Refactored spatial dimension data into a helper class.

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);
+    }
+
+}