648db22b |
1 | /* |
2 | * Copyright (c) Meta Platforms, Inc. and affiliates. |
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 | } |