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1 : // Move, forward and identity for C++11 + swap -*- C++ -*-
2 :
3 : // Copyright (C) 2007-2024 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 : #if __cplusplus < 201103L
35 : # include <bits/concept_check.h>
36 : #else
37 : # include <type_traits> // Brings in std::declval too.
38 : #endif
39 :
40 : namespace std _GLIBCXX_VISIBILITY(default)
41 : {
42 : _GLIBCXX_BEGIN_NAMESPACE_VERSION
43 :
44 : // Used, in C++03 mode too, by allocators, etc.
45 : /**
46 : * @brief Same as C++11 std::addressof
47 : * @ingroup utilities
48 : */
49 : template<typename _Tp>
50 : inline _GLIBCXX_CONSTEXPR _Tp*
51 0 : __addressof(_Tp& __r) _GLIBCXX_NOEXCEPT
52 0 : { return __builtin_addressof(__r); }
53 :
54 : #if __cplusplus >= 201103L
55 :
56 : /**
57 : * @addtogroup utilities
58 : * @{
59 : */
60 :
61 : /**
62 : * @brief Forward an lvalue.
63 : * @return The parameter cast to the specified type.
64 : *
65 : * This function is used to implement "perfect forwarding".
66 : * @since C++11
67 : */
68 : template<typename _Tp>
69 : _GLIBCXX_NODISCARD
70 : constexpr _Tp&&
71 4766262 : forward(typename std::remove_reference<_Tp>::type& __t) noexcept
72 4766262 : { return static_cast<_Tp&&>(__t); }
73 :
74 : /**
75 : * @brief Forward an rvalue.
76 : * @return The parameter cast to the specified type.
77 : *
78 : * This function is used to implement "perfect forwarding".
79 : * @since C++11
80 : */
81 : template<typename _Tp>
82 : _GLIBCXX_NODISCARD
83 : constexpr _Tp&&
84 : forward(typename std::remove_reference<_Tp>::type&& __t) noexcept
85 : {
86 : static_assert(!std::is_lvalue_reference<_Tp>::value,
87 : "std::forward must not be used to convert an rvalue to an lvalue");
88 : return static_cast<_Tp&&>(__t);
89 : }
90 :
91 : #if __glibcxx_forward_like // C++ >= 23
92 : template<typename _Tp, typename _Up>
93 : struct __like_impl; // _Tp must be a reference and _Up an lvalue reference
94 :
95 : template<typename _Tp, typename _Up>
96 : struct __like_impl<_Tp&, _Up&>
97 : { using type = _Up&; };
98 :
99 : template<typename _Tp, typename _Up>
100 : struct __like_impl<const _Tp&, _Up&>
101 : { using type = const _Up&; };
102 :
103 : template<typename _Tp, typename _Up>
104 : struct __like_impl<_Tp&&, _Up&>
105 : { using type = _Up&&; };
106 :
107 : template<typename _Tp, typename _Up>
108 : struct __like_impl<const _Tp&&, _Up&>
109 : { using type = const _Up&&; };
110 :
111 : template<typename _Tp, typename _Up>
112 : using __like_t = typename __like_impl<_Tp&&, _Up&>::type;
113 :
114 : /** @brief Forward with the cv-qualifiers and value category of another type.
115 : * @tparam _Tp An lvalue reference or rvalue reference.
116 : * @tparam _Up An lvalue reference type deduced from the function argument.
117 : * @param __x An lvalue.
118 : * @return `__x` converted to match the qualifiers of `_Tp`.
119 : * @since C++23
120 : */
121 : template<typename _Tp, typename _Up>
122 : [[nodiscard]]
123 : constexpr __like_t<_Tp, _Up>
124 : forward_like(_Up&& __x) noexcept
125 : { return static_cast<__like_t<_Tp, _Up>>(__x); }
126 : #endif
127 :
128 : /**
129 : * @brief Convert a value to an rvalue.
130 : * @param __t A thing of arbitrary type.
131 : * @return The parameter cast to an rvalue-reference to allow moving it.
132 : * @since C++11
133 : */
134 : template<typename _Tp>
135 : _GLIBCXX_NODISCARD
136 : constexpr typename std::remove_reference<_Tp>::type&&
137 1428273 : move(_Tp&& __t) noexcept
138 1428273 : { return static_cast<typename std::remove_reference<_Tp>::type&&>(__t); }
139 :
140 :
141 : template<typename _Tp>
142 : struct __move_if_noexcept_cond
143 : : public __and_<__not_<is_nothrow_move_constructible<_Tp>>,
144 : is_copy_constructible<_Tp>>::type { };
145 :
146 : /**
147 : * @brief Conditionally convert a value to an rvalue.
148 : * @param __x A thing of arbitrary type.
