1 // Pointer Traits -*- C++ -*- 2 3 // Copyright (C) 2011-2014 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 <type_traits> // For _GLIBCXX_HAS_NESTED_TYPE 36 37 namespace std _GLIBCXX_VISIBILITY(default) 38 { 39 _GLIBCXX_BEGIN_NAMESPACE_VERSION 40 41 _GLIBCXX_HAS_NESTED_TYPE(element_type) 42 _GLIBCXX_HAS_NESTED_TYPE(difference_type) 43 44 template<typename _Tp, bool = __has_element_type<_Tp>::value> 45 struct __ptrtr_elt_type; 46 47 template<typename _Tp> 48 struct __ptrtr_elt_type<_Tp, true> 49 { 50 typedef typename _Tp::element_type __type; 51 }; 52 53 template<template<typename, typename...> class _SomePtr, typename _Tp, 54 typename... _Args> 55 struct __ptrtr_elt_type<_SomePtr<_Tp, _Args...>, false> 56 { 57 typedef _Tp __type; 58 }; 59 60 template<typename _Tp, bool = __has_difference_type<_Tp>::value> 61 struct __ptrtr_diff_type 62 { 63 typedef typename _Tp::difference_type __type; 64 }; 65 66 template<typename _Tp> 67 struct __ptrtr_diff_type<_Tp, false> 68 { 69 typedef ptrdiff_t __type; 70 }; 71 72 template<typename _Ptr, typename _Up> 73 class __ptrtr_rebind_helper 74 { 75 template<typename _Ptr2, typename _Up2> 76 static constexpr true_type 77 _S_chk(typename _Ptr2::template rebind<_Up2>*); 78 79 template<typename, typename> 80 static constexpr false_type 81 _S_chk(...); 82 83 public: 84 using __type = decltype(_S_chk<_Ptr, _Up>(nullptr)); 85 }; 86 87 template<typename _Tp, typename _Up, 88 bool = __ptrtr_rebind_helper<_Tp, _Up>::__type::value> 89 struct __ptrtr_rebind; 90 91 template<typename _Tp, typename _Up> 92 struct __ptrtr_rebind<_Tp, _Up, true> 93 { 94 typedef typename _Tp::template rebind<_Up> __type; 95 }; 96 97 template<template<typename, typename...> class _SomePtr, typename _Up, 98 typename _Tp, typename... _Args> 99 struct __ptrtr_rebind<_SomePtr<_Tp, _Args...>, _Up, false> 100 { 101 typedef _SomePtr<_Up, _Args...> __type; 102 }; 103 104 template<typename _Tp, typename = typename remove_cv<_Tp>::type> 105 struct __ptrtr_not_void 106 { 107 typedef _Tp __type; 108 }; 109 110 template<typename _Tp> 111 struct __ptrtr_not_void<_Tp, void> 112 { 113 struct __type { }; 114 }; 115 116 template<typename _Ptr> 117 class __ptrtr_pointer_to 118 { 119 typedef typename __ptrtr_elt_type<_Ptr>::__type __orig_type; 120 typedef typename __ptrtr_not_void<__orig_type>::__type __element_type; 121 122 public: 123 static _Ptr pointer_to(__element_type& __e) 124 { return _Ptr::pointer_to(__e); } 125 }; 126 127 /** 128 * @brief Uniform interface to all pointer-like types 129 * @ingroup pointer_abstractions 130 */ 131 template<typename _Ptr> 132 struct pointer_traits : __ptrtr_pointer_to<_Ptr> 133 { 134 /// The pointer type 135 typedef _Ptr pointer; 136 /// The type pointed to 137 typedef typename __ptrtr_elt_type<_Ptr>::__type element_type; 138 /// Type used to represent the difference between two pointers 139 typedef typename __ptrtr_diff_type<_Ptr>::__type difference_type; 140 141 template<typename _Up> 142 using rebind = typename __ptrtr_rebind<_Ptr, _Up>::__type; 143 }; 144 145 /** 146 * @brief Partial specialization for built-in pointers. 147 * @ingroup pointer_abstractions 148 */ 149 template<typename _Tp> 150 struct pointer_traits<_Tp*> 151 { 152 /// The pointer type 153 typedef _Tp* pointer; 154 /// The type pointed to 155 typedef _Tp element_type; 156 /// Type used to represent the difference between two pointers 157 typedef ptrdiff_t difference_type; 158 159 template<typename _Up> 160 using rebind = _Up*; 161 162 /** 163 * @brief Obtain a pointer to an object 164 * @param __r A reference to an object of type @c element_type 165 * @return @c addressof(__r) 166 */ 167 static pointer 168 pointer_to(typename __ptrtr_not_void<element_type>::__type& __r) noexcept 169 { return std::addressof(__r); } 170 }; 171 172 _GLIBCXX_END_NAMESPACE_VERSION 173 } // namespace std 174 175 #endif 176 177 #endif 178
