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Document node removial API. 

Originally committed as revision 11402 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Michael Niedermayer 2008-01-04 18:46:53 +00:00
parent d5cb5fe86b
commit efbaf4deee
1 changed files with 18 additions and 6 deletions
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24
libavutil/tree.h
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@ -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]); 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 * Inserts or removes an element.
* is inserted into the tree. * 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 * @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 * the root node can change during insertions, this is required
* to keep the tree balanced. * to keep the tree balanced.
* @param next AVTreeNode used for the inserted element, must be allocated and * @param next Used to allocate and free AVTreeNodes. For insertion the user
* zeroed by the user. And will be set to NULL if used by * must set it to an allocated and zeroed object of at least
* av_tree_insert(). This allows the use of flat arrays, which have * 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. * lower overhead compared to many malloced elements.
* You might want to define a function like: * 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){ * 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); * if(!*next) *next= av_mallocz(av_tree_node_size);
* return av_tree_insert(rootp, key, cmp, next); * 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. * @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 * 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. * should make no assumptions that it's one or the other in the code.
*/ */