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  * @param cmp compare function used to compare elements in the tree,
60  *            API identical to that of Standard C's qsort
61  *            It is guranteed that the first and only the first argument to cmp()
62  *            will be the key parameter to av_tree_find(), thus it could if the
63  *            user wants, be a different type (like an opaque context).
64  * @return An element with cmp(key, elem) == 0 or NULL if no such element
65  *         exists in the tree.
66  */
67 void *av_tree_find(const struct AVTreeNode *root, void *key,
68                    int (*cmp)(const void *key, const void *b), void *next[2]);
69 
70 /**
71  * Insert or remove an element.
72  *
73  * If *next is NULL, then the supplied element will be removed if it exists.
74  * If *next is non-NULL, then the supplied element will be inserted, unless
75  * it already exists in the tree.
76  *
77  * @param rootp A pointer to a pointer to the root node of the tree; note that
78  *              the root node can change during insertions, this is required
79  *              to keep the tree balanced.
80  * @param key  pointer to the element key to insert in the tree
81  * @param next Used to allocate and free AVTreeNodes. For insertion the user
82  *             must set it to an allocated and zeroed object of at least
83  *             av_tree_node_size bytes size. av_tree_insert() will set it to
84  *             NULL if it has been consumed.
85  *             For deleting elements *next is set to NULL by the user and
86  *             av_tree_insert() will set it to the AVTreeNode which was
87  *             used for the removed element.
88  *             This allows the use of flat arrays, which have
89  *             lower overhead compared to many malloced elements.
90  *             You might want to define a function like:
91  *             @code
92  *             void *tree_insert(struct AVTreeNode **rootp, void *key,
93  *                               int (*cmp)(void *key, const void *b),
94  *                               AVTreeNode **next)
95  *             {
96  *                 if (!*next)
97  *                     *next = av_mallocz(av_tree_node_size);
98  *                 return av_tree_insert(rootp, key, cmp, next);
99  *             }
100  *             void *tree_remove(struct AVTreeNode **rootp, void *key,
101  *                               int (*cmp)(void *key, const void *b, AVTreeNode **next))
102  *             {
103  *                 av_freep(next);
104  *                 return av_tree_insert(rootp, key, cmp, next);
105  *             }
106  *             @endcode
107  * @param cmp compare function used to compare elements in the tree, API identical
108  *            to that of Standard C's qsort
109  * @return If no insertion happened, the found element; if an insertion or
110  *         removal happened, then either key or NULL will be returned.
111  *         Which one it is depends on the tree state and the implementation. You
112  *         should make no assumptions that it's one or the other in the code.
113  */
114 void *av_tree_insert(struct AVTreeNode **rootp, void *key,
115                      int (*cmp)(const void *key, const void *b),
116                      struct AVTreeNode **next);
117 
118 void av_tree_destroy(struct AVTreeNode *t);
119 
120 /**
121  * Apply enu(opaque, &elem) to all the elements in the tree in a given range.
122  *
123  * @param cmp a comparison function that returns < 0 for a element below the
124  *            range, > 0 for a element above the range and == 0 for a
125  *            element inside the range
126  *
127  * @note The cmp function should use the same ordering used to construct the
128  *       tree.
129  */
130 void av_tree_enumerate(struct AVTreeNode *t, void *opaque,
131                        int (*cmp)(void *opaque, void *elem),
132                        int (*enu)(void *opaque, void *elem));
133 
134 /**
135  * @}
136  */
137 
138 #endif /* AVUTIL_TREE_H */
139