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Red Black Trees
(C) 1999 Andrea Arcangeli <>
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
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
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...
Some example of insert and search follows here. The search is a plain
normal search over an ordered tree. The insert instead must be implemented
in two steps: First, the code must insert the element in order as a red leaf
in the tree, and then the support library function rb_insert_color() must
be called. Such function will do the not trivial work to rebalance the
rbtree, if necessary.
static inline struct page * rb_search_page_cache(struct inode * inode,
unsigned long offset)
struct rb_node * n = inode->i_rb_page_cache.rb_node;
struct page * page;
while (n)
page = rb_entry(n, struct page, rb_page_cache);
if (offset < page->offset)
n = n->rb_left;
else if (offset > page->offset)
n = n->rb_right;
return page;
return NULL;
static inline struct page * __rb_insert_page_cache(struct inode * inode,
unsigned long offset,
struct rb_node * node)
struct rb_node ** p = &inode->i_rb_page_cache.rb_node;
struct rb_node * parent = NULL;
struct page * page;
while (*p)
parent = *p;
page = rb_entry(parent, struct page, rb_page_cache);
if (offset < page->offset)
p = &(*p)->rb_left;
else if (offset > page->offset)
p = &(*p)->rb_right;
return page;
rb_link_node(node, parent, p);
return NULL;
static inline struct page * rb_insert_page_cache(struct inode * inode,
unsigned long offset,
struct rb_node * node)
struct page * ret;
if ((ret = __rb_insert_page_cache(inode, offset, node)))
goto out;
rb_insert_color(node, &inode->i_rb_page_cache);
return ret;
#include <stdlib.h>
#undef offsetof
#ifdef __compiler_offsetof
#define offsetof(TYPE,MEMBER) __compiler_offsetof(TYPE,MEMBER)
#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
#define container_of(ptr, type, member) ({ \
const __typeof__( ((type *)0)->member ) *__mptr = (ptr); \
(type *)( (char *)__mptr - offsetof(type,member) );})
struct rb_node
unsigned long rb_parent_color;
#define RB_RED 0
#define RB_BLACK 1
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 ext2fs_rb_parent(r) ((struct rb_node *)((r)->rb_parent_color & ~3))
#define ext2fs_rb_color(r) ((r)->rb_parent_color & 1)
#define ext2fs_rb_is_red(r) (!ext2fs_rb_color(r))
#define ext2fs_rb_is_black(r) ext2fs_rb_color(r)
#define ext2fs_rb_set_red(r) do { (r)->rb_parent_color &= ~1; } while (0)
#define ext2fs_rb_set_black(r) do { (r)->rb_parent_color |= 1; } while (0)
static inline void ext2fs_rb_set_parent(struct rb_node *rb, struct rb_node *p)
rb->rb_parent_color = (rb->rb_parent_color & 3) | (unsigned long)p;
static inline void ext2fs_rb_set_color(struct rb_node *rb, int color)
rb->rb_parent_color = (rb->rb_parent_color & ~1) | color;
#define RB_ROOT (struct rb_root) { NULL, }
#define ext2fs_rb_entry(ptr, type, member) container_of(ptr, type, member)
#define EXT2FS_RB_EMPTY_ROOT(root) ((root)->rb_node == NULL)
#define EXT2FS_RB_EMPTY_NODE(node) (ext2fs_rb_parent(node) == node)
#define EXT2FS_RB_CLEAR_NODE(node) (ext2fs_rb_set_parent(node, node))
extern void ext2fs_rb_insert_color(struct rb_node *, struct rb_root *);
extern void ext2fs_rb_erase(struct rb_node *, struct rb_root *);
typedef void (*rb_augment_f)(struct rb_node *node, void *data);
extern void ext2fs_rb_augment_insert(struct rb_node *node,
rb_augment_f func, void *data);
extern struct rb_node *ext2fs_rb_augment_erase_begin(struct rb_node *node);
extern void ext2fs_rb_augment_erase_end(struct rb_node *node,
rb_augment_f func, void *data);
/* Find logical next and previous nodes in a tree */
extern struct rb_node *ext2fs_rb_next(struct rb_node *);
extern struct rb_node *ext2fs_rb_prev(struct rb_node *);
extern struct rb_node *ext2fs_rb_first(const struct rb_root *);
extern struct rb_node *ext2fs_rb_last(const struct rb_root *);
/* Fast replacement of a single node without remove/rebalance/add/rebalance */
extern void ext2fs_rb_replace_node(struct rb_node *victim, struct rb_node *new,
struct rb_root *root);
static inline void ext2fs_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;
#endif /* _LINUX_RBTREE_H */