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/*
* rbtree.c
*
* Simple implementation of a left-leaning red-black tree with 64-bit
* integer keys. The search operation will return the highest node <=
* the key; only search and insert are supported, but additional
* standard llrbtree operations can be coded up at will.
*
* See http://www.cs.princeton.edu/~rs/talks/LLRB/RedBlack.pdf for
* information about left-leaning red-black trees.
*/
#include "rbtree.h"
struct rbtree *rb_search(struct rbtree *tree, uint64_t key)
{
struct rbtree *best = NULL;
while (tree) {
if (tree->key == key)
return tree;
else if (tree->key > key)
tree = tree->left;
else {
best = tree;
tree = tree->right;
}
}
return best;
}
static bool is_red(struct rbtree *h)
{
return h && h->red;
}
static struct rbtree *rotate_left(struct rbtree *h)
{
struct rbtree *x = h->right;
h->right = x->left;
x->left = h;
x->red = x->left->red;
x->left->red = true;
return x;
}
static struct rbtree *rotate_right(struct rbtree *h)
{
struct rbtree *x = h->left;
h->left = x->right;
x->right = h;
x->red = x->right->red;
x->right->red = true;
return x;
}
static void color_flip(struct rbtree *h)
{
h->red = !h->red;
h->left->red = !h->left->red;
h->right->red = !h->right->red;
}
struct rbtree *rb_insert(struct rbtree *tree, struct rbtree *node)
{
if (!tree) {
node->red = true;
return node;
}
if (is_red(tree->left) && is_red(tree->right))
color_flip(tree);
if (node->key < tree->key)
tree->left = rb_insert(tree->left, node);
else
tree->right = rb_insert(tree->right, node);
if (is_red(tree->right))
tree = rotate_left(tree);
if (is_red(tree->left) && is_red(tree->left->left))
tree = rotate_right(tree);
return tree;
}
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