tools/include/linux/rbtree_augmented.h

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   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
   9   tools/linux/include/linux/rbtree_augmented.h
  10
  11   Copied from:
  12   linux/include/linux/rbtree_augmented.h
  13 */
  14
  15 #ifndef _TOOLS_LINUX_RBTREE_AUGMENTED_H
  16 #define _TOOLS_LINUX_RBTREE_AUGMENTED_H
  17
  18 #include <linux/compiler.h>
  19 #include <linux/rbtree.h>
  20
  21 /*
  22  * Please note - only struct rb_augment_callbacks and the prototypes for
  23  * rb_insert_augmented() and rb_erase_augmented() are intended to be public.
  24  * The rest are implementation details you are not expected to depend on.
  25  *
  26  * See Documentation/core-api/rbtree.rst for documentation and samples.
  27  */
  28
  29 struct rb_augment_callbacks {
  30         void (*propagate)(struct rb_node *node, struct rb_node *stop);
  31         void (*copy)(struct rb_node *old, struct rb_node *new);
  32         void (*rotate)(struct rb_node *old, struct rb_node *new);
  33 };
  34
  35 extern void __rb_insert_augmented(struct rb_node *node, struct rb_root *root,
  36         void (*augment_rotate)(struct rb_node *old, struct rb_node *new));
  37
  38 /*
  39  * Fixup the rbtree and update the augmented information when rebalancing.
  40  *
  41  * On insertion, the user must update the augmented information on the path
  42  * leading to the inserted node, then call rb_link_node() as usual and
  43  * rb_insert_augmented() instead of the usual rb_insert_color() call.
  44  * If rb_insert_augmented() rebalances the rbtree, it will callback into
  45  * a user provided function to update the augmented information on the
  46  * affected subtrees.
  47  */
  48 static inline void
  49 rb_insert_augmented(struct rb_node *node, struct rb_root *root,
  50                     const struct rb_augment_callbacks *augment)
  51 {
  52         __rb_insert_augmented(node, root, augment->rotate);
  53 }
  54
  55 static inline void
  56 rb_insert_augmented_cached(struct rb_node *node,
  57                            struct rb_root_cached *root, bool newleft,
  58                            const struct rb_augment_callbacks *augment)
  59 {
  60         if (newleft)
  61                 root->rb_leftmost = node;
  62         rb_insert_augmented(node, &root->rb_root, augment);
  63 }
  64
  65 /*
  66  * Template for declaring augmented rbtree callbacks (generic case)
  67  *
  68  * RBSTATIC:    'static' or empty
  69  * RBNAME:      name of the rb_augment_callbacks structure
  70  * RBSTRUCT:    struct type of the tree nodes
  71  * RBFIELD:     name of struct rb_node field within RBSTRUCT
  72  * RBAUGMENTED: name of field within RBSTRUCT holding data for subtree
  73  * RBCOMPUTE:   name of function that recomputes the RBAUGMENTED data
  74  */
  75
  76 #define RB_DECLARE_CALLBACKS(RBSTATIC, RBNAME,                          \
  77                              RBSTRUCT, RBFIELD, RBAUGMENTED, RBCOMPUTE) \
  78 static inline void                                                      \
  79 RBNAME ## _propagate(struct rb_node *rb, struct rb_node *stop)          \
  80 {                                                                       \
  81         while (rb != stop) {                                            \
  82                 RBSTRUCT *node = rb_entry(rb, RBSTRUCT, RBFIELD);       \
  83                 if (RBCOMPUTE(node, true))                              \
  84                         break;                                          \
  85                 rb = rb_parent(&node->RBFIELD);                         \
  86         }                                                               \
  87 }                                                                       \
  88 static inline void                                                      \
  89 RBNAME ## _copy(struct rb_node *rb_old, struct rb_node *rb_new)         \
  90 {                                                                       \
  91         RBSTRUCT *old = rb_entry(rb_old, RBSTRUCT, RBFIELD);            \
  92         RBSTRUCT *new = rb_entry(rb_new, RBSTRUCT, RBFIELD);            \
  93         new->RBAUGMENTED = old->RBAUGMENTED;                            \
  94 }                                                                       \
  95 static void                                                             \
  96 RBNAME ## _rotate(struct rb_node *rb_old, struct rb_node *rb_new)       \
  97 {                                                                       \
  98         RBSTRUCT *old = rb_entry(rb_old, RBSTRUCT, RBFIELD);            \
  99         RBSTRUCT *new = rb_entry(rb_new, RBSTRUCT, RBFIELD);            \
 100         new->RBAUGMENTED = old->RBAUGMENTED;                            \
 101         RBCOMPUTE(old, false);                                          \
 102 }                                                                       \
 103 RBSTATIC const struct rb_augment_callbacks RBNAME = {                   \
 104         .propagate = RBNAME ## _propagate,                              \
 105         .copy = RBNAME ## _copy,                                        \
 106         .rotate = RBNAME ## _rotate                                     \
 107 };
 108
 109 /*
 110  * Template for declaring augmented rbtree callbacks,
 111  * computing RBAUGMENTED scalar as max(RBCOMPUTE(node)) for all subtree nodes.
