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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 - Archive Exceptions</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">Archive Exceptions</h2> | |
24 | </td> | |
25 | </tr> | |
26 | </table> | |
27 | <hr> | |
28 | <dl class="page-index"> | |
29 | <dt><a href="#unregistered_class"><code style="white-space: normal">unregistered_class</code></a> | |
30 | <dt><a href="#invalid_signature"><code style="white-space: normal">invalid_signature</code></a> | |
31 | <dt><a href="#unsupported_version"><code style="white-space: normal">unsupported_version</code></a> | |
32 | <dt><a href="#unsupported_class_version"><code style="white-space: normal">unsupported_class_version</code></a> | |
33 | <dt><a href="#pointer_conflict"><code style="white-space: normal">pointer_conflict</code></a> | |
34 | <dt><a href="#incompatible_native_format"><code style="white-space: normal">incompatible_native_format</code></a> | |
35 | <dt><a href="#array_size_too_short"><code style="white-space: normal">array_size_too_short</code></a> | |
36 | <dt><a href="#input_stream_error"><code style="white-space: normal">input_stream_error</code></a> | |
37 | <dt><a href="#output_stream_error"><code style="white-space: normal">output_stream_error</code></a> | |
38 | <dt><a href="#invalid_class_name"><code style="white-space: normal">invalid_class_name</code></a> | |
39 | <dt><a href="#unregistered_class"><code style="white-space: normal">unregistered_class</code></a> | |
40 | <dt><a href="#multiple_code_instantiation"><code style="white-space: normal">multiple_code_instantiation</code></a> | |
41 | <dt><a href="#xml_archive_parsing_error"><code style="white-space: normal">xml_archive_parsing_error</code></a> | |
42 | <dt><a href="#xml_archive_tag_mismatch"><code style="white-space: normal">xml_archive_tag_mismatch</code></a> | |
43 | <dt><a href="#xml_archive_tag_name_error"><code style="white-space: normal">xml_archive_tag_name_error</code></a> | |
44 | </dl> | |
45 | ||
46 | Archive operators can throw a <code style="white-space: normal">boost::archive_exception</code> | |
47 | object which can be caught by an application program. These exceptions are defined | |
48 | in the files <a target="archive_exception_hpp" href="../../../boost/archive/archive_exception.hpp"> | |
49 | archive_exception.hpp</a> | |
50 | and <a target="basic_xml_archive_hpp" href="../../../boost/archive/basic_xml_archive.hpp"> | |
51 | basic_xml_archive.hpp</a>. | |
52 | <pre><code> | |
53 | namespace boost { | |
54 | namespace archive { | |
55 | ||
56 | class archive_exception : public std::exception | |
57 | { | |
58 | public: | |
59 | typedef enum { | |
60 | unregistered_class, // attempt to serialize a pointer of | |
61 | // an unregistered class | |
62 | invalid_signature, // first line of archive does not contain | |
63 | // expected string | |
64 | unsupported_version, // archive created with library version subsequent | |
65 | // to this one | |
66 | pointer_conflict // an attempt has been made to directly serialize | |
67 | // an object after having already serialized the same | |
68 | // object through a pointer. Were this permitted, | |
69 | // the archive load would result in the creation | |
70 | // of an extraneous object. | |
71 | incompatible_native_format, // attempt to read native binary format | |
72 | // on incompatible platform | |
73 | array_size_too_short, // array being loaded doesn't fit in array allocated | |
74 | input_stream_error // error on stream input | |
75 | invalid_class_name, // class name greater than the maximum permitted. | |
76 | // most likely a corrupted archive or an attempt | |
77 | // to insert virus via buffer overrun method. | |
78 | unregistered_cast, // base - derived relationship not registered with | |
79 | // void_cast_register | |
80 | unsupported_class_version, // type saved with a version # greater than the | |
81 | // one used by the program. This indicates that the proggram | |
82 | // needs to be rebuilt. | |
83 | multiple_code_instantiation, // code for implementing serialization for some | |
84 | // type has been instantiated in more than one module. | |
85 | output_stream_error // error on stream output | |
86 | } exception_code; | |
87 | exception_code code; | |
88 | archive_exception(exception_code c) : code(c) {} | |
89 | virtual const char *what( ) const throw(); | |
90 | }; | |
91 | ||
92 | class xml_archive_exception : public virtual archive_exception | |
93 | { | |
94 | public: | |
95 | typedef enum { | |
96 | xml_archive_parsing_error, // archive doesn't contain expected data | |
97 | xml_archive_tag_mismatch, // start/end tag in archive doesn't match program | |
98 | xml_archive_tag_name_error // tag name contains invalid characters | |
99 | ||
100 | } exception_code; | |
101 | xml_archive_exception(exception_code c){} | |
102 | virtual const char *what( ) const throw(); | |
103 | }; | |
104 | ||
105 | } // archive | |
106 | } // boost | |
107 | </code></pre> | |
108 | <p> | |
109 | <h3><a name="unregistered_class"><code style="white-space: normal">unregistered_class</code></a></h3> | |
