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 "rbtree.h"
  28
  29 #ifdef __cplusplus
  30 extern "C" {
  31 #endif
  32
  33 /*
  34  * Please note - only struct rb_augment_callbacks and the prototypes for
  35  * rb_insert_augmented() and rb_erase_augmented() are intended to be public.
  36  * The rest are implementation details you are not expected to depend on.
  37  *
  38  * See Documentation/rbtree.txt for documentation and samples.
  39  */
  40
  41 struct rb_augment_callbacks {
  42         void (*propagate)(struct rb_node *node, struct rb_node *stop);
  43         void (*copy)(struct rb_node *old, struct rb_node *new);
  44         void (*rotate)(struct rb_node *old, struct rb_node *new);
  45 };
  46
  47 extern void __rb_insert_augmented(struct rb_node *node, struct rb_root *root,
  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, augment->rotate);
  64 }
  65
  66 #define RB_DECLARE_CALLBACKS(rbstatic, rbname, rbstruct, rbfield,       \
  67                              rbtype, rbaugmented, rbcompute)            \
  68 static inline void                                                      \
  69 rbname ## _propagate(struct rb_node *rb, struct rb_node *stop)          \
  70 {                                                                       \
  71         while (rb != stop) {                                            \
  72                 rbstruct *node = rb_entry(rb, rbstruct, rbfield);       \
  73                 rbtype augmented = rbcompute(node);                     \
  74                 if (node->rbaugmented == augmented)                     \
  75                         break;                                          \
  76                 node->rbaugmented = augmented;                          \
  77                 rb = rb_parent(&node->rbfield);                         \
  78         }                                                               \
  79 }                                                                       \
  80 static inline void                                                      \
  81 rbname ## _copy(struct rb_node *rb_old, struct rb_node *rb_new)         \
  82 {                                                                       \
  83         rbstruct *old = rb_entry(rb_old, rbstruct, rbfield);            \
  84         rbstruct *new = rb_entry(rb_new, rbstruct, rbfield);            \
  85         new->rbaugmented = old->rbaugmented;                            \
  86 }                                                                       \
  87 static void                                                             \
  88 rbname ## _rotate(struct rb_node *rb_old, struct rb_node *rb_new)       \
  89 {                                                                       \
  90         rbstruct *old = rb_entry(rb_old, rbstruct, rbfield);            \
  91         rbstruct *new = rb_entry(rb_new, rbstruct, rbfield);            \
  92         new->rbaugmented = old->rbaugmented;                            \
  93         old->rbaugmented = rbcompute(old);                              \
  94 }                                                                       \
  95 rbstatic const struct rb_augment_callbacks rbname = {                   \
  96         rbname ## _propagate, rbname ## _copy, rbname ## _rotate        \
  97 };
  98
  99
 100 #define RB_RED          0
 101 #define RB_BLACK        1
 102
 103 #define __rb_parent(pc)    ((struct rb_node *)(pc & ~3))
 104
 105 #define __rb_color(pc)     ((pc) & 1)
 106 #define __rb_is_black(pc)  __rb_color(pc)
 107 #define __rb_is_red(pc)    (!__rb_color(pc))
 108 #define rb_color(rb)       __rb_color((rb)->__rb_parent_color)
 109 #define rb_is_red(rb)      __rb_is_red((rb)->__rb_parent_color)
 110 #define rb_is_black(rb)    __rb_is_black((rb)->__rb_parent_color)
 111
 112 static inline void rb_set_parent(struct rb_node *rb, struct rb_node *p)
 113 {
 114         rb->__rb_parent_color = rb_color(rb) | (unsigned long)p;
 115 }
 116
 117 static inline void rb_set_parent_color(struct rb_node *rb,
 118                                        struct rb_node *p, int color)
 119 {
 120         rb->__rb_parent_color = (unsigned long)p | color;
 121 }
 122
 123 static inline void
 124 __rb_change_child(struct rb_node *old, struct rb_node *new,
 125                   struct rb_node *parent, struct rb_root *root)
 126 {
 127         if (parent) {
 128                 if (parent->rb_left == old)
 129                         parent->rb_left = new;
 130                 else
 131                         parent->rb_right = new;
 132         } else
 133                 root->rb_node = new;
 134 }
 135
 136 extern void __rb_erase_color(struct rb_node *parent, struct rb_root *root,
 137         void (*augment_rotate)(struct rb_node *old, struct rb_node *new));
 138
 139 static __always_inline struct rb_node *
 140 __rb_erase_augmented(struct rb_node *node, struct rb_root *root,
 141                      const struct rb_augment_callbacks *augment)
 142 {
 143         struct rb_node *child = node->rb_right, *tmp = node->rb_left;
 144         struct rb_node *parent, *rebalance;
 145         unsigned long pc;
 146
 147         if (!tmp) {
 148                 /*
 149                  * Case 1: node to erase has no more than 1 child (easy!)
