mirror of
https://github.com/mozilla/gecko-dev.git
synced 2024-10-17 23:35:34 +00:00
76a01325a7
Differential Revision: https://phabricator.services.mozilla.com/D68362 --HG-- extra : moz-landing-system : lando
797 lines
22 KiB
C++
797 lines
22 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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/* Template-based metaprogramming and type-testing facilities. */
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#ifndef mozilla_TypeTraits_h
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#define mozilla_TypeTraits_h
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#include "mozilla/Types.h"
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/*
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* These traits are approximate copies of the traits and semantics from C++11's
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* <type_traits> header. Don't add traits not in that header! When all
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* platforms provide that header, we can convert all users and remove this one.
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*/
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namespace mozilla {
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/* Forward declarations. */
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template <typename>
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struct RemoveCV;
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template <typename>
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struct AddRvalueReference;
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/* 20.2.4 Function template declval [declval] */
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/**
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* DeclVal simplifies the definition of expressions which occur as unevaluated
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* operands. It converts T to a reference type, making it possible to use in
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* decltype expressions even if T does not have a default constructor, e.g.:
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* decltype(DeclVal<TWithNoDefaultConstructor>().foo())
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*/
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template <typename T>
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typename AddRvalueReference<T>::Type DeclVal();
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/* 20.9.3 Helper classes [meta.help] */
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/**
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* Helper class used as a base for various type traits, exposed publicly
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* because <type_traits> exposes it as well.
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*/
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template <typename T, T Value>
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struct IntegralConstant {
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static constexpr T value = Value;
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typedef T ValueType;
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typedef IntegralConstant<T, Value> Type;
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};
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/** Convenient aliases. */
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typedef IntegralConstant<bool, true> TrueType;
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typedef IntegralConstant<bool, false> FalseType;
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/* 20.9.4 Unary type traits [meta.unary] */
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/* 20.9.4.1 Primary type categories [meta.unary.cat] */
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namespace detail {
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template <typename T>
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struct IsVoidHelper : FalseType {};
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template <>
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struct IsVoidHelper<void> : TrueType {};
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} // namespace detail
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/**
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* IsVoid determines whether a type is void.
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*
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* mozilla::IsVoid<int>::value is false;
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* mozilla::IsVoid<void>::value is true;
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* mozilla::IsVoid<void*>::value is false;
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* mozilla::IsVoid<volatile void>::value is true.
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*/
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template <typename T>
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struct IsVoid : detail::IsVoidHelper<typename RemoveCV<T>::Type> {};
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namespace detail {
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template <typename T>
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struct IsIntegralHelper : FalseType {};
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template <>
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struct IsIntegralHelper<char> : TrueType {};
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template <>
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struct IsIntegralHelper<signed char> : TrueType {};
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template <>
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struct IsIntegralHelper<unsigned char> : TrueType {};
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template <>
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struct IsIntegralHelper<short> : TrueType {};
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template <>
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struct IsIntegralHelper<unsigned short> : TrueType {};
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template <>
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struct IsIntegralHelper<int> : TrueType {};
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template <>
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struct IsIntegralHelper<unsigned int> : TrueType {};
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template <>
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struct IsIntegralHelper<long> : TrueType {};
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template <>
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struct IsIntegralHelper<unsigned long> : TrueType {};
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template <>
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struct IsIntegralHelper<long long> : TrueType {};
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template <>
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struct IsIntegralHelper<unsigned long long> : TrueType {};
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template <>
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struct IsIntegralHelper<bool> : TrueType {};
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template <>
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struct IsIntegralHelper<wchar_t> : TrueType {};
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template <>
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struct IsIntegralHelper<char16_t> : TrueType {};
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template <>
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struct IsIntegralHelper<char32_t> : TrueType {};
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} /* namespace detail */
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/**
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* IsIntegral determines whether a type is an integral type.
