This allows a BigInteger to be logically shifted right (filling with 0)

Shift Right Logical (SRL) for BigInteger

public static BigInteger srl(BigInteger l, int width, int shiftBy) {
    if (l.signum() >= 0)
        return l.shiftRight(shiftBy);
    BigInteger opener = BigInteger.ONE.shiftLeft(width + 1);
    BigInteger opened = l.subtract(opener);
    BigInteger mask = opener.subtract(BigInteger.ONE).shiftRight(shiftBy + 1);
    BigInteger res = opened.shiftRight(shiftBy).and(mask);
    return res;
}