mirror of
https://github.com/mozilla/gecko-dev.git
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13bfe75b97
Differential Revision: https://phabricator.services.mozilla.com/D68560 --HG-- extra : moz-landing-system : lando
108 lines
3.2 KiB
C++
108 lines
3.2 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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#include <type_traits>
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#include <utility>
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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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/* 20.9.4 Unary type traits [meta.unary] */
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/* 20.9.4.3 Type properties [meta.unary.prop] */
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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 std::true_type and
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* std::false_type (or equivalently std::integral_constant<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 std::false_type {};
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template <>
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struct IsPod<char> : std::true_type {};
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template <>
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struct IsPod<signed char> : std::true_type {};
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template <>
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struct IsPod<unsigned char> : std::true_type {};
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template <>
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struct IsPod<short> : std::true_type {};
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template <>
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struct IsPod<unsigned short> : std::true_type {};
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template <>
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struct IsPod<int> : std::true_type {};
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template <>
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struct IsPod<unsigned int> : std::true_type {};
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template <>
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struct IsPod<long> : std::true_type {};
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template <>
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struct IsPod<unsigned long> : std::true_type {};
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template <>
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struct IsPod<long long> : std::true_type {};
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template <>
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struct IsPod<unsigned long long> : std::true_type {};
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template <>
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struct IsPod<bool> : std::true_type {};
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template <>
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struct IsPod<float> : std::true_type {};
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template <>
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struct IsPod<double> : std::true_type {};
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template <>
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struct IsPod<wchar_t> : std::true_type {};
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template <>
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struct IsPod<char16_t> : std::true_type {};
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template <typename T>
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struct IsPod<T*> : std::true_type {};
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namespace detail {
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struct DoIsDestructibleImpl {
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template <typename T, typename = decltype(std::declval<T&>().~T())>
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static std::true_type test(int);
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template <typename T>
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static std::false_type 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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} /* namespace mozilla */
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#endif /* mozilla_TypeTraits_h */
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