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 #include &quot;randomlistmodel.h&quot;
 #include &lt;stdlib.h&gt;

 static const int bufferSize(500);
 static const int lookAhead(100);
 static const int halfLookAhead(lookAhead/2);

 RandomListModel::RandomListModel(QObject *parent)
 : QAbstractListModel(parent), m_rows(bufferSize), m_count(10000)
 {
 }

 RandomListModel::~RandomListModel()
 {
 }

 int RandomListModel::rowCount(const QModelIndex &amp;) const
 {
     return m_count;
 }

 QVariant RandomListModel::data(const QModelIndex &amp;index, int role) const
 {
     if (role != Qt::DisplayRole)
         return QVariant();

     int row = index.row();

     if (row &gt; m_rows.lastIndex()) {
         if (row - m_rows.lastIndex() &gt; lookAhead)
             cacheRows(row-halfLookAhead, qMin(m_count, row+halfLookAhead));
         else while (row &gt; m_rows.lastIndex())
             m_rows.append(fetchRow(m_rows.lastIndex()+1));
     } else if (row &lt; m_rows.firstIndex()) {
         if (m_rows.firstIndex() - row &gt; lookAhead)
             cacheRows(qMax(0, row-halfLookAhead), row+halfLookAhead);
         else while (row &lt; m_rows.firstIndex())
             m_rows.prepend(fetchRow(m_rows.firstIndex()-1));
     }

     return m_rows.at(row);
 }

 void RandomListModel::cacheRows(int from, int to) const
 {
     for (int i = from; i &lt;= to; ++i)
         m_rows.insert(i, fetchRow(i));
 }

 QString RandomListModel::fetchRow(int position) const
 {
     return QString::number(rand() % ++position);
 }</pre>
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