110 | An attempt has been made to serialize a polymorphic class through a pointer | |
111 | without either registering it or associating it with an export key. This can also occur | |
112 | when using a new archive whose class name has not been added to the system with the | |
113 | <code style="white-space: normal">BOOST_ARCHIVE_CUSTOM_ARCHIVE_TYPES</code> macro. | |
114 | ||
115 | <h3><a name="invalid_signature"><code style="white-space: normal">invalid_signature</code></a></h3> | |
116 | Archives are initiated with a known string. If this string is not found when | |
117 | the archive is opened, It is presumed that this file is not a valid archive and this | |
118 | exception is thrown. | |
119 | ||
120 | <h3><a name="unsupported_version"><code style="white-space: normal">unsupported_version</code></a></h3> | |
121 | This system records the current library version number to all archives created. Note that this is in | |
122 | no way related to version number of classes used by application programs. This refers | |
123 | to the version of the serialization system used to create the archive. Future versions | |
124 | of this serialization system will be able to identify archives created under a previous | |
125 | (i.e. this) system and alter the loading procedure accordingly. Hence, future enhancements | |
126 | to this serialization system should not obsolete any existing archive files. It is only | |
127 | necessary to increment this version number when the newer system creates archives | |
128 | incompatible in format with the current one. | |
129 | <p>Should it ever occur that an older program attempts to read newer archives whose | |
130 | format has changed, this exception is thrown. | |
131 | ||
132 | <h3><a name="unsupported_class_version"><code style="white-space: normal">unsupported_class_version</code></a></h3> | |
133 | An attempt has been made to load a class whose version has been incremented since the | |
134 | program was written. Suppose that a class has been assigned version number 3 and the program | |
135 | has been built and sent to third parties. Now suppose that the definition of that class | |
136 | has been altered, the version number has been incremented to 4 and new archives have been | |
137 | built. If one attempts to load these new archives with the original program, this | |
138 | exception will be thrown. | |
139 | ||
140 | <h3><a name="pointer_conflict"><code style="white-space: normal">pointer_conflict</code></a></h3> | |
141 | To understand what this exception means consider the following scenario | |
142 | <pre><code> | |
143 | template<class Archive> | |
144 | void T::save(Archive &ar) const | |
145 | { | |
146 | const A * aptr = &a; | |
147 | ar << aptr; // save an instance of object of class A through a pointer | |
148 | ... | |
149 | ar << a; // save an instance of an object of class A | |
150 | assert(aptr == &a); // this must be true | |
151 | } | |
152 | ||
153 | template<class Archive> | |
154 | void T::load(Archive &ar) | |
155 | { | |
156 | A * aptr; | |
157 | ar >> aptr; // create and initialize a new instance of class A | |
158 | ... | |
159 | ar >> a; // restore state of on object of class A | |
160 | assert(aptr == &a); // this won't be true | |
161 | } | |
162 | </pre></code> | |
163 | An object is saved first through a pointer then directly. Upon loading back | |
164 | in the same sequence, we first create an new object and load in its data. Then | |
165 | we load the data into another existing object. Where we started with one | |
166 | object during save, we have two objects after restore. In a more realistic | |
167 | situation, it could be very difficult to find this error. Fortunately, | |
168 | these situations can be detected when the archive is created. When | |
169 | this occurs, this exception is thrown. | |
170 | ||
171 | <h3><a name = "incompatible_native_format"><code style="white-space: normal">incompatible_native_format</code></a></h3> | |
172 | The library currently supports char text, wide char text and native binary | |
173 | archive files. At the beginning of every archive, a signature is written indicating | |
174 | the type of archive. This exception is thrown when an attempt is made to read | |
175 | an archive written in a different format. | |
176 | ||
177 | <h3><a name="array_size_too_short"><code style="white-space: normal">array_size_too_short</code></a></h3> | |
178 | An attempt has been made to read an array that is larger than the array size. | |
179 | This should only occur when the size of an array in code is reduced after an | |
180 | archive has already been created. | |
181 | ||
182 | <h3> | |
183 | <a name="input_stream_error"><code style="white-space: normal">input_stream_error</code></a> | |
184 | <br> | |
185 | <a name="output_stream_error"><code style="white-space: normal">output_stream_error</code></a> | |
186 | </h3> | |
187 | An error has occured during stream input or ouput. Aside from the common | |
188 | situations such as a corrupted or truncated input file, there are | |
