Robin Becker schrieb:
> def add32(x, y):
> "Calculate (x + y) modulo 2**32"
> return ((x&0xFFFFFFFFL)+(y&0xFFFFFFFFL)) & 0xffffffffL
That's redundant; it is sufficient to write
return (x+y) & 0xffffffff
> def calcChecksum(data):
> """Calculates TTF-style checksums"""
> if len(data)&3: data = data + (4-(len(data)&3))*"\0"
> sum = 0
> for n in unpack(">%dl" % (len(data)>>2), data):
> sum = add32(sum,n)
> return sum
That's also redundant; I'd write
def calcChecksum(data):
data += "\0\0\0\0"[:len(data)&3]
return sum(unpack(">%dl" % (len(data)>>2), data)) & 0xffffffff
I.e. it is sufficient to truncate to 32 bits at the end, instead of
doing so after each addition.
Regards,
Martin
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