diff options
Diffstat (limited to 'mfbt/TypeTraits.h')
| -rw-r--r-- | mfbt/TypeTraits.h | 1262 |
1 files changed, 1262 insertions, 0 deletions
diff --git a/mfbt/TypeTraits.h b/mfbt/TypeTraits.h new file mode 100644 index 0000000000..084f608caa --- /dev/null +++ b/mfbt/TypeTraits.h @@ -0,0 +1,1262 @@ +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ +/* vim: set ts=8 sts=2 et sw=2 tw=80: */ +/* This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ + +/* Template-based metaprogramming and type-testing facilities. */ + +#ifndef mozilla_TypeTraits_h +#define mozilla_TypeTraits_h + +#include "mozilla/Types.h" + +/* + * These traits are approximate copies of the traits and semantics from C++11's + * <type_traits> header. Don't add traits not in that header! When all + * platforms provide that header, we can convert all users and remove this one. + */ + +#include <wchar.h> + +namespace mozilla { + +/* Forward declarations. */ + +template<typename> struct RemoveCV; +template<typename> struct AddRvalueReference; + +/* 20.2.4 Function template declval [declval] */ + +/** + * DeclVal simplifies the definition of expressions which occur as unevaluated + * operands. It converts T to a reference type, making it possible to use in + * decltype expressions even if T does not have a default constructor, e.g.: + * decltype(DeclVal<TWithNoDefaultConstructor>().foo()) + */ +template<typename T> +typename AddRvalueReference<T>::Type DeclVal(); + +/* 20.9.3 Helper classes [meta.help] */ + +/** + * Helper class used as a base for various type traits, exposed publicly + * because <type_traits> exposes it as well. + */ +template<typename T, T Value> +struct IntegralConstant +{ + static const T value = Value; + typedef T ValueType; + typedef IntegralConstant<T, Value> Type; +}; + +/** Convenient aliases. */ +typedef IntegralConstant<bool, true> TrueType; +typedef IntegralConstant<bool, false> FalseType; + +/* 20.9.4 Unary type traits [meta.unary] */ + +/* 20.9.4.1 Primary type categories [meta.unary.cat] */ + +namespace detail { + +template<typename T> +struct IsVoidHelper : FalseType {}; + +template<> +struct IsVoidHelper<void> : TrueType {}; + +} // namespace detail + +/** + * IsVoid determines whether a type is void. + * + * mozilla::IsVoid<int>::value is false; + * mozilla::IsVoid<void>::value is true; + * mozilla::IsVoid<void*>::value is false; + * mozilla::IsVoid<volatile void>::value is true. + */ +template<typename T> +struct IsVoid : detail::IsVoidHelper<typename RemoveCV<T>::Type> {}; + +namespace detail { + +template <typename T> +struct IsIntegralHelper : FalseType {}; + +template<> struct IsIntegralHelper<char> : TrueType {}; +template<> struct IsIntegralHelper<signed char> : TrueType {}; +template<> struct IsIntegralHelper<unsigned char> : TrueType {}; +template<> struct IsIntegralHelper<short> : TrueType {}; +template<> struct IsIntegralHelper<unsigned short> : TrueType {}; +template<> struct IsIntegralHelper<int> : TrueType {}; +template<> struct IsIntegralHelper<unsigned int> : TrueType {}; +template<> struct IsIntegralHelper<long> : TrueType {}; +template<> struct IsIntegralHelper<unsigned long> : TrueType {}; +template<> struct IsIntegralHelper<long long> : TrueType {}; +template<> struct IsIntegralHelper<unsigned long long> : TrueType {}; +template<> struct IsIntegralHelper<bool> : TrueType {}; +template<> struct IsIntegralHelper<wchar_t> : TrueType {}; +template<> struct IsIntegralHelper<char16_t> : TrueType {}; + +} /* namespace detail */ + +/** + * IsIntegral determines whether a type is an integral type. + * + * mozilla::IsIntegral<int>::value is true; + * mozilla::IsIntegral<unsigned short>::value is true; + * mozilla::IsIntegral<const long>::value is