Messages in this thread | | | Date | Wed, 14 Apr 2004 15:34:36 +0200 | From | Jörn Engel <> | Subject | Re: Using compression before encryption in device-mapper |
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On Wed, 14 April 2004 13:44:33 +0100, Paulo Marques wrote: > Guillaume Lacôte wrote: > > >>>Oops ! I thought it was possible to guarantee with the Huffman encoding > >>>(which is more basic than Lempev-Zif) that the compressed data use no > >>>more than 1 bit for every byte (i.e. 12,5% more space). > > WTF?? > > Zlib gives a maximum increase of 0.1% + 12 bytes (from the zlib manual), > which for a 512 block will be a 2.4% guaranteed increase. > > I think that zlib already does the "if this is bigger than original, just > mark the block type as uncompressed" algorithm internally, so the increase > is minimal in the worst case.
Correct, but Guillaume doesn't care about compression efficiency. "mark the block uncompressed" is precisely what he does *not* want, unless I got him wrong.
Jörn
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