    oc = pOp->opcode;
+    pC->nullRow = 0;
+    if( pC->isTable ){
+      /* The input value in P3 might be of any type: integer, real, string,
+      ** blob, or NULL.  But it needs to be an integer before we can do
+      ** the seek, so covert it. */
+      pIn3 = &aMem[pOp->p3];
+      applyNumericAffinity(pIn3);
+      iKey = sqlite3VdbeIntValue(pIn3);
+      pC->rowidIsValid = 0;
+
+      /* If the P3 value could not be converted into an integer without
+      ** loss of information, then special processing is required... */
+      if( (pIn3->flags & MEM_Int)==0 ){
+        if( (pIn3->flags & MEM_Real)==0 ){
+          /* If the P3 value cannot be converted into any kind of a number,
+          ** then the seek is not possible, so jump to P2 */
+          pc = pOp->p2 - 1;
+          break;
+        }
+        /* If we reach this point, then the P3 value must be a floating
+        ** point number. */
+        assert( (pIn3->flags & MEM_Real)!=0 );
+
+        if( iKey==SMALLEST_INT64 && (pIn3->r<(double)iKey || pIn3->r>0) ){
+          /* The P3 value is too large in magnitude to be expressed as an
+          ** integer. */
+          res = 1;
+          if( pIn3->r<0 ){
+            if( oc>=OP_SeekGe ){  assert( oc==OP_SeekGe || oc==OP_SeekGt );
+              rc = sqlite3BtreeFirst(pC->pCursor, &res);
+              if( rc!=SQLITE_OK ) goto abort_due_to_error;
+            }
+          }else{
+            if( oc<=OP_SeekLe ){  assert( oc==OP_SeekLt || oc==OP_SeekLe );
+              rc = sqlite3BtreeLast(pC->pCursor, &res);
+              if( rc!=SQLITE_OK ) goto abort_due_to_error;
+            }
+          }
+          if( res ){
+            pc = pOp->p2 - 1;
+          }
+          break;
+        }else if( oc==OP_SeekLt || oc==OP_SeekGe ){
+          /* Use the ceiling() function to convert real->int */
+          if( pIn3->r > (double)iKey ) iKey++;
+        }else{
+          /* Use the floor() function to convert real->int */
+          assert( oc==OP_SeekLe || oc==OP_SeekGt );
+          if( pIn3->r < (double)iKey ) iKey--;
+        }
+      } 
+      rc = sqlite3BtreeMovetoUnpacked(pC->pCursor, 0, (u64)iKey, 0, &res);
+      if( rc!=SQLITE_OK ){
+        goto abort_due_to_error;
+      }
+      if( res==0 ){
+        pC->rowidIsValid = 1;
+        pC->lastRowid = iKey;
+      }
+    }else{
+      nField = pOp->p4.i;
+      assert( pOp->p4type==P4_INT32 );
+      assert( nField>0 );
+      r.pKeyInfo = pC->pKeyInfo;
+      r.nField = (u16)nField;
+
+      /* The next line of code computes as follows, only faster:
+      **   if( oc==OP_SeekGt || oc==OP_SeekLe ){
+      **     r.flags = UNPACKED_INCRKEY;
+      **   }else{
+      **     r.flags = 0;
+      **   }
+      */
+      r.flags = (u16)(UNPACKED_INCRKEY * (1 & (oc - OP_SeekLt)));
+      assert( oc!=OP_SeekGt || r.flags==UNPACKED_INCRKEY );
+      assert( oc!=OP_SeekLe || r.flags==UNPACKED_INCRKEY );
+      assert( oc!=OP_SeekGe || r.flags==0 );
+      assert( oc!=OP_SeekLt || r.flags==0 );
+
+      r.aMem = &aMem[pOp->p3];
+#ifdef SQLITE_DEBUG
+      { int i; for(i=0; i<r.nField; i++) assert( memIsValid(&r.aMem[i]) ); }
+#endif
+      ExpandBlob(r.aMem);
+      rc = sqlite3BtreeMovetoUnpacked(pC->pCursor, &r, 0, 0, &res);
+      if( rc!=SQLITE_OK ){
+        goto abort_due_to_error;
+      }
+      pC->rowidIsValid = 0;
+    }
+    pC->deferredMoveto = 0;
+    pC->cacheStatus = CACHE_STALE;
+#ifdef SQLITE_TEST
+    sqlite3_search_count++;
+#endif
+    if( oc>=OP_SeekGe ){  assert( oc==OP_SeekGe || oc==OP_SeekGt );
+      if( res<0 || (res==0 && oc==OP_SeekGt) ){
+        rc = sqlite3BtreeNext(pC->pCursor, &res);
+        if( rc!=SQLITE_OK ) goto abort_due_to_error;
+        pC->rowidIsValid = 0;
+      }else{
+        res = 0;
+      }
+    }else{
+      assert( oc==OP_SeekLt || oc==OP_SeekLe );
+      if( res>0 || (res==0 && oc==OP_SeekLt) ){
+        rc = sqlite3BtreePrevious(pC->pCursor, &res);
+        if( rc!=SQLITE_OK ) goto abort_due_to_error;
+        pC->rowidIsValid = 0;
+      }else{
+        /* res might be negative because the table is empty.  Check to
+        ** see if this is the case.
+        */
+        res = sqlite3BtreeEof(pC->pCursor);
+      }
+    }
+    assert( pOp->p2>0 );
+    if( res ){
+      pc = pOp->p2 - 1;
+    }
+  }else{
+    /* This happens when attempting to open the sqlite3_master table
+    ** for read access returns SQLITE_EMPTY. In this case always
+    ** take the jump (since there are no records in the table).
+    */
+    pc = pOp->p2 - 1;
+  }
+  break;
+}
+
+/* Opcode: Seek P1 P2 * * *
+**
+** P1 is an open table cursor and P2 is a rowid integer.  Arrange
+** for P1 to move so that it points to the rowid given by P2.
+**
+** This is actually a deferred seek.  Nothing actually happens until
+** the cursor is used to read a record.  That way, if no reads
+** occur, no unnecessary I/O happens.
+*/
+case OP_Seek: {    /* in2 */
+  VdbeCursor *pC;
+
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  if( ALWAYS(pC->pCursor!=0) ){
+    assert( pC->isTable );
+    pC->nullRow = 0;
+    pIn2 = &aMem[pOp->p2];
+    pC->movetoTarget = sqlite3VdbeIntValue(pIn2);
+    pC->rowidIsValid = 0;
+    pC->deferredMoveto = 1;
+  }
+  break;
+}
+  
+
+/* Opcode: Found P1 P2 P3 P4 *
+**
+** If P4==0 then register P3 holds a blob constructed by MakeRecord.  If
+** P4>0 then register P3 is the first of P4 registers that form an unpacked
+** record.
+**
+** Cursor P1 is on an index btree.  If the record identified by P3 and P4
+** is a prefix of any entry in P1 then a jump is made to P2 and
+** P1 is left pointing at the matching entry.
+*/
+/* Opcode: NotFound P1 P2 P3 P4 *
+**
+** If P4==0 then register P3 holds a blob constructed by MakeRecord.  If
+** P4>0 then register P3 is the first of P4 registers that form an unpacked
+** record.
+** 
+** Cursor P1 is on an index btree.  If the record identified by P3 and P4
+** is not the prefix of any entry in P1 then a jump is made to P2.  If P1 
+** does contain an entry whose prefix matches the P3/P4 record then control
+** falls through to the next instruction and P1 is left pointing at the
+** matching entry.
+**
+** See also: Found, NotExists, IsUnique
+*/
+case OP_NotFound:       /* jump, in3 */
+case OP_Found: {        /* jump, in3 */
+  int alreadyExists;
+  VdbeCursor *pC;
+  int res;
+  char *pFree;
+  UnpackedRecord *pIdxKey;
+  UnpackedRecord r;
+  char aTempRec[ROUND8(sizeof(UnpackedRecord)) + sizeof(Mem)*3 + 7];
+
+#ifdef SQLITE_TEST
+  sqlite3_found_count++;
+#endif
+
+  alreadyExists = 0;
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  assert( pOp->p4type==P4_INT32 );
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  pIn3 = &aMem[pOp->p3];
+  if( ALWAYS(pC->pCursor!=0) ){
+
+    assert( pC->isTable==0 );
+    if( pOp->p4.i>0 ){
+      r.pKeyInfo = pC->pKeyInfo;
+      r.nField = (u16)pOp->p4.i;
+      r.aMem = pIn3;
+#ifdef SQLITE_DEBUG
+      { int i; for(i=0; i<r.nField; i++) assert( memIsValid(&r.aMem[i]) ); }
+#endif
+      r.flags = UNPACKED_PREFIX_MATCH;
+      pIdxKey = &r;
+    }else{
+      pIdxKey = sqlite3VdbeAllocUnpackedRecord(
+          pC->pKeyInfo, aTempRec, sizeof(aTempRec), &pFree
+      ); 
+      if( pIdxKey==0 ) goto no_mem;
+      assert( pIn3->flags & MEM_Blob );
+      assert( (pIn3->flags & MEM_Zero)==0 );  /* zeroblobs already expanded */
+      sqlite3VdbeRecordUnpack(pC->pKeyInfo, pIn3->n, pIn3->z, pIdxKey);
+      pIdxKey->flags |= UNPACKED_PREFIX_MATCH;
+    }
+    rc = sqlite3BtreeMovetoUnpacked(pC->pCursor, pIdxKey, 0, 0, &res);
+    if( pOp->p4.i==0 ){
+      sqlite3DbFree(db, pFree);
+    }
+    if( rc!=SQLITE_OK ){
+      break;
+    }
+    alreadyExists = (res==0);
+    pC->deferredMoveto = 0;
+    pC->cacheStatus = CACHE_STALE;
+  }
+  if( pOp->opcode==OP_Found ){
+    if( alreadyExists ) pc = pOp->p2 - 1;
+  }else{
+    if( !alreadyExists ) pc = pOp->p2 - 1;
+  }
+  break;
+}
+
+/* Opcode: IsUnique P1 P2 P3 P4 *
+**
+** Cursor P1 is open on an index b-tree - that is to say, a btree which
+** no data and where the key are records generated by OP_MakeRecord with
+** the list field being the integer ROWID of the entry that the index
+** entry refers to.
+**
+** The P3 register contains an integer record number. Call this record 
+** number R. Register P4 is the first in a set of N contiguous registers
+** that make up an unpacked index key that can be used with cursor P1.
+** The value of N can be inferred from the cursor. N includes the rowid
+** value appended to the end of the index record. This rowid value may
+** or may not be the same as R.
+**
+** If any of the N registers beginning with register P4 contains a NULL
+** value, jump immediately to P2.
+**
+** Otherwise, this instruction checks if cursor P1 contains an entry
+** where the first (N-1) fields match but the rowid value at the end
+** of the index entry is not R. If there is no such entry, control jumps
+** to instruction P2. Otherwise, the rowid of the conflicting index
+** entry is copied to register P3 and control falls through to the next
+** instruction.
+**
+** See also: NotFound, NotExists, Found
+*/
+case OP_IsUnique: {        /* jump, in3 */
+  u16 ii;
+  VdbeCursor *pCx;
+  BtCursor *pCrsr;
+  u16 nField;
+  Mem *aMx;
+  UnpackedRecord r;                  /* B-Tree index search key */
+  i64 R;                             /* Rowid stored in register P3 */
+
+  pIn3 = &aMem[pOp->p3];
+  aMx = &aMem[pOp->p4.i];
+  /* Assert that the values of parameters P1 and P4 are in range. */
+  assert( pOp->p4type==P4_INT32 );
+  assert( pOp->p4.i>0 && pOp->p4.i<=p->nMem );
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+
+  /* Find the index cursor. */
+  pCx = p->apCsr[pOp->p1];
+  assert( pCx->deferredMoveto==0 );
+  pCx->seekResult = 0;
+  pCx->cacheStatus = CACHE_STALE;
+  pCrsr = pCx->pCursor;
+
+  /* If any of the values are NULL, take the jump. */
+  nField = pCx->pKeyInfo->nField;
+  for(ii=0; ii<nField; ii++){
+    if( aMx[ii].flags & MEM_Null ){
+      pc = pOp->p2 - 1;
+      pCrsr = 0;
+      break;
+    }
+  }
+  assert( (aMx[nField].flags & MEM_Null)==0 );
+
+  if( pCrsr!=0 ){
+    /* Populate the index search key. */
+    r.pKeyInfo = pCx->pKeyInfo;
+    r.nField = nField + 1;
+    r.flags = UNPACKED_PREFIX_SEARCH;
+    r.aMem = aMx;
+#ifdef SQLITE_DEBUG
+    { int i; for(i=0; i<r.nField; i++) assert( memIsValid(&r.aMem[i]) ); }
+#endif
+
+    /* Extract the value of R from register P3. */
+    sqlite3VdbeMemIntegerify(pIn3);
+    R = pIn3->u.i;
+
+    /* Search the B-Tree index. If no conflicting record is found, jump
+    ** to P2. Otherwise, copy the rowid of the conflicting record to
+    ** register P3 and fall through to the next instruction.  */
+    rc = sqlite3BtreeMovetoUnpacked(pCrsr, &r, 0, 0, &pCx->seekResult);
+    if( (r.flags & UNPACKED_PREFIX_SEARCH) || r.rowid==R ){
+      pc = pOp->p2 - 1;
+    }else{
+      pIn3->u.i = r.rowid;
+    }
+  }
+  break;
+}
+
+/* Opcode: NotExists P1 P2 P3 * *
+**
+** Use the content of register P3 as an integer key.  If a record 
+** with that key does not exist in table of P1, then jump to P2. 
+** If the record does exist, then fall through.  The cursor is left 
+** pointing to the record if it exists.
+**
+** The difference between this operation and NotFound is that this
+** operation assumes the key is an integer and that P1 is a table whereas
+** NotFound assumes key is a blob constructed from MakeRecord and
+** P1 is an index.
+**
+** See also: Found, NotFound, IsUnique
+*/
+case OP_NotExists: {        /* jump, in3 */
+  VdbeCursor *pC;
+  BtCursor *pCrsr;
+  int res;
+  u64 iKey;
+
+  pIn3 = &aMem[pOp->p3];
+  assert( pIn3->flags & MEM_Int );
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  assert( pC->isTable );
+  assert( pC->pseudoTableReg==0 );
+  pCrsr = pC->pCursor;
+  if( ALWAYS(pCrsr!=0) ){
+    res = 0;
+    iKey = pIn3->u.i;
+    rc = sqlite3BtreeMovetoUnpacked(pCrsr, 0, iKey, 0, &res);
+    pC->lastRowid = pIn3->u.i;
+    pC->rowidIsValid = res==0 ?1:0;
+    pC->nullRow = 0;
+    pC->cacheStatus = CACHE_STALE;
+    pC->deferredMoveto = 0;
+    if( res!=0 ){
+      pc = pOp->p2 - 1;
+      assert( pC->rowidIsValid==0 );
+    }
+    pC->seekResult = res;
+  }else{
+    /* This happens when an attempt to open a read cursor on the 
+    ** sqlite_master table returns SQLITE_EMPTY.
+    */
+    pc = pOp->p2 - 1;
+    assert( pC->rowidIsValid==0 );
+    pC->seekResult = 0;
+  }
+  break;
+}
+
+/* Opcode: Sequence P1 P2 * * *
+**
+** Find the next available sequence number for cursor P1.
+** Write the sequence number into register P2.
+** The sequence number on the cursor is incremented after this
+** instruction.  
+*/
+case OP_Sequence: {           /* out2-prerelease */
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  assert( p->apCsr[pOp->p1]!=0 );
+  pOut->u.i = p->apCsr[pOp->p1]->seqCount++;
+  break;
+}
+
+
+/* Opcode: NewRowid P1 P2 P3 * *
+**
+** Get a new integer record number (a.k.a "rowid") used as the key to a table.
+** The record number is not previously used as a key in the database
+** table that cursor P1 points to.  The new record number is written
+** written to register P2.
+**
+** If P3>0 then P3 is a register in the root frame of this VDBE that holds 
+** the largest previously generated record number. No new record numbers are
+** allowed to be less than this value. When this value reaches its maximum, 
+** an SQLITE_FULL error is generated. The P3 register is updated with the '
+** generated record number. This P3 mechanism is used to help implement the
+** AUTOINCREMENT feature.
+*/
+case OP_NewRowid: {           /* out2-prerelease */
+  i64 v;                 /* The new rowid */
+  VdbeCursor *pC;        /* Cursor of table to get the new rowid */
+  int res;               /* Result of an sqlite3BtreeLast() */
+  int cnt;               /* Counter to limit the number of searches */
+  Mem *pMem;             /* Register holding largest rowid for AUTOINCREMENT */
+  VdbeFrame *pFrame;     /* Root frame of VDBE */
+
+  v = 0;
+  res = 0;
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  if( NEVER(pC->pCursor==0) ){
+    /* The zero initialization above is all that is needed */
+  }else{
+    /* The next rowid or record number (different terms for the same
+    ** thing) is obtained in a two-step algorithm.
+    **
+    ** First we attempt to find the largest existing rowid and add one
+    ** to that.  But if the largest existing rowid is already the maximum
+    ** positive integer, we have to fall through to the second
+    ** probabilistic algorithm
+    **
+    ** The second algorithm is to select a rowid at random and see if
+    ** it already exists in the table.  If it does not exist, we have
+    ** succeeded.  If the random rowid does exist, we select a new one
+    ** and try again, up to 100 times.
+    */
+    assert( pC->isTable );
+
+#ifdef SQLITE_32BIT_ROWID
+#   define MAX_ROWID 0x7fffffff
+#else
+    /* Some compilers complain about constants of the form 0x7fffffffffffffff.
+    ** Others complain about 0x7ffffffffffffffffLL.  The following macro seems
+    ** to provide the constant while making all compilers happy.
+    */
+#   define MAX_ROWID  (i64)( (((u64)0x7fffffff)<<32) | (u64)0xffffffff )
+#endif
+
+    if( !pC->useRandomRowid ){
+      v = sqlite3BtreeGetCachedRowid(pC->pCursor);
+      if( v==0 ){
+        rc = sqlite3BtreeLast(pC->pCursor, &res);
+        if( rc!=SQLITE_OK ){
+          goto abort_due_to_error;
+        }
+        if( res ){
+          v = 1;   /* IMP: R-61914-48074 */
+        }else{
+          assert( sqlite3BtreeCursorIsValid(pC->pCursor) );
+          rc = sqlite3BtreeKeySize(pC->pCursor, &v);
+          assert( rc==SQLITE_OK );   /* Cannot fail following BtreeLast() */
+          if( v==MAX_ROWID ){
+            pC->useRandomRowid = 1;
+          }else{
+            v++;   /* IMP: R-29538-34987 */
+          }
+        }
+      }
+
+#ifndef SQLITE_OMIT_AUTOINCREMENT
+      if( pOp->p3 ){
+        /* Assert that P3 is a valid memory cell. */
+        assert( pOp->p3>0 );
+        if( p->pFrame ){
+          for(pFrame=p->pFrame; pFrame->pParent; pFrame=pFrame->pParent);
+          /* Assert that P3 is a valid memory cell. */
+          assert( pOp->p3<=pFrame->nMem );
+          pMem = &pFrame->aMem[pOp->p3];
+        }else{
+          /* Assert that P3 is a valid memory cell. */
+          assert( pOp->p3<=p->nMem );
+          pMem = &aMem[pOp->p3];
+          memAboutToChange(p, pMem);
+        }
+        assert( memIsValid(pMem) );
+
+        REGISTER_TRACE(pOp->p3, pMem);
+        sqlite3VdbeMemIntegerify(pMem);
+        assert( (pMem->flags & MEM_Int)!=0 );  /* mem(P3) holds an integer */
+        if( pMem->u.i==MAX_ROWID || pC->useRandomRowid ){
+          rc = SQLITE_FULL;   /* IMP: R-12275-61338 */
+          goto abort_due_to_error;
+        }
+        if( v<pMem->u.i+1 ){
+          v = pMem->u.i + 1;
+        }
+        pMem->u.i = v;
+      }
+#endif
+
+      sqlite3BtreeSetCachedRowid(pC->pCursor, v<MAX_ROWID ? v+1 : 0);
+    }
+    if( pC->useRandomRowid ){
+      /* IMPLEMENTATION-OF: R-07677-41881 If the largest ROWID is equal to the
+      ** largest possible integer (9223372036854775807) then the database
+      ** engine starts picking positive candidate ROWIDs at random until
+      ** it finds one that is not previously used. */
+      assert( pOp->p3==0 );  /* We cannot be in random rowid mode if this is
+                             ** an AUTOINCREMENT table. */
+      /* on the first attempt, simply do one more than previous */
+      v = lastRowid;
+      v &= (MAX_ROWID>>1); /* ensure doesn't go negative */
+      v++; /* ensure non-zero */
+      cnt = 0;
+      while(   ((rc = sqlite3BtreeMovetoUnpacked(pC->pCursor, 0, (u64)v,
+                                                 0, &res))==SQLITE_OK)
+            && (res==0)
+            && (++cnt<100)){
+        /* collision - try another random rowid */
+        sqlite3_randomness(sizeof(v), &v);
+        if( cnt<5 ){
+          /* try "small" random rowids for the initial attempts */
+          v &= 0xffffff;
+        }else{
+          v &= (MAX_ROWID>>1); /* ensure doesn't go negative */
+        }
+        v++; /* ensure non-zero */
+      }
+      if( rc==SQLITE_OK && res==0 ){
+        rc = SQLITE_FULL;   /* IMP: R-38219-53002 */
+        goto abort_due_to_error;
+      }
+      assert( v>0 );  /* EV: R-40812-03570 */
+    }
+    pC->rowidIsValid = 0;
+    pC->deferredMoveto = 0;
+    pC->cacheStatus = CACHE_STALE;
+  }
+  pOut->u.i = v;
+  break;
+}
+
+/* Opcode: Insert P1 P2 P3 P4 P5
+**
+** Write an entry into the table of cursor P1.  A new entry is
+** created if it doesn't already exist or the data for an existing
+** entry is overwritten.  The data is the value MEM_Blob stored in register
+** number P2. The key is stored in register P3. The key must
+** be a MEM_Int.
+**
+** If the OPFLAG_NCHANGE flag of P5 is set, then the row change count is
+** incremented (otherwise not).  If the OPFLAG_LASTROWID flag of P5 is set,
+** then rowid is stored for subsequent return by the
+** sqlite3_last_insert_rowid() function (otherwise it is unmodified).
+**
+** If the OPFLAG_USESEEKRESULT flag of P5 is set and if the result of
+** the last seek operation (OP_NotExists) was a success, then this
+** operation will not attempt to find the appropriate row before doing
+** the insert but will instead overwrite the row that the cursor is
+** currently pointing to.  Presumably, the prior OP_NotExists opcode
+** has already positioned the cursor correctly.  This is an optimization
+** that boosts performance by avoiding redundant seeks.
+**
+** If the OPFLAG_ISUPDATE flag is set, then this opcode is part of an
+** UPDATE operation.  Otherwise (if the flag is clear) then this opcode
+** is part of an INSERT operation.  The difference is only important to
+** the update hook.
+**
+** Parameter P4 may point to a string containing the table-name, or
+** may be NULL. If it is not NULL, then the update-hook 
+** (sqlite3.xUpdateCallback) is invoked following a successful insert.
+**
+** (WARNING/TODO: If P1 is a pseudo-cursor and P2 is dynamically
+** allocated, then ownership of P2 is transferred to the pseudo-cursor
+** and register P2 becomes ephemeral.  If the cursor is changed, the
+** value of register P2 will then change.  Make sure this does not
+** cause any problems.)
+**
+** This instruction only works on tables.  The equivalent instruction
+** for indices is OP_IdxInsert.
+*/
+/* Opcode: InsertInt P1 P2 P3 P4 P5
+**
+** This works exactly like OP_Insert except that the key is the
+** integer value P3, not the value of the integer stored in register P3.
+*/
+case OP_Insert: 
+case OP_InsertInt: {
+  Mem *pData;       /* MEM cell holding data for the record to be inserted */
+  Mem *pKey;        /* MEM cell holding key  for the record */
+  i64 iKey;         /* The integer ROWID or key for the record to be inserted */
+  VdbeCursor *pC;   /* Cursor to table into which insert is written */
+  int nZero;        /* Number of zero-bytes to append */
+  int seekResult;   /* Result of prior seek or 0 if no USESEEKRESULT flag */
+  const char *zDb;  /* database name - used by the update hook */
+  const char *zTbl; /* Table name - used by the opdate hook */
+  int op;           /* Opcode for update hook: SQLITE_UPDATE or SQLITE_INSERT */
+
+  pData = &aMem[pOp->p2];
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  assert( memIsValid(pData) );
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  assert( pC->pCursor!=0 );
+  assert( pC->pseudoTableReg==0 );
+  assert( pC->isTable );
+  REGISTER_TRACE(pOp->p2, pData);
+
+  if( pOp->opcode==OP_Insert ){
+    pKey = &aMem[pOp->p3];
+    assert( pKey->flags & MEM_Int );
+    assert( memIsValid(pKey) );
+    REGISTER_TRACE(pOp->p3, pKey);
+    iKey = pKey->u.i;
+  }else{
+    assert( pOp->opcode==OP_InsertInt );
+    iKey = pOp->p3;
+  }
+
+  if( pOp->p5 & OPFLAG_NCHANGE ) p->nChange++;
+  if( pOp->p5 & OPFLAG_LASTROWID ) db->lastRowid = lastRowid = iKey;
+  if( pData->flags & MEM_Null ){
+    pData->z = 0;
+    pData->n = 0;
+  }else{
+    assert( pData->flags & (MEM_Blob|MEM_Str) );
+  }
+  seekResult = ((pOp->p5 & OPFLAG_USESEEKRESULT) ? pC->seekResult : 0);
+  if( pData->flags & MEM_Zero ){
+    nZero = pData->u.nZero;
+  }else{
+    nZero = 0;
+  }
+  sqlite3BtreeSetCachedRowid(pC->pCursor, 0);
+  rc = sqlite3BtreeInsert(pC->pCursor, 0, iKey,
+                          pData->z, pData->n, nZero,
+                          pOp->p5 & OPFLAG_APPEND, seekResult
+  );
+  pC->rowidIsValid = 0;
+  pC->deferredMoveto = 0;
+  pC->cacheStatus = CACHE_STALE;
+
+  /* Invoke the update-hook if required. */
+  if( rc==SQLITE_OK && db->xUpdateCallback && pOp->p4.z ){
+    zDb = db->aDb[pC->iDb].zName;
+    zTbl = pOp->p4.z;
+    op = ((pOp->p5 & OPFLAG_ISUPDATE) ? SQLITE_UPDATE : SQLITE_INSERT);
+    assert( pC->isTable );
+    db->xUpdateCallback(db->pUpdateArg, op, zDb, zTbl, iKey);
+    assert( pC->iDb>=0 );
+  }
+  break;
+}
+
+/* Opcode: Delete P1 P2 * P4 *
+**
+** Delete the record at which the P1 cursor is currently pointing.
+**
+** The cursor will be left pointing at either the next or the previous
+** record in the table. If it is left pointing at the next record, then
+** the next Next instruction will be a no-op.  Hence it is OK to delete
+** a record from within an Next loop.
+**
+** If the OPFLAG_NCHANGE flag of P2 is set, then the row change count is
+** incremented (otherwise not).
+**
+** P1 must not be pseudo-table.  It has to be a real table with
+** multiple rows.
+**
+** If P4 is not NULL, then it is the name of the table that P1 is
+** pointing to.  The update hook will be invoked, if it exists.
+** If P4 is not NULL then the P1 cursor must have been positioned
+** using OP_NotFound prior to invoking this opcode.
+*/
+case OP_Delete: {
+  i64 iKey;
+  VdbeCursor *pC;
+
+  iKey = 0;
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  assert( pC->pCursor!=0 );  /* Only valid for real tables, no pseudotables */
+
+  /* If the update-hook will be invoked, set iKey to the rowid of the
+  ** row being deleted.
+  */
+  if( db->xUpdateCallback && pOp->p4.z ){
+    assert( pC->isTable );
+    assert( pC->rowidIsValid );  /* lastRowid set by previous OP_NotFound */
+    iKey = pC->lastRowid;
+  }
+
+  /* The OP_Delete opcode always follows an OP_NotExists or OP_Last or
+  ** OP_Column on the same table without any intervening operations that
+  ** might move or invalidate the cursor.  Hence cursor pC is always pointing
+  ** to the row to be deleted and the sqlite3VdbeCursorMoveto() operation
+  ** below is always a no-op and cannot fail.  We will run it anyhow, though,
+  ** to guard against future changes to the code generator.
+  **/
+  assert( pC->deferredMoveto==0 );
+  rc = sqlite3VdbeCursorMoveto(pC);
+  if( NEVER(rc!=SQLITE_OK) ) goto abort_due_to_error;
+
+  sqlite3BtreeSetCachedRowid(pC->pCursor, 0);
+  rc = sqlite3BtreeDelete(pC->pCursor);
+  pC->cacheStatus = CACHE_STALE;
+
+  /* Invoke the update-hook if required. */
+  if( rc==SQLITE_OK && db->xUpdateCallback && pOp->p4.z ){
+    const char *zDb = db->aDb[pC->iDb].zName;
+    const char *zTbl = pOp->p4.z;
+    db->xUpdateCallback(db->pUpdateArg, SQLITE_DELETE, zDb, zTbl, iKey);
+    assert( pC->iDb>=0 );
+  }
+  if( pOp->p2 & OPFLAG_NCHANGE ) p->nChange++;
+  break;
+}
+/* Opcode: ResetCount * * * * *
+**
+** The value of the change counter is copied to the database handle
+** change counter (returned by subsequent calls to sqlite3_changes()).
+** Then the VMs internal change counter resets to 0.
+** This is used by trigger programs.
+*/
+case OP_ResetCount: {
+  sqlite3VdbeSetChanges(db, p->nChange);
+  p->nChange = 0;
+  break;
+}
+
+/* Opcode: SorterCompare P1 P2 P3
+**
+** P1 is a sorter cursor. This instruction compares the record blob in 
+** register P3 with the entry that the sorter cursor currently points to.
+** If, excluding the rowid fields at the end, the two records are a match,
+** fall through to the next instruction. Otherwise, jump to instruction P2.
+*/
+case OP_SorterCompare: {
+  VdbeCursor *pC;
+  int res;
+
+  pC = p->apCsr[pOp->p1];
+  assert( isSorter(pC) );
+  pIn3 = &aMem[pOp->p3];
+  rc = sqlite3VdbeSorterCompare(pC, pIn3, &res);
+  if( res ){
+    pc = pOp->p2-1;
+  }
+  break;
+};
+
+/* Opcode: SorterData P1 P2 * * *
+**
+** Write into register P2 the current sorter data for sorter cursor P1.
+*/
+case OP_SorterData: {
+  VdbeCursor *pC;
+#ifndef SQLITE_OMIT_MERGE_SORT
+  pOut = &aMem[pOp->p2];
+  pC = p->apCsr[pOp->p1];
+  assert( pC->isSorter );
+  rc = sqlite3VdbeSorterRowkey(pC, pOut);
+#else
+  pOp->opcode = OP_RowKey;
+  pc--;
+#endif
+  break;
+}
+
+/* Opcode: RowData P1 P2 * * *
+**
+** Write into register P2 the complete row data for cursor P1.
+** There is no interpretation of the data.  
+** It is just copied onto the P2 register exactly as 
+** it is found in the database file.
+**
+** If the P1 cursor must be pointing to a valid row (not a NULL row)
+** of a real table, not a pseudo-table.
+*/
+/* Opcode: RowKey P1 P2 * * *
+**
+** Write into register P2 the complete row key for cursor P1.
+** There is no interpretation of the data.  
+** The key is copied onto the P3 register exactly as 
+** it is found in the database file.
+**
+** If the P1 cursor must be pointing to a valid row (not a NULL row)
+** of a real table, not a pseudo-table.
+*/
+case OP_RowKey:
+case OP_RowData: {
+  VdbeCursor *pC;
+  BtCursor *pCrsr;
+  u32 n;
+  i64 n64;
+
+  pOut = &aMem[pOp->p2];
+  memAboutToChange(p, pOut);
+
+  /* Note that RowKey and RowData are really exactly the same instruction */
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  assert( pC->isSorter==0 );
+  assert( pC->isTable || pOp->opcode!=OP_RowData );
+  assert( pC->isIndex || pOp->opcode==OP_RowData );
+  assert( pC!=0 );
+  assert( pC->nullRow==0 );
+  assert( pC->pseudoTableReg==0 );
+  assert( !pC->isSorter );
+  assert( pC->pCursor!=0 );
+  pCrsr = pC->pCursor;
+  assert( sqlite3BtreeCursorIsValid(pCrsr) );
+
+  /* The OP_RowKey and OP_RowData opcodes always follow OP_NotExists or
+  ** OP_Rewind/Op_Next with no intervening instructions that might invalidate
+  ** the cursor.  Hence the following sqlite3VdbeCursorMoveto() call is always
+  ** a no-op and can never fail.  But we leave it in place as a safety.
+  */
+  assert( pC->deferredMoveto==0 );
+  rc = sqlite3VdbeCursorMoveto(pC);
+  if( NEVER(rc!=SQLITE_OK) ) goto abort_due_to_error;
+
+  if( pC->isIndex ){
+    assert( !pC->isTable );
+    VVA_ONLY(rc =) sqlite3BtreeKeySize(pCrsr, &n64);
+    assert( rc==SQLITE_OK );    /* True because of CursorMoveto() call above */
+    if( n64>db->aLimit[SQLITE_LIMIT_LENGTH] ){
+      goto too_big;
+    }
+    n = (u32)n64;
+  }else{
+    VVA_ONLY(rc =) sqlite3BtreeDataSize(pCrsr, &n);
+    assert( rc==SQLITE_OK );    /* DataSize() cannot fail */
+    if( n>(u32)db->aLimit[SQLITE_LIMIT_LENGTH] ){
+      goto too_big;
+    }
+  }
+  if( sqlite3VdbeMemGrow(pOut, n, 0) ){
+    goto no_mem;
+  }
+  pOut->n = n;
+  MemSetTypeFlag(pOut, MEM_Blob);
+  if( pC->isIndex ){
+    rc = sqlite3BtreeKey(pCrsr, 0, n, pOut->z);
+  }else{
+    rc = sqlite3BtreeData(pCrsr, 0, n, pOut->z);
+  }
+  pOut->enc = SQLITE_UTF8;  /* In case the blob is ever cast to text */
+  UPDATE_MAX_BLOBSIZE(pOut);
+  break;
+}
+
+/* Opcode: Rowid P1 P2 * * *
+**
+** Store in register P2 an integer which is the key of the table entry that
+** P1 is currently point to.
+**
+** P1 can be either an ordinary table or a virtual table.  There used to
+** be a separate OP_VRowid opcode for use with virtual tables, but this
+** one opcode now works for both table types.
+*/
+case OP_Rowid: {                 /* out2-prerelease */
+  VdbeCursor *pC;
+  i64 v;
+  sqlite3_vtab *pVtab;
+  const sqlite3_module *pModule;
+
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  assert( pC->pseudoTableReg==0 );
+  if( pC->nullRow ){
+    pOut->flags = MEM_Null;
+    break;
+  }else if( pC->deferredMoveto ){
+    v = pC->movetoTarget;
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  }else if( pC->pVtabCursor ){
+    pVtab = pC->pVtabCursor->pVtab;
+    pModule = pVtab->pModule;
+    assert( pModule->xRowid );
+    rc = pModule->xRowid(pC->pVtabCursor, &v);
+    importVtabErrMsg(p, pVtab);
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+  }else{
+    assert( pC->pCursor!=0 );
+    rc = sqlite3VdbeCursorMoveto(pC);
+    if( rc ) goto abort_due_to_error;
+    if( pC->rowidIsValid ){
+      v = pC->lastRowid;
+    }else{
+      rc = sqlite3BtreeKeySize(pC->pCursor, &v);
+      assert( rc==SQLITE_OK );  /* Always so because of CursorMoveto() above */
+    }
+  }
+  pOut->u.i = v;
+  break;
+}
+
+/* Opcode: NullRow P1 * * * *
+**
+** Move the cursor P1 to a null row.  Any OP_Column operations
+** that occur while the cursor is on the null row will always
+** write a NULL.
+*/
+case OP_NullRow: {
+  VdbeCursor *pC;
+
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  pC->nullRow = 1;
+  pC->rowidIsValid = 0;
+  assert( pC->pCursor || pC->pVtabCursor );
+  if( pC->pCursor ){
+    sqlite3BtreeClearCursor(pC->pCursor);
+  }
+  break;
+}
+
+/* Opcode: Last P1 P2 * * *
+**
+** The next use of the Rowid or Column or Next instruction for P1 
+** will refer to the last entry in the database table or index.
+** If the table or index is empty and P2>0, then jump immediately to P2.
+** If P2 is 0 or if the table or index is not empty, fall through
+** to the following instruction.
+*/
+case OP_Last: {        /* jump */
+  VdbeCursor *pC;
+  BtCursor *pCrsr;
+  int res;
+
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  pCrsr = pC->pCursor;
+  res = 0;
+  if( ALWAYS(pCrsr!=0) ){
+    rc = sqlite3BtreeLast(pCrsr, &res);
+  }
+  pC->nullRow = (u8)res;
+  pC->deferredMoveto = 0;
+  pC->rowidIsValid = 0;
+  pC->cacheStatus = CACHE_STALE;
+  if( pOp->p2>0 && res ){
+    pc = pOp->p2 - 1;
+  }
+  break;
+}
+
+
+/* Opcode: Sort P1 P2 * * *
+**
+** This opcode does exactly the same thing as OP_Rewind except that
+** it increments an undocumented global variable used for testing.
+**
+** Sorting is accomplished by writing records into a sorting index,
+** then rewinding that index and playing it back from beginning to
+** end.  We use the OP_Sort opcode instead of OP_Rewind to do the
+** rewinding so that the global variable will be incremented and
+** regression tests can determine whether or not the optimizer is
+** correctly optimizing out sorts.
+*/
+case OP_SorterSort:    /* jump */
+#ifdef SQLITE_OMIT_MERGE_SORT
+  pOp->opcode = OP_Sort;
+#endif
+case OP_Sort: {        /* jump */
+#ifdef SQLITE_TEST
+  sqlite3_sort_count++;
+  sqlite3_search_count--;
+#endif
+  p->aCounter[SQLITE_STMTSTATUS_SORT-1]++;
+  /* Fall through into OP_Rewind */
+}
+/* Opcode: Rewind P1 P2 * * *
+**
+** The next use of the Rowid or Column or Next instruction for P1 
+** will refer to the first entry in the database table or index.
+** If the table or index is empty and P2>0, then jump immediately to P2.
+** If P2 is 0 or if the table or index is not empty, fall through
+** to the following instruction.
+*/
+case OP_Rewind: {        /* jump */
+  VdbeCursor *pC;
+  BtCursor *pCrsr;
+  int res;
+
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  assert( pC->isSorter==(pOp->opcode==OP_SorterSort) );
+  res = 1;
+  if( isSorter(pC) ){
+    rc = sqlite3VdbeSorterRewind(db, pC, &res);
+  }else{
+    pCrsr = pC->pCursor;
+    assert( pCrsr );
+    rc = sqlite3BtreeFirst(pCrsr, &res);
+    pC->atFirst = res==0 ?1:0;
+    pC->deferredMoveto = 0;
+    pC->cacheStatus = CACHE_STALE;
+    pC->rowidIsValid = 0;
+  }
+  pC->nullRow = (u8)res;
+  assert( pOp->p2>0 && pOp->p2<p->nOp );
+  if( res ){
+    pc = pOp->p2 - 1;
+  }
+  break;
+}
+
+/* Opcode: Next P1 P2 * P4 P5
+**
+** Advance cursor P1 so that it points to the next key/data pair in its
+** table or index.  If there are no more key/value pairs then fall through
+** to the following instruction.  But if the cursor advance was successful,
+** jump immediately to P2.
+**
+** The P1 cursor must be for a real table, not a pseudo-table.
+**
+** P4 is always of type P4_ADVANCE. The function pointer points to
+** sqlite3BtreeNext().
+**
+** If P5 is positive and the jump is taken, then event counter
+** number P5-1 in the prepared statement is incremented.
+**
+** See also: Prev
+*/
+/* Opcode: Prev P1 P2 * * P5
+**
+** Back up cursor P1 so that it points to the previous key/data pair in its
+** table or index.  If there is no previous key/value pairs then fall through
+** to the following instruction.  But if the cursor backup was successful,
+** jump immediately to P2.
+**
+** The P1 cursor must be for a real table, not a pseudo-table.
+**
+** P4 is always of type P4_ADVANCE. The function pointer points to
+** sqlite3BtreePrevious().
+**
+** If P5 is positive and the jump is taken, then event counter
+** number P5-1 in the prepared statement is incremented.
+*/
+case OP_SorterNext:    /* jump */
+#ifdef SQLITE_OMIT_MERGE_SORT
+  pOp->opcode = OP_Next;
+#endif
+case OP_Prev:          /* jump */
+case OP_Next: {        /* jump */
+  VdbeCursor *pC;
+  int res;
+
+  CHECK_FOR_INTERRUPT;
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  assert( pOp->p5<=ArraySize(p->aCounter) );
+  pC = p->apCsr[pOp->p1];
+  if( pC==0 ){
+    break;  /* See ticket #2273 */
+  }
+  assert( pC->isSorter==(pOp->opcode==OP_SorterNext) );
+  if( isSorter(pC) ){
+    assert( pOp->opcode==OP_SorterNext );
+    rc = sqlite3VdbeSorterNext(db, pC, &res);
+  }else{
+    res = 1;
+    assert( pC->deferredMoveto==0 );
+    assert( pC->pCursor );
+    assert( pOp->opcode!=OP_Next || pOp->p4.xAdvance==sqlite3BtreeNext );
+    assert( pOp->opcode!=OP_Prev || pOp->p4.xAdvance==sqlite3BtreePrevious );
+    rc = pOp->p4.xAdvance(pC->pCursor, &res);
+  }
+  pC->nullRow = (u8)res;
+  pC->cacheStatus = CACHE_STALE;
+  if( res==0 ){
+    pc = pOp->p2 - 1;
+    if( pOp->p5 ) p->aCounter[pOp->p5-1]++;
+#ifdef SQLITE_TEST
+    sqlite3_search_count++;
+#endif
+  }
+  pC->rowidIsValid = 0;
+  break;
+}
+
+/* Opcode: IdxInsert P1 P2 P3 * P5
+**
+** Register P2 holds an SQL index key made using the
+** MakeRecord instructions.  This opcode writes that key
+** into the index P1.  Data for the entry is nil.
+**
+** P3 is a flag that provides a hint to the b-tree layer that this
+** insert is likely to be an append.
+**
+** This instruction only works for indices.  The equivalent instruction
+** for tables is OP_Insert.
+*/
+case OP_SorterInsert:       /* in2 */
+#ifdef SQLITE_OMIT_MERGE_SORT
+  pOp->opcode = OP_IdxInsert;
+#endif
+case OP_IdxInsert: {        /* in2 */
+  VdbeCursor *pC;
+  BtCursor *pCrsr;
+  int nKey;
+  const char *zKey;
+
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  assert( pC->isSorter==(pOp->opcode==OP_SorterInsert) );
+  pIn2 = &aMem[pOp->p2];
+  assert( pIn2->flags & MEM_Blob );
+  pCrsr = pC->pCursor;
+  if( ALWAYS(pCrsr!=0) ){
+    assert( pC->isTable==0 );
+    rc = ExpandBlob(pIn2);
+    if( rc==SQLITE_OK ){
+      if( isSorter(pC) ){
+        rc = sqlite3VdbeSorterWrite(db, pC, pIn2);
+      }else{
+        nKey = pIn2->n;
+        zKey = pIn2->z;
+        rc = sqlite3BtreeInsert(pCrsr, zKey, nKey, "", 0, 0, pOp->p3, 
+            ((pOp->p5 & OPFLAG_USESEEKRESULT) ? pC->seekResult : 0)
+            );
+        assert( pC->deferredMoveto==0 );
+        pC->cacheStatus = CACHE_STALE;
+      }
+    }
+  }
+  break;
+}
+
+/* Opcode: IdxDelete P1 P2 P3 * *
+**
+** The content of P3 registers starting at register P2 form
+** an unpacked index key. This opcode removes that entry from the 
+** index opened by cursor P1.
+*/
+case OP_IdxDelete: {
+  VdbeCursor *pC;
+  BtCursor *pCrsr;
+  int res;
+  UnpackedRecord r;
+
+  assert( pOp->p3>0 );
+  assert( pOp->p2>0 && pOp->p2+pOp->p3<=p->nMem+1 );
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  pCrsr = pC->pCursor;
+  if( ALWAYS(pCrsr!=0) ){
+    r.pKeyInfo = pC->pKeyInfo;
+    r.nField = (u16)pOp->p3;
+    r.flags = 0;
+    r.aMem = &aMem[pOp->p2];
+#ifdef SQLITE_DEBUG
+    { int i; for(i=0; i<r.nField; i++) assert( memIsValid(&r.aMem[i]) ); }
+#endif
+    rc = sqlite3BtreeMovetoUnpacked(pCrsr, &r, 0, 0, &res);
+    if( rc==SQLITE_OK && res==0 ){
+      rc = sqlite3BtreeDelete(pCrsr);
+    }
+    assert( pC->deferredMoveto==0 );
+    pC->cacheStatus = CACHE_STALE;
+  }
+  break;
+}
+
+/* Opcode: IdxRowid P1 P2 * * *
+**
+** Write into register P2 an integer which is the last entry in the record at
+** the end of the index key pointed to by cursor P1.  This integer should be
+** the rowid of the table entry to which this index entry points.
+**
+** See also: Rowid, MakeRecord.
+*/
+case OP_IdxRowid: {              /* out2-prerelease */
+  BtCursor *pCrsr;
+  VdbeCursor *pC;
+  i64 rowid;
+
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  pCrsr = pC->pCursor;
+  pOut->flags = MEM_Null;
+  if( ALWAYS(pCrsr!=0) ){
+    rc = sqlite3VdbeCursorMoveto(pC);
+    if( NEVER(rc) ) goto abort_due_to_error;
+    assert( pC->deferredMoveto==0 );
+    assert( pC->isTable==0 );
+    if( !pC->nullRow ){
+      rc = sqlite3VdbeIdxRowid(db, pCrsr, &rowid);
+      if( rc!=SQLITE_OK ){
+        goto abort_due_to_error;
+      }
+      pOut->u.i = rowid;
+      pOut->flags = MEM_Int;
+    }
+  }
+  break;
+}
+
+/* Opcode: IdxGE P1 P2 P3 P4 P5
+**
+** The P4 register values beginning with P3 form an unpacked index 
+** key that omits the ROWID.  Compare this key value against the index 
+** that P1 is currently pointing to, ignoring the ROWID on the P1 index.
+**
+** If the P1 index entry is greater than or equal to the key value
+** then jump to P2.  Otherwise fall through to the next instruction.
+**
+** If P5 is non-zero then the key value is increased by an epsilon 
+** prior to the comparison.  This make the opcode work like IdxGT except
+** that if the key from register P3 is a prefix of the key in the cursor,
+** the result is false whereas it would be true with IdxGT.
+*/
+/* Opcode: IdxLT P1 P2 P3 P4 P5
+**
+** The P4 register values beginning with P3 form an unpacked index 
+** key that omits the ROWID.  Compare this key value against the index 
+** that P1 is currently pointing to, ignoring the ROWID on the P1 index.
+**
+** If the P1 index entry is less than the key value then jump to P2.
+** Otherwise fall through to the next instruction.
+**
+** If P5 is non-zero then the key value is increased by an epsilon prior 
+** to the comparison.  This makes the opcode work like IdxLE.
+*/
+case OP_IdxLT:          /* jump */
+case OP_IdxGE: {        /* jump */
+  VdbeCursor *pC;
+  int res;
+  UnpackedRecord r;
+
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  assert( pC->isOrdered );
+  if( ALWAYS(pC->pCursor!=0) ){
+    assert( pC->deferredMoveto==0 );
+    assert( pOp->p5==0 || pOp->p5==1 );
+    assert( pOp->p4type==P4_INT32 );
+    r.pKeyInfo = pC->pKeyInfo;
+    r.nField = (u16)pOp->p4.i;
+    if( pOp->p5 ){
+      r.flags = UNPACKED_INCRKEY | UNPACKED_IGNORE_ROWID;
+    }else{
+      r.flags = UNPACKED_IGNORE_ROWID;
+    }
+    r.aMem = &aMem[pOp->p3];
+#ifdef SQLITE_DEBUG
+    { int i; for(i=0; i<r.nField; i++) assert( memIsValid(&r.aMem[i]) ); }
+#endif
+    rc = sqlite3VdbeIdxKeyCompare(pC, &r, &res);
+    if( pOp->opcode==OP_IdxLT ){
+      res = -res;
+    }else{
+      assert( pOp->opcode==OP_IdxGE );
+      res++;
+    }
+    if( res>0 ){
+      pc = pOp->p2 - 1 ;
+    }
+  }
+  break;
+}
+
+/* Opcode: Destroy P1 P2 P3 * *
+**
+** Delete an entire database table or index whose root page in the database
+** file is given by P1.
+**
+** The table being destroyed is in the main database file if P3==0.  If
+** P3==1 then the table to be clear is in the auxiliary database file
+** that is used to store tables create using CREATE TEMPORARY TABLE.
+**
+** If AUTOVACUUM is enabled then it is possible that another root page
+** might be moved into the newly deleted root page in order to keep all
+** root pages contiguous at the beginning of the database.  The former
+** value of the root page that moved - its value before the move occurred -
+** is stored in register P2.  If no page 
+** movement was required (because the table being dropped was already 
+** the last one in the database) then a zero is stored in register P2.
+** If AUTOVACUUM is disabled then a zero is stored in register P2.
+**
+** See also: Clear
+*/
+case OP_Destroy: {     /* out2-prerelease */
+  int iMoved;
+  int iCnt;
+  Vdbe *pVdbe;
+  int iDb;
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  iCnt = 0;
+  for(pVdbe=db->pVdbe; pVdbe; pVdbe = pVdbe->pNext){
+    if( pVdbe->magic==VDBE_MAGIC_RUN && pVdbe->inVtabMethod<2 && pVdbe->pc>=0 ){
+      iCnt++;
+    }
+  }
+#else
+  iCnt = db->activeVdbeCnt;
+#endif
+  pOut->flags = MEM_Null;
+  if( iCnt>1 ){
+    rc = SQLITE_LOCKED;
+    p->errorAction = OE_Abort;
+  }else{
+    iDb = pOp->p3;
+    assert( iCnt==1 );
+    assert( (p->btreeMask & (((yDbMask)1)<<iDb))!=0 );
+    rc = sqlite3BtreeDropTable(db->aDb[iDb].pBt, pOp->p1, &iMoved);
+    pOut->flags = MEM_Int;
+    pOut->u.i = iMoved;
+#ifndef SQLITE_OMIT_AUTOVACUUM
+    if( rc==SQLITE_OK && iMoved!=0 ){
+      sqlite3RootPageMoved(db, iDb, iMoved, pOp->p1);
+      /* All OP_Destroy operations occur on the same btree */
+      assert( resetSchemaOnFault==0 || resetSchemaOnFault==iDb+1 );
+      resetSchemaOnFault = iDb+1;
+    }
+#endif
+  }
+  break;
+}
+
+/* Opcode: Clear P1 P2 P3
+**
+** Delete all contents of the database table or index whose root page
+** in the database file is given by P1.  But, unlike Destroy, do not
+** remove the table or index from the database file.
+**
+** The table being clear is in the main database file if P2==0.  If
+** P2==1 then the table to be clear is in the auxiliary database file
+** that is used to store tables create using CREATE TEMPORARY TABLE.
+**
+** If the P3 value is non-zero, then the table referred to must be an
+** intkey table (an SQL table, not an index). In this case the row change 
+** count is incremented by the number of rows in the table being cleared. 
+** If P3 is greater than zero, then the value stored in register P3 is
+** also incremented by the number of rows in the table being cleared.
+**
+** See also: Destroy
+*/
+case OP_Clear: {
+  int nChange;
+ 
+  nChange = 0;
+  assert( (p->btreeMask & (((yDbMask)1)<<pOp->p2))!=0 );
+  rc = sqlite3BtreeClearTable(
+      db->aDb[pOp->p2].pBt, pOp->p1, (pOp->p3 ? &nChange : 0)
+  );
+  if( pOp->p3 ){
+    p->nChange += nChange;
+    if( pOp->p3>0 ){
+      assert( memIsValid(&aMem[pOp->p3]) );
+      memAboutToChange(p, &aMem[pOp->p3]);
+      aMem[pOp->p3].u.i += nChange;
+    }
+  }
+  break;
+}
+
+/* Opcode: CreateTable P1 P2 * * *
+**
+** Allocate a new table in the main database file if P1==0 or in the
+** auxiliary database file if P1==1 or in an attached database if
+** P1>1.  Write the root page number of the new table into
+** register P2
+**
+** The difference between a table and an index is this:  A table must
+** have a 4-byte integer key and can have arbitrary data.  An index
+** has an arbitrary key but no data.
+**
+** See also: CreateIndex
+*/
+/* Opcode: CreateIndex P1 P2 * * *
+**
+** Allocate a new index in the main database file if P1==0 or in the
+** auxiliary database file if P1==1 or in an attached database if
+** P1>1.  Write the root page number of the new table into
+** register P2.
+**
+** See documentation on OP_CreateTable for additional information.
+*/
+case OP_CreateIndex:            /* out2-prerelease */
+case OP_CreateTable: {          /* out2-prerelease */
+  int pgno;
+  int flags;
+  Db *pDb;
+
+  pgno = 0;
+  assert( pOp->p1>=0 && pOp->p1<db->nDb );
+  assert( (p->btreeMask & (((yDbMask)1)<<pOp->p1))!=0 );
+  pDb = &db->aDb[pOp->p1];
+  assert( pDb->pBt!=0 );
+  if( pOp->opcode==OP_CreateTable ){
+    /* flags = BTREE_INTKEY; */
+    flags = BTREE_INTKEY;
+  }else{
+    flags = BTREE_BLOBKEY;
+  }
+  rc = sqlite3BtreeCreateTable(pDb->pBt, &pgno, flags);
+  pOut->u.i = pgno;
+  break;
+}
+
+/* Opcode: ParseSchema P1 * * P4 *
+**
+** Read and parse all entries from the SQLITE_MASTER table of database P1
+** that match the WHERE clause P4. 
+**
+** This opcode invokes the parser to create a new virtual machine,
+** then runs the new virtual machine.  It is thus a re-entrant opcode.
+*/
+case OP_ParseSchema: {
+  int iDb;
+  const char *zMaster;
+  char *zSql;
+  InitData initData;
+
+  /* Any prepared statement that invokes this opcode will hold mutexes
+  ** on every btree.  This is a prerequisite for invoking 
+  ** sqlite3InitCallback().
+  */
+#ifdef SQLITE_DEBUG
+  for(iDb=0; iDb<db->nDb; iDb++){
+    assert( iDb==1 || sqlite3BtreeHoldsMutex(db->aDb[iDb].pBt) );
+  }
+#endif
+
+  iDb = pOp->p1;
+  assert( iDb>=0 && iDb<db->nDb );
+  assert( DbHasProperty(db, iDb, DB_SchemaLoaded) );
+  /* Used to be a conditional */ {
+    zMaster = SCHEMA_TABLE(iDb);
+    initData.db = db;
+    initData.iDb = pOp->p1;
+    initData.pzErrMsg = &p->zErrMsg;
+    zSql = sqlite3MPrintf(db,
+       "SELECT name, rootpage, sql FROM '%q'.%s WHERE %s ORDER BY rowid",
+       db->aDb[iDb].zName, zMaster, pOp->p4.z);
+    if( zSql==0 ){
+      rc = SQLITE_NOMEM;
+    }else{
+      assert( db->init.busy==0 );
+      db->init.busy = 1;
+      initData.rc = SQLITE_OK;
+      assert( !db->mallocFailed );
+      rc = sqlite3_exec(db, zSql, sqlite3InitCallback, &initData, 0);
+      if( rc==SQLITE_OK ) rc = initData.rc;
+      sqlite3DbFree(db, zSql);
+      db->init.busy = 0;
+    }
+  }
+  if( rc==SQLITE_NOMEM ){
+    goto no_mem;
+  }
+  break;  
+}
+
+#if !defined(SQLITE_OMIT_ANALYZE)
+/* Opcode: LoadAnalysis P1 * * * *
+**
+** Read the sqlite_stat1 table for database P1 and load the content
+** of that table into the internal index hash table.  This will cause
+** the analysis to be used when preparing all subsequent queries.
+*/
+case OP_LoadAnalysis: {
+  assert( pOp->p1>=0 && pOp->p1<db->nDb );
+  rc = sqlite3AnalysisLoad(db, pOp->p1);
+  break;  
+}
+#endif /* !defined(SQLITE_OMIT_ANALYZE) */
+
+/* Opcode: DropTable P1 * * P4 *
+**
+** Remove the internal (in-memory) data structures that describe
+** the table named P4 in database P1.  This is called after a table
+** is dropped in order to keep the internal representation of the
+** schema consistent with what is on disk.
+*/
+case OP_DropTable: {
+  sqlite3UnlinkAndDeleteTable(db, pOp->p1, pOp->p4.z);
+  break;
+}
+
+/* Opcode: DropIndex P1 * * P4 *
+**
+** Remove the internal (in-memory) data structures that describe
+** the index named P4 in database P1.  This is called after an index
+** is dropped in order to keep the internal representation of the
+** schema consistent with what is on disk.
+*/
+case OP_DropIndex: {
+  sqlite3UnlinkAndDeleteIndex(db, pOp->p1, pOp->p4.z);
+  break;
+}
+
+/* Opcode: DropTrigger P1 * * P4 *
+**
+** Remove the internal (in-memory) data structures that describe
+** the trigger named P4 in database P1.  This is called after a trigger
+** is dropped in order to keep the internal representation of the
+** schema consistent with what is on disk.
+*/
+case OP_DropTrigger: {
+  sqlite3UnlinkAndDeleteTrigger(db, pOp->p1, pOp->p4.z);
+  break;
+}
+
+
+#ifndef SQLITE_OMIT_INTEGRITY_CHECK
+/* Opcode: IntegrityCk P1 P2 P3 * P5
+**
+** Do an analysis of the currently open database.  Store in
+** register P1 the text of an error message describing any problems.
+** If no problems are found, store a NULL in register P1.
+**
+** The register P3 contains the maximum number of allowed errors.
+** At most reg(P3) errors will be reported.
+** In other words, the analysis stops as soon as reg(P1) errors are 
+** seen.  Reg(P1) is updated with the number of errors remaining.
+**
+** The root page numbers of all tables in the database are integer
+** stored in reg(P1), reg(P1+1), reg(P1+2), ....  There are P2 tables
+** total.
+**
+** If P5 is not zero, the check is done on the auxiliary database
+** file, not the main database file.
+**
+** This opcode is used to implement the integrity_check pragma.
+*/
+case OP_IntegrityCk: {
+  int nRoot;      /* Number of tables to check.  (Number of root pages.) */
+  int *aRoot;     /* Array of rootpage numbers for tables to be checked */
+  int j;          /* Loop counter */
+  int nErr;       /* Number of errors reported */
+  char *z;        /* Text of the error report */
+  Mem *pnErr;     /* Register keeping track of errors remaining */
+  
+  nRoot = pOp->p2;
+  assert( nRoot>0 );
+  aRoot = sqlite3DbMallocRaw(db, sizeof(int)*(nRoot+1) );
+  if( aRoot==0 ) goto no_mem;
+  assert( pOp->p3>0 && pOp->p3<=p->nMem );
+  pnErr = &aMem[pOp->p3];
+  assert( (pnErr->flags & MEM_Int)!=0 );
+  assert( (pnErr->flags & (MEM_Str|MEM_Blob))==0 );
+  pIn1 = &aMem[pOp->p1];
+  for(j=0; j<nRoot; j++){
+    aRoot[j] = (int)sqlite3VdbeIntValue(&pIn1[j]);
+  }
+  aRoot[j] = 0;
+  assert( pOp->p5<db->nDb );
+  assert( (p->btreeMask & (((yDbMask)1)<<pOp->p5))!=0 );
+  z = sqlite3BtreeIntegrityCheck(db->aDb[pOp->p5].pBt, aRoot, nRoot,
+                                 (int)pnErr->u.i, &nErr);
+  sqlite3DbFree(db, aRoot);
+  pnErr->u.i -= nErr;
+  sqlite3VdbeMemSetNull(pIn1);
+  if( nErr==0 ){
+    assert( z==0 );
+  }else if( z==0 ){
+    goto no_mem;
+  }else{
+    sqlite3VdbeMemSetStr(pIn1, z, -1, SQLITE_UTF8, sqlite3_free);
+  }
+  UPDATE_MAX_BLOBSIZE(pIn1);
+  sqlite3VdbeChangeEncoding(pIn1, encoding);
+  break;
+}
+#endif /* SQLITE_OMIT_INTEGRITY_CHECK */
+
+/* Opcode: RowSetAdd P1 P2 * * *
+**
+** Insert the integer value held by register P2 into a boolean index
+** held in register P1.
+**
+** An assertion fails if P2 is not an integer.
+*/
+case OP_RowSetAdd: {       /* in1, in2 */
+  pIn1 = &aMem[pOp->p1];
+  pIn2 = &aMem[pOp->p2];
+  assert( (pIn2->flags & MEM_Int)!=0 );
+  if( (pIn1->flags & MEM_RowSet)==0 ){
+    sqlite3VdbeMemSetRowSet(pIn1);
+    if( (pIn1->flags & MEM_RowSet)==0 ) goto no_mem;
+  }
+  sqlite3RowSetInsert(pIn1->u.pRowSet, pIn2->u.i);
+  break;
+}
+
+/* Opcode: RowSetRead P1 P2 P3 * *
+**
+** Extract the smallest value from boolean index P1 and put that value into
+** register P3.  Or, if boolean index P1 is initially empty, leave P3
+** unchanged and jump to instruction P2.
+*/
+case OP_RowSetRead: {       /* jump, in1, out3 */
+  i64 val;
+  CHECK_FOR_INTERRUPT;
+  pIn1 = &aMem[pOp->p1];
+  if( (pIn1->flags & MEM_RowSet)==0 
+   || sqlite3RowSetNext(pIn1->u.pRowSet, &val)==0
+  ){
+    /* The boolean index is empty */
+    sqlite3VdbeMemSetNull(pIn1);
+    pc = pOp->p2 - 1;
+  }else{
+    /* A value was pulled from the index */
+    sqlite3VdbeMemSetInt64(&aMem[pOp->p3], val);
+  }
+  break;
+}
+
+/* Opcode: RowSetTest P1 P2 P3 P4
+**
+** Register P3 is assumed to hold a 64-bit integer value. If register P1
+** contains a RowSet object and that RowSet object contains
+** the value held in P3, jump to register P2. Otherwise, insert the
+** integer in P3 into the RowSet and continue on to the
+** next opcode.
+**
+** The RowSet object is optimized for the case where successive sets
+** of integers, where each set contains no duplicates. Each set
+** of values is identified by a unique P4 value. The first set
+** must have P4==0, the final set P4=-1.  P4 must be either -1 or
+** non-negative.  For non-negative values of P4 only the lower 4
+** bits are significant.
+**
+** This allows optimizations: (a) when P4==0 there is no need to test
+** the rowset object for P3, as it is guaranteed not to contain it,
+** (b) when P4==-1 there is no need to insert the value, as it will
+** never be tested for, and (c) when a value that is part of set X is
+** inserted, there is no need to search to see if the same value was
+** previously inserted as part of set X (only if it was previously
+** inserted as part of some other set).
+*/
+case OP_RowSetTest: {                     /* jump, in1, in3 */
+  int iSet;
+  int exists;
+
+  pIn1 = &aMem[pOp->p1];
+  pIn3 = &aMem[pOp->p3];
+  iSet = pOp->p4.i;
+  assert( pIn3->flags&MEM_Int );
+
+  /* If there is anything other than a rowset object in memory cell P1,
+  ** delete it now and initialize P1 with an empty rowset
+  */
+  if( (pIn1->flags & MEM_RowSet)==0 ){
+    sqlite3VdbeMemSetRowSet(pIn1);
+    if( (pIn1->flags & MEM_RowSet)==0 ) goto no_mem;
+  }
+
+  assert( pOp->p4type==P4_INT32 );
+  assert( iSet==-1 || iSet>=0 );
+  if( iSet ){
+    exists = sqlite3RowSetTest(pIn1->u.pRowSet, 
+                               (u8)(iSet>=0 ? iSet & 0xf : 0xff),
+                               pIn3->u.i);
+    if( exists ){
+      pc = pOp->p2 - 1;
+      break;
+    }
+  }
+  if( iSet>=0 ){
+    sqlite3RowSetInsert(pIn1->u.pRowSet, pIn3->u.i);
+  }
+  break;
+}
+
+
+#ifndef SQLITE_OMIT_TRIGGER
+
+/* Opcode: Program P1 P2 P3 P4 *
+**
+** Execute the trigger program passed as P4 (type P4_SUBPROGRAM). 
+**
+** P1 contains the address of the memory cell that contains the first memory 
+** cell in an array of values used as arguments to the sub-program. P2 
+** contains the address to jump to if the sub-program throws an IGNORE 
+** exception using the RAISE() function. Register P3 contains the address 
+** of a memory cell in this (the parent) VM that is used to allocate the 
+** memory required by the sub-vdbe at runtime.
+**
+** P4 is a pointer to the VM containing the trigger program.
+*/
+case OP_Program: {        /* jump */
+  int nMem;               /* Number of memory registers for sub-program */
+  int nByte;              /* Bytes of runtime space required for sub-program */
+  Mem *pRt;               /* Register to allocate runtime space */
+  Mem *pMem;              /* Used to iterate through memory cells */
+  Mem *pEnd;              /* Last memory cell in new array */
+  VdbeFrame *pFrame;      /* New vdbe frame to execute in */
+  SubProgram *pProgram;   /* Sub-program to execute */
+  void *t;                /* Token identifying trigger */
+
+  pProgram = pOp->p4.pProgram;
+  pRt = &aMem[pOp->p3];
+  assert( memIsValid(pRt) );
+  assert( pProgram->nOp>0 );
+  
+  /* If the p5 flag is clear, then recursive invocation of triggers is 
+  ** disabled for backwards compatibility (p5 is set if this sub-program
+  ** is really a trigger, not a foreign key action, and the flag set
+  ** and cleared by the "PRAGMA recursive_triggers" command is clear).
+  ** 
+  ** It is recursive invocation of triggers, at the SQL level, that is 
+  ** disabled. In some cases a single trigger may generate more than one 
+  ** SubProgram (if the trigger may be executed with more than one different 
+  ** ON CONFLICT algorithm). SubProgram structures associated with a
+  ** single trigger all have the same value for the SubProgram.token 
+  ** variable.  */
+  if( pOp->p5 ){
+    t = pProgram->token;
+    for(pFrame=p->pFrame; pFrame && pFrame->token!=t; pFrame=pFrame->pParent);
+    if( pFrame ) break;
+  }
+
+  if( p->nFrame>=db->aLimit[SQLITE_LIMIT_TRIGGER_DEPTH] ){
+    rc = SQLITE_ERROR;
+    sqlite3SetString(&p->zErrMsg, db, "too many levels of trigger recursion");
+    break;
+  }
+
+  /* Register pRt is used to store the memory required to save the state
+  ** of the current program, and the memory required at runtime to execute
+  ** the trigger program. If this trigger has been fired before, then pRt 
+  ** is already allocated. Otherwise, it must be initialized.  */
+  if( (pRt->flags&MEM_Frame)==0 ){
+    /* SubProgram.nMem is set to the number of memory cells used by the 
+    ** program stored in SubProgram.aOp. As well as these, one memory
+    ** cell is required for each cursor used by the program. Set local
+    ** variable nMem (and later, VdbeFrame.nChildMem) to this value.
+    */
+    nMem = pProgram->nMem + pProgram->nCsr;
+    nByte = ROUND8(sizeof(VdbeFrame))
+              + nMem * sizeof(Mem)
+              + pProgram->nCsr * sizeof(VdbeCursor *);
+    pFrame = sqlite3DbMallocZero(db, nByte);
+    if( !pFrame ){
+      goto no_mem;
+    }
+    sqlite3VdbeMemRelease(pRt);
+    pRt->flags = MEM_Frame;
+    pRt->u.pFrame = pFrame;
+
+    pFrame->v = p;
+    pFrame->nChildMem = nMem;
+    pFrame->nChildCsr = pProgram->nCsr;
+    pFrame->pc = pc;
+    pFrame->aMem = p->aMem;
+    pFrame->nMem = p->nMem;
+    pFrame->apCsr = p->apCsr;
+    pFrame->nCursor = p->nCursor;
+    pFrame->aOp = p->aOp;
+    pFrame->nOp = p->nOp;
+    pFrame->token = pProgram->token;
+
+    pEnd = &VdbeFrameMem(pFrame)[pFrame->nChildMem];
+    for(pMem=VdbeFrameMem(pFrame); pMem!=pEnd; pMem++){
+      pMem->flags = MEM_Null;
+      pMem->db = db;
+    }
+  }else{
+    pFrame = pRt->u.pFrame;
+    assert( pProgram->nMem+pProgram->nCsr==pFrame->nChildMem );
+    assert( pProgram->nCsr==pFrame->nChildCsr );
+    assert( pc==pFrame->pc );
+  }
+
+  p->nFrame++;
+  pFrame->pParent = p->pFrame;
+  pFrame->lastRowid = lastRowid;
+  pFrame->nChange = p->nChange;
+  p->nChange = 0;
+  p->pFrame = pFrame;
+  p->aMem = aMem = &VdbeFrameMem(pFrame)[-1];
+  p->nMem = pFrame->nChildMem;
+  p->nCursor = (u16)pFrame->nChildCsr;
+  p->apCsr = (VdbeCursor **)&aMem[p->nMem+1];
+  p->aOp = aOp = pProgram->aOp;
+  p->nOp = pProgram->nOp;
+  pc = -1;
+
+  break;
+}
+
+/* Opcode: Param P1 P2 * * *
+**
+** This opcode is only ever present in sub-programs called via the 
+** OP_Program instruction. Copy a value currently stored in a memory 
+** cell of the calling (parent) frame to cell P2 in the current frames 
+** address space. This is used by trigger programs to access the new.* 
+** and old.* values.
+**
+** The address of the cell in the parent frame is determined by adding
+** the value of the P1 argument to the value of the P1 argument to the
+** calling OP_Program instruction.
+*/
+case OP_Param: {           /* out2-prerelease */
+  VdbeFrame *pFrame;
+  Mem *pIn;
+  pFrame = p->pFrame;
+  pIn = &pFrame->aMem[pOp->p1 + pFrame->aOp[pFrame->pc].p1];   
+  sqlite3VdbeMemShallowCopy(pOut, pIn, MEM_Ephem);
+  break;
+}
+
+#endif /* #ifndef SQLITE_OMIT_TRIGGER */
+
+#ifndef SQLITE_OMIT_FOREIGN_KEY
+/* Opcode: FkCounter P1 P2 * * *
+**
+** Increment a "constraint counter" by P2 (P2 may be negative or positive).
+** If P1 is non-zero, the database constraint counter is incremented 
+** (deferred foreign key constraints). Otherwise, if P1 is zero, the 
+** statement counter is incremented (immediate foreign key constraints).
+*/
+case OP_FkCounter: {
+  if( pOp->p1 ){
+    db->nDeferredCons += pOp->p2;
+  }else{
+    p->nFkConstraint += pOp->p2;
+  }
+  break;
+}
+
+/* Opcode: FkIfZero P1 P2 * * *
+**
+** This opcode tests if a foreign key constraint-counter is currently zero.
+** If so, jump to instruction P2. Otherwise, fall through to the next 
+** instruction.
+**
+** If P1 is non-zero, then the jump is taken if the database constraint-counter
+** is zero (the one that counts deferred constraint violations). If P1 is
+** zero, the jump is taken if the statement constraint-counter is zero
+** (immediate foreign key constraint violations).
+*/
+case OP_FkIfZero: {         /* jump */
+  if( pOp->p1 ){
+    if( db->nDeferredCons==0 ) pc = pOp->p2-1;
+  }else{
+    if( p->nFkConstraint==0 ) pc = pOp->p2-1;
+  }
+  break;
+}
+#endif /* #ifndef SQLITE_OMIT_FOREIGN_KEY */
+
+#ifndef SQLITE_OMIT_AUTOINCREMENT
+/* Opcode: MemMax P1 P2 * * *
+**
+** P1 is a register in the root frame of this VM (the root frame is
+** different from the current frame if this instruction is being executed
+** within a sub-program). Set the value of register P1 to the maximum of 
+** its current value and the value in register P2.
+**
+** This instruction throws an error if the memory cell is not initially
+** an integer.
+*/
+case OP_MemMax: {        /* in2 */
+  Mem *pIn1;
+  VdbeFrame *pFrame;
+  if( p->pFrame ){
+    for(pFrame=p->pFrame; pFrame->pParent; pFrame=pFrame->pParent);
+    pIn1 = &pFrame->aMem[pOp->p1];
+  }else{
+    pIn1 = &aMem[pOp->p1];
+  }
+  assert( memIsValid(pIn1) );
+  sqlite3VdbeMemIntegerify(pIn1);
+  pIn2 = &aMem[pOp->p2];
+  sqlite3VdbeMemIntegerify(pIn2);
+  if( pIn1->u.i<pIn2->u.i){
+    pIn1->u.i = pIn2->u.i;
+  }
+  break;
+}
+#endif /* SQLITE_OMIT_AUTOINCREMENT */
+
+/* Opcode: IfPos P1 P2 * * *
+**
+** If the value of register P1 is 1 or greater, jump to P2.
+**
+** It is illegal to use this instruction on a register that does
+** not contain an integer.  An assertion fault will result if you try.
+*/
+case OP_IfPos: {        /* jump, in1 */
+  pIn1 = &aMem[pOp->p1];
+  assert( pIn1->flags&MEM_Int );
+  if( pIn1->u.i>0 ){
+     pc = pOp->p2 - 1;
+  }
+  break;
+}
+
+/* Opcode: IfNeg P1 P2 * * *
+**
+** If the value of register P1 is less than zero, jump to P2. 
+**
+** It is illegal to use this instruction on a register that does
+** not contain an integer.  An assertion fault will result if you try.
+*/
+case OP_IfNeg: {        /* jump, in1 */
+  pIn1 = &aMem[pOp->p1];
+  assert( pIn1->flags&MEM_Int );
+  if( pIn1->u.i<0 ){
+     pc = pOp->p2 - 1;
+  }
+  break;
+}
+
+/* Opcode: IfZero P1 P2 P3 * *
+**
+** The register P1 must contain an integer.  Add literal P3 to the
+** value in register P1.  If the result is exactly 0, jump to P2. 
+**
+** It is illegal to use this instruction on a register that does
+** not contain an integer.  An assertion fault will result if you try.
+*/
+case OP_IfZero: {        /* jump, in1 */
+  pIn1 = &aMem[pOp->p1];
+  assert( pIn1->flags&MEM_Int );
+  pIn1->u.i += pOp->p3;
+  if( pIn1->u.i==0 ){
+     pc = pOp->p2 - 1;
+  }
+  break;
+}
+
+/* Opcode: AggStep * P2 P3 P4 P5
+**
+** Execute the step function for an aggregate.  The
+** function has P5 arguments.   P4 is a pointer to the FuncDef
+** structure that specifies the function.  Use register
+** P3 as the accumulator.
+**
+** The P5 arguments are taken from register P2 and its
+** successors.
+*/
+case OP_AggStep: {
+  int n;
+  int i;
+  Mem *pMem;
+  Mem *pRec;
+  sqlite3_context ctx;
+  sqlite3_value **apVal;
+
+  n = pOp->p5;
+  assert( n>=0 );
+  pRec = &aMem[pOp->p2];
+  apVal = p->apArg;
+  assert( apVal || n==0 );
+  for(i=0; i<n; i++, pRec++){
+    assert( memIsValid(pRec) );
+    apVal[i] = pRec;
+    memAboutToChange(p, pRec);
+    sqlite3VdbeMemStoreType(pRec);
+  }
+  ctx.pFunc = pOp->p4.pFunc;
+  assert( pOp->p3>0 && pOp->p3<=p->nMem );
+  ctx.pMem = pMem = &aMem[pOp->p3];
+  pMem->n++;
+  ctx.s.flags = MEM_Null;
+  ctx.s.z = 0;
+  ctx.s.zMalloc = 0;
+  ctx.s.xDel = 0;
+  ctx.s.db = db;
+  ctx.isError = 0;
+  ctx.pColl = 0;
+  if( ctx.pFunc->flags & SQLITE_FUNC_NEEDCOLL ){
+    assert( pOp>p->aOp );
+    assert( pOp[-1].p4type==P4_COLLSEQ );
+    assert( pOp[-1].opcode==OP_CollSeq );
+    ctx.pColl = pOp[-1].p4.pColl;
+  }
+  (ctx.pFunc->xStep)(&ctx, n, apVal); /* IMP: R-24505-23230 */
+  if( ctx.isError ){
+    sqlite3SetString(&p->zErrMsg, db, "%s", sqlite3_value_text(&ctx.s));
+    rc = ctx.isError;
+  }
+
+  sqlite3VdbeMemRelease(&ctx.s);
+
+  break;
+}
+
+/* Opcode: AggFinal P1 P2 * P4 *
+**
+** Execute the finalizer function for an aggregate.  P1 is
+** the memory location that is the accumulator for the aggregate.
+**
+** P2 is the number of arguments that the step function takes and
+** P4 is a pointer to the FuncDef for this function.  The P2
+** argument is not used by this opcode.  It is only there to disambiguate
+** functions that can take varying numbers of arguments.  The
+** P4 argument is only needed for the degenerate case where
+** the step function was not previously called.
+*/
+case OP_AggFinal: {
+  Mem *pMem;
+  assert( pOp->p1>0 && pOp->p1<=p->nMem );
+  pMem = &aMem[pOp->p1];
+  assert( (pMem->flags & ~(MEM_Null|MEM_Agg))==0 );
+  rc = sqlite3VdbeMemFinalize(pMem, pOp->p4.pFunc);
+  if( rc ){
+    sqlite3SetString(&p->zErrMsg, db, "%s", sqlite3_value_text(pMem));
+  }
+  sqlite3VdbeChangeEncoding(pMem, encoding);
+  UPDATE_MAX_BLOBSIZE(pMem);
+  if( sqlite3VdbeMemTooBig(pMem) ){
+    goto too_big;
+  }
+  break;
+}
+
+#ifndef SQLITE_OMIT_WAL
+/* Opcode: Checkpoint P1 P2 P3 * *
+**
+** Checkpoint database P1. This is a no-op if P1 is not currently in
+** WAL mode. Parameter P2 is one of SQLITE_CHECKPOINT_PASSIVE, FULL
+** or RESTART.  Write 1 or 0 into mem[P3] if the checkpoint returns
+** SQLITE_BUSY or not, respectively.  Write the number of pages in the
+** WAL after the checkpoint into mem[P3+1] and the number of pages
+** in the WAL that have been checkpointed after the checkpoint
+** completes into mem[P3+2].  However on an error, mem[P3+1] and
+** mem[P3+2] are initialized to -1.
+*/
+case OP_Checkpoint: {
+  int i;                          /* Loop counter */
+  int aRes[3];                    /* Results */
+  Mem *pMem;                      /* Write results here */
+
+  aRes[0] = 0;
+  aRes[1] = aRes[2] = -1;
+  assert( pOp->p2==SQLITE_CHECKPOINT_PASSIVE
+       || pOp->p2==SQLITE_CHECKPOINT_FULL
+       || pOp->p2==SQLITE_CHECKPOINT_RESTART
+  );
+  rc = sqlite3Checkpoint(db, pOp->p1, pOp->p2, &aRes[1], &aRes[2]);
+  if( rc==SQLITE_BUSY ){
+    rc = SQLITE_OK;
+    aRes[0] = 1;
+  }
+  for(i=0, pMem = &aMem[pOp->p3]; i<3; i++, pMem++){
+    sqlite3VdbeMemSetInt64(pMem, (i64)aRes[i]);
+  }    
+  break;
+};  
+#endif
+
+#ifndef SQLITE_OMIT_PRAGMA
+/* Opcode: JournalMode P1 P2 P3 * P5
+**
+** Change the journal mode of database P1 to P3. P3 must be one of the
+** PAGER_JOURNALMODE_XXX values. If changing between the various rollback
+** modes (delete, truncate, persist, off and memory), this is a simple
+** operation. No IO is required.
+**
+** If changing into or out of WAL mode the procedure is more complicated.
+**
+** Write a string containing the final journal-mode to register P2.
+*/
+case OP_JournalMode: {    /* out2-prerelease */
+  Btree *pBt;                     /* Btree to change journal mode of */
+  Pager *pPager;                  /* Pager associated with pBt */
+  int eNew;                       /* New journal mode */
+  int eOld;                       /* The old journal mode */
+  const char *zFilename;          /* Name of database file for pPager */
+
+  eNew = pOp->p3;
+  assert( eNew==PAGER_JOURNALMODE_DELETE 
+       || eNew==PAGER_JOURNALMODE_TRUNCATE 
+       || eNew==PAGER_JOURNALMODE_PERSIST 
+       || eNew==PAGER_JOURNALMODE_OFF
+       || eNew==PAGER_JOURNALMODE_MEMORY
+       || eNew==PAGER_JOURNALMODE_WAL
+       || eNew==PAGER_JOURNALMODE_QUERY
+  );
+  assert( pOp->p1>=0 && pOp->p1<db->nDb );
+
+  pBt = db->aDb[pOp->p1].pBt;
+  pPager = sqlite3BtreePager(pBt);
+  eOld = sqlite3PagerGetJournalMode(pPager);
+  if( eNew==PAGER_JOURNALMODE_QUERY ) eNew = eOld;
+  if( !sqlite3PagerOkToChangeJournalMode(pPager) ) eNew = eOld;
+
+#ifndef SQLITE_OMIT_WAL
+  zFilename = sqlite3PagerFilename(pPager);
+
+  /* Do not allow a transition to journal_mode=WAL for a database
+  ** in temporary storage or if the VFS does not support shared memory 
+  */
+  if( eNew==PAGER_JOURNALMODE_WAL
+   && (sqlite3Strlen30(zFilename)==0           /* Temp file */
+       || !sqlite3PagerWalSupported(pPager))   /* No shared-memory support */
+  ){
+    eNew = eOld;
+  }
+
+  if( (eNew!=eOld)
+   && (eOld==PAGER_JOURNALMODE_WAL || eNew==PAGER_JOURNALMODE_WAL)
+  ){
+    if( !db->autoCommit || db->activeVdbeCnt>1 ){
+      rc = SQLITE_ERROR;
+      sqlite3SetString(&p->zErrMsg, db, 
+          "cannot change %s wal mode from within a transaction",
+          (eNew==PAGER_JOURNALMODE_WAL ? "into" : "out of")
+      );
+      break;
+    }else{
+ 
+      if( eOld==PAGER_JOURNALMODE_WAL ){
+        /* If leaving WAL mode, close the log file. If successful, the call
+        ** to PagerCloseWal() checkpoints and deletes the write-ahead-log 
+        ** file. An EXCLUSIVE lock may still be held on the database file 
+        ** after a successful return. 
+        */
+        rc = sqlite3PagerCloseWal(pPager);
+        if( rc==SQLITE_OK ){
+          sqlite3PagerSetJournalMode(pPager, eNew);
+        }
+      }else if( eOld==PAGER_JOURNALMODE_MEMORY ){
+        /* Cannot transition directly from MEMORY to WAL.  Use mode OFF
+        ** as an intermediate */
+        sqlite3PagerSetJournalMode(pPager, PAGER_JOURNALMODE_OFF);
+      }
+  
+      /* Open a transaction on the database file. Regardless of the journal
+      ** mode, this transaction always uses a rollback journal.
+      */
+      assert( sqlite3BtreeIsInTrans(pBt)==0 );
+      if( rc==SQLITE_OK ){
+        rc = sqlite3BtreeSetVersion(pBt, (eNew==PAGER_JOURNALMODE_WAL ? 2 : 1));
+      }
+    }
+  }
+#endif /* ifndef SQLITE_OMIT_WAL */
+
+  if( rc ){
+    eNew = eOld;
+  }
+  eNew = sqlite3PagerSetJournalMode(pPager, eNew);
+
+  pOut = &aMem[pOp->p2];
+  pOut->flags = MEM_Str|MEM_Static|MEM_Term;
+  pOut->z = (char *)sqlite3JournalModename(eNew);
+  pOut->n = sqlite3Strlen30(pOut->z);
+  pOut->enc = SQLITE_UTF8;
+  sqlite3VdbeChangeEncoding(pOut, encoding);
+  break;
+};
+#endif /* SQLITE_OMIT_PRAGMA */
+
+#if !defined(SQLITE_OMIT_VACUUM) && !defined(SQLITE_OMIT_ATTACH)
+/* Opcode: Vacuum * * * * *
+**
+** Vacuum the entire database.  This opcode will cause other virtual
+** machines to be created and run.  It may not be called from within
+** a transaction.
+*/
+case OP_Vacuum: {
+  rc = sqlite3RunVacuum(&p->zErrMsg, db);
+  break;
+}
+#endif
+
+#if !defined(SQLITE_OMIT_AUTOVACUUM)
+/* Opcode: IncrVacuum P1 P2 * * *
+**
+** Perform a single step of the incremental vacuum procedure on
+** the P1 database. If the vacuum has finished, jump to instruction
+** P2. Otherwise, fall through to the next instruction.
+*/
+case OP_IncrVacuum: {        /* jump */
+  Btree *pBt;
+
+  assert( pOp->p1>=0 && pOp->p1<db->nDb );
+  assert( (p->btreeMask & (((yDbMask)1)<<pOp->p1))!=0 );
+  pBt = db->aDb[pOp->p1].pBt;
+  rc = sqlite3BtreeIncrVacuum(pBt);
+  if( rc==SQLITE_DONE ){
+    pc = pOp->p2 - 1;
+    rc = SQLITE_OK;
+  }
+  break;
+}
+#endif
+
+/* Opcode: Expire P1 * * * *
+**
+** Cause precompiled statements to become expired. An expired statement
+** fails with an error code of SQLITE_SCHEMA if it is ever executed 
+** (via sqlite3_step()).
+** 
+** If P1 is 0, then all SQL statements become expired. If P1 is non-zero,
+** then only the currently executing statement is affected. 
+*/
+case OP_Expire: {
+  if( !pOp->p1 ){
+    sqlite3ExpirePreparedStatements(db);
+  }else{
+    p->expired = 1;
+  }
+  break;
+}
+
+#ifndef SQLITE_OMIT_SHARED_CACHE
+/* Opcode: TableLock P1 P2 P3 P4 *
+**
+** Obtain a lock on a particular table. This instruction is only used when
+** the shared-cache feature is enabled. 
+**
+** P1 is the index of the database in sqlite3.aDb[] of the database
+** on which the lock is acquired.  A readlock is obtained if P3==0 or
+** a write lock if P3==1.
+**
+** P2 contains the root-page of the table to lock.
+**
+** P4 contains a pointer to the name of the table being locked. This is only
+** used to generate an error message if the lock cannot be obtained.
+*/
+case OP_TableLock: {
+  u8 isWriteLock = (u8)pOp->p3;
+  if( isWriteLock || 0==(db->flags&SQLITE_ReadUncommitted) ){
+    int p1 = pOp->p1; 
+    assert( p1>=0 && p1<db->nDb );
+    assert( (p->btreeMask & (((yDbMask)1)<<p1))!=0 );
+    assert( isWriteLock==0 || isWriteLock==1 );
+    rc = sqlite3BtreeLockTable(db->aDb[p1].pBt, pOp->p2, isWriteLock);
+    if( (rc&0xFF)==SQLITE_LOCKED ){
+      const char *z = pOp->p4.z;
+      sqlite3SetString(&p->zErrMsg, db, "database table is locked: %s", z);
+    }
+  }
+  break;
+}
+#endif /* SQLITE_OMIT_SHARED_CACHE */
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/* Opcode: VBegin * * * P4 *
+**
+** P4 may be a pointer to an sqlite3_vtab structure. If so, call the 
+** xBegin method for that table.
+**
+** Also, whether or not P4 is set, check that this is not being called from
+** within a callback to a virtual table xSync() method. If it is, the error
+** code will be set to SQLITE_LOCKED.
+*/
+case OP_VBegin: {
+  VTable *pVTab;
+  pVTab = pOp->p4.pVtab;
+  rc = sqlite3VtabBegin(db, pVTab);
+  if( pVTab ) importVtabErrMsg(p, pVTab->pVtab);
+  break;
+}
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/* Opcode: VCreate P1 * * P4 *
+**
+** P4 is the name of a virtual table in database P1. Call the xCreate method
+** for that table.
+*/
+case OP_VCreate: {
+  rc = sqlite3VtabCallCreate(db, pOp->p1, pOp->p4.z, &p->zErrMsg);
+  break;
+}
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/* Opcode: VDestroy P1 * * P4 *
+**
+** P4 is the name of a virtual table in database P1.  Call the xDestroy method
+** of that table.
+*/
+case OP_VDestroy: {
+  p->inVtabMethod = 2;
+  rc = sqlite3VtabCallDestroy(db, pOp->p1, pOp->p4.z);
+  p->inVtabMethod = 0;
+  break;
+}
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/* Opcode: VOpen P1 * * P4 *
+**
+** P4 is a pointer to a virtual table object, an sqlite3_vtab structure.
+** P1 is a cursor number.  This opcode opens a cursor to the virtual
+** table and stores that cursor in P1.
+*/
+case OP_VOpen: {
+  VdbeCursor *pCur;
+  sqlite3_vtab_cursor *pVtabCursor;
+  sqlite3_vtab *pVtab;
+  sqlite3_module *pModule;
+
+  pCur = 0;
+  pVtabCursor = 0;
+  pVtab = pOp->p4.pVtab->pVtab;
+  pModule = (sqlite3_module *)pVtab->pModule;
+  assert(pVtab && pModule);
+  rc = pModule->xOpen(pVtab, &pVtabCursor);
+  importVtabErrMsg(p, pVtab);
+  if( SQLITE_OK==rc ){
+    /* Initialize sqlite3_vtab_cursor base class */
+    pVtabCursor->pVtab = pVtab;
+
+    /* Initialise vdbe cursor object */
+    pCur = allocateCursor(p, pOp->p1, 0, -1, 0);
+    if( pCur ){
+      pCur->pVtabCursor = pVtabCursor;
+      pCur->pModule = pVtabCursor->pVtab->pModule;
+    }else{
+      db->mallocFailed = 1;
+      pModule->xClose(pVtabCursor);
+    }
+  }
+  break;
+}
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/* Opcode: VFilter P1 P2 P3 P4 *
+**
+** P1 is a cursor opened using VOpen.  P2 is an address to jump to if
+** the filtered result set is empty.
+**
+** P4 is either NULL or a string that was generated by the xBestIndex
+** method of the module.  The interpretation of the P4 string is left
+** to the module implementation.
+**
+** This opcode invokes the xFilter method on the virtual table specified
+** by P1.  The integer query plan parameter to xFilter is stored in register
+** P3. Register P3+1 stores the argc parameter to be passed to the
+** xFilter method. Registers P3+2..P3+1+argc are the argc
+** additional parameters which are passed to
+** xFilter as argv. Register P3+2 becomes argv[0] when passed to xFilter.
+**
+** A jump is made to P2 if the result set after filtering would be empty.
+*/
+case OP_VFilter: {   /* jump */
+  int nArg;
+  int iQuery;
+  const sqlite3_module *pModule;
+  Mem *pQuery;
+  Mem *pArgc;
+  sqlite3_vtab_cursor *pVtabCursor;
+  sqlite3_vtab *pVtab;
+  VdbeCursor *pCur;
+  int res;
+  int i;
+  Mem **apArg;
+
+  pQuery = &aMem[pOp->p3];
+  pArgc = &pQuery[1];
+  pCur = p->apCsr[pOp->p1];
+  assert( memIsValid(pQuery) );
+  REGISTER_TRACE(pOp->p3, pQuery);
+  assert( pCur->pVtabCursor );
+  pVtabCursor = pCur->pVtabCursor;
+  pVtab = pVtabCursor->pVtab;
+  pModule = pVtab->pModule;
+
+  /* Grab the index number and argc parameters */
+  assert( (pQuery->flags&MEM_Int)!=0 && pArgc->flags==MEM_Int );
+  nArg = (int)pArgc->u.i;
+  iQuery = (int)pQuery->u.i;
+
+  /* Invoke the xFilter method */
+  {
+    res = 0;
+    apArg = p->apArg;
+    for(i = 0; i<nArg; i++){
+      apArg[i] = &pArgc[i+1];
+      sqlite3VdbeMemStoreType(apArg[i]);
+    }
+
+    p->inVtabMethod = 1;
+    rc = pModule->xFilter(pVtabCursor, iQuery, pOp->p4.z, nArg, apArg);
+    p->inVtabMethod = 0;
+    importVtabErrMsg(p, pVtab);
+    if( rc==SQLITE_OK ){
+      res = pModule->xEof(pVtabCursor);
+    }
+
+    if( res ){
+      pc = pOp->p2 - 1;
+    }
+  }
+  pCur->nullRow = 0;
+
+  break;
+}
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/* Opcode: VColumn P1 P2 P3 * *
+**
+** Store the value of the P2-th column of
+** the row of the virtual-table that the 
+** P1 cursor is pointing to into register P3.
+*/
+case OP_VColumn: {
+  sqlite3_vtab *pVtab;
+  const sqlite3_module *pModule;
+  Mem *pDest;
+  sqlite3_context sContext;
+
+  VdbeCursor *pCur = p->apCsr[pOp->p1];
+  assert( pCur->pVtabCursor );
+  assert( pOp->p3>0 && pOp->p3<=p->nMem );
+  pDest = &aMem[pOp->p3];
+  memAboutToChange(p, pDest);
+  if( pCur->nullRow ){
+    sqlite3VdbeMemSetNull(pDest);
+    break;
+  }
+  pVtab = pCur->pVtabCursor->pVtab;
+  pModule = pVtab->pModule;
+  assert( pModule->xColumn );
+  memset(&sContext, 0, sizeof(sContext));
+
+  /* The output cell may already have a buffer allocated. Move
+  ** the current contents to sContext.s so in case the user-function 
+  ** can use the already allocated buffer instead of allocating a 
+  ** new one.
+  */
+  sqlite3VdbeMemMove(&sContext.s, pDest);
+  MemSetTypeFlag(&sContext.s, MEM_Null);
+
+  rc = pModule->xColumn(pCur->pVtabCursor, &sContext, pOp->p2);
+  importVtabErrMsg(p, pVtab);
+  if( sContext.isError ){
+    rc = sContext.isError;
+  }
+
+  /* Copy the result of the function to the P3 register. We
+  ** do this regardless of whether or not an error occurred to ensure any
+  ** dynamic allocation in sContext.s (a Mem struct) is  released.
+  */
+  sqlite3VdbeChangeEncoding(&sContext.s, encoding);
+  sqlite3VdbeMemMove(pDest, &sContext.s);
+  REGISTER_TRACE(pOp->p3, pDest);
+  UPDATE_MAX_BLOBSIZE(pDest);
+
+  if( sqlite3VdbeMemTooBig(pDest) ){
+    goto too_big;
+  }
+  break;
+}
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/* Opcode: VNext P1 P2 * * *
+**
+** Advance virtual table P1 to the next row in its result set and
+** jump to instruction P2.  Or, if the virtual table has reached
+** the end of its result set, then fall through to the next instruction.
+*/
+case OP_VNext: {   /* jump */
+  sqlite3_vtab *pVtab;
+  const sqlite3_module *pModule;
+  int res;
+  VdbeCursor *pCur;
+
+  res = 0;
+  pCur = p->apCsr[pOp->p1];
+  assert( pCur->pVtabCursor );
+  if( pCur->nullRow ){
+    break;
+  }
+  pVtab = pCur->pVtabCursor->pVtab;
+  pModule = pVtab->pModule;
+  assert( pModule->xNext );
+
+  /* Invoke the xNext() method of the module. There is no way for the
+  ** underlying implementation to return an error if one occurs during
+  ** xNext(). Instead, if an error occurs, true is returned (indicating that 
+  ** data is available) and the error code returned when xColumn or
+  ** some other method is next invoked on the save virtual table cursor.
+  */
+  p->inVtabMethod = 1;
+  rc = pModule->xNext(pCur->pVtabCursor);
+  p->inVtabMethod = 0;
+  importVtabErrMsg(p, pVtab);
+  if( rc==SQLITE_OK ){
+    res = pModule->xEof(pCur->pVtabCursor);
+  }
+
+  if( !res ){
+    /* If there is data, jump to P2 */
+    pc = pOp->p2 - 1;
+  }
+  break;
+}
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/* Opcode: VRename P1 * * P4 *
+**
+** P4 is a pointer to a virtual table object, an sqlite3_vtab structure.
+** This opcode invokes the corresponding xRename method. The value
+** in register P1 is passed as the zName argument to the xRename method.
+*/
+case OP_VRename: {
+  sqlite3_vtab *pVtab;
+  Mem *pName;
+
+  pVtab = pOp->p4.pVtab->pVtab;
+  pName = &aMem[pOp->p1];
+  assert( pVtab->pModule->xRename );
+  assert( memIsValid(pName) );
+  REGISTER_TRACE(pOp->p1, pName);
+  assert( pName->flags & MEM_Str );
+  testcase( pName->enc==SQLITE_UTF8 );
+  testcase( pName->enc==SQLITE_UTF16BE );
+  testcase( pName->enc==SQLITE_UTF16LE );
+  rc = sqlite3VdbeChangeEncoding(pName, SQLITE_UTF8);
+  if( rc==SQLITE_OK ){
+    rc = pVtab->pModule->xRename(pVtab, pName->z);
+    importVtabErrMsg(p, pVtab);
+    p->expired = 0;
+  }
+  break;
+}
+#endif
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/* Opcode: VUpdate P1 P2 P3 P4 *
+**
+** P4 is a pointer to a virtual table object, an sqlite3_vtab structure.
+** This opcode invokes the corresponding xUpdate method. P2 values
+** are contiguous memory cells starting at P3 to pass to the xUpdate 
+** invocation. The value in register (P3+P2-1) corresponds to the 
+** p2th element of the argv array passed to xUpdate.
+**
+** The xUpdate method will do a DELETE or an INSERT or both.
+** The argv[0] element (which corresponds to memory cell P3)
+** is the rowid of a row to delete.  If argv[0] is NULL then no 
+** deletion occurs.  The argv[1] element is the rowid of the new 
+** row.  This can be NULL to have the virtual table select the new 
+** rowid for itself.  The subsequent elements in the array are 
+** the values of columns in the new row.
+**
+** If P2==1 then no insert is performed.  argv[0] is the rowid of
+** a row to delete.
+**
+** P1 is a boolean flag. If it is set to true and the xUpdate call
+** is successful, then the value returned by sqlite3_last_insert_rowid() 
+** is set to the value of the rowid for the row just inserted.
+*/
+case OP_VUpdate: {
+  sqlite3_vtab *pVtab;
+  sqlite3_module *pModule;
+  int nArg;
+  int i;
+  sqlite_int64 rowid;
+  Mem **apArg;
+  Mem *pX;
+
+  assert( pOp->p2==1        || pOp->p5==OE_Fail   || pOp->p5==OE_Rollback 
+       || pOp->p5==OE_Abort || pOp->p5==OE_Ignore || pOp->p5==OE_Replace
+  );
+  pVtab = pOp->p4.pVtab->pVtab;
+  pModule = (sqlite3_module *)pVtab->pModule;
+  nArg = pOp->p2;
+  assert( pOp->p4type==P4_VTAB );
+  if( ALWAYS(pModule->xUpdate) ){
+    u8 vtabOnConflict = db->vtabOnConflict;
+    apArg = p->apArg;
+    pX = &aMem[pOp->p3];
+    for(i=0; i<nArg; i++){
+      assert( memIsValid(pX) );
+      memAboutToChange(p, pX);
+      sqlite3VdbeMemStoreType(pX);
+      apArg[i] = pX;
+      pX++;
+    }
+    db->vtabOnConflict = pOp->p5;
+    rc = pModule->xUpdate(pVtab, nArg, apArg, &rowid);
+    db->vtabOnConflict = vtabOnConflict;
+    importVtabErrMsg(p, pVtab);
+    if( rc==SQLITE_OK && pOp->p1 ){
+      assert( nArg>1 && apArg[0] && (apArg[0]->flags&MEM_Null) );
+      db->lastRowid = lastRowid = rowid;
+    }
+    if( rc==SQLITE_CONSTRAINT && pOp->p4.pVtab->bConstraint ){
+      if( pOp->p5==OE_Ignore ){
+        rc = SQLITE_OK;
+      }else{
+        p->errorAction = ((pOp->p5==OE_Replace) ? OE_Abort : pOp->p5);
+      }
+    }else{
+      p->nChange++;
+    }
+  }
+  break;
+}
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+#ifndef  SQLITE_OMIT_PAGER_PRAGMAS
+/* Opcode: Pagecount P1 P2 * * *
+**
+** Write the current number of pages in database P1 to memory cell P2.
+*/
+case OP_Pagecount: {            /* out2-prerelease */
+  pOut->u.i = sqlite3BtreeLastPage(db->aDb[pOp->p1].pBt);
+  break;
+}
+#endif
+
+
+#ifndef  SQLITE_OMIT_PAGER_PRAGMAS
+/* Opcode: MaxPgcnt P1 P2 P3 * *
+**
+** Try to set the maximum page count for database P1 to the value in P3.
+** Do not let the maximum page count fall below the current page count and
+** do not change the maximum page count value if P3==0.
+**
+** Store the maximum page count after the change in register P2.
+*/
+case OP_MaxPgcnt: {            /* out2-prerelease */
+  unsigned int newMax;
+  Btree *pBt;
+
+  pBt = db->aDb[pOp->p1].pBt;
+  newMax = 0;
+  if( pOp->p3 ){
+    newMax = sqlite3BtreeLastPage(pBt);
+    if( newMax < (unsigned)pOp->p3 ) newMax = (unsigned)pOp->p3;
+  }
+  pOut->u.i = sqlite3BtreeMaxPageCount(pBt, newMax);
+  break;
+}
+#endif
+
+
+#ifndef SQLITE_OMIT_TRACE
+/* Opcode: Trace * * * P4 *
+**
+** If tracing is enabled (by the sqlite3_trace()) interface, then
+** the UTF-8 string contained in P4 is emitted on the trace callback.
+*/
+case OP_Trace: {
+  char *zTrace;
+  char *z;
+
+  if( db->xTrace && (zTrace = (pOp->p4.z ? pOp->p4.z : p->zSql))!=0 ){
+    z = sqlite3VdbeExpandSql(p, zTrace);
+    db->xTrace(db->pTraceArg, z);
+    sqlite3DbFree(db, z);
+  }
+#ifdef SQLITE_DEBUG
+  if( (db->flags & SQLITE_SqlTrace)!=0
+   && (zTrace = (pOp->p4.z ? pOp->p4.z : p->zSql))!=0
+  ){
+    sqlite3DebugPrintf("SQL-trace: %s\n", zTrace);
+  }
+#endif /* SQLITE_DEBUG */
+  break;
+}
+#endif
+
+
+/* Opcode: Noop * * * * *
+**
+** Do nothing.  This instruction is often useful as a jump
+** destination.
+*/
+/*
+** The magic Explain opcode are only inserted when explain==2 (which
+** is to say when the EXPLAIN QUERY PLAN syntax is used.)
+** This opcode records information from the optimizer.  It is the
+** the same as a no-op.  This opcodesnever appears in a real VM program.
+*/
+default: {          /* This is really OP_Noop and OP_Explain */
+  assert( pOp->opcode==OP_Noop || pOp->opcode==OP_Explain );
+  break;
+}
+
+/*****************************************************************************
+** The cases of the switch statement above this line should all be indented
+** by 6 spaces.  But the left-most 6 spaces have been removed to improve the
+** readability.  From this point on down, the normal indentation rules are
+** restored.
+*****************************************************************************/
+    }
+
+#ifdef VDBE_PROFILE
+    {
+      u64 elapsed = sqlite3Hwtime() - start;
+      pOp->cycles += elapsed;
+      pOp->cnt++;
+#if 0
+        fprintf(stdout, "%10llu ", elapsed);
+        sqlite3VdbePrintOp(stdout, origPc, &aOp[origPc]);
+#endif
+    }
+#endif
+
+    /* The following code adds nothing to the actual functionality
+    ** of the program.  It is only here for testing and debugging.
+    ** On the other hand, it does burn CPU cycles every time through
+    ** the evaluator loop.  So we can leave it out when NDEBUG is defined.
+    */
+#ifndef NDEBUG
+    assert( pc>=-1 && pc<p->nOp );
+
+#ifdef SQLITE_DEBUG
+    if( p->trace ){
+      if( rc!=0 ) fprintf(p->trace,"rc=%d\n",rc);
+      if( pOp->opflags & (OPFLG_OUT2_PRERELEASE|OPFLG_OUT2) ){
+        registerTrace(p->trace, pOp->p2, &aMem[pOp->p2]);
+      }
+      if( pOp->opflags & OPFLG_OUT3 ){
+        registerTrace(p->trace, pOp->p3, &aMem[pOp->p3]);
+      }
+    }
+#endif  /* SQLITE_DEBUG */
+#endif  /* NDEBUG */
+  }  /* The end of the for(;;) loop the loops through opcodes */
+
+  /* If we reach this point, it means that execution is finished with
+  ** an error of some kind.
