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,
  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_augment_inserted() instead of the usual rb_insert_color() call.
  55  * If rb_augment_inserted() 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 */