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.
5 #include "net/quic/quic_fec_group.h"
9 #include "base/logging.h"
11 using base::StringPiece;
12 using std::numeric_limits;
18 const QuicPacketSequenceNumber kNoSequenceNumber = kuint64max;
21 QuicFecGroup::QuicFecGroup()
22 : min_protected_packet_(kNoSequenceNumber),
23 max_protected_packet_(kNoSequenceNumber),
24 payload_parity_len_(0),
25 entropy_parity_(false) {
28 QuicFecGroup::~QuicFecGroup() {}
30 bool QuicFecGroup::Update(const QuicPacketHeader& header,
31 StringPiece decrypted_payload) {
32 if (received_packets_.count(header.packet_sequence_number) != 0) {
35 if (min_protected_packet_ != kNoSequenceNumber &&
36 max_protected_packet_ != kNoSequenceNumber &&
37 (header.packet_sequence_number < min_protected_packet_ ||
38 header.packet_sequence_number > max_protected_packet_)) {
39 DLOG(ERROR) << "FEC group does not cover received packet: "
40 << header.packet_sequence_number;
43 if (!UpdateParity(decrypted_payload, header.entropy_flag)) {
46 received_packets_.insert(header.packet_sequence_number);
50 bool QuicFecGroup::UpdateFec(
51 QuicPacketSequenceNumber fec_packet_sequence_number,
52 bool fec_packet_entropy,
53 const QuicFecData& fec) {
54 if (min_protected_packet_ != kNoSequenceNumber) {
57 SequenceNumberSet::const_iterator it = received_packets_.begin();
58 while (it != received_packets_.end()) {
59 if ((*it < fec.fec_group) ||
60 (*it >= fec_packet_sequence_number)) {
61 DLOG(ERROR) << "FEC group does not cover received packet: " << *it;
66 if (!UpdateParity(fec.redundancy, fec_packet_entropy)) {
69 min_protected_packet_ = fec.fec_group;
70 max_protected_packet_ = fec_packet_sequence_number - 1;
74 bool QuicFecGroup::CanRevive() const {
75 // We can revive if we're missing exactly 1 packet.
76 return NumMissingPackets() == 1;
79 bool QuicFecGroup::IsFinished() const {
80 // We are finished if we are not missing any packets.
81 return NumMissingPackets() == 0;
84 size_t QuicFecGroup::Revive(QuicPacketHeader* header,
85 char* decrypted_payload,
86 size_t decrypted_payload_len) {
91 // Identify the packet sequence number to be resurrected.
92 QuicPacketSequenceNumber missing = kNoSequenceNumber;
93 for (QuicPacketSequenceNumber i = min_protected_packet_;
94 i <= max_protected_packet_; ++i) {
95 // Is this packet missing?
96 if (received_packets_.count(i) == 0) {
101 DCHECK_NE(kNoSequenceNumber, missing);
103 DCHECK_LE(payload_parity_len_, decrypted_payload_len);
104 if (payload_parity_len_ > decrypted_payload_len) {
107 for (size_t i = 0; i < payload_parity_len_; ++i) {
108 decrypted_payload[i] = payload_parity_[i];
111 header->packet_sequence_number = missing;
112 header->entropy_flag = entropy_parity_;
114 received_packets_.insert(missing);
115 return payload_parity_len_;
118 bool QuicFecGroup::ProtectsPacketsBefore(QuicPacketSequenceNumber num) const {
119 if (max_protected_packet_ != kNoSequenceNumber) {
120 return max_protected_packet_ < num;
122 // Since we might not yet have recevied the FEC packet, we must check
123 // the packets we have received.
124 return *received_packets_.begin() < num;
127 bool QuicFecGroup::UpdateParity(StringPiece payload, bool entropy) {
128 DCHECK_LE(payload.size(), kMaxPacketSize);
129 if (payload.size() > kMaxPacketSize) {
130 DLOG(ERROR) << "Illegal payload size: " << payload.size();
133 if (payload_parity_len_ < payload.size()) {
134 payload_parity_len_ = payload.size();
136 DCHECK_LE(payload.size(), kMaxPacketSize);
137 if (received_packets_.size() == 0 &&
138 min_protected_packet_ == kNoSequenceNumber) {
139 // Initialize the parity to the value of this payload
140 memcpy(payload_parity_, payload.data(), payload.size());
141 if (payload.size() < kMaxPacketSize) {
142 // TODO(rch): expand as needed.
143 memset(payload_parity_ + payload.size(), 0,
144 kMaxPacketSize - payload.size());
146 entropy_parity_ = entropy;
149 // Update the parity by XORing in the data (padding with 0s if necessary).
150 for (size_t i = 0; i < kMaxPacketSize; ++i) {
151 uint8 byte = i < payload.size() ? payload[i] : 0x00;
152 payload_parity_[i] ^= byte;
154 // xor of boolean values.
155 entropy_parity_ = (entropy_parity_ != entropy);
159 size_t QuicFecGroup::NumMissingPackets() const {
160 if (min_protected_packet_ == kNoSequenceNumber)
161 return numeric_limits<size_t>::max();
162 return (max_protected_packet_ - min_protected_packet_ + 1) -
163 received_packets_.size();