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authorKostya Shishkov <kostya.shishkov@gmail.com>2006-10-26 04:15:48 +0000
committerKostya Shishkov <kostya.shishkov@gmail.com>2006-10-26 04:15:48 +0000
commitffc5430bc30a787ae684549df3afcb7b9dcc86d9 (patch)
tree1bd740823f9b05a010951f1c57dd4c2885b41a8c /libavcodec/lzw.c
parentb0c32a70b4ef12a5317841f83128a0597320577f (diff)
downloadffmpeg-ffc5430bc30a787ae684549df3afcb7b9dcc86d9.tar.gz
LZW decoder as separate module plus TIFF LZW support
Originally committed as revision 6795 to svn://svn.ffmpeg.org/ffmpeg/trunk
Diffstat (limited to 'libavcodec/lzw.c')
-rw-r--r--libavcodec/lzw.c262
1 files changed, 262 insertions, 0 deletions
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<<LZW_MAXBITS)
+
+static const uint16_t mask[17] =
+{
+ 0x0000, 0x0001, 0x0003, 0x0007,
+ 0x000F, 0x001F, 0x003F, 0x007F,
+ 0x00FF, 0x01FF, 0x03FF, 0x07FF,
+ 0x0FFF, 0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF
+};
+
+struct LZWState {
+ int eob_reached;
+ uint8_t *pbuf, *ebuf;
+ int bbits;
+ unsigned int bbuf;
+
+ int mode; ///< Decoder mode
+ int cursize; ///< The current code size
+ int curmask;
+ int codesize;
+ int clear_code;
+ int end_code;
+ int newcodes; ///< First available code
+ int top_slot; ///< Highest code for current size
+ int top_slot2; ///< Highest possible code for current size (<=top_slot)
+ int slot; ///< Last read code
+ int fc, oc;
+ uint8_t *sp;
+ uint8_t stack[LZW_SIZTABLE];
+ uint8_t suffix[LZW_SIZTABLE];
+ uint16_t prefix[LZW_SIZTABLE];
+ int bs; ///< current buffer size for GIF
+};
+
+/* get one code from stream */
+static int lzw_get_code(struct LZWState * s)
+{
+ int c, sizbuf;
+
+ if(s->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;
+}