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