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comparison: gfx/skia/trunk/src/gpu/GrRedBlackTree.h

gfx/skia/trunk/src/gpu/GrRedBlackTree.h

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1 /*
2 * Copyright 2011 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8 #ifndef GrRedBlackTree_DEFINED
9 #define GrRedBlackTree_DEFINED
10
11 #include "GrConfig.h"
12 #include "SkTypes.h"
13
14 template <typename T>
15 class GrLess {
16 public:
17 bool operator()(const T& a, const T& b) const { return a < b; }
18 };
19
20 template <typename T>
21 class GrLess<T*> {
22 public:
23 bool operator()(const T* a, const T* b) const { return *a < *b; }
24 };
25
26 class GrStrLess {
27 public:
28 bool operator()(const char* a, const char* b) const { return strcmp(a,b) < 0; }
29 };
30
31 /**
32 * In debug build this will cause full traversals of the tree when the validate
33 * is called on insert and remove. Useful for debugging but very slow.
34 */
35 #define DEEP_VALIDATE 0
36
37 /**
38 * A sorted tree that uses the red-black tree algorithm. Allows duplicate
39 * entries. Data is of type T and is compared using functor C. A single C object
40 * will be created and used for all comparisons.
41 */
42 template <typename T, typename C = GrLess<T> >
43 class GrRedBlackTree : public SkNoncopyable {
44 public:
45 /**
46 * Creates an empty tree.
47 */
48 GrRedBlackTree();
49 virtual ~GrRedBlackTree();
50
51 /**
52 * Class used to iterater through the tree. The valid range of the tree
53 * is given by [begin(), end()). It is legal to dereference begin() but not
54 * end(). The iterator has preincrement and predecrement operators, it is
55 * legal to decerement end() if the tree is not empty to get the last
56 * element. However, a last() helper is provided.
57 */
58 class Iter;
59
60 /**
61 * Add an element to the tree. Duplicates are allowed.
62 * @param t the item to add.
63 * @return an iterator to the item.
64 */
65 Iter insert(const T& t);
66
67 /**
68 * Removes all items in the tree.
69 */
70 void reset();
71
72 /**
73 * @return true if there are no items in the tree, false otherwise.
74 */
75 bool empty() const {return 0 == fCount;}
76
77 /**
78 * @return the number of items in the tree.
79 */
80 int count() const {return fCount;}
81
82 /**
83 * @return an iterator to the first item in sorted order, or end() if empty
84 */
85 Iter begin();
86 /**
87 * Gets the last valid iterator. This is always valid, even on an empty.
88 * However, it can never be dereferenced. Useful as a loop terminator.
89 * @return an iterator that is just beyond the last item in sorted order.
90 */
91 Iter end();
92 /**
93 * @return an iterator that to the last item in sorted order, or end() if
94 * empty.
95 */
96 Iter last();
97
98 /**
99 * Finds an occurrence of an item.
100 * @param t the item to find.
101 * @return an iterator to a tree element equal to t or end() if none exists.
102 */
103 Iter find(const T& t);
104 /**
105 * Finds the first of an item in iterator order.
106 * @param t the item to find.
107 * @return an iterator to the first element equal to t or end() if
108 * none exists.
109 */
110 Iter findFirst(const T& t);
111 /**
112 * Finds the last of an item in iterator order.
113 * @param t the item to find.
114 * @return an iterator to the last element equal to t or end() if
115 * none exists.
116 */
117 Iter findLast(const T& t);
118 /**
119 * Gets the number of items in the tree equal to t.
120 * @param t the item to count.
121 * @return number of items equal to t in the tree
122 */
123 int countOf(const T& t) const;
124
125 /**
126 * Removes the item indicated by an iterator. The iterator will not be valid
127 * afterwards.
128 *
129 * @param iter iterator of item to remove. Must be valid (not end()).
