extern void *afb_session_get_cookie(struct afb_session *session, const void *key);
extern void *afb_session_cookie(struct afb_session *session, const void *key, void *(*makecb)(void *closure), void (*freecb)(void *item), void *closure, int replace);
extern void *afb_session_get_cookie(struct afb_session *session, const void *key);
extern void *afb_session_cookie(struct afb_session *session, const void *key, void *(*makecb)(void *closure), void (*freecb)(void *item), void *closure, int replace);