Message-ID: <37F2B526.C8043DF5@hutch.com.au>
From: GAvin Alexander <gavina AT hutch DOT com DOT au>
Organization: Orange - Hutchison Telecoms
X-Mailer: Mozilla 4.51 [en] (WinNT; I)
X-Accept-Language: en
MIME-Version: 1.0
Newsgroups: comp.os.msdos.djgpp
Subject: Re: problem with far pointers
References: <7ssgdl$pg AT cs DOT vu DOT nl> <7sssfq$rds AT acp3bf DOT knirsch DOT de> <7su41v$a4q$1 AT solomon DOT cs DOT rose-hulman DOT edu>
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Lines: 87
Date: Thu, 30 Sep 1999 10:56:06 +1000
NNTP-Posting-Host: 203.12.80.8
X-Complaints-To: abuse AT telstra DOT net
X-Trace: nsw.nnrp.telstra.net 938652962 203.12.80.8 (Thu, 30 Sep 1999 10:56:02 EST)
NNTP-Posting-Date: Thu, 30 Sep 1999 10:56:02 EST
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp
Reply-To: djgpp AT delorie DOT com

I'm just learning all of this stuff now...so if I'm wrong just ignore
everything I have to say.

You can use the selector that djgpp provides (go32.h) i think it's called
_dos_ds.
To plot a pixel you can use the _farpokeb function.

I think a pixel function for this is
pixel(int x, int y, char color) {

        _farpokeb(_dos_ds, 0xA0000 +y*320+x, color);

}

make sure you include sys/farptr.h

Alternatively

The way I've been accessing video memory in DJGPP -
is to write to a buffer that's same size as the screen [64000] (mode13h).
and then copy this buffer to the screen.

eg

char buffer[64000];

/*clear the buffer*/
memset(buffer,0,sizeof(buffer));

/*write some stuff to the buffer*/
buffer[ /*some x,y coords*] = /*some color*/;

/*copy buffer info to the screen (physical address = 0xA0000)*/

/*sys/movedata.h*/
dosmemput(buffer,64000,0xA0000);


As I said I'm still learning but I hope this helps.
I think

A good source of info on these things is the DJGPP Web site
http://www.delorie.com/djgpp/ (do I really need to write down the address)

G.A


Damian Yerrick wrote:

> FokkemaDBRA has a selector that points to video RAM.
> S/he wants to access video RAM as if it were an array. In
> Borland C++, this worked:
>
> > > int far *pointer;
>
> Hans-Bernhard Broeker <broeker AT acp3bf DOT knirsch DOT de> responded:
>
> > 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()
>
> Shouldn't movedata() be called farmemmove() or farmemcpy()?
>
> > The one thing you won't get using these functions is use of
> > the 'standard' syntax, like 'video_mem[position] = content;'.
>
> Maybe someone could put true far pointer support
> (a la Borland) into DJGPP.
>
> > If you insist on that, you must effectively disable
> > memory protection using the 'near pointer method'.
>
> And risk overwriting other programs in memory (such as
> Windows, DOS, etc.). Overwriting DOS is a Bad Thing.
>
> > 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.