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/kernel.h>
  21 #include <linux/stddef.h>
  22 #include <linux/rcupdate.h>
  23
  24 struct rb_node {
  25         unsigned long  __rb_parent_color;
  26         struct rb_node *rb_right;
  27         struct rb_node *rb_left;
  28 } __attribute__((aligned(sizeof(long))));
  29     /* The alignment might seem pointless, but allegedly CRIS needs it */
  30
  31 struct rb_root {
  32         struct rb_node *rb_node;
  33 };
  34
  35 #define rb_parent(r)   ((struct rb_node *)((r)->__rb_parent_color & ~3))
  36
  37 #define RB_ROOT (struct rb_root) { NULL, }
  38 #define rb_entry(ptr, type, member) container_of(ptr, type, member)
  39
  40 #define RB_EMPTY_ROOT(root)  (READ_ONCE((root)->rb_node) == NULL)
  41
  42 /* 'empty' nodes are nodes that are known not to be inserted in an rbtree */
  43 #define RB_EMPTY_NODE(node)  \
  44         ((node)->__rb_parent_color == (unsigned long)(node))
  45 #define RB_CLEAR_NODE(node)  \
  46         ((node)->__rb_parent_color = (unsigned long)(node))
  47
  48
  49 extern void rb_insert_color(struct rb_node *, struct rb_root *);
  50 extern void rb_erase(struct rb_node *, struct rb_root *);
  51
  52
  53 /* Find logical next and previous nodes in a tree */
  54 extern struct rb_node *rb_next(const struct rb_node *);
  55 extern struct rb_node *rb_prev(const struct rb_node *);
  56 extern struct rb_node *rb_first(const struct rb_root *);
  57 extern struct rb_node *rb_last(const struct rb_root *);
  58
  59 /* Postorder iteration - always visit the parent after its children */
  60 extern struct rb_node *rb_first_postorder(const struct rb_root *);
  61 extern struct rb_node *rb_next_postorder(const struct rb_node *);
  62
  63 /* Fast replacement of a single node without remove/rebalance/add/rebalance */
  64 extern void rb_replace_node(struct rb_node *victim, struct rb_node *new,
  65                             struct rb_root *root);
  66 extern void rb_replace_node_rcu(struct rb_node *victim, struct rb_node *new,
  67                                 struct rb_root *root);
  68
  69 static inline void rb_link_node(struct rb_node *node, struct rb_node *parent,
  70                                 struct rb_node **rb_link)
  71 {
  72         node->__rb_parent_color = (unsigned long)parent;
  73         node->rb_left = node->rb_right = NULL;
  74
  75         *rb_link = node;
  76 }
  77
  78 static inline void rb_link_node_rcu(struct rb_node *node, struct rb_node *parent,
  79                                     struct rb_node **rb_link)
  80 {
  81         node->__rb_parent_color = (unsigned long)parent;
  82         node->rb_left = node->rb_right = NULL;
  83
  84         rcu_assign_pointer(*rb_link, node);
  85 }
  86
  87 #define rb_entry_safe(ptr, type, member) \
  88         ({ typeof(ptr) ____ptr = (ptr); \
  89            ____ptr ? rb_entry(____ptr, type, member) : NULL; \
  90         })
  91
  92 /**
  93  * rbtree_postorder_for_each_entry_safe - iterate in post-order over rb_root of
  94  * given type allowing the backing memory of @pos to be invalidated
  95  *
  96  * @pos:        the 'type *' to use as a loop cursor.
  97  * @n:          another 'type *' to use as temporary storage
  98  * @root:       'rb_root *' of the rbtree.
  99  * @field:      the name of the rb_node field within 'type'.
 100  *
 101  * rbtree_postorder_for_each_entry_safe() provides a similar guarantee as
 102  * list_for_each_entry_safe() and allows the iteration to continue independent
 103  * of changes to @pos by the body of the loop.
 104  *
 105  * Note, however, that it cannot handle other modifications that re-order the
 106  * rbtree it is iterating over. This includes calling rb_erase() on @pos, as
 107  * rb_erase() may rebalance the tree, causing us to miss some nodes.
