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  * SPDX-License-Identifier:     GPL-2.0+
   8
   9   linux/include/linux/rbtree_augmented.h
  10 */
  11
  12 #ifndef _LINUX_RBTREE_AUGMENTED_H
  13 #define _LINUX_RBTREE_AUGMENTED_H
  14
  15 #include <linux/compiler.h>
  16 #include <linux/rbtree.h>
  17
  18 /*
  19  * Please note - only struct rb_augment_callbacks and the prototypes for
  20  * rb_insert_augmented() and rb_erase_augmented() are intended to be public.
  21  * The rest are implementation details you are not expected to depend on.
  22  *
  23  * See Documentation/rbtree.txt for documentation and samples.
  24  */
  25
  26 struct rb_augment_callbacks {
  27         void (*propagate)(struct rb_node *node, struct rb_node *stop);
  28         void (*copy)(struct rb_node *old, struct rb_node *new);
  29         void (*rotate)(struct rb_node *old, struct rb_node *new);
  30 };
  31
  32 extern void __rb_insert_augmented(struct rb_node *node, struct rb_root *root,
  33         void (*augment_rotate)(struct rb_node *old, struct rb_node *new));
  34 static inline void
  35 rb_insert_augmented(struct rb_node *node, struct rb_root *root,
  36                     const struct rb_augment_callbacks *augment)
  37 {
  38         __rb_insert_augmented(node, root, augment->rotate);
  39 }
  40
  41 #define RB_DECLARE_CALLBACKS(rbstatic, rbname, rbstruct, rbfield,       \
  42                              rbtype, rbaugmented, rbcompute)            \
  43 static inline void                                                      \
  44 rbname ## _propagate(struct rb_node *rb, struct rb_node *stop)          \
  45 {                                                                       \
  46         while (rb != stop) {                                            \
  47                 rbstruct *node = rb_entry(rb, rbstruct, rbfield);       \
  48                 rbtype augmented = rbcompute(node);                     \
  49                 if (node->rbaugmented == augmented)                     \
  50                         break;                                          \
  51                 node->rbaugmented = augmented;                          \
  52                 rb = rb_parent(&node->rbfield);                         \
  53         }                                                               \
  54 }                                                                       \
  55 static inline void                                                      \
  56 rbname ## _copy(struct rb_node *rb_old, struct rb_node *rb_new)         \
  57 {                                                                       \
  58         rbstruct *old = rb_entry(rb_old, rbstruct, rbfield);            \
  59         rbstruct *new = rb_entry(rb_new, rbstruct, rbfield);            \
  60         new->rbaugmented = old->rbaugmented;                            \
  61 }                                                                       \
  62 static void                                                             \
  63 rbname ## _rotate(struct rb_node *rb_old, struct rb_node *rb_new)       \
  64 {                                                                       \
  65         rbstruct *old = rb_entry(rb_old, rbstruct, rbfield);            \
  66         rbstruct *new = rb_entry(rb_new, rbstruct, rbfield);            \
  67         new->rbaugmented = old->rbaugmented;                            \
  68         old->rbaugmented = rbcompute(old);                              \
  69 }                                                                       \
  70 rbstatic const struct rb_augment_callbacks rbname = {                   \
  71         rbname ## _propagate, rbname ## _copy, rbname ## _rotate        \
  72 };
  73
  74
  75 #define RB_RED          0
  76 #define RB_BLACK        1
  77
  78 #define __rb_parent(pc)    ((struct rb_node *)(pc & ~3))
  79
  80 #define __rb_color(pc)     ((pc) & 1)
  81 #define __rb_is_black(pc)  __rb_color(pc)
  82 #define __rb_is_red(pc)    (!__rb_color(pc))
  83 #define rb_color(rb)       __rb_color((rb)->__rb_parent_color)
  84 #define rb_is_red(rb)      __rb_is_red((rb)->__rb_parent_color)
  85 #define rb_is_black(rb)    __rb_is_black((rb)->__rb_parent_color)
  86
  87 static inline void rb_set_parent(struct rb_node *rb, struct rb_node *p)
  88 {
  89         rb->__rb_parent_color = rb_color(rb) | (unsigned long)p;
  90 }
  91
  92 static inline void rb_set_parent_color(struct rb_node *rb,
  93                                        struct rb_node *p, int color)
  94 {
  95         rb->__rb_parent_color = (unsigned long)p | color;
  96 }
  97
  98 static inline void
  99 __rb_change_child(struct rb_node *old, struct rb_node *new,
 100                   struct rb_node *parent, struct rb_root *root)
 101 {
 102         if (parent) {
 103                 if (parent->rb_left == old)
 104                         parent->rb_left = new;
 105                 else
 106                         parent->rb_right = new;
 107         } else
 108                 root->rb_node = new;
 109 }
 110
 111 extern void __rb_erase_color(struct rb_node *parent, struct rb_root *root,
 112         void (*augment_rotate)(struct rb_node *old, struct rb_node *new));
 113
 114 static __always_inline struct rb_node *
 115 __rb_erase_augmented(struct rb_node *node, struct rb_root *root,
 116                      const struct rb_augment_callbacks *augment)
 117 {
 118         struct rb_node *child = node->rb_right, *tmp = node->rb_left;
 119         struct rb_node *parent, *rebalance;
 120         unsigned long pc;
 121
 122         if (!tmp) {
 123                 /*
 124                  * Case 1: node to erase has no more than 1 child (easy!)
