LXR linux/tools/include/linux/rbtree

   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
  29struct 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
  35extern 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 */
  48static inline void
  49rb_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
  55static inline void
  56rb_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) \
  78static inline void                                                      \
  79RBNAME ## _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}                                                                       \
  88static inline void                                                      \
  89RBNAME ## _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}                                                                       \
  95static void                                                             \
  96RBNAME ## _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}                                                                       \
 103RBSTATIC 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)              \
 124static 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}                                                                             \
 143RB_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
 159static 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
 164static 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
 170static 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
 183extern 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
 186static __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
 290static __always_inline void
 291rb_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
 299static __always_inline void
 300rb_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 */
 309