serialize.hpp

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      if (!type) {
        object obj(value);
        type = obj.ptr()->ob_type;
      }

      register_type(default_saver<T>(), default_loader<T>(type), value, type);
    }

    /**
     * Register the type T for direct serialization.
     *
     *  @param saver A function object that will serialize a
     *  Boost.Python object (that represents a C++ object of type @c
     *  T) to an @c OArchive.
     *
     *  @param loader A function object that will deserialize from an
     *  @c IArchive into a Boost.Python object that represents a C++
     *  object of type @c T.
     *
     *  @param value A sample value of the type @c T. This may be used
     *  to compute the Python type associated with the C++ type @c T.
     *
     *  @param type The Python type associated with the C++ type @c
     *  T. If not provided, it will be computed from the same value @p
     *  value.
     */
    template<typename T>
    void register_type(const saver_t& saver, const loader_t& loader, 
                       const T& value = T(), PyTypeObject* type = 0)
    {
      // If the user did not provide us with a Python type, figure it
      // out for ourselves.
      if (!type) {
        object obj(value);
        type = obj.ptr()->ob_type;
      }

      int descriptor = savers.size() + 1;
      if (savers.find(type) != savers.end())
        return;

      savers[type] = std::make_pair(descriptor, saver);
      loaders[descriptor] = loader;
    }

  protected:
    template<typename T>
    struct default_saver {
      void operator()(OArchiver& ar, const object& obj, const unsigned int) {
        T value = extract<T>(obj)();
        ar << value;
      }
    };

    template<typename T>
    struct default_loader {
      default_loader(PyTypeObject* type) : type(type) { }

      void operator()(IArchiver& ar, object& obj, const unsigned int) {
        // If we can, extract the object in place.
        if (!is_fundamental<T>::value && obj && obj.ptr()->ob_type == type) {
          ar >> extract<T&>(obj)();
        } else {
          T value;
          ar >> value;
          obj = object(value);
        }
      }

    private:
      PyTypeObject* type;
    };

    savers_t savers;
    loaders_t loaders;
  };

  /**
   * @brief Retrieve the direct-serialization table for an
   * IArchiver/OArchiver pair.
   *
   * This function is responsible for returning a reference to the
   * singleton direct-serialization table. Its primary template is
   * left undefined, to force the use of an explicit specialization
   * with a definition in a single translation unit. Use the macro
   * BOOST_PYTHON_DIRECT_SERIALIZATION_ARCHIVE_IMPL to define this
   * explicit specialization.
   */
  template<typename IArchiver, typename OArchiver>
  direct_serialization_table<IArchiver, OArchiver>&
  get_direct_serialization_table();
} // end namespace detail 

/**
 * @brief Register the type T for direct serialization.
 *
 * The @c register_serialized function registers a C++ type for direct
 * serialization with the given @c IArchiver/@c OArchiver pair. Direct
 * serialization elides the use of the Python @c pickle package when
 * serializing Python objects that represent C++ values. Direct
 * serialization can be beneficial both to improve serialization
 * performance (Python pickling can be very inefficient) and to permit
 * serialization for Python-wrapped C++ objects that do not support
 * pickling.
 *
 *  @param value A sample value of the type @c T. This may be used
 *  to compute the Python type associated with the C++ type @c T.
 *
 *  @param type The Python type associated with the C++ type @c
 *  T. If not provided, it will be computed from the same value @p
 *  value.
 */
template<typename IArchiver, typename OArchiver, typename T>
void
register_serialized(const T& value = T(), PyTypeObject* type = 0)
{
  detail::direct_serialization_table<IArchiver, OArchiver>& table = 
    detail::get_direct_serialization_table<IArchiver, OArchiver>();
  table.register_type(value, type);
}

namespace detail {

/// Save a Python object by pickling it.
template<typename Archiver>
void 
save_impl(Archiver& ar, const boost::python::object& obj, 
          const unsigned int /*version*/,
          mpl::false_ /*has_direct_serialization*/)
{
  boost::python::str py_string = boost::python::pickle::dumps(obj);
  int len = boost::python::extract<int>(py_string.attr("__len__")());
  const char* string = boost::python::extract<const char*>(py_string);
  ar << len << boost::serialization::make_array(string, len);
}

