- Add extended support for casting between different types

of smart_ptr


git-svn-id: svn://svn.gna.org/svn/sgpemv2/trunk@507 3ecf2c5c-341e-0410-92b4-d18e462d057c

src/templates/smartp.hh

@@ -44,6 +44,10 @@ namespace memory {
    */
   template<typename T, bool isArray = false>
   class smart_ptr {
+    
+    template<typename T2, bool isArray2>
+    friend class smart_ptr;
+    
   public:
 
     /** \brief An alias for the smart_ptr which contains null 
@@ -117,36 +121,38 @@ namespace memory {
      * \return The number of references */
     inline unsigned int alive_refs() const throw();
 
-
     /** \brief Dynamic cast the stored pointer 
-     * to another type
+     * to another type, returning a smart_ptr
      *
      * This functions tries to cast the stored
      * object to the given type.
      *
-     * \param U The type to cast to.
-     * \return A reference of the casted type
+     * \param U The type to cast the stored pointer to
+     * \return A smart_ptr of the wanted type
      * \exception bad_alloc Raise this exception if 
-     * the cast isn't successful.
+     * the cast isn't successful or doable
      */
     template<typename U>
-    inline U& cast_to() throw(std::bad_cast);
+    inline smart_ptr<U,isArray> cast_to() throw(std::bad_cast);
 
     /** \brief Dynamic cast the stored pointer 
-     * to another type
+     * to another type, returning a smart_ptr
      *
      * This functions tries to cast the stored
      * object to the given type. 
      *
-     * \param U The type to cast to.
-     * \return A const reference of the casted type
+     * \param U The type to cast the stored pointer to
+     * \return A smart_ptr of the wanted type
      * \exception bad_alloc Raise this exception if 
-     * the cast isn't successful.
+     * the cast isn't successful or doable
      */
     template<typename U>
-    inline const U& cast_to() const throw(std::bad_cast);
+    inline const smart_ptr<U,isArray> cast_to() const throw(std::bad_cast);
     
   private:
+    template<typename U>
+    smart_ptr(const smart_ptr<U,isArray>& sptr) throw(std::bad_cast);
+
     struct contents_type {
       T*            ptr;
       unsigned int  rc;

src/templates/smartp.tcc

@@ -143,25 +143,33 @@ namespace memory {
 
   template<typename T, bool isArray>
   template<typename U>
-  U& 
-  smart_ptr<T,isArray>::cast_to() throw(std::bad_cast) 
+  smart_ptr<U, isArray>
+  smart_ptr<T, isArray>::cast_to() throw(std::bad_cast) 
   {
-    if(_contents->ptr != 0)
-      return dynamic_cast<U&>(*_contents->ptr);
-    else
-      throw std::bad_cast();
+    return smart_ptr<U, isArray>(*this);
   }
 
 
   template<typename T, bool isArray>
   template<typename U>
-  const U&
+  const smart_ptr<U, isArray>
   smart_ptr<T, isArray>::cast_to() const throw(std::bad_cast)
   {
-    if(_contents->ptr != 0)
-      return dynamic_cast<U&>(*_contents->ptr);
-    else
+    return smart_ptr<U, isArray>(*this);
+  }
+
+
+  template<typename T, bool isArray>
+  template<typename U>
+  smart_ptr<T,isArray>::smart_ptr(const smart_ptr<U,isArray>& sptr) 
+    throw(std::bad_cast)
+  {
+    if(!sptr._contents->ptr || dynamic_cast<T*>(sptr._contents->ptr) == 0)
       throw std::bad_cast();
+    
+    // I know, I know... this is Evil(TM):
+    _contents = reinterpret_cast<typename smart_ptr<T,isArray>::contents_type*>(sptr._contents);
+    (_contents->rc)++;
   }
 
 } //~ namespace memory