3 * Copyright (c) 2003 Fabrice Bellard.
4 * Copyright (c) 2006 Konstantin Shishkov.
6 * This file is part of FFmpeg.
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.
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.
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
25 * @brief LZW decoding routines
26 * @author Fabrice Bellard
27 * Modified for use in TIFF by Konstantin Shishkov
33 #define LZW_MAXBITS 12
34 #define LZW_SIZTABLE (1<<LZW_MAXBITS)
36 static const uint16_t mask[17] =
38 0x0000, 0x0001, 0x0003, 0x0007,
39 0x000F, 0x001F, 0x003F, 0x007F,
40 0x00FF, 0x01FF, 0x03FF, 0x07FF,
41 0x0FFF, 0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF
50 int mode; ///< Decoder mode
51 int cursize; ///< The current code size
56 int newcodes; ///< First available code
57 int top_slot; ///< Highest code for current size
58 int top_slot2; ///< Highest possible code for current size (<=top_slot)
59 int slot; ///< Last read code
62 uint8_t stack[LZW_SIZTABLE];
63 uint8_t suffix[LZW_SIZTABLE];
64 uint16_t prefix[LZW_SIZTABLE];
65 int bs; ///< current buffer size for GIF
68 /* get one code from stream */
69 static int lzw_get_code(struct LZWState * s)
73 if(s->mode == FF_LZW_GIF) {
74 while (s->bbits < s->cursize) {
82 s->bbuf |= (*s->pbuf++) << s->bbits;
86 c = s->bbuf & s->curmask;
87 s->bbuf >>= s->cursize;
89 while (s->bbits < s->cursize) {
90 if (s->pbuf >= s->ebuf) {
93 s->bbuf = (s->bbuf << 8) | (*s->pbuf++);
96 c = (s->bbuf >> (s->bbits - s->cursize)) & s->curmask;
98 s->bbits -= s->cursize;
102 uint8_t* ff_lzw_cur_ptr(LZWState *p)
104 return ((struct LZWState*)p)->pbuf;
107 void ff_lzw_decode_tail(LZWState *p)
109 struct LZWState *s = (struct LZWState *)p;
110 while(!s->eob_reached)
114 void ff_lzw_decode_open(LZWState **p)
116 *p = av_mallocz(sizeof(struct LZWState));
119 void ff_lzw_decode_close(LZWState **p)
125 * Initialize LZW decoder
126 * @param s LZW context
127 * @param csize initial code size in bits
128 * @param buf input data
129 * @param buf_size input data size
130 * @param mode decoder working mode - either GIF or TIFF
132 int ff_lzw_decode_init(LZWState *p, int csize, uint8_t *buf, int buf_size, int mode)
134 struct LZWState *s = (struct LZWState *)p;
136 if(csize < 1 || csize > LZW_MAXBITS)
141 s->ebuf = s->pbuf + buf_size;
148 s->cursize = s->codesize + 1;
149 s->curmask = mask[s->cursize];
150 s->top_slot = 1 << s->cursize;
151 s->clear_code = 1 << s->codesize;
152 s->end_code = s->clear_code + 1;
153 s->slot = s->newcodes = s->clear_code + 2;
160 s->top_slot2 = s->top_slot;
163 s->top_slot2 = s->top_slot - 1;
172 * Decode given number of bytes
173 * NOTE: the algorithm here is inspired from the LZW GIF decoder
174 * written by Steven A. Bennett in 1987.
176 * @param s LZW context
177 * @param buf output buffer
178 * @param len number of bytes to decode
179 * @return number of bytes decoded
181 int ff_lzw_decode(LZWState *p, uint8_t *buf, int len){
182 int l, c, code, oc, fc;
184 struct LZWState *s = (struct LZWState *)p;
194 while (sp > s->stack) {
202 if (c == s->end_code) {
205 } else if (c == s->clear_code) {
206 s->cursize = s->codesize + 1;
207 s->curmask = mask[s->cursize];
208 s->slot = s->newcodes;
209 s->top_slot = 1 << s->cursize;
210 s->top_slot2 = s->top_slot;
211 if(s->mode == FF_LZW_TIFF)
213 while ((c = lzw_get_code(s)) == s->clear_code);
214 if (c == s->end_code) {
227 if (code >= s->slot) {
231 while (code >= s->newcodes) {
232 *sp++ = s->suffix[code];
233 code = s->prefix[code];
236 if (s->slot < s->top_slot) {
237 s->suffix[s->slot] = fc = code;
238 s->prefix[s->slot++] = oc;
241 if (s->slot >= s->top_slot2) {
242 if (s->cursize < LZW_MAXBITS) {
244 s->top_slot2 = s->top_slot;
245 if(s->mode == FF_LZW_TIFF)
247 s->curmask = mask[++s->cursize];
250 while (sp > s->stack) {