130 */
131 void remove(const Iter& iter) { deleteAtNode(iter.fN); }
132
133 private:
134 enum Color {
135 kRed_Color,
136 kBlack_Color
137 };
138
139 enum Child {
140 kLeft_Child = 0,
141 kRight_Child = 1
142 };
143
144 struct Node {
145 T fItem;
146 Color fColor;
147
148 Node* fParent;
149 Node* fChildren[2];
150 };
151
152 void rotateRight(Node* n);
153 void rotateLeft(Node* n);
154
155 static Node* SuccessorNode(Node* x);
156 static Node* PredecessorNode(Node* x);
157
158 void deleteAtNode(Node* x);
159 static void RecursiveDelete(Node* x);
160
161 int onCountOf(const Node* n, const T& t) const;
162
163 #ifdef SK_DEBUG
164 void validate() const;
165 int checkNode(Node* n, int* blackHeight) const;
166 // checks relationship between a node and its children. allowRedRed means
167 // node may be in an intermediate state where a red parent has a red child.
168 bool validateChildRelations(const Node* n, bool allowRedRed) const;
169 // place to stick break point if validateChildRelations is failing.
170 bool validateChildRelationsFailed() const { return false; }
171 #else
172 void validate() const {}
173 #endif
174
175 int fCount;
176 Node* fRoot;
177 Node* fFirst;
178 Node* fLast;
179
180 const C fComp;
181 };
182
183 template <typename T, typename C>
184 class GrRedBlackTree<T,C>::Iter {
185 public:
186 Iter() {};
187 Iter(const Iter& i) {fN = i.fN; fTree = i.fTree;}
188 Iter& operator =(const Iter& i) {
189 fN = i.fN;
190 fTree = i.fTree;
191 return *this;
192 }
193 // altering the sort value of the item using this method will cause
194 // errors.
195 T& operator *() const { return fN->fItem; }
196 bool operator ==(const Iter& i) const {
197 return fN == i.fN && fTree == i.fTree;
198 }
199 bool operator !=(const Iter& i) const { return !(*this == i); }
200 Iter& operator ++() {
201 SkASSERT(*this != fTree->end());
202 fN = SuccessorNode(fN);
203 return *this;
204 }
205 Iter& operator --() {
206 SkASSERT(*this != fTree->begin());
207 if (NULL != fN) {
208 fN = PredecessorNode(fN);
209 } else {
210 *this = fTree->last();
211 }
212 return *this;
213 }
214
215 private:
216 friend class GrRedBlackTree;
217 explicit Iter(Node* n, GrRedBlackTree* tree) {
218 fN = n;
219 fTree = tree;
220 }
221 Node* fN;
222 GrRedBlackTree* fTree;
223 };
224
225 template <typename T, typename C>
226 GrRedBlackTree<T,C>::GrRedBlackTree() : fComp() {
227 fRoot = NULL;
228 fFirst = NULL;
229 fLast = NULL;
230 fCount = 0;
231 validate();
232 }
233
234 template <typename T, typename C>
235 GrRedBlackTree<T,C>::~GrRedBlackTree() {
236 RecursiveDelete(fRoot);
237 }
238
239 template <typename T, typename C>
240 typename GrRedBlackTree<T,C>::Iter GrRedBlackTree<T,C>::begin() {
241 return Iter(fFirst, this);
242 }
243
244 template <typename T, typename C>
245 typename GrRedBlackTree<T,C>::Iter GrRedBlackTree<T,C>::end() {
246 return Iter(NULL, this);
247 }
248
249 template <typename T, typename C>
250 typename GrRedBlackTree<T,C>::Iter GrRedBlackTree<T,C>::last() {
251 return Iter(fLast, this);
252 }
253
254 template <typename T, typename C>
255 typename GrRedBlackTree<T,C>::Iter GrRedBlackTree<T,C>::find(const T& t) {
256 Node* n = fRoot;
257 while (NULL != n) {
258 if (fComp(t, n->fItem)) {
259 n = n->fChildren[kLeft_Child];
260 } else {
261 if (!fComp(n->fItem, t)) {
262 return Iter(n, this);
263 }
264 n = n->fChildren[kRight_Child];
265 }
266 }
267 return end();
268 }
269
270 template <typename T, typename C>
271 typename GrRedBlackTree<T,C>::Iter GrRedBlackTree<T,C>::findFirst(const T& t) {
272 Node* n = fRoot;
273 Node* leftMost = NULL;
274 while (NULL != n) {
275 if (fComp(t, n->fItem)) {
276 n = n->fChildren[kLeft_Child];
277 } else {
278 if (!fComp(n->fItem, t)) {
279 // found one. check if another in left subtree.
