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Mail Archives: djgpp/2000/03/16/00:16:15

From: Damian Yerrick <Bullshitd_yerrick AT hotmail DOT comRemoveBullshit>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Some dodgy FILE hackery
Organization: Pin Eight Software http://pineight.8m.com/
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NNTP-Posting-Date: Thu, 16 Mar 2000 04:16:45 GMT
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Date: Thu, 16 Mar 2000 04:16:45 GMT
To: djgpp AT delorie DOT com
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Reply-To: djgpp AT delorie DOT com

On Tue, 14 Mar 2000 22:48:21 -0000, "Ben Davis"
<ben AT vjpoole DOT freeserve DOT co DOT uk> wrote:

>I use DJGPP and Allegro. Most of my files (eg. levels) are saved
>using the packfile functions of Allegro. I need to encrypt some
>of these files without making them bigger.

Why?

>I have to do the encryption manually; the built-in password function
>isn't secure enough.

I know; it's xor.

>I want to intercept all the low-level file inputs/outputs (where DOS
>takes over from Allegro) so that I can modify the bytes at this stage.
>But I don't want to modify the Allegro source.

Why not?  Allegro for DJGPP is static linked.

>The packfile functions of Allegro ultimately use read() and write(), and the
>DOS file handle is stored in the PACKFILE structure so I can access it
>readily.

The Allegro source code is stored in /.../allegro/src so you can
access it readily.

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