public static int packRowCount(long rowCount, int packId) {
        int packCount = rowCountToPackCount(rowCount);
        assert packId >= 0 && packId < packCount;
        if (packId < packCount - 1) {
            return DataPack.MAX_COUNT;
        } else {
            int packRowCount = (int) (rowCount & MASK);
            return packRowCount == 0 ? DataPack.MAX_COUNT : packRowCount;
        }
    }
Get the row valueCount of the pack by packId.
indexr-segment/src/main/java/io/indexr/segment/pack/DataPack.java