Introduced ChunkedByteBuffer class which will be needed by next speech recognition CLs.

content/browser/speech/chunked_byte_buffer.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.
+
+#ifndef CONTENT_BROWSER_SPEECH_CHUNKED_BYTE_BUFFER_H_
+#define CONTENT_BROWSER_SPEECH_CHUNKED_BYTE_BUFFER_H_
+#pragma once
+
+#include <string>
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/scoped_vector.h"
+
+namespace speech {
+
+// Models a chunk-oriented byte buffer. The term chunk is herein defined as an
+// arbitrary sequence of bytes that is preceeded by N header bytes, indicating
+// its size. Data may be appended to the buffer with no particular respect of
+// chunks boundaries. However, chunks can be extracted (FIFO) only when their
+// content (according to their header) is fully available in the buffer.
+// The current implementation support only 4 byte Big Endian headers.
+// Empty chunks (i.e. the sequence 00 00 00 00) are NOT allowed.
+//
+// E.g. 00 00 00 04 xx xx xx xx 00 00 00 02 yy yy 00 00 00 04 zz zz zz zz
+//      [----- CHUNK 1 -------] [--- CHUNK 2 ---] [------ CHUNK 3 ------]
+class ChunkedByteBuffer {
+ public:
+  ChunkedByteBuffer();
+  ~ChunkedByteBuffer();
+
+  // Appends |length| bytes starting from |start| to the buffer.
+  void Append(const uint8* start, size_t length);
+
+  // Appends bytes contained into the |string| to the buffer.
+  void Append(const std::string& string);
+
+  // Returns the length of the next complete chunk, or 0 if no complete chunk
+  // is available.
+  size_t GetNextChunkLength() const;
+
+  // If enough data is available, reads a chunk from the buffer, copying its
+  // start pointer in |start_ptr| and returning its length. Returns 0 if no
+  // complete chunk is available in the buffer.
+  // The chunk is NOT removed from the buffer after this call.
+  size_t GetNextChunk(const uint8** start_ptr) const;

[Satish, 2012/04/24 09:10:14]

since this class doesn't allow iterating through all available chunks and the
caller has to always pair a GetNextChunk with a RemoveNextChunk, I think we
could use a simpler interface by providing a 'Chunk* PopChunk()' method which
removes and returns the first entry, transferring ownership to the caller. Chunk
can be changed to a class, its data members hidden if required and will provide
2 methods, 'uint8* GetData()' and 'size_t GetDataLength()' for this to work.

+
+  // Shifts out the first chunk from the buffer.
+  void RemoveNextChunk();
+
+  // Clears all the content of the buffer.
+  void Clear();
+
+  // Returns the number of raw bytes (including headers) present.
+  size_t GetTotalLength() const { return total_bytes_stored_; }
+
+ private:
+  static uint32 ReadBigEndian32(const uint8* buffer);
+
+  struct Chunk {
+    Chunk() {}

[Satish, 2012/04/24 09:10:14]

ctor/dtor shouldn't be inlined, move these to the .cc file

+    ~Chunk() {}
+
+    std::vector<uint8> header;
+    std::vector<uint8> content;
+    inline size_t ExpectedContentLength() const;

[Satish, 2012/04/24 09:10:14]

remove 'inline'

+
+   private:
+    DISALLOW_COPY_AND_ASSIGN(Chunk);
+  };
+
+  ScopedVector<Chunk> chunks_;
+  scoped_ptr<Chunk> partial_chunk_;
+  size_t total_bytes_stored_;
+
+  DISALLOW_COPY_AND_ASSIGN(ChunkedByteBuffer);
+};
+
+}  // namespace speech
+
+#endif  // CONTENT_BROWSER_SPEECH_CHUNKED_BYTE_BUFFER_H_