50 lines
2.1 KiB
C++
50 lines
2.1 KiB
C++
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// 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 AS_TO_PYTHON_FUNCTION_DWA2002121_HPP
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# define AS_TO_PYTHON_FUNCTION_DWA2002121_HPP
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# include <boost/python/converter/to_python_function_type.hpp>
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namespace boost { namespace python { namespace converter {
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// Given a typesafe to_python conversion function, produces a
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// to_python_function_t which can be registered in the usual way.
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template <class T, class ToPython>
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struct as_to_python_function
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{
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// Assertion functions used to prevent wrapping of converters
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// which take non-const reference parameters. The T* argument in
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// the first overload ensures it isn't used in case T is a
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// reference.
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template <class U>
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static void convert_function_must_take_value_or_const_reference(U(*)(T), int, T* = 0) {}
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template <class U>
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static void convert_function_must_take_value_or_const_reference(U(*)(T const&), long ...) {}
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static PyObject* convert(void const* x)
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{
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convert_function_must_take_value_or_const_reference(&ToPython::convert, 1L);
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// Yes, the const_cast below opens a hole in const-correctness,
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// but it's needed to convert auto_ptr<U> to python.
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//
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// How big a hole is it? It allows ToPython::convert() to be
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// a function which modifies its argument. The upshot is that
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// client converters applied to const objects may invoke
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// undefined behavior. The damage, however, is limited by the
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// use of the assertion function. Thus, the only way this can
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// modify its argument is if T is an auto_ptr-like type. There
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// is still a const-correctness hole w.r.t. auto_ptr<U> const,
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// but c'est la vie.
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return ToPython::convert(*const_cast<T*>(static_cast<T const*>(x)));
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}
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#ifndef BOOST_PYTHON_NO_PY_SIGNATURES
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static PyTypeObject const * get_pytype() { return ToPython::get_pytype(); }
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#endif
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};
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}}} // namespace boost::python::converter
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#endif // AS_TO_PYTHON_FUNCTION_DWA2002121_HPP
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