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*
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* mozilla::IsIntegral<int>::value is true;
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* mozilla::IsIntegral<unsigned short>::value is true;
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* mozilla::IsIntegral<const long>::value is true;
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* mozilla::IsIntegral<int*>::value is false;
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* mozilla::IsIntegral<double>::value is false;
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*/
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template <typename T>
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struct IsIntegral : detail::IsIntegralHelper<typename RemoveCV<T>::Type> {};
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template <typename T, typename U>
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struct IsSame;
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namespace detail {
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template <typename T>
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struct IsFloatingPointHelper
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: IntegralConstant<bool, IsSame<T, float>::value ||
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IsSame<T, double>::value ||
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IsSame<T, long double>::value> {};
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} // namespace detail
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/**
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* IsFloatingPoint determines whether a type is a floating point type (float,
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* double, long double).
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*
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* mozilla::IsFloatingPoint<int>::value is false;
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* mozilla::IsFloatingPoint<const float>::value is true;
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* mozilla::IsFloatingPoint<long double>::value is true;
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* mozilla::IsFloatingPoint<double*>::value is false.
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*/
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template <typename T>
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struct IsFloatingPoint
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: detail::IsFloatingPointHelper<typename RemoveCV<T>::Type> {};
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namespace detail {
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template <typename T>
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struct IsArrayHelper : FalseType {};
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template <typename T, decltype(sizeof(1)) N>
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struct IsArrayHelper<T[N]> : TrueType {};
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template <typename T>
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struct IsArrayHelper<T[]> : TrueType {};
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} // namespace detail
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/**
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* IsArray determines whether a type is an array type, of known or unknown
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* length.
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*
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* mozilla::IsArray<int>::value is false;
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* mozilla::IsArray<int[]>::value is true;
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* mozilla::IsArray<int[5]>::value is true.
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*/
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template <typename T>
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struct IsArray : detail::IsArrayHelper<typename RemoveCV<T>::Type> {};
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namespace detail {
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template <typename T>
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struct IsFunPtr;
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template <typename>
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struct IsFunPtr : public FalseType {};
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template <typename Result, typename... ArgTypes>
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struct IsFunPtr<Result (*)(ArgTypes...)> : public TrueType {};
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}; // namespace detail
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/**
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* IsFunction determines whether a type is a function type. Function pointers
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* don't qualify here--only the type of an actual function symbol. We do not
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* correctly handle varags function types because of a bug in MSVC.
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*
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* Given the function:
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* void f(int) {}
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*
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* mozilla::IsFunction<void(int)> is true;
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* mozilla::IsFunction<void(*)(int)> is false;
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* mozilla::IsFunction<decltype(f)> is true.
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*/
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template <typename T>
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struct IsFunction : public detail::IsFunPtr<typename RemoveCV<T>::Type*> {};
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namespace detail {
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template <typename T>
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struct IsPointerHelper : FalseType {};
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template <typename T>
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struct IsPointerHelper<T*> : TrueType {};
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} // namespace detail
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/**
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* IsPointer determines whether a type is a possibly-CV-qualified pointer type
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* (but not a pointer-to-member type).
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*
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* mozilla::IsPointer<struct S*>::value is true;
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* mozilla::IsPointer<int*>::value is true;
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* mozilla::IsPointer<int**>::value is true;
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* mozilla::IsPointer<const int*>::value is true;
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* mozilla::IsPointer<int* const>::value is true;
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* mozilla::IsPointer<int* volatile>::value is true;
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* mozilla::IsPointer<void (*)(void)>::value is true;
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* mozilla::IsPointer<int>::value is false;
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* mozilla::IsPointer<struct S>::value is false.
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* mozilla::IsPointer<int(struct S::*)>::value is false
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*/
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template <typename T>
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struct IsPointer : detail::IsPointerHelper<typename RemoveCV<T>::Type> {};
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namespace detail {
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// __is_enum is a supported extension across all of our supported compilers.
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template <typename T>
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struct IsEnumHelper : IntegralConstant<bool, __is_enum(T)> {};
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} // namespace detail
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/**
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* IsEnum determines whether a type is an enum type.
