@haypo: Oh. Not:

   if sys.maxsize > _4G:
        # (64 bits system) crc32() and adler32() stores the buffer size into an
        # int, the maximum filesize is INT_MAX (0x7FFFFFFF)
        filesize = 0x7FFFFFFF
        crc_res = 0x709418e7
        adler_res = -2072837729
    else:
        # (32 bits system) On a 32 bits OS, a process cannot usually address
        # more than 2 GB, so test only 1 GB
        filesize = _1G
        crc_res = 0x2b09ee11
        adler_res = -1002962529

                    self.assertEqual(zlib.crc32(m), self.crc_res)
                    self.assertEqual(zlib.adler32(m), self.adler_res)

I'm not that fast.