Re: Package patch

[Goswin Brederlow <goswin.brederlow@student.uni-tuebingen.de>]

>>>>> " " == John O Sullivan <johno@cruithne.org> writes:
     > On Tue, 23 Jan 2001 01:46:00 Rob Browne wrote:
    >> Hi,
    >> 
    >> Now that we have package pools, how about this for large
    >> packages say > 1 MB. Or offen downloaded packages like libc6.
    >> 
    >> A patch file is included with the package. This patch would
    >> update a package from the stable version to unstable. But less
    >> downloading needed.
    >> 
    >> Some code would need to be added to check the users CDROM and
    >> get the stable version. Then download the patch and apply.
    >> 
    >> Would be great for modem users like me.
    >> 
    >> Cheers Rob.

     > It won't work well for certain packages - in particular
     > packages that install gzipped files, documentation packages do
     > this. The reason, gzipping two files with a tiny difference in
     > the original files creates two completely different compressed
     > versions.  Its the same reason rsync doesn't handle debian
     > packages well.  Otherwise rsync+apt would save loads of
     > bandwidth. Its probably a better way to solve the problem but I
     > don't think theres any simple solution.

     > johno

Thats the reason why gzip will get a --rsyncable (or even have that as
default). That makes gzip file fall back in sync when only small
changes are made.

Also there are other possibilities to sync compressed files using
precalculated checksum files on the server which carry rsync checksums
of the file as it would be when uncompressed together with offsets
into the compressed file. With the help of those one can download the
parts of the compressed file that contain the changes and reconstruct
the compressed file with the old file and those few blocks.

Someone has to write the support for that, but I'm doing that for gzip
and deb files anyway, so extending it to gzip in deb will be just one
more step.

MfG
        Goswin