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view src/rbtree.c @ 73:b4b7198986a6

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fixed a potential null dereference when deleting a bug in the redblack tree
author John Tsiombikas <nuclear@member.fsf.org>
date Sat, 15 Oct 2011 08:06:10 +0300
parents b45e2d5f0ae1
children
line source
1 #include <stdio.h>
2 #include <stdlib.h>
3 #include <string.h>
4 #include "rbtree.h"
5 #include "panic.h"
6
7 #define INT2PTR(x) ((void*)(x))
8 #define PTR2INT(x) ((int)(x))
9
10 static int cmpaddr(void *ap, void *bp);
11 static int cmpint(void *ap, void *bp);
12
13 static int count_nodes(struct rbnode *node);
14 static void del_tree(struct rbnode *node, void (*delfunc)(struct rbnode*, void*), void *cls);
15 static struct rbnode *insert(struct rbtree *rb, struct rbnode *tree, void *key, void *data);
16 static struct rbnode *delete(struct rbtree *rb, struct rbnode *tree, void *key);
17 static void traverse(struct rbnode *node, void (*func)(struct rbnode*, void*), void *cls);
18
19 struct rbtree *rb_create(rb_cmp_func_t cmp_func)
20 {
21 struct rbtree *rb;
22
23 if(!(rb = malloc(sizeof *rb))) {
24 return 0;
25 }
26 if(rb_init(rb, cmp_func) == -1) {
27 free(rb);
28 return 0;
29 }
30 return rb;
31 }
32
33 void rb_free(struct rbtree *rb)
34 {
35 rb_destroy(rb);
36 free(rb);
37 }
38
39
40 int rb_init(struct rbtree *rb, rb_cmp_func_t cmp_func)
41 {
42 memset(rb, 0, sizeof *rb);
43
44 if(cmp_func == RB_KEY_INT) {
45 rb->cmp = cmpint;
46 } else if(cmp_func == RB_KEY_STRING) {
47 rb->cmp = (rb_cmp_func_t)strcmp;
48 } else {
49 rb->cmp = cmpaddr;
50 }
51
52 rb->alloc = malloc;
53 rb->free = free;
54 return 0;
55 }
56
57 void rb_destroy(struct rbtree *rb)
58 {
59 del_tree(rb->root, rb->del, rb->del_cls);
60 }
61
62 void rb_clear(struct rbtree *rb)
63 {
64 del_tree(rb->root, rb->del, rb->del_cls);
65 rb->root = 0;
66 }
67
68 int rb_copy(struct rbtree *dest, struct rbtree *src)
69 {
70 struct rbnode *node;
71
72 rb_clear(dest);
73
74 rb_begin(src);
75 while((node = rb_next(src))) {
76 if(rb_insert(dest, node->key, node->data) == -1) {
77 return -1;
78 }
79 }
80 return 0;
81 }
82
83 void rb_set_allocator(struct rbtree *rb, rb_alloc_func_t alloc, rb_free_func_t free)
84 {
85 rb->alloc = alloc;
86 rb->free = free;
87 }
88
89
90 void rb_set_compare_func(struct rbtree *rb, rb_cmp_func_t func)
91 {
92 rb->cmp = func;
93 }
94
95 void rb_set_delete_func(struct rbtree *rb, rb_del_func_t func, void *cls)
96 {
97 rb->del = func;
98 rb->del_cls = cls;
99 }
100
101 int rb_size(struct rbtree *rb)
102 {
103 return count_nodes(rb->root);
104 }
105
106 int rb_insert(struct rbtree *rb, void *key, void *data)
107 {
108 rb->root = insert(rb, rb->root, key, data);
109 rb->root->red = 0;
110 return 0;
111 }
112
113 int rb_inserti(struct rbtree *rb, int key, void *data)
114 {
115 rb->root = insert(rb, rb->root, INT2PTR(key), data);
116 rb->root->red = 0;
117 return 0;
118 }
119
120
121 int rb_delete(struct rbtree *rb, void *key)
122 {
123 rb->root = delete(rb, rb->root, key);
124 rb->root->red = 0;
125 return 0;
126 }
127
128 int rb_deletei(struct rbtree *rb, int key)
129 {
130 rb->root = delete(rb, rb->root, INT2PTR(key));
131 rb->root->red = 0;
132 return 0;
133 }
134
135
136 void *rb_find(struct rbtree *rb, void *key)
137 {
138 struct rbnode *node = rb->root;
139
140 while(node) {
141 int cmp = rb->cmp(key, node->key);
142 if(cmp == 0) {
143 return node;
144 }
145 node = cmp < 0 ? node->left : node->right;
146 }
147 return 0;
148 }
149
150 void *rb_findi(struct rbtree *rb, int key)
151 {
152 return rb_find(rb, INT2PTR(key));
153 }
154
155
156 void rb_foreach(struct rbtree *rb, void (*func)(struct rbnode*, void*), void *cls)
157 {
158 traverse(rb->root, func, cls);
159 }
160
161
162 struct rbnode *rb_root(struct rbtree *rb)
163 {
164 return rb->root;
165 }
166
