Fix a bug with the bit operation

private:

  khash_t(k64_str) *barcode_translate_table;

  int from_bc_length;

  uint64_t mask;

  std::string Seed2Sequence(uint64_t seed, uint32_t seed_length) const {

    std::string sequence;

    barcode_translate_table = kh_init(k64_str);

    std::ifstream file_stream(file);

    std::string file_line;

    while (getline(file_stream, file_line)) {

      ProcessTranslateFileLine(file_line); 

    }

    mask = 0;

    for (int i = 0; i < from_bc_length; ++i)

    {

      mask |= (3ull << (2*i));

    }

  }

  std::string Translate(uint64_t bc, uint32_t bc_length) {

    std::string ret;  

    uint64_t i;

    for (i = 0; i < bc_length / from_bc_length; ++i) {

      uint64_t seed = (bc << (i * from_bc_length)) >> (bc_length - from_bc_length);

      uint64_t seed = (bc << (2 * i * from_bc_length)) >> (2 * (bc_length / from_bc_length - 1) * from_bc_length);

      seed &= mask;

      khiter_t barcode_translate_table_iter = kh_get(k64_str, barcode_translate_table, seed);

      if (barcode_translate_table_iter == kh_end(barcode_translate_table)) {

        std::cerr << "Barcode does not exist in the translation table.\n" << std::endl;