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
  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,
  45                                   struct rb_root *root,
  46                                   bool newleft, struct rb_node **leftmost,
  47         void (*augment_rotate)(struct rb_node *old, struct rb_node *new));
  48 /*
  49  * Fixup the rbtree and update the augmented information when rebalancing.
  50  *
  51  * On insertion, the user must update the augmented information on the path
  52  * leading to the inserted node, then call rb_link_node() as usual and
  53  * rb_augment_inserted() instead of the usual rb_insert_color() call.
  54  * If rb_augment_inserted() rebalances the rbtree, it will callback into
  55  * a user provided function to update the augmented information on the
  56  * affected subtrees.
  57  */
  58 static inline void
  59 rb_insert_augmented(struct rb_node *node, struct rb_root *root,
  60                     const struct rb_augment_callbacks *augment)
  61 {
  62         __rb_insert_augmented(node, root, false, NULL, augment->rotate);
  63 }
  64
  65 static inline void
  66 rb_insert_augmented_cached(struct rb_node *node,
  67                            struct rb_root_cached *root, bool newleft,
  68                            const struct rb_augment_callbacks *augment)
  69 {
  70         __rb_insert_augmented(node, &root->rb_root,
  71                               newleft, &root->rb_leftmost, augment->rotate);
  72 }
  73
  74 #define RB_DECLARE_CALLBACKS(rbstatic, rbname, rbstruct, rbfield,       \
  75                              rbtype, rbaugmented, rbcompute)            \
  76 static inline void                                                      \
  77 rbname ## _propagate(struct rb_node *rb, struct rb_node *stop)          \
  78 {                                                                       \
  79         while (rb != stop) {                                            \
  80                 rbstruct *node = rb_entry(rb, rbstruct, rbfield);       \
  81                 rbtype augmented = rbcompute(node);                     \
  82                 if (node->rbaugmented == augmented)                     \
  83                         break;                                          \
  84                 node->rbaugmented = augmented;                          \
  85                 rb = rb_parent(&node->rbfield);                         \
  86         }                                                               \
  87 }                                                                       \
  88 static inline void                                                      \
  89 rbname ## _copy(struct rb_node *rb_old, struct rb_node *rb_new)         \
  90 {                                                                       \
  91         rbstruct *old = rb_entry(rb_old, rbstruct, rbfield);            \
  92         rbstruct *new = rb_entry(rb_new, rbstruct, rbfield);            \
  93         new->rbaugmented = old->rbaugmented;                            \
  94 }                                                                       \
  95 static void                                                             \
  96 rbname ## _rotate(struct rb_node *rb_old, struct rb_node *rb_new)       \
  97 {                                                                       \
  98         rbstruct *old = rb_entry(rb_old, rbstruct, rbfield);            \
  99         rbstruct *new = rb_entry(rb_new, rbstruct, rbfield);            \
 100         new->rbaugmented = old->rbaugmented;                            \
 101         old->rbaugmented = rbcompute(old);                              \
 102 }                                                                       \
 103 rbstatic const struct rb_augment_callbacks rbname = {                   \
 104         rbname ## _propagate, rbname ## _copy, rbname ## _rotate        \
 105 };
 106
 107
 108 #define RB_RED          0
 109 #define RB_BLACK        1
 110
 111 #define __rb_parent(pc)    ((struct rb_node *)(pc & ~3))
 112
 113 #define __rb_color(pc)     ((pc) & 1)
 114 #define __rb_is_black(pc)  __rb_color(pc)
 115 #define __rb_is_red(pc)    (!__rb_color(pc))
 116 #define rb_color(rb)       __rb_color((rb)->__rb_parent_color)
 117 #define rb_is_red(rb)      __rb_is_red((rb)->__rb_parent_color)
 118 #define rb_is_black(rb)    __rb_is_black((rb)->__rb_parent_color)
 119
 120 static inline void rb_set_parent(struct rb_node *rb, struct rb_node *p)
 121 {
 122         rb->__rb_parent_color = rb_color(rb) | (unsigned long)p;
 123 }
 124
 125 static inline void rb_set_parent_color(struct rb_node *rb,
 126                                        struct rb_node *p, int color)
 127 {
 128         rb->__rb_parent_color = (unsigned long)p | color;
 129 }
 130
 131 static inline void
 132 __rb_change_child(struct rb_node *old, struct rb_node *new,
 133                   struct rb_node *parent, struct rb_root *root)
 134 {
 135         if (parent) {
 136                 if (parent->rb_left == old)
 137                         WRITE_ONCE(parent->rb_left, new);
 138                 else
 139                         WRITE_ONCE(parent->rb_right, new);
 140         } else
 141                 WRITE_ONCE(root->rb_node, new);
 142 }
 143
 144 extern void __rb_erase_color(struct rb_node *parent, struct rb_root *root,
 145         void (*augment_rotate)(struct rb_node *old, struct rb_node *new));
 146
 147 static __always_inline struct rb_node *
 148 __rb_erase_augmented(struct rb_node *node, struct rb_root *root,
 149                      struct rb_node **leftmost,
 150                      const struct rb_augment_callbacks *augment)
 151 {
 152         struct rb_node *child = node->rb_right;
 153         struct rb_node *tmp = node->rb_left;
 154         struct rb_node *parent, *rebalance;
 155         unsigned long pc;
 156
 157         if (leftmost && node == *leftmost)
 158                 *leftmost = rb_next(node);
 159
 160         if (!tmp) {
 161                 /*
 162                  * Case 1: node to erase has no more than 1 child (easy!)
