fix: add a WrapperChunk to allow "Invalidating" a ChunkHolder on submission

worldedit-core/src/main/java/com/fastasyncworldedit/core/queue/Filter.java

@@ -24,7 +24,7 @@ public interface Filter {
     /**
      * Do something with the IChunk<br>
      */
-    default @Nonnull <T extends IChunk> T applyChunk(T chunk, @Nullable Region region) {
+    default @Nonnull <U extends IChunk> U applyChunk(U chunk, @Nullable Region region) {
         return chunk;
     }
 

worldedit-core/src/main/java/com/fastasyncworldedit/core/queue/IQueueChunk.java

@@ -1,9 +1,14 @@
 package com.fastasyncworldedit.core.queue;
 
+import com.fastasyncworldedit.core.queue.implementation.chunk.ChunkHolder;
+import com.fastasyncworldedit.core.queue.implementation.chunk.WrapperChunk;
+import org.jetbrains.annotations.ApiStatus;
+
 import java.util.concurrent.Callable;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.Future;
 
+@ApiStatus.Internal
 public interface IQueueChunk<T extends Future<T>> extends IChunk, Callable<T> {
 
     /**
@@ -15,6 +20,25 @@ default IQueueChunk<T> reset() {
         return this;
     }
 
+    /**
+     * Set a new {@link WrapperChunk} that allows prevention of a {@link ChunkHolder} instance being cached "locally" whilst it
+     * has been called/submitted, causing issues with processing/postprocessing, etc.
+     * If a wrapper has already been set, throws {@link IllegalStateException} as there should be no circumstance for us to set
+     * a new wrapper (does nothing if attempting to set the same wrapper).
+     *
+     * @param parentWrapper wrapper wrapping this {@link ChunkHolder instance}
+     * @throws IllegalStateException if there is already a wrapper set and a new wrapper instance is attempted to be se
+     * @since TODO
+     */
+    void setWrapper(WrapperChunk<?> parentWrapper);
+
+    /**
+     * Invalidate the {@link WrapperChunk} if present.
+     *
+     * @since TODO
+     */
+    void invalidateWrapper();
+
     /**
      * Apply the queued changes to the world containing this chunk.
      * <p>The future returned may return another future. To ensure completion keep calling {@link

worldedit-core/src/main/java/com/fastasyncworldedit/core/queue/IQueueExtent.java

@@ -5,6 +5,8 @@
 import com.fastasyncworldedit.core.internal.simd.SimdSupport;
 import com.fastasyncworldedit.core.internal.simd.VectorizedCharFilterBlock;
 import com.fastasyncworldedit.core.internal.simd.VectorizedFilter;
+import com.fastasyncworldedit.core.queue.implementation.chunk.ChunkHolder;
+import com.fastasyncworldedit.core.queue.implementation.chunk.WrapperChunk;
 import com.sk89q.worldedit.extent.Extent;
 import com.sk89q.worldedit.function.operation.Operation;
 import com.sk89q.worldedit.math.BlockVector2;
@@ -166,11 +168,24 @@ default ChunkFilterBlock apply(
 //        if (!filter.appliesChunk(chunkX, chunkZ)) {
 //            return block;
 //        }
-        T chunk = this.getOrCreateChunk(chunkX, chunkZ);
+        T initial = this.getOrCreateChunk(chunkX, chunkZ);
+        WrapperChunk<T> chunk = new WrapperChunk<>(initial, () -> this.getOrCreateChunk(chunkX, chunkZ));
+        if (initial instanceof ChunkHolder<?> holder) {
+            holder.setWrapper(chunk);
+        }
 
-        T newChunk = filter.applyChunk(chunk, region);
+        IChunk newChunk = filter.applyChunk(chunk, region);
+        if (newChunk == chunk) {
+            newChunk = chunk.get();
+        } else {
+            T c = (T) newChunk;
+            chunk.setWrapped(c);
+            // The IDE lies, it is possible for it to be a ChunkHolder because we're a little loose with our generic types...
+            if (c instanceof ChunkHolder<?> holder) {
+                holder.setWrapper(chunk);
+            }
+        }
         if (newChunk != null) {
-            chunk = newChunk;
             if (block == null) {
                 if (SimdSupport.useVectorApi() && filter instanceof VectorizedFilter) {
                     block = new VectorizedCharFilterBlock(this);
@@ -181,12 +196,16 @@ default ChunkFilterBlock apply(
             block.initChunk(chunkX, chunkZ);
             chunk.filterBlocks(filter, block, region, full);
         }
-        this.submit(chunk);
+        // If null, then assume it has already been submitted and the WrapperChunk has therefore been invalidated
+        T toSubmit = chunk.get();
+        if (toSubmit != null) {
+            this.submit(toSubmit);
+        }
         return block;
     }
 
