libvpx: Pull from upstream

source/libvpx/vp9/decoder/vp9_dboolhuff.c

 /*
  *  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.
  */
 
 #include "vpx_ports/mem.h"
 #include "vpx_mem/vpx_mem.h"
 
 #include "vp9/decoder/vp9_dboolhuff.h"
 
 // This is meant to be a large, positive constant that can still be efficiently
 // loaded as an immediate (on platforms like ARM, for example).
 // Even relatively modest values like 100 would work fine.
 #define LOTS_OF_BITS 0x40000000
 
-
 int vp9_reader_init(vp9_reader *r, const uint8_t *buffer, size_t size) {
-  int marker_bit;
-
-  r->buffer_end = buffer + size;
-  r->buffer = buffer;
-  r->value = 0;
-  r->count = -8;
-  r->range = 255;
-
-  if (size && !buffer)
+  if (size && !buffer) {
     return 1;
-
-  vp9_reader_fill(r);
-  marker_bit = vp9_read_bit(r);
-  return marker_bit != 0;
+  } else {
+    r->buffer_end = buffer + size;
+    r->buffer = buffer;
+    r->value = 0;
+    r->count = -8;
+    r->range = 255;
+    vp9_reader_fill(r);
+    return vp9_read_bit(r) != 0;  // marker bit
+  }
 }
 
 void vp9_reader_fill(vp9_reader *r) {
   const uint8_t *const buffer_end = r->buffer_end;
   const uint8_t *buffer = r->buffer;
-  VP9_BD_VALUE value = r->value;
+  BD_VALUE value = r->value;
   int count = r->count;
-  int shift = BD_VALUE_SIZE - 8 - (count + 8);
+  int shift = BD_VALUE_SIZE - CHAR_BIT - (count + CHAR_BIT);
   int loop_end = 0;
-  const int bits_left = (int)((buffer_end - buffer)*CHAR_BIT);
+  const int bits_left = (int)((buffer_end - buffer) * CHAR_BIT);
   const int x = shift + CHAR_BIT - bits_left;
 
   if (x >= 0) {
     count += LOTS_OF_BITS;
     loop_end = x;
   }
 
   if (x < 0 || bits_left) {
     while (shift >= loop_end) {
       count += CHAR_BIT;
-      value |= (VP9_BD_VALUE)*buffer++ << shift;
+      value |= (BD_VALUE)*buffer++ << shift;
       shift -= CHAR_BIT;
     }
   }
 
   r->buffer = buffer;
   r->value = value;
   r->count = count;
 }
 
 const uint8_t *vp9_reader_find_end(vp9_reader *r) {
@@ skipping 15 matching lines @@
   //
   // 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 LOTS_OF_BITS. So when
   // count == LOTS_OF_BITS - 1, the user's data has been exhausted.
   //
   // 1 if we have tried to decode bits after the end of stream was encountered.
   // 0 No error.
   return r->count > BD_VALUE_SIZE && r->count < LOTS_OF_BITS;
 }