--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Framework/Messages/LockingEmitter.h	Fri Jun 14 12:14:16 2019 +0200
@@ -0,0 +1,106 @@
+/**
+ * Stone of Orthanc
+ * Copyright (C) 2012-2016 Sebastien Jodogne, Medical Physics
+ * Department, University Hospital of Liege, Belgium
+ * Copyright (C) 2017-2019 Osimis S.A., Belgium
+ *
+ * This program is free software: you can redistribute it and/or
+ * modify it under the terms of the GNU Affero General Public License
+ * as published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ **/
+
+#pragma once
+
+#include "IMessageEmitter.h"
+#include "IObservable.h"
+
+#include <boost/thread.hpp>
+
+namespace OrthancStone
+{
+  /**
+   * This class is used when using the ThreadedOracle : since messages
+   * can be sent from multiple Oracle threads, this IMessageEmitter
+   * implementation serializes the callbacks.
+   * 
+   * The internal mutex used in Oracle messaging can also be used to 
+   * protect the application data. Thus, this class can be used as a single
+   * application-wide mutex.
+   */
+  class LockingEmitter : public IMessageEmitter
+  {
+  private:
+    boost::shared_mutex                mutex_;
+    MessageBroker        broker_;
+    IObservable          oracleObservable_;
+
+  public:
+    LockingEmitter() :
+      oracleObservable_(broker_)
+    {
+    }
+
+    virtual void EmitMessage(const IObserver& observer,
+      const IMessage& message) ORTHANC_OVERRIDE
+    {
+      try
+      {
+        boost::unique_lock<boost::shared_mutex>  lock(mutex_);
+        oracleObservable_.EmitMessage(observer, message);
+      }
+      catch (Orthanc::OrthancException& e)
+      {
+        LOG(ERROR) << "Exception while emitting a message: " << e.What();
+      }
+    }
+
+
+    class ReaderLock : public boost::noncopyable
+    {
+    private:
+      LockingEmitter& that_;
+      boost::shared_lock<boost::shared_mutex>  lock_;
+
+    public:
+      ReaderLock(LockingEmitter& that) :
+        that_(that),
+        lock_(that.mutex_)
+      {
+      }
+    };
+
+
+    class WriterLock : public boost::noncopyable
+    {
+    private:
+      LockingEmitter& that_;
+      boost::unique_lock<boost::shared_mutex>  lock_;
+
+    public:
+      WriterLock(LockingEmitter& that) :
+        that_(that),
+        lock_(that.mutex_)
+      {
+      }
+
+      MessageBroker& GetBroker()
+      {
+        return that_.broker_;
+      }
+
+      IObservable& GetOracleObservable()
+      {
+        return that_.oracleObservable_;
+      }
+    };
+  };
+}