1 // Copyright David Abrahams 2002.
2 // Distributed under the Boost Software License, Version 1.0. (See
3 // accompanying file LICENSE_1_0.txt or copy at
4 // http://www.boost.org/LICENSE_1_0.txt)
5 #ifndef IMPLICIT_DWA2002326_HPP
6 # define IMPLICIT_DWA2002326_HPP
7 
8 # include <boost/python/converter/rvalue_from_python_data.hpp>
9 # include <boost/python/converter/registrations.hpp>
10 # include <boost/python/converter/registered.hpp>
11 
12 # include <boost/python/extract.hpp>
13 
14 namespace boost { namespace python { namespace converter {
15 
16 template <class Source, class Target>
17 struct implicit
18 {
convertibleboost::python::converter::implicit19     static void* convertible(PyObject* obj)
20     {
21         // Find a converter which can produce a Source instance from
22         // obj. The user has told us that Source can be converted to
23         // Target, and instantiating construct() below, ensures that
24         // at compile-time.
25         return implicit_rvalue_convertible_from_python(obj, registered<Source>::converters)
26             ? obj : 0;
27     }
28 
constructboost::python::converter::implicit29     static void construct(PyObject* obj, rvalue_from_python_stage1_data* data)
30     {
31         void* storage = ((rvalue_from_python_storage<Target>*)data)->storage.bytes;
32 
33         arg_from_python<Source> get_source(obj);
34         bool convertible = get_source.convertible();
35         BOOST_VERIFY(convertible);
36 
37         new (storage) Target(get_source());
38 
39         // record successful construction
40         data->convertible = storage;
41     }
42 };
43 
44 }}} // namespace boost::python::converter
45 
46 #endif // IMPLICIT_DWA2002326_HPP
47