linux/lib/rbtree.c

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/*
Red Black Trees
(C) 1999 Andrea Arcangeli <andrea@suse.de>
(C) 2002 David Woodhouse <dwmw2@infradead.org>
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/lib/rbtree.c
*/
#include <linux/rbtree.h>
#include <linux/export.h>
#define RB_RED 0
#define RB_BLACK 1
#define rb_color(r) ((r)->__rb_parent_color & 1)
#define rb_is_red(r) (!rb_color(r))
#define rb_is_black(r) rb_color(r)
#define rb_set_red(r) do { (r)->__rb_parent_color &= ~1; } while (0)
#define rb_set_black(r) do { (r)->__rb_parent_color |= 1; } while (0)
static inline void rb_set_parent(struct rb_node *rb, struct rb_node *p)
{
rb->__rb_parent_color = rb_color(rb) | (unsigned long)p;
}
static inline void rb_set_color(struct rb_node *rb, int color)
{
rb->__rb_parent_color = (rb->__rb_parent_color & ~1) | color;
}
static void __rb_rotate_left(struct rb_node *node, struct rb_root *root)
{
struct rb_node *right = node->rb_right;
struct rb_node *parent = rb_parent(node);
if ((node->rb_right = right->rb_left))
rb_set_parent(right->rb_left, node);
right->rb_left = node;
rb_set_parent(right, parent);
if (parent)
{
if (node == parent->rb_left)
parent->rb_left = right;
else
parent->rb_right = right;
}
else
root->rb_node = right;
rb_set_parent(node, right);
}
static void __rb_rotate_right(struct rb_node *node, struct rb_root *root)
{
struct rb_node *left = node->rb_left;
struct rb_node *parent = rb_parent(node);
if ((node->rb_left = left->rb_right))
rb_set_parent(left->rb_right, node);
left->rb_right = node;
rb_set_parent(left, parent);
if (parent)
{
if (node == parent->rb_right)
parent->rb_right = left;
else
parent->rb_left = left;
}
else
root->rb_node = left;
rb_set_parent(node, left);
}
void rb_insert_color(struct rb_node *node, struct rb_root *root)
{
struct rb_node *parent, *gparent;
while ((parent = rb_parent(node)) && rb_is_red(parent))
{
gparent = rb_parent(parent);
if (parent == gparent->rb_left)
{
{
register struct rb_node *uncle = gparent->rb_right;
if (uncle && rb_is_red(uncle))
{
rb_set_black(uncle);
rb_set_black(parent);
rb_set_red(gparent);
node = gparent;
continue;
}
}
if (parent->rb_right == node)
{
register struct rb_node *tmp;
__rb_rotate_left(parent, root);
tmp = parent;
parent = node;
node = tmp;
}
rb_set_black(parent);
rb_set_red(gparent);
__rb_rotate_right(gparent, root);
} else {
{
register struct rb_node *uncle = gparent->rb_left;
if (uncle && rb_is_red(uncle))
{
rb_set_black(uncle);
rb_set_black(parent);
rb_set_red(gparent);
node = gparent;
continue;
}
}
if (parent->rb_left == node)
{
register struct rb_node *tmp;
__rb_rotate_right(parent, root);
tmp = parent;
parent = node;
node = tmp;
}
rb_set_black(parent);
rb_set_red(gparent);
__rb_rotate_left(gparent, root);
}
}
rb_set_black(root->rb_node);
}
EXPORT_SYMBOL(rb_insert_color);
static void __rb_erase_color(struct rb_node *node, struct rb_node *parent,
struct rb_root *root)
{
struct rb_node *other;
while ((!node || rb_is_black(node)) && node != root->rb_node)
{
if (parent->rb_left == node)
{
other = parent->rb_right;
if (rb_is_red(other))
{
rb_set_black(other);
rb_set_red(parent);
__rb_rotate_left(parent, root);
other = parent->rb_right;
}
if ((!other->rb_left || rb_is_black(other->rb_left)) &&
(!other->rb_right || rb_is_black(other->rb_right)))
{
rb_set_red(other);
node = parent;
parent = rb_parent(node);
}
else
{
if (!other->rb_right || rb_is_black(other->rb_right))
{
rb_set_black(other->rb_left);
rb_set_red(other);
__rb_rotate_right(other, root);
other = parent->rb_right;
}
rb_set_color(other, rb_color(parent));
rb_set_black(parent);
