mirror of
https://gitlab.winehq.org/wine/wine-gecko.git
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129 lines
3.6 KiB
C++
129 lines
3.6 KiB
C++
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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/* Cast operations to supplement the built-in casting operations. */
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#ifndef mozilla_Casting_h_
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#define mozilla_Casting_h_
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#include "mozilla/Assertions.h"
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#include "mozilla/TypeTraits.h"
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#include <limits.h>
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namespace mozilla {
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namespace detail {
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enum ToSignedness { ToIsSigned, ToIsUnsigned };
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enum FromSignedness { FromIsSigned, FromIsUnsigned };
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template<typename From,
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typename To,
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FromSignedness = IsSigned<From>::value ? FromIsSigned : FromIsUnsigned,
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ToSignedness = IsSigned<To>::value ? ToIsSigned : ToIsUnsigned>
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struct BoundsCheckImpl;
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// Implicit conversions on operands to binary operations make this all a bit
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// hard to verify. Attempt to ease the pain below by *only* comparing values
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// that are obviously the same type (and will undergo no further conversions),
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// even when it's not strictly necessary, for explicitness.
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template<typename From, typename To>
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struct BoundsCheckImpl<From, To, FromIsUnsigned, ToIsUnsigned>
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{
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public:
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static bool check(const From from) {
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typedef typename Conditional<sizeof(From) >= sizeof(To), From, To>::Type
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LargerType;
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return LargerType(from) <= LargerType(To(-1));
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}
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};
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template<typename From, typename To>
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struct BoundsCheckImpl<From, To, FromIsSigned, ToIsUnsigned>
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{
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public:
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static bool check(const From from) {
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if (from < 0)
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return false;
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if (sizeof(To) >= sizeof(From))
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return To(from) <= To(-1);
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return from <= From(To(-1));
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}
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};
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template<typename From, typename To>
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struct BoundsCheckImpl<From, To, FromIsUnsigned, ToIsSigned>
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{
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public:
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static bool check(const From from) {
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if (sizeof(From) < sizeof(To))
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return true;
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const To MaxValue = To((1ULL << (CHAR_BIT * sizeof(To) - 1)) - 1);
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return from <= From(MaxValue);
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}
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};
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template<typename From, typename To>
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struct BoundsCheckImpl<From, To, FromIsSigned, ToIsSigned>
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{
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public:
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static bool check(const From from) {
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typedef typename Conditional<sizeof(To) >= sizeof(From), To, From>::Type
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LargerType;
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const To MaxValue = To((1ULL << (CHAR_BIT * sizeof(To) - 1)) - 1);
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const To MinValue = -MaxValue - To(1);
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return LargerType(MinValue) <= LargerType(from) &&
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LargerType(from) <= LargerType(MaxValue);
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}
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};
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template<typename From, typename To,
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bool TypesAreIntegral = IsIntegral<From>::value && IsIntegral<To>::value>
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class BoundsChecker;
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template<typename From>
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class BoundsChecker<From, From, true>
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{
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public:
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static bool check(const From from) { return true; }
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};
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template<typename From, typename To>
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class BoundsChecker<From, To, true>
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{
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public:
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static bool check(const From from) {
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return BoundsCheckImpl<From, To>::check(from);
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}
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};
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template<typename From, typename To>
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inline bool
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IsInBounds(const From from)
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{
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return BoundsChecker<From, To>::check(from);
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}
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} // namespace detail
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/**
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* Cast a value of integral type |From| to a value of integral type |To|,
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* asserting that the cast will be a safe cast per C++ (that is, that |to| is in
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* the range of values permitted for the type |From|).
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*/
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template<typename To, typename From>
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inline To
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SafeCast(const From from)
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{
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MOZ_ASSERT((detail::IsInBounds<From, To>(from)));
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return static_cast<To>(from);
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}
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} // namespace mozilla
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#endif /* mozilla_Casting_h_ */
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