126 lines
3.8 KiB
C
126 lines
3.8 KiB
C
/*
|
|
** 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;
|
|
uLongf 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{
|
|
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, &sz, pData, nData) ){
|
|
sqlite3_result_error(context, "error in uncompress()", -1);
|
|
}else{
|
|
sqlite3_result_blob(context, pOut, sz, 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;
|
|
}
|