net/quic/quic_fec_group.h

   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
  17 namespace net {
  18
  19 class 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_