From:	oak9755 AT silver DOT sdsmt DOT edu (Olav Kindt)
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Far Pointers in Protected Mode
Date:	21 Oct 1996 08:12:25 GMT
Organization:	South Dakota School of Mines and Technology
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Distribution:	world
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NNTP-Posting-Host:	silver.sdsmt.edu
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

Mohan Khurana (mohan AT stealth DOT net) wrote:
: 
: I am not very good with ASM, can you show me some source?
: 
: What does rep stosl do?

Ok here's a short example for you

		__asm__ __volatile__ ("
			movw %0, %%es
			movl $0xA0000, %%edi
			movl %1, %%eax
			movl $0x4000, %%ecx
			rep
			stosl"
			:
			: "g" (_dos_ds), "g" (Packed)
		);
This code will fill one page of the screen when when in 256 color mode.
The packed varaible is the color byte (0-255) repeated four times in a
word. (0x3D => 0x3D3D3D3D). The stosl command simply stores the DWORD
located in the eax register, into the memory pointed at by es:edi. The rep
command means that this operation should be repeated however many times as
the ecx registers says. 

If you don't understand this, I recommend the ASM tutorials on the AT&T
syntax that are available on the web at:
	http://remus.rutgers.edu/~avly/djgfx.html

If assembly simply doesn't appeal to you at all, you can get around the
problem by using the dosmemput command, but that would be slower i guess.
It depends on what kind of operations you are dong. If it is graphics, and
videomemory access, i recommend you learn the assembly stuff

Have fun.. :-)


-- 
Olav Kindt		     | email:	oak9755 AT silver DOT sdsmt DOT edu
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