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()

#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()

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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

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

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

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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] );
		}

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

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this is what I get!

10
FFFFFFA1
02

Why 0xA1 turned into 0xFFFFFFA1 ?!

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] );
        }

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

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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?