state of the rsync nation? (revisited 6/2003 from 11/2000)

Donovan Baarda abo at
Wed Jun 11 12:27:15 EST 2003

On Tue, 2003-06-10 at 14:25, Martin Pool wrote:
> On  8 Jun 2003, Donovan Baarda <abo at> wrote:
> > The "next big thing" in delta calculation is probably going to be the
> > vcdiff encoding format, which should allow a common delta format for
> > various applications and supports "self-referencing delta's", which
> > makes it capable of compression. According to the xdelta project this
> > has already been implemented, and I'm keen to see Josh's code, as it
> > could be used as the basis for a cleanup/replacement of at least the
> > "patch" component of librsync.
> Do you have a link for this?  Josh plays his cards pretty close to his
> chest.  The XDelta page seems to be even more inactive than librsync
> :-/

yeah, the xdelta page on SourceForge has a few announcements about
vcdiff support that are fairly recent, but everything else hasn't been
touched for ages. It looks like Josh is only using SF as a static
front-page where he posts announcements and all the real work is
happening somewhere else...

Unfortunately I don't know where that somewhere else is... hence my
eagerness to actually see the code.

The vcdiff standard is available as RFC3284, and Josh is listed as one
of the authors. 

I also had some correspondence with Josh ages ago where he talked about
how self-referencing delta's can directly do compression of the miss
data without using things like zlib and by default gives you the
benefits of rsync's "context compression" without the overheads (rsync
runs a decompressor _and_ a compressor on the receiving end just to
regenerate the compressed "hit" context data).

Donovan Baarda <abo at>

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