windows下实现微秒级延时

//常规

void sleep_micro_seconds(ULONG ulMicroSeconds)

{

 LARGE_INTEGER varFrequency = {0}, varCounter_Start = {0}, varCounter_End = {0};

 double dFrequency = 0;

 LONGLONG llCount = 0;

 ::QueryPerformanceFrequency(&varFrequency);

 dFrequency = varFrequency.QuadPart/1.0;

 ::QueryPerformanceCounter(&varCounter_Start);

 while(true)

 {

  ::QueryPerformanceCounter(&varCounter_End);

  llCount = varCounter_End.QuadPart - varCounter_Start.QuadPart;

  

  if((llCount/dFrequency) > (ulMicroSeconds/1000000.0) )

  {

   break;

  }

 }

}

 

//优化

void sleep_micro_seconds(ULONG ulMicroSeconds)

{

 LARGE_INTEGER varFrequency = {0}, varCounter_Start = {0}, varCounter_End = {0};

 LONGLONG llCount = 0;

 ::QueryPerformanceFrequency(&varFrequency);

 ::QueryPerformanceCounter(&varCounter_Start);

 while(true)

 {

  ::QueryPerformanceCounter(&varCounter_End);

  llCount = varCounter_End.QuadPart - varCounter_Start.QuadPart;

  if(1000000*llCount > ulMicroSeconds*varFrequency.QuadPart)

  {

   break;

  }

 }

}

 

 

int main(int argc, char* argv[])

{

 sleep_micro_seconds(40);

}