net/quic/quic_unacked_packet_map.h

// Copyright 2014 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_UNACKED_PACKET_MAP_H_
#define NET_QUIC_QUIC_UNACKED_PACKET_MAP_H_

#include "net/base/linked_hash_map.h"
#include "net/quic/quic_protocol.h"

namespace net {

// Class which tracks unacked packets, including those packets which are
// currently pending, and the relationship between packets which
// contain the same data (via retransmissions)
class NET_EXPORT_PRIVATE QuicUnackedPacketMap {
 public:
  struct NET_EXPORT_PRIVATE TransmissionInfo {
    // Used by STL when assinging into a map.
    TransmissionInfo();

    // Constructs a Transmission with a new all_tranmissions set
    // containing |sequence_number|.
    TransmissionInfo(RetransmittableFrames* retransmittable_frames,
                     QuicPacketSequenceNumber sequence_number,
                     QuicSequenceNumberLength sequence_number_length);

    // Constructs a Transmission with the specified |all_tranmissions| set
    // and inserts |sequence_number| into it.
    TransmissionInfo(RetransmittableFrames* retransmittable_frames,
                     QuicPacketSequenceNumber sequence_number,
                     QuicSequenceNumberLength sequence_number_length,
                     SequenceNumberSet* all_transmissions);

    RetransmittableFrames* retransmittable_frames;
    QuicSequenceNumberLength sequence_number_length;
    // Zero when the packet is serialized, non-zero once it's sent.
    QuicTime sent_time;
    // Zero when the packet is serialized, non-zero once it's sent.
    QuicByteCount bytes_sent;
    size_t nack_count;
    // Stores the sequence numbers of all transmissions of this packet.
    // Can never be null.
    SequenceNumberSet* all_transmissions;
    // Pending packets have not been abandoned or lost.
    bool pending;
  };

  explicit QuicUnackedPacketMap(bool is_server);
  ~QuicUnackedPacketMap();

  // Adds |serialized_packet| to the map.  Does not mark it pending.
  void AddPacket(const SerializedPacket& serialized_packet);

  // Called when a packet is retransmitted with a new sequence number.
  // |old_sequence_number| will remain unacked, but will have no
  // retransmittable data associated with it. |new_sequence_number| will
  // be both unacked and associated with retransmittable data.
  void OnRetransmittedPacket(QuicPacketSequenceNumber old_sequence_number,
                             QuicPacketSequenceNumber new_sequence_number);

  // Returns true if the packet |sequence_number| is unacked.
  bool IsUnacked(QuicPacketSequenceNumber sequence_number) const;

  // Returns true if the packet |sequence_number| is pending.
  bool IsPending(QuicPacketSequenceNumber sequence_number) const;

  // Sets the nack count to the max of the current nack count and |min_nacks|.
  void NackPacket(QuicPacketSequenceNumber sequence_number,
                  size_t min_nacks);

  // Marks |sequence_number| as no longer pending.
  void SetNotPending(QuicPacketSequenceNumber sequence_number);

  // Returns true if the unacked packet |sequence_number| has retransmittable
  // frames.  This will return false if the packet has been acked, if a
  // previous transmission of this packet was ACK'd, or if this packet has been
  // retransmitted as with different sequence number, or if the packet never
  // had any retransmittable packets in the first place.
  bool HasRetransmittableFrames(QuicPacketSequenceNumber sequence_number) const;

  // Returns true if there are any unacked packets.
  bool HasUnackedPackets() const;

  // Returns true if there are any unacked packets which have retransmittable
  // frames.
  bool HasUnackedRetransmittableFrames() const;

  // Returns the number of unacked packets which have retransmittable frames.
  size_t GetNumRetransmittablePackets() const;

  // Returns the total number of bytes associated with pending packets.
  size_t bytes_in_flight() const {
    return bytes_in_flight_;
  }

  // Returns the largest sequence number that has been sent.
  QuicPacketSequenceNumber largest_sent_packet() const {
    return largest_sent_packet_;
  }

  // Returns the smallest sequence number of a serialized packet which has not
  // been acked by the peer.  If there are no unacked packets, returns 0.
  QuicPacketSequenceNumber GetLeastUnackedSentPacket() const;

  // Returns the set of sequence numbers of all unacked packets.
  // Test only.
  SequenceNumberSet GetUnackedPackets() const;

  // Sets a packet pending, with the sent time |sent_time|.
  void SetPending(QuicPacketSequenceNumber sequence_number,
                  QuicTime sent_time,
                  QuicByteCount bytes_sent);

  // Clears up to |num_to_clear| previous transmissions in order to make room
  // in the ack frame for new acks.
  void ClearPreviousRetransmissions(size_t num_to_clear);

  typedef linked_hash_map<QuicPacketSequenceNumber,
                          TransmissionInfo> UnackedPacketMap;

  typedef UnackedPacketMap::const_iterator const_iterator;

  const_iterator begin() const { return unacked_packets_.begin(); }
  const_iterator end() const { return unacked_packets_.end(); }

  // Returns true if there are unacked packets that are pending.
  bool HasPendingPackets() const;

  // Returns the TransmissionInfo associated with |sequence_number|, which
  // must be unacked.
  const TransmissionInfo& GetTransmissionInfo(
      QuicPacketSequenceNumber sequence_number) const;

  // Returns the time that the last unacked packet was sent.
  QuicTime GetLastPacketSentTime() const;

  // Returns the time that the first pending packet was sent.
  QuicTime GetFirstPendingPacketSentTime() const;

  // Returns the number of unacked packets.
  size_t GetNumUnackedPackets() const;

  // Returns true if there are multiple packet pending.
  bool HasMultiplePendingPackets() const;

  // Removes entries from the unacked packet map, and deletes
  // the retransmittable frames associated with the packet.
  // Does not remove any previous or subsequent transmissions of this packet.
  void RemovePacket(QuicPacketSequenceNumber sequence_number);

  // Neuters the specified packet.  Deletes any retransmittable
  // frames, and sets all_transmissions to only include itself.
  void NeuterPacket(QuicPacketSequenceNumber sequence_number);

 private:
  QuicPacketSequenceNumber largest_sent_packet_;

  // Newly serialized retransmittable and fec packets are added to this map,
  // which contains owning pointers to any contained frames.  If a packet is
  // retransmitted, this map will contain entries for both the old and the new
  // packet. The old packet's retransmittable frames entry will be NULL, while
  // the new packet's entry will contain the frames to retransmit.
  // If the old packet is acked before the new packet, then the old entry will
  // be removed from the map and the new entry's retransmittable frames will be
  // set to NULL.
  UnackedPacketMap unacked_packets_;

  size_t bytes_in_flight_;

  bool is_server_;

  DISALLOW_COPY_AND_ASSIGN(QuicUnackedPacketMap);
};

}  // namespace net

#endif  // NET_QUIC_QUIC_UNACKED_PACKET_MAP_H_