def __init__(self, poly, size = DEFAULT_RABIN_FINGERPRINT_SIZE):
self._size = size
self._buff = bytearray(size)
self._shift = 0
self._fingerprint = 0
self._buffpos = -1
self._calculate_lookup_table(poly)
sizeshift = 1
for i in range(1, size):
sizeshift = self._add_byte(sizeshift, 0)
self._u = [0] + [ polymath.mmult(i, sizeshift, poly) for i in range(1, 256) ]
def _calculate_lookup_table(self, poly):
xshift = poly.bit_length() - 1
self._shift = xshift - 8
t1 = polymath.mod(1 << xshift, poly)
self._t = [ polymath.mmult(j, t1, poly) | j << xshift for j in range(0, 256) ]