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1 | ////////////////////////////////////////////////////////////////////////////// |
2 | // | |
3 | // (C) Copyright Ion Gaztanaga 2005-2012. Distributed under the Boost | |
4 | // Software License, Version 1.0. (See accompanying file | |
5 | // LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) | |
6 | // | |
7 | // See http://www.boost.org/libs/interprocess for documentation. | |
8 | // | |
9 | ////////////////////////////////////////////////////////////////////////////// | |
10 | // | |
11 | // This interface is inspired by Howard Hinnant's lock proposal. | |
12 | // http://home.twcny.rr.com/hinnant/cpp_extensions/threads_move.html | |
13 | // | |
14 | ////////////////////////////////////////////////////////////////////////////// | |
15 | ||
16 | #ifndef BOOST_INTERPROCESS_SHARABLE_LOCK_HPP | |
17 | #define BOOST_INTERPROCESS_SHARABLE_LOCK_HPP | |
18 | ||
19 | #ifndef BOOST_CONFIG_HPP | |
20 | # include <boost/config.hpp> | |
21 | #endif | |
22 | # | |
23 | #if defined(BOOST_HAS_PRAGMA_ONCE) | |
24 | # pragma once | |
25 | #endif | |
26 | ||
27 | #include <boost/interprocess/detail/config_begin.hpp> | |
28 | #include <boost/interprocess/detail/workaround.hpp> | |
29 | #include <boost/interprocess/interprocess_fwd.hpp> | |
30 | #include <boost/interprocess/sync/lock_options.hpp> | |
31 | #include <boost/interprocess/exceptions.hpp> | |
32 | #include <boost/interprocess/detail/mpl.hpp> | |
33 | #include <boost/interprocess/detail/type_traits.hpp> | |
34 | #include <boost/interprocess/detail/simple_swap.hpp> | |
35 | #include <boost/move/utility_core.hpp> | |
36 | #include <boost/interprocess/detail/posix_time_types_wrk.hpp> | |
37 | ||
38 | //!\file | |
39 | //!Describes the upgradable_lock class that serves to acquire the upgradable | |
40 | //!lock of a mutex. | |
41 | ||
42 | namespace boost { | |
43 | namespace interprocess { | |
44 | ||
45 | ||
46 | //!sharable_lock is meant to carry out the tasks for sharable-locking | |
47 | //!(such as read-locking), unlocking, try-sharable-locking and timed-sharable-locking | |
48 | //!(recursive or not) for the Mutex. The Mutex need not supply all of this | |
49 | //!functionality. If the client of sharable_lock<Mutex> does not use functionality which | |
50 | //!the Mutex does not supply, no harm is done. Mutex ownership can be shared among | |
51 | //!sharable_locks, and a single upgradable_lock. sharable_lock does not support | |
52 | //!copy semantics. But sharable_lock supports ownership transfer from an sharable_lock, | |
53 | //!upgradable_lock and scoped_lock via transfer_lock syntax.*/ | |
54 | template <class SharableMutex> | |
55 | class sharable_lock | |
56 | { | |
57 | public: | |
58 | typedef SharableMutex mutex_type; | |
59 | #if !defined(BOOST_INTERPROCESS_DOXYGEN_INVOKED) | |
60 | private: | |
61 | typedef sharable_lock<SharableMutex> this_type; | |
62 | explicit sharable_lock(scoped_lock<mutex_type>&); | |
63 | typedef bool this_type::*unspecified_bool_type; | |
64 | BOOST_MOVABLE_BUT_NOT_COPYABLE(sharable_lock) | |
65 | #endif //#ifndef BOOST_INTERPROCESS_DOXYGEN_INVOKED | |
66 | public: | |
67 | ||
68 | //!Effects: Default constructs a sharable_lock. | |
69 | //!Postconditions: owns() == false and mutex() == 0. | |
70 | sharable_lock() | |
71 | : mp_mutex(0), m_locked(false) | |
72 | {} | |
73 | ||
74 | //!Effects: m.lock_sharable(). | |
75 | //!Postconditions: owns() == true and mutex() == &m. | |
76 | //!Notes: The constructor will take sharable-ownership of the mutex. If | |
77 | //! another thread already owns the mutex with exclusive ownership | |
78 | //! (scoped_lock), this thread will block until the mutex is released. | |
