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From: dorner@pequod.cso.uiuc.edu (Steve Dorner)
Newsgroups: comp.sys.mac.programmer
Subject: Re: asynchronous question
Message-ID: <1990Nov19.223032.13372@ux1.cso.uiuc.edu>
Date: 19 Nov 90 22:30:32 GMT
References: <1990Nov19.130139.35978@eagle.wesleyan.edu>
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Reply-To: dorner@pequod.cso.uiuc.edu (Steve Dorner)
Organization: University of Illinois at Urbana-Champaign
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>In other words, when something is placed in an I/O queue, is a
>copy of the parameter block made or is a pointer to your data placed in the
>queue instead?  I assume it makes a copy

I would bet that it does NOT.  Why should it?  It has your parameter block,
into which it intends to store a result code.  Why make an extra copy?
Where would the copy be stored?  How many such "backup blocks" would be
allocated?  Would they go on the heap?  If so, then you'd never be able
to make device manager calls at interrupt level.

>but I want to hear this from someone
>who knows for sure.  Thanks.

I don't know for sure; sorry.
--
Steve Dorner, U of Illinois Computing Services Office
Internet: s-dorner@uiuc.edu  UUCP: uunet!uiucuxc!uiuc.edu!s-dorner