MFC 中怎么实现微秒级的延时

转自百度文库：

DelayUs

 1 void DelayUs(int uDelay)

 2 {

 3 

 4     LARGE_INTEGER litmp;

 5     LONGLONG QPart1,QPart2;

 6 

 7     double dfMinus,dfFreq,dfTim;

 8     

 9     /*

10         Pointer to a variable that the function sets, in counts per second, to the current performance-counter frequency. 

11         If the installed hardware does not support a high-resolution performance counter, 

12         the value passed back through this pointer can be zero. 

13 

14     */

15     QueryPerformanceFrequency(&litmp);

16 

17     dfFreq = (double)litmp.QuadPart;

18 

19     /*

20         Pointer to a variable that the function sets, in counts, to the current performance-counter value. 

21     */

22     QueryPerformanceCounter(&litmp);

23 

24     QPart1 = litmp.QuadPart;

25     do

26     {

27            QueryPerformanceCounter(&litmp);

28         QPart2 = litmp.QuadPart;

29         dfMinus = (double)(QPart2-QPart1);

30         dfTim = dfMinus/dfFreq;

31      }while(dfTim<0.000001 * uDelay);

32 }

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。