gf_reference/pack_poly.py

   1 """Polynomials with GF(2) coefficients."""
   2
   3
   4 def pack_poly(poly):
   5     """`poly` is a list where `poly[i]` is the coefficient for `x ** i`"""
   6     retval = 0
   7     for i, v in enumerate(poly):
   8         retval |= v << i
   9     return retval
  10
  11
  12 def unpack_poly(v):
  13     """returns a list `poly`, where `poly[i]` is the coefficient for `x ** i`.
  14     """
  15     poly = []
  16     while v != 0:
  17         poly.append(v & 1)
  18         v >>= 1
  19     return poly