QJsonValueConcreteRef: optimize concrete()

Inline the content to avoid a round-trip through qjsonarray.cpp and
qjsonobject.cpp.

This change revealed an inadviseable unit test check that dereferences
the end() iterator to get its type. I haven't changed it, but have
marked with ###. I also fixed a likely copy&paste mistake in that test.

Change-Id: I89446ea06b5742efb194fffd16bb774f3bfbe5f5
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

src/corelib/serialization/qjson_p.h

@@ -56,6 +56,9 @@
 #include <qcborvalue.h>
 #include <private/qcborvalue_p.h>
 
+#include <qjsonarray.h>
+#include <qjsonobject.h>
+
 QT_BEGIN_NAMESPACE
 
 namespace QJsonPrivate {
@@ -203,8 +206,27 @@ inline void swap(KeyIterator::reference a, KeyIterator::reference b)
 class Value
 {
 public:
-    static QCborContainerPrivate *container(const QCborValue &v) { return v.container; }
     static qint64 valueHelper(const QCborValue &v) { return v.n; }
+    static QCborContainerPrivate *container(const QCborValue &v) { return v.container; }
+    static const QCborContainerPrivate *container(QJsonValueConstRef r) noexcept
+    {
+        return (r.is_object ? r.o->o : r.a->a).data();
+    }
+    static QCborContainerPrivate *container(QJsonValueRef r) noexcept
+    {
+        return const_cast<QCborContainerPrivate *>(container(QJsonValueConstRef(r)));
+    }
+    static qsizetype indexHelper(QJsonValueConstRef r) noexcept
+    {
+        qsizetype index = r.index;
+        if (r.is_object)
+            index = index * 2 + 1;
+        return index;
+    }
+    static const QtCbor::Element &elementHelper(QJsonValueConstRef r) noexcept
+    {
+        return container(r)->elements.at(indexHelper(r));
+    }
 
     static QJsonValue fromTrustedCbor(const QCborValue &v)
     {

src/corelib/serialization/qjsonarray.h

@@ -262,6 +262,8 @@ public:
 
 private:
     friend class QJsonValue;
+    friend class QJsonValueConstRef;
+    friend class QJsonPrivate::Value;
     friend class QJsonDocument;
     friend class QCborArray;
     friend Q_CORE_EXPORT QDebug operator<<(QDebug, const QJsonArray &);

src/corelib/serialization/qjsonobject.h

@@ -284,6 +284,7 @@ public:
 private:
     friend class QJsonValue;
     friend class QJsonDocument;
+    friend class QJsonPrivate::Value;
     friend class QJsonValueConstRef;
     friend class QJsonValueRef;
     friend class QCborMap;

src/corelib/serialization/qjsonvalue.cpp

@@ -1,6 +1,7 @@
 /****************************************************************************
 **
 ** Copyright (C) 2020 The Qt Company Ltd.
+** Copyright (C) 2022 Intel Corporation.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the QtCore module of the Qt Toolkit.
@@ -951,9 +952,9 @@ QJsonObject QJsonValueConstRef::toObject() const
 
 QJsonValue QJsonValueConstRef::concrete(QJsonValueConstRef self) noexcept
 {
-    if (!self.is_object)
-        return self.a->at(self.index);
-    return self.o->valueAt(self.index);
+    const QCborContainerPrivate *d = QJsonPrivate::Value::container(self);
+    qsizetype index = QJsonPrivate::Value::indexHelper(self);
+    return QJsonPrivate::Value::fromTrustedCbor(d->valueAt(index));
 }
 
 #if QT_VERSION < QT_VERSION_CHECK(7, 0, 0) && !defined(QT_BOOTSTRAPPED)

src/corelib/serialization/qjsonvalue.h

@@ -206,6 +206,7 @@ protected:
 
     friend class QJsonArray;
     friend class QJsonObject;
+    friend class QJsonPrivate::Value;
 };
 
 class Q_CORE_EXPORT QJsonValueRef : public QJsonValueConstRef

tests/auto/corelib/serialization/json/tst_qtjson.cpp

@@ -1,7 +1,7 @@
 /****************************************************************************
 **
 ** Copyright (C) 2021 The Qt Company Ltd.
-** Copyright (C) 2021 Intel Corporation.
+** Copyright (C) 2022 Intel Corporation.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the test suite of the Qt Toolkit.
@@ -1226,14 +1226,12 @@ void tst_QtJson::testObjectFind()
     QJsonObject::iterator it = object.find(QLatin1String("1"));
     QCOMPARE((*it).toDouble(), 1.);
     it = object.find(QString("11"));
-    QCOMPARE((*it).type(), QJsonValue::Undefined);
     QCOMPARE(it, object.end());
 
     QJsonObject::const_iterator cit = object.constFind(QLatin1String("1"));
     QCOMPARE((*cit).toDouble(), 1.);
     cit = object.constFind(QString("11"));
-    QCOMPARE((*it).type(), QJsonValue::Undefined);
-    QCOMPARE(it, object.end());
+    QCOMPARE(cit, object.constEnd());
 }
 
 void tst_QtJson::testDocument()