79 | //! If another thread owns the mutex with sharable or upgradable ownership, | |
80 | //! then no blocking will occur. Whether or not this constructor handles | |
81 | //! recursive locking depends upon the mutex. | |
82 | explicit sharable_lock(mutex_type& m) | |
83 | : mp_mutex(&m), m_locked(false) | |
84 | { mp_mutex->lock_sharable(); m_locked = true; } | |
85 | ||
86 | //!Postconditions: owns() == false, and mutex() == &m. | |
87 | //!Notes: The constructor will not take ownership of the mutex. There is no effect | |
88 | //! required on the referenced mutex. | |
89 | sharable_lock(mutex_type& m, defer_lock_type) | |
90 | : mp_mutex(&m), m_locked(false) | |
91 | {} | |
92 | ||
93 | //!Postconditions: owns() == true, and mutex() == &m. | |
94 | //!Notes: The constructor will suppose that the mutex is already sharable | |
95 | //! locked. There is no effect required on the referenced mutex. | |
96 | sharable_lock(mutex_type& m, accept_ownership_type) | |
97 | : mp_mutex(&m), m_locked(true) | |
98 | {} | |
99 | ||
100 | //!Effects: m.try_lock_sharable() | |
101 | //!Postconditions: mutex() == &m. owns() == the return value of the | |
102 | //! m.try_lock_sharable() executed within the constructor. | |
103 | //!Notes: The constructor will take sharable-ownership of the mutex if it | |
104 | //! can do so without waiting. Whether or not this constructor handles | |
105 | //! recursive locking depends upon the mutex. If the mutex_type does not | |
106 | //! support try_lock_sharable, this constructor will fail at compile | |
107 | //! time if instantiated, but otherwise have no effect. | |
108 | sharable_lock(mutex_type& m, try_to_lock_type) | |
109 | : mp_mutex(&m), m_locked(false) | |
110 | { m_locked = mp_mutex->try_lock_sharable(); } | |
111 | ||
112 | //!Effects: m.timed_lock_sharable(abs_time) | |
113 | //!Postconditions: mutex() == &m. owns() == the return value of the | |
114 | //! m.timed_lock_sharable() executed within the constructor. | |
115 | //!Notes: The constructor will take sharable-ownership of the mutex if it | |
116 | //! can do so within the time specified. Whether or not this constructor | |
117 | //! handles recursive locking depends upon the mutex. If the mutex_type | |
118 | //! does not support timed_lock_sharable, this constructor will fail at | |
119 | //! compile time if instantiated, but otherwise have no effect. | |
120 | sharable_lock(mutex_type& m, const boost::posix_time::ptime& abs_time) | |
121 | : mp_mutex(&m), m_locked(false) | |
122 | { m_locked = mp_mutex->timed_lock_sharable(abs_time); } | |
123 | ||
124 | //!Postconditions: mutex() == upgr.mutex(). owns() == the value of upgr.owns() | |
125 | //! before the construction. upgr.owns() == false after the construction. | |
126 | //!Notes: If the upgr sharable_lock owns the mutex, ownership is moved to this | |
127 | //! sharable_lock with no blocking. If the upgr sharable_lock does not own the mutex, then | |
128 | //! neither will this sharable_lock. Only a moved sharable_lock's will match this | |
129 | //! signature. An non-moved sharable_lock can be moved with the expression: | |
130 | //! "boost::move(lock);". This constructor does not alter the state of the mutex, | |
131 | //! only potentially who owns it. | |
132 | sharable_lock(BOOST_RV_REF(sharable_lock<mutex_type>) upgr) | |
133 | : mp_mutex(0), m_locked(upgr.owns()) | |
134 | { mp_mutex = upgr.release(); } | |
135 | ||
136 | //!Effects: If upgr.owns() then calls unlock_upgradable_and_lock_sharable() on the | |
137 | //! referenced mutex. | |
138 | //!Postconditions: mutex() == the value upgr.mutex() had before the construction. | |
139 | //! upgr.mutex() == 0 owns() == the value of upgr.owns() before construction. | |
