Convert unsigned char to QString

aftershocker1

Hello

Looking for some help. I am trying to convert an unsigned char array to a string or QString. I have tried a few different ways so far with no success or crashing the application when testing.

The char array need into a string is buf[8] + buf[9] and these contain hex codes (ie f8 + 6f). So I want my string to read "f86f". I didn't think it would be as difficult as it is as it is no problem printing f8 and 6f to the console!

Thanks in advance!

sierdzio

Try something like this:

const QByteArray data = QByteArray::number(buf);
const QString string = data.toHex();

brain to terminal, not tested; you'll probably need to tweak it.

JonB

@aftershocker1 said in Convert unsigned char to QString:

The char array need into a string is buf[8] + buf[9] and these contain hex codes (ie f8 + 6f). So I want my string to read "f86f".

If you really mean this --- the string is to read f86f, i.e. showing the characters/bytes in hex --- you will want to use QString::toLatin1().toHex().

aftershocker1

I don't think I understood the problem properly in my initial post. The value in buf[9] is 248 (0xF8) and the value in buf[10] is 111 (0x6f) although these values may change(data is coming in from a hid).

In the console I can get it to print the value in hex format using

qDebug("%02hhx ", buf[9]);
qDebug("%02hhx ", buf[10]);

So, what I want to do is use the hex values and turn them into a string(once in a string I have a function to convert the string into binary which enables me to see the error flags from the hid).

What is the best way to convert buf[9] and buf[10] into the hex numbers and change them into a string?

sierdzio

@aftershocker1 said in Convert unsigned char to QString:

What is the best way to convert buf[9] and buf[10] into the hex numbers and change them into a string?

That's what we answered above already.

But isn't it wasteful for you to convert a number (which is already binary!) to string, then to hex, then to binary again? Why don't you just work on the numbers directly?

JonB

@aftershocker1
I already suggested QString::toLatin1().toHex(). Without bothering with a QString why not go straight from a QByteArray (you have bytes) via QByteArray QByteArray::toHex() const?

aftershocker1

@sierdzio Good point! I have just got a little lost in the process.

aftershocker1

So the code below why would data = 248 (which is the correct value of buf[9]) and data_as_hex_string = 323438?

  QByteArray data = QByteArray::number(buf[9]);
  QString data_as_hex_string = data.toHex();

I thought the data_as_hex would be F8?

JonB

@aftershocker1
My friend, you really need to sort your understanding of bytes, strings & numbers out! :)

why would data = 248

No! data is set to "248", a string, not a number. Look at https://doc.qt.io/qt-5/qbytearray.html#number

Returns a byte array containing the string equivalent of the number n to base base (10 by default).

So the string is 3 characters, and the hex string representation of those 3 bytes is "323438".

You want something more like:

QByteArray data(buf, sizeOfBuffer);    // wrap buffer (or some section of it) in a `QByteArray`
QString data_as_hex_string = data.mid(9, 2).toHex();    // pick out bytes [9,10] for conversion to hex

Unsolved Convert unsigned char to QString