Date: Fri, 01 Dec 2000 09:50:42 +0200
From: "Eli Zaretskii" <eliz AT is DOT elta DOT co DOT il>
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To: pjfarley AT banet DOT net
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	(pjfarley AT banet DOT net)
Subject: Re: Locking fcntl() and flock() patches
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> Date: Thu, 30 Nov 2000 21:56:19 -0500
> From: "Peter J. Farley III" <pjfarley AT banet DOT net>
> 
> At 09:27 AM 11/30/00 -0500, Mark E. wrote:
>  >> Does the IOCTL subfunction or poking the SFT allow to set the
>  >> SH_DENY* bits for files that are already open?
> 
>  >You can fiddle with those flags in the SFT, but I haven't 
> experimented >with them.
> 
> OK, you folk are beyond my level of knowledge here.  Are you saying 
> there is an alternate way to set up read locks?

Yes, you can implement a sort of shared locks on the entire file by
setting the sharing bits of the handle.

> Assuming that these bits can be set on an open file, how would it
> work?

The idea is to set the relevant bit(s) with either Int 21h/AX=4401h or
by directly poking the SFT.  Then Windows' VSHARE will refuse other
processes/handles access to the file.

However, I don't think this is worth your hassle to implement this
now.  Poking the SFT is not reliable enough, and doesn't allow to lock
parts of a file.  So I think leaving a FIXME comment about this
possibility in the sources, and treating shared locks as write locks
would be enough at this time.