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