ext/misc/rot13.c

   1 /*
   2 ** 2013-05-15
   3 **
   4 ** The author disclaims copyright to this source code.  In place of
   5 ** a legal notice, here is a blessing:
   6 **
   7 **    May you do good and not evil.
   8 **    May you find forgiveness for yourself and forgive others.
   9 **    May you share freely, never taking more than you give.
  10 **
  11 ******************************************************************************
  12 **
  13 ** This SQLite extension implements a rot13() function and a rot13
  14 ** collating sequence.
  15 */
  16 #include "sqlite3ext.h"
  17 SQLITE_EXTENSION_INIT1
  18 #include <assert.h>
  19 #include <string.h>
  20
  21 /*
  22 ** Perform rot13 encoding on a single ASCII character.
  23 */
  24 static unsigned char rot13(unsigned char c){
  25   if( c>='a' && c<='z' ){
  26     c += 13;
  27     if( c>'z' ) c -= 26;
  28   }else if( c>='A' && c<='Z' ){
  29     c += 13;
  30     if( c>'Z' ) c -= 26;
  31   }
  32   return c;
  33 }
  34
  35 /*
  36 ** Implementation of the rot13() function.
  37 **
  38 ** Rotate ASCII alphabetic characters by 13 character positions.
  39 ** Non-ASCII characters are unchanged.  rot13(rot13(X)) should always
  40 ** equal X.
  41 */
  42 static void rot13func(
  43   sqlite3_context *context,
  44   int argc,
  45   sqlite3_value **argv
  46 ){
  47   const unsigned char *zIn;
  48   int nIn;
  49   unsigned char *zOut;
  50   unsigned char *zToFree = 0;
  51   int i;
  52   unsigned char zTemp[100];
  53   assert( argc==1 );
  54   if( sqlite3_value_type(argv[0])==SQLITE_NULL ) return;
  55   zIn = (const unsigned char*)sqlite3_value_text(argv[0]);
  56   nIn = sqlite3_value_bytes(argv[0]);
  57   if( nIn<sizeof(zTemp)-1 ){
  58     zOut = zTemp;
  59   }else{
  60     zOut = zToFree = (unsigned char*)sqlite3_malloc64( nIn+1 );
  61     if( zOut==0 ){
  62       sqlite3_result_error_nomem(context);
  63       return;
  64     }
  65   }
  66   for(i=0; i<nIn; i++) zOut[i] = rot13(zIn[i]);
  67   zOut[i] = 0;
  68   sqlite3_result_text(context, (char*)zOut, i, SQLITE_TRANSIENT);
  69   sqlite3_free(zToFree);
  70 }
  71
  72 /*
  73 ** Implement the rot13 collating sequence so that if
  74 **
  75 **      x=y COLLATE rot13
  76 **
  77 ** Then
  78 **
  79 **      rot13(x)=rot13(y) COLLATE binary
  80 */
  81 static int rot13CollFunc(
  82   void *notUsed,
  83   int nKey1, const void *pKey1,
  84   int nKey2, const void *pKey2
  85 ){
  86   const char *zA = (const char*)pKey1;
  87   const char *zB = (const char*)pKey2;
  88   int i, x;
  89   for(i=0; i<nKey1 && i<nKey2; i++){
  90     x = (int)rot13(zA[i]) - (int)rot13(zB[i]);
  91     if( x!=0 ) return x;
  92   }
  93   return nKey1 - nKey2;
  94 }
  95
  96
  97 #ifdef _WIN32
  98 __declspec(dllexport)
  99 #endif
 100 int sqlite3_rot_init(
 101   sqlite3 *db,
 102   char **pzErrMsg,
 103   const sqlite3_api_routines *pApi
 104 ){
 105   int rc = SQLITE_OK;
 106   SQLITE_EXTENSION_INIT2(pApi);
 107   (void)pzErrMsg;  /* Unused parameter */
 108   rc = sqlite3_create_function(db, "rot13", 1, SQLITE_UTF8, 0,
 109                                rot13func, 0, 0);
 110   if( rc==SQLITE_OK ){
 111     rc = sqlite3_create_collation(db, "rot13", SQLITE_UTF8, 0, rot13CollFunc);
 112   }
 113   return rc;
 114 }