1/*
2 * Copyright (C) 2011-2019 Apple Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
17 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
18 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
19 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
20 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
21 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
23 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#pragma once
27
28#include <wtf/Assertions.h>
29
30#include <limits>
31#include <stdint.h>
32#include <type_traits>
33
34/* Checked<T>
35 *
36 * This class provides a mechanism to perform overflow-safe integer arithmetic
37 * without having to manually ensure that you have all the required bounds checks
38 * directly in your code.
39 *
40 * There are two modes of operation:
41 * - The default is Checked<T, CrashOnOverflow>, and crashes at the point
42 * and overflow has occurred.
43 * - The alternative is Checked<T, RecordOverflow>, which uses an additional
44 * byte of storage to track whether an overflow has occurred, subsequent
45 * unchecked operations will crash if an overflow has occured
46 *
47 * It is possible to provide a custom overflow handler, in which case you need
48 * to support these functions:
49 * - void overflowed();
50 * This function is called when an operation has produced an overflow.
51 * - bool hasOverflowed();
52 * This function must return true if overflowed() has been called on an
53 * instance and false if it has not.
54 * - void clearOverflow();
55 * Used to reset overflow tracking when a value is being overwritten with
56 * a new value.
57 *
58 * Checked<T> works for all integer types, with the following caveats:
59 * - Mixing signedness of operands is only supported for types narrower than
60 * 64bits.
61 * - It does have a performance impact, so tight loops may want to be careful
62 * when using it.
63 *
64 */
65
66namespace WTF {
67
68enum class CheckedState {
69 DidOverflow,
70 DidNotOverflow
71};
72
73class AssertNoOverflow {
74public:
75 static NO_RETURN_DUE_TO_ASSERT void overflowed()
76 {
77 ASSERT_NOT_REACHED();
78 }
79
80 void clearOverflow() { }
81
82 static NO_RETURN_DUE_TO_CRASH void crash()
83 {
84 CRASH();
85 }
86
87public:
88 constexpr bool hasOverflowed() const { return false; }
89};
90
91class ConditionalCrashOnOverflow {
92public:
93 void overflowed()
94 {
95 m_overflowed = true;
96 if (m_shouldCrashOnOverflow)
97 crash();
98 }
99
100 bool shouldCrashOnOverflow() const { return m_shouldCrashOnOverflow; }
101 void setShouldCrashOnOverflow(bool value) { m_shouldCrashOnOverflow = value; }
102
103 bool hasOverflowed() const { return m_overflowed; }
104 void clearOverflow() { m_overflowed = false; }
105
106 static NO_RETURN_DUE_TO_CRASH void crash()
107 {
108 CRASH();
109 }
110
111private:
112 bool m_overflowed { false };
113 bool m_shouldCrashOnOverflow { true };
114};
115
116class CrashOnOverflow {
117public:
118 static NO_RETURN_DUE_TO_CRASH void overflowed()
119 {
120 crash();
121 }
122
123 void clearOverflow() { }
124
125 static NO_RETURN_DUE_TO_CRASH void crash()
126 {
127 CRASH();
128 }
129
130public:
131 bool hasOverflowed() const { return false; }
132};
133
134class RecordOverflow {
135protected:
136 RecordOverflow()
137 : m_overflowed(false)
138 {
139 }
140
141 void clearOverflow()
142 {
143 m_overflowed = false;
144 }
145
146 static NO_RETURN_DUE_TO_CRASH void crash()
147 {
148 CRASH();
149 }
150
151public:
152 bool hasOverflowed() const { return m_overflowed; }
153 void overflowed() { m_overflowed = true; }
154
155private:
156 unsigned char m_overflowed;
157};
158
159template <typename T, class OverflowHandler = CrashOnOverflow> class Checked;
160template <typename T> struct RemoveChecked;
161template <typename T> struct RemoveChecked<Checked<T>>;
162
163template <typename Target, typename Source, bool isTargetBigger = sizeof(Target) >= sizeof(Source), bool targetSigned = std::numeric_limits<Target>::is_signed, bool sourceSigned = std::numeric_limits<Source>::is_signed> struct BoundsChecker;
164template <typename Target, typename Source> struct BoundsChecker<Target, Source, false, false, false> {
165 static bool inBounds(Source value)
166 {
167 // Same signedness so implicit type conversion will always increase precision to widest type.
