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#pragma once
#include <library/cpp/threading/future/core/future.h>
#include <util/generic/ptr.h>
namespace NThreading {
namespace NWaitGroup::NImpl {
template <class WaitPolicy>
struct TState;
template <class WaitPolicy>
using TStateRef = TIntrusivePtr<TState<WaitPolicy>>;
}
// a helper class which allows to
// wait for a set of futures which is
// not known beforehand. Might be useful, e.g., for graceful shutdown:
// while (!Stop()) {
// wg.Add(
// DoAsyncWork());
// }
// std::move(wg).Finish()
// .GetValueSync();
//
//
// the folowing are equivalent:
// {
// return WaitAll(futures);
// }
// {
// TWaitGroup<TWaitPolicy::TAll> wg;
// for (auto&& f: futures) { wg.Add(f); }
// return std::move(wg).Finish();
// }
template <class WaitPolicy>
class TWaitGroup {
public:
TWaitGroup();
// thread-safe, exception-safe
//
// adds the future to the set of futures to wait for
//
// if an exception is thrown during a call to ::Discover, the call has no effect
//
// accepts non-void T just for optimization
// (so that the caller does not have to use future.IgnoreResult())
template <class T>
TWaitGroup& Add(const TFuture<T>& future);
// finishes building phase
// and returns the future that combines the futures
// in the wait group according to WaitPolicy
[[nodiscard]] TFuture<void> Finish() &&;
private:
NWaitGroup::NImpl::TStateRef<WaitPolicy> State_;
};
}
#define INCLUDE_FUTURE_INL_H
#include "wait_group-inl.h"
#undef INCLUDE_FUTURE_INL_H
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