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tree.h
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1 /*
2  * copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
3  *
4  * This file is part of FFmpeg.
5  *
6  * FFmpeg is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU Lesser General Public
8  * License as published by the Free Software Foundation; either
9  * version 2.1 of the License, or (at your option) any later version.
10  *
11  * FFmpeg is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14  * Lesser General Public License for more details.
15  *
16  * You should have received a copy of the GNU Lesser General Public
17  * License along with FFmpeg; if not, write to the Free Software
18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19  */
20 
21 /**
22  * @file
23  * A tree container.
24  * @author Michael Niedermayer <michaelni@gmx.at>
25  */
26 
27 #ifndef AVUTIL_TREE_H
28 #define AVUTIL_TREE_H
29 
30 #include "attributes.h"
31 #include "version.h"
32 
33 /**
34  * @addtogroup lavu_tree AVTree
35  * @ingroup lavu_data
36  *
37  * Low complexity tree container
38  *
39  * Insertion, removal, finding equal, largest which is smaller than and
40  * smallest which is larger than, all have O(log n) worst case complexity.
41  * @{
42  */
43 
44 
45 struct AVTreeNode;
46 extern const int av_tree_node_size;
47 
48 /**
49  * Allocate an AVTreeNode.
50  */
51 struct AVTreeNode *av_tree_node_alloc(void);
52 
53 /**
54  * Find an element.
55  * @param root a pointer to the root node of the tree
56  * @param next If next is not NULL, then next[0] will contain the previous
57  * element and next[1] the next element. If either does not exist,
58  * then the corresponding entry in next is unchanged.
59  * @return An element with cmp(key, elem)==0 or NULL if no such element exists in
60  * the tree.
61  */
62 void *av_tree_find(const struct AVTreeNode *root, void *key, int (*cmp)(void *key, const void *b), void *next[2]);
63 
64 /**
65  * Insert or remove an element.
66  *
67  * If *next is NULL, then the supplied element will be removed if it exists.
68  * If *next is non-NULL, then the supplied element will be inserted, unless
69  * it already exists in the tree.
70  *
71  * @param rootp A pointer to a pointer to the root node of the tree; note that
72  * the root node can change during insertions, this is required
73  * to keep the tree balanced.
74  * @param key pointer to the element key to insert in the tree
75  * @param next Used to allocate and free AVTreeNodes. For insertion the user
76  * must set it to an allocated and zeroed object of at least
77  * av_tree_node_size bytes size. av_tree_insert() will set it to
78  * NULL if it has been consumed.
79  * For deleting elements *next is set to NULL by the user and
80  * av_tree_insert() will set it to the AVTreeNode which was
81  * used for the removed element.
82  * This allows the use of flat arrays, which have
83  * lower overhead compared to many malloced elements.
84  * You might want to define a function like:
85  * @code
86  * void *tree_insert(struct AVTreeNode **rootp, void *key, int (*cmp)(void *key, const void *b), AVTreeNode **next){
87  * if(!*next) *next= av_mallocz(av_tree_node_size);
88  * return av_tree_insert(rootp, key, cmp, next);
89  * }
90  * void *tree_remove(struct AVTreeNode **rootp, void *key, int (*cmp)(void *key, const void *b, AVTreeNode **next)){
91  * av_freep(next);
92  * return av_tree_insert(rootp, key, cmp, next);
93  * }
94  * @endcode
95  * @param cmp compare function used to compare elements in the tree
96  * @return If no insertion happened, the found element; if an insertion or
97  * removal happened, then either key or NULL will be returned.
98  * Which one it is depends on the tree state and the implementation. You
99  * should make no assumptions that it's one or the other in the code.
100  */
101 void *av_tree_insert(struct AVTreeNode **rootp, void *key, int (*cmp)(void *key, const void *b), struct AVTreeNode **next);
102 void av_tree_destroy(struct AVTreeNode *t);
103 
104 /**
105  * Apply enu(opaque, &elem) to all the elements in the tree in a given range.
106  *
107  * @param cmp a comparison function that returns < 0 for a element below the
108  * range, > 0 for a element above the range and == 0 for a
109  * element inside the range
110  *
111  * @note The cmp function should use the same ordering used to construct the
112  * tree.
113  */
114 void av_tree_enumerate(struct AVTreeNode *t, void *opaque, int (*cmp)(void *opaque, void *elem), int (*enu)(void *opaque, void *elem));
115 
116 /**
117  * @}
118  */
119 
120 #endif /* AVUTIL_TREE_H */