Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uflorida!haven!rutgers!att!pegasus!ech
From: ech@pegasus.ATT.COM (Edward C Horvath)
Newsgroups: comp.sys.mac
Subject: Re: Programming INITs
Message-ID: <2537@pegasus.ATT.COM>
Date: 23 Jan 89 03:57:46 GMT
References: <7238@batcomputer.tn.cornell.edu>
Organization: AT&T ISL Middletown NJ USA
Lines: 22

From article <7238@batcomputer.tn.cornell.edu>, by mha@batcomputer.tn.cornell.edu (Mark H. Anbinder):
> ...How do you write
> an INIT that hangs around in memory AFTER startup?

You have two problems: how to get your code to hang around, and how to get it
some cycles.

The first problem has two answers: install the code as System heap reasources;
at INIT time, LoadResource and DetachResource.  Make sure you supply a sysx
resource in your INIT file to let the INIT-31 process know how much to grow
the System heap.  The alternative, no longer recommended, is to decrease
BufPtr by a suitable amount and install your code between the new and old
values.

You can get your code cycles by installing it as a VBL task (which only gets
cycles, in effect, at interrupt time) or by SetTrapAddress on a commonly-used
trap (like SystemTask).  Don't tailPatch, i.e. do your thing, then call the
original SystemTask by jmp'ing to it.

Hope that helps, or at least points you in the right direction...

=Ned Horvath=