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From: yahnke@vms.macc.wisc.edu (Ross Yahnke, MACC)
Newsgroups: comp.sys.mac.programmer
Subject: Config File Resource Blues
Message-ID: <2002@dogie.macc.wisc.edu>
Date: 8 Jul 89 03:11:19 GMT
Sender: news@dogie.macc.wisc.edu
Organization: University of Wisconsin Academic Computing Center
Lines: 71

I'm having problems maintaining a configuration file for my
application. It lives in the System Folder and is a file w/a
resource fork containing some data that gets read in when I
open a certain type of document window in my app, and then gets
written out when I close the window.

My problem is when I re-open the window in the same session,
and try to reread the resource, the GetResource call goofs up.

Below are two code fragments, ReadConfig() gets called when I
open my document, the first time it's called it works fine,
GetResource returns a handle that points to my data, and
dataLen is correct. Then when I close the document I call
WriteConfig. The data that I'm maintaining may have changed and
the config file data would therefore be out of date, so I
automatically clear it, create a new handle, stream my data
into the handle, and add the resource. If I quit my app at this
point and examine my config file w/ResEdit, the data looks
hunky-dory. But if I instead try to reopen my document window,
thereby calling ReadConfig again, the GetResource mysteriously
returns some bogus handle (I think) that points to nothing
significant, and dataLen is bad as well.

ResError() never returns a bad value, to the best of my
knowledge. The value of CurResFile() never changes when I check
it a various locations around this code. The config file is
opened at the program start by a call to OpenResFile, which is
set to look in the System Folder. I'm not doing anything
significant, I guess, between opening, closing, and then
opening my document.

Any ideas/comments?

ReadConfig() 
{ Handle  dataHdl;
  long    dataLen;

  dataHdl = GetResource('DATA', 128);
  dataLen = SizeResource(dataHdl);

  /* At this point I stream the data into
   * a application maintained structure. This
   * data may change as the user interacts
   * w/the app.
   */ 
}

WriteConfig() 
{ Handle   dataHdl;
  Handle   aHdl;

  /* Zap the old data as it is most likely out of date */
  dataHdl = GetResource('DATA', 128);
  RmveResource(dataHdl);
  WriteResource(dataHdl);
  DisposHandle(dataHdl);

  aHdl = NewHandle(DATA_SIZE);
  /* At this point I init aHdl w/the data structure
   * that I've maintained, in preparation for
   * writing it back out.
   */
  AddResource(aHdl, 'DATA', 128, "");
  WriteResource(aHdl);
  DisposHandle(aHdl); 
}
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