true; + * mozilla::IsIntegral<int*>::value is false; + * mozilla::IsIntegral<double>::value is false; + */ +template<typename T> +struct IsIntegral : detail::IsIntegralHelper<typename RemoveCV<T>::Type> +{}; + +template<typename T, typename U> +struct IsSame; + +namespace detail { + +template<typename T> +struct IsFloatingPointHelper + : IntegralConstant<bool, + IsSame<T, float>::value || + IsSame<T, double>::value || + IsSame<T, long double>::value> +{}; + +} // namespace detail + +/** + * IsFloatingPoint determines whether a type is a floating point type (float, + * double, long double). + * + * mozilla::IsFloatingPoint<int>::value is false; + * mozilla::IsFloatingPoint<const float>::value is true; + * mozilla::IsFloatingPoint<long double>::value is true; + * mozilla::IsFloatingPoint<double*>::value is false. + */ +template<typename T> +struct IsFloatingPoint + : detail::IsFloatingPointHelper<typename RemoveCV<T>::Type> +{}; + +namespace detail { + +template<typename T> +struct IsArrayHelper : FalseType {}; + +template<typename T, decltype(sizeof(1)) N> +struct IsArrayHelper<T[N]> : TrueType {}; + +template<typename T> +struct IsArrayHelper<T[]> : TrueType {}; + +} // namespace detail + +/** + * IsArray determines whether a type is an array type, of known or unknown + * length. + * + * mozilla::IsArray<int>::value is false; + * mozilla::IsArray<int[]>::value is true; + * mozilla::IsArray<int[5]>::value is true. + */ +template<typename T> +struct IsArray : detail::IsArrayHelper<typename RemoveCV<T>::Type> +{}; + +namespace detail { + +template<typename T> +struct IsFunPtr; + +template<typename> +struct IsFunPtr + : public FalseType +{}; + +template<typename Result, typename... ArgTypes> +struct IsFunPtr<Result(*)(ArgTypes...)> + : public TrueType +{}; + +}; // namespace detail + +/** + * IsFunction determines whether a type is a function type. Function pointers + * don't qualify here--only the type of an actual function symbol. We do not + * correctly handle varags function types because of a bug in MSVC. + * + * Given the function: + * void f(int) {} + * + * mozilla::IsFunction<void(int)> is true; + * mozilla::IsFunction<void(*)(int)> is false; + * mozilla::IsFunction<decltype(f)> is true. + */ +template<typename T> +struct IsFunction + : public detail::IsFunPtr<typename RemoveCV<T>::Type *> +{}; + +namespace detail { + +template<typename T> +struct IsPointerHelper : FalseType {}; + +template<typename T> +struct IsPointerHelper<T*> : TrueType {}; + +} // namespace detail + +/** + * IsPointer determines whether a type is a possibly-CV-qualified pointer type + * (but not a pointer-to-member type). + * + * mozilla::IsPointer<struct S*>::value is true; + * mozilla::IsPointer<int*>::value is true; + * mozilla::IsPointer<int**>::value is true; + * mozilla::IsPointer<const int*>::value is true; + * mozilla::IsPointer<int* const>::value is true; + * mozilla::IsPointer<int* volatile>::value is true; + * mozilla::IsPointer<void (*)(void)>::value is true; + * mozilla::IsPointer<int>::value is false; + * mozilla::IsPointer<struct S>::value is false. + * mozilla::IsPointer<int(struct S::*)>::value is false + */ +template<typename T> +struct IsPointer : detail::IsPointerHelper<typename RemoveCV<T>::Type> +{}; + +/** + * IsLvalueReference determines whether a type is an lvalue reference. + * + * mozilla::IsLvalueReference<struct S*>::value is false; + * mozilla::IsLvalueReference<int**>::value is false; + * mozilla::IsLvalueReference<void (*)(void)>::value is false; + * mozilla::IsLvalueReference<int>::value is false; + * mozilla::IsLvalueReference<struct S>::value is false; + * mozilla::IsLvalueReference<struct S*&>::value is true; + * mozilla::IsLvalueReference<struct S&&>::value is false. + */ +template<typename