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Path: utzoo!watmath!clyde!rutgers!im4u!ut-sally!ut-ngp!mic
From: mic@ut-ngp.UUCP
Newsgroups: comp.sys.amiga
Subject: Re: ASSIGN: solution
Message-ID: <4645@ut-ngp.UUCP>
Date: Sun, 8-Feb-87 19:46:41 EST
Article-I.D.: ut-ngp.4645
Posted: Sun Feb  8 19:46:41 1987
Date-Received: Tue, 10-Feb-87 03:27:16 EST
References: <131@batcomputer.tn.cornell.edu>
Reply-To: mic@ngp.UUCP (Mic Kaczmarczik)
Organization: UTexas Computation Center, Austin, Texas
Lines: 35
Keywords: ASSIGN, Avoiding DOS Insert-Disk Requester
Summary: Using Forbid()/Permit() is a good idea

In article <131@batcomputer.tn.cornell.edu> hsgj@batcomputer.tn.cornell.edu (Dan Green) writes:
>If you remember, I had a problem where I needed to know whether
>a name was ASSIGNed before I used it.  Mike Meyer suggested checking
>the data structure Assign uses.  Following this advice, I was able to do
>just what I wanted.  Anyways, since the solution was prompted by a
>net suggestion, I thought I'd share it:
>
..... [ Program that searches the DOS device list to
	see if a particular name is ASSIGNED or not]
>
> -- Dan Green
>-- 
>ARPA:  hsgj%vax2.ccs.cornell.edu@cu-arpa.cs.cornell.edu
>UUCP:  ihnp4!cornell!batcomputer!hsgj   BITNET:  hsgj@cornella

If you go poking around system data structures, you should really use
Forbid() and Permit() to keep other processes from changing the data
while you're accessing it.

	get head of device list...
	Forbid();
	while (devinfo != NULL)
		use devinfo->whatever...
	Permit();
	return result...

Although it would be rare for this particular routine to get into
trouble (depends on how often you mount new devices, I guess), better
safe than sorry...

--mic--

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