/*
 * call-seq:
 *  encode_special_chars(string)
 *
 * Encode any special characters in +string+
 */
static VALUE encode_special_chars(VALUE self, VALUE string)
{
  xmlNodePtr node;
  xmlChar *encoded;
  VALUE encoded_str;

  Data_Get_Struct(self, xmlNode, node);
  encoded = xmlEncodeSpecialChars(
      node->doc,
      (const xmlChar *)StringValuePtr(string)
  );

  encoded_str = NOKOGIRI_STR_NEW2(encoded);
  xmlFree(encoded);

  return encoded_str;
}