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From: askrid@netmbx.UUCP (Dirk Ahrens)
Newsgroups: comp.sys.atari.st
Subject: Re: XBRA from C
Summary: It works from C directly
Keywords: XBRA TurboC
Message-ID: <692@netmbx.UUCP>
Date: 25 May 90 11:15:31 GMT
References: <759@imada.dk>
Reply-To: askrid@netmbx.UUCP (Dirk Ahrens)
Organization: netmbx, Berlin, West Germany
Lines: 47

In article <759@imada.dk> micro@imada.dk (Claus Pedersen) writes:
>   I have just started to use the XBRA protocol to intercept system 
>vectors. I want this standard to spread in order to keep my programs 
>running [-keep it selfish else they don't believe you ;-)].
>   Ok, I know that there are problems with the XBRA protocol - It's 
>for assembly programmers only...
  [ description of the library package deleted ]

>There are 4 entry points:
>      XB_isinstal(), XB_install(), XB_remove(), XB_kill().
How do you remove and kill when you already have done a Ptermres?

>   There is one minor short coming - the pack is for Borland TC only, 
>but you are free to modify the source to run with your favourite C 
>compiler.
> - Klaus  (micro@imada.dk).

if you want a version which doesn't depend on a specific Compiler, and 
you don't like Assembler (like me) try following definition.

typedef struct {
  char  xb_magic[4];
  char  xb_id[4];
  void  *xb_vec;
  short xb_jmpCode;     /* has to be 16-Bit. contents: 0x4EF9 */
  void  (*xb_newVec)();
} XBRA;

XBRA	xBra =
{ 'X','B','R','A',
  '_','i','d','_',
  0L,
  0x4EF9,		/* Code for jmp */
  NewFunktionName
};

Now you have to do only two things: Put the old Contents in xb_vec, and
write the adress of xb_jmpCode in the System-adress. Everything in Super-
visor mode of course.
I wrote my own library for install. I remove with an external tool.
This results in very small installing code, which is important for me for
resident tools.
			Dirk Ahrens
-- 
 Askrid	   netmbx, Jabba the Hutt.
 askrid@netmbx.UUCP  dirk@opal.cs.tu-berlin.de  AHRENS@TUBVM.CS.TU-BERLIN.DE
 Dirk Ahrens - Danckelmannstr 46 - 1000 Berlin 19 - Federal Republic of Germs