Cleanup QDBusPendingReply

Remove the limitation of max 8 arguments and clean up the
template code.

This required a bit of special work to ensure
QDBusPendingReply<void> works the same way
as QDBusPendingReply<>.

Change-Id: I8e822b2f97f0712746b917056ea8f3d5c219c7f6
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

2 files changed, 93 insertions, 96 deletions

diff --git a/src/dbus/qdbuspendingreply.cpp b/src/dbus/qdbuspendingreply.cpp
index df37d92211..f83b3d27a2 100644
--- a/src/dbus/qdbuspendingreply.cpp
+++ b/src/dbus/qdbuspendingreply.cpp
@@ -95,7 +95,7 @@
 */
 
 /*!
-    \fn template<typename T1, typename T2, typename T3, typename T4, typename T5, typename T6, typename T7, typename T8> QDBusPendingReply<T1, T2, T3, T4, T5, T6, T7, T8>::QDBusPendingReply()
+    \fn template<typename... Types> QDBusPendingReply<Types...>::QDBusPendingReply()
 
     Creates an empty QDBusPendingReply object. Without assigning a
     QDBusPendingCall object to this reply, QDBusPendingReply cannot do
@@ -103,7 +103,7 @@
 */
 
 /*!
-    \fn template<typename T1, typename T2, typename T3, typename T4, typename T5, typename T6, typename T7, typename T8> QDBusPendingReply<T1, T2, T3, T4, T5, T6, T7, T8>::QDBusPendingReply(const QDBusPendingReply &other)
+    \fn template<typename... Types> QDBusPendingReply<Types...>::QDBusPendingReply(const QDBusPendingReply &other)
 
     Creates a copy of the \a other QDBusPendingReply object. Just like
     QDBusPendingCall and QDBusPendingCallWatcher, this QDBusPendingReply
@@ -112,7 +112,7 @@
 */
 
 /*!
-    \fn template<typename T1, typename T2, typename T3, typename T4, typename T5, typename T6, typename T7, typename T8> QDBusPendingReply<T1, T2, T3, T4, T5, T6, T7, T8>::QDBusPendingReply(const QDBusPendingCall &call)
+    \fn template<typename... Types> QDBusPendingReply<Types...>::QDBusPendingReply(const QDBusPendingCall &call)
 
     Creates a QDBusPendingReply object that will take its contents from
     the \a call pending asynchronous call. This QDBusPendingReply object
@@ -120,7 +120,7 @@
 */
 
 /*!
-    \fn template<typename T1, typename T2, typename T3, typename T4, typename T5, typename T6, typename T7, typename T8> QDBusPendingReply<T1, T2, T3, T4, T5, T6, T7, T8>::QDBusPendingReply(const QDBusMessage &message)
+    \fn template<typename... Types> QDBusPendingReply<Types...>::QDBusPendingReply(const QDBusMessage &message)
 
     Creates a QDBusPendingReply object that will take its contents from
     the message \a message. In this case, this object will be already
@@ -130,7 +130,7 @@
 */
 
 /*!
-    \fn template<typename T1, typename T2, typename T3, typename T4, typename T5, typename T6, typename T7, typename T8> QDBusPendingReply &QDBusPendingReply<T1, T2, T3, T4, T5, T6, T7, T8>::operator=(const QDBusPendingReply &other)
+    \fn template<typename... Types> QDBusPendingReply &QDBusPendingReply<Types...>::operator=(const QDBusPendingReply &other)
 
     Makes a copy of \a other and drops the reference to the current
     pending call. If the current reference is to an unfinished pending
@@ -140,7 +140,7 @@
 */
 
 /*!
-    \fn template<typename T1, typename T2, typename T3, typename T4, typename T5, typename T6, typename T7, typename T8> QDBusPendingReply &QDBusPendingReply<T1, T2, T3, T4, T5, T6, T7, T8>::operator=(const QDBusPendingCall &call)
+    \fn template<typename... Types> QDBusPendingReply &QDBusPendingReply<Types...>::operator=(const QDBusPendingCall &call)
 
     Makes this object take its contents from the \a call pending call
     and drops the reference to the current pending call. If the
@@ -150,7 +150,7 @@
 */
 
 /*!
-    \fn template<typename T1, typename T2, typename T3, typename T4, typename T5, typename T6, typename T7, typename T8> QDBusPendingReply &QDBusPendingReply<T1, T2, T3, T4, T5, T6, T7, T8>::operator=(const QDBusMessage &message)
+    \fn template<typename... Types> QDBusPendingReply &QDBusPendingReply<Types...>::operator=(const QDBusMessage &message)
 
