// than n bytes, it also returns an error explaining why the read is short.
// The error is [ErrBufferFull] if n is larger than b's buffer size.
//
// Calling Peek prevents a [Reader.UnreadByte] or [Reader.UnreadRune] call from succeeding
// until the next read operation.
func (b *Reader) Peek(n int) ([]byte, error) {
	if n < 0 {
		return nil, ErrNegativeCount
	}

	b.lastByte = -1
	b.lastRuneSize = -1

authentication failed") func (g *GCM) Open(dst, nonce, ciphertext, data []byte) ([]byte, error) { if len(nonce) != g.nonceSize { panic("crypto/cipher: incorrect nonce length given to GCM") } // Sanity check to prevent the authentication from always succeeding if an // implementation leaves tagSize uninitialized, for example. if g.tagSize < gcmMinimumTagSize { panic("crypto/cipher: incorrect GCM tag size") } if len(ciphertext) < g.tagSize { return nil, errOpen } if uint64(len(ciphertext)) > uint64((1...