public static byte[] compress(byte[] datum) {

		byte[] ret = datum, tmp = new byte[ret.length];
		System.arraycopy(ret, 0, tmp, 0, ret.length);
		int ctr = 1, i = 0, idx = 0;

		for (i = 0; i + 1 < tmp.length && idx < tmp.length; i++) {
			tmp[idx++] = (byte) (tmp[i] << ctr | (tmp[i + 1] << 1 >>> (8 - ctr)));
			ctr++;
			if (ctr == 8) {
				ctr = 1;
				i++;
			}
		}

		if (idx < tmp.length && i < tmp.length && ret.length > 9) {
			tmp[idx] = (byte) (tmp[i] << ctr);
		}
		else {
			tmp[idx] = (byte) (ret[idx] << ctr);
		}

		ret = new byte[ret.length - ret.length / 8];
		System.arraycopy(tmp, 0, ret, 0, ret.length);
		return ret;
	}