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+// -*- c++ -*-
+#ifndef _GLIBMM_REFPTR_H
+#define _GLIBMM_REFPTR_H
+
+/* $Id$ */
+
+/* Copyright 2002 The gtkmm Development Team
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 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
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the Free
+ * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+
+namespace Glib
+{
+
+/** RefPtr<> is a reference-counting shared smartpointer.
+ *
+ * Some objects in gtkmm are obtained from a shared
+ * store. Consequently you cannot instantiate them yourself. Instead they
+ * return a RefPtr which behaves much like an ordinary pointer in that members
+ * can be reached with the usual <code>object_ptr->member</code> notation.
+ * Unlike most other smart pointers, RefPtr doesn't support dereferencing
+ * through <code>*object_ptr</code>.
+ *
+ * Reference counting means that a shared reference count is incremented each
+ * time a RefPtr is copied, and decremented each time a RefPtr is destroyed,
+ * for instance when it leaves its scope. When the reference count reaches
+ * zero, the contained object is deleted, meaning you don't need to remember
+ * to delete the object.
+ *
+ * RefPtr<> can store any class that has reference() and unreference() methods.
+ * In gtkmm, that is anything derived from Glib::ObjectBase, such as
+ * Gdk::Pixmap.
+ *
+ * See the "Memory Management" section in the "Programming with gtkmm"
+ * book for further information.
+ */
+template <class T_CppObject>
+class RefPtr
+{
+public:
+ /** Default constructor
+ *
+ * Afterwards it will be null and use of -> will cause a segmentation fault.
+ */
+ inline RefPtr();
+
+ /// Destructor - decrements reference count.
+ inline ~RefPtr();
+
+ /// For use only by the ::create() methods.
+ explicit inline RefPtr(T_CppObject* pCppObject);
+
+ /** Copy constructor
+ *
+ * This increments the shared reference count.
+ */
+ inline RefPtr(const RefPtr<T_CppObject>& src);
+
+ /** Copy constructor (from different, but castable type).
+ *
+ * Increments the reference count.
+ */
+ template <class T_CastFrom>
+ inline RefPtr(const RefPtr<T_CastFrom>& src);
+
+ /** Swap the contents of two RefPtr<>.
+ * This method swaps the internal pointers to T_CppObject. This can be
+ * done safely without involving a reference/unreference cycle and is
+ * therefore highly efficient.
+ */
+ inline void swap(RefPtr<T_CppObject>& other);
+
+ /// Copy from another RefPtr:
+ inline RefPtr<T_CppObject>& operator=(const RefPtr<T_CppObject>& src);
+
+ /** Copy from different, but castable type).
+ *
+ * Increments the reference count.
+ */
+ template <class T_CastFrom>
+ inline RefPtr<T_CppObject>& operator=(const RefPtr<T_CastFrom>& src);
+
+ /// Tests whether the RefPtr<> point to the same underlying instance.
+ inline bool operator==(const RefPtr<T_CppObject>& src) const;
+
+ /// See operator==().
+ inline bool operator!=(const RefPtr<T_CppObject>& src) const;
+
+ /** Dereferencing.
+ *
+ * Use the methods of the underlying instance like so:
+ * <code>refptr->memberfun()</code>.
+ */
+ inline T_CppObject* operator->() const;
+
+ /** Test whether the RefPtr<> points to any underlying instance.
+ *
+ * Mimics usage of ordinary pointers:
+ * @code
+ * if (ptr)
+ * do_something();
+ * @endcode
+ */
+ inline operator bool() const;
+
+ /// Set underlying instance to 0, decrementing reference count of existing instance appropriately.
+ inline void clear();
+
+
+ /** Dynamic cast to derived class.
+ *
+ * The RefPtr can't be cast with the usual notation so instead you can use
+ * @code
+ * ptr_derived = RefPtr<Derived>::cast_dynamic(ptr_base);
+ * @endcode
+ */
+ template <class T_CastFrom>
+ static inline RefPtr<T_CppObject> cast_dynamic(const RefPtr<T_CastFrom>& src);
+
+ /** Static cast to derived class.
+ *
+ * Like the dynamic cast; the notation is
+ * @code
+ * ptr_derived = RefPtr<Derived>::cast_static(ptr_base);
+ * @endcode
+ */
+ template <class T_CastFrom>
+ static inline RefPtr<T_CppObject> cast_static(const RefPtr<T_CastFrom>& src);
+
+private:
+ T_CppObject* pCppObject_;
+};
+
+
+#ifndef DOXYGEN_SHOULD_SKIP_THIS
+
+// RefPtr<>::operator->() comes first here since it's used by other methods.
+// If it would come after them it wouldn't be inlined.
+
+template <class T_CppObject> inline
+T_CppObject* RefPtr<T_CppObject>::operator->() const
+{
+ return pCppObject_;
+}
+
+template <class T_CppObject> inline
+RefPtr<T_CppObject>::RefPtr()
+:
+ pCppObject_ (0)
+{}
+
+template <class T_CppObject> inline
+RefPtr<T_CppObject>::~RefPtr()
+{
+ if(pCppObject_)
+ pCppObject_->unreference(); // This could cause pCppObject to be deleted.
