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# std::shared_lock

From cppreference.com
< cpp‎ | thread

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`.

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)

### [edit] Template parameters

Mutex | - | the type of the shared mutex to lock. The type must meet the `SharedMutex` requirements

### [edit] Member types

Type | Definition
`mutex_type` | Mutex

### [edit] Member functions

(constructor) | constructs a `shared_lock`, optionally locking the supplied mutex (public member function) [edit]
(destructor) | unlocks the associated mutex (public member function) [edit]
operator= | unlocks the mutex, if owned, and acquires ownership of another (public member function) [edit]
##### Shared locking
lock | locks the associated mutex (public member function) [edit]
try_lock | tries to lock the associated mutex (public member function) [edit]
try_lock_for | tries to lock the associated mutex, for the specified duration (public member function) [edit]
try_lock_until | tries to lock the associated mutex, until a specified time point (public member function) [edit]
unlock | unlocks the associated mutex (public member function) [edit]
##### Modifiers
swap | swaps the data members with another shared_lock (public member function) [edit]
release | disassociates the mutex without unlocking (public member function) [edit]
##### Observers
mutex | returns a pointer to the associated mutex (public member function) [edit]
owns_lock | tests whether the lock owns its associated mutex (public member function) [edit]
operator bool | tests whether the lock owns its associated mutex (public member function) [edit]

### [edit] Non-member functions

std::swap(std::shared_lock) | specialization of std::swap for `shared_lock` (function template) [edit]

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