First checkin for OpenMesh 2.0

git-svn-id: http://www.openmesh.org/svnrepo/OpenMesh/trunk@2 fdac6126-5c0c-442c-9429-916003d36597

Core/Utils/SingletonT.hh

@@ -0,0 +1,132 @@
+/*===========================================================================*\
+ *                                                                           *
+ *                               OpenMesh                                    *
+ *        Copyright (C) 2003 by Computer Graphics Group, RWTH Aachen         *
+ *                           www.openmesh.org                                *
+ *                                                                           *
+ *---------------------------------------------------------------------------* 
+ *                                                                           *
+ *                                License                                    *
+ *                                                                           *
+ *  This library is free software; you can redistribute it and/or modify it  *
+ *  under the terms of the GNU Lesser General Public License as published    *
+ *  by the Free Software Foundation, version 2.1.                            *
+ *                                                                           *
+ *  This library 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        *
+ *  Lesser General Public License for more details.                          *
+ *                                                                           *
+ *  You should have received a copy of the GNU Lesser General Public         *
+ *  License along with this library; if not, write to the Free Software      *
+ *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.                *
+ *                                                                           *
+\*===========================================================================*/
+
+
+//=============================================================================
+//
+//  Implements a simple singleton template
+//
+//=============================================================================
+
+
+#ifndef __SINGLETON_HH__
+#define __SINGLETON_HH__
+
+
+//=== INCLUDES ================================================================
+
+// OpenMesh
+#include <OpenMesh/Core/System/config.h>
+
+// STL
+#include <stdexcept>
+#include <iostream>
+
+
+//== NAMESPACES ===============================================================
+
+
+namespace OpenMesh {
+
+
+//=== IMPLEMENTATION ==========================================================
+
+
+/** A simple singleton template.
+    Encapsulates an arbitrary class and enforces its uniqueness.
+*/
+
+template <typename T>
+class SingletonT
+{
+public:
+
+  /** Singleton access function.
+      Use this function to obtain a reference to the instance of the 
+      encapsulated class. Note that this instance is unique and created
+      on the first call to Instance().
+  */
+
+  static T& Instance()
+  {
+    if (!pInstance__)
+    {
+      // check if singleton alive
+      if (destroyed__)
+      {
+	OnDeadReference();
+      }
+      // first time request -> initialize
+      else
+      {
+	Create();
+      }
+    }
+    return *pInstance__;
+  }
+
+
+private:
+
+  // Disable constructors/assignment to enforce uniqueness
+  SingletonT();
+  SingletonT(const SingletonT&);
+  SingletonT& operator=(const SingletonT&);
+
+  // Create a new singleton and store its pointer
+  static void Create()
+  {
+    static T theInstance;
+    pInstance__ = &theInstance;
+  }
+  
+  // Will be called if instance is accessed after its lifetime has expired
+  static void OnDeadReference()
+  {
+    throw std::runtime_error("[Singelton error] - Dead reference detected!\n");
+  }
+
+  virtual ~SingletonT()
+  {
+    pInstance__ = 0;
+    destroyed__ = true;
+  }
+  
+  static T*     pInstance__;
+  static bool   destroyed__;
+};
+
+
+
+//=============================================================================
+} // namespace OpenMesh
+//=============================================================================
+#if defined(OM_INCLUDE_TEMPLATES) && !defined(OPENMESH_SINGLETON_C)
+#  define OPENMESH_SINGLETON_TEMPLATES
+#  include "SingletonT.cc"
+#endif
+//=============================================================================
+#endif // __SINGLETON_HH__
+//=============================================================================