/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
  Red Black Trees
  (C) 1999  Andrea Arcangeli <andrea@suse.de>
  

  linux/include/linux/rbtree.h

  To use rbtrees you'll have to implement your own insert and search cores.
  This will avoid us to use callbacks and to drop drammatically performances.
  I know it's not the cleaner way,  but in C (not in C++) to get
  performances and genericity...

  See Documentation/core-api/rbtree.rst for documentation and samples.
*/

#ifndef _LINUX_RBTREE_H
#define _LINUX_RBTREE_H

#include <linux/kernel.h>
#include <linux/stddef.h>
#include <linux/rcupdate.h>

struct rb_node {
        unsigned long  __rb_parent_color;
        struct rb_node *rb_right;
        struct rb_node *rb_left;
} __attribute__((aligned(sizeof(long))));
    /* The alignment might seem pointless, but allegedly CRIS needs it */

struct rb_root {
        struct rb_node *rb_node;
};

#define rb_parent(r)   ((struct rb_node *)((r)->__rb_parent_color & ~3))

#define RB_ROOT (struct rb_root) { NULL, }
#define rb_entry(ptr, type, member) container_of(ptr, type, member)

#define RB_EMPTY_ROOT(root)  (READ_ONCE((root)->rb_node) == NULL)

/* 'empty' nodes are nodes that are known not to be inserted in an rbtree */
#define RB_EMPTY_NODE(node)  \
        ((node)->__rb_parent_color == (unsigned long)(node))
#define RB_CLEAR_NODE(node)  \
        ((node)->__rb_parent_color = (unsigned long)(node))


extern void rb_insert_color(struct rb_node *, struct rb_root *);
extern void rb_erase(struct rb_node *, struct rb_root *);


/* Find logical next and previous nodes in a tree */
extern struct rb_node *rb_next(const struct rb_node *);
extern struct rb_node *rb_prev(const struct rb_node *);
extern struct rb_node *rb_first(const struct rb_root *);
extern struct rb_node *rb_last(const struct rb_root *);

/* Postorder iteration - always visit the parent after its children */
extern struct rb_node *rb_first_postorder(const struct rb_root *);
extern struct rb_node *rb_next_postorder(const struct rb_node *);

/* Fast replacement of a single node without remove/rebalance/add/rebalance */
extern void rb_replace_node(struct rb_node *victim, struct rb_node *new,
                            struct rb_root *root);
extern void rb_replace_node_rcu(struct rb_node *victim, struct rb_node *new,
                                struct rb_root *root);

static inline void rb_link_node(struct rb_node *node, struct rb_node *parent,
                                struct rb_node **rb_link)
{
        node->__rb_parent_color = (unsigned long)parent;
        node->rb_left = node->rb_right = NULL;

        *rb_link = node;
}

static inline void rb_link_node_rcu(struct rb_node *node, struct rb_node *parent,
                                    struct rb_node **rb_link)
{
        node->__rb_parent_color = (unsigned long)parent;
        node->rb_left = node->rb_right = NULL;

        rcu_assign_pointer(*rb_link, node);
}

#define rb_entry_safe(ptr, type, member) \
        ({ typeof(ptr) ____ptr = (ptr); \
           ____ptr ? rb_entry(____ptr, type, member) : NULL; \
        })

/**
 * rbtree_postorder_for_each_entry_safe - iterate in post-order over rb_root of
 * given type allowing the backing memory of @pos to be invalidated
 *
 * @pos:        the 'type *' to use as a loop cursor.
 * @n:          another 'type *' to use as temporary storage
 * @root:       'rb_root *' of the rbtree.
 * @field:      the name of the rb_node field within 'type'.
 *
 * rbtree_postorder_for_each_entry_safe() provides a similar guarantee as
 * list_for_each_entry_safe() and allows the iteration to continue independent
 * of changes to @pos by the body of the loop.
 *
 * Note, however, that it cannot handle other modifications that re-order the
 * rbtree it is iterating over. This includes calling rb_erase() on @pos, as
 * rb_erase() may rebalance the tree, causing us to miss some nodes.
 */
#define rbtree_postorder_for_each_entry_safe(pos, n, root, field) \
        for (pos = rb_entry_safe(rb_first_postorder(root), typeof(*pos), field); \
             pos && ({ n = rb_entry_safe(rb_next_postorder(&pos->field), \
                        typeof(*pos), field); 1; }); \
             pos = n)

/*
 * Leftmost-cached rbtrees.
 *
 * We do not cache the rightmost node based on footprint
 * size vs number of potential users that could benefit
 * from O(1) rb_last(). Just not worth it, users that want
 * this feature can always implement the logic explicitly.
 * Furthermore, users that want to cache both pointers may
 * find it a bit asymmetric, but that's ok.
 */
struct rb_root_cached {
        struct rb_root rb_root;
        struct rb_node *rb_leftmost;
};

#define RB_ROOT_CACHED (struct rb_root_cached) { {NULL, }, NULL }

/* Same as rb_first(), but O(1) */
#define rb_first_cached(root) (root)->rb_leftmost

static inline void rb_insert_color_cached(struct rb_node *node,
                                          struct rb_root_cached *root,
                                          bool leftmost)
{
        if (leftmost)
                root->rb_leftmost = node;
        rb_insert_color(node, &root->rb_root);
}


static inline struct rb_node *
rb_erase_cached(struct rb_node *node, struct rb_root_cached *root)
{
        struct rb_node *leftmost = NULL;

        if (root->rb_leftmost == node)
                leftmost = root->rb_leftmost = rb_next(node);

        rb_erase(node, &root->rb_root);

        return leftmost;
}

static inline void rb_replace_node_cached(struct rb_node *victim,
                                          struct rb_node *new,
                                          struct rb_root_cached *root)
{
        if (root->rb_leftmost == victim)
                root->rb_leftmost = new;
        rb_replace_node(victim, new, &root->rb_root);
}

