Ruby bindings for zstd library

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See zstd library.

Installation

Please install zstd library first, use latest 1.4.0+ version.

Also some server installations (especially CentOS) might require libzstd-devel package installation.

gem install ruby-zstds

You can build it from source.

rake gem
gem install pkg/ruby-zstds-*.gem

You can also use overlay for gentoo.

Usage

There are simple APIs: String and File. Also you can use generic streaming API: Stream::Writer and Stream::Reader.

require "zstds"

data = ZSTDS::String.compress "sample string"
puts ZSTDS::String.decompress(data)

ZSTDS::File.compress "file.txt", "file.txt.zst"
ZSTDS::File.decompress "file.txt.zst", "file.txt"

ZSTDS::Stream::Writer.open("file.txt.zst") { |writer| writer << "sample string" }
puts ZSTDS::Stream::Reader.open("file.txt.zst") { |reader| reader.read }

writer = ZSTDS::Stream::Writer.new output_socket
begin
  bytes_written = writer.write_nonblock "sample string"
  # handle "bytes_written"
rescue IO::WaitWritable
  # handle wait
ensure
  writer.close
end

reader = ZSTDS::Stream::Reader.new input_socket
begin
  puts reader.read_nonblock(512)
rescue IO::WaitReadable
  # handle wait
rescue ::EOFError
  # handle eof
ensure
  reader.close
end

You can create dictionary using ZSTDS::Dictionary.

require "securerandom"
require "zstds"

samples = (Array.new(8) { ::SecureRandom.random_bytes(1 << 8) } + ["sample string"]).shuffle

dictionary = ZSTDS::Dictionary.train samples
File.write "dictionary.bin", dictionary.buffer, :mode => "wb"

dictionary_buffer = File.read "dictionary.bin", :mode => "rb"
dictionary        = ZSTDS::Dictionary.new dictionary_buffer

data = ZSTDS::String.compress "sample string", :dictionary => dictionary
puts ZSTDS::String.decompress(data, :dictionary => dictionary)

You can create and read tar.zst archives with minitar.

require "zstds"
require "minitar"

ZSTDS::Stream::Writer.open "file.tar.zst" do |writer|
  Minitar::Writer.open writer do |tar|
    tar.add_file_simple "file", :data => "sample string"
  end
end

ZSTDS::Stream::Reader.open "file.tar.zst" do |reader|
  Minitar::Reader.open reader do |tar|
    tar.each_entry do |entry|
      puts entry.name
      puts entry.read
    end
  end
end

You can also use Content-Encoding: zstd with sinatra:

require "zstds"
require "sinatra"

get "/" do
  headers["Content-Encoding"] = "zstd"
  ZSTDS::String.compress "sample string"
end

All functionality (including streaming) can be used inside multiple threads with parallel. This code will provide heavy load for your CPU.

require "zstds"
require "parallel"

Parallel.each large_datas do |large_data|
  ZSTDS::String.compress large_data
end

Options

Option	Values	Default	Description
source_buffer_length	0 - inf	0 (auto)	internal buffer length for source data
destination_buffer_length	0 - inf	0 (auto)	internal buffer length for description data
gvl	true/false	false	enables global VM lock where possible
compression_level	-131072 - 22	0 (auto)	compression level
window_log	10 - 31	0 (auto)	maximum back-reference distance (power of 2)
hash_log	6 - 30	0 (auto)	size of the initial probe table (power of 2)
chain_log	6 - 30	0 (auto)	size of the multi-probe search table (power of 2)
search_log	1 - 30	0 (auto)	number of search attempts (power of 2)
min_match	3 - 7	0 (auto)	minimum size of searched matches
target_length	0 - 131072	0 (auto)	distance between match sampling (for :fast strategy), length of match considered "good enough" for (for other strategies)
strategy	STRATEGIES	nil (auto)	choses strategy
enable_long_distance_matching	true/false	nil (auto)	enables long distance matching
ldm_hash_log	6 - 30	0 (auto)	size of the table for long distance matching (power of 2)
ldm_min_match	4 - 4096	0 (auto)	minimum match size for long distance matcher
ldm_bucket_size_log	1 - 8	0 (auto)	log size of each bucket in the LDM hash table for collision resolution
ldm_hash_rate_log	0 - 25	0 (auto)	frequency of inserting/looking up entries into the LDM hash table
content_size_flag	true/false	true	enables writing of content size into frame header (if known)
checksum_flag	true/false	false	enables writing of 32-bits checksum of content at end of frame
dict_id_flag	true/false	true	enables writing of dictionary id into frame header
nb_workers	0 - 200	0 (auto)	number of threads spawned in parallel
job_size	0 - 1073741824	0 (auto)	size of job (nb_workers >= 1)
overlap_log	0 - 9	0 (auto)	overlap size, as a fraction of window size
window_log_max	10 - 31	0 (auto)	size limit (power of 2)
dictionary	Dictionary	nil	chose dictionary
pledged_size	0 - inf	0 (auto)	size of input (if known)

