root/lib/rbtree.c

/*
  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/module.h>

static void __rb_rotate_left(struct rb_node *node, struct rb_root *root)
{
        struct rb_node *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(struct rb_node *node, struct rb_root *root)
{
        struct rb_node *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(struct rb_node *node, struct rb_root *root)
{
        struct rb_node *parent, *gparent;

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

                if (parent == gparent->rb_left)
                {
                        {
                                register struct rb_node *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 struct rb_node *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 struct rb_node *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 struct rb_node *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;
}
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 || 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 struct rb_node *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 struct rb_node *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(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;
                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);
}
EXPORT_SYMBOL(rb_erase);

/*
 * This function returns the first node (in sort order) of the tree.
 */
struct rb_node *rb_first(struct rb_root *root)
{
        struct rb_node  *n;

        n = root->rb_node;
        if (!n)
                return 0;
        while (n->rb_left)
                n = n->rb_left;
        return n;
}
EXPORT_SYMBOL(rb_first);

struct rb_node *rb_next(struct rb_node *node)
{
        /* 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 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 (node->rb_parent && node == node->rb_parent->rb_right)
                node = node->rb_parent;

        return node->rb_parent;
}
EXPORT_SYMBOL(rb_next);

struct rb_node *rb_prev(struct rb_node *node)
{
        /* 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 node;
        }

        /* No left-hand children. Go up till we find an ancestor which
           is a right-hand child of its parent */
        while (node->rb_parent && node == node->rb_parent->rb_left)
                node = node->rb_parent;

        return node->rb_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 = victim->rb_parent;

        /* 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)
                victim->rb_left->rb_parent = new;
        if (victim->rb_right)
                victim->rb_right->rb_parent = new;

        /* Copy the pointers/colour from the victim to the replacement */
        *new = *victim;
}
EXPORT_SYMBOL(rb_replace_node);