33 Concurrency support library [thread]

33.2 Requirements [thread.req]

33.2.5 Requirements for Cpp17Lockable types [thread.req.lockable]

33.2.5.6 Cpp17SharedTimedLockable requirements [thread.req.lockable.shared.timed]

A type L meets the Cpp17SharedTimedLockable requirements if it meets the Cpp17SharedLockable requirements, and the following expressions are well-formed, have type bool, and have the specified semantics (m denotes a value of type L, rel_time denotes a value of a specialization of chrono​::​duration, and abs_time denotes a value of a specialization of chrono​::​time_point).
m.try_lock_shared_for(rel_time)
Effects: Attempts to acquire a lock for the current execution agent within the relative timeout ([thread.req.timing]) specified by rel_time.
The function will not return within the timeout specified by rel_time unless it has obtained a lock on m for the current execution agent.
If an exception is thrown then a lock has not been acquired for the current execution agent.
Returns: true if the lock was acquired, false otherwise.
m.try_lock_shared_until(abs_time)
Effects: Attempts to acquire a lock for the current execution agent before the absolute timeout ([thread.req.timing]) specified by abs_time.
The function will not return before the timeout specified by abs_time unless it has obtained a lock on m for the current execution agent.
If an exception is thrown then a lock has not been acquired for the current execution agent.
Returns: true if the lock was acquired, false otherwise.