| // Copyright 2014 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef BASE_NUMERICS_SAFE_CONVERSIONS_IMPL_H_ |
| #define BASE_NUMERICS_SAFE_CONVERSIONS_IMPL_H_ |
| |
| #include <stdint.h> |
| |
| #include <limits> |
| #include <type_traits> |
| |
| #if defined(__GNUC__) || defined(__clang__) |
| #define BASE_NUMERICS_LIKELY(x) __builtin_expect(!!(x), 1) |
| #define BASE_NUMERICS_UNLIKELY(x) __builtin_expect(!!(x), 0) |
| #else |
| #define BASE_NUMERICS_LIKELY(x) (x) |
| #define BASE_NUMERICS_UNLIKELY(x) (x) |
| #endif |
| |
| namespace base { |
| namespace internal { |
| |
| // The std library doesn't provide a binary max_exponent for integers, however |
| // we can compute an analog using std::numeric_limits<>::digits. |
| template <typename NumericType> |
| struct MaxExponent { |
| static const int value = std::is_floating_point<NumericType>::value |
| ? std::numeric_limits<NumericType>::max_exponent |
| : std::numeric_limits<NumericType>::digits + 1; |
| }; |
| |
| // The number of bits (including the sign) in an integer. Eliminates sizeof |
| // hacks. |
| template <typename NumericType> |
| struct IntegerBitsPlusSign { |
| static const int value = std::numeric_limits<NumericType>::digits + |
| std::is_signed<NumericType>::value; |
| }; |
| |
| // Helper templates for integer manipulations. |
| |
| template <typename Integer> |
| struct PositionOfSignBit { |
| static const size_t value = IntegerBitsPlusSign<Integer>::value - 1; |
| }; |
| |
| // Determines if a numeric value is negative without throwing compiler |
| // warnings on: unsigned(value) < 0. |
| template <typename T, |
| typename std::enable_if<std::is_signed<T>::value>::type* = nullptr> |
| constexpr bool IsValueNegative(T value) { |
| static_assert(std::is_arithmetic<T>::value, "Argument must be numeric."); |
| return value < 0; |
| } |
| |
| template <typename T, |
| typename std::enable_if<!std::is_signed<T>::value>::type* = nullptr> |
| constexpr bool IsValueNegative(T) { |
| static_assert(std::is_arithmetic<T>::value, "Argument must be numeric."); |
| return false; |
| } |
| |
| // This performs a fast negation, returning a signed value. It works on unsigned |
| // arguments, but probably doesn't do what you want for any unsigned value |
| // larger than max / 2 + 1 (i.e. signed min cast to unsigned). |
| template <typename T> |
| constexpr typename std::make_signed<T>::type ConditionalNegate( |
| T x, |
| bool is_negative) { |
| static_assert(std::is_integral<T>::value, "Type must be integral"); |
| using SignedT = typename std::make_signed<T>::type; |
| using UnsignedT = typename std::make_unsigned<T>::type; |
| return static_cast<SignedT>( |
| (static_cast<UnsignedT>(x) ^ -SignedT(is_negative)) + is_negative); |
| } |
| |
| // This performs a safe, absolute value via unsigned overflow. |
| template <typename T> |
| constexpr typename std::make_unsigned<T>::type SafeUnsignedAbs(T value) { |
| static_assert(std::is_integral<T>::value, "Type must be integral"); |
| using UnsignedT = typename std::make_unsigned<T>::type; |
| return IsValueNegative(value) ? 0 - static_cast<UnsignedT>(value) |
| : static_cast<UnsignedT>(value); |
| } |
| |
| // This allows us to switch paths on known compile-time constants. |
| #if defined(__clang__) || defined(__GNUC__) |
| constexpr bool CanDetectCompileTimeConstant() { |
| return true; |
| } |
| template <typename T> |
| constexpr bool IsCompileTimeConstant(const T v) { |
| return __builtin_constant_p(v); |
| } |
| #else |
| constexpr bool CanDetectCompileTimeConstant() { |
| return false; |
| } |
| template <typename T> |
| constexpr bool IsCompileTimeConstant(const T) { |
| return false; |
| } |
| #endif |
| template <typename T> |
| constexpr bool MustTreatAsConstexpr(const T v) { |
| // Either we can't detect a compile-time constant, and must always use the |
| // constexpr path, or we know we have a compile-time constant. |
| return !CanDetectCompileTimeConstant() || IsCompileTimeConstant(v); |
| } |
| |
| // Forces a crash, like a CHECK(false). Used for numeric boundary errors. |
