code: public static final int lengthOf(WsByteBuffer[] list) {
          if (null == list) {
              return 0;
          }
          int length = 0;
          for (int i = 0; i < list.length && null != list[i]; i++) {
              length += list[i].remaining();
          }
          return length;
      }
docs: Calculate the total length of actual content in the buffers in the input
  list. This will stop on the first null buffer or the end of the list.
  
  @param list
  @return int