mirror of https://github.com/FFmpeg/FFmpeg.git
Originally committed as revision 6795 to svn://svn.ffmpeg.org/ffmpeg/trunkpull/126/head
Kostya Shishkov
19 years ago
parent
b0c32a70b4
commit
ffc5430bc3
6 changed files with 342 additions and 174 deletions
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/*
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* LZW decoder |
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* Copyright (c) 2003 Fabrice Bellard. |
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* Copyright (c) 2006 Konstantin Shishkov. |
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* |
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* This file is part of FFmpeg. |
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* |
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* FFmpeg is free software; you can redistribute it and/or |
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* modify it under the terms of the GNU Lesser General Public |
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* License as published by the Free Software Foundation; either |
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* version 2.1 of the License, or (at your option) any later version. |
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* |
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* FFmpeg is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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* Lesser General Public License for more details. |
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* |
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* You should have received a copy of the GNU Lesser General Public |
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* License along with FFmpeg; if not, write to the Free Software |
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
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*/ |
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/**
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* @file lzw.c |
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* @brief LZW decoding routines |
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* @author Fabrice Bellard |
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* Modified for use in TIFF by Konstantin Shishkov |
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*/ |
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#include "avcodec.h" |
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#include "lzw.h" |
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#define LZW_MAXBITS 12 |
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#define LZW_SIZTABLE (1<<LZW_MAXBITS) |
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static const uint16_t mask[17] = |
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{ |
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0x0000, 0x0001, 0x0003, 0x0007, |
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0x000F, 0x001F, 0x003F, 0x007F, |
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0x00FF, 0x01FF, 0x03FF, 0x07FF, |
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0x0FFF, 0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF |
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}; |
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struct LZWState { |
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int eob_reached; |
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uint8_t *pbuf, *ebuf; |
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int bbits; |
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unsigned int bbuf; |
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int mode; ///< Decoder mode
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int cursize; ///< The current code size
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int curmask; |
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int codesize; |
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int clear_code; |
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int end_code; |
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int newcodes; ///< First available code
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int top_slot; ///< Highest code for current size
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int top_slot2; ///< Highest possible code for current size (<=top_slot)
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int slot; ///< Last read code
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int fc, oc; |
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uint8_t *sp; |
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uint8_t stack[LZW_SIZTABLE]; |
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uint8_t suffix[LZW_SIZTABLE]; |
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uint16_t prefix[LZW_SIZTABLE]; |
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int bs; ///< current buffer size for GIF
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}; |
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/* get one code from stream */ |
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static int lzw_get_code(struct LZWState * s) |
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{ |
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int c, sizbuf; |
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if(s->mode == FF_LZW_GIF) { |
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while (s->bbits < s->cursize) { |
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if (!s->bs) { |
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sizbuf = *s->pbuf++; |
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s->bs = sizbuf; |
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if(!sizbuf) { |
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s->eob_reached = 1; |
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} |
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} |
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s->bbuf |= (*s->pbuf++) << s->bbits; |
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s->bbits += 8; |
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s->bs--; |
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} |
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c = s->bbuf & s->curmask; |
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s->bbuf >>= s->cursize; |
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} else { // TIFF
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while (s->bbits < s->cursize) { |
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if (s->pbuf >= s->ebuf) { |
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s->eob_reached = 1; |
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} |
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s->bbuf = (s->bbuf << 8) | (*s->pbuf++); |
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s->bbits += 8; |
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} |
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c = (s->bbuf >> (s->bbits - s->cursize)) & s->curmask; |
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} |
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s->bbits -= s->cursize; |
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return c; |
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} |
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uint8_t* ff_lzw_cur_ptr(LZWState *p) |
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{ |
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return ((struct LZWState*)p)->pbuf; |
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} |
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void ff_lzw_decode_tail(LZWState *p) |
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{ |
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struct LZWState *s = (struct LZWState *)p; |
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while(!s->eob_reached) |
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lzw_get_code(s); |
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} |
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void ff_lzw_decode_open(LZWState **p) |
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{ |
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*p = av_mallocz(sizeof(struct LZWState)); |
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} |
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void ff_lzw_decode_close(LZWState **p) |
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{ |
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av_freep(p); |
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} |
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/**
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* Initialize LZW decoder |
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* @param s LZW context |
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* @param csize initial code size in bits |
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* @param buf input data |
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* @param buf_size input data size |
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* @param mode decoder working mode - either GIF or TIFF |
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*/ |
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int ff_lzw_decode_init(LZWState *p, int csize, uint8_t *buf, int buf_size, int mode) |
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{ |
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struct LZWState *s = (struct LZWState *)p; |
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if(csize < 1 || csize > LZW_MAXBITS) |
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return -1; |
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/* read buffer */ |
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s->eob_reached = 0; |
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s->pbuf = buf; |
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s->ebuf = s->pbuf + buf_size; |
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s->bbuf = 0; |
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s->bbits = 0; |
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s->bs = 0; |
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/* decoder */ |
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s->codesize = csize; |
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s->cursize = s->codesize + 1; |
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s->curmask = mask[s->cursize]; |
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s->top_slot = 1 << s->cursize; |
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s->clear_code = 1 << s->codesize; |
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s->end_code = s->clear_code + 1; |
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s->slot = s->newcodes = s->clear_code + 2; |
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s->oc = s->fc = 0; |
