1 // Copyright David Abrahams 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 PURE_VIRTUAL_DWA2003810_HPP
6 # define PURE_VIRTUAL_DWA2003810_HPP
7
8 # include <boost/python/def_visitor.hpp>
9 # include <boost/python/default_call_policies.hpp>
10 # include <boost/mpl/push_front.hpp>
11 # include <boost/mpl/pop_front.hpp>
12
13 # include <boost/python/detail/nullary_function_adaptor.hpp>
14
15 namespace boost { namespace python {
16
17 namespace detail
18 {
19 //
20 // @group Helpers for pure_virtual_visitor. {
21 //
22
23 // Raises a Python RuntimeError reporting that a pure virtual
24 // function was called.
25 void BOOST_PYTHON_DECL pure_virtual_called();
26
27 // Replace the two front elements of S with T1 and T2
28 template <class S, class T1, class T2>
29 struct replace_front2
30 {
31 // Metafunction forwarding seemed to confound vc6
32 typedef typename mpl::push_front<
33 typename mpl::push_front<
34 typename mpl::pop_front<
35 typename mpl::pop_front<
36 S
37 >::type
38 >::type
39 , T2
40 >::type
41 , T1
42 >::type type;
43 };
44
45 // Given an MPL sequence representing a member function [object]
46 // signature, returns a new MPL sequence whose return type is
47 // replaced by void, and whose first argument is replaced by C&.
48 template <class C, class S>
49 typename replace_front2<S,void,C&>::type
error_signature(S)50 error_signature(S)
51 {
52 typedef typename replace_front2<S,void,C&>::type r;
53 return r();
54 }
55
56 //
57 // }
58 //
59
60 //
61 // A def_visitor which defines a method as usual, then adds a
62 // corresponding function which raises a "pure virtual called"
63 // exception unless it's been overridden.
64 //
65 template <class PointerToMemberFunction>
66 struct pure_virtual_visitor
67 : def_visitor<pure_virtual_visitor<PointerToMemberFunction> >
68 {
pure_virtual_visitorboost::python::detail::pure_virtual_visitor69 pure_virtual_visitor(PointerToMemberFunction pmf)
70 : m_pmf(pmf)
71 {}
72
73 private:
74 friend class python::def_visitor_access;
75
76 template <class C_, class Options>
visitboost::python::detail::pure_virtual_visitor77 void visit(C_& c, char const* name, Options& options) const
78 {
79 // This should probably be a nicer error message
80 BOOST_STATIC_ASSERT(!Options::has_default_implementation);
81
82 // Add the virtual function dispatcher
83 c.def(
84 name
85 , m_pmf
86 , options.doc()
87 , options.keywords()
88 , options.policies()
89 );
90
91 typedef BOOST_DEDUCED_TYPENAME C_::metadata::held_type held_type;
92
93 // Add the default implementation which raises the exception
94 c.def(
95 name
96 , make_function(
97 detail::nullary_function_adaptor<void(*)()>(pure_virtual_called)
98 , default_call_policies()
99 , detail::error_signature<held_type>(detail::get_signature(m_pmf))
100 )
101 );
102 }
103
104 private: // data members
105 PointerToMemberFunction m_pmf;
106 };
107 }
108
109 //
110 // Passed a pointer to member function, generates a def_visitor which
111 // creates a method that only dispatches to Python if the function has
112 // been overridden, either in C++ or in Python, raising a "pure
113 // virtual called" exception otherwise.
114 //
115 template <class PointerToMemberFunction>
116 detail::pure_virtual_visitor<PointerToMemberFunction>
pure_virtual(PointerToMemberFunction pmf)117 pure_virtual(PointerToMemberFunction pmf)
118 {
119 return detail::pure_virtual_visitor<PointerToMemberFunction>(pmf);
120 }
121
122 }} // namespace boost::python
123
124 #endif // PURE_VIRTUAL_DWA2003810_HPP
125