mirror of
https://github.com/mozilla/gecko-dev.git
synced 2024-12-05 03:54:35 +00:00
6249325181
--HG-- extra : rebase_source : fdd1fe8841d1bc42c1758cd4d477969b3f382b30
669 lines
20 KiB
C++
669 lines
20 KiB
C++
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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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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/*
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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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#include <wchar.h>
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namespace mozilla {
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/* Forward declarations. */
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template<typename> struct RemoveCV;
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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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{
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static const 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 IsIntegralHelper : FalseType {};
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template<> struct IsIntegralHelper<char> : TrueType {};
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template<> struct IsIntegralHelper<signed char> : TrueType {};
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template<> struct IsIntegralHelper<unsigned char> : TrueType {};
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template<> struct IsIntegralHelper<short> : TrueType {};
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template<> struct IsIntegralHelper<unsigned short> : TrueType {};
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template<> struct IsIntegralHelper<int> : TrueType {};
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template<> struct IsIntegralHelper<unsigned int> : TrueType {};
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template<> struct IsIntegralHelper<long> : TrueType {};
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template<> struct IsIntegralHelper<unsigned long> : TrueType {};
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template<> struct IsIntegralHelper<long long> : TrueType {};
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template<> struct IsIntegralHelper<unsigned long long> : TrueType {};
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template<> struct IsIntegralHelper<bool> : TrueType {};
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template<> struct IsIntegralHelper<wchar_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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* Note that the behavior of IsIntegral on char16_t and char32_t is
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* unspecified.
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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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{};
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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,
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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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{};
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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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{};
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/**
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* IsPointer determines whether a type is a pointer type (but not a pointer-to-
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* 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<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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*/
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template<typename T>
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struct IsPointer : FalseType {};
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template<typename T>
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struct IsPointer<T*> : TrueType {};
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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
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: IntegralConstant<bool, IsIntegral<T>::value || IsFloatingPoint<T>::value>
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{};
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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<> struct IsPod<char> : TrueType {};
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template<> struct IsPod<signed char> : TrueType {};
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template<> struct IsPod<unsigned char> : TrueType {};
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template<> struct IsPod<short> : TrueType {};
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template<> struct IsPod<unsigned short> : TrueType {};
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template<> struct IsPod<int> : TrueType {};
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template<> struct IsPod<unsigned int> : TrueType {};
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template<> struct IsPod<long> : TrueType {};
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template<> struct IsPod<unsigned long> : TrueType {};
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template<> struct IsPod<long long> : TrueType {};
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template<> struct IsPod<unsigned long long> : TrueType {};
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template<> struct IsPod<bool> : TrueType {};
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template<> struct IsPod<float> : TrueType {};
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template<> struct IsPod<double> : TrueType {};
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template<> struct IsPod<wchar_t> : TrueType {};
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template<typename T> 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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struct IsSignedHelper;
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template<typename T>
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struct IsSignedHelper<T, true> : TrueType {};
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template<typename T>
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struct IsSignedHelper<T, false>
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: IntegralConstant<bool, IsArithmetic<T>::value && T(-1) < T(1)>
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{};
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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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* Don't use this if the type might be user-defined! You might or might not get
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* a compile error, depending.
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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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struct IsUnsignedHelper;
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template<typename T>
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struct IsUnsignedHelper<T, true> : FalseType {};
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template<typename T>
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struct IsUnsignedHelper<T, false>
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: IntegralConstant<bool,
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IsArithmetic<T>::value &&
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(IsSame<typename RemoveCV<T>::Type, bool>::value ||
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T(1) < T(-1))>
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{};
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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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* Don't use this if the type might be user-defined! You might or might not get
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* a compile error, depending.
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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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/* 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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// The trickery used to implement IsBaseOf here makes it possible to use it for
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// the cases of private and multiple inheritance. This code was inspired by the
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// sample code here:
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//
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// http://stackoverflow.com/questions/2910979/how-is-base-of-works
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template<class Base, class Derived>
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struct BaseOfHelper
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{
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public:
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operator Base*() const;
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operator Derived*();
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};
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template<class Base, class Derived>
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struct BaseOfTester
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{
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private:
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template<class T>
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static char test(Derived*, T);
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static int test(Base*, int);
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public:
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static const bool value =
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sizeof(test(BaseOfHelper<Base, Derived>(), int())) == sizeof(char);
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};
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template<class Base, class Derived>
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struct BaseOfTester<Base, const Derived>
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{
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private:
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template<class T>
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static char test(Derived*, T);
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static int test(Base*, int);
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public:
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static const bool value =
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sizeof(test(BaseOfHelper<Base, Derived>(), int())) == sizeof(char);
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};
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template<class Base, class Derived>
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struct BaseOfTester<Base&, Derived&> : FalseType {};
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template<class Type>
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struct BaseOfTester<Type, Type> : TrueType {};
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template<class Type>
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struct BaseOfTester<Type, const Type> : TrueType {};
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} /* namespace detail */
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/*
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* IsBaseOf allows to know whether a given class is derived from another.