168 return value <= std::numeric_limits<Target>::max();
169 }
170};
171template <typename Target, typename Source> struct BoundsChecker<Target, Source, false, true, true> {
172 static bool inBounds(Source value)
173 {
174 // Same signedness so implicit type conversion will always increase precision to widest type.
175 return std::numeric_limits<Target>::min() <= value && value <= std::numeric_limits<Target>::max();
176 }
177};
178
179template <typename Target, typename Source> struct BoundsChecker<Target, Source, false, false, true> {
180 static bool inBounds(Source value)
181 {
182 // When converting value to unsigned Source, value will become a big value if value is negative.
183 // Casted value will become bigger than Target::max as Source is bigger than Target.
184 return static_cast<typename std::make_unsigned<Source>::type>(value) <= std::numeric_limits<Target>::max();
185 }
186};
187
188template <typename Target, typename Source> struct BoundsChecker<Target, Source, false, true, false> {
189 static bool inBounds(Source value)
190 {
191 // The unsigned Source type has greater precision than the target so max(Target) -> Source will widen.
192 return value <= static_cast<Source>(std::numeric_limits<Target>::max());
193 }
194};
195
196template <typename Target, typename Source> struct BoundsChecker<Target, Source, true, false, false> {
197 static bool inBounds(Source)
198 {
199 // Same sign, greater or same precision.
200 return true;
201 }
202};
203
204template <typename Target, typename Source> struct BoundsChecker<Target, Source, true, true, true> {
205 static bool inBounds(Source)
206 {
207 // Same sign, greater or same precision.
208 return true;
209 }
210};
211
212template <typename Target, typename Source> struct BoundsChecker<Target, Source, true, true, false> {
213 static bool inBounds(Source value)
214 {
215 // Target is signed with greater or same precision. If strictly greater, it is always safe.
216 if (sizeof(Target) > sizeof(Source))
217 return true;
218 return value <= static_cast<Source>(std::numeric_limits<Target>::max());
219 }
220};
221
222template <typename Target, typename Source> struct BoundsChecker<Target, Source, true, false, true> {
223 static bool inBounds(Source value)
224 {
225 // Target is unsigned with greater precision.
226 return value >= 0;
227 }
228};
229
230template <typename Target, typename Source> static inline bool isInBounds(Source value)
231{
232 return BoundsChecker<Target, Source>::inBounds(value);
233}
234
235template <typename Target, typename Source> static inline bool convertSafely(Source input, Target& output)
236{
237 if (!isInBounds<Target>(input))
238 return false;
239 output = static_cast<Target>(input);
240 return true;
241}
242
243template <typename T> struct RemoveChecked {
244 typedef T CleanType;
245 static const CleanType DefaultValue = 0;
246};
247
248template <typename T> struct RemoveChecked<Checked<T, ConditionalCrashOnOverflow>> {
249 using CleanType = typename RemoveChecked<T>::CleanType;
250 static const CleanType DefaultValue = 0;
251};
252
253template <typename T> struct RemoveChecked<Checked<T, CrashOnOverflow>> {
254 typedef typename RemoveChecked<T>::CleanType CleanType;
255 static const CleanType DefaultValue = 0;
256};
257
258template <typename T> struct RemoveChecked<Checked<T, RecordOverflow>> {
259 typedef typename RemoveChecked<T>::CleanType CleanType;
260 static const CleanType DefaultValue = 0;
261};
262
263// The ResultBase and SignednessSelector are used to workaround typeof not being
264// available in MSVC
265template <typename U, typename V, bool uIsBigger = (sizeof(U) > sizeof(V)), bool sameSize = (sizeof(U) == sizeof(V))> struct ResultBase;
