Mailing-List: contact cygwin-help@cygwin.com; run by ezmlm List-Subscribe: List-Archive: List-Post: List-Help: , Sender: cygwin-owner@cygwin.com Mail-Followup-To: cygwin@cygwin.com Delivered-To: mailing list cygwin@cygwin.com Message-ID: <3D2CD6BD.8060302@ece.gatech.edu> Date: Wed, 10 Jul 2002 20:52:13 -0400 From: Charles Wilson User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:0.9.4) Gecko/20011019 Netscape6/6.2 X-Accept-Language: en-us MIME-Version: 1.0 To: Nicholas Wourms CC: Robert Collins , cygwin@cygwin.com Subject: Re: Charles: Fwd: Re: NDBM & ODBM on Cygwin? References: <20020711002903.66899.qmail@web21006.mail.yahoo.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-milter (http://amavis.org/) Nicholas Wourms wrote: >>>Sure -- figure out a way to implement hardlinks on FAT. >>> >>It's called cross linked files... and checkdisk will 'fix' it :[. >> >> > > Then the only way to get around that is to emulate hard links, instead of > actually creating a cross-linked file? ndbm requires that both the .pag file and .dir file have exactly the same timestamp. Since gdbm actually implements "ndbm" functionality by putting a "native format" gdbm database into .pag, it simply hardlinks the .dir file to .pag, thus insuring that the timestamps are always identical -- and that file accesses are atomic. There may be other ways to solve the underlying problem -- but that would make cygwin-gdbm's ndbm-emulation different from the rest of the world. And, since any algorithm mod would change the on-disk format of gdbm-in-ndbm-mode, I doubt it would be accepted as a global mod. For instance, we could instead have two separate files, one is empty. All file accesses to .pag are accompanied by 'touch .dir' -- but that's not atomic, AND .dir is no longer itself a valid database. The folks on linux certainly don't want to see that backwards incompatible format change -- just to help US with a problem that only appears in certain cases (using ndbm emulation on FAT drives). --Chuck -- Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple Bug reporting: http://cygwin.com/bugs.html Documentation: http://cygwin.com/docs.html FAQ: http://cygwin.com/faq/