Ref T552 Added mixins for QDataStream marshalling.

src/blackmisc/datastream.h

@@ -0,0 +1,133 @@
+/* Copyright (C) 2019
+ * swift Project Community / Contributors
+ *
+ * This file is part of swift project. It is subject to the license terms in the LICENSE file found in the top-level
+ * directory of this distribution. No part of swift project, including this file, may be copied, modified, propagated,
+ * or distributed except according to the terms contained in the LICENSE file.
+ */
+
+//! \file
+
+#ifndef BLACKMISC_DATASTREAM_H
+#define BLACKMISC_DATASTREAM_H
+
+#include "blackmisc/typetraits.h"
+#include <QDataStream>
+
+namespace BlackMisc
+{
+    class CEmpty;
+
+    namespace Mixin
+    {
+        /*!
+         * CRTP class template to generate non-member QDataStream streaming operators.
+         *
+         * \tparam Derived Must implement public methods marshalToDataStream(QDataStream &) and unmarshalFromDataStream(QDataStream &).
+         */
+        template <class Derived>
+        class DataStreamOperators
+        {
+        public:
+            //! Marshal a value to a QDataStream.
+            friend QDataStream &operator <<(QDataStream &stream, const Derived &value)
+            {
+                value.marshalToDataStream(stream);
+                return stream;
+            }
+
+            //! Unmarshal a value from a QDataStream.
+            friend QDataStream &operator >>(QDataStream &stream, Derived &value)
+            {
+                value.unmarshalFromDataStream(stream);
+                return stream;
+            }
+        };
+
+        /*!
+         * CRTP class template to generate QDataStream marshalling methods using CMetaClass.
+         *
+         * \see BLACKMISC_DECLARE_USING_MIXIN_DATASTREAM
+         */
+        template <class Derived>
+        class DataStreamByMetaClass : public DataStreamOperators<Derived>
+        {
+        public:
+            //! Marshal a value to a QDataStream.
+            void marshalToDataStream(QDataStream &stream) const
+            {
+                baseMarshal(static_cast<const TBaseOfT<Derived> *>(derived()), stream);
+                constexpr auto meta = introspect<Derived>().without(MetaFlags<DisabledForMarshalling>());
+                meta.forEachMember([ &, this ](auto member) { stream << member.in(*this->derived()); });
+            }
+
+            //! Unmarshal a value from a QDataStream.
+            void unmarshalFromDataStream(QDataStream &stream)
+            {
+                baseUnmarshal(static_cast<TBaseOfT<Derived> *>(derived()), stream);
+                constexpr auto meta = introspect<Derived>().without(MetaFlags<DisabledForMarshalling>());
+                meta.forEachMember([ &, this ](auto member) { stream >> member.in(*this->derived()); });
+            }
+
+        private:
+            const Derived *derived() const { return static_cast<const Derived *>(this); }
+            Derived *derived() { return static_cast<Derived *>(this); }
+
+            template <typename T> static void baseMarshal(const T *base, QDataStream &stream) { base->marshalToDataStream(stream); }
+            template <typename T> static void baseUnmarshal(T *base, QDataStream &stream) { base->unmarshalFromDataStream(stream); }
+            static void baseMarshal(const void *, QDataStream &) {}
+            static void baseUnmarshal(void *, QDataStream &) {}
+            static void baseMarshal(const CEmpty *, QDataStream &) {}
+            static void baseUnmarshal(CEmpty *, QDataStream &) {}
+        };
+
+        /*!
+         * When a derived class and a base class both inherit from Mixin::DataStreamByMetaClass,
+         * the derived class uses this macro to disambiguate the inherited members.
+         */
+#       define BLACKMISC_DECLARE_USING_MIXIN_DATASTREAM(DERIVED)                            \
+            using ::BlackMisc::Mixin::DataStreamByMetaClass<DERIVED>::marshalToDataStream;  \
+            using ::BlackMisc::Mixin::DataStreamByMetaClass<DERIVED>::unmarshalFromDataStream;
+    }
+}
+
+/*!
+ * Operator for marshalling enums with QDataStream.
+ */
+template <typename E, typename = std::enable_if_t<std::is_enum<E>::value>>
+QDataStream &operator <<(QDataStream &stream, E value)
+{
+    return stream << static_cast<int>(value);
+}
+
+/*!
+ * Operator for unmarshalling enums with QDataStream.
+ */
+template <typename E, typename = std::enable_if_t<std::is_enum<E>::value>>
+QDataStream &operator >>(QDataStream &stream, E &value)
+{
+    int temp;
+    stream >> temp;
+    value = static_cast<E>(temp);
+    return stream;
+}
+
+/*!
+ * Operator for marshalling pairs with QDataStream.
+ */
+template <typename T, typename U>
+QDataStream &operator <<(QDataStream &stream, const std::pair<T, U> &pair)
+{
+    return stream << pair.first << pair.second;
+}
+
+/*!
+ * Operator for unmarshalling pairs with QDataStream.
+ */
+template <typename T, typename U>
+QDataStream &operator >>(QDataStream &stream, std::pair<T, U> &pair)
+{
+    return stream >> pair.first >> pair.second;
+}
+
+#endif

src/blackmisc/metaclass.h

@@ -182,7 +182,7 @@ namespace BlackMisc
     enum MetaFlag
     {
         DisabledForComparison = 1 << 0,     //!< Element will be ignored by compare() and comparison operators
-        DisabledForMarshalling = 1 << 1,    //!< Element will be ignored during DBus marshalling
+        DisabledForMarshalling = 1 << 1,    //!< Element will be ignored during DBus and QDataStream marshalling
         DisabledForDebugging = 1 << 2,      //!< Element will be ignored when streaming to QDebug
         DisabledForHashing = 1 << 3,        //!< Element will be ignored by qHash()
         DisabledForJson = 1 << 4,           //!< Element will be ignored during JSON serialization