Added CompoundBuffer that will be used to store data in the encoding/decoding

remoting/base/compound_buffer.h

+// Copyright (c) 2010 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.
+
+// CompoundBuffer implements a data buffer that is composed of several pieces,
+// each stored in a refcounted IOBuffer. It is needed for encoding/decoding
+// video pipeline to represent data packet and minimize data copying.
+// It is particularly useful for splitting data between multiple RTP packets
+// and assembling them into one buffer on the receiving side.
+//
+// CompoundBufferInputStream implements ZeroCopyInputStream interface
+// to be used by protobuf to decode data stored in CompoundBuffer into
+// a protocol buffer message.
+//
+// Mutations to the buffer are not thread-safe. Immutability can be ensured
+// with the Lock() method.
+
+#ifndef REMOTING_BASE_COMPOUND_BUFFER_H_
+#define REMOTING_BASE_COMPOUND_BUFFER_H_
+
+#include <deque>
+
+#include "base/basictypes.h"
+#include "base/ref_counted.h"
+#include "google/protobuf/io/zero_copy_stream.h"
+
+namespace net {
+class IOBuffer;
+class IOBufferWithSize;
+}  // namespace net
+
+namespace remoting {
+
+class CompoundBuffer {
+ public:
+  CompoundBuffer();
+  ~CompoundBuffer();
+
+  void Clear();
+
+  // Adds new chunk to the buffer. |start| defines position of the chunk
+  // within the |buffer|. |size| is the size of the chunk that is being
+  // added, not size of the |buffer|.
+  void Append(net::IOBuffer* buffer, int size);
+  void Append(net::IOBuffer* buffer, const char* start, int size);
+  void Append(const CompoundBuffer& buffer);
+  void Prepend(net::IOBuffer* buffer, int size);
+  void Prepend(net::IOBuffer* buffer, const char* start, int size);
+  void Prepend(const CompoundBuffer& buffer);
+
+  // Same as above, but creates new IOBuffer and copies the data.
+  void AppendCopyOf(const char* data, int data_size);
+  void PrependCopyOf(const char* data, int data_size);
+
+  // Current size of the buffer.
+  int total_bytes() const { return total_bytes_; }
+
+  // Locks the buffer. After the buffer is locked, no data can be
+  // added or removed (content can still be changed if some other
+  // object holds reference to the IOBuffer objects).
+  void Lock();
+
+  // Returns true if content is locked.
+  bool locked() const { return locked_; }
+
+  // Creates new IOBufferWithSize object and copies all data into it.
+  // Ownership of the result is given to the caller.
+  net::IOBufferWithSize* ToIOBufferWithSize() const;
+
+  // Copies all data into given location.
+  void CopyTo(char* data, int data_size) const;
+
+  // Clears the buffer, and initializes it with the interval from |buffer|
+  // starting at |start| and ending at |end|. The data itself isn't copied.
+  void CopyFrom(const CompoundBuffer& source, int start, int end);
+
+ private:
+  friend class CompoundBufferInputStream;
+
+  struct DataChunk {
+    DataChunk(net::IOBuffer* buffer, const char* start, int size);
+
+    scoped_refptr<net::IOBuffer> buffer;
+    const char* start;
+    int size;
+  };
+  typedef std::deque<DataChunk> DataChunkList;
+
+  DataChunkList chunks_;
+  int total_bytes_;
+  bool locked_;
+
+  DISALLOW_COPY_AND_ASSIGN(CompoundBuffer);
+};
+
+class CompoundBufferInputStream
+    : public google::protobuf::io::ZeroCopyInputStream  {
+ public:
+  // Caller keeps ownership of |buffer|. |buffer| must be locked.
+  explicit CompoundBufferInputStream(const CompoundBuffer* buffer);
+  virtual ~CompoundBufferInputStream();
+
+  // google::protobuf::io::ZeroCopyInputStream interface.
+  virtual bool Next(const void** data, int* size);
+  virtual void BackUp(int count);
+  virtual bool Skip(int count);
+  virtual int64 ByteCount() const;
+
+ private:
+  const CompoundBuffer* buffer_;
+
+  size_t current_chunk_;
+  int current_chunk_position_;
+  int position_;
+  int last_returned_size_;
+};
+
+}  // namespace remoting
+
+#endif  // REMOTING_BASE_COMPOUND_BUFFER_H_