QDataStream简单读写以及方便网络传输消息的作用

QDataStream类用于将任意常见类型的数据以二进制写入由QFile指定的磁盘文件中。同时也可以按写入的顺序读取这些类型的数据,并且还可以用在网络通信中传输消息，读取和传输都非常方便

//将数据写入文件中，但是数据会覆盖掉之前的
void MainWindow::on_pushButton_clicked()
{
    QFile file("test.txt");
    file.open(QIODevice::WriteOnly);
    QDataStream out(&file);
    QString str = "aaaa";
    QString str1 = "1111";
    QString str2 = "2222";
    out << str << str1 << str2;
    file.close();
}
//从文件中读出数据
void MainWindow::on_pushButton_2_clicked()
{
    QFile file("test.txt");
    file.open(QIODevice::ReadOnly);
    QDataStream in(&file);
    QString str,str1,str2;
    in >> str >> str1 >> str2;
    file.close();
    ui->textEdit->append(str);
    ui->textEdit->append(str1);
    ui->textEdit->append(str2);
}

//将要发送的数据包转为QDataStream 后发送
void novideo_send(uchar flg,QString local_ip,QString remote_ip,quint16 remote_port)
{
    QByteArray datagram;
    QDataStream in(&datagram,QIODevice::WriteOnly);
    unsigned short nMsgHead,nMsgLength,nMsgFlg,nMsgTail;
    nMsgHead= 0x66bb;
    nMsgLength = 0;
    nMsgFlg = 0x0003;//端口信息
    nMsgTail = 0x77cc;
    quint64 fill = 0;
    int local_ip1 = 0, local_ip2 = 0, local_ip3 = 0, local_ip4 = 0;
    if ( sscanf(local_ip.toLatin1().data(),"%d.%d.%d.%d",&local_ip1,&local_ip2,&local_ip3,&local_ip4) < 0 )
    {
        return ;
    }
    in<<nMsgHead<<nMsgLength<<nMsgFlg<<flg<<uchar(local_ip1)<<uchar(local_ip2)<<uchar(local_ip3)<<uchar(local_ip4)<<nMsgTail<<fill<<fill<<fill<<fill<<fill<<fill<<fill<<fill;
    udp_send->writeDatagram(datagram, QHostAddress(remote_ip), 8200);
}
//将接收到的数据包通过QDataStream解析出来
void novideo_receive(QByteArray datagram)
{
    QDataStream in(&datagram,QIODevice::ReadWrite);
    in.setVersion(QDataStream::Qt_5_1);
    unsigned short nMsgHead,nMsgLength,nMsgFlg,nMsgTail;
    uchar flg;
    uchar local_ip1 = 0, local_ip2 = 0, local_ip3 = 0, local_ip4 = 0;
    in>>nMsgHead>>nMsgLength>>nMsgFlg>>flg>>local_ip1>>local_ip2>>local_ip3>>local_ip4>>nMsgTail;

    QString ipstr,ipstr1;
    ipstr = QString("%1.%2.%3.%4").arg(local_ip1).arg(local_ip2).arg(local_ip3).arg(local_ip4);

}

QDataStream类实现了将QIODevice的二进制数据串行化。一个数据流就是一个二进制编码信息流 ，它完全独立于主机的 *** 作系统，cpu和字节顺序。数据流可以读写未编码的原始二进制数据。QDataStream类可以实现C++基本数据类型的串行化，比如char，short int，int，char*等。串行化更复杂的数据是通过将数据分解为基本的数据类型来完成的。

#include 
#include 
#include 
#include 
#include 
struct MyData
{
    int num;
    char ch[2];
    bool b;
    double d;
    qint16 count;
};//4+2+1+8+2=1
int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    //将二进制数据写入到数据流中
    QFile file("myFile.dat");
    QFileInfo info(file);
    qDebug()<<info.absoluteFilePath();
    if(!file.open(QIODevice::WriteOnly))
    {
        qDebug()<<file.errorString();
    }
    QDataStream out(&file);
    out<<QString("the answer is");
    out<<(qint32)42;
    file.flush();
    file.close();
    //从数据流中读取二进制数据
    if(!file.open(QIODevice::ReadOnly))
    {
        qDebug()<<file.errorString();
    }
    QDataStream in(&file);
    QString str;
    qint32 num;
    in>>str>>num;
    file.close();
    //写入结构体
    QFile file2;
    file2.setFileName("myFile2.dat");
    if(!file2.open(QIODevice::WriteOnly))
    {
        qDebug()<<file.errorString();
    }
    MyData data;
    data.b = true;
    data.num = 64;
    data.count = 16;
    data.ch[0] = 'a';
    data.ch[1] = 'b';
    data.d = 3.1415926;
    QDataStream out2(&file2);
    out2.writeBytes((const char*)&data,sizeof(MyData));
    file2.flush();
    file2.close();
    //读取结构体
    if(!file2.open(QIODevice::ReadOnly))
    {
        qDebug()<<file.errorString();
    }
    QDataStream in2(&file2);
    char *pBuf = new char[sizeof(MyData)];
    uint count;
    in2.readBytes(pBuf,count);
    MyData* pData = (MyData*)pBuf;
    qDebug()<<pData->b;
    qDebug()<<pData->ch;
    qDebug()<<pData->count;
    qDebug()<<pData->d;
    qDebug()<<pData->num;
    file2.close();
    return a.exec();
}

转自Qt 数据流QDataStream