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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/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
39extern void rb_insert_color(struct rb_node *, struct rb_root *);
40extern void rb_erase(struct rb_node *, struct rb_root *);
41
42
43/* Find logical next and previous nodes in a tree */
44extern struct rb_node *rb_next(const struct rb_node *);
45extern struct rb_node *rb_prev(const struct rb_node *);
46
47/*
48 * This function returns the first node (in sort order) of the tree.
49 */
50static inline struct rb_node *rb_first(const struct rb_root *root)
51{
52 struct rb_node *n;
53
54 n = root->rb_node;
55 if (!n)
56 return NULL;
57 while (n->rb_left)
58 n = n->rb_left;
59 return n;
60}
61
62/*
63 * This function returns the last node (in sort order) of the tree.
64 */
65static inline struct rb_node *rb_last(const struct rb_root *root)
66{
67 struct rb_node *n;
68
69 n = root->rb_node;
70 if (!n)
71 return NULL;
72 while (n->rb_right)
73 n = n->rb_right;
74 return n;
75}
76
77/* Postorder iteration - always visit the parent after its children */
78extern struct rb_node *rb_first_postorder(const struct rb_root *);
79extern struct rb_node *rb_next_postorder(const struct rb_node *);
80
81/* Fast replacement of a single node without remove/rebalance/add/rebalance */
82extern void rb_replace_node(struct rb_node *victim, struct rb_node *new,
83 struct rb_root *root);
84extern void rb_replace_node_rcu(struct rb_node *victim, struct rb_node *new,
85 struct rb_root *root);
86
87static inline void rb_link_node(struct rb_node *node, struct rb_node *parent,
88 struct rb_node **rb_link)
89{
90 node->__rb_parent_color = (unsigned long)parent;
91 node->rb_left = node->rb_right = NULL;
92
93 *rb_link = node;
94}
95
96static inline void rb_link_node_rcu(struct rb_node *node, struct rb_node *parent,
97 struct rb_node **rb_link)
98{
99 node->__rb_parent_color = (unsigned long)parent;
100 node->rb_left = node->rb_right = NULL;
101
102 rcu_assign_pointer(*rb_link, node);
103}
104
105#define rb_entry_safe(ptr, type, member) \
106 ({ typeof(ptr) ____ptr = (ptr); \
107 ____ptr ? rb_entry(____ptr, type, member) : NULL; \
108 })
109
110/**
111 * rbtree_postorder_for_each_entry_safe - iterate in post-order over rb_root of
112 * given type allowing the backing memory of @pos to be invalidated
113 *
114 * @pos: the 'type *' to use as a loop cursor.
115 * @n: another 'type *' to use as temporary storage
116 * @root: 'rb_root *' of the rbtree.
117 * @field: the name of the rb_node field within 'type'.
118 *
119 * rbtree_postorder_for_each_entry_safe() provides a similar guarantee as
120 * list_for_each_entry_safe() and allows the iteration to continue independent
121 * of changes to @pos by the body of the loop.
122 *
123 * Note, however, that it cannot handle other modifications that re-order the
124 * rbtree it is iterating over. This includes calling rb_erase() on @pos, as
125 * rb_erase() may rebalance the tree, causing us to miss some nodes.
126 */
127#define rbtree_postorder_for_each_entry_safe(pos, n, root, field) \
128 for (pos = rb_entry_safe(rb_first_postorder(root), typeof(*pos), field); \
129 pos && ({ n = rb_entry_safe(rb_next_postorder(&pos->field), \
130 typeof(*pos), field); 1; }); \
131 pos = n)
132
133/* Same as rb_first(), but O(1) */
134#define rb_first_cached(root) (root)->rb_leftmost
135
136static inline void rb_insert_color_cached(struct rb_node *node,
137 struct rb_root_cached *root,
138 bool leftmost)
139{
140 if (leftmost)
141 root->rb_leftmost = node;
142 rb_insert_color(node, &root->rb_root);
143}
144
145
146static inline struct rb_node *
147rb_erase_cached(struct rb_node *node, struct rb_root_cached *root)
148{
149 struct rb_node *leftmost = NULL;
150
151 if (root->rb_leftmost == node)
152 leftmost = root->rb_leftmost = rb_next(node);
153
154 rb_erase(node, &root->rb_root);
155
156 return leftmost;
157}
158
159static inline void rb_replace_node_cached(struct rb_node *victim,
160 struct rb_node *new,
161 struct rb_root_cached *root)
162{
163 if (root->rb_leftmost == victim)
164 root->rb_leftmost = new;
165 rb_replace_node(victim, new, root: &root->rb_root);
166}
167
168/*
169 * The below helper functions use 2 operators with 3 different
170 * calling conventions. The operators are related like:
171 *
172 * comp(a->key,b) < 0 := less(a,b)
173 * comp(a->key,b) > 0 := less(b,a)
174 * comp(a->key,b) == 0 := !less(a,b) && !less(b,a)
175 *
176 * If these operators define a partial order on the elements we make no
177 * guarantee on which of the elements matching the key is found. See
178 * rb_find().
