Programming language: Crystal
License: MIT License
Tags: Networking    
Latest version: v0.3.3

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An optimised IRC parsing library for crystal. Supports IRCv3 message tags. Getting started is as easy as FastIRC.parse(io) do |message|.

Fast_irc doesn't attempt to deal with the semantics of IRC messages. Messages are simply parsed into a machine-readable format and delivered to the user.


Here fast_irc was tested parsing a 63748 byte IRC log file collected from real IRC activity on the esper.net IRC network. Fast_irc's performance on a single core averaged over 150MB/s, taking only 740 nanoseconds to parse a single line.

In terms of memory performance, a single 8192 byte buffer is allocated per connection. All string values in the IRC prefix, the IRC command, and IRCv3 tag keys are interned in a global string pool to save memory. IRCv3 message tag values and IRC command parameters are not interned.


Add it to shard.yml

    github: RX14/fast_irc.cr
    version: 0.3.3


Build the documentation by cloning this repo and running crystal doc. HTML documentation will be placed in doc/.


It's easy to get started parsing IRC connections right away using fast_irc. Just pass an IO (likely a TCP connection to an IRC server) to FastIRC.parse. Message objects are yielded as they arrive on the connection. For a non-block way to read messages, see FastIRC::Reader.

FastIRC.parse(io) do |message|
  message.command       # => "PRIVMSG" : String
  message.params        # => ["#crystal-lang", "Test message using fast_irc.cr!"] : Array(String)?
  message.prefix.source # => "RX14" : String

Generating IRC is just as easy. Create your Message object and call to_s.

FastIRC::Message.new("PRIVMSG", ["#WAMM", "test message"]).to_s(io)

You can also add IRCv3 tags and a prefix. FastIRC::Tags is simply an alias for Hash(String, String?). It is recommended to use the FastIRC::Tags alias when creating tags hashes both to clear intent, and to make sure that you don't end up with a Hash(String, String) instead, which is a binary-incompatible type.

prefix = FastIRC::Prefix.new(source: "RX14", user: "rx14", host: "rx14.co.uk")
tags = FastIRC::Tags{"time" => "2016-11-11T22:27:15Z"}
FastIRC::Message.new("PRIVMSG", ["#WAMM", "test message"], prefix: prefix, tags: tags).to_s(io)


  1. Fork it ( https://github.com/RX14/fast_irc/fork )
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create a new Pull Request


  • RX14 Stephanie Wilde-Hobbs - creator, maintainer
  • Kilobyte22 Stephan Henrichs - IRC serialisation, specs