* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
-#ifndef TREE_H
-#define TREE_H
+/**
+ * @file libavutil/tree.h
+ * A tree container.
+ * Insertion, removal, finding equal, largest which is smaller than and
+ * smallest which is larger than, all have O(log n) worst case complexity.
+ * @author Michael Niedermayer <michaelni@gmx.at>
+ */
+
+#ifndef AVUTIL_TREE_H
+#define AVUTIL_TREE_H
struct AVTreeNode;
+extern const int av_tree_node_size;
/**
* Finds an element.
* @param root a pointer to the root node of the tree
- * @param next if next is not NULL then next[0] will contain the previous element and
- * next[1] the next element if either doesnt exist then the corresponding
- * entry in next is unchanged
- * @return an element with cmp(key, elem)==0 or NULL if no such element exists in
- * the tree
+ * @param next If next is not NULL, then next[0] will contain the previous
+ * element and next[1] the next element. If either does not exist,
+ * then the corresponding entry in next is unchanged.
+ * @return An element with cmp(key, elem)==0 or NULL if no such element exists in
+ * the tree.
*/
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.
- * @param rootp a pointer to a pointer to the root node of the tree note the
- * root node can change during insertions, this is required to
- * keep the tree balanced
+ * Inserts or removes an element.
+ * If *next is NULL, then the supplied element will be removed if it exists.
+ * If *next is not NULL, then the supplied element 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 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 a insertion happened, then either key or NULL is returned (which it is
- * depends on the tree state and the implemenattion, you should make no
- * asumtations that its one or the other in code)
+ * @return If no insertion happened, the found element; if an insertion or
+ * removal 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.
*/
-void *av_tree_insert(struct AVTreeNode **rootp, void *key, int (*cmp)(void *key, const void *b));
+void *av_tree_insert(struct AVTreeNode **rootp, void *key, int (*cmp)(void *key, const void *b), struct AVTreeNode **next);
void av_tree_destroy(struct AVTreeNode *t);
-#endif /* TREE_H */
+#endif /* AVUTIL_TREE_H */