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Re: Autoexpanding ZIP archives?

From: Daniel Berlin <dberlin_at_dberlin.org>
Date: 2005-12-08 17:57:36 CET

On Wed, 2005-12-07 at 10:17 -0600, Ben Collins-Sussman wrote:
> On 12/7/05, Hadmut Danisch <hadmut@danisch.de> wrote:
>
> > If I have a presentation with 10 MB of graphics, and enter just a
> > single word, SVN wastes another 10 MB just for every little change.
>
> I think you're exaggerating, this is the extreme worst case it could
> possibly ever be. It's what CVS does, in fact; it doesn't try to
> examine differences between binary files, it just stores each one in
> full.
>
> Try it yourself: make a .zip presentation with 10MB of graphics and
> commit it to an svn repository. Change one word in the presentation.
> Now commit that new .zip to the repository. The repository's size
> should only grow by the binary difference between the 2 zip files. I
> don't believe that every single byte will be different, maybe 50% of
> them will.

Let me go one further.

If you produce for me a testcase where the changed and original .zip
files are not actually different by more than 50%, and yet the delta
produced by the vdelta-test program in
 subversion/tests/libsvn_delta/vdelta-test is generating diffs that are
ridiculously large, i will attempt to fix your problem in a sane way.

Note that stream alignment is not an easy issue. It's also probably
*not* worth it to do it from a maintenance, etc perspective.

But i'll happily take a look.

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Received on Thu Dec 8 18:11:14 2005

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