Bump OculusVR RIFT SDK to 0.5.0.1vanilla_0.5.0.1

1 files changed, 117 insertions, 0 deletions

diff --git a/LibOVRKernel/Src/Kernel/OVR_Lockless.h b/LibOVRKernel/Src/Kernel/OVR_Lockless.h
new file mode 100644
index 0000000..f9043a9
--- /dev/null
+++ b/LibOVRKernel/Src/Kernel/OVR_Lockless.h
@@ -0,0 +1,117 @@
+/************************************************************************************
+
+PublicHeader:   OVR_Kernel.h
+Filename    :   OVR_Lockless.h
+Content     :   Lock-less classes for producer/consumer communication
+Created     :   November 9, 2013
+Authors     :   John Carmack
+
+Copyright   :   Copyright 2014 Oculus VR, LLC All Rights reserved.
+
+Licensed under the Oculus VR Rift SDK License Version 3.2 (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-3.2 
+
+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,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+
+*************************************************************************************/
+
+#ifndef OVR_Lockless_h
+#define OVR_Lockless_h
+
+#include "OVR_Atomic.h"
+
+// Define this to compile-in Lockless test logic
+//#define OVR_LOCKLESS_TEST
+
+namespace OVR {
+
+
+// ***** LocklessUpdater
+
+// For single producer cases where you only care about the most recent update, not
+// necessarily getting every one that happens (vsync timing, SensorFusion updates).
+//
+// This is multiple consumer safe, but is currently only used with a single consumer.
+//
+// The SlotType can be the same as T, but should probably be a larger fixed size.
+// This allows for forward compatibility when the updater is shared between processes.
+
+// FIXME: ExchangeAdd_Sync() should be replaced with a portable read-only primitive,
+// so that the lockless pose state can be read-only on remote processes and to reduce
+// false sharing between processes and improve performance.
+
+template<class T, class SlotType = T>
+class LocklessUpdater
+{
+public:
+	LocklessUpdater() : UpdateBegin( 0 ), UpdateEnd( 0 )
+    {
+        OVR_COMPILER_ASSERT(sizeof(T) <= sizeof(SlotType));
+    }
+
+	T GetState() const
+	{
+		// Copy the state out, then retry with the alternate slot
+		// if we determine that our copy may have been partially
+		// stepped on by a new update.
+		T	state;
+		int	begin, end, final;
+
+		for(;;)
+		{
+			// We are adding 0, only using these as atomic memory barriers, so it
+			// is ok to cast off the const, allowing GetState() to remain const.
+            end   = UpdateEnd.Load_Acquire();
+            state = Slots[ end & 1 ];
+            begin = UpdateBegin.Load_Acquire();
+			if ( begin == end ) {
+				break;
+			}
+
+			// The producer is potentially blocked while only having partially
+			// written the update, so copy out the other slot.
+            state = Slots[ (begin & 1) ^ 1 ];
+            final = UpdateBegin.Load_Acquire();
+			if ( final == begin ) {
+				break;
+			}
+
+			// The producer completed the last update and started a new one before
+			// we got it copied out, so try fetching the current buffer again.
+		}
+		return state;
+	}
+
+	void	SetState( const T& state )
+	{
+        const int slot = UpdateBegin.ExchangeAdd_Sync(1) & 1;
+        // Write to (slot ^ 1) because ExchangeAdd returns 'previous' value before add.
+        Slots[slot ^ 1] = state;
+        UpdateEnd.ExchangeAdd_Sync(1);
+	}
+
+    AtomicInt<int> UpdateBegin;
+    AtomicInt<int> UpdateEnd;
+    SlotType       Slots[2];
+};
+
+
+#ifdef OVR_LOCKLESS_TEST
+void StartLocklessTest();
+#endif
+
+
+} // namespace OVR
+
+#endif // OVR_Lockless_h
+