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diff --git a/Minecraft.Client/PS3/SPU_Tasks/CompressedTile/SparseDataStorage_SPU.h b/Minecraft.Client/PS3/SPU_Tasks/CompressedTile/SparseDataStorage_SPU.h
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+#pragma once
+
+// 4J added - Storage for data (ie the extra per tile storage). Data is normally stored as 4-bits per tile, in a DataLayer class of 16384 bytes ( 128 x 16 x 16 x 0.5 )
+// This class provides more economical storage for such data by taking into consideration that it is quite common for large parts of the data to be very compressible (ie zero).
+// We are aiming here to balance performance (this data is accessed very frequently) against size.
+
+// Details of storage method:
+
+// 1. Data is split into horizontal planes, of which there are 128, and each taking up 128 bytes (16 x 16 x 0.5)
+// 2. Each of these layers has a permanently allocated index in this class (planeIndices).
+// 3. Data for allocatedPlaneCount planes worth of data is allocated in the data array ( allocatedPlaneCount * 128 bytes )
+// 4. If a plane index for a layer is < 128, then the data for that layer is at data[ index * 128 ]
+// 5. If a plane index for a layer is 128, then all values for that plane are 0
+
+// This class needs to be thread safe as there are times where chunk data is shared between server & main threads. Data values are queried
+// very regularly so this needs to be as light-weight as possible.
+
+// To meet these requirements, this class is now implemented using a lock-free system, implemented using a read-copy-update (RCU) type algorithm. Some details...
+
+// (1) The storage details for the class are now packed into a single __int64, which contains both a pointer to the data that is required and a count of how many planes worth
+//     of storage are allocated. This allows the full storage to be updated atomically using compare and exchange operations (implemented with InterlockedCompareExchangeRelease64).
+// (2) The data pointer referenced in this __int64 points to an area of memory which is 128 + 128 * plane_count bytes long, where the first 128 bytes stoere the plane indices, and
+//     the rest of the data is variable in size to accomodate however many planes are required to be stored
+// (3) The RCU bit of the algorithm means that any read operations don't need to do any checks or locks at all. When the data needs to be updated, a copy of it is made and updated,
+//     then an attempt is made to swap the new data in - if this succeeds then the old data pointer is deleted later at some point where we know nothing will be reading from it anymore.
+//     This is achieved by putting the delete request in a queue which means it won't actually get deleted until 2 game ticks after the last time its reference existed, which should give
+//     us a large margin of safety. If the attempt to swap the new data in fails, then the whole write operation has to be attempted again - this is the only time there is really a
+//     high cost for this algorithm and such write collisions should be rare.
+
+//#define DATA_COMPRESSION_STATS
+
+class SparseDataStorage_SPU
+{
+private:
+//	unsigned char	planeIndices[128];
+	unsigned char* m_pData;	
+
+//	unsigned char	*data;
+//	unsigned int	allocatedPlaneCount;
+
+	static const int ALL_0_INDEX = 128;
+
+public:
+    SparseDataStorage_SPU(unsigned char* data) : m_pData(data) {}
+
+	unsigned char* getDataPtr() { return m_pData; }
+
+	int  get(int x, int y, int z)							// Get an individual data value
+	{
+		unsigned char *planeIndices, *data;
+		getPlaneIndicesAndData(&planeIndices, &data);
+
+		if( planeIndices[y] == ALL_0_INDEX )
+		{
+			return 0;
+		}
+		else
+		{
+			int planeIndex = x * 16 + z;				// Index within this xz plane
+			int byteIndex = planeIndex / 2;				// Byte index within the plane (2 tiles stored per byte)
+			int shift = ( planeIndex & 1 ) * 4;			// Bit shift within the byte
+			int retval = ( data[ planeIndices[y] * 128 + byteIndex ] >> shift ) & 15;
+
+			return retval;
+		}
+	}
+
+	void getPlaneIndicesAndData(unsigned char **planeIndices, unsigned char **data)
+	{
+		*planeIndices = m_pData;
+		*data = m_pData + 128;
+	}
+
+};
+