280 leftMost = n;
281 n = n->fChildren[kLeft_Child];
282 } else {
283 n = n->fChildren[kRight_Child];
284 }
285 }
286 }
287 return Iter(leftMost, this);
288 }
289
290 template <typename T, typename C>
291 typename GrRedBlackTree<T,C>::Iter GrRedBlackTree<T,C>::findLast(const T& t) {
292 Node* n = fRoot;
293 Node* rightMost = NULL;
294 while (NULL != n) {
295 if (fComp(t, n->fItem)) {
296 n = n->fChildren[kLeft_Child];
297 } else {
298 if (!fComp(n->fItem, t)) {
299 // found one. check if another in right subtree.
300 rightMost = n;
301 }
302 n = n->fChildren[kRight_Child];
303 }
304 }
305 return Iter(rightMost, this);
306 }
307
308 template <typename T, typename C>
309 int GrRedBlackTree<T,C>::countOf(const T& t) const {
310 return onCountOf(fRoot, t);
311 }
312
313 template <typename T, typename C>
314 int GrRedBlackTree<T,C>::onCountOf(const Node* n, const T& t) const {
315 // this is count*log(n) :(
316 while (NULL != n) {
317 if (fComp(t, n->fItem)) {
318 n = n->fChildren[kLeft_Child];
319 } else {
320 if (!fComp(n->fItem, t)) {
321 int count = 1;
322 count += onCountOf(n->fChildren[kLeft_Child], t);
323 count += onCountOf(n->fChildren[kRight_Child], t);
324 return count;
325 }
326 n = n->fChildren[kRight_Child];
327 }
328 }
329 return 0;
330
331 }
332
333 template <typename T, typename C>
334 void GrRedBlackTree<T,C>::reset() {
335 RecursiveDelete(fRoot);
336 fRoot = NULL;
337 fFirst = NULL;
338 fLast = NULL;
339 fCount = 0;
340 }
341
342 template <typename T, typename C>
343 typename GrRedBlackTree<T,C>::Iter GrRedBlackTree<T,C>::insert(const T& t) {
344 validate();
345
346 ++fCount;
347
348 Node* x = SkNEW(Node);
349 x->fChildren[kLeft_Child] = NULL;
350 x->fChildren[kRight_Child] = NULL;
351 x->fItem = t;
352
353 Node* returnNode = x;
354
355 Node* gp = NULL;
356 Node* p = NULL;
357 Node* n = fRoot;
358 Child pc = kLeft_Child; // suppress uninit warning
359 Child gpc = kLeft_Child;
360
361 bool first = true;
362 bool last = true;
363 while (NULL != n) {
364 gpc = pc;
365 pc = fComp(x->fItem, n->fItem) ? kLeft_Child : kRight_Child;
366 first = first && kLeft_Child == pc;
367 last = last && kRight_Child == pc;
368 gp = p;
369 p = n;
370 n = p->fChildren[pc];
371 }
372 if (last) {
373 fLast = x;
374 }
375 if (first) {
376 fFirst = x;
377 }
378
379 if (NULL == p) {
380 fRoot = x;
381 x->fColor = kBlack_Color;
382 x->fParent = NULL;
383 SkASSERT(1 == fCount);
384 return Iter(returnNode, this);
385 }
386 p->fChildren[pc] = x;
387 x->fColor = kRed_Color;
388 x->fParent = p;
389
390 do {
391 // assumptions at loop start.
392 SkASSERT(NULL != x);
393 SkASSERT(kRed_Color == x->fColor);
394 // can't have a grandparent but no parent.
395 SkASSERT(!(NULL != gp && NULL == p));
396 // make sure pc and gpc are correct
397 SkASSERT(NULL == p || p->fChildren[pc] == x);
398 SkASSERT(NULL == gp || gp->fChildren[gpc] == p);
399
400 // if x's parent is black then we didn't violate any of the
401 // red/black properties when we added x as red.
402 if (kBlack_Color == p->fColor) {
403 return Iter(returnNode, this);
404 }
405 // gp must be valid because if p was the root then it is black
406 SkASSERT(NULL != gp);
407 // gp must be black since it's child, p, is red.