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s->sp = s->stack; |
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s->mode = mode; |
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switch(s->mode){ |
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case FF_LZW_GIF: |
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s->top_slot2 = s->top_slot; |
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break; |
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case FF_LZW_TIFF: |
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s->top_slot2 = s->top_slot - 1; |
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break; |
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default: |
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return -1; |
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} |
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return 0; |
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} |
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/**
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* Decode given number of bytes |
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* NOTE: the algorithm here is inspired from the LZW GIF decoder |
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* written by Steven A. Bennett in 1987. |
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* |
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* @param s LZW context |
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* @param buf output buffer |
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* @param len number of bytes to decode |
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* @return number of bytes decoded |
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*/ |
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int ff_lzw_decode(LZWState *p, uint8_t *buf, int len){ |
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int l, c, code, oc, fc; |
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uint8_t *sp; |
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struct LZWState *s = (struct LZWState *)p; |
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if (s->end_code < 0) |
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return 0; |
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l = len; |
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sp = s->sp; |
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oc = s->oc; |
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fc = s->fc; |
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while (sp > s->stack) { |
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*buf++ = *(--sp); |
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if ((--l) == 0) |
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goto the_end; |
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} |
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for (;;) { |
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c = lzw_get_code(s); |
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if (c == s->end_code) { |
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s->end_code = -1; |
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break; |
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} else if (c == s->clear_code) { |
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s->cursize = s->codesize + 1; |
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s->curmask = mask[s->cursize]; |
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s->slot = s->newcodes; |
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s->top_slot = 1 << s->cursize; |
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s->top_slot2 = s->top_slot; |
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if(s->mode == FF_LZW_TIFF) |
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s->top_slot2--; |
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while ((c = lzw_get_code(s)) == s->clear_code); |
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if (c == s->end_code) { |
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s->end_code = -1; |
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break; |
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} |
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/* test error */ |
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if (c >= s->slot) |
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c = 0; |
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fc = oc = c; |
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*buf++ = c; |
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if ((--l) == 0) |
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break; |
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} else { |
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code = c; |
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if (code >= s->slot) { |
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*sp++ = fc; |
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code = oc; |
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} |
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while (code >= s->newcodes) { |
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*sp++ = s->suffix[code]; |
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code = s->prefix[code]; |
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} |
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*sp++ = code; |
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if (s->slot < s->top_slot) { |
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s->suffix[s->slot] = fc = code; |
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s->prefix[s->slot++] = oc; |
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oc = c; |
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} |
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if (s->slot >= s->top_slot2) { |
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if (s->cursize < LZW_MAXBITS) { |
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s->top_slot <<= 1; |
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s->top_slot2 = s->top_slot; |
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if(s->mode == FF_LZW_TIFF) |
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s->top_slot2--; |
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s->curmask = mask[++s->cursize]; |
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} |
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} |
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while (sp > s->stack) { |
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*buf++ = *(--sp); |
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if ((--l) == 0) |
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goto the_end; |
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} |
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} |
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} |
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the_end: |
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s->sp = sp; |
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s->oc = oc; |
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s->fc = fc; |
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return len - l; |
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} |
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@ -0,0 +1,49 @@ |
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/*
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* LZW decoder |
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* Copyright (c) 2003 Fabrice Bellard. |
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* Copyright (c) 2006 Konstantin Shishkov. |
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* |
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* This file is part of FFmpeg. |
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* |
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* FFmpeg is free software; you can redistribute it and/or |
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* modify it under the terms of the GNU Lesser General Public |
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* License as published by the Free Software Foundation; either |
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* version 2.1 of the License, or (at your option) any later version. |
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* |
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* FFmpeg is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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* Lesser General Public License for more details. |
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* |
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* You should have received a copy of the GNU Lesser General Public |
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* License along with FFmpeg; if not, write to the Free Software |
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
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*/ |
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|
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/**
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* @file lzw.h |
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* @brief LZW decoding routines |
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* @author Fabrice Bellard |
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* Modified for use in TIFF by Konstantin Shishkov |
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*/ |
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#ifndef LZW_H |
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#define LZW_H |
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enum FF_LZW_MODES{ |
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FF_LZW_GIF, |
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FF_LZW_TIFF |
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}; |
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/* clients should not know what LZWState is */ |
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typedef void LZWState; |
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/* first two functions de/allocate memory for LZWState */ |
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void ff_lzw_decode_open(LZWState **p); |
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void ff_lzw_decode_close(LZWState **p); |
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int ff_lzw_decode_init(LZWState *s, int csize, uint8_t *buf, int buf_size, int mode); |
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int ff_lzw_decode(LZWState *s, uint8_t *buf, int len); |
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uint8_t* ff_lzw_cur_ptr(LZWState *lzw); |
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void ff_lzw_decode_tail(LZWState *lzw); |
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#endif |
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