/*
 * This file is part of TelepathyQt4
 *
 * Copyright (C) 2008 Collabora Ltd. <http://www.collabora.co.uk/>
 * Copyright (C) 2008 Nokia Corporation
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

/**
 * \page shared_ptr Shared Pointer Usage
 *
 * \section shared_ptr_overview Overview
 *
 * The Qt parent/child object model does not fit well with Telepathy-Qt4 object
 * model, where in some places we either don't know the object parent or we
 * can't use a parent, as the object can stay alive without it.
 *
 * To avoid memory leaks, caused by objects that got instantiated and don't have
 * any parent, we decided to make some of our objects reference counted, by
 * making them inherit SharedData.
 *
 * Making the object reference counted, does not guarantee that it will get
 * deleted when nobody is referencing it.
 *
 * When instantiating new classes that inherits SharedData the reference count
 * is 0, this is referred to as the floating state. Again this may lead to
 * memory leaks, caused by objects in the floating state that never get deleted.
 *
 * So the solution is to put the object in a SharedPtr as soon as possible,
 * letting the SharedPtr manage the object lifetime.
 *
 * The pattern used is that classes inherit SharedData and are used
 * together with SharedPtr. When the reference count hits 0, the object
 * is deleted.
 *
 * In order to assure that the object is put in a SharedPtr as soon as possible,
 * our objects inheriting SharedData will have the constructor either private
 * or protected, in case we want to support custom classes, and will have a
 * public static create method that will return a SharedPtr pointing to the
 * object instance.
 *
 * Note that when developing custom classes, this pattern should be followed,
 * to avoid objects in floating state, avoiding memory leaks.
 */

/**
 * \fn static SharedPtr<T> Tp::SharedPtr<T>::dynamicCast(const SharedPtr<X> &)
 *
 * Casts the pointer given by src to a pointer pointing to an object of type T. The cast will
 * succeed if the C++ runtime type identification mechanism considers the type T to be the actual
 * runtime type of the object pointed to by src or one of its (possibly indirect) parent classes.
 * Otherwise, a null pointer is returned.
 *
 * Note that this also allows down-casting a baseclass pointer to a subclass pointer.
 *
 * This cast method should not be used for QObject-derived classes, as Qt provides a more portable
 * and efficient type identification mechanism, which is used by qObjectCast().
 *
 * This cast method requires the C++ dynamic runtime type identification facility to be enabled
 * (which might be disabled by eg. the -fno-rtti flag of the GNU G++ compiler).
 */

/**
 * \fn static SharedPtr<T> Tp::SharedPtr<T>::qObjectCast(const SharedPtr<X> &)
 *
 * Casts the pointer given by src to a pointer pointing to an object of type T. The cast will
 * succeed if the Qt runtime type identification mechanism considers the type T to be the actual
 * runtime type of the object pointed to by src or one of its (possibly indirect) parent classes.
 * Otherwise, a null pointer is returned.
 *
 * Note that this also allows down-casting a baseclass pointer to a subclass pointer.
 *
 * This cast method MUST not be used for classes not derived from QObject. However, dynamicCast()
 * provides the same semantics for all classes, provided the C++ runtime type identification
 * facility is enabled. This method, on the other hand, doesn't require the standard C++ facility
 * and is probably also faster for the types it can be used with.
 */