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_ 99
