question: public void processBytes ( byte [ ] in , int inOff , int len ) { if ( len == 0 ) { return ; } if ( len < 0 ) { throw new IllegalArgumentException ( "Can't have a negative input length!" ) ; } if ( bufOff + len > buf . length ) { throw new DataLengthException ( "attempt to process message too long for cipher" ) ; } System . arraycopy ( in , inOff , buf , bufOff , len ) ; bufOff += len ; }
target:  add len bytes to the buffer for processing.