LXR linux/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
  36struct 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
  43struct 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 */
  57struct 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
  77extern void rb_insert_color(struct rb_node *, struct rb_root *);
  78extern void rb_erase(struct rb_node *, struct rb_root *);
  79
  80
  81/* Find logical next and previous nodes in a tree */
  82extern struct rb_node *rb_next(const struct rb_node *);
  83extern struct rb_node *rb_prev(const struct rb_node *);
  84extern struct rb_node *rb_first(const struct rb_root *);
  85extern struct rb_node *rb_last(const struct rb_root *);
  86
  87extern void rb_insert_color_cached(struct rb_node *,
  88                                   struct rb_root_cached *, bool);
  89extern 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 */
  94extern struct rb_node *rb_first_postorder(const struct rb_root *);
  95extern struct rb_node *rb_next_postorder(const struct rb_node *);
  96
  97/* Fast replacement of a single node without remove/rebalance/add/rebalance */
  98extern void rb_replace_node(struct rb_node *victim, struct rb_node *new,
  99                            struct rb_root *root);
 100extern void rb_replace_node_rcu(struct rb_node *victim, struct rb_node *new,
 101                                struct rb_root *root);
 102extern void rb_replace_node_cached(struct rb_node *victim, struct rb_node *new,
 103                                   struct rb_root_cached *root);
 104
 105static 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
 114static 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 */
 152