rbtree.h 5.36 KB
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/*
  Red Black Trees
  (C) 1999  Andrea Arcangeli <andrea@suse.de>
  
  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation; either version 2 of the License, or
  (at your option) any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

  linux/include/linux/rbtree.h

  To use rbtrees you'll have to implement your own insert and search cores.
  This will avoid us to use callbacks and to drop drammatically performances.
  I know it's not the cleaner way,  but in C (not in C++) to get
  performances and genericity...

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  See Documentation/rbtree.txt for documentation and samples.
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*/

#ifndef	_LINUX_RBTREE_H
#define	_LINUX_RBTREE_H

#include <linux/kernel.h>
#include <linux/stddef.h>
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#include <linux/rcupdate.h>
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struct rb_node {
	unsigned long  __rb_parent_color;
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	struct rb_node *rb_right;
	struct rb_node *rb_left;
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} __attribute__((aligned(sizeof(long))));
    /* The alignment might seem pointless, but allegedly CRIS needs it */
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struct rb_root {
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	struct rb_node *rb_node;
};

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/*
 * Leftmost-cached rbtrees.
 *
 * We do not cache the rightmost node based on footprint
 * size vs number of potential users that could benefit
 * from O(1) rb_last(). Just not worth it, users that want
 * this feature can always implement the logic explicitly.
 * Furthermore, users that want to cache both pointers may
 * find it a bit asymmetric, but that's ok.
 */
struct rb_root_cached {
	struct rb_root rb_root;
	struct rb_node *rb_leftmost;
};
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#define rb_parent(r)   ((struct rb_node *)((r)->__rb_parent_color & ~3))
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#define RB_ROOT	(struct rb_root) { NULL, }
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#define RB_ROOT_CACHED (struct rb_root_cached) { {NULL, }, NULL }
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#define	rb_entry(ptr, type, member) container_of(ptr, type, member)

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#define RB_EMPTY_ROOT(root)  (READ_ONCE((root)->rb_node) == NULL)
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/* 'empty' nodes are nodes that are known not to be inserted in an rbtree */
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#define RB_EMPTY_NODE(node)  \
	((node)->__rb_parent_color == (unsigned long)(node))
#define RB_CLEAR_NODE(node)  \
	((node)->__rb_parent_color = (unsigned long)(node))
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extern void rb_insert_color(struct rb_node *, struct rb_root *);
extern void rb_erase(struct rb_node *, struct rb_root *);

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/* Find logical next and previous nodes in a tree */
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extern struct rb_node *rb_next(const struct rb_node *);
extern struct rb_node *rb_prev(const struct rb_node *);
extern struct rb_node *rb_first(const struct rb_root *);
extern struct rb_node *rb_last(const struct rb_root *);
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extern void rb_insert_color_cached(struct rb_node *,
				   struct rb_root_cached *, bool);
extern void rb_erase_cached(struct rb_node *node, struct rb_root_cached *);
/* Same as rb_first(), but O(1) */
#define rb_first_cached(root) (root)->rb_leftmost

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/* Postorder iteration - always visit the parent after its children */
extern struct rb_node *rb_first_postorder(const struct rb_root *);
extern struct rb_node *rb_next_postorder(const struct rb_node *);

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/* Fast replacement of a single node without remove/rebalance/add/rebalance */
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extern void rb_replace_node(struct rb_node *victim, struct rb_node *new,
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			    struct rb_root *root);
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extern void rb_replace_node_rcu(struct rb_node *victim, struct rb_node *new,
				struct rb_root *root);
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extern void rb_replace_node_cached(struct rb_node *victim, struct rb_node *new,
				   struct rb_root_cached *root);
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static inline void rb_link_node(struct rb_node *node, struct rb_node *parent,
				struct rb_node **rb_link)
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{
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	node->__rb_parent_color = (unsigned long)parent;
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	node->rb_left = node->rb_right = NULL;

	*rb_link = node;
}

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static inline void rb_link_node_rcu(struct rb_node *node, struct rb_node *parent,
				    struct rb_node **rb_link)
{
	node->__rb_parent_color = (unsigned long)parent;
	node->rb_left = node->rb_right = NULL;

	rcu_assign_pointer(*rb_link, node);
}

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#define rb_entry_safe(ptr, type, member) \
	({ typeof(ptr) ____ptr = (ptr); \
	   ____ptr ? rb_entry(____ptr, type, member) : NULL; \
	})

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/**
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 * rbtree_postorder_for_each_entry_safe - iterate in post-order over rb_root of
 * given type allowing the backing memory of @pos to be invalidated
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 *
 * @pos:	the 'type *' to use as a loop cursor.
 * @n:		another 'type *' to use as temporary storage
 * @root:	'rb_root *' of the rbtree.
 * @field:	the name of the rb_node field within 'type'.
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 *
 * rbtree_postorder_for_each_entry_safe() provides a similar guarantee as
 * list_for_each_entry_safe() and allows the iteration to continue independent
 * of changes to @pos by the body of the loop.
 *
 * Note, however, that it cannot handle other modifications that re-order the
 * rbtree it is iterating over. This includes calling rb_erase() on @pos, as
 * rb_erase() may rebalance the tree, causing us to miss some nodes.
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 */
#define rbtree_postorder_for_each_entry_safe(pos, n, root, field) \
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	for (pos = rb_entry_safe(rb_first_postorder(root), typeof(*pos), field); \
	     pos && ({ n = rb_entry_safe(rb_next_postorder(&pos->field), \
			typeof(*pos), field); 1; }); \
	     pos = n)
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#endif	/* _LINUX_RBTREE_H */