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 |
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 | { |
69 | 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> |
77 | 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> |
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 | |