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 | __addressof(_Tp& __r) _GLIBCXX_NOEXCEPT |
52 | { 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 | */ |
67 | template<typename _Tp> |
68 | _GLIBCXX_NODISCARD |
69 | constexpr _Tp&& |
70 | forward(typename std::remove_reference<_Tp>::type& __t) noexcept |
71 | { return static_cast<_Tp&&>(__t); } |
72 | |
73 | /** |
74 | * @brief Forward an rvalue. |
75 | * @return The parameter cast to the specified type. |
76 | * |
77 | * This function is used to implement "perfect forwarding". |
78 | */ |
79 | template<typename _Tp> |
80 | _GLIBCXX_NODISCARD |
81 | constexpr _Tp&& |
82 | forward(typename std::remove_reference<_Tp>::type&& __t) noexcept |
83 | { |
84 | static_assert(!std::is_lvalue_reference<_Tp>::value, |
85 | "std::forward must not be used to convert an rvalue to an lvalue" ); |
86 | return static_cast<_Tp&&>(__t); |
87 | } |
88 | |
89 | #if __glibcxx_forward_like // C++ >= 23 |
90 | template<typename _Tp, typename _Up> |
91 | [[nodiscard]] |
92 | constexpr decltype(auto) |
93 | forward_like(_Up&& __x) noexcept |
94 | { |
95 | constexpr bool __as_rval = is_rvalue_reference_v<_Tp&&>; |
96 | |
97 | if constexpr (is_const_v<remove_reference_t<_Tp>>) |
98 | { |
99 | using _Up2 = remove_reference_t<_Up>; |
100 | if constexpr (__as_rval) |
101 | return static_cast<const _Up2&&>(__x); |
102 | else |
103 | return static_cast<const _Up2&>(__x); |
104 | } |
105 | else |
106 | { |
107 | if constexpr (__as_rval) |
108 | return static_cast<remove_reference_t<_Up>&&>(__x); |
109 | else |
110 | return static_cast<_Up&>(__x); |
111 | } |
112 | } |
113 | |
114 | template<typename _Tp, typename _Up> |
115 | using __like_t = decltype(std::forward_like<_Tp>(std::declval<_Up>())); |
116 | #endif |
117 | |
118 | /** |
119 | * @brief Convert a value to an rvalue. |
120 | * @param __t A thing of arbitrary type. |
121 | * @return The parameter cast to an rvalue-reference to allow moving it. |
122 | */ |
123 | template<typename _Tp> |
124 | _GLIBCXX_NODISCARD |
125 | constexpr typename std::remove_reference<_Tp>::type&& |
126 | move(_Tp&& __t) noexcept |
127 | { return static_cast<typename std::remove_reference<_Tp>::type&&>(__t); } |
128 | |
129 | |
130 | template<typename _Tp> |
131 | struct __move_if_noexcept_cond |
132 | : public __and_<__not_<is_nothrow_move_constructible<_Tp>>, |
133 | is_copy_constructible<_Tp>>::type { }; |
134 | |
135 | /** |
136 | * @brief Conditionally convert a value to an rvalue. |
137 | * @param __x A thing of arbitrary type. |
138 | * @return The parameter, possibly cast to an rvalue-reference. |
139 | * |
140 | * Same as std::move unless the type's move constructor could throw and the |
141 | * type is copyable, in which case an lvalue-reference is returned instead. |
142 | */ |
143 | template<typename _Tp> |
144 | _GLIBCXX_NODISCARD |
145 | constexpr |
146 | __conditional_t<__move_if_noexcept_cond<_Tp>::value, const _Tp&, _Tp&&> |
147 | move_if_noexcept(_Tp& __x) noexcept |
148 | { return std::move(__x); } |
149 | |
150 | // declval, from type_traits. |
151 | |
152 | /** |
