Moved OpenThreads directly into OpenSceneGraph/trunk rather than being introduced via svn:externals.

This change has been done to make it easier for OpenSceneGraph users to check out the svn via https 
without any conflicts introduced with a http externals.

include/OpenThreads/Barrier

@@ -0,0 +1,100 @@
+/* -*-c++-*- OpenThreads library, Copyright (C) 2002 - 2007  The Open Thread Group
+ *
+ * This library is open source and may be redistributed and/or modified under  
+ * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or 
+ * (at your option) any later version.  The full license is in LICENSE file
+ * included with this distribution, and on the openscenegraph.org website.
+ * 
+ * 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 
+ * OpenSceneGraph Public License for more details.
+*/
+
+
+//
+// Barrier - C++ barrier class
+// ~~~~~~~
+// 
+
+#ifndef _OPENTHREADS_BARRIER_
+#define _OPENTHREADS_BARRIER_
+
+#include <OpenThreads/Exports>
+
+namespace OpenThreads {
+
+
+/**
+ *  @class Barrier
+ *  @brief This class provides an object-oriented thread barrier interface
+ *
+ *  @warning It is unwise to use the construct "Barrier barrier" in the
+ *           global namespace on sgi's.  The object "barrier"
+ *           will confilict with the c-library sproc function "barrier" and
+ *           unpredictable results may occur. You have been warned.
+ */
+class OPENTHREAD_EXPORT_DIRECTIVE Barrier {
+
+public:
+
+    /**
+     *  Constructor
+     */
+    Barrier(int numThreads=0);
+
+    /**
+     *  Destructor
+     */
+    virtual ~Barrier();
+
+    /**
+     *  Reset the barrier to it's original state.
+     */
+    virtual void reset();
+
+    /**
+     *  Block until numThreads threads have entered the barrier.
+     */
+    virtual void block(unsigned int numThreads=0);
+
+    /**
+     *  Release the barrier, now.
+     */
+    virtual void release();
+
+    /**
+     *  Return the number of threads currently blocked in the barrier,
+     *  Return -1 if error.
+     */ 
+    virtual int numThreadsCurrentlyBlocked();
+
+
+    void invalidate();
+    
+private:
+
+    /**
+     *  Private copy constructor, to prevent tampering.
+     */
+    Barrier(const Barrier &/*b*/) {};
+
+    /**
+     *  Private copy assignment, to prevent tampering.
+     */
+    Barrier &operator=(const Barrier &/*b*/) {return *(this);};
+
+    /**
+     *  Implementation-specific private data.
+     */
+    void *_prvData;
+
+
+    bool _valid;
+
+};
+
+}
+
+#endif // !_OPENTHREADS_BARRIER_
+