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From: minow@bolt.enet.dec.com (Martin Minow)
Newsgroups: comp.sys.mac.misc
Subject: Re: 7.0 CAN pipe (was Re: System 7.0 vs. NeXT Step)
Message-ID: <19566@shlump.nac.dec.com>
Date: 29 Jan 91 17:21:02 GMT
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Organization: Digital Equipment Corporation
Lines: 32


In article <FRANCIS.91Jan28105635@daisy.uchicago.edu>, francis@uchicago.edu
(Francis Stracke) writes...
> 
>That being said, it remains true that AppleEvents and other IAC may
>work reasonably well as pipes.  Anybody know how much data you can
>send with one call this way? (If nothing else, you could use same-node
>AppleTalk, which would work even pre-Sys7.)
>

I didn't notice any limit on the buffer sizes, but would recommend reasonably
small buffers to keep network latency reasonable (otherwise, you ruin the
for other people).  If you have long messages, you can send them in
multiple network packets. A few other minor points:

-- PPC Toolbox (and, I suppose, AppleEvents) work even if AppleTalk is
   disabled; which is nice if you have a stand-alone system with an
   ImageWriter.
-- PPC Toolbox sends the data buffer along with 3 32-bit words of additional
   information (userData, blockCreator, and blockType) along with a "partial
   message" bit, so many interactive applications don't even need a data buffer.
-- It doesn't appear to be trivial to write a package that supports
   PPC Toolbox on System 7, but defaults to AppleTalk (ATP, probably)
   on earlier systems.  It's obviously possible, but it might be a fair
   amount of work with little payback.

In general, I think that PPC Toolbox (and AppleEvents) offer a number
of advantages over Unix pipes, and might prove to be the most significant
new feature of System 7.

Martin Minow
minow@bolt.enet.dec.com