Path: utzoo!news-server.csri.toronto.edu!rutgers!uwm.edu!zaphod.mps.ohio-state.edu!wuarchive!udel!haven!ni.umd.edu!ni.umd.edu!zben
From: zben@ni.umd.edu (Ben Cranston)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Whaddya do in ioCompletion routine?
Summary: Anybody seen this weird behaviour?
Keywords: ioCompletion Asynchronous
Message-ID: <1991Mar10.231236.21526@ni.umd.edu>
Date: 10 Mar 91 23:12:36 GMT
References: <63044@bbn.BBN.COM> <49791@apple.Apple.COM> <1991Mar7.204208.20535@jato.jpl.nasa.gov>
Sender: usenet@ni.umd.edu (USENET News System)
Distribution: comp
Organization: University of Maryland at College Park
Lines: 26
Nntp-Posting-Host: ni.umd.edu

Anybody seen the behaviour with ASynch _Read calls:  whatever is in D0 when
the IO completion routine returns gets returned to the mainline in D0 rather
than the IO result for the operation itself?  I tend to code a check in the
mainline:

        LEA  IOPB,A0
        _Read  ASync
        BEq.S  around
        <ERROR DETECTED HERE>
around  ;

and in the completion routine

Compl	;
    Tst.W  D0
    BEq.S  around
    <ERROR DETECTED HERE>
around  ;

and I find I have to be very careful to clear D0 at the exit of the
completion routine or else the value will pop up as an error in the
mainline.

Also, anybody ever seen an asynch _Open and/or _Read return to the
mainline with D0 = 1 and ioResult(A0) = 2????  I've only seen this when
AppleShare Server was running in foreground...