1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
|
<!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=iso-8859-1">
<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> Revisted</h2>
</td>
</tr>
</table>
<hr>
The previously described serialization of <code style="white-space: normal">shared_ptr</code>
illustrates the straight forward way of serializing a moderatly compiicated 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 guarenteed 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 seriailize 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 poiter
ar >> boost::serialization::make_nvp("px", r);
// To Do - match up with other shared pointers which
// use this same raw pointer.
...
}
</code></pre>
In priniciple 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 identifing 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>
|
