1 // std::unique_lock implementation -*- C++ -*-
2
3 // Copyright (C) 2008-2023 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/unique_lock.h
26 * This is an internal header file, included by other library headers.
27 * Do not attempt to use it directly. @headername{mutex}
28 */
29
30 #ifndef _GLIBCXX_UNIQUE_LOCK_H
31 #define _GLIBCXX_UNIQUE_LOCK_H 1
32
33 #pragma GCC system_header
34
35 #if __cplusplus < 201103L
36 # include <bits/c++0x_warning.h>
37 #else
38
39 #include <bits/chrono.h>
40 #include <bits/move.h> // for std::swap
41 #include <bits/std_mutex.h> // for std::defer_lock_t
42
43 namespace std _GLIBCXX_VISIBILITY(default)
44 {
45 _GLIBCXX_BEGIN_NAMESPACE_VERSION
46
47 /** @brief A movable scoped lock type.
48 *
49 * A unique_lock controls mutex ownership within a scope. Ownership of the
50 * mutex can be delayed until after construction and can be transferred
51 * to another unique_lock by move construction or move assignment. If a
52 * mutex lock is owned when the destructor runs ownership will be released.
53 *
54 * @headerfile mutex
55 * @ingroup mutexes
56 * @since C++11
57 */
58 template<typename _Mutex>
59 class unique_lock
60 {
61 public:
62 typedef _Mutex mutex_type;
63
64 unique_lock() noexcept
65 : _M_device(0), _M_owns(false)
66 { }
67
68 explicit unique_lock(mutex_type& __m)
69 : _M_device(std::__addressof(__m)), _M_owns(false)
70 {
71 lock();
72 _M_owns = true;
73 }
74
75 unique_lock(mutex_type& __m, defer_lock_t) noexcept
76 : _M_device(std::__addressof(__m)), _M_owns(false)
77 { }
78
79 unique_lock(mutex_type& __m, try_to_lock_t)
80 : _M_device(std::__addressof(__m)), _M_owns(_M_device->try_lock())
81 { }
82
83 unique_lock(mutex_type& __m, adopt_lock_t) noexcept
84 : _M_device(std::__addressof(__m)), _M_owns(true)
85 {
86 // XXX calling thread owns mutex
87 }
88
89 template<typename _Clock, typename _Duration>
90 unique_lock(mutex_type& __m,
91 const chrono::time_point<_Clock, _Duration>& __atime)
92 : _M_device(std::__addressof(__m)),
93 _M_owns(_M_device->try_lock_until(__atime))
94 { }
95
96 template<typename _Rep, typename _Period>
97 unique_lock(mutex_type& __m,
98 const chrono::duration<_Rep, _Period>& __rtime)
99 : _M_device(std::__addressof(__m)),
100 _M_owns(_M_device->try_lock_for(__rtime))
101 { }
102
103 ~unique_lock()
104 {
105 if (_M_owns)
106 unlock();
107 }
108
109 unique_lock(const unique_lock&) = delete;
110 unique_lock& operator=(const unique_lock&) = delete;
111
112 unique_lock(unique_lock&& __u) noexcept
113 : _M_device(__u._M_device), _M_owns(__u._M_owns)
114 {
115 __u._M_device = 0;
116 __u._M_owns = false;
117 }
118
119 unique_lock& operator=(unique_lock&& __u) noexcept
120 {
121 if(_M_owns)
122 unlock();
123
124 unique_lock(std::move(__u)).swap(*this);
125
126 __u._M_device = 0;
127 __u._M_owns = false;
128
129 return *this;
130 }
131
132 void
133 lock()
134 {
135 if (!_M_device)
136 __throw_system_error(int(errc::operation_not_permitted));
137 else if (_M_owns)
138 __throw_system_error(int(errc::resource_deadlock_would_occur));
139 else
140 {
141 _M_device->lock();
142 _M_owns = true;
143 }
144 }
145
146 _GLIBCXX_NODISCARD
147 bool
148 try_lock()
149 {
150 if (!_M_device)
151 __throw_system_error(int(errc::operation_not_permitted));
152 else if (_M_owns)
153 __throw_system_error(int(errc::resource_deadlock_would_occur));
154 else
155 {
156 _M_owns = _M_device->try_lock();
157 return _M_owns;
158 }
159 }
160
161 template<typename _Clock, typename _Duration>
162 _GLIBCXX_NODISCARD
163 bool
164 try_lock_until(const chrono::time_point<_Clock, _Duration>& __atime)
165 {
166 if (!_M_device)
167 __throw_system_error(int(errc::operation_not_permitted));
168 else if (_M_owns)
169 __throw_system_error(int(errc::resource_deadlock_would_occur));
170 else
171 {
172 _M_owns = _M_device->try_lock_until(__atime);
173 return _M_owns;
174 }
175 }
176
177 template<typename _Rep, typename _Period>
178 _GLIBCXX_NODISCARD
179 bool
180 try_lock_for(const chrono::duration<_Rep, _Period>& __rtime)
181 {
182 if (!_M_device)
183 __throw_system_error(int(errc::operation_not_permitted));
184 else if (_M_owns)
185 __throw_system_error(int(errc::resource_deadlock_would_occur));
186 else
187 {
188 _M_owns = _M_device->try_lock_for(__rtime);
189 return _M_owns;
190 }
191 }
192
193 void
194 unlock()
195 {
196 if (!_M_owns)
197 __throw_system_error(int(errc::operation_not_permitted));
198 else if (_M_device)
199 {
200 _M_device->unlock();
201 _M_owns = false;
202 }
203 }
204
205 void
206 swap(unique_lock& __u) noexcept
207 {
208 std::swap(_M_device, __u._M_device);
209 std::swap(_M_owns, __u._M_owns);
210 }
211
212 mutex_type*
213 release() noexcept
214 {
215 mutex_type* __ret = _M_device;
216 _M_device = 0;
217 _M_owns = false;
218 return __ret;
219 }
220
221 _GLIBCXX_NODISCARD
222 bool
223 owns_lock() const noexcept
224 { return _M_owns; }
225
226 explicit operator bool() const noexcept
227 { return owns_lock(); }
228
229 _GLIBCXX_NODISCARD
230 mutex_type*
231 mutex() const noexcept
232 { return _M_device; }
233
234 private:
235 mutex_type* _M_device;
236 bool _M_owns;
237 };
238
239 /// Swap overload for unique_lock objects.
240 /// @relates unique_lock
241 template<typename _Mutex>
242 inline void
243 swap(unique_lock<_Mutex>& __x, unique_lock<_Mutex>& __y) noexcept
244 { __x.swap(__y); }
245
246 _GLIBCXX_END_NAMESPACE_VERSION
247 } // namespace
248
249 #endif // C++11
250 #endif // _GLIBCXX_UNIQUE_LOCK_H