zstandard-ruby
- Installation
- Usage
- Advanced Usage
- Configuration
- Docs
- Examples for installing
libzstd
- Contributing
- License
This gem implements FFI based bindings to the Zstandard compression library libzstd
. The Zstandard compression algorithm shines because it compresses data with the same or better ratio as Zlib but does this (much) faster, depending on the input. For the majority of cases it's faster and better then Zlib. It is tested to work with MRI from 1.9.3 to 2.6.x and with JRuby from >= 1.7.24, including 9.2.x.
It does not ship the actual libzstd
library but expects some version to be present on your system.
This gem is activly maintained. The tests are updated regularly, to keep up with the latest zstd version.
Installation
Make sure you have libzstd
installed on your system. In doubt, have a look at the examples for installing libzstd
.
Add this line to your application's Gemfile:
gem "zstandard"
And then execute:
bundle
Or install it yourself as:
gem install zstandard
Usage
The gem provides an API which aims compatibility the with zlib
gem. There are two module methods
deflate(string, level)
inflate(compressed_string)
The only difference between this and the zlib
gem is the interpretation of the compression level. For zlib
, this is a value between 1..9
, whereas for Zstandard
it's between 1..22
.
For most use cases, you should try to keep the compression level (very) low for Zstandard
, because often compression time increases without significant better compression ratios. If in doubt, do not specify a compression level at all, which will use the default compression level.
require "zstandard"
compressed_string = Zstandard.deflate(string)
decompressed_string = Zstandard.inflate(compressed_string)
Advanced Usage
This is not intended to be used by regular users.
Besides the high level API which targets compatibility with the well known zlib
gem there are two additional layers you can interact with. There is a low-level API which tries to cover differences between various libzstd
version, e.g. different frame header formats. You should only use this if you know, what you are doing.
require "zstandard"
compressed_string = Zstandard::API.simple_compress(string)
decompressed_string = Zstandard::API.simple_decompress(compressed_string)
The most low-level bindings are exposed via Zstandard::FFIBindings
. If there is any reason for this, you can do the following.
require "zstandard"
zstd_library_version = Zstandard::FFIBindings.zstd_version_number
Configuration
This gem can be configured by setting various environment variables. Please be carefull if you decide to change/overwrite any of these. The default values are carefully choosen and there should be no need to alter one of these for regular use cases.
ZSTANDARD_LIBRARY
If you have libzstd
installed in some unusual location or if you want to explictly tell, which library to use, you can set ZSTANDARD_LIBRARY
to the path of the library you want to use. This can be handy for example if you have the latest version compiled in /usr/local/lib
, but your system has an old version in /usr/lib
.
ZSTANDARD_LIBRARY=/usr/local/lib/libzstd.so bundle exec rspec
ZSTANDARD_MAX_SIMPLE_DECOMPRESS_SIZE
This specifies the maximum (decompressed) size of a string for which the simple decompression approach should be used. In order minimise memory consumption, if the expected decompressed size exceeds this limit, streaming decompression is used.
ZSTANDARD_MAX_STREAMING_DECOMRPESS_BUFFER_SIZE
For streaming decompression, this specifies the size of the decompression bufffer.
Docs
Yard generated docs can be found at http://www.rubydoc.info/github/msievers/zstandard-ruby.
Examples for installing libzstd
- Debian
- Fedora
- FreeBSD
- Mac
- NetBSD
- Ubuntu
Debian
Jessie (8.x)
The package is only included in sid
, the unstable Debian version. There are guides describing how to install unstable packages into a stable Debian, for example at Linuxaria or serverfault.com.
# run as root
apt-get install zstd
Fedora
Fedora 23
sudo dnf install libzstd
FreeBSD
FreeBSD 10
# run as root
portsnap fetch && portsnap extract
cd /usr/ports/archivers/zstd
make install
Mac
brew install zstd
NetBSD
NetBSD 7
# run as root
# the following assumes you are running a x86_64 system with NetBSD 7.0.x
export PATH="/usr/pkg/sbin:$PATH"
export PKG_PATH="ftp://ftp.netbsd.org/pub/pkgsrc/packages/NetBSD/x86_64/7.0_current/All/"
pkg_add zstd
Ubuntu
Xenial Xerus (16.04) and above
sudo apt-get install zstd
Contributing
Bug reports and pull requests are welcome on GitHub at https://github.com/msievers/zstandard-ruby.
License
The gem is available as open source under the terms of the MIT License.