Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!apple!keith
From: keith@Apple.COM (Keith Rollin)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Swapping Handles
Message-ID: <47225@apple.Apple.COM>
Date: 9 Dec 90 23:11:34 GMT
References: <2599@runxtsa.runx.oz.au>
Organization: Apple Computer Inc., Cupertino, CA
Lines: 36

In article <2599@runxtsa.runx.oz.au> karlg@runxtsa.runx.oz.au (Karl Goiser) writes:
>If I swap the master pointers (?) of two Handles like so:
> 
>VAR
>   H1, H2: Handle;
> 
>...
> 
>Ptemp:= H2^;
>H2^:= H1^;
>H1^:= H2^;
>...
> 
>will I hurt anybody or anything (including myself)?

Karl,

I think that you may also have to munge with the "relative handle" in
the block header. Take a look at figure 12 on page II-24. There it
shows that the block header for relocatable blocks contain a reference
to their master pointers. If you swap master pointers, then the master
pointer that the relocatable block points to will not, in turn, point
to that relocatable block.

So why are you trying to do this? What is the need for swapping
master pointers? As it notes on page II-24, "...your program shouldn't
normally have to deal with block headers directly...". Also, the block
header format has changed for 32-bit mode under 7.0, which means that
any block header munging you do today will change tomorrow.

-- 
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"Argue for your Apple, and sure enough, it's yours" - Keith Rollin, Contusions