     @Override
-    default <T extends Filter> T apply(Region region, T filter, boolean full) {
+    default <U extends Filter> U apply(Region region, U filter, boolean full) {
         final Set<BlockVector2> chunks = region.getChunks();
         ChunkFilterBlock block = null;
         for (BlockVector2 chunk : chunks) {

worldedit-core/src/main/java/com/fastasyncworldedit/core/queue/implementation/SingleThreadQueueExtent.java

@@ -36,6 +36,7 @@
 import java.util.concurrent.ConcurrentLinkedQueue;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.Future;
+import java.util.concurrent.atomic.AtomicReference;
 import java.util.concurrent.locks.ReentrantLock;
 
 /**
@@ -53,6 +54,7 @@ public class SingleThreadQueueExtent extends ExtentBatchProcessorHolder implemen
     private final Long2ObjectLinkedOpenHashMap<IQueueChunk<?>> chunks = new Long2ObjectLinkedOpenHashMap<>();
     private final ConcurrentLinkedQueue<Future<?>> submissions = new ConcurrentLinkedQueue<>();
     private final ReentrantLock getChunkLock = new ReentrantLock();
+    private final AtomicReference<IQueueChunk> lastChunk = new AtomicReference<>();
     private World world = null;
     private int minY = 0;
     private int maxY = 255;
@@ -61,7 +63,6 @@ public class SingleThreadQueueExtent extends ExtentBatchProcessorHolder implemen
     private boolean initialized;
     private Thread currentThread;
     // Last access pointers
-    private volatile IQueueChunk lastChunk;
     private boolean enabledQueue = true;
     private boolean fastmode = false;
     // Array for lazy avoidance of concurrent modification exceptions and needless overcomplication of code (synchronisation is
@@ -161,13 +162,13 @@ protected synchronized void reset() {
             return;
         }
         getChunkLock.lock();
+        this.lastChunk.set(null);
         try {
             this.chunks.clear();
         } finally {
             getChunkLock.unlock();
         }
         this.enabledQueue = true;
-        this.lastChunk = null;
         this.currentThread = null;
         this.initialized = false;
         this.setProcessor(EmptyBatchProcessor.getInstance());
@@ -221,9 +222,7 @@ public boolean isEmpty() {
 
     @Override
     public <V extends Future<V>> V submit(IQueueChunk chunk) {
-        if (lastChunk == chunk) {
-            lastChunk = null;
-        }
+        this.lastChunk.compareAndExchange(chunk, null);
         final long index = MathMan.pairInt(chunk.getX(), chunk.getZ());
         getChunkLock.lock();
         chunks.remove(index, chunk);
@@ -254,6 +253,8 @@ private <V extends Future<V>> V submitUnchecked(IQueueChunk chunk) {
             }
         }
 
+        chunk.invalidateWrapper();
+
         if (Fawe.isMainThread()) {
             V result = (V) chunk.call();
             if (result == null) {
@@ -277,8 +278,9 @@ public <V extends Future<V>> V submitTaskUnchecked(Callable<V> callable) {
     public synchronized boolean trim(boolean aggressive) {
         cacheGet.trim(aggressive);
         cacheSet.trim(aggressive);
+        LOGGER.info("trim");
         if (Thread.currentThread() == currentThread) {
-            lastChunk = null;
+            lastChunk.set(null);
             return chunks.isEmpty();
         }
         if (!submissions.isEmpty()) {
@@ -316,7 +318,7 @@ public IQueueChunk wrap(IQueueChunk chunk) {
 
