133 lines
3.5 KiB
C++
133 lines
3.5 KiB
C++
// Copyright David Abrahams 2002.
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// Distributed under the Boost Software License, Version 1.0. (See
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// accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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#ifndef INHERITANCE_DWA200216_HPP
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# define INHERITANCE_DWA200216_HPP
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# include <boost/python/type_id.hpp>
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# include <boost/shared_ptr.hpp>
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# include <boost/mpl/if.hpp>
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# include <boost/type_traits/is_polymorphic.hpp>
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# include <boost/type_traits/is_base_and_derived.hpp>
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# include <boost/detail/workaround.hpp>
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namespace boost { namespace python { namespace objects {
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typedef type_info class_id;
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using python::type_id;
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// Types used to get address and id of most derived type
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typedef std::pair<void*,class_id> dynamic_id_t;
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typedef dynamic_id_t (*dynamic_id_function)(void*);
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BOOST_PYTHON_DECL void register_dynamic_id_aux(
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class_id static_id, dynamic_id_function get_dynamic_id);
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BOOST_PYTHON_DECL void add_cast(
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class_id src_t, class_id dst_t, void* (*cast)(void*), bool is_downcast);
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//
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// a generator with an execute() function which, given a source type
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// and a pointer to an object of that type, returns its most-derived
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// /reachable/ type identifier and object pointer.
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//
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// first, the case where T has virtual functions
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template <class T>
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struct polymorphic_id_generator
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{
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static dynamic_id_t execute(void* p_)
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{
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T* p = static_cast<T*>(p_);
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return std::make_pair(dynamic_cast<void*>(p), class_id(typeid(*p)));
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}
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};
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// now, the non-polymorphic case.
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template <class T>
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struct non_polymorphic_id_generator
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{
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static dynamic_id_t execute(void* p_)
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{
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return std::make_pair(p_, python::type_id<T>());
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}
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};
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// Now the generalized selector
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template <class T>
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struct dynamic_id_generator
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: mpl::if_<
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boost::is_polymorphic<T>
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, boost::python::objects::polymorphic_id_generator<T>
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, boost::python::objects::non_polymorphic_id_generator<T>
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>
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{};
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// Register the dynamic id function for T with the type-conversion
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// system.
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template <class T>
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void register_dynamic_id(T* = 0)
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{
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typedef typename dynamic_id_generator<T>::type generator;
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register_dynamic_id_aux(
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python::type_id<T>(), &generator::execute);
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}
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//
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// a generator with an execute() function which, given a void*
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// pointing to an object of type Source will attempt to convert it to
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// an object of type Target.
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//
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template <class Source, class Target>
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struct dynamic_cast_generator
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{
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static void* execute(void* source)
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{
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return dynamic_cast<Target*>(
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static_cast<Source*>(source));
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}
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};
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template <class Source, class Target>
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struct implicit_cast_generator
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{
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static void* execute(void* source)
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{
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Target* result = static_cast<Source*>(source);
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return result;
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}
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};
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template <class Source, class Target>
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struct cast_generator
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: mpl::if_<
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is_base_and_derived<Target,Source>
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, implicit_cast_generator<Source,Target>
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, dynamic_cast_generator<Source,Target>
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>
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{
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};
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template <class Source, class Target>
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inline void register_conversion(
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bool is_downcast = ::boost::is_base_and_derived<Source,Target>::value
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// These parameters shouldn't be used; they're an MSVC bug workaround
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, Source* = 0, Target* = 0)
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{
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typedef typename cast_generator<Source,Target>::type generator;
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add_cast(
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python::type_id<Source>()
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, python::type_id<Target>()
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, &generator::execute
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, is_downcast
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);
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}
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}}} // namespace boost::python::object
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#endif // INHERITANCE_DWA200216_HPP
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