Unblocking the keyboard in EventMachine

demo.rb

#!/usr/bin/env ruby -wW1
require File.expand_path("../nb-keyboard", __FILE__)

EM.run {
  spinner = EventMachine::PeriodicTimer.new(0.5) do
    $stderr.print "."
  end

  Fiber.new {
    EM.open_keyboard(NbKeyboard) do |kb|
      inp = Readline.readline("enter something ")
      $stderr.puts "you entered: #{inp.inspect}"
      EM::Timer.new(0.75) { EM.stop }
    end
  }.resume
}

nb-keyboard.rb

# doesn't work with Stdlib Readline
require 'rb-readline'

require 'fiber'
require 'eventmachine'

module NbKeyboard
  def post_init
    @ostdin = $stdin
    $stdin  = self
    @buffer = ""
  end

  def receive_data(d)
    @buffer << d
    @waiting && @waiting[:cnt] <= @buffer.length && @waiting[:fiber].resume
  end

  def read(cnt)
    if @buffer.length < cnt
      @waiting = {:cnt => cnt, :fiber => Fiber.current}
      Fiber.yield
    end
    data, @buffer = @buffer[0...cnt], @buffer[cnt..-1]
    data
  end

  def unbind
    $stdin = @ostdin
  end

  def method_missing(meth, *args, &blk)
    @ostdin.send(meth, *args, &blk)
  end
end