QXmlStreamReader reader(xmlString); while (!reader.atEnd()) { switch (reader.readNext()) { case QXmlStreamReader::StartElement: // process start element break; case QXmlStreamReader::EndElement: // process end element break; case QXmlStreamReader::Characters: // process characters break; case QXmlStreamReader::EndDocument: // handle end of document break; case QXmlStreamReader::Error: // handle error if (reader.error() == QXmlStreamReader::PrematureEndOfDocumentError) { qDebug() << "Unexpected end of document error"; } break; default: break; } }This code reads an XML file represented by the `xmlString` variable, and iterates through its elements using `QXmlStreamReader`. If there is an error encountered during parsing, it checks whether the error is the "Unexpected end of document" error, and outputs a debug message accordingly. The package/library that provides the QXmlStreamReader class is the Qt library, which is a cross-platform development framework for building graphical user interfaces and applications. It is written in C++ and provides a comprehensive set of tools for developing desktop, mobile, and embedded applications on multiple platforms.