241 lines
8.5 KiB
C
241 lines
8.5 KiB
C
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// Copyright 2017 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef BASE_NUMERICS_SAFE_MATH_SHARED_IMPL_H_
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#define BASE_NUMERICS_SAFE_MATH_SHARED_IMPL_H_
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#include <stddef.h>
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#include <stdint.h>
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#include <cassert>
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#include <climits>
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#include <cmath>
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#include <cstdlib>
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#include <limits>
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#include <type_traits>
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#include "base/numerics/safe_conversions.h"
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#ifdef __asmjs__
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// Optimized safe math instructions are incompatible with asmjs.
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#define BASE_HAS_OPTIMIZED_SAFE_MATH (0)
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// Where available use builtin math overflow support on Clang and GCC.
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#elif !defined(__native_client__) && \
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((defined(__clang__) && \
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((__clang_major__ > 3) || \
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(__clang_major__ == 3 && __clang_minor__ >= 4))) || \
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(defined(__GNUC__) && __GNUC__ >= 5))
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#include "base/numerics/safe_math_clang_gcc_impl.h"
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#define BASE_HAS_OPTIMIZED_SAFE_MATH (1)
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#else
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#define BASE_HAS_OPTIMIZED_SAFE_MATH (0)
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#endif
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namespace base {
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namespace internal {
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// These are the non-functioning boilerplate implementations of the optimized
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// safe math routines.
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#if !BASE_HAS_OPTIMIZED_SAFE_MATH
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template <typename T, typename U>
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struct CheckedAddFastOp {
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static const bool is_supported = false;
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template <typename V>
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static constexpr bool Do(T, U, V*) {
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// Force a compile failure if instantiated.
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return CheckOnFailure::template HandleFailure<bool>();
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}
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};
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template <typename T, typename U>
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struct CheckedSubFastOp {
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static const bool is_supported = false;
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template <typename V>
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static constexpr bool Do(T, U, V*) {
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// Force a compile failure if instantiated.
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return CheckOnFailure::template HandleFailure<bool>();
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}
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};
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template <typename T, typename U>
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struct CheckedMulFastOp {
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static const bool is_supported = false;
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template <typename V>
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static constexpr bool Do(T, U, V*) {
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// Force a compile failure if instantiated.
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return CheckOnFailure::template HandleFailure<bool>();
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}
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};
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template <typename T, typename U>
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struct ClampedAddFastOp {
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static const bool is_supported = false;
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template <typename V>
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static constexpr V Do(T, U) {
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// Force a compile failure if instantiated.
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return CheckOnFailure::template HandleFailure<V>();
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}
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};
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template <typename T, typename U>
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struct ClampedSubFastOp {
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static const bool is_supported = false;
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template <typename V>
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static constexpr V Do(T, U) {
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// Force a compile failure if instantiated.
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return CheckOnFailure::template HandleFailure<V>();
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}
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};
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template <typename T, typename U>
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struct ClampedMulFastOp {
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static const bool is_supported = false;
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template <typename V>
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static constexpr V Do(T, U) {
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// Force a compile failure if instantiated.
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return CheckOnFailure::template HandleFailure<V>();
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}
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};
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template <typename T>
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struct ClampedNegFastOp {
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static const bool is_supported = false;
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static constexpr T Do(T) {
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// Force a compile failure if instantiated.
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return CheckOnFailure::template HandleFailure<T>();
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}
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};
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#endif // BASE_HAS_OPTIMIZED_SAFE_MATH
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#undef BASE_HAS_OPTIMIZED_SAFE_MATH
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// This is used for UnsignedAbs, where we need to support floating-point
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// template instantiations even though we don't actually support the operations.
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// However, there is no corresponding implementation of e.g. SafeUnsignedAbs,
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// so the float versions will not compile.
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template <typename Numeric,
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bool IsInteger = std::is_integral<Numeric>::value,
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bool IsFloat = std::is_floating_point<Numeric>::value>
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struct UnsignedOrFloatForSize;
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template <typename Numeric>
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struct UnsignedOrFloatForSize<Numeric, true, false> {
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using type = typename std::make_unsigned<Numeric>::type;
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};
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template <typename Numeric>
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struct UnsignedOrFloatForSize<Numeric, false, true> {
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using type = Numeric;
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};
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// Wrap the unary operations to allow SFINAE when instantiating integrals versus
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// floating points. These don't perform any overflow checking. Rather, they
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// exhibit well-defined overflow semantics and rely on the caller to detect
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// if an overflow occured.
