Question

I have an object with a char Array; where the first 5 bytes(char in C++) are additional data and everything afterwards is a string message.

So my question is how can I get a string from starting index 5 way up to the last byte?

I know there is memccpy, but it requires an ending char, which I can’t know beforehand.
I am aware there is a string object in C++, but the idea is to send back and forth a byte array which contains the data and message. So in a sense I serialize and deserialize back and forth.

Any suggestions?

Edit:

Packet * Packet::create(byte const data[])
{
    //Concat all first 4 byte values to a uint32
    unsigned int length = data[0] << 32 | data[1] << 16 | data[2] << 8 | data[3] << 0;

    //4th element is packet type
    PacketType type = (PacketType)data[4];

    string packetData;

    packetData.clear();
    char * cdata;
    //Check packet data is present
    if(sizeof(data) > 5)
    {
        //string s((char)data);
        //packetData = s.substr(4, s.length() - 4);
        strncat(cdata,data+5,sizeof(data)-5);
        packetData.append(cdata);
    }

    //Create new packet;
    Packet * packet = new Packet(length,type,packetData);

    return packet;
};

It won’t accept data[] even when I cast it to char.
The argument isn’t a pointer?

Edit::

Packet * Packet::create(char const * data)
{
    //Concat all first 4 byte values to a uint32
    unsigned int length = data[0] << 32 | data[1] << 16 | data[2] << 8 | data[3] << 0;

    //4th element is packet type
    PacketType type = (PacketType)data[4];

    //Set packet data, if available
    string packetData = (sizeof(data) > 5) ? string(data+5):"";

    Packet * packet = new Packet(length,type,packetData);
    return packet;
};

I still have to test this, but I had to use char, how do I use my own typedef in this situation?

Also what is the difference between
“char * data”
and
“char data[]”

I thought arrays and pointers are one and the same thing.

Answer 1

You mentioned “know there is memccpy, but it requires an ending char, which I can’t know beforehand”. Does that means that your serialized data doesn’t have neither the size of the data nor a delimiter? Without that how do you expect
“string packetData = (sizeof(data) > 5) ? string(data+5):””;”
to work?
For the serialization you could send the size of your data as well in the header. Then use the simple memcpy.