 150                  *
 151                  * Note that if there is one child it must be red due to 5)
 152                  * and node must be black due to 4). We adjust colors locally
 153                  * so as to bypass __rb_erase_color() later on.
 154                  */
 155                 pc = node->__rb_parent_color;
 156                 parent = __rb_parent(pc);
 157                 __rb_change_child(node, child, parent, root);
 158                 if (child) {
 159                         child->__rb_parent_color = pc;
 160                         rebalance = NULL;
 161                 } else
 162                         rebalance = __rb_is_black(pc) ? parent : NULL;
 163                 tmp = parent;
 164         } else if (!child) {
 165                 /* Still case 1, but this time the child is node->rb_left */
 166                 tmp->__rb_parent_color = pc = node->__rb_parent_color;
 167                 parent = __rb_parent(pc);
 168                 __rb_change_child(node, tmp, parent, root);
 169                 rebalance = NULL;
 170                 tmp = parent;
 171         } else {
 172                 struct rb_node *successor = child, *child2;
 173                 tmp = child->rb_left;
 174                 if (!tmp) {
 175                         /*
 176                          * Case 2: node's successor is its right child
 177                          *
 178                          *    (n)          (s)
 179                          *    / \          / \
 180                          *  (x) (s)  ->  (x) (c)
 181                          *        \
 182                          *        (c)
 183                          */
 184                         parent = successor;
 185                         child2 = successor->rb_right;
 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                         parent->rb_left = child2 = successor->rb_right;
 208                         successor->rb_right = child;
 209                         rb_set_parent(child, successor);
 210                         augment->copy(node, successor);
 211                         augment->propagate(parent, successor);
 212                 }
 213
 214                 successor->rb_left = tmp = node->rb_left;
 215                 rb_set_parent(tmp, successor);
 216
 217                 pc = node->__rb_parent_color;
 218                 tmp = __rb_parent(pc);
 219                 __rb_change_child(node, successor, tmp, root);
 220                 if (child2) {
 221                         successor->__rb_parent_color = pc;
 222                         rb_set_parent_color(child2, parent, RB_BLACK);
 223                         rebalance = NULL;
 224                 } else {
 225                         unsigned long pc2 = successor->__rb_parent_color;
 226                         successor->__rb_parent_color = pc;
 227                         rebalance = __rb_is_black(pc2) ? parent : NULL;
 228                 }
 229                 tmp = successor;
 230         }
 231
 232         augment->propagate(tmp, NULL);
 233         return rebalance;
 234 }
 235
 236 static __always_inline void
 237 rb_erase_augmented(struct rb_node *node, struct rb_root *root,
 238                    const struct rb_augment_callbacks *augment)
 239 {
 240         struct rb_node *rebalance = __rb_erase_augmented(node, root, augment);
 241         if (rebalance)
 242                 __rb_erase_color(rebalance, root, augment->rotate);
 243 }
 244
 245 #ifdef __cplusplus
 246 }
 247 #endif
 248
 249 #endif  /* _LINUX_RBTREE_AUGMENTED_H */