lzw: switch to bytestream2
[libav.git] / libavcodec / lzw.c
1 /*
2 * LZW decoder
3 * Copyright (c) 2003 Fabrice Bellard
4 * Copyright (c) 2006 Konstantin Shishkov
5 *
6 * This file is part of Libav.
7 *
8 * Libav 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 * Libav 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 Libav; 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 {
47 GetByteContext gb;
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;
55 int clear_code;
56 int end_code;
57 int newcodes; ///< First available code
58 int top_slot; ///< Highest code for current size
59 int extra_slot;
60 int slot; ///< Last read code
61 int fc, oc;
62 uint8_t *sp;
63 uint8_t stack[LZW_SIZTABLE];
64 uint8_t suffix[LZW_SIZTABLE];
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->mode == FF_LZW_GIF) {
75 while (s->bbits < s->cursize) {
76 if (!s->bs) {
77 s->bs = bytestream2_get_byte(&s->gb);
78 }
79 s->bbuf |= bytestream2_get_byte(&s->gb) << s->bbits;
80 s->bbits += 8;
81 s->bs--;
82 }
83 c = s->bbuf;
84 s->bbuf >>= s->cursize;
85 } else { // TIFF
86 while (s->bbits < s->cursize) {
87 s->bbuf = (s->bbuf << 8) | bytestream2_get_byte(&s->gb);
88 s->bbits += 8;
89 }
90 c = s->bbuf >> (s->bbits - s->cursize);
91 }
92 s->bbits -= s->cursize;
93 return c & s->curmask;
94 }
95
96 int ff_lzw_size_read(LZWState *p)
97 {
98 struct LZWState *s = p;
99 return bytestream2_tell(&s->gb);
100 }
101
102 void ff_lzw_decode_tail(LZWState *p)
103 {
104 struct LZWState *s = (struct LZWState *)p;
105
106 if(s->mode == FF_LZW_GIF) {
107 while (s->bs > 0 && bytestream2_get_bytes_left(&s->gb)) {
108 bytestream2_skip(&s->gb, s->bs);
109 s->bs = bytestream2_get_byte(&s->gb);
110 }
111 }else
112 bytestream2_skip(&s->gb, bytestream2_get_bytes_left(&s->gb));
113 }
114
115 av_cold void ff_lzw_decode_open(LZWState **p)
116 {
117 *p = av_mallocz(sizeof(struct LZWState));
118 }
119
120 av_cold void ff_lzw_decode_close(LZWState **p)
121 {
122 av_freep(p);
123 }
124
125 /**
126 * Initialize LZW decoder
127 * @param p LZW context
128 * @param csize initial code size in bits
129 * @param buf input data
130 * @param buf_size input data size
131 * @param mode decoder working mode - either GIF or TIFF
132 */
133 int ff_lzw_decode_init(LZWState *p, int csize, const uint8_t *buf, int buf_size, int mode)
134 {
135 struct LZWState *s = (struct LZWState *)p;
136
137 if(csize < 1 || csize >= LZW_MAXBITS)
138 return -1;
139 /* read buffer */
140 bytestream2_init(&s->gb, buf, buf_size);
141 s->bbuf = 0;
142 s->bbits = 0;
143 s->bs = 0;
144
145 /* decoder */
146 s->codesize = csize;
147 s->cursize = s->codesize + 1;
148 s->curmask = mask[s->cursize];
149 s->top_slot = 1 << s->cursize;
150 s->clear_code = 1 << s->codesize;
151 s->end_code = s->clear_code + 1;
152 s->slot = s->newcodes = s->clear_code + 2;
153 s->oc = s->fc = -1;
154 s->sp = s->stack;
155
156 s->mode = mode;
157 s->extra_slot = s->mode == FF_LZW_TIFF;
158 return 0;
159 }
160
161 /**
162 * Decode given number of bytes
163 * NOTE: the algorithm here is inspired from the LZW GIF decoder
164 * written by Steven A. Bennett in 1987.
165 *
166 * @param p LZW context
167 * @param buf output buffer
168 * @param len number of bytes to decode
169 * @return number of bytes decoded
170 */
171 int ff_lzw_decode(LZWState *p, uint8_t *buf, int len){
172 int l, c, code, oc, fc;
173 uint8_t *sp;
174 struct LZWState *s = (struct LZWState *)p;
175
176 if (s->end_code < 0)
177 return 0;
178
179 l = len;
180 sp = s->sp;
181 oc = s->oc;
182 fc = s->fc;
183
184 for (;;) {
185 while (sp > s->stack) {
186 *buf++ = *(--sp);
187 if ((--l) == 0)
188 goto the_end;
189 }
190 c = lzw_get_code(s);
191 if (c == s->end_code) {
192 break;
193 } else if (c == s->clear_code) {
194 s->cursize = s->codesize + 1;
195 s->curmask = mask[s->cursize];
196 s->slot = s->newcodes;
197 s->top_slot = 1 << s->cursize;
198 fc= oc= -1;
199 } else {
200 code = c;
201 if (code == s->slot && fc>=0) {
202 *sp++ = fc;
203 code = oc;
204 }else if(code >= s->slot)
205 break;
206 while (code >= s->newcodes) {
207 *sp++ = s->suffix[code];
208 code = s->prefix[code];
209 }
210 *sp++ = code;
211 if (s->slot < s->top_slot && oc>=0) {
212 s->suffix[s->slot] = code;
213 s->prefix[s->slot++] = oc;
214 }
215 fc = code;
216 oc = c;
217 if (s->slot >= s->top_slot - s->extra_slot) {
218 if (s->cursize < LZW_MAXBITS) {
219 s->top_slot <<= 1;
220 s->curmask = mask[++s->cursize];
221 }
222 }
223 }
224 }
225 s->end_code = -1;
226 the_end:
227 s->sp = sp;
228 s->oc = oc;
229 s->fc = fc;
230 return len - l;
231 }