sfn_checksum.py

filename = 'TEST    TXT'

total = 0
for newchar in filename:
    #rotate(一番右のビットは一番左に)
    total = ((total & 1) << 7) + (total >> 1)
    #add
    total += ord(newchar)
    #桁溢れ防止
    total = total & 0xFF

print(format(total, 'b'))
print(format(total, 'x'))

####結果
#$ python3 sfn_checksum.py 
#10001111
#8f