Revision efbaf4de libavutil/tree.h

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

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