QDataStream and serialization

[pdoria]

Ok ... maybe it's me who's got really tired :) but:

I have this struct:


#pragma pack(1)
typedef struct {
quint8 DLE; // ASCII DLE character (16 decimal)
quint8 packet_id;
quint8 size_app_payload; // number of bytes of packet data (bytes 3 to n-4)
char app_payload[255]; // 0 to 255 bytes
quint8 checksum; // 2's complement of the sum of all bytes from byte 1 to byte n-4 (end of the payload)
quint8 DLE_end; // same as DLE
quint8 ETX; // End of text - ASCII ETX character (3 decimal)
} serial_packet_format;
#pragma pack()


filled it with:
sPacket Contents
DLE: 10
Packet id: A1
size app payload: 02
Payload:
01
00
Checksum: 5C
DLE end: 10
ETX: 03

Now the serialization:

QByteArray byteArray;
QDataStream stream(&byteArray, QIODevice::WriteOnly);

stream<< sPacket.DLE // DLE
<< sPacket.packet_id // packet id
<< sPacket.size_app_payload; // app_payload size


and so on for the rest...

now when I print the resulting byte array

for (i = 0; i < byteArray.size(); i++) {
printf("%02X\r\n", (qint8) byteArray[i] );
}

this is what I get!

10
FFFFFFA1
02

Why 0xA1 turned into 0xFFFFFFA1 ?! :confused:

Could someone please take me out of my misery? :)

Best regards,
Pedro Doria Meunier

[pdoria]

:bump:

Guys I know this to be one the dumbest threads ever...
However... I'm baffled by it and it's interfering in sending data.

Any pointers highly appreciated.

BR,
Pedro.

[squidge]

You asking printf to treat an integer as a qint8, so what do you expect? Anything more than 0x7F will always be negative number.

Maybe this is what you meant:


for (i = 0; i < byteArray.size(); i++) {
printf("%02X\r\n", (quint8) byteArray[i] );
}


Note the quint8 instead of qint8 :)

[pdoria]

Done that my friend.

data still gets 0xFFFFFFA1 in the stream ...

Thanks.

[squidge]

Actually in the stream? Or just in the output?

Your putting 3 bytes into a QByteArray, so it can not be putting 0xFFFFFFA1 in the stream. Have you tried copying the QByteArray to a standard quint8 array and viewing the memory in the debugger?

[wysota]

What do you get if you read the data back from the stream?