1 files changed, 114 insertions, 0 deletions
diff --git a/ext/misc/rot13.c b/ext/misc/rot13.c
new file mode 100644
index 0000000..68fdf60
--- /dev/null
+++ b/ext/misc/rot13.c
@@ -0,0 +1,114 @@
+/*
+** 2013-05-15
+**
+** 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 SQLite extension implements a rot13() function and a rot13
+** collating sequence.
+*/
+#include "sqlite3ext.h"
+SQLITE_EXTENSION_INIT1
+#include <assert.h>
+#include <string.h>
+
+/*
+** Perform rot13 encoding on a single ASCII character.
+*/
+static unsigned char rot13(unsigned char c){
+  if( c>='a' && c<='z' ){
+    c += 13;
+    if( c>'z' ) c -= 26;
+  }else if( c>='A' && c<='Z' ){
+    c += 13;
+    if( c>'Z' ) c -= 26;
+  }
+  return c;
+}
+
+/*
+** Implementation of the rot13() function.
+**
+** Rotate ASCII alphabetic characters by 13 character positions.  
+** Non-ASCII characters are unchanged.  rot13(rot13(X)) should always
+** equal X.
+*/
+static void rot13func(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  const unsigned char *zIn;
+  int nIn;
+  unsigned char *zOut;
+  char *zToFree = 0;
+  int i;
+  char zTemp[100];
+  assert( argc==1 );
+  if( sqlite3_value_type(argv[0])==SQLITE_NULL ) return;
+  zIn = (const unsigned char*)sqlite3_value_text(argv[0]);
+  nIn = sqlite3_value_bytes(argv[0]);
+  if( nIn<sizeof(zTemp)-1 ){
+    zOut = zTemp;
+  }else{
+    zOut = zToFree = sqlite3_malloc( nIn+1 );
+    if( zOut==0 ){
+      sqlite3_result_error_nomem(context);
+      return;
+    }
+  }
+  for(i=0; i<nIn; i++) zOut[i] = rot13(zIn[i]);
+  zOut[i] = 0;
+  sqlite3_result_text(context, (char*)zOut, i, SQLITE_TRANSIENT);
+  sqlite3_free(zToFree);
+}
+
+/*
+** Implement the rot13 collating sequence so that if
+**
+**      x=y COLLATE rot13
+**
+** Then 
+**
+**      rot13(x)=rot13(y) COLLATE binary
+*/
+static int rot13CollFunc(
+  void *notUsed,
+  int nKey1, const void *pKey1,
+  int nKey2, const void *pKey2
+){
+  const char *zA = (const char*)pKey1;
+  const char *zB = (const char*)pKey2;
+  int i, x;
+  for(i=0; i<nKey1 && i<nKey2; i++){
+    x = (int)rot13(zA[i]) - (int)rot13(zB[i]);
+    if( x!=0 ) return x;
+  }
+  return nKey1 - nKey2;
+}
+
+
+#ifdef _WIN32
+__declspec(dllexport)
+#endif
+int sqlite3_rot_init(
+  sqlite3 *db, 
+  char **pzErrMsg, 
+  const sqlite3_api_routines *pApi
+){
+  int rc = SQLITE_OK;
+  SQLITE_EXTENSION_INIT2(pApi);
+  (void)pzErrMsg;  /* Unused parameter */
+  rc = sqlite3_create_function(db, "rot13", 1, SQLITE_UTF8, 0,
+                               rot13func, 0, 0);
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_create_collation(db, "rot13", SQLITE_UTF8, 0, rot13CollFunc);
+  }
+  return rc;
+}