+  */
+vdbe_error_halt:
+  assert( rc );
+  p->rc = rc;
+  testcase( sqlite3GlobalConfig.xLog!=0 );
+  sqlite3_log(rc, "statement aborts at %d: [%s] %s", 
+                   pc, p->zSql, p->zErrMsg);
+  sqlite3VdbeHalt(p);
+  if( rc==SQLITE_IOERR_NOMEM ) db->mallocFailed = 1;
+  rc = SQLITE_ERROR;
+  if( resetSchemaOnFault>0 ){
+    sqlite3ResetInternalSchema(db, resetSchemaOnFault-1);
+  }
+
+  /* This is the only way out of this procedure.  We have to
+  ** release the mutexes on btrees that were acquired at the
+  ** top. */
+vdbe_return:
+  db->lastRowid = lastRowid;
+  sqlite3VdbeLeave(p);
+  return rc;
+
+  /* Jump to here if a string or blob larger than SQLITE_MAX_LENGTH
+  ** is encountered.
+  */
+too_big:
+  sqlite3SetString(&p->zErrMsg, db, "string or blob too big");
+  rc = SQLITE_TOOBIG;
+  goto vdbe_error_halt;
+
+  /* Jump to here if a malloc() fails.
+  */
+no_mem:
+  db->mallocFailed = 1;
+  sqlite3SetString(&p->zErrMsg, db, "out of memory");
+  rc = SQLITE_NOMEM;
+  goto vdbe_error_halt;
+
+  /* Jump to here for any other kind of fatal error.  The "rc" variable
+  ** should hold the error number.
+  */
+abort_due_to_error:
+  assert( p->zErrMsg==0 );
+  if( db->mallocFailed ) rc = SQLITE_NOMEM;
+  if( rc!=SQLITE_IOERR_NOMEM ){
+    sqlite3SetString(&p->zErrMsg, db, "%s", sqlite3ErrStr(rc));
+  }
+  goto vdbe_error_halt;
+
+  /* Jump to here if the sqlite3_interrupt() API sets the interrupt
+  ** flag.
+  */
+abort_due_to_interrupt:
+  assert( db->u1.isInterrupted );
+  rc = SQLITE_INTERRUPT;
+  p->rc = rc;
+  sqlite3SetString(&p->zErrMsg, db, "%s", sqlite3ErrStr(rc));
+  goto vdbe_error_halt;
+}
diff --git a/src/vdbe.h b/src/vdbe.h
new file mode 100644
index 0000000..948c73b
--- /dev/null
+++ b/src/vdbe.h
@@ -0,0 +1,234 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Header file for the Virtual DataBase Engine (VDBE)
+**
+** This header defines the interface to the virtual database engine
+** or VDBE.  The VDBE implements an abstract machine that runs a
+** simple program to access and modify the underlying database.
+*/
+#ifndef _SQLITE_VDBE_H_
+#define _SQLITE_VDBE_H_
+#include <stdio.h>
+
+/*
+** A single VDBE is an opaque structure named "Vdbe".  Only routines
+** in the source file sqliteVdbe.c are allowed to see the insides
+** of this structure.
+*/
+typedef struct Vdbe Vdbe;
+
+/*
+** The names of the following types declared in vdbeInt.h are required
+** for the VdbeOp definition.
+*/
+typedef struct VdbeFunc VdbeFunc;
+typedef struct Mem Mem;
+typedef struct SubProgram SubProgram;
+
+/*
+** A single instruction of the virtual machine has an opcode
+** and as many as three operands.  The instruction is recorded
+** as an instance of the following structure:
+*/
+struct VdbeOp {
+  u8 opcode;          /* What operation to perform */
+  signed char p4type; /* One of the P4_xxx constants for p4 */
+  u8 opflags;         /* Mask of the OPFLG_* flags in opcodes.h */
+  u8 p5;              /* Fifth parameter is an unsigned character */
+  int p1;             /* First operand */
+  int p2;             /* Second parameter (often the jump destination) */
+  int p3;             /* The third parameter */
+  union {             /* fourth parameter */
+    int i;                 /* Integer value if p4type==P4_INT32 */
+    void *p;               /* Generic pointer */
+    char *z;               /* Pointer to data for string (char array) types */
+    i64 *pI64;             /* Used when p4type is P4_INT64 */
+    double *pReal;         /* Used when p4type is P4_REAL */
+    FuncDef *pFunc;        /* Used when p4type is P4_FUNCDEF */
+    VdbeFunc *pVdbeFunc;   /* Used when p4type is P4_VDBEFUNC */
+    CollSeq *pColl;        /* Used when p4type is P4_COLLSEQ */
+    Mem *pMem;             /* Used when p4type is P4_MEM */
+    VTable *pVtab;         /* Used when p4type is P4_VTAB */
+    KeyInfo *pKeyInfo;     /* Used when p4type is P4_KEYINFO */
+    int *ai;               /* Used when p4type is P4_INTARRAY */
+    SubProgram *pProgram;  /* Used when p4type is P4_SUBPROGRAM */
+    int (*xAdvance)(BtCursor *, int *);
+  } p4;
+#ifdef SQLITE_DEBUG
+  char *zComment;          /* Comment to improve readability */
+#endif
+#ifdef VDBE_PROFILE
+  int cnt;                 /* Number of times this instruction was executed */
+  u64 cycles;              /* Total time spent executing this instruction */
+#endif
+};
+typedef struct VdbeOp VdbeOp;
+
+
+/*
+** A sub-routine used to implement a trigger program.
+*/
+struct SubProgram {
+  VdbeOp *aOp;                  /* Array of opcodes for sub-program */
+  int nOp;                      /* Elements in aOp[] */
+  int nMem;                     /* Number of memory cells required */
+  int nCsr;                     /* Number of cursors required */
+  void *token;                  /* id that may be used to recursive triggers */
+  SubProgram *pNext;            /* Next sub-program already visited */
+};
+
+/*
+** A smaller version of VdbeOp used for the VdbeAddOpList() function because
+** it takes up less space.
+*/
+struct VdbeOpList {
+  u8 opcode;          /* What operation to perform */
+  signed char p1;     /* First operand */
+  signed char p2;     /* Second parameter (often the jump destination) */
+  signed char p3;     /* Third parameter */
+};
+typedef struct VdbeOpList VdbeOpList;
+
+/*
+** Allowed values of VdbeOp.p4type
+*/
+#define P4_NOTUSED    0   /* The P4 parameter is not used */
+#define P4_DYNAMIC  (-1)  /* Pointer to a string obtained from sqliteMalloc() */
+#define P4_STATIC   (-2)  /* Pointer to a static string */
+#define P4_COLLSEQ  (-4)  /* P4 is a pointer to a CollSeq structure */
+#define P4_FUNCDEF  (-5)  /* P4 is a pointer to a FuncDef structure */
+#define P4_KEYINFO  (-6)  /* P4 is a pointer to a KeyInfo structure */
+#define P4_VDBEFUNC (-7)  /* P4 is a pointer to a VdbeFunc structure */
+#define P4_MEM      (-8)  /* P4 is a pointer to a Mem*    structure */
+#define P4_TRANSIENT  0   /* P4 is a pointer to a transient string */
+#define P4_VTAB     (-10) /* P4 is a pointer to an sqlite3_vtab structure */
+#define P4_MPRINTF  (-11) /* P4 is a string obtained from sqlite3_mprintf() */
+#define P4_REAL     (-12) /* P4 is a 64-bit floating point value */
+#define P4_INT64    (-13) /* P4 is a 64-bit signed integer */
+#define P4_INT32    (-14) /* P4 is a 32-bit signed integer */
+#define P4_INTARRAY (-15) /* P4 is a vector of 32-bit integers */
+#define P4_SUBPROGRAM  (-18) /* P4 is a pointer to a SubProgram structure */
+#define P4_ADVANCE  (-19) /* P4 is a pointer to BtreeNext() or BtreePrev() */
+
+/* When adding a P4 argument using P4_KEYINFO, a copy of the KeyInfo structure
+** is made.  That copy is freed when the Vdbe is finalized.  But if the
+** argument is P4_KEYINFO_HANDOFF, the passed in pointer is used.  It still
+** gets freed when the Vdbe is finalized so it still should be obtained
+** from a single sqliteMalloc().  But no copy is made and the calling
+** function should *not* try to free the KeyInfo.
+*/
+#define P4_KEYINFO_HANDOFF (-16)
+#define P4_KEYINFO_STATIC  (-17)
+
+/*
+** The Vdbe.aColName array contains 5n Mem structures, where n is the 
+** number of columns of data returned by the statement.
+*/
+#define COLNAME_NAME     0
+#define COLNAME_DECLTYPE 1
+#define COLNAME_DATABASE 2
+#define COLNAME_TABLE    3
+#define COLNAME_COLUMN   4
+#ifdef SQLITE_ENABLE_COLUMN_METADATA
+# define COLNAME_N        5      /* Number of COLNAME_xxx symbols */
+#else
+# ifdef SQLITE_OMIT_DECLTYPE
+#   define COLNAME_N      1      /* Store only the name */
+# else
+#   define COLNAME_N      2      /* Store the name and decltype */
+# endif
+#endif
+
+/*
+** The following macro converts a relative address in the p2 field
+** of a VdbeOp structure into a negative number so that 
+** sqlite3VdbeAddOpList() knows that the address is relative.  Calling
+** the macro again restores the address.
+*/
+#define ADDR(X)  (-1-(X))
+
+/*
+** The makefile scans the vdbe.c source file and creates the "opcodes.h"
+** header file that defines a number for each opcode used by the VDBE.
+*/
+#include "opcodes.h"
+
+/*
+** Prototypes for the VDBE interface.  See comments on the implementation
+** for a description of what each of these routines does.
+*/
+Vdbe *sqlite3VdbeCreate(sqlite3*);
+int sqlite3VdbeAddOp0(Vdbe*,int);
+int sqlite3VdbeAddOp1(Vdbe*,int,int);
+int sqlite3VdbeAddOp2(Vdbe*,int,int,int);
+int sqlite3VdbeAddOp3(Vdbe*,int,int,int,int);
+int sqlite3VdbeAddOp4(Vdbe*,int,int,int,int,const char *zP4,int);
+int sqlite3VdbeAddOp4Int(Vdbe*,int,int,int,int,int);
+int sqlite3VdbeAddOpList(Vdbe*, int nOp, VdbeOpList const *aOp);
+void sqlite3VdbeAddParseSchemaOp(Vdbe*,int,char*);
+void sqlite3VdbeChangeP1(Vdbe*, u32 addr, int P1);
+void sqlite3VdbeChangeP2(Vdbe*, u32 addr, int P2);
+void sqlite3VdbeChangeP3(Vdbe*, u32 addr, int P3);
+void sqlite3VdbeChangeP5(Vdbe*, u8 P5);
+void sqlite3VdbeJumpHere(Vdbe*, int addr);
+void sqlite3VdbeChangeToNoop(Vdbe*, int addr);
+void sqlite3VdbeChangeP4(Vdbe*, int addr, const char *zP4, int N);
+void sqlite3VdbeUsesBtree(Vdbe*, int);
+VdbeOp *sqlite3VdbeGetOp(Vdbe*, int);
+int sqlite3VdbeMakeLabel(Vdbe*);
+void sqlite3VdbeRunOnlyOnce(Vdbe*);
+void sqlite3VdbeDelete(Vdbe*);
+void sqlite3VdbeDeleteObject(sqlite3*,Vdbe*);
+void sqlite3VdbeMakeReady(Vdbe*,Parse*);
+int sqlite3VdbeFinalize(Vdbe*);
+void sqlite3VdbeResolveLabel(Vdbe*, int);
+int sqlite3VdbeCurrentAddr(Vdbe*);
+#ifdef SQLITE_DEBUG
+  int sqlite3VdbeAssertMayAbort(Vdbe *, int);
+  void sqlite3VdbeTrace(Vdbe*,FILE*);
+#endif
+void sqlite3VdbeResetStepResult(Vdbe*);
+void sqlite3VdbeRewind(Vdbe*);
+int sqlite3VdbeReset(Vdbe*);
+void sqlite3VdbeSetNumCols(Vdbe*,int);
+int sqlite3VdbeSetColName(Vdbe*, int, int, const char *, void(*)(void*));
+void sqlite3VdbeCountChanges(Vdbe*);
+sqlite3 *sqlite3VdbeDb(Vdbe*);
+void sqlite3VdbeSetSql(Vdbe*, const char *z, int n, int);
+void sqlite3VdbeSwap(Vdbe*,Vdbe*);
+VdbeOp *sqlite3VdbeTakeOpArray(Vdbe*, int*, int*);
+sqlite3_value *sqlite3VdbeGetValue(Vdbe*, int, u8);
+void sqlite3VdbeSetVarmask(Vdbe*, int);
+#ifndef SQLITE_OMIT_TRACE
+  char *sqlite3VdbeExpandSql(Vdbe*, const char*);
+#endif
+
+void sqlite3VdbeRecordUnpack(KeyInfo*,int,const void*,UnpackedRecord*);
+int sqlite3VdbeRecordCompare(int,const void*,UnpackedRecord*);
+UnpackedRecord *sqlite3VdbeAllocUnpackedRecord(KeyInfo *, char *, int, char **);
+
+#ifndef SQLITE_OMIT_TRIGGER
+void sqlite3VdbeLinkSubProgram(Vdbe *, SubProgram *);
+#endif
+
+
+#ifndef NDEBUG
+  void sqlite3VdbeComment(Vdbe*, const char*, ...);
+# define VdbeComment(X)  sqlite3VdbeComment X
+  void sqlite3VdbeNoopComment(Vdbe*, const char*, ...);
+# define VdbeNoopComment(X)  sqlite3VdbeNoopComment X
+#else
+# define VdbeComment(X)
+# define VdbeNoopComment(X)
+#endif
+
+#endif
diff --git a/src/vdbeInt.h b/src/vdbeInt.h
new file mode 100644
index 0000000..803ae16
--- /dev/null
+++ b/src/vdbeInt.h
@@ -0,0 +1,449 @@
+/*
+** 2003 September 6
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This is the header file for information that is private to the
+** VDBE.  This information used to all be at the top of the single
+** source code file "vdbe.c".  When that file became too big (over
+** 6000 lines long) it was split up into several smaller files and
+** this header information was factored out.
+*/
+#ifndef _VDBEINT_H_
+#define _VDBEINT_H_
+
+/*
+** SQL is translated into a sequence of instructions to be
+** executed by a virtual machine.  Each instruction is an instance
+** of the following structure.
+*/
+typedef struct VdbeOp Op;
+
+/*
+** Boolean values
+*/
+typedef unsigned char Bool;
+
+/* Opaque type used by code in vdbesort.c */
+typedef struct VdbeSorter VdbeSorter;
+
+/*
+** A cursor is a pointer into a single BTree within a database file.
+** The cursor can seek to a BTree entry with a particular key, or
+** loop over all entries of the Btree.  You can also insert new BTree
+** entries or retrieve the key or data from the entry that the cursor
+** is currently pointing to.
+** 
+** Every cursor that the virtual machine has open is represented by an
+** instance of the following structure.
+*/
+struct VdbeCursor {
+  BtCursor *pCursor;    /* The cursor structure of the backend */
+  Btree *pBt;           /* Separate file holding temporary table */
+  KeyInfo *pKeyInfo;    /* Info about index keys needed by index cursors */
+  int iDb;              /* Index of cursor database in db->aDb[] (or -1) */
+  int pseudoTableReg;   /* Register holding pseudotable content. */
+  int nField;           /* Number of fields in the header */
+  Bool zeroed;          /* True if zeroed out and ready for reuse */
+  Bool rowidIsValid;    /* True if lastRowid is valid */
+  Bool atFirst;         /* True if pointing to first entry */
+  Bool useRandomRowid;  /* Generate new record numbers semi-randomly */
+  Bool nullRow;         /* True if pointing to a row with no data */
+  Bool deferredMoveto;  /* A call to sqlite3BtreeMoveto() is needed */
+  Bool isTable;         /* True if a table requiring integer keys */
+  Bool isIndex;         /* True if an index containing keys only - no data */
+  Bool isOrdered;       /* True if the underlying table is BTREE_UNORDERED */
+  Bool isSorter;        /* True if a new-style sorter */
+  sqlite3_vtab_cursor *pVtabCursor;  /* The cursor for a virtual table */
+  const sqlite3_module *pModule;     /* Module for cursor pVtabCursor */
+  i64 seqCount;         /* Sequence counter */
+  i64 movetoTarget;     /* Argument to the deferred sqlite3BtreeMoveto() */
+  i64 lastRowid;        /* Last rowid from a Next or NextIdx operation */
+  VdbeSorter *pSorter;  /* Sorter object for OP_SorterOpen cursors */
+
+  /* Result of last sqlite3BtreeMoveto() done by an OP_NotExists or 
+  ** OP_IsUnique opcode on this cursor. */
+  int seekResult;
+
+  /* Cached information about the header for the data record that the
+  ** cursor is currently pointing to.  Only valid if cacheStatus matches
+  ** Vdbe.cacheCtr.  Vdbe.cacheCtr will never take on the value of
+  ** CACHE_STALE and so setting cacheStatus=CACHE_STALE guarantees that
+  ** the cache is out of date.
+  **
+  ** aRow might point to (ephemeral) data for the current row, or it might
+  ** be NULL.
+  */
+  u32 cacheStatus;      /* Cache is valid if this matches Vdbe.cacheCtr */
+  int payloadSize;      /* Total number of bytes in the record */
+  u32 *aType;           /* Type values for all entries in the record */
+  u32 *aOffset;         /* Cached offsets to the start of each columns data */
+  u8 *aRow;             /* Data for the current row, if all on one page */
+};
+typedef struct VdbeCursor VdbeCursor;
+
+/*
+** When a sub-program is executed (OP_Program), a structure of this type
+** is allocated to store the current value of the program counter, as
+** well as the current memory cell array and various other frame specific
+** values stored in the Vdbe struct. When the sub-program is finished, 
+** these values are copied back to the Vdbe from the VdbeFrame structure,
+** restoring the state of the VM to as it was before the sub-program
+** began executing.
+**
+** The memory for a VdbeFrame object is allocated and managed by a memory
+** cell in the parent (calling) frame. When the memory cell is deleted or
+** overwritten, the VdbeFrame object is not freed immediately. Instead, it
+** is linked into the Vdbe.pDelFrame list. The contents of the Vdbe.pDelFrame
+** list is deleted when the VM is reset in VdbeHalt(). The reason for doing
+** this instead of deleting the VdbeFrame immediately is to avoid recursive
+** calls to sqlite3VdbeMemRelease() when the memory cells belonging to the
+** child frame are released.
+**
+** The currently executing frame is stored in Vdbe.pFrame. Vdbe.pFrame is
+** set to NULL if the currently executing frame is the main program.
+*/
+typedef struct VdbeFrame VdbeFrame;
+struct VdbeFrame {
+  Vdbe *v;                /* VM this frame belongs to */
+  int pc;                 /* Program Counter in parent (calling) frame */
+  Op *aOp;                /* Program instructions for parent frame */
+  int nOp;                /* Size of aOp array */
+  Mem *aMem;              /* Array of memory cells for parent frame */
+  int nMem;               /* Number of entries in aMem */
+  VdbeCursor **apCsr;     /* Array of Vdbe cursors for parent frame */
+  u16 nCursor;            /* Number of entries in apCsr */
+  void *token;            /* Copy of SubProgram.token */
+  int nChildMem;          /* Number of memory cells for child frame */
+  int nChildCsr;          /* Number of cursors for child frame */
+  i64 lastRowid;          /* Last insert rowid (sqlite3.lastRowid) */
+  int nChange;            /* Statement changes (Vdbe.nChanges)     */
+  VdbeFrame *pParent;     /* Parent of this frame, or NULL if parent is main */
+};
+
+#define VdbeFrameMem(p) ((Mem *)&((u8 *)p)[ROUND8(sizeof(VdbeFrame))])
+
+/*
+** A value for VdbeCursor.cacheValid that means the cache is always invalid.
+*/
+#define CACHE_STALE 0
+
+/*
+** Internally, the vdbe manipulates nearly all SQL values as Mem
+** structures. Each Mem struct may cache multiple representations (string,
+** integer etc.) of the same value.
+*/
+struct Mem {
+  sqlite3 *db;        /* The associated database connection */
+  char *z;            /* String or BLOB value */
+  double r;           /* Real value */
+  union {
+    i64 i;              /* Integer value used when MEM_Int is set in flags */
+    int nZero;          /* Used when bit MEM_Zero is set in flags */
+    FuncDef *pDef;      /* Used only when flags==MEM_Agg */
+    RowSet *pRowSet;    /* Used only when flags==MEM_RowSet */
+    VdbeFrame *pFrame;  /* Used when flags==MEM_Frame */
+  } u;
+  int n;              /* Number of characters in string value, excluding '\0' */
+  u16 flags;          /* Some combination of MEM_Null, MEM_Str, MEM_Dyn, etc. */
+  u8  type;           /* One of SQLITE_NULL, SQLITE_TEXT, SQLITE_INTEGER, etc */
+  u8  enc;            /* SQLITE_UTF8, SQLITE_UTF16BE, SQLITE_UTF16LE */
+#ifdef SQLITE_DEBUG
+  Mem *pScopyFrom;    /* This Mem is a shallow copy of pScopyFrom */
+  void *pFiller;      /* So that sizeof(Mem) is a multiple of 8 */
+#endif
+  void (*xDel)(void *);  /* If not null, call this function to delete Mem.z */
+  char *zMalloc;      /* Dynamic buffer allocated by sqlite3_malloc() */
+};
+
+/* One or more of the following flags are set to indicate the validOK
+** representations of the value stored in the Mem struct.
+**
+** If the MEM_Null flag is set, then the value is an SQL NULL value.
+** No other flags may be set in this case.
+**
+** If the MEM_Str flag is set then Mem.z points at a string representation.
+** Usually this is encoded in the same unicode encoding as the main
+** database (see below for exceptions). If the MEM_Term flag is also
+** set, then the string is nul terminated. The MEM_Int and MEM_Real 
+** flags may coexist with the MEM_Str flag.
+*/
+#define MEM_Null      0x0001   /* Value is NULL */
+#define MEM_Str       0x0002   /* Value is a string */
+#define MEM_Int       0x0004   /* Value is an integer */
+#define MEM_Real      0x0008   /* Value is a real number */
+#define MEM_Blob      0x0010   /* Value is a BLOB */
+#define MEM_RowSet    0x0020   /* Value is a RowSet object */
+#define MEM_Frame     0x0040   /* Value is a VdbeFrame object */
+#define MEM_Invalid   0x0080   /* Value is undefined */
+#define MEM_TypeMask  0x00ff   /* Mask of type bits */
+
+/* Whenever Mem contains a valid string or blob representation, one of
+** the following flags must be set to determine the memory management
+** policy for Mem.z.  The MEM_Term flag tells us whether or not the
+** string is \000 or \u0000 terminated
+*/
+#define MEM_Term      0x0200   /* String rep is nul terminated */
+#define MEM_Dyn       0x0400   /* Need to call sqliteFree() on Mem.z */
+#define MEM_Static    0x0800   /* Mem.z points to a static string */
+#define MEM_Ephem     0x1000   /* Mem.z points to an ephemeral string */
+#define MEM_Agg       0x2000   /* Mem.z points to an agg function context */
+#define MEM_Zero      0x4000   /* Mem.i contains count of 0s appended to blob */
+#ifdef SQLITE_OMIT_INCRBLOB
+  #undef MEM_Zero
+  #define MEM_Zero 0x0000
+#endif
+
+/*
+** Clear any existing type flags from a Mem and replace them with f
+*/
+#define MemSetTypeFlag(p, f) \
+   ((p)->flags = ((p)->flags&~(MEM_TypeMask|MEM_Zero))|f)
+
+/*
+** Return true if a memory cell is not marked as invalid.  This macro
+** is for use inside assert() statements only.
+*/
+#ifdef SQLITE_DEBUG
+#define memIsValid(M)  ((M)->flags & MEM_Invalid)==0
+#endif
+
+
+/* A VdbeFunc is just a FuncDef (defined in sqliteInt.h) that contains
+** additional information about auxiliary information bound to arguments
+** of the function.  This is used to implement the sqlite3_get_auxdata()
+** and sqlite3_set_auxdata() APIs.  The "auxdata" is some auxiliary data
+** that can be associated with a constant argument to a function.  This
+** allows functions such as "regexp" to compile their constant regular
+** expression argument once and reused the compiled code for multiple
+** invocations.
+*/
+struct VdbeFunc {
+  FuncDef *pFunc;               /* The definition of the function */
+  int nAux;                     /* Number of entries allocated for apAux[] */
+  struct AuxData {
+    void *pAux;                   /* Aux data for the i-th argument */
+    void (*xDelete)(void *);      /* Destructor for the aux data */
+  } apAux[1];                   /* One slot for each function argument */
+};
+
+/*
+** The "context" argument for a installable function.  A pointer to an
+** instance of this structure is the first argument to the routines used
+** implement the SQL functions.
+**
+** There is a typedef for this structure in sqlite.h.  So all routines,
+** even the public interface to SQLite, can use a pointer to this structure.
+** But this file is the only place where the internal details of this
+** structure are known.
+**
+** This structure is defined inside of vdbeInt.h because it uses substructures
+** (Mem) which are only defined there.
+*/
+struct sqlite3_context {
+  FuncDef *pFunc;       /* Pointer to function information.  MUST BE FIRST */
+  VdbeFunc *pVdbeFunc;  /* Auxilary data, if created. */
+  Mem s;                /* The return value is stored here */
+  Mem *pMem;            /* Memory cell used to store aggregate context */
+  int isError;          /* Error code returned by the function. */
+  CollSeq *pColl;       /* Collating sequence */
+};
+
+/*
+** An instance of the virtual machine.  This structure contains the complete
+** state of the virtual machine.
+**
+** The "sqlite3_stmt" structure pointer that is returned by sqlite3_prepare()
+** is really a pointer to an instance of this structure.
+**
+** The Vdbe.inVtabMethod variable is set to non-zero for the duration of
+** any virtual table method invocations made by the vdbe program. It is
+** set to 2 for xDestroy method calls and 1 for all other methods. This
+** variable is used for two purposes: to allow xDestroy methods to execute
+** "DROP TABLE" statements and to prevent some nasty side effects of
+** malloc failure when SQLite is invoked recursively by a virtual table 
+** method function.
+*/
+struct Vdbe {
+  sqlite3 *db;            /* The database connection that owns this statement */
+  Op *aOp;                /* Space to hold the virtual machine's program */
+  Mem *aMem;              /* The memory locations */
+  Mem **apArg;            /* Arguments to currently executing user function */
+  Mem *aColName;          /* Column names to return */
+  Mem *pResultSet;        /* Pointer to an array of results */
+  int nMem;               /* Number of memory locations currently allocated */
+  int nOp;                /* Number of instructions in the program */
+  int nOpAlloc;           /* Number of slots allocated for aOp[] */
+  int nLabel;             /* Number of labels used */
+  int nLabelAlloc;        /* Number of slots allocated in aLabel[] */
+  int *aLabel;            /* Space to hold the labels */
+  u16 nResColumn;         /* Number of columns in one row of the result set */
+  u16 nCursor;            /* Number of slots in apCsr[] */
+  u32 magic;              /* Magic number for sanity checking */
+  char *zErrMsg;          /* Error message written here */
+  Vdbe *pPrev,*pNext;     /* Linked list of VDBEs with the same Vdbe.db */
+  VdbeCursor **apCsr;     /* One element of this array for each open cursor */
+  Mem *aVar;              /* Values for the OP_Variable opcode. */
+  char **azVar;           /* Name of variables */
+  ynVar nVar;             /* Number of entries in aVar[] */
+  ynVar nzVar;            /* Number of entries in azVar[] */
+  u32 cacheCtr;           /* VdbeCursor row cache generation counter */
+  int pc;                 /* The program counter */
+  int rc;                 /* Value to return */
+  u8 errorAction;         /* Recovery action to do in case of an error */
+  u8 explain;             /* True if EXPLAIN present on SQL command */
+  u8 changeCntOn;         /* True to update the change-counter */
+  u8 expired;             /* True if the VM needs to be recompiled */
+  u8 runOnlyOnce;         /* Automatically expire on reset */
+  u8 minWriteFileFormat;  /* Minimum file format for writable database files */
+  u8 inVtabMethod;        /* See comments above */
+  u8 usesStmtJournal;     /* True if uses a statement journal */
+  u8 readOnly;            /* True for read-only statements */
+  u8 isPrepareV2;         /* True if prepared with prepare_v2() */
+  int nChange;            /* Number of db changes made since last reset */
+  yDbMask btreeMask;      /* Bitmask of db->aDb[] entries referenced */
+  yDbMask lockMask;       /* Subset of btreeMask that requires a lock */
+  int iStatement;         /* Statement number (or 0 if has not opened stmt) */
+  int aCounter[3];        /* Counters used by sqlite3_stmt_status() */
+#ifndef SQLITE_OMIT_TRACE
+  i64 startTime;          /* Time when query started - used for profiling */
+#endif
+  i64 nFkConstraint;      /* Number of imm. FK constraints this VM */
+  i64 nStmtDefCons;       /* Number of def. constraints when stmt started */
+  char *zSql;             /* Text of the SQL statement that generated this */
+  void *pFree;            /* Free this when deleting the vdbe */
+#ifdef SQLITE_DEBUG
+  FILE *trace;            /* Write an execution trace here, if not NULL */
+#endif
+  VdbeFrame *pFrame;      /* Parent frame */
+  VdbeFrame *pDelFrame;   /* List of frame objects to free on VM reset */
+  int nFrame;             /* Number of frames in pFrame list */
+  u32 expmask;            /* Binding to these vars invalidates VM */
+  SubProgram *pProgram;   /* Linked list of all sub-programs used by VM */
+};
+
+/*
+** The following are allowed values for Vdbe.magic
+*/
+#define VDBE_MAGIC_INIT     0x26bceaa5    /* Building a VDBE program */
+#define VDBE_MAGIC_RUN      0xbdf20da3    /* VDBE is ready to execute */
+#define VDBE_MAGIC_HALT     0x519c2973    /* VDBE has completed execution */
+#define VDBE_MAGIC_DEAD     0xb606c3c8    /* The VDBE has been deallocated */
+
+/*
+** Function prototypes
+*/
+void sqlite3VdbeFreeCursor(Vdbe *, VdbeCursor*);
+void sqliteVdbePopStack(Vdbe*,int);
+int sqlite3VdbeCursorMoveto(VdbeCursor*);
+#if defined(SQLITE_DEBUG) || defined(VDBE_PROFILE)
+void sqlite3VdbePrintOp(FILE*, int, Op*);
+#endif
+u32 sqlite3VdbeSerialTypeLen(u32);
+u32 sqlite3VdbeSerialType(Mem*, int);
+u32 sqlite3VdbeSerialPut(unsigned char*, int, Mem*, int);
+u32 sqlite3VdbeSerialGet(const unsigned char*, u32, Mem*);
+void sqlite3VdbeDeleteAuxData(VdbeFunc*, int);
+
+int sqlite2BtreeKeyCompare(BtCursor *, const void *, int, int, int *);
+int sqlite3VdbeIdxKeyCompare(VdbeCursor*,UnpackedRecord*,int*);
+int sqlite3VdbeIdxRowid(sqlite3*, BtCursor *, i64 *);
+int sqlite3MemCompare(const Mem*, const Mem*, const CollSeq*);
+int sqlite3VdbeExec(Vdbe*);
+int sqlite3VdbeList(Vdbe*);
+int sqlite3VdbeHalt(Vdbe*);
+int sqlite3VdbeChangeEncoding(Mem *, int);
+int sqlite3VdbeMemTooBig(Mem*);
+int sqlite3VdbeMemCopy(Mem*, const Mem*);
+void sqlite3VdbeMemShallowCopy(Mem*, const Mem*, int);
+void sqlite3VdbeMemMove(Mem*, Mem*);
+int sqlite3VdbeMemNulTerminate(Mem*);
+int sqlite3VdbeMemSetStr(Mem*, const char*, int, u8, void(*)(void*));
+void sqlite3VdbeMemSetInt64(Mem*, i64);
+#ifdef SQLITE_OMIT_FLOATING_POINT
+# define sqlite3VdbeMemSetDouble sqlite3VdbeMemSetInt64
+#else
+  void sqlite3VdbeMemSetDouble(Mem*, double);
+#endif
+void sqlite3VdbeMemSetNull(Mem*);
+void sqlite3VdbeMemSetZeroBlob(Mem*,int);
+void sqlite3VdbeMemSetRowSet(Mem*);
+int sqlite3VdbeMemMakeWriteable(Mem*);
+int sqlite3VdbeMemStringify(Mem*, int);
+i64 sqlite3VdbeIntValue(Mem*);
+int sqlite3VdbeMemIntegerify(Mem*);
+double sqlite3VdbeRealValue(Mem*);
+void sqlite3VdbeIntegerAffinity(Mem*);
+int sqlite3VdbeMemRealify(Mem*);
+int sqlite3VdbeMemNumerify(Mem*);
+int sqlite3VdbeMemFromBtree(BtCursor*,int,int,int,Mem*);
+void sqlite3VdbeMemRelease(Mem *p);
+void sqlite3VdbeMemReleaseExternal(Mem *p);
+#define MemReleaseExt(X)  \
+  if((X)->flags&(MEM_Agg|MEM_Dyn|MEM_RowSet|MEM_Frame)) \
+    sqlite3VdbeMemReleaseExternal(X);
+int sqlite3VdbeMemFinalize(Mem*, FuncDef*);
+const char *sqlite3OpcodeName(int);
+int sqlite3VdbeMemGrow(Mem *pMem, int n, int preserve);
+int sqlite3VdbeCloseStatement(Vdbe *, int);
+void sqlite3VdbeFrameDelete(VdbeFrame*);
+int sqlite3VdbeFrameRestore(VdbeFrame *);
+void sqlite3VdbeMemStoreType(Mem *pMem);
+int sqlite3VdbeTransferError(Vdbe *p);
+
+#ifdef SQLITE_OMIT_MERGE_SORT
+# define sqlite3VdbeSorterInit(Y,Z)      SQLITE_OK
+# define sqlite3VdbeSorterWrite(X,Y,Z)   SQLITE_OK
+# define sqlite3VdbeSorterClose(Y,Z)
+# define sqlite3VdbeSorterRowkey(Y,Z)    SQLITE_OK
+# define sqlite3VdbeSorterRewind(X,Y,Z)  SQLITE_OK
+# define sqlite3VdbeSorterNext(X,Y,Z)    SQLITE_OK
+# define sqlite3VdbeSorterCompare(X,Y,Z) SQLITE_OK
+#else
+int sqlite3VdbeSorterInit(sqlite3 *, VdbeCursor *);
+void sqlite3VdbeSorterClose(sqlite3 *, VdbeCursor *);
+int sqlite3VdbeSorterRowkey(VdbeCursor *, Mem *);
+int sqlite3VdbeSorterNext(sqlite3 *, VdbeCursor *, int *);
+int sqlite3VdbeSorterRewind(sqlite3 *, VdbeCursor *, int *);
+int sqlite3VdbeSorterWrite(sqlite3 *, VdbeCursor *, Mem *);
+int sqlite3VdbeSorterCompare(VdbeCursor *, Mem *, int *);
+#endif
+
+#if !defined(SQLITE_OMIT_SHARED_CACHE) && SQLITE_THREADSAFE>0
+  void sqlite3VdbeEnter(Vdbe*);
+  void sqlite3VdbeLeave(Vdbe*);
+#else
+# define sqlite3VdbeEnter(X)
+# define sqlite3VdbeLeave(X)
+#endif
+
+#ifdef SQLITE_DEBUG
+void sqlite3VdbeMemPrepareToChange(Vdbe*,Mem*);
+#endif
+
+#ifndef SQLITE_OMIT_FOREIGN_KEY
+int sqlite3VdbeCheckFk(Vdbe *, int);
+#else
+# define sqlite3VdbeCheckFk(p,i) 0
+#endif
+
+int sqlite3VdbeMemTranslate(Mem*, u8);
+#ifdef SQLITE_DEBUG
+  void sqlite3VdbePrintSql(Vdbe*);
+  void sqlite3VdbeMemPrettyPrint(Mem *pMem, char *zBuf);
+#endif
+int sqlite3VdbeMemHandleBom(Mem *pMem);
+
+#ifndef SQLITE_OMIT_INCRBLOB
+  int sqlite3VdbeMemExpandBlob(Mem *);
+#else
+  #define sqlite3VdbeMemExpandBlob(x) SQLITE_OK
+#endif
+
+#endif /* !defined(_VDBEINT_H_) */
diff --git a/src/vdbeapi.c b/src/vdbeapi.c
new file mode 100644
index 0000000..adc9dba
--- /dev/null
+++ b/src/vdbeapi.c
@@ -0,0 +1,1306 @@
+/*
+** 2004 May 26
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains code use to implement APIs that are part of the
+** VDBE.
+*/
+#include "sqliteInt.h"
+#include "vdbeInt.h"
+
+#ifndef SQLITE_OMIT_DEPRECATED
+/*
+** Return TRUE (non-zero) of the statement supplied as an argument needs
+** to be recompiled.  A statement needs to be recompiled whenever the
+** execution environment changes in a way that would alter the program
+** that sqlite3_prepare() generates.  For example, if new functions or
+** collating sequences are registered or if an authorizer function is
+** added or changed.
+*/
+int sqlite3_expired(sqlite3_stmt *pStmt){
+  Vdbe *p = (Vdbe*)pStmt;
+  return p==0 || p->expired;
+}
+#endif
+
+/*
+** Check on a Vdbe to make sure it has not been finalized.  Log
+** an error and return true if it has been finalized (or is otherwise
+** invalid).  Return false if it is ok.
+*/
+static int vdbeSafety(Vdbe *p){
+  if( p->db==0 ){
+    sqlite3_log(SQLITE_MISUSE, "API called with finalized prepared statement");
+    return 1;
+  }else{
+    return 0;
+  }
+}
+static int vdbeSafetyNotNull(Vdbe *p){
+  if( p==0 ){
+    sqlite3_log(SQLITE_MISUSE, "API called with NULL prepared statement");
+    return 1;
+  }else{
+    return vdbeSafety(p);
+  }
+}
+
+/*
+** The following routine destroys a virtual machine that is created by
+** the sqlite3_compile() routine. The integer returned is an SQLITE_
+** success/failure code that describes the result of executing the virtual
+** machine.
+**
+** This routine sets the error code and string returned by
+** sqlite3_errcode(), sqlite3_errmsg() and sqlite3_errmsg16().
+*/
+int sqlite3_finalize(sqlite3_stmt *pStmt){
+  int rc;
+  if( pStmt==0 ){
+    /* IMPLEMENTATION-OF: R-57228-12904 Invoking sqlite3_finalize() on a NULL
+    ** pointer is a harmless no-op. */
+    rc = SQLITE_OK;
+  }else{
+    Vdbe *v = (Vdbe*)pStmt;
+    sqlite3 *db = v->db;
+#if SQLITE_THREADSAFE
+    sqlite3_mutex *mutex;
+#endif
+    if( vdbeSafety(v) ) return SQLITE_MISUSE_BKPT;
+#if SQLITE_THREADSAFE
+    mutex = v->db->mutex;
+#endif
+    sqlite3_mutex_enter(mutex);
+    rc = sqlite3VdbeFinalize(v);
+    rc = sqlite3ApiExit(db, rc);
+    sqlite3_mutex_leave(mutex);
+  }
+  return rc;
+}
+
+/*
+** Terminate the current execution of an SQL statement and reset it
+** back to its starting state so that it can be reused. A success code from
+** the prior execution is returned.
+**
+** This routine sets the error code and string returned by
+** sqlite3_errcode(), sqlite3_errmsg() and sqlite3_errmsg16().
+*/
+int sqlite3_reset(sqlite3_stmt *pStmt){
+  int rc;
+  if( pStmt==0 ){
+    rc = SQLITE_OK;
+  }else{
+    Vdbe *v = (Vdbe*)pStmt;
+    sqlite3_mutex_enter(v->db->mutex);
+    rc = sqlite3VdbeReset(v);
+    sqlite3VdbeRewind(v);
+    assert( (rc & (v->db->errMask))==rc );
+    rc = sqlite3ApiExit(v->db, rc);
+    sqlite3_mutex_leave(v->db->mutex);
+  }
+  return rc;
+}
+
+/*
+** Set all the parameters in the compiled SQL statement to NULL.
+*/
+int sqlite3_clear_bindings(sqlite3_stmt *pStmt){
+  int i;
+  int rc = SQLITE_OK;
+  Vdbe *p = (Vdbe*)pStmt;
+#if SQLITE_THREADSAFE
+  sqlite3_mutex *mutex = ((Vdbe*)pStmt)->db->mutex;
+#endif
+  sqlite3_mutex_enter(mutex);
+  for(i=0; i<p->nVar; i++){
+    sqlite3VdbeMemRelease(&p->aVar[i]);
+    p->aVar[i].flags = MEM_Null;
+  }
+  if( p->isPrepareV2 && p->expmask ){
+    p->expired = 1;
+  }
+  sqlite3_mutex_leave(mutex);
+  return rc;
+}
+
+
+/**************************** sqlite3_value_  *******************************
+** The following routines extract information from a Mem or sqlite3_value
+** structure.
+*/
+const void *sqlite3_value_blob(sqlite3_value *pVal){
+  Mem *p = (Mem*)pVal;
+  if( p->flags & (MEM_Blob|MEM_Str) ){
+    sqlite3VdbeMemExpandBlob(p);
+    p->flags &= ~MEM_Str;
+    p->flags |= MEM_Blob;
+    return p->n ? p->z : 0;
+  }else{
+    return sqlite3_value_text(pVal);
+  }
+}
+int sqlite3_value_bytes(sqlite3_value *pVal){
+  return sqlite3ValueBytes(pVal, SQLITE_UTF8);
+}
+int sqlite3_value_bytes16(sqlite3_value *pVal){
+  return sqlite3ValueBytes(pVal, SQLITE_UTF16NATIVE);
+}
+double sqlite3_value_double(sqlite3_value *pVal){
+  return sqlite3VdbeRealValue((Mem*)pVal);
+}
+int sqlite3_value_int(sqlite3_value *pVal){
+  return (int)sqlite3VdbeIntValue((Mem*)pVal);
+}
+sqlite_int64 sqlite3_value_int64(sqlite3_value *pVal){
+  return sqlite3VdbeIntValue((Mem*)pVal);
+}
+const unsigned char *sqlite3_value_text(sqlite3_value *pVal){
+  return (const unsigned char *)sqlite3ValueText(pVal, SQLITE_UTF8);
+}
+#ifndef SQLITE_OMIT_UTF16
+const void *sqlite3_value_text16(sqlite3_value* pVal){
+  return sqlite3ValueText(pVal, SQLITE_UTF16NATIVE);
+}
+const void *sqlite3_value_text16be(sqlite3_value *pVal){
+  return sqlite3ValueText(pVal, SQLITE_UTF16BE);
+}
+const void *sqlite3_value_text16le(sqlite3_value *pVal){
+  return sqlite3ValueText(pVal, SQLITE_UTF16LE);
+}
+#endif /* SQLITE_OMIT_UTF16 */
+int sqlite3_value_type(sqlite3_value* pVal){
+  return pVal->type;
+}
+
+/**************************** sqlite3_result_  *******************************
+** The following routines are used by user-defined functions to specify
+** the function result.
+**
+** The setStrOrError() funtion calls sqlite3VdbeMemSetStr() to store the
+** result as a string or blob but if the string or blob is too large, it
+** then sets the error code to SQLITE_TOOBIG
+*/
+static void setResultStrOrError(
+  sqlite3_context *pCtx,  /* Function context */
+  const char *z,          /* String pointer */
+  int n,                  /* Bytes in string, or negative */
+  u8 enc,                 /* Encoding of z.  0 for BLOBs */
+  void (*xDel)(void*)     /* Destructor function */
+){
+  if( sqlite3VdbeMemSetStr(&pCtx->s, z, n, enc, xDel)==SQLITE_TOOBIG ){
+    sqlite3_result_error_toobig(pCtx);
+  }
+}
+void sqlite3_result_blob(
+  sqlite3_context *pCtx, 
+  const void *z, 
+  int n, 
+  void (*xDel)(void *)
+){
+  assert( n>=0 );
+  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
+  setResultStrOrError(pCtx, z, n, 0, xDel);
+}
+void sqlite3_result_double(sqlite3_context *pCtx, double rVal){
+  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
+  sqlite3VdbeMemSetDouble(&pCtx->s, rVal);
+}
+void sqlite3_result_error(sqlite3_context *pCtx, const char *z, int n){
+  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
+  pCtx->isError = SQLITE_ERROR;
+  sqlite3VdbeMemSetStr(&pCtx->s, z, n, SQLITE_UTF8, SQLITE_TRANSIENT);
+}
+#ifndef SQLITE_OMIT_UTF16
+void sqlite3_result_error16(sqlite3_context *pCtx, const void *z, int n){
+  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
+  pCtx->isError = SQLITE_ERROR;
+  sqlite3VdbeMemSetStr(&pCtx->s, z, n, SQLITE_UTF16NATIVE, SQLITE_TRANSIENT);
+}
+#endif
+void sqlite3_result_int(sqlite3_context *pCtx, int iVal){
+  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
+  sqlite3VdbeMemSetInt64(&pCtx->s, (i64)iVal);
+}
+void sqlite3_result_int64(sqlite3_context *pCtx, i64 iVal){
+  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
+  sqlite3VdbeMemSetInt64(&pCtx->s, iVal);
+}
+void sqlite3_result_null(sqlite3_context *pCtx){
+  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
+  sqlite3VdbeMemSetNull(&pCtx->s);
+}
+void sqlite3_result_text(
+  sqlite3_context *pCtx, 
+  const char *z, 
+  int n,
+  void (*xDel)(void *)
+){
+  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
+  setResultStrOrError(pCtx, z, n, SQLITE_UTF8, xDel);
+}
+#ifndef SQLITE_OMIT_UTF16
+void sqlite3_result_text16(
+  sqlite3_context *pCtx, 
+  const void *z, 
+  int n, 
+  void (*xDel)(void *)
+){
+  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
+  setResultStrOrError(pCtx, z, n, SQLITE_UTF16NATIVE, xDel);
+}
+void sqlite3_result_text16be(
+  sqlite3_context *pCtx, 
+  const void *z, 
+  int n, 
+  void (*xDel)(void *)
+){
+  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
+  setResultStrOrError(pCtx, z, n, SQLITE_UTF16BE, xDel);
+}
+void sqlite3_result_text16le(
+  sqlite3_context *pCtx, 
+  const void *z, 
+  int n, 
+  void (*xDel)(void *)
+){
+  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
+  setResultStrOrError(pCtx, z, n, SQLITE_UTF16LE, xDel);
+}
+#endif /* SQLITE_OMIT_UTF16 */
+void sqlite3_result_value(sqlite3_context *pCtx, sqlite3_value *pValue){
+  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
+  sqlite3VdbeMemCopy(&pCtx->s, pValue);
+}
+void sqlite3_result_zeroblob(sqlite3_context *pCtx, int n){
+  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
+  sqlite3VdbeMemSetZeroBlob(&pCtx->s, n);
+}
+void sqlite3_result_error_code(sqlite3_context *pCtx, int errCode){
+  pCtx->isError = errCode;
+  if( pCtx->s.flags & MEM_Null ){
+    sqlite3VdbeMemSetStr(&pCtx->s, sqlite3ErrStr(errCode), -1, 
+                         SQLITE_UTF8, SQLITE_STATIC);
+  }
+}
+
+/* Force an SQLITE_TOOBIG error. */
+void sqlite3_result_error_toobig(sqlite3_context *pCtx){
+  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
+  pCtx->isError = SQLITE_TOOBIG;
+  sqlite3VdbeMemSetStr(&pCtx->s, "string or blob too big", -1, 
+                       SQLITE_UTF8, SQLITE_STATIC);
+}
+
+/* An SQLITE_NOMEM error. */
+void sqlite3_result_error_nomem(sqlite3_context *pCtx){
+  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
+  sqlite3VdbeMemSetNull(&pCtx->s);
+  pCtx->isError = SQLITE_NOMEM;
+  pCtx->s.db->mallocFailed = 1;
+}
+
+/*
+** This function is called after a transaction has been committed. It 
+** invokes callbacks registered with sqlite3_wal_hook() as required.
+*/
+static int doWalCallbacks(sqlite3 *db){
+  int rc = SQLITE_OK;
+#ifndef SQLITE_OMIT_WAL
+  int i;
+  for(i=0; i<db->nDb; i++){
+    Btree *pBt = db->aDb[i].pBt;
+    if( pBt ){
+      int nEntry = sqlite3PagerWalCallback(sqlite3BtreePager(pBt));
+      if( db->xWalCallback && nEntry>0 && rc==SQLITE_OK ){
+        rc = db->xWalCallback(db->pWalArg, db, db->aDb[i].zName, nEntry);
+      }
+    }
+  }
+#endif
+  return rc;
+}
+
+/*
+** Execute the statement pStmt, either until a row of data is ready, the
+** statement is completely executed or an error occurs.
+**
+** This routine implements the bulk of the logic behind the sqlite_step()
+** API.  The only thing omitted is the automatic recompile if a 
+** schema change has occurred.  That detail is handled by the
+** outer sqlite3_step() wrapper procedure.
+*/
+static int sqlite3Step(Vdbe *p){
+  sqlite3 *db;
+  int rc;
+
+  assert(p);
+  if( p->magic!=VDBE_MAGIC_RUN ){
+    /* We used to require that sqlite3_reset() be called before retrying
+    ** sqlite3_step() after any error or after SQLITE_DONE.  But beginning
+    ** with version 3.7.0, we changed this so that sqlite3_reset() would
+    ** be called automatically instead of throwing the SQLITE_MISUSE error.
+    ** This "automatic-reset" change is not technically an incompatibility, 
+    ** since any application that receives an SQLITE_MISUSE is broken by
+    ** definition.
+    **
+    ** Nevertheless, some published applications that were originally written
+    ** for version 3.6.23 or earlier do in fact depend on SQLITE_MISUSE 
+    ** returns, and the so were broken by the automatic-reset change.  As a
+    ** a work-around, the SQLITE_OMIT_AUTORESET compile-time restores the
+    ** legacy behavior of returning SQLITE_MISUSE for cases where the 
+    ** previous sqlite3_step() returned something other than a SQLITE_LOCKED
+    ** or SQLITE_BUSY error.
+    */
+#ifdef SQLITE_OMIT_AUTORESET
+    if( p->rc==SQLITE_BUSY || p->rc==SQLITE_LOCKED ){
+      sqlite3_reset((sqlite3_stmt*)p);
+    }else{
+      return SQLITE_MISUSE_BKPT;
+    }
+#else
+    sqlite3_reset((sqlite3_stmt*)p);
+#endif
+  }
+
+  /* Check that malloc() has not failed. If it has, return early. */
+  db = p->db;
+  if( db->mallocFailed ){
+    p->rc = SQLITE_NOMEM;
+    return SQLITE_NOMEM;
+  }
+
+  if( p->pc<=0 && p->expired ){
+    p->rc = SQLITE_SCHEMA;
+    rc = SQLITE_ERROR;
+    goto end_of_step;
+  }
+  if( p->pc<0 ){
+    /* If there are no other statements currently running, then
+    ** reset the interrupt flag.  This prevents a call to sqlite3_interrupt
+    ** from interrupting a statement that has not yet started.
+    */
+    if( db->activeVdbeCnt==0 ){
+      db->u1.isInterrupted = 0;
+    }
+
+    assert( db->writeVdbeCnt>0 || db->autoCommit==0 || db->nDeferredCons==0 );
+
+#ifndef SQLITE_OMIT_TRACE
+    if( db->xProfile && !db->init.busy ){
+      sqlite3OsCurrentTimeInt64(db->pVfs, &p->startTime);
+    }
+#endif
+
+    db->activeVdbeCnt++;
+    if( p->readOnly==0 ) db->writeVdbeCnt++;
+    p->pc = 0;
+  }
+#ifndef SQLITE_OMIT_EXPLAIN
+  if( p->explain ){
+    rc = sqlite3VdbeList(p);
+  }else
+#endif /* SQLITE_OMIT_EXPLAIN */
+  {
+    db->vdbeExecCnt++;
+    rc = sqlite3VdbeExec(p);
+    db->vdbeExecCnt--;
+  }
+
+#ifndef SQLITE_OMIT_TRACE
+  /* Invoke the profile callback if there is one
+  */
+  if( rc!=SQLITE_ROW && db->xProfile && !db->init.busy && p->zSql ){
+    sqlite3_int64 iNow;
+    sqlite3OsCurrentTimeInt64(db->pVfs, &iNow);
+    db->xProfile(db->pProfileArg, p->zSql, (iNow - p->startTime)*1000000);
+  }
+#endif
+
+  if( rc==SQLITE_DONE ){
+    assert( p->rc==SQLITE_OK );
+    p->rc = doWalCallbacks(db);
+    if( p->rc!=SQLITE_OK ){
+      rc = SQLITE_ERROR;
+    }
+  }
+
+  db->errCode = rc;
+  if( SQLITE_NOMEM==sqlite3ApiExit(p->db, p->rc) ){
+    p->rc = SQLITE_NOMEM;
+  }
+end_of_step:
+  /* At this point local variable rc holds the value that should be 
+  ** returned if this statement was compiled using the legacy 
+  ** sqlite3_prepare() interface. According to the docs, this can only
+  ** be one of the values in the first assert() below. Variable p->rc 
+  ** contains the value that would be returned if sqlite3_finalize() 
+  ** were called on statement p.
+  */
+  assert( rc==SQLITE_ROW  || rc==SQLITE_DONE   || rc==SQLITE_ERROR 
+       || rc==SQLITE_BUSY || rc==SQLITE_MISUSE
+  );
+  assert( p->rc!=SQLITE_ROW && p->rc!=SQLITE_DONE );
+  if( p->isPrepareV2 && rc!=SQLITE_ROW && rc!=SQLITE_DONE ){
+    /* If this statement was prepared using sqlite3_prepare_v2(), and an
+    ** error has occured, then return the error code in p->rc to the
+    ** caller. Set the error code in the database handle to the same value.
+    */ 
+    rc = sqlite3VdbeTransferError(p);
+  }
+  return (rc&db->errMask);
+}
+
+/*
+** The maximum number of times that a statement will try to reparse
+** itself before giving up and returning SQLITE_SCHEMA.
+*/
+#ifndef SQLITE_MAX_SCHEMA_RETRY
+# define SQLITE_MAX_SCHEMA_RETRY 5
+#endif
+
+/*
+** This is the top-level implementation of sqlite3_step().  Call
+** sqlite3Step() to do most of the work.  If a schema error occurs,
+** call sqlite3Reprepare() and try again.
+*/
+int sqlite3_step(sqlite3_stmt *pStmt){
+  int rc = SQLITE_OK;      /* Result from sqlite3Step() */
+  int rc2 = SQLITE_OK;     /* Result from sqlite3Reprepare() */
+  Vdbe *v = (Vdbe*)pStmt;  /* the prepared statement */
+  int cnt = 0;             /* Counter to prevent infinite loop of reprepares */
+  sqlite3 *db;             /* The database connection */
+
+  if( vdbeSafetyNotNull(v) ){
+    return SQLITE_MISUSE_BKPT;
+  }
+  db = v->db;
+  sqlite3_mutex_enter(db->mutex);
+  while( (rc = sqlite3Step(v))==SQLITE_SCHEMA
+         && cnt++ < SQLITE_MAX_SCHEMA_RETRY
+         && (rc2 = rc = sqlite3Reprepare(v))==SQLITE_OK ){
+    sqlite3_reset(pStmt);
+    assert( v->expired==0 );
+  }
+  if( rc2!=SQLITE_OK && ALWAYS(v->isPrepareV2) && ALWAYS(db->pErr) ){
+    /* This case occurs after failing to recompile an sql statement. 
+    ** The error message from the SQL compiler has already been loaded 
+    ** into the database handle. This block copies the error message 
+    ** from the database handle into the statement and sets the statement
+    ** program counter to 0 to ensure that when the statement is 
+    ** finalized or reset the parser error message is available via
+    ** sqlite3_errmsg() and sqlite3_errcode().
+    */
+    const char *zErr = (const char *)sqlite3_value_text(db->pErr); 
+    sqlite3DbFree(db, v->zErrMsg);
+    if( !db->mallocFailed ){
+      v->zErrMsg = sqlite3DbStrDup(db, zErr);
+      v->rc = rc2;
+    } else {
+      v->zErrMsg = 0;
+      v->rc = rc = SQLITE_NOMEM;
+    }
+  }
+  rc = sqlite3ApiExit(db, rc);
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+
+/*
+** Extract the user data from a sqlite3_context structure and return a
+** pointer to it.
+*/
+void *sqlite3_user_data(sqlite3_context *p){
+  assert( p && p->pFunc );
+  return p->pFunc->pUserData;
+}
+
+/*
+** Extract the user data from a sqlite3_context structure and return a
+** pointer to it.
+**
+** IMPLEMENTATION-OF: R-46798-50301 The sqlite3_context_db_handle() interface
+** returns a copy of the pointer to the database connection (the 1st
+** parameter) of the sqlite3_create_function() and
+** sqlite3_create_function16() routines that originally registered the
+** application defined function.
+*/
+sqlite3 *sqlite3_context_db_handle(sqlite3_context *p){
+  assert( p && p->pFunc );
+  return p->s.db;
+}
+
+/*
+** The following is the implementation of an SQL function that always
+** fails with an error message stating that the function is used in the
+** wrong context.  The sqlite3_overload_function() API might construct
+** SQL function that use this routine so that the functions will exist
+** for name resolution but are actually overloaded by the xFindFunction
+** method of virtual tables.
+*/
+void sqlite3InvalidFunction(
+  sqlite3_context *context,  /* The function calling context */
+  int NotUsed,               /* Number of arguments to the function */
+  sqlite3_value **NotUsed2   /* Value of each argument */
+){
+  const char *zName = context->pFunc->zName;
+  char *zErr;
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  zErr = sqlite3_mprintf(
+      "unable to use function %s in the requested context", zName);
+  sqlite3_result_error(context, zErr, -1);
+  sqlite3_free(zErr);
+}
+
+/*
+** Allocate or return the aggregate context for a user function.  A new
+** context is allocated on the first call.  Subsequent calls return the
+** same context that was returned on prior calls.
+*/
+void *sqlite3_aggregate_context(sqlite3_context *p, int nByte){
+  Mem *pMem;
+  assert( p && p->pFunc && p->pFunc->xStep );
+  assert( sqlite3_mutex_held(p->s.db->mutex) );
+  pMem = p->pMem;
+  testcase( nByte<0 );
+  if( (pMem->flags & MEM_Agg)==0 ){
+    if( nByte<=0 ){
+      sqlite3VdbeMemReleaseExternal(pMem);
+      pMem->flags = MEM_Null;
+      pMem->z = 0;
+    }else{
+      sqlite3VdbeMemGrow(pMem, nByte, 0);
+      pMem->flags = MEM_Agg;
+      pMem->u.pDef = p->pFunc;
+      if( pMem->z ){
+        memset(pMem->z, 0, nByte);
+      }
+    }
+  }
+  return (void*)pMem->z;
+}
+
+/*
+** Return the auxilary data pointer, if any, for the iArg'th argument to
+** the user-function defined by pCtx.
+*/
+void *sqlite3_get_auxdata(sqlite3_context *pCtx, int iArg){
+  VdbeFunc *pVdbeFunc;
+
+  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
+  pVdbeFunc = pCtx->pVdbeFunc;
+  if( !pVdbeFunc || iArg>=pVdbeFunc->nAux || iArg<0 ){
+    return 0;
+  }
+  return pVdbeFunc->apAux[iArg].pAux;
+}
+
+/*
+** Set the auxilary data pointer and delete function, for the iArg'th
+** argument to the user-function defined by pCtx. Any previous value is
+** deleted by calling the delete function specified when it was set.
+*/
+void sqlite3_set_auxdata(
+  sqlite3_context *pCtx, 
+  int iArg, 
+  void *pAux, 
+  void (*xDelete)(void*)
+){
+  struct AuxData *pAuxData;
+  VdbeFunc *pVdbeFunc;
+  if( iArg<0 ) goto failed;
+
+  assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
+  pVdbeFunc = pCtx->pVdbeFunc;
+  if( !pVdbeFunc || pVdbeFunc->nAux<=iArg ){
+    int nAux = (pVdbeFunc ? pVdbeFunc->nAux : 0);
+    int nMalloc = sizeof(VdbeFunc) + sizeof(struct AuxData)*iArg;
+    pVdbeFunc = sqlite3DbRealloc(pCtx->s.db, pVdbeFunc, nMalloc);
+    if( !pVdbeFunc ){
+      goto failed;
+    }
+    pCtx->pVdbeFunc = pVdbeFunc;
+    memset(&pVdbeFunc->apAux[nAux], 0, sizeof(struct AuxData)*(iArg+1-nAux));
+    pVdbeFunc->nAux = iArg+1;
+    pVdbeFunc->pFunc = pCtx->pFunc;
+  }
+
+  pAuxData = &pVdbeFunc->apAux[iArg];
+  if( pAuxData->pAux && pAuxData->xDelete ){
+    pAuxData->xDelete(pAuxData->pAux);
+  }
+  pAuxData->pAux = pAux;
+  pAuxData->xDelete = xDelete;
+  return;
+
+failed:
+  if( xDelete ){
+    xDelete(pAux);
+  }
+}
+
+#ifndef SQLITE_OMIT_DEPRECATED
+/*
+** Return the number of times the Step function of a aggregate has been 
+** called.
+**
+** This function is deprecated.  Do not use it for new code.  It is
+** provide only to avoid breaking legacy code.  New aggregate function
+** implementations should keep their own counts within their aggregate
+** context.
+*/
+int sqlite3_aggregate_count(sqlite3_context *p){
+  assert( p && p->pMem && p->pFunc && p->pFunc->xStep );
+  return p->pMem->n;
+}
+#endif
+
+/*
+** Return the number of columns in the result set for the statement pStmt.
+*/
+int sqlite3_column_count(sqlite3_stmt *pStmt){
+  Vdbe *pVm = (Vdbe *)pStmt;
+  return pVm ? pVm->nResColumn : 0;
+}
+
+/*
+** Return the number of values available from the current row of the
+** currently executing statement pStmt.
+*/
+int sqlite3_data_count(sqlite3_stmt *pStmt){
+  Vdbe *pVm = (Vdbe *)pStmt;
+  if( pVm==0 || pVm->pResultSet==0 ) return 0;
+  return pVm->nResColumn;
+}
+
+
+/*
+** Check to see if column iCol of the given statement is valid.  If
+** it is, return a pointer to the Mem for the value of that column.
+** If iCol is not valid, return a pointer to a Mem which has a value
+** of NULL.
+*/
+static Mem *columnMem(sqlite3_stmt *pStmt, int i){
+  Vdbe *pVm;
+  Mem *pOut;
+
+  pVm = (Vdbe *)pStmt;
+  if( pVm && pVm->pResultSet!=0 && i<pVm->nResColumn && i>=0 ){
+    sqlite3_mutex_enter(pVm->db->mutex);
+    pOut = &pVm->pResultSet[i];
+  }else{
+    /* If the value passed as the second argument is out of range, return
+    ** a pointer to the following static Mem object which contains the
+    ** value SQL NULL. Even though the Mem structure contains an element
+    ** of type i64, on certain architecture (x86) with certain compiler
+    ** switches (-Os), gcc may align this Mem object on a 4-byte boundary
+    ** instead of an 8-byte one. This all works fine, except that when
+    ** running with SQLITE_DEBUG defined the SQLite code sometimes assert()s
+    ** that a Mem structure is located on an 8-byte boundary. To prevent
+    ** this assert() from failing, when building with SQLITE_DEBUG defined
+    ** using gcc, force nullMem to be 8-byte aligned using the magical
+    ** __attribute__((aligned(8))) macro.  */
+    static const Mem nullMem 
+#if defined(SQLITE_DEBUG) && defined(__GNUC__)
+      __attribute__((aligned(8))) 
+#endif
+      = {0, "", (double)0, {0}, 0, MEM_Null, SQLITE_NULL, 0,
+#ifdef SQLITE_DEBUG
+         0, 0,  /* pScopyFrom, pFiller */
+#endif
+         0, 0 };
+
+    if( pVm && ALWAYS(pVm->db) ){
+      sqlite3_mutex_enter(pVm->db->mutex);
+      sqlite3Error(pVm->db, SQLITE_RANGE, 0);
+    }
+    pOut = (Mem*)&nullMem;
+  }
+  return pOut;
+}
+
+/*
+** This function is called after invoking an sqlite3_value_XXX function on a 
+** column value (i.e. a value returned by evaluating an SQL expression in the
+** select list of a SELECT statement) that may cause a malloc() failure. If 
+** malloc() has failed, the threads mallocFailed flag is cleared and the result
+** code of statement pStmt set to SQLITE_NOMEM.
+**
+** Specifically, this is called from within:
+**
+**     sqlite3_column_int()
+**     sqlite3_column_int64()
+**     sqlite3_column_text()
+**     sqlite3_column_text16()
+**     sqlite3_column_real()
+**     sqlite3_column_bytes()
+**     sqlite3_column_bytes16()
+**     sqiite3_column_blob()
+*/
+static void columnMallocFailure(sqlite3_stmt *pStmt)
+{
+  /* If malloc() failed during an encoding conversion within an
+  ** sqlite3_column_XXX API, then set the return code of the statement to
+  ** SQLITE_NOMEM. The next call to _step() (if any) will return SQLITE_ERROR
+  ** and _finalize() will return NOMEM.
+  */
+  Vdbe *p = (Vdbe *)pStmt;
+  if( p ){
+    p->rc = sqlite3ApiExit(p->db, p->rc);
+    sqlite3_mutex_leave(p->db->mutex);
+  }
+}
+
+/**************************** sqlite3_column_  *******************************
+** The following routines are used to access elements of the current row
+** in the result set.
+*/
+const void *sqlite3_column_blob(sqlite3_stmt *pStmt, int i){
+  const void *val;
+  val = sqlite3_value_blob( columnMem(pStmt,i) );
+  /* Even though there is no encoding conversion, value_blob() might
+  ** need to call malloc() to expand the result of a zeroblob() 
+  ** expression. 
+  */
+  columnMallocFailure(pStmt);
+  return val;
+}
+int sqlite3_column_bytes(sqlite3_stmt *pStmt, int i){
+  int val = sqlite3_value_bytes( columnMem(pStmt,i) );
+  columnMallocFailure(pStmt);
+  return val;
+}
+int sqlite3_column_bytes16(sqlite3_stmt *pStmt, int i){
+  int val = sqlite3_value_bytes16( columnMem(pStmt,i) );
+  columnMallocFailure(pStmt);
+  return val;
+}
+double sqlite3_column_double(sqlite3_stmt *pStmt, int i){
+  double val = sqlite3_value_double( columnMem(pStmt,i) );
+  columnMallocFailure(pStmt);
+  return val;
+}
+int sqlite3_column_int(sqlite3_stmt *pStmt, int i){
+  int val = sqlite3_value_int( columnMem(pStmt,i) );
+  columnMallocFailure(pStmt);
+  return val;
+}
+sqlite_int64 sqlite3_column_int64(sqlite3_stmt *pStmt, int i){
+  sqlite_int64 val = sqlite3_value_int64( columnMem(pStmt,i) );
+  columnMallocFailure(pStmt);
+  return val;
+}
+const unsigned char *sqlite3_column_text(sqlite3_stmt *pStmt, int i){
+  const unsigned char *val = sqlite3_value_text( columnMem(pStmt,i) );
+  columnMallocFailure(pStmt);
+  return val;
+}
+sqlite3_value *sqlite3_column_value(sqlite3_stmt *pStmt, int i){
+  Mem *pOut = columnMem(pStmt, i);
+  if( pOut->flags&MEM_Static ){
+    pOut->flags &= ~MEM_Static;
+    pOut->flags |= MEM_Ephem;
+  }
+  columnMallocFailure(pStmt);
+  return (sqlite3_value *)pOut;
+}
+#ifndef SQLITE_OMIT_UTF16
+const void *sqlite3_column_text16(sqlite3_stmt *pStmt, int i){
+  const void *val = sqlite3_value_text16( columnMem(pStmt,i) );
+  columnMallocFailure(pStmt);
+  return val;
+}
+#endif /* SQLITE_OMIT_UTF16 */
+int sqlite3_column_type(sqlite3_stmt *pStmt, int i){
+  int iType = sqlite3_value_type( columnMem(pStmt,i) );
+  columnMallocFailure(pStmt);
+  return iType;
+}
+
+/* The following function is experimental and subject to change or
+** removal */
+/*int sqlite3_column_numeric_type(sqlite3_stmt *pStmt, int i){
+**  return sqlite3_value_numeric_type( columnMem(pStmt,i) );
+**}
+*/
+
+/*
+** Convert the N-th element of pStmt->pColName[] into a string using
+** xFunc() then return that string.  If N is out of range, return 0.
+**
+** There are up to 5 names for each column.  useType determines which
+** name is returned.  Here are the names:
+**
+**    0      The column name as it should be displayed for output
+**    1      The datatype name for the column
+**    2      The name of the database that the column derives from
+**    3      The name of the table that the column derives from
+**    4      The name of the table column that the result column derives from
+**
+** If the result is not a simple column reference (if it is an expression
+** or a constant) then useTypes 2, 3, and 4 return NULL.
+*/
+static const void *columnName(
+  sqlite3_stmt *pStmt,
+  int N,
+  const void *(*xFunc)(Mem*),
+  int useType
+){
+  const void *ret = 0;
+  Vdbe *p = (Vdbe *)pStmt;
+  int n;
+  sqlite3 *db = p->db;
+  
+  assert( db!=0 );
+  n = sqlite3_column_count(pStmt);
+  if( N<n && N>=0 ){
+    N += useType*n;
+    sqlite3_mutex_enter(db->mutex);
+    assert( db->mallocFailed==0 );
+    ret = xFunc(&p->aColName[N]);
+     /* A malloc may have failed inside of the xFunc() call. If this
+    ** is the case, clear the mallocFailed flag and return NULL.
+    */
+    if( db->mallocFailed ){
+      db->mallocFailed = 0;
+      ret = 0;
+    }
+    sqlite3_mutex_leave(db->mutex);
+  }
+  return ret;
+}
+
+/*
+** Return the name of the Nth column of the result set returned by SQL
+** statement pStmt.
+*/
+const char *sqlite3_column_name(sqlite3_stmt *pStmt, int N){
+  return columnName(
+      pStmt, N, (const void*(*)(Mem*))sqlite3_value_text, COLNAME_NAME);
+}
+#ifndef SQLITE_OMIT_UTF16
+const void *sqlite3_column_name16(sqlite3_stmt *pStmt, int N){
+  return columnName(
+      pStmt, N, (const void*(*)(Mem*))sqlite3_value_text16, COLNAME_NAME);
+}
+#endif
+
+/*
+** Constraint:  If you have ENABLE_COLUMN_METADATA then you must
+** not define OMIT_DECLTYPE.
+*/
+#if defined(SQLITE_OMIT_DECLTYPE) && defined(SQLITE_ENABLE_COLUMN_METADATA)
+# error "Must not define both SQLITE_OMIT_DECLTYPE \
+         and SQLITE_ENABLE_COLUMN_METADATA"
+#endif
+
+#ifndef SQLITE_OMIT_DECLTYPE
+/*
+** Return the column declaration type (if applicable) of the 'i'th column
+** of the result set of SQL statement pStmt.
+*/
+const char *sqlite3_column_decltype(sqlite3_stmt *pStmt, int N){
+  return columnName(
+      pStmt, N, (const void*(*)(Mem*))sqlite3_value_text, COLNAME_DECLTYPE);
+}
+#ifndef SQLITE_OMIT_UTF16
+const void *sqlite3_column_decltype16(sqlite3_stmt *pStmt, int N){
+  return columnName(
+      pStmt, N, (const void*(*)(Mem*))sqlite3_value_text16, COLNAME_DECLTYPE);
+}
+#endif /* SQLITE_OMIT_UTF16 */
+#endif /* SQLITE_OMIT_DECLTYPE */
+
+#ifdef SQLITE_ENABLE_COLUMN_METADATA
+/*
+** Return the name of the database from which a result column derives.
+** NULL is returned if the result column is an expression or constant or
+** anything else which is not an unabiguous reference to a database column.
+*/
+const char *sqlite3_column_database_name(sqlite3_stmt *pStmt, int N){
+  return columnName(
+      pStmt, N, (const void*(*)(Mem*))sqlite3_value_text, COLNAME_DATABASE);
+}
+#ifndef SQLITE_OMIT_UTF16
+const void *sqlite3_column_database_name16(sqlite3_stmt *pStmt, int N){
+  return columnName(
+      pStmt, N, (const void*(*)(Mem*))sqlite3_value_text16, COLNAME_DATABASE);
+}
+#endif /* SQLITE_OMIT_UTF16 */
+
+/*
+** Return the name of the table from which a result column derives.
+** NULL is returned if the result column is an expression or constant or
+** anything else which is not an unabiguous reference to a database column.
+*/
+const char *sqlite3_column_table_name(sqlite3_stmt *pStmt, int N){
+  return columnName(
+      pStmt, N, (const void*(*)(Mem*))sqlite3_value_text, COLNAME_TABLE);
+}
+#ifndef SQLITE_OMIT_UTF16
+const void *sqlite3_column_table_name16(sqlite3_stmt *pStmt, int N){
+  return columnName(
+      pStmt, N, (const void*(*)(Mem*))sqlite3_value_text16, COLNAME_TABLE);
+}
+#endif /* SQLITE_OMIT_UTF16 */
+
+/*
+** Return the name of the table column from which a result column derives.
+** NULL is returned if the result column is an expression or constant or
+** anything else which is not an unabiguous reference to a database column.
+*/
+const char *sqlite3_column_origin_name(sqlite3_stmt *pStmt, int N){
+  return columnName(
+      pStmt, N, (const void*(*)(Mem*))sqlite3_value_text, COLNAME_COLUMN);
+}
+#ifndef SQLITE_OMIT_UTF16
+const void *sqlite3_column_origin_name16(sqlite3_stmt *pStmt, int N){
+  return columnName(
+      pStmt, N, (const void*(*)(Mem*))sqlite3_value_text16, COLNAME_COLUMN);
+}
+#endif /* SQLITE_OMIT_UTF16 */
+#endif /* SQLITE_ENABLE_COLUMN_METADATA */
+
+
+/******************************* sqlite3_bind_  ***************************
+** 
+** Routines used to attach values to wildcards in a compiled SQL statement.
+*/
+/*
+** Unbind the value bound to variable i in virtual machine p. This is the 
+** the same as binding a NULL value to the column. If the "i" parameter is
+** out of range, then SQLITE_RANGE is returned. Othewise SQLITE_OK.
+**
+** A successful evaluation of this routine acquires the mutex on p.
+** the mutex is released if any kind of error occurs.
+**
+** The error code stored in database p->db is overwritten with the return
+** value in any case.
+*/
+static int vdbeUnbind(Vdbe *p, int i){
+  Mem *pVar;
+  if( vdbeSafetyNotNull(p) ){
+    return SQLITE_MISUSE_BKPT;
+  }
+  sqlite3_mutex_enter(p->db->mutex);
+  if( p->magic!=VDBE_MAGIC_RUN || p->pc>=0 ){
+    sqlite3Error(p->db, SQLITE_MISUSE, 0);
+    sqlite3_mutex_leave(p->db->mutex);
+    sqlite3_log(SQLITE_MISUSE, 
+        "bind on a busy prepared statement: [%s]", p->zSql);
+    return SQLITE_MISUSE_BKPT;
+  }
+  if( i<1 || i>p->nVar ){
+    sqlite3Error(p->db, SQLITE_RANGE, 0);
+    sqlite3_mutex_leave(p->db->mutex);
+    return SQLITE_RANGE;
+  }
+  i--;
+  pVar = &p->aVar[i];
+  sqlite3VdbeMemRelease(pVar);
+  pVar->flags = MEM_Null;
+  sqlite3Error(p->db, SQLITE_OK, 0);
+
+  /* If the bit corresponding to this variable in Vdbe.expmask is set, then 
+  ** binding a new value to this variable invalidates the current query plan.
+  **
+  ** IMPLEMENTATION-OF: R-48440-37595 If the specific value bound to host
+  ** parameter in the WHERE clause might influence the choice of query plan
+  ** for a statement, then the statement will be automatically recompiled,
+  ** as if there had been a schema change, on the first sqlite3_step() call
+  ** following any change to the bindings of that parameter.
+  */
+  if( p->isPrepareV2 &&
+     ((i<32 && p->expmask & ((u32)1 << i)) || p->expmask==0xffffffff)
+  ){
+    p->expired = 1;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Bind a text or BLOB value.
+*/
+static int bindText(
+  sqlite3_stmt *pStmt,   /* The statement to bind against */
+  int i,                 /* Index of the parameter to bind */
+  const void *zData,     /* Pointer to the data to be bound */
+  int nData,             /* Number of bytes of data to be bound */
+  void (*xDel)(void*),   /* Destructor for the data */
+  u8 encoding            /* Encoding for the data */
+){
+  Vdbe *p = (Vdbe *)pStmt;
+  Mem *pVar;
+  int rc;
+
+  rc = vdbeUnbind(p, i);
+  if( rc==SQLITE_OK ){
+    if( zData!=0 ){
+      pVar = &p->aVar[i-1];
+      rc = sqlite3VdbeMemSetStr(pVar, zData, nData, encoding, xDel);
+      if( rc==SQLITE_OK && encoding!=0 ){
+        rc = sqlite3VdbeChangeEncoding(pVar, ENC(p->db));
+      }
+      sqlite3Error(p->db, rc, 0);
+      rc = sqlite3ApiExit(p->db, rc);
+    }
+    sqlite3_mutex_leave(p->db->mutex);
+  }else if( xDel!=SQLITE_STATIC && xDel!=SQLITE_TRANSIENT ){
+    xDel((void*)zData);
+  }
+  return rc;
+}
+
+
+/*
+** Bind a blob value to an SQL statement variable.
+*/
+int sqlite3_bind_blob(
+  sqlite3_stmt *pStmt, 
+  int i, 
+  const void *zData, 
+  int nData, 
+  void (*xDel)(void*)
+){
+  return bindText(pStmt, i, zData, nData, xDel, 0);
+}
+int sqlite3_bind_double(sqlite3_stmt *pStmt, int i, double rValue){
+  int rc;
+  Vdbe *p = (Vdbe *)pStmt;
+  rc = vdbeUnbind(p, i);
+  if( rc==SQLITE_OK ){
+    sqlite3VdbeMemSetDouble(&p->aVar[i-1], rValue);
+    sqlite3_mutex_leave(p->db->mutex);
+  }
+  return rc;
+}
+int sqlite3_bind_int(sqlite3_stmt *p, int i, int iValue){
+  return sqlite3_bind_int64(p, i, (i64)iValue);
+}
+int sqlite3_bind_int64(sqlite3_stmt *pStmt, int i, sqlite_int64 iValue){
+  int rc;
+  Vdbe *p = (Vdbe *)pStmt;
+  rc = vdbeUnbind(p, i);
+  if( rc==SQLITE_OK ){
+    sqlite3VdbeMemSetInt64(&p->aVar[i-1], iValue);
+    sqlite3_mutex_leave(p->db->mutex);
+  }
+  return rc;
+}
+int sqlite3_bind_null(sqlite3_stmt *pStmt, int i){
+  int rc;
+  Vdbe *p = (Vdbe*)pStmt;
+  rc = vdbeUnbind(p, i);
+  if( rc==SQLITE_OK ){
+    sqlite3_mutex_leave(p->db->mutex);
+  }
+  return rc;
+}
+int sqlite3_bind_text( 
+  sqlite3_stmt *pStmt, 
+  int i, 
+  const char *zData, 
+  int nData, 
+  void (*xDel)(void*)
+){
+  return bindText(pStmt, i, zData, nData, xDel, SQLITE_UTF8);
+}
+#ifndef SQLITE_OMIT_UTF16
+int sqlite3_bind_text16(
+  sqlite3_stmt *pStmt, 
+  int i, 
+  const void *zData, 
+  int nData, 
+  void (*xDel)(void*)
+){
+  return bindText(pStmt, i, zData, nData, xDel, SQLITE_UTF16NATIVE);
+}
+#endif /* SQLITE_OMIT_UTF16 */
+int sqlite3_bind_value(sqlite3_stmt *pStmt, int i, const sqlite3_value *pValue){
+  int rc;
+  switch( pValue->type ){
+    case SQLITE_INTEGER: {
+      rc = sqlite3_bind_int64(pStmt, i, pValue->u.i);
+      break;
+    }
+    case SQLITE_FLOAT: {
+      rc = sqlite3_bind_double(pStmt, i, pValue->r);
+      break;
+    }
+    case SQLITE_BLOB: {
+      if( pValue->flags & MEM_Zero ){
+        rc = sqlite3_bind_zeroblob(pStmt, i, pValue->u.nZero);
+      }else{
+        rc = sqlite3_bind_blob(pStmt, i, pValue->z, pValue->n,SQLITE_TRANSIENT);
+      }
+      break;
+    }
+    case SQLITE_TEXT: {
+      rc = bindText(pStmt,i,  pValue->z, pValue->n, SQLITE_TRANSIENT,
+                              pValue->enc);
+      break;
+    }
+    default: {
+      rc = sqlite3_bind_null(pStmt, i);
+      break;
+    }
+  }
+  return rc;
+}
+int sqlite3_bind_zeroblob(sqlite3_stmt *pStmt, int i, int n){
+  int rc;
+  Vdbe *p = (Vdbe *)pStmt;
+  rc = vdbeUnbind(p, i);
+  if( rc==SQLITE_OK ){
+    sqlite3VdbeMemSetZeroBlob(&p->aVar[i-1], n);
+    sqlite3_mutex_leave(p->db->mutex);
+  }
+  return rc;
+}
+
+/*
+** Return the number of wildcards that can be potentially bound to.
+** This routine is added to support DBD::SQLite.  
+*/
+int sqlite3_bind_parameter_count(sqlite3_stmt *pStmt){
+  Vdbe *p = (Vdbe*)pStmt;
+  return p ? p->nVar : 0;
+}
+
+/*
+** Return the name of a wildcard parameter.  Return NULL if the index
+** is out of range or if the wildcard is unnamed.
+**
+** The result is always UTF-8.
+*/
+const char *sqlite3_bind_parameter_name(sqlite3_stmt *pStmt, int i){
+  Vdbe *p = (Vdbe*)pStmt;
+  if( p==0 || i<1 || i>p->nzVar ){
+    return 0;
+  }
+  return p->azVar[i-1];
+}
+
+/*
+** Given a wildcard parameter name, return the index of the variable
+** with that name.  If there is no variable with the given name,
+** return 0.
+*/
+int sqlite3VdbeParameterIndex(Vdbe *p, const char *zName, int nName){
+  int i;
+  if( p==0 ){
+    return 0;
+  }
+  if( zName ){
+    for(i=0; i<p->nzVar; i++){
+      const char *z = p->azVar[i];
+      if( z && memcmp(z,zName,nName)==0 && z[nName]==0 ){
+        return i+1;
+      }
+    }
+  }
+  return 0;
+}
+int sqlite3_bind_parameter_index(sqlite3_stmt *pStmt, const char *zName){
+  return sqlite3VdbeParameterIndex((Vdbe*)pStmt, zName, sqlite3Strlen30(zName));
+}
+
+/*
+** Transfer all bindings from the first statement over to the second.
+*/
+int sqlite3TransferBindings(sqlite3_stmt *pFromStmt, sqlite3_stmt *pToStmt){
+  Vdbe *pFrom = (Vdbe*)pFromStmt;
+  Vdbe *pTo = (Vdbe*)pToStmt;
+  int i;
+  assert( pTo->db==pFrom->db );
+  assert( pTo->nVar==pFrom->nVar );
+  sqlite3_mutex_enter(pTo->db->mutex);
+  for(i=0; i<pFrom->nVar; i++){
+    sqlite3VdbeMemMove(&pTo->aVar[i], &pFrom->aVar[i]);
+  }
+  sqlite3_mutex_leave(pTo->db->mutex);
+  return SQLITE_OK;
+}
+
+#ifndef SQLITE_OMIT_DEPRECATED
+/*
+** Deprecated external interface.  Internal/core SQLite code
+** should call sqlite3TransferBindings.
+**
+** Is is misuse to call this routine with statements from different
+** database connections.  But as this is a deprecated interface, we
+** will not bother to check for that condition.
+**
+** If the two statements contain a different number of bindings, then
+** an SQLITE_ERROR is returned.  Nothing else can go wrong, so otherwise
+** SQLITE_OK is returned.
+*/
+int sqlite3_transfer_bindings(sqlite3_stmt *pFromStmt, sqlite3_stmt *pToStmt){
+  Vdbe *pFrom = (Vdbe*)pFromStmt;
+  Vdbe *pTo = (Vdbe*)pToStmt;
+  if( pFrom->nVar!=pTo->nVar ){
+    return SQLITE_ERROR;
+  }
+  if( pTo->isPrepareV2 && pTo->expmask ){
+    pTo->expired = 1;
+  }
+  if( pFrom->isPrepareV2 && pFrom->expmask ){
+    pFrom->expired = 1;
+  }
+  return sqlite3TransferBindings(pFromStmt, pToStmt);
+}
+#endif
+
+/*
+** Return the sqlite3* database handle to which the prepared statement given
+** in the argument belongs.  This is the same database handle that was
+** the first argument to the sqlite3_prepare() that was used to create
+** the statement in the first place.
+*/
+sqlite3 *sqlite3_db_handle(sqlite3_stmt *pStmt){
+  return pStmt ? ((Vdbe*)pStmt)->db : 0;
+}
+
+/*
+** Return true if the prepared statement is guaranteed to not modify the
+** database.
+*/
+int sqlite3_stmt_readonly(sqlite3_stmt *pStmt){
+  return pStmt ? ((Vdbe*)pStmt)->readOnly : 1;
+}
+
+/*
+** Return a pointer to the next prepared statement after pStmt associated
+** with database connection pDb.  If pStmt is NULL, return the first
+** prepared statement for the database connection.  Return NULL if there
+** are no more.
+*/
+sqlite3_stmt *sqlite3_next_stmt(sqlite3 *pDb, sqlite3_stmt *pStmt){
+  sqlite3_stmt *pNext;
+  sqlite3_mutex_enter(pDb->mutex);
+  if( pStmt==0 ){
+    pNext = (sqlite3_stmt*)pDb->pVdbe;
+  }else{
+    pNext = (sqlite3_stmt*)((Vdbe*)pStmt)->pNext;
+  }
+  sqlite3_mutex_leave(pDb->mutex);
+  return pNext;
+}
+
+/*
+** Return the value of a status counter for a prepared statement
+*/
+int sqlite3_stmt_status(sqlite3_stmt *pStmt, int op, int resetFlag){
+  Vdbe *pVdbe = (Vdbe*)pStmt;
+  int v = pVdbe->aCounter[op-1];
+  if( resetFlag ) pVdbe->aCounter[op-1] = 0;
+  return v;
+}
diff --git a/src/vdbeaux.c b/src/vdbeaux.c
new file mode 100644
index 0000000..75250238
--- /dev/null
+++ b/src/vdbeaux.c
@@ -0,0 +1,3254 @@
+/*
+** 2003 September 6
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains code used for creating, destroying, and populating
+** a VDBE (or an "sqlite3_stmt" as it is known to the outside world.)  Prior
+** to version 2.8.7, all this code was combined into the vdbe.c source file.
+** But that file was getting too big so this subroutines were split out.
+*/
+#include "sqliteInt.h"
+#include "vdbeInt.h"
+
+
+
+/*
+** When debugging the code generator in a symbolic debugger, one can
+** set the sqlite3VdbeAddopTrace to 1 and all opcodes will be printed
+** as they are added to the instruction stream.
+*/
+#ifdef SQLITE_DEBUG
+int sqlite3VdbeAddopTrace = 0;
+#endif
+
+
+/*
+** Create a new virtual database engine.
+*/
+Vdbe *sqlite3VdbeCreate(sqlite3 *db){
+  Vdbe *p;
+  p = sqlite3DbMallocZero(db, sizeof(Vdbe) );
+  if( p==0 ) return 0;
+  p->db = db;
+  if( db->pVdbe ){
+    db->pVdbe->pPrev = p;
+  }
+  p->pNext = db->pVdbe;
+  p->pPrev = 0;
+  db->pVdbe = p;
+  p->magic = VDBE_MAGIC_INIT;
+  return p;
+}
+
+/*
+** Remember the SQL string for a prepared statement.
+*/
+void sqlite3VdbeSetSql(Vdbe *p, const char *z, int n, int isPrepareV2){
+  assert( isPrepareV2==1 || isPrepareV2==0 );
+  if( p==0 ) return;
+#ifdef SQLITE_OMIT_TRACE
+  if( !isPrepareV2 ) return;
+#endif
+  assert( p->zSql==0 );
+  p->zSql = sqlite3DbStrNDup(p->db, z, n);
+  p->isPrepareV2 = (u8)isPrepareV2;
+}
+
+/*
+** Return the SQL associated with a prepared statement
+*/
+const char *sqlite3_sql(sqlite3_stmt *pStmt){
+  Vdbe *p = (Vdbe *)pStmt;
+  return (p && p->isPrepareV2) ? p->zSql : 0;
+}
+
+/*
+** Swap all content between two VDBE structures.
+*/
+void sqlite3VdbeSwap(Vdbe *pA, Vdbe *pB){
+  Vdbe tmp, *pTmp;
+  char *zTmp;
+  tmp = *pA;
+  *pA = *pB;
+  *pB = tmp;
+  pTmp = pA->pNext;
+  pA->pNext = pB->pNext;
+  pB->pNext = pTmp;
+  pTmp = pA->pPrev;
+  pA->pPrev = pB->pPrev;
+  pB->pPrev = pTmp;
+  zTmp = pA->zSql;
+  pA->zSql = pB->zSql;
+  pB->zSql = zTmp;
+  pB->isPrepareV2 = pA->isPrepareV2;
+}
+
+#ifdef SQLITE_DEBUG
+/*
+** Turn tracing on or off
+*/
+void sqlite3VdbeTrace(Vdbe *p, FILE *trace){
+  p->trace = trace;
+}
+#endif
+
+/*
+** Resize the Vdbe.aOp array so that it is at least one op larger than 
+** it was.
+**
+** If an out-of-memory error occurs while resizing the array, return
+** SQLITE_NOMEM. In this case Vdbe.aOp and Vdbe.nOpAlloc remain 
+** unchanged (this is so that any opcodes already allocated can be 
+** correctly deallocated along with the rest of the Vdbe).
+*/
+static int growOpArray(Vdbe *p){
+  VdbeOp *pNew;
+  int nNew = (p->nOpAlloc ? p->nOpAlloc*2 : (int)(1024/sizeof(Op)));
+  pNew = sqlite3DbRealloc(p->db, p->aOp, nNew*sizeof(Op));
+  if( pNew ){
+    p->nOpAlloc = sqlite3DbMallocSize(p->db, pNew)/sizeof(Op);
+    p->aOp = pNew;
+  }
+  return (pNew ? SQLITE_OK : SQLITE_NOMEM);
+}
+
+/*
+** Add a new instruction to the list of instructions current in the
+** VDBE.  Return the address of the new instruction.
+**
+** Parameters:
+**
+**    p               Pointer to the VDBE
+**
+**    op              The opcode for this instruction
+**
+**    p1, p2, p3      Operands
+**
+** Use the sqlite3VdbeResolveLabel() function to fix an address and
+** the sqlite3VdbeChangeP4() function to change the value of the P4
+** operand.
+*/
+int sqlite3VdbeAddOp3(Vdbe *p, int op, int p1, int p2, int p3){
+  int i;
+  VdbeOp *pOp;
+
+  i = p->nOp;
+  assert( p->magic==VDBE_MAGIC_INIT );
+  assert( op>0 && op<0xff );
+  if( p->nOpAlloc<=i ){
+    if( growOpArray(p) ){
+      return 1;
+    }
+  }
+  p->nOp++;
+  pOp = &p->aOp[i];
+  pOp->opcode = (u8)op;
+  pOp->p5 = 0;
+  pOp->p1 = p1;
+  pOp->p2 = p2;
+  pOp->p3 = p3;
+  pOp->p4.p = 0;
+  pOp->p4type = P4_NOTUSED;
+#ifdef SQLITE_DEBUG
+  pOp->zComment = 0;
+  if( sqlite3VdbeAddopTrace ) sqlite3VdbePrintOp(0, i, &p->aOp[i]);
+#endif
+#ifdef VDBE_PROFILE
+  pOp->cycles = 0;
+  pOp->cnt = 0;
+#endif
+  return i;
+}
+int sqlite3VdbeAddOp0(Vdbe *p, int op){
+  return sqlite3VdbeAddOp3(p, op, 0, 0, 0);
+}
+int sqlite3VdbeAddOp1(Vdbe *p, int op, int p1){
+  return sqlite3VdbeAddOp3(p, op, p1, 0, 0);
+}
+int sqlite3VdbeAddOp2(Vdbe *p, int op, int p1, int p2){
+  return sqlite3VdbeAddOp3(p, op, p1, p2, 0);
+}
+
+
+/*
+** Add an opcode that includes the p4 value as a pointer.
+*/
+int sqlite3VdbeAddOp4(
+  Vdbe *p,            /* Add the opcode to this VM */
+  int op,             /* The new opcode */
+  int p1,             /* The P1 operand */
+  int p2,             /* The P2 operand */
+  int p3,             /* The P3 operand */
+  const char *zP4,    /* The P4 operand */
+  int p4type          /* P4 operand type */
+){
+  int addr = sqlite3VdbeAddOp3(p, op, p1, p2, p3);
+  sqlite3VdbeChangeP4(p, addr, zP4, p4type);
+  return addr;
+}
+
+/*
+** Add an OP_ParseSchema opcode.  This routine is broken out from
+** sqlite3VdbeAddOp4() since it needs to also local all btrees.
+**
+** The zWhere string must have been obtained from sqlite3_malloc().
+** This routine will take ownership of the allocated memory.
+*/
+void sqlite3VdbeAddParseSchemaOp(Vdbe *p, int iDb, char *zWhere){
+  int j;
+  int addr = sqlite3VdbeAddOp3(p, OP_ParseSchema, iDb, 0, 0);
+  sqlite3VdbeChangeP4(p, addr, zWhere, P4_DYNAMIC);
+  for(j=0; j<p->db->nDb; j++) sqlite3VdbeUsesBtree(p, j);
+}
+
+/*
+** Add an opcode that includes the p4 value as an integer.
+*/
+int sqlite3VdbeAddOp4Int(
+  Vdbe *p,            /* Add the opcode to this VM */
+  int op,             /* The new opcode */
+  int p1,             /* The P1 operand */
+  int p2,             /* The P2 operand */
+  int p3,             /* The P3 operand */
+  int p4              /* The P4 operand as an integer */
+){
+  int addr = sqlite3VdbeAddOp3(p, op, p1, p2, p3);
+  sqlite3VdbeChangeP4(p, addr, SQLITE_INT_TO_PTR(p4), P4_INT32);
+  return addr;
+}
+
+/*
+** Create a new symbolic label for an instruction that has yet to be
+** coded.  The symbolic label is really just a negative number.  The
+** label can be used as the P2 value of an operation.  Later, when
+** the label is resolved to a specific address, the VDBE will scan
+** through its operation list and change all values of P2 which match
+** the label into the resolved address.
+**
+** The VDBE knows that a P2 value is a label because labels are
+** always negative and P2 values are suppose to be non-negative.
+** Hence, a negative P2 value is a label that has yet to be resolved.
+**
+** Zero is returned if a malloc() fails.
+*/
+int sqlite3VdbeMakeLabel(Vdbe *p){
+  int i;
+  i = p->nLabel++;
+  assert( p->magic==VDBE_MAGIC_INIT );
+  if( i>=p->nLabelAlloc ){
+    int n = p->nLabelAlloc*2 + 5;
+    p->aLabel = sqlite3DbReallocOrFree(p->db, p->aLabel,
+                                       n*sizeof(p->aLabel[0]));
+    p->nLabelAlloc = sqlite3DbMallocSize(p->db, p->aLabel)/sizeof(p->aLabel[0]);
+  }
+  if( p->aLabel ){
+    p->aLabel[i] = -1;
+  }
+  return -1-i;
+}
+
+/*
+** Resolve label "x" to be the address of the next instruction to
+** be inserted.  The parameter "x" must have been obtained from
+** a prior call to sqlite3VdbeMakeLabel().
+*/
+void sqlite3VdbeResolveLabel(Vdbe *p, int x){
+  int j = -1-x;
+  assert( p->magic==VDBE_MAGIC_INIT );
+  assert( j>=0 && j<p->nLabel );
+  if( p->aLabel ){
+    p->aLabel[j] = p->nOp;
+  }
+}
+
+/*
+** Mark the VDBE as one that can only be run one time.
+*/
+void sqlite3VdbeRunOnlyOnce(Vdbe *p){
+  p->runOnlyOnce = 1;
+}
+
+#ifdef SQLITE_DEBUG /* sqlite3AssertMayAbort() logic */
+
+/*
+** The following type and function are used to iterate through all opcodes
+** in a Vdbe main program and each of the sub-programs (triggers) it may 
+** invoke directly or indirectly. It should be used as follows:
+**
+**   Op *pOp;
+**   VdbeOpIter sIter;
+**
+**   memset(&sIter, 0, sizeof(sIter));
+**   sIter.v = v;                            // v is of type Vdbe* 
+**   while( (pOp = opIterNext(&sIter)) ){
+**     // Do something with pOp
+**   }
+**   sqlite3DbFree(v->db, sIter.apSub);
+** 
+*/
+typedef struct VdbeOpIter VdbeOpIter;
+struct VdbeOpIter {
+  Vdbe *v;                   /* Vdbe to iterate through the opcodes of */
+  SubProgram **apSub;        /* Array of subprograms */
+  int nSub;                  /* Number of entries in apSub */
+  int iAddr;                 /* Address of next instruction to return */
+  int iSub;                  /* 0 = main program, 1 = first sub-program etc. */
+};
+static Op *opIterNext(VdbeOpIter *p){
+  Vdbe *v = p->v;
+  Op *pRet = 0;
+  Op *aOp;
+  int nOp;
+
+  if( p->iSub<=p->nSub ){
+
+    if( p->iSub==0 ){
+      aOp = v->aOp;
+      nOp = v->nOp;
+    }else{
+      aOp = p->apSub[p->iSub-1]->aOp;
+      nOp = p->apSub[p->iSub-1]->nOp;
+    }
+    assert( p->iAddr<nOp );
+
+    pRet = &aOp[p->iAddr];
+    p->iAddr++;
+    if( p->iAddr==nOp ){
+      p->iSub++;
+      p->iAddr = 0;
+    }
+  
+    if( pRet->p4type==P4_SUBPROGRAM ){
+      int nByte = (p->nSub+1)*sizeof(SubProgram*);
+      int j;
+      for(j=0; j<p->nSub; j++){
+        if( p->apSub[j]==pRet->p4.pProgram ) break;
+      }
+      if( j==p->nSub ){
+        p->apSub = sqlite3DbReallocOrFree(v->db, p->apSub, nByte);
+        if( !p->apSub ){
+          pRet = 0;
+        }else{
+          p->apSub[p->nSub++] = pRet->p4.pProgram;
+        }
+      }
+    }
+  }
+
+  return pRet;
+}
+
+/*
+** Check if the program stored in the VM associated with pParse may
+** throw an ABORT exception (causing the statement, but not entire transaction
+** to be rolled back). This condition is true if the main program or any
+** sub-programs contains any of the following:
+**
+**   *  OP_Halt with P1=SQLITE_CONSTRAINT and P2=OE_Abort.
+**   *  OP_HaltIfNull with P1=SQLITE_CONSTRAINT and P2=OE_Abort.
+**   *  OP_Destroy
+**   *  OP_VUpdate
+**   *  OP_VRename
+**   *  OP_FkCounter with P2==0 (immediate foreign key constraint)
+**
+** Then check that the value of Parse.mayAbort is true if an
+** ABORT may be thrown, or false otherwise. Return true if it does
+** match, or false otherwise. This function is intended to be used as
+** part of an assert statement in the compiler. Similar to:
+**
+**   assert( sqlite3VdbeAssertMayAbort(pParse->pVdbe, pParse->mayAbort) );
+*/
+int sqlite3VdbeAssertMayAbort(Vdbe *v, int mayAbort){
+  int hasAbort = 0;
+  Op *pOp;
+  VdbeOpIter sIter;
+  memset(&sIter, 0, sizeof(sIter));
+  sIter.v = v;
+
+  while( (pOp = opIterNext(&sIter))!=0 ){
+    int opcode = pOp->opcode;
+    if( opcode==OP_Destroy || opcode==OP_VUpdate || opcode==OP_VRename 
+#ifndef SQLITE_OMIT_FOREIGN_KEY
+     || (opcode==OP_FkCounter && pOp->p1==0 && pOp->p2==1) 
+#endif
+     || ((opcode==OP_Halt || opcode==OP_HaltIfNull) 
+      && (pOp->p1==SQLITE_CONSTRAINT && pOp->p2==OE_Abort))
+    ){
+      hasAbort = 1;
+      break;
+    }
+  }
+  sqlite3DbFree(v->db, sIter.apSub);
+
+  /* Return true if hasAbort==mayAbort. Or if a malloc failure occured.
+  ** If malloc failed, then the while() loop above may not have iterated
+  ** through all opcodes and hasAbort may be set incorrectly. Return
+  ** true for this case to prevent the assert() in the callers frame
+  ** from failing.  */
+  return ( v->db->mallocFailed || hasAbort==mayAbort );
+}
+#endif /* SQLITE_DEBUG - the sqlite3AssertMayAbort() function */
+
+/*
+** Loop through the program looking for P2 values that are negative
+** on jump instructions.  Each such value is a label.  Resolve the
+** label by setting the P2 value to its correct non-zero value.
+**
+** This routine is called once after all opcodes have been inserted.
+**
+** Variable *pMaxFuncArgs is set to the maximum value of any P2 argument 
+** to an OP_Function, OP_AggStep or OP_VFilter opcode. This is used by 
+** sqlite3VdbeMakeReady() to size the Vdbe.apArg[] array.
+**
+** The Op.opflags field is set on all opcodes.
+*/
+static void resolveP2Values(Vdbe *p, int *pMaxFuncArgs){
+  int i;
+  int nMaxArgs = *pMaxFuncArgs;
+  Op *pOp;
+  int *aLabel = p->aLabel;
+  p->readOnly = 1;
+  for(pOp=p->aOp, i=p->nOp-1; i>=0; i--, pOp++){
+    u8 opcode = pOp->opcode;
+
+    pOp->opflags = sqlite3OpcodeProperty[opcode];
+    if( opcode==OP_Function || opcode==OP_AggStep ){
+      if( pOp->p5>nMaxArgs ) nMaxArgs = pOp->p5;
+    }else if( (opcode==OP_Transaction && pOp->p2!=0) || opcode==OP_Vacuum ){
+      p->readOnly = 0;
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+    }else if( opcode==OP_VUpdate ){
+      if( pOp->p2>nMaxArgs ) nMaxArgs = pOp->p2;
+    }else if( opcode==OP_VFilter ){
+      int n;
+      assert( p->nOp - i >= 3 );
+      assert( pOp[-1].opcode==OP_Integer );
+      n = pOp[-1].p1;
+      if( n>nMaxArgs ) nMaxArgs = n;
+#endif
+    }else if( opcode==OP_Next || opcode==OP_SorterNext ){
+      pOp->p4.xAdvance = sqlite3BtreeNext;
+      pOp->p4type = P4_ADVANCE;
+    }else if( opcode==OP_Prev ){
+      pOp->p4.xAdvance = sqlite3BtreePrevious;
+      pOp->p4type = P4_ADVANCE;
+    }
+
+    if( (pOp->opflags & OPFLG_JUMP)!=0 && pOp->p2<0 ){
+      assert( -1-pOp->p2<p->nLabel );
+      pOp->p2 = aLabel[-1-pOp->p2];
+    }
+  }
+  sqlite3DbFree(p->db, p->aLabel);
+  p->aLabel = 0;
+
+  *pMaxFuncArgs = nMaxArgs;
+}
+
+/*
+** Return the address of the next instruction to be inserted.
+*/
+int sqlite3VdbeCurrentAddr(Vdbe *p){
+  assert( p->magic==VDBE_MAGIC_INIT );
+  return p->nOp;
+}
+
+/*
+** This function returns a pointer to the array of opcodes associated with
+** the Vdbe passed as the first argument. It is the callers responsibility
+** to arrange for the returned array to be eventually freed using the 
+** vdbeFreeOpArray() function.
+**
+** Before returning, *pnOp is set to the number of entries in the returned
+** array. Also, *pnMaxArg is set to the larger of its current value and 
+** the number of entries in the Vdbe.apArg[] array required to execute the 
+** returned program.
+*/
+VdbeOp *sqlite3VdbeTakeOpArray(Vdbe *p, int *pnOp, int *pnMaxArg){
+  VdbeOp *aOp = p->aOp;
+  assert( aOp && !p->db->mallocFailed );
+
+  /* Check that sqlite3VdbeUsesBtree() was not called on this VM */
+  assert( p->btreeMask==0 );
+
+  resolveP2Values(p, pnMaxArg);
+  *pnOp = p->nOp;
+  p->aOp = 0;
+  return aOp;
+}
+
+/*
+** Add a whole list of operations to the operation stack.  Return the
+** address of the first operation added.
