void xbt_swag_free(xbt_swag_t swag);
void xbt_swag_init(xbt_swag_t swag, size_t offset);
void xbt_swag_insert(void *obj, xbt_swag_t swag);
+void xbt_swag_insert_at_head(void *obj, xbt_swag_t swag);
+void xbt_swag_insert_at_tail(void *obj, xbt_swag_t swag);
void *xbt_swag_remove(void *obj, xbt_swag_t swag);
void *xbt_swag_extract(xbt_swag_t swag);
int xbt_swag_size(xbt_swag_t swag);