Can i get a array Slicing where the top from?and how?

[Dsby via Digitalmars-d-learn]

Like this:

ubyte[] fun()
{
    ubyte[] str = cast(ubyte[])"hello world";
    ubyte[] by = Mallocator.instance.allocate(str.length);
    by[] = str[];
    return by[5..$];
}
void mian()
{
    ubyte[] aa = fun();
   // i want free the aa's momeny.
   //Mallocator.instance.deallocate(aa);// it is erro, aa.ptr != 
by.ptr?
 // can I get the by's ptr and length?
}


can I get "by" in main function by aa?
i can get the way?is it possible ？