127 lines
3.8 KiB
C
127 lines
3.8 KiB
C
/*
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** 2017-12-17
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**
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** The author disclaims copyright to this source code. In place of
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** a legal notice, here is a blessing:
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**
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** May you do good and not evil.
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** May you find forgiveness for yourself and forgive others.
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** May you share freely, never taking more than you give.
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**
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******************************************************************************
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**
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** Utility functions sqlar_compress() and sqlar_uncompress(). Useful
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** for working with sqlar archives and used by the shell tool's built-in
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** sqlar support.
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*/
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#include "sqlite3ext.h"
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SQLITE_EXTENSION_INIT1
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#include <zlib.h>
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#include <assert.h>
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/*
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** Implementation of the "sqlar_compress(X)" SQL function.
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**
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** If the type of X is SQLITE_BLOB, and compressing that blob using
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** zlib utility function compress() yields a smaller blob, return the
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** compressed blob. Otherwise, return a copy of X.
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**
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** SQLar uses the "zlib format" for compressed content. The zlib format
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** contains a two-byte identification header and a four-byte checksum at
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** the end. This is different from ZIP which uses the raw deflate format.
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**
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** Future enhancements to SQLar might add support for new compression formats.
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** If so, those new formats will be identified by alternative headers in the
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** compressed data.
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*/
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static void sqlarCompressFunc(
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sqlite3_context *context,
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int argc,
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sqlite3_value **argv
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){
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assert( argc==1 );
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if( sqlite3_value_type(argv[0])==SQLITE_BLOB ){
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const Bytef *pData = sqlite3_value_blob(argv[0]);
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uLong nData = sqlite3_value_bytes(argv[0]);
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uLongf nOut = compressBound(nData);
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Bytef *pOut;
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pOut = (Bytef*)sqlite3_malloc(nOut);
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if( pOut==0 ){
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sqlite3_result_error_nomem(context);
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return;
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}else{
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if( Z_OK!=compress(pOut, &nOut, pData, nData) ){
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sqlite3_result_error(context, "error in compress()", -1);
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}else if( nOut<nData ){
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sqlite3_result_blob(context, pOut, nOut, SQLITE_TRANSIENT);
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}else{
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sqlite3_result_value(context, argv[0]);
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}
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sqlite3_free(pOut);
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}
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}else{
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sqlite3_result_value(context, argv[0]);
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}
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}
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/*
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** Implementation of the "sqlar_uncompress(X,SZ)" SQL function
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**
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** Parameter SZ is interpreted as an integer. If it is less than or
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** equal to zero, then this function returns a copy of X. Or, if
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** SZ is equal to the size of X when interpreted as a blob, also
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** return a copy of X. Otherwise, decompress blob X using zlib
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** utility function uncompress() and return the results (another
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** blob).
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*/
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static void sqlarUncompressFunc(
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sqlite3_context *context,
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int argc,
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sqlite3_value **argv
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){
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uLong nData;
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sqlite3_int64 sz;
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assert( argc==2 );
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sz = sqlite3_value_int(argv[1]);
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if( sz<=0 || sz==(nData = sqlite3_value_bytes(argv[0])) ){
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sqlite3_result_value(context, argv[0]);
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}else{
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uLongf szf = sz;
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const Bytef *pData= sqlite3_value_blob(argv[0]);
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Bytef *pOut = sqlite3_malloc(sz);
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if( pOut==0 ){
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sqlite3_result_error_nomem(context);
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}else if( Z_OK!=uncompress(pOut, &szf, pData, nData) ){
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sqlite3_result_error(context, "error in uncompress()", -1);
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}else{
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sqlite3_result_blob(context, pOut, szf, SQLITE_TRANSIENT);
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}
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sqlite3_free(pOut);
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}
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}
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#ifdef _WIN32
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__declspec(dllexport)
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#endif
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int sqlite3_sqlar_init(
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sqlite3 *db,
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char **pzErrMsg,
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const sqlite3_api_routines *pApi
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){
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int rc = SQLITE_OK;
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SQLITE_EXTENSION_INIT2(pApi);
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(void)pzErrMsg; /* Unused parameter */
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rc = sqlite3_create_function(db, "sqlar_compress", 1,
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SQLITE_UTF8|SQLITE_INNOCUOUS, 0,
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sqlarCompressFunc, 0, 0);
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if( rc==SQLITE_OK ){
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rc = sqlite3_create_function(db, "sqlar_uncompress", 2,
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SQLITE_UTF8|SQLITE_INNOCUOUS, 0,
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sqlarUncompressFunc, 0, 0);
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}
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return rc;
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}
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