1// boost polymorphic_cast.hpp header file ----------------------------------------------//
2
3// (C) Copyright Kevlin Henney and Dave Abrahams 1999.
4// (C) Copyright Boris Rasin 2014.
5// Distributed under the Boost
6// Software License, Version 1.0. (See accompanying file
7// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
8
9// See http://www.boost.org/libs/conversion for Documentation.
10
11// Revision History
12// 10 Nov 14 polymorphic_pointer_downcast moved to a separate header,
13// minor improvements to stisfy latest Boost coding style
14// 08 Nov 14 Add polymorphic_pointer_downcast (Boris Rasin)
15// 09 Jun 14 "cast.hpp" was renamed to "polymorphic_cast.hpp" and
16// inclusion of numeric_cast was removed (Antony Polukhin)
17// 23 Jun 05 numeric_cast removed and redirected to the new verion (Fernando Cacciola)
18// 02 Apr 01 Removed BOOST_NO_LIMITS workarounds and included
19// <boost/limits.hpp> instead (the workaround did not
20// actually compile when BOOST_NO_LIMITS was defined in
21// any case, so we loose nothing). (John Maddock)
22// 21 Jan 01 Undid a bug I introduced yesterday. numeric_cast<> never
23// worked with stock GCC; trying to get it to do that broke
24// vc-stlport.
25// 20 Jan 01 Moved BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS to config.hpp.
26// Removed unused BOOST_EXPLICIT_TARGET macro. Moved
27// boost::detail::type to boost/type.hpp. Made it compile with
28// stock gcc again (Dave Abrahams)
29// 29 Nov 00 Remove nested namespace cast, cleanup spacing before Formal
30// Review (Beman Dawes)
31// 19 Oct 00 Fix numeric_cast for floating-point types (Dave Abrahams)
32// 15 Jul 00 Suppress numeric_cast warnings for GCC, Borland and MSVC
33// (Dave Abrahams)
34// 30 Jun 00 More MSVC6 wordarounds. See comments below. (Dave Abrahams)
35// 28 Jun 00 Removed implicit_cast<>. See comment below. (Beman Dawes)
36// 27 Jun 00 More MSVC6 workarounds
37// 15 Jun 00 Add workarounds for MSVC6
38// 2 Feb 00 Remove bad_numeric_cast ";" syntax error (Doncho Angelov)
39// 26 Jan 00 Add missing throw() to bad_numeric_cast::what(0 (Adam Levar)
40// 29 Dec 99 Change using declarations so usages in other namespaces work
41// correctly (Dave Abrahams)
42// 23 Sep 99 Change polymorphic_downcast assert to also detect M.I. errors
43// as suggested Darin Adler and improved by Valentin Bonnard.
44// 2 Sep 99 Remove controversial asserts, simplify, rename.
45// 30 Aug 99 Move to cast.hpp, replace value_cast with numeric_cast,
46// place in nested namespace.
47// 3 Aug 99 Initial version
48
49#ifndef BOOST_POLYMORPHIC_CAST_HPP
50#define BOOST_POLYMORPHIC_CAST_HPP
51
52#include <boost/config.hpp>
53
54#ifdef BOOST_HAS_PRAGMA_ONCE
55# pragma once
56#endif
57
58# include <boost/assert.hpp>
59# include <boost/throw_exception.hpp>
60
61# include <memory> // std::addressof
62# include <typeinfo>
63# include <type_traits>
64
65namespace boost
66{
67// See the documentation for descriptions of how to choose between
68// static_cast<>, dynamic_cast<>, polymorphic_cast<> and polymorphic_downcast<>
69
70// polymorphic_cast --------------------------------------------------------//
71
72 // Runtime checked polymorphic downcasts and crosscasts.
73 // Suggested in The C++ Programming Language, 3rd Ed, Bjarne Stroustrup,
74 // section 15.8 exercise 1, page 425.
75
76 template <class Target, class Source>
77 inline Target polymorphic_cast(Source* x)
78 {
79 Target tmp = dynamic_cast<Target>(x);
80 if ( tmp == 0 ) boost::throw_exception( e: std::bad_cast() );
81 return tmp;
82 }
83
84// polymorphic_downcast ----------------------------------------------------//
85
86 // BOOST_ASSERT() checked raw pointer polymorphic downcast. Crosscasts prohibited.
87
88 // WARNING: Because this cast uses BOOST_ASSERT(), it violates
89 // the One Definition Rule if used in multiple translation units
90 // where BOOST_DISABLE_ASSERTS, BOOST_ENABLE_ASSERT_HANDLER
91 // NDEBUG are defined inconsistently.
92
93 // Contributed by Dave Abrahams
94
95 template <class Target, class Source>
96 inline Target polymorphic_downcast(Source* x)
97 {
98 BOOST_ASSERT( dynamic_cast<Target>(x) == x ); // detect logic error
99 return static_cast<Target>(x);
100 }
101
102 // BOOST_ASSERT() checked reference polymorphic downcast. Crosscasts prohibited.
103
104 // WARNING: Because this cast uses BOOST_ASSERT(), it violates
105 // the One Definition Rule if used in multiple translation units
106 // where BOOST_DISABLE_ASSERTS, BOOST_ENABLE_ASSERT_HANDLER
107 // NDEBUG are defined inconsistently.
108
109 // Contributed by Julien Delacroix
110
111 template <class Target, class Source>
112 inline typename std::enable_if<
113 std::is_reference<Target>::value, Target
114 >::type polymorphic_downcast(Source& x)
115 {
116 typedef typename std::remove_reference<Target>::type* target_pointer_type;
117 return *boost::polymorphic_downcast<target_pointer_type>(
118 std::addressof(x)
119 );
120 }
121
122} // namespace boost
123
124#endif // BOOST_POLYMORPHIC_CAST_HPP
125

source code of boost/libs/conversion/include/boost/polymorphic_cast.hpp