| // Also used in a constexpr template to trigger a compilation failure on |
| // an error condition. |
| struct CheckOnFailure { |
| template <typename T> |
| static T HandleFailure() { |
| #if defined(_MSC_VER) |
| __debugbreak(); |
| #elif defined(__GNUC__) || defined(__clang__) |
| __builtin_trap(); |
| #else |
| ((void)(*(volatile char*)0 = 0)); |
| #endif |
| return T(); |
| } |
| }; |
| |
| enum IntegerRepresentation { |
| INTEGER_REPRESENTATION_UNSIGNED, |
| INTEGER_REPRESENTATION_SIGNED |
| }; |
| |
| // A range for a given nunmeric Src type is contained for a given numeric Dst |
| // type if both numeric_limits<Src>::max() <= numeric_limits<Dst>::max() and |
| // numeric_limits<Src>::lowest() >= numeric_limits<Dst>::lowest() are true. |
| // We implement this as template specializations rather than simple static |
| // comparisons to ensure type correctness in our comparisons. |
| enum NumericRangeRepresentation { |
| NUMERIC_RANGE_NOT_CONTAINED, |
| NUMERIC_RANGE_CONTAINED |
| }; |
| |
| // Helper templates to statically determine if our destination type can contain |
| // maximum and minimum values represented by the source type. |
| |
| template <typename Dst, |
| typename Src, |
| IntegerRepresentation DstSign = std::is_signed<Dst>::value |
| ? INTEGER_REPRESENTATION_SIGNED |
| : INTEGER_REPRESENTATION_UNSIGNED, |
| IntegerRepresentation SrcSign = std::is_signed<Src>::value |
| ? INTEGER_REPRESENTATION_SIGNED |
| : INTEGER_REPRESENTATION_UNSIGNED> |
| struct StaticDstRangeRelationToSrcRange; |
| |
| // Same sign: Dst is guaranteed to contain Src only if its range is equal or |
| // larger. |
| template <typename Dst, typename Src, IntegerRepresentation Sign> |
| struct StaticDstRangeRelationToSrcRange<Dst, Src, Sign, Sign> { |
| static const NumericRangeRepresentation value = |
| MaxExponent<Dst>::value >= MaxExponent<Src>::value |
| ? NUMERIC_RANGE_CONTAINED |
| : NUMERIC_RANGE_NOT_CONTAINED; |
| }; |
| |
| // Unsigned to signed: Dst is guaranteed to contain source only if its range is |
| // larger. |
| template <typename Dst, typename Src> |
| struct StaticDstRangeRelationToSrcRange<Dst, |
| Src, |
| INTEGER_REPRESENTATION_SIGNED, |
| INTEGER_REPRESENTATION_UNSIGNED> { |
| static const NumericRangeRepresentation value = |
| MaxExponent<Dst>::value > MaxExponent<Src>::value |
| ? NUMERIC_RANGE_CONTAINED |
| : NUMERIC_RANGE_NOT_CONTAINED; |
| }; |
| |
| // Signed to unsigned: Dst cannot be statically determined to contain Src. |
| template <typename Dst, typename Src> |
| struct StaticDstRangeRelationToSrcRange<Dst, |
| Src, |
| INTEGER_REPRESENTATION_UNSIGNED, |
| INTEGER_REPRESENTATION_SIGNED> { |
| static const NumericRangeRepresentation value = NUMERIC_RANGE_NOT_CONTAINED; |
| }; |
| |
| // This class wraps the range constraints as separate booleans so the compiler |
| // can identify constants and eliminate unused code paths. |
| class RangeCheck { |
| public: |
| constexpr RangeCheck(bool is_in_lower_bound, bool is_in_upper_bound) |
| : is_underflow_(!is_in_lower_bound), is_overflow_(!is_in_upper_bound) {} |
| constexpr RangeCheck() : is_underflow_(0), is_overflow_(0) {} |
| constexpr bool IsValid() const { return !is_overflow_ && !is_underflow_; } |
| constexpr bool IsInvalid() const { return is_overflow_ && is_underflow_; } |
| constexpr bool IsOverflow() const { return is_overflow_ && !is_underflow_; } |
| constexpr bool IsUnderflow() const { return !is_overflow_ && is_underflow_; } |
| constexpr bool IsOverflowFlagSet() const { return is_overflow_; } |
| constexpr bool IsUnderflowFlagSet() const { return is_underflow_; } |
| constexpr bool operator==(const RangeCheck rhs) const { |
| return is_underflow_ == rhs.is_underflow_ && |
| is_overflow_ == rhs.is_overflow_; |
| } |
| constexpr bool operator!=(const RangeCheck rhs) const { |
| return !(*this == rhs); |
| } |
| |
| private: |
| // Do not change the order of these member variables. The integral conversion |
| // optimization depends on this exact order. |
| const bool is_underflow_; |
| const bool is_overflow_; |
