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+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+/*
+ * Copyright 2009 Sun Microsystems, Inc. All rights reserved.
+ * Use is subject to license terms.
+ */
+
+#ifndef _AVL_H
+#define _AVL_H
+
+/*
+ * This is a private header file. Applications should not directly include
+ * this file.
+ */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <sys/types.h>
+#include <sys/avl_impl.h>
+
+/*
+ * This is a generic implemenatation of AVL trees for use in the Solaris kernel.
+ * The interfaces provide an efficient way of implementing an ordered set of
+ * data structures.
+ *
+ * AVL trees provide an alternative to using an ordered linked list. Using AVL
+ * trees will usually be faster, however they requires more storage. An ordered
+ * linked list in general requires 2 pointers in each data structure. The
+ * AVL tree implementation uses 3 pointers. The following chart gives the
+ * approximate performance of operations with the different approaches:
+ *
+ * Operation Link List AVL tree
+ * --------- -------- --------
+ * lookup O(n) O(log(n))
+ *
+ * insert 1 node constant constant
+ *
+ * delete 1 node constant between constant and O(log(n))
+ *
+ * delete all nodes O(n) O(n)
+ *
+ * visit the next
+ * or prev node constant between constant and O(log(n))
+ *
+ *
+ * The data structure nodes are anchored at an "avl_tree_t" (the equivalent
+ * of a list header) and the individual nodes will have a field of
+ * type "avl_node_t" (corresponding to list pointers).
+ *
+ * The type "avl_index_t" is used to indicate a position in the list for
+ * certain calls.
+ *
+ * The usage scenario is generally:
+ *
+ * 1. Create the list/tree with: avl_create()
+ *
+ * followed by any mixture of:
+ *
+ * 2a. Insert nodes with: avl_add(), or avl_find() and avl_insert()
+ *
+ * 2b. Visited elements with:
+ * avl_first() - returns the lowest valued node
+ * avl_last() - returns the highest valued node
+ * AVL_NEXT() - given a node go to next higher one
+ * AVL_PREV() - given a node go to previous lower one
+ *
+ * 2c. Find the node with the closest value either less than or greater
+ * than a given value with avl_nearest().
+ *
+ * 2d. Remove individual nodes from the list/tree with avl_remove().
+ *
+ * and finally when the list is being destroyed
+ *
+ * 3. Use avl_destroy_nodes() to quickly process/free up any remaining nodes.
+ * Note that once you use avl_destroy_nodes(), you can no longer
+ * use any routine except avl_destroy_nodes() and avl_destoy().
+ *
+ * 4. Use avl_destroy() to destroy the AVL tree itself.
+ *
+ * Any locking for multiple thread access is up to the user to provide, just
+ * as is needed for any linked list implementation.
+ */
+
+
+/*
+ * Type used for the root of the AVL tree.
+ */
+typedef struct avl_tree avl_tree_t;
+
+/*
+ * The data nodes in the AVL tree must have a field of this type.
+ */
+typedef struct avl_node avl_node_t;
+
+/*
+ * An opaque type used to locate a position in the tree where a node
+ * would be inserted.
+ */
+typedef uintptr_t avl_index_t;
+
+
+/*
+ * Direction constants used for avl_nearest().
+ */
+#define AVL_BEFORE (0)
+#define AVL_AFTER (1)
+
+
+/*
+ * Prototypes
+ *
+ * Where not otherwise mentioned, "void *" arguments are a pointer to the
+ * user data structure which must contain a field of type avl_node_t.
+ *
+ * Also assume the user data structures looks like:
+ * stuct my_type {
+ * ...
+ * avl_node_t my_link;
+ * ...
+ * };
+ */
+
+/*
+ * Initialize an AVL tree. Arguments are:
+ *
+ * tree - the tree to be initialized
+ * compar - function to compare two nodes, it must return exactly: -1, 0, or +1
+ * -1 for <, 0 for ==, and +1 for >
+ * size - the value of sizeof(struct my_type)
+ * offset - the value of OFFSETOF(struct my_type, my_link)
+ */
+extern void avl_create(avl_tree_t *tree,
+ int (*compar) (const void *, const void *), size_t size, size_t offset);
+
+
+/*
+ * Find a node with a matching value in the tree. Returns the matching node
+ * found. If not found, it returns NULL and then if "where" is not NULL it sets
+ * "where" for use with avl_insert() or avl_nearest().
+ *
+ * node - node that has the value being looked for
+ * where - position for use with avl_nearest() or avl_insert(), may be NULL
+ */
+extern void *avl_find(avl_tree_t *tree, const void *node, avl_index_t *where);
+
+/*
+ * Insert a node into the tree.