+*/
+int sqlite3VdbeAddOpList(Vdbe *p, int nOp, VdbeOpList const *aOp){
+  int addr;
+  assert( p->magic==VDBE_MAGIC_INIT );
+  if( p->nOp + nOp > p->nOpAlloc && growOpArray(p) ){
+    return 0;
+  }
+  addr = p->nOp;
+  if( ALWAYS(nOp>0) ){
+    int i;
+    VdbeOpList const *pIn = aOp;
+    for(i=0; i<nOp; i++, pIn++){
+      int p2 = pIn->p2;
+      VdbeOp *pOut = &p->aOp[i+addr];
+      pOut->opcode = pIn->opcode;
+      pOut->p1 = pIn->p1;
+      if( p2<0 && (sqlite3OpcodeProperty[pOut->opcode] & OPFLG_JUMP)!=0 ){
+        pOut->p2 = addr + ADDR(p2);
+      }else{
+        pOut->p2 = p2;
+      }
+      pOut->p3 = pIn->p3;
+      pOut->p4type = P4_NOTUSED;
+      pOut->p4.p = 0;
+      pOut->p5 = 0;
+#ifdef SQLITE_DEBUG
+      pOut->zComment = 0;
+      if( sqlite3VdbeAddopTrace ){
+        sqlite3VdbePrintOp(0, i+addr, &p->aOp[i+addr]);
+      }
+#endif
+    }
+    p->nOp += nOp;
+  }
+  return addr;
+}
+
+/*
+** Change the value of the P1 operand for a specific instruction.
+** This routine is useful when a large program is loaded from a
+** static array using sqlite3VdbeAddOpList but we want to make a
+** few minor changes to the program.
+*/
+void sqlite3VdbeChangeP1(Vdbe *p, u32 addr, int val){
+  assert( p!=0 );
+  if( ((u32)p->nOp)>addr ){
+    p->aOp[addr].p1 = val;
+  }
+}
+
+/*
+** Change the value of the P2 operand for a specific instruction.
+** This routine is useful for setting a jump destination.
+*/
+void sqlite3VdbeChangeP2(Vdbe *p, u32 addr, int val){
+  assert( p!=0 );
+  if( ((u32)p->nOp)>addr ){
+    p->aOp[addr].p2 = val;
+  }
+}
+
+/*
+** Change the value of the P3 operand for a specific instruction.
+*/
+void sqlite3VdbeChangeP3(Vdbe *p, u32 addr, int val){
+  assert( p!=0 );
+  if( ((u32)p->nOp)>addr ){
+    p->aOp[addr].p3 = val;
+  }
+}
+
+/*
+** Change the value of the P5 operand for the most recently
+** added operation.
+*/
+void sqlite3VdbeChangeP5(Vdbe *p, u8 val){
+  assert( p!=0 );
+  if( p->aOp ){
+    assert( p->nOp>0 );
+    p->aOp[p->nOp-1].p5 = val;
+  }
+}
+
+/*
+** Change the P2 operand of instruction addr so that it points to
+** the address of the next instruction to be coded.
+*/
+void sqlite3VdbeJumpHere(Vdbe *p, int addr){
+  assert( addr>=0 || p->db->mallocFailed );
+  if( addr>=0 ) sqlite3VdbeChangeP2(p, addr, p->nOp);
+}
+
+
+/*
+** If the input FuncDef structure is ephemeral, then free it.  If
+** the FuncDef is not ephermal, then do nothing.
+*/
+static void freeEphemeralFunction(sqlite3 *db, FuncDef *pDef){
+  if( ALWAYS(pDef) && (pDef->flags & SQLITE_FUNC_EPHEM)!=0 ){
+    sqlite3DbFree(db, pDef);
+  }
+}
+
+static void vdbeFreeOpArray(sqlite3 *, Op *, int);
+
+/*
+** Delete a P4 value if necessary.
+*/
+static void freeP4(sqlite3 *db, int p4type, void *p4){
+  if( p4 ){
+    assert( db );
+    switch( p4type ){
+      case P4_REAL:
+      case P4_INT64:
+      case P4_DYNAMIC:
+      case P4_KEYINFO:
+      case P4_INTARRAY:
+      case P4_KEYINFO_HANDOFF: {
+        sqlite3DbFree(db, p4);
+        break;
+      }
+      case P4_MPRINTF: {
+        if( db->pnBytesFreed==0 ) sqlite3_free(p4);
+        break;
+      }
+      case P4_VDBEFUNC: {
+        VdbeFunc *pVdbeFunc = (VdbeFunc *)p4;
+        freeEphemeralFunction(db, pVdbeFunc->pFunc);
+        if( db->pnBytesFreed==0 ) sqlite3VdbeDeleteAuxData(pVdbeFunc, 0);
+        sqlite3DbFree(db, pVdbeFunc);
+        break;
+      }
+      case P4_FUNCDEF: {
+        freeEphemeralFunction(db, (FuncDef*)p4);
+        break;
+      }
+      case P4_MEM: {
+        if( db->pnBytesFreed==0 ){
+          sqlite3ValueFree((sqlite3_value*)p4);
+        }else{
+          Mem *p = (Mem*)p4;
+          sqlite3DbFree(db, p->zMalloc);
+          sqlite3DbFree(db, p);
+        }
+        break;
+      }
+      case P4_VTAB : {
+        if( db->pnBytesFreed==0 ) sqlite3VtabUnlock((VTable *)p4);
+        break;
+      }
+    }
+  }
+}
+
+/*
+** Free the space allocated for aOp and any p4 values allocated for the
+** opcodes contained within. If aOp is not NULL it is assumed to contain 
+** nOp entries. 
+*/
+static void vdbeFreeOpArray(sqlite3 *db, Op *aOp, int nOp){
+  if( aOp ){
+    Op *pOp;
+    for(pOp=aOp; pOp<&aOp[nOp]; pOp++){
+      freeP4(db, pOp->p4type, pOp->p4.p);
+#ifdef SQLITE_DEBUG
+      sqlite3DbFree(db, pOp->zComment);
+#endif     
+    }
+  }
+  sqlite3DbFree(db, aOp);
+}
+
+/*
+** Link the SubProgram object passed as the second argument into the linked
+** list at Vdbe.pSubProgram. This list is used to delete all sub-program
+** objects when the VM is no longer required.
+*/
+void sqlite3VdbeLinkSubProgram(Vdbe *pVdbe, SubProgram *p){
+  p->pNext = pVdbe->pProgram;
+  pVdbe->pProgram = p;
+}
+
+/*
+** Change the opcode at addr into OP_Noop
+*/
+void sqlite3VdbeChangeToNoop(Vdbe *p, int addr){
+  if( p->aOp ){
+    VdbeOp *pOp = &p->aOp[addr];
+    sqlite3 *db = p->db;
+    freeP4(db, pOp->p4type, pOp->p4.p);
+    memset(pOp, 0, sizeof(pOp[0]));
+    pOp->opcode = OP_Noop;
+  }
+}
+
+/*
+** Change the value of the P4 operand for a specific instruction.
+** This routine is useful when a large program is loaded from a
+** static array using sqlite3VdbeAddOpList but we want to make a
+** few minor changes to the program.
+**
+** If n>=0 then the P4 operand is dynamic, meaning that a copy of
+** the string is made into memory obtained from sqlite3_malloc().
+** A value of n==0 means copy bytes of zP4 up to and including the
+** first null byte.  If n>0 then copy n+1 bytes of zP4.
+**
+** If n==P4_KEYINFO it means that zP4 is a pointer to a KeyInfo structure.
+** A copy is made of the KeyInfo structure into memory obtained from
+** sqlite3_malloc, to be freed when the Vdbe is finalized.
+** n==P4_KEYINFO_HANDOFF indicates that zP4 points to a KeyInfo structure
+** stored in memory that the caller has obtained from sqlite3_malloc. The 
+** caller should not free the allocation, it will be freed when the Vdbe is
+** finalized.
+** 
+** Other values of n (P4_STATIC, P4_COLLSEQ etc.) indicate that zP4 points
+** to a string or structure that is guaranteed to exist for the lifetime of
+** the Vdbe. In these cases we can just copy the pointer.
+**
+** If addr<0 then change P4 on the most recently inserted instruction.
+*/
+void sqlite3VdbeChangeP4(Vdbe *p, int addr, const char *zP4, int n){
+  Op *pOp;
+  sqlite3 *db;
+  assert( p!=0 );
+  db = p->db;
+  assert( p->magic==VDBE_MAGIC_INIT );
+  if( p->aOp==0 || db->mallocFailed ){
+    if ( n!=P4_KEYINFO && n!=P4_VTAB ) {
+      freeP4(db, n, (void*)*(char**)&zP4);
+    }
+    return;
+  }
+  assert( p->nOp>0 );
+  assert( addr<p->nOp );
+  if( addr<0 ){
+    addr = p->nOp - 1;
+  }
+  pOp = &p->aOp[addr];
+  freeP4(db, pOp->p4type, pOp->p4.p);
+  pOp->p4.p = 0;
+  if( n==P4_INT32 ){
+    /* Note: this cast is safe, because the origin data point was an int
+    ** that was cast to a (const char *). */
+    pOp->p4.i = SQLITE_PTR_TO_INT(zP4);
+    pOp->p4type = P4_INT32;
+  }else if( zP4==0 ){
+    pOp->p4.p = 0;
+    pOp->p4type = P4_NOTUSED;
+  }else if( n==P4_KEYINFO ){
+    KeyInfo *pKeyInfo;
+    int nField, nByte;
+
+    nField = ((KeyInfo*)zP4)->nField;
+    nByte = sizeof(*pKeyInfo) + (nField-1)*sizeof(pKeyInfo->aColl[0]) + nField;
+    pKeyInfo = sqlite3DbMallocRaw(0, nByte);
+    pOp->p4.pKeyInfo = pKeyInfo;
+    if( pKeyInfo ){
+      u8 *aSortOrder;
+      memcpy((char*)pKeyInfo, zP4, nByte - nField);
+      aSortOrder = pKeyInfo->aSortOrder;
+      if( aSortOrder ){
+        pKeyInfo->aSortOrder = (unsigned char*)&pKeyInfo->aColl[nField];
+        memcpy(pKeyInfo->aSortOrder, aSortOrder, nField);
+      }
+      pOp->p4type = P4_KEYINFO;
+    }else{
+      p->db->mallocFailed = 1;
+      pOp->p4type = P4_NOTUSED;
+    }
+  }else if( n==P4_KEYINFO_HANDOFF ){
+    pOp->p4.p = (void*)zP4;
+    pOp->p4type = P4_KEYINFO;
+  }else if( n==P4_VTAB ){
+    pOp->p4.p = (void*)zP4;
+    pOp->p4type = P4_VTAB;
+    sqlite3VtabLock((VTable *)zP4);
+    assert( ((VTable *)zP4)->db==p->db );
+  }else if( n<0 ){
+    pOp->p4.p = (void*)zP4;
+    pOp->p4type = (signed char)n;
+  }else{
+    if( n==0 ) n = sqlite3Strlen30(zP4);
+    pOp->p4.z = sqlite3DbStrNDup(p->db, zP4, n);
+    pOp->p4type = P4_DYNAMIC;
+  }
+}
+
+#ifndef NDEBUG
+/*
+** Change the comment on the the most recently coded instruction.  Or
+** insert a No-op and add the comment to that new instruction.  This
+** makes the code easier to read during debugging.  None of this happens
+** in a production build.
+*/
+static void vdbeVComment(Vdbe *p, const char *zFormat, va_list ap){
+  assert( p->nOp>0 || p->aOp==0 );
+  assert( p->aOp==0 || p->aOp[p->nOp-1].zComment==0 || p->db->mallocFailed );
+  if( p->nOp ){
+    assert( p->aOp );
+    sqlite3DbFree(p->db, p->aOp[p->nOp-1].zComment);
+    p->aOp[p->nOp-1].zComment = sqlite3VMPrintf(p->db, zFormat, ap);
+  }
+}
+void sqlite3VdbeComment(Vdbe *p, const char *zFormat, ...){
+  va_list ap;
+  if( p ){
+    va_start(ap, zFormat);
+    vdbeVComment(p, zFormat, ap);
+    va_end(ap);
+  }
+}
+void sqlite3VdbeNoopComment(Vdbe *p, const char *zFormat, ...){
+  va_list ap;
+  if( p ){
+    sqlite3VdbeAddOp0(p, OP_Noop);
+    va_start(ap, zFormat);
+    vdbeVComment(p, zFormat, ap);
+    va_end(ap);
+  }
+}
+#endif  /* NDEBUG */
+
+/*
+** Return the opcode for a given address.  If the address is -1, then
+** return the most recently inserted opcode.
+**
+** If a memory allocation error has occurred prior to the calling of this
+** routine, then a pointer to a dummy VdbeOp will be returned.  That opcode
+** is readable but not writable, though it is cast to a writable value.
+** The return of a dummy opcode allows the call to continue functioning
+** after a OOM fault without having to check to see if the return from 
+** this routine is a valid pointer.  But because the dummy.opcode is 0,
+** dummy will never be written to.  This is verified by code inspection and
+** by running with Valgrind.
+**
+** About the #ifdef SQLITE_OMIT_TRACE:  Normally, this routine is never called
+** unless p->nOp>0.  This is because in the absense of SQLITE_OMIT_TRACE,
+** an OP_Trace instruction is always inserted by sqlite3VdbeGet() as soon as
+** a new VDBE is created.  So we are free to set addr to p->nOp-1 without
+** having to double-check to make sure that the result is non-negative. But
+** if SQLITE_OMIT_TRACE is defined, the OP_Trace is omitted and we do need to
+** check the value of p->nOp-1 before continuing.
+*/
+VdbeOp *sqlite3VdbeGetOp(Vdbe *p, int addr){
+  /* C89 specifies that the constant "dummy" will be initialized to all
+  ** zeros, which is correct.  MSVC generates a warning, nevertheless. */
+  static VdbeOp dummy;  /* Ignore the MSVC warning about no initializer */
+  assert( p->magic==VDBE_MAGIC_INIT );
+  if( addr<0 ){
+#ifdef SQLITE_OMIT_TRACE
+    if( p->nOp==0 ) return (VdbeOp*)&dummy;
+#endif
+    addr = p->nOp - 1;
+  }
+  assert( (addr>=0 && addr<p->nOp) || p->db->mallocFailed );
+  if( p->db->mallocFailed ){
+    return (VdbeOp*)&dummy;
+  }else{
+    return &p->aOp[addr];
+  }
+}
+
+#if !defined(SQLITE_OMIT_EXPLAIN) || !defined(NDEBUG) \
+     || defined(VDBE_PROFILE) || defined(SQLITE_DEBUG)
+/*
+** Compute a string that describes the P4 parameter for an opcode.
+** Use zTemp for any required temporary buffer space.
+*/
+static char *displayP4(Op *pOp, char *zTemp, int nTemp){
+  char *zP4 = zTemp;
+  assert( nTemp>=20 );
+  switch( pOp->p4type ){
+    case P4_KEYINFO_STATIC:
+    case P4_KEYINFO: {
+      int i, j;
+      KeyInfo *pKeyInfo = pOp->p4.pKeyInfo;
+      sqlite3_snprintf(nTemp, zTemp, "keyinfo(%d", pKeyInfo->nField);
+      i = sqlite3Strlen30(zTemp);
+      for(j=0; j<pKeyInfo->nField; j++){
+        CollSeq *pColl = pKeyInfo->aColl[j];
+        if( pColl ){
+          int n = sqlite3Strlen30(pColl->zName);
+          if( i+n>nTemp-6 ){
+            memcpy(&zTemp[i],",...",4);
+            break;
+          }
+          zTemp[i++] = ',';
+          if( pKeyInfo->aSortOrder && pKeyInfo->aSortOrder[j] ){
+            zTemp[i++] = '-';
+          }
+          memcpy(&zTemp[i], pColl->zName,n+1);
+          i += n;
+        }else if( i+4<nTemp-6 ){
+          memcpy(&zTemp[i],",nil",4);
+          i += 4;
+        }
+      }
+      zTemp[i++] = ')';
+      zTemp[i] = 0;
+      assert( i<nTemp );
+      break;
+    }
+    case P4_COLLSEQ: {
+      CollSeq *pColl = pOp->p4.pColl;
+      sqlite3_snprintf(nTemp, zTemp, "collseq(%.20s)", pColl->zName);
+      break;
+    }
+    case P4_FUNCDEF: {
+      FuncDef *pDef = pOp->p4.pFunc;
+      sqlite3_snprintf(nTemp, zTemp, "%s(%d)", pDef->zName, pDef->nArg);
+      break;
+    }
+    case P4_INT64: {
+      sqlite3_snprintf(nTemp, zTemp, "%lld", *pOp->p4.pI64);
+      break;
+    }
+    case P4_INT32: {
+      sqlite3_snprintf(nTemp, zTemp, "%d", pOp->p4.i);
+      break;
+    }
+    case P4_REAL: {
+      sqlite3_snprintf(nTemp, zTemp, "%.16g", *pOp->p4.pReal);
+      break;
+    }
+    case P4_MEM: {
+      Mem *pMem = pOp->p4.pMem;
+      assert( (pMem->flags & MEM_Null)==0 );
+      if( pMem->flags & MEM_Str ){
+        zP4 = pMem->z;
+      }else if( pMem->flags & MEM_Int ){
+        sqlite3_snprintf(nTemp, zTemp, "%lld", pMem->u.i);
+      }else if( pMem->flags & MEM_Real ){
+        sqlite3_snprintf(nTemp, zTemp, "%.16g", pMem->r);
+      }else{
+        assert( pMem->flags & MEM_Blob );
+        zP4 = "(blob)";
+      }
+      break;
+    }
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+    case P4_VTAB: {
+      sqlite3_vtab *pVtab = pOp->p4.pVtab->pVtab;
+      sqlite3_snprintf(nTemp, zTemp, "vtab:%p:%p", pVtab, pVtab->pModule);
+      break;
+    }
+#endif
+    case P4_INTARRAY: {
+      sqlite3_snprintf(nTemp, zTemp, "intarray");
+      break;
+    }
+    case P4_SUBPROGRAM: {
+      sqlite3_snprintf(nTemp, zTemp, "program");
+      break;
+    }
+    case P4_ADVANCE: {
+      zTemp[0] = 0;
+      break;
+    }
+    default: {
+      zP4 = pOp->p4.z;
+      if( zP4==0 ){
+        zP4 = zTemp;
+        zTemp[0] = 0;
+      }
+    }
+  }
+  assert( zP4!=0 );
+  return zP4;
+}
+#endif
+
+/*
+** Declare to the Vdbe that the BTree object at db->aDb[i] is used.
+**
+** The prepared statements need to know in advance the complete set of
+** attached databases that they will be using.  A mask of these databases
+** is maintained in p->btreeMask and is used for locking and other purposes.
+*/
+void sqlite3VdbeUsesBtree(Vdbe *p, int i){
+  assert( i>=0 && i<p->db->nDb && i<(int)sizeof(yDbMask)*8 );
+  assert( i<(int)sizeof(p->btreeMask)*8 );
+  p->btreeMask |= ((yDbMask)1)<<i;
+  if( i!=1 && sqlite3BtreeSharable(p->db->aDb[i].pBt) ){
+    p->lockMask |= ((yDbMask)1)<<i;
+  }
+}
+
+#if !defined(SQLITE_OMIT_SHARED_CACHE) && SQLITE_THREADSAFE>0
+/*
+** If SQLite is compiled to support shared-cache mode and to be threadsafe,
+** this routine obtains the mutex associated with each BtShared structure
+** that may be accessed by the VM passed as an argument. In doing so it also
+** sets the BtShared.db member of each of the BtShared structures, ensuring
+** that the correct busy-handler callback is invoked if required.
+**
+** If SQLite is not threadsafe but does support shared-cache mode, then
+** sqlite3BtreeEnter() is invoked to set the BtShared.db variables
+** of all of BtShared structures accessible via the database handle 
+** associated with the VM.
+**
+** If SQLite is not threadsafe and does not support shared-cache mode, this
+** function is a no-op.
+**
+** The p->btreeMask field is a bitmask of all btrees that the prepared 
+** statement p will ever use.  Let N be the number of bits in p->btreeMask
+** corresponding to btrees that use shared cache.  Then the runtime of
+** this routine is N*N.  But as N is rarely more than 1, this should not
+** be a problem.
+*/
+void sqlite3VdbeEnter(Vdbe *p){
+  int i;
+  yDbMask mask;
+  sqlite3 *db;
+  Db *aDb;
+  int nDb;
+  if( p->lockMask==0 ) return;  /* The common case */
+  db = p->db;
+  aDb = db->aDb;
+  nDb = db->nDb;
+  for(i=0, mask=1; i<nDb; i++, mask += mask){
+    if( i!=1 && (mask & p->lockMask)!=0 && ALWAYS(aDb[i].pBt!=0) ){
+      sqlite3BtreeEnter(aDb[i].pBt);
+    }
+  }
+}
+#endif
+
+#if !defined(SQLITE_OMIT_SHARED_CACHE) && SQLITE_THREADSAFE>0
+/*
+** Unlock all of the btrees previously locked by a call to sqlite3VdbeEnter().
+*/
+void sqlite3VdbeLeave(Vdbe *p){
+  int i;
+  yDbMask mask;
+  sqlite3 *db;
+  Db *aDb;
+  int nDb;
+  if( p->lockMask==0 ) return;  /* The common case */
+  db = p->db;
+  aDb = db->aDb;
+  nDb = db->nDb;
+  for(i=0, mask=1; i<nDb; i++, mask += mask){
+    if( i!=1 && (mask & p->lockMask)!=0 && ALWAYS(aDb[i].pBt!=0) ){
+      sqlite3BtreeLeave(aDb[i].pBt);
+    }
+  }
+}
+#endif
+
+#if defined(VDBE_PROFILE) || defined(SQLITE_DEBUG)
+/*
+** Print a single opcode.  This routine is used for debugging only.
+*/
+void sqlite3VdbePrintOp(FILE *pOut, int pc, Op *pOp){
+  char *zP4;
+  char zPtr[50];
+  static const char *zFormat1 = "%4d %-13s %4d %4d %4d %-4s %.2X %s\n";
+  if( pOut==0 ) pOut = stdout;
+  zP4 = displayP4(pOp, zPtr, sizeof(zPtr));
+  fprintf(pOut, zFormat1, pc, 
+      sqlite3OpcodeName(pOp->opcode), pOp->p1, pOp->p2, pOp->p3, zP4, pOp->p5,
+#ifdef SQLITE_DEBUG
+      pOp->zComment ? pOp->zComment : ""
+#else
+      ""
+#endif
+  );
+  fflush(pOut);
+}
+#endif
+
+/*
+** Release an array of N Mem elements
+*/
+static void releaseMemArray(Mem *p, int N){
+  if( p && N ){
+    Mem *pEnd;
+    sqlite3 *db = p->db;
+    u8 malloc_failed = db->mallocFailed;
+    if( db->pnBytesFreed ){
+      for(pEnd=&p[N]; p<pEnd; p++){
+        sqlite3DbFree(db, p->zMalloc);
+      }
+      return;
+    }
+    for(pEnd=&p[N]; p<pEnd; p++){
+      assert( (&p[1])==pEnd || p[0].db==p[1].db );
+
+      /* This block is really an inlined version of sqlite3VdbeMemRelease()
+      ** that takes advantage of the fact that the memory cell value is 
+      ** being set to NULL after releasing any dynamic resources.
+      **
+      ** The justification for duplicating code is that according to 
+      ** callgrind, this causes a certain test case to hit the CPU 4.7 
+      ** percent less (x86 linux, gcc version 4.1.2, -O6) than if 
+      ** sqlite3MemRelease() were called from here. With -O2, this jumps
+      ** to 6.6 percent. The test case is inserting 1000 rows into a table 
+      ** with no indexes using a single prepared INSERT statement, bind() 
+      ** and reset(). Inserts are grouped into a transaction.
+      */
+      if( p->flags&(MEM_Agg|MEM_Dyn|MEM_Frame|MEM_RowSet) ){
+        sqlite3VdbeMemRelease(p);
+      }else if( p->zMalloc ){
+        sqlite3DbFree(db, p->zMalloc);
+        p->zMalloc = 0;
+      }
+
+      p->flags = MEM_Null;
+    }
+    db->mallocFailed = malloc_failed;
+  }
+}
+
+/*
+** Delete a VdbeFrame object and its contents. VdbeFrame objects are
+** allocated by the OP_Program opcode in sqlite3VdbeExec().
+*/
+void sqlite3VdbeFrameDelete(VdbeFrame *p){
+  int i;
+  Mem *aMem = VdbeFrameMem(p);
+  VdbeCursor **apCsr = (VdbeCursor **)&aMem[p->nChildMem];
+  for(i=0; i<p->nChildCsr; i++){
+    sqlite3VdbeFreeCursor(p->v, apCsr[i]);
+  }
+  releaseMemArray(aMem, p->nChildMem);
+  sqlite3DbFree(p->v->db, p);
+}
+
+#ifndef SQLITE_OMIT_EXPLAIN
+/*
+** Give a listing of the program in the virtual machine.
+**
+** The interface is the same as sqlite3VdbeExec().  But instead of
+** running the code, it invokes the callback once for each instruction.
+** This feature is used to implement "EXPLAIN".
+**
+** When p->explain==1, each instruction is listed.  When
+** p->explain==2, only OP_Explain instructions are listed and these
+** are shown in a different format.  p->explain==2 is used to implement
+** EXPLAIN QUERY PLAN.
+**
+** When p->explain==1, first the main program is listed, then each of
+** the trigger subprograms are listed one by one.
+*/
+int sqlite3VdbeList(
+  Vdbe *p                   /* The VDBE */
+){
+  int nRow;                            /* Stop when row count reaches this */
+  int nSub = 0;                        /* Number of sub-vdbes seen so far */
+  SubProgram **apSub = 0;              /* Array of sub-vdbes */
+  Mem *pSub = 0;                       /* Memory cell hold array of subprogs */
+  sqlite3 *db = p->db;                 /* The database connection */
+  int i;                               /* Loop counter */
+  int rc = SQLITE_OK;                  /* Return code */
+  Mem *pMem = &p->aMem[1];             /* First Mem of result set */
+
+  assert( p->explain );
+  assert( p->magic==VDBE_MAGIC_RUN );
+  assert( p->rc==SQLITE_OK || p->rc==SQLITE_BUSY || p->rc==SQLITE_NOMEM );
+
+  /* Even though this opcode does not use dynamic strings for
+  ** the result, result columns may become dynamic if the user calls
+  ** sqlite3_column_text16(), causing a translation to UTF-16 encoding.
+  */
+  releaseMemArray(pMem, 8);
+  p->pResultSet = 0;
+
+  if( p->rc==SQLITE_NOMEM ){
+    /* This happens if a malloc() inside a call to sqlite3_column_text() or
+    ** sqlite3_column_text16() failed.  */
+    db->mallocFailed = 1;
+    return SQLITE_ERROR;
+  }
+
+  /* When the number of output rows reaches nRow, that means the
+  ** listing has finished and sqlite3_step() should return SQLITE_DONE.
+  ** nRow is the sum of the number of rows in the main program, plus
+  ** the sum of the number of rows in all trigger subprograms encountered
+  ** so far.  The nRow value will increase as new trigger subprograms are
+  ** encountered, but p->pc will eventually catch up to nRow.
+  */
+  nRow = p->nOp;
+  if( p->explain==1 ){
+    /* The first 8 memory cells are used for the result set.  So we will
+    ** commandeer the 9th cell to use as storage for an array of pointers
+    ** to trigger subprograms.  The VDBE is guaranteed to have at least 9
+    ** cells.  */
+    assert( p->nMem>9 );
+    pSub = &p->aMem[9];
+    if( pSub->flags&MEM_Blob ){
+      /* On the first call to sqlite3_step(), pSub will hold a NULL.  It is
+      ** initialized to a BLOB by the P4_SUBPROGRAM processing logic below */
+      nSub = pSub->n/sizeof(Vdbe*);
+      apSub = (SubProgram **)pSub->z;
+    }
+    for(i=0; i<nSub; i++){
+      nRow += apSub[i]->nOp;
+    }
+  }
+
+  do{
+    i = p->pc++;
+  }while( i<nRow && p->explain==2 && p->aOp[i].opcode!=OP_Explain );
+  if( i>=nRow ){
+    p->rc = SQLITE_OK;
+    rc = SQLITE_DONE;
+  }else if( db->u1.isInterrupted ){
+    p->rc = SQLITE_INTERRUPT;
+    rc = SQLITE_ERROR;
+    sqlite3SetString(&p->zErrMsg, db, "%s", sqlite3ErrStr(p->rc));
+  }else{
+    char *z;
+    Op *pOp;
+    if( i<p->nOp ){
+      /* The output line number is small enough that we are still in the
+      ** main program. */
+      pOp = &p->aOp[i];
+    }else{
+      /* We are currently listing subprograms.  Figure out which one and
+      ** pick up the appropriate opcode. */
+      int j;
+      i -= p->nOp;
+      for(j=0; i>=apSub[j]->nOp; j++){
+        i -= apSub[j]->nOp;
+      }
+      pOp = &apSub[j]->aOp[i];
+    }
+    if( p->explain==1 ){
+      pMem->flags = MEM_Int;
+      pMem->type = SQLITE_INTEGER;
+      pMem->u.i = i;                                /* Program counter */
+      pMem++;
+  
+      pMem->flags = MEM_Static|MEM_Str|MEM_Term;
+      pMem->z = (char*)sqlite3OpcodeName(pOp->opcode);  /* Opcode */
+      assert( pMem->z!=0 );
+      pMem->n = sqlite3Strlen30(pMem->z);
+      pMem->type = SQLITE_TEXT;
+      pMem->enc = SQLITE_UTF8;
+      pMem++;
+
+      /* When an OP_Program opcode is encounter (the only opcode that has
+      ** a P4_SUBPROGRAM argument), expand the size of the array of subprograms
+      ** kept in p->aMem[9].z to hold the new program - assuming this subprogram
+      ** has not already been seen.
+      */
+      if( pOp->p4type==P4_SUBPROGRAM ){
+        int nByte = (nSub+1)*sizeof(SubProgram*);
+        int j;
+        for(j=0; j<nSub; j++){
+          if( apSub[j]==pOp->p4.pProgram ) break;
+        }
+        if( j==nSub && SQLITE_OK==sqlite3VdbeMemGrow(pSub, nByte, 1) ){
+          apSub = (SubProgram **)pSub->z;
+          apSub[nSub++] = pOp->p4.pProgram;
+          pSub->flags |= MEM_Blob;
+          pSub->n = nSub*sizeof(SubProgram*);
+        }
+      }
+    }
+
+    pMem->flags = MEM_Int;
+    pMem->u.i = pOp->p1;                          /* P1 */
+    pMem->type = SQLITE_INTEGER;
+    pMem++;
+
+    pMem->flags = MEM_Int;
+    pMem->u.i = pOp->p2;                          /* P2 */
+    pMem->type = SQLITE_INTEGER;
+    pMem++;
+
+    pMem->flags = MEM_Int;
+    pMem->u.i = pOp->p3;                          /* P3 */
+    pMem->type = SQLITE_INTEGER;
+    pMem++;
+
+    if( sqlite3VdbeMemGrow(pMem, 32, 0) ){            /* P4 */
+      assert( p->db->mallocFailed );
+      return SQLITE_ERROR;
+    }
+    pMem->flags = MEM_Dyn|MEM_Str|MEM_Term;
+    z = displayP4(pOp, pMem->z, 32);
+    if( z!=pMem->z ){
+      sqlite3VdbeMemSetStr(pMem, z, -1, SQLITE_UTF8, 0);
+    }else{
+      assert( pMem->z!=0 );
+      pMem->n = sqlite3Strlen30(pMem->z);
+      pMem->enc = SQLITE_UTF8;
+    }
+    pMem->type = SQLITE_TEXT;
+    pMem++;
+
+    if( p->explain==1 ){
+      if( sqlite3VdbeMemGrow(pMem, 4, 0) ){
+        assert( p->db->mallocFailed );
+        return SQLITE_ERROR;
+      }
+      pMem->flags = MEM_Dyn|MEM_Str|MEM_Term;
+      pMem->n = 2;
+      sqlite3_snprintf(3, pMem->z, "%.2x", pOp->p5);   /* P5 */
+      pMem->type = SQLITE_TEXT;
+      pMem->enc = SQLITE_UTF8;
+      pMem++;
+  
+#ifdef SQLITE_DEBUG
+      if( pOp->zComment ){
+        pMem->flags = MEM_Str|MEM_Term;
+        pMem->z = pOp->zComment;
+        pMem->n = sqlite3Strlen30(pMem->z);
+        pMem->enc = SQLITE_UTF8;
+        pMem->type = SQLITE_TEXT;
+      }else
+#endif
+      {
+        pMem->flags = MEM_Null;                       /* Comment */
+        pMem->type = SQLITE_NULL;
+      }
+    }
+
+    p->nResColumn = 8 - 4*(p->explain-1);
+    p->pResultSet = &p->aMem[1];
+    p->rc = SQLITE_OK;
+    rc = SQLITE_ROW;
+  }
+  return rc;
+}
+#endif /* SQLITE_OMIT_EXPLAIN */
+
+#ifdef SQLITE_DEBUG
+/*
+** Print the SQL that was used to generate a VDBE program.
+*/
+void sqlite3VdbePrintSql(Vdbe *p){
+  int nOp = p->nOp;
+  VdbeOp *pOp;
+  if( nOp<1 ) return;
+  pOp = &p->aOp[0];
+  if( pOp->opcode==OP_Trace && pOp->p4.z!=0 ){
+    const char *z = pOp->p4.z;
+    while( sqlite3Isspace(*z) ) z++;
+    printf("SQL: [%s]\n", z);
+  }
+}
+#endif
+
+#if !defined(SQLITE_OMIT_TRACE) && defined(SQLITE_ENABLE_IOTRACE)
+/*
+** Print an IOTRACE message showing SQL content.
+*/
+void sqlite3VdbeIOTraceSql(Vdbe *p){
+  int nOp = p->nOp;
+  VdbeOp *pOp;
+  if( sqlite3IoTrace==0 ) return;
+  if( nOp<1 ) return;
+  pOp = &p->aOp[0];
+  if( pOp->opcode==OP_Trace && pOp->p4.z!=0 ){
+    int i, j;
+    char z[1000];
+    sqlite3_snprintf(sizeof(z), z, "%s", pOp->p4.z);
+    for(i=0; sqlite3Isspace(z[i]); i++){}
+    for(j=0; z[i]; i++){
+      if( sqlite3Isspace(z[i]) ){
+        if( z[i-1]!=' ' ){
+          z[j++] = ' ';
+        }
+      }else{
+        z[j++] = z[i];
+      }
+    }
+    z[j] = 0;
+    sqlite3IoTrace("SQL %s\n", z);
+  }
+}
+#endif /* !SQLITE_OMIT_TRACE && SQLITE_ENABLE_IOTRACE */
+
+/*
+** Allocate space from a fixed size buffer and return a pointer to
+** that space.  If insufficient space is available, return NULL.
+**
+** The pBuf parameter is the initial value of a pointer which will
+** receive the new memory.  pBuf is normally NULL.  If pBuf is not
+** NULL, it means that memory space has already been allocated and that
+** this routine should not allocate any new memory.  When pBuf is not
+** NULL simply return pBuf.  Only allocate new memory space when pBuf
+** is NULL.
+**
+** nByte is the number of bytes of space needed.
+**
+** *ppFrom points to available space and pEnd points to the end of the
+** available space.  When space is allocated, *ppFrom is advanced past
+** the end of the allocated space.
+**
+** *pnByte is a counter of the number of bytes of space that have failed
+** to allocate.  If there is insufficient space in *ppFrom to satisfy the
+** request, then increment *pnByte by the amount of the request.
+*/
+static void *allocSpace(
+  void *pBuf,          /* Where return pointer will be stored */
+  int nByte,           /* Number of bytes to allocate */
+  u8 **ppFrom,         /* IN/OUT: Allocate from *ppFrom */
+  u8 *pEnd,            /* Pointer to 1 byte past the end of *ppFrom buffer */
+  int *pnByte          /* If allocation cannot be made, increment *pnByte */
+){
+  assert( EIGHT_BYTE_ALIGNMENT(*ppFrom) );
+  if( pBuf ) return pBuf;
+  nByte = ROUND8(nByte);
+  if( &(*ppFrom)[nByte] <= pEnd ){
+    pBuf = (void*)*ppFrom;
+    *ppFrom += nByte;
+  }else{
+    *pnByte += nByte;
+  }
+  return pBuf;
+}
+
+/*
+** Rewind the VDBE back to the beginning in preparation for
+** running it.
+*/
+void sqlite3VdbeRewind(Vdbe *p){
+#if defined(SQLITE_DEBUG) || defined(VDBE_PROFILE)
+  int i;
+#endif
+  assert( p!=0 );
+  assert( p->magic==VDBE_MAGIC_INIT );
+
+  /* There should be at least one opcode.
+  */
+  assert( p->nOp>0 );
+
+  /* Set the magic to VDBE_MAGIC_RUN sooner rather than later. */
+  p->magic = VDBE_MAGIC_RUN;
+
+#ifdef SQLITE_DEBUG
+  for(i=1; i<p->nMem; i++){
+    assert( p->aMem[i].db==p->db );
+  }
+#endif
+  p->pc = -1;
+  p->rc = SQLITE_OK;
+  p->errorAction = OE_Abort;
+  p->magic = VDBE_MAGIC_RUN;
+  p->nChange = 0;
+  p->cacheCtr = 1;
+  p->minWriteFileFormat = 255;
+  p->iStatement = 0;
+  p->nFkConstraint = 0;
+#ifdef VDBE_PROFILE
+  for(i=0; i<p->nOp; i++){
+    p->aOp[i].cnt = 0;
+    p->aOp[i].cycles = 0;
+  }
+#endif
+}
+
+/*
+** Prepare a virtual machine for execution for the first time after
+** creating the virtual machine.  This involves things such
+** as allocating stack space and initializing the program counter.
+** After the VDBE has be prepped, it can be executed by one or more
+** calls to sqlite3VdbeExec().  
+**
+** This function may be called exact once on a each virtual machine.
+** After this routine is called the VM has been "packaged" and is ready
+** to run.  After this routine is called, futher calls to 
+** sqlite3VdbeAddOp() functions are prohibited.  This routine disconnects
+** the Vdbe from the Parse object that helped generate it so that the
+** the Vdbe becomes an independent entity and the Parse object can be
+** destroyed.
+**
+** Use the sqlite3VdbeRewind() procedure to restore a virtual machine back
+** to its initial state after it has been run.
+*/
+void sqlite3VdbeMakeReady(
+  Vdbe *p,                       /* The VDBE */
+  Parse *pParse                  /* Parsing context */
+){
+  sqlite3 *db;                   /* The database connection */
+  int nVar;                      /* Number of parameters */
+  int nMem;                      /* Number of VM memory registers */
+  int nCursor;                   /* Number of cursors required */
+  int nArg;                      /* Number of arguments in subprograms */
+  int n;                         /* Loop counter */
+  u8 *zCsr;                      /* Memory available for allocation */
+  u8 *zEnd;                      /* First byte past allocated memory */
+  int nByte;                     /* How much extra memory is needed */
+
+  assert( p!=0 );
+  assert( p->nOp>0 );
+  assert( pParse!=0 );
+  assert( p->magic==VDBE_MAGIC_INIT );
+  db = p->db;
+  assert( db->mallocFailed==0 );
+  nVar = pParse->nVar;
+  nMem = pParse->nMem;
+  nCursor = pParse->nTab;
+  nArg = pParse->nMaxArg;
+  
+  /* For each cursor required, also allocate a memory cell. Memory
+  ** cells (nMem+1-nCursor)..nMem, inclusive, will never be used by
+  ** the vdbe program. Instead they are used to allocate space for
+  ** VdbeCursor/BtCursor structures. The blob of memory associated with 
+  ** cursor 0 is stored in memory cell nMem. Memory cell (nMem-1)
+  ** stores the blob of memory associated with cursor 1, etc.
+  **
+  ** See also: allocateCursor().
+  */
+  nMem += nCursor;
+
+  /* Allocate space for memory registers, SQL variables, VDBE cursors and 
+  ** an array to marshal SQL function arguments in.
+  */
+  zCsr = (u8*)&p->aOp[p->nOp];       /* Memory avaliable for allocation */
+  zEnd = (u8*)&p->aOp[p->nOpAlloc];  /* First byte past end of zCsr[] */
+
+  resolveP2Values(p, &nArg);
+  p->usesStmtJournal = (u8)(pParse->isMultiWrite && pParse->mayAbort);
+  if( pParse->explain && nMem<10 ){
+    nMem = 10;
+  }
+  memset(zCsr, 0, zEnd-zCsr);
+  zCsr += (zCsr - (u8*)0)&7;
+  assert( EIGHT_BYTE_ALIGNMENT(zCsr) );
+  p->expired = 0;
+
+  /* Memory for registers, parameters, cursor, etc, is allocated in two
+  ** passes.  On the first pass, we try to reuse unused space at the 
+  ** end of the opcode array.  If we are unable to satisfy all memory
+  ** requirements by reusing the opcode array tail, then the second
+  ** pass will fill in the rest using a fresh allocation.  
+  **
+  ** This two-pass approach that reuses as much memory as possible from
+  ** the leftover space at the end of the opcode array can significantly
+  ** reduce the amount of memory held by a prepared statement.
+  */
+  do {
+    nByte = 0;
+    p->aMem = allocSpace(p->aMem, nMem*sizeof(Mem), &zCsr, zEnd, &nByte);
+    p->aVar = allocSpace(p->aVar, nVar*sizeof(Mem), &zCsr, zEnd, &nByte);
+    p->apArg = allocSpace(p->apArg, nArg*sizeof(Mem*), &zCsr, zEnd, &nByte);
+    p->azVar = allocSpace(p->azVar, nVar*sizeof(char*), &zCsr, zEnd, &nByte);
+    p->apCsr = allocSpace(p->apCsr, nCursor*sizeof(VdbeCursor*),
+                          &zCsr, zEnd, &nByte);
+    if( nByte ){
+      p->pFree = sqlite3DbMallocZero(db, nByte);
+    }
+    zCsr = p->pFree;
+    zEnd = &zCsr[nByte];
+  }while( nByte && !db->mallocFailed );
+
+  p->nCursor = (u16)nCursor;
+  if( p->aVar ){
+    p->nVar = (ynVar)nVar;
+    for(n=0; n<nVar; n++){
+      p->aVar[n].flags = MEM_Null;
+      p->aVar[n].db = db;
+    }
+  }
+  if( p->azVar ){
+    p->nzVar = pParse->nzVar;
+    memcpy(p->azVar, pParse->azVar, p->nzVar*sizeof(p->azVar[0]));
+    memset(pParse->azVar, 0, pParse->nzVar*sizeof(pParse->azVar[0]));
+  }
+  if( p->aMem ){
+    p->aMem--;                      /* aMem[] goes from 1..nMem */
+    p->nMem = nMem;                 /*       not from 0..nMem-1 */
+    for(n=1; n<=nMem; n++){
+      p->aMem[n].flags = MEM_Null;
+      p->aMem[n].db = db;
+    }
+  }
+  p->explain = pParse->explain;
+  sqlite3VdbeRewind(p);
+}
+
+/*
+** Close a VDBE cursor and release all the resources that cursor 
+** happens to hold.
+*/
+void sqlite3VdbeFreeCursor(Vdbe *p, VdbeCursor *pCx){
+  if( pCx==0 ){
+    return;
+  }
+  sqlite3VdbeSorterClose(p->db, pCx);
+  if( pCx->pBt ){
+    sqlite3BtreeClose(pCx->pBt);
+    /* The pCx->pCursor will be close automatically, if it exists, by
+    ** the call above. */
+  }else if( pCx->pCursor ){
+    sqlite3BtreeCloseCursor(pCx->pCursor);
+  }
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  if( pCx->pVtabCursor ){
+    sqlite3_vtab_cursor *pVtabCursor = pCx->pVtabCursor;
+    const sqlite3_module *pModule = pCx->pModule;
+    p->inVtabMethod = 1;
+    pModule->xClose(pVtabCursor);
+    p->inVtabMethod = 0;
+  }
+#endif
+}
+
+/*
+** Copy the values stored in the VdbeFrame structure to its Vdbe. This
+** is used, for example, when a trigger sub-program is halted to restore
+** control to the main program.
+*/
+int sqlite3VdbeFrameRestore(VdbeFrame *pFrame){
+  Vdbe *v = pFrame->v;
+  v->aOp = pFrame->aOp;
+  v->nOp = pFrame->nOp;
+  v->aMem = pFrame->aMem;
+  v->nMem = pFrame->nMem;
+  v->apCsr = pFrame->apCsr;
+  v->nCursor = pFrame->nCursor;
+  v->db->lastRowid = pFrame->lastRowid;
+  v->nChange = pFrame->nChange;
+  return pFrame->pc;
+}
+
+/*
+** Close all cursors.
+**
+** Also release any dynamic memory held by the VM in the Vdbe.aMem memory 
+** cell array. This is necessary as the memory cell array may contain
+** pointers to VdbeFrame objects, which may in turn contain pointers to
+** open cursors.
+*/
+static void closeAllCursors(Vdbe *p){
+  if( p->pFrame ){
+    VdbeFrame *pFrame;
+    for(pFrame=p->pFrame; pFrame->pParent; pFrame=pFrame->pParent);
+    sqlite3VdbeFrameRestore(pFrame);
+  }
+  p->pFrame = 0;
+  p->nFrame = 0;
+
+  if( p->apCsr ){
+    int i;
+    for(i=0; i<p->nCursor; i++){
+      VdbeCursor *pC = p->apCsr[i];
+      if( pC ){
+        sqlite3VdbeFreeCursor(p, pC);
+        p->apCsr[i] = 0;
+      }
+    }
+  }
+  if( p->aMem ){
+    releaseMemArray(&p->aMem[1], p->nMem);
+  }
+  while( p->pDelFrame ){
+    VdbeFrame *pDel = p->pDelFrame;
+    p->pDelFrame = pDel->pParent;
+    sqlite3VdbeFrameDelete(pDel);
+  }
+}
+
+/*
+** Clean up the VM after execution.
+**
+** This routine will automatically close any cursors, lists, and/or
+** sorters that were left open.  It also deletes the values of
+** variables in the aVar[] array.
+*/
+static void Cleanup(Vdbe *p){
+  sqlite3 *db = p->db;
+
+#ifdef SQLITE_DEBUG
+  /* Execute assert() statements to ensure that the Vdbe.apCsr[] and 
+  ** Vdbe.aMem[] arrays have already been cleaned up.  */
+  int i;
+  for(i=0; i<p->nCursor; i++) assert( p->apCsr==0 || p->apCsr[i]==0 );
+  for(i=1; i<=p->nMem; i++) assert( p->aMem==0 || p->aMem[i].flags==MEM_Null );
+#endif
+
+  sqlite3DbFree(db, p->zErrMsg);
+  p->zErrMsg = 0;
+  p->pResultSet = 0;
+}
+
+/*
+** Set the number of result columns that will be returned by this SQL
+** statement. This is now set at compile time, rather than during
+** execution of the vdbe program so that sqlite3_column_count() can
+** be called on an SQL statement before sqlite3_step().
+*/
+void sqlite3VdbeSetNumCols(Vdbe *p, int nResColumn){
+  Mem *pColName;
+  int n;
+  sqlite3 *db = p->db;
+
+  releaseMemArray(p->aColName, p->nResColumn*COLNAME_N);
+  sqlite3DbFree(db, p->aColName);
+  n = nResColumn*COLNAME_N;
+  p->nResColumn = (u16)nResColumn;
+  p->aColName = pColName = (Mem*)sqlite3DbMallocZero(db, sizeof(Mem)*n );
+  if( p->aColName==0 ) return;
+  while( n-- > 0 ){
+    pColName->flags = MEM_Null;
+    pColName->db = p->db;
+    pColName++;
+  }
+}
+
+/*
+** Set the name of the idx'th column to be returned by the SQL statement.
+** zName must be a pointer to a nul terminated string.
+**
+** This call must be made after a call to sqlite3VdbeSetNumCols().
+**
+** The final parameter, xDel, must be one of SQLITE_DYNAMIC, SQLITE_STATIC
+** or SQLITE_TRANSIENT. If it is SQLITE_DYNAMIC, then the buffer pointed
+** to by zName will be freed by sqlite3DbFree() when the vdbe is destroyed.
+*/
+int sqlite3VdbeSetColName(
+  Vdbe *p,                         /* Vdbe being configured */
+  int idx,                         /* Index of column zName applies to */
+  int var,                         /* One of the COLNAME_* constants */
+  const char *zName,               /* Pointer to buffer containing name */
+  void (*xDel)(void*)              /* Memory management strategy for zName */
+){
+  int rc;
+  Mem *pColName;
+  assert( idx<p->nResColumn );
+  assert( var<COLNAME_N );
+  if( p->db->mallocFailed ){
+    assert( !zName || xDel!=SQLITE_DYNAMIC );
+    return SQLITE_NOMEM;
+  }
+  assert( p->aColName!=0 );
+  pColName = &(p->aColName[idx+var*p->nResColumn]);
+  rc = sqlite3VdbeMemSetStr(pColName, zName, -1, SQLITE_UTF8, xDel);
+  assert( rc!=0 || !zName || (pColName->flags&MEM_Term)!=0 );
+  return rc;
+}
+
+/*
+** A read or write transaction may or may not be active on database handle
+** db. If a transaction is active, commit it. If there is a
+** write-transaction spanning more than one database file, this routine
+** takes care of the master journal trickery.
+*/
+static int vdbeCommit(sqlite3 *db, Vdbe *p){
+  int i;
+  int nTrans = 0;  /* Number of databases with an active write-transaction */
+  int rc = SQLITE_OK;
+  int needXcommit = 0;
+
+#ifdef SQLITE_OMIT_VIRTUALTABLE
+  /* With this option, sqlite3VtabSync() is defined to be simply 
+  ** SQLITE_OK so p is not used. 
+  */
+  UNUSED_PARAMETER(p);
+#endif
+
+  /* Before doing anything else, call the xSync() callback for any
+  ** virtual module tables written in this transaction. This has to
+  ** be done before determining whether a master journal file is 
+  ** required, as an xSync() callback may add an attached database
+  ** to the transaction.
+  */
+  rc = sqlite3VtabSync(db, &p->zErrMsg);
+
+  /* This loop determines (a) if the commit hook should be invoked and
+  ** (b) how many database files have open write transactions, not 
+  ** including the temp database. (b) is important because if more than 
+  ** one database file has an open write transaction, a master journal
+  ** file is required for an atomic commit.
+  */ 
+  for(i=0; rc==SQLITE_OK && i<db->nDb; i++){ 
+    Btree *pBt = db->aDb[i].pBt;
+    if( sqlite3BtreeIsInTrans(pBt) ){
+      needXcommit = 1;
+      if( i!=1 ) nTrans++;
+      rc = sqlite3PagerExclusiveLock(sqlite3BtreePager(pBt));
+    }
+  }
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+
+  /* If there are any write-transactions at all, invoke the commit hook */
+  if( needXcommit && db->xCommitCallback ){
+    rc = db->xCommitCallback(db->pCommitArg);
+    if( rc ){
+      return SQLITE_CONSTRAINT;
+    }
+  }
+
+  /* The simple case - no more than one database file (not counting the
+  ** TEMP database) has a transaction active.   There is no need for the
+  ** master-journal.
+  **
+  ** If the return value of sqlite3BtreeGetFilename() is a zero length
+  ** string, it means the main database is :memory: or a temp file.  In 
+  ** that case we do not support atomic multi-file commits, so use the 
+  ** simple case then too.
+  */
+  if( 0==sqlite3Strlen30(sqlite3BtreeGetFilename(db->aDb[0].pBt))
+   || nTrans<=1
+  ){
+    for(i=0; rc==SQLITE_OK && i<db->nDb; i++){
+      Btree *pBt = db->aDb[i].pBt;
+      if( pBt ){
+        rc = sqlite3BtreeCommitPhaseOne(pBt, 0);
+      }
+    }
+
+    /* Do the commit only if all databases successfully complete phase 1. 
+    ** If one of the BtreeCommitPhaseOne() calls fails, this indicates an
+    ** IO error while deleting or truncating a journal file. It is unlikely,
+    ** but could happen. In this case abandon processing and return the error.
+    */
+    for(i=0; rc==SQLITE_OK && i<db->nDb; i++){
+      Btree *pBt = db->aDb[i].pBt;
+      if( pBt ){
+        rc = sqlite3BtreeCommitPhaseTwo(pBt, 0);
+      }
+    }
+    if( rc==SQLITE_OK ){
+      sqlite3VtabCommit(db);
+    }
+  }
+
+  /* The complex case - There is a multi-file write-transaction active.
+  ** This requires a master journal file to ensure the transaction is
+  ** committed atomicly.
+  */
+#ifndef SQLITE_OMIT_DISKIO
+  else{
+    sqlite3_vfs *pVfs = db->pVfs;
+    int needSync = 0;
+    char *zMaster = 0;   /* File-name for the master journal */
+    char const *zMainFile = sqlite3BtreeGetFilename(db->aDb[0].pBt);
+    sqlite3_file *pMaster = 0;
+    i64 offset = 0;
+    int res;
+
+    /* Select a master journal file name */
+    do {
+      u32 iRandom;
+      sqlite3DbFree(db, zMaster);
+      sqlite3_randomness(sizeof(iRandom), &iRandom);
+      zMaster = sqlite3MPrintf(db, "%s-mj%08X", zMainFile, iRandom&0x7fffffff);
+      if( !zMaster ){
+        return SQLITE_NOMEM;
+      }
+      sqlite3FileSuffix3(zMainFile, zMaster);
+      rc = sqlite3OsAccess(pVfs, zMaster, SQLITE_ACCESS_EXISTS, &res);
+    }while( rc==SQLITE_OK && res );
+    if( rc==SQLITE_OK ){
+      /* Open the master journal. */
+      rc = sqlite3OsOpenMalloc(pVfs, zMaster, &pMaster, 
+          SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE|
+          SQLITE_OPEN_EXCLUSIVE|SQLITE_OPEN_MASTER_JOURNAL, 0
+      );
+    }
+    if( rc!=SQLITE_OK ){
+      sqlite3DbFree(db, zMaster);
+      return rc;
+    }
+ 
+    /* Write the name of each database file in the transaction into the new
+    ** master journal file. If an error occurs at this point close
+    ** and delete the master journal file. All the individual journal files
+    ** still have 'null' as the master journal pointer, so they will roll
+    ** back independently if a failure occurs.
+    */
+    for(i=0; i<db->nDb; i++){
+      Btree *pBt = db->aDb[i].pBt;
+      if( sqlite3BtreeIsInTrans(pBt) ){
+        char const *zFile = sqlite3BtreeGetJournalname(pBt);
+        if( zFile==0 ){
+          continue;  /* Ignore TEMP and :memory: databases */
+        }
+        assert( zFile[0]!=0 );
+        if( !needSync && !sqlite3BtreeSyncDisabled(pBt) ){
+          needSync = 1;
+        }
+        rc = sqlite3OsWrite(pMaster, zFile, sqlite3Strlen30(zFile)+1, offset);
+        offset += sqlite3Strlen30(zFile)+1;
+        if( rc!=SQLITE_OK ){
+          sqlite3OsCloseFree(pMaster);
+          sqlite3OsDelete(pVfs, zMaster, 0);
+          sqlite3DbFree(db, zMaster);
+          return rc;
+        }
+      }
+    }
+
+    /* Sync the master journal file. If the IOCAP_SEQUENTIAL device
+    ** flag is set this is not required.
+    */
+    if( needSync 
+     && 0==(sqlite3OsDeviceCharacteristics(pMaster)&SQLITE_IOCAP_SEQUENTIAL)
+     && SQLITE_OK!=(rc = sqlite3OsSync(pMaster, SQLITE_SYNC_NORMAL))
+    ){
+      sqlite3OsCloseFree(pMaster);
+      sqlite3OsDelete(pVfs, zMaster, 0);
+      sqlite3DbFree(db, zMaster);
+      return rc;
+    }
+
+    /* Sync all the db files involved in the transaction. The same call
+    ** sets the master journal pointer in each individual journal. If
+    ** an error occurs here, do not delete the master journal file.
+    **
+    ** If the error occurs during the first call to
+    ** sqlite3BtreeCommitPhaseOne(), then there is a chance that the
+    ** master journal file will be orphaned. But we cannot delete it,
+    ** in case the master journal file name was written into the journal
+    ** file before the failure occurred.
+    */
+    for(i=0; rc==SQLITE_OK && i<db->nDb; i++){ 
+      Btree *pBt = db->aDb[i].pBt;
+      if( pBt ){
+        rc = sqlite3BtreeCommitPhaseOne(pBt, zMaster);
+      }
+    }
+    sqlite3OsCloseFree(pMaster);
+    assert( rc!=SQLITE_BUSY );
+    if( rc!=SQLITE_OK ){
+      sqlite3DbFree(db, zMaster);
+      return rc;
+    }
+
+    /* Delete the master journal file. This commits the transaction. After
+    ** doing this the directory is synced again before any individual
+    ** transaction files are deleted.
+    */
+    rc = sqlite3OsDelete(pVfs, zMaster, 1);
+    sqlite3DbFree(db, zMaster);
+    zMaster = 0;
+    if( rc ){
+      return rc;
+    }
+
+    /* All files and directories have already been synced, so the following
+    ** calls to sqlite3BtreeCommitPhaseTwo() are only closing files and
+    ** deleting or truncating journals. If something goes wrong while
+    ** this is happening we don't really care. The integrity of the
+    ** transaction is already guaranteed, but some stray 'cold' journals
+    ** may be lying around. Returning an error code won't help matters.
+    */
+    disable_simulated_io_errors();
+    sqlite3BeginBenignMalloc();
+    for(i=0; i<db->nDb; i++){ 
+      Btree *pBt = db->aDb[i].pBt;
+      if( pBt ){
+        sqlite3BtreeCommitPhaseTwo(pBt, 1);
+      }
+    }
+    sqlite3EndBenignMalloc();
+    enable_simulated_io_errors();
+
+    sqlite3VtabCommit(db);
+  }
+#endif
+
+  return rc;
+}
+
+/* 
+** This routine checks that the sqlite3.activeVdbeCnt count variable
+** matches the number of vdbe's in the list sqlite3.pVdbe that are
+** currently active. An assertion fails if the two counts do not match.
+** This is an internal self-check only - it is not an essential processing
+** step.
+**
+** This is a no-op if NDEBUG is defined.
+*/
+#ifndef NDEBUG
+static void checkActiveVdbeCnt(sqlite3 *db){
+  Vdbe *p;
+  int cnt = 0;
+  int nWrite = 0;
+  p = db->pVdbe;
+  while( p ){
+    if( p->magic==VDBE_MAGIC_RUN && p->pc>=0 ){
+      cnt++;
+      if( p->readOnly==0 ) nWrite++;
+    }
+    p = p->pNext;
+  }
+  assert( cnt==db->activeVdbeCnt );
+  assert( nWrite==db->writeVdbeCnt );
+}
+#else
+#define checkActiveVdbeCnt(x)
+#endif
+
+/*
+** For every Btree that in database connection db which 
+** has been modified, "trip" or invalidate each cursor in
+** that Btree might have been modified so that the cursor
+** can never be used again.  This happens when a rollback
+*** occurs.  We have to trip all the other cursors, even
+** cursor from other VMs in different database connections,
+** so that none of them try to use the data at which they
+** were pointing and which now may have been changed due
+** to the rollback.
+**
+** Remember that a rollback can delete tables complete and
+** reorder rootpages.  So it is not sufficient just to save
+** the state of the cursor.  We have to invalidate the cursor
+** so that it is never used again.
+*/
+static void invalidateCursorsOnModifiedBtrees(sqlite3 *db){
+  int i;
+  for(i=0; i<db->nDb; i++){
+    Btree *p = db->aDb[i].pBt;
+    if( p && sqlite3BtreeIsInTrans(p) ){
+      sqlite3BtreeTripAllCursors(p, SQLITE_ABORT);
+    }
+  }
+}
+
+/*
+** If the Vdbe passed as the first argument opened a statement-transaction,
+** close it now. Argument eOp must be either SAVEPOINT_ROLLBACK or
+** SAVEPOINT_RELEASE. If it is SAVEPOINT_ROLLBACK, then the statement
+** transaction is rolled back. If eOp is SAVEPOINT_RELEASE, then the 
+** statement transaction is commtted.
+**
+** If an IO error occurs, an SQLITE_IOERR_XXX error code is returned. 
+** Otherwise SQLITE_OK.
+*/
+int sqlite3VdbeCloseStatement(Vdbe *p, int eOp){
+  sqlite3 *const db = p->db;
+  int rc = SQLITE_OK;
+
+  /* If p->iStatement is greater than zero, then this Vdbe opened a 
+  ** statement transaction that should be closed here. The only exception
+  ** is that an IO error may have occured, causing an emergency rollback.
+  ** In this case (db->nStatement==0), and there is nothing to do.
+  */
+  if( db->nStatement && p->iStatement ){
+    int i;
+    const int iSavepoint = p->iStatement-1;
+
+    assert( eOp==SAVEPOINT_ROLLBACK || eOp==SAVEPOINT_RELEASE);
+    assert( db->nStatement>0 );
+    assert( p->iStatement==(db->nStatement+db->nSavepoint) );
+
+    for(i=0; i<db->nDb; i++){ 
+      int rc2 = SQLITE_OK;
+      Btree *pBt = db->aDb[i].pBt;
+      if( pBt ){
+        if( eOp==SAVEPOINT_ROLLBACK ){
+          rc2 = sqlite3BtreeSavepoint(pBt, SAVEPOINT_ROLLBACK, iSavepoint);
+        }
+        if( rc2==SQLITE_OK ){
+          rc2 = sqlite3BtreeSavepoint(pBt, SAVEPOINT_RELEASE, iSavepoint);
+        }
+        if( rc==SQLITE_OK ){
+          rc = rc2;
+        }
+      }
+    }
+    db->nStatement--;
+    p->iStatement = 0;
+
+    if( rc==SQLITE_OK ){
+      if( eOp==SAVEPOINT_ROLLBACK ){
+        rc = sqlite3VtabSavepoint(db, SAVEPOINT_ROLLBACK, iSavepoint);
+      }
+      if( rc==SQLITE_OK ){
+        rc = sqlite3VtabSavepoint(db, SAVEPOINT_RELEASE, iSavepoint);
+      }
+    }
+
+    /* If the statement transaction is being rolled back, also restore the 
+    ** database handles deferred constraint counter to the value it had when 
+    ** the statement transaction was opened.  */
+    if( eOp==SAVEPOINT_ROLLBACK ){
+      db->nDeferredCons = p->nStmtDefCons;
+    }
+  }
+  return rc;
+}
+
+/*
+** This function is called when a transaction opened by the database 
+** handle associated with the VM passed as an argument is about to be 
+** committed. If there are outstanding deferred foreign key constraint
+** violations, return SQLITE_ERROR. Otherwise, SQLITE_OK.
+**
+** If there are outstanding FK violations and this function returns 
+** SQLITE_ERROR, set the result of the VM to SQLITE_CONSTRAINT and write
+** an error message to it. Then return SQLITE_ERROR.
+*/
+#ifndef SQLITE_OMIT_FOREIGN_KEY
+int sqlite3VdbeCheckFk(Vdbe *p, int deferred){
+  sqlite3 *db = p->db;
+  if( (deferred && db->nDeferredCons>0) || (!deferred && p->nFkConstraint>0) ){
+    p->rc = SQLITE_CONSTRAINT;
+    p->errorAction = OE_Abort;
+    sqlite3SetString(&p->zErrMsg, db, "foreign key constraint failed");
+    return SQLITE_ERROR;
+  }
+  return SQLITE_OK;
+}
+#endif
+
+/*
+** This routine is called the when a VDBE tries to halt.  If the VDBE
+** has made changes and is in autocommit mode, then commit those
+** changes.  If a rollback is needed, then do the rollback.
+**
+** This routine is the only way to move the state of a VM from
+** SQLITE_MAGIC_RUN to SQLITE_MAGIC_HALT.  It is harmless to
+** call this on a VM that is in the SQLITE_MAGIC_HALT state.
+**
+** Return an error code.  If the commit could not complete because of
+** lock contention, return SQLITE_BUSY.  If SQLITE_BUSY is returned, it
+** means the close did not happen and needs to be repeated.
+*/
+int sqlite3VdbeHalt(Vdbe *p){
+  int rc;                         /* Used to store transient return codes */
+  sqlite3 *db = p->db;
+
+  /* This function contains the logic that determines if a statement or
+  ** transaction will be committed or rolled back as a result of the
+  ** execution of this virtual machine. 
+  **
+  ** If any of the following errors occur:
+  **
+  **     SQLITE_NOMEM
+  **     SQLITE_IOERR
+  **     SQLITE_FULL
+  **     SQLITE_INTERRUPT
+  **
+  ** Then the internal cache might have been left in an inconsistent
+  ** state.  We need to rollback the statement transaction, if there is
+  ** one, or the complete transaction if there is no statement transaction.
+  */
+
+  if( p->db->mallocFailed ){
+    p->rc = SQLITE_NOMEM;
+  }
+  closeAllCursors(p);
+  if( p->magic!=VDBE_MAGIC_RUN ){
+    return SQLITE_OK;
+  }
+  checkActiveVdbeCnt(db);
+
+  /* No commit or rollback needed if the program never started */
+  if( p->pc>=0 ){
+    int mrc;   /* Primary error code from p->rc */
+    int eStatementOp = 0;
+    int isSpecialError;            /* Set to true if a 'special' error */
+
+    /* Lock all btrees used by the statement */
+    sqlite3VdbeEnter(p);
+
+    /* Check for one of the special errors */
+    mrc = p->rc & 0xff;
+    assert( p->rc!=SQLITE_IOERR_BLOCKED );  /* This error no longer exists */
+    isSpecialError = mrc==SQLITE_NOMEM || mrc==SQLITE_IOERR
+                     || mrc==SQLITE_INTERRUPT || mrc==SQLITE_FULL;
+    if( isSpecialError ){
+      /* If the query was read-only and the error code is SQLITE_INTERRUPT, 
+      ** no rollback is necessary. Otherwise, at least a savepoint 
+      ** transaction must be rolled back to restore the database to a 
+      ** consistent state.
+      **
+      ** Even if the statement is read-only, it is important to perform
+      ** a statement or transaction rollback operation. If the error 
+      ** occured while writing to the journal, sub-journal or database
+      ** file as part of an effort to free up cache space (see function
+      ** pagerStress() in pager.c), the rollback is required to restore 
+      ** the pager to a consistent state.
+      */
+      if( !p->readOnly || mrc!=SQLITE_INTERRUPT ){
+        if( (mrc==SQLITE_NOMEM || mrc==SQLITE_FULL) && p->usesStmtJournal ){
+          eStatementOp = SAVEPOINT_ROLLBACK;
+        }else{
+          /* We are forced to roll back the active transaction. Before doing
+          ** so, abort any other statements this handle currently has active.
+          */
+          invalidateCursorsOnModifiedBtrees(db);
+          sqlite3RollbackAll(db);
+          sqlite3CloseSavepoints(db);
+          db->autoCommit = 1;
+        }
+      }
+    }
+
+    /* Check for immediate foreign key violations. */
+    if( p->rc==SQLITE_OK ){
+      sqlite3VdbeCheckFk(p, 0);
+    }
+  
+    /* If the auto-commit flag is set and this is the only active writer 
+    ** VM, then we do either a commit or rollback of the current transaction. 
+    **
+    ** Note: This block also runs if one of the special errors handled 
+    ** above has occurred. 
+    */
+    if( !sqlite3VtabInSync(db) 
+     && db->autoCommit 
+     && db->writeVdbeCnt==(p->readOnly==0) 
+    ){
+      if( p->rc==SQLITE_OK || (p->errorAction==OE_Fail && !isSpecialError) ){
+        rc = sqlite3VdbeCheckFk(p, 1);
+        if( rc!=SQLITE_OK ){
+          if( NEVER(p->readOnly) ){
+            sqlite3VdbeLeave(p);
+            return SQLITE_ERROR;
+          }
+          rc = SQLITE_CONSTRAINT;
+        }else{ 
+          /* The auto-commit flag is true, the vdbe program was successful 
+          ** or hit an 'OR FAIL' constraint and there are no deferred foreign
+          ** key constraints to hold up the transaction. This means a commit 
+          ** is required. */
+          rc = vdbeCommit(db, p);
+        }
+        if( rc==SQLITE_BUSY && p->readOnly ){
+          sqlite3VdbeLeave(p);
+          return SQLITE_BUSY;
+        }else if( rc!=SQLITE_OK ){
+          p->rc = rc;
+          sqlite3RollbackAll(db);
+        }else{
+          db->nDeferredCons = 0;
+          sqlite3CommitInternalChanges(db);
+        }
+      }else{
+        sqlite3RollbackAll(db);
+      }
+      db->nStatement = 0;
+    }else if( eStatementOp==0 ){
+      if( p->rc==SQLITE_OK || p->errorAction==OE_Fail ){
+        eStatementOp = SAVEPOINT_RELEASE;
+      }else if( p->errorAction==OE_Abort ){
+        eStatementOp = SAVEPOINT_ROLLBACK;
+      }else{
+        invalidateCursorsOnModifiedBtrees(db);
+        sqlite3RollbackAll(db);
+        sqlite3CloseSavepoints(db);
+        db->autoCommit = 1;
+      }
+    }
+  
+    /* If eStatementOp is non-zero, then a statement transaction needs to
+    ** be committed or rolled back. Call sqlite3VdbeCloseStatement() to
+    ** do so. If this operation returns an error, and the current statement
+    ** error code is SQLITE_OK or SQLITE_CONSTRAINT, then promote the
+    ** current statement error code.
+    */
+    if( eStatementOp ){
+      rc = sqlite3VdbeCloseStatement(p, eStatementOp);
+      if( rc ){
+        if( p->rc==SQLITE_OK || p->rc==SQLITE_CONSTRAINT ){
+          p->rc = rc;
+          sqlite3DbFree(db, p->zErrMsg);
+          p->zErrMsg = 0;
+        }
+        invalidateCursorsOnModifiedBtrees(db);
+        sqlite3RollbackAll(db);
+        sqlite3CloseSavepoints(db);
+        db->autoCommit = 1;
+      }
+    }
+  
+    /* If this was an INSERT, UPDATE or DELETE and no statement transaction
+    ** has been rolled back, update the database connection change-counter. 
+    */
+    if( p->changeCntOn ){
+      if( eStatementOp!=SAVEPOINT_ROLLBACK ){
+        sqlite3VdbeSetChanges(db, p->nChange);
+      }else{
+        sqlite3VdbeSetChanges(db, 0);
+      }
+      p->nChange = 0;
+    }
+  
+    /* Rollback or commit any schema changes that occurred. */
+    if( p->rc!=SQLITE_OK && db->flags&SQLITE_InternChanges ){
+      sqlite3ResetInternalSchema(db, -1);
+      db->flags = (db->flags | SQLITE_InternChanges);
+    }
+
+    /* Release the locks */
+    sqlite3VdbeLeave(p);
+  }
+
+  /* We have successfully halted and closed the VM.  Record this fact. */
+  if( p->pc>=0 ){
+    db->activeVdbeCnt--;
+    if( !p->readOnly ){
+      db->writeVdbeCnt--;
+    }
+    assert( db->activeVdbeCnt>=db->writeVdbeCnt );
+  }
+  p->magic = VDBE_MAGIC_HALT;
+  checkActiveVdbeCnt(db);
+  if( p->db->mallocFailed ){
+    p->rc = SQLITE_NOMEM;
+  }
+
+  /* If the auto-commit flag is set to true, then any locks that were held
+  ** by connection db have now been released. Call sqlite3ConnectionUnlocked() 
+  ** to invoke any required unlock-notify callbacks.
+  */
+  if( db->autoCommit ){
+    sqlite3ConnectionUnlocked(db);
+  }
+
+  assert( db->activeVdbeCnt>0 || db->autoCommit==0 || db->nStatement==0 );
+  return (p->rc==SQLITE_BUSY ? SQLITE_BUSY : SQLITE_OK);
+}
+
+
+/*
+** Each VDBE holds the result of the most recent sqlite3_step() call
+** in p->rc.  This routine sets that result back to SQLITE_OK.
+*/
+void sqlite3VdbeResetStepResult(Vdbe *p){
+  p->rc = SQLITE_OK;
+}
+
+/*
+** Copy the error code and error message belonging to the VDBE passed
+** as the first argument to its database handle (so that they will be 
+** returned by calls to sqlite3_errcode() and sqlite3_errmsg()).
+**
+** This function does not clear the VDBE error code or message, just
+** copies them to the database handle.
+*/
+int sqlite3VdbeTransferError(Vdbe *p){
+  sqlite3 *db = p->db;
+  int rc = p->rc;
+  if( p->zErrMsg ){
+    u8 mallocFailed = db->mallocFailed;
+    sqlite3BeginBenignMalloc();
+    sqlite3ValueSetStr(db->pErr, -1, p->zErrMsg, SQLITE_UTF8, SQLITE_TRANSIENT);
+    sqlite3EndBenignMalloc();
+    db->mallocFailed = mallocFailed;
+    db->errCode = rc;
+  }else{
+    sqlite3Error(db, rc, 0);
+  }
+  return rc;
+}
+
+/*
+** Clean up a VDBE after execution but do not delete the VDBE just yet.
+** Write any error messages into *pzErrMsg.  Return the result code.
+**
+** After this routine is run, the VDBE should be ready to be executed
+** again.
+**
+** To look at it another way, this routine resets the state of the
+** virtual machine from VDBE_MAGIC_RUN or VDBE_MAGIC_HALT back to
+** VDBE_MAGIC_INIT.
+*/
+int sqlite3VdbeReset(Vdbe *p){
+  sqlite3 *db;
+  db = p->db;
+
+  /* If the VM did not run to completion or if it encountered an
+  ** error, then it might not have been halted properly.  So halt
+  ** it now.
+  */
+  sqlite3VdbeHalt(p);
+
+  /* If the VDBE has be run even partially, then transfer the error code
+  ** and error message from the VDBE into the main database structure.  But
+  ** if the VDBE has just been set to run but has not actually executed any
+  ** instructions yet, leave the main database error information unchanged.
+  */
+  if( p->pc>=0 ){
+    sqlite3VdbeTransferError(p);
+    sqlite3DbFree(db, p->zErrMsg);
+    p->zErrMsg = 0;
+    if( p->runOnlyOnce ) p->expired = 1;
+  }else if( p->rc && p->expired ){
+    /* The expired flag was set on the VDBE before the first call
+    ** to sqlite3_step(). For consistency (since sqlite3_step() was
+    ** called), set the database error in this case as well.
+    */
+    sqlite3Error(db, p->rc, 0);
+    sqlite3ValueSetStr(db->pErr, -1, p->zErrMsg, SQLITE_UTF8, SQLITE_TRANSIENT);
+    sqlite3DbFree(db, p->zErrMsg);
+    p->zErrMsg = 0;
+  }
+
+  /* Reclaim all memory used by the VDBE
+  */
+  Cleanup(p);
+
+  /* Save profiling information from this VDBE run.
+  */
+#ifdef VDBE_PROFILE
+  {
+    FILE *out = fopen("vdbe_profile.out", "a");
+    if( out ){
+      int i;
+      fprintf(out, "---- ");
+      for(i=0; i<p->nOp; i++){
+        fprintf(out, "%02x", p->aOp[i].opcode);
+      }
+      fprintf(out, "\n");
+      for(i=0; i<p->nOp; i++){
+        fprintf(out, "%6d %10lld %8lld ",
+           p->aOp[i].cnt,
+           p->aOp[i].cycles,
+           p->aOp[i].cnt>0 ? p->aOp[i].cycles/p->aOp[i].cnt : 0
+        );
+        sqlite3VdbePrintOp(out, i, &p->aOp[i]);
+      }
+      fclose(out);
+    }
+  }
+#endif
+  p->magic = VDBE_MAGIC_INIT;
+  return p->rc & db->errMask;
+}
+ 
+/*
+** Clean up and delete a VDBE after execution.  Return an integer which is
+** the result code.  Write any error message text into *pzErrMsg.
+*/
+int sqlite3VdbeFinalize(Vdbe *p){
+  int rc = SQLITE_OK;
+  if( p->magic==VDBE_MAGIC_RUN || p->magic==VDBE_MAGIC_HALT ){
+    rc = sqlite3VdbeReset(p);
+    assert( (rc & p->db->errMask)==rc );
+  }
+  sqlite3VdbeDelete(p);
+  return rc;
+}
+
+/*
+** Call the destructor for each auxdata entry in pVdbeFunc for which
+** the corresponding bit in mask is clear.  Auxdata entries beyond 31
+** are always destroyed.  To destroy all auxdata entries, call this
+** routine with mask==0.
+*/
+void sqlite3VdbeDeleteAuxData(VdbeFunc *pVdbeFunc, int mask){
+  int i;
+  for(i=0; i<pVdbeFunc->nAux; i++){
+    struct AuxData *pAux = &pVdbeFunc->apAux[i];
+    if( (i>31 || !(mask&(((u32)1)<<i))) && pAux->pAux ){
+      if( pAux->xDelete ){
+        pAux->xDelete(pAux->pAux);
+      }
+      pAux->pAux = 0;
+    }
+  }
+}
+
+/*
+** Free all memory associated with the Vdbe passed as the second argument.
+** The difference between this function and sqlite3VdbeDelete() is that
+** VdbeDelete() also unlinks the Vdbe from the list of VMs associated with
+** the database connection.
+*/
+void sqlite3VdbeDeleteObject(sqlite3 *db, Vdbe *p){
+  SubProgram *pSub, *pNext;
+  int i;
+  assert( p->db==0 || p->db==db );
+  releaseMemArray(p->aVar, p->nVar);
+  releaseMemArray(p->aColName, p->nResColumn*COLNAME_N);
+  for(pSub=p->pProgram; pSub; pSub=pNext){
+    pNext = pSub->pNext;
+    vdbeFreeOpArray(db, pSub->aOp, pSub->nOp);
+    sqlite3DbFree(db, pSub);
+  }
+  for(i=p->nzVar-1; i>=0; i--) sqlite3DbFree(db, p->azVar[i]);
+  vdbeFreeOpArray(db, p->aOp, p->nOp);
+  sqlite3DbFree(db, p->aLabel);
+  sqlite3DbFree(db, p->aColName);
+  sqlite3DbFree(db, p->zSql);
+  sqlite3DbFree(db, p->pFree);
+  sqlite3DbFree(db, p);
+}
+
+/*
+** Delete an entire VDBE.
+*/
+void sqlite3VdbeDelete(Vdbe *p){
+  sqlite3 *db;
+
+  if( NEVER(p==0) ) return;
+  db = p->db;
+  if( p->pPrev ){
+    p->pPrev->pNext = p->pNext;
+  }else{
+    assert( db->pVdbe==p );
+    db->pVdbe = p->pNext;
+  }
+  if( p->pNext ){
+    p->pNext->pPrev = p->pPrev;
+  }
+  p->magic = VDBE_MAGIC_DEAD;
+  p->db = 0;
+  sqlite3VdbeDeleteObject(db, p);
+}
+
+/*
+** Make sure the cursor p is ready to read or write the row to which it
+** was last positioned.  Return an error code if an OOM fault or I/O error
+** prevents us from positioning the cursor to its correct position.
+**
+** If a MoveTo operation is pending on the given cursor, then do that
+** MoveTo now.  If no move is pending, check to see if the row has been
+** deleted out from under the cursor and if it has, mark the row as
+** a NULL row.
+**
+** If the cursor is already pointing to the correct row and that row has
+** not been deleted out from under the cursor, then this routine is a no-op.
+*/
+int sqlite3VdbeCursorMoveto(VdbeCursor *p){
+  if( p->deferredMoveto ){
+    int res, rc;
+#ifdef SQLITE_TEST
+    extern int sqlite3_search_count;
+#endif
+    assert( p->isTable );
+    rc = sqlite3BtreeMovetoUnpacked(p->pCursor, 0, p->movetoTarget, 0, &res);
+    if( rc ) return rc;
+    p->lastRowid = p->movetoTarget;
+    if( res!=0 ) return SQLITE_CORRUPT_BKPT;
+    p->rowidIsValid = 1;
+#ifdef SQLITE_TEST
+    sqlite3_search_count++;
+#endif
+    p->deferredMoveto = 0;
+    p->cacheStatus = CACHE_STALE;
+  }else if( ALWAYS(p->pCursor) ){
+    int hasMoved;
+    int rc = sqlite3BtreeCursorHasMoved(p->pCursor, &hasMoved);
+    if( rc ) return rc;
+    if( hasMoved ){
+      p->cacheStatus = CACHE_STALE;
+      p->nullRow = 1;
+    }
+  }
+  return SQLITE_OK;
+}
+
+/*
+** The following functions:
+**
+** sqlite3VdbeSerialType()
+** sqlite3VdbeSerialTypeLen()
+** sqlite3VdbeSerialLen()
+** sqlite3VdbeSerialPut()
+** sqlite3VdbeSerialGet()
+**
+** encapsulate the code that serializes values for storage in SQLite
+** data and index records. Each serialized value consists of a
+** 'serial-type' and a blob of data. The serial type is an 8-byte unsigned
+** integer, stored as a varint.
+**
+** In an SQLite index record, the serial type is stored directly before
+** the blob of data that it corresponds to. In a table record, all serial
+** types are stored at the start of the record, and the blobs of data at
+** the end. Hence these functions allow the caller to handle the
+** serial-type and data blob seperately.
+**
+** The following table describes the various storage classes for data:
+**
+**   serial type        bytes of data      type
+**   --------------     ---------------    ---------------
+**      0                     0            NULL
+**      1                     1            signed integer
+**      2                     2            signed integer
+**      3                     3            signed integer
+**      4                     4            signed integer
+**      5                     6            signed integer
+**      6                     8            signed integer
+**      7                     8            IEEE float
+**      8                     0            Integer constant 0
+**      9                     0            Integer constant 1
+**     10,11                               reserved for expansion
+**    N>=12 and even       (N-12)/2        BLOB
+**    N>=13 and odd        (N-13)/2        text
+**
+** The 8 and 9 types were added in 3.3.0, file format 4.  Prior versions
+** of SQLite will not understand those serial types.
+*/
+
+/*
+** Return the serial-type for the value stored in pMem.
+*/
+u32 sqlite3VdbeSerialType(Mem *pMem, int file_format){
+  int flags = pMem->flags;
+  int n;
+
+  if( flags&MEM_Null ){
+    return 0;
+  }
+  if( flags&MEM_Int ){
+    /* Figure out whether to use 1, 2, 4, 6 or 8 bytes. */
+#   define MAX_6BYTE ((((i64)0x00008000)<<32)-1)
+    i64 i = pMem->u.i;
+    u64 u;
+    if( file_format>=4 && (i&1)==i ){
+      return 8+(u32)i;
+    }
+    if( i<0 ){
+      if( i<(-MAX_6BYTE) ) return 6;
+      /* Previous test prevents:  u = -(-9223372036854775808) */
+      u = -i;
+    }else{
+      u = i;
+    }
+    if( u<=127 ) return 1;
+    if( u<=32767 ) return 2;
+    if( u<=8388607 ) return 3;
+    if( u<=2147483647 ) return 4;
+    if( u<=MAX_6BYTE ) return 5;
+    return 6;
+  }
+  if( flags&MEM_Real ){
+    return 7;
+  }
+  assert( pMem->db->mallocFailed || flags&(MEM_Str|MEM_Blob) );
+  n = pMem->n;
+  if( flags & MEM_Zero ){
+    n += pMem->u.nZero;
+  }
+  assert( n>=0 );
+  return ((n*2) + 12 + ((flags&MEM_Str)!=0));
+}
+
+/*
+** Return the length of the data corresponding to the supplied serial-type.
+*/
+u32 sqlite3VdbeSerialTypeLen(u32 serial_type){
+  if( serial_type>=12 ){
+    return (serial_type-12)/2;
+  }else{
+    static const u8 aSize[] = { 0, 1, 2, 3, 4, 6, 8, 8, 0, 0, 0, 0 };
+    return aSize[serial_type];
+  }
+}
+
+/*
+** If we are on an architecture with mixed-endian floating 
+** points (ex: ARM7) then swap the lower 4 bytes with the 
+** upper 4 bytes.  Return the result.
+**
+** For most architectures, this is a no-op.
+**
+** (later):  It is reported to me that the mixed-endian problem
+** on ARM7 is an issue with GCC, not with the ARM7 chip.  It seems
+** that early versions of GCC stored the two words of a 64-bit
+** float in the wrong order.  And that error has been propagated
+** ever since.  The blame is not necessarily with GCC, though.
+** GCC might have just copying the problem from a prior compiler.
+** I am also told that newer versions of GCC that follow a different
+** ABI get the byte order right.
+**
+** Developers using SQLite on an ARM7 should compile and run their
+** application using -DSQLITE_DEBUG=1 at least once.  With DEBUG
+** enabled, some asserts below will ensure that the byte order of
+** floating point values is correct.
+**
+** (2007-08-30)  Frank van Vugt has studied this problem closely
+** and has send his findings to the SQLite developers.  Frank
+** writes that some Linux kernels offer floating point hardware
+** emulation that uses only 32-bit mantissas instead of a full 
+** 48-bits as required by the IEEE standard.  (This is the
+** CONFIG_FPE_FASTFPE option.)  On such systems, floating point
+** byte swapping becomes very complicated.  To avoid problems,
+** the necessary byte swapping is carried out using a 64-bit integer
+** rather than a 64-bit float.  Frank assures us that the code here
+** works for him.  We, the developers, have no way to independently
+** verify this, but Frank seems to know what he is talking about
+** so we trust him.
+*/
+#ifdef SQLITE_MIXED_ENDIAN_64BIT_FLOAT
+static u64 floatSwap(u64 in){
+  union {
+    u64 r;
+    u32 i[2];
+  } u;
+  u32 t;
+
+  u.r = in;
+  t = u.i[0];
+  u.i[0] = u.i[1];
+  u.i[1] = t;
+  return u.r;
+}
+# define swapMixedEndianFloat(X)  X = floatSwap(X)
+#else
+# define swapMixedEndianFloat(X)
+#endif
+
+/*
+** Write the serialized data blob for the value stored in pMem into 
+** buf. It is assumed that the caller has allocated sufficient space.
+** Return the number of bytes written.
+**
+** nBuf is the amount of space left in buf[].  nBuf must always be
+** large enough to hold the entire field.  Except, if the field is
+** a blob with a zero-filled tail, then buf[] might be just the right
+** size to hold everything except for the zero-filled tail.  If buf[]
+** is only big enough to hold the non-zero prefix, then only write that
+** prefix into buf[].  But if buf[] is large enough to hold both the
+** prefix and the tail then write the prefix and set the tail to all
+** zeros.
+**
+** Return the number of bytes actually written into buf[].  The number
+** of bytes in the zero-filled tail is included in the return value only
+** if those bytes were zeroed in buf[].
+*/ 
+u32 sqlite3VdbeSerialPut(u8 *buf, int nBuf, Mem *pMem, int file_format){
+  u32 serial_type = sqlite3VdbeSerialType(pMem, file_format);
+  u32 len;
+
+  /* Integer and Real */
+  if( serial_type<=7 && serial_type>0 ){
+    u64 v;
+    u32 i;
+    if( serial_type==7 ){
+      assert( sizeof(v)==sizeof(pMem->r) );
+      memcpy(&v, &pMem->r, sizeof(v));
+      swapMixedEndianFloat(v);
+    }else{
+      v = pMem->u.i;
+    }
+    len = i = sqlite3VdbeSerialTypeLen(serial_type);
+    assert( len<=(u32)nBuf );
+    while( i-- ){
+      buf[i] = (u8)(v&0xFF);
+      v >>= 8;
+    }
+    return len;
+  }
+
+  /* String or blob */
+  if( serial_type>=12 ){
+    assert( pMem->n + ((pMem->flags & MEM_Zero)?pMem->u.nZero:0)
+             == (int)sqlite3VdbeSerialTypeLen(serial_type) );
+    assert( pMem->n<=nBuf );
+    len = pMem->n;
+    memcpy(buf, pMem->z, len);
+    if( pMem->flags & MEM_Zero ){
+      len += pMem->u.nZero;
+      assert( nBuf>=0 );
+      if( len > (u32)nBuf ){
+        len = (u32)nBuf;
+      }
+      memset(&buf[pMem->n], 0, len-pMem->n);
+    }
+    return len;
+  }
+
+  /* NULL or constants 0 or 1 */
+  return 0;
+}
+
+/*
+** Deserialize the data blob pointed to by buf as serial type serial_type
+** and store the result in pMem.  Return the number of bytes read.
+*/ 
+u32 sqlite3VdbeSerialGet(
+  const unsigned char *buf,     /* Buffer to deserialize from */
+  u32 serial_type,              /* Serial type to deserialize */
+  Mem *pMem                     /* Memory cell to write value into */
+){
+  switch( serial_type ){
+    case 10:   /* Reserved for future use */
+    case 11:   /* Reserved for future use */
+    case 0: {  /* NULL */
+      pMem->flags = MEM_Null;
+      break;
+    }
+    case 1: { /* 1-byte signed integer */
+      pMem->u.i = (signed char)buf[0];
+      pMem->flags = MEM_Int;
+      return 1;
+    }
+    case 2: { /* 2-byte signed integer */
+      pMem->u.i = (((signed char)buf[0])<<8) | buf[1];
+      pMem->flags = MEM_Int;
+      return 2;
+    }
+    case 3: { /* 3-byte signed integer */
+      pMem->u.i = (((signed char)buf[0])<<16) | (buf[1]<<8) | buf[2];
+      pMem->flags = MEM_Int;
+      return 3;
+    }
+    case 4: { /* 4-byte signed integer */
+      pMem->u.i = (buf[0]<<24) | (buf[1]<<16) | (buf[2]<<8) | buf[3];
+      pMem->flags = MEM_Int;
+      return 4;
+    }
+    case 5: { /* 6-byte signed integer */
+      u64 x = (((signed char)buf[0])<<8) | buf[1];
+      u32 y = (buf[2]<<24) | (buf[3]<<16) | (buf[4]<<8) | buf[5];
+      x = (x<<32) | y;
+      pMem->u.i = *(i64*)&x;
+      pMem->flags = MEM_Int;
+      return 6;
+    }
+    case 6:   /* 8-byte signed integer */
+    case 7: { /* IEEE floating point */
+      u64 x;
+      u32 y;
+#if !defined(NDEBUG) && !defined(SQLITE_OMIT_FLOATING_POINT)
+      /* Verify that integers and floating point values use the same
+      ** byte order.  Or, that if SQLITE_MIXED_ENDIAN_64BIT_FLOAT is
+      ** defined that 64-bit floating point values really are mixed
+      ** endian.
+      */
+      static const u64 t1 = ((u64)0x3ff00000)<<32;
+      static const double r1 = 1.0;
+      u64 t2 = t1;
+      swapMixedEndianFloat(t2);
+      assert( sizeof(r1)==sizeof(t2) && memcmp(&r1, &t2, sizeof(r1))==0 );
+#endif
+
+      x = (buf[0]<<24) | (buf[1]<<16) | (buf[2]<<8) | buf[3];
+      y = (buf[4]<<24) | (buf[5]<<16) | (buf[6]<<8) | buf[7];
+      x = (x<<32) | y;
+      if( serial_type==6 ){
+        pMem->u.i = *(i64*)&x;
+        pMem->flags = MEM_Int;
+      }else{
+        assert( sizeof(x)==8 && sizeof(pMem->r)==8 );
+        swapMixedEndianFloat(x);
+        memcpy(&pMem->r, &x, sizeof(x));
+        pMem->flags = sqlite3IsNaN(pMem->r) ? MEM_Null : MEM_Real;
+      }
+      return 8;
+    }
+    case 8:    /* Integer 0 */
+    case 9: {  /* Integer 1 */
+      pMem->u.i = serial_type-8;
+      pMem->flags = MEM_Int;
+      return 0;
+    }
+    default: {
+      u32 len = (serial_type-12)/2;
+      pMem->z = (char *)buf;
+      pMem->n = len;
+      pMem->xDel = 0;
+      if( serial_type&0x01 ){
+        pMem->flags = MEM_Str | MEM_Ephem;
+      }else{
+        pMem->flags = MEM_Blob | MEM_Ephem;
+      }
+      return len;
+    }
+  }
+  return 0;
+}
+
+/*
+** This routine is used to allocate sufficient space for an UnpackedRecord
+** structure large enough to be used with sqlite3VdbeRecordUnpack() if
+** the first argument is a pointer to KeyInfo structure pKeyInfo.
+**
+** The space is either allocated using sqlite3DbMallocRaw() or from within
+** the unaligned buffer passed via the second and third arguments (presumably
+** stack space). If the former, then *ppFree is set to a pointer that should
+** be eventually freed by the caller using sqlite3DbFree(). Or, if the 
+** allocation comes from the pSpace/szSpace buffer, *ppFree is set to NULL
+** before returning.
+**
+** If an OOM error occurs, NULL is returned.
+*/
+UnpackedRecord *sqlite3VdbeAllocUnpackedRecord(
+  KeyInfo *pKeyInfo,              /* Description of the record */
+  char *pSpace,                   /* Unaligned space available */
+  int szSpace,                    /* Size of pSpace[] in bytes */
+  char **ppFree                   /* OUT: Caller should free this pointer */
+){
+  UnpackedRecord *p;              /* Unpacked record to return */
+  int nOff;                       /* Increment pSpace by nOff to align it */
+  int nByte;                      /* Number of bytes required for *p */
+
+  /* We want to shift the pointer pSpace up such that it is 8-byte aligned.
+  ** Thus, we need to calculate a value, nOff, between 0 and 7, to shift 
+  ** it by.  If pSpace is already 8-byte aligned, nOff should be zero.
+  */
+  nOff = (8 - (SQLITE_PTR_TO_INT(pSpace) & 7)) & 7;
+  nByte = ROUND8(sizeof(UnpackedRecord)) + sizeof(Mem)*(pKeyInfo->nField+1);
+  if( nByte>szSpace+nOff ){
+    p = (UnpackedRecord *)sqlite3DbMallocRaw(pKeyInfo->db, nByte);
+    *ppFree = (char *)p;
+    if( !p ) return 0;
+  }else{
+    p = (UnpackedRecord*)&pSpace[nOff];
+    *ppFree = 0;
+  }
+
+  p->aMem = (Mem*)&((char*)p)[ROUND8(sizeof(UnpackedRecord))];
+  p->pKeyInfo = pKeyInfo;
+  p->nField = pKeyInfo->nField + 1;
+  return p;
+}
+
+/*
+** Given the nKey-byte encoding of a record in pKey[], populate the 
+** UnpackedRecord structure indicated by the fourth argument with the
+** contents of the decoded record.
+*/ 
+void sqlite3VdbeRecordUnpack(
+  KeyInfo *pKeyInfo,     /* Information about the record format */
+  int nKey,              /* Size of the binary record */
+  const void *pKey,      /* The binary record */
+  UnpackedRecord *p      /* Populate this structure before returning. */
+){
+  const unsigned char *aKey = (const unsigned char *)pKey;
+  int d; 
+  u32 idx;                        /* Offset in aKey[] to read from */
+  u16 u;                          /* Unsigned loop counter */
+  u32 szHdr;
+  Mem *pMem = p->aMem;
+
+  p->flags = 0;
+  assert( EIGHT_BYTE_ALIGNMENT(pMem) );
+  idx = getVarint32(aKey, szHdr);
+  d = szHdr;
+  u = 0;
+  while( idx<szHdr && u<p->nField && d<=nKey ){
+    u32 serial_type;
+
+    idx += getVarint32(&aKey[idx], serial_type);
+    pMem->enc = pKeyInfo->enc;
+    pMem->db = pKeyInfo->db;
+    /* pMem->flags = 0; // sqlite3VdbeSerialGet() will set this for us */
+    pMem->zMalloc = 0;
+    d += sqlite3VdbeSerialGet(&aKey[d], serial_type, pMem);
+    pMem++;
+    u++;
+  }
+  assert( u<=pKeyInfo->nField + 1 );
+  p->nField = u;
+}
+
+/*
+** This function compares the two table rows or index records
+** specified by {nKey1, pKey1} and pPKey2.  It returns a negative, zero
+** or positive integer if key1 is less than, equal to or 
+** greater than key2.  The {nKey1, pKey1} key must be a blob
+** created by th OP_MakeRecord opcode of the VDBE.  The pPKey2
+** key must be a parsed key such as obtained from
+** sqlite3VdbeParseRecord.
+**
+** Key1 and Key2 do not have to contain the same number of fields.
+** The key with fewer fields is usually compares less than the 
+** longer key.  However if the UNPACKED_INCRKEY flags in pPKey2 is set
+** and the common prefixes are equal, then key1 is less than key2.
+** Or if the UNPACKED_MATCH_PREFIX flag is set and the prefixes are
+** equal, then the keys are considered to be equal and
+** the parts beyond the common prefix are ignored.
+**
+** If the UNPACKED_IGNORE_ROWID flag is set, then the last byte of
+** the header of pKey1 is ignored.  It is assumed that pKey1 is
+** an index key, and thus ends with a rowid value.  The last byte
+** of the header will therefore be the serial type of the rowid:
+** one of 1, 2, 3, 4, 5, 6, 8, or 9 - the integer serial types.
+** The serial type of the final rowid will always be a single byte.
+** By ignoring this last byte of the header, we force the comparison
+** to ignore the rowid at the end of key1.
+*/
+int sqlite3VdbeRecordCompare(
+  int nKey1, const void *pKey1, /* Left key */
+  UnpackedRecord *pPKey2        /* Right key */
+){
+  int d1;            /* Offset into aKey[] of next data element */
+  u32 idx1;          /* Offset into aKey[] of next header element */
+  u32 szHdr1;        /* Number of bytes in header */
+  int i = 0;
+  int nField;
+  int rc = 0;
+  const unsigned char *aKey1 = (const unsigned char *)pKey1;
+  KeyInfo *pKeyInfo;
+  Mem mem1;
+
+  pKeyInfo = pPKey2->pKeyInfo;
+  mem1.enc = pKeyInfo->enc;
+  mem1.db = pKeyInfo->db;
+  /* mem1.flags = 0;  // Will be initialized by sqlite3VdbeSerialGet() */
+  VVA_ONLY( mem1.zMalloc = 0; ) /* Only needed by assert() statements */
+
+  /* Compilers may complain that mem1.u.i is potentially uninitialized.
+  ** We could initialize it, as shown here, to silence those complaints.
+  ** But in fact, mem1.u.i will never actually be used uninitialized, and doing 
+  ** the unnecessary initialization has a measurable negative performance
+  ** impact, since this routine is a very high runner.  And so, we choose
+  ** to ignore the compiler warnings and leave this variable uninitialized.
+  */
+  /*  mem1.u.i = 0;  // not needed, here to silence compiler warning */
+  
+  idx1 = getVarint32(aKey1, szHdr1);
+  d1 = szHdr1;
+  if( pPKey2->flags & UNPACKED_IGNORE_ROWID ){
+    szHdr1--;
+  }
+  nField = pKeyInfo->nField;
+  while( idx1<szHdr1 && i<pPKey2->nField ){
+    u32 serial_type1;
+
+    /* Read the serial types for the next element in each key. */
+    idx1 += getVarint32( aKey1+idx1, serial_type1 );
+    if( d1>=nKey1 && sqlite3VdbeSerialTypeLen(serial_type1)>0 ) break;
+
+    /* Extract the values to be compared.
+    */
+    d1 += sqlite3VdbeSerialGet(&aKey1[d1], serial_type1, &mem1);
+
+    /* Do the comparison
+    */
+    rc = sqlite3MemCompare(&mem1, &pPKey2->aMem[i],
+                           i<nField ? pKeyInfo->aColl[i] : 0);
+    if( rc!=0 ){
+      assert( mem1.zMalloc==0 );  /* See comment below */
+
+      /* Invert the result if we are using DESC sort order. */
+      if( pKeyInfo->aSortOrder && i<nField && pKeyInfo->aSortOrder[i] ){
+        rc = -rc;
+      }
+    
+      /* If the PREFIX_SEARCH flag is set and all fields except the final
+      ** rowid field were equal, then clear the PREFIX_SEARCH flag and set 
+      ** pPKey2->rowid to the value of the rowid field in (pKey1, nKey1).
+      ** This is used by the OP_IsUnique opcode.
+      */
+      if( (pPKey2->flags & UNPACKED_PREFIX_SEARCH) && i==(pPKey2->nField-1) ){
+        assert( idx1==szHdr1 && rc );
+        assert( mem1.flags & MEM_Int );
+        pPKey2->flags &= ~UNPACKED_PREFIX_SEARCH;
+        pPKey2->rowid = mem1.u.i;
+      }
+    
+      return rc;
+    }
+    i++;
+  }
+
+  /* No memory allocation is ever used on mem1.  Prove this using
+  ** the following assert().  If the assert() fails, it indicates a
+  ** memory leak and a need to call sqlite3VdbeMemRelease(&mem1).
+  */
+  assert( mem1.zMalloc==0 );
+
+  /* rc==0 here means that one of the keys ran out of fields and
+  ** all the fields up to that point were equal. If the UNPACKED_INCRKEY
+  ** flag is set, then break the tie by treating key2 as larger.
+  ** If the UPACKED_PREFIX_MATCH flag is set, then keys with common prefixes
+  ** are considered to be equal.  Otherwise, the longer key is the 
+  ** larger.  As it happens, the pPKey2 will always be the longer
+  ** if there is a difference.
+  */
+  assert( rc==0 );
+  if( pPKey2->flags & UNPACKED_INCRKEY ){
+    rc = -1;
+  }else if( pPKey2->flags & UNPACKED_PREFIX_MATCH ){
+    /* Leave rc==0 */
+  }else if( idx1<szHdr1 ){
+    rc = 1;
+  }
+  return rc;
+}
+ 
+
+/*
+** pCur points at an index entry created using the OP_MakeRecord opcode.
+** Read the rowid (the last field in the record) and store it in *rowid.
+** Return SQLITE_OK if everything works, or an error code otherwise.
+**
+** pCur might be pointing to text obtained from a corrupt database file.
+** So the content cannot be trusted.  Do appropriate checks on the content.
+*/
+int sqlite3VdbeIdxRowid(sqlite3 *db, BtCursor *pCur, i64 *rowid){
+  i64 nCellKey = 0;
+  int rc;
+  u32 szHdr;        /* Size of the header */
+  u32 typeRowid;    /* Serial type of the rowid */
+  u32 lenRowid;     /* Size of the rowid */
+  Mem m, v;
+
+  UNUSED_PARAMETER(db);
+
+  /* Get the size of the index entry.  Only indices entries of less
+  ** than 2GiB are support - anything large must be database corruption.
+  ** Any corruption is detected in sqlite3BtreeParseCellPtr(), though, so
+  ** this code can safely assume that nCellKey is 32-bits  
+  */
+  assert( sqlite3BtreeCursorIsValid(pCur) );
+  VVA_ONLY(rc =) sqlite3BtreeKeySize(pCur, &nCellKey);
+  assert( rc==SQLITE_OK );     /* pCur is always valid so KeySize cannot fail */
+  assert( (nCellKey & SQLITE_MAX_U32)==(u64)nCellKey );
+
+  /* Read in the complete content of the index entry */
+  memset(&m, 0, sizeof(m));
+  rc = sqlite3VdbeMemFromBtree(pCur, 0, (int)nCellKey, 1, &m);
+  if( rc ){
+    return rc;
+  }
+
+  /* The index entry must begin with a header size */
+  (void)getVarint32((u8*)m.z, szHdr);
+  testcase( szHdr==3 );
+  testcase( szHdr==m.n );
+  if( unlikely(szHdr<3 || (int)szHdr>m.n) ){
+    goto idx_rowid_corruption;
+  }
+
+  /* The last field of the index should be an integer - the ROWID.
+  ** Verify that the last entry really is an integer. */
+  (void)getVarint32((u8*)&m.z[szHdr-1], typeRowid);
+  testcase( typeRowid==1 );
+  testcase( typeRowid==2 );
+  testcase( typeRowid==3 );
+  testcase( typeRowid==4 );
+  testcase( typeRowid==5 );
+  testcase( typeRowid==6 );
+  testcase( typeRowid==8 );
+  testcase( typeRowid==9 );
+  if( unlikely(typeRowid<1 || typeRowid>9 || typeRowid==7) ){
+    goto idx_rowid_corruption;
+  }
+  lenRowid = sqlite3VdbeSerialTypeLen(typeRowid);
+  testcase( (u32)m.n==szHdr+lenRowid );
+  if( unlikely((u32)m.n<szHdr+lenRowid) ){
+    goto idx_rowid_corruption;
+  }
+
+  /* Fetch the integer off the end of the index record */
+  sqlite3VdbeSerialGet((u8*)&m.z[m.n-lenRowid], typeRowid, &v);
+  *rowid = v.u.i;
+  sqlite3VdbeMemRelease(&m);
+  return SQLITE_OK;
+
+  /* Jump here if database corruption is detected after m has been
+  ** allocated.  Free the m object and return SQLITE_CORRUPT. */
+idx_rowid_corruption:
+  testcase( m.zMalloc!=0 );
+  sqlite3VdbeMemRelease(&m);
+  return SQLITE_CORRUPT_BKPT;
+}
+
+/*
+** Compare the key of the index entry that cursor pC is pointing to against
+** the key string in pUnpacked.  Write into *pRes a number
+** that is negative, zero, or positive if pC is less than, equal to,
+** or greater than pUnpacked.  Return SQLITE_OK on success.
