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Diffstat (limited to 'security/sandbox/chromium/base/numerics/checked_math.h')
| -rw-r--r-- | security/sandbox/chromium/base/numerics/checked_math.h | 393 |
1 files changed, 393 insertions, 0 deletions
diff --git a/security/sandbox/chromium/base/numerics/checked_math.h b/security/sandbox/chromium/base/numerics/checked_math.h new file mode 100644 index 0000000000..ede3344f82 --- /dev/null +++ b/security/sandbox/chromium/base/numerics/checked_math.h @@ -0,0 +1,393 @@ +// Copyright 2017 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_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 base { +namespace internal { + +template <typename T> +class CheckedNumeric { + static_assert(std::is_arithmetic<T>::value, + "CheckedNumeric<T>: T must be a numeric type."); + + public: + using type = T; + + constexpr CheckedNumeric() = default; + + // Copy constructor. + template <typename Src> + constexpr CheckedNumeric(const CheckedNumeric<Src>& rhs) + : state_(rhs.state_.value(), rhs.IsValid()) {} + + template <typename Src> + friend class CheckedNumeric; + + // This is not an explicit constructor because we implicitly upgrade regular + // numerics to CheckedNumerics to make them easier to use. + template <typename Src> + constexpr CheckedNumeric(Src value) // NOLINT(runtime/explicit) + : state_(value) { + static_assert(std::is_arithmetic<Src>::value, "Argument must be numeric."); + } + + // This is not an explicit constructor because we want a seamless conversion + // from StrictNumeric types. + template <typename Src> + constexpr CheckedNumeric( + StrictNumeric<Src> value) // NOLINT(runtime/explicit) + : 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 CHECK and crash. + // A range checked destination type can be supplied using the Dst template + // parameter, which will trigger a CHECK if the value is not in bounds for + // the destination. + // The 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 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 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 { + // The negation of two's complement int min is int min, so we simply + // check for that in the constexpr case. + // We use an optimized code path for a known run-time variable. + return MustTreatAsConstexpr(state_.value()) || !std::is_signed<T>::value || + std::is_floating_point<T>::value + ? CheckedNumeric<T>( + NegateWrapper(state_.value()), + IsValid() && (!std::is_signed<T>::value || + std::is_floating_point<T>::value || + NegateWrapper(state_.value()) != + std::numeric_limits<T>::lowest())) + : FastRuntimeNegate(); + } + + 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 { + using R = typename UnderlyingType<U>::type; + using result_type = typename MathWrapper<CheckedMaxOp, T, U>::type; + // TODO(jschuh): This can be converted to the MathOp version and remain + // constexpr once we have C++14 support. + return CheckedNumeric<result_type>( + static_cast<result_type>( + IsGreater<T, R>::Test(state_.value(), Wrapper<U>::value(rhs)) + ? state_.value() + : Wrapper<U>::value(rhs)), + state_.is_valid() && Wrapper<U>::is_valid(rhs)); + } + + template <typename U> + constexpr CheckedNumeric<typename MathWrapper<CheckedMinOp, T, U>::type> Min( + const U rhs) const { + using R = typename UnderlyingType<U>::type; + using result_type = typename MathWrapper<CheckedMinOp, T, U>::type; + // TODO(jschuh): This can be converted to the MathOp version and remain + // constexpr once we have C++14 support. + return CheckedNumeric<result_type>( + static_cast<result_type>( + IsLess<T, R>::Test(state_.value(), Wrapper<U>::value(rhs)) + ? state_.value() + : Wrapper<U>::value(rhs)), + state_.is_valid() && Wrapper<U>::is_valid(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) { + 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; + 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. + 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; + 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); +} + +// Convience 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 CheckedNumeric<typename ResultType<M, L, R, Args...>::type> +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 CHECK condition here. +template <typename L, typename R> +L* operator+(L* lhs, const StrictNumeric<R> rhs) { + 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) { + 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::CheckedNumeric; +using internal::IsValidForType; +using internal::ValueOrDieForType; +using internal::ValueOrDefaultForType; +using internal::MakeCheckedNum; +using internal::CheckMax; +using internal::CheckMin; +using internal::CheckAdd; +using internal::CheckSub; +using internal::CheckMul; +using internal::CheckDiv; +using internal::CheckMod; +using internal::CheckLsh; +using internal::CheckRsh; +using internal::CheckAnd; +using internal::CheckOr; +using internal::CheckXor; + +} // namespace base + +#endif // BASE_NUMERICS_CHECKED_MATH_H_ |