rbtree_augmented.h

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/*
  Red Black Trees
  (C) 1999  Andrea Arcangeli <[email protected]>
  (C) 2002  David Woodhouse <[email protected]>
  (C) 2012  Michel Lespinasse <[email protected]>

  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/include/linux/rbtree_augmented.h
*/

#ifndef _LINUX_RBTREE_AUGMENTED_H
#define _LINUX_RBTREE_AUGMENTED_H

#include <linux/compiler.h>
#include <linux/rbtree.h>

/*
 * Please note - only struct rb_augment_callbacks and the prototypes for
 * rb_insert_augmented() and rb_erase_augmented() are intended to be public.
 * The rest are implementation details you are not expected to depend on.
 *
 * See Documentation/rbtree.txt for documentation and samples.
 */

struct rb_augment_callbacks {
    void (*propagate)(struct rb_node *node, struct rb_node *stop);
    void (*copy)(struct rb_node *old, struct rb_node *new);
    void (*rotate)(struct rb_node *old, struct rb_node *new);
};

extern void __rb_insert_augmented(struct rb_node *node, struct rb_root *root,
    void (*augment_rotate)(struct rb_node *old, struct rb_node *new));
static inline void
rb_insert_augmented(struct rb_node *node, struct rb_root *root,
            const struct rb_augment_callbacks *augment)
{
    __rb_insert_augmented(node, root, augment->rotate);
}

#define RB_DECLARE_CALLBACKS(rbstatic, rbname, rbstruct, rbfield,   \
                 rbtype, rbaugmented, rbcompute)        \
static inline void                          \
rbname ## _propagate(struct rb_node *rb, struct rb_node *stop)      \
{                                   \
    while (rb != stop) {                        \
        rbstruct *node = rb_entry(rb, rbstruct, rbfield);   \
        rbtype augmented = rbcompute(node);         \
        if (node->rbaugmented == augmented)         \
            break;                      \
        node->rbaugmented = augmented;              \
        rb = rb_parent(&node->rbfield);             \
    }                               \
}                                   \
static inline void                          \
rbname ## _copy(struct rb_node *rb_old, struct rb_node *rb_new)     \
{                                   \
    rbstruct *old = rb_entry(rb_old, rbstruct, rbfield);        \
    rbstruct *new = rb_entry(rb_new, rbstruct, rbfield);        \
    new->rbaugmented = old->rbaugmented;                \
}                                   \
static void                             \
rbname ## _rotate(struct rb_node *rb_old, struct rb_node *rb_new)   \
{                                   \
    rbstruct *old = rb_entry(rb_old, rbstruct, rbfield);        \
    rbstruct *new = rb_entry(rb_new, rbstruct, rbfield);        \
    new->rbaugmented = old->rbaugmented;                \
    old->rbaugmented = rbcompute(old);              \
}                                   \
rbstatic const struct rb_augment_callbacks rbname = {           \
    rbname ## _propagate, rbname ## _copy, rbname ## _rotate    \
};


#define RB_RED      0
#define RB_BLACK    1

#define __rb_parent(pc)    ((struct rb_node *)(pc & ~3))

#define __rb_color(pc)     ((pc) & 1)
#define __rb_is_black(pc)  __rb_color(pc)
#define __rb_is_red(pc)    (!__rb_color(pc))
#define rb_color(rb)       __rb_color((rb)->__rb_parent_color)
#define rb_is_red(rb)      __rb_is_red((rb)->__rb_parent_color)
#define rb_is_black(rb)    __rb_is_black((rb)->__rb_parent_color)

static inline void rb_set_parent(struct rb_node *rb, struct rb_node *p)
{
    rb->__rb_parent_color = rb_color(rb) | (unsigned long)p;
}

static inline void rb_set_parent_color(struct rb_node *rb,
                       struct rb_node *p, int color)
{
    rb->__rb_parent_color = (unsigned long)p | color;
}

static inline void
__rb_change_child(struct rb_node *old, struct rb_node *new,
          struct rb_node *parent, struct rb_root *root)
{
    if (parent) {
        if (parent->rb_left == old)
            parent->rb_left = new;
        else
            parent->rb_right = new;
    } else
        root->rb_node = new;
}

extern void __rb_erase_color(struct rb_node *parent, struct rb_root *root,
    void (*augment_rotate)(struct rb_node *old, struct rb_node *new));

static __always_inline void
rb_erase_augmented(struct rb_node *node, struct rb_root *root,
           const struct rb_augment_callbacks *augment)
{
    struct rb_node *child = node->rb_right, *tmp = node->rb_left;
    struct rb_node *parent, *rebalance;
    unsigned long pc;

    if (!tmp) {
        /*
         * Case 1: node to erase has no more than 1 child (easy!)
         *
         * Note that if there is one child it must be red due to 5)
         * and node must be black due to 4). We adjust colors locally
         * so as to bypass __rb_erase_color() later on.
         */
        pc = node->__rb_parent_color;
        parent = __rb_parent(pc);
        __rb_change_child(node, child, parent, root);
        if (child) {
            child->__rb_parent_color = pc;
            rebalance = NULL;
        } else
            rebalance = __rb_is_black(pc) ? parent : NULL;
        tmp = parent;
    } else if (!child) {
        /* Still case 1, but this time the child is node->rb_left */
        tmp->__rb_parent_color = pc = node->__rb_parent_color;
        parent = __rb_parent(pc);
        __rb_change_child(node, tmp, parent, root);
        rebalance = NULL;
        tmp = parent;
    } else {
        struct rb_node *successor = child, *child2;
        tmp = child->rb_left;
        if (!tmp) {
            /*
             * Case 2: node's successor is its right child
             *
             *    (n)          (s)
             *    / \          / \
             *  (x) (s)  ->  (x) (c)
             *        \
             *        (c)
             */
            parent = successor;
            child2 = successor->rb_right;
            augment->copy(node, successor);
        } else {
            /*
             * Case 3: node's successor is leftmost under
             * node's right child subtree
             *
             *    (n)          (s)
             *    / \          / \
             *  (x) (y)  ->  (x) (y)
             *      /            /
             *    (p)          (p)
             *    /            /
             *  (s)          (c)
             *    \
             *    (c)
             */
            do {
                parent = successor;
                successor = tmp;
                tmp = tmp->rb_left;
            } while (tmp);
            parent->rb_left = child2 = successor->rb_right;
            successor->rb_right = child;
            rb_set_parent(child, successor);
            augment->copy(node, successor);
            augment->propagate(parent, successor);
        }

        successor->rb_left = tmp = node->rb_left;
        rb_set_parent(tmp, successor);

        pc = node->__rb_parent_color;
        tmp = __rb_parent(pc);
        __rb_change_child(node, successor, tmp, root);
        if (child2) {
            successor->__rb_parent_color = pc;
            rb_set_parent_color(child2, parent, RB_BLACK);
            rebalance = NULL;
        } else {
            unsigned long pc2 = successor->__rb_parent_color;
            successor->__rb_parent_color = pc;
            rebalance = __rb_is_black(pc2) ? parent : NULL;
        }
        tmp = successor;
    }

    augment->propagate(tmp, NULL);
    if (rebalance)
        __rb_erase_color(rebalance, root, augment->rotate);
}

#endif  /* _LINUX_RBTREE_AUGMENTED_H */