266template <typename U, typename V> struct ResultBase<U, V, true, false> {
267 typedef U ResultType;
268};
269
270template <typename U, typename V> struct ResultBase<U, V, false, false> {
271 typedef V ResultType;
272};
273
274template <typename U> struct ResultBase<U, U, false, true> {
275 typedef U ResultType;
276};
277
278template <typename U, typename V, bool uIsSigned = std::numeric_limits<U>::is_signed, bool vIsSigned = std::numeric_limits<V>::is_signed> struct SignednessSelector;
279template <typename U, typename V> struct SignednessSelector<U, V, true, true> {
280 typedef U ResultType;
281};
282
283template <typename U, typename V> struct SignednessSelector<U, V, false, false> {
284 typedef U ResultType;
285};
286
287template <typename U, typename V> struct SignednessSelector<U, V, true, false> {
288 typedef V ResultType;
289};
290
291template <typename U, typename V> struct SignednessSelector<U, V, false, true> {
292 typedef U ResultType;
293};
294
295template <typename U, typename V> struct ResultBase<U, V, false, true> {
296 typedef typename SignednessSelector<U, V>::ResultType ResultType;
297};
298
299template <typename U, typename V> struct Result : ResultBase<typename RemoveChecked<U>::CleanType, typename RemoveChecked<V>::CleanType> {
300};
301
302template <typename LHS, typename RHS, typename ResultType = typename Result<LHS, RHS>::ResultType,
303 bool lhsSigned = std::numeric_limits<LHS>::is_signed, bool rhsSigned = std::numeric_limits<RHS>::is_signed> struct ArithmeticOperations;
304
305template <typename LHS, typename RHS, typename ResultType> struct ArithmeticOperations<LHS, RHS, ResultType, true, true> {
306 // LHS and RHS are signed types
307
308 // Helper function
309 static inline bool signsMatch(LHS lhs, RHS rhs)
310 {
311 return (lhs ^ rhs) >= 0;
312 }
313
314 static inline bool add(LHS lhs, RHS rhs, ResultType& result) WARN_UNUSED_RETURN
315 {
316#if COMPILER(GCC_COMPATIBLE)
317 ResultType temp;
318 if (__builtin_add_overflow(lhs, rhs, &temp))
319 return false;
320 result = temp;
321 return true;
322#else
323 if (signsMatch(lhs, rhs)) {
324 if (lhs >= 0) {
325 if ((std::numeric_limits<ResultType>::max() - rhs) < lhs)
326 return false;
327 } else {
328 ResultType temp = lhs - std::numeric_limits<ResultType>::min();
329 if (rhs < -temp)
330 return false;
331 }
332 } // if the signs do not match this operation can't overflow
333 result = lhs + rhs;
334 return true;
335#endif
336 }
337
338 static inline bool sub(LHS lhs, RHS rhs, ResultType& result) WARN_UNUSED_RETURN
339 {
340#if COMPILER(GCC_COMPATIBLE)
341 ResultType temp;
342 if (__builtin_sub_overflow(lhs, rhs, &temp))
343 return false;
344 result = temp;
345 return true;
346#else
347 if (!signsMatch(lhs, rhs)) {
348 if (lhs >= 0) {
349 if (lhs > std::numeric_limits<ResultType>::max() + rhs)
350 return false;
351 } else {
352 if (rhs > std::numeric_limits<ResultType>::max() + lhs)
353 return false;
354 }
355 } // if the signs match this operation can't overflow
356 result = lhs - rhs;
357 return true;
358#endif
359 }
360
361 static inline bool multiply(LHS lhs, RHS rhs, ResultType& result) WARN_UNUSED_RETURN
362 {
363#if COMPILER(GCC_COMPATIBLE)
364 ResultType temp;
365 if (__builtin_mul_overflow(lhs, rhs, &temp))
366 return false;
367 result = temp;
368 return true;
369#else
370 if (signsMatch(lhs, rhs)) {
371 if (lhs >= 0) {
372 if (lhs && (std::numeric_limits<ResultType>::max() / lhs) < rhs)
373 return false;
374 } else {
375 if (static_cast<ResultType>(lhs) == std::numeric_limits<ResultType>::min() || static_cast<ResultType>(rhs) == std::numeric_limits<ResultType>::min())
376 return false;
377 if ((std::numeric_limits<ResultType>::max() / -lhs) < -rhs)
378 return false;
