364 lines
6.8 KiB
C
364 lines
6.8 KiB
C
/* rbtree.c - red black tree implementation
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*
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* Copyright (C) 2010 Henrik Hautakoski <henrik@fiktivkod.org>
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* Based on the work of Julienne Walker's rbtree implementation
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* http://www.eternallyconfuzzled.com/tuts/datastructures/jsw_tut_rbtree.aspx
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*/
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#include <stdlib.h>
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#include <string.h>
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#ifdef __DEBUG__
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#include <assert.h>
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#include <stdio.h>
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#endif
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#include "xalloc.h"
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#include "rbtree.h"
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#define RB_RED 0
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#define RB_BLACK 1
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/* node definition */
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typedef struct _rbn {
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const void *key;
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struct _rbn *child[2];
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unsigned char color;
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} rbnode;
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#define is_red(n) ((n) != NULL && (n)->color == RB_RED)
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#define swap(n,d,q) ((n)->child[(n)->child[d] == (q)])
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static rbnode* node_alloc(const void *key) {
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rbnode *n = xmalloc(sizeof(rbnode));
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n->key = key;
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n->color = RB_RED;
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n->child[0] = NULL;
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n->child[1] = NULL;
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return n;
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}
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/*
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* Recursivly deallocate a tree.
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*/
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static void node_dealloc(rbnode *n, void (*dealloc)(void *)) {
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if (!n)
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return;
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if (dealloc)
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dealloc((void *)n->key);
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node_dealloc(n->child[0], dealloc);
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node_dealloc(n->child[1], dealloc);
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free(n);
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}
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#ifdef __DEBUG__
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#define rb_err(msg) fputs("rbtree error: " msg, stderr)
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static int rb_assert_r(rbnode *node, int (*cmp)(const void *, const void *)) {
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int rh, lh;
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rbnode *ln, *rn;
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if (node == NULL)
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return 1;
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ln = node->child[0];
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rn = node->child[1];
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if (is_red(node)) {
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/* double red violation */
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if (is_red(ln) || is_red(rn)) {
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rb_err("Double red violation");
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return 0;
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}
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}
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lh = rb_assert_r(ln, cmp);
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rh = rb_assert_r(rn, cmp);
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if ( (ln && cmp(ln->key, node->key) >= 0) &&
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(rn && cmp(rn->key, node->key) <= 0) ) {
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rb_err("Binary tree violation");
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return 0;
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}
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if (rh != 0 && lh != 0) {
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if (rh != lh) {
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rb_err("Black height violation");
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return 0;
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}
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return is_red(node) ? lh : lh+1;
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}
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return 0;
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}
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#undef rb_err
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static void rb_assert(rbtree *tree) {
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if (!tree || !tree->cmp_fn)
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return;
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assert(rb_assert_r(tree->root, tree->cmp_fn));
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}
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#endif /* __DEBUG__ */
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/*
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* Recursivly walks a tree, applying action function on every node
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*/
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static void rbwalk(rbnode *n, void (*action)(const void *)) {
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if (!n)
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return;
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rbwalk(n->child[0], action);
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action(n->key);
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rbwalk(n->child[1], action);
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}
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static rbnode* rotate_single(rbnode *root, int dir) {
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rbnode *save = root->child[!dir];
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root->child[!dir] = save->child[dir];
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save->child[dir] = root;
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root->color = RB_RED;
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save->color = RB_BLACK;
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return save;
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}
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static rbnode* rotate_double(rbnode *root, int dir) {
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root->child[!dir] = rotate_single(root->child[!dir], !dir);
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return rotate_single(root, dir);
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}
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int rbtree_is_empty(rbtree *tree) {
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return tree == NULL || tree->root == NULL;
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}
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/*
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* Searches a tree by key.
