Added ReentrantMutex

src/osgDB/ReentrantMutex.cpp

@@ -0,0 +1,75 @@
+/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2003 Robert Osfield 
+ *
+ * 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.
+*/
+
+#include <osgDB/ReentrantMutex>
+
+
+using namespace osgDB;
+
+ReentrantMutex::ReentrantMutex():
+    _threadHoldingMutex(0),
+    _lockCount(0)
+{
+}
+
+ReentrantMutex::~ReentrantMutex()
+{
+}
+
+int ReentrantMutex::lock()
+{
+    if (_threadHoldingMutex==OpenThreads::Thread::CurrentThread())
+    {
+        ++_lockCount;
+        return 0;
+    }
+    else
+    {
+        int result = Mutex::lock();
+        if (result==0)
+        {
+            _threadHoldingMutex = OpenThreads::Thread::CurrentThread();
+            _lockCount = 1;
+        }
+        return result;
+    }
+}
+
+int ReentrantMutex::unlock()
+{
+    if (_threadHoldingMutex==OpenThreads::Thread::CurrentThread())
+    {
+        --_lockCount;
+        if (_lockCount<=0) return Mutex::unlock();
+    }
+    return 0;
+}
+
+int ReentrantMutex::trylock()
+{
+    if (_threadHoldingMutex==OpenThreads::Thread::CurrentThread())
+    {
+        ++_lockCount;
+        return 0;
+    }
+    else
+    {
+        int result = Mutex::trylock();
+        if (result==0)
+        {
+            _threadHoldingMutex = OpenThreads::Thread::CurrentThread();
+            _lockCount = 1;
+        }
+        return result;
+    }
+}