+}
+
+template <class T_CppObject> inline
+RefPtr<T_CppObject>::RefPtr(T_CppObject* pCppObject)
+:
+ pCppObject_ (pCppObject)
+{}
+
+template <class T_CppObject> inline
+RefPtr<T_CppObject>::RefPtr(const RefPtr<T_CppObject>& src)
+:
+ pCppObject_ (src.pCppObject_)
+{
+ if(pCppObject_)
+ pCppObject_->reference();
+}
+
+// The templated ctor allows copy construction from any object that's
+// castable. Thus, it does downcasts:
+// base_ref = derived_ref
+template <class T_CppObject>
+ template <class T_CastFrom>
+inline
+RefPtr<T_CppObject>::RefPtr(const RefPtr<T_CastFrom>& src)
+:
+ // A different RefPtr<> will not allow us access to pCppObject_. We need
+ // to add a get_underlying() for this, but that would encourage incorrect
+ // use, so we use the less well-known operator->() accessor:
+ pCppObject_ (src.operator->())
+{
+ if(pCppObject_)
+ pCppObject_->reference();
+}
+
+template <class T_CppObject> inline
+void RefPtr<T_CppObject>::swap(RefPtr<T_CppObject>& other)
+{
+ T_CppObject *const temp = pCppObject_;
+ pCppObject_ = other.pCppObject_;
+ other.pCppObject_ = temp;
+}
+
+template <class T_CppObject> inline
+RefPtr<T_CppObject>& RefPtr<T_CppObject>::operator=(const RefPtr<T_CppObject>& src)
+{
+ // In case you haven't seen the swap() technique to implement copy
+ // assignment before, here's what it does:
+ //
+ // 1) Create a temporary RefPtr<> instance via the copy ctor, thereby
+ // increasing the reference count of the source object.
+ //
+ // 2) Swap the internal object pointers of *this and the temporary
+ // RefPtr<>. After this step, *this already contains the new pointer,
+ // and the old pointer is now managed by temp.
+ //
+ // 3) The destructor of temp is executed, thereby unreferencing the
+ // old object pointer.
+ //
+ // This technique is described in Herb Sutter's "Exceptional C++", and
+ // has a number of advantages over conventional approaches:
+ //
+ // - Code reuse by calling the copy ctor.
+ // - Strong exception safety for free.
+ // - Self assignment is handled implicitely.
+ // - Simplicity.
+ // - It just works and is hard to get wrong; i.e. you can use it without
+ // even thinking about it to implement copy assignment whereever the
+ // object data is managed indirectly via a pointer, which is very common.
+
+ RefPtr<T_CppObject> temp (src);
+ this->swap(temp);
+ return *this;
+}
+
+template <class T_CppObject>
+ template <class T_CastFrom>
+inline
+RefPtr<T_CppObject>& RefPtr<T_CppObject>::operator=(const RefPtr<T_CastFrom>& src)
+{
+ RefPtr<T_CppObject> temp (src);
+ this->swap(temp);
+ return *this;
+}
+
+template <class T_CppObject> inline
+bool RefPtr<T_CppObject>::operator==(const RefPtr<T_CppObject>& src) const
+{
+ return (pCppObject_ == src.pCppObject_);
+}
+
+template <class T_CppObject> inline
+bool RefPtr<T_CppObject>::operator!=(const RefPtr<T_CppObject>& src) const
+{
+ return (pCppObject_ != src.pCppObject_);
+}
+
+template <class T_CppObject> inline
+RefPtr<T_CppObject>::operator bool() const
+{
+ return (pCppObject_ != 0);
+}
+
+template <class T_CppObject> inline
+void RefPtr<T_CppObject>::clear()
+{
+ RefPtr<T_CppObject> temp; // swap with an empty RefPtr<> to clear *this
+ this->swap(temp);
+}
+
+template <class T_CppObject>
+ template <class T_CastFrom>
+inline
+RefPtr<T_CppObject> RefPtr<T_CppObject>::cast_dynamic(const RefPtr<T_CastFrom>& src)
+{
+ T_CppObject *const pCppObject = dynamic_cast<T_CppObject*>(src.operator->());
+
+ if(pCppObject)
+ pCppObject->reference();
+
+ return RefPtr<T_CppObject>(pCppObject);
+}
+
+template <class T_CppObject>
+ template <class T_CastFrom>
+inline
+RefPtr<T_CppObject> RefPtr<T_CppObject>::cast_static(const RefPtr<T_CastFrom>& src)
+{
+ T_CppObject *const pCppObject = static_cast<T_CppObject*>(src.operator->());
+
+ if(pCppObject)
+ pCppObject->reference();
+
+ return RefPtr<T_CppObject>(pCppObject);
+}
+
+#endif /* DOXYGEN_SHOULD_SKIP_THIS */
+
+/** @relates Glib::RefPtr */
+template <class T_CppObject> inline
+void swap(RefPtr<T_CppObject>& lhs, RefPtr<T_CppObject>& rhs)
+{
+ lhs.swap(rhs);
+}
+
+} // namespace Glib
+
+
+#endif /* _GLIBMM_REFPTR_H */
+