C++ named requirements:SharedLockable(since C++14)

 

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C++ named requirements

Basic DefaultConstructible MoveConstructible (C++11) CopyConstructible CopyAssignable MoveAssignable (C++11) Destructible Type properties ScalarType PODType TriviallyCopyable (C++11) TrivialType (C++11) StandardLayoutType (C++11)   ImplicitLifetimeType Library-wide BooleanTestable EqualityComparable LessThanComparable Swappable ValueSwappable (C++11) NullablePointer (C++11) Hash (C++11) Allocator FunctionObject Callable Predicate BinaryPredicate Compare

Container Container ReversibleContainer AllocatorAwareContainer SequenceContainer ContiguousContainer (C++17) AssociativeContainer UnorderedAssociativeContainer (C++11)   Container element DefaultInsertable (C++11) CopyInsertable (C++11) MoveInsertable (C++11) EmplaceConstructible (C++11) Erasable (C++11) Iterator LegacyIterator LegacyInputIterator LegacyOutputIterator LegacyForwardIterator LegacyBidirectionalIterator LegacyRandomAccessIterator LegacyContiguousIterator (C++17) ConstexprIterator (C++20) Stream I/O FormattedInputFunction UnformattedInputFunction FormattedOutputFunction UnformattedOutputFunction Formatters BasicFormatter (C++20) Formatter (C++20)

Random Numbers SeedSequence (C++11) RandomNumberEngine (C++11) RandomNumberDistribution (C++11) UniformRandomBitGenerator (C++11) RandomNumberEngineAdaptor (C++11) Concurrency BasicLockable (C++11) Lockable (C++11) TimedLockable (C++11) SharedLockable (C++14) SharedTimedLockable (C++14) Mutex (C++11) TimedMutex (C++11) SharedMutex (C++17) SharedTimedMutex (C++14) Ranges RangeAdaptorObject (C++20) RangeAdaptorClosureObject (C++20) Multidimensional View LayoutMapping (C++23) LayoutMappingPolicy (C++23) AccessorPolicy (C++23) Other CharTraits RegexTraits (C++11)   BitmaskType LiteralType (C++11) NumericType UnaryTypeTrait (C++11) BinaryTypeTrait (C++11) TransformationTrait (C++11) Clock (C++11) TrivialClock (C++11)

 

The SharedLockable requirements describe the minimal characteristics of types that provide shared blocking semantics for execution agents (i.e. threads).

Requirements

For type L to be SharedLockable, the following conditions have to be satisfied for an object m of type L:

Expression	Preconditions	Effects	Return value
m.lock_shared()		Blocks until a lock can be obtained for the current execution agent (thread, process, task). If an exception is thrown, no lock is obtained.
m.try_lock_shared()		Attempts to obtain a lock for the current execution agent (thread, process, task) without blocking. If an exception is thrown, no lock is obtained.	true if the lock was obtained, false otherwise
m.unlock_shared()	The current execution agent holds a shared lock on m.	Releases the shared lock held by the execution agent. Throws no exceptions.

Shared locks

A lock on an object is said to be shared lock if it is acquired by a call to lock_shared, try_lock_shared, try_lock_shared_for, or try_lock_shared_until member function.

Standard library

The following standard library types satisfy SharedLockable requirements:

shared_mutex (C++17)	provides shared mutual exclusion facility (class)
shared_timed_mutex (C++14)	provides shared mutual exclusion facility and implements locking with a timeout (class)

See also

• Thread support library
• SharedTimedLockable
• SharedMutex