[Zlib-devel] Deflate 64 and zLib

[Gilles Vollant]

Just for info, Nico Mak said me he'll introduce building ZIPfile with
deflate 64 in WinZip 9.0 (actual winzip 8.1 can uncompress deflate 64 but
only compress on traditional deflate).

So there is a risk that we see on the world somes zipfile with deflate 64,
and my minizip contribution will need a deflate64 support in uncompress part
of zlib to be a generic zip decompressor.

We can consider deflate 64 as an open format defined in infozip appnotes.txt
and created by winzip (winzip used the appnotes specification for their
deflate 64 engine, I suppose). 

-----Message d'origine-----
De : Zlib-devel-admin at zlib.net [mailto:Zlib-devel-admin at zlib.net] De la part
de Mark Adler
Envoyé : dimanche 15 juin 2003 23:37
À : Zlib-devel at zlib.net
Objet : Re: [Zlib-devel] Deflate 64 and zLib

On Sunday, June 15, 2003, at 02:26  PM, Gilles Vollant wrote:
> Do you known if we can imagine a zLib that support Deflate64 stream ?

 From the FAQ in 1.2.0.1:

37. Does zlib support the new "Deflate64" format introduced by PKWare?

     No. PKWare has apparently decided to keep that format proprietary,
since
     they have not documented it as they have previous compression formats.
     In any case, the compression improvements are so modest compared to
other
     more modern approaches, that it's not worth the effort to implement.

Interestingly, PKWare just recently (June 2nd) put out a new appnote, and it
still does not document deflate64.  This confirms that in fact it is a
conscious decision on the part of PKWare to reverse their open format policy
of the past.  I have an issue with supporting a format (and therefore, their
product) through reverse-engineering.  In my judgment, open formats are even
more important than open source to promote quality software, and so I do not
want to support closed formats.

mark