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/*
 * ANSI C Library for maintainance of AVL Balanced Trees
 *
 * ref.:
 *  G. M. Adelson-Velskij & E. M. Landis
 *  Doklady Akad. Nauk SSSR 146 (1962), 263-266
 *
 * see also:
 *  D. E. Knuth: The Art of Computer Programming Vol.3 (Sorting and Searching)
 *
 * (C) 2000 Daniel Nagy, Budapest University of Technology and Economics
 * Released under GNU General Public License (GPL) version 2
 *
 */
#ifndef _AVL_H
#define _AVL_H 1

#include <pthread.h>

// #define AVL_LOCK_WITH_MUTEX 1

/* Data structures */

/* One element of the AVL tree */
typedef struct avl {
	struct avl* left;
	struct avl* right;
	signed char balance;
} avl;

/* An AVL tree */
typedef struct avl_tree {
	avl* root;
	int (*compar)(void* a, void* b);

#ifdef AVL_LOCK_WITH_MUTEX
	pthread_mutex_t mutex;
#else
	pthread_rwlock_t rwlock;
#endif
} avl_tree;

/* Public methods */

/* Insert element a into the AVL tree t
 * returns 1 if the depth of the tree has grown
 * Warning: do not insert elements already present
 */
int avl_insert(avl_tree* t, avl* a);

/* Remove an element a from the AVL tree t
 * returns -1 if the depth of the tree has shrunk
 * Warning: if the element is not present in the tree,
 *          returns 0 as if it had been removed succesfully.
 */
int avl_remove(avl_tree* t, avl* a);

/* Remove the root of the AVL tree t
 * Warning: dumps core if t is empty
 */
int avl_removeroot(avl_tree* t);

/* Iterate through elements in t from a range between a and b (inclusive)
 * for each element calls iter(a) until it returns 0
 * returns the last value returned by iterator or 0 if there were no calls
 * Warning: a<=b must hold
 */
int avl_range(avl_tree* t, avl* a, avl* b, int (*iter)(avl*), avl** ret);

/* Iterate through elements in t equal to a
 * for each element calls iter(a) until it returns 0
 * returns the last value returned by iterator or 0 if there were no calls
 */
int avl_search(avl_tree* t, avl* a, int (*iter)(avl*), avl** ret);

/* Initialize the avl_tree
 */
void avl_init(avl_tree* t, int (*compar)(void* a, void* b));

#endif /* avl.h */