| // Copyright 2017 The Chromium Authors |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef BASE_NUMERICS_CHECKED_MATH_H_ |
| #define BASE_NUMERICS_CHECKED_MATH_H_ |
| |
| #include <stddef.h> |
| |
| #include <limits> |
| #include <type_traits> |
| |
| #include "base/numerics/checked_math_impl.h" |
| |
| namespace gurl_base { |
| namespace internal { |
| |
| template <typename T> |
| class CheckedNumeric { |
| static_assert(std::is_arithmetic_v<T>, |
| "CheckedNumeric<T>: T must be a numeric type."); |
| |
| public: |
| template <typename Src> |
| friend class CheckedNumeric; |
| |
| using type = T; |
| |
| constexpr CheckedNumeric() = default; |
| |
| // Copy constructor. |
| template <typename Src> |
| constexpr CheckedNumeric(const CheckedNumeric<Src>& rhs) |
| : state_(rhs.state_.value(), rhs.IsValid()) {} |
| |
| // Strictly speaking, this is not necessary, but declaring this allows class |
| // template argument deduction to be used so that it is possible to simply |
| // write `CheckedNumeric(777)` instead of `CheckedNumeric<int>(777)`. |
| // NOLINTNEXTLINE(google-explicit-constructor) |
| constexpr CheckedNumeric(T value) : state_(value) {} |
| |
| // This is not an explicit constructor because we implicitly upgrade regular |
| // numerics to CheckedNumerics to make them easier to use. |
| template <typename Src, |
| typename = std::enable_if_t<std::is_arithmetic_v<Src>>> |
| // NOLINTNEXTLINE(google-explicit-constructor) |
| constexpr CheckedNumeric(Src value) : state_(value) {} |
| |
| // This is not an explicit constructor because we want a seamless conversion |
| // from StrictNumeric types. |
| template <typename Src> |
| // NOLINTNEXTLINE(google-explicit-constructor) |
| constexpr CheckedNumeric(StrictNumeric<Src> value) |
| : state_(static_cast<Src>(value)) {} |
| |
| // IsValid() - The public API to test if a CheckedNumeric is currently valid. |
| // A range checked destination type can be supplied using the Dst template |
| // parameter. |
| template <typename Dst = T> |
| constexpr bool IsValid() const { |
| return state_.is_valid() && |
| IsValueInRangeForNumericType<Dst>(state_.value()); |
| } |
| |
| // AssignIfValid(Dst) - Assigns the underlying value if it is currently valid |
| // and is within the range supported by the destination type. Returns true if |
| // successful and false otherwise. |
| template <typename Dst> |
| #if defined(__clang__) || defined(__GNUC__) |
| __attribute__((warn_unused_result)) |
| #elif defined(_MSC_VER) |
| _Check_return_ |
| #endif |
| constexpr bool |
| AssignIfValid(Dst* result) const { |
| return BASE_NUMERICS_LIKELY(IsValid<Dst>()) |
| ? ((*result = static_cast<Dst>(state_.value())), true) |
| : false; |
| } |
| |
| // ValueOrDie() - The primary accessor for the underlying value. If the |
| // current state is not valid it will GURL_CHECK and crash. |
| // A range checked destination type can be supplied using the Dst template |
| // parameter, which will trigger a GURL_CHECK if the value is not in bounds for |
| // the destination. |
| // The GURL_CHECK behavior can be overridden by supplying a handler as a |
| // template parameter, for test code, etc. However, the handler cannot access |
| // the underlying value, and it is not available through other means. |
| template <typename Dst = T, class CheckHandler = CheckOnFailure> |
| constexpr StrictNumeric<Dst> ValueOrDie() const { |
| return BASE_NUMERICS_LIKELY(IsValid<Dst>()) |
| ? static_cast<Dst>(state_.value()) |
| : CheckHandler::template HandleFailure<Dst>(); |
| } |
| |
