## zlib-ng
*zlib data compression library for the next generation systems*

Maintained by Hans Kristian Rosbach
          aka Dead2 (zlib-ng àt circlestorm dót org)

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|:-|-|
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Fork Motivation
---------------------------

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 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 various reasons.

A lot of improvements have gone into zlib-ng since its start, and
numerous people have contributed both small and big improvements,
or valuable testing.

Please read LICENSE.md, it is very simple and very liberal.

Features
--------

* Zlib compatible API with support for dual-linking
* Modernized native API based on zlib API for ease of porting
* Intel deflate medium and quick algorithms
* Support for CPU intrinsics when available
  * Adler32 implementation using SSSE3, AVX2, Neon, & VSX
  * Intel CRC32-B implementation using PCLMULQDQ
  * Intel CRC32-C intrinsics for hash tables
  * ARM CRC32-B implementation using ACLE
  * Slide hash implementations using SSE2, AVX2, Neon, & VSX
  * Inflate chunk copying using SSE2 & Neon
  * Deflate hooks for IBM Z DFLTCC
* Code sanitizers, fuzzing, and coverage
* GitHub Actions continuous integration on Windows, macOS, and Linux
  * Emulated CI for ARM, AARCH64, PPC, PPC64, SPARC64, S390x using qemu
* Unaligned memory read/writes and large bit buffer improvements
* Includes improvements from Cloudflare and Intel forks
* Configure, CMake, and NMake build system support
* Modern C99 syntax and a clean code layout
* Comprehensive set of CMake unit tests

Build
-----

There are two ways to build zlib-ng:

### Cmake

To build zlib-ng using the cross-platform makefile generator cmake.

```
cmake .
cmake --build . --config Release
ctest --verbose -C Release
```

Alternatively, you can use the cmake configuration GUI tool ccmake:

```
ccmake .
```

### Configure

To build zlib-ng using the bash configure script:

```
./configure
make
make test
```

Build Options
-------------
| CMake                    | configure                | Description                                                                           | Default |
|:-------------------------|:-------------------------|:--------------------------------------------------------------------------------------|---------|
| ZLIB_COMPAT              | --zlib-compat            | Compile with zlib compatible API                                                      | OFF     |
| ZLIB_ENABLE_TESTS        |                          | Build test binaries                                                                   | ON      |
| WITH_GZFILEOP            | --with-gzfileops         | Compile with support for gzFile related functions                                     | OFF     |
| WITH_MSAN                | --with-msan              | Build with memory sanitizer                                                           | OFF     |
| WITH_OPTIM               | --without-optimizations  | Build with optimisations                                                              | ON      |
| WITH_NEW_STRATEGIES      | --without-new-strategies | Use new strategies                                                                    | ON      |
| WITH_NATIVE_INSTRUCTIONS | --native                 | Compiles with full instruction set supported on this host (gcc/clang -march=native)   | OFF     |
| WITH_SANITIZERS          | --with-sanitizers        | Build with address sanitizer and all supported sanitizers other than memory sanitizer | OFF     |
| WITH_FUZZERS             | --with-fuzzers           | Build test/fuzz                                                                       | OFF     |
| WITH_MAINTAINER_WARNINGS |                          | Build with project maintainer warnings                                                | OFF     |
| WITH_CODE_COVERAGE       |                          | Enable code coverage reporting                                                        | OFF     |

Install
-------

WARNING: We do not recommend manually installing unless you really
know what you are doing, because this can potentially override the system
default zlib library, and any incompatibility or wrong configuration of
zlib-ng can make the whole system unusable, requiring recovery or reinstall.
If you still want a manual install, we recommend using the /opt/ path prefix.

For Linux distros, an alternative way to use zlib-ng (if compiled in
zlib-compat mode) instead of zlib, is through the use of the
_LD_PRELOAD_ environment variable. If the program is dynamically linked
with zlib, then zlib-ng will temporarily be used instead by the program,
without risking system-wide instability.

```
LD_PRELOAD=/opt/zlib-ng/libz.so.1.2.11.zlib-ng /usr/bin/program
```

### Cmake

To install zlib-ng system-wide using cmake:

```
cmake --build . --target install
```

### Configure

To install zlib-ng system-wide using the configure script:

```
make install
```

Contributing
------------

Zlib-ng is a young project, and we aim to be open to contributions,
and we would be delighted to receive pull requests on github.
Just remember that any code you submit must be your own and it must
be zlib licensed.
Help with testing and reviewing of pull requests etc is also very
much appreciated.

If you are interested in contributing, please consider joining our
IRC channel #zlib-ng on the Freenode IRC network.


Acknowledgments
----------------

Thanks to Servebolt.com for sponsoring my maintainership of zlib-ng.

Thanks go out to all the people and companies who have taken the time
to contribute code reviews, testing and/or patches. Zlib-ng would not
have been nearly as good without you.

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).

Advanced Build Options
----------------------

| CMake                           | configure             | Description                                                         | Default                |
|:--------------------------------|:----------------------|:--------------------------------------------------------------------|------------------------|
| ZLIB_DUAL_LINK                  |                       | Dual link tests with system zlib                                    | OFF                    |
| UNALIGNED_OK                    |                       | Allow unaligned reads                                               | ON (x86, arm)          |
|                                 | --force-sse2          | Assume SSE2 instructions are always available                       | ON (x86), OFF (x86_64) |
| WITH_AVX2                       |                       | Build with AVX2 intrinsics                                          | ON                     |
| WITH_SSE2                       |                       | Build with SSE2 intrinsics                                          | ON                     |
| WITH_SSE4                       |                       | Build with SSE4 intrinsics                                          | ON                     |
| WITH_PCLMULQDQ                  |                       | Build with PCLMULQDQ intrinsics                                     | ON                     |
| WITH_ACLE                       | --without-acle        | Build with ACLE intrinsics                                          | ON                     |
| WITH_NEON                       | --without-neon        | Build with NEON intrinsics                                          | ON                     |
| WITH_POWER8                     |                       | Build with POWER8 optimisations                                     | ON                     |
| WITH_DFLTCC_DEFLATE             | --with-dfltcc-deflate | Use DEFLATE COMPRESSION CALL instruction for compression on IBM Z   | OFF                    |
| WITH_DFLTCC_INFLATE             | --with-dfltcc-inflate | Use DEFLATE COMPRESSION CALL instruction for decompression on IBM Z | OFF                    |
| WITH_INFLATE_STRICT             |                       | Build with strict inflate distance checking                         | OFF                    |
| WITH_INFLATE_ALLOW_INVALID_DIST |                       | Build with zero fill for inflate invalid distances                  | OFF                    |
| INSTALL_UTILS                   |                       | Copy minigzip and minigzip during install                           | OFF                    |
