presto-orc/src/main/java/io/prestosql/orc/stream/LongBitPacker.java/LongBitPacker/unpack
class LongBitPacker:    public void unpack(long[] buffer, int offset, int len, int bitSize, InputStream input)
            throws IOException
    {
        checkArgument(len <= MAX_BUFFERED_POSITIONS, "Expected ORC files to have runs of at most 512 bit packed longs");
        switch (bitSize) {
            case 1:
                unpack1(buffer, offset, len, input);
                break;
            case 2:
                unpack2(buffer, offset, len, input);
                break;
            case 4:
                unpack4(buffer, offset, len, input);
                break;
            case 8:
                unpack8(buffer, offset, len, input);
                break;
            case 16:
                unpack16(buffer, offset, len, input);
                break;
            case 24:
                unpack24(buffer, offset, len, input);
                break;
            case 32:
                unpack32(buffer, offset, len, input);
                break;
            case 40:
                unpack40(buffer, offset, len, input);
                break;
            case 48:
                unpack48(buffer, offset, len, input);
                break;
            case 56:
                unpack56(buffer, offset, len, input);
                break;
            case 64:
                unpack64(buffer, offset, len, input);
                break;
            default:
                unpackGeneric(buffer, offset, len, bitSize, input);
        }
    }