| }; |
| |
| // The following helper template addresses a corner case in range checks for |
| // conversion from a floating-point type to an integral type of smaller range |
| // but larger precision (e.g. float -> unsigned). The problem is as follows: |
| // 1. Integral maximum is always one less than a power of two, so it must be |
| // truncated to fit the mantissa of the floating point. The direction of |
| // rounding is implementation defined, but by default it's always IEEE |
| // floats, which round to nearest and thus result in a value of larger |
| // magnitude than the integral value. |
| // Example: float f = UINT_MAX; // f is 4294967296f but UINT_MAX |
| // // is 4294967295u. |
| // 2. If the floating point value is equal to the promoted integral maximum |
| // value, a range check will erroneously pass. |
| // Example: (4294967296f <= 4294967295u) // This is true due to a precision |
| // // loss in rounding up to float. |
| // 3. When the floating point value is then converted to an integral, the |
| // resulting value is out of range for the target integral type and |
| // thus is implementation defined. |
| // Example: unsigned u = (float)INT_MAX; // u will typically overflow to 0. |
| // To fix this bug we manually truncate the maximum value when the destination |
| // type is an integral of larger precision than the source floating-point type, |
| // such that the resulting maximum is represented exactly as a floating point. |
| template <typename Dst, typename Src, template <typename> class Bounds> |
| struct NarrowingRange { |
| using SrcLimits = std::numeric_limits<Src>; |
| using DstLimits = typename std::numeric_limits<Dst>; |
| |
| // Computes the mask required to make an accurate comparison between types. |
| static const int kShift = |
| (MaxExponent<Src>::value > MaxExponent<Dst>::value && |
| SrcLimits::digits < DstLimits::digits) |
| ? (DstLimits::digits - SrcLimits::digits) |
| : 0; |
| template < |
| typename T, |
| typename std::enable_if<std::is_integral<T>::value>::type* = nullptr> |
| |
| // Masks out the integer bits that are beyond the precision of the |
| // intermediate type used for comparison. |
| static constexpr T Adjust(T value) { |
| static_assert(std::is_same<T, Dst>::value, ""); |
| static_assert(kShift < DstLimits::digits, ""); |
| return static_cast<T>( |
| ConditionalNegate(SafeUnsignedAbs(value) & ~((T(1) << kShift) - T(1)), |
| IsValueNegative(value))); |
| } |
| |
| template <typename T, |
| typename std::enable_if<std::is_floating_point<T>::value>::type* = |
| nullptr> |
| static constexpr T Adjust(T value) { |
| static_assert(std::is_same<T, Dst>::value, ""); |
| static_assert(kShift == 0, ""); |
| return value; |
| } |
| |
| static constexpr Dst max() { return Adjust(Bounds<Dst>::max()); } |
| static constexpr Dst lowest() { return Adjust(Bounds<Dst>::lowest()); } |
| }; |
| |
| template <typename Dst, |
| typename Src, |
| template <typename> |
| class Bounds, |
| IntegerRepresentation DstSign = std::is_signed<Dst>::value |
| ? INTEGER_REPRESENTATION_SIGNED |
| : INTEGER_REPRESENTATION_UNSIGNED, |
| IntegerRepresentation SrcSign = std::is_signed<Src>::value |
| ? INTEGER_REPRESENTATION_SIGNED |
| : INTEGER_REPRESENTATION_UNSIGNED, |
| NumericRangeRepresentation DstRange = |
| StaticDstRangeRelationToSrcRange<Dst, Src>::value> |
| struct DstRangeRelationToSrcRangeImpl; |
| |
| // The following templates are for ranges that must be verified at runtime. We |
| // split it into checks based on signedness to avoid confusing casts and |
| // compiler warnings on signed an unsigned comparisons. |
| |
| // Same sign narrowing: The range is contained for normal limits. |
| template <typename Dst, |
| typename Src, |
| template <typename> |
| class Bounds, |
| IntegerRepresentation DstSign, |
| IntegerRepresentation SrcSign> |
| struct DstRangeRelationToSrcRangeImpl<Dst, |
| Src, |
| Bounds, |
| DstSign, |
| SrcSign, |
| NUMERIC_RANGE_CONTAINED> { |
| static constexpr RangeCheck Check(Src value) { |
| using SrcLimits = std::numeric_limits<Src>; |
