include/linux/rbtree.h

   1 /*
   2   Red Black Trees
   3   (C) 1999  Andrea Arcangeli <andrea@suse.de>
   4
   5  * SPDX-License-Identifier:     GPL-2.0+
   6
   7   linux/include/linux/rbtree.h
   8
   9   To use rbtrees you'll have to implement your own insert and search cores.
  10   This will avoid us to use callbacks and to drop drammatically performances.
  11   I know it's not the cleaner way,  but in C (not in C++) to get
  12   performances and genericity...
  13
  14   Some example of insert and search follows here. The search is a plain
  15   normal search over an ordered tree. The insert instead must be implemented
  16   int two steps: as first thing the code must insert the element in
  17   order as a red leaf in the tree, then the support library function
  18   rb_insert_color() must be called. Such function will do the
  19   not trivial work to rebalance the rbtree if necessary.
  20
  21 -----------------------------------------------------------------------
  22 static inline struct page * rb_search_page_cache(struct inode * inode,
  23                                                  unsigned long offset)
  24 {
  25         struct rb_node * n = inode->i_rb_page_cache.rb_node;
  26         struct page * page;
  27
  28         while (n)
  29         {
  30                 page = rb_entry(n, struct page, rb_page_cache);
  31
  32                 if (offset < page->offset)
  33                         n = n->rb_left;
  34                 else if (offset > page->offset)
  35                         n = n->rb_right;
  36                 else
  37                         return page;
  38         }
  39         return NULL;
  40 }
  41
  42 static inline struct page * __rb_insert_page_cache(struct inode * inode,
  43                                                    unsigned long offset,
  44                                                    struct rb_node * node)
  45 {
  46         struct rb_node ** p = &inode->i_rb_page_cache.rb_node;
  47         struct rb_node * parent = NULL;
  48         struct page * page;
  49
  50         while (*p)
  51         {
  52                 parent = *p;
  53                 page = rb_entry(parent, struct page, rb_page_cache);
  54
  55                 if (offset < page->offset)
  56                         p = &(*p)->rb_left;
  57                 else if (offset > page->offset)
  58                         p = &(*p)->rb_right;
  59                 else
  60                         return page;
  61         }
  62
  63         rb_link_node(node, parent, p);
  64
  65         return NULL;
  66 }
  67
  68 static inline struct page * rb_insert_page_cache(struct inode * inode,
  69                                                  unsigned long offset,
  70                                                  struct rb_node * node)
  71 {
  72         struct page * ret;
  73         if ((ret = __rb_insert_page_cache(inode, offset, node)))
  74                 goto out;
  75         rb_insert_color(node, &inode->i_rb_page_cache);
  76  out:
  77         return ret;
  78 }
  79 -----------------------------------------------------------------------
  80 */
  81
  82 #ifndef _LINUX_RBTREE_H
  83 #define _LINUX_RBTREE_H
  84
  85 #include <linux/stddef.h>
  86
  87 struct rb_node
  88 {
  89         unsigned long  rb_parent_color;
  90 #define RB_RED          0
  91 #define RB_BLACK        1
  92         struct rb_node *rb_right;
  93         struct rb_node *rb_left;
  94 } __attribute__((aligned(sizeof(long))));
  95     /* The alignment might seem pointless, but allegedly CRIS needs it */
  96
  97 struct rb_root
  98 {
  99         struct rb_node *rb_node;
 100 };
 101
 102
 103 #define rb_parent(r)   ((struct rb_node *)((r)->rb_parent_color & ~3))
 104 #define rb_color(r)   ((r)->rb_parent_color & 1)
 105 #define rb_is_red(r)   (!rb_color(r))
 106 #define rb_is_black(r) rb_color(r)
 107 #define rb_set_red(r)  do { (r)->rb_parent_color &= ~1; } while (0)
 108 #define rb_set_black(r)  do { (r)->rb_parent_color |= 1; } while (0)
 109
 110 static inline void rb_set_parent(struct rb_node *rb, struct rb_node *p)
 111 {
 112         rb->rb_parent_color = (rb->rb_parent_color & 3) | (unsigned long)p;
 113 }
 114 static inline void rb_set_color(struct rb_node *rb, int color)
 115 {
 116         rb->rb_parent_color = (rb->rb_parent_color & ~1) | color;
 117 }
 118
 119 #define RB_ROOT (struct rb_root) { NULL, }
 120 #define rb_entry(ptr, type, member) container_of(ptr, type, member)
 121
 122 #define RB_EMPTY_ROOT(root)     ((root)->rb_node == NULL)
 123 #define RB_EMPTY_NODE(node)     (rb_parent(node) == node)
 124 #define RB_CLEAR_NODE(node)     (rb_set_parent(node, node))
 125
 126 extern void rb_insert_color(struct rb_node *, struct rb_root *);
 127 extern void rb_erase(struct rb_node *, struct rb_root *);
 128
 129 /* Find logical next and previous nodes in a tree */
 130 extern struct rb_node *rb_next(struct rb_node *);
 131 extern struct rb_node *rb_prev(struct rb_node *);
 132 extern struct rb_node *rb_first(struct rb_root *);
 133 extern struct rb_node *rb_last(struct rb_root *);
 134
 135 /* Fast replacement of a single node without remove/rebalance/add/rebalance */
 136 extern void rb_replace_node(struct rb_node *victim, struct rb_node *new,
 137                             struct rb_root *root);
 138
 139 static inline void rb_link_node(struct rb_node * node, struct rb_node * parent,
 140                                 struct rb_node ** rb_link)
 141 {
 142         node->rb_parent_color = (unsigned long )parent;
 143         node->rb_left = node->rb_right = NULL;
 144
 145         *rb_link = node;
 146 }
 147
 148 #endif  /* _LINUX_RBTREE_H */