zstd

Crystal bindings to the Zstandard (zstd) compression library

Features

• [x] Performance optimized. 20M small decompression messages/sec.
• [x] All API calls allow reusable buffers to reduce GC overhead.
• [x] No heap allocations after #initialize.
• [x] Crystal IO compatible Streaming API.
• [x] Snappy like buffer API for handling small messages.
• [x] export ZSTD_CLEVEL=1 sets the default compression level just like the zstd command line utilities.
• [x] Only require what you need for faster compilation. (require "zstd/compress/context")

Experimental Features. API's subject to change.

• [x] Custom dictionaries.

Todo

• [x] Linux: Auto install the most recent zstd if the system library is old or unavailable.
• [ ] OSX: Auto install the most recent zstd if the system library is old or unavailable.
• [ ] Support more zstd params.
• [ ] More specs.

Installation

0. On OSX ensure that zstd is installed (brew install zstd).
   On Linux it will be downloaded and compiled automatically if missing.

1. Add the dependency to your shard.yml:

   dependencies:
     zstd:
       github: didactic-drunk/zstd.cr

2. Run shards install

Usage

require "zstd"

Buffer API

cctx = Zstd::Compress::Context.new(level: 1)
cbuf = cctx.compress buf

dctx = Zstd::Decompress::Context.new
dbuf = dctx.decompress cbuf

Streaming API

buf = Bytes.new 5
mio = IO::Memory.new
Zstd::Compress::IO.open(mio, level: 1) do |cio|
  cio.write buf
end

mio.rewind
str = Zstd::Decompress::IO.open(mio) do |dio|
  dio.gets_to_end
end

Dictionary API

dict_buffer = File.read("dictionary").to_slice
dict = Zstd::Dict.new dict_buffer, level: 3

cctx = Zstd::Compress::Context.new dict: dict
dctx = Zstd::Decompress::Context.new dict: dict

# Compress or decompress using the Buffer or Streaming API's

p dict.dict_id
p dict.memsize

Contributing

1. Fork it (https://github.com/your-github-user/zstd/fork)
2. Install a formatting check git hook (ln -sf ../../scripts/git/pre-commit .git/hooks)
3. Create your feature branch (git checkout -b my-new-feature)
4. Commit your changes (git commit -am 'Add some feature')
5. Push to the branch (git push origin my-new-feature)
6. Create a new Pull Request

Contributors

• Didactic Drunk - creator and maintainer