限制每个时间单位的迭代次数

Now() GetTickCount()

 for (int i = 0; i < 1000; i++){
     DWORD have_to_sleep_until = GetTickCount() + EXPECTED_ITERATION_TIME_MS;
     // do stuff
     Sleep(max(0, have_to_sleep_until - GetTickCount()));
};

QueryPerformanceCounter()

QueryPerformanceFrequency(&freq)
timeWanted = 1.0/30.0   //time per iteration if 30 iterations / sec
for i
    QueryPerf(count1)
    do stuff
    queryPerf(count2)
    timeElapsed = (double)(c2 - c1) * (double)(1e3) / double(freq)  //time in milliseconds
    timeDiff = timeWanted - timeElapsed
    if (timeDiff > 0) 
        QueryPerf(c3)
        QueryPerf(c4) 
        while ((double)(c4 - c3) * (double)(1e3) / double(freq) < timeDiff)
            queryPerf(c4)
end for