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Telegram/lib_base/base/never_freed_pointer.h

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+// This file is part of Desktop App Toolkit,
+// a set of libraries for developing nice desktop applications.
+//
+// For license and copyright information please follow this link:
+// https://github.com/desktop-app/legal/blob/master/LEGAL
+//
+#pragma once
+
+#include "base/assertion.h"
+
+namespace base {
+
+// This pointer is used for global non-POD variables that are allocated
+// on demand by createIfNull(lambda) and are never automatically freed.
+template <typename T>
+class NeverFreedPointer {
+public:
+	NeverFreedPointer() = default;
+	NeverFreedPointer(const NeverFreedPointer<T> &other) = delete;
+	NeverFreedPointer &operator=(const NeverFreedPointer<T> &other) = delete;
+
+	template <typename... Args>
+	void createIfNull(Args&&... args) {
+		if (isNull()) {
+			reset(new T(std::forward<Args>(args)...));
+		}
+	};
+
+	T *data() const {
+		return _p;
+	}
+	T *release() {
+		return base::take(_p);
+	}
+	void reset(T *p = nullptr) {
+		delete _p;
+		_p = p;
+	}
+	bool isNull() const {
+		return data() == nullptr;
+	}
+
+	void clear() {
+		reset();
+	}
+	T *operator->() const {
+		return data();
+	}
+	T &operator*() const {
+		Assert(!isNull());
+		return *data();
+	}
+	explicit operator bool() const {
+		return !isNull();
+	}
+
+private:
+	T *_p;
+
+};
+
+} // namespace base