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