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Date: Mon, 19 Sep 2005 15:10:52 -0400 (EDT)
From: Igor Pechtchanski <pechtcha AT cs DOT nyu DOT edu>
Reply-To: cygwin AT cygwin DOT com
To: cygwin AT cygwin DOT com
Subject: Re: Bug: Setup tool doesn't respect managed mountpoints/filesystems
In-Reply-To: <432F06FB.7A5422B6@dessent.net>
Message-ID: <Pine.GSO.4.63.0509191502560.21521@slinky.cs.nyu.edu>
References: <0IN2009A5RCXL6 AT pmismtp01 DOT mcilink DOT com>  <Pine DOT GSO DOT 4 DOT 63 DOT 0509191358260 DOT 21521 AT slinky DOT cs DOT nyu DOT edu> <432F06FB DOT 7A5422B6 AT dessent DOT net>
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On Mon, 19 Sep 2005, Brian Dessent wrote:

> Igor Pechtchanski wrote:
>
> > OTOH, one of the changes that would be worth making in the managed mount
> > code is to leave the filename alone unless there's a clash, in which case
> > the clashing filename becomes encoded.
>
> But then any file creation/renaming operation would have to check and
> see if there was a clash first.  That would kill performance.  It would
> also create race conditions, like two processes trying to create
> clashing files at the same time.

Yes, there are issues to work out here, but they are not very different
from, say, those arising when two programs try creating a file with the
same name simultaneously...  In fact, the case-insensitivity of both NTFS
and VFAT plays into our hands here, as you say below: creating a new file
that differs only in case will always fail, so Cygwin simply has to encode
the file name if its creation failed.

> > This should work since both NTFS and FAT are case-preserving
> > filesystems (of course, Cygwin will have to
>
> Preserving, yes, but not sensitive.  As far as I know it is impossible
> to make (V)FAT case sensitive, so creating a new file that differs only
> in case will always fail.  NTFS is only case sensitive if you use the
> Native API, otherwise it is not case sensitive either.  I seem to
> remember a paragraph on MSDN that states this.
>
> Even if Cygwin did use the Native API, this would only work for NT with
> NTFS volumes.  9x/ME has no way to do this, so you're back to encoding
> filenames anyway.

How is this relevant?  I didn't say we don't need to encode filenames -- I
said that we only need to encode filenames *if* there is a clash (or the
name is special).  If there is no clash, a file like "README" should be
stored as-is.

The only caveat I see here is that now *accesses* to files on managed
mounts would have to check for case -- i.e., the managed mount code would
need to replicate some of the "check_case:strict" logic.  Otherwise,
creating "README" and accessing it as "readme" would work (which we don't
want to happen).
	Igor
-- 
				http://cs.nyu.edu/~pechtcha/
      |\      _,,,---,,_		pechtcha AT cs DOT nyu DOT edu
ZZZzz /,`.-'`'    -.  ;-;;,_		igor AT watson DOT ibm DOT com
     |,4-  ) )-,_. ,\ (  `'-'		Igor Pechtchanski, Ph.D.
    '---''(_/--'  `-'\_) fL	a.k.a JaguaR-R-R-r-r-r-.-.-.  Meow!

If there's any real truth it's that the entire multidimensional infinity
of the Universe is almost certainly being run by a bunch of maniacs. /DA

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