Optimize client initialization by using QJson directly.

Before, we constructed QVariant maps and lists and then converted them
to JSON to send the data to the webchannel.

By obsoleting the conversion step, benchInitializeClients shows a good
performance boost of ca. 19% (11.81ms vs 14.58ms).

Change-Id: Ief8e8127207a046f481488a478cd6a18fa0ebffe
Reviewed-by: Zeno Albisser <zeno.albisser@digia.com>

3 files changed, 44 insertions, 38 deletions

diff --git a/src/webchannel/qmetaobjectpublisher.cpp b/src/webchannel/qmetaobjectpublisher.cpp
index 375cf1b..0de25c5 100644
--- a/src/webchannel/qmetaobjectpublisher.cpp
+++ b/src/webchannel/qmetaobjectpublisher.cpp
@@ -122,11 +122,11 @@ void QMetaObjectPublisherPrivate::initializeClients()
     {
         const QHash<QString, QObject *>::const_iterator end = registeredObjects.constEnd();
         for (QHash<QString, QObject *>::const_iterator it = registeredObjects.constBegin(); it != end; ++it) {
-            const QVariantMap &info = q->classInfoForObject(it.value());
+            const QJsonObject &info = q->classInfoForObject(it.value());
             if (!propertyUpdatesInitialized) {
                 initializePropertyUpdates(it.value(), info);
             }
-            objectInfos[it.key()] = QJsonObject::fromVariantMap(info);
+            objectInfos[it.key()] = info;
         }
     }
     webChannel->sendMessage(TYPE_INIT, objectInfos);
@@ -134,16 +134,16 @@ void QMetaObjectPublisherPrivate::initializeClients()
     pendingInit = false;
 }
 
-void QMetaObjectPublisherPrivate::initializePropertyUpdates(const QObject *const object, const QVariantMap &objectInfo)
+void QMetaObjectPublisherPrivate::initializePropertyUpdates(const QObject *const object, const QJsonObject &objectInfo)
 {
-    foreach (const QVariant &propertyInfoVar, objectInfo[KEY_PROPERTIES].toList()) {
-        const QVariantList &propertyInfo = propertyInfoVar.toList();
+    foreach (const QJsonValue &propertyInfoVar, objectInfo[KEY_PROPERTIES].toArray()) {
+        const QJsonArray &propertyInfo = propertyInfoVar.toArray();
         if (propertyInfo.size() < 2) {
             qWarning() << "Invalid property info encountered:" << propertyInfoVar;
             continue;
         }
         const QString &propertyName = propertyInfo.at(0).toString();
-        const QVariantList &signalData = propertyInfo.at(1).toList();
+        const QJsonArray &signalData = propertyInfo.at(1).toArray();
 
         if (signalData.isEmpty()) {
             // Property without NOTIFY signal
@@ -259,7 +259,7 @@ bool QMetaObjectPublisherPrivate::invokeMethod(QObject *const object, const int
                   arguments[5], arguments[6], arguments[7], arguments[8], arguments[9]);
 
     // and send the return value to the client
-    webChannel->respond(id, QJsonValue::fromVariant(wrapResult(returnValue)));
+    webChannel->respond(id, wrapResult(returnValue));
 
     return true;
 }
@@ -305,10 +305,10 @@ void QMetaObjectPublisherPrivate::objectDestroyed(const QObject *object)
     wrappedObjects.remove(object);
 }
 
-QVariant QMetaObjectPublisherPrivate::wrapResult(const QVariant &result)
+QJsonValue QMetaObjectPublisherPrivate::wrapResult(const QVariant &result)
 {
     if (QObject *object = result.value<QObject *>()) {
-        QVariantMap &objectInfo = wrappedObjects[object];
+        QJsonObject &objectInfo = wrappedObjects[object];
         if (!objectInfo.isEmpty()) {
             // already registered, use cached information
             Q_ASSERT(registeredObjectIds.contains(object));
@@ -332,7 +332,7 @@ QVariant QMetaObjectPublisherPrivate::wrapResult(const QVariant &result)
     }
 
