include/sys/avl.h

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21 /*
  22  * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
  23  * Use is subject to license terms.
  24  */
  25
  26 /*
  27  * Copyright (c) 2014 by Delphix. All rights reserved.
  28  */
  29
  30 #ifndef _AVL_H
  31 #define _AVL_H
  32
  33 #ifdef  __cplusplus
  34 extern "C" {
  35 #endif
  36
  37 #include <sys/types.h>
  38 #include <sys/avl_impl.h>
  39
  40 /*
  41  * This is a generic implementation of AVL trees for use in the illumos. The
  42  * interfaces provide an efficient way of implementing an ordered set of data
  43  * structures.
  44  *
  45  * AVL trees provide an alternative to using an ordered linked list. Using AVL
  46  * trees will usually be faster, however they requires more storage. An ordered
  47  * linked list in general requires 2 pointers in each data structure. The
  48  * AVL tree implementation uses 3 pointers. The following chart gives the
  49  * approximate performance of operations with the different approaches:
  50  *
  51  *      Operation        Link List      AVL tree
  52  *      ---------        --------       --------
  53  *      lookup             O(n)         O(log(n))
  54  *
  55  *      insert 1 node    constant       O(log(n))
  56  *
  57  *      delete 1 node    constant       between constant and O(log(n))
  58  *
  59  *      delete all nodes   O(n)         O(n)
  60  *
  61  *      visit the next
  62  *      or prev node     constant       between constant and O(log(n))
  63  *
  64  *
  65  * The data structure nodes are anchored at an "avl_tree_t" (the equivalent
  66  * of a list header) and the individual nodes will have a field of
  67  * type "avl_node_t" (corresponding to list pointers).
  68  *
  69  * The type "avl_index_t" is used to indicate a position in the list for
  70  * certain calls.
  71  *
  72  * The usage scenario is generally:
  73  *
  74  * 1. Create the list/tree with: avl_create()
  75  *
  76  * followed by any mixture of:
  77  *
  78  * 2a. Insert nodes with: avl_add(), or avl_find() and avl_insert()
  79  *
  80  * 2b. Visited elements with:
  81  *       avl_first() - returns the lowest valued node
  82  *       avl_last() - returns the highest valued node
  83  *       AVL_NEXT() - given a node go to next higher one
  84  *       AVL_PREV() - given a node go to previous lower one
  85  *
  86  * 2c.  Find the node with the closest value either less than or greater
  87  *      than a given value with avl_nearest().
  88  *
  89  * 2d. Remove individual nodes from the list/tree with avl_remove().
  90  *
  91  * and finally when the list is being destroyed
  92  *
  93  * 3. Use avl_destroy_nodes() to quickly process/free up any remaining nodes.
  94  *    Note that once you use avl_destroy_nodes(), you can no longer
  95  *    use any routine except avl_destroy_nodes() and avl_destoy().
  96  *
  97  * 4. Use avl_destroy() to destroy the AVL tree itself.
  98  *
  99  * Any locking for multiple thread access is up to the user to provide, just
 100  * as is needed for any linked list implementation.
 101  */
 102
 103
 104 /*
 105  * Type used for the root of the AVL tree.
 106  */
 107 typedef struct avl_tree avl_tree_t;
 108
 109 /*
 110  * The data nodes in the AVL tree must have a field of this type.
 111  */
 112 typedef struct avl_node avl_node_t;
 113
 114 /*
 115  * An opaque type used to locate a position in the tree where a node
 116  * would be inserted.
 117  */
 118 typedef uintptr_t avl_index_t;
 119
 120
 121 /*
 122  * Direction constants used for avl_nearest().
 123  */
 124 #define AVL_BEFORE      (0)
 125 #define AVL_AFTER       (1)
 126
 127
 128 /*
 129  * Prototypes
 130  *
 131  * Where not otherwise mentioned, "void *" arguments are a pointer to the
 132  * user data structure which must contain a field of type avl_node_t.
 133  *
 134  * Also assume the user data structures looks like:
 135  *      stuct my_type {
 136  *              ...
 137  *              avl_node_t      my_link;
 138  *              ...
 139  *      };
 140  */
 141
 142 /*
 143  * Initialize an AVL tree. Arguments are:
 144  *
 145  * tree   - the tree to be initialized
 146  * compar - function to compare two nodes, it must return exactly: -1, 0, or +1
 147  *          -1 for <, 0 for ==, and +1 for >
 148  * size   - the value of sizeof(struct my_type)
 149  * offset - the value of OFFSETOF(struct my_type, my_link)
 150  */
 151 extern void avl_create(avl_tree_t *tree,
 152         int (*compar) (const void *, const void *), size_t size, size_t offset);
 153
 154
 155 /*
 156  * Find a node with a matching value in the tree. Returns the matching node
 157  * found. If not found, it returns NULL and then if "where" is not NULL it sets
 158  * "where" for use with avl_insert() or avl_nearest().
 159  *
 160  * node   - node that has the value being looked for
 161  * where  - position for use with avl_nearest() or avl_insert(), may be NULL
 162  */
 163 extern void *avl_find(avl_tree_t *tree, const void *node, avl_index_t *where);
 164
 165 /*
 166  * Insert a node into the tree.