+ *
+ * node - the node to insert
+ * where - position as returned from avl_find()
+ */
+extern void avl_insert(avl_tree_t *tree, void *node, avl_index_t where);
+
+/*
+ * Insert "new_data" in "tree" in the given "direction" either after
+ * or before the data "here".
+ *
+ * This might be usefull for avl clients caching recently accessed
+ * data to avoid doing avl_find() again for insertion.
+ *
+ * new_data - new data to insert
+ * here - existing node in "tree"
+ * direction - either AVL_AFTER or AVL_BEFORE the data "here".
+ */
+extern void avl_insert_here(avl_tree_t *tree, void *new_data, void *here,
+ int direction);
+
+
+/*
+ * Return the first or last valued node in the tree. Will return NULL
+ * if the tree is empty.
+ *
+ */
+extern void *avl_first(avl_tree_t *tree);
+extern void *avl_last(avl_tree_t *tree);
+
+
+/*
+ * Return the next or previous valued node in the tree.
+ * AVL_NEXT() will return NULL if at the last node.
+ * AVL_PREV() will return NULL if at the first node.
+ *
+ * node - the node from which the next or previous node is found
+ */
+#define AVL_NEXT(tree, node) avl_walk(tree, node, AVL_AFTER)
+#define AVL_PREV(tree, node) avl_walk(tree, node, AVL_BEFORE)
+
+
+/*
+ * Find the node with the nearest value either greater or less than
+ * the value from a previous avl_find(). Returns the node or NULL if
+ * there isn't a matching one.
+ *
+ * where - position as returned from avl_find()
+ * direction - either AVL_BEFORE or AVL_AFTER
+ *
+ * EXAMPLE get the greatest node that is less than a given value:
+ *
+ * avl_tree_t *tree;
+ * struct my_data look_for_value = {....};
+ * struct my_data *node;
+ * struct my_data *less;
+ * avl_index_t where;
+ *
+ * node = avl_find(tree, &look_for_value, &where);
+ * if (node != NULL)
+ * less = AVL_PREV(tree, node);
+ * else
+ * less = avl_nearest(tree, where, AVL_BEFORE);
+ */
+extern void *avl_nearest(avl_tree_t *tree, avl_index_t where, int direction);
+
+
+/*
+ * Add a single node to the tree.
+ * The node must not be in the tree, and it must not
+ * compare equal to any other node already in the tree.
+ *
+ * node - the node to add
+ */
+extern void avl_add(avl_tree_t *tree, void *node);
+
+
+/*
+ * Remove a single node from the tree. The node must be in the tree.
+ *
+ * node - the node to remove
+ */
+extern void avl_remove(avl_tree_t *tree, void *node);
+
+/*
+ * Reinsert a node only if its order has changed relative to its nearest
+ * neighbors. To optimize performance avl_update_lt() checks only the previous
+ * node and avl_update_gt() checks only the next node. Use avl_update_lt() and
+ * avl_update_gt() only if you know the direction in which the order of the
+ * node may change.
+ */
+extern boolean_t avl_update(avl_tree_t *, void *);
+extern boolean_t avl_update_lt(avl_tree_t *, void *);
+extern boolean_t avl_update_gt(avl_tree_t *, void *);
+
+/*
+ * Return the number of nodes in the tree
+ */
+extern ulong_t avl_numnodes(avl_tree_t *tree);
+
+/*
+ * Return B_TRUE if there are zero nodes in the tree, B_FALSE otherwise.
+ */
+extern boolean_t avl_is_empty(avl_tree_t *tree);
+
+/*
+ * Used to destroy any remaining nodes in a tree. The cookie argument should
+ * be initialized to NULL before the first call. Returns a node that has been
+ * removed from the tree and may be free()'d. Returns NULL when the tree is
+ * empty.
+ *
+ * Once you call avl_destroy_nodes(), you can only continuing calling it and
+ * finally avl_destroy(). No other AVL routines will be valid.
+ *
+ * cookie - a "void *" used to save state between calls to avl_destroy_nodes()
+ *
+ * EXAMPLE:
+ * avl_tree_t *tree;
+ * struct my_data *node;
+ * void *cookie;
+ *
+ * cookie = NULL;
+ * while ((node = avl_destroy_nodes(tree, &cookie)) != NULL)
+ * free(node);
+ * avl_destroy(tree);
+ */
+extern void *avl_destroy_nodes(avl_tree_t *tree, void **cookie);
+
+
+/*
+ * Final destroy of an AVL tree. Arguments are:
+ *
+ * tree - the empty tree to destroy
+ */
+extern void avl_destroy(avl_tree_t *tree);
+
+
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _AVL_H */