2 * rbtree.c -- generic red black tree
4 * Taken from Unbound, modified for ldns
6 * Copyright (c) 2001-2008, NLnet Labs. All rights reserved.
8 * This software is open source.
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
14 * Redistributions of source code must retain the above copyright notice,
15 * this list of conditions and the following disclaimer.
17 * Redistributions in binary form must reproduce the above copyright notice,
18 * this list of conditions and the following disclaimer in the documentation
19 * and/or other materials provided with the distribution.
21 * Neither the name of the NLNET LABS nor the names of its contributors may
22 * be used to endorse or promote products derived from this software without
23 * specific prior written permission.
25 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
26 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
27 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
28 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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31 * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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35 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
41 * Implementation of a redblack tree.
44 #include <ldns/config.h>
45 #include <ldns/rbtree.h>
46 #include <ldns/util.h>
49 /** Node colour black */
51 /** Node colour red */
54 /** the NULL node, global alloc */
55 ldns_rbnode_t ldns_rbtree_null_node = {
56 LDNS_RBTREE_NULL, /* Parent. */
57 LDNS_RBTREE_NULL, /* Left. */
58 LDNS_RBTREE_NULL, /* Right. */
64 /** rotate subtree left (to preserve redblack property) */
65 static void ldns_rbtree_rotate_left(ldns_rbtree_t *rbtree, ldns_rbnode_t *node);
66 /** rotate subtree right (to preserve redblack property) */
67 static void ldns_rbtree_rotate_right(ldns_rbtree_t *rbtree, ldns_rbnode_t *node);
68 /** Fixup node colours when insert happened */
69 static void ldns_rbtree_insert_fixup(ldns_rbtree_t *rbtree, ldns_rbnode_t *node);
70 /** Fixup node colours when delete happened */
71 static void ldns_rbtree_delete_fixup(ldns_rbtree_t* rbtree, ldns_rbnode_t* child, ldns_rbnode_t* child_parent);
74 * Creates a new red black tree, intializes and returns a pointer to it.
76 * Return NULL on failure.
80 ldns_rbtree_create (int (*cmpf)(const void *, const void *))
82 ldns_rbtree_t *rbtree;
84 /* Allocate memory for it */
85 rbtree = (ldns_rbtree_t *) LDNS_MALLOC(ldns_rbtree_t);
91 ldns_rbtree_init(rbtree, cmpf);
97 ldns_rbtree_init(ldns_rbtree_t *rbtree, int (*cmpf)(const void *, const void *))
100 rbtree->root = LDNS_RBTREE_NULL;
106 ldns_rbtree_free(ldns_rbtree_t *rbtree)
112 * Rotates the node to the left.
116 ldns_rbtree_rotate_left(ldns_rbtree_t *rbtree, ldns_rbnode_t *node)
118 ldns_rbnode_t *right = node->right;
119 node->right = right->left;
120 if (right->left != LDNS_RBTREE_NULL)
121 right->left->parent = node;
123 right->parent = node->parent;
125 if (node->parent != LDNS_RBTREE_NULL) {
126 if (node == node->parent->left) {
127 node->parent->left = right;
129 node->parent->right = right;
132 rbtree->root = right;
135 node->parent = right;
139 * Rotates the node to the right.
