[Boost-users] [ASIO] Timer question

Subject: [Boost-users] [ASIO] Timer question
From: OvermindDL1 (overminddl1_at_[hidden])
Date: 2009-11-20 21:12:15

Greetings.

I programming library that I use (WT) had a bug in their asynchronous
timer handling, and although they fixed it, they are thinking of
moving over to Boost::ASIO timers since they already use Boost::ASIO
for the networking stack.  However, an interesting question was posed
about how Boost::ASIO timers handle the time changing on the host
computer (which is a possible scenario for this library due to its
up-time requirements).  Below is the basic part of the thread in
question.  Does anyone know the answer?  I attempted a quick look
through the timer source, however I cannot really seem to tell since I
know not the internals of ASIO nor the posix datetime library in
Boost...

On Fri, Nov 20, 2009 at 12:55 AM, Pau Garcia i Quiles
<pgquiles_at_[hidden]> wrote:
> On Fri, Nov 20, 2009 at 8:05 AM, Koen Deforche <koen_at_[hidden]> wrote:
>> Hey all,
>>
>> 2009/11/19 OvermindDL1 <overminddl1_at_[hidden]>:
>>>>> Speaking about WTimer, I think its implementation is wrong on Unix and
>>>>> could be more precise on Windows (although I'm not sure more precision
>>>>> is required; I've not checked if Wt::Time is used server-side).
>>>>
>>>> I haven't looked, but is there any reason that boost::asio::deadline_timer isn't being used to back WTimer? Â I'm pretty sure this addresses all of the concerns listed below. Â -sc
>>>>
>>>>
>>>> http://www.boost.org/doc/libs/1_41_0/doc/html/boost_asio/reference/deadline_timer.html
>>>
>>> Much of Boost already handles a lot of things better, since boost is
>>> linked in anyway then we should use them, they have already been well
>>> debugged and optimized.
>>
>> That is very true. I guess a motivation at the time was to avoid the
>> dependency on boost date_time for such a seemingly easy thing. But in
>> the meantime, we are relying on boost date_time anyway, and it is
>> clear that it is not that seemingly easy ?
>
> Actually, it is pretty easy. You've got 90% of the code there. Take a
> look at the OSG file I said. Fixing this on Unix is straightforward,
> fixing on Windows is easy too.
>
> Further, I think using boost date_time is not the right solution, as
> it does not provide timers - i. e. you'll be basing the timer on the
> clock time (hh:mm:ss) instead of processor ticks or some other entity
> independent of clock time. If timers are based on hh:mm:ss -
> hh':mm':ss' differences, they will fail when you change the computer
> clock time.
>
> I have only looked slightly into the implementation of Asio timers and
> they do not use gettimeofday but they don't use clock_gettime either,
> therefore I wouldn't use them without carefully looking into the
> implementation.