MFC 中怎么实现微秒级的延时
转自百度文库:
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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。