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      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, Version 1.0 only
      6  * (the "License").  You may not use this file except in compliance
      7  * with the License.
      8  *
      9  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
     10  * or http://www.opensolaris.org/os/licensing.
     11  * See the License for the specific language governing permissions
     12  * and limitations under the License.
     13  *
     14  * When distributing Covered Code, include this CDDL HEADER in each
     15  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
     16  * If applicable, add the following below this CDDL HEADER, with the
     17  * fields enclosed by brackets "[]" replaced with your own identifying
     18  * information: Portions Copyright [yyyy] [name of copyright owner]
     19  *
     20  * CDDL HEADER END
     21  */
     22 /*
     23  * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.
     24  * Use is subject to license terms.
     25  */
     26 
     27 #ifndef	_AVL_IMPL_H
     28 #define	_AVL_IMPL_H
     29 
     30 #pragma ident	"%Z%%M%	%I%	%E% SMI"
     31 
     32 /*
     33  * This is a private header file.  Applications should not directly include
     34  * this file.
     35  */
     36 
     37 #include <sys/types.h>
     38 
     39 #ifdef	__cplusplus
     40 extern "C" {
     41 #endif
     42 
     43 
     44 /*
     45  * generic AVL tree implementation for kernel use
     46  *
     47  * There are 5 pieces of information stored for each node in an AVL tree
     48  *
     49  * 	pointer to less than child
     50  * 	pointer to greater than child
     51  * 	a pointer to the parent of this node
     52  *	an indication  [0/1]  of which child I am of my parent
     53  * 	a "balance" (-1, 0, +1)  indicating which child tree is taller
     54  *
     55  * Since they only need 3 bits, the last two fields are packed into the
     56  * bottom bits of the parent pointer on 64 bit machines to save on space.
     57  */
     58 
     59 #ifndef _LP64
     60 
     61 struct avl_node {
     62 	struct avl_node *avl_child[2];	/* left/right children */
     63 	struct avl_node *avl_parent;	/* this node's parent */
     64 	unsigned short avl_child_index;	/* my index in parent's avl_child[] */
     65 	short avl_balance;		/* balance value: -1, 0, +1 */
     66 };
     67 
     68 #define	AVL_XPARENT(n)		((n)->avl_parent)
     69 #define	AVL_SETPARENT(n, p)	((n)->avl_parent = (p))
     70 
     71 #define	AVL_XCHILD(n)		((n)->avl_child_index)
     72 #define	AVL_SETCHILD(n, c)	((n)->avl_child_index = (unsigned short)(c))
     73 
     74 #define	AVL_XBALANCE(n)		((n)->avl_balance)
     75 #define	AVL_SETBALANCE(n, b)	((n)->avl_balance = (short)(b))
     76 
     77 #else /* _LP64 */
     78 
     79 /*
     80  * for 64 bit machines, avl_pcb contains parent pointer, balance and child_index
     81  * values packed in the following manner:
     82  *
     83  * |63                                  3|        2        |1          0 |
     84  * |-------------------------------------|-----------------|-------------|
     85  * |      avl_parent hi order bits       | avl_child_index | avl_balance |
     86  * |                                     |                 |     + 1     |
     87  * |-------------------------------------|-----------------|-------------|
     88  *
     89  */
     90 struct avl_node {
     91 	struct avl_node *avl_child[2];	/* left/right children nodes */
     92 	uintptr_t avl_pcb;		/* parent, child_index, balance */
     93 };
     94 
     95 /*
     96  * macros to extract/set fields in avl_pcb
     97  *
     98  * pointer to the parent of the current node is the high order bits
     99  */
    100 #define	AVL_XPARENT(n)		((struct avl_node *)((n)->avl_pcb & ~7))
    101 #define	AVL_SETPARENT(n, p)						\
    102 	((n)->avl_pcb = (((n)->avl_pcb & 7) | (uintptr_t)(p)))
    103 
    104 /*
    105  * index of this node in its parent's avl_child[]: bit #2
    106  */
    107 #define	AVL_XCHILD(n)		(((n)->avl_pcb >> 2) & 1)
    108 #define	AVL_SETCHILD(n, c)						\
    109 	((n)->avl_pcb = (uintptr_t)(((n)->avl_pcb & ~4) | ((c) << 2)))
    110 
    111 /*
    112  * balance indication for a node, lowest 2 bits. A valid balance is
    113  * -1, 0, or +1, and is encoded by adding 1 to the value to get the
    114  * unsigned values of 0, 1, 2.
    115  */
    116 #define	AVL_XBALANCE(n)		((int)(((n)->avl_pcb & 3) - 1))
    117 #define	AVL_SETBALANCE(n, b)						\
    118 	((n)->avl_pcb = (uintptr_t)((((n)->avl_pcb & ~3) | ((b) + 1))))
    119 
    120 #endif /* _LP64 */
    121 
    122 
    123 
    124 /*
    125  * switch between a node and data pointer for a given tree
    126  * the value of "o" is tree->avl_offset
    127  */
    128 #define	AVL_NODE2DATA(n, o)	((void *)((uintptr_t)(n) - (o)))
    129 #define	AVL_DATA2NODE(d, o)	((struct avl_node *)((uintptr_t)(d) + (o)))
    130 
    131 
    132 
    133 /*
    134  * macros used to create/access an avl_index_t
    135  */
    136 #define	AVL_INDEX2NODE(x)	((avl_node_t *)((x) & ~1))
    137 #define	AVL_INDEX2CHILD(x)	((x) & 1)
    138 #define	AVL_MKINDEX(n, c)	((avl_index_t)(n) | (c))
    139 
    140 
    141 /*
    142  * The tree structure. The fields avl_root, avl_compar, and avl_offset come
    143  * first since they are needed for avl_find().  We want them to fit into
    144  * a single 64 byte cache line to make avl_find() as fast as possible.
    145  */
    146 struct avl_tree {
    147 	struct avl_node *avl_root;	/* root node in tree */
    148 	int (*avl_compar)(const void *, const void *);
    149 	size_t avl_offset;		/* offsetof(type, avl_link_t field) */
    150 	ulong_t avl_numnodes;		/* number of nodes in the tree */
    151 	size_t avl_size;		/* sizeof user type struct */
    152 };
    153 
    154 
    155 /*
    156  * This will only by used via AVL_NEXT() or AVL_PREV()
    157  */
    158 extern void *avl_walk(struct avl_tree *, void *, int);
    159 
    160 #ifdef	__cplusplus
    161 }
    162 #endif
    163 
    164 #endif	/* _AVL_IMPL_H */
    165