     Makes this object take its contents from the \a message message
     and drops the reference to the current pending call. If the
@@ -172,7 +172,7 @@
  */
 
 /*!
-    \fn template<typename T1, typename T2, typename T3, typename T4, typename T5, typename T6, typename T7, typename T8> int QDBusPendingReply<T1, T2, T3, T4, T5, T6, T7, T8>::count() const
+    \fn template<typename... Types> int QDBusPendingReply<Types...>::count() const
 
     Return the number of arguments the reply is supposed to have. This
     number matches the number of non-void template parameters in this
@@ -184,7 +184,7 @@
 */
 
 /*!
-    \fn template<typename T1, typename T2, typename T3, typename T4, typename T5, typename T6, typename T7, typename T8> QVariant QDBusPendingReply<T1, T2, T3, T4, T5, T6, T7, T8>::argumentAt(int index) const
+    \fn template<typename... Types> QVariant QDBusPendingReply<Types...>::argumentAt(int index) const
 
     Returns the argument at position \a index in the reply's
     contents. If the reply doesn't have that many elements, this
@@ -199,7 +199,7 @@
 */
 
 /*!
-    \fn template<typename T1, typename T2, typename T3, typename T4, typename T5, typename T6, typename T7, typename T8> T1 QDBusPendingReply<T1, T2, T3, T4, T5, T6, T7, T8>::value() const
+    \fn template<typename... Types> T1 QDBusPendingReply<Types...>::value() const
 
     Returns the first argument in this reply, cast to type \c T1 (the
     first template parameter of this class). This is equivalent to
@@ -217,7 +217,7 @@
 */
 
 /*!
-    \fn template<typename T1, typename T2, typename T3, typename T4, typename T5, typename T6, typename T7, typename T8> QDBusPendingReply<T1, T2, T3, T4, T5, T6, T7, T8>::operator T1() const
+    \fn template<typename... Types> QDBusPendingReply<Types...>::operator T1() const
 
     Returns the first argument in this reply, cast to type \c T1 (the
     first template parameter of this class). This is equivalent to
@@ -235,7 +235,7 @@
 */
 
 /*!
-    \fn template<typename T1, typename T2, typename T3, typename T4, typename T5, typename T6, typename T7, typename T8> void QDBusPendingReply<T1, T2, T3, T4, T5, T6, T7, T8>::waitForFinished()
+    \fn template<typename... Types> void QDBusPendingReply<Types...>::waitForFinished()
 
     Suspends the execution of the calling thread until the reply is
     received and processed. After this function returns, isFinished()
@@ -245,27 +245,27 @@
     \sa QDBusPendingCallWatcher::waitForFinished()
 */
 
-QDBusPendingReplyData::QDBusPendingReplyData()
+QDBusPendingReplyBase::QDBusPendingReplyBase()
     : QDBusPendingCall(nullptr)         // initialize base class empty
 {
 }
 
-QDBusPendingReplyData::~QDBusPendingReplyData()
+QDBusPendingReplyBase::~QDBusPendingReplyBase()
 {
 }
 
-void QDBusPendingReplyData::assign(const QDBusPendingCall &other)
+void QDBusPendingReplyBase::assign(const QDBusPendingCall &other)
 {
     QDBusPendingCall::operator=(other);
 }
 
-void QDBusPendingReplyData::assign(const QDBusMessage &message)
+void QDBusPendingReplyBase::assign(const QDBusMessage &message)
 {
     d = new QDBusPendingCallPrivate(QDBusMessage(), nullptr); // drops the reference to the old one
     d->replyMessage = message;
 }
 
-QVariant QDBusPendingReplyData::argumentAt(int index) const
+QVariant QDBusPendingReplyBase::argumentAt(int index) const
 {
     if (!d)
         return QVariant();
@@ -275,7 +275,7 @@ QVariant QDBusPendingReplyData::argumentAt(int index) const
     return d->replyMessage.arguments().value(index);
 }
 
-void QDBusPendingReplyData::setMetaTypes(int count, const int *types)
+void QDBusPendingReplyBase::setMetaTypes(int count, const int *types)
 {
     Q_ASSERT(d);
     const auto locker = qt_scoped_lock(d->mutex);
diff --git a/src/dbus/qdbuspendingreply.h b/src/dbus/qdbuspendingreply.h
index 62e955a82b..18c02508a0 100644
--- a/src/dbus/qdbuspendingreply.h
+++ b/src/dbus/qdbuspendingreply.h
@@ -49,11 +49,11 @@
 QT_BEGIN_NAMESPACE
 
