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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)
 
 /* '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)
 
 /* 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 */

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