Question

问题很复杂。我用调试器中的内容简化了它。

QFile file(fileName);
file.open(QIODevice::WriteOnly);
QDataStream psudoStream(&file);
psudoStream.setVersion(QDataStream::Qt_4_7);
psudoStream << *packet;// Data is being serialized Properly as I can see The File in Hex Editor
file.close();
QFile file1(fileName);
file1.open(QIODevice::ReadOnly);
QDataStream pS(&file);
pS.setVersion(QDataStream::Qt_4_7);
DG::MouseEventsPacket* msd = new DG::MouseEventsPacket;
qDebug() << pS.device()->size() << pS.device()->pos();
pS >> *msd;//But the Problem Starts from Here
file1.close();

DG :: MouseEventsPacket继承DG :: Packet。和DG :: Packet有＆lt;＆lt;和＆gt;＆gt; QDataStream的运算符重载。 DG :: Packet序列化或Unserializedits数据然后调用this-＆gt; serialize（）或unserialize（）这是纯虚拟传递其流。

qDebug() << pS.device()->size() << pS.device()->pos();
pS >> *msd;

这两行在终端中打印156 0。确认有156个字节可用，当前搜索位置在文件的开头。

然后呼叫转到

QDataStream& DG::operator>>(QDataStream& stream, Packet& packet){
  int _type;
  stream >> packet._state >> _type;
  packet._type = (DG::Packet::PacketType)_type;
  return packet.unserialize(stream);
}

packet._state是quint32，呼叫转到

QDataStream &QDataStream::operator>>(qint32 &i){
i = 0;
CHECK_STREAM_PRECOND(*this)
if (dev->read((char *)&i, 4) != 4) {
    i = 0;
    setStatus(ReadPastEnd);
} else {
    if (!noswap) {
        i = qbswap(i);
    }
}
return *this;
}

这里呼叫转到If。它确实是setStatus（ReadPastEnd）;.但为什么？它在酝酿中。和pos（）返回0，仍然有156个字节要读。

Answer 1

因为你正在做

QDataStream pS(&file);

应该是

QDataStream pS(&file1);

QIODevice使用QDataStream进行首次读取时获取ReadPastEnd

1 个答案: