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From: UK4H@DKAUNI2.BITNET ("JAE")
Newsgroups: comp.sys.amiga.tech
Subject: User Extensions to System Structures
Message-ID: <"90-01-04-21:33:00.95*UK4H"@DKAUNI2.BITNET>
Date: 5 Jan 90 05:33:00 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Lines: 53

Hi usenet! (this is my first time here, but who cares...)

The recent discussion about mutualExclude striked a chord in me.
One thing that was said (I can't remeber who said it) was about
those 'user' fields in various (all?) intuition/exec etc. structures.
I agree with those who say that one should use these fileds for
one's own purposes instead of using ANY fields in a system struct.

Now: what if two programs (independend ones) want to share, say,
a window. Both want to link some private information to the
window.
Unnecessary? Well, I can't think of an application right now, but
I'm almost sure there is one.
Anyway, what will happen. Both will user that 'userExt' field
(I don't know real name now). Both will write something to it.
Well, who's last is lucky in that case.

What I'm thinkin' of is some standard userExtension struct. Just like

  struct userExtension {
    struct userExtension *nextExt;
    LONG id;
  }

The id field must just be uniq. This would best be accomplished by
providing a (system) function 'AddExtension'. Oh, give a C func head:

  BOOL AddUserExtension(root,userExt);
    struct userExtension **root;  /*points to the field in struct*/
    struct userExtension *userExt;  /*points to node to add*/

Anyone who'd like to use this would define his own extension as s.th.
like:

  struct myExt {
    struct userExtension extLink;
    /*my fields*/
  }

Hey, CBM (jim or anyone), are you listening? How about 1.5????
(Yeah, that version blues again...)
Of course this userExt stuff could be a Node (would probably be the
best...)

I'd really like to hear any comments from anyone...

                                             bye, JAE

Juergen A. Erhard
eMail: uk4h@dkauni2.bitnet
phone: (GERMANY) 0721/591602
"You know that it's monday when you wake up and it's tuesday."
                                                    Garfield