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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 2064395 : pointer_to(__make_not_void<element_type>& __r) noexcept
142 2064395 : { 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 6892 : __to_address(_Tp* __ptr) noexcept
152 : {
153 : static_assert(!std::is_function<_Tp>::value, "not a function pointer");
154 6892 : 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
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