379 }
380 } else {
381 if (lhs < 0) {
382 if (rhs && lhs < (std::numeric_limits<ResultType>::min() / rhs))
383 return false;
384 } else {
385 if (lhs && rhs < (std::numeric_limits<ResultType>::min() / lhs))
386 return false;
387 }
388 }
389 result = lhs * rhs;
390 return true;
391#endif
392 }
393
394 static inline bool equals(LHS lhs, RHS rhs) { return lhs == rhs; }
395
396};
397
398template <typename LHS, typename RHS, typename ResultType> struct ArithmeticOperations<LHS, RHS, ResultType, false, false> {
399 // LHS and RHS are unsigned types so bounds checks are nice and easy
400 static inline bool add(LHS lhs, RHS rhs, ResultType& result) WARN_UNUSED_RETURN
401 {
402#if COMPILER(GCC_COMPATIBLE)
403 ResultType temp;
404 if (__builtin_add_overflow(lhs, rhs, &temp))
405 return false;
406 result = temp;
407 return true;
408#else
409 ResultType temp = lhs + rhs;
410 if (temp < lhs)
411 return false;
412 result = temp;
413 return true;
414#endif
415 }
416
417 static inline bool sub(LHS lhs, RHS rhs, ResultType& result) WARN_UNUSED_RETURN
418 {
419#if COMPILER(GCC_COMPATIBLE)
420 ResultType temp;
421 if (__builtin_sub_overflow(lhs, rhs, &temp))
422 return false;
423 result = temp;
424 return true;
425#else
426 ResultType temp = lhs - rhs;
427 if (temp > lhs)
428 return false;
429 result = temp;
430 return true;
431#endif
432 }
433
434 static inline bool multiply(LHS lhs, RHS rhs, ResultType& result) WARN_UNUSED_RETURN
435 {
436#if COMPILER(GCC_COMPATIBLE)
437 ResultType temp;
438 if (__builtin_mul_overflow(lhs, rhs, &temp))
439 return false;
440 result = temp;
441 return true;
442#else
443 if (!lhs || !rhs) {
444 result = 0;
445 return true;
446 }
447 if (std::numeric_limits<ResultType>::max() / lhs < rhs)
448 return false;
449 result = lhs * rhs;
450 return true;
451#endif
452 }
453
454 static inline bool equals(LHS lhs, RHS rhs) { return lhs == rhs; }
455
456};
457
458template <typename ResultType> struct ArithmeticOperations<int, unsigned, ResultType, true, false> {
459 static inline bool add(int64_t lhs, int64_t rhs, ResultType& result)
460 {
461#if COMPILER(GCC_COMPATIBLE)
462 ResultType temp;
463 if (__builtin_add_overflow(lhs, rhs, &temp))
464 return false;
465 result = temp;
466 return true;
467#else
468 int64_t temp = lhs + rhs;
469 if (temp < std::numeric_limits<ResultType>::min())
470 return false;
471 if (temp > std::numeric_limits<ResultType>::max())
472 return false;
473 result = static_cast<ResultType>(temp);
474 return true;
475#endif
476 }
477
478 static inline bool sub(int64_t lhs, int64_t rhs, ResultType& result)
479 {
480#if COMPILER(GCC_COMPATIBLE)
481 ResultType temp;
482 if (__builtin_sub_overflow(lhs, rhs, &temp))
483 return false;
484 result = temp;
485 return true;
486#else
487 int64_t temp = lhs - rhs;
488 if (temp < std::numeric_limits<ResultType>::min())
489 return false;
490 if (temp > std::numeric_limits<ResultType>::max())
491 return false;
492 result = static_cast<ResultType>(temp);
493 return true;
494#endif
495 }
496
497 static inline bool multiply(int64_t lhs, int64_t rhs, ResultType& result)
498 {
499#if COMPILER(GCC_COMPATIBLE)
500 ResultType temp;
501 if (__builtin_mul_overflow(lhs, rhs, &temp))
502 return false;
503 result = temp;
504 return true;
505#else
506 int64_t temp = lhs * rhs;
507 if (temp < std::numeric_limits<ResultType>::min())
508 return false;
509 if (temp > std::numeric_limits<ResultType>::max())
510 return false;
511 result = static_cast<ResultType>(temp);
512 return true;
513#endif
514 }
515
516 static inline bool equals(int lhs, unsigned rhs)
517 {
518 return static_cast<int64_t>(lhs) == static_cast<int64_t>(rhs);
519 }
520};
521
522template <typename ResultType> struct ArithmeticOperations<unsigned, int, ResultType, false, true> {