179 *
180 * The reason for this is to allow the find() interface without requiring an
181 * on-stack dummy object, which might not be feasible due to object size.
182 */
183
184/**
185 * rb_add_cached() - insert @node into the leftmost cached tree @tree
186 * @node: node to insert
187 * @tree: leftmost cached tree to insert @node into
188 * @less: operator defining the (partial) node order
189 *
190 * Returns @node when it is the new leftmost, or NULL.
191 */
192static __always_inline struct rb_node *
193rb_add_cached(struct rb_node *node, struct rb_root_cached *tree,
194 bool (*less)(struct rb_node *, const struct rb_node *))
195{
196 struct rb_node **link = &tree->rb_root.rb_node;
197 struct rb_node *parent = NULL;
198 bool leftmost = true;
199
200 while (*link) {
201 parent = *link;
202 if (less(node, parent)) {
203 link = &parent->rb_left;
204 } else {
205 link = &parent->rb_right;
206 leftmost = false;
207 }
208 }
209
210 rb_link_node(node, parent, rb_link: link);
211 rb_insert_color_cached(node, root: tree, leftmost);
212
213 return leftmost ? node : NULL;
214}
215
216/**
217 * rb_add() - insert @node into @tree
218 * @node: node to insert
219 * @tree: tree to insert @node into
220 * @less: operator defining the (partial) node order
221 */
222static __always_inline void
223rb_add(struct rb_node *node, struct rb_root *tree,
224 bool (*less)(struct rb_node *, const struct rb_node *))
225{
226 struct rb_node **link = &tree->rb_node;
227 struct rb_node *parent = NULL;
228
229 while (*link) {
230 parent = *link;
231 if (less(node, parent))
232 link = &parent->rb_left;
233 else
234 link = &parent->rb_right;
235 }
236
237 rb_link_node(node, parent, rb_link: link);
238 rb_insert_color(node, tree);
239}
240
241/**
242 * rb_find_add_cached() - find equivalent @node in @tree, or add @node
243 * @node: node to look-for / insert
244 * @tree: tree to search / modify
245 * @cmp: operator defining the node order
246 *
247 * Returns the rb_node matching @node, or NULL when no match is found and @node
248 * is inserted.
249 */
250static __always_inline struct rb_node *
251rb_find_add_cached(struct rb_node *node, struct rb_root_cached *tree,
252 int (*cmp)(const struct rb_node *new, const struct rb_node *exist))
253{
254 bool leftmost = true;
255 struct rb_node **link = &tree->rb_root.rb_node;
256 struct rb_node *parent = NULL;
257 int c;
258
259 while (*link) {
260 parent = *link;
261 c = cmp(node, parent);
262
263 if (c < 0) {
264 link = &parent->rb_left;
265 } else if (c > 0) {
266 link = &parent->rb_right;
267 leftmost = false;
268 } else {
269 return parent;
270 }
271 }
272
273 rb_link_node(node, parent, rb_link: link);
274 rb_insert_color_cached(node, root: tree, leftmost);
275 return NULL;
276}
277
278/**
279 * rb_find_add() - find equivalent @node in @tree, or add @node
280 * @node: node to look-for / insert
281 * @tree: tree to search / modify
282 * @cmp: operator defining the node order
283 *
284 * Returns the rb_node matching @node, or NULL when no match is found and @node
285 * is inserted.
286 */
287static __always_inline struct rb_node *
288rb_find_add(struct rb_node *node, struct rb_root *tree,
289 int (*cmp)(struct rb_node *, const struct rb_node *))
290{
291 struct rb_node **link = &tree->rb_node;
292 struct rb_node *parent = NULL;
293 int c;
294
295 while (*link) {
296 parent = *link;
297 c = cmp(node, parent);
298
299 if (c < 0)
300 link = &parent->rb_left;
301 else if (c > 0)
302 link = &parent->rb_right;
303 else
304 return parent;
305 }
306
307 rb_link_node(node, parent, rb_link: link);
308 rb_insert_color(node, tree);
309 return NULL;
310}
311
312/**
313 * rb_find_add_rcu() - find equivalent @node in @tree, or add @node
314 * @node: node to look-for / insert
315 * @tree: tree to search / modify
316 * @cmp: operator defining the node order
317 *
318 * Adds a Store-Release for link_node.
