blob: 7e50986e37aabe54a6ce266f5b710aa8ee6ae308 [file] [log] [blame]
* Copyright (c) 2016-2020, Yann Collet, Facebook, Inc.
* All rights reserved.
* This source code is licensed under both the BSD-style license (found in the
* LICENSE file in the root directory of this source tree) and the GPLv2 (found
* in the COPYING file in the root directory of this source tree).
* You may select, at your option, one of the above-listed licenses.
#include <stdio.h> // printf
#include <stdlib.h> // free
#include <zstd.h> // presumes zstd library is installed
#include "common.h" // Helper functions, CHECK(), and CHECK_ZSTD()
/* createDict() :
`dictFileName` is supposed to have been created using `zstd --train` */
static ZSTD_DDict* createDict_orDie(const char* dictFileName)
size_t dictSize;
printf("loading dictionary %s \n", dictFileName);
void* const dictBuffer = mallocAndLoadFile_orDie(dictFileName, &dictSize);
ZSTD_DDict* const ddict = ZSTD_createDDict(dictBuffer, dictSize);
CHECK(ddict != NULL, "ZSTD_createDDict() failed!");
return ddict;
static void decompress(const char* fname, const ZSTD_DDict* ddict)
size_t cSize;
void* const cBuff = mallocAndLoadFile_orDie(fname, &cSize);
/* Read the content size from the frame header. For simplicity we require
* that it is always present. By default, zstd will write the content size
* in the header when it is known. If you can't guarantee that the frame
* content size is always written into the header, either use streaming
* decompression, or ZSTD_decompressBound().
unsigned long long const rSize = ZSTD_getFrameContentSize(cBuff, cSize);
CHECK(rSize != ZSTD_CONTENTSIZE_ERROR, "%s: not compressed by zstd!", fname);
CHECK(rSize != ZSTD_CONTENTSIZE_UNKNOWN, "%s: original size unknown!", fname);
void* const rBuff = malloc_orDie((size_t)rSize);
/* Check that the dictionary ID matches.
* If a non-zstd dictionary is used, then both will be zero.
* By default zstd always writes the dictionary ID into the frame.
* Zstd will check if there is a dictionary ID mismatch as well.
unsigned const expectedDictID = ZSTD_getDictID_fromDDict(ddict);
unsigned const actualDictID = ZSTD_getDictID_fromFrame(cBuff, cSize);
CHECK(actualDictID == expectedDictID,
"DictID mismatch: expected %u got %u",
/* Decompress using the dictionary.
* If you need to control the decompression parameters, then use the
* advanced API: ZSTD_DCtx_setParameter(), ZSTD_DCtx_refDDict(), and
* ZSTD_decompressDCtx().
ZSTD_DCtx* const dctx = ZSTD_createDCtx();
CHECK(dctx != NULL, "ZSTD_createDCtx() failed!");
size_t const dSize = ZSTD_decompress_usingDDict(dctx, rBuff, rSize, cBuff, cSize, ddict);
/* When zstd knows the content size, it will error if it doesn't match. */
CHECK(dSize == rSize, "Impossible because zstd will check this condition!");
/* success */
printf("%25s : %6u -> %7u \n", fname, (unsigned)cSize, (unsigned)rSize);
int main(int argc, const char** argv)
const char* const exeName = argv[0];
if (argc<3) {
printf("wrong arguments\n");
printf("%s [FILES] dictionary\n", exeName);
return 1;
/* load dictionary only once */
const char* const dictName = argv[argc-1];
ZSTD_DDict* const dictPtr = createDict_orDie(dictName);
int u;
for (u=1; u<argc-1; u++) decompress(argv[u], dictPtr);
printf("All %u files correctly decoded (in memory) \n", argc-2);
return 0;