libstdc++

ptr_traits.h
Go to the documentation of this file.
1 // Pointer Traits -*- C++ -*-
2
3 // Copyright (C) 2011-2013 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 bool
77 _S_chk(typename _Ptr2::template rebind<_Up2>*)
78 { return true; }
79
80 template<typename, typename>
81 static constexpr bool
82 _S_chk(...)
83 { return false; }
84
85 public:
86 static const bool __value = _S_chk<_Ptr, _Up>(nullptr);
87 };
88
89 template<typename _Ptr, typename _Up>
90 const bool __ptrtr_rebind_helper<_Ptr, _Up>::__value;
91
92 template<typename _Tp, typename _Up,
93 bool = __ptrtr_rebind_helper<_Tp, _Up>::__value>
94 struct __ptrtr_rebind;
95
96 template<typename _Tp, typename _Up>
97 struct __ptrtr_rebind<_Tp, _Up, true>
98 {
99 typedef typename _Tp::template rebind<_Up> __type;
100 };
101
102 template<template<typename, typename...> class _SomePtr, typename _Up,
103 typename _Tp, typename... _Args>
104 struct __ptrtr_rebind<_SomePtr<_Tp, _Args...>, _Up, false>
105 {
106 typedef _SomePtr<_Up, _Args...> __type;
107 };
108
109 template<typename _Tp, typename = typename remove_cv<_Tp>::type>
110 struct __ptrtr_not_void
111 {
112 typedef _Tp __type;
113 };
114
115 template<typename _Tp>
116 struct __ptrtr_not_void<_Tp, void>
117 {
118 struct __type { };
119 };
120
121 template<typename _Ptr>
122 class __ptrtr_pointer_to
123 {
124 typedef typename __ptrtr_elt_type<_Ptr>::__type __orig_type;
125 typedef typename __ptrtr_not_void<__orig_type>::__type __element_type;
126
127 public:
128 static _Ptr pointer_to(__element_type& __e)
129 { return _Ptr::pointer_to(__e); }
130 };
131
132 /**
133 * @brief Uniform interface to all pointer-like types
134 * @ingroup pointer_abstractions
135 */
136 template<typename _Ptr>
137 struct pointer_traits : __ptrtr_pointer_to<_Ptr>
138 {
139 /// The pointer type
140 typedef _Ptr pointer;
141 /// The type pointed to
142 typedef typename __ptrtr_elt_type<_Ptr>::__type element_type;
143 /// Type used to represent the difference between two pointers
144 typedef typename __ptrtr_diff_type<_Ptr>::__type difference_type;
145
146 template<typename _Up>
147 using rebind = typename __ptrtr_rebind<_Ptr, _Up>::__type;
148 };
149
150 /**
151 * @brief Partial specialization for built-in pointers.
152 * @ingroup pointer_abstractions
153 */
154 template<typename _Tp>
155 struct pointer_traits<_Tp*>
156 {
157 /// The pointer type
158 typedef _Tp* pointer;
159 /// The type pointed to
160 typedef _Tp element_type;
161 /// Type used to represent the difference between two pointers
162 typedef ptrdiff_t difference_type;
163
164 template<typename _Up>
165 using rebind = _Up*;
166
167 /**
168 * @brief Obtain a pointer to an object
169 * @param __r A reference to an object of type @c element_type
170 * @return @c addressof(__r)
171 */
172 static pointer
173 pointer_to(typename __ptrtr_not_void<element_type>::__type& __r) noexcept
174 { return std::addressof(__r); }
175 };
176
177 _GLIBCXX_END_NAMESPACE_VERSION
178 } // namespace std
179
180 #endif
181
182 #endif