kshift
be = bits + ((nbits - 1) >> kshift);
n0 = n = nbits >> kshift;
for(k = 0; n > (1 << (kshift-2)) - 1; n >>= 1)
if (x[k>>kshift] & 1 << (k & kmask)) {
if (x[k>>kshift] & 1 << (k & kmask))
&& x[nbits >> kshift] & 1 << (nbits & kmask))
n = k >> kshift;
x = x0 + (nbits >> kshift);
n = k >> kshift;
ce = c + ((n-1) >> kshift) + 1;
n = k >> kshift;
xe = x + (n >> kshift);
k = (n + ((1 << kshift) - 1)) >> kshift;
k = n >> kshift;
if (b->x[k>>kshift] & ((ULong)1 << (k & kmask)))
carry = b->x[k1>>kshift] & (1 << (k1 & kmask));