def mark(id)
      found = false
      @entries.each do |entry|
        if entry[ID] == id
          entry[MARKED] = 1
          found = true
          break
        end
      end

      unless found
        PEROBS.log.fatal "Cannot find an entry for ID #{'%016X' % id} " +
          "#{id} to mark"
      end

      write_index
    end
def mark(id)
      found = false
      @entries.each do |entry|
        if entry[ID] == id
          entry[MARKED] = 1
          found = true
          break
        end
      end

      unless found
        PEROBS.log.fatal "Cannot find an entry for ID #{'%016X' % id} " +
          "#{id} to mark"
      end

      write_index
    end
Set a mark on the entry with the given ID.
 @param id [Integer] ID of the entry