 112  *
 113  * RBSTATIC:    'static' or empty
 114  * RBNAME:      name of the rb_augment_callbacks structure
 115  * RBSTRUCT:    struct type of the tree nodes
 116  * RBFIELD:     name of struct rb_node field within RBSTRUCT
 117  * RBTYPE:      type of the RBAUGMENTED field
 118  * RBAUGMENTED: name of RBTYPE field within RBSTRUCT holding data for subtree
 119  * RBCOMPUTE:   name of function that returns the per-node RBTYPE scalar
 120  */
 121
 122 #define RB_DECLARE_CALLBACKS_MAX(RBSTATIC, RBNAME, RBSTRUCT, RBFIELD,         \
 123                                  RBTYPE, RBAUGMENTED, RBCOMPUTE)              \
 124 static inline bool RBNAME ## _compute_max(RBSTRUCT *node, bool exit)          \
 125 {                                                                             \
 126         RBSTRUCT *child;                                                      \
 127         RBTYPE max = RBCOMPUTE(node);                                         \
 128         if (node->RBFIELD.rb_left) {                                          \
 129                 child = rb_entry(node->RBFIELD.rb_left, RBSTRUCT, RBFIELD);   \
 130                 if (child->RBAUGMENTED > max)                                 \
 131                         max = child->RBAUGMENTED;                             \
 132         }                                                                     \
 133         if (node->RBFIELD.rb_right) {                                         \
 134                 child = rb_entry(node->RBFIELD.rb_right, RBSTRUCT, RBFIELD);  \
 135                 if (child->RBAUGMENTED > max)                                 \
 136                         max = child->RBAUGMENTED;                             \
 137         }                                                                     \
 138         if (exit && node->RBAUGMENTED == max)                                 \
 139                 return true;                                                  \
 140         node->RBAUGMENTED = max;                                              \
 141         return false;                                                         \
 142 }                                                                             \
 143 RB_DECLARE_CALLBACKS(RBSTATIC, RBNAME,                                        \
 144                      RBSTRUCT, RBFIELD, RBAUGMENTED, RBNAME ## _compute_max)
 145
 146
 147 #define RB_RED          0
 148 #define RB_BLACK        1
 149
 150 #define __rb_parent(pc)    ((struct rb_node *)(pc & ~3))
 151
 152 #define __rb_color(pc)     ((pc) & 1)
 153 #define __rb_is_black(pc)  __rb_color(pc)
 154 #define __rb_is_red(pc)    (!__rb_color(pc))
 155 #define rb_color(rb)       __rb_color((rb)->__rb_parent_color)
 156 #define rb_is_red(rb)      __rb_is_red((rb)->__rb_parent_color)
 157 #define rb_is_black(rb)    __rb_is_black((rb)->__rb_parent_color)
 158
 159 static inline void rb_set_parent(struct rb_node *rb, struct rb_node *p)
 160 {
 161         rb->__rb_parent_color = rb_color(rb) | (unsigned long)p;
 162 }
 163
 164 static inline void rb_set_parent_color(struct rb_node *rb,
 165                                        struct rb_node *p, int color)
 166 {
 167         rb->__rb_parent_color = (unsigned long)p | color;
 168 }
 169
 170 static inline void
 171 __rb_change_child(struct rb_node *old, struct rb_node *new,
 172                   struct rb_node *parent, struct rb_root *root)
 173 {
 174         if (parent) {
 175                 if (parent->rb_left == old)
 176                         WRITE_ONCE(parent->rb_left, new);
 177                 else
 178                         WRITE_ONCE(parent->rb_right, new);
 179         } else
 180                 WRITE_ONCE(root->rb_node, new);
 181 }
 182
 183 extern void __rb_erase_color(struct rb_node *parent, struct rb_root *root,
 184         void (*augment_rotate)(struct rb_node *old, struct rb_node *new));
 185
 186 static __always_inline struct rb_node *
 187 __rb_erase_augmented(struct rb_node *node, struct rb_root *root,
 188                      const struct rb_augment_callbacks *augment)
 189 {
 190         struct rb_node *child = node->rb_right;
 191         struct rb_node *tmp = node->rb_left;
 192         struct rb_node *parent, *rebalance;
 193         unsigned long pc;
 194
 195         if (!tmp) {
 196                 /*
 197                  * Case 1: node to erase has no more than 1 child (easy!)