T> +struct IsLvalueReference : FalseType {}; + +template<typename T> +struct IsLvalueReference<T&> : TrueType {}; + +/** + * IsRvalueReference determines whether a type is an rvalue reference. + * + * mozilla::IsRvalueReference<struct S*>::value is false; + * mozilla::IsRvalueReference<int**>::value is false; + * mozilla::IsRvalueReference<void (*)(void)>::value is false; + * mozilla::IsRvalueReference<int>::value is false; + * mozilla::IsRvalueReference<struct S>::value is false; + * mozilla::IsRvalueReference<struct S*&>::value is false; + * mozilla::IsRvalueReference<struct S&&>::value is true. + */ +template<typename T> +struct IsRvalueReference : FalseType {}; + +template<typename T> +struct IsRvalueReference<T&&> : TrueType {}; + +namespace detail { + +// __is_enum is a supported extension across all of our supported compilers. +template<typename T> +struct IsEnumHelper + : IntegralConstant<bool, __is_enum(T)> +{}; + +} // namespace detail + +/** + * IsEnum determines whether a type is an enum type. + * + * mozilla::IsEnum<enum S>::value is true; + * mozilla::IsEnum<enum S*>::value is false; + * mozilla::IsEnum<int>::value is false; + */ +template<typename T> +struct IsEnum + : detail::IsEnumHelper<typename RemoveCV<T>::Type> +{}; + +namespace detail { + +// __is_class is a supported extension across all of our supported compilers: +// http://llvm.org/releases/3.0/docs/ClangReleaseNotes.html +// http://gcc.gnu.org/onlinedocs/gcc-4.4.7/gcc/Type-Traits.html#Type-Traits +// http://msdn.microsoft.com/en-us/library/ms177194%28v=vs.100%29.aspx +template<typename T> +struct IsClassHelper + : IntegralConstant<bool, __is_class(T)> +{}; + +} // namespace detail + +/** + * IsClass determines whether a type is a class type (but not a union). + * + * struct S {}; + * union U {}; + * mozilla::IsClass<int>::value is false; + * mozilla::IsClass<const S>::value is true; + * mozilla::IsClass<U>::value is false; + */ +template<typename T> +struct IsClass + : detail::IsClassHelper<typename RemoveCV<T>::Type> +{}; + +/* 20.9.4.2 Composite type traits [meta.unary.comp] */ + +/** + * IsReference determines whether a type is an lvalue or rvalue reference. + * + * mozilla::IsReference<struct S*>::value is false; + * mozilla::IsReference<int**>::value is false; + * mozilla::IsReference<int&>::value is true; + * mozilla::IsReference<void (*)(void)>::value is false; + * mozilla::IsReference<const int&>::value is true; + * mozilla::IsReference<int>::value is false; + * mozilla::IsReference<struct S>::value is false; + * mozilla::IsReference<struct S&>::value is true; + * mozilla::IsReference<struct S*&>::value is true; + * mozilla::IsReference<struct S&&>::value is true. + */ +template<typename T> +struct IsReference + : IntegralConstant<bool, + IsLvalueReference<T>::value || IsRvalueReference<T>::value> +{}; + +/** + * IsArithmetic determines whether a type is arithmetic. A type is arithmetic + * iff it is an integral type or a floating point type. + * + * mozilla::IsArithmetic<int>::value is true; + * mozilla::IsArithmetic<double>::value is true; + * mozilla::IsArithmetic<long double*>::value is false. + */ +template<typename T> +struct IsArithmetic + : IntegralConstant<bool, IsIntegral<T>::value || IsFloatingPoint<T>::value> +{}; + +namespace detail { + +template<typename T> +struct IsMemberPointerHelper : FalseType {}; + +template<typename T, typename U> +struct IsMemberPointerHelper<T U::*> : TrueType {}; + +} // namespace detail + +/** + * IsMemberPointer determines whether a type is pointer to non-static member + * object or a pointer to non-static member function. + * + * mozilla::IsMemberPointer<int(cls::*)>::value is true + * mozilla::IsMemberPointer<int*>::value is false + */ +template<typename T> +struct IsMemberPointer + : detail::IsMemberPointerHelper<typename RemoveCV<T>::Type> +{}; + +/** + * IsScalar determines whether a type is a scalar type. + * + * mozilla::IsScalar<int>::value is true + * mozilla::IsScalar<int*>::value is true + * mozilla::IsScalar<cls>::value is false + */ +template<typename T> +struct IsScalar + : IntegralConstant<bool, IsArithmetic<T>::value || IsEnum<T>::value || + IsPointer<T>::value || IsMemberPointer<T>::value> +{}; + +/* 20.9.4.3 Type properties [meta.unary.prop] */ + +/** + * IsConst determines whether a type is const or not. + * + * mozilla::IsConst<int>::value is false; + * mozilla::IsConst<void* const>::value is true; + * mozilla::IsConst<const char*>::value is false. + */ +template<typename T> +struct IsConst : FalseType {}; + +template<typename T> +struct IsConst<const T> : TrueType {}; + +/** + * IsVolatile determines whether a type is volatile or not. + * + * mozilla::IsVolatile<int>::value is false; + * mozilla::IsVolatile<void* volatile>::value is true; + * mozilla::IsVolatile<volatile char*>::value is false. + */ +template<typename T> +struct IsVolatile : FalseType {}; + +template<typename T> +struct IsVolatile<volatile T> : TrueType {}; + +/** + * Traits class for identifying POD types. Until C++11 there's no automatic + * way to detect PODs, so for the moment this is done manually. Users may + * define specializations of this class that inherit from mozilla::TrueType and + * mozilla::FalseType (or equivalently mozilla::IntegralConstant<bool, true or + * false>, or conveniently from mozilla::IsPod for composite types) as needed to + * ensure correct IsPod behavior. + */ +template<typename T> +struct IsPod : public FalseType {}; + +template<> struct IsPod<char> : TrueType {}; +template<> struct IsPod<signed char> : TrueType {}; +template<> struct IsPod<unsigned char> : TrueType {}; +template<> struct IsPod<short> : TrueType {}; +template<> struct IsPod<unsigned short> : TrueType {}; +template<> struct IsPod<int> : TrueType {}; +template<> struct IsPod<unsigned int> : TrueType {}; +template<> struct IsPod<long> : TrueType {}; +template<> struct IsPod<unsigned long> : TrueType {}; +template<> struct IsPod<long long> : TrueType {}; +template<> struct IsPod<unsigned long long> : TrueType {}; +template<> struct IsPod<bool> : TrueType {}; +template<> struct IsPod<float> : TrueType {}; +template<> struct IsPod<double> : TrueType {}; +template<> struct IsPod<wchar_t> : TrueType {}; +template<> struct IsPod<char16_t> : TrueType {}; +template<typename T> struct IsPod<T*> : TrueType {}; + +namespace detail { + +// __is_empty is a supported extension across all of our supported compilers: +// http://llvm.org/releases/3.0/docs/ClangReleaseNotes.html +// http://gcc.gnu.org/onlinedocs/gcc-4.4.7/gcc/Type-Traits.html#Type-Traits +// http://msdn.microsoft.com/en-us/library/ms177194%28v=vs.100%29.aspx +template<typename T> +struct IsEmptyHelper + : IntegralConstant<bool, IsClass<T>::value && __is_empty(T)> +{}; + +} // namespace detail + +/** + * IsEmpty determines whether a type is a class (but not a union) that is empty. + * + * A class is empty iff it and all its base classes have no non-static data + * members (except bit-fields of length 0) and no virtual member functions, and + * no base class is empty or a virtual base class. + * + * Intuitively, empty classes don't have any data that has to be stored in + * instances of those classes. (The size of the class must still be non-zero, + * because distinct array elements of any type must have different addresses. + * However, if the Empty Base Optimization is implemented by the compiler [most + * compilers implement it, and in certain cases C++11 requires it], the size of + * a class inheriting from an empty |Base| class need not be inflated by + * |sizeof(Base)|.) And intuitively, non-empty classes have data members and/or + * vtable pointers that must be stored in each instance for proper behavior. + * + * static_assert(!mozilla::IsEmpty<int>::value, "not a class => not empty"); + * union U1 { int x; }; + * static_assert(!mozilla::IsEmpty<U1>::value, "not a class => not empty"); + * struct E1 {}; + * struct E2 { int : 0 }; + * struct E3 : E1 {}; + * struct E4 : E2 {}; + * static_assert(mozilla::IsEmpty<E1>::value && + * mozilla::IsEmpty<E2>::value && + * mozilla::IsEmpty<E3>::value && + * mozilla::IsEmpty<E4>::value, + * "all empty"); + * union U2 { E1 e1; }; + * static_assert(!mozilla::IsEmpty<U2>::value, "not a class => not empty"); + * struct NE1 { int x; }; + * struct NE2 : virtual E1 {}; + * struct NE3 : E2 { virtual ~NE3() {} }; + * struct NE4 { virtual void f() {} }; + * static_assert(!mozilla::IsEmpty<NE1>::value && + * !mozilla::IsEmpty<NE2>::value && + * !mozilla::IsEmpty<NE3>::value && + * !mozilla::IsEmpty<NE4>::value, + * "all empty"); + */ +template<typename T> +struct IsEmpty : detail::IsEmptyHelper<typename RemoveCV<T>::Type> +{}; + + +namespace detail { + +template<typename T, + bool = IsFloatingPoint<T>::value, + bool = IsIntegral<T>::value, + typename NoCV = typename RemoveCV<T>::Type> +struct IsSignedHelper; + +// Floating point is signed. +template<typename T, typename NoCV> +struct IsSignedHelper<T, true, false, NoCV> : TrueType {}; + +// Integral is conditionally signed. +template<typename T, typename NoCV> +struct IsSignedHelper<T, false, true, NoCV> + : IntegralConstant<bool, bool(NoCV(-1) < NoCV(1))> +{}; + +// Non-floating point, non-integral is not signed. +template<typename T, typename NoCV> +struct IsSignedHelper<T, false, false, NoCV> : FalseType {}; + +} // namespace detail + +/** + * IsSigned determines whether a type is a signed arithmetic type. |char| is + * considered a signed type if it has the same representation as |signed char|. + * + * mozilla::IsSigned<int>::value is true; + * mozilla::IsSigned<const unsigned int>::value is false; + * mozilla::IsSigned<unsigned char>::value is false; + * mozilla::IsSigned<float>::value is true. + */ +template<typename T> +struct IsSigned : detail::IsSignedHelper<T> {}; + +namespace detail { + +template<typename T, + bool = IsFloatingPoint<T>::value, + bool = IsIntegral<T>::value, + typename NoCV = typename RemoveCV<T>::Type> +struct IsUnsignedHelper; + +// Floating point is not unsigned. +template<typename T, typename NoCV> +struct IsUnsignedHelper<T, true, false, NoCV> : FalseType {}; + +// Integral is conditionally unsigned. +template<typename T, typename NoCV> +struct IsUnsignedHelper<T, false, true, NoCV> + : IntegralConstant<bool, + (IsSame<NoCV, bool>::value || bool(NoCV(1) < NoCV(-1)))> +{}; + +// Non-floating point, non-integral is not unsigned. +template<typename T, typename NoCV> +struct IsUnsignedHelper<T, false, false, NoCV> : FalseType {}; + +} // namespace detail + +/** + * IsUnsigned determines whether a type is an unsigned arithmetic type. + * + * mozilla::IsUnsigned<int>::value is false; + * mozilla::IsUnsigned<const unsigned int>::value is true; + * mozilla::IsUnsigned<unsigned char>::value is true; + * mozilla::IsUnsigned<float>::value is false. + */ +template<typename T> +struct IsUnsigned : detail::IsUnsignedHelper<T> {}; + +namespace detail { + +struct DoIsDestructibleImpl +{ + template<typename T, typename = decltype(DeclVal<T&>().