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Newsgroups: comp.sys.apple2.programmer Path: news.weeg.uiowa.edu!news.uiowa.edu!hobbes.physics.uiowa.edu!newsrelay.iastate.edu!newsxfer.itd.umich.edu!gatech!swrinde!ihnp4.ucsd.edu!munnari.oz.au!cs.mu.OZ.AU!amorton From: amorton@ee.mu.OZ.AU (Anthony Morton) Subject: Patching protocols Message-ID: <9406711.2665@mulga.cs.mu.OZ.AU> Summary: Do any exist? Keywords: patch tool vector DTUtils Sender: news@cs.mu.OZ.AU Organization: Dept of Electrical & Electronic Engineering, University of Melbourne Date: Tue, 8 Mar 1994 01:07:59 GMT Lines: 30 Apple IIgs Tech Note #87 gives the protocol for patching the tool locator dispatch vectors at $E10000-$E1000F. As far as I'm aware, there is no protocol currently defined for patching other system vectors, or for patching individual tool calls, that allows patches to be removed after being patched over. Assuming that this is the case, I intend to define a protocol for use by Desktop Utilities 4.0 and its modules, which combines features of Tech Note #87 and the generalised queue protocol, and allows patches to cooperate. I propose that in order to comply with this protocol, patches to individual tool calls and system vectors (other than the tool dispatch vectors) include an eight-byte header before the actual patch code, defined as follows: Offset Length Description 0 4 Long JMP instruction to next call handler 4 2 Flags describing nature of patch (use zero) 6 2 Signature word; must be set to $A55A Desktop Utilities 4.0 will contain routines for patching individual tool calls and system vectors, that manage patches according to this protocol. If you have any comments, please reply. In particular, I want to be sure that this isn't already covered by a Tech Note I've missed. Tony Morton (amorton@ee.mu.oz.au) Electrical Engineering Masters student & diehard IIGS lover University of Melbourne, Australia