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| <title>Serialization - Archive Exceptions</title> |
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| <h3><a href="../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../boost.png" border="0"></a></h3> |
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| <td valign="top"> |
| <h1 align="center">Serialization</h1> |
| <h2 align="center">Archive Exceptions</h2> |
| </td> |
| </tr> |
| </table> |
| <hr> |
| <dl class="page-index"> |
| <dt><a href="#unregistered_class"><code style="white-space: normal">unregistered_class</code></a> |
| <dt><a href="#invalid_signature"><code style="white-space: normal">invalid_signature</code></a> |
| <dt><a href="#unsupported_version"><code style="white-space: normal">unsupported_version</code></a> |
| <dt><a href="#unsupported_class_version"><code style="white-space: normal">unsupported_class_version</code></a> |
| <dt><a href="#pointer_conflict"><code style="white-space: normal">pointer_conflict</code></a> |
| <dt><a href="#incompatible_native_format"><code style="white-space: normal">incompatible_native_format</code></a> |
| <dt><a href="#array_size_too_short"><code style="white-space: normal">array_size_too_short</code></a> |
| <dt><a href="#input_stream_error"><code style="white-space: normal">input_stream_error</code></a> |
| <dt><a href="#output_stream_error"><code style="white-space: normal">output_stream_error</code></a> |
| <dt><a href="#invalid_class_name"><code style="white-space: normal">invalid_class_name</code></a> |
| <dt><a href="#unregistered_class"><code style="white-space: normal">unregistered_class</code></a> |
| <dt><a href="#multiple_code_instantiation"><code style="white-space: normal">multiple_code_instantiation</code></a> |
| <dt><a href="#xml_archive_parsing_error"><code style="white-space: normal">xml_archive_parsing_error</code></a> |
| <dt><a href="#xml_archive_tag_mismatch"><code style="white-space: normal">xml_archive_tag_mismatch</code></a> |
| <dt><a href="#xml_archive_tag_name_error"><code style="white-space: normal">xml_archive_tag_name_error</code></a> |
| </dl> |
| |
| Archive operators can throw a <code style="white-space: normal">boost::archive_exception</code> |
| object which can be caught by an application program. These exceptions are defined |
| in the files <a target="archive_exception_hpp" href="../../../boost/archive/archive_exception.hpp"> |
| archive_exception.hpp</a> |
| and <a target="basic_xml_archive_hpp" href="../../../boost/archive/basic_xml_archive.hpp"> |
| basic_xml_archive.hpp</a>. |
| <pre><code> |
| namespace boost { |
| namespace archive { |
| |
| class archive_exception : public std::exception |
| { |
| public: |
| typedef enum { |
| unregistered_class, // attempt to serialize a pointer of an |
| // an unregistered class |
| invalid_signature, // first line of archive does not contain |
| // expected string |
| unsupported_version, // archive created with library version subsequent |
| // to this one |
| pointer_conflict // an attempt has been made to directly serialize |
| // an object after having already serialized the same |
| // object through a pointer. Were this permitted, |
| // it the archive load would result in the creation |
| // of extraneous object. |
| incompatible_native_format, // attempt to read native binary format |
| // on incompatible platform |
| array_size_too_short, // array being loaded doesn't fit in array allocated |
| input_stream_error // error on stream input |
| invalid_class_name, // class name greater than the maximum permitted. |
| // most likely a corrupted archive or an attempt |
| // to insert virus via buffer overrun method. |
| unregistered_cast, // base - derived relationship not registered with |
| // void_cast_register |
| unsupported_class_version, // type saved with a version # greater than the |
| // one used by the program. This indicates that the proggram |
| // needs to be rebuilt. |
| multiple_code_instantiation, // code for implementing serialization for some |
| // type has been instantiated in more than one module. |
| output_stream_error // error on stream output |
| } exception_code; |
| exception_code code; |
| archive_exception(exception_code c) : code(c) {} |
| virtual const char *what( ) const throw(); |
| }; |
| |
| class xml_archive_exception : public virtual archive_exception |
| { |
| public: |
| typedef enum { |
| xml_archive_parsing_error, // archive doesn't contain expected data |
| xml_archive_tag_mismatch, // start/end tag in archive doesn't match program |
| xml_archive_tag_name_error // tag name contains invalid characters |