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*
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* Consider the following class definitions:
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*
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* class A {};
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* class B : public A {};
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* class C {};
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*
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* mozilla::IsBaseOf<A, B>::value is true;
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* mozilla::IsBaseOf<A, C>::value is false;
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*/
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template<class Base, class Derived>
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struct IsBaseOf
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: IntegralConstant<bool, detail::BaseOfTester<Base, Derived>::value>
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{};
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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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{
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private:
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static From create();
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template<typename From1, typename To1>
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static char test(To to);
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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 =
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sizeof(test<From, To>(create())) == 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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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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{};
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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;
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* mozilla::RemoveConst<const int>::Type is int;
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* mozilla::RemoveConst<const int*>::Type is const int*;
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* mozilla::RemoveConst<int* const>::Type is int*.
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*/
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template<typename T>
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struct RemoveConst
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{
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typedef T Type;
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};
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template<typename T>
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struct RemoveConst<const T>
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{
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typedef T Type;
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};
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/**
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* RemoveVolatile removes top-level volatile qualifications on a type.
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*
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* mozilla::RemoveVolatile<int>::Type is int;
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* mozilla::RemoveVolatile<volatile int>::Type is int;
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* mozilla::RemoveVolatile<volatile int*>::Type is volatile int*;
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* mozilla::RemoveVolatile<int* volatile>::Type is int*.
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*/
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template<typename T>
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struct RemoveVolatile
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{
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typedef T Type;
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};
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template<typename T>
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struct RemoveVolatile<volatile T>
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{
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typedef T Type;
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};
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/**
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* RemoveCV removes top-level const and volatile qualifications on a type.
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*
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* mozilla::RemoveCV<int>::Type is int;
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* mozilla::RemoveCV<const int>::Type is int;
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* mozilla::RemoveCV<volatile int>::Type is int;
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* mozilla::RemoveCV<int* const volatile>::Type is int*.
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*/
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template<typename T>
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struct RemoveCV
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{
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typedef typename RemoveConst<typename RemoveVolatile<T>::Type>::Type Type;
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};
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/* 20.9.7.2 Reference modifications [meta.trans.ref] */
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/* 20.9.7.3 Sign modifications [meta.trans.sign] */
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template<bool B, typename T = void>
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struct EnableIf;
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template<bool Condition, typename A, typename B>
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struct Conditional;
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namespace detail {
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template<bool MakeConst, typename T>
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struct WithC : Conditional<MakeConst, const T, T>
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{};
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template<bool MakeVolatile, typename T>
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struct WithV : Conditional<MakeVolatile, volatile T, T>
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{};
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template<bool MakeConst, bool MakeVolatile, typename T>
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struct WithCV : WithC<MakeConst, typename WithV<MakeVolatile, T>::Type>
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{};
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template<typename T>
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struct CorrespondingSigned;
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template<>
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struct CorrespondingSigned<char> { typedef signed char Type; };
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template<>
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struct CorrespondingSigned<unsigned char> { typedef signed char Type; };
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template<>
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struct CorrespondingSigned<unsigned short> { typedef short Type; };
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template<>
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struct CorrespondingSigned<unsigned int> { typedef int Type; };
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template<>
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struct CorrespondingSigned<unsigned long> { typedef long Type; };
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template<>
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struct CorrespondingSigned<unsigned long long> { typedef long long Type; };
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template<typename T,
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typename CVRemoved = typename RemoveCV<T>::Type,
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bool IsSignedIntegerType = IsSigned<CVRemoved>::value &&
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!IsSame<char, CVRemoved>::value>
|
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struct MakeSigned;
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template<typename T, typename CVRemoved>
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struct MakeSigned<T, CVRemoved, true>
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{
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typedef T Type;
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};
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template<typename T, typename CVRemoved>
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struct MakeSigned<T, CVRemoved, false>
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: WithCV<IsConst<T>::value, IsVolatile<T>::value,
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typename CorrespondingSigned<CVRemoved>::Type>
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{};
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} // namespace detail
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/**
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* MakeSigned produces the corresponding signed integer type for a given
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* integral type T, with the const/volatile qualifiers of T. T must be a
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* possibly-const/volatile-qualified integral type that isn't bool.
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*
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|
* If T is already a signed integer type (not including char!), then T is
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* produced.
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*
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* Otherwise, if T is an unsigned integer type, the signed variety of T, with
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* T's const/volatile qualifiers, is produced.
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*
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* Otherwise, the integral type of the same size as T, with the lowest rank,
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* with T's const/volatile qualifiers, is produced. (This basically only acts
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* to produce signed char when T = char.)
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*
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* 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] */
|
|
|
|
/* 20.9.7.5 Pointer modifications [meta.trans.ptr] */
|
|
|
|
/* 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 mozilla */
|
|
|
|
#endif /* mozilla_TypeTraits_h_ */
|