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/*
* Copyright © 2017 Jason Ekstrand
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*/
#ifndef RB_TREE_H
#define RB_TREE_H
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
/** A red-black tree node
*
* This struct represents a node in the red-black tree. This struct should
* be embedded as a member in whatever structure you wish to put in the
* tree.
*/
struct rb_node {
/** Parent and color of this node
*
* The least significant bit represents the color and is est to 1 for
* black and 0 for red. The other bits are the pointer to the parent
* and that pointer can be retrieved by masking off the bottom bit and
* casting to a pointer.
*/
uintptr_t parent;
/** Left child of this node, null for a leaf */
struct rb_node *left;
/** Right child of this node, null for a leaf */
struct rb_node *right;
};
/** Return the parent node of the given node or NULL if it is the root */
static inline struct rb_node *
rb_node_parent(struct rb_node *n)
{
return (struct rb_node *)(n->parent & ~(uintptr_t)1);
}
/** A red-black tree
*
* This struct represents the red-black tree itself. It is just a pointer
* to the root node with no other metadata.
*/
struct rb_tree {
struct rb_node *root;
};
/** Initialize a red-black tree */
void rb_tree_init(struct rb_tree *T);
/** Returns true if the red-black tree is empty */
static inline bool
rb_tree_is_empty(const struct rb_tree *T)
{
return T->root == NULL;
}
/** Retrieve the data structure containing a node
*
* \param type The type of the containing data structure
*
* \param node A pointer to a rb_node
*
* \param field The rb_node field in the containing data structure
*/
#define rb_node_data(type, node, field) \
((type *)(((char *)(node)) - offsetof(type, field)))
/** Insert a node into a tree at a particular location
*
* This function should probably not be used directly as it relies on the
* caller to ensure that the parent node is correct. Use rb_tree_insert
* instead.
*
* \param T The red-black tree into which to insert the new node
*
* \param parent The node in the tree that will be the parent of the
* newly inserted node
*
* \param node The node to insert
*
* \param insert_left If true, the new node will be the left child of
* \p parent, otherwise it will be the right child
*/
void rb_tree_insert_at(struct rb_tree *T, struct rb_node *parent,
struct rb_node *node, bool insert_left);
/** Insert a node into a tree
*
* \param T The red-black tree into which to insert the new node
*
* \param node The node to insert
*
* \param cmp A comparison function to use to order the nodes.
*/
static inline void
rb_tree_insert(struct rb_tree *T, struct rb_node *node,
int (*cmp)(const struct rb_node *, const struct rb_node *))
{
/* This function is declared inline in the hopes that the compiler can
* optimize away the comparison function pointer call.
*/
struct rb_node *y = NULL;
struct rb_node *x = T->root;
bool left = false;
while (x != NULL) {
y = x;
left = cmp(node, x) < 0;
if (left)
x = x->left;
else
x = x->right;
}
rb_tree_insert_at(T, y, node, left);
}
/** Remove a node from a tree
*
* \param T The red-black tree from which to remove the node
*
* \param node The node to remove
*/
void rb_tree_remove(struct rb_tree *T, struct rb_node *z);
/** Search the tree for a node
*
* If a node with a matching key exists, the first matching node found will
* be returned. If no matching node exists, NULL is returned.
*
* \param T The red-black tree to search
*
* \param key The key to search for
*
* \param cmp A comparison function to use to order the nodes
*/
static inline struct rb_node *
rb_tree_search(struct rb_tree *T, const void *key,
int (*cmp)(const struct rb_node *, const void *))
{
/* This function is declared inline in the hopes that the compiler can
* optimize away the comparison function pointer call.
*/
struct rb_node *x = T->root;
while (x != NULL) {
int c = cmp(x, key);
if (c < 0)
x = x->right;
else if (c > 0)
x = x->left;
else
return x;
}
return x;
}
/** Sloppily search the tree for a node
*
* This function searches the tree for a given node. If a node with a
* matching key exists, that first matching node found will be returned.
* If no node with an exactly matching key exists, the node returned will
* be either the right-most node comparing less than \p key or the
* right-most node comparing greater than \p key. If the tree is empty,
* NULL is returned.
*
* \param T The red-black tree to search
*
* \param key The key to search for
*
* \param cmp A comparison function to use to order the nodes
*/
static inline struct rb_node *
rb_tree_search_sloppy(struct rb_tree *T, const void *key,
int (*cmp)(const struct rb_node *, const void *))
{
/* This function is declared inline in the hopes that the compiler can
* optimize away the comparison function pointer call.
*/
struct rb_node *y = NULL;
struct rb_node *x = T->root;
while (x != NULL) {
y = x;
int c = cmp(x, key);
if (c < 0)
x = x->right;
else if (c > 0)
x = x->left;
else
return x;
}
return y;
}
/** Get the first (left-most) node in the tree or NULL */
struct rb_node *rb_tree_first(struct rb_tree *T);
/** Get the last (right-most) node in the tree or NULL */
struct rb_node *rb_tree_last(struct rb_tree *T);
/** Get the next node (to the right) in the tree or NULL */
struct rb_node *rb_node_next(struct rb_node *node);
/** Get the next previous (to the left) in the tree or NULL */
struct rb_node *rb_node_prev(struct rb_node *node);
/** Iterate over the nodes in the tree
*
* \param type The type of the containing data structure
*
* \param node The variable name for current node in the iteration;
* this will be declared as a pointer to \p type
*
* \param T The red-black tree
*
* \param field The rb_node field in containing data structure
*/
#define rb_tree_foreach(type, node, T, field) \
for (type *node = rb_node_data(type, rb_tree_first(T), field); \
&node->field != NULL; \
node = rb_node_data(type, rb_node_next(&node->field), field))
/** Iterate over the nodes in the tree in reverse
*
* \param type The type of the containing data structure
*
* \param node The variable name for current node in the iteration;
* this will be declared as a pointer to \p type
*
* \param T The red-black tree
*
* \param field The rb_node field in containing data structure
*/
#define rb_tree_foreach_rev(type, node, T, field) \
for (type *node = rb_node_data(type, rb_tree_last(T), field); \
&node->field != NULL; \
node = rb_node_data(type, rb_node_prev(&node->field), field))
/** Validate a red-black tree
*
* This function walks the tree and validates that this is a valid red-
* black tree. If anything is wrong, it will assert-fail.
*/
void rb_tree_validate(struct rb_tree *T);
#endif /* RB_TREE_H */
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