Re: Timer with Micro seconds

In Chandra's code there is design flaw. Under some conditions the expression

liTimeOut.QuadPart += liDelay.QuadPart

can result in small value, when the addition overflows. The better way is to
calculate the difference between current time and start time and compare it
with the timeout.

I must admit that the probability for the overflow is small, but it's
different from zero.

LARGE_INTEGER liDelay;
// Query number of ticks per second
if (QueryPerformanceFrequency(&liDelay))
{
// 1ms delay
liDelay.QuadPart /= 1000;

LARGE_INTEGER liTimeOut;
// Get current ticks
if (QueryPerformanceCounter(&liTimeOut))
{
// Create timeout value
liTimeOut.QuadPart += liDelay.QuadPart;
LARGE_INTEGER liCurrent;
do
{
// Get current ticks
QueryPerformanceCounter(&liCurrent);
// Delay until timeout
} while (liCurrent.QuadPart<liTimeOut.QuadPart);
}
}


LARGE_INTEGER liStart;
// Get current ticks
if (QueryPerformanceCounter(&liStart))
{
do
{
LARGE_INTEGER liCurrent;
LARGE_INTEGER liSpan;

// Get current ticks
QueryPerformanceCounter(&liCurrent);
liSpan.QuadPart = liCurrent.QuadPart - liStart.QuadPart;
} while (liSpan.QuadPart<liTimeOut.QuadPart);
}

/Helge


.

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