def result = new StringBuilder()
        reader.readNextLine(result)
        result.toString() == ""

        result.setLength(0)
        reader.readNextLine(result)
        result.toString() == "line 1"

        result.setLength(0)
        reader.readNextLine(result)
        result.toString() == ""


        result.setLength(0)
        reader.readNextLine(result)
        result.toString() == "line 2"

     *
     * @return true if next line is available (possibly empty), false when end of stream reached.
     */
    public boolean readNextLine(Appendable buffer) throws IOException {
        int ch;
        boolean read = false;
        while ((ch = read()) >= 0) {
            if (ch == '\n') {
                return true;
            }

        PreprocessingReader lineReader = new PreprocessingReader(reader);
        Buffer buffer = new Buffer();
        while (true) {
            buffer.reset();
            if (!lineReader.readNextLine(buffer.value)) {
                break;
            }
            buffer.consumeWhitespace();
            if (!buffer.consume('#')) {
                continue;
            }
            buffer.consumeWhitespace();