从ipc fifo文件描述符读取缓冲区时，QDataStream未初始化

Question

我想使用fifo（ipc）在两个应用程序之间进行通信，我已经通过“mkfifo MyPipe”命令创建了一个fifo。

第一个App：

....
....
fd = open("MyPipe", O_NONBLOCK | O_WRONLY);

QByteArray buf;
QDataStream bdwr(&buf,QIODevice::WriteOnly);
bdwr.setVersion(kDSVersion);

myclassObjWr.lname = "AAAAA";
myclassObjWr.fname = "BBBBB";

bdwr << myclassObjWr.lname << myclassObjWr.fname ;

ssize_t written = write(fd,buf.data() , buf.length());

.....
.....

第二个App：

....
....
fd = open("MyPipe", O_NONBLOCK | O_RDONLY);
ssize_t nread;
QByteArray rxbuf;
static const QDataStream::Version kDSVersion = QDataStream::Qt_5_12;
QDataStream bdrd(&rxbuf, QIODevice::ReadWrite);
bdrd.setVersion(kDSVersion);

nread = read(fd, rxbuf.data(),200);

if ( nread > 0)
{
    bdrd.writeRawData(rxbuf.data(),nread);
    bdrd >> myclassObjrd.lname >> myclassObjrd.fname;  
    qDebug() << "lname: " << myclassObjrd.lname;
}
....

....

在读取ipc fifo之后，“rxbuf”被完全初始化，但是“myclassObjrd.lname”和“myclassObjrd.fname”都是空的并且没有初始化。

Answer 1

它通过使用中间无符号字符缓冲区来解决，以在第二个应用程序中初始化QByteArray，如下所示。

# ...
ssize_t nread;

QByteArray buf;

unsigned char* rxbuf;

static const QDataStream::Version kDSVersion = QDataStream::Qt_5_12;

QDataStream bdrd(&buf, QIODevice::ReadOnly);

bdrd.setVersion(kDSVersion);

rxbuf = (unsigned char*)malloc(200);

nread = read(fd, rxbuf,200);

if ( nread > 0)
{

   for (int i = 0 ; i < nread; i++) {

   buf[i] = rxbuf[i] ;   //init QByteArray

   }

bdrd >> myclassObjrd.lname >> myclassObjrd.fname;  

qDebug() << "lname: " << myclassObjrd.lname;

}
# ...