1 /*
2   Red Black Trees
3   (C) 1999  Andrea Arcangeli <andrea@suse.de>
4   (C) 2002  David Woodhouse <dwmw2@infradead.org>
5   (C) 2012  Michel Lespinasse <walken@google.com>
6 
7   This program is free software; you can redistribute it and/or modify
8   it under the terms of the GNU General Public License as published by
9   the Free Software Foundation; either version 2 of the License, or
10   (at your option) any later version.
11 
12   This program is distributed in the hope that it will be useful,
13   but WITHOUT ANY WARRANTY; without even the implied warranty of
14   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15   GNU General Public License for more details.
16 
17   You should have received a copy of the GNU General Public License
18   along with this program; if not, write to the Free Software
19   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
20 
21   linux/include/linux/rbtree_augmented.h
22 */
23 
24 #ifndef _LINUX_RBTREE_AUGMENTED_H
25 #define _LINUX_RBTREE_AUGMENTED_H
26 
27 #include <linux/compiler.h>
28 #include <linux/rbtree.h>
29 #include <linux/rcupdate.h>
30 
31 /*
32  * Please note - only struct rb_augment_callbacks and the prototypes for
33  * rb_insert_augmented() and rb_erase_augmented() are intended to be public.
34  * The rest are implementation details you are not expected to depend on.
35  *
36  * See Documentation/rbtree.txt for documentation and samples.
37  */
38 
39 struct rb_augment_callbacks {
40 	void (*propagate)(struct rb_node *node, struct rb_node *stop);
41 	void (*copy)(struct rb_node *old, struct rb_node *new);
42 	void (*rotate)(struct rb_node *old, struct rb_node *new);
43 };
44 
45 extern void __rb_insert_augmented(struct rb_node *node,
46 				  struct rb_root *root,
47 				  bool newleft, struct rb_node **leftmost,
48 	void (*augment_rotate)(struct rb_node *old, struct rb_node *new));
49 /*
50  * Fixup the rbtree and update the augmented information when rebalancing.
51  *
52  * On insertion, the user must update the augmented information on the path
53  * leading to the inserted node, then call rb_link_node() as usual and
54  * rb_insert_augmented() instead of the usual rb_insert_color() call.
55  * If rb_insert_augmented() rebalances the rbtree, it will callback into
56  * a user provided function to update the augmented information on the
57  * affected subtrees.
58  */
59 static inline void
60 rb_insert_augmented(struct rb_node *node, struct rb_root *root,
61 		    const struct rb_augment_callbacks *augment)
62 {
63 	__rb_insert_augmented(node, root, false, NULL, augment->rotate);
64 }
65 
66 static inline void
67 rb_insert_augmented_cached(struct rb_node *node,
68 			   struct rb_root_cached *root, bool newleft,
69 			   const struct rb_augment_callbacks *augment)
70 {
71 	__rb_insert_augmented(node, &root->rb_root,
72 			      newleft, &root->rb_leftmost, augment->rotate);
73 }
74 
75 #define RB_DECLARE_CALLBACKS(rbstatic, rbname, rbstruct, rbfield,	\
76 			     rbtype, rbaugmented, rbcompute)		\
77 static inline void							\
78 rbname ## _propagate(struct rb_node *rb, struct rb_node *stop)		\
79 {									\
80 	while (rb != stop) {						\
81 		rbstruct *node = rb_entry(rb, rbstruct, rbfield);	\
82 		rbtype augmented = rbcompute(node);			\
83 		if (node->rbaugmented == augmented)			\
84 			break;						\
85 		node->rbaugmented = augmented;				\
