QFile保留指定位置的数据

QFile file(path);
bool ok = file.open(QIODevice::ReadOnly);
if (ok)
{
    int off = 10;
    file.seek(file.size() - off);   //将当前读取文件指针移动到指定位置
    QString str = QString::fromLocal8Bit(file.read(off));
    file.close();

    ok = file.open(QIODevice::WriteOnly);
    if (ok)
    {
        file.write(str.toUtf8());
        file.close();
    }
}


file.resize(10);   //保留文件前面10个字节的数据