user_obj = lu_find_user_obj (user_class, vl);
if (user_obj == NULL)
{
/* call lookup_class_callback_t() and insert into the list of user objects. */
user_obj = lu_create_user_obj (obj, ds, vl, user_class);
user_obj = lu_find_user_obj (user_class, vl);
if (user_obj == NULL)
{
/* call lookup_class_callback_t() and insert into the list of user objects. */
user_obj = lu_create_user_obj (obj, ds, vl, user_class);