| // ValueOrDefault(T default_value) - A convenience method that returns the |
| // current value if the state is valid, and the supplied default_value for |
| // any other state. |
| // A range checked destination type can be supplied using the Dst template |
| // parameter. WARNING: This function may fail to compile or GURL_CHECK at runtime |
| // if the supplied default_value is not within range of the destination type. |
| template <typename Dst = T, typename Src> |
| constexpr StrictNumeric<Dst> ValueOrDefault(const Src default_value) const { |
| return BASE_NUMERICS_LIKELY(IsValid<Dst>()) |
| ? static_cast<Dst>(state_.value()) |
| : checked_cast<Dst>(default_value); |
| } |
| |
| // Returns a checked numeric of the specified type, cast from the current |
| // CheckedNumeric. If the current state is invalid or the destination cannot |
| // represent the result then the returned CheckedNumeric will be invalid. |
| template <typename Dst> |
| constexpr CheckedNumeric<typename UnderlyingType<Dst>::type> Cast() const { |
| return *this; |
| } |
| |
| // This friend method is available solely for providing more detailed logging |
| // in the tests. Do not implement it in production code, because the |
| // underlying values may change at any time. |
| template <typename U> |
| friend U GetNumericValueForTest(const CheckedNumeric<U>& src); |
| |
| // Prototypes for the supported arithmetic operator overloads. |
| template <typename Src> |
| constexpr CheckedNumeric& operator+=(const Src rhs); |
| template <typename Src> |
| constexpr CheckedNumeric& operator-=(const Src rhs); |
| template <typename Src> |
| constexpr CheckedNumeric& operator*=(const Src rhs); |
| template <typename Src> |
| constexpr CheckedNumeric& operator/=(const Src rhs); |
| template <typename Src> |
| constexpr CheckedNumeric& operator%=(const Src rhs); |
| template <typename Src> |
| constexpr CheckedNumeric& operator<<=(const Src rhs); |
| template <typename Src> |
| constexpr CheckedNumeric& operator>>=(const Src rhs); |
| template <typename Src> |
| constexpr CheckedNumeric& operator&=(const Src rhs); |
| template <typename Src> |
| constexpr CheckedNumeric& operator|=(const Src rhs); |
| template <typename Src> |
| constexpr CheckedNumeric& operator^=(const Src rhs); |
| |
| constexpr CheckedNumeric operator-() const { |
| // Use an optimized code path for a known run-time variable. |
| if (!IsConstantEvaluated() && std::is_signed_v<T> && |
| std::is_floating_point_v<T>) { |
| return FastRuntimeNegate(); |
| } |
| // The negation of two's complement int min is int min. |
| const bool is_valid = |
| IsValid() && |
| (!std::is_signed_v<T> || std::is_floating_point_v<T> || |
| NegateWrapper(state_.value()) != std::numeric_limits<T>::lowest()); |
| return CheckedNumeric<T>(NegateWrapper(state_.value()), is_valid); |
| } |
| |
| constexpr CheckedNumeric operator~() const { |
| return CheckedNumeric<decltype(InvertWrapper(T()))>( |
| InvertWrapper(state_.value()), IsValid()); |
| } |
| |
| constexpr CheckedNumeric Abs() const { |
| return !IsValueNegative(state_.value()) ? *this : -*this; |
| } |
| |
| template <typename U> |
| constexpr CheckedNumeric<typename MathWrapper<CheckedMaxOp, T, U>::type> Max( |
| const U rhs) const { |
| return CheckMax(*this, rhs); |
| } |
| |
| template <typename U> |
| constexpr CheckedNumeric<typename MathWrapper<CheckedMinOp, T, U>::type> Min( |
| const U rhs) const { |
| return CheckMin(*this, rhs); |
| } |
| |
| // This function is available only for integral types. It returns an unsigned |
