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 rc; 42 int i, j; 43 44 pIn = sqlite3_value_blob(argv[0]); 45 nIn = sqlite3_value_bytes(argv[0]); 46 nOut = 13 + nIn + (nIn+999)/1000; 47 pOut = sqlite3_malloc( nOut+5 ); 48 for(i=4; i>=0; i--){ 49 x[i] = (nIn >> (7*(4-i)))&0x7f; 50 } 51 for(i=0; i<4 && x[i]==0; i++){} 52 for(j=0; i<=4; i++, j++) pOut[j] = x[i]; 53 pOut[j-1] |= 0x80; 54 rc = compress(&pOut[j], &nOut, pIn, nIn); 55 if( rc==Z_OK ){ 56 sqlite3_result_blob(context, pOut, nOut+j, sqlite3_free); 57 }else{ 58 sqlite3_free(pOut); 59 } 60 } 61 62 /* 63 ** Implementation of the "uncompress(X)" SQL function. The argument X 64 ** is a blob which was obtained from compress(Y). The output will be 65 ** the value Y. 66 */ 67 static void uncompressFunc( 68 sqlite3_context *context, 69 int argc, 70 sqlite3_value **argv 71 ){ 72 const unsigned char *pIn; 73 unsigned char *pOut; 74 unsigned int nIn; 75 unsigned long int nOut; 76 int rc; 77 int i; 78 79 pIn = sqlite3_value_blob(argv[0]); 80 nIn = sqlite3_value_bytes(argv[0]); 81 nOut = 0; 82 for(i=0; i<nIn && i<5; i++){ 83 nOut = (nOut<<7) | (pIn[i]&0x7f); 84 if( (pIn[i]&0x80)!=0 ){ i++; break; } 85 } 86 pOut = sqlite3_malloc( nOut+1 ); 87 rc = uncompress(pOut, &nOut, &pIn[i], nIn-i); 88 if( rc==Z_OK ){ 89 sqlite3_result_blob(context, pOut, nOut, sqlite3_free); 90 }else{ 91 sqlite3_free(pOut); 92 } 93 } 94 95 96 #ifdef _WIN32 97 __declspec(dllexport) 98 #endif 99 int sqlite3_compress_init( 100 sqlite3 *db, 101 char **pzErrMsg, 102 const sqlite3_api_routines *pApi 103 ){ 104 int rc = SQLITE_OK; 105 SQLITE_EXTENSION_INIT2(pApi); 106 (void)pzErrMsg; /* Unused parameter */ 107 rc = sqlite3_create_function(db, "compress", 1, SQLITE_UTF8, 0, 108 compressFunc, 0, 0); 109 if( rc==SQLITE_OK ){ 110 rc = sqlite3_create_function(db, "uncompress", 1, SQLITE_UTF8, 0, 111 uncompressFunc, 0, 0); 112 } 113 return rc; 114 } 115