SQLite: sqlar.c (original) (raw)

`/* ** 2017-12-17 ** ** 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. **

** ** Utility functions sqlar_compress() and sqlar_uncompress(). Useful ** for working with sqlar archives and used by the shell tool's built-in ** sqlar support. */ #include "sqlite3ext.h" SQLITE_EXTENSION_INIT1 #include <zlib.h> #include <assert.h>

/* ** Implementation of the "sqlar_compress(X)" SQL function. ** ** If the type of X is SQLITE_BLOB, and compressing that blob using ** zlib utility function compress() yields a smaller blob, return the ** compressed blob. Otherwise, return a copy of X. ** ** SQLar uses the "zlib format" for compressed content. The zlib format ** contains a two-byte identification header and a four-byte checksum at ** the end. This is different from ZIP which uses the raw deflate format. ** ** Future enhancements to SQLar might add support for new compression formats. ** If so, those new formats will be identified by alternative headers in the ** compressed data. */ static void sqlarCompressFunc( sqlite3_context *context, int argc, sqlite3_value **argv ){ assert( argc==1 ); if( sqlite3_value_type(argv[0])==SQLITE_BLOB ){ const Bytef *pData = sqlite3_value_blob(argv[0]); uLong nData = sqlite3_value_bytes(argv[0]); uLongf nOut = compressBound(nData); Bytef *pOut;

pOut = (Bytef*)sqlite3_malloc(nOut);
if( pOut==0 ){
  sqlite3_result_error_nomem(context);
  return;
}else{
  if( Z_OK!=compress(pOut, &nOut, pData, nData) ){
    sqlite3_result_error(context, "error in compress()", -1);
  }else if( nOut<nData ){
    sqlite3_result_blob(context, pOut, nOut, SQLITE_TRANSIENT);
  }else{
    sqlite3_result_value(context, argv[0]);
  }
  sqlite3_free(pOut);
}

}else{ sqlite3_result_value(context, argv[0]); } }

/* ** Implementation of the "sqlar_uncompress(X,SZ)" SQL function ** ** Parameter SZ is interpreted as an integer. If it is less than or ** equal to zero, then this function returns a copy of X. Or, if ** SZ is equal to the size of X when interpreted as a blob, also ** return a copy of X. Otherwise, decompress blob X using zlib ** utility function uncompress() and return the results (another ** blob). */ static void sqlarUncompressFunc( sqlite3_context *context, int argc, sqlite3_value **argv ){ uLong nData; sqlite3_int64 sz;

assert( argc==2 ); sz = sqlite3_value_int(argv[1]);

if( sz<=0 || sz==(nData = sqlite3_value_bytes(argv[0])) ){ sqlite3_result_value(context, argv[0]); }else{ uLongf szf = sz; const Bytef *pData= sqlite3_value_blob(argv[0]); Bytef *pOut = sqlite3_malloc(sz); if( pOut==0 ){ sqlite3_result_error_nomem(context); }else if( Z_OK!=uncompress(pOut, &szf, pData, nData) ){ sqlite3_result_error(context, "error in uncompress()", -1); }else{ sqlite3_result_blob(context, pOut, szf, SQLITE_TRANSIENT); } sqlite3_free(pOut); } }

#ifdef _WIN32 __declspec(dllexport) #endif int sqlite3_sqlar_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, "sqlar_compress", 1, SQLITE_UTF8|SQLITE_INNOCUOUS, 0, sqlarCompressFunc, 0, 0); if( rc==SQLITE_OK ){ rc = sqlite3_create_function(db, "sqlar_uncompress", 2, SQLITE_UTF8|SQLITE_INNOCUOUS, 0, sqlarUncompressFunc, 0, 0); } return rc; } `