 125                  *
 126                  * Note that if there is one child it must be red due to 5)
 127                  * and node must be black due to 4). We adjust colors locally
 128                  * so as to bypass __rb_erase_color() later on.
 129                  */
 130                 pc = node->__rb_parent_color;
 131                 parent = __rb_parent(pc);
 132                 __rb_change_child(node, child, parent, root);
 133                 if (child) {
 134                         child->__rb_parent_color = pc;
 135                         rebalance = NULL;
 136                 } else
 137                         rebalance = __rb_is_black(pc) ? parent : NULL;
 138                 tmp = parent;
 139         } else if (!child) {
 140                 /* Still case 1, but this time the child is node->rb_left */
 141                 tmp->__rb_parent_color = pc = node->__rb_parent_color;
 142                 parent = __rb_parent(pc);
 143                 __rb_change_child(node, tmp, parent, root);
 144                 rebalance = NULL;
 145                 tmp = parent;
 146         } else {
 147                 struct rb_node *successor = child, *child2;
 148                 tmp = child->rb_left;
 149                 if (!tmp) {
 150                         /*
 151                          * Case 2: node's successor is its right child
 152                          *
 153                          *    (n)          (s)
 154                          *    / \          / \
 155                          *  (x) (s)  ->  (x) (c)
 156                          *        \
 157                          *        (c)
 158                          */
 159                         parent = successor;
 160                         child2 = successor->rb_right;
 161                         augment->copy(node, successor);
 162                 } else {
 163                         /*
 164                          * Case 3: node's successor is leftmost under
 165                          * node's right child subtree
 166                          *
 167                          *    (n)          (s)
 168                          *    / \          / \
 169                          *  (x) (y)  ->  (x) (y)
 170                          *      /            /
 171                          *    (p)          (p)
 172                          *    /            /
 173                          *  (s)          (c)
 174                          *    \
 175                          *    (c)
 176                          */
 177                         do {
 178                                 parent = successor;
 179                                 successor = tmp;
 180                                 tmp = tmp->rb_left;
 181                         } while (tmp);
 182                         parent->rb_left = child2 = successor->rb_right;
 183                         successor->rb_right = child;
 184                         rb_set_parent(child, successor);
 185                         augment->copy(node, successor);
 186                         augment->propagate(parent, successor);
 187                 }
 188
 189                 successor->rb_left = tmp = node->rb_left;
 190                 rb_set_parent(tmp, successor);
 191
 192                 pc = node->__rb_parent_color;
 193                 tmp = __rb_parent(pc);
 194                 __rb_change_child(node, successor, tmp, root);
 195                 if (child2) {
 196                         successor->__rb_parent_color = pc;
 197                         rb_set_parent_color(child2, parent, RB_BLACK);
 198                         rebalance = NULL;
 199                 } else {
 200                         unsigned long pc2 = successor->__rb_parent_color;
 201                         successor->__rb_parent_color = pc;
 202                         rebalance = __rb_is_black(pc2) ? parent : NULL;
 203                 }
 204                 tmp = successor;
 205         }
 206
 207         augment->propagate(tmp, NULL);
 208         return rebalance;
 209 }
 210
 211 static __always_inline void
 212 rb_erase_augmented(struct rb_node *node, struct rb_root *root,
 213                    const struct rb_augment_callbacks *augment)
 214 {
 215         struct rb_node *rebalance = __rb_erase_augmented(node, root, augment);
 216         if (rebalance)
 217                 __rb_erase_color(rebalance, root, augment->rotate);
 218 }
 219
 220 #endif  /* _LINUX_RBTREE_AUGMENTED_H */