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*
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* mozilla::IsEnum<enum S>::value is true;
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* mozilla::IsEnum<enum S*>::value is false;
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* mozilla::IsEnum<int>::value is false;
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*/
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template <typename T>
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struct IsEnum : detail::IsEnumHelper<typename RemoveCV<T>::Type> {};
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/* 20.9.4.2 Composite type traits [meta.unary.comp] */
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/**
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* IsArithmetic determines whether a type is arithmetic. A type is arithmetic
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* iff it is an integral type or a floating point type.
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*
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* mozilla::IsArithmetic<int>::value is true;
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* mozilla::IsArithmetic<double>::value is true;
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* mozilla::IsArithmetic<long double*>::value is false.
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*/
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template <typename T>
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struct IsArithmetic : IntegralConstant<bool, IsIntegral<T>::value ||
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IsFloatingPoint<T>::value> {};
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/* 20.9.4.3 Type properties [meta.unary.prop] */
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/**
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* IsConst determines whether a type is const or not.
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*
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* mozilla::IsConst<int>::value is false;
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* mozilla::IsConst<void* const>::value is true;
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* mozilla::IsConst<const char*>::value is false.
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*/
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template <typename T>
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struct IsConst : FalseType {};
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template <typename T>
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struct IsConst<const T> : TrueType {};
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/**
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* IsVolatile determines whether a type is volatile or not.
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*
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* mozilla::IsVolatile<int>::value is false;
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* mozilla::IsVolatile<void* volatile>::value is true;
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* mozilla::IsVolatile<volatile char*>::value is false.
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*/
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template <typename T>
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struct IsVolatile : FalseType {};
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template <typename T>
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struct IsVolatile<volatile T> : TrueType {};
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/**
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* Traits class for identifying POD types. Until C++11 there's no automatic
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* way to detect PODs, so for the moment this is done manually. Users may
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* define specializations of this class that inherit from mozilla::TrueType and
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* mozilla::FalseType (or equivalently mozilla::IntegralConstant<bool, true or
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* false>, or conveniently from mozilla::IsPod for composite types) as needed to
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* ensure correct IsPod behavior.
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*/
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template <typename T>
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struct IsPod : public FalseType {};
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template <>
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struct IsPod<char> : TrueType {};
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template <>
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struct IsPod<signed char> : TrueType {};
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template <>
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struct IsPod<unsigned char> : TrueType {};
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template <>
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struct IsPod<short> : TrueType {};
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template <>
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struct IsPod<unsigned short> : TrueType {};
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template <>
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struct IsPod<int> : TrueType {};
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template <>
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struct IsPod<unsigned int> : TrueType {};
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template <>
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struct IsPod<long> : TrueType {};
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template <>
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struct IsPod<unsigned long> : TrueType {};
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template <>
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struct IsPod<long long> : TrueType {};
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template <>
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struct IsPod<unsigned long long> : TrueType {};
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template <>
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struct IsPod<bool> : TrueType {};
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template <>
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struct IsPod<float> : TrueType {};
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template <>
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struct IsPod<double> : TrueType {};
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template <>
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struct IsPod<wchar_t> : TrueType {};
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template <>
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struct IsPod<char16_t> : TrueType {};
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template <typename T>
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struct IsPod<T*> : TrueType {};
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namespace detail {
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template <typename T, bool = IsFloatingPoint<T>::value,
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bool = IsIntegral<T>::value,
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typename NoCV = typename RemoveCV<T>::Type>
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struct IsSignedHelper;
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// Floating point is signed.
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template <typename T, typename NoCV>
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struct IsSignedHelper<T, true, false, NoCV> : TrueType {};
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// Integral is conditionally signed.
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template <typename T, typename NoCV>
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struct IsSignedHelper<T, false, true, NoCV>
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: IntegralConstant<bool, bool(NoCV(-1) < NoCV(1))> {};
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// Non-floating point, non-integral is not signed.
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template <typename T, typename NoCV>
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struct IsSignedHelper<T, false, false, NoCV> : FalseType {};
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} // namespace detail
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/**
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* IsSigned determines whether a type is a signed arithmetic type. |char| is
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* considered a signed type if it has the same representation as |signed char|.
