hpx/futures/future_fwd.hpp#
Defined in header hpx/futures/future_fwd.hpp.
See Public API for a list of names and headers that are part of the public HPX API.
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namespace hpx
Top level HPX namespace.
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template<typename R>
class future : public hpx::lcos::detail::future_base<future<R>, R> - #include <future_fwd.hpp>
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template<typename R>
class promise# - #include <promise.hpp>
The class template hpx::promise provides a facility to store a value or an exception that is later acquired asynchronously via a hpx::future object created by the hpx::promise object. Note that the hpx::promise object is meant to be used only once. Each promise is associated with a shared state, which contains some state information and a result which may be not yet evaluated, evaluated to a value (possibly void) or evaluated to an exception. A promise may do three things with the shared state:
make ready: the promise stores the result or the exception in the shared state. Marks the state ready and unblocks any thread waiting on a future associated with the shared state.
release: the promise gives up its reference to the shared state. If this was the last such reference, the shared state is destroyed. Unless this was a shared state created by hpx::async which is not yet ready, this operation does not block.
abandon: the promise stores the exception of type hpx::future_error with error code hpx::error::broken_promise, makes the shared state ready, and then releases it. The promise is the “push” end of the promise-future communication channel: the operation that stores a value in the shared state synchronizes-with (as defined in hpx::memory_order) the successful return from any function that is waiting on the shared state (such as hpx::future::get). Concurrent access to the same shared state may conflict otherwise: for example multiple callers of hpx::shared_future::get must either all be read-only or provide external synchronization.
- #include <future_fwd.hpp>
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namespace lcos
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template<typename R>
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namespace lcos#