Xref:	news2.mv.net comp.os.msdos.djgpp:2013
From:	gaggi AT cs DOT unibo DOT it (Nicola Gaggi)
Newsgroups:	comp.os.msdos.djgpp
Subject:	Help me solving my first Page Fault!
Date:	20 Mar 1996 09:24:31 GMT
Organization:	Department of Computer Science, University of Bologna, Italy
Lines:	96
Message-ID:	<4ioisf$ms9@leporello.cs.unibo.it>
NNTP-Posting-Host:	130.136.1.164
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

Hello guys,

I'm using DJGPP for the first time and i'm learnimg protected mode 
programming too. Just as an exercize I'm trying to code a simple .PCX file
viewer but the only result is that I get Page Fault errors, I have 
seen the sources of XLIB porting under DJGPP and everything seems correct 
and working. I have tried to use the same techincs but with no result.
Here is the code:

#include <stdio.h>
#include <conio.h>
#include <string.h>
#include <go32.h>
#include <dpmi.h>

/* ------------------------------------------------------------- */

static unsigned char Line[1024];
static unsigned char Palette[768];

static unsigned short LinearMem;

/* ------------------------------------------------------------- */

void BlastLine(unsigned Offset)
{
    asm("
        pushw   %es
        pushl   %esi
        pushl   %edi
        pushl   %ecx

        movw    _LinearMem, %ax
        movw    %ax, %es

        movl    8(%ebp), %edi
        addl    $0x0a00000, %edi
        movl    $_Line, %esi

        movl    $320, %ecx

        cld
        rep
        movsb		<---- Here is the istruction generating the fault!

        popl    %ecx
        popl    %edi
        popl    %esi
        popw    %es
    ");
}

void DisplayPCX(FILE *fp)
{
    unsigned RowOffset;
    register unsigned i;

    /* Reads and sets the palette */
    ....

    fseek(fp, 128L, SEEK_SET);

    for (RowOffset= 0; RowOffset < 64000; RowOffset += 320) {
        DecodeLine(fp);		/* Reads and decode a PCX line, the read 
				   line is stored in the Line[] array */
        BlastLine(RowOffset);	/* Draws the line on the screen */
    };
}

int main(int argc, char *argv[])
{
    FILE *fd;

    LinearMem= _go32_conventional_mem_selector();
    ....
/* Open the file set graphic, mode etc ... */

    DisplayPCX(fd);
    fclose(fd);

/* Waiting for keyboard input and return */
}

Pleas tell me where I go wrong ...

Reply via e-mail or via newsgroup ...
Thank you,

--
--------------------------------------------------------------------
Nicola Gaggi                                  University of Bologna.
e-mail  : gaggi AT cs DOT unibo DOT it  WWW page: http://www.cs.unibo.it/~gaggi
--------------------------------------------------------------------
... Be yourself, no matter what they say
  from "Englishman in New York" by Sting

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