code: @Override
      public int writeComment(String data) throws IOException
      {
          if (mCheckContent) {
              int ix = verifyCommentContent(data);
              if (ix >= 0) {
                  if (!mFixContent) { // Can we fix it?
                      return ix;
                  }
                  // Yes we can! (...Bob the Builder...)
                  writeSegmentedComment(data, ix);
                  return -1;
              }
          }
          fastWriteRaw("<!--");
          writeRaw(data);
          fastWriteRaw("-->");
          return -1;
      }
docs: Method that will try to output the content as specified. If
  the content passed in has embedded "--" in it, it will either
  add an intervening space between consequtive hyphens (if content
  fixing is enabled), or return the offset of the first hyphen in
  multi-hyphen sequence.