~T())> + static TrueType test(int); + template<typename T> + static FalseType test(...); +}; + +template<typename T> +struct IsDestructibleImpl : public DoIsDestructibleImpl +{ + typedef decltype(test<T>(0)) Type; +}; + +} // namespace detail + +template<typename T> +struct IsDestructible : public detail::IsDestructibleImpl<T>::Type {}; + +/* 20.9.5 Type property queries [meta.unary.prop.query] */ + +/* 20.9.6 Relationships between types [meta.rel] */ + +/** + * IsSame tests whether two types are the same type. + * + * mozilla::IsSame<int, int>::value is true; + * mozilla::IsSame<int*, int*>::value is true; + * mozilla::IsSame<int, unsigned int>::value is false; + * mozilla::IsSame<void, void>::value is true; + * mozilla::IsSame<const int, int>::value is false; + * mozilla::IsSame<struct S, struct S>::value is true. + */ +template<typename T, typename U> +struct IsSame : FalseType {}; + +template<typename T> +struct IsSame<T, T> : TrueType {}; + +namespace detail { + +#if defined(__GNUC__) || defined(__clang__) || defined(_MSC_VER) + +template<class Base, class Derived> +struct BaseOfTester : IntegralConstant<bool, __is_base_of(Base, Derived)> {}; + +#else + +// The trickery used to implement IsBaseOf here makes it possible to use it for +// the cases of private and multiple inheritance. This code was inspired by the +// sample code here: +// +// http://stackoverflow.com/questions/2910979/how-is-base-of-works +template<class Base, class Derived> +struct BaseOfHelper +{ +public: + operator Base*() const; + operator Derived*(); +}; + +template<class Base, class Derived> +struct BaseOfTester +{ +private: + template<class T> + static char test(Derived*, T); + static int test(Base*, int); + +public: + static const bool value = + sizeof(test(BaseOfHelper<Base, Derived>(), int())) == sizeof(char); +}; + +template<class Base, class Derived> +struct BaseOfTester<Base, const Derived> +{ +private: + template<class T> + static char test(Derived*, T); + static int test(Base*, int); + +public: + static const bool value = + sizeof(test(BaseOfHelper<Base, Derived>(), int())) == sizeof(char); +}; + +template<class Base, class Derived> +struct BaseOfTester<Base&, Derived&> : FalseType {}; + +template<class Type> +struct BaseOfTester<Type, Type> : TrueType {}; + +template<class Type> +struct BaseOfTester<Type, const Type> : TrueType {}; + +#endif + +} /* namespace detail */ + +/* + * IsBaseOf allows to know whether a given class is derived from another. + * + * Consider the following class definitions: + * + * class A {}; + * class B : public A {}; + * class C {}; + * + * mozilla::IsBaseOf<A, B>::value is true; + * mozilla::IsBaseOf<A, C>::value is false; + */ +template<class Base, class Derived> +struct IsBaseOf + : IntegralConstant<bool, detail::BaseOfTester<Base, Derived>::value> +{}; + +namespace detail { + +template<typename From, typename To> +struct ConvertibleTester +{ +private: + template<typename To1> + static char test_helper(To1); + + template<typename From1, typename To1> + static decltype(test_helper<To1>(DeclVal<From1>())) test(int); + + template<typename From1, typename To1> + static int test(...); + +public: + static const bool value = + sizeof(test<From, To>(0)) == sizeof(char); +}; + +} // namespace detail + +/** + * IsConvertible determines whether a value of type From will implicitly convert + * to a value of type To. For example: + * + * struct A {}; + * struct B : public A {}; + * struct C {}; + * + * mozilla::IsConvertible<A, A>::value is true; + * mozilla::IsConvertible<A*, A*>::value is true; + * mozilla::IsConvertible<B, A>::value is true; + * mozilla::IsConvertible<B*, A*>::value is true; + * mozilla::IsConvertible<C, A>::value is false; + * mozilla::IsConvertible<A, C>::value is false; + * mozilla::IsConvertible<A*, C*>::value is false; + * mozilla::IsConvertible<C*, A*>::value is false. + * + * For obscure reasons, you can't use IsConvertible when the types being tested + * are related