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Edit File: ptr_traits.h

// Pointer Traits -*- C++ -*- // Copyright (C) 2011-2018 Free Software Foundation, Inc. // // This file is part of the GNU ISO C++ Library. This library is free // software; you can redistribute it and/or modify it under the // terms of the GNU General Public License as published by the // Free Software Foundation; either version 3, or (at your option) // any later version. // This library is distributed in the hope that it will be useful, // but WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the // GNU General Public License for more details. // Under Section 7 of GPL version 3, you are granted additional // permissions described in the GCC Runtime Library Exception, version // 3.1, as published by the Free Software Foundation. // You should have received a copy of the GNU General Public License and // a copy of the GCC Runtime Library Exception along with this program; // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see // <http://www.gnu.org/licenses/>. /** @file bits/ptr_traits.h * This is an internal header file, included by other library headers. * Do not attempt to use it directly. @headername{memory} */ #ifndef _PTR_TRAITS_H #define _PTR_TRAITS_H 1 #if __cplusplus >= 201103L #include <bits/move.h> #if __cplusplus > 201703L namespace __gnu_debug { struct _Safe_iterator_base; } #endif namespace std _GLIBCXX_VISIBILITY(default) { _GLIBCXX_BEGIN_NAMESPACE_VERSION class __undefined; // Given Template<T, ...> return T, otherwise invalid. template<typename _Tp> struct __get_first_arg { using type = __undefined; }; template<template<typename, typename...> class _Template, typename _Tp, typename... _Types> struct __get_first_arg<_Template<_Tp, _Types...>> { using type = _Tp; }; template<typename _Tp> using __get_first_arg_t = typename __get_first_arg<_Tp>::type; // Given Template<T, ...> and U return Template<U, ...>, otherwise invalid. template<typename _Tp, typename _Up> struct __replace_first_arg { }; template<template<typename, typename...> class _Template, typename _Up, typename _Tp, typename... _Types> struct __replace_first_arg<_Template<_Tp, _Types...>, _Up> { using type = _Template<_Up, _Types...>; }; template<typename _Tp, typename _Up> using __replace_first_arg_t = typename __replace_first_arg<_Tp, _Up>::type; template<typename _Tp> using __make_not_void = typename conditional<is_void<_Tp>::value, __undefined, _Tp>::type; /** * @brief Uniform interface to all pointer-like types * @ingroup pointer_abstractions */ template<typename _Ptr> struct pointer_traits { private: template<typename _Tp> using __element_type = typename _Tp::element_type; template<typename _Tp> using __difference_type = typename _Tp::difference_type; template<typename _Tp, typename _Up, typename = void> struct __rebind : __replace_first_arg<_Tp, _Up> { }; template<typename _Tp, typename _Up> struct __rebind<_Tp, _Up, __void_t<typename _Tp::template rebind<_Up>>> { using type = typename _Tp::template rebind<_Up>; }; public: /// The pointer type. using pointer = _Ptr; /// The type pointed to. using element_type = __detected_or_t<__get_first_arg_t<_Ptr>, __element_type, _Ptr>; /// The type used to represent the difference between two pointers. using difference_type = __detected_or_t<ptrdiff_t, __difference_type, _Ptr>; /// A pointer to a different type. template<typename _Up> using rebind = typename __rebind<_Ptr, _Up>::type; static _Ptr pointer_to(__make_not_void<element_type>& __e) { return _Ptr::pointer_to(__e); } static_assert(!is_same<element_type, __undefined>::value, "pointer type defines element_type or is like SomePointer<T, Args>"); }; /** * @brief Partial specialization for built-in pointers. * @ingroup pointer_abstractions */ template<typename _Tp> struct pointer_traits<_Tp*> { /// The pointer type typedef _Tp* pointer; /// The type pointed to typedef _Tp element_type; /// Type used to represent the difference between two pointers typedef ptrdiff_t difference_type; template<typename _Up> using rebind = _Up*; /** * @brief Obtain a pointer to an object * @param __r A reference to an object of type @c element_type * @return @c addressof(__r) */ static pointer pointer_to(__make_not_void<element_type>& __r) noexcept { return std::addressof(__r); } }; /// Convenience alias for rebinding pointers. template<typename _Ptr, typename _Tp> using __ptr_rebind = typename pointer_traits<_Ptr>::template rebind<_Tp>; template<typename _Tp> constexpr _Tp* __to_address(_Tp* __ptr) noexcept { static_assert(!std::is_function<_Tp>::value, "not a function pointer"); return __ptr; } #if __cplusplus <= 201703L template<typename _Ptr> constexpr typename std::pointer_traits<_Ptr>::element_type* __to_address(const _Ptr& __ptr) { return std::__to_address(__ptr.operator->()); } #else template<typename _Ptr> constexpr auto __to_address(const _Ptr& __ptr) noexcept -> decltype(std::pointer_traits<_Ptr>::to_address(__ptr)) { return std::pointer_traits<_Ptr>::to_address(__ptr); } template<typename _Ptr, typename... _None> constexpr auto __to_address(const _Ptr& __ptr, _None...) noexcept { if constexpr (is_base_of_v<__gnu_debug::_Safe_iterator_base, _Ptr>) return std::__to_address(__ptr.base().operator->()); else return std::__to_address(__ptr.operator->()); } /** * @brief Obtain address referenced by a pointer to an object * @param __ptr A pointer to an object * @return @c __ptr * @ingroup pointer_abstractions */ template<typename _Tp> constexpr _Tp* to_address(_Tp* __ptr) noexcept { return std::__to_address(__ptr); } /** * @brief Obtain address referenced by a pointer to an object * @param __ptr A pointer to an object * @return @c pointer_traits<_Ptr>::to_address(__ptr) if that expression is well-formed, otherwise @c to_address(__ptr.operator->()) * @ingroup pointer_abstractions */ template<typename _Ptr> constexpr auto to_address(const _Ptr& __ptr) noexcept { return std::__to_address(__ptr); } #endif // C++2a _GLIBCXX_END_NAMESPACE_VERSION } // namespace std #endif #endif