| using DstLimits = NarrowingRange<Dst, Src, Bounds>; |
| return RangeCheck( |
| static_cast<Dst>(SrcLimits::lowest()) >= DstLimits::lowest() || |
| static_cast<Dst>(value) >= DstLimits::lowest(), |
| static_cast<Dst>(SrcLimits::max()) <= DstLimits::max() || |
| static_cast<Dst>(value) <= DstLimits::max()); |
| } |
| }; |
| |
| // Signed to signed narrowing: Both the upper and lower boundaries may be |
| // exceeded for standard limits. |
| template <typename Dst, typename Src, template <typename> class Bounds> |
| struct DstRangeRelationToSrcRangeImpl<Dst, |
| Src, |
| Bounds, |
| INTEGER_REPRESENTATION_SIGNED, |
| INTEGER_REPRESENTATION_SIGNED, |
| NUMERIC_RANGE_NOT_CONTAINED> { |
| static constexpr RangeCheck Check(Src value) { |
| using DstLimits = NarrowingRange<Dst, Src, Bounds>; |
| return RangeCheck(value >= DstLimits::lowest(), value <= DstLimits::max()); |
| } |
| }; |
| |
| // Unsigned to unsigned narrowing: Only the upper bound can be exceeded for |
| // standard limits. |
| template <typename Dst, typename Src, template <typename> class Bounds> |
| struct DstRangeRelationToSrcRangeImpl<Dst, |
| Src, |
| Bounds, |
| INTEGER_REPRESENTATION_UNSIGNED, |
| INTEGER_REPRESENTATION_UNSIGNED, |
| NUMERIC_RANGE_NOT_CONTAINED> { |
| static constexpr RangeCheck Check(Src value) { |
| using DstLimits = NarrowingRange<Dst, Src, Bounds>; |
| return RangeCheck( |
| DstLimits::lowest() == Dst(0) || value >= DstLimits::lowest(), |
| value <= DstLimits::max()); |
| } |
| }; |
| |
| // Unsigned to signed: Only the upper bound can be exceeded for standard limits. |
| template <typename Dst, typename Src, template <typename> class Bounds> |
| struct DstRangeRelationToSrcRangeImpl<Dst, |
| Src, |
| Bounds, |
| INTEGER_REPRESENTATION_SIGNED, |
| INTEGER_REPRESENTATION_UNSIGNED, |
| NUMERIC_RANGE_NOT_CONTAINED> { |
| static constexpr RangeCheck Check(Src value) { |
| using DstLimits = NarrowingRange<Dst, Src, Bounds>; |
| using Promotion = decltype(Src() + Dst()); |
| return RangeCheck(DstLimits::lowest() <= Dst(0) || |
| static_cast<Promotion>(value) >= |
| static_cast<Promotion>(DstLimits::lowest()), |
| static_cast<Promotion>(value) <= |
| static_cast<Promotion>(DstLimits::max())); |
| } |
| }; |
| |
| // Signed to unsigned: The upper boundary may be exceeded for a narrower Dst, |
| // and any negative value exceeds the lower boundary for standard limits. |
| template <typename Dst, typename Src, template <typename> class Bounds> |
| struct DstRangeRelationToSrcRangeImpl<Dst, |
| Src, |
| Bounds, |
| INTEGER_REPRESENTATION_UNSIGNED, |
| INTEGER_REPRESENTATION_SIGNED, |
| NUMERIC_RANGE_NOT_CONTAINED> { |
| static constexpr RangeCheck Check(Src value) { |
| using SrcLimits = std::numeric_limits<Src>; |
| using DstLimits = NarrowingRange<Dst, Src, Bounds>; |
| using Promotion = decltype(Src() + Dst()); |
| return RangeCheck( |
| value >= Src(0) && (DstLimits::lowest() == 0 || |
| static_cast<Dst>(value) >= DstLimits::lowest()), |
| static_cast<Promotion>(SrcLimits::max()) <= |
| static_cast<Promotion>(DstLimits::max()) || |
| static_cast<Promotion>(value) <= |
| static_cast<Promotion>(DstLimits::max())); |
| } |
| }; |
| |
| // Simple wrapper for statically checking if a type's range is contained. |
| template <typename Dst, typename Src> |
| struct IsTypeInRangeForNumericType { |
| static const bool value = StaticDstRangeRelationToSrcRange<Dst, Src>::value == |
| NUMERIC_RANGE_CONTAINED; |
| }; |
| |
| template <typename Dst, |
| template <typename> class Bounds = std::numeric_limits, |
| typename Src> |
| constexpr RangeCheck DstRangeRelationToSrcRange(Src value) { |
| static_assert(std::is_arithmetic<Src>::value, "Argument must be numeric."); |
| static_assert(std::is_arithmetic<Dst>::value, "Result must be numeric."); |
| static_assert(Bounds<Dst>::lowest() < Bounds<Dst>::max(), ""); |
| return DstRangeRelationToSrcRangeImpl<Dst, Src, Bounds>::Check(value); |
| } |
| |
| // Integer promotion templates used by the portable checked integer arithmetic. |
| template <size_t Size, bool IsSigned> |