140 | //! upgr.owns() == false after the construction. | |
141 | //!Notes: If upgr is locked, this constructor will lock this sharable_lock while | |
142 | //! unlocking upgr. Only a moved sharable_lock's will match this | |
143 | //! signature. An non-moved upgradable_lock can be moved with the expression: | |
144 | //! "boost::move(lock);".*/ | |
145 | template<class T> | |
146 | sharable_lock(BOOST_RV_REF(upgradable_lock<T>) upgr | |
147 | , typename ipcdetail::enable_if< ipcdetail::is_same<T, SharableMutex> >::type * = 0) | |
148 | : mp_mutex(0), m_locked(false) | |
149 | { | |
150 | upgradable_lock<mutex_type> &u_lock = upgr; | |
151 | if(u_lock.owns()){ | |
152 | u_lock.mutex()->unlock_upgradable_and_lock_sharable(); | |
153 | m_locked = true; | |
154 | } | |
155 | mp_mutex = u_lock.release(); | |
156 | } | |
157 | ||
158 | //!Effects: If scop.owns() then calls unlock_and_lock_sharable() on the | |
159 | //! referenced mutex. | |
160 | //!Postconditions: mutex() == the value scop.mutex() had before the construction. | |
161 | //! scop.mutex() == 0 owns() == scop.owns() before the constructor. After the | |
162 | //! construction, scop.owns() == false. | |
163 | //!Notes: If scop is locked, this constructor will transfer the exclusive ownership | |
164 | //! to a sharable-ownership of this sharable_lock. | |
165 | //! Only a moved scoped_lock's will match this | |
166 | //! signature. An non-moved scoped_lock can be moved with the expression: | |
167 | //! "boost::move(lock);". | |
168 | template<class T> | |
169 | sharable_lock(BOOST_RV_REF(scoped_lock<T>) scop | |
170 | , typename ipcdetail::enable_if< ipcdetail::is_same<T, SharableMutex> >::type * = 0) | |
171 | : mp_mutex(0), m_locked(false) | |
172 | { | |
173 | scoped_lock<mutex_type> &e_lock = scop; | |
174 | if(e_lock.owns()){ | |
175 | e_lock.mutex()->unlock_and_lock_sharable(); | |
176 | m_locked = true; | |
177 | } | |
178 | mp_mutex = e_lock.release(); | |
179 | } | |
180 | ||
181 | //!Effects: if (owns()) mp_mutex->unlock_sharable(). | |
182 | //!Notes: The destructor behavior ensures that the mutex lock is not leaked. | |
183 | ~sharable_lock() | |
184 | { | |
185 | try{ | |
186 | if(m_locked && mp_mutex) mp_mutex->unlock_sharable(); | |
187 | } | |
188 | catch(...){} | |
189 | } | |
190 | ||
191 | //!Effects: If owns() before the call, then unlock_sharable() is called on mutex(). | |
192 | //! *this gets the state of upgr and upgr gets set to a default constructed state. | |
193 | //!Notes: With a recursive mutex it is possible that both this and upgr own the mutex | |
194 | //! before the assignment. In this case, this will own the mutex after the assignment | |
195 | //! (and upgr will not), but the mutex's lock count will be decremented by one. | |
196 | sharable_lock &operator=(BOOST_RV_REF(sharable_lock<mutex_type>) upgr) | |
197 | { | |
198 | if(this->owns()) | |
199 | this->unlock(); | |
200 | m_locked = upgr.owns(); | |
201 | mp_mutex = upgr.release(); | |
202 | return *this; | |
203 | } | |
204 | ||
205 | //!Effects: If mutex() == 0 or already locked, throws a lock_exception() | |
206 | //! exception. Calls lock_sharable() on the referenced mutex. | |
207 | //!Postconditions: owns() == true. | |
208 | //!Notes: The sharable_lock changes from a state of not owning the | |
209 | //! mutex, to owning the mutex, blocking if necessary. | |
210 | void lock() | |
211 | { | |
212 | if(!mp_mutex || m_locked) | |
213 | throw lock_exception(); | |
214 | mp_mutex->lock_sharable(); | |
215 | m_locked = true; | |
216 | } | |
217 | ||
218 | //!Effects: If mutex() == 0 or already locked, throws a lock_exception() | |
219 | //! exception. Calls try_lock_sharable() on the referenced mutex. | |