 108  */
 109 #define rbtree_postorder_for_each_entry_safe(pos, n, root, field) \
 110         for (pos = rb_entry_safe(rb_first_postorder(root), typeof(*pos), field); \
 111              pos && ({ n = rb_entry_safe(rb_next_postorder(&pos->field), \
 112                         typeof(*pos), field); 1; }); \
 113              pos = n)
 114
 115 /*
 116  * Leftmost-cached rbtrees.
 117  *
 118  * We do not cache the rightmost node based on footprint
 119  * size vs number of potential users that could benefit
 120  * from O(1) rb_last(). Just not worth it, users that want
 121  * this feature can always implement the logic explicitly.
 122  * Furthermore, users that want to cache both pointers may
 123  * find it a bit asymmetric, but that's ok.
 124  */
 125 struct rb_root_cached {
 126         struct rb_root rb_root;
 127         struct rb_node *rb_leftmost;
 128 };
 129
 130 #define RB_ROOT_CACHED (struct rb_root_cached) { {NULL, }, NULL }
 131
 132 /* Same as rb_first(), but O(1) */
 133 #define rb_first_cached(root) (root)->rb_leftmost
 134
 135 static inline void rb_insert_color_cached(struct rb_node *node,
 136                                           struct rb_root_cached *root,
 137                                           bool leftmost)
 138 {
 139         if (leftmost)
 140                 root->rb_leftmost = node;
 141         rb_insert_color(node, &root->rb_root);
 142 }
 143
 144
 145 static inline struct rb_node *
 146 rb_erase_cached(struct rb_node *node, struct rb_root_cached *root)
 147 {
 148         struct rb_node *leftmost = NULL;
 149
 150         if (root->rb_leftmost == node)
 151                 leftmost = root->rb_leftmost = rb_next(node);
 152
 153         rb_erase(node, &root->rb_root);
 154
 155         return leftmost;
 156 }
 157
 158 static inline void rb_replace_node_cached(struct rb_node *victim,
 159                                           struct rb_node *new,
 160                                           struct rb_root_cached *root)
 161 {
 162         if (root->rb_leftmost == victim)
 163                 root->rb_leftmost = new;
 164         rb_replace_node(victim, new, &root->rb_root);
 165 }
 166
 167 /*
 168  * The below helper functions use 2 operators with 3 different
 169  * calling conventions. The operators are related like:
 170  *
 171  *      comp(a->key,b) < 0  := less(a,b)
 172  *      comp(a->key,b) > 0  := less(b,a)
 173  *      comp(a->key,b) == 0 := !less(a,b) && !less(b,a)
 174  *
 175  * If these operators define a partial order on the elements we make no
 176  * guarantee on which of the elements matching the key is found. See
 177  * rb_find().
 178  *
 179  * The reason for this is to allow the find() interface without requiring an
 180  * on-stack dummy object, which might not be feasible due to object size.
 181  */
 182
 183 /**
 184  * rb_add_cached() - insert @node into the leftmost cached tree @tree
 185  * @node: node to insert
 186  * @tree: leftmost cached tree to insert @node into
 187  * @less: operator defining the (partial) node order
 188  *
 189  * Returns @node when it is the new leftmost, or NULL.
 190  */
 191 static __always_inline struct rb_node *
 192 rb_add_cached(struct rb_node *node, struct rb_root_cached *tree,
 193               bool (*less)(struct rb_node *, const struct rb_node *))
 194 {
 195         struct rb_node **link = &tree->rb_root.rb_node;
 196         struct rb_node *parent = NULL;
 197         bool leftmost = true;
 198
 199         while (*link) {
 200                 parent = *link;
 201                 if (less(node, parent)) {
 202                         link = &parent->rb_left;
 203                 } else {
 204                         link = &parent->rb_right;
 205                         leftmost = false;
 206                 }
 207         }
 208
 209         rb_link_node(node, parent, link);
 210         rb_insert_color_cached(node, tree, leftmost);
 211
 212         return leftmost ? node : NULL;
 213 }
 214
 215 /**
 216  * rb_add() - insert @node into @tree
 217  * @node: node to insert
 218  * @tree: tree to insert @node into
 219  * @less: operator defining the (partial) node order
 220  */
 221 static __always_inline void
 222 rb_add(struct rb_node *node, struct rb_root *tree,
 223        bool (*less)(struct rb_node *, const struct rb_node *))
 224 {
 225         struct rb_node **link = &tree->rb_node;
 226         struct rb_node *parent = NULL;
 227
 228         while (*link) {
 229                 parent = *link;
 230                 if (less(node, parent))
 231                         link = &parent->rb_left;
 232                 else
 233                         link = &parent->rb_right;
 234         }
 235
 236         rb_link_node(node, parent, link);
 237         rb_insert_color(node, tree);
 238 }
 239
 240 /**
 241  * rb_find_add() - find equivalent @node in @tree, or add @node
 242  * @node: node to look-for / insert
 243  * @tree: tree to search / modify
 244  * @cmp: operator defining the node order
 245  *
 246  * Returns the rb_node matching @node, or NULL when no match is found and @node
 247  * is inserted.