through private inheritance, and you'll get a compile error if + * you try. Just don't do it! + * + * Note - we need special handling for void, which ConvertibleTester doesn't + * handle. The void handling here doesn't handle const/volatile void correctly, + * which could be easily fixed if the need arises. + */ +template<typename From, typename To> +struct IsConvertible + : IntegralConstant<bool, detail::ConvertibleTester<From, To>::value> +{}; + +template<typename B> +struct IsConvertible<void, B> + : IntegralConstant<bool, IsVoid<B>::value> +{}; + +template<typename A> +struct IsConvertible<A, void> + : IntegralConstant<bool, IsVoid<A>::value> +{}; + +template<> +struct IsConvertible<void, void> + : TrueType +{}; + +/* 20.9.7 Transformations between types [meta.trans] */ + +/* 20.9.7.1 Const-volatile modifications [meta.trans.cv] */ + +/** + * RemoveConst removes top-level const qualifications on a type. + * + * 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; +}; + +template<bool Condition, typename A, typename B> +struct Conditional; + +namespace detail { + +enum Voidness { TIsVoid, TIsNotVoid }; + +template<typename T, Voidness V = IsVoid<T>::value ? TIsVoid : TIsNotVoid> +struct AddLvalueReferenceHelper; + +template<typename T> +struct AddLvalueReferenceHelper<T, TIsVoid> +{ + typedef void Type; +}; + +template<typename T> +struct AddLvalueReferenceHelper<T, TIsNotVoid> +{ + typedef T& Type; +}; + +} // namespace detail + +/** + * AddLvalueReference adds an lvalue & reference to T if one isn't already + * present. (Note: adding an lvalue reference to an rvalue && reference in + * essence replaces the && with a &&, per C+11 reference collapsing rules. For + * example, int&& would become int&.) + * + * The final computed type will only *not* be an lvalue reference if T is void. + * + * mozilla::AddLvalueReference<int>::Type is int&; + * mozilla::AddLvalueRference<volatile int&>::Type is volatile int&; + * mozilla::AddLvalueReference<void*>::Type is void*&; + * mozilla::AddLvalueReference<void>::Type is void; + * mozilla::AddLvalueReference<struct S&&>::Type is struct S&. + */ +template<typename T> +struct AddLvalueReference + : detail::AddLvalueReferenceHelper<T> +{}; + +namespace detail { + +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> +{}; + +/* 20.9.7.3 Sign modifications [meta.trans.sign] */ + +template<bool B, typename T = void> +struct EnableIf; + +namespace detail { + +template<bool MakeConst, typename T> +struct WithC : Conditional<MakeConst, const T, T> +{}; + +template<bool MakeVolatile, typename T> +struct WithV : Conditional<MakeVolatile, volatile T, T> +{}; + + +template<bool MakeConst, bool MakeVolatile, typename T> +struct WithCV : WithC<MakeConst, typename WithV<MakeVolatile, T>::Type> +{}; + +template<typename T> +struct CorrespondingSigned; + +template<> +struct CorrespondingSigned<char> { typedef signed char Type; }; +template<> +struct CorrespondingSigned<unsigned char> { typedef signed char Type; }; +template<> +struct CorrespondingSigned<unsigned short> { typedef short Type; }; +template<> +struct CorrespondingSigned<unsigned int> { typedef int Type; }; +template<> +struct CorrespondingSigned<unsigned long> { typedef long Type; }; +template<> +struct CorrespondingSigned<unsigned long long> { typedef long long Type; }; + +template<typename T, + typename CVRemoved = typename RemoveCV<T>::Type, + bool IsSignedIntegerType = IsSigned<CVRemoved>::value && + !IsSame<char, CVRemoved>::value> +struct MakeSigned; + +template<typename T, typename CVRemoved> +struct MakeSigned<T, CVRemoved, true> +{ + typedef T Type; +}; + +template<typename T, typename CVRemoved> +struct MakeSigned<T, CVRemoved, false> + : WithCV<IsConst<T>::value, IsVolatile<T>::value, + typename