tdesktop/Telegram/SourceFiles/rpl/skip.h

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2018-05-21 21:31:46 +00:00
/*
This file is part of Telegram Desktop,
the official desktop application for the Telegram messaging service.
For license and copyright information please follow this link:
https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
*/
#pragma once
namespace rpl {
namespace details {
class skip_helper {
public:
skip_helper(int count) : _count(count) {
}
template <
typename Value,
typename Error,
typename Generator>
auto operator()(producer<Value, Error, Generator> &&initial) {
return make_producer<Value, Error>([
initial = std::move(initial),
skipping = _count
](const auto &consumer) mutable {
auto count = consumer.template make_state<int>(skipping);
auto initial_consumer = make_consumer<Value, Error>(
[consumer, count](auto &&value) {
if (*count) {
--*count;
} else {
consumer.put_next_forward(
std::forward<decltype(value)>(value));
}
}, [consumer](auto &&error) {
consumer.put_error_forward(
std::forward<decltype(error)>(error));
}, [consumer] {
consumer.put_done();
});
consumer.add_lifetime(initial_consumer.terminator());
return std::move(initial).start_existing(initial_consumer);
});
}
private:
int _count = 0;
};
} // namespace details
inline auto skip(int count)
-> details::skip_helper {
Expects(count >= 0);
return details::skip_helper(count);
}
} // namespace rpl