Split the bit reader functionalities from the byte stream provider.

media/base/bit_reader_h264.h

+// Copyright (c) 2013 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.
+
+#ifndef MEDIA_BASE_BIT_READER_H264_H_
+#define MEDIA_BASE_BIT_READER_H264_H_
+
+#include <sys/types.h>
+
+#include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
+#include "media/base/bit_reader_core.h"
+#include "media/base/media_export.h"
+
+namespace media {
+
+class MEDIA_EXPORT BitReaderH264 {

[acolwell GONE FROM CHROMIUM, 2013/12/28 01:54:42]

Why create this? I thought you'd just be moving
content/common/gpu/media/h264_bit_reader.h into media/base and updating its
implementation to use BitReaderCore. That seems like it would be the path of
least work.

[damienv1, 2013/12/28 04:02:23]

I was planning to do another CL which:
- remove the previous H264 bit reader
- and then use this one instead.

+ public:
+  // Initialize the reader to start reading at |data|, |size| being size
+  // of |data| in bytes.
+  BitReaderH264(const uint8* data, off_t size);
+  ~BitReaderH264();
+
+  template<typename T> bool ReadBits(int num_bits, T *out) {
+    return bit_reader_core_.ReadBits(num_bits, out);
+  }
+
+  bool ReadFlag(bool* flag) {
+    return bit_reader_core_.ReadFlag(flag);
+  }
+
+  bool ReadUE(uint32* out) {
+    return bit_reader_core_.ReadUE(out);
+  }
+
+  bool SkipBits(int num_bits) {
+    return bit_reader_core_.SkipBits(num_bits);
+  }
+
+  int NumBitsLeft() const {

[damienv1, 2013/12/28 01:32:25]

This method should not be exposed.
This is confusing as the number of bits truly depends on whether some start code
emulation prevention bytes are detected.

The user of this class should not have to rely on that method.

[damienv1, 2013/12/28 02:26:17]

Will do.

+    return bit_reader_core_.bits_available();
+  }
+
+  int GetBitCount() {
+    return bit_reader_core_.GetBitCount();
+  }
+
+  // See the definition of more_rbsp_data() in spec.
+  bool HasMoreRBSPData() {
+    return bit_reader_core_.HasMoreRBSPData();
+  }
+
+ private:
+  scoped_ptr<BitReaderCore::ByteStreamProvider> byte_stream_provider_;

[acolwell GONE FROM CHROMIUM, 2013/12/28 01:54:42]

nit: Since this can't be changed and has the same lifetime as this object,
consider just using H264ByteStreamProvider here or move the functionality into
this class an privately derive from ByteStreamProvider.

[damienv1, 2013/12/28 04:02:23]

Done: now derives from ByteStreamProvider.

+
+  BitReaderCore bit_reader_core_;
+
+  DISALLOW_COPY_AND_ASSIGN(BitReaderH264);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_BASE_BIT_READER_H264_H_