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Newsgroups: comp.lang.ada
Subject: Re: Getting delay of two events
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From: Stephen Leake <stephen_leake@stephe-leake.org>
Date: Sun, 31 Dec 2006 08:04:13 -0500
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Date: 2006-12-31T08:04:13-05:00
List-Id: <comp.lang.ada>

Jeffrey Creem <jeff@thecreems.com> writes:

>> mark wrote:
>>
>>>Hello,
>>>
>>>I have an external library with a task and a function getSync which
>>>returns boolean value (true if it is in sync position, false
>>>otherwise). Now I would like to create another task which will get the
>>>time between two sync (i.e. moments of time when the get_sync function
>>>returns true). Any ideas how can I make it??
>
> The options I see are
>
> 1) Yuck - Create a task that is higher priority than the 'external
> library task' and have it poll at some fixed rate that you know is
> faster than the library task could possibly run (at least 2x faster
> but obviously even faster than that depending on what sort of
> resolution you were looking for on the timer).
>
> 2) Less Yucky - Modify the library task to call someone else at the
> start and stop. Tends to introduce artificial coupling and start the
> spider web of coupling that wrecks a nice SW design.
>
> 3)Still less -  Add two new entry points to the library task that it
> accepts (with essentially a zero timeout) at the start and stop then
> rendevous with them from the new task - Again you will need to be sure
> that the new task is higher priority so that it can 'make it' to the
> second rendevous point before the library task hits the second accept.
> Downside of this approach is that it will only really work well for
> one external observer.

4) modify the library task to do the timing. 

Since the library task knows when the events occur, it needs to do the
timing!

-- 
-- Stephe