From ffc5430bc30a787ae684549df3afcb7b9dcc86d9 Mon Sep 17 00:00:00 2001 From: Kostya Shishkov Date: Thu, 26 Oct 2006 04:15:48 +0000 Subject: LZW decoder as separate module plus TIFF LZW support Originally committed as revision 6795 to svn://svn.ffmpeg.org/ffmpeg/trunk --- libavcodec/lzw.c | 262 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 262 insertions(+) create mode 100644 libavcodec/lzw.c (limited to 'libavcodec/lzw.c') diff --git a/libavcodec/lzw.c b/libavcodec/lzw.c new file mode 100644 index 0000000000..b5bb33a219 --- /dev/null +++ b/libavcodec/lzw.c @@ -0,0 +1,262 @@ +/* + * LZW decoder + * Copyright (c) 2003 Fabrice Bellard. + * Copyright (c) 2006 Konstantin Shishkov. + * + * This file is part of FFmpeg. + * + * FFmpeg is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * FFmpeg is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with FFmpeg; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + */ + +/** + * @file lzw.c + * @brief LZW decoding routines + * @author Fabrice Bellard + * Modified for use in TIFF by Konstantin Shishkov + */ + +#include "avcodec.h" +#include "lzw.h" + +#define LZW_MAXBITS 12 +#define LZW_SIZTABLE (1<mode == FF_LZW_GIF) { + while (s->bbits < s->cursize) { + if (!s->bs) { + sizbuf = *s->pbuf++; + s->bs = sizbuf; + if(!sizbuf) { + s->eob_reached = 1; + } + } + s->bbuf |= (*s->pbuf++) << s->bbits; + s->bbits += 8; + s->bs--; + } + c = s->bbuf & s->curmask; + s->bbuf >>= s->cursize; + } else { // TIFF + while (s->bbits < s->cursize) { + if (s->pbuf >= s->ebuf) { + s->eob_reached = 1; + } + s->bbuf = (s->bbuf << 8) | (*s->pbuf++); + s->bbits += 8; + } + c = (s->bbuf >> (s->bbits - s->cursize)) & s->curmask; + } + s->bbits -= s->cursize; + return c; +} + +uint8_t* ff_lzw_cur_ptr(LZWState *p) +{ + return ((struct LZWState*)p)->pbuf; +} + +void ff_lzw_decode_tail(LZWState *p) +{ + struct LZWState *s = (struct LZWState *)p; + while(!s->eob_reached) + lzw_get_code(s); +} + +void ff_lzw_decode_open(LZWState **p) +{ + *p = av_mallocz(sizeof(struct LZWState)); +} + +void ff_lzw_decode_close(LZWState **p) +{ + av_freep(p); +} + +/** + * Initialize LZW decoder + * @param s LZW context + * @param csize initial code size in bits + * @param buf input data + * @param buf_size input data size + * @param mode decoder working mode - either GIF or TIFF + */ +int ff_lzw_decode_init(LZWState *p, int csize, uint8_t *buf, int buf_size, int mode) +{ + struct LZWState *s = (struct LZWState *)p; + + if(csize < 1 || csize > LZW_MAXBITS) + return -1; + /* read buffer */ + s->eob_reached = 0; + s->pbuf = buf; + s->ebuf = s->pbuf + buf_size; + s->bbuf = 0; + s->bbits = 0; + s->bs = 0; + + /* decoder */ + s->codesize = csize; + s->cursize = s->codesize + 1; + s->curmask = mask[s->cursize]; + s->top_slot = 1 << s->cursize; + s->clear_code = 1 << s->codesize; + s->end_code = s->clear_code + 1; + s->slot = s->newcodes = s->clear_code + 2; + s->oc = s->fc = 0; + s->sp = s->stack; + + s->mode = mode; + switch(s->mode){ + case FF_LZW_GIF: + s->top_slot2 = s->top_slot; + break; + case FF_LZW_TIFF: + s->top_slot2 = s->top_slot - 1; + break; + default: + return -1; + } + return 0; +} + +/** + * Decode given number of bytes + * NOTE: the algorithm here is inspired from the LZW GIF decoder + * written by Steven A. Bennett in 1987. + * + * @param s LZW context + * @param buf output buffer + * @param len number of bytes to decode + * @return number of bytes decoded + */ +int ff_lzw_decode(LZWState *p, uint8_t *buf, int len){ + int l, c, code, oc, fc; + uint8_t *sp; + struct LZWState *s = (struct LZWState *)p; + + if (s->end_code < 0) + return 0; + + l = len; + sp = s->sp; + oc = s->oc; + fc = s->fc; + + while (sp > s->stack) { + *buf++ = *(--sp); + if ((--l) == 0) + goto the_end; + } + + for (;;) { + c = lzw_get_code(s); + if (c == s->end_code) { + s->end_code = -1; + break; + } else if (c == s->clear_code) { + s->cursize = s->codesize + 1; + s->curmask = mask[s->cursize]; + s->slot = s->newcodes; + s->top_slot = 1 << s->cursize; + s->top_slot2 = s->top_slot; + if(s->mode == FF_LZW_TIFF) + s->top_slot2--; + while ((c = lzw_get_code(s)) == s->clear_code); + if (c == s->end_code) { + s->end_code = -1; + break; + } + /* test error */ + if (c >= s->slot) + c = 0; + fc = oc = c; + *buf++ = c; + if ((--l) == 0) + break; + } else { + code = c; + if (code >= s->slot) { + *sp++ = fc; + code = oc; + } + while (code >= s->newcodes) { + *sp++ = s->suffix[code]; + code = s->prefix[code]; + } + *sp++ = code; + if (s->slot < s->top_slot) { + s->suffix[s->slot] = fc = code; + s->prefix[s->slot++] = oc; + oc = c; + } + if (s->slot >= s->top_slot2) { + if (s->cursize < LZW_MAXBITS) { + s->top_slot <<= 1; + s->top_slot2 = s->top_slot; + if(s->mode == FF_LZW_TIFF) + s->top_slot2--; + s->curmask = mask[++s->cursize]; + } + } + while (sp > s->stack) { + *buf++ = *(--sp); + if ((--l) == 0) + goto the_end; + } + } + } + the_end: + s->sp = sp; + s->oc = oc; + s->fc = fc; + return len - l; +} -- cgit v1.2.3