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From: ari@eleazar.dartmouth.edu (Ari Halberstadt)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Why link with '-ad 4' ?
Message-ID: <17662@dartvax.Dartmouth.EDU>
Date: 4 Dec 89 03:37:26 GMT
References: <oZReQbO00UhWQ1WF02@andrew.cmu.edu> <9162@hoptoad.uucp>
Sender: news@dartvax.Dartmouth.EDU
Reply-To: ari@eleazar.dartmouth.edu (Ari Halberstadt)
Organization: Dartmouth College, Hanover, NH
Lines: 35

Here's a question for you folks out on NetLand. I'm trying
to figure out, with a reasonable degree of success, if the refCon
field of a window contains a valid handle. This must be determined
by a driver, which is separate from the the program which actually
created the window. The tests currently performed are:

Boolean ValidHandle(Handle hndl)
{
	hndl = (Handle) GetWRefCon(window); /* copied here for brevity */
	if (! hndl)
		return(false);
	if ((long) hndl & 1L) /* check for odd address */
		return(false);
	if (GetHandleSize(hndl) != expected_size)
		return(false);
}

Actually, I've got three questions.
1. Is it ok to check for odd adresses on a 680x0? I assume Apple
wouldn't write NewHandle to create something on an odd adress, since
access times are slower.
2. I would like to check that the handle is within a reasonable area
of memory, i.e., within the application heap. However, since the
application may have several heap zones, what is the correct way to
check this? Is it sufficient to use ApplicZone and GetApplLimit?
3. Any more ideas for useful checks? I've already got a special
long int stuck at the head of the place where the correct handle
would point to, and I've thought of making sure the handle is
below RomBase.


--

Ari Halberstadt '91, "Long live succinct signatures"
ari@eleazar.dartmouth.edu	Disclaimer: "Live Free or Die"