Added support for target_type() member function (returns an std::type_info of

the underlying function object) and casting to retrieve the underyling target.


[SVN r11360]

include/boost/function/function_base.hpp

@@ -19,6 +19,8 @@
 #include <string>
 #include <stdexcept>
 #include <memory>
+#include <new>
+#include <typeinfo>
 #include <boost/config.hpp>
 #include <boost/type_traits.hpp>
 
@@ -78,9 +80,11 @@ namespace boost {
       union any_pointer 
       {
         void* obj_ptr;
+        const void* const_obj_ptr;
         void (*func_ptr)();
 
         explicit any_pointer(void* p) : obj_ptr(p) {}
+        explicit any_pointer(const void* p) : const_obj_ptr(p) {}
         explicit any_pointer(void (*p)()) : func_ptr(p) {}
       };
 
@@ -109,7 +113,11 @@ namespace boost {
       };
 
       // The operation type to perform on the given functor/function pointer
-      enum functor_manager_operation_type { clone_functor, destroy_functor };
+      enum functor_manager_operation_type { 
+        clone_functor, 
+        destroy_functor,
+        retrieve_type_info
+      };
 
       // Tags used to decide between function and function object pointers.
       struct function_ptr_tag {};
@@ -140,8 +148,10 @@ namespace boost {
         {
           if (op == clone_functor)
             return function_ptr;
-          else
+          else if (op == destroy_functor)
             return any_pointer(static_cast<void (*)()>(0));
+          else
+            return any_pointer(&typeid(Functor));
         }
 
         // For function object pointers, we clone the pointer to each 
@@ -171,7 +181,7 @@ namespace boost {
 #  endif // BOOST_NO_STD_ALLOCATOR
             return any_pointer(static_cast<void*>(new_f));
           }
-          else {
+          else if (op == destroy_functor) {
             /* Cast from the void pointer to the functor pointer type */
             functor_type* f = 
               reinterpret_cast<functor_type*>(function_obj_ptr.obj_ptr);
@@ -190,8 +200,10 @@ namespace boost {
 
             return any_pointer(static_cast<void*>(0));
           }
+          else {
+            return any_pointer(&typeid(Functor));
+          }
         }
-
       public:
         /* Dispatch to an appropriate manager based on whether we have a
            function pointer or a function object pointer. */

include/boost/function/function_template.hpp

@@ -46,6 +46,8 @@ namespace boost {
         virtual R call(BOOST_FUNCTION_PARMS) const = 0;
         virtual BOOST_FUNCTION_INVOKER_BASE* clone() const = 0;
         virtual void destroy(BOOST_FUNCTION_INVOKER_BASE*) = 0;
+        virtual const std::type_info& type() const = 0;
+        virtual any_pointer pointer() const = 0;
       };
 #endif // BOOST_FUNCTION_USE_VIRTUAL_FUNCTIONS
 
@@ -113,8 +115,18 @@ namespace boost {
 #  endif // BOOST_NO_STD_ALLOCATOR
         }
 
+        virtual const std::type_info& type() const
+        {
+          return typeid(FunctionPtr);
+        }
+
+        virtual any_pointer pointer() const
+        {
+          return any_pointer(reinterpret_cast<void (*)()>(function_ptr));
+        }
+
       private:
-        FunctionPtr function_ptr;
+        mutable FunctionPtr function_ptr;
 #else
         static R invoke(any_pointer function_ptr BOOST_FUNCTION_COMMA
                         BOOST_FUNCTION_PARMS)
@@ -190,8 +202,18 @@ namespace boost {
 #    endif // BOOST_NO_STD_ALLOCATOR
         }
 
+        virtual const std::type_info& type() const
+        {
+          return typeid(FunctionPtr);
+        }
+
+        virtual any_pointer pointer() const
+        {
+          return any_pointer(reinterpret_cast<void (*)()>(function_ptr));
+        }
+
       private:
-        FunctionPtr function_ptr;
+        mutable FunctionPtr function_ptr;
 #  else
         static unusable invoke(any_pointer function_ptr BOOST_FUNCTION_COMMA
                                BOOST_FUNCTION_PARMS)
@@ -268,6 +290,16 @@ namespace boost {
 #endif // BOOST_NO_STD_ALLOCATOR
         }
 
+        virtual const std::type_info& type() const
+        {
+          return typeid(FunctionObj);
+        }
+
+        virtual any_pointer pointer() const
+        {
+          return any_pointer(&function_obj);
+        }
+
       private:
         mutable FunctionObj function_obj;
 #else
@@ -346,6 +378,16 @@ namespace boost {
 #  endif // BOOST_NO_STD_ALLOCATOR
         }
 
