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Telegram/SourceFiles/data/data_abstract_structure.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
+
+namespace Data {
+
+// This module suggests a way to hold global data structures, that are
+// created on demand and deleted at the end of the app launch.
+//
+// Usage:
+//
+// class MyData : public Data::AbstractStruct { .. data .. };
+// Data::GlobalStructurePointer<MyData> myData;
+// .. somewhere when needed ..
+// myData.createIfNull();
+
+class AbstractStructure {
+public:
+	virtual ~AbstractStructure() = 0;
+};
+inline AbstractStructure::~AbstractStructure() = default;
+
+namespace internal {
+
+void registerAbstractStructure(AbstractStructure **p);
+
+} // namespace
+
+  // Must be created in global scope!
+  // Structure is derived from AbstractStructure.
+template <typename Structure>
+class GlobalStructurePointer {
+public:
+	GlobalStructurePointer() = default;
+	GlobalStructurePointer(const GlobalStructurePointer<Structure> &other) = delete;
+	GlobalStructurePointer &operator=(const GlobalStructurePointer<Structure> &other) = delete;
+
+	void createIfNull() {
+		if (!_p) {
+			_p = new Structure();
+			internal::registerAbstractStructure(&_p);
+		}
+	}
+	Structure *operator->() {
+		Assert(_p != nullptr);
+		return static_cast<Structure*>(_p);
+	}
+	const Structure *operator->() const {
+		Assert(_p != nullptr);
+		return static_cast<const Structure*>(_p);
+	}
+	explicit operator bool() const {
+		return _p != nullptr;
+	}
+
+private:
+	AbstractStructure *_p;
+
+};
+
+// This method should be called at the end of the app launch.
+// It will destroy all data structures created by Data::GlobalStructurePointer.
+void clearGlobalStructures();
+
+} // namespace Data