408 SkASSERT(kBlack_Color == gp->fColor);
409
410
411 // x and its parent are red, violating red-black property.
412 Node* u = gp->fChildren[1-gpc];
413 // if x's uncle (p's sibling) is also red then we can flip
414 // p and u to black and make gp red. But then we have to recurse
415 // up to gp since it's parent may also be red.
416 if (NULL != u && kRed_Color == u->fColor) {
417 p->fColor = kBlack_Color;
418 u->fColor = kBlack_Color;
419 gp->fColor = kRed_Color;
420 x = gp;
421 p = x->fParent;
422 if (NULL == p) {
423 // x (prev gp) is the root, color it black and be done.
424 SkASSERT(fRoot == x);
425 x->fColor = kBlack_Color;
426 validate();
427 return Iter(returnNode, this);
428 }
429 gp = p->fParent;
430 pc = (p->fChildren[kLeft_Child] == x) ? kLeft_Child :
431 kRight_Child;
432 if (NULL != gp) {
433 gpc = (gp->fChildren[kLeft_Child] == p) ? kLeft_Child :
434 kRight_Child;
435 }
436 continue;
437 } break;
438 } while (true);
439 // Here p is red but u is black and we still have to resolve the fact
440 // that x and p are both red.
441 SkASSERT(NULL == gp->fChildren[1-gpc] || kBlack_Color == gp->fChildren[1-gpc]->fColor);
442 SkASSERT(kRed_Color == x->fColor);
443 SkASSERT(kRed_Color == p->fColor);
444 SkASSERT(kBlack_Color == gp->fColor);
445
446 // make x be on the same side of p as p is of gp. If it isn't already
447 // the case then rotate x up to p and swap their labels.
448 if (pc != gpc) {
449 if (kRight_Child == pc) {
450 rotateLeft(p);
451 Node* temp = p;
452 p = x;
453 x = temp;
454 pc = kLeft_Child;
455 } else {
456 rotateRight(p);
457 Node* temp = p;
458 p = x;
459 x = temp;
460 pc = kRight_Child;
461 }
462 }
463 // we now rotate gp down, pulling up p to be it's new parent.
464 // gp's child, u, that is not affected we know to be black. gp's new
465 // child is p's previous child (x's pre-rotation sibling) which must be
466 // black since p is red.
467 SkASSERT(NULL == p->fChildren[1-pc] ||
468 kBlack_Color == p->fChildren[1-pc]->fColor);
469 // Since gp's two children are black it can become red if p is made
470 // black. This leaves the black-height of both of p's new subtrees
471 // preserved and removes the red/red parent child relationship.
472 p->fColor = kBlack_Color;
473 gp->fColor = kRed_Color;
474 if (kLeft_Child == pc) {
475 rotateRight(gp);
476 } else {
477 rotateLeft(gp);
478 }
479 validate();
480 return Iter(returnNode, this);
481 }
482
483
484 template <typename T, typename C>
485 void GrRedBlackTree<T,C>::rotateRight(Node* n) {
486 /* d? d?
487 * / /
488 * n s
489 * / \ ---> / \
490 * s a? c? n
491 * / \ / \
492 * c? b? b? a?
