readline_nonblock.rb

class IO
  def readline_nonblock(length)
    eoferror = nil
    begin
      data = read_nonblock(length)
    rescue Errno::EAGAIN, Errno::EWOULDBLOCK => e
    rescue EOFError => e
      eoferror = e
    end
    if not data.nil?
      if @readline_nonblock_buf.nil?
        @readline_nonblock_buf = data
      else
        @readline_nonblock_buf += data
      end
    end
    if @readline_nonblock_buf.nil?
      if not eoferror.nil?
        raise eoferror
      else
        raise Errno::EAGAIN
      end
    else
      pos = @readline_nonblock_buf.index($/)
      if pos.nil?
        if not eoferror.nil?
          return_value = @readline_nonblock_buf
          @readline_nonblock_buf = nil
        else
          raise Errno::EAGAIN
        end
      else
        return_value = @readline_nonblock_buf[0..(pos - 1)]
        @readline_nonblock_buf = @readline_nonblock_buf[(pos + 1)..-1]
      end
      return_value
    end
  end
end