1<!doctype HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 2<html> 3<!-- 4(C) Copyright 2002-4 Robert Ramey - http://www.rrsd.com . 5Use, modification and distribution is subject to the Boost Software 6License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at 7http://www.boost.org/LICENSE_1_0.txt) 8--> 9<head> 10<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 11<link rel="stylesheet" type="text/css" href="../../../boost.css"> 12<link rel="stylesheet" type="text/css" href="style.css"> 13<title>Template serialization - shared_ptr</title> 14</head> 15<body link="#0000ff" vlink="#800080"> 16<table border="0" cellpadding="7" cellspacing="0" width="100%" summary="header"> 17 <tr> 18 <td valign="top" width="300"> 19 <h3><a href="../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../boost.png" border="0"></a></h3> 20 </td> 21 <td valign="top"> 22 <h1 align="center">Serialization</h1> 23 <h2 align="center"><code style="white-space: normal">shared_ptr<class T></code> Revisited</h2> 24 </td> 25 </tr> 26</table> 27<hr> 28The previously described serialization of <code style="white-space: normal">shared_ptr</code> 29illustrates the straightforward way of serializing a moderately complicated class structure. 30Unfortunately, this way of doing it suffered from some undesirable features 31<ul> 32 <li>It was dependent on the Boost implementation of <code style="white-space: normal">shared_ptr</code>. 33 The <code style="white-space: normal">shared_ptr</code> interface has been included 34 in <code style="white-space: normal">std::tr1</code> and may someday be included in the standard 35 C++ library. An implementation which depends only on the public interface can be guaranteed to 36 function with any other future implementation of <code style="white-space: normal">shared_ptr</code>. 37 <li>It required extra macros for export. 38</ul> 39 40<pre><code> 41template<class Archive, class T> 42inline void save( 43 Archive & ar, 44 const boost::shared_ptr<T> &t, 45 const unsigned int /* file_version */ 46){ 47 const T * t_ptr = t.get(); 48 // just serialize the underlying raw pointer 49 ar <<: boost::serialization::make_nvp("px", t_ptr); 50} 51 52template<class Archive, class T> 53inline void load( 54 Archive & ar, 55 boost::shared_ptr<T> &t, 56 const unsigned int file_version 57){ 58 T* r; 59 // recover the underlying raw pointer 60 ar >> boost::serialization::make_nvp("px", r); 61 62 // To Do - match up with other shared pointers which 63 // use this same raw pointer. 64 ... 65} 66</code></pre> 67 68In principle, this is very much simpler than the original implementation. Completion of 69this code requires: 70 71<ol> 72 <li>Filling in the "To Do". This required making an extra map for 73 <code style="white-space: normal">shared_ptr</code> instances. 74 <li>A method for identifying pointers to the same objects from pointers to their base classes. 75 <li>Backward compatibility with pointers serialized by the previous method. This exploits 76 the serialization class versioning. 77 <li>Proper handling of <code style="white-space: normal">weak_ptr</code>. 78</ol> 79 80The result of this effort can be found in 81<a target = serialization_shared_ptr href="../../../boost/serialization/shared_ptr.hpp"> 82<code style="white-space: normal">boost::serialization::shared_ptr.hpp</code> 83</a> 84<p> 85Note that if your code needs to read archives created under boost version 1.32, you will 86have to include the following 87 88<pre><code> 89#include <boost/serialization/shared_ptr_132.hpp> 90#include <boost/serialization/shared_ptr.hpp> 91</code></pre> 92rather than just 93<pre><code> 94#include <boost/serialization/shared_ptr.hpp> 95</code></pre> 96 97<hr> 98<p><i>© Copyright <a href="http://www.rrsd.com">Robert Ramey</a> 2002-2004. 99Distributed under the Boost Software License, Version 1.0. (See 100accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) 101</i></p> 102</body> 103</html> 104
