1 /*
2   Red Black Trees
3   (C) 1999  Andrea Arcangeli <andrea@suse.de>
4 
5   This program is free software; you can redistribute it and/or modify
6   it under the terms of the GNU General Public License as published by
7   the Free Software Foundation; either version 2 of the License, or
8   (at your option) any later version.
9 
10   This program is distributed in the hope that it will be useful,
11   but WITHOUT ANY WARRANTY; without even the implied warranty of
12   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13   GNU General Public License for more details.
14 
15   You should have received a copy of the GNU General Public License
16   along with this program; if not, write to the Free Software
17   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
18 
19   linux/include/linux/rbtree.h
20 
21   To use rbtrees you'll have to implement your own insert and search cores.
22   This will avoid us to use callbacks and to drop drammatically performances.
23   I know it's not the cleaner way,  but in C (not in C++) to get
24   performances and genericity...
25 
26   See Documentation/rbtree.txt for documentation and samples.
27 */
28 
29 #ifndef	_LINUX_RBTREE_H
30 #define	_LINUX_RBTREE_H
31 
32 #include <linux/kernel.h>
33 #include <linux/stddef.h>
34 #include <linux/rcupdate.h>
35 
36 struct rb_node {
37 	unsigned long  __rb_parent_color;
38 	struct rb_node *rb_right;
39 	struct rb_node *rb_left;
40 } __attribute__((aligned(sizeof(long))));
41     /* The alignment might seem pointless, but allegedly CRIS needs it */
42 
43 struct rb_root {
44 	struct rb_node *rb_node;
45 };
46 
47 /*
48  * Leftmost-cached rbtrees.
49  *
50  * We do not cache the rightmost node based on footprint
51  * size vs number of potential users that could benefit
52  * from O(1) rb_last(). Just not worth it, users that want
53  * this feature can always implement the logic explicitly.
54  * Furthermore, users that want to cache both pointers may
55  * find it a bit asymmetric, but that's ok.
56  */
57 struct rb_root_cached {
58 	struct rb_root rb_root;
59 	struct rb_node *rb_leftmost;
60 };
61 
62 #define rb_parent(r)   ((struct rb_node *)((r)->__rb_parent_color & ~3))
63 
64 #define RB_ROOT	(struct rb_root) { NULL, }
65 #define RB_ROOT_CACHED (struct rb_root_cached) { {NULL, }, NULL }
66 #define	rb_entry(ptr, type, member) container_of(ptr, type, member)
67 
68 #define RB_EMPTY_ROOT(root)  (READ_ONCE((root)->rb_node) == NULL)
69 
70 /* 'empty' nodes are nodes that are known not to be inserted in an rbtree */
71 #define RB_EMPTY_NODE(node)  \
72 	((node)->__rb_parent_color == (unsigned long)(node))
73 #define RB_CLEAR_NODE(node)  \
74 	((node)->__rb_parent_color = (unsigned long)(node))
75 
76 
77 extern void rb_insert_color(struct rb_node *, struct rb_root *);
78 extern void rb_erase(struct rb_node *, struct rb_root *);
79 
80 
81 /* Find logical next and previous nodes in a tree */
82 extern struct rb_node *rb_next(const struct rb_node *);
83 extern struct rb_node *rb_prev(const struct rb_node *);
84 extern struct rb_node *rb_first(const struct rb_root *);
85 extern struct rb_node *rb_last(const struct rb_root *);
86 
87 extern void rb_insert_color_cached(struct rb_node *,
88 				   struct rb_root_cached *, bool);
89 extern void rb_erase_cached(struct rb_node *node, struct rb_root_cached *);
90 /* Same as rb_first(), but O(1) */
91 #define rb_first_cached(root) (root)->rb_leftmost
92 
93 /* Postorder iteration - always visit the parent after its children */
94 extern struct rb_node *rb_first_postorder(const struct rb_root *);
95 extern struct rb_node *rb_next_postorder(const struct rb_node *);
96 
97 /* Fast replacement of a single node without remove/rebalance/add/rebalance */
98 extern void rb_replace_node(struct rb_node *victim, struct rb_node *new,
99 			    struct rb_root *root);
100 extern void rb_replace_node_rcu(struct rb_node *victim, struct rb_node *new,
101 				struct rb_root *root);
102 extern void rb_replace_node_cached(struct rb_node *victim, struct rb_node *new,
103 				   struct rb_root_cached *root);
104 
rb_link_node(struct rb_node * node,struct rb_node * parent,struct rb_node ** rb_link)105 static inline void rb_link_node(struct rb_node *node, struct rb_node *parent,
106 				struct rb_node **rb_link)
107 {
108 	node->__rb_parent_color = (unsigned long)parent;
109 	node->rb_left = node->rb_right = NULL;
110 
111 	*rb_link = node;
112 }
113 
rb_link_node_rcu(struct rb_node * node,struct rb_node * parent,struct rb_node ** rb_link)114 static inline void rb_link_node_rcu(struct rb_node *node, struct rb_node *parent,
115 				    struct rb_node **rb_link)
116 {
117 	node->__rb_parent_color = (unsigned long)parent;
118 	node->rb_left = node->rb_right = NULL;
119 
120 	rcu_assign_pointer(*rb_link, node);
121 }
122 
123 #define rb_entry_safe(ptr, type, member) \
124 	({ typeof(ptr) ____ptr = (ptr); \
125 	   ____ptr ? rb_entry(____ptr, type, member) : NULL; \
126 	})
127 
128 /**
129  * rbtree_postorder_for_each_entry_safe - iterate in post-order over rb_root of
130  * given type allowing the backing memory of @pos to be invalidated
131  *
132  * @pos:	the 'type *' to use as a loop cursor.
133  * @n:		another 'type *' to use as temporary storage
134  * @root:	'rb_root *' of the rbtree.
135  * @field:	the name of the rb_node field within 'type'.
136  *
137  * rbtree_postorder_for_each_entry_safe() provides a similar guarantee as
138  * list_for_each_entry_safe() and allows the iteration to continue independent
139  * of changes to @pos by the body of the loop.
140  *
141  * Note, however, that it cannot handle other modifications that re-order the
142  * rbtree it is iterating over. This includes calling rb_erase() on @pos, as
143  * rb_erase() may rebalance the tree, causing us to miss some nodes.
144  */
145 #define rbtree_postorder_for_each_entry_safe(pos, n, root, field) \
146 	for (pos = rb_entry_safe(rb_first_postorder(root), typeof(*pos), field); \
147 	     pos && ({ n = rb_entry_safe(rb_next_postorder(&pos->field), \
148 			typeof(*pos), field); 1; }); \
149 	     pos = n)
150 
151 #endif	/* _LINUX_RBTREE_H */
152