libstdc++
ptr_traits.h
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1 // Pointer Traits -*- C++ -*-
2 
3 // Copyright (C) 2011-2015 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 true_type
77  _S_chk(typename _Ptr2::template rebind<_Up2>*);
78 
79  template<typename, typename>
80  static constexpr false_type
81  _S_chk(...);
82 
83  public:
84  using __type = decltype(_S_chk<_Ptr, _Up>(nullptr));
85  };
86 
87  template<typename _Tp, typename _Up,
88  bool = __ptrtr_rebind_helper<_Tp, _Up>::__type::value>
89  struct __ptrtr_rebind;
90 
91  template<typename _Tp, typename _Up>
92  struct __ptrtr_rebind<_Tp, _Up, true>
93  {
94  typedef typename _Tp::template rebind<_Up> __type;
95  };
96 
97  template<template<typename, typename...> class _SomePtr, typename _Up,
98  typename _Tp, typename... _Args>
99  struct __ptrtr_rebind<_SomePtr<_Tp, _Args...>, _Up, false>
100  {
101  typedef _SomePtr<_Up, _Args...> __type;
102  };
103 
104  template<typename _Tp, typename = typename remove_cv<_Tp>::type>
105  struct __ptrtr_not_void
106  {
107  typedef _Tp __type;
108  };
109 
110  template<typename _Tp>
111  struct __ptrtr_not_void<_Tp, void>
112  {
113  struct __type { };
114  };
115 
116  template<typename _Ptr>
117  class __ptrtr_pointer_to
118  {
119  typedef typename __ptrtr_elt_type<_Ptr>::__type __orig_type;
120  typedef typename __ptrtr_not_void<__orig_type>::__type __element_type;
121 
122  public:
123  static _Ptr pointer_to(__element_type& __e)
124  { return _Ptr::pointer_to(__e); }
125  };
126 
127  /**
128  * @brief Uniform interface to all pointer-like types
129  * @ingroup pointer_abstractions
130  */
131  template<typename _Ptr>
132  struct pointer_traits : __ptrtr_pointer_to<_Ptr>
133  {
134  /// The pointer type
135  typedef _Ptr pointer;
136  /// The type pointed to
137  typedef typename __ptrtr_elt_type<_Ptr>::__type element_type;
138  /// Type used to represent the difference between two pointers
139  typedef typename __ptrtr_diff_type<_Ptr>::__type difference_type;
140 
141  template<typename _Up>
142  using rebind = typename __ptrtr_rebind<_Ptr, _Up>::__type;
143  };
144 
145  /**
146  * @brief Partial specialization for built-in pointers.
147  * @ingroup pointer_abstractions
148  */
149  template<typename _Tp>
150  struct pointer_traits<_Tp*>
151  {
152  /// The pointer type
153  typedef _Tp* pointer;
154  /// The type pointed to
155  typedef _Tp element_type;
156  /// Type used to represent the difference between two pointers
157  typedef ptrdiff_t difference_type;
158 
159  template<typename _Up>
160  using rebind = _Up*;
161 
162  /**
163  * @brief Obtain a pointer to an object
164  * @param __r A reference to an object of type @c element_type
165  * @return @c addressof(__r)
166  */
167  static pointer
168  pointer_to(typename __ptrtr_not_void<element_type>::__type& __r) noexcept
169  { return std::addressof(__r); }
170  };
171 
172 _GLIBCXX_END_NAMESPACE_VERSION
173 } // namespace std
174 
175 #endif
176 
177 #endif
__ptrtr_diff_type< _Ptr >::__type difference_type
Type used to represent the difference between two pointers.
Definition: ptr_traits.h:139
integral_constant< bool, true > true_type
The type used as a compile-time boolean with true value.
Definition: type_traits:87
_Tp element_type
The type pointed to.
Definition: ptr_traits.h:155
integral_constant< bool, false > false_type
The type used as a compile-time boolean with false value.
Definition: type_traits:90
ptrdiff_t difference_type
Type used to represent the difference between two pointers.
Definition: ptr_traits.h:157
_Tp * addressof(_Tp &__r) noexcept
Returns the actual address of the object or function referenced by r, even in the presence of an over...
Definition: move.h:135
static pointer pointer_to(typename __ptrtr_not_void< element_type >::__type &__r) noexcept
Obtain a pointer to an object.
Definition: ptr_traits.h:168
__ptrtr_elt_type< _Ptr >::__type element_type
The type pointed to.
Definition: ptr_traits.h:137
Uniform interface to all pointer-like types.
Definition: ptr_traits.h:132
_Tp * pointer
The pointer type.
Definition: ptr_traits.h:153
ISO C++ entities toplevel namespace is std.
_Ptr pointer
The pointer type.
Definition: ptr_traits.h:135