Re: xtime

From: williamkempf_at_[hidden]
Date: 2001-08-03 08:46:03

--- In boost_at_y..., "Scott McCaskill" <scott_at_m...> wrote:
> Is xtime going to continue to play a part in the public interface 
of the
> boost thread library (like in condition::timed_wait())?  If so, it 
might be
> useful to expose some of the functions in timeconv.inl, such as
> to_time(unsigned milliseconds, boost::xtime& xt).  It seems more 
common to
> want to specify a duration than an absolute time when using 
timed_wait-type
> operations.

Yes, it will remain in the public interface, and needs to be 
documented.  Unfortunately, this is a minimalist implementation of 
the full spec, since I don't have the expertise to provide a full 
implementation.  If anyone knows a lot about time algorithms and 
would like to volunteer to provide Boost with a full implementation 
I'd love to hear it!

As for exposing the stuff in timeconv.inl, I'm not so sure.  These 
routines are used to translate to/from the native types for the 
various platforms, and it's just an (unfortunate) coincedence that 
the Win32 type is a duration.  Originally all timed operations in 
Boost.Threads followed the Win32 route using durations, mostly 
because of my own bias towards this platform, until you realize that 
a duration wait for a condition is extremely problematic.  The reason 
is that the condition may return from a wait when the logically 
associated predicate is not/no longer true and the loop should re-
enter the wait.  If a duration were used you'd have to recalculate 
the duration before entering the loop again.

To wait for a duration you simply create an xtime instance and add 
the seconds and nanoseconds, an operation that really doesn't need a 
function.  The to_time() routine in timeconv.inl exists solely to 
translate milliseconds to seconds and nanoseconds, something that 
typically won't be needed by programmers (they should precalculate 
this stuff instead of doing it at run time).

In any event, the conversions to and from milliseconds would be the 
only ones that you could argue for exposing in any event.

Bill Kempf