Chris@16: // Copyright David Abrahams 2002.
Chris@16: // Distributed under the Boost Software License, Version 1.0. (See
Chris@16: // accompanying file LICENSE_1_0.txt or copy at
Chris@16: // http://www.boost.org/LICENSE_1_0.txt)
Chris@16: #ifndef OBJECT_MANAGER_DWA2002614_HPP
Chris@16: # define OBJECT_MANAGER_DWA2002614_HPP
Chris@16: 
Chris@16: # include <boost/python/handle.hpp>
Chris@16: # include <boost/python/cast.hpp>
Chris@16: # include <boost/python/converter/pyobject_traits.hpp>
Chris@16: # include <boost/type_traits/object_traits.hpp>
Chris@16: # include <boost/mpl/if.hpp>
Chris@16: # include <boost/python/detail/indirect_traits.hpp>
Chris@16: # include <boost/mpl/bool.hpp>
Chris@16: 
Chris@16: // Facilities for dealing with types which always manage Python
Chris@16: // objects. Some examples are object, list, str, et. al. Different
Chris@16: // to_python/from_python conversion rules apply here because in
Chris@16: // contrast to other types which are typically embedded inside a
Chris@16: // Python object, these are wrapped around a Python object. For most
Chris@16: // object managers T, a C++ non-const T reference argument does not
Chris@16: // imply the existence of a T lvalue embedded in the corresponding
Chris@16: // Python argument, since mutating member functions on T actually only
Chris@16: // modify the held Python object.
Chris@16: //
Chris@16: // handle<T> is an object manager, though strictly speaking it should
Chris@16: // not be. In other words, even though mutating member functions of
Chris@16: // hanlde<T> actually modify the handle<T> and not the T object,
Chris@16: // handle<T>& arguments of wrapped functions will bind to "rvalues"
Chris@16: // wrapping the actual Python argument, just as with other object
Chris@16: // manager classes. Making an exception for handle<T> is simply not
Chris@16: // worth the trouble.
Chris@16: //
Chris@16: // borrowed<T> cv* is an object manager so that we can use the general
Chris@16: // to_python mechanisms to convert raw Python object pointers to
Chris@16: // python, without the usual semantic problems of using raw pointers.
Chris@16: 
Chris@16: 
Chris@16: // Object Manager Concept requirements:
Chris@16: //
Chris@16: //    T is an Object Manager
Chris@16: //    p is a PyObject*
Chris@16: //    x is a T
Chris@16: //
Chris@16: //    * object_manager_traits<T>::is_specialized == true
Chris@16: //
Chris@16: //    * T(detail::borrowed_reference(p))
Chris@16: //        Manages p without checking its type
Chris@16: //
Chris@16: //    * get_managed_object(x, boost::python::tag)
Chris@16: //        Convertible to PyObject*
Chris@16: //
Chris@16: // Additional requirements if T can be converted from_python:
Chris@16: //
Chris@16: //    * T(object_manager_traits<T>::adopt(p))
Chris@16: //        steals a reference to p, or throws a TypeError exception if
Chris@16: //        p doesn't have an appropriate type. May assume p is non-null
Chris@16: //
Chris@16: //    * X::check(p)
Chris@16: //        convertible to bool. True iff T(X::construct(p)) will not
Chris@16: //        throw.
Chris@16: 
Chris@16: // Forward declarations
Chris@16: //
Chris@16: namespace boost { namespace python
Chris@16: {
Chris@16:   namespace api
Chris@16:   {
Chris@16:     class object; 
Chris@16:   }
Chris@16: }}
Chris@16: 
Chris@16: namespace boost { namespace python { namespace converter { 
Chris@16: 
Chris@16: 
Chris@16: // Specializations for handle<T>
Chris@16: template <class T>
Chris@16: struct handle_object_manager_traits
Chris@16:     : pyobject_traits<typename T::element_type>
Chris@16: {
Chris@16:  private:
Chris@16:   typedef pyobject_traits<typename T::element_type> base;
Chris@16:   
Chris@16:  public:
Chris@16:   BOOST_STATIC_CONSTANT(bool, is_specialized = true);
Chris@16: 
Chris@16:   // Initialize with a null_ok pointer for efficiency, bypassing the
Chris@16:   // null check since the source is always non-null.
Chris@16:   static null_ok<typename T::element_type>* adopt(PyObject* p)
Chris@16:   {
Chris@16:       return python::allow_null(base::checked_downcast(p));
Chris@16:   }
Chris@16: };
Chris@16: 
Chris@16: template <class T>
Chris@16: struct default_object_manager_traits
Chris@16: {
Chris@16:     BOOST_STATIC_CONSTANT(
Chris@16:         bool, is_specialized = python::detail::is_borrowed_ptr<T>::value
Chris@16:         );
Chris@16: };
Chris@16: 
Chris@16: template <class T>
Chris@16: struct object_manager_traits
Chris@16:     : mpl::if_c<
Chris@16:          is_handle<T>::value
Chris@16:        , handle_object_manager_traits<T>
Chris@16:        , default_object_manager_traits<T>
Chris@16:     >::type
Chris@16: {
Chris@16: };
Chris@16: 
Chris@16: //
Chris@16: // Traits for detecting whether a type is an object manager or a
Chris@16: // (cv-qualified) reference to an object manager.
