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80 lines
2.2 KiB
C++
80 lines
2.2 KiB
C++
// (C) Copyright David Abrahams 2000. Permission to copy, use, modify, sell and
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// distribute this software is granted provided this copyright notice appears
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// in all copies. This software is provided "as is" without express or implied
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// warranty, and with no claim as to its suitability for any purpose.
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//
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// The author gratefully acknowleges the support of Dragon Systems, Inc., in
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// producing this work.
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#ifndef CAST_DWA052500_H_
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# define CAST_DWA052500_H_
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# include "wrap_python.h"
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# include <boost/operators.hpp>
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namespace py {
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// The default way of converting a PyObject* or PyTypeObject* to a T*
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template <class T>
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struct DowncastTraits
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{
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template <class U>
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static T* cast(U* p) { return static_cast<T*>(p); }
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};
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inline PyTypeObject* as_base_object(const PyTypeObject*, PyObject* p)
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{
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return reinterpret_cast<PyTypeObject*>(p);
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}
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inline PyObject* as_base_object(const PyObject*, PyObject* p)
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{
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return p;
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}
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inline const PyTypeObject* as_base_object(const PyTypeObject*, const PyObject* p)
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{
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return reinterpret_cast<const PyTypeObject*>(p);
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}
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inline const PyObject* as_base_object(const PyObject*, const PyObject* p)
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{
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return p;
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}
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// Convert a pointer to any type derived from PyObject or PyTypeObject to a PyObject*
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inline PyObject* as_object(PyObject* p) { return p; }
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inline PyObject* as_object(PyTypeObject* p) { return reinterpret_cast<PyObject*>(p); }
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// If I didn't have to support stupid MSVC6 we could just use a simple template function:
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// template <class T> T* downcast(PyObject*).
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template <class T>
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struct Downcast : boost::dereferenceable<Downcast<T>, T*>
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{
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Downcast(PyObject* p)
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: m_p(DowncastTraits<T>::cast(as_base_object((T*)0, p)))
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{}
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Downcast(const PyObject* p)
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: m_p(DowncastTraits<T>::cast(as_base_object((const T*)0, p)))
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{}
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Downcast(PyTypeObject* p)
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: m_p(DowncastTraits<T>::cast(p))
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{}
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Downcast(const PyTypeObject* p)
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: m_p(DowncastTraits<T>::cast(p))
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{}
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operator T*() const { return m_p; }
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T* get() const { return m_p; }
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T& operator*() const { return *m_p; }
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private:
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T* m_p;
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};
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}
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#endif // CAST_DWA052500_H_
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