Import rbtrees from Linux
[akaros.git] / kern / include / rbtree_augmented.h
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
30 /*
31  * Please note - only struct rb_augment_callbacks and the prototypes for
32  * rb_insert_augmented() and rb_erase_augmented() are intended to be public.
33  * The rest are implementation details you are not expected to depend on.
34  *
35  * See Documentation/rbtree.txt for documentation and samples.
36  */
37
38 struct rb_augment_callbacks {
39         void (*propagate)(struct rb_node *node, struct rb_node *stop);
40         void (*copy)(struct rb_node *old, struct rb_node *new);
41         void (*rotate)(struct rb_node *old, struct rb_node *new);
42 };
43
44 extern void __rb_insert_augmented(struct rb_node *node, struct rb_root *root,
45         void (*augment_rotate)(struct rb_node *old, struct rb_node *new));
46 /*
47  * Fixup the rbtree and update the augmented information when rebalancing.
48  *
49  * On insertion, the user must update the augmented information on the path
50  * leading to the inserted node, then call rb_link_node() as usual and
51  * rb_augment_inserted() instead of the usual rb_insert_color() call.
52  * If rb_augment_inserted() rebalances the rbtree, it will callback into
53  * a user provided function to update the augmented information on the
54  * affected subtrees.
55  */
56 static inline void
57 rb_insert_augmented(struct rb_node *node, struct rb_root *root,
58                     const struct rb_augment_callbacks *augment)
59 {
60         __rb_insert_augmented(node, root, augment->rotate);
61 }
62
63 #define RB_DECLARE_CALLBACKS(rbstatic, rbname, rbstruct, rbfield,       \
64                              rbtype, rbaugmented, rbcompute)            \
65 static inline void                                                      \
66 rbname ## _propagate(struct rb_node *rb, struct rb_node *stop)          \
67 {                                                                       \
68         while (rb != stop) {                                            \
69                 rbstruct *node = rb_entry(rb, rbstruct, rbfield);       \
70                 rbtype augmented = rbcompute(node);                     \
71                 if (node->rbaugmented == augmented)                     \
72                         break;                                          \
73                 node->rbaugmented = augmented;                          \
74                 rb = rb_parent(&node->rbfield);                         \
75         }                                                               \
76 }                                                                       \
77 static inline void                                                      \
78 rbname ## _copy(struct rb_node *rb_old, struct rb_node *rb_new)         \
79 {                                                                       \
80         rbstruct *old = rb_entry(rb_old, rbstruct, rbfield);            \
81         rbstruct *new = rb_entry(rb_new, rbstruct, rbfield);            \
82         new->rbaugmented = old->rbaugmented;                            \
83 }                                                                       \
84 static void                                                             \
85 rbname ## _rotate(struct rb_node *rb_old, struct rb_node *rb_new)       \
86 {                                                                       \
87         rbstruct *old = rb_entry(rb_old, rbstruct, rbfield);            \
88         rbstruct *new = rb_entry(rb_new, rbstruct, rbfield);            \
89         new->rbaugmented = old->rbaugmented;                            \
90         old->rbaugmented = rbcompute(old);                              \
91 }                                                                       \
92 rbstatic const struct rb_augment_callbacks rbname = {                   \
93         rbname ## _propagate, rbname ## _copy, rbname ## _rotate        \
94 };
95
96
97 #define RB_RED          0
98 #define RB_BLACK        1
99
100 #define __rb_parent(pc)    ((struct rb_node *)(pc & ~3))
101
102 #define __rb_color(pc)     ((pc) & 1)
103 #define __rb_is_black(pc)  __rb_color(pc)
104 #define __rb_is_red(pc)    (!__rb_color(pc))
105 #define rb_color(rb)       __rb_color((rb)->__rb_parent_color)
106 #define rb_is_red(rb)      __rb_is_red((rb)->__rb_parent_color)
107 #define rb_is_black(rb)    __rb_is_black((rb)->__rb_parent_color)
108
109 static inline void rb_set_parent(struct rb_node *rb, struct rb_node *p)
110 {
111         rb->__rb_parent_color = rb_color(rb) | (unsigned long)p;
112 }
113
114 static inline void rb_set_parent_color(struct rb_node *rb,
115                                        struct rb_node *p, int color)
116 {
117         rb->__rb_parent_color = (unsigned long)p | color;
118 }
119
120 static inline void
121 __rb_change_child(struct rb_node *old, struct rb_node *new,
122                   struct rb_node *parent, struct rb_root *root)
123 {
124         if (parent) {
125                 if (parent->rb_left == old)
126                         WRITE_ONCE(parent->rb_left, new);
127                 else
128                         WRITE_ONCE(parent->rb_right, new);
129         } else
130                 WRITE_ONCE(root->rb_node, new);
131 }
132
133 static inline void
134 __rb_change_child_rcu(struct rb_node *old, struct rb_node *new,
135                       struct rb_node *parent, struct rb_root *root)
136 {
137         if (parent) {
138                 if (parent->rb_left == old)
139                         rcu_assign_pointer(parent->rb_left, new);
140                 else
141                         rcu_assign_pointer(parent->rb_right, new);
142         } else
143                 rcu_assign_pointer(root->rb_node, new);
144 }
145
146 extern void __rb_erase_color(struct rb_node *parent, struct rb_root *root,
147         void (*augment_rotate)(struct rb_node *old, struct rb_node *new));
148
149 static __always_inline struct rb_node *
150 __rb_erase_augmented(struct rb_node *node, struct rb_root *root,
151                      const struct rb_augment_callbacks *augment)
152 {
153         struct rb_node *child = node->rb_right;
154         struct rb_node *tmp = node->rb_left;
155         struct rb_node *parent, *rebalance;
156         unsigned long pc;
157
158         if (!tmp) {
159                 /*
160                  * Case 1: node to erase has no more than 1 child (easy!)
