blob: 26eda3441b7fb6453495f15094568350b974102e [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> // fprintf
#include <stdlib.h> // free
#include <zstd.h> // presumes zstd library is installed
#include "common.h" // Helper functions, CHECK(), and CHECK_ZSTD()
static void decompressFile_orDie(const char* fname)
FILE* const fin = fopen_orDie(fname, "rb");
size_t const buffInSize = ZSTD_DStreamInSize();
void* const buffIn = malloc_orDie(buffInSize);
FILE* const fout = stdout;
size_t const buffOutSize = ZSTD_DStreamOutSize(); /* Guarantee to successfully flush at least one complete compressed block in all circumstances. */
void* const buffOut = malloc_orDie(buffOutSize);
ZSTD_DCtx* const dctx = ZSTD_createDCtx();
CHECK(dctx != NULL, "ZSTD_createDCtx() failed!");
/* This loop assumes that the input file is one or more concatenated zstd
* streams. This example won't work if there is trailing non-zstd data at
* the end, but streaming decompression in general handles this case.
* ZSTD_decompressStream() returns 0 exactly when the frame is completed,
* and doesn't consume input after the frame.
size_t const toRead = buffInSize;
size_t read;
size_t lastRet = 0;
int isEmpty = 1;
while ( (read = fread_orDie(buffIn, toRead, fin)) ) {
isEmpty = 0;
ZSTD_inBuffer input = { buffIn, read, 0 };
/* Given a valid frame, zstd won't consume the last byte of the frame
* until it has flushed all of the decompressed data of the frame.
* Therefore, instead of checking if the return code is 0, we can
* decompress just check if input.pos < input.size.
while (input.pos < input.size) {
ZSTD_outBuffer output = { buffOut, buffOutSize, 0 };
/* The return code is zero if the frame is complete, but there may
* be multiple frames concatenated together. Zstd will automatically
* reset the context when a frame is complete. Still, calling
* ZSTD_DCtx_reset() can be useful to reset the context to a clean
* state, for instance if the last decompression call returned an
* error.
size_t const ret = ZSTD_decompressStream(dctx, &output , &input);
fwrite_orDie(buffOut, output.pos, fout);
lastRet = ret;
if (isEmpty) {
fprintf(stderr, "input is empty\n");
if (lastRet != 0) {
/* The last return value from ZSTD_decompressStream did not end on a
* frame, but we reached the end of the file! We assume this is an
* error, and the input was truncated.
fprintf(stderr, "EOF before end of stream: %zu\n", lastRet);
int main(int argc, const char** argv)
const char* const exeName = argv[0];
if (argc!=2) {
fprintf(stderr, "wrong arguments\n");
fprintf(stderr, "usage:\n");
fprintf(stderr, "%s FILE\n", exeName);
return 1;
const char* const inFilename = argv[1];
return 0;