FFmpeg  4.4.5
lzw.c
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1 /*
2  * LZW decoder
3  * Copyright (c) 2003 Fabrice Bellard
4  * Copyright (c) 2006 Konstantin Shishkov
5  *
6  * This file is part of FFmpeg.
7  *
8  * FFmpeg is free software; you can redistribute it and/or
9  * modify it under the terms of the GNU Lesser General Public
10  * License as published by the Free Software Foundation; either
11  * version 2.1 of the License, or (at your option) any later version.
12  *
13  * FFmpeg is distributed in the hope that it will be useful,
14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16  * Lesser General Public License for more details.
17  *
18  * You should have received a copy of the GNU Lesser General Public
19  * License along with FFmpeg; if not, write to the Free Software
20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21  */
22 
23 /**
24  * @file
25  * @brief LZW decoding routines
26  * @author Fabrice Bellard
27  * @author modified for use in TIFF by Konstantin Shishkov
28  */
29 
30 #include "avcodec.h"
31 #include "bytestream.h"
32 #include "lzw.h"
33 #include "libavutil/mem.h"
34 
35 #define LZW_MAXBITS 12
36 #define LZW_SIZTABLE (1<<LZW_MAXBITS)
37 
38 static const uint16_t mask[17] =
39 {
40  0x0000, 0x0001, 0x0003, 0x0007,
41  0x000F, 0x001F, 0x003F, 0x007F,
42  0x00FF, 0x01FF, 0x03FF, 0x07FF,
43  0x0FFF, 0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF
44 };
45 
46 struct LZWState {
48  int bbits;
49  unsigned int bbuf;
50 
51  int mode; ///< Decoder mode
52  int cursize; ///< The current code size
53  int curmask;
54  int codesize;
56  int end_code;
57  int newcodes; ///< First available code
58  int top_slot; ///< Highest code for current size
60  int slot; ///< Last read code
61  int fc, oc;
65  uint16_t prefix[LZW_SIZTABLE];
66  int bs; ///< current buffer size for GIF
67 };
68 
69 /* get one code from stream */
70 static int lzw_get_code(struct LZWState * s)
71 {
72  int c;
73 
74  if (s->bbits < s->cursize && bytestream2_get_bytes_left(&s->gb) <= 0)
75  return s->end_code;
76 
77  if(s->mode == FF_LZW_GIF) {
78  while (s->bbits < s->cursize) {
79  if (!s->bs) {
80  s->bs = bytestream2_get_byte(&s->gb);
81  }
82  s->bbuf |= bytestream2_get_byte(&s->gb) << s->bbits;
83  s->bbits += 8;
84  s->bs--;
85  }
86  c = s->bbuf;
87  s->bbuf >>= s->cursize;
88  } else { // TIFF
89  while (s->bbits < s->cursize) {
90  s->bbuf = (s->bbuf << 8) | bytestream2_get_byte(&s->gb);
91  s->bbits += 8;
92  }
93  c = s->bbuf >> (s->bbits - s->cursize);
94  }
95  s->bbits -= s->cursize;
96  return c & s->curmask;
97 }
98 
100 {
101  struct LZWState *s = (struct LZWState *)p;
102 
103  if(s->mode == FF_LZW_GIF) {
104  while (s->bs > 0 && bytestream2_get_bytes_left(&s->gb)) {
105  bytestream2_skip(&s->gb, s->bs);
106  s->bs = bytestream2_get_byte(&s->gb);
107  }
108  }else
110  return bytestream2_tell(&s->gb);
111 }
112 
114 {
115  *p = av_mallocz(sizeof(struct LZWState));
116 }
117 
119 {
120  av_freep(p);
121 }
122 
123 /**
124  * Initialize LZW decoder
125  * @param p LZW context
126  * @param csize initial code size in bits
127  * @param buf input data
128  * @param buf_size input data size
129  * @param mode decoder working mode - either GIF or TIFF
130  */
131 int ff_lzw_decode_init(LZWState *p, int csize, const uint8_t *buf, int buf_size, int mode)
132 {
133  struct LZWState *s = (struct LZWState *)p;
134 
135  if(csize < 1 || csize >= LZW_MAXBITS)
136  return -1;
137  /* read buffer */
138  bytestream2_init(&s->gb, buf, buf_size);
139  s->bbuf = 0;
140  s->bbits = 0;
141  s->bs = 0;
142 
143  /* decoder */
144  s->codesize = csize;
145  s->cursize = s->codesize + 1;
146  s->curmask = mask[s->cursize];
147  s->top_slot = 1 << s->cursize;
148  s->clear_code = 1 << s->codesize;
149  s->end_code = s->clear_code + 1;
150  s->slot = s->newcodes = s->clear_code + 2;
151  s->oc = s->fc = -1;
152  s->sp = s->stack;
153 
154  s->mode = mode;
155  s->extra_slot = s->mode == FF_LZW_TIFF;
156  return 0;
157 }
158 
159 /**
160  * Decode given number of bytes
161  * NOTE: the algorithm here is inspired from the LZW GIF decoder
162  * written by Steven A. Bennett in 1987.
