static String htmlencode(Object o) {
  ret htmlencode(str(o));
}

static String htmlencode(String s) {
  if (s == null) ret "";
  StringBuilder out = new StringBuilder(Math.max(16, s.length()));
  for (int i = 0; i < s.length(); i++) {
    char c = s.charAt(i);
    if (c > 127 || c == '"' || c == '<' || c == '>' || c == '&') {
      int cp = s.codePointAt(i);
      out.append("&#x");
      out.append(intToHex_flexLength(cp));
      out.append(';');
      i += Character.charCount(cp)-1;
    } else
      out.append(c);
  }
  ret out.toString();
}