include/linux/rbtree.h

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2 /*
   3   Red Black Trees
   4   (C) 1999  Andrea Arcangeli <andrea@suse.de>
   5
   6
   7   linux/include/linux/rbtree.h
   8
   9   To use rbtrees you'll have to implement your own insert and search cores.
  10   This will avoid us to use callbacks and to drop drammatically performances.
  11   I know it's not the cleaner way,  but in C (not in C++) to get
  12   performances and genericity...
  13
  14   See Documentation/core-api/rbtree.rst for documentation and samples.
  15 */
  16
  17 #ifndef _LINUX_RBTREE_H
  18 #define _LINUX_RBTREE_H
  19
  20 #include <linux/rbtree_types.h>
  21
  22 #include <linux/kernel.h>
  23 #include <linux/stddef.h>
  24 #include <linux/rcupdate.h>
  25
  26 #define rb_parent(r)   ((struct rb_node *)((r)->__rb_parent_color & ~3))
  27
  28 #define rb_entry(ptr, type, member) container_of(ptr, type, member)
  29
  30 #define RB_EMPTY_ROOT(root)  (READ_ONCE((root)->rb_node) == NULL)
  31
  32 /* 'empty' nodes are nodes that are known not to be inserted in an rbtree */
  33 #define RB_EMPTY_NODE(node)  \
  34         ((node)->__rb_parent_color == (unsigned long)(node))
  35 #define RB_CLEAR_NODE(node)  \
  36         ((node)->__rb_parent_color = (unsigned long)(node))
  37
  38
  39 extern void rb_insert_color(struct rb_node *, struct rb_root *);
  40 extern void rb_erase(struct rb_node *, struct rb_root *);
  41
  42
  43 /* Find logical next and previous nodes in a tree */
  44 extern struct rb_node *rb_next(const struct rb_node *);
  45 extern struct rb_node *rb_prev(const struct rb_node *);
  46 extern struct rb_node *rb_first(const struct rb_root *);
  47 extern struct rb_node *rb_last(const struct rb_root *);
  48
  49 /* Postorder iteration - always visit the parent after its children */
  50 extern struct rb_node *rb_first_postorder(const struct rb_root *);
  51 extern struct rb_node *rb_next_postorder(const struct rb_node *);
  52
  53 /* Fast replacement of a single node without remove/rebalance/add/rebalance */
  54 extern void rb_replace_node(struct rb_node *victim, struct rb_node *new,
  55                             struct rb_root *root);
  56 extern void rb_replace_node_rcu(struct rb_node *victim, struct rb_node *new,
  57                                 struct rb_root *root);
  58
  59 static inline void rb_link_node(struct rb_node *node, struct rb_node *parent,
  60                                 struct rb_node **rb_link)
  61 {
  62         node->__rb_parent_color = (unsigned long)parent;
  63         node->rb_left = node->rb_right = NULL;
  64
  65         *rb_link = node;
  66 }
  67
  68 static inline void rb_link_node_rcu(struct rb_node *node, struct rb_node *parent,
  69                                     struct rb_node **rb_link)
  70 {
  71         node->__rb_parent_color = (unsigned long)parent;
  72         node->rb_left = node->rb_right = NULL;
  73
  74         rcu_assign_pointer(*rb_link, node);
  75 }
  76
  77 #define rb_entry_safe(ptr, type, member) \
  78         ({ typeof(ptr) ____ptr = (ptr); \
  79            ____ptr ? rb_entry(____ptr, type, member) : NULL; \
  80         })
  81
  82 /**
  83  * rbtree_postorder_for_each_entry_safe - iterate in post-order over rb_root of
  84  * given type allowing the backing memory of @pos to be invalidated
  85  *
  86  * @pos:        the 'type *' to use as a loop cursor.
  87  * @n:          another 'type *' to use as temporary storage
  88  * @root:       'rb_root *' of the rbtree.
  89  * @field:      the name of the rb_node field within 'type'.
  90  *
  91  * rbtree_postorder_for_each_entry_safe() provides a similar guarantee as
  92  * list_for_each_entry_safe() and allows the iteration to continue independent
  93  * of changes to @pos by the body of the loop.