rb_set_black(other->rb_right);
__rb_rotate_left(parent, root);
node = root->rb_node;
break;
}
}
else
{
other = parent->rb_left;
if (rb_is_red(other))
{
rb_set_black(other);
rb_set_red(parent);
__rb_rotate_right(parent, root);
other = parent->rb_left;
}
if ((!other->rb_left || rb_is_black(other->rb_left)) &&
(!other->rb_right || rb_is_black(other->rb_right)))
{
rb_set_red(other);
node = parent;
parent = rb_parent(node);
}
else
{
if (!other->rb_left || rb_is_black(other->rb_left))
{
rb_set_black(other->rb_right);
rb_set_red(other);
__rb_rotate_left(other, root);
other = parent->rb_left;
}
rb_set_color(other, rb_color(parent));
rb_set_black(parent);
rb_set_black(other->rb_left);
__rb_rotate_right(parent, root);
node = root->rb_node;
break;
}
}
}
if (node)
rb_set_black(node);
}
void rb_erase(struct rb_node *node, struct rb_root *root)
{
struct rb_node *child, *parent;
int color;
if (!node->rb_left)
child = node->rb_right;
else if (!node->rb_right)
child = node->rb_left;
else
{
struct rb_node *old = node, *left;
node = node->rb_right;
while ((left = node->rb_left) != NULL)
node = left;
if (rb_parent(old)) {
if (rb_parent(old)->rb_left == old)
rb_parent(old)->rb_left = node;
else
rb_parent(old)->rb_right = node;
} else
root->rb_node = node;
child = node->rb_right;
parent = rb_parent(node);
color = rb_color(node);
if (parent == old) {
parent = node;
} else {
if (child)
rb_set_parent(child, parent);
parent->rb_left = child;
node->rb_right = old->rb_right;
rb_set_parent(old->rb_right, node);
}
node->__rb_parent_color = old->__rb_parent_color;
node->rb_left = old->rb_left;
rb_set_parent(old->rb_left, node);
goto color;
}
parent = rb_parent(node);
color = rb_color(node);
if (child)
rb_set_parent(child, parent);
if (parent)
{
if (parent->rb_left == node)
parent->rb_left = child;
else
parent->rb_right = child;
}
else
root->rb_node = child;
color:
if (color == RB_BLACK)
__rb_erase_color(child, parent, root);
}
EXPORT_SYMBOL(rb_erase);
static void rb_augment_path(struct rb_node *node, rb_augment_f func, void *data)
{
struct rb_node *parent;
up:
func(node, data);
parent = rb_parent(node);
if (!parent)
return;
if (node == parent->rb_left && parent->rb_right)
func(parent->rb_right, data);
else if (parent->rb_left)
func(parent->rb_left, data);
node = parent;
goto up;
}
/*
* after inserting @node into the tree, update the tree to account for
* both the new entry and any damage done by rebalance
*/
void rb_augment_insert(struct rb_node *node, rb_augment_f func, void *data)
{
if (node->rb_left)
node = node->rb_left;
else if (node->rb_right)
node = node->rb_right;
rb_augment_path(node, func, data);
}
EXPORT_SYMBOL(rb_augment_insert);
/*
* before removing the node, find the deepest node on the rebalance path
* that will still be there after @node gets removed
*/
struct rb_node *rb_augment_erase_begin(struct rb_node *node)
{
struct rb_node *deepest;
if (!node->rb_right && !node->rb_left)
deepest = rb_parent(node);
else if (!node->rb_right)
deepest = node->rb_left;
else if (!node->rb_left)
deepest = node->rb_right;
else {
deepest = rb_next(node);
if (deepest->rb_right)
deepest = deepest->rb_right;
else if (rb_parent(deepest) != node)
deepest = rb_parent(deepest);
}
return deepest;
}
EXPORT_SYMBOL(rb_augment_erase_begin);
/*
* after removal, update the tree to account for the removed entry
* and any rebalance damage.
*/
void rb_augment_erase_end(struct rb_node *node, rb_augment_f func, void *data)
{
if (node)
rb_augment_path(node, func, data);
}
EXPORT_SYMBOL(rb_augment_erase_end);
/*
* This function returns the first node (in sort order) of the tree.
