projects / ceph.git / blame
| Commit | Line | Data |
|---|---|---|
| 7c673cae FG |
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 . | |
| 5 | Use, modification and distribution is subject to the Boost Software | |
| 6 | License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at | |
| 7 | http://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>Serialization - BOOST_STATIC_WARNING</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>void_cast</code></h2> | |
| 24 | </td> | |
| 25 | </tr> | |
| 26 | </table> | |
| 27 | <hr> | |
| 28 | <h3>Motivation</h3> | |
| 29 | C++ includes the operator <code style="white-space: normal">dynamic_cast<T>(U * u)</code> | |
| 30 | for casting a pointer at runtime between two related types. However, this can only be | |
| 31 | used for polymorphic classes. That is, it can only be used with related classes which have at least one virtual function. | |
| 32 | Limiting the serializaton of pointers to only such classes would diminish the applicability | |
| 33 | of the library. | |
| 34 | ||
| 35 | <h3>Usage</h3> | |
| 36 | ||
| 37 | The following functions are defined in the header | |
| 38 | <a target="void_cast" href="../../../boost/serialization/void_cast.hpp">void_cast.hpp</a>. | |
| 39 | They are declared in the namespace | |
| 40 | <code style="white-space: normal">boost::serialization</code>. | |
| 41 | ||
| 42 | <dl> | |
| 43 | <dt><h4><pre><code> | |
| 44 | template<class Derived, class Base> | |
| 45 | const void_cast_detail::void_caster & | |
| 46 | void_cast_register( | |
| 47 | Derived const * derived = NULL, | |
| 48 | Base * const base = NULL | |
| 49 | ); | |
| 50 | </code></pre></h4></dt> | |
| 51 | <dd> | |
| 52 | This function "registers" a pair of related types. It stores the fact that | |
| 53 | <code style="white-space: normal">Derived</code> is immediately derived from | |
| 54 | <code style="white-space: normal">Base</code> in a global table. | |
| 55 | <ul> | |
| 56 | <li>This "registration" can be invoked anywhere in the program. The table is built at | |
| 57 | pre-runtime and is available anywhere else in the program. | |
| 58 | <li>only adjacent base/derived pairs need be registered. That is, | |
| 59 | <pre><code> | |
| 60 | void_cast_register<A, B>(); | |
| 61 | void_cast_register<B, C>(); | |
| 62 | </code></pre> | |
| 63 | automatically derives the fact that A can be upcast to C and vice-versa. | |
| 64 | </ul> | |
| 65 | </dd> | |
| 66 | ||
| 67 | <dt><h4><pre><code> | |
| 68 | void * | |
| 69 | void_upcast( | |
| 70 | extended_type_info const & derived_type, | |
| 71 | extended_type_info const & base_type, | |
| 72 | void * const t | |
| 73 | ); | |
| 74 | </code></pre></h4></dt> | |
| 75 | ||
| 76 | <dt><h4><pre><code> | |
| 77 | void * | |
| 78 | void_downcast( | |
| 79 | extended_type_info const & derived_type, | |
| 80 | extended_type_info const & base_type, | |
| 81 | void * const t | |
| 82 | ); | |
| 83 | </code></pre></h4></dt> | |
| 84 | <dd> | |
| 85 | These functions cast a void pointer from one type to another. The source and | |
| 86 | definition types are specified by passing references to the corresponding | |
| 87 | <a href="extended_type_info.html"><code style="white-space: normal"> | |
| 88 | extended_type_info</code></a> | |
| 89 | records. An attempt to cast between types not "registered" with | |
| 90 | <code style="white-space: normal">void_cast_register</code> | |
| 91 | will throw a | |
| 92 | <a href="exceptions.html"><code style="white-space: normal">boost::archive::archive_exception</code></a> | |
| 93 | with value equal to | |
| 94 | <code style="white-space: normal">unregistered_cast</code> | |
| 95 | </dd> | |
| 96 | </dl> | |
| 97 | ||
| 98 | <hr> | |
| 99 | <p><i>© Copyright <a href="http://www.rrsd.com">Robert Ramey</a> 2002-2004. | |
| 100 | Distributed under the Boost Software License, Version 1.0. (See | |
| 101 | accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) | |
| 102 | </i></p> | |
| 103 | </body> | |
| 104 | </html> |