libstdc++
move.h
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1 // Move, forward and identity for C++0x + swap -*- C++ -*-
2 
3 // Copyright (C) 2007-2014 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/move.h
26  * This is an internal header file, included by other library headers.
27  * Do not attempt to use it directly. @headername{utility}
28  */
29 
30 #ifndef _MOVE_H
31 #define _MOVE_H 1
32 
33 #include <bits/c++config.h>
34 #include <bits/concept_check.h>
35 
36 namespace std _GLIBCXX_VISIBILITY(default)
37 {
38 _GLIBCXX_BEGIN_NAMESPACE_VERSION
39 
40  // Used, in C++03 mode too, by allocators, etc.
41  /**
42  * @brief Same as C++11 std::addressof
43  * @ingroup utilities
44  */
45  template<typename _Tp>
46  inline _Tp*
47  __addressof(_Tp& __r) _GLIBCXX_NOEXCEPT
48  {
49  return reinterpret_cast<_Tp*>
50  (&const_cast<char&>(reinterpret_cast<const volatile char&>(__r)));
51  }
52 
53 _GLIBCXX_END_NAMESPACE_VERSION
54 } // namespace
55 
56 #if __cplusplus >= 201103L
57 #include <type_traits> // Brings in std::declval too.
58 
59 namespace std _GLIBCXX_VISIBILITY(default)
60 {
61 _GLIBCXX_BEGIN_NAMESPACE_VERSION
62 
63  /**
64  * @addtogroup utilities
65  * @{
66  */
67 
68  /**
69  * @brief Forward an lvalue.
70  * @return The parameter cast to the specified type.
71  *
72  * This function is used to implement "perfect forwarding".
73  */
74  template<typename _Tp>
75  constexpr _Tp&&
76  forward(typename std::remove_reference<_Tp>::type& __t) noexcept
77  { return static_cast<_Tp&&>(__t); }
78 
79  /**
80  * @brief Forward an rvalue.
81  * @return The parameter cast to the specified type.
82  *
83  * This function is used to implement "perfect forwarding".
84  */
85  template<typename _Tp>
86  constexpr _Tp&&
87  forward(typename std::remove_reference<_Tp>::type&& __t) noexcept
88  {
89  static_assert(!std::is_lvalue_reference<_Tp>::value, "template argument"
90  " substituting _Tp is an lvalue reference type");
91  return static_cast<_Tp&&>(__t);
92  }
93 
94  /**
95  * @brief Convert a value to an rvalue.
96  * @param __t A thing of arbitrary type.
97  * @return The parameter cast to an rvalue-reference to allow moving it.
98  */
99  template<typename _Tp>
100  constexpr typename std::remove_reference<_Tp>::type&&
101  move(_Tp&& __t) noexcept
102  { return static_cast<typename std::remove_reference<_Tp>::type&&>(__t); }
103 
104 
105  template<typename _Tp>
106  struct __move_if_noexcept_cond
107  : public __and_<__not_<is_nothrow_move_constructible<_Tp>>,
108  is_copy_constructible<_Tp>>::type { };
109 
110  /**
111  * @brief Conditionally convert a value to an rvalue.
112  * @param __x A thing of arbitrary type.
113  * @return The parameter, possibly cast to an rvalue-reference.
114  *
115  * Same as std::move unless the type's move constructor could throw and the
116  * type is copyable, in which case an lvalue-reference is returned instead.
117  */
118  template<typename _Tp>
119  constexpr typename
120  conditional<__move_if_noexcept_cond<_Tp>::value, const _Tp&, _Tp&&>::type
121  move_if_noexcept(_Tp& __x) noexcept
122  { return std::move(__x); }
123 
124  // declval, from type_traits.
125 
126  /**
127  * @brief Returns the actual address of the object or function
128  * referenced by r, even in the presence of an overloaded
129  * operator&.
130  * @param __r Reference to an object or function.
131  * @return The actual address.
132  */
133  template<typename _Tp>
134  inline _Tp*
135  addressof(_Tp& __r) noexcept
136  { return std::__addressof(__r); }
137 
138  /// @} group utilities
139 _GLIBCXX_END_NAMESPACE_VERSION
140 } // namespace
141 
142 #define _GLIBCXX_MOVE(__val) std::move(__val)
143 #define _GLIBCXX_FORWARD(_Tp, __val) std::forward<_Tp>(__val)
144 #else
145 #define _GLIBCXX_MOVE(__val) (__val)
146 #define _GLIBCXX_FORWARD(_Tp, __val) (__val)
147 #endif
148 
149 namespace std _GLIBCXX_VISIBILITY(default)
150 {
151 _GLIBCXX_BEGIN_NAMESPACE_VERSION
152 
153  /**
154  * @addtogroup utilities
155  * @{
156  */
157 
158  /**
159  * @brief Swaps two values.
160  * @param __a A thing of arbitrary type.
161  * @param __b Another thing of arbitrary type.
162  * @return Nothing.
163  */
164  template<typename _Tp>
165  inline void
166  swap(_Tp& __a, _Tp& __b)
167 #if __cplusplus >= 201103L
168  noexcept(__and_<is_nothrow_move_constructible<_Tp>,
169  is_nothrow_move_assignable<_Tp>>::value)
170 #endif
171  {
172  // concept requirements
173  __glibcxx_function_requires(_SGIAssignableConcept<_Tp>)
174 
175  _Tp __tmp = _GLIBCXX_MOVE(__a);
176  __a = _GLIBCXX_MOVE(__b);
177  __b = _GLIBCXX_MOVE(__tmp);
178  }
179 
180  // _GLIBCXX_RESOLVE_LIB_DEFECTS
181  // DR 809. std::swap should be overloaded for array types.
182  /// Swap the contents of two arrays.
183  template<typename _Tp, size_t _Nm>
184  inline void
185  swap(_Tp (&__a)[_Nm], _Tp (&__b)[_Nm])
186 #if __cplusplus >= 201103L
187  noexcept(noexcept(swap(*__a, *__b)))
188 #endif
189  {
190  for (size_t __n = 0; __n < _Nm; ++__n)
191  swap(__a[__n], __b[__n]);
192  }
193 
194  /// @} group utilities
195 _GLIBCXX_END_NAMESPACE_VERSION
196 } // namespace
197 
198 #endif /* _MOVE_H */
_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
is_lvalue_reference
Definition: type_traits:303
constexpr _Tp && forward(typename std::remove_reference< _Tp >::type &__t) noexcept
Forward an lvalue.
Definition: move.h:76
void swap(function< _Res(_Args...)> &__x, function< _Res(_Args...)> &__y)
Swap the targets of two polymorphic function object wrappers.
Definition: functional:2534
_Tp * __addressof(_Tp &__r) noexcept
Same as C++11 std::addressof.
Definition: move.h:47
constexpr conditional< __move_if_noexcept_cond< _Tp >::value, const _Tp &, _Tp && >::type move_if_noexcept(_Tp &__x) noexcept
Conditionally convert a value to an rvalue.
Definition: move.h:121