/*
 * The below helper functions use 2 operators with 3 different
 * calling conventions. The operators are related like:
 *
 *      comp(a->key,b) < 0  := less(a,b)
 *      comp(a->key,b) > 0  := less(b,a)
 *      comp(a->key,b) == 0 := !less(a,b) && !less(b,a)
 *
 * If these operators define a partial order on the elements we make no
 * guarantee on which of the elements matching the key is found. See
 * rb_find().
 *
 * The reason for this is to allow the find() interface without requiring an
 * on-stack dummy object, which might not be feasible due to object size.
 */

/**
 * rb_add_cached() - insert @node into the leftmost cached tree @tree
 * @node: node to insert
 * @tree: leftmost cached tree to insert @node into
 * @less: operator defining the (partial) node order
 *
 * Returns @node when it is the new leftmost, or NULL.
 */
static __always_inline struct rb_node *
rb_add_cached(struct rb_node *node, struct rb_root_cached *tree,
              bool (*less)(struct rb_node *, const struct rb_node *))
{
        struct rb_node **link = &tree->rb_root.rb_node;
        struct rb_node *parent = NULL;
        bool leftmost = true;

        while (*link) {
                parent = *link;
                if (less(node, parent)) {
                        link = &parent->rb_left;
                } else {
                        link = &parent->rb_right;
                        leftmost = false;
                }
        }

        rb_link_node(node, parent, link);
        rb_insert_color_cached(node, tree, leftmost);

        return leftmost ? node : NULL;
}

/**
 * rb_add() - insert @node into @tree
 * @node: node to insert
 * @tree: tree to insert @node into
 * @less: operator defining the (partial) node order
 */
static __always_inline void
rb_add(struct rb_node *node, struct rb_root *tree,
       bool (*less)(struct rb_node *, const struct rb_node *))
{
        struct rb_node **link = &tree->rb_node;
        struct rb_node *parent = NULL;

        while (*link) {
                parent = *link;
                if (less(node, parent))
                        link = &parent->rb_left;
                else
                        link = &parent->rb_right;
        }

        rb_link_node(node, parent, link);
        rb_insert_color(node, tree);
}

/**
 * rb_find_add() - find equivalent @node in @tree, or add @node
 * @node: node to look-for / insert
 * @tree: tree to search / modify
 * @cmp: operator defining the node order
 *
 * Returns the rb_node matching @node, or NULL when no match is found and @node
 * is inserted.
 */
static __always_inline struct rb_node *
rb_find_add(struct rb_node *node, struct rb_root *tree,
            int (*cmp)(struct rb_node *, const struct rb_node *))
{
        struct rb_node **link = &tree->rb_node;
        struct rb_node *parent = NULL;
        int c;

        while (*link) {
                parent = *link;
                c = cmp(node, parent);

                if (c < 0)
                        link = &parent->rb_left;
                else if (c > 0)
                        link = &parent->rb_right;
                else
                        return parent;
        }

        rb_link_node(node, parent, link);
        rb_insert_color(node, tree);
        return NULL;
}

/**
 * rb_find() - find @key in tree @tree
 * @key: key to match
 * @tree: tree to search
 * @cmp: operator defining the node order
 *
 * Returns the rb_node matching @key or NULL.
 */
static __always_inline struct rb_node *
rb_find(const void *key, const struct rb_root *tree,
        int (*cmp)(const void *key, const struct rb_node *))
{
        struct rb_node *node = tree->rb_node;

        while (node) {
                int c = cmp(key, node);

                if (c < 0)
                        node = node->rb_left;
                else if (c > 0)
                        node = node->rb_right;
                else
                        return node;
        }

        return NULL;
}

/**
 * rb_find_first() - find the first @key in @tree
 * @key: key to match
 * @tree: tree to search
 * @cmp: operator defining node order
 *
 * Returns the leftmost node matching @key, or NULL.
 */
static __always_inline struct rb_node *
rb_find_first(const void *key, const struct rb_root *tree,
              int (*cmp)(const void *key, const struct rb_node *))
{
        struct rb_node *node = tree->rb_node;
        struct rb_node *match = NULL;

        while (node) {
                int c = cmp(key, node);

                if (c <= 0) {
                        if (!c)
                                match = node;
                        node = node->rb_left;
                } else if (c > 0) {
                        node = node->rb_right;
                }
        }

        return match;
}

/**
 * rb_next_match() - find the next @key in @tree
 * @key: key to match
 * @tree: tree to search
 * @cmp: operator defining node order
 *
 * Returns the next node matching @key, or NULL.
 */
static __always_inline struct rb_node *
rb_next_match(const void *key, struct rb_node *node,
              int (*cmp)(const void *key, const struct rb_node *))
{
        node = rb_next(node);
        if (node && cmp(key, node))
                node = NULL;
        return node;
}

/**
 * rb_for_each() - iterates a subtree matching @key
 * @node: iterator
 * @key: key to match
 * @tree: tree to search
 * @cmp: operator defining node order
 */
#define rb_for_each(node, key, tree, cmp) \
        for ((node) = rb_find_first((key), (tree), (cmp)); \
             (node); (node) = rb_next_match((key), (node), (cmp)))

#endif  /* _LINUX_RBTREE_H */