module BinData::ByteAlignPlugin

def align_obj?(obj)
  obj.has_parameter?(:byte_align)
end

def bytes_to_align(obj, rel_offset)
  align = obj.eval_parameter(:byte_align)
  (align - (rel_offset % align)) % align
end

def do_read(io)
  initial_offset = io.offset
  instantiate_all_objs
  @field_objs.each do |f|
    if include_obj?(f)
      if align_obj?(f)
        io.seekbytes(bytes_to_align(f, io.offset - initial_offset))
      end
      f.do_read(io)
    end
  end
end

def do_write(io)
  initial_offset = io.offset
  instantiate_all_objs
  @field_objs.each do |f|
    if include_obj?(f)
      if align_obj?(f)
        io.writebytes("\x00" * bytes_to_align(f, io.offset - initial_offset))
      end
      f.do_write(io)
    end
  end
end

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