Path: utzoo!censor!geac!torsqnt!hybrid!scifi!bywater!uunet!mcrware!dibble
From: dibble@mcrware.UUCP (Peter Dibble)
Newsgroups: comp.os.os9
Subject: Re: GIME & IRQ
Message-ID: <4862@mcrware.UUCP>
Date: 31 Jan 91 17:44:40 GMT
References: <1991Jan27.011002.21385@lsuc.on.ca> <1991Jan28.023048.24497@ncsuvx.ncsu.edu> <1991Jan30.090914.11090@tkou02.enet.dec.com>
Reply-To: dibble@mcrware.UUCP (Peter Dibble)
Distribution: na
Organization: Microware Systems Corp., Des Moines, Iowa
Lines: 20

>It seesm that the PD does not store the full name of that path if it is a block
>device file name!
>
>How does OS9 know when multiple processes open the same file (in order
>to keep track of file sharing and byte range locking)?

File names turn out not to be good ways for RBF to identify files.
Comparing them involves a slow string comparison, but
the clincher is that given multiply linked files (not supported by
standard OS-9 utilities, but widely supported anyway.),
a file name, even a full path name, does not identify a
file  one-to-one.

The best (for RBF, and, reluctantly, for pcf) way to identify a file is
the the FD sector number.  Each file has one FD even if it has been
multiply linked with different names.

Now wonder why the PD stores the file name at all. :-)

Peter