function_base.hpp:

- Switch over to using is_reference_wrapper instead of homegrown is_ref
  - Identify stateless function objects

function_template.hpp:
  - Optimize away construction/allocator for stateless function objects.


[SVN r12559]

include/boost/function/function_base.hpp

@@ -77,37 +77,6 @@ namespace boost {
         typedef typename select::template Result<Then,Else>::type type;
       };
 
-      // Determine if the incoming argument is a reference_wrapper
-#ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
-      template<typename T>
-      struct is_ref
-      {
-        BOOST_STATIC_CONSTANT(bool, value = false); 
-      };
-
-      template<typename T>
-      struct is_ref<reference_wrapper<T> >
-      {
-        BOOST_STATIC_CONSTANT(bool, value = true);
-      };
-#else // no partial specialization
-      typedef char yes_type;
-      typedef double no_type;
-      
-      no_type is_ref_tester(...);
-
-      template<typename T>
-      yes_type is_ref_tester(reference_wrapper<T>*);
-
-      template<typename T>
-      struct is_ref
-      {
-        static T* t;
-        BOOST_STATIC_CONSTANT(bool, 
-          value = (sizeof(is_ref_tester(t)) == sizeof(yes_type)));
-      };
-#endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
-
       /**
        * A union of a function pointer and a void pointer. This is necessary
        * because 5.2.10/6 allows reinterpret_cast<> to safely cast between 
@@ -161,6 +130,7 @@ namespace boost {
       struct function_obj_tag {};
       struct member_ptr_tag {};
       struct function_obj_ref_tag {};
+      struct stateless_function_obj_tag {};
 
       template<typename F>
       class get_function_tag
@@ -172,10 +142,15 @@ namespace boost {
         typedef typename IF<(is_member_pointer<F>::value),
                             member_ptr_tag,
                             ptr_or_obj_tag>::type ptr_or_obj_or_mem_tag;
-      public:
+
-        typedef typename IF<(is_ref<F>::value),
+        typedef typename IF<(is_reference_wrapper<F>::value),
                              function_obj_ref_tag,
-                             ptr_or_obj_or_mem_tag>::type type;
+                             ptr_or_obj_or_mem_tag>::type or_ref_tag;
+
+      public:
+        typedef typename IF<(is_stateless<F>::value),
+                            stateless_function_obj_tag,
+                            or_ref_tag>::type type;
       };
 
       // The trivial manager does nothing but return the same pointer (if we

include/boost/function/function_template.hpp

@@ -50,10 +50,16 @@
   BOOST_JOIN(function_obj_invoker,BOOST_FUNCTION_NUM_ARGS)
 #define BOOST_FUNCTION_VOID_FUNCTION_OBJ_INVOKER \
   BOOST_JOIN(void_function_obj_invoker,BOOST_FUNCTION_NUM_ARGS)
+#define BOOST_FUNCTION_STATELESS_FUNCTION_OBJ_INVOKER \
+  BOOST_JOIN(stateless_function_obj_invoker,BOOST_FUNCTION_NUM_ARGS)
+#define BOOST_FUNCTION_STATELESS_VOID_FUNCTION_OBJ_INVOKER \
+  BOOST_JOIN(stateless_void_function_obj_invoker,BOOST_FUNCTION_NUM_ARGS)
 #define BOOST_FUNCTION_GET_FUNCTION_INVOKER \
   BOOST_JOIN(get_function_invoker,BOOST_FUNCTION_NUM_ARGS)
 #define BOOST_FUNCTION_GET_FUNCTION_OBJ_INVOKER \
   BOOST_JOIN(get_function_obj_invoker,BOOST_FUNCTION_NUM_ARGS)
+#define BOOST_FUNCTION_GET_STATELESS_FUNCTION_OBJ_INVOKER \
+  BOOST_JOIN(get_stateless_function_obj_invoker,BOOST_FUNCTION_NUM_ARGS)
 
 namespace boost {
   namespace detail {
@@ -124,6 +130,37 @@ namespace boost {
         }
       };
 