  94  *
  95  * Note, however, that it cannot handle other modifications that re-order the
  96  * rbtree it is iterating over. This includes calling rb_erase() on @pos, as
  97  * rb_erase() may rebalance the tree, causing us to miss some nodes.
  98  */
  99 #define rbtree_postorder_for_each_entry_safe(pos, n, root, field) \
 100         for (pos = rb_entry_safe(rb_first_postorder(root), typeof(*pos), field); \
 101              pos && ({ n = rb_entry_safe(rb_next_postorder(&pos->field), \
 102                         typeof(*pos), field); 1; }); \
 103              pos = n)
 104
 105 /* Same as rb_first(), but O(1) */
 106 #define rb_first_cached(root) (root)->rb_leftmost
 107
 108 static inline void rb_insert_color_cached(struct rb_node *node,
 109                                           struct rb_root_cached *root,
 110                                           bool leftmost)
 111 {
 112         if (leftmost)
 113                 root->rb_leftmost = node;
 114         rb_insert_color(node, &root->rb_root);
 115 }
 116
 117
 118 static inline struct rb_node *
 119 rb_erase_cached(struct rb_node *node, struct rb_root_cached *root)
 120 {
 121         struct rb_node *leftmost = NULL;
 122
 123         if (root->rb_leftmost == node)
 124                 leftmost = root->rb_leftmost = rb_next(node);
 125
 126         rb_erase(node, &root->rb_root);
 127
 128         return leftmost;
 129 }
 130
 131 static inline void rb_replace_node_cached(struct rb_node *victim,
 132                                           struct rb_node *new,
 133                                           struct rb_root_cached *root)
 134 {
 135         if (root->rb_leftmost == victim)
 136                 root->rb_leftmost = new;
 137         rb_replace_node(victim, new, &root->rb_root);
 138 }
 139
 140 /*
 141  * The below helper functions use 2 operators with 3 different
 142  * calling conventions. The operators are related like:
 143  *
 144  *      comp(a->key,b) < 0  := less(a,b)
 145  *      comp(a->key,b) > 0  := less(b,a)
 146  *      comp(a->key,b) == 0 := !less(a,b) && !less(b,a)
 147  *
 148  * If these operators define a partial order on the elements we make no
 149  * guarantee on which of the elements matching the key is found. See
 150  * rb_find().
 151  *
 152  * The reason for this is to allow the find() interface without requiring an
 153  * on-stack dummy object, which might not be feasible due to object size.
 154  */
 155
 156 /**
 157  * rb_add_cached() - insert @node into the leftmost cached tree @tree
 158  * @node: node to insert
 159  * @tree: leftmost cached tree to insert @node into
 160  * @less: operator defining the (partial) node order
 161  *
 162  * Returns @node when it is the new leftmost, or NULL.
 163  */
 164 static __always_inline struct rb_node *
 165 rb_add_cached(struct rb_node *node, struct rb_root_cached *tree,
 166               bool (*less)(struct rb_node *, const struct rb_node *))
 167 {
 168         struct rb_node **link = &tree->rb_root.rb_node;
 169         struct rb_node *parent = NULL;
 170         bool leftmost = true;
 171
 172         while (*link) {
 173                 parent = *link;
 174                 if (less(node, parent)) {
 175                         link = &parent->rb_left;
 176                 } else {
 177                         link = &parent->rb_right;
 178                         leftmost = false;
 179                 }
 180         }
 181
 182         rb_link_node(node, parent, link);
 183         rb_insert_color_cached(node, tree, leftmost);
 184
 185         return leftmost ? node : NULL;
 186 }
 187
 188 /**
 189  * rb_add() - insert @node into @tree
 190  * @node: node to insert
 191  * @tree: tree to insert @node into
 192  * @less: operator defining the (partial) node order
 193  */
 194 static __always_inline void
 195 rb_add(struct rb_node *node, struct rb_root *tree,
 196        bool (*less)(struct rb_node *, const struct rb_node *))
 197 {
 198         struct rb_node **link = &tree->rb_node;
 199         struct rb_node *parent = NULL;
 200
 201         while (*link) {
 202                 parent = *link;
 203                 if (less(node, parent))
 204                         link = &parent->rb_left;
 205                 else
 206                         link = &parent->rb_right;
 207         }
 208
 209         rb_link_node(node, parent, link);
 210         rb_insert_color(node, tree);
 211 }
 212
 213 /**
 214  * rb_find_add() - find equivalent @node in @tree, or add @node
 215  * @node: node to look-for / insert
 216  * @tree: tree to search / modify
 217  * @cmp: operator defining the node order
 218  *
 219  * Returns the rb_node matching @node, or NULL when no match is found and @node
 220  * is inserted.
