modernc.org/cc@v1.0.1/v2/testdata/_sqlite/ext/misc/rot13.c (about)

     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    char *zToFree = 0;
    51    int i;
    52    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 = sqlite3_malloc( 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  }