1 /* 2 * Copyright (c) 2016-2020, 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 size_t lastRet = 0; 38 int isEmpty = 1; 39 while ( (read = fread_orDie(buffIn, toRead, fin)) ) { 40 isEmpty = 0; 41 ZSTD_inBuffer input = { buffIn, read, 0 }; 42 /* Given a valid frame, zstd won't consume the last byte of the frame 43 * until it has flushed all of the decompressed data of the frame. 44 * Therefore, instead of checking if the return code is 0, we can 45 * decompress just check if input.pos < input.size. 46 */ 47 while (input.pos < input.size) { 48 ZSTD_outBuffer output = { buffOut, buffOutSize, 0 }; 49 /* The return code is zero if the frame is complete, but there may 50 * be multiple frames concatenated together. Zstd will automatically 51 * reset the context when a frame is complete. Still, calling 52 * ZSTD_DCtx_reset() can be useful to reset the context to a clean 53 * state, for instance if the last decompression call returned an 54 * error. 55 */ 56 size_t const ret = ZSTD_decompressStream(dctx, &output , &input); 57 CHECK_ZSTD(ret); 58 fwrite_orDie(buffOut, output.pos, fout); 59 lastRet = ret; 60 } 61 } 62 63 if (isEmpty) { 64 fprintf(stderr, "input is empty\n"); 65 exit(1); 66 } 67 68 if (lastRet != 0) { 69 /* The last return value from ZSTD_decompressStream did not end on a 70 * frame, but we reached the end of the file! We assume this is an 71 * error, and the input was truncated. 72 */ 73 fprintf(stderr, "EOF before end of stream: %zu\n", lastRet); 74 exit(1); 75 } 76 77 ZSTD_freeDCtx(dctx); 78 fclose_orDie(fin); 79 fclose_orDie(fout); 80 free(buffIn); 81 free(buffOut); 82 } 83 84 85 int main(int argc, const char** argv) 86 { 87 const char* const exeName = argv[0]; 88 89 if (argc!=2) { 90 fprintf(stderr, "wrong arguments\n"); 91 fprintf(stderr, "usage:\n"); 92 fprintf(stderr, "%s FILE\n", exeName); 93 return 1; 94 } 95 96 const char* const inFilename = argv[1]; 97 98 decompressFile_orDie(inFilename); 99 return 0; 100 } 101