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From: russotto@eng.umd.edu (Matthew T. Russotto)
Newsgroups: comp.sys.mac.programmer
Subject: Re: 32-bit Cleanliness
Message-ID: <1991Jan8.012444.4466@eng.umd.edu>
Date: 8 Jan 91 01:24:44 GMT
References: <29193@usc>
Sender: news@eng.umd.edu (C-News)
Organization: College of Engineering, Maryversity of Uniland, College Park
Lines: 36

In article <29193@usc> dank@calvin.usc.edu (Dan King) writes:
>
>I've got a question on the Politically Correct way to dereference a
>resource.
>
>Example (using C-ish syntax):
>I call GetResource(blah) to get a handle to the resource.  I then
>Detach() it and HLock() it.  What should I do to dereference it?
>Should I kill the upper 8 bits (I don't think so), should I
>StripAddress it (TN212 says not, but who knows?), or should I just go
>ahead and dereference it (Ptr x; x=*handle;)?  HELP!!!!

Handles should never need to be StripAddress()ed.  Go ahead and dereference it.
>
>I've read the technote on being 32-bit clean and the technote on
>StripAddress.  Neither really tells me (explicitly) what I need to do.
>I believe that just dereferencing the handle without worrying about
>the upper 8 bits will work, but doesn't the resource manager use those
>for different states (like locked, purgeable, etc)?  Or do those go
>away when you detach the handle?

Those things are in the master pointer, not the handle.  There are only a few
cases where you need to worry about this.  One is when comparing master 
pointers (i.e. *foohandle > *barhandle-- why one compares master pointers
I don't know...) .  Another is if you are on a machine with a 24 bit memory
manager running and you use SwapMMUMode to go to 32 bit mode.  All dereferences
of master pointers when you have the MMUMode at 32 bits must be StripAddressed

>
>Thanks for putting up with boring questions,
>dank


--
Matthew T. Russotto	russotto@eng.umd.edu	russotto@wam.umd.edu
     .sig under construction, like the rest of this campus.