libhv/base/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 "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))
            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 (struct rb_node *)0;
    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 (struct rb_node *)0;
    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 *newnode,
             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 = newnode;
        else
            parent->rb_right = newnode;
    } else {
        root->rb_node = newnode;
    }
    if (victim->rb_left)
        victim->rb_left->rb_parent = newnode;
    if (victim->rb_right)
        victim->rb_right->rb_parent = newnode;

    /* Copy the pointers/colour from the victim to the replacement */
    *newnode = *victim;
}