include/linux/rbtree_augmented.h

   1 /* SPDX-License-Identifier: GPL-2.0+ */
   2 /*
   3   Red Black Trees
   4   (C) 1999  Andrea Arcangeli <andrea@suse.de>
   5   (C) 2002  David Woodhouse <dwmw2@infradead.org>
   6   (C) 2012  Michel Lespinasse <walken@google.com>
   7
   8   linux/include/linux/rbtree_augmented.h
   9 */
  10
  11 #ifndef _LINUX_RBTREE_AUGMENTED_H
  12 #define _LINUX_RBTREE_AUGMENTED_H
  13
  14 #include <linux/compiler.h>
  15 #include <linux/rbtree.h>
  16
  17 /*
  18  * Please note - only struct rb_augment_callbacks and the prototypes for
  19  * rb_insert_augmented() and rb_erase_augmented() are intended to be public.
  20  * The rest are implementation details you are not expected to depend on.
  21  *
  22  * See Documentation/rbtree.txt for documentation and samples.
  23  */
  24
  25 struct rb_augment_callbacks {
  26         void (*propagate)(struct rb_node *node, struct rb_node *stop);
  27         void (*copy)(struct rb_node *old, struct rb_node *new);
  28         void (*rotate)(struct rb_node *old, struct rb_node *new);
  29 };
  30
  31 extern void __rb_insert_augmented(struct rb_node *node, struct rb_root *root,
  32         void (*augment_rotate)(struct rb_node *old, struct rb_node *new));
  33 static inline void
  34 rb_insert_augmented(struct rb_node *node, struct rb_root *root,
  35                     const struct rb_augment_callbacks *augment)
  36 {
  37         __rb_insert_augmented(node, root, augment->rotate);
  38 }
  39
  40 #define RB_DECLARE_CALLBACKS(rbstatic, rbname, rbstruct, rbfield,       \
  41                              rbtype, rbaugmented, rbcompute)            \
  42 static inline void                                                      \
  43 rbname ## _propagate(struct rb_node *rb, struct rb_node *stop)          \
  44 {                                                                       \
  45         while (rb != stop) {                                            \
  46                 rbstruct *node = rb_entry(rb, rbstruct, rbfield);       \
  47                 rbtype augmented = rbcompute(node);                     \
  48                 if (node->rbaugmented == augmented)                     \
  49                         break;                                          \
  50                 node->rbaugmented = augmented;                          \
  51                 rb = rb_parent(&node->rbfield);                         \
  52         }                                                               \
  53 }                                                                       \
  54 static inline void                                                      \
  55 rbname ## _copy(struct rb_node *rb_old, struct rb_node *rb_new)         \
  56 {                                                                       \
  57         rbstruct *old = rb_entry(rb_old, rbstruct, rbfield);            \
  58         rbstruct *new = rb_entry(rb_new, rbstruct, rbfield);            \
  59         new->rbaugmented = old->rbaugmented;                            \
  60 }                                                                       \
  61 static void                                                             \
  62 rbname ## _rotate(struct rb_node *rb_old, struct rb_node *rb_new)       \
  63 {                                                                       \
  64         rbstruct *old = rb_entry(rb_old, rbstruct, rbfield);            \
  65         rbstruct *new = rb_entry(rb_new, rbstruct, rbfield);            \
  66         new->rbaugmented = old->rbaugmented;                            \
  67         old->rbaugmented = rbcompute(old);                              \
  68 }                                                                       \
  69 rbstatic const struct rb_augment_callbacks rbname = {                   \
  70         rbname ## _propagate, rbname ## _copy, rbname ## _rotate        \
  71 };
  72
  73
  74 #define RB_RED          0
  75 #define RB_BLACK        1
  76
  77 #define __rb_parent(pc)    ((struct rb_node *)(pc & ~3))
  78
  79 #define __rb_color(pc)     ((pc) & 1)
  80 #define __rb_is_black(pc)  __rb_color(pc)
  81 #define __rb_is_red(pc)    (!__rb_color(pc))
  82 #define rb_color(rb)       __rb_color((rb)->__rb_parent_color)
  83 #define rb_is_red(rb)      __rb_is_red((rb)->__rb_parent_color)
  84 #define rb_is_black(rb)    __rb_is_black((rb)->__rb_parent_color)
  85
  86 static inline void rb_set_parent(struct rb_node *rb, struct rb_node *p)
  87 {
  88         rb->__rb_parent_color = rb_color(rb) | (unsigned long)p;
  89 }
  90
  91 static inline void rb_set_parent_color(struct rb_node *rb,
  92                                        struct rb_node *p, int color)
  93 {
  94         rb->__rb_parent_color = (unsigned long)p | color;
  95 }
  96
  97 static inline void
  98 __rb_change_child(struct rb_node *old, struct rb_node *new,
  99                   struct rb_node *parent, struct rb_root *root)
 100 {
 101         if (parent) {
 102                 if (parent->rb_left == old)
 103                         parent->rb_left = new;
 104                 else
 105                         parent->rb_right = new;
 106         } else
 107                 root->rb_node = new;
 108 }
 109
 110 extern void __rb_erase_color(struct rb_node *parent, struct rb_root *root,
 111         void (*augment_rotate)(struct rb_node *old, struct rb_node *new));
 112
 113 static __always_inline struct rb_node *
 114 __rb_erase_augmented(struct rb_node *node, struct rb_root *root,
 115                      const struct rb_augment_callbacks *augment)
 116 {
 117         struct rb_node *child = node->rb_right, *tmp = node->rb_left;
 118         struct rb_node *parent, *rebalance;
 119         unsigned long pc;
 120
 121         if (!tmp) {
 122                 /*
 123                  * Case 1: node to erase has no more than 1 child (easy!)