There are internal buffers for compressed and decompressed data. For example you want to use 1 KB as source_buffer_length for compressor - please use 256 B as destination_buffer_length. You want to use 256 B as source_buffer_length for decompressor - please use 1 KB as destination_buffer_length.

gvl is disabled by default, this mode allows running multiple compressors/decompressors in different threads simultaneously. Please consider enabling gvl if you don't want to launch processors in separate threads. If gvl is enabled ruby won't waste time on acquiring/releasing VM lock.

String and File will set :pledged_size automaticaly.

You can also read zstd docs for more info about options.

Option	Related constants
compression_level	ZSTDS::Option::MIN_COMPRESSION_LEVEL = -131072, ZSTDS::Option::MAX_COMPRESSION_LEVEL = 22
window_log	ZSTDS::Option::MIN_WINDOW_LOG = 10, ZSTDS::Option::MAX_WINDOW_LOG = 31
hash_log	ZSTDS::Option::MIN_HASH_LOG = 6, ZSTDS::Option::MAX_HASH_LOG = 30
chain_log	ZSTDS::Option::MIN_CHAIN_LOG = 6, ZSTDS::Option::MAX_CHAIN_LOG = 30
search_log	ZSTDS::Option::MIN_SEARCH_LOG = 1, ZSTDS::Option::MAX_SEARCH_LOG = 30
min_match	ZSTDS::Option::MIN_MIN_MATCH = 3, ZSTDS::Option::MAX_MIN_MATCH = 7
target_length	ZSTDS::Option::MIN_TARGET_LENGTH = 0, ZSTDS::Option::MAX_TARGET_LENGTH = 131072
strategy	ZSTDS::Option::STRATEGIES = %i[fast dfast greedy lazy lazy2 btlazy2 btopt btultra btultra2]
ldm_hash_log	ZSTDS::Option::MIN_LDM_HASH_LOG = 6, ZSTDS::Option::MAX_LDM_HASH_LOG = 30
ldm_min_match	ZSTDS::Option::MIN_LDM_MIN_MATCH = 4, ZSTDS::Option::MAX_LDM_MIN_MATCH = 4096
ldm_bucket_size_log	ZSTDS::Option::MIN_LDM_BUCKET_SIZE_LOG = 1, ZSTDS::Option::MAX_LDM_BUCKET_SIZE_LOG = 8
ldm_hash_rate_log	ZSTDS::Option::MIN_LDM_HASH_RATE_LOG = 0, ZSTDS::Option::MAX_LDM_HASH_RATE_LOG = 25
nb_workers	ZSTDS::Option::MIN_NB_WORKERS = 0, ZSTDS::Option::MAX_NB_WORKERS = 200
job_size	ZSTDS::Option::MIN_JOB_SIZE = 0, ZSTDS::Option::MAX_JOB_SIZE = 1073741824
overlap_log	ZSTDS::Option::MIN_OVERLAP_LOG = 0, ZSTDS::Option::MAX_OVERLAP_LOG = 9
window_log_max	ZSTDS::Option::MIN_WINDOW_LOG_MAX = 10, ZSTDS::Option::MAX_WINDOW_LOG_MAX = 31

Possible compressor options:

:source_buffer_length
:destination_buffer_length
:gvl
:compression_level
:window_log
:hash_log
:chain_log
:search_log
:min_match
:target_length
:strategy
:enable_long_distance_matching
:ldm_hash_log
:ldm_min_match
:ldm_bucket_size_log
:ldm_hash_rate_log
:content_size_flag
:checksum_flag
:dict_id_flag
:nb_workers
:job_size
:overlap_log
:dictionary
:pledged_size

Possible decompressor options:

:source_buffer_length
:destination_buffer_length
:gvl
:window_log_max
:dictionary

Example:

require "zstds"

data = ZSTDS::String.compress "sample string", :compression_level => 5
puts ZSTDS::String.decompress(data, :window_log_max => 11)

String

String maintains destination buffer only, so it accepts destination_buffer_length option only.

