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 static inline void rb_erase_cached(struct rb_node *node,
 145                                    struct rb_root_cached *root)
 146 {
 147         if (root->rb_leftmost == node)
 148                 root->rb_leftmost = rb_next(node);
 149         rb_erase(node, &root->rb_root);
 150 }
 151
 152 static inline void rb_replace_node_cached(struct rb_node *victim,
 153                                           struct rb_node *new,
 154                                           struct rb_root_cached *root)
 155 {
 156         if (root->rb_leftmost == victim)
 157                 root->rb_leftmost = new;
 158         rb_replace_node(victim, new, &root->rb_root);
 159 }
 160
 161 #endif  /* _LINUX_RBTREE_H */