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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/*
36 * Leftmost-cached rbtrees.
37 *
38 * We do not cache the rightmost node based on footprint
39 * size vs number of potential users that could benefit
40 * from O(1) rb_last(). Just not worth it, users that want
41 * this feature can always implement the logic explicitly.
42 * Furthermore, users that want to cache both pointers may
43 * find it a bit asymmetric, but that's ok.
44 */
45struct rb_root_cached {
46 struct rb_root rb_root;
47 struct rb_node *rb_leftmost;
48};
49
50#define rb_parent(r) ((struct rb_node *)((r)->__rb_parent_color & ~3))
51
52#define RB_ROOT (struct rb_root) { NULL, }
53#define RB_ROOT_CACHED (struct rb_root_cached) { {NULL, }, NULL }
54#define rb_entry(ptr, type, member) container_of(ptr, type, member)
55
56#define RB_EMPTY_ROOT(root) (READ_ONCE((root)->rb_node) == NULL)
57
58/* 'empty' nodes are nodes that are known not to be inserted in an rbtree */
59#define RB_EMPTY_NODE(node) \
60 ((node)->__rb_parent_color == (unsigned long)(node))
61#define RB_CLEAR_NODE(node) \
62 ((node)->__rb_parent_color = (unsigned long)(node))
63
64
65extern void rb_insert_color(struct rb_node *, struct rb_root *);
66extern void rb_erase(struct rb_node *, struct rb_root *);
67
68
69/* Find logical next and previous nodes in a tree */
70extern struct rb_node *rb_next(const struct rb_node *);
71extern struct rb_node *rb_prev(const struct rb_node *);
72extern struct rb_node *rb_first(const struct rb_root *);
73extern struct rb_node *rb_last(const struct rb_root *);
74
75extern void rb_insert_color_cached(struct rb_node *,
76 struct rb_root_cached *, bool);
77extern void rb_erase_cached(struct rb_node *node, struct rb_root_cached *);
78/* Same as rb_first(), but O(1) */
79#define rb_first_cached(root) (root)->rb_leftmost
80
81/* Postorder iteration - always visit the parent after its children */
82extern struct rb_node *rb_first_postorder(const struct rb_root *);
83extern struct rb_node *rb_next_postorder(const struct rb_node *);
84
85/* Fast replacement of a single node without remove/rebalance/add/rebalance */
86extern void rb_replace_node(struct rb_node *victim, struct rb_node *new,
87 struct rb_root *root);
88extern void rb_replace_node_rcu(struct rb_node *victim, struct rb_node *new,
89 struct rb_root *root);
90extern void rb_replace_node_cached(struct rb_node *victim, struct rb_node *new,
91 struct rb_root_cached *root);
92
93static inline void rb_link_node(struct rb_node *node, struct rb_node *parent,
94 struct rb_node **rb_link)
95{
96 node->__rb_parent_color = (unsigned long)parent;
97 node->rb_left = node->rb_right = NULL;
98
99 *rb_link = node;
100}
101
102static inline void rb_link_node_rcu(struct rb_node *node, struct rb_node *parent,
103 struct rb_node **rb_link)
104{
105 node->__rb_parent_color = (unsigned long)parent;
106 node->rb_left = node->rb_right = NULL;
107
108 rcu_assign_pointer(*rb_link, node);
109}
110
111#define rb_entry_safe(ptr, type, member) \
112 ({ typeof(ptr) ____ptr = (ptr); \
113 ____ptr ? rb_entry(____ptr, type, member) : NULL; \
114 })
115
116/**
117 * rbtree_postorder_for_each_entry_safe - iterate in post-order over rb_root of
118 * given type allowing the backing memory of @pos to be invalidated
119 *
120 * @pos: the 'type *' to use as a loop cursor.
121 * @n: another 'type *' to use as temporary storage
122 * @root: 'rb_root *' of the rbtree.
123 * @field: the name of the rb_node field within 'type'.
124 *
125 * rbtree_postorder_for_each_entry_safe() provides a similar guarantee as
126 * list_for_each_entry_safe() and allows the iteration to continue independent
127 * of changes to @pos by the body of the loop.
128 *
129 * Note, however, that it cannot handle other modifications that re-order the
130 * rbtree it is iterating over. This includes calling rb_erase() on @pos, as
131 * rb_erase() may rebalance the tree, causing us to miss some nodes.
132 */
133#define rbtree_postorder_for_each_entry_safe(pos, n, root, field) \
134 for (pos = rb_entry_safe(rb_first_postorder(root), typeof(*pos), field); \
135 pos && ({ n = rb_entry_safe(rb_next_postorder(&pos->field), \
136 typeof(*pos), field); 1; }); \
137 pos = n)
138
139#endif /* _LINUX_RBTREE_H */