493 */
494 Node* d = n->fParent;
495 Node* s = n->fChildren[kLeft_Child];
496 SkASSERT(NULL != s);
497 Node* b = s->fChildren[kRight_Child];
498
499 if (NULL != d) {
500 Child c = d->fChildren[kLeft_Child] == n ? kLeft_Child :
501 kRight_Child;
502 d->fChildren[c] = s;
503 } else {
504 SkASSERT(fRoot == n);
505 fRoot = s;
506 }
507 s->fParent = d;
508 s->fChildren[kRight_Child] = n;
509 n->fParent = s;
510 n->fChildren[kLeft_Child] = b;
511 if (NULL != b) {
512 b->fParent = n;
513 }
514
515 GR_DEBUGASSERT(validateChildRelations(d, true));
516 GR_DEBUGASSERT(validateChildRelations(s, true));
517 GR_DEBUGASSERT(validateChildRelations(n, false));
518 GR_DEBUGASSERT(validateChildRelations(n->fChildren[kRight_Child], true));
519 GR_DEBUGASSERT(validateChildRelations(b, true));
520 GR_DEBUGASSERT(validateChildRelations(s->fChildren[kLeft_Child], true));
521 }
522
523 template <typename T, typename C>
524 void GrRedBlackTree<T,C>::rotateLeft(Node* n) {
525
526 Node* d = n->fParent;
527 Node* s = n->fChildren[kRight_Child];
528 SkASSERT(NULL != s);
529 Node* b = s->fChildren[kLeft_Child];
530
531 if (NULL != d) {
532 Child c = d->fChildren[kRight_Child] == n ? kRight_Child :
533 kLeft_Child;
534 d->fChildren[c] = s;
535 } else {
536 SkASSERT(fRoot == n);
537 fRoot = s;
538 }
539 s->fParent = d;
540 s->fChildren[kLeft_Child] = n;
541 n->fParent = s;
542 n->fChildren[kRight_Child] = b;
543 if (NULL != b) {
544 b->fParent = n;
545 }
546
547 GR_DEBUGASSERT(validateChildRelations(d, true));
548 GR_DEBUGASSERT(validateChildRelations(s, true));
549 GR_DEBUGASSERT(validateChildRelations(n, true));
550 GR_DEBUGASSERT(validateChildRelations(n->fChildren[kLeft_Child], true));
551 GR_DEBUGASSERT(validateChildRelations(b, true));
552 GR_DEBUGASSERT(validateChildRelations(s->fChildren[kRight_Child], true));
553 }
554
555 template <typename T, typename C>
556 typename GrRedBlackTree<T,C>::Node* GrRedBlackTree<T,C>::SuccessorNode(Node* x) {
557 SkASSERT(NULL != x);
558 if (NULL != x->fChildren[kRight_Child]) {
559 x = x->fChildren[kRight_Child];
560 while (NULL != x->fChildren[kLeft_Child]) {
561 x = x->fChildren[kLeft_Child];
562 }
563 return x;
564 }
565 while (NULL != x->fParent && x == x->fParent->fChildren[kRight_Child]) {
566 x = x->fParent;
567 }
568 return x->fParent;
569 }
570
571 template <typename T, typename C>
572 typename GrRedBlackTree<T,C>::Node* GrRedBlackTree<T,C>::PredecessorNode(Node* x) {
573 SkASSERT(NULL != x);
574 if (NULL != x->fChildren[kLeft_Child]) {
575 x = x->fChildren[kLeft_Child];
576 while (NULL != x->fChildren[kRight_Child]) {
577 x = x->fChildren[kRight_Child];
578 }
579 return x;
580 }
581 while (NULL != x->fParent && x == x->fParent->fChildren[kLeft_Child]) {
582 x = x->fParent;
583 }
584 return x->fParent;
585 }
586
587 template <typename T, typename C>
588 void GrRedBlackTree<T,C>::deleteAtNode(Node* x) {
589 SkASSERT(NULL != x);
590 validate();
591 --fCount;
592
593 bool hasLeft = NULL != x->fChildren[kLeft_Child];
594 bool hasRight = NULL != x->fChildren[kRight_Child];
595 Child c = hasLeft ? kLeft_Child : kRight_Child;
596
597 if (hasLeft && hasRight) {
598 // first and last can't have two children.
599 SkASSERT(fFirst != x);
600 SkASSERT(fLast != x);
601 // if x is an interior node then we find it's successor
602 // and swap them.
603 Node* s = x->fChildren[kRight_Child];
604 while (NULL != s->fChildren[kLeft_Child]) {
605 s = s->fChildren[kLeft_Child];
606 }
607 SkASSERT(NULL != s);
608 // this might be expensive relative to swapping node ptrs around.
609 // depends on T.
610 x->fItem = s->fItem;
611 x = s;
612 c = kRight_Child;
613 } else if (NULL == x->fParent) {
614 // if x was the root we just replace it with its child and make
615 // the new root (if the tree is not empty) black.
