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1 : // Pointer Traits -*- C++ -*-
2 :
3 : // Copyright (C) 2011-2019 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 : #if __cplusplus > 201703L
38 : #define __cpp_lib_constexpr_memory 201811L
39 : namespace __gnu_debug { struct _Safe_iterator_base; }
40 : #endif
41 :
42 : namespace std _GLIBCXX_VISIBILITY(default)
43 : {
44 : _GLIBCXX_BEGIN_NAMESPACE_VERSION
45 :
46 : class __undefined;
47 :
48 : // Given Template<T, ...> return T, otherwise invalid.
49 : template<typename _Tp>
50 : struct __get_first_arg
51 : { using type = __undefined; };
52 :
53 : template<template<typename, typename...> class _Template, typename _Tp,
54 : typename... _Types>
55 : struct __get_first_arg<_Template<_Tp, _Types...>>
56 : { using type = _Tp; };
57 :
58 : template<typename _Tp>
59 : using __get_first_arg_t = typename __get_first_arg<_Tp>::type;
60 :
61 : // Given Template<T, ...> and U return Template<U, ...>, otherwise invalid.
62 : template<typename _Tp, typename _Up>
63 : struct __replace_first_arg
64 : { };
65 :
66 : template<template<typename, typename...> class _Template, typename _Up,
67 : typename _Tp, typename... _Types>
68 : struct __replace_first_arg<_Template<_Tp, _Types...>, _Up>
69 : { using type = _Template<_Up, _Types...>; };
70 :
71 : template<typename _Tp, typename _Up>
72 : using __replace_first_arg_t = typename __replace_first_arg<_Tp, _Up>::type;
73 :
74 : template<typename _Tp>
75 : using __make_not_void
76 : = typename conditional<is_void<_Tp>::value, __undefined, _Tp>::type;
77 :
78 : /**
79 : * @brief Uniform interface to all pointer-like types
80 : * @ingroup pointer_abstractions
81 : */
82 : template<typename _Ptr>
83 : struct pointer_traits
84 : {
85 : private:
86 : template<typename _Tp>
87 : using __element_type = typename _Tp::element_type;
88 :
89 : template<typename _Tp>
90 : using __difference_type = typename _Tp::difference_type;
91 :
92 : template<typename _Tp, typename _Up, typename = void>
93 : struct __rebind : __replace_first_arg<_Tp, _Up> { };
94 :
95 : template<typename _Tp, typename _Up>
96 : struct __rebind<_Tp, _Up, __void_t<typename _Tp::template rebind<_Up>>>
97 : { using type = typename _Tp::template rebind<_Up>; };
98 :
99 : public:
100 : /// The pointer type.
101 : using pointer = _Ptr;
102 :
103 : /// The type pointed to.
104 : using element_type
105 : = __detected_or_t<__get_first_arg_t<_Ptr>, __element_type, _Ptr>;
106 :
107 : /// The type used to represent the difference between two pointers.
108 : using difference_type
109 : = __detected_or_t<ptrdiff_t, __difference_type, _Ptr>;
110 :
111 : /// A pointer to a different type.
112 : template<typename _Up>
113 : using rebind = typename __rebind<_Ptr, _Up>::type;
114 :
115 : static _Ptr
116 : pointer_to(__make_not_void<element_type>& __e)
117 : { return _Ptr::pointer_to(__e); }
118 :
119 : static_assert(!is_same<element_type, __undefined>::value,
120 : "pointer type defines element_type or is like SomePointer<T, Args>");
121 : };
122 :
123 : /**
124 : * @brief Partial specialization for built-in pointers.
125 : * @ingroup pointer_abstractions
126 : */
127 : template<typename _Tp>
128 : struct pointer_traits<_Tp*>
129 : {
130 : /// The pointer type
131 : typedef _Tp* pointer;
132 : /// The type pointed to
133 : typedef _Tp element_type;
134 : /// Type used to represent the difference between two pointers
135 : typedef ptrdiff_t difference_type;
136 :
137 : template<typename _Up>
138 : using rebind = _Up*;
139 :
140 : /**
141 : * @brief Obtain a pointer to an object
142 : * @param __r A reference to an object of type @c element_type
143 : * @return @c addressof(__r)
144 : */
145 : static _GLIBCXX20_CONSTEXPR pointer
146 5741216431 : pointer_to(__make_not_void<element_type>& __r) noexcept
147 5741216431 : { return std::addressof(__r); }
148 : };
149 :
150 : /// Convenience alias for rebinding pointers.
151 : template<typename _Ptr, typename _Tp>
152 : using __ptr_rebind = typename pointer_traits<_Ptr>::template rebind<_Tp>;
153 :
154 : template<typename _Tp>
155 : constexpr _Tp*
156 955 : __to_address(_Tp* __ptr) noexcept
157 : {
158 : static_assert(!std::is_function<_Tp>::value, "not a function pointer");
159 : return __ptr;
160 : }
161 :
162 : #if __cplusplus <= 201703L
163 : template<typename _Ptr>
164 : constexpr typename std::pointer_traits<_Ptr>::element_type*
165 : __to_address(const _Ptr& __ptr)
166 : { return std::__to_address(__ptr.operator->()); }
167 : #else
168 : template<typename _Ptr>
169 : constexpr auto
170 : __to_address(const _Ptr& __ptr) noexcept
171 : -> decltype(std::pointer_traits<_Ptr>::to_address(__ptr))
172 : { return std::pointer_traits<_Ptr>::to_address(__ptr); }
173 :
174 : template<typename _Ptr, typename... _None>
175 : constexpr auto
176 : __to_address(const _Ptr& __ptr, _None...) noexcept
177 : {
178 : if constexpr (is_base_of_v<__gnu_debug::_Safe_iterator_base, _Ptr>)
179 : return std::__to_address(__ptr.base().operator->());
180 : else
181 : return std::__to_address(__ptr.operator->());
182 : }
183 :
184 : #define __cpp_lib_to_address 201711L
185 :
186 : /**
187 : * @brief Obtain address referenced by a pointer to an object
188 : * @param __ptr A pointer to an object
189 : * @return @c __ptr
190 : * @ingroup pointer_abstractions
191 : */
192 : template<typename _Tp>
193 : constexpr _Tp*
194 : to_address(_Tp* __ptr) noexcept
195 : { return std::__to_address(__ptr); }
196 :
197 : /**
198 : * @brief Obtain address referenced by a pointer to an object
199 : * @param __ptr A pointer to an object
200 : * @return @c pointer_traits<_Ptr>::to_address(__ptr) if that expression is
201 : well-formed, otherwise @c to_address(__ptr.operator->())
202 : * @ingroup pointer_abstractions
203 : */
204 : template<typename _Ptr>
205 : constexpr auto
206 : to_address(const _Ptr& __ptr) noexcept
207 : { return std::__to_address(__ptr); }
208 : #endif // C++2a
209 :
210 : _GLIBCXX_END_NAMESPACE_VERSION
211 : } // namespace std
212 :
213 : #endif
214 :
215 : #endif
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