+**
+** pUnpacked is either created without a rowid or is truncated so that it
+** omits the rowid at the end.  The rowid at the end of the index entry
+** is ignored as well.  Hence, this routine only compares the prefixes 
+** of the keys prior to the final rowid, not the entire key.
+*/
+int sqlite3VdbeIdxKeyCompare(
+  VdbeCursor *pC,             /* The cursor to compare against */
+  UnpackedRecord *pUnpacked,  /* Unpacked version of key to compare against */
+  int *res                    /* Write the comparison result here */
+){
+  i64 nCellKey = 0;
+  int rc;
+  BtCursor *pCur = pC->pCursor;
+  Mem m;
+
+  assert( sqlite3BtreeCursorIsValid(pCur) );
+  VVA_ONLY(rc =) sqlite3BtreeKeySize(pCur, &nCellKey);
+  assert( rc==SQLITE_OK );    /* pCur is always valid so KeySize cannot fail */
+  /* nCellKey will always be between 0 and 0xffffffff because of the say
+  ** that btreeParseCellPtr() and sqlite3GetVarint32() are implemented */
+  if( nCellKey<=0 || nCellKey>0x7fffffff ){
+    *res = 0;
+    return SQLITE_CORRUPT_BKPT;
+  }
+  memset(&m, 0, sizeof(m));
+  rc = sqlite3VdbeMemFromBtree(pC->pCursor, 0, (int)nCellKey, 1, &m);
+  if( rc ){
+    return rc;
+  }
+  assert( pUnpacked->flags & UNPACKED_IGNORE_ROWID );
+  *res = sqlite3VdbeRecordCompare(m.n, m.z, pUnpacked);
+  sqlite3VdbeMemRelease(&m);
+  return SQLITE_OK;
+}
+
+/*
+** This routine sets the value to be returned by subsequent calls to
+** sqlite3_changes() on the database handle 'db'. 
+*/
+void sqlite3VdbeSetChanges(sqlite3 *db, int nChange){
+  assert( sqlite3_mutex_held(db->mutex) );
+  db->nChange = nChange;
+  db->nTotalChange += nChange;
+}
+
+/*
+** Set a flag in the vdbe to update the change counter when it is finalised
+** or reset.
+*/
+void sqlite3VdbeCountChanges(Vdbe *v){
+  v->changeCntOn = 1;
+}
+
+/*
+** Mark every prepared statement associated with a database connection
+** as expired.
+**
+** An expired statement means that recompilation of the statement is
+** recommend.  Statements expire when things happen that make their
+** programs obsolete.  Removing user-defined functions or collating
+** sequences, or changing an authorization function are the types of
+** things that make prepared statements obsolete.
+*/
+void sqlite3ExpirePreparedStatements(sqlite3 *db){
+  Vdbe *p;
+  for(p = db->pVdbe; p; p=p->pNext){
+    p->expired = 1;
+  }
+}
+
+/*
+** Return the database associated with the Vdbe.
+*/
+sqlite3 *sqlite3VdbeDb(Vdbe *v){
+  return v->db;
+}
+
+/*
+** Return a pointer to an sqlite3_value structure containing the value bound
+** parameter iVar of VM v. Except, if the value is an SQL NULL, return 
+** 0 instead. Unless it is NULL, apply affinity aff (one of the SQLITE_AFF_*
+** constants) to the value before returning it.
+**
+** The returned value must be freed by the caller using sqlite3ValueFree().
+*/
+sqlite3_value *sqlite3VdbeGetValue(Vdbe *v, int iVar, u8 aff){
+  assert( iVar>0 );
+  if( v ){
+    Mem *pMem = &v->aVar[iVar-1];
+    if( 0==(pMem->flags & MEM_Null) ){
+      sqlite3_value *pRet = sqlite3ValueNew(v->db);
+      if( pRet ){
+        sqlite3VdbeMemCopy((Mem *)pRet, pMem);
+        sqlite3ValueApplyAffinity(pRet, aff, SQLITE_UTF8);
+        sqlite3VdbeMemStoreType((Mem *)pRet);
+      }
+      return pRet;
+    }
+  }
+  return 0;
+}
+
+/*
+** Configure SQL variable iVar so that binding a new value to it signals
+** to sqlite3_reoptimize() that re-preparing the statement may result
+** in a better query plan.
+*/
+void sqlite3VdbeSetVarmask(Vdbe *v, int iVar){
+  assert( iVar>0 );
+  if( iVar>32 ){
+    v->expmask = 0xffffffff;
+  }else{
+    v->expmask |= ((u32)1 << (iVar-1));
+  }
+}
diff --git a/src/vdbeblob.c b/src/vdbeblob.c
new file mode 100644
index 0000000..ae77a47
--- /dev/null
+++ b/src/vdbeblob.c
@@ -0,0 +1,469 @@
+/*
+** 2007 May 1
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains code used to implement incremental BLOB I/O.
+*/
+
+#include "sqliteInt.h"
+#include "vdbeInt.h"
+
+#ifndef SQLITE_OMIT_INCRBLOB
+
+/*
+** Valid sqlite3_blob* handles point to Incrblob structures.
+*/
+typedef struct Incrblob Incrblob;
+struct Incrblob {
+  int flags;              /* Copy of "flags" passed to sqlite3_blob_open() */
+  int nByte;              /* Size of open blob, in bytes */
+  int iOffset;            /* Byte offset of blob in cursor data */
+  int iCol;               /* Table column this handle is open on */
+  BtCursor *pCsr;         /* Cursor pointing at blob row */
+  sqlite3_stmt *pStmt;    /* Statement holding cursor open */
+  sqlite3 *db;            /* The associated database */
+};
+
+
+/*
+** This function is used by both blob_open() and blob_reopen(). It seeks
+** the b-tree cursor associated with blob handle p to point to row iRow.
+** If successful, SQLITE_OK is returned and subsequent calls to
+** sqlite3_blob_read() or sqlite3_blob_write() access the specified row.
+**
+** If an error occurs, or if the specified row does not exist or does not
+** contain a value of type TEXT or BLOB in the column nominated when the
+** blob handle was opened, then an error code is returned and *pzErr may
+** be set to point to a buffer containing an error message. It is the
+** responsibility of the caller to free the error message buffer using
+** sqlite3DbFree().
+**
+** If an error does occur, then the b-tree cursor is closed. All subsequent
+** calls to sqlite3_blob_read(), blob_write() or blob_reopen() will 
+** immediately return SQLITE_ABORT.
+*/
+static int blobSeekToRow(Incrblob *p, sqlite3_int64 iRow, char **pzErr){
+  int rc;                         /* Error code */
+  char *zErr = 0;                 /* Error message */
+  Vdbe *v = (Vdbe *)p->pStmt;
+
+  /* Set the value of the SQL statements only variable to integer iRow. 
+  ** This is done directly instead of using sqlite3_bind_int64() to avoid 
+  ** triggering asserts related to mutexes.
+  */
+  assert( v->aVar[0].flags&MEM_Int );
+  v->aVar[0].u.i = iRow;
+
+  rc = sqlite3_step(p->pStmt);
+  if( rc==SQLITE_ROW ){
+    u32 type = v->apCsr[0]->aType[p->iCol];
+    if( type<12 ){
+      zErr = sqlite3MPrintf(p->db, "cannot open value of type %s",
+          type==0?"null": type==7?"real": "integer"
+      );
+      rc = SQLITE_ERROR;
+      sqlite3_finalize(p->pStmt);
+      p->pStmt = 0;
+    }else{
+      p->iOffset = v->apCsr[0]->aOffset[p->iCol];
+      p->nByte = sqlite3VdbeSerialTypeLen(type);
+      p->pCsr =  v->apCsr[0]->pCursor;
+      sqlite3BtreeEnterCursor(p->pCsr);
+      sqlite3BtreeCacheOverflow(p->pCsr);
+      sqlite3BtreeLeaveCursor(p->pCsr);
+    }
+  }
+
+  if( rc==SQLITE_ROW ){
+    rc = SQLITE_OK;
+  }else if( p->pStmt ){
+    rc = sqlite3_finalize(p->pStmt);
+    p->pStmt = 0;
+    if( rc==SQLITE_OK ){
+      zErr = sqlite3MPrintf(p->db, "no such rowid: %lld", iRow);
+      rc = SQLITE_ERROR;
+    }else{
+      zErr = sqlite3MPrintf(p->db, "%s", sqlite3_errmsg(p->db));
+    }
+  }
+
+  assert( rc!=SQLITE_OK || zErr==0 );
+  assert( rc!=SQLITE_ROW && rc!=SQLITE_DONE );
+
+  *pzErr = zErr;
+  return rc;
+}
+
+/*
+** Open a blob handle.
+*/
+int sqlite3_blob_open(
+  sqlite3* db,            /* The database connection */
+  const char *zDb,        /* The attached database containing the blob */
+  const char *zTable,     /* The table containing the blob */
+  const char *zColumn,    /* The column containing the blob */
+  sqlite_int64 iRow,      /* The row containing the glob */
+  int flags,              /* True -> read/write access, false -> read-only */
+  sqlite3_blob **ppBlob   /* Handle for accessing the blob returned here */
+){
+  int nAttempt = 0;
+  int iCol;               /* Index of zColumn in row-record */
+
+  /* This VDBE program seeks a btree cursor to the identified 
+  ** db/table/row entry. The reason for using a vdbe program instead
+  ** of writing code to use the b-tree layer directly is that the
+  ** vdbe program will take advantage of the various transaction,
+  ** locking and error handling infrastructure built into the vdbe.
+  **
+  ** After seeking the cursor, the vdbe executes an OP_ResultRow.
+  ** Code external to the Vdbe then "borrows" the b-tree cursor and
+  ** uses it to implement the blob_read(), blob_write() and 
+  ** blob_bytes() functions.
+  **
+  ** The sqlite3_blob_close() function finalizes the vdbe program,
+  ** which closes the b-tree cursor and (possibly) commits the 
+  ** transaction.
+  */
+  static const VdbeOpList openBlob[] = {
+    {OP_Transaction, 0, 0, 0},     /* 0: Start a transaction */
+    {OP_VerifyCookie, 0, 0, 0},    /* 1: Check the schema cookie */
+    {OP_TableLock, 0, 0, 0},       /* 2: Acquire a read or write lock */
+
+    /* One of the following two instructions is replaced by an OP_Noop. */
+    {OP_OpenRead, 0, 0, 0},        /* 3: Open cursor 0 for reading */
+    {OP_OpenWrite, 0, 0, 0},       /* 4: Open cursor 0 for read/write */
+
+    {OP_Variable, 1, 1, 1},        /* 5: Push the rowid to the stack */
+    {OP_NotExists, 0, 10, 1},      /* 6: Seek the cursor */
+    {OP_Column, 0, 0, 1},          /* 7  */
+    {OP_ResultRow, 1, 0, 0},       /* 8  */
+    {OP_Goto, 0, 5, 0},            /* 9  */
+    {OP_Close, 0, 0, 0},           /* 10 */
+    {OP_Halt, 0, 0, 0},            /* 11 */
+  };
+
+  int rc = SQLITE_OK;
+  char *zErr = 0;
+  Table *pTab;
+  Parse *pParse = 0;
+  Incrblob *pBlob = 0;
+
+  flags = !!flags;                /* flags = (flags ? 1 : 0); */
+  *ppBlob = 0;
+
+  sqlite3_mutex_enter(db->mutex);
+
+  pBlob = (Incrblob *)sqlite3DbMallocZero(db, sizeof(Incrblob));
+  if( !pBlob ) goto blob_open_out;
+  pParse = sqlite3StackAllocRaw(db, sizeof(*pParse));
+  if( !pParse ) goto blob_open_out;
+
+  do {
+    memset(pParse, 0, sizeof(Parse));
+    pParse->db = db;
+    sqlite3DbFree(db, zErr);
+    zErr = 0;
+
+    sqlite3BtreeEnterAll(db);
+    pTab = sqlite3LocateTable(pParse, 0, zTable, zDb);
+    if( pTab && IsVirtual(pTab) ){
+      pTab = 0;
+      sqlite3ErrorMsg(pParse, "cannot open virtual table: %s", zTable);
+    }
+#ifndef SQLITE_OMIT_VIEW
+    if( pTab && pTab->pSelect ){
+      pTab = 0;
+      sqlite3ErrorMsg(pParse, "cannot open view: %s", zTable);
+    }
+#endif
+    if( !pTab ){
+      if( pParse->zErrMsg ){
+        sqlite3DbFree(db, zErr);
+        zErr = pParse->zErrMsg;
+        pParse->zErrMsg = 0;
+      }
+      rc = SQLITE_ERROR;
+      sqlite3BtreeLeaveAll(db);
+      goto blob_open_out;
+    }
+
+    /* Now search pTab for the exact column. */
+    for(iCol=0; iCol<pTab->nCol; iCol++) {
+      if( sqlite3StrICmp(pTab->aCol[iCol].zName, zColumn)==0 ){
+        break;
+      }
+    }
+    if( iCol==pTab->nCol ){
+      sqlite3DbFree(db, zErr);
+      zErr = sqlite3MPrintf(db, "no such column: \"%s\"", zColumn);
+      rc = SQLITE_ERROR;
+      sqlite3BtreeLeaveAll(db);
+      goto blob_open_out;
+    }
+
+    /* If the value is being opened for writing, check that the
+    ** column is not indexed, and that it is not part of a foreign key. 
+    ** It is against the rules to open a column to which either of these
+    ** descriptions applies for writing.  */
+    if( flags ){
+      const char *zFault = 0;
+      Index *pIdx;
+#ifndef SQLITE_OMIT_FOREIGN_KEY
+      if( db->flags&SQLITE_ForeignKeys ){
+        /* Check that the column is not part of an FK child key definition. It
+        ** is not necessary to check if it is part of a parent key, as parent
+        ** key columns must be indexed. The check below will pick up this 
+        ** case.  */
+        FKey *pFKey;
+        for(pFKey=pTab->pFKey; pFKey; pFKey=pFKey->pNextFrom){
+          int j;
+          for(j=0; j<pFKey->nCol; j++){
+            if( pFKey->aCol[j].iFrom==iCol ){
+              zFault = "foreign key";
+            }
+          }
+        }
+      }
+#endif
+      for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+        int j;
+        for(j=0; j<pIdx->nColumn; j++){
+          if( pIdx->aiColumn[j]==iCol ){
+            zFault = "indexed";
+          }
+        }
+      }
+      if( zFault ){
+        sqlite3DbFree(db, zErr);
+        zErr = sqlite3MPrintf(db, "cannot open %s column for writing", zFault);
+        rc = SQLITE_ERROR;
+        sqlite3BtreeLeaveAll(db);
+        goto blob_open_out;
+      }
+    }
+
+    pBlob->pStmt = (sqlite3_stmt *)sqlite3VdbeCreate(db);
+    assert( pBlob->pStmt || db->mallocFailed );
+    if( pBlob->pStmt ){
+      Vdbe *v = (Vdbe *)pBlob->pStmt;
+      int iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+
+      sqlite3VdbeAddOpList(v, sizeof(openBlob)/sizeof(VdbeOpList), openBlob);
+
+
+      /* Configure the OP_Transaction */
+      sqlite3VdbeChangeP1(v, 0, iDb);
+      sqlite3VdbeChangeP2(v, 0, flags);
+
+      /* Configure the OP_VerifyCookie */
+      sqlite3VdbeChangeP1(v, 1, iDb);
+      sqlite3VdbeChangeP2(v, 1, pTab->pSchema->schema_cookie);
+      sqlite3VdbeChangeP3(v, 1, pTab->pSchema->iGeneration);
+
+      /* Make sure a mutex is held on the table to be accessed */
+      sqlite3VdbeUsesBtree(v, iDb); 
+
+      /* Configure the OP_TableLock instruction */
+#ifdef SQLITE_OMIT_SHARED_CACHE
+      sqlite3VdbeChangeToNoop(v, 2);
+#else
+      sqlite3VdbeChangeP1(v, 2, iDb);
+      sqlite3VdbeChangeP2(v, 2, pTab->tnum);
+      sqlite3VdbeChangeP3(v, 2, flags);
+      sqlite3VdbeChangeP4(v, 2, pTab->zName, P4_TRANSIENT);
+#endif
+
+      /* Remove either the OP_OpenWrite or OpenRead. Set the P2 
+      ** parameter of the other to pTab->tnum.  */
+      sqlite3VdbeChangeToNoop(v, 4 - flags);
+      sqlite3VdbeChangeP2(v, 3 + flags, pTab->tnum);
+      sqlite3VdbeChangeP3(v, 3 + flags, iDb);
+
+      /* Configure the number of columns. Configure the cursor to
+      ** think that the table has one more column than it really
+      ** does. An OP_Column to retrieve this imaginary column will
+      ** always return an SQL NULL. This is useful because it means
+      ** we can invoke OP_Column to fill in the vdbe cursors type 
+      ** and offset cache without causing any IO.
+      */
+      sqlite3VdbeChangeP4(v, 3+flags, SQLITE_INT_TO_PTR(pTab->nCol+1),P4_INT32);
+      sqlite3VdbeChangeP2(v, 7, pTab->nCol);
+      if( !db->mallocFailed ){
+        pParse->nVar = 1;
+        pParse->nMem = 1;
+        pParse->nTab = 1;
+        sqlite3VdbeMakeReady(v, pParse);
+      }
+    }
+   
+    pBlob->flags = flags;
+    pBlob->iCol = iCol;
+    pBlob->db = db;
+    sqlite3BtreeLeaveAll(db);
+    if( db->mallocFailed ){
+      goto blob_open_out;
+    }
+    sqlite3_bind_int64(pBlob->pStmt, 1, iRow);
+    rc = blobSeekToRow(pBlob, iRow, &zErr);
+  } while( (++nAttempt)<5 && rc==SQLITE_SCHEMA );
+
+blob_open_out:
+  if( rc==SQLITE_OK && db->mallocFailed==0 ){
+    *ppBlob = (sqlite3_blob *)pBlob;
+  }else{
+    if( pBlob && pBlob->pStmt ) sqlite3VdbeFinalize((Vdbe *)pBlob->pStmt);
+    sqlite3DbFree(db, pBlob);
+  }
+  sqlite3Error(db, rc, (zErr ? "%s" : 0), zErr);
+  sqlite3DbFree(db, zErr);
+  sqlite3StackFree(db, pParse);
+  rc = sqlite3ApiExit(db, rc);
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+
+/*
+** Close a blob handle that was previously created using
+** sqlite3_blob_open().
+*/
+int sqlite3_blob_close(sqlite3_blob *pBlob){
+  Incrblob *p = (Incrblob *)pBlob;
+  int rc;
+  sqlite3 *db;
+
+  if( p ){
+    db = p->db;
+    sqlite3_mutex_enter(db->mutex);
+    rc = sqlite3_finalize(p->pStmt);
+    sqlite3DbFree(db, p);
+    sqlite3_mutex_leave(db->mutex);
+  }else{
+    rc = SQLITE_OK;
+  }
+  return rc;
+}
+
+/*
+** Perform a read or write operation on a blob
+*/
+static int blobReadWrite(
+  sqlite3_blob *pBlob, 
+  void *z, 
+  int n, 
+  int iOffset, 
+  int (*xCall)(BtCursor*, u32, u32, void*)
+){
+  int rc;
+  Incrblob *p = (Incrblob *)pBlob;
+  Vdbe *v;
+  sqlite3 *db;
+
+  if( p==0 ) return SQLITE_MISUSE_BKPT;
+  db = p->db;
+  sqlite3_mutex_enter(db->mutex);
+  v = (Vdbe*)p->pStmt;
+
+  if( n<0 || iOffset<0 || (iOffset+n)>p->nByte ){
+    /* Request is out of range. Return a transient error. */
+    rc = SQLITE_ERROR;
+    sqlite3Error(db, SQLITE_ERROR, 0);
+  }else if( v==0 ){
+    /* If there is no statement handle, then the blob-handle has
+    ** already been invalidated. Return SQLITE_ABORT in this case.
+    */
+    rc = SQLITE_ABORT;
+  }else{
+    /* Call either BtreeData() or BtreePutData(). If SQLITE_ABORT is
+    ** returned, clean-up the statement handle.
+    */
+    assert( db == v->db );
+    sqlite3BtreeEnterCursor(p->pCsr);
+    rc = xCall(p->pCsr, iOffset+p->iOffset, n, z);
+    sqlite3BtreeLeaveCursor(p->pCsr);
+    if( rc==SQLITE_ABORT ){
+      sqlite3VdbeFinalize(v);
+      p->pStmt = 0;
+    }else{
+      db->errCode = rc;
+      v->rc = rc;
+    }
+  }
+  rc = sqlite3ApiExit(db, rc);
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+
+/*
+** Read data from a blob handle.
+*/
+int sqlite3_blob_read(sqlite3_blob *pBlob, void *z, int n, int iOffset){
+  return blobReadWrite(pBlob, z, n, iOffset, sqlite3BtreeData);
+}
+
+/*
+** Write data to a blob handle.
+*/
+int sqlite3_blob_write(sqlite3_blob *pBlob, const void *z, int n, int iOffset){
+  return blobReadWrite(pBlob, (void *)z, n, iOffset, sqlite3BtreePutData);
+}
+
+/*
+** Query a blob handle for the size of the data.
+**
+** The Incrblob.nByte field is fixed for the lifetime of the Incrblob
+** so no mutex is required for access.
+*/
+int sqlite3_blob_bytes(sqlite3_blob *pBlob){
+  Incrblob *p = (Incrblob *)pBlob;
+  return (p && p->pStmt) ? p->nByte : 0;
+}
+
+/*
+** Move an existing blob handle to point to a different row of the same
+** database table.
+**
+** If an error occurs, or if the specified row does not exist or does not
+** contain a blob or text value, then an error code is returned and the
+** database handle error code and message set. If this happens, then all 
+** subsequent calls to sqlite3_blob_xxx() functions (except blob_close()) 
+** immediately return SQLITE_ABORT.
+*/
+int sqlite3_blob_reopen(sqlite3_blob *pBlob, sqlite3_int64 iRow){
+  int rc;
+  Incrblob *p = (Incrblob *)pBlob;
+  sqlite3 *db;
+
+  if( p==0 ) return SQLITE_MISUSE_BKPT;
+  db = p->db;
+  sqlite3_mutex_enter(db->mutex);
+
+  if( p->pStmt==0 ){
+    /* If there is no statement handle, then the blob-handle has
+    ** already been invalidated. Return SQLITE_ABORT in this case.
+    */
+    rc = SQLITE_ABORT;
+  }else{
+    char *zErr;
+    rc = blobSeekToRow(p, iRow, &zErr);
+    if( rc!=SQLITE_OK ){
+      sqlite3Error(db, rc, (zErr ? "%s" : 0), zErr);
+      sqlite3DbFree(db, zErr);
+    }
+    assert( rc!=SQLITE_SCHEMA );
+  }
+
+  rc = sqlite3ApiExit(db, rc);
+  assert( rc==SQLITE_OK || p->pStmt==0 );
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+
+#endif /* #ifndef SQLITE_OMIT_INCRBLOB */
diff --git a/src/vdbemem.c b/src/vdbemem.c
new file mode 100644
index 0000000..e6e9156
--- /dev/null
+++ b/src/vdbemem.c
@@ -0,0 +1,1153 @@
+/*
+** 2004 May 26
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains code use to manipulate "Mem" structure.  A "Mem"
+** stores a single value in the VDBE.  Mem is an opaque structure visible
+** only within the VDBE.  Interface routines refer to a Mem using the
+** name sqlite_value
+*/
+#include "sqliteInt.h"
+#include "vdbeInt.h"
+
+/*
+** Call sqlite3VdbeMemExpandBlob() on the supplied value (type Mem*)
+** P if required.
+*/
+#define expandBlob(P) (((P)->flags&MEM_Zero)?sqlite3VdbeMemExpandBlob(P):0)
+
+/*
+** If pMem is an object with a valid string representation, this routine
+** ensures the internal encoding for the string representation is
+** 'desiredEnc', one of SQLITE_UTF8, SQLITE_UTF16LE or SQLITE_UTF16BE.
+**
+** If pMem is not a string object, or the encoding of the string
+** representation is already stored using the requested encoding, then this
+** routine is a no-op.
+**
+** SQLITE_OK is returned if the conversion is successful (or not required).
+** SQLITE_NOMEM may be returned if a malloc() fails during conversion
+** between formats.
+*/
+int sqlite3VdbeChangeEncoding(Mem *pMem, int desiredEnc){
+  int rc;
+  assert( (pMem->flags&MEM_RowSet)==0 );
+  assert( desiredEnc==SQLITE_UTF8 || desiredEnc==SQLITE_UTF16LE
+           || desiredEnc==SQLITE_UTF16BE );
+  if( !(pMem->flags&MEM_Str) || pMem->enc==desiredEnc ){
+    return SQLITE_OK;
+  }
+  assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+#ifdef SQLITE_OMIT_UTF16
+  return SQLITE_ERROR;
+#else
+
+  /* MemTranslate() may return SQLITE_OK or SQLITE_NOMEM. If NOMEM is returned,
+  ** then the encoding of the value may not have changed.
+  */
+  rc = sqlite3VdbeMemTranslate(pMem, (u8)desiredEnc);
+  assert(rc==SQLITE_OK    || rc==SQLITE_NOMEM);
+  assert(rc==SQLITE_OK    || pMem->enc!=desiredEnc);
+  assert(rc==SQLITE_NOMEM || pMem->enc==desiredEnc);
+  return rc;
+#endif
+}
+
+/*
+** Make sure pMem->z points to a writable allocation of at least 
+** n bytes.
+**
+** If the memory cell currently contains string or blob data
+** and the third argument passed to this function is true, the 
+** current content of the cell is preserved. Otherwise, it may
+** be discarded.  
+**
+** This function sets the MEM_Dyn flag and clears any xDel callback.
+** It also clears MEM_Ephem and MEM_Static. If the preserve flag is 
+** not set, Mem.n is zeroed.
+*/
+int sqlite3VdbeMemGrow(Mem *pMem, int n, int preserve){
+  assert( 1 >=
+    ((pMem->zMalloc && pMem->zMalloc==pMem->z) ? 1 : 0) +
+    (((pMem->flags&MEM_Dyn)&&pMem->xDel) ? 1 : 0) + 
+    ((pMem->flags&MEM_Ephem) ? 1 : 0) + 
+    ((pMem->flags&MEM_Static) ? 1 : 0)
+  );
+  assert( (pMem->flags&MEM_RowSet)==0 );
+
+  if( n<32 ) n = 32;
+  if( sqlite3DbMallocSize(pMem->db, pMem->zMalloc)<n ){
+    if( preserve && pMem->z==pMem->zMalloc ){
+      pMem->z = pMem->zMalloc = sqlite3DbReallocOrFree(pMem->db, pMem->z, n);
+      preserve = 0;
+    }else{
+      sqlite3DbFree(pMem->db, pMem->zMalloc);
+      pMem->zMalloc = sqlite3DbMallocRaw(pMem->db, n);
+    }
+  }
+
+  if( pMem->z && preserve && pMem->zMalloc && pMem->z!=pMem->zMalloc ){
+    memcpy(pMem->zMalloc, pMem->z, pMem->n);
+  }
+  if( pMem->flags&MEM_Dyn && pMem->xDel ){
+    pMem->xDel((void *)(pMem->z));
+  }
+
+  pMem->z = pMem->zMalloc;
+  if( pMem->z==0 ){
+    pMem->flags = MEM_Null;
+  }else{
+    pMem->flags &= ~(MEM_Ephem|MEM_Static);
+  }
+  pMem->xDel = 0;
+  return (pMem->z ? SQLITE_OK : SQLITE_NOMEM);
+}
+
+/*
+** Make the given Mem object MEM_Dyn.  In other words, make it so
+** that any TEXT or BLOB content is stored in memory obtained from
+** malloc().  In this way, we know that the memory is safe to be
+** overwritten or altered.
+**
+** Return SQLITE_OK on success or SQLITE_NOMEM if malloc fails.
+*/
+int sqlite3VdbeMemMakeWriteable(Mem *pMem){
+  int f;
+  assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+  assert( (pMem->flags&MEM_RowSet)==0 );
+  expandBlob(pMem);
+  f = pMem->flags;
+  if( (f&(MEM_Str|MEM_Blob)) && pMem->z!=pMem->zMalloc ){
+    if( sqlite3VdbeMemGrow(pMem, pMem->n + 2, 1) ){
+      return SQLITE_NOMEM;
+    }
+    pMem->z[pMem->n] = 0;
+    pMem->z[pMem->n+1] = 0;
+    pMem->flags |= MEM_Term;
+#ifdef SQLITE_DEBUG
+    pMem->pScopyFrom = 0;
+#endif
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** If the given Mem* has a zero-filled tail, turn it into an ordinary
+** blob stored in dynamically allocated space.
+*/
+#ifndef SQLITE_OMIT_INCRBLOB
+int sqlite3VdbeMemExpandBlob(Mem *pMem){
+  if( pMem->flags & MEM_Zero ){
+    int nByte;
+    assert( pMem->flags&MEM_Blob );
+    assert( (pMem->flags&MEM_RowSet)==0 );
+    assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+
+    /* Set nByte to the number of bytes required to store the expanded blob. */
+    nByte = pMem->n + pMem->u.nZero;
+    if( nByte<=0 ){
+      nByte = 1;
+    }
+    if( sqlite3VdbeMemGrow(pMem, nByte, 1) ){
+      return SQLITE_NOMEM;
+    }
+
+    memset(&pMem->z[pMem->n], 0, pMem->u.nZero);
+    pMem->n += pMem->u.nZero;
+    pMem->flags &= ~(MEM_Zero|MEM_Term);
+  }
+  return SQLITE_OK;
+}
+#endif
+
+
+/*
+** Make sure the given Mem is \u0000 terminated.
+*/
+int sqlite3VdbeMemNulTerminate(Mem *pMem){
+  assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+  if( (pMem->flags & MEM_Term)!=0 || (pMem->flags & MEM_Str)==0 ){
+    return SQLITE_OK;   /* Nothing to do */
+  }
+  if( sqlite3VdbeMemGrow(pMem, pMem->n+2, 1) ){
+    return SQLITE_NOMEM;
+  }
+  pMem->z[pMem->n] = 0;
+  pMem->z[pMem->n+1] = 0;
+  pMem->flags |= MEM_Term;
+  return SQLITE_OK;
+}
+
+/*
+** Add MEM_Str to the set of representations for the given Mem.  Numbers
+** are converted using sqlite3_snprintf().  Converting a BLOB to a string
+** is a no-op.
+**
+** Existing representations MEM_Int and MEM_Real are *not* invalidated.
+**
+** A MEM_Null value will never be passed to this function. This function is
+** used for converting values to text for returning to the user (i.e. via
+** sqlite3_value_text()), or for ensuring that values to be used as btree
+** keys are strings. In the former case a NULL pointer is returned the
+** user and the later is an internal programming error.
+*/
+int sqlite3VdbeMemStringify(Mem *pMem, int enc){
+  int rc = SQLITE_OK;
+  int fg = pMem->flags;
+  const int nByte = 32;
+
+  assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+  assert( !(fg&MEM_Zero) );
+  assert( !(fg&(MEM_Str|MEM_Blob)) );
+  assert( fg&(MEM_Int|MEM_Real) );
+  assert( (pMem->flags&MEM_RowSet)==0 );
+  assert( EIGHT_BYTE_ALIGNMENT(pMem) );
+
+
+  if( sqlite3VdbeMemGrow(pMem, nByte, 0) ){
+    return SQLITE_NOMEM;
+  }
+
+  /* For a Real or Integer, use sqlite3_mprintf() to produce the UTF-8
+  ** string representation of the value. Then, if the required encoding
+  ** is UTF-16le or UTF-16be do a translation.
+  ** 
+  ** FIX ME: It would be better if sqlite3_snprintf() could do UTF-16.
+  */
+  if( fg & MEM_Int ){
+    sqlite3_snprintf(nByte, pMem->z, "%lld", pMem->u.i);
+  }else{
+    assert( fg & MEM_Real );
+    sqlite3_snprintf(nByte, pMem->z, "%!.15g", pMem->r);
+  }
+  pMem->n = sqlite3Strlen30(pMem->z);
+  pMem->enc = SQLITE_UTF8;
+  pMem->flags |= MEM_Str|MEM_Term;
+  sqlite3VdbeChangeEncoding(pMem, enc);
+  return rc;
+}
+
+/*
+** Memory cell pMem contains the context of an aggregate function.
+** This routine calls the finalize method for that function.  The
+** result of the aggregate is stored back into pMem.
+**
+** Return SQLITE_ERROR if the finalizer reports an error.  SQLITE_OK
+** otherwise.
+*/
+int sqlite3VdbeMemFinalize(Mem *pMem, FuncDef *pFunc){
+  int rc = SQLITE_OK;
+  if( ALWAYS(pFunc && pFunc->xFinalize) ){
+    sqlite3_context ctx;
+    assert( (pMem->flags & MEM_Null)!=0 || pFunc==pMem->u.pDef );
+    assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+    memset(&ctx, 0, sizeof(ctx));
+    ctx.s.flags = MEM_Null;
+    ctx.s.db = pMem->db;
+    ctx.pMem = pMem;
+    ctx.pFunc = pFunc;
+    pFunc->xFinalize(&ctx); /* IMP: R-24505-23230 */
+    assert( 0==(pMem->flags&MEM_Dyn) && !pMem->xDel );
+    sqlite3DbFree(pMem->db, pMem->zMalloc);
+    memcpy(pMem, &ctx.s, sizeof(ctx.s));
+    rc = ctx.isError;
+  }
+  return rc;
+}
+
+/*
+** If the memory cell contains a string value that must be freed by
+** invoking an external callback, free it now. Calling this function
+** does not free any Mem.zMalloc buffer.
+*/
+void sqlite3VdbeMemReleaseExternal(Mem *p){
+  assert( p->db==0 || sqlite3_mutex_held(p->db->mutex) );
+  if( p->flags&MEM_Agg ){
+    sqlite3VdbeMemFinalize(p, p->u.pDef);
+    assert( (p->flags & MEM_Agg)==0 );
+    sqlite3VdbeMemRelease(p);
+  }else if( p->flags&MEM_Dyn && p->xDel ){
+    assert( (p->flags&MEM_RowSet)==0 );
+    p->xDel((void *)p->z);
+    p->xDel = 0;
+  }else if( p->flags&MEM_RowSet ){
+    sqlite3RowSetClear(p->u.pRowSet);
+  }else if( p->flags&MEM_Frame ){
+    sqlite3VdbeMemSetNull(p);
+  }
+}
+
+/*
+** Release any memory held by the Mem. This may leave the Mem in an
+** inconsistent state, for example with (Mem.z==0) and
+** (Mem.type==SQLITE_TEXT).
+*/
+void sqlite3VdbeMemRelease(Mem *p){
+  MemReleaseExt(p);
+  sqlite3DbFree(p->db, p->zMalloc);
+  p->z = 0;
+  p->zMalloc = 0;
+  p->xDel = 0;
+}
+
+/*
+** Convert a 64-bit IEEE double into a 64-bit signed integer.
+** If the double is too large, return 0x8000000000000000.
+**
+** Most systems appear to do this simply by assigning
+** variables and without the extra range tests.  But
+** there are reports that windows throws an expection
+** if the floating point value is out of range. (See ticket #2880.)
+** Because we do not completely understand the problem, we will
+** take the conservative approach and always do range tests
+** before attempting the conversion.
+*/
+static i64 doubleToInt64(double r){
+#ifdef SQLITE_OMIT_FLOATING_POINT
+  /* When floating-point is omitted, double and int64 are the same thing */
+  return r;
+#else
+  /*
+  ** Many compilers we encounter do not define constants for the
+  ** minimum and maximum 64-bit integers, or they define them
+  ** inconsistently.  And many do not understand the "LL" notation.
+  ** So we define our own static constants here using nothing
+  ** larger than a 32-bit integer constant.
+  */
+  static const i64 maxInt = LARGEST_INT64;
+  static const i64 minInt = SMALLEST_INT64;
+
+  if( r<(double)minInt ){
+    return minInt;
+  }else if( r>(double)maxInt ){
+    /* minInt is correct here - not maxInt.  It turns out that assigning
+    ** a very large positive number to an integer results in a very large
+    ** negative integer.  This makes no sense, but it is what x86 hardware
+    ** does so for compatibility we will do the same in software. */
+    return minInt;
+  }else{
+    return (i64)r;
+  }
+#endif
+}
+
+/*
+** Return some kind of integer value which is the best we can do
+** at representing the value that *pMem describes as an integer.
+** If pMem is an integer, then the value is exact.  If pMem is
+** a floating-point then the value returned is the integer part.
+** If pMem is a string or blob, then we make an attempt to convert
+** it into a integer and return that.  If pMem represents an
+** an SQL-NULL value, return 0.
+**
+** If pMem represents a string value, its encoding might be changed.
+*/
+i64 sqlite3VdbeIntValue(Mem *pMem){
+  int flags;
+  assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+  assert( EIGHT_BYTE_ALIGNMENT(pMem) );
+  flags = pMem->flags;
+  if( flags & MEM_Int ){
+    return pMem->u.i;
+  }else if( flags & MEM_Real ){
+    return doubleToInt64(pMem->r);
+  }else if( flags & (MEM_Str|MEM_Blob) ){
+    i64 value = 0;
+    assert( pMem->z || pMem->n==0 );
+    testcase( pMem->z==0 );
+    sqlite3Atoi64(pMem->z, &value, pMem->n, pMem->enc);
+    return value;
+  }else{
+    return 0;
+  }
+}
+
+/*
+** Return the best representation of pMem that we can get into a
+** double.  If pMem is already a double or an integer, return its
+** value.  If it is a string or blob, try to convert it to a double.
+** If it is a NULL, return 0.0.
+*/
+double sqlite3VdbeRealValue(Mem *pMem){
+  assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+  assert( EIGHT_BYTE_ALIGNMENT(pMem) );
+  if( pMem->flags & MEM_Real ){
+    return pMem->r;
+  }else if( pMem->flags & MEM_Int ){
+    return (double)pMem->u.i;
+  }else if( pMem->flags & (MEM_Str|MEM_Blob) ){
+    /* (double)0 In case of SQLITE_OMIT_FLOATING_POINT... */
+    double val = (double)0;
+    sqlite3AtoF(pMem->z, &val, pMem->n, pMem->enc);
+    return val;
+  }else{
+    /* (double)0 In case of SQLITE_OMIT_FLOATING_POINT... */
+    return (double)0;
+  }
+}
+
+/*
+** The MEM structure is already a MEM_Real.  Try to also make it a
+** MEM_Int if we can.
+*/
+void sqlite3VdbeIntegerAffinity(Mem *pMem){
+  assert( pMem->flags & MEM_Real );
+  assert( (pMem->flags & MEM_RowSet)==0 );
+  assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+  assert( EIGHT_BYTE_ALIGNMENT(pMem) );
+
+  pMem->u.i = doubleToInt64(pMem->r);
+
+  /* Only mark the value as an integer if
+  **
+  **    (1) the round-trip conversion real->int->real is a no-op, and
+  **    (2) The integer is neither the largest nor the smallest
+  **        possible integer (ticket #3922)
+  **
+  ** The second and third terms in the following conditional enforces
+  ** the second condition under the assumption that addition overflow causes
+  ** values to wrap around.  On x86 hardware, the third term is always
+  ** true and could be omitted.  But we leave it in because other
+  ** architectures might behave differently.
+  */
+  if( pMem->r==(double)pMem->u.i && pMem->u.i>SMALLEST_INT64
+      && ALWAYS(pMem->u.i<LARGEST_INT64) ){
+    pMem->flags |= MEM_Int;
+  }
+}
+
+/*
+** Convert pMem to type integer.  Invalidate any prior representations.
+*/
+int sqlite3VdbeMemIntegerify(Mem *pMem){
+  assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+  assert( (pMem->flags & MEM_RowSet)==0 );
+  assert( EIGHT_BYTE_ALIGNMENT(pMem) );
+
+  pMem->u.i = sqlite3VdbeIntValue(pMem);
+  MemSetTypeFlag(pMem, MEM_Int);
+  return SQLITE_OK;
+}
+
+/*
+** Convert pMem so that it is of type MEM_Real.
+** Invalidate any prior representations.
+*/
+int sqlite3VdbeMemRealify(Mem *pMem){
+  assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+  assert( EIGHT_BYTE_ALIGNMENT(pMem) );
+
+  pMem->r = sqlite3VdbeRealValue(pMem);
+  MemSetTypeFlag(pMem, MEM_Real);
+  return SQLITE_OK;
+}
+
+/*
+** Convert pMem so that it has types MEM_Real or MEM_Int or both.
+** Invalidate any prior representations.
+**
+** Every effort is made to force the conversion, even if the input
+** is a string that does not look completely like a number.  Convert
+** as much of the string as we can and ignore the rest.
+*/
+int sqlite3VdbeMemNumerify(Mem *pMem){
+  if( (pMem->flags & (MEM_Int|MEM_Real|MEM_Null))==0 ){
+    assert( (pMem->flags & (MEM_Blob|MEM_Str))!=0 );
+    assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+    if( 0==sqlite3Atoi64(pMem->z, &pMem->u.i, pMem->n, pMem->enc) ){
+      MemSetTypeFlag(pMem, MEM_Int);
+    }else{
+      pMem->r = sqlite3VdbeRealValue(pMem);
+      MemSetTypeFlag(pMem, MEM_Real);
+      sqlite3VdbeIntegerAffinity(pMem);
+    }
+  }
+  assert( (pMem->flags & (MEM_Int|MEM_Real|MEM_Null))!=0 );
+  pMem->flags &= ~(MEM_Str|MEM_Blob);
+  return SQLITE_OK;
+}
+
+/*
+** Delete any previous value and set the value stored in *pMem to NULL.
+*/
+void sqlite3VdbeMemSetNull(Mem *pMem){
+  if( pMem->flags & MEM_Frame ){
+    VdbeFrame *pFrame = pMem->u.pFrame;
+    pFrame->pParent = pFrame->v->pDelFrame;
+    pFrame->v->pDelFrame = pFrame;
+  }
+  if( pMem->flags & MEM_RowSet ){
+    sqlite3RowSetClear(pMem->u.pRowSet);
+  }
+  MemSetTypeFlag(pMem, MEM_Null);
+  pMem->type = SQLITE_NULL;
+}
+
+/*
+** Delete any previous value and set the value to be a BLOB of length
+** n containing all zeros.
+*/
+void sqlite3VdbeMemSetZeroBlob(Mem *pMem, int n){
+  sqlite3VdbeMemRelease(pMem);
+  pMem->flags = MEM_Blob|MEM_Zero;
+  pMem->type = SQLITE_BLOB;
+  pMem->n = 0;
+  if( n<0 ) n = 0;
+  pMem->u.nZero = n;
+  pMem->enc = SQLITE_UTF8;
+
+#ifdef SQLITE_OMIT_INCRBLOB
+  sqlite3VdbeMemGrow(pMem, n, 0);
+  if( pMem->z ){
+    pMem->n = n;
+    memset(pMem->z, 0, n);
+  }
+#endif
+}
+
+/*
+** Delete any previous value and set the value stored in *pMem to val,
+** manifest type INTEGER.
+*/
+void sqlite3VdbeMemSetInt64(Mem *pMem, i64 val){
+  sqlite3VdbeMemRelease(pMem);
+  pMem->u.i = val;
+  pMem->flags = MEM_Int;
+  pMem->type = SQLITE_INTEGER;
+}
+
+#ifndef SQLITE_OMIT_FLOATING_POINT
+/*
+** Delete any previous value and set the value stored in *pMem to val,
+** manifest type REAL.
+*/
+void sqlite3VdbeMemSetDouble(Mem *pMem, double val){
+  if( sqlite3IsNaN(val) ){
+    sqlite3VdbeMemSetNull(pMem);
+  }else{
+    sqlite3VdbeMemRelease(pMem);
+    pMem->r = val;
+    pMem->flags = MEM_Real;
+    pMem->type = SQLITE_FLOAT;
+  }
+}
+#endif
+
+/*
+** Delete any previous value and set the value of pMem to be an
+** empty boolean index.
+*/
+void sqlite3VdbeMemSetRowSet(Mem *pMem){
+  sqlite3 *db = pMem->db;
+  assert( db!=0 );
+  assert( (pMem->flags & MEM_RowSet)==0 );
+  sqlite3VdbeMemRelease(pMem);
+  pMem->zMalloc = sqlite3DbMallocRaw(db, 64);
+  if( db->mallocFailed ){
+    pMem->flags = MEM_Null;
+  }else{
+    assert( pMem->zMalloc );
+    pMem->u.pRowSet = sqlite3RowSetInit(db, pMem->zMalloc, 
+                                       sqlite3DbMallocSize(db, pMem->zMalloc));
+    assert( pMem->u.pRowSet!=0 );
+    pMem->flags = MEM_RowSet;
+  }
+}
+
+/*
+** Return true if the Mem object contains a TEXT or BLOB that is
+** too large - whose size exceeds SQLITE_MAX_LENGTH.
+*/
+int sqlite3VdbeMemTooBig(Mem *p){
+  assert( p->db!=0 );
+  if( p->flags & (MEM_Str|MEM_Blob) ){
+    int n = p->n;
+    if( p->flags & MEM_Zero ){
+      n += p->u.nZero;
+    }
+    return n>p->db->aLimit[SQLITE_LIMIT_LENGTH];
+  }
+  return 0; 
+}
+
+#ifdef SQLITE_DEBUG
+/*
+** This routine prepares a memory cell for modication by breaking
+** its link to a shallow copy and by marking any current shallow
+** copies of this cell as invalid.
+**
+** This is used for testing and debugging only - to make sure shallow
+** copies are not misused.
+*/
+void sqlite3VdbeMemPrepareToChange(Vdbe *pVdbe, Mem *pMem){
+  int i;
+  Mem *pX;
+  for(i=1, pX=&pVdbe->aMem[1]; i<=pVdbe->nMem; i++, pX++){
+    if( pX->pScopyFrom==pMem ){
+      pX->flags |= MEM_Invalid;
+      pX->pScopyFrom = 0;
+    }
+  }
+  pMem->pScopyFrom = 0;
+}
+#endif /* SQLITE_DEBUG */
+
+/*
+** Size of struct Mem not including the Mem.zMalloc member.
+*/
+#define MEMCELLSIZE (size_t)(&(((Mem *)0)->zMalloc))
+
+/*
+** Make an shallow copy of pFrom into pTo.  Prior contents of
+** pTo are freed.  The pFrom->z field is not duplicated.  If
+** pFrom->z is used, then pTo->z points to the same thing as pFrom->z
+** and flags gets srcType (either MEM_Ephem or MEM_Static).
+*/
+void sqlite3VdbeMemShallowCopy(Mem *pTo, const Mem *pFrom, int srcType){
+  assert( (pFrom->flags & MEM_RowSet)==0 );
+  MemReleaseExt(pTo);
+  memcpy(pTo, pFrom, MEMCELLSIZE);
+  pTo->xDel = 0;
+  if( (pFrom->flags&MEM_Static)==0 ){
+    pTo->flags &= ~(MEM_Dyn|MEM_Static|MEM_Ephem);
+    assert( srcType==MEM_Ephem || srcType==MEM_Static );
+    pTo->flags |= srcType;
+  }
+}
+
+/*
+** Make a full copy of pFrom into pTo.  Prior contents of pTo are
+** freed before the copy is made.
+*/
+int sqlite3VdbeMemCopy(Mem *pTo, const Mem *pFrom){
+  int rc = SQLITE_OK;
+
+  assert( (pFrom->flags & MEM_RowSet)==0 );
+  MemReleaseExt(pTo);
+  memcpy(pTo, pFrom, MEMCELLSIZE);
+  pTo->flags &= ~MEM_Dyn;
+
+  if( pTo->flags&(MEM_Str|MEM_Blob) ){
+    if( 0==(pFrom->flags&MEM_Static) ){
+      pTo->flags |= MEM_Ephem;
+      rc = sqlite3VdbeMemMakeWriteable(pTo);
+    }
+  }
+
+  return rc;
+}
+
+/*
+** Transfer the contents of pFrom to pTo. Any existing value in pTo is
+** freed. If pFrom contains ephemeral data, a copy is made.
+**
+** pFrom contains an SQL NULL when this routine returns.
+*/
+void sqlite3VdbeMemMove(Mem *pTo, Mem *pFrom){
+  assert( pFrom->db==0 || sqlite3_mutex_held(pFrom->db->mutex) );
+  assert( pTo->db==0 || sqlite3_mutex_held(pTo->db->mutex) );
+  assert( pFrom->db==0 || pTo->db==0 || pFrom->db==pTo->db );
+
+  sqlite3VdbeMemRelease(pTo);
+  memcpy(pTo, pFrom, sizeof(Mem));
+  pFrom->flags = MEM_Null;
+  pFrom->xDel = 0;
+  pFrom->zMalloc = 0;
+}
+
+/*
+** Change the value of a Mem to be a string or a BLOB.
+**
+** The memory management strategy depends on the value of the xDel
+** parameter. If the value passed is SQLITE_TRANSIENT, then the 
+** string is copied into a (possibly existing) buffer managed by the 
+** Mem structure. Otherwise, any existing buffer is freed and the
+** pointer copied.
+**
+** If the string is too large (if it exceeds the SQLITE_LIMIT_LENGTH
+** size limit) then no memory allocation occurs.  If the string can be
+** stored without allocating memory, then it is.  If a memory allocation
+** is required to store the string, then value of pMem is unchanged.  In
+** either case, SQLITE_TOOBIG is returned.
+*/
+int sqlite3VdbeMemSetStr(
+  Mem *pMem,          /* Memory cell to set to string value */
+  const char *z,      /* String pointer */
+  int n,              /* Bytes in string, or negative */
+  u8 enc,             /* Encoding of z.  0 for BLOBs */
+  void (*xDel)(void*) /* Destructor function */
+){
+  int nByte = n;      /* New value for pMem->n */
+  int iLimit;         /* Maximum allowed string or blob size */
+  u16 flags = 0;      /* New value for pMem->flags */
+
+  assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
+  assert( (pMem->flags & MEM_RowSet)==0 );
+
+  /* If z is a NULL pointer, set pMem to contain an SQL NULL. */
+  if( !z ){
+    sqlite3VdbeMemSetNull(pMem);
+    return SQLITE_OK;
+  }
+
+  if( pMem->db ){
+    iLimit = pMem->db->aLimit[SQLITE_LIMIT_LENGTH];
+  }else{
+    iLimit = SQLITE_MAX_LENGTH;
+  }
+  flags = (enc==0?MEM_Blob:MEM_Str);
+  if( nByte<0 ){
+    assert( enc!=0 );
+    if( enc==SQLITE_UTF8 ){
+      for(nByte=0; nByte<=iLimit && z[nByte]; nByte++){}
+    }else{
+      for(nByte=0; nByte<=iLimit && (z[nByte] | z[nByte+1]); nByte+=2){}
+    }
+    flags |= MEM_Term;
+  }
+
+  /* The following block sets the new values of Mem.z and Mem.xDel. It
+  ** also sets a flag in local variable "flags" to indicate the memory
+  ** management (one of MEM_Dyn or MEM_Static).
+  */
+  if( xDel==SQLITE_TRANSIENT ){
+    int nAlloc = nByte;
+    if( flags&MEM_Term ){
+      nAlloc += (enc==SQLITE_UTF8?1:2);
+    }
+    if( nByte>iLimit ){
+      return SQLITE_TOOBIG;
+    }
+    if( sqlite3VdbeMemGrow(pMem, nAlloc, 0) ){
+      return SQLITE_NOMEM;
+    }
+    memcpy(pMem->z, z, nAlloc);
+  }else if( xDel==SQLITE_DYNAMIC ){
+    sqlite3VdbeMemRelease(pMem);
+    pMem->zMalloc = pMem->z = (char *)z;
+    pMem->xDel = 0;
+  }else{
+    sqlite3VdbeMemRelease(pMem);
+    pMem->z = (char *)z;
+    pMem->xDel = xDel;
+    flags |= ((xDel==SQLITE_STATIC)?MEM_Static:MEM_Dyn);
+  }
+
+  pMem->n = nByte;
+  pMem->flags = flags;
+  pMem->enc = (enc==0 ? SQLITE_UTF8 : enc);
+  pMem->type = (enc==0 ? SQLITE_BLOB : SQLITE_TEXT);
+
+#ifndef SQLITE_OMIT_UTF16
+  if( pMem->enc!=SQLITE_UTF8 && sqlite3VdbeMemHandleBom(pMem) ){
+    return SQLITE_NOMEM;
+  }
+#endif
+
+  if( nByte>iLimit ){
+    return SQLITE_TOOBIG;
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** Compare the values contained by the two memory cells, returning
+** negative, zero or positive if pMem1 is less than, equal to, or greater
+** than pMem2. Sorting order is NULL's first, followed by numbers (integers
+** and reals) sorted numerically, followed by text ordered by the collating
+** sequence pColl and finally blob's ordered by memcmp().
+**
+** Two NULL values are considered equal by this function.
+*/
+int sqlite3MemCompare(const Mem *pMem1, const Mem *pMem2, const CollSeq *pColl){
+  int rc;
+  int f1, f2;
+  int combined_flags;
+
+  f1 = pMem1->flags;
+  f2 = pMem2->flags;
+  combined_flags = f1|f2;
+  assert( (combined_flags & MEM_RowSet)==0 );
+ 
+  /* If one value is NULL, it is less than the other. If both values
+  ** are NULL, return 0.
+  */
+  if( combined_flags&MEM_Null ){
+    return (f2&MEM_Null) - (f1&MEM_Null);
+  }
+
+  /* If one value is a number and the other is not, the number is less.
+  ** If both are numbers, compare as reals if one is a real, or as integers
+  ** if both values are integers.
+  */
+  if( combined_flags&(MEM_Int|MEM_Real) ){
+    if( !(f1&(MEM_Int|MEM_Real)) ){
+      return 1;
+    }
+    if( !(f2&(MEM_Int|MEM_Real)) ){
+      return -1;
+    }
+    if( (f1 & f2 & MEM_Int)==0 ){
+      double r1, r2;
+      if( (f1&MEM_Real)==0 ){
+        r1 = (double)pMem1->u.i;
+      }else{
+        r1 = pMem1->r;
+      }
+      if( (f2&MEM_Real)==0 ){
+        r2 = (double)pMem2->u.i;
+      }else{
+        r2 = pMem2->r;
+      }
+      if( r1<r2 ) return -1;
+      if( r1>r2 ) return 1;
+      return 0;
+    }else{
+      assert( f1&MEM_Int );
+      assert( f2&MEM_Int );
+      if( pMem1->u.i < pMem2->u.i ) return -1;
+      if( pMem1->u.i > pMem2->u.i ) return 1;
+      return 0;
+    }
+  }
+
+  /* If one value is a string and the other is a blob, the string is less.
+  ** If both are strings, compare using the collating functions.
+  */
+  if( combined_flags&MEM_Str ){
+    if( (f1 & MEM_Str)==0 ){
+      return 1;
+    }
+    if( (f2 & MEM_Str)==0 ){
+      return -1;
+    }
+
+    assert( pMem1->enc==pMem2->enc );
+    assert( pMem1->enc==SQLITE_UTF8 || 
+            pMem1->enc==SQLITE_UTF16LE || pMem1->enc==SQLITE_UTF16BE );
+
+    /* The collation sequence must be defined at this point, even if
+    ** the user deletes the collation sequence after the vdbe program is
+    ** compiled (this was not always the case).
+    */
+    assert( !pColl || pColl->xCmp );
+
+    if( pColl ){
+      if( pMem1->enc==pColl->enc ){
+        /* The strings are already in the correct encoding.  Call the
+        ** comparison function directly */
+        return pColl->xCmp(pColl->pUser,pMem1->n,pMem1->z,pMem2->n,pMem2->z);
+      }else{
+        const void *v1, *v2;
+        int n1, n2;
+        Mem c1;
+        Mem c2;
+        memset(&c1, 0, sizeof(c1));
+        memset(&c2, 0, sizeof(c2));
+        sqlite3VdbeMemShallowCopy(&c1, pMem1, MEM_Ephem);
+        sqlite3VdbeMemShallowCopy(&c2, pMem2, MEM_Ephem);
+        v1 = sqlite3ValueText((sqlite3_value*)&c1, pColl->enc);
+        n1 = v1==0 ? 0 : c1.n;
+        v2 = sqlite3ValueText((sqlite3_value*)&c2, pColl->enc);
+        n2 = v2==0 ? 0 : c2.n;
+        rc = pColl->xCmp(pColl->pUser, n1, v1, n2, v2);
+        sqlite3VdbeMemRelease(&c1);
+        sqlite3VdbeMemRelease(&c2);
+        return rc;
+      }
+    }
+    /* If a NULL pointer was passed as the collate function, fall through
+    ** to the blob case and use memcmp().  */
+  }
+ 
+  /* Both values must be blobs.  Compare using memcmp().  */
+  rc = memcmp(pMem1->z, pMem2->z, (pMem1->n>pMem2->n)?pMem2->n:pMem1->n);
+  if( rc==0 ){
+    rc = pMem1->n - pMem2->n;
+  }
+  return rc;
+}
+
+/*
+** Move data out of a btree key or data field and into a Mem structure.
+** The data or key is taken from the entry that pCur is currently pointing
+** to.  offset and amt determine what portion of the data or key to retrieve.
+** key is true to get the key or false to get data.  The result is written
+** into the pMem element.
+**
+** The pMem structure is assumed to be uninitialized.  Any prior content
+** is overwritten without being freed.
+**
+** If this routine fails for any reason (malloc returns NULL or unable
+** to read from the disk) then the pMem is left in an inconsistent state.
+*/
+int sqlite3VdbeMemFromBtree(
+  BtCursor *pCur,   /* Cursor pointing at record to retrieve. */
+  int offset,       /* Offset from the start of data to return bytes from. */
+  int amt,          /* Number of bytes to return. */
+  int key,          /* If true, retrieve from the btree key, not data. */
+  Mem *pMem         /* OUT: Return data in this Mem structure. */
+){
+  char *zData;        /* Data from the btree layer */
+  int available = 0;  /* Number of bytes available on the local btree page */
+  int rc = SQLITE_OK; /* Return code */
+
+  assert( sqlite3BtreeCursorIsValid(pCur) );
+
+  /* Note: the calls to BtreeKeyFetch() and DataFetch() below assert() 
+  ** that both the BtShared and database handle mutexes are held. */
+  assert( (pMem->flags & MEM_RowSet)==0 );
+  if( key ){
+    zData = (char *)sqlite3BtreeKeyFetch(pCur, &available);
+  }else{
+    zData = (char *)sqlite3BtreeDataFetch(pCur, &available);
+  }
+  assert( zData!=0 );
+
+  if( offset+amt<=available && (pMem->flags&MEM_Dyn)==0 ){
+    sqlite3VdbeMemRelease(pMem);
+    pMem->z = &zData[offset];
+    pMem->flags = MEM_Blob|MEM_Ephem;
+  }else if( SQLITE_OK==(rc = sqlite3VdbeMemGrow(pMem, amt+2, 0)) ){
+    pMem->flags = MEM_Blob|MEM_Dyn|MEM_Term;
+    pMem->enc = 0;
+    pMem->type = SQLITE_BLOB;
+    if( key ){
+      rc = sqlite3BtreeKey(pCur, offset, amt, pMem->z);
+    }else{
+      rc = sqlite3BtreeData(pCur, offset, amt, pMem->z);
+    }
+    pMem->z[amt] = 0;
+    pMem->z[amt+1] = 0;
+    if( rc!=SQLITE_OK ){
+      sqlite3VdbeMemRelease(pMem);
+    }
+  }
+  pMem->n = amt;
+
+  return rc;
+}
+
+/* This function is only available internally, it is not part of the
+** external API. It works in a similar way to sqlite3_value_text(),
+** except the data returned is in the encoding specified by the second
+** parameter, which must be one of SQLITE_UTF16BE, SQLITE_UTF16LE or
+** SQLITE_UTF8.
+**
+** (2006-02-16:)  The enc value can be or-ed with SQLITE_UTF16_ALIGNED.
+** If that is the case, then the result must be aligned on an even byte
+** boundary.
+*/
+const void *sqlite3ValueText(sqlite3_value* pVal, u8 enc){
+  if( !pVal ) return 0;
+
+  assert( pVal->db==0 || sqlite3_mutex_held(pVal->db->mutex) );
+  assert( (enc&3)==(enc&~SQLITE_UTF16_ALIGNED) );
+  assert( (pVal->flags & MEM_RowSet)==0 );
+
+  if( pVal->flags&MEM_Null ){
+    return 0;
+  }
+  assert( (MEM_Blob>>3) == MEM_Str );
+  pVal->flags |= (pVal->flags & MEM_Blob)>>3;
+  expandBlob(pVal);
+  if( pVal->flags&MEM_Str ){
+    sqlite3VdbeChangeEncoding(pVal, enc & ~SQLITE_UTF16_ALIGNED);
+    if( (enc & SQLITE_UTF16_ALIGNED)!=0 && 1==(1&SQLITE_PTR_TO_INT(pVal->z)) ){
+      assert( (pVal->flags & (MEM_Ephem|MEM_Static))!=0 );
+      if( sqlite3VdbeMemMakeWriteable(pVal)!=SQLITE_OK ){
+        return 0;
+      }
+    }
+    sqlite3VdbeMemNulTerminate(pVal); /* IMP: R-59893-45467 */
+  }else{
+    assert( (pVal->flags&MEM_Blob)==0 );
+    sqlite3VdbeMemStringify(pVal, enc);
+    assert( 0==(1&SQLITE_PTR_TO_INT(pVal->z)) );
+  }
+  assert(pVal->enc==(enc & ~SQLITE_UTF16_ALIGNED) || pVal->db==0
+              || pVal->db->mallocFailed );
+  if( pVal->enc==(enc & ~SQLITE_UTF16_ALIGNED) ){
+    return pVal->z;
+  }else{
+    return 0;
+  }
+}
+
+/*
+** Create a new sqlite3_value object.
+*/
+sqlite3_value *sqlite3ValueNew(sqlite3 *db){
+  Mem *p = sqlite3DbMallocZero(db, sizeof(*p));
+  if( p ){
+    p->flags = MEM_Null;
+    p->type = SQLITE_NULL;
+    p->db = db;
+  }
+  return p;
+}
+
+/*
+** Create a new sqlite3_value object, containing the value of pExpr.
+**
+** This only works for very simple expressions that consist of one constant
+** token (i.e. "5", "5.1", "'a string'"). If the expression can
+** be converted directly into a value, then the value is allocated and
+** a pointer written to *ppVal. The caller is responsible for deallocating
+** the value by passing it to sqlite3ValueFree() later on. If the expression
+** cannot be converted to a value, then *ppVal is set to NULL.
+*/
+int sqlite3ValueFromExpr(
+  sqlite3 *db,              /* The database connection */
+  Expr *pExpr,              /* The expression to evaluate */
+  u8 enc,                   /* Encoding to use */
+  u8 affinity,              /* Affinity to use */
+  sqlite3_value **ppVal     /* Write the new value here */
+){
+  int op;
+  char *zVal = 0;
+  sqlite3_value *pVal = 0;
+  int negInt = 1;
+  const char *zNeg = "";
+
+  if( !pExpr ){
+    *ppVal = 0;
+    return SQLITE_OK;
+  }
+  op = pExpr->op;
+
+  /* op can only be TK_REGISTER if we have compiled with SQLITE_ENABLE_STAT3.
+  ** The ifdef here is to enable us to achieve 100% branch test coverage even
+  ** when SQLITE_ENABLE_STAT3 is omitted.
+  */
+#ifdef SQLITE_ENABLE_STAT3
+  if( op==TK_REGISTER ) op = pExpr->op2;
+#else
+  if( NEVER(op==TK_REGISTER) ) op = pExpr->op2;
+#endif
+
+  /* Handle negative integers in a single step.  This is needed in the
+  ** case when the value is -9223372036854775808.
+  */
+  if( op==TK_UMINUS
+   && (pExpr->pLeft->op==TK_INTEGER || pExpr->pLeft->op==TK_FLOAT) ){
+    pExpr = pExpr->pLeft;
+    op = pExpr->op;
+    negInt = -1;
+    zNeg = "-";
+  }
+
+  if( op==TK_STRING || op==TK_FLOAT || op==TK_INTEGER ){
+    pVal = sqlite3ValueNew(db);
+    if( pVal==0 ) goto no_mem;
+    if( ExprHasProperty(pExpr, EP_IntValue) ){
+      sqlite3VdbeMemSetInt64(pVal, (i64)pExpr->u.iValue*negInt);
+    }else{
+      zVal = sqlite3MPrintf(db, "%s%s", zNeg, pExpr->u.zToken);
+      if( zVal==0 ) goto no_mem;
+      sqlite3ValueSetStr(pVal, -1, zVal, SQLITE_UTF8, SQLITE_DYNAMIC);
+      if( op==TK_FLOAT ) pVal->type = SQLITE_FLOAT;
+    }
+    if( (op==TK_INTEGER || op==TK_FLOAT ) && affinity==SQLITE_AFF_NONE ){
+      sqlite3ValueApplyAffinity(pVal, SQLITE_AFF_NUMERIC, SQLITE_UTF8);
+    }else{
+      sqlite3ValueApplyAffinity(pVal, affinity, SQLITE_UTF8);
+    }
+    if( pVal->flags & (MEM_Int|MEM_Real) ) pVal->flags &= ~MEM_Str;
+    if( enc!=SQLITE_UTF8 ){
+      sqlite3VdbeChangeEncoding(pVal, enc);
+    }
+  }else if( op==TK_UMINUS ) {
+    /* This branch happens for multiple negative signs.  Ex: -(-5) */
+    if( SQLITE_OK==sqlite3ValueFromExpr(db,pExpr->pLeft,enc,affinity,&pVal) ){
+      sqlite3VdbeMemNumerify(pVal);
+      if( pVal->u.i==SMALLEST_INT64 ){
+        pVal->flags &= MEM_Int;
+        pVal->flags |= MEM_Real;
+        pVal->r = (double)LARGEST_INT64;
+      }else{
+        pVal->u.i = -pVal->u.i;
+      }
+      pVal->r = -pVal->r;
+      sqlite3ValueApplyAffinity(pVal, affinity, enc);
+    }
+  }else if( op==TK_NULL ){
+    pVal = sqlite3ValueNew(db);
+    if( pVal==0 ) goto no_mem;
+  }
+#ifndef SQLITE_OMIT_BLOB_LITERAL
+  else if( op==TK_BLOB ){
+    int nVal;
+    assert( pExpr->u.zToken[0]=='x' || pExpr->u.zToken[0]=='X' );
+    assert( pExpr->u.zToken[1]=='\'' );
+    pVal = sqlite3ValueNew(db);
+    if( !pVal ) goto no_mem;
+    zVal = &pExpr->u.zToken[2];
+    nVal = sqlite3Strlen30(zVal)-1;
+    assert( zVal[nVal]=='\'' );
+    sqlite3VdbeMemSetStr(pVal, sqlite3HexToBlob(db, zVal, nVal), nVal/2,
+                         0, SQLITE_DYNAMIC);
+  }
+#endif
+
+  if( pVal ){
+    sqlite3VdbeMemStoreType(pVal);
+  }
+  *ppVal = pVal;
+  return SQLITE_OK;
+
+no_mem:
+  db->mallocFailed = 1;
+  sqlite3DbFree(db, zVal);
+  sqlite3ValueFree(pVal);
+  *ppVal = 0;
+  return SQLITE_NOMEM;
+}
+
+/*
+** Change the string value of an sqlite3_value object
+*/
+void sqlite3ValueSetStr(
+  sqlite3_value *v,     /* Value to be set */
+  int n,                /* Length of string z */
+  const void *z,        /* Text of the new string */
+  u8 enc,               /* Encoding to use */
+  void (*xDel)(void*)   /* Destructor for the string */
+){
+  if( v ) sqlite3VdbeMemSetStr((Mem *)v, z, n, enc, xDel);
+}
+
+/*
+** Free an sqlite3_value object
+*/
+void sqlite3ValueFree(sqlite3_value *v){
+  if( !v ) return;
+  sqlite3VdbeMemRelease((Mem *)v);
+  sqlite3DbFree(((Mem*)v)->db, v);
+}
+
+/*
+** Return the number of bytes in the sqlite3_value object assuming
+** that it uses the encoding "enc"
+*/
+int sqlite3ValueBytes(sqlite3_value *pVal, u8 enc){
+  Mem *p = (Mem*)pVal;
+  if( (p->flags & MEM_Blob)!=0 || sqlite3ValueText(pVal, enc) ){
+    if( p->flags & MEM_Zero ){
+      return p->n + p->u.nZero;
+    }else{
+      return p->n;
+    }
+  }
+  return 0;
+}
diff --git a/src/vdbesort.c b/src/vdbesort.c
new file mode 100644
index 0000000..c449997
--- /dev/null
+++ b/src/vdbesort.c
@@ -0,0 +1,882 @@
+/*
+** 2011 July 9
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains code for the VdbeSorter object, used in concert with
+** a VdbeCursor to sort large numbers of keys (as may be required, for
+** example, by CREATE INDEX statements on tables too large to fit in main
+** memory).
+*/
+
+#include "sqliteInt.h"
+#include "vdbeInt.h"
+
+#ifndef SQLITE_OMIT_MERGE_SORT
+
+typedef struct VdbeSorterIter VdbeSorterIter;
+typedef struct SorterRecord SorterRecord;
+
+/*
+** NOTES ON DATA STRUCTURE USED FOR N-WAY MERGES:
+**
+** As keys are added to the sorter, they are written to disk in a series
+** of sorted packed-memory-arrays (PMAs). The size of each PMA is roughly
+** the same as the cache-size allowed for temporary databases. In order
+** to allow the caller to extract keys from the sorter in sorted order,
+** all PMAs currently stored on disk must be merged together. This comment
+** describes the data structure used to do so. The structure supports 
+** merging any number of arrays in a single pass with no redundant comparison 
+** operations.
+**
+** The aIter[] array contains an iterator for each of the PMAs being merged.
+** An aIter[] iterator either points to a valid key or else is at EOF. For 
+** the purposes of the paragraphs below, we assume that the array is actually 
+** N elements in size, where N is the smallest power of 2 greater to or equal 
+** to the number of iterators being merged. The extra aIter[] elements are 
+** treated as if they are empty (always at EOF).
+**
+** The aTree[] array is also N elements in size. The value of N is stored in
+** the VdbeSorter.nTree variable.
+**
+** The final (N/2) elements of aTree[] contain the results of comparing
+** pairs of iterator keys together. Element i contains the result of 
+** comparing aIter[2*i-N] and aIter[2*i-N+1]. Whichever key is smaller, the
+** aTree element is set to the index of it. 
+**
+** For the purposes of this comparison, EOF is considered greater than any
+** other key value. If the keys are equal (only possible with two EOF
+** values), it doesn't matter which index is stored.
+**
+** The (N/4) elements of aTree[] that preceed the final (N/2) described 
+** above contains the index of the smallest of each block of 4 iterators.
+** And so on. So that aTree[1] contains the index of the iterator that 
+** currently points to the smallest key value. aTree[0] is unused.
+**
+** Example:
+**
+**     aIter[0] -> Banana
+**     aIter[1] -> Feijoa
+**     aIter[2] -> Elderberry
+**     aIter[3] -> Currant
+**     aIter[4] -> Grapefruit
+**     aIter[5] -> Apple
+**     aIter[6] -> Durian
+**     aIter[7] -> EOF
+**
+**     aTree[] = { X, 5   0, 5    0, 3, 5, 6 }
+**
+** The current element is "Apple" (the value of the key indicated by 
+** iterator 5). When the Next() operation is invoked, iterator 5 will
+** be advanced to the next key in its segment. Say the next key is
+** "Eggplant":
+**
+**     aIter[5] -> Eggplant
+**
+** The contents of aTree[] are updated first by comparing the new iterator
+** 5 key to the current key of iterator 4 (still "Grapefruit"). The iterator
+** 5 value is still smaller, so aTree[6] is set to 5. And so on up the tree.
+** The value of iterator 6 - "Durian" - is now smaller than that of iterator
+** 5, so aTree[3] is set to 6. Key 0 is smaller than key 6 (Banana<Durian),
+** so the value written into element 1 of the array is 0. As follows:
+**
+**     aTree[] = { X, 0   0, 6    0, 3, 5, 6 }
+**
+** In other words, each time we advance to the next sorter element, log2(N)
+** key comparison operations are required, where N is the number of segments
+** being merged (rounded up to the next power of 2).
+*/
+struct VdbeSorter {
+  int nInMemory;                  /* Current size of pRecord list as PMA */
+  int nTree;                      /* Used size of aTree/aIter (power of 2) */
+  VdbeSorterIter *aIter;          /* Array of iterators to merge */
+  int *aTree;                     /* Current state of incremental merge */
+  i64 iWriteOff;                  /* Current write offset within file pTemp1 */
+  i64 iReadOff;                   /* Current read offset within file pTemp1 */
+  sqlite3_file *pTemp1;           /* PMA file 1 */
+  int nPMA;                       /* Number of PMAs stored in pTemp1 */
+  SorterRecord *pRecord;          /* Head of in-memory record list */
+  int mnPmaSize;                  /* Minimum PMA size, in bytes */
+  int mxPmaSize;                  /* Maximum PMA size, in bytes.  0==no limit */
+  UnpackedRecord *pUnpacked;      /* Used to unpack keys */
+};
+
+/*
+** The following type is an iterator for a PMA. It caches the current key in 
+** variables nKey/aKey. If the iterator is at EOF, pFile==0.
+*/
+struct VdbeSorterIter {
+  i64 iReadOff;                   /* Current read offset */
+  i64 iEof;                       /* 1 byte past EOF for this iterator */
+  sqlite3_file *pFile;            /* File iterator is reading from */
+  int nAlloc;                     /* Bytes of space at aAlloc */
+  u8 *aAlloc;                     /* Allocated space */
+  int nKey;                       /* Number of bytes in key */
+  u8 *aKey;                       /* Pointer to current key */
+};
+
+/*
+** A structure to store a single record. All in-memory records are connected
+** together into a linked list headed at VdbeSorter.pRecord using the 
+** SorterRecord.pNext pointer.
+*/
+struct SorterRecord {
+  void *pVal;
+  int nVal;
+  SorterRecord *pNext;
+};
+
+/* Minimum allowable value for the VdbeSorter.nWorking variable */
+#define SORTER_MIN_WORKING 10
+
+/* Maximum number of segments to merge in a single pass. */
+#define SORTER_MAX_MERGE_COUNT 16
+
+/*
+** Free all memory belonging to the VdbeSorterIter object passed as the second
+** argument. All structure fields are set to zero before returning.
+*/
+static void vdbeSorterIterZero(sqlite3 *db, VdbeSorterIter *pIter){
+  sqlite3DbFree(db, pIter->aAlloc);
+  memset(pIter, 0, sizeof(VdbeSorterIter));
+}
+
+/*
+** Advance iterator pIter to the next key in its PMA. Return SQLITE_OK if
+** no error occurs, or an SQLite error code if one does.
+*/
+static int vdbeSorterIterNext(
+  sqlite3 *db,                    /* Database handle (for sqlite3DbMalloc() ) */
+  VdbeSorterIter *pIter           /* Iterator to advance */
+){
+  int rc;                         /* Return Code */
+  int nRead;                      /* Number of bytes read */
+  int nRec = 0;                   /* Size of record in bytes */
+  int iOff = 0;                   /* Size of serialized size varint in bytes */
+
+  assert( pIter->iEof>=pIter->iReadOff );
+  if( pIter->iEof-pIter->iReadOff>5 ){
+    nRead = 5;
+  }else{
+    nRead = (int)(pIter->iEof - pIter->iReadOff);
+  }
+  if( nRead<=0 ){
+    /* This is an EOF condition */
+    vdbeSorterIterZero(db, pIter);
+    return SQLITE_OK;
+  }
+
+  rc = sqlite3OsRead(pIter->pFile, pIter->aAlloc, nRead, pIter->iReadOff);
+  if( rc==SQLITE_OK ){
+    iOff = getVarint32(pIter->aAlloc, nRec);
+    if( (iOff+nRec)>nRead ){
+      int nRead2;                   /* Number of extra bytes to read */
+      if( (iOff+nRec)>pIter->nAlloc ){
+        int nNew = pIter->nAlloc*2;
+        while( (iOff+nRec)>nNew ) nNew = nNew*2;
+        pIter->aAlloc = sqlite3DbReallocOrFree(db, pIter->aAlloc, nNew);
+        if( !pIter->aAlloc ) return SQLITE_NOMEM;
+        pIter->nAlloc = nNew;
+      }
+  
+      nRead2 = iOff + nRec - nRead;
+      rc = sqlite3OsRead(
+          pIter->pFile, &pIter->aAlloc[nRead], nRead2, pIter->iReadOff+nRead
+      );
+    }
+  }
+
+  assert( rc!=SQLITE_OK || nRec>0 );
+  pIter->iReadOff += iOff+nRec;
+  pIter->nKey = nRec;
+  pIter->aKey = &pIter->aAlloc[iOff];
+  return rc;
+}
+
+/*
+** Write a single varint, value iVal, to file-descriptor pFile. Return
+** SQLITE_OK if successful, or an SQLite error code if some error occurs.
+**
+** The value of *piOffset when this function is called is used as the byte
+** offset in file pFile to write to. Before returning, *piOffset is 
+** incremented by the number of bytes written.
+*/
+static int vdbeSorterWriteVarint(
+  sqlite3_file *pFile,            /* File to write to */
+  i64 iVal,                       /* Value to write as a varint */
+  i64 *piOffset                   /* IN/OUT: Write offset in file pFile */
+){
+  u8 aVarint[9];                  /* Buffer large enough for a varint */
+  int nVarint;                    /* Number of used bytes in varint */
+  int rc;                         /* Result of write() call */
+
+  nVarint = sqlite3PutVarint(aVarint, iVal);
+  rc = sqlite3OsWrite(pFile, aVarint, nVarint, *piOffset);
+  *piOffset += nVarint;
+
+  return rc;
+}
+
+/*
+** Read a single varint from file-descriptor pFile. Return SQLITE_OK if
+** successful, or an SQLite error code if some error occurs.
+**
+** The value of *piOffset when this function is called is used as the
+** byte offset in file pFile from whence to read the varint. If successful
+** (i.e. if no IO error occurs), then *piOffset is set to the offset of
+** the first byte past the end of the varint before returning. *piVal is
+** set to the integer value read. If an error occurs, the final values of
+** both *piOffset and *piVal are undefined.
+*/
+static int vdbeSorterReadVarint(
+  sqlite3_file *pFile,            /* File to read from */
+  i64 *piOffset,                  /* IN/OUT: Read offset in pFile */
+  i64 *piVal                      /* OUT: Value read from file */
+){
+  u8 aVarint[9];                  /* Buffer large enough for a varint */
+  i64 iOff = *piOffset;           /* Offset in file to read from */
+  int rc;                         /* Return code */
+
+  rc = sqlite3OsRead(pFile, aVarint, 9, iOff);
+  if( rc==SQLITE_OK ){
+    *piOffset += getVarint(aVarint, (u64 *)piVal);
+  }
+
+  return rc;
+}
+
+/*
+** Initialize iterator pIter to scan through the PMA stored in file pFile
+** starting at offset iStart and ending at offset iEof-1. This function 
+** leaves the iterator pointing to the first key in the PMA (or EOF if the 
+** PMA is empty).
+*/
+static int vdbeSorterIterInit(
+  sqlite3 *db,                    /* Database handle */
+  VdbeSorter *pSorter,            /* Sorter object */
+  i64 iStart,                     /* Start offset in pFile */
+  VdbeSorterIter *pIter,          /* Iterator to populate */
+  i64 *pnByte                     /* IN/OUT: Increment this value by PMA size */
+){
+  int rc;
+
+  assert( pSorter->iWriteOff>iStart );
+  assert( pIter->aAlloc==0 );
+  pIter->pFile = pSorter->pTemp1;
+  pIter->iReadOff = iStart;
+  pIter->nAlloc = 128;
+  pIter->aAlloc = (u8 *)sqlite3DbMallocRaw(db, pIter->nAlloc);
+  if( !pIter->aAlloc ){
+    rc = SQLITE_NOMEM;
+  }else{
+    i64 nByte;                         /* Total size of PMA in bytes */
+    rc = vdbeSorterReadVarint(pSorter->pTemp1, &pIter->iReadOff, &nByte);
+    *pnByte += nByte;
+    pIter->iEof = pIter->iReadOff + nByte;
+  }
+  if( rc==SQLITE_OK ){
+    rc = vdbeSorterIterNext(db, pIter);
+  }
+  return rc;
+}
+
+
+/*
+** Compare key1 (buffer pKey1, size nKey1 bytes) with key2 (buffer pKey2, 
+** size nKey2 bytes).  Argument pKeyInfo supplies the collation functions
+** used by the comparison. If an error occurs, return an SQLite error code.
+** Otherwise, return SQLITE_OK and set *pRes to a negative, zero or positive
+** value, depending on whether key1 is smaller, equal to or larger than key2.
+**
+** If the bOmitRowid argument is non-zero, assume both keys end in a rowid
+** field. For the purposes of the comparison, ignore it. Also, if bOmitRowid
+** is true and key1 contains even a single NULL value, it is considered to
+** be less than key2. Even if key2 also contains NULL values.
+**
+** If pKey2 is passed a NULL pointer, then it is assumed that the pCsr->aSpace
+** has been allocated and contains an unpacked record that is used as key2.
+*/
+static void vdbeSorterCompare(
+  VdbeCursor *pCsr,               /* Cursor object (for pKeyInfo) */
+  int bOmitRowid,                 /* Ignore rowid field at end of keys */
+  void *pKey1, int nKey1,         /* Left side of comparison */
+  void *pKey2, int nKey2,         /* Right side of comparison */
+  int *pRes                       /* OUT: Result of comparison */
+){
+  KeyInfo *pKeyInfo = pCsr->pKeyInfo;
+  VdbeSorter *pSorter = pCsr->pSorter;
+  UnpackedRecord *r2 = pSorter->pUnpacked;
+  int i;
+
+  if( pKey2 ){
+    sqlite3VdbeRecordUnpack(pKeyInfo, nKey2, pKey2, r2);
+  }
+
+  if( bOmitRowid ){
+    r2->nField = pKeyInfo->nField;
+    assert( r2->nField>0 );
+    for(i=0; i<r2->nField; i++){
+      if( r2->aMem[i].flags & MEM_Null ){
+        *pRes = -1;
+        return;
+      }
+    }
+    r2->flags |= UNPACKED_PREFIX_MATCH;
+  }
+
+  *pRes = sqlite3VdbeRecordCompare(nKey1, pKey1, r2);
+}
+
+/*
+** This function is called to compare two iterator keys when merging 
+** multiple b-tree segments. Parameter iOut is the index of the aTree[] 
+** value to recalculate.
+*/
+static int vdbeSorterDoCompare(VdbeCursor *pCsr, int iOut){
+  VdbeSorter *pSorter = pCsr->pSorter;
+  int i1;
+  int i2;
+  int iRes;
+  VdbeSorterIter *p1;
+  VdbeSorterIter *p2;
+
+  assert( iOut<pSorter->nTree && iOut>0 );
+
+  if( iOut>=(pSorter->nTree/2) ){
+    i1 = (iOut - pSorter->nTree/2) * 2;
+    i2 = i1 + 1;
+  }else{
+    i1 = pSorter->aTree[iOut*2];
+    i2 = pSorter->aTree[iOut*2+1];
+  }
+
+  p1 = &pSorter->aIter[i1];
+  p2 = &pSorter->aIter[i2];
+
+  if( p1->pFile==0 ){
+    iRes = i2;
+  }else if( p2->pFile==0 ){
+    iRes = i1;
+  }else{
+    int res;
+    assert( pCsr->pSorter->pUnpacked!=0 );  /* allocated in vdbeSorterMerge() */
+    vdbeSorterCompare(
+        pCsr, 0, p1->aKey, p1->nKey, p2->aKey, p2->nKey, &res
+    );
+    if( res<=0 ){
+      iRes = i1;
+    }else{
+      iRes = i2;
+    }
+  }
+
+  pSorter->aTree[iOut] = iRes;
+  return SQLITE_OK;
+}
+
+/*
+** Initialize the temporary index cursor just opened as a sorter cursor.
+*/
+int sqlite3VdbeSorterInit(sqlite3 *db, VdbeCursor *pCsr){
+  int pgsz;                       /* Page size of main database */
+  int mxCache;                    /* Cache size */
+  VdbeSorter *pSorter;            /* The new sorter */
+  char *d;                        /* Dummy */
+
+  assert( pCsr->pKeyInfo && pCsr->pBt==0 );
+  pCsr->pSorter = pSorter = sqlite3DbMallocZero(db, sizeof(VdbeSorter));
+  if( pSorter==0 ){
+    return SQLITE_NOMEM;
+  }
+  
+  pSorter->pUnpacked = sqlite3VdbeAllocUnpackedRecord(pCsr->pKeyInfo, 0, 0, &d);
+  if( pSorter->pUnpacked==0 ) return SQLITE_NOMEM;
+  assert( pSorter->pUnpacked==(UnpackedRecord *)d );
+
+  if( !sqlite3TempInMemory(db) ){
+    pgsz = sqlite3BtreeGetPageSize(db->aDb[0].pBt);
+    pSorter->mnPmaSize = SORTER_MIN_WORKING * pgsz;
+    mxCache = db->aDb[0].pSchema->cache_size;
+    if( mxCache<SORTER_MIN_WORKING ) mxCache = SORTER_MIN_WORKING;
+    pSorter->mxPmaSize = mxCache * pgsz;
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** Free the list of sorted records starting at pRecord.
+*/
+static void vdbeSorterRecordFree(sqlite3 *db, SorterRecord *pRecord){
+  SorterRecord *p;
+  SorterRecord *pNext;
+  for(p=pRecord; p; p=pNext){
+    pNext = p->pNext;
+    sqlite3DbFree(db, p);
+  }
+}
+
+/*
+** Free any cursor components allocated by sqlite3VdbeSorterXXX routines.
+*/
+void sqlite3VdbeSorterClose(sqlite3 *db, VdbeCursor *pCsr){
+  VdbeSorter *pSorter = pCsr->pSorter;
+  if( pSorter ){
+    if( pSorter->aIter ){
+      int i;
+      for(i=0; i<pSorter->nTree; i++){
+        vdbeSorterIterZero(db, &pSorter->aIter[i]);
+      }
+      sqlite3DbFree(db, pSorter->aIter);
+    }
+    if( pSorter->pTemp1 ){
+      sqlite3OsCloseFree(pSorter->pTemp1);
+    }
+    vdbeSorterRecordFree(db, pSorter->pRecord);
+    sqlite3DbFree(db, pSorter->pUnpacked);
+    sqlite3DbFree(db, pSorter);
+    pCsr->pSorter = 0;
+  }
+}
+
+/*
+** Allocate space for a file-handle and open a temporary file. If successful,
+** set *ppFile to point to the malloc'd file-handle and return SQLITE_OK.
+** Otherwise, set *ppFile to 0 and return an SQLite error code.
+*/
+static int vdbeSorterOpenTempFile(sqlite3 *db, sqlite3_file **ppFile){
+  int dummy;
+  return sqlite3OsOpenMalloc(db->pVfs, 0, ppFile,
+      SQLITE_OPEN_TEMP_JOURNAL |
+      SQLITE_OPEN_READWRITE    | SQLITE_OPEN_CREATE |
+      SQLITE_OPEN_EXCLUSIVE    | SQLITE_OPEN_DELETEONCLOSE, &dummy
+  );
+}
+
+/*
+** Merge the two sorted lists p1 and p2 into a single list.
+** Set *ppOut to the head of the new list.
+*/
+static void vdbeSorterMerge(
+  VdbeCursor *pCsr,               /* For pKeyInfo */
+  SorterRecord *p1,               /* First list to merge */
+  SorterRecord *p2,               /* Second list to merge */
+  SorterRecord **ppOut            /* OUT: Head of merged list */
+){
+  SorterRecord *pFinal = 0;
+  SorterRecord **pp = &pFinal;
+  void *pVal2 = p2 ? p2->pVal : 0;
+
+  while( p1 && p2 ){
+    int res;
+    vdbeSorterCompare(pCsr, 0, p1->pVal, p1->nVal, pVal2, p2->nVal, &res);
+    if( res<=0 ){
+      *pp = p1;
+      pp = &p1->pNext;
+      p1 = p1->pNext;
+      pVal2 = 0;
+    }else{
+      *pp = p2;
+       pp = &p2->pNext;
+      p2 = p2->pNext;
+      if( p2==0 ) break;
+      pVal2 = p2->pVal;
+    }
+  }
+  *pp = p1 ? p1 : p2;
+  *ppOut = pFinal;
+}
+
+/*
+** Sort the linked list of records headed at pCsr->pRecord. Return SQLITE_OK
+** if successful, or an SQLite error code (i.e. SQLITE_NOMEM) if an error
+** occurs.
+*/
+static int vdbeSorterSort(VdbeCursor *pCsr){
+  int i;
+  SorterRecord **aSlot;
+  SorterRecord *p;
+  VdbeSorter *pSorter = pCsr->pSorter;
+
+  aSlot = (SorterRecord **)sqlite3MallocZero(64 * sizeof(SorterRecord *));
+  if( !aSlot ){
+    return SQLITE_NOMEM;
+  }
+
+  p = pSorter->pRecord;
+  while( p ){
+    SorterRecord *pNext = p->pNext;
+    p->pNext = 0;
+    for(i=0; aSlot[i]; i++){
+      vdbeSorterMerge(pCsr, p, aSlot[i], &p);
+      aSlot[i] = 0;
+    }
+    aSlot[i] = p;
+    p = pNext;
+  }
+
+  p = 0;
+  for(i=0; i<64; i++){
+    vdbeSorterMerge(pCsr, p, aSlot[i], &p);
+  }
+  pSorter->pRecord = p;
+
+  sqlite3_free(aSlot);
+  return SQLITE_OK;
+}
+
+
+/*
+** Write the current contents of the in-memory linked-list to a PMA. Return
+** SQLITE_OK if successful, or an SQLite error code otherwise.
+**
+** The format of a PMA is:
+**
+**     * A varint. This varint contains the total number of bytes of content
+**       in the PMA (not including the varint itself).
+**
+**     * One or more records packed end-to-end in order of ascending keys. 
+**       Each record consists of a varint followed by a blob of data (the 
+**       key). The varint is the number of bytes in the blob of data.
+*/
+static int vdbeSorterListToPMA(sqlite3 *db, VdbeCursor *pCsr){
+  int rc = SQLITE_OK;             /* Return code */
+  VdbeSorter *pSorter = pCsr->pSorter;
+
+  if( pSorter->nInMemory==0 ){
+    assert( pSorter->pRecord==0 );
+    return rc;
+  }
+
+  rc = vdbeSorterSort(pCsr);
+
+  /* If the first temporary PMA file has not been opened, open it now. */
+  if( rc==SQLITE_OK && pSorter->pTemp1==0 ){
+    rc = vdbeSorterOpenTempFile(db, &pSorter->pTemp1);
+    assert( rc!=SQLITE_OK || pSorter->pTemp1 );
+    assert( pSorter->iWriteOff==0 );
+    assert( pSorter->nPMA==0 );
+  }
+
+  if( rc==SQLITE_OK ){
+    i64 iOff = pSorter->iWriteOff;
+    SorterRecord *p;
+    SorterRecord *pNext = 0;
+    static const char eightZeros[8] = { 0, 0, 0, 0, 0, 0, 0, 0 };
+
+    pSorter->nPMA++;
+    rc = vdbeSorterWriteVarint(pSorter->pTemp1, pSorter->nInMemory, &iOff);
+    for(p=pSorter->pRecord; rc==SQLITE_OK && p; p=pNext){
+      pNext = p->pNext;
+      rc = vdbeSorterWriteVarint(pSorter->pTemp1, p->nVal, &iOff);
+
+      if( rc==SQLITE_OK ){
+        rc = sqlite3OsWrite(pSorter->pTemp1, p->pVal, p->nVal, iOff);
+        iOff += p->nVal;
+      }
+
+      sqlite3DbFree(db, p);
+    }
+
+    /* This assert verifies that unless an error has occurred, the size of 
+    ** the PMA on disk is the same as the expected size stored in
+    ** pSorter->nInMemory. */ 
+    assert( rc!=SQLITE_OK || pSorter->nInMemory==(
+          iOff-pSorter->iWriteOff-sqlite3VarintLen(pSorter->nInMemory)
+    ));
+
+    pSorter->iWriteOff = iOff;
+    if( rc==SQLITE_OK ){
+      /* Terminate each file with 8 extra bytes so that from any offset
+      ** in the file we can always read 9 bytes without a SHORT_READ error */
+      rc = sqlite3OsWrite(pSorter->pTemp1, eightZeros, 8, iOff);
+    }
+    pSorter->pRecord = p;
+  }
+
+  return rc;
+}
+
+/*
+** Add a record to the sorter.
+*/
+int sqlite3VdbeSorterWrite(
+  sqlite3 *db,                    /* Database handle */
+  VdbeCursor *pCsr,               /* Sorter cursor */
+  Mem *pVal                       /* Memory cell containing record */
+){
+  VdbeSorter *pSorter = pCsr->pSorter;
+  int rc = SQLITE_OK;             /* Return Code */
+  SorterRecord *pNew;             /* New list element */
+
+  assert( pSorter );
+  pSorter->nInMemory += sqlite3VarintLen(pVal->n) + pVal->n;
+
+  pNew = (SorterRecord *)sqlite3DbMallocRaw(db, pVal->n + sizeof(SorterRecord));
+  if( pNew==0 ){
+    rc = SQLITE_NOMEM;
+  }else{
+    pNew->pVal = (void *)&pNew[1];
+    memcpy(pNew->pVal, pVal->z, pVal->n);
+    pNew->nVal = pVal->n;
+    pNew->pNext = pSorter->pRecord;
+    pSorter->pRecord = pNew;
+  }
+
+  /* See if the contents of the sorter should now be written out. They
+  ** are written out when either of the following are true:
+  **
+  **   * The total memory allocated for the in-memory list is greater 
+  **     than (page-size * cache-size), or
+  **
+  **   * The total memory allocated for the in-memory list is greater 
+  **     than (page-size * 10) and sqlite3HeapNearlyFull() returns true.
+  */
+  if( rc==SQLITE_OK && pSorter->mxPmaSize>0 && (
+        (pSorter->nInMemory>pSorter->mxPmaSize)
+     || (pSorter->nInMemory>pSorter->mnPmaSize && sqlite3HeapNearlyFull())
+  )){
+    rc = vdbeSorterListToPMA(db, pCsr);
+    pSorter->nInMemory = 0;
+  }
+
+  return rc;
+}
+
+/*
+** Helper function for sqlite3VdbeSorterRewind(). 
+*/
+static int vdbeSorterInitMerge(
+  sqlite3 *db,                    /* Database handle */
+  VdbeCursor *pCsr,               /* Cursor handle for this sorter */
+  i64 *pnByte                     /* Sum of bytes in all opened PMAs */
+){
+  VdbeSorter *pSorter = pCsr->pSorter;
+  int rc = SQLITE_OK;             /* Return code */
+  int i;                          /* Used to iterator through aIter[] */
+  i64 nByte = 0;                  /* Total bytes in all opened PMAs */
+
+  /* Initialize the iterators. */
+  for(i=0; i<SORTER_MAX_MERGE_COUNT; i++){
+    VdbeSorterIter *pIter = &pSorter->aIter[i];
+    rc = vdbeSorterIterInit(db, pSorter, pSorter->iReadOff, pIter, &nByte);
+    pSorter->iReadOff = pIter->iEof;
+    assert( rc!=SQLITE_OK || pSorter->iReadOff<=pSorter->iWriteOff );
+    if( rc!=SQLITE_OK || pSorter->iReadOff>=pSorter->iWriteOff ) break;
+  }
+
+  /* Initialize the aTree[] array. */
+  for(i=pSorter->nTree-1; rc==SQLITE_OK && i>0; i--){
+    rc = vdbeSorterDoCompare(pCsr, i);
+  }
+
+  *pnByte = nByte;
+  return rc;
+}
+
+/*
+** Once the sorter has been populated, this function is called to prepare
+** for iterating through its contents in sorted order.
+*/
+int sqlite3VdbeSorterRewind(sqlite3 *db, VdbeCursor *pCsr, int *pbEof){
+  VdbeSorter *pSorter = pCsr->pSorter;
+  int rc;                         /* Return code */
+  sqlite3_file *pTemp2 = 0;       /* Second temp file to use */
+  i64 iWrite2 = 0;                /* Write offset for pTemp2 */
+  int nIter;                      /* Number of iterators used */
+  int nByte;                      /* Bytes of space required for aIter/aTree */
+  int N = 2;                      /* Power of 2 >= nIter */
+
+  assert( pSorter );
+
+  /* If no data has been written to disk, then do not do so now. Instead,
+  ** sort the VdbeSorter.pRecord list. The vdbe layer will read data directly
+  ** from the in-memory list.  */
+  if( pSorter->nPMA==0 ){
+    *pbEof = !pSorter->pRecord;
+    assert( pSorter->aTree==0 );
+    return vdbeSorterSort(pCsr);
+  }
+
+  /* Write the current b-tree to a PMA. Close the b-tree cursor. */
+  rc = vdbeSorterListToPMA(db, pCsr);
+  if( rc!=SQLITE_OK ) return rc;
+
+  /* Allocate space for aIter[] and aTree[]. */
+  nIter = pSorter->nPMA;
+  if( nIter>SORTER_MAX_MERGE_COUNT ) nIter = SORTER_MAX_MERGE_COUNT;
+  assert( nIter>0 );
+  while( N<nIter ) N += N;
+  nByte = N * (sizeof(int) + sizeof(VdbeSorterIter));
+  pSorter->aIter = (VdbeSorterIter *)sqlite3DbMallocZero(db, nByte);
+  if( !pSorter->aIter ) return SQLITE_NOMEM;
+  pSorter->aTree = (int *)&pSorter->aIter[N];
+  pSorter->nTree = N;
+
+  do {
+    int iNew;                     /* Index of new, merged, PMA */
+
+    for(iNew=0; 
+        rc==SQLITE_OK && iNew*SORTER_MAX_MERGE_COUNT<pSorter->nPMA; 
+        iNew++
+    ){
+      i64 nWrite;                 /* Number of bytes in new PMA */
+
+      /* If there are SORTER_MAX_MERGE_COUNT or less PMAs in file pTemp1,
+      ** initialize an iterator for each of them and break out of the loop.
+      ** These iterators will be incrementally merged as the VDBE layer calls
+      ** sqlite3VdbeSorterNext().
+      **
+      ** Otherwise, if pTemp1 contains more than SORTER_MAX_MERGE_COUNT PMAs,
+      ** initialize interators for SORTER_MAX_MERGE_COUNT of them. These PMAs
+      ** are merged into a single PMA that is written to file pTemp2.
+      */
+      rc = vdbeSorterInitMerge(db, pCsr, &nWrite);
+      assert( rc!=SQLITE_OK || pSorter->aIter[ pSorter->aTree[1] ].pFile );
+      if( rc!=SQLITE_OK || pSorter->nPMA<=SORTER_MAX_MERGE_COUNT ){
+        break;
+      }
+
+      /* Open the second temp file, if it is not already open. */
+      if( pTemp2==0 ){
+        assert( iWrite2==0 );
+        rc = vdbeSorterOpenTempFile(db, &pTemp2);
+      }
+
+      if( rc==SQLITE_OK ){
+        rc = vdbeSorterWriteVarint(pTemp2, nWrite, &iWrite2);
+      }
+
+      if( rc==SQLITE_OK ){
+        int bEof = 0;
+        while( rc==SQLITE_OK && bEof==0 ){
+          int nToWrite;
+          VdbeSorterIter *pIter = &pSorter->aIter[ pSorter->aTree[1] ];
+          assert( pIter->pFile );
+          nToWrite = pIter->nKey + sqlite3VarintLen(pIter->nKey);
+          rc = sqlite3OsWrite(pTemp2, pIter->aAlloc, nToWrite, iWrite2);
+          iWrite2 += nToWrite;
+          if( rc==SQLITE_OK ){
+            rc = sqlite3VdbeSorterNext(db, pCsr, &bEof);
+          }
+        }
+      }
+    }
+
+    if( pSorter->nPMA<=SORTER_MAX_MERGE_COUNT ){
+      break;
+    }else{
+      sqlite3_file *pTmp = pSorter->pTemp1;
+      pSorter->nPMA = iNew;
+      pSorter->pTemp1 = pTemp2;
+      pTemp2 = pTmp;
+      pSorter->iWriteOff = iWrite2;
+      pSorter->iReadOff = 0;
+      iWrite2 = 0;
+    }
+  }while( rc==SQLITE_OK );
+
+  if( pTemp2 ){
+    sqlite3OsCloseFree(pTemp2);
+  }
+  *pbEof = (pSorter->aIter[pSorter->aTree[1]].pFile==0);
+  return rc;
+}
+
+/*
+** Advance to the next element in the sorter.
+*/
+int sqlite3VdbeSorterNext(sqlite3 *db, VdbeCursor *pCsr, int *pbEof){
+  VdbeSorter *pSorter = pCsr->pSorter;
+  int rc;                         /* Return code */
+
+  if( pSorter->aTree ){
+    int iPrev = pSorter->aTree[1];/* Index of iterator to advance */
+    int i;                        /* Index of aTree[] to recalculate */
+
+    rc = vdbeSorterIterNext(db, &pSorter->aIter[iPrev]);
+    for(i=(pSorter->nTree+iPrev)/2; rc==SQLITE_OK && i>0; i=i/2){
+      rc = vdbeSorterDoCompare(pCsr, i);
+    }
+
+    *pbEof = (pSorter->aIter[pSorter->aTree[1]].pFile==0);
+  }else{
+    SorterRecord *pFree = pSorter->pRecord;
+    pSorter->pRecord = pFree->pNext;
+    pFree->pNext = 0;
+    vdbeSorterRecordFree(db, pFree);
+    *pbEof = !pSorter->pRecord;
+    rc = SQLITE_OK;
+  }
+  return rc;
+}
+
+/*
+** Return a pointer to a buffer owned by the sorter that contains the 
+** current key.
+*/
+static void *vdbeSorterRowkey(
+  VdbeSorter *pSorter,            /* Sorter object */
+  int *pnKey                      /* OUT: Size of current key in bytes */
+){
+  void *pKey;
+  if( pSorter->aTree ){
+    VdbeSorterIter *pIter;
+    pIter = &pSorter->aIter[ pSorter->aTree[1] ];
+    *pnKey = pIter->nKey;
+    pKey = pIter->aKey;
+  }else{
+    *pnKey = pSorter->pRecord->nVal;
+    pKey = pSorter->pRecord->pVal;
+  }
+  return pKey;
+}
+
+/*
+** Copy the current sorter key into the memory cell pOut.
+*/
+int sqlite3VdbeSorterRowkey(VdbeCursor *pCsr, Mem *pOut){
+  VdbeSorter *pSorter = pCsr->pSorter;
+  void *pKey; int nKey;           /* Sorter key to copy into pOut */
+
+  pKey = vdbeSorterRowkey(pSorter, &nKey);
+  if( sqlite3VdbeMemGrow(pOut, nKey, 0) ){
+    return SQLITE_NOMEM;
+  }
+  pOut->n = nKey;
+  MemSetTypeFlag(pOut, MEM_Blob);
+  memcpy(pOut->z, pKey, nKey);
+
+  return SQLITE_OK;
+}
+
+/*
+** Compare the key in memory cell pVal with the key that the sorter cursor
+** passed as the first argument currently points to. For the purposes of
+** the comparison, ignore the rowid field at the end of each record.
+**
+** If an error occurs, return an SQLite error code (i.e. SQLITE_NOMEM).
+** Otherwise, set *pRes to a negative, zero or positive value if the
+** key in pVal is smaller than, equal to or larger than the current sorter
+** key.
+*/
+int sqlite3VdbeSorterCompare(
+  VdbeCursor *pCsr,               /* Sorter cursor */
+  Mem *pVal,                      /* Value to compare to current sorter key */
+  int *pRes                       /* OUT: Result of comparison */
+){
+  VdbeSorter *pSorter = pCsr->pSorter;
+  void *pKey; int nKey;           /* Sorter key to compare pVal with */
+
+  pKey = vdbeSorterRowkey(pSorter, &nKey);
+  vdbeSorterCompare(pCsr, 1, pVal->z, pVal->n, pKey, nKey, pRes);
+  return SQLITE_OK;
+}
+
+#endif /* #ifndef SQLITE_OMIT_MERGE_SORT */
diff --git a/src/vdbetrace.c b/src/vdbetrace.c
new file mode 100644
index 0000000..de123b5
--- /dev/null
+++ b/src/vdbetrace.c
@@ -0,0 +1,154 @@
+/*
+** 2009 November 25
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains code used to insert the values of host parameters
+** (aka "wildcards") into the SQL text output by sqlite3_trace().
+*/
+#include "sqliteInt.h"
+#include "vdbeInt.h"
+
+#ifndef SQLITE_OMIT_TRACE
+
+/*
+** zSql is a zero-terminated string of UTF-8 SQL text.  Return the number of
+** bytes in this text up to but excluding the first character in
+** a host parameter.  If the text contains no host parameters, return
+** the total number of bytes in the text.