| // integer of the same width as the source type, containing the absolute value |
| // of the source, and properly handling signed min. |
| constexpr CheckedNumeric<typename UnsignedOrFloatForSize<T>::type> |
| UnsignedAbs() const { |
| return CheckedNumeric<typename UnsignedOrFloatForSize<T>::type>( |
| SafeUnsignedAbs(state_.value()), state_.is_valid()); |
| } |
| |
| constexpr CheckedNumeric& operator++() { |
| *this += 1; |
| return *this; |
| } |
| |
| constexpr CheckedNumeric operator++(int) { |
| CheckedNumeric value = *this; |
| *this += 1; |
| return value; |
| } |
| |
| constexpr CheckedNumeric& operator--() { |
| *this -= 1; |
| return *this; |
| } |
| |
| constexpr CheckedNumeric operator--(int) { |
| // TODO(pkasting): Consider std::exchange() once it's constexpr in C++20. |
| const CheckedNumeric value = *this; |
| *this -= 1; |
| return value; |
| } |
| |
| // These perform the actual math operations on the CheckedNumerics. |
| // Binary arithmetic operations. |
| template <template <typename, typename, typename> class M, |
| typename L, |
| typename R> |
| static constexpr CheckedNumeric MathOp(const L lhs, const R rhs) { |
| using Math = typename MathWrapper<M, L, R>::math; |
| T result = 0; |
| const bool is_valid = |
| Wrapper<L>::is_valid(lhs) && Wrapper<R>::is_valid(rhs) && |
| Math::Do(Wrapper<L>::value(lhs), Wrapper<R>::value(rhs), &result); |
| return CheckedNumeric<T>(result, is_valid); |
| } |
| |
| // Assignment arithmetic operations. |
| template <template <typename, typename, typename> class M, typename R> |
| constexpr CheckedNumeric& MathOp(const R rhs) { |
| using Math = typename MathWrapper<M, T, R>::math; |
| T result = 0; // Using T as the destination saves a range check. |
| const bool is_valid = |
| state_.is_valid() && Wrapper<R>::is_valid(rhs) && |
| Math::Do(state_.value(), Wrapper<R>::value(rhs), &result); |
| *this = CheckedNumeric<T>(result, is_valid); |
| return *this; |
| } |
| |
| private: |
| CheckedNumericState<T> state_; |
| |
| CheckedNumeric FastRuntimeNegate() const { |
| T result; |
| const bool success = CheckedSubOp<T, T>::Do(T(0), state_.value(), &result); |
| return CheckedNumeric<T>(result, IsValid() && success); |
| } |
| |
| template <typename Src> |
| constexpr CheckedNumeric(Src value, bool is_valid) |
| : state_(value, is_valid) {} |
| |
| // These wrappers allow us to handle state the same way for both |
| // CheckedNumeric and POD arithmetic types. |
| template <typename Src> |
| struct Wrapper { |
| static constexpr bool is_valid(Src) { return true; } |
| static constexpr Src value(Src value) { return value; } |
| }; |
| |
| template <typename Src> |
| struct Wrapper<CheckedNumeric<Src>> { |
| static constexpr bool is_valid(const CheckedNumeric<Src> v) { |
| return v.IsValid(); |
| } |
| static constexpr Src value(const CheckedNumeric<Src> v) { |
| return v.state_.value(); |
| } |
| }; |
| |
| template <typename Src> |
| struct Wrapper<StrictNumeric<Src>> { |
| static constexpr bool is_valid(const StrictNumeric<Src>) { return true; } |
| static constexpr Src value(const StrictNumeric<Src> v) { |
| return static_cast<Src>(v); |
| } |
| }; |
| }; |
| |
| // Convenience functions to avoid the ugly template disambiguator syntax. |
| template <typename Dst, typename Src> |
| constexpr bool IsValidForType(const CheckedNumeric<Src> value) { |
| return value.template IsValid<Dst>(); |
| } |
| |
| template <typename Dst, typename Src> |
| constexpr StrictNumeric<Dst> ValueOrDieForType( |
| const CheckedNumeric<Src> value) { |
| return value.template ValueOrDie<Dst>(); |
