@Override
  public BytesImpl set(int pos, byte []buffer, int offset, int length)
  {
    System.arraycopy(buffer, offset, _data, pos, length);

    return this;
  }
@ Override public BytesImpl set ( int pos , byte [ ] buffer , int offset , int length ) { System . arraycopy ( buffer , offset , _data , pos , length ) ; return this ; }
adds bytes from the buffer