reimpl nonce

peer/internal/uprng/uprng.go

@@ -41,20 +41,22 @@ const (
 
 // nonce implements a 12-byte little endian counter suitable for use as an
 // incrementing ChaCha20 nonce.
-type nonce struct {
-	limbs [3]uint32
-	bytes [chacha20.NonceSize]byte
-}
+type nonce [chacha20.NonceSize]byte
 
 func (n *nonce) inc() {
+	n0 := binary.LittleEndian.Uint32(n[0:4])
+	n1 := binary.LittleEndian.Uint32(n[4:8])
+	n2 := binary.LittleEndian.Uint32(n[8:12])
+
 	var carry uint32
-	n.limbs[0], carry = bits.Add32(n.limbs[0], 1, carry)
-	n.limbs[1], carry = bits.Add32(n.limbs[1], 0, carry)
-	n.limbs[2], carry = bits.Add32(n.limbs[2], 0, carry)
-	n.limbs[0], _ = bits.Add32(n.limbs[0], 0, carry)
-	binary.LittleEndian.PutUint32(n.bytes[0:4], n.limbs[0])
-	binary.LittleEndian.PutUint32(n.bytes[4:8], n.limbs[1])
-	binary.LittleEndian.PutUint32(n.bytes[8:12], n.limbs[2])
+	n0, carry = bits.Add32(n0, 1, carry)
+	n1, carry = bits.Add32(n1, 0, carry)
+	n2, carry = bits.Add32(n2, 0, carry)
+	n0, _ = bits.Add32(n0, 0, carry)
+
+	binary.LittleEndian.PutUint32(n[0:4], n0)
+	binary.LittleEndian.PutUint32(n[4:8], n1)
+	binary.LittleEndian.PutUint32(n[8:12], n2)
 }
 
 type prng struct {
@@ -87,7 +89,7 @@ func (p *prng) seed() {
 	}
 
 	// never errors with correct key and nonce sizes
-	cipher, _ := chacha20.NewUnauthenticatedCipher(p.key, p.nonce.bytes[:])
+	cipher, _ := chacha20.NewUnauthenticatedCipher(p.key, p.nonce[:])
 	p.nonce.inc()
 
 	p.cipher = cipher