# File lib/zip/zip_file.rb, line 279
    def mkdir(entryName, permissionInt = 0755)
      if find_entry(entryName)
        raise Errno::EEXIST, "File exists - #{entryName}"
      end
      entryName = entryName.dup.to_s
      entryName << '/' unless entryName.end_with?('/')
      @entrySet << ZipStreamableDirectory.new(@name, entryName, nil, permissionInt)
    end