class FDB::DirectoryLayer

def check_version(tr, write_access)
  version = tr[@root_node['version']]
  initialize_directory(tr) if !version && write_access
  return if !version
  version = version.to_s.unpack('III<')
  
  dir_ver = "#{version[0]}.#{version[1]}.#{version[2]}"
  layer_ver = "#{@@VERSION[0]}.#{@@VERSION[1]}.#{@@VERSION[2]}"
  if version[0] != @@VERSION[0]
    raise "Cannot load directory with version #{dir_ver} using directory layer #{layer_ver}"
  elsif version[1] != @@VERSION[1] && write_access
    raise "Directory with version #{dir_ver} is read-only 
          when opened using directory layer #{layer_ver}"
  end
end