33 Thread support library [thread]

33.4 Mutual exclusion [thread.mutex]

33.4.4 Locks [thread.lock]

33.4.4.3 Class template unique_­lock [thread.lock.unique]

33.4.4.3.1 unique_­lock constructors, destructor, and assignment [thread.lock.unique.cons]

unique_lock() noexcept;
Effects: Constructs an object of type unique_­lock.
Postconditions: pm == 0 and owns == false.
explicit unique_lock(mutex_type& m);
Requires: If mutex_­type is not a recursive mutex the calling thread does not own the mutex.
Effects: Constructs an object of type unique_­lock and calls m.lock().
Postconditions: pm == addressof(m) and owns == true.
unique_lock(mutex_type& m, defer_lock_t) noexcept;
Effects: Constructs an object of type unique_­lock.
Postconditions: pm == addressof(m) and owns == false.
unique_lock(mutex_type& m, try_to_lock_t);
Requires: The supplied Mutex type shall meet the Lockable requirements.
If mutex_­type is not a recursive mutex the calling thread does not own the mutex.
Effects: Constructs an object of type unique_­lock and calls m.try_­lock().
Postconditions: pm == addressof(m) and owns == res, where res is the value returned by the call to m.try_­lock().
unique_lock(mutex_type& m, adopt_lock_t);
Requires: The calling thread owns the mutex.
Effects: Constructs an object of type unique_­lock.
Postconditions: pm == addressof(m) and owns == true.
Throws: Nothing.
template <class Clock, class Duration> unique_lock(mutex_type& m, const chrono::time_point<Clock, Duration>& abs_time);
Requires: If mutex_­type is not a recursive mutex the calling thread does not own the mutex.
The supplied Mutex type shall meet the TimedLockable requirements.
Effects: Constructs an object of type unique_­lock and calls m.try_­lock_­until(abs_­time).
Postconditions: pm == addressof(m) and owns == res, where res is the value returned by the call to m.try_­lock_­until(abs_­time).
template <class Rep, class Period> unique_lock(mutex_type& m, const chrono::duration<Rep, Period>& rel_time);
Requires: If mutex_­type is not a recursive mutex the calling thread does not own the mutex.
The supplied Mutex type shall meet the TimedLockable requirements.
Effects: Constructs an object of type unique_­lock and calls m.try_­lock_­for(rel_­time).
Postconditions: pm == addressof(m) and owns == res, where res is the value returned by the call to m.try_­lock_­for(rel_­time).
unique_lock(unique_lock&& u) noexcept;
Postconditions: pm == u_­p.pm and owns == u_­p.owns (where u_­p is the state of u just prior to this construction), u.pm == 0 and u.owns == false.
unique_lock& operator=(unique_lock&& u);
Effects: If owns calls pm->unlock().
Postconditions: pm == u_­p.pm and owns == u_­p.owns (where u_­p is the state of u just prior to this construction), u.pm == 0 and u.owns == false.
[Note
:
With a recursive mutex it is possible for both *this and u to own the same mutex before the assignment.
In this case, *this will own the mutex after the assignment and u will not.
end note
]
Throws: Nothing.
~unique_lock();
Effects: If owns calls pm->unlock().