+      template<
+        typename FunctionObj,
+        typename R BOOST_FUNCTION_COMMA
+        BOOST_FUNCTION_TEMPLATE_PARMS
+      >
+      struct BOOST_FUNCTION_STATELESS_FUNCTION_OBJ_INVOKER
+      {
+        static R invoke(any_pointer BOOST_FUNCTION_COMMA BOOST_FUNCTION_PARMS)
+        {
+          FunctionObj f;
+          return f(BOOST_FUNCTION_ARGS);
+        }
+      };
+
+      template<
+        typename FunctionObj,
+        typename R BOOST_FUNCTION_COMMA
+        BOOST_FUNCTION_TEMPLATE_PARMS
+      >
+      struct BOOST_FUNCTION_STATELESS_VOID_FUNCTION_OBJ_INVOKER
+      {
+        static unusable invoke(any_pointer BOOST_FUNCTION_COMMA 
+                               BOOST_FUNCTION_PARMS)
+
+        {
+          FunctionObj f;
+          f(BOOST_FUNCTION_ARGS);
+          return unusable();
+        }
+      };
+
       template<
         typename FunctionPtr,
         typename R BOOST_FUNCTION_COMMA
@@ -165,6 +202,28 @@ namespace boost {
                           >
                        >::type type;
       };
+
+      template<
+        typename FunctionObj,
+        typename R BOOST_FUNCTION_COMMA
+        BOOST_FUNCTION_TEMPLATE_PARMS
+       >
+      struct BOOST_FUNCTION_GET_STATELESS_FUNCTION_OBJ_INVOKER
+      {
+        typedef typename IF<(is_void<R>::value),
+                            BOOST_FUNCTION_STATELESS_VOID_FUNCTION_OBJ_INVOKER<
+                            FunctionObj,
+                            R BOOST_FUNCTION_COMMA
+                            BOOST_FUNCTION_TEMPLATE_ARGS
+                          >,
+                          BOOST_FUNCTION_STATELESS_FUNCTION_OBJ_INVOKER<
+                            FunctionObj,
+                            R BOOST_FUNCTION_COMMA
+                            BOOST_FUNCTION_TEMPLATE_ARGS
+                          >
+                       >::type type;
+      };
+
     } // end namespace function
   } // end namespace detail
 
@@ -390,6 +449,22 @@ namespace boost {
       }
     }
     
+    template<typename FunctionObj>
+    void assign_to(FunctionObj f, detail::function::stateless_function_obj_tag)
+    {
+      typedef 
+          typename detail::function::
+                     BOOST_FUNCTION_GET_STATELESS_FUNCTION_OBJ_INVOKER<
+                       FunctionObj,
+                       R BOOST_FUNCTION_COMMA
+                       BOOST_FUNCTION_TEMPLATE_ARGS
+                     >::type
+          invoker_type;
+      invoker = &invoker_type::invoke;
+      function_base::manager = &detail::function::trivial_manager;
+      function_base::functor = detail::function::any_pointer(this);
+    }
+
     typedef result_type (*invoker_type)(detail::function::any_pointer
                                         BOOST_FUNCTION_COMMA
                                         BOOST_FUNCTION_TEMPLATE_ARGS);
@@ -428,7 +503,10 @@ namespace boost {
 #undef BOOST_FUNCTION_VOID_FUNCTION_INVOKER
 #undef BOOST_FUNCTION_FUNCTION_OBJ_INVOKER
 #undef BOOST_FUNCTION_VOID_FUNCTION_OBJ_INVOKER
+#undef BOOST_FUNCTION_STATELESS_FUNCTION_OBJ_INVOKER
+#undef BOOST_FUNCTION_STATELESS_VOID_FUNCTION_OBJ_INVOKER
 #undef BOOST_FUNCTION_GET_FUNCTION_INVOKER
 #undef BOOST_FUNCTION_GET_FUNCTION_OBJ_INVOKER
+#undef BOOST_FUNCTION_GET_STATELESS_FUNCTION_OBJ_INVOKER
 #undef BOOST_FUNCTION_GET_MEM_FUNCTION_INVOKER