+        virtual const std::type_info& type() const
+        {
+          return typeid(FunctionObj);
+        }
+
+        virtual any_pointer pointer() const
+        {
+          return any_pointer(&function_obj);
+        }
+
       private:
         mutable FunctionObj function_obj;
 #  else
@@ -601,7 +643,73 @@ namespace boost {
 #endif // BOOST_FUNCTION_USE_VIRTUAL_FUNCTIONS
     }
 
+    const std::type_info& target_type() const
+    {
+      if (this->empty())
+        return typeid(void);
+      else {
+#ifdef BOOST_FUNCTION_USE_VIRTUAL_FUNCTIONS
+        impl_type* i = reinterpret_cast<impl_type*>(impl);
+        return i->type();
+#else
+        detail::function::any_pointer p = 
+          manager(functor, detail::function::retrieve_type_info);
+        return *static_cast<const std::type_info*>(p.const_obj_ptr);
+#endif // BOOST_FUNCTION_USE_VIRTUAL_FUNCTIONS
+      }
+    }
+
+    template<typename To>
+    To& cast(To* = 0)
+    {
+      assert(typeid(To) != typeid(void));
+      assert(typeid(To) == this->target_type());
+      typedef typename detail::function::IF<(is_pointer<To>::value),
+                         detail::function::function_ptr_tag,
+                         detail::function::function_obj_tag>::type tag;
+
+#ifdef BOOST_FUNCTION_USE_VIRTUAL_FUNCTIONS
+      impl_type* i = reinterpret_cast<impl_type*>(impl);
+      return cast_helper<To>(i->pointer(), tag());
+#else
+      return cast_helper<To>(functor, tag());
+#endif // BOOST_FUNCTION_USE_VIRTUAL_FUNCTIONS
+    }
+
+    template<typename To>
+    const To& cast(To* = 0) const
+    {
+      assert(typeid(To) != typeid(void));
+      assert(typeid(To) == this->target_type());
+      typedef typename detail::function::IF<(is_pointer<To>::value),
+                         detail::function::function_ptr_tag,
+                         detail::function::function_obj_tag>::type tag;
+
+#ifdef BOOST_FUNCTION_USE_VIRTUAL_FUNCTIONS
+      impl_type* i = reinterpret_cast<impl_type*>(impl);
+      return cast_helper<To>(i->pointer(), tag());
+#else
+      return cast_helper<To>(functor, tag());
+#endif // BOOST_FUNCTION_USE_VIRTUAL_FUNCTIONS
+    }
+
   private:
+    template<typename To>
+    To& cast_helper(detail::function::any_pointer p, 
+                    detail::function::function_ptr_tag,
+                    To* = 0) const
+    {
+      return reinterpret_cast<To>(p.func_ptr);
+    }
+
+    template<typename To>
+    To& cast_helper(detail::function::any_pointer p, 
+                    detail::function::function_obj_tag,
+                    To* = 0) const
+    {
+      return *static_cast<To*>(p.obj_ptr);
+    }
+
     void assign_to_own(const BOOST_FUNCTION_FUNCTION& f)
     {
       if (!f.empty()) {
@@ -731,6 +839,36 @@ namespace boost {
   {
     f1.swap(f2);
   }                   
+
+  template<typename To, typename R 
+           BOOST_FUNCTION_COMMA BOOST_FUNCTION_TEMPLATE_PARMS ,
+           typename Policy, typename Mixin, typename Allocator>
+  inline To& function_cast(BOOST_FUNCTION_FUNCTION<
+                             R BOOST_FUNCTION_COMMA
+                             BOOST_FUNCTION_TEMPLATE_ARGS ,
+                             Policy,
+                             Mixin,
+                             Allocator
+                           >& f,
+                           To* = 0)
+  {
+    return f.template cast<To>();
+  }
+
+  template<typename To, typename R 
+           BOOST_FUNCTION_COMMA BOOST_FUNCTION_TEMPLATE_PARMS ,
+           typename Policy, typename Mixin, typename Allocator>
+  inline const To& function_cast(const BOOST_FUNCTION_FUNCTION<
+                                         R BOOST_FUNCTION_COMMA
+                                         BOOST_FUNCTION_TEMPLATE_ARGS ,
+                                         Policy,
+                                         Mixin,
+                                         Allocator
+                                       >& f,
+                                 To* = 0)
+  {
+    return f.template cast<To>();
+  }
 }
 
 // Cleanup after ourselves...