     @Override
     public final IQueueChunk getOrCreateChunk(int x, int z) {
-        final IQueueChunk lastChunk = this.lastChunk;
+        final IQueueChunk lastChunk = this.lastChunk.get();
         if (lastChunk != null && lastChunk.getX() == x && lastChunk.getZ() == z) {
             return lastChunk;
         }
@@ -330,7 +332,7 @@ public final IQueueChunk getOrCreateChunk(int x, int z) {
         try {
             IQueueChunk chunk = chunks.get(pair);
             if (chunk != null) {
-                this.lastChunk = chunk;
+                this.lastChunk.set(chunk);
                 return chunk;
             }
             final int size = chunks.size();
@@ -340,8 +342,9 @@ public final IQueueChunk getOrCreateChunk(int x, int z) {
             //  - queue size > target size and primary queue has less than num threads submissions
             int targetSize = lowMem ? Settings.settings().QUEUE.PARALLEL_THREADS + 8 : this.targetSize;
             if (enabledQueue && size > targetSize && (lowMem || Fawe.instance().getQueueHandler().isUnderutilized())) {
-                chunk = chunks.removeFirst();
-                final Future future = submitUnchecked(chunk);
+                IQueueChunk toSubmit = chunks.removeFirst();
+                this.lastChunk.compareAndExchange(toSubmit, null);
+                final Future future = submitUnchecked(toSubmit);
                 if (future != null && !future.isDone()) {
                     pollSubmissions(targetSize, lowMem);
                     submissions.add(future);
@@ -351,7 +354,7 @@ public final IQueueChunk getOrCreateChunk(int x, int z) {
             chunk = wrap(chunk);
 
             chunks.put(pair, chunk);
-            this.lastChunk = chunk;
+            this.lastChunk.set(chunk);
 
             return chunk;
         } finally {
@@ -481,6 +484,7 @@ public synchronized void flush() {
             if (MemUtil.isMemoryLimited()) {
                 while (!chunks.isEmpty()) {
                     IQueueChunk chunk = chunks.removeFirst();
+                    this.lastChunk.compareAndExchange(chunk, null);
                     final Future future = submitUnchecked(chunk);
                     if (future != null && !future.isDone()) {
                         pollSubmissions(Settings.settings().QUEUE.PARALLEL_THREADS, true);
@@ -490,6 +494,7 @@ public synchronized void flush() {
             } else {
                 while (!chunks.isEmpty()) {
                     IQueueChunk chunk = chunks.removeFirst();
+                    this.lastChunk.compareAndExchange(chunk, null);
                     final Future future = submitUnchecked(chunk);
                     if (future != null && !future.isDone()) {
                         submissions.add(future);

worldedit-core/src/main/java/com/fastasyncworldedit/core/queue/implementation/chunk/ChunkHolder.java

@@ -36,6 +36,7 @@
  */
 @SuppressWarnings("rawtypes")
 public class ChunkHolder<T extends Future<T>> implements IQueueChunk<T> {
+
     private static final Logger LOGGER = LogManagerCompat.getLogger();
 
     public static ChunkHolder newInstance() {
@@ -45,7 +46,7 @@ public static ChunkHolder newInstance() {
     private volatile IChunkGet chunkExisting; // The existing chunk (e.g. a clipboard, or the world, before changes)
     private volatile IChunkSet chunkSet; // The blocks to be set to the chunkExisting
     private IBlockDelegate delegate; // delegate handles the abstraction of the chunk layers
-    private IQueueExtent<? extends IChunk> extent; // the parent queue extent which has this chunk
+    private IQueueExtent<?> extent; // the parent queue extent which has this chunk
     private int chunkX;
     private int chunkZ;
     private boolean fastmode;
@@ -54,6 +55,7 @@ public static ChunkHolder newInstance() {
     private boolean createCopy = false;
     private long initTime = -1L;
     private SideEffectSet sideEffectSet;
+    private WrapperChunk<?> parentWrapper = null;
 
     private ChunkHolder() {
         this.delegate = NULL;
@@ -63,7 +65,28 @@ public void init(IBlockDelegate delegate) {
         this.delegate = delegate;
     }
 
+    @Override
+    public void setWrapper(WrapperChunk<?> parentWrapper) {
+        if (parentWrapper == this.parentWrapper) {
+            return;
+        }
+        if (this.parentWrapper != null) {
+            throw new IllegalStateException("Wrapper already set");
+        }
+        this.parentWrapper = parentWrapper;
+    }
+
+    @Override
+    public void invalidateWrapper() {
+        if (this.parentWrapper != null) {
+            if (!this.parentWrapper.invalidate(this)) {
+                throw new IllegalStateException("Existing chunk not equal to expected");
+            }
+        }
+    }
+
     private static final AtomicBoolean recycleWarning = new AtomicBoolean(false);
+
     @Override
     public void recycle() {
         if (!recycleWarning.getAndSet(true)) {
@@ -346,10 +369,12 @@ public int[] getHeightMap(ChunkHolder chunk, HeightMapType type) {
 
