Convert QByteArray to int

Damian7546

Hi,
I have QByteArray like below:
"\x00\x00\x00\x00\x02\x00"
How convert above array to int value = 200 ?

In this way : .toInt(nullptr,10) doesn't work.

Damian7546

@Axel-Spoerl said in Convert QByteArray to int:

Check out how int 200 was converted into bytes and then implement a reverse conversion.

I do like below:

QByteArray buf1 = "000000002000"
QByteArray buf2 = QByteArray::fromHex(buf1);

Consequently in buf2 I have "\x00\x00\x00\x00\x02\x00"

So,to reverse conversion I do:

quint16 val = buf2.toHex().toInt(nullptr,10);

Axel Spoerl

@Damian7546
This code parses the byte array as a string with digits. That’s why it doesn’t work.

Maybe I overlook something, but I see hex 000000200, which would be an int value of 512, not 200.

Check out how int 200 was converted into bytes and then implement a reverse conversion.

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Kent-Dorfman

basic C language coding: Qt/QByteArray is not required, nor warranted

uint8_t array[] = { 0x00U, 0x00U, 0x02U, 0x00U };
uint32_t hostValue = ntohl(*(uint32_t*)array);
// should return 0x200U, but beware some architectures don't like 
// dereferencing raw memory as an aritrary type unless guarantees
// are made that the data is native aligned with the expected data type

A workaround is:

uint32_t source = 0UL; // source will be properly aligned
memcpy(&source, array, sizeof(uint32_t));
uint32_t hostValue = ntohl(source);

Damian7546

@Axel-Spoerl said in Convert QByteArray to int:

Check out how int 200 was converted into bytes and then implement a reverse conversion.

I do like below:

QByteArray buf1 = "000000002000"
QByteArray buf2 = QByteArray::fromHex(buf1);

Consequently in buf2 I have "\x00\x00\x00\x00\x02\x00"

So,to reverse conversion I do:

quint16 val = buf2.toHex().toInt(nullptr,10);

Christian Ehrlicher

@Damian7546 said in Convert QByteArray to int:

quint16 val = buf2.toHex().toInt(nullptr,10);

No, since toInt() converts readable characters written as integers, not binary stuff - please read the documentation.