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From: jbs30000 AT aol DOT com (Joel)
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Interrupt handler question
Date: 11 Apr 2004 18:48:25 -0700
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Hans-Bernhard Broeker <broeker AT physik DOT rwth-aachen DOT de> wrote in message news:<c5be5c$phh$1 AT nets3 DOT rz DOT RWTH-Aachen DOT DE>...
> Joel <jbs30000 AT aol DOT com> wrote:
> > Anyway, is it possible to call the old routine stored with
> > _go32_dpmi_get_real_mode_interrupt_vector while in the middle of the
> > new routine?
> 
> I doubt it.  The problem being that the end of an interrupt handler is
> signalled by a IRET instruction.  The old routine will be ending in
> such an IRET.  So at the minimum, you'ld have to use the DPMI simulate
> interrupt call method to call it, and I'm not sure that's allowed from
> inside an interrupt handler.

OK, how about this then, I saw an example somewhere on line of a
program (which I can't find now) that hooks int 21h and screws with
the delete file function, but for any other function called, it just
chains to the original handler.

So how would I do that?  See why an interrupt is being called, then
decide whether or not to handle it myself, or let the original handler
deal with it?