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 guaranteed 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 an element below the 124 * range, > 0 for an element above the range and == 0 for an 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