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