Re: [boost] Date time query

26 Jul 2004

      On Sat, 24 Jul 2004 11:24:39 +0100, John Maddock <john@johnmaddock.co.uk> wrote:
...
Just out of interest, what is the problem that prevents the date-time
library from implementing a microsecond clock using GetSystemTimeAsFileTime
on Win32?
Thanks,
John.
The resolution supplied by GetSystemTimeAsFileTime may not be what you
think.  I get 10 milliseconds resolution out of my machine from the
following code.

#include <Windows.h>
#include <iostream>

int main () {

    FILETIME ft1,ft2;
    GetSystemTimeAsFileTime( &ft1 );

    GetSystemTimeAsFileTime( &ft2 );
    std::size_t diff = ft2.dwLowDateTime - ft1.dwLowDateTime;
    while (diff == 0)
    {
        GetSystemTimeAsFileTime( &ft2 );
        diff = ft2.dwLowDateTime - ft1.dwLowDateTime;

    }
    std::cout << "time taken = " << double(ft2.dwLowDateTime -
ft1.dwLowDateTime) /10000 << "milliseconds\n";

    system("pause");
    return 0;
}

Regards,

Matt Hurd.