CorrespondingSigned<CVRemoved>::Type> +{}; + +} // namespace detail + +/** + * MakeSigned produces the corresponding signed integer type for a given + * integral type T, with the const/volatile qualifiers of T. T must be a + * possibly-const/volatile-qualified integral type that isn't bool. + * + * If T is already a signed integer type (not including char!), then T is + * produced. + * + * Otherwise, if T is an unsigned integer type, the signed variety of T, with + * T's const/volatile qualifiers, is produced. + * + * Otherwise, the integral type of the same size as T, with the lowest rank, + * with T's const/volatile qualifiers, is produced. (This basically only acts + * to produce signed char when T = char.) + * + * mozilla::MakeSigned<unsigned long>::Type is signed long; + * mozilla::MakeSigned<volatile int>::Type is volatile int; + * mozilla::MakeSigned<const unsigned short>::Type is const signed short; + * mozilla::MakeSigned<const char>::Type is const signed char; + * mozilla::MakeSigned<bool> is an error; + * mozilla::MakeSigned<void*> is an error. + */ +template<typename T> +struct MakeSigned + : EnableIf<IsIntegral<T>::value && + !IsSame<bool, typename RemoveCV<T>::Type>::value, + typename detail::MakeSigned<T> + >::Type +{}; + +namespace detail { + +template<typename T> +struct CorrespondingUnsigned; + +template<> +struct CorrespondingUnsigned<char> { typedef unsigned char Type; }; +template<> +struct CorrespondingUnsigned<signed char> { typedef unsigned char Type; }; +template<> +struct CorrespondingUnsigned<short> { typedef unsigned short Type; }; +template<> +struct CorrespondingUnsigned<int> { typedef unsigned int Type; }; +template<> +struct CorrespondingUnsigned<long> { typedef unsigned long Type; }; +template<> +struct CorrespondingUnsigned<long long> { typedef unsigned long long Type; }; + + +template<typename T, + typename CVRemoved = typename RemoveCV<T>::Type, + bool IsUnsignedIntegerType = IsUnsigned<CVRemoved>::value && + !IsSame<char, CVRemoved>::value> +struct MakeUnsigned; + +template<typename T, typename CVRemoved> +struct MakeUnsigned<T, CVRemoved, true> +{ + typedef T Type; +}; + +template<typename T, typename CVRemoved> +struct MakeUnsigned<T, CVRemoved, false> + : WithCV<IsConst<T>::value, IsVolatile<T>::value, + typename CorrespondingUnsigned<CVRemoved>::Type> +{}; + +} // namespace detail + +/** + * MakeUnsigned produces the corresponding unsigned integer type for a given + * integral type T, with the const/volatile qualifiers of T. T must be a + * possibly-const/volatile-qualified integral type that isn't bool. + * + * If T is already an unsigned integer type (not including char!), then T is + * produced. + * + * Otherwise, if T is an signed integer type, the unsigned variety of T, with + * T's const/volatile qualifiers, is produced. + * + * Otherwise, the unsigned integral type of the same size as T, with the lowest + * rank, with T's const/volatile qualifiers, is produced. (This basically only + * acts to produce unsigned char when T = char.) + * + * mozilla::MakeUnsigned<signed long>::Type is unsigned long; + * mozilla::MakeUnsigned<volatile unsigned int>::Type is volatile unsigned int; + * mozilla::MakeUnsigned<const signed short>::Type is const unsigned short; + * mozilla::MakeUnsigned<const char>::Type is const unsigned char; + * mozilla::MakeUnsigned<bool> is an error; + * mozilla::MakeUnsigned<void*> is an error. + */ +template<typename T> +struct MakeUnsigned + : EnableIf<IsIntegral<T>::value && + !IsSame<bool, typename RemoveCV<T>::Type>::value, + typename detail::MakeUnsigned<T> + >::Type +{}; + +/* 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> +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 */ |