 221  */
 222 static __always_inline struct rb_node *
 223 rb_find_add(struct rb_node *node, struct rb_root *tree,
 224             int (*cmp)(struct rb_node *, const struct rb_node *))
 225 {
 226         struct rb_node **link = &tree->rb_node;
 227         struct rb_node *parent = NULL;
 228         int c;
 229
 230         while (*link) {
 231                 parent = *link;
 232                 c = cmp(node, parent);
 233
 234                 if (c < 0)
 235                         link = &parent->rb_left;
 236                 else if (c > 0)
 237                         link = &parent->rb_right;
 238                 else
 239                         return parent;
 240         }
 241
 242         rb_link_node(node, parent, link);
 243         rb_insert_color(node, tree);
 244         return NULL;
 245 }
 246
 247 /**
 248  * rb_find() - find @key in tree @tree
 249  * @key: key to match
 250  * @tree: tree to search
 251  * @cmp: operator defining the node order
 252  *
 253  * Returns the rb_node matching @key or NULL.
 254  */
 255 static __always_inline struct rb_node *
 256 rb_find(const void *key, const struct rb_root *tree,
 257         int (*cmp)(const void *key, const struct rb_node *))
 258 {
 259         struct rb_node *node = tree->rb_node;
 260
 261         while (node) {
 262                 int c = cmp(key, node);
 263
 264                 if (c < 0)
 265                         node = node->rb_left;
 266                 else if (c > 0)
 267                         node = node->rb_right;
 268                 else
 269                         return node;
 270         }
 271
 272         return NULL;
 273 }
 274
 275 /**
 276  * rb_find_first() - find the first @key in @tree
 277  * @key: key to match
 278  * @tree: tree to search
 279  * @cmp: operator defining node order
 280  *
 281  * Returns the leftmost node matching @key, or NULL.
 282  */
 283 static __always_inline struct rb_node *
 284 rb_find_first(const void *key, const struct rb_root *tree,
 285               int (*cmp)(const void *key, const struct rb_node *))
 286 {
 287         struct rb_node *node = tree->rb_node;
 288         struct rb_node *match = NULL;
 289
 290         while (node) {
 291                 int c = cmp(key, node);
 292
 293                 if (c <= 0) {
 294                         if (!c)
 295                                 match = node;
 296                         node = node->rb_left;
 297                 } else if (c > 0) {
 298                         node = node->rb_right;
 299                 }
 300         }
 301
 302         return match;
 303 }
 304
 305 /**
 306  * rb_next_match() - find the next @key in @tree
 307  * @key: key to match
 308  * @tree: tree to search
 309  * @cmp: operator defining node order
 310  *
 311  * Returns the next node matching @key, or NULL.
 312  */
 313 static __always_inline struct rb_node *
 314 rb_next_match(const void *key, struct rb_node *node,
 315               int (*cmp)(const void *key, const struct rb_node *))
 316 {
 317         node = rb_next(node);
 318         if (node && cmp(key, node))
 319                 node = NULL;
 320         return node;
 321 }
 322
 323 /**
 324  * rb_for_each() - iterates a subtree matching @key
 325  * @node: iterator
 326  * @key: key to match
 327  * @tree: tree to search
 328  * @cmp: operator defining node order
 329  */
 330 #define rb_for_each(node, key, tree, cmp) \
 331         for ((node) = rb_find_first((key), (tree), (cmp)); \
 332              (node); (node) = rb_next_match((key), (node), (cmp)))
 333
 334 #endif  /* _LINUX_RBTREE_H */