319 *
320 * Returns the rb_node matching @node, or NULL when no match is found and @node
321 * is inserted.
322 */
323static __always_inline struct rb_node *
324rb_find_add_rcu(struct rb_node *node, struct rb_root *tree,
325 int (*cmp)(struct rb_node *, const struct rb_node *))
326{
327 struct rb_node **link = &tree->rb_node;
328 struct rb_node *parent = NULL;
329 int c;
330
331 while (*link) {
332 parent = *link;
333 c = cmp(node, parent);
334
335 if (c < 0)
336 link = &parent->rb_left;
337 else if (c > 0)
338 link = &parent->rb_right;
339 else
340 return parent;
341 }
342
343 rb_link_node_rcu(node, parent, rb_link: link);
344 rb_insert_color(node, tree);
345 return NULL;
346}
347
348/**
349 * rb_find() - find @key in tree @tree
350 * @key: key to match
351 * @tree: tree to search
352 * @cmp: operator defining the node order
353 *
354 * Returns the rb_node matching @key or NULL.
355 */
356static __always_inline struct rb_node *
357rb_find(const void *key, const struct rb_root *tree,
358 int (*cmp)(const void *key, const struct rb_node *))
359{
360 struct rb_node *node = tree->rb_node;
361
362 while (node) {
363 int c = cmp(key, node);
364
365 if (c < 0)
366 node = node->rb_left;
367 else if (c > 0)
368 node = node->rb_right;
369 else
370 return node;
371 }
372
373 return NULL;
374}
375
376/**
377 * rb_find_rcu() - find @key in tree @tree
378 * @key: key to match
379 * @tree: tree to search
380 * @cmp: operator defining the node order
381 *
382 * Notably, tree descent vs concurrent tree rotations is unsound and can result
383 * in false-negatives.
384 *
385 * Returns the rb_node matching @key or NULL.
386 */
387static __always_inline struct rb_node *
388rb_find_rcu(const void *key, const struct rb_root *tree,
389 int (*cmp)(const void *key, const struct rb_node *))
390{
391 struct rb_node *node = tree->rb_node;
392
393 while (node) {
394 int c = cmp(key, node);
395
396 if (c < 0)
397 node = rcu_dereference_raw(node->rb_left);
398 else if (c > 0)
399 node = rcu_dereference_raw(node->rb_right);
400 else
401 return node;
402 }
403
404 return NULL;
405}
406
407/**
408 * rb_find_first() - find the first @key in @tree
409 * @key: key to match
410 * @tree: tree to search
411 * @cmp: operator defining node order
412 *
413 * Returns the leftmost node matching @key, or NULL.
414 */
415static __always_inline struct rb_node *
416rb_find_first(const void *key, const struct rb_root *tree,
417 int (*cmp)(const void *key, const struct rb_node *))
418{
419 struct rb_node *node = tree->rb_node;
420 struct rb_node *match = NULL;
421
422 while (node) {
423 int c = cmp(key, node);
424
425 if (c <= 0) {
426 if (!c)
427 match = node;
428 node = node->rb_left;
429 } else if (c > 0) {
430 node = node->rb_right;
431 }
432 }
433
434 return match;
435}
436
437/**
438 * rb_next_match() - find the next @key in @tree
439 * @key: key to match
440 * @tree: tree to search
441 * @cmp: operator defining node order
442 *
443 * Returns the next node matching @key, or NULL.
444 */
445static __always_inline struct rb_node *
446rb_next_match(const void *key, struct rb_node *node,
447 int (*cmp)(const void *key, const struct rb_node *))
448{
449 node = rb_next(node);
450 if (node && cmp(key, node))
451 node = NULL;
452 return node;
453}
454
455/**
456 * rb_for_each() - iterates a subtree matching @key
457 * @node: iterator
458 * @key: key to match
459 * @tree: tree to search
460 * @cmp: operator defining node order
461 */
462#define rb_for_each(node, key, tree, cmp) \
463 for ((node) = rb_find_first((key), (tree), (cmp)); \
464 (node); (node) = rb_next_match((key), (node), (cmp)))
465
466#endif /* _LINUX_RBTREE_H */
467

source code of linux/include/linux/rbtree.h