 
-class Q_DBUS_EXPORT QDBusPendingReplyData: public QDBusPendingCall
+class Q_DBUS_EXPORT QDBusPendingReplyBase : public QDBusPendingCall
 {
 protected:
-    QDBusPendingReplyData();
-    ~QDBusPendingReplyData();
+    QDBusPendingReplyBase();
+    ~QDBusPendingReplyBase();
     void assign(const QDBusPendingCall &call);
     void assign(const QDBusMessage &message);
 
@@ -62,79 +62,45 @@ protected:
 };
 
 namespace QDBusPendingReplyTypes {
-    template<int Index,
-             typename T1, typename T2, typename T3, typename T4,
-             typename T5, typename T6, typename T7, typename T8>
+    template<int Index, typename T, typename... Types>
     struct Select
     {
-        typedef Select<Index - 1, T2, T3, T4, T5, T6, T7, T8, void> Next;
+        typedef Select<Index - 1, Types...> Next;
         typedef typename Next::Type Type;
     };
-    template<typename T1, typename T2, typename T3, typename T4,
-             typename T5, typename T6, typename T7, typename T8>
-    struct Select<0, T1, T2, T3, T4, T5, T6, T7, T8>
+    template<typename T, typename... Types>
+    struct Select<0, T, Types...>
     {
-        typedef T1 Type;
+        typedef T Type;
     };
 
-    template<typename T1> inline int metaTypeFor(T1 * = nullptr)
-    { return qMetaTypeId<T1>(); }
+    template<typename T> inline QMetaType metaTypeFor()
+    { return QMetaType::fromType<T>(); }
     // specialize for QVariant, allowing it to be used in place of QDBusVariant
-    template<> inline int metaTypeFor<QVariant>(QVariant *)
-    { return qMetaTypeId<QDBusVariant>(); }
+    template<> inline QMetaType metaTypeFor<QVariant>()
+    { return QMetaType::fromType<QDBusVariant>(); }
+}
 
-    template<typename T1, typename T2, typename T3, typename T4,
-             typename T5, typename T6, typename T7, typename T8>
-    struct ForEach
-    {
-        typedef ForEach<T2, T3, T4, T5, T6, T7, T8, void> Next;
-        enum { Total = Next::Total + 1 };
-        static inline void fillMetaTypes(int *p)
-        {
-            *p = metaTypeFor<T1>(nullptr);
-            Next::fillMetaTypes(++p);
-        }
-    };
-    template<>
-    struct ForEach<void, void, void, void,   void, void, void, void>
-    {
-        enum { Total = 0 };
-        static inline void fillMetaTypes(int *)
-        { }
-    };
 
-    struct TypeIsVoid {};
-    template <typename T> struct NotVoid       { typedef T Type; };
-    template <>           struct NotVoid<void> { typedef TypeIsVoid Type; };
-} // namespace QDBusPendingReplyTypes
-
-template<typename T1 = void, typename T2 = void, typename T3 = void, typename T4 = void,
-         typename T5 = void, typename T6 = void, typename T7 = void, typename T8 = void>
-class QDBusPendingReply:
-#ifdef Q_CLANG_QDOC
-    public QDBusPendingCall
-#else
-    public QDBusPendingReplyData
-#endif
+template<typename... Types>
+class QDBusPendingReply : public QDBusPendingReplyBase
 {
-    typedef QDBusPendingReplyTypes::ForEach<T1, T2, T3, T4, T5, T6, T7, T8> ForEach;
-    template<int Index> struct Select :
-    QDBusPendingReplyTypes::Select<Index, T1, T2, T3, T4, T5, T6, T7, T8>
-    {
-    };
-
+    template<int Index> using Select = QDBusPendingReplyTypes::Select<Index, Types...>;
 public:
-    enum { Count = ForEach::Total };
+    enum { Count = std::is_same_v<typename Select<0>::Type, void> ? 0 : sizeof...(Types) };
 
