code: private int removeExplicitCodes() {
          int w = 0;
          for (int i = 0; i < textLength; ++i) {
              byte t = initialTypes[i];
              if (!(t == LRE || t == RLE || t == LRO || t == RLO || t == PDF || t == BN)) {
                  embeddings[w] = embeddings[i];
                  resultTypes[w] = resultTypes[i];
                  resultLevels[w] = resultLevels[i];
                  w++;
              }
          }
          return w; // new textLength while explicit levels are removed
      }
docs: Rules X9.
  Remove explicit codes so that they may be ignored during the remainder
  of the main portion of the algorithm.  The length of the resulting text
  is returned.
  @return the length of the data excluding explicit codes and BN.