     // no need to wrap this
-    return result;
+    return QJsonValue::fromVariant(result);
 }
 
 void QMetaObjectPublisherPrivate::deleteWrappedObject(QObject *object) const
@@ -355,14 +355,14 @@ QMetaObjectPublisher::~QMetaObjectPublisher()
 
 }
 
-QVariantMap QMetaObjectPublisher::classInfoForObjects(const QVariantMap &objectMap) const
+QJsonObject QMetaObjectPublisher::classInfoForObjects(const QVariantMap &objectMap) const
 {
-    QVariantMap ret;
+    QJsonObject ret;
     QMap<QString, QVariant>::const_iterator it = objectMap.constBegin();
     while (it != objectMap.constEnd()) {
         QObject *object = it.value().value<QObject *>();
         if (object) {
-            const QVariantMap &info = classInfoForObject(object);
+            const QJsonObject &info = classInfoForObject(object);
             if (!info.isEmpty()) {
                 ret[it.key()] = info;
             }
@@ -372,25 +372,29 @@ QVariantMap QMetaObjectPublisher::classInfoForObjects(const QVariantMap &objectM
     return ret;
 }
 
-QVariantMap QMetaObjectPublisher::classInfoForObject(QObject *object) const
+QJsonObject QMetaObjectPublisher::classInfoForObject(QObject *object) const
 {
-    QVariantMap data;
+    QJsonObject data;
     if (!object) {
         qWarning("null object given to MetaObjectPublisher - bad API usage?");
         return data;
     }
-    QVariantList qtSignals, qtMethods;
-    QVariantList qtProperties;
-    QVariantMap qtEnums;
+
+    QJsonArray qtSignals;
+    QJsonArray qtMethods;
+    QJsonArray qtProperties;
+    QJsonObject qtEnums;
+
     const QMetaObject *metaObject = object->metaObject();
     QSet<int> notifySignals;
     QSet<QString> identifiers;
     for (int i = 0; i < metaObject->propertyCount(); ++i) {
         const QMetaProperty &prop = metaObject->property(i);
-        QVariantList propertyInfo;
+        QJsonArray propertyInfo;
         const QString &propertyName = QString::fromLatin1(prop.name());
         propertyInfo.append(propertyName);
         identifiers << propertyName;
+        QJsonArray signalInfo;
         if (prop.hasNotifySignal()) {
             notifySignals << prop.notifySignalIndex();
             const int numParams = prop.notifySignal().parameterCount();
@@ -404,20 +408,19 @@ QVariantMap QMetaObjectPublisher::classInfoForObject(QObject *object) const
             if (notifySignal.length() == changedSuffix.length() + propertyName.length() &&
                 notifySignal.endsWith(changedSuffix) && notifySignal.startsWith(prop.name()))
             {
-                propertyInfo.append(QVariant::fromValue(QVariantList() << 1 << prop.notifySignalIndex()));
+                signalInfo.append(1);
             } else {
-                propertyInfo.append(QVariant::fromValue(QVariantList() << QString::fromLatin1(notifySignal) << prop.notifySignalIndex()));
-            }
-        } else {
-            if (!prop.isConstant()) {
-                qWarning("Property '%s'' of object '%s' has no notify signal and is not constant, "
-                         "value updates in HTML will be broken!",
-                         prop.name(), object->metaObject()->className());
+                signalInfo.append(QString::fromLatin1(notifySignal));
             }
-            propertyInfo.append(QVariant::fromValue(QVariantList()));
+            signalInfo.append(prop.notifySignalIndex());
+        } else if (!prop.isConstant()) {
+            qWarning("Property '%s'' of object '%s' has no notify signal and is not constant, "
+                     "value updates in HTML will be broken!",
+                     prop.name(), object->metaObject()->className());
         }
-        propertyInfo.append(prop.read(object));
-        qtProperties.append(QVariant::fromValue(propertyInfo));
+        propertyInfo.append(signalInfo);
+        propertyInfo.append(QJsonValue::fromVariant(prop.read(object)));
+        qtProperties.append(propertyInfo);
     }
     for (int i = 0; i < metaObject->methodCount(); ++i) {
         if (notifySignals.contains(i)) {
@@ -434,7 +437,9 @@ QVariantMap QMetaObjectPublisher::classInfoForObject(QObject *object) const
         }
         identifiers << name;
         // send data as array to client with format: [name, index]
-        const QVariant data = QVariant::fromValue(QVariantList() << name << i);
+        QJsonArray data;
+        data.append(name);
+        data.append(i);
         if (method.methodType() == QMetaMethod::Signal) {
             qtSignals.append(data);
         } else if (method.access() == QMetaMethod::Public) {
@@ -443,7 +448,7 @@ QVariantMap QMetaObjectPublisher::classInfoForObject(QObject *object) const
     }
     for (int i = 0; i < metaObject->enumeratorCount(); ++i) {
         QMetaEnum enumerator = metaObject->enumerator(i);
-        QVariantMap values;
+        QJsonObject values;
         for (int k = 0; k < enumerator.keyCount(); ++k) {
             values[QString::fromLatin1(enumerator.key(k))] = enumerator.value(k);
         }
@@ -451,7 +456,7 @@ QVariantMap QMetaObjectPublisher::classInfoForObject(QObject *object) const
     }
     data[KEY_SIGNALS] = qtSignals;
     data[KEY_METHODS] = qtMethods;
-    data[KEY_PROPERTIES] = QVariant::fromValue(qtProperties);
+    data[KEY_PROPERTIES] = qtProperties;
     data[KEY_ENUMS] = qtEnums;
     return data;
 }
diff --git a/src/webchannel/qmetaobjectpublisher.h b/src/webchannel/qmetaobjectpublisher.h
index f4763a7..9d17aff 100644
--- a/src/webchannel/qmetaobjectpublisher.h
+++ b/src/webchannel/qmetaobjectpublisher.h
@@ -45,6 +45,7 @@
 