616 SkASSERT(fRoot == x);
617 fRoot = x->fChildren[c];
618 if (NULL != fRoot) {
619 fRoot->fParent = NULL;
620 fRoot->fColor = kBlack_Color;
621 if (x == fLast) {
622 SkASSERT(c == kLeft_Child);
623 fLast = fRoot;
624 } else if (x == fFirst) {
625 SkASSERT(c == kRight_Child);
626 fFirst = fRoot;
627 }
628 } else {
629 SkASSERT(fFirst == fLast && x == fFirst);
630 fFirst = NULL;
631 fLast = NULL;
632 SkASSERT(0 == fCount);
633 }
634 delete x;
635 validate();
636 return;
637 }
638
639 Child pc;
640 Node* p = x->fParent;
641 pc = p->fChildren[kLeft_Child] == x ? kLeft_Child : kRight_Child;
642
643 if (NULL == x->fChildren[c]) {
644 if (fLast == x) {
645 fLast = p;
646 SkASSERT(p == PredecessorNode(x));
647 } else if (fFirst == x) {
648 fFirst = p;
649 SkASSERT(p == SuccessorNode(x));
650 }
651 // x has two implicit black children.
652 Color xcolor = x->fColor;
653 p->fChildren[pc] = NULL;
654 delete x;
655 x = NULL;
656 // when x is red it can be with an implicit black leaf without
657 // violating any of the red-black tree properties.
658 if (kRed_Color == xcolor) {
659 validate();
660 return;
661 }
662 // s is p's other child (x's sibling)
663 Node* s = p->fChildren[1-pc];
664
665 //s cannot be an implicit black node because the original
666 // black-height at x was >= 2 and s's black-height must equal the
667 // initial black height of x.
668 SkASSERT(NULL != s);
669 SkASSERT(p == s->fParent);
670
671 // assigned in loop
672 Node* sl;
673 Node* sr;
674 bool slRed;
675 bool srRed;
676
677 do {
678 // When we start this loop x may already be deleted it is/was
679 // p's child on its pc side. x's children are/were black. The
680 // first time through the loop they are implict children.
681 // On later passes we will be walking up the tree and they will
682 // be real nodes.
683 // The x side of p has a black-height that is one less than the
684 // s side. It must be rebalanced.
685 SkASSERT(NULL != s);
686 SkASSERT(p == s->fParent);
687 SkASSERT(NULL == x || x->fParent == p);
688
689 //sl and sr are s's children, which may be implicit.
690 sl = s->fChildren[kLeft_Child];
691 sr = s->fChildren[kRight_Child];
692
693 // if the s is red we will rotate s and p, swap their colors so
694 // that x's new sibling is black
695 if (kRed_Color == s->fColor) {
696 // if s is red then it's parent must be black.
697 SkASSERT(kBlack_Color == p->fColor);
698 // s's children must also be black since s is red. They can't
699 // be implicit since s is red and it's black-height is >= 2.
700 SkASSERT(NULL != sl && kBlack_Color == sl->fColor);
701 SkASSERT(NULL != sr && kBlack_Color == sr->fColor);
702 p->fColor = kRed_Color;
703 s->fColor = kBlack_Color;
704 if (kLeft_Child == pc) {
705 rotateLeft(p);
706 s = sl;
707 } else {
708 rotateRight(p);
709 s = sr;
710 }
711 sl = s->fChildren[kLeft_Child];
712 sr = s->fChildren[kRight_Child];
713 }
714 // x and s are now both black.
715 SkASSERT(kBlack_Color == s->fColor);
716 SkASSERT(NULL == x || kBlack_Color == x->fColor);
717 SkASSERT(p == s->fParent);
718 SkASSERT(NULL == x || p == x->fParent);
719
720 // when x is deleted its subtree will have reduced black-height.
721 slRed = (NULL != sl && kRed_Color == sl->fColor);
722 srRed = (NULL != sr && kRed_Color == sr->fColor);
723 if (!slRed && !srRed) {
724 // if s can be made red that will balance out x's removal
725 // to make both subtrees of p have the same black-height.
726 if (kBlack_Color == p->fColor) {
727 s->fColor = kRed_Color;
728 // now subtree at p has black-height of one less than
729 // p's parent's other child's subtree. We move x up to
730 // p and go through the loop again. At the top of loop
731 // we assumed x and x's children are black, which holds
732 // by above ifs.
733 // if p is the root there is no other subtree to balance
734 // against.
