1// Copyright (c) 2012 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4//
5// Tracks information about an FEC group, including the packets
6// that have been seen, and the running parity.  Provided the ability
7// to revive a dropped packet.
8
9#ifndef NET_QUIC_QUIC_FEC_GROUP_H_
10#define NET_QUIC_QUIC_FEC_GROUP_H_
11
12#include <set>
13
14#include "base/strings/string_piece.h"
15#include "net/quic/quic_protocol.h"
16
17namespace net {
18
19class NET_EXPORT_PRIVATE QuicFecGroup {
20 public:
21  QuicFecGroup();
22  ~QuicFecGroup();
23
24  // Updates the FEC group based on the delivery of a data packet.
25  // Returns false if this packet has already been seen, true otherwise.
26  bool Update(const QuicPacketHeader& header,
27              base::StringPiece decrypted_payload);
28
29  // Updates the FEC group based on the delivery of an FEC packet.
30  // Returns false if this packet has already been seen or if it does
31  // not claim to protect all the packets previously seen in this group.
32  //   |fec_packet_entropy|: XOR of entropy of all packets in the fec group.
33  bool UpdateFec(QuicPacketSequenceNumber fec_packet_sequence_number,
34                 bool fec_packet_entropy,
35                 const QuicFecData& fec);
36
37  // Returns true if a packet can be revived from this FEC group.
38  bool CanRevive() const;
39
40  // Returns true if all packets (FEC and data) from this FEC group have been
41  // seen or revived
42  bool IsFinished() const;
43
44  // Revives the missing packet from this FEC group.  This may return a packet
45  // that is null padded to a greater length than the original packet, but
46  // the framer will handle it correctly.  Returns the length of the data
47  // written to |decrypted_payload|, or 0 if the packet could not be revived.
48  size_t Revive(QuicPacketHeader* header,
49                char* decrypted_payload,
50                size_t decrypted_payload_len);
51
52  // Returns true of this FEC group protects any packets with sequence
53  // numbers less than |num|.
54  bool ProtectsPacketsBefore(QuicPacketSequenceNumber num) const;
55
56  const base::StringPiece payload_parity() const {
57    return base::StringPiece(payload_parity_, payload_parity_len_);
58  }
59
60  bool entropy_parity() const {
61    return entropy_parity_;
62  }
63
64  QuicPacketSequenceNumber min_protected_packet() const {
65    return min_protected_packet_;
66  }
67
68  size_t NumReceivedPackets() const {
69    return received_packets_.size();
70  }
71
72 private:
73  bool UpdateParity(base::StringPiece payload, bool entropy);
74  // Returns the number of missing packets, or size_t max if the number
75  // of missing packets is not known.
76  size_t NumMissingPackets() const;
77
78  // Set of packets that we have recevied.
79  SequenceNumberSet received_packets_;
80  // Sequence number of the first protected packet in this group (the one
81  // with the lowest packet sequence number).  Will only be set once the FEC
82  // packet has been seen.
83  QuicPacketSequenceNumber min_protected_packet_;
84  // Sequence number of the last protected packet in this group (the one
85  // with the highest packet sequence number).  Will only be set once the FEC
86  // packet has been seen.
87  QuicPacketSequenceNumber max_protected_packet_;
88  // The cumulative parity calculation of all received packets.
89  char payload_parity_[kMaxPacketSize];
90  size_t payload_parity_len_;
91  bool entropy_parity_;
92
93  DISALLOW_COPY_AND_ASSIGN(QuicFecGroup);
94};
95
96}  // namespace net
97
98#endif  // NET_QUIC_QUIC_FEC_GROUP_H_
99