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/core-api/rbtree.rst for documentation and samples.
15 */
16
17 #ifndef _LINUX_RBTREE_H
18 #define _LINUX_RBTREE_H
19
20 #include <linux/container_of.h>
21 #include <linux/rbtree_types.h>
22
23 #include <linux/stddef.h>
24 #include <linux/rcupdate.h>
25
26 #define rb_parent(r) ((struct rb_node *)((r)->__rb_parent_color & ~3))
27
28 #define rb_entry(ptr, type, member) container_of(ptr, type, member)
29
30 #define RB_EMPTY_ROOT(root) (READ_ONCE((root)->rb_node) == NULL)
31
32 /* 'empty' nodes are nodes that are known not to be inserted in an rbtree */
33 #define RB_EMPTY_NODE(node) \
34 ((node)->__rb_parent_color == (unsigned long)(node))
35 #define RB_CLEAR_NODE(node) \
36 ((node)->__rb_parent_color = (unsigned long)(node))
37
38
39 extern void rb_insert_color(struct rb_node *, struct rb_root *);
40 extern void rb_erase(struct rb_node *, struct rb_root *);
41
42
43 /* Find logical next and previous nodes in a tree */
44 extern struct rb_node *rb_next(const struct rb_node *);
45 extern struct rb_node *rb_prev(const struct rb_node *);
46 extern struct rb_node *rb_first(const struct rb_root *);
47 extern struct rb_node *rb_last(const struct rb_root *);
48
49 /* Postorder iteration - always visit the parent after its children */
50 extern struct rb_node *rb_first_postorder(const struct rb_root *);
51 extern struct rb_node *rb_next_postorder(const struct rb_node *);
52
53 /* Fast replacement of a single node without remove/rebalance/add/rebalance */
54 extern void rb_replace_node(struct rb_node *victim, struct rb_node *new,
55 struct rb_root *root);
56 extern void rb_replace_node_rcu(struct rb_node *victim, struct rb_node *new,
57 struct rb_root *root);
58
59 static inline void rb_link_node(struct rb_node *node, struct rb_node *parent,
60 struct rb_node **rb_link)
61 {
62 node->__rb_parent_color = (unsigned long)parent;
63 node->rb_left = node->rb_right = NULL;
64
65 *rb_link = node;
66 }
67
68 static inline void rb_link_node_rcu(struct rb_node *node, struct rb_node *parent,
69 struct rb_node **rb_link)
70 {
71 node->__rb_parent_color = (unsigned long)parent;
72 node->rb_left = node->rb_right = NULL;
73
74 rcu_assign_pointer(*rb_link, node);
75 }
76
77 #define rb_entry_safe(ptr, type, member) \
78 ({ typeof(ptr) ____ptr = (ptr); \
79 ____ptr ? rb_entry(____ptr, type, member) : NULL; \
80 })
81
82 /**
83 * rbtree_postorder_for_each_entry_safe - iterate in post-order over rb_root of
84 * given type allowing the backing memory of @pos to be invalidated
85 *
86 * @pos: the 'type *' to use as a loop cursor.
87 * @n: another 'type *' to use as temporary storage
88 * @root: 'rb_root *' of the rbtree.
89 * @field: the name of the rb_node field within 'type'.
90 *
91 * rbtree_postorder_for_each_entry_safe() provides a similar guarantee as
92 * list_for_each_entry_safe() and allows the iteration to continue independent
93 * of changes to @pos by the body of the loop.
94 *
95 * Note, however, that it cannot handle other modifications that re-order the
96 * rbtree it is iterating over. This includes calling rb_erase() on @pos, as
97 * rb_erase() may rebalance the tree, causing us to miss some nodes.
98 */
99 #define rbtree_postorder_for_each_entry_safe(pos, n, root, field) \
100 for (pos = rb_entry_safe(rb_first_postorder(root), typeof(*pos), field); \
101 pos && ({ n = rb_entry_safe(rb_next_postorder(&pos->field), \
102 typeof(*pos), field); 1; }); \
103 pos = n)
104
105 /* Same as rb_first(), but O(1) */
106 #define rb_first_cached(root) (root)->rb_leftmost
107
108 static inline void rb_insert_color_cached(struct rb_node *node,
109 struct rb_root_cached *root,
110 bool leftmost)
111 {
112 if (leftmost)
113 root->rb_leftmost = node;
114 rb_insert_color(node, &root->rb_root);
115 }
116
117
118 static inline struct rb_node *
119 rb_erase_cached(struct rb_node *node, struct rb_root_cached *root)
120 {
121 struct rb_node *leftmost = NULL;
122
123 if (root->rb_leftmost == node)
124 leftmost = root->rb_leftmost = rb_next(node);
125
126 rb_erase(node, &root->rb_root);
127
128 return leftmost;
129 }
130
131 static inline void rb_replace_node_cached(struct rb_node *victim,
132 struct rb_node *new,
133 struct rb_root_cached *root)
134 {
135 if (root->rb_leftmost == victim)
136 root->rb_leftmost = new;
137 rb_replace_node(victim, new, &root->rb_root);
138 }
139
140 /*
141 * The below helper functions use 2 operators with 3 different
142 * calling conventions. The operators are related like:
143 *
144 * comp(a->key,b) < 0 := less(a,b)
145 * comp(a->key,b) > 0 := less(b,a)
146 * comp(a->key,b) == 0 := !less(a,b) && !less(b,a)
147 *
148 * If these operators define a partial order on the elements we make no
149 * guarantee on which of the elements matching the key is found. See
150 * rb_find().
