Updating RPMs using binary deltas (demo)

[Toshio]

On Mon, 2004-01-26 at 18:18, Leonard den Ottolander wrote:
> Hello Toshio, Michael,
> 
> >                  binutils:   3.64% of original:  96.36% savings
> 
> I seem to be unable to patch with just the .cpio.delta. I need the
> .delta to make this work. What is the saving here? And why do I need
> minigzip instead of gzip?

The list of savings I compiled included both the .cpio.delta and the
.delta so they should be correct.
100*(cpioDeltaSize+headerDeltaSize)/rpmSize = % of original
100 - % of original = percent savings

The .cpio.delta is the delta of the rpm payload.  The .delta is the
delta of the header information.

rpm uses zlib to compress its payload.  This does not create the same
compressed data as gzip.  minigzip, which links to zlib to get its
compression routines, can generate files that are the same as those
created by rpm.  This matters because the compressed payload has been
gpg-signed.  If the payload is different, the reconstructed rpm won't
have a valid signature.

-Toshio

P.S. my short python hack to compute the savings on files is attached in
case you want to check my methodology :-)
-- 
Toshio <toshio at tiki-lounge.com>
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