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From: urlichs@smurf.sub.org (Matthias Urlichs)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Calling AppleTalk async.
Message-ID: <1kb8f2.d#5@smurf.sub.org>
Date: 3 Sep 90 19:44:42 GMT
References: <1990Sep2.141941.5964@lth.se>
Organization: University of Karlsruhe, FRG
Lines: 34

In comp.sys.mac.programmer, article <1990Sep2.141941.5964@lth.se>,
  sund@tde.lth.se (Lars Sundstr|m) writes:
< 
< There is a warning about using the SelfSend option in AppleTalk
< because some programs may not expect to get packets from its own
< node. [...]
< 
I'd say don't bother, and leave it on.

< 2. Sync. calls are executed after the last queued call and everything
< will work just fine.
< 
You can only depend on the fact that the driver will start processing your
requests in the order they come in, and that the individual call is finished
when the ioResult of your parameter block becomes <= zero.

You cannot depend on any order in which the calls get executed. (This is a
good thing -- we're talking about networking here. Packets get lost, buses are
busy, some remote machines are faster than others...)

The only difference between sync and async, from the MacOS' point of view,
is that the OS waits for the completion of the call (and that it clears the
ioCompletion parameter). The driver, of course, may take additional shortcuts
when it sees a sync call, like making other sync calls (which are expressly
forbidden if you are doing anything asynchronously).

< Couldn't find the answer in any of the IMs or TNs. So I'm asking you.
< 
This is a problem in most technical documentation -- the authors already know
what they're talking about and take some things for granted.

-- 
Matthias Urlichs -- urlichs@smurf.sub.org -- urlichs@smurf.ira.uka.de
Humboldtstrasse 7 - 7500 Karlsruhe 1 - FRG -- +49+721+621127(Voice)/621227(PEP)