Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!yale!quasi-eli!cs.yale.edu!fischer-michael
From: fischer-michael@cs.yale.edu (Michael Fischer)
Newsgroups: comp.sys.atari.st.tech
Subject: Re: How to write config info into mail .PRG or .ACC file?
Message-ID: <25854@cs.yale.edu>
Date: 22 Aug 90 01:10:34 GMT
References: <3300@syma.sussex.ac.uk>
Sender: news@cs.yale.edu
Organization: Yale University Computer Science Dept., New Haven, CT 06520-2158
Lines: 40
Nntp-Posting-Host: ginkgo.theory.cs.yale.edu
Originator: fischer@ginkgo.CS.Yale.Edu

In article <3300@syma.sussex.ac.uk> grahamt@syma.sussex.ac.uk (Graham Thomas) writes:
>
>My options are either to read from / write to a separate .CFG or .INF
>file, which I could do but would rather not (I've incorporated my
>resource file info into the main program file and I'd like to keep
>everything in a single place if possible), or save the info directly to
>the program itself.  How is this done?

It's easy enough to rewrite bytes in the middle of the .prg file using
the Gemdos functions Fseek and Fwrite.  Your only problems are to find
the file (not so easy) and to figure out which bytes to change.

I don't know of a reliable way to find the name and location of the
.prg file which is currently running.  It will often be in the default
directory on the default device (depending on how the program was
invoked), but it doesn't have to be.  The Pexec that invokes your
program probably leaves this information behind in some undocumented
memory locations somewhere, but you can't count on that not changing
in the future. 

The second part is easier.  Declare all of your configuration
variables at the top of your program as static, and initialize them to
appropriate default values.  This should cause the compiler to place
them at the start of the data segment of your program.  Information in
the header of a .prg file tells the lengths of the text and data
segments.  Read that information and calculate the position in the
.prg file of the start of the data segment.  Seek to that position and
rewrite your variables.  To be on the safe side, put a magic number as
the first thing in the data segment and check that it is there before
you start writing.  This may save you from clobbering the wrong file.
Thus, your program might start as follows:
	static char magic[8] = "myprogxx";
	static int width = 85;
	...

Hope this helps.
-- 
==================================================
| Michael Fischer <fischer-michael@cs.yale.edu>  |
==================================================