151 *
152 * The reason for this is to allow the find() interface without requiring an
153 * on-stack dummy object, which might not be feasible due to object size.
154 */
155
156 /**
157 * rb_add_cached() - insert @node into the leftmost cached tree @tree
158 * @node: node to insert
159 * @tree: leftmost cached tree to insert @node into
160 * @less: operator defining the (partial) node order
161 *
162 * Returns @node when it is the new leftmost, or NULL.
163 */
164 static __always_inline struct rb_node *
165 rb_add_cached(struct rb_node *node, struct rb_root_cached *tree,
166 bool (*less)(struct rb_node *, const struct rb_node *))
167 {
168 struct rb_node **link = &tree->rb_root.rb_node;
169 struct rb_node *parent = NULL;
170 bool leftmost = true;
171
172 while (*link) {
173 parent = *link;
174 if (less(node, parent)) {
175 link = &parent->rb_left;
176 } else {
177 link = &parent->rb_right;
178 leftmost = false;
179 }
180 }
181
182 rb_link_node(node, parent, link);
183 rb_insert_color_cached(node, tree, leftmost);
184
185 return leftmost ? node : NULL;
186 }
187
188 /**
189 * rb_add() - insert @node into @tree
190 * @node: node to insert
191 * @tree: tree to insert @node into
192 * @less: operator defining the (partial) node order
193 */
194 static __always_inline void
195 rb_add(struct rb_node *node, struct rb_root *tree,
196 bool (*less)(struct rb_node *, const struct rb_node *))
197 {
198 struct rb_node **link = &tree->rb_node;
199 struct rb_node *parent = NULL;
200
201 while (*link) {
202 parent = *link;
203 if (less(node, parent))
204 link = &parent->rb_left;
205 else
206 link = &parent->rb_right;
207 }
208
209 rb_link_node(node, parent, link);
210 rb_insert_color(node, tree);
211 }
212
213 /**
214 * rb_find_add() - find equivalent @node in @tree, or add @node
215 * @node: node to look-for / insert
216 * @tree: tree to search / modify
217 * @cmp: operator defining the node order
218 *
219 * Returns the rb_node matching @node, or NULL when no match is found and @node
220 * is inserted.
221 */
222 static __always_inline struct rb_node *
223 rb_find_add(struct rb_node *node, struct rb_root *tree,
224 int (*cmp)(struct rb_node *, const struct rb_node *))
225 {
226 struct rb_node **link = &tree->rb_node;
227 struct rb_node *parent = NULL;
228 int c;
229
230 while (*link) {
231 parent = *link;
232 c = cmp(node, parent);
233
234 if (c < 0)
235 link = &parent->rb_left;
236 else if (c > 0)
237 link = &parent->rb_right;
238 else
239 return parent;
240 }
241
242 rb_link_node(node, parent, link);
243 rb_insert_color(node, tree);
244 return NULL;
245 }
246
247 /**
248 * rb_find() - find @key in tree @tree
249 * @key: key to match
250 * @tree: tree to search
251 * @cmp: operator defining the node order
252 *
253 * Returns the rb_node matching @key or NULL.
254 */
255 static __always_inline struct rb_node *
256 rb_find(const void *key, const struct rb_root *tree,
257 int (*cmp)(const void *key, const struct rb_node *))
258 {
259 struct rb_node *node = tree->rb_node;
260
261 while (node) {
262 int c = cmp(key, node);
263
264 if (c < 0)
265 node = node->rb_left;
266 else if (c > 0)
267 node = node->rb_right;
268 else
269 return node;
270 }
271
272 return NULL;
273 }
274
275 /**
276 * rb_find_first() - find the first @key in @tree
277 * @key: key to match
278 * @tree: tree to search
279 * @cmp: operator defining node order
280 *
281 * Returns the leftmost node matching @key, or NULL.
282 */
283 static __always_inline struct rb_node *
284 rb_find_first(const void *key, const struct rb_root *tree,
285 int (*cmp)(const void *key, const struct rb_node *))
286 {
287 struct rb_node *node = tree->rb_node;
288 struct rb_node *match = NULL;
289
290 while (node) {
291 int c = cmp(key, node);
292
293 if (c <= 0) {
294 if (!c)
295 match = node;
296 node = node->rb_left;
297 } else if (c > 0) {
298 node = node->rb_right;
299 }
300 }
301
302 return match;
303 }
304
305 /**
306 * rb_next_match() - find the next @key in @tree
307 * @key: key to match
308 * @tree: tree to search
309 * @cmp: operator defining node order
310 *
311 * Returns the next node matching @key, or NULL.
312 */
313 static __always_inline struct rb_node *
314 rb_next_match(const void *key, struct rb_node *node,
315 int (*cmp)(const void *key, const struct rb_node *))
316 {
317 node = rb_next(node);
318 if (node && cmp(key, node))
319 node = NULL;
320 return node;
321 }
322
323 /**
324 * rb_for_each() - iterates a subtree matching @key
325 * @node: iterator
326 * @key: key to match
327 * @tree: tree to search
328 * @cmp: operator defining node order
329 */
330 #define rb_for_each(node, key, tree, cmp) \
331 for ((node) = rb_find_first((key), (tree), (cmp)); \
332 (node); (node) = rb_next_match((key), (node), (cmp)))
333
334 #endif /* _LINUX_RBTREE_H */
335
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