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/core/addressof.hpp> 60 # include <boost/core/enable_if.hpp> 61 # include <boost/throw_exception.hpp> 62 # include <boost/type_traits/is_reference.hpp> 63 # include <boost/type_traits/remove_reference.hpp> 64 65 # include <typeinfo> 66 67 namespace boost 68 { 69 // See the documentation for descriptions of how to choose between 70 // static_cast<>, dynamic_cast<>, polymorphic_cast<> and polymorphic_downcast<> 71 72 // polymorphic_cast --------------------------------------------------------// 73 74 // Runtime checked polymorphic downcasts and crosscasts. 75 // Suggested in The C++ Programming Language, 3rd Ed, Bjarne Stroustrup, 76 // section 15.8 exercise 1, page 425. 77 78 template <class Target, class Source> polymorphic_cast(Source * x)79 inline Target polymorphic_cast(Source* x) 80 { 81 Target tmp = dynamic_cast<Target>(x); 82 if ( tmp == 0 ) boost::throw_exception( std::bad_cast() ); 83 return tmp; 84 } 85 86 // polymorphic_downcast ----------------------------------------------------// 87 88 // BOOST_ASSERT() checked raw pointer polymorphic downcast. Crosscasts prohibited. 89 90 // WARNING: Because this cast uses BOOST_ASSERT(), it violates 91 // the One Definition Rule if used in multiple translation units 92 // where BOOST_DISABLE_ASSERTS, BOOST_ENABLE_ASSERT_HANDLER 93 // NDEBUG are defined inconsistently. 94 95 // Contributed by Dave Abrahams 96 97 template <class Target, class Source> polymorphic_downcast(Source * x)98 inline Target polymorphic_downcast(Source* x) 99 { 100 BOOST_ASSERT( dynamic_cast<Target>(x) == x ); // detect logic error 101 return static_cast<Target>(x); 102 } 103 104 // BOOST_ASSERT() checked reference polymorphic downcast. Crosscasts prohibited. 105 106 // WARNING: Because this cast uses BOOST_ASSERT(), it violates 107 // the One Definition Rule if used in multiple translation units 108 // where BOOST_DISABLE_ASSERTS, BOOST_ENABLE_ASSERT_HANDLER 109 // NDEBUG are defined inconsistently. 110 111 // Contributed by Julien Delacroix 112 113 template <class Target, class Source> 114 inline typename boost::enable_if_c< 115 boost::is_reference<Target>::value, Target polymorphic_downcast(Source & x)116 >::type polymorphic_downcast(Source& x) 117 { 118 typedef typename boost::remove_reference<Target>::type* target_pointer_type; 119 return *boost::polymorphic_downcast<target_pointer_type>( 120 boost::addressof(x) 121 ); 122 } 123 124 } // namespace boost 125 126 #endif // BOOST_POLYMORPHIC_CAST_HPP 127