From: "Mark E." <snowball3 AT bigfoot DOT com>
To: djgpp-workers AT delorie DOT com
Date: Thu, 30 Nov 2000 22:08:00 -0500
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Subject: Re: Locking fcntl() and flock() patches
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> 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?  Assuming that these 
> bits can be set on an open file, how would it work?

A file handle's SH_DENY* flags are stored in the JFT like a lot of other 
flags passed to open(). If you manipulate them using undocumented methods, 
you just might be able to have a read lock for the whole file that can then 
be unlocked by fiddling with the handle's open flagst. However, I haven't 
tried this and I doubt it's worth the effort to work on this just to get one 
special case of read locks working.

Mark