Converting qint8 to string

roboterprogrammer

hi,

ah okay. but when i do like this, i get an " QIODevice::read: WriteOnly device" advice.

@ qint8 integ = 0b00001111;
QByteArray helparray = "GUISTATUS";
QByteArray data;
QDataStream s(&data, QIODevice::WriteOnly);
QString helpstring;

s << integ <<" test";
qDebug() << "data: " << data;
s >> helpstring;

  qDebug() << "helpstring: " <<  helpstring; @

the output in the qdebug is not correct.
data: " -> incomplete
helpstring: "" -> empty

its important its a string i send, because then i can check if there are unwanted signs inside like /n i could remove manually.
i feel like qt put some of those with the << operator, so i keep full control.

andre

Hmmm.... Perhaps QDataStream isn't for you after all. I am sorry I suggested it. QDataStream does not only stream the raw data, but also some meta data (like the length of a QByteArray you stream in) if needed. You can circumvent that using QDataStream::writeBytes or QDataStream::writeRawBytes, but that defeats the point of using it in the first place, right?

Note that your warning is caused by your line 9 above. If you use a WriteOnly stream, you can't obviouly read from it. Also, streaming into a QString probably doesn't do what you expect it does... Instead, use one of the QString::from<Encoding>() methods to construct a string from a QByteArray.

Anyway, you can probably get rid of QDataStream completely, as it screws up your data in your case if you add a QByteArray. Instead, you could try this:

@
//again, untested code:
QByteArray data;
data += "GUISTATUS";
data.append( reinterpret_cast<char*>(&myUInt8Variable), 1 ); //Warning: no idea if this will work ok
qDebug() << "data:" << data;
@

Or, using QDataStream again, but only for the integer:
@
//again, untested code:
QByteArray data;
data += "GUISTATUS";
QDataStream s(&data, QIODevice::WriteOnly);
s << myUInt8Variable;
qDebug() << "data:" << data;
@

Neutron Stein

did you try QString().setNum(myUInt8Variable) to convert ?

andre

[quote author="Neutron Stein" date="1342534822"]did you try QString().setNum(myUInt8Variable) to convert ?[/quote]

He was looking for a QByteArray (to send over a TCP socket). Converting to a string does not help for that.

Neutron Stein

isn't the topic?converting from quint8 to string?

andre

[quote author="Neutron Stein" date="1342535272"]isn't the topic?converting from quint8 to string?[/quote]

Not really:
[quote author="roboterprogrammer" date="1342524761"]i want to send an qint8 via tcpip, and for that, after the connection is etablished via the socket,
i want to use the
@
socket->write("GUISTATUS: \n");@
directive
and i want to add one qint8 variable, in which 8 independent informations are included, in each bit one.[/quote]

You need to read more than just the subject header... And yes, I sometimes fail to do that as well.

Neutron Stein

I think this can help.
@
QByteArray paquet;
QDataStream data(&paquet,QIODevice::WriteOnly);
data << (quint8)0;
data << theStringToSend;
data.device()->seek(0);
data << (quint8)(paquet.size() - sizeof(quint8));
socket->write(paquet);
@

roboterprogrammer

hi,

solution 2 works now, so i can send data (changes that operator made) to gui,
but its not nice.

if no better solution i will keep it like this.
the thing is:

with @s << myUInt8Variable;@

it writes it to the first postiton of data.

so in qdebug instead of GUISTATUSX i get XUISTATUS

how can i put it on the end?

roboterprogrammer

wow so many replys i will read them, and try the new stuff out.

thanks

Neutron Stein

sorry I sent the wrong code.but it might be something like that. there i put the packet size at the beginning of the packet to be sent.i think you just need to put there what you want to send.
Sorry for mistakes i'm newbie