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// 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_SAFE_MATH_SHARED_IMPL_H_
#define BASE_NUMERICS_SAFE_MATH_SHARED_IMPL_H_
// IWYU pragma: private
#include <concepts>
#include <type_traits>
#include "base/numerics/safe_conversions.h"
#include "build/build_config.h"
#if defined(__asmjs__) || defined(__wasm__)
// Optimized safe math instructions are incompatible with asmjs.
#define BASE_HAS_OPTIMIZED_SAFE_MATH (0)
// Where available use builtin math overflow support on Clang and GCC.
#elif !defined(__native_client__) && \
((defined(__clang__) && \
((__clang_major__ > 3) || \
(__clang_major__ == 3 && __clang_minor__ >= 4))) || \
(defined(__GNUC__) && __GNUC__ >= 5))
#include "base/numerics/safe_math_clang_gcc_impl.h" // IWYU pragma: export
#define BASE_HAS_OPTIMIZED_SAFE_MATH (1)
#else
#define BASE_HAS_OPTIMIZED_SAFE_MATH (0)
#endif
namespace base {
namespace internal {
// These are the non-functioning boilerplate implementations of the optimized
// safe math routines.
#if !BASE_HAS_OPTIMIZED_SAFE_MATH
template <typename T, typename U>
struct CheckedAddFastOp {
static const bool is_supported = false;
template <typename V>
static constexpr bool Do(T, U, V*) {
// Force a compile failure if instantiated.
return CheckOnFailure::template HandleFailure<bool>();
}
};
template <typename T, typename U>
struct CheckedSubFastOp {
static const bool is_supported = false;
template <typename V>
static constexpr bool Do(T, U, V*) {
// Force a compile failure if instantiated.
return CheckOnFailure::template HandleFailure<bool>();
}
};
template <typename T, typename U>
struct CheckedMulFastOp {
static const bool is_supported = false;
template <typename V>
static constexpr bool Do(T, U, V*) {
// Force a compile failure if instantiated.
return CheckOnFailure::template HandleFailure<bool>();
}
};
template <typename T, typename U>
struct ClampedAddFastOp {
static const bool is_supported = false;
template <typename V>
static constexpr V Do(T, U) {
// Force a compile failure if instantiated.
return CheckOnFailure::template HandleFailure<V>();
}
};
template <typename T, typename U>
struct ClampedSubFastOp {
static const bool is_supported = false;
template <typename V>
static constexpr V Do(T, U) {
// Force a compile failure if instantiated.
return CheckOnFailure::template HandleFailure<V>();
}
};
template <typename T, typename U>
struct ClampedMulFastOp {
static const bool is_supported = false;
template <typename V>
static constexpr V Do(T, U) {
// Force a compile failure if instantiated.
return CheckOnFailure::template HandleFailure<V>();
}
};
template <typename T>
struct ClampedNegFastOp {
static const bool is_supported = false;
static constexpr T Do(T) {
// Force a compile failure if instantiated.
return CheckOnFailure::template HandleFailure<T>();
}
};
#endif // BASE_HAS_OPTIMIZED_SAFE_MATH
#undef BASE_HAS_OPTIMIZED_SAFE_MATH
// This is used for UnsignedAbs, where we need to support floating-point
// template instantiations even though we don't actually support the operations.
// However, there is no corresponding implementation of e.g. SafeUnsignedAbs,
// so the float versions will not compile.
template <typename Numeric>
struct UnsignedOrFloatForSize;
template <typename Numeric>
requires(std::integral<Numeric>)
struct UnsignedOrFloatForSize<Numeric> {
using type = typename std::make_unsigned<Numeric>::type;
};
template <typename Numeric>
requires(std::floating_point<Numeric>)
struct UnsignedOrFloatForSize<Numeric> {
using type = Numeric;
};
// Wrap the unary operations to allow SFINAE when instantiating integrals versus
// floating points. These don't perform any overflow checking. Rather, they
// exhibit well-defined overflow semantics and rely on the caller to detect
// if an overflow occurred.
template <typename T>
requires(std::integral<T>)
constexpr T NegateWrapper(T value) {
using UnsignedT = typename std::make_unsigned<T>::type;
// This will compile to a NEG on Intel, and is normal negation on ARM.
return static_cast<T>(UnsignedT(0) - static_cast<UnsignedT>(value));
}
template <typename T>
requires(std::floating_point<T>)
constexpr T NegateWrapper(T value) {
return -value;
}
template <typename T>
requires(std::integral<T>)
constexpr typename std::make_unsigned<T>::type InvertWrapper(T value) {
return ~value;
}
template <typename T>
requires(std::integral<T>)
constexpr T AbsWrapper(T value) {
return static_cast<T>(SafeUnsignedAbs(value));
}
template <typename T>
requires(std::floating_point<T>)
constexpr T AbsWrapper(T value) {
return value < 0 ? -value : value;
}
template <template <typename, typename> class M,
typename L,
typename R,
typename Math = M<UnderlyingType<L>, UnderlyingType<R>>>
requires requires { typename Math::result_type; }
struct MathWrapper {
using math = Math;
using type = typename math::result_type;
};
// The following macros are just boilerplate for the standard arithmetic
// operator overloads and variadic function templates. A macro isn't the nicest
// solution, but it beats rewriting these over and over again.
#define BASE_NUMERIC_ARITHMETIC_VARIADIC(CLASS, CL_ABBR, OP_NAME) \
template <typename L, typename R, typename... Args> \
constexpr auto CL_ABBR##OP_NAME(L lhs, R rhs, Args... args) { \
return CL_ABBR##MathOp<CLASS##OP_NAME##Op, L, R, Args...>(lhs, rhs, \
args...); \
}
#define BASE_NUMERIC_ARITHMETIC_OPERATORS(CLASS, CL_ABBR, OP_NAME, OP, CMP_OP) \
/* Binary arithmetic operator for all CLASS##Numeric operations. */ \
template <typename L, typename R> \
requires(Is##CLASS##Op<L, R>) \
constexpr CLASS##Numeric< \
typename MathWrapper<CLASS##OP_NAME##Op, L, R>::type> \
operator OP(L lhs, R rhs) { \
return decltype(lhs OP rhs)::template MathOp<CLASS##OP_NAME##Op>(lhs, \
rhs); \
} \
/* Assignment arithmetic operator implementation from CLASS##Numeric. */ \
template <typename L> \
requires std::is_arithmetic_v<L> \
template <typename R> \
constexpr CLASS##Numeric<L>& CLASS##Numeric<L>::operator CMP_OP(R rhs) { \
return MathOp<CLASS##OP_NAME##Op>(rhs); \
} \
/* Variadic arithmetic functions that return CLASS##Numeric. */ \
BASE_NUMERIC_ARITHMETIC_VARIADIC(CLASS, CL_ABBR, OP_NAME)
} // namespace internal
} // namespace base
#endif // BASE_NUMERICS_SAFE_MATH_SHARED_IMPL_H_
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