161                  *
162                  * Note that if there is one child it must be red due to 5)
163                  * and node must be black due to 4). We adjust colors locally
164                  * so as to bypass __rb_erase_color() later on.
165                  */
166                 pc = node->__rb_parent_color;
167                 parent = __rb_parent(pc);
168                 __rb_change_child(node, child, parent, root);
169                 if (child) {
170                         child->__rb_parent_color = pc;
171                         rebalance = NULL;
172                 } else
173                         rebalance = __rb_is_black(pc) ? parent : NULL;
174                 tmp = parent;
175         } else if (!child) {
176                 /* Still case 1, but this time the child is node->rb_left */
177                 tmp->__rb_parent_color = pc = node->__rb_parent_color;
178                 parent = __rb_parent(pc);
179                 __rb_change_child(node, tmp, parent, root);
180                 rebalance = NULL;
181                 tmp = parent;
182         } else {
183                 struct rb_node *successor = child, *child2;
184
185                 tmp = child->rb_left;
186                 if (!tmp) {
187                         /*
188                          * Case 2: node's successor is its right child
189                          *
190                          *    (n)          (s)
191                          *    / \          / \
192                          *  (x) (s)  ->  (x) (c)
193                          *        \
194                          *        (c)
195                          */
196                         parent = successor;
197                         child2 = successor->rb_right;
198
199                         augment->copy(node, successor);
200                 } else {
201                         /*
202                          * Case 3: node's successor is leftmost under
203                          * node's right child subtree
204                          *
205                          *    (n)          (s)
206                          *    / \          / \
207                          *  (x) (y)  ->  (x) (y)
208                          *      /            /
209                          *    (p)          (p)
210                          *    /            /
211                          *  (s)          (c)
212                          *    \
213                          *    (c)
214                          */
215                         do {
216                                 parent = successor;
217                                 successor = tmp;
218                                 tmp = tmp->rb_left;
219                         } while (tmp);
220                         child2 = successor->rb_right;
221                         WRITE_ONCE(parent->rb_left, child2);
222                         WRITE_ONCE(successor->rb_right, child);
223                         rb_set_parent(child, successor);
224
225                         augment->copy(node, successor);
226                         augment->propagate(parent, successor);
227                 }
228
229                 tmp = node->rb_left;
230                 WRITE_ONCE(successor->rb_left, tmp);
231                 rb_set_parent(tmp, successor);
232
233                 pc = node->__rb_parent_color;
234                 tmp = __rb_parent(pc);
235                 __rb_change_child(node, successor, tmp, root);
236
237                 if (child2) {
238                         successor->__rb_parent_color = pc;
239                         rb_set_parent_color(child2, parent, RB_BLACK);
240                         rebalance = NULL;
241                 } else {
242                         unsigned long pc2 = successor->__rb_parent_color;
243                         successor->__rb_parent_color = pc;
244                         rebalance = __rb_is_black(pc2) ? parent : NULL;
245                 }
246                 tmp = successor;
247         }
248
249         augment->propagate(tmp, NULL);
250         return rebalance;
251 }
252
253 static __always_inline void
254 rb_erase_augmented(struct rb_node *node, struct rb_root *root,
255                    const struct rb_augment_callbacks *augment)
256 {
257         struct rb_node *rebalance = __rb_erase_augmented(node, root, augment);
258         if (rebalance)
259                 __rb_erase_color(rebalance, root, augment->rotate);
260 }
261
262 #endif  /* _LINUX_RBTREE_AUGMENTED_H */