std::shared_future<T>::wait_until
template< class Clock, class Duration > std::future_status wait_until( const std::chrono::time_point<Clock,Duration>& timeout_time ) const; | (since C++11) |
wait_until
waits for a result to become available. It blocks until specified timeout_time
has been reached or the result becomes available, whichever comes first. The return value indicates why wait_until
returned.
The behavior is undefined if valid()
== false
before the call to this function.
Parameters
timeout_time | - | maximum time point to block until |
Return value
Constant | Explanation |
---|---|
future_status::deferred | The function to calculate the result has not been started yet |
future_status::ready | The result is ready |
future_status::timeout | The timeout has expired |
Exceptions
Any exception thrown by clock, time_point, or duration during the execution (clocks, time points, and durations provided by the standard library never throw).
Notes
The implementations are encouraged to detect the case when valid == false
before the call and throw a future_error
with an error condition of future_errc::no_state
.
The clock tied to timeout_time
is used, which is not required to be a monotonic clock.There are no guarantees regarding the behavior of this function if the clock is adjusted discontinuously, but the existing implementations convert timeout_time
from Clock
to std::chrono::system_clock
and delegate to POSIX pthread_cond_timedwait so that the wait honors ajustments to the system clock, but not to the the user-provided Clock
. In any case, the function also may wait for longer than until after timeout_time
has been reached due to scheduling or resource contention delays.
Example
See also
waits for the result to become available (public member function) |
|
waits for the result, returns if it is not available for the specified timeout duration (public member function) |
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