anope/include/base.h

// Anope IRC Services <https://www.anope.org/>
//
// Copyright (C) 2003-2026 Anope Contributors
// Copyright (C) 2008-2011 Adam <Adam@anope.org>
//
// Anope is free software. You can use, modify, and/or distribute it under the
// terms of version 2 of the GNU General Public License. See docs/LICENSE.txt
// for the complete terms of this license and docs/AUTHORS.txt for a list of
// contributors.
//
// Based on the original code of Epona by Lara
// Based on the original code of Services by Andy Church
//
// SPDX-License-Identifier: GPL-2.0-only

#pragma once

#include "services.h"

/** The base class that most classes in Anope inherit from
 */
class CoreExport Base
{
	/* References to this base class */
	std::set<ReferenceBase *> *references = nullptr;
public:
	virtual ~Base();

	/** Adds a reference to this object. Eg, when a Reference
	 * is created referring to this object this is called. It is used to
	 * cleanup references when this object is destructed.
	 */
	void AddReference(ReferenceBase *r);

	void DelReference(ReferenceBase *r);
};

class ReferenceBase
{
protected:
	bool invalid = false;
public:
	ReferenceBase() = default;
	ReferenceBase(const ReferenceBase &other) : invalid(other.invalid) { }
	virtual ~ReferenceBase() = default;
	inline void Invalidate() { this->invalid = true; }
};

/** Used to hold pointers to objects that may be deleted. A Reference will
 * no longer be valid once the object it refers is destructed.
 */
template<typename T>
class Reference
	: public ReferenceBase
{
protected:
	T *ref = nullptr;
public:
	Reference() = default;

	Reference(T *obj) : ref(obj)
	{
		if (ref)
			ref->AddReference(this);
	}

	Reference(const Reference<T> &other) : ReferenceBase(other), ref(other.ref)
	{
		if (operator bool())
			ref->AddReference(this);
	}

	virtual ~Reference()
	{
		if (operator bool())
			ref->DelReference(this);
	}

	inline Reference<T>& operator=(const Reference<T> &other)
	{
		if (this != &other)
		{
			if (*this)
				this->ref->DelReference(this);

			this->ref = other.ref;
			this->invalid = other.invalid;

			if (*this)
				this->ref->AddReference(this);
		}
		return *this;
	}

	/* We explicitly call operator bool here in several places to prevent other
	 * operators, such operator T*, from being called instead, which will mess
	 * with any class inheriting from this that overloads this operator.
	 */
	virtual operator bool()
	{
		if (!this->invalid)
			return this->ref != NULL;
		return false;
	}

	inline operator T*()
	{
		if (operator bool())
			return this->ref;
		return NULL;
	}

	inline T *operator->()
	{
		if (operator bool())
			return this->ref;
		return NULL;
	}

	inline T *operator*()
	{
		if (operator bool())
			return this->ref;
		return NULL;
	}

	/** Note that we can't have an operator< that returns this->ref < other.ref
	 * because this function is used to sort objects in containers (such as set
	 * or map), and if the references themselves can change if the object they
	 * refer to is invalidated or changed, then this screws with the order that
	 * the objects would be in the container without properly adjusting the
	 * container, resulting in weird stuff.
	 *
	 * As such, we don't allow storing references in containers that require
	 * operator<, because they would not be able to compare what the references
	 * actually referred to.
	 */

	inline bool operator==(const Reference<T> &other)
	{
		if (!this->invalid)
			return this->ref == other;
		return false;
	}
};