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// Pointer Traits -*- C++ -*- |
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// Copyright (C) 2011-2021 Free Software Foundation, Inc. |
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// |
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// This file is part of the GNU ISO C++ Library. This library is free |
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// software; you can redistribute it and/or modify it under the |
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// terms of the GNU General Public License as published by the |
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// Free Software Foundation; either version 3, or (at your option) |
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// any later version. |
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// This library is distributed in the hope that it will be useful, |
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// but WITHOUT ANY WARRANTY; without even the implied warranty of |
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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// GNU General Public License for more details. |
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|
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// Under Section 7 of GPL version 3, you are granted additional |
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// permissions described in the GCC Runtime Library Exception, version |
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// 3.1, as published by the Free Software Foundation. |
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// You should have received a copy of the GNU General Public License and |
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// a copy of the GCC Runtime Library Exception along with this program; |
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// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see |
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// <http://www.gnu.org/licenses/>. |
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/** @file bits/ptr_traits.h |
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* This is an internal header file, included by other library headers. |
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* Do not attempt to use it directly. @headername{memory} |
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*/ |
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#ifndef _PTR_TRAITS_H |
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#define _PTR_TRAITS_H 1 |
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#if __cplusplus >= 201103L |
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#include <bits/move.h> |
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#if __cplusplus > 201703L |
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#define __cpp_lib_constexpr_memory 201811L |
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namespace __gnu_debug { struct _Safe_iterator_base; } |
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#endif |
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|
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namespace std _GLIBCXX_VISIBILITY(default) |
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{ |
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_GLIBCXX_BEGIN_NAMESPACE_VERSION |
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class __undefined; |
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// Given Template<T, ...> return T, otherwise invalid. |
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template<typename _Tp> |
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struct __get_first_arg |
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{ using type = __undefined; }; |
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|
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template<template<typename, typename...> class _Template, typename _Tp, |
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typename... _Types> |
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struct __get_first_arg<_Template<_Tp, _Types...>> |
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{ using type = _Tp; }; |
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template<typename _Tp> |
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using __get_first_arg_t = typename __get_first_arg<_Tp>::type; |
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// Given Template<T, ...> and U return Template<U, ...>, otherwise invalid. |
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template<typename _Tp, typename _Up> |
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struct __replace_first_arg |
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{ }; |
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template<template<typename, typename...> class _Template, typename _Up, |
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typename _Tp, typename... _Types> |
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struct __replace_first_arg<_Template<_Tp, _Types...>, _Up> |
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{ using type = _Template<_Up, _Types...>; }; |
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|
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template<typename _Tp, typename _Up> |
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using __replace_first_arg_t = typename __replace_first_arg<_Tp, _Up>::type; |
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template<typename _Tp> |
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using __make_not_void |
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= typename conditional<is_void<_Tp>::value, __undefined, _Tp>::type; |
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|
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/** |
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* @brief Uniform interface to all pointer-like types |
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* @ingroup pointer_abstractions |
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*/ |
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template<typename _Ptr> |
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struct pointer_traits |
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{ |
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private: |
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template<typename _Tp> |
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using __element_type = typename _Tp::element_type; |
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template<typename _Tp> |
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using __difference_type = typename _Tp::difference_type; |
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|
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template<typename _Tp, typename _Up, typename = void> |
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struct __rebind : __replace_first_arg<_Tp, _Up> { }; |
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template<typename _Tp, typename _Up> |
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struct __rebind<_Tp, _Up, __void_t<typename _Tp::template rebind<_Up>>> |
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{ using type = typename _Tp::template rebind<_Up>; }; |
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public: |
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/// The pointer type. |
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using pointer = _Ptr; |
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/// The type pointed to. |
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using element_type |
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= __detected_or_t<__get_first_arg_t<_Ptr>, __element_type, _Ptr>; |
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/// The type used to represent the difference between two pointers. |
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using difference_type |
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= __detected_or_t<ptrdiff_t, __difference_type, _Ptr>; |
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/// A pointer to a different type. |
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template<typename _Up> |
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using rebind = typename __rebind<_Ptr, _Up>::type; |
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static _Ptr |
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pointer_to(__make_not_void<element_type>& __e) |
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{ return _Ptr::pointer_to(__e); } |
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|
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static_assert(!is_same<element_type, __undefined>::value, |
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"pointer type defines element_type or is like SomePointer<T, Args>"); |
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}; |
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/** |
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* @brief Partial specialization for built-in pointers. |
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* @ingroup pointer_abstractions |
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*/ |
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template<typename _Tp> |
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struct pointer_traits<_Tp*> |
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{ |
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/// The pointer type |
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typedef _Tp* pointer; |
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/// The type pointed to |
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typedef _Tp element_type; |
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/// Type used to represent the difference between two pointers |
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typedef ptrdiff_t difference_type; |
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template<typename _Up> |
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using rebind = _Up*; |
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/** |
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* @brief Obtain a pointer to an object |
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* @param __r A reference to an object of type @c element_type |
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* @return @c addressof(__r) |
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*/ |
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static _GLIBCXX20_CONSTEXPR pointer |
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pointer_to(__make_not_void<element_type>& __r) noexcept |
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{ return std::addressof(__r); } |
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}; |
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/// Convenience alias for rebinding pointers. |
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template<typename _Ptr, typename _Tp> |
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using __ptr_rebind = typename pointer_traits<_Ptr>::template rebind<_Tp>; |
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template<typename _Tp> |
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constexpr _Tp* |
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__to_address(_Tp* __ptr) noexcept |
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{ |
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static_assert(!std::is_function<_Tp>::value, "not a function pointer"); |
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return __ptr; |
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} |
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#if __cplusplus <= 201703L |
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template<typename _Ptr> |
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constexpr typename std::pointer_traits<_Ptr>::element_type* |
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__to_address(const _Ptr& __ptr) |
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{ return std::__to_address(__ptr.operator->()); } |
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#else |
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template<typename _Ptr> |
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constexpr auto |
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__to_address(const _Ptr& __ptr) noexcept |
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-> decltype(std::pointer_traits<_Ptr>::to_address(__ptr)) |
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{ return std::pointer_traits<_Ptr>::to_address(__ptr); } |
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template<typename _Ptr, typename... _None> |
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constexpr auto |
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__to_address(const _Ptr& __ptr, _None...) noexcept |
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{ |
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if constexpr (is_base_of_v<__gnu_debug::_Safe_iterator_base, _Ptr>) |
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return std::__to_address(__ptr.base().operator->()); |
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else |
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return std::__to_address(__ptr.operator->()); |
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} |
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#define __cpp_lib_to_address 201711L |
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/** |
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* @brief Obtain address referenced by a pointer to an object |
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* @param __ptr A pointer to an object |
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* @return @c __ptr |
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* @ingroup pointer_abstractions |
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*/ |
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template<typename _Tp> |
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constexpr _Tp* |
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to_address(_Tp* __ptr) noexcept |
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{ return std::__to_address(__ptr); } |
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/** |
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* @brief Obtain address referenced by a pointer to an object |
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* @param __ptr A pointer to an object |
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* @return @c pointer_traits<_Ptr>::to_address(__ptr) if that expression is |
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well-formed, otherwise @c to_address(__ptr.operator->()) |
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* @ingroup pointer_abstractions |
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*/ |
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template<typename _Ptr> |
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constexpr auto |
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to_address(const _Ptr& __ptr) noexcept |
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{ return std::__to_address(__ptr); } |
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#endif // C++2a |
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_GLIBCXX_END_NAMESPACE_VERSION |
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} // namespace std |
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#endif |
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#endif |
