#ifndef _GLIBMM_REFPTR_H
#define _GLIBMM_REFPTR_H
/* 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 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, see <http://www.gnu.org/licenses/>.
*/
#include <glibmmconfig.h>
#include <glib.h>
#include <utility>
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,
* and whose destructor is noexcept (the default for destructors).
* In gtkmm, that is anything derived from Glib::ObjectBase, such as
* Gdk::Pixbuf.
*
* See the "Memory Management" section in the "Programming with gtkmm"
* book for further information.
*/
template <class T_CppObject>
class RefPtr
{
private:
#ifndef DOXYGEN_SHOULD_SKIP_THIS
/** Helper class for disallowing use of Glib::RefPtr with certain classes.
*
* Disallow for instance in Gtk::Widget and its subclasses.
* Glib::RefPtr<T>::is_allowed_type::value is false if
* T:dont_allow_use_in_glib_refptr_ is a public type, else it's true.
* Example:
* @code
* using dont_allow_use_in_glib_refptr_ = int;
* @endcode
*/
class is_allowed_type
{
private:
struct big
{
int memory[64];
};
static big check(...);
// If X::dont_allow_use_in_glib_refptr_ is not a type, this check() overload
// is ignored because of the SFINAE rule (Substitution Failure Is Not An Error).
template <typename X>
static typename X::dont_allow_use_in_glib_refptr_ check(X* obj);
public:
static const bool value = sizeof(check(static_cast<T_CppObject*>(nullptr))) == sizeof(big);
};
static_assert(is_allowed_type::value, "Glib::RefPtr must not be used with this class.");
#endif /* DOXYGEN_SHOULD_SKIP_THIS */
public:
/** Default constructor
*
* Afterwards it will be null and use of -> will invoke undefined behaviour.
*/
inline RefPtr() noexcept;
/// Destructor - decrements reference count.
inline ~RefPtr() noexcept;
/// For use only by the \::create() methods.
explicit inline RefPtr(T_CppObject* pCppObject) noexcept;
/** Copy constructor
*
* This increments the shared reference count.
*/
inline RefPtr(const RefPtr& src) noexcept;
/** Move constructor
*/
inline RefPtr(RefPtr&& src) noexcept;
/** Move constructor (from different, but castable type).
*/
template <class T_CastFrom>
inline RefPtr(RefPtr<T_CastFrom>&& src) noexcept;
/** Copy constructor (from different, but castable type).
*
* Increments the reference count.
*/
template <class T_CastFrom>
inline RefPtr(const RefPtr<T_CastFrom>& src) noexcept;
/** 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& other) noexcept;
/// Copy from another RefPtr:
inline RefPtr& operator=(const RefPtr& src) noexcept;
/// Move assignment operator:
inline RefPtr& operator=(RefPtr&& src) noexcept;
/// Move assignment operator (from different, but castable type):
template <class T_CastFrom>
inline RefPtr& operator=(RefPtr<T_CastFrom>&& src) noexcept;
/** Copy from different, but castable type.
*
* Increments the reference count.
*/
template <class T_CastFrom>
inline RefPtr& operator=(const RefPtr<T_CastFrom>& src) noexcept;
/// Tests whether the RefPtr<> point to the same underlying instance.
inline bool operator==(const RefPtr& src) const noexcept;
/// See operator==().
inline bool operator!=(const RefPtr& src) const noexcept;
/** Dereferencing.
*
* Use the methods of the underlying instance like so:
* <code>refptr->memberfun()</code>.
*/
inline T_CppObject* operator->() const noexcept;
/** Returns the stored pointer.
*
* @newin{2,56}
*/
inline T_CppObject* get() const noexcept;
/** Test whether the RefPtr<> points to any underlying instance.
*
* Mimics usage of ordinary pointers:
* @code
* if (ptr)
* do_something();
* @endcode
*/
inline explicit operator bool() const noexcept;
#ifndef GLIBMM_DISABLE_DEPRECATED
/// @deprecated Use reset() instead because this leads to confusion with clear() methods on the
/// underlying class. For instance, people use .clear() when they mean ->clear().
inline void clear() noexcept;
#endif // GLIBMM_DISABLE_DEPRECATED
/** Set underlying instance to nullptr, decrementing reference count of existing instance
* appropriately.
* @newin{2,16}
*/
inline void reset() noexcept;
/** Release the ownership of underlying instance.
*
* RefPtr's underlying instance is set to nullptr, therefore underlying object can't be accessed
* through this RefPtr anymore.
* @return an underlying instance.
*
* Most users should not use release(). It can spoil the automatic destruction
* of the managed object. A legitimate use is if you immediately give RefPtr's
* reference to another object.
*/
inline T_CppObject* release() noexcept G_GNUC_WARN_UNUSED_RESULT;
/** 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 cast_dynamic(const RefPtr<T_CastFrom>& src) noexcept;
/** 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 cast_static(const RefPtr<T_CastFrom>& src) noexcept;
/** Cast to non-const.
*
* The RefPtr can't be cast with the usual notation so instead you can use
* @code
* ptr_unconst = RefPtr<UnConstType>::cast_const(ptr_const);
* @endcode
*/
template <class T_CastFrom>
static inline RefPtr cast_const(const RefPtr<T_CastFrom>& src) noexcept;
/** Compare based on the underlying instance address.
*
* This is needed in code that requires an ordering on
* RefPtr<T_CppObject> instances, e.g. std::set<RefPtr<T_CppObject> >.
*
* Without these, comparing two RefPtr<T_CppObject> instances
* is still syntactically possible, but the result is semantically
* wrong, as p1 REL_OP p2 is interpreted as (bool)p1 REL_OP (bool)p2.