523 static inline bool add(int64_t lhs, int64_t rhs, ResultType& result)
524 {
525 return ArithmeticOperations<int, unsigned, ResultType>::add(rhs, lhs, result);
526 }
527
528 static inline bool sub(int64_t lhs, int64_t rhs, ResultType& result)
529 {
530 return ArithmeticOperations<int, unsigned, ResultType>::sub(lhs, rhs, result);
531 }
532
533 static inline bool multiply(int64_t lhs, int64_t rhs, ResultType& result)
534 {
535 return ArithmeticOperations<int, unsigned, ResultType>::multiply(lhs, rhs, result);
536 }
537
538 static inline bool equals(unsigned lhs, int rhs)
539 {
540 return ArithmeticOperations<int, unsigned, ResultType>::equals(rhs, lhs);
541 }
542};
543
544template <class OverflowHandler, typename = typename std::enable_if<!std::is_scalar<OverflowHandler>::value>::type>
545inline constexpr bool observesOverflow() { return true; }
546
547template <>
548inline constexpr bool observesOverflow<AssertNoOverflow>() { return !ASSERT_DISABLED; }
549
550template <typename U, typename V, typename R> static inline bool safeAdd(U lhs, V rhs, R& result)
551{
552 return ArithmeticOperations<U, V, R>::add(lhs, rhs, result);
553 return true;
554}
555
556template <class OverflowHandler, typename U, typename V, typename R, typename = typename std::enable_if<!std::is_scalar<OverflowHandler>::value>::type>
557static inline bool safeAdd(U lhs, V rhs, R& result)
558{
559 if (observesOverflow<OverflowHandler>())
560 return safeAdd(lhs, rhs, result);
561 result = lhs + rhs;
562 return true;
563}
564
565template <typename U, typename V, typename R> static inline bool safeSub(U lhs, V rhs, R& result)
566{
567 return ArithmeticOperations<U, V, R>::sub(lhs, rhs, result);
568}
569
570template <class OverflowHandler, typename U, typename V, typename R, typename = typename std::enable_if<!std::is_scalar<OverflowHandler>::value>::type>
571static inline bool safeSub(U lhs, V rhs, R& result)
572{
573 if (observesOverflow<OverflowHandler>())
574 return safeSub(lhs, rhs, result);
575 result = lhs - rhs;
576 return true;
577}
578
579template <typename U, typename V, typename R> static inline bool safeMultiply(U lhs, V rhs, R& result)
580{
581 return ArithmeticOperations<U, V, R>::multiply(lhs, rhs, result);
582}
583
584template <class OverflowHandler, typename U, typename V, typename R, typename = typename std::enable_if<!std::is_scalar<OverflowHandler>::value>::type>
585static inline bool safeMultiply(U lhs, V rhs, R& result)
586{
587 if (observesOverflow<OverflowHandler>())
588 return safeMultiply(lhs, rhs, result);
589 result = lhs * rhs;
590 return true;
591}
592
593template <typename U, typename V> static inline bool safeEquals(U lhs, V rhs)
594{
595 return ArithmeticOperations<U, V>::equals(lhs, rhs);
596}
597
598enum ResultOverflowedTag { ResultOverflowed };
599
600template <typename T, class OverflowHandler> class Checked : public OverflowHandler {
601public:
602 template <typename _T, class _OverflowHandler> friend class Checked;
603 Checked()
604 : m_value(0)
605 {
606 }
607
608 Checked(ResultOverflowedTag)
609 : m_value(0)
610 {
611 this->overflowed();
612 }
613
614 Checked(const Checked& value)
615 {
616 if (value.hasOverflowed())
617 this->overflowed();
618 m_value = static_cast<T>(value.m_value);
619 }
620
621 template <typename U> Checked(U value)
622 {
623 if (!isInBounds<T>(value))
624 this->overflowed();
625 m_value = static_cast<T>(value);
626 }
627
628 template <typename V> Checked(const Checked<T, V>& rhs)
629 : m_value(rhs.m_value)
630 {
631 if (rhs.hasOverflowed())
632 this->overflowed();
633 }
634
635 template <typename U> Checked(const Checked<U, OverflowHandler>& rhs)
636 : OverflowHandler(rhs)