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*
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* mozilla::IsSigned<int>::value is true;
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* mozilla::IsSigned<const unsigned int>::value is false;
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* mozilla::IsSigned<unsigned char>::value is false;
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* mozilla::IsSigned<float>::value is true.
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*/
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template <typename T>
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struct IsSigned : detail::IsSignedHelper<T> {};
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namespace detail {
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template <typename T, bool = IsFloatingPoint<T>::value,
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bool = IsIntegral<T>::value,
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typename NoCV = typename RemoveCV<T>::Type>
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struct IsUnsignedHelper;
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// Floating point is not unsigned.
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template <typename T, typename NoCV>
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struct IsUnsignedHelper<T, true, false, NoCV> : FalseType {};
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// Integral is conditionally unsigned.
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template <typename T, typename NoCV>
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struct IsUnsignedHelper<T, false, true, NoCV>
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: IntegralConstant<bool, (IsSame<NoCV, bool>::value ||
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bool(NoCV(1) < NoCV(-1)))> {};
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// Non-floating point, non-integral is not unsigned.
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template <typename T, typename NoCV>
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struct IsUnsignedHelper<T, false, false, NoCV> : FalseType {};
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} // namespace detail
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/**
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* IsUnsigned determines whether a type is an unsigned arithmetic type.
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*
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* mozilla::IsUnsigned<int>::value is false;
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* mozilla::IsUnsigned<const unsigned int>::value is true;
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* mozilla::IsUnsigned<unsigned char>::value is true;
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* mozilla::IsUnsigned<float>::value is false.
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*/
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template <typename T>
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struct IsUnsigned : detail::IsUnsignedHelper<T> {};
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namespace detail {
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struct DoIsDestructibleImpl {
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template <typename T, typename = decltype(DeclVal<T&>().~T())>
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static TrueType test(int);
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template <typename T>
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static FalseType test(...);
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};
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template <typename T>
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struct IsDestructibleImpl : public DoIsDestructibleImpl {
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typedef decltype(test<T>(0)) Type;
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};
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} // namespace detail
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/**
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* IsDestructible determines whether a type has a public destructor.
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*
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* struct S0 {}; // Implicit default destructor.
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* struct S1 { ~S1(); };
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* class C2 { ~C2(); }; // private destructor.
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*
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* mozilla::IsDestructible<S0>::value is true;
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* mozilla::IsDestructible<S1>::value is true;
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* mozilla::IsDestructible<C2>::value is false.
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*/
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template <typename T>
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struct IsDestructible : public detail::IsDestructibleImpl<T>::Type {};
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/* 20.9.5 Type property queries [meta.unary.prop.query] */
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/* 20.9.6 Relationships between types [meta.rel] */
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/**
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* IsSame tests whether two types are the same type.
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*
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* mozilla::IsSame<int, int>::value is true;
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* mozilla::IsSame<int*, int*>::value is true;
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* mozilla::IsSame<int, unsigned int>::value is false;
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* mozilla::IsSame<void, void>::value is true;
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* mozilla::IsSame<const int, int>::value is false;
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* mozilla::IsSame<struct S, struct S>::value is true.
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*/
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template <typename T, typename U>
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struct IsSame : FalseType {};
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template <typename T>
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struct IsSame<T, T> : TrueType {};
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namespace detail {
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template <typename From, typename To>
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struct ConvertibleTester {
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private:
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template <typename To1>
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static char test_helper(To1);
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template <typename From1, typename To1>
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static decltype(test_helper<To1>(DeclVal<From1>())) test(int);
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template <typename From1, typename To1>
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static int test(...);
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public:
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static const bool value = sizeof(test<From, To>(0)) == sizeof(char);
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};
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} // namespace detail
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/**
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* IsConvertible determines whether a value of type From will implicitly convert
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* to a value of type To. For example:
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*
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* struct A {};
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* struct B : public A {};
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* struct C {};
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*
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* mozilla::IsConvertible<A, A>::value is true;
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* mozilla::IsConvertible<A*, A*>::value is true;
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* mozilla::IsConvertible<B, A>::value is true;
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* mozilla::IsConvertible<B*, A*>::value is true;
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* mozilla::IsConvertible<C, A>::value is false;
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* mozilla::IsConvertible<A, C>::value is false;
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* mozilla::IsConvertible<A*, C*>::value is false;
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* mozilla::IsConvertible<C*, A*>::value is false.
