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Re: Solving the compression dilema when rsync-ing Debian versions

>>>>> " " == Daniel Burrows <Daniel_Burrows@brown.edu> writes:

     > On Sun, Jan 14, 2001 at 01:51:02AM +0100, Goswin Brederlow
     > <goswin.brederlow@student.uni-tuebingen.de> was heard to say:
    >> This forced flush happens at random places and not too often
    >> (increases linux.tar.gz by ~3%). The flush does not depend on
    >> the position but on the data compressed. So when two files
    >> match for a few K, they will both hit a flush at the same
    >> position. When the file is altered at the front gzip will still
    >> flush the dictionary at the same places at the end, so the
    >> files will match at the end.

     >   I suspect I'm missing something obvious..if I alter the first
     > few bytes of a long file, won't the flushes and dictionaries be
     > out of sync for the rest of the file?  (since the checksums
     > will all be thrown off by those modifications)

The cheksum is calculated over a block of 4K, so 4K after the changes
the block will be identical to the unchaned one.


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