* This file is part of LyX, the document processor.
* Licence details can be found in the file COPYING.
*
- * \author Yonat Sharon http://ootips.org/yonat/
+ * \author Angus Leeming
*
- * simple copy-on-create/assign pointer.
+ * A templated class that can serve as a pointer to an object, with the
+ * property that when the copied_ptr is copied, it creates its own copy
+ * of the object pointed to as well.
*
- * Note: If the actual object pointed to belongs to a derived class,
- * then copied_ptr will not create a copy of the derived class object,
- * but a new base class object.
- * If you want to use a polymorphic copy-on-assign pointer, use
- * cloned_ptr.
+ * The implementation was based originally on Yonat Sharon's copied_ptr templated
+ * class, as described at http://ootips.org/yonat/, but has evolved toward's
+ * Herb Sutter's HolderPtr, as described at http://www.gotw.ca/gotw/062.htm.
+ * (Note, HolderPtr became ValuePtr in his book, More Exceptional C++.)
+ *
+ * Warning: if the class stores 'Base * ptr_', but the actual object pointed to
+ * belongs to a derived class, then you must specialise memory_traits<Base> so that
+ * its clone and destroy member functions do the right thing. Otherwise, you'll
+ * end up slicing the data.
*/
#ifndef COPIED_PTR_H
namespace support {
template <typename T>
+struct memory_traits {
+ static T * clone(T const * ptr) { return new T(*ptr); }
+ static void destroy(T * ptr) { delete ptr; }
+};
+
+
+template <typename T, typename Traits=memory_traits<T> >
class copied_ptr {
public:
explicit copied_ptr(T * = 0);
- ~copied_ptr();
copied_ptr(copied_ptr const &);
+ ~copied_ptr();
copied_ptr & operator=(copied_ptr const &);
T & operator*() const;
private:
T * ptr_;
- void copy(copied_ptr const &);
};
-template <typename T>
-copied_ptr<T>::copied_ptr(T * p)
+template <typename T, typename Traits>
+copied_ptr<T, Traits>::copied_ptr(T * p)
: ptr_(p)
{}
-template <typename T>
-copied_ptr<T>::~copied_ptr()
-{
- delete ptr_;
-}
+template <typename T, typename Traits>
+copied_ptr<T, Traits>::copied_ptr(copied_ptr const & other)
+ : ptr_(other.ptr_ ? Traits::clone(other.ptr_) : 0)
+{}
-template <typename T>
-copied_ptr<T>::copied_ptr(copied_ptr const & other)
+template <typename T, typename Traits>
+copied_ptr<T, Traits>::~copied_ptr()
{
- copy(other.get());
+ Traits::destroy(ptr_);
}
-template <typename T>
-copied_ptr<T> & copied_ptr<T>::operator=(copied_ptr const & other)
+template <typename T, typename Traits>
+copied_ptr<T, Traits> & copied_ptr<T, Traits>::operator=(copied_ptr const & other)
{
- if (&other != this) {
- delete ptr_;
- copy(other);
- }
- return *this;
+ if (&other != this) {
+ copied_ptr temp(other);
+ std::swap(ptr_, temp.ptr_);
+ }
+ return *this;
}
-template <typename T>
-T & copied_ptr<T>::operator*() const
+template <typename T, typename Traits>
+T & copied_ptr<T, Traits>::operator*() const
{
return *ptr_;
}
-template <typename T>
-T * copied_ptr<T>::operator->() const
+template <typename T, typename Traits>
+T * copied_ptr<T, Traits>::operator->() const
{
return ptr_;
}
-template <typename T>
-T * copied_ptr<T>::get() const
+template <typename T, typename Traits>
+T * copied_ptr<T, Traits>::get() const
{
return ptr_;
}
-
-template <typename T>
-void copied_ptr<T>::copy(copied_ptr const & other)
-{
- ptr_ = other.ptr_ ? new T(*other.ptr_) : 0;
-}
-
} // namespace support
} // namespace lyx