Chris@16: // 
Chris@16: 
Chris@16: template <class T>
Chris@16: struct is_object_manager
Chris@16:     : mpl::bool_<object_manager_traits<T>::is_specialized>
Chris@16: {
Chris@16: };
Chris@16: 
Chris@16: # ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
Chris@16: template <class T>
Chris@16: struct is_reference_to_object_manager
Chris@16:     : mpl::false_
Chris@16: {
Chris@16: };
Chris@16: 
Chris@16: template <class T>
Chris@16: struct is_reference_to_object_manager<T&>
Chris@16:     : is_object_manager<T>
Chris@16: {
Chris@16: };
Chris@16: 
Chris@16: template <class T>
Chris@16: struct is_reference_to_object_manager<T const&>
Chris@16:     : is_object_manager<T>
Chris@16: {
Chris@16: };
Chris@16: 
Chris@16: template <class T>
Chris@16: struct is_reference_to_object_manager<T volatile&>
Chris@16:     : is_object_manager<T>
Chris@16: {
Chris@16: };
Chris@16: 
Chris@16: template <class T>
Chris@16: struct is_reference_to_object_manager<T const volatile&>
Chris@16:     : is_object_manager<T>
Chris@16: {
Chris@16: };
Chris@16: # else
Chris@16: 
Chris@16: namespace detail
Chris@16: {
Chris@16:   typedef char (&yes_reference_to_object_manager)[1];
Chris@16:   typedef char (&no_reference_to_object_manager)[2];
Chris@16: 
Chris@16:   // A number of nastinesses go on here in order to work around MSVC6
Chris@16:   // bugs.
Chris@16:   template <class T>
Chris@16:   struct is_object_manager_help
Chris@16:   {
Chris@16:       typedef typename mpl::if_<
Chris@16:           is_object_manager<T>
Chris@16:           , yes_reference_to_object_manager
Chris@16:           , no_reference_to_object_manager
Chris@16:           >::type type;
Chris@16: 
Chris@16:       // If we just use the type instead of the result of calling this
Chris@16:       // function, VC6 will ICE.
Chris@16:       static type call();
Chris@16:   };
Chris@16: 
Chris@16:   // A set of overloads for each cv-qualification. The same argument
Chris@16:   // is passed twice: the first one is used to unwind the cv*, and the
Chris@16:   // second one is used to avoid relying on partial ordering for
Chris@16:   // overload resolution.
Chris@16:   template <class U>
Chris@16:   typename is_object_manager_help<U>
Chris@16:   is_object_manager_helper(U*, void*);
Chris@16:   
Chris@16:   template <class U>
Chris@16:   typename is_object_manager_help<U>
Chris@16:   is_object_manager_helper(U const*, void const*);
Chris@16:   
Chris@16:   template <class U>
Chris@16:   typename is_object_manager_help<U>
Chris@16:   is_object_manager_helper(U volatile*, void volatile*);
Chris@16:   
Chris@16:   template <class U>
Chris@16:   typename is_object_manager_help<U>
Chris@16:   is_object_manager_helper(U const volatile*, void const volatile*);
Chris@16:   
Chris@16:   template <class T>
Chris@16:   struct is_reference_to_object_manager_nonref
Chris@16:       : mpl::false_
Chris@16:   {
Chris@16:   };
Chris@16: 
Chris@16:   template <class T>
Chris@16:   struct is_reference_to_object_manager_ref
Chris@16:   {
Chris@16:       static T sample_object;
Chris@16:       BOOST_STATIC_CONSTANT(
Chris@16:         bool, value
Chris@16:         = (sizeof(is_object_manager_helper(&sample_object, &sample_object).call())
Chris@16:             == sizeof(detail::yes_reference_to_object_manager)
Chris@16:           )
Chris@16:         );
Chris@16:       typedef mpl::bool_<value> type;
Chris@16:   };
Chris@16: }
Chris@16: 
Chris@16: template <class T>
Chris@16: struct is_reference_to_object_manager
Chris@16:     : mpl::if_<
Chris@16:         is_reference<T>
Chris@16:         , detail::is_reference_to_object_manager_ref<T>
Chris@16:         , detail::is_reference_to_object_manager_nonref<T>
Chris@16:     >::type
Chris@16: {
Chris@16: };
Chris@16: # endif 
Chris@16: 
Chris@16: }}} // namespace boost::python::converter
Chris@16: 
Chris@16: #endif // OBJECT_MANAGER_DWA2002614_HPP