 198                  *
 199                  * Note that if there is one child it must be red due to 5)
 200                  * and node must be black due to 4). We adjust colors locally
 201                  * so as to bypass __rb_erase_color() later on.
 202                  */
 203                 pc = node->__rb_parent_color;
 204                 parent = __rb_parent(pc);
 205                 __rb_change_child(node, child, parent, root);
 206                 if (child) {
 207                         child->__rb_parent_color = pc;
 208                         rebalance = NULL;
 209                 } else
 210                         rebalance = __rb_is_black(pc) ? parent : NULL;
 211                 tmp = parent;
 212         } else if (!child) {
 213                 /* Still case 1, but this time the child is node->rb_left */
 214                 tmp->__rb_parent_color = pc = node->__rb_parent_color;
 215                 parent = __rb_parent(pc);
 216                 __rb_change_child(node, tmp, parent, root);
 217                 rebalance = NULL;
 218                 tmp = parent;
 219         } else {
 220                 struct rb_node *successor = child, *child2;
 221
 222                 tmp = child->rb_left;
 223                 if (!tmp) {
 224                         /*
 225                          * Case 2: node's successor is its right child
 226                          *
 227                          *    (n)          (s)
 228                          *    / \          / \
 229                          *  (x) (s)  ->  (x) (c)
 230                          *        \
 231                          *        (c)
 232                          */
 233                         parent = successor;
 234                         child2 = successor->rb_right;
 235
 236                         augment->copy(node, successor);
 237                 } else {
 238                         /*
 239                          * Case 3: node's successor is leftmost under
 240                          * node's right child subtree
 241                          *
 242                          *    (n)          (s)
 243                          *    / \          / \
 244                          *  (x) (y)  ->  (x) (y)
 245                          *      /            /
 246                          *    (p)          (p)
 247                          *    /            /
 248                          *  (s)          (c)
 249                          *    \
 250                          *    (c)
 251                          */
 252                         do {
 253                                 parent = successor;
 254                                 successor = tmp;
 255                                 tmp = tmp->rb_left;
 256                         } while (tmp);
 257                         child2 = successor->rb_right;
 258                         WRITE_ONCE(parent->rb_left, child2);
 259                         WRITE_ONCE(successor->rb_right, child);
 260                         rb_set_parent(child, successor);
 261
 262                         augment->copy(node, successor);
 263                         augment->propagate(parent, successor);
 264                 }
 265
 266                 tmp = node->rb_left;
 267                 WRITE_ONCE(successor->rb_left, tmp);
 268                 rb_set_parent(tmp, successor);
 269
 270                 pc = node->__rb_parent_color;
 271                 tmp = __rb_parent(pc);
 272                 __rb_change_child(node, successor, tmp, root);
 273
 274                 if (child2) {
 275                         successor->__rb_parent_color = pc;
 276                         rb_set_parent_color(child2, parent, RB_BLACK);
 277                         rebalance = NULL;
 278                 } else {
 279                         unsigned long pc2 = successor->__rb_parent_color;
 280                         successor->__rb_parent_color = pc;
 281                         rebalance = __rb_is_black(pc2) ? parent : NULL;
 282                 }
 283                 tmp = successor;
 284         }
 285
 286         augment->propagate(tmp, NULL);
 287         return rebalance;
 288 }
 289
 290 static __always_inline void
 291 rb_erase_augmented(struct rb_node *node, struct rb_root *root,
 292                    const struct rb_augment_callbacks *augment)
 293 {
 294         struct rb_node *rebalance = __rb_erase_augmented(node, root, augment);
 295         if (rebalance)
 296                 __rb_erase_color(rebalance, root, augment->rotate);
 297 }
 298
 299 static __always_inline void
 300 rb_erase_augmented_cached(struct rb_node *node, struct rb_root_cached *root,
 301                           const struct rb_augment_callbacks *augment)
 302 {
 303         if (root->rb_leftmost == node)
 304                 root->rb_leftmost = rb_next(node);
 305         rb_erase_augmented(node, &root->rb_root, augment);
 306 }
 307
 308 #endif /* _TOOLS_LINUX_RBTREE_AUGMENTED_H */