ptr arithmetics?

[MarcL]

Hello,

How can one do pointer artihmetic in nim? I had to cheat with a fake uint8 type 
to make it work: 
    
    
    type
        UDP_packet = tuple
            port_src: uint16
            port_dst: uint16
            length: uint16
            chksum: uint16
            data:char #cheat here but works perfectly
    
    var my_str = "hi, it is me"
    copyMem(addr t.data, addr mystr[0], mystr.len)
    
    
    Run

but I would have preferred something like 
    
    
    copyMem(addr t + sizeof(UDP_packet), addr mystr[0], mystr.len)
    
    
    Run

Thanks