         @Override
         public void flushLightToGet(ChunkHolder chunk) {
-            chunk.chunkExisting.setLightingToGet(chunk.chunkSet.getLight(), chunk.chunkSet.getMinSectionPosition(),
+            chunk.chunkExisting.setLightingToGet(
+                    chunk.chunkSet.getLight(), chunk.chunkSet.getMinSectionPosition(),
                     chunk.chunkSet.getMaxSectionPosition()
             );
-            chunk.chunkExisting.setSkyLightingToGet(chunk.chunkSet.getSkyLight(), chunk.chunkSet.getMinSectionPosition(),
+            chunk.chunkExisting.setSkyLightingToGet(
+                    chunk.chunkSet.getSkyLight(), chunk.chunkSet.getMinSectionPosition(),
                     chunk.chunkSet.getMaxSectionPosition()
             );
         }
@@ -892,10 +917,15 @@ public boolean hasNonEmptySection(final int layer) {
     public synchronized void filterBlocks(Filter filter, ChunkFilterBlock block, @Nullable Region region, boolean full) {
         final IChunkGet get = getOrCreateGet();
         final IChunkSet set = getOrCreateSet();
+        if (parentWrapper == null) {
+            parentWrapper = new WrapperChunk<>(this, () -> this.extent.getOrCreateChunk(getX(), getZ()));
+        } else if (parentWrapper.get() != this) {
+            throw new IllegalStateException("Parent WrapperChunk is not storing this chunk!?");
+        }
         try {
-            block.filter(this, get, set, filter, region, full);
+            block.filter(parentWrapper, get, set, filter, region, full);
         } finally {
-            filter.finishChunk(this);
+            filter.finishChunk(parentWrapper);
         }
     }
 
@@ -998,6 +1028,12 @@ public synchronized <V extends IChunk> void init(IQueueExtent<V> extent, int chu
         this.extent = extent;
         this.chunkX = chunkX;
         this.chunkZ = chunkZ;
+        if (this.parentWrapper != null) {
+            if (!this.parentWrapper.invalidate(this)) {
+                throw new IllegalStateException("Existing chunk not equal to expected");
+            }
+            this.parentWrapper = null;
+        }
         if (chunkSet != null) {
             chunkSet.reset();
             delegate = SET;
@@ -1013,9 +1049,11 @@ public synchronized T call() {
         if (chunkSet != null && !chunkSet.isEmpty()) {
             IChunkSet copy = chunkSet.createCopy();
 
-            return this.call(extent, copy, () -> {
-                // Do nothing
-            });
+            return this.call(
+                    extent, copy, () -> {
+                        // Do nothing
+                    }
+            );
         }
         return null;
     }
@@ -1025,14 +1063,20 @@ public synchronized T call() {
      */
 
     @Override
-    public <U extends Future<U>> U call(IQueueExtent<? extends IChunk> owner, IChunkSet set, Runnable finalize) {
+    public <U extends Future<U>> U call(IQueueExtent<?> owner, IChunkSet set, Runnable finalize) {
         if (set != null) {
+            if (parentWrapper != null) {
+                if (!parentWrapper.invalidate(this)) {
+                    throw new IllegalStateException("Existing chunk not equal to expected");
+                }
+            }
             IChunkGet get = getOrCreateGet();
             try {
                 get.lockCall();
                 trackExtent();
                 boolean postProcess = !(getExtent().getPostProcessor() instanceof EmptyBatchProcessor);
                 final int copyKey = get.setCreateCopy(postProcess);
+                // We should always be performing processing/postprocessing with this instance (i.e. not with this.parentWrapper)
                 final IChunkSet iChunkSet = getExtent().processSet(this, get, set);
                 Runnable finalizer;
                 if (postProcess) {
@@ -1067,7 +1111,7 @@ private void untrackExtent() {
     /**
      * Get the extent this chunk is in.
      */
-    public IQueueExtent<? extends IChunk> getExtent() {
+    public IQueueExtent<?> getExtent() {
         return extent;
     }
 

worldedit-core/src/main/java/com/fastasyncworldedit/core/queue/implementation/chunk/NullChunk.java

@@ -47,6 +47,14 @@ public boolean isEmpty() {
         return true;
     }
 
+    @Override
+    public void setWrapper(final WrapperChunk parentWrapper) {
+    }
+
+    @Override
+    public void invalidateWrapper() {
+    }
+
     public Future call() {
         return null;
     }