167 void rb_begin(struct rbtree *rb)
168 {
169 rb->rstack = 0;
170 rb->iter = rb->root;
171 }
172
173 #define push(sp, x) ((x)->next = (sp), (sp) = (x))
174 #define pop(sp) ((sp) = (sp)->next)
175 #define top(sp) (sp)
176
177 struct rbnode *rb_next(struct rbtree *rb)
178 {
179 struct rbnode *res = 0;
180
181 while(rb->rstack || rb->iter) {
182 if(rb->iter) {
183 push(rb->rstack, rb->iter);
184 rb->iter = rb->iter->left;
185 } else {
186 rb->iter = top(rb->rstack);
187 pop(rb->rstack);
188 res = rb->iter;
189 rb->iter = rb->iter->right;
190 break;
191 }
192 }
193 return res;
194 }
195
196 void *rb_node_key(struct rbnode *node)
197 {
198 return node ? node->key : 0;
199 }
200
201 int rb_node_keyi(struct rbnode *node)
202 {
203 return node ? PTR2INT(node->key) : 0;
204 }
205
206 void *rb_node_data(struct rbnode *node)
207 {
208 return node ? node->data : 0;
209 }
210
211 static int cmpaddr(void *ap, void *bp)
212 {
213 return ap < bp ? -1 : (ap > bp ? 1 : 0);
214 }
215
216 static int cmpint(void *ap, void *bp)
217 {
218 return PTR2INT(ap) - PTR2INT(bp);
219 }
220
221
222 /* ---- left-leaning 2-3 red-black implementation ---- */
223
224 /* helper prototypes */
225 static int is_red(struct rbnode *tree);
226 static void color_flip(struct rbnode *tree);
227 static struct rbnode *rot_left(struct rbnode *a);
228 static struct rbnode *rot_right(struct rbnode *a);
229 static struct rbnode *find_min(struct rbnode *tree);
230 static struct rbnode *del_min(struct rbtree *rb, struct rbnode *tree);
231 /*static struct rbnode *move_red_right(struct rbnode *tree);*/
232 static struct rbnode *move_red_left(struct rbnode *tree);
233 static struct rbnode *fix_up(struct rbnode *tree);
234
235 static int count_nodes(struct rbnode *node)
236 {
237 if(!node)
238 return 0;
239
240 return 1 + count_nodes(node->left) + count_nodes(node->right);
241 }
242
243 static void del_tree(struct rbnode *node, rb_del_func_t delfunc, void *cls)
244 {
245 if(!node)
246 return;
247
248 del_tree(node->left, delfunc, cls);
249 del_tree(node->right, delfunc, cls);
250
251 if(delfunc) {
252 delfunc(node, cls);
253 }
254 free(node);
255 }
256
257 static struct rbnode *insert(struct rbtree *rb, struct rbnode *tree, void *key, void *data)
258 {
259 int cmp;
260
261 if(!tree) {
262 struct rbnode *node = rb->alloc(sizeof *node);
263 if(!node) {
264 panic("failed to allocate tree node\n");
265 }
266 node->red = 1;
267 node->key = key;
268 node->data = data;
269 node->left = node->right = 0;
270 return node;
271 }
272
273 cmp = rb->cmp(key, tree->key);
274
275 if(cmp < 0) {
276 tree->left = insert(rb, tree->left, key, data);
277 } else if(cmp > 0) {
278 tree->right = insert(rb, tree->right, key, data);
279 } else {
280 tree->data = data;
281 }
282
283 /* fix right-leaning reds */
284 if(is_red(tree->right)) {
285 tree = rot_left(tree);
286 }
287 /* fix two reds in a row */
288 if(is_red(tree->left) && is_red(tree->left->left)) {
289 tree = rot_right(tree);
290 }
291
292 /* if 4-node, split it by color inversion */
293 if(is_red(tree->left) && is_red(tree->right)) {
294 color_flip(tree);
295 }
296
297 return tree;
298 }
299
300 static struct rbnode *delete(struct rbtree *rb, struct rbnode *tree, void *key)
301 {
302 int cmp;
303
304 if(!tree) {
305 return 0;
306 }
307
308 cmp = rb->cmp(key, tree->key);
309
310 if(cmp < 0) {
311 if(!is_red(tree->left) && !is_red(tree->left->left)) {
312 tree = move_red_left(tree);
313 }
314 tree->left = delete(rb, tree->left, key);
315 } else {
316 /* need reds on the right */
317 if(is_red(tree->left)) {
318 tree = rot_right(tree);
319 }
320
321 /* found it at the bottom (XXX what certifies left is null?) */
322 if(cmp == 0 && !tree->right) {
323 if(rb->del) {
324 rb->del(tree, rb->del_cls);
325 }
326 rb->free(tree);
327 return 0;
328 }
329
330 if(!is_red(tree->right) && !is_red(tree->right->left)) {
