}

func (c *aesctr) XORKeyStream(dst, src []byte) {
	if len(dst) < len(src) {
		panic("crypto/cipher: output smaller than input")
	}
	if alias.InexactOverlap(dst[:len(src)], src) {
		panic("crypto/cipher: invalid buffer overlap")
	}
	for len(src) > 0 {
		if len(c.buffer) == 0 {
			c.refill()
		}
		n := xorBytes(dst, src, c.buffer)
		c.buffer = c.buffer[n:]

	}
	if uint64(len(plaintext)) > ((1<<32)-2)*uint64(g.cipher.BlockSize()) {
		panic("crypto/cipher: message too large for GCM")
	}

	ret, out := sliceForAppend(dst, len(plaintext)+g.tagSize)
	if alias.InexactOverlap(out, plaintext) {
		panic("crypto/cipher: invalid buffer overlap")
	}

	var counter, tagMask [gcmBlockSize]byte
	g.deriveCounter(&counter, nonce)

	g.cipher.Encrypt(tagMask[:], counter[:])

func (s *Cipher) XORKeyStream(dst, src []byte) {
	if len(src) == 0 {
		return
	}
	if len(dst) < len(src) {
		panic("chacha20: output smaller than input")
	}
	dst = dst[:len(src)]
	if alias.InexactOverlap(dst, src) {
		panic("chacha20: invalid buffer overlap")
	}

	// First, drain any remaining key stream from a previous XORKeyStream.
	if s.len != 0 {
		keyStream := s.buf[bufSize-s.len:]