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 32struct AVTreeNode; 33extern 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 */ 44void *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 * void *tree_insert(struct AVTreeNode **rootp, void *key, int (*cmp)(void *key, const void *b), AVTreeNode **next){ 65 * if(!*next) *next= av_mallocz(av_tree_node_size); 66 * return av_tree_insert(rootp, key, cmp, next); 67 * } 68 * void *tree_remove(struct AVTreeNode **rootp, void *key, int (*cmp)(void *key, const void *b, AVTreeNode **next)){ 69 * if(*next) av_freep(next); 70 * return av_tree_insert(rootp, key, cmp, next); 71 * } 72 * 73 * @return If no insertion happened, the found element; if an insertion or 74 removal happened, then either key or NULL will be returned. 75 * Which one it is depends on the tree state and the implementation. You 76 * should make no assumptions that it's one or the other in the code. 77 */ 78void *av_tree_insert(struct AVTreeNode **rootp, void *key, int (*cmp)(void *key, const void *b), struct AVTreeNode **next); 79void av_tree_destroy(struct AVTreeNode *t); 80 81#endif /* AVUTIL_TREE_H */ 82