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kernel-rbtree.c

/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 * 
 * kernel-rbtree.c
 *
 * This is imported from the Linux kernel to give us a tested and
 * portable tree library.
 */
/*
  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 "kernel-rbtree.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;
}

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) != NULL)
                  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);
}

/*
 * 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 NULL;
      while (n->rb_left)
            n = n->rb_left;
      return n;
}

struct rb_node *rb_last(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(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;
}

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;
}

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;
}

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