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, 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 extern void __rb_erase_color(struct rb_node *parent, struct rb_root *root,
 134         void (*augment_rotate)(struct rb_node *old, struct rb_node *new));
 135
 136 static __always_inline struct rb_node *
 137 __rb_erase_augmented(struct rb_node *node, struct rb_root *root,
 138                      const struct rb_augment_callbacks *augment)
 139 {
 140         struct rb_node *child = node->rb_right;
 141         struct rb_node *tmp = node->rb_left;
 142         struct rb_node *parent, *rebalance;
 143         unsigned long pc;
 144
 145         if (!tmp) {
 146                 /*
 147                  * Case 1: node to erase has no more than 1 child (easy!)
 148                  *
 149                  * Note that if there is one child it must be red due to 5)
 150                  * and node must be black due to 4). We adjust colors locally
 151                  * so as to bypass __rb_erase_color() later on.
 152                  */
 153                 pc = node->__rb_parent_color;
 154                 parent = __rb_parent(pc);
 155                 __rb_change_child(node, child, parent, root);
 156                 if (child) {
 157                         child->__rb_parent_color = pc;
 158                         rebalance = NULL;
 159                 } else
 160                         rebalance = __rb_is_black(pc) ? parent : NULL;
 161                 tmp = parent;
 162         } else if (!child) {
 163                 /* Still case 1, but this time the child is node->rb_left */
 164                 tmp->__rb_parent_color = pc = node->__rb_parent_color;
 165                 parent = __rb_parent(pc);
 166                 __rb_change_child(node, tmp, parent, root);
 167                 rebalance = NULL;
 168                 tmp = parent;
 169         } else {
 170                 struct rb_node *successor = child, *child2;
 171
 172                 tmp = child->rb_left;
 173                 if (!tmp) {
 174                         /*
 175                          * Case 2: node's successor is its right child
 176                          *
 177                          *    (n)          (s)
 178                          *    / \          / \
 179                          *  (x) (s)  ->  (x) (c)
 180                          *        \
 181                          *        (c)
 182                          */
 183                         parent = successor;
 184                         child2 = successor->rb_right;
 185
 186                         augment->copy(node, successor);
 187                 } else {
 188                         /*
 189                          * Case 3: node's successor is leftmost under
 190                          * node's right child subtree
 191                          *
 192                          *    (n)          (s)
 193                          *    / \          / \
 194                          *  (x) (y)  ->  (x) (y)
 195                          *      /            /
 196                          *    (p)          (p)
 197                          *    /            /
 198                          *  (s)          (c)
 199                          *    \
 200                          *    (c)
 201                          */
 202                         do {
 203                                 parent = successor;
 204                                 successor = tmp;
 205                                 tmp = tmp->rb_left;
 206                         } while (tmp);
 207                         child2 = successor->rb_right;
 208                         WRITE_ONCE(parent->rb_left, child2);
 209                         WRITE_ONCE(successor->rb_right, child);
 210                         rb_set_parent(child, successor);
 211
 212                         augment->copy(node, successor);
 213                         augment->propagate(parent, successor);
 214                 }
 215
 216                 tmp = node->rb_left;
 217                 WRITE_ONCE(successor->rb_left, tmp);
 218                 rb_set_parent(tmp, successor);
 219
 220                 pc = node->__rb_parent_color;
 221                 tmp = __rb_parent(pc);
 222                 __rb_change_child(node, successor, tmp, root);
 223
 224                 if (child2) {
 225                         successor->__rb_parent_color = pc;
 226                         rb_set_parent_color(child2, parent, RB_BLACK);
 227                         rebalance = NULL;
 228                 } else {
 229                         unsigned long pc2 = successor->__rb_parent_color;
 230                         successor->__rb_parent_color = pc;
 231                         rebalance = __rb_is_black(pc2) ? parent : NULL;
 232                 }
 233                 tmp = successor;
 234         }
 235
 236         augment->propagate(tmp, NULL);
 237         return rebalance;
 238 }
 239
 240 static __always_inline void
 241 rb_erase_augmented(struct rb_node *node, struct rb_root *root,
 242                    const struct rb_augment_callbacks *augment)
 243 {
 244         struct rb_node *rebalance = __rb_erase_augmented(node, root, augment);
 245         if (rebalance)
 246                 __rb_erase_color(rebalance, root, augment->rotate);
 247 }
 248
 249 #endif  /* _LINUX_RBTREE_AUGMENTED_H */