1// Pointer Traits -*- C++ -*-
2
3// Copyright (C) 2011-2016 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
37namespace 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 { using type = __undefined; };
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>
88 using __rebind = typename _Tp::template rebind<_Up>;
89
90 public:
91 /// The pointer type.
92 using pointer = _Ptr;
93
94 /// The type pointed to.
95 using element_type
96 = __detected_or_t_<__get_first_arg_t, __element_type, _Ptr>;
97
98 /// The type used to represent the difference between two pointers.
99 using difference_type
100 = __detected_or_t<ptrdiff_t, __difference_type, _Ptr>;
101
102 /// A pointer to a different type.
103 template<typename _Up>
104 using rebind
105 = __detected_or_t_<__replace_first_arg_t, __rebind, _Ptr, _Up>;
106
107 static _Ptr
108 pointer_to(__make_not_void<element_type>& __e)
109 { return _Ptr::pointer_to(__e); }
110
111 static_assert(!is_same<element_type, __undefined>::value,
112 "pointer type defines element_type or is like SomePointer<T, Args>");
113 static_assert(!is_same<rebind<element_type>, __undefined>::value,
114 "pointer type defines rebind<U> or is like SomePointer<T, Args>");
115 };
116
117 /**
118 * @brief Partial specialization for built-in pointers.
119 * @ingroup pointer_abstractions
120 */
121 template<typename _Tp>
122 struct pointer_traits<_Tp*>
123 {
124 /// The pointer type
125 typedef _Tp* pointer;
126 /// The type pointed to
127 typedef _Tp element_type;
128 /// Type used to represent the difference between two pointers
129 typedef ptrdiff_t difference_type;
130
131 template<typename _Up>
132 using rebind = _Up*;
133
134 /**
135 * @brief Obtain a pointer to an object
136 * @param __r A reference to an object of type @c element_type
137 * @return @c addressof(__r)
138 */
139 static pointer
140 pointer_to(__make_not_void<element_type>& __r) noexcept
141 { return std::addressof(__r); }
142 };
143
144 /// Convenience alias for rebinding pointers.
145 template<typename _Ptr, typename _Tp>
146 using __ptr_rebind = typename pointer_traits<_Ptr>::template rebind<_Tp>;
147
148_GLIBCXX_END_NAMESPACE_VERSION
149} // namespace std
150
151#endif
152
153#endif
154