// or space is needed.
		if s.start > 0 && (s.end == len(s.buf) || s.start > len(s.buf)/2) {
			copy(s.buf, s.buf[s.start:s.end])
			s.end -= s.start
			s.start = 0
		}
		// Is the buffer full? If so, resize.
		if s.end == len(s.buf) {
			// Guarantee no overflow in the multiplication below.
			const maxInt = int(^uint(0) >> 1)
			if len(s.buf) >= s.maxTokenSize || len(s.buf) > maxInt/2 {
				s.setErr(ErrTooLong)

pkg crypto, type PublicKey interface {}
pkg crypto/cipher, func NewGCM(Block) (AEAD, error)
pkg crypto/cipher, type AEAD interface { NonceSize, Open, Overhead, Seal }
pkg crypto/cipher, type AEAD interface, NonceSize() int
pkg crypto/cipher, type AEAD interface, Open([]uint8, []uint8, []uint8, []uint8) ([]uint8, error)
pkg crypto/cipher, type AEAD interface, Overhead() int