1// Copyright David Abrahams and Nikolay Mladenov 2003.
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 RETURN_ARG_DWA2003719_HPP
6# define RETURN_ARG_DWA2003719_HPP
7# include <boost/python/default_call_policies.hpp>
8# include <boost/python/detail/none.hpp>
9# include <boost/python/detail/value_arg.hpp>
10
11#ifndef BOOST_PYTHON_NO_PY_SIGNATURES
12# include <boost/python/converter/pytype_function.hpp>
13#endif
14
15# include <boost/type_traits/add_reference.hpp>
16# include <boost/type_traits/add_const.hpp>
17
18# include <boost/mpl/int.hpp>
19# include <boost/mpl/at.hpp>
20
21# include <boost/static_assert.hpp>
22# include <boost/python/refcount.hpp>
23
24# include <cstddef>
25
26namespace boost { namespace python {
27
28namespace detail
29{
30 template <std::size_t>
31 struct return_arg_pos_argument_must_be_positive
32# if defined(__GNUC__) || defined(__EDG__)
33 {}
34# endif
35 ;
36
37 struct return_none
38 {
39 template <class T> struct apply
40 {
41 struct type
42 {
43 static bool convertible()
44 {
45 return true;
46 }
47
48 PyObject *operator()( typename value_arg<T>::type ) const
49 {
50 return none();
51 }
52#ifndef BOOST_PYTHON_NO_PY_SIGNATURES
53 PyTypeObject const *get_pytype() const { return converter::expected_pytype_for_arg<T>::get_pytype() ; }
54#endif
55 };
56 };
57 };
58}
59
60template <
61 std::size_t arg_pos=1
62 , class Base = default_call_policies
63>
64struct return_arg : Base
65{
66 private:
67 BOOST_STATIC_CONSTANT(bool, legal = arg_pos > 0);
68
69 public:
70 typedef typename mpl::if_c<
71 legal
72 , detail::return_none
73 , detail::return_arg_pos_argument_must_be_positive<arg_pos>
74 // we could default to the base result_converter in case or
75 // arg_pos==0 since return arg 0 means return result, but I
76 // think it is better to issue an error instead, cause it can
77 // lead to confusions
78 >::type result_converter;
79
80 template <class ArgumentPackage>
81 static PyObject* postcall(ArgumentPackage const& args, PyObject* result)
82 {
83 // In case of arg_pos == 0 we could simply return Base::postcall,
84 // but this is redundant
85 BOOST_STATIC_ASSERT(arg_pos > 0);
86
87 result = Base::postcall(args,result);
88 if (!result)
89 return 0;
90 Py_DECREF(result);
91 return incref( detail::get(mpl::int_<arg_pos-1>(),args) );
92 }
93
94 template <class Sig>
95 struct extract_return_type : mpl::at_c<Sig, arg_pos>
96 {
97 };
98
99};
100
101template <
102 class Base = default_call_policies
103 >
104struct return_self
105 : return_arg<1,Base>
106{};
107
108}} // namespace boost::python
109
110#endif // RETURN_ARG_DWA2003719_HPP
111

source code of boost/boost/python/return_arg.hpp