 124                  *
 125                  * Note that if there is one child it must be red due to 5)
 126                  * and node must be black due to 4). We adjust colors locally
 127                  * so as to bypass __rb_erase_color() later on.
 128                  */
 129                 pc = node->__rb_parent_color;
 130                 parent = __rb_parent(pc);
 131                 __rb_change_child(node, child, parent, root);
 132                 if (child) {
 133                         child->__rb_parent_color = pc;
 134                         rebalance = NULL;
 135                 } else
 136                         rebalance = __rb_is_black(pc) ? parent : NULL;
 137                 tmp = parent;
 138         } else if (!child) {
 139                 /* Still case 1, but this time the child is node->rb_left */
 140                 tmp->__rb_parent_color = pc = node->__rb_parent_color;
 141                 parent = __rb_parent(pc);
 142                 __rb_change_child(node, tmp, parent, root);
 143                 rebalance = NULL;
 144                 tmp = parent;
 145         } else {
 146                 struct rb_node *successor = child, *child2;
 147                 tmp = child->rb_left;
 148                 if (!tmp) {
 149                         /*
 150                          * Case 2: node's successor is its right child
 151                          *
 152                          *    (n)          (s)
 153                          *    / \          / \
 154                          *  (x) (s)  ->  (x) (c)
 155                          *        \
 156                          *        (c)
 157                          */
 158                         parent = successor;
 159                         child2 = successor->rb_right;
 160                         augment->copy(node, successor);
 161                 } else {
 162                         /*
 163                          * Case 3: node's successor is leftmost under
 164                          * node's right child subtree
 165                          *
 166                          *    (n)          (s)
 167                          *    / \          / \
 168                          *  (x) (y)  ->  (x) (y)
 169                          *      /            /
 170                          *    (p)          (p)
 171                          *    /            /
 172                          *  (s)          (c)
 173                          *    \
 174                          *    (c)
 175                          */
 176                         do {
 177                                 parent = successor;
 178                                 successor = tmp;
 179                                 tmp = tmp->rb_left;
 180                         } while (tmp);
 181                         parent->rb_left = child2 = successor->rb_right;
 182                         successor->rb_right = child;
 183                         rb_set_parent(child, successor);
 184                         augment->copy(node, successor);
 185                         augment->propagate(parent, successor);
 186                 }
 187
 188                 successor->rb_left = tmp = node->rb_left;
 189                 rb_set_parent(tmp, successor);
 190
 191                 pc = node->__rb_parent_color;
 192                 tmp = __rb_parent(pc);
 193                 __rb_change_child(node, successor, tmp, root);
 194                 if (child2) {
 195                         successor->__rb_parent_color = pc;
 196                         rb_set_parent_color(child2, parent, RB_BLACK);
 197                         rebalance = NULL;
 198                 } else {
 199                         unsigned long pc2 = successor->__rb_parent_color;
 200                         successor->__rb_parent_color = pc;
 201                         rebalance = __rb_is_black(pc2) ? parent : NULL;
 202                 }
 203                 tmp = successor;
 204         }
 205
 206         augment->propagate(tmp, NULL);
 207         return rebalance;
 208 }
 209
 210 static __always_inline void
 211 rb_erase_augmented(struct rb_node *node, struct rb_root *root,
 212                    const struct rb_augment_callbacks *augment)
 213 {
 214         struct rb_node *rebalance = __rb_erase_augmented(node, root, augment);
 215         if (rebalance)
 216                 __rb_erase_color(rebalance, root, augment->rotate);
 217 }
 218
 219 #endif  /* _LINUX_RBTREE_AUGMENTED_H */