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Date:	Fri, 01 Dec 2000 01:01:47 -0500
To:	"Mark E." <snowball3 AT bigfoot DOT com>
From:	"Peter J. Farley III" <pjfarley AT banet DOT net>
Subject:	Re: Locking fcntl() and flock() patches
Cc:	djgpp-workers AT delorie DOT com
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At 10:08 PM 11/30/00 -0500, Mark E. wrote:
>> 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.

OK, then we stay with the current F_RDLCK workaround, and allow whole-file 
read locks as previously discussed?

BTW, I was looking through RBIL, and I didn't see anything that suggested
SH_DENY* equivalents in the SFT, but maybe I'm not reading the right 
section.

And I also don't see anything in a JFT except the SFT number.  Am I missing something there?  It's only one byte per file in the JFT, right?



---------------------------------------------------------
Peter J. Farley III (pjfarley AT dorsai DOT org OR
                     pjfarley AT banet DOT net)

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