153 | * @brief Returns the actual address of the object or function |
154 | * referenced by r, even in the presence of an overloaded |
155 | * operator&. |
156 | * @param __r Reference to an object or function. |
157 | * @return The actual address. |
158 | */ |
159 | template<typename _Tp> |
160 | _GLIBCXX_NODISCARD |
161 | inline _GLIBCXX17_CONSTEXPR _Tp* |
162 | addressof(_Tp& __r) noexcept |
163 | { return std::__addressof(__r); } |
164 | |
165 | // _GLIBCXX_RESOLVE_LIB_DEFECTS |
166 | // 2598. addressof works on temporaries |
167 | template<typename _Tp> |
168 | const _Tp* addressof(const _Tp&&) = delete; |
169 | |
170 | // C++11 version of std::exchange for internal use. |
171 | template <typename _Tp, typename _Up = _Tp> |
172 | _GLIBCXX20_CONSTEXPR |
173 | inline _Tp |
174 | __exchange(_Tp& __obj, _Up&& __new_val) |
175 | { |
176 | _Tp __old_val = std::move(__obj); |
177 | __obj = std::forward<_Up>(__new_val); |
178 | return __old_val; |
179 | } |
180 | |
181 | /// @} group utilities |
182 | |
183 | #define _GLIBCXX_FWDREF(_Tp) _Tp&& |
184 | #define _GLIBCXX_MOVE(__val) std::move(__val) |
185 | #define _GLIBCXX_FORWARD(_Tp, __val) std::forward<_Tp>(__val) |
186 | #else |
187 | #define _GLIBCXX_FWDREF(_Tp) const _Tp& |
188 | #define _GLIBCXX_MOVE(__val) (__val) |
189 | #define _GLIBCXX_FORWARD(_Tp, __val) (__val) |
190 | #endif |
191 | |
192 | /** |
193 | * @addtogroup utilities |
194 | * @{ |
195 | */ |
196 | |
197 | /** |
198 | * @brief Swaps two values. |
199 | * @param __a A thing of arbitrary type. |
200 | * @param __b Another thing of arbitrary type. |
201 | * @return Nothing. |
202 | */ |
203 | template<typename _Tp> |
204 | _GLIBCXX20_CONSTEXPR |
205 | inline |
206 | #if __cplusplus >= 201103L |
207 | typename enable_if<__and_<__not_<__is_tuple_like<_Tp>>, |
208 | is_move_constructible<_Tp>, |
209 | is_move_assignable<_Tp>>::value>::type |
210 | #else |
211 | void |
212 | #endif |
213 | swap(_Tp& __a, _Tp& __b) |
214 | _GLIBCXX_NOEXCEPT_IF(__and_<is_nothrow_move_constructible<_Tp>, |
215 | is_nothrow_move_assignable<_Tp>>::value) |
216 | { |
217 | #if __cplusplus < 201103L |
218 | // concept requirements |
219 | __glibcxx_function_requires(_SGIAssignableConcept<_Tp>) |
220 | #endif |
221 | _Tp __tmp = _GLIBCXX_MOVE(__a); |
222 | __a = _GLIBCXX_MOVE(__b); |
223 | __b = _GLIBCXX_MOVE(__tmp); |
224 | } |
225 | |
226 | // _GLIBCXX_RESOLVE_LIB_DEFECTS |
227 | // DR 809. std::swap should be overloaded for array types. |
228 | /// Swap the contents of two arrays. |
229 | template<typename _Tp, size_t _Nm> |
230 | _GLIBCXX20_CONSTEXPR |
231 | inline |
232 | #if __cplusplus >= 201103L |
233 | typename enable_if<__is_swappable<_Tp>::value>::type |
234 | #else |
235 | void |
236 | #endif |
237 | swap(_Tp (&__a)[_Nm], _Tp (&__b)[_Nm]) |
238 | _GLIBCXX_NOEXCEPT_IF(__is_nothrow_swappable<_Tp>::value) |
239 | { |
240 | for (size_t __n = 0; __n < _Nm; ++__n) |
241 | swap(__a[__n], __b[__n]); |
242 | } |
243 | |
244 | /// @} group utilities |
245 | _GLIBCXX_END_NAMESPACE_VERSION |
246 | } // namespace |
247 | |
248 | #endif /* _MOVE_H */ |
249 | |