source: trunk/kernel/libk/rbtree.c @ 114

/*
  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 <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);

        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);
}

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);
}

/*
 * 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;
}