| // Copyright David Abrahams 2002. |
| // Distributed under the Boost Software License, Version 1.0. (See |
| // accompanying file LICENSE_1_0.txt or copy at |
| // http://www.boost.org/LICENSE_1_0.txt) |
| #ifndef AS_TO_PYTHON_FUNCTION_DWA2002121_HPP |
| # define AS_TO_PYTHON_FUNCTION_DWA2002121_HPP |
| # include <boost/python/converter/to_python_function_type.hpp> |
| |
| namespace boost { namespace python { namespace converter { |
| |
| // Given a typesafe to_python conversion function, produces a |
| // to_python_function_t which can be registered in the usual way. |
| template <class T, class ToPython> |
| struct as_to_python_function |
| { |
| // Assertion functions used to prevent wrapping of converters |
| // which take non-const reference parameters. The T* argument in |
| // the first overload ensures it isn't used in case T is a |
| // reference. |
| template <class U> |
| static void convert_function_must_take_value_or_const_reference(U(*)(T), int, T* = 0) {} |
| template <class U> |
| static void convert_function_must_take_value_or_const_reference(U(*)(T const&), long ...) {} |
| |
| static PyObject* convert(void const* x) |
| { |
| convert_function_must_take_value_or_const_reference(&ToPython::convert, 1L); |
| |
| // Yes, the const_cast below opens a hole in const-correctness, |
| // but it's needed to convert auto_ptr<U> to python. |
| // |
| // How big a hole is it? It allows ToPython::convert() to be |
| // a function which modifies its argument. The upshot is that |
| // client converters applied to const objects may invoke |
| // undefined behavior. The damage, however, is limited by the |
| // use of the assertion function. Thus, the only way this can |
| // modify its argument is if T is an auto_ptr-like type. There |
| // is still a const-correctness hole w.r.t. auto_ptr<U> const, |
| // but c'est la vie. |
| return ToPython::convert(*const_cast<T*>(static_cast<T const*>(x))); |
| } |
| #ifndef BOOST_PYTHON_NO_PY_SIGNATURES |
| static PyTypeObject const * get_pytype() { return ToPython::get_pytype(); } |
| #endif |
| }; |
| |
| }}} // namespace boost::python::converter |
| |
| #endif // AS_TO_PYTHON_FUNCTION_DWA2002121_HPP |