1 // Pointer Traits -*- C++ -*-
3 // Copyright (C) 2011-2015 Free Software Foundation, Inc.
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)
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.
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.
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/>.
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}
31 #define _PTR_TRAITS_H 1
33 #if __cplusplus >= 201103L
35 #include <bits/move.h>
37 namespace std
_GLIBCXX_VISIBILITY(default)
39 _GLIBCXX_BEGIN_NAMESPACE_VERSION
43 // Given Template<T, ...> return T, otherwise invalid.
44 template<typename _Tp
>
45 struct __get_first_arg
46 { using type
= __undefined
; };
48 template<template<typename
, typename
...> class _Template
, typename _Tp
,
50 struct __get_first_arg
<_Template
<_Tp
, _Types
...>>
51 { using type
= _Tp
; };
53 template<typename _Tp
>
54 using __get_first_arg_t
= typename __get_first_arg
<_Tp
>::type
;
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
; };
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
...>; };
66 template<typename _Tp
, typename _Up
>
67 using __replace_first_arg_t
= typename __replace_first_arg
<_Tp
, _Up
>::type
;
69 template<typename _Tp
>
71 = typename conditional
<is_void
<_Tp
>::value
, __undefined
, _Tp
>::type
;
74 * @brief Uniform interface to all pointer-like types
75 * @ingroup pointer_abstractions
77 template<typename _Ptr
>
81 template<typename _Tp
>
82 using __element_type
= typename
_Tp::element_type
;
84 template<typename _Tp
>
85 using __difference_type
= typename
_Tp::difference_type
;
87 template<typename _Tp
, typename _Up
>
88 using __rebind
= typename
_Tp::template rebind
<_Up
>;
94 /// The type pointed to.
96 = __detected_or_t_
<__get_first_arg_t
, __element_type
, _Ptr
>;
98 /// The type used to represent the difference between two pointers.
100 = __detected_or_t
<ptrdiff_t, __difference_type
, _Ptr
>;
102 /// A pointer to a different type.
103 template<typename _Up
>
105 = __detected_or_t_
<__replace_first_arg_t
, __rebind
, _Ptr
, _Up
>;
108 pointer_to(__make_not_void
<element_type
>& __e
)
109 { return _Ptr::pointer_to(__e
); }
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>");
118 * @brief Partial specialization for built-in pointers.
119 * @ingroup pointer_abstractions
121 template<typename _Tp
>
122 struct pointer_traits
<_Tp
*>
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
;
131 template<typename _Up
>
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)
140 pointer_to(__make_not_void
<element_type
>& __r
) noexcept
141 { return std::addressof(__r
); }
144 /// Convenience alias for rebinding pointers.
145 template<typename _Ptr
, typename _Tp
>
146 using __ptr_rebind
= typename pointer_traits
<_Ptr
>::template rebind
<_Tp
>;
148 _GLIBCXX_END_NAMESPACE_VERSION