namespace std {
template <class Mutex>
class shared_lock {
public:
using mutex_type = Mutex;
// [thread.lock.shared.cons], construct/copy/destroy
shared_lock() noexcept;
explicit shared_lock(mutex_type& m); // blocking
shared_lock(mutex_type& m, defer_lock_t) noexcept;
shared_lock(mutex_type& m, try_to_lock_t);
shared_lock(mutex_type& m, adopt_lock_t);
template <class Clock, class Duration>
shared_lock(mutex_type& m,
const chrono::time_point<Clock, Duration>& abs_time);
template <class Rep, class Period>
shared_lock(mutex_type& m,
const chrono::duration<Rep, Period>& rel_time);
~shared_lock();
shared_lock(const shared_lock&) = delete;
shared_lock& operator=(const shared_lock&) = delete;
shared_lock(shared_lock&& u) noexcept;
shared_lock& operator=(shared_lock&& u) noexcept;
// [thread.lock.shared.locking], locking
void lock(); // blocking
bool try_lock();
template <class Rep, class Period>
bool try_lock_for(const chrono::duration<Rep, Period>& rel_time);
template <class Clock, class Duration>
bool try_lock_until(const chrono::time_point<Clock, Duration>& abs_time);
void unlock();
// [thread.lock.shared.mod], modifiers
void swap(shared_lock& u) noexcept;
mutex_type* release() noexcept;
// [thread.lock.shared.obs], observers
bool owns_lock() const noexcept;
explicit operator bool () const noexcept;
mutex_type* mutex() const noexcept;
private:
mutex_type* pm; // exposition only
bool owns; // exposition only
};
template<class Mutex> shared_lock(shared_lock<Mutex>) -> shared_lock<Mutex>;
template <class Mutex>
void swap(shared_lock<Mutex>& x, shared_lock<Mutex>& y) noexcept;
}An object of type shared_lock controls the shared ownership of a lockable object within a scope. Shared ownership of the lockable object may be acquired at construction or after construction, and may be transferred, after acquisition, to another shared_lock object. Objects of type shared_lock are not copyable but are movable. The behavior of a program is undefined if the contained pointer pm is not null and the lockable object pointed to by pm does not exist for the entire remaining lifetime of the shared_lock object. The supplied Mutex type shall meet the shared mutex requirements.
[ Note: shared_lock<Mutex> meets the TimedLockable requirements ([thread.req.lockable.timed]). — end note ]
shared_lock() noexcept;
explicit shared_lock(mutex_type& m);
shared_lock(mutex_type& m, defer_lock_t) noexcept;
shared_lock(mutex_type& m, try_to_lock_t);
Postconditions: pm == addressof(m) and owns == res where res is the value returned by the call to m.try_lock_shared().
shared_lock(mutex_type& m, adopt_lock_t);
template <class Clock, class Duration>
shared_lock(mutex_type& m,
const chrono::time_point<Clock, Duration>& abs_time);
Effects: Constructs an object of type shared_lock and calls m.try_lock_shared_until(abs_time).
Postconditions: pm == addressof(m) and owns == res where res is the value returned by the call to m.try_lock_shared_until(abs_time).
template <class Rep, class Period>
shared_lock(mutex_type& m,
const chrono::duration<Rep, Period>& rel_time);
Effects: Constructs an object of type shared_lock and calls m.try_lock_shared_for(rel_time).
Postconditions: pm == addressof(m) and owns == res where res is the value returned by the call to m.try_lock_shared_for(rel_time).
~shared_lock();
shared_lock(shared_lock&& sl) noexcept;
Postconditions: pm == sl_p.pm and owns == sl_p.owns (where sl_p is the state of sl just prior to this construction), sl.pm == nullptr and sl.owns == false.
shared_lock& operator=(shared_lock&& sl) noexcept;
void lock();
Throws: Any exception thrown by pm->lock_shared(). system_error when an exception is required ([thread.req.exception]).
bool try_lock();
Postconditions: owns == res, where res is the value returned by the call to pm->try_lock_shared().
Throws: Any exception thrown by pm->try_lock_shared(). system_error when an exception is required ([thread.req.exception]).
template <class Clock, class Duration>
bool
try_lock_until(const chrono::time_point<Clock, Duration>& abs_time);
Postconditions: owns == res, where res is the value returned by the call to pm->try_lock_shared_until(abs_time).
Throws: Any exception thrown by pm->try_lock_shared_until(abs_time). system_error when an exception is required ([thread.req.exception]).
template <class Rep, class Period>
bool try_lock_for(const chrono::duration<Rep, Period>& rel_time);
Postconditions: owns == res, where res is the value returned by the call to pm->try_lock_shared_for(rel_time).
Throws: Any exception thrown by pm->try_lock_shared_for(rel_time). system_error when an exception is required ([thread.req.exception]).
void unlock();
Throws: system_error when an exception is required ([thread.req.exception]).
void swap(shared_lock& sl) noexcept;
mutex_type* release() noexcept;
template <class Mutex>
void swap(shared_lock<Mutex>& x, shared_lock<Mutex>& y) noexcept;
bool owns_lock() const noexcept;
explicit operator bool() const noexcept;
mutex_type* mutex() const noexcept;