SVGALIB and memory offsets

[Lionel Pinkhard <lionelpi@mweb.co.za>]

Hi,

I've only recently started using SVGALIB under Linux, and so far so good, but I only have one little problem. I'm writing a game, I started out under Dos, but I decided to write both Dos and Linux at the same time, since it's mostly only graphics that's different, and I'm using #define's to select Dos/Linux. But anyways, this is my problem:

I'm using the following loop to write an image to the screen (under Dos, imagepos is unsigned int):

	for (imagepos = 0; imagepos < 64000; imagepos++) {
		imageread = fgetc(filehandle);
		asm {
			mov ax, 0a000h
			mov es, ax
			mov ax, imagepos
			mov di, ax
			mov ax, imagepos
			mov [es:di], ax
		}
	}

This works fine under Dos, but when I try to re-write it for Linux, I get the problem: The Asm routine uses memory offsets, but vga_drawpixel() uses x/y locations. How do I convert them? I know how to calculate an offset from x/y, but how do I do the opposite? I tried working something out, but it looks like I'm just too stupid :-). Can somebody please tell me what to do?

This is what it looks like so far:

	for (imagepos = 0; imagepos < 64000; imagepos++) {
		imageread = fgetc(filehandle);
		vga_setcolor(imageread);
		vga_drawpixel(?, ?);
	}

Does this look okay? I'm quite a newbie (especially to SVGALIB), so it might be all wrong! I've also been thinking about using something like:

	vga_drawpixel(offset, 0);

If I'm correct, when SVGALIB calculates the offset, it would do:

	offset = 320 * 0 + offset;

Is this correct? Would it work? Or wouldn't the funcion accept an X value higher than that of the screen resolution? Or not above 32k? Since it is an int.

Kind regards,

Lionel Pinkhard

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