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Excerpts from netnews.comp.soft-sys.andrew: 17-Nov-92 message queue with
ATK Isabelle Tourneux@shamin (691)

> - is it possible to use the usual msgrcv and msgsnd in an
> infinite loop ? I have tried to put an infinite loop in the
> "controller_go" of an Adew view-controller, but it disturbs the
> usual functionnning of the controller.

Yes, the normal function of an interactive ATK function assumes that the
event loop in im/xim is run whenever waiting for input.  You could peek
into the internals of im and xim, and add the appropriate select call
and then call im_Interact(FALSE) if there is input for im.  I'm not very
familiar with message queues, as far as I can tell the only way to know
when a message has arrived is to be waiting for it, or to poll
continually.

Excerpts from netnews.comp.soft-sys.andrew: 17-Nov-92 message queue with
ATK Isabelle Tourneux@shamin (691)


> - does an object-oriented function (a sort of "im_AddMessageQueue")
> exist to set an input handler when something arrives on a
> message queue, just as it does for sockets in im_AddFileHandler ?

No.  Adding such a function might be quite difficult.  You could use
im_EnqueueEvent to periodically poll a message queue, but this could
hurt performance substantially.  

In an environment without threads I don't see how message queues make
sense to use.  (Though some of their features are certianly useful.)

If the main feature you're looking for is access control via the
permission bits, then a unix domain socket, or fifo might be better than
message queues for use with ATK.

-Rob

In article <1992Nov17.163509.662@csi.uottawa.ca>  
isabelle@shamin.genie.uottawa.ca (Isabelle Tourneux) writes:
> 
> I would like to use message queues with ATK and ADEW.
> 
> - is it possible to use the usual msgrcv and msgsnd in an
> infinite loop ? I have tried to put an infinite loop in the
> "controller_go" of an Adew view-controller, but it disturbs the
> usual functionnning of the controller.
> 
> - does an object-oriented function (a sort of "im_AddMessageQueue")
> exist to set an input handler when something arrives on a
> message queue, just as it does for sockets in im_AddFileHandler ?
> 
> In short, is there a way I can use message queues, or can I use 
> only sockets to communicate with other processes ?
> 
> Thanks
> 
> Isabelle Tourneux
> Multimedia Lab of the University of Ottawa,
> isabelle@shamin.genie.uottawa.ca
The namespace for System V message queues is disjoint from the file  
descriptor namespace. They do not work with select and hence do not fit into  
ATK interaction model. In short the SysV message and shared memory  
interfaces are evil crud which never should have been implemented in a UNIX  
kernel. Use the BSD send and recv calls instead. Or if you have SysVr4, you  
might try putmsg and getmsg on streams but I'm not sure how that stuff  
interacts with select. (And it undoubtedly depends on the particular version  
of UNIX you are running.)
--
Zalman Stern		   zalman@adobe.com		    (415) 962 3824
Adobe Systems, 1585 Charleston Rd., POB 7900, Mountain View, CA 94039-7900
  "Yeah. Ask 'em if they'll upgrade my shifters too." Bill Watterson

>Or if you have SysVr4, you might try putmsg and getmsg on streams

On what *kind* of streams?  (I.e., STREAMS is a general framework; to do
IPC on top of it, you need some particular thing that plugs into that
framework.  There's probably something in SVR4 that'll do....)

>but I'm not sure how that stuff interacts with select.

"select()", in SVR4, is implemented atop "poll()", so anything that
supports "poll()" - which should include anything implemented atop
STREAMS - should work with "select()", modulo bugs in the "select()"
implementation.