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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "net/quic/quic_fec_group.h"
#include <limits>
#include "base/logging.h"
#include "base/stl_util.h"
using base::StringPiece;
using std::numeric_limits;
using std::set;
namespace net {
QuicFecGroup::QuicFecGroup(QuicPacketNumber fec_group_number)
: QuicFecGroupInterface(),
min_protected_packet_(fec_group_number),
max_protected_packet_(kInvalidPacketNumber),
payload_parity_len_(0),
effective_encryption_level_(NUM_ENCRYPTION_LEVELS) {}
QuicFecGroup::~QuicFecGroup() {}
bool QuicFecGroup::Update(EncryptionLevel encryption_level,
const QuicPacketHeader& header,
StringPiece decrypted_payload) {
DCHECK_EQ(min_protected_packet_, header.fec_group);
DCHECK_NE(kInvalidPacketNumber, header.packet_number);
if (ContainsKey(received_packets_, header.packet_number)) {
return false;
}
if (header.packet_number < min_protected_packet_ ||
(has_received_fec_packet() &&
header.packet_number > max_protected_packet_)) {
DLOG(ERROR) << "FEC group does not cover received packet: "
<< header.packet_number;
return false;
}
if (!UpdateParity(decrypted_payload)) {
return false;
}
received_packets_.insert(header.packet_number);
if (encryption_level < effective_encryption_level_) {
effective_encryption_level_ = encryption_level;
}
return true;
}
bool QuicFecGroup::UpdateFec(EncryptionLevel encryption_level,
const QuicPacketHeader& header,
StringPiece redundancy) {
DCHECK_EQ(min_protected_packet_, header.fec_group);
DCHECK_NE(kInvalidPacketNumber, header.packet_number);
if (has_received_fec_packet()) {
return false;
}
for (QuicPacketNumber packet : received_packets_) {
if (packet >= header.packet_number) {
DLOG(ERROR) << "FEC group does not cover received packet: " << packet;
return false;
}
}
if (!UpdateParity(redundancy)) {
return false;
}
max_protected_packet_ = header.packet_number - 1;
if (encryption_level < effective_encryption_level_) {
effective_encryption_level_ = encryption_level;
}
return true;
}
bool QuicFecGroup::CanRevive() const {
// We can revive if we're missing exactly 1 packet.
return NumMissingPackets() == 1;
}
bool QuicFecGroup::IsFinished() const {
// We are finished if we are not missing any packets.
return NumMissingPackets() == 0;
}
size_t QuicFecGroup::Revive(QuicPacketHeader* header,
char* decrypted_payload,
size_t decrypted_payload_len) {
if (!CanRevive()) {
return 0;
}
// Identify the packet number to be resurrected.
QuicPacketNumber missing = kInvalidPacketNumber;
for (QuicPacketNumber i = min_protected_packet_; i <= max_protected_packet_;
++i) {
// Is this packet missing?
if (received_packets_.count(i) == 0) {
missing = i;
break;
}
}
DCHECK_NE(kInvalidPacketNumber, missing);
DCHECK_LE(payload_parity_len_, decrypted_payload_len);
if (payload_parity_len_ > decrypted_payload_len) {
return 0;
}
for (size_t i = 0; i < payload_parity_len_; ++i) {
decrypted_payload[i] = payload_parity_[i];
}
header->packet_number = missing;
header->entropy_flag = false; // Unknown entropy.
received_packets_.insert(missing);
return payload_parity_len_;
}
bool QuicFecGroup::IsWaitingForPacketBefore(QuicPacketNumber num) const {
// Entire range is larger than the threshold.
if (min_protected_packet_ >= num) {
return false;
}
// Entire range is smaller than the threshold.
if (received_packets_.size() > 0 ? *received_packets_.rbegin() + 1 < num
: min_protected_packet_ < num) {
return true;
}
// Range spans the threshold so look for a missing packet below the threshold.
QuicPacketNumber target = min_protected_packet_;
for (QuicPacketNumber packet : received_packets_) {
if (target++ != packet) {
return true;
}
if (target >= num) {
return false;
}
}
// No missing packets below the threshold.
return false;
}
bool QuicFecGroup::UpdateParity(StringPiece payload) {
DCHECK_GE(kMaxPacketSize, payload.size());
if (payload.size() > kMaxPacketSize) {
DLOG(ERROR) << "Illegal payload size: " << payload.size();
return false;
}
if (payload_parity_len_ < payload.size()) {
payload_parity_len_ = payload.size();
}
if (received_packets_.empty() && !has_received_fec_packet()) {
// Initialize the parity to the value of this payload
memcpy(payload_parity_, payload.data(), payload.size());
if (payload.size() < kMaxPacketSize) {
// TODO(rch): expand as needed.
memset(payload_parity_ + payload.size(), 0,
kMaxPacketSize - payload.size());
}
return true;
}
// Update the parity by XORing in the data (padding with 0s if necessary).
XorBuffers(payload.data(), payload.size(), payload_parity_);
return true;
}
QuicPacketCount QuicFecGroup::NumMissingPackets() const {
if (!has_received_fec_packet()) {
return numeric_limits<QuicPacketCount>::max();
}
return static_cast<QuicPacketCount>(
(max_protected_packet_ - min_protected_packet_ + 1) -
received_packets_.size());
}
const StringPiece QuicFecGroup::PayloadParity() const {
return StringPiece(payload_parity_, payload_parity_len_);
}
QuicPacketCount QuicFecGroup::NumReceivedPackets() const {
return received_packets_.size();
}
EncryptionLevel QuicFecGroup::EffectiveEncryptionLevel() const {
return effective_encryption_level_;
}
QuicFecGroupNumber QuicFecGroup::FecGroupNumber() const {
return min_protected_packet_;
}
} // namespace net
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