What's the most efficient and portable way of getting a millisecond timestamp, relative to any ancient epoch? I find

TimeStampToMSecs(DateTimeToTimeStamp(Now))

hard to swallow since Now() is hardly efficient and the resulting Comp is marked as non-potable in the documentation.

Where does it say that ?

And why do you think now returns a comp ? It returns a double.

Michael.

TimeStampToMSecs returns comp (not Now).

Tomas

Mark Morgan Lloyd wrote

What's the most efficient and portable way of getting a millisecond timestamp.

Do you run some "realtime" OS ? Otherwise millisecond timestamp don't make much sense, as the OS might delay you application for a second now and then.

-Michael

http://www.freepascal.org/docs-html/prog/progsu157.html#x200-2050008.2.5 "On other processors, the comp type is not supported."

And why do you think now returns a comp ? It returns a double.

http://lazarus-ccr.sourceforge.net/docs/rtl/sysutils/timestamptomsecs.html returns comp.

And I hardly see the point of converting something coming from the hardware and/or a kernel counter to a double and then back to a quadword.

Yes, my bad, I was referring to "Now".

And I hardly see the point of converting something coming from the hardware and/or a kernel counter to a double and then back to a quadword.

Nevertheless, Now() is the only portable construct available. Multiply it with msecsperday and round to int64 if you need an integer value.

Michael.

What about non-portable, e.g. unix-only? I don't see anything obvious in the BaseUnix documentation.

I'm sure there's something in EpikTimer I could use, but I'm trying to keep things fairly lean.

That's because there is nothing.
Most platforms support get_clock() but in FPC this is linux-only, as far as I know.

I'm sure there's something in EpikTimer I could use, but I'm trying to keep things fairly lean.

Last time I looked, EpikTimer used Now() on Unixes, definitely if you were not on intel platforms.
But maybe the situation has improved meanwhile, you would need to check the code.

Michael.

Yes, I know. And I don't care much since the object of the exercise is to convert a chunk of existing code into Pascal... and almost anything I do will have better timing than Javascript running in the context of a web browser :-)

If it turns out that the timer needs to be accurate rather than simply monotonic then I'll come back to it later. But I'm not even sure whether the filesystem supports things like timestamps... we're talking 1960 here.

Thanks, I'll investigate.

OK, I'll look at that presently. My recollection is that it ran OK on Linux SPARC etc. (although I didn't check /how/ it ran IYSWIM) but not on Solaris SPARC.

Michael Van Canneyt wrote

Last time I looked, EpikTimer used Now() on Unixes, definitely if you were not on intel platforms.

On i386 systems it uses Intel CPU hardware timers. On other Windows systems it uses the Windows QueryPerformanceCounter API. On Unixes it uses fpgettimeofday() and fpnanosleep()

Does Now() use the fpgettimeofday() call? Sorry, I didn't delve into the compiler code to find out.

Regards,
- Graeme -

Yes, Now() uses fpgettimeofday.

Michael.