From: "John M. Aldrich" <fighteer AT cs DOT com>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: 'FAR' under DJGPP
Date: Sat, 02 May 1998 13:39:51 -0400
Organization: Two pounds of chaos and a pinch of salt.
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Bruno Barberi Gnecco wrote:
> 
> I'd like to output a file generated by TheDraw. It's documentation says to use:
> 
> #include <stdio.h>
> #include <memory.h>
> #include "file.h" // this is the file containing data
> int main () {
>            void far *screen;
>            int offset = -162;  t
>            int x;
>            for (x=0; x<IMAGEDATA_DEPTH; x++) {
>              (long) screen = 0xB8000000+x*160+offset;
>              memcpy (screen,&IMAGEDATA[x*IMAGEDATA_WIDTH*2],IMAGEDATA_WIDTH*2);
>            }
> }
> 
> But DJGPP doesn't accept the FAR keyword. How do I do?

That's because DJGPP applications run in protected mode, where the
methodology for accessing video memory (or any absolute hardware
address) is completely different.  A full explanation is lengthy, but
you can find out for yourself by reading chapters 10, 17, and 18 of the
DJGPP Frequently Asked Questions list (v2/faq210b.zip from SimTel or
online at http://www.delorie.com/djgpp/v2faq/).  There are also some
tutorials available; see the DJGPP User's Guide
(http://www.delorie.com/djgpp/doc/ug/) and Brennan's DJGPP2+Games
Resources (http://www.rt66.com/~brennan/djgpp/).

Just for kicks, I'll correct the above code for you using one of the
three methods described in FAQ chapter 18.4:

#include <stdio.h>
#include <sys/movedata.h>
#include "file.h" // this is the file containing data

int main( void )
{
    int offset = -162;
    int x;

    for ( x = 0; x < IMAGEDATA_DEPTH; x++ )
        dosmemput( &IMAGEDATA[x * IMAGEDATA_WIDTH * 2], IMAGEDATA_WIDTH
* 2, 0xb8000 + x * 160 + offset );

    return 0;
}

I _think_ this will work.  I can't test it because I don't have your
header file.  It's not quite as fast as using near pointers but it's
safer.

hth

-- 
John M. Aldrich, aka Fighteer I <fighteer AT cs DOT com>  UIN# 7406319

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