source: NonGTP/Boost/boost/python/cast.hpp @ 857

Revision 857, 3.0 KB checked in by igarcia, 19 years ago (diff)
RevLine 
[857]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 CAST_DWA200269_HPP
6# define CAST_DWA200269_HPP
7
8# include <boost/python/detail/prefix.hpp>
9
10# include <boost/type_traits/same_traits.hpp>
11# include <boost/type_traits/cv_traits.hpp>
12# include <boost/type.hpp>
13# include <boost/python/base_type_traits.hpp>
14# include <boost/python/detail/convertible.hpp>
15
16namespace boost { namespace python {
17
18namespace detail
19{
20  template <class Source, class Target> inline Target* upcast_impl(Source*, Target*);
21 
22  template <class Source, class Target>
23  inline Target* upcast(Source* p, yes_convertible, no_convertible, Target*)
24  {
25      return p;
26  }
27
28  template <class Source, class Target>
29  inline Target* upcast(Source* p, no_convertible, no_convertible, Target*)
30  {
31      typedef typename base_type_traits<Source>::type base;
32     
33      return detail::upcast_impl((base*)p, (Target*)0);
34  }
35
36  template <bool is_same = true>
37  struct upcaster
38  {
39      template <class T>
40      static inline T* execute(T* x, T*) { return x; }
41  };
42 
43  template <>
44  struct upcaster<false>
45  {
46      template <class Source, class Target>
47      static inline Target* execute(Source* x, Target*)
48      {
49          return detail::upcast(
50              x, detail::convertible<Target*>::check(x)
51              , detail::convertible<Source*>::check((Target*)0)
52              , (Target*)0);
53      }
54  };
55
56
57  template <class Target, class Source>
58  inline Target* downcast(Source* p, yes_convertible)
59  {
60      return static_cast<Target*>(p);
61  }
62
63  template <class Target, class Source>
64  inline Target* downcast(Source* p, no_convertible, boost::type<Target>* = 0)
65  {
66      typedef typename base_type_traits<Source>::type base;
67      return (Target*)detail::downcast<base>(p, convertible<Source*>::check((base*)0));
68  }
69
70  template <class T>
71  inline void assert_castable(boost::type<T>* = 0)
72  {
73      typedef char must_be_a_complete_type[sizeof(T)];
74  }
75
76  template <class Source, class Target>
77  inline Target* upcast_impl(Source* x, Target*)
78  {
79      typedef typename add_cv<Source>::type src_t;
80      typedef typename add_cv<Target>::type target_t;
81      bool const same = is_same<src_t,target_t>::value;
82     
83      return detail::upcaster<same>::execute(x, (Target*)0);
84  }
85}
86
87template <class Target, class Source>
88inline Target* upcast(Source* x, Target* = 0)
89{
90    detail::assert_castable<Source>();
91    detail::assert_castable<Target>();
92    return detail::upcast_impl(x, (Target*)0);
93   
94}
95
96template <class Target, class Source>
97inline Target* downcast(Source* x, Target* = 0)
98{
99    detail::assert_castable<Source>();
100    detail::assert_castable<Target>();
101    return detail::downcast<Target>(x, detail::convertible<Source*>::check((Target*)0));
102}
103
104}} // namespace boost::python
105
106#endif // CAST_DWA200269_HPP
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