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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 | ||
25 | namespace 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( std::bad_cast() ); | |
72 | ||
73 | return tmp; | |
74 | } | |
75 | ||
76 | } // namespace boost | |
77 | ||
78 | #endif // BOOST_CONVERSION_POLYMORPHIC_POINTER_CAST_HPP |