Add VP9 raw bits reader

media/filters/vp9_raw_bits_reader.h

Index: media/filters/vp9_raw_bits_reader.h
diff --git a/media/filters/vp9_raw_bits_reader.h b/media/filters/vp9_raw_bits_reader.h
new file mode 100644
index 0000000000000000000000000000000000000000..38f54a3cc2f0344077ab130dca9a2a1713649a51
--- /dev/null
+++ b/media/filters/vp9_raw_bits_reader.h
@@ -0,0 +1,62 @@
+// Copyright 2015 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_FILTERS_VP9_RAW_BITS_READER_
+#define MEDIA_FILTERS_VP9_RAW_BITS_READER_
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+#include "media/base/media_export.h"
+
+namespace media {
+
+class BitReader;
+
+// A class to read raw bits stream. See VP9 spec, "RAW-BITS DECODING" section
+// for detail.
+class MEDIA_EXPORT Vp9RawBitsReader {
+ public:
+  Vp9RawBitsReader();
+  ~Vp9RawBitsReader();
+
+  // |data| is the input buffer with |size| bytes.
+  void Initialize(const uint8_t* data, size_t size);
+
+  // Returns true if none of the reads since the last Initialize() call has
+  // gone beyond the end of available data.
+  bool IsValid() const { return valid_; }
+
+  // Returns how many bytes were read since the last Initialize() call.
+  // Partial bytes will be counted as one byte. For example, it will return 1
+  // if 3 bits were read.
+  size_t GetBytesRead() const;
+
+  // Reads one bit.
+  // If the read goes beyond the end of buffer, the return value is undefined.
+  int ReadBit();
+
+  // Reads a literal with |bits| bits.
+  // If the read goes beyond the end of buffer, the return value is undefined.
+  int ReadLiteral(int bits);
+
+  // Reads a signed literal with |bits| bits (not including the sign bit).
+  // If the read goes beyond the end of buffer, the return value is undefined.
+  int ReadSignedLiteral(int bits);
+
+ private:
+  scoped_ptr<BitReader> reader_;
+
+  // Indicates if none of the reads since the last Initialize() call has gone
+  // beyond the end of available data.
+  bool valid_;
+
+  DISALLOW_COPY_AND_ASSIGN(Vp9RawBitsReader);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_FILTERS_VP9_RAW_BITS_READER_