+*/
+static int findNextHostParameter(const char *zSql, int *pnToken){
+  int tokenType;
+  int nTotal = 0;
+  int n;
+
+  *pnToken = 0;
+  while( zSql[0] ){
+    n = sqlite3GetToken((u8*)zSql, &tokenType);
+    assert( n>0 && tokenType!=TK_ILLEGAL );
+    if( tokenType==TK_VARIABLE ){
+      *pnToken = n;
+      break;
+    }
+    nTotal += n;
+    zSql += n;
+  }
+  return nTotal;
+}
+
+/*
+** This function returns a pointer to a nul-terminated string in memory
+** obtained from sqlite3DbMalloc(). If sqlite3.vdbeExecCnt is 1, then the
+** string contains a copy of zRawSql but with host parameters expanded to 
+** their current bindings. Or, if sqlite3.vdbeExecCnt is greater than 1, 
+** then the returned string holds a copy of zRawSql with "-- " prepended
+** to each line of text.
+**
+** The calling function is responsible for making sure the memory returned
+** is eventually freed.
+**
+** ALGORITHM:  Scan the input string looking for host parameters in any of
+** these forms:  ?, ?N, $A, @A, :A.  Take care to avoid text within
+** string literals, quoted identifier names, and comments.  For text forms,
+** the host parameter index is found by scanning the perpared
+** statement for the corresponding OP_Variable opcode.  Once the host
+** parameter index is known, locate the value in p->aVar[].  Then render
+** the value as a literal in place of the host parameter name.
+*/
+char *sqlite3VdbeExpandSql(
+  Vdbe *p,                 /* The prepared statement being evaluated */
+  const char *zRawSql      /* Raw text of the SQL statement */
+){
+  sqlite3 *db;             /* The database connection */
+  int idx = 0;             /* Index of a host parameter */
+  int nextIndex = 1;       /* Index of next ? host parameter */
+  int n;                   /* Length of a token prefix */
+  int nToken;              /* Length of the parameter token */
+  int i;                   /* Loop counter */
+  Mem *pVar;               /* Value of a host parameter */
+  StrAccum out;            /* Accumulate the output here */
+  char zBase[100];         /* Initial working space */
+
+  db = p->db;
+  sqlite3StrAccumInit(&out, zBase, sizeof(zBase), 
+                      db->aLimit[SQLITE_LIMIT_LENGTH]);
+  out.db = db;
+  if( db->vdbeExecCnt>1 ){
+    while( *zRawSql ){
+      const char *zStart = zRawSql;
+      while( *(zRawSql++)!='\n' && *zRawSql );
+      sqlite3StrAccumAppend(&out, "-- ", 3);
+      sqlite3StrAccumAppend(&out, zStart, (int)(zRawSql-zStart));
+    }
+  }else{
+    while( zRawSql[0] ){
+      n = findNextHostParameter(zRawSql, &nToken);
+      assert( n>0 );
+      sqlite3StrAccumAppend(&out, zRawSql, n);
+      zRawSql += n;
+      assert( zRawSql[0] || nToken==0 );
+      if( nToken==0 ) break;
+      if( zRawSql[0]=='?' ){
+        if( nToken>1 ){
+          assert( sqlite3Isdigit(zRawSql[1]) );
+          sqlite3GetInt32(&zRawSql[1], &idx);
+        }else{
+          idx = nextIndex;
+        }
+      }else{
+        assert( zRawSql[0]==':' || zRawSql[0]=='$' || zRawSql[0]=='@' );
+        testcase( zRawSql[0]==':' );
+        testcase( zRawSql[0]=='$' );
+        testcase( zRawSql[0]=='@' );
+        idx = sqlite3VdbeParameterIndex(p, zRawSql, nToken);
+        assert( idx>0 );
+      }
+      zRawSql += nToken;
+      nextIndex = idx + 1;
+      assert( idx>0 && idx<=p->nVar );
+      pVar = &p->aVar[idx-1];
+      if( pVar->flags & MEM_Null ){
+        sqlite3StrAccumAppend(&out, "NULL", 4);
+      }else if( pVar->flags & MEM_Int ){
+        sqlite3XPrintf(&out, "%lld", pVar->u.i);
+      }else if( pVar->flags & MEM_Real ){
+        sqlite3XPrintf(&out, "%!.15g", pVar->r);
+      }else if( pVar->flags & MEM_Str ){
+#ifndef SQLITE_OMIT_UTF16
+        u8 enc = ENC(db);
+        if( enc!=SQLITE_UTF8 ){
+          Mem utf8;
+          memset(&utf8, 0, sizeof(utf8));
+          utf8.db = db;
+          sqlite3VdbeMemSetStr(&utf8, pVar->z, pVar->n, enc, SQLITE_STATIC);
+          sqlite3VdbeChangeEncoding(&utf8, SQLITE_UTF8);
+          sqlite3XPrintf(&out, "'%.*q'", utf8.n, utf8.z);
+          sqlite3VdbeMemRelease(&utf8);
+        }else
+#endif
+        {
+          sqlite3XPrintf(&out, "'%.*q'", pVar->n, pVar->z);
+        }
+      }else if( pVar->flags & MEM_Zero ){
+        sqlite3XPrintf(&out, "zeroblob(%d)", pVar->u.nZero);
+      }else{
+        assert( pVar->flags & MEM_Blob );
+        sqlite3StrAccumAppend(&out, "x'", 2);
+        for(i=0; i<pVar->n; i++){
+          sqlite3XPrintf(&out, "%02x", pVar->z[i]&0xff);
+        }
+        sqlite3StrAccumAppend(&out, "'", 1);
+      }
+    }
+  }
+  return sqlite3StrAccumFinish(&out);
+}
+
+#endif /* #ifndef SQLITE_OMIT_TRACE */
diff --git a/src/vtab.c b/src/vtab.c
new file mode 100644
index 0000000..8119cb5
--- /dev/null
+++ b/src/vtab.c
@@ -0,0 +1,1066 @@
+/*
+** 2006 June 10
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains code used to help implement virtual tables.
+*/
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+#include "sqliteInt.h"
+
+/*
+** Before a virtual table xCreate() or xConnect() method is invoked, the
+** sqlite3.pVtabCtx member variable is set to point to an instance of
+** this struct allocated on the stack. It is used by the implementation of 
+** the sqlite3_declare_vtab() and sqlite3_vtab_config() APIs, both of which
+** are invoked only from within xCreate and xConnect methods.
+*/
+struct VtabCtx {
+  Table *pTab;
+  VTable *pVTable;
+};
+
+/*
+** The actual function that does the work of creating a new module.
+** This function implements the sqlite3_create_module() and
+** sqlite3_create_module_v2() interfaces.
+*/
+static int createModule(
+  sqlite3 *db,                    /* Database in which module is registered */
+  const char *zName,              /* Name assigned to this module */
+  const sqlite3_module *pModule,  /* The definition of the module */
+  void *pAux,                     /* Context pointer for xCreate/xConnect */
+  void (*xDestroy)(void *)        /* Module destructor function */
+){
+  int rc, nName;
+  Module *pMod;
+
+  sqlite3_mutex_enter(db->mutex);
+  nName = sqlite3Strlen30(zName);
+  pMod = (Module *)sqlite3DbMallocRaw(db, sizeof(Module) + nName + 1);
+  if( pMod ){
+    Module *pDel;
+    char *zCopy = (char *)(&pMod[1]);
+    memcpy(zCopy, zName, nName+1);
+    pMod->zName = zCopy;
+    pMod->pModule = pModule;
+    pMod->pAux = pAux;
+    pMod->xDestroy = xDestroy;
+    pDel = (Module *)sqlite3HashInsert(&db->aModule, zCopy, nName, (void*)pMod);
+    if( pDel && pDel->xDestroy ){
+      sqlite3ResetInternalSchema(db, -1);
+      pDel->xDestroy(pDel->pAux);
+    }
+    sqlite3DbFree(db, pDel);
+    if( pDel==pMod ){
+      db->mallocFailed = 1;
+    }
+  }else if( xDestroy ){
+    xDestroy(pAux);
+  }
+  rc = sqlite3ApiExit(db, SQLITE_OK);
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+
+
+/*
+** External API function used to create a new virtual-table module.
+*/
+int sqlite3_create_module(
+  sqlite3 *db,                    /* Database in which module is registered */
+  const char *zName,              /* Name assigned to this module */
+  const sqlite3_module *pModule,  /* The definition of the module */
+  void *pAux                      /* Context pointer for xCreate/xConnect */
+){
+  return createModule(db, zName, pModule, pAux, 0);
+}
+
+/*
+** External API function used to create a new virtual-table module.
+*/
+int sqlite3_create_module_v2(
+  sqlite3 *db,                    /* Database in which module is registered */
+  const char *zName,              /* Name assigned to this module */
+  const sqlite3_module *pModule,  /* The definition of the module */
+  void *pAux,                     /* Context pointer for xCreate/xConnect */
+  void (*xDestroy)(void *)        /* Module destructor function */
+){
+  return createModule(db, zName, pModule, pAux, xDestroy);
+}
+
+/*
+** Lock the virtual table so that it cannot be disconnected.
+** Locks nest.  Every lock should have a corresponding unlock.
+** If an unlock is omitted, resources leaks will occur.  
+**
+** If a disconnect is attempted while a virtual table is locked,
+** the disconnect is deferred until all locks have been removed.
+*/
+void sqlite3VtabLock(VTable *pVTab){
+  pVTab->nRef++;
+}
+
+
+/*
+** pTab is a pointer to a Table structure representing a virtual-table.
+** Return a pointer to the VTable object used by connection db to access 
+** this virtual-table, if one has been created, or NULL otherwise.
+*/
+VTable *sqlite3GetVTable(sqlite3 *db, Table *pTab){
+  VTable *pVtab;
+  assert( IsVirtual(pTab) );
+  for(pVtab=pTab->pVTable; pVtab && pVtab->db!=db; pVtab=pVtab->pNext);
+  return pVtab;
+}
+
+/*
+** Decrement the ref-count on a virtual table object. When the ref-count
+** reaches zero, call the xDisconnect() method to delete the object.
+*/
+void sqlite3VtabUnlock(VTable *pVTab){
+  sqlite3 *db = pVTab->db;
+
+  assert( db );
+  assert( pVTab->nRef>0 );
+  assert( sqlite3SafetyCheckOk(db) );
+
+  pVTab->nRef--;
+  if( pVTab->nRef==0 ){
+    sqlite3_vtab *p = pVTab->pVtab;
+    if( p ){
+      p->pModule->xDisconnect(p);
+    }
+    sqlite3DbFree(db, pVTab);
+  }
+}
+
+/*
+** Table p is a virtual table. This function moves all elements in the
+** p->pVTable list to the sqlite3.pDisconnect lists of their associated
+** database connections to be disconnected at the next opportunity. 
+** Except, if argument db is not NULL, then the entry associated with
+** connection db is left in the p->pVTable list.
+*/
+static VTable *vtabDisconnectAll(sqlite3 *db, Table *p){
+  VTable *pRet = 0;
+  VTable *pVTable = p->pVTable;
+  p->pVTable = 0;
+
+  /* Assert that the mutex (if any) associated with the BtShared database 
+  ** that contains table p is held by the caller. See header comments 
+  ** above function sqlite3VtabUnlockList() for an explanation of why
+  ** this makes it safe to access the sqlite3.pDisconnect list of any
+  ** database connection that may have an entry in the p->pVTable list.
+  */
+  assert( db==0 || sqlite3SchemaMutexHeld(db, 0, p->pSchema) );
+
+  while( pVTable ){
+    sqlite3 *db2 = pVTable->db;
+    VTable *pNext = pVTable->pNext;
+    assert( db2 );
+    if( db2==db ){
+      pRet = pVTable;
+      p->pVTable = pRet;
+      pRet->pNext = 0;
+    }else{
+      pVTable->pNext = db2->pDisconnect;
+      db2->pDisconnect = pVTable;
+    }
+    pVTable = pNext;
+  }
+
+  assert( !db || pRet );
+  return pRet;
+}
+
+
+/*
+** Disconnect all the virtual table objects in the sqlite3.pDisconnect list.
+**
+** This function may only be called when the mutexes associated with all
+** shared b-tree databases opened using connection db are held by the 
+** caller. This is done to protect the sqlite3.pDisconnect list. The
+** sqlite3.pDisconnect list is accessed only as follows:
+**
+**   1) By this function. In this case, all BtShared mutexes and the mutex
+**      associated with the database handle itself must be held.
+**
+**   2) By function vtabDisconnectAll(), when it adds a VTable entry to
+**      the sqlite3.pDisconnect list. In this case either the BtShared mutex
+**      associated with the database the virtual table is stored in is held
+**      or, if the virtual table is stored in a non-sharable database, then
+**      the database handle mutex is held.
+**
+** As a result, a sqlite3.pDisconnect cannot be accessed simultaneously 
+** by multiple threads. It is thread-safe.
+*/
+void sqlite3VtabUnlockList(sqlite3 *db){
+  VTable *p = db->pDisconnect;
+  db->pDisconnect = 0;
+
+  assert( sqlite3BtreeHoldsAllMutexes(db) );
+  assert( sqlite3_mutex_held(db->mutex) );
+
+  if( p ){
+    sqlite3ExpirePreparedStatements(db);
+    do {
+      VTable *pNext = p->pNext;
+      sqlite3VtabUnlock(p);
+      p = pNext;
+    }while( p );
+  }
+}
+
+/*
+** Clear any and all virtual-table information from the Table record.
+** This routine is called, for example, just before deleting the Table
+** record.
+**
+** Since it is a virtual-table, the Table structure contains a pointer
+** to the head of a linked list of VTable structures. Each VTable 
+** structure is associated with a single sqlite3* user of the schema.
+** The reference count of the VTable structure associated with database 
+** connection db is decremented immediately (which may lead to the 
+** structure being xDisconnected and free). Any other VTable structures
+** in the list are moved to the sqlite3.pDisconnect list of the associated 
+** database connection.
+*/
+void sqlite3VtabClear(sqlite3 *db, Table *p){
+  if( !db || db->pnBytesFreed==0 ) vtabDisconnectAll(0, p);
+  if( p->azModuleArg ){
+    int i;
+    for(i=0; i<p->nModuleArg; i++){
+      sqlite3DbFree(db, p->azModuleArg[i]);
+    }
+    sqlite3DbFree(db, p->azModuleArg);
+  }
+}
+
+/*
+** Add a new module argument to pTable->azModuleArg[].
+** The string is not copied - the pointer is stored.  The
+** string will be freed automatically when the table is
+** deleted.
+*/
+static void addModuleArgument(sqlite3 *db, Table *pTable, char *zArg){
+  int i = pTable->nModuleArg++;
+  int nBytes = sizeof(char *)*(1+pTable->nModuleArg);
+  char **azModuleArg;
+  azModuleArg = sqlite3DbRealloc(db, pTable->azModuleArg, nBytes);
+  if( azModuleArg==0 ){
+    int j;
+    for(j=0; j<i; j++){
+      sqlite3DbFree(db, pTable->azModuleArg[j]);
+    }
+    sqlite3DbFree(db, zArg);
+    sqlite3DbFree(db, pTable->azModuleArg);
+    pTable->nModuleArg = 0;
+  }else{
+    azModuleArg[i] = zArg;
+    azModuleArg[i+1] = 0;
+  }
+  pTable->azModuleArg = azModuleArg;
+}
+
+/*
+** The parser calls this routine when it first sees a CREATE VIRTUAL TABLE
+** statement.  The module name has been parsed, but the optional list
+** of parameters that follow the module name are still pending.
+*/
+void sqlite3VtabBeginParse(
+  Parse *pParse,        /* Parsing context */
+  Token *pName1,        /* Name of new table, or database name */
+  Token *pName2,        /* Name of new table or NULL */
+  Token *pModuleName    /* Name of the module for the virtual table */
+){
+  int iDb;              /* The database the table is being created in */
+  Table *pTable;        /* The new virtual table */
+  sqlite3 *db;          /* Database connection */
+
+  sqlite3StartTable(pParse, pName1, pName2, 0, 0, 1, 0);
+  pTable = pParse->pNewTable;
+  if( pTable==0 ) return;
+  assert( 0==pTable->pIndex );
+
+  db = pParse->db;
+  iDb = sqlite3SchemaToIndex(db, pTable->pSchema);
+  assert( iDb>=0 );
+
+  pTable->tabFlags |= TF_Virtual;
+  pTable->nModuleArg = 0;
+  addModuleArgument(db, pTable, sqlite3NameFromToken(db, pModuleName));
+  addModuleArgument(db, pTable, sqlite3DbStrDup(db, db->aDb[iDb].zName));
+  addModuleArgument(db, pTable, sqlite3DbStrDup(db, pTable->zName));
+  pParse->sNameToken.n = (int)(&pModuleName->z[pModuleName->n] - pName1->z);
+
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  /* Creating a virtual table invokes the authorization callback twice.
+  ** The first invocation, to obtain permission to INSERT a row into the
+  ** sqlite_master table, has already been made by sqlite3StartTable().
+  ** The second call, to obtain permission to create the table, is made now.
+  */
+  if( pTable->azModuleArg ){
+    sqlite3AuthCheck(pParse, SQLITE_CREATE_VTABLE, pTable->zName, 
+            pTable->azModuleArg[0], pParse->db->aDb[iDb].zName);
+  }
+#endif
+}
+
+/*
+** This routine takes the module argument that has been accumulating
+** in pParse->zArg[] and appends it to the list of arguments on the
+** virtual table currently under construction in pParse->pTable.
+*/
+static void addArgumentToVtab(Parse *pParse){
+  if( pParse->sArg.z && ALWAYS(pParse->pNewTable) ){
+    const char *z = (const char*)pParse->sArg.z;
+    int n = pParse->sArg.n;
+    sqlite3 *db = pParse->db;
+    addModuleArgument(db, pParse->pNewTable, sqlite3DbStrNDup(db, z, n));
+  }
+}
+
+/*
+** The parser calls this routine after the CREATE VIRTUAL TABLE statement
+** has been completely parsed.
+*/
+void sqlite3VtabFinishParse(Parse *pParse, Token *pEnd){
+  Table *pTab = pParse->pNewTable;  /* The table being constructed */
+  sqlite3 *db = pParse->db;         /* The database connection */
+
+  if( pTab==0 ) return;
+  addArgumentToVtab(pParse);
+  pParse->sArg.z = 0;
+  if( pTab->nModuleArg<1 ) return;
+  
+  /* If the CREATE VIRTUAL TABLE statement is being entered for the
+  ** first time (in other words if the virtual table is actually being
+  ** created now instead of just being read out of sqlite_master) then
+  ** do additional initialization work and store the statement text
+  ** in the sqlite_master table.
+  */
+  if( !db->init.busy ){
+    char *zStmt;
+    char *zWhere;
+    int iDb;
+    Vdbe *v;
+
+    /* Compute the complete text of the CREATE VIRTUAL TABLE statement */
+    if( pEnd ){
+      pParse->sNameToken.n = (int)(pEnd->z - pParse->sNameToken.z) + pEnd->n;
+    }
+    zStmt = sqlite3MPrintf(db, "CREATE VIRTUAL TABLE %T", &pParse->sNameToken);
+
+    /* A slot for the record has already been allocated in the 
+    ** SQLITE_MASTER table.  We just need to update that slot with all
+    ** the information we've collected.  
+    **
+    ** The VM register number pParse->regRowid holds the rowid of an
+    ** entry in the sqlite_master table tht was created for this vtab
+    ** by sqlite3StartTable().
+    */
+    iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+    sqlite3NestedParse(pParse,
+      "UPDATE %Q.%s "
+         "SET type='table', name=%Q, tbl_name=%Q, rootpage=0, sql=%Q "
+       "WHERE rowid=#%d",
+      db->aDb[iDb].zName, SCHEMA_TABLE(iDb),
+      pTab->zName,
+      pTab->zName,
+      zStmt,
+      pParse->regRowid
+    );
+    sqlite3DbFree(db, zStmt);
+    v = sqlite3GetVdbe(pParse);
+    sqlite3ChangeCookie(pParse, iDb);
+
+    sqlite3VdbeAddOp2(v, OP_Expire, 0, 0);
+    zWhere = sqlite3MPrintf(db, "name='%q' AND type='table'", pTab->zName);
+    sqlite3VdbeAddParseSchemaOp(v, iDb, zWhere);
+    sqlite3VdbeAddOp4(v, OP_VCreate, iDb, 0, 0, 
+                         pTab->zName, sqlite3Strlen30(pTab->zName) + 1);
+  }
+
+  /* If we are rereading the sqlite_master table create the in-memory
+  ** record of the table. The xConnect() method is not called until
+  ** the first time the virtual table is used in an SQL statement. This
+  ** allows a schema that contains virtual tables to be loaded before
+  ** the required virtual table implementations are registered.  */
+  else {
+    Table *pOld;
+    Schema *pSchema = pTab->pSchema;
+    const char *zName = pTab->zName;
+    int nName = sqlite3Strlen30(zName);
+    assert( sqlite3SchemaMutexHeld(db, 0, pSchema) );
+    pOld = sqlite3HashInsert(&pSchema->tblHash, zName, nName, pTab);
+    if( pOld ){
+      db->mallocFailed = 1;
+      assert( pTab==pOld );  /* Malloc must have failed inside HashInsert() */
+      return;
+    }
+    pParse->pNewTable = 0;
+  }
+}
+
+/*
+** The parser calls this routine when it sees the first token
+** of an argument to the module name in a CREATE VIRTUAL TABLE statement.
+*/
+void sqlite3VtabArgInit(Parse *pParse){
+  addArgumentToVtab(pParse);
+  pParse->sArg.z = 0;
+  pParse->sArg.n = 0;
+}
+
+/*
+** The parser calls this routine for each token after the first token
+** in an argument to the module name in a CREATE VIRTUAL TABLE statement.
+*/
+void sqlite3VtabArgExtend(Parse *pParse, Token *p){
+  Token *pArg = &pParse->sArg;
+  if( pArg->z==0 ){
+    pArg->z = p->z;
+    pArg->n = p->n;
+  }else{
+    assert(pArg->z < p->z);
+    pArg->n = (int)(&p->z[p->n] - pArg->z);
+  }
+}
+
+/*
+** Invoke a virtual table constructor (either xCreate or xConnect). The
+** pointer to the function to invoke is passed as the fourth parameter
+** to this procedure.
+*/
+static int vtabCallConstructor(
+  sqlite3 *db, 
+  Table *pTab,
+  Module *pMod,
+  int (*xConstruct)(sqlite3*,void*,int,const char*const*,sqlite3_vtab**,char**),
+  char **pzErr
+){
+  VtabCtx sCtx;
+  VTable *pVTable;
+  int rc;
+  const char *const*azArg = (const char *const*)pTab->azModuleArg;
+  int nArg = pTab->nModuleArg;
+  char *zErr = 0;
+  char *zModuleName = sqlite3MPrintf(db, "%s", pTab->zName);
+
+  if( !zModuleName ){
+    return SQLITE_NOMEM;
+  }
+
+  pVTable = sqlite3DbMallocZero(db, sizeof(VTable));
+  if( !pVTable ){
+    sqlite3DbFree(db, zModuleName);
+    return SQLITE_NOMEM;
+  }
+  pVTable->db = db;
+  pVTable->pMod = pMod;
+
+  /* Invoke the virtual table constructor */
+  assert( &db->pVtabCtx );
+  assert( xConstruct );
+  sCtx.pTab = pTab;
+  sCtx.pVTable = pVTable;
+  db->pVtabCtx = &sCtx;
+  rc = xConstruct(db, pMod->pAux, nArg, azArg, &pVTable->pVtab, &zErr);
+  db->pVtabCtx = 0;
+  if( rc==SQLITE_NOMEM ) db->mallocFailed = 1;
+
+  if( SQLITE_OK!=rc ){
+    if( zErr==0 ){
+      *pzErr = sqlite3MPrintf(db, "vtable constructor failed: %s", zModuleName);
+    }else {
+      *pzErr = sqlite3MPrintf(db, "%s", zErr);
+      sqlite3_free(zErr);
+    }
+    sqlite3DbFree(db, pVTable);
+  }else if( ALWAYS(pVTable->pVtab) ){
+    /* Justification of ALWAYS():  A correct vtab constructor must allocate
+    ** the sqlite3_vtab object if successful.  */
+    pVTable->pVtab->pModule = pMod->pModule;
+    pVTable->nRef = 1;
+    if( sCtx.pTab ){
+      const char *zFormat = "vtable constructor did not declare schema: %s";
+      *pzErr = sqlite3MPrintf(db, zFormat, pTab->zName);
+      sqlite3VtabUnlock(pVTable);
+      rc = SQLITE_ERROR;
+    }else{
+      int iCol;
+      /* If everything went according to plan, link the new VTable structure
+      ** into the linked list headed by pTab->pVTable. Then loop through the 
+      ** columns of the table to see if any of them contain the token "hidden".
+      ** If so, set the Column.isHidden flag and remove the token from
+      ** the type string.  */
+      pVTable->pNext = pTab->pVTable;
+      pTab->pVTable = pVTable;
+
+      for(iCol=0; iCol<pTab->nCol; iCol++){
+        char *zType = pTab->aCol[iCol].zType;
+        int nType;
+        int i = 0;
+        if( !zType ) continue;
+        nType = sqlite3Strlen30(zType);
+        if( sqlite3StrNICmp("hidden", zType, 6)||(zType[6] && zType[6]!=' ') ){
+          for(i=0; i<nType; i++){
+            if( (0==sqlite3StrNICmp(" hidden", &zType[i], 7))
+             && (zType[i+7]=='\0' || zType[i+7]==' ')
+            ){
+              i++;
+              break;
+            }
+          }
+        }
+        if( i<nType ){
+          int j;
+          int nDel = 6 + (zType[i+6] ? 1 : 0);
+          for(j=i; (j+nDel)<=nType; j++){
+            zType[j] = zType[j+nDel];
+          }
+          if( zType[i]=='\0' && i>0 ){
+            assert(zType[i-1]==' ');
+            zType[i-1] = '\0';
+          }
+          pTab->aCol[iCol].isHidden = 1;
+        }
+      }
+    }
+  }
+
+  sqlite3DbFree(db, zModuleName);
+  return rc;
+}
+
+/*
+** This function is invoked by the parser to call the xConnect() method
+** of the virtual table pTab. If an error occurs, an error code is returned 
+** and an error left in pParse.
+**
+** This call is a no-op if table pTab is not a virtual table.
+*/
+int sqlite3VtabCallConnect(Parse *pParse, Table *pTab){
+  sqlite3 *db = pParse->db;
+  const char *zMod;
+  Module *pMod;
+  int rc;
+
+  assert( pTab );
+  if( (pTab->tabFlags & TF_Virtual)==0 || sqlite3GetVTable(db, pTab) ){
+    return SQLITE_OK;
+  }
+
+  /* Locate the required virtual table module */
+  zMod = pTab->azModuleArg[0];
+  pMod = (Module*)sqlite3HashFind(&db->aModule, zMod, sqlite3Strlen30(zMod));
+
+  if( !pMod ){
+    const char *zModule = pTab->azModuleArg[0];
+    sqlite3ErrorMsg(pParse, "no such module: %s", zModule);
+    rc = SQLITE_ERROR;
+  }else{
+    char *zErr = 0;
+    rc = vtabCallConstructor(db, pTab, pMod, pMod->pModule->xConnect, &zErr);
+    if( rc!=SQLITE_OK ){
+      sqlite3ErrorMsg(pParse, "%s", zErr);
+    }
+    sqlite3DbFree(db, zErr);
+  }
+
+  return rc;
+}
+/*
+** Grow the db->aVTrans[] array so that there is room for at least one
+** more v-table. Return SQLITE_NOMEM if a malloc fails, or SQLITE_OK otherwise.
+*/
+static int growVTrans(sqlite3 *db){
+  const int ARRAY_INCR = 5;
+
+  /* Grow the sqlite3.aVTrans array if required */
+  if( (db->nVTrans%ARRAY_INCR)==0 ){
+    VTable **aVTrans;
+    int nBytes = sizeof(sqlite3_vtab *) * (db->nVTrans + ARRAY_INCR);
+    aVTrans = sqlite3DbRealloc(db, (void *)db->aVTrans, nBytes);
+    if( !aVTrans ){
+      return SQLITE_NOMEM;
+    }
+    memset(&aVTrans[db->nVTrans], 0, sizeof(sqlite3_vtab *)*ARRAY_INCR);
+    db->aVTrans = aVTrans;
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** Add the virtual table pVTab to the array sqlite3.aVTrans[]. Space should
+** have already been reserved using growVTrans().
+*/
+static void addToVTrans(sqlite3 *db, VTable *pVTab){
+  /* Add pVtab to the end of sqlite3.aVTrans */
+  db->aVTrans[db->nVTrans++] = pVTab;
+  sqlite3VtabLock(pVTab);
+}
+
+/*
+** This function is invoked by the vdbe to call the xCreate method
+** of the virtual table named zTab in database iDb. 
+**
+** If an error occurs, *pzErr is set to point an an English language
+** description of the error and an SQLITE_XXX error code is returned.
+** In this case the caller must call sqlite3DbFree(db, ) on *pzErr.
+*/
+int sqlite3VtabCallCreate(sqlite3 *db, int iDb, const char *zTab, char **pzErr){
+  int rc = SQLITE_OK;
+  Table *pTab;
+  Module *pMod;
+  const char *zMod;
+
+  pTab = sqlite3FindTable(db, zTab, db->aDb[iDb].zName);
+  assert( pTab && (pTab->tabFlags & TF_Virtual)!=0 && !pTab->pVTable );
+
+  /* Locate the required virtual table module */
+  zMod = pTab->azModuleArg[0];
+  pMod = (Module*)sqlite3HashFind(&db->aModule, zMod, sqlite3Strlen30(zMod));
+
+  /* If the module has been registered and includes a Create method, 
+  ** invoke it now. If the module has not been registered, return an 
+  ** error. Otherwise, do nothing.
+  */
+  if( !pMod ){
+    *pzErr = sqlite3MPrintf(db, "no such module: %s", zMod);
+    rc = SQLITE_ERROR;
+  }else{
+    rc = vtabCallConstructor(db, pTab, pMod, pMod->pModule->xCreate, pzErr);
+  }
+
+  /* Justification of ALWAYS():  The xConstructor method is required to
+  ** create a valid sqlite3_vtab if it returns SQLITE_OK. */
+  if( rc==SQLITE_OK && ALWAYS(sqlite3GetVTable(db, pTab)) ){
+    rc = growVTrans(db);
+    if( rc==SQLITE_OK ){
+      addToVTrans(db, sqlite3GetVTable(db, pTab));
+    }
+  }
+
+  return rc;
+}
+
+/*
+** This function is used to set the schema of a virtual table.  It is only
+** valid to call this function from within the xCreate() or xConnect() of a
+** virtual table module.
+*/
+int sqlite3_declare_vtab(sqlite3 *db, const char *zCreateTable){
+  Parse *pParse;
+
+  int rc = SQLITE_OK;
+  Table *pTab;
+  char *zErr = 0;
+
+  sqlite3_mutex_enter(db->mutex);
+  if( !db->pVtabCtx || !(pTab = db->pVtabCtx->pTab) ){
+    sqlite3Error(db, SQLITE_MISUSE, 0);
+    sqlite3_mutex_leave(db->mutex);
+    return SQLITE_MISUSE_BKPT;
+  }
+  assert( (pTab->tabFlags & TF_Virtual)!=0 );
+
+  pParse = sqlite3StackAllocZero(db, sizeof(*pParse));
+  if( pParse==0 ){
+    rc = SQLITE_NOMEM;
+  }else{
+    pParse->declareVtab = 1;
+    pParse->db = db;
+    pParse->nQueryLoop = 1;
+  
+    if( SQLITE_OK==sqlite3RunParser(pParse, zCreateTable, &zErr) 
+     && pParse->pNewTable
+     && !db->mallocFailed
+     && !pParse->pNewTable->pSelect
+     && (pParse->pNewTable->tabFlags & TF_Virtual)==0
+    ){
+      if( !pTab->aCol ){
+        pTab->aCol = pParse->pNewTable->aCol;
+        pTab->nCol = pParse->pNewTable->nCol;
+        pParse->pNewTable->nCol = 0;
+        pParse->pNewTable->aCol = 0;
+      }
+      db->pVtabCtx->pTab = 0;
+    }else{
+      sqlite3Error(db, SQLITE_ERROR, (zErr ? "%s" : 0), zErr);
+      sqlite3DbFree(db, zErr);
+      rc = SQLITE_ERROR;
+    }
+    pParse->declareVtab = 0;
+  
+    if( pParse->pVdbe ){
+      sqlite3VdbeFinalize(pParse->pVdbe);
+    }
+    sqlite3DeleteTable(db, pParse->pNewTable);
+    sqlite3StackFree(db, pParse);
+  }
+
+  assert( (rc&0xff)==rc );
+  rc = sqlite3ApiExit(db, rc);
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+
+/*
+** This function is invoked by the vdbe to call the xDestroy method
+** of the virtual table named zTab in database iDb. This occurs
+** when a DROP TABLE is mentioned.
+**
+** This call is a no-op if zTab is not a virtual table.
+*/
+int sqlite3VtabCallDestroy(sqlite3 *db, int iDb, const char *zTab){
+  int rc = SQLITE_OK;
+  Table *pTab;
+
+  pTab = sqlite3FindTable(db, zTab, db->aDb[iDb].zName);
+  if( ALWAYS(pTab!=0 && pTab->pVTable!=0) ){
+    VTable *p = vtabDisconnectAll(db, pTab);
+
+    assert( rc==SQLITE_OK );
+    rc = p->pMod->pModule->xDestroy(p->pVtab);
+
+    /* Remove the sqlite3_vtab* from the aVTrans[] array, if applicable */
+    if( rc==SQLITE_OK ){
+      assert( pTab->pVTable==p && p->pNext==0 );
+      p->pVtab = 0;
+      pTab->pVTable = 0;
+      sqlite3VtabUnlock(p);
+    }
+  }
+
+  return rc;
+}
+
+/*
+** This function invokes either the xRollback or xCommit method
+** of each of the virtual tables in the sqlite3.aVTrans array. The method
+** called is identified by the second argument, "offset", which is
+** the offset of the method to call in the sqlite3_module structure.
+**
+** The array is cleared after invoking the callbacks. 
+*/
+static void callFinaliser(sqlite3 *db, int offset){
+  int i;
+  if( db->aVTrans ){
+    for(i=0; i<db->nVTrans; i++){
+      VTable *pVTab = db->aVTrans[i];
+      sqlite3_vtab *p = pVTab->pVtab;
+      if( p ){
+        int (*x)(sqlite3_vtab *);
+        x = *(int (**)(sqlite3_vtab *))((char *)p->pModule + offset);
+        if( x ) x(p);
+      }
+      pVTab->iSavepoint = 0;
+      sqlite3VtabUnlock(pVTab);
+    }
+    sqlite3DbFree(db, db->aVTrans);
+    db->nVTrans = 0;
+    db->aVTrans = 0;
+  }
+}
+
+/*
+** Invoke the xSync method of all virtual tables in the sqlite3.aVTrans
+** array. Return the error code for the first error that occurs, or
+** SQLITE_OK if all xSync operations are successful.
+**
+** Set *pzErrmsg to point to a buffer that should be released using 
+** sqlite3DbFree() containing an error message, if one is available.
+*/
+int sqlite3VtabSync(sqlite3 *db, char **pzErrmsg){
+  int i;
+  int rc = SQLITE_OK;
+  VTable **aVTrans = db->aVTrans;
+
+  db->aVTrans = 0;
+  for(i=0; rc==SQLITE_OK && i<db->nVTrans; i++){
+    int (*x)(sqlite3_vtab *);
+    sqlite3_vtab *pVtab = aVTrans[i]->pVtab;
+    if( pVtab && (x = pVtab->pModule->xSync)!=0 ){
+      rc = x(pVtab);
+      sqlite3DbFree(db, *pzErrmsg);
+      *pzErrmsg = sqlite3DbStrDup(db, pVtab->zErrMsg);
+      sqlite3_free(pVtab->zErrMsg);
+    }
+  }
+  db->aVTrans = aVTrans;
+  return rc;
+}
+
+/*
+** Invoke the xRollback method of all virtual tables in the 
+** sqlite3.aVTrans array. Then clear the array itself.
+*/
+int sqlite3VtabRollback(sqlite3 *db){
+  callFinaliser(db, offsetof(sqlite3_module,xRollback));
+  return SQLITE_OK;
+}
+
+/*
+** Invoke the xCommit method of all virtual tables in the 
+** sqlite3.aVTrans array. Then clear the array itself.
+*/
+int sqlite3VtabCommit(sqlite3 *db){
+  callFinaliser(db, offsetof(sqlite3_module,xCommit));
+  return SQLITE_OK;
+}
+
+/*
+** If the virtual table pVtab supports the transaction interface
+** (xBegin/xRollback/xCommit and optionally xSync) and a transaction is
+** not currently open, invoke the xBegin method now.
+**
+** If the xBegin call is successful, place the sqlite3_vtab pointer
+** in the sqlite3.aVTrans array.
+*/
+int sqlite3VtabBegin(sqlite3 *db, VTable *pVTab){
+  int rc = SQLITE_OK;
+  const sqlite3_module *pModule;
+
+  /* Special case: If db->aVTrans is NULL and db->nVTrans is greater
+  ** than zero, then this function is being called from within a
+  ** virtual module xSync() callback. It is illegal to write to 
+  ** virtual module tables in this case, so return SQLITE_LOCKED.
+  */
+  if( sqlite3VtabInSync(db) ){
+    return SQLITE_LOCKED;
+  }
+  if( !pVTab ){
+    return SQLITE_OK;
+  } 
+  pModule = pVTab->pVtab->pModule;
+
+  if( pModule->xBegin ){
+    int i;
+
+    /* If pVtab is already in the aVTrans array, return early */
+    for(i=0; i<db->nVTrans; i++){
+      if( db->aVTrans[i]==pVTab ){
+        return SQLITE_OK;
+      }
+    }
+
+    /* Invoke the xBegin method. If successful, add the vtab to the 
+    ** sqlite3.aVTrans[] array. */
+    rc = growVTrans(db);
+    if( rc==SQLITE_OK ){
+      rc = pModule->xBegin(pVTab->pVtab);
+      if( rc==SQLITE_OK ){
+        addToVTrans(db, pVTab);
+      }
+    }
+  }
+  return rc;
+}
+
+/*
+** Invoke either the xSavepoint, xRollbackTo or xRelease method of all
+** virtual tables that currently have an open transaction. Pass iSavepoint
+** as the second argument to the virtual table method invoked.
+**
+** If op is SAVEPOINT_BEGIN, the xSavepoint method is invoked. If it is
+** SAVEPOINT_ROLLBACK, the xRollbackTo method. Otherwise, if op is 
+** SAVEPOINT_RELEASE, then the xRelease method of each virtual table with
+** an open transaction is invoked.
+**
+** If any virtual table method returns an error code other than SQLITE_OK, 
+** processing is abandoned and the error returned to the caller of this
+** function immediately. If all calls to virtual table methods are successful,
+** SQLITE_OK is returned.
+*/
+int sqlite3VtabSavepoint(sqlite3 *db, int op, int iSavepoint){
+  int rc = SQLITE_OK;
+
+  assert( op==SAVEPOINT_RELEASE||op==SAVEPOINT_ROLLBACK||op==SAVEPOINT_BEGIN );
+  assert( iSavepoint>=0 );
+  if( db->aVTrans ){
+    int i;
+    for(i=0; rc==SQLITE_OK && i<db->nVTrans; i++){
+      VTable *pVTab = db->aVTrans[i];
+      const sqlite3_module *pMod = pVTab->pMod->pModule;
+      if( pVTab->pVtab && pMod->iVersion>=2 ){
+        int (*xMethod)(sqlite3_vtab *, int);
+        switch( op ){
+          case SAVEPOINT_BEGIN:
+            xMethod = pMod->xSavepoint;
+            pVTab->iSavepoint = iSavepoint+1;
+            break;
+          case SAVEPOINT_ROLLBACK:
+            xMethod = pMod->xRollbackTo;
+            break;
+          default:
+            xMethod = pMod->xRelease;
+            break;
+        }
+        if( xMethod && pVTab->iSavepoint>iSavepoint ){
+          rc = xMethod(pVTab->pVtab, iSavepoint);
+        }
+      }
+    }
+  }
+  return rc;
+}
+
+/*
+** The first parameter (pDef) is a function implementation.  The
+** second parameter (pExpr) is the first argument to this function.
+** If pExpr is a column in a virtual table, then let the virtual
+** table implementation have an opportunity to overload the function.
+**
+** This routine is used to allow virtual table implementations to
+** overload MATCH, LIKE, GLOB, and REGEXP operators.
+**
+** Return either the pDef argument (indicating no change) or a 
+** new FuncDef structure that is marked as ephemeral using the
+** SQLITE_FUNC_EPHEM flag.
+*/
+FuncDef *sqlite3VtabOverloadFunction(
+  sqlite3 *db,    /* Database connection for reporting malloc problems */
+  FuncDef *pDef,  /* Function to possibly overload */
+  int nArg,       /* Number of arguments to the function */
+  Expr *pExpr     /* First argument to the function */
+){
+  Table *pTab;
+  sqlite3_vtab *pVtab;
+  sqlite3_module *pMod;
+  void (*xFunc)(sqlite3_context*,int,sqlite3_value**) = 0;
+  void *pArg = 0;
+  FuncDef *pNew;
+  int rc = 0;
+  char *zLowerName;
+  unsigned char *z;
+
+
+  /* Check to see the left operand is a column in a virtual table */
+  if( NEVER(pExpr==0) ) return pDef;
+  if( pExpr->op!=TK_COLUMN ) return pDef;
+  pTab = pExpr->pTab;
+  if( NEVER(pTab==0) ) return pDef;
+  if( (pTab->tabFlags & TF_Virtual)==0 ) return pDef;
+  pVtab = sqlite3GetVTable(db, pTab)->pVtab;
+  assert( pVtab!=0 );
+  assert( pVtab->pModule!=0 );
+  pMod = (sqlite3_module *)pVtab->pModule;
+  if( pMod->xFindFunction==0 ) return pDef;
+ 
+  /* Call the xFindFunction method on the virtual table implementation
+  ** to see if the implementation wants to overload this function 
+  */
+  zLowerName = sqlite3DbStrDup(db, pDef->zName);
+  if( zLowerName ){
+    for(z=(unsigned char*)zLowerName; *z; z++){
+      *z = sqlite3UpperToLower[*z];
+    }
+    rc = pMod->xFindFunction(pVtab, nArg, zLowerName, &xFunc, &pArg);
+    sqlite3DbFree(db, zLowerName);
+  }
+  if( rc==0 ){
+    return pDef;
+  }
+
+  /* Create a new ephemeral function definition for the overloaded
+  ** function */
+  pNew = sqlite3DbMallocZero(db, sizeof(*pNew)
+                             + sqlite3Strlen30(pDef->zName) + 1);
+  if( pNew==0 ){
+    return pDef;
+  }
+  *pNew = *pDef;
+  pNew->zName = (char *)&pNew[1];
+  memcpy(pNew->zName, pDef->zName, sqlite3Strlen30(pDef->zName)+1);
+  pNew->xFunc = xFunc;
+  pNew->pUserData = pArg;
+  pNew->flags |= SQLITE_FUNC_EPHEM;
+  return pNew;
+}
+
+/*
+** Make sure virtual table pTab is contained in the pParse->apVirtualLock[]
+** array so that an OP_VBegin will get generated for it.  Add pTab to the
+** array if it is missing.  If pTab is already in the array, this routine
+** is a no-op.
+*/
+void sqlite3VtabMakeWritable(Parse *pParse, Table *pTab){
+  Parse *pToplevel = sqlite3ParseToplevel(pParse);
+  int i, n;
+  Table **apVtabLock;
+
+  assert( IsVirtual(pTab) );
+  for(i=0; i<pToplevel->nVtabLock; i++){
+    if( pTab==pToplevel->apVtabLock[i] ) return;
+  }
+  n = (pToplevel->nVtabLock+1)*sizeof(pToplevel->apVtabLock[0]);
+  apVtabLock = sqlite3_realloc(pToplevel->apVtabLock, n);
+  if( apVtabLock ){
+    pToplevel->apVtabLock = apVtabLock;
+    pToplevel->apVtabLock[pToplevel->nVtabLock++] = pTab;
+  }else{
+    pToplevel->db->mallocFailed = 1;
+  }
+}
+
+/*
+** Return the ON CONFLICT resolution mode in effect for the virtual
+** table update operation currently in progress.
+**
+** The results of this routine are undefined unless it is called from
+** within an xUpdate method.
+*/
+int sqlite3_vtab_on_conflict(sqlite3 *db){
+  static const unsigned char aMap[] = { 
+    SQLITE_ROLLBACK, SQLITE_ABORT, SQLITE_FAIL, SQLITE_IGNORE, SQLITE_REPLACE 
+  };
+  assert( OE_Rollback==1 && OE_Abort==2 && OE_Fail==3 );
+  assert( OE_Ignore==4 && OE_Replace==5 );
+  assert( db->vtabOnConflict>=1 && db->vtabOnConflict<=5 );
+  return (int)aMap[db->vtabOnConflict-1];
+}
+
+/*
+** Call from within the xCreate() or xConnect() methods to provide 
+** the SQLite core with additional information about the behavior
+** of the virtual table being implemented.
+*/
+int sqlite3_vtab_config(sqlite3 *db, int op, ...){
+  va_list ap;
+  int rc = SQLITE_OK;
+
+  sqlite3_mutex_enter(db->mutex);
+
+  va_start(ap, op);
+  switch( op ){
+    case SQLITE_VTAB_CONSTRAINT_SUPPORT: {
+      VtabCtx *p = db->pVtabCtx;
+      if( !p ){
+        rc = SQLITE_MISUSE_BKPT;
+      }else{
+        assert( p->pTab==0 || (p->pTab->tabFlags & TF_Virtual)!=0 );
+        p->pVTable->bConstraint = (u8)va_arg(ap, int);
+      }
+      break;
+    }
+    default:
+      rc = SQLITE_MISUSE_BKPT;
+      break;
+  }
+  va_end(ap);
+
+  if( rc!=SQLITE_OK ) sqlite3Error(db, rc, 0);
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+}
+
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
diff --git a/src/wal.c b/src/wal.c
new file mode 100644
index 0000000..f2b3187
--- /dev/null
+++ b/src/wal.c
@@ -0,0 +1,2952 @@
+/*
+** 2010 February 1
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains the implementation of a write-ahead log (WAL) used in 
+** "journal_mode=WAL" mode.
+**
+** WRITE-AHEAD LOG (WAL) FILE FORMAT
+**
+** A WAL file consists of a header followed by zero or more "frames".
+** Each frame records the revised content of a single page from the
+** database file.  All changes to the database are recorded by writing
+** frames into the WAL.  Transactions commit when a frame is written that
+** contains a commit marker.  A single WAL can and usually does record 
+** multiple transactions.  Periodically, the content of the WAL is
+** transferred back into the database file in an operation called a
+** "checkpoint".
+**
+** A single WAL file can be used multiple times.  In other words, the
+** WAL can fill up with frames and then be checkpointed and then new
+** frames can overwrite the old ones.  A WAL always grows from beginning
+** toward the end.  Checksums and counters attached to each frame are
+** used to determine which frames within the WAL are valid and which
+** are leftovers from prior checkpoints.
+**
+** The WAL header is 32 bytes in size and consists of the following eight
+** big-endian 32-bit unsigned integer values:
+**
+**     0: Magic number.  0x377f0682 or 0x377f0683
+**     4: File format version.  Currently 3007000
+**     8: Database page size.  Example: 1024
+**    12: Checkpoint sequence number
+**    16: Salt-1, random integer incremented with each checkpoint
+**    20: Salt-2, a different random integer changing with each ckpt
+**    24: Checksum-1 (first part of checksum for first 24 bytes of header).
+**    28: Checksum-2 (second part of checksum for first 24 bytes of header).
+**
+** Immediately following the wal-header are zero or more frames. Each
+** frame consists of a 24-byte frame-header followed by a <page-size> bytes
+** of page data. The frame-header is six big-endian 32-bit unsigned 
+** integer values, as follows:
+**
+**     0: Page number.
+**     4: For commit records, the size of the database image in pages 
+**        after the commit. For all other records, zero.
+**     8: Salt-1 (copied from the header)
+**    12: Salt-2 (copied from the header)
+**    16: Checksum-1.
+**    20: Checksum-2.
+**
+** A frame is considered valid if and only if the following conditions are
+** true:
+**
+**    (1) The salt-1 and salt-2 values in the frame-header match
+**        salt values in the wal-header
+**
+**    (2) The checksum values in the final 8 bytes of the frame-header
+**        exactly match the checksum computed consecutively on the
+**        WAL header and the first 8 bytes and the content of all frames
+**        up to and including the current frame.
+**
+** The checksum is computed using 32-bit big-endian integers if the
+** magic number in the first 4 bytes of the WAL is 0x377f0683 and it
+** is computed using little-endian if the magic number is 0x377f0682.
+** The checksum values are always stored in the frame header in a
+** big-endian format regardless of which byte order is used to compute
+** the checksum.  The checksum is computed by interpreting the input as
+** an even number of unsigned 32-bit integers: x[0] through x[N].  The
+** algorithm used for the checksum is as follows:
+** 
+**   for i from 0 to n-1 step 2:
+**     s0 += x[i] + s1;
+**     s1 += x[i+1] + s0;
+**   endfor
+**
+** Note that s0 and s1 are both weighted checksums using fibonacci weights
+** in reverse order (the largest fibonacci weight occurs on the first element
+** of the sequence being summed.)  The s1 value spans all 32-bit 
+** terms of the sequence whereas s0 omits the final term.
+**
+** On a checkpoint, the WAL is first VFS.xSync-ed, then valid content of the
+** WAL is transferred into the database, then the database is VFS.xSync-ed.
+** The VFS.xSync operations serve as write barriers - all writes launched
+** before the xSync must complete before any write that launches after the
+** xSync begins.
+**
+** After each checkpoint, the salt-1 value is incremented and the salt-2
+** value is randomized.  This prevents old and new frames in the WAL from
+** being considered valid at the same time and being checkpointing together
+** following a crash.
+**
+** READER ALGORITHM
+**
+** To read a page from the database (call it page number P), a reader
+** first checks the WAL to see if it contains page P.  If so, then the
+** last valid instance of page P that is a followed by a commit frame
+** or is a commit frame itself becomes the value read.  If the WAL
+** contains no copies of page P that are valid and which are a commit
+** frame or are followed by a commit frame, then page P is read from
+** the database file.
+**
+** To start a read transaction, the reader records the index of the last
+** valid frame in the WAL.  The reader uses this recorded "mxFrame" value
+** for all subsequent read operations.  New transactions can be appended
+** to the WAL, but as long as the reader uses its original mxFrame value
+** and ignores the newly appended content, it will see a consistent snapshot
+** of the database from a single point in time.  This technique allows
+** multiple concurrent readers to view different versions of the database
+** content simultaneously.
+**
+** The reader algorithm in the previous paragraphs works correctly, but 
+** because frames for page P can appear anywhere within the WAL, the
+** reader has to scan the entire WAL looking for page P frames.  If the
+** WAL is large (multiple megabytes is typical) that scan can be slow,
+** and read performance suffers.  To overcome this problem, a separate
+** data structure called the wal-index is maintained to expedite the
+** search for frames of a particular page.
+** 
+** WAL-INDEX FORMAT
+**
+** Conceptually, the wal-index is shared memory, though VFS implementations
+** might choose to implement the wal-index using a mmapped file.  Because
+** the wal-index is shared memory, SQLite does not support journal_mode=WAL 
+** on a network filesystem.  All users of the database must be able to
+** share memory.
+**
+** The wal-index is transient.  After a crash, the wal-index can (and should
+** be) reconstructed from the original WAL file.  In fact, the VFS is required
+** to either truncate or zero the header of the wal-index when the last
+** connection to it closes.  Because the wal-index is transient, it can
+** use an architecture-specific format; it does not have to be cross-platform.
+** Hence, unlike the database and WAL file formats which store all values
+** as big endian, the wal-index can store multi-byte values in the native
+** byte order of the host computer.
+**
+** The purpose of the wal-index is to answer this question quickly:  Given
+** a page number P, return the index of the last frame for page P in the WAL,
+** or return NULL if there are no frames for page P in the WAL.
+**
+** The wal-index consists of a header region, followed by an one or
+** more index blocks.  
+**
+** The wal-index header contains the total number of frames within the WAL
+** in the the mxFrame field.  
+**
+** Each index block except for the first contains information on 
+** HASHTABLE_NPAGE frames. The first index block contains information on
+** HASHTABLE_NPAGE_ONE frames. The values of HASHTABLE_NPAGE_ONE and 
+** HASHTABLE_NPAGE are selected so that together the wal-index header and
+** first index block are the same size as all other index blocks in the
+** wal-index.
+**
+** Each index block contains two sections, a page-mapping that contains the
+** database page number associated with each wal frame, and a hash-table 
+** that allows readers to query an index block for a specific page number.
+** The page-mapping is an array of HASHTABLE_NPAGE (or HASHTABLE_NPAGE_ONE
+** for the first index block) 32-bit page numbers. The first entry in the 
+** first index-block contains the database page number corresponding to the
+** first frame in the WAL file. The first entry in the second index block
+** in the WAL file corresponds to the (HASHTABLE_NPAGE_ONE+1)th frame in
+** the log, and so on.
+**
+** The last index block in a wal-index usually contains less than the full
+** complement of HASHTABLE_NPAGE (or HASHTABLE_NPAGE_ONE) page-numbers,
+** depending on the contents of the WAL file. This does not change the
+** allocated size of the page-mapping array - the page-mapping array merely
+** contains unused entries.
+**
+** Even without using the hash table, the last frame for page P
+** can be found by scanning the page-mapping sections of each index block
+** starting with the last index block and moving toward the first, and
+** within each index block, starting at the end and moving toward the
+** beginning.  The first entry that equals P corresponds to the frame
+** holding the content for that page.
+**
+** The hash table consists of HASHTABLE_NSLOT 16-bit unsigned integers.
+** HASHTABLE_NSLOT = 2*HASHTABLE_NPAGE, and there is one entry in the
+** hash table for each page number in the mapping section, so the hash 
+** table is never more than half full.  The expected number of collisions 
+** prior to finding a match is 1.  Each entry of the hash table is an
+** 1-based index of an entry in the mapping section of the same
+** index block.   Let K be the 1-based index of the largest entry in
+** the mapping section.  (For index blocks other than the last, K will
+** always be exactly HASHTABLE_NPAGE (4096) and for the last index block
+** K will be (mxFrame%HASHTABLE_NPAGE).)  Unused slots of the hash table
+** contain a value of 0.
+**
+** To look for page P in the hash table, first compute a hash iKey on
+** P as follows:
+**
+**      iKey = (P * 383) % HASHTABLE_NSLOT
+**
+** Then start scanning entries of the hash table, starting with iKey
+** (wrapping around to the beginning when the end of the hash table is
+** reached) until an unused hash slot is found. Let the first unused slot
+** be at index iUnused.  (iUnused might be less than iKey if there was
+** wrap-around.) Because the hash table is never more than half full,
+** the search is guaranteed to eventually hit an unused entry.  Let 
+** iMax be the value between iKey and iUnused, closest to iUnused,
+** where aHash[iMax]==P.  If there is no iMax entry (if there exists
+** no hash slot such that aHash[i]==p) then page P is not in the
+** current index block.  Otherwise the iMax-th mapping entry of the
+** current index block corresponds to the last entry that references 
+** page P.
+**
+** A hash search begins with the last index block and moves toward the
+** first index block, looking for entries corresponding to page P.  On
+** average, only two or three slots in each index block need to be
+** examined in order to either find the last entry for page P, or to
+** establish that no such entry exists in the block.  Each index block
+** holds over 4000 entries.  So two or three index blocks are sufficient
+** to cover a typical 10 megabyte WAL file, assuming 1K pages.  8 or 10
+** comparisons (on average) suffice to either locate a frame in the
+** WAL or to establish that the frame does not exist in the WAL.  This
+** is much faster than scanning the entire 10MB WAL.
+**
+** Note that entries are added in order of increasing K.  Hence, one
+** reader might be using some value K0 and a second reader that started
+** at a later time (after additional transactions were added to the WAL
+** and to the wal-index) might be using a different value K1, where K1>K0.
+** Both readers can use the same hash table and mapping section to get
+** the correct result.  There may be entries in the hash table with
+** K>K0 but to the first reader, those entries will appear to be unused
+** slots in the hash table and so the first reader will get an answer as
+** if no values greater than K0 had ever been inserted into the hash table
+** in the first place - which is what reader one wants.  Meanwhile, the
+** second reader using K1 will see additional values that were inserted
+** later, which is exactly what reader two wants.  
+**
+** When a rollback occurs, the value of K is decreased. Hash table entries
+** that correspond to frames greater than the new K value are removed
+** from the hash table at this point.
+*/
+#ifndef SQLITE_OMIT_WAL
+
+#include "wal.h"
+
+/*
+** Trace output macros
+*/
+#if defined(SQLITE_TEST) && defined(SQLITE_DEBUG)
+int sqlite3WalTrace = 0;
+# define WALTRACE(X)  if(sqlite3WalTrace) sqlite3DebugPrintf X
+#else
+# define WALTRACE(X)
+#endif
+
+/*
+** The maximum (and only) versions of the wal and wal-index formats
+** that may be interpreted by this version of SQLite.
+**
+** If a client begins recovering a WAL file and finds that (a) the checksum
+** values in the wal-header are correct and (b) the version field is not
+** WAL_MAX_VERSION, recovery fails and SQLite returns SQLITE_CANTOPEN.
+**
+** Similarly, if a client successfully reads a wal-index header (i.e. the 
+** checksum test is successful) and finds that the version field is not
+** WALINDEX_MAX_VERSION, then no read-transaction is opened and SQLite
+** returns SQLITE_CANTOPEN.
+*/
+#define WAL_MAX_VERSION      3007000
+#define WALINDEX_MAX_VERSION 3007000
+
+/*
+** Indices of various locking bytes.   WAL_NREADER is the number
+** of available reader locks and should be at least 3.
+*/
+#define WAL_WRITE_LOCK         0
+#define WAL_ALL_BUT_WRITE      1
+#define WAL_CKPT_LOCK          1
+#define WAL_RECOVER_LOCK       2
+#define WAL_READ_LOCK(I)       (3+(I))
+#define WAL_NREADER            (SQLITE_SHM_NLOCK-3)
+
+
+/* Object declarations */
+typedef struct WalIndexHdr WalIndexHdr;
+typedef struct WalIterator WalIterator;
+typedef struct WalCkptInfo WalCkptInfo;
+
+
+/*
+** The following object holds a copy of the wal-index header content.
+**
+** The actual header in the wal-index consists of two copies of this
+** object.
+**
+** The szPage value can be any power of 2 between 512 and 32768, inclusive.
+** Or it can be 1 to represent a 65536-byte page.  The latter case was
+** added in 3.7.1 when support for 64K pages was added.  
+*/
+struct WalIndexHdr {
+  u32 iVersion;                   /* Wal-index version */
+  u32 unused;                     /* Unused (padding) field */
+  u32 iChange;                    /* Counter incremented each transaction */
+  u8 isInit;                      /* 1 when initialized */
+  u8 bigEndCksum;                 /* True if checksums in WAL are big-endian */
+  u16 szPage;                     /* Database page size in bytes. 1==64K */
+  u32 mxFrame;                    /* Index of last valid frame in the WAL */
+  u32 nPage;                      /* Size of database in pages */
+  u32 aFrameCksum[2];             /* Checksum of last frame in log */
+  u32 aSalt[2];                   /* Two salt values copied from WAL header */
+  u32 aCksum[2];                  /* Checksum over all prior fields */
+};
+
+/*
+** A copy of the following object occurs in the wal-index immediately
+** following the second copy of the WalIndexHdr.  This object stores
+** information used by checkpoint.
+**
+** nBackfill is the number of frames in the WAL that have been written
+** back into the database. (We call the act of moving content from WAL to
+** database "backfilling".)  The nBackfill number is never greater than
+** WalIndexHdr.mxFrame.  nBackfill can only be increased by threads
+** holding the WAL_CKPT_LOCK lock (which includes a recovery thread).
+** However, a WAL_WRITE_LOCK thread can move the value of nBackfill from
+** mxFrame back to zero when the WAL is reset.
+**
+** There is one entry in aReadMark[] for each reader lock.  If a reader
+** holds read-lock K, then the value in aReadMark[K] is no greater than
+** the mxFrame for that reader.  The value READMARK_NOT_USED (0xffffffff)
+** for any aReadMark[] means that entry is unused.  aReadMark[0] is 
+** a special case; its value is never used and it exists as a place-holder
+** to avoid having to offset aReadMark[] indexs by one.  Readers holding
+** WAL_READ_LOCK(0) always ignore the entire WAL and read all content
+** directly from the database.
+**
+** The value of aReadMark[K] may only be changed by a thread that
+** is holding an exclusive lock on WAL_READ_LOCK(K).  Thus, the value of
+** aReadMark[K] cannot changed while there is a reader is using that mark
+** since the reader will be holding a shared lock on WAL_READ_LOCK(K).
+**
+** The checkpointer may only transfer frames from WAL to database where
+** the frame numbers are less than or equal to every aReadMark[] that is
+** in use (that is, every aReadMark[j] for which there is a corresponding
+** WAL_READ_LOCK(j)).  New readers (usually) pick the aReadMark[] with the
+** largest value and will increase an unused aReadMark[] to mxFrame if there
+** is not already an aReadMark[] equal to mxFrame.  The exception to the
+** previous sentence is when nBackfill equals mxFrame (meaning that everything
+** in the WAL has been backfilled into the database) then new readers
+** will choose aReadMark[0] which has value 0 and hence such reader will
+** get all their all content directly from the database file and ignore 
+** the WAL.
+**
+** Writers normally append new frames to the end of the WAL.  However,
+** if nBackfill equals mxFrame (meaning that all WAL content has been
+** written back into the database) and if no readers are using the WAL
+** (in other words, if there are no WAL_READ_LOCK(i) where i>0) then
+** the writer will first "reset" the WAL back to the beginning and start
+** writing new content beginning at frame 1.
+**
+** We assume that 32-bit loads are atomic and so no locks are needed in
+** order to read from any aReadMark[] entries.
+*/
+struct WalCkptInfo {
+  u32 nBackfill;                  /* Number of WAL frames backfilled into DB */
+  u32 aReadMark[WAL_NREADER];     /* Reader marks */
+};
+#define READMARK_NOT_USED  0xffffffff
+
+
+/* A block of WALINDEX_LOCK_RESERVED bytes beginning at
+** WALINDEX_LOCK_OFFSET is reserved for locks. Since some systems
+** only support mandatory file-locks, we do not read or write data
+** from the region of the file on which locks are applied.
+*/
+#define WALINDEX_LOCK_OFFSET   (sizeof(WalIndexHdr)*2 + sizeof(WalCkptInfo))
+#define WALINDEX_LOCK_RESERVED 16
+#define WALINDEX_HDR_SIZE      (WALINDEX_LOCK_OFFSET+WALINDEX_LOCK_RESERVED)
+
+/* Size of header before each frame in wal */
+#define WAL_FRAME_HDRSIZE 24
+
+/* Size of write ahead log header, including checksum. */
+/* #define WAL_HDRSIZE 24 */
+#define WAL_HDRSIZE 32
+
+/* WAL magic value. Either this value, or the same value with the least
+** significant bit also set (WAL_MAGIC | 0x00000001) is stored in 32-bit
+** big-endian format in the first 4 bytes of a WAL file.
+**
+** If the LSB is set, then the checksums for each frame within the WAL
+** file are calculated by treating all data as an array of 32-bit 
+** big-endian words. Otherwise, they are calculated by interpreting 
+** all data as 32-bit little-endian words.
+*/
+#define WAL_MAGIC 0x377f0682
+
+/*
+** Return the offset of frame iFrame in the write-ahead log file, 
+** assuming a database page size of szPage bytes. The offset returned
+** is to the start of the write-ahead log frame-header.
+*/
+#define walFrameOffset(iFrame, szPage) (                               \
+  WAL_HDRSIZE + ((iFrame)-1)*(i64)((szPage)+WAL_FRAME_HDRSIZE)         \
+)
+
+/*
+** An open write-ahead log file is represented by an instance of the
+** following object.
+*/
+struct Wal {
+  sqlite3_vfs *pVfs;         /* The VFS used to create pDbFd */
+  sqlite3_file *pDbFd;       /* File handle for the database file */
+  sqlite3_file *pWalFd;      /* File handle for WAL file */
+  u32 iCallback;             /* Value to pass to log callback (or 0) */
+  i64 mxWalSize;             /* Truncate WAL to this size upon reset */
+  int nWiData;               /* Size of array apWiData */
+  volatile u32 **apWiData;   /* Pointer to wal-index content in memory */
+  u32 szPage;                /* Database page size */
+  i16 readLock;              /* Which read lock is being held.  -1 for none */
+  u8 exclusiveMode;          /* Non-zero if connection is in exclusive mode */
+  u8 writeLock;              /* True if in a write transaction */
+  u8 ckptLock;               /* True if holding a checkpoint lock */
+  u8 readOnly;               /* WAL_RDWR, WAL_RDONLY, or WAL_SHM_RDONLY */
+  WalIndexHdr hdr;           /* Wal-index header for current transaction */
+  const char *zWalName;      /* Name of WAL file */
+  u32 nCkpt;                 /* Checkpoint sequence counter in the wal-header */
+#ifdef SQLITE_DEBUG
+  u8 lockError;              /* True if a locking error has occurred */
+#endif
+};
+
+/*
+** Candidate values for Wal.exclusiveMode.
+*/
+#define WAL_NORMAL_MODE     0
+#define WAL_EXCLUSIVE_MODE  1     
+#define WAL_HEAPMEMORY_MODE 2
+
+/*
+** Possible values for WAL.readOnly
+*/
+#define WAL_RDWR        0    /* Normal read/write connection */
+#define WAL_RDONLY      1    /* The WAL file is readonly */
+#define WAL_SHM_RDONLY  2    /* The SHM file is readonly */
+
+/*
+** Each page of the wal-index mapping contains a hash-table made up of
+** an array of HASHTABLE_NSLOT elements of the following type.
+*/
+typedef u16 ht_slot;
+
+/*
+** This structure is used to implement an iterator that loops through
+** all frames in the WAL in database page order. Where two or more frames
+** correspond to the same database page, the iterator visits only the 
+** frame most recently written to the WAL (in other words, the frame with
+** the largest index).
+**
+** The internals of this structure are only accessed by:
+**
+**   walIteratorInit() - Create a new iterator,
+**   walIteratorNext() - Step an iterator,
+**   walIteratorFree() - Free an iterator.
+**
+** This functionality is used by the checkpoint code (see walCheckpoint()).
+*/
+struct WalIterator {
+  int iPrior;                     /* Last result returned from the iterator */
+  int nSegment;                   /* Number of entries in aSegment[] */
+  struct WalSegment {
+    int iNext;                    /* Next slot in aIndex[] not yet returned */
+    ht_slot *aIndex;              /* i0, i1, i2... such that aPgno[iN] ascend */
+    u32 *aPgno;                   /* Array of page numbers. */
+    int nEntry;                   /* Nr. of entries in aPgno[] and aIndex[] */
+    int iZero;                    /* Frame number associated with aPgno[0] */
+  } aSegment[1];                  /* One for every 32KB page in the wal-index */
+};
+
+/*
+** Define the parameters of the hash tables in the wal-index file. There
+** is a hash-table following every HASHTABLE_NPAGE page numbers in the
+** wal-index.
+**
+** Changing any of these constants will alter the wal-index format and
+** create incompatibilities.
+*/
+#define HASHTABLE_NPAGE      4096                 /* Must be power of 2 */
+#define HASHTABLE_HASH_1     383                  /* Should be prime */
+#define HASHTABLE_NSLOT      (HASHTABLE_NPAGE*2)  /* Must be a power of 2 */
+
+/* 
+** The block of page numbers associated with the first hash-table in a
+** wal-index is smaller than usual. This is so that there is a complete
+** hash-table on each aligned 32KB page of the wal-index.
+*/
+#define HASHTABLE_NPAGE_ONE  (HASHTABLE_NPAGE - (WALINDEX_HDR_SIZE/sizeof(u32)))
+
+/* The wal-index is divided into pages of WALINDEX_PGSZ bytes each. */
+#define WALINDEX_PGSZ   (                                         \
+    sizeof(ht_slot)*HASHTABLE_NSLOT + HASHTABLE_NPAGE*sizeof(u32) \
+)
+
+/*
+** Obtain a pointer to the iPage'th page of the wal-index. The wal-index
+** is broken into pages of WALINDEX_PGSZ bytes. Wal-index pages are
+** numbered from zero.
+**
+** If this call is successful, *ppPage is set to point to the wal-index
+** page and SQLITE_OK is returned. If an error (an OOM or VFS error) occurs,
+** then an SQLite error code is returned and *ppPage is set to 0.
+*/
+static int walIndexPage(Wal *pWal, int iPage, volatile u32 **ppPage){
+  int rc = SQLITE_OK;
+
+  /* Enlarge the pWal->apWiData[] array if required */
+  if( pWal->nWiData<=iPage ){
+    int nByte = sizeof(u32*)*(iPage+1);
+    volatile u32 **apNew;
+    apNew = (volatile u32 **)sqlite3_realloc((void *)pWal->apWiData, nByte);
+    if( !apNew ){
+      *ppPage = 0;
+      return SQLITE_NOMEM;
+    }
+    memset((void*)&apNew[pWal->nWiData], 0,
+           sizeof(u32*)*(iPage+1-pWal->nWiData));
+    pWal->apWiData = apNew;
+    pWal->nWiData = iPage+1;
+  }
+
+  /* Request a pointer to the required page from the VFS */
+  if( pWal->apWiData[iPage]==0 ){
+    if( pWal->exclusiveMode==WAL_HEAPMEMORY_MODE ){
+      pWal->apWiData[iPage] = (u32 volatile *)sqlite3MallocZero(WALINDEX_PGSZ);
+      if( !pWal->apWiData[iPage] ) rc = SQLITE_NOMEM;
+    }else{
+      rc = sqlite3OsShmMap(pWal->pDbFd, iPage, WALINDEX_PGSZ, 
+          pWal->writeLock, (void volatile **)&pWal->apWiData[iPage]
+      );
+      if( rc==SQLITE_READONLY ){
+        pWal->readOnly |= WAL_SHM_RDONLY;
+        rc = SQLITE_OK;
+      }
+    }
+  }
+
+  *ppPage = pWal->apWiData[iPage];
+  assert( iPage==0 || *ppPage || rc!=SQLITE_OK );
+  return rc;
+}
+
+/*
+** Return a pointer to the WalCkptInfo structure in the wal-index.
+*/
+static volatile WalCkptInfo *walCkptInfo(Wal *pWal){
+  assert( pWal->nWiData>0 && pWal->apWiData[0] );
+  return (volatile WalCkptInfo*)&(pWal->apWiData[0][sizeof(WalIndexHdr)/2]);
+}
+
+/*
+** Return a pointer to the WalIndexHdr structure in the wal-index.
+*/
+static volatile WalIndexHdr *walIndexHdr(Wal *pWal){
+  assert( pWal->nWiData>0 && pWal->apWiData[0] );
+  return (volatile WalIndexHdr*)pWal->apWiData[0];
+}
+
+/*
+** The argument to this macro must be of type u32. On a little-endian
+** architecture, it returns the u32 value that results from interpreting
+** the 4 bytes as a big-endian value. On a big-endian architecture, it
+** returns the value that would be produced by intepreting the 4 bytes
+** of the input value as a little-endian integer.
+*/
+#define BYTESWAP32(x) ( \
+    (((x)&0x000000FF)<<24) + (((x)&0x0000FF00)<<8)  \
+  + (((x)&0x00FF0000)>>8)  + (((x)&0xFF000000)>>24) \
+)
+
+/*
+** Generate or extend an 8 byte checksum based on the data in 
+** array aByte[] and the initial values of aIn[0] and aIn[1] (or
+** initial values of 0 and 0 if aIn==NULL).
+**
+** The checksum is written back into aOut[] before returning.
+**
+** nByte must be a positive multiple of 8.
+*/
+static void walChecksumBytes(
+  int nativeCksum, /* True for native byte-order, false for non-native */
+  u8 *a,           /* Content to be checksummed */
+  int nByte,       /* Bytes of content in a[].  Must be a multiple of 8. */
+  const u32 *aIn,  /* Initial checksum value input */
+  u32 *aOut        /* OUT: Final checksum value output */
+){
+  u32 s1, s2;
+  u32 *aData = (u32 *)a;
+  u32 *aEnd = (u32 *)&a[nByte];
+
+  if( aIn ){
+    s1 = aIn[0];
+    s2 = aIn[1];
+  }else{
+    s1 = s2 = 0;
+  }
+
+  assert( nByte>=8 );
+  assert( (nByte&0x00000007)==0 );
+
+  if( nativeCksum ){
+    do {
+      s1 += *aData++ + s2;
+      s2 += *aData++ + s1;
+    }while( aData<aEnd );
+  }else{
+    do {
+      s1 += BYTESWAP32(aData[0]) + s2;
+      s2 += BYTESWAP32(aData[1]) + s1;
+      aData += 2;
+    }while( aData<aEnd );
+  }
+
+  aOut[0] = s1;
+  aOut[1] = s2;
+}
+
+static void walShmBarrier(Wal *pWal){
+  if( pWal->exclusiveMode!=WAL_HEAPMEMORY_MODE ){
+    sqlite3OsShmBarrier(pWal->pDbFd);
+  }
+}
+
+/*
+** Write the header information in pWal->hdr into the wal-index.
+**
+** The checksum on pWal->hdr is updated before it is written.
+*/
+static void walIndexWriteHdr(Wal *pWal){
+  volatile WalIndexHdr *aHdr = walIndexHdr(pWal);
+  const int nCksum = offsetof(WalIndexHdr, aCksum);
+
+  assert( pWal->writeLock );
+  pWal->hdr.isInit = 1;
+  pWal->hdr.iVersion = WALINDEX_MAX_VERSION;
+  walChecksumBytes(1, (u8*)&pWal->hdr, nCksum, 0, pWal->hdr.aCksum);
+  memcpy((void *)&aHdr[1], (void *)&pWal->hdr, sizeof(WalIndexHdr));
+  walShmBarrier(pWal);
+  memcpy((void *)&aHdr[0], (void *)&pWal->hdr, sizeof(WalIndexHdr));
+}
+
+/*
+** This function encodes a single frame header and writes it to a buffer
+** supplied by the caller. A frame-header is made up of a series of 
+** 4-byte big-endian integers, as follows:
+**
+**     0: Page number.
+**     4: For commit records, the size of the database image in pages 
+**        after the commit. For all other records, zero.
+**     8: Salt-1 (copied from the wal-header)
+**    12: Salt-2 (copied from the wal-header)
+**    16: Checksum-1.
+**    20: Checksum-2.
+*/
+static void walEncodeFrame(
+  Wal *pWal,                      /* The write-ahead log */
+  u32 iPage,                      /* Database page number for frame */
+  u32 nTruncate,                  /* New db size (or 0 for non-commit frames) */
+  u8 *aData,                      /* Pointer to page data */
+  u8 *aFrame                      /* OUT: Write encoded frame here */
+){
+  int nativeCksum;                /* True for native byte-order checksums */
+  u32 *aCksum = pWal->hdr.aFrameCksum;
+  assert( WAL_FRAME_HDRSIZE==24 );
+  sqlite3Put4byte(&aFrame[0], iPage);
+  sqlite3Put4byte(&aFrame[4], nTruncate);
+  memcpy(&aFrame[8], pWal->hdr.aSalt, 8);
+
+  nativeCksum = (pWal->hdr.bigEndCksum==SQLITE_BIGENDIAN);
+  walChecksumBytes(nativeCksum, aFrame, 8, aCksum, aCksum);
+  walChecksumBytes(nativeCksum, aData, pWal->szPage, aCksum, aCksum);
+
+  sqlite3Put4byte(&aFrame[16], aCksum[0]);
+  sqlite3Put4byte(&aFrame[20], aCksum[1]);
+}
+
+/*
+** Check to see if the frame with header in aFrame[] and content
+** in aData[] is valid.  If it is a valid frame, fill *piPage and
+** *pnTruncate and return true.  Return if the frame is not valid.
+*/
+static int walDecodeFrame(
+  Wal *pWal,                      /* The write-ahead log */
+  u32 *piPage,                    /* OUT: Database page number for frame */
+  u32 *pnTruncate,                /* OUT: New db size (or 0 if not commit) */
+  u8 *aData,                      /* Pointer to page data (for checksum) */
+  u8 *aFrame                      /* Frame data */
+){
+  int nativeCksum;                /* True for native byte-order checksums */
+  u32 *aCksum = pWal->hdr.aFrameCksum;
+  u32 pgno;                       /* Page number of the frame */
+  assert( WAL_FRAME_HDRSIZE==24 );
+
+  /* A frame is only valid if the salt values in the frame-header
+  ** match the salt values in the wal-header. 
+  */
+  if( memcmp(&pWal->hdr.aSalt, &aFrame[8], 8)!=0 ){
+    return 0;
+  }
+
+  /* A frame is only valid if the page number is creater than zero.
+  */
+  pgno = sqlite3Get4byte(&aFrame[0]);
+  if( pgno==0 ){
+    return 0;
+  }
+
+  /* A frame is only valid if a checksum of the WAL header,
+  ** all prior frams, the first 16 bytes of this frame-header, 
+  ** and the frame-data matches the checksum in the last 8 
+  ** bytes of this frame-header.
+  */
+  nativeCksum = (pWal->hdr.bigEndCksum==SQLITE_BIGENDIAN);
+  walChecksumBytes(nativeCksum, aFrame, 8, aCksum, aCksum);
+  walChecksumBytes(nativeCksum, aData, pWal->szPage, aCksum, aCksum);
+  if( aCksum[0]!=sqlite3Get4byte(&aFrame[16]) 
+   || aCksum[1]!=sqlite3Get4byte(&aFrame[20]) 
+  ){
+    /* Checksum failed. */
+    return 0;
+  }
+
+  /* If we reach this point, the frame is valid.  Return the page number
+  ** and the new database size.
+  */
+  *piPage = pgno;
+  *pnTruncate = sqlite3Get4byte(&aFrame[4]);
+  return 1;
+}
+
+
+#if defined(SQLITE_TEST) && defined(SQLITE_DEBUG)
+/*
+** Names of locks.  This routine is used to provide debugging output and is not
+** a part of an ordinary build.
+*/
+static const char *walLockName(int lockIdx){
+  if( lockIdx==WAL_WRITE_LOCK ){
+    return "WRITE-LOCK";
+  }else if( lockIdx==WAL_CKPT_LOCK ){
+    return "CKPT-LOCK";
+  }else if( lockIdx==WAL_RECOVER_LOCK ){
+    return "RECOVER-LOCK";
+  }else{
+    static char zName[15];
+    sqlite3_snprintf(sizeof(zName), zName, "READ-LOCK[%d]",
+                     lockIdx-WAL_READ_LOCK(0));
+    return zName;
+  }
+}
+#endif /*defined(SQLITE_TEST) || defined(SQLITE_DEBUG) */
+    
+
+/*
+** Set or release locks on the WAL.  Locks are either shared or exclusive.
+** A lock cannot be moved directly between shared and exclusive - it must go
+** through the unlocked state first.
+**
+** In locking_mode=EXCLUSIVE, all of these routines become no-ops.
+*/
+static int walLockShared(Wal *pWal, int lockIdx){
+  int rc;
+  if( pWal->exclusiveMode ) return SQLITE_OK;
+  rc = sqlite3OsShmLock(pWal->pDbFd, lockIdx, 1,
+                        SQLITE_SHM_LOCK | SQLITE_SHM_SHARED);
+  WALTRACE(("WAL%p: acquire SHARED-%s %s\n", pWal,
+            walLockName(lockIdx), rc ? "failed" : "ok"));
+  VVA_ONLY( pWal->lockError = (u8)(rc!=SQLITE_OK && rc!=SQLITE_BUSY); )
+  return rc;
+}
+static void walUnlockShared(Wal *pWal, int lockIdx){
+  if( pWal->exclusiveMode ) return;
+  (void)sqlite3OsShmLock(pWal->pDbFd, lockIdx, 1,
+                         SQLITE_SHM_UNLOCK | SQLITE_SHM_SHARED);
+  WALTRACE(("WAL%p: release SHARED-%s\n", pWal, walLockName(lockIdx)));
+}
+static int walLockExclusive(Wal *pWal, int lockIdx, int n){
+  int rc;
+  if( pWal->exclusiveMode ) return SQLITE_OK;
+  rc = sqlite3OsShmLock(pWal->pDbFd, lockIdx, n,
+                        SQLITE_SHM_LOCK | SQLITE_SHM_EXCLUSIVE);
+  WALTRACE(("WAL%p: acquire EXCLUSIVE-%s cnt=%d %s\n", pWal,
+            walLockName(lockIdx), n, rc ? "failed" : "ok"));
+  VVA_ONLY( pWal->lockError = (u8)(rc!=SQLITE_OK && rc!=SQLITE_BUSY); )
+  return rc;
+}
+static void walUnlockExclusive(Wal *pWal, int lockIdx, int n){
+  if( pWal->exclusiveMode ) return;
+  (void)sqlite3OsShmLock(pWal->pDbFd, lockIdx, n,
+                         SQLITE_SHM_UNLOCK | SQLITE_SHM_EXCLUSIVE);
+  WALTRACE(("WAL%p: release EXCLUSIVE-%s cnt=%d\n", pWal,
+             walLockName(lockIdx), n));
+}
+
+/*
+** Compute a hash on a page number.  The resulting hash value must land
+** between 0 and (HASHTABLE_NSLOT-1).  The walHashNext() function advances
+** the hash to the next value in the event of a collision.
+*/
+static int walHash(u32 iPage){
+  assert( iPage>0 );
+  assert( (HASHTABLE_NSLOT & (HASHTABLE_NSLOT-1))==0 );
+  return (iPage*HASHTABLE_HASH_1) & (HASHTABLE_NSLOT-1);
+}
+static int walNextHash(int iPriorHash){
+  return (iPriorHash+1)&(HASHTABLE_NSLOT-1);
+}
+
+/* 
+** Return pointers to the hash table and page number array stored on
+** page iHash of the wal-index. The wal-index is broken into 32KB pages
+** numbered starting from 0.
+**
+** Set output variable *paHash to point to the start of the hash table
+** in the wal-index file. Set *piZero to one less than the frame 
+** number of the first frame indexed by this hash table. If a
+** slot in the hash table is set to N, it refers to frame number 
+** (*piZero+N) in the log.
+**
+** Finally, set *paPgno so that *paPgno[1] is the page number of the
+** first frame indexed by the hash table, frame (*piZero+1).
+*/
+static int walHashGet(
+  Wal *pWal,                      /* WAL handle */
+  int iHash,                      /* Find the iHash'th table */
+  volatile ht_slot **paHash,      /* OUT: Pointer to hash index */
+  volatile u32 **paPgno,          /* OUT: Pointer to page number array */
+  u32 *piZero                     /* OUT: Frame associated with *paPgno[0] */
+){
+  int rc;                         /* Return code */
+  volatile u32 *aPgno;
+
+  rc = walIndexPage(pWal, iHash, &aPgno);
+  assert( rc==SQLITE_OK || iHash>0 );
+
+  if( rc==SQLITE_OK ){
+    u32 iZero;
+    volatile ht_slot *aHash;
+
+    aHash = (volatile ht_slot *)&aPgno[HASHTABLE_NPAGE];
+    if( iHash==0 ){
+      aPgno = &aPgno[WALINDEX_HDR_SIZE/sizeof(u32)];
+      iZero = 0;
+    }else{
+      iZero = HASHTABLE_NPAGE_ONE + (iHash-1)*HASHTABLE_NPAGE;
+    }
+  
+    *paPgno = &aPgno[-1];
+    *paHash = aHash;
+    *piZero = iZero;
+  }
+  return rc;
+}
+
+/*
+** Return the number of the wal-index page that contains the hash-table
+** and page-number array that contain entries corresponding to WAL frame
+** iFrame. The wal-index is broken up into 32KB pages. Wal-index pages 
+** are numbered starting from 0.
+*/
+static int walFramePage(u32 iFrame){
+  int iHash = (iFrame+HASHTABLE_NPAGE-HASHTABLE_NPAGE_ONE-1) / HASHTABLE_NPAGE;
+  assert( (iHash==0 || iFrame>HASHTABLE_NPAGE_ONE)
+       && (iHash>=1 || iFrame<=HASHTABLE_NPAGE_ONE)
+       && (iHash<=1 || iFrame>(HASHTABLE_NPAGE_ONE+HASHTABLE_NPAGE))
+       && (iHash>=2 || iFrame<=HASHTABLE_NPAGE_ONE+HASHTABLE_NPAGE)
+       && (iHash<=2 || iFrame>(HASHTABLE_NPAGE_ONE+2*HASHTABLE_NPAGE))
+  );
+  return iHash;
+}
+
+/*
+** Return the page number associated with frame iFrame in this WAL.
+*/
+static u32 walFramePgno(Wal *pWal, u32 iFrame){
+  int iHash = walFramePage(iFrame);
+  if( iHash==0 ){
+    return pWal->apWiData[0][WALINDEX_HDR_SIZE/sizeof(u32) + iFrame - 1];
+  }
+  return pWal->apWiData[iHash][(iFrame-1-HASHTABLE_NPAGE_ONE)%HASHTABLE_NPAGE];
+}
+
+/*
+** Remove entries from the hash table that point to WAL slots greater
+** than pWal->hdr.mxFrame.
+**
+** This function is called whenever pWal->hdr.mxFrame is decreased due
+** to a rollback or savepoint.
+**
+** At most only the hash table containing pWal->hdr.mxFrame needs to be
+** updated.  Any later hash tables will be automatically cleared when
+** pWal->hdr.mxFrame advances to the point where those hash tables are
+** actually needed.
+*/
+static void walCleanupHash(Wal *pWal){
+  volatile ht_slot *aHash = 0;    /* Pointer to hash table to clear */
+  volatile u32 *aPgno = 0;        /* Page number array for hash table */
+  u32 iZero = 0;                  /* frame == (aHash[x]+iZero) */
+  int iLimit = 0;                 /* Zero values greater than this */
+  int nByte;                      /* Number of bytes to zero in aPgno[] */
+  int i;                          /* Used to iterate through aHash[] */
+
+  assert( pWal->writeLock );
+  testcase( pWal->hdr.mxFrame==HASHTABLE_NPAGE_ONE-1 );
+  testcase( pWal->hdr.mxFrame==HASHTABLE_NPAGE_ONE );
+  testcase( pWal->hdr.mxFrame==HASHTABLE_NPAGE_ONE+1 );
+
+  if( pWal->hdr.mxFrame==0 ) return;
+
+  /* Obtain pointers to the hash-table and page-number array containing 
+  ** the entry that corresponds to frame pWal->hdr.mxFrame. It is guaranteed
+  ** that the page said hash-table and array reside on is already mapped.
+  */
+  assert( pWal->nWiData>walFramePage(pWal->hdr.mxFrame) );
+  assert( pWal->apWiData[walFramePage(pWal->hdr.mxFrame)] );
+  walHashGet(pWal, walFramePage(pWal->hdr.mxFrame), &aHash, &aPgno, &iZero);
+
+  /* Zero all hash-table entries that correspond to frame numbers greater
+  ** than pWal->hdr.mxFrame.
+  */
+  iLimit = pWal->hdr.mxFrame - iZero;
+  assert( iLimit>0 );
+  for(i=0; i<HASHTABLE_NSLOT; i++){
+    if( aHash[i]>iLimit ){
+      aHash[i] = 0;
+    }
+  }
+  
+  /* Zero the entries in the aPgno array that correspond to frames with
+  ** frame numbers greater than pWal->hdr.mxFrame. 
+  */
+  nByte = (int)((char *)aHash - (char *)&aPgno[iLimit+1]);
+  memset((void *)&aPgno[iLimit+1], 0, nByte);
+
+#ifdef SQLITE_ENABLE_EXPENSIVE_ASSERT
+  /* Verify that the every entry in the mapping region is still reachable
+  ** via the hash table even after the cleanup.
+  */
+  if( iLimit ){
+    int i;           /* Loop counter */
+    int iKey;        /* Hash key */
+    for(i=1; i<=iLimit; i++){
+      for(iKey=walHash(aPgno[i]); aHash[iKey]; iKey=walNextHash(iKey)){
+        if( aHash[iKey]==i ) break;
+      }
+      assert( aHash[iKey]==i );
+    }
+  }
+#endif /* SQLITE_ENABLE_EXPENSIVE_ASSERT */
+}
+
+
+/*
+** Set an entry in the wal-index that will map database page number
+** pPage into WAL frame iFrame.
+*/
+static int walIndexAppend(Wal *pWal, u32 iFrame, u32 iPage){
+  int rc;                         /* Return code */
+  u32 iZero = 0;                  /* One less than frame number of aPgno[1] */
+  volatile u32 *aPgno = 0;        /* Page number array */
+  volatile ht_slot *aHash = 0;    /* Hash table */
+
+  rc = walHashGet(pWal, walFramePage(iFrame), &aHash, &aPgno, &iZero);
+
+  /* Assuming the wal-index file was successfully mapped, populate the
+  ** page number array and hash table entry.
+  */
+  if( rc==SQLITE_OK ){
+    int iKey;                     /* Hash table key */
+    int idx;                      /* Value to write to hash-table slot */
+    int nCollide;                 /* Number of hash collisions */
+
+    idx = iFrame - iZero;
+    assert( idx <= HASHTABLE_NSLOT/2 + 1 );
+    
+    /* If this is the first entry to be added to this hash-table, zero the
+    ** entire hash table and aPgno[] array before proceding. 
+    */
+    if( idx==1 ){
+      int nByte = (int)((u8 *)&aHash[HASHTABLE_NSLOT] - (u8 *)&aPgno[1]);
+      memset((void*)&aPgno[1], 0, nByte);
+    }
+
+    /* If the entry in aPgno[] is already set, then the previous writer
+    ** must have exited unexpectedly in the middle of a transaction (after
+    ** writing one or more dirty pages to the WAL to free up memory). 
+    ** Remove the remnants of that writers uncommitted transaction from 
+    ** the hash-table before writing any new entries.
+    */
+    if( aPgno[idx] ){
+      walCleanupHash(pWal);
+      assert( !aPgno[idx] );
+    }
+
+    /* Write the aPgno[] array entry and the hash-table slot. */
+    nCollide = idx;
+    for(iKey=walHash(iPage); aHash[iKey]; iKey=walNextHash(iKey)){
+      if( (nCollide--)==0 ) return SQLITE_CORRUPT_BKPT;
+    }
+    aPgno[idx] = iPage;
+    aHash[iKey] = (ht_slot)idx;
+
+#ifdef SQLITE_ENABLE_EXPENSIVE_ASSERT
+    /* Verify that the number of entries in the hash table exactly equals
+    ** the number of entries in the mapping region.
+    */
+    {
+      int i;           /* Loop counter */
+      int nEntry = 0;  /* Number of entries in the hash table */
+      for(i=0; i<HASHTABLE_NSLOT; i++){ if( aHash[i] ) nEntry++; }
+      assert( nEntry==idx );
+    }
+
+    /* Verify that the every entry in the mapping region is reachable
+    ** via the hash table.  This turns out to be a really, really expensive
+    ** thing to check, so only do this occasionally - not on every
+    ** iteration.
+    */
+    if( (idx&0x3ff)==0 ){
+      int i;           /* Loop counter */
+      for(i=1; i<=idx; i++){
+        for(iKey=walHash(aPgno[i]); aHash[iKey]; iKey=walNextHash(iKey)){
+          if( aHash[iKey]==i ) break;
+        }
+        assert( aHash[iKey]==i );
+      }
+    }
+#endif /* SQLITE_ENABLE_EXPENSIVE_ASSERT */
+  }
+
+
+  return rc;
+}
+
+
+/*
+** Recover the wal-index by reading the write-ahead log file. 
+**
+** This routine first tries to establish an exclusive lock on the
+** wal-index to prevent other threads/processes from doing anything
+** with the WAL or wal-index while recovery is running.  The
+** WAL_RECOVER_LOCK is also held so that other threads will know
+** that this thread is running recovery.  If unable to establish
+** the necessary locks, this routine returns SQLITE_BUSY.
+*/
+static int walIndexRecover(Wal *pWal){
+  int rc;                         /* Return Code */
+  i64 nSize;                      /* Size of log file */
+  u32 aFrameCksum[2] = {0, 0};
+  int iLock;                      /* Lock offset to lock for checkpoint */
+  int nLock;                      /* Number of locks to hold */
+
+  /* Obtain an exclusive lock on all byte in the locking range not already
+  ** locked by the caller. The caller is guaranteed to have locked the
+  ** WAL_WRITE_LOCK byte, and may have also locked the WAL_CKPT_LOCK byte.
+  ** If successful, the same bytes that are locked here are unlocked before
+  ** this function returns.
+  */
+  assert( pWal->ckptLock==1 || pWal->ckptLock==0 );
+  assert( WAL_ALL_BUT_WRITE==WAL_WRITE_LOCK+1 );
+  assert( WAL_CKPT_LOCK==WAL_ALL_BUT_WRITE );
+  assert( pWal->writeLock );
+  iLock = WAL_ALL_BUT_WRITE + pWal->ckptLock;
+  nLock = SQLITE_SHM_NLOCK - iLock;
+  rc = walLockExclusive(pWal, iLock, nLock);
+  if( rc ){
+    return rc;
+  }
+  WALTRACE(("WAL%p: recovery begin...\n", pWal));
+
+  memset(&pWal->hdr, 0, sizeof(WalIndexHdr));
+
+  rc = sqlite3OsFileSize(pWal->pWalFd, &nSize);
+  if( rc!=SQLITE_OK ){
+    goto recovery_error;
+  }
+
+  if( nSize>WAL_HDRSIZE ){
+    u8 aBuf[WAL_HDRSIZE];         /* Buffer to load WAL header into */
+    u8 *aFrame = 0;               /* Malloc'd buffer to load entire frame */
+    int szFrame;                  /* Number of bytes in buffer aFrame[] */
+    u8 *aData;                    /* Pointer to data part of aFrame buffer */
+    int iFrame;                   /* Index of last frame read */
+    i64 iOffset;                  /* Next offset to read from log file */
+    int szPage;                   /* Page size according to the log */
+    u32 magic;                    /* Magic value read from WAL header */
+    u32 version;                  /* Magic value read from WAL header */
+
+    /* Read in the WAL header. */
+    rc = sqlite3OsRead(pWal->pWalFd, aBuf, WAL_HDRSIZE, 0);
+    if( rc!=SQLITE_OK ){
+      goto recovery_error;
+    }
+
+    /* If the database page size is not a power of two, or is greater than
+    ** SQLITE_MAX_PAGE_SIZE, conclude that the WAL file contains no valid 
+    ** data. Similarly, if the 'magic' value is invalid, ignore the whole
+    ** WAL file.
+    */
+    magic = sqlite3Get4byte(&aBuf[0]);
+    szPage = sqlite3Get4byte(&aBuf[8]);
+    if( (magic&0xFFFFFFFE)!=WAL_MAGIC 
+     || szPage&(szPage-1) 
+     || szPage>SQLITE_MAX_PAGE_SIZE 
+     || szPage<512 
+    ){
+      goto finished;
+    }
+    pWal->hdr.bigEndCksum = (u8)(magic&0x00000001);
+    pWal->szPage = szPage;
+    pWal->nCkpt = sqlite3Get4byte(&aBuf[12]);
+    memcpy(&pWal->hdr.aSalt, &aBuf[16], 8);
+
+    /* Verify that the WAL header checksum is correct */
+    walChecksumBytes(pWal->hdr.bigEndCksum==SQLITE_BIGENDIAN, 
+        aBuf, WAL_HDRSIZE-2*4, 0, pWal->hdr.aFrameCksum
+    );
+    if( pWal->hdr.aFrameCksum[0]!=sqlite3Get4byte(&aBuf[24])
+     || pWal->hdr.aFrameCksum[1]!=sqlite3Get4byte(&aBuf[28])
+    ){
+      goto finished;
+    }
+
+    /* Verify that the version number on the WAL format is one that
+    ** are able to understand */
+    version = sqlite3Get4byte(&aBuf[4]);
+    if( version!=WAL_MAX_VERSION ){
+      rc = SQLITE_CANTOPEN_BKPT;
+      goto finished;
+    }
+
+    /* Malloc a buffer to read frames into. */
+    szFrame = szPage + WAL_FRAME_HDRSIZE;
+    aFrame = (u8 *)sqlite3_malloc(szFrame);
+    if( !aFrame ){
+      rc = SQLITE_NOMEM;
+      goto recovery_error;
+    }
+    aData = &aFrame[WAL_FRAME_HDRSIZE];
+
+    /* Read all frames from the log file. */
+    iFrame = 0;
+    for(iOffset=WAL_HDRSIZE; (iOffset+szFrame)<=nSize; iOffset+=szFrame){
+      u32 pgno;                   /* Database page number for frame */
+      u32 nTruncate;              /* dbsize field from frame header */
+      int isValid;                /* True if this frame is valid */
+
+      /* Read and decode the next log frame. */
+      rc = sqlite3OsRead(pWal->pWalFd, aFrame, szFrame, iOffset);
+      if( rc!=SQLITE_OK ) break;
+      isValid = walDecodeFrame(pWal, &pgno, &nTruncate, aData, aFrame);
+      if( !isValid ) break;
+      rc = walIndexAppend(pWal, ++iFrame, pgno);
+      if( rc!=SQLITE_OK ) break;
+
+      /* If nTruncate is non-zero, this is a commit record. */
+      if( nTruncate ){
+        pWal->hdr.mxFrame = iFrame;
+        pWal->hdr.nPage = nTruncate;
+        pWal->hdr.szPage = (u16)((szPage&0xff00) | (szPage>>16));
+        testcase( szPage<=32768 );
+        testcase( szPage>=65536 );
+        aFrameCksum[0] = pWal->hdr.aFrameCksum[0];
+        aFrameCksum[1] = pWal->hdr.aFrameCksum[1];
+      }
+    }
+
+    sqlite3_free(aFrame);
+  }
+
+finished:
+  if( rc==SQLITE_OK ){
+    volatile WalCkptInfo *pInfo;
+    int i;
+    pWal->hdr.aFrameCksum[0] = aFrameCksum[0];
+    pWal->hdr.aFrameCksum[1] = aFrameCksum[1];
+    walIndexWriteHdr(pWal);
+
+    /* Reset the checkpoint-header. This is safe because this thread is 
+    ** currently holding locks that exclude all other readers, writers and
+    ** checkpointers.
+    */
+    pInfo = walCkptInfo(pWal);
+    pInfo->nBackfill = 0;
+    pInfo->aReadMark[0] = 0;
+    for(i=1; i<WAL_NREADER; i++) pInfo->aReadMark[i] = READMARK_NOT_USED;
+
+    /* If more than one frame was recovered from the log file, report an
+    ** event via sqlite3_log(). This is to help with identifying performance
+    ** problems caused by applications routinely shutting down without
+    ** checkpointing the log file.
+    */
+    if( pWal->hdr.nPage ){
+      sqlite3_log(SQLITE_OK, "Recovered %d frames from WAL file %s",
+          pWal->hdr.nPage, pWal->zWalName
+      );
+    }
+  }
+
+recovery_error:
+  WALTRACE(("WAL%p: recovery %s\n", pWal, rc ? "failed" : "ok"));
+  walUnlockExclusive(pWal, iLock, nLock);
+  return rc;
+}
+
+/*
+** Close an open wal-index.
+*/
+static void walIndexClose(Wal *pWal, int isDelete){
+  if( pWal->exclusiveMode==WAL_HEAPMEMORY_MODE ){
+    int i;
+    for(i=0; i<pWal->nWiData; i++){
+      sqlite3_free((void *)pWal->apWiData[i]);
+      pWal->apWiData[i] = 0;
+    }
+  }else{
+    sqlite3OsShmUnmap(pWal->pDbFd, isDelete);
+  }
+}
+
+/* 
+** Open a connection to the WAL file zWalName. The database file must 
+** already be opened on connection pDbFd. The buffer that zWalName points
+** to must remain valid for the lifetime of the returned Wal* handle.
+**
+** A SHARED lock should be held on the database file when this function
+** is called. The purpose of this SHARED lock is to prevent any other
+** client from unlinking the WAL or wal-index file. If another process
+** were to do this just after this client opened one of these files, the
+** system would be badly broken.
+**
+** If the log file is successfully opened, SQLITE_OK is returned and 
+** *ppWal is set to point to a new WAL handle. If an error occurs,
+** an SQLite error code is returned and *ppWal is left unmodified.
+*/
+int sqlite3WalOpen(
+  sqlite3_vfs *pVfs,              /* vfs module to open wal and wal-index */
+  sqlite3_file *pDbFd,            /* The open database file */
+  const char *zWalName,           /* Name of the WAL file */
+  int bNoShm,                     /* True to run in heap-memory mode */
+  i64 mxWalSize,                  /* Truncate WAL to this size on reset */
+  Wal **ppWal                     /* OUT: Allocated Wal handle */
+){
+  int rc;                         /* Return Code */
+  Wal *pRet;                      /* Object to allocate and return */
+  int flags;                      /* Flags passed to OsOpen() */
+
+  assert( zWalName && zWalName[0] );
+  assert( pDbFd );
+
+  /* In the amalgamation, the os_unix.c and os_win.c source files come before
+  ** this source file.  Verify that the #defines of the locking byte offsets
+  ** in os_unix.c and os_win.c agree with the WALINDEX_LOCK_OFFSET value.
+  */
+#ifdef WIN_SHM_BASE
+  assert( WIN_SHM_BASE==WALINDEX_LOCK_OFFSET );
+#endif
+#ifdef UNIX_SHM_BASE
+  assert( UNIX_SHM_BASE==WALINDEX_LOCK_OFFSET );
+#endif
+
+
+  /* Allocate an instance of struct Wal to return. */
+  *ppWal = 0;
+  pRet = (Wal*)sqlite3MallocZero(sizeof(Wal) + pVfs->szOsFile);
+  if( !pRet ){
+    return SQLITE_NOMEM;
+  }
+
+  pRet->pVfs = pVfs;
+  pRet->pWalFd = (sqlite3_file *)&pRet[1];
+  pRet->pDbFd = pDbFd;
+  pRet->readLock = -1;
+  pRet->mxWalSize = mxWalSize;
+  pRet->zWalName = zWalName;
+  pRet->exclusiveMode = (bNoShm ? WAL_HEAPMEMORY_MODE: WAL_NORMAL_MODE);
+
+  /* Open file handle on the write-ahead log file. */
+  flags = (SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE|SQLITE_OPEN_WAL);
+  rc = sqlite3OsOpen(pVfs, zWalName, pRet->pWalFd, flags, &flags);
+  if( rc==SQLITE_OK && flags&SQLITE_OPEN_READONLY ){
+    pRet->readOnly = WAL_RDONLY;
+  }
+
+  if( rc!=SQLITE_OK ){
+    walIndexClose(pRet, 0);
+    sqlite3OsClose(pRet->pWalFd);
+    sqlite3_free(pRet);
+  }else{
+    *ppWal = pRet;
+    WALTRACE(("WAL%d: opened\n", pRet));
+  }
+  return rc;
+}
+
+/*
+** Change the size to which the WAL file is trucated on each reset.
+*/
+void sqlite3WalLimit(Wal *pWal, i64 iLimit){
+  if( pWal ) pWal->mxWalSize = iLimit;
+}
+
+/*
+** Find the smallest page number out of all pages held in the WAL that
+** has not been returned by any prior invocation of this method on the
+** same WalIterator object.   Write into *piFrame the frame index where
+** that page was last written into the WAL.  Write into *piPage the page
+** number.
+**
+** Return 0 on success.  If there are no pages in the WAL with a page
+** number larger than *piPage, then return 1.
+*/
+static int walIteratorNext(
+  WalIterator *p,               /* Iterator */
+  u32 *piPage,                  /* OUT: The page number of the next page */
+  u32 *piFrame                  /* OUT: Wal frame index of next page */
+){
+  u32 iMin;                     /* Result pgno must be greater than iMin */
+  u32 iRet = 0xFFFFFFFF;        /* 0xffffffff is never a valid page number */
+  int i;                        /* For looping through segments */
+
+  iMin = p->iPrior;
+  assert( iMin<0xffffffff );
+  for(i=p->nSegment-1; i>=0; i--){
+    struct WalSegment *pSegment = &p->aSegment[i];
+    while( pSegment->iNext<pSegment->nEntry ){
+      u32 iPg = pSegment->aPgno[pSegment->aIndex[pSegment->iNext]];
+      if( iPg>iMin ){
+        if( iPg<iRet ){
+          iRet = iPg;
+          *piFrame = pSegment->iZero + pSegment->aIndex[pSegment->iNext];
+        }
+        break;
+      }
+      pSegment->iNext++;
+    }
+  }
+
+  *piPage = p->iPrior = iRet;
+  return (iRet==0xFFFFFFFF);
+}
+
+/*
+** This function merges two sorted lists into a single sorted list.
+**
+** aLeft[] and aRight[] are arrays of indices.  The sort key is
+** aContent[aLeft[]] and aContent[aRight[]].  Upon entry, the following
+** is guaranteed for all J<K:
+**
+**        aContent[aLeft[J]] < aContent[aLeft[K]]
+**        aContent[aRight[J]] < aContent[aRight[K]]
+**
+** This routine overwrites aRight[] with a new (probably longer) sequence
+** of indices such that the aRight[] contains every index that appears in
+** either aLeft[] or the old aRight[] and such that the second condition
+** above is still met.
