LZW decoder as separate module plus TIFF LZW support

Originally committed as revision 6795 to svn://svn.ffmpeg.org/ffmpeg/trunk

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;
+}