1 files changed, 73 insertions, 4 deletions
diff --git a/LibOVR/Src/Kernel/OVR_Atomic.cpp b/LibOVR/Src/Kernel/OVR_Atomic.cpp
index 1c0efc2..9ea6e76 100644
--- a/LibOVR/Src/Kernel/OVR_Atomic.cpp
+++ b/LibOVR/Src/Kernel/OVR_Atomic.cpp
@@ -7,16 +7,16 @@ Content     :   Contains atomic operations and inline fastest locking
 Created     :   September 19, 2012
 Notes       : 
 
-Copyright   :   Copyright 2013 Oculus VR, Inc. All Rights reserved.
+Copyright   :   Copyright 2014 Oculus VR, Inc. All Rights reserved.
 
-Licensed under the Oculus VR SDK License Version 2.0 (the "License"); 
-you may not use the Oculus VR SDK except in compliance with the License, 
+Licensed under the Oculus VR Rift SDK License Version 3.1 (the "License"); 
+you may not use the Oculus VR Rift SDK except in compliance with the License, 
 which is provided at the time of installation or download, or which 
 otherwise accompanies this software in either electronic or hard copy form.
 
 You may obtain a copy of the License at
 
-http://www.oculusvr.com/licenses/LICENSE-2.0 
+http://www.oculusvr.com/licenses/LICENSE-3.1 
 
 Unless required by applicable law or agreed to in writing, the Oculus VR SDK 
 distributed under the License is distributed on an "AS IS" BASIS,
@@ -27,6 +27,7 @@ limitations under the License.
 ************************************************************************************/
 
 #include "OVR_Atomic.h"
+#include "OVR_Allocator.h"
 
 #ifdef OVR_ENABLE_THREADS
 
@@ -88,6 +89,74 @@ Lock::~Lock()
 
 #endif
 
+
+//-------------------------------------------------------------------------------------
+// ***** SharedLock
+
+// This is a general purpose globally shared Lock implementation that should probably be
+// moved to Kernel.
+// May in theory busy spin-wait if we hit contention on first lock creation,
+// but this shouldn't matter in practice since Lock* should be cached.
+
+
+enum { LockInitMarker = 0xFFFFFFFF };
+
+Lock* SharedLock::GetLockAddRef()
+{
+    int oldUseCount;
+
+    do {
+        oldUseCount = UseCount;
+        if (oldUseCount == LockInitMarker)
+            continue;
+
+        if (oldUseCount == 0)
+        {
+            // Initialize marker
+            if (AtomicOps<int>::CompareAndSet_Sync(&UseCount, 0, LockInitMarker))
+            {
+                Construct<Lock>(Buffer);
+                do { }
+                while (!AtomicOps<int>::CompareAndSet_Sync(&UseCount, LockInitMarker, 1));
+                return toLock();
+            }
+            continue;
+        }
+
+    } while (!AtomicOps<int>::CompareAndSet_NoSync(&UseCount, oldUseCount, oldUseCount + 1));
+
+    return toLock();
+}
+
+void SharedLock::ReleaseLock(Lock* plock)
+{
+    OVR_UNUSED(plock);
+    OVR_ASSERT(plock == toLock());
+
+    int oldUseCount;
+
+    do {
+        oldUseCount = UseCount;
+        OVR_ASSERT(oldUseCount != LockInitMarker);
+
+        if (oldUseCount == 1)
+        {
+            // Initialize marker
+            if (AtomicOps<int>::CompareAndSet_Sync(&UseCount, 1, LockInitMarker))
+            {
+                Destruct<Lock>(toLock());
+
+                do { }
+                while (!AtomicOps<int>::CompareAndSet_Sync(&UseCount, LockInitMarker, 0));
+
+                return;
+            }
+            continue;
+        }
+
+    } while (!AtomicOps<int>::CompareAndSet_NoSync(&UseCount, oldUseCount, oldUseCount - 1));
+}
+
 } // OVR
 
 #endif // OVR_ENABLE_THREADS