Re: Zip-files
Re: Zip-files
- Subject: Re: Zip-files
- From: John Stiles <email@hidden>
- Date: Fri, 14 Jan 2005 16:37:31 -0800
Zlib implements one algorithm used by Zip. It is hardly all-inclusive
or all one would need to read a Zip file.
With just Zlib, you're missing things like:
- a container format which Zlib cannot read (however they include
pointers to utilities which can get into these containers, i.e.
Info-zip)
- older, separate algorithms which Zlib cannot read (although Zlib's
contrib folder includes code called "blast" which implements a
decompressor for one of these older formats)
- options such as encryption which Zlib cannot read (think you're on
your own for this one :) )
The list goes on, but this is a good example. Zlib is a great
compression algorithm--they balance compression quality and speed very
well for most applications--but it's not the same as full Zip support.
(And FWIW, IMHO Zip is a crappy format.)
On Jan 14, 2005, at 4:25 PM, Mike Hall wrote:
On 14 Jan 2005, at 03:34, Mike Hall wrote:
On Jan 13, 2005, at 12:17 PM, Fredrik Olsson wrote:
And no I am not interested in Mac specific data, as the source files
comes from Windows users.
You might take a look at http://www.gzip.org/zlib/
zlib and pkzip are neither identical nor compatible.
I would prefer the requestor do his own googling for specific
documentation
he is interested in, but consider
http://datacompression.info/Zlib.shtml
where we find...
zlib
zlib is a freeware multiplatform compression library written in highly
portable C. zlib implements the deflate algorithm used by PKZip, which
means
it can be used as the compression engine for Zip compatible archivers.
It
has also found use as the standard compressor in quite a few other
products,
and is rightly hailed as a wonderful piece of work.
Although I think I was to some extent confusing PKZip and it's
originating
company PKWare, if I remember right there, who pretty much decided how
it is
implemented.
Was it this mix up that bothers you or do you in fact consider the
implementations in zlib and PKZip incompatible?
You might consider as well
http://www.faqs.org/rfcs/rfc1950.html
although that indicates P. Deutsch associated with Aladdin I thought
when he
originally did a lot of this it was while still with PKWare.
zlib would be to my understanding the opensource, unencumbered
(patents or
whatever), implementation of what was originally PKWare proprietary..
There still may be some incompatability I'm unaware of though. What
specific
incompatability or plural of that were you thinking of?
Mike Hall mikehall at spacestar dot net
http://www.spacestar.net/users/mikehall
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