| } |
| |
| template <typename Dst, typename Src, typename Default> |
| constexpr StrictNumeric<Dst> ValueOrDefaultForType( |
| const CheckedNumeric<Src> value, |
| const Default default_value) { |
| return value.template ValueOrDefault<Dst>(default_value); |
| } |
| |
| // Convenience wrapper to return a new CheckedNumeric from the provided |
| // arithmetic or CheckedNumericType. |
| template <typename T> |
| constexpr CheckedNumeric<typename UnderlyingType<T>::type> MakeCheckedNum( |
| const T value) { |
| return value; |
| } |
| |
| // These implement the variadic wrapper for the math operations. |
| template <template <typename, typename, typename> class M, |
| typename L, |
| typename R> |
| constexpr CheckedNumeric<typename MathWrapper<M, L, R>::type> CheckMathOp( |
| const L lhs, |
| const R rhs) { |
| using Math = typename MathWrapper<M, L, R>::math; |
| return CheckedNumeric<typename Math::result_type>::template MathOp<M>(lhs, |
| rhs); |
| } |
| |
| // General purpose wrapper template for arithmetic operations. |
| template <template <typename, typename, typename> class M, |
| typename L, |
| typename R, |
| typename... Args> |
| constexpr auto CheckMathOp(const L lhs, const R rhs, const Args... args) { |
| return CheckMathOp<M>(CheckMathOp<M>(lhs, rhs), args...); |
| } |
| |
| BASE_NUMERIC_ARITHMETIC_OPERATORS(Checked, Check, Add, +, +=) |
| BASE_NUMERIC_ARITHMETIC_OPERATORS(Checked, Check, Sub, -, -=) |
| BASE_NUMERIC_ARITHMETIC_OPERATORS(Checked, Check, Mul, *, *=) |
| BASE_NUMERIC_ARITHMETIC_OPERATORS(Checked, Check, Div, /, /=) |
| BASE_NUMERIC_ARITHMETIC_OPERATORS(Checked, Check, Mod, %, %=) |
| BASE_NUMERIC_ARITHMETIC_OPERATORS(Checked, Check, Lsh, <<, <<=) |
| BASE_NUMERIC_ARITHMETIC_OPERATORS(Checked, Check, Rsh, >>, >>=) |
| BASE_NUMERIC_ARITHMETIC_OPERATORS(Checked, Check, And, &, &=) |
| BASE_NUMERIC_ARITHMETIC_OPERATORS(Checked, Check, Or, |, |=) |
| BASE_NUMERIC_ARITHMETIC_OPERATORS(Checked, Check, Xor, ^, ^=) |
| BASE_NUMERIC_ARITHMETIC_VARIADIC(Checked, Check, Max) |
| BASE_NUMERIC_ARITHMETIC_VARIADIC(Checked, Check, Min) |
| |
| // These are some extra StrictNumeric operators to support simple pointer |
| // arithmetic with our result types. Since wrapping on a pointer is always |
| // bad, we trigger the GURL_CHECK condition here. |
| template <typename L, typename R> |
| L* operator+(L* lhs, const StrictNumeric<R> rhs) { |
| const uintptr_t result = CheckAdd(reinterpret_cast<uintptr_t>(lhs), |
| CheckMul(sizeof(L), static_cast<R>(rhs))) |
| .template ValueOrDie<uintptr_t>(); |
| return reinterpret_cast<L*>(result); |
| } |
| |
| template <typename L, typename R> |
| L* operator-(L* lhs, const StrictNumeric<R> rhs) { |
| const uintptr_t result = CheckSub(reinterpret_cast<uintptr_t>(lhs), |
| CheckMul(sizeof(L), static_cast<R>(rhs))) |
| .template ValueOrDie<uintptr_t>(); |
| return reinterpret_cast<L*>(result); |
| } |
| |
| } // namespace internal |
| |
| using internal::CheckAdd; |
| using internal::CheckAnd; |
| using internal::CheckDiv; |
| using internal::CheckedNumeric; |
| using internal::CheckLsh; |
| using internal::CheckMax; |
| using internal::CheckMin; |
| using internal::CheckMod; |
| using internal::CheckMul; |
| using internal::CheckOr; |
| using internal::CheckRsh; |
| using internal::CheckSub; |
| using internal::CheckXor; |
| using internal::IsValidForType; |
| using internal::MakeCheckedNum; |
| using internal::ValueOrDefaultForType; |
| using internal::ValueOrDieForType; |
| |
| } // namespace base |
| |
| #endif // BASE_NUMERICS_CHECKED_MATH_H_ |