Newsgroups: comp.sys.mac.programmer
Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!wuarchive!psuvax1!swatsun!jackiw
From: jackiw@cs.swarthmore.edu (Nick Jackiw)
Subject: Re: Inter-Process Communication
Message-ID: <4KPN20@cs.swarthmore.edu>
Reply-To: jackiw@cs.swarthmore.edu (Nick Jackiw)
Organization: Visual Geometry Project, Swarthmore College, PA
References: <2286@polari.UUCP> <JMLN7T@cs.swarthmore.edu> <9596@goofy.Apple.COM>
Date: Tue, 7 Aug 90 18:30:47 GMT

chewy@apple.com (Paul Snively) writes:
> In article <JMLN7T@cs.swarthmore.edu> jackiw@cs.swarthmore.edu (Nick 
> Jackiw) writes:
> > The MacTutor stuff, which is excellent...
> >... is probably more general than you
> > need, if your suite of programs require only a rigidly specified 
> > protocol.
> 
> Huh?  The IPC driver in MacTutor doesn't deal with "protocol" at all; it 
> just lets you poll to see if the data (which can be in any format you 
> like; it's just a block of bytes) has changed since the last time you 
> checked.  It's more like the Edition Manager than any of Apple's IAC 
> protocols.

Wrong. Protocol means code (in the non-programmer's sense of the word).
Any set of routines is governed by a protocol.  Determining whether
data have changed, registering and querying about existing data types,
and other features of your driver may be unnecessary in a given IPC
situation. They are all necessary in the *general* IPC scenario, as I
stated.

> 
> > Its worth reading anyway, if you're thinking of a driver-based IPC.
> 
> This I'll agree with, and I'll even go so far as to ask what other kind of 
> IPC makes sense on the Macintosh?

Are you serious?  Any cdev which communicates with an active INIT is doing
IPC, usually by accessing common storage in the system heap.  Any program
which launches another program with a customized AppFile record is doing
IPC. (Remember MDS's integrated-but-separate editor, linker, and compiler?) 
If your requirements aren't too serious, you could even do IPC by means
of the global deskscrap.


> > Neither of these schemes has System 7-IPC's advantage of having a nicely
> > developed protocol for IPC between applications of which only one is
> > currently running.
> 
> Unfortunately, neither does System 7.0's IAC suite; "store and forward" 
> messages didn't make it in.  [sigh]

Ouch. 
>                                 Paul Snively


-- 
-----Nick Jackiw [jackiw@cs.swarthmore.edu|jackiw@swarthmr.bitnet------
"This orbe of starres fixed infinitely vp extendeth hitself in altitvde 
sphericallye, and therefore immovable the pallace of foelicity garnished
with perpetvall shining glorious lightes innvmerable." - Thomas Digges
