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AVL Trees
Copyright 1993-1999 Bruno Haible, <>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
To use AVL trees you'll have to implement your own insert and search cores.
This will avoid us to use callbacks and to drop drammatically performances.
I know it's not the cleaner way, but in C (not in C++) to get
performances and genericity...
Some example of insert and search follows here. The search is a plain
normal search over an ordered tree. The insert instead must be implemented
int two steps: as first thing the code must insert the element in
order as a leaf in the tree, then the support library function
avl_rebalance() must be called. Such function will do the
not trivial work to rebalance the tree if necessary.
static inline struct page *avl_search_page_cache(struct inode *inode,
unsigned long offset)
avl_node_t *n = inode->i_avl_page_cache;
struct page *page;
while (n)
page = (struct page *) n;
if (offset < page->offset)
n = n->avl_left;
else if (offset > page->offset)
n = n->avl_right;
return page;
return NULL;
static inline struct page *avl_insert_page_cache(struct inode *inode,
unsigned long offset,
avl_node_t *node)
avl_node_t **p = &inode->i_avl_page_cache;
avl_node_t *parent = NULL;
struct page *page;
while (*p)
parent = *p;
page = (struct page *) parent;
if (offset < page->offset)
p = &(*p)->avl_left;
else if (offset > page->offset)
p = &(*p)->avl_right;
return page;
node->avl_parent = parent;
node->avl_left = node->avl_right = NULL;
*p = node;
avl_rebalance(node, &inode->i_avl_page_cache);
return NULL;
#ifndef AVLTREES_H
#define AVLTREES_H
typedef struct avl_node_t
struct avl_node_t *avl_parent;
struct avl_node_t *avl_right;
struct avl_node_t *avl_left;
int avl_height;
typedef struct avl_traverse_t
struct avl_node_t *node;
extern void avl_rebalance(avl_node_t *, avl_node_t **);
extern void avl_erase(avl_node_t *, avl_node_t **);
extern void avl_destroy(avl_node_t *);
extern avl_node_t *avl_first(avl_node_t *, avl_traverse_t *);
extern avl_node_t *avl_next(avl_traverse_t *);
#endif /* AVLTREES_H */