libavutil/tree.h

   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 */