def write(self):
        """Return a string encoding of the page header and data.

        A ValueError is raised if the data is too big to fit in a
        single page.
        """

        data = [
            struct.pack("<4sBBqIIi", b"OggS", self.version, self.__type_flags,
                        self.position, self.serial, self.sequence, 0)
        ]

        lacing_data = []
        for datum in self.packets:
            quot, rem = divmod(len(datum), 255)
            lacing_data.append(b"\xff" * quot + bytes((rem,)))
        lacing_data = b"".join(lacing_data)
        if not self.complete and lacing_data.endswith(b"\x00"):
            lacing_data = lacing_data[:-1]
        data.append(bytes((len(lacing_data),)))
        data.append(lacing_data)
        data.extend(self.packets)
        data = b"".join(data)

        # Python's CRC is swapped relative to Ogg's needs.
        # crc32 returns uint prior to py2.6 on some platforms, so force uint
        crc = (~zlib.crc32(data.translate(cdata.bitswap), -1)) & 0xffffffff
        # Although we're using to_uint_be, this actually makes the CRC
        # a proper le integer, since Python's CRC is byteswapped.
        crc = cdata.to_uint_be(crc).translate(cdata.bitswap)
        data = data[:22] + crc + data[26:]
        return data

 def __update_parents(self, fileobj, path, delta, offset):
     # Update all parent atoms with the new size.
     for atom in path:
         fileobj.seek(atom.offset + offset)
         size = cdata.uint_be(fileobj.read(4)) + delta
         fileobj.seek(atom.offset + offset)
         fileobj.write(cdata.to_uint_be(size))

 def __update_parents(self, fileobj, path, delta):
     """Update all parent atoms with the new size."""
     for atom in path:
         fileobj.seek(atom.offset)
         size = cdata.uint_be(fileobj.read(4))
         if size == 1: # 64bit
             # skip name (4B) and read size (8B)
             size = cdata.ulonglong_be(fileobj.read(12)[4:])
             fileobj.seek(atom.offset + 8)
             fileobj.write(cdata.to_ulonglong_be(size + delta))
         else: # 32bit
             fileobj.seek(atom.offset)
             fileobj.write(cdata.to_uint_be(size + delta))

 def zlib_int(*args):
     return cdata.int_be(cdata.to_uint_be(old_crc(*args) & 0xffffffff))