| /* |
| ** 2014-06-13 |
| ** |
| ** The author disclaims copyright to this source code. In place of |
| ** a legal notice, here is a blessing: |
| ** |
| ** May you do good and not evil. |
| ** May you find forgiveness for yourself and forgive others. |
| ** May you share freely, never taking more than you give. |
| ** |
| ****************************************************************************** |
| ** |
| ** This SQLite extension implements SQL compression functions |
| ** compress() and uncompress() using ZLIB. |
| */ |
| #include "sqlite3ext.h" |
| SQLITE_EXTENSION_INIT1 |
| #include <zlib.h> |
| |
| /* |
| ** Implementation of the "compress(X)" SQL function. The input X is |
| ** compressed using zLib and the output is returned. |
| ** |
| ** The output is a BLOB that begins with a variable-length integer that |
| ** is the input size in bytes (the size of X before compression). The |
| ** variable-length integer is implemented as 1 to 5 bytes. There are |
| ** seven bits per integer stored in the lower seven bits of each byte. |
| ** More significant bits occur first. The most significant bit (0x80) |
| ** is a flag to indicate the end of the integer. |
| ** |
| ** This function, SQLAR, and ZIP all use the same "deflate" compression |
| ** algorithm, but each is subtly different: |
| ** |
| ** * ZIP uses raw deflate. |
| ** |
| ** * SQLAR uses the "zlib format" which is raw deflate with a two-byte |
| ** algorithm-identification header and a four-byte checksum at the end. |
| ** |
| ** * This utility uses the "zlib format" like SQLAR, but adds the variable- |
| ** length integer uncompressed size value at the beginning. |
| ** |
| ** This function might be extended in the future to support compression |
| ** formats other than deflate, by providing a different algorithm-id |
| ** mark following the variable-length integer size parameter. |
| */ |
| static void compressFunc( |
| sqlite3_context *context, |
| int argc, |
| sqlite3_value **argv |
| ){ |
| const unsigned char *pIn; |
| unsigned char *pOut; |
| unsigned int nIn; |
| unsigned long int nOut; |
| unsigned char x[8]; |
| int rc; |
| int i, j; |
| |
| pIn = sqlite3_value_blob(argv[0]); |
| nIn = sqlite3_value_bytes(argv[0]); |
| nOut = 13 + nIn + (nIn+999)/1000; |
| pOut = sqlite3_malloc( nOut+5 ); |
| for(i=4; i>=0; i--){ |
| x[i] = (nIn >> (7*(4-i)))&0x7f; |
| } |
| for(i=0; i<4 && x[i]==0; i++){} |
| for(j=0; i<=4; i++, j++) pOut[j] = x[i]; |
| pOut[j-1] |= 0x80; |
| rc = compress(&pOut[j], &nOut, pIn, nIn); |
| if( rc==Z_OK ){ |
| sqlite3_result_blob(context, pOut, nOut+j, sqlite3_free); |
| }else{ |
| sqlite3_free(pOut); |
| } |
| } |
| |
| /* |
| ** Implementation of the "uncompress(X)" SQL function. The argument X |
| ** is a blob which was obtained from compress(Y). The output will be |
| ** the value Y. |
| */ |
| static void uncompressFunc( |
| sqlite3_context *context, |
| int argc, |
| sqlite3_value **argv |
| ){ |
| const unsigned char *pIn; |
| unsigned char *pOut; |
| unsigned int nIn; |
| unsigned long int nOut; |
| int rc; |
| int i; |
| |
| pIn = sqlite3_value_blob(argv[0]); |
| nIn = sqlite3_value_bytes(argv[0]); |
| nOut = 0; |
| for(i=0; i<nIn && i<5; i++){ |
| nOut = (nOut<<7) | (pIn[i]&0x7f); |
| if( (pIn[i]&0x80)!=0 ){ i++; break; } |
| } |
| pOut = sqlite3_malloc( nOut+1 ); |
| rc = uncompress(pOut, &nOut, &pIn[i], nIn-i); |
| if( rc==Z_OK ){ |
| sqlite3_result_blob(context, pOut, nOut, sqlite3_free); |
| }else{ |
| sqlite3_free(pOut); |
| } |
| } |
| |
| |
| #ifdef _WIN32 |
| __declspec(dllexport) |
| #endif |
| int sqlite3_compress_init( |
| sqlite3 *db, |
| char **pzErrMsg, |
| const sqlite3_api_routines *pApi |
| ){ |
| int rc = SQLITE_OK; |
| SQLITE_EXTENSION_INIT2(pApi); |
| (void)pzErrMsg; /* Unused parameter */ |
| rc = sqlite3_create_function(db, "compress", 1, |
| SQLITE_UTF8 | SQLITE_INNOCUOUS, |
| 0, compressFunc, 0, 0); |
| if( rc==SQLITE_OK ){ |
| rc = sqlite3_create_function(db, "uncompress", 1, |
| SQLITE_UTF8 | SQLITE_INNOCUOUS | SQLITE_DETERMINISTIC, |
| 0, uncompressFunc, 0, 0); |
| } |
| return rc; |
| } |