1 | // Copyright David Abrahams 2002.
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2 | // Distributed under the Boost Software License, Version 1.0. (See
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3 | // accompanying file LICENSE_1_0.txt or copy at
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4 | // http://www.boost.org/LICENSE_1_0.txt)
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5 | #ifndef INHERITANCE_DWA200216_HPP
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6 | # define INHERITANCE_DWA200216_HPP
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7 |
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8 | # include <boost/python/type_id.hpp>
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9 | # include <boost/shared_ptr.hpp>
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10 | # include <boost/mpl/if.hpp>
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11 | # include <boost/type_traits/is_polymorphic.hpp>
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12 | # include <boost/type_traits/is_base_and_derived.hpp>
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13 | # include <boost/detail/workaround.hpp>
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14 |
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15 | namespace boost { namespace python { namespace objects {
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16 |
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17 | typedef type_info class_id;
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18 | using python::type_id;
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19 |
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20 | // Types used to get address and id of most derived type
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21 | typedef std::pair<void*,class_id> dynamic_id_t;
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22 | typedef dynamic_id_t (*dynamic_id_function)(void*);
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23 |
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24 | BOOST_PYTHON_DECL void register_dynamic_id_aux(
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25 | class_id static_id, dynamic_id_function get_dynamic_id);
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26 |
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27 | BOOST_PYTHON_DECL void add_cast(
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28 | class_id src_t, class_id dst_t, void* (*cast)(void*), bool is_downcast);
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29 |
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30 | //
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31 | // a generator with an execute() function which, given a source type
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32 | // and a pointer to an object of that type, returns its most-derived
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33 | // /reachable/ type identifier and object pointer.
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34 | //
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35 |
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36 | // first, the case where T has virtual functions
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37 | template <class T>
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38 | struct polymorphic_id_generator
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39 | {
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40 | static dynamic_id_t execute(void* p_)
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41 | {
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42 | T* p = static_cast<T*>(p_);
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43 | return std::make_pair(dynamic_cast<void*>(p), class_id(typeid(*p)));
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44 | }
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45 | };
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46 |
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47 | // now, the non-polymorphic case.
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48 | template <class T>
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49 | struct non_polymorphic_id_generator
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50 | {
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51 | static dynamic_id_t execute(void* p_)
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52 | {
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53 | return std::make_pair(p_, python::type_id<T>());
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54 | }
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55 | };
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56 |
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57 | // Now the generalized selector
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58 | template <class T>
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59 | struct dynamic_id_generator
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60 | : mpl::if_<
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61 | boost::is_polymorphic<T>
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62 | , boost::python::objects::polymorphic_id_generator<T>
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63 | , boost::python::objects::non_polymorphic_id_generator<T>
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64 | >
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65 | {};
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66 |
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67 | // Register the dynamic id function for T with the type-conversion
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68 | // system.
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69 | template <class T>
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70 | void register_dynamic_id(T* = 0)
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71 | {
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72 | typedef typename dynamic_id_generator<T>::type generator;
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73 | register_dynamic_id_aux(
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74 | python::type_id<T>(), &generator::execute);
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75 | }
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76 |
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77 | //
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78 | // a generator with an execute() function which, given a void*
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79 | // pointing to an object of type Source will attempt to convert it to
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80 | // an object of type Target.
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81 | //
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82 |
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83 | template <class Source, class Target>
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84 | struct dynamic_cast_generator
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85 | {
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86 | static void* execute(void* source)
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87 | {
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88 | return dynamic_cast<Target*>(
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89 | static_cast<Source*>(source));
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90 | }
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91 |
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92 | };
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93 |
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94 | template <class Source, class Target>
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95 | struct implicit_cast_generator
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96 | {
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97 | static void* execute(void* source)
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98 | {
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99 | Target* result = static_cast<Source*>(source);
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100 | return result;
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101 | }
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102 | };
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103 |
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104 | template <class Source, class Target>
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105 | struct cast_generator
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106 | : mpl::if_<
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107 | is_base_and_derived<Target,Source>
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108 | , implicit_cast_generator<Source,Target>
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109 | , dynamic_cast_generator<Source,Target>
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110 | >
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111 | {
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112 | };
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113 |
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114 | template <class Source, class Target>
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115 | inline void register_conversion(
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116 | bool is_downcast = ::boost::is_base_and_derived<Source,Target>::value
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117 | // These parameters shouldn't be used; they're an MSVC bug workaround
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118 | , Source* = 0, Target* = 0)
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119 | {
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120 | typedef typename cast_generator<Source,Target>::type generator;
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121 |
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122 | add_cast(
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123 | python::type_id<Source>()
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124 | , python::type_id<Target>()
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125 | , &generator::execute
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126 | , is_downcast
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127 | );
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128 | }
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129 |
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130 | }}} // namespace boost::python::object
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131 |
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132 | #endif // INHERITANCE_DWA200216_HPP
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