| |
| } exception_code; |
| xml_archive_exception(exception_code c){} |
| virtual const char *what( ) const throw(); |
| }; |
| |
| } // archive |
| } // boost |
| </code></pre> |
| <p> |
| <h3><a name="unregistered_class"><code style="white-space: normal">unregistered_class</code></a></h3> |
| An attempt has been made to serialize a polymorphic class through a pointer |
| without either registering it or associating it with an export key. This can also occur |
| when using a new archive how class name has not been added to the system with the |
| <code style="white-space: normal">BOOST_ARCHIVE_CUSTOM_ARCHIVE_TYPES</code> macro. |
| |
| <h3><a name="invalid_signature"><code style="white-space: normal">invalid_signature</code></a></h3> |
| Archives are initiated with a known string. If this string is not found when |
| the archive is opened, It is presumed that this file is not a valid archive and this |
| exception is thrown. |
| |
| <h3><a name="unsupported_version"><code style="white-space: normal">unsupported_version</code></a></h3> |
| This system assigns a version number of 3 to all archives created. Note that this is in |
| no way related to version number of classes used by application programs. This refers |
| to the version of the serialization system used to create the archive. Future versions |
| of this serialization system will be able to identify archives created under previous |
| (i.e. this) system and alter the loading procedure accordingly. Hence, future enhancements |
| to this serialization system should not obsolete any existing archive files. It is only |
| necessary to increment this version number when the newer system creates archives |
| incompatible in format with the current one. |
| <p>Should it ever occur that an older program attempts to read newer archives whose |
| format has changed, this exception is thrown. |
| |
| <h3><a name="unsupported_class_version"><code style="white-space: normal">unsupported_class_version</code></a></h3> |
| An attempt has been made to load a class whose version has been incremented since the |
| program was written. Suppose that a class has been assigned version number 3 and the program |
| has been built and sent to third parties. Now suppose that the definition of that class |
| has been altered, the version number has been incremented to 4 and new archives have been |
| built. If one attempts to load these new archives with the original program, this |
| exception will be thrown. |
| |
| <h3><a name="pointer_conflict"><code style="white-space: normal">pointer_conflict</code></a></h3> |
| To understand what this exception means consider the following scenario |
| <pre><code> |
| template<class Archive> |
| void T::save(Archive &ar) const |
| { |
| const A * aptr = &a; |
| ar << aptr; // save an instance of object of class A through a pointer |
| ... |
| ar << a; // save an instance of an object of class A |
| assert(aptr == &a); // this must be true |
| } |
| |
| template<class Archive> |
| void T::load(Archive &ar) |
| { |
| A * aptr; |
| ar >> aptr; // create and initialize a new instance of class A |
| ... |
| ar >> a; // restore state of on object of class A |
| assert(aptr == &a); // this won't be true |
| } |
| </pre></code> |
| An object is saved first through a pointer then directly. Upon loading back |
| in the same sequence, we first create an new object and load in its data. Then |
| we load the data into another existing object. Where we started with one |
| object during save, we have two objects after restore. In a more realistic |
| situation, it could be very difficult to find this error. Fortunately, |
| these situations can be detected when the archive is created. When |
| this occurs, this exception is thrown. |
| |
| <h3><a name = "incompatible_native_format"><code style="white-space: normal">incompatible_native_format</code></a></h3> |
| The library currently supports char text, wide char text and native binary |
| archive files. At the beginning of every archive, a signature is written indicating |
| the type of archive. This exception is thrown when an attempt is made to read |
| an archive written in a different format. |
| |
| <h3><a name="array_size_too_short"><code style="white-space: normal">array_size_too_short</code></a></h3> |
| An attempt has been made to read an array that is larger than the array size. |
| This should only occur when the size of an array in code is reduced after an |
| archive has already been created. |
| |
| <h3> |
| <a name="input_stream_error"><code style="white-space: normal">input_stream_error</code></a> |
| <br> |
