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rbtree.c

/* Stolen from Linux 2.6.34 */

/*
  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;
}

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