ffmpeg/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 #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 */