rbtree.h

   1 /*
   2   SPDX-License-Identifier: GPL-2.0-or-later
   3
   4   Red Black Trees
   5   (C) 1999  Andrea Arcangeli <andrea@suse.de>
   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 <stddef.h>
  86
  87 /**
  88  * container_of - cast a member of a structure out to the containing structure
  89  * @ptr:        the pointer to the member.
  90  * @type:       the type of the container struct this is embedded in.
  91  * @member:     the name of the member within the struct.
  92  *
  93  */
  94 #define container_of(ptr, type, member) ({                      \
  95         const typeof( ((type *)0)->member ) *__mptr = (ptr);    \
  96         (type *)( (char *)__mptr - offsetof(type,member) );})
  97
  98 struct rb_node
  99 {
 100         unsigned long  rb_parent_color;
 101 #define RB_RED          0
 102 #define RB_BLACK        1
 103         struct rb_node *rb_right;
 104         struct rb_node *rb_left;
 105 } __attribute__((aligned(sizeof(long))));
 106     /* The alignment might seem pointless, but allegedly CRIS needs it */
 107
 108 struct rb_root
 109 {
 110         struct rb_node *rb_node;
 111 };
 112
 113
 114 #define rb_parent(r)   ((struct rb_node *)((r)->rb_parent_color & ~3))
 115 #define rb_color(r)   ((r)->rb_parent_color & 1)
 116 #define rb_is_red(r)   (!rb_color(r))
 117 #define rb_is_black(r) rb_color(r)
 118 #define rb_set_red(r)  do { (r)->rb_parent_color &= ~1; } while (0)
 119 #define rb_set_black(r)  do { (r)->rb_parent_color |= 1; } while (0)
 120
 121 static inline void rb_set_parent(struct rb_node *rb, struct rb_node *p)
 122 {
 123         rb->rb_parent_color = (rb->rb_parent_color & 3) | (unsigned long)p;
 124 }
 125 static inline void rb_set_color(struct rb_node *rb, int color)
 126 {
 127         rb->rb_parent_color = (rb->rb_parent_color & ~1) | color;
 128 }
 129
 130 #define RB_ROOT (struct rb_root) { NULL, }
 131 #define rb_entry(ptr, type, member) container_of(ptr, type, member)
 132
 133 #define RB_EMPTY_ROOT(root)     ((root)->rb_node == NULL)
 134 #define RB_EMPTY_NODE(node)     (rb_parent(node) == node)
 135 #define RB_CLEAR_NODE(node)     (rb_set_parent(node, node))
 136
 137 extern void rb_insert_color(struct rb_node *, struct rb_root *);
 138 extern void rb_erase(struct rb_node *, struct rb_root *);
 139
 140 /* Find logical next and previous nodes in a tree */
 141 extern struct rb_node *rb_next(const struct rb_node *);
 142 extern struct rb_node *rb_prev(const struct rb_node *);
 143 extern struct rb_node *rb_first(const struct rb_root *);
 144 extern struct rb_node *rb_last(const struct rb_root *);
 145
 146 /* Fast replacement of a single node without remove/rebalance/add/rebalance */
 147 extern void rb_replace_node(struct rb_node *victim, struct rb_node *new,
 148                             struct rb_root *root);
 149
 150 static inline void rb_link_node(struct rb_node * node, struct rb_node * parent,
 151                                 struct rb_node ** rb_link)
 152 {
 153         node->rb_parent_color = (unsigned long )parent;
 154         node->rb_left = node->rb_right = NULL;
 155
 156         *rb_link = node;
 157 }
 158
 159 #endif  /* _LINUX_RBTREE_H */