FreeBSD/Linux Kernel Cross Reference
sys/contrib/openzfs/include/sys/avl_impl.h

     /*
      * CDDL HEADER START
      *
      * The contents of this file are subject to the terms of the
      * Common Development and Distribution License, Version 1.0 only
      * (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 https://opensource.org/licenses/CDDL-1.0.
     * 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 2004 Sun Microsystems, Inc.  All rights reserved.
     * Use is subject to license terms.
     */
    
    #ifndef _AVL_IMPL_H
    #define _AVL_IMPL_H extern __attribute__((visibility("default")))
    
    
    /*
     * This is a private header file.  Applications should not directly include
     * this file.
     */
    
    #include <sys/types.h>
    
    #ifdef  __cplusplus
    extern "C" {
    #endif
    
    
    /*
     * generic AVL tree implementation for kernel use
     *
     * There are 5 pieces of information stored for each node in an AVL tree
     *
     *      pointer to less than child
     *      pointer to greater than child
     *      a pointer to the parent of this node
     *      an indication  [0/1]  of which child I am of my parent
     *      a "balance" (-1, 0, +1)  indicating which child tree is taller
     *
     * Since they only need 3 bits, the last two fields are packed into the
     * bottom bits of the parent pointer on 64 bit machines to save on space.
     */
    
    #ifndef _LP64
    
    struct avl_node {
            struct avl_node *avl_child[2];  /* left/right children */
            struct avl_node *avl_parent;    /* this node's parent */
            unsigned short avl_child_index; /* my index in parent's avl_child[] */
            short avl_balance;              /* balance value: -1, 0, +1 */
    };
    
    #define AVL_XPARENT(n)          ((n)->avl_parent)
    #define AVL_SETPARENT(n, p)     ((n)->avl_parent = (p))
    
    #define AVL_XCHILD(n)           ((n)->avl_child_index)
    #define AVL_SETCHILD(n, c)      ((n)->avl_child_index = (unsigned short)(c))
    
    #define AVL_XBALANCE(n)         ((n)->avl_balance)
    #define AVL_SETBALANCE(n, b)    ((n)->avl_balance = (short)(b))
    
    #else /* _LP64 */
    
    /*
     * for 64 bit machines, avl_pcb contains parent pointer, balance and child_index
     * values packed in the following manner:
     *
     * |63                                  3|        2        |1          0 |
     * |-------------------------------------|-----------------|-------------|
     * |      avl_parent hi order bits       | avl_child_index | avl_balance |
     * |                                     |                 |     + 1     |
     * |-------------------------------------|-----------------|-------------|
     *
     */
    struct avl_node {
            struct avl_node *avl_child[2];  /* left/right children nodes */
            uintptr_t avl_pcb;              /* parent, child_index, balance */
    };
    
    /*
     * macros to extract/set fields in avl_pcb
     *
     * pointer to the parent of the current node is the high order bits
     */
    #define AVL_XPARENT(n)          ((struct avl_node *)((n)->avl_pcb & ~7))
   #define AVL_SETPARENT(n, p)                                             \
           ((n)->avl_pcb = (((n)->avl_pcb & 7) | (uintptr_t)(p)))
   
   /*
    * index of this node in its parent's avl_child[]: bit #2
    */
   #define AVL_XCHILD(n)           (((n)->avl_pcb >> 2) & 1)
   #define AVL_SETCHILD(n, c)                                              \
           ((n)->avl_pcb = (uintptr_t)(((n)->avl_pcb & ~4) | ((c) << 2)))
   
   /*
    * balance indication for a node, lowest 2 bits. A valid balance is
    * -1, 0, or +1, and is encoded by adding 1 to the value to get the
    * unsigned values of 0, 1, 2.
    */
   #define AVL_XBALANCE(n)         ((int)(((n)->avl_pcb & 3) - 1))
   #define AVL_SETBALANCE(n, b)                                            \
           ((n)->avl_pcb = (uintptr_t)((((n)->avl_pcb & ~3) | ((b) + 1))))
   
   #endif /* _LP64 */
   
   
   
   /*
    * switch between a node and data pointer for a given tree
    * the value of "o" is tree->avl_offset
    */
   #define AVL_NODE2DATA(n, o)     ((void *)((uintptr_t)(n) - (o)))
   #define AVL_DATA2NODE(d, o)     ((struct avl_node *)((uintptr_t)(d) + (o)))
   
   
   
   /*
    * macros used to create/access an avl_index_t
    */
   #define AVL_INDEX2NODE(x)       ((avl_node_t *)((x) & ~1))
   #define AVL_INDEX2CHILD(x)      ((x) & 1)
   #define AVL_MKINDEX(n, c)       ((avl_index_t)(n) | (c))
   
   
   /*
    * The tree structure. The fields avl_root, avl_compar, and avl_offset come
    * first since they are needed for avl_find().  We want them to fit into
    * a single 64 byte cache line to make avl_find() as fast as possible.
    */
   struct avl_tree {
           struct avl_node *avl_root;      /* root node in tree */
           int (*avl_compar)(const void *, const void *);
           size_t avl_offset;              /* offsetof(type, avl_link_t field) */
           ulong_t avl_numnodes;           /* number of nodes in the tree */
   #ifndef _KERNEL
           size_t avl_pad;                 /* For backwards ABI compatibility. */
   #endif
   };
   
   
   /*
    * This will only by used via AVL_NEXT() or AVL_PREV()
    */
   _AVL_IMPL_H void *avl_walk(struct avl_tree *, void *, int);
   
   #ifdef  __cplusplus
   }
   #endif
   
   #endif  /* _AVL_IMPL_H */

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