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dabrahamsdabrahams
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implemented back_reference<>
[SVN r13811]
1 parent 63deae3 commit 390bb19

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‎include/boost/python/back_reference.hpp‎

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// Copyright David Abrahams 2002. Permission to copy, use,
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// modify, sell and distribute this software is granted provided this
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// copyright notice appears in all copies. This software is provided
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// "as is" without express or implied warranty, and with no claim as
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// to its suitability for any purpose.
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#ifndef BACK_REFERENCE_DWA2002510_HPP
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# define BACK_REFERENCE_DWA2002510_HPP
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# include <boost/python/reference.hpp>
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namespace boost { namespace python {
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template <class T>
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struct back_reference
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{
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public:
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typedef T type;
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back_reference(PyObject*, T);
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ref reference() const;
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T get() const;
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private:
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ref m_reference;
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T m_value;
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};
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# ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
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template<typename T>
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class is_back_reference
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{
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public:
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BOOST_STATIC_CONSTANT(bool, value = false);
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};
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template<typename T>
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class is_back_reference<back_reference<T> >
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{
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public:
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BOOST_STATIC_CONSTANT(bool, value = true);
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};
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# else // no partial specialization
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}} // namespace boost::python
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#include <boost/type.hpp>
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namespace boost { namespace python {
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namespace detail
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{
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typedef char (&yes_back_reference_t)[1];
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typedef char (&no_back_reference_t)[2];
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no_back_reference_t is_back_reference_test(...);
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template<typename T>
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yes_back_reference_t is_back_reference_test(type< back_reference<T> >);
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}
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template<typename T>
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class is_back_reference
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{
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public:
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BOOST_STATIC_CONSTANT(
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bool, value = (
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sizeof(detail::is_back_reference_test(type<T>()))
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== sizeof(detail::yes_back_reference_t)));
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};
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# endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
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//
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// implementations
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//
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template <class T>
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back_reference<T>::back_reference(PyObject* p, T x)
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: m_reference(p, ref::increment_count)
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, m_value(x)
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{
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}
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template <class T>
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ref back_reference<T>::reference() const
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{
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return m_reference;
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}
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template <class T>
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T back_reference<T>::get() const
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{
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return m_value;
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}
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}} // namespace boost::python
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#endif // BACK_REFERENCE_DWA2002510_HPP

‎include/boost/python/converter/from_python.hpp‎

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# include <boost/python/converter/lvalue_from_python_chain.hpp>
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# include <boost/python/converter/rvalue_from_python_chain.hpp>
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# include <boost/python/detail/void_ptr.hpp>
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# include <boost/python/back_reference.hpp>
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namespace boost { namespace python
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{
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template <class T> struct from_python;
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}}
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namespace boost { namespace python { namespace converter {
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@@ -82,6 +88,21 @@ class rvalue_from_python
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rvalue_data<result_type> m_data;
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};
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// ------- back-reference converters --------
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// Converts to a (PyObject*,T) bundle, for when you need a reference
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// back to the Python object
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template <class T>
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struct back_reference_from_python
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: boost::python::from_python<typename T::type>
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{
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back_reference_from_python(PyObject*);
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T operator()(PyObject*);
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private:
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typedef boost::python::from_python<typename T::type> base;
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};
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template <class T>
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struct select_from_python
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{
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boost::python::detail::is_reference_to_non_const<T>::value
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|| boost::python::detail::is_reference_to_volatile<T>::value);
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BOOST_STATIC_CONSTANT(
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bool, back_ref =
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boost::python::is_back_reference<T>::value);
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typedef typename mpl::select_type<
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ptr
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, pointer_from_python<T>
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, typename mpl::select_type<
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ref
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, reference_from_python<T>
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, rvalue_from_python<T>
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, typename mpl::select_type<
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back_ref
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, back_reference_from_python<T>
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, rvalue_from_python<T>
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>::type
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>::type
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>::type
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>::type type;
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return python::detail::void_ptr_to_reference(m_data.stage1.convertible, (result_type(*)())0);
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}
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template <class T>
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back_reference_from_python<T>::back_reference_from_python(PyObject* x)
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: base(x)
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{
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}
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template <class T>
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inline T
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back_reference_from_python<T>::operator()(PyObject* x)
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{
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return T(x, base::operator()(x));
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}
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}}} // namespace boost::python::converter
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#endif // FROM_PYTHON_DWA2002127_HPP

‎test/back_reference.cpp‎

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#include <boost/python/class.hpp>
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#include <boost/python/module.hpp>
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#include <boost/python/has_back_reference.hpp>
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#include <boost/python/back_reference.hpp>
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#include <boost/ref.hpp>
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#include <boost/utility.hpp>
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#include <memory>
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};
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}}
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// prove that back_references get initialized with the right PyObject*
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PyObject* y_identity(back_reference<Y const&> y)
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{
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return y.reference().release();
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}
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// prove that back_references contain the right value
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bool y_equality(back_reference<Y const&> y1, Y const& y2)
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{
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return &y1.get() == &y2;
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}
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BOOST_PYTHON_MODULE_INIT(back_reference_ext)
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{
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.def("value", &Z::value)
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.def("set", &Z::set)
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)
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.def("y_identity", y_identity)
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.def("y_equality", y_equality)
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;
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}
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‎test/back_reference.py‎

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>>> z2 = copy_Z(z)
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>>> x_instances()
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4
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>>> y_identity(y) is y
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1
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>>> y_equality(y, y)
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1
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'''
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def run(args = None):

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