Add UMA stats for audio/video containers.

media/base/bit_reader.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/base/bit_reader.h"
 
 namespace media {
 
 BitReader::BitReader(const uint8* data, off_t size)
     : data_(data), bytes_left_(size), num_remaining_bits_in_curr_byte_(0) {
   DCHECK(data_ != NULL && bytes_left_ > 0);
 
   UpdateCurrByte();
 }
 
 BitReader::~BitReader() {}
 
+bool BitReader::SkipBits(int num_bits) {

[xhwang, 2013/05/20 23:24:24]

This seems mostly duplicate of ReadBitsInternal. How about calling
ReadBitsInternal and just drop the result? If num_bits > 64, we can call
ReadBitsInternal multiple times.

[jrummell, 2013/05/22 18:27:39]

Implemented Aaron's suggestion instead.

+  while (num_remaining_bits_in_curr_byte_ != 0 && num_bits != 0) {

[acolwell GONE FROM CHROMIUM, 2013/05/18 01:22:09]

You might want to take a stab at implementing this w/o a loop. I think it could
be pretty straight forward if you do the following.
- Use ReadBitsInternal() to byte align.
- Update curr_byte_ and friends to reflect full byte reads.
- Use ReadBitsInternal() again to get any remaining bits.

[jrummell, 2013/05/22 18:27:39]

Done.

+    int bits_to_take = std::min(num_remaining_bits_in_curr_byte_, num_bits);
+    num_bits -= bits_to_take;
+    num_remaining_bits_in_curr_byte_ -= bits_to_take;
+    curr_byte_ &= (1 << num_remaining_bits_in_curr_byte_) - 1;
+
+    if (num_remaining_bits_in_curr_byte_ == 0)
+      UpdateCurrByte();
+  }
+
+  return num_bits == 0;
+}
+
 int BitReader::bits_available() const {
   return 8 * bytes_left_ + num_remaining_bits_in_curr_byte_;
 }
 
 bool BitReader::ReadBitsInternal(int num_bits, uint64* out) {
   DCHECK_LE(num_bits, 64);
 
   *out = 0;
 
   while (num_remaining_bits_in_curr_byte_ != 0 && num_bits != 0) {
@@ skipping 19 matching lines @@
     return;
 
   // Load a new byte and advance pointers.
   curr_byte_ = *data_;
   ++data_;
   --bytes_left_;
   num_remaining_bits_in_curr_byte_ = 8;
 }
 
 }  // namespace media