net/quic/quic_stream_sequencer.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 NET_QUIC_QUIC_STREAM_SEQUENCER_H_
#define NET_QUIC_QUIC_STREAM_SEQUENCER_H_

#include <map>

#include "base/basictypes.h"
#include "base/memory/scoped_ptr.h"
#include "net/base/iovec.h"
#include "net/quic/quic_protocol.h"

using std::map;
using std::string;

namespace net {

namespace test {
class QuicStreamSequencerPeer;
}  // namespace test

class QuicSession;
class ReliableQuicStream;

// Buffers frames until we have something which can be passed
// up to the next layer.
// TOOD(alyssar) add some checks for overflow attempts [1, 256,] [2, 256]
class NET_EXPORT_PRIVATE QuicStreamSequencer {
 public:
  explicit QuicStreamSequencer(ReliableQuicStream* quic_stream);
  QuicStreamSequencer(size_t max_frame_memory,
                      ReliableQuicStream* quic_stream);

  virtual ~QuicStreamSequencer();

  // Returns the expected value of OnStreamFrame for this frame.
  bool WillAcceptStreamFrame(const QuicStreamFrame& frame) const;

  // If the frame is the next one we need in order to process in-order data,
  // ProcessData will be immediately called on the stream until all buffered
  // data is processed or the stream fails to consume data.  Any unconsumed
  // data will be buffered.
  //
  // If the frame is not the next in line, it will either be buffered, and
  // this will return true, or it will be rejected and this will return false.
  bool OnStreamFrame(const QuicStreamFrame& frame);

  // Once data is buffered, it's up to the stream to read it when the stream
  // can handle more data.  The following three functions make that possible.

  // Fills in up to iov_len iovecs with the next readable regions.  Returns the
  // number of iovs used.  Non-destructive of the underlying data.
  int GetReadableRegions(iovec* iov, size_t iov_len);

  // Copies the data into the iov_len buffers provided.  Returns the number of
  // bytes read.  Any buffered data no longer in use will be released.
  int Readv(const struct iovec* iov, size_t iov_len);

  // Consumes |num_bytes| data.  Used in conjunction with |GetReadableRegions|
  // to do zero-copy reads.
  void MarkConsumed(size_t num_bytes);

  // Returns true if the sequncer has bytes available for reading.
  bool HasBytesToRead() const;

  // Returns true if the sequencer has delivered a half close.
  bool IsHalfClosed() const;

  // Returns true if the sequencer has received this frame before.
  bool IsDuplicate(const QuicStreamFrame& frame) const;

  // Calls |ProcessRawData| on |stream_| for each buffered frame that may
  // be processed.
  void FlushBufferedFrames();

 private:
  friend class test::QuicStreamSequencerPeer;

  // TODO(alyssar) use something better than strings.
  typedef map<QuicStreamOffset, string> FrameMap;

  // Wait until we've seen 'offset' bytes, and then terminate the stream.
  void CloseStreamAtOffset(QuicStreamOffset offset);

  bool MaybeCloseStream();

  ReliableQuicStream* stream_;  // The stream which owns this sequencer.
  QuicStreamOffset num_bytes_consumed_;  // The last data consumed by the stream
  FrameMap frames_;  // sequence number -> frame
  size_t max_frame_memory_;  //  the maximum memory the sequencer can buffer.
  // The offset, if any, we got a stream termination for.  When this many bytes
  // have been processed, the stream will be half closed.
  QuicStreamOffset close_offset_;
};

}  // namespace net

#endif  // NET_QUIC_QUIC_STREAM_SEQUENCER_H_