735 x = p;
736 p = x->fParent;
737 if (NULL == p) {
738 SkASSERT(fRoot == x);
739 validate();
740 return;
741 } else {
742 pc = p->fChildren[kLeft_Child] == x ? kLeft_Child :
743 kRight_Child;
744
745 }
746 s = p->fChildren[1-pc];
747 SkASSERT(NULL != s);
748 SkASSERT(p == s->fParent);
749 continue;
750 } else if (kRed_Color == p->fColor) {
751 // we can make p black and s red. This balance out p's
752 // two subtrees and keep the same black-height as it was
753 // before the delete.
754 s->fColor = kRed_Color;
755 p->fColor = kBlack_Color;
756 validate();
757 return;
758 }
759 }
760 break;
761 } while (true);
762 // if we made it here one or both of sl and sr is red.
763 // s and x are black. We make sure that a red child is on
764 // the same side of s as s is of p.
765 SkASSERT(slRed || srRed);
766 if (kLeft_Child == pc && !srRed) {
767 s->fColor = kRed_Color;
768 sl->fColor = kBlack_Color;
769 rotateRight(s);
770 sr = s;
771 s = sl;
772 //sl = s->fChildren[kLeft_Child]; don't need this
773 } else if (kRight_Child == pc && !slRed) {
774 s->fColor = kRed_Color;
775 sr->fColor = kBlack_Color;
776 rotateLeft(s);
777 sl = s;
778 s = sr;
779 //sr = s->fChildren[kRight_Child]; don't need this
780 }
781 // now p is either red or black, x and s are red and s's 1-pc
782 // child is red.
783 // We rotate p towards x, pulling s up to replace p. We make
784 // p be black and s takes p's old color.
785 // Whether p was red or black, we've increased its pc subtree
786 // rooted at x by 1 (balancing the imbalance at the start) and
787 // we've also its subtree rooted at s's black-height by 1. This
788 // can be balanced by making s's red child be black.
789 s->fColor = p->fColor;
790 p->fColor = kBlack_Color;
791 if (kLeft_Child == pc) {
792 SkASSERT(NULL != sr && kRed_Color == sr->fColor);
793 sr->fColor = kBlack_Color;
794 rotateLeft(p);
795 } else {
796 SkASSERT(NULL != sl && kRed_Color == sl->fColor);
797 sl->fColor = kBlack_Color;
798 rotateRight(p);
799 }
800 }
801 else {
802 // x has exactly one implicit black child. x cannot be red.
803 // Proof by contradiction: Assume X is red. Let c0 be x's implicit
804 // child and c1 be its non-implicit child. c1 must be black because
805 // red nodes always have two black children. Then the two subtrees
806 // of x rooted at c0 and c1 will have different black-heights.
807 SkASSERT(kBlack_Color == x->fColor);
808 // So we know x is black and has one implicit black child, c0. c1
809 // must be red, otherwise the subtree at c1 will have a different
810 // black-height than the subtree rooted at c0.
811 SkASSERT(kRed_Color == x->fChildren[c]->fColor);
812 // replace x with c1, making c1 black, preserves all red-black tree
813 // props.
