/* 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 void rb_erase_cached(struct rb_node *node,
  				   struct rb_root_cached *root)
  {
  	if (root->rb_leftmost == node)
  		root->rb_leftmost = rb_next(node);
  	rb_erase(node, &root->rb_root);
  }
  
  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);
  }

  #endif	/* _LINUX_RBTREE_H */