xref: /third_party/ffmpeg/libavcodec/lzf.c (revision cabdff1a) 
1/*
2 * lzf decompression algorithm
3 * Copyright (c) 2015 Luca Barbato
4 *
5 * This file is part of FFmpeg.
6 *
7 * FFmpeg is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
11 *
12 * FFmpeg is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 */
21
22/**
23 * @file
24 * lzf decompression
25 *
26 * LZF is a fast compression/decompression algorithm that takes very little
27 * code space and working memory, ideal for real-time and block compression.
28 *
29 * https://en.wikibooks.org/wiki/Data_Compression/Dictionary_compression#LZF
30 */
31
32#include "libavutil/mem.h"
33
34#include "bytestream.h"
35#include "lzf.h"
36
37#define LZF_LITERAL_MAX (1 << 5)
38#define LZF_LONG_BACKREF 7 + 2
39
40int ff_lzf_uncompress(GetByteContext *gb, uint8_t **buf, int64_t *size)
41{
42    int ret     = 0;
43    uint8_t *p  = *buf;
44    int64_t len = 0;
45
46    while (bytestream2_get_bytes_left(gb) > 2) {
47        uint8_t s = bytestream2_get_byte(gb);
48
49        if (s < LZF_LITERAL_MAX) {
50            s++;
51            if (s > *size - len) {
52                *size += s + *size /2;
53                ret = av_reallocp(buf, *size);
54                if (ret < 0)
55                    return ret;
56                p = *buf + len;
57            }
58
59            bytestream2_get_buffer(gb, p, s);
60            p   += s;
61            len += s;
62        } else {
63            int l   = 2 + (s >> 5);
64            int off = ((s & 0x1f) << 8) + 1;
65
66            if (l == LZF_LONG_BACKREF)
67                l += bytestream2_get_byte(gb);
68
69            off += bytestream2_get_byte(gb);
70
71            if (off > len)
72                return AVERROR_INVALIDDATA;
73
74            if (l > *size - len) {
75                *size += l + *size / 2;
76                ret = av_reallocp(buf, *size);
77                if (ret < 0)
78                    return ret;
79                p = *buf + len;
80            }
81
82            av_memcpy_backptr(p, off, l);
83
84            p   += l;
85            len += l;
86        }
87    }
88
89    *size = len;
90
91    return 0;
92}
93