diff options
-rw-r--r-- | libavutil/tree.h | 24 |
1 files changed, 18 insertions, 6 deletions
diff --git a/libavutil/tree.h b/libavutil/tree.h index d801a4e028..9450d96653 100644 --- a/libavutil/tree.h +++ b/libavutil/tree.h @@ -42,23 +42,35 @@ extern const int av_tree_node_size; void *av_tree_find(const struct AVTreeNode *root, void *key, int (*cmp)(void *key, const void *b), void *next[2]); /** - * Finds a element for which cmp(key, elem)==0, if no such element is found key - * is inserted into the tree. + * Inserts or removes an element. + * If *next is NULL then the element supplied will be removed, if no such + * element exists behavior is undefined. + * If *next is not NULL then the element supplied will be inserted, unless + * it already exists in the tree. * @param rootp A pointer to a pointer to the root node of the tree. Note that * the root node can change during insertions, this is required * to keep the tree balanced. - * @param next AVTreeNode used for the inserted element, must be allocated and - * zeroed by the user. And will be set to NULL if used by - * av_tree_insert(). This allows the use of flat arrays, which have + * @param next Used to allocate and free AVTreeNodes. For insertion the user + * must set it to an allocated and zeroed object of at least + * av_tree_node_size bytes size. av_tree_insert() will set it to + * NULL if it has been consumed. + * For deleting elements *next is set to NULL by the user and + * av_tree_node_size() will set it to the AVTreeNode which was + * used for the removed element. + * This allows the use of flat arrays, which have * lower overhead compared to many malloced elements. * You might want to define a function like: * void *tree_insert(struct AVTreeNode **rootp, void *key, int (*cmp)(void *key, const void *b), AVTreeNode **next){ * if(!*next) *next= av_mallocz(av_tree_node_size); * return av_tree_insert(rootp, key, cmp, next); * } + * void *tree_remove(struct AVTreeNode **rootp, void *key, int (*cmp)(void *key, const void *b, AVTreeNode **next)){ + * if(*next) av_freep(next); + * return av_tree_insert(rootp, key, cmp, next); + * } * * @return If no insertion happened, the found element. - * If an insertion happened, then either key or NULL will be returned. + * If an insertion or removial happened, then either key or NULL will be returned. * Which one it is depends on the tree state and the implementation. You * should make no assumptions that it's one or the other in the code. */ |