86 		rb = rb_parent(&node->rbfield);				\
87 	}								\
88 }									\
89 static inline void							\
90 rbname ## _copy(struct rb_node *rb_old, struct rb_node *rb_new)		\
91 {									\
92 	rbstruct *old = rb_entry(rb_old, rbstruct, rbfield);		\
93 	rbstruct *new = rb_entry(rb_new, rbstruct, rbfield);		\
94 	new->rbaugmented = old->rbaugmented;				\
95 }									\
96 static void								\
97 rbname ## _rotate(struct rb_node *rb_old, struct rb_node *rb_new)	\
98 {									\
99 	rbstruct *old = rb_entry(rb_old, rbstruct, rbfield);		\
100 	rbstruct *new = rb_entry(rb_new, rbstruct, rbfield);		\
101 	new->rbaugmented = old->rbaugmented;				\
102 	old->rbaugmented = rbcompute(old);				\
103 }									\
104 rbstatic const struct rb_augment_callbacks rbname = {			\
105 	.propagate = rbname ## _propagate,				\
106 	.copy = rbname ## _copy,					\
107 	.rotate = rbname ## _rotate					\
108 };
109 
110 
111 #define	RB_RED		0
112 #define	RB_BLACK	1
113 
114 #define __rb_parent(pc)    ((struct rb_node *)(pc & ~3))
115 
116 #define __rb_color(pc)     ((pc) & 1)
117 #define __rb_is_black(pc)  __rb_color(pc)
118 #define __rb_is_red(pc)    (!__rb_color(pc))
119 #define rb_color(rb)       __rb_color((rb)->__rb_parent_color)
120 #define rb_is_red(rb)      __rb_is_red((rb)->__rb_parent_color)
121 #define rb_is_black(rb)    __rb_is_black((rb)->__rb_parent_color)
122 
123 static inline void rb_set_parent(struct rb_node *rb, struct rb_node *p)
124 {
125 	rb->__rb_parent_color = rb_color(rb) | (unsigned long)p;
126 }
127 
128 static inline void rb_set_parent_color(struct rb_node *rb,
129 				       struct rb_node *p, int color)
130 {
131 	rb->__rb_parent_color = (unsigned long)p | color;
132 }
133 
134 static inline void
135 __rb_change_child(struct rb_node *old, struct rb_node *new,
136 		  struct rb_node *parent, struct rb_root *root)
137 {
138 	if (parent) {
139 		if (parent->rb_left == old)
140 			WRITE_ONCE(parent->rb_left, new);
141 		else
142 			WRITE_ONCE(parent->rb_right, new);
143 	} else
144 		WRITE_ONCE(root->rb_node, new);
145 }
146 
147 static inline void
148 __rb_change_child_rcu(struct rb_node *old, struct rb_node *new,
149 		      struct rb_node *parent, struct rb_root *root)
150 {
151 	if (parent) {
152 		if (parent->rb_left == old)
153 			rcu_assign_pointer(parent->rb_left, new);
154 		else
155 			rcu_assign_pointer(parent->rb_right, new);
156 	} else
157 		rcu_assign_pointer(root->rb_node, new);
158 }
159 
160 extern void __rb_erase_color(struct rb_node *parent, struct rb_root *root,
161 	void (*augment_rotate)(struct rb_node *old, struct rb_node *new));
162 
163 static __always_inline struct rb_node *
164 __rb_erase_augmented(struct rb_node *node, struct rb_root *root,
165 		     struct rb_node **leftmost,
166 		     const struct rb_augment_callbacks *augment)
167 {
168 	struct rb_node *child = node->rb_right;
169 	struct rb_node *tmp = node->rb_left;
170 	struct rb_node *parent, *rebalance;
171 	unsigned long pc;
172 
173 	if (leftmost && node == *leftmost)
174 		*leftmost = rb_next(node);
175 
176 	if (!tmp) {
177 		/*
178 		 * Case 1: node to erase has no more than 1 child (easy!)
179 		 *
180 		 * Note that if there is one child it must be red due to 5)
181 		 * and node must be black due to 4). We adjust colors locally
182 		 * so as to bypass __rb_erase_color() later on.