331 tree = move_red_left(tree);
332 }
333
334 if(key == tree->key) {
335 struct rbnode *rmin = find_min(tree->right);
336 tree->key = rmin->key;
337 tree->data = rmin->data;
338 tree->right = del_min(rb, tree->right);
339 } else {
340 tree->right = delete(rb, tree->right, key);
341 }
342 }
343
344 return fix_up(tree);
345 }
346
347 /*static struct rbnode *find(struct rbtree *rb, struct rbnode *node, void *key)
348 {
349 int cmp;
350
351 if(!node)
352 return 0;
353
354 if((cmp = rb->cmp(key, node->key)) == 0) {
355 return node;
356 }
357 return find(rb, cmp < 0 ? node->left : node->right, key);
358 }*/
359
360 static void traverse(struct rbnode *node, void (*func)(struct rbnode*, void*), void *cls)
361 {
362 if(!node)
363 return;
364
365 traverse(node->left, func, cls);
366 func(node, cls);
367 traverse(node->right, func, cls);
368 }
369
370 /* helpers */
371
372 static int is_red(struct rbnode *tree)
373 {
374 return tree && tree->red;
375 }
376
377 static void color_flip(struct rbnode *tree)
378 {
379 tree->red = !tree->red;
380 tree->left->red = !tree->left->red;
381 tree->right->red = !tree->right->red;
382 }
383
384 static struct rbnode *rot_left(struct rbnode *a)
385 {
386 struct rbnode *b = a->right;
387 a->right = b->left;
388 b->left = a;
389 b->red = a->red;
390 a->red = 1;
391 return b;
392 }
393
394 static struct rbnode *rot_right(struct rbnode *a)
395 {
396 struct rbnode *b = a->left;
397 a->left = b->right;
398 b->right = a;
399 b->red = a->red;
400 a->red = 1;
401 return b;
402 }
403
404 static struct rbnode *find_min(struct rbnode *tree)
405 {
406 struct rbnode *node;
407
408 if(!tree)
409 return 0;
410
411 while(node->left) {
412 node = node->left;
413 }
414 return node;
415 }
416
417 static struct rbnode *del_min(struct rbtree *rb, struct rbnode *tree)
418 {
419 if(!tree->left) {
420 if(rb->del) {
421 rb->del(tree->left, rb->del_cls);
422 }
423 rb->free(tree->left);
424 return 0;
425 }
426
427 /* make sure we've got red (3/4-nodes) at the left side so we can delete at the bottom */
428 if(!is_red(tree->left) && !is_red(tree->left->left)) {
429 tree = move_red_left(tree);
430 }
431 tree->left = del_min(rb, tree->left);
432
433 /* fix right-reds, red-reds, and split 4-nodes on the way up */
434 return fix_up(tree);
435 }
436
437 #if 0
438 /* push a red link on this node to the right */
439 static struct rbnode *move_red_right(struct rbnode *tree)
440 {
441 /* flipping it makes both children go red, so we have a red to the right */
442 color_flip(tree);
443
444 /* if after the flip we've got a red-red situation to the left, fix it */
445 if(is_red(tree->left->left)) {
446 tree = rot_right(tree);
447 color_flip(tree);
448 }
449 return tree;
450 }
451 #endif
452
453 /* push a red link on this node to the left */
454 static struct rbnode *move_red_left(struct rbnode *tree)
455 {
456 /* flipping it makes both children go red, so we have a red to the left */
457 color_flip(tree);
458
459 /* if after the flip we've got a red-red on the right-left, fix it */
460 if(is_red(tree->right->left)) {
461 tree->right = rot_right(tree->right);
462 tree = rot_left(tree);
463 color_flip(tree);
464 }
465 return tree;
466 }
467
468 static struct rbnode *fix_up(struct rbnode *tree)
469 {
470 /* fix right-leaning */
471 if(is_red(tree->right)) {
472 tree = rot_left(tree);
473 }
474 /* change invalid red-red pairs into a proper 4-node */
475 if(is_red(tree->left) && is_red(tree->left->left)) {
476 tree = rot_right(tree);
477 }
478 /* split 4-nodes */
479 if(is_red(tree->left) && is_red(tree->right)) {
480 color_flip(tree);
481 }
482 return tree;
483 }
484
485 void rb_dbg_print_tree(struct rbtree *tree)
486 {
487 struct rbnode *node;
488
489 rb_begin(tree);
490 while((node = rb_next(tree))) {
491 printf("%d ", rb_node_keyi(node));
492 }
493 printf("\n");
494 }