Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!caen.engin.umich.edu!netnews
From: netnews@caen.engin.umich.edu (netnews)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Config File Resource Blues
Message-ID: <444accf7.a590@mag.engin.umich.edu>
Date: 8 Jul 89 07:11:00 GMT
References: <2002@dogie.macc.wisc.edu>
Reply-To: mystone@sol.engin.umich.edu
Organization: Computer Aided Engineering Network, University of Michigan
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In article <2002@dogie.macc.wisc.edu> yahnke@vms.macc.wisc.edu (Ross Yahnke, MACC) writes:
>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the config file data would therefore be out of date, so I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); 
   ^^^^^^^^^^^^^^^^^^^
>}

  Never, ever call DisposHandle for a resource!  Use ReleaseResource to
de-allocate the memory that a resource is using.

_______________________________________________________________________________
Dean Yu                            | E-mail: mystone@{sol,caen}.engin.umich.edu
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