Fiddle::Pointer#[]

static VALUE
rb_fiddle_ptr_aref(int argc, VALUE argv[], VALUE self)
{
    VALUE arg0, arg1;
    VALUE retval = Qnil;
    size_t offset, len;
    struct ptr_data *data;

    TypedData_Get_Struct(self, struct ptr_data, &fiddle_ptr_data_type, data);
    if (!data->ptr) rb_raise(rb_eFiddleDLError, "NULL pointer dereference");
    switch( rb_scan_args(argc, argv, "11", &arg0, &arg1) ){
      case 1:
        offset = NUM2ULONG(arg0);
        retval = INT2NUM(*((char *)data->ptr + offset));
        break;
      case 2:
        offset = NUM2ULONG(arg0);
        len    = NUM2ULONG(arg1);
        retval = rb_str_new((char *)data->ptr + offset, len);
        break;
      default:
        rb_bug("rb_fiddle_ptr_aref()");
    }
    return retval;
}