Refactored spatial dimension data into a helper class.

src/main/java/appeng/items/storage/ItemSpatialStorageCell.java

@@ -25,7 +25,7 @@ import appeng.api.storage.ISpatialDimension;
 import appeng.api.util.WorldCoord;
 import appeng.core.AELog;
 import appeng.core.localization.GuiText;
-import appeng.core.worlddata.SpatialDimensionManager;
+import appeng.spatial.SpatialDimensionManager;
 import appeng.items.AEBaseItem;
 import appeng.spatial.StorageHelper;
 import net.minecraft.client.util.ITooltipFlag;

src/main/java/appeng/spatial/SpatialDimensionExtraData.java

@@ -0,0 +1,45 @@
+package appeng.spatial;
+
+import io.netty.buffer.Unpooled;
+import net.minecraft.network.PacketBuffer;
+import net.minecraft.util.math.BlockPos;
+
+import javax.annotation.Nullable;
+
+/**
+ * Helps with encoding and decoding the extra data we attach to the
+ * spatial {@link net.minecraft.world.dimension.DimensionType} as "extra data".
+ * Keep in mind this data will also be sent to the client unless
+ * {@link net.minecraftforge.common.ModDimension#write(PacketBuffer, boolean)} is overridden.
+ */
+public final class SpatialDimensionExtraData {
+
+    private static final int FORMAT_VERSION = 1;
+    private static final int OFFSET_VERSION = 0;
+    private static final int OFFSET_CONTENT_SIZE = 1;
+
+    private SpatialDimensionExtraData() {
+    }
+
+    public static PacketBuffer create(BlockPos contentSize) {
+        PacketBuffer extraData = new PacketBuffer(Unpooled.buffer());
+        extraData.writeByte(FORMAT_VERSION);
+        extraData.writeBlockPos(contentSize);
+        // Cut the buffer to minimal size
+        extraData.capacity(extraData.writerIndex());
+        return extraData;
+    }
+
+    private static boolean checkVersion(PacketBuffer data){
+        return data.getByte(OFFSET_VERSION) == FORMAT_VERSION;
+    }
+
+    public static BlockPos getContentSize(@Nullable PacketBuffer data) {
+        if (data == null || !checkVersion(data)) {
+            return BlockPos.ZERO;
+        }
+
+        data.readerIndex(OFFSET_CONTENT_SIZE);
+        return data.readBlockPos();
+    }
+}

src/main/java/appeng/spatial/SpatialDimensionManager.java

@@ -16,15 +16,12 @@
  * along with Applied Energistics 2.  If not, see <http://www.gnu.org/licenses/lgpl>.
  */
 
-package appeng.core.worlddata;
+package appeng.spatial;
 
 
 import appeng.api.storage.ISpatialDimension;
 import appeng.core.AELog;
 import appeng.core.AppEng;
-import appeng.spatial.StorageCellDimension;
-import appeng.spatial.StorageCellModDimension;
-import io.netty.buffer.Unpooled;
 import net.minecraft.network.PacketBuffer;
 import net.minecraft.server.MinecraftServer;
 import net.minecraft.util.ResourceLocation;
@@ -51,8 +48,7 @@ public class SpatialDimensionManager implements ISpatialDimension
 		ResourceLocation dimKey = findFreeDimensionId();
 		AELog.info("Allocating storage cell dimension '%s' for %d", dimKey);
 
-		PacketBuffer extraData = new PacketBuffer(Unpooled.buffer());
+		PacketBuffer extraData = SpatialDimensionExtraData.create(contentSize);
-		extraData.writeBlockPos(contentSize);
 
 		return DimensionManager.registerDimension(dimKey, StorageCellModDimension.INSTANCE, extraData, true);
 	}
@@ -100,10 +96,6 @@ public class SpatialDimensionManager implements ISpatialDimension
 		DimensionManager.unregisterDimension(cellDim.getId());
 	}
 
-	private static MinecraftServer getServer() {
-		return ServerLifecycleHooks.getCurrentServer();
-	}
-
 	@Override
 	public boolean isCellDimension( DimensionType cellDim )
 	{
@@ -128,12 +120,11 @@ public class SpatialDimensionManager implements ISpatialDimension
 			return BlockPos.ZERO;
 		}
 
-		PacketBuffer data = cellDim.getData();
+		return SpatialDimensionExtraData.getContentSize(cellDim.getData());
-		if (data == null) {
+	}
-			return BlockPos.ZERO;
+
-		}
+	private static MinecraftServer getServer() {
-		data.readerIndex(4);
+		return ServerLifecycleHooks.getCurrentServer();
-		return data.readBlockPos();
 	}
 
 }

src/main/java/appeng/spatial/StorageCellDimension.java

@@ -43,7 +43,7 @@ public class StorageCellDimension extends Dimension
 	// A region file is 512x512 blocks (32x32 chunks),
 	// to avoid creating the 4 regions around 0,0,0,
 	// we move the origin to the middle of region 0,0
-	public static final BlockPos REGION_CENTER = new BlockPos(512 / 2, 61, 512 / 2);
+	public static final BlockPos REGION_CENTER = new BlockPos(512 / 2, 64, 512 / 2);
 
 	public StorageCellDimension(World world, DimensionType dimensionType) {
 		// FIXME: check light value

src/test/java/appeng/core/worlddata/SpatialDimensionExtraDataTest.java

@@ -0,0 +1,47 @@
+package appeng.core.worlddata;
+
+import appeng.spatial.SpatialDimensionExtraData;
+import io.netty.buffer.Unpooled;
+import net.minecraft.network.PacketBuffer;
+import net.minecraft.util.math.BlockPos;
+import org.junit.Test;
+
+import static org.junit.Assert.*;
+
+public class SpatialDimensionExtraDataTest {
+
+    /**
+     * The returned buffer should have just the right capacity.
+     */
+    @Test
+    public void testCreatedBufferSize() {
+        PacketBuffer buffer = SpatialDimensionExtraData.create(BlockPos.ZERO);
+        assertEquals(9, buffer.array().length);
+    }
+
+    @Test
+    public void testReadWriteSize() {
+        BlockPos pos = new BlockPos(1, 2, 3);
+        PacketBuffer buffer = SpatialDimensionExtraData.create(pos);
+
+        PacketBuffer readBackBuf = new PacketBuffer(Unpooled.wrappedBuffer(buffer.array()));
+        BlockPos actualPos = SpatialDimensionExtraData.getContentSize(readBackBuf);
+        assertEquals(pos, actualPos);
+    }
+
+    /**
+     * Gracefully handle format version errors.
+     */
+    @Test
+    public void testHandleInvalidFormatVersion() {
+        BlockPos pos = new BlockPos(1, 2, 3);
+        PacketBuffer buffer = SpatialDimensionExtraData.create(pos);
+        buffer.writerIndex(0);
+        buffer.writeByte(5);
+
+        PacketBuffer readBackBuf = new PacketBuffer(Unpooled.wrappedBuffer(buffer.array()));
+        BlockPos actualPos = SpatialDimensionExtraData.getContentSize(readBackBuf);
+        assertEquals(BlockPos.ZERO, actualPos);
+    }
+
+}