 163                  *
 164                  * Note that if there is one child it must be red due to 5)
 165                  * and node must be black due to 4). We adjust colors locally
 166                  * so as to bypass __rb_erase_color() later on.
 167                  */
 168                 pc = node->__rb_parent_color;
 169                 parent = __rb_parent(pc);
 170                 __rb_change_child(node, child, parent, root);
 171                 if (child) {
 172                         child->__rb_parent_color = pc;
 173                         rebalance = NULL;
 174                 } else
 175                         rebalance = __rb_is_black(pc) ? parent : NULL;
 176                 tmp = parent;
 177         } else if (!child) {
 178                 /* Still case 1, but this time the child is node->rb_left */
 179                 tmp->__rb_parent_color = pc = node->__rb_parent_color;
 180                 parent = __rb_parent(pc);
 181                 __rb_change_child(node, tmp, parent, root);
 182                 rebalance = NULL;
 183                 tmp = parent;
 184         } else {
 185                 struct rb_node *successor = child, *child2;
 186
 187                 tmp = child->rb_left;
 188                 if (!tmp) {
 189                         /*
 190                          * Case 2: node's successor is its right child
 191                          *
 192                          *    (n)          (s)
 193                          *    / \          / \
 194                          *  (x) (s)  ->  (x) (c)
 195                          *        \
 196                          *        (c)
 197                          */
 198                         parent = successor;
 199                         child2 = successor->rb_right;
 200
 201                         augment->copy(node, successor);
 202                 } else {
 203                         /*
 204                          * Case 3: node's successor is leftmost under
 205                          * node's right child subtree
 206                          *
 207                          *    (n)          (s)
 208                          *    / \          / \
 209                          *  (x) (y)  ->  (x) (y)
 210                          *      /            /
 211                          *    (p)          (p)
 212                          *    /            /
 213                          *  (s)          (c)
 214                          *    \
 215                          *    (c)
 216                          */
 217                         do {
 218                                 parent = successor;
 219                                 successor = tmp;
 220                                 tmp = tmp->rb_left;
 221                         } while (tmp);
 222                         child2 = successor->rb_right;
 223                         WRITE_ONCE(parent->rb_left, child2);
 224                         WRITE_ONCE(successor->rb_right, child);
 225                         rb_set_parent(child, successor);
 226
 227                         augment->copy(node, successor);
 228                         augment->propagate(parent, successor);
 229                 }
 230
 231                 tmp = node->rb_left;
 232                 WRITE_ONCE(successor->rb_left, tmp);
 233                 rb_set_parent(tmp, successor);
 234
 235                 pc = node->__rb_parent_color;
 236                 tmp = __rb_parent(pc);
 237                 __rb_change_child(node, successor, tmp, root);
 238
 239                 if (child2) {
 240                         successor->__rb_parent_color = pc;
 241                         rb_set_parent_color(child2, parent, RB_BLACK);
 242                         rebalance = NULL;
 243                 } else {
 244                         unsigned long pc2 = successor->__rb_parent_color;
 245                         successor->__rb_parent_color = pc;
 246                         rebalance = __rb_is_black(pc2) ? parent : NULL;
 247                 }
 248                 tmp = successor;
 249         }
 250
 251         augment->propagate(tmp, NULL);
 252         return rebalance;
 253 }
 254
 255 static __always_inline void
 256 rb_erase_augmented(struct rb_node *node, struct rb_root *root,
 257                    const struct rb_augment_callbacks *augment)
 258 {
 259         struct rb_node *rebalance = __rb_erase_augmented(node, root,
 260                                                          NULL, augment);
 261         if (rebalance)
 262                 __rb_erase_color(rebalance, root, augment->rotate);
 263 }
 264
 265 static __always_inline void
 266 rb_erase_augmented_cached(struct rb_node *node, struct rb_root_cached *root,
 267                           const struct rb_augment_callbacks *augment)
 268 {
 269         struct rb_node *rebalance = __rb_erase_augmented(node, &root->rb_root,
 270                                                          &root->rb_leftmost,
 271                                                          augment);
 272         if (rebalance)
 273                 __rb_erase_color(rebalance, &root->rb_root, augment->rotate);
 274 }
 275
 276 #endif  /* _LINUX_RBTREE_AUGMENTED_H */