189 | several less obvious ones that sometimes occur. | |
190 | <p> | |
191 | This includes | |
192 | an attempt to read past the end of the file. Text files need a terminating | |
193 | new line character at the end of the file which is appended when the | |
194 | archive destructor is invoked. Be sure that an output archive on a stream | |
195 | is destroyed before opening an input archive on that same stream. That is, | |
196 | rather than using something like: | |
197 | <pre><code> | |
198 | std::stringstream ss; | |
199 | std::vector<V> v; | |
200 | boost::archive::text_oarchive oa(ss); | |
201 | oa << v; | |
202 | boost::archive::text_iarchive ia(ss); | |
203 | ia >> v; | |
204 | </code></pre> | |
205 | use | |
206 | <pre><code> | |
207 | std::stringstream ss; | |
208 | std::vector<V> v; | |
209 | { | |
210 | boost::archive::text_oarchive oa(ss); | |
211 | oa << v; | |
212 | } | |
213 | { | |
214 | boost::archive::text_iarchive ia(ss); | |
215 | ia >> v; | |
216 | } | |
217 | </code></pre> | |
218 | <p> | |
219 | Another one is the passing of uninitialized data. In general, the behavior | |
220 | of the serialization library when passed uninitialized data is undefined. | |
221 | If it can be detected, it will invoke an assertion in debug builds. | |
222 | Otherwise, depending on the type of archive, it may pass through without | |
223 | incident or it may result in an archive with unexpected data in it. | |
224 | This, in turn, can result in the throwing of this exception. | |
225 | ||
226 | <h3><a name="invalid_class_name"><code style="white-space: normal">invalid_class_name</code></a></h3> | |
227 | Class name length greater than the maximum permitted. Most likely cause is a corrupted | |
228 | archive or an attempt to insert a virus via the buffer overrun method. | |
229 | ||
230 | <h3><a name="unregistered_cast"><code style="white-space: normal">unregistered_cast</code></a></h3> | |
231 | In order to support casting between pointers of base and derived classes | |
232 | at runtime, a collection of legitimate conversions is maintained by the system. | |
233 | Normally this collection is maintained without any explicit action | |
234 | on the part of the user of the library. However, there are special cases | |
235 | where this might have to be done explicitly and could be overlooked. This | |
236 | is described in <a href="serialization.html#runtimecasting">Runtime Casting</a>. | |
237 | This exception is thrown if an attempt is made to convert between two pointers | |
238 | whose relationship has not been registered, | |
239 | ||
240 | <h3><a name="multiple_code_instantiation"><code style="white-space: normal">multiple_code_instantiation</code></a></h3> | |
241 | This exception is thrown when it is detected that the serialization of the same type | |
242 | has been instantiated more than once. This might occur when | |
243 | serialization code is instantiated in both the mainline and one or more DLLS. | |
244 | ||
245 | <h3><a name="xml_archive_parsing_error"><code style="white-space: normal">xml_archive_parsing_error</code></a></h3> | |
246 | The XML generated by the serialization process is intimately coupled to the | |
247 | C++ class structure, relationships between objects and the serialization | |
248 | specifications. If these become out of sync in any way, the XML may not map | |
249 | to the loading serialization and this exception might be thrown. This might | |
250 | occur for one of the following reasons: | |
251 | <ul> | |
252 | <li>The archive has been edited outside the serialization system. This might | |
253 | be possible if only the data is changed and the XML attributes and nesting | |
254 | structure are left unaltered. But any other editing is likely to render the | |
255 | archive unreadable by the serialization library. | |
256 | <li>The serialization has been altered and an archive generated by the old | |
257 | code is being read. That is, versioning has not been properly employed to | |
258 | properly deserialize previously created archives. | |
259 | </ul> | |
260 | ||
261 | <h3><a name="xml_archive_tag_mismatch"><code style="white-space: normal">xml_archive_tag_mismatch</code></a></h3> | |
262 | This exception will be thrown if the start or end tag of an XML element doesn't match | |
263 | the name specified for the object in the program. | |
264 | ||
265 | <h3><a name="xml_archive_tag_name_error"><code style="white-space: normal">xml_archive_tag_name_error</code></a></h3> | |
266 | This exception will be thrown if the tag name contains invalid characters. Valid characters | |
267 | for an XML tag are: upper and lower case letters, digits, and the following punctuation: .(period), | |
268 | _(underscore), :(colon), and -(hyphen). | |
269 | ||
270 | <hr> | |
271 | <p><i>© Copyright <a href="http://www.rrsd.com">Robert Ramey</a> 2002-2004. | |
272 | Distributed under the Boost Software License, Version 1.0. (See | |
273 | accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) | |
274 | </i></p> | |
275 | </body> | |
276 | </html> |