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Re: Filesystem View

Hi Mike,

Many thanks for your reply. What I really want to do is create a filesystem in which Spotlight queries map directly to paths, e.g.:

$ ls /.spotlightfs/kMDItemFSName==\'test.txt\'/

would give you the same result as:

$ mdfind "kMDItemFSName=='test.txt'"

This shares some common ground with volfs, in that a readdir in /.spotlightfs/ would yield only . and .. (as enumerating all the possible entries would make no sense). Also, like volfs it should report identical inode numbers for the files it references (i.e., they should be akin to hard links). However, as you say I would want it to behave like WebDAVfs in caching its results (using kernel notification or "live updates" in Spotlight terminology).

Having thought about this some more I realise, given that MDQuery apparently requires a run loop to yield results (although the documentation says it can run synchronously), I would probably need a daemon process to take queries from feed results to my filesystem (via Mach messages?). It strikes me that the process "mds" is already that daemon (feeding results to the MDQuery), and it would be a shame to duplicate the functionality, but I don't suppose you know how MDQuery and the mds daemon actually communicate?

Thanks,
Hamish

On 19 May 2005, at 20:19, Mike Smith wrote:


On May 18, 2005, at 12:13 PM, email@hidden wrote:


From: Hamish Allan <email@hidden>
Subject: Filesystem View

Hi,

I'm looking for a way to create a filesystem that is actually a view
onto another filesystem. Something akin to what is described here:

http://bryanmills.net:8086/archives/2005/05/meta-filesystem/

Bryan's implementation, however, uses FUSE, which as far as I can
tell is Linux-specific, as is LUFS. Is there anything similar for
Darwin / OS X? If not, how do I best go about my task? I tried
looking for information about the VFS, but all I found were mails on
this list saying that it was now finally stable in Tiger. Anyway I'm
not sure that VFS would be quite what I'm looking for (please excuse
my ignorance, I'm usually an application developer).


Please ignore the other suggestions you've been abused with to date;
including the reference to volfs which isn't very helpful for a variety of
reasons.

If you are looking to make a straight pathname->pathname transformation,
i.e. you're able to use lookup by pathname on the base filesystem, you
should take a look at WebDAVfs.

Essentially, it presents a filesystem hierarchy as represented on the
server, but backs it with cache files in a directory on a local filesystem;
this is the same disconnect between namespace geometries that
I think you're looking for.

If you're able to post a few more details on the namespace transform
that you're looking to achieve, it might be possible to offer some more
concrete suggestions, however I think for most cases the WebDAVfs
model will work fine.

 = Mike




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