| struct IntegerForDigitsAndSign; |
| |
| #define INTEGER_FOR_DIGITS_AND_SIGN(I) \ |
| template <> \ |
| struct IntegerForDigitsAndSign<IntegerBitsPlusSign<I>::value, \ |
| std::is_signed<I>::value> { \ |
| using type = I; \ |
| } |
| |
| INTEGER_FOR_DIGITS_AND_SIGN(int8_t); |
| INTEGER_FOR_DIGITS_AND_SIGN(uint8_t); |
| INTEGER_FOR_DIGITS_AND_SIGN(int16_t); |
| INTEGER_FOR_DIGITS_AND_SIGN(uint16_t); |
| INTEGER_FOR_DIGITS_AND_SIGN(int32_t); |
| INTEGER_FOR_DIGITS_AND_SIGN(uint32_t); |
| INTEGER_FOR_DIGITS_AND_SIGN(int64_t); |
| INTEGER_FOR_DIGITS_AND_SIGN(uint64_t); |
| #undef INTEGER_FOR_DIGITS_AND_SIGN |
| |
| // WARNING: We have no IntegerForSizeAndSign<16, *>. If we ever add one to |
| // support 128-bit math, then the ArithmeticPromotion template below will need |
| // to be updated (or more likely replaced with a decltype expression). |
| static_assert(IntegerBitsPlusSign<intmax_t>::value == 64, |
| "Max integer size not supported for this toolchain."); |
| |
| template <typename Integer, bool IsSigned = std::is_signed<Integer>::value> |
| struct TwiceWiderInteger { |
| using type = |
| typename IntegerForDigitsAndSign<IntegerBitsPlusSign<Integer>::value * 2, |
| IsSigned>::type; |
| }; |
| |
| enum ArithmeticPromotionCategory { |
| LEFT_PROMOTION, // Use the type of the left-hand argument. |
| RIGHT_PROMOTION // Use the type of the right-hand argument. |
| }; |
| |
| // Determines the type that can represent the largest positive value. |
| template <typename Lhs, |
| typename Rhs, |
| ArithmeticPromotionCategory Promotion = |
| (MaxExponent<Lhs>::value > MaxExponent<Rhs>::value) |
| ? LEFT_PROMOTION |
| : RIGHT_PROMOTION> |
| struct MaxExponentPromotion; |
| |
| template <typename Lhs, typename Rhs> |
| struct MaxExponentPromotion<Lhs, Rhs, LEFT_PROMOTION> { |
| using type = Lhs; |
| }; |
| |
| template <typename Lhs, typename Rhs> |
| struct MaxExponentPromotion<Lhs, Rhs, RIGHT_PROMOTION> { |
| using type = Rhs; |
| }; |
| |
| // Determines the type that can represent the lowest arithmetic value. |
| template <typename Lhs, |
| typename Rhs, |
| ArithmeticPromotionCategory Promotion = |
| std::is_signed<Lhs>::value |
| ? (std::is_signed<Rhs>::value |
| ? (MaxExponent<Lhs>::value > MaxExponent<Rhs>::value |
| ? LEFT_PROMOTION |
| : RIGHT_PROMOTION) |
| : LEFT_PROMOTION) |
| : (std::is_signed<Rhs>::value |
| ? RIGHT_PROMOTION |
| : (MaxExponent<Lhs>::value < MaxExponent<Rhs>::value |
| ? LEFT_PROMOTION |
| : RIGHT_PROMOTION))> |
| struct LowestValuePromotion; |
| |
| template <typename Lhs, typename Rhs> |
| struct LowestValuePromotion<Lhs, Rhs, LEFT_PROMOTION> { |
| using type = Lhs; |
| }; |
| |
| template <typename Lhs, typename Rhs> |
| struct LowestValuePromotion<Lhs, Rhs, RIGHT_PROMOTION> { |
| using type = Rhs; |
| }; |
| |
| // Determines the type that is best able to represent an arithmetic result. |
| template < |
| typename Lhs, |
| typename Rhs = Lhs, |
| bool is_intmax_type = |
| std::is_integral< |
| typename MaxExponentPromotion<Lhs, Rhs>::type>::value && |
| IntegerBitsPlusSign<typename MaxExponentPromotion<Lhs, Rhs>::type>:: |
| value == IntegerBitsPlusSign<intmax_t>::value, |
| bool is_max_exponent = StaticDstRangeRelationToSrcRange< |
| typename MaxExponentPromotion<Lhs, Rhs>::type, |
| Lhs>::value == NUMERIC_RANGE_CONTAINED && |
| StaticDstRangeRelationToSrcRange< |
| typename MaxExponentPromotion<Lhs, Rhs>::type, |
| Rhs>::value == NUMERIC_RANGE_CONTAINED> |
| struct BigEnoughPromotion; |
| |
| // The side with the max exponent is big enough. |
| template <typename Lhs, typename Rhs, bool is_intmax_type> |
| struct BigEnoughPromotion<Lhs, Rhs, is_intmax_type, true> { |
| using type = typename MaxExponentPromotion<Lhs, Rhs>::type; |
| static const bool is_contained = true; |
| }; |
| |
| // We can use a twice wider type to fit. |
| template <typename Lhs, typename Rhs> |
| struct BigEnoughPromotion<Lhs, Rhs, false, false> { |
| using type = |
| typename TwiceWiderInteger<typename MaxExponentPromotion<Lhs, Rhs>::type, |
| std::is_signed<Lhs>::value || |