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*
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* For obscure reasons, you can't use IsConvertible when the types being tested
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* are related through private inheritance, and you'll get a compile error if
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* you try. Just don't do it!
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*
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* Note - we need special handling for void, which ConvertibleTester doesn't
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* handle. The void handling here doesn't handle const/volatile void correctly,
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* which could be easily fixed if the need arises.
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*/
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template <typename From, typename To>
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struct IsConvertible
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: IntegralConstant<bool, detail::ConvertibleTester<From, To>::value> {};
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template <typename B>
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struct IsConvertible<void, B> : IntegralConstant<bool, IsVoid<B>::value> {};
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template <typename A>
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struct IsConvertible<A, void> : IntegralConstant<bool, IsVoid<A>::value> {};
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template <>
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struct IsConvertible<void, void> : TrueType {};
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/* 20.9.7 Transformations between types [meta.trans] */
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/* 20.9.7.1 Const-volatile modifications [meta.trans.cv] */
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/**
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* RemoveConst removes top-level const qualifications on a type.
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*
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* mozilla::RemoveConst<int>::Type is int;
|
|
* mozilla::RemoveConst<const int>::Type is int;
|
|
* mozilla::RemoveConst<const int*>::Type is const int*;
|
|
* mozilla::RemoveConst<int* const>::Type is int*.
|
|
*/
|
|
template <typename T>
|
|
struct RemoveConst {
|
|
typedef T Type;
|
|
};
|
|
|
|
template <typename T>
|
|
struct RemoveConst<const T> {
|
|
typedef T Type;
|
|
};
|
|
|
|
/**
|
|
* RemoveVolatile removes top-level volatile qualifications on a type.
|
|
*
|
|
* mozilla::RemoveVolatile<int>::Type is int;
|
|
* mozilla::RemoveVolatile<volatile int>::Type is int;
|
|
* mozilla::RemoveVolatile<volatile int*>::Type is volatile int*;
|
|
* mozilla::RemoveVolatile<int* volatile>::Type is int*.
|
|
*/
|
|
template <typename T>
|
|
struct RemoveVolatile {
|
|
typedef T Type;
|
|
};
|
|
|
|
template <typename T>
|
|
struct RemoveVolatile<volatile T> {
|
|
typedef T Type;
|
|
};
|
|
|
|
/**
|
|
* RemoveCV removes top-level const and volatile qualifications on a type.
|
|
*
|
|
* mozilla::RemoveCV<int>::Type is int;
|
|
* mozilla::RemoveCV<const int>::Type is int;
|
|
* mozilla::RemoveCV<volatile int>::Type is int;
|
|
* mozilla::RemoveCV<int* const volatile>::Type is int*.
|
|
*/
|
|
template <typename T>
|
|
struct RemoveCV {
|
|
typedef typename RemoveConst<typename RemoveVolatile<T>::Type>::Type Type;
|
|
};
|
|
|
|
/* 20.9.7.2 Reference modifications [meta.trans.ref] */
|
|
|
|
/**
|
|
* Converts reference types to the underlying types.
