From: broeker AT acp3bf DOT knirsch DOT de (Hans-Bernhard Broeker)
Newsgroups: comp.os.msdos.djgpp
Subject: Re: problem with far pointers
Date: 29 Sep 1999 13:17:14 +0200
Organization: RWTH Aachen, III. physikalisches Institut B
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FokkemaDBRA wrote:
> Hi there!

> I'm new to djgpp and I'm trying to port my os (it's not finished yet) to c.
> Well, I have a problem. I built a selector for the video memory and want to
> write to the screen using this selector. How do I tell djgpp that I want to
> use that specific selector? I tried using a far pointer, but was unable to
> code something like:
> 	int far *pointer;

There is no such thing as a 'far pointer' in DJGPP. But there are specialised
functions (inline assembly, so they should be fast enough for just about
every application you can come up with), conveniently called the 'far pointer
functions'. Look up

	farpokeb()
	farpeekb()
	movedata()

and their friends in the libc documentation.

The one thing you won't get using these functions is use of the
'standard' syntax, like 'video_mem[position] = content;'. If you
insist on that, you must effectively disable memory protection using
the 'near pointer method'.

See the FAQ for more details about all of this.
-- 
Hans-Bernhard Broeker (broeker AT physik DOT rwth-aachen DOT de)
Even if all the snow were burnt, ashes would remain.