private static CharBuffer grow(CharBuffer buf) {
    char[] copy = Arrays.copyOf(buf.array(), buf.capacity() * 2);
    CharBuffer bigger = CharBuffer.wrap(copy);
    Java8Compatibility.position(bigger, buf.position());
    Java8Compatibility.limit(bigger, buf.limit());
    return bigger;
  }

  /** Handle the case of underflow caused by needing more input characters. */
  private void readMoreChars() throws IOException {