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Overview
Comment: | Add an extension that implements compress() and uncompress() SQL functions. |
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Downloads: | Tarball | ZIP archive |
Timelines: | family | ancestors | descendants | both | trunk |
Files: | files | file ages | folders |
SHA1: |
d5c17d1a423321f766616d82c9b27ef8 |
User & Date: | drh 2014-06-13 13:08:21.440 |
Context
2014-06-13
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13:43 | Add the fileio.c loadable extension, that implements readfile() and writefile() SQL functions. (check-in: 0ca104d821 user: drh tags: trunk) | |
13:08 | Add an extension that implements compress() and uncompress() SQL functions. (check-in: d5c17d1a42 user: drh tags: trunk) | |
2014-06-12
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17:10 | Increase the WAL-mode SQLITE_PROTOCOL timeout to 10 seconds. (check-in: 2aeacf81df user: drh tags: trunk) | |
Changes
Added ext/misc/compress.c.
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 | /* ** 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. */ 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 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; compress(&pOut[j], &nOut, pIn, nIn); sqlite3_result_blob(context, pOut, nOut+j, sqlite3_free); } /* ** 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); } } #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, 0, compressFunc, 0, 0); if( rc==SQLITE_OK ){ rc = sqlite3_create_function(db, "uncompress", 1, SQLITE_UTF8, 0, uncompressFunc, 0, 0); } return rc; } |