tdesktop/Telegram/SourceFiles/rpl/flatten_latest.h

88 lines
2.3 KiB
C++

/*
This file is part of Telegram Desktop,
the official desktop version of Telegram messaging app, see https://telegram.org
Telegram Desktop is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
It is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
In addition, as a special exception, the copyright holders give permission
to link the code of portions of this program with the OpenSSL library.
Full license: https://github.com/telegramdesktop/tdesktop/blob/master/LICENSE
Copyright (c) 2014-2017 John Preston, https://desktop.telegram.org
*/
#pragma once
#include <rpl/producer.h>
namespace rpl {
namespace details {
class flatten_latest_helper {
public:
template <
typename Value,
typename Error,
typename Generator,
typename MetaGenerator>
auto operator()(producer<
producer<Value, Error, Generator>,
Error,
MetaGenerator> &&initial) const {
return make_producer<Value, Error>([
initial = std::move(initial)
](const auto &consumer) mutable {
auto state = consumer.template make_state<State>();
return std::move(initial).start(
[consumer, state](producer<Value, Error> &&inner) {
state->finished = false;
state->alive = lifetime();
std::move(inner).start(
[consumer](auto &&value) {
consumer.put_next_forward(std::forward<decltype(value)>(value));
}, [consumer](auto &&error) {
consumer.put_error_forward(std::forward<decltype(error)>(error));
}, [consumer, state] {
if (state->finished) {
consumer.put_done();
} else {
state->finished = true;
}
}, state->alive);
}, [consumer](auto &&error) {
consumer.put_error_forward(std::forward<decltype(error)>(error));
}, [consumer, state] {
if (state->finished) {
consumer.put_done();
} else {
state->finished = true;
}
});
});
}
private:
struct State {
lifetime alive;
bool finished = false;
};
};
} // namespace details
inline auto flatten_latest()
-> details::flatten_latest_helper {
return details::flatten_latest_helper();
}
} // namespace rpl