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From: han@apple.UUCP
Newsgroups: comp.sys.mac
Subject: Re: GetTrapAddress and SetTrapAddress?
Message-ID: <986@apple.UUCP>
Date: Wed, 10-Jun-87 19:37:44 EDT
Article-I.D.: apple.986
Posted: Wed Jun 10 19:37:44 1987
Date-Received: Sat, 13-Jun-87 06:43:21 EDT
References: <164500036@uiucdcsb>
Organization: Apple Computer, Inc., Cupertino, USA
Lines: 37

In article <164500036@uiucdcsb>, kkim@uiucdcsb.cs.uiuc.edu writes:
> 
>     I would like to intercept calls to an Operating System or
> Toolbox routine (specifically, GetNextEvent) and do some pre- or
> post-processing of my own.  GetTrapAddress and SetTrapAddress
> seem useful to do it.

Actually, there is a hook for GetNextEvent which may be used (although
the use of low memory globals that are not documented in Inside Macintosh
is discouraged).  There was an article about it in MacTutor last year or
so.  I believe the global is JGNEFilter or something like that.  You might
want to look up that issue.
> ...
> 
>     2.  I also have one question.  It is said that
> 
>         Since the trap dispatch table can address locations within a
>       range of only 64K bytes from the beginning of the system heap,
>       the routine you install should be in the system heap.
> 
> How can I put my own version in the system heap?
> 
Traps patches, when done, should be placed in the Application Heap according
to current doctrine.  This is to maintain compatability with future operating
system considerations.


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Byron Han            |   UUCP: {sun,voder,nsc,mtxinu,dual}!apple!han
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