814 Node* c1 = x->fChildren[c];
815 if (x == fFirst) {
816 SkASSERT(c == kRight_Child);
817 fFirst = c1;
818 while (NULL != fFirst->fChildren[kLeft_Child]) {
819 fFirst = fFirst->fChildren[kLeft_Child];
820 }
821 SkASSERT(fFirst == SuccessorNode(x));
822 } else if (x == fLast) {
823 SkASSERT(c == kLeft_Child);
824 fLast = c1;
825 while (NULL != fLast->fChildren[kRight_Child]) {
826 fLast = fLast->fChildren[kRight_Child];
827 }
828 SkASSERT(fLast == PredecessorNode(x));
829 }
830 c1->fParent = p;
831 p->fChildren[pc] = c1;
832 c1->fColor = kBlack_Color;
833 delete x;
834 validate();
835 }
836 validate();
837 }
838
839 template <typename T, typename C>
840 void GrRedBlackTree<T,C>::RecursiveDelete(Node* x) {
841 if (NULL != x) {
842 RecursiveDelete(x->fChildren[kLeft_Child]);
843 RecursiveDelete(x->fChildren[kRight_Child]);
844 delete x;
845 }
846 }
847
848 #ifdef SK_DEBUG
849 template <typename T, typename C>
850 void GrRedBlackTree<T,C>::validate() const {
851 if (fCount) {
852 SkASSERT(NULL == fRoot->fParent);
853 SkASSERT(NULL != fFirst);
854 SkASSERT(NULL != fLast);
855
856 SkASSERT(kBlack_Color == fRoot->fColor);
857 if (1 == fCount) {
858 SkASSERT(fFirst == fRoot);
859 SkASSERT(fLast == fRoot);
860 SkASSERT(0 == fRoot->fChildren[kLeft_Child]);
861 SkASSERT(0 == fRoot->fChildren[kRight_Child]);
862 }
863 } else {
864 SkASSERT(NULL == fRoot);
865 SkASSERT(NULL == fFirst);
866 SkASSERT(NULL == fLast);
867 }
868 #if DEEP_VALIDATE
869 int bh;
870 int count = checkNode(fRoot, &bh);
871 SkASSERT(count == fCount);
872 #endif
873 }
874
875 template <typename T, typename C>
876 int GrRedBlackTree<T,C>::checkNode(Node* n, int* bh) const {
877 if (NULL != n) {
878 SkASSERT(validateChildRelations(n, false));
879 if (kBlack_Color == n->fColor) {
880 *bh += 1;
881 }
882 SkASSERT(!fComp(n->fItem, fFirst->fItem));
883 SkASSERT(!fComp(fLast->fItem, n->fItem));
884 int leftBh = *bh;
885 int rightBh = *bh;
886 int cl = checkNode(n->fChildren[kLeft_Child], &leftBh);
887 int cr = checkNode(n->fChildren[kRight_Child], &rightBh);
888 SkASSERT(leftBh == rightBh);
889 *bh = leftBh;
890 return 1 + cl + cr;
891 }
892 return 0;
893 }
894
895 template <typename T, typename C>
896 bool GrRedBlackTree<T,C>::validateChildRelations(const Node* n,
897 bool allowRedRed) const {
898 if (NULL != n) {
899 if (NULL != n->fChildren[kLeft_Child] ||
900 NULL != n->fChildren[kRight_Child]) {
901 if (n->fChildren[kLeft_Child] == n->fChildren[kRight_Child]) {
902 return validateChildRelationsFailed();
903 }
904 if (n->fChildren[kLeft_Child] == n->fParent &&
905 NULL != n->fParent) {
906 return validateChildRelationsFailed();
907 }
908 if (n->fChildren[kRight_Child] == n->fParent &&
909 NULL != n->fParent) {
910 return validateChildRelationsFailed();
911 }
912 if (NULL != n->fChildren[kLeft_Child]) {
913 if (!allowRedRed &&
914 kRed_Color == n->fChildren[kLeft_Child]->fColor &&
915 kRed_Color == n->fColor) {
916 return validateChildRelationsFailed();
917 }
918 if (n->fChildren[kLeft_Child]->fParent != n) {
919 return validateChildRelationsFailed();
920 }
921 if (!(fComp(n->fChildren[kLeft_Child]->fItem, n->fItem) ||
922 (!fComp(n->fChildren[kLeft_Child]->fItem, n->fItem) &&
923 !fComp(n->fItem, n->fChildren[kLeft_Child]->fItem)))) {
924 return validateChildRelationsFailed();
925 }
926 }
927 if (NULL != n->fChildren[kRight_Child]) {
928 if (!allowRedRed &&
929 kRed_Color == n->fChildren[kRight_Child]->fColor &&
930 kRed_Color == n->fColor) {
931 return validateChildRelationsFailed();
932 }
933 if (n->fChildren[kRight_Child]->fParent != n) {
934 return validateChildRelationsFailed();
935 }
936 if (!(fComp(n->fItem, n->fChildren[kRight_Child]->fItem) ||
937 (!fComp(n->fChildren[kRight_Child]->fItem, n->fItem) &&
938 !fComp(n->fItem, n->fChildren[kRight_Child]->fItem)))) {
939 return validateChildRelationsFailed();
940 }
941 }
942 }
943 }
944 return true;
945 }
946 #endif
947
948 #endif

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