Small refactorings of rpc package

mtproto/rpc/rpc_nonce_request.go

@@ -9,52 +9,36 @@ import (
 	"github.com/juju/errors"
 )
 
-const (
-	rpcNonceLength            = 16
-	rpcNonceKeySelectorLength = 4
-	rpcNonceCryptoTSLength    = 4
-	rpcNonceTagLength         = 4
-	rpcNonceCryptoAESLength   = 4
-
-	rpcNonceRequestLength = rpcNonceTagLength + rpcNonceKeySelectorLength + rpcNonceCryptoAESLength + rpcNonceCryptoTSLength + rpcNonceLength
-)
-
-var (
-	rpcNonceTag          = [rpcNonceTagLength]byte{0xaa, 0x87, 0xcb, 0x7a}
-	rpcNonceCryptoAESTag = [rpcNonceCryptoAESLength]byte{0x01, 0x00, 0x00, 0x00}
-)
-
 type RPCNonceRequest struct {
-	KeySelector [rpcNonceKeySelectorLength]byte
-	CryptoTS    [rpcNonceCryptoTSLength]byte
-	Nonce       [rpcNonceLength]byte
+	KeySelector []byte
+	CryptoTS    []byte
+	Nonce       []byte
 }
 
 func (r *RPCNonceRequest) Bytes() []byte {
 	buf := &bytes.Buffer{}
-	buf.Grow(rpcNonceRequestLength)
 
-	buf.Write(rpcNonceTag[:])
-	buf.Write(r.KeySelector[:])
-	buf.Write(rpcNonceCryptoAESTag[:])
-	buf.Write(r.CryptoTS[:])
-	buf.Write(r.Nonce[:])
+	buf.Write(RPCTagNonce)
+	buf.Write(r.KeySelector)
+	buf.Write(RPCNonceCryptoAES)
+	buf.Write(r.CryptoTS)
+	buf.Write(r.Nonce)
 
 	return buf.Bytes()
 }
 
 func NewRPCNonceRequest(proxySecret []byte) (*RPCNonceRequest, error) {
-	var nonce [rpcNonceLength]byte
-	var keySelector [rpcNonceKeySelectorLength]byte
-	var cryptoTS [rpcNonceCryptoTSLength]byte
+	nonce := make([]byte, 16)
+	keySelector := make([]byte, 4)
+	cryptoTS := make([]byte, 4)
 
-	if _, err := rand.Read(nonce[:]); err != nil {
+	if _, err := rand.Read(nonce); err != nil {
 		return nil, errors.Annotate(err, "Cannot generate nonce")
 	}
-	copy(keySelector[:], proxySecret)
+	copy(keySelector, proxySecret)
 
 	timestamp := time.Now().Truncate(time.Second).Unix() % 4294967296 // 256 ^ 4 - do not know how to name
-	binary.LittleEndian.PutUint32(cryptoTS[:], uint32(timestamp))
+	binary.LittleEndian.PutUint32(cryptoTS, uint32(timestamp))
 
 	return &RPCNonceRequest{
 		KeySelector: keySelector,