Update libvpx snapshot to v0.9.7-p1 (Cayuga).

source/libvpx/vp8/decoder/dboolhuff.h

 /*
  *  Copyright (c) 2010 The WebM project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 16 matching lines @@
 
 typedef struct
 {
     const unsigned char *user_buffer_end;
     const unsigned char *user_buffer;
     VP8_BD_VALUE         value;
     int                  count;
     unsigned int         range;
 } BOOL_DECODER;
 
-DECLARE_ALIGNED(16, extern const unsigned char, vp8dx_bitreader_norm[256]);
+DECLARE_ALIGNED(16, extern const unsigned char, vp8_norm[256]);
 
 int vp8dx_start_decode(BOOL_DECODER *br,
                        const unsigned char *source,
                        unsigned int source_sz);
 
 void vp8dx_bool_decoder_fill(BOOL_DECODER *br);
 
 /*The refill loop is used in several places, so define it in a macro to make
    sure they're all consistent.
   An inline function would be cleaner, but has a significant penalty, because
    multiple BOOL_DECODER fields must be modified, and the compiler is not smart
    enough to eliminate the stores to those fields and the subsequent reloads
    from them when inlining the function.*/
 #define VP8DX_BOOL_DECODER_FILL(_count,_value,_bufptr,_bufend) \
     do \
     { \
-        int shift; \
-        for(shift = VP8_BD_VALUE_SIZE - 8 - ((_count) + 8); shift >= 0; ) \
+        int shift = VP8_BD_VALUE_SIZE - 8 - ((_count) + 8); \
+        int loop_end, x; \
+        size_t bits_left = ((_bufend)-(_bufptr))*CHAR_BIT; \
+        \
+        x = shift + CHAR_BIT - bits_left; \
+        loop_end = 0; \
+        if(x >= 0) \
         { \
-            if((_bufptr) >= (_bufend)) { \
-                (_count) = VP8_LOTS_OF_BITS; \
-                break; \
-            } \
-            (_count) += 8; \
+            (_count) += VP8_LOTS_OF_BITS; \
+            loop_end = x; \
+            if(!bits_left) break; \
+        } \
+        while(shift >= loop_end) \
+        { \
+            (_count) += CHAR_BIT; \
             (_value) |= (VP8_BD_VALUE)*(_bufptr)++ << shift; \
-            shift -= 8; \
+            shift -= CHAR_BIT; \
         } \
     } \
-    while(0)
+    while(0) \
 
 
 static int vp8dx_decode_bool(BOOL_DECODER *br, int probability) {
     unsigned int bit = 0;
     VP8_BD_VALUE value;
     unsigned int split;
     VP8_BD_VALUE bigsplit;
     int count;
     unsigned int range;
 
+    split = 1 + (((br->range - 1) * probability) >> 8);
+
+    if(br->count < 0)
+        vp8dx_bool_decoder_fill(br);
+
     value = br->value;
     count = br->count;
-    range = br->range;
 
-    split = 1 + (((range - 1) * probability) >> 8);
     bigsplit = (VP8_BD_VALUE)split << (VP8_BD_VALUE_SIZE - 8);
 
     range = split;
 
     if (value >= bigsplit)
     {
         range = br->range - split;
         value = value - bigsplit;
         bit = 1;
     }
 
     {
-        register unsigned int shift = vp8dx_bitreader_norm[range];
+        register unsigned int shift = vp8_norm[range];
         range <<= shift;
         value <<= shift;
         count -= shift;
     }
     br->value = value;
     br->count = count;
     br->range = range;
-    if(count < 0)
-        vp8dx_bool_decoder_fill(br);
+
     return bit;
 }
 
 static int vp8_decode_value(BOOL_DECODER *br, int bits)
 {
     int z = 0;
     int bit;
 
     for (bit = bits - 1; bit >= 0; bit--)
     {
         z |= (vp8dx_decode_bool(br, 0x80) << bit);
     }
 
     return z;
 }
 
 static int vp8dx_bool_error(BOOL_DECODER *br)
 {
-  /* Check if we have reached the end of the buffer.
-   *
-   * Variable 'count' stores the number of bits in the 'value' buffer,
-   * minus 8. So if count == 8, there are 16 bits available to be read.
-   * Normally, count is filled with 8 and one byte is filled into the
-   * value buffer. When we reach the end of the buffer, count is instead
-   * filled with VP8_LOTS_OF_BITS, 8 of which represent the last 8 real
-   * bits from the bitstream. So the last bit in the bitstream will be
-   * represented by count == VP8_LOTS_OF_BITS - 16.
-   */
-    if ((br->count > VP8_BD_VALUE_SIZE)
-        && (br->count <= VP8_LOTS_OF_BITS - 16))
+    /* Check if we have reached the end of the buffer.
+     *
+     * Variable 'count' stores the number of bits in the 'value' buffer, minus
+     * 8. The top byte is part of the algorithm, and the remainder is buffered
+     * to be shifted into it. So if count == 8, the top 16 bits of 'value' are
+     * occupied, 8 for the algorithm and 8 in the buffer.
+     *
+     * When reading a byte from the user's buffer, count is filled with 8 and
+     * one byte is filled into the value buffer. When we reach the end of the
+     * data, count is additionally filled with VP8_LOTS_OF_BITS. So when
+     * count == VP8_LOTS_OF_BITS - 1, the user's data has been exhausted.
+     */
+    if ((br->count > VP8_BD_VALUE_SIZE) && (br->count < VP8_LOTS_OF_BITS))
     {
        /* We have tried to decode bits after the end of
         * stream was encountered.
         */
         return 1;
     }
 
     /* No error. */
     return 0;
 }
 #endif