module BinData::ByteAlignPlugin

def sum_num_bytes_below_index(index)
  sum = 0
  (0...@field_objs.length).each do |i|
    obj = @field_objs[i]
    if include_obj?(obj)
      sum = sum.ceil + bytes_to_align(obj, sum.ceil) if align_obj?(obj)
      break if i >= index
      nbytes = obj.do_num_bytes
      sum = (nbytes.is_a?(Integer) ? sum.ceil : sum) + nbytes
    end
  end
  sum
end