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<h1 align="center">Serialization</h1>
<h2 align="center"><code style="white-space: normal">shared_ptr<class T></code> Revisited</h2>
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<hr>
The previously described serialization of <code style="white-space: normal">shared_ptr</code>
illustrates the straightforward way of serializing a moderately complicated class structure.
Unfortunately, this way of doing it suffered from some undesirable features
<ul>
<li>It was dependent on the Boost implementation of <code style="white-space: normal">shared_ptr</code>.
The <code style="white-space: normal">shared_ptr</code> interface has been included
in <code style="white-space: normal">std::tr1</code> and may someday be included in the standard
C++ library. An implementation which depends only on the public interface can be guaranteed to
function with any other future implementation of <code style="white-space: normal">shared_ptr</code>.
<li>It required extra macros for export.
</ul>
<pre><code>
template<class Archive, class T>
inline void save(
Archive & ar,
const boost::shared_ptr<T> &t,
const unsigned int /* file_version */
){
const T * t_ptr = t.get();
// just serialize the underlying raw pointer
ar <<: boost::serialization::make_nvp("px", t_ptr);
}
template<class Archive, class T>
inline void load(
Archive & ar,
boost::shared_ptr<T> &t,
const unsigned int file_version
){
T* r;
// recover the underlying raw pointer
ar >> boost::serialization::make_nvp("px", r);
// To Do - match up with other shared pointers which
// use this same raw pointer.
...
}
</code></pre>
In principle, this is very much simpler than the original implementation. Completion of
this code requires:
<ol>
<li>Filling in the "To Do". This required making an extra map for
<code style="white-space: normal">shared_ptr</code> instances.
<li>A method for identifying pointers to the same objects from pointers to their base classes.
<li>Backward compatibility with pointers serialized by the previous method. This exploits
the serialization class versioning.
<li>Proper handling of <code style="white-space: normal">weak_ptr</code>.
</ol>
The result of this effort can be found in
<a target = serialization_shared_ptr href="../../../boost/serialization/shared_ptr.hpp">
<code style="white-space: normal">boost::serialization::shared_ptr.hpp</code>
</a>
<p>
Note that if your code needs to read archives created under boost version 1.32, you will
have to include the following
<pre><code>
#include <boost/serialization/shared_ptr_132.hpp>
#include <boost/serialization/shared_ptr.hpp>
</code></pre>
rather than just
<pre><code>
#include <boost/serialization/shared_ptr.hpp>
</code></pre>
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<p><i>© Copyright <a href="http://www.rrsd.com">Robert Ramey</a> 2002-2004.
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)
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