|
|
*
|
|
* mozilla::RemoveReference<T>::Type is T;
|
|
* mozilla::RemoveReference<T&>::Type is T;
|
|
* mozilla::RemoveReference<T&&>::Type is T;
|
|
*/
|
|
|
|
template <typename T>
|
|
struct RemoveReference {
|
|
typedef T Type;
|
|
};
|
|
|
|
template <typename T>
|
|
struct RemoveReference<T&> {
|
|
typedef T Type;
|
|
};
|
|
|
|
template <typename T>
|
|
struct RemoveReference<T&&> {
|
|
typedef T Type;
|
|
};
|
|
|
|
namespace detail {
|
|
|
|
enum Voidness { TIsVoid, TIsNotVoid };
|
|
|
|
template <typename T, Voidness V = IsVoid<T>::value ? TIsVoid : TIsNotVoid>
|
|
struct AddRvalueReferenceHelper;
|
|
|
|
template <typename T>
|
|
struct AddRvalueReferenceHelper<T, TIsVoid> {
|
|
typedef void Type;
|
|
};
|
|
|
|
template <typename T>
|
|
struct AddRvalueReferenceHelper<T, TIsNotVoid> {
|
|
typedef T&& Type;
|
|
};
|
|
|
|
} // namespace detail
|
|
|
|
/**
|
|
* AddRvalueReference adds an rvalue && reference to T if one isn't already
|
|
* present. (Note: adding an rvalue reference to an lvalue & reference in
|
|
* essence keeps the &, per C+11 reference collapsing rules. For example,
|
|
* int& would remain int&.)
|
|
*
|
|
* The final computed type will only *not* be a reference if T is void.
|
|
*
|
|
* mozilla::AddRvalueReference<int>::Type is int&&;
|
|
* mozilla::AddRvalueRference<volatile int&>::Type is volatile int&;
|
|
* mozilla::AddRvalueRference<const int&&>::Type is const int&&;
|
|
* mozilla::AddRvalueReference<void*>::Type is void*&&;
|
|
* mozilla::AddRvalueReference<void>::Type is void;
|
|
* mozilla::AddRvalueReference<struct S&>::Type is struct S&.
|
|
*/
|
|
template <typename T>
|
|
struct AddRvalueReference : detail::AddRvalueReferenceHelper<T> {};
|
|
|
|
/* 20.9.7.4 Array modifications [meta.trans.arr] */
|
|
|
|
/**
|
|
* RemoveExtent produces either the type of the elements of the array T, or T
|
|
* itself.
|
|
*
|
|
* mozilla::RemoveExtent<int>::Type is int;
|
|
* mozilla::RemoveExtent<const int[]>::Type is const int;
|
|
* mozilla::RemoveExtent<volatile int[5]>::Type is volatile int;
|
|
* mozilla::RemoveExtent<long[][17]>::Type is long[17].
|
|
*/
|
|
template <typename T>
|
|
struct RemoveExtent {
|
|
typedef T Type;
|
|
};
|
|
|
|
template <typename T>
|
|
struct RemoveExtent<T[]> {
|
|
typedef T Type;
|
|
};
|
|
|
|
template <typename T, decltype(sizeof(1)) N>
|
|
struct RemoveExtent<T[N]> {
|
|
typedef T Type;
|
|
};
|
|
|
|
/* 20.9.7.5 Pointer modifications [meta.trans.ptr] */
|
|
|
|
namespace detail {
|
|
|
|
template <typename T, typename CVRemoved>
|
|
struct RemovePointerHelper {
|
|
typedef T Type;
|
|
};
|
|
|
|
template <typename T, typename Pointee>
|
|
struct RemovePointerHelper<T, Pointee*> {
|
|
typedef Pointee Type;
|
|
};
|
|
|
|
} // namespace detail
|
|
|
|
/**
|
|
* Produces the pointed-to type if a pointer is provided, else returns the input
|
|
* type. Note that this does not dereference pointer-to-member pointers.
|
|
*
|
|
* struct S { bool m; void f(); };
|
|
* mozilla::RemovePointer<int>::Type is int;
|
|
* mozilla::RemovePointer<int*>::Type is int;
|
|
* mozilla::RemovePointer<int* const>::Type is int;
|
|
* mozilla::RemovePointer<int* volatile>::Type is int;
|
|
* mozilla::RemovePointer<const long*>::Type is const long;
|
|
* mozilla::RemovePointer<void* const>::Type is void;
|
|
* mozilla::RemovePointer<void (S::*)()>::Type is void (S::*)();
|
|
* mozilla::RemovePointer<void (*)()>::Type is void();
|
|
* mozilla::RemovePointer<bool S::*>::Type is bool S::*.