*/
inline bool operator<(const RefPtr& src) const noexcept;
/// See operator<().
inline bool operator<=(const RefPtr& src) const noexcept;
/// See operator<().
inline bool operator>(const RefPtr& src) const noexcept;
/// See operator<().
inline bool operator>=(const RefPtr& src) const noexcept;
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 noexcept
{
return pCppObject_;
}
template <class T_CppObject>
inline RefPtr<T_CppObject>::RefPtr() noexcept : pCppObject_(nullptr)
{
}
template <class T_CppObject>
inline RefPtr<T_CppObject>::~RefPtr() noexcept
{
if (pCppObject_)
pCppObject_->unreference(); // This could cause pCppObject to be deleted.
}
template <class T_CppObject>
inline RefPtr<T_CppObject>::RefPtr(T_CppObject* pCppObject) noexcept : pCppObject_(pCppObject)
{
}
template <class T_CppObject>
inline RefPtr<T_CppObject>::RefPtr(const RefPtr& src) noexcept : pCppObject_(src.pCppObject_)
{
if (pCppObject_)
pCppObject_->reference();
}
template <class T_CppObject>
inline RefPtr<T_CppObject>::RefPtr(RefPtr&& src) noexcept : pCppObject_(src.pCppObject_)
{
src.pCppObject_ = nullptr;
}
template <class T_CppObject>
template <class T_CastFrom>
inline RefPtr<T_CppObject>::RefPtr(RefPtr<T_CastFrom>&& src) noexcept : pCppObject_(src.release())
{
}
// 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) noexcept :
// 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& other) noexcept
{
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& src) noexcept
{
// 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>
inline RefPtr<T_CppObject>&
RefPtr<T_CppObject>::operator=(RefPtr&& src) noexcept
{
RefPtr<T_CppObject> temp(std::move(src));
this->swap(temp);
src.pCppObject_ = nullptr;
return *this;
}
template <class T_CppObject>
template <class T_CastFrom>
inline RefPtr<T_CppObject>&
RefPtr<T_CppObject>::operator=(RefPtr<T_CastFrom>&& src) noexcept
{
if (pCppObject_)
pCppObject_->unreference();
pCppObject_ = src.release();
return *this;
}
template <class T_CppObject>
template <class T_CastFrom>
inline RefPtr<T_CppObject>&
RefPtr<T_CppObject>::operator=(const RefPtr<T_CastFrom>& src) noexcept
{
RefPtr<T_CppObject> temp(src);
this->swap(temp);
return *this;
}
template <class T_CppObject>
inline bool
RefPtr<T_CppObject>::operator==(const RefPtr& src) const noexcept
{
return (pCppObject_ == src.pCppObject_);
}
template <class T_CppObject>
inline bool
RefPtr<T_CppObject>::operator!=(const RefPtr& src) const noexcept
{
return (pCppObject_ != src.pCppObject_);
}
template <class T_CppObject>
inline T_CppObject* RefPtr<T_CppObject>::get() const noexcept
{
return pCppObject_;
}
template <class T_CppObject>
inline RefPtr<T_CppObject>::operator bool() const noexcept
{
return (pCppObject_ != nullptr);
}
#ifndef GLIBMM_DISABLE_DEPRECATED
template <class T_CppObject>
inline void
RefPtr<T_CppObject>::clear() noexcept
{
reset();
}
#endif // GLIBMM_DISABLE_DEPRECATED
template <class T_CppObject>
inline void
RefPtr<T_CppObject>::reset() noexcept
{
RefPtr<T_CppObject> temp; // swap with an empty RefPtr<> to clear *this
this->swap(temp);
}
template <class T_CppObject>
inline T_CppObject*
RefPtr<T_CppObject>::release() noexcept
{
T_CppObject* tmp = pCppObject_;
pCppObject_ = nullptr;
return tmp;
}
template <class T_CppObject>
template <class T_CastFrom>
inline RefPtr<T_CppObject>
RefPtr<T_CppObject>::cast_dynamic(const RefPtr<T_CastFrom>& src) noexcept
{
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) noexcept
{
T_CppObject* const pCppObject = static_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_const(const RefPtr<T_CastFrom>& src) noexcept
{
T_CppObject* const pCppObject = const_cast<T_CppObject*>(src.operator->());
if (pCppObject)
pCppObject->reference();
return RefPtr<T_CppObject>(pCppObject);
}
template <class T_CppObject>
inline bool
RefPtr<T_CppObject>::operator<(const RefPtr& src) const noexcept
{
return (pCppObject_ < src.pCppObject_);
}
template <class T_CppObject>
inline bool
RefPtr<T_CppObject>::operator<=(const RefPtr& src) const noexcept
{
return (pCppObject_ <= src.pCppObject_);
}
template <class T_CppObject>
inline bool
RefPtr<T_CppObject>::operator>(const RefPtr& src) const noexcept
{
return (pCppObject_ > src.pCppObject_);
}
template <class T_CppObject>
inline bool
RefPtr<T_CppObject>::operator>=(const RefPtr& src) const noexcept
{
return (pCppObject_ >= src.pCppObject_);
}
#endif /* DOXYGEN_SHOULD_SKIP_THIS */
/** @relates Glib::RefPtr */
template <class T_CppObject>
inline void
swap(RefPtr<T_CppObject>& lhs, RefPtr<T_CppObject>& rhs) noexcept
{
lhs.swap(rhs);
}
} // namespace Glib
#endif /* _GLIBMM_REFPTR_H */