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* Copyright 2017 The WebRTC Project Authors. All rights reserved.
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
#include <stdint.h>
#include <string>
#include <unordered_map>
namespace cricket {
// Estimates the response rate for a series of messages expecting responses.
// Messages and their corresponding responses are identified by a string id.
// Responses are considered lost if they are not received within
// |consider_lost_after_ms|. If a response is received after
// |consider_lost_after_ms|, it is still considered as a response.
// Messages sent more than |forget_after_ms| ago are not considered
// anymore. The response rate is initially assumed to be 1.0.
// If the current time is 7, |forget_after_ms| is 6, and
// |consider_lost_after_ms| is 2, the response rate considers messages sent
// between times 1 and 5, so only messages in the following window can be
// considered lost:
// Time: 0 1 2 3 4 5 6 7
// Wind: <-------> |
// Responses received to the right of the window are still counted.
class PacketLossEstimator {
explicit PacketLossEstimator(int64_t consider_lost_after_ms,
int64_t forget_after_ms);
// Registers that a message with the given |id| was sent at |sent_time|.
void ExpectResponse(std::string id, int64_t sent_time);
// Registers a response with the given |id| was received at |received_time|.
void ReceivedResponse(std::string id, int64_t received_time);
// Calculates the current response rate based on the expected and received
// messages. Messages sent more than |forget_after| ms ago will be forgotten.
void UpdateResponseRate(int64_t now);
// Gets the current response rate as updated by UpdateResponseRate.
double get_response_rate() const { return response_rate_; }
std::size_t tracked_packet_count_for_testing() const;
// Output tracked packet state as a string.
std::string TrackedPacketsStringForTesting(std::size_t max) const;
struct PacketInfo {
int64_t sent_time;
bool response_received;
// Called periodically by ExpectResponse and ReceivedResponse to manage memory
// usage.
void MaybeForgetOldRequests(int64_t now);
bool ConsiderLost(const PacketInfo&, int64_t now) const;
bool Forget(const PacketInfo&, int64_t now) const;
int64_t consider_lost_after_ms_;
int64_t forget_after_ms_;
int64_t last_forgot_at_ = 0;
std::unordered_map<std::string, PacketInfo> tracked_packets_;
double response_rate_ = 1.0;
} // namespace cricket