On 9/23/11 8:35 AM, Poul-Henning Kamp wrote:
Take a look at FreeBSD's timecounters, what you are asking for sounds pretty much like what I did 15 years:http://phk.freebsd.dk/pubs/timecounter.pdf I used a 32.64 internal format, to avoid rounding errors, particularly in your "k1" term. I'm headed for the US east-coast the next week, if we get anywhere near each other, I'd be happy to talk, shoot me an email: p...@freebsd.org
AH yes... I forgot to mention that phk's timecounter stuff has already been incorporated in our implementation (thanks Poul-Henning!) (and we truncate to match the API requirement of uint32 for the nanoseconds) For what it's worth, my implementation is using RTEMS as the base OS, but at this stage, I'm trying to define an architecture standard for others to use, with selected implementation standards as well (e.g. API or message formats)
It's all the more complex stuff.. how does one represent a more sophisticated transformation? How does one represent changes in the transformation (either in a log file, or in a schedule for the future) so that one can "reconstruct" a time in the past, for instance.
There's plenty of standards for how to represent "time" (in the space biz, we use CCSDS unsegmented time a lot), but the more abstract "time management" is sort of left up in the air. For instance, there's a standard/recommendation that says something along the lines of consider the time of the first bit in the message as the "tone" in the "at the tone, the time is" concept. And plenty of descriptions of various time scales (TAI, UTC, UT1, etc.)
What I'd like to do is take the next step beyond what you promulgated with a representation of time and the conversion between count and time with a linear equation.
I'd like to propose a standard description of a higher order model of time and the transformation between raw clock and time (in some agreed upon time scale).
And I'd like to describe an architecture for manipulating this. e.g. when you "set the time", at a simple level it means measuring the difference between what you have now and what you want and adjusting your transformation to match.
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