[ntp:questions] Start of new GPS 1024 week epoch

Martin Burnicki martin.burnicki at meinberg.de
Tue Aug 27 10:54:48 UTC 2013

Rob schrieb:
> Martin Burnicki <martin.burnicki at meinberg.de> wrote:
>> Rob wrote:
>>> Martin Burnicki <martin.burnicki at meinberg.de> wrote:
>>>> Extracting some refclock driver code from ntpd, modify it so that it
>>>> uses the SHM interface instead of ntpd's "native" refclock interface,
>>>> and putting all this into an own Windows service would be quite some effort.
>>>> Maybe it would make more sense to try to port gpsd or something similar
>>>> to Windows, if this is not yet supported.
>>> The SHM interface in gpsd is Unix-specifc (shmget/shmat).
>>> Maybe it is better to investigate what SHM interfaces Windows supports
>>> and find if one of them is compatible with something available on
>>> Linux/Unix, and then use that as the SHM for the new improved driver.
>>> That would make the porting between Unix and Windows easier.
>> As far as I know there is only a single type of shared memory support in
>> Windows.
> Ok.  That amazes me.  I thought that Windows always retained all earlier
> API methods for backward compatability, starting from the days of DOS.
> I would not be surprised when there was still a Windows API to create
> and attach an EMS/XMS/HMA or whatever it was once called block.
> And there were also the days of Windows NT when Windows tried to be
> a Posix-compatible OS (because that was required to get US Government
> jobs).  So I expected that there would be at least an API for Posix
> shared memory, a current Windows API, and maybe 2 or 3 backward compatible
> APIs.

What I meant is the usage of CreateFileMapping() and MapViewOfFile() for 
shared memory segments, as it is done in ntpd's refclock_shm.c.

We are using this in the Windows driver package for our PCI cards, but 
this usage is not related to NTP. AFAIK this is supported in all Windows 
version at least starting with NT.

Ntpd has already implemented this (which I also didn't know until 
recently), and it should not be too hard for something like gpsd to 
implement this also, if this han't already been done, yet.

Martin Burnicki

Meinberg Funkuhren
Bad Pyrmont

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