Re: [ECOS] cyg_ticks_to_timespec()

[Jonathan Larmour <jlarmour at redhat dot com>]

Hugo Tyson wrote:
> 
> > From: Jonathan Larmour <jlarmour@redhat.com>
> 
> Oh, I get it now.  The code in cyg_ticks_to_timespec() is using a clock
> converter to convert to whole seconds, then subtracting to get the nS part
> left over!  No wonder it gives a "wrong" answer, of course the whole
> seconds answer is rounded.
> 
> Use it to convert to nS and do a divide by 10^9 - that way the right answer
> would emerge, that's what clock converters are meant for.
> 
> > tweak cyg_ticks_to_timespec to fix up the value if tv_nsec is negative.
> > Before I do it, I just want to check my understanding that the convertors
> > are doing the right thing by rounding not truncating.
> 
> Of course they are.  Someone misunderstood the purpose of the converters.
> They do conversion taking care that overflow will be avoided at all costs,
> even if it means discarding trailing digits; ie. they will be right at the
> cost of precision even if the conversion factor is great in either
> direction and the arguments are large.
[snip]

I've checked in something that just post-adjusts the timespec if the
nanoseconds are negative. I believe this should produce consistent results
because the sec_convertor and sec_invertor used by the clock convertors
_should_ be the inverse of each other, and therefore conversion in one
direction should always be the inverse mapping of the other.

Jifl
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