 167  *
 168  * node   - the node to insert
 169  * where  - position as returned from avl_find()
 170  */
 171 extern void avl_insert(avl_tree_t *tree, void *node, avl_index_t where);
 172
 173 /*
 174  * Insert "new_data" in "tree" in the given "direction" either after
 175  * or before the data "here".
 176  *
 177  * This might be useful for avl clients caching recently accessed
 178  * data to avoid doing avl_find() again for insertion.
 179  *
 180  * new_data     - new data to insert
 181  * here         - existing node in "tree"
 182  * direction    - either AVL_AFTER or AVL_BEFORE the data "here".
 183  */
 184 extern void avl_insert_here(avl_tree_t *tree, void *new_data, void *here,
 185     int direction);
 186
 187
 188 /*
 189  * Return the first or last valued node in the tree. Will return NULL
 190  * if the tree is empty.
 191  *
 192  */
 193 extern void *avl_first(avl_tree_t *tree);
 194 extern void *avl_last(avl_tree_t *tree);
 195
 196
 197 /*
 198  * Return the next or previous valued node in the tree.
 199  * AVL_NEXT() will return NULL if at the last node.
 200  * AVL_PREV() will return NULL if at the first node.
 201  *
 202  * node   - the node from which the next or previous node is found
 203  */
 204 #define AVL_NEXT(tree, node)    avl_walk(tree, node, AVL_AFTER)
 205 #define AVL_PREV(tree, node)    avl_walk(tree, node, AVL_BEFORE)
 206
 207
 208 /*
 209  * Find the node with the nearest value either greater or less than
 210  * the value from a previous avl_find(). Returns the node or NULL if
 211  * there isn't a matching one.
 212  *
 213  * where     - position as returned from avl_find()
 214  * direction - either AVL_BEFORE or AVL_AFTER
 215  *
 216  * EXAMPLE get the greatest node that is less than a given value:
 217  *
 218  *      avl_tree_t *tree;
 219  *      struct my_data look_for_value = {....};
 220  *      struct my_data *node;
 221  *      struct my_data *less;
 222  *      avl_index_t where;
 223  *
 224  *      node = avl_find(tree, &look_for_value, &where);
 225  *      if (node != NULL)
 226  *              less = AVL_PREV(tree, node);
 227  *      else
 228  *              less = avl_nearest(tree, where, AVL_BEFORE);
 229  */
 230 extern void *avl_nearest(avl_tree_t *tree, avl_index_t where, int direction);
 231
 232
 233 /*
 234  * Add a single node to the tree.
 235  * The node must not be in the tree, and it must not
 236  * compare equal to any other node already in the tree.
 237  *
 238  * node   - the node to add
 239  */
 240 extern void avl_add(avl_tree_t *tree, void *node);
 241
 242
 243 /*
 244  * Remove a single node from the tree.  The node must be in the tree.
 245  *
 246  * node   - the node to remove
 247  */
 248 extern void avl_remove(avl_tree_t *tree, void *node);
 249
 250 /*
 251  * Reinsert a node only if its order has changed relative to its nearest
 252  * neighbors. To optimize performance avl_update_lt() checks only the previous
 253  * node and avl_update_gt() checks only the next node. Use avl_update_lt() and
 254  * avl_update_gt() only if you know the direction in which the order of the
 255  * node may change.
 256  */
 257 extern boolean_t avl_update(avl_tree_t *, void *);
 258 extern boolean_t avl_update_lt(avl_tree_t *, void *);
 259 extern boolean_t avl_update_gt(avl_tree_t *, void *);
 260
 261 /*
 262  * Swaps the contents of the two trees.
 263  */
 264 extern void avl_swap(avl_tree_t *tree1, avl_tree_t *tree2);
 265
 266 /*
 267  * Return the number of nodes in the tree
 268  */
 269 extern ulong_t avl_numnodes(avl_tree_t *tree);
 270
 271 /*
 272  * Return B_TRUE if there are zero nodes in the tree, B_FALSE otherwise.
 273  */
 274 extern boolean_t avl_is_empty(avl_tree_t *tree);
 275
 276 /*
 277  * Used to destroy any remaining nodes in a tree. The cookie argument should
 278  * be initialized to NULL before the first call. Returns a node that has been
 279  * removed from the tree and may be free()'d. Returns NULL when the tree is
 280  * empty.
 281  *
 282  * Once you call avl_destroy_nodes(), you can only continuing calling it and
 283  * finally avl_destroy(). No other AVL routines will be valid.
 284  *
 285  * cookie - a "void *" used to save state between calls to avl_destroy_nodes()
 286  *
 287  * EXAMPLE:
 288  *      avl_tree_t *tree;
 289  *      struct my_data *node;
 290  *      void *cookie;
 291  *
 292  *      cookie = NULL;
 293  *      while ((node = avl_destroy_nodes(tree, &cookie)) != NULL)
 294  *              free(node);
 295  *      avl_destroy(tree);
 296  */
 297 extern void *avl_destroy_nodes(avl_tree_t *tree, void **cookie);
 298
 299
 300 /*
 301  * Final destroy of an AVL tree. Arguments are:
 302  *
 303  * tree   - the empty tree to destroy
 304  */
 305 extern void avl_destroy(avl_tree_t *tree);
 306
 307
 308
 309 #ifdef  __cplusplus
 310 }
 311 #endif
 312
 313 #endif  /* _AVL_H */