149 : * @return The parameter, possibly cast to an rvalue-reference.
150 : *
151 : * Same as std::move unless the type's move constructor could throw and the
152 : * type is copyable, in which case an lvalue-reference is returned instead.
153 : * @since C++11
154 : */
155 : template<typename _Tp>
156 : _GLIBCXX_NODISCARD
157 : constexpr
158 : __conditional_t<__move_if_noexcept_cond<_Tp>::value, const _Tp&, _Tp&&>
159 : move_if_noexcept(_Tp& __x) noexcept
160 : { return std::move(__x); }
161 :
162 : // declval, from type_traits.
163 :
164 : /**
165 : * @brief Returns the actual address of the object or function
166 : * referenced by r, even in the presence of an overloaded
167 : * operator&.
168 : * @param __r Reference to an object or function.
169 : * @return The actual address.
170 : * @since C++11
171 : */
172 : template<typename _Tp>
173 : _GLIBCXX_NODISCARD
174 : inline _GLIBCXX17_CONSTEXPR _Tp*
175 : addressof(_Tp& __r) noexcept
176 : { return std::__addressof(__r); }
177 :
178 : // _GLIBCXX_RESOLVE_LIB_DEFECTS
179 : // 2598. addressof works on temporaries
180 : template<typename _Tp>
181 : const _Tp* addressof(const _Tp&&) = delete;
182 :
183 : // C++11 version of std::exchange for internal use.
184 : template <typename _Tp, typename _Up = _Tp>
185 : _GLIBCXX20_CONSTEXPR
186 : inline _Tp
187 : __exchange(_Tp& __obj, _Up&& __new_val)
188 : {
189 : _Tp __old_val = std::move(__obj);
190 : __obj = std::forward<_Up>(__new_val);
191 : return __old_val;
192 : }
193 :
194 : /// @} group utilities
195 :
196 : #define _GLIBCXX_FWDREF(_Tp) _Tp&&
197 : #define _GLIBCXX_MOVE(__val) std::move(__val)
198 : #define _GLIBCXX_FORWARD(_Tp, __val) std::forward<_Tp>(__val)
199 : #else
200 : #define _GLIBCXX_FWDREF(_Tp) const _Tp&
201 : #define _GLIBCXX_MOVE(__val) (__val)
202 : #define _GLIBCXX_FORWARD(_Tp, __val) (__val)
203 : #endif
204 :
205 : /**
206 : * @addtogroup utilities
207 : * @{
208 : */
209 :
210 : /**
211 : * @brief Swaps two values.
212 : * @param __a A thing of arbitrary type.
213 : * @param __b Another thing of arbitrary type.
214 : * @return Nothing.
215 : */
216 : template<typename _Tp>
217 : _GLIBCXX20_CONSTEXPR
218 : inline
219 : #if __cplusplus >= 201103L
220 : typename enable_if<__and_<__not_<__is_tuple_like<_Tp>>,
221 : is_move_constructible<_Tp>,
222 : is_move_assignable<_Tp>>::value>::type
223 : #else
224 : void
225 : #endif
226 : swap(_Tp& __a, _Tp& __b)
227 : _GLIBCXX_NOEXCEPT_IF(__and_<is_nothrow_move_constructible<_Tp>,
228 : is_nothrow_move_assignable<_Tp>>::value)
229 : {
230 : #if __cplusplus < 201103L
231 : // concept requirements
232 : __glibcxx_function_requires(_SGIAssignableConcept<_Tp>)
233 : #endif
234 : _Tp __tmp = _GLIBCXX_MOVE(__a);
235 : __a = _GLIBCXX_MOVE(__b);
236 : __b = _GLIBCXX_MOVE(__tmp);
237 : }
238 :
239 : // _GLIBCXX_RESOLVE_LIB_DEFECTS
240 : // DR 809. std::swap should be overloaded for array types.
241 : /// Swap the contents of two arrays.
242 : template<typename _Tp, size_t _Nm>
243 : _GLIBCXX20_CONSTEXPR
244 : inline
245 : #if __cplusplus >= 201103L
246 : typename enable_if<__is_swappable<_Tp>::value>::type
247 : #else
248 : void
249 : #endif
250 : swap(_Tp (&__a)[_Nm], _Tp (&__b)[_Nm])
251 : _GLIBCXX_NOEXCEPT_IF(__is_nothrow_swappable<_Tp>::value)
252 : {
253 : for (size_t __n = 0; __n < _Nm; ++__n)
254 : swap(__a[__n], __b[__n]);
255 : }
256 :
257 : /// @} group utilities
258 : _GLIBCXX_END_NAMESPACE_VERSION
259 : } // namespace
260 :
261 : #endif /* _MOVE_H */
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