+**
+** The aContent[aLeft[X]] values will be unique for all X.  And the
+** aContent[aRight[X]] values will be unique too.  But there might be
+** one or more combinations of X and Y such that
+**
+**      aLeft[X]!=aRight[Y]  &&  aContent[aLeft[X]] == aContent[aRight[Y]]
+**
+** When that happens, omit the aLeft[X] and use the aRight[Y] index.
+*/
+static void walMerge(
+  const u32 *aContent,            /* Pages in wal - keys for the sort */
+  ht_slot *aLeft,                 /* IN: Left hand input list */
+  int nLeft,                      /* IN: Elements in array *paLeft */
+  ht_slot **paRight,              /* IN/OUT: Right hand input list */
+  int *pnRight,                   /* IN/OUT: Elements in *paRight */
+  ht_slot *aTmp                   /* Temporary buffer */
+){
+  int iLeft = 0;                  /* Current index in aLeft */
+  int iRight = 0;                 /* Current index in aRight */
+  int iOut = 0;                   /* Current index in output buffer */
+  int nRight = *pnRight;
+  ht_slot *aRight = *paRight;
+
+  assert( nLeft>0 && nRight>0 );
+  while( iRight<nRight || iLeft<nLeft ){
+    ht_slot logpage;
+    Pgno dbpage;
+
+    if( (iLeft<nLeft) 
+     && (iRight>=nRight || aContent[aLeft[iLeft]]<aContent[aRight[iRight]])
+    ){
+      logpage = aLeft[iLeft++];
+    }else{
+      logpage = aRight[iRight++];
+    }
+    dbpage = aContent[logpage];
+
+    aTmp[iOut++] = logpage;
+    if( iLeft<nLeft && aContent[aLeft[iLeft]]==dbpage ) iLeft++;
+
+    assert( iLeft>=nLeft || aContent[aLeft[iLeft]]>dbpage );
+    assert( iRight>=nRight || aContent[aRight[iRight]]>dbpage );
+  }
+
+  *paRight = aLeft;
+  *pnRight = iOut;
+  memcpy(aLeft, aTmp, sizeof(aTmp[0])*iOut);
+}
+
+/*
+** Sort the elements in list aList using aContent[] as the sort key.
+** Remove elements with duplicate keys, preferring to keep the
+** larger aList[] values.
+**
+** The aList[] entries are indices into aContent[].  The values in
+** aList[] are to be sorted so that for all J<K:
+**
+**      aContent[aList[J]] < aContent[aList[K]]
+**
+** For any X and Y such that
+**
+**      aContent[aList[X]] == aContent[aList[Y]]
+**
+** Keep the larger of the two values aList[X] and aList[Y] and discard
+** the smaller.
+*/
+static void walMergesort(
+  const u32 *aContent,            /* Pages in wal */
+  ht_slot *aBuffer,               /* Buffer of at least *pnList items to use */
+  ht_slot *aList,                 /* IN/OUT: List to sort */
+  int *pnList                     /* IN/OUT: Number of elements in aList[] */
+){
+  struct Sublist {
+    int nList;                    /* Number of elements in aList */
+    ht_slot *aList;               /* Pointer to sub-list content */
+  };
+
+  const int nList = *pnList;      /* Size of input list */
+  int nMerge = 0;                 /* Number of elements in list aMerge */
+  ht_slot *aMerge = 0;            /* List to be merged */
+  int iList;                      /* Index into input list */
+  int iSub = 0;                   /* Index into aSub array */
+  struct Sublist aSub[13];        /* Array of sub-lists */
+
+  memset(aSub, 0, sizeof(aSub));
+  assert( nList<=HASHTABLE_NPAGE && nList>0 );
+  assert( HASHTABLE_NPAGE==(1<<(ArraySize(aSub)-1)) );
+
+  for(iList=0; iList<nList; iList++){
+    nMerge = 1;
+    aMerge = &aList[iList];
+    for(iSub=0; iList & (1<<iSub); iSub++){
+      struct Sublist *p = &aSub[iSub];
+      assert( p->aList && p->nList<=(1<<iSub) );
+      assert( p->aList==&aList[iList&~((2<<iSub)-1)] );
+      walMerge(aContent, p->aList, p->nList, &aMerge, &nMerge, aBuffer);
+    }
+    aSub[iSub].aList = aMerge;
+    aSub[iSub].nList = nMerge;
+  }
+
+  for(iSub++; iSub<ArraySize(aSub); iSub++){
+    if( nList & (1<<iSub) ){
+      struct Sublist *p = &aSub[iSub];
+      assert( p->nList<=(1<<iSub) );
+      assert( p->aList==&aList[nList&~((2<<iSub)-1)] );
+      walMerge(aContent, p->aList, p->nList, &aMerge, &nMerge, aBuffer);
+    }
+  }
+  assert( aMerge==aList );
+  *pnList = nMerge;
+
+#ifdef SQLITE_DEBUG
+  {
+    int i;
+    for(i=1; i<*pnList; i++){
+      assert( aContent[aList[i]] > aContent[aList[i-1]] );
+    }
+  }
+#endif
+}
+
+/* 
+** Free an iterator allocated by walIteratorInit().
+*/
+static void walIteratorFree(WalIterator *p){
+  sqlite3ScratchFree(p);
+}
+
+/*
+** Construct a WalInterator object that can be used to loop over all 
+** pages in the WAL in ascending order. The caller must hold the checkpoint
+** lock.
+**
+** On success, make *pp point to the newly allocated WalInterator object
+** return SQLITE_OK. Otherwise, return an error code. If this routine
+** returns an error, the value of *pp is undefined.
+**
+** The calling routine should invoke walIteratorFree() to destroy the
+** WalIterator object when it has finished with it.
+*/
+static int walIteratorInit(Wal *pWal, WalIterator **pp){
+  WalIterator *p;                 /* Return value */
+  int nSegment;                   /* Number of segments to merge */
+  u32 iLast;                      /* Last frame in log */
+  int nByte;                      /* Number of bytes to allocate */
+  int i;                          /* Iterator variable */
+  ht_slot *aTmp;                  /* Temp space used by merge-sort */
+  int rc = SQLITE_OK;             /* Return Code */
+
+  /* This routine only runs while holding the checkpoint lock. And
+  ** it only runs if there is actually content in the log (mxFrame>0).
+  */
+  assert( pWal->ckptLock && pWal->hdr.mxFrame>0 );
+  iLast = pWal->hdr.mxFrame;
+
+  /* Allocate space for the WalIterator object. */
+  nSegment = walFramePage(iLast) + 1;
+  nByte = sizeof(WalIterator) 
+        + (nSegment-1)*sizeof(struct WalSegment)
+        + iLast*sizeof(ht_slot);
+  p = (WalIterator *)sqlite3ScratchMalloc(nByte);
+  if( !p ){
+    return SQLITE_NOMEM;
+  }
+  memset(p, 0, nByte);
+  p->nSegment = nSegment;
+
+  /* Allocate temporary space used by the merge-sort routine. This block
+  ** of memory will be freed before this function returns.
+  */
+  aTmp = (ht_slot *)sqlite3ScratchMalloc(
+      sizeof(ht_slot) * (iLast>HASHTABLE_NPAGE?HASHTABLE_NPAGE:iLast)
+  );
+  if( !aTmp ){
+    rc = SQLITE_NOMEM;
+  }
+
+  for(i=0; rc==SQLITE_OK && i<nSegment; i++){
+    volatile ht_slot *aHash;
+    u32 iZero;
+    volatile u32 *aPgno;
+
+    rc = walHashGet(pWal, i, &aHash, &aPgno, &iZero);
+    if( rc==SQLITE_OK ){
+      int j;                      /* Counter variable */
+      int nEntry;                 /* Number of entries in this segment */
+      ht_slot *aIndex;            /* Sorted index for this segment */
+
+      aPgno++;
+      if( (i+1)==nSegment ){
+        nEntry = (int)(iLast - iZero);
+      }else{
+        nEntry = (int)((u32*)aHash - (u32*)aPgno);
+      }
+      aIndex = &((ht_slot *)&p->aSegment[p->nSegment])[iZero];
+      iZero++;
+  
+      for(j=0; j<nEntry; j++){
+        aIndex[j] = (ht_slot)j;
+      }
+      walMergesort((u32 *)aPgno, aTmp, aIndex, &nEntry);
+      p->aSegment[i].iZero = iZero;
+      p->aSegment[i].nEntry = nEntry;
+      p->aSegment[i].aIndex = aIndex;
+      p->aSegment[i].aPgno = (u32 *)aPgno;
+    }
+  }
+  sqlite3ScratchFree(aTmp);
+
+  if( rc!=SQLITE_OK ){
+    walIteratorFree(p);
+  }
+  *pp = p;
+  return rc;
+}
+
+/*
+** Attempt to obtain the exclusive WAL lock defined by parameters lockIdx and
+** n. If the attempt fails and parameter xBusy is not NULL, then it is a
+** busy-handler function. Invoke it and retry the lock until either the
+** lock is successfully obtained or the busy-handler returns 0.
+*/
+static int walBusyLock(
+  Wal *pWal,                      /* WAL connection */
+  int (*xBusy)(void*),            /* Function to call when busy */
+  void *pBusyArg,                 /* Context argument for xBusyHandler */
+  int lockIdx,                    /* Offset of first byte to lock */
+  int n                           /* Number of bytes to lock */
+){
+  int rc;
+  do {
+    rc = walLockExclusive(pWal, lockIdx, n);
+  }while( xBusy && rc==SQLITE_BUSY && xBusy(pBusyArg) );
+  return rc;
+}
+
+/*
+** The cache of the wal-index header must be valid to call this function.
+** Return the page-size in bytes used by the database.
+*/
+static int walPagesize(Wal *pWal){
+  return (pWal->hdr.szPage&0xfe00) + ((pWal->hdr.szPage&0x0001)<<16);
+}
+
+/*
+** Copy as much content as we can from the WAL back into the database file
+** in response to an sqlite3_wal_checkpoint() request or the equivalent.
+**
+** The amount of information copies from WAL to database might be limited
+** by active readers.  This routine will never overwrite a database page
+** that a concurrent reader might be using.
+**
+** All I/O barrier operations (a.k.a fsyncs) occur in this routine when
+** SQLite is in WAL-mode in synchronous=NORMAL.  That means that if 
+** checkpoints are always run by a background thread or background 
+** process, foreground threads will never block on a lengthy fsync call.
+**
+** Fsync is called on the WAL before writing content out of the WAL and
+** into the database.  This ensures that if the new content is persistent
+** in the WAL and can be recovered following a power-loss or hard reset.
+**
+** Fsync is also called on the database file if (and only if) the entire
+** WAL content is copied into the database file.  This second fsync makes
+** it safe to delete the WAL since the new content will persist in the
+** database file.
+**
+** This routine uses and updates the nBackfill field of the wal-index header.
+** This is the only routine tha will increase the value of nBackfill.  
+** (A WAL reset or recovery will revert nBackfill to zero, but not increase
+** its value.)
+**
+** The caller must be holding sufficient locks to ensure that no other
+** checkpoint is running (in any other thread or process) at the same
+** time.
+*/
+static int walCheckpoint(
+  Wal *pWal,                      /* Wal connection */
+  int eMode,                      /* One of PASSIVE, FULL or RESTART */
+  int (*xBusyCall)(void*),        /* Function to call when busy */
+  void *pBusyArg,                 /* Context argument for xBusyHandler */
+  int sync_flags,                 /* Flags for OsSync() (or 0) */
+  u8 *zBuf                        /* Temporary buffer to use */
+){
+  int rc;                         /* Return code */
+  int szPage;                     /* Database page-size */
+  WalIterator *pIter = 0;         /* Wal iterator context */
+  u32 iDbpage = 0;                /* Next database page to write */
+  u32 iFrame = 0;                 /* Wal frame containing data for iDbpage */
+  u32 mxSafeFrame;                /* Max frame that can be backfilled */
+  u32 mxPage;                     /* Max database page to write */
+  int i;                          /* Loop counter */
+  volatile WalCkptInfo *pInfo;    /* The checkpoint status information */
+  int (*xBusy)(void*) = 0;        /* Function to call when waiting for locks */
+
+  szPage = walPagesize(pWal);
+  testcase( szPage<=32768 );
+  testcase( szPage>=65536 );
+  pInfo = walCkptInfo(pWal);
+  if( pInfo->nBackfill>=pWal->hdr.mxFrame ) return SQLITE_OK;
+
+  /* Allocate the iterator */
+  rc = walIteratorInit(pWal, &pIter);
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+  assert( pIter );
+
+  if( eMode!=SQLITE_CHECKPOINT_PASSIVE ) xBusy = xBusyCall;
+
+  /* Compute in mxSafeFrame the index of the last frame of the WAL that is
+  ** safe to write into the database.  Frames beyond mxSafeFrame might
+  ** overwrite database pages that are in use by active readers and thus
+  ** cannot be backfilled from the WAL.
+  */
+  mxSafeFrame = pWal->hdr.mxFrame;
+  mxPage = pWal->hdr.nPage;
+  for(i=1; i<WAL_NREADER; i++){
+    u32 y = pInfo->aReadMark[i];
+    if( mxSafeFrame>y ){
+      assert( y<=pWal->hdr.mxFrame );
+      rc = walBusyLock(pWal, xBusy, pBusyArg, WAL_READ_LOCK(i), 1);
+      if( rc==SQLITE_OK ){
+        pInfo->aReadMark[i] = READMARK_NOT_USED;
+        walUnlockExclusive(pWal, WAL_READ_LOCK(i), 1);
+      }else if( rc==SQLITE_BUSY ){
+        mxSafeFrame = y;
+        xBusy = 0;
+      }else{
+        goto walcheckpoint_out;
+      }
+    }
+  }
+
+  if( pInfo->nBackfill<mxSafeFrame
+   && (rc = walBusyLock(pWal, xBusy, pBusyArg, WAL_READ_LOCK(0), 1))==SQLITE_OK
+  ){
+    i64 nSize;                    /* Current size of database file */
+    u32 nBackfill = pInfo->nBackfill;
+
+    /* Sync the WAL to disk */
+    if( sync_flags ){
+      rc = sqlite3OsSync(pWal->pWalFd, sync_flags);
+    }
+
+    /* If the database file may grow as a result of this checkpoint, hint
+    ** about the eventual size of the db file to the VFS layer. 
+    */
+    if( rc==SQLITE_OK ){
+      i64 nReq = ((i64)mxPage * szPage);
+      rc = sqlite3OsFileSize(pWal->pDbFd, &nSize);
+      if( rc==SQLITE_OK && nSize<nReq ){
+        sqlite3OsFileControl(pWal->pDbFd, SQLITE_FCNTL_SIZE_HINT, &nReq);
+      }
+    }
+
+    /* Iterate through the contents of the WAL, copying data to the db file. */
+    while( rc==SQLITE_OK && 0==walIteratorNext(pIter, &iDbpage, &iFrame) ){
+      i64 iOffset;
+      assert( walFramePgno(pWal, iFrame)==iDbpage );
+      if( iFrame<=nBackfill || iFrame>mxSafeFrame || iDbpage>mxPage ) continue;
+      iOffset = walFrameOffset(iFrame, szPage) + WAL_FRAME_HDRSIZE;
+      /* testcase( IS_BIG_INT(iOffset) ); // requires a 4GiB WAL file */
+      rc = sqlite3OsRead(pWal->pWalFd, zBuf, szPage, iOffset);
+      if( rc!=SQLITE_OK ) break;
+      iOffset = (iDbpage-1)*(i64)szPage;
+      testcase( IS_BIG_INT(iOffset) );
+      rc = sqlite3OsWrite(pWal->pDbFd, zBuf, szPage, iOffset);
+      if( rc!=SQLITE_OK ) break;
+    }
+
+    /* If work was actually accomplished... */
+    if( rc==SQLITE_OK ){
+      if( mxSafeFrame==walIndexHdr(pWal)->mxFrame ){
+        i64 szDb = pWal->hdr.nPage*(i64)szPage;
+        testcase( IS_BIG_INT(szDb) );
+        rc = sqlite3OsTruncate(pWal->pDbFd, szDb);
+        if( rc==SQLITE_OK && sync_flags ){
+          rc = sqlite3OsSync(pWal->pDbFd, sync_flags);
+        }
+      }
+      if( rc==SQLITE_OK ){
+        pInfo->nBackfill = mxSafeFrame;
+      }
+    }
+
+    /* Release the reader lock held while backfilling */
+    walUnlockExclusive(pWal, WAL_READ_LOCK(0), 1);
+  }
+
+  if( rc==SQLITE_BUSY ){
+    /* Reset the return code so as not to report a checkpoint failure
+    ** just because there are active readers.  */
+    rc = SQLITE_OK;
+  }
+
+  /* If this is an SQLITE_CHECKPOINT_RESTART operation, and the entire wal
+  ** file has been copied into the database file, then block until all
+  ** readers have finished using the wal file. This ensures that the next
+  ** process to write to the database restarts the wal file.
+  */
+  if( rc==SQLITE_OK && eMode!=SQLITE_CHECKPOINT_PASSIVE ){
+    assert( pWal->writeLock );
+    if( pInfo->nBackfill<pWal->hdr.mxFrame ){
+      rc = SQLITE_BUSY;
+    }else if( eMode==SQLITE_CHECKPOINT_RESTART ){
+      assert( mxSafeFrame==pWal->hdr.mxFrame );
+      rc = walBusyLock(pWal, xBusy, pBusyArg, WAL_READ_LOCK(1), WAL_NREADER-1);
+      if( rc==SQLITE_OK ){
+        walUnlockExclusive(pWal, WAL_READ_LOCK(1), WAL_NREADER-1);
+      }
+    }
+  }
+
+ walcheckpoint_out:
+  walIteratorFree(pIter);
+  return rc;
+}
+
+/*
+** Close a connection to a log file.
+*/
+int sqlite3WalClose(
+  Wal *pWal,                      /* Wal to close */
+  int sync_flags,                 /* Flags to pass to OsSync() (or 0) */
+  int nBuf,
+  u8 *zBuf                        /* Buffer of at least nBuf bytes */
+){
+  int rc = SQLITE_OK;
+  if( pWal ){
+    int isDelete = 0;             /* True to unlink wal and wal-index files */
+
+    /* If an EXCLUSIVE lock can be obtained on the database file (using the
+    ** ordinary, rollback-mode locking methods, this guarantees that the
+    ** connection associated with this log file is the only connection to
+    ** the database. In this case checkpoint the database and unlink both
+    ** the wal and wal-index files.
+    **
+    ** The EXCLUSIVE lock is not released before returning.
+    */
+    rc = sqlite3OsLock(pWal->pDbFd, SQLITE_LOCK_EXCLUSIVE);
+    if( rc==SQLITE_OK ){
+      int bPersistWal = -1;
+      if( pWal->exclusiveMode==WAL_NORMAL_MODE ){
+        pWal->exclusiveMode = WAL_EXCLUSIVE_MODE;
+      }
+      rc = sqlite3WalCheckpoint(
+          pWal, SQLITE_CHECKPOINT_PASSIVE, 0, 0, sync_flags, nBuf, zBuf, 0, 0
+      );
+      sqlite3OsFileControl(pWal->pDbFd, SQLITE_FCNTL_PERSIST_WAL, &bPersistWal);
+      if( rc==SQLITE_OK && bPersistWal!=1 ){
+        isDelete = 1;
+      }
+    }
+
+    walIndexClose(pWal, isDelete);
+    sqlite3OsClose(pWal->pWalFd);
+    if( isDelete ){
+      sqlite3OsDelete(pWal->pVfs, pWal->zWalName, 0);
+    }
+    WALTRACE(("WAL%p: closed\n", pWal));
+    sqlite3_free((void *)pWal->apWiData);
+    sqlite3_free(pWal);
+  }
+  return rc;
+}
+
+/*
+** Try to read the wal-index header.  Return 0 on success and 1 if
+** there is a problem.
+**
+** The wal-index is in shared memory.  Another thread or process might
+** be writing the header at the same time this procedure is trying to
+** read it, which might result in inconsistency.  A dirty read is detected
+** by verifying that both copies of the header are the same and also by
+** a checksum on the header.
+**
+** If and only if the read is consistent and the header is different from
+** pWal->hdr, then pWal->hdr is updated to the content of the new header
+** and *pChanged is set to 1.
+**
+** If the checksum cannot be verified return non-zero. If the header
+** is read successfully and the checksum verified, return zero.
+*/
+static int walIndexTryHdr(Wal *pWal, int *pChanged){
+  u32 aCksum[2];                  /* Checksum on the header content */
+  WalIndexHdr h1, h2;             /* Two copies of the header content */
+  WalIndexHdr volatile *aHdr;     /* Header in shared memory */
+
+  /* The first page of the wal-index must be mapped at this point. */
+  assert( pWal->nWiData>0 && pWal->apWiData[0] );
+
+  /* Read the header. This might happen concurrently with a write to the
+  ** same area of shared memory on a different CPU in a SMP,
+  ** meaning it is possible that an inconsistent snapshot is read
+  ** from the file. If this happens, return non-zero.
+  **
+  ** There are two copies of the header at the beginning of the wal-index.
+  ** When reading, read [0] first then [1].  Writes are in the reverse order.
+  ** Memory barriers are used to prevent the compiler or the hardware from
+  ** reordering the reads and writes.
+  */
+  aHdr = walIndexHdr(pWal);
+  memcpy(&h1, (void *)&aHdr[0], sizeof(h1));
+  walShmBarrier(pWal);
+  memcpy(&h2, (void *)&aHdr[1], sizeof(h2));
+
+  if( memcmp(&h1, &h2, sizeof(h1))!=0 ){
+    return 1;   /* Dirty read */
+  }  
+  if( h1.isInit==0 ){
+    return 1;   /* Malformed header - probably all zeros */
+  }
+  walChecksumBytes(1, (u8*)&h1, sizeof(h1)-sizeof(h1.aCksum), 0, aCksum);
+  if( aCksum[0]!=h1.aCksum[0] || aCksum[1]!=h1.aCksum[1] ){
+    return 1;   /* Checksum does not match */
+  }
+
+  if( memcmp(&pWal->hdr, &h1, sizeof(WalIndexHdr)) ){
+    *pChanged = 1;
+    memcpy(&pWal->hdr, &h1, sizeof(WalIndexHdr));
+    pWal->szPage = (pWal->hdr.szPage&0xfe00) + ((pWal->hdr.szPage&0x0001)<<16);
+    testcase( pWal->szPage<=32768 );
+    testcase( pWal->szPage>=65536 );
+  }
+
+  /* The header was successfully read. Return zero. */
+  return 0;
+}
+
+/*
+** Read the wal-index header from the wal-index and into pWal->hdr.
+** If the wal-header appears to be corrupt, try to reconstruct the
+** wal-index from the WAL before returning.
+**
+** Set *pChanged to 1 if the wal-index header value in pWal->hdr is
+** changed by this opertion.  If pWal->hdr is unchanged, set *pChanged
+** to 0.
+**
+** If the wal-index header is successfully read, return SQLITE_OK. 
+** Otherwise an SQLite error code.
+*/
+static int walIndexReadHdr(Wal *pWal, int *pChanged){
+  int rc;                         /* Return code */
+  int badHdr;                     /* True if a header read failed */
+  volatile u32 *page0;            /* Chunk of wal-index containing header */
+
+  /* Ensure that page 0 of the wal-index (the page that contains the 
+  ** wal-index header) is mapped. Return early if an error occurs here.
+  */
+  assert( pChanged );
+  rc = walIndexPage(pWal, 0, &page0);
+  if( rc!=SQLITE_OK ){
+    return rc;
+  };
+  assert( page0 || pWal->writeLock==0 );
+
+  /* If the first page of the wal-index has been mapped, try to read the
+  ** wal-index header immediately, without holding any lock. This usually
+  ** works, but may fail if the wal-index header is corrupt or currently 
+  ** being modified by another thread or process.
+  */
+  badHdr = (page0 ? walIndexTryHdr(pWal, pChanged) : 1);
+
+  /* If the first attempt failed, it might have been due to a race
+  ** with a writer.  So get a WRITE lock and try again.
+  */
+  assert( badHdr==0 || pWal->writeLock==0 );
+  if( badHdr ){
+    if( pWal->readOnly & WAL_SHM_RDONLY ){
+      if( SQLITE_OK==(rc = walLockShared(pWal, WAL_WRITE_LOCK)) ){
+        walUnlockShared(pWal, WAL_WRITE_LOCK);
+        rc = SQLITE_READONLY_RECOVERY;
+      }
+    }else if( SQLITE_OK==(rc = walLockExclusive(pWal, WAL_WRITE_LOCK, 1)) ){
+      pWal->writeLock = 1;
+      if( SQLITE_OK==(rc = walIndexPage(pWal, 0, &page0)) ){
+        badHdr = walIndexTryHdr(pWal, pChanged);
+        if( badHdr ){
+          /* If the wal-index header is still malformed even while holding
+          ** a WRITE lock, it can only mean that the header is corrupted and
+          ** needs to be reconstructed.  So run recovery to do exactly that.
+          */
+          rc = walIndexRecover(pWal);
+          *pChanged = 1;
+        }
+      }
+      pWal->writeLock = 0;
+      walUnlockExclusive(pWal, WAL_WRITE_LOCK, 1);
+    }
+  }
+
+  /* If the header is read successfully, check the version number to make
+  ** sure the wal-index was not constructed with some future format that
+  ** this version of SQLite cannot understand.
+  */
+  if( badHdr==0 && pWal->hdr.iVersion!=WALINDEX_MAX_VERSION ){
+    rc = SQLITE_CANTOPEN_BKPT;
+  }
+
+  return rc;
+}
+
+/*
+** This is the value that walTryBeginRead returns when it needs to
+** be retried.
+*/
+#define WAL_RETRY  (-1)
+
+/*
+** Attempt to start a read transaction.  This might fail due to a race or
+** other transient condition.  When that happens, it returns WAL_RETRY to
+** indicate to the caller that it is safe to retry immediately.
+**
+** On success return SQLITE_OK.  On a permanent failure (such an
+** I/O error or an SQLITE_BUSY because another process is running
+** recovery) return a positive error code.
+**
+** The useWal parameter is true to force the use of the WAL and disable
+** the case where the WAL is bypassed because it has been completely
+** checkpointed.  If useWal==0 then this routine calls walIndexReadHdr() 
+** to make a copy of the wal-index header into pWal->hdr.  If the 
+** wal-index header has changed, *pChanged is set to 1 (as an indication 
+** to the caller that the local paget cache is obsolete and needs to be 
+** flushed.)  When useWal==1, the wal-index header is assumed to already
+** be loaded and the pChanged parameter is unused.
+**
+** The caller must set the cnt parameter to the number of prior calls to
+** this routine during the current read attempt that returned WAL_RETRY.
+** This routine will start taking more aggressive measures to clear the
+** race conditions after multiple WAL_RETRY returns, and after an excessive
+** number of errors will ultimately return SQLITE_PROTOCOL.  The
+** SQLITE_PROTOCOL return indicates that some other process has gone rogue
+** and is not honoring the locking protocol.  There is a vanishingly small
+** chance that SQLITE_PROTOCOL could be returned because of a run of really
+** bad luck when there is lots of contention for the wal-index, but that
+** possibility is so small that it can be safely neglected, we believe.
+**
+** On success, this routine obtains a read lock on 
+** WAL_READ_LOCK(pWal->readLock).  The pWal->readLock integer is
+** in the range 0 <= pWal->readLock < WAL_NREADER.  If pWal->readLock==(-1)
+** that means the Wal does not hold any read lock.  The reader must not
+** access any database page that is modified by a WAL frame up to and
+** including frame number aReadMark[pWal->readLock].  The reader will
+** use WAL frames up to and including pWal->hdr.mxFrame if pWal->readLock>0
+** Or if pWal->readLock==0, then the reader will ignore the WAL
+** completely and get all content directly from the database file.
+** If the useWal parameter is 1 then the WAL will never be ignored and
+** this routine will always set pWal->readLock>0 on success.
+** When the read transaction is completed, the caller must release the
+** lock on WAL_READ_LOCK(pWal->readLock) and set pWal->readLock to -1.
+**
+** This routine uses the nBackfill and aReadMark[] fields of the header
+** to select a particular WAL_READ_LOCK() that strives to let the
+** checkpoint process do as much work as possible.  This routine might
+** update values of the aReadMark[] array in the header, but if it does
+** so it takes care to hold an exclusive lock on the corresponding
+** WAL_READ_LOCK() while changing values.
+*/
+static int walTryBeginRead(Wal *pWal, int *pChanged, int useWal, int cnt){
+  volatile WalCkptInfo *pInfo;    /* Checkpoint information in wal-index */
+  u32 mxReadMark;                 /* Largest aReadMark[] value */
+  int mxI;                        /* Index of largest aReadMark[] value */
+  int i;                          /* Loop counter */
+  int rc = SQLITE_OK;             /* Return code  */
+
+  assert( pWal->readLock<0 );     /* Not currently locked */
+
+  /* Take steps to avoid spinning forever if there is a protocol error.
+  **
+  ** Circumstances that cause a RETRY should only last for the briefest
+  ** instances of time.  No I/O or other system calls are done while the
+  ** locks are held, so the locks should not be held for very long. But 
+  ** if we are unlucky, another process that is holding a lock might get
+  ** paged out or take a page-fault that is time-consuming to resolve, 
+  ** during the few nanoseconds that it is holding the lock.  In that case,
+  ** it might take longer than normal for the lock to free.
+  **
+  ** After 5 RETRYs, we begin calling sqlite3OsSleep().  The first few
+  ** calls to sqlite3OsSleep() have a delay of 1 microsecond.  Really this
+  ** is more of a scheduler yield than an actual delay.  But on the 10th
+  ** an subsequent retries, the delays start becoming longer and longer, 
+  ** so that on the 100th (and last) RETRY we delay for 21 milliseconds.
+  ** The total delay time before giving up is less than 1 second.
+  */
+  if( cnt>5 ){
+    int nDelay = 1;                      /* Pause time in microseconds */
+    if( cnt>100 ){
+      VVA_ONLY( pWal->lockError = 1; )
+      return SQLITE_PROTOCOL;
+    }
+    if( cnt>=10 ) nDelay = (cnt-9)*238;  /* Max delay 21ms. Total delay 996ms */
+    sqlite3OsSleep(pWal->pVfs, nDelay);
+  }
+
+  if( !useWal ){
+    rc = walIndexReadHdr(pWal, pChanged);
+    if( rc==SQLITE_BUSY ){
+      /* If there is not a recovery running in another thread or process
+      ** then convert BUSY errors to WAL_RETRY.  If recovery is known to
+      ** be running, convert BUSY to BUSY_RECOVERY.  There is a race here
+      ** which might cause WAL_RETRY to be returned even if BUSY_RECOVERY
+      ** would be technically correct.  But the race is benign since with
+      ** WAL_RETRY this routine will be called again and will probably be
+      ** right on the second iteration.
+      */
+      if( pWal->apWiData[0]==0 ){
+        /* This branch is taken when the xShmMap() method returns SQLITE_BUSY.
+        ** We assume this is a transient condition, so return WAL_RETRY. The
+        ** xShmMap() implementation used by the default unix and win32 VFS 
+        ** modules may return SQLITE_BUSY due to a race condition in the 
+        ** code that determines whether or not the shared-memory region 
+        ** must be zeroed before the requested page is returned.
+        */
+        rc = WAL_RETRY;
+      }else if( SQLITE_OK==(rc = walLockShared(pWal, WAL_RECOVER_LOCK)) ){
+        walUnlockShared(pWal, WAL_RECOVER_LOCK);
+        rc = WAL_RETRY;
+      }else if( rc==SQLITE_BUSY ){
+        rc = SQLITE_BUSY_RECOVERY;
+      }
+    }
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+  }
+
+  pInfo = walCkptInfo(pWal);
+  if( !useWal && pInfo->nBackfill==pWal->hdr.mxFrame ){
+    /* The WAL has been completely backfilled (or it is empty).
+    ** and can be safely ignored.
+    */
+    rc = walLockShared(pWal, WAL_READ_LOCK(0));
+    walShmBarrier(pWal);
+    if( rc==SQLITE_OK ){
+      if( memcmp((void *)walIndexHdr(pWal), &pWal->hdr, sizeof(WalIndexHdr)) ){
+        /* It is not safe to allow the reader to continue here if frames
+        ** may have been appended to the log before READ_LOCK(0) was obtained.
+        ** When holding READ_LOCK(0), the reader ignores the entire log file,
+        ** which implies that the database file contains a trustworthy
+        ** snapshoT. Since holding READ_LOCK(0) prevents a checkpoint from
+        ** happening, this is usually correct.
+        **
+        ** However, if frames have been appended to the log (or if the log 
+        ** is wrapped and written for that matter) before the READ_LOCK(0)
+        ** is obtained, that is not necessarily true. A checkpointer may
+        ** have started to backfill the appended frames but crashed before
+        ** it finished. Leaving a corrupt image in the database file.
+        */
+        walUnlockShared(pWal, WAL_READ_LOCK(0));
+        return WAL_RETRY;
+      }
+      pWal->readLock = 0;
+      return SQLITE_OK;
+    }else if( rc!=SQLITE_BUSY ){
+      return rc;
+    }
+  }
+
+  /* If we get this far, it means that the reader will want to use
+  ** the WAL to get at content from recent commits.  The job now is
+  ** to select one of the aReadMark[] entries that is closest to
+  ** but not exceeding pWal->hdr.mxFrame and lock that entry.
+  */
+  mxReadMark = 0;
+  mxI = 0;
+  for(i=1; i<WAL_NREADER; i++){
+    u32 thisMark = pInfo->aReadMark[i];
+    if( mxReadMark<=thisMark && thisMark<=pWal->hdr.mxFrame ){
+      assert( thisMark!=READMARK_NOT_USED );
+      mxReadMark = thisMark;
+      mxI = i;
+    }
+  }
+  /* There was once an "if" here. The extra "{" is to preserve indentation. */
+  {
+    if( (pWal->readOnly & WAL_SHM_RDONLY)==0
+     && (mxReadMark<pWal->hdr.mxFrame || mxI==0)
+    ){
+      for(i=1; i<WAL_NREADER; i++){
+        rc = walLockExclusive(pWal, WAL_READ_LOCK(i), 1);
+        if( rc==SQLITE_OK ){
+          mxReadMark = pInfo->aReadMark[i] = pWal->hdr.mxFrame;
+          mxI = i;
+          walUnlockExclusive(pWal, WAL_READ_LOCK(i), 1);
+          break;
+        }else if( rc!=SQLITE_BUSY ){
+          return rc;
+        }
+      }
+    }
+    if( mxI==0 ){
+      assert( rc==SQLITE_BUSY || (pWal->readOnly & WAL_SHM_RDONLY)!=0 );
+      return rc==SQLITE_BUSY ? WAL_RETRY : SQLITE_READONLY_CANTLOCK;
+    }
+
+    rc = walLockShared(pWal, WAL_READ_LOCK(mxI));
+    if( rc ){
+      return rc==SQLITE_BUSY ? WAL_RETRY : rc;
+    }
+    /* Now that the read-lock has been obtained, check that neither the
+    ** value in the aReadMark[] array or the contents of the wal-index
+    ** header have changed.
+    **
+    ** It is necessary to check that the wal-index header did not change
+    ** between the time it was read and when the shared-lock was obtained
+    ** on WAL_READ_LOCK(mxI) was obtained to account for the possibility
+    ** that the log file may have been wrapped by a writer, or that frames
+    ** that occur later in the log than pWal->hdr.mxFrame may have been
+    ** copied into the database by a checkpointer. If either of these things
+    ** happened, then reading the database with the current value of
+    ** pWal->hdr.mxFrame risks reading a corrupted snapshot. So, retry
+    ** instead.
+    **
+    ** This does not guarantee that the copy of the wal-index header is up to
+    ** date before proceeding. That would not be possible without somehow
+    ** blocking writers. It only guarantees that a dangerous checkpoint or 
+    ** log-wrap (either of which would require an exclusive lock on
+    ** WAL_READ_LOCK(mxI)) has not occurred since the snapshot was valid.
+    */
+    walShmBarrier(pWal);
+    if( pInfo->aReadMark[mxI]!=mxReadMark
+     || memcmp((void *)walIndexHdr(pWal), &pWal->hdr, sizeof(WalIndexHdr))
+    ){
+      walUnlockShared(pWal, WAL_READ_LOCK(mxI));
+      return WAL_RETRY;
+    }else{
+      assert( mxReadMark<=pWal->hdr.mxFrame );
+      pWal->readLock = (i16)mxI;
+    }
+  }
+  return rc;
+}
+
+/*
+** Begin a read transaction on the database.
+**
+** This routine used to be called sqlite3OpenSnapshot() and with good reason:
+** it takes a snapshot of the state of the WAL and wal-index for the current
+** instant in time.  The current thread will continue to use this snapshot.
+** Other threads might append new content to the WAL and wal-index but
+** that extra content is ignored by the current thread.
+**
+** If the database contents have changes since the previous read
+** transaction, then *pChanged is set to 1 before returning.  The
+** Pager layer will use this to know that is cache is stale and
+** needs to be flushed.
+*/
+int sqlite3WalBeginReadTransaction(Wal *pWal, int *pChanged){
+  int rc;                         /* Return code */
+  int cnt = 0;                    /* Number of TryBeginRead attempts */
+
+  do{
+    rc = walTryBeginRead(pWal, pChanged, 0, ++cnt);
+  }while( rc==WAL_RETRY );
+  testcase( (rc&0xff)==SQLITE_BUSY );
+  testcase( (rc&0xff)==SQLITE_IOERR );
+  testcase( rc==SQLITE_PROTOCOL );
+  testcase( rc==SQLITE_OK );
+  return rc;
+}
+
+/*
+** Finish with a read transaction.  All this does is release the
+** read-lock.
+*/
+void sqlite3WalEndReadTransaction(Wal *pWal){
+  sqlite3WalEndWriteTransaction(pWal);
+  if( pWal->readLock>=0 ){
+    walUnlockShared(pWal, WAL_READ_LOCK(pWal->readLock));
+    pWal->readLock = -1;
+  }
+}
+
+/*
+** Read a page from the WAL, if it is present in the WAL and if the 
+** current read transaction is configured to use the WAL.  
+**
+** The *pInWal is set to 1 if the requested page is in the WAL and
+** has been loaded.  Or *pInWal is set to 0 if the page was not in 
+** the WAL and needs to be read out of the database.
+*/
+int sqlite3WalRead(
+  Wal *pWal,                      /* WAL handle */
+  Pgno pgno,                      /* Database page number to read data for */
+  int *pInWal,                    /* OUT: True if data is read from WAL */
+  int nOut,                       /* Size of buffer pOut in bytes */
+  u8 *pOut                        /* Buffer to write page data to */
+){
+  u32 iRead = 0;                  /* If !=0, WAL frame to return data from */
+  u32 iLast = pWal->hdr.mxFrame;  /* Last page in WAL for this reader */
+  int iHash;                      /* Used to loop through N hash tables */
+
+  /* This routine is only be called from within a read transaction. */
+  assert( pWal->readLock>=0 || pWal->lockError );
+
+  /* If the "last page" field of the wal-index header snapshot is 0, then
+  ** no data will be read from the wal under any circumstances. Return early
+  ** in this case as an optimization.  Likewise, if pWal->readLock==0, 
+  ** then the WAL is ignored by the reader so return early, as if the 
+  ** WAL were empty.
+  */
+  if( iLast==0 || pWal->readLock==0 ){
+    *pInWal = 0;
+    return SQLITE_OK;
+  }
+
+  /* Search the hash table or tables for an entry matching page number
+  ** pgno. Each iteration of the following for() loop searches one
+  ** hash table (each hash table indexes up to HASHTABLE_NPAGE frames).
+  **
+  ** This code might run concurrently to the code in walIndexAppend()
+  ** that adds entries to the wal-index (and possibly to this hash 
+  ** table). This means the value just read from the hash 
+  ** slot (aHash[iKey]) may have been added before or after the 
+  ** current read transaction was opened. Values added after the
+  ** read transaction was opened may have been written incorrectly -
+  ** i.e. these slots may contain garbage data. However, we assume
+  ** that any slots written before the current read transaction was
+  ** opened remain unmodified.
+  **
+  ** For the reasons above, the if(...) condition featured in the inner
+  ** loop of the following block is more stringent that would be required 
+  ** if we had exclusive access to the hash-table:
+  **
+  **   (aPgno[iFrame]==pgno): 
+  **     This condition filters out normal hash-table collisions.
+  **
+  **   (iFrame<=iLast): 
+  **     This condition filters out entries that were added to the hash
+  **     table after the current read-transaction had started.
+  */
+  for(iHash=walFramePage(iLast); iHash>=0 && iRead==0; iHash--){
+    volatile ht_slot *aHash;      /* Pointer to hash table */
+    volatile u32 *aPgno;          /* Pointer to array of page numbers */
+    u32 iZero;                    /* Frame number corresponding to aPgno[0] */
+    int iKey;                     /* Hash slot index */
+    int nCollide;                 /* Number of hash collisions remaining */
+    int rc;                       /* Error code */
+
+    rc = walHashGet(pWal, iHash, &aHash, &aPgno, &iZero);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+    nCollide = HASHTABLE_NSLOT;
+    for(iKey=walHash(pgno); aHash[iKey]; iKey=walNextHash(iKey)){
+      u32 iFrame = aHash[iKey] + iZero;
+      if( iFrame<=iLast && aPgno[aHash[iKey]]==pgno ){
+        assert( iFrame>iRead );
+        iRead = iFrame;
+      }
+      if( (nCollide--)==0 ){
+        return SQLITE_CORRUPT_BKPT;
+      }
+    }
+  }
+
+#ifdef SQLITE_ENABLE_EXPENSIVE_ASSERT
+  /* If expensive assert() statements are available, do a linear search
+  ** of the wal-index file content. Make sure the results agree with the
+  ** result obtained using the hash indexes above.  */
+  {
+    u32 iRead2 = 0;
+    u32 iTest;
+    for(iTest=iLast; iTest>0; iTest--){
+      if( walFramePgno(pWal, iTest)==pgno ){
+        iRead2 = iTest;
+        break;
+      }
+    }
+    assert( iRead==iRead2 );
+  }
+#endif
+
+  /* If iRead is non-zero, then it is the log frame number that contains the
+  ** required page. Read and return data from the log file.
+  */
+  if( iRead ){
+    int sz;
+    i64 iOffset;
+    sz = pWal->hdr.szPage;
+    sz = (sz&0xfe00) + ((sz&0x0001)<<16);
+    testcase( sz<=32768 );
+    testcase( sz>=65536 );
+    iOffset = walFrameOffset(iRead, sz) + WAL_FRAME_HDRSIZE;
+    *pInWal = 1;
+    /* testcase( IS_BIG_INT(iOffset) ); // requires a 4GiB WAL */
+    return sqlite3OsRead(pWal->pWalFd, pOut, nOut, iOffset);
+  }
+
+  *pInWal = 0;
+  return SQLITE_OK;
+}
+
+
+/* 
+** Return the size of the database in pages (or zero, if unknown).
+*/
+Pgno sqlite3WalDbsize(Wal *pWal){
+  if( pWal && ALWAYS(pWal->readLock>=0) ){
+    return pWal->hdr.nPage;
+  }
+  return 0;
+}
+
+
+/* 
+** This function starts a write transaction on the WAL.
+**
+** A read transaction must have already been started by a prior call
+** to sqlite3WalBeginReadTransaction().
+**
+** If another thread or process has written into the database since
+** the read transaction was started, then it is not possible for this
+** thread to write as doing so would cause a fork.  So this routine
+** returns SQLITE_BUSY in that case and no write transaction is started.
+**
+** There can only be a single writer active at a time.
+*/
+int sqlite3WalBeginWriteTransaction(Wal *pWal){
+  int rc;
+
+  /* Cannot start a write transaction without first holding a read
+  ** transaction. */
+  assert( pWal->readLock>=0 );
+
+  if( pWal->readOnly ){
+    return SQLITE_READONLY;
+  }
+
+  /* Only one writer allowed at a time.  Get the write lock.  Return
+  ** SQLITE_BUSY if unable.
+  */
+  rc = walLockExclusive(pWal, WAL_WRITE_LOCK, 1);
+  if( rc ){
+    return rc;
+  }
+  pWal->writeLock = 1;
+
+  /* If another connection has written to the database file since the
+  ** time the read transaction on this connection was started, then
+  ** the write is disallowed.
+  */
+  if( memcmp(&pWal->hdr, (void *)walIndexHdr(pWal), sizeof(WalIndexHdr))!=0 ){
+    walUnlockExclusive(pWal, WAL_WRITE_LOCK, 1);
+    pWal->writeLock = 0;
+    rc = SQLITE_BUSY;
+  }
+
+  return rc;
+}
+
+/*
+** End a write transaction.  The commit has already been done.  This
+** routine merely releases the lock.
+*/
+int sqlite3WalEndWriteTransaction(Wal *pWal){
+  if( pWal->writeLock ){
+    walUnlockExclusive(pWal, WAL_WRITE_LOCK, 1);
+    pWal->writeLock = 0;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** If any data has been written (but not committed) to the log file, this
+** function moves the write-pointer back to the start of the transaction.
+**
+** Additionally, the callback function is invoked for each frame written
+** to the WAL since the start of the transaction. If the callback returns
+** other than SQLITE_OK, it is not invoked again and the error code is
+** returned to the caller.
+**
+** Otherwise, if the callback function does not return an error, this
+** function returns SQLITE_OK.
+*/
+int sqlite3WalUndo(Wal *pWal, int (*xUndo)(void *, Pgno), void *pUndoCtx){
+  int rc = SQLITE_OK;
+  if( ALWAYS(pWal->writeLock) ){
+    Pgno iMax = pWal->hdr.mxFrame;
+    Pgno iFrame;
+  
+    /* Restore the clients cache of the wal-index header to the state it
+    ** was in before the client began writing to the database. 
+    */
+    memcpy(&pWal->hdr, (void *)walIndexHdr(pWal), sizeof(WalIndexHdr));
+
+    for(iFrame=pWal->hdr.mxFrame+1; 
+        ALWAYS(rc==SQLITE_OK) && iFrame<=iMax; 
+        iFrame++
+    ){
+      /* This call cannot fail. Unless the page for which the page number
+      ** is passed as the second argument is (a) in the cache and 
+      ** (b) has an outstanding reference, then xUndo is either a no-op
+      ** (if (a) is false) or simply expels the page from the cache (if (b)
+      ** is false).
+      **
+      ** If the upper layer is doing a rollback, it is guaranteed that there
+      ** are no outstanding references to any page other than page 1. And
+      ** page 1 is never written to the log until the transaction is
+      ** committed. As a result, the call to xUndo may not fail.
+      */
+      assert( walFramePgno(pWal, iFrame)!=1 );
+      rc = xUndo(pUndoCtx, walFramePgno(pWal, iFrame));
+    }
+    walCleanupHash(pWal);
+  }
+  assert( rc==SQLITE_OK );
+  return rc;
+}
+
+/* 
+** Argument aWalData must point to an array of WAL_SAVEPOINT_NDATA u32 
+** values. This function populates the array with values required to 
+** "rollback" the write position of the WAL handle back to the current 
+** point in the event of a savepoint rollback (via WalSavepointUndo()).
+*/
+void sqlite3WalSavepoint(Wal *pWal, u32 *aWalData){
+  assert( pWal->writeLock );
+  aWalData[0] = pWal->hdr.mxFrame;
+  aWalData[1] = pWal->hdr.aFrameCksum[0];
+  aWalData[2] = pWal->hdr.aFrameCksum[1];
+  aWalData[3] = pWal->nCkpt;
+}
+
+/* 
+** Move the write position of the WAL back to the point identified by
+** the values in the aWalData[] array. aWalData must point to an array
+** of WAL_SAVEPOINT_NDATA u32 values that has been previously populated
+** by a call to WalSavepoint().
+*/
+int sqlite3WalSavepointUndo(Wal *pWal, u32 *aWalData){
+  int rc = SQLITE_OK;
+
+  assert( pWal->writeLock );
+  assert( aWalData[3]!=pWal->nCkpt || aWalData[0]<=pWal->hdr.mxFrame );
+
+  if( aWalData[3]!=pWal->nCkpt ){
+    /* This savepoint was opened immediately after the write-transaction
+    ** was started. Right after that, the writer decided to wrap around
+    ** to the start of the log. Update the savepoint values to match.
+    */
+    aWalData[0] = 0;
+    aWalData[3] = pWal->nCkpt;
+  }
+
+  if( aWalData[0]<pWal->hdr.mxFrame ){
+    pWal->hdr.mxFrame = aWalData[0];
+    pWal->hdr.aFrameCksum[0] = aWalData[1];
+    pWal->hdr.aFrameCksum[1] = aWalData[2];
+    walCleanupHash(pWal);
+  }
+
+  return rc;
+}
+
+/*
+** This function is called just before writing a set of frames to the log
+** file (see sqlite3WalFrames()). It checks to see if, instead of appending
+** to the current log file, it is possible to overwrite the start of the
+** existing log file with the new frames (i.e. "reset" the log). If so,
+** it sets pWal->hdr.mxFrame to 0. Otherwise, pWal->hdr.mxFrame is left
+** unchanged.
+**
+** SQLITE_OK is returned if no error is encountered (regardless of whether
+** or not pWal->hdr.mxFrame is modified). An SQLite error code is returned
+** if an error occurs.
+*/
+static int walRestartLog(Wal *pWal){
+  int rc = SQLITE_OK;
+  int cnt;
+
+  if( pWal->readLock==0 ){
+    volatile WalCkptInfo *pInfo = walCkptInfo(pWal);
+    assert( pInfo->nBackfill==pWal->hdr.mxFrame );
+    if( pInfo->nBackfill>0 ){
+      u32 salt1;
+      sqlite3_randomness(4, &salt1);
+      rc = walLockExclusive(pWal, WAL_READ_LOCK(1), WAL_NREADER-1);
+      if( rc==SQLITE_OK ){
+        /* If all readers are using WAL_READ_LOCK(0) (in other words if no
+        ** readers are currently using the WAL), then the transactions
+        ** frames will overwrite the start of the existing log. Update the
+        ** wal-index header to reflect this.
+        **
+        ** In theory it would be Ok to update the cache of the header only
+        ** at this point. But updating the actual wal-index header is also
+        ** safe and means there is no special case for sqlite3WalUndo()
+        ** to handle if this transaction is rolled back.
+        */
+        int i;                    /* Loop counter */
+        u32 *aSalt = pWal->hdr.aSalt;       /* Big-endian salt values */
+
+        /* Limit the size of WAL file if the journal_size_limit PRAGMA is
+        ** set to a non-negative value.  Log errors encountered
+        ** during the truncation attempt. */
+        if( pWal->mxWalSize>=0 ){
+          i64 sz;
+          int rx;
+          sqlite3BeginBenignMalloc();
+          rx = sqlite3OsFileSize(pWal->pWalFd, &sz);
+          if( rx==SQLITE_OK && (sz > pWal->mxWalSize) ){
+            rx = sqlite3OsTruncate(pWal->pWalFd, pWal->mxWalSize);
+          }
+          sqlite3EndBenignMalloc();
+          if( rx ){
+            sqlite3_log(rx, "cannot limit WAL size: %s", pWal->zWalName);
+          }
+        }
+
+        pWal->nCkpt++;
+        pWal->hdr.mxFrame = 0;
+        sqlite3Put4byte((u8*)&aSalt[0], 1 + sqlite3Get4byte((u8*)&aSalt[0]));
+        aSalt[1] = salt1;
+        walIndexWriteHdr(pWal);
+        pInfo->nBackfill = 0;
+        for(i=1; i<WAL_NREADER; i++) pInfo->aReadMark[i] = READMARK_NOT_USED;
+        assert( pInfo->aReadMark[0]==0 );
+        walUnlockExclusive(pWal, WAL_READ_LOCK(1), WAL_NREADER-1);
+      }else if( rc!=SQLITE_BUSY ){
+        return rc;
+      }
+    }
+    walUnlockShared(pWal, WAL_READ_LOCK(0));
+    pWal->readLock = -1;
+    cnt = 0;
+    do{
+      int notUsed;
+      rc = walTryBeginRead(pWal, &notUsed, 1, ++cnt);
+    }while( rc==WAL_RETRY );
+    assert( (rc&0xff)!=SQLITE_BUSY ); /* BUSY not possible when useWal==1 */
+    testcase( (rc&0xff)==SQLITE_IOERR );
+    testcase( rc==SQLITE_PROTOCOL );
+    testcase( rc==SQLITE_OK );
+  }
+  return rc;
+}
+
+/* 
+** Write a set of frames to the log. The caller must hold the write-lock
+** on the log file (obtained using sqlite3WalBeginWriteTransaction()).
+*/
+int sqlite3WalFrames(
+  Wal *pWal,                      /* Wal handle to write to */
+  int szPage,                     /* Database page-size in bytes */
+  PgHdr *pList,                   /* List of dirty pages to write */
+  Pgno nTruncate,                 /* Database size after this commit */
+  int isCommit,                   /* True if this is a commit */
+  int sync_flags                  /* Flags to pass to OsSync() (or 0) */
+){
+  int rc;                         /* Used to catch return codes */
+  u32 iFrame;                     /* Next frame address */
+  u8 aFrame[WAL_FRAME_HDRSIZE];   /* Buffer to assemble frame-header in */
+  PgHdr *p;                       /* Iterator to run through pList with. */
+  PgHdr *pLast = 0;               /* Last frame in list */
+  int nLast = 0;                  /* Number of extra copies of last page */
+
+  assert( pList );
+  assert( pWal->writeLock );
+
+#if defined(SQLITE_TEST) && defined(SQLITE_DEBUG)
+  { int cnt; for(cnt=0, p=pList; p; p=p->pDirty, cnt++){}
+    WALTRACE(("WAL%p: frame write begin. %d frames. mxFrame=%d. %s\n",
+              pWal, cnt, pWal->hdr.mxFrame, isCommit ? "Commit" : "Spill"));
+  }
+#endif
+
+  /* See if it is possible to write these frames into the start of the
+  ** log file, instead of appending to it at pWal->hdr.mxFrame.
+  */
+  if( SQLITE_OK!=(rc = walRestartLog(pWal)) ){
+    return rc;
+  }
+
+  /* If this is the first frame written into the log, write the WAL
+  ** header to the start of the WAL file. See comments at the top of
+  ** this source file for a description of the WAL header format.
+  */
+  iFrame = pWal->hdr.mxFrame;
+  if( iFrame==0 ){
+    u8 aWalHdr[WAL_HDRSIZE];      /* Buffer to assemble wal-header in */
+    u32 aCksum[2];                /* Checksum for wal-header */
+
+    sqlite3Put4byte(&aWalHdr[0], (WAL_MAGIC | SQLITE_BIGENDIAN));
+    sqlite3Put4byte(&aWalHdr[4], WAL_MAX_VERSION);
+    sqlite3Put4byte(&aWalHdr[8], szPage);
+    sqlite3Put4byte(&aWalHdr[12], pWal->nCkpt);
+    sqlite3_randomness(8, pWal->hdr.aSalt);
+    memcpy(&aWalHdr[16], pWal->hdr.aSalt, 8);
+    walChecksumBytes(1, aWalHdr, WAL_HDRSIZE-2*4, 0, aCksum);
+    sqlite3Put4byte(&aWalHdr[24], aCksum[0]);
+    sqlite3Put4byte(&aWalHdr[28], aCksum[1]);
+    
+    pWal->szPage = szPage;
+    pWal->hdr.bigEndCksum = SQLITE_BIGENDIAN;
+    pWal->hdr.aFrameCksum[0] = aCksum[0];
+    pWal->hdr.aFrameCksum[1] = aCksum[1];
+
+    rc = sqlite3OsWrite(pWal->pWalFd, aWalHdr, sizeof(aWalHdr), 0);
+    WALTRACE(("WAL%p: wal-header write %s\n", pWal, rc ? "failed" : "ok"));
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+  }
+  assert( (int)pWal->szPage==szPage );
+
+  /* Write the log file. */
+  for(p=pList; p; p=p->pDirty){
+    u32 nDbsize;                  /* Db-size field for frame header */
+    i64 iOffset;                  /* Write offset in log file */
+    void *pData;
+   
+    iOffset = walFrameOffset(++iFrame, szPage);
+    /* testcase( IS_BIG_INT(iOffset) ); // requires a 4GiB WAL */
+    
+    /* Populate and write the frame header */
+    nDbsize = (isCommit && p->pDirty==0) ? nTruncate : 0;
+#if defined(SQLITE_HAS_CODEC)
+    if( (pData = sqlite3PagerCodec(p))==0 ) return SQLITE_NOMEM;
+#else
+    pData = p->pData;
+#endif
+    walEncodeFrame(pWal, p->pgno, nDbsize, pData, aFrame);
+    rc = sqlite3OsWrite(pWal->pWalFd, aFrame, sizeof(aFrame), iOffset);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+
+    /* Write the page data */
+    rc = sqlite3OsWrite(pWal->pWalFd, pData, szPage, iOffset+sizeof(aFrame));
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+    pLast = p;
+  }
+
+  /* Sync the log file if the 'isSync' flag was specified. */
+  if( sync_flags ){
+    i64 iSegment = sqlite3OsSectorSize(pWal->pWalFd);
+    i64 iOffset = walFrameOffset(iFrame+1, szPage);
+
+    assert( isCommit );
+    assert( iSegment>0 );
+
+    iSegment = (((iOffset+iSegment-1)/iSegment) * iSegment);
+    while( iOffset<iSegment ){
+      void *pData;
+#if defined(SQLITE_HAS_CODEC)
+      if( (pData = sqlite3PagerCodec(pLast))==0 ) return SQLITE_NOMEM;
+#else
+      pData = pLast->pData;
+#endif
+      walEncodeFrame(pWal, pLast->pgno, nTruncate, pData, aFrame);
+      /* testcase( IS_BIG_INT(iOffset) ); // requires a 4GiB WAL */
+      rc = sqlite3OsWrite(pWal->pWalFd, aFrame, sizeof(aFrame), iOffset);
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+      iOffset += WAL_FRAME_HDRSIZE;
+      rc = sqlite3OsWrite(pWal->pWalFd, pData, szPage, iOffset); 
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+      nLast++;
+      iOffset += szPage;
+    }
+
+    rc = sqlite3OsSync(pWal->pWalFd, sync_flags);
+  }
+
+  /* Append data to the wal-index. It is not necessary to lock the 
+  ** wal-index to do this as the SQLITE_SHM_WRITE lock held on the wal-index
+  ** guarantees that there are no other writers, and no data that may
+  ** be in use by existing readers is being overwritten.
+  */
+  iFrame = pWal->hdr.mxFrame;
+  for(p=pList; p && rc==SQLITE_OK; p=p->pDirty){
+    iFrame++;
+    rc = walIndexAppend(pWal, iFrame, p->pgno);
+  }
+  while( nLast>0 && rc==SQLITE_OK ){
+    iFrame++;
+    nLast--;
+    rc = walIndexAppend(pWal, iFrame, pLast->pgno);
+  }
+
+  if( rc==SQLITE_OK ){
+    /* Update the private copy of the header. */
+    pWal->hdr.szPage = (u16)((szPage&0xff00) | (szPage>>16));
+    testcase( szPage<=32768 );
+    testcase( szPage>=65536 );
+    pWal->hdr.mxFrame = iFrame;
+    if( isCommit ){
+      pWal->hdr.iChange++;
+      pWal->hdr.nPage = nTruncate;
+    }
+    /* If this is a commit, update the wal-index header too. */
+    if( isCommit ){
+      walIndexWriteHdr(pWal);
+      pWal->iCallback = iFrame;
+    }
+  }
+
+  WALTRACE(("WAL%p: frame write %s\n", pWal, rc ? "failed" : "ok"));
+  return rc;
+}
+
+/* 
+** This routine is called to implement sqlite3_wal_checkpoint() and
+** related interfaces.
+**
+** Obtain a CHECKPOINT lock and then backfill as much information as
+** we can from WAL into the database.
+**
+** If parameter xBusy is not NULL, it is a pointer to a busy-handler
+** callback. In this case this function runs a blocking checkpoint.
+*/
+int sqlite3WalCheckpoint(
+  Wal *pWal,                      /* Wal connection */
+  int eMode,                      /* PASSIVE, FULL or RESTART */
+  int (*xBusy)(void*),            /* Function to call when busy */
+  void *pBusyArg,                 /* Context argument for xBusyHandler */
+  int sync_flags,                 /* Flags to sync db file with (or 0) */
+  int nBuf,                       /* Size of temporary buffer */
+  u8 *zBuf,                       /* Temporary buffer to use */
+  int *pnLog,                     /* OUT: Number of frames in WAL */
+  int *pnCkpt                     /* OUT: Number of backfilled frames in WAL */
+){
+  int rc;                         /* Return code */
+  int isChanged = 0;              /* True if a new wal-index header is loaded */
+  int eMode2 = eMode;             /* Mode to pass to walCheckpoint() */
+
+  assert( pWal->ckptLock==0 );
+  assert( pWal->writeLock==0 );
+
+  if( pWal->readOnly ) return SQLITE_READONLY;
+  WALTRACE(("WAL%p: checkpoint begins\n", pWal));
+  rc = walLockExclusive(pWal, WAL_CKPT_LOCK, 1);
+  if( rc ){
+    /* Usually this is SQLITE_BUSY meaning that another thread or process
+    ** is already running a checkpoint, or maybe a recovery.  But it might
+    ** also be SQLITE_IOERR. */
+    return rc;
+  }
+  pWal->ckptLock = 1;
+
+  /* If this is a blocking-checkpoint, then obtain the write-lock as well
+  ** to prevent any writers from running while the checkpoint is underway.
+  ** This has to be done before the call to walIndexReadHdr() below.
+  **
+  ** If the writer lock cannot be obtained, then a passive checkpoint is
+  ** run instead. Since the checkpointer is not holding the writer lock,
+  ** there is no point in blocking waiting for any readers. Assuming no 
+  ** other error occurs, this function will return SQLITE_BUSY to the caller.
+  */
+  if( eMode!=SQLITE_CHECKPOINT_PASSIVE ){
+    rc = walBusyLock(pWal, xBusy, pBusyArg, WAL_WRITE_LOCK, 1);
+    if( rc==SQLITE_OK ){
+      pWal->writeLock = 1;
+    }else if( rc==SQLITE_BUSY ){
+      eMode2 = SQLITE_CHECKPOINT_PASSIVE;
+      rc = SQLITE_OK;
+    }
+  }
+
+  /* Read the wal-index header. */
+  if( rc==SQLITE_OK ){
+    rc = walIndexReadHdr(pWal, &isChanged);
+  }
+
+  /* Copy data from the log to the database file. */
+  if( rc==SQLITE_OK ){
+    if( pWal->hdr.mxFrame && walPagesize(pWal)!=nBuf ){
+      rc = SQLITE_CORRUPT_BKPT;
+    }else{
+      rc = walCheckpoint(pWal, eMode2, xBusy, pBusyArg, sync_flags, zBuf);
+    }
+
+    /* If no error occurred, set the output variables. */
+    if( rc==SQLITE_OK || rc==SQLITE_BUSY ){
+      if( pnLog ) *pnLog = (int)pWal->hdr.mxFrame;
+      if( pnCkpt ) *pnCkpt = (int)(walCkptInfo(pWal)->nBackfill);
+    }
+  }
+
+  if( isChanged ){
+    /* If a new wal-index header was loaded before the checkpoint was 
+    ** performed, then the pager-cache associated with pWal is now
+    ** out of date. So zero the cached wal-index header to ensure that
+    ** next time the pager opens a snapshot on this database it knows that
+    ** the cache needs to be reset.
+    */
+    memset(&pWal->hdr, 0, sizeof(WalIndexHdr));
+  }
+
+  /* Release the locks. */
+  sqlite3WalEndWriteTransaction(pWal);
+  walUnlockExclusive(pWal, WAL_CKPT_LOCK, 1);
+  pWal->ckptLock = 0;
+  WALTRACE(("WAL%p: checkpoint %s\n", pWal, rc ? "failed" : "ok"));
+  return (rc==SQLITE_OK && eMode!=eMode2 ? SQLITE_BUSY : rc);
+}
+
+/* Return the value to pass to a sqlite3_wal_hook callback, the
+** number of frames in the WAL at the point of the last commit since
+** sqlite3WalCallback() was called.  If no commits have occurred since
+** the last call, then return 0.
+*/
+int sqlite3WalCallback(Wal *pWal){
+  u32 ret = 0;
+  if( pWal ){
+    ret = pWal->iCallback;
+    pWal->iCallback = 0;
+  }
+  return (int)ret;
+}
+
+/*
+** This function is called to change the WAL subsystem into or out
+** of locking_mode=EXCLUSIVE.
+**
+** If op is zero, then attempt to change from locking_mode=EXCLUSIVE
+** into locking_mode=NORMAL.  This means that we must acquire a lock
+** on the pWal->readLock byte.  If the WAL is already in locking_mode=NORMAL
+** or if the acquisition of the lock fails, then return 0.  If the
+** transition out of exclusive-mode is successful, return 1.  This
+** operation must occur while the pager is still holding the exclusive
+** lock on the main database file.
+**
+** If op is one, then change from locking_mode=NORMAL into 
+** locking_mode=EXCLUSIVE.  This means that the pWal->readLock must
+** be released.  Return 1 if the transition is made and 0 if the
+** WAL is already in exclusive-locking mode - meaning that this
+** routine is a no-op.  The pager must already hold the exclusive lock
+** on the main database file before invoking this operation.
+**
+** If op is negative, then do a dry-run of the op==1 case but do
+** not actually change anything. The pager uses this to see if it
+** should acquire the database exclusive lock prior to invoking
+** the op==1 case.
+*/
+int sqlite3WalExclusiveMode(Wal *pWal, int op){
+  int rc;
+  assert( pWal->writeLock==0 );
+  assert( pWal->exclusiveMode!=WAL_HEAPMEMORY_MODE || op==-1 );
+
+  /* pWal->readLock is usually set, but might be -1 if there was a 
+  ** prior error while attempting to acquire are read-lock. This cannot 
+  ** happen if the connection is actually in exclusive mode (as no xShmLock
+  ** locks are taken in this case). Nor should the pager attempt to
+  ** upgrade to exclusive-mode following such an error.
+  */
+  assert( pWal->readLock>=0 || pWal->lockError );
+  assert( pWal->readLock>=0 || (op<=0 && pWal->exclusiveMode==0) );
+
+  if( op==0 ){
+    if( pWal->exclusiveMode ){
+      pWal->exclusiveMode = 0;
+      if( walLockShared(pWal, WAL_READ_LOCK(pWal->readLock))!=SQLITE_OK ){
+        pWal->exclusiveMode = 1;
+      }
+      rc = pWal->exclusiveMode==0;
+    }else{
+      /* Already in locking_mode=NORMAL */
+      rc = 0;
+    }
+  }else if( op>0 ){
+    assert( pWal->exclusiveMode==0 );
+    assert( pWal->readLock>=0 );
+    walUnlockShared(pWal, WAL_READ_LOCK(pWal->readLock));
+    pWal->exclusiveMode = 1;
+    rc = 1;
+  }else{
+    rc = pWal->exclusiveMode==0;
+  }
+  return rc;
+}
+
+/* 
+** Return true if the argument is non-NULL and the WAL module is using
+** heap-memory for the wal-index. Otherwise, if the argument is NULL or the
+** WAL module is using shared-memory, return false. 
+*/
+int sqlite3WalHeapMemory(Wal *pWal){
+  return (pWal && pWal->exclusiveMode==WAL_HEAPMEMORY_MODE );
+}
+
+#endif /* #ifndef SQLITE_OMIT_WAL */
diff --git a/src/wal.h b/src/wal.h
new file mode 100644
index 0000000..a62b23b
--- /dev/null
+++ b/src/wal.h
@@ -0,0 +1,122 @@
+/*
+** 2010 February 1
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This header file defines the interface to the write-ahead logging 
+** system. Refer to the comments below and the header comment attached to 
+** the implementation of each function in log.c for further details.
+*/
+
+#ifndef _WAL_H_
+#define _WAL_H_
+
+#include "sqliteInt.h"
+
+#ifdef SQLITE_OMIT_WAL
+# define sqlite3WalOpen(x,y,z)                   0
+# define sqlite3WalLimit(x,y)
+# define sqlite3WalClose(w,x,y,z)                0
+# define sqlite3WalBeginReadTransaction(y,z)     0
+# define sqlite3WalEndReadTransaction(z)
+# define sqlite3WalRead(v,w,x,y,z)               0
+# define sqlite3WalDbsize(y)                     0
+# define sqlite3WalBeginWriteTransaction(y)      0
+# define sqlite3WalEndWriteTransaction(x)        0
+# define sqlite3WalUndo(x,y,z)                   0
+# define sqlite3WalSavepoint(y,z)
+# define sqlite3WalSavepointUndo(y,z)            0
+# define sqlite3WalFrames(u,v,w,x,y,z)           0
+# define sqlite3WalCheckpoint(r,s,t,u,v,w,x,y,z) 0
+# define sqlite3WalCallback(z)                   0
+# define sqlite3WalExclusiveMode(y,z)            0
+# define sqlite3WalHeapMemory(z)                 0
+#else
+
+#define WAL_SAVEPOINT_NDATA 4
+
+/* Connection to a write-ahead log (WAL) file. 
+** There is one object of this type for each pager. 
+*/
+typedef struct Wal Wal;
+
+/* Open and close a connection to a write-ahead log. */
+int sqlite3WalOpen(sqlite3_vfs*, sqlite3_file*, const char *, int, i64, Wal**);
+int sqlite3WalClose(Wal *pWal, int sync_flags, int, u8 *);
+
+/* Set the limiting size of a WAL file. */
+void sqlite3WalLimit(Wal*, i64);
+
+/* Used by readers to open (lock) and close (unlock) a snapshot.  A 
+** snapshot is like a read-transaction.  It is the state of the database
+** at an instant in time.  sqlite3WalOpenSnapshot gets a read lock and
+** preserves the current state even if the other threads or processes
+** write to or checkpoint the WAL.  sqlite3WalCloseSnapshot() closes the
+** transaction and releases the lock.
+*/
+int sqlite3WalBeginReadTransaction(Wal *pWal, int *);
+void sqlite3WalEndReadTransaction(Wal *pWal);
+
+/* Read a page from the write-ahead log, if it is present. */
+int sqlite3WalRead(Wal *pWal, Pgno pgno, int *pInWal, int nOut, u8 *pOut);
+
+/* If the WAL is not empty, return the size of the database. */
+Pgno sqlite3WalDbsize(Wal *pWal);
+
+/* Obtain or release the WRITER lock. */
+int sqlite3WalBeginWriteTransaction(Wal *pWal);
+int sqlite3WalEndWriteTransaction(Wal *pWal);
+
+/* Undo any frames written (but not committed) to the log */
+int sqlite3WalUndo(Wal *pWal, int (*xUndo)(void *, Pgno), void *pUndoCtx);
+
+/* Return an integer that records the current (uncommitted) write
+** position in the WAL */
+void sqlite3WalSavepoint(Wal *pWal, u32 *aWalData);
+
+/* Move the write position of the WAL back to iFrame.  Called in
+** response to a ROLLBACK TO command. */
+int sqlite3WalSavepointUndo(Wal *pWal, u32 *aWalData);
+
+/* Write a frame or frames to the log. */
+int sqlite3WalFrames(Wal *pWal, int, PgHdr *, Pgno, int, int);
+
+/* Copy pages from the log to the database file */ 
+int sqlite3WalCheckpoint(
+  Wal *pWal,                      /* Write-ahead log connection */
+  int eMode,                      /* One of PASSIVE, FULL and RESTART */
+  int (*xBusy)(void*),            /* Function to call when busy */
+  void *pBusyArg,                 /* Context argument for xBusyHandler */
+  int sync_flags,                 /* Flags to sync db file with (or 0) */
+  int nBuf,                       /* Size of buffer nBuf */
+  u8 *zBuf,                       /* Temporary buffer to use */
+  int *pnLog,                     /* OUT: Number of frames in WAL */
+  int *pnCkpt                     /* OUT: Number of backfilled frames in WAL */
+);
+
+/* Return the value to pass to a sqlite3_wal_hook callback, the
+** number of frames in the WAL at the point of the last commit since
+** sqlite3WalCallback() was called.  If no commits have occurred since
+** the last call, then return 0.
+*/
+int sqlite3WalCallback(Wal *pWal);
+
+/* Tell the wal layer that an EXCLUSIVE lock has been obtained (or released)
+** by the pager layer on the database file.
+*/
+int sqlite3WalExclusiveMode(Wal *pWal, int op);
+
+/* Return true if the argument is non-NULL and the WAL module is using
+** heap-memory for the wal-index. Otherwise, if the argument is NULL or the
+** WAL module is using shared-memory, return false. 
+*/
+int sqlite3WalHeapMemory(Wal *pWal);
+
+#endif /* ifndef SQLITE_OMIT_WAL */
+#endif /* _WAL_H_ */
diff --git a/src/walker.c b/src/walker.c
new file mode 100644
index 0000000..c95a9c1
--- /dev/null
+++ b/src/walker.c
@@ -0,0 +1,136 @@
+/*
+** 2008 August 16
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains routines used for walking the parser tree for
+** an SQL statement.
+*/
+#include "sqliteInt.h"
+#include <stdlib.h>
+#include <string.h>
+
+
+/*
+** Walk an expression tree.  Invoke the callback once for each node
+** of the expression, while decending.  (In other words, the callback
+** is invoked before visiting children.)
+**
+** The return value from the callback should be one of the WRC_*
+** constants to specify how to proceed with the walk.
+**
+**    WRC_Continue      Continue descending down the tree.
+**
+**    WRC_Prune         Do not descend into child nodes.  But allow
+**                      the walk to continue with sibling nodes.
+**
+**    WRC_Abort         Do no more callbacks.  Unwind the stack and
+**                      return the top-level walk call.
+**
+** The return value from this routine is WRC_Abort to abandon the tree walk
+** and WRC_Continue to continue.
+*/
+int sqlite3WalkExpr(Walker *pWalker, Expr *pExpr){
+  int rc;
+  if( pExpr==0 ) return WRC_Continue;
+  testcase( ExprHasProperty(pExpr, EP_TokenOnly) );
+  testcase( ExprHasProperty(pExpr, EP_Reduced) );
+  rc = pWalker->xExprCallback(pWalker, pExpr);
+  if( rc==WRC_Continue
+              && !ExprHasAnyProperty(pExpr,EP_TokenOnly) ){
+    if( sqlite3WalkExpr(pWalker, pExpr->pLeft) ) return WRC_Abort;
+    if( sqlite3WalkExpr(pWalker, pExpr->pRight) ) return WRC_Abort;
+    if( ExprHasProperty(pExpr, EP_xIsSelect) ){
+      if( sqlite3WalkSelect(pWalker, pExpr->x.pSelect) ) return WRC_Abort;
+    }else{
+      if( sqlite3WalkExprList(pWalker, pExpr->x.pList) ) return WRC_Abort;
+    }
+  }
+  return rc & WRC_Abort;
+}
+
+/*
+** Call sqlite3WalkExpr() for every expression in list p or until
+** an abort request is seen.
+*/
+int sqlite3WalkExprList(Walker *pWalker, ExprList *p){
+  int i;
+  struct ExprList_item *pItem;
+  if( p ){
+    for(i=p->nExpr, pItem=p->a; i>0; i--, pItem++){
+      if( sqlite3WalkExpr(pWalker, pItem->pExpr) ) return WRC_Abort;
+    }
+  }
+  return WRC_Continue;
+}
+
+/*
+** Walk all expressions associated with SELECT statement p.  Do
+** not invoke the SELECT callback on p, but do (of course) invoke
+** any expr callbacks and SELECT callbacks that come from subqueries.
+** Return WRC_Abort or WRC_Continue.
+*/
+int sqlite3WalkSelectExpr(Walker *pWalker, Select *p){
+  if( sqlite3WalkExprList(pWalker, p->pEList) ) return WRC_Abort;
+  if( sqlite3WalkExpr(pWalker, p->pWhere) ) return WRC_Abort;
+  if( sqlite3WalkExprList(pWalker, p->pGroupBy) ) return WRC_Abort;
+  if( sqlite3WalkExpr(pWalker, p->pHaving) ) return WRC_Abort;
+  if( sqlite3WalkExprList(pWalker, p->pOrderBy) ) return WRC_Abort;
+  if( sqlite3WalkExpr(pWalker, p->pLimit) ) return WRC_Abort;
+  if( sqlite3WalkExpr(pWalker, p->pOffset) ) return WRC_Abort;
+  return WRC_Continue;
+}
+
+/*
+** Walk the parse trees associated with all subqueries in the
+** FROM clause of SELECT statement p.  Do not invoke the select
+** callback on p, but do invoke it on each FROM clause subquery
+** and on any subqueries further down in the tree.  Return 
+** WRC_Abort or WRC_Continue;
+*/
+int sqlite3WalkSelectFrom(Walker *pWalker, Select *p){
+  SrcList *pSrc;
+  int i;
+  struct SrcList_item *pItem;
+
+  pSrc = p->pSrc;
+  if( ALWAYS(pSrc) ){
+    for(i=pSrc->nSrc, pItem=pSrc->a; i>0; i--, pItem++){
+      if( sqlite3WalkSelect(pWalker, pItem->pSelect) ){
+        return WRC_Abort;
+      }
+    }
+  }
+  return WRC_Continue;
+} 
+
+/*
+** Call sqlite3WalkExpr() for every expression in Select statement p.
+** Invoke sqlite3WalkSelect() for subqueries in the FROM clause and
+** on the compound select chain, p->pPrior.
+**
+** Return WRC_Continue under normal conditions.  Return WRC_Abort if
+** there is an abort request.
+**
+** If the Walker does not have an xSelectCallback() then this routine
+** is a no-op returning WRC_Continue.
+*/
+int sqlite3WalkSelect(Walker *pWalker, Select *p){
+  int rc;
+  if( p==0 || pWalker->xSelectCallback==0 ) return WRC_Continue;
+  rc = WRC_Continue;
+  while( p  ){
+    rc = pWalker->xSelectCallback(pWalker, p);
+    if( rc ) break;
+    if( sqlite3WalkSelectExpr(pWalker, p) ) return WRC_Abort;
+    if( sqlite3WalkSelectFrom(pWalker, p) ) return WRC_Abort;
+    p = p->pPrior;
+  }
+  return rc & WRC_Abort;
+}
diff --git a/src/where.c b/src/where.c
new file mode 100644
index 0000000..05414da
--- /dev/null
+++ b/src/where.c
@@ -0,0 +1,5226 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This module contains C code that generates VDBE code used to process
+** the WHERE clause of SQL statements.  This module is responsible for
+** generating the code that loops through a table looking for applicable
+** rows.  Indices are selected and used to speed the search when doing
+** so is applicable.  Because this module is responsible for selecting
+** indices, you might also think of this module as the "query optimizer".
+*/
+#include "sqliteInt.h"
+
+
+/*
+** Trace output macros
+*/
+#if defined(SQLITE_TEST) || defined(SQLITE_DEBUG)
+int sqlite3WhereTrace = 0;
+#endif
+#if defined(SQLITE_TEST) && defined(SQLITE_DEBUG)
+# define WHERETRACE(X)  if(sqlite3WhereTrace) sqlite3DebugPrintf X
+#else
+# define WHERETRACE(X)
+#endif
+
+/* Forward reference
+*/
+typedef struct WhereClause WhereClause;
+typedef struct WhereMaskSet WhereMaskSet;
+typedef struct WhereOrInfo WhereOrInfo;
+typedef struct WhereAndInfo WhereAndInfo;
+typedef struct WhereCost WhereCost;
+
+/*
+** The query generator uses an array of instances of this structure to
+** help it analyze the subexpressions of the WHERE clause.  Each WHERE
+** clause subexpression is separated from the others by AND operators,
+** usually, or sometimes subexpressions separated by OR.
+**
+** All WhereTerms are collected into a single WhereClause structure.  
+** The following identity holds:
+**
+**        WhereTerm.pWC->a[WhereTerm.idx] == WhereTerm
+**
+** When a term is of the form:
+**
+**              X <op> <expr>
+**
+** where X is a column name and <op> is one of certain operators,
+** then WhereTerm.leftCursor and WhereTerm.u.leftColumn record the
+** cursor number and column number for X.  WhereTerm.eOperator records
+** the <op> using a bitmask encoding defined by WO_xxx below.  The
+** use of a bitmask encoding for the operator allows us to search
+** quickly for terms that match any of several different operators.
+**
+** A WhereTerm might also be two or more subterms connected by OR:
+**
+**         (t1.X <op> <expr>) OR (t1.Y <op> <expr>) OR ....
+**
+** In this second case, wtFlag as the TERM_ORINFO set and eOperator==WO_OR
+** and the WhereTerm.u.pOrInfo field points to auxiliary information that
+** is collected about the
+**
+** If a term in the WHERE clause does not match either of the two previous
+** categories, then eOperator==0.  The WhereTerm.pExpr field is still set
+** to the original subexpression content and wtFlags is set up appropriately
+** but no other fields in the WhereTerm object are meaningful.
+**
+** When eOperator!=0, prereqRight and prereqAll record sets of cursor numbers,
+** but they do so indirectly.  A single WhereMaskSet structure translates
+** cursor number into bits and the translated bit is stored in the prereq
+** fields.  The translation is used in order to maximize the number of
+** bits that will fit in a Bitmask.  The VDBE cursor numbers might be
+** spread out over the non-negative integers.  For example, the cursor
+** numbers might be 3, 8, 9, 10, 20, 23, 41, and 45.  The WhereMaskSet
+** translates these sparse cursor numbers into consecutive integers
+** beginning with 0 in order to make the best possible use of the available
+** bits in the Bitmask.  So, in the example above, the cursor numbers
+** would be mapped into integers 0 through 7.
+**
+** The number of terms in a join is limited by the number of bits
+** in prereqRight and prereqAll.  The default is 64 bits, hence SQLite
+** is only able to process joins with 64 or fewer tables.
+*/
+typedef struct WhereTerm WhereTerm;
+struct WhereTerm {
+  Expr *pExpr;            /* Pointer to the subexpression that is this term */
+  int iParent;            /* Disable pWC->a[iParent] when this term disabled */
+  int leftCursor;         /* Cursor number of X in "X <op> <expr>" */
+  union {
+    int leftColumn;         /* Column number of X in "X <op> <expr>" */
+    WhereOrInfo *pOrInfo;   /* Extra information if eOperator==WO_OR */
+    WhereAndInfo *pAndInfo; /* Extra information if eOperator==WO_AND */
+  } u;
+  u16 eOperator;          /* A WO_xx value describing <op> */
+  u8 wtFlags;             /* TERM_xxx bit flags.  See below */
+  u8 nChild;              /* Number of children that must disable us */
+  WhereClause *pWC;       /* The clause this term is part of */
+  Bitmask prereqRight;    /* Bitmask of tables used by pExpr->pRight */
+  Bitmask prereqAll;      /* Bitmask of tables referenced by pExpr */
+};
+
+/*
+** Allowed values of WhereTerm.wtFlags
+*/
+#define TERM_DYNAMIC    0x01   /* Need to call sqlite3ExprDelete(db, pExpr) */
+#define TERM_VIRTUAL    0x02   /* Added by the optimizer.  Do not code */
+#define TERM_CODED      0x04   /* This term is already coded */
+#define TERM_COPIED     0x08   /* Has a child */
+#define TERM_ORINFO     0x10   /* Need to free the WhereTerm.u.pOrInfo object */
+#define TERM_ANDINFO    0x20   /* Need to free the WhereTerm.u.pAndInfo obj */
+#define TERM_OR_OK      0x40   /* Used during OR-clause processing */
+#ifdef SQLITE_ENABLE_STAT3
+#  define TERM_VNULL    0x80   /* Manufactured x>NULL or x<=NULL term */
+#else
+#  define TERM_VNULL    0x00   /* Disabled if not using stat3 */
+#endif
+
+/*
+** An instance of the following structure holds all information about a
+** WHERE clause.  Mostly this is a container for one or more WhereTerms.
+**
+** Explanation of pOuter:  For a WHERE clause of the form
+**
+**           a AND ((b AND c) OR (d AND e)) AND f
+**
+** There are separate WhereClause objects for the whole clause and for
+** the subclauses "(b AND c)" and "(d AND e)".  The pOuter field of the
+** subclauses points to the WhereClause object for the whole clause.
+*/
+struct WhereClause {
+  Parse *pParse;           /* The parser context */
+  WhereMaskSet *pMaskSet;  /* Mapping of table cursor numbers to bitmasks */
+  Bitmask vmask;           /* Bitmask identifying virtual table cursors */
+  WhereClause *pOuter;     /* Outer conjunction */
+  u8 op;                   /* Split operator.  TK_AND or TK_OR */
+  u16 wctrlFlags;          /* Might include WHERE_AND_ONLY */
+  int nTerm;               /* Number of terms */
+  int nSlot;               /* Number of entries in a[] */
+  WhereTerm *a;            /* Each a[] describes a term of the WHERE cluase */
+#if defined(SQLITE_SMALL_STACK)
+  WhereTerm aStatic[1];    /* Initial static space for a[] */
+#else
+  WhereTerm aStatic[8];    /* Initial static space for a[] */
+#endif
+};
+
+/*
+** A WhereTerm with eOperator==WO_OR has its u.pOrInfo pointer set to
+** a dynamically allocated instance of the following structure.
+*/
+struct WhereOrInfo {
+  WhereClause wc;          /* Decomposition into subterms */
+  Bitmask indexable;       /* Bitmask of all indexable tables in the clause */
+};
+
+/*
+** A WhereTerm with eOperator==WO_AND has its u.pAndInfo pointer set to
+** a dynamically allocated instance of the following structure.
+*/
+struct WhereAndInfo {
+  WhereClause wc;          /* The subexpression broken out */
+};
+
+/*
+** An instance of the following structure keeps track of a mapping
+** between VDBE cursor numbers and bits of the bitmasks in WhereTerm.
+**
+** The VDBE cursor numbers are small integers contained in 
+** SrcList_item.iCursor and Expr.iTable fields.  For any given WHERE 
+** clause, the cursor numbers might not begin with 0 and they might
+** contain gaps in the numbering sequence.  But we want to make maximum
+** use of the bits in our bitmasks.  This structure provides a mapping
+** from the sparse cursor numbers into consecutive integers beginning
+** with 0.
+**
+** If WhereMaskSet.ix[A]==B it means that The A-th bit of a Bitmask
+** corresponds VDBE cursor number B.  The A-th bit of a bitmask is 1<<A.
+**
+** For example, if the WHERE clause expression used these VDBE
+** cursors:  4, 5, 8, 29, 57, 73.  Then the  WhereMaskSet structure
+** would map those cursor numbers into bits 0 through 5.
+**
+** Note that the mapping is not necessarily ordered.  In the example
+** above, the mapping might go like this:  4->3, 5->1, 8->2, 29->0,
+** 57->5, 73->4.  Or one of 719 other combinations might be used. It
+** does not really matter.  What is important is that sparse cursor
+** numbers all get mapped into bit numbers that begin with 0 and contain
+** no gaps.
+*/
+struct WhereMaskSet {
+  int n;                        /* Number of assigned cursor values */
+  int ix[BMS];                  /* Cursor assigned to each bit */
+};
+
+/*
+** A WhereCost object records a lookup strategy and the estimated
+** cost of pursuing that strategy.
+*/
+struct WhereCost {
+  WherePlan plan;    /* The lookup strategy */
+  double rCost;      /* Overall cost of pursuing this search strategy */
+  Bitmask used;      /* Bitmask of cursors used by this plan */
+};
+
+/*
+** Bitmasks for the operators that indices are able to exploit.  An
+** OR-ed combination of these values can be used when searching for
+** terms in the where clause.
+*/
+#define WO_IN     0x001
+#define WO_EQ     0x002
+#define WO_LT     (WO_EQ<<(TK_LT-TK_EQ))
+#define WO_LE     (WO_EQ<<(TK_LE-TK_EQ))
+#define WO_GT     (WO_EQ<<(TK_GT-TK_EQ))
+#define WO_GE     (WO_EQ<<(TK_GE-TK_EQ))
+#define WO_MATCH  0x040
+#define WO_ISNULL 0x080
+#define WO_OR     0x100       /* Two or more OR-connected terms */
+#define WO_AND    0x200       /* Two or more AND-connected terms */
+#define WO_NOOP   0x800       /* This term does not restrict search space */
+
+#define WO_ALL    0xfff       /* Mask of all possible WO_* values */
+#define WO_SINGLE 0x0ff       /* Mask of all non-compound WO_* values */
+
+/*
+** Value for wsFlags returned by bestIndex() and stored in
+** WhereLevel.wsFlags.  These flags determine which search
+** strategies are appropriate.
+**
+** The least significant 12 bits is reserved as a mask for WO_ values above.
+** The WhereLevel.wsFlags field is usually set to WO_IN|WO_EQ|WO_ISNULL.
+** But if the table is the right table of a left join, WhereLevel.wsFlags
+** is set to WO_IN|WO_EQ.  The WhereLevel.wsFlags field can then be used as
+** the "op" parameter to findTerm when we are resolving equality constraints.
+** ISNULL constraints will then not be used on the right table of a left
+** join.  Tickets #2177 and #2189.
+*/
+#define WHERE_ROWID_EQ     0x00001000  /* rowid=EXPR or rowid IN (...) */
+#define WHERE_ROWID_RANGE  0x00002000  /* rowid<EXPR and/or rowid>EXPR */
+#define WHERE_COLUMN_EQ    0x00010000  /* x=EXPR or x IN (...) or x IS NULL */
+#define WHERE_COLUMN_RANGE 0x00020000  /* x<EXPR and/or x>EXPR */
+#define WHERE_COLUMN_IN    0x00040000  /* x IN (...) */
+#define WHERE_COLUMN_NULL  0x00080000  /* x IS NULL */
+#define WHERE_INDEXED      0x000f0000  /* Anything that uses an index */
+#define WHERE_NOT_FULLSCAN 0x100f3000  /* Does not do a full table scan */
+#define WHERE_IN_ABLE      0x000f1000  /* Able to support an IN operator */
+#define WHERE_TOP_LIMIT    0x00100000  /* x<EXPR or x<=EXPR constraint */
+#define WHERE_BTM_LIMIT    0x00200000  /* x>EXPR or x>=EXPR constraint */
+#define WHERE_BOTH_LIMIT   0x00300000  /* Both x>EXPR and x<EXPR */
+#define WHERE_IDX_ONLY     0x00800000  /* Use index only - omit table */
+#define WHERE_ORDERBY      0x01000000  /* Output will appear in correct order */
+#define WHERE_REVERSE      0x02000000  /* Scan in reverse order */
+#define WHERE_UNIQUE       0x04000000  /* Selects no more than one row */
+#define WHERE_VIRTUALTABLE 0x08000000  /* Use virtual-table processing */
+#define WHERE_MULTI_OR     0x10000000  /* OR using multiple indices */
+#define WHERE_TEMP_INDEX   0x20000000  /* Uses an ephemeral index */
+#define WHERE_DISTINCT     0x40000000  /* Correct order for DISTINCT */
+
+/*
+** Initialize a preallocated WhereClause structure.
+*/
+static void whereClauseInit(
+  WhereClause *pWC,        /* The WhereClause to be initialized */
+  Parse *pParse,           /* The parsing context */
+  WhereMaskSet *pMaskSet,  /* Mapping from table cursor numbers to bitmasks */
+  u16 wctrlFlags           /* Might include WHERE_AND_ONLY */
+){
+  pWC->pParse = pParse;
+  pWC->pMaskSet = pMaskSet;
+  pWC->pOuter = 0;
+  pWC->nTerm = 0;
+  pWC->nSlot = ArraySize(pWC->aStatic);
+  pWC->a = pWC->aStatic;
+  pWC->vmask = 0;
+  pWC->wctrlFlags = wctrlFlags;
+}
+
+/* Forward reference */
+static void whereClauseClear(WhereClause*);
+
+/*
+** Deallocate all memory associated with a WhereOrInfo object.
+*/
+static void whereOrInfoDelete(sqlite3 *db, WhereOrInfo *p){
+  whereClauseClear(&p->wc);
+  sqlite3DbFree(db, p);
+}
+
+/*
+** Deallocate all memory associated with a WhereAndInfo object.
+*/
+static void whereAndInfoDelete(sqlite3 *db, WhereAndInfo *p){
+  whereClauseClear(&p->wc);
+  sqlite3DbFree(db, p);
+}
+
+/*
+** Deallocate a WhereClause structure.  The WhereClause structure
+** itself is not freed.  This routine is the inverse of whereClauseInit().
+*/
+static void whereClauseClear(WhereClause *pWC){
+  int i;
+  WhereTerm *a;
+  sqlite3 *db = pWC->pParse->db;
+  for(i=pWC->nTerm-1, a=pWC->a; i>=0; i--, a++){
+    if( a->wtFlags & TERM_DYNAMIC ){
+      sqlite3ExprDelete(db, a->pExpr);
+    }
+    if( a->wtFlags & TERM_ORINFO ){
+      whereOrInfoDelete(db, a->u.pOrInfo);
+    }else if( a->wtFlags & TERM_ANDINFO ){
+      whereAndInfoDelete(db, a->u.pAndInfo);
+    }
+  }
+  if( pWC->a!=pWC->aStatic ){
+    sqlite3DbFree(db, pWC->a);
+  }
+}
+
+/*
+** Add a single new WhereTerm entry to the WhereClause object pWC.
+** The new WhereTerm object is constructed from Expr p and with wtFlags.
+** The index in pWC->a[] of the new WhereTerm is returned on success.
+** 0 is returned if the new WhereTerm could not be added due to a memory
+** allocation error.  The memory allocation failure will be recorded in
+** the db->mallocFailed flag so that higher-level functions can detect it.
+**
+** This routine will increase the size of the pWC->a[] array as necessary.
+**
+** If the wtFlags argument includes TERM_DYNAMIC, then responsibility
+** for freeing the expression p is assumed by the WhereClause object pWC.
+** This is true even if this routine fails to allocate a new WhereTerm.
+**
+** WARNING:  This routine might reallocate the space used to store
+** WhereTerms.  All pointers to WhereTerms should be invalidated after
+** calling this routine.  Such pointers may be reinitialized by referencing
+** the pWC->a[] array.
+*/
+static int whereClauseInsert(WhereClause *pWC, Expr *p, u8 wtFlags){
+  WhereTerm *pTerm;
+  int idx;
+  testcase( wtFlags & TERM_VIRTUAL );  /* EV: R-00211-15100 */
+  if( pWC->nTerm>=pWC->nSlot ){
+    WhereTerm *pOld = pWC->a;
+    sqlite3 *db = pWC->pParse->db;
+    pWC->a = sqlite3DbMallocRaw(db, sizeof(pWC->a[0])*pWC->nSlot*2 );
+    if( pWC->a==0 ){
+      if( wtFlags & TERM_DYNAMIC ){
+        sqlite3ExprDelete(db, p);
+      }
+      pWC->a = pOld;
+      return 0;
+    }
+    memcpy(pWC->a, pOld, sizeof(pWC->a[0])*pWC->nTerm);
+    if( pOld!=pWC->aStatic ){
+      sqlite3DbFree(db, pOld);
+    }
+    pWC->nSlot = sqlite3DbMallocSize(db, pWC->a)/sizeof(pWC->a[0]);
+  }
+  pTerm = &pWC->a[idx = pWC->nTerm++];
+  pTerm->pExpr = p;
+  pTerm->wtFlags = wtFlags;
+  pTerm->pWC = pWC;
+  pTerm->iParent = -1;
+  return idx;
+}
+
+/*
+** This routine identifies subexpressions in the WHERE clause where
+** each subexpression is separated by the AND operator or some other
+** operator specified in the op parameter.  The WhereClause structure
+** is filled with pointers to subexpressions.  For example:
+**
+**    WHERE  a=='hello' AND coalesce(b,11)<10 AND (c+12!=d OR c==22)
+**           \________/     \_______________/     \________________/
+**            slot[0]            slot[1]               slot[2]
+**
+** The original WHERE clause in pExpr is unaltered.  All this routine
+** does is make slot[] entries point to substructure within pExpr.
+**
+** In the previous sentence and in the diagram, "slot[]" refers to
+** the WhereClause.a[] array.  The slot[] array grows as needed to contain
+** all terms of the WHERE clause.
+*/
+static void whereSplit(WhereClause *pWC, Expr *pExpr, int op){
+  pWC->op = (u8)op;
+  if( pExpr==0 ) return;
+  if( pExpr->op!=op ){
+    whereClauseInsert(pWC, pExpr, 0);
+  }else{
+    whereSplit(pWC, pExpr->pLeft, op);
+    whereSplit(pWC, pExpr->pRight, op);
+  }
+}
+
+/*
+** Initialize an expression mask set (a WhereMaskSet object)
+*/
+#define initMaskSet(P)  memset(P, 0, sizeof(*P))
+
+/*
+** Return the bitmask for the given cursor number.  Return 0 if
+** iCursor is not in the set.
+*/
+static Bitmask getMask(WhereMaskSet *pMaskSet, int iCursor){
+  int i;
+  assert( pMaskSet->n<=(int)sizeof(Bitmask)*8 );
+  for(i=0; i<pMaskSet->n; i++){
+    if( pMaskSet->ix[i]==iCursor ){
+      return ((Bitmask)1)<<i;
+    }
+  }
+  return 0;
+}
+
+/*
+** Create a new mask for cursor iCursor.
+**
+** There is one cursor per table in the FROM clause.  The number of
+** tables in the FROM clause is limited by a test early in the
+** sqlite3WhereBegin() routine.  So we know that the pMaskSet->ix[]
+** array will never overflow.
+*/
+static void createMask(WhereMaskSet *pMaskSet, int iCursor){
+  assert( pMaskSet->n < ArraySize(pMaskSet->ix) );
+  pMaskSet->ix[pMaskSet->n++] = iCursor;
+}
+
+/*
+** This routine walks (recursively) an expression tree and generates
+** a bitmask indicating which tables are used in that expression
+** tree.
+**
+** In order for this routine to work, the calling function must have
+** previously invoked sqlite3ResolveExprNames() on the expression.  See
+** the header comment on that routine for additional information.
+** The sqlite3ResolveExprNames() routines looks for column names and
+** sets their opcodes to TK_COLUMN and their Expr.iTable fields to
+** the VDBE cursor number of the table.  This routine just has to
+** translate the cursor numbers into bitmask values and OR all
+** the bitmasks together.
+*/
+static Bitmask exprListTableUsage(WhereMaskSet*, ExprList*);
+static Bitmask exprSelectTableUsage(WhereMaskSet*, Select*);
+static Bitmask exprTableUsage(WhereMaskSet *pMaskSet, Expr *p){
+  Bitmask mask = 0;
+  if( p==0 ) return 0;
+  if( p->op==TK_COLUMN ){
+    mask = getMask(pMaskSet, p->iTable);
+    return mask;
+  }
+  mask = exprTableUsage(pMaskSet, p->pRight);
+  mask |= exprTableUsage(pMaskSet, p->pLeft);
+  if( ExprHasProperty(p, EP_xIsSelect) ){
+    mask |= exprSelectTableUsage(pMaskSet, p->x.pSelect);
+  }else{
+    mask |= exprListTableUsage(pMaskSet, p->x.pList);
+  }
+  return mask;
+}
+static Bitmask exprListTableUsage(WhereMaskSet *pMaskSet, ExprList *pList){
+  int i;
+  Bitmask mask = 0;
+  if( pList ){
+    for(i=0; i<pList->nExpr; i++){
+      mask |= exprTableUsage(pMaskSet, pList->a[i].pExpr);
+    }
+  }
+  return mask;
+}
+static Bitmask exprSelectTableUsage(WhereMaskSet *pMaskSet, Select *pS){
+  Bitmask mask = 0;
+  while( pS ){
+    SrcList *pSrc = pS->pSrc;
+    mask |= exprListTableUsage(pMaskSet, pS->pEList);
+    mask |= exprListTableUsage(pMaskSet, pS->pGroupBy);
+    mask |= exprListTableUsage(pMaskSet, pS->pOrderBy);
+    mask |= exprTableUsage(pMaskSet, pS->pWhere);
+    mask |= exprTableUsage(pMaskSet, pS->pHaving);
+    if( ALWAYS(pSrc!=0) ){
+      int i;
+      for(i=0; i<pSrc->nSrc; i++){
+        mask |= exprSelectTableUsage(pMaskSet, pSrc->a[i].pSelect);
+        mask |= exprTableUsage(pMaskSet, pSrc->a[i].pOn);
+      }
+    }
+    pS = pS->pPrior;
+  }
+  return mask;
+}
+
+/*
+** Return TRUE if the given operator is one of the operators that is
+** allowed for an indexable WHERE clause term.  The allowed operators are
+** "=", "<", ">", "<=", ">=", and "IN".
+**
+** IMPLEMENTATION-OF: R-59926-26393 To be usable by an index a term must be
+** of one of the following forms: column = expression column > expression
+** column >= expression column < expression column <= expression
+** expression = column expression > column expression >= column
+** expression < column expression <= column column IN
+** (expression-list) column IN (subquery) column IS NULL
+*/
+static int allowedOp(int op){
+  assert( TK_GT>TK_EQ && TK_GT<TK_GE );
+  assert( TK_LT>TK_EQ && TK_LT<TK_GE );
+  assert( TK_LE>TK_EQ && TK_LE<TK_GE );
+  assert( TK_GE==TK_EQ+4 );
+  return op==TK_IN || (op>=TK_EQ && op<=TK_GE) || op==TK_ISNULL;
+}
+
+/*
+** Swap two objects of type TYPE.
+*/
+#define SWAP(TYPE,A,B) {TYPE t=A; A=B; B=t;}
+
+/*
+** Commute a comparison operator.  Expressions of the form "X op Y"
+** are converted into "Y op X".
+**
+** If a collation sequence is associated with either the left or right
+** side of the comparison, it remains associated with the same side after
+** the commutation. So "Y collate NOCASE op X" becomes 
+** "X collate NOCASE op Y". This is because any collation sequence on
+** the left hand side of a comparison overrides any collation sequence 
+** attached to the right. For the same reason the EP_ExpCollate flag
+** is not commuted.
+*/
+static void exprCommute(Parse *pParse, Expr *pExpr){
+  u16 expRight = (pExpr->pRight->flags & EP_ExpCollate);
+  u16 expLeft = (pExpr->pLeft->flags & EP_ExpCollate);
+  assert( allowedOp(pExpr->op) && pExpr->op!=TK_IN );
+  pExpr->pRight->pColl = sqlite3ExprCollSeq(pParse, pExpr->pRight);
+  pExpr->pLeft->pColl = sqlite3ExprCollSeq(pParse, pExpr->pLeft);
+  SWAP(CollSeq*,pExpr->pRight->pColl,pExpr->pLeft->pColl);
+  pExpr->pRight->flags = (pExpr->pRight->flags & ~EP_ExpCollate) | expLeft;
+  pExpr->pLeft->flags = (pExpr->pLeft->flags & ~EP_ExpCollate) | expRight;
+  SWAP(Expr*,pExpr->pRight,pExpr->pLeft);
+  if( pExpr->op>=TK_GT ){
+    assert( TK_LT==TK_GT+2 );
+    assert( TK_GE==TK_LE+2 );
+    assert( TK_GT>TK_EQ );
+    assert( TK_GT<TK_LE );
+    assert( pExpr->op>=TK_GT && pExpr->op<=TK_GE );
+    pExpr->op = ((pExpr->op-TK_GT)^2)+TK_GT;
+  }
+}
+
+/*
+** Translate from TK_xx operator to WO_xx bitmask.
+*/
+static u16 operatorMask(int op){
+  u16 c;
+  assert( allowedOp(op) );
+  if( op==TK_IN ){
+    c = WO_IN;
+  }else if( op==TK_ISNULL ){
+    c = WO_ISNULL;
+  }else{
+    assert( (WO_EQ<<(op-TK_EQ)) < 0x7fff );
+    c = (u16)(WO_EQ<<(op-TK_EQ));
+  }
+  assert( op!=TK_ISNULL || c==WO_ISNULL );
+  assert( op!=TK_IN || c==WO_IN );
+  assert( op!=TK_EQ || c==WO_EQ );
+  assert( op!=TK_LT || c==WO_LT );
+  assert( op!=TK_LE || c==WO_LE );
+  assert( op!=TK_GT || c==WO_GT );
+  assert( op!=TK_GE || c==WO_GE );
+  return c;
+}
+
+/*
+** Search for a term in the WHERE clause that is of the form "X <op> <expr>"
+** where X is a reference to the iColumn of table iCur and <op> is one of
+** the WO_xx operator codes specified by the op parameter.
+** Return a pointer to the term.  Return 0 if not found.
+*/
+static WhereTerm *findTerm(
+  WhereClause *pWC,     /* The WHERE clause to be searched */
+  int iCur,             /* Cursor number of LHS */
+  int iColumn,          /* Column number of LHS */
+  Bitmask notReady,     /* RHS must not overlap with this mask */
+  u32 op,               /* Mask of WO_xx values describing operator */
+  Index *pIdx           /* Must be compatible with this index, if not NULL */
+){
+  WhereTerm *pTerm;
+  int k;
+  assert( iCur>=0 );
+  op &= WO_ALL;
+  for(; pWC; pWC=pWC->pOuter){
+    for(pTerm=pWC->a, k=pWC->nTerm; k; k--, pTerm++){
+      if( pTerm->leftCursor==iCur
+         && (pTerm->prereqRight & notReady)==0
+         && pTerm->u.leftColumn==iColumn
+         && (pTerm->eOperator & op)!=0
+      ){
+        if( pIdx && pTerm->eOperator!=WO_ISNULL ){
+          Expr *pX = pTerm->pExpr;
+          CollSeq *pColl;
+          char idxaff;
+          int j;
+          Parse *pParse = pWC->pParse;
+  
+          idxaff = pIdx->pTable->aCol[iColumn].affinity;
+          if( !sqlite3IndexAffinityOk(pX, idxaff) ) continue;
+  
+          /* Figure out the collation sequence required from an index for
+          ** it to be useful for optimising expression pX. Store this
+          ** value in variable pColl.
