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1 // boost cast.hpp header file ----------------------------------------------// |
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2 |
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3 // (C) Copyright Kevlin Henney and Dave Abrahams 1999. |
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4 // Distributed under the Boost |
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5 // Software License, Version 1.0. (See accompanying file |
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6 // LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) |
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7 |
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8 // See http://www.boost.org/libs/conversion for Documentation. |
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9 |
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10 // Revision History |
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11 // 23 JUn 05 numeric_cast removed and redirected to the new verion (Fernando Cacciola) |
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12 // 02 Apr 01 Removed BOOST_NO_LIMITS workarounds and included |
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13 // <boost/limits.hpp> instead (the workaround did not |
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14 // actually compile when BOOST_NO_LIMITS was defined in |
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15 // any case, so we loose nothing). (John Maddock) |
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16 // 21 Jan 01 Undid a bug I introduced yesterday. numeric_cast<> never |
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17 // worked with stock GCC; trying to get it to do that broke |
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18 // vc-stlport. |
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19 // 20 Jan 01 Moved BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS to config.hpp. |
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20 // Removed unused BOOST_EXPLICIT_TARGET macro. Moved |
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21 // boost::detail::type to boost/type.hpp. Made it compile with |
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22 // stock gcc again (Dave Abrahams) |
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23 // 29 Nov 00 Remove nested namespace cast, cleanup spacing before Formal |
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24 // Review (Beman Dawes) |
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25 // 19 Oct 00 Fix numeric_cast for floating-point types (Dave Abrahams) |
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26 // 15 Jul 00 Suppress numeric_cast warnings for GCC, Borland and MSVC |
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27 // (Dave Abrahams) |
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28 // 30 Jun 00 More MSVC6 wordarounds. See comments below. (Dave Abrahams) |
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29 // 28 Jun 00 Removed implicit_cast<>. See comment below. (Beman Dawes) |
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30 // 27 Jun 00 More MSVC6 workarounds |
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31 // 15 Jun 00 Add workarounds for MSVC6 |
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32 // 2 Feb 00 Remove bad_numeric_cast ";" syntax error (Doncho Angelov) |
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33 // 26 Jan 00 Add missing throw() to bad_numeric_cast::what(0 (Adam Levar) |
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34 // 29 Dec 99 Change using declarations so usages in other namespaces work |
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35 // correctly (Dave Abrahams) |
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36 // 23 Sep 99 Change polymorphic_downcast assert to also detect M.I. errors |
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37 // as suggested Darin Adler and improved by Valentin Bonnard. |
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38 // 2 Sep 99 Remove controversial asserts, simplify, rename. |
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39 // 30 Aug 99 Move to cast.hpp, replace value_cast with numeric_cast, |
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40 // place in nested namespace. |
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41 // 3 Aug 99 Initial version |
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42 |
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43 #ifndef BOOST_CAST_HPP |
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44 #define BOOST_CAST_HPP |
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45 |
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46 # include <boost/config.hpp> |
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47 # include <boost/assert.hpp> |
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48 # include <typeinfo> |
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49 # include <boost/type.hpp> |
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50 # include <boost/limits.hpp> |
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51 # include <boost/detail/select_type.hpp> |
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52 |
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53 // It has been demonstrated numerous times that MSVC 6.0 fails silently at link |
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54 // time if you use a template function which has template parameters that don't |
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55 // appear in the function's argument list. |
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56 // |
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57 // TODO: Add this to config.hpp? |
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58 # if defined(BOOST_MSVC) && BOOST_MSVC < 1300 |
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59 # define BOOST_EXPLICIT_DEFAULT_TARGET , ::boost::type<Target>* = 0 |
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60 # else |
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61 # define BOOST_EXPLICIT_DEFAULT_TARGET |
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62 # endif |
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63 |
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64 namespace boost |
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65 { |
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66 // See the documentation for descriptions of how to choose between |
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67 // static_cast<>, dynamic_cast<>, polymorphic_cast<> and polymorphic_downcast<> |
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68 |
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69 // polymorphic_cast --------------------------------------------------------// |
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70 |
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71 // Runtime checked polymorphic downcasts and crosscasts. |
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72 // Suggested in The C++ Programming Language, 3rd Ed, Bjarne Stroustrup, |
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73 // section 15.8 exercise 1, page 425. |
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74 |
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75 template <class Target, class Source> |
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76 inline Target polymorphic_cast(Source* x BOOST_EXPLICIT_DEFAULT_TARGET) |
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77 { |
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78 Target tmp = dynamic_cast<Target>(x); |
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79 if ( tmp == 0 ) throw std::bad_cast(); |
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80 return tmp; |
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81 } |
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82 |
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83 // polymorphic_downcast ----------------------------------------------------// |
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84 |
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85 // BOOST_ASSERT() checked polymorphic downcast. Crosscasts prohibited. |
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86 |
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87 // WARNING: Because this cast uses BOOST_ASSERT(), it violates |
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88 // the One Definition Rule if used in multiple translation units |
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89 // where BOOST_DISABLE_ASSERTS, BOOST_ENABLE_ASSERT_HANDLER |
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90 // NDEBUG are defined inconsistently. |
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91 |
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92 // Contributed by Dave Abrahams |
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93 |
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94 template <class Target, class Source> |
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95 inline Target polymorphic_downcast(Source* x BOOST_EXPLICIT_DEFAULT_TARGET) |
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96 { |
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97 BOOST_ASSERT( dynamic_cast<Target>(x) == x ); // detect logic error |
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98 return static_cast<Target>(x); |
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99 } |
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100 |
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101 # undef BOOST_EXPLICIT_DEFAULT_TARGET |
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102 |
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103 } // namespace boost |
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104 |
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105 # include <boost/numeric/conversion/cast.hpp> |
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106 |
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107 #endif // BOOST_CAST_HPP |