LARGE_INTEGER high_precision_sleep(LARGE_INTEGER preTime, unsigned long long sleepTime) { LARGE_INTEGER t; QueryPerformanceCounter(&t); while(t.QuadPart-preTime.QuadPart<sleepTime)QueryPerformanceCounter(&t); //printf("sleepTime=%d\n", t.QuadPart-preTime.QuadPart);//调试时用来观察每次暂停时间。一般应略有不同才正确 /*//这种方式与直接返回t精度差不多,但多了一个运算,划不来
preTime.QuadPart += sleepTime; return preTime;*/ return t; }
使用方法:
LARGE_INTEGER freq,t0,t1,t3;
QueryPerformanceFrequency(&freq);//频率 计数/秒
//当前频率 TIMES_PER_SECOND 下间隔的计数
auto SLEEP_COUNT = freq.QuadPart / TIMES_PER_SECOND;
QueryPerformanceCounter(&t0);
QueryPerformanceCounter(&t3);
for (int i = 0; i < number; i++) {
//do something
srand(t3.LowPart);//srand()函数产生一个以当前时间开始的随机种子
Sleep(rand() %20 );//TIMES_PER_SECOND=30,理论上每次Sleep(33.33ms),但不能Sleep(rand()%30),因为Sleep精度问题,可能实际上超过
//BitBlt(dcMem, 0, 0, 1920, 1080, dcScreen, 0, 0, SRCCOPY);
t3=high_precision_sleep(t3, SLEEP_COUNT);
}
QueryPerformanceCounter(&t1);
cout << "执行 "<< number << " 次, 耗时 " << (((t1.QuadPart - t0.QuadPart) * 1000000) / freq.QuadPart)<< " 微秒" << std::endl;
当TIMES_PER_SECOND=30,number=500时,理论耗时:秒
实际耗时:耗时 16668737 微秒、耗时 16668737 微秒、耗时 16667480 微秒...每次相差不大,在1ms左右