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