boost/python/cast.hpp

0001 // Copyright David Abrahams 2002.
0002 // Distributed under the Boost Software License, Version 1.0. (See
0003 // accompanying file LICENSE_1_0.txt or copy at
0004 // http://www.boost.org/LICENSE_1_0.txt)
0005 #ifndef CAST_DWA200269_HPP
0006 # define CAST_DWA200269_HPP
0007
0008 # include <boost/python/detail/prefix.hpp>
0009 # include <boost/python/detail/type_traits.hpp>
0010
0011 # include <boost/type.hpp>
0012 # include <boost/python/base_type_traits.hpp>
0013 # include <boost/python/detail/convertible.hpp>
0014
0015 namespace boost { namespace python {
0016
0017 namespace detail
0018 {
0019   template <class Source, class Target> inline Target* upcast_impl(Source*, Target*);
0020
0021   template <class Source, class Target>
0022   inline Target* upcast(Source* p, yes_convertible, no_convertible, Target*)
0023   {
0024       return p;
0025   }
0026
0027   template <class Source, class Target>
0028   inline Target* upcast(Source* p, no_convertible, no_convertible, Target*)
0029   {
0030       typedef typename base_type_traits<Source>::type base;
0031
0032       return detail::upcast_impl((base*)p, (Target*)0);
0033   }
0034
0035   template <bool is_same = true>
0036   struct upcaster
0037   {
0038       template <class T>
0039       static inline T* execute(T* x, T*) { return x; }
0040   };
0041
0042   template <>
0043   struct upcaster<false>
0044   {
0045       template <class Source, class Target>
0046       static inline Target* execute(Source* x, Target*)
0047       {
0048           return detail::upcast(
0049               x, detail::convertible<Target*>::check(x)
0050               , detail::convertible<Source*>::check((Target*)0)
0051               , (Target*)0);
0052       }
0053   };
0054
0055
0056   template <class Target, class Source>
0057   inline Target* downcast(Source* p, yes_convertible)
0058   {
0059       return static_cast<Target*>(p);
0060   }
0061
0062   template <class Target, class Source>
0063   inline Target* downcast(Source* p, no_convertible, boost::type<Target>* = 0)
0064   {
0065       typedef typename base_type_traits<Source>::type base;
0066       return (Target*)detail::downcast<base>(p, convertible<Source*>::check((base*)0));
0067   }
0068
0069   template <class T>
0070   inline void assert_castable(boost::type<T>* = 0)
0071   {
0072       typedef char must_be_a_complete_type[sizeof(T)] BOOST_ATTRIBUTE_UNUSED;
0073   }
0074
0075   template <class Source, class Target>
0076   inline Target* upcast_impl(Source* x, Target*)
0077   {
0078       typedef typename detail::add_cv<Source>::type src_t;
0079       typedef typename detail::add_cv<Target>::type target_t;
0080       bool const same = detail::is_same<src_t,target_t>::value;
0081
0082       return detail::upcaster<same>::execute(x, (Target*)0);
0083   }
0084 }
0085
0086 template <class Target, class Source>
0087 inline Target* upcast(Source* x, Target* = 0)
0088 {
0089     detail::assert_castable<Source>();
0090     detail::assert_castable<Target>();
0091     return detail::upcast_impl(x, (Target*)0);
0092
0093 }
0094
0095 template <class Target, class Source>
0096 inline Target* downcast(Source* x, Target* = 0)
0097 {
0098     detail::assert_castable<Source>();
0099     detail::assert_castable<Target>();
0100     return detail::downcast<Target>(x, detail::convertible<Source*>::check((Target*)0));
0101 }
0102
0103 }} // namespace boost::python
0104
0105 #endif // CAST_DWA200269_HPP