-    inline QDBusPendingReply()
-    { }
+    inline constexpr int count() const { return Count; }
+
+
+    inline QDBusPendingReply() = default;
     inline QDBusPendingReply(const QDBusPendingReply &other)
-        : QDBusPendingReplyData(other)
+        : QDBusPendingReplyBase(other)
     { }
     inline /*implicit*/ QDBusPendingReply(const QDBusPendingCall &call) // required by qdbusxml2cpp-generated code
     { *this = call; }
     inline /*implicit*/ QDBusPendingReply(const QDBusMessage &message)
     { *this = message; }
+
     inline QDBusPendingReply &operator=(const QDBusPendingReply &other)
     { assign(other); return *this; }
     inline QDBusPendingReply &operator=(const QDBusPendingCall &call)
@@ -142,23 +108,14 @@ public:
     inline QDBusPendingReply &operator=(const QDBusMessage &message)
     { assign(message); return *this; }
 
-    inline int count() const { return Count; }
-
-#if defined(Q_CLANG_QDOC)
-    QVariant argumentAt(int index) const;
-#else
-    using QDBusPendingReplyData::argumentAt;
-#endif
-
-#ifndef Q_CLANG_QDOC
+    using QDBusPendingReplyBase::argumentAt;
     template<int Index> inline
-    const typename Select<Index>::Type argumentAt() const
+    typename Select<Index>::Type argumentAt() const
     {
         static_assert(Index >= 0 && Index < Count, "Index out of bounds");
         typedef typename Select<Index>::Type ResultType;
         return qdbus_cast<ResultType>(argumentAt(Index));
     }
-#endif
 
 #if defined(Q_CLANG_QDOC)
     bool isFinished() const;
@@ -168,43 +125,83 @@ public:
     bool isError() const;
     QDBusError error() const;
     QDBusMessage reply() const;
+#endif
 
-    inline T1 value() const;
-    inline operator T1() const;
-#else
     inline typename Select<0>::Type value() const
     {
         return argumentAt<0>();
     }
 
-    inline operator typename QDBusPendingReplyTypes::NotVoid<T1>::Type() const
+    inline operator typename Select<0>::Type() const
     {
         return argumentAt<0>();
     }
-#endif
 
 private:
     inline void calculateMetaTypes()
     {
         if (!d) return;
-        int typeIds[Count > 0 ? Count : 1]; // use at least one since zero-sized arrays aren't valid
-        ForEach::fillMetaTypes(typeIds);
-        setMetaTypes(Count, typeIds);
+        if constexpr (Count == 0) {
+                setMetaTypes(0, nullptr);
+        } else {
+            std::array<int, Count> typeIds = { QDBusPendingReplyTypes::metaTypeFor<Types>().id()... };
+            setMetaTypes(Count, typeIds.data());
+        }
     }
 
     inline void assign(const QDBusPendingCall &call)
     {
-        QDBusPendingReplyData::assign(call);
+        QDBusPendingReplyBase::assign(call);
         calculateMetaTypes();
     }
 
     inline void assign(const QDBusMessage &message)
     {
-        QDBusPendingReplyData::assign(message);
+        QDBusPendingReplyBase::assign(message);
         calculateMetaTypes();
     }
 };
 
+template<>
+class QDBusPendingReply<> : public QDBusPendingReplyBase
+{
+public:
+    enum { Count = 0 };
+    inline int count() const { return Count; }
+
+    inline QDBusPendingReply() = default;
+    inline QDBusPendingReply(const QDBusPendingReply &other)
+        : QDBusPendingReplyBase(other)
+    { }
+    inline /*implicit*/ QDBusPendingReply(const QDBusPendingCall &call) // required by qdbusxml2cpp-generated code
+    { *this = call; }
+    inline /*implicit*/ QDBusPendingReply(const QDBusMessage &message)
+    { *this = message; }
+
+    inline QDBusPendingReply &operator=(const QDBusPendingReply &other)
+    { assign(other); return *this; }
+    inline QDBusPendingReply &operator=(const QDBusPendingCall &call)
+    { assign(call); return *this; }
+    inline QDBusPendingReply &operator=(const QDBusMessage &message)
+    { assign(message); return *this; }
+
+private:
+    inline void assign(const QDBusPendingCall &call)
+    {
+        QDBusPendingReplyBase::assign(call);
+        if (d)
+            setMetaTypes(0, nullptr);
+    }
+
+    inline void assign(const QDBusMessage &message)
+    {
+        QDBusPendingReplyBase::assign(message);
+        if (d)
+            setMetaTypes(0, nullptr);
+    }
+
+};
+
 QT_END_NAMESPACE
 
 #endif // QT_NO_DBUS