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  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 */
  133.