FFmpeg: libavcodec/lzf.c Source File

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lzf.c

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1 /*

2 * lzf decompression algorithm

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 */

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 */

32 #include "libavutil/mem.h"

34 #include "bytestream.h"

35 #include "lzf.h"

37 #define LZF_LITERAL_MAX (1 << 5)

38 #define LZF_LONG_BACKREF 7 + 2

40 int 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;

46 while (bytestream2_get_bytes_left(gb) > 2) {

47 uint8_t s = bytestream2_get_byte(gb);

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 }

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;

66 if (l == LZF_LONG_BACKREF)

67 l += bytestream2_get_byte(gb);

69 off += bytestream2_get_byte(gb);

71 if (off > len)

72 return AVERROR_INVALIDDATA;

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 }

82 av_memcpy_backptr(p, off, l);

84 p += l;

85 len += l;

86 }

87 }

89 *size = len;

91 return 0;

92 }

GetByteContext

Definition: bytestream.h:33

av_memcpy_backptr

void av_memcpy_backptr(uint8_t *dst, int back, int cnt)

Overlapping memcpy() implementation.

Definition: mem.c:454

#define s(width, name)

Definition: cbs_vp9.c:257

LZF_LITERAL_MAX

#define LZF_LITERAL_MAX

Definition: lzf.c:37

bytestream2_get_buffer

static av_always_inline unsigned int bytestream2_get_buffer(GetByteContext *g, uint8_t *dst, unsigned int size)

Definition: bytestream.h:267

bytestream2_get_bytes_left

static av_always_inline int bytestream2_get_bytes_left(GetByteContext *g)

Definition: bytestream.h:158

size

int size

Definition: twinvq_data.h:10344

av_reallocp

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:185

ff_lzf_uncompress

int ff_lzf_uncompress(GetByteContext *gb, uint8_t **buf, int64_t *size)

Definition: lzf.c:40

LZF_LONG_BACKREF

#define LZF_LONG_BACKREF

Definition: lzf.c:38

len

int len

Definition: vorbis_enc_data.h:426

ret

Definition: filter_design.txt:187

mem.h

bytestream.h

AVERROR_INVALIDDATA

#define AVERROR_INVALIDDATA

Invalid data found when processing input.

Definition: error.h:61

lzf.h

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