--- close_read

    ɤ߹Ѥ IO  close ޤ˥ѥפɤ߽ξѤ˺
     IO ֥ȤǻѤޤ

    self ɤ߹Ѥ˥ץ󤵤ƤʤС㳰 
    IOError ȯޤ

    nil ֤ޤ

