ceph/src/boost/libs/serialization/doc/shared_ptr2.html

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  13 <title>Template serialization - shared_ptr</title>
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  22       <h1 align="center">Serialization</h1>
  23       <h2 align="center"><code style="white-space: normal">shared_ptr&lt;class T&gt;</code> Revisited</h2>
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  27 <hr>
  28 The previously described serialization of <code style="white-space: normal">shared_ptr</code>
  29 illustrates the straightforward way of serializing a moderately complicated class structure.
  30 Unfortunately, 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>
  41 template&lt;class Archive, class T&gt;
  42 inline void save(
  43     Archive & ar,
  44     const boost::shared_ptr&ltT&gt; &t,
  45     const unsigned int /* file_version */
  46 ){
  47     const T * t_ptr = t.get();
  48     // just serialize the underlying raw pointer
  49     ar &lt;&lt: boost::serialization::make_nvp("px", t_ptr);
  50 }
  51
  52 template&lt;class Archive, class T&gt
  53 inline void load(
  54     Archive & ar,
  55     boost::shared_ptr&lt;T&gt; &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
  68 In principle, this is very much simpler than the original implementation.  Completion of
  69 this 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
  80 The 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>
  85 Note that if your code needs to read archives created under boost version 1.32, you will
  86 have to include the following
  87
  88 <pre><code>
  89 #include &lt;boost/serialization/shared_ptr_132.hpp&gt;
  90 #include &lt;boost/serialization/shared_ptr.hpp&gt;
  91 </code></pre>
  92 rather than just
  93 <pre><code>
  94 #include &lt;boost/serialization/shared_ptr.hpp&gt;
  95 </code></pre>
  96
  97 <hr>
  98 <p><i>&copy; Copyright <a href="http://www.rrsd.com">Robert Ramey</a> 2002-2004.
  99 Distributed under the Boost Software License, Version 1.0. (See
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