1 /* 2 * Copyright (c) 2016-present, Yann Collet, Facebook, Inc. 3 * All rights reserved. 4 * 5 * This source code is licensed under both the BSD-style license (found in the 6 * LICENSE file in the root directory of this source tree) and the GPLv2 (found 7 * in the COPYING file in the root directory of this source tree). 8 * You may select, at your option, one of the above-listed licenses. 9 */ 10 11 12 #include <stdio.h> // fprintf 13 #include <stdlib.h> // free 14 #include <zstd.h> // presumes zstd library is installed 15 #include "common.h" // Helper functions, CHECK(), and CHECK_ZSTD() 16 17 static void decompressFile_orDie(const char* fname) 18 { 19 FILE* const fin = fopen_orDie(fname, "rb"); 20 size_t const buffInSize = ZSTD_DStreamInSize(); 21 void* const buffIn = malloc_orDie(buffInSize); 22 FILE* const fout = stdout; 23 size_t const buffOutSize = ZSTD_DStreamOutSize(); /* Guarantee to successfully flush at least one complete compressed block in all circumstances. */ 24 void* const buffOut = malloc_orDie(buffOutSize); 25 26 ZSTD_DCtx* const dctx = ZSTD_createDCtx(); 27 CHECK(dctx != NULL, "ZSTD_createDCtx() failed!"); 28 29 /* This loop assumes that the input file is one or more concatenated zstd 30 * streams. This example won't work if there is trailing non-zstd data at 31 * the end, but streaming decompression in general handles this case. 32 * ZSTD_decompressStream() returns 0 exactly when the frame is completed, 33 * and doesn't consume input after the frame. 34 */ 35 size_t const toRead = buffInSize; 36 size_t read; 37 while ( (read = fread_orDie(buffIn, toRead, fin)) ) { 38 ZSTD_inBuffer input = { buffIn, read, 0 }; 39 /* Given a valid frame, zstd won't consume the last byte of the frame 40 * until it has flushed all of the decompressed data of the frame. 41 * Therefore, instead of checking if the return code is 0, we can 42 * decompress just check if input.pos < input.size. 43 */ 44 while (input.pos < input.size) { 45 ZSTD_outBuffer output = { buffOut, buffOutSize, 0 }; 46 /* The return code is zero if the frame is complete, but there may 47 * be multiple frames concatenated together. Zstd will automatically 48 * reset the context when a frame is complete. Still, calling 49 * ZSTD_DCtx_reset() can be useful to reset the context to a clean 50 * state, for instance if the last decompression call returned an 51 * error. 52 */ 53 size_t const ret = ZSTD_decompressStream(dctx, &output , &input); 54 CHECK_ZSTD(ret); 55 fwrite_orDie(buffOut, output.pos, fout); 56 } 57 } 58 59 ZSTD_freeDCtx(dctx); 60 fclose_orDie(fin); 61 fclose_orDie(fout); 62 free(buffIn); 63 free(buffOut); 64 } 65 66 67 int main(int argc, const char** argv) 68 { 69 const char* const exeName = argv[0]; 70 71 if (argc!=2) { 72 fprintf(stderr, "wrong arguments\n"); 73 fprintf(stderr, "usage:\n"); 74 fprintf(stderr, "%s FILE\n", exeName); 75 return 1; 76 } 77 78 const char* const inFilename = argv[1]; 79 80 decompressFile_orDie(inFilename); 81 return 0; 82 } 83