637 {
638 if (!isInBounds<T>(rhs.m_value))
639 this->overflowed();
640 m_value = static_cast<T>(rhs.m_value);
641 }
642
643 template <typename U, typename V> Checked(const Checked<U, V>& rhs)
644 {
645 if (rhs.hasOverflowed())
646 this->overflowed();
647 if (!isInBounds<T>(rhs.m_value))
648 this->overflowed();
649 m_value = static_cast<T>(rhs.m_value);
650 }
651
652 const Checked& operator=(Checked rhs)
653 {
654 this->clearOverflow();
655 if (rhs.hasOverflowed())
656 this->overflowed();
657 m_value = static_cast<T>(rhs.m_value);
658 return *this;
659 }
660
661 template <typename U> const Checked& operator=(U value)
662 {
663 return *this = Checked(value);
664 }
665
666 template <typename U, typename V> const Checked& operator=(const Checked<U, V>& rhs)
667 {
668 return *this = Checked(rhs);
669 }
670
671 // prefix
672 const Checked& operator++()
673 {
674 if (m_value == std::numeric_limits<T>::max())
675 this->overflowed();
676 m_value++;
677 return *this;
678 }
679
680 const Checked& operator--()
681 {
682 if (m_value == std::numeric_limits<T>::min())
683 this->overflowed();
684 m_value--;
685 return *this;
686 }
687
688 // postfix operators
689 const Checked operator++(int)
690 {
691 if (m_value == std::numeric_limits<T>::max())
692 this->overflowed();
693 return Checked(m_value++);
694 }
695
696 const Checked operator--(int)
697 {
698 if (m_value == std::numeric_limits<T>::min())
699 this->overflowed();
700 return Checked(m_value--);
701 }
702
703 // Boolean operators
704 bool operator!() const
705 {
706 if (this->hasOverflowed())
707 this->crash();
708 return !m_value;
709 }
710
711 explicit operator bool() const
712 {
713 if (this->hasOverflowed())
714 this->crash();
715 return m_value;
716 }
717
718 // Value accessors. unsafeGet() will crash if there's been an overflow.
719 template<typename U = T>
720 U unsafeGet() const
721 {
722 if (this->hasOverflowed())
723 this->crash();
724 return static_cast<U>(m_value);
725 }
726
727 inline CheckedState safeGet(T& value) const WARN_UNUSED_RETURN
728 {
729 value = m_value;
730 if (this->hasOverflowed())
731 return CheckedState::DidOverflow;
732 return CheckedState::DidNotOverflow;
733 }
734
735 // Mutating assignment
736 template <typename U> const Checked operator+=(U rhs)
737 {
738 if (!safeAdd<OverflowHandler>(m_value, rhs, m_value))
739 this->overflowed();
740 return *this;
741 }
742
743 template <typename U> const Checked operator-=(U rhs)
744 {
745 if (!safeSub<OverflowHandler>(m_value, rhs, m_value))
746 this->overflowed();
747 return *this;
748 }
749
750 template <typename U> const Checked operator*=(U rhs)
751 {
752 if (!safeMultiply<OverflowHandler>(m_value, rhs, m_value))
753 this->overflowed();
754 return *this;
755 }
756
757 const Checked operator*=(double rhs)
758 {
759 double result = rhs * m_value;
760 // Handle +/- infinity and NaN
761 if (!(std::numeric_limits<T>::min() <= result && std::numeric_limits<T>::max() >= result))
762 this->overflowed();
763 m_value = (T)result;
764 return *this;
765 }
766
767 const Checked operator*=(float rhs)
768 {
769 return *this *= (double)rhs;
770 }
771
772 template <typename U, typename V> const Checked operator+=(Checked<U, V> rhs)
773 {
774 if (rhs.hasOverflowed())
775 this->overflowed();
776 return *this += rhs.m_value;
777 }
778
779 template <typename U, typename V> const Checked operator-=(Checked<U, V> rhs)
780 {
781 if (rhs.hasOverflowed())
782 this->overflowed();
783 return *this -= rhs.m_value;
784 }
785
786 template <typename U, typename V> const Checked operator*=(Checked<U, V> rhs)
787 {
788 if (rhs.hasOverflowed())
789 this->overflowed();
790 return *this *= rhs.m_value;
791 }
792
793 // Equality comparisons
