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 libavutil/tree.h
  23  * A tree container.
  24  * Insertion, removal, finding equal, largest which is smaller than and
  25  * smallest which is larger than, all have O(log n) worst case complexity.
  26  * @author Michael Niedermayer <michaelni@gmx.at>
  27  */
  28
  29 #ifndef AVUTIL_TREE_H
  30 #define AVUTIL_TREE_H
  31
  32 struct AVTreeNode;
  33 extern const int av_tree_node_size;
  34
  35 /**
  36  * Finds an element.
  37  * @param root a pointer to the root node of the tree
  38  * @param next If next is not NULL, then next[0] will contain the previous
  39  *             element and next[1] the next element. If either does not exist,
  40  *             then the corresponding entry in next is unchanged.
  41  * @return An element with cmp(key, elem)==0 or NULL if no such element exists in
  42  *         the tree.
  43  */
  44 void *av_tree_find(const struct AVTreeNode *root, void *key, int (*cmp)(void *key, const void *b), void *next[2]);
  45
  46 /**
  47  * Inserts or removes an element.
  48  * If *next is NULL, then the supplied element will be removed if it exists.
  49  * If *next is not NULL, then the supplied element will be inserted, unless
  50  * it already exists in the tree.
  51  * @param rootp A pointer to a pointer to the root node of the tree; note that
  52  *              the root node can change during insertions, this is required
  53  *              to keep the tree balanced.
  54  * @param next Used to allocate and free AVTreeNodes. For insertion the user
  55  *             must set it to an allocated and zeroed object of at least
  56  *             av_tree_node_size bytes size. av_tree_insert() will set it to
  57  *             NULL if it has been consumed.
  58  *             For deleting elements *next is set to NULL by the user and
  59  *             av_tree_node_size() will set it to the AVTreeNode which was
  60  *             used for the removed element.
  61  *             This allows the use of flat arrays, which have
  62  *             lower overhead compared to many malloced elements.
  63  *             You might want to define a function like:
  64  *             @code
  65  *             void *tree_insert(struct AVTreeNode **rootp, void *key, int (*cmp)(void *key, const void *b), AVTreeNode **next){
  66  *                 if(!*next) *next= av_mallocz(av_tree_node_size);
  67  *                 return av_tree_insert(rootp, key, cmp, next);
  68  *             }
  69  *             void *tree_remove(struct AVTreeNode **rootp, void *key, int (*cmp)(void *key, const void *b, AVTreeNode **next)){
  70  *                 if(*next) av_freep(next);
  71  *                 return av_tree_insert(rootp, key, cmp, next);
  72  *             }
  73  *             @endcode
  74  * @return If no insertion happened, the found element; if an insertion or
  75  *         removal happened, then either key or NULL will be returned.
  76  *         Which one it is depends on the tree state and the implementation. You
  77  *         should make no assumptions that it's one or the other in the code.
  78  */
  79 void *av_tree_insert(struct AVTreeNode **rootp, void *key, int (*cmp)(void *key, const void *b), struct AVTreeNode **next);
  80 void av_tree_destroy(struct AVTreeNode *t);
  81
  82 #endif /* AVUTIL_TREE_H */