No subject

[ha bo]

hi i use this programme in my application django:
import structMASK_CCITT  = 0x1021     # CRC-CCITT mask (ISO 3309, used in X25, HDLC)MASK_CRC16  = 0xA001     # CRC16 mask (used in ARC files)def updcrc(crc, data, mask=MASK_CRC16):     data_length = len(data)     unpackFormat = '%db' % data_length     unpackedData = struct.unpack(unpackFormat, data)     for char in data:            c = ord(char)            c = c << 8                for j in xrange(8):                if (crc ^ c) & 0x8000:                    crc = (crc << 1) ^ mask                else:                    crc = crc << 1                c = c << 1     return crc & 0xffff


and i call this function in other function in my view:


def encodekey(var, expires=None, user='', trusted=False):          import random, base64        import updcrc        key = "%02X" % len(var) + var        key += "%02X" % len(user) + user        if expires is not None:            key += expires.strftime('%Y%m%d%H%M')        else:            year = random.choice(range(2000,2100))            month = 23            day = random.choice(range(1,32))            hour = random.choice(range(1,25))            minute = random.choice(range(1,60))            key += "%04d%02d%02d%02d%02d" % (year, month, day, hour, minute)        if trusted:            checksum = updcrc(42, key)        else:                checksum = updcrc(0, key)        key += "%04X" % checksum        return base64.b64encode(key)
but it give me this error:
unpack requires a string argument of length 31
someone can help me 


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