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 
32 /**
33  * @addtogroup lavu_tree AVTree
34  * @ingroup lavu_data
35  *
36  * Low-complexity tree container
37  *
38  * Insertion, removal, finding equal, largest which is smaller than and
39  * smallest which is larger than, all have O(log n) worst-case complexity.
40  * @{
41  */
42 
43 
44 struct AVTreeNode;
45 extern const int av_tree_node_size;
46 
47 /**
48  * Allocate an AVTreeNode.
49  */
50 struct AVTreeNode *av_tree_node_alloc(void);
51 
52 /**
53  * Find an element.
54  * @param root a pointer to the root node of the tree
55  * @param next If next is not NULL, then next[0] will contain the previous
56  *             element and next[1] the next element. If either does not exist,
57  *             then the corresponding entry in next is unchanged.
58  * @param cmp compare function used to compare elements in the tree,
59  *            API identical to that of Standard C's qsort
60  *            It is guaranteed that the first and only the first argument to cmp()
61  *            will be the key parameter to av_tree_find(), thus it could if the
62  *            user wants, be a different type (like an opaque context).
63  * @return An element with cmp(key, elem) == 0 or NULL if no such element
64  *         exists in the tree.
65  */
66 void *av_tree_find(const struct AVTreeNode *root, void *key,
67                    int (*cmp)(const void *key, const void *b), void *next[2]);
68 
69 /**
70  * Insert or remove an element.
71  *
72  * If *next is NULL, then the supplied element will be removed if it exists.
73  * If *next is non-NULL, then the supplied element will be inserted, unless
74  * it already exists in the tree.
75  *
76  * @param rootp A pointer to a pointer to the root node of the tree; note that
77  *              the root node can change during insertions, this is required
78  *              to keep the tree balanced.
79  * @param key  pointer to the element key to insert in the tree
80  * @param next Used to allocate and free AVTreeNodes. For insertion the user
81  *             must set it to an allocated and zeroed object of at least
82  *             av_tree_node_size bytes size. av_tree_insert() will set it to
83  *             NULL if it has been consumed.
84  *             For deleting elements *next is set to NULL by the user and
85  *             av_tree_insert() will set it to the AVTreeNode which was
86  *             used for the removed element.
87  *             This allows the use of flat arrays, which have
88  *             lower overhead compared to many malloced elements.
89  *             You might want to define a function like:
90  *             @code
91  *             void *tree_insert(struct AVTreeNode **rootp, void *key,
92  *                               int (*cmp)(void *key, const void *b),
93  *                               AVTreeNode **next)
94  *             {
95  *                 if (!*next)
96  *                     *next = av_mallocz(av_tree_node_size);
97  *                 return av_tree_insert(rootp, key, cmp, next);
98  *             }
99  *             void *tree_remove(struct AVTreeNode **rootp, void *key,
100  *                               int (*cmp)(void *key, const void *b, AVTreeNode **next))
101  *             {
102  *                 av_freep(next);
103  *                 return av_tree_insert(rootp, key, cmp, next);
104  *             }
105  *             @endcode
106  * @param cmp compare function used to compare elements in the tree, API identical
107  *            to that of Standard C's qsort
108  * @return If no insertion happened, the found element; if an insertion or
109  *         removal happened, then either key or NULL will be returned.
110  *         Which one it is depends on the tree state and the implementation. You
111  *         should make no assumptions that it's one or the other in the code.
112  */
113 void *av_tree_insert(struct AVTreeNode **rootp, void *key,
114                      int (*cmp)(const void *key, const void *b),
115                      struct AVTreeNode **next);
116 
117 void av_tree_destroy(struct AVTreeNode *t);
118 
119 /**
120  * Apply enu(opaque, &elem) to all the elements in the tree in a given range.
121  *
122  * @param cmp a comparison function that returns < 0 for an element below the
123  *            range, > 0 for an element above the range and == 0 for an
124  *            element inside the range
125  *
126  * @note The cmp function should use the same ordering used to construct the
127  *       tree.
128  */
129 void av_tree_enumerate(struct AVTreeNode *t, void *opaque,
130                        int (*cmp)(void *opaque, void *elem),
131                        int (*enu)(void *opaque, void *elem));
132 
133 /**
134  * @}
135  */
136 
137 #endif /* AVUTIL_TREE_H */
138