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*/
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void* rbtree_search(rbtree *tree, const void *key) {
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rbnode *n;
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if (!tree || !tree->cmp_fn)
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return NULL;
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n = tree->root;
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while(n) {
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int cmp = tree->cmp_fn(n->key, key);
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if (cmp == 0)
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return (void *) n->key;
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n = n->child[cmp < 0];
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}
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return NULL;
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}
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void rbtree_walk(rbtree *tree, void (*action)(const void *)) {
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if (!tree || !action)
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return;
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rbwalk(tree->root, action);
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#ifdef __DEBUG__
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rb_assert(tree);
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#endif
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}
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void rbtree_free(rbtree *tree) {
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if (!tree)
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return;
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node_dealloc(tree->root, tree->delete_fn);
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tree->root = NULL;
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#ifdef __DEBUG__
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rb_assert(tree);
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#endif
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}
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int rbtree_insert(rbtree *tree, const void *key) {
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rbnode head = {0};
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/* grandparent and parent */
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rbnode *g, *t;
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/* iterator and parent */
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rbnode *p, *q;
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int dir = 0, last;
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if (!tree || !tree->cmp_fn)
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return 0;
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if (!tree->root) {
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tree->root = node_alloc(key);
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goto done;
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}
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t = &head;
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g = p = NULL;
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q = t->child[1] = tree->root;
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/* somewhere in here, there should be dragons */
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for(;;) {
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int cmp;
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if (q == NULL) {
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p->child[dir] = q = node_alloc(key);
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} else if (is_red(q->child[0]) && is_red(q->child[1])) {
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/* color flip case */
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q->color = RB_RED;
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q->child[0]->color = RB_BLACK;
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q->child[1]->color = RB_BLACK;
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}
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/* fix red validation */
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if (is_red(q) && is_red(p)) {
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int dir2 = (t->child[1] == g);
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if (q == p->child[last])
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t->child[dir2] = rotate_single(g, !last);
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else
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t->child[dir2] = rotate_double(g, !last);
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}
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cmp = tree->cmp_fn(q->key, key);
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if (cmp == 0)
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break;
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last = dir;
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dir = cmp < 0;
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if (g)
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t = g;
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g = p, p = q;
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q = q->child[dir];
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}
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if (q->key != key) {
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if (tree->delete_fn)
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tree->delete_fn((void*)q->key);
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q->key = key;
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}
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tree->root = head.child[1];
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done:
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/* root should be black */
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tree->root->color = RB_BLACK;
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#ifdef __DEBUG__
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rb_assert(tree);
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#endif
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return 1;
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}
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int rbtree_delete(rbtree *tree, const void *key) {
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rbnode head = {0};
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/* helpers*/
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rbnode *q, *p, *g, *s;
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/* found item */
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rbnode *f = NULL;
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int dir = 1, dir2, last;
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if (rbtree_is_empty(tree) || !tree->cmp_fn)
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return 0;
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q = &head;
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g = p = NULL;
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q->child[1] = tree->root;
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/* more dragons (killed some of them though) */
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while(q->child[dir]) {
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int cmp;
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g = p, p = q;
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q = q->child[dir];
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last = dir;
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cmp = tree->cmp_fn(q->key, key);
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dir = cmp < 0;
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if (cmp == 0)
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f = q;
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if (is_red(q) || is_red(q->child[dir]))
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continue;
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if (is_red(q->child[!dir])) {
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p = p->child[last] = rotate_single(q, dir);
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} else {
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s = p->child[!last];
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if (s == NULL)
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continue;
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if (!is_red(s->child[!last]) && !is_red(s->child[last])) {
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p->color = RB_BLACK;
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s->color = q->color = RB_RED;
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} else {
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dir2 = (g->child[1] == p);
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if (is_red(s->child[last]))
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g->child[dir2] = rotate_double(p, last);
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else if (is_red(s->child[!last]))
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g->child[dir2] = rotate_single(p, last);
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q->color = g->child[dir2]->color = RB_RED;
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g->child[dir2]->child[0]->color = RB_BLACK;
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g->child[dir2]->child[1]->color = RB_BLACK;
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}
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}
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}
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/* remove if found */
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if (f) {
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if (tree->delete_fn)
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tree->delete_fn((void*)f->key);
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if (f != q)
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f->key = q->key;
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swap(p, 1, q) = swap(q, 0, NULL);
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xfree(q);
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}
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tree->root = head.child[1];
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if (tree->root)
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tree->root->color = RB_BLACK;
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#ifdef __DEBUG__
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rb_assert(tree);
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#endif
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return f != NULL;
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}
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