inspircd/include/base.h

/*
 * InspIRCd -- Internet Relay Chat Daemon
 *
 *   Copyright (C) 2020 Matt Schatz <genius3000@g3k.solutions>
 *   Copyright (C) 2013, 2017, 2020-2021 Sadie Powell <sadie@witchery.services>
 *   Copyright (C) 2013, 2015 Attila Molnar <attilamolnar@hush.com>
 *   Copyright (C) 2012 Robby <robby@chatbelgie.be>
 *   Copyright (C) 2012 ChrisTX <xpipe@hotmail.de>
 *   Copyright (C) 2011-2012 Adam <Adam@anope.org>
 *   Copyright (C) 2009-2010 Daniel De Graaf <danieldg@inspircd.org>
 *   Copyright (C) 2007 Oliver Lupton <om@inspircd.org>
 *   Copyright (C) 2007 Dennis Friis <peavey@inspircd.org>
 *   Copyright (C) 2006, 2010 Craig Edwards <brain@inspircd.org>
 *
 * This file is part of InspIRCd.  InspIRCd is free software: you can
 * redistribute it and/or modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation, version 2.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
 * details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */


#pragma once

#include "compat.h"
#include <string>

#include "utility/uncopiable.h"
#include "cull.h"

/** The base class for inspircd classes that support reference counting.
 * Any objects that do not have a well-defined lifetime should inherit from
 * this, and should be assigned to a reference<type> object to establish their
 * lifetime.
 *
 * Reference objects should not hold circular references back to themselves,
 * even indirectly; this will cause a memory leak because the count will never
 * drop to zero.
 *
 * Using a normal pointer for the object is recommended if you can assure that
 * at least one reference<> will remain as long as that pointer is used; this
 * will avoid the slight overhead of changing the reference count.
 */
class CoreExport refcountbase
	: private insp::uncopiable
{
	mutable unsigned int refcount = 0;
 public:
	refcountbase();
	virtual ~refcountbase();
	inline unsigned int GetReferenceCount() const { return refcount; }
	static inline void* operator new(size_t, void* m) { return m; }
	static void* operator new(size_t);
	static void operator delete(void*);
	inline void refcount_inc() const { refcount++; }
	inline bool refcount_dec() const { refcount--; return !refcount; }
};

/** Base class for use count tracking. Uses reference<>, but does not
 * cause object deletion when the last user is removed.
 *
 * Safe for use as a second parent class; will not add a second vtable.
 */
class CoreExport usecountbase
	: private insp::uncopiable
{
	mutable unsigned int usecount = 0;
 public:
	usecountbase() = default;
	~usecountbase();
	inline unsigned int GetUseCount() const { return usecount; }
	inline void refcount_inc() const { usecount++; }
	inline bool refcount_dec() const { usecount--; return false; }
};

template <typename T>
class reference
{
	T* value = nullptr;
 public:
	reference() = default;
	reference(T* v) : value(v) { if (value) value->refcount_inc(); }
	reference(const reference<T>& v) : value(v.value) { if (value) value->refcount_inc(); }
	reference<T>& operator=(const reference<T>& other)
	{
		if (other.value)
			other.value->refcount_inc();
		this->reference::~reference();
		value = other.value;
		return *this;
	}

	~reference()
	{
		if (value && value->refcount_dec())
			delete value;
	}

	inline reference<T>& operator=(T* other)
	{
		if (value != other)
		{
			if (value && value->refcount_dec())
				delete value;
			value = other;
			if (value)
				value->refcount_inc();
		}

		return *this;
	}

	inline operator bool() const { return (value != NULL); }
	inline operator T*() const { return value; }
	inline T* operator->() const { return value; }
	inline T& operator*() const { return *value; }
	inline bool operator<(const reference<T>& other) const { return value < other.value; }
	inline bool operator>(const reference<T>& other) const { return value > other.value; }
	static inline void* operator new(size_t, void* m) { return m; }
 private:
#ifndef _WIN32
	static void* operator new(size_t);
	static void operator delete(void*);
#endif
};

/** This class can be used on its own to represent an exception, or derived to represent a module-specific exception.
 * When a module whishes to abort, e.g. within a constructor, it should throw an exception using ModuleException or
 * a class derived from ModuleException. If a module throws an exception during its constructor, the module will not
 * be loaded. If this happens, the error message returned by ModuleException::GetReason will be displayed to the user
 * attempting to load the module, or dumped to the console if the ircd is currently loading for the first time.
 */
class CoreExport CoreException : public std::exception
{
 protected:
	/** Holds the error message to be displayed
	 */
	const std::string err;
	/** Source of the exception
	 */
	const std::string source;

 public:
	/** This constructor can be used to specify an error message before throwing.
	 * @param message Human readable error message
	 */
	CoreException(const std::string &message) : err(message), source("The core") {}
	/** This constructor can be used to specify an error message before throwing,
	 * and to specify the source of the exception.
	 * @param message Human readable error message
	 * @param src Source of the exception
	 */
	CoreException(const std::string &message, const std::string &src) : err(message), source(src) {}
	/** This destructor solves world hunger, cancels the world debt, and causes the world to end.
	 * Actually no, it does nothing. Never mind.
	 * @throws Nothing!
	 */
	virtual ~CoreException() noexcept = default;
	/** Returns the reason for the exception.
	 * @return Human readable description of the error
	 */
	const std::string& GetReason() const { return err; }

	/** Returns the source of the exception
	 * @return Source of the exception
	 */
	const std::string& GetSource() const { return source; }
};

class Module;
class CoreExport ModuleException : public CoreException
{
 public:
	/** This constructor can be used to specify an error message before throwing.
	 */
	ModuleException(const std::string &message, Module* me = NULL);
};

typedef const reference<Module> ModuleRef;

enum ServiceType {
	/** is a Command */
	SERVICE_COMMAND,
	/** is a ModeHandler */
	SERVICE_MODE,
	/** is a metadata descriptor */
	SERVICE_METADATA,
	/** is a data processing provider (MD5, SQL) */
	SERVICE_DATA,
	/** is an I/O hook provider */
	SERVICE_IOHOOK,
	/** Service managed by a module */
	SERVICE_CUSTOM
};

/** A structure defining something that a module can provide */
class CoreExport ServiceProvider : public Cullable
{
 public:
	/** Module that is providing this service */
	ModuleRef creator;
	/** Name of the service being provided */
	const std::string name;
	/** Type of service (must match object type) */
	const ServiceType service;
	ServiceProvider(Module* Creator, const std::string& Name, ServiceType Type);

	/** Retrieves a string that represents the type of this service. */
	const char* GetTypeString() const;

	/** Register this service in the appropriate registrar
	 */
	virtual void RegisterService();

	/** If called, this ServiceProvider won't be registered automatically
	 */
	void DisableAutoRegister();
};