code: def __dbfHeaderLength(self):
          
          if not self.__dbfHdrLength:
              if not self.dbf:
                  raise ShapefileException("Shapefile Reader requires a shapefile or file-like object. (no dbf file found)")
              dbf = self.dbf
              (self.numRecords, self.__dbfHdrLength) = \
                      unpack("<xxxxLH22x", dbf.read(32))
          return self.__dbfHdrLength
docs: Retrieves the header length of a dbf file header.