def _gf2bitlength_linear(a):
    """
    Computes the length of a polynomial coefficient bit vector = degree + 1. 

    Parameters
    ----------
    a : integer
        Polynomial coefficient bit vector.

    Returns
    -------
    n : integer
        length of  polynomial `a`.    
    """     
    n = 0
    while a > 0:
        n += 1
        a >>= 1
    return n