--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Framework/Toolbox/ObserversRegistry.h	Fri Oct 14 15:34:11 2016 +0200
@@ -0,0 +1,136 @@
+/**
+ * Stone of Orthanc
+ * Copyright (C) 2012-2016 Sebastien Jodogne, Medical Physics
+ * Department, University Hospital of Liege, Belgium
+ *
+ * This program is free software: you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * In addition, as a special exception, the copyright holders of this
+ * program give permission to link the code of its release with the
+ * OpenSSL project's "OpenSSL" library (or with modified versions of it
+ * that use the same license as the "OpenSSL" library), and distribute
+ * the linked executables. You must obey the GNU General Public License
+ * in all respects for all of the code used other than "OpenSSL". If you
+ * modify file(s) with this exception, you may extend this exception to
+ * your version of the file(s), but you are not obligated to do so. If
+ * you do not wish to do so, delete this exception statement from your
+ * version. If you delete this exception statement from all source files
+ * in the program, then also delete it here.
+ * 
+ * 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
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ **/
+
+
+#pragma once
+
+#include "../Orthanc/Core/OrthancException.h"
+
+#include <boost/noncopyable.hpp>
+#include <boost/thread/mutex.hpp>
+#include <set>
+
+namespace OrthancStone
+{
+  template <
+    typename Source,
+    typename Observer = typename Source::IChangeObserver
+    >
+  class ObserversRegistry : public boost::noncopyable
+  {
+  private:
+    struct ChangeFunctor : public boost::noncopyable
+    {
+      void operator() (Observer& observer,
+                       const Source& source)
+      {
+        observer.NotifyChange(source);
+      }
+    };
+
+    typedef std::set<Observer*>  Observers;
+
+    boost::mutex  mutex_;
+    Observers     observers_;
+    bool          empty_;
+
+  public:
+    ObserversRegistry() : empty_(true)
+    {
+    }
+
+    template <typename Functor>
+    void Notify(const Source* source,
+                Functor& functor)
+    {
+      if (empty_)
+      {
+        // Optimization to avoid the unnecessary locking of the mutex
+        return;
+      }
+
+      if (source == NULL)
+      {
+        throw Orthanc::OrthancException(Orthanc::ErrorCode_ParameterOutOfRange);
+      }
+
+      boost::mutex::scoped_lock lock(mutex_);
+
+      for (typename Observers::const_iterator observer = observers_.begin();
+           observer != observers_.end(); ++observer)
+      {
+        functor(**observer, *source);
+      }
+    }
+
+    template <typename Functor>
+    void Notify(const Source* source)
+    {
+      // Use the default functor
+      Functor functor;
+      Notify(source, functor);
+    }
+
+    void NotifyChange(const Source* source)
+    {
+      Notify<ChangeFunctor>(source);
+    }
+
+    void Register(Observer& observer)
+    {
+      empty_ = false;
+
+      boost::mutex::scoped_lock lock(mutex_);
+      observers_.insert(&observer);
+    }
+
+    void Unregister(Observer& observer)
+    {
+      boost::mutex::scoped_lock lock(mutex_);
+      observers_.erase(&observer);
+
+      if (observers_.empty())
+      {
+        empty_ = true;
+      }
+    }
+
+    bool IsEmpty()
+    {
+#if 0
+      boost::mutex::scoped_lock lock(mutex_);
+      return observers_.empty();
+#else
+      return empty_;
+#endif
+    }
+  };
+}