rbtree.h

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/* 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/container_of.h>
#include <linux/rbtree_types.h>
 
#include <linux/stddef.h>
#include <linux/rcupdate.h>
 
#define rb_parent(r)   ((struct rb_node *)((r)->__rb_parent_color & ~3))
 
#define rb_entry(ptr, type, member) container_of(ptr, type, member)
 
#define RB_EMPTY_ROOT(root)  (READ_ONCE((root)->rb_node) == NULL)
 
/*
 * DCL delta -- `uintptr_t` where mainline writes `unsigned long`, at the two
 * macros here and the two rb_link_node variants below; rbtree_augmented.h
 * has the same two in rb_set_parent()/rb_set_parent_color().  The field
 * holds a pointer (see rbtree_types.h for why the width matters).
 */
/* 'empty' nodes are nodes that are known not to be inserted in an rbtree */
#define RB_EMPTY_NODE(node)  \
    ((node)->__rb_parent_color == (uintptr_t)(node))
#define RB_CLEAR_NODE(node)  \
    ((node)->__rb_parent_color = (uintptr_t)(node))
 
#define RB_EMPTY_LINKED_NODE(lnode)  RB_EMPTY_NODE(&(lnode)->node)
#define RB_CLEAR_LINKED_NODE(lnode)  ({                 \
    RB_CLEAR_NODE(&(lnode)->node);                  \
    (lnode)->prev = (lnode)->next = NULL;               \
})
 
extern void rb_insert_color(struct rb_node *, struct rb_root *);
extern void rb_erase(struct rb_node *, struct rb_root *);
extern bool rb_erase_linked(struct rb_node_linked *, struct rb_root_linked *);
 
/* 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 *);
 
/*
 * This function returns the first node (in sort order) of the tree.
 */
static inline struct rb_node *rb_first(const 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;
}
 
/*
 * This function returns the last node (in sort order) of the tree.
 */
static inline struct rb_node *rb_last(const 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;
}
 
/* 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 = (uintptr_t)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 = (uintptr_t)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; \
    })
 
#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)
 
/* 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.
 */
 
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;
}
 
static __always_inline void
__rb_add(struct rb_node *node, struct rb_root *tree,
     bool (*less)(struct rb_node *, const struct rb_node *),
     void (*linkop)(struct rb_node *, struct rb_node *, 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;
    }
 
    linkop(node, parent, link);
    rb_link_node(node, parent, link);
    rb_insert_color(node, tree);
}
 
#define __node_2_linked_node(_n) \
    rb_entry((_n), struct rb_node_linked, node)
 
static inline void
rb_link_linked_node(struct rb_node *node, struct rb_node *parent, struct rb_node **link)
{
    if (!parent)
        return;
 
    struct rb_node_linked *nnew = __node_2_linked_node(node);
    struct rb_node_linked *npar = __node_2_linked_node(parent);
 
    if (link == &parent->rb_left) {
        nnew->prev = npar->prev;
        nnew->next = npar;
        npar->prev = nnew;
        if (nnew->prev)
            nnew->prev->next = nnew;
    } else {
        nnew->next = npar->next;
        nnew->prev = npar;
        npar->next = nnew;
        if (nnew->next)
            nnew->next->prev = nnew;
    }
}
 
static __always_inline bool
rb_add_linked(struct rb_node_linked *node, struct rb_root_linked *tree,
          bool (*less)(struct rb_node *, const struct rb_node *))
{
    __rb_add(&node->node, &tree->rb_root, less, rb_link_linked_node);
    if (!node->prev)
        tree->rb_leftmost = node;
    return !node->prev;
}
 
/* Empty linkop function which is optimized away by the compiler */
static __always_inline void
rb_link_noop(struct rb_node *n, struct rb_node *p, struct rb_node **l) { }
 
static __always_inline void
rb_add(struct rb_node *node, struct rb_root *tree,
       bool (*less)(struct rb_node *, const struct rb_node *))
{
    __rb_add(node, tree, less, rb_link_noop);
}
 
static __always_inline struct rb_node *
rb_find_add_cached(struct rb_node *node, struct rb_root_cached *tree,
        int (*cmp)(const struct rb_node *new, const struct rb_node *exist))
{
    bool leftmost = true;
    struct rb_node **link = &tree->rb_root.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;
            leftmost = false;
        } else {
            return parent;
        }
    }
 
    rb_link_node(node, parent, link);
    rb_insert_color_cached(node, tree, leftmost);
    return NULL;
}
 
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;
}
 
static __always_inline struct rb_node *
rb_find_add_rcu(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_rcu(node, parent, link);
    rb_insert_color(node, tree);
    return 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;
}
 
static __always_inline struct rb_node *
rb_find_rcu(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 = rcu_dereference_raw(node->rb_left);
        else if (c > 0)
            node = rcu_dereference_raw(node->rb_right);
        else
            return node;
    }
 
    return 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;
}
 
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;
}
 
#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 */