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