typename boost::enable_if<
traits::is_future<typename util::result_of<Func(Future)>::type>
>::type invoke_continuation(Func& func, Future& future, Continuation& cont)
{
try {
typedef
typename util::result_of<Func(Future)>::type
inner_future;
typedef
typename shared_state_ptr_for<inner_future>::type
inner_shared_state_ptr;
// take by value, as the future may go away immediately
inner_shared_state_ptr inner_state =
future_access::get_shared_state(func(std::move(future)));
if (inner_state.get() == 0)
{
HPX_THROW_EXCEPTION(no_state,
"invoke_continuation",
"the inner future has no valid shared state");
}
// Bind an on_completed handler to this future which will transfer
// its result to the new future.
boost::intrusive_ptr<Continuation> cont_(&cont);
inner_state->set_on_completed(util::bind(
transfer_result<inner_future>(),
inner_state, cont_));
}
catch (...) {
cont.set_exception(boost::current_exception());
}
}
typename std::enable_if<
traits::detail::is_unique_future<
typename util::invoke_result<Func, Future>::type
>::value
>::type
invoke_continuation(Func& func, Future && future, Continuation& cont)
{
try {
typedef
typename util::invoke_result<Func, Future>::type
inner_future;
typedef
typename traits::detail::shared_state_ptr_for<inner_future>::type
inner_shared_state_ptr;
// take by value, as the future may go away immediately
inner_shared_state_ptr inner_state =
traits::detail::get_shared_state(func(std::forward<Future>(future)));
typename inner_shared_state_ptr::element_type* ptr =
inner_state.get();
if (ptr == nullptr)
{
HPX_THROW_EXCEPTION(no_state,
"invoke_continuation",
"the inner future has no valid shared state");
}
// Bind an on_completed handler to this future which will transfer
// its result to the new future.
boost::intrusive_ptr<Continuation> cont_(&cont);
ptr->execute_deferred();
ptr->set_on_completed(
util::deferred_call(transfer_result<inner_future>(),
std::move(inner_state), std::move(cont_)));
}
catch (...) {
cont.set_exception(std::current_exception());
}
}
