text: /*
    Red Black Trees
    (C) 1999  Andrea Arcangeli <andrea@suse.de>
  
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.
  
    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.
  
    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  
    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/rbtree.txt 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)  ((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);
  
  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)
  
  #endif  /* _LINUX_RBTREE_H */
  