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Re: Autoexpanding ZIP archives?

From: Peter Samuelson <peter_at_p12n.org>
Date: 2005-12-09 09:51:43 CET

[John Peacock]
> I don't think that there is too much hope for that (as pointed out by
> someone else, zip archives are a collection of individually zipped
> files, which is AFAIK, not true of gzip, even though the actual
> compression algorithms are related).

The compression algorithm is identical. (Well, .zip is actually a
container format whose member files can use any of several codecs, but
"deflate", the codec used by gzip, is the only one used in practice.)

As such, it is probably possible to patch zlib (the library almost
always used for handling .zip files, and often used for .gz files) to
support an 'rsyncable' mode just like the one Rusty Russell wrote for
gzip. The output stream is compatible with the standard codec, so
there's not even a backward compatibility problem, and as such I'd
argue that rsyncable mode should be the default - in both gzip and
zlib. The 1% space penalty is well worth it, IMHO.

The problem is finding someone comfortable enough with compression
codecs in general to port Rusty's patch to zlib and bug the maintainers
of both projects about incorporating it. I don't think I'm that guy -
I even had problems figuring out old-school Huffman coding.

Received on Fri Dec 9 09:53:46 2005

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