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Date: Fri, 04 Nov 2005 11:15:18 -0600
From: "Marc A. Criley" <mcNOSPAM@mckae.com>
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Subject: Re: Advice on abort
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Date: 2005-11-04T11:15:18-06:00
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REH wrote:
> What are the best options when a task needs to be terminated, but
> signaling the task may not be possible?  We have tasks that sometimes
> need to be terminated, but may potentially be blocked on a resource,
> such as a socket.  Currently we use OS-specific calls to terminate the
> task, but I've never liked that.  I've been thinking of using the abort
> statement, but I don't think that's very graceful either.  I also would
> rather not complicate the code (or force polling behavior) by making
> the sockets non-blocking.  Any advice?

For the _specific_ case of blocking on a socket...

IF you're using GNAT, and
IF you're using GNAT.Sockets,

then take a look at the Selector functionality.  (This is an abstraction 
over the C select() function.)

Basically, once you get your socket and set up your selector you wait 
for traffic with a Check_Selector(...) call.  When you're ready to shut 
down, you can call Abort_Selector(...).  CheckSelector() then returns 
with a status of Aborted, and you can then go on about your termination.

I changed over to this in the version of DTraq that's getting updated 
and the code is now _much_ cleaner in this area.

(I don't know when Check_Selector and Abort_Selector were added to 
GNAT.Sockets, coulda been years ago.  I just happened to stumble across 
them when scanning through the spec a few months ago :-)

-- Marc A. Criley
-- McKae Technologies
-- www.mckae.com
-- DTraq - XPath In Ada - XML EZ Out