rtt_estimator.h

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// BSD 3-Clause License
// Copyright (c) 2024, 🍀☀🌕🌥 🌊
// See the LICENSE file in the project root for full license information.
 
#pragma once
 
#include <chrono>
#include <cstdint>
 
namespace kcenon::network::protocols::quic
{
 
class rtt_estimator
{
public:
    rtt_estimator();
 
    explicit rtt_estimator(std::chrono::microseconds initial_rtt,
                           std::chrono::microseconds max_ack_delay =
                               std::chrono::microseconds{25000});
 
    auto update(std::chrono::microseconds latest_rtt,
                std::chrono::microseconds ack_delay,
                bool is_handshake_confirmed = true) -> void;
 
    [[nodiscard]] auto smoothed_rtt() const noexcept -> std::chrono::microseconds
    {
        return smoothed_rtt_;
    }
 
    [[nodiscard]] auto rttvar() const noexcept -> std::chrono::microseconds
    {
        return rttvar_;
    }
 
    [[nodiscard]] auto min_rtt() const noexcept -> std::chrono::microseconds
    {
        return min_rtt_;
    }
 
    [[nodiscard]] auto latest_rtt() const noexcept -> std::chrono::microseconds
    {
        return latest_rtt_;
    }
 
    [[nodiscard]] auto pto() const noexcept -> std::chrono::microseconds;
 
    auto set_max_ack_delay(std::chrono::microseconds delay) noexcept -> void
    {
        max_ack_delay_ = delay;
    }
 
    [[nodiscard]] auto max_ack_delay() const noexcept -> std::chrono::microseconds
    {
        return max_ack_delay_;
    }
 
    [[nodiscard]] auto has_sample() const noexcept -> bool
    {
        return !first_sample_;
    }
 
    auto reset() -> void;
 
private:
    std::chrono::microseconds smoothed_rtt_;
 
    std::chrono::microseconds rttvar_;
 
    std::chrono::microseconds min_rtt_;
 
    std::chrono::microseconds latest_rtt_;
 
    std::chrono::microseconds max_ack_delay_;
 
    std::chrono::microseconds initial_rtt_;
 
    bool first_sample_;
 
    static constexpr auto kGranularity = std::chrono::milliseconds{1};
 
    static constexpr auto kInitialRtt = std::chrono::microseconds{333000};
 
    static constexpr auto kDefaultMaxAckDelay = std::chrono::microseconds{25000};
};
 
} // namespace kcenon::network::protocols::quic