docs: protected int[] colsBitsetToIDs(long[] cols) {
      int[] colIDs = new int[BitsUtil.cardinality(cols)];
      int colsIndex = 0;
      for(int cpos = 0, clpos = 0; clpos < cols.length; ++clpos) {
        long clong = cols[clpos];
        if(clong == 0L) {
          cpos += Long.SIZE;
          continue;
        }
        for(int j = 0; j < Long.SIZE; ++j, ++cpos, clong >>>= 1) {
          if((clong & 1L) == 1L) {
            colIDs[colsIndex] = cpos;
            ++colsIndex;
          }
        }
      }
      return colIDs;
    }