Re: [sqlite] Compress function

[drh]

"Cesar David Rodas Maldonado" <[EMAIL PROTECTED]> wrote:
> I need a funcion from compress a row with Zlib and  I am wondering if SQLite
> support or if someone did it  and want to share him or her code.
> 

Here some code that might help:

/*
** SQL function to compress content into a blob using libz
*/
static void compressFunc(
  sqlite3_context *context,
  int argc,
  sqlite3_value **argv
){
  int nIn, nOut;
  long int nOut2;
  const unsigned char *inBuf;
  unsigned char *outBuf;
  assert( argc==1 );
  nIn = sqlite3_value_bytes(argv[0]);
  inBuf = sqlite3_value_blob(argv[0]);
  nOut = 13 + nIn + (nIn+999)/1000;
  outBuf = malloc( nOut+4 );
  outBuf[0] = nIn>>24 & 0xff;
  outBuf[1] = nIn>>16 & 0xff;
  outBuf[2] = nIn>>8 & 0xff;
  outBuf[3] = nIn & 0xff;
  nOut2 = (long int)nOut;
  compress(&outBuf[4], &nOut2, inBuf, nIn);
  sqlite3_result_blob(context, outBuf, nOut2+4, free);  
}

/*
** An SQL function to decompress.
*/
static void uncompressFunc(
  sqlite3_context *context,
  int argc,
  sqlite3_value **argv
){
  unsigned int nIn, nOut, rc;
  const unsigned char *inBuf;
  unsigned char *outBuf;
  long int nOut2;

  assert( argc==1 );
  nIn = sqlite3_value_bytes(argv[0]);
  if( nIn<=4 ){
    return;
  }
  inBuf = sqlite3_value_blob(argv[0]);
  nOut = (inBuf[0]<<24) + (inBuf[1]<<16) + (inBuf[2]<<8) + inBuf[3];
  outBuf = malloc( nOut );
  nOut2 = (long int)nOut;
  rc = uncompress(outBuf, &nOut2, &inBuf[4], nIn);
  if( rc!=Z_OK ){
    free(outBuf);
  }else{
    sqlite3_result_blob(context, outBuf, nOut2, free);
  }
}

/* Make the functions above accessible to SQLite as follows:
*/
  sqlite3_create_function(db, "compress", 1, SQLITE_UTF8, 0,
     compressFunc, 0, 0);
  sqlite3_create_function(db, "uncompress", 1, SQLITE_UTF8, 0,
     uncompressFunc, 0, 0);

--
D. Richard Hipp   <[EMAIL PROTECTED]>