readline_nonblock.rb

module ReadlineNonblock
  def readline_nonblock
    @readline_nonblock_buf ||= ""
    until @readline_nonblock_buf[-1] == "\n"
      # read_nonblock may raise e.g. IO::WaitReadable, or EOFError
      @readline_nonblock_buf << read_nonblock(1)
    end

    complete_line = @readline_nonblock_buf
    @readline_nonblock_buf = ""

    return complete_line
  end
end

::IO.include ReadlineNonblock