def notice(relative_position)
      data = nil
      @subscanners.each {|scanner| scanner.notice(relative_position) {
          data = yield if data.nil?
          data
        }
      }
    end
def notice(relative_position)
      data = nil
      @subscanners.each {|scanner| scanner.notice(relative_position) {
          data = yield if data.nil?
          data
        }
      }
    end
Notice a file during scanning.

 === Block
 Return the data for this file.  We use a block because it may
 not always be necessary to read the data.

 === Parameters
 relative_position(String):: relative pathname for the file from the root of resource