/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
  Red Black Trees
  (C) 1999  Andrea Arcangeli <andrea@suse.de>
  (C) 2002  David Woodhouse <dwmw2@infradead.org>
  (C) 2012  Michel Lespinasse <walken@google.com>


  linux/include/linux/rbtree_augmented.h
*/

#ifndef _LINUX_RBTREE_AUGMENTED_H
#define _LINUX_RBTREE_AUGMENTED_H

#include <linux/compiler.h>
#include <linux/rbtree.h>
#include <linux/rcupdate.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,
                                  bool newleft, struct rb_node **leftmost,
        void (*augment_rotate)(struct rb_node *old, struct rb_node *new));
/*
 * Fixup the rbtree and update the augmented information when rebalancing.
 *
 * On insertion, the user must update the augmented information on the path
 * leading to the inserted node, then call rb_link_node() as usual and
 * rb_insert_augmented() instead of the usual rb_insert_color() call.
 * If rb_insert_augmented() rebalances the rbtree, it will callback into
 * a user provided function to update the augmented information on the
 * affected subtrees.
 */
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, false, NULL, augment->rotate);
}

static inline void
rb_insert_augmented_cached(struct rb_node *node,
                           struct rb_root_cached *root, bool newleft,
                           const struct rb_augment_callbacks *augment)
{
        __rb_insert_augmented(node, &root->rb_root,
                              newleft, &root->rb_leftmost, 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 = {                   \
        .propagate = rbname ## _propagate,                              \
        .copy = rbname ## _copy,                                        \
        .rotate = 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)
                        WRITE_ONCE(parent->rb_left, new);
                else
                        WRITE_ONCE(parent->rb_right, new);
        } else
                WRITE_ONCE(root->rb_node, new);
}

static inline void
__rb_change_child_rcu(struct rb_node *old, struct rb_node *new,
                      struct rb_node *parent, struct rb_root *root)
{
        if (parent) {
                if (parent->rb_left == old)
                        rcu_assign_pointer(parent->rb_left, new);
                else
                        rcu_assign_pointer(parent->rb_right, new);
        } else
                rcu_assign_pointer(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 struct rb_node *
__rb_erase_augmented(struct rb_node *node, struct rb_root *root,
                     struct rb_node **leftmost,
                     const struct rb_augment_callbacks *augment)
{
        struct rb_node *child = node->rb_right;
        struct rb_node *tmp = node->rb_left;
        struct rb_node *parent, *rebalance;
        unsigned long pc;

        if (leftmost && node == *leftmost)
                *leftmost = rb_next(node);

        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);
                        child2 = successor->rb_right;
                        WRITE_ONCE(parent->rb_left, child2);
                        WRITE_ONCE(successor->rb_right, child);
                        rb_set_parent(child, successor);

                        augment->copy(node, successor);
                        augment->propagate(parent, successor);
                }

                tmp = node->rb_left;
                WRITE_ONCE(successor->rb_left, tmp);
                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);
        return rebalance;
}

static __always_inline void
rb_erase_augmented(struct rb_node *node, struct rb_root *root,
                   const struct rb_augment_callbacks *augment)
{
        struct rb_node *rebalance = __rb_erase_augmented(node, root,
                                                         NULL, augment);
        if (rebalance)
                __rb_erase_color(rebalance, root, augment->rotate);
}

static __always_inline void
rb_erase_augmented_cached(struct rb_node *node, struct rb_root_cached *root,
                          const struct rb_augment_callbacks *augment)
{
        struct rb_node *rebalance = __rb_erase_augmented(node, &root->rb_root,
                                                         &root->rb_leftmost,
                                                         augment);
        if (rebalance)
                __rb_erase_color(rebalance, &root->rb_root, augment->rotate);
}

#endif  /* _LINUX_RBTREE_AUGMENTED_H */