-size_t btr_get_input_queue_size(struct btr_node *btrn);
-size_t btr_get_output_queue_size(struct btr_node *btrn);
-bool btr_no_parent(struct btr_node *btrn);
-size_t btr_next_buffer(struct btr_node *btrn, char **bufp);
-size_t btr_next_buffer_omit(struct btr_node *btrn, size_t omit, char **bufp);
+void btr_add_output_dont_free(const char *buf, size_t size, struct btr_node *btrn);
+size_t btr_get_input_queue_size(const struct btr_node *btrn);
+size_t btr_get_output_queue_size(const struct btr_node *btrn);
+bool btr_no_parent(const struct btr_node *btrn);
+size_t btr_next_buffer(const struct btr_node *btrn, char **bufp);
+size_t btr_next_buffer_omit(const struct btr_node *btrn, size_t omit,
+ char **bufp);