cppdraft_translate/cppdraft/thread/lock/unique.md

[thread.lock.unique]

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 {templateclass unique_lock {public:using mutex_type = Mutex; // [thread.lock.unique.cons], construct/copy/destroy 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; // [thread.lock.unique.locking], lockingvoid 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(); // [thread.lock.unique.mod], modifiersvoid swap(unique_lock& u) noexcept; mutex_type* release() noexcept; // [thread.lock.unique.obs], observersbool owns_lock() const noexcept; explicit operator bool() const noexcept; mutex_type* mutex() const noexcept; private: mutex_type* pm; // exposition onlybool owns; // exposition only};}

1

#

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.

The suppliedMutex type shall meet the Cpp17BasicLockable requirements ([thread.req.lockable.basic]).

2

#

[Note 1:

unique_lock meets the Cpp17BasicLockable requirements.

If Mutex meets the Cpp17Lockable requirements ([thread.req.lockable.req]),unique_lock also meets the Cpp17Lockable requirements; if Mutex meets the Cpp17TimedLockable requirements ([thread.req.lockable.timed]),unique_lock also meets the Cpp17TimedLockable requirements.

— end note]

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

🔗

unique_lock() noexcept;

1

#

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

🔗

explicit unique_lock(mutex_type& m);

2

#

Effects: Calls m.lock().

3

#

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

🔗

unique_lock(mutex_type& m, defer_lock_t) noexcept;

4

#

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

🔗

unique_lock(mutex_type& m, try_to_lock_t);

5

#

Preconditions: The supplied Mutex type meets the Cpp17Lockable requirements ([thread.req.lockable.req]).

6

#

Effects: Calls m.try_lock().

7

#

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);

8

#

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

9

#

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

10

#

Throws: Nothing.

🔗

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

11

#

Preconditions: The supplied Mutex type meets theCpp17TimedLockable requirements ([thread.req.lockable.timed]).

12

#

Effects: Calls m.try_lock_until(abs_time).

13

#

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);

14

#

Preconditions: The supplied Mutex type meets the Cpp17TimedLockable requirements ([thread.req.lockable.timed]).

15

#

Effects: Calls m.try_lock_for(rel_time).

16

#

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;

17

#

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;

18

#

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

19

#

Returns: *this.

🔗

~unique_lock();

20

#

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

32.6.5.4.3 Locking [thread.lock.unique.locking]

🔗

void lock();

1

#

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

2

#

Postconditions: owns == true.

3

#

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

system_error when an exception is required ([thread.req.exception]).

4

#

Error conditions:

• (4.1)

  operation_not_permitted — if pm is nullptr.

• (4.2)

  resource_deadlock_would_occur — if on entry owns is true.

🔗

bool try_lock();

5

#

Preconditions: The supplied Mutex meets the Cpp17Lockable requirements ([thread.req.lockable.req]).

6

#

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

7

#

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

8

#

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

9

#

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

system_error when an exception is required ([thread.req.exception]).

10

#

Error conditions:

• (10.1)

  operation_not_permitted — if pm is nullptr.

• (10.2)

  resource_deadlock_would_occur — if on entry owns is true.

🔗

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

11

#

Preconditions: The supplied Mutex type meets the Cpp17TimedLockable requirements ([thread.req.lockable.timed]).

12

#

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

13

#

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

14

#

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

15

#

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

system_error when an exception is required ([thread.req.exception]).

16

#

Error conditions:

• (16.1)

  operation_not_permitted — if pm is nullptr.

• (16.2)

  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);

17

#

Preconditions: The supplied Mutex type meets the Cpp17TimedLockable requirements ([thread.req.lockable.timed]).

18

#

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

19

#

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

20

#

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

21

#

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

system_error when an exception is required ([thread.req.exception]).

22

#

Error conditions:

• (22.1)

  operation_not_permitted — if pm is nullptr.

• (22.2)

  resource_deadlock_would_occur — if on entry owns istrue.

🔗

void unlock();

23

#

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

24

#

Postconditions: owns == false.

25

#

Throws: system_error when an exception is required ([thread.req.exception]).

26

#

Error conditions:

• (26.1)

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;

1

#

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

🔗

mutex_type* release() noexcept;

2

#

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

3

#

Returns: The previous value of pm.

🔗

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

4

#

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

32.6.5.4.5 Observers [thread.lock.unique.obs]

🔗

bool owns_lock() const noexcept;

1

#

Returns: owns.

🔗

explicit operator bool() const noexcept;

2

#

Returns: owns.

🔗

mutex_type *mutex() const noexcept;

3

#

Returns: pm.