143 ldns_rbtree_rotate_right(ldns_rbtree_t *rbtree, ldns_rbnode_t *node)
145 ldns_rbnode_t *left = node->left;
146 node->left = left->right;
147 if (left->right != LDNS_RBTREE_NULL)
148 left->right->parent = node;
150 left->parent = node->parent;
152 if (node->parent != LDNS_RBTREE_NULL) {
153 if (node == node->parent->right) {
154 node->parent->right = left;
156 node->parent->left = left;
166 ldns_rbtree_insert_fixup(ldns_rbtree_t *rbtree, ldns_rbnode_t *node)
168 ldns_rbnode_t *uncle;
170 /* While not at the root and need fixing... */
171 while (node != rbtree->root && node->parent->color == RED) {
172 /* If our parent is left child of our grandparent... */
173 if (node->parent == node->parent->parent->left) {
174 uncle = node->parent->parent->right;
176 /* If our uncle is red... */
177 if (uncle->color == RED) {
178 /* Paint the parent and the uncle black... */
179 node->parent->color = BLACK;
180 uncle->color = BLACK;
182 /* And the grandparent red... */
183 node->parent->parent->color = RED;
185 /* And continue fixing the grandparent */
186 node = node->parent->parent;
187 } else { /* Our uncle is black... */
188 /* Are we the right child? */
189 if (node == node->parent->right) {
191 ldns_rbtree_rotate_left(rbtree, node);
193 /* Now we're the left child, repaint and rotate... */
194 node->parent->color = BLACK;
195 node->parent->parent->color = RED;
196 ldns_rbtree_rotate_right(rbtree, node->parent->parent);
199 uncle = node->parent->parent->left;
201 /* If our uncle is red... */
202 if (uncle->color == RED) {
203 /* Paint the parent and the uncle black... */
204 node->parent->color = BLACK;
205 uncle->color = BLACK;
207 /* And the grandparent red... */
208 node->parent->parent->color = RED;
210 /* And continue fixing the grandparent */
211 node = node->parent->parent;
212 } else { /* Our uncle is black... */
213 /* Are we the right child? */
214 if (node == node->parent->left) {
216 ldns_rbtree_rotate_right(rbtree, node);
218 /* Now we're the right child, repaint and rotate... */
219 node->parent->color = BLACK;
220 node->parent->parent->color = RED;
221 ldns_rbtree_rotate_left(rbtree, node->parent->parent);
225 rbtree->root->color = BLACK;
229 ldns_rbtree_insert_vref(ldns_rbnode_t *data, void *rbtree)
231 (void) ldns_rbtree_insert((ldns_rbtree_t *) rbtree,
236 * Inserts a node into a red black tree.
238 * Returns NULL on failure or the pointer to the newly added node
242 ldns_rbtree_insert (ldns_rbtree_t *rbtree, ldns_rbnode_t *data)
244 /* XXX Not necessary, but keeps compiler quiet... */
247 /* We start at the root of the tree */
248 ldns_rbnode_t *node = rbtree->root;
249 ldns_rbnode_t *parent = LDNS_RBTREE_NULL;
251 /* Lets find the new parent... */
252 while (node != LDNS_RBTREE_NULL) {
253 /* Compare two keys, do we have a duplicate? */
254 if ((r = rbtree->cmp(data->key, node->key)) == 0) {
266 /* Initialize the new node */
267 data->parent = parent;
268 data->left = data->right = LDNS_RBTREE_NULL;
272 /* Insert it into the tree... */
273 if (parent != LDNS_RBTREE_NULL) {
277 parent->right = data;
283 /* Fix up the red-black properties... */
284 ldns_rbtree_insert_fixup(rbtree, data);
290 * Searches the red black tree, returns the data if key is found or NULL otherwise.
294 ldns_rbtree_search (ldns_rbtree_t *rbtree, const void *key)
298 if (ldns_rbtree_find_less_equal(rbtree, key, &node)) {
305 /** helpers for delete: swap node colours */
306 static void swap_int8(uint8_t* x, uint8_t* y)
308 uint8_t t = *x; *x = *y; *y = t;
311 /** helpers for delete: swap node pointers */
312 static void swap_np(ldns_rbnode_t** x, ldns_rbnode_t** y)
314 ldns_rbnode_t* t = *x; *x = *y; *y = t;
317 /** Update parent pointers of child trees of 'parent' */
318 static void change_parent_ptr(ldns_rbtree_t* rbtree, ldns_rbnode_t* parent, ldns_rbnode_t* old, ldns_rbnode_t* new)
320 if(parent == LDNS_RBTREE_NULL)
322 if(rbtree->root == old) rbtree->root = new;
325 if(parent->left == old) parent->left = new;
326 if(parent->right == old) parent->right = new;
328 /** Update parent pointer of a node 'child' */
329 static void change_child_ptr(ldns_rbnode_t* child, ldns_rbnode_t* old, ldns_rbnode_t* new)