794 template <typename V> bool operator==(Checked<T, V> rhs)
795 {
796 return unsafeGet() == rhs.unsafeGet();
797 }
798
799 template <typename U> bool operator==(U rhs)
800 {
801 if (this->hasOverflowed())
802 this->crash();
803 return safeEquals(m_value, rhs);
804 }
805
806 template <typename U, typename V> const Checked operator==(Checked<U, V> rhs)
807 {
808 return unsafeGet() == Checked(rhs.unsafeGet());
809 }
810
811 template <typename U> bool operator!=(U rhs)
812 {
813 return !(*this == rhs);
814 }
815
816 // Other comparisons
817 template <typename V> bool operator<(Checked<T, V> rhs) const
818 {
819 return unsafeGet() < rhs.unsafeGet();
820 }
821
822 bool operator<(T rhs) const
823 {
824 return unsafeGet() < rhs;
825 }
826
827 template <typename V> bool operator<=(Checked<T, V> rhs) const
828 {
829 return unsafeGet() <= rhs.unsafeGet();
830 }
831
832 bool operator<=(T rhs) const
833 {
834 return unsafeGet() <= rhs;
835 }
836
837 template <typename V> bool operator>(Checked<T, V> rhs) const
838 {
839 return unsafeGet() > rhs.unsafeGet();
840 }
841
842 bool operator>(T rhs) const
843 {
844 return unsafeGet() > rhs;
845 }
846
847 template <typename V> bool operator>=(Checked<T, V> rhs) const
848 {
849 return unsafeGet() >= rhs.unsafeGet();
850 }
851
852 bool operator>=(T rhs) const
853 {
854 return unsafeGet() >= rhs;
855 }
856
857private:
858 // Disallow implicit conversion of floating point to integer types
859 Checked(float);
860 Checked(double);
861 void operator=(float);
862 void operator=(double);
863 void operator+=(float);
864 void operator+=(double);
865 void operator-=(float);
866 void operator-=(double);
867 T m_value;
868};
869
870template <typename U, typename V, typename OverflowHandler> static inline Checked<typename Result<U, V>::ResultType, OverflowHandler> operator+(Checked<U, OverflowHandler> lhs, Checked<V, OverflowHandler> rhs)
871{
872 U x = 0;
873 V y = 0;
874 bool overflowed = lhs.safeGet(x) == CheckedState::DidOverflow || rhs.safeGet(y) == CheckedState::DidOverflow;
875 typename Result<U, V>::ResultType result = 0;
876 overflowed |= !safeAdd<OverflowHandler>(x, y, result);
877 if (overflowed)
878 return ResultOverflowed;
879 return result;
880}
881
882template <typename U, typename V, typename OverflowHandler> static inline Checked<typename Result<U, V>::ResultType, OverflowHandler> operator-(Checked<U, OverflowHandler> lhs, Checked<V, OverflowHandler> rhs)
883{
884 U x = 0;
885 V y = 0;
886 bool overflowed = lhs.safeGet(x) == CheckedState::DidOverflow || rhs.safeGet(y) == CheckedState::DidOverflow;
887 typename Result<U, V>::ResultType result = 0;
888 overflowed |= !safeSub<OverflowHandler>(x, y, result);
889 if (overflowed)
890 return ResultOverflowed;
891 return result;
892}
893
894template <typename U, typename V, typename OverflowHandler> static inline Checked<typename Result<U, V>::ResultType, OverflowHandler> operator*(Checked<U, OverflowHandler> lhs, Checked<V, OverflowHandler> rhs)
895{
896 U x = 0;
897 V y = 0;
898 bool overflowed = lhs.safeGet(x) == CheckedState::DidOverflow || rhs.safeGet(y) == CheckedState::DidOverflow;
899 typename Result<U, V>::ResultType result = 0;
900 overflowed |= !safeMultiply<OverflowHandler>(x, y, result);
901 if (overflowed)
902 return ResultOverflowed;
903 return result;
904}
905
906template <typename U, typename V, typename OverflowHandler> static inline Checked<typename Result<U, V>::ResultType, OverflowHandler> operator+(Checked<U, OverflowHandler> lhs, V rhs)
907{
908 return lhs + Checked<V, OverflowHandler>(rhs);
909}
910
911template <typename U, typename V, typename OverflowHandler> static inline Checked<typename Result<U, V>::ResultType, OverflowHandler> operator-(Checked<U, OverflowHandler> lhs, V rhs)
