docs: public long fastIterate() {
          final Object[] table = this.table;
          final int len = table.length;
          int ri = 0;
          int ci;
          while (ri < len) {
              final Object item = table[ri];
              if (item != null) {
                  if (item instanceof HeaderValues) {
                      return (long)ri << 32L;
                  } else {
                      final HeaderValues[] row = (HeaderValues[]) item;
                      ci = 0;
                      final int rowLen = row.length;
                      while (ci < rowLen) {
                          if (row[ci] != null) {
                              return (long)ri << 32L | (ci & 0xffffffffL);
                          }
                          ci ++;
                      }
                  }
              }
              ri++;
          }
          return -1L;
      }