monotone_time_point.h

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/*
 * Copyright 2021 MusicScience37 (Kenta Kabashima)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
#pragma once
 
#include <chrono>
 
#include "stat_bench/clock/duration.h"
 
#if defined(STAT_BENCH_DOCUMENTATION)
#include <cstdint>
 
#include <time.h>
#elif defined(_WIN32)
#define STAT_BENCH_HAS_WIN_MONOTONE_CLOCK 1
#include <cstdint>
#elif defined(__unix__)
#define STAT_BENCH_HAS_UNIX_MONOTONE_CLOCK 1
#include <time.h>  // NOLINT: std::timespec doesn't exist in C++ 14.
#else
// No definition here.
#endif
 
namespace stat_bench {
namespace clock {
 
#if defined(STAT_BENCH_DOCUMENTATION) || \
    defined(STAT_BENCH_HAS_WIN_MONOTONE_CLOCK)

class WinMonotoneTimePoint {
public:
    [[nodiscard]] auto operator-(
        const WinMonotoneTimePoint& right) const noexcept -> Duration;

    [[nodiscard]] static auto now() noexcept -> WinMonotoneTimePoint;

    [[nodiscard]] static auto resolution() noexcept -> Duration;
 
private:
    using DataType = std::int64_t;

    explicit WinMonotoneTimePoint(DataType data) noexcept;

    DataType data_;
};
 
#endif
 
#if defined(STAT_BENCH_DOCUMENTATION) || \
    defined(STAT_BENCH_HAS_UNIX_MONOTONE_CLOCK)

class UnixMonotoneTimePoint {
public:
    [[nodiscard]] auto operator-(
        const UnixMonotoneTimePoint& right) const noexcept -> Duration;

    [[nodiscard]] static auto now() noexcept -> UnixMonotoneTimePoint;

    [[nodiscard]] static auto resolution() noexcept -> Duration;
 
private:
    using DataType = timespec;

    explicit UnixMonotoneTimePoint(DataType data) noexcept;

    DataType data_;
};
 
#endif

class StdMonotoneTimePoint {
public:
    [[nodiscard]] auto operator-(
        const StdMonotoneTimePoint& right) const noexcept -> Duration;

    [[nodiscard]] static auto now() noexcept -> StdMonotoneTimePoint;

    [[nodiscard]] static auto resolution() noexcept -> Duration;
 
private:
    using DataType = std::chrono::steady_clock::time_point;

    explicit StdMonotoneTimePoint(DataType data) noexcept;

    DataType data_;
};
 
#if defined(STAT_BENCH_DOCUMENTATION)
using MonotoneTimePoint = <platform_dependent_type>;
#elif defined(STAT_BENCH_HAS_WIN_MONOTONE_CLOCK)
// Monotone clock in Windows.
using MonotoneTimePoint = WinMonotoneTimePoint;
#elif defined(STAT_BENCH_HAS_UNIX_MONOTONE_CLOCK)
// Monotone clock in Unix.
using MonotoneTimePoint = UnixMonotoneTimePoint;
#else
// Fallback using C++ standard library.
using MonotoneTimePoint = StdMonotoneTimePoint;
#endif
 
}  // namespace clock
}  // namespace stat_bench