*
     * @param writer
     *            ライター
     * @return ラップされたライター
     */
    protected static Writer wrap(final Writer writer) {
        if (writer instanceof BufferedWriter) {
            return writer;
        }
        if (writer instanceof StringWriter) {
            return writer;
        }
        return new BufferedWriter(writer, DEFAULT_BUF_SIZE);
    }