rbtree.c

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/*
  Red Black Trees
  (C) 1999  Andrea Arcangeli <[e-mail]>
  
  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>

static void __rb_rotate_left(rb_node_t * node, rb_root_t * root)
{
	rb_node_t * right = node->rb_right;

	if ((node->rb_right = right->rb_left))
		right->rb_left->rb_parent = node;
	right->rb_left = node;

	if ((right->rb_parent = node->rb_parent))
	{
		if (node == node->rb_parent->rb_left)
			node->rb_parent->rb_left = right;
		else
			node->rb_parent->rb_right = right;
	}
	else
		root->rb_node = right;
	node->rb_parent = right;
}

static void __rb_rotate_right(rb_node_t * node, rb_root_t * root)
{
	rb_node_t * left = node->rb_left;

	if ((node->rb_left = left->rb_right))
		left->rb_right->rb_parent = node;
	left->rb_right = node;

	if ((left->rb_parent = node->rb_parent))
	{
		if (node == node->rb_parent->rb_right)
			node->rb_parent->rb_right = left;
		else
			node->rb_parent->rb_left = left;
	}
	else
		root->rb_node = left;
	node->rb_parent = left;
}

void rb_insert_color(rb_node_t * node, rb_root_t * root)
{
	rb_node_t * parent, * gparent;

	while ((parent = node->rb_parent) && parent->rb_color == RB_RED)
	{
		gparent = parent->rb_parent;

		if (parent == gparent->rb_left)
		{
			{
				register rb_node_t * uncle = gparent->rb_right;
				if (uncle && uncle->rb_color == RB_RED)
				{
					uncle->rb_color = RB_BLACK;
					parent->rb_color = RB_BLACK;
					gparent->rb_color = RB_RED;
					node = gparent;
					continue;
				}
			}

			if (parent->rb_right == node)
			{
				register rb_node_t * tmp;
				__rb_rotate_left(parent, root);
				tmp = parent;
				parent = node;
				node = tmp;
			}

			parent->rb_color = RB_BLACK;
			gparent->rb_color = RB_RED;
			__rb_rotate_right(gparent, root);
		} else {
			{
				register rb_node_t * uncle = gparent->rb_left;
				if (uncle && uncle->rb_color == RB_RED)
				{
					uncle->rb_color = RB_BLACK;
					parent->rb_color = RB_BLACK;
					gparent->rb_color = RB_RED;
					node = gparent;
					continue;
				}
			}

			if (parent->rb_left == node)
			{
				register rb_node_t * tmp;
				__rb_rotate_right(parent, root);
				tmp = parent;
				parent = node;
				node = tmp;
			}

			parent->rb_color = RB_BLACK;
			gparent->rb_color = RB_RED;
			__rb_rotate_left(gparent, root);
		}
	}

	root->rb_node->rb_color = RB_BLACK;
}

static void __rb_erase_color(rb_node_t * node, rb_node_t * parent,
			     rb_root_t * root)
{
	rb_node_t * other;

	while ((!node || node->rb_color == RB_BLACK) && node != root->rb_node)
	{
		if (parent->rb_left == node)
		{
			other = parent->rb_right;
			if (other->rb_color == RB_RED)
			{
				other->rb_color = RB_BLACK;
				parent->rb_color = RB_RED;
				__rb_rotate_left(parent, root);
				other = parent->rb_right;
			}
			if ((!other->rb_left ||
			     other->rb_left->rb_color == RB_BLACK)
			    && (!other->rb_right ||
				other->rb_right->rb_color == RB_BLACK))
			{
				other->rb_color = RB_RED;
				node = parent;
				parent = node->rb_parent;
			}
			else
			{
				if (!other->rb_right ||
				    other->rb_right->rb_color == RB_BLACK)
				{
					register rb_node_t * o_left;
					if ((o_left = other->rb_left))
						o_left->rb_color = RB_BLACK;
					other->rb_color = RB_RED;
					__rb_rotate_right(other, root);
					other = parent->rb_right;
				}
				other->rb_color = parent->rb_color;
				parent->rb_color = RB_BLACK;
				if (other->rb_right)
					other->rb_right->rb_color = RB_BLACK;
				__rb_rotate_left(parent, root);
				node = root->rb_node;
				break;
			}
		}
		else
		{
			other = parent->rb_left;
			if (other->rb_color == RB_RED)
			{
				other->rb_color = RB_BLACK;
				parent->rb_color = RB_RED;
				__rb_rotate_right(parent, root);
				other = parent->rb_left;
			}
			if ((!other->rb_left ||
			     other->rb_left->rb_color == RB_BLACK)
			    && (!other->rb_right ||
				other->rb_right->rb_color == RB_BLACK))
			{
				other->rb_color = RB_RED;
				node = parent;
				parent = node->rb_parent;
			}
			else
			{
				if (!other->rb_left ||
				    other->rb_left->rb_color == RB_BLACK)
				{
					register rb_node_t * o_right;
					if ((o_right = other->rb_right))
						o_right->rb_color = RB_BLACK;
					other->rb_color = RB_RED;
					__rb_rotate_left(other, root);
					other = parent->rb_left;
				}
				other->rb_color = parent->rb_color;
				parent->rb_color = RB_BLACK;
				if (other->rb_left)
					other->rb_left->rb_color = RB_BLACK;
				__rb_rotate_right(parent, root);
				node = root->rb_node;
				break;
			}
		}
	}
	if (node)
		node->rb_color = RB_BLACK;
}

void rb_erase(rb_node_t * node, rb_root_t * root)
{
	rb_node_t * child, * parent;
	int color;

	if (!node->rb_left)
		child = node->rb_right;
	else if (!node->rb_right)
		child = node->rb_left;
	else
	{
		rb_node_t * old = node, * left;

		node = node->rb_right;
		while ((left = node->rb_left))
			node = left;
		child = node->rb_right;
		parent = node->rb_parent;
		color = node->rb_color;

		if (child)
			child->rb_parent = parent;
		if (parent)
		{
			if (parent->rb_left == node)
				parent->rb_left = child;
			else
				parent->rb_right = child;
		}
		else
			root->rb_node = child;

		if (node->rb_parent == old)
			parent = node;
		node->rb_parent = old->rb_parent;
		node->rb_color = old->rb_color;
		node->rb_right = old->rb_right;
		node->rb_left = old->rb_left;

		if (old->rb_parent)
		{
			if (old->rb_parent->rb_left == old)
				old->rb_parent->rb_left = node;
			else
				old->rb_parent->rb_right = node;
		} else
			root->rb_node = node;

		old->rb_left->rb_parent = node;
		if (old->rb_right)
			old->rb_right->rb_parent = node;
		goto color;
	}

	parent = node->rb_parent;
	color = node->rb_color;

	if (child)
		child->rb_parent = 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);
}