/// Try to save a Python object by directly serializing it; fall back
/// on pickling if required.
template<typename Archiver>
void 
save_impl(Archiver& ar, const boost::python::object& obj, 
          const unsigned int version,
          mpl::true_ /*has_direct_serialization*/)
{
  typedef Archiver OArchiver;
  typedef typename input_archiver<OArchiver>::type IArchiver;
  typedef typename direct_serialization_table<IArchiver, OArchiver>::saver_t
    saver_t;

  direct_serialization_table<IArchiver, OArchiver>& table = 
    get_direct_serialization_table<IArchiver, OArchiver>();

  int descriptor = 0;
  if (saver_t saver = table.saver(obj, descriptor)) {
    ar << descriptor;
    saver(ar, obj, version);
  } else {
    // Pickle it
    ar << descriptor;
    detail::save_impl(ar, obj, version, mpl::false_());
  }
}

/// Load a Python object by unpickling it
template<typename Archiver>
void 
load_impl(Archiver& ar, boost::python::object& obj, 
          const unsigned int /*version*/, 
          mpl::false_ /*has_direct_serialization*/)
{
  int len;
  ar >> len;

  std::auto_ptr<char> string(new char[len]);
  ar >> boost::serialization::make_array(string.get(), len);
  boost::python::str py_string(string.get(), len);
  obj = boost::python::pickle::loads(py_string);
}

/// Try to load a Python object by directly deserializing it; fall back
/// on unpickling if required.
template<typename Archiver>
void 
load_impl(Archiver& ar, boost::python::object& obj, 
          const unsigned int version,
          mpl::true_ /*has_direct_serialization*/)
{
  typedef Archiver IArchiver;
  typedef typename output_archiver<IArchiver>::type OArchiver;
  typedef typename direct_serialization_table<IArchiver, OArchiver>::loader_t
    loader_t;

  direct_serialization_table<IArchiver, OArchiver>& table = 
    get_direct_serialization_table<IArchiver, OArchiver>();

  int descriptor;
  ar >> descriptor;

  if (descriptor) {
    loader_t loader = table.loader(descriptor);
    BOOST_ASSERT(loader);

    loader(ar, obj, version);
  } else {
    // Unpickle it
    detail::load_impl(ar, obj, version, mpl::false_());
  }
}

} // end namespace detail

template<typename Archiver>
void 
save(Archiver& ar, const boost::python::object& obj, 
     const unsigned int version)
{
  typedef Archiver OArchiver;
  typedef typename input_archiver<OArchiver>::type IArchiver;

  detail::save_impl(ar, obj, version, 
                    has_direct_serialization<IArchiver, OArchiver>());
}

template<typename Archiver>
void 
load(Archiver& ar, boost::python::object& obj, 
     const unsigned int version)
{
  typedef Archiver IArchiver;
  typedef typename output_archiver<IArchiver>::type OArchiver;

  detail::load_impl(ar, obj, version, 
                    has_direct_serialization<IArchiver, OArchiver>());
}

template<typename Archive>
inline void 
serialize(Archive& ar, boost::python::object& obj, const unsigned int version)
{
  boost::serialization::split_free(ar, obj, version);
}

} } // end namespace boost::python

/************************************************************************
 * Boost.MPI-Specific Section                                           *
 ************************************************************************/
namespace boost { namespace mpi {
 class packed_iarchive;
 class packed_oarchive;
} } // end namespace boost::mpi

BOOST_PYTHON_DIRECT_SERIALIZATION_ARCHIVE(
  ::boost::mpi::packed_iarchive,
  ::boost::mpi::packed_oarchive)

namespace boost { namespace mpi { namespace python {

template<typename T>
void
register_serialized(const T& value, PyTypeObject* type)
{
  using boost::python::register_serialized;
  register_serialized<packed_iarchive, packed_oarchive>(value, type);
}

} } } // end namespace boost::mpi::python

#endif // BOOST_MPI_PYTHON_SERIALIZE_HPP