[SOLVED] Unable to read data by QDataStream

[karankumar1609]

Hello All,

I am currently trying to read data from socket, but it is something new to me that i want to read a structure from socket.
I have the following structure with implemented overloaded <<, and >> operator

typedef struct hShakeAckPkt
{
    unsigned short Id;              // 0XFEFE
    unsigned short BlockSize;       // 45
    long Reserved1[2];               // fill with 0
    unsigned short FeedType;        // fill with 0
    unsigned short Reserved2[3];    // fill with 0
    unsigned short Major;           // 1
    unsigned short Minor;           // 4
    unsigned char ProgramId[21];    // "CTCL" rest with '\0'
 
}hShakeAckPkt;
 
QDataStream & operator << (QDataStream &out, const hShakeAckPkt &hand_shake_pkt);
QDataStream & operator >> (QDataStream &in, hShakeAckPkt &hand_shake_pkt);

typedef struct hShakeAckPkt
{
    unsigned short Id;              // 0XFEFE
    unsigned short BlockSize;       // 45
    long Reserved1[2];               // fill with 0
    unsigned short FeedType;        // fill with 0
    unsigned short Reserved2[3];    // fill with 0
    unsigned short Major;           // 1
    unsigned short Minor;           // 4
    unsigned char ProgramId[21];    // "CTCL" rest with '\0'

}hShakeAckPkt;

QDataStream & operator << (QDataStream &out, const hShakeAckPkt &hand_shake_pkt);
QDataStream & operator >> (QDataStream &in, hShakeAckPkt &hand_shake_pkt);

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for reading from datastream i have implemented the above operator as :

QDataStream &operator <<(QDataStream &out, const hShakeAckPkt &hand_shake_pkt)
{
    out << hand_shake_pkt.Id;
    out << hand_shake_pkt.BlockSize;
    out.writeRawData(reinterpret_cast<const char*>(hand_shake_pkt.Reserved1), 2);
    out << hand_shake_pkt.FeedType;
    out.writeRawData(reinterpret_cast<const char*>(hand_shake_pkt.Reserved2), 3);
    out << hand_shake_pkt.Major;
    out << hand_shake_pkt.Minor;
    out.writeRawData(reinterpret_cast<const char*>(hand_shake_pkt.ProgramId), 21);
 
    return out;
}
 
QDataStream &operator >>(QDataStream &in, hShakeAckPkt &hand_shake_pkt)
{
    in >> hand_shake_pkt.Id;
    in >> hand_shake_pkt.BlockSize;
    in.readRawData(reinterpret_cast<char*>(hand_shake_pkt.Reserved1), 2);
    in >> hand_shake_pkt.FeedType;
    in.readRawData(reinterpret_cast<char*>(hand_shake_pkt.Reserved2), 3);
    in >> hand_shake_pkt.Major;
    in >> hand_shake_pkt.Minor;
    in.readRawData(reinterpret_cast<char*>(hand_shake_pkt.ProgramId), 21);
 
    return in;
}

QDataStream &operator <<(QDataStream &out, const hShakeAckPkt &hand_shake_pkt)
{
    out << hand_shake_pkt.Id;
    out << hand_shake_pkt.BlockSize;
    out.writeRawData(reinterpret_cast<const char*>(hand_shake_pkt.Reserved1), 2);
    out << hand_shake_pkt.FeedType;
    out.writeRawData(reinterpret_cast<const char*>(hand_shake_pkt.Reserved2), 3);
    out << hand_shake_pkt.Major;
    out << hand_shake_pkt.Minor;
    out.writeRawData(reinterpret_cast<const char*>(hand_shake_pkt.ProgramId), 21);

    return out;
}

QDataStream &operator >>(QDataStream &in, hShakeAckPkt &hand_shake_pkt)
{
    in >> hand_shake_pkt.Id;
    in >> hand_shake_pkt.BlockSize;
    in.readRawData(reinterpret_cast<char*>(hand_shake_pkt.Reserved1), 2);
    in >> hand_shake_pkt.FeedType;
    in.readRawData(reinterpret_cast<char*>(hand_shake_pkt.Reserved2), 3);
    in >> hand_shake_pkt.Major;
    in >> hand_shake_pkt.Minor;
    in.readRawData(reinterpret_cast<char*>(hand_shake_pkt.ProgramId), 21);

    return in;
}

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The problem is when i read the data it is not the original one.
And what is the procedure to read array??

Anyone have idea about that?

[ChrisW67]

Reserved1: How do you propose to recover 2 longs from the file if you only write 2 bytes to the file in the first place?
Reserved2: How do you propose to recover 3 unsigned shorts from the file if you only write 3 bytes to the file in the first place?

Write and read an array one element at a time for as many elements as the array contains.

[anda_skoa]

Aside from your code obviously being wrong (a single long has more than 2 bytes, two longs have way more than that), I would say the way to serialize an array is to loop over its entries and serialize them individually.