912{
913 return lhs - Checked<V, OverflowHandler>(rhs);
914}
915
916template <typename U, typename V, typename OverflowHandler> static inline Checked<typename Result<U, V>::ResultType, OverflowHandler> operator*(Checked<U, OverflowHandler> lhs, V rhs)
917{
918 return lhs * Checked<V, OverflowHandler>(rhs);
919}
920
921template <typename U, typename V, typename OverflowHandler> static inline Checked<typename Result<U, V>::ResultType, OverflowHandler> operator+(U lhs, Checked<V, OverflowHandler> rhs)
922{
923 return Checked<U, OverflowHandler>(lhs) + rhs;
924}
925
926template <typename U, typename V, typename OverflowHandler> static inline Checked<typename Result<U, V>::ResultType, OverflowHandler> operator-(U lhs, Checked<V, OverflowHandler> rhs)
927{
928 return Checked<U, OverflowHandler>(lhs) - rhs;
929}
930
931template <typename U, typename V, typename OverflowHandler> static inline Checked<typename Result<U, V>::ResultType, OverflowHandler> operator*(U lhs, Checked<V, OverflowHandler> rhs)
932{
933 return Checked<U, OverflowHandler>(lhs) * rhs;
934}
935
936// Convenience typedefs.
937typedef Checked<int8_t, RecordOverflow> CheckedInt8;
938typedef Checked<uint8_t, RecordOverflow> CheckedUint8;
939typedef Checked<int16_t, RecordOverflow> CheckedInt16;
940typedef Checked<uint16_t, RecordOverflow> CheckedUint16;
941typedef Checked<int32_t, RecordOverflow> CheckedInt32;
942typedef Checked<uint32_t, RecordOverflow> CheckedUint32;
943typedef Checked<int64_t, RecordOverflow> CheckedInt64;
944typedef Checked<uint64_t, RecordOverflow> CheckedUint64;
945typedef Checked<size_t, RecordOverflow> CheckedSize;
946
947template<typename T, typename U>
948Checked<T, RecordOverflow> checkedSum(U value)
949{
950 return Checked<T, RecordOverflow>(value);
951}
952template<typename T, typename U, typename... Args>
953Checked<T, RecordOverflow> checkedSum(U value, Args... args)
954{
955 return Checked<T, RecordOverflow>(value) + checkedSum<T>(args...);
956}
957
958// Sometimes, you just want to check if some math would overflow - the code to do the math is
959// already in place, and you want to guard it.
960
961template<typename T, typename... Args> bool sumOverflows(Args... args)
962{
963 return checkedSum<T>(args...).hasOverflowed();
964}
965
966template<typename T, typename U> bool differenceOverflows(U left, U right)
967{
968 return (Checked<T, RecordOverflow>(left) - Checked<T, RecordOverflow>(right)).hasOverflowed();
969}
970
971template<typename T, typename U>
972Checked<T, RecordOverflow> checkedProduct(U value)
973{
974 return Checked<T, RecordOverflow>(value);
975}
976template<typename T, typename U, typename... Args>
977Checked<T, RecordOverflow> checkedProduct(U value, Args... args)
978{
979 return Checked<T, RecordOverflow>(value) * checkedProduct<T>(args...);
980}
981
982// Sometimes, you just want to check if some math would overflow - the code to do the math is
983// already in place, and you want to guard it.
984
985template<typename T, typename... Args> bool productOverflows(Args... args)
986{
987 return checkedProduct<T>(args...).hasOverflowed();
988}
989
990}
991
992using WTF::AssertNoOverflow;
993using WTF::Checked;
994using WTF::CheckedState;
995using WTF::CheckedInt8;
996using WTF::CheckedUint8;
997using WTF::CheckedInt16;
998using WTF::CheckedUint16;
999using WTF::CheckedInt32;
1000using WTF::CheckedUint32;
1001using WTF::CheckedInt64;
1002using WTF::CheckedUint64;
1003using WTF::CheckedSize;
1004using WTF::ConditionalCrashOnOverflow;
1005using WTF::CrashOnOverflow;
1006using WTF::RecordOverflow;
1007using WTF::checkedSum;
1008using WTF::differenceOverflows;
1009using WTF::productOverflows;
1010using WTF::sumOverflows;
1011