NetNews Usenet Archive 1992 #27/NN_1992_27.iso/spool/comp/softsys/andrew/1392

Text File | 1992-11-20 | 3.4 KB | 76 lines

Newsgroups: comp.soft-sys.andrew
Path: sparky!uunet!usc!zaphod.mps.ohio-state.edu!cs.utexas.edu!torn!nott!cunews!csi.uottawa.ca!news
From: [e-mail] (Isabelle Tourneux)
Subject: communication between Adew controllers
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Organization: MCRLab - University of Ottawa
Date: Fri, 20 Nov 92 20:55:16 GMT
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First, thank you very much for all the detailed answers you have
given me concerning message queues. This has however led me to
other questions :

I have several adew "view+controller" in the same machine, which
are spawned successively with forks and execs. I would like to have
them communicate with each other. So I have looked at all the
possible means of communication between these controllers. I am
using System V.

- FIFO and message queues work but they are not directly usable to
read a message that can come any time. I would have to be waiting
for it or to have an infinite loop in the code of the adew
controller, which is not possible. I know it is possible to
modify xim.c and to add a message queue to the select, , but I do
not wish to do such low-level modifications on xim.c.

- interruptions would be a nice solution, but I have not managed
to get the pid of the controller without clicking somewhere on the
view. A getpid() in controller_go gives the pid of runadew I guess.
Moreover, runadew puts the group id of the controller equal to the
pid of this controller, so I cannot get the group id of the
controller without clicking on the view, as for the pid. Is it
possible to change the code of runadew to prevent it from
initializing the group id of the controller ? Do you think
interruptions would work as I am working under System V and Xwindows
?

- I know sockets would be a solution, but I would prefer not to
use them for internal communication between processes runing on
the same machine : I am afraid I will not be able to send a huge
file through a socket without cutting it into smaller parts, and I
would like to avoid that. Do you think Unix Domain Sockets could
allow me to send huge file without cutting them ?

- as all my controllers have got different names, I have thought
about memorizing the pointers on each controller in a memory shared
by all the processes :
 struct controlleri * ptri ( i = 1, 2...),
and call functions of a controller from another controller, using
this pointers : controller1_thisFunction(ptr1) in the code of the
2nd controller for instance.
The 1st controller is running, but the function is not called
successfully, and there is a segmentation fault. Before, I had
never had problems with memorizing pointers on an ATK view or
dataobject in another ATK view or dataobject, and calling
functions with these pointers. Is there something specific to adew
which prevents from doing that ?


                         I am trying at any rate to establish a
communication between Adew controllers, but it is hard because adew
and runadew were not written for that kind of application, but were
supposed to be used only for prototyping. Anyway I really want to
find a way of establishing these connections, even if the solution
is not the most elegant.

Thanks for your help.

isabelle Tourneux
Multimadia Lab of the University of Ottawa.
[e-mail]