Converting from cpio to tar formats in a pipeline?

[Albert den Haan <e4k3l9lb@umail.corel.com>]

Does anyone have a pipline that will convert a cpio archive into a tarfile
on stdout?

I'm working on a proof of concept implementation of a new package archive
handler for the Linux Standards Base's current "lowest common denominator"
packaging format.  The current lowest common denominator *archive file*
format[1] is RPM -- which currently uses cpio.

So, I'm writing a peer to dpkg-deb, dpkg-lsb, and using librpm for the
archive disection bits.  Current RPM archive formats use cpio, and dpkg
wants a tarfile on stdout.

I'm hoping someone has written a hyper-efficent conversion filter. 
However, I will accept the use of temporary directories (for this proof of
concept of course :).  This will be a couple steps up from Alien (amazing
stuff in there, expect to see bits again :) because I can duck the
expensive (read compression) stages of constructing a .deb archive by
providing the information directly to dpkg on stdout.

	Albert.

[1] Let's not start a flamewar over what the best archive file format for
packages is.  It's been done before -- better.  This archive file format is
a starting point and any common format is better for cross distribution
packages than none.  Look at
http://lists.debian.org/lsb-discuss-0010/threads.html for discussions on
what the perfect world would look like.

--
Albert den Haan, Lead Developer @ Linux Port Team . Corel Corporation
albertd@corel.com  (613) 728-0826 x 5318
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