1 // Pointer Traits -*- C++ -*- 2 3 // Copyright (C) 2011-2018 Free Software Foundation, Inc. 4 // 5 // This file is part of the GNU ISO C++ Library. This library is free 6 // software; you can redistribute it and/or modify it under the 7 // terms of the GNU General Public License as published by the 8 // Free Software Foundation; either version 3, or (at your option) 9 // any later version. 10 11 // This library is distributed in the hope that it will be useful, 12 // but WITHOUT ANY WARRANTY; without even the implied warranty of 13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 // GNU General Public License for more details. 15 16 // Under Section 7 of GPL version 3, you are granted additional 17 // permissions described in the GCC Runtime Library Exception, version 18 // 3.1, as published by the Free Software Foundation. 19 20 // You should have received a copy of the GNU General Public License and 21 // a copy of the GCC Runtime Library Exception along with this program; 22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 23 // <http://www.gnu.org/licenses/>. 24 25 /** @file bits/ptr_traits.h 26 * This is an internal header file, included by other library headers. 27 * Do not attempt to use it directly. @headername{memory} 28 */ 29 30 #ifndef _PTR_TRAITS_H 31 #define _PTR_TRAITS_H 1 32 33 #if __cplusplus >= 201103L 34 35 #include <bits/move.h> 36 37 namespace std _GLIBCXX_VISIBILITY(default) 38 { 39 _GLIBCXX_BEGIN_NAMESPACE_VERSION 40 41 class __undefined; 42 43 // Given Template<T, ...> return T, otherwise invalid. 44 template<typename _Tp> 45 struct __get_first_arg 46 { using type = __undefined; }; 47 48 template<template<typename, typename...> class _Template, typename _Tp, 49 typename... _Types> 50 struct __get_first_arg<_Template<_Tp, _Types...>> 51 { using type = _Tp; }; 52 53 template<typename _Tp> 54 using __get_first_arg_t = typename __get_first_arg<_Tp>::type; 55 56 // Given Template<T, ...> and U return Template<U, ...>, otherwise invalid. 57 template<typename _Tp, typename _Up> 58 struct __replace_first_arg 59 { }; 60 61 template<template<typename, typename...> class _Template, typename _Up, 62 typename _Tp, typename... _Types> 63 struct __replace_first_arg<_Template<_Tp, _Types...>, _Up> 64 { using type = _Template<_Up, _Types...>; }; 65 66 template<typename _Tp, typename _Up> 67 using __replace_first_arg_t = typename __replace_first_arg<_Tp, _Up>::type; 68 69 template<typename _Tp> 70 using __make_not_void 71 = typename conditional<is_void<_Tp>::value, __undefined, _Tp>::type; 72 73 /** 74 * @brief Uniform interface to all pointer-like types 75 * @ingroup pointer_abstractions 76 */ 77 template<typename _Ptr> 78 struct pointer_traits 79 { 80 private: 81 template<typename _Tp> 82 using __element_type = typename _Tp::element_type; 83 84 template<typename _Tp> 85 using __difference_type = typename _Tp::difference_type; 86 87 template<typename _Tp, typename _Up, typename = void> 88 struct __rebind : __replace_first_arg<_Tp, _Up> { }; 89 90 template<typename _Tp, typename _Up> 91 struct __rebind<_Tp, _Up, __void_t<typename _Tp::template rebind<_Up>>> 92 { using type = typename _Tp::template rebind<_Up>; }; 93 94 public: 95 /// The pointer type. 96 using pointer = _Ptr; 97 98 /// The type pointed to. 99 using element_type 100 = __detected_or_t<__get_first_arg_t<_Ptr>, __element_type, _Ptr>; 101 102 /// The type used to represent the difference between two pointers. 103 using difference_type 104 = __detected_or_t<ptrdiff_t, __difference_type, _Ptr>; 105 106 /// A pointer to a different type. 107 template<typename _Up> 108 using rebind = typename __rebind<_Ptr, _Up>::type; 109 110 static _Ptr 111 pointer_to(__make_not_void<element_type>& __e) 112 { return _Ptr::pointer_to(__e); } 113 114 static_assert(!is_same<element_type, __undefined>::value, 115 "pointer type defines element_type or is like SomePointer<T, Args>"); 116 }; 117 118 /** 119 * @brief Partial specialization for built-in pointers. 120 * @ingroup pointer_abstractions 121 */ 122 template<typename _Tp> 123 struct pointer_traits<_Tp*> 124 { 125 /// The pointer type 126 typedef _Tp* pointer; 127 /// The type pointed to 128 typedef _Tp element_type; 129 /// Type used to represent the difference between two pointers 130 typedef ptrdiff_t difference_type; 131 132 template<typename _Up> 133 using rebind = _Up*; 134 135 /** 136 * @brief Obtain a pointer to an object 137 * @param __r A reference to an object of type @c element_type 138 * @return @c addressof(__r) 139 */ 140 static pointer 141 pointer_to(__make_not_void<element_type>& __r) noexcept 142 { return std::addressof(__r); } 143 }; 144 145 /// Convenience alias for rebinding pointers. 146 template<typename _Ptr, typename _Tp> 147 using __ptr_rebind = typename pointer_traits<_Ptr>::template rebind<_Tp>; 148 149 template<typename _Tp> 150 constexpr _Tp* 151 __to_address(_Tp* __ptr) noexcept 152 { 153 static_assert(!std::is_function<_Tp>::value, "not a function pointer"); 154 return __ptr; 155 } 156 157 #if __cplusplus <= 201703L 158 template<typename _Ptr> 159 constexpr typename std::pointer_traits<_Ptr>::element_type* 160 __to_address(const _Ptr& __ptr) 161 { return std::__to_address(__ptr.operator->()); } 162 #else 163 template<typename _Ptr> 164 constexpr auto 165 __to_address(const _Ptr& __ptr) noexcept 166 -> decltype(std::pointer_traits<_Ptr>::to_address(__ptr)) 167 { return std::pointer_traits<_Ptr>::to_address(__ptr); } 168 169 template<typename _Ptr, typename... _None> 170 constexpr auto 171 __to_address(const _Ptr& __ptr, _None...) noexcept 172 { return std::__to_address(__ptr.operator->()); } 173 174 /** 175 * @brief Obtain address referenced by a pointer to an object 176 * @param __ptr A pointer to an object 177 * @return @c __ptr 178 * @ingroup pointer_abstractions 179 */ 180 template<typename _Tp> 181 constexpr _Tp* 182 to_address(_Tp* __ptr) noexcept 183 { return std::__to_address(__ptr); } 184 185 /** 186 * @brief Obtain address referenced by a pointer to an object 187 * @param __ptr A pointer to an object 188 * @return @c pointer_traits<_Ptr>::to_address(__ptr) if that expression is 189 well-formed, otherwise @c to_address(__ptr.operator->()) 190 * @ingroup pointer_abstractions 191 */ 192 template<typename _Ptr> 193 constexpr auto 194 to_address(const _Ptr& __ptr) noexcept 195 { return std::__to_address(__ptr); } 196 #endif // C++2a 197 198 _GLIBCXX_END_NAMESPACE_VERSION 199 } // namespace std 200 201 #endif 202 203 #endif 204