| std::is_signed<Rhs>::value>::type; |
| static const bool is_contained = true; |
| }; |
| |
| // No type is large enough. |
| template <typename Lhs, typename Rhs> |
| struct BigEnoughPromotion<Lhs, Rhs, true, false> { |
| using type = typename MaxExponentPromotion<Lhs, Rhs>::type; |
| static const bool is_contained = false; |
| }; |
| |
| // We can statically check if operations on the provided types can wrap, so we |
| // can skip the checked operations if they're not needed. So, for an integer we |
| // care if the destination type preserves the sign and is twice the width of |
| // the source. |
| template <typename T, typename Lhs, typename Rhs = Lhs> |
| struct IsIntegerArithmeticSafe { |
| static const bool value = |
| !std::is_floating_point<T>::value && |
| !std::is_floating_point<Lhs>::value && |
| !std::is_floating_point<Rhs>::value && |
| std::is_signed<T>::value >= std::is_signed<Lhs>::value && |
| IntegerBitsPlusSign<T>::value >= (2 * IntegerBitsPlusSign<Lhs>::value) && |
| std::is_signed<T>::value >= std::is_signed<Rhs>::value && |
| IntegerBitsPlusSign<T>::value >= (2 * IntegerBitsPlusSign<Rhs>::value); |
| }; |
| |
| // Promotes to a type that can represent any possible result of a binary |
| // arithmetic operation with the source types. |
| template <typename Lhs, |
| typename Rhs, |
| bool is_promotion_possible = IsIntegerArithmeticSafe< |
| typename std::conditional<std::is_signed<Lhs>::value || |
| std::is_signed<Rhs>::value, |
| intmax_t, |
| uintmax_t>::type, |
| typename MaxExponentPromotion<Lhs, Rhs>::type>::value> |
| struct FastIntegerArithmeticPromotion; |
| |
| template <typename Lhs, typename Rhs> |
| struct FastIntegerArithmeticPromotion<Lhs, Rhs, true> { |
| using type = |
| typename TwiceWiderInteger<typename MaxExponentPromotion<Lhs, Rhs>::type, |
| std::is_signed<Lhs>::value || |
| std::is_signed<Rhs>::value>::type; |
| static_assert(IsIntegerArithmeticSafe<type, Lhs, Rhs>::value, ""); |
| static const bool is_contained = true; |
| }; |
| |
| template <typename Lhs, typename Rhs> |
| struct FastIntegerArithmeticPromotion<Lhs, Rhs, false> { |
| using type = typename BigEnoughPromotion<Lhs, Rhs>::type; |
| static const bool is_contained = false; |
| }; |
| |
| // Extracts the underlying type from an enum. |
| template <typename T, bool is_enum = std::is_enum<T>::value> |
| struct ArithmeticOrUnderlyingEnum; |
| |
| template <typename T> |
| struct ArithmeticOrUnderlyingEnum<T, true> { |
| using type = typename std::underlying_type<T>::type; |
| static const bool value = std::is_arithmetic<type>::value; |
| }; |
| |
| template <typename T> |
| struct ArithmeticOrUnderlyingEnum<T, false> { |
| using type = T; |
| static const bool value = std::is_arithmetic<type>::value; |
| }; |
| |
| // The following are helper templates used in the CheckedNumeric class. |
| template <typename T> |
| class CheckedNumeric; |
| |
| template <typename T> |
| class ClampedNumeric; |
| |
| template <typename T> |
| class StrictNumeric; |
| |
| // Used to treat CheckedNumeric and arithmetic underlying types the same. |
| template <typename T> |
| struct UnderlyingType { |
| using type = typename ArithmeticOrUnderlyingEnum<T>::type; |
| static const bool is_numeric = std::is_arithmetic<type>::value; |
| static const bool is_checked = false; |
| static const bool is_clamped = false; |
| static const bool is_strict = false; |
| }; |
| |
| template <typename T> |
| struct UnderlyingType<CheckedNumeric<T>> { |
| using type = T; |
| static const bool is_numeric = true; |
| static const bool is_checked = true; |
| static const bool is_clamped = false; |
| static const bool is_strict = false; |
| }; |
| |
| template <typename T> |
| struct UnderlyingType<ClampedNumeric<T>> { |
| using type = T; |
| static const bool is_numeric = true; |
| static const bool is_checked = false; |
| static const bool is_clamped = true; |
| static const bool is_strict = false; |
| }; |
| |
| template <typename T> |
| struct UnderlyingType<StrictNumeric<T>> { |
| using type = T; |
| static const bool is_numeric = true; |
