Path: utzoo!attcan!uunet!lll-winken!lll-tis!ames!mailrus!cornell!uw-beaver!microsoft!t-benw
From: t-benw@microsoft.UUCP (Benjamin Waldmin)
Newsgroups: comp.sys.mac.programmer
Subject: Re: sharing data between cdevs and INITs
Keywords: INIT cdev LSC DRVR
Message-ID: <1749@microsoft.UUCP>
Date: 23 Aug 88 18:16:37 GMT
References: <1739@microsoft.UUCP> <15808@apple.Apple.COM> <1745@microsoft.UUCP> <2413@spray.CalComp.COM>
Reply-To: t-benw@microsoft.uucp (Benjamin Waldman)
Organization: Microsoft Corporation, Redmond, WA
Lines: 32

In article <2413@spray.CalComp.COM> anson@spray.UUCP (Ed Anson) writes:
>In article <1745@microsoft.UUCP> t-benw@microsoft.uucp (Benjamin Waldman) writes:
>>But, wait, it gets worse.  Think C lets you have global data in your
>>drivers by allocating a block in the heap for you, locking it, pointing
>>A4 to it, and referencing your globals off of A4.  But my data has to
>>be in the system heap!!!
>
>When you allocate globals for a driver, they are stored in a DATA resource.
>You could try just setting the System bit for that resource. It may solve
>your problem.
>
>Im not sure, but it looks like LSC is using GetResource, not NewHandle.

Actually, someone from THINK mailed me a neat suggestion (the day after my
posting - how's that for customer service!).  Since my driver is being
opened by an INIT, I can just save the current zone, set the zone to be
the system heap, and open my driver.  Since the system heap will be the
current zone when the driver is opened, both it and its data will be
in the system heap. Finally I restore the old zone.  Since I do want to
keep the driver in memory though, and not close it when the INIT is closed,
I do a GetResource('DRVR',theID), OpenDriver(...), and a DetachResource.

Still though, if I wasn't opening the driver at INIT time, I'd have to
go and manually set the bits with ResEdit every time I rebuilt the
driver, which is a pain.  I guess this is just a small oversight on
THINK's part, which, one hopes, will be corrected in the next release.

Ben Waldman
Software Design Engineer,
Microsoft Corp.

Disclaimer:  These are my thoughts, opinions, and ideas only, and do not
reflect those of my employer in any way.