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From: joel@gould9.UUCP (Joel West)
Newsgroups: net.micro.mac
Subject: Re: Desktop file comments from Get Info
Message-ID: <488@gould9.UUCP>
Date: Sun, 20-Apr-86 13:10:37 EST
Article-I.D.: gould9.488
Posted: Sun Apr 20 13:10:37 1986
Date-Received: Mon, 21-Apr-86 08:01:54 EST
References: <588@talcott.UUCP>
Organization: CACI, Inc. -- La Jolla, Calif.
Lines: 50
Summary: Tech note #29

In article <588@talcott.UUCP>, mandel@talcott.UUCP (Victor Mandel) writes:
> Given a file, how can you tell if there is a comment in the Get Info box
> for that file. What is the formula to link the ID of the 'fcmt' resource
> in the Desktop file  to the owning file?

Tech Note #29, "Resources Contained in the Desktop File", says that
the ID on an MFS volume is a hashed result from the object name
the algorithm:
;	HashString(str: 255): INTEGER;
	move.l	(sp)+,a0
	move.l	(sp)+,a1
	moveq	#0,d0
	move.b	(a1)+,d0
	moveq	#0,d2
@0
	move.b	(a1)+,d1
	eor.b	d1,d2
	ror	#1,d2
	bmi.s	@1
	neg	d2
@1
	subq	#1,d0
	bne	@0
	move	d2,(sp)
	jmp	(a0)

For an HFS document it's even easier; the ID is in "kept in the
Finder file information record in a new filed called FFComment
([offset] $5E)."

I cannot say strongly enough that everyone who's forked out $ for 
Inside Mac should also send $25 for one year to
	Macintosh Technical Notes
	Apple Computer, Inc
	20525 Mariania Ave MS3-T
	Cupertino, CA  95014
I'm not a certified developer, but I couldn't get by without these
notes.  The software supplements are valuable, too, but at $25 a
quarter, they're not as clear-cut a value.

I believe many of them are also available for FTP for ARPA sites
from the INFO-MAC headquarters.

Does anyone want to start a mod.mac.technotes?
-- 
	Joel West	 	(619) 457-9681
	CACI, Inc. Federal, 3344 N. Torrey Pines Ct., La Jolla, CA  92037
	{cbosgd, ihnp4, sdcsvax, ucla-cs} !gould9!joel
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