Cheers,
_

[karankumar1609]

This means if i write

QDataStream &operator <<(QDataStream &out, const hShakeAckPkt &hand_shake_pkt)
    {
    out << hand_shake_pkt.Id;
    out << hand_shake_pkt.BlockSize;
    out.writeRawData(reinterpret_cast<const char*>(hand_shake_pkt.Reserved1), 16);
    out << hand_shake_pkt.FeedType;
    out.writeRawData(reinterpret_cast<const char*>(hand_shake_pkt.Reserved2), 6);
    out << hand_shake_pkt.Major;
    out << hand_shake_pkt.Minor;
    out.writeRawData(reinterpret_cast<const char*>(hand_shake_pkt.ProgramId), 21);
 
    return out;
    }
 
    QDataStream &operator >>(QDataStream &in, hShakeAckPkt &hand_shake_pkt)
    {
    in >> hand_shake_pkt.Id;
    in >> hand_shake_pkt.BlockSize;
    in.readRawData(reinterpret_cast<char*>(hand_shake_pkt.Reserved1), 16);
    in >> hand_shake_pkt.FeedType;
    in.readRawData(reinterpret_cast<char*>(hand_shake_pkt.Reserved2), 6);
    in >> hand_shake_pkt.Major;
    in >> hand_shake_pkt.Minor;
    in.readRawData(reinterpret_cast<char*>(hand_shake_pkt.ProgramId), 21);
 
    return in;
    }

QDataStream &operator <<(QDataStream &out, const hShakeAckPkt &hand_shake_pkt)
    {
    out << hand_shake_pkt.Id;
    out << hand_shake_pkt.BlockSize;
    out.writeRawData(reinterpret_cast<const char*>(hand_shake_pkt.Reserved1), 16);
    out << hand_shake_pkt.FeedType;
    out.writeRawData(reinterpret_cast<const char*>(hand_shake_pkt.Reserved2), 6);
    out << hand_shake_pkt.Major;
    out << hand_shake_pkt.Minor;
    out.writeRawData(reinterpret_cast<const char*>(hand_shake_pkt.ProgramId), 21);
     
    return out;
    }
     
    QDataStream &operator >>(QDataStream &in, hShakeAckPkt &hand_shake_pkt)
    {
    in >> hand_shake_pkt.Id;
    in >> hand_shake_pkt.BlockSize;
    in.readRawData(reinterpret_cast<char*>(hand_shake_pkt.Reserved1), 16);
    in >> hand_shake_pkt.FeedType;
    in.readRawData(reinterpret_cast<char*>(hand_shake_pkt.Reserved2), 6);
    in >> hand_shake_pkt.Major;
    in >> hand_shake_pkt.Minor;
    in.readRawData(reinterpret_cast<char*>(hand_shake_pkt.ProgramId), 21);
     
    return in;
    }

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This would be correct????

[stampede]

Serializing a long without taking endianness into account will result in bugs on machines with different byte ordering.
You can let Qt handle this by using QDataStream operators for built-in types (Qt defaults to big endian).

[karankumar1609]

Thanks for the effective and quick response.
It works,,,,,
Now i use

QDataStream &operator <<(QDataStream &out, const hShakeAckPkt &hand_shake_pkt)
{
    out << hand_shake_pkt.Id;
    out << hand_shake_pkt.BlockSize;
 
    for(int i = 0; i < 2; ++i)
        out << hand_shake_pkt.Reserved1[i];
 
    out << hand_shake_pkt.FeedType;
 
    for(int i = 0; i < 3; ++i)
        out << hand_shake_pkt.Reserved2[i];
 
    out << hand_shake_pkt.Major;
    out << hand_shake_pkt.Minor;
 
    for(int i = 0; i < 21; ++i)
        out << hand_shake_pkt.ProgramId[i];
 
    return out;
}
 
QDataStream &operator >>(QDataStream &in, hShakeAckPkt &hand_shake_pkt)
{
    in >> hand_shake_pkt.Id;
    in >> hand_shake_pkt.BlockSize;
 
    for(int i = 0; i < 2; ++i)
        in >> hand_shake_pkt.Reserved1[i];
 
    in >> hand_shake_pkt.FeedType;
 
    for(int i = 0; i < 3; ++i)
        in >> hand_shake_pkt.Reserved2[i];
 
    in >> hand_shake_pkt.Major;
    in >> hand_shake_pkt.Minor;
 
    for(int i = 0; i < 21; ++i)
        in >> hand_shake_pkt.ProgramId[i];
 
    return in;
}

QDataStream &operator <<(QDataStream &out, const hShakeAckPkt &hand_shake_pkt)
{
    out << hand_shake_pkt.Id;
    out << hand_shake_pkt.BlockSize;

    for(int i = 0; i < 2; ++i)
        out << hand_shake_pkt.Reserved1[i];

    out << hand_shake_pkt.FeedType;

    for(int i = 0; i < 3; ++i)
        out << hand_shake_pkt.Reserved2[i];

    out << hand_shake_pkt.Major;
    out << hand_shake_pkt.Minor;

    for(int i = 0; i < 21; ++i)
        out << hand_shake_pkt.ProgramId[i];

    return out;
}

QDataStream &operator >>(QDataStream &in, hShakeAckPkt &hand_shake_pkt)
{
    in >> hand_shake_pkt.Id;
    in >> hand_shake_pkt.BlockSize;

    for(int i = 0; i < 2; ++i)
        in >> hand_shake_pkt.Reserved1[i];

    in >> hand_shake_pkt.FeedType;

    for(int i = 0; i < 3; ++i)
        in >> hand_shake_pkt.Reserved2[i];

    in >> hand_shake_pkt.Major;
    in >> hand_shake_pkt.Minor;

    for(int i = 0; i < 21; ++i)
        in >> hand_shake_pkt.ProgramId[i];

    return in;
}

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