Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!apple!dlyons
From: dlyons@Apple.COM (David A. Lyons)
Newsgroups: comp.sys.apple2
Subject: Re: Handles  Re: Handle Dereferencing (was Re: Q: Orca/C and SFMultiGet2)
Message-ID: <47562@apple.Apple.COM>
Date: 22 Dec 90 19:00:24 GMT
References: <18830@netcom.UUCP> <1990Dec15.080751.20819@ee.ualberta.ca> <1990Dec22.041312.347@ddsw1.MCS.COM>
Organization: Apple Computer Inc., Cupertino, CA
Lines: 29

In article <1990Dec22.041312.347@ddsw1.MCS.COM> zane@ddsw1.MCS.COM (Sameer Parekh) writes:
>
>	Why DO handles exist?  Why can't one just use the pointers?
>(I am learning programming now. . .)
>
>-- 
>zane@ddsw1.MCS.COM

Handles exist so that after you allocate lots of hunks of memory, dispose
of a lot of them, allocate more of different sizes, etc, you don't have
to be stuck with all the weird-sized "holes" between hunks.

By having handles, the Memory Manager can move many memory block around
to consolidate the free space into bigger chunks, and whoever allocated
those memory blocks can still get at them, because they have a handle.

(Each handle points to a "master pointer," which never moves.  The master
pointer *changes* when the block gets moved.)

Read the Memory Manager chapter in Toolbox Ref Volume 1!

-- 
David A. Lyons, Apple Computer, Inc.      |   DAL Systems
Apple II System Software Engineer         |   P.O. Box 875
America Online: Dave Lyons                |   Cupertino, CA 95015-0875
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My opinions are my own, not Apple's.