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Re: Autoexpanding ZIP archives?

From: Hadmut Danisch <hadmut_at_danisch.de>
Date: 2005-12-07 18:39:18 CET

On Wed, Dec 07, 2005 at 10:17:22AM -0600, Ben Collins-Sussman wrote:
> 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. So I would expect the repository to grow to 15MB, not
> 20MB.

The zip archives store everything with a modification date. So just
slight changes can cause large differenes. Keep in mind that LZ
compression is not byte aligned. A change of just a single bit in the
uncompressed source (e.g. the mod date of a directory) could leave the
10 MB unmodified in principle, but shift it by one bit. The full
archive is modified, 10 MB of storage wasted.


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Received on Wed Dec 7 18:41:32 2005

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