49 lines
1.7 KiB
C++
49 lines
1.7 KiB
C++
/*
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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 <mapbox/variant.hpp>
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// We use base::variant<> alias and base::get_if() helper while we don't have std::variant<>.
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namespace base {
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template <typename... Types>
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using variant = mapbox::util::variant<Types...>;
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template <typename... Types>
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using optional_variant = variant<std::nullptr_t, Types...>;
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template <typename T, typename... Types>
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inline T *get_if(variant<Types...> *v) {
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return (v && v->template is<T>()) ? &v->template get_unchecked<T>() : nullptr;
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}
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template <typename T, typename... Types>
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inline const T *get_if(const variant<Types...> *v) {
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return (v && v->template is<T>()) ? &v->template get_unchecked<T>() : nullptr;
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}
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template <typename... Types>
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inline bool is_null_variant(const optional_variant<Types...> &variant) {
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return get_if<std::nullptr_t>(&variant) != nullptr;
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}
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} // namespace base
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