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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 |