/**
 * Get the application identifier of the client application for the
 * request 'req'.
 *
 * Returns the application identifier or NULL when the application
 * can not be identified.
 *
 * The returned value if not NULL must be freed by the caller
 *
 * @param req the request
 *
 * @return the string for the application id of the client MUST BE FREED
 */
static inline
char *afb_req_x2_get_application_id(                                                                                                                                                                                                                                                                                         
            struct afb_req_x2 *req)
{
    return req->itf->get_application_id(req);
}