Path: utzoo!attcan!uunet!ginosko!bbn!apple!agate!ucbvax!hoptoad!tim
From: tim@hoptoad.uucp (Tim Maroney)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Config File Resource Blues
Message-ID: <7907@hoptoad.uucp>
Date: 8 Jul 89 20:44:28 GMT
References: <2002@dogie.macc.wisc.edu>
Reply-To: tim@hoptoad.UUCP (Tim Maroney)
Organization: Eclectic Software, San Francisco
Lines: 59

In article <2002@dogie.macc.wisc.edu> yahnke@vms.macc.wisc.edu
(Ross Yahnke, MACC) writes:
>  /* Zap the old data as it is most likely out of date */
>  dataHdl = GetResource('DATA', 128);
>  RmveResource(dataHdl);
>  WriteResource(dataHdl);
>  DisposHandle(dataHdl);

You shouldn't call WriteResource after calling RmveResource.  However,
according to Inside Mac, WriteResource will do nothing if the handle
isn't a resource, so this should not cause you any problems.  Still,
you ought to realize that after you call RmveResource, dataHdl is
no longer a resource handle -- it's just an ordinary handle.

However, as you can see from reading the description of RmveResource,
you are right to call DisposHandle.  (Sorry, Dean.  If he calls
ReleaseResource at this point, he's asking for trouble.)

>  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); 

Here Dean Yu is correct to point out that you should not use
DisposHandle.  The actual handle that you pass to AddResource is
inserted in the resource map; if you dispose of it, the resource map
becomes bad.  Future calls to GetResource will attempt to retrieve this
handle, which is no longer valid after the DisposHandle.

I want to point out that this is a very ineficient way of doing
things.  There's no need to remove and re-add the resource; you can
just change it and call ChangedResource.  This would reduce the memory
operations involved in removing and re-adding (which can be quite
significant, leading the entire resource map to be resized in RAM) and
reduce the size and complexity of your routine.  Your whole update
routine would be just:

   aHdl = GetResource('DATA', 128);
   /* At this point I init aHdl w/the data structure
    * that I've maintained, in preparation for
    * writing it back out.
    */
   ChangedResource(aHdl);
   WriteResource(aHdl);	/* optional */
-- 
Tim Maroney, Mac Software Consultant, sun!hoptoad!tim, tim@toad.com
Postal: 424 Tehama, SF CA 94103; Phone: (415) 495-2934

"Those Mayas were sacrificing not only pagan children, but baptized
 Christian children, for crying out loud!  And they were carrying out
 those sacrifices, those barbarities, with great savagery, without
 giving the victims the benefit of the humane types of death that the
 European Church accorded even to heretics and witches during that
 century, such as burning at the stake."
		-- Matthew Rosenblatt, rec.arts.books