hires_utc_clock.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 <array>
#include <atomic>
#include <chrono>
#include <thread>
 
namespace tt {
class time_stamp_count;
 
struct hires_utc_clock {
    using rep = int64_t;
    using period = std::nano;
    using duration = std::chrono::duration<rep, period>;
    using time_point = std::chrono::time_point<hires_utc_clock>;
    static const bool is_steady = false;
 
    [[nodiscard]] static time_point now() noexcept;
 
    [[nodiscard]] static time_point now(time_stamp_count &tsc) noexcept;
 
    [[nodiscard]] static time_point 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::atomic<bool> subsystem_is_running = false;
    static inline std::jthread subsystem_thread;
    static inline unfair_mutex mutex;
    static inline std::array<std::atomic<hires_utc_clock::time_point>, 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(hires_utc_clock::duration duration);
 
std::string format_iso8601_utc(hires_utc_clock::time_point utc_timestamp) noexcept;
 
std::string format_iso8601(hires_utc_clock::time_point utc_timestamp, std::chrono::time_zone const *time_zone = nullptr) noexcept;
 
} // namespace tt