Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!cs.utexas.edu!uunet!snjsn1!bilbo!greg
From: greg@bilbo (Greg Wageman)
Newsgroups: comp.sys.atari.st
Subject: Re: rsc_gaddr() bug
Message-ID: <1107@snjsn1.SJ.ATE.SLB.COM>
Date: 21 Jun 89 22:05:09 GMT
References: <43ed07d6.14a1f@gtephx.UUCP>
Sender: news@SJ.ATE.SLB.COM
Reply-To: greg@sj.ate.slb.com (Greg Wageman)
Organization: Schlumberger ATE, San Jose, CA
Lines: 52

In article <43ed07d6.14a1f@gtephx.UUCP> covertr@gtephx.UUCP (Richard E. Covert) writes:
>
>	The March/April issue of "Atari Explorer" has an article by John
>Jainschigg titled "An introduction to the resource files". In this article John
>describes how to use the rsc_gaddr() function. John also said that you should only
>attempt to locate the address of "tree" objects. To quote John:
>
>	OBJECT *p;
>
>	rsc_gaddr( type, index, &p);
>
>where "type" is an integer between 0 and 16 denoting the type of object
>sought (there are bugs in the function that make it useless for object
>types other then trees; type 0), .....
>
>
>	Anyway, is this a generic bug in GEMDOS, for all versions of TOS??
>Is it a bug in the compiler that John uses?? Does Mark Williams C, 3.09, have
>this bug??
>
>	This bug reduces the usefullness of rsc_gaddr() if it does exist.
>There are times were you want a child of a tree, and it is easily to get the
>child's address then to get the tree's address and have to index off of it.

I have not seen the article.  However, I have successfully used
rsc_gaddr() to obtain the address of free strings and alerts, which
are not type-zero objects.  I have not tried to obtain the address of
children, and it is not clear to me how one would, since while the
index of a tree is unique among all trees, the index of a child isn't
unique among all children.  I suppose one could set "p" equal to the
address of the desired tree object, but the documentation didn't make
it clear that that would work.

In any event, why is it so difficult to do &tree[CHILD]?  Even in
assembler, this is just a load of the address of tree into an address
register, a load of the index of child ("CHILD") into a data register, a
multiply of CHILD by the size of the object structure, and an add of
the resulting byte offset to the address of the tree (or an indexed
load).  Am I missing something here?

	
Longish .signature follows.  Skip now.

Greg Wageman			DOMAIN: greg@sj.ate.slb.com
Schlumberger Technologies	UUCP:   ...!uunet!sjsca4!greg
1601 Technology Drive		BIX:    gwage
San Jose, CA 95110-1397		CIS:    74016,352
(408) 437-5198			GEnie:  G.WAGEMAN
------------------
"Live Free; Die Anyway."
------------------
Opinions expressed herein are solely the responsibility of the author.