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From: toddpw@nntp-server.caltech.edu (Todd P. Whitesel)
Newsgroups: comp.sys.apple2
Subject: Re: Handles
Message-ID: <1990Dec22.103638.4287@nntp-server.caltech.edu>
Date: 22 Dec 90 10:36:38 GMT
References: <1198@dg.dg.com> <18830@netcom.UUCP>
Organization: California Institute of Technology, Pasadena
Lines: 23

>zane@ddsw1.MCS.COM (Sameer Parekh) writes:

>>	Why DO handles exist?  Why can't one just use the pointers?
>>(I am learning programming now. . .)

Heh.. the half screen lecture I just posted buries the real answer to your
question -- it's so the memory manager can move blocks around without worrying
about what you're doing. Here's how to politely use memory:

If the block is going to be used a lot, allocate it as Fixed and Locked.
Dereference the handle and use the pointer for whatever evil purposes.

If the block is not going to be used a lot, allocate it without restrictions
and either always reference it through the handle or call HLock(handle) before
making and using a pointer to it and HUnlock(handle) afterwards. This way the
block is always fixed &/or locked (I haven't bothered with purgable yet) while
a pointer to it exists. If all you need is a handle, unlock it so the memory
manager can move it around if the situation warrants. This is what Apple asks
you to do and it helps the memory manager keep down the number of little
pockets of wasted memory (i.e. it helps avoid "memory fragmentation").

Todd Whitesel
toddpw @ tybalt.caltech.edu