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 ** This function, SQLAR, and ZIP all use the same "deflate" compression 32 ** algorithm, but each is subtly different: 33 ** 34 ** * ZIP uses raw deflate. 35 ** 36 ** * SQLAR uses the "zlib format" which is raw deflate with a two-byte 37 ** algorithm-identification header and a four-byte checksum at the end. 38 ** 39 ** * This utility uses the "zlib format" like SQLAR, but adds the variable- 40 ** length integer uncompressed size value at the beginning. 41 ** 42 ** This function might be extended in the future to support compression 43 ** formats other than deflate, by providing a different algorithm-id 44 ** mark following the variable-length integer size parameter. 45 */ 46 static void compressFunc( 47 sqlite3_context *context, 48 int argc, 49 sqlite3_value **argv 50 ){ 51 const unsigned char *pIn; 52 unsigned char *pOut; 53 unsigned int nIn; 54 unsigned long int nOut; 55 unsigned char x[8]; 56 int rc; 57 int i, j; 58 59 pIn = sqlite3_value_blob(argv[0]); 60 nIn = sqlite3_value_bytes(argv[0]); 61 nOut = 13 + nIn + (nIn+999)/1000; 62 pOut = sqlite3_malloc( nOut+5 ); 63 for(i=4; i>=0; i--){ 64 x[i] = (nIn >> (7*(4-i)))&0x7f; 65 } 66 for(i=0; i<4 && x[i]==0; i++){} 67 for(j=0; i<=4; i++, j++) pOut[j] = x[i]; 68 pOut[j-1] |= 0x80; 69 rc = compress(&pOut[j], &nOut, pIn, nIn); 70 if( rc==Z_OK ){ 71 sqlite3_result_blob(context, pOut, nOut+j, sqlite3_free); 72 }else{ 73 sqlite3_free(pOut); 74 } 75 } 76 77 /* 78 ** Implementation of the "uncompress(X)" SQL function. The argument X 79 ** is a blob which was obtained from compress(Y). The output will be 80 ** the value Y. 81 */ 82 static void uncompressFunc( 83 sqlite3_context *context, 84 int argc, 85 sqlite3_value **argv 86 ){ 87 const unsigned char *pIn; 88 unsigned char *pOut; 89 unsigned int nIn; 90 unsigned long int nOut; 91 int rc; 92 int i; 93 94 pIn = sqlite3_value_blob(argv[0]); 95 nIn = sqlite3_value_bytes(argv[0]); 96 nOut = 0; 97 for(i=0; i<nIn && i<5; i++){ 98 nOut = (nOut<<7) | (pIn[i]&0x7f); 99 if( (pIn[i]&0x80)!=0 ){ i++; break; } 100 } 101 pOut = sqlite3_malloc( nOut+1 ); 102 rc = uncompress(pOut, &nOut, &pIn[i], nIn-i); 103 if( rc==Z_OK ){ 104 sqlite3_result_blob(context, pOut, nOut, sqlite3_free); 105 }else{ 106 sqlite3_free(pOut); 107 } 108 } 109 110 111 #ifdef _WIN32 112 __declspec(dllexport) 113 #endif 114 int sqlite3_compress_init( 115 sqlite3 *db, 116 char **pzErrMsg, 117 const sqlite3_api_routines *pApi 118 ){ 119 int rc = SQLITE_OK; 120 SQLITE_EXTENSION_INIT2(pApi); 121 (void)pzErrMsg; /* Unused parameter */ 122 rc = sqlite3_create_function(db, "compress", 1, 123 SQLITE_UTF8 | SQLITE_INNOCUOUS, 124 0, compressFunc, 0, 0); 125 if( rc==SQLITE_OK ){ 126 rc = sqlite3_create_function(db, "uncompress", 1, 127 SQLITE_UTF8 | SQLITE_INNOCUOUS | SQLITE_DETERMINISTIC, 128 0, uncompressFunc, 0, 0); 129 } 130 return rc; 131 } 132