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template <typename T,
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typename std::enable_if<std::is_integral<T>::value>::type* = nullptr>
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constexpr T NegateWrapper(T value) {
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using UnsignedT = typename std::make_unsigned<T>::type;
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// This will compile to a NEG on Intel, and is normal negation on ARM.
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return static_cast<T>(UnsignedT(0) - static_cast<UnsignedT>(value));
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}
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template <
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typename T,
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typename std::enable_if<std::is_floating_point<T>::value>::type* = nullptr>
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constexpr T NegateWrapper(T value) {
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return -value;
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}
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template <typename T,
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typename std::enable_if<std::is_integral<T>::value>::type* = nullptr>
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constexpr typename std::make_unsigned<T>::type InvertWrapper(T value) {
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return ~value;
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}
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template <typename T,
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typename std::enable_if<std::is_integral<T>::value>::type* = nullptr>
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constexpr T AbsWrapper(T value) {
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return static_cast<T>(SafeUnsignedAbs(value));
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}
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template <
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typename T,
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typename std::enable_if<std::is_floating_point<T>::value>::type* = nullptr>
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constexpr T AbsWrapper(T value) {
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return value < 0 ? -value : value;
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}
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template <template <typename, typename, typename> class M,
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typename L,
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typename R>
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struct MathWrapper {
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using math = M<typename UnderlyingType<L>::type,
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typename UnderlyingType<R>::type,
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void>;
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using type = typename math::result_type;
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};
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// These variadic templates work out the return types.
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// TODO(jschuh): Rip all this out once we have C++14 non-trailing auto support.
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template <template <typename, typename, typename> class M,
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typename L,
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typename R,
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typename... Args>
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struct ResultType;
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template <template <typename, typename, typename> class M,
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typename L,
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typename R>
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struct ResultType<M, L, R> {
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using type = typename MathWrapper<M, L, R>::type;
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};
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template <template <typename, typename, typename> class M,
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typename L,
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typename R,
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typename... Args>
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struct ResultType {
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using type =
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typename ResultType<M, typename ResultType<M, L, R>::type, Args...>::type;
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};
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// The following macros are just boilerplate for the standard arithmetic
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// operator overloads and variadic function templates. A macro isn't the nicest
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// solution, but it beats rewriting these over and over again.
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#define BASE_NUMERIC_ARITHMETIC_VARIADIC(CLASS, CL_ABBR, OP_NAME) \
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template <typename L, typename R, typename... Args> \
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constexpr CLASS##Numeric< \
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typename ResultType<CLASS##OP_NAME##Op, L, R, Args...>::type> \
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CL_ABBR##OP_NAME(const L lhs, const R rhs, const Args... args) { \
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return CL_ABBR##MathOp<CLASS##OP_NAME##Op, L, R, Args...>(lhs, rhs, \
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args...); \
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}
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#define BASE_NUMERIC_ARITHMETIC_OPERATORS(CLASS, CL_ABBR, OP_NAME, OP, CMP_OP) \
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/* Binary arithmetic operator for all CLASS##Numeric operations. */ \
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template <typename L, typename R, \
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typename std::enable_if<Is##CLASS##Op<L, R>::value>::type* = \
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nullptr> \
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constexpr CLASS##Numeric< \
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typename MathWrapper<CLASS##OP_NAME##Op, L, R>::type> \
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operator OP(const L lhs, const R rhs) { \
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return decltype(lhs OP rhs)::template MathOp<CLASS##OP_NAME##Op>(lhs, \
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rhs); \
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} \
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/* Assignment arithmetic operator implementation from CLASS##Numeric. */ \
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template <typename L> \
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template <typename R> \
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constexpr CLASS##Numeric<L>& CLASS##Numeric<L>::operator CMP_OP( \
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const R rhs) { \
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return MathOp<CLASS##OP_NAME##Op>(rhs); \
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} \
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/* Variadic arithmetic functions that return CLASS##Numeric. */ \
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BASE_NUMERIC_ARITHMETIC_VARIADIC(CLASS, CL_ABBR, OP_NAME)
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} // namespace internal
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} // namespace base
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#endif // BASE_NUMERICS_SAFE_MATH_SHARED_IMPL_H_
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