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Telegram/SourceFiles/data/data_flags.h

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+/*
+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
+
+#include <rpl/event_stream.h>
+
+namespace Data {
+
+template <typename FlagsType>
+using FlagsUnderlying = typename FlagsType::Type;
+
+template <
+	typename FlagsType,
+	FlagsUnderlying<FlagsType> kEssential = FlagsUnderlying<FlagsType>(-1)>
+class Flags {
+public:
+	using Type = FlagsType;
+	using Enum = typename Type::Enum;
+
+	struct Change {
+		using Type = FlagsType;
+		using Enum = typename Type::Enum;
+
+		Change(Type diff, Type value)
+		: diff(diff)
+		, value(value) {
+		}
+		Type diff = 0;
+		Type value = 0;
+	};
+
+	Flags() = default;
+	Flags(Type value) : _value(value) {
+	}
+
+	void set(Type which) {
+		if (auto diff = which ^ _value) {
+			_value = which;
+			updated(diff);
+		}
+	}
+	void add(Type which) {
+		if (auto diff = which & ~_value) {
+			_value |= which;
+			updated(diff);
+		}
+	}
+	void remove(Type which) {
+		if (auto diff = which & _value) {
+			_value &= ~which;
+			updated(diff);
+		}
+	}
+	auto current() const {
+		return _value;
+	}
+	auto changes() const {
+		return _changes.events();
+	}
+	auto value() const {
+		return _changes.events_starting_with({
+			Type::from_raw(kEssential),
+			_value });
+	}
+
+private:
+	void updated(Type diff) {
+		if ((diff &= Type::from_raw(kEssential))) {
+			_changes.fire({ diff, _value });
+		}
+	}
+
+	Type _value = 0;
+	rpl::event_stream<Change> _changes;
+
+};
+
+} // namespace Data