FFmpeg
 All Data Structures Namespaces Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
tree.h
Go to the documentation of this file.
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
60  * exists in the tree.
61  */
62 void *av_tree_find(const struct AVTreeNode *root, void *key,
63  int (*cmp)(void *key, const void *b), void *next[2]);
64 
65 /**
66  * Insert or remove an element.
67  *
68  * If *next is NULL, then the supplied element will be removed if it exists.
69  * If *next is non-NULL, then the supplied element will be inserted, unless
70  * it already exists in the tree.
71  *
72  * @param rootp A pointer to a pointer to the root node of the tree; note that
73  * the root node can change during insertions, this is required
74  * to keep the tree balanced.
75  * @param key pointer to the element key to insert in the tree
76  * @param next Used to allocate and free AVTreeNodes. For insertion the user
77  * must set it to an allocated and zeroed object of at least
78  * av_tree_node_size bytes size. av_tree_insert() will set it to
79  * NULL if it has been consumed.
80  * For deleting elements *next is set to NULL by the user and
81  * av_tree_insert() will set it to the AVTreeNode which was
82  * used for the removed element.
83  * This allows the use of flat arrays, which have
84  * lower overhead compared to many malloced elements.
85  * You might want to define a function like:
86  * @code
87  * void *tree_insert(struct AVTreeNode **rootp, void *key,
88  * int (*cmp)(void *key, const void *b),
89  * AVTreeNode **next)
90  * {
91  * if (!*next)
92  * *next = av_mallocz(av_tree_node_size);
93  * return av_tree_insert(rootp, key, cmp, next);
94  * }
95  * void *tree_remove(struct AVTreeNode **rootp, void *key,
96  * int (*cmp)(void *key, const void *b, AVTreeNode **next))
97  * {
98  * av_freep(next);
99  * return av_tree_insert(rootp, key, cmp, next);
100  * }
101  * @endcode
102  * @param cmp compare function used to compare elements in the tree
103  * @return If no insertion happened, the found element; if an insertion or
104  * removal happened, then either key or NULL will be returned.
105  * Which one it is depends on the tree state and the implementation. You
106  * should make no assumptions that it's one or the other in the code.
107  */
108 void *av_tree_insert(struct AVTreeNode **rootp, void *key,
109  int (*cmp)(void *key, const void *b),
110  struct AVTreeNode **next);
111 
112 void av_tree_destroy(struct AVTreeNode *t);
113 
114 /**
115  * Apply enu(opaque, &elem) to all the elements in the tree in a given range.
116  *
117  * @param cmp a comparison function that returns < 0 for a element below the
118  * range, > 0 for a element above the range and == 0 for a
119  * element inside the range
120  *
121  * @note The cmp function should use the same ordering used to construct the
122  * tree.
123  */
124 void av_tree_enumerate(struct AVTreeNode *t, void *opaque,
125  int (*cmp)(void *opaque, void *elem),
126  int (*enu)(void *opaque, void *elem));
127 
128 /**
129  * @}
130  */
131 
132 #endif /* AVUTIL_TREE_H */