From: Davide Libenzi <davidel@xmailserver.org>
To: Linus Torvalds <torvalds@osdl.org>
Cc: Alon Ziv <alonz@nolaviz.org>, git@vger.kernel.org
Subject: Re: RFC: adding xdelta compression to git
Date: Mon, 2 May 2005 22:30:17 -0700 (PDT) [thread overview]
Message-ID: <Pine.LNX.4.58.0505022215110.21733@bigblue.dev.mdolabs.com> (raw)
In-Reply-To: <Pine.LNX.4.58.0505022131380.3594@ppc970.osdl.org>
On Mon, 2 May 2005, Linus Torvalds wrote:
> Yes. EXCEPT for one thing. fsck. I'd _really_ like fsck to be able to know
> something about any xdelta objects, if only because if/when things go
> wrong, it's really nasty to suddenly see a million "blob" objects not work
> any more, with no indication of _why_ they don't work. The core reason may
> be that one original object (that just got used as a base for tons of
> other objects through deltas) is corrupt or missing. And then you want to
> show that _one_ object.
Linus, xdelta-based algorithms already stores informations regarding the
object that originated the diff. Since they have no context (like
text-based diffs) and are simply based on offset-driven copy/insert
operations, this is a requirement. Libxdiff uses an adler32+size of the
original object, but you can get as fancy as you like in your own
implementation. Before a delta patching, the stored information are cross
checked with the input base object, and the delta patch will fail in the
eventuality of mismatch. So an fsck is simply a walk backward (or forward,
depending on your metadata model) of the whole delta chain.
- Davide
next prev parent reply other threads:[~2005-05-03 5:24 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-05-03 3:57 RFC: adding xdelta compression to git Alon Ziv
2005-05-03 4:12 ` Nicolas Pitre
2005-05-03 4:52 ` Linus Torvalds
2005-05-03 5:30 ` Davide Libenzi [this message]
2005-05-03 15:52 ` C. Scott Ananian
2005-05-03 17:35 ` Linus Torvalds
2005-05-03 18:10 ` Davide Libenzi
2005-05-03 8:06 ` [PATCH] add the ability to create and retrieve delta objects Nicolas Pitre
2005-05-03 11:24 ` Chris Mason
2005-05-03 12:51 ` Nicolas Pitre
2005-05-03 15:07 ` Linus Torvalds
2005-05-03 16:09 ` Chris Mason
2005-05-03 15:57 ` C. Scott Ananian
2005-05-03 16:35 ` Chris Mason
2005-05-03 14:13 ` Chris Mason
2005-05-03 14:24 ` Nicolas Pitre
2005-05-03 14:37 ` Chris Mason
2005-05-03 15:04 ` Nicolas Pitre
2005-05-03 16:54 ` Chris Mason
2005-05-03 14:48 ` Linus Torvalds
2005-05-03 15:52 ` Nicolas Pitre
2005-05-04 15:56 ` Chris Mason
2005-05-04 16:12 ` C. Scott Ananian
2005-05-04 17:44 ` Chris Mason
2005-05-04 22:03 ` Linus Torvalds
2005-05-04 22:43 ` Chris Mason
2005-05-05 3:25 ` Nicolas Pitre
2005-05-04 21:47 ` Geert Bosch
2005-05-04 22:34 ` Chris Mason
2005-05-05 3:10 ` Nicolas Pitre
2005-05-03 12:48 ` RFC: adding xdelta compression to git Dan Holmsand
2005-05-03 15:50 ` C. Scott Ananian
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