ClickHouse/contrib/libzlib-ng/README.md
2017-01-08 21:26:03 +03:00

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zlib-ng - zlib for the next generation systems
Maintained by Hans Kristian Rosbach
aka Dead2 (zlib-ng àt circlestorm dót org)
Fork Motivation and History
---------------------------
The motivation for this fork was due to seeing several 3rd party
contributions containing new optimizations not getting implemented
into the official zlib repository.
Mark Adler has been maintaining zlib for a very long time, and he has
done a great job and hopefully he will continue for a long time yet.
The idea of zlib-ng is not to replace zlib, but to co-exist as a
drop-in replacement with a lower threshold for code change.
zlib has a long history and is incredibly portable, even supporting
lots of systems that predate the Internet. This is great, but it does
complicate further development and maintainability.
The zlib code has to make numerous workarounds for old compilers that
do not understand ANSI-C or to accommodate systems with limitations
such as operating in a 16-bit environment.
Many of these workarounds are only maintenance burdens, some of them
are pretty huge code-wise. For example, the [v]s[n]printf workaround
code has a whopping 8 different implementations just to cater to
various old compilers. With this many workarounds cluttered throughout
the code, new programmers with an idea/interest for zlib will need
to take some time to figure out why all of these seemingly strange
things are used, and how to work within those confines.
So I decided to make a fork, merge all the Intel optimizations, merge
the Cloudflare optimizations that did not conflict, plus a couple
of other smaller patches. Then I started cleaning out workarounds,
various dead code, all contrib and example code as there is little
point in having those in this fork for different reasons.
Lastly I have been cleaning up the handling of different arches,
so that it will be easier to implement arch-specific code without
cluttering up the main code too much.
Now, there is still a lot to do and I am sure there are better ways
of doing several of the changes I have done. And I would be delighted
to receive patches, preferably as pull requests on github.
Just remember that any code you submit must be your own and it must
be zlib licensed.
Please read LICENSE.md, it is very simple and very liberal.
Acknowledgments
----------------
Big thanks to Raske Sider AS / raskesider.no for sponsoring my
maintainership of zlib-ng.
The deflate format used by zlib was defined by Phil Katz.
The deflate and zlib specifications were written by L. Peter Deutsch.
zlib was originally created by Jean-loup Gailly (compression)
and Mark Adler (decompression).