code: func (r *Rar) Open(in io.Reader, size int64) error {
  	if r.rr != nil {
  		return fmt.Errorf("rar archive is already open for reading")
  	}
  	var err error
  	r.rr, err = rardecode.NewReader(in, r.Password)
  	return err
  }
docs: // Open opens t for reading an archive from
  // in. The size parameter is not used.