Class function_base

mars/boost/function/function_base.hpp:620–715

* The function_base class contains the basic elements needed for the * function1, function2, function3, etc. classes. It is common to all * functions (and as such can be used to tell if we have one of the * functionN objects). */

 * functionN objects).
 */
class function_base
{
public:
  function_base() : vtable(0) { }

  /** Determine if the function is empty (i.e., has no target). */
  bool empty() const { return !vtable; }

  /** Retrieve the type of the stored function object, or BOOST_SP_TYPEID(void)
      if this is empty. */
  const detail::sp_typeinfo& target_type() const
  {
    if (!vtable) return BOOST_SP_TYPEID(void);

    detail::function::function_buffer type;
    get_vtable()->manager(functor, type, detail::function::get_functor_type_tag);
    return *type.type.type;
  }

  template<typename Functor>
    Functor* target()
    {
      if (!vtable) return 0;

      detail::function::function_buffer type_result;
      type_result.type.type = &BOOST_SP_TYPEID(Functor);
      type_result.type.const_qualified = is_const<Functor>::value;
      type_result.type.volatile_qualified = is_volatile<Functor>::value;
      get_vtable()->manager(functor, type_result, 
                      detail::function::check_functor_type_tag);
      return static_cast<Functor*>(type_result.obj_ptr);
    }

  template<typename Functor>
    const Functor* target() const
    {
      if (!vtable) return 0;

      detail::function::function_buffer type_result;
      type_result.type.type = &BOOST_SP_TYPEID(Functor);
      type_result.type.const_qualified = true;
      type_result.type.volatile_qualified = is_volatile<Functor>::value;
      get_vtable()->manager(functor, type_result, 
                      detail::function::check_functor_type_tag);
      // GCC 2.95.3 gets the CV qualifiers wrong here, so we
      // can't do the static_cast that we should do.
      return static_cast<const Functor*>(type_result.obj_ptr);
    }

  template<typename F>
    bool contains(const F& f) const
    {
      if (const F* fp = this->template target<F>())
      {
        return function_equal(*fp, f);
      } else {
        return false;
      }