Clang: Use MessageEnvelop instead of QVariant

QVariant has unwanted dependencies so we provided our own simpler solution.
We want to support move only types and calling the copy constructor as you
move the value in and outside. This copying is adding unwanted overhead
too.

Change-Id: I2e27a7924868efe81e8b8ff3415499c9fa22c2bc
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@theqtcompany.com>

src/libs/clangbackendipc/messageenvelop.h

@@ -0,0 +1,112 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of Qt Creator.
+**
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-3.0.html.
+**
+****************************************************************************/
+
+#ifndef CLANGBACKEND_MESSAGEENVELOP_H
+#define CLANGBACKEND_MESSAGEENVELOP_H
+
+#include "clangbackendipc_global.h"
+
+#include <QByteArray>
+#include <QDataStream>
+
+namespace ClangBackEnd {
+
+class MessageEnvelop
+{
+public:
+    MessageEnvelop() = default;
+
+    template <class Message>
+    MessageEnvelop(const Message &message)
+        : messageType_(MessageTrait<Message>::enumeration)
+    {
+        QDataStream stream(&data, QIODevice::WriteOnly);
+        stream << message;
+    }
+
+    template <class Message>
+    Message message() const
+    {
+        Message message;
+
+        QDataStream stream(&data, QIODevice::ReadOnly);
+        stream >> message;
+
+        return message;
+    }
+
+    MessageType messageType() const
+    {
+        return messageType_;
+    }
+
+    bool isValid() const
+    {
+        return messageType_ != MessageType::InvalidMessage;
+    }
+
+    friend
+    QDataStream &operator >>(QDataStream& in, MessageType& messageType)
+    {
+        quint32 messageTypeAsInt;
+        in >> messageTypeAsInt;
+        messageType = MessageType(messageTypeAsInt);
+
+        return in;
+    }
+
+    friend
+    QDataStream &operator<<(QDataStream &out, const MessageEnvelop &messageEnvelop)
+    {
+        out << reinterpret_cast<const quint8&>(messageEnvelop.messageType_);
+        out << messageEnvelop.data;
+
+        return out;
+    }
+
+    friend
+    QDataStream &operator>>(QDataStream &in, MessageEnvelop &messageEnvelop)
+    {
+        in >> reinterpret_cast<quint8&>(messageEnvelop.messageType_);
+        in >> messageEnvelop.data;
+
+        return in;
+    }
+
+    friend
+    bool operator==(const MessageEnvelop &first, const MessageEnvelop &second)
+    {
+        return first.messageType_ == second.messageType_
+            && first.data == second.data;
+    }
+
+private:
+    mutable QByteArray data;
+    MessageType messageType_ = MessageType::InvalidMessage;
+};
+
+} // namespace ClangBackEnd
+
+#endif // CLANGBACKEND_MESSAGEENVELOP_H