331 if(child == LDNS_RBTREE_NULL) return;
332 if(child->parent == old) child->parent = new;
336 ldns_rbtree_delete(ldns_rbtree_t *rbtree, const void *key)
338 ldns_rbnode_t *to_delete;
339 ldns_rbnode_t *child;
340 if((to_delete = ldns_rbtree_search(rbtree, key)) == 0) return 0;
343 /* make sure we have at most one non-leaf child */
344 if(to_delete->left != LDNS_RBTREE_NULL &&
345 to_delete->right != LDNS_RBTREE_NULL)
347 /* swap with smallest from right subtree (or largest from left) */
348 ldns_rbnode_t *smright = to_delete->right;
349 while(smright->left != LDNS_RBTREE_NULL)
350 smright = smright->left;
351 /* swap the smright and to_delete elements in the tree,
352 * but the ldns_rbnode_t is first part of user data struct
353 * so cannot just swap the keys and data pointers. Instead
354 * readjust the pointers left,right,parent */
356 /* swap colors - colors are tied to the position in the tree */
357 swap_int8(&to_delete->color, &smright->color);
359 /* swap child pointers in parents of smright/to_delete */
360 change_parent_ptr(rbtree, to_delete->parent, to_delete, smright);
361 if(to_delete->right != smright)
362 change_parent_ptr(rbtree, smright->parent, smright, to_delete);
364 /* swap parent pointers in children of smright/to_delete */
365 change_child_ptr(smright->left, smright, to_delete);
366 change_child_ptr(smright->left, smright, to_delete);
367 change_child_ptr(smright->right, smright, to_delete);
368 change_child_ptr(smright->right, smright, to_delete);
369 change_child_ptr(to_delete->left, to_delete, smright);
370 if(to_delete->right != smright)
371 change_child_ptr(to_delete->right, to_delete, smright);
372 if(to_delete->right == smright)
374 /* set up so after swap they work */
375 to_delete->right = to_delete;
376 smright->parent = smright;
379 /* swap pointers in to_delete/smright nodes */
380 swap_np(&to_delete->parent, &smright->parent);
381 swap_np(&to_delete->left, &smright->left);
382 swap_np(&to_delete->right, &smright->right);
384 /* now delete to_delete (which is at the location where the smright previously was) */
387 if(to_delete->left != LDNS_RBTREE_NULL) child = to_delete->left;
388 else child = to_delete->right;
390 /* unlink to_delete from the tree, replace to_delete with child */
391 change_parent_ptr(rbtree, to_delete->parent, to_delete, child);
392 change_child_ptr(child, to_delete, to_delete->parent);
394 if(to_delete->color == RED)
396 /* if node is red then the child (black) can be swapped in */
398 else if(child->color == RED)
400 /* change child to BLACK, removing a RED node is no problem */
401 if(child!=LDNS_RBTREE_NULL) child->color = BLACK;
403 else ldns_rbtree_delete_fixup(rbtree, child, to_delete->parent);
405 /* unlink completely */
406 to_delete->parent = LDNS_RBTREE_NULL;
407 to_delete->left = LDNS_RBTREE_NULL;
408 to_delete->right = LDNS_RBTREE_NULL;
409 to_delete->color = BLACK;
413 static void ldns_rbtree_delete_fixup(ldns_rbtree_t* rbtree, ldns_rbnode_t* child, ldns_rbnode_t* child_parent)
415 ldns_rbnode_t* sibling;
418 /* determine sibling to the node that is one-black short */
419 if(child_parent->right == child) sibling = child_parent->left;
420 else sibling = child_parent->right;
424 if(child_parent == LDNS_RBTREE_NULL)
426 /* removed parent==black from root, every path, so ok */
430 if(sibling->color == RED)
431 { /* rotate to get a black sibling */
432 child_parent->color = RED;
433 sibling->color = BLACK;
434 if(child_parent->right == child)
435 ldns_rbtree_rotate_right(rbtree, child_parent);
436 else ldns_rbtree_rotate_left(rbtree, child_parent);
437 /* new sibling after rotation */
438 if(child_parent->right == child) sibling = child_parent->left;
439 else sibling = child_parent->right;
442 if(child_parent->color == BLACK
443 && sibling->color == BLACK
444 && sibling->left->color == BLACK
445 && sibling->right->color == BLACK)
446 { /* fixup local with recolor of sibling */
447 if(sibling != LDNS_RBTREE_NULL)
448 sibling->color = RED;
450 child = child_parent;
451 child_parent = child_parent->parent;
452 /* prepare to go up, new sibling */
453 if(child_parent->right == child) sibling = child_parent->left;
