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