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83 lines
3.8 KiB
C
83 lines
3.8 KiB
C
/*
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* copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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/**
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* @file tree.h
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* A tree container.
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* Insertion, Removial, Finding equal, largest which is smaller than and
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* smallest which is larger than all have O(log n) worst case time.
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* @author Michael Niedermayer <michaelni@gmx.at>
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*/
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#ifndef FFMPEG_TREE_H
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#define FFMPEG_TREE_H
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struct AVTreeNode;
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extern const int av_tree_node_size;
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/**
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* Finds an element.
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* @param root a pointer to the root node of the tree
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* @param next If next is not NULL then next[0] will contain the previous
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* element and next[1] the next element if either does not exist
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* then the corresponding entry in next is unchanged.
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* @return An element with cmp(key, elem)==0 or NULL if no such element exists in
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* the tree.
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*/
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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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* 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 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 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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void *av_tree_insert(struct AVTreeNode **rootp, void *key, int (*cmp)(void *key, const void *b), struct AVTreeNode **next);
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void av_tree_destroy(struct AVTreeNode *t);
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#endif /* FFMPEG_TREE_H */
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