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/*
* Copyright (c) 2010, 2011 Richard Braun.
*
* 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.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#ifndef _KERN_RBTREE_I_H
#define _KERN_RBTREE_I_H
#include <kern/assert.h>
/*
* Red-black node structure.
*
* To reduce the number of branches and the instruction cache footprint,
* the left and right child pointers are stored in an array, and the symmetry
* of most tree operations is exploited by using left/right variables when
* referring to children.
*
* In addition, this implementation assumes that all nodes are 4-byte aligned,
* so that the least significant bit of the parent member can be used to store
* the color of the node. This is true for all modern 32 and 64 bits
* architectures, as long as the nodes aren't embedded in structures with
* special alignment constraints such as member packing.
*/
struct rbtree_node {
unsigned long parent;
struct rbtree_node *children[2];
};
/*
* Red-black tree structure.
*/
struct rbtree {
struct rbtree_node *root;
};
/*
* Masks applied on the parent member of a node to obtain either the
* color or the parent address.
*/
#define RBTREE_COLOR_MASK 0x1UL
#define RBTREE_PARENT_MASK (~0x3UL)
/*
* Node colors.
*/
#define RBTREE_COLOR_RED 0
#define RBTREE_COLOR_BLACK 1
/*
* Masks applied on slots to obtain either the child index or the parent
* address.
*/
#define RBTREE_SLOT_INDEX_MASK 0x1UL
#define RBTREE_SLOT_PARENT_MASK (~RBTREE_SLOT_INDEX_MASK)
/*
* Return true if the given pointer is suitably aligned.
*/
static inline int rbtree_check_alignment(const struct rbtree_node *node)
{
return ((unsigned long)node & (~RBTREE_PARENT_MASK)) == 0;
}
/*
* Return true if the given index is a valid child index.
*/
static inline int rbtree_check_index(int index)
{
return index == (index & 1);
}
/*
* Convert the result of a comparison into an index in the children array
* (0 or 1).
*
* This function is mostly used when looking up a node.
*/
static inline int rbtree_d2i(int diff)
{
return !(diff <= 0);
}
/*
* Return the parent of a node.
*/
static inline struct rbtree_node * rbtree_parent(const struct rbtree_node *node)
{
return (struct rbtree_node *)(node->parent & RBTREE_PARENT_MASK);
}
/*
* Translate an insertion point into a slot.
*/
static inline unsigned long rbtree_slot(struct rbtree_node *parent, int index)
{
assert(rbtree_check_alignment(parent));
assert(rbtree_check_index(index));
return (unsigned long)parent | index;
}
/*
* Extract the parent address from a slot.
*/
static inline struct rbtree_node * rbtree_slot_parent(unsigned long slot)
{
return (struct rbtree_node *)(slot & RBTREE_SLOT_PARENT_MASK);
}
/*
* Extract the index from a slot.
*/
static inline int rbtree_slot_index(unsigned long slot)
{
return slot & RBTREE_SLOT_INDEX_MASK;
}
/*
* Insert a node in a tree, rebalancing it if necessary.
*
* The index parameter is the index in the children array of the parent where
* the new node is to be inserted. It is ignored if the parent is null.
*
* This function is intended to be used by the rbtree_insert() macro only.
*/
void rbtree_insert_rebalance(struct rbtree *tree, struct rbtree_node *parent,
int index, struct rbtree_node *node);
/*
* Return the previous or next node relative to a location in a tree.
*
* The parent and index parameters define the location, which can be empty.
* The direction parameter is either RBTREE_LEFT (to obtain the previous
* node) or RBTREE_RIGHT (to obtain the next one).
*/
struct rbtree_node * rbtree_nearest(struct rbtree_node *parent, int index,
int direction);
/*
* Return the first or last node of a tree.
*
* The direction parameter is either RBTREE_LEFT (to obtain the first node)
* or RBTREE_RIGHT (to obtain the last one).
*/
struct rbtree_node * rbtree_firstlast(const struct rbtree *tree, int direction);
/*
* Return the node next to, or previous to the given node.
*
* The direction parameter is either RBTREE_LEFT (to obtain the previous node)
* or RBTREE_RIGHT (to obtain the next one).
*/
struct rbtree_node * rbtree_walk(struct rbtree_node *node, int direction);
/*
* Return the left-most deepest node of a tree, which is the starting point of
* the postorder traversal performed by rbtree_for_each_remove().
*/
struct rbtree_node * rbtree_postwalk_deepest(const struct rbtree *tree);
/*
* Unlink a node from its tree and return the next (right) node in postorder.
*/
struct rbtree_node * rbtree_postwalk_unlink(struct rbtree_node *node);
#endif /* _KERN_RBTREE_I_H */
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