MFC 中怎么实现微秒级的延时

转自百度文库：

DelayUs

void DelayUs(int uDelay)
{

LARGE_INTEGER litmp;
LONGLONG QPart1,QPart2;

double dfMinus,dfFreq,dfTim;

/*
Pointer to a variable that the function sets, in counts per second, to the current performance-counter frequency.
If the installed hardware does not support a high-resolution performance counter,
the value passed back through this pointer can be zero.

*/
QueryPerformanceFrequency(&litmp);

dfFreq = (double)litmp.QuadPart;

/*
Pointer to a variable that the function sets, in counts, to the current performance-counter value.
*/
QueryPerformanceCounter(&litmp);

QPart1 = litmp.QuadPart;
do
{
QueryPerformanceCounter(&litmp);
QPart2 = litmp.QuadPart;
dfMinus = (double)(QPart2-QPart1);
dfTim = dfMinus/dfFreq;
}while(dfTim<0.000001 * uDelay);
}

如果你看懂了上述函数，还可以用它里面的部分代码来测试很多函数的执行时间。

当然，这个函数还是有点隐患，如果在一个延时期间，定时器溢出，那么这个值就有可能不准，需要你小心处理。

如：if (dfMinus < 0)

　　　　break;

这个假设硬件定时器是以增加的方式计数的。