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