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/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->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, link);
211	rb_insert_color_cached(node, 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, 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, link);
274	rb_insert_color_cached(node, 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, 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, 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 */