code: public static int lengthOf(WsByteBuffer[] src, int startIndex) {
          int length = 0;
          if (null != src) {
              for (int i = startIndex; i < src.length && null != src[i]; i++) {
                  length += src[i].remaining();
              }
          }
          return length;
      }
docs: Find the amount of data in the source buffers, starting at the input index.
  
  @param src
  @param startIndex
  @return int