processBytes method

@override void processBytes(Uint8List inp, int inpOff, int len, Uint8List out, int outOff,)

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 (!_initialised) {
    throw StateError('ChaCha20 not initialized: please call init() first');
  }

  if ((inpOff + len) > inp.length) {
    throw ArgumentError(
        'Input buffer too short or requested length too long');
  }

  if ((outOff + len) > out.length) {
    throw ArgumentError(
        'Output buffer too short or requested length too long');
  }

  for (var i = 0; i < len; i++) {
    if (_keyStreamOffset == 0) {
      generateKeyStream(_keyStream);

      if (++_state[12] == 0) throw StateError('Illegal increase of counter');
    }

    out[i + outOff] = clip8(_keyStream[_keyStreamOffset] ^ inp[i + inpOff]);
    _keyStreamOffset = (_keyStreamOffset + 1) & 63;
  }
}