From 08119c361d1181b3e8f1abb429236e488a664753 Mon Sep 17 00:00:00 2001 From: Hans-Christoph Steiner Date: Tue, 13 Aug 2013 15:42:54 -0400 Subject: Imported Upstream version 2.2.1 --- ext/misc/nextchar.c | 265 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 265 insertions(+) create mode 100644 ext/misc/nextchar.c (limited to 'ext/misc/nextchar.c') diff --git a/ext/misc/nextchar.c b/ext/misc/nextchar.c new file mode 100644 index 0000000..e063043 --- /dev/null +++ b/ext/misc/nextchar.c @@ -0,0 +1,265 @@ +/* +** 2013-02-28 +** +** 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 code to implement the next_char(A,T,F,W) SQL function. +** +** The next_char(A,T,F,H) function finds all valid "next" characters for +** string A given the vocabulary in T.F. The T.F field should be indexed. +** If the W value exists and is a non-empty string, then it is an SQL +** expression that limits the entries in T.F that will be considered. +** +** For example, suppose an application has a dictionary like this: +** +** CREATE TABLE dictionary(word TEXT UNIQUE); +** +** Further suppose that for user keypad entry, it is desired to disable +** (gray out) keys that are not valid as the next character. If the +** the user has previously entered (say) 'cha' then to find all allowed +** next characters (and thereby determine when keys should not be grayed +** out) run the following query: +** +** SELECT next_char('cha','dictionary','word'); +*/ +#include "sqlite3ext.h" +SQLITE_EXTENSION_INIT1 +#include + +/* +** A structure to hold context of the next_char() computation across +** nested function calls. +*/ +typedef struct nextCharContext nextCharContext; +struct nextCharContext { + sqlite3 *db; /* Database connection */ + sqlite3_stmt *pStmt; /* Prepared statement used to query */ + const unsigned char *zPrefix; /* Prefix to scan */ + int nPrefix; /* Size of zPrefix in bytes */ + int nAlloc; /* Space allocated to aResult */ + int nUsed; /* Space used in aResult */ + unsigned int *aResult; /* Array of next characters */ + int mallocFailed; /* True if malloc fails */ + int otherError; /* True for any other failure */ +}; + +/* +** Append a result character if the character is not already in the +** result. +*/ +static void nextCharAppend(nextCharContext *p, unsigned c){ + int i; + for(i=0; inUsed; i++){ + if( p->aResult[i]==c ) return; + } + if( p->nUsed+1 > p->nAlloc ){ + unsigned int *aNew; + int n = p->nAlloc*2 + 30; + aNew = sqlite3_realloc(p->aResult, n*sizeof(unsigned int)); + if( aNew==0 ){ + p->mallocFailed = 1; + return; + }else{ + p->aResult = aNew; + p->nAlloc = n; + } + } + p->aResult[p->nUsed++] = c; +} + +/* +** Write a character into z[] as UTF8. Return the number of bytes needed +** to hold the character +*/ +static int writeUtf8(unsigned char *z, unsigned c){ + if( c<0x00080 ){ + z[0] = (unsigned char)(c&0xff); + return 1; + } + if( c<0x00800 ){ + z[0] = 0xC0 + (unsigned char)((c>>6)&0x1F); + z[1] = 0x80 + (unsigned char)(c & 0x3F); + return 2; + } + if( c<0x10000 ){ + z[0] = 0xE0 + (unsigned char)((c>>12)&0x0F); + z[1] = 0x80 + (unsigned char)((c>>6) & 0x3F); + z[2] = 0x80 + (unsigned char)(c & 0x3F); + return 3; + } + z[0] = 0xF0 + (unsigned char)((c>>18) & 0x07); + z[1] = 0x80 + (unsigned char)((c>>12) & 0x3F); + z[2] = 0x80 + (unsigned