def read_header(input)
      raise 'Not a Daybreak database' if input.read(MAGIC.bytesize) != MAGIC
      ver = input.read(2).unpack('n').first
      raise "Expected database version #{VERSION}, got #{ver}" if ver != VERSION
    end
def read_header(input)
      raise 'Not a Daybreak database' if input.read(MAGIC.bytesize) != MAGIC
      ver = input.read(2).unpack('n').first
      raise "Expected database version #{VERSION}, got #{ver}" if ver != VERSION
    end
Read database header from input stream
 @param [#read] input the input stream
 @return void