::compress(source, options = {})
::decompress(source, options = {})

source is a source string.

File

File maintains both source and destination buffers, it accepts both source_buffer_length and destination_buffer_length options.

::compress(source, destination, options = {})
::decompress(source, destination, options = {})

source and destination are file pathes.

Stream::Writer

Its behaviour is similar to builtin Zlib::GzipWriter.

Writer maintains destination buffer only, so it accepts destination_buffer_length option only.

::open(file_path, options = {}, :external_encoding => nil, :transcode_options => {}, &block)

Open file path and create stream writer associated with opened file. Data will be transcoded to :external_encoding using :transcode_options before compressing.

It may be tricky to use both :pledged_size and :transcode_options. You have to provide size of transcoded input.

::new(destination_io, options = {}, :external_encoding => nil, :transcode_options => {})

Create stream writer associated with destination io. Data will be transcoded to :external_encoding using :transcode_options before compressing.

It may be tricky to use both :pledged_size and :transcode_options. You have to provide size of transcoded input.

#set_encoding(external_encoding, nil, transcode_options)

Set another encodings, nil is just for compatibility with IO.

#io
#to_io
#stat
#external_encoding
#transcode_options
#pos
#tell

See IO docs.

#write(*objects)
#flush
#rewind
#close
#closed?

See Zlib::GzipWriter docs.

#write_nonblock(object, *options)
#flush_nonblock(*options)
#rewind_nonblock(*options)
#close_nonblock(*options)

Special asynchronous methods missing in Zlib::GzipWriter. rewind wants to close, close wants to write something and flush, flush want to write something. So it is possible to have asynchronous variants for these synchronous methods. Behaviour is the same as IO#write_nonblock method.

All nonblock operations for file will raise EBADF error on Windows. Setting file into nonblocking mode is not available on Windows.

#<<(object)
#print(*objects)
#printf(*args)
#putc(object, encoding: ::Encoding::BINARY)
#puts(*objects)

Typical helpers, see Zlib::GzipWriter docs.

Stream::Reader

Its behaviour is similar to builtin Zlib::GzipReader.

Reader maintains both source and destination buffers, it accepts both source_buffer_length and destination_buffer_length options.

::open(file_path, options = {}, :external_encoding => nil, :internal_encoding => nil, :transcode_options => {}, &block)

Open file path and create stream reader associated with opened file. Data will be force encoded to :external_encoding and transcoded to :internal_encoding using :transcode_options after decompressing.

::new(source_io, options = {}, :external_encoding => nil, :internal_encoding => nil, :transcode_options => {})

Create stream reader associated with source io. Data will be force encoded to :external_encoding and transcoded to :internal_encoding using :transcode_options after decompressing.

#set_encoding(external_encoding, internal_encoding, transcode_options)

Set another encodings.

#io
#to_io
#stat
#external_encoding
#internal_encoding
#transcode_options
#pos
#tell

See IO docs.

#read(bytes_to_read = nil, out_buffer = nil)
#eof?
#rewind
#close
#closed?

See Zlib::GzipReader docs.

#readpartial(bytes_to_read = nil, out_buffer = nil)
#read_nonblock(bytes_to_read, out_buffer = nil, *options)

See IO docs.

#getbyte
#each_byte(&block)
#readbyte
#ungetbyte(byte)

#getc
#readchar
#each_char(&block)
#ungetc(char)

#lineno
#lineno=
#gets(separator = $OUTPUT_RECORD_SEPARATOR, limit = nil)
#readline
#readlines
#each(&block)
#each_line(&block)
#ungetline(line)

Typical helpers, see Zlib::GzipReader docs.

Dictionary

You can train dictionary from samples using train class method.

::train(samples, :capacity => 0)

Please review zstd code before using it. There are many validation requirements and it changes between versions.

#buffer

There is an attribute reader for buffer. You can use it to store dictionary somewhere.

::new(buffer)

Please use regular constructor to create dictionary from buffer.

#id

Read dictionary id from buffer.

Thread safety

:gvl option is disabled by default, you can use bindings effectively in multiple threads. Please be careful: bindings are not thread safe. You should lock all shared data between threads.

For example: you should not use same compressor/decompressor inside multiple threads. Please verify that you are using each processor inside single thread at the same time.

Operating systems

GNU/Linux, FreeBSD, OSX, Windows (MinGW).

CI

Please visit scripts/test-images. See universal test script scripts/ci_test.sh for CI.

License

MIT license, see LICENSE and AUTHORS.