104 lines
3.9 KiB
HTML
104 lines
3.9 KiB
HTML
<!doctype HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
|
|
<html>
|
|
<!--
|
|
(C) Copyright 2002-4 Robert Ramey - http://www.rrsd.com .
|
|
Use, modification and distribution is subject to 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)
|
|
-->
|
|
<head>
|
|
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
|
|
<link rel="stylesheet" type="text/css" href="../../../boost.css">
|
|
<link rel="stylesheet" type="text/css" href="style.css">
|
|
<title>Template serialization - shared_ptr</title>
|
|
</head>
|
|
<body link="#0000ff" vlink="#800080">
|
|
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary="header">
|
|
<tr>
|
|
<td valign="top" width="300">
|
|
<h3><a href="../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../boost.png" border="0"></a></h3>
|
|
</td>
|
|
<td valign="top">
|
|
<h1 align="center">Serialization</h1>
|
|
<h2 align="center"><code style="white-space: normal">shared_ptr<class T></code> Revisited</h2>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
<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>
|
|
|
|
<hr>
|
|
<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)
|
|
</i></p>
|
|
</body>
|
|
</html>
|