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 AS_TO_PYTHON_FUNCTION_DWA2002121_HPP
Chris@16: # define AS_TO_PYTHON_FUNCTION_DWA2002121_HPP
Chris@16: # include <boost/python/converter/to_python_function_type.hpp>
Chris@16: 
Chris@16: namespace boost { namespace python { namespace converter { 
Chris@16: 
Chris@16: // Given a typesafe to_python conversion function, produces a
Chris@16: // to_python_function_t which can be registered in the usual way.
Chris@16: template <class T, class ToPython>
Chris@16: struct as_to_python_function
Chris@16: {
Chris@16:     // Assertion functions used to prevent wrapping of converters
Chris@16:     // which take non-const reference parameters. The T* argument in
Chris@16:     // the first overload ensures it isn't used in case T is a
Chris@16:     // reference.
Chris@16:     template <class U>
Chris@16:     static void convert_function_must_take_value_or_const_reference(U(*)(T), int, T* = 0) {}
Chris@16:     template <class U>
Chris@16:     static void convert_function_must_take_value_or_const_reference(U(*)(T const&), long ...) {}
Chris@16:         
Chris@16:     static PyObject* convert(void const* x)
Chris@16:     {
Chris@16:         convert_function_must_take_value_or_const_reference(&ToPython::convert, 1L);
Chris@16:         
Chris@16:         // Yes, the const_cast below opens a hole in const-correctness,
Chris@16:         // but it's needed to convert auto_ptr<U> to python.
Chris@16:         //
Chris@16:         // How big a hole is it?  It allows ToPython::convert() to be
Chris@16:         // a function which modifies its argument. The upshot is that
Chris@16:         // client converters applied to const objects may invoke
Chris@16:         // undefined behavior. The damage, however, is limited by the
Chris@16:         // use of the assertion function. Thus, the only way this can
Chris@16:         // modify its argument is if T is an auto_ptr-like type. There
Chris@16:         // is still a const-correctness hole w.r.t. auto_ptr<U> const,
Chris@16:         // but c'est la vie.
Chris@16:         return ToPython::convert(*const_cast<T*>(static_cast<T const*>(x)));
Chris@16:     }
Chris@16: #ifndef BOOST_PYTHON_NO_PY_SIGNATURES
Chris@16:     static PyTypeObject const * get_pytype() { return ToPython::get_pytype(); }
Chris@16: #endif
Chris@16: };
Chris@16: 
Chris@16: }}} // namespace boost::python::converter
Chris@16: 
Chris@16: #endif // AS_TO_PYTHON_FUNCTION_DWA2002121_HPP