public final int pack(long[] in, byte[] out) {
        return pack(in.length, in, 0, out, 0);
    }
unpack bitWidth bytes from input into 8 values in output.
nextPosition: input = (inAddr + bitWidth), output = (outAddr + 8 * 4)
indexr-vlt-segment/src/main/java/io/indexr/vlt/codec/pack/LongPacker.java