220 | //!Postconditions: owns() == the value returned from | |
221 | //! mutex()->try_lock_sharable(). | |
222 | //!Notes: The sharable_lock changes from a state of not owning the mutex, | |
223 | //! to owning the mutex, but only if blocking was not required. If the | |
224 | //! mutex_type does not support try_lock_sharable(), this function will | |
225 | //! fail at compile time if instantiated, but otherwise have no effect. | |
226 | bool try_lock() | |
227 | { | |
228 | if(!mp_mutex || m_locked) | |
229 | throw lock_exception(); | |
230 | m_locked = mp_mutex->try_lock_sharable(); | |
231 | return m_locked; | |
232 | } | |
233 | ||
234 | //!Effects: If mutex() == 0 or already locked, throws a lock_exception() | |
235 | //! exception. Calls timed_lock_sharable(abs_time) on the referenced mutex. | |
236 | //!Postconditions: owns() == the value returned from | |
237 | //! mutex()->timed_lock_sharable(elps_time). | |
238 | //!Notes: The sharable_lock changes from a state of not owning the mutex, | |
239 | //! to owning the mutex, but only if it can obtain ownership within the | |
240 | //! specified time interval. If the mutex_type does not support | |
241 | //! timed_lock_sharable(), this function will fail at compile time if | |
242 | //! instantiated, but otherwise have no effect. | |
243 | bool timed_lock(const boost::posix_time::ptime& abs_time) | |
244 | { | |
245 | if(!mp_mutex || m_locked) | |
246 | throw lock_exception(); | |
247 | m_locked = mp_mutex->timed_lock_sharable(abs_time); | |
248 | return m_locked; | |
249 | } | |
250 | ||
251 | //!Effects: If mutex() == 0 or not locked, throws a lock_exception() exception. | |
252 | //! Calls unlock_sharable() on the referenced mutex. | |
253 | //!Postconditions: owns() == false. | |
254 | //!Notes: The sharable_lock changes from a state of owning the mutex, to | |
255 | //! not owning the mutex. | |
256 | void unlock() | |
257 | { | |
258 | if(!mp_mutex || !m_locked) | |
259 | throw lock_exception(); | |
260 | mp_mutex->unlock_sharable(); | |
261 | m_locked = false; | |
262 | } | |
263 | ||
264 | //!Effects: Returns true if this scoped_lock has | |
265 | //!acquired the referenced mutex. | |
266 | bool owns() const | |
267 | { return m_locked && mp_mutex; } | |
268 | ||
269 | //!Conversion to bool. | |
270 | //!Returns owns(). | |
271 | operator unspecified_bool_type() const | |
272 | { return m_locked? &this_type::m_locked : 0; } | |
273 | ||
274 | //!Effects: Returns a pointer to the referenced mutex, or 0 if | |
275 | //!there is no mutex to reference. | |
276 | mutex_type* mutex() const | |
277 | { return mp_mutex; } | |
278 | ||
279 | //!Effects: Returns a pointer to the referenced mutex, or 0 if there is no | |
280 | //! mutex to reference. | |
281 | //!Postconditions: mutex() == 0 and owns() == false. | |
282 | mutex_type* release() | |
283 | { | |
284 | mutex_type *mut = mp_mutex; | |
285 | mp_mutex = 0; | |
286 | m_locked = false; | |
287 | return mut; | |
288 | } | |
289 | ||
290 | //!Effects: Swaps state with moved lock. | |
291 | //!Throws: Nothing. | |
292 | void swap(sharable_lock<mutex_type> &other) | |
293 | { | |
294 | (simple_swap)(mp_mutex, other.mp_mutex); | |
295 | (simple_swap)(m_locked, other.m_locked); | |
296 | } | |
297 | ||
298 | #if !defined(BOOST_INTERPROCESS_DOXYGEN_INVOKED) | |
299 | private: | |
300 | mutex_type *mp_mutex; | |
301 | bool m_locked; | |
302 | #endif //#ifndef BOOST_INTERPROCESS_DOXYGEN_INVOKED | |
303 | }; | |
304 | ||
305 | } // namespace interprocess | |
306 | } // namespace boost | |
307 | ||
308 | #include <boost/interprocess/detail/config_end.hpp> | |
309 | ||
310 | #endif // BOOST_INTERPROCESS_SHARABLE_LOCK_HPP |