processBytes method
      
  
void
processBytes()
       
    
override
    Process len bytes of data given by inp and starting at offset inpOff.
The resulting cipher text is put in out beginning at position outOff.
Implementation
@override
void processBytes(
    Uint8List inp, int inpOff, int len, Uint8List out, int outOff) {
  if ((inpOff + len) > inp.length) {
    throw ArgumentError('input buffer too short');
  }
  if ((outOff + len) > out.length) {
    throw ArgumentError('output buffer too short');
  }
  for (var i = 0; i < len; i++) {
    _x = (_x + 1) & 0xff;
    _y = (_engineState![_x] + _y) & 0xff;
    // swap
    var tmp = _engineState![_x];
    _engineState![_x] = _engineState![_y];
    _engineState![_y] = tmp;
    // xor
    out[i + outOff] = inp[i + inpOff] ^
        _engineState![(_engineState![_x] + _engineState![_y]) & 0xff];
  }
}