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);
+
+  // Checks whether one or more complete chunks are available in the buffer.
+  bool HasChunks() const;
+
+  // Returns a reference to the first complete chunk, if any, or to an empty
+  // chunk otherwise.
+  const std::vector<uint8>& GetFirstChunk() const;
+
+  // If enough data is available, reads and removes the first complete chunk
+  // from the buffer. Returns a NULL pointer if no complete chunk is available.
+  scoped_ptr< std::vector<uint8> > PopChunk();
+
+  // 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:
+  struct Chunk {
+    Chunk();
+    ~Chunk();
+
+    std::vector<uint8> header;
+    scoped_ptr< std::vector<uint8> > content;
+    size_t ExpectedContentLength() const;
+
+   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_