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 <cstddef>
  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 decrypted at
  25   // |encryption_level|. Returns false if this packet has already been seen,
  26   // true otherwise.
  27   bool Update(EncryptionLevel encryption_level,
  28               const QuicPacketHeader& header,
  29               base::StringPiece decrypted_payload);
  30
  31   // Updates the FEC group based on the delivery of an FEC packet decrypted at
  32   // |encryption_level|. Returns false if this packet has already been seen or
  33   // if it does not claim to protect all the packets previously seen in this
  34   // group.
  35   bool UpdateFec(EncryptionLevel encryption_level,
  36                  QuicPacketNumber fec_packet_packet_number,
  37                  const QuicFecData& fec);
  38
  39   // Returns true if a packet can be revived from this FEC group.
  40   bool CanRevive() const;
  41
  42   // Returns true if all packets (FEC and data) from this FEC group have been
  43   // seen or revived
  44   bool IsFinished() const;
  45
  46   // Revives the missing packet from this FEC group.  This may return a packet
  47   // that is null padded to a greater length than the original packet, but
  48   // the framer will handle it correctly.  Returns the length of the data
  49   // written to |decrypted_payload|, or 0 if the packet could not be revived.
  50   size_t Revive(QuicPacketHeader* header,
  51                 char* decrypted_payload,
  52                 size_t decrypted_payload_len);
  53
  54   // Returns true of this FEC group protects any packets with sequence
  55   // numbers less than |num|.
  56   bool ProtectsPacketsBefore(QuicPacketNumber num) const;
  57
  58   const base::StringPiece payload_parity() const {
  59     return base::StringPiece(payload_parity_, payload_parity_len_);
  60   }
  61
  62   QuicPacketNumber min_protected_packet() const {
  63     return min_protected_packet_;
  64   }
  65
  66   QuicPacketCount NumReceivedPackets() const {
  67     return received_packets_.size();
  68   }
  69
  70   // Returns the effective encryption level of the FEC group.
  71   EncryptionLevel effective_encryption_level() const {
  72     return effective_encryption_level_;
  73   }
  74
  75   // An optimized version of running |output| ^= |input|, where ^ is
  76   // byte-by-byte XOR and both |output| and |input| are of size |size_in_bytes|.
  77   static void XorBuffers(const char* input, size_t size_in_bytes, char* output);
  78
  79  private:
  80   bool UpdateParity(base::StringPiece payload);
  81   // Returns the number of missing packets, or QuicPacketCount max
  82   // if the number of missing packets is not known.
  83   QuicPacketCount NumMissingPackets() const;
  84
  85   // Set of packets that we have recevied.
  86   PacketNumberSet received_packets_;
  87   // packet number of the first protected packet in this group (the one
  88   // with the lowest packet number).  Will only be set once the FEC
  89   // packet has been seen.
  90   QuicPacketNumber min_protected_packet_;
  91   // packet number of the last protected packet in this group (the one
  92   // with the highest packet number).  Will only be set once the FEC
  93   // packet has been seen.
  94   QuicPacketNumber max_protected_packet_;
  95   // The cumulative parity calculation of all received packets.
  96   char payload_parity_[kMaxPacketSize];
  97   size_t payload_parity_len_;
  98   // The effective encryption level, which is the lowest encryption level of
  99   // the data and FEC in the group.
 100   EncryptionLevel effective_encryption_level_;
 101
 102   DISALLOW_COPY_AND_ASSIGN(QuicFecGroup);
 103 };
 104
 105 }  // namespace net
 106
 107 #endif  // NET_QUIC_QUIC_FEC_GROUP_H_