 #include <QObject>
 #include <QVariant>
+#include <QJsonObject>
 
 #include "qwebchannelglobal.h"
 
@@ -62,8 +63,8 @@ public:
     explicit QMetaObjectPublisher(QObject *parent = 0);
     virtual ~QMetaObjectPublisher();
 
-    Q_INVOKABLE QVariantMap classInfoForObjects(const QVariantMap &objects) const;
-    Q_INVOKABLE QVariantMap classInfoForObject(QObject *object) const;
+    Q_INVOKABLE QJsonObject classInfoForObjects(const QVariantMap &objects) const;
+    Q_INVOKABLE QJsonObject classInfoForObject(QObject *object) const;
 
     /**
      * Register a map of string ID to QObject* objects.
diff --git a/src/webchannel/qmetaobjectpublisher_p.h b/src/webchannel/qmetaobjectpublisher_p.h
index e364510..969421a 100644
--- a/src/webchannel/qmetaobjectpublisher_p.h
+++ b/src/webchannel/qmetaobjectpublisher_p.h
@@ -80,7 +80,7 @@ struct Q_WEBCHANNEL_EXPORT QMetaObjectPublisherPrivate
      * When receiving a notify signal, it will store the information in pendingPropertyUpdates which
      * gets send via a Qt.propertyUpdate message to the server when the grouping timer timeouts.
      */
-    void initializePropertyUpdates(const QObject *const object, const QVariantMap &objectInfo);
+    void initializePropertyUpdates(const QObject *const object, const QJsonObject &objectInfo);
 
     /**
      * Send the clients the new property values since the last time this function was invoked.
@@ -121,7 +121,7 @@ struct Q_WEBCHANNEL_EXPORT QMetaObjectPublisherPrivate
      *
      * TODO: support wrapping of initially-registered objects
      */
-    QVariant wrapResult(const QVariant &result);
+    QJsonValue wrapResult(const QVariant &result);
 
     /**
      * Invoke delete later on @p object.
@@ -165,7 +165,7 @@ struct Q_WEBCHANNEL_EXPORT QMetaObjectPublisherPrivate
     PendingPropertyUpdates pendingPropertyUpdates;
 
     // Maps wrapped object to class info
-    QHash<const QObject *, QVariantMap> wrappedObjects;
+    QHash<const QObject *, QJsonObject> wrappedObjects;
 
     // Aggregate property updates since we get multiple Qt.idle message when we have multiple
     // clients. They all share the same QWebProcess though so we must take special care to