|
|
*/
|
|
template <typename T>
|
|
struct RemovePointer
|
|
: detail::RemovePointerHelper<T, typename RemoveCV<T>::Type> {};
|
|
|
|
/**
|
|
* Converts T& to T*. Otherwise returns T* given T. Note that C++17 wants
|
|
* std::add_pointer to work differently for function types. We don't implement
|
|
* that behavior here.
|
|
*
|
|
* mozilla::AddPointer<int> is int*;
|
|
* mozilla::AddPointer<int*> is int**;
|
|
* mozilla::AddPointer<int&> is int*;
|
|
* mozilla::AddPointer<int* const> is int** const.
|
|
*/
|
|
template <typename T>
|
|
struct AddPointer {
|
|
typedef typename RemoveReference<T>::Type* Type;
|
|
};
|
|
|
|
/* 20.9.7.6 Other transformations [meta.trans.other] */
|
|
|
|
/**
|
|
* EnableIf is a struct containing a typedef of T if and only if B is true.
|
|
*
|
|
* mozilla::EnableIf<true, int>::Type is int;
|
|
* mozilla::EnableIf<false, int>::Type is a compile-time error.
|
|
*
|
|
* Use this template to implement SFINAE-style (Substitution Failure Is not An
|
|
* Error) requirements. For example, you might use it to impose a restriction
|
|
* on a template parameter:
|
|
*
|
|
* template<typename T>
|
|
* class PodVector // vector optimized to store POD (memcpy-able) types
|
|
* {
|
|
* EnableIf<IsPod<T>::value, T>::Type* vector;
|
|
* size_t length;
|
|
* ...
|
|
* };
|
|
*/
|
|
template <bool B, typename T = void>
|
|
struct EnableIf {};
|
|
|
|
template <typename T>
|
|
struct EnableIf<true, T> {
|
|
typedef T Type;
|
|
};
|
|
|
|
/**
|
|
* Conditional selects a class between two, depending on a given boolean value.
|
|
*
|
|
* mozilla::Conditional<true, A, B>::Type is A;
|
|
* mozilla::Conditional<false, A, B>::Type is B;
|
|
*/
|
|
template <bool Condition, typename A, typename B>
|
|
struct Conditional {
|
|
typedef A Type;
|
|
};
|
|
|
|
template <class A, class B>
|
|
struct Conditional<false, A, B> {
|
|
typedef B Type;
|
|
};
|
|
|
|
namespace detail {
|
|
|
|
template <typename U, bool IsArray = IsArray<U>::value,
|
|
bool IsFunction = IsFunction<U>::value>
|
|
struct DecaySelector;
|
|
|
|
template <typename U>
|
|
struct DecaySelector<U, false, false> {
|
|
typedef typename RemoveCV<U>::Type Type;
|
|
};
|
|
|
|
template <typename U>
|
|
struct DecaySelector<U, true, false> {
|
|
typedef typename RemoveExtent<U>::Type* Type;
|
|
};
|
|
|
|
template <typename U>
|
|
struct DecaySelector<U, false, true> {
|
|
typedef typename AddPointer<U>::Type Type;
|
|
};
|
|
|
|
}; // namespace detail
|
|
|
|
/**
|
|
* Strips const/volatile off a type and decays it from an lvalue to an
|
|
* rvalue. So function types are converted to function pointers, arrays to
|
|
* pointers, and references are removed.
|
|
*
|
|
* mozilla::Decay<int>::Type is int
|
|
* mozilla::Decay<int&>::Type is int
|
|
* mozilla::Decay<int&&>::Type is int
|
|
* mozilla::Decay<const int&>::Type is int
|
|
* mozilla::Decay<int[2]>::Type is int*
|
|
* mozilla::Decay<int(int)>::Type is int(*)(int)
|
|
*/
|
|
template <typename T>
|
|
class Decay : public detail::DecaySelector<typename RemoveReference<T>::Type> {
|
|
};
|
|
|
|
} /* namespace mozilla */
|
|
|
|
#endif /* mozilla_TypeTraits_h */
|