[PATCH 3/7] ntdll: Use CLOCK_REALTIME_COARSE for NtQuerySystemTime() if it has sufficient resolution.

Huw Davies huw at codeweavers.com
Thu May 2 09:07:58 CDT 2019


On Thu, May 02, 2019 at 08:47:29AM -0500, Ken Thomases wrote:
> On May 2, 2019, at 3:45 AM, Huw Davies <huw at codeweavers.com> wrote:
> > -NTSTATUS WINAPI NtQuerySystemTime( PLARGE_INTEGER Time )
> > +NTSTATUS WINAPI NtQuerySystemTime( LARGE_INTEGER *time )
> > {
> > -    struct timeval now;
> > +#if defined(HAVE_CLOCK_GETTIME)
> > +    struct timespec ts;
> > +    static clockid_t clock_id = -1;
> > 
> > -    gettimeofday( &now, 0 );
> > -    Time->QuadPart = now.tv_sec * (ULONGLONG)TICKSPERSEC + TICKS_1601_TO_1970;
> > -    Time->QuadPart += now.tv_usec * 10;
> > +    if (clock_id == -1)
> > +    {
> > +        struct timespec res;
> > +
> > +        /* Use CLOCK_REALTIME_COARSE if it has 1 ms or better resolution */
> > +        if (!clock_getres( CLOCK_REALTIME_COARSE, &res ) && res.tv_sec == 0 && res.tv_nsec <= 1000000)
> > +            clock_id = CLOCK_REALTIME_COARSE;
> > +        else
> > +            clock_id = CLOCK_REALTIME;
>
> Having clock_gettime() doesn't necessarily imply having
> CLOCK_REALTIME_COARSE.  It seems that baseline POSIX only requires
> CLOCK_REALTIME.

Good point, thanks!

Huw.



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