| <a name="output_stream_error"><code style="white-space: normal">output_stream_error</code></a> |
| </h3> |
| An error has occured during stream input or ouput. Aside from the common |
| situations such as a corrupted or truncated input file, there are |
| several less obvious ones that sometimes occur. |
| <p> |
| This includes |
| an attempt to read past the end of the file. Text files need a terminating |
| new line character at the end of the file which is appended when the |
| archive destructor is invoked. Be sure that an output archive on a stream |
| is destroyed before opening an input archive on that same stream. That is, |
| rather than using something like: |
| <pre><code> |
| std::stringstream ss; |
| std::vector<V> v; |
| boost::archive::text_oarchive oa(ss); |
| oa << v; |
| boost::archive::text_iarchive ia(ss); |
| ia >> v; |
| </code></pre> |
| use |
| <pre><code> |
| std::stringstream ss; |
| std::vector<V> v; |
| { |
| boost::archive::text_oarchive oa(ss); |
| oa << v; |
| } |
| { |
| boost::archive::text_iarchive ia(ss); |
| ia >> v; |
| } |
| </code></pre> |
| <p> |
| Another one is the passing of uninitialized data. In general, the behavior |
| of the serialization library when passed uninitialized data is undefined. |
| If it can be detected, it will invoke an assertion in debug builds. |
| Otherwise, depending on the type of archive, it may pass through without |
| incident or it may result in an archive with unexpected data in it. |
| This, in turn, can result in the throwing of this exception. |
| |
| <h3><a name="invalid_class_name"><code style="white-space: normal">invalid_class_name</code></a></h3> |
| Class name length greater than the maximum permitted. Most likely cause is a corrupted |
| archive or an attempt to insert virus via buffer overrun method. |
| |
| <h3><a name="unregistered_cast"><code style="white-space: normal">unregistered_cast</code></a></h3> |
| In order to support casting between pointers of base and derived classes |
| at runtime, a collection of legitimate conversions is maintained by the system. |
| Normally this collection is maintained without any explicit action |
| on the part of the user of the library. However, there are special cases |
| where this might have to be done explicitly and could be overlooked. This |
| is described in <a href="serialization.html#runtimecasting">Runtime Casting</a>. |
| This exception is thrown if an attempt is made to convert between two pointers |
| whose relationship has not been registered, |
| |
| <h3><a name="multiple_code_instantiation"><code style="white-space: normal">multiple_code_instantiation</code></a></h3> |
| This exception is thrown when it is detected that the serialization of the same type |
| has been instantiated more that once. This might occur when |
| serialization code is instantiated in both the mainline and one or more DLLS. |
| |
| <h3><a name="xml_archive_parsing_error"><code style="white-space: normal">xml_archive_parsing_error</code></a></h3> |
| The XML generated by the serialization process is intimately coupled to the |
| C++ class structure, relationships between objects and the serialization |
| specifications. If these become out of sync in any way, the XML may not map |
| to the loading serialization and this exception might be thrown. This might |
| occur for one of the following reasons: |
| <ul> |
| <li>The archive has been edited outside the serialization system. This might |
| be possible if only the data is changed and not the XML attributes and nesting |
| structure is left unaltered. But any other editing is likely to render the |
| archive unreadable by the serialization library. |
| <li>The serialization has been altered and an archive generated by the old |
| code is being read. That is, versioning has not been properly employed to |
| properly deserialize previously created archives. |
| </ul> |
| |
| <h3><a name="xml_archive_tag_mismatch"><code style="white-space: normal">xml_archive_tag_mismatch</code></a></h3> |
| This exception will be thrown if the start or end tag of and XML element doesn't match |
| the name specified for the object in the program. |
| |
| <h3><a name="xml_archive_tag_name_error"><code style="white-space: normal">xml_archive_tag_name_error</code></a></h3> |
| This exception will be thrown if the tag name contains invalid characters. Valid characters |
| for an XML tag are: upper and lower case letters, digits, and the following punctuation: .(period), |
| _(underscore), :(colon), and -(hyphen). |
| |
| <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> |
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