char)((c>>6) & 0x3F); + z[3] = 0x80 + (unsigned char)(c & 0x3F); + return 4; +} + +/* +** Read a UTF8 character out of z[] and write it into *pOut. Return +** the number of bytes in z[] that were used to construct the character. +*/ +static int readUtf8(const unsigned char *z, unsigned *pOut){ + static const unsigned char validBits[] = { + 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, + }; + unsigned c = z[0]; + if( c<0xc0 ){ + *pOut = c; + return 1; + }else{ + int n = 1; + c = validBits[c-0xc0]; + while( (z[n] & 0xc0)==0x80 ){ + c = (c<<6) + (0x3f & z[n++]); + } + if( c<0x80 || (c&0xFFFFF800)==0xD800 || (c&0xFFFFFFFE)==0xFFFE ){ + c = 0xFFFD; + } + *pOut = c; + return n; + } +} + +/* +** The nextCharContext structure has been set up. Add all "next" characters +** to the result set. +*/ +static void findNextChars(nextCharContext *p){ + unsigned cPrev = 0; + unsigned char zPrev[8]; + int n, rc; + + for(;;){ + sqlite3_bind_text(p->pStmt, 1, (char*)p->zPrefix, p->nPrefix, + SQLITE_STATIC); + n = writeUtf8(zPrev, cPrev+1); + sqlite3_bind_text(p->pStmt, 2, (char*)zPrev, n, SQLITE_STATIC); + rc = sqlite3_step(p->pStmt); + if( rc==SQLITE_DONE ){ + sqlite3_reset(p->pStmt); + return; + }else if( rc!=SQLITE_ROW ){ + p->otherError = rc; + return; + }else{ + const unsigned char *zOut = sqlite3_column_text(p->pStmt, 0); + unsigned cNext; + n = readUtf8(zOut+p->nPrefix, &cNext); + sqlite3_reset(p->pStmt); + nextCharAppend(p, cNext); + cPrev = cNext; + if( p->mallocFailed ) return; + } + } +} + + +/* +** next_character(A,T,F,W) +** +** Return a string composted of all next possible characters after +** A for elements of T.F. If W is supplied, then it is an SQL expression +** that limits the elements in T.F that are considered. +*/ +static void nextCharFunc( + sqlite3_context *context, + int argc, + sqlite3_value **argv +){ + nextCharContext c; + const unsigned char *zTable = sqlite3_value_text(argv[1]); + const unsigned char *zField = sqlite3_value_text(argv[2]); + const unsigned char *zWhere; + char *zSql; + int rc; + + memset(&c, 0, sizeof(c)); + c.db = sqlite3_context_db_handle(context); + c.zPrefix = sqlite3_value_text(argv[0]); + c.nPrefix = sqlite3_value_bytes(argv[0]); + if( zTable==0 || zField==0 || c.zPrefix==0 ) return; + if( argc<4 + || (zWhere = sqlite3_value_text(argv[3]))==0 + || zWhere[0]==0 + ){ + zSql = sqlite3_mprintf( + "SELECT \"%w\" FROM \"%w\"" + " WHERE \"%w\">=(?1 || ?2)" + " AND \"%w\"<=(?1 || char(1114111))" /* 1114111 == 0x10ffff */ + " ORDER BY 1 ASC LIMIT 1", + zField, zTable, zField, zField); + }else{ + zSql = sqlite3_mprintf( + "SELECT \"%w\" FROM \"%w\"" + " WHERE \"%w\">=(?1 || ?2)" + " AND \"%w\"<=(?1 || char(1114111))" /* 1114111 == 0x10ffff */ + " AND (%s)" + " ORDER BY 1 ASC LIMIT 1", + zField, zTable, zField, zField, zWhere); + } + if( zSql==0 ){ + sqlite3_result_error_nomem(context); + return; + } + + rc = sqlite3_prepare_v2(c.db, zSql, -1, &c.pStmt, 0); + sqlite3_free(zSql); + if( rc ){ + sqlite3_result_error(context, sqlite3_errmsg(c.db), -1); + return; + } + findNextChars(&c); + if( c.mallocFailed ){ + sqlite3_result_error_nomem(context); + }else{ + unsigned char *pRes; + pRes = sqlite3_malloc( c.nUsed*4 + 1 ); + if( pRes==0 ){ + sqlite3_result_error_nomem(context); + }else{ + int i; + int n = 0; + for(i=0; i