 248  */
 249 static __always_inline struct rb_node *
 250 rb_find_add(struct rb_node *node, struct rb_root *tree,
 251             int (*cmp)(struct rb_node *, const struct rb_node *))
 252 {
 253         struct rb_node **link = &tree->rb_node;
 254         struct rb_node *parent = NULL;
 255         int c;
 256
 257         while (*link) {
 258                 parent = *link;
 259                 c = cmp(node, parent);
 260
 261                 if (c < 0)
 262                         link = &parent->rb_left;
 263                 else if (c > 0)
 264                         link = &parent->rb_right;
 265                 else
 266                         return parent;
 267         }
 268
 269         rb_link_node(node, parent, link);
 270         rb_insert_color(node, tree);
 271         return NULL;
 272 }
 273
 274 /**
 275  * rb_find() - find @key in tree @tree
 276  * @key: key to match
 277  * @tree: tree to search
 278  * @cmp: operator defining the node order
 279  *
 280  * Returns the rb_node matching @key or NULL.
 281  */
 282 static __always_inline struct rb_node *
 283 rb_find(const void *key, const struct rb_root *tree,
 284         int (*cmp)(const void *key, const struct rb_node *))
 285 {
 286         struct rb_node *node = tree->rb_node;
 287
 288         while (node) {
 289                 int c = cmp(key, node);
 290
 291                 if (c < 0)
 292                         node = node->rb_left;
 293                 else if (c > 0)
 294                         node = node->rb_right;
 295                 else
 296                         return node;
 297         }
 298
 299         return NULL;
 300 }
 301
 302 /**
 303  * rb_find_first() - find the first @key in @tree
 304  * @key: key to match
 305  * @tree: tree to search
 306  * @cmp: operator defining node order
 307  *
 308  * Returns the leftmost node matching @key, or NULL.
 309  */
 310 static __always_inline struct rb_node *
 311 rb_find_first(const void *key, const struct rb_root *tree,
 312               int (*cmp)(const void *key, const struct rb_node *))
 313 {
 314         struct rb_node *node = tree->rb_node;
 315         struct rb_node *match = NULL;
 316
 317         while (node) {
 318                 int c = cmp(key, node);
 319
 320                 if (c <= 0) {
 321                         if (!c)
 322                                 match = node;
 323                         node = node->rb_left;
 324                 } else if (c > 0) {
 325                         node = node->rb_right;
 326                 }
 327         }
 328
 329         return match;
 330 }
 331
 332 /**
 333  * rb_next_match() - find the next @key in @tree
 334  * @key: key to match
 335  * @tree: tree to search
 336  * @cmp: operator defining node order
 337  *
 338  * Returns the next node matching @key, or NULL.
 339  */
 340 static __always_inline struct rb_node *
 341 rb_next_match(const void *key, struct rb_node *node,
 342               int (*cmp)(const void *key, const struct rb_node *))
 343 {
 344         node = rb_next(node);
 345         if (node && cmp(key, node))
 346                 node = NULL;
 347         return node;
 348 }
 349
 350 /**
 351  * rb_for_each() - iterates a subtree matching @key
 352  * @node: iterator
 353  * @key: key to match
 354  * @tree: tree to search
 355  * @cmp: operator defining node order
 356  */
 357 #define rb_for_each(node, key, tree, cmp) \
 358         for ((node) = rb_find_first((key), (tree), (cmp)); \
 359              (node); (node) = rb_next_match((key), (node), (cmp)))
 360
 361 #endif  /* _LINUX_RBTREE_H */