+          */
+          assert(pX->pLeft);
+          pColl = sqlite3BinaryCompareCollSeq(pParse, pX->pLeft, pX->pRight);
+          assert(pColl || pParse->nErr);
+  
+          for(j=0; pIdx->aiColumn[j]!=iColumn; j++){
+            if( NEVER(j>=pIdx->nColumn) ) return 0;
+          }
+          if( pColl && sqlite3StrICmp(pColl->zName, pIdx->azColl[j]) ) continue;
+        }
+        return pTerm;
+      }
+    }
+  }
+  return 0;
+}
+
+/* Forward reference */
+static void exprAnalyze(SrcList*, WhereClause*, int);
+
+/*
+** Call exprAnalyze on all terms in a WHERE clause.  
+**
+**
+*/
+static void exprAnalyzeAll(
+  SrcList *pTabList,       /* the FROM clause */
+  WhereClause *pWC         /* the WHERE clause to be analyzed */
+){
+  int i;
+  for(i=pWC->nTerm-1; i>=0; i--){
+    exprAnalyze(pTabList, pWC, i);
+  }
+}
+
+#ifndef SQLITE_OMIT_LIKE_OPTIMIZATION
+/*
+** Check to see if the given expression is a LIKE or GLOB operator that
+** can be optimized using inequality constraints.  Return TRUE if it is
+** so and false if not.
+**
+** In order for the operator to be optimizible, the RHS must be a string
+** literal that does not begin with a wildcard.  
+*/
+static int isLikeOrGlob(
+  Parse *pParse,    /* Parsing and code generating context */
+  Expr *pExpr,      /* Test this expression */
+  Expr **ppPrefix,  /* Pointer to TK_STRING expression with pattern prefix */
+  int *pisComplete, /* True if the only wildcard is % in the last character */
+  int *pnoCase      /* True if uppercase is equivalent to lowercase */
+){
+  const char *z = 0;         /* String on RHS of LIKE operator */
+  Expr *pRight, *pLeft;      /* Right and left size of LIKE operator */
+  ExprList *pList;           /* List of operands to the LIKE operator */
+  int c;                     /* One character in z[] */
+  int cnt;                   /* Number of non-wildcard prefix characters */
+  char wc[3];                /* Wildcard characters */
+  sqlite3 *db = pParse->db;  /* Database connection */
+  sqlite3_value *pVal = 0;
+  int op;                    /* Opcode of pRight */
+
+  if( !sqlite3IsLikeFunction(db, pExpr, pnoCase, wc) ){
+    return 0;
+  }
+#ifdef SQLITE_EBCDIC
+  if( *pnoCase ) return 0;
+#endif
+  pList = pExpr->x.pList;
+  pLeft = pList->a[1].pExpr;
+  if( pLeft->op!=TK_COLUMN || sqlite3ExprAffinity(pLeft)!=SQLITE_AFF_TEXT ){
+    /* IMP: R-02065-49465 The left-hand side of the LIKE or GLOB operator must
+    ** be the name of an indexed column with TEXT affinity. */
+    return 0;
+  }
+  assert( pLeft->iColumn!=(-1) ); /* Because IPK never has AFF_TEXT */
+
+  pRight = pList->a[0].pExpr;
+  op = pRight->op;
+  if( op==TK_REGISTER ){
+    op = pRight->op2;
+  }
+  if( op==TK_VARIABLE ){
+    Vdbe *pReprepare = pParse->pReprepare;
+    int iCol = pRight->iColumn;
+    pVal = sqlite3VdbeGetValue(pReprepare, iCol, SQLITE_AFF_NONE);
+    if( pVal && sqlite3_value_type(pVal)==SQLITE_TEXT ){
+      z = (char *)sqlite3_value_text(pVal);
+    }
+    sqlite3VdbeSetVarmask(pParse->pVdbe, iCol);
+    assert( pRight->op==TK_VARIABLE || pRight->op==TK_REGISTER );
+  }else if( op==TK_STRING ){
+    z = pRight->u.zToken;
+  }
+  if( z ){
+    cnt = 0;
+    while( (c=z[cnt])!=0 && c!=wc[0] && c!=wc[1] && c!=wc[2] ){
+      cnt++;
+    }
+    if( cnt!=0 && 255!=(u8)z[cnt-1] ){
+      Expr *pPrefix;
+      *pisComplete = c==wc[0] && z[cnt+1]==0;
+      pPrefix = sqlite3Expr(db, TK_STRING, z);
+      if( pPrefix ) pPrefix->u.zToken[cnt] = 0;
+      *ppPrefix = pPrefix;
+      if( op==TK_VARIABLE ){
+        Vdbe *v = pParse->pVdbe;
+        sqlite3VdbeSetVarmask(v, pRight->iColumn);
+        if( *pisComplete && pRight->u.zToken[1] ){
+          /* If the rhs of the LIKE expression is a variable, and the current
+          ** value of the variable means there is no need to invoke the LIKE
+          ** function, then no OP_Variable will be added to the program.
+          ** This causes problems for the sqlite3_bind_parameter_name()
+          ** API. To workaround them, add a dummy OP_Variable here.
+          */ 
+          int r1 = sqlite3GetTempReg(pParse);
+          sqlite3ExprCodeTarget(pParse, pRight, r1);
+          sqlite3VdbeChangeP3(v, sqlite3VdbeCurrentAddr(v)-1, 0);
+          sqlite3ReleaseTempReg(pParse, r1);
+        }
+      }
+    }else{
+      z = 0;
+    }
+  }
+
+  sqlite3ValueFree(pVal);
+  return (z!=0);
+}
+#endif /* SQLITE_OMIT_LIKE_OPTIMIZATION */
+
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/*
+** Check to see if the given expression is of the form
+**
+**         column MATCH expr
+**
+** If it is then return TRUE.  If not, return FALSE.
+*/
+static int isMatchOfColumn(
+  Expr *pExpr      /* Test this expression */
+){
+  ExprList *pList;
+
+  if( pExpr->op!=TK_FUNCTION ){
+    return 0;
+  }
+  if( sqlite3StrICmp(pExpr->u.zToken,"match")!=0 ){
+    return 0;
+  }
+  pList = pExpr->x.pList;
+  if( pList->nExpr!=2 ){
+    return 0;
+  }
+  if( pList->a[1].pExpr->op != TK_COLUMN ){
+    return 0;
+  }
+  return 1;
+}
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+/*
+** If the pBase expression originated in the ON or USING clause of
+** a join, then transfer the appropriate markings over to derived.
+*/
+static void transferJoinMarkings(Expr *pDerived, Expr *pBase){
+  pDerived->flags |= pBase->flags & EP_FromJoin;
+  pDerived->iRightJoinTable = pBase->iRightJoinTable;
+}
+
+#if !defined(SQLITE_OMIT_OR_OPTIMIZATION) && !defined(SQLITE_OMIT_SUBQUERY)
+/*
+** Analyze a term that consists of two or more OR-connected
+** subterms.  So in:
+**
+**     ... WHERE  (a=5) AND (b=7 OR c=9 OR d=13) AND (d=13)
+**                          ^^^^^^^^^^^^^^^^^^^^
+**
+** This routine analyzes terms such as the middle term in the above example.
+** A WhereOrTerm object is computed and attached to the term under
+** analysis, regardless of the outcome of the analysis.  Hence:
+**
+**     WhereTerm.wtFlags   |=  TERM_ORINFO
+**     WhereTerm.u.pOrInfo  =  a dynamically allocated WhereOrTerm object
+**
+** The term being analyzed must have two or more of OR-connected subterms.
+** A single subterm might be a set of AND-connected sub-subterms.
+** Examples of terms under analysis:
+**
+**     (A)     t1.x=t2.y OR t1.x=t2.z OR t1.y=15 OR t1.z=t3.a+5
+**     (B)     x=expr1 OR expr2=x OR x=expr3
+**     (C)     t1.x=t2.y OR (t1.x=t2.z AND t1.y=15)
+**     (D)     x=expr1 OR (y>11 AND y<22 AND z LIKE '*hello*')
+**     (E)     (p.a=1 AND q.b=2 AND r.c=3) OR (p.x=4 AND q.y=5 AND r.z=6)
+**
+** CASE 1:
+**
+** If all subterms are of the form T.C=expr for some single column of C
+** a single table T (as shown in example B above) then create a new virtual
+** term that is an equivalent IN expression.  In other words, if the term
+** being analyzed is:
+**
+**      x = expr1  OR  expr2 = x  OR  x = expr3
+**
+** then create a new virtual term like this:
+**
+**      x IN (expr1,expr2,expr3)
+**
+** CASE 2:
+**
+** If all subterms are indexable by a single table T, then set
+**
+**     WhereTerm.eOperator              =  WO_OR
+**     WhereTerm.u.pOrInfo->indexable  |=  the cursor number for table T
+**
+** A subterm is "indexable" if it is of the form
+** "T.C <op> <expr>" where C is any column of table T and 
+** <op> is one of "=", "<", "<=", ">", ">=", "IS NULL", or "IN".
+** A subterm is also indexable if it is an AND of two or more
+** subsubterms at least one of which is indexable.  Indexable AND 
+** subterms have their eOperator set to WO_AND and they have
+** u.pAndInfo set to a dynamically allocated WhereAndTerm object.
+**
+** From another point of view, "indexable" means that the subterm could
+** potentially be used with an index if an appropriate index exists.
+** This analysis does not consider whether or not the index exists; that
+** is something the bestIndex() routine will determine.  This analysis
+** only looks at whether subterms appropriate for indexing exist.
+**
+** All examples A through E above all satisfy case 2.  But if a term
+** also statisfies case 1 (such as B) we know that the optimizer will
+** always prefer case 1, so in that case we pretend that case 2 is not
+** satisfied.
+**
+** It might be the case that multiple tables are indexable.  For example,
+** (E) above is indexable on tables P, Q, and R.
+**
+** Terms that satisfy case 2 are candidates for lookup by using
+** separate indices to find rowids for each subterm and composing
+** the union of all rowids using a RowSet object.  This is similar
+** to "bitmap indices" in other database engines.
+**
+** OTHERWISE:
+**
+** If neither case 1 nor case 2 apply, then leave the eOperator set to
+** zero.  This term is not useful for search.
+*/
+static void exprAnalyzeOrTerm(
+  SrcList *pSrc,            /* the FROM clause */
+  WhereClause *pWC,         /* the complete WHERE clause */
+  int idxTerm               /* Index of the OR-term to be analyzed */
+){
+  Parse *pParse = pWC->pParse;            /* Parser context */
+  sqlite3 *db = pParse->db;               /* Database connection */
+  WhereTerm *pTerm = &pWC->a[idxTerm];    /* The term to be analyzed */
+  Expr *pExpr = pTerm->pExpr;             /* The expression of the term */
+  WhereMaskSet *pMaskSet = pWC->pMaskSet; /* Table use masks */
+  int i;                                  /* Loop counters */
+  WhereClause *pOrWc;       /* Breakup of pTerm into subterms */
+  WhereTerm *pOrTerm;       /* A Sub-term within the pOrWc */
+  WhereOrInfo *pOrInfo;     /* Additional information associated with pTerm */
+  Bitmask chngToIN;         /* Tables that might satisfy case 1 */
+  Bitmask indexable;        /* Tables that are indexable, satisfying case 2 */
+
+  /*
+  ** Break the OR clause into its separate subterms.  The subterms are
+  ** stored in a WhereClause structure containing within the WhereOrInfo
+  ** object that is attached to the original OR clause term.
+  */
+  assert( (pTerm->wtFlags & (TERM_DYNAMIC|TERM_ORINFO|TERM_ANDINFO))==0 );
+  assert( pExpr->op==TK_OR );
+  pTerm->u.pOrInfo = pOrInfo = sqlite3DbMallocZero(db, sizeof(*pOrInfo));
+  if( pOrInfo==0 ) return;
+  pTerm->wtFlags |= TERM_ORINFO;
+  pOrWc = &pOrInfo->wc;
+  whereClauseInit(pOrWc, pWC->pParse, pMaskSet, pWC->wctrlFlags);
+  whereSplit(pOrWc, pExpr, TK_OR);
+  exprAnalyzeAll(pSrc, pOrWc);
+  if( db->mallocFailed ) return;
+  assert( pOrWc->nTerm>=2 );
+
+  /*
+  ** Compute the set of tables that might satisfy cases 1 or 2.
+  */
+  indexable = ~(Bitmask)0;
+  chngToIN = ~(pWC->vmask);
+  for(i=pOrWc->nTerm-1, pOrTerm=pOrWc->a; i>=0 && indexable; i--, pOrTerm++){
+    if( (pOrTerm->eOperator & WO_SINGLE)==0 ){
+      WhereAndInfo *pAndInfo;
+      assert( pOrTerm->eOperator==0 );
+      assert( (pOrTerm->wtFlags & (TERM_ANDINFO|TERM_ORINFO))==0 );
+      chngToIN = 0;
+      pAndInfo = sqlite3DbMallocRaw(db, sizeof(*pAndInfo));
+      if( pAndInfo ){
+        WhereClause *pAndWC;
+        WhereTerm *pAndTerm;
+        int j;
+        Bitmask b = 0;
+        pOrTerm->u.pAndInfo = pAndInfo;
+        pOrTerm->wtFlags |= TERM_ANDINFO;
+        pOrTerm->eOperator = WO_AND;
+        pAndWC = &pAndInfo->wc;
+        whereClauseInit(pAndWC, pWC->pParse, pMaskSet, pWC->wctrlFlags);
+        whereSplit(pAndWC, pOrTerm->pExpr, TK_AND);
+        exprAnalyzeAll(pSrc, pAndWC);
+        pAndWC->pOuter = pWC;
+        testcase( db->mallocFailed );
+        if( !db->mallocFailed ){
+          for(j=0, pAndTerm=pAndWC->a; j<pAndWC->nTerm; j++, pAndTerm++){
+            assert( pAndTerm->pExpr );
+            if( allowedOp(pAndTerm->pExpr->op) ){
+              b |= getMask(pMaskSet, pAndTerm->leftCursor);
+            }
+          }
+        }
+        indexable &= b;
+      }
+    }else if( pOrTerm->wtFlags & TERM_COPIED ){
+      /* Skip this term for now.  We revisit it when we process the
+      ** corresponding TERM_VIRTUAL term */
+    }else{
+      Bitmask b;
+      b = getMask(pMaskSet, pOrTerm->leftCursor);
+      if( pOrTerm->wtFlags & TERM_VIRTUAL ){
+        WhereTerm *pOther = &pOrWc->a[pOrTerm->iParent];
+        b |= getMask(pMaskSet, pOther->leftCursor);
+      }
+      indexable &= b;
+      if( pOrTerm->eOperator!=WO_EQ ){
+        chngToIN = 0;
+      }else{
+        chngToIN &= b;
+      }
+    }
+  }
+
+  /*
+  ** Record the set of tables that satisfy case 2.  The set might be
+  ** empty.
+  */
+  pOrInfo->indexable = indexable;
+  pTerm->eOperator = indexable==0 ? 0 : WO_OR;
+
+  /*
+  ** chngToIN holds a set of tables that *might* satisfy case 1.  But
+  ** we have to do some additional checking to see if case 1 really
+  ** is satisfied.
+  **
+  ** chngToIN will hold either 0, 1, or 2 bits.  The 0-bit case means
+  ** that there is no possibility of transforming the OR clause into an
+  ** IN operator because one or more terms in the OR clause contain
+  ** something other than == on a column in the single table.  The 1-bit
+  ** case means that every term of the OR clause is of the form
+  ** "table.column=expr" for some single table.  The one bit that is set
+  ** will correspond to the common table.  We still need to check to make
+  ** sure the same column is used on all terms.  The 2-bit case is when
+  ** the all terms are of the form "table1.column=table2.column".  It
+  ** might be possible to form an IN operator with either table1.column
+  ** or table2.column as the LHS if either is common to every term of
+  ** the OR clause.
+  **
+  ** Note that terms of the form "table.column1=table.column2" (the
+  ** same table on both sizes of the ==) cannot be optimized.
+  */
+  if( chngToIN ){
+    int okToChngToIN = 0;     /* True if the conversion to IN is valid */
+    int iColumn = -1;         /* Column index on lhs of IN operator */
+    int iCursor = -1;         /* Table cursor common to all terms */
+    int j = 0;                /* Loop counter */
+
+    /* Search for a table and column that appears on one side or the
+    ** other of the == operator in every subterm.  That table and column
+    ** will be recorded in iCursor and iColumn.  There might not be any
+    ** such table and column.  Set okToChngToIN if an appropriate table
+    ** and column is found but leave okToChngToIN false if not found.
+    */
+    for(j=0; j<2 && !okToChngToIN; j++){
+      pOrTerm = pOrWc->a;
+      for(i=pOrWc->nTerm-1; i>=0; i--, pOrTerm++){
+        assert( pOrTerm->eOperator==WO_EQ );
+        pOrTerm->wtFlags &= ~TERM_OR_OK;
+        if( pOrTerm->leftCursor==iCursor ){
+          /* This is the 2-bit case and we are on the second iteration and
+          ** current term is from the first iteration.  So skip this term. */
+          assert( j==1 );
+          continue;
+        }
+        if( (chngToIN & getMask(pMaskSet, pOrTerm->leftCursor))==0 ){
+          /* This term must be of the form t1.a==t2.b where t2 is in the
+          ** chngToIN set but t1 is not.  This term will be either preceeded
+          ** or follwed by an inverted copy (t2.b==t1.a).  Skip this term 
+          ** and use its inversion. */
+          testcase( pOrTerm->wtFlags & TERM_COPIED );
+          testcase( pOrTerm->wtFlags & TERM_VIRTUAL );
+          assert( pOrTerm->wtFlags & (TERM_COPIED|TERM_VIRTUAL) );
+          continue;
+        }
+        iColumn = pOrTerm->u.leftColumn;
+        iCursor = pOrTerm->leftCursor;
+        break;
+      }
+      if( i<0 ){
+        /* No candidate table+column was found.  This can only occur
+        ** on the second iteration */
+        assert( j==1 );
+        assert( (chngToIN&(chngToIN-1))==0 );
+        assert( chngToIN==getMask(pMaskSet, iCursor) );
+        break;
+      }
+      testcase( j==1 );
+
+      /* We have found a candidate table and column.  Check to see if that
+      ** table and column is common to every term in the OR clause */
+      okToChngToIN = 1;
+      for(; i>=0 && okToChngToIN; i--, pOrTerm++){
+        assert( pOrTerm->eOperator==WO_EQ );
+        if( pOrTerm->leftCursor!=iCursor ){
+          pOrTerm->wtFlags &= ~TERM_OR_OK;
+        }else if( pOrTerm->u.leftColumn!=iColumn ){
+          okToChngToIN = 0;
+        }else{
+          int affLeft, affRight;
+          /* If the right-hand side is also a column, then the affinities
+          ** of both right and left sides must be such that no type
+          ** conversions are required on the right.  (Ticket #2249)
+          */
+          affRight = sqlite3ExprAffinity(pOrTerm->pExpr->pRight);
+          affLeft = sqlite3ExprAffinity(pOrTerm->pExpr->pLeft);
+          if( affRight!=0 && affRight!=affLeft ){
+            okToChngToIN = 0;
+          }else{
+            pOrTerm->wtFlags |= TERM_OR_OK;
+          }
+        }
+      }
+    }
+
+    /* At this point, okToChngToIN is true if original pTerm satisfies
+    ** case 1.  In that case, construct a new virtual term that is 
+    ** pTerm converted into an IN operator.
+    **
+    ** EV: R-00211-15100
+    */
+    if( okToChngToIN ){
+      Expr *pDup;            /* A transient duplicate expression */
+      ExprList *pList = 0;   /* The RHS of the IN operator */
+      Expr *pLeft = 0;       /* The LHS of the IN operator */
+      Expr *pNew;            /* The complete IN operator */
+
+      for(i=pOrWc->nTerm-1, pOrTerm=pOrWc->a; i>=0; i--, pOrTerm++){
+        if( (pOrTerm->wtFlags & TERM_OR_OK)==0 ) continue;
+        assert( pOrTerm->eOperator==WO_EQ );
+        assert( pOrTerm->leftCursor==iCursor );
+        assert( pOrTerm->u.leftColumn==iColumn );
+        pDup = sqlite3ExprDup(db, pOrTerm->pExpr->pRight, 0);
+        pList = sqlite3ExprListAppend(pWC->pParse, pList, pDup);
+        pLeft = pOrTerm->pExpr->pLeft;
+      }
+      assert( pLeft!=0 );
+      pDup = sqlite3ExprDup(db, pLeft, 0);
+      pNew = sqlite3PExpr(pParse, TK_IN, pDup, 0, 0);
+      if( pNew ){
+        int idxNew;
+        transferJoinMarkings(pNew, pExpr);
+        assert( !ExprHasProperty(pNew, EP_xIsSelect) );
+        pNew->x.pList = pList;
+        idxNew = whereClauseInsert(pWC, pNew, TERM_VIRTUAL|TERM_DYNAMIC);
+        testcase( idxNew==0 );
+        exprAnalyze(pSrc, pWC, idxNew);
+        pTerm = &pWC->a[idxTerm];
+        pWC->a[idxNew].iParent = idxTerm;
+        pTerm->nChild = 1;
+      }else{
+        sqlite3ExprListDelete(db, pList);
+      }
+      pTerm->eOperator = WO_NOOP;  /* case 1 trumps case 2 */
+    }
+  }
+}
+#endif /* !SQLITE_OMIT_OR_OPTIMIZATION && !SQLITE_OMIT_SUBQUERY */
+
+
+/*
+** The input to this routine is an WhereTerm structure with only the
+** "pExpr" field filled in.  The job of this routine is to analyze the
+** subexpression and populate all the other fields of the WhereTerm
+** structure.
+**
+** If the expression is of the form "<expr> <op> X" it gets commuted
+** to the standard form of "X <op> <expr>".
+**
+** If the expression is of the form "X <op> Y" where both X and Y are
+** columns, then the original expression is unchanged and a new virtual
+** term of the form "Y <op> X" is added to the WHERE clause and
+** analyzed separately.  The original term is marked with TERM_COPIED
+** and the new term is marked with TERM_DYNAMIC (because it's pExpr
+** needs to be freed with the WhereClause) and TERM_VIRTUAL (because it
+** is a commuted copy of a prior term.)  The original term has nChild=1
+** and the copy has idxParent set to the index of the original term.
+*/
+static void exprAnalyze(
+  SrcList *pSrc,            /* the FROM clause */
+  WhereClause *pWC,         /* the WHERE clause */
+  int idxTerm               /* Index of the term to be analyzed */
+){
+  WhereTerm *pTerm;                /* The term to be analyzed */
+  WhereMaskSet *pMaskSet;          /* Set of table index masks */
+  Expr *pExpr;                     /* The expression to be analyzed */
+  Bitmask prereqLeft;              /* Prerequesites of the pExpr->pLeft */
+  Bitmask prereqAll;               /* Prerequesites of pExpr */
+  Bitmask extraRight = 0;          /* Extra dependencies on LEFT JOIN */
+  Expr *pStr1 = 0;                 /* RHS of LIKE/GLOB operator */
+  int isComplete = 0;              /* RHS of LIKE/GLOB ends with wildcard */
+  int noCase = 0;                  /* LIKE/GLOB distinguishes case */
+  int op;                          /* Top-level operator.  pExpr->op */
+  Parse *pParse = pWC->pParse;     /* Parsing context */
+  sqlite3 *db = pParse->db;        /* Database connection */
+
+  if( db->mallocFailed ){
+    return;
+  }
+  pTerm = &pWC->a[idxTerm];
+  pMaskSet = pWC->pMaskSet;
+  pExpr = pTerm->pExpr;
+  prereqLeft = exprTableUsage(pMaskSet, pExpr->pLeft);
+  op = pExpr->op;
+  if( op==TK_IN ){
+    assert( pExpr->pRight==0 );
+    if( ExprHasProperty(pExpr, EP_xIsSelect) ){
+      pTerm->prereqRight = exprSelectTableUsage(pMaskSet, pExpr->x.pSelect);
+    }else{
+      pTerm->prereqRight = exprListTableUsage(pMaskSet, pExpr->x.pList);
+    }
+  }else if( op==TK_ISNULL ){
+    pTerm->prereqRight = 0;
+  }else{
+    pTerm->prereqRight = exprTableUsage(pMaskSet, pExpr->pRight);
+  }
+  prereqAll = exprTableUsage(pMaskSet, pExpr);
+  if( ExprHasProperty(pExpr, EP_FromJoin) ){
+    Bitmask x = getMask(pMaskSet, pExpr->iRightJoinTable);
+    prereqAll |= x;
+    extraRight = x-1;  /* ON clause terms may not be used with an index
+                       ** on left table of a LEFT JOIN.  Ticket #3015 */
+  }
+  pTerm->prereqAll = prereqAll;
+  pTerm->leftCursor = -1;
+  pTerm->iParent = -1;
+  pTerm->eOperator = 0;
+  if( allowedOp(op) && (pTerm->prereqRight & prereqLeft)==0 ){
+    Expr *pLeft = pExpr->pLeft;
+    Expr *pRight = pExpr->pRight;
+    if( pLeft->op==TK_COLUMN ){
+      pTerm->leftCursor = pLeft->iTable;
+      pTerm->u.leftColumn = pLeft->iColumn;
+      pTerm->eOperator = operatorMask(op);
+    }
+    if( pRight && pRight->op==TK_COLUMN ){
+      WhereTerm *pNew;
+      Expr *pDup;
+      if( pTerm->leftCursor>=0 ){
+        int idxNew;
+        pDup = sqlite3ExprDup(db, pExpr, 0);
+        if( db->mallocFailed ){
+          sqlite3ExprDelete(db, pDup);
+          return;
+        }
+        idxNew = whereClauseInsert(pWC, pDup, TERM_VIRTUAL|TERM_DYNAMIC);
+        if( idxNew==0 ) return;
+        pNew = &pWC->a[idxNew];
+        pNew->iParent = idxTerm;
+        pTerm = &pWC->a[idxTerm];
+        pTerm->nChild = 1;
+        pTerm->wtFlags |= TERM_COPIED;
+      }else{
+        pDup = pExpr;
+        pNew = pTerm;
+      }
+      exprCommute(pParse, pDup);
+      pLeft = pDup->pLeft;
+      pNew->leftCursor = pLeft->iTable;
+      pNew->u.leftColumn = pLeft->iColumn;
+      testcase( (prereqLeft | extraRight) != prereqLeft );
+      pNew->prereqRight = prereqLeft | extraRight;
+      pNew->prereqAll = prereqAll;
+      pNew->eOperator = operatorMask(pDup->op);
+    }
+  }
+
+#ifndef SQLITE_OMIT_BETWEEN_OPTIMIZATION
+  /* If a term is the BETWEEN operator, create two new virtual terms
+  ** that define the range that the BETWEEN implements.  For example:
+  **
+  **      a BETWEEN b AND c
+  **
+  ** is converted into:
+  **
+  **      (a BETWEEN b AND c) AND (a>=b) AND (a<=c)
+  **
+  ** The two new terms are added onto the end of the WhereClause object.
+  ** The new terms are "dynamic" and are children of the original BETWEEN
+  ** term.  That means that if the BETWEEN term is coded, the children are
+  ** skipped.  Or, if the children are satisfied by an index, the original
+  ** BETWEEN term is skipped.
+  */
+  else if( pExpr->op==TK_BETWEEN && pWC->op==TK_AND ){
+    ExprList *pList = pExpr->x.pList;
+    int i;
+    static const u8 ops[] = {TK_GE, TK_LE};
+    assert( pList!=0 );
+    assert( pList->nExpr==2 );
+    for(i=0; i<2; i++){
+      Expr *pNewExpr;
+      int idxNew;
+      pNewExpr = sqlite3PExpr(pParse, ops[i], 
+                             sqlite3ExprDup(db, pExpr->pLeft, 0),
+                             sqlite3ExprDup(db, pList->a[i].pExpr, 0), 0);
+      idxNew = whereClauseInsert(pWC, pNewExpr, TERM_VIRTUAL|TERM_DYNAMIC);
+      testcase( idxNew==0 );
+      exprAnalyze(pSrc, pWC, idxNew);
+      pTerm = &pWC->a[idxTerm];
+      pWC->a[idxNew].iParent = idxTerm;
+    }
+    pTerm->nChild = 2;
+  }
+#endif /* SQLITE_OMIT_BETWEEN_OPTIMIZATION */
+
+#if !defined(SQLITE_OMIT_OR_OPTIMIZATION) && !defined(SQLITE_OMIT_SUBQUERY)
+  /* Analyze a term that is composed of two or more subterms connected by
+  ** an OR operator.
+  */
+  else if( pExpr->op==TK_OR ){
+    assert( pWC->op==TK_AND );
+    exprAnalyzeOrTerm(pSrc, pWC, idxTerm);
+    pTerm = &pWC->a[idxTerm];
+  }
+#endif /* SQLITE_OMIT_OR_OPTIMIZATION */
+
+#ifndef SQLITE_OMIT_LIKE_OPTIMIZATION
+  /* Add constraints to reduce the search space on a LIKE or GLOB
+  ** operator.
+  **
+  ** A like pattern of the form "x LIKE 'abc%'" is changed into constraints
+  **
+  **          x>='abc' AND x<'abd' AND x LIKE 'abc%'
+  **
+  ** The last character of the prefix "abc" is incremented to form the
+  ** termination condition "abd".
+  */
+  if( pWC->op==TK_AND 
+   && isLikeOrGlob(pParse, pExpr, &pStr1, &isComplete, &noCase)
+  ){
+    Expr *pLeft;       /* LHS of LIKE/GLOB operator */
+    Expr *pStr2;       /* Copy of pStr1 - RHS of LIKE/GLOB operator */
+    Expr *pNewExpr1;
+    Expr *pNewExpr2;
+    int idxNew1;
+    int idxNew2;
+    CollSeq *pColl;    /* Collating sequence to use */
+
+    pLeft = pExpr->x.pList->a[1].pExpr;
+    pStr2 = sqlite3ExprDup(db, pStr1, 0);
+    if( !db->mallocFailed ){
+      u8 c, *pC;       /* Last character before the first wildcard */
+      pC = (u8*)&pStr2->u.zToken[sqlite3Strlen30(pStr2->u.zToken)-1];
+      c = *pC;
+      if( noCase ){
+        /* The point is to increment the last character before the first
+        ** wildcard.  But if we increment '@', that will push it into the
+        ** alphabetic range where case conversions will mess up the 
+        ** inequality.  To avoid this, make sure to also run the full
+        ** LIKE on all candidate expressions by clearing the isComplete flag
+        */
+        if( c=='A'-1 ) isComplete = 0;   /* EV: R-64339-08207 */
+
+
+        c = sqlite3UpperToLower[c];
+      }
+      *pC = c + 1;
+    }
+    pColl = sqlite3FindCollSeq(db, SQLITE_UTF8, noCase ? "NOCASE" : "BINARY",0);
+    pNewExpr1 = sqlite3PExpr(pParse, TK_GE, 
+                     sqlite3ExprSetColl(sqlite3ExprDup(db,pLeft,0), pColl),
+                     pStr1, 0);
+    idxNew1 = whereClauseInsert(pWC, pNewExpr1, TERM_VIRTUAL|TERM_DYNAMIC);
+    testcase( idxNew1==0 );
+    exprAnalyze(pSrc, pWC, idxNew1);
+    pNewExpr2 = sqlite3PExpr(pParse, TK_LT,
+                     sqlite3ExprSetColl(sqlite3ExprDup(db,pLeft,0), pColl),
+                     pStr2, 0);
+    idxNew2 = whereClauseInsert(pWC, pNewExpr2, TERM_VIRTUAL|TERM_DYNAMIC);
+    testcase( idxNew2==0 );
+    exprAnalyze(pSrc, pWC, idxNew2);
+    pTerm = &pWC->a[idxTerm];
+    if( isComplete ){
+      pWC->a[idxNew1].iParent = idxTerm;
+      pWC->a[idxNew2].iParent = idxTerm;
+      pTerm->nChild = 2;
+    }
+  }
+#endif /* SQLITE_OMIT_LIKE_OPTIMIZATION */
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  /* Add a WO_MATCH auxiliary term to the constraint set if the
+  ** current expression is of the form:  column MATCH expr.
+  ** This information is used by the xBestIndex methods of
+  ** virtual tables.  The native query optimizer does not attempt
+  ** to do anything with MATCH functions.
+  */
+  if( isMatchOfColumn(pExpr) ){
+    int idxNew;
+    Expr *pRight, *pLeft;
+    WhereTerm *pNewTerm;
+    Bitmask prereqColumn, prereqExpr;
+
+    pRight = pExpr->x.pList->a[0].pExpr;
+    pLeft = pExpr->x.pList->a[1].pExpr;
+    prereqExpr = exprTableUsage(pMaskSet, pRight);
+    prereqColumn = exprTableUsage(pMaskSet, pLeft);
+    if( (prereqExpr & prereqColumn)==0 ){
+      Expr *pNewExpr;
+      pNewExpr = sqlite3PExpr(pParse, TK_MATCH, 
+                              0, sqlite3ExprDup(db, pRight, 0), 0);
+      idxNew = whereClauseInsert(pWC, pNewExpr, TERM_VIRTUAL|TERM_DYNAMIC);
+      testcase( idxNew==0 );
+      pNewTerm = &pWC->a[idxNew];
+      pNewTerm->prereqRight = prereqExpr;
+      pNewTerm->leftCursor = pLeft->iTable;
+      pNewTerm->u.leftColumn = pLeft->iColumn;
+      pNewTerm->eOperator = WO_MATCH;
+      pNewTerm->iParent = idxTerm;
+      pTerm = &pWC->a[idxTerm];
+      pTerm->nChild = 1;
+      pTerm->wtFlags |= TERM_COPIED;
+      pNewTerm->prereqAll = pTerm->prereqAll;
+    }
+  }
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+#ifdef SQLITE_ENABLE_STAT3
+  /* When sqlite_stat3 histogram data is available an operator of the
+  ** form "x IS NOT NULL" can sometimes be evaluated more efficiently
+  ** as "x>NULL" if x is not an INTEGER PRIMARY KEY.  So construct a
+  ** virtual term of that form.
+  **
+  ** Note that the virtual term must be tagged with TERM_VNULL.  This
+  ** TERM_VNULL tag will suppress the not-null check at the beginning
+  ** of the loop.  Without the TERM_VNULL flag, the not-null check at
+  ** the start of the loop will prevent any results from being returned.
+  */
+  if( pExpr->op==TK_NOTNULL
+   && pExpr->pLeft->op==TK_COLUMN
+   && pExpr->pLeft->iColumn>=0
+  ){
+    Expr *pNewExpr;
+    Expr *pLeft = pExpr->pLeft;
+    int idxNew;
+    WhereTerm *pNewTerm;
+
+    pNewExpr = sqlite3PExpr(pParse, TK_GT,
+                            sqlite3ExprDup(db, pLeft, 0),
+                            sqlite3PExpr(pParse, TK_NULL, 0, 0, 0), 0);
+
+    idxNew = whereClauseInsert(pWC, pNewExpr,
+                              TERM_VIRTUAL|TERM_DYNAMIC|TERM_VNULL);
+    if( idxNew ){
+      pNewTerm = &pWC->a[idxNew];
+      pNewTerm->prereqRight = 0;
+      pNewTerm->leftCursor = pLeft->iTable;
+      pNewTerm->u.leftColumn = pLeft->iColumn;
+      pNewTerm->eOperator = WO_GT;
+      pNewTerm->iParent = idxTerm;
+      pTerm = &pWC->a[idxTerm];
+      pTerm->nChild = 1;
+      pTerm->wtFlags |= TERM_COPIED;
+      pNewTerm->prereqAll = pTerm->prereqAll;
+    }
+  }
+#endif /* SQLITE_ENABLE_STAT */
+
+  /* Prevent ON clause terms of a LEFT JOIN from being used to drive
+  ** an index for tables to the left of the join.
+  */
+  pTerm->prereqRight |= extraRight;
+}
+
+/*
+** Return TRUE if any of the expressions in pList->a[iFirst...] contain
+** a reference to any table other than the iBase table.
+*/
+static int referencesOtherTables(
+  ExprList *pList,          /* Search expressions in ths list */
+  WhereMaskSet *pMaskSet,   /* Mapping from tables to bitmaps */
+  int iFirst,               /* Be searching with the iFirst-th expression */
+  int iBase                 /* Ignore references to this table */
+){
+  Bitmask allowed = ~getMask(pMaskSet, iBase);
+  while( iFirst<pList->nExpr ){
+    if( (exprTableUsage(pMaskSet, pList->a[iFirst++].pExpr)&allowed)!=0 ){
+      return 1;
+    }
+  }
+  return 0;
+}
+
+/*
+** This function searches the expression list passed as the second argument
+** for an expression of type TK_COLUMN that refers to the same column and
+** uses the same collation sequence as the iCol'th column of index pIdx.
+** Argument iBase is the cursor number used for the table that pIdx refers
+** to.
+**
+** If such an expression is found, its index in pList->a[] is returned. If
+** no expression is found, -1 is returned.
+*/
+static int findIndexCol(
+  Parse *pParse,                  /* Parse context */
+  ExprList *pList,                /* Expression list to search */
+  int iBase,                      /* Cursor for table associated with pIdx */
+  Index *pIdx,                    /* Index to match column of */
+  int iCol                        /* Column of index to match */
+){
+  int i;
+  const char *zColl = pIdx->azColl[iCol];
+
+  for(i=0; i<pList->nExpr; i++){
+    Expr *p = pList->a[i].pExpr;
+    if( p->op==TK_COLUMN
+     && p->iColumn==pIdx->aiColumn[iCol]
+     && p->iTable==iBase
+    ){
+      CollSeq *pColl = sqlite3ExprCollSeq(pParse, p);
+      if( ALWAYS(pColl) && 0==sqlite3StrICmp(pColl->zName, zColl) ){
+        return i;
+      }
+    }
+  }
+
+  return -1;
+}
+
+/*
+** This routine determines if pIdx can be used to assist in processing a
+** DISTINCT qualifier. In other words, it tests whether or not using this
+** index for the outer loop guarantees that rows with equal values for
+** all expressions in the pDistinct list are delivered grouped together.
+**
+** For example, the query 
+**
+**   SELECT DISTINCT a, b, c FROM tbl WHERE a = ?
+**
+** can benefit from any index on columns "b" and "c".
+*/
+static int isDistinctIndex(
+  Parse *pParse,                  /* Parsing context */
+  WhereClause *pWC,               /* The WHERE clause */
+  Index *pIdx,                    /* The index being considered */
+  int base,                       /* Cursor number for the table pIdx is on */
+  ExprList *pDistinct,            /* The DISTINCT expressions */
+  int nEqCol                      /* Number of index columns with == */
+){
+  Bitmask mask = 0;               /* Mask of unaccounted for pDistinct exprs */
+  int i;                          /* Iterator variable */
+
+  if( pIdx->zName==0 || pDistinct==0 || pDistinct->nExpr>=BMS ) return 0;
+  testcase( pDistinct->nExpr==BMS-1 );
+
+  /* Loop through all the expressions in the distinct list. If any of them
+  ** are not simple column references, return early. Otherwise, test if the
+  ** WHERE clause contains a "col=X" clause. If it does, the expression
+  ** can be ignored. If it does not, and the column does not belong to the
+  ** same table as index pIdx, return early. Finally, if there is no
+  ** matching "col=X" expression and the column is on the same table as pIdx,
+  ** set the corresponding bit in variable mask.
+  */
+  for(i=0; i<pDistinct->nExpr; i++){
+    WhereTerm *pTerm;
+    Expr *p = pDistinct->a[i].pExpr;
+    if( p->op!=TK_COLUMN ) return 0;
+    pTerm = findTerm(pWC, p->iTable, p->iColumn, ~(Bitmask)0, WO_EQ, 0);
+    if( pTerm ){
+      Expr *pX = pTerm->pExpr;
+      CollSeq *p1 = sqlite3BinaryCompareCollSeq(pParse, pX->pLeft, pX->pRight);
+      CollSeq *p2 = sqlite3ExprCollSeq(pParse, p);
+      if( p1==p2 ) continue;
+    }
+    if( p->iTable!=base ) return 0;
+    mask |= (((Bitmask)1) << i);
+  }
+
+  for(i=nEqCol; mask && i<pIdx->nColumn; i++){
+    int iExpr = findIndexCol(pParse, pDistinct, base, pIdx, i);
+    if( iExpr<0 ) break;
+    mask &= ~(((Bitmask)1) << iExpr);
+  }
+
+  return (mask==0);
+}
+
+
+/*
+** Return true if the DISTINCT expression-list passed as the third argument
+** is redundant. A DISTINCT list is redundant if the database contains a
+** UNIQUE index that guarantees that the result of the query will be distinct
+** anyway.
+*/
+static int isDistinctRedundant(
+  Parse *pParse,
+  SrcList *pTabList,
+  WhereClause *pWC,
+  ExprList *pDistinct
+){
+  Table *pTab;
+  Index *pIdx;
+  int i;                          
+  int iBase;
+
+  /* If there is more than one table or sub-select in the FROM clause of
+  ** this query, then it will not be possible to show that the DISTINCT 
+  ** clause is redundant. */
+  if( pTabList->nSrc!=1 ) return 0;
+  iBase = pTabList->a[0].iCursor;
+  pTab = pTabList->a[0].pTab;
+
+  /* If any of the expressions is an IPK column on table iBase, then return 
+  ** true. Note: The (p->iTable==iBase) part of this test may be false if the
+  ** current SELECT is a correlated sub-query.
+  */
+  for(i=0; i<pDistinct->nExpr; i++){
+    Expr *p = pDistinct->a[i].pExpr;
+    if( p->op==TK_COLUMN && p->iTable==iBase && p->iColumn<0 ) return 1;
+  }
+
+  /* Loop through all indices on the table, checking each to see if it makes
+  ** the DISTINCT qualifier redundant. It does so if:
+  **
+  **   1. The index is itself UNIQUE, and
+  **
+  **   2. All of the columns in the index are either part of the pDistinct
+  **      list, or else the WHERE clause contains a term of the form "col=X",
+  **      where X is a constant value. The collation sequences of the
+  **      comparison and select-list expressions must match those of the index.
+  */
+  for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+    if( pIdx->onError==OE_None ) continue;
+    for(i=0; i<pIdx->nColumn; i++){
+      int iCol = pIdx->aiColumn[i];
+      if( 0==findTerm(pWC, iBase, iCol, ~(Bitmask)0, WO_EQ, pIdx) 
+       && 0>findIndexCol(pParse, pDistinct, iBase, pIdx, i)
+      ){
+        break;
+      }
+    }
+    if( i==pIdx->nColumn ){
+      /* This index implies that the DISTINCT qualifier is redundant. */
+      return 1;
+    }
+  }
+
+  return 0;
+}
+
+/*
+** This routine decides if pIdx can be used to satisfy the ORDER BY
+** clause.  If it can, it returns 1.  If pIdx cannot satisfy the
+** ORDER BY clause, this routine returns 0.
+**
+** pOrderBy is an ORDER BY clause from a SELECT statement.  pTab is the
+** left-most table in the FROM clause of that same SELECT statement and
+** the table has a cursor number of "base".  pIdx is an index on pTab.
+**
+** nEqCol is the number of columns of pIdx that are used as equality
+** constraints.  Any of these columns may be missing from the ORDER BY
+** clause and the match can still be a success.
+**
+** All terms of the ORDER BY that match against the index must be either
+** ASC or DESC.  (Terms of the ORDER BY clause past the end of a UNIQUE
+** index do not need to satisfy this constraint.)  The *pbRev value is
+** set to 1 if the ORDER BY clause is all DESC and it is set to 0 if
+** the ORDER BY clause is all ASC.
+*/
+static int isSortingIndex(
+  Parse *pParse,          /* Parsing context */
+  WhereMaskSet *pMaskSet, /* Mapping from table cursor numbers to bitmaps */
+  Index *pIdx,            /* The index we are testing */
+  int base,               /* Cursor number for the table to be sorted */
+  ExprList *pOrderBy,     /* The ORDER BY clause */
+  int nEqCol,             /* Number of index columns with == constraints */
+  int wsFlags,            /* Index usages flags */
+  int *pbRev              /* Set to 1 if ORDER BY is DESC */
+){
+  int i, j;                       /* Loop counters */
+  int sortOrder = 0;              /* XOR of index and ORDER BY sort direction */
+  int nTerm;                      /* Number of ORDER BY terms */
+  struct ExprList_item *pTerm;    /* A term of the ORDER BY clause */
+  sqlite3 *db = pParse->db;
+
+  if( !pOrderBy ) return 0;
+  if( wsFlags & WHERE_COLUMN_IN ) return 0;
+  if( pIdx->bUnordered ) return 0;
+
+  nTerm = pOrderBy->nExpr;
+  assert( nTerm>0 );
+
+  /* Argument pIdx must either point to a 'real' named index structure, 
+  ** or an index structure allocated on the stack by bestBtreeIndex() to
+  ** represent the rowid index that is part of every table.  */
+  assert( pIdx->zName || (pIdx->nColumn==1 && pIdx->aiColumn[0]==-1) );
+
+  /* Match terms of the ORDER BY clause against columns of
+  ** the index.
+  **
+  ** Note that indices have pIdx->nColumn regular columns plus
+  ** one additional column containing the rowid.  The rowid column
+  ** of the index is also allowed to match against the ORDER BY
+  ** clause.
+  */
+  for(i=j=0, pTerm=pOrderBy->a; j<nTerm && i<=pIdx->nColumn; i++){
+    Expr *pExpr;       /* The expression of the ORDER BY pTerm */
+    CollSeq *pColl;    /* The collating sequence of pExpr */
+    int termSortOrder; /* Sort order for this term */
+    int iColumn;       /* The i-th column of the index.  -1 for rowid */
+    int iSortOrder;    /* 1 for DESC, 0 for ASC on the i-th index term */
+    const char *zColl; /* Name of the collating sequence for i-th index term */
+
+    pExpr = pTerm->pExpr;
+    if( pExpr->op!=TK_COLUMN || pExpr->iTable!=base ){
+      /* Can not use an index sort on anything that is not a column in the
+      ** left-most table of the FROM clause */
+      break;
+    }
+    pColl = sqlite3ExprCollSeq(pParse, pExpr);
+    if( !pColl ){
+      pColl = db->pDfltColl;
+    }
+    if( pIdx->zName && i<pIdx->nColumn ){
+      iColumn = pIdx->aiColumn[i];
+      if( iColumn==pIdx->pTable->iPKey ){
+        iColumn = -1;
+      }
+      iSortOrder = pIdx->aSortOrder[i];
+      zColl = pIdx->azColl[i];
+    }else{
+      iColumn = -1;
+      iSortOrder = 0;
+      zColl = pColl->zName;
+    }
+    if( pExpr->iColumn!=iColumn || sqlite3StrICmp(pColl->zName, zColl) ){
+      /* Term j of the ORDER BY clause does not match column i of the index */
+      if( i<nEqCol ){
+        /* If an index column that is constrained by == fails to match an
+        ** ORDER BY term, that is OK.  Just ignore that column of the index
+        */
+        continue;
+      }else if( i==pIdx->nColumn ){
+        /* Index column i is the rowid.  All other terms match. */
+        break;
+      }else{
+        /* If an index column fails to match and is not constrained by ==
+        ** then the index cannot satisfy the ORDER BY constraint.
+        */
+        return 0;
+      }
+    }
+    assert( pIdx->aSortOrder!=0 || iColumn==-1 );
+    assert( pTerm->sortOrder==0 || pTerm->sortOrder==1 );
+    assert( iSortOrder==0 || iSortOrder==1 );
+    termSortOrder = iSortOrder ^ pTerm->sortOrder;
+    if( i>nEqCol ){
+      if( termSortOrder!=sortOrder ){
+        /* Indices can only be used if all ORDER BY terms past the
+        ** equality constraints are all either DESC or ASC. */
+        return 0;
+      }
+    }else{
+      sortOrder = termSortOrder;
+    }
+    j++;
+    pTerm++;
+    if( iColumn<0 && !referencesOtherTables(pOrderBy, pMaskSet, j, base) ){
+      /* If the indexed column is the primary key and everything matches
+      ** so far and none of the ORDER BY terms to the right reference other
+      ** tables in the join, then we are assured that the index can be used 
+      ** to sort because the primary key is unique and so none of the other
+      ** columns will make any difference
+      */
+      j = nTerm;
+    }
+  }
+
+  *pbRev = sortOrder!=0;
+  if( j>=nTerm ){
+    /* All terms of the ORDER BY clause are covered by this index so
+    ** this index can be used for sorting. */
+    return 1;
+  }
+  if( pIdx->onError!=OE_None && i==pIdx->nColumn
+      && (wsFlags & WHERE_COLUMN_NULL)==0
+      && !referencesOtherTables(pOrderBy, pMaskSet, j, base) ){
+    /* All terms of this index match some prefix of the ORDER BY clause
+    ** and the index is UNIQUE and no terms on the tail of the ORDER BY
+    ** clause reference other tables in a join.  If this is all true then
+    ** the order by clause is superfluous.  Not that if the matching
+    ** condition is IS NULL then the result is not necessarily unique
+    ** even on a UNIQUE index, so disallow those cases. */
+    return 1;
+  }
+  return 0;
+}
+
+/*
+** Prepare a crude estimate of the logarithm of the input value.
+** The results need not be exact.  This is only used for estimating
+** the total cost of performing operations with O(logN) or O(NlogN)
+** complexity.  Because N is just a guess, it is no great tragedy if
+** logN is a little off.
+*/
+static double estLog(double N){
+  double logN = 1;
+  double x = 10;
+  while( N>x ){
+    logN += 1;
+    x *= 10;
+  }
+  return logN;
+}
+
+/*
+** Two routines for printing the content of an sqlite3_index_info
+** structure.  Used for testing and debugging only.  If neither
+** SQLITE_TEST or SQLITE_DEBUG are defined, then these routines
+** are no-ops.
+*/
+#if !defined(SQLITE_OMIT_VIRTUALTABLE) && defined(SQLITE_DEBUG)
+static void TRACE_IDX_INPUTS(sqlite3_index_info *p){
+  int i;
+  if( !sqlite3WhereTrace ) return;
+  for(i=0; i<p->nConstraint; i++){
+    sqlite3DebugPrintf("  constraint[%d]: col=%d termid=%d op=%d usabled=%d\n",
+       i,
+       p->aConstraint[i].iColumn,
+       p->aConstraint[i].iTermOffset,
+       p->aConstraint[i].op,
+       p->aConstraint[i].usable);
+  }
+  for(i=0; i<p->nOrderBy; i++){
+    sqlite3DebugPrintf("  orderby[%d]: col=%d desc=%d\n",
+       i,
+       p->aOrderBy[i].iColumn,
+       p->aOrderBy[i].desc);
+  }
+}
+static void TRACE_IDX_OUTPUTS(sqlite3_index_info *p){
+  int i;
+  if( !sqlite3WhereTrace ) return;
+  for(i=0; i<p->nConstraint; i++){
+    sqlite3DebugPrintf("  usage[%d]: argvIdx=%d omit=%d\n",
+       i,
+       p->aConstraintUsage[i].argvIndex,
+       p->aConstraintUsage[i].omit);
+  }
+  sqlite3DebugPrintf("  idxNum=%d\n", p->idxNum);
+  sqlite3DebugPrintf("  idxStr=%s\n", p->idxStr);
+  sqlite3DebugPrintf("  orderByConsumed=%d\n", p->orderByConsumed);
+  sqlite3DebugPrintf("  estimatedCost=%g\n", p->estimatedCost);
+}
+#else
+#define TRACE_IDX_INPUTS(A)
+#define TRACE_IDX_OUTPUTS(A)
+#endif
+
+/* 
+** Required because bestIndex() is called by bestOrClauseIndex() 
+*/
+static void bestIndex(
+    Parse*, WhereClause*, struct SrcList_item*,
+    Bitmask, Bitmask, ExprList*, WhereCost*);
+
+/*
+** This routine attempts to find an scanning strategy that can be used 
+** to optimize an 'OR' expression that is part of a WHERE clause. 
+**
+** The table associated with FROM clause term pSrc may be either a
+** regular B-Tree table or a virtual table.
+*/
+static void bestOrClauseIndex(
+  Parse *pParse,              /* The parsing context */
+  WhereClause *pWC,           /* The WHERE clause */
+  struct SrcList_item *pSrc,  /* The FROM clause term to search */
+  Bitmask notReady,           /* Mask of cursors not available for indexing */
+  Bitmask notValid,           /* Cursors not available for any purpose */
+  ExprList *pOrderBy,         /* The ORDER BY clause */
+  WhereCost *pCost            /* Lowest cost query plan */
+){
+#ifndef SQLITE_OMIT_OR_OPTIMIZATION
+  const int iCur = pSrc->iCursor;   /* The cursor of the table to be accessed */
+  const Bitmask maskSrc = getMask(pWC->pMaskSet, iCur);  /* Bitmask for pSrc */
+  WhereTerm * const pWCEnd = &pWC->a[pWC->nTerm];        /* End of pWC->a[] */
+  WhereTerm *pTerm;                 /* A single term of the WHERE clause */
+
+  /* The OR-clause optimization is disallowed if the INDEXED BY or
+  ** NOT INDEXED clauses are used or if the WHERE_AND_ONLY bit is set. */
+  if( pSrc->notIndexed || pSrc->pIndex!=0 ){
+    return;
+  }
+  if( pWC->wctrlFlags & WHERE_AND_ONLY ){
+    return;
+  }
+
+  /* Search the WHERE clause terms for a usable WO_OR term. */
+  for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
+    if( pTerm->eOperator==WO_OR 
+     && ((pTerm->prereqAll & ~maskSrc) & notReady)==0
+     && (pTerm->u.pOrInfo->indexable & maskSrc)!=0 
+    ){
+      WhereClause * const pOrWC = &pTerm->u.pOrInfo->wc;
+      WhereTerm * const pOrWCEnd = &pOrWC->a[pOrWC->nTerm];
+      WhereTerm *pOrTerm;
+      int flags = WHERE_MULTI_OR;
+      double rTotal = 0;
+      double nRow = 0;
+      Bitmask used = 0;
+
+      for(pOrTerm=pOrWC->a; pOrTerm<pOrWCEnd; pOrTerm++){
+        WhereCost sTermCost;
+        WHERETRACE(("... Multi-index OR testing for term %d of %d....\n", 
+          (pOrTerm - pOrWC->a), (pTerm - pWC->a)
+        ));
+        if( pOrTerm->eOperator==WO_AND ){
+          WhereClause *pAndWC = &pOrTerm->u.pAndInfo->wc;
+          bestIndex(pParse, pAndWC, pSrc, notReady, notValid, 0, &sTermCost);
+        }else if( pOrTerm->leftCursor==iCur ){
+          WhereClause tempWC;
+          tempWC.pParse = pWC->pParse;
+          tempWC.pMaskSet = pWC->pMaskSet;
+          tempWC.pOuter = pWC;
+          tempWC.op = TK_AND;
+          tempWC.a = pOrTerm;
+          tempWC.wctrlFlags = 0;
+          tempWC.nTerm = 1;
+          bestIndex(pParse, &tempWC, pSrc, notReady, notValid, 0, &sTermCost);
+        }else{
+          continue;
+        }
+        rTotal += sTermCost.rCost;
+        nRow += sTermCost.plan.nRow;
+        used |= sTermCost.used;
+        if( rTotal>=pCost->rCost ) break;
+      }
+
+      /* If there is an ORDER BY clause, increase the scan cost to account 
+      ** for the cost of the sort. */
+      if( pOrderBy!=0 ){
+        WHERETRACE(("... sorting increases OR cost %.9g to %.9g\n",
+                    rTotal, rTotal+nRow*estLog(nRow)));
+        rTotal += nRow*estLog(nRow);
+      }
+
+      /* If the cost of scanning using this OR term for optimization is
+      ** less than the current cost stored in pCost, replace the contents
+      ** of pCost. */
+      WHERETRACE(("... multi-index OR cost=%.9g nrow=%.9g\n", rTotal, nRow));
+      if( rTotal<pCost->rCost ){
+        pCost->rCost = rTotal;
+        pCost->used = used;
+        pCost->plan.nRow = nRow;
+        pCost->plan.wsFlags = flags;
+        pCost->plan.u.pTerm = pTerm;
+      }
+    }
+  }
+#endif /* SQLITE_OMIT_OR_OPTIMIZATION */
+}
+
+#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
+/*
+** Return TRUE if the WHERE clause term pTerm is of a form where it
+** could be used with an index to access pSrc, assuming an appropriate
+** index existed.
+*/
+static int termCanDriveIndex(
+  WhereTerm *pTerm,              /* WHERE clause term to check */
+  struct SrcList_item *pSrc,     /* Table we are trying to access */
+  Bitmask notReady               /* Tables in outer loops of the join */
+){
+  char aff;
+  if( pTerm->leftCursor!=pSrc->iCursor ) return 0;
+  if( pTerm->eOperator!=WO_EQ ) return 0;
+  if( (pTerm->prereqRight & notReady)!=0 ) return 0;
+  aff = pSrc->pTab->aCol[pTerm->u.leftColumn].affinity;
+  if( !sqlite3IndexAffinityOk(pTerm->pExpr, aff) ) return 0;
+  return 1;
+}
+#endif
+
+#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
+/*
+** If the query plan for pSrc specified in pCost is a full table scan
+** and indexing is allows (if there is no NOT INDEXED clause) and it
+** possible to construct a transient index that would perform better
+** than a full table scan even when the cost of constructing the index
+** is taken into account, then alter the query plan to use the
+** transient index.
+*/
+static void bestAutomaticIndex(
+  Parse *pParse,              /* The parsing context */
+  WhereClause *pWC,           /* The WHERE clause */
+  struct SrcList_item *pSrc,  /* The FROM clause term to search */
+  Bitmask notReady,           /* Mask of cursors that are not available */
+  WhereCost *pCost            /* Lowest cost query plan */
+){
+  double nTableRow;           /* Rows in the input table */
+  double logN;                /* log(nTableRow) */
+  double costTempIdx;         /* per-query cost of the transient index */
+  WhereTerm *pTerm;           /* A single term of the WHERE clause */
+  WhereTerm *pWCEnd;          /* End of pWC->a[] */
+  Table *pTable;              /* Table tht might be indexed */
+
+  if( pParse->nQueryLoop<=(double)1 ){
+    /* There is no point in building an automatic index for a single scan */
+    return;
+  }
+  if( (pParse->db->flags & SQLITE_AutoIndex)==0 ){
+    /* Automatic indices are disabled at run-time */
+    return;
+  }
+  if( (pCost->plan.wsFlags & WHERE_NOT_FULLSCAN)!=0 ){
+    /* We already have some kind of index in use for this query. */
+    return;
+  }
+  if( pSrc->notIndexed ){
+    /* The NOT INDEXED clause appears in the SQL. */
+    return;
+  }
+  if( pSrc->isCorrelated ){
+    /* The source is a correlated sub-query. No point in indexing it. */
+    return;
+  }
+
+  assert( pParse->nQueryLoop >= (double)1 );
+  pTable = pSrc->pTab;
+  nTableRow = pTable->nRowEst;
+  logN = estLog(nTableRow);
+  costTempIdx = 2*logN*(nTableRow/pParse->nQueryLoop + 1);
+  if( costTempIdx>=pCost->rCost ){
+    /* The cost of creating the transient table would be greater than
+    ** doing the full table scan */
+    return;
+  }
+
+  /* Search for any equality comparison term */
+  pWCEnd = &pWC->a[pWC->nTerm];
+  for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
+    if( termCanDriveIndex(pTerm, pSrc, notReady) ){
+      WHERETRACE(("auto-index reduces cost from %.1f to %.1f\n",
+                    pCost->rCost, costTempIdx));
+      pCost->rCost = costTempIdx;
+      pCost->plan.nRow = logN + 1;
+      pCost->plan.wsFlags = WHERE_TEMP_INDEX;
+      pCost->used = pTerm->prereqRight;
+      break;
+    }
+  }
+}
+#else
+# define bestAutomaticIndex(A,B,C,D,E)  /* no-op */
+#endif /* SQLITE_OMIT_AUTOMATIC_INDEX */
+
+
+#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
+/*
+** Generate code to construct the Index object for an automatic index
+** and to set up the WhereLevel object pLevel so that the code generator
+** makes use of the automatic index.
+*/
+static void constructAutomaticIndex(
+  Parse *pParse,              /* The parsing context */
+  WhereClause *pWC,           /* The WHERE clause */
+  struct SrcList_item *pSrc,  /* The FROM clause term to get the next index */
+  Bitmask notReady,           /* Mask of cursors that are not available */
+  WhereLevel *pLevel          /* Write new index here */
+){
+  int nColumn;                /* Number of columns in the constructed index */
+  WhereTerm *pTerm;           /* A single term of the WHERE clause */
+  WhereTerm *pWCEnd;          /* End of pWC->a[] */
+  int nByte;                  /* Byte of memory needed for pIdx */
+  Index *pIdx;                /* Object describing the transient index */
+  Vdbe *v;                    /* Prepared statement under construction */
+  int regIsInit;              /* Register set by initialization */
+  int addrInit;               /* Address of the initialization bypass jump */
+  Table *pTable;              /* The table being indexed */
+  KeyInfo *pKeyinfo;          /* Key information for the index */   
+  int addrTop;                /* Top of the index fill loop */
+  int regRecord;              /* Register holding an index record */
+  int n;                      /* Column counter */
+  int i;                      /* Loop counter */
+  int mxBitCol;               /* Maximum column in pSrc->colUsed */
+  CollSeq *pColl;             /* Collating sequence to on a column */
+  Bitmask idxCols;            /* Bitmap of columns used for indexing */
+  Bitmask extraCols;          /* Bitmap of additional columns */
+
+  /* Generate code to skip over the creation and initialization of the
+  ** transient index on 2nd and subsequent iterations of the loop. */
+  v = pParse->pVdbe;
+  assert( v!=0 );
+  regIsInit = ++pParse->nMem;
+  addrInit = sqlite3VdbeAddOp1(v, OP_Once, regIsInit);
+
+  /* Count the number of columns that will be added to the index
+  ** and used to match WHERE clause constraints */
+  nColumn = 0;
+  pTable = pSrc->pTab;
+  pWCEnd = &pWC->a[pWC->nTerm];
+  idxCols = 0;
+  for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
+    if( termCanDriveIndex(pTerm, pSrc, notReady) ){
+      int iCol = pTerm->u.leftColumn;
+      Bitmask cMask = iCol>=BMS ? ((Bitmask)1)<<(BMS-1) : ((Bitmask)1)<<iCol;
+      testcase( iCol==BMS );
+      testcase( iCol==BMS-1 );
+      if( (idxCols & cMask)==0 ){
+        nColumn++;
+        idxCols |= cMask;
+      }
+    }
+  }
+  assert( nColumn>0 );
+  pLevel->plan.nEq = nColumn;
+
+  /* Count the number of additional columns needed to create a
+  ** covering index.  A "covering index" is an index that contains all
+  ** columns that are needed by the query.  With a covering index, the
+  ** original table never needs to be accessed.  Automatic indices must
+  ** be a covering index because the index will not be updated if the
+  ** original table changes and the index and table cannot both be used
+  ** if they go out of sync.
+  */
+  extraCols = pSrc->colUsed & (~idxCols | (((Bitmask)1)<<(BMS-1)));
+  mxBitCol = (pTable->nCol >= BMS-1) ? BMS-1 : pTable->nCol;
+  testcase( pTable->nCol==BMS-1 );
+  testcase( pTable->nCol==BMS-2 );
+  for(i=0; i<mxBitCol; i++){
+    if( extraCols & (((Bitmask)1)<<i) ) nColumn++;
+  }
+  if( pSrc->colUsed & (((Bitmask)1)<<(BMS-1)) ){
+    nColumn += pTable->nCol - BMS + 1;
+  }
+  pLevel->plan.wsFlags |= WHERE_COLUMN_EQ | WHERE_IDX_ONLY | WO_EQ;
+
+  /* Construct the Index object to describe this index */
+  nByte = sizeof(Index);
+  nByte += nColumn*sizeof(int);     /* Index.aiColumn */
+  nByte += nColumn*sizeof(char*);   /* Index.azColl */
+  nByte += nColumn;                 /* Index.aSortOrder */
+  pIdx = sqlite3DbMallocZero(pParse->db, nByte);
+  if( pIdx==0 ) return;
+  pLevel->plan.u.pIdx = pIdx;
+  pIdx->azColl = (char**)&pIdx[1];
+  pIdx->aiColumn = (int*)&pIdx->azColl[nColumn];
+  pIdx->aSortOrder = (u8*)&pIdx->aiColumn[nColumn];
+  pIdx->zName = "auto-index";
+  pIdx->nColumn = nColumn;
+  pIdx->pTable = pTable;
+  n = 0;
+  idxCols = 0;
+  for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
+    if( termCanDriveIndex(pTerm, pSrc, notReady) ){
+      int iCol = pTerm->u.leftColumn;
+      Bitmask cMask = iCol>=BMS ? ((Bitmask)1)<<(BMS-1) : ((Bitmask)1)<<iCol;
+      if( (idxCols & cMask)==0 ){
+        Expr *pX = pTerm->pExpr;
+        idxCols |= cMask;
+        pIdx->aiColumn[n] = pTerm->u.leftColumn;
+        pColl = sqlite3BinaryCompareCollSeq(pParse, pX->pLeft, pX->pRight);
+        pIdx->azColl[n] = ALWAYS(pColl) ? pColl->zName : "BINARY";
+        n++;
+      }
+    }
+  }
+  assert( (u32)n==pLevel->plan.nEq );
+
+  /* Add additional columns needed to make the automatic index into
+  ** a covering index */
+  for(i=0; i<mxBitCol; i++){
+    if( extraCols & (((Bitmask)1)<<i) ){
+      pIdx->aiColumn[n] = i;
+      pIdx->azColl[n] = "BINARY";
+      n++;
+    }
+  }
+  if( pSrc->colUsed & (((Bitmask)1)<<(BMS-1)) ){
+    for(i=BMS-1; i<pTable->nCol; i++){
+      pIdx->aiColumn[n] = i;
+      pIdx->azColl[n] = "BINARY";
+      n++;
+    }
+  }
+  assert( n==nColumn );
+
+  /* Create the automatic index */
+  pKeyinfo = sqlite3IndexKeyinfo(pParse, pIdx);
+  assert( pLevel->iIdxCur>=0 );
+  sqlite3VdbeAddOp4(v, OP_OpenAutoindex, pLevel->iIdxCur, nColumn+1, 0,
+                    (char*)pKeyinfo, P4_KEYINFO_HANDOFF);
+  VdbeComment((v, "for %s", pTable->zName));
+
+  /* Fill the automatic index with content */
+  addrTop = sqlite3VdbeAddOp1(v, OP_Rewind, pLevel->iTabCur);
+  regRecord = sqlite3GetTempReg(pParse);
+  sqlite3GenerateIndexKey(pParse, pIdx, pLevel->iTabCur, regRecord, 1);
+  sqlite3VdbeAddOp2(v, OP_IdxInsert, pLevel->iIdxCur, regRecord);
+  sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);
+  sqlite3VdbeAddOp2(v, OP_Next, pLevel->iTabCur, addrTop+1);
+  sqlite3VdbeChangeP5(v, SQLITE_STMTSTATUS_AUTOINDEX);
+  sqlite3VdbeJumpHere(v, addrTop);
+  sqlite3ReleaseTempReg(pParse, regRecord);
+  
+  /* Jump here when skipping the initialization */
+  sqlite3VdbeJumpHere(v, addrInit);
+}
+#endif /* SQLITE_OMIT_AUTOMATIC_INDEX */
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/*
+** Allocate and populate an sqlite3_index_info structure. It is the 
+** responsibility of the caller to eventually release the structure
+** by passing the pointer returned by this function to sqlite3_free().
+*/
+static sqlite3_index_info *allocateIndexInfo(
+  Parse *pParse, 
+  WhereClause *pWC,
+  struct SrcList_item *pSrc,
+  ExprList *pOrderBy
+){
+  int i, j;
+  int nTerm;
+  struct sqlite3_index_constraint *pIdxCons;
+  struct sqlite3_index_orderby *pIdxOrderBy;
+  struct sqlite3_index_constraint_usage *pUsage;
+  WhereTerm *pTerm;
+  int nOrderBy;
+  sqlite3_index_info *pIdxInfo;
+
+  WHERETRACE(("Recomputing index info for %s...\n", pSrc->pTab->zName));
+
+  /* Count the number of possible WHERE clause constraints referring
+  ** to this virtual table */
+  for(i=nTerm=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
+    if( pTerm->leftCursor != pSrc->iCursor ) continue;
+    assert( (pTerm->eOperator&(pTerm->eOperator-1))==0 );
+    testcase( pTerm->eOperator==WO_IN );
+    testcase( pTerm->eOperator==WO_ISNULL );
+    if( pTerm->eOperator & (WO_IN|WO_ISNULL) ) continue;
+    if( pTerm->wtFlags & TERM_VNULL ) continue;
+    nTerm++;
+  }
+
+  /* If the ORDER BY clause contains only columns in the current 
+  ** virtual table then allocate space for the aOrderBy part of
+  ** the sqlite3_index_info structure.
+  */
+  nOrderBy = 0;
+  if( pOrderBy ){
+    for(i=0; i<pOrderBy->nExpr; i++){
+      Expr *pExpr = pOrderBy->a[i].pExpr;
+      if( pExpr->op!=TK_COLUMN || pExpr->iTable!=pSrc->iCursor ) break;
+    }
+    if( i==pOrderBy->nExpr ){
+      nOrderBy = pOrderBy->nExpr;
+    }
+  }
+
+  /* Allocate the sqlite3_index_info structure
+  */
+  pIdxInfo = sqlite3DbMallocZero(pParse->db, sizeof(*pIdxInfo)
+                           + (sizeof(*pIdxCons) + sizeof(*pUsage))*nTerm
+                           + sizeof(*pIdxOrderBy)*nOrderBy );
+  if( pIdxInfo==0 ){
+    sqlite3ErrorMsg(pParse, "out of memory");
+    /* (double)0 In case of SQLITE_OMIT_FLOATING_POINT... */
+    return 0;
+  }
+
+  /* Initialize the structure.  The sqlite3_index_info structure contains
+  ** many fields that are declared "const" to prevent xBestIndex from
+  ** changing them.  We have to do some funky casting in order to
+  ** initialize those fields.
+  */
+  pIdxCons = (struct sqlite3_index_constraint*)&pIdxInfo[1];
+  pIdxOrderBy = (struct sqlite3_index_orderby*)&pIdxCons[nTerm];
+  pUsage = (struct sqlite3_index_constraint_usage*)&pIdxOrderBy[nOrderBy];
+  *(int*)&pIdxInfo->nConstraint = nTerm;
+  *(int*)&pIdxInfo->nOrderBy = nOrderBy;
+  *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint = pIdxCons;
+  *(struct sqlite3_index_orderby**)&pIdxInfo->aOrderBy = pIdxOrderBy;
+  *(struct sqlite3_index_constraint_usage**)&pIdxInfo->aConstraintUsage =
+                                                                   pUsage;
+
+  for(i=j=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
+    if( pTerm->leftCursor != pSrc->iCursor ) continue;
+    assert( (pTerm->eOperator&(pTerm->eOperator-1))==0 );
+    testcase( pTerm->eOperator==WO_IN );
+    testcase( pTerm->eOperator==WO_ISNULL );
+    if( pTerm->eOperator & (WO_IN|WO_ISNULL) ) continue;
+    if( pTerm->wtFlags & TERM_VNULL ) continue;
+    pIdxCons[j].iColumn = pTerm->u.leftColumn;
+    pIdxCons[j].iTermOffset = i;
+    pIdxCons[j].op = (u8)pTerm->eOperator;
+    /* The direct assignment in the previous line is possible only because
+    ** the WO_ and SQLITE_INDEX_CONSTRAINT_ codes are identical.  The
+    ** following asserts verify this fact. */
+    assert( WO_EQ==SQLITE_INDEX_CONSTRAINT_EQ );
+    assert( WO_LT==SQLITE_INDEX_CONSTRAINT_LT );
+    assert( WO_LE==SQLITE_INDEX_CONSTRAINT_LE );
+    assert( WO_GT==SQLITE_INDEX_CONSTRAINT_GT );
+    assert( WO_GE==SQLITE_INDEX_CONSTRAINT_GE );
+    assert( WO_MATCH==SQLITE_INDEX_CONSTRAINT_MATCH );
+    assert( pTerm->eOperator & (WO_EQ|WO_LT|WO_LE|WO_GT|WO_GE|WO_MATCH) );
+    j++;
+  }
+  for(i=0; i<nOrderBy; i++){
+    Expr *pExpr = pOrderBy->a[i].pExpr;
+    pIdxOrderBy[i].iColumn = pExpr->iColumn;
+    pIdxOrderBy[i].desc = pOrderBy->a[i].sortOrder;
+  }
+
+  return pIdxInfo;
+}
+
+/*
+** The table object reference passed as the second argument to this function
+** must represent a virtual table. This function invokes the xBestIndex()
+** method of the virtual table with the sqlite3_index_info pointer passed
+** as the argument.
+**
+** If an error occurs, pParse is populated with an error message and a
+** non-zero value is returned. Otherwise, 0 is returned and the output
+** part of the sqlite3_index_info structure is left populated.
+**
+** Whether or not an error is returned, it is the responsibility of the
+** caller to eventually free p->idxStr if p->needToFreeIdxStr indicates
+** that this is required.
+*/
+static int vtabBestIndex(Parse *pParse, Table *pTab, sqlite3_index_info *p){
+  sqlite3_vtab *pVtab = sqlite3GetVTable(pParse->db, pTab)->pVtab;
+  int i;
+  int rc;
+
+  WHERETRACE(("xBestIndex for %s\n", pTab->zName));
+  TRACE_IDX_INPUTS(p);
+  rc = pVtab->pModule->xBestIndex(pVtab, p);
+  TRACE_IDX_OUTPUTS(p);
+
+  if( rc!=SQLITE_OK ){
+    if( rc==SQLITE_NOMEM ){
+      pParse->db->mallocFailed = 1;
+    }else if( !pVtab->zErrMsg ){
+      sqlite3ErrorMsg(pParse, "%s", sqlite3ErrStr(rc));
+    }else{
+      sqlite3ErrorMsg(pParse, "%s", pVtab->zErrMsg);
+    }
+  }
+  sqlite3_free(pVtab->zErrMsg);
+  pVtab->zErrMsg = 0;
+
+  for(i=0; i<p->nConstraint; i++){
+    if( !p->aConstraint[i].usable && p->aConstraintUsage[i].argvIndex>0 ){
+      sqlite3ErrorMsg(pParse, 
+          "table %s: xBestIndex returned an invalid plan", pTab->zName);
+    }
+  }
+
+  return pParse->nErr;
+}
+
+
+/*
+** Compute the best index for a virtual table.
+**
+** The best index is computed by the xBestIndex method of the virtual
+** table module.  This routine is really just a wrapper that sets up
+** the sqlite3_index_info structure that is used to communicate with
+** xBestIndex.
+**
+** In a join, this routine might be called multiple times for the
+** same virtual table.  The sqlite3_index_info structure is created
+** and initialized on the first invocation and reused on all subsequent
+** invocations.  The sqlite3_index_info structure is also used when
+** code is generated to access the virtual table.  The whereInfoDelete() 
+** routine takes care of freeing the sqlite3_index_info structure after
+** everybody has finished with it.
+*/
+static void bestVirtualIndex(
+  Parse *pParse,                  /* The parsing context */
+  WhereClause *pWC,               /* The WHERE clause */
+  struct SrcList_item *pSrc,      /* The FROM clause term to search */
+  Bitmask notReady,               /* Mask of cursors not available for index */
+  Bitmask notValid,               /* Cursors not valid for any purpose */
+  ExprList *pOrderBy,             /* The order by clause */
+  WhereCost *pCost,               /* Lowest cost query plan */
+  sqlite3_index_info **ppIdxInfo  /* Index information passed to xBestIndex */
+){
+  Table *pTab = pSrc->pTab;
+  sqlite3_index_info *pIdxInfo;
+  struct sqlite3_index_constraint *pIdxCons;
+  struct sqlite3_index_constraint_usage *pUsage;
+  WhereTerm *pTerm;
+  int i, j;
+  int nOrderBy;
+  double rCost;
+
+  /* Make sure wsFlags is initialized to some sane value. Otherwise, if the 
+  ** malloc in allocateIndexInfo() fails and this function returns leaving
+  ** wsFlags in an uninitialized state, the caller may behave unpredictably.
+  */
+  memset(pCost, 0, sizeof(*pCost));
+  pCost->plan.wsFlags = WHERE_VIRTUALTABLE;
+
+  /* If the sqlite3_index_info structure has not been previously
+  ** allocated and initialized, then allocate and initialize it now.
+  */
+  pIdxInfo = *ppIdxInfo;
+  if( pIdxInfo==0 ){
+    *ppIdxInfo = pIdxInfo = allocateIndexInfo(pParse, pWC, pSrc, pOrderBy);
+  }
+  if( pIdxInfo==0 ){
+    return;
+  }
+
+  /* At this point, the sqlite3_index_info structure that pIdxInfo points
+  ** to will have been initialized, either during the current invocation or
+  ** during some prior invocation.  Now we just have to customize the
+  ** details of pIdxInfo for the current invocation and pass it to
+  ** xBestIndex.
+  */
+
+  /* The module name must be defined. Also, by this point there must
+  ** be a pointer to an sqlite3_vtab structure. Otherwise
+  ** sqlite3ViewGetColumnNames() would have picked up the error. 
+  */
+  assert( pTab->azModuleArg && pTab->azModuleArg[0] );
+  assert( sqlite3GetVTable(pParse->db, pTab) );
+
+  /* Set the aConstraint[].usable fields and initialize all 
+  ** output variables to zero.
+  **
+  ** aConstraint[].usable is true for constraints where the right-hand
+  ** side contains only references to tables to the left of the current
+  ** table.  In other words, if the constraint is of the form:
+  **
+  **           column = expr
+  **
+  ** and we are evaluating a join, then the constraint on column is 
+  ** only valid if all tables referenced in expr occur to the left
+  ** of the table containing column.
+  **
+  ** The aConstraints[] array contains entries for all constraints
+  ** on the current table.  That way we only have to compute it once
+  ** even though we might try to pick the best index multiple times.
+  ** For each attempt at picking an index, the order of tables in the
+  ** join might be different so we have to recompute the usable flag
+  ** each time.
+  */
+  pIdxCons = *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint;
+  pUsage = pIdxInfo->aConstraintUsage;
+  for(i=0; i<pIdxInfo->nConstraint; i++, pIdxCons++){
+    j = pIdxCons->iTermOffset;
+    pTerm = &pWC->a[j];
+    pIdxCons->usable = (pTerm->prereqRight&notReady) ? 0 : 1;
+  }
+  memset(pUsage, 0, sizeof(pUsage[0])*pIdxInfo->nConstraint);
+  if( pIdxInfo->needToFreeIdxStr ){
+    sqlite3_free(pIdxInfo->idxStr);
+  }
+  pIdxInfo->idxStr = 0;
+  pIdxInfo->idxNum = 0;
+  pIdxInfo->needToFreeIdxStr = 0;
+  pIdxInfo->orderByConsumed = 0;
+  /* ((double)2) In case of SQLITE_OMIT_FLOATING_POINT... */
+  pIdxInfo->estimatedCost = SQLITE_BIG_DBL / ((double)2);
+  nOrderBy = pIdxInfo->nOrderBy;
+  if( !pOrderBy ){
+    pIdxInfo->nOrderBy = 0;
+  }
+
+  if( vtabBestIndex(pParse, pTab, pIdxInfo) ){
+    return;
+  }
+
+  pIdxCons = *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint;
+  for(i=0; i<pIdxInfo->nConstraint; i++){
+    if( pUsage[i].argvIndex>0 ){
+      pCost->used |= pWC->a[pIdxCons[i].iTermOffset].prereqRight;
+    }
+  }
+
+  /* If there is an ORDER BY clause, and the selected virtual table index
+  ** does not satisfy it, increase the cost of the scan accordingly. This
+  ** matches the processing for non-virtual tables in bestBtreeIndex().
+  */
+  rCost = pIdxInfo->estimatedCost;
+  if( pOrderBy && pIdxInfo->orderByConsumed==0 ){
+    rCost += estLog(rCost)*rCost;
+  }
+
+  /* The cost is not allowed to be larger than SQLITE_BIG_DBL (the
+  ** inital value of lowestCost in this loop. If it is, then the
+  ** (cost<lowestCost) test below will never be true.
+  ** 
+  ** Use "(double)2" instead of "2.0" in case OMIT_FLOATING_POINT 
+  ** is defined.
+  */
+  if( (SQLITE_BIG_DBL/((double)2))<rCost ){
+    pCost->rCost = (SQLITE_BIG_DBL/((double)2));
+  }else{
+    pCost->rCost = rCost;
+  }
+  pCost->plan.u.pVtabIdx = pIdxInfo;
+  if( pIdxInfo->orderByConsumed ){
+    pCost->plan.wsFlags |= WHERE_ORDERBY;
+  }
+  pCost->plan.nEq = 0;
+  pIdxInfo->nOrderBy = nOrderBy;
+
+  /* Try to find a more efficient access pattern by using multiple indexes
+  ** to optimize an OR expression within the WHERE clause. 
+  */
+  bestOrClauseIndex(pParse, pWC, pSrc, notReady, notValid, pOrderBy, pCost);
+}
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+#ifdef SQLITE_ENABLE_STAT3
+/*
+** Estimate the location of a particular key among all keys in an
+** index.  Store the results in aStat as follows:
+**
+**    aStat[0]      Est. number of rows less than pVal
+**    aStat[1]      Est. number of rows equal to pVal
+**
+** Return SQLITE_OK on success.
+*/
+static int whereKeyStats(
+  Parse *pParse,              /* Database connection */
+  Index *pIdx,                /* Index to consider domain of */
+  sqlite3_value *pVal,        /* Value to consider */
+  int roundUp,                /* Round up if true.  Round down if false */
+  tRowcnt *aStat              /* OUT: stats written here */
+){
+  tRowcnt n;
+  IndexSample *aSample;
+  int i, eType;
+  int isEq = 0;
+  i64 v;
+  double r, rS;
+
+  assert( roundUp==0 || roundUp==1 );
+  assert( pIdx->nSample>0 );
+  if( pVal==0 ) return SQLITE_ERROR;
+  n = pIdx->aiRowEst[0];
+  aSample = pIdx->aSample;
+  eType = sqlite3_value_type(pVal);
+
+  if( eType==SQLITE_INTEGER ){
+    v = sqlite3_value_int64(pVal);
+    r = (i64)v;
+    for(i=0; i<pIdx->nSample; i++){
+      if( aSample[i].eType==SQLITE_NULL ) continue;
+      if( aSample[i].eType>=SQLITE_TEXT ) break;
+      if( aSample[i].eType==SQLITE_INTEGER ){
+        if( aSample[i].u.i>=v ){
+          isEq = aSample[i].u.i==v;
+          break;
+        }
+      }else{
+        assert( aSample[i].eType==SQLITE_FLOAT );
+        if( aSample[i].u.r>=r ){
+          isEq = aSample[i].u.r==r;
+          break;
+        }
+      }
+    }
+  }else if( eType==SQLITE_FLOAT ){
+    r = sqlite3_value_double(pVal);
+    for(i=0; i<pIdx->nSample; i++){
+      if( aSample[i].eType==SQLITE_NULL ) continue;
+      if( aSample[i].eType>=SQLITE_TEXT ) break;
+      if( aSample[i].eType==SQLITE_FLOAT ){
+        rS = aSample[i].u.r;
+      }else{
+        rS = aSample[i].u.i;
+      }
+      if( rS>=r ){
+        isEq = rS==r;
+        break;
+      }
+    }
+  }else if( eType==SQLITE_NULL ){
+    i = 0;
+    if( aSample[0].eType==SQLITE_NULL ) isEq = 1;
+  }else{
+    assert( eType==SQLITE_TEXT || eType==SQLITE_BLOB );
+    for(i=0; i<pIdx->nSample; i++){
+      if( aSample[i].eType==SQLITE_TEXT || aSample[i].eType==SQLITE_BLOB ){
+        break;
+      }
+    }
+    if( i<pIdx->nSample ){      
+      sqlite3 *db = pParse->db;
+      CollSeq *pColl;
+      const u8 *z;
+      if( eType==SQLITE_BLOB ){
+        z = (const u8 *)sqlite3_value_blob(pVal);
+        pColl = db->pDfltColl;
+        assert( pColl->enc==SQLITE_UTF8 );
+      }else{
+        pColl = sqlite3GetCollSeq(db, SQLITE_UTF8, 0, *pIdx->azColl);
+        if( pColl==0 ){
+          sqlite3ErrorMsg(pParse, "no such collation sequence: %s",
+                          *pIdx->azColl);
+          return SQLITE_ERROR;
+        }
+        z = (const u8 *)sqlite3ValueText(pVal, pColl->enc);
+        if( !z ){
+          return SQLITE_NOMEM;
+        }
+        assert( z && pColl && pColl->xCmp );
+      }
+      n = sqlite3ValueBytes(pVal, pColl->enc);
+  
+      for(; i<pIdx->nSample; i++){
+        int c;
+        int eSampletype = aSample[i].eType;
+        if( eSampletype<eType ) continue;
+        if( eSampletype!=eType ) break;
+#ifndef SQLITE_OMIT_UTF16
+        if( pColl->enc!=SQLITE_UTF8 ){
+          int nSample;
+          char *zSample = sqlite3Utf8to16(
+              db, pColl->enc, aSample[i].u.z, aSample[i].nByte, &nSample
+          );
+          if( !zSample ){
+            assert( db->mallocFailed );
+            return SQLITE_NOMEM;
+          }
+          c = pColl->xCmp(pColl->pUser, nSample, zSample, n, z);
+          sqlite3DbFree(db, zSample);
+        }else
+#endif
+        {
+          c = pColl->xCmp(pColl->pUser, aSample[i].nByte, aSample[i].u.z, n, z);
+        }
+        if( c>=0 ){
+          if( c==0 ) isEq = 1;
+          break;
+        }
+      }
+    }
+  }
+
+  /* At this point, aSample[i] is the first sample that is greater than
+  ** or equal to pVal.  Or if i==pIdx->nSample, then all samples are less
+  ** than pVal.  If aSample[i]==pVal, then isEq==1.
+  */
+  if( isEq ){
+    assert( i<pIdx->nSample );
+    aStat[0] = aSample[i].nLt;
+    aStat[1] = aSample[i].nEq;
+  }else{
+    tRowcnt iLower, iUpper, iGap;
+    if( i==0 ){
+      iLower = 0;
+      iUpper = aSample[0].nLt;
+    }else{
+      iUpper = i>=pIdx->nSample ? n : aSample[i].nLt;
+      iLower = aSample[i-1].nEq + aSample[i-1].nLt;
+    }
+    aStat[1] = pIdx->avgEq;
+    if( iLower>=iUpper ){
+      iGap = 0;
+    }else{
+      iGap = iUpper - iLower;
+    }
+    if( roundUp ){
+      iGap = (iGap*2)/3;
+    }else{
+      iGap = iGap/3;
+    }
+    aStat[0] = iLower + iGap;
+  }
+  return SQLITE_OK;
+}
+#endif /* SQLITE_ENABLE_STAT3 */
+
+/*
+** If expression pExpr represents a literal value, set *pp to point to
+** an sqlite3_value structure containing the same value, with affinity
+** aff applied to it, before returning. It is the responsibility of the 
+** caller to eventually release this structure by passing it to 
+** sqlite3ValueFree().
+**
+** If the current parse is a recompile (sqlite3Reprepare()) and pExpr
+** is an SQL variable that currently has a non-NULL value bound to it,
+** create an sqlite3_value structure containing this value, again with
+** affinity aff applied to it, instead.
+**
+** If neither of the above apply, set *pp to NULL.
+**
+** If an error occurs, return an error code. Otherwise, SQLITE_OK.
+*/
+#ifdef SQLITE_ENABLE_STAT3
+static int valueFromExpr(
+  Parse *pParse, 
+  Expr *pExpr, 
+  u8 aff, 
+  sqlite3_value **pp
+){
+  if( pExpr->op==TK_VARIABLE
+   || (pExpr->op==TK_REGISTER && pExpr->op2==TK_VARIABLE)
+  ){
+    int iVar = pExpr->iColumn;
+    sqlite3VdbeSetVarmask(pParse->pVdbe, iVar);
+    *pp = sqlite3VdbeGetValue(pParse->pReprepare, iVar, aff);
+    return SQLITE_OK;
+  }
+  return sqlite3ValueFromExpr(pParse->db, pExpr, SQLITE_UTF8, aff, pp);
+}
+#endif
+
+/*
+** This function is used to estimate the number of rows that will be visited
+** by scanning an index for a range of values. The range may have an upper
+** bound, a lower bound, or both. The WHERE clause terms that set the upper
+** and lower bounds are represented by pLower and pUpper respectively. For
+** example, assuming that index p is on t1(a):
+**
+**   ... FROM t1 WHERE a > ? AND a < ? ...
+**                    |_____|   |_____|
+**                       |         |
+**                     pLower    pUpper
+**
+** If either of the upper or lower bound is not present, then NULL is passed in
+** place of the corresponding WhereTerm.
+**
+** The nEq parameter is passed the index of the index column subject to the
+** range constraint. Or, equivalently, the number of equality constraints
+** optimized by the proposed index scan. For example, assuming index p is
+** on t1(a, b), and the SQL query is:
+**
+**   ... FROM t1 WHERE a = ? AND b > ? AND b < ? ...
+**
+** then nEq should be passed the value 1 (as the range restricted column,
+** b, is the second left-most column of the index). Or, if the query is:
+**
+**   ... FROM t1 WHERE a > ? AND a < ? ...
+**
+** then nEq should be passed 0.
+**
+** The returned value is an integer divisor to reduce the estimated
+** search space.  A return value of 1 means that range constraints are
+** no help at all.  A return value of 2 means range constraints are
+** expected to reduce the search space by half.  And so forth...
+**
+** In the absence of sqlite_stat3 ANALYZE data, each range inequality
+** reduces the search space by a factor of 4.  Hence a single constraint (x>?)
+** results in a return of 4 and a range constraint (x>? AND x<?) results
+** in a return of 16.
+*/
+static int whereRangeScanEst(
+  Parse *pParse,       /* Parsing & code generating context */
+  Index *p,            /* The index containing the range-compared column; "x" */
+  int nEq,             /* index into p->aCol[] of the range-compared column */
+  WhereTerm *pLower,   /* Lower bound on the range. ex: "x>123" Might be NULL */
+  WhereTerm *pUpper,   /* Upper bound on the range. ex: "x<455" Might be NULL */
+  double *pRangeDiv   /* OUT: Reduce search space by this divisor */
+){
+  int rc = SQLITE_OK;
+
+#ifdef SQLITE_ENABLE_STAT3
+
+  if( nEq==0 && p->nSample ){
+    sqlite3_value *pRangeVal;
+    tRowcnt iLower = 0;
+    tRowcnt iUpper = p->aiRowEst[0];
+    tRowcnt a[2];
+    u8 aff = p->pTable->aCol[p->aiColumn[0]].affinity;
+
+    if( pLower ){
+      Expr *pExpr = pLower->pExpr->pRight;
+      rc = valueFromExpr(pParse, pExpr, aff, &pRangeVal);
+      assert( pLower->eOperator==WO_GT || pLower->eOperator==WO_GE );
+      if( rc==SQLITE_OK
+       && whereKeyStats(pParse, p, pRangeVal, 0, a)==SQLITE_OK
+      ){
+        iLower = a[0];
+        if( pLower->eOperator==WO_GT ) iLower += a[1];
+      }
+      sqlite3ValueFree(pRangeVal);
+    }
+    if( rc==SQLITE_OK && pUpper ){
+      Expr *pExpr = pUpper->pExpr->pRight;
+      rc = valueFromExpr(pParse, pExpr, aff, &pRangeVal);
+      assert( pUpper->eOperator==WO_LT || pUpper->eOperator==WO_LE );
+      if( rc==SQLITE_OK
+       && whereKeyStats(pParse, p, pRangeVal, 1, a)==SQLITE_OK
+      ){
+        iUpper = a[0];
+        if( pUpper->eOperator==WO_LE ) iUpper += a[1];
+      }
+      sqlite3ValueFree(pRangeVal);
+    }
+    if( rc==SQLITE_OK ){
+      if( iUpper<=iLower ){
+        *pRangeDiv = (double)p->aiRowEst[0];
+      }else{
+        *pRangeDiv = (double)p->aiRowEst[0]/(double)(iUpper - iLower);
+      }
+      WHERETRACE(("range scan regions: %u..%u  div=%g\n",
+                  (u32)iLower, (u32)iUpper, *pRangeDiv));
+      return SQLITE_OK;
+    }
+  }
+#else
+  UNUSED_PARAMETER(pParse);
+  UNUSED_PARAMETER(p);
+  UNUSED_PARAMETER(nEq);
+#endif
+  assert( pLower || pUpper );
+  *pRangeDiv = (double)1;
+  if( pLower && (pLower->wtFlags & TERM_VNULL)==0 ) *pRangeDiv *= (double)4;
+  if( pUpper ) *pRangeDiv *= (double)4;
+  return rc;
+}
+
+#ifdef SQLITE_ENABLE_STAT3
+/*
+** Estimate the number of rows that will be returned based on
+** an equality constraint x=VALUE and where that VALUE occurs in
+** the histogram data.  This only works when x is the left-most
+** column of an index and sqlite_stat3 histogram data is available
+** for that index.  When pExpr==NULL that means the constraint is
+** "x IS NULL" instead of "x=VALUE".
+**
+** Write the estimated row count into *pnRow and return SQLITE_OK. 
+** If unable to make an estimate, leave *pnRow unchanged and return
+** non-zero.
+**
+** This routine can fail if it is unable to load a collating sequence
+** required for string comparison, or if unable to allocate memory
+** for a UTF conversion required for comparison.  The error is stored
+** in the pParse structure.
+*/
+static int whereEqualScanEst(
+  Parse *pParse,       /* Parsing & code generating context */
+  Index *p,            /* The index whose left-most column is pTerm */
+  Expr *pExpr,         /* Expression for VALUE in the x=VALUE constraint */
+  double *pnRow        /* Write the revised row estimate here */
+){
+  sqlite3_value *pRhs = 0;  /* VALUE on right-hand side of pTerm */
+  u8 aff;                   /* Column affinity */
+  int rc;                   /* Subfunction return code */
+  tRowcnt a[2];             /* Statistics */
+
+  assert( p->aSample!=0 );
+  assert( p->nSample>0 );
+  aff = p->pTable->aCol[p->aiColumn[0]].affinity;
+  if( pExpr ){
+    rc = valueFromExpr(pParse, pExpr, aff, &pRhs);
+    if( rc ) goto whereEqualScanEst_cancel;
+  }else{
+    pRhs = sqlite3ValueNew(pParse->db);
+  }
+  if( pRhs==0 ) return SQLITE_NOTFOUND;
+  rc = whereKeyStats(pParse, p, pRhs, 0, a);
+  if( rc==SQLITE_OK ){
+    WHERETRACE(("equality scan regions: %d\n", (int)a[1]));
+    *pnRow = a[1];
+  }
+whereEqualScanEst_cancel:
+  sqlite3ValueFree(pRhs);
+  return rc;
+}
+#endif /* defined(SQLITE_ENABLE_STAT3) */
+
+#ifdef SQLITE_ENABLE_STAT3
+/*
+** Estimate the number of rows that will be returned based on
+** an IN constraint where the right-hand side of the IN operator
+** is a list of values.  Example:
+**
+**        WHERE x IN (1,2,3,4)
+**
+** Write the estimated row count into *pnRow and return SQLITE_OK. 
+** If unable to make an estimate, leave *pnRow unchanged and return
+** non-zero.
+**
+** This routine can fail if it is unable to load a collating sequence
+** required for string comparison, or if unable to allocate memory
+** for a UTF conversion required for comparison.  The error is stored
+** in the pParse structure.
+*/
+static int whereInScanEst(
+  Parse *pParse,       /* Parsing & code generating context */
+  Index *p,            /* The index whose left-most column is pTerm */
+  ExprList *pList,     /* The value list on the RHS of "x IN (v1,v2,v3,...)" */
+  double *pnRow        /* Write the revised row estimate here */
+){
+  int rc = SQLITE_OK;         /* Subfunction return code */
+  double nEst;                /* Number of rows for a single term */
+  double nRowEst = (double)0; /* New estimate of the number of rows */
+  int i;                      /* Loop counter */
+
+  assert( p->aSample!=0 );
+  for(i=0; rc==SQLITE_OK && i<pList->nExpr; i++){
+    nEst = p->aiRowEst[0];
+    rc = whereEqualScanEst(pParse, p, pList->a[i].pExpr, &nEst);
+    nRowEst += nEst;
+  }
+  if( rc==SQLITE_OK ){
+    if( nRowEst > p->aiRowEst[0] ) nRowEst = p->aiRowEst[0];
+    *pnRow = nRowEst;
+    WHERETRACE(("IN row estimate: est=%g\n", nRowEst));
+  }
+  return rc;
+}
+#endif /* defined(SQLITE_ENABLE_STAT3) */
+
+
+/*
+** Find the best query plan for accessing a particular table.  Write the
+** best query plan and its cost into the WhereCost object supplied as the
+** last parameter.
+**
+** The lowest cost plan wins.  The cost is an estimate of the amount of
+** CPU and disk I/O needed to process the requested result.
+** Factors that influence cost include:
+**
+**    *  The estimated number of rows that will be retrieved.  (The
+**       fewer the better.)
+**
+**    *  Whether or not sorting must occur.
+**
+**    *  Whether or not there must be separate lookups in the
+**       index and in the main table.
+**
+** If there was an INDEXED BY clause (pSrc->pIndex) attached to the table in
+** the SQL statement, then this function only considers plans using the 
+** named index. If no such plan is found, then the returned cost is
+** SQLITE_BIG_DBL. If a plan is found that uses the named index, 
+** then the cost is calculated in the usual way.
+**
+** If a NOT INDEXED clause (pSrc->notIndexed!=0) was attached to the table 
+** in the SELECT statement, then no indexes are considered. However, the 
+** selected plan may still take advantage of the built-in rowid primary key
+** index.
+*/
+static void bestBtreeIndex(
+  Parse *pParse,              /* The parsing context */
+  WhereClause *pWC,           /* The WHERE clause */
+  struct SrcList_item *pSrc,  /* The FROM clause term to search */
+  Bitmask notReady,           /* Mask of cursors not available for indexing */
+  Bitmask notValid,           /* Cursors not available for any purpose */
+  ExprList *pOrderBy,         /* The ORDER BY clause */
+  ExprList *pDistinct,        /* The select-list if query is DISTINCT */
+  WhereCost *pCost            /* Lowest cost query plan */
+){
+  int iCur = pSrc->iCursor;   /* The cursor of the table to be accessed */
+  Index *pProbe;              /* An index we are evaluating */
+  Index *pIdx;                /* Copy of pProbe, or zero for IPK index */
+  int eqTermMask;             /* Current mask of valid equality operators */
+  int idxEqTermMask;          /* Index mask of valid equality operators */
+  Index sPk;                  /* A fake index object for the primary key */
+  tRowcnt aiRowEstPk[2];      /* The aiRowEst[] value for the sPk index */
+  int aiColumnPk = -1;        /* The aColumn[] value for the sPk index */
+  int wsFlagMask;             /* Allowed flags in pCost->plan.wsFlag */
+
+  /* Initialize the cost to a worst-case value */
+  memset(pCost, 0, sizeof(*pCost));
+  pCost->rCost = SQLITE_BIG_DBL;
+
+  /* If the pSrc table is the right table of a LEFT JOIN then we may not
+  ** use an index to satisfy IS NULL constraints on that table.  This is
+  ** because columns might end up being NULL if the table does not match -
+  ** a circumstance which the index cannot help us discover.  Ticket #2177.
+  */
+  if( pSrc->jointype & JT_LEFT ){
+    idxEqTermMask = WO_EQ|WO_IN;
+  }else{
+    idxEqTermMask = WO_EQ|WO_IN|WO_ISNULL;
+  }
+
+  if( pSrc->pIndex ){
+    /* An INDEXED BY clause specifies a particular index to use */
+    pIdx = pProbe = pSrc->pIndex;
+    wsFlagMask = ~(WHERE_ROWID_EQ|WHERE_ROWID_RANGE);
+    eqTermMask = idxEqTermMask;
+  }else{
+    /* There is no INDEXED BY clause.  Create a fake Index object in local
+    ** variable sPk to represent the rowid primary key index.  Make this
+    ** fake index the first in a chain of Index objects with all of the real
+    ** indices to follow */
+    Index *pFirst;                  /* First of real indices on the table */
+    memset(&sPk, 0, sizeof(Index));
+    sPk.nColumn = 1;
+    sPk.aiColumn = &aiColumnPk;
+    sPk.aiRowEst = aiRowEstPk;
+    sPk.onError = OE_Replace;
+    sPk.pTable = pSrc->pTab;
+    aiRowEstPk[0] = pSrc->pTab->nRowEst;
+    aiRowEstPk[1] = 1;
+    pFirst = pSrc->pTab->pIndex;
+    if( pSrc->notIndexed==0 ){
+      /* The real indices of the table are only considered if the
+      ** NOT INDEXED qualifier is omitted from the FROM clause */
+      sPk.pNext = pFirst;
+    }
+    pProbe = &sPk;
+    wsFlagMask = ~(
+        WHERE_COLUMN_IN|WHERE_COLUMN_EQ|WHERE_COLUMN_NULL|WHERE_COLUMN_RANGE
+    );
+    eqTermMask = WO_EQ|WO_IN;
+    pIdx = 0;
+  }
+
+  /* Loop over all indices looking for the best one to use
+  */
+  for(; pProbe; pIdx=pProbe=pProbe->pNext){
+    const tRowcnt * const aiRowEst = pProbe->aiRowEst;
+    double cost;                /* Cost of using pProbe */
+    double nRow;                /* Estimated number of rows in result set */
+    double log10N = (double)1;  /* base-10 logarithm of nRow (inexact) */
+    int rev;                    /* True to scan in reverse order */
+    int wsFlags = 0;
+    Bitmask used = 0;
+
+    /* The following variables are populated based on the properties of
+    ** index being evaluated. They are then used to determine the expected
+    ** cost and number of rows returned.
+    **
+    **  nEq: 
+    **    Number of equality terms that can be implemented using the index.
+    **    In other words, the number of initial fields in the index that
+    **    are used in == or IN or NOT NULL constraints of the WHERE clause.
+    **
+    **  nInMul:  
+    **    The "in-multiplier". This is an estimate of how many seek operations 
+    **    SQLite must perform on the index in question. For example, if the 
+    **    WHERE clause is:
+    **
+    **      WHERE a IN (1, 2, 3) AND b IN (4, 5, 6)
+    **
+    **    SQLite must perform 9 lookups on an index on (a, b), so nInMul is 
+    **    set to 9. Given the same schema and either of the following WHERE 
+    **    clauses:
+    **
+    **      WHERE a =  1
+    **      WHERE a >= 2
+    **
+    **    nInMul is set to 1.
+    **
+    **    If there exists a WHERE term of the form "x IN (SELECT ...)", then 
+    **    the sub-select is assumed to return 25 rows for the purposes of 
+    **    determining nInMul.
+    **
+    **  bInEst:  
+    **    Set to true if there was at least one "x IN (SELECT ...)" term used 
+    **    in determining the value of nInMul.  Note that the RHS of the
+    **    IN operator must be a SELECT, not a value list, for this variable
+    **    to be true.
+    **
+    **  rangeDiv:
+    **    An estimate of a divisor by which to reduce the search space due
+    **    to inequality constraints.  In the absence of sqlite_stat3 ANALYZE
+    **    data, a single inequality reduces the search space to 1/4rd its
+    **    original size (rangeDiv==4).  Two inequalities reduce the search
+    **    space to 1/16th of its original size (rangeDiv==16).
+    **
+    **  bSort:   
+    **    Boolean. True if there is an ORDER BY clause that will require an 
+    **    external sort (i.e. scanning the index being evaluated will not 
+    **    correctly order records).
+    **
+    **  bLookup: 
+    **    Boolean. True if a table lookup is required for each index entry
+    **    visited.  In other words, true if this is not a covering index.
+    **    This is always false for the rowid primary key index of a table.
+    **    For other indexes, it is true unless all the columns of the table
+    **    used by the SELECT statement are present in the index (such an
+    **    index is sometimes described as a covering index).
+    **    For example, given the index on (a, b), the second of the following 
+    **    two queries requires table b-tree lookups in order to find the value
+    **    of column c, but the first does not because columns a and b are
+    **    both available in the index.
