Re: LZ: Compression program (and questions for asm programmers)
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At 05:18 PM 9/12/96 -0700, you wrote:
>I was just responding to his question. Anyways, I was looking in
>ti-ram.txt to remember the pointers. $8b25 is the pointer to last byte
>of free mem. $8b27 is the first byte. You can subtract those to see if
>you have enough room to uncompreess, and then write it there. Since only
>your program is running, (besides interuppts), you can be sure nothing
>will mess eith it. Dont' change the pointers though...
>
>Alan B.
>
>oh yeah, you can leave stuff there, you don't have to clear it.
What if the program being run used those pointer to find out how much memory
is left, as in the case of graylib (gray8lib) programs? Wouldn't it end up
overwriting itself? I suppose it would confuse the calc during a ROM call
if those pointers had been changed, so I don't think we can do that. But
the uncompressed program must seem, at least to itself, like it is part of
_used_ memory so it doesn't overwrite itself. I think...
In order for this to be compatible with every ZShell program, we must make
it believe it exists in memory and that it is being run straight from ZShell.
Ben
shakal@ns.net
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