Int16 to QByteArray

TomHoe

Hello Everyone,

I am trying to convert a int into 4 bytes, using the following code:

unsigned int id =  0x2113; // = 8467
QByteArray name;

name.append((id >> 24) & 0XFF);
name.append((id >> 16) & 0XFF);
name.append((id >> 8) & 0XFF);
name.append(id & 0XFF);

qDebug() << name;

And it works until id is bigger than 0xFF, then the result is like \x00\x00\bA and it has to be \x00\x00\x21\x13

What is going wrong?

Thanks

m.sue

Hi,
Your code is correct if you run it on a normal PC under, say, Windows 10. I tried it and got: "\x00\x00!\x13" (! is 33 which is 0x21). On which OS do you run the code? Is it maybe a big endian machine?
-Michael.

SGaist

Hi,

Out of curiosity, why not use QByteArray::number ?

m.sue

Hi,
with qDebug() << QByteArray::number(id,16); you will get the four characters "2113". So it depends on what you really need.
-Michael.

TomHoe

@m-sue
I also got \x00\x00!\x13 on Windows, but didn't knew that '!' is the same as 0x21..

Is there a way to rewrite it as 0x21 ?

Thanks!

TomHoe

@m.sue said in Int16 to QByteArray:

Hi,
with qDebug() << QByteArray::number(id,16); you will get the four characters "2113". So it depends on what you really need.
-Michael.

@SGaist
Yes I've tried that function but I'll send the byteArray with TCP to a micro controller after the transformation, so QByteArray::nummer or .setNum is not an option.

kshegunov

Use QDataStream over the bytearray.

qint32 whatever = 5;

QByteArray data;
QDataStream out(&data, QIODevice::WriteOnly);  // By default is in big endian
out << whatever;

TomHoe

@kshegunov Thanks, less code this way. But still x00!\x13 and not 0x00\0x21\0x13.

Is there a way to rewrite it to regular hex codes ? Or does every controller understand this notation ?

mrjj

Hi
Will the micro controller also run Qt and be able to use QDataStream ?

kshegunov

! and \0x21 are one and the same binary-wise, I don't understand the question, rewrite it to what? It already is \0x21.

JKSH

@TomHoe said in Int16 to QByteArray:

didn't knew that '!' is the same as 0x21..

See http://www.ascii-code.com/

'!' == 33 == 0x21 == 0b00100001

@TomHoe said in Int16 to QByteArray:

Is there a way to rewrite it to regular hex codes ? Or does every controller understand this notation ?

Again, '!' == 33 == 0x21 == 0b00100001

Those are different ways of displaying the same bytes. The controller does not see any "hex" or "notation"; it only sees the sequence of 0's and 1's.

I recommend you learn about how bits/bytes are stored in computer memory: http://statmath.wu.ac.at/courses/data-analysis/itdtHTML/node55.html