+    **
+    **             SELECT a, b    FROM tbl WHERE a = 1;
+    **             SELECT a, b, c FROM tbl WHERE a = 1;
+    */
+    int nEq;                      /* Number of == or IN terms matching index */
+    int bInEst = 0;               /* True if "x IN (SELECT...)" seen */
+    int nInMul = 1;               /* Number of distinct equalities to lookup */
+    double rangeDiv = (double)1;  /* Estimated reduction in search space */
+    int nBound = 0;               /* Number of range constraints seen */
+    int bSort = !!pOrderBy;       /* True if external sort required */
+    int bDist = !!pDistinct;      /* True if index cannot help with DISTINCT */
+    int bLookup = 0;              /* True if not a covering index */
+    WhereTerm *pTerm;             /* A single term of the WHERE clause */
+#ifdef SQLITE_ENABLE_STAT3
+    WhereTerm *pFirstTerm = 0;    /* First term matching the index */
+#endif
+
+    /* Determine the values of nEq and nInMul */
+    for(nEq=0; nEq<pProbe->nColumn; nEq++){
+      int j = pProbe->aiColumn[nEq];
+      pTerm = findTerm(pWC, iCur, j, notReady, eqTermMask, pIdx);
+      if( pTerm==0 ) break;
+      wsFlags |= (WHERE_COLUMN_EQ|WHERE_ROWID_EQ);
+      testcase( pTerm->pWC!=pWC );
+      if( pTerm->eOperator & WO_IN ){
+        Expr *pExpr = pTerm->pExpr;
+        wsFlags |= WHERE_COLUMN_IN;
+        if( ExprHasProperty(pExpr, EP_xIsSelect) ){
+          /* "x IN (SELECT ...)":  Assume the SELECT returns 25 rows */
+          nInMul *= 25;
+          bInEst = 1;
+        }else if( ALWAYS(pExpr->x.pList && pExpr->x.pList->nExpr) ){
+          /* "x IN (value, value, ...)" */
+          nInMul *= pExpr->x.pList->nExpr;
+        }
+      }else if( pTerm->eOperator & WO_ISNULL ){
+        wsFlags |= WHERE_COLUMN_NULL;
+      }
+#ifdef SQLITE_ENABLE_STAT3
+      if( nEq==0 && pProbe->aSample ) pFirstTerm = pTerm;
+#endif
+      used |= pTerm->prereqRight;
+    }
+
+    /* Determine the value of rangeDiv */
+    if( nEq<pProbe->nColumn && pProbe->bUnordered==0 ){
+      int j = pProbe->aiColumn[nEq];
+      if( findTerm(pWC, iCur, j, notReady, WO_LT|WO_LE|WO_GT|WO_GE, pIdx) ){
+        WhereTerm *pTop = findTerm(pWC, iCur, j, notReady, WO_LT|WO_LE, pIdx);
+        WhereTerm *pBtm = findTerm(pWC, iCur, j, notReady, WO_GT|WO_GE, pIdx);
+        whereRangeScanEst(pParse, pProbe, nEq, pBtm, pTop, &rangeDiv);
+        if( pTop ){
+          nBound = 1;
+          wsFlags |= WHERE_TOP_LIMIT;
+          used |= pTop->prereqRight;
+          testcase( pTop->pWC!=pWC );
+        }
+        if( pBtm ){
+          nBound++;
+          wsFlags |= WHERE_BTM_LIMIT;
+          used |= pBtm->prereqRight;
+          testcase( pBtm->pWC!=pWC );
+        }
+        wsFlags |= (WHERE_COLUMN_RANGE|WHERE_ROWID_RANGE);
+      }
+    }else if( pProbe->onError!=OE_None ){
+      testcase( wsFlags & WHERE_COLUMN_IN );
+      testcase( wsFlags & WHERE_COLUMN_NULL );
+      if( (wsFlags & (WHERE_COLUMN_IN|WHERE_COLUMN_NULL))==0 ){
+        wsFlags |= WHERE_UNIQUE;
+      }
+    }
+
+    /* If there is an ORDER BY clause and the index being considered will
+    ** naturally scan rows in the required order, set the appropriate flags
+    ** in wsFlags. Otherwise, if there is an ORDER BY clause but the index
+    ** will scan rows in a different order, set the bSort variable.  */
+    if( isSortingIndex(
+          pParse, pWC->pMaskSet, pProbe, iCur, pOrderBy, nEq, wsFlags, &rev)
+    ){
+      bSort = 0;
+      wsFlags |= WHERE_ROWID_RANGE|WHERE_COLUMN_RANGE|WHERE_ORDERBY;
+      wsFlags |= (rev ? WHERE_REVERSE : 0);
+    }
+
+    /* If there is a DISTINCT qualifier and this index will scan rows in
+    ** order of the DISTINCT expressions, clear bDist and set the appropriate
+    ** flags in wsFlags. */
+    if( isDistinctIndex(pParse, pWC, pProbe, iCur, pDistinct, nEq) ){
+      bDist = 0;
+      wsFlags |= WHERE_ROWID_RANGE|WHERE_COLUMN_RANGE|WHERE_DISTINCT;
+    }
+
+    /* If currently calculating the cost of using an index (not the IPK
+    ** index), determine if all required column data may be obtained without 
+    ** using the main table (i.e. if the index is a covering
+    ** index for this query). If it is, set the WHERE_IDX_ONLY flag in
+    ** wsFlags. Otherwise, set the bLookup variable to true.  */
+    if( pIdx && wsFlags ){
+      Bitmask m = pSrc->colUsed;
+      int j;
+      for(j=0; j<pIdx->nColumn; j++){
+        int x = pIdx->aiColumn[j];
+        if( x<BMS-1 ){
+          m &= ~(((Bitmask)1)<<x);
+        }
+      }
+      if( m==0 ){
+        wsFlags |= WHERE_IDX_ONLY;
+      }else{
+        bLookup = 1;
+      }
+    }
+
+    /*
+    ** Estimate the number of rows of output.  For an "x IN (SELECT...)"
+    ** constraint, do not let the estimate exceed half the rows in the table.
+    */
+    nRow = (double)(aiRowEst[nEq] * nInMul);
+    if( bInEst && nRow*2>aiRowEst[0] ){
+      nRow = aiRowEst[0]/2;
+      nInMul = (int)(nRow / aiRowEst[nEq]);
+    }
+
+#ifdef SQLITE_ENABLE_STAT3
+    /* If the constraint is of the form x=VALUE or x IN (E1,E2,...)
+    ** and we do not think that values of x are unique and if histogram
+    ** data is available for column x, then it might be possible
+    ** to get a better estimate on the number of rows based on
+    ** VALUE and how common that value is according to the histogram.
+    */
+    if( nRow>(double)1 && nEq==1 && pFirstTerm!=0 && aiRowEst[1]>1 ){
+      assert( (pFirstTerm->eOperator & (WO_EQ|WO_ISNULL|WO_IN))!=0 );
+      if( pFirstTerm->eOperator & (WO_EQ|WO_ISNULL) ){
+        testcase( pFirstTerm->eOperator==WO_EQ );
+        testcase( pFirstTerm->eOperator==WO_ISNULL );
+        whereEqualScanEst(pParse, pProbe, pFirstTerm->pExpr->pRight, &nRow);
+      }else if( bInEst==0 ){
+        assert( pFirstTerm->eOperator==WO_IN );
+        whereInScanEst(pParse, pProbe, pFirstTerm->pExpr->x.pList, &nRow);
+      }
+    }
+#endif /* SQLITE_ENABLE_STAT3 */
+
+    /* Adjust the number of output rows and downward to reflect rows
+    ** that are excluded by range constraints.
+    */
+    nRow = nRow/rangeDiv;
+    if( nRow<1 ) nRow = 1;
+
+    /* Experiments run on real SQLite databases show that the time needed
+    ** to do a binary search to locate a row in a table or index is roughly
+    ** log10(N) times the time to move from one row to the next row within
+    ** a table or index.  The actual times can vary, with the size of
+    ** records being an important factor.  Both moves and searches are
+    ** slower with larger records, presumably because fewer records fit
+    ** on one page and hence more pages have to be fetched.
+    **
+    ** The ANALYZE command and the sqlite_stat1 and sqlite_stat3 tables do
+    ** not give us data on the relative sizes of table and index records.
+    ** So this computation assumes table records are about twice as big
+    ** as index records
+    */
+    if( (wsFlags & WHERE_NOT_FULLSCAN)==0 ){
+      /* The cost of a full table scan is a number of move operations equal
+      ** to the number of rows in the table.
+      **
+      ** We add an additional 4x penalty to full table scans.  This causes
+      ** the cost function to err on the side of choosing an index over
+      ** choosing a full scan.  This 4x full-scan penalty is an arguable
+      ** decision and one which we expect to revisit in the future.  But
+      ** it seems to be working well enough at the moment.
+      */
+      cost = aiRowEst[0]*4;
+    }else{
+      log10N = estLog(aiRowEst[0]);
+      cost = nRow;
+      if( pIdx ){
+        if( bLookup ){
+          /* For an index lookup followed by a table lookup:
+          **    nInMul index searches to find the start of each index range
+          **  + nRow steps through the index
+          **  + nRow table searches to lookup the table entry using the rowid
+          */
+          cost += (nInMul + nRow)*log10N;
+        }else{
+          /* For a covering index:
+          **     nInMul index searches to find the initial entry 
+          **   + nRow steps through the index
+          */
+          cost += nInMul*log10N;
+        }
+      }else{
+        /* For a rowid primary key lookup:
+        **    nInMult table searches to find the initial entry for each range
+        **  + nRow steps through the table
+        */
+        cost += nInMul*log10N;
+      }
+    }
+
+    /* Add in the estimated cost of sorting the result.  Actual experimental
+    ** measurements of sorting performance in SQLite show that sorting time
+    ** adds C*N*log10(N) to the cost, where N is the number of rows to be 
+    ** sorted and C is a factor between 1.95 and 4.3.  We will split the
+    ** difference and select C of 3.0.
+    */
+    if( bSort ){
+      cost += nRow*estLog(nRow)*3;
+    }
+    if( bDist ){
+      cost += nRow*estLog(nRow)*3;
+    }
+
+    /**** Cost of using this index has now been computed ****/
+
+    /* If there are additional constraints on this table that cannot
+    ** be used with the current index, but which might lower the number
+    ** of output rows, adjust the nRow value accordingly.  This only 
+    ** matters if the current index is the least costly, so do not bother
+    ** with this step if we already know this index will not be chosen.
+    ** Also, never reduce the output row count below 2 using this step.
+    **
+    ** It is critical that the notValid mask be used here instead of
+    ** the notReady mask.  When computing an "optimal" index, the notReady
+    ** mask will only have one bit set - the bit for the current table.
+    ** The notValid mask, on the other hand, always has all bits set for
+    ** tables that are not in outer loops.  If notReady is used here instead
+    ** of notValid, then a optimal index that depends on inner joins loops
+    ** might be selected even when there exists an optimal index that has
+    ** no such dependency.
+    */
+    if( nRow>2 && cost<=pCost->rCost ){
+      int k;                       /* Loop counter */
+      int nSkipEq = nEq;           /* Number of == constraints to skip */
+      int nSkipRange = nBound;     /* Number of < constraints to skip */
+      Bitmask thisTab;             /* Bitmap for pSrc */
+
+      thisTab = getMask(pWC->pMaskSet, iCur);
+      for(pTerm=pWC->a, k=pWC->nTerm; nRow>2 && k; k--, pTerm++){
+        if( pTerm->wtFlags & TERM_VIRTUAL ) continue;
+        if( (pTerm->prereqAll & notValid)!=thisTab ) continue;
+        if( pTerm->eOperator & (WO_EQ|WO_IN|WO_ISNULL) ){
+          if( nSkipEq ){
+            /* Ignore the first nEq equality matches since the index
+            ** has already accounted for these */
+            nSkipEq--;
+          }else{
+            /* Assume each additional equality match reduces the result
+            ** set size by a factor of 10 */
+            nRow /= 10;
+          }
+        }else if( pTerm->eOperator & (WO_LT|WO_LE|WO_GT|WO_GE) ){
+          if( nSkipRange ){
+            /* Ignore the first nSkipRange range constraints since the index
+            ** has already accounted for these */
+            nSkipRange--;
+          }else{
+            /* Assume each additional range constraint reduces the result
+            ** set size by a factor of 3.  Indexed range constraints reduce
+            ** the search space by a larger factor: 4.  We make indexed range
+            ** more selective intentionally because of the subjective 
+            ** observation that indexed range constraints really are more
+            ** selective in practice, on average. */
+            nRow /= 3;
+          }
+        }else if( pTerm->eOperator!=WO_NOOP ){
+          /* Any other expression lowers the output row count by half */
+          nRow /= 2;
+        }
+      }
+      if( nRow<2 ) nRow = 2;
+    }
+
+
+    WHERETRACE((
+      "%s(%s): nEq=%d nInMul=%d rangeDiv=%d bSort=%d bLookup=%d wsFlags=0x%x\n"
+      "         notReady=0x%llx log10N=%.1f nRow=%.1f cost=%.1f used=0x%llx\n",
+      pSrc->pTab->zName, (pIdx ? pIdx->zName : "ipk"), 
+      nEq, nInMul, (int)rangeDiv, bSort, bLookup, wsFlags,
+      notReady, log10N, nRow, cost, used
+    ));
+
+    /* If this index is the best we have seen so far, then record this
+    ** index and its cost in the pCost structure.
+    */
+    if( (!pIdx || wsFlags)
+     && (cost<pCost->rCost || (cost<=pCost->rCost && nRow<pCost->plan.nRow))
+    ){
+      pCost->rCost = cost;
+      pCost->used = used;
+      pCost->plan.nRow = nRow;
+      pCost->plan.wsFlags = (wsFlags&wsFlagMask);
+      pCost->plan.nEq = nEq;
+      pCost->plan.u.pIdx = pIdx;
+    }
+
+    /* If there was an INDEXED BY clause, then only that one index is
+    ** considered. */
+    if( pSrc->pIndex ) break;
+
+    /* Reset masks for the next index in the loop */
+    wsFlagMask = ~(WHERE_ROWID_EQ|WHERE_ROWID_RANGE);
+    eqTermMask = idxEqTermMask;
+  }
+
+  /* If there is no ORDER BY clause and the SQLITE_ReverseOrder flag
+  ** is set, then reverse the order that the index will be scanned
+  ** in. This is used for application testing, to help find cases
+  ** where application behaviour depends on the (undefined) order that
+  ** SQLite outputs rows in in the absence of an ORDER BY clause.  */
+  if( !pOrderBy && pParse->db->flags & SQLITE_ReverseOrder ){
+    pCost->plan.wsFlags |= WHERE_REVERSE;
+  }
+
+  assert( pOrderBy || (pCost->plan.wsFlags&WHERE_ORDERBY)==0 );
+  assert( pCost->plan.u.pIdx==0 || (pCost->plan.wsFlags&WHERE_ROWID_EQ)==0 );
+  assert( pSrc->pIndex==0 
+       || pCost->plan.u.pIdx==0 
+       || pCost->plan.u.pIdx==pSrc->pIndex 
+  );
+
+  WHERETRACE(("best index is: %s\n", 
+    ((pCost->plan.wsFlags & WHERE_NOT_FULLSCAN)==0 ? "none" : 
+         pCost->plan.u.pIdx ? pCost->plan.u.pIdx->zName : "ipk")
+  ));
+  
+  bestOrClauseIndex(pParse, pWC, pSrc, notReady, notValid, pOrderBy, pCost);
+  bestAutomaticIndex(pParse, pWC, pSrc, notReady, pCost);
+  pCost->plan.wsFlags |= eqTermMask;
+}
+
+/*
+** Find the query plan for accessing table pSrc->pTab. Write the
+** best query plan and its cost into the WhereCost object supplied 
+** as the last parameter. This function may calculate the cost of
+** both real and virtual table scans.
+*/
+static void bestIndex(
+  Parse *pParse,              /* The parsing context */
+  WhereClause *pWC,           /* The WHERE clause */
+  struct SrcList_item *pSrc,  /* The FROM clause term to search */
+  Bitmask notReady,           /* Mask of cursors not available for indexing */
+  Bitmask notValid,           /* Cursors not available for any purpose */
+  ExprList *pOrderBy,         /* The ORDER BY clause */
+  WhereCost *pCost            /* Lowest cost query plan */
+){
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  if( IsVirtual(pSrc->pTab) ){
+    sqlite3_index_info *p = 0;
+    bestVirtualIndex(pParse, pWC, pSrc, notReady, notValid, pOrderBy, pCost,&p);
+    if( p->needToFreeIdxStr ){
+      sqlite3_free(p->idxStr);
+    }
+    sqlite3DbFree(pParse->db, p);
+  }else
+#endif
+  {
+    bestBtreeIndex(pParse, pWC, pSrc, notReady, notValid, pOrderBy, 0, pCost);
+  }
+}
+
+/*
+** Disable a term in the WHERE clause.  Except, do not disable the term
+** if it controls a LEFT OUTER JOIN and it did not originate in the ON
+** or USING clause of that join.
+**
+** Consider the term t2.z='ok' in the following queries:
+**
+**   (1)  SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x WHERE t2.z='ok'
+**   (2)  SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x AND t2.z='ok'
+**   (3)  SELECT * FROM t1, t2 WHERE t1.a=t2.x AND t2.z='ok'
+**
+** The t2.z='ok' is disabled in the in (2) because it originates
+** in the ON clause.  The term is disabled in (3) because it is not part
+** of a LEFT OUTER JOIN.  In (1), the term is not disabled.
+**
+** IMPLEMENTATION-OF: R-24597-58655 No tests are done for terms that are
+** completely satisfied by indices.
+**
+** Disabling a term causes that term to not be tested in the inner loop
+** of the join.  Disabling is an optimization.  When terms are satisfied
+** by indices, we disable them to prevent redundant tests in the inner
+** loop.  We would get the correct results if nothing were ever disabled,
+** but joins might run a little slower.  The trick is to disable as much
+** as we can without disabling too much.  If we disabled in (1), we'd get
+** the wrong answer.  See ticket #813.
+*/
+static void disableTerm(WhereLevel *pLevel, WhereTerm *pTerm){
+  if( pTerm
+      && (pTerm->wtFlags & TERM_CODED)==0
+      && (pLevel->iLeftJoin==0 || ExprHasProperty(pTerm->pExpr, EP_FromJoin))
+  ){
+    pTerm->wtFlags |= TERM_CODED;
+    if( pTerm->iParent>=0 ){
+      WhereTerm *pOther = &pTerm->pWC->a[pTerm->iParent];
+      if( (--pOther->nChild)==0 ){
+        disableTerm(pLevel, pOther);
+      }
+    }
+  }
+}
+
+/*
+** Code an OP_Affinity opcode to apply the column affinity string zAff
+** to the n registers starting at base. 
+**
+** As an optimization, SQLITE_AFF_NONE entries (which are no-ops) at the
+** beginning and end of zAff are ignored.  If all entries in zAff are
+** SQLITE_AFF_NONE, then no code gets generated.
+**
+** This routine makes its own copy of zAff so that the caller is free
+** to modify zAff after this routine returns.
+*/
+static void codeApplyAffinity(Parse *pParse, int base, int n, char *zAff){
+  Vdbe *v = pParse->pVdbe;
+  if( zAff==0 ){
+    assert( pParse->db->mallocFailed );
+    return;
+  }
+  assert( v!=0 );
+
+  /* Adjust base and n to skip over SQLITE_AFF_NONE entries at the beginning
+  ** and end of the affinity string.
+  */
+  while( n>0 && zAff[0]==SQLITE_AFF_NONE ){
+    n--;
+    base++;
+    zAff++;
+  }
+  while( n>1 && zAff[n-1]==SQLITE_AFF_NONE ){
+    n--;
+  }
+
+  /* Code the OP_Affinity opcode if there is anything left to do. */
+  if( n>0 ){
+    sqlite3VdbeAddOp2(v, OP_Affinity, base, n);
+    sqlite3VdbeChangeP4(v, -1, zAff, n);
+    sqlite3ExprCacheAffinityChange(pParse, base, n);
+  }
+}
+
+
+/*
+** Generate code for a single equality term of the WHERE clause.  An equality
+** term can be either X=expr or X IN (...).   pTerm is the term to be 
+** coded.
+**
+** The current value for the constraint is left in register iReg.
+**
+** For a constraint of the form X=expr, the expression is evaluated and its
+** result is left on the stack.  For constraints of the form X IN (...)
+** this routine sets up a loop that will iterate over all values of X.
+*/
+static int codeEqualityTerm(
+  Parse *pParse,      /* The parsing context */
+  WhereTerm *pTerm,   /* The term of the WHERE clause to be coded */
+  WhereLevel *pLevel, /* When level of the FROM clause we are working on */
+  int iTarget         /* Attempt to leave results in this register */
+){
+  Expr *pX = pTerm->pExpr;
+  Vdbe *v = pParse->pVdbe;
+  int iReg;                  /* Register holding results */
+
+  assert( iTarget>0 );
+  if( pX->op==TK_EQ ){
+    iReg = sqlite3ExprCodeTarget(pParse, pX->pRight, iTarget);
+  }else if( pX->op==TK_ISNULL ){
+    iReg = iTarget;
+    sqlite3VdbeAddOp2(v, OP_Null, 0, iReg);
+#ifndef SQLITE_OMIT_SUBQUERY
+  }else{
+    int eType;
+    int iTab;
+    struct InLoop *pIn;
+
+    assert( pX->op==TK_IN );
+    iReg = iTarget;
+    eType = sqlite3FindInIndex(pParse, pX, 0);
+    iTab = pX->iTable;
+    sqlite3VdbeAddOp2(v, OP_Rewind, iTab, 0);
+    assert( pLevel->plan.wsFlags & WHERE_IN_ABLE );
+    if( pLevel->u.in.nIn==0 ){
+      pLevel->addrNxt = sqlite3VdbeMakeLabel(v);
+    }
+    pLevel->u.in.nIn++;
+    pLevel->u.in.aInLoop =
+       sqlite3DbReallocOrFree(pParse->db, pLevel->u.in.aInLoop,
+                              sizeof(pLevel->u.in.aInLoop[0])*pLevel->u.in.nIn);
+    pIn = pLevel->u.in.aInLoop;
+    if( pIn ){
+      pIn += pLevel->u.in.nIn - 1;
+      pIn->iCur = iTab;
+      if( eType==IN_INDEX_ROWID ){
+        pIn->addrInTop = sqlite3VdbeAddOp2(v, OP_Rowid, iTab, iReg);
+      }else{
+        pIn->addrInTop = sqlite3VdbeAddOp3(v, OP_Column, iTab, 0, iReg);
+      }
+      sqlite3VdbeAddOp1(v, OP_IsNull, iReg);
+    }else{
+      pLevel->u.in.nIn = 0;
+    }
+#endif
+  }
+  disableTerm(pLevel, pTerm);
+  return iReg;
+}
+
+/*
+** Generate code that will evaluate all == and IN constraints for an
+** index.
+**
+** For example, consider table t1(a,b,c,d,e,f) with index i1(a,b,c).
+** Suppose the WHERE clause is this:  a==5 AND b IN (1,2,3) AND c>5 AND c<10
+** The index has as many as three equality constraints, but in this
+** example, the third "c" value is an inequality.  So only two 
+** constraints are coded.  This routine will generate code to evaluate
+** a==5 and b IN (1,2,3).  The current values for a and b will be stored
+** in consecutive registers and the index of the first register is returned.
+**
+** In the example above nEq==2.  But this subroutine works for any value
+** of nEq including 0.  If nEq==0, this routine is nearly a no-op.
+** The only thing it does is allocate the pLevel->iMem memory cell and
+** compute the affinity string.
+**
+** This routine always allocates at least one memory cell and returns
+** the index of that memory cell. The code that
+** calls this routine will use that memory cell to store the termination
+** key value of the loop.  If one or more IN operators appear, then
+** this routine allocates an additional nEq memory cells for internal
+** use.
+**
+** Before returning, *pzAff is set to point to a buffer containing a
+** copy of the column affinity string of the index allocated using
+** sqlite3DbMalloc(). Except, entries in the copy of the string associated
+** with equality constraints that use NONE affinity are set to
+** SQLITE_AFF_NONE. This is to deal with SQL such as the following:
+**
+**   CREATE TABLE t1(a TEXT PRIMARY KEY, b);
+**   SELECT ... FROM t1 AS t2, t1 WHERE t1.a = t2.b;
+**
+** In the example above, the index on t1(a) has TEXT affinity. But since
+** the right hand side of the equality constraint (t2.b) has NONE affinity,
+** no conversion should be attempted before using a t2.b value as part of
+** a key to search the index. Hence the first byte in the returned affinity
+** string in this example would be set to SQLITE_AFF_NONE.
+*/
+static int codeAllEqualityTerms(
+  Parse *pParse,        /* Parsing context */
+  WhereLevel *pLevel,   /* Which nested loop of the FROM we are coding */
+  WhereClause *pWC,     /* The WHERE clause */
+  Bitmask notReady,     /* Which parts of FROM have not yet been coded */
+  int nExtraReg,        /* Number of extra registers to allocate */
+  char **pzAff          /* OUT: Set to point to affinity string */
+){
+  int nEq = pLevel->plan.nEq;   /* The number of == or IN constraints to code */
+  Vdbe *v = pParse->pVdbe;      /* The vm under construction */
+  Index *pIdx;                  /* The index being used for this loop */
+  int iCur = pLevel->iTabCur;   /* The cursor of the table */
+  WhereTerm *pTerm;             /* A single constraint term */
+  int j;                        /* Loop counter */
+  int regBase;                  /* Base register */
+  int nReg;                     /* Number of registers to allocate */
+  char *zAff;                   /* Affinity string to return */
+
+  /* This module is only called on query plans that use an index. */
+  assert( pLevel->plan.wsFlags & WHERE_INDEXED );
+  pIdx = pLevel->plan.u.pIdx;
+
+  /* Figure out how many memory cells we will need then allocate them.
+  */
+  regBase = pParse->nMem + 1;
+  nReg = pLevel->plan.nEq + nExtraReg;
+  pParse->nMem += nReg;
+
+  zAff = sqlite3DbStrDup(pParse->db, sqlite3IndexAffinityStr(v, pIdx));
+  if( !zAff ){
+    pParse->db->mallocFailed = 1;
+  }
+
+  /* Evaluate the equality constraints
+  */
+  assert( pIdx->nColumn>=nEq );
+  for(j=0; j<nEq; j++){
+    int r1;
+    int k = pIdx->aiColumn[j];
+    pTerm = findTerm(pWC, iCur, k, notReady, pLevel->plan.wsFlags, pIdx);
+    if( NEVER(pTerm==0) ) break;
+    /* The following true for indices with redundant columns. 
+    ** Ex: CREATE INDEX i1 ON t1(a,b,a); SELECT * FROM t1 WHERE a=0 AND b=0; */
+    testcase( (pTerm->wtFlags & TERM_CODED)!=0 );
+    testcase( pTerm->wtFlags & TERM_VIRTUAL ); /* EV: R-30575-11662 */
+    r1 = codeEqualityTerm(pParse, pTerm, pLevel, regBase+j);
+    if( r1!=regBase+j ){
+      if( nReg==1 ){
+        sqlite3ReleaseTempReg(pParse, regBase);
+        regBase = r1;
+      }else{
+        sqlite3VdbeAddOp2(v, OP_SCopy, r1, regBase+j);
+      }
+    }
+    testcase( pTerm->eOperator & WO_ISNULL );
+    testcase( pTerm->eOperator & WO_IN );
+    if( (pTerm->eOperator & (WO_ISNULL|WO_IN))==0 ){
+      Expr *pRight = pTerm->pExpr->pRight;
+      sqlite3ExprCodeIsNullJump(v, pRight, regBase+j, pLevel->addrBrk);
+      if( zAff ){
+        if( sqlite3CompareAffinity(pRight, zAff[j])==SQLITE_AFF_NONE ){
+          zAff[j] = SQLITE_AFF_NONE;
+        }
+        if( sqlite3ExprNeedsNoAffinityChange(pRight, zAff[j]) ){
+          zAff[j] = SQLITE_AFF_NONE;
+        }
+      }
+    }
+  }
+  *pzAff = zAff;
+  return regBase;
+}
+
+#ifndef SQLITE_OMIT_EXPLAIN
+/*
+** This routine is a helper for explainIndexRange() below
+**
+** pStr holds the text of an expression that we are building up one term
+** at a time.  This routine adds a new term to the end of the expression.
+** Terms are separated by AND so add the "AND" text for second and subsequent
+** terms only.
+*/
+static void explainAppendTerm(
+  StrAccum *pStr,             /* The text expression being built */
+  int iTerm,                  /* Index of this term.  First is zero */
+  const char *zColumn,        /* Name of the column */
+  const char *zOp             /* Name of the operator */
+){
+  if( iTerm ) sqlite3StrAccumAppend(pStr, " AND ", 5);
+  sqlite3StrAccumAppend(pStr, zColumn, -1);
+  sqlite3StrAccumAppend(pStr, zOp, 1);
+  sqlite3StrAccumAppend(pStr, "?", 1);
+}
+
+/*
+** Argument pLevel describes a strategy for scanning table pTab. This 
+** function returns a pointer to a string buffer containing a description
+** of the subset of table rows scanned by the strategy in the form of an
+** SQL expression. Or, if all rows are scanned, NULL is returned.
+**
+** For example, if the query:
+**
+**   SELECT * FROM t1 WHERE a=1 AND b>2;
+**
+** is run and there is an index on (a, b), then this function returns a
+** string similar to:
+**
+**   "a=? AND b>?"
+**
+** The returned pointer points to memory obtained from sqlite3DbMalloc().
+** It is the responsibility of the caller to free the buffer when it is
+** no longer required.
+*/
+static char *explainIndexRange(sqlite3 *db, WhereLevel *pLevel, Table *pTab){
+  WherePlan *pPlan = &pLevel->plan;
+  Index *pIndex = pPlan->u.pIdx;
+  int nEq = pPlan->nEq;
+  int i, j;
+  Column *aCol = pTab->aCol;
+  int *aiColumn = pIndex->aiColumn;
+  StrAccum txt;
+
+  if( nEq==0 && (pPlan->wsFlags & (WHERE_BTM_LIMIT|WHERE_TOP_LIMIT))==0 ){
+    return 0;
+  }
+  sqlite3StrAccumInit(&txt, 0, 0, SQLITE_MAX_LENGTH);
+  txt.db = db;
+  sqlite3StrAccumAppend(&txt, " (", 2);
+  for(i=0; i<nEq; i++){
+    explainAppendTerm(&txt, i, aCol[aiColumn[i]].zName, "=");
+  }
+
+  j = i;
+  if( pPlan->wsFlags&WHERE_BTM_LIMIT ){
+    explainAppendTerm(&txt, i++, aCol[aiColumn[j]].zName, ">");
+  }
+  if( pPlan->wsFlags&WHERE_TOP_LIMIT ){
+    explainAppendTerm(&txt, i, aCol[aiColumn[j]].zName, "<");
+  }
+  sqlite3StrAccumAppend(&txt, ")", 1);
+  return sqlite3StrAccumFinish(&txt);
+}
+
+/*
+** This function is a no-op unless currently processing an EXPLAIN QUERY PLAN
+** command. If the query being compiled is an EXPLAIN QUERY PLAN, a single
+** record is added to the output to describe the table scan strategy in 
+** pLevel.
+*/
+static void explainOneScan(
+  Parse *pParse,                  /* Parse context */
+  SrcList *pTabList,              /* Table list this loop refers to */
+  WhereLevel *pLevel,             /* Scan to write OP_Explain opcode for */
+  int iLevel,                     /* Value for "level" column of output */
+  int iFrom,                      /* Value for "from" column of output */
+  u16 wctrlFlags                  /* Flags passed to sqlite3WhereBegin() */
+){
+  if( pParse->explain==2 ){
+    u32 flags = pLevel->plan.wsFlags;
+    struct SrcList_item *pItem = &pTabList->a[pLevel->iFrom];
+    Vdbe *v = pParse->pVdbe;      /* VM being constructed */
+    sqlite3 *db = pParse->db;     /* Database handle */
+    char *zMsg;                   /* Text to add to EQP output */
+    sqlite3_int64 nRow;           /* Expected number of rows visited by scan */
+    int iId = pParse->iSelectId;  /* Select id (left-most output column) */
+    int isSearch;                 /* True for a SEARCH. False for SCAN. */
+
+    if( (flags&WHERE_MULTI_OR) || (wctrlFlags&WHERE_ONETABLE_ONLY) ) return;
+
+    isSearch = (pLevel->plan.nEq>0)
+             || (flags&(WHERE_BTM_LIMIT|WHERE_TOP_LIMIT))!=0
+             || (wctrlFlags&(WHERE_ORDERBY_MIN|WHERE_ORDERBY_MAX));
+
+    zMsg = sqlite3MPrintf(db, "%s", isSearch?"SEARCH":"SCAN");
+    if( pItem->pSelect ){
+      zMsg = sqlite3MAppendf(db, zMsg, "%s SUBQUERY %d", zMsg,pItem->iSelectId);
+    }else{
+      zMsg = sqlite3MAppendf(db, zMsg, "%s TABLE %s", zMsg, pItem->zName);
+    }
+
+    if( pItem->zAlias ){
+      zMsg = sqlite3MAppendf(db, zMsg, "%s AS %s", zMsg, pItem->zAlias);
+    }
+    if( (flags & WHERE_INDEXED)!=0 ){
+      char *zWhere = explainIndexRange(db, pLevel, pItem->pTab);
+      zMsg = sqlite3MAppendf(db, zMsg, "%s USING %s%sINDEX%s%s%s", zMsg, 
+          ((flags & WHERE_TEMP_INDEX)?"AUTOMATIC ":""),
+          ((flags & WHERE_IDX_ONLY)?"COVERING ":""),
+          ((flags & WHERE_TEMP_INDEX)?"":" "),
+          ((flags & WHERE_TEMP_INDEX)?"": pLevel->plan.u.pIdx->zName),
+          zWhere
+      );
+      sqlite3DbFree(db, zWhere);
+    }else if( flags & (WHERE_ROWID_EQ|WHERE_ROWID_RANGE) ){
+      zMsg = sqlite3MAppendf(db, zMsg, "%s USING INTEGER PRIMARY KEY", zMsg);
+
+      if( flags&WHERE_ROWID_EQ ){
+        zMsg = sqlite3MAppendf(db, zMsg, "%s (rowid=?)", zMsg);
+      }else if( (flags&WHERE_BOTH_LIMIT)==WHERE_BOTH_LIMIT ){
+        zMsg = sqlite3MAppendf(db, zMsg, "%s (rowid>? AND rowid<?)", zMsg);
+      }else if( flags&WHERE_BTM_LIMIT ){
+        zMsg = sqlite3MAppendf(db, zMsg, "%s (rowid>?)", zMsg);
+      }else if( flags&WHERE_TOP_LIMIT ){
+        zMsg = sqlite3MAppendf(db, zMsg, "%s (rowid<?)", zMsg);
+      }
+    }
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+    else if( (flags & WHERE_VIRTUALTABLE)!=0 ){
+      sqlite3_index_info *pVtabIdx = pLevel->plan.u.pVtabIdx;
+      zMsg = sqlite3MAppendf(db, zMsg, "%s VIRTUAL TABLE INDEX %d:%s", zMsg,
+                  pVtabIdx->idxNum, pVtabIdx->idxStr);
+    }
+#endif
+    if( wctrlFlags&(WHERE_ORDERBY_MIN|WHERE_ORDERBY_MAX) ){
+      testcase( wctrlFlags & WHERE_ORDERBY_MIN );
+      nRow = 1;
+    }else{
+      nRow = (sqlite3_int64)pLevel->plan.nRow;
+    }
+    zMsg = sqlite3MAppendf(db, zMsg, "%s (~%lld rows)", zMsg, nRow);
+    sqlite3VdbeAddOp4(v, OP_Explain, iId, iLevel, iFrom, zMsg, P4_DYNAMIC);
+  }
+}
+#else
+# define explainOneScan(u,v,w,x,y,z)
+#endif /* SQLITE_OMIT_EXPLAIN */
+
+
+/*
+** Generate code for the start of the iLevel-th loop in the WHERE clause
+** implementation described by pWInfo.
+*/
+static Bitmask codeOneLoopStart(
+  WhereInfo *pWInfo,   /* Complete information about the WHERE clause */
+  int iLevel,          /* Which level of pWInfo->a[] should be coded */
+  u16 wctrlFlags,      /* One of the WHERE_* flags defined in sqliteInt.h */
+  Bitmask notReady,    /* Which tables are currently available */
+  Expr *pWhere         /* Complete WHERE clause */
+){
+  int j, k;            /* Loop counters */
+  int iCur;            /* The VDBE cursor for the table */
+  int addrNxt;         /* Where to jump to continue with the next IN case */
+  int omitTable;       /* True if we use the index only */
+  int bRev;            /* True if we need to scan in reverse order */
+  WhereLevel *pLevel;  /* The where level to be coded */
+  WhereClause *pWC;    /* Decomposition of the entire WHERE clause */
+  WhereTerm *pTerm;               /* A WHERE clause term */
+  Parse *pParse;                  /* Parsing context */
+  Vdbe *v;                        /* The prepared stmt under constructions */
+  struct SrcList_item *pTabItem;  /* FROM clause term being coded */
+  int addrBrk;                    /* Jump here to break out of the loop */
+  int addrCont;                   /* Jump here to continue with next cycle */
+  int iRowidReg = 0;        /* Rowid is stored in this register, if not zero */
+  int iReleaseReg = 0;      /* Temp register to free before returning */
+
+  pParse = pWInfo->pParse;
+  v = pParse->pVdbe;
+  pWC = pWInfo->pWC;
+  pLevel = &pWInfo->a[iLevel];
+  pTabItem = &pWInfo->pTabList->a[pLevel->iFrom];
+  iCur = pTabItem->iCursor;
+  bRev = (pLevel->plan.wsFlags & WHERE_REVERSE)!=0;
+  omitTable = (pLevel->plan.wsFlags & WHERE_IDX_ONLY)!=0 
+           && (wctrlFlags & WHERE_FORCE_TABLE)==0;
+
+  /* Create labels for the "break" and "continue" instructions
+  ** for the current loop.  Jump to addrBrk to break out of a loop.
+  ** Jump to cont to go immediately to the next iteration of the
+  ** loop.
+  **
+  ** When there is an IN operator, we also have a "addrNxt" label that
+  ** means to continue with the next IN value combination.  When
+  ** there are no IN operators in the constraints, the "addrNxt" label
+  ** is the same as "addrBrk".
+  */
+  addrBrk = pLevel->addrBrk = pLevel->addrNxt = sqlite3VdbeMakeLabel(v);
+  addrCont = pLevel->addrCont = sqlite3VdbeMakeLabel(v);
+
+  /* If this is the right table of a LEFT OUTER JOIN, allocate and
+  ** initialize a memory cell that records if this table matches any
+  ** row of the left table of the join.
+  */
+  if( pLevel->iFrom>0 && (pTabItem[0].jointype & JT_LEFT)!=0 ){
+    pLevel->iLeftJoin = ++pParse->nMem;
+    sqlite3VdbeAddOp2(v, OP_Integer, 0, pLevel->iLeftJoin);
+    VdbeComment((v, "init LEFT JOIN no-match flag"));
+  }
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  if(  (pLevel->plan.wsFlags & WHERE_VIRTUALTABLE)!=0 ){
+    /* Case 0:  The table is a virtual-table.  Use the VFilter and VNext
+    **          to access the data.
+    */
+    int iReg;   /* P3 Value for OP_VFilter */
+    sqlite3_index_info *pVtabIdx = pLevel->plan.u.pVtabIdx;
+    int nConstraint = pVtabIdx->nConstraint;
+    struct sqlite3_index_constraint_usage *aUsage =
+                                                pVtabIdx->aConstraintUsage;
+    const struct sqlite3_index_constraint *aConstraint =
+                                                pVtabIdx->aConstraint;
+
+    sqlite3ExprCachePush(pParse);
+    iReg = sqlite3GetTempRange(pParse, nConstraint+2);
+    for(j=1; j<=nConstraint; j++){
+      for(k=0; k<nConstraint; k++){
+        if( aUsage[k].argvIndex==j ){
+          int iTerm = aConstraint[k].iTermOffset;
+          sqlite3ExprCode(pParse, pWC->a[iTerm].pExpr->pRight, iReg+j+1);
+          break;
+        }
+      }
+      if( k==nConstraint ) break;
+    }
+    sqlite3VdbeAddOp2(v, OP_Integer, pVtabIdx->idxNum, iReg);
+    sqlite3VdbeAddOp2(v, OP_Integer, j-1, iReg+1);
+    sqlite3VdbeAddOp4(v, OP_VFilter, iCur, addrBrk, iReg, pVtabIdx->idxStr,
+                      pVtabIdx->needToFreeIdxStr ? P4_MPRINTF : P4_STATIC);
+    pVtabIdx->needToFreeIdxStr = 0;
+    for(j=0; j<nConstraint; j++){
+      if( aUsage[j].omit ){
+        int iTerm = aConstraint[j].iTermOffset;
+        disableTerm(pLevel, &pWC->a[iTerm]);
+      }
+    }
+    pLevel->op = OP_VNext;
+    pLevel->p1 = iCur;
+    pLevel->p2 = sqlite3VdbeCurrentAddr(v);
+    sqlite3ReleaseTempRange(pParse, iReg, nConstraint+2);
+    sqlite3ExprCachePop(pParse, 1);
+  }else
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+  if( pLevel->plan.wsFlags & WHERE_ROWID_EQ ){
+    /* Case 1:  We can directly reference a single row using an
+    **          equality comparison against the ROWID field.  Or
+    **          we reference multiple rows using a "rowid IN (...)"
+    **          construct.
+    */
+    iReleaseReg = sqlite3GetTempReg(pParse);
+    pTerm = findTerm(pWC, iCur, -1, notReady, WO_EQ|WO_IN, 0);
+    assert( pTerm!=0 );
+    assert( pTerm->pExpr!=0 );
+    assert( pTerm->leftCursor==iCur );
+    assert( omitTable==0 );
+    testcase( pTerm->wtFlags & TERM_VIRTUAL ); /* EV: R-30575-11662 */
+    iRowidReg = codeEqualityTerm(pParse, pTerm, pLevel, iReleaseReg);
+    addrNxt = pLevel->addrNxt;
+    sqlite3VdbeAddOp2(v, OP_MustBeInt, iRowidReg, addrNxt);
+    sqlite3VdbeAddOp3(v, OP_NotExists, iCur, addrNxt, iRowidReg);
+    sqlite3ExprCacheStore(pParse, iCur, -1, iRowidReg);
+    VdbeComment((v, "pk"));
+    pLevel->op = OP_Noop;
+  }else if( pLevel->plan.wsFlags & WHERE_ROWID_RANGE ){
+    /* Case 2:  We have an inequality comparison against the ROWID field.
+    */
+    int testOp = OP_Noop;
+    int start;
+    int memEndValue = 0;
+    WhereTerm *pStart, *pEnd;
+
+    assert( omitTable==0 );
+    pStart = findTerm(pWC, iCur, -1, notReady, WO_GT|WO_GE, 0);
+    pEnd = findTerm(pWC, iCur, -1, notReady, WO_LT|WO_LE, 0);
+    if( bRev ){
+      pTerm = pStart;
+      pStart = pEnd;
+      pEnd = pTerm;
+    }
+    if( pStart ){
+      Expr *pX;             /* The expression that defines the start bound */
+      int r1, rTemp;        /* Registers for holding the start boundary */
+
+      /* The following constant maps TK_xx codes into corresponding 
+      ** seek opcodes.  It depends on a particular ordering of TK_xx
+      */
+      const u8 aMoveOp[] = {
+           /* TK_GT */  OP_SeekGt,
+           /* TK_LE */  OP_SeekLe,
+           /* TK_LT */  OP_SeekLt,
+           /* TK_GE */  OP_SeekGe
+      };
+      assert( TK_LE==TK_GT+1 );      /* Make sure the ordering.. */
+      assert( TK_LT==TK_GT+2 );      /*  ... of the TK_xx values... */
+      assert( TK_GE==TK_GT+3 );      /*  ... is correcct. */
+
+      testcase( pStart->wtFlags & TERM_VIRTUAL ); /* EV: R-30575-11662 */
+      pX = pStart->pExpr;
+      assert( pX!=0 );
+      assert( pStart->leftCursor==iCur );
+      r1 = sqlite3ExprCodeTemp(pParse, pX->pRight, &rTemp);
+      sqlite3VdbeAddOp3(v, aMoveOp[pX->op-TK_GT], iCur, addrBrk, r1);
+      VdbeComment((v, "pk"));
+      sqlite3ExprCacheAffinityChange(pParse, r1, 1);
+      sqlite3ReleaseTempReg(pParse, rTemp);
+      disableTerm(pLevel, pStart);
+    }else{
+      sqlite3VdbeAddOp2(v, bRev ? OP_Last : OP_Rewind, iCur, addrBrk);
+    }
+    if( pEnd ){
+      Expr *pX;
+      pX = pEnd->pExpr;
+      assert( pX!=0 );
+      assert( pEnd->leftCursor==iCur );
+      testcase( pEnd->wtFlags & TERM_VIRTUAL ); /* EV: R-30575-11662 */
+      memEndValue = ++pParse->nMem;
+      sqlite3ExprCode(pParse, pX->pRight, memEndValue);
+      if( pX->op==TK_LT || pX->op==TK_GT ){
+        testOp = bRev ? OP_Le : OP_Ge;
+      }else{
+        testOp = bRev ? OP_Lt : OP_Gt;
+      }
+      disableTerm(pLevel, pEnd);
+    }
+    start = sqlite3VdbeCurrentAddr(v);
+    pLevel->op = bRev ? OP_Prev : OP_Next;
+    pLevel->p1 = iCur;
+    pLevel->p2 = start;
+    if( pStart==0 && pEnd==0 ){
+      pLevel->p5 = SQLITE_STMTSTATUS_FULLSCAN_STEP;
+    }else{
+      assert( pLevel->p5==0 );
+    }
+    if( testOp!=OP_Noop ){
+      iRowidReg = iReleaseReg = sqlite3GetTempReg(pParse);
+      sqlite3VdbeAddOp2(v, OP_Rowid, iCur, iRowidReg);
+      sqlite3ExprCacheStore(pParse, iCur, -1, iRowidReg);
+      sqlite3VdbeAddOp3(v, testOp, memEndValue, addrBrk, iRowidReg);
+      sqlite3VdbeChangeP5(v, SQLITE_AFF_NUMERIC | SQLITE_JUMPIFNULL);
+    }
+  }else if( pLevel->plan.wsFlags & (WHERE_COLUMN_RANGE|WHERE_COLUMN_EQ) ){
+    /* Case 3: A scan using an index.
+    **
+    **         The WHERE clause may contain zero or more equality 
+    **         terms ("==" or "IN" operators) that refer to the N
+    **         left-most columns of the index. It may also contain
+    **         inequality constraints (>, <, >= or <=) on the indexed
+    **         column that immediately follows the N equalities. Only 
+    **         the right-most column can be an inequality - the rest must
+    **         use the "==" and "IN" operators. For example, if the 
+    **         index is on (x,y,z), then the following clauses are all 
+    **         optimized:
+    **
+    **            x=5
+    **            x=5 AND y=10
+    **            x=5 AND y<10
+    **            x=5 AND y>5 AND y<10
+    **            x=5 AND y=5 AND z<=10
+    **
+    **         The z<10 term of the following cannot be used, only
+    **         the x=5 term:
+    **
+    **            x=5 AND z<10
+    **
+    **         N may be zero if there are inequality constraints.
+    **         If there are no inequality constraints, then N is at
+    **         least one.
+    **
+    **         This case is also used when there are no WHERE clause
+    **         constraints but an index is selected anyway, in order
+    **         to force the output order to conform to an ORDER BY.
+    */  
+    static const u8 aStartOp[] = {
+      0,
+      0,
+      OP_Rewind,           /* 2: (!start_constraints && startEq &&  !bRev) */
+      OP_Last,             /* 3: (!start_constraints && startEq &&   bRev) */
+      OP_SeekGt,           /* 4: (start_constraints  && !startEq && !bRev) */
+      OP_SeekLt,           /* 5: (start_constraints  && !startEq &&  bRev) */
+      OP_SeekGe,           /* 6: (start_constraints  &&  startEq && !bRev) */
+      OP_SeekLe            /* 7: (start_constraints  &&  startEq &&  bRev) */
+    };
+    static const u8 aEndOp[] = {
+      OP_Noop,             /* 0: (!end_constraints) */
+      OP_IdxGE,            /* 1: (end_constraints && !bRev) */
+      OP_IdxLT             /* 2: (end_constraints && bRev) */
+    };
+    int nEq = pLevel->plan.nEq;  /* Number of == or IN terms */
+    int isMinQuery = 0;          /* If this is an optimized SELECT min(x).. */
+    int regBase;                 /* Base register holding constraint values */
+    int r1;                      /* Temp register */
+    WhereTerm *pRangeStart = 0;  /* Inequality constraint at range start */
+    WhereTerm *pRangeEnd = 0;    /* Inequality constraint at range end */
+    int startEq;                 /* True if range start uses ==, >= or <= */
+    int endEq;                   /* True if range end uses ==, >= or <= */
+    int start_constraints;       /* Start of range is constrained */
+    int nConstraint;             /* Number of constraint terms */
+    Index *pIdx;                 /* The index we will be using */
+    int iIdxCur;                 /* The VDBE cursor for the index */
+    int nExtraReg = 0;           /* Number of extra registers needed */
+    int op;                      /* Instruction opcode */
+    char *zStartAff;             /* Affinity for start of range constraint */
+    char *zEndAff;               /* Affinity for end of range constraint */
+
+    pIdx = pLevel->plan.u.pIdx;
+    iIdxCur = pLevel->iIdxCur;
+    k = pIdx->aiColumn[nEq];     /* Column for inequality constraints */
+
+    /* If this loop satisfies a sort order (pOrderBy) request that 
+    ** was passed to this function to implement a "SELECT min(x) ..." 
+    ** query, then the caller will only allow the loop to run for
+    ** a single iteration. This means that the first row returned
+    ** should not have a NULL value stored in 'x'. If column 'x' is
+    ** the first one after the nEq equality constraints in the index,
+    ** this requires some special handling.
+    */
+    if( (wctrlFlags&WHERE_ORDERBY_MIN)!=0
+     && (pLevel->plan.wsFlags&WHERE_ORDERBY)
+     && (pIdx->nColumn>nEq)
+    ){
+      /* assert( pOrderBy->nExpr==1 ); */
+      /* assert( pOrderBy->a[0].pExpr->iColumn==pIdx->aiColumn[nEq] ); */
+      isMinQuery = 1;
+      nExtraReg = 1;
+    }
+
+    /* Find any inequality constraint terms for the start and end 
+    ** of the range. 
+    */
+    if( pLevel->plan.wsFlags & WHERE_TOP_LIMIT ){
+      pRangeEnd = findTerm(pWC, iCur, k, notReady, (WO_LT|WO_LE), pIdx);
+      nExtraReg = 1;
+    }
+    if( pLevel->plan.wsFlags & WHERE_BTM_LIMIT ){
+      pRangeStart = findTerm(pWC, iCur, k, notReady, (WO_GT|WO_GE), pIdx);
+      nExtraReg = 1;
+    }
+
+    /* Generate code to evaluate all constraint terms using == or IN
+    ** and store the values of those terms in an array of registers
+    ** starting at regBase.
+    */
+    regBase = codeAllEqualityTerms(
+        pParse, pLevel, pWC, notReady, nExtraReg, &zStartAff
+    );
+    zEndAff = sqlite3DbStrDup(pParse->db, zStartAff);
+    addrNxt = pLevel->addrNxt;
+
+    /* If we are doing a reverse order scan on an ascending index, or
+    ** a forward order scan on a descending index, interchange the 
+    ** start and end terms (pRangeStart and pRangeEnd).
+    */
+    if( nEq<pIdx->nColumn && bRev==(pIdx->aSortOrder[nEq]==SQLITE_SO_ASC) ){
+      SWAP(WhereTerm *, pRangeEnd, pRangeStart);
+    }
+
+    testcase( pRangeStart && pRangeStart->eOperator & WO_LE );
+    testcase( pRangeStart && pRangeStart->eOperator & WO_GE );
+    testcase( pRangeEnd && pRangeEnd->eOperator & WO_LE );
+    testcase( pRangeEnd && pRangeEnd->eOperator & WO_GE );
+    startEq = !pRangeStart || pRangeStart->eOperator & (WO_LE|WO_GE);
+    endEq =   !pRangeEnd || pRangeEnd->eOperator & (WO_LE|WO_GE);
+    start_constraints = pRangeStart || nEq>0;
+
+    /* Seek the index cursor to the start of the range. */
+    nConstraint = nEq;
+    if( pRangeStart ){
+      Expr *pRight = pRangeStart->pExpr->pRight;
+      sqlite3ExprCode(pParse, pRight, regBase+nEq);
+      if( (pRangeStart->wtFlags & TERM_VNULL)==0 ){
+        sqlite3ExprCodeIsNullJump(v, pRight, regBase+nEq, addrNxt);
+      }
+      if( zStartAff ){
+        if( sqlite3CompareAffinity(pRight, zStartAff[nEq])==SQLITE_AFF_NONE){
+          /* Since the comparison is to be performed with no conversions
+          ** applied to the operands, set the affinity to apply to pRight to 
+          ** SQLITE_AFF_NONE.  */
+          zStartAff[nEq] = SQLITE_AFF_NONE;
+        }
+        if( sqlite3ExprNeedsNoAffinityChange(pRight, zStartAff[nEq]) ){
+          zStartAff[nEq] = SQLITE_AFF_NONE;
+        }
+      }  
+      nConstraint++;
+      testcase( pRangeStart->wtFlags & TERM_VIRTUAL ); /* EV: R-30575-11662 */
+    }else if( isMinQuery ){
+      sqlite3VdbeAddOp2(v, OP_Null, 0, regBase+nEq);
+      nConstraint++;
+      startEq = 0;
+      start_constraints = 1;
+    }
+    codeApplyAffinity(pParse, regBase, nConstraint, zStartAff);
+    op = aStartOp[(start_constraints<<2) + (startEq<<1) + bRev];
+    assert( op!=0 );
+    testcase( op==OP_Rewind );
+    testcase( op==OP_Last );
+    testcase( op==OP_SeekGt );
+    testcase( op==OP_SeekGe );
+    testcase( op==OP_SeekLe );
+    testcase( op==OP_SeekLt );
+    sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint);
+
+    /* Load the value for the inequality constraint at the end of the
+    ** range (if any).
+    */
+    nConstraint = nEq;
+    if( pRangeEnd ){
+      Expr *pRight = pRangeEnd->pExpr->pRight;
+      sqlite3ExprCacheRemove(pParse, regBase+nEq, 1);
+      sqlite3ExprCode(pParse, pRight, regBase+nEq);
+      if( (pRangeEnd->wtFlags & TERM_VNULL)==0 ){
+        sqlite3ExprCodeIsNullJump(v, pRight, regBase+nEq, addrNxt);
+      }
+      if( zEndAff ){
+        if( sqlite3CompareAffinity(pRight, zEndAff[nEq])==SQLITE_AFF_NONE){
+          /* Since the comparison is to be performed with no conversions
+          ** applied to the operands, set the affinity to apply to pRight to 
+          ** SQLITE_AFF_NONE.  */
+          zEndAff[nEq] = SQLITE_AFF_NONE;
+        }
+        if( sqlite3ExprNeedsNoAffinityChange(pRight, zEndAff[nEq]) ){
+          zEndAff[nEq] = SQLITE_AFF_NONE;
+        }
+      }  
+      codeApplyAffinity(pParse, regBase, nEq+1, zEndAff);
+      nConstraint++;
+      testcase( pRangeEnd->wtFlags & TERM_VIRTUAL ); /* EV: R-30575-11662 */
+    }
+    sqlite3DbFree(pParse->db, zStartAff);
+    sqlite3DbFree(pParse->db, zEndAff);
+
+    /* Top of the loop body */
+    pLevel->p2 = sqlite3VdbeCurrentAddr(v);
+
+    /* Check if the index cursor is past the end of the range. */
+    op = aEndOp[(pRangeEnd || nEq) * (1 + bRev)];
+    testcase( op==OP_Noop );
+    testcase( op==OP_IdxGE );
+    testcase( op==OP_IdxLT );
+    if( op!=OP_Noop ){
+      sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint);
+      sqlite3VdbeChangeP5(v, endEq!=bRev ?1:0);
+    }
+
+    /* If there are inequality constraints, check that the value
+    ** of the table column that the inequality contrains is not NULL.
+    ** If it is, jump to the next iteration of the loop.
+    */
+    r1 = sqlite3GetTempReg(pParse);
+    testcase( pLevel->plan.wsFlags & WHERE_BTM_LIMIT );
+    testcase( pLevel->plan.wsFlags & WHERE_TOP_LIMIT );
+    if( (pLevel->plan.wsFlags & (WHERE_BTM_LIMIT|WHERE_TOP_LIMIT))!=0 ){
+      sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, nEq, r1);
+      sqlite3VdbeAddOp2(v, OP_IsNull, r1, addrCont);
+    }
+    sqlite3ReleaseTempReg(pParse, r1);
+
+    /* Seek the table cursor, if required */
+    disableTerm(pLevel, pRangeStart);
+    disableTerm(pLevel, pRangeEnd);
+    if( !omitTable ){
+      iRowidReg = iReleaseReg = sqlite3GetTempReg(pParse);
+      sqlite3VdbeAddOp2(v, OP_IdxRowid, iIdxCur, iRowidReg);
+      sqlite3ExprCacheStore(pParse, iCur, -1, iRowidReg);
+      sqlite3VdbeAddOp2(v, OP_Seek, iCur, iRowidReg);  /* Deferred seek */
+    }
+
+    /* Record the instruction used to terminate the loop. Disable 
+    ** WHERE clause terms made redundant by the index range scan.
+    */
+    if( pLevel->plan.wsFlags & WHERE_UNIQUE ){
+      pLevel->op = OP_Noop;
+    }else if( bRev ){
+      pLevel->op = OP_Prev;
+    }else{
+      pLevel->op = OP_Next;
+    }
+    pLevel->p1 = iIdxCur;
+  }else
+
+#ifndef SQLITE_OMIT_OR_OPTIMIZATION
+  if( pLevel->plan.wsFlags & WHERE_MULTI_OR ){
+    /* Case 4:  Two or more separately indexed terms connected by OR
+    **
+    ** Example:
+    **
+    **   CREATE TABLE t1(a,b,c,d);
+    **   CREATE INDEX i1 ON t1(a);
+    **   CREATE INDEX i2 ON t1(b);
+    **   CREATE INDEX i3 ON t1(c);
+    **
+    **   SELECT * FROM t1 WHERE a=5 OR b=7 OR (c=11 AND d=13)
+    **
+    ** In the example, there are three indexed terms connected by OR.
+    ** The top of the loop looks like this:
+    **
+    **          Null       1                # Zero the rowset in reg 1
+    **
+    ** Then, for each indexed term, the following. The arguments to
+    ** RowSetTest are such that the rowid of the current row is inserted
+    ** into the RowSet. If it is already present, control skips the
+    ** Gosub opcode and jumps straight to the code generated by WhereEnd().
+    **
+    **        sqlite3WhereBegin(<term>)
+    **          RowSetTest                  # Insert rowid into rowset
+    **          Gosub      2 A
+    **        sqlite3WhereEnd()
+    **
+    ** Following the above, code to terminate the loop. Label A, the target
+    ** of the Gosub above, jumps to the instruction right after the Goto.
+    **
+    **          Null       1                # Zero the rowset in reg 1
+    **          Goto       B                # The loop is finished.
+    **
+    **       A: <loop body>                 # Return data, whatever.
+    **
+    **          Return     2                # Jump back to the Gosub
+    **
+    **       B: <after the loop>
+    **
+    */
+    WhereClause *pOrWc;    /* The OR-clause broken out into subterms */
+    SrcList *pOrTab;       /* Shortened table list or OR-clause generation */
+
+    int regReturn = ++pParse->nMem;           /* Register used with OP_Gosub */
+    int regRowset = 0;                        /* Register for RowSet object */
+    int regRowid = 0;                         /* Register holding rowid */
+    int iLoopBody = sqlite3VdbeMakeLabel(v);  /* Start of loop body */
+    int iRetInit;                             /* Address of regReturn init */
+    int untestedTerms = 0;             /* Some terms not completely tested */
+    int ii;                            /* Loop counter */
+    Expr *pAndExpr = 0;                /* An ".. AND (...)" expression */
+   
+    pTerm = pLevel->plan.u.pTerm;
+    assert( pTerm!=0 );
+    assert( pTerm->eOperator==WO_OR );
+    assert( (pTerm->wtFlags & TERM_ORINFO)!=0 );
+    pOrWc = &pTerm->u.pOrInfo->wc;
+    pLevel->op = OP_Return;
+    pLevel->p1 = regReturn;
+
+    /* Set up a new SrcList ni pOrTab containing the table being scanned
+    ** by this loop in the a[0] slot and all notReady tables in a[1..] slots.
+    ** This becomes the SrcList in the recursive call to sqlite3WhereBegin().
+    */
+    if( pWInfo->nLevel>1 ){
+      int nNotReady;                 /* The number of notReady tables */
+      struct SrcList_item *origSrc;     /* Original list of tables */
+      nNotReady = pWInfo->nLevel - iLevel - 1;
+      pOrTab = sqlite3StackAllocRaw(pParse->db,
+                            sizeof(*pOrTab)+ nNotReady*sizeof(pOrTab->a[0]));
+      if( pOrTab==0 ) return notReady;
+      pOrTab->nAlloc = (i16)(nNotReady + 1);
+      pOrTab->nSrc = pOrTab->nAlloc;
+      memcpy(pOrTab->a, pTabItem, sizeof(*pTabItem));
+      origSrc = pWInfo->pTabList->a;
+      for(k=1; k<=nNotReady; k++){
+        memcpy(&pOrTab->a[k], &origSrc[pLevel[k].iFrom], sizeof(pOrTab->a[k]));
+      }
+    }else{
+      pOrTab = pWInfo->pTabList;
+    }
+
+    /* Initialize the rowset register to contain NULL. An SQL NULL is 
+    ** equivalent to an empty rowset.
+    **
+    ** Also initialize regReturn to contain the address of the instruction 
+    ** immediately following the OP_Return at the bottom of the loop. This
+    ** is required in a few obscure LEFT JOIN cases where control jumps
+    ** over the top of the loop into the body of it. In this case the 
+    ** correct response for the end-of-loop code (the OP_Return) is to 
+    ** fall through to the next instruction, just as an OP_Next does if
+    ** called on an uninitialized cursor.
+    */
+    if( (wctrlFlags & WHERE_DUPLICATES_OK)==0 ){
+      regRowset = ++pParse->nMem;
+      regRowid = ++pParse->nMem;
+      sqlite3VdbeAddOp2(v, OP_Null, 0, regRowset);
+    }
+    iRetInit = sqlite3VdbeAddOp2(v, OP_Integer, 0, regReturn);
+
+    /* If the original WHERE clause is z of the form:  (x1 OR x2 OR ...) AND y
+    ** Then for every term xN, evaluate as the subexpression: xN AND z
+    ** That way, terms in y that are factored into the disjunction will
+    ** be picked up by the recursive calls to sqlite3WhereBegin() below.
+    */
+    if( pWC->nTerm>1 ){
+      pAndExpr = sqlite3ExprAlloc(pParse->db, TK_AND, 0, 0);
+      pAndExpr->pRight = pWhere;
+    }
+
+    for(ii=0; ii<pOrWc->nTerm; ii++){
+      WhereTerm *pOrTerm = &pOrWc->a[ii];
+      if( pOrTerm->leftCursor==iCur || pOrTerm->eOperator==WO_AND ){
+        WhereInfo *pSubWInfo;          /* Info for single OR-term scan */
+        Expr *pOrExpr = pOrTerm->pExpr;
+        if( pAndExpr ){
+          pAndExpr->pLeft = pOrExpr;
+          pOrExpr = pAndExpr;
+        }
+        /* Loop through table entries that match term pOrTerm. */
+        pSubWInfo = sqlite3WhereBegin(pParse, pOrTab, pOrExpr, 0, 0,
+                        WHERE_OMIT_OPEN_CLOSE | WHERE_AND_ONLY |
+                        WHERE_FORCE_TABLE | WHERE_ONETABLE_ONLY);
+        if( pSubWInfo ){
+          explainOneScan(
+              pParse, pOrTab, &pSubWInfo->a[0], iLevel, pLevel->iFrom, 0
+          );
+          if( (wctrlFlags & WHERE_DUPLICATES_OK)==0 ){
+            int iSet = ((ii==pOrWc->nTerm-1)?-1:ii);
+            int r;
+            r = sqlite3ExprCodeGetColumn(pParse, pTabItem->pTab, -1, iCur, 
+                                         regRowid);
+            sqlite3VdbeAddOp4Int(v, OP_RowSetTest, regRowset,
+                                 sqlite3VdbeCurrentAddr(v)+2, r, iSet);
+          }
+          sqlite3VdbeAddOp2(v, OP_Gosub, regReturn, iLoopBody);
+
+          /* The pSubWInfo->untestedTerms flag means that this OR term
+          ** contained one or more AND term from a notReady table.  The
+          ** terms from the notReady table could not be tested and will
+          ** need to be tested later.
+          */
+          if( pSubWInfo->untestedTerms ) untestedTerms = 1;
+
+          /* Finish the loop through table entries that match term pOrTerm. */
+          sqlite3WhereEnd(pSubWInfo);
+        }
+      }
+    }
+    sqlite3DbFree(pParse->db, pAndExpr);
+    sqlite3VdbeChangeP1(v, iRetInit, sqlite3VdbeCurrentAddr(v));
+    sqlite3VdbeAddOp2(v, OP_Goto, 0, pLevel->addrBrk);
+    sqlite3VdbeResolveLabel(v, iLoopBody);
+
+    if( pWInfo->nLevel>1 ) sqlite3StackFree(pParse->db, pOrTab);
+    if( !untestedTerms ) disableTerm(pLevel, pTerm);
+  }else
+#endif /* SQLITE_OMIT_OR_OPTIMIZATION */
+
+  {
+    /* Case 5:  There is no usable index.  We must do a complete
+    **          scan of the entire table.
+    */
+    static const u8 aStep[] = { OP_Next, OP_Prev };
+    static const u8 aStart[] = { OP_Rewind, OP_Last };
+    assert( bRev==0 || bRev==1 );
+    assert( omitTable==0 );
+    pLevel->op = aStep[bRev];
+    pLevel->p1 = iCur;
+    pLevel->p2 = 1 + sqlite3VdbeAddOp2(v, aStart[bRev], iCur, addrBrk);
+    pLevel->p5 = SQLITE_STMTSTATUS_FULLSCAN_STEP;
+  }
+  notReady &= ~getMask(pWC->pMaskSet, iCur);
+
+  /* Insert code to test every subexpression that can be completely
+  ** computed using the current set of tables.
+  **
+  ** IMPLEMENTATION-OF: R-49525-50935 Terms that cannot be satisfied through
+  ** the use of indices become tests that are evaluated against each row of
+  ** the relevant input tables.
+  */
+  for(pTerm=pWC->a, j=pWC->nTerm; j>0; j--, pTerm++){
+    Expr *pE;
+    testcase( pTerm->wtFlags & TERM_VIRTUAL ); /* IMP: R-30575-11662 */
+    testcase( pTerm->wtFlags & TERM_CODED );
+    if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
+    if( (pTerm->prereqAll & notReady)!=0 ){
+      testcase( pWInfo->untestedTerms==0
+               && (pWInfo->wctrlFlags & WHERE_ONETABLE_ONLY)!=0 );
+      pWInfo->untestedTerms = 1;
+      continue;
+    }
+    pE = pTerm->pExpr;
+    assert( pE!=0 );
+    if( pLevel->iLeftJoin && !ExprHasProperty(pE, EP_FromJoin) ){
+      continue;
+    }
+    sqlite3ExprIfFalse(pParse, pE, addrCont, SQLITE_JUMPIFNULL);
+    pTerm->wtFlags |= TERM_CODED;
+  }
+
+  /* For a LEFT OUTER JOIN, generate code that will record the fact that
+  ** at least one row of the right table has matched the left table.  
+  */
+  if( pLevel->iLeftJoin ){
+    pLevel->addrFirst = sqlite3VdbeCurrentAddr(v);
+    sqlite3VdbeAddOp2(v, OP_Integer, 1, pLevel->iLeftJoin);
+    VdbeComment((v, "record LEFT JOIN hit"));
+    sqlite3ExprCacheClear(pParse);
+    for(pTerm=pWC->a, j=0; j<pWC->nTerm; j++, pTerm++){
+      testcase( pTerm->wtFlags & TERM_VIRTUAL );  /* IMP: R-30575-11662 */
+      testcase( pTerm->wtFlags & TERM_CODED );
+      if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
+      if( (pTerm->prereqAll & notReady)!=0 ){
+        assert( pWInfo->untestedTerms );
+        continue;
+      }
+      assert( pTerm->pExpr );
+      sqlite3ExprIfFalse(pParse, pTerm->pExpr, addrCont, SQLITE_JUMPIFNULL);
+      pTerm->wtFlags |= TERM_CODED;
+    }
+  }
+  sqlite3ReleaseTempReg(pParse, iReleaseReg);
+
+  return notReady;
+}
+
+#if defined(SQLITE_TEST)
+/*
+** The following variable holds a text description of query plan generated
+** by the most recent call to sqlite3WhereBegin().  Each call to WhereBegin
+** overwrites the previous.  This information is used for testing and
+** analysis only.
+*/
+char sqlite3_query_plan[BMS*2*40];  /* Text of the join */
+static int nQPlan = 0;              /* Next free slow in _query_plan[] */
+
+#endif /* SQLITE_TEST */
+
+
+/*
+** Free a WhereInfo structure
+*/
+static void whereInfoFree(sqlite3 *db, WhereInfo *pWInfo){
+  if( ALWAYS(pWInfo) ){
+    int i;
+    for(i=0; i<pWInfo->nLevel; i++){
+      sqlite3_index_info *pInfo = pWInfo->a[i].pIdxInfo;
+      if( pInfo ){
+        /* assert( pInfo->needToFreeIdxStr==0 || db->mallocFailed ); */
+        if( pInfo->needToFreeIdxStr ){
+          sqlite3_free(pInfo->idxStr);
+        }
+        sqlite3DbFree(db, pInfo);
+      }
+      if( pWInfo->a[i].plan.wsFlags & WHERE_TEMP_INDEX ){
+        Index *pIdx = pWInfo->a[i].plan.u.pIdx;
+        if( pIdx ){
+          sqlite3DbFree(db, pIdx->zColAff);
+          sqlite3DbFree(db, pIdx);
+        }
+      }
+    }
+    whereClauseClear(pWInfo->pWC);
+    sqlite3DbFree(db, pWInfo);
+  }
+}
+
+
+/*
+** Generate the beginning of the loop used for WHERE clause processing.
+** The return value is a pointer to an opaque structure that contains
+** information needed to terminate the loop.  Later, the calling routine
+** should invoke sqlite3WhereEnd() with the return value of this function
+** in order to complete the WHERE clause processing.
+**
+** If an error occurs, this routine returns NULL.
+**
+** The basic idea is to do a nested loop, one loop for each table in
+** the FROM clause of a select.  (INSERT and UPDATE statements are the
+** same as a SELECT with only a single table in the FROM clause.)  For
+** example, if the SQL is this:
+**
+**       SELECT * FROM t1, t2, t3 WHERE ...;
+**
+** Then the code generated is conceptually like the following:
+**
+**      foreach row1 in t1 do       \    Code generated
+**        foreach row2 in t2 do      |-- by sqlite3WhereBegin()
+**          foreach row3 in t3 do   /
+**            ...
+**          end                     \    Code generated
+**        end                        |-- by sqlite3WhereEnd()
+**      end                         /
+**
+** Note that the loops might not be nested in the order in which they
+** appear in the FROM clause if a different order is better able to make
+** use of indices.  Note also that when the IN operator appears in
+** the WHERE clause, it might result in additional nested loops for
+** scanning through all values on the right-hand side of the IN.
+**
+** There are Btree cursors associated with each table.  t1 uses cursor
+** number pTabList->a[0].iCursor.  t2 uses the cursor pTabList->a[1].iCursor.
+** And so forth.  This routine generates code to open those VDBE cursors
+** and sqlite3WhereEnd() generates the code to close them.
+**
+** The code that sqlite3WhereBegin() generates leaves the cursors named
+** in pTabList pointing at their appropriate entries.  The [...] code
+** can use OP_Column and OP_Rowid opcodes on these cursors to extract
+** data from the various tables of the loop.
+**
+** If the WHERE clause is empty, the foreach loops must each scan their
+** entire tables.  Thus a three-way join is an O(N^3) operation.  But if
+** the tables have indices and there are terms in the WHERE clause that
+** refer to those indices, a complete table scan can be avoided and the
+** code will run much faster.  Most of the work of this routine is checking
+** to see if there are indices that can be used to speed up the loop.
+**
+** Terms of the WHERE clause are also used to limit which rows actually
+** make it to the "..." in the middle of the loop.  After each "foreach",
+** terms of the WHERE clause that use only terms in that loop and outer
+** loops are evaluated and if false a jump is made around all subsequent
+** inner loops (or around the "..." if the test occurs within the inner-
+** most loop)
+**
+** OUTER JOINS
+**
+** An outer join of tables t1 and t2 is conceptally coded as follows:
+**
+**    foreach row1 in t1 do
+**      flag = 0
+**      foreach row2 in t2 do
+**        start:
+**          ...
+**          flag = 1
+**      end
+**      if flag==0 then
+**        move the row2 cursor to a null row
+**        goto start
+**      fi
+**    end
+**
+** ORDER BY CLAUSE PROCESSING
+**
+** *ppOrderBy is a pointer to the ORDER BY clause of a SELECT statement,
+** if there is one.  If there is no ORDER BY clause or if this routine
+** is called from an UPDATE or DELETE statement, then ppOrderBy is NULL.
+**
+** If an index can be used so that the natural output order of the table
+** scan is correct for the ORDER BY clause, then that index is used and
+** *ppOrderBy is set to NULL.  This is an optimization that prevents an
+** unnecessary sort of the result set if an index appropriate for the
+** ORDER BY clause already exists.
+**
+** If the where clause loops cannot be arranged to provide the correct
+** output order, then the *ppOrderBy is unchanged.
+*/
+WhereInfo *sqlite3WhereBegin(
+  Parse *pParse,        /* The parser context */
+  SrcList *pTabList,    /* A list of all tables to be scanned */
+  Expr *pWhere,         /* The WHERE clause */
+  ExprList **ppOrderBy, /* An ORDER BY clause, or NULL */
+  ExprList *pDistinct,  /* The select-list for DISTINCT queries - or NULL */
+  u16 wctrlFlags        /* One of the WHERE_* flags defined in sqliteInt.h */
+){
+  int i;                     /* Loop counter */
+  int nByteWInfo;            /* Num. bytes allocated for WhereInfo struct */
+  int nTabList;              /* Number of elements in pTabList */
+  WhereInfo *pWInfo;         /* Will become the return value of this function */
+  Vdbe *v = pParse->pVdbe;   /* The virtual database engine */
+  Bitmask notReady;          /* Cursors that are not yet positioned */
+  WhereMaskSet *pMaskSet;    /* The expression mask set */
+  WhereClause *pWC;               /* Decomposition of the WHERE clause */
+  struct SrcList_item *pTabItem;  /* A single entry from pTabList */
+  WhereLevel *pLevel;             /* A single level in the pWInfo list */
+  int iFrom;                      /* First unused FROM clause element */
+  int andFlags;              /* AND-ed combination of all pWC->a[].wtFlags */
+  sqlite3 *db;               /* Database connection */
+
+  /* The number of tables in the FROM clause is limited by the number of
+  ** bits in a Bitmask 
+  */
+  testcase( pTabList->nSrc==BMS );
+  if( pTabList->nSrc>BMS ){
+    sqlite3ErrorMsg(pParse, "at most %d tables in a join", BMS);
+    return 0;
+  }
+
+  /* This function normally generates a nested loop for all tables in 
+  ** pTabList.  But if the WHERE_ONETABLE_ONLY flag is set, then we should
+  ** only generate code for the first table in pTabList and assume that
+  ** any cursors associated with subsequent tables are uninitialized.
+  */
+  nTabList = (wctrlFlags & WHERE_ONETABLE_ONLY) ? 1 : pTabList->nSrc;
+
+  /* Allocate and initialize the WhereInfo structure that will become the
+  ** return value. A single allocation is used to store the WhereInfo
+  ** struct, the contents of WhereInfo.a[], the WhereClause structure
+  ** and the WhereMaskSet structure. Since WhereClause contains an 8-byte
+  ** field (type Bitmask) it must be aligned on an 8-byte boundary on
+  ** some architectures. Hence the ROUND8() below.
+  */
+  db = pParse->db;
+  nByteWInfo = ROUND8(sizeof(WhereInfo)+(nTabList-1)*sizeof(WhereLevel));
+  pWInfo = sqlite3DbMallocZero(db, 
+      nByteWInfo + 
+      sizeof(WhereClause) +
+      sizeof(WhereMaskSet)
+  );
+  if( db->mallocFailed ){
+    sqlite3DbFree(db, pWInfo);
+    pWInfo = 0;
+    goto whereBeginError;
+  }
+  pWInfo->nLevel = nTabList;
+  pWInfo->pParse = pParse;
+  pWInfo->pTabList = pTabList;
+  pWInfo->iBreak = sqlite3VdbeMakeLabel(v);
+  pWInfo->pWC = pWC = (WhereClause *)&((u8 *)pWInfo)[nByteWInfo];
+  pWInfo->wctrlFlags = wctrlFlags;
+  pWInfo->savedNQueryLoop = pParse->nQueryLoop;
+  pMaskSet = (WhereMaskSet*)&pWC[1];
+
+  /* Disable the DISTINCT optimization if SQLITE_DistinctOpt is set via
+  ** sqlite3_test_ctrl(SQLITE_TESTCTRL_OPTIMIZATIONS,...) */
+  if( db->flags & SQLITE_DistinctOpt ) pDistinct = 0;
+
+  /* Split the WHERE clause into separate subexpressions where each
+  ** subexpression is separated by an AND operator.
+  */
+  initMaskSet(pMaskSet);
+  whereClauseInit(pWC, pParse, pMaskSet, wctrlFlags);
+  sqlite3ExprCodeConstants(pParse, pWhere);
+  whereSplit(pWC, pWhere, TK_AND);   /* IMP: R-15842-53296 */
+    
+  /* Special case: a WHERE clause that is constant.  Evaluate the
+  ** expression and either jump over all of the code or fall thru.
+  */
+  if( pWhere && (nTabList==0 || sqlite3ExprIsConstantNotJoin(pWhere)) ){
+    sqlite3ExprIfFalse(pParse, pWhere, pWInfo->iBreak, SQLITE_JUMPIFNULL);
+    pWhere = 0;
+  }
+
+  /* Assign a bit from the bitmask to every term in the FROM clause.
+  **
+  ** When assigning bitmask values to FROM clause cursors, it must be
+  ** the case that if X is the bitmask for the N-th FROM clause term then
+  ** the bitmask for all FROM clause terms to the left of the N-th term
+  ** is (X-1).   An expression from the ON clause of a LEFT JOIN can use
+  ** its Expr.iRightJoinTable value to find the bitmask of the right table
+  ** of the join.  Subtracting one from the right table bitmask gives a
+  ** bitmask for all tables to the left of the join.  Knowing the bitmask
+  ** for all tables to the left of a left join is important.  Ticket #3015.
+  **
+  ** Configure the WhereClause.vmask variable so that bits that correspond
+  ** to virtual table cursors are set. This is used to selectively disable 
+  ** the OR-to-IN transformation in exprAnalyzeOrTerm(). It is not helpful 
+  ** with virtual tables.
+  **
+  ** Note that bitmasks are created for all pTabList->nSrc tables in
+  ** pTabList, not just the first nTabList tables.  nTabList is normally
+  ** equal to pTabList->nSrc but might be shortened to 1 if the
+  ** WHERE_ONETABLE_ONLY flag is set.
+  */
+  assert( pWC->vmask==0 && pMaskSet->n==0 );
+  for(i=0; i<pTabList->nSrc; i++){
+    createMask(pMaskSet, pTabList->a[i].iCursor);
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+    if( ALWAYS(pTabList->a[i].pTab) && IsVirtual(pTabList->a[i].pTab) ){
+      pWC->vmask |= ((Bitmask)1 << i);
+    }
+#endif
+  }
+#ifndef NDEBUG
+  {
+    Bitmask toTheLeft = 0;
+    for(i=0; i<pTabList->nSrc; i++){
+      Bitmask m = getMask(pMaskSet, pTabList->a[i].iCursor);
+      assert( (m-1)==toTheLeft );
+      toTheLeft |= m;
+    }
+  }
+#endif
+
+  /* Analyze all of the subexpressions.  Note that exprAnalyze() might
+  ** add new virtual terms onto the end of the WHERE clause.  We do not
+  ** want to analyze these virtual terms, so start analyzing at the end
+  ** and work forward so that the added virtual terms are never processed.
+  */
+  exprAnalyzeAll(pTabList, pWC);
+  if( db->mallocFailed ){
+    goto whereBeginError;
+  }
+
+  /* Check if the DISTINCT qualifier, if there is one, is redundant. 
+  ** If it is, then set pDistinct to NULL and WhereInfo.eDistinct to
+  ** WHERE_DISTINCT_UNIQUE to tell the caller to ignore the DISTINCT.
+  */
+  if( pDistinct && isDistinctRedundant(pParse, pTabList, pWC, pDistinct) ){
+    pDistinct = 0;
+    pWInfo->eDistinct = WHERE_DISTINCT_UNIQUE;
+  }
+
+  /* Chose the best index to use for each table in the FROM clause.
+  **
+  ** This loop fills in the following fields:
+  **
+  **   pWInfo->a[].pIdx      The index to use for this level of the loop.
+  **   pWInfo->a[].wsFlags   WHERE_xxx flags associated with pIdx
+  **   pWInfo->a[].nEq       The number of == and IN constraints
+  **   pWInfo->a[].iFrom     Which term of the FROM clause is being coded
+  **   pWInfo->a[].iTabCur   The VDBE cursor for the database table
+  **   pWInfo->a[].iIdxCur   The VDBE cursor for the index
+  **   pWInfo->a[].pTerm     When wsFlags==WO_OR, the OR-clause term
+  **
+  ** This loop also figures out the nesting order of tables in the FROM
+  ** clause.
+  */
+  notReady = ~(Bitmask)0;
+  andFlags = ~0;
+  WHERETRACE(("*** Optimizer Start ***\n"));
+  for(i=iFrom=0, pLevel=pWInfo->a; i<nTabList; i++, pLevel++){
+    WhereCost bestPlan;         /* Most efficient plan seen so far */
+    Index *pIdx;                /* Index for FROM table at pTabItem */
+    int j;                      /* For looping over FROM tables */
+    int bestJ = -1;             /* The value of j */
+    Bitmask m;                  /* Bitmask value for j or bestJ */
+    int isOptimal;              /* Iterator for optimal/non-optimal search */
+    int nUnconstrained;         /* Number tables without INDEXED BY */
+    Bitmask notIndexed;         /* Mask of tables that cannot use an index */
+
+    memset(&bestPlan, 0, sizeof(bestPlan));
+    bestPlan.rCost = SQLITE_BIG_DBL;
+    WHERETRACE(("*** Begin search for loop %d ***\n", i));
+
+    /* Loop through the remaining entries in the FROM clause to find the
+    ** next nested loop. The loop tests all FROM clause entries
+    ** either once or twice. 
+    **
+    ** The first test is always performed if there are two or more entries
+    ** remaining and never performed if there is only one FROM clause entry
+    ** to choose from.  The first test looks for an "optimal" scan.  In
+    ** this context an optimal scan is one that uses the same strategy
+    ** for the given FROM clause entry as would be selected if the entry
+    ** were used as the innermost nested loop.  In other words, a table
+    ** is chosen such that the cost of running that table cannot be reduced
+    ** by waiting for other tables to run first.  This "optimal" test works
+    ** by first assuming that the FROM clause is on the inner loop and finding
+    ** its query plan, then checking to see if that query plan uses any
+    ** other FROM clause terms that are notReady.  If no notReady terms are
+    ** used then the "optimal" query plan works.
+    **
+    ** Note that the WhereCost.nRow parameter for an optimal scan might
+    ** not be as small as it would be if the table really were the innermost
+    ** join.  The nRow value can be reduced by WHERE clause constraints
+    ** that do not use indices.  But this nRow reduction only happens if the
+    ** table really is the innermost join.  
+    **
+    ** The second loop iteration is only performed if no optimal scan
+    ** strategies were found by the first iteration. This second iteration
+    ** is used to search for the lowest cost scan overall.
+    **
+    ** Previous versions of SQLite performed only the second iteration -
+    ** the next outermost loop was always that with the lowest overall
+    ** cost. However, this meant that SQLite could select the wrong plan
+    ** for scripts such as the following:
+    **   
+    **   CREATE TABLE t1(a, b); 
+    **   CREATE TABLE t2(c, d);
+    **   SELECT * FROM t2, t1 WHERE t2.rowid = t1.a;
+    **
+    ** The best strategy is to iterate through table t1 first. However it
+    ** is not possible to determine this with a simple greedy algorithm.
+    ** Since the cost of a linear scan through table t2 is the same 
+    ** as the cost of a linear scan through table t1, a simple greedy 
+    ** algorithm may choose to use t2 for the outer loop, which is a much
+    ** costlier approach.
+    */
+    nUnconstrained = 0;
+    notIndexed = 0;
+    for(isOptimal=(iFrom<nTabList-1); isOptimal>=0 && bestJ<0; isOptimal--){
+      Bitmask mask;             /* Mask of tables not yet ready */
+      for(j=iFrom, pTabItem=&pTabList->a[j]; j<nTabList; j++, pTabItem++){
+        int doNotReorder;    /* True if this table should not be reordered */
+        WhereCost sCost;     /* Cost information from best[Virtual]Index() */
+        ExprList *pOrderBy;  /* ORDER BY clause for index to optimize */
+        ExprList *pDist;     /* DISTINCT clause for index to optimize */
+  
+        doNotReorder =  (pTabItem->jointype & (JT_LEFT|JT_CROSS))!=0;
+        if( j!=iFrom && doNotReorder ) break;
+        m = getMask(pMaskSet, pTabItem->iCursor);
+        if( (m & notReady)==0 ){
+          if( j==iFrom ) iFrom++;
+          continue;
+        }
+        mask = (isOptimal ? m : notReady);
+        pOrderBy = ((i==0 && ppOrderBy )?*ppOrderBy:0);
+        pDist = (i==0 ? pDistinct : 0);
+        if( pTabItem->pIndex==0 ) nUnconstrained++;
+  
+        WHERETRACE(("=== trying table %d with isOptimal=%d ===\n",
+                    j, isOptimal));
+        assert( pTabItem->pTab );
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+        if( IsVirtual(pTabItem->pTab) ){
+          sqlite3_index_info **pp = &pWInfo->a[j].pIdxInfo;
+          bestVirtualIndex(pParse, pWC, pTabItem, mask, notReady, pOrderBy,
+                           &sCost, pp);
+        }else 
+#endif
+        {
+          bestBtreeIndex(pParse, pWC, pTabItem, mask, notReady, pOrderBy,
+              pDist, &sCost);
+        }
+        assert( isOptimal || (sCost.used&notReady)==0 );
+
+        /* If an INDEXED BY clause is present, then the plan must use that
+        ** index if it uses any index at all */
+        assert( pTabItem->pIndex==0 
+                  || (sCost.plan.wsFlags & WHERE_NOT_FULLSCAN)==0
+                  || sCost.plan.u.pIdx==pTabItem->pIndex );
+
+        if( isOptimal && (sCost.plan.wsFlags & WHERE_NOT_FULLSCAN)==0 ){
+          notIndexed |= m;
+        }
+
+        /* Conditions under which this table becomes the best so far:
+        **
+        **   (1) The table must not depend on other tables that have not
+        **       yet run.
+        **
+        **   (2) A full-table-scan plan cannot supercede indexed plan unless
+        **       the full-table-scan is an "optimal" plan as defined above.
+        **
+        **   (3) All tables have an INDEXED BY clause or this table lacks an
+        **       INDEXED BY clause or this table uses the specific
+        **       index specified by its INDEXED BY clause.  This rule ensures
+        **       that a best-so-far is always selected even if an impossible
+        **       combination of INDEXED BY clauses are given.  The error
+        **       will be detected and relayed back to the application later.
+        **       The NEVER() comes about because rule (2) above prevents
+        **       An indexable full-table-scan from reaching rule (3).
+        **
+        **   (4) The plan cost must be lower than prior plans or else the
+        **       cost must be the same and the number of rows must be lower.
+        */
+        if( (sCost.used&notReady)==0                       /* (1) */
+            && (bestJ<0 || (notIndexed&m)!=0               /* (2) */
+                || (bestPlan.plan.wsFlags & WHERE_NOT_FULLSCAN)==0
+                || (sCost.plan.wsFlags & WHERE_NOT_FULLSCAN)!=0)
+            && (nUnconstrained==0 || pTabItem->pIndex==0   /* (3) */
+                || NEVER((sCost.plan.wsFlags & WHERE_NOT_FULLSCAN)!=0))
+            && (bestJ<0 || sCost.rCost<bestPlan.rCost      /* (4) */
+                || (sCost.rCost<=bestPlan.rCost 
+                 && sCost.plan.nRow<bestPlan.plan.nRow))
+        ){
+          WHERETRACE(("=== table %d is best so far"
+                      " with cost=%g and nRow=%g\n",
+                      j, sCost.rCost, sCost.plan.nRow));
+          bestPlan = sCost;
+          bestJ = j;
+        }
+        if( doNotReorder ) break;
+      }
+    }
+    assert( bestJ>=0 );
+    assert( notReady & getMask(pMaskSet, pTabList->a[bestJ].iCursor) );
+    WHERETRACE(("*** Optimizer selects table %d for loop %d"
+                " with cost=%g and nRow=%g\n",
+                bestJ, pLevel-pWInfo->a, bestPlan.rCost, bestPlan.plan.nRow));
+    /* The ALWAYS() that follows was added to hush up clang scan-build */
+    if( (bestPlan.plan.wsFlags & WHERE_ORDERBY)!=0 && ALWAYS(ppOrderBy) ){
+      *ppOrderBy = 0;
+    }
+    if( (bestPlan.plan.wsFlags & WHERE_DISTINCT)!=0 ){
+      assert( pWInfo->eDistinct==0 );
+      pWInfo->eDistinct = WHERE_DISTINCT_ORDERED;
+    }
+    andFlags &= bestPlan.plan.wsFlags;
+    pLevel->plan = bestPlan.plan;
+    testcase( bestPlan.plan.wsFlags & WHERE_INDEXED );
+    testcase( bestPlan.plan.wsFlags & WHERE_TEMP_INDEX );
+    if( bestPlan.plan.wsFlags & (WHERE_INDEXED|WHERE_TEMP_INDEX) ){
+      pLevel->iIdxCur = pParse->nTab++;
+    }else{
+      pLevel->iIdxCur = -1;
+    }
+    notReady &= ~getMask(pMaskSet, pTabList->a[bestJ].iCursor);
+    pLevel->iFrom = (u8)bestJ;
+    if( bestPlan.plan.nRow>=(double)1 ){
+      pParse->nQueryLoop *= bestPlan.plan.nRow;
+    }
+
+    /* Check that if the table scanned by this loop iteration had an
+    ** INDEXED BY clause attached to it, that the named index is being
+    ** used for the scan. If not, then query compilation has failed.
+    ** Return an error.
+    */
+    pIdx = pTabList->a[bestJ].pIndex;
+    if( pIdx ){
+      if( (bestPlan.plan.wsFlags & WHERE_INDEXED)==0 ){
+        sqlite3ErrorMsg(pParse, "cannot use index: %s", pIdx->zName);
+        goto whereBeginError;
+      }else{
+        /* If an INDEXED BY clause is used, the bestIndex() function is
+        ** guaranteed to find the index specified in the INDEXED BY clause
+        ** if it find an index at all. */
+        assert( bestPlan.plan.u.pIdx==pIdx );
+      }
+    }
+  }
+  WHERETRACE(("*** Optimizer Finished ***\n"));
+  if( pParse->nErr || db->mallocFailed ){
+    goto whereBeginError;
+  }
+
+  /* If the total query only selects a single row, then the ORDER BY
+  ** clause is irrelevant.
+  */
+  if( (andFlags & WHERE_UNIQUE)!=0 && ppOrderBy ){
+    *ppOrderBy = 0;
+  }
+
+  /* If the caller is an UPDATE or DELETE statement that is requesting
+  ** to use a one-pass algorithm, determine if this is appropriate.
+  ** The one-pass algorithm only works if the WHERE clause constraints
+  ** the statement to update a single row.
+  */
+  assert( (wctrlFlags & WHERE_ONEPASS_DESIRED)==0 || pWInfo->nLevel==1 );
+  if( (wctrlFlags & WHERE_ONEPASS_DESIRED)!=0 && (andFlags & WHERE_UNIQUE)!=0 ){
+    pWInfo->okOnePass = 1;
+    pWInfo->a[0].plan.wsFlags &= ~WHERE_IDX_ONLY;
+  }
+
+  /* Open all tables in the pTabList and any indices selected for
+  ** searching those tables.
+  */
+  sqlite3CodeVerifySchema(pParse, -1); /* Insert the cookie verifier Goto */
+  notReady = ~(Bitmask)0;
+  pWInfo->nRowOut = (double)1;
+  for(i=0, pLevel=pWInfo->a; i<nTabList; i++, pLevel++){
+    Table *pTab;     /* Table to open */
+    int iDb;         /* Index of database containing table/index */
+
+    pTabItem = &pTabList->a[pLevel->iFrom];
+    pTab = pTabItem->pTab;
+    pLevel->iTabCur = pTabItem->iCursor;
+    pWInfo->nRowOut *= pLevel->plan.nRow;
+    iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+    if( (pTab->tabFlags & TF_Ephemeral)!=0 || pTab->pSelect ){
+      /* Do nothing */
+    }else
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+    if( (pLevel->plan.wsFlags & WHERE_VIRTUALTABLE)!=0 ){
+      const char *pVTab = (const char *)sqlite3GetVTable(db, pTab);
+      int iCur = pTabItem->iCursor;
+      sqlite3VdbeAddOp4(v, OP_VOpen, iCur, 0, 0, pVTab, P4_VTAB);
+    }else
+#endif
+    if( (pLevel->plan.wsFlags & WHERE_IDX_ONLY)==0
+         && (wctrlFlags & WHERE_OMIT_OPEN_CLOSE)==0 ){
+      int op = pWInfo->okOnePass ? OP_OpenWrite : OP_OpenRead;
+      sqlite3OpenTable(pParse, pTabItem->iCursor, iDb, pTab, op);
+      testcase( pTab->nCol==BMS-1 );
+      testcase( pTab->nCol==BMS );
+      if( !pWInfo->okOnePass && pTab->nCol<BMS ){
+        Bitmask b = pTabItem->colUsed;
+        int n = 0;
+        for(; b; b=b>>1, n++){}
+        sqlite3VdbeChangeP4(v, sqlite3VdbeCurrentAddr(v)-1, 
+                            SQLITE_INT_TO_PTR(n), P4_INT32);
+        assert( n<=pTab->nCol );
+      }
+    }else{
+      sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);
+    }
+#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
+    if( (pLevel->plan.wsFlags & WHERE_TEMP_INDEX)!=0 ){
+      constructAutomaticIndex(pParse, pWC, pTabItem, notReady, pLevel);
+    }else
+#endif
+    if( (pLevel->plan.wsFlags & WHERE_INDEXED)!=0 ){
+      Index *pIx = pLevel->plan.u.pIdx;
+      KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIx);
+      int iIdxCur = pLevel->iIdxCur;
+      assert( pIx->pSchema==pTab->pSchema );
+      assert( iIdxCur>=0 );
+      sqlite3VdbeAddOp4(v, OP_OpenRead, iIdxCur, pIx->tnum, iDb,
+                        (char*)pKey, P4_KEYINFO_HANDOFF);
+      VdbeComment((v, "%s", pIx->zName));
+    }
+    sqlite3CodeVerifySchema(pParse, iDb);
+    notReady &= ~getMask(pWC->pMaskSet, pTabItem->iCursor);
+  }
+  pWInfo->iTop = sqlite3VdbeCurrentAddr(v);
+  if( db->mallocFailed ) goto whereBeginError;
+
+  /* Generate the code to do the search.  Each iteration of the for
+  ** loop below generates code for a single nested loop of the VM
+  ** program.
+  */
+  notReady = ~(Bitmask)0;
+  for(i=0; i<nTabList; i++){
+    pLevel = &pWInfo->a[i];
+    explainOneScan(pParse, pTabList, pLevel, i, pLevel->iFrom, wctrlFlags);
+    notReady = codeOneLoopStart(pWInfo, i, wctrlFlags, notReady, pWhere);
+    pWInfo->iContinue = pLevel->addrCont;
+  }
+
+#ifdef SQLITE_TEST  /* For testing and debugging use only */
+  /* Record in the query plan information about the current table
+  ** and the index used to access it (if any).  If the table itself
+  ** is not used, its name is just '{}'.  If no index is used
+  ** the index is listed as "{}".  If the primary key is used the
+  ** index name is '*'.
+  */
+  for(i=0; i<nTabList; i++){
+    char *z;
+    int n;
+    pLevel = &pWInfo->a[i];
+    pTabItem = &pTabList->a[pLevel->iFrom];
+    z = pTabItem->zAlias;
+    if( z==0 ) z = pTabItem->pTab->zName;
+    n = sqlite3Strlen30(z);
+    if( n+nQPlan < sizeof(sqlite3_query_plan)-10 ){
+      if( pLevel->plan.wsFlags & WHERE_IDX_ONLY ){
+        memcpy(&sqlite3_query_plan[nQPlan], "{}", 2);
+        nQPlan += 2;
+      }else{
+        memcpy(&sqlite3_query_plan[nQPlan], z, n);
+        nQPlan += n;
+      }
+      sqlite3_query_plan[nQPlan++] = ' ';
+    }
+    testcase( pLevel->plan.wsFlags & WHERE_ROWID_EQ );
+    testcase( pLevel->plan.wsFlags & WHERE_ROWID_RANGE );
+    if( pLevel->plan.wsFlags & (WHERE_ROWID_EQ|WHERE_ROWID_RANGE) ){
+      memcpy(&sqlite3_query_plan[nQPlan], "* ", 2);
+      nQPlan += 2;
+    }else if( (pLevel->plan.wsFlags & WHERE_INDEXED)!=0 ){
+      n = sqlite3Strlen30(pLevel->plan.u.pIdx->zName);
+      if( n+nQPlan < sizeof(sqlite3_query_plan)-2 ){
+        memcpy(&sqlite3_query_plan[nQPlan], pLevel->plan.u.pIdx->zName, n);
+        nQPlan += n;
+        sqlite3_query_plan[nQPlan++] = ' ';
+      }
+    }else{
+      memcpy(&sqlite3_query_plan[nQPlan], "{} ", 3);
+      nQPlan += 3;
+    }
+  }
+  while( nQPlan>0 && sqlite3_query_plan[nQPlan-1]==' ' ){
+    sqlite3_query_plan[--nQPlan] = 0;
+  }
+  sqlite3_query_plan[nQPlan] = 0;
+  nQPlan = 0;
+#endif /* SQLITE_TEST // Testing and debugging use only */
+
+  /* Record the continuation address in the WhereInfo structure.  Then
+  ** clean up and return.
+  */
+  return pWInfo;
+
+  /* Jump here if malloc fails */
+whereBeginError:
+  if( pWInfo ){
+    pParse->nQueryLoop = pWInfo->savedNQueryLoop;
+    whereInfoFree(db, pWInfo);
+  }
+  return 0;
+}
+
+/*
+** Generate the end of the WHERE loop.  See comments on 
+** sqlite3WhereBegin() for additional information.
+*/
+void sqlite3WhereEnd(WhereInfo *pWInfo){
+  Parse *pParse = pWInfo->pParse;
+  Vdbe *v = pParse->pVdbe;
+  int i;
+  WhereLevel *pLevel;
+  SrcList *pTabList = pWInfo->pTabList;
+  sqlite3 *db = pParse->db;
+
+  /* Generate loop termination code.
+  */
+  sqlite3ExprCacheClear(pParse);
+  for(i=pWInfo->nLevel-1; i>=0; i--){
+    pLevel = &pWInfo->a[i];
+    sqlite3VdbeResolveLabel(v, pLevel->addrCont);
+    if( pLevel->op!=OP_Noop ){
+      sqlite3VdbeAddOp2(v, pLevel->op, pLevel->p1, pLevel->p2);
+      sqlite3VdbeChangeP5(v, pLevel->p5);
+    }
+    if( pLevel->plan.wsFlags & WHERE_IN_ABLE && pLevel->u.in.nIn>0 ){
+      struct InLoop *pIn;
+      int j;
+      sqlite3VdbeResolveLabel(v, pLevel->addrNxt);
+      for(j=pLevel->u.in.nIn, pIn=&pLevel->u.in.aInLoop[j-1]; j>0; j--, pIn--){
+        sqlite3VdbeJumpHere(v, pIn->addrInTop+1);
+        sqlite3VdbeAddOp2(v, OP_Next, pIn->iCur, pIn->addrInTop);
+        sqlite3VdbeJumpHere(v, pIn->addrInTop-1);
+      }
+      sqlite3DbFree(db, pLevel->u.in.aInLoop);
+    }
+    sqlite3VdbeResolveLabel(v, pLevel->addrBrk);
+    if( pLevel->iLeftJoin ){
+      int addr;
+      addr = sqlite3VdbeAddOp1(v, OP_IfPos, pLevel->iLeftJoin);
+      assert( (pLevel->plan.wsFlags & WHERE_IDX_ONLY)==0
+           || (pLevel->plan.wsFlags & WHERE_INDEXED)!=0 );
+      if( (pLevel->plan.wsFlags & WHERE_IDX_ONLY)==0 ){
+        sqlite3VdbeAddOp1(v, OP_NullRow, pTabList->a[i].iCursor);
+      }
+      if( pLevel->iIdxCur>=0 ){
+        sqlite3VdbeAddOp1(v, OP_NullRow, pLevel->iIdxCur);
+      }
+      if( pLevel->op==OP_Return ){
+        sqlite3VdbeAddOp2(v, OP_Gosub, pLevel->p1, pLevel->addrFirst);
+      }else{
+        sqlite3VdbeAddOp2(v, OP_Goto, 0, pLevel->addrFirst);
+      }
+      sqlite3VdbeJumpHere(v, addr);
+    }
+  }
+
+  /* The "break" point is here, just past the end of the outer loop.
+  ** Set it.
+  */
+  sqlite3VdbeResolveLabel(v, pWInfo->iBreak);
+
+  /* Close all of the cursors that were opened by sqlite3WhereBegin.
+  */
+  assert( pWInfo->nLevel==1 || pWInfo->nLevel==pTabList->nSrc );
+  for(i=0, pLevel=pWInfo->a; i<pWInfo->nLevel; i++, pLevel++){
+    struct SrcList_item *pTabItem = &pTabList->a[pLevel->iFrom];
+    Table *pTab = pTabItem->pTab;
+    assert( pTab!=0 );
+    if( (pTab->tabFlags & TF_Ephemeral)==0
+     && pTab->pSelect==0
+     && (pWInfo->wctrlFlags & WHERE_OMIT_OPEN_CLOSE)==0
+    ){
+      int ws = pLevel->plan.wsFlags;
+      if( !pWInfo->okOnePass && (ws & WHERE_IDX_ONLY)==0 ){
+        sqlite3VdbeAddOp1(v, OP_Close, pTabItem->iCursor);
+      }
+      if( (ws & WHERE_INDEXED)!=0 && (ws & WHERE_TEMP_INDEX)==0 ){
+        sqlite3VdbeAddOp1(v, OP_Close, pLevel->iIdxCur);
+      }
+    }
+
+    /* If this scan uses an index, make code substitutions to read data
+    ** from the index in preference to the table. Sometimes, this means
+    ** the table need never be read from. This is a performance boost,
+    ** as the vdbe level waits until the table is read before actually
+    ** seeking the table cursor to the record corresponding to the current
+    ** position in the index.
+    ** 
+    ** Calls to the code generator in between sqlite3WhereBegin and
+    ** sqlite3WhereEnd will have created code that references the table
+    ** directly.  This loop scans all that code looking for opcodes
+    ** that reference the table and converts them into opcodes that
+    ** reference the index.
+    */
+    if( (pLevel->plan.wsFlags & WHERE_INDEXED)!=0 && !db->mallocFailed){
+      int k, j, last;
+      VdbeOp *pOp;
+      Index *pIdx = pLevel->plan.u.pIdx;
+
+      assert( pIdx!=0 );
+      pOp = sqlite3VdbeGetOp(v, pWInfo->iTop);
+      last = sqlite3VdbeCurrentAddr(v);
+      for(k=pWInfo->iTop; k<last; k++, pOp++){
+        if( pOp->p1!=pLevel->iTabCur ) continue;
+        if( pOp->opcode==OP_Column ){
+          for(j=0; j<pIdx->nColumn; j++){
+            if( pOp->p2==pIdx->aiColumn[j] ){
+              pOp->p2 = j;
+              pOp->p1 = pLevel->iIdxCur;
+              break;
+            }
+          }
+          assert( (pLevel->plan.wsFlags & WHERE_IDX_ONLY)==0
+               || j<pIdx->nColumn );
+        }else if( pOp->opcode==OP_Rowid ){
+          pOp->p1 = pLevel->iIdxCur;
+          pOp->opcode = OP_IdxRowid;
+        }
+      }
+    }
+  }
+
+  /* Final cleanup
+  */
+  pParse->nQueryLoop = pWInfo->savedNQueryLoop;
+  whereInfoFree(db, pWInfo);
+  return;
+}