X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=libavutil%2Ftree.h;h=e96d1fa12e5ab7c49ab58656864db69d0e1e1f31;hb=4b2be143cd5ab216c6a7ebd8715b732169077e5d;hp=146d35d56ecbcf7a5957386856f36279eb5c8d18;hpb=5b21bdabe43611385d1d55a21d5b1f607b133d29;p=ffmpeg

diff --git a/libavutil/tree.h b/libavutil/tree.h
index 146d35d56ec..e96d1fa12e5 100644
--- a/libavutil/tree.h
+++ b/libavutil/tree.h
@@ -19,21 +19,24 @@
  */
 
 /**
- * @file 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 FFMPEG_TREE_H
-#define FFMPEG_TREE_H
+#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 does not exist
+ * @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.
@@ -41,18 +44,39 @@ struct AVTreeNode;
 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 that
+ * 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.
- *
- * @return If no insertion happened, the found element.
- *         If an insertion happened, then either key or NULL will be returned.
+ * @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:
+ *             @code
+ *             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);
+ *             }
+ *             @endcode
+ * @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 /* FFMPEG_TREE_H */
+#endif /* AVUTIL_TREE_H */