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Re: [PATCH] Replace vdelta with xdelta variant

From: Branko ─îibej <brane_at_xbc.nu>
Date: Mon, 21 Jan 2008 12:01:30 +0100

Malcolm Rowe wrote:
> On Fri, Jan 18, 2008 at 07:54:59PM +0100, Niels Werensteijn wrote:
>
>> Malcolm Rowe wrote:
>>
>>> On Thu, Jan 17, 2008 at 11:49:32PM +0100, Niels Werensteijn wrote:
>>> Interesting. This sounds similar to a patch that Dan Berlin (cc'd)
>>> produced around the time of the Subversion conference, which used
>>> Rabin fingerprinting (basically a CRC) and a match table.
>>>
>> Is this in the mailinglist archive? If so, please give me a hint where to
>> find it? :)
>>
>>
>
> Afraid not. It's on my laptop :-/, and Dan should also have a copy.
>
> Thinking about it a little more, we weren't actually planning on
> replacing vdelta -- we were going to replace xdelta, with something
> faster and/or better performing.
>
> vdelta-against-empty-stream is essentially just compression, so I wonder
> if we can just adapt/use zlib in some way (sorry, been a while since I
> looked at this). Though you mentioned that your changes would help if a
> large binary file changed significantly -- why's that? (because as far
> as I'm aware we need to make a decision about what compression/delta
> scheme to use _before_ we see the whole file, which means we can't say
> things like 'use xdelta, or just self-compress if that's better'.
>

Please note that we currently expect things to be either plaintext, or
svndiff; and that we can always combine svndiffs. Introducing a
zlib-compressed thing would affect the delta combiner and a lot of other
things.

Just nothing that this may be slighlty more work than you expect.

-- Brane

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Received on 2008-01-21 12:22:02 CET

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