125 lines
3.6 KiB
C++
125 lines
3.6 KiB
C++
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// Copyright David Abrahams 2003.
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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 PURE_VIRTUAL_DWA2003810_HPP
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# define PURE_VIRTUAL_DWA2003810_HPP
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# include <boost/python/def_visitor.hpp>
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# include <boost/python/default_call_policies.hpp>
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# include <boost/mpl/push_front.hpp>
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# include <boost/mpl/pop_front.hpp>
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# include <boost/python/detail/nullary_function_adaptor.hpp>
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namespace boost { namespace python {
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namespace detail
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{
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//
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// @group Helpers for pure_virtual_visitor. {
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//
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// Raises a Python RuntimeError reporting that a pure virtual
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// function was called.
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void BOOST_PYTHON_DECL pure_virtual_called();
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// Replace the two front elements of S with T1 and T2
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template <class S, class T1, class T2>
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struct replace_front2
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{
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// Metafunction forwarding seemed to confound vc6
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typedef typename mpl::push_front<
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typename mpl::push_front<
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typename mpl::pop_front<
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typename mpl::pop_front<
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S
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>::type
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>::type
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, T2
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>::type
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, T1
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>::type type;
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};
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// Given an MPL sequence representing a member function [object]
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// signature, returns a new MPL sequence whose return type is
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// replaced by void, and whose first argument is replaced by C&.
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template <class C, class S>
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typename replace_front2<S,void,C&>::type
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error_signature(S BOOST_APPEND_EXPLICIT_TEMPLATE_TYPE(C))
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{
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typedef typename replace_front2<S,void,C&>::type r;
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return r();
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}
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//
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// }
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//
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//
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// A def_visitor which defines a method as usual, then adds a
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// corresponding function which raises a "pure virtual called"
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// exception unless it's been overridden.
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//
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template <class PointerToMemberFunction>
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struct pure_virtual_visitor
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: def_visitor<pure_virtual_visitor<PointerToMemberFunction> >
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{
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pure_virtual_visitor(PointerToMemberFunction pmf)
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: m_pmf(pmf)
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{}
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private:
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friend class python::def_visitor_access;
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template <class C_, class Options>
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void visit(C_& c, char const* name, Options& options) const
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{
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// This should probably be a nicer error message
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BOOST_STATIC_ASSERT(!Options::has_default_implementation);
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// Add the virtual function dispatcher
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c.def(
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name
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, m_pmf
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, options.doc()
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, options.keywords()
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, options.policies()
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);
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typedef BOOST_DEDUCED_TYPENAME C_::metadata::held_type held_type;
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// Add the default implementation which raises the exception
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c.def(
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name
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, make_function(
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detail::nullary_function_adaptor<void(*)()>(pure_virtual_called)
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, default_call_policies()
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, detail::error_signature<held_type>(detail::get_signature(m_pmf))
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)
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);
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}
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private: // data members
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PointerToMemberFunction m_pmf;
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};
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}
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//
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// Passed a pointer to member function, generates a def_visitor which
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// creates a method that only dispatches to Python if the function has
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// been overridden, either in C++ or in Python, raising a "pure
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// virtual called" exception otherwise.
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//
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template <class PointerToMemberFunction>
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detail::pure_virtual_visitor<PointerToMemberFunction>
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pure_virtual(PointerToMemberFunction pmf)
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{
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return detail::pure_virtual_visitor<PointerToMemberFunction>(pmf);
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}
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}} // namespace boost::python
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#endif // PURE_VIRTUAL_DWA2003810_HPP
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