bd09c82521
This implementation provides a consistent, high performance, and high resolution clock where/when std::chrono::steady_clock does not provide sufficient precision.
56 lines
1.6 KiB
C++
56 lines
1.6 KiB
C++
// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
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// SPDX-License-Identifier: GPL-2.0-or-later
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#if defined(_WIN32)
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#include <windows.h>
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#else
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#include <time.h>
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#endif
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#include "common/steady_clock.h"
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namespace Common {
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#ifdef _WIN32
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static s64 WindowsQueryPerformanceFrequency() {
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LARGE_INTEGER frequency;
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QueryPerformanceFrequency(&frequency);
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return frequency.QuadPart;
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}
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static s64 WindowsQueryPerformanceCounter() {
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LARGE_INTEGER counter;
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QueryPerformanceCounter(&counter);
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return counter.QuadPart;
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}
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#endif
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SteadyClock::time_point SteadyClock::Now() noexcept {
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#if defined(_WIN32)
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static const auto freq = WindowsQueryPerformanceFrequency();
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const auto counter = WindowsQueryPerformanceCounter();
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// 10 MHz is a very common QPC frequency on modern PCs.
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// Optimizing for this specific frequency can double the performance of
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// this function by avoiding the expensive frequency conversion path.
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static constexpr s64 TenMHz = 10'000'000;
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if (freq == TenMHz) [[likely]] {
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static_assert(period::den % TenMHz == 0);
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static constexpr s64 Multiplier = period::den / TenMHz;
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return time_point{duration{counter * Multiplier}};
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}
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const auto whole = (counter / freq) * period::den;
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const auto part = (counter % freq) * period::den / freq;
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return time_point{duration{whole + part}};
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#elif defined(__APPLE__)
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return time_point{duration{clock_gettime_nsec_np(CLOCK_MONOTONIC_RAW)}};
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#else
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timespec ts;
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clock_gettime(CLOCK_MONOTONIC, &ts);
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return time_point{std::chrono::seconds{ts.tv_sec} + std::chrono::nanoseconds{ts.tv_nsec}};
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#endif
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}
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}; // namespace Common
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