include/linux/rbtree.h

   1 /*
   2   Red Black Trees
   3   (C) 1999  Andrea Arcangeli <andrea@suse.de>
   4
   5   This program is free software; you can redistribute it and/or modify
   6   it under the terms of the GNU General Public License as published by
   7   the Free Software Foundation; either version 2 of the License, or
   8   (at your option) any later version.
   9
  10   This program is distributed in the hope that it will be useful,
  11   but WITHOUT ANY WARRANTY; without even the implied warranty of
  12   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13   GNU General Public License for more details.
  14
  15   You should have received a copy of the GNU General Public License
  16   along with this program; if not, write to the Free Software
  17   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  18
  19   linux/include/linux/rbtree.h
  20
  21   To use rbtrees you'll have to implement your own insert and search cores.
  22   This will avoid us to use callbacks and to drop drammatically performances.
  23   I know it's not the cleaner way,  but in C (not in C++) to get
  24   performances and genericity...
  25
  26   See Documentation/rbtree.txt for documentation and samples.
  27 */
  28
  29 #ifndef _LINUX_RBTREE_H
  30 #define _LINUX_RBTREE_H
  31
  32 #include <linux/kernel.h>
  33 #include <linux/stddef.h>
  34 #include <linux/rcupdate.h>
  35
  36 struct rb_node {
  37         unsigned long  __rb_parent_color;
  38         struct rb_node *rb_right;
  39         struct rb_node *rb_left;
  40 } __attribute__((aligned(sizeof(long))));
  41     /* The alignment might seem pointless, but allegedly CRIS needs it */
  42
  43 struct rb_root {
  44         struct rb_node *rb_node;
  45 };
  46
  47 /*
  48  * Leftmost-cached rbtrees.
  49  *
  50  * We do not cache the rightmost node based on footprint
  51  * size vs number of potential users that could benefit
  52  * from O(1) rb_last(). Just not worth it, users that want
  53  * this feature can always implement the logic explicitly.
  54  * Furthermore, users that want to cache both pointers may
  55  * find it a bit asymmetric, but that's ok.
  56  */
  57 struct rb_root_cached {
  58         struct rb_root rb_root;
  59         struct rb_node *rb_leftmost;
  60 };
  61
  62 #define rb_parent(r)   ((struct rb_node *)((r)->__rb_parent_color & ~3))
  63
  64 #define RB_ROOT (struct rb_root) { NULL, }
  65 #define RB_ROOT_CACHED (struct rb_root_cached) { {NULL, }, NULL }
  66 #define rb_entry(ptr, type, member) container_of(ptr, type, member)
  67
  68 #define RB_EMPTY_ROOT(root)  (READ_ONCE((root)->rb_node) == NULL)
  69
  70 /* 'empty' nodes are nodes that are known not to be inserted in an rbtree */
  71 #define RB_EMPTY_NODE(node)  \
  72         ((node)->__rb_parent_color == (unsigned long)(node))
  73 #define RB_CLEAR_NODE(node)  \
  74         ((node)->__rb_parent_color = (unsigned long)(node))
  75
  76
  77 extern void rb_insert_color(struct rb_node *, struct rb_root *);
  78 extern void rb_erase(struct rb_node *, struct rb_root *);
  79
  80
  81 /* Find logical next and previous nodes in a tree */
  82 extern struct rb_node *rb_next(const struct rb_node *);
  83 extern struct rb_node *rb_prev(const struct rb_node *);
  84 extern struct rb_node *rb_first(const struct rb_root *);
  85 extern struct rb_node *rb_last(const struct rb_root *);
  86
  87 extern void rb_insert_color_cached(struct rb_node *,
  88                                    struct rb_root_cached *, bool);
  89 extern void rb_erase_cached(struct rb_node *node, struct rb_root_cached *);
  90 /* Same as rb_first(), but O(1) */
  91 #define rb_first_cached(root) (root)->rb_leftmost
  92
  93 /* Postorder iteration - always visit the parent after its children */
  94 extern struct rb_node *rb_first_postorder(const struct rb_root *);
  95 extern struct rb_node *rb_next_postorder(const struct rb_node *);
  96
  97 /* Fast replacement of a single node without remove/rebalance/add/rebalance */
  98 extern void rb_replace_node(struct rb_node *victim, struct rb_node *new,
  99                             struct rb_root *root);
 100 extern void rb_replace_node_rcu(struct rb_node *victim, struct rb_node *new,
 101                                 struct rb_root *root);
 102 extern void rb_replace_node_cached(struct rb_node *victim, struct rb_node *new,
 103                                    struct rb_root_cached *root);
 104
 105 static inline void rb_link_node(struct rb_node *node, struct rb_node *parent,
 106                                 struct rb_node **rb_link)
 107 {
 108         node->__rb_parent_color = (unsigned long)parent;
 109         node->rb_left = node->rb_right = NULL;
 110
 111         *rb_link = node;
 112 }
 113
 114 static inline void rb_link_node_rcu(struct rb_node *node, struct rb_node *parent,
 115                                     struct rb_node **rb_link)
 116 {
 117         node->__rb_parent_color = (unsigned long)parent;
 118         node->rb_left = node->rb_right = NULL;
 119
 120         rcu_assign_pointer(*rb_link, node);
 121 }
 122
 123 #define rb_entry_safe(ptr, type, member) \
 124         ({ typeof(ptr) ____ptr = (ptr); \
 125            ____ptr ? rb_entry(____ptr, type, member) : NULL; \
 126         })
 127
 128 /**
 129  * rbtree_postorder_for_each_entry_safe - iterate in post-order over rb_root of
 130  * given type allowing the backing memory of @pos to be invalidated
 131  *
 132  * @pos:        the 'type *' to use as a loop cursor.
 133  * @n:          another 'type *' to use as temporary storage
 134  * @root:       'rb_root *' of the rbtree.
 135  * @field:      the name of the rb_node field within 'type'.
 136  *
 137  * rbtree_postorder_for_each_entry_safe() provides a similar guarantee as
 138  * list_for_each_entry_safe() and allows the iteration to continue independent
 139  * of changes to @pos by the body of the loop.
 140  *
 141  * Note, however, that it cannot handle other modifications that re-order the
 142  * rbtree it is iterating over. This includes calling rb_erase() on @pos, as
 143  * rb_erase() may rebalance the tree, causing us to miss some nodes.
 144  */
 145 #define rbtree_postorder_for_each_entry_safe(pos, n, root, field) \
 146         for (pos = rb_entry_safe(rb_first_postorder(root), typeof(*pos), field); \
 147              pos && ({ n = rb_entry_safe(rb_next_postorder(&pos->field), \
 148                         typeof(*pos), field); 1; }); \
 149              pos = n)
 150
 151 #endif  /* _LINUX_RBTREE_H */