| static const bool is_checked = false; |
| static const bool is_clamped = false; |
| static const bool is_strict = true; |
| }; |
| |
| template <typename L, typename R> |
| struct IsCheckedOp { |
| static const bool value = |
| UnderlyingType<L>::is_numeric && UnderlyingType<R>::is_numeric && |
| (UnderlyingType<L>::is_checked || UnderlyingType<R>::is_checked); |
| }; |
| |
| template <typename L, typename R> |
| struct IsClampedOp { |
| static const bool value = |
| UnderlyingType<L>::is_numeric && UnderlyingType<R>::is_numeric && |
| (UnderlyingType<L>::is_clamped || UnderlyingType<R>::is_clamped) && |
| !(UnderlyingType<L>::is_checked || UnderlyingType<R>::is_checked); |
| }; |
| |
| template <typename L, typename R> |
| struct IsStrictOp { |
| static const bool value = |
| UnderlyingType<L>::is_numeric && UnderlyingType<R>::is_numeric && |
| (UnderlyingType<L>::is_strict || UnderlyingType<R>::is_strict) && |
| !(UnderlyingType<L>::is_checked || UnderlyingType<R>::is_checked) && |
| !(UnderlyingType<L>::is_clamped || UnderlyingType<R>::is_clamped); |
| }; |
| |
| // as_signed<> returns the supplied integral value (or integral castable |
| // Numeric template) cast as a signed integral of equivalent precision. |
| // I.e. it's mostly an alias for: static_cast<std::make_signed<T>::type>(t) |
| template <typename Src> |
| constexpr typename std::make_signed< |
| typename base::internal::UnderlyingType<Src>::type>::type |
| as_signed(const Src value) { |
| static_assert(std::is_integral<decltype(as_signed(value))>::value, |
| "Argument must be a signed or unsigned integer type."); |
| return static_cast<decltype(as_signed(value))>(value); |
| } |
| |
| // as_unsigned<> returns the supplied integral value (or integral castable |
| // Numeric template) cast as an unsigned integral of equivalent precision. |
| // I.e. it's mostly an alias for: static_cast<std::make_unsigned<T>::type>(t) |
| template <typename Src> |
| constexpr typename std::make_unsigned< |
| typename base::internal::UnderlyingType<Src>::type>::type |
| as_unsigned(const Src value) { |
| static_assert(std::is_integral<decltype(as_unsigned(value))>::value, |
| "Argument must be a signed or unsigned integer type."); |
| return static_cast<decltype(as_unsigned(value))>(value); |
| } |
| |
| template <typename L, typename R> |
| constexpr bool IsLessImpl(const L lhs, |
| const R rhs, |
| const RangeCheck l_range, |
| const RangeCheck r_range) { |
| return l_range.IsUnderflow() || r_range.IsOverflow() || |
| (l_range == r_range && static_cast<decltype(lhs + rhs)>(lhs) < |
| static_cast<decltype(lhs + rhs)>(rhs)); |
| } |
| |
| template <typename L, typename R> |
| struct IsLess { |
| static_assert(std::is_arithmetic<L>::value && std::is_arithmetic<R>::value, |
| "Types must be numeric."); |
| static constexpr bool Test(const L lhs, const R rhs) { |
| return IsLessImpl(lhs, rhs, DstRangeRelationToSrcRange<R>(lhs), |
| DstRangeRelationToSrcRange<L>(rhs)); |
| } |
| }; |
| |
| template <typename L, typename R> |
| constexpr bool IsLessOrEqualImpl(const L lhs, |
| const R rhs, |
| const RangeCheck l_range, |
| const RangeCheck r_range) { |
| return l_range.IsUnderflow() || r_range.IsOverflow() || |
| (l_range == r_range && static_cast<decltype(lhs + rhs)>(lhs) <= |
| static_cast<decltype(lhs + rhs)>(rhs)); |
| } |
| |
| template <typename L, typename R> |
| struct IsLessOrEqual { |
| static_assert(std::is_arithmetic<L>::value && std::is_arithmetic<R>::value, |
| "Types must be numeric."); |
| static constexpr bool Test(const L lhs, const R rhs) { |
| return IsLessOrEqualImpl(lhs, rhs, DstRangeRelationToSrcRange<R>(lhs), |
| DstRangeRelationToSrcRange<L>(rhs)); |
| } |
| }; |
| |
| template <typename L, typename R> |
| constexpr bool IsGreaterImpl(const L lhs, |
| const R rhs, |
| const RangeCheck l_range, |
| const RangeCheck r_range) { |
| return l_range.IsOverflow() || r_range.IsUnderflow() || |
| (l_range == r_range && static_cast<decltype(lhs + rhs)>(lhs) > |
| static_cast<decltype(lhs + rhs)>(rhs)); |
| } |
| |
| template <typename L, typename R> |
