Add unittest for H264BitReader.

content/common/gpu/media/h264_bit_reader.h

+// 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.
+//
+// This file contains an implementation of an H264 Annex-B video stream parser.

[Ami GONE FROM CHROMIUM, 2012/07/31 23:22:12]

s/stream parser/bit reader/

+
+#ifndef CONTENT_COMMON_GPU_MEDIA_H264_BIT_READER_H_
+#define CONTENT_COMMON_GPU_MEDIA_H264_BIT_READER_H_
+
+#include <sys/types.h>
+
+#include "base/basictypes.h"
+#include "content/common/content_export.h"
+
+namespace content {
+
+// A class to provide bit-granularity reading of H.264 streams.
+// This is not a generic bit reader class, as it takes into account
+// H.264 stream-specific constraints, such as skipping emulation-prevention
+// bytes and stop bits. See spec for more details.
+class CONTENT_EXPORT H264BitReader {
+ public:
+  H264BitReader();
+  ~H264BitReader();
+
+  // Initialize the reader to start reading at |data|, |size| being size
+  // of |data| in bytes.
+  // Return false on insufficient size of stream..
+  // TODO(posciak,fischman): consider replacing Initialize() with
+  // heap-allocating and creating bit readers on demand instead.
+  bool Initialize(const uint8* data, off_t size);
+
+  // Read |num_bits| next bits from stream and return in |*out|, first bit
+  // from the stream starting at |num_bits| position in |*out|.
+  // |num_bits| may be 1-32, inclusive.
+  // Return false if the given number of bits cannot be read (not enough
+  // bits in the stream), true otherwise.
+  bool ReadBits(int num_bits, int *out);
+
+  // Return the number of bits left in the stream.
+  off_t NumBitsLeft();
+
+  // See the definition of more_rbsp_data() in spec.
+  bool HasMoreRBSPData();
+
+ private:
+  // Advance to the next byte, loading it into curr_byte_.
+  // Return false on end of stream.
+  bool UpdateCurrByte();
+
+  // Pointer to the next unread (not in curr_byte_) byte in the stream.
+  const uint8* data_;
+
+  // Bytes left in the stream (without the curr_byte_).
+  off_t bytes_left_;
+
+  // Contents of the current byte; first unread bit starting at position
+  // 8 - num_remaining_bits_in_curr_byte_ from MSB.
+  int curr_byte_;
+
+  // Number of bits remaining in curr_byte_
+  int num_remaining_bits_in_curr_byte_;
+
+  // Used in emulation prevention three byte detection (see spec).
+  // Initially set to 0xffff to accept all initial two-byte sequences.
+  int prev_two_bytes_;
+
+  DISALLOW_COPY_AND_ASSIGN(H264BitReader);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_COMMON_GPU_MEDIA_H264_BIT_READER_H_