go/zodb/zeo: Factor-out code to prepare pkt from message into pktEncode

go/zodb/storage/zeo/proto.go

@@ -50,6 +50,17 @@ const (
 
 // ---- message encode/decode ↔ packet ----
 
+// pktEncode encodes message into raw packet.
+func pktEncode(m msg) *pktBuf {
+	pkb := allocPkb()
+	p := pickle.NewEncoder(pkb)
+	err := p.Encode(pickle.Tuple{m.msgid, m.flags, m.method, m.arg})
+	if err != nil {
+		panic(err) // all our types are expected to be supported by pickle
+	}
+	return pkb
+}
+
 // pktDecode decodes raw packet into message.
 func pktDecode(pkb *pktBuf) (msg, error) {
 	var m msg

go/zodb/storage/zeo/zrpc.go

@@ -183,12 +183,12 @@ func (zl *zLink) Call(ctx context.Context, method string, argv ...interface{}) (
 	zl.callMu.Unlock()
 
 	// (msgid, async, method, argv)
-	pkb := allocPkb()
-	p := pickle.NewEncoder(pkb)
-	err = p.Encode(pickle.Tuple{callID, false, method, pickle.Tuple(argv)})
-	if err != nil {
-		panic(err) // all our types are expected to be supported by pickle
-	}
+	pkb := pktEncode(msg{
+			msgid:  callID,
+			flags:  0,
+			method: method,
+			arg:    pickle.Tuple(argv),
+	})
 
 	// ok, pkt is ready to go
 	err = zl.sendPkt(pkb) // XXX ctx cancel