ext/misc/sqlar.c

   1 /*
   2 ** 2017-12-17
   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 ** Utility functions sqlar_compress() and sqlar_uncompress(). Useful
  14 ** for working with sqlar archives and used by the shell tool's built-in
  15 ** sqlar support.
  16 */
  17 #include "sqlite3ext.h"
  18 SQLITE_EXTENSION_INIT1
  19 #include <zlib.h>
  20
  21 /*
  22 ** Implementation of the "sqlar_compress(X)" SQL function.
  23 **
  24 ** If the type of X is SQLITE_BLOB, and compressing that blob using
  25 ** zlib utility function compress() yields a smaller blob, return the
  26 ** compressed blob. Otherwise, return a copy of X.
  27 */
  28 static void sqlarCompressFunc(
  29   sqlite3_context *context,
  30   int argc,
  31   sqlite3_value **argv
  32 ){
  33   assert( argc==1 );
  34   if( sqlite3_value_type(argv[0])==SQLITE_BLOB ){
  35     const Bytef *pData = sqlite3_value_blob(argv[0]);
  36     uLong nData = sqlite3_value_bytes(argv[0]);
  37     uLongf nOut = compressBound(nData);
  38     Bytef *pOut;
  39
  40     pOut = (Bytef*)sqlite3_malloc(nOut);
  41     if( pOut==0 ){
  42       sqlite3_result_error_nomem(context);
  43       return;
  44     }else{
  45       if( Z_OK!=compress(pOut, &nOut, pData, nData) ){
  46         sqlite3_result_error(context, "error in compress()", -1);
  47       }else if( nOut<nData ){
  48         sqlite3_result_blob(context, pOut, nOut, SQLITE_TRANSIENT);
  49       }else{
  50         sqlite3_result_value(context, argv[0]);
  51       }
  52       sqlite3_free(pOut);
  53     }
  54   }else{
  55     sqlite3_result_value(context, argv[0]);
  56   }
  57 }
  58
  59 /*
  60 ** Implementation of the "sqlar_uncompress(X,SZ)" SQL function
  61 **
  62 ** Parameter SZ is interpreted as an integer. If it is less than or
  63 ** equal to zero, then this function returns a copy of X. Or, if
  64 ** SZ is equal to the size of X when interpreted as a blob, also
  65 ** return a copy of X. Otherwise, decompress blob X using zlib
  66 ** utility function uncompress() and return the results (another
  67 ** blob).
  68 */
  69 static void sqlarUncompressFunc(
  70   sqlite3_context *context,
  71   int argc,
  72   sqlite3_value **argv
  73 ){
  74   uLong nData;
  75   uLongf sz;
  76
  77   assert( argc==2 );
  78   sz = sqlite3_value_int(argv[1]);
  79
  80   if( sz<=0 || sz==(nData = sqlite3_value_bytes(argv[0])) ){
  81     sqlite3_result_value(context, argv[0]);
  82   }else{
  83     const Bytef *pData= sqlite3_value_blob(argv[0]);
  84     Bytef *pOut = sqlite3_malloc(sz);
  85     if( Z_OK!=uncompress(pOut, &sz, pData, nData) ){
  86       sqlite3_result_error(context, "error in uncompress()", -1);
  87     }else{
  88       sqlite3_result_blob(context, pOut, sz, SQLITE_TRANSIENT);
  89     }
  90     sqlite3_free(pOut);
  91   }
  92 }
  93
  94
  95 #ifdef _WIN32
  96 __declspec(dllexport)
  97 #endif
  98 int sqlite3_sqlar_init(
  99   sqlite3 *db,
 100   char **pzErrMsg,
 101   const sqlite3_api_routines *pApi
 102 ){
 103   int rc = SQLITE_OK;
 104   SQLITE_EXTENSION_INIT2(pApi);
 105   (void)pzErrMsg;  /* Unused parameter */
 106   rc = sqlite3_create_function(db, "sqlar_compress", 1, SQLITE_UTF8, 0,
 107                                sqlarCompressFunc, 0, 0);
 108   if( rc==SQLITE_OK ){
 109     rc = sqlite3_create_function(db, "sqlar_uncompress", 2, SQLITE_UTF8, 0,
 110                                  sqlarUncompressFunc, 0, 0);
 111   }
 112   return rc;
 113 }