std::shared_future<T>::wait_until
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| Member functions | ||||
| Getting the result | ||||
| State | ||||
shared_future::wait_until |
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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
If the future is the result of a call to async
The behavior is undefined if valid() is false before the call to this function, or Clock does not meet the Clock requirements.
The programs is ill-formed if
std::chrono::is_clock_v
<Clock>
is false
(since C++20)
Parameters
| timeout_time | - | maximum time point to block until |
Return value
| Constant | Explanation |
| future_status::deferred | The shared state contains a deferred function using lazy evaluation, so the result will be computed only when explicitly requested |
| 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 std::future_error with an error condition of future_errc::no_state
The standard recommends that the clock tied to
timeout_time
be used to measure time; that clock 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 adjustments to the system clock, but not to the user-provided Clock. In any case, the function also may wait for longer than until after timeout_time
Example
| This section is incomplete Reason: no example |
See also
| waits for the result to become available (public member function) |
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| waits for the result, returns if it is not available for the specified timeout duration (public member function) |