third_party/sqlite/sqlite-src-3080704/ext/misc/compress.c

   1 /*
   2 ** 2014-06-13
   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 SQL compression functions
  14 ** compress() and uncompress() using ZLIB.
  15 */
  16 #include "sqlite3ext.h"
  17 SQLITE_EXTENSION_INIT1
  18 #include <zlib.h>
  19
  20 /*
  21 ** Implementation of the "compress(X)" SQL function.  The input X is
  22 ** compressed using zLib and the output is returned.
  23 **
  24 ** The output is a BLOB that begins with a variable-length integer that
  25 ** is the input size in bytes (the size of X before compression).  The
  26 ** variable-length integer is implemented as 1 to 5 bytes.  There are
  27 ** seven bits per integer stored in the lower seven bits of each byte.
  28 ** More significant bits occur first.  The most significant bit (0x80)
  29 ** is a flag to indicate the end of the integer.
  30 */
  31 static void compressFunc(
  32   sqlite3_context *context,
  33   int argc,
  34   sqlite3_value **argv
  35 ){
  36   const unsigned char *pIn;
  37   unsigned char *pOut;
  38   unsigned int nIn;
  39   unsigned long int nOut;
  40   unsigned char x[8];
  41   int i, j;
  42
  43   pIn = sqlite3_value_blob(argv[0]);
  44   nIn = sqlite3_value_bytes(argv[0]);
  45   nOut = 13 + nIn + (nIn+999)/1000;
  46   pOut = sqlite3_malloc( nOut+5 );
  47   for(i=4; i>=0; i--){
  48     x[i] = (nIn >> (7*(4-i)))&0x7f;
  49   }
  50   for(i=0; i<4 && x[i]==0; i++){}
  51   for(j=0; i<=4; i++, j++) pOut[j] = x[i];
  52   pOut[j-1] |= 0x80;
  53   compress(&pOut[j], &nOut, pIn, nIn);
  54   sqlite3_result_blob(context, pOut, nOut+j, sqlite3_free);
  55 }
  56
  57 /*
  58 ** Implementation of the "uncompress(X)" SQL function.  The argument X
  59 ** is a blob which was obtained from compress(Y).  The output will be
  60 ** the value Y.
  61 */
  62 static void uncompressFunc(
  63   sqlite3_context *context,
  64   int argc,
  65   sqlite3_value **argv
  66 ){
  67   const unsigned char *pIn;
  68   unsigned char *pOut;
  69   unsigned int nIn;
  70   unsigned long int nOut;
  71   int rc;
  72   int i;
  73
  74   pIn = sqlite3_value_blob(argv[0]);
  75   nIn = sqlite3_value_bytes(argv[0]);
  76   nOut = 0;
  77   for(i=0; i<nIn && i<5; i++){
  78     nOut = (nOut<<7) | (pIn[i]&0x7f);
  79     if( (pIn[i]&0x80)!=0 ){ i++; break; }
  80   }
  81   pOut = sqlite3_malloc( nOut+1 );
  82   rc = uncompress(pOut, &nOut, &pIn[i], nIn-i);
  83   if( rc==Z_OK ){
  84     sqlite3_result_blob(context, pOut, nOut, sqlite3_free);
  85   }
  86 }
  87
  88
  89 #ifdef _WIN32
  90 __declspec(dllexport)
  91 #endif
  92 int sqlite3_compress_init(
  93   sqlite3 *db,
  94   char **pzErrMsg,
  95   const sqlite3_api_routines *pApi
  96 ){
  97   int rc = SQLITE_OK;
  98   SQLITE_EXTENSION_INIT2(pApi);
  99   (void)pzErrMsg;  /* Unused parameter */
 100   rc = sqlite3_create_function(db, "compress", 1, SQLITE_UTF8, 0,
 101                                compressFunc, 0, 0);
 102   if( rc==SQLITE_OK ){
 103     rc = sqlite3_create_function(db, "uncompress", 1, SQLITE_UTF8, 0,
 104                                  uncompressFunc, 0, 0);
 105   }
 106   return rc;
 107 }