1// boost polymorphic_pointer_cast.hpp header file ----------------------------------------------//
2// (C) Copyright Boris Rasin and Antony Polukhin 2014-2015.
3// Distributed under the Boost
4// Software License, Version 1.0. (See accompanying file
5// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
6
7// See http://www.boost.org/libs/conversion for Documentation.
8
9#ifndef BOOST_CONVERSION_POLYMORPHIC_POINTER_CAST_HPP
10#define BOOST_CONVERSION_POLYMORPHIC_POINTER_CAST_HPP
11
12# include <boost/config.hpp>
13# include <boost/assert.hpp>
14# include <boost/pointer_cast.hpp>
15# include <boost/throw_exception.hpp>
16# include <boost/utility/declval.hpp>
17# ifdef BOOST_NO_CXX11_DECLTYPE
18# include <boost/typeof/typeof.hpp>
19# endif
20
21#ifdef BOOST_HAS_PRAGMA_ONCE
22# pragma once
23#endif
24
25namespace boost
26{
27// See the documentation for descriptions of how to choose between
28// static_pointer_cast<>, dynamic_pointer_cast<>, polymorphic_pointer_cast<> and polymorphic_pointer_downcast<>
29
30// polymorphic_pointer_downcast --------------------------------------------//
31
32 // BOOST_ASSERT() checked polymorphic downcast. Crosscasts prohibited.
33 // Supports any type with static_pointer_cast/dynamic_pointer_cast functions:
34 // built-in pointers, std::shared_ptr, boost::shared_ptr, boost::intrusive_ptr, etc.
35
36 // WARNING: Because this cast uses BOOST_ASSERT(), it violates
37 // the One Definition Rule if used in multiple translation units
38 // where BOOST_DISABLE_ASSERTS, BOOST_ENABLE_ASSERT_HANDLER
39 // NDEBUG are defined inconsistently.
40
41 // Contributed by Boris Rasin
42
43 namespace detail
44 {
45 template <typename Target, typename Source>
46 struct dynamic_pointer_cast_result
47 {
48#ifdef BOOST_NO_CXX11_DECLTYPE
49 BOOST_TYPEOF_NESTED_TYPEDEF_TPL(nested, dynamic_pointer_cast<Target>(boost::declval<Source>()))
50 typedef typename nested::type type;
51#else
52 typedef decltype(dynamic_pointer_cast<Target>(boost::declval<Source>())) type;
53#endif
54 };
55 }
56
57 template <typename Target, typename Source>
58 inline typename detail::dynamic_pointer_cast_result<Target, Source>::type
59 polymorphic_pointer_downcast (const Source& x)
60 {
61 BOOST_ASSERT(dynamic_pointer_cast<Target> (x) == x);
62 return static_pointer_cast<Target> (x);
63 }
64
65 template <typename Target, typename Source>
66 inline typename detail::dynamic_pointer_cast_result<Target, Source>::type
67 polymorphic_pointer_cast (const Source& x)
68 {
69 typename detail::dynamic_pointer_cast_result<Target, Source>::type tmp
70 = dynamic_pointer_cast<Target> (x);
71 if ( !tmp ) boost::throw_exception( e: std::bad_cast() );
72
73 return tmp;
74 }
75
76} // namespace boost
77
78#endif // BOOST_CONVERSION_POLYMORPHIC_POINTER_CAST_HPP
79

source code of boost/boost/polymorphic_pointer_cast.hpp