*/
struct rb_node *rb_first(const struct rb_root *root)
{
struct rb_node *n;
n = root->rb_node;
if (!n)
return NULL;
while (n->rb_left)
n = n->rb_left;
return n;
}
EXPORT_SYMBOL(rb_first);
struct rb_node *rb_last(const struct rb_root *root)
{
struct rb_node *n;
n = root->rb_node;
if (!n)
return NULL;
while (n->rb_right)
n = n->rb_right;
return n;
}
EXPORT_SYMBOL(rb_last);
struct rb_node *rb_next(const struct rb_node *node)
{
struct rb_node *parent;
rbtree: empty nodes have no color Empty nodes have no color. We can make use of this property to simplify the code emitted by the RB_EMPTY_NODE and RB_CLEAR_NODE macros. Also, we can get rid of the rb_init_node function which had been introduced by commit 88d19cf37952 ("timers: Add rb_init_node() to allow for stack allocated rb nodes") to avoid some issue with the empty node's color not being initialized. I'm not sure what the RB_EMPTY_NODE checks in rb_prev() / rb_next() are doing there, though. axboe introduced them in commit 10fd48f2376d ("rbtree: fixed reversed RB_EMPTY_NODE and rb_next/prev"). The way I see it, the 'empty node' abstraction is only used by rbtree users to flag nodes that they haven't inserted in any rbtree, so asking the predecessor or successor of such nodes doesn't make any sense. One final rb_init_node() caller was recently added in sysctl code to implement faster sysctl name lookups. This code doesn't make use of RB_EMPTY_NODE at all, and from what I could see it only called rb_init_node() under the mistaken assumption that such initialization was required before node insertion. [sfr@canb.auug.org.au: fix net/ceph/osd_client.c build] Signed-off-by: Michel Lespinasse <walken@google.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Acked-by: David Woodhouse <David.Woodhouse@intel.com> Cc: Rik van Riel <riel@redhat.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Daniel Santos <daniel.santos@pobox.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: John Stultz <john.stultz@linaro.org> Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-10-08 23:30:32 +00:00
if (RB_EMPTY_NODE(node))
return NULL;
/* If we have a right-hand child, go down and then left as far
as we can. */
if (node->rb_right) {
node = node->rb_right;
while (node->rb_left)
node=node->rb_left;
return (struct rb_node *)node;
}
/* No right-hand children. Everything down and left is
smaller than us, so any 'next' node must be in the general
direction of our parent. Go up the tree; any time the
ancestor is a right-hand child of its parent, keep going
up. First time it's a left-hand child of its parent, said
parent is our 'next' node. */
while ((parent = rb_parent(node)) && node == parent->rb_right)
node = parent;
return parent;
}
EXPORT_SYMBOL(rb_next);
struct rb_node *rb_prev(const struct rb_node *node)
{
struct rb_node *parent;
rbtree: empty nodes have no color Empty nodes have no color. We can make use of this property to simplify the code emitted by the RB_EMPTY_NODE and RB_CLEAR_NODE macros. Also, we can get rid of the rb_init_node function which had been introduced by commit 88d19cf37952 ("timers: Add rb_init_node() to allow for stack allocated rb nodes") to avoid some issue with the empty node's color not being initialized. I'm not sure what the RB_EMPTY_NODE checks in rb_prev() / rb_next() are doing there, though. axboe introduced them in commit 10fd48f2376d ("rbtree: fixed reversed RB_EMPTY_NODE and rb_next/prev"). The way I see it, the 'empty node' abstraction is only used by rbtree users to flag nodes that they haven't inserted in any rbtree, so asking the predecessor or successor of such nodes doesn't make any sense. One final rb_init_node() caller was recently added in sysctl code to implement faster sysctl name lookups. This code doesn't make use of RB_EMPTY_NODE at all, and from what I could see it only called rb_init_node() under the mistaken assumption that such initialization was required before node insertion. [sfr@canb.auug.org.au: fix net/ceph/osd_client.c build] Signed-off-by: Michel Lespinasse <walken@google.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Acked-by: David Woodhouse <David.Woodhouse@intel.com> Cc: Rik van Riel <riel@redhat.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Daniel Santos <daniel.santos@pobox.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: John Stultz <john.stultz@linaro.org> Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-10-08 23:30:32 +00:00
if (RB_EMPTY_NODE(node))
return NULL;
/* If we have a left-hand child, go down and then right as far
as we can. */
if (node->rb_left) {
node = node->rb_left;
while (node->rb_right)
node=node->rb_right;
return (struct rb_node *)node;
}
/* No left-hand children. Go up till we find an ancestor which
is a right-hand child of its parent */
while ((parent = rb_parent(node)) && node == parent->rb_left)
node = parent;
return parent;
}
EXPORT_SYMBOL(rb_prev);
void rb_replace_node(struct rb_node *victim, struct rb_node *new,
struct rb_root *root)
{
struct rb_node *parent = rb_parent(victim);
/* Set the surrounding nodes to point to the replacement */
if (parent) {
if (victim == parent->rb_left)
parent->rb_left = new;
else
parent->rb_right = new;
} else {
root->rb_node = new;
}
if (victim->rb_left)
rb_set_parent(victim->rb_left, new);
if (victim->rb_right)
rb_set_parent(victim->rb_right, new);
/* Copy the pointers/colour from the victim to the replacement */
*new = *victim;
}
EXPORT_SYMBOL(rb_replace_node);