119 lines
2.9 KiB
C++
119 lines
2.9 KiB
C++
#include "std_chrono_throttle.hpp"
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#include <thread>
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using namespace std::chrono;
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void Throttle::set_frame_rate(double frame_rate)
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{
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max_frame_rate = frame_rate;
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frame_duration = 1.0 / max_frame_rate;
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frame_duration_us = microseconds(int64_t(frame_duration * 1000000.0));
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}
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microseconds Throttle::remaining()
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{
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auto now = time_point_cast<microseconds>(steady_clock::now());
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auto diff = (now - then);
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return frame_duration_us - diff;
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}
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#if defined(_WIN32)
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#define WIN32_LEAN_AND_MEAN
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#include <windows.h>
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void Throttle::wait_for_frame()
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{
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static UINT (WINAPI *NtDelayExecution)(BOOL, LARGE_INTEGER *) = nullptr;
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static UINT (WINAPI *NtQueryTimerResolution) (ULONG *, ULONG *, ULONG *) = nullptr;
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static UINT (WINAPI *NtSetTimerResolution) (ULONG, BOOL, ULONG *) = nullptr;
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static int timer_resolution = 12500;
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if (NtDelayExecution == nullptr)
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{
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HMODULE ntdll = ::GetModuleHandleW(L"ntdll.dll");
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if (ntdll)
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{
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NtDelayExecution = reinterpret_cast<typeof NtDelayExecution>(GetProcAddress(ntdll, "NtDelayExecution"));
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NtQueryTimerResolution = reinterpret_cast<typeof NtQueryTimerResolution>(GetProcAddress(ntdll, "NtQueryTimerResolution"));
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NtSetTimerResolution = reinterpret_cast<typeof NtSetTimerResolution>(GetProcAddress(ntdll, "NtSetTimerResolution"));
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}
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if (NtQueryTimerResolution)
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{
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ULONG min, max, current;
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NtQueryTimerResolution(&min, &max, ¤t);
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if (NtSetTimerResolution)
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NtSetTimerResolution(max, true, ¤t);
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timer_resolution = current * 5 / 4;
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}
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}
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auto time_to_wait = remaining();
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if (time_to_wait < -(frame_duration_us / 8))
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{
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reset();
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return;
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}
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if (NtDelayExecution)
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{
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if (time_to_wait.count() * 10 > timer_resolution)
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{
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LARGE_INTEGER li;
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li.QuadPart = -(time_to_wait.count() * 10 - timer_resolution);
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NtDelayExecution(false, &li);
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}
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}
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time_to_wait = remaining();
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while (time_to_wait.count() > 0)
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{
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std::this_thread::yield();
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time_to_wait = remaining();
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}
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}
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#endif
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#if !defined(_WIN32)
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void Throttle::wait_for_frame()
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{
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auto time_to_wait = remaining();
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if (time_to_wait < -frame_duration_us)
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{
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reset();
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return;
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}
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if (time_to_wait.count() > 1000)
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std::this_thread::sleep_for(time_to_wait - 1000us);
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time_to_wait = remaining();
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while (time_to_wait.count() > 0)
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{
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std::this_thread::yield();
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time_to_wait = remaining();
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}
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}
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#endif
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void Throttle::wait_for_frame_and_rebase_time()
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{
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wait_for_frame();
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advance();
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}
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void Throttle::advance()
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{
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then += frame_duration_us;
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}
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void Throttle::reset()
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{
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auto now = time_point_cast<microseconds>(steady_clock::now());
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then = now;
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}
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