std::shared_lock
Defined in header <shared_mutex> | ||
|---|---|---|
template< class Mutex > class shared_lock; | (since C++14) |
The class shared_lock is a general-purpose shared mutex ownership wrapper allowing deferred locking, timed locking and transfer of lock ownership. Locking a shared_lock locks the associated shared mutex in shared mode (to lock it in exclusive mode, std::unique_lock can be used).
The shared_lock class is movable, but not copyable – it meets the requirements of MoveConstructible and MoveAssignable but not of CopyConstructible or CopyAssignable.
shared_lock meets the Lockable requirements. If Mutex meets the SharedTimedLockable requirements, shared_lock also meets TimedLockable requirements.
In order to wait in a shared mutex in shared ownership mode, std::condition_variable_any can be used (std::condition_variable requires std::unique_lock and so can only wait in unique ownership mode).
Template parameters
| Mutex | - | the type of the shared mutex to lock. The type must meet the SharedLockable requirements |
Member types
| Type | Definition |
|---|---|
mutex_type |
Mutex |
Member functions
constructs a shared_lock, optionally locking the supplied mutex (public member function) |
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| unlocks the associated mutex (public member function) |
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| unlocks the mutex, if owned, and acquires ownership of another (public member function) |
|
Shared locking |
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| locks the associated mutex (public member function) |
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| tries to lock the associated mutex (public member function) |
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| tries to lock the associated mutex, for the specified duration (public member function) |
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| tries to lock the associated mutex, until a specified time point (public member function) |
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| unlocks the associated mutex (public member function) |
|
Modifiers |
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swaps the data members with another shared_lock (public member function) |
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| disassociates the mutex without unlocking (public member function) |
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Observers |
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| returns a pointer to the associated mutex (public member function) |
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| tests whether the lock owns its associated mutex (public member function) |
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| tests whether the lock owns its associated mutex (public member function) |
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Non-member functions
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(C++14) | specializes the std::swap algorithm (function template) |
Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 2981 | C++17 | redundant deduction guide from shared_lock<Mutex> was provided | removed |
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