NetNews Usenet Archive 1992 #20/NN_1992_20.iso/spool/comp/sys/atari/st/tech/4706

Text File | 1992-09-08 | 1.9 KB | 41 lines

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Path: sparky!uunet!cs.utexas.edu!torn!newshost.uwo.ca!uwovax.uwo.ca!7103_2622
From: [e-mail] (Eric Smith)
Subject: Re: How do I replace an existing GemDos routine or add a new one?
Organization: University of Western Ont, London
Date: Mon, 7 Sep 1992 18:29:56 GMT
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In article <[e-mail]>, [e-mail] (Michel Forget) writes:
> The reason I am asking about this is I am thinking about writing an ANSI
> emulator, and I would like to see if it is feasible to write it in the form of
> a TSR that any program could use simply by calling the appropriate routines.
>

That's certainly feasible, but there are better ways to do it than replacing
(or adding new) GEMDOS calls, I think. I would set up a cookie in the cookie
jar, say with the name 'ANSI' and with a pointer to a function table as
its value. Programs which want to use the ANSI functions would look up the
cookie, get the table of functions from the cookie, and then jump through
the table to the appropriate functions.

(I think this is better than trying to add/replace GEMDOS calls because it
doesn't add any overhead on the trap #1 vector.)

Under MiNT (and probably under MultiTOS) you could write your ANSI emulator
as a device driver, and have it install a device like U:\DEV\ANSI; programs
could then open this device and use it just like any other. It probably
wouldn't be too hard to make your program work either as a device driver
(if MiNT is active) or as a 'cookie-driven' TSR; just make the functions
in the cookie's function tables the same as the functions needed for a MiNT
device.
--
Eric R. Smith                     email:
Dept. of Mathematics            [e-mail]
University of Western Ontario