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 *      ...
 *      writer->setProps(props);
 * @endcode
 * 
 * You could set the playlist's creation time like this:
 * 
 * @code
 *      XspfDateTime dateTime(2006, 8, 28, 11, 30, 11, 1, 0);
 *      props.lendDate(&dateTime);
 * @endcode
 * 
 * Similar to the steal/get duality introduced earlier you have to choose
 * between the "lend" and "give" function family when setting
 * information. The whole thing again is only about memory ownership:
 * The lend functions do not transfer ownership, the give functions do.
 * The give family also offers to copy the memory or to assign
 * existing memory. To make this more clear calling 
 *
 * @code
 *      props.giveTitle(_PT("Some title"), XspfData::TRANSFER);
 * @endcode
 * 
 * would be a bad idea since the memory would not be copied but still
 * be deleted on destruction. You should use
 *
 * @code
 *      props.lendTitle(_PT("Some title"));
 * @endcode
 * 
 * in this case.
 *
 * Back to the writer: When you have created a XspfWriter instance
 * you can let it write its content to file:
 *
 * @code
 *      writer.writeFile(_PT("TEST.xspf"));
 * @endcode
 * 
 * In this case that would make a valid playlist without any tracks.
 * So before writing the playlist you should add your tracks:
 *
 * @code
 *      XspfTrack track;
 *      ...
 *      track.lendCreator(_PT("Breaking Benjamin"));
 *      ...
 *      writer.addTrack(track);
 * @endcode
 * 
 * When addTrack() is called the track information is appended to an
 * internal buffer which is written when writeFile() is called eventually.
 * You can add the same track several times and you can call writeFile()
 * several times to write the same playlist to several files;
 * what you cannot do is add more tracks after writing the playlist
 * to a file: You will have to call reset() to start over with an empty track list first.
 * 
 *
 * @section SEC_MALICIOUS Handling malicious XML
 * Let us assume you are using libxspf to power some kind of web service with XSPF
 * reading cabilities.  Let us further assume this service can accept XSPF input
 * from a user. Due to the nature of XML your service would be vulnerable to
 * an <i>XML entity explosion attack</i>. What this means is that a rather small
 * malicious XML file can make the running XML processor a huge amount of memory
 * or CPU time or both.
 *
 * A popular example is <i>billion laughs</i>, of which an XSPF version
 * could look like this:
 *
 * @code
 *      <?xml version="1.0"?>
 *      <!DOCTYPE billion [
 *      <!ELEMENT billion (#PCDATA)>
 *      <!ENTITY laugh0 "ha">
 *      <!ENTITY laugh1 "&laugh0;&laugh0;">
 *      <!ENTITY laugh2 "&laugh1;&laugh1;">
 *      <!ENTITY laugh3 "&laugh2;&laugh2;">
 *      <!ENTITY laugh4 "&laugh3;&laugh3;">
 *      ...
 *      <!ENTITY laugh30 "&laugh29;&laugh29;">
 *      ]>
 *      <playlist version="1" xmlns="http://xspf.org/ns/0/">
 *        <title>&laugh30;</title>
 *        <trackList />
 *      </playlist>
 * @endcode
 *
 * With malicious XML detection enabled, libxspf sets certain limits
 * to the values of entities.  Currently these limits are:
 * - Length of entity values
 * - Sum of lookups per entity value
 * - Lookup depth per entity value
 *
 * The above <i>billion laughs</i> example has these metrics:
 * <table border="0">
 * <tr><td class="indexkey">Entity</td><td class="indexkey">Length</td><td class="indexkey">Lookup Sum</td><td class="indexkey">Lookup Depth</td></tr>
 * <tr><td class="indexvalue">laugh0</td><td class="indexvalue">2</td><td class="indexvalue">0</td><td class="indexvalue">0</td></tr>
 * <tr><td class="indexvalue">laugh1</td><td class="indexvalue">4</td><td class="indexvalue">2</td><td class="indexvalue">1</td></tr>
 * <tr><td class="indexvalue">laugh2</td><td class="indexvalue">8</td><td class="indexvalue">6</td><td class="indexvalue">2</td></tr>
 * <tr><td class="indexvalue">laugh3</td><td class="indexvalue">16</td><td class="indexvalue">14</td><td class="indexvalue">3</td></tr>
 * <tr><td class="indexvalue">laugh4</td><td class="indexvalue">32</td><td class="indexvalue">30</td><td class="indexvalue">4</td></tr>
 * <tr><td class="indexvalue">...</td><td class="indexvalue">...</td><td class="indexvalue">...</td><td class="indexvalue">...</td></tr>
 * <tr><td class="indexvalue">laugh30</td><td class="indexvalue">2,147,483,648</td><td class="indexvalue">2,147,483,646</td><td class="indexvalue">30</td></tr>
 * <tr><td class="indexvalue">laugh<i>n</i></td><td class="indexvalue">2^(<i>n</i>+1)</td><td class="indexvalue">2^(<i>n</i>+1)-2</td><td class="indexvalue"><i>n</i></td></tr>
 * </table>
 *
 * Looking at <i>laugh30</i> all three values are much higher than those of most peaceful XML files.
 * Through calling
 *
 * @code
 *      reader.enableMaliciousXmlDetection(true);
 * @endcode
 *
 * you can make a XspfReader instance protocol these metrics in order to detect
 * malicious XML.  Also, all of these metrics can be limited and adjusted individually;
 * for instance this is how to limit the lookup depth to a maximum of 2:
 *
 * @code
 *      reader.limitLookupDepthPerEntityValue(true);
 *      reader.setMaxLookupDepthPerEntityValue(2);
 * @endcode
 *
 * @attention
 * Malicious XML detection can only work for you if you are clear
 * about your software's use cases.  Tune the detection parameters to
 * what you have to allow and reject everything else.
 */