-- Returns number of bits required to represent val in binary vector
function bits_req(val : natural) return natural is
  variable res_v    : natural;  -- Result
  variable remain_v : natural;  -- Remainder used in iteration
begin
  res_v := 0;
  remain_v := val;
  while remain_v > 0 loop  -- Iteration for each bit required
    res_v := res_v + 1;
    remain_v := remain_v / 2;
  end loop;
  return res_v;
end function;