| struct IsGreater { |
| static_assert(std::is_arithmetic<L>::value && std::is_arithmetic<R>::value, |
| "Types must be numeric."); |
| static constexpr bool Test(const L lhs, const R rhs) { |
| return IsGreaterImpl(lhs, rhs, DstRangeRelationToSrcRange<R>(lhs), |
| DstRangeRelationToSrcRange<L>(rhs)); |
| } |
| }; |
| |
| template <typename L, typename R> |
| constexpr bool IsGreaterOrEqualImpl(const L lhs, |
| const R rhs, |
| const RangeCheck l_range, |
| const RangeCheck r_range) { |
| return l_range.IsOverflow() || r_range.IsUnderflow() || |
| (l_range == r_range && static_cast<decltype(lhs + rhs)>(lhs) >= |
| static_cast<decltype(lhs + rhs)>(rhs)); |
| } |
| |
| template <typename L, typename R> |
| struct IsGreaterOrEqual { |
| static_assert(std::is_arithmetic<L>::value && std::is_arithmetic<R>::value, |
| "Types must be numeric."); |
| static constexpr bool Test(const L lhs, const R rhs) { |
| return IsGreaterOrEqualImpl(lhs, rhs, DstRangeRelationToSrcRange<R>(lhs), |
| DstRangeRelationToSrcRange<L>(rhs)); |
| } |
| }; |
| |
| template <typename L, typename R> |
| struct IsEqual { |
| static_assert(std::is_arithmetic<L>::value && std::is_arithmetic<R>::value, |
| "Types must be numeric."); |
| static constexpr bool Test(const L lhs, const R rhs) { |
| return DstRangeRelationToSrcRange<R>(lhs) == |
| DstRangeRelationToSrcRange<L>(rhs) && |
| static_cast<decltype(lhs + rhs)>(lhs) == |
| static_cast<decltype(lhs + rhs)>(rhs); |
| } |
| }; |
| |
| template <typename L, typename R> |
| struct IsNotEqual { |
| static_assert(std::is_arithmetic<L>::value && std::is_arithmetic<R>::value, |
| "Types must be numeric."); |
| static constexpr bool Test(const L lhs, const R rhs) { |
| return DstRangeRelationToSrcRange<R>(lhs) != |
| DstRangeRelationToSrcRange<L>(rhs) || |
| static_cast<decltype(lhs + rhs)>(lhs) != |
| static_cast<decltype(lhs + rhs)>(rhs); |
| } |
| }; |
| |
| // These perform the actual math operations on the CheckedNumerics. |
| // Binary arithmetic operations. |
| template <template <typename, typename> class C, typename L, typename R> |
| constexpr bool SafeCompare(const L lhs, const R rhs) { |
| static_assert(std::is_arithmetic<L>::value && std::is_arithmetic<R>::value, |
| "Types must be numeric."); |
| using Promotion = BigEnoughPromotion<L, R>; |
| using BigType = typename Promotion::type; |
| return Promotion::is_contained |
| // Force to a larger type for speed if both are contained. |
| ? C<BigType, BigType>::Test( |
| static_cast<BigType>(static_cast<L>(lhs)), |
| static_cast<BigType>(static_cast<R>(rhs))) |
| // Let the template functions figure it out for mixed types. |
| : C<L, R>::Test(lhs, rhs); |
| } |
| |
| template <typename Dst, typename Src> |
| constexpr bool IsMaxInRangeForNumericType() { |
| return IsGreaterOrEqual<Dst, Src>::Test(std::numeric_limits<Dst>::max(), |
| std::numeric_limits<Src>::max()); |
| } |
| |
| template <typename Dst, typename Src> |
| constexpr bool IsMinInRangeForNumericType() { |
| return IsLessOrEqual<Dst, Src>::Test(std::numeric_limits<Dst>::lowest(), |
| std::numeric_limits<Src>::lowest()); |
| } |
| |
| template <typename Dst, typename Src> |
| constexpr Dst CommonMax() { |
| return !IsMaxInRangeForNumericType<Dst, Src>() |
| ? Dst(std::numeric_limits<Dst>::max()) |
| : Dst(std::numeric_limits<Src>::max()); |
| } |
| |
| template <typename Dst, typename Src> |
| constexpr Dst CommonMin() { |
| return !IsMinInRangeForNumericType<Dst, Src>() |
| ? Dst(std::numeric_limits<Dst>::lowest()) |
| : Dst(std::numeric_limits<Src>::lowest()); |
| } |
| |
| // This is a wrapper to generate return the max or min for a supplied type. |
| // If the argument is false, the returned value is the maximum. If true the |
| // returned value is the minimum. |
| template <typename Dst, typename Src = Dst> |
| constexpr Dst CommonMaxOrMin(bool is_min) { |
| return is_min ? CommonMin<Dst, Src>() : CommonMax<Dst, Src>(); |
| } |
| |
| } // namespace internal |
| } // namespace base |
| |
| #endif // BASE_NUMERICS_SAFE_CONVERSIONS_IMPL_H_ |
