public static void appendHexChar(StringBuilder s, String src) {
		int n = src.length();
		for (int i = 0; i < n; ++i) {
			char c = src.charAt(i);
			if ((c >= '0' && c <= '9') || (c >= 'a' && c <= 'f')) {
				s.append(c);
			} else if (c >= 'A' && c <= 'F') {
				s.append((char) ((int) c + 32));
			}
		}
	}