FFmpeg
lzf.c
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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 
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 += *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 += *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 }
#define AVERROR_INVALIDDATA
Invalid data found when processing input.
Definition: error.h:59
Memory handling functions.
uint8_t
#define LZF_LONG_BACKREF
Definition: lzf.c:38
void av_memcpy_backptr(uint8_t *dst, int back, int cnt)
Overlapping memcpy() implementation.
Definition: mem.c:426
ptrdiff_t size
Definition: opengl_enc.c:100
int ff_lzf_uncompress(GetByteContext *gb, uint8_t **buf, int64_t *size)
Definition: lzf.c:40
static av_always_inline unsigned int bytestream2_get_buffer(GetByteContext *g, uint8_t *dst, unsigned int size)
Definition: bytestream.h:263
static av_always_inline unsigned int bytestream2_get_bytes_left(GetByteContext *g)
Definition: bytestream.h:154
#define s(width, name)
Definition: cbs_vp9.c:257
int av_reallocp(void *ptr, size_t size)
Allocate, reallocate, or free a block of memory through a pointer to a pointer.
Definition: mem.c:163
void * buf
Definition: avisynth_c.h:766
#define LZF_LITERAL_MAX
Definition: lzf.c:37
int len