LXR linux/include/linux/rbtree.h

   1/* SPDX-License-Identifier: GPL-2.0-or-later */
   2/*
   3  Red Black Trees
   4  (C) 1999  Andrea Arcangeli <andrea@suse.de>
   5  
   6
   7  linux/include/linux/rbtree.h
   8
   9  To use rbtrees you'll have to implement your own insert and search cores.
  10  This will avoid us to use callbacks and to drop drammatically performances.
  11  I know it's not the cleaner way,  but in C (not in C++) to get
  12  performances and genericity...
  13
  14  See Documentation/rbtree.txt for documentation and samples.
  15*/
  16
  17#ifndef _LINUX_RBTREE_H
  18#define _LINUX_RBTREE_H
  19
  20#include <linux/kernel.h>
  21#include <linux/stddef.h>
  22#include <linux/rcupdate.h>
  23
  24struct rb_node {
  25        unsigned long  __rb_parent_color;
  26        struct rb_node *rb_right;
  27        struct rb_node *rb_left;
  28} __attribute__((aligned(sizeof(long))));
  29    /* The alignment might seem pointless, but allegedly CRIS needs it */
  30
  31struct rb_root {
  32        struct rb_node *rb_node;
  33};
  34
  35#define rb_parent(r)   ((struct rb_node *)((r)->__rb_parent_color & ~3))
  36
  37#define RB_ROOT (struct rb_root) { NULL, }
  38#define rb_entry(ptr, type, member) container_of(ptr, type, member)
  39
  40#define RB_EMPTY_ROOT(root)  (READ_ONCE((root)->rb_node) == NULL)
  41
  42/* 'empty' nodes are nodes that are known not to be inserted in an rbtree */
  43#define RB_EMPTY_NODE(node)  \
  44        ((node)->__rb_parent_color == (unsigned long)(node))
  45#define RB_CLEAR_NODE(node)  \
  46        ((node)->__rb_parent_color = (unsigned long)(node))
  47
  48
  49extern void rb_insert_color(struct rb_node *, struct rb_root *);
  50extern void rb_erase(struct rb_node *, struct rb_root *);
  51
  52
  53/* Find logical next and previous nodes in a tree */
  54extern struct rb_node *rb_next(const struct rb_node *);
  55extern struct rb_node *rb_prev(const struct rb_node *);
  56extern struct rb_node *rb_first(const struct rb_root *);
  57extern struct rb_node *rb_last(const struct rb_root *);
  58
  59/* Postorder iteration - always visit the parent after its children */
  60extern struct rb_node *rb_first_postorder(const struct rb_root *);
  61extern struct rb_node *rb_next_postorder(const struct rb_node *);
  62
  63/* Fast replacement of a single node without remove/rebalance/add/rebalance */
  64extern void rb_replace_node(struct rb_node *victim, struct rb_node *new,
  65                            struct rb_root *root);
  66extern void rb_replace_node_rcu(struct rb_node *victim, struct rb_node *new,
  67                                struct rb_root *root);
  68
  69static inline void rb_link_node(struct rb_node *node, struct rb_node *parent,
  70                                struct rb_node **rb_link)
  71{
  72        node->__rb_parent_color = (unsigned long)parent;
  73        node->rb_left = node->rb_right = NULL;
  74
  75        *rb_link = node;
  76}
  77
  78static inline void rb_link_node_rcu(struct rb_node *node, struct rb_node *parent,
  79                                    struct rb_node **rb_link)
  80{
  81        node->__rb_parent_color = (unsigned long)parent;
  82        node->rb_left = node->rb_right = NULL;
  83
  84        rcu_assign_pointer(*rb_link, node);
  85}
  86
  87#define rb_entry_safe(ptr, type, member) \
  88        ({ typeof(ptr) ____ptr = (ptr); \
  89           ____ptr ? rb_entry(____ptr, type, member) : NULL; \
  90        })
  91
  92/**
  93 * rbtree_postorder_for_each_entry_safe - iterate in post-order over rb_root of
  94 * given type allowing the backing memory of @pos to be invalidated
  95 *
  96 * @pos:        the 'type *' to use as a loop cursor.
  97 * @n:          another 'type *' to use as temporary storage
  98 * @root:       'rb_root *' of the rbtree.
  99 * @field:      the name of the rb_node field within 'type'.
 100 *
 101 * rbtree_postorder_for_each_entry_safe() provides a similar guarantee as
 102 * list_for_each_entry_safe() and allows the iteration to continue independent
 103 * of changes to @pos by the body of the loop.
 104 *
 105 * Note, however, that it cannot handle other modifications that re-order the
 106 * rbtree it is iterating over. This includes calling rb_erase() on @pos, as
 107 * rb_erase() may rebalance the tree, causing us to miss some nodes.
 108 */
 109#define rbtree_postorder_for_each_entry_safe(pos, n, root, field) \
 110        for (pos = rb_entry_safe(rb_first_postorder(root), typeof(*pos), field); \
 111             pos && ({ n = rb_entry_safe(rb_next_postorder(&pos->field), \
 112                        typeof(*pos), field); 1; }); \
 113             pos = n)
 114
 115/*
 116 * Leftmost-cached rbtrees.
 117 *
 118 * We do not cache the rightmost node based on footprint
 119 * size vs number of potential users that could benefit
 120 * from O(1) rb_last(). Just not worth it, users that want
 121 * this feature can always implement the logic explicitly.
 122 * Furthermore, users that want to cache both pointers may
 123 * find it a bit asymmetric, but that's ok.
 124 */
 125struct rb_root_cached {
 126        struct rb_root rb_root;
 127        struct rb_node *rb_leftmost;
 128};
 129
 130#define RB_ROOT_CACHED (struct rb_root_cached) { {NULL, }, NULL }
 131
 132/* Same as rb_first(), but O(1) */
 133#define rb_first_cached(root) (root)->rb_leftmost
 134
 135static inline void rb_insert_color_cached(struct rb_node *node,
 136                                          struct rb_root_cached *root,
 137                                          bool leftmost)
 138{
 139        if (leftmost)
 140                root->rb_leftmost = node;
 141        rb_insert_color(node, &root->rb_root);
 142}
 143
 144static inline void rb_erase_cached(struct rb_node *node,
 145                                   struct rb_root_cached *root)
 146{
 147        if (root->rb_leftmost == node)
 148                root->rb_leftmost = rb_next(node);
 149        rb_erase(node, &root->rb_root);
 150}
 151
 152static inline void rb_replace_node_cached(struct rb_node *victim,
 153                                          struct rb_node *new,
 154                                          struct rb_root_cached *root)
 155{
 156        if (root->rb_leftmost == victim)
 157                root->rb_leftmost = new;
 158        rb_replace_node(victim, new, &root->rb_root);
 159}
 160
 161#endif  /* _LINUX_RBTREE_H */
 162