From 0b4d0757dc593cdaa05d957468fad8bc5bc7bf30 Mon Sep 17 00:00:00 2001
From: Alexander Lohnau <alexander.lohnau@gmx.de>
Date: Sun, 8 Sep 2024 16:21:28 +0200
Subject: [PATCH] NetworkPacket: Optimize serialization/deserialization

We don't need to convert the data to an intermediate QVariantMap just to
make JSON out of it. This siginificantly improves performance.
The measurements were done with 3000000 iterations each:

Before serialization: 0.0045009 msecs
Before deserialization: 0.002293 msecs

After serialization: 0.0034216 msecs (32% faster)
After deserialization: 0.001776 msecs (29% faster)
---
 core/networkpacket.cpp | 34 +++++++++++++++-------------------
 1 file changed, 15 insertions(+), 19 deletions(-)

diff --git a/core/networkpacket.cpp b/core/networkpacket.cpp
index 52f826169..603e991c6 100644
--- a/core/networkpacket.cpp
+++ b/core/networkpacket.cpp
@@ -43,26 +43,20 @@ NetworkPacket::NetworkPacket(const QString &type, const QVariantMap &body)
 
 QByteArray NetworkPacket::serialize() const
 {
-    // Object -> QVariant
-    QVariantMap variant;
-    variant.insert(QStringLiteral("id"), m_id);
-    variant.insert(QStringLiteral("type"), m_type);
-    variant.insert(QStringLiteral("body"), m_body);
+    QJsonObject obj;
+    obj.insert(QLatin1String("id"), m_id);
+    obj.insert(QLatin1String("type"), m_type);
+    obj.insert(QLatin1String("body"), QJsonObject::fromVariantMap(m_body));
 
     if (hasPayload()) {
-        variant.insert(QStringLiteral("payloadSize"), m_payloadSize);
-        variant.insert(QStringLiteral("payloadTransferInfo"), m_payloadTransferInfo);
+        obj.insert(QLatin1String("payloadSize"), m_payloadSize);
+        obj.insert(QLatin1String("payloadTransferInfo"), QJsonObject::fromVariantMap(m_payloadTransferInfo));
     }
 
-    // QVariant -> json
-    auto jsonDocument = QJsonDocument::fromVariant(variant);
-    QByteArray json = jsonDocument.toJson(QJsonDocument::Compact);
+    QByteArray json = QJsonDocument(obj).toJson(QJsonDocument::Compact);
     if (json.isEmpty()) {
         qCDebug(KDECONNECT_CORE) << "Serialization error:";
     } else {
-        /*if (!isEncrypted()) {
-            //qCDebug(KDECONNECT_CORE) << "Serialized packet:" << json;
-        }*/
         json.append('\n');
     }
 
@@ -70,9 +64,9 @@ QByteArray NetworkPacket::serialize() const
 }
 
 template<class T>
-void qvariant2qobject(const QVariantMap &variant, T *object)
+void qjsonobject2qobject(const QJsonObject &obj, T *object)
 {
-    for (QVariantMap::const_iterator iter = variant.begin(); iter != variant.end(); ++iter) {
+    for (auto iter = obj.begin(); iter != obj.end(); ++iter) {
         const int propertyIndex = T::staticMetaObject.indexOfProperty(iter.key().toLatin1().data());
         if (propertyIndex < 0) {
             qCWarning(KDECONNECT_CORE) << "missing property" << object << iter.key();
@@ -80,7 +74,7 @@ void qvariant2qobject(const QVariantMap &variant, T *object)
         }
 
         QMetaProperty property = T::staticMetaObject.property(propertyIndex);
-        bool ret = property.writeOnGadget(object, *iter);
+        bool ret = property.writeOnGadget(object, iter.value().toVariant());
         if (!ret) {
             qCWarning(KDECONNECT_CORE) << "couldn't set" << object << "->" << property.name() << '=' << *iter;
         }
@@ -97,10 +91,12 @@ bool NetworkPacket::unserialize(const QByteArray &a, NetworkPacket *np)
         return false;
     }
 
-    auto variant = parser.toVariant().toMap();
-    qvariant2qobject(variant, np);
+    const QJsonObject obj = parser.object();
 
-    np->m_payloadTransferInfo = variant[QStringLiteral("payloadTransferInfo")].toMap(); // Will return an empty qvariantmap if was not present, which is ok
+    qjsonobject2qobject(obj, np);
+
+    // Will return an empty qvariantmap if was not present, which is ok
+    np->m_payloadTransferInfo = obj.value(QLatin1String("payloadTransferInfo")).toVariant().toMap();
 
     // Ids containing characters that are not allowed as dbus paths would make app crash
     if (np->m_body.contains(QStringLiteral("deviceId"))) {