QByteArray conversions/manipulation.... HOW TO DO IT?

[daemonna]

i got several questions regarding QByteArray conversion and manipulation...

1. how do i convert QByteArray to QBitArray and vice versa? following code should put bytearray to bitarray... is it OK? how it is other way? only change of operator <<?



QBitArray bita;
QByteArray byta;
QDataStream bytads(&byta, QIODevice::ReadWrite);

operator>>(bytads,bita);



2. how do I write/read bytearray from sharedmemory? following code should read 8 bytes form shared memory into bytearray... how to write it?


sharedmem.lock();
QByteArray memar=QByteArray((char*)sharedmem.constData(), 8);
sharedmem.unlock();

[daemonna]

just thought on conversion... can I do it this way?

QVariant(some_qbytearray).toBitArray

and

QVariant(some_qbitarray).toByteArray

[tbscope]

The main question is:
How do you convert
101011100101001001110
To an array of bytes?

Note that a bit array is something completely different than a byte array.
The bit array is mainly used for setting flags.

[daemonna]

Note that a bit array is something completely different than a byte array.
The bit array is mainly used for setting flags.

yes, but i got data from socket as bytearray...
with QByteArray.mid(x, 1) i will extract some byte and i need to change specific bits on that byte.

How to do that?

[tbscope]

Just use bitwise operators.

Either shift to the left or right, use AND, OR, XOR etc...

Example:


unsigned char byte1 = 4; // This is the binary number: 00000100
unsigned char byte2 = 2; // This is the binary number: 00000010

usigned char byte1and2 = byte1 & byte2; // This is the binary number: 00000000
usigned char byte1or2 = byte1 | byte2; // This is the binary number: 000001100
etc...

[wysota]

with QByteArray.mid(x, 1) i will extract some byte and i need to change specific bits on that byte.

How to do that?

You don't need QBitArray for that. Just access the data you need and set respective bits using regular C/C++ bit operators. Transforming QByteArray to QBitArray and then back would just give you needless overhead.

[MTK358]

To set a bit:

byte |= 1 << bitnum

To clear a bit:

byte &= ~(1 << bitnum)