rbtree.c

/*
 * RBtree implementation adopted from the Linux kernel sources.
 */

#include <sys/types.h>
#include "rbtree.h"

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);

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

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

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))
			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);
}

/*
 * 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;
}

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;
}

struct rb_node *rb_next(const struct rb_node *node)
{
	struct rb_node *parent;

	if (rb_parent(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;
}

struct rb_node *rb_prev(const struct rb_node *node)
{
	struct rb_node *parent;

	if (rb_parent(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;
}

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;
}