linux/include/linux/rbtree_augmented.h
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   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
  38struct 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
  44extern void __rb_insert_augmented(struct rb_node *node, struct rb_root *root,
  45        void (*augment_rotate)(struct rb_node *old, struct rb_node *new));
  46static inline void
  47rb_insert_augmented(struct rb_node *node, struct rb_root *root,
  48                    const struct rb_augment_callbacks *augment)
  49{
  50        __rb_insert_augmented(node, root, augment->rotate);
  51}
  52
  53#define RB_DECLARE_CALLBACKS(rbstatic, rbname, rbstruct, rbfield,       \
  54                             rbtype, rbaugmented, rbcompute)            \
  55static inline void                                                      \
  56rbname ## _propagate(struct rb_node *rb, struct rb_node *stop)          \
  57{                                                                       \
  58        while (rb != stop) {                                            \
  59                rbstruct *node = rb_entry(rb, rbstruct, rbfield);       \
  60                rbtype augmented = rbcompute(node);                     \
  61                if (node->rbaugmented == augmented)                     \
  62                        break;                                          \
  63                node->rbaugmented = augmented;                          \
  64                rb = rb_parent(&node->rbfield);                         \
  65        }                                                               \
  66}                                                                       \
  67static inline void                                                      \
  68rbname ## _copy(struct rb_node *rb_old, struct rb_node *rb_new)         \
  69{                                                                       \
  70        rbstruct *old = rb_entry(rb_old, rbstruct, rbfield);            \
  71        rbstruct *new = rb_entry(rb_new, rbstruct, rbfield);            \
  72        new->rbaugmented = old->rbaugmented;                            \
  73}                                                                       \
  74static void                                                             \
  75rbname ## _rotate(struct rb_node *rb_old, struct rb_node *rb_new)       \
  76{                                                                       \
  77        rbstruct *old = rb_entry(rb_old, rbstruct, rbfield);            \
  78        rbstruct *new = rb_entry(rb_new, rbstruct, rbfield);            \
  79        new->rbaugmented = old->rbaugmented;                            \
  80        old->rbaugmented = rbcompute(old);                              \
  81}                                                                       \
  82rbstatic const struct rb_augment_callbacks rbname = {                   \
  83        rbname ## _propagate, rbname ## _copy, rbname ## _rotate        \
  84};
  85
  86
  87#define RB_RED          0
  88#define RB_BLACK        1
  89
  90#define __rb_parent(pc)    ((struct rb_node *)(pc & ~3))
  91
  92#define __rb_color(pc)     ((pc) & 1)
  93#define __rb_is_black(pc)  __rb_color(pc)
  94#define __rb_is_red(pc)    (!__rb_color(pc))
  95#define rb_color(rb)       __rb_color((rb)->__rb_parent_color)
  96#define rb_is_red(rb)      __rb_is_red((rb)->__rb_parent_color)
  97#define rb_is_black(rb)    __rb_is_black((rb)->__rb_parent_color)
  98
  99static inline void rb_set_parent(struct rb_node *rb, struct rb_node *p)
 100{
 101        rb->__rb_parent_color = rb_color(rb) | (unsigned long)p;
 102}
 103
 104static inline void rb_set_parent_color(struct rb_node *rb,
 105                                       struct rb_node *p, int color)
 106{
 107        rb->__rb_parent_color = (unsigned long)p | color;
 108}
 109
 110static inline void
 111__rb_change_child(struct rb_node *old, struct rb_node *new,
 112                  struct rb_node *parent, struct rb_root *root)
 113{
 114        if (parent) {
 115                if (parent->rb_left == old)
 116                        parent->rb_left = new;
 117                else
 118                        parent->rb_right = new;
 119        } else
 120                root->rb_node = new;
 121}
 122
 123extern void __rb_erase_color(struct rb_node *parent, struct rb_root *root,
 124        void (*augment_rotate)(struct rb_node *old, struct rb_node *new));
 125
 126static __always_inline void
 127rb_erase_augmented(struct rb_node *node, struct rb_root *root,
 128                   const struct rb_augment_callbacks *augment)
 129{
 130        struct rb_node *child = node->rb_right, *tmp = node->rb_left;
 131        struct rb_node *parent, *rebalance;
 132        unsigned long pc;
 133
 134        if (!tmp) {
 135                /*
 136                 * Case 1: node to erase has no more than 1 child (easy!)
 137                 *
 138                 * Note that if there is one child it must be red due to 5)
 139                 * and node must be black due to 4). We adjust colors locally
 140                 * so as to bypass __rb_erase_color() later on.
 141                 */
 142                pc = node->__rb_parent_color;
 143                parent = __rb_parent(pc);
 144                __rb_change_child(node, child, parent, root);
 145                if (child) {
 146                        child->__rb_parent_color = pc;
 147                        rebalance = NULL;
 148                } else
 149                        rebalance = __rb_is_black(pc) ? parent : NULL;
 150                tmp = parent;
 151        } else if (!child) {
 152                /* Still case 1, but this time the child is node->rb_left */
 153                tmp->__rb_parent_color = pc = node->__rb_parent_color;
 154                parent = __rb_parent(pc);
 155                __rb_change_child(node, tmp, parent, root);
 156                rebalance = NULL;
 157                tmp = parent;
 158        } else {
 159                struct rb_node *successor = child, *child2;
 160                tmp = child->rb_left;
 161                if (!tmp) {
 162                        /*
 163                         * Case 2: node's successor is its right child
 164                         *
 165                         *    (n)          (s)
 166                         *    / \          / \
 167                         *  (x) (s)  ->  (x) (c)
 168                         *        \
 169                         *        (c)
 170                         */
 171                        parent = successor;
 172                        child2 = successor->rb_right;
 173                        augment->copy(node, successor);
 174                } else {
 175                        /*
 176                         * Case 3: node's successor is leftmost under
 177                         * node's right child subtree
 178                         *
 179                         *    (n)          (s)
 180                         *    / \          / \
 181                         *  (x) (y)  ->  (x) (y)
 182                         *      /            /
 183                         *    (p)          (p)
 184                         *    /            /
 185                         *  (s)          (c)
 186                         *    \
 187                         *    (c)
 188                         */
 189                        do {
 190                                parent = successor;
 191                                successor = tmp;
 192                                tmp = tmp->rb_left;
 193                        } while (tmp);
 194                        parent->rb_left = child2 = successor->rb_right;
 195                        successor->rb_right = child;
 196                        rb_set_parent(child, successor);
 197                        augment->copy(node, successor);
 198                        augment->propagate(parent, successor);
 199                }
 200
 201                successor->rb_left = tmp = node->rb_left;
 202                rb_set_parent(tmp, successor);
 203
 204                pc = node->__rb_parent_color;
 205                tmp = __rb_parent(pc);
 206                __rb_change_child(node, successor, tmp, root);
 207                if (child2) {
 208                        successor->__rb_parent_color = pc;
 209                        rb_set_parent_color(child2, parent, RB_BLACK);
 210                        rebalance = NULL;
 211                } else {
 212                        unsigned long pc2 = successor->__rb_parent_color;
 213                        successor->__rb_parent_color = pc;
 214                        rebalance = __rb_is_black(pc2) ? parent : NULL;
 215                }
 216                tmp = successor;
 217        }
 218
 219        augment->propagate(tmp, NULL);
 220        if (rebalance)
 221                __rb_erase_color(rebalance, root, augment->rotate);
 222}
 223
 224#endif  /* _LINUX_RBTREE_AUGMENTED_H */
 225
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