code: public int writeTo(ByteBuffer bb) throws IOException
      {
          return writeTo((srcs, offset, len)->ByteBuffers.move(srcs, offset, len, bb), writeToSplitter);
      }
docs: Writes bytes from mark (included) to position (excluded) to bb as much as
  bb has remaining. bb positions are updated.
  @param bb
  @return
  @throws IOException