Current Time with microsecond precision on windows

[Dwarf007]

Hello,

Does anyone know how, under Windows, I can get the exact current microsecond so that I can display a time with the microsecond precision ?

Thanks!

[Zatraz]

Is it that you are searching?

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/sysinfo/base/getfiletime.asp

[Dwarf007]

Not at all... It has nothing to do with files and I need microsecond.
Sorry.

[Kapil]

Not at all... It has nothing to do with files and I need microsecond.
Sorry.


There can be many ways thru which u can get time..

The include files are :

ctime.h, time.h, windows.h... they help you in extracting the current system time...

u can get time in milliseconds.. once you have that, you can extract to microseconds...

I hope this is what you wanted...

[Dwarf007]

u can get time in milliseconds.. once you have that, you can extract to microseconds...

I need microseconds, milliseconds are not precise enough.
What do you mean with extract to microseconds ?

[wysota]

Does Windows handle microseconds at all?

[Dwarf007]

Does Windows handle microseconds at all?

I heared and read a bit, that using the following Windows API functions : QueryPerformanceFrequency() and QueryPerformanceCounter() it should do...

but I didn't manage to display the current microsecond under windows, therefore I was wondering if anybody here had an example or an easy way to do that.

[brcain]

Are you trying to handle something with a hard real-time requirement? I've heard of extensions (patches to kernel) for Windows to do this.

Most timers (at least standard APIs) that I've used only have a resolution of 1 millisecond ... even though they may indicate a higher resolution value.

[wysota]

It would be hard to get higher resolutions with standard system as the internal system clock would have to tick with frequency higher than 1kHz, meaning there would need to be more than 1000 clock interrupts per second.

[Dwarf007]

Linux can.
gettimeofday() is accurate to the microsecond

[wysota]

Are you sure it doesn't only display in microseconds? I believe microseconds can be obtained when using hardware alarms from the real time clock, but I doubt system clock can be that accurate on its own. AFAIR modern Linux distros on i386 architecture have the clock interrupts set at 1kHz, so it would mean they can measure time with accuracy of 0.001s = 1ms. This is only my logic explanation, if someone knows better, please say so.

[Dwarf007]

you mean it just gives a millisecond accurate time and the microseconds are a kind of rand() % 999 ?

[wysota]

you mean it just gives a millisecond accurate time and the microseconds are a kind of rand() % 999 ?

Or set to 0. But generaly yes, it might be so.

[Dwarf007]

:eek: *grumpfl*

Ok thanks.. I think I will do something like that then.. (rand() % 999)

[wysota]

Why do you need microseconds anyway?

[Dwarf007]

wysota: I want to do a kind of portable and accurate gettimeofday();

Here is the solution, in case someone wants to do the same one day.
No garantie on it but it seems to work.

Windows part for a portable gettimeofday():


#ifdef _WIN32_

#include <windows.h>

int gettimeofday( struct timeval *tv, struct timezone *tz )
{
time_t rawtime;

time(&rawtime);
tv->tv_sec = (long)rawtime;

// here starts the microsecond resolution:

LARGE_INTEGER tickPerSecond;
LARGE_INTEGER tick; // a point in time

// get the high resolution counter's accuracy
QueryPerformanceFrequency(&tickPerSecond);

// what time is it ?
QueryPerformanceCounter(&tick);

// and here we get the current microsecond! \o/
tv->tv_usec = (tick.QuadPart % tickPerSecond.QuadPart);

return 0;
}
#endif // _WIN32_

[TheKedge]

.... and here's a class using those funcs (if it's any help)

K