snes9x/vulkan/std_chrono_throttle.cpp

119 lines
2.9 KiB
C++

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