time_stamp_utc.hpp

// Copyright Take Vos 2021.
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt)
 
#pragma once
 
#include "required.hpp"
#include "unfair_mutex.hpp"
#include "chrono.hpp"
#include <array>
#include <atomic>
#include <thread>
 
namespace tt {
class time_stamp_count;
 
struct time_stamp_utc {
    [[nodiscard]] static utc_nanoseconds now(time_stamp_count &tsc) noexcept;
 
    [[nodiscard]] static utc_nanoseconds make(time_stamp_count const &tsc) noexcept;
 
    static bool start_subsystem() noexcept;
 
    static void stop_subsystem() noexcept;
 
    static void adjust_for_drift() noexcept;
 
private:
    static inline std::jthread subsystem_thread;
    static inline unfair_mutex mutex;
    static inline std::array<std::atomic<utc_nanoseconds>, maximum_num_cpus> tsc_epochs = {};
 
    static void subsystem_proc_frequency_calibration(std::stop_token stop_token) noexcept;
    static void subsystem_proc(std::stop_token stop_token) noexcept;
 
    static bool init_subsystem() noexcept;
 
    static void deinit_subsystem() noexcept;
 
    [[nodiscard]] static size_t find_cpu_id(uint32_t cpu_id) noexcept;
};
 
std::string format_engineering(std::chrono::nanoseconds duration);
 
} // namespace tt