454 else sibling = child_parent->right;
459 if(child_parent->color == RED
460 && sibling->color == BLACK
461 && sibling->left->color == BLACK
462 && sibling->right->color == BLACK)
464 /* move red to sibling to rebalance */
465 if(sibling != LDNS_RBTREE_NULL)
466 sibling->color = RED;
467 child_parent->color = BLACK;
471 /* get a new sibling, by rotating at sibling. See which child
473 if(child_parent->right == child
474 && sibling->color == BLACK
475 && sibling->right->color == RED
476 && sibling->left->color == BLACK)
478 sibling->color = RED;
479 sibling->right->color = BLACK;
480 ldns_rbtree_rotate_left(rbtree, sibling);
481 /* new sibling after rotation */
482 if(child_parent->right == child) sibling = child_parent->left;
483 else sibling = child_parent->right;
485 else if(child_parent->left == child
486 && sibling->color == BLACK
487 && sibling->left->color == RED
488 && sibling->right->color == BLACK)
490 sibling->color = RED;
491 sibling->left->color = BLACK;
492 ldns_rbtree_rotate_right(rbtree, sibling);
493 /* new sibling after rotation */
494 if(child_parent->right == child) sibling = child_parent->left;
495 else sibling = child_parent->right;
498 /* now we have a black sibling with a red child. rotate and exchange colors. */
499 sibling->color = child_parent->color;
500 child_parent->color = BLACK;
501 if(child_parent->right == child)
503 sibling->left->color = BLACK;
504 ldns_rbtree_rotate_right(rbtree, child_parent);
508 sibling->right->color = BLACK;
509 ldns_rbtree_rotate_left(rbtree, child_parent);
514 ldns_rbtree_find_less_equal(ldns_rbtree_t *rbtree, const void *key, ldns_rbnode_t **result)
519 /* We start at root... */
524 /* While there are children... */
525 while (node != LDNS_RBTREE_NULL) {
526 r = rbtree->cmp(key, node->key);
535 /* Temporary match */
544 * Finds the first element in the red black tree
548 ldns_rbtree_first(const ldns_rbtree_t *rbtree)
550 ldns_rbnode_t *node = rbtree->root;
552 if (rbtree->root != LDNS_RBTREE_NULL) {
553 for (node = rbtree->root; node->left != LDNS_RBTREE_NULL; node = node->left);
559 ldns_rbtree_last(const ldns_rbtree_t *rbtree)
561 ldns_rbnode_t *node = rbtree->root;
563 if (rbtree->root != LDNS_RBTREE_NULL) {
564 for (node = rbtree->root; node->right != LDNS_RBTREE_NULL; node = node->right);
570 * Returns the next node...
574 ldns_rbtree_next(ldns_rbnode_t *node)
576 ldns_rbnode_t *parent;
578 if (node->right != LDNS_RBTREE_NULL) {
579 /* One right, then keep on going left... */
580 for (node = node->right;
581 node->left != LDNS_RBTREE_NULL;
584 parent = node->parent;
585 while (parent != LDNS_RBTREE_NULL && node == parent->right) {
587 parent = parent->parent;
595 ldns_rbtree_previous(ldns_rbnode_t *node)
597 ldns_rbnode_t *parent;
599 if (node->left != LDNS_RBTREE_NULL) {
600 /* One left, then keep on going right... */
601 for (node = node->left;
602 node->right != LDNS_RBTREE_NULL;
605 parent = node->parent;
606 while (parent != LDNS_RBTREE_NULL && node == parent->left) {
608 parent = parent->parent;
616 * split off elements number of elements from the start
617 * of the name tree and return a new tree
620 ldns_rbtree_split(ldns_rbtree_t *tree,
623 ldns_rbtree_t *new_tree;
624 ldns_rbnode_t *cur_node;
625 ldns_rbnode_t *move_node;
628 new_tree = ldns_rbtree_create(tree->cmp);
630 cur_node = ldns_rbtree_first(tree);
631 while (count < elements && cur_node != LDNS_RBTREE_NULL) {
632 move_node = ldns_rbtree_delete(tree, cur_node->key);
633 (void)ldns_rbtree_insert(new_tree, move_node);
634 cur_node = ldns_rbtree_first(tree);
642 * add all node from the second tree to the first (removing them from the
643 * second), and fix up nsec(3)s if present
646 ldns_rbtree_join(ldns_rbtree_t *tree1, ldns_rbtree_t *tree2)
648 ldns_traverse_postorder(tree2, ldns_rbtree_insert_vref, tree1);
651 /** recursive descent traverse */
653 traverse_post(void (*func)(ldns_rbnode_t*, void*), void* arg,
656 if(!node || node == LDNS_RBTREE_NULL)
659 traverse_post(func, arg, node->left);
660 traverse_post(func, arg, node->right);
666 ldns_traverse_postorder(ldns_rbtree_t* tree,
667 void (*func)(ldns_rbnode_t*, void*), void* arg)
669 traverse_post(func, arg, tree->root);