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Re: translators compared to a reiser4 object

From: Richard Braun
Subject: Re: translators compared to a reiser4 object
Date: Mon, 17 Sep 2007 11:15:00 +0200
User-agent: Icedove (X11/20070730)

Si St wrote:
> The below quotation is taken from
> I faintly understand that it probably has nothing to do or can not be 
> compared to the concept of translator in HURD,where a file can be used and 
> changed to a mountpoint - and thus on the screen suddenly look like a 
> directory -, but how would you briefly, if possible, explain the difference?
> "In Reiser4 (but not ReiserFS 3) an object can be both a file and a directory 
> at the same time. If you access it as a file, you obtain the named sequence 
> of bytes. If you use it as a directory you can obtain files within it, 
> directory listings, etc."
> Thanks Yours,
> Sigbjorn Storset, Norway

The big difference is that, in the Hurd VFS, objects are nodes. What
makes them files or directories or anything else is the translator
behind them. It has nothing to do with the underlying file system layout
or implementation. A translator can implement the I/O (hurd/io.defs)
and/or the File System (hurd/fs.defs) interfaces. What is implemented
and what data is returned defines how programs such as ls see the file
system nodes and how they interpret their type and content. Keep in mind
that one use of the VFS in the Hurd is to look up services, i.e. each
path (or each node) is also a name for a service.

Richard Braun

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