Message-ID:	<34D0FA3F.9B8BD192@csun.edu>
Date:	Thu, 29 Jan 1998 13:53:03 -0800
From:	Ryan Bright <rmb56313 AT csun DOT edu>
MIME-Version:	1.0
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Simultaneous Datafiles in Allegro
References:	<MPG DOT f3aa7216d220b029896c0 AT news>
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Organization:	California State University, Northridge
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To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

Solution at bottom.
Nitpicks up top.

Matt Riker wrote:
> 
> Hello:
> 
> I've spent much time trying to figure out why my program won't
> successfully open a second datafile while one is already opened.
[clip]

> strcpy(get_filename(buf), "c:/maped/maped.dat");
First off, you haven't told us what buf is, but I'm just gonna take a
wild guess and assume that you cut n' pasted it straight out of the
examples and, as a result, it's an uninitialized string.  If buf is
automatic (local), then it could easily be filled with junk.

> maped_datafile = load_datafile(buf);
Secondly, as Shawn mentioned already, try :

  maped_datafile = load_datafile("c:/maped/maped.dat");

But you should keep in mind that if anyone else uses this program,
chances are pretty good that it won't be in C:/maped/, so consider just
using :

  maped_datafile = load_datafile("maped.dat");

Which assumes that maped.dat is in the current working directory--a more
likely assumption than the first.

> if (!maped_datafile) {
>    allegro_exit();
>    printf("Error loading MAPED.DAT!\n\n");

>    return 1;
Actually, I think you're supposed to use 'return EXIT_FAILURE;' (defined
in STDLIB.H) here.  I know this isn't a C newsgroup, but whatever.

> }
> 
> strcpy(get_filename(buf), "c:/maped/testspr.dat");
> user_datafile = load_datafile(buf);
This is actually, probably, where your problem lies.  I'll assume that
buf is global.

Global variables, like buf, are initialized to zero.
Then, you get_filename a zero'd array, returning the first position.
  buf = ""
You copy the name of the first datafile
  buf = "c:/maped/maped.dat"
You load that datafile successfully.
Then, you get_filename buf, returning a pointer to "maped.dat"
Then, you copy in the name of the second datafile to that position.
  buf = "c:/maped/c:/maped/testspr.dat"

I doubt that file exists.

-Ryan

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