// Copyright David Abrahams 2002.

// 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 INSTANCE_HOLDER_DWA2002517_HPP

# define INSTANCE_HOLDER_DWA2002517_HPP

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

# include <boost/utility.hpp>

# include <boost/python/type_id.hpp>

# include <cstddef>

namespace boost { namespace python { 

// Base class for all holders

struct BOOST_PYTHON_DECL instance_holder : private noncopyable

{

 public:

    instance_holder();

    virtual ~instance_holder();

    // return the next holder in a chain

    instance_holder* next() const;

    // When the derived holder actually holds by [smart] pointer and

    // null_ptr_only is set, only report that the type is held when

    // the pointer is null.  This is needed for proper shared_ptr

    // support, to prevent holding shared_ptrs from being found when

    // converting from python so that we can use the conversion method

    // that always holds the Python object.

    virtual void* holds(type_info, bool null_ptr_only) = 0;

    void install(PyObject* inst) throw();

    // These functions should probably be located elsewhere.

    // Allocate storage for an object of the given size at the given

    // offset in the Python instance<> object if bytes are available

    // there. Otherwise allocate size bytes of heap memory.

    static void* allocate(PyObject*, std::size_t offset, std::size_t size);

    // Deallocate storage from the heap if it was not carved out of

    // the given Python object by allocate(), above.

    static void deallocate(PyObject*, void* storage) throw();

 private:

    instance_holder* m_next;

};

// This macro is needed for implementation of derived holders

# define BOOST_PYTHON_UNFORWARD(N,ignored) (typename unforward<A##N>::type)(a##N)

//

// implementation

//

inline instance_holder* instance_holder::next() const

{

    return m_next;

}

}} // namespace boost::python

#endif // INSTANCE_HOLDER_DWA2002517_HPP