[fpc-devel] NowUTC in the RTL

[Sven Barth]

Am 09.12.2011 16:44, schrieb zeljko:
> On Friday 09 of December 2011 16:10:54 Sven Barth wrote:
>
>  > Am 09.12.2011 15:37, schrieb zeljko:
>
>  > > On Friday 09 of December 2011 14:52:56 Sven Barth wrote:
>
>  > > > Am 09.12.2011 13:30, schrieb Michael Schnell:
>
>  > > > > On 12/09/2011 01:17 PM, Felipe Monteiro de Carvalho wrote:
>
>  > > > >> I would like to define it like this: "FPGetTickCount returns the
>
>  > > > >>
>
>  > > > >> amount of ticks since an unspecified initial time. This initial
>
>  > > > >> time
>
>  > > > >>
>
>  > > > >> is unknown, but is fixed for the entire duration of the
>
>  > > > >> application.
>
>  > > > >>
>
>  > > > >> Ticks are time intervals and all of them have the same duration,
>
>  > > > >> but
>
>  > > > >>
>
>  > > > >> their exact meaning in terms of real world units like milliseconds
>
>  > > > >> is
>
>  > > > >>
>
>  > > > >> unspecified. FPGetTickCount is not affected by timezones and also
>
>  > > > >> not
>
>  > > > >>
>
>  > > > >> by the user changing the system clock." So it matches
>
>  > > > >>
>
>  > > > >> Windows.GetTickCount well but still is flexible enough to be
>
>  > > > >>
>
>  > > > >> implemented in other platforms.
>
>  > > > >
>
>  > > > > What if the PC is polling a time server or similar ? IMHO
>
>  > >
>
>  > > FPGetTickCount
>
>  > >
>
>  > > > > should not be affected by such interference. This rules out
> using OS
>
>  > > > >
>
>  > > > > time API calls.
>
>  > > >
>
>  > > > The description of Felipe mathes Windows' GetTickCount (number of
>
>  > > >
>
>  > > > milliseconds since system start) and Linux' MONOTONIC_RAW time (or
>
>  > > >
>
>  > > > however it is called exactly). So I don't see why this should
> rule out
>
>  > > >
>
>  > > > OS time API calls...
>
>  > >
>
>  > > No, MONOTONIC_RAW is introduced in 2.6.26 afair, so it won't run on
>
>  > > older kernels.
>
>  >
>
>  > My comment was less for which timer type we should support, but more to
>
>  > have a argument for what Felipe said.
>
>
> Ok, also I forgot to mention that MONOTNIC_RAW isn't interrupted by ntp
> but MONOTONIC IS so it's big diff.

Yes, Henry wrote that already as well...

Regards,
Sven