public function __construct($key_, $name_, Io_Charset $charset_ = null)
 {
     parent::__construct($key_, $name_);
     if (null === $charset_) {
         $charset_ = Io_Charset::defaultCharset();
     }
     $this->m_charset = $charset_;
 }
 /**
  * @return \Components\Io_Charset
  */
 public function getCharset()
 {
     if ($mimeType = $this->getMimetype()) {
         return $mimeType->charset();
     }
     return Io_Charset::defaultCharset();
 }