1/*
2 * Copyright (c) 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
17static 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
85int 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