Revert r97185 "Update libvpx snapshot to v0.9.7-p1 (Cayuga)."

libvpx/source/libvpx/vp8/decoder/dboolhuff.h

Index: libvpx/source/libvpx/vp8/decoder/dboolhuff.h
diff --git a/libvpx/source/libvpx/vp8/decoder/dboolhuff.h b/libvpx/source/libvpx/vp8/decoder/dboolhuff.h
index 853c10f145234c20a44e409c91739886eb9e4c0a..a83e3f012ac4edeb76526a546be57ed64c4ea1e0 100644
--- a/libvpx/source/libvpx/vp8/decoder/dboolhuff.h
+++ b/libvpx/source/libvpx/vp8/decoder/dboolhuff.h
@@ -34,7 +34,7 @@ typedef struct
     unsigned int         range;
 } BOOL_DECODER;
 
-DECLARE_ALIGNED(16, extern const unsigned char, vp8_norm[256]);
+DECLARE_ALIGNED(16, extern const unsigned char, vp8dx_bitreader_norm[256]);
 
 int vp8dx_start_decode(BOOL_DECODER *br,
                        const unsigned char *source,
@@ -51,26 +51,19 @@ void vp8dx_bool_decoder_fill(BOOL_DECODER *br);
 #define VP8DX_BOOL_DECODER_FILL(_count,_value,_bufptr,_bufend) \
     do \
     { \
-        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) \
+        int shift; \
+        for(shift = VP8_BD_VALUE_SIZE - 8 - ((_count) + 8); shift >= 0; ) \
         { \
-            (_count) += VP8_LOTS_OF_BITS; \
-            loop_end = x; \
-            if(!bits_left) break; \
-        } \
-        while(shift >= loop_end) \
-        { \
-            (_count) += CHAR_BIT; \
+            if((_bufptr) >= (_bufend)) { \
+                (_count) = VP8_LOTS_OF_BITS; \
+                break; \
+            } \
+            (_count) += 8; \
             (_value) |= (VP8_BD_VALUE)*(_bufptr)++ << shift; \
-            shift -= CHAR_BIT; \
+            shift -= 8; \
         } \
     } \
-    while(0) \
+    while(0)
 
 
 static int vp8dx_decode_bool(BOOL_DECODER *br, int probability) {
@@ -81,14 +74,11 @@ static int vp8dx_decode_bool(BOOL_DECODER *br, int probability) {
     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;
@@ -101,7 +91,7 @@ static int vp8dx_decode_bool(BOOL_DECODER *br, int probability) {
     }
 
     {
-        register unsigned int shift = vp8_norm[range];
+        register unsigned int shift = vp8dx_bitreader_norm[range];
         range <<= shift;
         value <<= shift;
         count -= shift;
@@ -109,7 +99,8 @@ static int vp8dx_decode_bool(BOOL_DECODER *br, int probability) {
     br->value = value;
     br->count = count;
     br->range = range;
-
+    if(count < 0)
+        vp8dx_bool_decoder_fill(br);
     return bit;
 }
 
@@ -128,19 +119,18 @@ static int vp8_decode_value(BOOL_DECODER *br, int bits)
 
 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. 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))
+  /* 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))
     {
        /* We have tried to decode bits after the end of
         * stream was encountered.