Path: utzoo!attcan!uunet!aplcen!samsung!cs.utexas.edu!tut.cis.ohio-state.edu!ucbvax!hoptoad!tim
From: tim@hoptoad.uucp (Tim Maroney)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Need info on multitasking capabilities on the mac
Message-ID: <9080@hoptoad.uucp>
Date: 25 Nov 89 01:57:37 GMT
References: <6391@tank.uchicago.edu> <9072@hoptoad.uucp> <17247@dartvax.Dartmouth.EDU>
Reply-To: tim@hoptoad.UUCP (Tim Maroney)
Organization: Eclectic Software, San Francisco
Lines: 31

In article <17247@dartvax.Dartmouth.EDU> earleh@eleazar.dartmouth.edu
(Earle R. Horton) writes:
>I don't know, but won't an asynchronous read/write with an
>ioCompletion routine installed work?  IO operation gets completed,
>then ioCompletion routine gets called, and file transfer can be
>restarted at that point.  Make sure you get the correct A5 before
>storing your data!

I thought that MultiFinder would refuse to context switch if the file
or device system had any pending asynchronous requests.  But maybe I'm
thinking of an earlier incarnation.  It's fairly painful to write a
complete protocol scheduled from completion routines, but it can be
done.

>The protocols used by VersaTerm use handshaking on each packet.  You
>don't get a new packet, in other words, until you acknowledge the last
>one.  With these protocols, you can actually pause a fairly long time
>between times when you service the file transfer.  I suspect that
>VersaTerm doesn't do anything special to make sure it gets time, but
>that you just never see it time out because you never push it that
>hard.

Um, not with XMODEM.  Most implementations will time out if they don't
get an acknowledgement before the timeout period expires.  Doesn't
VersaTerm use XMODEM?
-- 
Tim Maroney, Mac Software Consultant, sun!hoptoad!tim, tim@toad.com

"`Truth' never set anyone free.  It is only *doubt* which will bring
 mental emancipation."
        -- Anton LaVey, quoted by Arthur Lyons, SATAN WANTS YOU