[thread.lock.unique] (original) (raw)

32 Concurrency support library [thread]

32.6 Mutual exclusion [thread.mutex]

32.6.5 Locks [thread.lock]

32.6.5.4 Class template unique_lock [thread.lock.unique]

32.6.5.4.1 General [thread.lock.unique.general]

namespace std { template<class Mutex> class unique_lock { public: using mutex_type = Mutex; unique_lock() noexcept;explicit unique_lock(mutex_type& m); unique_lock(mutex_type& m, defer_lock_t) noexcept; unique_lock(mutex_type& m, try_to_lock_t); unique_lock(mutex_type& m, adopt_lock_t);template<class Clock, class Duration> unique_lock(mutex_type& m, const chrono::time_point<Clock, Duration>& abs_time);template<class Rep, class Period> unique_lock(mutex_type& m, const chrono::duration<Rep, Period>& rel_time);~unique_lock(); unique_lock(const unique_lock&) = delete; unique_lock& operator=(const unique_lock&) = delete; unique_lock(unique_lock&& u) noexcept; unique_lock& operator=(unique_lock&& u) noexcept;void lock();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();void swap(unique_lock& u) noexcept; mutex_type* release() noexcept;bool owns_lock() const noexcept;explicit operator bool() const noexcept; mutex_type* mutex() const noexcept;private: mutex_type* pm; bool owns; };}

An object of type unique_lock controls the ownership of a lockable object within a scope.

Ownership of the lockable object may be acquired at construction or after construction, and may be transferred, after acquisition, to another unique_lock object.

Objects of type unique_lock are not copyable but are movable.

The behavior of a program is undefined if the contained pointerpm is not null and the lockable object pointed to by pm does not exist for the entire remaining lifetime ([basic.life]) of the unique_lock object.

32.6.5.4.2 Constructors, destructor, and assignment [thread.lock.unique.cons]

Postconditions: pm == nullptr and owns == false.

explicit unique_lock(mutex_type& m);

Postconditions: pm == addressof(m) and owns == true.

unique_lock(mutex_type& m, defer_lock_t) noexcept;

Postconditions: pm == addressof(m) and owns == false.

unique_lock(mutex_type& m, try_to_lock_t);

Effects: 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);

Preconditions: The calling thread holds a non-shared lock on m.

Postconditions: pm == addressof(m) and owns == true.

template<class Clock, class Duration> unique_lock(mutex_type& m, const chrono::time_point<Clock, Duration>& abs_time);

Effects: 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);

Effects: 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) noexcept;

Effects: Equivalent to: unique_lock(std​::​move(u)).swap(*this)

Effects: If owns calls pm->unlock().

32.6.5.4.3 Locking [thread.lock.unique.locking]

Effects: As if by pm->lock().

Postconditions: owns == true.

Throws: Any exception thrown by pm->lock().

Error conditions:

• operation_not_permitted — if pm is nullptr.
• resource_deadlock_would_occur — if on entry ownsis true.

Effects: As if by pm->try_lock().

Postconditions: owns == res, where res is the value returned bypm->try_lock().

Returns: The value returned by pm->try_lock().

Throws: Any exception thrown by pm->try_lock().

Error conditions:

• operation_not_permitted — if pm is nullptr.
• resource_deadlock_would_occur — if on entry ownsis true.

template<class Clock, class Duration> bool try_lock_until(const chrono::time_point<Clock, Duration>& abs_time);

Effects: As if by pm->try_lock_until(abs_time).

Postconditions: owns == res, where res is the value returned bypm->try_lock_until(abs_time).

Returns: The value returned by pm->try_lock_until(abs_time).

Throws: Any exception thrown by pm->try_lock_until(abstime).

Error conditions:

• operation_not_permitted — if pm is nullptr.
• resource_deadlock_would_occur — if on entry owns istrue.

template<class Rep, class Period> bool try_lock_for(const chrono::duration<Rep, Period>& rel_time);

Effects: As if by pm->try_lock_for(rel_time).

Postconditions: owns == res, where res is the value returned by pm->try_lock_for(rel_time).

Returns: The value returned by pm->try_lock_for(rel_time).

Throws: Any exception thrown by pm->try_lock_for(rel_time).

Error conditions:

• operation_not_permitted — if pm is nullptr.
• resource_deadlock_would_occur — if on entry owns istrue.

Effects: As if by pm->unlock().

Postconditions: owns == false.

Error conditions:

• operation_not_permitted — if on entry owns is false.

32.6.5.4.4 Modifiers [thread.lock.unique.mod]

void swap(unique_lock& u) noexcept;

Effects: Swaps the data members of *this and u.

mutex_type* release() noexcept;

Postconditions: pm == 0 and owns == false.

Returns: The previous value of pm.

template<class Mutex> void swap(unique_lock<Mutex>& x, unique_lock<Mutex>& y) noexcept;

Effects: As if by x.swap(y).

32.6.5.4.5 Observers [thread.lock.unique.obs]

bool owns_lock() const noexcept;

explicit operator bool() const noexcept;

mutex_type *mutex() const noexcept;