183 		 */
184 		pc = node->__rb_parent_color;
185 		parent = __rb_parent(pc);
186 		__rb_change_child(node, child, parent, root);
187 		if (child) {
188 			child->__rb_parent_color = pc;
189 			rebalance = NULL;
190 		} else
191 			rebalance = __rb_is_black(pc) ? parent : NULL;
192 		tmp = parent;
193 	} else if (!child) {
194 		/* Still case 1, but this time the child is node->rb_left */
195 		tmp->__rb_parent_color = pc = node->__rb_parent_color;
196 		parent = __rb_parent(pc);
197 		__rb_change_child(node, tmp, parent, root);
198 		rebalance = NULL;
199 		tmp = parent;
200 	} else {
201 		struct rb_node *successor = child, *child2;
202 
203 		tmp = child->rb_left;
204 		if (!tmp) {
205 			/*
206 			 * Case 2: node's successor is its right child
207 			 *
208 			 *    (n)          (s)
209 			 *    / \          / \
210 			 *  (x) (s)  ->  (x) (c)
211 			 *        \
212 			 *        (c)
213 			 */
214 			parent = successor;
215 			child2 = successor->rb_right;
216 
217 			augment->copy(node, successor);
218 		} else {
219 			/*
220 			 * Case 3: node's successor is leftmost under
221 			 * node's right child subtree
222 			 *
223 			 *    (n)          (s)
224 			 *    / \          / \
225 			 *  (x) (y)  ->  (x) (y)
226 			 *      /            /
227 			 *    (p)          (p)
228 			 *    /            /
229 			 *  (s)          (c)
230 			 *    \
231 			 *    (c)
232 			 */
233 			do {
234 				parent = successor;
235 				successor = tmp;
236 				tmp = tmp->rb_left;
237 			} while (tmp);
238 			child2 = successor->rb_right;
239 			WRITE_ONCE(parent->rb_left, child2);
240 			WRITE_ONCE(successor->rb_right, child);
241 			rb_set_parent(child, successor);
242 
243 			augment->copy(node, successor);
244 			augment->propagate(parent, successor);
245 		}
246 
247 		tmp = node->rb_left;
248 		WRITE_ONCE(successor->rb_left, tmp);
249 		rb_set_parent(tmp, successor);
250 
251 		pc = node->__rb_parent_color;
252 		tmp = __rb_parent(pc);
253 		__rb_change_child(node, successor, tmp, root);
254 
255 		if (child2) {
256 			successor->__rb_parent_color = pc;
257 			rb_set_parent_color(child2, parent, RB_BLACK);
258 			rebalance = NULL;
259 		} else {
260 			unsigned long pc2 = successor->__rb_parent_color;
261 			successor->__rb_parent_color = pc;
262 			rebalance = __rb_is_black(pc2) ? parent : NULL;
263 		}
264 		tmp = successor;
265 	}
266 
267 	augment->propagate(tmp, NULL);
268 	return rebalance;
269 }
270 
271 static __always_inline void
272 rb_erase_augmented(struct rb_node *node, struct rb_root *root,
273 		   const struct rb_augment_callbacks *augment)
274 {
275 	struct rb_node *rebalance = __rb_erase_augmented(node, root,
276 							 NULL, augment);
277 	if (rebalance)
278 		__rb_erase_color(rebalance, root, augment->rotate);
279 }
280 
281 static __always_inline void
282 rb_erase_augmented_cached(struct rb_node *node, struct rb_root_cached *root,
283 			  const struct rb_augment_callbacks *augment)
284 {
285 	struct rb_node *rebalance = __rb_erase_augmented(node, &root->rb_root,
286 							 &root->rb_leftmost,
287 							 augment);
288 	if (rebalance)
289 		__rb_erase_color(rebalance, &root->rb_root, augment->rotate);
290 }
291 
292 #endif	/* _LINUX_RBTREE_AUGMENTED_H */
293