Fix segault

[frescor/ffmpeg.git] / libavcodec / lzw.c

diff --git a/libavcodec/lzw.c b/libavcodec/lzw.c
index 7e313ac6cc6060d4c5a996d40cea302e2dbdd278..0447225834d4bd3c7ba62db8b13a618b5f1df221 100644 (file)
--- a/libavcodec/lzw.c
+++ b/libavcodec/lzw.c
@@ -1,7 +1,7 @@
 /*
  * LZW decoder
- * Copyright (c) 2003 Fabrice Bellard.
- * Copyright (c) 2006 Konstantin Shishkov.
+ * Copyright (c) 2003 Fabrice Bellard
+ * Copyright (c) 2006 Konstantin Shishkov
  *
  * This file is part of FFmpeg.
  *
@@ -21,7 +21,7 @@
  */
 
 /**
- * @file lzw.c
+ * @file libavcodec/lzw.c
  * @brief LZW decoding routines
  * @author Fabrice Bellard
  * Modified for use in TIFF by Konstantin Shishkov
@@ -42,7 +42,7 @@ static const uint16_t mask[17] =
 };
 
 struct LZWState {
-    uint8_t *pbuf, *ebuf;
+    const uint8_t *pbuf, *ebuf;
     int bbits;
     unsigned int bbuf;
 
@@ -78,20 +78,20 @@ static int lzw_get_code(struct LZWState * s)
             s->bbits += 8;
             s->bs--;
         }
-        c = s->bbuf & s->curmask;
+        c = s->bbuf;
         s->bbuf >>= s->cursize;
     } else { // TIFF
         while (s->bbits < s->cursize) {
             s->bbuf = (s->bbuf << 8) | (*s->pbuf++);
             s->bbits += 8;
         }
-        c = (s->bbuf >> (s->bbits - s->cursize)) & s->curmask;
+        c = s->bbuf >> (s->bbits - s->cursize);
     }
     s->bbits -= s->cursize;
-    return c;
+    return c & s->curmask;
 }
 
-uint8_t* ff_lzw_cur_ptr(LZWState *p)
+const uint8_t* ff_lzw_cur_ptr(LZWState *p)
 {
     return ((struct LZWState*)p)->pbuf;
 }
@@ -109,12 +109,12 @@ void ff_lzw_decode_tail(LZWState *p)
         s->pbuf= s->ebuf;
 }
 
-void ff_lzw_decode_open(LZWState **p)
+av_cold void ff_lzw_decode_open(LZWState **p)
 {
     *p = av_mallocz(sizeof(struct LZWState));
 }
 
-void ff_lzw_decode_close(LZWState **p)
+av_cold void ff_lzw_decode_close(LZWState **p)
 {
     av_freep(p);
 }
@@ -127,11 +127,11 @@ void ff_lzw_decode_close(LZWState **p)
  * @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)
+int ff_lzw_decode_init(LZWState *p, int csize, const uint8_t *buf, int buf_size, int mode)
 {
     struct LZWState *s = (struct LZWState *)p;
 
-    if(csize < 1 || csize > LZW_MAXBITS)
+    if(csize < 1 || csize >= LZW_MAXBITS)
         return -1;
     /* read buffer */
     s->pbuf = buf;
@@ -148,20 +148,11 @@ int ff_lzw_decode_init(LZWState *p, int csize, uint8_t *buf, int buf_size, int m
     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->oc = s->fc = -1;
     s->sp = s->stack;
 
     s->mode = mode;
-    switch(s->mode){
-    case FF_LZW_GIF:
-        s->extra_slot= 0;
-        break;
-    case FF_LZW_TIFF:
-        s->extra_slot= 1;
-        break;
-    default:
-        return -1;
-    }
+    s->extra_slot = s->mode == FF_LZW_TIFF;
     return 0;
 }
 
@@ -196,41 +187,31 @@ int ff_lzw_decode(LZWState *p, uint8_t *buf, int len){
         }
         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;
-            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;
+            fc= oc= -1;
         } else {
             code = c;
-            if (code >= s->slot) {
+            if (code == s->slot && fc>=0) {
                 *sp++ = fc;
                 code = oc;
-            }
+            }else if(code >= s->slot)
+                break;
             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;
+            if (s->slot < s->top_slot && oc>=0) {
+                s->suffix[s->slot] = code;
                 s->prefix[s->slot++] = oc;
-                oc = c;
             }
+            fc = code;
+            oc = c;
             if (s->slot >= s->top_slot - s->extra_slot) {
                 if (s->cursize < LZW_MAXBITS) {
                     s->top_slot <<= 1;
@@ -239,6 +220,7 @@ int ff_lzw_decode(LZWState *p, uint8_t *buf, int len){
             }
         }
     }
+    s->end_code = -1;
   the_end:
     s->sp = sp;
     s->oc = oc;