Some sort of filter based filesystem

[Lowell Gilbert]

Svein Halvor Halvorsen writes:

> * Svein Halvor Halvorsen <svein-freebsd-questions at theloosingend.net> writes:
> >  > What would be nice, is some kind of nullfs-like read only filesystem 
> >  > that would send all files through a configurable filter when opened. 
> >  > That way I could put all my music in FLAC format on hdd, and then, 
> >  > when I wanted to transfer some tracks to my portable player, I could 
> >  > grab the files from the ogg-directory. Or when I wanted to burn to 
> >  > CD-A, I could grab 'em from the wav-dir.
> 
> * Lowell Gilbert [2005-07-19 12:18 -0400]
> >  It's a clever idea, but not really very useful; usually a virtual
> >  filesystem approach is good when you can generate the data as needed.
> >  For something like this, you would need to pregenerate the various
> >  forms anyway, so you wouldn't save disk space.
> 
> Why would the various forms need to be pre-generated?
> 
> I can easily imagine some mechanism where my flac files are filtered 
> through a flac decoder and into a vorbis encoder on-the-fly. 
> The same goes for iconv conversion, image processing, etc.
> 
> In fact, this is the sole purpose of my suggestion.

You're right that the outputs wouldn't *have* to be pre-generated, but
doing it on the fly would make the project both more difficult to
implement and (I think) less convenient to use.  It would be pretty
slow if you really did generate it on the fly.  Also, a lot of other
things would get very tricky: for example, you wouldn't have the file
size available when listing a directory of "virtual" files.

Be well.
-- 
Lowell Gilbert, embedded/networking software engineer, Boston area
		http://be-well.ilk.org/~lowell/