python/include/boost/python/pure_virtual.hpp at develop · shelltdf/python · GitHub

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// Copyright David Abrahams 2003.

// Distributed under the Boost Software License, Version 1.0. (See

// accompanying file LICENSE_1_0.txt or copy at

// http://www.boost.org/LICENSE_1_0.txt)

#ifndef PURE_VIRTUAL_DWA2003810_HPP

# define PURE_VIRTUAL_DWA2003810_HPP

# include <boost/python/def_visitor.hpp>

# include <boost/python/default_call_policies.hpp>

# include <boost/mpl/push_front.hpp>

# include <boost/mpl/pop_front.hpp>

# include <boost/python/detail/nullary_function_adaptor.hpp>

namespace boost { namespace python {

namespace detail

{

// @group Helpers for pure_virtual_visitor. {

// Raises a Python RuntimeError reporting that a pure virtual

// function was called.

void BOOST_PYTHON_DECL pure_virtual_called();

// Replace the two front elements of S with T1 and T2

template <class S, class T1, class T2>

struct replace_front2

{

// Metafunction forwarding seemed to confound vc6

typedef typename mpl::push_front<

typename mpl::push_front<

typename mpl::pop_front<

>::type

, T2

>::type

, T1

>::type type;

};

// Given an MPL sequence representing a member function [object]

// signature, returns a new MPL sequence whose return type is

// replaced by void, and whose first argument is replaced by C&.

template <class C, class S>

typename replace_front2<S,void,C&>::type

error_signature(S)

{

typedef typename replace_front2<S,void,C&>::type r;

return r();

}

// }

// A def_visitor which defines a method as usual, then adds a

// corresponding function which raises a "pure virtual called"

// exception unless it's been overridden.

template <class PointerToMemberFunction>

struct pure_virtual_visitor

: def_visitor<pure_virtual_visitor<PointerToMemberFunction> >

{

pure_virtual_visitor(PointerToMemberFunction pmf)

: m_pmf(pmf)

{}

private:

friend class python::def_visitor_access;

template <class C_, class Options>

void visit(C_& c, char const* name, Options& options) const

{

// This should probably be a nicer error message

BOOST_STATIC_ASSERT(!Options::has_default_implementation);

// Add the virtual function dispatcher

c.def(

name

, m_pmf

, options.doc()

, options.keywords()

, options.policies()

);

typedef BOOST_DEDUCED_TYPENAME C_::metadata::held_type held_type;

// Add the default implementation which raises the exception

c.def(

name

, make_function(

detail::nullary_function_adaptor<void(*)()>(pure_virtual_called)

, default_call_policies()

, detail::error_signature<held_type>(detail::get_signature(m_pmf))

)

);

}

private: // data members

PointerToMemberFunction m_pmf;

};

}

// Passed a pointer to member function, generates a def_visitor which

// creates a method that only dispatches to Python if the function has

// been overridden, either in C++ or in Python, raising a "pure

// virtual called" exception otherwise.

template <class PointerToMemberFunction>

detail::pure_virtual_visitor<PointerToMemberFunction>

pure_virtual(PointerToMemberFunction pmf)

{

return detail::pure_virtual_visitor<PointerToMemberFunction>(pmf);

}

}} // namespace boost::python

#endif // PURE_VIRTUAL_DWA2003810_HPP

python/include/boost/python/pure_virtual.hpp at develop · shelltdf/python · GitHub

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