Yo Eric! On Sat, 11 Mar 2017 06:20:46 -0500 "Eric S. Raymond" <e...@thyrsus.com> wrote:
> Achim Gratz <strom...@nexgo.de>:
> > No, most certainly not. What you're looking at really is a simple
> > 64bit integer type that needs to be scaled by 2^-32 in order to be
> > interpreted in seconds. It's not a separate number format or
> > anything like that and I suspect most of the uses of the integer
> > and fractional half were initially inserted in order to more
> > effectively deal with that type on machines with only 32bit
> > arithmetic. I don't think that's still a valid concern, but those
> > half-word accesses may be hard to excise from the code.
>
> I confirm that Achim is correct. I had to grok all this stuff while
> turning the type into a scalar.
True, but a lot of the code still uses l_fp as a two part object, hi
and lo.
And that will remain a useful mental abstraction for conversions
from and to timespec, timeval, etc. When the NTP Epoch gets ready to
roll over it will become a three part object.
I'll bet a lot of the machine code handles l_fp as if it were a
structure instead of doing all the 32 bit shifts. When the C compiler
optimizes it is using the same mental abstraction to see optimizations.
I have no objections to the changed comments. They just keep getting
better and better.
RGDS
GARY
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