163  *
164  * @param p LZW context
165  * @param buf output buffer
166  * @param len number of bytes to decode
167  * @return number of bytes decoded
168  */
169 int ff_lzw_decode(LZWState *p, uint8_t *buf, int len){
170  int l, c, code, oc, fc;
171  uint8_t *sp;
172  struct LZWState *s = (struct LZWState *)p;
173 
174  if (s->end_code < 0)
175  return 0;
176 
177  l = len;
178  sp = s->sp;
179  oc = s->oc;
180  fc = s->fc;
181 
182  for (;;) {
183  while (sp > s->stack) {
184  *buf++ = *(--sp);
185  if ((--l) == 0)
186  goto the_end;
187  }
188  c = lzw_get_code(s);
189  if (c == s->end_code) {
190  break;
191  } else if (c == s->clear_code) {
192  s->cursize = s->codesize + 1;
193  s->curmask = mask[s->cursize];
194  s->slot = s->newcodes;
195  s->top_slot = 1 << s->cursize;
196  fc= oc= -1;
197  } else {
198  code = c;
199  if (code == s->slot && fc>=0) {
200  *sp++ = fc;
201  code = oc;
202  }else if(code >= s->slot)
203  break;
204  while (code >= s->newcodes) {
205  *sp++ = s->suffix[code];
206  code = s->prefix[code];
207  }
208  *sp++ = code;
209  if (s->slot < s->top_slot && oc>=0) {
210  s->suffix[s->slot] = code;
211  s->prefix[s->slot++] = oc;
212  }
213  fc = code;
214  oc = c;
215  if (s->slot >= s->top_slot - s->extra_slot) {
216  if (s->cursize < LZW_MAXBITS) {
217  s->top_slot <<= 1;
218  s->curmask = mask[++s->cursize];
219  }
220  }
221  }
222  }
223  s->end_code = -1;
224  the_end:
225  s->sp = sp;
226  s->oc = oc;
227  s->fc = fc;
228  return len - l;
229 }
#define av_cold
Definition: attributes.h:88
uint8_t
Libavcodec external API header.
static av_always_inline int bytestream2_get_bytes_left(GetByteContext *g)
Definition: bytestream.h:158
static av_always_inline void bytestream2_init(GetByteContext *g, const uint8_t *buf, int buf_size)
Definition: bytestream.h:137
static av_always_inline void bytestream2_skip(GetByteContext *g, unsigned int size)
Definition: bytestream.h:168
static av_always_inline int bytestream2_tell(GetByteContext *g)
Definition: bytestream.h:192
#define fc(width, name, range_min, range_max)
Definition: cbs_av1.c:562
#define s(width, name)
Definition: cbs_vp9.c:257
mode
Use these values in ebur128_init (or'ed).
Definition: ebur128.h:83
void * av_mallocz(size_t size)
Allocate a memory block with alignment suitable for all memory accesses (including vectors if availab...
Definition: mem.c:237
av_cold void ff_lzw_decode_close(LZWState **p)
Definition: lzw.c:118
int ff_lzw_decode_init(LZWState *p, int csize, const uint8_t *buf, int buf_size, int mode)
Initialize LZW decoder.
Definition: lzw.c:131
static const uint16_t mask[17]
Definition: lzw.c:38
#define LZW_MAXBITS
Definition: lzw.c:35
static int lzw_get_code(struct LZWState *s)
Definition: lzw.c:70
#define LZW_SIZTABLE
Definition: lzw.c:36
int ff_lzw_decode(LZWState *p, uint8_t *buf, int len)
Decode given number of bytes NOTE: the algorithm here is inspired from the LZW GIF decoder written by...
Definition: lzw.c:169
av_cold void ff_lzw_decode_open(LZWState **p)
Definition: lzw.c:113
int ff_lzw_decode_tail(LZWState *p)
Definition: lzw.c:99
LZW decoding routines.
@ FF_LZW_TIFF
Definition: lzw.h:39
@ FF_LZW_GIF
Definition: lzw.h:38
Memory handling functions.
#define sp
Definition: regdef.h:63
const uint8_t * code
Definition: spdifenc.c:413
Definition: lzw.c:46
GetByteContext gb
Definition: lzw.c:47
int codesize
Definition: lzw.c:54
int fc
Definition: lzw.c:61
int newcodes
First available code.
Definition: lzw.c:57
int mode
Decoder mode.
Definition: lzw.c:51
unsigned int bbuf
Definition: lzw.c:49
int clear_code
Definition: lzw.c:55
uint16_t prefix[LZW_SIZTABLE]
Definition: lzw.c:65
int slot
Last read code.
Definition: lzw.c:60
int curmask
Definition: lzw.c:53
int bs
current buffer size for GIF
Definition: lzw.c:66
int extra_slot
Definition: lzw.c:59
uint8_t stack[LZW_SIZTABLE]
Definition: lzw.c:63
int top_slot
Highest code for current size.
Definition: lzw.c:58
uint8_t * sp
Definition: lzw.c:62
int oc
Definition: lzw.c:61
int cursize
The current code size.
Definition: lzw.c:52
int end_code
Definition: lzw.c:56
int bbits
Definition: lzw.c:48
uint8_t suffix[LZW_SIZTABLE]
Definition: lzw.c:64
#define av_freep(p)
int len
static double c[64]