// 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 |